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AUTOMOBILE ENGINEERING Basic Fundamentals to Advanced Concepts of Automobile Engineering Prabhu TL Nestfame Creations Pvt. Ltd.
[Automobile Engineering] Copyright ©  Prabhu TL. All rights reserved. Publisher - Nestfame Creations Pvt. Ltd. Publisher Website - www.nestfamecreations.com The contents of this book may not be reproduced, duplicated or transmitted without direct written permission from the Author . Under no circumstances will any legal responsibility or blame be held against the publisher for any reparation, damages, or monetary loss due to the information herein, either directly or indirectly. Author - Prabhu TL Indexer - Akshai Kumar RY
Legal Notice: This book is copyright protected. This is only for personal use. You cannot amend, distribute, sell, quote or paraphrase any part or the content within this book without the consent of the author.
Disclaimer Notice: Please note the information contained within this document is for educational and entertainment purpose only .every attempt has been made to provide accurate, up to date and reliable complete information. No warranties of any kind are expressed or implied. Please consult a licensed professional before attempting any techniques outlined in this book . By reading this document, the reader agrees that under no circumstances are is the author responsible for any losses, direct or indirect, which are incurred as a result of the use of information contained within this document, including, but not limited to, __eRrors, omissions, or inaccuracies.
PREFACE Automobile or Automotive Engineering has gained recognition and importance ever since motor vehicles capable for transporting passengers has been in vogue. Now due to the rapid growth of auto component manufacturers and automobile industries, there is a great demand for Automobile Engineers. Automobile Engineering alias Automotive Engineering or Vehicle Engineering is one of the most challenging careers in the field of engineering with a wide scope. This branch deals with the designing, developing, manufacturing, testing and repairing and servicing automobiles such as cars, trucks, motorcycles, scooters etc & the related sub Engineering systems. For the perfect blend of manufacturing and designing automobiles, Automobile Engineering uses the features of different elements of Engineering such as mechanical, electrical, electronic, software and safety engineering. To become a proficient automobile engineer, specialized training is essential and it is a profession, which requires a lot of hard work, dedication, determination and commitment. The major task of an Automobile Engineer is the designing, developing, manufacturing and testing of vehicles from the concept stage to the production stage The automotive industry is one of the largest and most important industries in the world. Cars, buses, and other engine-based vehicles abound in every country on the planet, and it is continually evolving, with electric cars, hybrids, self-driving vehicles, and so on. Technologies that were once thought to be decades away are now on our roads right now. Engineers, technicians, and managers are constantly needed in the industry, and, often, they come from other areas of engineering, such as electrical engineering, process engineering, or chemical engineering. Introductory books like this one are very useful for engineers who are new to the industry and need a tutorial. Also valuable as a textbook for students, this introductory volume not only covers the basics of automotive engineering, but also the latest trends, such as self-driving vehicles, hybrids, and electric cars. Not only useful as an introduction to the science or a textbook, it can also serve as a valuable
reference for technicians and engineers alike. The volume also goes into other subjects, such as maintenance and performance. Data has always been used in every company irrespective of its domain to improve the operational efficiency and performance of engines. This work deals with details of various automotive systems with focus on designing various components of these system to suit the working conditions on roads. Whether a textbook for the student, an introduction to the industry for the newly hired engineer, or a reference for the technician or veteran engineer, this volume is the perfect introduction to the science of automotive engineering.
TABLE OF CONTENT FUNDAMENTALS 1. 2. 3. 4. 5. 6. 7. 8. 9.
What Is Automobile Engineering? Anti-Lock Braking System (abs) Adaptive Cruise Control Crdi (common Rail Direct Injection) Dtsi (digital Twin Spark Ignition System) Electromagnetic Brake Spark Plug Turbocharger Windshield Washer 10. Blink Code In Antilock Braking System(abs) 11. Working Of A Car 12. Layout Of A Car 13. Battery Introduction 14. Advantages Of Using Rechargeable Batteries 15. Are Primary And Rechargeable Batteries Interchangeable Amongst Each Other? 16. The Batteries Work Better In Different Devices 17. Types Of Batteries 18. Battery Principle Of Operation 19. Brake Introduction 20. Types Of Brakes 21. Frictional, Pumping, Electromagnetic Brakes 22. Hydraulic Brake 23. Air Brake System 24. Clutch Introduction 25. Requirements Of A Good Clutch 26. Different Types Of Clutch 27. Fluid Coupling 28. Differential Introduction 29. Advantages & Disadvantages Of Front Wheel Drive 30. Advantages & Disadvantages Of Rear Wheel Drive 31. Advantages & Disadvantages Of All Or 4- Wheel Drive
32. Need Of A Differential 33. Construction And Working Of Differential Assembly 34. Components Of Automobile Engine 35. Engine Problems 36. How To Produce More Engine Power 37. Efficiency Of The Engine 38. Overall Power Loss In Engine 39. Gear Introduction 40. Types Of Gears 41. Terminology Of Spur Gear 42. Use Of Gear Advantage Of Teeth On Gear 43. Gear Ratio 44. How Does A Gear Ratio Affect Speed? 45. How Does Gear Ratio Affects Torque 46. Gear Train 47. Simple & Compound Gear Train 48. Planetary Or Epicyclic Gear Train 49. Reverted Gear Train 50. Mechanical Advantage 51. Suspension System Introduction 52. Principle Of Suspension System 53. Components Of Suspension System 54. Common Problems Of The Suspension System 55. Preventive Measures For Suspension System 56. Comparison Between Macpherson Double Wishbone Suspension Systems 57. Transmission System Introduction 58. Need For A Transmission 59. Types Of Transmission System 60. Manual Transmission 61. Components Of Manual Transmission 62. Working Of Manual Transmission 63. Five-Speed Manual Transmission 64. Double Clutching 65. Synchronized Transmission 66. Automatic Transmission 67. Planetary Gear Sets
68. Clutches & Bands, Torque Converter, Valve Body 69. Comparison Between Manual & Automatic Transmission70. Semi-Automatic Transmission 71. Dual Clutch Transmission 72. Sequential Transmission 73. Continuously Variable Transmissions 74. Future Developments In Automotive Transmission Systems 75. Terms Connected With I. C. Engines: 76. Fuel Supply System In Spark Ignition Engine 77. Fuel Supply System In Diesel Engine 78. Carburetor 79. Mpfi 80. Cooling System 81. Air Cooling System 82. Water Cooling System 83. Lubrication 84. Types Of Lubricating Systems 85. Need Of Lubrication System 86. Additives In Lubricating Oil 87. Valve Operating Systems 88. Anti-Friction Bearings 89. Straight-Tooth Spur & Helical Spur Gears 90. Straight-Tooth Bevel, Spiral Bevel & Hypoid Gears 91. Four-Wheel Drive (4wd) And All-Wheel Drive (awd) 92. Steering Mechanisms 93. Wheel Alignment 94. Toe & Caster 95. Effect Of Improper Alignment On Vehicle 96. Vehicle Rollover 97. Hotchkiss Suspensions 98. Disc Brakes 99. Lead-Acid Batteries 100. Nickel-Cadmium (nicd) Batteries 101. Nickel-Metal Hydride (nimh) Batteries 102. Lithium Ion (li-1on)llithium Polymer Batteries
103. Dual Hybrid Systems 104. Tire 105. Lean-Burn Nox-Reducing Catalysts, "denox” 106. Automobile History - Top 10 Interesting Facts 107. Difference Between Turbocharging And Supercharging 108. Why Diesel Cannot Be Used In Petrol Engine? 109. What Is Scavenging? 110. Why Petrol Cannot Be Used In Diesel Engine? 111. Flywheel 112. Unmanned Aerial Vehicles 113. Laser Ignition System 114. Technology Of Hydrogen Fuelled Rotary Engine 115. Common Rail Type Fuel Injection System 116. Disi Turbo | Direct Injection Spark Ignition Technology 117. Biotech Materials | Bio-Plastics | Bio-Fabrics 118. Hybrid Synergy Drive (hsd) Technology 119. Ultimate Eco Car Challenge - Development 120. Fuel Cell Technology 121. World’s First Air-Powered Car | Zero Emissions 122. Air Car Is Heading For Mass Production 123. Air-Powered Car Coming To Hit 1000-Mile Range 124. Future Of Car Infotainment Systems 125. Fuel Cell Car | How Fuel Cell Works | Detail Explanation 126. How Fuel Cells Work 127. Kinetic Energy Recovery System | Kers | Formula One (f1) 128. New Battery Technology | Fast Recharge 3d Film Technology 129. Advanced Battery Storage Technology 130. New Powerful Capacitors Nano Composite Processing Technique 131. Rtv Molding | Urethane Casting | Room Temperature Vulcanized 132. Tdi Blue Motion Technologies 133. Turbocharged Stratified Injection (tsi) Engines | Tsi Technology
134. Turbocharged Direct Injection (tdi) Diesel Engines 135. Fuel Cell-Powered Electric Vehicles | Mercedes Benz FCell World Drive 136. Driver Assistance Technologies 137. Compressed Air Cars | Air Motion Racing Car 138. Idling Devices Of Automobile | Anti-Dieseling Device 139. Choking Device | Functions Of Choking Device 140. Antilock Or Antiskid Device | Anti-Lock Braking System In Detail 141. Power Steering | Electronic Power Steering 142. Components Of Automatic Transmission System 143. Safety Systems In Vehicles | Seat Belts | Air Bags 144. Engine Speed Governors | Speed Control Governor | Speed Limiters 145. Steering Systems 146. Gorilla Glass Manufacturing Process 147. Gorilla Glass History | Gorilla Glass Scratch | Gorilla Glass Touch Screen 148. Magnetic Bearing Technology 149. Artificial Photosynthesis 150. The Future Of Bicycling Hydration 151. Wireless Battery Charger 152. Hydraulic Hybrid Vehicles 153. Nvh | Noise Vibration And Harshness 154. Durability Analysis 155. What Is Nvh 156. Nvh Terms | Nvh Terminology -1 157. Nvh Terms | Nvh Terminology - 2 158. Aerogel | World’s Lightest Material 159. Led Light Bulbs | Bonded Fin Heat Sink 160. Nano-Nuclear Batteries | Beta-Voltaic Power 161. Self-Driving Car Technology 162. Electro Chromatic Auto Dimming Mirror 163. Rain Sensors 164. Tandem Wipers | Windshield Wiper Blades 165. Ambient Light Sensor 166. Optoelectronic Materials
167. 168. 169. 170. 171. 172. 173. 174. 175. Control 176. 177. 178. 179. 180. 181. 182. 183. 184. 185. 186. 187. 188. 189. 190. 191. 192. 193. 194. 195. 196. 197. 198. 199. 200. 201. 202.
Opto Electronics | Fiber Optics Technology Hybrid Drive Trains | Hybrid Vehicles Variable Turbo Chargers Geometry (vtg) Trends In Common Rail Fuel Injection System Chassis Frame | Frame Rails | Auto Chassis Types Of Chassis Frame | Auto Chassis Piston-Engine Cycles Of Operation Engine Components And Terms Crankcase Disc-Valve And Reed-Valve Inlet Charge Engine Torque Engine Power Engine Cylinder Capacity Compression-Ratio Digital Engine Control Systems Digital Engine Control Digital Engine Control Features Control Modes For Fuel Control Engine Crank Engine Warm-Up Open-Loop Control Closed-Loop Control Acceleration Enrichment Deceleration Leaning Idle Speed Control Idle Air Control. Egr Control Electronic Ignition Control Closed-Loop Ignition Timing Integrated Engine Control System Evaporative Emissions Canister Purge Automatic System Adjustment System Diagnosis Summary Of Control Modes Improvements In Electronic Engine Control Flywheel Energy Storage General Characteristics Of Wheel Suspensions
Independent Wheel Suspensions – General Steering System
ADVANCED CONCEPTS 1. Motor Technology – The ‘Centre’ of an Electric Vehicle Efficiency 2. Electromagnetic Stir Casting: An Approach to Produce Hybrid Metal Matrix Composite (MMC) 3. Challenges and Opportunities in lithium-ion battery technologies for electric vehicles 4. 90 Degree Steering Mechanism 5. Thermoelectric Cooler : A new horizon in Mechanical and Electronics Engineering 6. Performance And Cost Of Other Types Of Light-Duty Vehicles 7. Emissions Performance 8. Safety Of Lightweight Vehicles 9. Spark Ignition and Diesel Engines 10. Battery Technologies 11. Technologies for Advanced Vehicles Performance and Cost Expectations 12. Materials Selection Criteria 13. Aerodynamic Drag Reduction 14. Rolling Resistance Reduction 15. Improvements To Spark Ignition Engines 16. Reducing Mechanical Friction 17. Reducing Pumping Loss 18. DISC and Two-Stroke Engines 19. Electric Drivetrain Technologies 20. Battery Characteristics 21. Bringing an Advanced Battery to Market 22. Other Engine And Fuel Technologies 23. Improvements To Automatic Transmissions
AUTOMOTIVE ENGINES 1. Engine & Working Principles
2. Constructional Features of IC Engine 3. Principles of Operation Of IC Engines: Four-Stroke Cycle Diesel Engine 4. Two-Stroke Cycle Diesel Engine: 5. Four-Stroke Spark Ignition Engine 6. Two-Stroke Cycle Petrol Engine 7. Comparison Of CI And SI Engines 8. Advantages and Disadvantages Of Two-Stroke Cycle Over FourStroke Cycle Engines 9. Internal Combustion Engines
HYBRID ELECTRIC VEHICLES 1. Introduction to Trends and Hybridization Factor for Heavy-Duty Working Vehicles 2. Introduction to Development of Bus Drive Technology towards Zero Emissions: A Review 3. Introduction to Advanced Charging System for Plug-in Hybrid Electric Vehicles and Battery Electric Vehicles 4. Introduction to Hybrid Energy Storage System for a Coaxial Power-Split Hybrid Powertrain 5. Introduction to Performance Analysis of an Integrated StarterAlternator-Booster for Hybrid Electric Vehicles 6. Introduction toDesign, Optimization and Modelling of High Power Density Direct-Drive Wheel Motor for Light Hybrid Electric Vehicles
AUTOMOTIVE TRANSMISSIONS 1. 2. 3. 4. 5. 6. 7.
Automotive Clutches Clutch Construction Coil Spring Pressure Plate Diaphragm Pressure Plate Flywheel Pilot Bearing Clutch Operation
8. Pressure Plate Adjustment 9. Hydraulic Clutch 10. Slipping 11. Grabbing 12. Dragging 13. Abnormal Noises 14. Pedal Pulsation 15. Clutch Overhaul 16. Manual Transmissions 17. Transmission Construction 18. Transmission Gears 19. Synchronizers 20. Shift Forks, Shift Linkage and Levers 21. Transmission Types 22. Auxiliary Transmissions 23. Transmission Troubleshooting 24. Transmission Overhaul 25. Automatic Transmissions 26. Torque Converters 27. Planetary Gearsets 28. Clutches and Bands 29. Overrunning Clutch 30. Hydraulic System of an Automatic Transmission 31. Automatic Transmission Service 32. Electronic Systems of an Automatic Transmission 33. Transaxles
VEHICLE DYNAMICS 1. 2. 3. 4. 5. 6. 7.
Suspensions, Functions, and Main Components Desired Features of Suspension Systems Functions and Basic Principles Suspension systems Functions of Suspension Systems Classification of Suspensions Basic Principles of Suspension System Lateral Acceleration.
8. Springs 9. Sprung and Unsprung Weight 10. Shock Absorbers 11. Control Arms 12. Ball Joints 13. Steering Knuckles 14. Types of Suspension Systems 15. 4wd Suspensions
IC ENGINES 1. 2. 3. 4. 5. 6. 7. 8. 9.
Detonation or Knocking in IC Engines Cetane Number - Rating of CI Engine Fuels Ignition System of Petrol Engines Definition and Classification of I.C. Engines Difference between four stroke and two stroke engines:Efficiency of an IC Engine Brake power of IC Engine Comparison of Petrol and Diesel Engines Difference between SI and CI engines 10. I.C Engines Important definitions and formulas 11. Internal Combustion Engines- Basic Differences 12. Air Standard Otto Cycle 13. Governing of IC Engines 14. Carburetor of an IC Engine 15. Air Standard Cycles 16. Spark Plug in IC Engines 17. Supercharging of IC Engines 18. Two Stroke vs Four Stroke Engines 19. Octane Number - Rating of S.I. Engine Fuels 20. Valve Timing Diagram of Diesel Engine 21. Thermodynamic Tests for I.C. Engines 22. Lubrication of IC Engines 23. Testing of IC Engines 24. Indicated power of an IC Engine 25. Scavenging of IC Engines
Valve Timing Diagram of Petrol Engine Sequence of Operations in IC Engine
AUTOMOBILE FUEL AND LUBRICANTS 1. 2. 3. 4. 5. 6. 7. 8. 9.
Petroleum Petroleum Refining and Formation Process Visbreaking, thermal cracking, and coking Cracking methodologies Polymerization in Petroleum Refinery Alkylation Isomerization Process Gasoline blending Bearing Lubrication 10. Lubricant base stocks 11. Engine Friction and Lubrication 12. Hydrodynamic Lubrication (HL) 13. Pressure-Viscosity Coefficient and Characteristics of Lubricants 14. Function of Lubrication system 15. Requirements and characteristics of lubricants 16. Determining the Cause of Oil Degradation 17. Additives in lubricating oils 18. Lubricant additives, explained 19. Synthetic Lubricants 20. Lubricants : Classification and properties 21. Requirements and properties of lubricants 22. Lubricants Testing 23. What is Grease? 24. Fuel Thermochemistry 25. Relative Density 26. Fuel Calorific Values 27. Flash point and fire point 28. Vapor pressure 29. Fuel viscosity control
30. 31. 32. 33. 34. 35. 36.
What is API Gravity? Aniline point Copper Strip Corrosion SI ENGINE What is octane rating? Rating of CI Engine Fuels: Diesel Fuel Cetane
AUTOMOTIVE ELECTRICAL AND ELECTRONICS SYSTEMS 1. 2. 3. 4. 5. 6. 7. 8. 9.
What Is Battery And Why It Is Used? Types Of Batteries Battery Working Principle History Of The Battery Testing, Charging And Replacing A Battery Starter The Starting System Ignition Switch Difference Between Alternator & Generator 10. What Is The Charging System? 11. Charging System Components 12. How It Works - The Cut-Out 13. The Voltage Regulator 14. Interior Lighting: 15. Exterior Lighting 16. Design Of Lighting System: 17. Dashboard Gauges 18. How Electronic Ignition System Works? 19. Electronic Ignition System Main Components 20. Three Types Of Vehicle Ignition Systems And How They Work 21. The Evolution Of Fuel Injection 22. Multi Point Fuel Injection (mpfi) 23. Different Types Of Sensors Used In Automobiles 24. Oxygen Sensor Working And Applications
25. 26. 27. 28. 29. 30.
Hot Wire Anemometer Vehicle Speed Sensor (vss) Accelerometers: Crankshaft Position Sensor Microcontroller Vs Microprocessor What Is Keyless Entry And How Does It Work?
URBAN TRANSPORTATION SYSTEM 1. What Is Urbanization? 2. 7 Transportation Challenges in Urban Areas 3. Changing Urban Transportation Systems for Improved Quality of Life 4. Urban Transport Challenges 5. Automobile Dependency 6. Congestion 7. Mitigating Congestion 8. The Urban Transit Challenge 9. Global Urbanization 10. Evolution of Transportation and Urban Form 11. The Spatial Constraints of Urban Transportation 12. Transportation and the Urban Structure 13. Process and Top 5 stages of Transportation Planning 14. The Benefits Of Urban Mass Transit 15. Effects of public policy 16. Mass Transit Finance 17. Marketing Mass Transit 18. Trip characteristics 19. The Future Of Mass Transportation 20. 7 Problems of Urban Transport 21. Role of Transport in Urban Growth 22. 8 Helpful Steps for Solving the Problems of Urban Transport 23. Vehicle To Vehicle Communication 24. Components of an Urban Transit System 25. What is a BRT Corridor?
26. 27. 28. 29. 30. 31. 32.
The Land Use – Transport System Urban Land Use Models Transportation and Urban Dynamics Transportation-Land Use Interactions Land Requirement and Consumption Spatial Form, Pattern and Interaction Environmental Externalities of Land Use
Vehicle Design Data Characteristics 1. 2. 3. 4. 5. 6. 7. 8. 9.
Vehicle Chassis And Frame Design Gross Vehicle Weight Rating Speed Limits What Is The Maximum Acceleration Types Of Gears Resistance To Motion Vehicle Power Requirements Force Required To Accelerate A Load Vehicle Acceleration And Maximum Speed Modeling And Simulation 10. Curve Interpolation Methods And Options 11. What Is The Mean Effective Pressure (mep) Of An Engine ? 12. What Is Engine Capacity (cc): 13. How Engine Capacity Affects Its Performance: 14. What Is Bore-Stroke Ratio? 15. How Rod Lengths And Ratios Affect Performance 16. Best Rod Ratio? 17. Oversquare Vs Undersquare 18. Piston Motion Equations 19. Gear Ratios 20. Classical Design Of Gear Train 21. How To Determine Gear Ratio 22. Vehicle Performance 23. Coordinate Systems
What is Automobile Engineering? Automobile Engineering is a branch of engineering which deals with designing, manufacturing and operating automobiles. It is a segment of vehicle engineering which deals with motorcycles, buses, trucks, etc. It includes mechanical, electrical, electronic, software and safety elements. Skills Required:
Automotive engineering is one of the most exciting professions you can choose. From the global concerns of sustainable mobility, and teaching cars to drive themselves, to working out how we’ll get around on the surface of Mars, automotive engineering is all about the future. The challenges facing personal mobility are endless. Automotive engineers work in every area of the industry, from the look and feel of current cars, to the safety and security of new forms of transport. Attempting to make cars as fast as possible whilst keeping them fuel efficient may seem like an impossible task, but this is the kind of problem automotive engineer’s deal with every day. The work of an automotive engineer breaks down into three categories: Design Designing new products and improving existing ones Research and Development Finding solutions to engineering problems Production Planning and designing new production processes
What does an automotive engineer really do?
They study One of the first steps in becoming an automotive engineer is going to university. Most automotive engineers start out by studying Mechanical Engineering, but increasingly more specific Automotive Engineering degrees are becoming available. Don’t just look to apply in your home country - the automotive industry is truly international, and studying abroad might be your way into this popular job market. For a growing list of courses available worldwide If you’re not sure that university is right for you, you could also explore apprenticeships as your route into automotive. Before you get to university, the most important subject area to be focussing on is STEM (Science, Technology, Engineering, and Maths).Once at University taking an internship can be a really important step on your route into automotive. Having the right internship on your CV is an announcement to the industry how passionate and dedicated you are to your career.
They think big The automotive industry represents some of the largest companies in the world, from car manufacturers to fuel specialists. As an engineer you can expect to work for one of these industrial titans.
They work in a global profession Automotive engineers and automotive companies exist all over the world, based in completely different
cultures and speaking totally different languages. The automotive engineer needs to know how to communicate on a global level and have a horizon broader than just their own culture.
They do more Automotive engineers are forward thinking people. They are dynamic, visionary, and are employed based on their ability to think outside the box. One way to expand your horizons, engage your passion, and to start thinking like an automotive engineer is to get involved with extracurricular activities and competitions. Additional skills and activities The variety of skills and tasks automotive engineers get involved with are almost endless here are some examples to get you started. ● Developing new test procedures, using both conventional and innovative methods ● Bringing new products to market and being involved in problem-solving and project management ● Devising and organising tests, to answer questions from clients, consumers and other engineers involved in vehicle development ● Anticipating vehicle or component behaviour in different conditions with computer modelling software ● Analysing and interpreting technical data into reports or presentations and answering any queries about the results ● Building an individual specialism within a larger team and working independently ● Contributing to regular team meetings to update colleagues on progress, problems and new developments ● Managing all details of projects, including projected costs ● Recognising the benefits of engineering developments to related departments in order to market projects and secure internal funding ● Negotiating costs of development and engineering work with commercial departments ● Monitoring any related systems or engineering issues associated with the component and final product ● Supervising technical staff, engineers or designers (dependent upon specific role) ● Operating in cross-functional or internationally-based teams to design experiments in order to test the validity and competence of new technology. Employment Opportunities: Automobile engineering is a huge industry. There is great number of employment opportunities in the
Private national and multinational automobile companies
Private transport companies
Self-employment by setting up automobile garage or maintenance workshops
Scope: There are plenty of employment opportunities for the qualified people and they can select a career in automobile industry, which leads to bright future. Who This Career is For? A career as an automobile engineer is for people who are driven and passionate about cars. They must have considerable understanding and interest in mechanics, electronics, and mathematics as these are vital skills required for this career path. Automobile engineers must be organized individuals who are able to work in a methodical manner. People in this career are required to communicate with other professionals on a regular basis, both from within the field and outside it. Hence, this career is only for those with fluent communication skills. While automobile engineers must be innovative, eager workers, they must not get carried away. Want to know more about it? Automobile engineers hold a wide variety of responsibilities. Their primary purpose is to maximize the feasibility and design of automobiles keeping costs to an absolute minimum. A typical professional in this field spends a lot of time on researching and designing both systems and machines for automobiles. The designs are initially done in the form of drawings and blueprints. Automobile engineers then apply physical and mathematical principles to these plans to make sure they are viable. The planning is done after considerable research, and then altered again after linking the plans to the available research. Once the planning process is done, the designing begins. Automobile engineers are responsible for transforming their plans and research into a viable end product. They must oversee the entire process of manufacturing, with meticulous attention to detail. After the end product is manufactured, the most important part of an automobile engineer’s job begins. Testing is a rigorous process that must be done with utmost care. This procedure generally entails focusing on each and every component of an automobile to ensure it is able to function in every imaginable condition in a safe and secure manner. Automobile engineers generally tend to specialize in a particular area. The most common areas of specialization include exhaust systems, engines and structural designs. No matter what an engineer decides to specialize in, he or she is almost always required to work on all three aspects of the automobile engineering process; research, designing as well as testing. There is also often a financial side to this job, which involves preparing costs of buying materials and
producing systems. It is also important to realize the legal aspects of this job. Automobile engineers must be up to date with all safety regulations, so that they do not violate legislation related to automobile engineering procedure. Automobile engineers generally know they want to get into the field at a fairly young age, so they are generally people who studied natural sciences and mathematics in high school. This gives them the edge to get a degree in engineering, which is an essential prerequisite to become an automobile engineer. Additionally, while it is not necessary, a master’s degree in a field such as auto motives or automotive engineering gives prospective automobile engineers a distinct advantage. How is Life? Automobile engineers work varying hours per week depending on the amount of work they have assigned during a particular week. They may work anywhere between a 40 hour week and a 55 hour week, but may even be required to work overtime if there are some outstanding deadlines or emergencies. Automobile engineers spend a lot of time in front of a computer on their desks. When they are not doing research in their office, they are at plants monitoring the manufacturing of the automobiles they planned and their testing. This may involve spending lengthy periods of time in noisy, dirty factory environments. What Perks come along with this career? Automobile engineering is a career path that no one will deny is unimportant. There are millions of vehicles on roads in every corner of the world, and automobile engineers are the people responsible for that. They feel an immense amount of satisfaction when they see a machine as intricate as a modern automobile completed when they are the ones who contributed towards its design. Automobile engineers earn a considerable salary, more so than many other types of engineers. They have a fair amount of job security as they begin gaining experience. People in the field are generally passionate about automobiles, and so have the added advantage of working with something they truly appreciate. Which Downsides are there in this career? The job often requires automobile engineers to work under the immense pressure of tight deadlines. Moreover, they have the lives of millions of people in their hands as they do their work. The slightest mistakes in planning, designing or testing could be catastrophic. Automobile engineers often have to deal with noisy factory conditions for extended periods of time. They have to pay scrupulous attention to detail at every aspect of their job, which can often get monotonous. How is Competition? While the automobile industry has been on a decline in the past five years in most areas of the world, the number of people who opt for this career is quite low because of the high level of training and specialization required to become successful. As a result, there is a fair amount of competition in the field, especially for the most lucrative jobs. The number of jobs in the field is likely to increase at a slow pace in the next few years. Locations where this career is good? In the USA, the Midwest is the best place to be an automobile engineer because of the concentration of automobile manufacturing firms in the region. In Europe, Germany is the leading automobile
manufacturer. There is a large demand for automobile engineers in Japan, South Korea, China and India.
Anti-Lock Braking System (ABS) It is a safety system in automobiles. It prevents the wheels from locking while braking. The purpose of this is to allow the driver to maintain steering control under heavy braking and, in some situations, to shorten braking distances (by allowing the driver to hit the brake fully without skidding or loss of control).
How Do Wheels Lock? During braking, wheels lock if the brake force applied is more than the friction between the road and tyre. This often happens in a panic braking situation, especially on a slippery road. When the front wheels lock, the vehicle slides in direction of motion. When the rear wheels locks, the vehicle swings around. It is impossible to steer around an obstacle with wheels locked. Locked wheels can thus result in accident. Skidding also reduce tyre life.
What Does ABS Do? The system detects when the wheel are about to lock and momentarily release the pressure on locking wheel. The brakes are reapplied as soon as the wheels have recovered. A toothed wheel (pole wheel) is fitted to the rotating wheel hub. A magnetic sensor mounted on each wheel in close in close proximity to the teeth, generates electrical pulses when the pole wheel rotates. The rate at which the pulses are generated (frequency) is a measure of wheel speed. This signal is read by electronic control unit (ECU). When a wheel is lock, the ECU sends an electrical signal to the modulator valve solenoid, which release pressure from the brake chamber. When the wheel recovers sufficiently, the brake pressure is reapplied again by the switch off signal to the modulator valve. The modulator valve has an addition ‘hold’ state which maintains pressure. In break in the chamber, thus optimizing the braking process. The cycling of modulator valve (5 to 6 times per second) is continued till the vehicle comes to a controlled stop. With ABS, the vehicle remains completely stable even when the driver continues to press the brake pedal during braking, thus avoiding accidents.
Components: The anti-lock braking system consists of following components.
