汽车专业英语翻译及课后答案-黄韶炯(全部单元都有)

Unit1AutomotiveBasicsAutomobiles,trucks,andbusesareessentialformsoftransportation.Theyarecomplexmachinesmadeupofmanyparts.Thesepartscanbegroupedintoanumberofsystems.Anunderstandingofhowthesystemworkwillhelpyouunderstandhowtheautomobileworks.轿车、卡车和客车是交通运输的重要组成部分。它们都是由许多部件组成的复杂机器。这些部件可以归类为汽车的几个组成系统。了解这些各个小系统是如何工作的将有助于我们理解整个汽车系统是如何工作。Anautomobilecanbedividedintotwobasicparts:abodyandachassis.Thebodyistheenclosurethathousestheengine,passengers,andcargo.Itisthepartoftheautomobilethatyousee.Thechassisisthatpartoftheautomobilebeneaththebody.汽车可以分为两个基本部分：车身和底盘。车身包围发动机、乘客和行李，它是汽车你所看到的部分。而车身以下的部分就是底盘。1.1THEBODYAnautomobilebodyisasheetmetalshellwithwindows,doors,ahood,andatrunkdeckbuiltintoit.Itprovidesaprotectivecoveringfortheengine,passengers,andcargo.Thebodyisdesignedtokeeppassengerssafeandcomfortable.Forexample,insulationinthebodyreducesnoiseandprotectsagainstheatandcold.Thebodystylingprovidesanattractive,colorful,modernappearanceforthevehicle.Itisstreamlinedtolessenwindresistanceandtokeepthecarfromswayingatdrivingspeeds.轿车车身是一个钣金件壳体，它上面有车窗、车门、发送机罩和行李舱门等部件，它给发动机、乘客和行李提供防护。车身设计来确保乘客乘坐的安全和舒适。比如：车身绝热层可以减少噪音和抵御冷热。车身造型设计使得汽车有一个华美、现代、吸引人的外观。车身的流线型设计可以减少风阻，防止汽车行驰过程中发生摆动。Theautomobilebodyhastwobasicparts-theupperbodyandtheunderbody.车身有两个基本部分-车身上部和车身下部。1.2ThechassisThechassisisanassemblyofthosesystemsthatarethemajoroperatingpartsofavehicle.Thechassisincludeseverythingexceptthebody.Thethreeimportantpartsofthechassisaretheframe,theengine,andthepowertrain(alsocalledthedrivetrain).Eachofthesethreepartsismadeupofanumberofsystems.Asystemisamechanicalorelectricalunitthatperformsaspecificfunction.Thus,eachsystem(suchassteering,brake,orfuel)hasacertainjobtodoinrunningavehicle.Weshalllookateachofthesepartsandsystemstoseehowtheyfittogethertoformtheautomobilechassis.底盘集中了汽车大部分的运动组件，它包括除了车身以外的所有部件。底盘有三个重要的系统：车架、发动机和传动系统。这三个系统又都有许多个完成某一个特定功能的机械或电气系统组成。为了保证汽车正常运转，每个系统（比如：转向、制动或燃油系统）都要实现一定的功能。下来我们看看这些系统和组件是如何相互连接从而组成汽车底盘的。1.2.1TheframeThefirstmajorpartofthechassisistheframe.Itismadefromtoughsteelsectionswelded,riveted,orboltedtogether.Theframelookslikeasteelladder,thoughitsometimehasanXshapeforextrastrength.Itformsafoundationforthecarbodyandthepartsoftheseveralsystems.Thebodyisjoinedtotheframewithbolts.Rubbershockmountsorwashersareusedateachjoint.Thesereducevibrationandroadnoise.Inmostmoderncarstheframeisbuiltintothebody.Acarwiththeframebuiltintothebodyhasaunitizedbodyorunibody.Theframesupportsthesuspensionsystem,steeringsystem,andthebrakingsystem.底盘最重要的部分就是车架。车架由钢件通过焊接、铆接或螺栓联接而成，看上去就像一架钢梯。有时为了得到额外的强度，车架做成了X形状。车架为车身和很多系统部件提供了底1座。车身和车架使用螺栓联接。每个联接使用橡胶防震支架或垫圈来减振降噪。现代轿车车架和车身做在了一起。采用这个形式的汽车车身叫做承载式车身。车架支撑悬架、转向和刹车系统。Thefrontandrearwheelsareattachedtothechassisbyasuspensionsystem.Thissystemismadeupofsprings,shockabsorbers,controlarms,andstabilizers.Thesesupportthevehicleandcushionitfromroadbumpsforbetterrideandhandling.前后轮通过悬架系统和底盘相连。悬架系统由弹簧、减振器、控制臂和横向稳定杆组成。它们支撑着车身，并减缓由于路面不平引起的颠簸，以获得更好的乘坐舒适性和操作稳定性。