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外文翻译--自动变速器.doc

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外文翻译--自动变速器.doc

英文原文AUTOMATICTRANSMISSIONThemodernautomatictransmissionisbyfar,themostcomplicatedmechanicalcomponentintodaysautomobile.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)PlanetarygearsetsAutomatictransmissioncontainmanygearsinvariouscombinations.Inamanualtransmission,gearsslidealongshaftsasyoumovetheshiftleverfromonepositiontoanother,engagingvarioussizesgearsasrequiredinordertoprovidethecorrectgearratio.Inanautomatictransmission,however,thegearsareneverphysicallymovedandarealwaysengagedtothesamegears.Thisisaccomplishedthroughtheuseofplanetarygearsets.Thebasicplanetarygearsetconsistsofasungear,aringandtwoormoreplanetgears,allremaininginconstantmesh.Theplanetgearsareconnectedtoeachotherthroughacommoncarrierwhichallowsthegearstospinonshaftscalledpinionswhichareattachedtothecarrier.Oneexampleofawaythatthissystemcanbeusedisbyconnectingtheringgeartotheinputshaftcomingfromtheengine,connectingtheplanetcarriertotheoutputshaft,andlockingthesungearsothatitcantmove.Inthisscenario,whenweturntheringgear,theplanetswillwalkalongthesungearwhichisheldstationarycausingtheplanetcarriertoturntheoutputshaftinthesamedirectionastheinputshaftbutataslowerspeedcausinggearreductionsimilartoacarinfirstgear.Ifweunlockthesungearandlockanytwoelementstogether,thiswillcauseallthreeelementstoturnatthesamespeedsothattooutputshaftwillturnatthesamerateofspeedastheinputshaft.Thisislikeacarthatisthirdorhighgear.Anotherwaywecanuseaplanetarygearsetisbylockingtheplanetcarrierfrommoving,thenapplyingpowertotheringgearwhichwillcausethesungeartoturninoppositedirectiongivingusreversegear.TheillustrationinFigureshowshowthesimplesystemdescribedabovewouldlookinanactualtransmission.Theinputshaftisconnectedtotheringgear,theoutputshaftisconnectedtotheplanetcarrierwhichisalsoconnectedtoaMultidiskclutchpack.Thesungearisconnectedtodrumwhichisalsoconnectedtotheotherhalfoftheclutchpack.Surroundingtheoutsideofthedrumisabandthatcanbetightenedaroundthedrumwhenrequiredtopreventthedrumwiththeattachedsungearfromturning.Theclutchpackisused,inthisinstance,tolocktheplanetcarrierwiththesungearforcingbothtoturnatthesamespeed.Ifboththeclutchpackandthebandwerereleased,thesystemwouldbeinneutral.Turningtheinputshaftwouldturntheplanetgearsagainstthesungear,butsincenotingisholdingthesungear,itwilljustspinfreeandhavenoeffectontheoutputshaft.Toplacetheunitinfirstgear,thebandisappliedtoholdthesungearfrommoving.Toshiftfromfirsttohighgear,thebandisreleasedandtheclutchisappliedcausingtheoutputshafttoturnatthesamespeedastheinputshaft.Manymorecombinationsarepossibleusingtwoormoreplanetarysetsconnectedinvariouswaytoprovidethedifferentforwardspeedsandreversethatarefoundinmodernautomatictransmission.2)ClutchpackAclutchpackconsistsofalternatingdisksthatfitinsideaclutchdrum.Halfofthedisksaresteelandhavesplinesthatfitintogrovesontheinsideofthedrum.Theotherhalfhaveafrictionmaterialbondedtotheirsurfaceandhavesplinesontheinsideedgethatfitgrovesontheoutersurfaceoftheadjoininghub.Thereisapistoninsidethedrumthatisactivatedbyoilpressureattheappropriatetimetosqueezetheclutchpacktogethersothatthetwocomponentsbecomelockedandturnasone.3)OnewayClutchAonewayclutchalsoknownasaspragclutchisadevicethatwillallowacomponentsuchasringgeartoturnfreelyinonedirectionbutnotintheother.Thiseffectisjustlikethatbicycle,wherethepedalswillturnthewheelwhenpedalingforward,butwillspinfreewhenpedalingbackward.Acommonplacewhereaonewayclutchisusedisinfirstgearwhentheshifterisinthedriveposition.Whenyoubegintoacceleratefromastop,thetransmissionstartsoutinfirstgear.ButhaveyouevernoticedwhathappensifyoureleasethegaswhileitisstillinfirstgearThevehiclecontinuestocoastasifyouwereinneutral.Now,shiftintoLowgearinsteadofDrive.Whenyouletgoofthegasinthiscase,youwillfeeltheengineslowyoudownjustlikeastandardshiftcar.ThereasonforthisisthatinDrive,onewayclutchisusedwhereasinLow,aclutchpackorabandisused.4)TorqueConverterOnautomatictransmission,thetorqueconvertertakestheplaceoftheclutchfoundonstandardshiftvehicles.Itistheretoallowtheenginetocontinuerunningwhenthevehiclecomestoastop.Theprinciplebehindatorqueconverterisliketakingafanthatispluggedintothewallandblowingairintoanotherfanwhichisunplugged.Ifyougrabthebladeontheunpluggedfan,youareabletoholditfromturningbutassoonasyouletgo,itwillbegintospeedupuntilitcomesclosetospeedofthepoweredfan.Thedifferencewithatorqueconverteristhatinsteadofusingairitusedoilortransmissionfluid,tobemoreprecise.Atorqueconverterisalagerdoughnutshapeddevicethatismountedbetweentheengineandthetransmission.Itconsistsofthreeinternalelementsthatworktogethertotransmitpowertothetransmission.Thethreeelementsofthetorqueconverterarethepump,theTurbine,andtheStator.Thepumpismounteddirectlytothetorquehousingwhichinturnisbolteddirectlytotheenginescrankshaftandturnsatenginespeed.Theturbineisinsidethehousingandisconnecteddirectlytotheinputshaftofthetransmissionprovidingpowertomovethevehicle.Thestatorismountedtoaonewayclutchsothatitcanspinfreelyinonedirectionbutnotintheother.Eachofthethreeelementshasfinsmountedinthemtopreciselydirecttheflowofoilthroughtheconverter.Withtheenginerunning,transmissionfluidispulledintothepumpsectionandispushedoutwardbycentrifugalforceuntilitreachestheturbinesectionwhichstarsitrunning.Thefluidcontinuesinacircularmotionbacktowardsthecenteroftheturbinewhereitentersthestator.Iftheturbineismovingconsiderablyslowerthanthepump,thefluidwillmakecontactwiththefrontofthestatorfinswhichpushthestatorintotheonewayclutchandpreventitfromturning.Withthestatorstopped,thefluidisdirectedbythestatorfinstoreenterthepumpatahelpangleprovidingatorqueincrease.Asthespeedoftheturbinecatchesupwiththepump,thefluidstartshittingthestatorbladesonthebacksidecausingthestatortoturninthesamedirectionasthepumpandturbine.Asthespeedincrease,allthreeelementsbegintoturnatapproximatelythesamespeed.Sinethe80s,inordertoimprovefueleconomy,torqueconvertershavebeenequippedwithalockupclutchwhichlockstheturbinetothepumpasthevehiclereachesapproximately4050mph.Thislockupiscontrolledbycomputerandusuallywontengageunlessthetransmissionisin3or4gear.5)HydraulicSystemThehydraulicsystemisacomplexmazeofpassageandtubesthatsendsthatsendstransmissionfluidandunderpressuretoallpartsofthetransmissionandtorqueconverterand.Transmissionfluidservesanumberofpurposeincludingshiftcontrol,generallubricationandtransmissioncooling。Unliketheengine,whichusesoilprimaryforlubrication,everyaspectofatransmissionsfunctionisdependantonaconstantsupplyoffluidissendpressure.Inordertokeepthetransmissionatnormaloperatingtemperature,aportionofthefluidissendtothroughoneoftwosteeltubestoaspecialchamberthatissubmergedinantifreezeintheradiator.Fluidpassingthroughthischamberiscooledandthenreturnedtothetransmissionthroughtheothersteeltube.Atypicaltransmissionhasanavengeoftenquartsoffluidbetweenthetransmission,torqueconverter,andcoolertank,Infact,mostofthecomponentsofatransmissionareconstantlysubmergedinfluidincludingtheclutchpacksandbands.Thefrictionsurfacesonthesepartsaredesignedtooperateproperlyonlywhentheyaresubmergedinoil.6)OilPumpThetransmissionoilpumpnottoconfusedwiththepumpelementinsidethetorqueconverterisresponsibleforproducingalltheoilpressurethatisrequiredinthetransmission.Theoilpumpismountedtofrontofthetransmissioncaseandisdirectlyconnectedtoaflangeontheenginecrankshaft,thepumpwillproducepressurewhenevertheengineisrunningasthereisasufficientamountoftransmissionfluidavailable.Theoilentersthepumpthroughafilterthatislocatedatbottomofthetransmissionoilpanandtravelsupapickuptubedirectlytotheoilpump.Theoilisthensent,underpressuretothepressureregulator,thevalvebodyandtherestofthecomponents,asrequired.7)ValveBodyThevalvebodyisthecontrolcenteroftheautomatictransmission.Itcontainsamazeofchannelsandpassagesthatdirecthydraulicfluidtothenumerousvalveswhichwhenactivatetheappropriateclutchpackofbandservotosmoothlyshifttotheappropriategearforeachdrivingsituation.Eachofthemanyvalvesinthevalvebodyhasaspecificpurposeandisnamedforthatfunction.Forexamplethe23shiftvalveactivatesthe2ndgearupshiftorthe32shifttimingvalvewhichdetermineswhenadownshiftshouldoccur.Themostimportantvalveandtheonethatyouhavedirectcontroloveristhemanualvalve.Themanualvalveisdirectlyconnectedtothegearshifthandleandcoversanduncoversvariouspassagesdependingonwhatpositionthegearshiftispacedin.WhenyouplacethegearshiftinDrive,forinstance,themanualvalvedirectsfluidtotheclutchpacksthatactivates1stgear.Italsosetsuptomonitorvehiclespeedandthrottlepositionsothatitcandeterminetheoptimaltimeandtheforceforthe12shift.Oncomputercontrolledtransmission,youwillalsohaveelectricalsolenoidsthataremountedinthevalvebodytodirectfluidtotheappropriateclutchpacksorbandsundercomputercontroltomorepreciselycontrolshiftpoints.8)SealsandGasketsAnautomatictransmissionhasmanysealsandgasketstocontroltheflowofhydraulicfluidandtokeepitfromleakingout.Therearetwomainexternalsealsthefrontsealandtherearseal.Thefrontsealsealsthepointwherethetorqueconvertermountstothetransmissioncase.Thissealallowsfluidtofreelymovefromtheconvertertothetransmissionbutkeepsthefluidfromleakingout.Therearsealkeepsfluidfromleakingpasttheoutputshaft.Asealisusuallymadeofrubbersimilartotherubberinawindshieldwiperbladeandisusedtokeepoilfromleakingpastamovingpartsuchasaspinningshaft.Insomecases,therubberisassistedbyaspringthatholdsherubberinclosecontactwiththespinningshaft.Agasketisatypeofsealusedtosealtwostationarypartsthatarefastedtogether.Somecommongasketmaterialsarepaper,cork,rubber,siliconeandsoftmetal.Asidefromthemainseals,therearealsoanumberofothersealsandgasketthatvaryfromtransmissiontotransmission.AcommonexampleistherubberOringthatsealstheshaftfortheshiftcontrollever.Thisistheshaftthatyoumovewhenyoumanipulatethegearshifter.Anotherexamplethatiscommontomosttransmissionistheoilpangasket.Infact,sealsarerequiredanywherethatadeviceneedstopassthroughthetransmissioncasewitheachonebeingapotentialsourceforleaks.9)ComputerControlsThecomputerusessensorsontheengineandtransmissiontodetectsuchthingsasthrottleposition,vehiclespeed,enginespeed,engineload,stoplightswitchposition,etc.tocontrolexactshiftpointsaswellashowsoftorfirmtheshiftshouldbe.Somecomputerizedtransmissionevenlearnyourdrivingstyleandconstantlyadapttoitsothateveryshiftistimedpreciselywhenyouwouldneedit.Becauseofcomputercontrols,sportsmodelsarecomingoutwiththeabilitytotakemanualcontrolofthetransmissionasthroughitwereastickshiftleverthroughaspecialgate,thentappingitinonedirectionortheotherinordertoupshiftatwill.Thecomputermonitorsthis

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