Wheel Speed Sensor The wheel speed sensor consists of a permanent magnet and coil assembly. It generates electrical pulses when the pole wheel rotates. The rate at which the pulses are generated is a measure of wheel speed. The voltage induced increases with the speed of rotation of the wheel and reduces with increasing gap between the pole wheel and the sensor. Pole Wheel Pole Wheel is a toothed wheel made of ferrous material. It normally has teeth on the face. In some cases where it is not possible to install the sensor parallel to the axle, the pole wheels are designed with teeth on periphery. The pole wheel fitted on standard 9-20, 10-20 tires has normally 100 evenly spaced teeth. 80 evenly spaced teeth pole wheels are used for the vehicles having the tyre diameter less than 9mm. Sensor Extension Cable The sensor extension cable is a two core cable which connects the wheel speed sensor to the Electronic Control Unit. The inner core sheathing is of EPDM rubber and the outer sheathing is polyurethane which provide abrasion resistance to the cable. The cable has a module plug with two pins is connected to the control assembly. The cable has two cores-brown and black in colour. Electronic Control Unit The ECU is the core component of the ABS system. Wheel speed sensor signal are the input to the Electronic Control Unit. The ECU computers wheel speeds, wheel deceleration and acceleration. If any wheel tends to lock, the ECU actuates the corresponding Modulator valve to prevent wheel lock. The ECU is normally mounted in driver's cabin. The ECU consists of 7 major circuits, > Input circuit > Master circuit > Slave circuit > Driver circuit > Feedback circuit > Power supply circuit > Fail safe circuit The functions of ECU, > It receives wheel speed signal from the sensor. The wheel speed signals are processed and appropriate output signals are sent to the modular valves in the event of a wheel lock. > It continuously monitors the status and operation of ABS components and wiring. > It alerts the driver in the event of occurrence of any electrical fault in the ABS system by actuating a warning lamp. > It disconnects the exhaust brakes during ABS operations. > It enables the service technician to read the faults in the system either through a diagnostic controller or a blink code lamp. Modulator Valve Cable The Modulator valve cable has thee cores. There are two solenoid interface lines and a common ground line. The inner core sheathing is of EPDM type and the outer sheathing is polyurethane which provide abrasion resistance to the cable. The cable has a three pin moulded socket is connected to the modulator valve solenoid at one and an interlock connector with locking feature at the other end. The cores are brown, blue and green. Modulator Valve
ABS Modulator valve regulate the air pressure to the brake chamber during ABS action. During normal braking it allows air to flow directly from inlet to delivery. Modulator valve cannot automatically apply the brakes, or increase the brake application pressure above the level applied by the driver through the dual brake valve. There is an inlet port, Delivery port and Exhaust passage. > The inlet port is connected to the delivery of quick release valve or relay valve. > The delivery port is connected to the brake chamber. > The exhaust passage vents air from the brake chambers. The modulator valve has two solenoids. By energizing the solenoids, the modular valve can be switched to any of the following modes. > Pressure > Pressure hold > Pressure release Quick Release Valve Quick release valve are fitted in air braking system to release the air from the brake chamber quickly after release of brake pedal. This prevents delay in brake release due to long piping runs or multiples of brake chamber being exhausted through the brake valve. Relay Valve Relay valve provides a means of admitting and releasing air to and from brake chamber quickly, in accordance with the signal pressure from the delivery of the dual brake valve. Air from the reservoir passes through the valve into the brake chamber. The pressure applied to the brake is equal to the signal pressure from the dual brake valve. When the brake pedal is released the signal pressure is released. The pressure in the brake chamber is released directly through the exhaust port of the relay valve. Warning Lamp Vehicle are fitted with an ABS warning lamp. It is a LED indicator lamp amber in colour and lights up when the system has detected any electrical fault. ABS warning lamp is located on the instrument panel in form of a driver. Blink Code Lamp This lamp is green in colour and is used to indicate the stored faults in the system to the service technician on operating a blink code switch. The nature of fault in the system can be diagnosed by the number of flashes. Off Highway Switch This is an optional switch in front of the driver which can be switched ON when the vehicle is operating off highway. In this mode, ABS control will; allow higher wheel slip to achieve shorter stopping distance than with normal ABS control. Blink Code Switch A momentary switch that grounds the ABS Indicator Lamp output is used to place the ECU into the diagnostic blink code mode and is typically located on the vehicle's dash panel.
ADAPTIVE CRUISE CONTROL Adaptive Cruise Control (ACC) is an automotive feature that allows a vehicle’s cruise control system to adapt the vehicle speed to the environment. A radar system attached to the front of the vehicle is used to detect whether slower moving vehicles are in the ACC vehicle path. If a slower moving vehicle is detected, the ACC system will slow the vehicle down and control the clearance, or time gap, between the ACC vehicle and the forward vehicle. If the system detects that the forward vehicle is no longer in the ACC vehicle path, the ACC system will accelerate the back to its set cruise control speed. This operation allows the ACC vehicle to autonomously slow down and speed up is controlled is via engine throttle control and limited brake operation. HOW DOES IT WORK? The radar headway sensor sends information to a digital signal processor, which in turn translates the speed and distance information for a longitudinal controller. The result? If the lead vehicle slows down, or if another object is detected, the system sends a signal to the engine or braking system to decelerate. Then, when the road is clear, the system will re-accelerate the vehicle back to the set speed. The adaptive cruise control (ACC) system depends on two infrared sensors to detect cars up ahead. Each sensor has an emitter, which sends out a beam of infrared light energy, and a receiver, which captures light reflected back from the vehicle ahead. The first sensor, called the sweep long-range sensor, uses a narrow infrared beam to detect objects six to 50 yards away. At its widest point, the beam covers no more than the width of one highway lane, so this sensor detects only vehicles directly ahead and doesn't detect cars in other lanes. Even so, it has to deal with some tricky situations, like keeping track of the right target when the car goes around a curve. To deal with that problem, the system has a solid-state gyro that instantaneously transmits curve-radius information to the sweep sensor, which steers its beam accordingly. Another challenge arises when a car suddenly cuts in front of an ACC-
equipped car. Because the sweep sensor's beam is so narrow, it doesn't "see" the other car until it's smack in the middle of the lane. That's where the other sensor, called the cut-in sensor, comes in. It has two wide beams that "look" into adjacent lanes, up to a distance of 30 yards ahead. And because it ignores anything that isn't moving at least 30 percent as fast as the car in which it is mounted, highway signs and parked cars on the side of the road don't confuse it. Information from the sensors goes to the Vehicle Application Controller (VAC), the system's computing and communication centre. The VAC reads the settings the driver has selected and figures out such things as how fast the car should go to maintain the proper distance from cars ahead and when the car should release the throttle or downshift to slow down. Then it communicates that information to devices that control the engine and the transmission. There are several inputs: System on/off: If on, denotes that the cruise-control system should maintain the car speed. Engine on/off: If on, denotes that the car engine is turned on; the cruisecontrol system is only active if the engine is on. Pulses from wheel: A pulse is sent for every revolution of the wheel. Accelerator: Indication of how far the accelerator has been pressed. Brake: On when the brake is pressed; the cruise-control system temporarily reverts to manual control if the brake is pressed. Increase/Decrease Speed: Increase or decrease the maintained speed; only applicable if the cruise-control system is on. Resume: Resume the last maintained speed; only applicable if the cruisecontrol system is on. Clock: Timing pulse every millisecond. There is one output from the system: Throttle: Digital value for the engineer throttle setting. ADAPTIVE CRUISE CONTROL FEATURES - Maintains a safe, comfortable distance between vehicles without driver interventions - Maintains a consistent performance in poor visibility conditions. - Maintains a continuous performance during road turns and elevation changes
- Alerts drivers by way of automatic braking. PHYSICAL LAYOUT The ACC system consists of a series of interconnecting components and systems. The method of communication between the different modules is via a serial communication network known as the Controller Area Network (CAN). ACC Module – The primary function of the ACC module is to process the radar information and determine if a forward vehicle is present. When the ACC system is in 'time gap control', it sends information to the Engine Control and Brake Control modules to control the clearance between the ACC Vehicle and the Target Vehicle. Engine Control Module – The primary function of the Engine Control Module is to receive information from the ACC module and Instrument Cluster and control the vehicle's speed based on this information. The Engine Control Module controls vehicle speed by controlling the engine's throttle. Brake Control Module – The primary function of the Brake Control Module is to determine vehicle speed via each wheel and to decelerate the vehicle by applying the brakes when requested by the ACC Module. The braking system is hydraulic with electronic enhancement, such as an ABS brake system, and is not full authority brake by wire. Instrument Cluster – The primary function of the Instrument Cluster is to process the Cruise Switches and send their information to the ACC and Engine Control Modules. The Instrument Cluster also displays text messages and tell-tales for the driver so that the driver has information regarding the state of the ACC system. CAN – The Controller Area Network (CAN) is an automotive standard network that utilizes a 2 wire bus to transmit and receive data. Each node on the network has the capability to transmit 0 to 8 bytes of data in a message frame. A message frame consists of a message header, followed by 0 to 8 data bytes, and then a checksum. The message header is a unique identifier that determines the message priority. Any node on the network can transmit data if the bus is free. If multiple nodes attempt to transmit at the same time, an arbitration scheme is used to determine which node will control the bus. The message with the highest priority, as defined in its header, will win the arbitration and its message will be transmitted. The losing message will retry to send its message as soon as it detects a bus free state.
Cruise Switches – The Cruise Switches are mounted on the steering wheel and have several buttons which allow the driver to command operation of the ACC system. The switches include: 'On': place system in the 'ACC standby' state 'Off'': cancel ACC operation and place system in the 'ACC off' state 'Set +': activate ACC and establish set speed or accelerate 'Coast': decelerate 'Resume': resume to set speed 'Time Gap +': increase gap 'Time gap –': decrease gap ADVANTAGES 1. The driver is relieved from the task of careful acceleration, deceleration and braking in congested traffics. 2. A highly responsive traffic system that adjusts itself to avoid accidents can be developed. 3. Since the braking and acceleration are done in a systematic way, the fuel efficiency of the vehicle is increased. DISADVANTAGES 1. A cheap version is not yet realized. 2. A high market penetration is required if a society of intelligent vehicles is to be formed. 3. Encourages the driver to become careless. It can lead to severe accidents if the system is malfunctioning. 4. The ACC systems yet evolved enable vehicles to cooperate with the other vehicles and hence do not respond directly to the traffic signals.
CRDI (Common Rail Direct Injection) CRDi stands for Common Rail Direct Injection meaning, direct injection of the fuel into the cylinders of a diesel engine via a single, common line, called the common rail which is connected to all the fuel injectors. Whereas ordinary diesel direct fuel-injection systems have to build up pressure anew for each and every injection cycle, the new common rail (line) engines maintain constant pressure regardless of the injection sequence. This pressure then remains permanently available throughout the fuel line. The engine's electronic timing regulates injection pressure according to engine speed and load. The electronic control unit (ECU) modifies injection pressure precisely and as needed, based on data obtained from sensors on the cam and crankshafts. In other words, compression and injection occur independently of each other. This technique allows fuel to be injected as needed, saving fuel and lowering emissions. More accurately measured and timed mixture spray in the combustion chamber significantly reducing unburned fuel gives CRDi the potential to meet future emission guidelines such as Euro V. CRDi engines are now being used in almost all Mercedes-Benz, Toyota, Hyundai, Ford and many other diesel automobiles.
History The common rail system prototype was developed in the late 1960s by Robert Huber of Switzerland and the technology further developed by Dr. Marco Ganser at the Swiss Federal Institute of Technology in Zurich, later of Ganser-Hydromag AG (est.1995) in Oberägeri. The first successful usage in a production vehicle began in Japan by the mid-1990s. Modern common rail systems, whilst working on the same principle, are governed by an engine control unit (ECU) which opens each injector electronically rather than mechanically. This was extensively prototyped in the 1990s with collaboration between Magnetic Marelli, Centro Ricerche Fiat and Elasis. The first passenger car that used the common rail system was the 1997 model Alfa Romeo 156 2.4 JTD, and later on that same year Mercedes-Benz C 220 CDI. Common rail engines have been used in marine and locomotive applications for some time. The Cooper-Bessemer GN-8 (circa 1942) is an example of a hydraulically operated common rail diesel engine, also known as a modified common rail. Vickers used common rail systems in submarine engines circa 1916. Early engines had a pair of timing cams, one for ahead running and one for astern. Later engines had two injectors per cylinder, and the final series of constant-pressure turbocharged engines were fitted with four injectors per cylinder. This system was used for the injection of both diesel oil and heavy fuel oil (600cSt heated to a temperature of approximately 130 °C). The common rail system is suitable for all types of road cars with diesel engines, ranging from city cars such as the Fiat Nuova Panda to executive cars such as the Audi A6.
Operating Principle Solenoid or piezoelectric valves make possible fine electronic control over the fuel injection time and quantity, and the higher pressure that the common rail technology makes available provides better fuel atomisation. In order to lower engine noise, the engine's electronic control unit can inject a small amount of diesel just before the main injection event ("pilot" injection), thus reducing its explosiveness and vibration, as well as optimizing injection timing and quantity for variations in fuel quality, cold
starting and so on. Some advanced common rail fuel systems perform as many as five injections per stroke. Common rail engines require very short (< 10 second) or no heating-up time at all , dependent on ambient temperature, and produce lower engine noise and emissions than older systems. Diesel engines have historically used various forms of fuel injection. Two common types include the unit injection system and the distributor/inline pump systems (See diesel engine and unit injector for more information). While these older systems provided accurate fuel quantity and injection timing control, they were limited by several factors: • They were cam driven, and injection pressure was proportional to engine speed. This typically meant that the highest injection pressure could only be achieved at the highest engine speed and the maximum achievable injection pressure decreased as engine speed decreased. This relationship is true with all pumps, even those used on common rail systems; with the unit or distributor systems, however, the injection pressure is tied to the instantaneous pressure of a single pumping event with no accumulator, and thus the relationship is more prominent and troublesome. • They were limited in the number and timing of injection events that could be commanded during a single combustion event. While multiple injection events are possible with these older systems, it is much more difficult and costly to achieve. • For the typical distributor/inline system, the start of injection occurred at a pre-determined pressure (often referred to as: pop pressure) and ended at a pre-determined pressure. This characteristic resulted from "dummy" injectors in the cylinder head which opened and closed at pressures determined by the spring preload applied to the plunger in the injector. Once the pressure in the injector reached a predetermined level, the plunger would lift and injection would start.
In common rail systems, a high-pressure pump stores a reservoir of fuel at high pressure — up to and above 2,000 bars (psi). The term "common rail" refers to the fact that all of the fuel injectors are supplied by a common fuel rail which is nothing more than a pressure accumulator where the fuel is stored at high pressure. This accumulator supplies multiple fuel injectors with high-pressure fuel. This simplifies the purpose of the high-pressure pump in that it only has to maintain a commanded pressure at a target (either mechanically or electronically controlled). The fuel injectors are typically ECUcontrolled. When the fuel injectors are electrically activated, a hydraulic valve (consisting of a nozzle
and plunger) is mechanically or hydraulically opened and fuel is sprayed into the cylinders at the desired pressure. Since the fuel pressure energy is stored remotely and the injectors are electrically actuated, the injection pressure at the start and end of injection is very near the pressure in the accumulator (rail), thus producing a square injection rate. If the accumulator, pump and plumbing are sized properly, the injection pressure and rate will be the same for each of the multiple injection events. Advantages CRDi engines are advantageous in many ways. Cars fitted with this new engine technology are believed to deliver 25% more power and torque than the normal direct injection engine. It also offers superior pick up, lower levels of noise and vibration, higher mileage, lower emissions, lower fuel consumption, and improved performance. Disadvantages Like all good things have a negative side, this engine also have few disadvantages. The key disadvantage of the CRDi engine is that it is costly than the conventional engine. The list also includes high degree of engine maintenance and costly spare parts. Also this technology can’t be employed to ordinary engines.
Applications The most common applications of common rail engines are marine and locomotive applications. Also, in the present day they are widely used in a variety of car models ranging from city cars to premium executive cars. However, most of the car manufacturers have started using the new engine concept and are appreciating the long term benefits of the same. The technology that has revolutionized the diesel engine market is now gaining prominence in the global car industry. CRDi technology revolutionized diesel engines and also petrol engines (by introduction of GDI technology). By introduction of CRDi a lot of advantages are obtained, some of them are, more power is developed, increased fuel efficiency, reduced noise, more stability, pollutants are reduced, particulates of exhaust are reduced, exhaust gas recirculation is enhanced, precise injection timing is obtained, pilot and post injection increase the combustion quality, more pulverization of fuel is obtained, very high injection pressure can be achieved, the powerful microcomputer make the whole system more perfect, it doubles the torque at lower engine speeds. The main disadvantage is that this technology increase the cost of the engine. Also this technology can’t be employed to ordinary engines.
DTSI (Digital Twin Spark Ignition System) It is very interesting to know about complete combustion in automobile engineering, because in actual practice, perfect combustion is not at all possible due to various losses in the combustion chamber as well as design of the internal combustion engine. Moreover the process of burning of the fuel is also not instantaneous. However an alternate solution to it is by making the combustion of fuel as fast as possible. This can be done by using two spark plugs which spark alternatively at a certain time interval so as increase the diameter of the flame & burn the fuel instantaneously. This system is called DTSI (Digital Twin Spark Ignition system). In this system, due to twin sparks, combustion will be complete. This paper represents the working of digital twin spark ignition system, how twin sparks are produced at 20,000 Volts, their timings, efficiency, advantages & disadvantages, diameter of the flame, how complete combustion is possible & how to decrease smoke & exhausts from the exhaust pipe of the bike using Twin Spark System.
How Does It Works? Digital Twin Spark ignition engine has two Spark plugs located at opposite ends of the combustion chamber and hence fast and efficient combustion is obtained. The benefits of this efficient combustion process can be felt in terms of better fuel efficiency and lower emissions. The ignition system on the Twin spark is a digital system with static spark advance and no moving parts subject to wear. It is mapped by the integrated digital electronic control box which also handles fuel injection and valve timing. It features two plugs per cylinder.
This innovative solution, also entailing a special configuration of the hemispherical combustion chambers and piston heads, ensures a fast, wide flame front when the air-fuel mixture is ignited, and therefore less ignition advance, enabling, moreover, relatively lean mixtures to be used. This technology provides a combination of the light weight and twice the power offered by two-stroke engines with a significant power boost, i.e. a considerable "power-to-weight ratio" compared to quite a few four-stroke engines. Moreover, such a system can adjust idling speed & even cuts off fuel feed when the accelerator pedal is released, and meters the enrichment of the air-fuel mixture for cold starting and accelerating purposes; if necessary, it also prevents the upper rev limit from being exceeded. At low revs, the over boost is mostly used when overtaking, and this is why it cuts out automatically. At higher speeds the over boost will enhance full power delivery and will stay on as long as the driver exercises maximum pressure on the accelerator.
Main characteristics • Digital electronic ignition with two plugs per cylinder and two ignition distributors. • Twin overhead cams with camshaft timing variation. • Injection fuel feed with integrated electronic twin spark ignition. • A high specific power. • Compact design and Superior balance.
Construction Digital twin spark ignition technology powered engine has two spark plugs. It is located at opposite sides of combustion chamber. This DTS-I technology will have greater combustion rate because of twin spark plug located around it. The engine combust fuel at double rate than normal. This enhances both engine life and fuel efficiency. It is mapped by the digital electronic control box which also handles fuel ignition and valve timing. A microprocessor continuously senses speed and load of the engine and respond by altering the ignition timing thereby optimizing power and fuel economy. Advantages • Less vibrations and noise • Long life of the engine parts such as piston rings and valve stem. • Decrease in the specific fuel consumption • No over heating • Increase the Thermal Efficiency of the Engine & even bear high loads on it. • Better starting of engine even in winter season & cold climatic conditions or at very low temperatures because of increased Compression ratio. • Because of twin Sparks the diameter of the flame increases rapidly that would result in instantaneous burning of fuels. Thus force exerted on the piston would increase leading to better work output. Disadvantages • There is high NOx emission • If one spark plug get damaged then we have to replace both • The cost is relatively more
Electromagnetic Brake Electromagnetic brakes are the brakes working on the electric power & magnetic power. They works on the principle of electromagnetism. These are totally friction less. Due to this they are more durable & have longer life span. Less maintenance is there. These brakes are an excellent replacement on the convectional brakes due to their many advantages. The reason for implementing this brake in automobiles is to reduce wear in brakes as it friction less. Therefore there will also be no heat loss. It can be used in heavy vehicles as well as in light vehicles. The electromagnetic brakes are much effective than conventional brakes & the time taken for application of brakes are also smaller. There is very few need of lubrication. Electromagnetic brakes gives such better performance with less cost which is today’s need. There are also many more advantages of Electromagnetic brakes. That’s why electromagnetic brakes are an excellent replacement on conventional brakes. Electromagnetic brakes are of today’s automobiles. An electromagnetic braking system for automobiles like cars, an effective braking system. And, by using this electromagnetic brakes, we can increase the life of the braking unit. The working principle of this system is that when the magnetic flux passes through and perpendicular to the rotating wheel the eddy current flows opposite to the rotating wheel/rotor direction. This eddy current trying to stop the rotating wheel or rotor. This results in the rotating wheel or rotor comes to rest/ neutral. HISTORY It is found that electromagnetic brakes can develop a negative power which represents nearly twice the maximum power output of a typical engine, and at least three times the braking power of an exhaust brake. (Reverdin 1994). These performance of electromagnetic brakes make them much more competitive candidate for alternative retardation equipment’s compared with other retarders. By using by using the electromagnetic brakes are supplementary retardation equipment, the friction brakes can be used less frequently, and therefore practically never reach high temperatures. The brake linings would last considerably longer before requiring maintenance and the potentially “brake fade” problem could be avoided. In research conducted by a truck manufacturer, it was proved that the electromagnetic brake assumed 80% of the duty which would otherwise have been demanded of the regular service brake (Reverdin 1974). Furthermore the electromagnetic brakes prevents the danger that can arise from the prolonged use of brake beyond their capability to dissipate heat. This is most likely to occur while a vehicle descending a long gradient at high speed. In A study with a vehicle with 5 axles and weighing 40 tons powered by a powered by an engine of 310 b.h.p travelling down a gradient of 6% at a steady speed between 35 and 40 m.h.p, it can be calculated that the braking power necessary to maintain this speed at the order of 450 hp. The brakes, therefore, would have to absorb 300 hp, meaning that each brake in the 5 axles must absorb 30 hp, that a friction brake can normally absorb with self-destruction. The magnetic brake is well suited to such conditions since it will independently absorb more than 300 hp (Reverdin 1974). It therefore can exceed the requirements of continuous uninterrupted braking, leaving the friction brakes cool and ready for emergency braking in total safety. The installation of an electromagnetic brake is not very difficulty if there is enough space between the gearbox and the rear axle. If did not need a subsidiary cooling system. It relay on the efficiency of
engine components for its use, so do exhaust and hydrokinetic brakes. The exhaust brake is an on/off device and hydrokinetic brakes have very complex control system. The electromagnetic brake control system is an electric switching system which gives it superior controllability. CONSTRUCTION The construction of the electromagnetic braking system is very simple. The parts needed for the construction are electromagnetic, rheostat, sensors and magnetic insulator. A cylindrical ring shaped electromagnet with winding is placed parallel to rotating wheel disc/ rotor. The electro magnet is fixed, like as stator and coils are wounded along the electromagnet. These coils are connected with electrical circuit containing one rheostat which is connected with brake pedal. And the rheostat is used to control the current flowing is used to control the magnetic flux. And also it is used to prevent the magnetization of other parts like axle and it act as a support frame for the electromagnet. The sensor used to indicate the disconnection in the whole circuit. If there is any error it gives an alert, so we can avoid accident. WORKING PRINCIPLE The working principle of the electric retarder is based on the electric retarder is based on the creation of eddy currents within a metal discs rotating between two electro magnets, which set up a force opposing the rotation of the discs. If the electromagnet is not energized, the rotation of the disc free and accelerates uniformly under the action of the weight to which its shaft is connected. When the electromagnet is energized, the rotation of the disc is retarded and the energy absorbed appears as heating of the discs. If the current exciting the electromagnet is varied by a rheostat, the raking force varies indirect proportion of the value of the current. The development of this invention began when the French company Thelma, associated with Raoul Sarasin, developed and marketed several generations of electric brake based on the functioning principle described above. A typical retarder consists of stator and rotor. The stator hold 16 induction coils, energized separately in group of four. The coils are made up of varnished aluminium wire mounted in epoxy resin. The stator assembly is supported resiliently through anti-vibration mountings on the chasisframe of the vehicle. The rotor is made up of two discs, which provide the braking force when subjected to the electromagnetic influence when the coil are excited. Carefully design of the fins, which are integral to the disc, permit independent cooling of the arrangement. ADVANTAGES 1. Electromagnetic brakes can develop a negative power which represents nearly twice the maximum power output of a typical engine. 2. Electromagnetic brakes work in a relatively cool condition and satisfy all The energy requirements of braking at high speeds, completely without the use of friction. Due to its specific installation location (transmission line of rigid vehicles), electromagnetic brakes have better heat dissipation capability to avoid problems that friction brakes face times the braking power of an exhaust brake. 3. Electromagnetic brakes have been used as supplementary retardation equipment in addition to the regular friction brakes on heavy vehicles. 4. Electromagnetic brakes has great braking efficiency and has the potential to regain energy lost in braking. 5. Its component cost is less. DISADVANTAGES
1. The installation of an electromagnetic brake is very difficult if there is Not enough space between the gearbox and the rear axle. 2. Need a separate compressor. 3. Maintenance of the equipment components such as hoses, valves has to done periodically. 4. It cannot use grease or oil. APPLICATIONS 1. Used in crane control system. 2. Used in winch controlling. 3. Used in lift controlling. 4. Used in automatic purpose. The lots of new technologies are arriving in world. They create a lot of effect. Most industries got their new faces due to this arrival of technologies. Automobile industry is also one of them. There is a boom in World’s automobile industry. So lots of research is also going here. As an important part of automobile, there are also innovations in brakes. Electromagnetic brake is one of them. A electromagnetic braking for automobiles like cars, an effective braking system. And, by using this electromagnetic brakes, we can increase the life of the braking unit. The working principle of this system is that when the electromagnetic flux passes through and perpendicular to the rotating wheel the eddy current is induced in the rotating wheel or rotor. This eddy current flows opposite to the rotating wheel. This eddy current tries to stop the rotating wheel or rotor. This results in the rotating wheel or rotor comes to rest.
SPARK PLUG Spark plug is a device used to produce electric spark to ignite the compressed air fuel mixture inside the cylinder. The spark plug is screwed in the top of the cylinder so that it electrode project in the combustion chamber. A spark plug consist of mainly three parts: 1. Center electrode or insulated electrode. 2. Ground electrode or outer electrode. 3. Insulation separating the two electrodes.
The upper end of the centre electrode is connected to the spark plug terminal, where cable from the ignition coil is connected. It is surrounded by insulator. The lower half portion of the insulator is fastened with a metal shell. The lower portion of the shell has a short electrode attached to one side and bent in towards the centre electrode, so that there is a gap between the two electrodes. The two electrodes are thus separated by the insulator. The sealing gaskets are provided between the insulator and the shell to prevent the escape of gas under various temperature and pressure conditions. The lower part of the shell has screw threads and the upper part is made in hexagonal shape like a nut, so that the spark plug may be screwed in or unscrewed from the cylinder head. Cleaning the Spark Plug Due to the combustion of fuel in the cylinder, carbon particles deposit on and around the electrode which not only reduce the plug gap but also prevent the spark to occur. If the spark is still occurring, it is too weak that it cannot ignite the fuel. Hence the spark plug is to be cleaned. Carbon particles can deposit due to any reason like, nature of fuel, mixture strength, lubricating oil, etc. The spark plug can be cleaned by a sand paper.
TURBOCHARGER A turbocharger or turbo is a forced induction device used to allow more power to be produced for an engine of a given size. A turbocharged engine can be more powerful and efficient than a naturally aspirated engine because the turbine forces more intake air, proportionately more fuel, into the combustion chamber than if atmospheric pressure alone is used. Turbo are commonly used on truck, car, train, and construction equipment engines. Turbo are popularly used with Otto cycle and Diesel cycle internal combustion engines.
There are two ways of increasing the power of an engine. One of them would be to make the fuel-air mixture richer by adding more fuel. This will increase the power but at the cost of fuel efficiency and increase in pollution levels… prohibitive! The other would be to somehow increase the volume of air entering into the cylinder and increasing the fuel intake proportionately, increasing power and fuel efficiency without hurting the environment or efficiency. This is exactly what Turbochargers do, increasing the volumetric efficiency of an engine. In a naturally aspirated engine, the downward stroke of the piston creates an area of low pressure in order to draw more air into the cylinder through the intake valves. Now because of the pressure in the cylinder cannot go below 0 (zero) psi (vacuum) and relatively constant atmospheric pressure (about 15 psi) there will be a limit to the pressure difference across the intake valves and hence the amount of air entering the combustion chamber or the cylinder. The ability to fill the cylinder with air is its volumetric efficiency. Now if we can increase the pressure difference across the intake valves by some way we can make more air enter into the cylinder and hence increasing the volumetric efficiency of the engine. It increases the pressure at the point where air is entering the cylinder, thereby increasing the pressure difference across the intake valves and thus more air enters into the combustion chamber. The additional air makes it possible to add more fuel, increasing the power and torque output of the engine, particularly at higher engine speeds. Turbochargers were originally known as Turbo superchargers when all forced induction devices were classified as superchargers; nowadays the term "supercharger" is usually applied to only mechanicallydriven forced induction devices. The key difference between a turbocharger and a conventional supercharger is that the latter is mechanically driven from the engine, often from a belt connected to the crankshaft, whereas a turbocharger is driven by the engine's exhaust gas turbine. Compared to a mechanically-driven supercharger, turbochargers tend to be more efficient but less responsive. HISTORICAL PERSPECTIVE The turbocharger was invented by Swiss engineer Alfred Büchi. His patent for a turbocharger was applied for use in 1905. Diesel ships and locomotives with turbochargers began appearing in the 1920s. AVIATION: During the First World War French engineer Auguste Rateau fitted turbochargers to Renault engines powering various French fighters with some success. In1918, General Electric engineer Sanford Moss attached a turbo to a V12 Liberty aircraft engine. The engine was tested at Pikes Peak in Colorado at 4,300 m to demonstrate that it could eliminate the power losses usually experienced in internal combustion engines as a result of reduced air pressure and density at high altitude. Turbochargers were first used in production aircraft engines in the 1920s, although they were less common than engine-driven centrifugal superchargers. The primary purpose behind most aircraft-based applications was to increase the altitude at which the airplane could fly, by compensating for the lower atmospheric pressure present at high altitude. PRODUCTION AUTOMOBILES: The first turbocharged diesel truck was produced by Schweizer Maschinenfabrik Saurer(Swiss Machine Works Saurer) in 1938 .The first production turbocharged automobile engines came from General Motors in 1962. At the Paris auto show in1974, during the height of the oil crisis, Porsche introduced the 911 Turbo – the world’s first production sports car with an exhaust turbocharger and pressure regulator. This was made possible by the introduction of a waste gate to direct excess exhaust gasses away from the exhaust turbine. The world's first production turbo diesel automobiles were the Garrettturbocharged Mercedes 300SD and the Peugeot 604, both introduced in 1978. Today, most automotive
diesels are turbocharged. 1962 Oldsmobile Cutlass Jet fire 1962 Chevrolet Corvair Monza Spyder 1973 BMW 2002 Turbo 1974 Porsche 911 Turbo 1978 Saab 99 1978 Peugeot 604 turbo diesel 1978 Mercedes-Benz 300SD turbo diesel (United States/Canada) 1979 Alfa Romeo Alfetta GTV 2000 Turbodelta 1980 Mitsubishi Lancer GT Turbo 1980 Pontiac Firebird 1980 Renault 5 Turbo 1981 Volvo 240-series Turbo OPERATING PRINCIPLE A turbocharger is a small radial fan pump driven by the energy of the exhaust gases of an engine. A turbocharger consists of a turbine and a compressor on a shared shaft. The turbine converts exhaust heat to rotational force, which is in turn used to drive the compressor. The compressor draws in ambient air and pumps it in to the intake manifold at increased pressure resulting in a greater mass of air entering the cylinders on each intake stroke. The objective of a turbocharger is the same as a supercharger; to improve the engine's volumetric efficiency by solving one of its cardinal limitations. A naturally aspirated automobile engine uses only the downward stroke of a piston to create an area of low pressure in order to draw air into the cylinder through the intake valves. Because the pressure in the atmosphere is no more than 1 atm (approximately 14.7 psi), there ultimately will be a limit to the pressure difference across the intake valves and thus the amount of airflow entering the combustion chamber. Because the turbocharger increases the pressure at the point where air is entering the cylinder, a greater mass of air (oxygen) will be forced in as the inlet manifold pressure increases. The additional air flow makes it possible to maintain the combustion chamber pressure and fuel/air load even at high engine revolution speeds, increasing the power and torque output of the engine. Because the pressure in the cylinder must not go too high to avoid detonation and physical damage, the intake pressure must be controlled by venting excess gas. The control function is performed by a waste gate, which routes some of the exhaust flow away from the turbine. This regulates air pressure in the intake manifold.
COMPONENTS OF A TURBOCHARGER The turbocharger has four main components. The turbine (almost always a radial turbine) and impeller/compressor wheels are each contained within their own folded conical housing on opposite
sides of the third component, the centre housing/hub rotating assembly. The housings fitted around the compressor impeller and turbine collect and direct the gas flow through the wheels as they spin. The size and shape can dictate some performance characteristics of the overall turbocharger. The turbine and impeller wheel sizes dictate the amount of air or exhaust that can be flowed through the system, and the relative efficiency at which they operate. Generally, the larger the turbine wheel and compressor wheel, the larger the flow capacity. The centre hub rotating assembly houses the shaft which connects the compressor impeller and turbine. It also must contain a bearing system to suspend the shaft, allowing it to rotate at very high speed with minimal friction. Waste gates for the exhaust flow.
