Introduction.pdf
- 2. At first ... ▪ Complex system ▪ Many individual parts ▪ Real engineering problems ▪ Mixed study fields: mechanical, electrical, ergonomics, control engineering ...
- 5. Drivetrain elements must perform the following functions: ❑ Keep the vehicle stationary even with the engine running ❑ Achieve the transition from stationary to mobile state ❑ Convert torque and rotation speed ❑ Provide for forward and reverse motion ❑ Changing drive-wheel speed when cornering ❑ Secure minimum fuel consumption, exhaust emission and high efficiency
- 6. Purpose: The suspension system has a influence on the vibration characteristics and therefore on both comfort (ride quality) and driving safety (vehicle handling /roadholding) Construction Main subsystems: 1. Elastic elements 2. Damping elements 3. Suspension mechanism (linkage)
- 7. Types of steering box 1. Rack-and-pinion steering 2. Recirculation-ball steering (for trucks and heavy vehicles) Power-assisted steering systems General requirements ▪ The steering system converts the driver’s rotation input at the steering wheel into a change in the steering angle of the vehicle’s steered road wheels ▪ The steering train must be highly rigid ▪ Light, safe steering of the vehicle must be facilitated
- 9. Purpose of a system ▪ Reduce vehicle speed or bring the vehicle to a stop or to hold the vehicle stationary if already stopped ▪ Motor vehicles must have at least two separate brake systems, one must be lockable
- 10. • When you start your car: a) power from your battery is used to operate a small electric motor called the starter motor, b) the starter motor turns the flywheel and crankshaft of the engine so that the engine can attain sufficient momentum and speed to start and run on its own, c) delivering rotational power to the crankshaft which supplies power to the remainder of the power train.
- 11. • This power is ignited by exploding gas inside cylinders which drives pistons up and down, through connecting rods. Inside the pistons a mixture of compressed air and gas is delivered to the cylinders by a carburetor and intake manifold or a fuel injection system. • The moving parts of the engine must be lubricated. Oil which accumulates in your engine’s oil pan is pumped by the oil pump through an oil filter and then through tubes that deliver the oil to the moving parts to be lubricated.
- 12. • Naturally Aspirated. No intake air pressure boost system. • Supercharged. Intake air pressure increased with the compressor driven off of the engine crankshaft. • Turbocharged. Intake air pressure increased with the turbine compressor driven by the engine exhaust gases. • Crankcase Compressed.Two-stroke cycle engine which uses the crankcase as the intake air compressor.
- 13. • Compression system • Valve train • Fuel system • Ignition system • Lubricating system • Cooling system • Starting system • Charging system • Emission controls • Exhaust system 13
- 14. • Fuel and air is delivered to the engine through components which include: (a) the fuel tank which is used to store the gas, (b) a fuel pump which pumps the fuel from the tank through a fuel line and furl filter to a carburetor or fuel injection system. • This fuel injection system or carburetor delivers the proper mix of air and gas to the cylinders by means of an intake manifold after passing through an air cleaner. 14
- 15. ▪ The purpose of the fuel system is to store, move and deliver the fuel and air in the proper proportion to the engine operating conditions. 15
- 16. ▪ Ignition systems are mechanically or electronically computer controlled ▪ The purpose is to deliver a high voltage spark (20,000 volts) to cylinders at the right time to ignite the fuel. ▪ Spark plugs /wires /coil/distributor/COIL PACK
- 17. ▪ The fully-electronic ignition system generates a separate, dedicated control signal for the individual cylinders, each of which must be equipped with its own ignition coil. ▪ Dual spark ignition uses one coil for two cylinders.
