汽車專業(yè)英語(yǔ)讀譯教程 第3版 教案 UNIT 5 DIESEL FUEL INJECTION

授課題目UNIT7

CLUTCHES,MANUALTRANSMISSIONSANDDRIVELINE

TEXTA

ClutchesandManualTransmissions授課類型理論課首次授課時(shí)間學(xué)時(shí)2學(xué)時(shí)教學(xué)目標(biāo)1、離合器的結(jié)構(gòu)英文術(shù)語(yǔ)；重點(diǎn)與難點(diǎn)重點(diǎn)：離合器的結(jié)構(gòu)英文術(shù)語(yǔ)；難點(diǎn)：離合器的結(jié)構(gòu)英文；。教學(xué)手段與方法多媒體教學(xué)教學(xué)過程：（包括授課思路、過程設(shè)計(jì)、講解要點(diǎn)及各部分具體內(nèi)容、時(shí)間分配等）1.授課思路在學(xué)習(xí)了前置課程之后，通過專業(yè)英語(yǔ)的學(xué)習(xí)，進(jìn)行與汽車相關(guān)技術(shù)結(jié)構(gòu)原理的中文英文對(duì)接，培養(yǎng)和提高英文專業(yè)資料（信息）的閱讀能力，從而為與專業(yè)英語(yǔ)密切相關(guān)的后續(xù)課程奠定了必要的基礎(chǔ)。2.過程設(shè)計(jì)：（1）課程內(nèi)容簡(jiǎn)介（5分鐘）（2）導(dǎo)入新課（15分鐘）。（3）新課內(nèi)容（75分鐘）教師根據(jù)學(xué)生學(xué)習(xí)的情況，對(duì)課程內(nèi)容的重點(diǎn)和難點(diǎn)進(jìn)行講解。（4）課程小結(jié)（5分鐘）3.授課內(nèi)容：ClutchesThefunctionoftheclutchassemblyincarsandtruckswithmanualtransmissionsortransaxlesistoconnectordisconnecttheflowofpowerfromtheenginetothedriveline.Althoughtherearemanyvariationsinthedesignofclutches,allworkonthesamebasicprinciple.ClutchPurposeAclutchisamechanismdesignedtoconnectordisconnectpowerfromoneworkingparttoanother.Inavehicle,theclutchisusedtotransmitenginepowerandtodisengagetheengineandtransmissionwhenshiftinggears.Italsoallowstheenginetooperatewhenthevehicleisstoppedwithoutplacingthetransmissioninneutral(outofgear).ClutchConstructionThemodernclutchisasingleplate,drydisc(seeFigure8-1).Itconsistsoffivemajorparts:flywheel,clutchdisc,pressureplateassembly,throw-outbearing,andclutchlinkage.Otherpartswhichmakeuptheclutchassemblyarethetransmissioninputshaftandclutchhousing.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.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.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.TransmissionConstructionAtypicaltransmissionconsistsofacase,fourshafts,bearings,gears,synchronizers,andashiftingmechanism.Figure8-3showstherelativepositionsofthefourshaftsandtheirgearsinthecase.TransmissionCaseThetransmissioncaseholdsthetransmissiongears,shafts,bearings,andwashers.Itisboltedtotherearoftheengine,ortotheclutchhousing.Manytransmissioncasesandclutchhousingsareone-pieceunits.Mosttransmissioncasesaremadeofcastironoraluminumandhaveaseparateextensionhousing,whichsupportstheoutputshaft.Thishousingmayalsocontainthespeedometergear.Therearenginemountisusuallyattachedtotheextensionhousing.TransmissionGearTransmissiongearsaremadeofhighqualitysteel,carefullyheat-treatedtoproducesmooth,hardsurfacegearteethwithasofter,butverytoughinterior[1].Theyaredrop-forged(machinehammeredintoshape)whileredhot.Theteethandothercriticalareasarecutonprecisionmachinery.Theteethontransmissiongearsarecutintospurandhelicalpatterns.Thehelicalgearissuperiorinthatitrunsmorequietlyandisstrongerbecausemoretoothareaisincontact[2].Helicalgearsmustbemountedfirmly,sincethereisatendencyforthemtoslideapartduetothespiralshape.Gearendplayintheclustergearandsomeothergearsandshaftsiscontrolledbytheuseofbronzeandsteelthrustwashers.Thesewashersareinstalledontheendofthegearshaftsbetweenthemovinggearsandthestationarytransmissioncase.SynchronizingMechanismOncethevehicleisinmotion,thedrivelinewillturntheoutputshaftcontinuously.Asaresult,theslidinggearswillalsobeturning.Whenanatt