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IP屬地：江西

IP屬地：江西 上傳時(shí)間：2022-07-10 格式：PPT 頁(yè)數(shù)：351 大?。?.12MB 積分：11 舉報(bào) 版權(quán)申訴

1、 Unit 1 Automotive BasicsLesson 1Fundamentals of Automobile The modern automobile contains more than 15000 separate individual parts that must work together. These parts can be grouped into four major categories: engine、chassis、body and electrical equipment. There are two types of engine: gasoline(a

2、 spark-ignition engine)diesel(a compression-ignition engine). 1Engine Fuel system 1.1 The fuel system is designed to mix air and fuel in the engine for combustion. This air and fuel mixing should produce an efficient combustion process. Ignition system 1.2 The ignition system is designed to ignite t

3、he air and fuel that have been mixed in the fuel system. In order to do this，a very high voltage is deeded to produce a spark within the combustion chamber. Starting and charging systems 1.3 The starting and charging systems are designed to start the engine and keep the battery fully charged during

4、operation. Lubrication system 1.4 This system is designed to keep all of the engine parts lubricated so that friction is reduced . Without lubrication inside the engine，the moving parts that are continuously rubbing against each other would heat up. If overheat，they may be damaged by heat. Cooling s

5、ystem 1.5 The cooling system is used to keep the engine at the most efficient operating temperature. It is very important that the engine run as hot as possible. So the engine has a cooling system to remove just the right amount of heat. Air intake and exhaust systems 1.6 The air intake and exhaust

6、systems get clean air into the engine and remove the dirty exhaust gases from the combustion chamber with minimum pollution. The engines use the sophisticated duct and exhaust pipe to do this. Pollution control system 1.7 This system is adopted to reduce varies emissions from the engine. Some of the

7、 more common pollutants include carbon monoxide，nitrogen oxide，and hydrocarbons.(1)Power train systemconveys the drive to the wheels.(2)Suspension systemabsorbs the road shocks.(3)Steering systemcontrols the direction of the movement.(4)Brake systemslows down the vehicle. 2Chassis Power train system

8、 conveys the drive to the wheels. The main components are clutch，gearbox，driveshaft，final drive，and differential.Power train system 2.1 The purpose of the complete suspension system is to isolate the vehicle body from road shocks and vibrations，which will otherwise be transferred to the passengers a

9、nd load. It must also keep the tire in contact with the road regardless of road surface.Suspension system 2.2 The steering system，under the control of the driver at the steering wheel，provides the means by which the front wheels are directionally turned. The steering system may be the power assisted

10、 to reduce the effort required to turn the steering wheel and make the vehicle easier to maneuver.Steering system 2.3The braking system has three main functions，F(xiàn)irst，to reduce the speed of the vehicle，whenNecessarySecond，to stop the car in as short a distance as possibleThird，to hold the vehicle st

11、ationary. Steering system 2.4 An automobile body is a sheet metal shell with windows，doors，a hood，and a trunk deck builtinto it. It provides a protective covering for the engine，passengers，and cargo. The body is designed to keep passengers safe and comfortable. The body styling provides an attractiv

12、e，colorful，modern appearance for the vehicle. 3 Body The electrical system supplies electricity for the ignition，horn，lights，heater，and starter. The electricity level is maintained by a charging circuit. This circuit consists of battery and alternator (or generator). The battery stores electricity.

13、The alternator changes the engines mechanical energy into electrical energy and recharges the battery. 4 Electrical equipment Unit 2 Engine ConstructionInternal Combustion Engine Basics Engine Body Fuel Injection System The Fuel Delivery System Valve SystemLesson 2Lesson 3Lesson 6Lesson 5Lesson 4 Co

14、oling System Lubrication System VR6 / W12 Engine Emission Control SystemsTurbochargers and SuperchargersLesson 7Lesson 8Lesson 11Lesson 10Lesson 9Lesson 12 Hybrid-electric VehicleLesson 2Internal Combustion Engine Basics internal combustion engine.external combustion engine. 1 Engine termsEngine ter

