1、1 Engine Cooling System The purpose of the cooling system is to keep the engine at its most efficient operting temperature at all engine speeds and all driving con-ditionsSection 4 Engine Cooling and Section 4 Engine Cooling and Lubricating Systems Lubricating Systems 发动机冷却与润滑系统发动机冷却与润滑系统（一）发动机冷却系统（
2、一）发动机冷却系统 冷却系统的作用是控制发动机的温度，使发动冷却系统的作用是控制发动机的温度，使发动机在各种转速和各种行驶状态下都能有效地工作。机在各种转速和各种行驶状态下都能有效地工作。A great deal of heat is produced in the engine by the burning of the air-fuel mixtureSome of this heat escapes from the engine through the exhaust gases to keep the engine from over-heatingBut enough remain
3、s in the engine to cause serious trouble，the cooling system takes care of this ad-ditional heatAnother important job of the cooling system is to allow the engine to heat up as quickly as pos-sible，and then to keep the engine at a constant temperature There are two types of cooling sys-tems found on
4、cars：liquid-cooled and air-cooled 混合气的燃烧在混合气的燃烧在发动机中产生大量发动机中产生大量的热，其中部分热的热，其中部分热量通过废气被排出量通过废气被排出以阻止发动机过热。以阻止发动机过热。但是，残留在发动但是，残留在发动机中的余热仍足以机中的余热仍足以使发动机受到严重使发动机受到严重损坏，冷却系统就损坏，冷却系统就是专门用来消除余是专门用来消除余热的。冷却系统还热的。冷却系统还有一个重要任务，有一个重要任务，就是让发动机迅速就是让发动机迅速预热，然后就让发预热，然后就让发动机保持恒定的温动机保持恒定的温度。度。冷却系统有两种：冷却系统有两种：液冷和风冷。
5、液冷和风冷。The cooling system on liquid-cooled cars circulates a fluid through pipes and passageways in the engineAs this liquid passes through the hot en-gine it absorbs heat，cooling the en-gineAfter the fluid leaves the engine，it passes through a heat exchanger，or radiator，which transfers the heat from
6、 the fluid to the air blowing through the exchanger Some older cars，and very few mo-dem cars，are air-cooledSince most cars are liquid-cooled，we will focus on that system in this article 液冷系统的流体液冷系统的流体在发动机中的管路在发动机中的管路和通道中循环流动。和通道中循环流动。当液体流过发热的当液体流过发热的发动机时，就吸收发动机时，就吸收了大量热量。当液了大量热量。当液体流出发动机时，体流出发动机时，通过
7、热交换器或散通过热交换器或散热器，将液体变为热器，将液体变为气体吹走。气体吹走。有些老式汽车和有些老式汽车和少数现代汽车采用少数现代汽车采用风冷系统。因为大风冷系统。因为大部分的汽车采用液部分的汽车采用液体冷却，所以我们体冷却，所以我们主要讨论液冷系统。主要讨论液冷系统。The liquid cooling system consists of water pumps，water jackets，engine fan，radiator，coolant reservoir tank，radiator cap，thermostat，hoses and so on，as is shown in Fi
8、g.7-26The cooling system is built into the engineThere are hollow spaces around each engine cylinder and combustion chamberThese hollow spaces are called water jackets，since they are filled with waterWhen the engine is running，the water takes heat from the engine，becoming hot in the processA water p
9、ump pumps the hot water from the engine water jackets into the radiator 液体冷却系由水液体冷却系由水泵、水套、发动机泵、水套、发动机风扇、散热器（水风扇、散热器（水箱）、副水箱、箱）、副水箱、压力式水箱盖、节压力式水箱盖、节温器、水管等组成，温器、水管等组成，如图如图7-26所示。冷所示。冷却系统就设置在发却系统就设置在发动机中。每个气缸动机中。每个气缸体和燃烧室周围都体和燃烧室周围都留有空腔，这些空留有空腔，这些空腔装满了水，称之腔装满了水，称之为水套。在发动机为水套。在发动机运行过程中水被加运行过程中水被加热，并以水循
10、环方热，并以水循环方式把热量从发动机式把热量从发动机中带走。水泵从发中带走。水泵从发动机水套中把热水动机水套中把热水抽到散热器中，抽到散热器中，The radiator has two sets of pas-sagesOne set carries waterThe other set carries air（pulled through by car motion and the engine fan）As the hot water passes through，it gives up its heat to the air passing throughThe cooled water
