UNIT-1-VEHICLE STRUCTURE AND ENGINES.ppt
- 1. KONGUNADU COLLEGE OF ENGINEERING AND TECHNOLOGY (AUTONOMOUS) NAMAKKAL- TRICHY MAIN ROAD, THOTTIAM, TRICHY DEPARTMENT OF MECHANICAL ENGINEERING 20ME603PE - AUTOMOBILE ENGINEERING SIXTH SEMESTER PRESENTED BY M.DINESHKUMAR, ASSISTANT PROFESSOR, DEPARTMENT OF MECHANICAL ENGINEERING, KONGUNADU COLLEGE OF ENGINEERING AND TECHNOLOGY.
- 2. UNIT I VEHICLE STRUCTURE AND ENGINES
- 3. TYPES OF AUTOMOBILES (i) with respect to the purpose (a) Passenger vehicles. Ex. Car, bus, jeep, scooter, mopeds and motor cycles (b) Goods carriers: ex. Trucks and lorries (ii) weight of the vehicles: - Heavy weight vehicle- buses, trucks and trailers - Light weight vehicles - cars, jeeps - Medium weigh vehicles – minibus and station wagon (iii) With respect to the fuel: - Petrol vehicles – scooters, cars motors cycles - Diesel vehicles - Buses , trucks Gas vehicles – Coal gas, LPG, CNG vehicles Electric vehicle – Heavy cranes, battery truck, cars and fork lifts Solar vehicles.
- 4. • (iv) with respect to capacity: • Heavy transport vehicles – Bus lorries, trucks, tractors • Light transport vehicles _ Car, scooter, mopeds, motor cycles, jeeps • (v) with respect to number of wheels: • Two wheelers – Scooters, mopeds • Four wheelers – car, jeep, buses, truckes • Three wheelers – Auto, tempos • Six wheelers - heavy trucks • (vi) With respect to side of driver seat • - Left hand drive- American, European and UAE • -Right hand drive – Indian vehicles
- 5. A bullock cart consists of the following main parts. i) Frame. ii) Wheels and axle. iii) Yoke. iv) Body or superstructure and platform These parts can be divided into the following two main portions . (i) Machine portion. (ii) Carriage portion.
- 6. LAYOUT OF A CAR
- 9. CHASSIS To construct any automobile, chassis is the basic requirement. Chassis is a French term and it was initially used to denote the frame or main structure of a vehicle. It is extensively used in complex vehicles except the body. A vehicle without body is called chassis.
- 10. Basic Construction of Chassis Chassis is the back bone of the vehicle. The components of the vehicle such as power plants, transmission system, axles, wheels and tyres, suspension, controlling systems such as braking, steering etc., and also electrical system parts are mounted on the chassis frame. It is the main mounting of all components including the body. So, it is also called carrying unit.
- 11. MAIN COMPONENTS OF CHASSIS • 1. Frame. • 2. Front suspension. • 3. Steering mechanism. • 4. Engine, clutch and gear box. • 5. Radiator. • 6. Propeller shaft. • 7. Wheels. • 8. Rear and front springs and shock absorber. • 9. Differential unit. • 10. Universal joint. • 11. Brakes and braking systems. • 12. Storage battery. • 13. Fuel tank. • 14. Electrical systems. • 15. Silencer.
- 12. • Classification of chassis: According to the fitting of engine: - Full-forward – ex cars, mahindra jeeps -semi- forward – Tata Se series of vehicles - Bus chassis – Busses and trucks - Engine at back- Volkswagen cars, Leyland bus of England. - Engine at centre- Royal tiger world master buses of Delhi transport. According to the number of wheels fitted in the vehicles and number of driving wheels:
- 13. CHARACTERISTICS OF A GOOD CHASSIS: Fast pickup, strength, safety, durability, dependability, ease of control, quietness, speed, power accessibility, economy of operation low centre of gravity stability load clearance, braking ability, simplicity of lubrication. Chassis Components: Frame, suspension systems, steering system, braking system, internal combustion engine, clutch, gear box , propeller shaft, universal joint ,differential, springs
- 18. VEHICLE AERODYNAMICS: Resistance to vehicle motion: 1.Air resistance or aerodynamic drag: A vehicle travelling at a particular speed in air encounters a force resisting its motion. A) Size of the vehicle (b) shape of the vehicle C) Speed of the vehicle (d) wind velocity 2. Gradient resistance: component of the vehicle weight which is parallel to the plane of the road. 3. Rolling resistance: of tyres on hard surfaces is due to hysteresis in the tyre material. Tyre rolling resistance Road rolling resistance Resistance due to tyre slip angle Resistance due to bearing friction and residual braking
- 19. Aerodynamics of Automobile body: Various aerodynamic force acting on the vehicle. (i) Drag force (Fx): Force of air drag is acting in the direction of vehicle motion with the wind acting along the longitudinal direction axis. The main causes (i) shape drag (ii)Skin friction drag. (ii) Lift force(Fz):Aerodynamics lift force is the vertical component of the resultant force caused by the pressure distribution on the body. (iii) Cross wind force (Fy):It is acting in the lateral direction on the side of the vehicle. These forces acting at the centre of pressure instead of centre of gravity & various cause of moments
- 20. • (i)Pitching moment (My): is caused by the drag force Fx or lift force Fz about Y axis. This moment makes the rear wheels lift off from the ground and further it reduces the available traction. • (ii) Yawing moment(Mz): Cross wind force Fy about Z axis • (iii) Rolling moment(Mx): Cross wind force Fy about X axis •
- 23. CYLINDER BLOCK
- 24. CYLINDER BLOCK It is the main body of an engine which contains cylinders. The piston reciprocates inside the cylinder to develop power. The cylinders are accurately finished to accommodate pistons. The cylinder block also houses crank, crankshaft, piston and other engine parts. During combustion, high pressure and temperature will be developed inside the cylinder. Therefore, it should be made of a material which can resist high temperature and pressure. It is made of grey cast iron or aluminium with steel sleeves.