15、ms are as shown in Fig. 2-1.TDC :the position of the crank and piston when the piston is farther away from the crankshaft.BDC :the position of the crank and piston when the piston is nearest to the crankshaft.Stroke :the distance between BDC and TDC.Bore :the internal diameter of the cylinder.Swept

16、volume :the volume between TDC and BDC.Engine capacity :this is the swept volume of all the cylinderClearance volume :the volume of the space above the piston when it is at TDC.Two-stroke :a power stroke every revolution of the crank.Four-stroke :a power stroke every other revolution of the crank. 2

17、 The four-stroke engine principle The most common engine is the four-stroke piston engine. Each stroke is named after the action it performs: intake，compression，power，and exhaust. Intake stroke 2.1 As the piston moves down，the vaporized mixture of fuel and air enters the cylinder through the open in

18、take valve. To obtain the maximum filling of the cylinder，the intake valve opens about 10before TDC，giving 20overlap. The inlet valve remains open until some 50after BDC to take advantage of incoming mixture. Compression stroke 2.2 The piston turns up，the intake valve closes，the mixture is compresse

19、d within the combustion Chamber，while the pressure rise to about 1MPa，depending on various factors including the compression ratio，throttle opening and engine speed. Near the top of the stroke the mixture is ignited by a spark which bridges the gap of the spark plug. Power stroke 2.3 The expanding g

20、ases of combustion produces a rise in pressure of the gas to some 3. 5MPa， and the piston forced down in the cylinder. The exhaust valve opens near the bottom of the stroke. Exhaust stroke 2.4 The piston moves back up with the exhaust valve open some 50before BDC allowing the pressure within the cyl

21、inder to fall and to reduce “back” pressure on the piston during the exhaust Stroke，and the burned gases are pushed out to prepare for next intake stroke. The intake valve usually opens just before the exhaust stroke. The major parts of the engine are engine block，engine head，pistons，connecting Rods

22、，crankshaft，and valves. The other parts are joined to make systems. These systems are the fuel System，intake system，ignition system，cooling system，lubrication system，and exhaust system. 3 Engine systemsLesson 3 Engine Body Basic body includes the engine block，cylinder head，crankshaft，pistons，connect

23、ing rods，and flywheel. The engine block is the main supporting structure to which all other engine parts are attached. 1 Engine blockThe cylinder head fastens to the top of the block. The underside forms the combustion chamber with the top of the piston.Most cylinder heads are made from cast aluminu

24、m or cast iron. The cylinder head contains at least one intake valve and one exhaust valve for each cylinder. The joint between the engine block and the cylinder head must be tight and able to withstand pressure and the heat developed in the combustion chamber. 2 Cylinder head The crankshaft，in conj

25、unction with the connecting rod，converts the reciprocating motion of the piston to the rotary motion needed to drive the vehicle. 3 Crankshaft The piston converts the potential energy of the fuel into the kinetic energy that turns the crankshaft. The piston is a cylindrical shaped hollow part that m

26、oves up and down inside the cylinder. The piston is used to ensure a snug “air tight” fit. 4 Piston The connecting rod is made of forged high-strength steel. It transmits force and motion from the piston pin，or “wrist pin”，which connects the rod to the piston，the pin is usually pressed into the smal

27、l end of the connecting rod. Some rods have a lock bolt in the small end. The big end of connecting rod is attached to a crank-pin by a rod bearing cap. 5 Connecting rod A heavy flywheel is attached to the rear of the crankshaft with bolts. The function of the flywheel is to smooth out engine speed

28、and keep the crankshaft spinning between power strokes. 6 Flywheel In some engines，the flywheel also serves as a mounting surface for the clutch. The outer rim of the flywheel has a large ring attached with gear teeth cut into it. The teeth of the starter motor engage these teeth and spin the flywhe

29、el to crank the engine. When an automatic transmission is used，the torque converter assembly works with the flywheel.Lesson 4 Valve SystemThe valve system is made up of those parts needed to open and close the valves at just the right time. These valve moments must take place at exactly the right mo

