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Lesson4DrivetrainInordertotransmitthepoweroftheenginetotheroadwheelsofamotorcar,adrivetrainisnormallyemployed.Althoughthedetailsofthedrivetrainsvarywidelyindifferenttypesofcars,thegeneralprinciplesarethesameinallcases.为了把发动机的动力传递到机动车车的车轮，通常使用传动系统。尽管在不同类型的汽车上，传动系统的细节有很大不同，但基本的原理都是一样的。inanycase无论如何inallcases在任何情况下ineither(every)case在任何情况下Theclutchisadevicetoengageanddisengagepowerfromtheengine,allowingthevehicletostopandstart.离合器是用来接合或分离发动机动力的装置，允许车辆停止或起动。Apressureplateordrivingmemberisboltedtotheengineflywheelandaclutchplateordrivenmemberislocatedbetweentheflywheelandthepressureplate.压盘或主动件用螺栓固定在发动机飞轮上，离合器片或从动件位于飞轮和压盘之间。Theclutchplateissplinedtotheshaftextandingfromthetransmissionorgearboxtotheflywheel,commonlycalledaclutchshaftorinputshaft.离合器片用花键与从传动系或变速箱伸向飞轮的轴（通常称为离合器轴或输入轴）联接。spline词性及解释n.曲线尺,齿条,塞缝片,花键vt.用花键联接,开键槽Whentheclutchandpressureplatearelockedtogetherbyfriction,theclutchshaftrotateswiththeenginecrankshaft.当离合器和压盘由摩擦锁在一起，离合器轴就会随着发动机曲轴旋转。Poweristransferredfromtheenginetothetransmission,whereitisroutedthroughdifferentgearratiostoobtainthebestspeedandpowertostartandkeepthevehiclemoving.动力由发动机传递到传动系，在这里通过采用不同齿轮齿数比以获得最优的速度及功率以起动或使车辆保持运行。1.1thepressureplateThedrivingmemberiscommonlycalledthepressureplate.Itisboltedtotheengineflywheelanditsmainpurposeistoexertpressureagainsttheclutchplate.主动件通常称作压盘。它由螺栓固定在发动机飞轮上，它的主要作用是对离合器片施加压力.Itmustalsobecapableofinterruptingthepowerbyreleasingthepressureontheclutchplate.Thisallowstheclutchplatetostoprotatingwhiletheflywheelandpressureplatecontinuestorotate.它必须能够通过释放离合器片上的压力来切断功率。这允许在飞轮和压盘继续旋转时离合器片停止旋转。Thepressureplateconsistsofaheavymetalplate,coilspringsoradiaphragmspring,releaselevers,andacover.压盘由一个厚金属盘、螺旋弹簧或膜片弹簧、分离杠杆以及离合器盖组成。Whencoilspringsareused,theyareevenlyspacedaroundthemetalplateandlocatedbetweentheplateandmetalcover.当使用螺旋弹簧时，它们金属盘上均布，且位于金属盘和离合器盖之间。Thisplacesanevenpressureagainsttheplate,whichinturnpressestheclutchplatetightagainsttheflywheel.Thecoverisboltedtightlytotheflywheelandthemetalplateismovable,duetointernallinkages.这样会在压盘上施加均匀压力，依次又会将离合器片压紧在飞轮上。离合器盖用螺栓紧连在飞轮上，由于内部的联接，金属盘可以移动。Thecoilspringsarearrangedtoexertdirectorindirecttensiononthemetalplate,dependinguponthemanufacturer’sdesign.螺旋弹簧用于在金属盘上施加直接或间接的压力，这取决于制造商的设计。Threereleaselevers(fingers),evenlyspacedaroundthecover,areusedonmostpressureplatestoreleasetheholdingpressureoftheclutchplate,allowingittodisengagethepowerflow.在离合器盖上均布的三个分离杠杆，用于大多数压盘以释放离合器片上弹簧的保持压力，允许它切断动力。