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1、Transmission(mechanics)Atransmissionorgearboxprovidesspeedandtorqueconversionsfromarotatingpowersourcetoanotherdeviceusinggearratios.InBritishEnglishthetermtransmissionreferstothewholedrivetrain,includinggearbox,clutch,propshaft(forrear-wheeldrive),differentialandfinaldriveshafts.Themostcommonusei
2、sinmotorvehicles,wherethetransmissionadaptstheoutputoftheinternalcombustionenginetothedrivewheels.Suchenginesneedtooperateatarelativelyhighrotationalspeed,whichisinappropriateforstarting,stopping,andslowertravel.Thetransmissionreducesthehigherenginespeedtotheslowerwheelspeed,increasingtorqueinthep
3、rocess.Transmissionsarealsousedonpedalbicycles,fixedmachines,andanywhereelserotationalspeedandtorqueneedstobeadapted.Often,atransmissionwillhavemultiplegearratios(orsimply"gears"),withtheabilitytoswitchbetweenthemasspeedvaries.Thisswitchingmaybedonemanually(bytheoperator),orautomatically.Direction
4、al(forwardandreverse)controlmayalsobeprovided.Single-ratiotransmissionsalsoexist,whichsimplychangethespeedandtorque(andsometimesdirection)ofmotoroutput.Inmotorvehicleapplications,thetransmissionwillgenerallybeconnectedtothecrankshaftoftheengine.Theoutputofthetransmissionistransmittedviadriveshaftt
5、ooneormoredifferentials,whichinturndrivethewheels.Whileadifferentialmayalsoprovidegearreduction,itsprimarypurposeistochangethedirectionofrotation.Conventionalgear/belttransmissionsarenottheonlymechanismforspeed/torqueadaptation.Alternativemechanismsincludetorqueconvertersandpowertransformation(e.g
6、.,diesel-electrictransmission,hydraulicdrivesystem,etc.).Hybridconfigurationsalsoexist.ExplanationEarlytransmissionsincludedtheright-angledrivesandothergearinginwindmills,horse-powereddevices,andsteamengines,insupportofpumping,milling,andhoisting.Mostmoderngearboxesareusedtoincreasetorquewhileredu
7、cingthespeedofaprimemoveroutputshaft(e.g.amotorcrankshaft).Thismeansthattheoutputshaftofagearboxwillrotateatslowerratethantheinputshaft,andthisreductioninspeedwillproduceamechanicaladvantage,causinganincreaseinto
