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1、更多汽车资料请访问中国汽车技术论坛：CHAPTER 1 AUTOMOTIVE BASICS1.1 Principal ComponentsTodays average car contains more than 15,000 separate, individual parts that must work together. These parts can grouped into four major categories: engine, body, chassis and electrical equipment.1.2 EngineThe engine acts as the po
2、wer unit. The internal combustion engine is most common: this obtains its power by burning a liquid fuel inside the engine cylinder. There are two types of engine :gasoline(also called a spark-ignition engine) and diesel(also called a compression-ignition engine).Both engines are called heat engines
3、; the burning fuel generates heat which causes the gas inside the cylinder to increase its pressure and supply power to rotate a shaft connected to the transmission.1.3 BodyAn automobile body is a sheet metal shell with windows, doors, a hood, and a trunk deck built into it. It provides a protective
4、 covering for the engine, passengers, and cargo. The body is designed to keep passengers safe and comfortable. The body styling provides an attractive, colorful, modern appearance for the vehicle.1.4 ChassisThe chassis is an assembly of those systems that are the major operating part of a vehicle. T
5、he chassis includes the transmission, suspension, steering, and brake systems.Transmission systems conveys the drive to the wheels. The main components are clutch, gearbox, driveshaft, final drive, and differential.Suspension absorbs the road shocks.Steering controls the direction of the movement.Br
6、ake slows down the vehicle.1.5 Electrical EquipmentThe 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 the battery, alternator (or generator). The battery stores electricit
7、y. The alternator changes the engines mechanical energy into electrical energy and recharges the battery.New WordsPrincipal component 主要部件category 种类，类型body 车身chassis 底盘layout 布置power unit 动力装置internal combustion engine 内燃机cylinder 汽缸gasoline 汽油spark 火花ignition 点燃，点火diesel 柴油机compression 压缩shaft 轴tr
8、ansmission 传动系sheet metal 金属板shell 外壳hood （发动机）罩trunk deck 行李舱盖cargo 货物styling 样式assembly 总成，装配suspension 悬挂，悬置shock 冲击steering 转向，操纵brake 刹车，制动器clutch 离合器gearbox 变速器driveshaft 传动轴final drive 主减速器，后桥differential 差速器slow down （使）慢下来，减速horn 喇叭starter 起动机charge 充电alternator 交流发电机Review Questions1. List
9、 the main parts of an automobile?2. What are the common types of a vehicle according to body styling?3. Which systems does a chassis include and what are the main functions of the chassis?4. Why are suspension systems used on vehicles?CHAPTER2 INTERNAL COMBUSTION ENGINE2.1 principle of operation 2.1
10、.1 Engine and power Engine is used to produce power. The chemical energy in fuel is converted to heat by the burning of the fuel at a controlled rate. This process is called combustion. If engine combustion occurs with the power chamber. ,the engine is called internal combustion engine. If combustio
11、n takes place outside the cylinder, the engine is called an external combustion engine. Engine used in automobiles are internal combustion heat engines. Heat energy released in the combustion chamber raises the temperature of the combustion gases with the chamber. The increase in gas temperature cau
12、ses the pressure of the gases to increase. The pressure developed within the combustion chamber is applied to the head of a piston to produce a usable mechanical force, which is then converted into useful mechanical power.2.1.2 Engine Terms Linking the piston by a connecting rod to a crankshaft caus
13、es the gas to rotate the shaft through half a turn. The power stroke “uses up” the gas , so means must be provided to expel the burnt gas and recharge the cylinder with a fresh petrol-air mixture :this control of gas movement is the duty of the valves ;an inlet valve allows the new mixture to enter
14、at the right time and an exhaust valve lets out the burnt gas after the gas has done its job. Engine terms are : TDC(Top Dead Center):the position of the crank and piston when the piston is farther away from the crankshaft. BDC(Bottom Dead Center):the position of the crank and piston when the piston
15、 is nearest to the crankshaft. Stroke : the distance between BDC and TDC; stroke is controlled by the crankshaft. Bore : the internal diameter of the cylinder. Swept volume : the volume between TDC and BDC. Engine capacity : this is the swept volume of all the cylinder e.g. a four-stroke having a ca