- 18. ▪ Force feed or pressure fed system via an oil pump ▪ Provides lubrication and protection for all the metal parts inside the engine ▪ Oil pump/pan ▪ galleries 18
- 19. ▪ Liquid cooled system ▪ Provides protection from the excessive heat which builds up inside the cylinder ▪ Radiator, water jacket, hoses, thermostat, heater core, fan
- 20. ▪ Heat caused by the friction of moving engine parts and the explosion of gasoline is removed through the vehicles cooling system. ▪ In this system, heat is absorbed by coolant flowing through passages inside the engine.The coolant is a mixture of water and chemicals that protect the cooling system from corrosion, lubricate the water pump, and prevent freezing. ▪ It is stored in the radiator which transfers the heat to the outside environment. ▪ The radiator is cooled by a fan, and most have a recovery tank to capture coolant as it expands due to the heat, and returns it to the radiator when it cools. ▪ This coolant also allows your engine to heat up to its proper operating temperature and is controlled by a heat sensing valve called a thermostat. ▪ Some engine could be cooled by air cooled system
- 21. • The battery is the vehicle’s primary source of electrical power.When the ignition switch is turned on to start your car, electricity is used to close another switch called a solenoid that transmits the large amount of current needed to turn the starter motor. • Once the engine is running, power is generated by the alternator, which also keeps your battery charged. • Then there is a voltage regulator, distributor, and coil which controls the amount of electricity needed by the spark plugs. • Electricity is distributed throughout the vehicle by various electrical circuits for lighting, computers, radio, interior cooling, heating, etc. • These circuits have fuses to disable a circuit that is drawing too much current so as to prevent a fire and protect the components that the circuit serves.
- 22. Uses a battery and electric starting motor (cranking motor) to crank over the engine for starting • Battery • Cranking (starter) motor 22 • Solenoid • Key switch • Wires
- 23. ▪ The charging system has two functions: ▪ To recharge the battery after starting. ▪ To provide all the electricity for the vehicle while the engine is running. ▪ The battery provides power while the engine is not running ▪ Battery/alternator/voltage regulator 23
- 24. ▪ Removes gases from engine ▪ Quiets vehicle ▪ Provides back pressure ▪ Exhaust manifold ▪ Crossover ▪ Tail pipe ▪ Muffler 24
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- 26. • To clean up the air pollution caused by the automobile. • Capture any vapor which might escape the the fuel tank and engines crankcase. • Clean up exhaust for any un burnt fuel, carbon monoxide, or oxides of nitrogen. • Many types of devices are employed. • PCV/Catalytic convertor/gas cap/EGR. Fuel TankVapor Recovery • Captures the vapor of gasoline from the fuel tank. • The charcoal canister holds them . • When the engine runs the vapors are sucked into the engine and burned. 26
- 27. ▪ One of the most important emission controls on the car. ▪ Literally burns up pollution in the exhaust system. 27
- 28. The A/C primary function is to remove heat from within the passenger compartment of the vehicle. It is also used for dehumidification.
- 29. ▪ Most made of stamped steel parts ▪ A few cars made of aluminum (NSX Cadillac Allenta) ▪ Some use composite materials (Saturn or GM Minivan) 29 Chassis or Frame The purpose of a vehicle’s frame is to support the body, engine, and other components • Under lying structure of all vehicles Three types of frame: • 1 – Full frame • 2 – Unitized frame called unibody • 3 – Space frame The frame itself is supported by the wheels and tires through the vehicles suspension system.
- 30. ▪ Uses welded steel alloy metal ▪ C-channel or box frame construction ▪ Note engine cradle in front and rear axle hump in rear ▪ Used on large cars and most all trucks ▪ Body made in separate unit and bolted to chassis Unitized Body Construction • Called Unibody • All body and frame parts welded together • Light weight but strong structurally • Most cars use this construction
- 31. ▪ Newest type of construction ▪ Hybrid unibody ▪ Used on race cars first but now used in passenger cars ▪ Many use plastic fenders and body panels 31
- 32. ▪ Braking system ▪ Suspension system ▪ Steering system
- 33. • There are two independent braking systems in the vehicle: ▪ the service brakes ▪ the parking brake (also referred to as the emergency brake). • The service brakes are used to slow your vehicle while you are driving. • The parking brake can also be used to slow your vehicle in an emergency, but is mainly used to hold your vehicle in one place while stopped or parked. 33
- 34. • The purpose of the braking system is of course, to stop the car. • Brakes are used on all wheels and is hydraulically operated. • Two common types of brake assemblies are used. – Disc Brakes use a rotor that spins with the wheel and a stationary calliper to press friction material against the spinning rotor. Used on most all front brakes and some rear brakes. 34 – Drum Brakes use a drum which spins with the wheel. Stationary brake shoes are pressed out from the inside to cause friction. Used on rear brakes of many cars.
