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1、Transmission(mechanics)Atransmissionorgearboxprovidesspeedandtorqueconversionsfromarotatingpowersourcetoanotherdeviceusinggearratios.InBritishEnglishthetermtransmissionreferstothewholedrivetrain,includinggearbox,clutch,propshaft(forrear-wheeldrive),differentialandfinaldriveshafts.Themostcom
2、monuseisinmotorvehicles,wherethetransmissionadaptstheoutputoftheinternalcombustionenginetothedrivewheels.Suchenginesneedtooperateatarelativelyhighrotationalspeed,whichisinappropriateforstarting,stopping,andslowertravel.Thetransmissionreducesthehigherenginespeedtotheslowerwheelspeed,increasi
3、ngtorqueintheprocess.Transmissionsarealsousedonpedalbicycles,fixedmachines,andanywhereelserotationalspeedandtorqueneedstobeadapted.Often,atransmissionwillhavemultiplegearratios(orsimply"gears"),withtheabilitytoswitchbetweenthemasspeedvaries.Thisswitchingmaybedonemanually(bytheoperator),orau
4、tomatically.Directional(forwardandreverse)controlmayalsobeprovided.Single-ratiotransmissionsalsoexist,whichsimplychangethespeedandtorque(andsometimesdirection)ofmotoroutput.Inmotorvehicleapplications,thetransmissionwillgenerallybeconnectedtothecrankshaftoftheengine.Theoutputofthetransmissio
5、nistransmittedviadriveshafttooneormoredifferentials,whichinturndrivethewheels.Whileadifferentialmayalsoprovidegearreduction,itsprimarypurposeistochangethedirectionofrotation.Conventionalgear/belttransmissionsarenottheonlymechanismforspeed/torqueadaptation.Alternativemechanismsincludetorquec
6、onvertersandpowertransformation(e.g.,diesel-electrictransmission,hydraulicdrivesystem,etc.).Hybridconfigurationsalsoexist.ExplanationEarlytransmissionsincludedtheright-angledrivesandothergearinginwindmills,horse-powereddevices,andsteamengines,insupportofpumping,milling,andhoisting.Mostmoder
7、ngearboxesareusedtoincreasetorquewhilereducingthespeedofaprimemoveroutputshaft(e.g.amotorcrankshaft).Thismeansthattheoutputshaftofagearboxwillrotateatslowerratethantheinputshaft,andthisreductioninspeedwillproduceamechanicaladvantage,causinganincreaseinto
