汽车离合器课程毕业设计外文文献翻译中英文翻译外文翻译.docx
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汽车离合器课程毕业设计外文文献翻译中英文翻译外文翻译
CLUTCH
Theengineproducesthepowertodrivethevehicle.Thedrivelineordrivetraintransfersthepoweroftheenginetothewheels.Thedrivetrainconsistsofthepartsfromthebackoftheflywheeltothewheels.Thesepartsincludetheclutch,thetransmission,thedriveshaft,andthefinaldriveassembly(Figure8-1).
Theclutchwhichincludestheflywheel,clutchdisc,pressureplate,springs,pressureplatecoverandthelinkagenecessarytooperatetheclutchisarotatingmechanismbetweentheengineandthetransmission(Figure8-2).Itoperatesthroughfrictionwhichcomesfromcontactbetweentheparts.Thatisthereasonwhytheclutchiscalledafrictionmechanism.Afterengagement,theclutchmustcontinuetotransmitalltheenginetorquetothetransmissiondependingonthefrictionwithoutslippage.Theclutchisalsousedtodisengagetheenginefromthedrivetrainwheneverthegearsinthetransmissionarebeingshiftedfromonegearratiotoanother.
Tostarttheengineorshiftthegears,thedriverhastodepresstheclutchpedalwiththepurposeofdisengagementthetransmissionfromtheengine.Atthattime,thedrivenmembersconnectedtothetransmissioninputshaftareeitherstationaryorrotatingataspeedthatisslowerorfasterthanthedrivingmembersconnectedtotheenginecrankshaft.Thereisnospringpressureontheclutchassemblyparts.Sothereisnofrictionbetweenthedrivingmembersanddrivenmembers.Asthedriverletsloosetheclutchpedal,springpressureincreasesontheclutchparts.Frictionbetweenthepartsalsoincreases.Thepressureexertedbythespringsonthedrivenmembersiscontrolledbythedriverthroughtheclutchpedalandlinkage.Thepositiveengagementofthedrivinganddrivenmembersismadepossiblebythefrictionbetweenthesurfacesofthemembers.Whenfullspringpressureisapplied,thespeedofthedrivinganddrivenmembersshouldbethesame.Atthemoment,theclutchmustactasasolidcouplingdeviceandtransmitallenginepowertothetransmission,withoutslipping.
However,thetransmissionshouldbeengagedtotheenginegraduallyinordertooperatethecarsmoothlyandminimizetorsionalshockonthedrivetrainbecauseanengineatidlejustdevelopslittlepower.Otherwise,thedrivingmembersareconnectedwiththedrivenmemberstooquicklyandtheenginewouldbestalled.
Theflywheelisamajorpartoftheclutch.Theflywheelmountstotheengine’scrankshaftandtransmitsenginetorquetotheclutchassembly.Theflywheel,whencoupledwiththeclutchdiscandpressureplatemakesandbreakstheflowofpowerfromtheenginetothetransmission.
Theflywheelprovidesamountinglocationfortheclutchassemblyaswell.Whentheclutchisapplied,theflywheeltransfersenginetorquetotheclutchdisc.Becauseofitsweight,theflywheelhelpstosmoothengineoperation.Theflywheelalsohasalargeringgearatitsouteredge,whichengageswithapiniongearonthestartermotorduringenginecranking.
Theclutchdiscfitsbetweentheflywheelandthepressureplate.Theclutchdischasasplinedhubthatfitsoversplinesonthetransmissioninputshaft.Asplinedhubhasgroovesthatmatchsplinesontheshaft.Thesesplinesfitinthegrooves.Thus,thetwopartsareheldtogether.However,back-and-forthmovementofthediscontheshaftispossible.Attachedtotheinputshaft,Atdiscturnsatthespeedoftheshaft.
Theclutchpressureplateisgenerallymadeofcastiron.Itisroundandaboutthesamediameterastheclutchdisc.Onesideofthepressureplateismachinedsmooth.Thissidewillpresstheclutchdiscfacingareagainsttheflywheel.Theoutersidehasvariousshapestofacilitateattachmentofspringandreleasemechanisms.Thetwoprimarytypesofpressureplateassembliesarecoilspringassemblyanddiaphragmspring(Figure8-3).
Inacoilspringclutchthepressureplateisbackedbyanumberofcoilspringsandhousedwiththeminapressed-steelcoverboltedtotheflywheel.Thespringspushagainstthecover.Neitherthedrivenplatenorthepressureplateisconnectedrigidlytotheflywheelandbothcanmoveeithertowardsitoraway.Whentheclutchpedalisdepressedathrustpadridingonacarbonorballthrustbearingisforcedtowardstheflywheel.Leverspivotedsothattheyengagewiththethrustpadatoneendandthepressureplateattheotherendpullthepressureplatebackagainstitssprings.Thisreleasespressureonthedrivenplatedisconnectingthegearboxfromtheengine(Figure8-4).
