车辆工程专业 毕业设计外文翻译5Word文档下载推荐.docx
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车辆工程专业 毕业设计外文翻译5Word文档下载推荐.docx
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around96percentoftheenergythatisputincomesoutoftheotherend.Butnoteveryonecandriveoneorwantsto.Becauseyouhavetodiptheclutchpedal,it'
slesscomfortabletodriveinheavytraffic.Itmakesthedrivertiredandthetorqueinterruptions'
head-nodeffectonpassengerscanbewearing.
Thedriver'
sclutchcontrolandcorrespondingtorqueinterruptionsarealsothemanual'
sweakpoint.Whenacceleratingupthroughthegearbox,eachup-shiftrequiresthedrivertocutthetorquemomentarilybyliftingthegaspedalanddippingtheclutch.Itmayjusttakeasecondtocompletetheoperation,butduringthistimethevehicleislosingspeedandacceleration.
Attheoppositeandofthespectrumisthetraditionalautomatic.Itsshiftqualityisgoodthankstoitstorqueconverter,butefficiencyisrelativelypoordespiterecentadvances.Becauseofthis,alotofthecurrentresearchistryingtofindanefficientalternativetotheconventionalautomatic.
Themaintechnologiesarecontinuouslyvariabletransmissions(CVTs);
dualclutchtransmissions(DCTs)andautomatedmanualtransmissions(AMTs).Theyallofferdifferentbenefitsovertheconventionalplanetaryautomatic.
TheCVTusesabeltchainortoroidalshapeddishdrivetovaryaninfinitenumberofgearratios.Ithasimprovedefficiencyandcostwhencomparedtoconventionalautomatics.Itsadvantagecomesfromitssimplicitu.Itconsistsofveryfewcomponents;
usuallyarubberormetal-linkbelt;
ahydraulicallyoperateddrivingpulley,amechanicaltorque-sensingdrivingpulley,microprocessorsandsomesensors.
Thetransmissionsworksbyvaryingthedistancebetweenthefacesofthetwomainpulleys.ThepulleyshaveV-shapedgroovesinwhichtheconnectingbeltrides.Onesideofthepulleyisfixedaxially;
theothersidemoves,actuatedbyhydraulics.
Whenactuatec,thecylindercanincreaseorreducetheamountofspacebetweenthetwosidesofthepulley.Thisallowsthebelttoridelowerorhigheralongthewallsofthepulley,dependingondrivingconditions.Thischangesthegearratio.Atorodial-typedesignworksinasimilarwaybutrunsondiscsandpower-rollers.
The"
stepless"
natureofitsdesignisCVT'
sbiggestdrawforautomotiveengineers.Becauseofthis,aCVTcanworktokeeptheengineinitsoptimumpowerrange,therebyincreasingefficiencyandmileage.ACVTcanconverteverypointontheengine'
soperatingcurvetoacorrespondingpointonitsownoperatingcurve.
ThetransmissionismostpopularwithJapanesecarmakersandJapanesesupplierJATCOisamajorproducer.ButintheUSandEuropedrivingstylesaredifferent.UptakehasbeenslowdespiteAudiandothermanufacturershavingofferedCVTotionsontheirranges.
TheDCTis,ineffect,twomanualgearboxescoupledtogether.Gearshiftsaremadebyswitchingfromoneclutchononegearboxtoanotherclutchontheother.Theshiftqualityisequaltoaconventionalautomatic,butslip,fluiddragandlydrauliclossesinthesystemresultinonlyslightlyimprovedefficiencyandaccelerationovertheconventionalplanetaryautomatic.Developingthecontrolstrategyiscostlytoo.
"
RecentadvancesinconventionalautomatictechnologyhaveweakenedtheargumenttodevelopandsetupproductionforCVTorDCT."
saysBillMartin,managingdirectoroftransmissionfirmzeroshift."
SomecarmakershavecancelledDCTprojectsbecauseofthecost."
ThecheapestwaytobuildanautomaticiswithanAMT.AMTsuseactuatorstoreplacetheclutchpedalandgearstickofaconventionalmanual.Theykeepthehighefficiencyandaccelerationofamanualgearbox,buttheshiftqualityonsomemodelsislacking.Torqueinterruptionsandthehead-nodeffectarethemostcommoncomplaint.
sowhatisthealternative?
Therearealwaysnewideasintransmissions,butZeroshiftsaysthatitstechnologyhasefficiencybenefitsoveramanual,deliveringfueleconomyimprovementstocitydriving.Shiftqualitycanalsobeequaltothatofarefinedautomatic.
Zeroshift'
sapproachisanupgradetotheAMT.Thesynchromeshisreplacedwithanadvanceddogenqaqementsystem.
Dogengagementhasbeenusedformanyyearsinmotorsporttoallowfastshifts.Conventionaldogboxesareunsuitableforroaduseasthelargespacesbetweenthedrivelugsor"
dogs"
createbacklash,anuncomfortableshuntcausedbythesuddenchangeintorquedirection.
stechnologysolvesthisproblembyaddingasecondsetofdrivedogs.Ithasalsomadeeachofthetwosetsofdogsonlycapableoftransmittingtorqueinoneorotheropposingdirections."
