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1、Transmission(mechanics)Atransmissionorgearboxprovidesspeedandtorqueconversionsfromarotatingpowersourcetoanotherdeviceusinggearratios.InBritishEnglishthetermtransmissionreferstothewholedrivetrain,includinggearbox,clutch,propshaft(forrear-wheeldrive),differ
2、entialandfinaldriveshafts.Themostcommonuseisinmotorvehicles,wherethetransmissionadaptstheoutputoftheinternalcombustionenginetothedrivewheels.Suchenginesneedtooperateatarelativelyhighrotationalspeed,whichisinappropriateforstarting,stopping,andslowertravel.
3、Thetransmissionreducesthehigherenginespeedtotheslowerwheelspeed,increasingtorqueintheprocess.Transmissionsarealsousedonpedalbicycles,fixedmachines,andanywhereelserotationalspeedandtorqueneedstobeadapted.Often,atransmissionwillhavemultiplegearratios(orsimp
4、ly"gears"),withtheabilitytoswitchbetweenthemasspeedvaries.Thisswitchingmaybedonemanually(bytheoperator),orautomatically.Directional(forwardandreverse)controlmayalsobeprovided.Single-ratiotransmissionsalsoexist,whichsimplychangethespeedandtorque(andsometim
5、esdirection)ofmotoroutput.Inmotorvehicleapplications,thetransmissionwillgenerallybeconnectedtothecrankshaftoftheengine.Theoutputofthetransmissionistransmittedviadriveshafttooneormoredifferentials,whichinturndrivethewheels.Whileadifferentialmayalsoprovideg
6、earreduction,itsprimarypurposeistochangethedirectionofrotation.Conventionalgear/belttransmissionsarenottheonlymechanismforspeed/torqueadaptation.Alternativemechanismsincludetorqueconvertersandpowertransformation(e.g.,diesel-electrictransmission,hydraulicd
7、rivesystem,etc.).Hybridconfigurationsalsoexist.ExplanationEarlytransmissionsincludedtheright-angledrivesandothergearinginwindmills,horse-powereddevices,andsteamengines,insupportofpumping,milling,andhoisting.Mostmoderngearboxesareusedtoincreasetorquewhiler
8、educingthespeedofaprimemoveroutputshaft(e.g.amotorcrankshaft).Thismeansthattheoutputshaftofagearboxwillrotateatslowerratethantheinputshaft,andthisreductioninspeedwillproduceamechanicaladvantage,causinganincreaseinto
