汽车悬架原理外文文献翻译中英文文档格式.docx

汽车悬架原理外文文献翻译中英文文档格式.docx

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英文原文

TherincipleofCarSuspensions

WilliamHarris

UniversityofMichigan

Whenpeoplethinkofautomobileperformance,theynormallythinkofhorsepower,torqueandzero-to-60acceleration.Butallofthepowergeneratedbyapistonengineisuselessifthedrivercan'

tcontrolthecar.That'

swhyautomobileengineersturnedtheirattentiontothesuspensionsystemalmostassoonastheyhadmasteredthefour-strokeinternalcombustionengine.

Thejobofacarsuspensionistomaximizethefrictionbetweenthetiresandtheroadsurface,toprovidesteeringstabilitywithgoodhandlingandtoensurethecomfortofthepassengers.Inthisarticle,we'

llexplorehowcarsuspensionswork,howthey'

veevolvedovertheyearsandwherethedesignofsuspensionsisheadedinthefuture.

1.VehicleDynamics

Ifaroadwereperfectlyflat,withnoirregularities,suspensionswouldn'

tbenecessary.Butroadsarefarfromflat.Evenfreshlypavedhighwayshavesubtleimperfectionsthatcaninteractwiththewheelsofacar.It'

stheseimperfectionsthatapplyforcestothewheels.AccordingtoNewton'

slawsofmotion,allforceshavebothmagnitudeanddirection.Abumpintheroadcausesthewheeltomoveupanddownperpendiculartotheroadsurface.Themagnitude,ofcourse,dependsonwhetherthewheelisstrikingagiantbumporatinyspeck.Eitherway,thecarwheelexperiencesaverticalaccelerationasitpassesoveranimperfection.Withoutaninterveningstructure,allofwheel'

sverticalenergyistransferredtotheframe,whichmovesinthesamedirection.Insuchasituation,thewheelscanlosecontactwiththeroadcompletely.Then,underthedownwardforceofgravity,thewheelscanslambackintotheroadsurface.Whatyouneedisasystemthatwillabsorbtheenergyoftheverticallyacceleratedwheel,allowingtheframeandbodytorideundisturbedwhilethewheelsfollowbumpsintheroad.

Thestudyoftheforcesatworkonamovingcariscalledvehicledynamics,andyouneedtounderstandsomeoftheseconceptsinordertoappreciatewhyasuspensionisnecessaryinthefirstplace.Mostautomobileengineersconsiderthedynamicsofamovingcarfromtwoperspectives:

1）Ride-acar'

sabilitytosmoothoutabumpyroad

2）Handling-acar'

sabilitytosafelyaccelerate,brakeandcorner

Thesetwocharacteristicscanbefurtherdescribedinthreeimportantprinciples-roadisolation,roadholdingandcornering.Thetablebelowdescribestheseprinciplesandhowengineersattempttosolvethechallengesuniquetoeach.

Acar'

ssuspension,withitsvariouscomponents,providesallofthesolutionsdescribed.

2.TheChassisSystem

Thesuspensionofacarisactuallypartofthechassis,whichcomprisesalloftheimportantsystemslocatedbeneaththecar'

sbody.

Thesesystemsinclude:

1）Theframe-structural,load-carryingcomponentthatsupportsthecar'

sengineandbody,whichareinturnsupportedbythesuspension

2）Thesuspensionsystem-setupthatsupportsweight,absorbsanddampensshockandhelpsmaintaintirecontact

3）Thesteeringsystem-mechanismthatenablesthedrivertoguideanddirectthevehicle

4）Thetiresandwheels-componentsthatmakevehiclemotionpossiblebywayofgripand/orfrictionwiththeroad

Sothesuspensionisjustoneofthemajorsystemsinanyvehicle.

Withthisbig-pictureoverviewinmind,it'

stimetolookatthethreefundamentalcomponentsofanysuspension:

springs,dampersandanti-swaybars.

3.Springs

Today'

sspringingsystemsarebasedononeoffourbasicdesigns:

1）Coilsprings-Thisisthemostcommontypeofspringandis,inessence,aheavy-dutytorsionbarcoiledaroundanaxis.Coilspringscompressandexpandtoabsorbthemotionofthewheels.

2）Leafsprings-Thistypeofspringconsistsofseverallayersofmetal（called"

leaves"

）boundtogethertoactasasingleunit.Leafspringswerefirstusedonhorse-drawncarriagesandwerefoundonmostAmericanautomobilesuntil1985.Theyarestillusedtodayonmosttrucksandheavy-dutyvehicles.

3）Torsionbars-Torsionbarsusethetwistingpropertiesofasteelbartoprovidecoil-spring-likeperformance.Thisishowtheywork:

Oneendofabarisanchoredtothevehicleframe.Theotherendisattachedtoawishbone,whichactslikealeverthatmovesperpendiculartothetorsionbar.Whenthewheelhitsabump,verticalmotionistransferredtothewishboneandthen,throughtheleveringaction,tothetorsionbar.Thetorsionbarthentwistsalongitsaxistoprovidethespringforce.Europeancarmakersusedthissystemextensively,asdidPackardandChryslerintheUnitedStates,throughthe1950sand1960s.4）Airsprings-Airsprings,whichconsistofacylindricalchamberofairpositionedbetweenthewheelandthecar'

sbody,usethecompressivequalitiesofairtoabsorbwheelvibrations.Theconceptisactuallymorethanacenturyoldandcouldbefoundonhorse-drawnbuggies.Airspringsfromthiseraweremadefromair-filled,leatherdiaphragms,muchlikeabellows;

theywerereplacedwithmolded-rubberairspringsinthe1930s.

