汽车自动变速器中英文资料外文翻译文献.docx
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汽车自动变速器中英文资料外文翻译文献.docx
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汽车自动变速器中英文资料外文翻译文献
中英文资料外文翻译
AUTOMATICTRANSMISSION
Themodernautomatictransmissionisbyfar,themostcomplicatedmechanicalcomponentintoday’sautomobile.Itisatypeoftransmissionthatsiftsitself.Afluidcouplingortorqueconverterisusedinsteadofamanuallyoperatedclutchtoconnectthetransmissiontotheengine.
Therearetwobasictypesofautomatictransmissionbasedonwhetherthevehicleisrearwheeldriveorfrontwheeldrive.Onarearwheeldrivecar,thetransmissionisusuallymountedtothebackoftheengineandislocatedunderthehumpinthecenterofthefloorboardalongsidethegaspedalposition.Adriveshaftconnectsthetransmissiontothefinaldrivewhichislocatedintherearaxleandisusedtosendpowertotherearwheels.Powerflowonthissystemissimpleandstraightforwardgoingfromtheengine,throughthetorqueconverter,thentroughthetransmissionanddriveshaftuntilitreachesthefinaldrivewhereitissplitandsenttothetworeartransmission.
Onafrontwheeldrivecar,thetransmissionisusuallycombinedwiththefinaldrivetoformwhatiscalledatransaxle.Theengineonafrontwheeldrivecarisusuallymountedsidewaysinthecarwiththetransaxletuckedunderitonthesideoftheenginefacingtherearofthecar.Frontaxlesareconnecteddirectlytothetransaxleandprovidepowertofrontwheels.Inthisexample,powerfloesfromtheengine,throughthetorqueconvertertoalargerchainthatsendsthepowerthrougha180degreeturntothetransmissionthatisalongsidetheengine.Fromthere,thepowerisroutedthroughthetransmissiontothefinaldrivewhereitissplitandsenttothetwofrontwheelsthroughthedriveaxles.
Thereareanumberofotherarrangementsincludingfrontdrivevehicleswheretheengineismountedfronttobackinsteadofsidewaysandthereareothersystemsthatdriveallfourwheelsbutthetwosystemsdescribedherearebyfarthemostpopular.Amuchlesspopularrearandisconnectedbyadriveshafttothetorqueconverterwhichisstillmountedontheengine.ThissystemisfoundonthenewCorvetteandisusedinordertobalancetheweightevenlybetweenthefrontandrearwheelsforimprovedperformanceandhandling.Anotherreardrivesystemmountseverything,theengine,transmissionandfinaldriveintherear.ThisrearenginearrangementispopularonthePorsche。
Themodernautomatictransmissionconsistsofmanycomponentsandsystemsthatdesignedtoworktogetherinasymphonyofplanetarygearsets,thehydraulicsystem,sealsandgaskets,thetorqueconverter,thegovernorandthemodulatororthrottlecableandcomputercontrolsthathasevolvedovertheyearsintowhatmanymechanicalinclinedindividualsconsidertobeanartfrom.Heretrytousedsimple,genericexplanationwherepossibletodescribethesesystems.
1)Planetarygearsets
Automatictransmissioncontainmanygearsinvariouscombinations.Inamanualtransmission,gearsslidealongshaftsasyoumovetheshiftleverfromonepositiontoanother,engagingvarioussizesgearsasrequiredinordertoprovidethecorrectgearratio.Inanautomatictransmission,however,thegearsareneverphysicallymovedandarealwaysengagedtothesamegears.Thisisaccomplishedthroughtheuseofplanetarygearsets.
Thebasicplanetarygearsetconsistsofasungear,aringandtwoormoreplanetgears,allremaininginconstantmesh.Theplanetgearsareconnectedtoeachotherthroughacommoncarrierwhichallowsthegearstospinonshaftscalled“pinions”whichareattachedtothecarrier.
Oneexampleofawaythatthissystemcanbeusedisbyconnectingtheringgeartotheinputshaftcomingfromtheengine,connectingtheplanetcarriertotheoutputshaft,andlockingthesungearsothatitcan’tmove.Inthisscenario,whenweturntheringgear,theplanetswill“walk”alongthesungear(whichisheldstationary)causingtheplanetcarriertoturntheoutputshaftinthesamedirectionastheinputshaftbutataslowerspeedcausinggearreduction(similartoacarinfirstgear).
Ifweunlockthesungearandlockanytwoelementstogether,thiswillcauseallthreeelementstoturnatthesamespeedsothattooutputshaftwillturnatthesamerateofspeedastheinputshaft.Thisislikeacarthatisthirdorhighgear.Anotherwaywecanuseaplanetarygearsetisbylockingtheplanetcarrierfrommoving,thenapplyingpowertotheringgearwhichwillcausethesungeartoturninoppositedirectiongivingusreversegear.
TheillustrationinFigureshowshowthesimplesystemdescribedabovewouldlookinanactualtransmission.Theinputshaftisconnectedtotheringgear,theoutputshaftisconnectedtotheplanetcarrierwhichisalsoconnectedtoa“Multi-disk”clutchpack.Thesungearisconnectedtodrumwhichisalsoconnectedtotheotherhalfoftheclutchpack.Surroundingtheoutsideofthedrumisabandthatcanbetightenedaroundthedrumwhenrequiredtopreventthedrumwiththeattachedsungearfromturning.