TURBINE WHEEL: The Turbine Wheel is housed in the turbine casing and is connected to a shaft that in turn rotates the compressor wheel.
COMPRESSOR WHEEL (IMPELLER) Compressor impellers are produced using a variant of the aluminium investment casting process. A rubber former is made to replicate the impeller around which a casting mould is created. The rubber former can then be extracted from the mould into which the metal is poured. Accurate blade sections and profiles are important in achieving compressor performance. Back face profile machining optimizes impeller stress conditions. Boring to tight tolerance and burnishing assist balancing and fatigue resistance. The impeller is located on the shaft assembly using a threaded nut. WASTE GATES: On the exhaust side, a Waste gate provides us a means to control the boost pressure of the engine. Some commercial diesel applications do not use a Waste gate at all. This type of system is called a freefloating turbocharger. However, the vast majority of gasoline performance applications require Waste gates. Waste gates provide a means to bypass exhaust flow from the turbine wheel. Bypassing this energy (e.g. exhaust flow) reduces the power driving the turbine wheel to match the power required for a given boost level.
ADVANTAGES 1. More specific power over naturally aspirated engine. This means a turbocharged engine can achieve more power from same engine volume. 2. Better thermal efficiency over both naturally aspirated and supercharged engine when under full load (i.e. on boost). This is because the excess exhaust heat and pressure, which would normally be wasted, contributes some of the work required to compress the air. 3. Weight/Packaging. Smaller and lighter than alternative forced induction systems and may be more easily fitted in an engine bay. 4. Fuel Economy. Although adding a turbocharger itself does not save fuel, it will allow a vehicle to use a smaller engine while achieving power levels of a much larger engine, while attaining near normal fuel economy while off boost/cruising. This is because without boost, less fuel is used to create a proper air/fuel ratio. DISADVANTAGES 1. Lack of responsiveness if an incorrectly sized turbocharger is used. If a turbocharger that is too large is used it reduces throttle response as it builds up boost slowly otherwise known as "lag". However, doing this may result in more peak power. 2. Boost threshold- A turbocharger starts producing boost only above a certain rpm due to a lack of exhaust gas volume to overcome inertia of rest of the turbo propeller. This results in a rapid and nonlinear rise in torque, and will reduce the usable power band of the engine. The sudden surge of power could overwhelm the tires and result in loss of grip, which could lead to under steer/over steer, depending on the drive train and suspension setup of the vehicle. Lag can be disadvantageous in racing, if throttle is applied in a turn, power may unexpectedly increase when the turbo spools up, which can cause excessive wheel spin. 3. Cost- Turbocharger parts are costly to add to naturally aspirated engines. Heavily modifying OEM turbocharger systems also require extensive upgrades that in most cases requires most (if not all) of the original components to be replaced. 4. Complexity- Further to cost, turbochargers require numerous additional systems if they are not to damage an engine. Even an engine under only light boost requires a system for properly routing (and sometimes cooling) the lubricating oil, turbo-specific exhaust manifold, application specific downpipe, boosts regulation. In addition inter -cooled turbo engines require additional plumbing, while highly tuned turbocharged engines will require extensive upgrades to their lubrication, cooling, and breathing systems; while reinforcing internal engine and transmission parts. TURBO LAG AND BOOST The time required to bring the turbo up to a speed where it can function effectively is called turbo lag. This is noticed as a hesitation in throttle response when coming off idle. This is symptomatic of the
time taken for the exhaust system driving the turbine to come to high pressure and for the turbine rotor to overcome its rotational inertia and reach the speed necessary to supply boost pressure. The directlydriven compressor in a supercharger does not suffer from this problem. Conversely on light loads or at low RPM a turbocharger supplies less boost and the engine acts like a naturally aspirated engine. Turbochargers start producing boost only above a certain exhaust mass flow rate (depending on the size of the turbo). Without an appropriate exhaust gas flow, they logically cannot force air into the engine. The point at full throttle in which the mass flow in the exhaust is strong enough to force air into the engine is known as the boost threshold rpm. Engineers have, in some cases, been able to reduce the boost threshold rpm to idle speed to allow for instant response. Both Lag and Threshold characteristics can be acquired through the use of a compressor map and a mathematical equation. APPLICATIONS Gasoline-powered cars Today, turbocharging is commonly used by many manufacturers of both diesel and gasoline-powered cars. Turbo charging can be used to increase power output for a given capacity or to increase fuel efficiency by allowing a smaller displacement engine to be used. Low pressure turbocharging is the optimum when driving in the city, whereas high pressure turbocharging is more for racing and driving on highways/motorways/freeways. Diesel-powered cars Today, many automotive diesels are turbocharged, since the use of turbocharging improved efficiency, driveability and performance of diesel engines, greatly increasing their popularity. Motorcycles The first example of a turbocharged bike is the 1978 Kawasaki Z1R TC. Several Japanese companies produced turbocharged high performance motorcycles in the early 1980s. Since then, few turbocharged motorcycles have been produced. Trucks The first turbocharged diesel truck was produced by Schweizer Maschinenfabrik Saurer(Swiss Machine Works Saurer) in 1938. Aircraft A natural use of the turbocharger is with aircraft engines. As an aircraft climbs to higher altitudes the pressure of the surrounding air quickly falls off. At 5,486 m (18,000 ft), the air is at half the pressure of sea level and the airframe experiences only half the aerodynamic drag. However, since the charge in the cylinders is being pushed in by this air pressure, it means that the engine will normally produce only half-power at full throttle at this altitude. Pilots would like to take advantage of the low drag at high altitudes in order to go faster, but a naturally aspirated engine will not produce enough power at the same altitude to do so. Here the main aim is to effectively utilize the non-renewable energy such as petrol and diesel. Complete combustion of the fuels can be achieved. Power output can be increased. Wind energy can be used for air compression. We conclude that the power as well as the efficiency is increasing 10 to 15 % and pollution can also decrease. From the observation we can conclude that when the full throttle valve is open at that time the engine speed is 4000 rpm and by this the turbocharger generate 1.60 bar pressurized air. Generally the naturally aspirated engine takes atmospheric pressurized air to the carburettor for air fuel mixture but we can add the high density air for the combustion so as the result the power and the complete combustion take place so efficiency is increasing.
WINDSHIELD WASHER A windshield washer system for an automotive vehicle includes a fluid reservoir, a pump mounted within the fluid reservoir and a heater mounted in proximity to the pump so as to provide heat to fluid contained within the reservoir. The system further includes a nozzle operatively associated with the pump for applying fluid from the reservoir to an outside surface of an automotive vehicle. The heater may comprise an electric resistance element, such as a positive temperature coefficient element mounted about a pumping chamber of the pump. In any event, the heater provides sufficient heat to the fluid contained within the reservoir to prevent water in the fluid from freezing at ambient temperatures normally encountered by automobiles. According to another aspect of the present invention, a nozzle incorporated in the present system may be of the telescoping variety such that it has a first position for spraying and a second, or retracted, position when it is not spraying. In this fashion, a neat, uncluttered appearance may be achieved, while protecting the nozzle from damage. In any event, the nozzle is close-coupled to the pump, so as to minimize the fluid volume between the pump and nozzle. This promotes drain back of fluid from the nozzle to the pump, while allowing heat to flow from the pump to the nozzle, thereby further inhibiting freezing of water within the nozzle.
WINDSHIELD WASHER FLUID Windshield washer fluid is sold in many formulations, and some may require dilution before being applied, although most solutions available in North America come premixed with no diluting required. The most common washer fluid solutions are given labels such as "All-Season", "Bug Remover", or "De-icer", and usually are a combination of solvents with a detergent. Dilution factors will vary depending on season, for example in winter the dilution factor may be 1:1, whereas during summer the dilution factor may be 1:10. It is sometimes sold as sachet of crystals, which is also diluted with water. Distilled water is the preferred diluent, since it will not leave trace mineral deposits on the glass. Antifreeze, or methylated spirits, may be added to a mixture to give the product a lower freezing temperature. But methanol vapour is harmful when breathed in, so more popular now is an ethanol winter mix, e.g. PAV, water, ethanol (or isopropanol), and ethylene glycol. Concerns have been raised about the overall environmental aspects of washer fluid. Widespread, ground-level use of wiper fluid (amounting to billions of litres each year) can lead to cumulative air pollution and water pollution. Consumer advocacy groups and auto enthusiasts believe that the alcohols and solvents present in some, but not all, windshield washer fluid can damage the vehicle. These critics point to the corrosive effects of ethanol, methanol, and other components on paint, rubber, car wax, and
plastics, and groups propose various alternatives and homemade recipes so as to protect the finish and mechanics of the motor vehicle. WINDSHIELD WASHER NOZZLE(S) This model is equipped with two hood mounted washer nozzles. Each nozzle emits two streams into the wiper pattern. If the nozzle performance is unsatisfactory they can be adjusted. To adjust insert a pin into the nozzle ball and move to proper pattern. The right and left nozzles are identical. It is an advantage of the present system that separated fluid lines and nozzles are eliminated, with the entire system being contained in a single assembly, so as to allow the protection of the fluid and the entire system from freezing with a single heat source.
WINDSHIELD WASHER SYSTEM All models are equipped with electrically operated windshield washer pumps. The wash function can be accessed in the OFF position of the wiper control switch. Holding the wash button depressed when the switch is in the OFF position will operate the wipers and washer motor pump continuously until the washer button is released. Releasing the button will stop the washer pump but the wipers will complete the current wipe cycle. Followed by an average of two more wipe cycles before the wipers park and the module turns off. The electric pump assembly is mounted directly to the reservoir. A permanently lubricated motor is coupled to a rotor type pump. Fluid, gravity fed from the reservoir, is forced by the pump through rubber hoses to the hood mounted nozzles which direct the fluid streams to the windshield. The pump and reservoir are serviced as separate assemblies.
ADVANTAGES - It is an advantage of the present system that the use of hydrocarbon-based freezing point depressants may be eliminated with the present system. - It is another advantage of the present system that the nozzle included with the system is self-draining so as to allow the nozzle to purge itself of fluid when the system is not being energized and therefore to further protect the system against freezing. DISADVANTAGES - Windshield washer fluid can damage the vehicle. These critics point to the corrosive effects of ethanol, methanol, and other components. >In conclusion, it can be said that windshield washer is one of the most important parts of a vehicle’s equipment and that, despite the fact that most people do not pay much attention to this, they are really helpful when it comes to keeping the windshield clean and ensuring that visibility levels are as high as possible.
Blink Code in Antilock Braking System(ABS) Blink Code Blink code is a method of visual indication of the components fault to the service technician, by means of flashing Blink Code Lamp. The number and sequence of flashes indicate the status of the system or the nature of failure. This is useful to the service technician both during periodic checkup as well as during troubleshooting the system whenever a failure is observed through the Warning Lamp. How to use Blink Code? The Blink code can be read by pressing the blink code switch. The blink code switch should be pressed till the first flash appears. This typically takes about 5 second. The exact number of flashes, which are separated by pauses, should be noted. Using the blink code table, the corresponding failure can be easily identified. If the stored fault is not erased, it remains in the memory till it is erased, even if the fault is physically repaired. If there are more than one error, the user can read the errors one after the other by repairing and deleting the errors displayed and once again pressing the blink code switch. How to erase Blink Code? The fault which is stored in the system memory can be erased by once again invoking the blink code switch and keeping the switch pressed for the first three flashing.
Working of a Car When a driver turns a key in the ignition: ● The car battery powers up sending ●
Power to the starter motor, which
Turns the crankshaft, which
Gets the pistons moving
With the pistons moving the engine fires up and ticks over
A fan draws air into the engine via an air filter
The air filter removes dirt and grit from the air
The cleaned air is drawn into a chamber where fuel (petrol or diesel) is added ●
This fuel-air mix (a vaporised gas) is stored in the chamber
The driver presses the accelerator pedal
The throttle valve is opened
The gas-air mix passes through an intake manifold and is distributed, through intake valves, into the cylinders. The camshaft controls the opening and closing of the valves. ●
The distributor makes the spark plugs spark, which ignites the fuel-air mix. The resulting explosion forces a piston to move down which in turn causes the crankshaft to rotate. ●
Layout of a Car In automotive design, the automobile layout describes where on the vehicle the engine anddrive wheels are found. Many different combinations of engine location and driven wheels are found in practice, and the location of each is dependent on the application the vehicle will be used for. Factors influencing the design choice include cost, complexity, reliability, packaging (location and size of the passenger compartment and boot), weight distribution and the vehicle's intended handling characteristics. Layouts can roughly be divided into two categories: front- or rear-wheel drive. Four-wheel-drive vehicles may take on the characteristics of either, depending on how power is distributed to the wheels.
Battery Introduction An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Batteries come in many sizes, from miniature cells used to power hearing aids and wristwatches to battery banks the size of rooms that provide standby power for telephone exchanges and computer data centres. Battery has two terminals. One terminal is marked (+), or positive, while the other is marked (-), or negative. In normal flashlight batteries, like AA, C or D cell, the terminals are located on the ends. On a 9-volt or car battery, however, the terminals are situated next to each other on the top of the unit. If you connect a wire between the two terminals, the electrons will flow from the negative end to the positive end as fast as they can. This will quickly wear out the battery and can also be dangerous, particularly on larger batteries. To properly harness the electric charge produced by a battery, you must connect it to a load. The load might be something like a light bulb, a motor or an electronic circuit like a radio.
Advantages of Using Rechargeable Batteries 1. Performance – Since rechargeable batteries can be recharged many times over, the cumulative total service life exceeds that of primary batteries by a wide margin. 2. Savings – Recharging rechargeable batteries many hundred times is giving the consumer tremendous savings in the long run. 3. Environmentally friendly – Since the cumulative service is so much longer than primary batteries, only a fraction of the solid waste is generated and a solid waste reduction of 90% and more is possible. If the battery contains no toxins, such as rechargeable alkalines, they can be even disposed of in regular landfills. Other rechargeables, which do contain toxins such as NiMH should be recycled. Most stores nowadays do take old rechargeables back.
Are Primary and Rechargeable interchangeable amongst each other?
Not all battery types are interchangeable. However, in the consumer, household small format battery category, the following types of the same format can in most cases be interchanged: Heavy Duty, Alkaline, Rechargeable Alkaline and NiMH batteries. Although primary and rechargeable alkaline batteries are rated at a nominal voltage of 1.5 volts, as they begin discharging, their voltage continuously drops. Over the course of discharge, the average voltage of alkaline batteries is in fact about 1.2 volts, very close to NiMH batteries. The main difference is that alkaline batteries start at 1.5 volts and gradually drop to less than 1.0 volt, while NiMH batteries stay at about 1.2 volts for most of the service time. However, NiMH batteries make only practical sense in very high drain devices such as digital cameras as their self-discharge rate is too high for applications that require power of long periods of time. For those slow discharges, a battery type with a very low self-discharge rate is required. Rechargeable Alkaline will fit the bill there. Remember, whatever battery type you use, NEVER mix battery types for use at the same time and never mix old and new batteries. Keep batteries in sets for best performance. How should batteries be stored? Remember, batteries are like any other chemical system. Heat will accelerate the chemical reaction and shorten cell life. Therefore, the greatest threat to a battery's useful life and shelf life is heat. So, avoid storing batteries or battery-operated devices in extremely warm places; store them in a cool, dry place.
The Batteries Work Better In Different Devices 1. HEAVY DUTY BATTERIES are still very popular and have been around for many years because they are so cheap to purchase. Heavy Duty batteries work best in low drain devices such as AM/FM radios flashlights, smoke alarms and remote controls. Over the lifetime of the device, rechargeable alkaline batteries will provide the better value and result actual in cost savings although the initial cost is higher. 2. ALKALINE BATTERIES are the most popular battery used today. Alkaline will last 5 to 10 times longer than heavy duty batteries on higher current drains, making them more economical. They get their long life from unique construction and the purity of the materials used. Alkaline batteries are best suited for moderate to high drain devices such as portable CD players, electronic games, motorized toys, tape recorders and cassette players. Again, over the lifetime of the device, rechargeable alkaline batteries will provide the better value and result actual in cost savings although the initial cost is slightly higher. 3. RECHARGEABLE ALKALINE BATTERIES are specially designed for use 25 times or more when charged properly in a dedicated charger for rechargeable alkaline batteries. Rechargeable alkaline batteries come fully charged, have no memory problems, up to a seven-year shelf life and will last up to three times longer than a fully charged nickel cadmium rechargeable battery. They do not require to be fully drained before recharge and will actually last longer if frequently recharged. They will work in all applications where Heavy Duty Primary Batteries are being used and in all applications for Alkaline Primary Batteries with not too high drain rates. 4. RECHARGEABLE NiMH BATTERIES are an extension of the old fashioned NiCdbatteries. These batteries offer capacities at least 30% higher per charge than NiCdbatteries of the same size. NiMH batteries can be recharged without having to be fully drained and can be charged several hundred times. NiMH work best in high drain devices that chew through alkaline batteries quickly such as digital cameras, hand held TV’s and remote controlled racing toy cars. 5. RECHARGEABLE Li-Ion BATTERIES are mainly used in Laptop
computers and cell phones. They have a 3 times higher voltage on a per cell basis than NiMH batteries and are usually only sold as a ‘system’ (device w/ built-in charger), as they require a special type of charger. More recently, single Li- Ion cells with dedicated chargers are being offered for cameras that take Lithium cells. 6. RECHARGEABLE NiCd BATTERIES should not be used due to the toxic cadmium, but are still in high demand for power tools due to their rugged design and performance. However, NiCd batteries have to be recycled to prevent toxic, carcinogenic cadmium entering the waste stream. 7. PRIMARY LITHIUM BATTERIES offer an outstanding shelf-life of above 10-years and they will work at very low temperatures. They are mainly used in imaging applications, i.ecameras.
Types of Batteries Unfortunately there is no single battery technology available on the market today that can be considered as “The Solution” for all classes of portable battery operated devices. There are a variety of batteries in use, each with its own advantages and disadvantages. There are two main categories of batteries: (1) PRIMARY BATTERIES, sometimes also called single-use, or “throwaway” batteries because they have to be discarded after they run empty as they cannot be recharged for reuse. Primary batteries can produce current immediately on assembly. Disposable batteries are intended to be used once and discarded. These are most commonly used in portable devices that have low current drain, are only used intermittently, or are used well away from an alternative power source, such as in alarm and communication circuits where other electric power is only intermittently available. Disposable primary cells cannot be reliably recharged, since the chemical reactions are not easily reversible and active materials may not return to their original forms. Battery manufacturers recommend against attempting to recharge primary cells. Primary Batteries includeA) Carbon Zinc (aka. ‘Heavy Duty’) -- The lowest cost primary cell (household) is the zinc-acidic manganese dioxide battery. They provide only very low power, but have a good shelf life and are well suited for clocks and remote controls. B) Alkaline -- The most commonly used primary cell (household) is the zincalkaline manganese dioxide battery. They provide more power-per-use than Carbon-zinc and secondary batteries and have an excellent shelf life. C) Lithium Cells -- Lithium batteries offer performance advantages well beyond the capabilities of conventional aqueous electrolyte battery systems. Their shelf-life can be well above 10-years and they will work at very low temperatures. Lithium batteries are mainly used in small formats (coins cells up to about AA size) because bigger sizes of lithium batteries are a safety concern in consumer applications. Bigger (i.e. ‘D’) sizes are only used in military applications.
D) Silver Oxide Cells – These batteries have a very high energy density, but are very expensive due to the high cost of silver. Therefore, silver oxide cells are mainly used in button cell format for watches and calculators. E) Zinc Air Cells – These batteries have become the standard for hearing aid batteries. They have a very long run time, because they store only the anode material inside the cell and use the oxygen from the ambient air as cathode. (2) SECONDARY BATTERIES, mostly called rechargeable batteries because they can be recharged for reuse. They are usually assembled with active materials in the discharged state. Rechargeable batteries or secondary cells can be recharged by applying electric current, which reverses the chemical reactions that occur during its use. Devices to supply the appropriate current are called chargers or rechargers. Secondary batteries includea) Rechargeable Alkaline - Secondary alkaline batteries, the lowest cost rechargeable cells, have a long shelf life and are useful for moderate-power applications. Their cycle life is less than most other secondary batteries, but they are a great consumer’s choice as they combine the benefits of the popular alkaline cells with the added benefit of re-use after recharging. They have no toxic ingredients and can be disposed in regular landfills (local regulations permitting). b) Nickel-Cadmium - Secondary Ni-Cd batteries are rugged and reliable. They exhibit a high power capability, a wide operating temperature range, and a long cycle life, but have a low run time per charge. They have a selfdischarge rate of approximately 30% per month. They contain about 15% toxic, carcinogenic cadmium and have to be recycled. c) Nickel-Metal Hydride - Secondary NiMH batteries are an extension of the old fashionedNiCd batteries. NiMH batteries provide the same voltage as NiCd batteries, but offer at least 30% more capacity. They exhibit good high current capability, and have a long cycle life. The self-discharge rate is higher than NiCd at approximately 40% per month. NiMH cells contain no toxic cadmium, but they still contain a large amount of nickel oxides and also some cobalt, which are known human carcinogens and should be recycled.
d) Lithium Ion - Secondary Li-Ion batteries are the latest breakthrough in rechargeable batteries. They are at least 30% lighter in weight than NiMH batteries and provide at least 30% more capacity. They exhibit good high current capability, and have a long cycle life. The self-discharge rate is better than NiMH at approximately 20% per month. Overheating will damage the batteries and could cause a fire. Li-Ion cells contain no toxic cadmium, but they still contain either cobalt oxides or nickel oxides, which are known human carcinogens and should be recycled. e) Lead-Acid -- Secondary lead-acid batteries are the most popular rechargeable batteries worldwide. Both the battery product and the manufacturing process are proven, economical, and reliable. However, because they are heavy, Lead-Acid batteries are not being used in portable, consumer applications. Lead is a toxic, carcinogenic compound and should not enter the regular waste stream. Recycling of Lead-Acid batteries is the environmental success story of our time, approx. 93% of all battery lead is being recycled today in reused in the production of new Lead-Acid batteries. Primary Alkaline Batteries are long lasting, single-use batteries. They will give good performance in all battery devices. Most standard alkaline batteries give you similar performance, regardless of brand. Rechargeable Alkaline Batteries use a revolutionary type of battery technology that provides the long life of alkaline cells, but can be reused 25 times or more. Rechargeable batteries are ideal for many of your frequently used electronic devices. And because Rechargeable Alkaline Batteries give longer life per charge, hold their power in storage and are recharged when you buy them, they work far better than the old fashioned NiCd rechargeable batteries. Using rechargeable alkaline batteries instead of single use, primary batteries will result in cost savings that can add up to hundreds of dollars. Nickel Metal Hydride (NiMH) batteries meet the demanding power needs for today’s high-tech devices, such as digital cameras, handheld TVs, two-way radios, and personal organizers. NiMH batteries can last three times longer than any alkaline in digital cameras. NiMH can be charged many hundred times resulting in cost savings that can add up to hundreds of dollars. Heavy Duty batteries can be used in non-motor driven devices with low drain, such as radios, remote controls, smoke alarms and clocks.
In devices like these, Heavy Duty batteries will give good performance at a minimal initial cost. However, over the lifetime of the application a rechargeable alkaline cell would provide a much better value and actually save you some money. Most batteries can be stored for long periods of time. Heavy Duty batteries will retain more than 80 % of their power, even when stored at normal household temperatures for up to four years. Single use alkaline and rechargeable alkaline batteries can be stored for up to seven years retaining 80% of its power. NiMH batteries on the other hand have a fairly rapid self-discharge losing about 40% of their rated capacity per month; hence, one pretty much has to recharge a NiMH battery before each use after prolonged periods of storage.
Battery Principle of Operation A battery is a device that converts chemical energy directly to electrical energy. It consists of a number of voltaic cells; each voltaic cell consists of two half cells connected in series by a conductive electrolyte containing anions and cations. One half-cell includes electrolyte and the electrode to which anions (negatively charged ions) migrate, i.e., the anode or negative electrode; the other half-cell includes electrolyte and the electrode to which cations (positively charged ions) migrate, i.e., the cathode or positive electrode. In the redox reaction that powers the battery, cations are reduced (electrons are added) at the cathode, while anions are oxidized (electrons are removed) at the anode. The electrodes do not touch each other but are electrically connected by the electrolyte. Some cells use two half-cells with different electrolytes. A separator between half cells allows ions to flow, but prevents mixing of the electrolytes. Each half cell has an electromotive force (or emf), determined by its ability to drive electric current from the interior to the exterior of the cell. The net emf of the cell is the difference between the emfs of its half-cells, as first recognized by Volta. The net emf is the difference between the reduction potentials of the half-reactions. The electrical driving force across the terminals of a cell is known as the terminal voltage (difference) and is measured in volts. The terminal voltage of a cell that is neither charging nor discharging is called the open-circuit voltage and equals the emf of the cell. Because of internal resistance, the terminal voltage of a cell that is discharging is smaller in magnitude than the open-circuit voltage and the terminal voltage of a cell that is charging exceeds the open-circuit voltage. An ideal cell has negligible internal resistance, so it would maintain a constant terminal voltage until exhausted, then dropping to zero. If such a cell maintained 1.5 volts and stored a charge of one coulomb then on complete discharge it would perform 1.5 joule of work. In actual cells, the internal resistance increases under discharge, and the open circuit voltage also decreases under discharge. If the voltage and resistance are plotted against time, the resulting graphs typically are a curve; the shape of the curve varies according to the chemistry and internal arrangement employed.
Brake Introduction A brake is a mechanical device which inhibits motion. Its opposite component is a clutch. Brake pedal slows a car to a stop. When you depress your brake pedal, your car transmits the force from your foot to its brakes through a fluid. Since the actual brakes require a much greater force than you could apply with your leg, your car must also multiply the force of your foot. The brakes transmit the force to the tires using friction, and the tires transmit that force to the road using friction also.
Almost all wheeled vehicles have a brake of some sort. Even baggage carts and shopping carts may have them for use on a moving ramp. Most fixedwing aircraft are fitted with wheel brakes on the undercarriage. Some aircraft also feature air brakes designed to reduce their speed in flight. Friction brakes on automobiles store braking heat in the drum brake or disc brake while braking then conduct it to the air gradually. When traveling downhill some vehicles can use their engines to brake.
Types of Brakes Brakes may be broadly described as using friction, pumping, or electromagnetics. One brake may use several principles: for example, a pump may pass fluid through an orifice to create friction: 1.
Frictional, Pumping, Electromagnetic brakes 1. Frictional brakes are most common and can be divided broadly into "shoe" or "pad" brakes, using an explicit wear surface, and hydrodynamic brakes, such as parachutes, which use friction in a working fluid and do not explicitly wear. Typically the term "friction brake" is used to mean pad/shoe brakes and excludes hydrodynamic brakes, even though hydrodynamic brakes use friction. Friction (pad/shoe) brakes are often rotating devices with a stationary pad and a rotating wear surface. Common configurations include shoes that contract to rub on the outside of a rotating drum, such as a band brake; a rotating drum with shoes that expand to rub the inside of a drum, commonly called a "drum brake", although other drum configurations are possible; and pads that pinch a rotating disc, commonly called a "disc brake". Other brake configurations are used, but less often. For example, PCC trolley brakes include a flat shoe which is clamped to the rail with an electromagnet; the Murphy brake pinches a rotating drum, and the Ausco Lambert disc brake uses a hollow disc (two parallel discs with a structural bridge) with shoes that sit between the disc surfaces and expand laterally.
2. Pumping brakes are often used where a pump is already part of the machinery. For example, an internal-combustion piston motor can have the fuel supply stopped, and then internal pumping losses of the engine create some braking. Some engines use a valve override called a Jake brake to greatly increase pumping losses. Pumping brakes can dump energy as heat, or can be regenerative brakes that recharge a pressure reservoir called a hydraulic accumulator.
3. Electromagnetic brakes are likewise often used where an electric motor is already part of the machinery. For example, many hybrid gasoline/electric vehicles use the electric motor as a generator to charge electric batteries and also as a regenerative brake. Some diesel/electric railroad locomotives use the electric motors to generate electricity which is
then sent to a resistor bank and dumped as heat. Some vehicles, such as some transit buses, do not already have an electric motor but use a secondary "retarder" brake that is effectively a generator with an internal short-circuit. Related types of such a brake are eddy current brakes, and electro-mechanical brakes (which actually are magnetically driven friction brakes, but nowadays are often just called “electromagnetic brakes” as well).
Hydraulic Brake Hydraulic Brake is an arrangement of braking mechanism which uses brake fluid, typically containing ethylene glycol, to transfer pressure from the controlling unit, which is usually near the operator of the vehicle, to the actual brake mechanism, which is usually at or near the wheel of the vehicle. The most common arrangement of hydraulic brakes for passenger vehicles, motorcycles, scooters, and mopeds, consists of the following: a) Brake pedal or lever b) A push rod (also called an actuating rod) c) A master cylinder assembly containing a piston assembly (made up of either one or two pistons, a return spring, a series of gaskets/ O-rings and a fluid reservoir) d) Reinforced hydraulic lines e) Brake calliper assembly usually consisting of one or two hollow aluminium or chrome-plated steel pistons (called calliper pistons), a set of thermally conductive brake pads and arotor (also called a brake disc) or drum attached to an axle.
At one time, passenger vehicles commonly employed drum brakes on all four wheels. Later, disc brakes were used for the front and drum brakes for the rear. However, because disc brakes have shown a better stopping performance and are therefore generally safer and more effective than drum brakes, four-wheel disc brakes have become increasingly popular, replacing drums on all but the most basic vehicles. Many two-wheel vehicles designs, however, continue to employ a drum brake for the rear wheel.
Air Brake System
Air Brake System is the brake system used in automobiles such as buses, trailers, trucks, and semi-trailers. George Westinghouse created air brakes for utilizing it in trains for railway service. A secured air brake was patented by him on 5th, March 1872. At first air brake is produced for use on trains and now it is used common in automobiles. Westinghouse made various modifications to enhance his creation, directing to several appearances of the automatic brake which was extended to include road vehicles. Compressed Air Brake System- The Compressed Air Brake System is a different air brake used in trucks which contains a standard disc or drum brake using compressed air instead of hydraulic fluid. Most types of truck air brakes are drum units, though there is growing trend to the use of disc brakes. The compressed air brake system works by drawing clean air from the environment, compressing it, and hold it in high pressure tanks at around 120 PSI. Whenever the air is needed for braking, this air is directed to the functioning cylinders on brakes to activate the braking hardware and slow the vehicle. Air brakes use compressed air to increase braking forces. The large vehicles also have an emergency brake system, in which the compressed air holds back a mechanical force using springs which will otherwise engage the brakes. If air pressure is lost for any reason, the brakes will hold and vehicle is stopped. Design and Function- the Compressed air brake system is separated into control system and supply system. The supply system compresses, stores and provides high pressure air to the control system and also to other air operated secondary truck systems such as gearbox shift control, clutch pedal air assistance servo, etc., Control system- The control system is separated into two service brake circuits. They are the parking brake circuit and the trailer brake circuit. This two brake circuits is again separated into front and rear wheel circuits which gets compressed air from their individual tanks for more protection in case of air leak. The service brakes are applied by brake pedal air valve which controls both circuits. The parking brake is the air controlled spring brake which is applied by spring force in the spring brake cylinder and released by compressed air through the hand control valve. The trailer brake consists of a direct two line system the supply line which is
marked red and the separate control or service line which is marked blue. The supply line gets air from the main mover park brake air tank through a park brake relay valve and the control line is regulated through the trailer brake relay valve. The working signals for the relay are offered by the prime mover brake pedal air valve, trailer service brake hand control and Prime Mover Park brake hand control. Supply system- The air compressor is driven off of the automobile engine by crankshaft pulley through a belt or straightly off of the engine timing gears. It is lubricated and cooled by the engine lubrication and cooling systems. The Compressed air is initially directed through a cooling coil and into an air dryer which eliminates moisture and oil impurities and also contains a pressure regulator, safety valve and a little purge reservoir. The supply system is outfitted with an anti-freeze device and oil separator which is an alternative to the air dryer. The compressed air is then stored in a tank and then it is issued through a 4 - way protection valve into the front and rear brake circuit air reservoir, a parking brake reservoir and an auxiliary air supply distribution point. The Supply system also contains many check, pressure limiting, drain and safety valves.
