HowCarSuspensionsWorkTableofContents:›IntroductiontoHowCarSuspensionsWork›VehicleDynamics›TheChassis›Springs›Springs:SprungandUnsprungMass›Dampers:ShockAbsorbers›Dampers:StrutsandAnti-swayBars›SuspensionTypes:Front›SuspensionTypes:Rear›SpecializedSuspensions:TheBajaBug›SpecializedSuspensions:FormulaOneRacers›SpecializedSuspensions:HotRods›TheFutureofCarSuspensions›LotsMoreInformation›ComparePricesforCarSuspensionsWhenpeoplethinkofautomobileperformance,theynormallythinkofhorsepower,torqueandzero-to-60acceleration.Butallofthepowergeneratedbyapistonengineisuselessifthedrivercan'tcontrolthecar.That'swhyautomobileengineersturnedtheirattentiontothesuspensionsystemalmostassoonastheyhadmasteredthefour-strokeinternalcombustionengine.PhotocourtesyHondaMotorCo.,Ltd.Double-wishbonesuspensiononHondaAccord2005CoupeThejobofacarsuspensionistomaximizethefrictionbetweenthetiresandtheroadsurface,toprovidesteeringstabilitywithgoodhandlingandtoensurethecomfortofthepassengers.Inthisarticle,we'llexplorehowcarsuspensionswork,howthey'veevolvedovertheyearsandwherethedesignofsuspensionsisheadedinthefuture.VehicleDynamics(汽车动力学)Ifaroadwereperfectlyflat,withnoirregularities,suspensionswouldn'tbenecessary.Butroadsarefarfromflat.Evenfreshlypavedhighwayshavesubtleimperfectionsthatcaninteractwiththewheelsofacar.It'stheseimperfectionsthatapplyforcestothewheels.AccordingtoNewton'slawsofmotion(牛顿运动理论),allforceshavebothmagnitude(大小)anddirection.Abump(撞击)intheroadcausesthewheeltomoveupanddownperpendicular(垂直的)totheroadsurface.Themagnitude,ofcourse,dependsonwhetherthewheelisstrikingagiantbumporatinyspeck(斑点).Eitherway,thecarwheelexperiencesaverticalaccelerationasitpassesoveranimperfection.Withoutanintervening(介入)structure,allofwheel'sverticalenergyistransferredtotheframe,whichmovesinthesamedirection.Insuchasituation,thewheelscanlosecontactwiththeroadcompletely.Then,underthedownwardforceofgravity,thewheelscanslambackintotheroadsurface.Whatyouneedisasystemthatwillabsorbtheenergyoftheverticallyacceleratedwheel,allowingtheframeandbodytorideundisturbedwhilethewheelsfollowbumpsintheroad.Thestudyoftheforcesatworkonamovingcariscalledvehicledynamics,andyouneedtounderstandsomeoftheseconceptsinordertoappreciatewhyasuspensionisnecessaryinthefirstplace.Mostautomobileengineersconsiderthedynamicsofamovingcarfromtwoperspectives:Ride-acar'sabilitytosmoothoutabumpyroadHandling-acar'sabilitytosafelyaccelerate,brakeandcornerThesetwocharacteristicscanbefurtherdescribedinthreeimportantprinciples-roadisolation,roadholdingandcornering.Thetablebelowdescribestheseprinciplesandhowengineersattempttosolvethechallengesuniquetoeach.PrincipleDefinitionGoalSolutionRoadIsolationThevehicle'sabilitytoabsorborisolateroadshockfromthepassengercompartmentAllowthevehiclebodytorideundisturbedwhiletravelingoverroughroads.Absorbenergyfromroadbumpsanddissipate(驱散)itwithoutcausingundue(不恰当的)oscillation(振动)inthevehicle.RoadHoldingThedegreetowhichacarmaintainscontactwiththeroadsurfaceinvarioustypesofdirectionalchangesandinastraightline(Example:Theweightofacarwillshiftfromthereartirestothefronttiresduringbraking.Becausethenoseofthecardipstowardtheroad,thistypeofmotionisknownasdive.Theoppositeeffect--squat--occursduringacceleration,whichshiftstheweightofthecarfromthefronttirestotheback.)Keepthetiresincontactwiththeground,becauseitisthefrictionbetweenthetiresandtheroadthataffectsavehicle'sabilitytosteer,brakeandaccelerate.Minimizethetransferofvehicleweightfromsidetosideandfronttoback,asthistransferofweightreducesthetire'sgripontheroad.CorneringTheabilityofavehicletotravelacurvedpathMinimizebodyroll,whichoccursascentrifugalforcepushesoutwardonacar'scenterofgravitywhilecornering,raisingonesideofthevehicleandloweringtheoppositeside.Transfertheweightofthecarduringcorneringfromthehighsideofthevehicletothelowside.Acar'ssuspension,withitsvariouscomponents,providesallofthesolutionsdescribed.Let'slookatthepartsofatypicalsuspension,workingfromthebiggerpictureofthechassisdowntotheindividualcomponentsthatmakeupthesuspensionproper.TheChassisThesuspensionofacarisactuallypartofthechassis,whichcomprisesalloftheimportantsystemslocatedbeneaththecar'sbody.ChassisThesesystemsinclude:Theframe-structural,load-carryingcomponentthatsupportsthecar'sengineandbody,whichareinturnsupportedbythesuspensionThesuspensionsystem-setupthatsupportsweight,absorbsanddampensshockandhelpsmaintaintirecontactThesteeringsystem-mechanismthatenablesthedrivertoguideanddirectthevehicleThetiresandwheels-componentsthatmakevehiclemotionpossiblebywayofgripand/orfrictionwiththeroadSothesuspensionisjustoneofthemajorsystemsinanyvehicle.Withthisbig-pictureoverviewinmind,it'stimetolookatthethreefundamentalcomponentsofanysuspension:springs,dampersandanti-swaybars.SpringsToday'sspringingsystemsarebasedononeoffourbasicdesigns:Coilsprings-Thisisthemostcommontypeofspringandis,inessence,aheavy-dutytorsionbarcoiledaroundanaxis.Coilspringscompressandexpandtoabsorbthemotionofthewheels.PhotocourtesyCarDomainCoilspringsLeafsprings-Thistypeofspringconsist