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

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