Basedonwherespringsarelocatedonacar--i.e.,betweenthewheelsandtheframe--engineersoftenfinditconvenienttotalkaboutthesprungmassandtheunsprungmass.

4.SprungandUnsprungMass

Thesprungmassisthemassofthevehiclesupportedonthesprings,whiletheunsprungmassislooselydefinedasthemassbetweentheroadandthesuspensionsprings.Thestiffnessofthespringsaffectshowthesprungmassrespondswhilethecarisbeingdriven.Looselysprungcars,suchasluxurycars（thinkLincolnTownCar）,canswallowbumpsandprovideasuper-smoothride;

however,suchacarispronetodiveandsquatduringbrakingandaccelerationandtendstoexperiencebodyswayorrollduringcornering.Tightlysprungcars,suchassportscars（thinkMazdaMiata）,arelessforgivingonbumpyroads,buttheyminimizebodymotionwell,whichmeanstheycanbedrivenaggressively,evenaroundcorners.

So,whilespringsbythemselvesseemlikesimpledevices,designingandimplementingthemonacartobalancepassengercomfortwithhandlingisacomplextask.Andtomakemattersmorecomplex,springsalonecan'

tprovideaperfectlysmoothride.Why?

Becausespringsaregreatatabsorbingenergy,butnotsogoodatdissipatingit.Otherstructures,knownasdampers,arerequiredtodothis.

5.ShockAbsorbers

Unlessadampeningstructureispresent,acarspringwillextendandreleasetheenergyitabsorbsfromabumpatanuncontrolledrate.Thespringwillcontinuetobounceatitsnaturalfrequencyuntilalloftheenergyoriginallyputintoitisusedup.Asuspensionbuiltonspringsalonewouldmakeforanextremelybouncyrideand,dependingontheterrain,anuncontrollablecar.

Entertheshockabsorber,orsnubber,adevicethatcontrolsunwantedspringmotionthroughaprocessknownasdampening.Shockabsorbersslowdownandreducethemagnitudeofvibratorymotionsbyturningthekineticenergyofsuspensionmovementintoheatenergythatcanbedissipatedthroughhydraulicfluid.Tounderstandhowthisworks,it'

sbesttolookinsideashockabsorbertoseeitsstructureandfunction.

Ashockabsorberisbasicallyanoilpumpplacedbetweentheframeofthecarandthewheels.Theuppermountoftheshockconnectstotheframe（i.e.,thesprungweight）,whilethelowermountconnectstotheaxle,nearthewheel（i.e.,theunsprungweight）.Inatwin-tubedesign,oneofthemostcommontypesofshockabsorbers,theuppermountisconnectedtoapistonrod,whichinturnisconnectedtoapiston,whichinturnsitsinatubefilledwithhydraulicfluid.Theinnertubeisknownasthepressuretube,andtheoutertubeisknownasthereservetube.Thereservetubestoresexcesshydraulicfluid.

Whenthecarwheelencountersabumpintheroadandcausesthespringtocoilanduncoil,theenergyofthespringistransferredtotheshockabsorberthroughtheuppermount,downthroughthepistonrodandintothepiston.Orificesperforatethepistonandallowfluidtoleakthroughasthepistonmovesupanddowninthepressuretube.Becausetheorificesarerelativelytiny,onlyasmallamountoffluid,undergreatpressure,passesthrough.Thisslowsdownthepiston,whichinturnslowsdownthespring.

Shockabsorbersworkintwocycles--thecompressioncycleandtheextensioncycle.Thecompressioncycleoccursasthepistonmovesdownward,compressingthehydraulicfluidinthechamberbelowthepiston.Theextensioncycleoccursasthepistonmovestowardthetopofthepressuretube,compressingthefluidinthechamberabovethepiston.Atypicalcarorlighttruckwillhavemoreresistanceduringitsextensioncyclethanitscompressioncycle.Withthatinmind,thecompressioncyclecontrolsthemotionofthevehicle'

sunsprungweight,whileextensioncontrolstheheavier,sprungweight.

Allmodernshockabsorbersarevelocity-sensitive--thefasterthesuspensionmoves,themoreresistancetheshockabsorberprovides.Thisenablesshockstoadjusttoroadconditionsandtocontrolalloftheunwantedmotionsthatcanoccurinamovingvehicle,includingbounce,sway,brakediveandaccelerationsquat.

6.StrutsandAnti-swayBars

Anothercommondampeningstructureisthestrut--basicallyashockabsorbermountedinsideacoilspring.Strutsperformtwojobs:

Theyprovideadampeningfunctionlikeshockabsorbers,andtheyprovidestructuralsupportforthevehiclesuspension.Thatmeansstrutsdeliverabitmorethanshockabsorbers,whichdon'

tsupportvehicleweight--theyonlycontrolthespeedatwhichweightistransferredinacar,nottheweightitself.

Bec