汽车专业英语课件-与汽车专业英语读译教程课件、参考译文19-U11TA

UNIT11SUSPENSIONANDSTEERINGSYSTEMSTEXTABasicPartsandTypesoftheSuspensionandSteeringSystems,PROFESSIONALENGLISH,TEXTABasicPartsandTypesoftheSuspensionandSteeringSystemsBasicSuspensionSystemComponentsTypesSteeringSystemSteeringGearPowerSteering,本次课学习内容,本次课学习目标,掌握转向与悬架系统的英文专业词汇掌握转向与悬架系统主要类型训练快速阅读能力，提高阅读速度,NEWWORDS,PHRASESANDEXPRESSIONS,BasicPartsandTypesoftheSuspensionandSteeringSystemsSuspensionSystemIfavehiclesaxleswerebolteddirectlytoitsframeorbody,everyroughspotintheroadwouldtransmitajarringforcethroughoutthevehicle.Ridingwouldbeuncomfortable,andhandlingatfreewayspeedswouldbeimpossible.Thefactthatthemodernvehicleridesandhandleswellisadirectresultofasuspensionsystem.Eventhoughthetiresandwheelsmustfollowtheroadcontour,thebodyshouldbeinfluencedaslittleaspossible1.Thepurposeofanysuspensionsystemistoallowthebodyofthevehicletotravelforwardwithaminimumamountofup-and-downmovement.Thesuspensionshouldalsopermitthevehicletomaketurnswithoutexcessivebodyrollortireskidding.,SuspensionSystemComponentsVehicleFrameAvehiclesframeorbodymustformarigidstructuralfoundationandprovidesolidanchoragepointsforthesuspensionsystem.Therearetwotypesofvehicleconstructionincommonusetoday:body-over-frameconstruction,whichusesaseparatesteelframetowhichthebodyisboltedatvariouspointsandunibodyconstruction,inwhichthebodysectionsserveasstructuralmembers.Unibodyconstructionisthemostcommon,butbody-over-frameconstructionisstillusedonpickuptrucksandlargecars.SpringsThespringsarethemostobviouspartofthesuspensionsystem.Everyvehiclehasaspringofsomekindbetweentheframeorbodyandtheaxles.Therearethreetypesofspringsingeneralusetoday:leafspring,coilspring,andtorsionbar.Twodifferenttypesofspringscanbeusedononevehicle.Airspringswereonceusedinplaceoftheothertypesofsprings,butarenowobsolete.Manymodernvehicleshaveair-operatedsuspensions,buttheyareusedtosupplementthesprings.,ShockAbsorbersWhenthevehicleistravelingforwardonalevelsurfaceandthewheelsstrikeabump,thespringisrapidlycompressed(coilsprings)ortwisted(leafspringsandtorsionbars).Thespringwillattempttoreturntoitsnormalloadedlength.Insodoing,itwillrebound,causingthebodyofthevehicletobelifted.Sincethespringhasstoredenergy,itwillreboundpastitsnormallength.Theupwardmovementofthevehiclealsoassistsinreboundingpastthespringsnormallength.Theweightofthevehiclethenpushesthespringdownafterthespringrebounds.Theweightofthevehiclewillpushthespringdown,butsincethevehicleistravelingdownward,theenergybuiltupbythedescendingbodywillpushthespringbelowitsnormalloadedheight.Thiscausesthespringtoreboundagain.Thisprocess,calledspringoscillation,graduallydiminishesuntilthevehicleisfinallystill.Springoscillationcanaffecthandlingandridequalityandmustbecontrolled.,AirShockAbsorbersSomesuspensionsystemsincorporatetwoadjustableairshockabsorbersthatareattachedtotherearsuspensionandconnectedtoanairvalvewithflexibletubing.Airoperatedshockabsorbershavehydraulicdampeningsystemswhichoperateinthesamemannerasthoseonconventionalshocks.Inaddition,theycontainasealedairchamber,whichisactedonbypressurefromaheightcontrolsensor.Varyingthepressuretotheairchambercausestheairshocktoincreaseordecreaseitslengthoroperatingrange.Airpressureisdeliveredtotheairshocksthroughplastictubing.Thetubingconnectstheshockstoanairvalve.Airpressureforraisingtheshocksisgenerallyobtainedfromanoutsidesource,suchasaservicestationcompressor,andisadmittedthroughtheairvalve.Todepletetheshocksofunwantedair(lowervehiclecurbheight),theairvalvecoreisdepressed,allowingairtoescape.,ControlArmsAllvehicleshaveeithercontrolarmsorstrutstokeepthewheelassemblyintheproperposition.Thecontrolarmsandstrutsallowthewheeltomoveupanddownwhilepreventingitfrommovinginanyotherdirection.Thewheelwilltendtomoveinundesirabledirectionswheneverthevehicleisaccelerated,braked,orturned.Vehiclesuspensionsmayhavecontrolarmsonlyoracombinationofcontrolarmsandstruts.TypesoftheSuspensionFrontSuspensionSystemsAlmostallmodernfrontsuspensionsystemsareindependent.Withanindependentsuspension,eachfrontwheelisfreetomoveupanddownwithaminimumeffectontheotherwheel.Inanindependentsuspensionsystem,thereisalsofarlesstwistingmotionimposedontheframethaninasystemwithasolidaxle.Nevertheless,afewoff-road,fourwheeldrivevehiclesandlargetruckscontinuetouseasolidaxlefrontsuspension.ThetwomajortypesofindependentfrontsuspensionaretheconventionalfrontsuspensionandtheMacPhersonstrutfrontsuspension.,ConventionalFrontSuspensionIntheconventionalfrontsuspensionsystem,oneortwocontrolarmsareusedateachwheel.Inmostsystems,thecoilspringsaremountedbetweenthevehiclesframeandthelowercontrolarm.Inoldersystems,coilspringsaremountedbetweentheuppercontrolarmandvehiclebody.Inatorsionbarfrontsuspensionsystem,thelowerarmmovesupward,ittwiststhetorsionbar.CoilSpringFrontSuspensionFig.11-1showsatypicalindependentfrontsuspensionthatusesrubberbushingcontrolarmpivots.Thetopofthecoilspringrestsinacup-likespotagainsttheframe(unshown).Thebottomofthecoilspringissupportedbyapadonthelowercontrolarm.Thetopofeachshockabsorberisfastenedtotheframe;thebottomisattachedtothelowercontrolarm.Whenthewheelstrikesabump,itisdrivenupward.Thiscausesarmstopivotupward,compressingthespringandshock.Rubberbumperslimitcontrolarmtravelandsoftentheblowwhenthelimitisreached.Forsteering,thefrontwheelsteeringknucklepivotsonballjoints.,TorsionBarFrontSuspensionAtorsionbarislocatedoneachsideoftheframeinthefrontofthevehicle.Thelowercontrolarmisattachedtothefreeendofthetorsionbar.Whenthewheelisdrivenupward,thelowercontrolarmmovesupward,twistingthelongspringsteelbar.MacphersonStrutFrontSuspensionMostmodernvehicles,especiallythosewithfront-wheeldrive,usetheMacPhersonstrutfrontsuspensionsystems,Fig.11-2.NotethattheMacPhersonstrutcontainsacoilspring,whichismountedontopoftheheavystrut-and-pedestalassembly.TheentireMacPhersonstrutassemblyisattachedtothesteeringknuckleatthelowerpartofthepedestal.ThebottomoftheMacPhersonstrutassemblyisattachedtothesinglecontrolarmthroughaballjoint.,Fig.11-1Atypicalindependentfrontsuspension,Fig.11-2AMacPhersonstrutfrontsuspensionsystem,Theentirestrutassemblyturnswhenthewheelisturned.Abearingorthrustplateatthetopofthestrutassemblyallowsrelativemovementbetweentheassemblyandthevehiclebody.Theballjointallowsthestrutassemblytoturninrelationtothecontrolarm.Thestrutcontainsadamper,whichoperatesinthesamemannerasaconventionalshockabsorber.Mostdamperassemblieshaveaprotectivecoverthatkeepsdirtandwaterawayfromthedamperpistonrod.TheadvantageoftheMacPhersonstrutisitscompactdesign,whichallowsmoreroomforserviceonsmallcarbodies.SolidAxleFrontSuspensionTheuseofthesolidaxlefrontsuspension(ordependentsuspension)isgenerallyconfinedtotrucksandoff-roadvehicles.Thissystemusesasolidsteeldeadaxle(doesnotturnwithwheels)withaleafspringateachside.Pivotarrangementsbetweentheaxleandthewheelspindlesallowthewheelstoswiveloneachend.Anyupordownmovementofeitherfrontwheelcausesaverticaltippingeffectofbothwheelsbecausetheyshareacommonaxle.,RearSuspensionSystemsRearsuspensionsonvehicleswithasolidrearaxlehousinggenerallyutilizecoilspringsorleafsprings.Whenthevehiclehasanindependentrearsuspensionsystem,coilsprings,MacPhersonstruts,asingletransverseleafspring,oreventorsionbarscanbeused.SteeringSystemThesteeringsystemisdesignedtoallowthedrivertomovethefrontwheelstotherightorleftwithaminimumofeffortandwithoutexcessivemovementofthesteeringwheel.Althoughthedrivercanmovethewheelseasily,roadshocksarenottransmittedtothedriver.Thisabsenceofroadshocktransferisreferredtoasthenonreversiblefeatureofsteeringsystems.,Thebasicsteeringsystemcanbedividedintothreemainassemblies:Thespindleandsteeringarmassemblies.Thelinkageassemblyconnectingthesteeringarmsandsteeringgear.Thesteeringwheel,steeringshaft,andsteeringgearassembly.SteeringGearThesteeringgearisdesignedtomultiplythedriversturningtorquesothefrontwheelsmaybeturnedeasily.Whentheparallelogramlinkageisused,thetorquedevelopedbythedriverismultipliedthroughgearsandisthentransmittedtothewheelspindleassembliesthroughthelinkage.Ontherack-and-pinionsteeringsystem,thesteeringshaftisconnecteddirectlytothepinionshaft.Turningthepinionmovestheracksection,witchmovesthelinkage.Late-modelvehiclesuseeithermanualsteeringgearsorpowersteeringgears.Therearethreetypesofthesteeringgearsinuse:recirculatingballsteeringgear,worm-and-rollersteeringgearandrack-and-pinionsteeringgear.,PowerSteeringPowersteeringisdesignedtoreducetheeffortneededtoturnthesteeringwheelbyutilizinghydraulicpressuretobolster(strengthen)thenormaltorquedevelopedbythesteeringgear.Powersteeringsystemsshouldeasesteeringwheelmanipulationand,atthesametime,offerenoughresistancesothatthedrivercanretainsomeroadfeel.Powersteeringisusedwithbothconventionalandrack-and-pinions