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外文翻译ClutchTheclutchislocatedinthepowertrainbetweentheengineandthetransmission.Itspurposeistopermitthedrivertocoupleoruncoupletheengineandtransmission.Theclutchisafriction-typeuncouplingdevice.Itislinkedtoaclutchpedalintheriver’scompartment.Whenthedriverpushesdowntheclutchpedal,thelinkageforcesaflatdisk,orplate,tomove.Themovementreleasesthepressurefromafrictiondisk.Withthepressurereleased.Thereisnofrictionatworkintheclutch.Andthepowerflowisthereforeinterrupted.Then,theenginerunswithouttransmittingpowertothepowertrain.Whentheclutchisinthecoupling(ornormalrunning)position,powerflowsthroughitfromtheenginetothetransmission.Ifthetransmissionisingear,thenpowerflowsonthroughtothecarwheelssothatthecarmoves.Essentially,then,theclutchhathejobofpermittingthedrivertouncoupletheenginetemporarilysothatthegearscanbeshiftedfromonetoanotherforwardgearposition(orintoreverseorneutral).Itisnecessarytointerrupttheflowofpower(byuncoupling)beforegearsareshifted.Otherwise,gearshiftingwouldbeextremelydifficultifnotimpossible.Theclutchcontainsfrictiondisk(ordrivenplate)about300millimetreindiameter.Italsocontainsaspringarrangementandapressureplateforpressingthisdisktightlyagainstthesmoothrearfaceoftheflywheel.Thefrictiondiskissplinedtotheclutchshaft.Thesplinesconsistoftwosetsofteeth,aninternalsetonthehubofthefrictiondiskandamatchingexternalsetontheclutchshaft.Theypermitthefrictiondisktoslidebackandforthalongtheshaftbutforcethediskandtheshafttorotatetogether.Allautomotiveclutchesusedwithstandardtransmissionsareverysimilarinconstructionandoperation.Therearesomedifferencesinthedetailsofthelinkagesaswellasinthepressure-plateassemblies.Inaddition,someclutchesforheavy-dutyapplicationshavetwofrictiondisksandanintermediatepressureplate.Also,someclutchesareoperatedbyhydraulicmeans.Threetypesofclutcharethecoil-pressure-springtype,diaphragm-springtype,andsemicentrefugaltype.Carsequippedwithautomatictransmissionoperatedsautomaticallysothatthedriverisnotrequiredtouseaclutchtoshiftgears.离合器在传动系统中,离合器位于发动机与变速器之间,其作用是使驾驶员可以把发动机与变速器结合或脱离.离合器是一种摩擦式分离装置,与驾驶室中离合踏板相连接.当驾驶员踩下离合器踏板时,联动装置使离合器的压盘移动.这一运动减少了作用在摩擦盘上的压力.随着压力的减小,离合器工作状态下的摩擦力消失,动力被切断.这样,虽然发动机仍在转动,而动力却不在传递到传动系统.当离合器处于结合状态时(或者说处于正常运行状态时),动力从发动机传递到变速器.如果变速器已挂上适当的档位,那么动力就会传动到车轮上,汽车即开动起来.从本质上说,离合器的作用是使驾驶员可以暂时地切断发动机的动力.这样一来,传动装置就可以从某一档换到另一档(或者换到倒档或空档).在变速之前,一定要切断动力传递.不然,换档即使不是完全不可能,也会是十分困难的.离合器有一直径大约300毫米,并带有摩擦衬片的圆盘,还有一弹簧装置和一压力盘,用来把摩擦盘紧紧地压在飞轮光滑地壁面上.带有摩擦衬片的圆盘,通过花键与离合器轴相连.花键包括二套花键齿.可以使摩擦盘沿着主轴向后或向前滑动,又可以使圆盘和主轴同时移动.所有使用标准传动系统的汽车离合器在构造和操作上都很相似.只是在压紧机构和连动装置的细节上稍有不同.此外,一些在重载荷情况下工作的离合器,有两个带摩擦衬片的圆盘和一个中间压力盘.还有一些离合器是液压式的.离合器的三种类型为:螺旋弹簧式,嗼片弹簧式和半离心式.装有自动变速装置的汽车一般不需要离合器.在这些汽车上,变速器自动操作,因此驾驶员不必使用离合器来换档.BrakeSystemBrakesarenecessarytosloworstopthecar.Moderncarscantravelveryfast,sogoodbrakesareessentialforsafety.Practicallyallcarsusehydraulicsbrakes(whichoperatebyapplyingpressuretoafluid).Thebrakessystemcanbedividedintotwoprincipalparts,hydraulicsystemandwheelbrakeassemblies.Inmostmodernbrakesystems,thereisafluid-filledcylinder,calledthemastercylinder,whichcontainstwoseparatesections,thereisapistonineachsectionandbothpistonsareconnectedtoabrakepedalinthedriver’scompartment.Whenthebrakepedalispushedbythedriverthetwopistonsmoveinthetwosectionsofthemastercylinder.Thisforcesbrakefluidoutandthroughthebrakelines,ortubes,tothebrakemechanismsatthewheels.Inatypicalsystem,thebrakefluidfromonesectionofthemastercylindergoestothetwofront-wheelbrakes.Thebrakefluidfromtheothersectiongoestothetworear-wheelbrakes.Thepurposeofthisisthat,ifonesectionfails,theothersectionwillstillprovidebraking.Therearetwodifferenttypesofbrakemechanismsatthewheels,the

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