11、 then reen-ters the engine，where it can pick up more heatIn operation，water conti-nuously circulates between the engine and radiator，carrying heat from the engine to the radiatorBy this means，excessive engine temperatures are prevented散热器有两条通道：散热器有两条通道：一条是水道，另一一条是水道，另一条是气道（空气是条是气道（空气是通过汽车行驶和发通过汽车行驶和
12、发动机的风扇抽入动机的风扇抽入的）。当热水流过的）。当热水流过水道时，气道中流水道时，气道中流通的空气使热水冷通的空气使热水冷却，冷却后的水又却，冷却后的水又重新进入发动机，重新进入发动机，再把发动机中的热再把发动机中的热量传导出去。在这量传导出去。在这一过程中，水不断一过程中，水不断地在发动机与散热地在发动机与散热器之间循环，水携器之间循环，水携带着热量从发动机带着热量从发动机流到散热器再散发流到散热器再散发出去。通过这个方出去。通过这个方法可避免发动机温法可避免发动机温度过高。度过高。98764532110Fig.7-261Water Jacket；水套2Heater；暖气水箱3Heate
13、r Hose；暖气水管4Thermostat；节温器5Water Pump；水泵6Pressure Cap；压力式水箱盖7Coolant Reservoir Tank；副水箱8Radiator Core；散热器芯9Hoses；水管10Fan Belt；风扇皮带 The water pump is a simple cen-trifugal pumpThe water pump，driven by a belt from the engine crankshaft，circulates the cooling liquid between the radiator and engine wate
14、r jacketsThe cooling liquid is waterAntifreeze com-pounds are added to the water during the winterThe water jacket are cast into the cylinder blocks and headsThe engine fan is us-ually mounted on the water pump shaft and is driven by the same belt that drives the pump and the ge-nerator，see Fig.7-27
15、 水泵就是个简单水泵就是个简单的离心泵。水泵由的离心泵。水泵由发动机曲轴上的皮发动机曲轴上的皮带驱动，使冷却液带驱动，使冷却液在散热器与发动机在散热器与发动机水套之间循环流动。水套之间循环流动。冷却液是水，冬季冷却液是水，冬季在水中须加入防冻在水中须加入防冻剂。水套被铸入气剂。水套被铸入气缸体和气缸盖内部。缸体和气缸盖内部。发动机风扇通常安发动机风扇通常安装在水泵轴上，由装在水泵轴上，由驱动水泵和发电机驱动水泵和发电机的同一条皮带驱动，的同一条皮带驱动，参见图参见图7-27。The purpose of the fan is to provide a powerful draft of air
16、 through the radiatorThe radiator is a device for holding a large volume of water in close contact with a large volume of air so that heat will transfer from the water to the airThe radiator core is divided into two separate and intri-cate compartments；water passes through one，and air passes through
17、 the other 风扇的作用是向风扇的作用是向散热器提供强大的散热器提供强大的空气流，与大量空空气流，与大量空气密切接触的散热气密切接触的散热器内可以容纳大量器内可以容纳大量的水，这样热量可的水，这样热量可以通过水散发到空以通过水散发到空气中。散热器芯为气中。散热器芯为分离和间隔交错的分离和间隔交错的两部分。冷却水在两部分。冷却水在其中一部分中流过，其中一部分中流过，空气在另一部分中空气在另一部分中通过。通过。Fig.7-271231Water Pump；水泵2Pulley；皮带盘3Cooling Fan；冷却风扇 The radiator is the largest part of t
18、he cooling system，most of the heat from the engine is transferred from the coolant to the surroun-ding air，as is shown in Fig.7-28The reservoir tank is connected to the overflow hoseWhen the hot coolant expands in the radiator，the reservoir tank allows coolant to flow inAs the system cools，the coola
19、nt will be drawn back into the radiator 水箱是冷却系水箱是冷却系最大的零件，大最大的零件，大部分发动机的热部分发动机的热量由冷却液散发量由冷却液散发至周围空气中，至周围空气中，如图如图7-28所示。所示。副水箱连接溢流副水箱连接溢流管，当热冷却液管，当热冷却液在水箱内膨胀，在水箱内膨胀，冷却液便流入副冷却液便流入副水箱；当冷却系水箱；当冷却系温度下降后，冷温度下降后，冷却液又再从副水却液又再从副水箱流回水箱。箱流回水箱。876543219Fig.7-281Reservoir Tank；副水箱2Pressure Cap；压力式水箱盖3Upper Tank；
20、上水箱4Upper Hose；上水管5Lower Hose；下水管6Drain；放水塞7Lower Tank；下水箱8Radiator Core；水箱芯子9Overflow Hose；溢流管 The radiator is normally equipped with a pressure cap or radiator cap that tightly seals the radiator，as is shown in Fig.7-29This allows the coolant to rise above 100 in temperature without boilingThe the