Diaphragmspringpressureplateassembliesarewidelyusedinmostmoderncars.Thediaphragmspringisasinglethinsheetofmetalwhichyieldswhenpressureisappliedtoit.Whenpressureisremovedthemetalspringsbacktoitsoriginalshape.Thecentreportionofthediaphragmspringisslitintonumerousfingersthatactasreleaselevers.Whentheclutchassemblyrotateswiththeenginetheseweightsareflungoutwardsbycentrifugalforcesandcausetheleverstopressagainstthepressureplate.Duringdisengagementoftheclutchthefingersaremovedforwardbythereleasebearing.Thespringpivotsoverthefulcrumringanditsouterrimmovesawayfromtheflywheel.Theretractingspringpullsthepressureplateawayfromtheclutchplatethusdisengagingtheclutch(Figure8-5).
Whenengagedthereleasebearingandthefingersofthediaphragmspringmovetowardsthetransmission.Asthediaphragmpivotsoverthepivotringitsouterrimforcesthepressureplateagainsttheclutchdiscsothattheclutchplateisengagedtotheflywheel.
Theadvantagesofadiaphragmtypepressureplateassemblyareitscompactness,lowerweight,fewermovingparts,lessefforttoengage,reducesrotationalimbalancebyprovidingabalancedforcearoundthepressureplateandlesschancesofclutchslippage.
Theclutchpedalisconnectedtothedisengagementmechanismeitherbyacableor,morecommonly,byahydraulicsystem.Eitherway,pushingthepedaldownoperatesthedisengagementmechanismwhichputspressureonthefingersoftheclutchdiaphragmviaareleasebearingandcausesthediaphragmtoreleasetheclutchplate.Withahydraulicmechanism,theclutchpedalarmoperatesapistonintheclutchmastercylinder.Thisforceshydraulicfluidthroughapipetotheclutchreleasecylinderwhereanotherpistonoperatestheclutchdisengagementmechanism.Thealternativeistolinktheclutchpedaltothedisengagementmechanismbyacable.
Theotherpartsincludingtheclutchfork,releasebearing,bell-housing,bellhousingcover,andpilotbushingareneededtocoupleanduncouplethetransmission.Theclutchfork,whichconnectstothelinkage,actuallyoperatestheclutch.Thereleasebearingfitsbetweentheclutchforkandthepressureplateassembly.Thebellhousingcoverstheclutchassembly.Thebellhousingcoverfastenstothebottomofthebellhousing.Thisremovablecoverallowsamechanictoinspecttheclutchwithoutremovingthetransmissionandbellhousing.Apilotbushingfitsintothebackofthecrankshaftandholdsthetransmissioninputshaft.
TorqueConverter
TheBasics
Justlikemanualtransmissioncars,carswithautomatictransmissionsneedawaytolettheengineturnwhilethewheelsandgearsinthetransmissioncometoastop.Manualtransmissioncarsuseaclutch,whichcompletelydisconnectstheenginefromthetransmission.Automatictransmissioncarsuseatorqueconverter.
Atorqueconverterisatypeoffluidcoupling,whichallowstheenginetospinsomewhatindependentlyofthetransmission.Iftheengineisturningslowly,suchaswhenthecarisidlingatastoplight,theamountoftorquepassedthroughthetorqueconverterisverysmall,sokeepingthecarstillrequiresonlyalightpressureonthebrakepedal.
Ifyouweretosteponthegaspedalwhilethecarisstopped,youwouldhavetopressharderonthebraketokeepthecarfrommoving.Thisisbecausewhenyousteponthegas,theenginespeedsupandpumpsmorefluidintothetorqueconverter,causingmoretorquetobetransmittedtothewheels.
InsideaTorqueConverter
Therearefourcomponentsinsidetheverystronghousingofthetorqueconverter:
1.Pump;2.Turbine;3.Stator;4.Transmissionfluid.
Thehousingofthetorqueconverterisboltedtotheflywheeloftheengine,soitturnsatwhateverspeedtheengineisrunningat.Thefinsthatmakeupthepumpofthetorqueconverterareattachedtothehousing,sotheyalsoturnatthesamespeedastheengine.Thecutawaybelowshowshoweverythingisconnectedinsidethetorqueconverter(Figure8-6).
Thepumpinsideatorqueconverterisatypeofcentrifugalpump.Asitspins,fluidisflungtotheoutside,muchasthespincycleofawashingmachineflingswaterandclothestotheoutsideofthewashtub.Asfluidisflungtotheoutside,avacuumiscreatedthatdrawsmorefluidinatthecenter.
Thefluidthenentersthebladesoftheturbine,whichisconnectedtothetransmission.Theturbinecausesthetransmissiontospin,whichbasicallymovesthecar.Thebladesoftheturbinearecurved.Thismeansthatthefluid,whichenterstheturbinefromtheoutside,hastochangedirectionbeforeitexitsthecenteroftheturbine.Itisthisdirectionalchangethatcausestheturbinetospin.
Thefluidexitstheturbineatthecenter,movinginadifferentdirectionthanwhenitentered.Thefluidexitstheturbinemovingoppositethedirectionthatthepump(andengine)isturning.Ifthefluidwereallowedtohitthepump,itwouldslowtheenginedown,wastingpower.Thisiswhyatorqueconverterhasastator.
Thestatorresidesintheverycenterofthetorqueconverter.Itsjobistoredirectthefluidreturningfromtheturbinebe