Thesteeringsystemcontrolsthecar’sdirectionoftravel.Itincludesawheelandcolumn,stegears,rods,andlinkages.Asthesteeringwheelisturned,itsmotionistransferredtotheidlerarmandtierods.Thesecausethefrontwheelstoturntotherightofleft.Onsomecars,apowerunit(calledpowersteering)makessteeringeasier.转向系统控制车辆行驰的方向。它包括方向盘、转向管柱、转向器、转向拉杆和转向传动装置。当转动方向盘，方向盘的运动被传递到随动臂和横拉杆，从而使得前轮向左或向右转动。有些车辆使用助力转向装置，从而使得转向更加轻便。Thebrakesystemgivestheautomobileitsstoppingpower.Hydraulicbrakesarefoundonallmoderncars.Asthebrakepedalispushedwiththefoot,brakefluidisforcedthroughbrakelinesintocylindersthatpressthebrakeshoesagainstadrum.Thisstopsthemotionofthecar.Powerunits(powerbrakes)areusedtomakebrakingeasier.Mostmoderncarshavediscbrakesonthefrontwheels.(Somehavethemonboththefrontandrearwheels.)Discbrakesworklikeapairofplierssqueezingarotatingdisc.Drumbrakesarealsoused.制动系统给车辆制动的动力。现代轿车都使用液压制动。当踩下制动踏板，制动液通过制动管路流入制动缸，强迫制动蹄接触制动鼓，从而阻止车辆运动。为了使刹车更加轻便，车辆也使用助力制动。现代轿车在前轮装备盘式制动器（。一些轿车在前后轮都使用盘式制动器。）盘式制动器工作原理类似一对钳子夹住旋转的盘片。也有前后轮都使用鼓式制动器的汽车。1.2.2TheengineTheengineprovidespowertomovetheautomobile.Themostcommontypeofautomobileengineisthegasoline-burningpistonengine.Itisfoundinmostautomobiles.Diesel-fuelburningenginesarealsousedinmodernpassengercars,aswellasinlargetrucks.Allengineshavefuel,exhaust,cooling,andlubricationsystems.Gasolineenginesalsohaveanignitionsystem.发动机给汽车提供动力。最常见的发动机是汽油机。大多数汽车都使用它。现代客车和大型卡车使用柴油机。所有的发动机都具有燃油、排放、冷却和润滑系统。汽油发动机还有一套点火系统。Theignitionsystemsuppliestheelectricsparkneededtoignitetheair-fuelmixtureinthecylinders.Whentheignitionswitchisturnedon,currentflowsfromthe12-voltstoragebatterytotheignitioncoil.Thecoilbooststhevoltagetoproducethestrongsparkof20,000Vneededtoignitetheenginefuel.Thedistributordirectstheelectricalcurrenttotherightsparkplugattherighttime.Dieselenginesusetheheatcausedbyenginecompressiontoignitethefuelcharge.Theseenginesarecalledcompressionignitionengines.点火系统提供点燃气缸内油气混和物的电火花。当打开点火开关，电流从12V电池流向点火线圈。点火线圈升高电压，产生用于点火的20000V尖峰电压。分电器引导电流在正确的时刻流向正确的火花塞。柴油机使用压缩发动机产生的热量来点燃燃料，因此被称为压燃式发动机。Theautomobilesuppliesalltheelectricityitneedsthroughitselectricalsystem.Forexample,the2electricalsystemsupplieselectricityfortheignition,horn,lights,heater,andstarter.Theelectricitylevelismaintainedbyachargingcircuit.Thiscircuitconsistsofthebattery,alternator(orgenerator),andtheregulator.Thebatterystoreselectricity.Thealternatorchangestheengine’smechanicalenergyintoelectricalenergyandrechargethebattery.Theregulatorpreventsdamagetothesystembyregulatingthemaximumvoltageinthecircuit汽车通过自身的电气系统给自身供电。比如：电气系统给点火系统、喇叭、灯光、供暖系统和起动器供电。系统电压通过充电系统保持稳定。充电系统由电池、发电机和调节器组成。电池储存电能。发电机将发动机的机械能转变为电能，并给电池充电。调节器调节电气系统的最大电压，提供过压保护。Thefuelsystemstoresliquidfuelanddeliversittotheengines.Thefuelisstoredinthetank,whichisconnectedtoafuelpumpbyafuelline.Thefuelispumpedfromthefueltankthroughthefuellines.Itisforcedthroughafilter(whichremovesmoistureanddirt)intothecarburetor,whereitismixedwithair,orintothefuelinjectionsystem.Thefuelismixedwithairtoformacombustiblemixtureinthecarburetor,themanifold,orthecylindersthemselves.