汽车英语翻译.docx
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汽车英语翻译.docx
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汽车英语翻译
英文翻译
BrakingSystem
Energyisrequiredwhenavehicleisacceleratedfromresttoacertainspeed.Aproportionofthatenergyisnowstoredinthevehicleandiscalledkineticenergy.Inordertoreducethespeedofthevehicle,thebrakeshavetoconvertthekineticenergytoheatenergy;thespeedofconversiongovernstherateatwhichthevehicleslowsdown.
Thethreetypesofbrakingsystemsareinusetoday:
servicebrakingsystem,parkingbrakingsystemandadditionalretarding-brakingsystem.Theservicebrakingsystemandtheparkingbrakingsystemhaveseparatecontrolandtransmissiondevices.Theservicebrakingsystemisnormallyfoot-operated,whiletheparkingbrakingsystemishand-operated.
Twotypesofbrakesareusedinmoderncars:
drumbrakesanddiscbrakes.Since1976,allcarshaveuseddiscbrakesonthefrontwheels.Mostcarsusedrumbrakesontherearwheels.Inbothdrumanddiscbrakes,ahydraulicsystemappliesthebrakes.Thehydraulicsystemconnectsthebrakepedaltothebrakepartsateachwheel.
Thesehavetwoshoes,anchoredtoastationaryback-plate,whichareinternallyexpandedtocontactthedrumbyhydrauliccylindersoramechanicallinkage.
Inthecaseofthesimplexbrake,C*(brakefactor)isthesumofthevaluesfortheindividualshoes,andis≈2.0(referredtoaspecificcoefficientoffriction).Adisadvantageofthisdesignisthegreatdifferenceinthebrakingeffectbetweenthetwobrakeshoes,andtheresultinggreatlyincreasedwearontheleadingshoe.Forthisreason,thetrailingshoeisoftenequippedwithamuchthinnerliningthantheleadingshoe.
Anadvantageofthistypeofbrakeisthenearlyequalbrakeliningwearonbothshoesandthehigherinternaltransmissionratioincomparisontosimplexbrakes.
Manycarshave2L.S.frontbrakesandL.&T.rearbrakes.Themorepowerfulfrontbrakestakeadvantageofthetransferenceofweightfromthereartothefrontwhichoccurswhenthebrakesareapplied.
Duo-servodrumbrake
Thistypeofdrumbrakehasanapplicationmechanismwhichissimpler,morereliableandinsensitivetotemperature.Itcomprisesdiaphragmcylinder,automaticslackadjuster,brakeshaftandS-cam.
Themaindisadvantageofdrumbrakesisthatthefrictionareaisalmostentirelycoveredbyalining,somostheatmustbeconductedthroughthedrumtoreachtheoutsideairtocool.
Exposedtotheair,discbrakesradiatetheheattotheairbetterthandrumbrakes:
Thismeansthatthebrakecanbeoperatedcontinuouslyforalongerperiod,i.e.theyhaveagreaterresistancetofade(fall-offinbrakeefficiencyduetoheat).
Discbrakesasusedinmostpassengercarsareslowlybeginningtobeusedincommercialvehiclesaswell.Asidefromtheiruseinfastcoaches,currentuseofdiscbrakesincommercialvehiclesisprimarilylimitedtofront-axlebrakesforcommercialvehiclesuptoaweightofapprox.7.5twhicharedriveninamannersimilartopassengercars.
Themastercylindercontainstwoseparatesections,thereisapistonineachsectionandbothpistonsareconnectedtoabrakepedalinthedriver'scompartment.
Whenthebrakepedalispushedbythedriver,thetwopistonsmoveinthetwosectionsofthemastercylinder.Thisforcesbrakefluidoutandthroughthebrakelines,ortubes,tothebrakemechanismsatthewheels.Inatypicalsystem,thebrakefluidfromonesectionofthemastercylindergoestothetwofront-wheelbrakes.Thebrakefluidfromtheothersectiongoestothetworear-wheelbrakes.Thepurposeofthisthat,ifonesectionfails,theothersectionwillstillprovidebraking.
heoperatingprincipleofthepower-assistedsystemisthesameasforanon-powersystem.However,brakingforceisincreasedthroughtheuseofavacuumboosterunit.Atmosphericpressurehelpstopushthebrakepedal.Thus,lessmuscleeffortisrequired.
InSIengines,vacuumisgeneratedviaaconnectiontotheengineintakemanifold,anddieselenginesuseavacuumpump.
Operationprinciple(Tandemmastercylinder):
afterpassingoversnifterholeⅠ,thepush-rodpistonforcesthebrakefluidintobrakecircuitⅠ.ThecompressionofthespringandthepressurebuildupinbrakecircuitIactuatestheintermediatepiston,whichpassesoversnifterholeⅡandbuildsuppressureinbrakecircuitⅡ
TheportforbrakecircuitI,whichsuppliesthereardrumbrakes,hasapre-pressurevalvewhichassuresaresidualpressureofapprox150kPawhenthebrakesarereleased.Thispreventstheentryofairthroughthewheel-cylinderseals.