16、pacity of two liters(2000cm) has a cylinder swept volume of 50cm. Clearance volume: the volume of the space above the piston when it is at TDC. Compression ratio = (swept vol + clearance vol)(clearance vol) Two-stroke : a power stroke every revolution of the crank. Four-stroke : a power stroke every
17、 other revolution of the crank.2.1.3 The Four-stroke Spark-ignition Engine Cycle The spark-ignition engine is an internal-combustion engine with externally supplied in ignition , which converts the energy contained in the fuel to kinetic energy. The cycle of operations is spread over four piston str
18、okes. To complete the full cycle it takes two revolutions of the crankshaft.The operating strokes are : This stroke introduces a mixture of atomized gasoline and air into the cylinder. The stroke starts when the piston moves downward from a position near the top of the cylinder. As the piston moves
19、downward, a vacuum, or low-pressure area, is created. During the intake stroke, one of the ports is opened by moving the inlet valve. The exhaust valve remains tightly closed.Compression strokeAs the piston moves upward to compress the fuel mixture trapped in the cylinder, the valves are closed tigh
20、tly. This compression action heats the air/fuel mixture slightly and confines it within a small area called the combustion chamber.Power strokeJust before the piston reaches the top of its compression stroke, an electrical spark is introduced from a spark plug screwed into the cylinder head.The spar
21、k ignites the compressed, heated mixture of fuel and air in the combustion chamber to cause rapid burning. The burning fuel produces intense heat that causes rapid expansion of the gases compressed within the cylinder. This pressure forces the piston downward. The downward stroke turns the crankshaf
22、t with great force.Exhaust strokeJust before the bottom of the power stroke, the exhaust valve opens. This allows the piston, as it moves upward, to push the hot, burned gases out through the open exhaust valve.Then, just before the piston reaches its highest point, the exhaust valve closes and the
23、inlet valve opens. As the piston reaches the highest point in the cylinder, known as TDC, it starts back down again. Thus, one cycle ends and another begins immediately.2.1.4 Engine Overall Mechanics The engine has hundreds of other parts . The major parts of engine are engine block , engine heads,
24、pistons, connecting rods, 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. Each of these systems has a definite function. These systems will discussed in detail
25、 later. NEW WORDPiston 活塞Connecting rod 连杆Crankshaft 曲轴Power stoke 活塞行程Expel 排出Valve 气阀inlet(intake) valve 进气阀exhaust valve 排气阀term 术语TDC 上止点BDC 下止点Bore 缸径swept volume 有效容积engine capacity 发动机排量clearance volume 余隙容积,燃烧室容积compression ratio 压缩比revolution 旋转,转数every other 每隔一个cycle 循环spread over 分布,遍及in
26、take stroke 进气行程 compression stroke 压缩行程knock 敲缸,敲打exhaust stroke 排气行程engine block 发动机缸体lubrication 润滑2.2 Engine Block and Cylinder Head2.2.1 Engine BlockThe engine block is the basic frame of the engine. All other engine parts either fit inside it or fasten to it. It holds the cylinders, water jack
27、ets, and oil galleries. The engine block also holds the crankshaft, which fastens to the bottom of the block. The camshaft also fits inside the block, except on overhead-cam engines (OHC). In most cars, this block is made of gray iron, or an alloy (mixture) of gray iron and other metals, such as nic
28、kel or chromium. Engine blocks are castings.Some engine blocks, especially those in smaller cars, are made of cast aluminum. This metal is much lighter than iron. However, iron wears better than aluminum. Therefore, the cylinders in most aluminum engines are lined with iron or steel sleeves. These s
29、leeves are called cylinder sleeves. Some engine blocks are made entirely of aluminum.2.2.2 Cylinder HeadThe cylinder head fastens to the top of the block, just as a roof fits over a house. The underside forms the combustion chamber with the top of the piston. The most common cylinder head types are
30、the hemi, wedge, and semi-hemi. All three of these terms refer to the shape of the engines combustion chamber. The cylinder head carries the valves, valve springs and the rockers on the rocker shaft, this part of the valve gear being worked by the push-rods. Sometimes the camshaft is fitted directly
31、 into the cylinder head and operates on the valves without rockers. This is called an overhead camshaft arrangement. Like the cylinder block, the head is made from either cast iron or aluminum alloy.2.2.3 GasketThe cylinder head is attached to the block with high-tensile steel studs. The joint betwe
