外文翻译--手动变速器.doc
附录:ManualTransmissionsMarshallBrainTheearliestformofamanualtransmissionisthoughttohavebeeninventedbyLouis-RenéPanhardandEmileLevassorinthelate19thcenturyAmanualtransmission,alsoknownasamanualgearboxorstandardtransmission,itisatypeoftransmissionusedinmotorvehicleapplicationsItgenerallyusesadriver-operatedclutch,typicallyoperatedbyapedalorlever,forregulatingtorquetransferfromtheinternalcombustionenginetothetransmissionAconventionalmanualtransmissionisfrequentlythebaseequipmentinacar,otheroptionsincludeautomatedtransmissionssuchasanautomatictransmission,asemi-automatictransmission,oracontinuouslyvariabletransmission(CVT)Manualtransmissionsoftenfeatureadriver-operatedclutchandamovablegearstickMostautomobilemanualtransmissionsallowthedrivertoselectanyforwardgearratioatanytime,butsome,suchasthosecommonlymountedonmotorcyclesandsometypesofracingcars,onlyallowthedrivertoselectthenext-higherornext-lowergearThistypeoftransmissionissometimescalledasequentialmanualtransmissionSequentialtransmissionsarecommonlyusedinautoracingfortheirabilitytomakequickshiftsManualtransmissionsarecharacterizedbygearratiosthatareselectablebylockingselectedgearpairstotheoutputshaftinsidethetransmissionConversely,mostautomatictransmissionsfeatureisplanetarygearingcontrolledbybrakebandsand/orclutchpackstoselectgearratioAutomatictransmissionsthatallowthedrivertomanuallyselectthecurrentgeararecalledManumaticsAmanual-styletransmissionoperatedbycomputerisoftencalledanautomatedtransmissionratherthananautomaticContemporaryautomobilemanualtransmissionstypicallyusefourtosixforwardgearsandonereversegear,althoughautomobilemanualtransmissionshavebeenbuiltwithasfewastwoandasmanyaseightgearsTransmissionforheavytrucksandotherheavyequipmentusuallyhaveatleast9gearssothetransmissioncanofferbothawiderangeofgearsandclosegearratiostokeeptheenginerunninginthepowerbandAnyenginehasaredline-amaximumrpmvalueabovewhichtheenginecannotgowithoutexplodingEngineshavenarrowrpmrangeswherehorsepowerandtorqueareattheirmaximumForexample,anenginemightproduceitsmaximumhorsepowerat5,500rpmThetransmissionallowsthegearratiobetweentheengineandthedrivewheelstochangeasthecarspeedsupandslowsdownYoushiftgearssotheenginecanstaybelowtheredlineandneartheRPMbandofitsbestperformanceMercedes-BenzActros,manualtransmissionIdeally,thetransmissionwouldbesoflexibleinitsratiosthattheenginecouldalwaysrunatitssingle,best-performancerpmvalueThatistheideabehindthecontinuouslyvariabletransmission(CVT)ContinuouslyVariableTransmissionsACVThasanearlyinfiniterangeofgearratiosInthepast,cvtscouldnotcompetewithfour-speedandfive-speedtransmissionsintermsofcost,sizeandreliability,soyoudidntseetheminproductionautomobiles,Thesedays,improvementsindesignhavemadecvtsmorecommonTheToyotaPriusisahybridcarthatusesaCVTThetransmissionisconnectedtotheenginethroughtheclutchTheinputshaftofthetransmissionthereforeturnsatthesamerpmastheengineMercedes-Benz,six-speedmanualtransmission,graphicillustrationAfive-speedtransmissionappliesoneoffivedifferentgearratiostotheinputshafttoproduceadifferentrpmvalueattheoutputshaftHerearesometypicalgearratios:GearRatioRPMatTransmissionOutputShaftwithEngineat3,000rpm1st2.315:11,2952nd1.568:11,9133rd1.195:12,5104th1.000:13,0005th0.915:13,278AVerySimpleTransmissionTounderstandthebasicideabehindastandardtransmission,thediagrambelowshowsaverysimpletwo-speedtransmissioninneutral:Letslookateachofthepartsinthisdiagramtounderstandhowtheyfittogether:ThegreenshaftcomesfromtheenginethroughtheclutchThegreenshaftandgreengearareconnectedasasingleunit(TheclutchisadevicethatletsyouconnectanddisconnecttheengineandthetransmissionWhenyoupushintheclutchpedal,theengineandthetransmissionaredisconnectedsotheenginecanrunevenifthecarisstandingstillWhenyoureleasetheclutchpedal,theengineandthegreenshaftaredirectlyconnectedtooneanotherThegreenshaftandgearturnatthesamerpmastheengine)TheredshaftandgearsarecalledthelayshaftThesearealsoconnectedasasinglepiece,soallofthegearsonthelayshaftandthelayshaftitselfspinasoneunit.Thegreenshaftandtheredshaftaredirectlyconnectedthroughtheirmeshedgearssothatifthegreenshaftisspinning,soistheredshaftInthisway,thelayshaftreceivesitspowerdirectlyfromtheenginewhenevertheclutchisengagedTheyellowshaftisasplinedshaftthatconnectsdirectlytothedriveshaftthroughthedifferentialtothedrivewheelsofthecarIfthewheelsarespinning,theyellowshaftisspinningThebluegearsrideonbearings,sotheyspinontheyellowshaft.Iftheengineisoffbutthecariscoasting,theyellowshaftcanturninsidethebluegearswhilethebluegearsandthelayshaftaremotionlessThepurposeofthecollaristoconnectoneofthetwobluegearstotheyellowdriveshaft.Thecollarisconnected,throughthesplines,directlytotheyellowshaftandspinswiththeyellowshaftHowever,thecollarcanslideleftorrightalongtheyellowshafttoengageeitherofthebluegearsTeethonthecollar,calleddogteeth,fitintoholesonthesidesofthebluegearstoengagethem