离合器汽车制动系统外文文献翻译中英文翻译外文翻译.docx

离合器汽车制动系统外文文献翻译中英文翻译外文翻译.docx

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离合器汽车制动系统外文文献翻译中英文翻译外文翻译

3.1Clutch

Theengineproducesthepowertodrivethevehicle.Thedrivelineordrivetraintransfersthepoweroftheenginetothewheels.Thedrivetrainconsistsofthepartsfromthebackoftheflywheeltothewheels.Thesepartsincludetheclutch,thetransmission,thedriveshaft,andthefinaldriveassembly.

Theclutchwhichincludestheflywheel,clutchdisc,pressureplate,springs,pressureplatecoverandthelinkagenecessarytooperatetheclutchisarotatingmechanismbetweentheengineandthetransmission.Itoperatesthroughfrictionwhichcomesfromcontactbetweentheparts.Thatisthereasonwhytheclutchiscalledafrictionmechanism.Afterengagement,theclutchmustcontinuetotransmitallenginetorquetotransmissiondependingonthefrictionwithoutslippage.Theclutchisalsousedtodisengagetheenginefromthedrivetrainwheneverthegearsinthetransmissionarebeingshiftedfromgearratiotoanother.

Tostarttheengineorshiftthegears,thedriverhastodepresstheclutchpedalwiththepurposeofdisengagementthetransmissionfromtheengine.Atthattime,thedrivenmembersconnectedtothetransmissioninputshaftareeitherstationaryorrotatingataspeedthatissloweroffasterthanthedrivingmembersconnectedtoenginecrankshaft.Thereisnospringpressureontheclutchassemblyparts.Sothereisnofrictionbetweenthedrivingmembersanddrivenmembers.Asthedriverlet’sloosetheclutchpedal,springpressureincreaseontheclutchparts.Frictionbetweenthepartsalsoincreases.Thepressureexertedbythespringsonthedrivenmembersiscontrolledbythedriverthroughtheclutchpedalandlinkage.Thepositiveengagementofthedrivinganddrivenmembersismadepossiblethefrictionbetweenthesurfacesofthemembers.Whenfullspringpressureisapplied,thespeedofthedrivinganddrivenmembersshouldbethesame.Atthemoment,theclutchmustactasacouplingdeviceandtransmitallenginepowertothetransmission,withoutslipping.

However,thetransmissionshouldbeengagedtotheenginegraduallyinordertooperatethecarsmoothlyandminimizetensionalshockonthedrivetrainbecauseanengineatidlejustdeveloplittlepower.Otherwise,thedrivingmembersareconnectedwiththedrivenmemberstooquicklyandtheenginewouldbestalled.

Theflywheelisamajorpartoftheclutch.Theflywheelmountstotheengine’scrankshaftandtransmitsenginetorquetotheclutchassembly.Theflywheel,whencoupledwiththeclutchdiscandpressureplatemakesandbreakstheflowofpowertheenginetothetransmission.

Theflywheelprovidesamountinglocationfortheclutchassemblyaswell.Whentheclutchisapplied,theflywheeltransfersenginetorquetotheclutchdisc.Becauseofitsweight,theflywheelhelpstosmoothengineoperation.Theflywheelalsohasalargeringgearatitsouteredge,whichengageswithapiniongearonthestartermotorduringenginecranking.

Theclutchdiscfitsbetweentheflywheelandthepressureplate.Theclutchdischasasplintedhubthatfitsoversplintsonthetransmissioninputshaft.Asplintedhubhasgroovesthatmatchsplintsontheshaft.Thesesplintsfitinthegrooves.Thus,thetwopartsheldtogether.However,back–and–forthmovementofthediscontheshaftispossible.Attachedtotheinputshaft,thediscturnsatthespeedoftheshaft.

Theclutchpressureplateisgenerallymadeofcastiron.Itisroundandaboutthesamediameterastheclutchdisc.Onesideofthepressureplateismachinedsmooth.Thissidewillpresstheclutchdiscfacingareagainsttheflywheel.Theoutersidehasshapestofacilitateattachmentofspringandreleasemechanism.Thetwoprimarytypesofpressureplateassembliesarecoilspringassemblyanddiaphragmspring.

Inacoilspringclutchthepressureplateisbackedbyanumberofcoilspringsandhousedwiththeminapressed–steedcoverboltedtotheflywheel.Thespringpushesagainstthecover.Neitherthedrivenplatenorthepressureplateisconnectedrigidlytotheflywheelandbothcanmoveeithertowardsitoaway.Whentheclutchpedalisdepressedathrustpadridingonacarbonorballthrustbearingisforcedtowardstheflywheel.Leverspivotedsothattheyengagewiththethrustpadatoneendandthepressureplatetattheotherendpullthepressureplatebackagainstitssprings.Thisreleasespressureonthedrivenplatedisconnectingthegearboxfromtheengine.

