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.Theplanetgearsareconnectedtoeachotherthroughacommoncarrierwhichallowsthegearstospinonshaftscalled“pinions”whichareattachedtothecarrier.Oneexampleofawaythatthissystemcanbeusedisbyconnectingtheringgeartotheinputshaftcomingfromtheengine，connectingtheplanetcarriertotheoutputshaft，andlockingthesungearsothatitcantmove.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）ClutchpackAclutchpackconsistsofalternatingdisksthatfitinsideaclutchdrum.Halfofthedisksaresteelandhavesplinesthatfitintogrovesontheinsideofthedrum.Theotherhalfhaveafrictionmaterialbondedtotheirsurfaceandhavesplinesontheinsideedgethatfitgrovesontheoutersurfaceoftheadjoininghub.Thereisapistoninsidethedrumthatisactivatedbyoilpressureattheappropriatetimetosqueezetheclutchpacktogethersothatthetwocomponentsbecomelockedandturnasone.3）One-wayClutchAone-wayclutch(alsoknownasa“sprag”clutch)isadevicethatwillallowacomponentsuchasringgeartoturnfreelyinonedirectionbutnotintheother.Thiseffectisjustlikethatbicycle，wherethepedalswillturnthewheelwhenpedalingforward，butwillspinfreewhenpedalingbackward.Acommonplacewhereaone-wayclutchisusedisinfirstgearwhentheshifterisinthedriveposition.Whenyoubegintoacceleratefromastop，thetransmissionstartsoutinfirstgear.Buthaveyouevernoticedwhathappensifyoureleasethegaswhileitisstillinfirstgear?Thevehiclecontinuestocoastasifyouwereinneutral.Now，shiftintoLowgearinsteadofDrive.Whenyouletgoofthegasinthiscase，youwillfeeltheengineslowyoudownjustlikeastandardshiftcar.ThereasonforthisisthatinDrive，one-wayclutchisusedwhereasinLow，aclutchpackorabandisused.4）TorqueConverterOnautomatictransmission，thetorqueconvertertakestheplaceoftheclutchfoundonstandardshiftvehicles.Itistheretoallowtheenginetocontinuerunningwhenthevehiclecomestoastop.Theprinciplebehindatorqueconverterisliketakingafanthatispluggedintothewallandblowingairintoanotherfanwhichisunplugged.Ifyougrabthebladeontheunpluggedfan，youareabletoholditfromturningbutassoonasyouletgo，itwillbegintospeedupuntilitcomesclosetospeedofthepoweredfan.Thedifferencewithatorqueconverteristhatinsteadofusingairitusedoilortransmissionfluid，tobemoreprecise.Atorqueconverterisalagerdoughnutshapeddevicethatismountedbetweentheengineandthetransmission.Itconsistsofthreeinternalelementsthatworktogethertotransmitpowertothetransmission.Thethreeelementsofthetorqueconverterarethepump，theTurbine，andtheStator.Thepumpismounteddirectlytothetorquehousingwhichinturnisbolteddirectlytotheenginescrankshaftandturnsatenginespeed.Theturbineisinsidethehousingandisconnecteddirectlytotheinputshaftofthetransmissionprovidingpowertomovethevehicle.Thestatorismountedtoaone-wayclutchsothatitcanspinfreelyinonedirectionbutnotintheother.Eachofthethreeelementshasfinsmountedinthemtopreciselydirecttheflowofoilthroughtheconverter.Withtheenginerunning，transmissionfluidispulledintothepumpsectionandispushedoutwardbycentrifugalforceuntilitreachestheturbinesectionwhichstarsitrunning.Thefluidcontinuesinacircularmotionbacktowardsthecenteroftheturbinewhereitentersthestator.Iftheturbineismovingconsiderablyslowerthanthepump，thefluidwillmakecontactwiththefrontofthestatorfinswhichpushthestatorintotheonewayclutchandpreventitfromturning.Withthestatorstopped，thefluidisdirectedbythestatorfinstore-enterthepumpata“help”angleprovidingatorqueincrease.Asthespeedoftheturbinecatchesupwiththepump，thefluidstartshittingthestatorbladesontheback-sidecausingthestatortoturninthesamedirectionasthepumpandturbine.Asthespeedincrease，allthreeelementsbegintoturnatapproximatelythesamespeed.Sinethe80s，inordertoimprovefueleconomy，torqueconvertershavebeenequippedwithalockupclutchwhichlockstheturbinetothepumpasthevehiclereachesapproximately40-50mph.Thislockupiscontrolledbycomputerandusuallywontengageunlessthetransmissionisin3or4gear.5）HydraulicSystemThehydraulicsystemisacomplexmazeofpassageandtubesthatsendsthatsendstransmissionfluidandunderpressuretoallpartsofthetransmissionandtorqueconverterand.Transmissionfluidservesanumberofpurposeincluding:shiftcontrol,generallubricationandtransmissioncooling。