转向系设计英文文献及翻译.docx

转向系设计英文文献及翻译.docx

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转向系设计英文文献及翻译

FundamentalsofAutomobile

 Todayisaveragecarcontainsmorethan15,000separate,individualpartsthatmustworktogether.Thesepartscanbegroupedintofourmajorcategories:

engine,body,chassisandelectricalandelectronicequipment（Fig.1.1）.

1Engine

The engineactsasthepowerunit.Theinternalcombustionengineismostcommon:

thisobtainitspowerbyburningaliquidfuelinsidetheenginecylinder.Therearetwotypesofengines:

gasolineengine（alsocalledasparkignitionengine）anddiesel（alsocalledacompression-ignitionengine）.Bothenginesarecalledheatengines;theburningfuelgeneratesheatwhichcausesthegasinsidethecylindertoincreaseitspressureandsupplypowertorotateashaftconnectedtothetransmission.

2Body

 Anautomobilebodyisasheetmetalshellwithwindows,doors,ahood,andatrunkdeckbuiltintoit.Itprovidesaprotectivecoveringfortheengine,passengers,andcargo.Thebodyisdesignedtokeeppassengerssafeandcomfortable.Thebodystylingprovidesanattractive,colorful,modernappearanceforthevehicle.

3chassis

 Thechassisisanassemblyofthosesystemsthatarethemajoroperatingpartsofavehicle.TheChassisincludesthetransmission,suspension,steering,andbrakesystem.

3.1Transmission

Thetransmissionsystemcomprisesclutch,gearbox,propellershaft,rearaxleanddifferentialandthedrivenroadwheels.

Clutch

 Theclutchortorqueconverterhasthetaskofdisconnectingandconnectingtheengine'spowerfromandtothedrivingwheelsofthevehicle.Thisactionmaybemanualorautomatic.

Gearbox

Themainpurposeofthegearboxistoprovideaselectionofgearratiosbetweentheengineanddrivingwheels,sothatthevehiclecanoperatesatisfactorilyunderalldrivingconditions.Gearselectionmaybedonemanuallybythedriverorautomaticallybyahydrauliccontrolsystem.

Propellorshaft

 Thefunctionofthepropeller（drive）shaftistotransmitthedrivefromthegearboxtotheinputshaftoftherearaxleanddifferentialassembly.Flexiblejointsallowtherearaxleandwheelstomoveupanddownwithoutaffectingoperation.

Theroleofthedriveshaftfromthetransmissionthedrivingforcetransmittedtotherearaxleinputshaftandthedifferentialassembly.Universaljointallowstherearaxleandwheelsmoveupanddownwithoutaffectingoperation.

Rearaxleanddifferential

The rearaxleanddifferentialunittransmitstheengine'srotationalpowerthrough90frompropshafttoaxleshafttoaxleshafttoroadwheels.Afurtherfunctionistoalloweachdrivenwheeltoturnatadifferentspeed;essentialwhencorneringbecausetheouterwheelmustturnfurtherthantheinsidewheel.Athirdfunctionistointroduceanothergearratiofortorquemultiplication.

3.2Suspension

Theaxlesandwheelsareisolatedfromthechassisbyasuspensionsystem.Thebasicjobofthesuspensionsystemistoabsorbtheshockscausedbyirregularroadsurfacesthatwouldotherwisebetransmittedtothevehicleanditsoccupants,thushelpingtokeepthevehicleonacontrolledandlevelcourse,regardlessofroadconditions.

3.3Steering

Thesteeringsystem,underthecontrolofthedriveratthesteeringwheel,providesthemeansbywhichthefrontwheelsaredirectionallyturned.Thesteeringsystemmaybepowerassistedtoreducetheeffortrequiredtoturnthesteeringwheelandmakethevehicleeasiertomanoeuvre.

3.4Brakes

 Thebrakingsystemonavehiclehasthreemainfunctions.Itmustbeabletoreducethespeedofthevehicle,whennecessary;itmustbeabletostopthecarinasshortadistanceaspossible;itmustbeabletoholdthevehiclestationary.Thebrakingactionisachievedasaresultofthefrictiondevelopedbyforcingastationarysurface（thebrakelining）intocontactwitharotatingsurface（thedrumordisc）.

Eachwheelhasabrakeassemblyofeitherthedrumtypeorthedisctype,hydraulicallyoperatedwhenthedriverappliesthefootbrakepedal.

4ElectricalEquipmentandInstrumentation

 The electricalsystemsupplieselectricityfortheignition,horn,lights,heater,andstarter.Theelectricitylevelismaintainedbyachargingcircuit.Thiscircuitconsistsofabattery,andanalternator（orgenerator）.Thebatterystoreselectricity.Thealternatorchangestheengine'smechanicalenergyintoelectricalenergyandrechargesthebattery.

Themotorvehicleincorporatesanumberofelectricaldevicesthatareusedfor:

Batterycharging–alternatorandregulator.

Enginepurposes–startingandignition.

Safetyandconvenience–lighting,horn,wipers,washersetc.

Driverinformation–instrumentationandwarninglamps.

Ofthesedevicesinstrumentationis,perhaps,mostinfluencedbytheadvanceofmicroelectronics.Thebasicelectromechanicalsystemsof:

Speedometer–forindicatingvehiclespeed.