30、ments. The opening of each valve is controlled by a camshaft. The valve train typically includes the camshaft，valves，valve springs，rocker arms，valve lifter，and pushed. 1Valve train typesOverhead camshaft(OHC)valve trainPushrod valve trainOverhead camshaft(OHC)valve train 1.1 The cam is an egg-shaped

31、 piece of metal on a shaft that rotates in coordination with the crankshaft. The metal shaft，called the camshaft，typically has individual cams for each valve in the engine.Pushrod valve train 1.2 The camshaft also can be located in the lower part of the engine，within the engine block. To transfer th

32、e motion of the cam upward to the valve additional parts are needed. 2Valve clearance When the engine runs in compression stroke and power stoke，the valves must close tightly on their seats to produce a gas-tight seal and thus prevent the gases escaping from the combustion chamber. Some clearance is

33、 needed in the operating mechanism，so that the valves can close fully. 3Valve timing The time at which valves open and close(valve timing)and the duration of valve opening is stated in degrees of crankshaft rotation. valve overlap：the end of the exhaust stroke and the beginning of the intake stoke o

34、verlap for a short period of time. Valve timing and valve overlap vary on different engines.Lesson 5 The Fuel Delivery System The fuel system is critical to engine operation. Its function is to store and supply fuel to the cylinder chamber where it can be mixed with air，vaporized，and burned to produ

35、ce energy. 1Gasoline Gasoline is a complex blend of carbon and hydrogen compounds. Additives are then added to improve performance. The two most important features of gasoline are volatility and resistance to knock(octane). Volatility is a measurement of how easily the fuel vaporizes. Resistance to

36、knock or octane is simply the temperature the gas will burn at. Higher octane fuel requires a higher temperature to burn. Other factors that affect the octane requirements of the engine are: air/fuel ratio，ignition timing，engine temperature，and carbon build up in the cylinder. 2Fuel tank1.The fuel t

37、ank is used to store the fuel of engine needed. It is usually located in the rear of the vehicle. The fuel tank is designed to fit around frame and to be protected from impacts. 2.The fuel cap on the fuel tank is used to keep the fuel from splashing out，release the vacuum created by the fuel removin

38、g，and prevent vapors from escaping directly into the atmosphere. 3Fuel pump Two types of fuel pumps are used in the automobiles: mechanical and electric. All fuel injected cars today used electric fuel pumps，while most carburated cars used mechanical fuel pumps. Many cars today，locate the fuel pump

39、inside the fuel tank. 4Fuel filters Fuel filters are used to stop any contamination from getting into the fuel system of both gasoline and diesel engines. The gasoline engines may have one or two filters in the fuel system .The first filter is usually placed inside the fuel tank to prevent large pie

40、ces of contaminant from damaging the fuel pump. The second one is an in-line type or an in-carburetor type used to filter out small dirt particles. 5Carburetor A carburetor delivers fuel in proportion to the amount of air flowing through it. To meet complicated demands，a carburetor is a highly intri

41、cate device，with many internal passages and parts.Venturi 5.1 A venturi is streamlined restriction that partly closes the carburetor bore. The air entering the venturi is forced to speed up. The greater the velocity of air passed through the venturi，the greater the vacuum produced，and the more the f

42、uel is drawn in.Throttle valve 5.2 The flow of air and fuel through the carburetor is controlled with a throttle valve. The throttle valve is placed below the venturi and connected to the acceleration pedal. As the drivers foot on the pedal is depressed，the throttle valve opens，and there is very lit

43、tle restriction of air and fuel. The load and speed are increased.Float chamber 5.3 The float chamber is a reservoir for storing and supplying fuel to the carburetor. As the engine uses fuel，the float chamber replenishes it automatically. A float rests on top of the fuel in the reservoir. As fuel is

44、 used，the float level drops. When the float drops，a needle valve is opened. The open needle valve permits the flow of fuel from the fuel pump into the carburetors float chamber. When the chamber is full again，the needle valve is pushed upward and closes the fuel inlet.Metering the fuel 5.4 The press