Clutch Introduction A Clutch is a machine member used to connect the driving shaft to a driven shaft, so that the driven shaft may be started or stopped at will, without stopping the driving shaft. A clutch thus provides an interruptible connection between two rotating shafts. Clutches allow a high inertia load to be stated with a small power. Clutches are used whenever the ability to limit the transmission of power or motion needs to be controlled either in amount or over time (e.g. electric screwdrivers limit how much torque is transmitted through use of a clutch; clutches control whether automobiles transmit engine power to the wheels). In the simplest application clutches are employed in devices which have two rotating shafts. In these devices one shaft is typically attached to a motor or other power unit (the driving member) while the other shaft (the driven member) provides output power for work to be done. In a drill for instance, one shaft is driven by a motor and the other drives a drill chuck. The clutch connects the two shafts so that they may be locked together and spin at the same speed (engaged), locked together but spinning at different speeds (slipping), or unlocked and spinning at different speeds (disengaged). A popularly known application of clutch is in automotive vehicles where it is used to connect the engine and the gear box. Here the clutch enables to crank and start the engine disengaging the transmission Disengage the transmission and change the gear to alter the torque on the wheels. Clutches are also used extensively in production machinery of all types.
When your foot is off the pedal, the springs push the pressure plate against the clutch disc, which in turn presses against the flywheel. This locks the engine to the transmission input shaft, causing them to spin at the same speed. Clutch for a drive shaft: The clutch disc (centre) spins with the flywheel (left). To disengage, the lever is pulled (black arrow), causing a white pressure plate (right) to disengage the green clutch disc from turning the drive shaft, which turns within the thrust-bearing ring of the lever. Never will all 3 rings connect, with no gaps. In a car's clutch, a flywheel connects to the engine, and a clutch plate connects to the transmission.
The amount of force the clutch can hold depends on the friction between the clutch plate and the flywheel, and how much force the spring puts on the pressure plate. When the clutch pedal is pressed, a cable or hydraulic piston pushes on the release fork, which presses the throw-out bearing against the middle of the diaphragm spring. As the middle of the diaphragm spring is pushed in, a series of pins near the outside of the spring causes the spring to pull the pressure plate away from the clutch disc (see below). This releases the clutch from the spinning engine.
Requirements of a Good Clutch 1. Torque Transmission 2. Gradual Engagement 3. Good Heat Dissipation 4. Compact Size 5. Sufficient Clutch Pedal Free Play 6. Ease of Operation
Different Types of Clutch Friction Clutch Friction clutches are the most commonly used clutch mechanisms. They are used to transmit torque by using the surface friction between two faces of the clutch. Dog Clutch A dog clutch couples two rotating shafts or other rotating components not by friction, but by interference. Both the parts of the clutch are designed so that one pushes into the other, causing both to rotate at the same speed, so that they never slip. Cone Clutch Cone clutches are nothing, but frictional clutches with conical surfaces. The area of contact differs from normal frictional surfaces. The conical surface provides a taper, which means that while a given amount of actuating force brings the surfaces of the clutch into contact really slowly, the pressure on the mating surfaces increases rapidly. Overrunning Clutch Also known as the freewheel mechanisms, this type of clutch disengage the drive shaft from the driven shaft, when the driven shaft rotates faster than the drive shaft. An example of such a situation can be when a cyclist stops pedalling and cruises. However, in case of automobiles going down the hill, you cannot take your feet off the gas pedal, as there is no free wheel system. If you do so, the whole engine system can be damaged. Safety Clutch Also known as the torque limiter, this device allows a rotating shaft to "slip" or disengage when higher than normal resistance is encountered on a machine. An example of a safety clutch is the one mounted on the driving shaft of a large grass mower. If a stone or something else is encountered by the grass mower, it stops immediately and does not hamper the blades. Centrifugal clutch Centrifugal and semi-centrifugal clutches are employed where they need to engage only at some specific speeds. There is a rotating member on the driving shaft, which rises up as the speed of the shaft increases and engages
the clutch, which then drives the driven shaft. Hydraulic Clutch In a hydraulic clutch system, the coupling is hydrodynamic and the shafts are not actually in contact. They work as an alternative to mechanical clutches. They are known to have common problems associated with hydraulic couplings, and are a bit unsteady in transmitting torque. Electromagnetic Clutch These clutches engage the theory of magnetism on to the clutch mechanisms. The ends of the driven and driving pieces are kept separate and they act as the pole pieces of a magnet. When a DC current is passed through the clutch system, the electromagnet activates and the clutch is engaged.
Fluid Coupling It is a device for transmitting rotation between shafts by means of the acceleration and deceleration of a hydraulic fluid (such as oil). Also known as hydraulic coupling. Structurally, a fluid coupling consists of an impeller on the input or driving shaft and a runner on the output or driven shaft. The two contain the fluid. Impeller and runner are bladed rotors, the impeller acting as a pump and the runner reacting as a turbine. Basically, the impeller accelerates the fluid from near its axis, at which the tangential component of absolute velocity is low, to near its periphery, at which the tangential component of absolute velocity is high. This increase in velocity represents an increase in kinetic energy. The fluid mass emerges at high velocity from the impeller, impinges on the runner blades, gives up its energy, and leaves the runner at low velocity.
Hydraulic fluid couplings transfer rotational force from a transmitting axis to a receiving axis. The coupling consists of two toroid’s -- doughnut-shaped objects -- in a sealed container of hydraulic fluid. One toroid is attached to the driving shaft and spins with the rotational force. The spinning toroid moves the hydraulic fluid around the receiving toroid. The movement of the fluid turns the receiving toroid and thus turns the connected shaft. Although fluid couplings use hydraulic fluid within their construction, the mechanism loses a portion of its force to friction and results in the creation of heat. No fluid coupling can run at 100 percent efficiency. Excessive heat production from poorly maintained couplings can result in damage to the coupling and surrounding systems.
A fluid coupling is a hydrodynamic device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch. It also has widespread application in marine and industrial machine drives, where variable speed operation and/or controlled start-up without shock loading of the power transmission system is essential.
Differential Introduction A differential is a device, usually, but not necessarily, employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways: in one way, it receives one input and provides two outputs—this is found in most automobiles - and in the other way, it combines two inputs to create an output that is the sum, difference, or average, of the inputs. In automobiles and other wheeled vehicles, the differential allows each of the driving road wheels to rotate at different speeds. The differential has three jobs: 1. To aim the engine power at the wheels 2. To act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one final time before it hits the wheels 3. To transmit the power to the wheels while allowing them to rotate at different speeds (This is the one that earned the differential its name.)
Advantages & Disadvantages of Front Wheel Drive
Advantages of Front Wheel Drive1. Interior space: Since the powertrain is a single unit contained in the engine compartment of the vehicle, there is no need to devote interior space for a driveshaft tunnel or rear differential, increasing the volume available for passengers and cargo. 2. Cost: Fewer components overall 3. Weight: Fewer components mean lower weight 4. Fuel economy: Lower weight means better gasoline mileage 5. Improved drivetrain efficiency: the direct connection between engine and transaxle reduce the mass and mechanical inertia of the drivetrain compared to a rear-wheel drive vehicle with a similar engine and transmission, allowing greater fuel economy. 6. Assembly efficiency: the powertrain can be often be assembled and installed as a unit, which allows more efficient production. 7. Slippery-surface traction: placing the mass of the drivetrain over the driven wheels improves traction on wet, snowy, or icy surfaces. Although heavy cargo can be beneficial for traction on rear-wheel drive pickup trucks. 8. Predictable handling characteristics: front-wheel drive cars, with a front weight bias, tend to understeer at the limit, which is commonly believed to be easier for average drivers to correct than terminal
oversteer, and less prone to result in fishtailing or a spin. 9. Better crosswind stability. 10. Tactile feedback via the steering wheel informing driver if a wheel is slipping. 11. Front wheel drive allows the use of left-foot braking as a driving technique. Disadvantages of Front Wheel Drive1. The centre of gravity of the vehicle is typically farther forward than a comparable rear-wheel drive layout. In front wheel drive cars, the front axle typically supports around 2/3rd of the weight of the car (quite far off the "ideal" 50/50 weight distribution). This is a contributing factor in the tendency of front wheel drive cars to understeer. 2. Torque steer can be a problem on front wheel drive cars with higher torque engines ( > 210 N·m ) and transverse layout. This is the name given to the tendency for some front wheel drive cars to pull to the left or right under hard acceleration. It is a result of the offset between the point about which the wheel steers (which falls at a point which is aligned with the points at which the wheel is connected to the steering mechanisms) and the centroid of its contact patch. The tractive force acts through the centroid of the contact patch, and the offset of the steering point means that a turning moment about the axis of steering is generated. In an ideal situation, the left and right wheels would generate equal and opposite moments, cancelling each other out, however in reality this is less likely to happen. Torque steer is often incorrectly attributed to differing rates of twist along the lengths of unequal front drive shafts. However, Centre-point steering geometry can be incorporated in the design to avoid torque steer. This is how the powerful Citroen SM front-wheel drive car avoided the problem. 3. Lack of weight shifting will limit the acceleration of a front wheel drive vehicle. In a rear wheel drive car the weight shifts back during acceleration giving more traction to the driving wheels. This is the main reason why nearly all racing cars are rear wheel drive. However, since
front wheel cars have the weight of the engine over the driving wheels the problem only applies in extreme conditions. 4. In some towing situations front wheel drive cars can be at a traction disadvantage since there will be less weight on the driving wheels. Because of this, the weight that the vehicle is rated to safely tow is likely to be less than that of a rear wheel drive or four wheel drive vehicle of the same size and power. 5. Due to geometry and packaging constraints, the CV joints (constantvelocity joints) attached to the wheel hub have a tendency to wear out much earlier than their rear wheel drivecounterparts? The significantly shorter drive axles on a front wheel drive car causes the joint to flex through a much wider degree of motion, compounded by additional stress and angles of steering, while the CV joints of a rear wheel drive car regularly see angles and wear of less than half that of front wheel drive vehicles. 6. The driveshaft’s may limit the amount by which the front wheels can turn, thus it may increase the turning circle of a front wheel drive car compared to a rear wheel drive one with the same wheelbase. 7. In low traction conditions (i.e.: ice or gravel) the front (Drive) Wheels lose traction first making steering ineffective.
Advantages & Disadvantages of Rear Wheel Drive
Advantages of Rear Wheel Drive1. Better handling in dry conditions - accelerating force is applied to the rear wheels, on which the down force increases, due to load transfer in acceleration, making the rear tires better able to take simultaneous acceleration and curving than the front tires. 2. More predictable steering in low traction conditions (i.e.: ice or gravel) because the steering wheels maintain traction and the ability to affect the motion of the vehicle even if the drive wheels are slipping. 3. Less costly and easier maintenance - Rear wheel drive is mechanically simpler and typically does not involve packing as many parts into as small a space as does front wheel drive, thus requiring less disassembly or specialized tools in order to replace parts. 4. No torque steer. 5. Even weight distribution - The division of weight between the front and rear wheels has a significant impact on a car's handling, and it is much easier to get a 50/50 weight distribution in a rear wheel drive car than in a front wheel drive car, as more of the engine can lie between the front and rear wheels (in the case of a mid-engine layout, the entire engine), and the transmission is moved much farther back. 6. Steering radius - As no complicated drive shaft joints are required at the front wheels, it is possible to turn them further than would be possible using front wheel drive, resulting in a smaller steering radius. 7. Towing - Rear wheel drive puts the wheels which are pulling the
load closer to the point where a trailer articulates, helping steering, especially for large loads. 8. Weight transfer during acceleration. (During heavy acceleration, the front end rises, and more weight is placed on the rear, or driving wheels). 9. Drifting - Drifting is a controlled skid, where the rear wheels break free from the pavement as they spin, allowing the rear end of the car to move freely left and right. This is of course easier to do on slippery surfaces. Severe damage and wear to tires and mechanical components can result from drifting on dry asphalt. Drifting can be used to help in cornering quickly, or in turning the car around in a very small space. Many enthusiasts make a sport of drifting, and will drift just for the sake of drifting. Drifting requires a great deal of skill, and is not recommended for most drivers. It should be mentioned that front wheel drive and four wheel drive cars may also drift, but only with much more difficulty. When front wheel drive cars drift, the driver usually pulls on the emergency brake in order for the back wheels to stop and thus skid. This technique is also used for 'long' drifts, where the turn is accomplished by pulling the e-brake while turning the steering wheel to the direction the driver desires. With drifting, there is also the importance of 'counter-steering' - where while temporarily out of control, the driver regains it by turning the wheel in the opposite direction and thus preparing for the next turn or straight-away. Disadvantages of Rear Wheel Drive1. More difficult to master - While the handling characteristics of rearwheel drive may be more fun for some drivers, for others having rear wheel drive is less intuitive. The unique driving dynamics of rear wheel drive typically do not create a problem when used on vehicles that also offer electronic stability control and traction control. 2. Decreased interior space - This isn't an issue in a vehicle with a ladder frame like a pickup truck, where the space used by the drive line is unusable for passengers or cargo. But in a passenger car, rear wheel
drive means: Less front leg room (the transmission tunnel takes up a lot of space between the driver and front passenger), less leg room for centre rear passengers (due to the tunnel needed for the drive shaft), and sometimes less trunk space (since there is also more hardware that must be placed underneath the trunk). 3. Increased weight - The drive shaft, which connects the engine at the front to the drive axle in the back, adds weight. There is extra sheet metal to form the transmission tunnel. A rear wheel drive car will weigh slightly more than a comparable front wheel drive car, but less than four wheel drive. 4. Higher purchase price - Due to the added cost of materials, rear wheel drive is typically slightly more expensive to purchase than a comparable front wheel drive vehicle. This might also be explained by production volumes, however. Rear drive is typically the platform for luxury performance vehicles, which makes read drive appear to be more expensive. In reality, even luxury performance front drive vehicles are more expensive than average. 5. More difficult handling on low grip surfaces (wet road, ice, snow, gravel...) as the car is pushed rather than pulled. In modern rear drive cars, this disadvantage is offset by electronic stability control and traction control.
Advantages & Disadvantages of All Or 4- Wheel Drive The differential is found on all modern cars and trucks, and also in many allwheel-drive (full-time four-wheel-drive) vehicles. These all-wheel-drive vehicles need a differential between each set of drive wheels, and they need one between the front and the back wheels as well, because the front wheels travel a different distance through a turn than the rear wheels.
Part-time four-wheel-drive systems don't have a differential between the front and rear wheels; instead, they are locked together so that the front and rear wheels have to turn at the same average speed. This is why these vehicles are hard to turn on concrete when the four-wheel-drive system is engaged. The Advantages & Disadvantages of All Wheel Drive All Wheel Drive (or AWD) is a system in which all four wheels of a car operate simultaneously to improve traction and handling. While it is possible for a car to have continuous AWD capabilities, it is far more common for one pair of wheels to engage only when sensors detect that the other pair has begun to slip. There are both advantages and disadvantages to AWD systems
In intermittent AWD systems, the rear wheels engage when sensors detect slippage from the front wheels. Under these circumstances, the vehicle effectively detects and compensates for dangerous driving conditions such as standing water, snow, ice or gravel that could otherwise compromise control of the vehicle. By engaging the second set of wheels, the vehicle experiences two additional points of contact on the surface of the road, allowing greater likelihood that its tires will grip the surface and allow the driver to retain control. The additional weight of AWD systems also encourages more grip on the road and the added points of contact distribute the vehicle's weight more evenly over points of propulsion.
2. Fuel Efficiency The primary disadvantage of an AWD vehicle is its cost. The drive train and related equipment necessary to provide both continuous and intermittent AWD is complex and expensive, often requiring sensors and computers that are not necessary on two- or four-wheel-drive vehicles. This cost increases the initial market value of the vehicle and can also affect the cost of repairs. In addition to these costs, AWD systems require more fuel to power the additional wheels and are less fuel efficient than comparable two-wheel-drive vehicles.
3. Braking Distance and Collision Avoidance While the weight of AWD vehicles improves their handling, it also increases the distance they require to stop. In a scenario where the vehicle must make a sudden stop and cannot swerve or turn, a collision becomes more likely than with a lighter car. Under similar circumstance, but ones in which an accident can be avoided by turning, AWD vehicles offer superior collision avoidance than similar vehicles with less effective handling and turning capabilities.
Need of a Differential Car wheels spin at different speeds, especially when turning. Each wheel
travels a different distance through the turn, and that the inside wheels travel a shorter distance than the outside wheels. Since speed is equal to the distance travelled divided by the time it takes to go that distance, the wheels that travel a shorter distance travel at a lower speed. Also note that the front wheels travel a different distance than the rear wheels. For the non-driven wheels on your car -- the front wheels on a rear-wheel drive car, the back wheels on a front-wheel drive car -- this is not an issue. There is no connection between them, so they spin independently. But the driven wheels are linked together so that a single engine and transmission can turn both wheels. If your car did not have a differential, the wheels would have to be locked together, forced to spin at the same speed. This would make turning difficult and hard on your car: For the car to be able to turn, one tire would have to slip. With modern tires and concrete roads, a great deal of force is required to make a tire slip. That force would have to be transmitted through the axle from one wheel to another, putting a heavy strain on the axle components.
Construction and Working of Differential Assembly Torque is supplied from the engine, via the transmission, to a drive shaft (British term: 'propeller shaft', commonly and informally abbreviated to 'prop-shaft'), which runs to thefinal drive unit that contains the differential. A spiral bevel pinion gear takes its drive from the end of the propeller shaft, and is encased within the housing of the final drive unit. This meshes with the large spiral bevel ring gear, known as the crown wheel. The crown wheel and pinion may mesh in hypoid orientation, not shown. The crown wheel gear is attached to the differential carrier or cage, which contains the 'sun' and 'planet' wheels or gears, which are a cluster of four opposed bevel gears in perpendicular plane, so each bevel gear meshes with two neighbours, and rotates counter to the third, that it faces and does not mesh with. The two sun wheel gears are aligned on the same axis as the crown wheel gear, and drive the axle half shafts connected to the vehicle's driven wheels. The other two planet gears are aligned on a perpendicular axis which changes orientation with the ring gear's rotation.
Input torque is applied to the ring gear (blue), which turns the entire carrier (blue). The carrier is connected to both the side gears (red and yellow) only through the planet gear (green) (visual appearances in the diagram notwithstanding). Torque is transmitted to the side gears through the planet gear. The planet gear revolves around the axis of the carrier, driving the side gears. If the resistance at both wheels is equal, the planet gear revolves without spinning about its own axis, and both wheels turn at the same rate.
If the left side gear (red) encounters resistance, the planet gear (green) spins as well as revolving, allowing the left side gear to slow down, with an equal speeding up of the right side gear (yellow). Thus, for example, if the vehicle is making a turn to the right, the main crown wheel may make 10 full rotations. During that time, the left wheel will make more rotations because it has further to travel, and the right wheel will make fewer rotations as it has less distance to travel. The sun gears (which drive the axle half-shafts) will rotate in opposite directions relative to the ring gear by, say, 2 full turns each (4 full turns relative to each other), resulting in the left wheel making 12 rotations, and the right wheel making 8 rotations. The rotation of the crown wheel gear is always the average of the rotations of the side sun gears. This is why, if the driven road wheels are lifted clear of the ground with the engine off, and the drive shaft is held (say leaving the transmission 'in gear', preventing the ring gear from turning inside the differential), manually rotating one driven road wheel causes the opposite road wheel to rotate in the opposite direction by the same amount.
When the vehicle is traveling in a straight line, there will be no differential movement of the planetary system of gears other than the minute movements necessary to compensate for slight differences in wheel diameter, undulations in the road (which make for a longer or shorter wheel path), etc.
· This is a depiction of an open differential, which is commonly found in most vehicles. They are quite trouble-free, but do have one disadvantage. On a dry road with good traction, the power is evenly applied to both wheels. When one of the tires hits ice or a slippery surface, it begins to spin and the majority of torque is directed to the spinning wheel, leaving very little for the wheel with the good traction. This is how vehicles can get stuck in snow or mud. · Another type of differential is the limited slip differential, which is an option on most new cars. It has a distinct advantage by having a set of clutches and springs within the differential. Their function is to apply pressure to the side gears should one of the tires begin to slip. By applying pressure to the opposite wheel from the one spinning, it allows for more torque to be applied to the wheel with traction. If is far superior to the open differential when it comes to traction in bad weather.
Components of Automobile Engine 1) Camshaft: Camshaft is a type of rotating device or apparatus used in piston engines for propelling or operating poppet valves. Camshaft comprises of series of cams that regulates the opening and closing of valves in the piston engines. The camshaft works with the help of a belt, chain and gears.
2) Crankshaft: Crankshaft is a device, which converts the up and down movement of the piston into rotatory motion. This shaft is presented at the bottom of an engine and its main function is to rotate the pistons in a circular motion. Crankshaft is further connected to flywheel, clutch, and main shaft of the transmission, torque converter and belt pulley. To convert Reciprocating motion of the Piston into Rotary motion, the Crankshaft and Connecting Rod combination is used. The Crankshaft which is made by Steel Forging or Casting is held on the Axis around which it rotates, by the Main Bearings, which is fit round the main Journals provided. There are always at least two such bearings, one at the rear end and another at front end. The increase in number of Main Bearings for a given size of the Crankshaft means less possibility of Vibration and Distortion. But it will also increase the difficulty of correct alignment in addition to increased production cost. The Main Bearings are mounted on the Crankcase of the Engine. The Balance weight or Counterweight keep the system in perfect balance. The Crank Webs are extended and enlarged on the side of Journal opposite the Crank Throw so as to from balance weights. The Crankshaft may be made from Carbon Steel, Nickel Chrome or other Alloy Steel.
3) Connecting Rod: Connecting rods are made of metals, which are used, for joining a rotating wheel to a reciprocating shaft. More precisely, connecting rods also referred to as con rod are used for conjoining the piston to the crankshaft. The load on the piston due to combustion of fuel in the combustion chamber is transmitted to crankshaft through the connecting rod. One end of connecting rod known as small end and is connected to the piston through gudgeon pin while the other end known as big end and is connected to crankshaft through crank pin. Connecting rods are usually made up of drop forged I section. In large size internal combustion engine, the connecting rods of rectangular section have been employed. In such cases, the larger dimensions are kept in the plane of rotation. In petrol engine, the connecting rod's big end is generally split to enable its clamping around the crankshaft. Suitable diameter holes are provided to accommodate connecting rod bolts for clamping. The big end of connecting rod is clamped with crankshaft with the help of connecting rod bolt,nut and split pin or cotter pin. Generally, plain carbon steel is used as material to manufacture connecting rod but where low weight is most important factor, aluminium alloys are most suitable. Nickel alloy steel are also used for heavy duty engine's connecting rod. Connecting rods can be made of steel, aluminum, titanium, iron and other types of metals.
4) Crankcase: A crankcase is a metallic cover that holds together the crankshaft and its attachments. It is the largest cavity within an engine that protects the crankshaft, connecting rods and other components from foreign objects. Automotive crankcases are filled with air and oil, while Magnesium, Cast Iron, Aluminium and alloys are some common materials used to make crankcases. 5) Cylinder Heads: Cylinder heads refers to a detachable plate, which is used for covering the closed end of a cylinder assembled in an automotive engine. It comprises of combustion chamber valve train and spark plugs. Different types of automobiles have different engine configurations such as Straight engine has only one cylinder head while an engine has two cylinder heads.
6) Engine Belts: Engine belts are the bands made of flexible material used for connecting or
joining two rotating shafts or pulleys together. These belts work in coordination with wheels and axles for transferring energy. When the wheels or shafts are positioned at extremely different angles, then the engine belts have the ability to change the direction of a force. Engine pulley is a type of machine or a wheel having either a broad rim or groomed rim attached to a rope or chain for lifting heavy objects. 7) Engine Oil System: Oil is one of the necessities of an automobile engine. Oil is distributed under strong pressure to all other moving parts of an engine with the help of an oil pump. This oil pump is placed at the bottom of an engine in the oil pan and is joined by a gear to either the crankshaft or the camshaft. Near the oil pump, there is an oil pressure sensor, which sends information about the status of oil to a warning light or meter gauge. The different parts of engine oil systems include: - Engine Oil - Engine Oil Cooler - Engine Oil Filter - Engine Oil Gaskets - Engine Oil Pan - Engine Oil Pipe 8) Engine Valve: Automobile engine valves are devices that regulate the flow of air and fuel mixture into the cylinder and assist in expelling exhaust gases after fuel combustion. They are indispensable to the system of coordinated opening and closing of valves, known as valve train. Engine valves are made from varied materials such as Structural Ceramics, Steels, Super alloys and Titanium alloys. Valve materials are selected based on the temperatures and pressures the valves are to endure. The primary components of engine valve are: - Inlet Valve - Exhaust Valve - Combination Valve - Check Valve - EGR Valve
Thermostat Valve Overhead Valve Valve Guide Schrader Valve Vacuum Delay Parts
Inlet Valve & Exhaust ValveFunction-Inlet valve allow the fresh charge of air-fuel mixture to enter the cylinder bore. Exhaust valve permits the burnt gases to escape from the cylinder bore at proper timing. 9) Engine Block: An engine block is a metal casting that serves as a basic structure on which other engine parts are installed. A typical block contains bores for pistons, pumps or other devices to be attached to it. Even engines are sometimes classified as small-block or big-block based on the distance between cylinder bores of engine blocks. Engine blocks are made from different materials including Aluminium alloys, grey cast iron, ferrous alloys, white iron, grey iron, ductile iron, malleable iron, etc.
10) Engine Pulley: An engine pulley is a wheel with a groove around its circumference, upon which engine belts run and transmit mechanical power, torque and speed across different shafts of an engine. An engine houses pulley units of different sizes for cam shaft drive, accessory drive and timing belts. Moulded plastics, iron and steel are normally used to make engine pulleys.
11) Engine Brackets: An engine bracket is a metallic part used to join an engine mount to the power unit or the body of a vehicle. These auto parts are installed between a vehicle's body and power unit to dampen the vibrations generated by the engine, thus preventing a vehicle's body from shaking due to the vibrations. Engine brackets are made from Ductile Iron Cast, Aluminium, Polypropylene, Fiberglass and alloys. 12) Engine Mounting Bolts: Automotive mounting bolts secure different automobile components viz. air bags, brake fittings, etc. on to a supporting structure. Likewise, engine mounting bolts help secure an automobile's engine in place. Based on usage, a number of materials such as alloys, silicon bronze, bronze, ceramic, carbon, aluminium, nylon, phosphor bronze, nickel silver, plastic, titanium, zirconium and stainless steel are utilized to produce these bolts. 13) Piston: Piston is a cylindrical plug which is used for moving up and down the cylinder according to the position of the crankshaft in its rotation. Piston has multiple uses and functions. In the case of four-stroke engine the piston is pulled or pushed with the help of crankshaft while in the case of compression stroke, piston is pushed with the powerful explosion of mixture of air and fuel. Piston comprises of several components namely: a) Piston Pins b) Piston Floor Mat c) Piston Rings d) Piston Valve 14) Piston rings: Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes: · They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion. · They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.
15) Push Rods: Push rods are thin metallic tubes with rounded ends that move through the holes within a cylinder block and head, to actuate the rocker arms. Pushrods are found in valve-in-head type engines and are essential for the motion of engine valves. Some commonly used materials for manufacturing pushrods are Titanium, Aluminium, Chrome Moly and Tempered Chrome Moly. 16) Valve train: Valve train consists of various components and parts, which enables valves to operate and function smoothly. Valve train comprises of three main components: camshafts, several components which are used for turning the camshaft’s rotating movement into reciprocating movement, and lastly valves and its various parts. The primary components of valve train are: a) Tappet b) Rocker Arms c) Valve Timing System 17) Governor It controls the speed of engine at a different load by regulating fuel supply in diesel engine. In petrol engine, supplying the mixture of air-petrol and controlling the speed at various load condition. 18) Carburettor It converts petrol in fine spray and mixes with air in proper ratio as per requirement of the engine. 19) Fuel Pump This device supplies the petrol to the carburettor sucking from the fuel tank. 20) Spark Plug This device is used in petrol engine only and ignite the charge of fuel for combustion. 21) Fuel Injector This device is used in diesel engine only and delivers fuel in fine spray under pressure. 22) Gudgeon Pin
Connects the piston with small end of connecting rod. This pin connects the piston with small end of the connecting rod, and also known as piston pin. It is made up of case hardened steel and accurately ground to the required diameters. Gudgeon pins are made hollow to reduce its weight, resulting low inertia effect of reciprocating parts. This pin is also known as "Fully Floating" as this is free to turn or oscillate both in the piston bosses as well as the small end of the connecting rod. There are very less chances of seizure in this case but the end movement of the pin must be restricted to score the cylinder walls. This can be achieved by using any one of the following three methods, A) One spring circlip at each end is fitted into the groove in the piston bosses. B) On spring circlip is provided in the middle. C) Bronze or Aluminium pads are fitted at both ends of the pin, which prevents the cylinder walls from being damaged. The gudgeon pin may also be semi-floating type, in which either the pin is free to turn or oscillate in the small end bearing but secured in the piston bosses or it may secured in the small end bearing and allowed a free oscillating movement in the piston bosses. This method provides more bearing area at the bosses and hence no need for providing bushes therein, is preferred. 23) Crank Pin Hand over the power and motion to the crankshaft which come from piston through connecting rod. 24) Sump The sump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the sump (the oil pan). 25) Distributor It operates the ignition coil making it spark at exactly the right moment. It also distributes the spark to the right cylinder and at the right time. If the timing is off by a fraction then the engine won't run properly.
Engine Problems Three fundamental things can happen: a bad fuel mix, lack of compression or lack of spark. Beyond that, thousands of minor things can create problems, but these are the "big three." Based on the simple engine we have been discussing, here is a quick rundown on how these problems affect your engine: Bad fuel mix - A bad fuel mix can occur in several ways: · You are out of gas, so the engine is getting air but no fuel. · The air intake might be clogged, so there is fuel but not enough air. · The fuel system might be supplying too much or too little fuel to the mix, meaning that combustion does not occur properly. · There might be an impurity in the fuel (like water in your gas tank) that makes the fuel not burn. Lack of compression - If the charge of air and fuel cannot be compressed properly, the combustion process will not work like it should. Lack of compression might occur for these reasons: · Your piston rings are worn (allowing air/fuel to leak past the piston during compression). · The intake or exhaust valves are not sealing properly, again allowing a leak during compression. · There is a hole in the cylinder. The most common "hole" in a cylinder occurs where the top of the cylinder (holding the valves and spark plug and also known as the cylinder head) attaches to the cylinder itself. Generally, the cylinder and the cylinder head bolt together with a thin gasket pressed between them to ensure a good seal. If the gasket breaks down, small holes develop between the cylinder and the cylinder head, and these holes cause leaks. Lack of spark - The spark might be non-existent or weak for a number of reasons: · If your spark plug or the wire leading to it is worn out, the spark will be weak. · If the wire is cut or missing, or if the system that sends a spark down the wire is not working properly, there will be no spark. · If the spark occurs either too early or too late in the cycle (i.e. if the ignition timing is off), the fuel will not ignite at the right time, and
this can cause all sorts of problems. Many other things can go wrong. For example: ·If the battery is dead, you cannot turn over the engine to start it. ·If the bearings that allow the crankshaft to turn freely are worn out, the crankshaft cannot turn so the engine cannot run. ·If the valves do not open and close at the right time or at all, air cannot get in and exhaust cannot get out, so the engine cannot run. ·If someone sticks a potato up your tailpipe, exhaust cannot exit the cylinder so the engine will not run. ·If you run out of oil, the piston cannot move up and down freely in the cylinder, and the engine will seize. In a properly running engine, all of these factors are within tolerance.