燃油系统储存液态燃料，并且把燃料送至发动机。燃料储存在通过油管与油泵连接的油箱里。油泵通过油管将油箱内的油泵出，并通过滤清器（去除湿气和杂污）送达化油器与空气混合或者喷油系统。燃油在化油器、歧管或气缸自身内与空气混合，形成可燃混和物。Theexhaustsystemhasfourjobs:Tocollectburnedgasesfromtheengines.Toremovedangerousemissionthatpollutestheair.Toreduceexhaustnoises.Togetridoftheexhaustgases.排放系统要实现四个功能：、收集发动机的废气。2、去除污染空气的排放物。3、减少排放噪音。4、排出废气。Exhaustgasescontaincarbonmonoxide,unburnedhydrocarbons,andoxidesofnitrogen.Sincealloftheseareharmful,theexhaustsystemisdesignedtoreducethemasmuchaspossible.IntheUnitedStaresallmodernautomobileshaveemissioncontrolsystems.汽车废气包含一氧化碳，未燃烧的碳氢化合物和氮氧化合物。所有的这些都是有害的，排放系统设计要尽可能多减少这些有害物质。美国所有的现代车都配备了排放系统。Thecoolingsystemremovesexcessiveheatfromtheengine.Thetemperatureinenginecombustionchambersisabout1094°C.Sincesteelmeltsataround1354°C,thisheatmustbecarriedawaytopreventenginedamage.Airandacoolantareusedtocarryawaytheheat.Theradiatorisfilledwithacoolant.Thewaterpumpcircuitsthiscoolantthroughtheengineandthewallsoftheengineblockandhead.Heatalsoisremovedbytheradiatorfan,whichdrawsairthroughthenarrowfinsoftheradiator.Thissystemalsosuppliesheattothepassengercompartmentandthewindowdefroster.冷却系统去除发动机多余的热量。发动机燃烧室的温度可以达到1094摄氏度。钢的熔点大约是1354摄氏度，发动机多余的热量必须消除来防止发动机过热。空气和冷却剂用来带走这个热量。散热器内装满了冷却剂。水泵使冷却剂在发动机、发动机壳体和发动机盖循环流动。也可以使用冷却风扇来降温。冷却风扇将风从散热器狭窄的孔径吹出，从而带走热量。这个系统可以给乘客舱和车窗除霜器提供热量。Thelubricationsystemisimportantinkeepingtheenginerunningsmoothly.Motoroilisthelubricantusedinthesystem.Thelubricationsystemhasfourfunctions:Itcutsdownfrictionbycoatingmovingpartswithoil.3Itproducesasealbetweenthepitonringsandthecylinderwalls.Itcarriesawaysludge,dirt,andacids.Itcoolstheenginebycirculatingthemotoroil.润滑系统非常重要，它使得发动机平滑工作。润滑系统使用机油作为润滑剂。润滑系统有四个功能：1、通过运动部件油膜，它可以减小摩擦。2、它在活塞环和气缸壁之间产生油封。、它可以带走金属碎屑、杂污和酸。4、通过机油的循环，它可以冷却发动机。Tokeepthissystemworkingeffectively,oilfiltersandmotoroilmustbechangeregularly.Allothermovingpartsinanautomobilemustalsobelubricated.Theseincludethetransmission,differential,wheelbearings,andsteeringlinkage.为了使得润滑系统有效工作，机油滤清器和机油必须定期更换。汽车内所有的运动部件都必须要润滑，这包括变速器、差速器、轮轴轴承和转向传动机构。1.2.3ThepowertrainThepowertrain,ordrivesystem,deliverspowerfromtheenginetothewheels.Thepowerfromtheenginemovesthroughthetransmission.Transmissionsareeitherstandard,withamanualshiftleverandfootclutch,orautomatic.传动系统将发动机动力传给车轮。来自发动机的动力传递给变速器。变速器可以是一个带手动换档杆和离合器的手动变速器或者自动变速器。Thetransmissionhasgearsthatcontroltheamountofpowerdeliveredtothewheels.Thetransmissionincreasesthepower(torque)tostartthecarmoving.Thistorqueisreducedwhenthetransmissionchangesgearsathigherspeeds.Thetransmissionalsocontainsasetofgearsthatcanreversethedirectionofthewheels.Thetransmissiondeliversthepowertothedifferential.Adrive(orpropeller)shaftwithuniversaljointsateitherendofthedriveshaftallowsaxlemovementoffront-engine,rear-wheeldrivecars.Theseflexibleuniversaljointpreventthedriveshaftfrombreaking.Thedifferentialdeliverspowertothewheelsthroughaxle.Certaingearsallowonewheeltoturnfasterthantheotherwheelwhenthevehicleisturningacorner.