Themoreheavilythedriverbrakes,thegreateristhedynamicshiftingofweightfromtherearaxletothefrontaxle.Withthevehicleempty,thebrakingforceattherearaxlemaybesogreatthattherearaxlelocksbeforethefrontaxle.Thiscanleadtoinstabilitywhenbraking,i.e.toskidding.Brakingstabilityisobtainedwhen,irrespectiveofvehicleloading,thefrontaxlealwayslocksbeforetherearaxle.Thecorrectbraking-forcedistributioncanbeachievedbybrake–pressure-regulatingvalveswhichareinstalledinthebrakelinestothewheelsoftherearaxle.
Acompressorisusedastheenergysource,andisusuallyoftheplungertype;theintakeairiscompressedviaautomaticsuctionanddeliveryvalves.
Thecombinationbrakecylinderconsistsofasingle-chamberdiaphragmcylinderfortheservicebrakesandaspring-brakeactuatorfortheparkingbrakes.Thecylinderandspringbrakeactuatorareintandemandactonacommonpressurerod.
Electrohydraulicbrakingsystemsaredesignedtoallowelectoniccontrolofvehiclebrakingwhileretainingareducedhydraulicsystem.TheEHBcontrolunitreceivesinputsfromsensorsconnectedtothebrakepedal.Innormaloperation,abackupvalveisclosedandthecontrolleractivatesthebrakesofthewheelthroughanelectricmotordrivenhydraulicpump.Whenthecontrollergoesintoafail-safemode,thebackupvalveisopened,whichallowsthebrakestobecontrolledthroughaconventionalhydrauliccircuit.
Inordertobrakethevehicle,thefieldcoilsaresuppliedwithcurrent(fromthebatteryoralternator)andgenerateamagneticfield.Eddycurrentsareinducedintherotorsastheypassthroughthisfield.Thisgeneratesabrakingtorquewhosemagnitudeisafunctionoftheexcitationofthestatorcoils.
hefunctionofananti-lock,oranti-skid,brakingsystemistopreventthewheelsfromlockingunderhardbraking.Maximumbrakingforceisobtainedjustbeforethewheelslockandskid.Suchanti-skidsystemsareusefulonslipperysurfaces,suchasiceandsnow,wherethewheelsmaylockeasily.
Thewheel-speedsensormonitorsthemotionofthewheel.Ifonewheelshowssignsoflocking,thereisasharpriseinperipheralwheeldecelerationandinwheelslip.Iftheseexceeddefinedcriticalvalues,thecontrollersendscommandstothesolenoid-valveunittostoporreducethebuildupofwheel-brakepressureuntilthedangeroflock-uphaspassed.Thebrakepressuremustthenbebuiltupagaininordertoensurethatthewheelisnotunder-braked.
Awheel-speedsensorconsistsofatoothedpulseringandaninductivewheel-speedpickup.Thepulseringismountedonthehuband,astherotates,producesinthewheel-speedpickupanA.C.voltage,thefrequencyofwhichisproportionaltothewheelspeed.
Fromthesignalsfromthewheel-speedpickups,thesemicrocomputerscalculatethewheelspeedsaswellasthewheeldecelerationsandaccelerations.Avehiclereferencespeedisformedfromthewheelspeedsoftwodiagonallyoppositewheels.Withthisreferencespeedandtheindividualwheelspeedsitispossibletocalculatethebrakeslipforeachwheel.Ifawheelhasatendencytolock,thisisdeterminedfromthewheel-accelerationandslipsignals.
Aseparateframemustbelightyetstrongenoughtoresistthevariousloadsandroadforces.Commercialvehiclesnormallyuseaseparatesteelframetoprovidetherigidityneededtosupportthevariousloads.Thetwolongsidemembersofchannelsectionarerivetedtoanumberofcrossmemberstogivealowweightframewhichoffersgreatresistancetobending,twisting.
Mostcarsuseaunitizedbodyconstruction,acombinedbodyandframe.Unitizedbodyconstructionislighterthanbody/frameconstruction,butnoisier.Rubbermountsareusedbetweenthebodysectionandmechanicalpartstoabsorbvibrations.Thefloorpanismadeofsectionsthatsupporttherearsuspensionandthetransmission.
Moderncarshaveablend-airsystemthatmixeswarmandunwarmedairtoheatthecar.The"heart''ofthesystemistheheatercore.Hotenginecoolantflowsfromtheradiator,throughthewaterpumphoses,andtotheheatercore.Therefore,theheatercoreisalwayshot.Thetemperatureofairenteringthepassengercompartmentiscontrolledbytheamountofairmovingthroughtheheatercore.Thisheatedairisblendedwithfresh,coolairthatbypassestheheater.Smalldoorsintheheatingsystemregulatetheair-flow.Controlleversonthedashpanelopenandclosethesedoorstodirectairtotheheatductsandwindowdefrosters
Thepurposeofventingsystemsistodrawinfreshairandremovestaleairfromtheinteriorofthecar.Freshairventingsystemsdirectairtotwodifferentplaces.First,theycandirectoutsideairintotheheaterhousing.Thisaireithercanbypassthecoiloritcanbeheatedbythecoil.Second,theaircanmovedirectlyintothepassengercompartmentthroughsmallventdoorsinthedashpaneloratfloorlevel.Ventingalsocantakeplacebyopeningthewindows.
Leversandswitchtoregulateairandheatarelocatedonthedashpanel.Someheatercontrolsusesmallvacuummotorsforsimpler,morepositiveaction.Othersusecables,whilesomeuseacombinationofthetwo.Theva
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