1、Unit Three Engine Systems Passage BIgnition,Starting and Fuel Systems Ignition system Ignition system is the most important part of the gasoline engine Its purpose is to ignite the compressed fuel-air mixture at proper time,producing power to move the car A good ignition system has a great impact on
2、 the engine performance,fuel economy and exhaust pollution Ignition system is divided into 3 types:contact-point ignition system(Fig.3-15),non-point ignition system(Fig.3-16)and non-distributor ignition system(Fig.3-17)First one is convention ignition system(CIS),the last two ones are electronic ign
3、ition system(EIS).In non-point ignition system,a reluctor disk and an electronic control module(ECM)take the place of the contact points in the contact-point ignition system With the development of the automotive technology,non-distributor ignition system is replacing the other two types of the igni
4、tion systems mentioned above So we mainly introduce the non-distributor ignition system The major components of a non-distributor ignition system are engine control unit(ECU),ignition control unit(ICU),a set of ignition coils and some sensors such as crankshaft position sensor,camshaft position sens
5、or and knock sensor The spark plugs are fired directly from the coils The spark timing is controlled by ECU and ICU according to the information received from the sensors There are multiple coils on cars so each one serves one or two spark plugs If there are 3 coils that mounted together in a coil p
6、ack in a car with a 6-cylinder engine,each coil is connected to two spark plugs with spark plug wires The coil fires bothspark plugs at the same time One spark plug fires on the compression stroke igniting the fuel-air mixture to produce power while the other spark plug fires on the exhaust stroke a
7、nd does nothing(see Fig.3-17a).If there are 4 coils,each coil is mounted directly on the top of each spark plugas shown in 3-17b This design completely eliminates the spark plug wires for even better reliability Starting system Starting system functions to crank the engine fast enough to allow the e
8、ngine to start(see Fig.3-18).The starting system and ignition system must work together for good engine starting This system includes the following main components:Battery serves as an electrical energy source It produces electric current for starting the car,powering the ignition system and turning
9、 on the lights The battery converts electrical energy into chemical energy during charging and then converts it back into electricity during discharging Ignition switch,also called key switch,controls the ignition circuit,starting system and the power for the car instruments Starter is a very powerf
10、ul direct-current electric motor designed to crank the engine The starter has a small pinion gear which meshes with the ring gear on the flywheel When the driver turns the key switch,the starter drives the pinion gear,which,in turn,drives the flywheel and cranks the engine Solenoid is mounted on the
11、 top of the starter It has two important functions:it controls the electrical circuit between the battery and starter;it shifts the pinion in and out of mesh with the ring gear(see Fig.3-19).Fuelsupply system The purposes of the fuel supply system are to supply the right amount of fuel for the engin
12、e to burn,and control the speed of the engine Lets look at the major parts of the fuel system as shown in Fig.3-20.Fuel tank(see Fig.3-21)is the energy storage for the engine.All cars have a single tank located in the rear of the cars In the tank there is a sending unit which tells the fuel gauge ho
13、w much fuel is left in the tank Fuel pump(see Fig.3-22)is usually located inside the fuel tank so as to keep the pump cool and quiet Nowdays,a fuel injected car uses an electric pump.Its purposes are to draw the fuel from the fuel tank and deliver it to the fuel system Fuel line uses steel lines and
14、 flexible hoses that carry the fuel from the tank to the engine Fuel filter(see Fig.3-23)has an important job that removes dirt,rust and water from the fuel before it can reach the injection system.Fuel injector(see Fig.3-24)is nothing but an electronically controlled valve The function of the fuel
15、injector is to deliver finely atomized fuel under high pressure to the combustion chamber of the engine.New Words and Expressions performance pfmns n 性能 replace ripleis vt 取代,代替 sensor sens n 传感器 multiple mltipl adj 多个的 eliminate ilimineit vt 淘汰 reliability rilaibilti n 可靠性 charging tdi n 充电 dischar
16、ging dista:di n 放电 crank krk vt 起动 flexible fleksibl adj 有弹性的 injection indekn n 喷射 atomized tmaizd adj 雾化的 haveimpact on对影响 engine performance发动机性能 exhaust pollution排气污染 spark timing点火正时 electric current电流 electrical energy电能 chemical energy化学能Common Automobile Terms battery btri n 蓄电池 starter stt
17、n 起动机 solenoid sulnid n 电磁开关 pinion pinjn n 小齿轮;驱动齿轮 starting system起动系统 fuelsupply system燃油供给系统 contact-point ignition system触点式点火系统 non-point ignition system无触点点火系统 non-distributor ignition system无分电器点火系统 conventional ignition system(CIS)传统点火系统 electronic ignition system(EIS)电子点火系统 reluctor disk磁阻
18、盘 electronic control module(ECM)电子控制模块 engine control unit(ECU)发动机控制单元 ignition control unit(ICU)点火控制单元 ignition coil点火线圈 crankshaft position sensor曲轴位置传感器 camshaft position sensor凸轮轴位置传感器 knock sensor爆燃传感器 coil pack点火线圈包 spark plug wire火花塞高压线 ignition switch点火开关 fuel tank油箱,燃油箱 fuel gauge燃油表 fuel pump燃油泵 sending unit燃油表传感器 fuel line燃料管路,燃料管线 fuel filter燃油滤清器
