汽车悬架如何工作毕业设计外文翻译外文翻译.docx
- 文档编号:4880076
- 上传时间:2022-12-11
- 格式:DOCX
- 页数:10
- 大小:225.73KB
汽车悬架如何工作毕业设计外文翻译外文翻译.docx
《汽车悬架如何工作毕业设计外文翻译外文翻译.docx》由会员分享,可在线阅读,更多相关《汽车悬架如何工作毕业设计外文翻译外文翻译.docx(10页珍藏版)》请在冰豆网上搜索。
汽车悬架如何工作毕业设计外文翻译外文翻译
TherincipleOfCarSuspensions
ByWilliamHarris
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.
figure2-1Chassis
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
figure6-1Commonstrutdesign
Anothercommondampeningstructureisthestrut--basicallyashockabsorbermountedinsideacoilspring.Strutsperformtwojobs:
Theyprovideadampeningfunctionlikeshockabsorbers,andtheyprovidestructuralsupportforthevehiclesuspension.Thatmeansstrutsdeliverabitmorethanshockabsorbers,whichdon'tsupportvehicleweight--theyonlycontrolthespeedatwhichweightistransferredinacar,nottheweightitself.
Becauseshocksand
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 汽车 悬架 如何 工作 毕业设计 外文 翻译