Theclutchpackisused,inthisinstance,tolocktheplanetcarrierwiththesungearforcingbothtoturnatthesamespeed.Ifboththeclutchpackandthebandwerereleased,thesystemwouldbeinneutral.Turningtheinputshaftwouldturntheplanetgearsagainstthesungear,butsincenotingisholdingthesungear,itwilljustspinfreeandhavenoeffectontheoutputshaft.Toplacetheunitinfirstgear,thebandisappliedtoholdthesungearfrommoving.Toshiftfromfirsttohighgear,thebandisreleasedandtheclutchisappliedcausingtheoutputshafttoturnatthesamespeedastheinputshaft.
Manymorecombinationsarepossibleusingtwoormoreplanetarysetsconnectedinvariouswaytoprovidethedifferentforwardspeedsandreversethatarefoundinmodernautomatictransmission.
2)Clutchpack
Aclutchpackconsistsofalternatingdisksthatfitinsideaclutchdrum.Halfofthedisksaresteelandhavesplinesthatfitintogrovesontheinsideofthedrum.Theotherhalfhaveafrictionmaterialbondedtotheirsurfaceandhavesplinesontheinsideedgethatfitgrovesontheoutersurfaceoftheadjoininghub.Thereisapistoninsidethedrumthatisactivatedbyoilpressureattheappropriatetimetosqueezetheclutchpacktogethersothatthetwocomponentsbecomelockedandturnasone.
3)One-wayClutch
Aone-wayclutch(alsoknownasa“sprag”clutch)isadevicethatwillallowacomponentsuchasringgeartoturnfreelyinonedirectionbutnotintheother.Thiseffectisjustlikethatbicycle,wherethepedalswillturnthewheelwhenpedalingforward,butwillspinfreewhenpedalingbackward.
Acommonplacewhereaone-wayclutchisusedisinfirstgearwhentheshifterisinthedriveposition.Whenyoubegintoacceleratefromastop,thetransmissionstartsoutinfirstgear.Buthaveyouevernoticedwhathappensifyoureleasethegaswhileitisstillinfirstgear?
Thevehiclecontinuestocoastasifyouwereinneutral.Now,shiftintoLowgearinsteadofDrive.Whenyouletgoofthegasinthiscase,youwillfeeltheengineslowyoudownjustlikeastandardshiftcar.ThereasonforthisisthatinDrive,one-wayclutchisusedwhereasinLow,aclutchpackorabandisused.
4)TorqueConverter
Onautomatictransmission,thetorqueconvertertakestheplaceoftheclutchfoundonstandardshiftvehicles.Itistheretoallowtheenginetocontinuerunningwhenthevehiclecomestoastop.Theprinciplebehindatorqueconverterisliketakingafanthatispluggedintothewallandblowingairintoanotherfanwhichisunplugged.Ifyougrabthebladeontheunpluggedfan,youareabletoholditfromturningbutassoonasyouletgo,itwillbegintospeedupuntilitcomesclosetospeedofthepoweredfan.Thedifferencewithatorqueconverteristhatinsteadofusingairitusedoilortransmissionfluid,tobemoreprecise.
Atorqueconverterisalagerdoughnutshapeddevicethatismountedbetweentheengineandthetransmission.Itconsistsofthreeinternalelementsthatworktogethertotransmitpowertothetransmission.Thethreeelementsofthetorqueconverterarethepump,theTurbine,andtheStator.Thepumpismounteddirectlytothetorquehousingwhichinturnisbolteddirectlytotheengine’scrankshaftandturnsatenginespeed.Theturbineisinsidethehousingandisconnecteddirectlytotheinputshaftofthetransmissionprovidingpowertomovethevehicle.Thestatorismountedtoaone-wayclutchsothatitcanspinfreelyinonedirectionbutnotintheother.Eachofthethreeelementshasfinsmountedinthemtopreciselydirecttheflowofoilthroughtheconverter.
Withtheenginerunning,transmissionfluidispulledintothepumpsectionandispushedoutwardbycentrifugalforceuntilitreachestheturbinesectionwhichstarsitrunning.Thefluidcontinuesinacircularmotionbacktowardsthecenteroftheturbinewhereitentersthestator.Iftheturbineismovingconsiderablyslowerthanthepump,thefluidwillmakecontactwiththefrontofthestatorfinswhichpushthestatorintotheonewayclutchandpreventitfromturning.Withthestatorstopped,thefluidisdirectedbythestatorfinstore-enterthepumpata“help”angleprovidingatorqueincrease.Asthespeedoftheturbinecatchesupwiththepump,thefluidstartshittingthestatorbladesontheback-sidecausingthestatortoturninthesamedirectionasthepumpandturbine.Asthespeedincrease,allthreeelementsbegintoturnatapproximatelythesamespeed.Sinethe‘80s,inordertoimprovefueleconomy,torqueconvertershavebeenequippedwithalockupclutchwhichlockstheturbinetothepumpasthevehiclereachesapproximately40-50mph.Thislockupiscontrolledbycomputerandusuallywon’tengageunlessthetransmission
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