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Vol.20NO.3

DRIVESYSTEMTECHNIQUESeptember2006

文章編號：1006—8244(2006)03—03—10

TheZF··ASTronicFamily·-AutomotiveTransmissionsforAIICommercialVehicleClasses

Dr．Frank-DetlefSpeck，MarcusRaeder，Dr．ChristophRiichardt，

[Abstract]ZFdevelopedanewautomatictransmission--ASTronicFamily，whichcanfulfillthecustomersrequirements．TheASTronicFamilycoverstrucksinthelowertorquerangeupto2600Nmandhas6、10、12and16speed．TheASTroniccanmakeanimportantcontributioninruelconsumption．10wnoiseemissions，morecomfortabledrivingandsafelytraffic．

1RequirementsforCommercialVehicleTransmissions

Customersdemandhighefficiencyalongwithin—creasingvehiclecomfortandsafety．Asaninderpendenttransmissionmanufacturer，ZFcustomerneedsincludetheneedsofdrivers，forwardingcompaniis，andvehiclemanufacturers．Therefore，ZFconsidersthemanyrequirementsthatanewtransmissionconceptmustfulfillwhendevelopingatransmission，F(xiàn)igure1．Keepingcostslowisaconsiderablechallenge，initiallyintermsofacquisitionandlaterduringoperation．Thatiswhyfuelconsumptionisincreasinglyoneofthedecisivevehiclefeaturesthatseparatethepetition．Amoderntransmissioncanmakeanimportantcontributionhere：Ontheonehandbyimprovingefficiencyandontheotherhandinautomatictransmissionsbytheoptimalselectionofthegearratiodependentonthedrivingsituation．Redueingthetransmissionweightalsoleadstoreduedcosts：Usinglessmaterialreducesacquisitioncostsandenablingahigherpayloadreducesoperatingcosts．Ontheonehand。decreasedoilconsumptioncontributestoenvironmentalprotection：additionally，ithasanimmediateinfluenceonthecosts，however，thataccruethroughoutthevehicleservice1ife．Thedemandforsystemcomfortincreasinglyapproachesthestandardsetbycartechnology，whereasinthiseaselimitsaresetbymassratiosandcostconstraints．LOWnoiseemissionsareare—suitoflegalregulationsontheonehandbutalsocontributetomorecomfortabledriverworkplaceswhenmet．Furthermore，electronicsystemsincreasinglysupportthedriverandrelievehim／herfromroutinetasks．Thisbenefitssafetyintraffic．

2AdvanceswithAutomaticTransmissions

Automatictransmissionscansatisfymanyofthedemandsthatcustomersmakeoncommereivehicleconsiderablybetterthanmanualtransmissions．Despitethefactthatautomatictransmissionaregenerallymoreexpensive，ifonetakesthetompleteinstalledmanualtransmissionsystemincludingthegearshiftsystemintoaccount，thedifferenceinacquisitioncostsisnolongerasgreat．Moreover，thegoaloffuturedevelopmentsistofurtherreducethecostsforautomatictransmissions．EventodaythehigheracquisitioncostsarealreadypayingforthemselvesrelativelyquicklyduetoloweroperatingcostSOthatautomatictransmissionsareeconomicallyadvantageousintherun．TheefficiencyoftheASTronicfamilyoftransmissionsiscomparabletoamanualtransition；however，asarule，theshiftingpointselectionisbetterduetotheapplicationofanautomaticdrivingstrategy，whichpositivelyaffectsfuelconsumption．AlongtermstudyconductedbyZFandDEKRAfoundthattheautomaticshiftingpointse—lectionrepresentstheconsumptionperformanceofverygood，concentrateddriver．Thus，averagingalldriversanddrivingsituationsinacommercialfleet，consumptionisreducedontheorderof3per—centsincetheengineoperatesreliablyintheopti—mumspeedrangewithregardtofuelconsumption；aprocessthatiscontrolledindependentlyofthedriver’Squalification．Anadditionaladvantageintermsofoperating