Diaphragmspringpressureplateassembliesarewidelyusedinmostmoderncars.Thediaphragmspringisasinglethinsheetofmetalwhichyieldswhenpressureisappliedtoit.Whenpressureisremovedthemetalspringbacktoitsoriginalshape.Thecenterportionofthediaphragmspringisslitintonumerousfingersthatactasreleaselevers.Whentheclutchassemblyrotateswiththeenginetheseweightsareflungoutwardsbycentrifugalplateandcausetheleverstopressagainstthepressureplate.Duringdisengagementoftheclutchthefingersaremovedforwardbythereleasebearing.Thespringpivotsoverthefulcrumringanditsouterrimmovesawayfromtheflywheel.Theretractingspringpullsthepressureplateawayfromtheclutchplatethusdisengagingtheclutch.

Whenengagedthereleasebearingandthefingersofthediaphragmspringmovetowardsthetransmission.Asthediaphragmpivotsoverthepivotringitsouterrimforcesthepressureplateagainsttheclutchdiscsothattheclutchplateisengagedtoflywheel.

Theadvantagesofadiaphragmtypepressureplateassemblyareitscompactness,lowerweight,fewermovingparts,lessefforttoengage,reducesrotationalimbalancebyprovidingabalancedforcearoundthepressureplateandlesschancesofclutchslippage.

Theclutchpedalisconnectedtothedisengagementmechanismeitherbyacableor,morecommonly,byahydraulicsystem.Eitherway,pushingthepedaldownoperatesthedisengagementmechanismwhichputspressureonthefingersoftheclutchdiaphragmviaareleasebearingandcausesthediaphragmtoreleasetheclutchplate.Withahydraulicmechanism,theclutchpedalarmoperatesapistonintheclutchmastercylinder.Thisforceshydraulicfluidthroughapipetothecutchreleasecylinderwhereanotheroperatestheclutchdisengagementmechanismbyacable.

Theotherpartsincludingtheclutchfork,releasebearing,bell–housing,bellhousingcover,andpilotbushingareneededtocoupleanduncouplethetransmission.Theclutchfork,whichconnectstothelinkage,actuallyoperatestheclutch.Thereleasebearingfitsbetweentheclutchforkandthepressureplateassembly.Thebellhousingcoverstheclutchassembly.Thebellhousingcoverfastenstothebottomofthebellhousing.Thisremovablecoverallowsamechanictoinspecttheclutchwithoutremovingthetransmissionandbellhousing.Apilotbushingfitsintothebackofthecrankshaftandholdsthetransmissioninputshaft.

3.2BrakeSystem

Thebreakingsystemisthemostimportantsystemincars.Ifthebrakesfail,theresultcanbedisastrous.Brakesareactuallyenergyconversiondevices,whichconvertthekineticenergy（momentum）ofthevehicleintothermal（heat）.Whensteppingonthebrakes,thedrivercommandsastoppingforcetentimesaspowerfulastheforcethatputsthecarinmotion.Thebrakingsystemcanexertthousandsofpoundsofpressureoneachofthefourbrakes.

Thebrakesystemiscomposedofthefollowingbasiccomponents:

the“mastercylinder”whichislocatedunderthehood,andisdirectlyconnectedtothebrakepedal,convertsdriverfoot’smechanicalpressureintohydraulicpressure.Steel“brakelines”andflexible“brakehoses”connectthemastercylindertothe“slavecylinders”locatedateachwheel.Brakefluid,speciallydesignedtoworkinextremecondition,fillsthesystem.“Shoes”and“Pads”arepushedbythesalvecylinderstocontactthe“drum”and“rotors”thuscausingdrag,which（hopefully）slowsthecar.

Thetypicalbrakesystemconsistsofdiskbrakesinfrontandeitherdiskordrumbrakesintherearconnectedbyasystemoftubesandhosesthatlinkthebrakeateachwheeltothemastercylinder.

Steppingonthebrakepedal,aplungerisactuallybeenpushingagainstinthemastercylinderwhichforceshydraulicoil（brakefluid）throughaseriesoftubesandhosestothebrakingunitateachwheel.Sincehydraulicfluid（oranyfluidforthatmatter）cannotbecompressed,pushingfluidthroughapipeisjustlikepushingasteelbarthroughpipe.Unlikeasteelbar,however,fluidcanbedirectedthroughmanytwistsandturnsonitswaytoitsdestination,arrivingwiththeexactsamemotionandpressurethatitstartedwith.Itisveryimportantthatthefluidispureliquidandthatthereisnoairbubblesinit.Aircancompresswhichcausessponginesstothepedalandseverelyreducedbrakingefficiency.Ifairissuspected,thenthesystemmustbebledtoremovetheair.Thereare“bleederscrews”ateachwheelandcaliperforthispurpose.

Ondiskbrakes,thefluidfromthemastercylinderisforcedintoacaliperwhereitpressureagainstapiston.Thepiton,in-turn,squeezestwobrakepadsagainstthedisk（rotor）whichisattachedtothewheel,forcingittoslowdownorstop.Thisprocessissimilartothewheel,causingthewheeltostop.Ineithercase,thefrictionsurfaceofthepadsonadiskbrakesystem,ontheshoesonadrumbrakeconverttheforwardmotionofthevehicleintoheat.Heatiswhatcausesthefrictionsurfaces（lining）ofthepadsandshoestoeventuallywearoutandrequirereplacement.

Brakefluidisspecialoilthathasspecificsproperties.Itisdesignedtowithstandcoldtemperatureswithoutthickeningaswellasveryhightemperatureswith