汽车专业英语课件-与汽车专业英语读译教程2版配套13-U8TA

UNIT8CLUTCHES,MANUALTRANSMISSIONSANDDRIVELINETEXTAClutchesandManualTransmissions,PROFESSIONALENGLISH,UNIT7CLUTCHES,MANUALTRANSMISSIONSANDDRIVELINETEXTAClutchesandManualTransmissionsClutchesManualTransmission(M/T),本次课学习内容,本次课学习目标,掌握离合器和手动变速器的有关英文专业词汇能够较好地用已知翻译技巧进行课文翻译具有较高的阅读速度,NEWWORDS,PHRASESANDEXPRESSIONS,endplay轴向间隙clustergear齿轮组，塔齿轮thrustwasher止推垫片synchronizingmechanism同步机构synchronizedgear同步器，同步机构,ClutchesandManualTransmissionsClutchesThefunctionoftheclutchassemblyincarsandtruckswithmanualtransmissionsortransaxlesistoconnectordisconnecttheflowofpowerfromtheenginetothedriveline.Althoughtherearemanyvariationsinthedesignofclutches,allworkonthesamebasicprinciple.ClutchPurposeAclutchisamechanismdesignedtoconnectordisconnectpowerfromoneworkingparttoanother.Inavehicle,theclutchisusedtotransmitenginepowerandtodisengagetheengineandtransmissionwhenshiftinggears.Italsoallowstheenginetooperatewhenthevehicleisstoppedwithoutplacingthetransmissioninneutral(outofgear).,ClutchConstructionThemodernclutchisasingleplate,drydisc(seeFigure8-1).Itconsistsoffivemajorparts:flywheel,clutchdisc,pressureplateassembly,throw-outbearing,andclutchlinkage.Otherpartswhichmakeuptheclutchassemblyarethetransmissioninputshaftandclutchhousing.,Figure8-1Atypicalclutch,FlywheelInadditiontoprovidingabaseforthestarterringgear,theflywheelformsthefoundationonwhichtheotherclutchpartsareattached.Theflywheelusedwithmanualtransmissionsisthicktoenableittoabsorbalargeamountofheatgeneratedbyclutchoperation.Theclutchsideismachinedsmoothtoprovideafrictionsurface.Holesaredrilledintotheflywheeltoprovideameansofmountingtheclutchassembly.Aholeisusuallydrilleddirectlyintotherearofthecrankshaft.Thisholeallowsabearingtobeinstalledinthecenteroftheflywheel.Thebearinginthecenteroftheflywheelwillactasasupportfortheoutboardendofthetransmissioninputshaft.Itisreferredtoasapilotbearing.Thepilotbearingmaybeeitheraballbearingorabronzebushing.,DualMassFlywheelAdualmassflywheelissometimesusedwithdieselengines.Tohelpabsorbenginepowerstrokepulsations,springsmountedinsidetheflywheelactasashockabsorbingunitwhentheflywheelsectionspartiallycompress,smoothingoutthepowerflow.Theyalsohelptoreducestressontheclutchandtransmissionparts.ClutchDiscTheclutchdiscisroundandconstructedofthin,highqualitysteelwithasplined(grooved)hubplacedinthecenter.Thehubsplinesengagesplinesonthetransmissioninputshaft.Theclutchdisccanmovebackandforthontheshaft,butwhenthediscisturned,theshaftmustturnalso.Bothsidesofitsouteredgearecoveredwithfrictionmaterial.Itisoftenmadeofasbestosorotherhightemperaturematerialandcopperwireseitherwovenormoldedtogether.Itisrivetedtothedisc.,Toassistinsmoothengagement,thediscouteredgesareoftensplitandeachpiececupped.Thefrictionmaterialisrivetedtothesesegments.Whenthedisciscompressed,thesecuppedsegmentsactasaspring-likecushion.PressurePlateTheclutchpressureplatediscisthesameineachtypeofpressureplateassembly.Itismadeofathickpieceofcastironformaximumheatabsorption.Itisroundandaboutthesamediameterastheclutchdisc.Onesideofthepressureplateismachinedsmooth.Thissidewillpresstheclutchdiscfacingareaagainsttheflywheel.Theoutersidehasvariousshapestofacilitateattachmentofspringsandreleasemechanisms.ReleaseLeverOperatingMechanismThismechanismconsistsofaballbearingnormallyreferredtoasathrow-outbearingorreleasebearing.Thisbearingismountedonasleeveorcollarthatslidesbackandforthonahubthatisanintegralpartofthetransmissionfrontbearingretainer