45、ure differential between the float chamber and the venturi causes fuel to flow. However，to maintain the proper air-fuel ratio，the carburetor must provide just the right amount of fuel. To do so，the main discharge tube has a small hole. This allows a precise amount of fuel to enter the airstream. In

46、most cases，this small hole is in the float chamber at the end of the main discharge tube. There，its small size limits fuel flow.Lesson 6 Fuel Injection System The Electronic Fuel Injection system can be divided into three basic subsystems. These are the fuel delivery system，air induction system，and

47、the electronic control system. 1Fuel delivery system The fuel delivery system consists of the fuel tank，fuel pump，fuel filter，fuel delivery pipe(fuel rail)，fuel injector，fuel pressure regulator，and fuel return pipe. Fuel is delivered from the tank to the injector by means of an electric fuel pump. T

48、he pump is typically located in or near the fuel tank. Contaminants are filtered out by a high capacity in line fuel filter. Fuel is maintained at a constant pressure by means of a fuel pressure regulator. Any fuel which is not delivered to the intake manifold by the injector is returned to the tank

49、 through a fuel return pipe. 2Air induction system The air induction system consists of the air cleaner，air flow meter，throttle valve，air intake Chamber，intake manifold runner，and intake valve. When the throttle valve is opened，air flows through the air cleaner through the air flow meter(on L type s

50、ystems)，past the throttle valve，and through a well tuned intake manifold runner to the intake valve. The L type EFI system measures air flow directly by using an air flow meter. The D type EFI system measures air flow indirectly by monitoring the pressure in the intake manifold. 3Electronic control

51、system The electronic control system consists of various engine sensors，ECU，fuel injector assemblies，and related wiring. The ECU determines precisely how much fuel needs to be delivered by the injector by monitoring the engine sensors. The ECU turns the injectors on for a precise amount of time，whic

52、h is referred to as injection pulse width or injection duration，to deliver the proper air-fuel ratio to the engine. 4Operation Air enters the engine through the air induction system where it is measured by the air flow meter. As the air flows into the cylinder，fuel is mixed into the air by the fuel

53、injector. Fuel injectors are arranged in the intake manifold behind each intake valve. The injectors are electrical solenoids which are operated by the ECU. The ECU pulses the injector by switching the injector ground circuit on and off. When the injector is turned on，it opens，spraying atomized fuel

54、 at the back side of the intake valve. As fuel is sprayed into the intake air stream，it mixes with the incoming air and vaporizes due to the low pressures in the intake manifold. The ECU signals the injector to deliver just enough fuel to achieve an ideal air/fuel ratio of 14.71，often referred to as

55、 stoichiometry. The precise amount of fuel delivered to the engine is a function of ECU control. The ECU determines the basic injection quantity based upon measured intake air volume and engine rpm. Depending on engine operating conditions，injection quantity will vary. Uniform air / fuel mixture dis

56、tribution 5.1 Each cylinder has its own injector which delivers fuel directly to the intake valve. This eliminates the need for fuel to travel through the intake manifold，improving cylinder to cylinder distribution. 5Advantages of EFIHighly accurate air / fuel ratio control throughout all engine ope

57、rating conditions 5.2 EFI supplies a continuously accurate air/ fuel ratio to the engine no matter what operating conditions are encountered. This provides better drivability，fuel economy，and emissions control.Superior throttle response and power 5.3 By delivering fuel directly at the back of the in

58、take valve，the intake manifold design can be optimized to improve air velocity at the intake valve. This improves torque and throttle response.Excellent fuel economy with improved emissions control 5.4 Cold engine and wide open throttle enrichment can be reduced with an EFI engine because fuel puddl

59、ing in the intake manifold is not a problem. This results in better overall fuel economy and improved emissions control.Improved cold engine start ability and operation 5.5 The combination of better fuel atomization and injection directly at the intake valve improves ability to start and run a cold

60、engine.Simpler mechanics，reduced adjustment sensitivity 5.6 The EFI system does not rely on any major adjustments for cold enrichment or fuel metering. Because the system is mechanically simple，maintenance requirements are reduced.Lesson 7 Cooling System Basically，there are two types of automobile c