Engineoilpressure–warninglamporgaugetoshowoperatinglimits.

Enginecoolanttemperature–warninglamporgaugetoshowoperatinglimits.

Batterycharging–warninglamporgaugetoindicatesatisfactory/unsatisfactoryaction.

Fueltankcontent–gaugetoshowamountoffuelinthefueltank.

aregivingwaytocomputerizedvehiclemanagementinformationcentres.

TheSteeringSystem

1TheSteeringGear

Thesteeringgearmechanismenablesthedrivertoturnthefrontwheelsofthecar.Themechanismconsistsofasteeringgearbox,pitmanarm,draglink,tierods,steeringarms,andsteeringknuckles,thelattersupportingthefrontwheels（Fig.6.1）.

 Turningthesteeringwheelturnsthesteeringshafttowhichawormgearisattachedwithinthesteeringgearbox.Thesteeringwormmovesarollerthroughapartofanarc,themotionofwhichistransmittedtothepitmanarm,whichmovesbackandforthacrossthewidthoftheframe.Severalarrangementsofrodsandleversareincommonusebut,ingeneral,adraglink,connectedtothepitmenarm,transmitsthemovementtotierodswhichareconnectedtothesteeringarms.Sidewardmovementofthesteeringarmsturnsthesteeringknuckles,andthewheels,astheyarepivotedonfrontendsupportmechanism.

 Therearetwotypesofsteeringsystem:

manualsteeringsystemandpowersteeringsystem.Inthemanualtype,thedriverdoesalltheworkofturningthesteeringwheel,steeringgears,wheels,andtires.Inthepowertype,hydraulicfluidassiststheoperationsothatthedriver'seffortisreduced.

Mechanicalsteeringsystem:

Andchangesthetransmissionsystembythedivertertobecomposed.

Diverter:

Bythesteeringwheel,thesteeringwheelsteeringaxle,changesmeshingtopay（diverter）tobecomposed.

Steeringtransmissionsystem:

Bydroparm（droparm）,draglink,draglinkarm,abouttrapezoidalarm,steeringknuckletierod,ifadrybulbjointcomposes.

Powersteeringsystem:

ChangestheaugmenterconstitutionbymechanicalsteeringsystemCanada.

  Atypicalpowersteeringsystemneedsapowersteeringpumpandreservoirinadditiontothesteeringgear（Fig.6.2）.Thesepartsstorethehydraulicfluidandprovidethehydraulicpressuretoassiststeering.Inmostinstances,aV-beltfromtheenginepowerthehydraulicpump.Hosesleadfromthepumptothesteeringgearandbacktothepump.

Insteeringgearboxthegearisslightlylargerandhasotherparts.Thewormshaftisthesameinbothsystems.Insteadofaballnut,though,thepowersteeringsystemusesapowerpistonorrackpistoninsteeringgearbox.Thepowerpistonhasteethononesidethatmeshwiththesectorteeth.Theforwardandbackwardmotionofthepowerpistonmovesthesector,pitmanshaft,andsteeringlinkage.

Thepowersteeringgearalsousesacontrolvalvetosendhydraulicfluidintothesteeringgearattherighttime.Whenthesteeringwheelstartstomoveineitherdirection,thevalveopensitsportstosentfluidunderpressureintothemainchamberofthesteeringgear.Thefluidpushesagainstthepowerpistonandassiststhemotionofthesteeringwheel.

Fig.6.2Inanintegralpowersteeringsystem,thepowerand

controlareinthesamehousingasthesteeringgear

2Front-Geometry

  Thefrontwheelsarearrangedatvariousanglestothecarframetoprovidegoodsteeringcontrolandstability.Theanglesarediscussedinthefollowingorder:

caster,camber,steeringaxisinclination,toe,andturningradius.

 Casteristheslantofthekingpinforwardatthebottom（Fig.6.3）.（NOTE:

Modernpassengercardoesnotuseakingpininanindependentlymountedfrontwheelsuspension,butreferencetoitsformerpositionhelpstoclarifysomefrontendconcepts.Thepositionofthekingpinwouldbeonadirectlinedrawnbetweenthetwoballjoints）.Thefrontwheels,whenprovidedwiththeproperamountofcaster,willalignthemselvesinthedirectioninwhichthecarismoving.Toomuchcasterwillcausehardsteeringandshimmyatlowspeed.Toolittlecasterwillcausewanderorweaveathighspeedanderraticsteeringwhenapplyingthebrakes.

  Camberistheanglebetweenaverticallineandalinedrawnthroughthecenterofthewheel（Fig.6.4）.Thetopofthewheelisinclinedawayfromthecar.Thepurposeofcamberistoplacethecenterofthetiredirectlyundertheextendedlineofthekingpinforeasiersteering.Thisplacestheweightofthecardirectlyoverthepivotpoint.

 SteeringAxisInclinationistheoutwardtiltofthebottomofthekingpintowardthewheel（Fig.6.5）.Modernengineeringpracticeistominimizecamberinordertoreduceuneventirewear,andincreasethe

Fig.6.3CasterFig.6.4Camber

angularinclinationofthekingpintoplaceitscenterlinedirectlyunderthecenterofthetireforeaseinsteering.

Steeringaxisinclinationalsoprovidessteeringstabilitybyraisingtheentirefrontendofthevehi