变速器使用齿轮来控制传递到车轮力矩的大小。当车辆起步时，变速器增大扭矩。当车速增大，变速器改变齿轮来减小扭矩。变速器还有一套使得车轮反向运动的齿轮。变速器将扭矩传递给差速器。发动机前置后轮驱动轿车的驱动轴两侧装有万向节，可允许产生轴向运动。万向节防止驱动轴断裂。差速器通过半轴将扭矩传递给车轮。当车辆转弯时，齿轮使得一侧车轮比另一侧车轮旋转得更快。Thesearethebasicsystemsoftheautomobile.Eachofthesystemsisdesignedforaspecificjob.以上就是汽车的基本系统。每个系统都为了一个专门的功能而设计。ExercisesTheautomobile’sfurtherdevelopmentwillbedeterminedbyalreadyexistingandsteadilyincreasingrequirements,byadditionalfurtherrequirementsandbythetechnicalpossibilitiesformeetingtheserequirements.Thefollowingfocalpointsfordevelopmentandresearcheffortscanbediscerned:汽车的进一步发展取决于已经存在的、目前稳定增长和未来的需求以及为了满足这些需求的技术。下来给出发展研究的几个要点：Furtherimprovementsoftheautomobilethroughproductsinnovationinallclassisfunctions,i.e.performance,fueleconomy,environmentalimpact,safety,comfortandreliability.Furtherdevelopmentofnewtechnologiessuchaselectrics,alternativematerials,newtestandproductionmethods.Long-rangesolutionsfortrafficproblemssuchashighwaycongestion,smogincitiesandcarbondioxideenrichmentofouratmosphere.4传统功能的产品革新，比如：性能、燃油经济性、环境友好、安全、舒适性和可靠性。新技术的发展，比如：电气、替代材料、新型测试和生产技术。解决交通问题的技术，比如：交通拥堵，城市烟雾和温室效应。Unit2 Automotiveengine2.1PurposeandlocationsofenginesThepurposeofanautomobileengineistosupplythepowerneededtomovethevehicle.Theengineproducesthispowerbyburningfuelinsideit.Becausetheengineburnsfuelinside,orinternally,theengineisknownasaninternalcombustionengine(ICE).汽车发动机的功用是提供汽车行驰所需的动力。发动机通过发动机内部燃烧燃料来产生这个动力。由于燃料燃烧在发动机内部进行，这种发动机被称作内燃机。Mostautomobileenginesarelocatedatthefrontofthevehicle.Manyenginesdrivetherearwheels.Thisrequiresalongdriveshaftextendingfromthefrontwheelstotherearwheels.Otherenginesdrivethefrontwheels.Intherear-wheel-drivearrangement,theenginesitslongitudinally.Itslongdimensionisfromfronttoback.对于大多数汽车，发动机布置在汽车前部。许多发动机驱动后轮，这就要求从前轮到后轮的长驱动轴。其余发动机驱动前轮。对于后轮驱动的汽车而言，发动机由前到后纵向布置。Inthefront-wheel-drivearrangement,theenginesitscrosswise,transversely.Witheitherarrangement,thepoweriscarriedtothedrivewheels(rearorfront)bygearsandshafts.对于前轮驱动的布置，发动机横置。无论哪种布置方式，能量都是通过齿轮和传动轴传到驱动轮（前轮或后轮）。Somecarshavetheenginemountedinbackofthefrontseat.Thisiscalledamid-enginearrangement.Othercarshavebeenbuiltwiththeenginemountedattherear,inbackofrearseat.TheVolkswagen“beettle”isanexampleofrear.有些汽车的发动机位于前排座椅的后面。这种布置被称为发动机中置。还有些汽车的发动机位于后部，安置在后排座椅后面。大众汽车的甲壳虫就是发动机后置的一个例子。2.2EnginetypesVariouskindsofengineareusedinautomotivevehicles.Thetwomajortypesare:Thepistonengineinwhichpistonsmoveupanddown,orreciprocate,intheenginecylinder.Thisistheengineusedinallcarestoday,exceptforsomemodelsofMazda.TheWankelrotaryengineinwhichrotate,orspin.TheMazdaMotorCorporationofJapanisthemajormanufacturerofthisengine.汽车上使用着不同种类的发动机。它们可以分成两大类：、往复活塞式发动机：发动机在气缸内作上下往复运动。除了马自达公司的几款以外，现今几乎全部轿车都采用这种发动机。、转子发动机：活塞在气缸内作旋转运动。日本的马自达公司是这类发动机的主要生产商。Therearetwotypesofpistonengines-sparkignition(SI)andcompressionignition(CI).Spark-ignitionenginesuseanelectricsystemwithsparkplugs.Electricsparksatthesparkplugsignite,orsetfire,thefuelintheenginecylinders.Thecombustionofthefuelmakestheenginerunandproducepower.Thisistheengineusedinmostproducepower.Thisisthetypeofengineusedinmostautomotivevehicles.