汽车变速器-毕业论文外文翻译

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1、AutomobileTransmissionAsweknow，anenginecangenerateonlylimitedtorqueatlowspeeds.Drivingconditionisverycomplicatedandthisrequiredthetractiveeffortandspeedvaryinalargescope.Andwithoutsufficienttorque，movingaheavilyloadedvehiclefromastandingstartisimpossible.Inanyengine，thecrankshaftalwaysrotates

2、inthesamedirection.Iftheenginetransmitteditspowerdirectlytothedriveaxles，thewheelscouldbedrivenonlyinonedirection.Givenalevelroad，anautomobilewithoutatransmissioncouldbemadetomovebyacceleratingtheengineandengagingtheclutch.However，astartundertheseconditionswouldbeslow，noisyanduncomfortable•In

3、condition，itwouldplaceatremendousstrainontheengineanddrivingpartsoftheautomobile.Soinordertogetsmoothstartsandhavepowertopassandclimbhills，apowerratiomustbeprovidedtomultiplythetorqueandturningeffortoftheengine.Alsorequiredisaspeedratiotoavoidtheneedforextremelyhighenginerpmathighroadspeeds.T

4、hetransmissionisgearedtoperformthesefunctions.Atransmissionisaspeedandpowerchangingdeviceinstalledatsomepointbetweentheengineanddrivingwheelsofthevehicle.Itisdesignedforchangingthetorquetransmittedformtheenginecrankshafttothepropellershaft，reversingthevehiclemovementanddisengagingtheenginefro

5、mthedrivelineforalongtimeatparkingorcoasting.Ahighertorqueshouldbeappliedtothewheelstosetanautomobileinmotionormoveuphillwithafullloadthantokeepitrollingafteritgetsunderwayonlevelstretchesoftheroad，wheninertiaishighandtractiveresistanceislow.Tomeetthesevariabletorquerequirement，specialgearbox

6、esareused.Suchgearboxesarecalledfixed—ratiotransmissions.Thetransmissionconsistsofahousing，aninputshaftandgear，anoutputshaftandgear，anidlershaft，areversegear，aclusterofgearsandagearshiftmechanism.Thehousingiscastofironwhichhasupperandsidecoversandboresfortheinstallationofshafts.Thebottomandsi

7、dewallsareprovidedwithholesforfillinganddrainingoil•Theinputshaftismadeofsteelintegralwiththedrivinggearandtherim•Thefrontendoftheinputshaftisinstalledonthebearingintheboreofthecrankshaft，whiletherearendrotatesintheboreofthefrontwallofthehous