21、rmostat is an important compo-nent that controls coolant flow and engine temperatureIt is operated by a wax capsule or pelletIf you see a thermostat marked 82，it means the thermostat will begin to open at 82 水箱通常配有水箱通常配有压力式水箱盖压力式水箱盖（压力盖或水箱（压力盖或水箱盖）以紧紧密封盖）以紧紧密封水箱，如图水箱，如图7-29所示。如此可让所示。如此可让冷却液温度升高冷却液温度
22、升高至至100以上而以上而不沸腾。节温器不沸腾。节温器是控制冷却液流是控制冷却液流动及发动机温度动及发动机温度的重要元件，它的重要元件，它由石蜡制小容器由石蜡制小容器或石蜡丸来动作，或石蜡丸来动作，如果你看到节温如果你看到节温器上标有器上标有82，它表示节温器将它表示节温器将在在82时打开。时打开。12431Vacuum Valve；真空阀2Pressure Cap；压力式水箱盖3Overflow Tube；溢流管4Wax；蜡丸Fig.7-29 A radiator is a type of heat ex-changerIt is designed to tran-sfer heat fro
23、m the hot coolant that flows through it to the air blown through it by the fan The thermostats main job is to allow the engine to heat up quickly，and then to keep the engine at a constant tempe-ratureIt does this by regulating the amount of water that goes through the radiator Like the thermostat，th
24、e coo-ling fan has to be controlled so that it allows the engine to main-tain a constant temperature 散热器（水箱）散热器（水箱）是热交换器的一是热交换器的一种。散热器将发种。散热器将发热的冷却液的热热的冷却液的热量传递给空气，量传递给空气，然后用风扇吹入然后用风扇吹入大气。大气。节温器的主要节温器的主要任务是使发动机任务是使发动机迅速预热，然后迅速预热，然后使发动机保持一使发动机保持一个恒定的温度。个恒定的温度。这是通过调节流这是通过调节流过散热器的水流过散热器的水流量来调节的。量来调节的。就
25、像节温器一就像节温器一样，冷却风扇能样，冷却风扇能使发动机维持在使发动机维持在一个恒定温度。一个恒定温度。2 Engine Lubricating System The main components of engine lubri-cation system are the oil pan，oil pump，engine oil passages and oil fil-ter，as is shown in Fig.7-30 and Fig.7-31 发动机润滑系发动机润滑系统主要元件有油统主要元件有油底壳、机油泵、底壳、机油泵、发动机油道和机发动机油道和机油滤清器，如图油滤清器，如图7-3
26、0、7-31所示。所示。654321Fig.7-301Cylinder Head Oil Gallery；汽缸盖油道2Hydraulic Valve Lifter；液压阀挺杆3Main Oil Gallery；主油道4Oil Filter；滤油器5Oil Pump；油泵6Oil Pan；油底壳1Valve of Oil Radiator Passage；通机油散热器的阀门2Centrifugal Oil Fine Filter；离心式机油细滤器3Oiled Relief Valve of Fine Filter；细滤器进油限压阀4Oil strainer；机油集滤器5Magnetism Pur
27、ge Cock；磁性放油螺塞6Oil Relief Valve；机油限压阀7Oil Pump；机油泵8Oil Tube；油管9Oil First Filter；机油粗滤器10Oil bypass-valve；机油旁通阀Fig.7-3111Oil Passage of Connecting Rod Small End；连杆小头油道12Injector to Lubricate Timing Gear；润滑正时齿轮喷油嘴13Tabula Oil Passage；横隔油道14Main Oil Gallery；主油道15Transmission Shaft of Oil Pump；油泵传动轴16Oil
28、 Passage Lead to rockshaft；通摇臂轴油道17Arm Shaft；臂轴Fig.7-31 The most common types of oil pumps are the gear type and the rotor type，as is shown in Fig.7-32The gear type uses a drive gear and a driven gearWhen the engine starts，oil is pushed into the small spaces between the gears and the housingThe oil，
29、under pres-sure，will be sent to the oil fil-terThe rotor type contains two ro-tors in the pump bodyThe rotors rotate in the same direction causing the oil to be drawn into or out of the oil pump when the volume increases or decreases 机油泵最常见机油泵最常见的是齿轮式和转的是齿轮式和转子式，如图子式，如图7-32所示。齿轮式机所示。齿轮式机油泵利用一个主油泵利用一
30、个主动齿轮和一个被动齿轮和一个被动齿轮，只要发动齿轮，只要发动机一启动，机动机一启动，机油便被挤入介于油便被挤入介于齿轮与外壳间的齿轮与外壳间的小空间中，接着小空间中，接着被压送至机油滤被压送至机油滤清器。转子式机清器。转子式机油泵在泵体内有油泵在泵体内有两个转子，转子两个转子，转子以相同方向旋转以相同方向旋转并改变两者间的并改变两者间的容积，当容积增容积，当容积增加或减少时，机加或减少时，机油则流入或流出油则流入或流出机油泵。机油泵。Fig.7-32123435（a）Gear Type 齿轮式 （b）Rotor Type 转子式1Drive Gear；主动齿轮2Driven Dear；从动齿