How to Produce More Engine Power Car manufacturers are constantly playing with all of the following variables to make an engine more powerful and/or more fuel efficient. 1. Increase displacement - More displacement means more power because you can burn more gas during each revolution of the engine. You can increase displacement by making the cylinders bigger or by adding more cylinders. Twelve cylinders seems to be the practical limit. 2. Increase the compression ratio - Higher compression ratios produce more power, up to a point. The more you compress the air/fuel mixture, however, the more likely it is to spontaneously burst into flame (before the spark plug ignites it). Higher-octane gasolines prevent this sort of early combustion. That is why high-performance cars generally need high-octane gasoline -- their engines are using higher compression ratios to get more power. 3.Stuff more into each cylinder - If you can cram more air (and therefore fuel) into a cylinder of a given size, you can get more power from the cylinder (in the same way that you would by increasing the size of the cylinder). Turbochargers and superchargers pressurize the incoming air to effectively cram more air into a cylinder. See How Turbochargers Work for details. 4. Cool the incoming air - Compressing air raises its temperature. However, you would like to have the coolest air possible in the cylinder because the hotter the air is, the less it will expand when combustion takes place. Therefore, many turbocharged and supercharged cars have an intercooler. An intercooler is a special radiator through which the compressed air passes to cool it off before it enters the cylinder. See How Car Cooling Systems Work for details. 5. Let air come in more easily - As a piston moves down in the intake stroke, air resistance can rob power from the engine. Air resistance can be lessened dramatically by putting two intake valves in each cylinder. Some newer cars are also using polished intake manifolds to eliminate air resistance there. Bigger air filters can also improve air flow. 6. Let exhaust exit more easily - If air resistance makes it hard for exhaust to exit a cylinder, it robs the engine of power. Air resistance can be lessened by adding a second exhaust valve to each cylinder (a car with two intake and
two exhaust valves has four valves per cylinder, which improves performance -- when you hear a car ad tell you the car has four cylinders and 16 valves, what the ad is saying is that the engine has four valves per cylinder). If the exhaust pipe is too small or the muffler has a lot of air resistance, this can cause back-pressure, which has the same effect. High-performance exhaust systems use headers, big tail pipes and free-flowing mufflers to eliminate back-pressure in the exhaust system. When you hear that a car has "dual exhaust," the goal is to improve the flow of exhaust by having two exhaust pipes instead of one. 7. Make everything lighter - Lightweight parts help the engine perform better. Each time a piston changes direction, it uses up energy to stop the travel in one direction and start it in another. The lighter the piston, the less energy it takes. 8. Inject the fuel - Fuel injection allows very precise metering of fuel to each cylinder. This improves performance and fuel economy.
Efficiency of the engine The efficiency of the engine depends to a large extent upon the following criteria: · Compression · Combustion Process · Air/Fuel Mixture · Mechanical Design · Lubrication
1) Compression The higher the Compression Ratio or the pre-compression pressure, then the higher is the thermal efficiency of the internal combustion engine. This results in a better fuel usage and more power is developed while less fuel is consumed. The maximum compression is however limited by the Octane Rating of the Gasoline that will be used. The higher the Octane Rating the higher the compression can be. Unfortunately, higher Octane Gasoline costs more to produce than low Octane Gasoline. Therefore the increase in fuel efficiency can be offset by increase in fuel costs. The Compression Ratio is based on the mechanical design of the engine and is expressed as:
Where: e = Compression Ratio Vh = Cylinder swept Volume Vc = Combustion space Volume of Cylinder Even more important than Compression Ratio is the actual pre-compression pressure also called Final Compression Pressure. Although its value can be also described and figured out mathematically, it is always substantially less than the mathematical result. The actual Final Compression Pressure can be reliably obtained only by a measurement with a special tool, the Compression
Tester. It is however important to know what the Final Compression Pressure should be for the particular engine. This specification can be usually found in a "Shop Manual" for the particular engine. The difference between the measured and specified values for the Final Compression Pressure determines the "Sealing Quality" of the combustion chamber. The quality of the combustion chamber sealing by means of the Piston Rings and the Valves is a measure of the condition of the engine. Lubricant can also affect the quality of the sealing between the Rings and the Cylinder bore. When the Final Compression Pressure is too high on a used engine, it usually means that the combustion chamber and the piston crown have excessive amounts of carbon deposits that have been formed due to any of the following: 1.
Use of poor quality fuel
Use of poor quality lubricant
If the Final Compression Pressure is too low on a used engine, it usually means that the engine has any of the following problems: Has excessive amount of cylinder wear (due to poor lubrication) Has sticking piston rings (poor lubricant) Has burned exhaust valves (poor fuel or incorrect ignition timing) Has damaged cylinder head gasket Has sticking intake or exhaust valves (poor lubricant)
2) Combustion Process For the quality of the combustion process it is of prime importance that the fuel mixes intimately with the air, so that it can be burnt as completely as possible. It is important that the flame front progresses spatially and in regular form during the power stroke, until the whole mixture has been burnt. The combustion process is considerably influenced by the point in the combustion chamber at which the mixture is ignited, and by the mixture ratio
as well as the manner in which it is fed into the combustion chamber. Combustion is optimal and the efficiency of the engine is at its best when the residual gases contain no unburned fuel and as little of Oxygen as possible. The Hydrocarbons are broken up during the combustion into their constituent parts, they are Hydrogen and Carbon. On complete combustion the Carbon and Hydrogen burn to form Carbon Dioxide and Water vapour. When the combustion is incomplete the exhaust gases also contain other undesirable constituents.
3) Air/Fuel Mixture The Specific Fuel Consumption of an engine is defined as the amount of energy produced per given amount of fuel consumed in the combustion process. The amount of fuel is quoted in grams or kilograms and the amount of energy produced in Kilo-Watt-Hours or Horsepower per hour. Internal combustion engines can consume as little as 300 grams per kWh or as much as 1,200 grams per kWh. In general the Specific Fuel Consumption is at its greatest (least efficient) when the engine is subjected to low loads, such as idle. This is because the ratio between the idling losses (due to friction, leaks, and poor fuel distribution) and the brake horsepower is the most unfavourable. Most engines have the lowest Specific Fuel Consumption at three-quarter load, which is at 75% of the maximum power output and at about 2,000 RPM. The Specific Fuel Consumption of engine is for the most part dependent on the mixture ratio of the Air/Fuel mixture. Consumption is at its lowest with an Air/Fuel Ratio of approximately 15 pounds of Air to one pound of Fuel. This means that 10,000 gallons of Air are needed to burn one gallon of Gasoline.
4) Mechanical Design The mechanical design of the internal combustion engine has not changed since its conception in 1876, mainly because it works. The problem is, that it has been invented long before there was thorough understanding of thermodynamics or of the chemical reactions during combustion process. Further cheap and plentiful fuel -- Gasoline was easily available and until few years ago there was no concern with conservation or pollution. As a result the internal combustion engine is an energy efficiency dinosaur
that refuses to die. To give you some idea why that is so, let’s consider this: Gasoline contains about 42 to 43.5 Mega-Joules of energy in one Kilogram that is equal to about 18,060 to 18,705 Btu per pound. The pie chart on next page will show you where all that energy that is available in Gasoline goes:
Overall Power Loss In Engine
Gear Introduction A gear also known as "gear wheel" is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine. Geared devices can change the speed, magnitude, and direction of a power source. The most common situation is for a gear to mesh with another gear, however a gear can also mesh a nonrotating toothed part, called a rack, thereby producing translation instead of rotation. The gears in a transmission are analogous to the wheels in a pulley. An advantage of gears is that the teeth of a gear prevent slipping. When two gears of unequal number of teeth are combined a mechanical advantage is produced, with both the rotational speeds and the torques of the two gears differing in a simple relationship. There are tiny gears for devices like wrist watches and there are large gears that some of you might have noticed in the movie Titanic. Gears form vital elements of mechanisms in many machines such as vehicles, metal tooling machine tools, rolling mills, hoisting and transmitting machinery, marine engines, and the like. Toothed gears are used to change the speed, power, and direction between an input and output shaft. 1) 2) · · · · ·
Gears are the most common source used for power transmission. They can be applied for two shafts which areParallel Collinear Perpendicular & Intersecting Perpendicular and Non-intersecting Inclined at an arbitrary angle
Gear Parameters 1)
Number of teeth
Form of teeth
Size of teeth
Face width of teeth
Style and dimension of gear blank
Design of the hub of the gear
Degree of precision required
Means of attaching the gear to the shaft
Means of locating the gear axially to the shaft
Types of Gears 1.
Rack and Pinion
Internal and External Gear
1) Spur Gear-Parallel and coplanar shafts connected by gears are called spur gears. The arrangement is called spur gearing. Spur gears have straight teeth and are parallel to the axis of the wheel. Spur gears are the most common type of gears. The advantages of spur gears are their simplicity in design, economy of manufacture and maintenance, and absence of end thrust. They impose only radial loads on the bearings. Spur gears are known as slow speed gears. If noise is not a serious design problem, spur gears can be used at almost any speed.
2) Helical Gear-Helical gears have their teeth inclined to the axis of the shafts in the form of a helix, hence the name helical gears. These gears are usually thought of as high speed gears. Helical gears can take
higher loads than similarly sized spur gears. The motion of helical gears is smoother and quieter than the motion of spur gears. Single helical gears impose both radial loads and thrust loads on their bearings and so require the use of thrust bearings. The angle of the helix on both the gear and the must be same in magnitude but opposite in direction, i.e., a right hand pinion meshes with a left hand gear.
3) Herringbone Gear - Herringbone gears resemble two helical gears that have been placed side by side. They are often referred to as "double helical". In the double helical gears arrangement, the thrusts are counter-balanced. In such double helical gears there is no thrust loading on the bearings.
4) Bevel/Miter Gear-Intersecting but coplanar shafts connected by gears are called bevel gears. This arrangement is known as bevel gearing. Straight bevel gears can be used on shafts at any angle, but right angle is the most common. Bevel Gears have conical blanks. The teeth of straight bevel gears are tapered in both thickness and tooth height. Spiral Bevel gears: In these Spiral Bevel gears, the teeth are oblique. Spiral Bevel gears are quieter and can take up more load as compared to straight bevel gears.
Zero Bevel gear: Zero Bevel gears are similar to straight bevel gears, but their teeth are curved lengthwise. These curved teeth of zero bevel gears are arranged in a manner that the effective spiral angle is zero.
5) Worm Gear- Worm gears are used to transmit power at 90° and where high reductions are required. The axes of worm gears shafts cross in space. The shafts of worm gears lie in parallel planes and may be skewed at any angle between zero and a right angle. In worm gears, one gear has screw threads. Due to this, worm gears are quiet, vibration free and give a smooth output. Worm gears and worm gear shafts are almost invariably at right angles.
6) Rack and Pinion- A rack is a toothed bar or rod that can be thought of as a sector gear with an infinitely large radius of curvature. Torque can be
converted to linear force by meshing a rack with a pinion: the pinion turns; the rack moves in a straight line. Such a mechanism is used in automobiles to convert the rotation of the steering wheel into the left-to-right motion of the tie rod(s). Racks also feature in the theory of gear geometry, where, for instance, the tooth shape of an interchangeable set of gears may be specified for the rack (infinite radius), and the tooth shapes for gears of particular actual radii then derived from that. The rack and pinion gear type is employed in a rack railway.
7) Internal & External Gear- An external gear is one with the teeth formed on the outer surface of a cylinder or cone. Conversely, an internal gear is one with the teeth formed on the inner surface of a cylinder or cone. For bevel gears, an internal gear is one with the pitch angle exceeding 90 degrees. Internal gears do not cause direction reversal. 8) Face Gears- Face gears transmit power at (usually) right angles in a circular motion. Face gears are not very common in industrial application.
9) Sprockets-Sprockets are used to run chains or belts. They are typically used in conveyor systems.
Gears may also be classified according to the position of axis of shaft: a. Parallel 1. Spur Gear 2. Helical Gear 3. Rack and Pinion b. Intersecting Bevel Gear c. Non-intersecting and Non-parallel Worm and worm gears
Terminology of Spur Gear
Pitch surface: The surface of the imaginary rolling cylinder (cone, etc.) that the toothed gear may be considered to replace. ●
Pitch circle: A right section of the pitch surface.
Addendum circle: A circle bounding the ends of the teeth, in a right section of the gear. ●
Root (or dedendum) circle: The circle bounding the spaces between the teeth, in a right section of the gear. ●
Addendum: The radial distance between the pitch circle and the addendum circle. ●
Dedendum: The radial distance between the pitch circle and the root circle. ●
Clearance: The difference between the dedendum of one gear and the addendum of the mating gear. ●
Face of a tooth: That part of the tooth surface lying outside the pitch surface. ●
Flank of a tooth: The part of the tooth surface lying inside the pitch surface. ●
Circular thickness (also called the tooth thickness): The thickness of the tooth measured on the pitch circle. It is the length of ●
an arc and not the length of a straight line. Tooth space: The distance between adjacent teeth measured on the pitch circle. ●
Backlash: The difference between the circle thickness of one gear and the tooth space of the mating gear. ●
Backlash =Space width – Tooth thickness ● Circular pitch p: The width of a tooth and a space, measured on the pitch circle. Diametral pitch P: The number of teeth of a gear per inch of its pitch diameter. A toothed gear must have an integral number of teeth. The circular pitch, therefore, equals the pitch circumference divided by the number of teeth. The diametral pitch is, by definition, the number of teeth divided by the pitch diameter. ●
Module m: Pitch diameter divided by number of teeth. The pitch diameter is usually specified in inches or millimetres; in the former case the module is the inverse ofdiametral pitch. ●
Fillet: The small radius that connects the profile of a tooth to the root circle. ●
Pinion: The smallest of any pair of mating gears. The largest of the pair is called simply the gear. ●
Velocity ratio: The ratio of the number of revolutions of the driving (or input) gear to the number of revolutions of the driven (or output) gear, in a unit of time. ●
Pitch point: The point of tangency of the pitch circles of a pair of mating gears. ●
Common tangent: The line tangent to the pitch circle at the pitch point. ●
Base circle: An imaginary circle used in involute gearing to generate the involutes that form the tooth profiles. ●
· Line of Action or Pressure Line: The force, which the driving tooth exerts at point of contact of the two teeth. This line is also the common tangent at the point of contact of the mating gears and is known as the line of action or the pressure line. The component of the force along the common tangent at the p point is responsible for the power transmission. The component of the force perpendicular to the common tangent through the pitch point produces the required thrust. · Pressure Angle or Angle of Obliquity (φ): The angle between pressure line and the common tangent to the pitch circles is known as the pressure angle or the angle of obliquity. For more power ‘transmission and lesser pressure on the bearing pressure angle must be kept small. Standard pressure angles arc and 25°. Gears with 14.5° pressure angles have become almost obsolete. · Path of Contact or Contact Length: Locus of the point of contact between two mating teeth from the beginning of engagement to the end is known as the path of contact or the contact length. It is CD in the figure. Pitch point P is always one point on the path of contact. It can be subdivided as follows: Path of Approach: Portion of the path of contact from the beginning of engagement to the pitch point, i.e. the length CP. Path of Recess: Portion of the path of contact from the pitch point to the end of engagement i.e. length PD. · Arc of Contact: Locus of a point on the pitch circle from the beginning to the end of engagement of two mating gears is known as the arc of contact in fig. 3.22, APB or EPF is the arc of contact. It has also been divided into sub-portions. Arc of Approach: It is the portion of the arc of contact from the beginning of engagement to the pitch point, i.e. length AP or EP. Arc of Recess: Portion of the arc of contact from the pitch point to the end of engagement is the arc of recess i.e. length PB or PF. · Angle of Action (δ): It is the angle turned by a gear from the beginning of engagement to the end of engagement of a pair of teeth i.e. the angle turned by arcs of contact of respective gear wheels. Similarly, angle of approach (a) and angle of recess (β) can be defined.
Use of Gear Advantage of Teeth on Gear Use of Gears●
To reverse the direction of rotation
To increase or decrease the speed of rotation
To move rotational motion to a different axis
To keep the rotation of two axis synchronized
Advantages of TeethThey prevent slippage between the gears - therefore axles connected by gears are always synchronized exactly with one another. ●
They make it possible to determine exact gear ratios - you just count the number of teeth in the two gears and divide. So if one gear has 60 teeth and another has 20, the gear ratio when these two gears are connected together is 3:1. ●
They make it so that slight imperfections in the actual diameter and circumference of two gears don't matter. The gear ratio is controlled by the number of teeth even if the diameters are a bit off. ●
Gear Ratio The gear ratio of a gear train is the ratio of the angular velocity of the input gear to the angular velocity of the output gear, also known as the speed ratio of the gear train. The gear ratio can be computed directly from the numbers of teeth of the various gears that engage to form the gear train. In simple words, gear ratio defines the relationship between multiple gears. Gear Ratio= Output gear # teeth / Input gear # teeth For example, if our motor is attached to a gear with 60 teeth and this gear is then attached to a gear with 20 teeth that drives a wheel, our gear ratio is 60:20, or more accurately 3:1 If you do not want to count a gears teeth (or if they do not exist), gear ratios can also be determined by measuring the distance between the centre of each gear to the point of contact. For example, if our motor is attached to a gear with a 1" diameter and this gear is connected to a gear with a 2" diameter attached to a wheel, From the centre to edge of our input gear is 0.5" From the centre to edge of our output gear is 1" Our ratio is 1/0.5 or more accurately 2:1
How Does a Gear Ratio Affect Speed? The gear ratio tells us how fast one gear is rotating when compared to another. If our input gear (10 teeth) is rotating at 5 rpms, and it is connected to our output gear (50 teeth), our output gear will rotate at 1 rpms. Why? Our gear ratio is 50:10... Or 5:1 If our small gear rotates 1x, our large gear only rotates 1/5. It takes 5 rotations of our small gear to = 1 rotation of our large gear. Thus our large gear is rotating at 1/5 the speed = 1rpm. What if our gear ratio where 1:3? In this case our input gear is 3x larger as large as our output gear. If our input gear were rotating at 20 rpms.... each rotation, would result in 3 rotations of our output gear. Our output would be 60 rpms.
How Does Gear Ratio Affects Torque First....What is torque? Torque is a twisting force- (it doesn't do any 'work' itself- it is simple an application of energy). Work (or 'stuff') happens, when torque is applied and movement occurs. "Torque is a force that tends to rotate or turn things. You generate a torque any time you apply a force using a wrench. Tightening the lug nuts on your wheels is a good example. When you use a wrench, you apply a force to the handle. This force creates a torque on the lug nut, which tends to turn the lug nut. English units of torque are pound-inches or pound-feet; the SI unit is the Newton-meter. Notice that the torque units contain a distance and a force. To calculate the torque, you just multiply the force by the distance from the centre. In the case of lug nuts, if the wrench is a foot long, and you put 200 pounds of force on it, you are generating 200 pound-feet of torque. If you use a two-foot wrench, you only need to put 100 pounds of force on it to generate the same torque." In summary: Torque equals Force multiplied by Distance How does gear ratio affect Torque? Simply put, torque at work (such as at a wheel) is your motor's torque times your gear ratio. Motor Torque x gear ratio = torque at the wheel Let’s say we have a 10rmps motor that is capable of 5 oz. Torque (we know this from our motor spec.) Let’s say we have 2 gears. Our input gear (attached to our motor) has 10 teeth our output gear has 50 teeth Our Gear ratio is 5:1 Motor Torque x gear ratio = torque at the wheel 5oz x 5:1 = 25 oz.
What if our gear ratio were 1:3? 5oz x 1:3 = 1.6oz
Gear Train A gear train is formed by mounting gears on a frame so that the teeth of the gears engage. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping; this provides a smooth transmission of rotation from one gear to the next. • A gear train is two or more gear working together by meshing their teeth and turning each other in a system to generate power and speed • It reduces speed and increases torque • Electric motors are used with the gear systems to reduce the speed and increase the torque
Types of gear train Simple gear train - Compound gear train - Epicyclic gear train - Reverted gear train -
Simple & Compound Gear Train Simple Gear TrainThe simple gear train is used where there is a large distance to be covered between the input shaft and the output shaft. Each gear in a simple gear train is mounted on its own shaft. When examining simple gear trains, it is necessary to decide whether the output gear will turn faster, slower, or the same speed as the input gear. The circumference (distance around the outside edge) of these two gears will determine their relative speeds. Suppose the input gear's circumference is larger than the output gear's circumference. The output gear will turn faster than the input gear. On the other hand, the input gear's circumference could be smaller than the output gear's circumference. In this case the output gear would turn more slowly than the input gear. If the input and output gears are exactly the same size, they will turn at the same speed. In many simple gear trains there are several gears between the input gear and the output gear. These middle gears are called idler gears. Idler gears do not affect the speed of the output gear.
Compound Gear TrainIn a compound gear train at least one of the shafts in the train must hold two gears. Compound gear trains are used when large changes in speed or power output are needed and there is only a small space between the input and output shafts. The number of shafts and direction of rotation of the input gear determine the direction of rotation of the output gear in a compound gear train. The train in Figure has two gears in between the input and output gears. These two gears are on one shaft. They rotate in the same direction and act like one gear. There are an odd number of gear shafts in this example. As a result, the input
gear and output gear rotate in the same direction. Since two pairs of gears are involved, their ratios are “compounded”, or multiplied together.
Example- The input gear, with 12 teeth, drives its mating gear on the countershaft, which has 24 teeth. This is a ratio of 2 to 1. This ratio of DRIVEN over DRIVER at the Input - 2 to 1 - is then multiplied by the Output ratio, which has a DRIVEN to DRIVER ratio of 3 to 1. This gives a gear ratio of 6 to 1 between the input and the output, resulting in a speed reduction and a corresponding increase in torque.
Planetary Or Epicyclic Gear Train Like a compound gear train, planetary trains are used when a large change in speed or power is needed across a small distance. There are four different ways that a planetary train can be hooked up. A planetary gear train is a little more complex than other types of gear trains. In a planetary train at least one of the gears must revolve around another gear in the gear train. A planetary gear train is very much like our own solar system, and that's how it gets its name. In the solar system the planets revolve around the sun. Gravity holds them all together. In a planetary gear train the sun gear is at the centre. A planet gear revolves around the sun gear. The system is held together by the planet carrier. In some planetary trains, more than one planet gear rotates around the sun gear. The system is then held together by an arm connecting the planet gears in combination with a ring gear.
The planetary gear set is the device that produces different gear ratios through the same set of gears. Any planetary gear set has three main components: · The sun gear · The planet gears and the planet gears' carrier · The ring gear Each of these three components can be the input, the output or can be held stationary. Choosing which piece plays which role determines the gear ratio for the gearset. These four combinations and the resulting speed and power outputs are listed in Table
• They have higher gear ratios. • They are popular for automatic transmissions in automobiles. • They are also used in bicycles for controlling power of pedalling automatically or manually. • They are also used for power train between internal combustion engine and an electric motor.
Reverted Gear Train A reverted gear train is very similar to a compound gear train. They are both used when there is only a small space between the input and output shafts and large changes in speed or power are needed.
There are two major differences between compound and reverted gear trains. First, the input and output shafts of a reverted train must be on the same axis (in a straight line with one another). Second, the distance between the centres of the two gears in each pair must be the same.
Mechanical Advantage Gear teeth are designed so that the number of teeth on a gear is proportional to the radius of its pitch circle, and so that the pitch circles of meshing gears roll on each other without slipping. The speed ratio for a pair of meshing gears can be computed from ratio of the radii of the pitch circles and the ratio of the number of teeth on each gear.. Two meshing gears transmit rotational motion. The velocity v of the point of contact on the pitch circles is the same on both gears, and is given by Where input gear A has radius rA and meshes with output gear B of radius rB, therefore,
Where NA is the number of teeth on the input gear and NB is the number of teeth on the output gear. The mechanical advantage of a pair of meshing gears for which the input gear has NA teeth and the output gear has NBteeth is given by
This shows that if the output gear GB has more teeth than the input gear GA, then the gear train amplifies the input torque. And, if the output gear has fewer teeth than the input gear, then the gear train reduces the input torque. If the output gear of a gear train rotates more slowly than the input gear, then the gear train is called a speed reducer. In this case, because the output gear must have more teeth than the input gear, the speed reducer will amplify the input torque.
Suspension System Introduction Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose — contributing to the car's road holding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants comfortable and reasonably well isolated from road noise, bumps, and vibrations, etc. These goals are generally at odds, so the tuning of suspensions involves finding the right compromise. It is important for the suspension to keep the road wheel in contact with the road surface as much as possible, because all the forces acting on the vehicle do so through the contact patches of the tires. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear.
Principle of Suspension System 1.
To restrict road vibrations from being transmitted to the various
components of the vehicle 2.
To protect the passengers from road shocks
To maintain the stability of the vehicle in pitching and rolling
Components of Suspension System Control Arm: A movable lever that fastens the steering knuckle to the frame of the vehicle. 1.
Control Arm Busing: This is a sleeve which allows the control arm to move up and down on the frame. 2.
Strut Rod: Prevents the control arm from swinging forward and backwards. 3.
Ball Joints: A joint that allows the control arm and steering knuckle to move up and down and sideways as well 4.
Shock absorbers or Struts: prevents the suspension from bounce after spring compression and extension 5.
Stabilizer Bar: Limits body roll of the vehicle during cornering
Spring: Supports the weight of the vehicle
Common Problems of the Suspension System Shocks and Struts: Shocks and Struts are located behind the wheels of a vehicle. Shocks and Struts are subject to wear and tear just like other vehicle parts. The signs of a shock wear out are if the car bounces excessively, leans hard in corners and jerks at brakes then the shocks and struts are definitely calling for a change. Ball joints: The wearing out of ball joints can get dangerous because if they separate they cause you to lose control over the vehicle which could also be a life risk.
Preventive Measures for Suspension System The shocks and struts should be check frequently for leakages Ball joints should be checked immediately in case the motion of the car is not right. Make sure to lubricate the ball joints of your car frequently.
Comparison between MacPherson Wishbone Suspension Systems
Two of the most popular suspensions systems for passenger cars today are the double wishbone suspension system and the MacPherson strut suspension system. While it is more usual to see the double wishbone system at the rear end of the car, MacPherson’s solution normally finds its place at the front end of the car. Both types of suspensions have their own sets of benefits and limitations, thus let us look at both the advantages and disadvantages of both systems, starting with the simpler of the two, the MacPherson struts. MacPherson Struts- The struts are designed with more simplicity, and thus takes up less space horizontally. As a result, passengers get more compartment place in the car. They also display low un-sprung weight, an advantage that reduces the overall weight of the vehicle as well as increases the car’s acceleration. Lower un-sprung weight also makes your ride more comfortable. Another major advantage of this system is its ease of manufacturing as well as low cost of manufacture compared to other standalone suspension systems. Without an upper arm, the suspension system designers can directly block vibration from reaching the passenger compartment. Nevertheless, the MacPherson struts come with their own drawbacks. Being a long, vertical assembly, you would encounter difficulties if you lower your car as they may be collision with the structure of your car. Thus they do not work well with racing cars that are normally lowered. The MacPherson struts also have problems working with wider wheels that have increased scrub radius, where you would need extra effort to navigate your car in this situation. There is also the problem with the small camber change with vertical movement of the suspension, which could mean the tires have less contact with the road during cornering. This could reduce handling abilities of your vehicle.
Double Wishbone Suspension System- One of its primary benefits is the increase of negative chamber as a result of the vertical suspension movement of the upper and lower arms. This translates to better stability properties for the car as the tires on the outside maintain more contact with the road surface. Handling performance also increases. The double suspension system is much more rigid and stable than other suspension systems, thus you would realize that your steering and wheel alignments are constant even when undergoing high amounts of stress.
Moving on to the drawbacks of the double wishbone suspension system, it is normally bugged by cost issues as it is a more complicated design to produce. There are many parts to the system, and thus every time any of these malfunction of fail, your whole system fails. Repair, modification and
maintenance costs and complexities for double wishbone suspension systems are normally higher due to these reasons. This suspension system also proves to be flexible for design engineers, as the arms of the system can be fixed at different angles to the surface, parameters such as camber gain, roll center height and swing arm length can be determined and designed flexibly to suit and road surface in condition. As we have seen, both suspension systems have their own plus points and limitations. To conclude, double wishbones may perform better, but the MacPherson struts would prove to be more affordable in the long run.
Transmission system Introduction Transmission system in a car helps to transmit mechanical power from the car engine to give kinetic energy to the wheels. It is an interconnected system of gears, shafts, and other electrical gadgets that form a bridge to transfer power and energy from the engine to the wheels. The complete setup of the system helps to maintain the cruising speed of the car without any disturbance to the car’s performance. The oldest variant of the transmission system in India is the manual transmission that has undergone various modifications and alterations to form the present day automatic transmission. A transmission or gearbox provides speed and torque conversions from a rotating power source to another device using gear ratios. The transmission reduces the higher engine speed to the slower wheel speed, increasing torque in the process. A transmission will have multiple gear ratios (or simply "gears"), with the ability to switch between them as speed varies. This switching may be done manually (by the operator), or automatically. Directional (forward and reverse) control may also be provided. In motor vehicle applications, the transmission will generally be connected to the crankshaft of the engine. The output of the transmission is transmitted via drive shaft to one or more differentials, which in turn drive the wheels. Most modern gearboxes are used to increase torque while reducing the speed of a prime mover output shaft (e.g. a motor crankshaft). This means that the output shaft of a gearbox will rotate at slower rate than the input shaft, and this reduction in speed will produce a mechanical advantage, causing an increase in torque.
Need For a Transmission The need for a transmission in an automobile is a consequence of the characteristics of the internal combustion engine. Engines typically operate over a range of 600 to about 7000 revolutions per minute (though this varies, and is typically less for diesel engines), while the car's wheels rotate between 0 rpm and around 1800 rpm. Furthermore, the engine provides its highest torque outputs approximately in the middle of its range, while often the greatest torque is required when the vehicle is moving from rest or traveling slowly. Therefore, a system that transforms the engine's output so that it can supply high torque at low speeds, but also operate at highway speeds with the motor still operating within its limits, is required. Transmissions perform this transformation. The transmission allows the gear ratio between the engine and the drive wheels to change as the car speeds up and slows down.
Types of Transmission System 1. Manual Transmission 2. Automatic Transmission 3. Semi-automatic Transmission:a) Dual-clutch Transmission b) Sequential Transmission
4. Continuously Variable Transmission
Manual Transmission The first transmission invented was the manual transmission system. A manual transmission, also known as a manual gearbox or standard transmission (informally, a "manual", "stick shift", "straight shift", or "straight drive") is a type of transmission used in motor vehicle applications. It generally uses a driver-operated clutch, typically operated by a pedal or lever, for regulating torque transfer from the internal combustion engine to the transmission, and a gear-shift, either operated by hand (as in a car) or by foot (as on a motorcycle). In manual transmission the driver needs to disengage the clutch to disconnect the power from the engine first, select the target gear, and engage the clutch again to perform the gear change.
Components of Manual Transmission The diagram below shows a very simple two-speed transmission in neutral: · The green shaft comes from the engine through the clutch. The green shaft and green gear are connected as a single unit. (The clutch is a device that lets you connect and disconnect the engine and the transmission. When you push in the clutch pedal, the engine and the transmission are disconnected so the engine can run even if the car is standing still. When you release the clutch pedal, the engine and the green shaft are directly connected to one another. The green shaft and gear turn at the same rpm as the engine.) · The red shaft and gears are called the lay shaft. These are also connected as a single piece, so all of the gears on the lay shaft and the lay shaft itself spin as one unit. The green shaft and the red shaft are directly connected through their meshed gears so that if the green shaft is spinning, so is the red shaft. In this way, the lay shaft receives its power directly from the engine whenever the clutch is engaged. ● The yellow shaft is a splined shaft that connects directly to the drive shaft through thedifferential to the drive wheels of the car. If the wheels are spinning, the yellow shaft is spinning.
· The blue gears ride on bearings, so they spin on the yellow shaft. If the engine is off but the car is coasting, the yellow shaft can turn inside the blue gears while the blue gears and the lay shaft are motionless.
· The purpose of the collar is to connect one of the two blue gears to the yellow drive shaft. The collar is connected, through the splines, directly to the yellow shaft and spins with the yellow shaft. However, the collar can slide left or right along the yellow shaft to engage either of the blue gears. Teeth on the collar, called dog teeth, fit into holes on the sides of the blue gears to engage them.