- 35. ▪ Helps driver stop under control ▪ Keeps brakes from locking up ▪ Pulses brakes ▪ Enables car to be turned ▪ Does not replace hydraulic brakes ▪ Does not make vehicle stop faster ▪ Does not work if brake petal is pumped Without ABS: wheels lock up…no steering control. With ABS: wheels do not lock up…you have steering control. Let’s now consider driver controls
- 36. ▪ Uses springs and shock absorbers to provide a good ride and improved handling. ▪ Coil & leaf springs, torsion bars and air suspension are all used. ▪ Most shock absorbers are hydraulic or gas operated. ▪ Stop bouncing action ▪ Struts The suspension system: • The purpose of your vehicle’s suspension system is to connect the wheels to the frame and body and keep the movement of your wheels from being transmitted fully to the body of the vehicle. • This allows you to maintain control of the car in turns, when you hit potholes, and on rough roads. It makes riding in the car more comfortable. As the up and down movement of your wheels is absorbed by the springs in your suspension system, your shock absorbers keep the springs from continuing to bounce.
- 37. • There are different designs for suspension systems involving various linkages, struts, joints, torsion bars, and so on. Independent Suspension • Allows each wheel to move up and down independently with out effect from the opposite wheel. • Used on most all front wheels and many rear wheels now. Straight Axle (Non Independent Suspension) • Wheels are held together on a common axle. • Very rugged but poor on handling. • Used mostly on the rear wheels.
- 38. • Passive damper: unable to generate force, able to dissipate energy at a constant rate • Semi-active damper: unable to generate force, able to dissipate energy at a variable rate - Variable orifice - Variable fluid viscosity • Force generation device: able to generate external force to oppose unwanted motion of vehicle – Hydraulic actuator – Pneumatic system – Electromagnetic system
- 39. • Two types used: – Conventional or parallelogram steering used on larger cars and trucks. – Rack and pinion steering used on most cars. • In power steering systems, turning the steering wheel actuates a hydraulic system or electric motor which amplifies the force necessary to rotate and move the linkages leading to the wheels.
- 40. • Takes the engines torque and sends to the drive wheels. • Major types are: front wheel drive, rear wheel drive, four wheel drive and all wheel drive. • Major components of all drive trains: clutch, transmission, differential, and drive shaft(s). Drive Train Components • Basic purpose is to get the engines torque to the wheels. • Clutches used with manual transmissions a torque converter used with automatics transmission n order to disconnects engine from transmission • Transmission/transaxle. • Drive shafts and drive axles. • Differentials or final drive. 40
- 41. Clutch • flywheel is connected to the engine, and the clutch plate is connected to the transmission • 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. Manual Transmission • Components: – Input shaft – Layshaft – Gears (incl. idler) – Output shaft – Dog collars – Synchronizers
- 42. Torque Converter • A pump inside a torque converter is a type of centrifugal pump as it spins, fluid is flung to the outside a vacuum is created that draws more fluid in at the centre. • fluid then enters the blades of the turbine, which is connected to the transmission, turbine causes the transmission to spin. Automatic Transmission • It is planetary gearsets • Components: – Ring – Sun – Planet carrier – Control system
- 43. ▪ Ideally, the transmission would be so flexible in its ratios that the engine could always run at its single, best- performance rpm value. ▪ A CVT has a nearly infinite range of gear ratios ▪ Components: ▪ Ring ▪ Sun ▪ Planet carrier ▪ Control system
- 44. ▪ All drive train components under the hood (transaxle) ▪ Reduces weight and size of vehicle ▪ Good traction in rain and snow 44
- 45. ▪ Components spread from front to rear ▪ Transmission ▪ Heavier than FWD cars ▪ Poor handling in rain and snow ▪ Better traction for performance purposes
- 46. ▪ RWD vehicles equipped with an added transfer case, a front drive shaft, a front differential, and front drive axles ▪ Part-time 4WD - Typically systems that ▪ operate in two-wheel drive until the driver commands four-wheel drive operation. ▪ Torque is then divided (50/50 fixed) between the front and rear drive-shaft.Drive all four wheel when engaged ▪ Heavy, poor fuel economy ▪ Excellent traction on rain, snow or off road conditions 46
- 47. ▪ Full-time four-wheel drive (4WD) - Constantly ▪ provides power to all four wheels. ▪ Usually equipped with a center “differential” instead of a transfer-case.