costsISreducedclutchwear．Reduceddifferentialspeedsduringstartingandshiftingoperationslengthentheservicelifeoftheclutch，whichhasal—SObeenproveninlong—termtests．ManyvehicleemanufacturerstakethisintoaccountandofferasignfieantlylongerwarrantycoverontheclutchinASTronictransmissions．Byautomatingtheclutch，theclutchpedalisnolongerneeded，whichclearlysimplifiesoperationforthedriverparticularlyinstop—and—go—trafficorwhenmaneuvering．Theautomaticgearselectionrelievesthedriverfromshiftingaswell，wherebyhe／shecanconcentratebetteronroadtraffic．HOW—ever，atthesametime，thedrivercanengagemanuallyatanytime，forinstanceindrivingsituationswherethedriverforwardfieldofvisionISinquestion．ThistakesplaceaccordingtoShift—by—Wireviaanelectromechanicalcontr01switchSOthatonlyverylittleactuatingforcesareappliedwhenmanuallyselectinggears．Therapidautomaticshiftingandtheprotectionagainstoperatingerrorals0contributetotheincreaseindrivercomfortwhileatthesametimeprotectingthetransmissionanddriveline．Inaddition，theabsenceofamechanicallinkbetweenshiftleverandtransmissionredcabinnoise．Usinganautomatictransmissionalsohasad—vantagesforvehiclemanufacturers．Liketheclutchcontrol。thecompleteshiftlinkageisnolongerneeded，whichmakesbothleftandrighthandsteeringvehicleseasytomanufacture．Whendesigningthedriverworkplace，anythingispossibleintermsofoperatingthetransmission．

3TheZF-ASTronicFamily

andanoutput—endplanetarydrivestage(rangechangegroup)．Synchronizationsareusedinthesplitterandrangechangegroup；themaintransmissionshiftingelementsaredesignedasdogs．Thegearstepshasaslightlyprogressivegearintervalduetoasmallincreaseinthegearratio．Thus，atatotalgearspreadofapprox．12．8，thegearratioof23．8％from11thto12thspeedisonparwithacomparable16一speedtransmission．Forthefirsttime，thegearratioofthereversegearwasdesigned13．1，i．e．slowerthan1gearonarangechangegrouptrans—missionbyanoffsetengagementoverthereverseidlergear．Inclosecooperationwiththecustomers，highdrivabilitywasalreadyemphasizedinthespec—ifcationphase．Uponcompletionoftheroughde—sign，thedrivabilityreleasecriteriaofonecustomer

werealreadyproveninsimulations．AdetailedcostanalysisofthegearunitsinZFtransmissionsledtothedesignoftheplanetanyrear-mountedrange—changegroupintheASTronicmid，inwhichthemostcost-effectivesolutionswereadoptedineachcase．Thus，thedesignofthe

newgearunitismarkedbythesynchronizationoftheASTronicandthegearsetdesignoftheEco—split，F(xiàn)igure5．Thebearingsoftheswingforkintherangechangegrouparerealizedbetweenthetwohousingparts，whichminimizessealpointstotheoutsideandpossiblecorrosionweakpoints．Theclutchactuatingcylinderwasturnedindrivingdirectionfromthe6clockpositionforASTronictothe8clockpositionforASTronicmid．Thisnotonlyincreasesvehicleroadclearanceandbringstheactuatingcylinderoutofthedangerzone，ital—soofferstheflexibilitytoreacttopotentialrequirementspushedclutchreleaseundercompression．DifferentfromtheASTronic，theASTronicmidgearsetwillonlybedesignedwithonecounter—shaft．Thesolutionwasthebestinaparameterstudyforthetorquerangeconsidered，whichtakesintoaccountboththemodulardesignaspectsasregardsoptimalgearsetlengthvariationaswellasthelegallypermittednoiserequirements．Asare一suit，thedeveloperfacedanadditionalchallenge．IftheoilpumpandtransmissionbrakeareeachdrivenbyonecountershaftintheASTronic，thenbothcomponentsnowmustbecombinedinajoint，cost—effectivebrake—pumpmodule．Maximizingtransmissionefficiencyinordertoreducefuelconsumptionattractedmuchinterestduringdevelopment．Byconsistentlychangingsplashlubricationtoinjectionlubrication．Quasidrysump1ubricationwasachievedSOthatdivinglossesdonotoccur．Inordertooptimizethelubricationsystem，oilflowcalculationswereconducted．TheoilitselfWashandledlikeastructural／designelement，ZFhasworkedintensivelyforyearswithlubricantmanufacturersinordertodevelopsyntheticcoilssuchastheZF-EcofluidM．whichisusedIthesetransmissions．ThisoilhaslowviscosityandthereforecontributesWinternollosses；however，atthesametimeitofferssufficientlubricatingguaranteetheservicelifeofgears，bear