Working of Manual Transmission When the gear selector fork is shifted into first gear, the collar engages the blue gear on the right:
In this picture, the green shaft from the engine turns the lay shaft, which turns the blue gear on the right. This gear transmits its energy through the collar to drive the yellow drive shaft. Meanwhile, the blue gear on the left is turning, but it is freewheeling on its bearing so it has no effect on the yellow shaft.
Five-Speed Manual Transmission The five-speed manual transmission is fairly standard on cars today. Internally, it looks something like this:
There are three forks controlled by three rods that are engaged by the shift lever. The shift lever has a rotation point in the middle. When you push the knob forward to engage first gear, you are actually pulling the rod and fork for first gear back. When you move the shifter left and right you are engaging different forks (and therefore different collars). Moving the knob forward and backward moves the collar to engage one of the gears. Idler Gear or Reverse GearIdler gear is a small gear (purple) and is slid between red and blue gear. At all times, the blue reverse gear in this diagram is turning in a direction opposite to all of the other blue gears. The idler has teeth which mesh with both gears, and thus it couples these gears together and reverses the direction of rotation without changing the gear ratio.
Double Clutching Double-clutching was common in older cars and is still common in some modern Race Cars. In double-clutching, you first push the clutch pedal in once to disengage the engine from the transmission. This takes the pressure off the dog teeth so you can move the collar into neutral. Then you release the clutch pedal and rev the engine to the "right speed." The right speed is the rpm value at which the engine should be running in the next gear. The idea is to get the blue gear of the next gear and the collar rotating at the same speed so that the dog teeth can engage. Then you push the clutch pedal in again and lock the collar into the new gear. At every gear change you have to press and release the clutch twice, hence the name "double-clutching."
Synchronized Transmission Manual transmissions in modern passenger cars use synchronizers to eliminate the need for double-clutching. A synchro's purpose is to allow the collar and the gear to make frictional contact before the dog teeth make contact. This lets the collar and the gear synchronize their speeds before the teeth need to engage as shown in figures.
Synchronized gearbox consists of cone shaped brass clutch engaged to the gear. The cone on the blue gear fits into the cone-shaped area in the collar, and friction between the cone and the collar synchronize the collar and the gear. The outer portion of the collar then slides so that the dog teeth can engage the gear.
Automatic Transmission The concept of an automatic transmission is new in India. An automatic transmission is amotor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears. In this transmission system the gears are never physically moved and are always engaged to the same gears. Automatic transmissions contain mechanical systems, hydraulic systems, electrical systems and computer controls, all working together in perfect harmony manually. Main Components of an Automatic Transmission1.
Planetary Gear Sets
Clutches and Bands
Planetary Gear Sets The planetary gear set is the device that produces different gear ratios through the same set of gears. Any planetary gear set has three main components: · The sun gear ·
The planet gears and the planet gears' carrier
The ring gear
Each of these three components can be the input, the output or can be held stationary. Choosing which piece plays which role determines the gear ratio for the gear set. Compound Planetary gear set - The automatic transmission uses a set of gears, called a compound planetary gear set that looks like a single planetary gear set but actually behaves like two planetary gear sets combined. It has one ring gear that is always the output of the transmission, but it has two sun gears and two sets of planets. The figure below shows a compound planetary gear set:
First Gear- In first gear, the smaller sun gear is driven clockwise by the turbine in thetorque converter. The planet carrier tries to spin counter clockwise, but is held still by the one-way clutch (which only allows rotation in the clockwise direction) and the ring gear turns the output. The small gear has 30 teeth and the ring gear has 72, so the gear ratio is: Ratio = -R/S = - 72/30 = -2.4:1 So the rotation is negative 2.4:1, which means that the output direction would
be opposite the input direction. But the output direction is really the same as the input direction -- this is where the trick with the two sets of planets comes in. The first set of planets engages the second set, and the second set turns the ring gear; this combination reverses the direction. You can see that this would also cause the bigger sun gear to spin but because that clutch is released, the bigger sun gear is free to spin in the opposite direction of the turbine (counter clockwise). Second Gear - The two planetary gear sets connected to each other with a common planet carrier. The first stage of the planet carrier actually uses the larger sun gear as the ring gear. So the first stage consists of the sun (the smaller sun gear), the planet carrier, and the ring (the larger sun gear). The input is the small sun gear; the ring gear (large sun gear) is held stationary by the band, and the output is the planet carrier. For this stage, with the sun as input, planet carrier as output, and the ring gear fixed, the formula is: 1 + R/S = 1 + 36/30 = 2.2:1 The planet carrier turns 2.2 times for each rotation of the small sun gear. At the second stage, the planet carrier acts as the input for the second planetary gear set, the larger sun gear (which is held stationary) acts as the sun, and the ring gear acts as the output, so the gear ratio is: 1 / (1 + S/R) = 1 / (1 + 36/72) = 0.67:1 To get the overall reduction for second gear, we multiply the first stage by the second, 2.2 x 0.67, to get a 1.47:1 reduction. Third Gear- Most automatic transmissions have a 1:1 ratio in third gear. To achieve a ratio of 1:1 engage the clutches that lock each of the sun gears to the turbine. If both sun gears turn in the same direction, the planet gears lockup because they can only spin in opposite directions. This locks the ring gear to the planets and causes everything to spin as a unit, producing a 1:1 ratio. Overdrive Gear- An overdrive has a faster output speed than input speed. When overdrive is engaged, a shaft that is attached to the housing of the
torque converter (which is bolted to the flywheel of the engine) is connected by clutch to the planet carrier. The small sun gear freewheels, and the larger sun gear is held by the overdrive band. Nothing is connected to the turbine; the only input comes from the converter housing. This time with the planet carrier for input, the sun gear fixed and the ring gear for output. Ratio = 1 / (1 + S/R) = 1 / (1 + 36/72) = 0.67:1 So the output spins once for every two-thirds of a rotation of the engine. If the engine is turning at 2000 rotations per minute (RPM), the output speed is 3000 RPM. This allows cars to drive at freeway speed while the engine speed stays nice and slow. Reverse Gear- Reverse is very similar to first gear, except that instead of the small sun gear being driven by the torque converter turbine, the bigger sun gear is driven, and the small one freewheels in the opposite direction. The planet carrier is held by the reverse band to the housing. So, according to our equations from the last page, we have: Ratio = -R/S = 72/36 = 2.0:1 So the ratio in reverse is a little less than first gear in this transmission. Summary of Gear Ratios- Transmission having four forward gears and one reverse gear.
Clutches & Bands, Torque Converter, Valve Body 1. Clutches & Bands - These are friction devices that drive or lock planetary gear sets members. They are used to cause the gear set to transfer power. In other words, they are used to hold a particular member of the planetary gear set motionless, while allowing another member to rotate, thereby transmitting torque and producing gear reductions or overdrive ratios. These clutches are actuated by the valve body their sequence controlled by the transmission's internal programming. 2. Torque Converter - It is a hydraulic device that connects the engine and the transmission. It takes the place of a mechanical clutch, allowing the transmission to stay 'in gear' and the engine to remain running whilst the vehicle is stationary, without stalling. A torque converter is a fluid coupling that also provides a variable amount of torque multiplication at low engine speeds, increasing "breakaway" acceleration.
3. Valve Body - The valve body is the control centre of the automatic transmission. It contains a maze of channels and passages that direct hydraulic fluid to the numerous valves. Depending on which gear is selected, the manual valve feeds hydraulic circuits that inhibit certain gears. For instance, if the shift lever is in third gear, it feeds a circuit that prevents overdrive from engaging. The valve body of the transmission contains several shift valves. Shift valves supply hydraulic pressure to the clutches and bands to engage each gear. The shift valve determines when to shift from one gear to the next
Comparison between Transmission-
Both the automatic transmission and a manual transmission accomplish exactly the same thing, but they do it in totally different way. Advantages of manual transmission over automatic transmission1. It is easier to build a strong manual transmission than an automatic one. This is because a manual system has one clutch to operate, whereas an automatic system has a number of clutch packs that function in harmony with each other. 2. Manual transmissions normally do not require active cooling, because not much power is dissipated as heat through the transmission. 3. Manual gearshifts are more fuel efficient as compared to their automatic counterpart. Torque convertor used to engage and disengage automatic gears may lose power and reduce acceleration as well as fuel economy. 4. Manual transmissions generally require less maintenance than automatic transmissions. An automatic transmission is made up of several components and a breakdown of even a single component can stall the car completely. Advantages of automatic transmission over manual transmission1. The manual transmission locks and unlocks different sets of gears to the output shaft to achieve the various gear ratios, while in an automatic transmission; the same set of gears produces all of the different gear ratios. The planetary gear set is the device that makes this possible in an automatic transmission. 2. Automatic cars are easier to use, especially for the inexperienced car driver. Manual system requires better driving skills, whereas with an automatic, the clever system does it all on its own. This holds a greater advantage for new and inexperienced drivers and also helps during congested traffic situations where it becomes difficult to change gears every second. 3. Automatic transmission requires less attention and concentration from the driver because the automatic gears start functioning as soon as the system feels the need of a gear change. For car with manual gear shifts, the driver has to be more alert while driving and better coordinated. 4. There is no clutch pedal and gear shift in an automatic transmission car.
Once you put the transmission into drive, everything else is automatic. 5. Automatic cars have better ability to control traction when approaching steep hills or engine braking during descents. Manual gears are difficult to operate on steep climbs.
Semi-Automatic Transmission A semi-automatic transmission (also known as clutch less manual transmission, automated manual transmission, flappy-paddle gearbox, or paddle shift gearbox) is a system which uses electronic sensors, processors and actuators to execute gearshifts on the command of the driver. This removes the need for a clutch pedal which the driver otherwise needs to depress before making a gear change, since the clutch itself is actuated by electronic equipment which can synchronise the timing and torque required to make gear shifts quick and smooth. The two most common semi-automatic transmissions are1. Dual-clutch Transmission 2. Sequential Transmission
Dual Clutch Transmission A dual clutch transmission, commonly abbreviated to DCT uses two clutches, but has no clutch pedal. Sophisticated electronics and hydraulics control the clutches, just as they do in a standard automatic transmission. In a DCT, however, the clutches operate independently. One clutch controls the odd gears (first, third, fifth and reverse), while the other controls the even gears (second and fourth) as shown in figure. Using this arrangement, gears can be changed without interrupting the power flow from the engine to the transmission. A two-part transmission shaft is at the heart of a DCT. Unlike a conventional manual gearbox, which houses all of its gears on a single input shaft, the DCT splits up odd and even gears on two input shafts. The outer shaft is hollowed out, making room for an inner shaft, which is nested inside. The outer hollow shaft feeds second and fourth gears, while the inner shaft feeds first, third and fifth.
Sequential Transmission A sequential transmission is a type of transmission used on motorcycles and high-performance cars for auto racing, where gears are selected in order, and direct access to specific gears is not possible. Cars with SMTs have a manual transmission with no clutch pedal; the clutch is automatically engaged. In a race car, the motion of the shift lever is either "push forward" to upshift or "pull backward" to downshift. If you are in a gear and you want to go to a higher gear (e.g. from 2nd to 3rd), you push the shift lever forward. To go from 3rd to 4th, you push the lever forward again. To go from 4th to 5th, you press it forward again. It is the same motion every time. To drop back down a gear, say from 5th to 4th, you pull the lever backward. In European mass-produced automobiles, the shift lever, the motion of the shift lever is either "push forward" to upshift or "pull backward" to downshift moves forward and backward to shift into higher and lower gears, respectively. In Formula One cars, there are actually two paddles on the sides of the steering wheel, instead of a shift lever. The left paddle upshifts, while the right paddle downshifts. On a motorcycle, you do the same thing, but instead of moving a lever back and forth with your hand, you move a lever up and down with your foot.
Advantages of using Sequential Transmission1. It provides a direct connection between engine and transmission, allowing 100 percent of the engine's power to be transmitted to the wheels. 2. The SMT provides more immediate response and ensures that the engine RPMs do not drop when the driver lifts off the accelerator (as happens with an automatic), giving her more precise control over power output. 3. It uses a solid coupling, as opposed to a fluid coupling (torque converter) 4. The sequential shift lever takes up less space in the race car cockpit. 5. The sequential shift is quicker. 6. The sequential shift is consistent. You do not have to think before gear change. 7. The hand location is consistent; the shift lever is always in the same place for the next shift. 8. The gearbox reduces the risk of blowing up engine due to mis-shift.
Continuously Variable Transmissions CVT is an “infinite speed” transmission which can change steplessly through an infinite number of effective gear ratios between maximum and minimum values. Unlike traditional automatic transmissions, continuously variable transmissions don't have a gearbox with a set number of gears, which means they don't have interlocking toothed wheels. The word gear in CVT refers to a ratio of engine shaft speed to driveshaft speed. Moreover, CVTs change this ratio without using a set of planetary gears. Different types of CVTs – 1. Pulley-based CVTs 2. Toroidal CVTs 3. Hydrostatic CVTs The most common CVT design uses a segmented metal V-belt running between two pulleys. Each pulley consists of a pair of cones that can be moved close together or further apart to adjust the diameter at which the belt operates. The pulley ratios are electronically controlled to select the best overall drive ratio based on throttle position, vehicle speed and engine speed.
Future Developments in Automotive Transmission Systems 1. The CVT will gradually replace the conventional automatic transmission due to its high fuel efficiency and smooth gear shift. 2. The technology of semi-automatic transmission systems will also be improved to perform smooth gear shift and extend the cars' lifetime, without losing fast acceleration and fuel efficiency. 3.The torque converter with fluid coupling may be improved, or may no longer be used for cars in the future due to its low-efficiency power transfer. 4. Auto Shift Manual Transmission – This transmission system combines the advantages of an automatic transmission with the flexibility and low fuel consumption of a manual transmission. This is an advanced Shift-By-Wire electronic control system technology. Shift-by-wire totally eliminates mechanical lever shifting, keeping both of driver's hands on the wheel. The clutch is used only for starting and stopping. Once the vehicle is in motion, Auto Shift operates like an automatic transmission, with the efficiency of a manual transmission. 5. Adaptive transmission control - ATC has also been invented by using a computer to recognize and memorize different drivers' styles, and determining the best shifting timing for different drivers. 6. A transmission system is needed for a vehicle due to the internal combustion engines property of running at high pressure at high speed but low pressure at low speed. If someday an engine with different properties is invented, the transmission system may no longer be necessary, but can still get the vehicle to reach its maximum speed in a couple of seconds.
TERMS CONNECTED ENGINES:
Bore: The inside diameter of the cylinder is called bore. Stroke: when the piston reciprocate in the cylinder it has the limiting upper and lower positions beyond which it can not move. The linear distance between the two limiting positions of the cylinder is called Stroke. Top Dead Centre (TDC): The top most position of the piston towards top end side is called top dead center. But, in case of Horizontal Engines it is known as inner dead center. Bottom Dead Center (BDC): The lowest position of the piston towards crank end side is called Bottom dead center. But, in case of Horizontal Engines it is known as outerdead center. Clearance Volume: The volume contained in the cylinder above the top of the piston when piston is at the top is called Clearance Volume. When L = D - Called Square Engines When L D - Under Square Engine Swept Volume: The volume swept by piston between between top and bottom dead center is called swept volume / piston displacement. Compression Ratio: It is ratio of total cylinder volume to clearance Volume. Compression ratio (r) = Vs + Vc / Vc Piston Speed: The average speed of the piston is called Piston Speed & = 2LN where L = Stroke of Piston & N = RPM of engine. Average engine speed of engines is 5 to 15 m/sec. ( This speed is kept in this range Because of – strength of material& noise consideration. Direct Injection: Fu el injected to the main combustion chamber of an engine. Indirect Injection: Fuel injected to the secondary combustion chamber of an engine. Smart Engine: The Engines made with computer controls that regulate operating characteristics such as air-fuel ratio, ignition timings, valve timings, intake tuning and exhaust control.
Air fuel Ratio: It is ratio of the mass of Air to mass of Fuel.
FUEL SUPPLY SYSTEM IN SPARK IGNITION ENGINE The fuel supply system of spark ignition engine consists of 1. Fuel tank 2. Sediment bowl 3. Fuel lift pump 4. Carburetor 5. Fuel pipes In some spark ignition engines the fuel tank is placed above the level of the carburetor. The fuel flows from fuel tank to the carburetor under the action of gravity. There are one or two filters between fuel tank and carburetor. A transparent sediment bowl is also provided to hold the dust and dirt of the fuel. If the tank is below the level of carburetor, a lift pump is provided in between the tank and the carburetor for forcing fuel from tank to the carburetor of the engine. The fuel comes from fuel tank to sediment bowl and then to the lift pump. From there the fuel goes to the carburetor through suitable pipes. From carburetor the fuel goes to the engine cylinder through inlet manifold of the engine.
FUEL SUPPLY SYSTEM IN DIESEL ENGINE Fuel supply system of diesel engine consists of the following components 1. Fuel tank 2. Fuel lift pump or fuel feed pump 3. Fuel filter 4. Fuel injection pump 5. High pressure pipe 6. Over flow valve 7. Fuel injector Fuel is drawn from fuel tank by fuel feed pump and forced to injection pump through fuel filter. The injection pump supplies high pressure fuel to injection nozzles through delivery valves and high pressure pipes. Fuel is injected into the combustion chamber through injection nozzles. The fuel that leaks out from the injection nozzles passes out through leakage pipe and returns to the fuel tank through the over flow pipe. Over flow valve installed at the top of the filter keeps the feed pressure under specified limit. If the feed pressure exceeds the specified limit , the over flow valve opens and then the excess fuel returns to fuel tank through over flow pipe.
Fuel tank It is a storage tank for diesel. A wire gauge strainer is provided under the cap to prevent foreign particles entering the tank
Fuel lift pump It transfers fuel from fuel tank to inlet gallery of fuel injection pump Preliminary filter (sediment bowl assembly) This filter is mostly fitted on fuel lifts pump. It prevents foreign materials from reaching inside the fuel line. It consists of a glass cap with a gasket.
Fuel filter Mostly two stage filters are used in diesel engines 1. Primary filter
2. Secondary filter Primary filter removes coarse materials, water and dust. Secondary filter removes fine dust particles.
Fuel Injection Pump It is a high pressure pump which supplies fuel to the injectors according to the firing order of the engine. It is used to create pressure varying from 120 kg/cm2 to 300 kg/cm2. It supplies the required quantity of fuel to each cylinder at the appropriate time.
Air Venting of Fuel System When air has entered the fuel lines or suction chamber of the injection pump, venting should be done properly.. Air is removed by the priming pump through the bleeding holes of the injection pump.
Fuel Injector It is the component which delivers finely atomized fuel under high pressure to combustion chamber of the engine. Modern tractor engines use fuel injectors which have multiple holes. Main parts of injectors are nozzle body, and needle valve. The needle valve is pressed against a conical seat in the nozzle body by a spring. The injection pressure is adjusted by adjusting a screw. In operation, fuel from injection pump enters the nozzle body through high pressure pipe. When fuel pressure becomes so high that it exceeds the set spring pressure, the needle valve lifts off its seat. The fuel is forced out of the nozzle spray holes into the combustion Main types of modern fuel injection systems: 1. Common-rail injection system. 2. Individual pump injection system. 3. Distributor system.
Carburetor The earliest form of fuel supply mechanism for modern automobile is carburetor. The primary function of carburetor is to provide the air-fuel mixture to the engine in the required proportion. The goal of a carburetor is to mix just the right amount of gasoline with air so that the engine runs properly. If there is not enough fuel mixed with the air, the engine "runs lean" and either will not run or potentially damages the engine. If there is too much fuel mixed with the air, the engine runs rich and either will not run (it floods), runs very smoky, runs poorly (bogs down, stalls easily), or at the very least wastes fuel. The car is in charge of getting the mixture just right.
Carburetor Basics A carburetor basically consists of an open pipe, a "barrel" through which the air passes into the inlet manifold of the engine. The pipe is in the form of a venturi: it narrows in section and then widens again, causing the airflow to increase in speed in the narrowest part. Below the venturi is a butterfly valve called the throttle valve — a rotating disc that can be turned end-on to the airflow, so as to hardly restrict the flow at all, or can be rotated so that it (almost) completely blocks the flow of air. This valve controls the flow of air through the carburetor throat and thus the quantity of air/fuel mixture the system will deliver, thereby regulating engine power and speed. The throttle is connected, usually through a cable or a mechanical linkage of rods and joints or rarely by pneumatic link, to the accelerator pedal on a car or the equivalent control on other vehicles or equipment. Fuel is introduced into the air stream through small holes at the narrowest part of the venturi and at other places where pressure will be lowered when not running on full throttle. Fuel flow is adjusted by means of precisely-calibrated orifices, referred to as jets, in the fuel path.
Parts of carburetor · A carburetor is essentially a tube. · There is an adjustable plate across the tube called the throttle plate that controls how much air can flow through the tube. · At some point in the tube there is a narrowing, called the venturi, and in this narrowing a vacuum is created. · In this narrowing there is a hole, called a jet, that lets the vacuum
draw in fuel.
How carburetors work ? All carburetors work on "the Bernoulli Principle. Bernoulli principle states that as the velocity of an ideal gas increases, the pressure drops. Within a certain range of velocity and pressure, the change in pressure is pretty much linear with velocity-if the velocity doubles the pressure halves. However, this linear relationship only holds within a certain range. Carburetors work because as air is pulled into the carburetor throat, the venturi. It has to accelerate from rest, to some speed. How fast depends upon the air flow demanded by the engine speed and the throttle butterfly setting. According to Bernoulli, this air flowing through the throat of the carb will be at a pressure less than atmospheric pressure, and related to the velocity (and hence to how much air is being fed into the engine). If a small port is drilled into the carb throat in this low pressure region, there will be a pressure difference between the throat side of the port, and the side that is exposed to the atmosphere. If a reservoir of gasoline, the float bowl, is between the inside of the port, and the atmosphere, the pressure difference will pull gasoline through the port, into the air stream. At this point, the port gets the name of a jet in the concept of a carburetor. The more air that the engine pulls through the carburetor throat, the greater the pressure drop across the jet, and the more fuel that gets pulled in. As noted above, within a range of airflow in the throat, and fuel flow in the jet, the ratio of fuel to air that flows will stay constant. And if the jet is the right size, that ratio will be what the engine wants for best performance. A venturi/jet arrangement can only meter fuel accurately over a certain range of flow rates and pressures. As flow rates increase, either the venturi or the jet, or both, will begin to choke, that is they reach a point where the flow rate will not increase, no matter how hard the engine tries to pull air through. At the other extreme, when the velocity of the air in the venturi is very low-like at idle or during startup, the pressure drop across the jet becomes vanishingly small. It is this extreme that concerns us with respect to starting, idle and low-speed throttle response. At idle, the pressure drop in a 32 mm venturi is so small that essentially no
fuel will be pulled through the main jets. But the pressure difference across the throttle butterfly (which is almost completely closed) can be as high as 25+ mm Hg. Carb designers take advantage of this situation by placing an extra jet, the "idle jet" notch, just downstream of the throttle butterfly. Because of the very high pressure difference at idle, and the very small amount of fuel required, this jet is tiny. When the throttle is open any significant amount, the amount of fuel that flows through this jet is small, and for all intents and purposes, constant. So its effect on the midrange and up mixture is easily compensated for. During startup, the amount of air flowing through the carburetor is smaller still. At least till the engine begins to run on it's own. But when it is being turned by the starter or the kicker, rpm is in the sub 100 range sometimes. So the pressure difference across the jets is again in the insignificant range. If the engine is cold, it wants the mixture extra-rich to compensate for the fact that a lot of the fuel that does get mixed with air in the carb precipitates out on the cold walls of the intake port. Bing carburetors, and most bike carburetors, use enrich circuits. All this really is another port or jet from the float bowl to just downstream of the throttle butterfly. Except that the fuel flow to this jet is regulated by a valve that is built into the carb body. At startup, when the lever is in the full on position, the valve is wide open, and the fuel supply to the cold start jet is more or less unlimited. In this condition, the amount of fuel that flows through the cold start jet is regulated just like the idle jet is. When the throttle is closed, the pressure drop across the jet is high, and lots of fuel flows, resulting in a very rich mixture, just perfect for ignition of a cold motor. If the throttle butterfly is opened, the pressure difference is less, and less fuel flows. This is why R bikes like no throttle at all until the engine catches. However, the mixture quickly gets too rich, and opening the throttle will make things better. Just like the idle jet, this cold start jet is small enough that even when the circuit is wide open, the amount of fuel that can flow is small enough that at large throttle openings, it has little impact on the mixture. This is why you can ride off with the starting circuit on full, and the bike will run pretty well-until you close the throttle for the first time, and the mixture gets so rich the engine stalls. The valve that controls fuel supply to the cold start jet allows the rider to cut the fuel available through that jet down from full during startup, to none or almost none once the engine is warm.
In most cases, at the intermediate setting, fuel to the cold start jet is cut to the point where the engine will still idle when warm, although very poorly since it is way too rich. True "chokes" are different. But very aptly named. A choke is simply a plate that can be maneuvered so that it completely (or very nearly) blocks off the carburetor throat at it's entrance ("choking" the carb, just like a killer to a victim in a bad movie). That means that the main, idle, intermediate, etc., jets are all down stream of the choke plate. Then, when the engine tries to pull air through the crab, it can't. The only place that anything at all can come in to the carb venturi is through the various jets. Since there is little or no air coming in, this results in an extremely rich mixture. The effect is maximized if the throttle butterfly (which is downstream of the big main jets and the choke plate) is wide open, not impeding things in any way. If the throttle butterfly is completely closed, the engine does not really know that the choke is there-all the engine "sees" is a closed throttle, so there is little enrichening effect. The engine will pull as much fuel as possible through the idle jet, but that is so small it won't have much effect. So a carb with a choke behaves in exactly the opposite manner as one with an enrichener. During the cranking phase, it is best to have the throttle pegged at WFO so that the most fuel gets pulled in, resulting in a nice rich mixture. But as soon as the motor starts, you want to close the throttle to cut down the effect of the choke. Even that is not enough, and most chokes are designed so that as soon as there is any significant airflow, they automatically open part way. Otherwise the engine would flood. Even "manual" chokes have this feature most of the time.
MPFI Multi-point fuel injection injects fuel into the intake port just upstream of the cylinder's intake valve, rather than at a central point within an intake manifold. MPFI (or just MPI) systems can be sequential, in which injection is timed to coincide with each cylinder's intake stroke, batched, in which fuel is injected to the cylinders in groups, without precise synchronization to any particular cylinder's intake stroke, or Simultaneous, in which fuel is injected at the same time to all the cylinders. Many modern EFI systems utilize sequential MPFI; however, it is beginning to be replaced by direct injection systems in newer gasoline engines. The multi-point injector is an electromechanical device which is fed by a 12 volt supply from either the fuel injection relay or from the Electronic Control Module (ECM). The voltage in both cases will only be present when the engine is cranking or running, due to both voltage supplies being controlled by a tachometric relay. The injector is supplied with fuel from a common fuel rail. The length of time that the injector is held open for will depend on the input signals seen by the engine management ECM from its various engine sensors. These input signals will include:· The resistance of the coolant temperature. • The output voltage from the airflow meter (when fitted). • The resistance of the air temperature sensor. • The signal from the Manifold Absolute Pressure (MAP) sensor (when fitted). • The position of the throttle switch / potentiometer. The held open time or injector duration will vary to compensate for cold engine starting and warm-up periods, i.e. a large duration that decreases the injection time as the engine warms to operating temperature. Duration time will also expand under acceleration and contract under light load conditions. Depending on the system encountered the injectors can fire either once or twice per cycle. The injectors are wired in parallel with simultaneous injection and will all fire together at the same time. Sequential injection, as with simultaneous, has a common supply to each injector but unlike
simultaneous has a separate earth path for each injector. This individual firing allows the system, when used in conjunction with a phase sensor, to deliver the fuel when the inlet valve is open and the incoming air helps to atomize the fuel. It is also common for injectors to be fired in 'banks' on 'V' configured engines. The fuel will be delivered to each bank alternately, because of the frequency of the firing of the injectors, it is expected that a sequential injector will have twice the duration, or opening, than that of a simultaneous pulse. This will however be determined by the injector flow rate.
COOLING SYSTEM Fuel is burnt inside the cylinder of an internal combustion engine to produce power. The temperature produced on the power stroke of an engine can be as high as 1600 ºC and this is greater than melting point of engine parts.. The best operating temperature of IC engines lie between 140 F and 200 ºF and hence cooling of an IC engine is highly essential. . It is estimated that about 40% of total heat produced is passed to atmosphere via exhaust, 30% is removed by cooling and about 30% is used to produce power.
Purpose of Cooling 1. To maintain optimum temperature of engine for efficient operation under all conditions. 2. To dissipate surplus heat for protection of engine components like cylinder, cylinder head, piston, piston rings, and valves 3. To maintain the lubricating property of oil inside engine. Methods of Cooling 1. Air cooled system 2. Water cooled system
AIR COOLING SYSTEM Air cooled engines are those engines in which heat is conducted from the working components of the engine to the atmosphere directly. Principle of air cooling- The cylinder of an air cooled engine has fins to increase the area of contact of air for speedy cooling. The cylinder is normally enclosed in a sheet metal casing called cowling. The fly wheel has blades projecting from its face, so that it acts like a fan drawing air through a hole in the cowling and directed it around the finned cylinder. For maintenance of air cooled system, passage of air is kept clean by removing grasses etc. by a stiff brush of compressed air.
Advantages of Air Cooled Engine: 1. It is simple in design and construction 2. Water jackets, radiators, water pump, thermostat, pipes, hoses are not required. 3. It is more compact 4. Lighter in weight
Disadvantages: 1. There is uneven cooling of engine parts 2. Engine temperature is generally high during working period Air cooled engine
WATER COOLING SYSTEM Engines using water as cooling medium are called water cooled engines. Water is circulated round the cylinders to absorb heat from the cylinder walls. The heated water is conducted through a radiator to remove the heat and cool the water.
Methods of Water Cooling 1. Open jacket or hopper method 2. Thermo siphon method 3. Forced circulation method
1. Open Jacket Method There is a hopper or jacket containing water which surrounds the engine cylinder. So long as the hopper contains water the engine continues to operate satisfactorily. As soon as the water starts boiling it is replaced by cold water. The hopper is large enough to run for several hours without refilling. A drain plug is provided in a low accessible position for draining water as and when required.
2. Thermo Siphon Method It consists of a radiator, water jacket, fan, temperature gauge and hose connections. The system is based on the principle that heated water which surrounds the cylinder becomes lighter and it rises upwards in liquid column. Hot water goes to the radiator where it passes through tubes surrounded by air. Circulation of water takes place due to the reason that water jacket and radiator are connected at both sides i.e. at top and bottom. A fan is driven with the help of a V belt to suck air through tubes of the radiator unit, cooling radiator water. The disadvantage of the system is that circulation of water is greatly reduced by accumulation of scale or foreign matter in the passage and consequently causing overheating of the engine.
3. Forced Circulation System In this method, a water pump is used to force water from radiator to the water jacket of the engine. After circulating the entire run of water jacket, water comes back to the radiator where it loses its heat by the process of radiation. To maintain the correct engine temperature, a thermostat valve is placed at
the outer end of cylinder head. Cooling liquid is by-passed through the water jacket of th3e engine until the engine attains the desired temperature. The thermostat valve opens and the by-pass is closed, allowing the water to go to the radiator. The system consists of the following components: 1. Water pump 2. Radiator 3. Fan 4. Fan-belt 5. Water jacket 6. Thermostat valve 7. Temperature gauge 8. Hose pipe
Water Pump: It is a centrifugal pump. It draws the cooled water from bottom of the radiator and delivers it to the water jackets surrounding the engine.
Thermostat Valve: It is a control valve used in cooling system to control the flow of water when activated by a temperature signal.
