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英文原文HowCarSuspensionWorkByWilliamHarrisUniversityofMichiganWhenpeoplethinlyofautomobileperformance,theynormallythinkofhorsepower,torqueandzero-to-60acceleration.Butallofthepowergeneratedbyapistonengineisuselessifthedriercan'tcontrolthecar.That'swhyautomobileengineersturnedtheirattentiontothesuspensionsystemalmostassoonastheyhadmasteredthefour-Strokeinternalcombustionengine.Double-wishbonesuspensiononHondaAccord2005CoupeThejobofacarsuspensionistomaximizethefrictionbetweenthetiresandtheroadsurface,toprovidesteeringstabilitywithgoodhandlingandtoensurethecomfortofthepassengers.Inthisarticle,we'llexplorehowcarSuspensionswork,howthey'reevolvedovertheyearsandwherethedesignofsuspensionsisheadedinthefuture.1.VehicleDynamicsIfaroadwereperfectlyt1at,withnoirregularities,suspensionswouldn'tbenecessary.Butroadsarefarfromt1at.Evenfreshlypavedhighwayshavesubtleimperfectionsthatcaninteractwiththewheelsofacar.It'stheseimperfectionsthatapplyforcestothewheels.AccordingtoNewton'slawsofmotion,allforceshavebothmagnitudeanddirection.Abumpintheroadcausesthewheeltomoveupanddownperpendiculartotheroadsurface.Themagnitude,ofcourse,dependsonwhetherthewheelisStrikingagiantbumporatinyspeck.Eitherway,theca.rwheelexperiencesaverticalaccelerationasitpassesoveranimperfection.Withoutaninterveningstructure,allofwheel'sverticalenergyistransferredtotheframe,whichmovesintheSamedirection.Insuchasituation,thewheelscanlosecontactwiththeroadcompletely.Then,underthedownwardforceofgravity,wheelscanslambackintotheroadsurface.Whatyouneedisasystemthatabsorbtheenergyoftheverticallyacceleratedwheel,allowingtheframeandbodytorideundisturbedwhilethewheelsfollowbumpsintheroad.TheStudyofthefarcesatworkanamovingcariscalledvehicledynamics,andyouneedtosuspensionisnecessaryofneedtounderstandsameoftheseconceptsinordertoappreciatewhyanecessaryinthefirstplace.MastautomobileengineersconsiderthemovingcarPramtwoperspectives:1)Ride-acar'sabilitytosmoothoutabumpyroad2)Handling-acar'sabilitytosafelyaccelerate,brakeandcornerThesetwocharacteristicscanbefurtherdescribedinthreeimportantprinciples-roadisolation,roadholdingandcornering.Thetablebelowdescribestheseprinciplesandhowengineersattempttosolvethechallengesuniquetoeach.Acar'ssuspension,withitsvariouscomponents,providesalloftheSolutionsdescribed.2.TheChassisSystemThesuspensionofacarisactuallypartofthechassis,whichcomprisesalloftheimportantsystemslocatedbeneaththecar'sbody.figure2-1ChassisThesesystemsinclude:1)Theframe-structural,load-carryingcomponentthatsupportsthecar'sengineandbody,whichareinturnsupportedbythesuspension2)TheSuspensionsystem-setupthatsupportsweight,absorbsanddampensshockandhelpsmaintaintirecontact3)Thesteeringsystem-mechanismthatenablesthedrivertoguideanddirectthevehicle4)Thetiresandwheels-componentsthatmakevehiclemotionpossiblebywayofgripand/orfrictionwiththeroadSothesuspensionisjustoneofthemajorsystemsinanyvehicle.Withthisbig-pictureoverviewinmind,it'stimetolookatthethreefundamentalcomponentsofanysuspension:springs,dampersandanti-swaybars.3.springsToday'sspringingsystemsarebasedononeoffourbasicdesign:1)Coilspring-Thisisthemastcommontypeofspringandis,inessence,aheavy-dutytorsionbarcoiledaroundanaxis.Coilspringscompressandexpandtoabsorbthemotionofthewheels.2)Leafspring-Thistypeofspringconsistsofseverallayersofmetal(calledleaves)boundtogethertoactasasingleunit.Leafspringswerefirstusedonhorse-drawncarriagesandwerefoundanmostAmericanautomobilesuntil1985.Theyarestillusedtodayonmosttrucksandheavy-dutyvehicles.3)Torsionbars-TorsionbarsusethetwistingpropertiesofasteelGartoprovidecoil-spring-likeperformance.Thisishowtheywork:Oneendofabarisanchoredtothevehicleframe.Theotherendi5attachedtoawishbone,whichactslikealeverthatmaresperpendiculartothetorsionbar.Whenthewheelhitsabump,verticalmotionistransferredtothewishboneandthen,throughtheleveringaction,tothetorsionbar.Thetorsionbarthentwistsalongitsaxistoprovidethespringfarce.Europeancaretakersusedthissystemextensively,asdidPackardandChryslerintheUnitedStates,throughthe1950sand1960s.4)Airsprings-AirSprings,whichconsistofacylindricalchamberofairpositionedbetweenthewheelandthecar'sbody,usethecompres5irequalitiesofairtoabsorbwheelvibrations.Theconceptisactuallymorethanacenturyoldandcouldbefoundanhorse-drawnbuggies.Airspringsfromthiseraweremadefromair-filled,leatherdiaphragms,muchlikeabellows;theywerereplacedwithmolded-rubberairspringsinthe1930s.Basedonwherespringsarelocatedonacar-i.e.,betweenthewheelsandtheframe-engineersoftenfinditconvenienttotalkaboutthesprungmassandtheunsprungmass.4.SprungandUnsprungMassThesprungmassisthemassofthevehiclesupportedanthesprings,whiletheunsprungmassislooselydefinedasthemassbetweentheroadandthesuspensionSprings.Thestiffnessofthespringsaffectshowthesprungmassrespondswhilethecarisbeingdriven.Looselysprungcars,suchasluxurycars{thinkLincolnTawsCard,canSwallowbumpsandprovideasuper-smoothride;however,suchacarisprunetodiveandsquatduringbrakingandaccelerationandtendstoexperiencebodyawayorrollduringcornering.Tightlysprungcars,suchassportscars(thinkMazd