- 25. CYLINDER HEAD • The cylinder head is bolted at the top of the cylinder block. • It houses the inlet and exhaust valves through which the charge is taken inside the cylinder and burnt gases are exhausted to the atmosphere from the cylinder. • It also contains a spark plug hole or injector hole and cooling water jacket. • The materials used for cylinder heads are cast iron, aluminium alloy etc.
- 26. CRANKCASE • It may be cast integrally with the cylinder block. Sometimes, it is separately cast and bolted to the cylinder block. • It supports crankshaft and camshaft with the help of bearings. Sometimes, the bottom of crankcase may be used as oil sump. • It is made of cast iron, aluminium alloys or alloy steels.
- 27. OIL SUMP OR OIL PAN • Oil sump is fitted at the bottom of crankcase by using a gasket. • It contains lubricating oil. • A drain plug is provided at the bottom of the oil sump to drain out the oil when needed. • It is made of pressed steel sheet.
- 29. CYLINDER LINERS Inside the cylinder, the piston constantly moves up and down which causes wear in cylinders. When the cylinder diameter is increased beyond a certain limit, the entire cylinder block should be discarded and it is costly. To avoid cylinder wear, a separate liner which is in the form of the sleeve is inserted into the cylinder bore. Hence, the wear takes place in the liner only which can be replaced easily when worn out.
- 30. 1. Wet liner: The liners are surrounded by cooling water . It provides a wear resisting surface for the piston to reciprocate. It also acts as a seal for the water jacket. 2. Dry liner: • Dry liners have metal-to-metal contact with the cylinder block. • They are not directly in contact with cooling water. Liner material should withstand abrasive wear and corrosive wear. • Chromium plated mild steel tubes are used as liners.
- 31. Piston The piston is made of cast iron, aluminium alloy, chrome-nickel alloy, nickel-iron alloy and cast steel. They are manufactured by casting or forging method.
- 32. Piston It is a cylindrical shaped mass which reciprocates inside the cylinder. The piston serves the following purposes. It acts as a movable gas-tight seal to keep gases inside the cylinder. It transmits the force of explosion in the cylinder to the crankshaft through connecting rod. The top of the piston is called crown and sides are called skirt. It has grooves to hold piston rings and oil ring. It is opened at the bottom end and closed at the top. Sometimes, T slots are provided in the skirt to allow expansion
- 33. CONNECTING ROD
- 35. CONNECTING ROD It is used to connect the piston and crankshaft with the help of bearings. It is usually steel forging of circular, rectangular, I, T or H cross-sections. Its small end is connected to the piston by the piston pin and its big end is connected to the crank by the crank pin. It has a passage for the transfer of lubricating oil from big end bearing to small end bearing.
- 36. Connecting rod must withstand heavy thrust. So, it must have great strength and rigidity They are generally made of plain carbon steel, aluminium alloy and nickel alloy steels.
- 37. GUDGEON PIN OR PISTON PIN The gudgeon pin or piston pin of the IC engine connects the piston to the connecting rod It provides a bearing for the connecting rod to pivot upon as the piston moves. As the piston pins carry high loads imposed upon them due to gas pressure on the piston, they are made of steel alloyed with 3-4% of nickel to increase toughness and then case- hardened to obtain wear resistance surface.
- 38. PISTON RINGS They are used to maintain air-tight sealing between piston and cylinder to prevent gas leakages. Piston rings are fitted into grooves which are provided for them at the top portion of the piston skirt. Two types of piston rings are used in a piston
- 40. (a) Compression rings: These rings provide an effective seal for high-pressure gases inside the cylinder. Each piston is provided with at least two compression rings (b) Oil rings: These rings wipe off the excess oil from cylinder walls. It also returns excess oil to the oil sump through slots provided in rings. The materials used for piston rings are cast iron, alloy cast iron containing silicon and manganese, alloy steels etc. Piston rings are generally coated with chromium or cadmium.
- 42. CRANKSHAFT The crankshaft is used to convert the reciprocating motion of the piston into rotary motion. The big end of the connecting rod is connected to the crankshaft. It can be a single crank type for single cylinder engines and a multiple crank type for multi-cylinder engines. The crankshaft is held in position by main bearings. There are minimum two bearings provided to support the crankshaft.