Fan The fan is mounted on the water pump shaft. It is driven by the same belt that drives the pump and dynamo. The purpose of radiator is to provide strong draft of air through the radiator to improve engine cooling
Water jacket Water jackets are passages cored out around the engine cylinder as well as around the valve opening Forced Circulation cooling system- Water cooled engine
LUBRICATION IC engine is made of moving parts. Duo to continuous movement of two
metallic surfaces over each other, there is wearing of moving parts, generation of heat and loss of power in engine. Lubrication of moving parts is essential to prevent all these harmful effects.
Purpose of lubrication – 1. Reducing frictional effect 2. Cooling effect 3. Sealing effect 4. Cleaning effect
Types of Lubricants: Lubricants are obtained from animal fat, vegetables and minerals. Vegetable lubricants are obtained from seeds, fruits and plants. Cotton seed oil, olive oil, linseed oil, caster oil are used as lubricants. Mineral lubricants are most popular for engines and machines. It is obtained from crude petroleum found in nature.. Petroleum lubricants are less expensive and suitable for internal combustion engines.
Engine Lubrication System The lubricating system of an engine is an arrangement of mechanisms which maintains the supply of lubricating oil to the rubbing surfaces of an engine at correct pressure and temperature. The parts which require lubrication are 1. Cylinder walls and piston 2. Piston pin 3. Crankshaft and connecting rod bearings 4. Camshaft bearings 5. Valve operating mechanism 6. Cooling fan 7. Water pump and 8. Ignition mechanism
Types of Lubricating Systems 1. Splash system 2. Forced feed system
Splash Lubrication Splash lubrication is a method of applying lubricant, a compound that reduces friction, to parts of a machine. In the splash lubrication of an engine, dippers on the connecting-rod bearing caps are submerged in oil with every rotation. When the dippers emerge from the oil trough, the oil is splashed onto the cylinders and pistons, lubricating them. Experts agree that splash lubrication is suitable for small engines such as those used in lawnmowers and outboard boat motors, but not for automobile engines. This is because the amount of oil in the trough has a dramatic impact on how well the engine parts can be lubricated. If there is not enough oil, the amount splashed onto the machinery will be insufficient. Too much oil will cause excessive lubrication, which can also cause problems. Engines are often lubricated through a combination of splash lubrication and force feeding. In some cases, an oil pump keeps the trough full so that the engine bearings can always splash enough oil onto the other parts of the engine. As the engine speeds up, so does the oil pump, producing a stream of lubricant powerful enough to coat the dippers directly and ensure a sufficient splash. In other cases, the oil pump directs oil to the bearings. Holes drilled in the bearings allow it to flow to the crankshaft and connecting rod bearings, lubricating them in the process.
Combination Splash and Force Feed In a combination splash and force feed, oil is delivered to some parts by means of splashing and other parts through oil passages under pressure from the oil pump. The oil from the pump enters the oil galleries. From the oil galleries, it flows to the main bearings and camshaft bearings. The main bearings have oil-feed holes or grooves that feed oil into drilled passages in the crankshaft. The oil flows through these passages to the connecting rod bearings. From there, on some engines, it flows through holes drilled in the connecting rods to the piston-pin bearings. Cylinder walls are lubricated by splashing oil
thrown off from the connecting-rod bearings. Some engines use small troughs under each connecting rod that are kept full by small nozzles which deliver oil under pressure from the oil pump. These oil nozzles deliver an increasingly heavy stream as speed increases. At very high speeds these oil streams are powerful enough to strike the dippers directly. This causes a much heavier splash so that adequate lubrication of the pistons and the connecting-rod bearings is provided at higher speeds. If a combination system is used on an overhead valve engine, the upper valve train is lubricated by pressure from the pump.
Force-Feed A somewhat more complete pressurization of lubrication is achieved in the forcefeed lubrication system. Oil is forced by the oil pump from the crankcase to the main bearings and the camshaft bearings. Unlike the combination system the connecting-rod bearings are also fed oil under pressure from the pump. Oil passages are drilled in the crankshaft to lead oil to the connecting-rod bearings. The passages deliver oil from the main bearing journals to the rod bearing journals. In some engines, these opening are holes that line up once for every crankshaft revolution. In other engines, there are annular grooves in the main bearings through which oil can feed constantly into the hole in the crankshaft. The pressurized oil that lubricates the connecting-rod bearings goes on to lubricate the pistons and walls by squirting out through strategically drilled holes. This lubrication system is used in virtually all engines that are equipped with semi floating piston pins.
Full Force Feed In a full force-feed lubrication system, the main bearings, rod bearings, camshaft bearings, and the complete valve mechanism are lubricated by oil under pressure. In addition, the full force-feed lubrication system provides lubrication under pressure to the pistons and the piston pins. This is accomplished by holes drilled the length of the connecting rod, creating an oil passage from the connecting rod bearing to the piston pin bearing. This passage not only feeds the piston pin bearings but also provides lubrication for the pistons and cylinder walls. This system is used in virtually all engines that are equipped with full-floating piston pins.
Need of Lubrication System Lubrication is the admittance of oil between two surfaces having relative motion. The objects of lubrication may be one or more of the following: 1. To reduce motion between the parts having relative motion. 2. To reduce wear of the moving part. 3. To cool the surfaces by carrying away heat generated due to friction. 4. To seal a space adjoining the surfaces. 5. To absorb shocks between bearings and other parts and consequently reduce noise. 6. To remove dirt and grit that might have crept between the rubbing parts.
Additives in lubricating oil In addition to the viscosity index improvers, motor oil manufacturers often include other additives such as detergents and dispersants to help keep the engine clean by minimizing sludge buildup, corrosion inhibitors, and alkaline additives to neutralize acidic oxidation products of the oil. Most commercial oils have a minimal amount of zinc dialkyldithiophosphate as an anti-wear additive to protect contacting metal surfaces with zinc and other compounds in case of metal to metal contact. The quantity of zinc dialkyldithiophosphate is limited to minimize adverse effect on catalytic converters. Another aspect for aftertreatment devices is the deposition of oil ash, which increases the exhaust back pressure and reduces over time the fuel economy. The so-called "chemical box" limits today the concentrations of sulfur, ash and phosphorus (SAP). There are other additives available commercially which can be added to the oil by the user for purported additional benefit.
Gasoline and Diesel Additives Legislation is now restricting the use of organo-metallic compounds for improving the octane rating of gasoline. Consequently, they are not covered here, but a discussion of their use, the other additives that must be used in association with them, and the consequences of their withdrawal are discussed in Stone (1999). The most significant additives are detergents and antioxidants, but corrosion inhibitors, metal deactivators, biocides, anti-static additives demulsifiers, dyes and markers, and anti-icing additives also are used. These are discussed in detail by Owen and Coley (1995). Antioxidants are needed in gasoline to inhibit the formation of gum, which usually is associated with the unsaturated hydrocarbons in fuel. Formation of gum can interfere with the operation of fuel injectors. Detergents are added to reduce the deposits in fuel injectors, the inlet manifold, and the combustion chamber. Surfactants inhibit the formation of deposits in the injectors and the inlet manifold, but a different mechanism is needed to combat valve and port deposits because these deposits are associated with higher temperatures. High-boiling point, thermally stable, oily materials such as polybutene are used, and these appear to dissolve the deposits. 49 Diesel additives to improve the cetane number will be discussed
first, followed by additives to lower the cold filter plugging point temperature, then additives that are used with low sulfur fuels, and finally other additives. The most widely used ignition-improving additive currently is 2-ethyl hexyl nitrate (2EHN), because of its good response in a wide range of fuels and comparatively low cost (Thompson et al., 1997). Adding 1000 ppm of 2EHN will increase the cetane rating by approximately 5 units. In some parts of the world, legislation limits the nitrogen content of diesel fuels, because although the mass of nitrogen is negligible to that available from the air, fuel-bound nitrogen contributes disproportionately to nitric oxide formation. Under these circumstances, peroxides can be used, such as ditertiary butyl peroxide (Nandi and Jacobs, 1995). Diesel fuel contains molecules with approximately 12 to 22 carbon atoms, and many of the higher molar mass components (e.g., cetane, C16H34) would be solid at room temperature if they were not mixed with other hydrocarbons. Thus, when diesel fuel is cooled, a point will be reached at which the higher molar mass components will start to solidify and form a waxy precipitate. As little as 2% wax out of the solution can be enough to gel the remaining 98%. This will affect the pouring properties and (more seriously at a slightly higher temperature) block the filter in the fuel-injection system. These and other related low-temperature issues are discussed comprehensively by Owen and Coley (1995), who point out that as much as 20% of the diesel fuel can consist of higher molar mass alkanes. It would be undesirable to remove these alkanes because they have higher cetane ratings than many of the other components. Instead, use is made of anti-waxing additives that modify the shape of the wax crystals. Wax crystals tend to form as thin "plates" that can overlap and interlock. Anti-waxing additives do not prevent wax formation. They work by modifying the wax crystal shape to a dendritic (needle-like) form, and this reduces the tendency for the wax crystals to interlock. The crystals are still collected on the outside of the filter, but they do not block the passage of the liquid fuel. The anti-waxing additives in commercial use are copolymers of ethylene and vinyl acetate, or other alkene-ester copolymers. The performance of these additives varies with different fuels, and the improvement decreases as the dosage rate is increased. It is possible for 200 ppm of additive to reduce the cold filter plugging point (CFPP) temperature
by approximately 10 K. Additives can be used with low-sulfur diesel fuels to compensate for their lower lubricity, lower electrical conductivity, and reduced stability. To restore the lubricity of a low-sulfur fuel to that of a fuel with 0.2% sulfur by mass, then a dosage on the order of 100 mg/L is needed. Care is required in the selection of the additive, if it is not to interact unfavorably with other additives (Batt et al., 1996). Electrical conductivity usually is not subject to legislation, but if fuels have a very low conductivity, then there is the risk of a static electrical charge being built up. If a road tanker, previously filled with gasoline, is being filled with diesel, then there is the possibility of a flammable mixture being formed. The conductivity of untreated low-sulfur diesel fuels can be less than 5 pS/m (Merchant et al., 1997). Conductivities greater than 100 pS/m can be obtained by adding a few parts per million of a chromium-based static dispersant additive. Low-sulfur fuels and fuels that have been hydro-treated to reduce the aromatic content also are prone to the formation of hydroperoxides. These are known to degrade neoprene and nitrile rubbers, but this can be prevented by using antioxidants such as phenylenediamines (suitable only in low-sulfur fuels) or hindered phenols (Owen and Coley, 1995). Other additives used in diesel fuels are detergents, anti-ices, biocides, and anti-foamants. Detergents (e.g., amines and amides) are used to inhibit the formation of combustion deposits. Most significant are deposits around the injector nozzles, which interfere with the spray formation. Deposits then can lead to poor air-fuel mixing and particulate emissions. A typical dosage level is 100200 ppm. Anti-ices (e.g., alcohols or glycols) have a high affinity for water and are soluble in diesel fuel. Water is present through contamination and as a consequence of humid air above the fuel in vented tanks being cooled below its dewpoint temperature. If ice formed, it could block both fuel pipes and filters. Biocides act against anaerobic bacteria that can form growths at the wateddiesel interface in storage tanks. These are capable of blocking fuel filters. Anti-foamants (1 0-20 ppm silicone-based compounds) facilitate the rapid and complete filling of vehicle fuel tanks.
Valve Operating Systems In engines with overhead poppet valves (OHV-verhead valves), the camshaft is either mounted in the cylinder block, or in the cylinder head (OHCoverhead camshaft). Figure 2.21a shows an overhead valve engine in which the valves are operated from the camshaft, via cam followers, pushrods, and rocker arms. This is a cheap solution because the drive to the camshaft is simple (either gear or chain), and the machining is in the cylinder block. In a "V" engine, this arrangement is particularly suitable because a single camshaft can be mounted in the valley between the two cylinder banks. In overhead camshaft (OHC) engines (Fig. 2.2 lb), the camshaft can be mounted either directly over the valve stems, or it can be offset. When the camshaft is offset, the valves are operated by rockers, and the valve clearances can be adjusted by altering the pivot height or, as in the case of the exhaust valves in Fig. 2.21 b, different thickness shims can be used. For the inlet valves in Fig. 2.21b, the cam operates on a follower or "bucket." The clearance between the follower and the valve end is adjusted by a shim. Although this adjustment is more difficult than in systems using rockers, it is much less prone to change. The spring retainer is connected to the valve spindle by a tapered split collet. The valve guide is a press-fit into the cylinder head, so that it can be replaced when worn. Valve seat inserts are used, especially in engines with aluminum alloy cylinder heads, to ensure minimal wear. Normally, poppet valves rotate to even out any wear and to maintain good seating. This rotation can be promoted if the center of the cam is offset from the valve axis. Invariably, oil seals are placed at the top of the
valve guide to restrict the flow of oil into the cylinder. This is most significant with overhead cast-iron camshafts, which require a copious supply of lubricant. When the valves are not in line (b), it is more usual to use two camshafts because this gives more flexibility on valve timing and greater control if a variable valve timing system is to be used. The use of four valves per combustion chamber is quite common in highperformance spark ignition engines and is used increasingly in compression ignition engines. The advantages of four valves per combustion chamber are larger valve throat areas for gas flow, smaller valve forces, and a larger valve seat area. Smaller valve forces occur because a lighter valve with a less stiff spring can be used. This also will reduce the hammering effect on the valve seat when the valve closes. The larger valve seat area is important because this is how heat is transferred (intermittently) from the valve head to the cylinder head. In the case of diesel engines, four valves per cylinder allow the injector to be placed in the center of the combustion chamber, which facilitates the development of low-emission combustion systems. To reduce maintenance requirements, it is now common to use some form of
hydraulic lash adjuster (also known as a hydraulic lifter or tappet), an example of which is shown in Fig This consists of a pistonlcylinder arrangement that is pressurized by engine lubricant. However, when the cam starts to displace its follower, a sudden rise in pressure occurs in the lower oil chamber. This causes a check valve (a ball loaded by a weak spring) to close, so that the cam motion then is transmitted to the valve. There is always a small leakage flow from the lash adjuster so that the valve will always seat properly, even when there is a reduction
in the clearances within the valvetrain. The lash adjusters can be incorporated into the follower of the overhead valve arrangement (Fig.a) or the bucket tappet of Fig. b, or the pivot post of a cam-over-rocker system. A disadvantage of this simple substitution is an increase in frictional losses because the cam follower will always be loaded when sliding on the cam base circle. Friction can be reduced by using a roller follower on the rocker of the
system in Fig. 2.22, and this cam-over-rocker system also minimizes the mass of the moving valvetrain components. A hydraulic lash adjuster reduces the stiffness of the valvetrain, which will reduce the maximum speed limit for the valve gear. The drive to the camshaft usually is by chain or toothed belt. Gear drives also are possible but tend to be expensive, noisy, and cumbersome with overhead camshafts. The advantage of a toothed belt drive is that it can be mounted externally to the engine, and the rubber damps out torsional vibrations that otherwise might be troublesome. Antioxidants are needed in gasoline to inhibit the formation of gum, which usually is associated with the unsaturated hydrocarbons in fuel. Formation of gum can interfere with the operation of fuel injectors. Detergents are added to reduce the deposits in fuel injectors, the inlet manifold, and the combustion chamber. Surfactants inhibit the formation of deposits in the injectors and the inlet manifold, but a different mechanism is needed to combat valve and port deposits because these deposits are associated with higher temperatures. High-boiling point, thermally stable, oily materials such as polybutene are used, and these appear to dissolve the deposits. 49 Diesel additives to improve the cetane number will be discussed first, followed by additives to lower the cold filter plugging point temperature, then additives that are used with low sulfur fuels, and finally other additives. The most widely used ignition-improving additive currently is 2-ethyl hexyl nitrate (2EHN), because of its good response in a wide range of fuels and comparatively low cost (Thompson et al., 1997). Adding 1000 ppm of 2EHN will increase the cetane rating by approximately 5 units. In some parts of the world, legislation limits the nitrogen content of diesel fuels, because although the mass of nitrogen is negligible to that available from the air, fuel-bound nitrogen contributes disproportionately to nitric oxide formation. Under these circumstances, peroxides can be used, such as ditertiary butyl peroxide (Nandi and Jacobs, 1995). Diesel fuel contains molecules with approximately 12 to 22 carbon atoms, and many of the higher molar mass components (e.g., cetane, C16H34) would be solid at room temperature if they were not mixed with other hydrocarbons. Thus, when diesel fuel is cooled, a point will be reached at
which the higher molar mass components will start to solidify and form a waxy precipitate. As little as 2% wax out of the solution can be enough to gel the remaining 98%. This will affect the pouring properties and (more seriously at a slightly higher temperature) block the filter in the fuel-injection system. These and other related low-temperature issues are discussed comprehensively by Owen and Coley (1995), who point out that as much as 20% of the diesel fuel can consist of higher molar mass alkanes. It would be undesirable to remove these alkanes because they have higher cetane ratings than many of the other components. Instead, use is made of anti-waxing additives that modify the shape of the wax crystals. Wax crystals tend to form as thin "plates" that can overlap and interlock. Anti-waxing additives do not prevent wax formation. They work by modifying the wax crystal shape to a dendritic (needle-like) form, and this reduces the tendency for the wax crystals to interlock. The crystals are still collected on the outside of the filter, but they do not block the passage of the liquid fuel. The anti-waxing additives in commercial use are copolymers of ethylene and vinyl acetate, or other alkene-ester copolymers. The performance of these additives varies with different fuels, and the improvement decreases as the dosage rate is increased. It is possible for 200 ppm of additive to reduce the cold filter plugging point (CFPP) temperature by approximately 10 K. Additives can be used with low-sulfur diesel fuels to compensate for their lower lubricity, lower electrical conductivity, and reduced stability. To restore the lubricity of a low-sulfur fuel to that of a fuel with 0.2% sulfur by mass, then a dosage on the order of 100 mg/L is needed. Care is required in the selection of the additive, if it is not to interact unfavorably with other additives (Batt et al., 1996). Electrical conductivity usually is not subject to legislation, but if fuels have a very low conductivity, then there is the risk of a static electrical charge being built up. If a road tanker, previously filled with gasoline, is being filled with diesel, then there is the possibility of a flammable mixture being formed. The conductivity of untreated low-sulfur diesel fuels can be less than 5 pS/m (Merchant et al., 1997). Conductivities greater than 100 pS/m can be obtained by adding a few parts per million of a chromium-based static dispersant additive. Low-sulfur fuels and fuels that have been hydro-treated to reduce the aromatic content also are prone to the formation of hydroperoxides. These
are known to degrade neoprene and nitrile rubbers, but this can be prevented by using antioxidants such as phenylenediamines (suitable only in low-sulfur fuels) or hindered phenols (Owen and Coley, 1995). Other additives used in diesel fuels are detergents, anti-ices, biocides, and anti-foamants. Detergents (e.g., amines and amides) are used to inhibit the formation of combustion deposits. Most significant are deposits around the injector nozzles, which interfere with the spray formation. Deposits then can lead to poor air-fuel mixing and particulate emissions. A typical dosage level is 100200 ppm. Anti-ices (e.g., alcohols or glycols) have a high affinity for water and are soluble in diesel fuel. Water is present through contamination and as a consequence of humid air above the fuel in vented tanks being cooled below its dewpoint temperature. If ice formed, it could block both fuel pipes and filters. Biocides act against anaerobic bacteria that can form growths at the wateddiesel interface in storage tanks. These are capable of blocking fuel filters. Anti-foamants (1 0-20 ppm silicone-based compounds) facilitate the rapid and complete filling of vehicle fuel tanks.
Anti-Friction Bearings Anti-friction bearings, also called rolling contact bearings, are not widely used in the engine proper. They are used more prevalently in the transmission and drivetrain. Nonetheless, they are found in several engine components such as alternators and water pumps. Their primary function is to support a rotating shaft. Figure 5.1 shows a selection of types of anti-friction bearings.
Anti-friction bearings offer very low coefficients of friction. Furthermore, some types are able tosupport axial (thrust) loads in addition to the radial, or shaft, loads. Deep groove ball bearings can support small thrust loads. Tapered roller bearings are specifically designed to support significant thrust loads; hence, they are used as wheel bearings. The rollers or balls are made of hardened, high carbon chromium alloy steels, and their construction is somewhat complicated. Furthermore, these bearings do not handle shock loads very well, and their performance is greatly reduced by the presence of dirt. Thus, anti-friction bearings must be well sealed to keep in the lubricant and keep out dirt and other contaminants.
Straight-Tooth Spur & Helical Spur Gears Figure shows an example of this type of gear. Straight-tooth spur gears have straight teeth parallel to the axis of rotation. When the teeth engage, they do so instantaneously along the tooth face. This sudden meshing results in high impact stresses and noise. Thus, these gears have been replaced with helical gears in most transmissions. However, these gears do not generate axial (or thrust) loads along the shaft axis. Furthermore, they are easier to manufacture and can transmit high torque loads. For these reasons, many transmissions use spur gears for first and reverse gears. This accounts for the distinctive "whine" when a car is reversed rapidly.
Helical Spur Gears Figure shows an example of a helical gear. Helical gears have teeth that are cut in the form of a helix on a cylindrical surface. As the teeth begin to mesh, contact begins at the leading edge of the tooth and progresses across the tooth face. Although this greatly reduces the impact load and noise, it generates a thrust load that must be absorbed at the end of the shaft by a suitable bearing.
Straight-Tooth Hypoid Gears
Straight-Tooth Bevel Gears Transmissions and Driveline These gears, shown in Fig. 6.11, have straight teeth cut on a conical surface. They are used to transmit power between shafts that intersect but are not parallel. They are used in differentials. Similar to straight-tooth spur gears, they will be noisy. However, in the differential, they rotate only when the axles are rotating at different speeds.
Spiral Bevel Gears These gears have teeth cut in the shape of a helix on a conical surface. They can be used for final drives to connect intersecting shafts.
Hypoid Gears These gears have helical teeth cut on a hyperbolic surface. They are used in final drives to connect shafts that are neither parallel nor intersecting. These gears have high tooth loads and must be lubricated with special heavy-duty hypoid gear oil because greater sliding occurs between the teeth. The sliding increases with the amount of offset between the shaft axes. With zero offset, a spiral bevel gear results, whereas the maximum offset corresponds to a worm/wheel configuration. Despite having a lower efficiency than spiral bevel gears, hypoid gears allow the driveshaft to be lowered, thereby requiring a smaller "transmission tunnel" in the body.
Four-wheel Drive (4WD) and All-Wheel Drive (AWD) A vehicle that provides power to all four wheels has some key advantages in slippery or rough terrain. First and foremost, four-wheel drive (4WD) enables the vehicle to move under conditions of reduced traction. What is lost on many drivers is that four-wheel drive does not enable the vehicle to stop more rapidly, evidence of this being commonly seen in the mountainous states of the western United States. Nevertheless, the U.S. market has seen an explosion in the sale of four-wheel-drive sport utility vehicles (SUVs). Several automakers also have successfully marketed all-wheel-drive (AWD) vehicles, most notably Subaru and Audi. Furthermore, there is a vast array of adjectives used to define the systems, including part-time four-wheel drive, full-time four-wheel drive, all-wheel drive, and so forth. The differences among these systems often owe more to marketing than engineering. Adding to the confusion is the fact that the automakers themselves use various terms for their systems, often meaning something quite different to a competitor. In short, any attempt to classify four- or all-wheel drive systems invariably will meet with exceptions to the classification. This work will classify these systems into three broad categories: part-time four-wheel drive, full-time fourwheeldrive. and all-wheel drive.
Part-Time Four-wheel Drive (4WD) The key feature of a part-time four-wheel-drive system is the inclusion of a separate transfer case aft of the transmission. This is the lowest cost option and can be considered the first-generation option. It is called part-time because it can be used only in conditions that will allow for wheel slip, such as dirt roads, full snow coverage, and so forth. The reason for this is that there is no mechanism to eliminate driveline wind-up. Recall that a differential is used at the rear axle to allow differences in wheel rotation while the vehicle is cornering. With four-wheel drive, the same thing is happening with the front axle and the rear axle. One is traveling faster than the other; therefore, something must allow for the speed difference. In the absence of a center differential, the only mechanism allowing wheel speed variation is for the wheel to break free at the contact patch. Because this requires large forces on dry pavement, the part-time system cannot be used
on dry pavement without serious drivetrain damage.
The transfer case also incorporates two selectable gear ratios-low and high. In four-wheel drive low, the vehicle has a limited top speed. However, because of the large gear ratio in low, the vehicle has a large amount of torque available at the drive wheels to enable the driver to extricate the vehicle from difficult situations. Transmissions and Driveline The other feature of this system is that'the front hubs usually are locked manually. In twowheel drive, the front wheels spin freely around the spindles. When the driver desires fourwheel drive, the hubs must be locked manually onto the drive spindles for torque to be applied through the front wheels. The Isuzu Rodeo, Ford Bronco, and Dodge Ram all have part-time four-wheel drive.
On-Demand Four-Wheel Drive (4WD) This is the next option in terms of increasing convenience and cost. An open differential is incorporated between the front and rear axles. The open differential absorbs shaft speed variations between the front and rear output shafts. However, being an open differential, it sends torque to the axle with least resistance. This system allows driving in four-wheel drive on dry pavement, but this will decrease the fuel economy of the vehicle. For this reason, it is referred to as on-demand. The driver may use two-wheel drive
when there is no need for fourwheel drive. This system also will have automatic locking hubs that are either vacuum operated or electrically operated, saving the driver from a trip out of the cab in inclement weather to lock the hubs. Often "on-demand" (a configuration) is confused with "shifton-the-fly" (an engagement method). The Chevrolet Blazer is an example of a vehicle with on-demand fourwheel drive.
Full-Time Four-Wheel Drive (4WD) This is the highest cost option. This system has differentials everywhere, at both front and rear axles and in the transfer case. This allows the vehicle to be in four-wheel drive on dry pavement. The system allows for slip, but something had to be done about situations of very low traction-that is, the open differentials would send torque to the wheel with the least traction. Some vehicles, most notably the AM General Hummer, can lock all of the differentials. Other vehicles, such as the 1995 Jeep Grand Cherokee, have a viscous coupling that transmits power from the wheels that slip to the wheels that grip. In this category, the distinction between four-wheel drive and allwheel drive begins to blur. For the purposes of this work, full-time fourwheel drive is applied to vehicles that still require the driver to select the four-wheel-drive option.
All-Wheel Drive (AWD) For the purposes of this work, an all-wheel drive vehicle does not have a selectable transfer case. Generally, these vehicles are not intended for offroad use, but use four-wheel drive for inherent stability. Usually, they use
viscous couplings to send power from the spinning wheels to the gripping wheels. The system operates automatically and requires no driver intervention. This system also is used on high-performance cars to eliminate wheel spin caused by the enormous torque generated at the rear wheels.
Steering Mechanisms The fundamental problem in steering is to enable the vehicle to traverse an arc such that all four wheels travel about the identical center point. In the days of horse-drawn carriages, this was accomplished with the fifth-wheel system depicted in Fig.
Although this system worked well for carriages, it soon proved unsuitable for automobiles. In addition to the high forces required of the driver to rotate the entire front axle, the system proved unstable, especially as vehicle speeds increased. The solution to this problem was developed by a German engineer named Lankensperger in 18 17. Lankensperger had an inherent distrust of the German government, so he hired an agent in England to patent his idea. His chosen agent was a lawyer named Rudolph Ackerman. The lawyer secured the patent, but the system became known as the Ackerman system.
Figure depicts the key features of this system. The end of each axle has a spindle that pivots around a kingpin. The linkages connecting the spindles form a trapezoid, with the base of the trapezoid formed by the rack and tie rods. The distance between the tie rod ends is less than the distance between the kingpins. The wheels are parallel to each other when they are in the straight-ahead position. However, when the wheels are turned, the inner wheel turns through a greater angle than the outer wheel. Figure 7.2 also shows that the layout is governed by the ratio of track (distance between the wheels) to wheelbase (distance between front and rear wheels). The Ackerman layout is accurate only in three positions: straight ahead, and at one position in each direction. The slight errors present in other positions are compensated for by the deflection of the pneumatic tires. For the purposes of this book, "steering mechanism" refers to those components required to realize the Ackerman system. Of course, all vehicles today use a steering wheel as the interface between the system and driver. (This has not always been the case. Early automobiles used a tiller.) The steering wheel rotates a column, and this column is the input to the steering mechanism. These mechanisms can be broadly grouped into two categories: (I) worm-type mechanisms, and (2) rack and pinion mechanisms.
Worm Systems The steering linkages required by worm gear steering systems. The Pitman arm converts the rotational motion of the steering box output into side-to-side motion of the center link. The center link is tied to the steering arms by the tie rods, and the side-to-side motion causes the spindles to pivot around their
respective steering axes (kingpins). To achieve Ackerman steering, the fourbar linkages must form a trapezoid instead of a parallelogram. Although all worm-type steering systems use linkages similar to these, the specifics of the steering boxes differ and are explained next.
Worm and Sector The shaft to the Pitman arm is connected to a gear that meshes with a worm gear on the steering column. Because the Pitrnan shaft gear needs to rotate through only approximately 70°, only a sector of the gear is actually used. The worm gear is assembled on tapered roller bearings to absorb some thrust load, and an adjusting nut is provided to regulate the amount of end-play in the worm.
Worm and Roller The worm and roller system is very similar to the worm and sector system. In this case, a roller is supported by ball bearings within the sector on the Pitman shaft. The bearings reduce sliding friction between the worm and sector. The worm also can be shaped similarly to an hourglass, that is, tapered from each end to the center. This provides better contact between the worm and the roller, as well as a variable steering ratio. When the wheels are at the center (straight-ahead) position, the steering reduction ratio is high to provide better control. As the wheels are turned farther off-center, the ratio lowers. This gives better maneuverability during low-speed maneuvers such as parking.
Recirculating Ball The recirculating ball system, another form of worm and nut system. In this system, a nut is meshed onto the worm gear by means of a continuous row of ball bearings. As the worm turns, the nut moves up and down the worm threads. The ball bearings not only reduce the friction between the worm and nut, but they greatly reduce the wear because the balls continually recirculate through the system, thereby preventing any one area from bearing the brunt of the wear. The primary advantage of all worm-type steering systems is reduced steering effort on the part of the driver. However, due to the worm gear, the driver receives no feedback from the wheels. For these reasons, worm-type steering systems are found primarily on large vehicles such as luxury cars, sport utility vehicles, pickup trucks, and commercial vehicles.
Rack and Pinion Steering The rack and pinion steering system is simpler, lighter, and generally cheaper than worm-type systems (Fig. 7.7). The steering column rotates a pinion gear that is meshed to a rack. The rack converts the rotary motion directly to sideto-side motion and is connected to the tie rods. The tie rods cause the wheels to pivot about the kingpins, thus turning the front wheels.
Rack and pinion systems have the advantage of providing feedback to the driver. Furthermore, rack and pinion systems tend to be more responsive to driver input, and for this reason, rack and pinion steering is found on most small and sports cars.
Wheel Alignment In addition to allowing the vehicle to be turned, the steering system must be set up to allow the vehicle to track straight ahead without steering input from the driver. Thus, an important design factor for the vehicle is the wheel alignment. Four parameters are set by the designer, and these must be checked regularly to ensure they are within the original vehicle specifications. The four parameters discussed here are as follows: 1. Camber 2. Steering axis inclination (SAI) 3. Toe 4. Caster
Camber Camber is the angle of the tire/wheel with respect to the vertical as viewed from the front of the vehicle. Camber angles usually are very small, on the order of 1 "; the camber angles shown in Fig. are exaggerated. Positive camber is defined as the top of the wheel being tilted away from the vehicle, whereas negative camber tilts the top of the wheel toward the vehicle. Most vehicles use a small amount of positive camber, for reasons that will be discussed in the next section. However, some off-road vehicles and race cars have zero or slightly negative camber.