Unliketheengine,whichusesoilprimaryforlubrication,everyaspectofatransmissionsfunctionisdependantonaconstantsupplyoffluidissendpressure.Inordertokeepthetransmissionatnormaloperatingtemperature，aportionofthefluidissendtothroughoneoftwosteeltubestoaspecialchamberthatissubmergedinanti-freezeintheradiator.Fluidpassingthroughthischamberiscooledandthenreturnedtothetransmissionthroughtheothersteeltube.Atypicaltransmissionhasanavengeoftenquartsoffluidbetweenthetransmission，torqueconverter，andcoolertank，Infact，mostofthecomponentsofatransmissionareconstantlysubmergedinfluidincludingtheclutchpacksandbands.Thefrictionsurfacesonthesepartsaredesignedtooperateproperlyonlywhentheyaresubmergedinoil.6）OilPumpThetransmissionoilpump(nottoconfusedwiththepumpelementinsidethetorqueconverter)isresponsibleforproducingalltheoilpressurethatisrequiredinthetransmission.Theoilpumpismountedtofrontofthetransmissioncaseandisdirectlyconnectedtoaflangeontheenginecrankshaft，thepumpwillproducepressurewhenevertheengineisrunningasthereisasufficientamountoftransmissionfluidavailable.Theoilentersthepumpthroughafilterthatislocatedatbottomofthetransmissionoilpanandtravelsupapickuptubedirectlytotheoilpump.Theoilisthensent，underpressuretothepressureregulator，thevalvebodyandtherestofthecomponents，asrequired.7）ValveBodyThevalvebodyisthecontrolcenteroftheautomatictransmission.Itcontainsamazeofchannelsandpassagesthatdirecthydraulicfluidtothenumerousvalveswhichwhenactivatetheappropriateclutchpackofbandservotosmoothlyshifttotheappropriategearforeachdrivingsituation.Eachofthemanyvalvesinthevalvebodyhasaspecificpurposeandisnamedforthatfunction.Forexamplethe2-3shiftvalveactivatesthe2ndgearup-shiftorthe3-2shifttimingvalvewhichdetermineswhenadownshiftshouldoccur.Themostimportantvalveandtheonethatyouhavedirectcontroloveristhemanualvalve.Themanualvalveisdirectlyconnectedtothegearshifthandleandcoversanduncoversvariouspassagesdependingonwhatpositionthegearshiftispacedin.WhenyouplacethegearshiftinDrive，forinstance，themanualvalvedirectsfluidtotheclutchpack(s)thatactivates1stgear.Italsosetsuptomonitorvehiclespeedandthrottlepositionsothatitcandeterminetheoptimaltimeandtheforceforthe1-2shift.Oncomputercontrolledtransmission，youwillalsohaveelectricalsolenoidsthataremountedinthevalvebodytodirectfluidtotheappropriateclutchpacksorbandsundercomputercontroltomorepreciselycontrolshiftpoints.8）SealsandGasketsAnautomatictransmissionhasmanysealsandgasketstocontroltheflowofhydraulicfluidandtokeepitfromleakingout.Therearetwomainexternalseals:thefrontsealandtherearseal.Thefrontsealsealsthepointwherethetorqueconvertermountstothetransmissioncase.Thissealallowsfluidtofreelymovefromtheconvertertothetransmissionbutkeepsthefluidfromleakingout.Therearsealkeepsfluidfromleakingpasttheoutputshaft.Asealisusuallymadeofrubber(similartotherubberinawindshieldwiperblade)andisusedtokeepoilfromleakingpastamovingpartsuchasaspinningshaft.Insomecases，therubberisassistedbyaspringthatholdsherubberinclosecontactwiththespinningshaft.Agasketisatypeofsealusedtosealtwostationarypartsthatarefastedtogether.Somecommongasketmaterialsare:paper，cork，rubber，siliconeandsoftmetal.Asidefromthemainseals，therearealsoanumberofothersealsandgasketthatvaryfromtransmissiontotransmission.AcommonexampleistherubberO-ringthatsealstheshaftfortheshiftcontrollever.Thisistheshaftthatyoumovewhenyoumanipulatethegearshifter.Anotherexamplethatiscommontomosttransmissionistheoilpangasket.Infact，sealsarerequiredanywherethatadeviceneedstopassthroughthetransmissioncasewitheachonebeingapotentialsourceforleaks.9）ComputerControlsThecomputerusessensorsontheengineandtransmissiontodetectsuchthingsasthrottleposition，vehiclespeed，enginespeed，engineload，stoplightswitchposition，etc.tocontrolexactshiftpointsaswellashowsoftorfirmtheshiftshouldbe.Somecomputerizedtransmissionevenlearnyourdrivingstyleandconstantlyadapttoitsothateveryshiftistimedpreciselywhenyouwouldneedit.Becauseofcomputercontrols，sportsmodelsarecomingoutwiththeabilitytotakemanualcontrolofthetransmissionasthroughitwereastickshiftleverthroughaspecialgate，thentappingitinonedirectionortheotherinordertoup-shiftatwill.Thecomputermonitorsthis