- 43. The flywheel is mounted at the rear end of the crankshaft. The material of the crankshaft should be strong enough to resist heavy impact force of the piston. They are made from a hot billet steel, carbon steel, nickel-chromium and other heat-treated alloy steels.
- 44. FLYWHEEL The flywheel is heavy and perfectly balanced wheel usually connected to the rear end of the crankshaft. Flywheel serves as an energy reservoir. It stores energy during power stroke and releases energy during other strokes. Thus, it gives a constant output torque. It is usually made of cast iron or cast steel.
- 46. CAMSHAFT It is used to convert the rotary motion of the camshaft into linear motion of the follower or lifter. Thus, it operates the inlet and exhaust valves through rocker arms. It has as many cams as the number of valves in an engine. An additional cam is also provided to drive the fuel pump. The camshaft rotates inside the plain bearings. It is driven by crankshaft through chain or gear train. It is rotated at half of the speed of the crankshaft. The camshaft is usually made of chilled cast iron and billet steel; however forged steel, grey cast iron or nickel steel may be used depending upon the application
- 47. SPARK PLUG The function of the spark plug is to ignite the air-fuel mixture after completing the compression stroke in the petrol engine. It is usually mounted in the cylinder head. It is only used in petrol engines.
- 48. VALVES Valves are used for closing and opening the passage of a cylinder. There are two valves in an engine cylinder such as inlet and exhaust valves. A fresh air-fuel mixture or air alone enters into the cylinder through the inlet valve. Exhaust gases are forced out through the exhaust valves. Valves are operated by cam and rocker arm mechanisms
- 50. • There are three types of valves such as sleeve valve, rotary valve and poppet valve. • The poppet valve (also called mushroom valve) valves are most commonly used. Figure shows a poppet valve. • Normally, this valve contains head or poppet (angular face ground 30° to 45°), face, stem and spring retainer lock groove. • The head of the inlet valve is bigger than the head of the exhaust valve. • The inlet valve is made of plain nickel, nickel- chrome or chrome-molybdenum
- 51. VALVE MECHANISMS The valves are actuated by cams mounted on a cam shaft. The different types of valve operating mechanisms are as follows. (a) side valve mechanism (b) overhead valve mechanism (c) overhead inlet and side exhaust valve mechanisms.
- 53. SIDE VALVE MECHANISM • The cam mounted on the camshaft operates the valve tappet during its rotation. • The valve tappet is pushed up. • The valve tappet pushes the valve from its sheet against the spring force. • Thus, the valve is opened. • When the cam is not in action, the valve returns to its seat by the valve spring and spring retainer.
- 55. OVERHEAD VALVE MECHANISM • Here, the valves are located in the cylinder head. When the cam rotates, the valve lifter pushes the push rod upwards. • The push rod moves the rocker arm. • Since the rocker arm is pivoted at its centre, it pushes the valve off its seat against the spring force. • Thus, the valve is opened. When the cam is not in action, the valve returns to its seat by the valve spring and spring retainer.
- 56. Overhead inlet and side exhaust valve mechanism • In this system, inlet valve is located in the cylinder head whereas the exhaust valve is located in the cylinder block. • The inlet valve is actuated by overhead valve mechanism. • The exhaust valve is actuated by a side valve mechanism.
- 57. LUBRICATION PUMP The lubricating oil pump is used to pressurize the oil and circulate it to different engine parts. It is generally driven by a spiral or warm gear on the cam shaft. The different types of oil pumps in use are 1. Gear pump. 2. Eccentric rotor pump. 3. Eccentric vane pump. 4. Plunger pump.
- 58. Variable valve timing for four- cylinder engine
- 59. VARIABLE VALVE TIMING (VVT) Fixed valve timing has been a standard feature of all engines until relatively recent times. The valves opened and closed at a fixed period in relation to crankshaft rotation at all engine speeds and loads. When the inlet and exhaust valve timing is fixed, the timing is not suitable for all engine operating speeds and loads. So, there is increase in use of mechanisms to provide variable valve timing (VVT).
- 60. • The variable valve timing systems alter the valve timing to suit engine speed and load conditions. • Although systems are purely mechanical based systems, most modern systems make use of the electronic engine management system to regulate the mechanical actuation of changes to the valve timing. • Practically, VVT systems are used to enable good power or torque to be achieved over the whole engine speed range but the added benefit of valve overlap is to facilitate the mixing of some exhaust gas with the fresh charge of air. • Therefore, the combustion temperature and NOx emission are reduced.
- 61. Types of Variable Valve Timing There are three types of variable valve timing such as cam-changing VVT cam-phasing VVT and combined cam-changing and cam- phasing VVT.
- 62. Advantage: • It is very much powerful at top end. Disadvantages: • 1. Stage 2 or stage 3 is non-continuous and not much improvement to torque. • 2. It is also complex in nature. Applications: • This type of VVT technology is used in various engines such as Honda VTEC, Mitsubishi MIVEC, Nissan Neo VVL