Steering Axis Inclination (SAI) Steering axis inclination (SAI) is the angle from the vertical defined by the centerline passing through the upper and lower ball joints. Usually, the upper ball joint is closer to the vehicle centerline than the lower.
the advantage of combining positive camber with an inclined steering axis. If a vertical steering axis is combined with zero camber (left side of Fig.), any steering input requires the wheel to scrub in an arc around the steering axis. In addition to increasing driver effort, it causes increased tire wear. The combination of SAI and positive camber reduces the scrub radius (right side of Fig.). This reduces driver effort under low-speed turning conditions and minimizes tire wear. An additional benefit of this system is that the wheel arc is no longer parallel to the ground. Any turning of the wheel away from straight ahead causes it to arc toward the ground. Because the ground is not movable, this causes the front of the vehicle to be raised. This is not the minimum potential energy position for the vehicle; thus, the weight of the vehicle tends to turn the wheel back to the straight ahead position. This phenomenon is very evident on most vehicles-merely turning the steering wheel to full lock while the vehicle is standing still will make the front end of the vehicle rise visibly. Although the stationary the weight of the vehicle may not be sufficient to rotate the wheels back to the straight-ahead position, as soon as the vehicle begins to move, the wheels will return to the straightahead position without driver input. Caster angle also contributes to this selfaligning torque. Note that the diagrams in the preceding figures have been simplified to facilitate discussion. In practice, the wheel is dished so that the
scrub radius is further reduced.
Toe & Caster Toe Toe is defined as the difference of the distance between the leading edge of the wheels and the distance between the trailing edge of the wheels when viewed from above. Toe-in means the front of the wheels are closer than the rear; toe-out implies the opposite.
For a rear-wheel-drive vehicle, the front wheels normally have a slight amount of toe-in. When the vehicle begins to roll, rolling resistance produces a force through the tire contact patch perpendicular to the rolling axis. Due to the existence of the scrub radius, this force produces a torque around the steering axis that tends to cause the wheels to toe-out. The slight toe-in allows for this, and when rolling, the wheels align along the axis of the vehicle. Conversely, front-wheel-drive vehicles require slight toeout. In this case, the tractive force of the front wheels produces a moment about the steering axis that tends to toe the wheels inward. In this case, proper toe-out absorbs this motion and allows the wheels to parallel the direction of motion of the vehicle.
Caster Caster is the angle of the steering axis from the vertical as viewed from the side. Positive caster is defined as the steering axis inclined toward the rear of the vehicle.
With positive caster, the tire contact patch is aft of the intersection of the steering axis and the ground. This is a desirable feature for stability. When the wheel is turned, the cornering force acts perpendicular to the wheel axis and through the contact patch. This creates a torque about the steering axis that acts to center the wheel. Obviously, negative caster results in the opposite effect, and the wheel would tend to continue turning about the steering axis. The most common example of positive caster is a shopping cart. The wheels are free to turn around the steering axis, and when the cart is pushed straight ahead, the wheels self-align to the straight-ahead position.
Effect Of Improper Alignment On Vehicle
Vehicle Rollover One aspect of cornering behavior that can be terrifying for a driver is vehicle rollover. Rollover is defined as the vehicle rotating 90' or more about its longitudinal axis (Gillespie, 1994) and can be caused by many factors. It can occur on a level surface if the tires can generate sufficient cornering force that the vehicle rolls before it slips. Any cross slope of the road also will excite (or inhibit) rollover. The most frequent cause of rollover is a skidding vehicle coming into contact with a surface irregularity such as a curb, dirt shoulder, or similar situation. The process is influenced by a large number of complex phenomena, and a detailed analysis goes beyond the scope of an introductory text. Nevertheless, some simple models exist that can aid one's understanding of vehicle rollover.
Hotchkiss Suspensions The Hotchkiss drive was used extensively on passenger cars through the 1960s and is shown in Fig. 8.26. The system consists of a longitudinal driveshaft connected to a center differential by U-joints. The solid axle is mounted to the frame by longitudinally mounted leaf springs. Although the Hotchkiss suspension is simple, reliable, and rugged, it has been superseded by other designs for several reasons. First, as designers sought better ride qualities, the spring rates on the leaf springs dropped. This led to lateral stability difficulties because softening leaf springs requires that they be longer. Second, the longer leaf springs were susceptible to wind-up, especially as braking power and engine power began to rise. Finally, as frontwheel-drive cars became more prevalent, rear-wheel-drive cars were forced to adopt independent rear suspensions to attain similar ride and handling qualities. Nevertheless, the Hotchkiss drive is still used on many four-wheel-drive trucks and SUVs at both ends of the vehicle. One disadvantage of this suspension is that the stocky axles and differential contribute to a relatively large unsprung mass.
Disc Brakes Although drum brakes have the advantages of self-energization and ease of parking brake incorporation, they suffer from several disadvantages. Their heat dissipation is problematic, and drum brakes are prone to brake fade as the drum becomes hot due to extended or frequent heavy braking. Also, drum brakes are very sensitive to moisture or contamination inside the drum. Any water in the drum rapidly vaporizes under braking, causing the coefficient of friction of the shoe to become nearly zero. On the other hand, disc brakes do not suffer these handicaps. The rotors can be vented to aid heat dissipation, and any water or contamination of the rotor is quickly removed by the scraping action of the pads. Figure 9.14 shows a typical disc brake system.
Disc Brake Components Brake Disc The brake disc, also called the rotor, is connected to the wheel hub. The rotor provides the friction surface for the pads, thus generating the braking torque. Rotors usually are vented to aid in the dissipation of heat. Some rotors also are cross drilled to save weight. High-performance brakes now are using carbon fiber as a rotor material. Carbon fiber provides good, fade-free performance when the material has been heated. Many Formula 1 teams use carbon fiber brakes, and the driver must ride the brake during the warm-up laps to bring them up to operating temperature. The performance of these brakes under such demanding conditions is attested to by the fact that the rotors often glow red hot after the brakes have been applied during a race. The wheels are connected to the rotor by the lugs.
Brake Pads The brake pads, consist of a stamped steel backing plate to which the friction material is attached. The material, also called the lining, may be bonded to the plate with adhesive, or it may be riveted. Most disc brakes also contain a wear indicator. This indicator is a small tab of spring steel, the edge of which is set to a predetermined height below the surface of the new pad. When the pad wears to the point where it should be replaced, the spring steel begins to rub on the rotor when the brakes are applied. This produces an irritating squeal that is intended to motivate the driver to have the brake pads replaced. Should the driver ignore the warning, the brakes will continue to function to the point where no lining material remains. The author has had the experience of a fairly new disc brake pad disintegrating during a stop. During the subsequent trip home, the rivet heads remaining on the backing plate
provided more than adequate stopping power, although at great damage to the rotor.
Caliper The brake caliper houses the pistons, and these pistons apply the activation force to the brake pads. The caliper may house as few as one or as many as six pistons, depending on the specific vehicle in question. Calipers fall into two categories: (1) fixed, or (2) floating.
Lead-Acid Batteries Lead-acid batteries are currently used in commercially available electric vehicles (EVs). Despite continuous development since 1859, the possibility of further development still exists to increase the specific power and energy. Lead-acid batteries are selected for their low cost, high reliability, and an established recycling infrastructure. However, problems including low energy density, poor cold-temperature performance, and low cycle life limit their desirability. The lead-acid cell consists of a metallic lead anode and a lead oxide (Pb02) cathode held in a sulfuric acid (H2S04) and water electrolyte. The discharge of the battery is through the chemical reaction The electron transfer between the lead and the sulfuric acid is passed through an external electrical connection, thus creating a current. In recharging the cell, the reaction is reversed. Lead-acid batteries have been used as car batteries for many years and can be regarded as a mature technology. The lead-acid battery is suited to traction application because it is capable of a high power output. However, due to the relatively low energy density, leadacid batteries become large and heavy to meet the energy storage requirements
Nickel-Cadmium (NiCd) Batteries Nickel-cadmium (NiCd) batteries are used routinely in communication and medical equipment and offer reasonable energy and power capabilities. They have a longer cycle life than lead-acid batteries and can be recharged quickly. The battery has been used successfully in developmental EVs. The main problems with nickel-cadmium batteries are high raw-material costs, recyclability, the toxicity of cadmium, and temperature limitations on recharging. Their performance does not appear to be significantly better than that of lead-acid batteries, and the energy storage can be compromised by partial discharges-referred to as memory effects.
Nickel-Metal Hydride (NiMH) Batteries Nickel-metal hydride (NiMH) batteries currently are used in computers, medical equipment, and other applications. They have greater specific energy and specific power capabilities than lead-acid or nickel-cadmium batteries, but they are more expensive. The components are recyclable, so the main challenges with nickel-metal hydride batteries are their high cost, the high temperature they create during charging, the need to control hydrogen loss, their poor charge retention, and their low cell efficiency. Metal hydrides have been developed for high hydrogen storage densities and can be incorporated directly as a negative electrode, with a nickel hydroxyoxide (NiOOH) positive electrode and a potassium/lithium hydroxide electrolyte. The electrolyte and positive electrode had been extensively developed for use in nickel-cadmium cells. The electrochemical reaction is During discharge, hydroxyl (OH-) ions are generated at the nickel hydroxyoxide positive electrode and consumed at the metal hydride negative electrode. The converse is true for water molecules, which means that the overall concentration of the electrolyte does not vary during chargingldischarging. There are local variations, and care must be taken to ensure that the flow of ions across the separator is high enough to prevent the electrolyte "drying out" locally. The conductivity of the electrolyte remains constant through the chargeldischarge cycle because the concentration remains constant. In addition, there is no loss of structural material from the electrodes; thus, they do not change their electrical characteristics. These two details give the cell very stable voltage operating characteristics over almost the full range of charge and discharge.
Lithium Ion Batteries
The best prospects for future electric and hybrid electric vehicle battery technology probably come from lithium battery chemistries. Lithium is the lightest and most reactive of the metals, and its ionic structure means that it freely gives up one of its three electrons to produce an electric current. Several types of lithium chemistry batteries are being developed. The two most promising of these appear to be the lithium ion (Li-ion) type and a further enhancement of this, the lithium polymer type. The Li-ion battery construction is similar to that of other batteries except for the lack of any rare earth metals that are a major environmental problem when disposal or recycling of the batteries becomes necessary. The battery discharges by the passage of electrons from the lithiated metal oxide to the carbonaceous anode by current flowing via the external electrical circuit. Liion represents a general principle, not a particular system. For example, lithium/aluminium /iron sulphide has been used for vehicle batteries. Li-ion batteries have a very linear discharge characteristic, and this facilitates monitoring the state of charge. The charge/discharge efficiency of Li-ion batteries is approximately 80%, which compares favorably with nickelcadmium batteries (approximately 65%) but unfavourably with nickel-metal hydride batteries (approximately 90%). Although the materials used are nontoxic, a concern with the use of lithium is, of course, its flammability. Lithium polymer batteries use a solid polymer electrolyte, and the battery can be constructed similar to a capacitor, by rolling up the anode. polymer electrode, composite cathode, current collector from the cathode, and insulator. This results in a large surface area for the electrodes (to give a high current density) and a low ohmic loss.
Dual Hybrid Systems If the parallel system is modified by the addition of a second electrical machine (which is equivalent to adding a mechanical power transmission route to the series system), the result is a system that allows transmission of the prime mover power through two parallel routes: (1) electrically, and (2) mechanically. This is equivalent to the use of a mechanical shunt transmission with a continuously variable transmission (CVT) to give an infinitely variable transmission (IVT) (Ironside and Stubbs, 198 1). The result is a transmission that enables the engine to operate at a high efficiency for a wider range of vehicle operating points. A well-documented example of this configuration is the "dual" hybrid system developed by Equos Research (Yamaguchi et al., 1996) and used in the Toyota Prius. Figure below shows this system.
The planetary gears act as a "torque divider," sending a proportion of the engine power mechanically to the wheels and driving an electric machine (M 1) with the remainder. Consequently, the configuration acts simultaneously as a parallel and a series hybrid. Engine speed is controlled using Machine 1, removing the need for a transmission, a clutch, or a starter motor. Machine 2 acts in the same way as the motor in a parallel system, supplementing or absorbing torque as required. The diagrams below show the possible modes of operation, and each mode is explained next.
Electric Mode. (a) The engine is switched off, and Machine 1 acts as a "virtual clutch," keeping the engine speed at zero. Torque and regenerative braking are provided by Machine 2. Parallel Mode. (b) Machine 1 is stationary (perhaps with a brake applied), and the configuration is a simple parallel one, with a fixed engine-to-road gear ratio. Charging Mode. (c) The vehicle is stationary, and all of the engine power is used to drive Machine 1 and charge the batteries. Torque is still transferred to the wheels, allowing the car to "creep." Dual Mode. (d) Some power is used to drive the wheels directly, while the remainder powers Machine 1. The speed of Machine 1 determines the engine operating speed. The charging and parallel modes are effectively subsets of the dual mode, and this continuity in control is the real strength of the configuration. The dual
hybrid configuration combines the advantages of both series and parallel, as follows: Optimal engine operating point at all times. Much of the power (especially at cruising speeds) is delivered mechanically to the wheels, thereby increasing efficiency. Charging is possible, even when the vehicle is stationary. The combined torque of the engine and Machine 2 is available, improving performance. Compared to a series hybrid (where the electrical machines must be rated for the prime mover and the vehicle power requirement), only a fraction of the prime mover power is transmitted electrically in the dual hybrid system. The main difficulty with the dual hybrid is in the design of a control system, which must resolve the two degrees of freedom (engine speed and engine torque) and the associated transients into an optimal and robust control strategy. System modeling is essential for optimizing this.
The tire’s INNERLINER -- keeps air inside the tire. The CASING (or CARCASS) – the internal substructure of the tire. The tire’s BEAD -- assures an airtight fit with the wheel and efficient transfer of forces from the wheel to the carcass of the tire. BEAD FILLER – reduces flex and aids in deflection. A Tire’s BODY PLIES – withstands the forces of the tire’s inflation pressure, provides the mechanical link from the from the wheel movement to the tread are and flexibility to supplement the vehicle’s suspension system. The SIDEWALL -- protects the side of the tire from road and curb attack from atmospheric degradation. A tire’s BELTS -- stabilize and strengthen the tread, allowing forces to be efficiently transferred to thetread area. Its BELT EDGE INSULATION – helps to reduce friction. The TREAD -- provides the frictional coupling to the road surface to generate traction and steering Forces.
Ribs are a pattern that includes grooves around the tire in the direction of rotation. Lugs are the sections of rubber that make contact with the terrain. Tread blocks are raised rubber compound segments on the outside visible part of a tire. Sipes are small lateral cuts made in the surface of the tread to improve traction. Kerfs are shallow slits molded into the tire tread for added traction – this term often used interchangeably with sipes. Grooves are circumferential or lateral channels between adjacent tread ribs or tread blocks. Shoulder blocks are the tread elements of segments on the tire tread nearest to the sidewall. Voids are the spaces that are located between the lugs.
It has already been reported how stoichiometric operation compromises the efficiency of engines, but that for control of NOx, it is necessary to operate either at stoichiometric or sufficiently weak (say, an equivalence ratio of O.6), such that there is no need for NOx reduction in the catalyst. If a system can be devised for NOx to be reduced in an oxidizing environment, this gives scope to operate the engine at a higher efficiency. A number of technologies are being developed for "DENOx," some of which are more suitable for diesel engines than spark ignition engines. The different systems are designated active or passive (passive being when nothing must be added to the exhaust gases). The systems are as follows:
Selective Catalytic Reduction (SCR). In this technique, ammonia (NH3) or urea (CO(NH&) is added to the exhaust stream. This is likely to be more suited to stationary engine applications. Conversion efficiencies of up to 80% are quoted, but the NO level must be known, because if too much reductant is added, ammonia would be emitted.
Passive DENOx. These use the hydrocarbons present in the exhaust to chemically reduce the NO. There is a narrow temperature window (in the range 160-220°C [320- 428"FI for platinum catalysts) within which the competition for HC between oxygen and nitric oxide leads to a reduction in the NOx (Joccheim et al., 1996). The temperature range is a limitation and is more suited to diesel engine operation. More recent work with copperexchanged zeolite catalysts has shown them to be effective at higher temperatures. By modifying the zeolite chemistry, a peak NOx conversion efficiency of 40% has been achieved at 400°C (752°F) (Brogan et al., 1998).
Active DENOx Catalysts. These use the injection of fuel to reduce the NOx, and a reduction in NOx of approximately 20% is achievable with diesel-engined vehicles on typical drive cycles, but with a 1.5% increase in fuel consumption (Pouille et a]., 1998). Current systems inject fuel into the
exhaust system, but there is the possibility of late in-cylinder injection with future diesel engines.
NOx Trap Catalysts. In this technology (first developed by Toyota), a three-way catalyst is combined with a NOx-absorbing material to store the NOx when the engine is operating in lean-burn mode. When the engine operates under rich conditions, the NOx is released from the storage media and reduced in the three-way catalyst. NOx trap catalysts have barium carbonate deposits between the platinum and the alumina base. During lean operation, the nitric oxide and oxygen convert the barium carbonate to barium nitrate. A rich transient (approximately 5 s at an equivalence ratio of 1.4) is needed every five minutes or so, such that the carbon monoxide, unburned hydrocarbons, and hydrogen regenerate the barium nitrate to barium carbonate. The NOx that is released is then reduced by the partial products of combustion over the rhodium in the catalyst. Sulhr in the fuel causes the NOx trap to lose its effectiveness because of the formation of barium sulfate. However, operating the engine at high load to give an inlet temperature of 600°C (1 112"F), with an equivalence ratio of 1.05, for 600 s can be used to remove the sulfate deposits (Brogan et al., 1998)
Automobile History - Top 10 Interesting Facts 1. Adolf Hitler ordered Ferdinand Porsche to manufacture a Volkswagen, which literally means 'People's Car' in German. This car went on to become the Volkswagen Beetle.
2. In 1971, the cabinet of Prime Minister Indira Gandhi proposed the production of a 'People's Car' for India - the contract of which was given to Sanjay Gandhi. Before contacting Suzuki, Sanjay Gandhi held talks with Volkswagen AG for a possible joint venture, encompassing transfer of technology and joint production of the Indian version of the 'People's car', that would also mirror Volkswagen's global success with the Beetle. However, it was Suzuki that won the final contract since it was quicker in providing a feasible design. The resulting car was based on Suzuki's Model 796 and went on to rewrite automotive history in India as the Maruti 800. 3. Rolls-Royce Ltd. was essentially a car and airplane engine making company, established in 1906 by Charles Stewart Rolls and Frederick Henry Royce. The same year, Rolls-Royce rolled out its first car, the Silver Ghost. In 1907, the car set a record for traversing 24,000 kilometers during the Scottish reliability trials. 4. The most expensive car ever sold at a public auction was a 1954 MercedesBenz W196R Formula 1 race car, which went for a staggering $30 million at Bonhams in July 2013. The record was previously held by a 1957 Ferrari Testa Rossa Prototype, sold in California at an auction for $16.4 million.
5. As a young man, Henry Ford used to repair watches for his friends and family using tools he made himself. He used a corset stay as tweezers and a filed shingle nail as a screwdriver.
6.British luxury car marque Aston Martin's name came from one of the founders Lionel Martin who used to race at Aston Hill near Aston Clinton.
Difference between supercharging
A supercharger is an air compressor used for forced induction of an internal combustion engine. The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine. Supercharger allows more fuel to be burned and more work to be done per cycle, increasing the power output of the engine. Power for the unit can come mechanically by a belt, gear, shaft, or chain connected to the engine's crankshaft. A turbocharger or turbo is a centrifugal compressor powered by a turbine that is driven by an engine's exhaust gases. Its benefit lies with the compressor increasing the mass of air entering the engine (forced induction), thereby resulting in greater performance (for either, or both, power and efficiency). They are popularly used with internal combustion engines. Supercharging and turbocharging are similar in process and differ in operation, it means, both are used for same purpose i.e to increase engine power, efficiency, torque by compressing the air in multistage for increasing quantity of air, pressure and temperature. But the difference is , In turbocharging, the exhaust gases from the engine cylinder is used to drive the turbine. The turbine and compressor are mounted on the same shaft. When the exhaust gases are passed through turbine, the turbine rotates as the gases import heat energy, hence the turbine produces mechanical energy i.e rotation of shaft for driving compressor. Now the compressor also rotates to compress the inlet air to the cylinder. The inlet air is compressed before reaching engine cylinder. In supercharging, the rotation of crank shaft is used to drive the turbine through gears and chains or pulleys and belts. The turbine and compressor are mounted on the same shaft. When the crank shaft rotates, the shaft of the turbine also rotates since both are connected mechanically through gear and chain or pulley and belt arrangements. Hence the turbine produces mechanical energy i.e rotation of shaft for driving compressor.
Why diesel cannot be used in petrol engine? We know that, petrol is ignited by spark and diesel is ignited by compression ignition, the volatility of the petrol is greater than diesel. The spark plug produces the spark only at some places, not at all the point of air-fuel mixture. If the air-fuel mixture from the carburetor is completely vapourised the fire produced by the spark can penetrate throughout the mixture to burn all the mixture. Hence to produce the complete vapour of air-fuel mixture, the volatility of the fuel should be more. Since the volatility of the petrol is greater than diesel, if we use diesel on petrol engine, the carburetor cannot produce fine vapourised mixture of airdiesel due to low volatility of diesel, hence this improper mixture reaches the combustion chamber. Now at the end of the compression stroke the spark will be produced, this spark only will burn the diesel where it is produced, the rest of the mixture will not receive the enough heat from fire produced by the spark for burning and the mixture will remain as a unburnt mixture tend to various efficiency loss, this is due to the improper penetration of fire. The improper penetration of fire results from improper vapourisation of air-diesel mixture and it results from low volatility of diesel.This is the reason for Why diesel cannot be used in petrol engine?.
What is Scavenging? Scavenging is the process used in IC engines in which the burnt gases are forced or pushed to atmosphere from the engine cylinder by using the inlet pressure of fresh air.
Importance and Causes of Scavenging: If the burnt gases inside the engine cylinder are not completely exhausted, then the following incidents will happen: Already burnt gases will be compressed again during the compression stroke if they are left inside the cylinder. This causes the temperature of air fuel mixture to exceed the maximum temperature as the burnt gases have already some temperature because of burning. Because of this maximum temperature, the fuel can burn before the power stroke, so this tends to abnormal combustion. We know that, the abnormal combustion causes the knocking phenomenon.
Why petrol cannot be used in diesel engine? The fire point of the diesel is greater than petrol and compression ratio of diesel engine is greater than petrol engine. If we use petrol on the diesel engine, since diesel engine has greater compression ratio the air heated during the compression has temperature which is enough to burn the diesel, but here we use petrol, the petrol injected at the end of compression would burn immediately before the power stroke gets started unlike diesel to burn completely during power stroke. This due to excessive burning temperature of air for petrol, but for diesel it will be normal burning temperature. Hence piston can start to move to BDC before reaching the TDC during the compression stroke, this would reverse the engine and may cause engine vibration and noise. This is the reason for Why petrol cannot be used in diesel engine?.
Flywheel A flywheel is an inertial energy-storage device. It absorbs mechanical energy and serves as a reservoir, storing energy during the period when the supply of energy is more than the requirement and releases it during the period when the requirement of energy is more than the supply. Flywheels-Function need and Operation The main function of a fly wheel is to smoothen out variations in the speed of a shaft caused by torque fluctuations. If the source of the driving torque or load torque is fluctuating in nature, then a flywheel is usually called for. Many machines have load patterns that cause the torque time function to vary over the cycle. Internal combustion engines with one or two cylinders are a typical example. Piston compressors, punch presses, rock crushers etc. are the other systems that have fly wheel. Flywheel absorbs mechanical energy by increasing its angular velocity and delivers the stored energy by decreasing its velocity.
Design Approach There are two stages to the design of a flywheel. First, the amount of energy required for the desired degree of smoothening must be found and the (mass) moment of inertia needed to absorb that energy determined. Then flywheel geometry must be defined that caters the required moment of inertia in a reasonably sized package and is safe against failure at the designed speeds of operation.
Design Parameters Flywheel inertia (size) needed directly depends upon the acceptable changes in the speed.
Unmanned Aerial Vehicles
Unmanned Aerial Vehicles (UAVs) are expected to serve as aerial robotic vehicles to perform tasks on their own. Computer vision is applied in UAVs to improve their autonomies both in flight control and perception of environment around them. A survey of researches in such a field is presented. Based on images and videos captured by on-board camera(s), vision measures, such as stereo vision, optical flow fields etc. extract useful features which can be integrated with flight control system to form visual servoing. Aiming at the use of hand gestures for human- computer interaction, this paper presents a novel approach for hand gesture-based control of UAVs. The research was mainly focused on solving some of the most important problems that current HRI (Human-Robot Interaction) systems fight with. Presenting a simple approach to recognizing gestures through image processing techniques and web cameras, the problem of hand gestures recognition has been addressed using motion detection and algorithm based on histograms, which makes it efficient in unconstrained environments, easy to implement and fast enough. Highly flexible manufacturing (HFM) is a methodology that integrates vision and flexible robotic grasping.
The proposed set of hand grasping shapes presented here is based on the capabilities and mechanical constraints of the robotic hand. Pre-grasp shapes for a Barrett Hand are studied and defined using finger spread and flexion. In addition, a simple and efficient vision algorithm is used to servo the robot and to select the pre-grasp shape in the pick-and-place task of 9 different vehicle handle parts. Finally, experimental results evaluate the ability of the robotic hand to grasp both pliable and rigid parts and successfully control the UAV.
Visual Navigation: GPS and inertial sensors are typically combined to estimate UAV’s state and form a navigation solution. However, in some circumstances, such as urban or low altitude areas, GPS signal may be very weak or even lost. Under these situations, visual data can be used as an alternative or substitute to GPS measurements for the formulation of a navigation solution. This section describes vision-based UA V navigation. A. Autonomous Landing Autonomous landing is a crucial capability and requirement for UAV autonomous navigation. It gives basic idea and method for UA V autonomy. Generally, UAVs are classified into Vertical Take-Off and Landing (VTOL) UAVs and fixed-wing UAVs. As to VTOL UA V vision-based landing, Sharp et al. Designed a landing target with simple pattern, on which comer points can be easily detected and tracked. By tracking these comers, UAV could determine its relative position to landing target using computer vision method. Details are described as follows. Given the comer points, estimating the UA V state is an optimization problem. The equation relating a point in the landing pad coordinate frame to the image of that point in the camera frame is given by Geometry of the coordinate frames and Euclidean motions involved in the vision-based state estimation problem Fixed -wing UA V's autonomous landing is similar to that of VTOL in theory but more complicated in practice. Vision subsystem should recognize runway and keeps tracking on it during landing. Kalman filter is introduced to keep stability of tracking.Horizon also needs detecting. According to runway and horizon, vision subsystem could estimate UAV's state , I.e. location (x,y,z), attitude (pitch, roll, yaw) etc
Autonomous Refuelling The deployment of UAVs has been tested in overseas conflicts. People found
that one of the biggest limitations of UAVs is their limited range. To enlarge their range, UAVs are expected capable of Autonomous Aerial Refuelling (AAR). There are two ways for aerial refuelling, i.e. refuelling boom and "probe and drogue". Very similar to auto landing, vision -based method for UA V keeping pose and position to flying tanker during docking and refuelling receives great attention. AAR also needs considering some reference frames, such as UA V, tanker, camera frame etc. But AAR is much more sensitive and facing more subtle air disturbance. It requires 0.5 to 1.0 cm accuracy in the relative position. A fixed number of visible optical markers are assumed to be available to help vision subsystem detect. However, temporary loss of visibility may occur because of hardware failures and/or physical interference. Fravolini et al. Proposed a specific docking control scheme featuring a fusion of GPS and MV distance measurements to tackle this problem. Such studies are still under stage of simulation.
Autonomous Flight Auto flight is the extension of auto landing. Ideally, it means that UA V is capable of high level environment understanding and decision making e.g. Defining its position, attitude estimation, obstacle detecting and avoidance, path planning etc. without outside instruction, guidance and intervention. Some studies related to UA V auto manoeuvring considered different conditions, including GPS signal failure, unstructured or unknown flying zone etc. Madison et al. discussed miniature UAV's visual navigation in GPS -challenged environment, e.g. indoor. Vision subsystem geo--locates some landmarks while GPS provides accurate navigation. Once GPS is unavailable, vision subsystem geo-locates new landmarks with predefined landmarks. Using these landmarks, VISi On subsystem provides information for navigation. Tests show that vision aided navigation drift is significantly lower than under inertial only navigation. NASA Ames Research Centre runs a Precision Autonomous Landing Adaptive Control Experiment.
Laser Ignition System Economic as well as environmental constraints demand a further reduction in the fuel consumption and the exhaust emissions of motor vehicles. At the moment, direct Injected fuel engines show the highest potential in reducing fuel consumption and exhaust emissions. Unfortunately, conventional spark plug ignition shows a major disadvantage with modern spray-guided combustion processes since the ignition location cannot be chosen optimally. It is important that the spark plug electrodes are not hit by the injected fuel because otherwise severe damage will occur.Additionally, the spark plug electrodes can influence the gas flow inside the combustion chamber. It is well know that short and intensive laser pulses are able to produce an ”optical breakdown” in air. Necessary intensities are in the range between 10101011W/cm2.1, 2 at such intensities, gas molecules are dissociated and ionized Within the vicinity of the focal spot of a laser beam and a hot plasma is generated. This Plasma is heated by the incoming laser beam and a strong shock wave occurs. The expanding hot plasma can be used for the ignition of fuel-gas mixtures.
Drawbacks Of Conventional Spark Ignition · Location of spark plug is not flexible as it require shielding of plug from immense heat and fuel spray. · It is not possible to ignite inside the fuel spray. · It require frequent maintenance to remove carbon deposits.. · Leaner mixtures cannot be burned. · Degradation of electrodes at high pressure and temperature. · Flame propagation is slow. · Multi point fuel ignition is not feasible. · Higher turbulence levels are required.
What Is Laser? Lasers provide intense and unidirectional beam of light. Laser light is monochromatic (one specific wavelength). Wavelength of light is determined by amount of energy released when electron drops to lower orbit. Light is coherent; all the photons have same wave fronts that launch to unison. Laser light has tight beam and is strong and concentrated.
To make these three properties occur takes something called “Stimulated Emission”, in which photon emission is organized. Main parts of laser are power supply, lasing medium and a pair of precisely aligned mirrors. One has totally reflective surface and other is partially reflective (96 %). The most important part of laser apparatus is laser crystal. Most commonly used laser crystals manmade ruby consisting of aluminium oxide and 0.05% chromium. Crystal rods are round and end surfaces are made reflective. A laser rod for 3 J is 6 mm in diameter and70 mm in length approximately. Laser rod is excited by xenon filled lamp, which surrounds it. Both are enclosed in highly reflective cylinder, which directs light from flash lamp in to the rod. Chromium atoms are excited to higher energy levels. The excited ions meet photons when they return to normal state. Thus very high energy is obtained in short pulses. Ruby rod becomes less efficient at higher temperatures, so it is continuously cooled with water, air or liquid nitrogen. The Ruby rod is the lasing medium and flashtube pumps it.
Laser Induced Spark Ignition The process begins with multi-photon ionization of few gas molecules which releases electrons that readily absorb more photons via the inverse bremsstrahlung process to increase their kinetic energy. Electrons liberated by this means collide with other molecules and ionize them, leading to an electron avalanche, and breakdown of the gas. Multiphoton absorption processes are usually essential for the initial stage of breakdown because the
available photon energy at visible and near IR wavelengths is much smaller than the ionization energy. For very short pulse duration (few picoseconds) the multiphoton processes alone must provide breakdown, since there is insufficient time for electronmolecule collision to occur. Thus this avalanche of electrons and resultant ions collide with each other producing immense heat hence creating plasma which is sufficiently strong to ignite the fuel. The wavelength of laser depend upon the absorption properties of the laser and the minimum energy required depends upon the number of photons required for producing the electron avalanche.
The minimum ignition energy required for laser ignition is more than that for electric spark ignition because of following reasons: An initial comparison is useful for establishing the model requirements, and for identifying causes of the higher laser MIE. First, the volume of a typical electrical ignition spark is 10^-3 cm3. The focal volume for a typical laser spark is 10^-5 cm3. Since atmospheric air contains _1000 charged particles/cm3, the probability of finding a charged particle in the discharge volume is very low for a laser spark. Second, an electrical discharge is part of an external circuit that controls the power input, which may last milliseconds, although high power input to ignition sparks is usually designed to last