32、en the block and the head must be gas-tight so that none of the burning mixture can escape. This is achieved by using cylinder head gasket. This is a sandwich gasket, i.e. a sheet of asbestos between two sheets of copper, both these materials being able to withstand the high temperature and pressure
33、s within the engine.2.2.4 Oil Pan or SumpThe oil pan is usually formed of pressed steel. The oil pan and the lower part of the cylinder block together are called the crankcase; they enclose, or encase, the crankshaft. The oil pump in the lubricating system draws oil from the oil pan and sends it to
34、all working parts in the engine. The oil drains off and runs down into the pan. Thus, there is constant circulation of oil between the pan and the working parts of the engine.New Wordsengine block 缸体cylinder head 气缸盖fasten 使固定water jacket 水套oil gallery 油道camshaft 凸轮轴overhead-cam(OHC) 顶置凸轮gray iron 灰
35、铸铁alloy 合金nickel 镍chromium 铬casting 铸件head cover 汽缸盖罩intake manifold 进气总管distributor 分电器oil pan 油底壳aluminum 铝be lined with 镶有cylinder sleeve 气缸套hemi 半球形wedge 楔型，楔入semi-hemi 准半球形rocker 摇臂push-rod 推杆gasket 衬垫high-tensile 高强度的stud 螺栓gas-tight 密封的asbestos 石棉crankcase 曲轴箱，曲柄箱encase 封闭，把包起来drain off 排出，流出
36、Review Question1. What do TDC, BDC, stroke, compression ratio and engine capacity stand for?2. How do you calculate swept volume and compression ratio?3. What controls the length of the stroke?4. List the main parts of the engine overall mechanics?5. What are the main function of the engine block?2.
37、3 Piston Connecting Rod and Crankshaft2.3.1 Piston Assembly The piston is an important part of a four-stroke cycle engine. Most pistons are made from cast aluminum. The piston , through the connecting rod, transfers to the crankshaft the force create by the burning fuel mixture. This force turns the
38、 crankshaft .Thin, circular , steel bands fit into grooves around the piston to seal the bottom of the combustion chamber. These bands are called piston rings. The grooves into which they fit are called ring grooves. A piston pin fits into a round hole in the piston . The piston pin joins the piston
39、 to the connecting rod . The thick part of the piston that holds the piston is the pin boss.The piston itself , its rings and the piston pin are together called the piston assembly. 2.3.2.PistonTo withstand the heat of the combustion chamber, the piston must be strong. It also must be light, since i
40、t travels at high speeds as it moves up and down inside the cylinder. The piston is hollow. It is thick at the top where it take the brunt of the heat and the expansion force. It is thin at the bottom, where there is less heat. The top part of the piston is the head , or crown . The thin part is the
41、 skirt The sections between the ring grooves are called ring lands.The piston crown may be flat , concave ,dome or recessed . In diesel engine , the combustion chamber may be formed totally or in part in the piston crown , depending on the method of injection . So they use pistons with different sha
42、pes.2.3.3Piston RingsAs Fig.2-9 shows , piston rings fit into ring grooves near the of the piston. In simplest terms, piston rings are thin, circular pieces of metal that fit into grooves in the tops of the pistons. In modern engines ,each piston has three rings. (Piston in older engines sometimes h
43、ad four rings, or even five.) The rings outside surface presses against the cylinder walls. Rings provide the needed seal between the piston and the cylinder walls. That is, only the rings contact the cylinder walls. The top two rings are to keep the gases in the cylinder and are called compression
44、rings. The lower one prevents the oil splashed onto the cylinder bore from entering the combustion chamber , and is called an oil ring. Chrome-face cast-iron compression rings are commonly used in automobile engines. The chrome face provide a very smooth , wear-resistant surface.During the power sto
45、ke , combustion pressure on the combustion rings is very high. It causes them to untwist . Some of the high-pressure gas gets in back of the rings. This force the ring face into full contact with the cylinder wall. The combustion pressure also holds the bottom of the ring tightly against the bottom
46、of the ring groove. Therefore , high combustion pressure causes a tighter seal between the ring face and the cylinder wall.2.3.4 Piston Pin The piston pin holds together the piston and the connecting rod . This pin fits into the piston pin holes and into a hole in the top end of the connecting rod. The top end of is much smaller than the end that fits on the crankshaft . This small end fits inside the bottom of the piston