活塞式发动机可以分为两类：点燃式和压燃式。点燃式发动机使用带火花塞的点火系统。火花塞的电火花点燃发动机气缸内的燃料。燃料燃烧驱动发动机，并做功。这是大多数动力源采用的发动机，也是大多数汽车采用的发动机形式。Thecompression-ignitionengineusestheheatofcompressiontoignitethefuel.Whenairiscompressed,itgetsveryhot.Inthedieselengine,theairiscompressedsomuchthatits5temperaturegoesupto538degreesCelsiusorhigher.Thedieselfuelissprayedintothisveryhotairandisignitedbytheheat.Someautomobileshavedieselengines.Manyheavy-dutytrucksandbusesarepoweredbydieselengines.压燃式发动机使用压缩产生的热量来点燃燃料。当空气被压缩，它可以达到非常高的温度。对于柴油式发动机，压缩空气可以使得空气温度达到538度或者更高。此时，柴油被喷射到这炽热的空气中，被空气的热量点燃。一些轿车使用柴油发动机。重型卡车和客车普遍使用柴油发动机。Thereareotherenginesstillintheexperimentalstagethatmightsomedaybecomeimportant.Theseincludegas-turbineengines,steamengines,Stirlingengines,andelectricmotors.还有一些目前尚且处于试验阶段，但未来可能会非常重要的发动机，比如：燃气涡轮机、蒸汽机、斯特灵发动机和电动机。2.3BasicenginesystemsAspark-ignitionenginerequiresfourbasicsystemstorun.Dieselenginesrequiresthreeofthesesystems.Theyarefuelsystem,ignitionsystem(expectdiesel),lubricatingsystemandcoolingsystem.Eachperformsabasicjobinmakingtheenginerun.Thesearedescribedbrieflybelow.点燃式发动机运转需要4个基本系统，而柴油发动机需要3个基本系统。它们是燃油系统、点火系统（柴油发动机不需要），润滑系统和冷却系统。每个系统实现一个基本功能来使得发动机运转。下文将简短介绍这些系统。2.3.1fuelsystemThefuelsystemsuppliesgasolineordieselfueltotheengine.Thisfuelismixedwithairtomakeacombustiblemixture(amixturethatwillrun).Eachcylinderisrepeatedlyfilledwiththemixture.Then,themixtureisignitedorburned,producinghighpressure.Thehighpressuremakesthepistonmove(orrotorsspin).Thisturnsshaftsthatrotatethewheels,causingthevehicletomove.燃油系统给发动机提供汽油或柴油燃料。燃油与空气混合形成可燃混合气。发动机的每个气缸重复充满这种可燃混合气，然后它们被点燃或压燃，产生高压。这个高压使得发动机活塞运动（或者转子旋转），驱动轴来旋转车轮，从而使得汽车行驶。2.3.2ignitionsystemEverytimethefuelsystemdeliversair/fuelmixturetoacylinder,theignitionsystemfollowsupbyadeliveringanelectricspark.Thisignitethemixturewhichcreatesthehighpressurethatmovesthepistonsandturnsthecarwheels.Theactionisrepeatedmanytimeseachsecondwhiletheengineisrunning.每当燃油系统将可燃混合气送至气缸，点火系统接着就发出电火花来点燃缸内的可燃混合气，从而产生高压，使得活塞运动和汽车行驶。当发动机运转时，每秒钟要点火多次。Theignitesystemtakesthelowvoltageofthebatteryandbuildsituptoaveryhighvoltage:ashighas47,000voltsinsomesystems.Thishighvoltagejumpsthegapsinthesparkplugs,producingthesparksthatignitetheair/fuelmixtureintheenginecylinders.点火系统将电池的低电压升压到高压。对于某些系统，可以达到47000伏。这个高压击穿火花塞间隙，产生电火花，点燃发动机气缸内的可燃混合气。2.3.3ThelubricatingsystemTheenginehasmanymovingmetalparts.Ifmetalpartsrubagainsteachother,theywillwearrapidly.Topreventthis,engineshavelubricatingoil.Theoilgetsbetweenthemetalpartssotheyslideontheoil,andnotoneachother.发动机有许多运动金属部件。如果这些金属部件相互摩擦，那它们磨损就会很快。为了防止这种情况，发动机使用润滑油。润滑油在金属部件之间，使得金属部件在油膜上滑动，而不是彼此之间的摩擦。6Thelubricatingsystemhasanoilpanatthebottomoftheenginewhichholdsseveralquarts(liters)ofoil.Anoilpump,drivenbytheengine,sendsoilfromthisreservoirthroughtheengine.Aftercirculatingthroughtheengine,theoildropsbacktotheoilpan.Theoilpumpcontinuestocirculatetheoilaslongastheengineisrunning.