31、轮3Housing；外壳4Driven Rotor；从动转子5Drive Rotor；主动转子 The oil pan contains oil and trans-fer heat from the hot oil to the sur-rounding airThe oil pump supplies oil under pressure to the moving parts of the engine The engine oil filter is designed to remove minute panicles of metal and dirt from the engine
32、 oilWhen the filter is restricted，the oil cant reach the bearings and damage will occurAt this point，the pressure relief valve will open and the unfil-tered oil can flow to lubricate the en-gine，see Fig.7-33 油底壳能保存油底壳能保存机油并将机油的机油并将机油的热量传递到周围热量传递到周围的空气中，机油的空气中，机油泵再将机油压送泵再将机油压送至友动机的旋转至友动机的旋转元件。元件。机油滤清
33、器的机油滤清器的作用是滤除机油作用是滤除机油中细小的金属微中细小的金属微粒和污物。当机粒和污物。当机油滤清器堵塞，油滤清器堵塞，机油无法到达轴机油无法到达轴承时，发动机会承时，发动机会损坏，此时减压损坏，此时减压阀将会开启，未阀将会开启，未经过滤的机油就经过滤的机油就能流出以润滑发能流出以润滑发动机，参见图动机，参见图7-33。1Pressure Relief Valve；泄压阀2Pressure Relief Valve Open；打开单向阀2121Fig.7-33 The lubricant is used to protect the automotive componentIn som
34、e cases this protection is in the form of a fluid film that keeps opposing surfaces separatedIn other cases，the lubri-cant provides wear protection by for-ming a chemical film on a surface，to generate boundary lubrication prote-ctionAutomotive lubricants protect against corrosion by virtue of alka-l
35、ine agents to neutralize acids that form in hot spots Under highly loaded and high tem-perature conditions，fluid film lub-rication may not be sufficient to provide complete wear protection，润滑剂是用来润滑剂是用来保护汽车零件的。保护汽车零件的。有时候通过在零有时候通过在零件表面形成油膜件表面形成油膜使相接触表面分使相接触表面分开来保护零件，开来保护零件，有时候通过提供有时候通过提供化学膜而增加零化学膜而增加
36、零件表面抗磨性来件表面抗磨性来保护零件。汽车保护零件。汽车润滑剂通过利用润滑剂通过利用其碱性中和酸起其碱性中和酸起到对高温零件表到对高温零件表面的防腐作用。面的防腐作用。在高负荷高温在高负荷高温条件下，油膜润条件下，油膜润滑不能完全有效滑不能完全有效地提供摩擦保护，地提供摩擦保护，the lubricant must contain additives so that interact with rubbing surfaces to form antiwear films The engine lubrication system must perform many direct funct
37、ion，but how successful the lubrication system is in performing all these functions depends on a number of factors and conditionsFor example，there must be an adequate supply of good-quality lubricant delivered to all moving engine parts under sufficient pressure to provide hydrodynamic lubrication fo
38、r rotating parts and oil adhesion to surfaces subject to sliding frictionIn addition，润滑油必须含有润滑油必须含有添加剂，从而在添加剂，从而在摩擦表面起作用，摩擦表面起作用，形成耐磨层。形成耐磨层。润滑系统必须润滑系统必须执行很多功能，执行很多功能，但是否能成功地但是否能成功地实现所有这些功实现所有这些功能与很多因素和能与很多因素和条件有关。例如，条件有关。例如，必须要有足够的必须要有足够的质量好的润滑剂质量好的润滑剂输送到所有的发输送到所有的发动机运动零件上，动机运动零件上，为运动零件提供为运动零件提供液力润
39、滑，同时液力润滑，同时也为受滑动摩擦也为受滑动摩擦影响的表面提供影响的表面提供液力润滑。此外，液力润滑。此外，The oil and filter must be chan-ged at regular intervals The engine must operate at its most efficient temperature Engine oil temperatures must not be excessively hot or cold 在规定的时间在规定的时间间隔内更换机油和间隔内更换机油和过滤器。过滤器。发动机必须在发动机必须在有效的温度下工作。有效的温度下工作。发动机机
40、油温发动机机油温度不许过热或过冷。度不许过热或过冷。Reading Material1 Thermostat（节温器）The thermostat is the engine temperature control unitSee Fig.7-34，The thermostat blocks the coolant flow to the radiator until the engine reaches normal operating temperatures1652437Cold CoolentHot CoolentHot Coolent to Radiator（a）Engine Col