1.2theclutchplateTheclutchplateordrivenmembersconsistsofaroundmetalplateattachedtoasplinedhub.Theouterportionoftheroundplateiscoveredwithafrictionmaterialofmoldedorwovenasbestosandisrivetedorbondedtotheplate.rivetn.铆钉vt.用铆钉固定,敲进去,注目,吸引住bondn.捆绑物,结合,债券,契约,粘合剂,保证人,键,关栈保留vt.使黏合vi.结合离合器盘或从动件由与花键毂相连的圆金属盘组成。圆盘的外面覆盖着模压或编织石棉摩擦材料且分别通过铆接或粘接在圆盘上。Thethicknessoftheclutchplateand/orfacingsmaybewarpedtogiveasofterclutchengagement.离合器片或贴面可以被弯曲以产生柔和的离合器接合。Warpn.变形,弯曲,歪曲,乖僻,偏差,偏见vt.使变形,弄歪,使翘曲,使不正常,歪曲,使有偏见vi.变弯,变歪Coilspringsareofteninstalledinthehubtohelpprovideacushionagainstthetwistingforceofclutchengagement.螺旋弹簧经常被安装到在盘毂上以提供软垫帮助防止离合器接合时带来的圆周冲击力。Thesplinedhubismatedtoasplinedtransmissionshaftwhentheclutchisengaged.当离合器接合时，花键毂与花键传动轴相配。Theclutchpedalprovidesmechanicalmeansforthedrivertocontroltheengagementanddisengagementoftheclutch.离合器踏板为司机提供离合器接合与分离的装置。Thepedalisconnectedmechanicallytoeitheracableorrods,whicharedirectlyconnectedtothereleasebearinglever.踏板或者与绳索或者与杆件机械式相连，它直接与分离轴承杠杆相连。Whentheclutchpedalisdepressed,thelinkagemovesthereleasebearinglever.当离合器踏板被踩下时，联动装置使分离轴承运动。Thereleaselevelisattachedattheoppositeendtoareleasebearingwhichstraddlesthetransmissionclutchshaft,andpressesinwardonthepressureplatefingersofthediaphragmspring.分离杠杆连接在分离轴承的反端，该轴承骑在传动系离合器轴上并且向内压在膜片弹簧压盘指上。Thisinwardpressureactsuponthefingersandinternallinkageofthepressureplateandallowstheclutchplatetomoveawayfromtheflywheel,interruptingtheflowofpower.这一向内的压力作用在分离指和压盘的内部连接装置上，允许离合器片从飞轮脱开，切断动力。2GearboxAhighertorqueisrequiredtodriveaheavily-loadedtruckupahillthanthatrequiredtodriveanemptytruckonaflatroad.Theenginewillprovidethenecessarytorquewithinalimitedspeedrange.重载货车爬坡比空车平路行驶需要更大的转矩。发动机会在有限的速度范围内提供必要的转矩。Theprovisionofagearboxallowsforoptimumutilizationoftheenginetorqueindrivingthetruck.Inaddition,thedirectionoftheroadwheelscanbechangedwithouttheneedforstoppingtheengineandrestartingitinthereversedirection.变速器的供给在驱动货车的过程中，使得发动机转矩得到最优化的利用。此外，车轮的方向能够被改变，不需要停止发动机，在相反的方向重新启动发动机。Therearetwotypesofgearboxes-manualandautomatic.有两种类型的变速器—手动的和自动的。Thegearboxcontainsanumberofgearwheels(Fig.4.2).Ifgearwheelsofdifferentsizerotateinmeshwitheachother,theshaftofthelargerwheelwillrotatemoreslowlythanthatofthesmallerwheel.变速器包含很多齿轮（图4.2）。如果不同尺寸的齿轮互相啮合进行旋转的话，大齿轮的轴要比小齿轮的轴旋转地更慢。Ifthesmallerwheelistheonedrivingtheassembly,thespeedwillthereforebereducedatthelargerwheel.Asaresultthetorqueatthelargerwheelwillbegreaterbyacorrespondingamount.如果小齿轮是驱动总成的齿轮的话，因而在大齿轮上速度减小。结果大齿轮上的扭矩会相应的大一点。Agearboxnormallyconsistsofaninputshaft,acountershaft(layshaft)andanoutputshaftknownasthemainshaft.Theenginetorqueisappliedattheinpu