1、Unit Three Engine Systems Passage ALubrication and Cooling Systems Lubrication system The purpose of the engine lubrication system(see Fig.3-1)is to deliver clean en-gine oil at the correct temperature and pressure to every moving part of the engine to reducefriction between the surfaces of the part
2、s which contact each other The major parts of thelubrication system are listed below:Oil pump is the key part in the lubrication system Its task is to produce the pressure high enough to draw the engine oil from the oil pan and circulate it throughout the sys-tem Two types of the oil pumps are often
3、 found on most cars:gear-type and rotor-type oil pumps as shown in Fig.3-2 Oil screen(see Fig.3-3)is located at the bottom of the oil pan It is connected to the oil pump Its job is to collect any large particles of dirt before the engine oil entering the pump.Oil filter(see Fig.3-4)is a very importa
4、nt part in this system It takes in dirty oil,removes crud and keeps it trapped in the filter media,and returns the clean oil back to the engine Oil pan(see Fig.3-5)is a container mounted at the bottom of the crankcase which serves as engine oil storage It collects the oil as it flows down from sides
5、 of the crankcase when the engine is at rest.Engine oil(see Fig.3-6)has several important jobs in the engine It lubricates the moving engine components with less friction The circulating oil cools the engine by carry-ing heat away from the hot engine components It cleans dirt and deposits off the en
6、gine parts It also seals between the cylinder walls and piston rings,improving the engines com-pression.In modern engine designs,two methods of lubrication are combined:pressure lubrication and splash lubrication(see Fig.3-7).Cooling system The purposes of the cooling system are to remove excess hea
7、t from the engine,to keep the engine operating at its most efficient temperature,and to warm up the engine to the efficient temperature as soon as possible after starting(see Fig.3-8).The major parts of the cooling system are listed below:Radiator(see Fig.3-9)is designed to dissipate the heat which
8、the coolant has absorbed from the engine It consists of radiator core,water-carrying tubes,an inlet tank and an outlet tank Usually,the radiator is mounted in front of the engine compartment,just behind the grill.Radiator fan(see Fig.3-10)is designed to keep the air flow going through the radiator w
9、hile the car is going or it stops with the engine running Usually,two fans are mounted on the back of the radiator.Water pump(see Fig.3-11)is a simple device that can keep the coolant flowing as long as the engine is running It is driven by the engine through the timing belt.Pressure cap(see Fig.3-1
10、2)is designed to maintain pressure in the cooling system If the pressure rises up higher than the set pressure point,the cap with a spring loaded valve will release the pressure to the expansion tank to prevent loss of coolant and return the coolant to the radiator when it cools down.Expansion tank(
11、see Fig.3-13)is used to fill the coolant In addition,when the coolant in the engine expands and is forced out of the radiator,it overflows into the expansion tank When the engine cools down and coolant contracts,the vacuum draws the coolant back into the radiator in order to make it always completel
12、y full.Thermostat(see Fig.3-14)is simply a valve that measures the temperature of the coolant The thermostat helps the engine reach the operating temperature sooner by keeping the coolant from flowing to the radiator As the engine reaches operating temperature,the thermostat opens and allows the coo
13、lant to flow to the radiator through the upper hose.Coolant or antifreeze performs two functions:it keeps the radiator fluid from freezing in wintry conditions and keeps the engine from overheating in warm weatherNew Words and Expressions lubrication lubrikein n 润滑 friction frikn n 摩擦 contact kntkt
14、vt 使接触 task t:sk n 工作,任务 circulate skjleit vt 使循环,使流通 particle ptikl n 颗粒,粒子 remove rimuv vt 删除,除去 crud krd n 渣滓;杂质 media midi n 媒质 mount maunt vt 安装 deposit dipzit n 沉积物 excess ikses adj 过量;过分;过度 efficient ififnt adj 有效率的,效率高的 coolant kulnt n 冷却液 absorb bsb vt 吸收 tube tjub n 管 release rilis vt 释放 o
15、verflow uvflu vt 溢流 contract kntrkt vi 收缩 vacuum vkjum n 真空 antifreeze ntifriz n 防冻液 freeze friz vt 结冰 wintry wintri adj 寒冷的,冬天的 overheat uvhit vi 过热 moving part运转部件,运动件 take in吸收 filter media过滤介质 serve as作为;充当 at rest静止 warm up热机 be designed to目的是;设计用于 spring loaded valve弹簧加载阀 force out of把压出来Commo
16、n Automobile Terms radiator reidieit n 散热器 grill gril n 格栅 thermostat mstt n 节温器 lubrication system润滑系统 cooling system冷却系统 oil pump机油泵 oil screen滤油网,集滤器 oil filter机油滤清器 pressure lubrication压力润滑 splash lubrication飞溅润滑 radiator core散热器芯 inlet tank进水箱 outlet tank出水箱 radiator fan散热器风扇 water pump水泵 pressure cap压力盖 expansion tank膨胀水箱 upper hose(散热器)上软管
