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1、一.IntroductiontoHowAutomaticTransmissionsWorkIfyouhaveeverdrivenacarwithanautomatictransmission,thenyouknowthattherearetwobigdifferencesbetweenanautomatictransmissionandamanualtransmission:Thereisnoclutchpedalinanautomatictransmissioncar.Thereisnogearshiftinana
2、utomatictransmissioncar.Onceyouputthetransmissionintodrive,everythingelseisautomatic.Boththeautomatictransmission(plusitstorqueconverter)andamanualtransmission(withitsclutch)accomplishexactlythesamething,buttheydoitintotallydifferentways.Itturnsoutthatthewayana
3、utomatictransmissiondoesitisabsolutelyamazing!PurposeofanAutomaticTransmissionJustlikethatofamanualtransmission,theautomatictransmission'sprimaryjobistoallowtheenginetooperateinitsnarrowrangeofspeedswhileprovidingawiderangeofoutputspeeds.Withoutatransmission,ca
4、rswouldbelimitedtoonegearratio,andthatratiowouldhavetobeselectedtoallowthecartotravelatthedesiredtopspeed.Ifyouwantedatopspeedof80mph,thenthegearratiowouldbesimilartothirdgearinmostmanualtransmissioncars.You'veprobablynevertrieddrivingamanualtransmissioncarusin
5、gonlythirdgear.Ifyoudid,you'dquicklyfindoutthatyouhadalmostnoaccelerationwhenstartingout,andathighspeeds,theenginewouldbescreamingalongnearthered-line.Acarlikethiswouldwearoutveryquicklyandwouldbenearlyundriveable.Sothetransmissionusesgearstomakemoreeffectiveus
6、eoftheengine'storque,andtokeeptheengineoperatingatanappropriatespeed.Whentowingorhaulingheavyobjects,yourvehicle'stransmissioncangethotenoughtoburnupthetransmissionfluid.Inordertoprotectthetransmissionfromseriousdamage,driverswhotowshouldbuyvehiclesequippedwith
7、transmissioncoolers.Thekeydifferencebetweenamanualandanautomatictransmissionisthatthemanualtransmissionlocksandunlocksdifferentsetsofgearstotheoutputshafttoachievethevariousgearratios,whileinanautomatictransmission,thesamesetofgearsproducesallofthedifferentgear
8、ratios.TheplanetarygearsetisthedevicethatmakesthispossibleinanautomatictransmissionThePlanetaryGearsetFromlefttoright:theringgear,planetcarrier,andtwosungearsWhenyoutakeapar