发动机润滑系统在发动机底部有一个储存几升汽油的油底壳。由发动机驱动的油泵将油从油底壳泵到发动机循环流动。在发动机循环后，润滑油流回到油底壳。只要发动机在运转，油泵就始终使润滑油循环流动。2.3.4CoolingsystemWherethereisfire(combustion),thereisheat.Burningoftheair/fuelmixtureraisesthetemperatureinsidetheenginecylindersseveralthousanddegrees.Someofthisheatproducesthehighpressurethatmovesthepistonstoproducepower.Someoftheheatleavesthecylinderswiththeexhaustgas.Theexhaustgasiswhatisleftaftertheair/fuelmixtureburns.Itisclearedoutofthecylindersafterthecombustioniscomplete.哪里有燃烧，哪里就有热量。可燃混合气的燃烧使得发动机气缸内温度上升数千度。部分热量产生高压来驱动活塞产生动力。部分热量伴随排放气体被带出气缸。排放气体指的是可燃混合气燃烧后剩余物。当燃烧结束，排放气体被排出气缸。Someoftheheatisremovedbythecirculatingoil.Afterthehotoildropsdownintotheoilpan,theoilgivesupsomeofthisheattotheairpassingundertheoilpan.Therestoftheheatisremovedbythecoolingsystem.部分热量被循环油带走。当温度较高的油流回到油底壳，热量通过油底壳下流动的空气带走。剩余的热量就要使用冷却系统来带走。2.3.5OtherenginesystemAnenginewillrunwiththefourbasicsystemsdescribedabove-fuel,ignition,lubricatingandcooling.However,threeotherrelatedsystemsarealsonecessary.Thesearetheexhaustsystem,theemission-controlsystem,andthestartingsystem.具备上述的燃油、点火、润滑和冷却系统，发动机就可以运转。但是，其余相关的3个系统也是非常必需的。它们是排放系统、排放控制系统和启动系统。Theexhaustsystemreducesthenoiseoftheburnedgasesleavingtheenginecylindersandcarriestheseexhaustgasessafelyawayfromthepeopleinthecar.Theemission-controlsystemisrequiredbylawtoreducetheairpollutiontheenginecouldproduce.Thestartingsystemisneededtocranktheengine.Abatteryprovidestheelectricpowertooperatethestartingmotorandtheignitionsystemduringcranking.排放系统减少发动机气缸可燃混合气燃烧时的噪音，并且将废气安全带走，使其远离车厢内的人。排放控制系统是法律强制要求的，用来减少发动机产生的空气污染。启动系统是用来启动发动机。启动过程中，由电池给启动电机和点火系统提供能量。2.4EnergyconversionTheinternalcombustionengineisadeviceusedtoconvertthechemicalenergytothefuel(gasolineordieselfuel)intoheatenergy,andthentoconvertthisheatenergyintousablemechanicalenergy.Thisisachievedbycombiningtheappropriateamountsofairandfuel,andburningthemixtureinanenclosedcylinderatacontrolledrate.Amovablepistoninthecylinderisforceddownbytheexpandinggasesofcombustion.发动机是一个将燃料（汽油或柴油）的化学能转化成热能，再将热能转化成可利用的机械能的装置。实现这个能量的转化是通过混合适当的空气和燃油，并在密封的气缸内以一个可控的速率燃烧这个可燃混合气来实现的。燃烧产生的膨胀气体强迫气缸内的活塞运动。Anaverageair/fuelratioforgoodcombustionisabout15partsofairto1partoffuelbyweight.Thismeansthatforeverygallonofgasolineburned,theoxygenisabout9,000to10,000gallonsofairisrequired.Airisabout21%oxygenand78%nitrogen.7可燃烧良好的空燃比，按质量大约是15：1。这就意味着燃烧1加仑汽油需要的9000到10000加仑的空气里的氧气。空气大约有21%的氧气和78%的氮气。Dieselengineoperateonamuchwiderair/fuelratio,sinceairintakeisnotregulatedonmostdiesels.Ratiosmayrangefromabout20:1to100:1.Thefact,plusthehighcompressionofthediesel,makesitaveryfuelefficientengine.由于大多数的柴油机并不控制进气，柴油机的空燃比范围很宽，从20：1到100：1。再加上柴油混合气具有很高的压缩比，这使得柴油机的效率很高。Themovablepistoninthecylinderisconnectedtothetopofaconnectingrod.Thebottomoftheconnectingrodisattachedtotheoffsetportionofacrankshaft.Asthepistonisforceddown,thisforceistransferredtothecrankshaft,causingthecrankshafttorotate.Thereciprocating(backandforthorupanddown)movementofthepistonisconvertedtorotary(turning)motionofthecrankshaft,whichsuppliesthepowertodrivethevehicle.