41、d Thermostat Closed （b）Engine Hot Thermostat Open Fig.7-34 Thermostat Situation1Bypass Passage；2Thermostat Housing；3Valve（Closed）；4Metal Piston；5Return Spring；6Wax Pellet；7Valve（Open）Until engine warm-up occurs，the thermostat remains clo-sedCoolant flows back through the engine block via the water p
42、ump bypass passageThereforethe coolant flows past the cylinders again without the advantage of radiator coolingThus the engine warms quickly and evenly When the temperature rises to a preset point determined by the thermostats calibration，the thermostat begins to openThe coo-lant then flows through
43、the thermostatThe flow continues through the upper radiator hoseThe coolant then enters the inlet tank of the radiatorFrom there，it passes through file radiator cooling tubes If the thermostat stick is closed，the engine will overheat be-cause of inadequate coolant flowIf the thermostat stick opens(o
44、r is removed)，the engine will not warm up as quickly as it shouldLonger warm-up time can result in poor fuel economy，high exhaust Emissions，and deposit build-up in the engine.2 Oil Temperature Sending Unit（油温传感器）An oil temperature sending unit is used on some vehiclesThis sending unit is a thermisto
45、r（热敏电阻）Changes in engine oil（机油）temperature affect the resistance of the thermistorAs with an oil pressure display，the sending unit resistance determines the amount of current flow through the display circuitIn this case the instrument panel（仪表盘）displays oil temperature instead of oil pressure（油压）1）
46、Motor Oil（机油；马达油）Motor oil is the lifeblood（命根子）of an engineWithout a good-quality oil，engine life would be very shortMotor oil performs five tasksIt must：LubricateIt prevents excessive friction（过份摩擦）between moving parts CoolThe circulating oil（循环油）carries heat away from high-temperature components
47、such as pistons and bearings SealAn oil film helps seal（密封）between the piston rings and cylinder Walls CleanOil additives help to prevent deposit buildup on engine parts and surfaces ProtectOil additives protect against rust（生锈），corrosion（腐蚀）and abnormal wear（不规则磨损）Motor oil consists of base oils pl
48、us an additive packageBase oils may be made from either petroleum（mineral oil）or synthetic（ma-nufactured）materialsAn additive package improves the natural properties of the oil to make a better lubricant 2）Oil Viscosity（油黏度）Water and gasoline are“thin”（稀的；低黏度的）liquids that flow easilyThey have low v
49、iscosityViscosity is a measure of a liquids resistance to flowMotor oils and gear oils are“thicker（稠化剂；增稠剂）”liquids with more resistance to flowThey have higher visco-sityThe viscosity of oil is affected by（受影响）temperature A thin and low viscosity oil will flow easily at low temperaturesHowever，it w
50、ill be too thin for good lubrication when the engine warms upA thicker and higher viscosity oil flows more slowlyIt will provide good lubrication at high temperatures but may be too thick to flow through the engine when it is coldThe correct oil viscosity is critical for good lubrication at all temp