.,Thethrow-outbearingisfilledwithgreaseatthefactoryanddoesnotneedserviceduringitsusefullife.Anothertypeofthrow-outbearingisthegraphitetype.Thisbearingemploysaringofgraphitetopressagainstasmoothplatefastenedtotheclutchlevers.Thethrow-outbearingsleeveismovedinandoutbyathrow-outforkorclutchfork.Thisforkisusuallypivotedonaballheadstud.Areturnspringpullstheforkawayfromthepressureplate.ClutchOperationTheflywheel,clutchcover,releaselevers,andpressureplateallrevolveasasingleunit.Thetransmissioninputshaftandtheclutchdiscaresplinedtogether,forminganotherunit.Theonlytimetheclutchdiscwillturn(vehiclestandingstill)iswhenitispinchedbetweentheflywheelandpressureplate.Whenthereleaseleversdrawthepressureplateawayfromtheflywheel,theclutchdiscwillstandstillwhileeverythingelsecontinuestorevolve.Whenthepressureplatetravelsbacktowardtheflywheel,thediscisseizedandforcedtoturnthetransmissioninputshaft,Figure8-2.,a)disengagedb)engagedFigure8-2Clutchoperationsimplified,ManualTransmission(M/T)TransmissionGearRatiosThemodernmanualtransmissioncanprovidethedriverwithuptosixforwardgearratios.Thereductiongearsprovidegearratiosofapproximately3.5:1(statedas3.5to1)forthelowestgear,toabout1.5:1forthehighest.Thedirectdrivegearhasa1:1gearratio.Theoverdrivegearshaveagearratioofabout0.7:1.Byselectingoneoftheratios,itispossibletooperatethevehicleunderallnormalconditions.Inaddition,torqueismultipliedmorethroughthedifferentialgears.Ratiosvaryfromvehicletovehicle,dependingonenginehorsepowerandvehicleweight.Areversegearisalsoused.Thereverseratioisusuallyabout3:1.Thefive-speedtransmissionhasanoverdriveratio.Theoverdriveratioisincorporatedintonewertransmissionstoincreasefuelmileageandloweremissions.,Figure8-3Therelativepositionsofthefourshaftsinthetransmissioncase,TransmissionConstructionAtypicaltransmissionconsistsofacase,fourshafts,bearings,gears,synchronizers,andashiftingmechanism.Figure8-3showstherelativepositionsofthefourshaftsandtheirgearsinthecase.TransmissionCaseThetransmissioncaseholdsthetransmissiongears,shafts,bearings,andwashers.Itisboltedtotherearoftheengine,ortotheclutchhousing.Manytransmissioncasesandclutchhousingsareone-pieceunits.Mosttransmissioncasesaremadeofcastironoraluminumandhaveaseparateextensionhousing,whichsupportstheoutputshaft.Thishousingmayalsocontainthespeedometergear.Therearenginemountisusuallyattachedtotheextensionhousing.,TransmissionGearTransmissiongearsaremadeofhighqualitysteel,carefullyheat-treatedtoproducesmooth,hardsurfacegearteethwithasofter,butverytoughinterior1.Theyaredrop-forged(machinehammeredintoshape)whileredhot.Theteethandothercriticalareasarecutonprecisionmachinery.Theteethontransmissiongearsarecutintospurandhelicalpatterns.Thehelicalgearissuperiorinthatitrunsmorequietlyandisstrongerbecausemoretoothareaisincontact2.Helicalgearsmustbemountedfirmly,sincethereisatendencyforthemtoslideapartduetothespiralshape.Gearendplayintheclustergearandsomeothergearsandshaftsiscontrolledbytheuseofbronzeandsteelthrustwashers.Thesewashersareinstalledontheendofthegearshaftsbetweenthemovinggearsandthestationarytransmissioncase.Theremustbesomeclearancebetweenthegearteethtoallowforlubrication,expansionandpossiblesizeirregularity.Thisclearanceisverysmall(afewthousandthsofaninch).,SynchronizingMechanismOncethevehicleisinmotion,thedrivelinewillturntheoutputshaftcontinuously.Asaresult,theslidinggearswillalsobeturning.Whenanattemptismadetomeshthemwithanyoftheclustergears(whichtendtostopwhentheclutchisdepressed),