气缸内的活塞与连杆的上部相连，而连杆的下部与曲轴的偏移部连接。因此，当活塞向下运动时，这个运动传递到曲轴，使得曲轴旋转。活塞的往复运动（前后或者上下）就转化为曲轴的旋转运动，从而给汽车行驶提供动力。Theefficiencyoftheinternalcombustion,reciprocatingpistonengineinconvertingthepotentialenergyinfuelintomechanicalenergyisonlyabout33%.Oftheavailableheatenergyinthefuel,aboutone-thirdislostthroughthroughtheexhaustsystemandone-thirdisabsorbedanddissipatedbythecoolingsystem.Oftheremainingone-third,aboutone-halfislostthroughavailableatthevehicle’sdrivewheels.往复活塞式内燃机将燃料的能量转化为机械能的效率大约是33%。燃料中可利用的热量有三分之一通过排气系统丢失掉，另有三分之一被冷却系统吸收和带走，剩下的三分之一大约有一半的能量在汽车的驱动轮消耗掉。Theoverallefficiencyofthedieselengineisconsiderablyhigherthanthatofthegasolineengine.Thereasonforthisare:thehighercompressionratio,thehigherair/fuelratio,andthehigherheatvalueofthefuel.Theusefulpowerdevelopedatthedrivewheelsbyadieselengineisabout25%comparedto15%byagasoline.与汽油机相比，柴油机的总体效率要高很多。这是因为柴油机具有更高的压缩比，更高的空燃比，柴油的热量也要更高。对于柴油机，驱动轮得到的能量大约可以达到总能量的25%，而汽油机只有15%。2.5fourstroke-cyclegasolineengineoperation Themovementofthepistonfromitsuppermostposition(TDC,topdeadcenter)toitslowestposition(BDC,bottomdeadcenter)iscalledastroke.Mostautomobileenginesoperateonthefourstroke-cycleprinciple.Aseriesofeventsinvolvingfourstrokesofthepistoncompletesonecycle.Theseeventsare:(1)theintakestroke,(2)thecompressionstroke,(3)thepowerstroke,and(4)theexhauststroke.Tworevolutionsofthecrankshaftandonerevolutionofthecamshaftarerequiredtocompleteonecycle.活塞从它在气缸内的最高位置(上止点)运动到最低位置(下止点)称为一个冲程。大多数汽车发动机采用四冲程工作循环，由活塞的四个冲程组成一个工作循环，分别是：进气冲程、压缩冲程、作功冲程和排气冲程。发动机的一个工作循环需要曲轴旋转两次，凸轮轴旋转一次。Ontheintakestrokethepistonispulleddowninthecylinderbythecrankshaftandconnectingrod.Duringthistimetheintakevalveisheldopenbythecamshaft.Sincethepistonhasmoveddowninthecylinder,creatingalow-pressurearea(vacuum),atmosphericpressureforcesamixtureofairandfuelpasttheintakevalveintothecylinder.Atmosphericpressureis8approximately14.7poundspersquareinch(about101.35kilopascals)atsealevel.Pressureinthecylinderduringtheintakestrokeisconsiderablylessthanthis.Thepressuredifferenceistheforcethatcausestheair/fuelmixturetoflowintothecylinder,sincetheliquidoragas(vapor)willalwaysflowfromahigh-pressuretoalow-pressurearea.吸气冲程过程中，气缸内的活塞被曲轴和连杆向下拉动。此时，凸轮轴使得进气门打开。由于活塞在气缸壁向下运动，产生了一个低压区（真空区），大气压力使得可燃混和气从进气门进入气缸。海平面的大气压大约是每平方英寸14.7磅（大约101.35千帕）。吸气冲程时，气缸内的压力要远远小于大气压。由于液体和气体总是从高压区流向低压区，因此，气缸内外的压力差就使得可燃混和气流入气缸。AsthepistonismovedupbythecrankshaftfromBDC,theintakevalvecloses.Theair/fuelmixtureistrappedinthecylinderabovethepiston.Furtherpistontravelcompressestheair/fuelmixturetoapproximatelyone-eighthofitsoriginalvolume(approximately8:1compressionratio)whenthepistonhasreachedTDC.Thiscompletesthecompressionstroke.当曲轴推动活塞从下止点起向上运动，进气门关闭。可燃混和气被限制在活塞以上的气缸区域内。当活塞达到上止点时，活塞压缩可燃混合气至其原有容积的1/8（大约8:1的压缩比）。此时，压缩冲程结束。