Bycontrollingtheengagementanddisengagementofthetwosetsyoucanshiftintothenewgearbefordisengagingthepreviousgear,"
saysMartin."
Theshiftqualityissmootherthanatypicalmodernsix-speedautomaticluxurycar."
Theshiftisinstantandthetorqueisnotinterrupted.Thisphilosophyisusedforbothupanddownshifts.
InconventionalAMTthereisanemissionsspikeduringashiftduetotheneedtobackoffandreintroducethrottle,thisiseliminatedbygoingseamless,"
Thisalsoreducesfuelconsumption."
Itisarelativenewcomertothetransmissionsector,butthefirmsaysthatitisalreadyattractingtheattentionofmajorEuropeanandUScarmakers.Thebigdrawisasalow-costalternativetoDCT,saysMartin.
Becausethemanualgearboxarchitectureislargelymaintained,productioncostsandcomplexityarenotgreaterthanforaconventionalAMT.Developmentofthecontrolssideisalsoconsiderablycheaper.Musictotheearsofengineerstryingtocutemissionsandcosts.
Mostofthecarmakershaveseenthesystematleastonce,"
saysMartion."
Somesignedusimmediately.Somehavesaidnotyet.Nonehavesaidno."
Thatmaybetheclearestsignyetthatwhenitcomestopowertraindevelopments,carmakersarestartingtofocusonthetransmission.
HOWZWROSHIFTWORKS
Thehardwareconsistsoftwosetsofbullets.mountedandactuatedontwoindependentbulletrings.bothsetsofbulletsrunonthecommonhub,whichisattachedtotheshaftwithsplines.
Eachbullethasaspecialprofile.Ononesidetheyhaveanangledfaceforengagement.Thesearediagonallyopposed,allowingthebullettohaveadrivefunctionforonegearandanoverrunfunctionfortheothergear.Theengagementfacestaperbackwardsslightlytoensurethebulletlatchesontotheengagedgearunderload.
theoppositecornershavearamp,whichpushesthebulletoutofthepreviousgearoncethenewgearhasbeenengaged.
Inneutralbothbulletringsarepositionedmidwaybetweentheratios.Toselectfirstgear,thebulletsaremovedintomeshwiththeengagementdogs.Thebulletsareactuatedviashiftforksconectedtotheshiftactuators.
Thedrivingbulletslockfirstgeartotheoutputshaftandtransfertorquefromthegearwheelontotheoutputshaft.Thefirstgearoverrunbulletsarealsomovedintogeartolockthewheeltotheoutputshaftintheoppositedirection.Thistransfrstorquefromthegearwheelontotheoutputshaftwhenthethrottleclosesandtheengineoverruns.Thiseliminatesthebacklashyou'
dexpectfromadogengagementgearbox.
Toshiftupwithanopenthrottle,firstgear'
soverrunbulletsareunloadedandmoveintoengagesecondgear.Thisisfollowedbythepreviousdrivingringwhichbecomesunloadedwhensecondgearistakenup.
Ifthebulletisstoppedfromengagingfully-dog-facetodog-face-thesecondgearwheelopensanengagementwindowduetotherelativespeeddifference.Withthebulletpushedagainsttheengagementdogcompliancebetweentheforkandactuatorallowsthestoredenergy
tofirethebulletintothewindow.
Thefirstgearoverrunbulletshavenowbecomethesecondgeardrivebullets.Assecondgeartakesover,theloadisremovedfromthefirstgeardrivebullets.Thesebulletsarenownolongerheldbytheirretentionangieandcanbeeithermovedoutofgearbyactuatorsorpushedoutofgearbycontactwiththerampfaceofthebullet.
Thefirstgeardrivebulletsthenmoveacrossintoengagementwithsecondgear.Insecondgear,therolesofthebulletsarereversed.
AudiRoadjet
Audiplanstoaddcomfort,luxuryandpracticalitywithoutincreasingemissions
TheRoadjetconcept,firstshownatDetroitinJanuary2006,indicatesanumberoftechnicaldirectionsthatAudigoingtotakeinthecomingyear.Thefirmisfocusingoninteriordesign,powertrain,chassis,electronicsandsafetyinnovations.
ThesenewdirectionswillhelpAudistrengthenitspositioninthesub-luxurymarketthatitpreviouslyhadtoitself.AudihastwomaintacticstoattractnewcustomersintheUS.Itisbreakingintothesportsutilityvehicle(SUV)andcompactutilityvehicle(CUV)markets.
ItalsointroducesnewluxuryandlifestylefeaturestostrengthenitspositionintheUS;
salestherestilllagbehindthoseofBMW,LexusandMercedes-Benz.TherecentlylaunchedQ7off-roadluxuryvehicleisalatebidtocapitaliseontheSUVboom.
InEurope,thecarmaker'
stechnicalinnovationssuchasaluminium
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