WhenthepistonisatornearTDC,theair/fuelmixtureisignited.Theburningoftheair/fuelmixture(combustion)takesplaceatacontrolledrate.Expansionoftheburningmixturecausesarapidriseinpressure.Theincreasedpressureforcesthepistondownonthepowerstroke,causingthecrankshafttorotate.当活塞达到或接近上止点时，可燃混和气被点燃，并且在一个可控的节奏下进行。可燃混和气的膨胀使得压力急剧上升，并推动活塞向下运动作功，使得曲轴旋转。当活塞达到或接近上止点时，可燃混和气被点燃，并且在一个可控的节奏下进行。可燃混和气的膨胀使得压力急剧上升，并推动活塞向下运动作功，使得曲轴旋转。Attheendofthepowerstroke,thecamshaftopenstheexhaustvalve,andtheexhauststrokebegins.Remainingpressureinthecylinder,andupwardmovementofpiston,forcetheexhaustgasesoutofthecylinder.Attheendoftheexhauststroke,theexhaustvalveclosesandtheintakevalveopens,repeatingtheentirecycleofeventsoverandoveragain.作功冲程结束时，凸轮轴打开排气门，排气冲程开始。气缸内剩余的压力和活塞向上的运动把废气排出气缸。排气冲程结束时，排气门关闭，进气门开启，从而再次重复整个循环。Tostarttheengine,somemethodofcrankingtheengineisrequiredtoturnthecrankshaftandcausepistonmovement.Thisisdonebythestartermotorwhentheignitionkeyisinthestartposition.Whensufficientair/fuelmixturehasenteredthecylindersandisignited,thepowerstrokescreateenoughenergytocontinuecrankshaftrotation.Atthepoint,theignitionkeyisreleasedtotherunpositionandstarterisdisengaged.为了起动发动机，需要转动曲柄来使得活塞运动。当点火开关置于起动位置时，起动电机转动曲柄，起动发动机。当足量的可燃混和气进入气缸并被点燃，作功冲程产生的能量足以使得曲轴连续转动。此时，点火开关释放到正常位置，起动机推出啮合。Sufficientenergyisstoredintheflywheelandotherrotatingpartsonthepowerstroketomovethepistonandrelatedpartsthroughtheotherthreestrokes(exhaust,intake,andcompression).Theamountofair/fuelmixtureallowedtoenterthecylinderdeterminesthepowerandspeeddevelopedbytheengine.在作功冲程中，大量的能量被储存在飞轮和其他旋转部件上，从而在其余三个冲程中可以使得活塞和相连部件运动。进入气缸的可燃混合气的数量决定了该发动机的功率和转速。92ExercisesⅠWhatisthepurposeofanautomotiveengine?ⅠTosupplythepowerneededtomovethevehicle.Whatisthedifferencebetweenagasolineengineandadieselengine?Agasolineengineusesanelectricignitionsystemwithsparkplugstoignitethefuel.Andadieselengineusestheheatofcompressiontoignitethefuel.Whatarethebasicsystemstorunaspark-ignitionenginerequired?Fuelsystem,ignitionsystem,lubricatingsystemandcoolingsystem.Listthestrokesofafour-stroke-cyclegasolineengineoperation.Theintakestroke,thecompressionstroke,thepowerstrokeandtheexhauststroke.Whatisthefunctionoftheflywheel?Itisusedtostoresufficientenergytomovethepistonandrelatedpartsthroughtheotherstrokes(exhaust,intakeandcompression).1Acarusuallyhasapistonengine.Itconsistsofseveralmovingpart:pistons,connectingrods,crankshaft,camshaft,valvelifters,intakevalvesandexhaustvalves.Thecastironoraluminumengineblockholdsthemovingparts.Theengineblockhasaseriesofholeswhicharecalledcylinders.ThecylinderscanbearrangedinlineorinaV-shapeandintheupperpartoftheblock.Eachcylinderholdsapistonandtheconnectingrod.Acircularringisusedtosealthesmallgapbetweenthepistonandthecylinderwall.Thelowerpartoftheblockiscalledcrankcasewhichholdsthecrankshaftwithbearingmounts.Pistonsareconnectedtothecrankshaftbyconnectingrods.汽车一般使用活塞式发动机。活塞式发动机由活塞、连杆、曲轴、凸轮轴、气门挺杆、进气门和排气门等运动部件组成。这些运动部件安置在铸铁或铝合金机体内。发动机体上有些凹洞，这些凹洞被称作气缸。气缸在机体上部呈直列式或V型排列。每个气缸都有活塞和连杆。活塞和气缸壁之间的微小缝隙通过一个圆环密封。机体的下部是曲轴箱，里面是带有轴承的曲轴。活塞和曲轴之间通过连杆连接。2Thecylinderheadsarethetopcovers