串联驱动桥系统

英文原文版出处欧洲专利数据库.专利-EP19820102738译文成绩：指导教师（导师组长）签名：译文：串联驱动桥系统摘要：串联驱动桥系统是不同的，其能够从车辆处将电源供给输入扭矩，既第一、第二后驱动桥以及前驱动桥。设置为允许电源从它们的侧齿轮一端被发送到第二后驱动桥，然后通过差速齿轮的输入转矩划分。另一侧齿轮的输出齿轮能够发送至少一部分的输出转矩，从而可操作性的耦合至第一后驱动桥的第一齿轮。一个惰轮与输出齿轮驱动啮合，并且反过来，驱动第二齿轮选择性地耦合到传输的其余部分，即从输出齿轮输出转矩到前驱动桥。如果选择性地脱开正向驱动桥，惰齿轮和第二齿轮，第二齿轮将被允许自由运行。本专利是在技术领域的发明。本发明涉及到串联驱动桥系统，更具体地来说，其中的有关改进装置是用于有选择地将动力传递到具有前驱动桥以及第一和第二后驱动桥的车辆的前驱动桥。在现有技术的说明下，此串联6×6的车辆也就是俗称的车辆驱动桥系统，具体而言，6×6的车辆，其中包括六个轮子在地面上都被驱动车辆用作电源。通常情况下，一个6×6的车辆在正常行驶条件下，驱动系统能够被选择性地改变，以消除权力的应用，这样的前驱动桥其实只有用在正在供电电源两个后轴上。在这种情况下，车辆将被适当地描述为一个6×4辆可以在一个6×4模式操作。

在图2和图3中可以看出，差速器壳体18包括本发明的分裂和发送功率是各车轴的主要元素。具体而言，输入轴34可转动地安装在轴承36与差速器壳体18之内，包括一个连接件38的驱动轴16（图中未示出）接合。一个差速器齿轮组40被安装在输入轴34的后端，并包括一个差分笼和蜘蛛42刚性地联接到轴34。差保持架和蜘蛛42包括小齿轮44，它能够将动力传递到第一差动侧齿轮46和第二差动侧齿轮48。

差动侧齿轮46安装在输入轴34上，并能够独立的相对转动。同样，第二个差动侧齿轮48安装在输入轴34上能够独立的相对转动，基本上是由轴承50用于支撑所述输入轴32的后端部的方式支持，其中侧齿轮48的输入轴34在其中接收的后端。第二差动侧齿轮48是刚性地连接到向后延伸的轴装置48，从差速器壳体18的后部延伸，有与第二向后延伸的驱动轴24（图中未示出）耦合。因此，接收功率在第二个差动侧齿轮48上，能够提供电源的方式是在向后定位的后轴22上的。

第一差动侧齿轮46包括在其前端的输出齿轮54，它能够发送接收由所述第一差动侧齿轮46的输出功率。要传输的输出功率的一部分从所述第一差分侧齿轮46的向前定位的后轴20出与第一齿轮56对准并与输出齿轮54啮合接触。第一齿轮56刚性地安装在一个轴58上，反过来，可转动地安装在轴承60内的差速器壳体18的内部。输入小齿轮62安装在轴58的后端，并在一个差分驱动桥差速器上提供向前定位的后驱动桥20的输出转矩的机构（图中未示出）的环形齿轮64啮合接触。如这样描述，从电源12的输入转矩能够提供给后轴20和22，因为它是被除以差速器齿轮组40。具体而言，根据在一个理想的操作条件下，其中在车辆运行大致均匀分布的各车轴上的负荷与相对水平的表面上，在每个差侧齿轮46，48的输出转矩上将大约一半的从电源12接收输入扭矩。如果车辆是在一个6×4模式操作，从而所述驱动桥系统将工作在本领域中公知的方式与基本除以两个后置串联轴20和22之间的所有的负载间差速器40被认为是必要的，因为，在实际操作中的负载不会被均匀地分布在两轴差速器之间仍然可以进行车辆操作，同时允许一些偏差，或者在两轴之间的不同taction条件现实可能性。

然而，由于是驱动桥在艺术上也是众所周知的，差速器40提供的分化有的是在不希望的场合。因为它可能是车轮与车轴20，22相关的，在这样非牵引没有电源的情况下，可以适用于驱动车辆的运动表面，经常包括装置，用于“锁定“的差，以确保两个轴同时移动，其中轴与驱动表面的足够接触。将能够推进车辆。要做到这一点，离合器装置66将要被安装在输入轴34上的一组向外延伸的齿67上。如图3所示，离合器装置66的向前位置，不影响分化差速器40提供的运动。然而，为了实现“锁定”状态，以防止分化，有些装置的换档杆和叉的形式（未示出），它可以作用于周向槽68的离合器装置66，导致在输入轴34上的齿67沿轴向向后移动。当离合器装置66被充分地向后移动时，它将被带进对应与第一差动侧齿轮46连接的第一差动侧齿轮46，同时直接连接到输入轴34的前端上的一组齿轮齿70进行啮合。当第一差动侧齿轮46联接到输入轴34上，就没有进一步的分化，然后将要发送的输入转矩，输出齿轮54或向后延伸的轴52通过根据创建的每个后部的电阻轴20，22进行与驱动面接触。如上所述，本发明和美国专利号4050534中公开的驱动桥系统都是包含在差速器壳体18内的装置，用于提供输出的前驱动桥28。在美国专利号4050534中，这是通过有一个额外的驱动啮合齿轮与第一齿轮56中进行的，当输出齿轮54接收到输出转矩时，将能够提供电源给前部驱动器轴28和向前定位后驱动桥20。其结果是，所有的功率将被发送到这两个车轴具体在一个单一的输出齿轮54与第一齿轮58之间的啮合接触点来进行发送。然而，在最坏的情况下，也有可能是足够的滑动，以使离合器装置66被用来防止分化差速器40在向后定位中车辆操作的后轴22。如果车辆负载较大，并且有优良的道路牵引前驱动桥28和向前定位的后轴20，所有的输入功率将与电源连接发送到这两个轴通过单一的输出齿轮54。虽然这不会是一个正常的运行状态，它不会是不寻常的，在这种高负荷的情况下也会定期发生。由此产生的应力在单个啮合接触点的输出齿轮54与第一齿轮56的齿磨损可能是显然不利影响整体驱动桥系统的可靠性和寿命。

因此，在优选实施例中，提供电源到前驱动桥28包括一个惰轮72，它是与输出齿轮54啮合接触，但其上的位置处的周向间隔开的接合点与所述第一齿轮56是断开的。惰齿轮72刚性地安装在惰轴74上，其可转动地安装在轴承76内的差速器壳体18之间。提供动力的前驱动桥28，包括第二齿轮78相啮合的从动齿轮72，使两个齿轮72，78进行响应的输出齿轮54旋转转动。

第二齿轮78安装在轴80上，并能够独立的相对转动，其上的轴80被安装在轴承82与差速器壳体18之内，并包括一个前端，其向前延伸的驱动轴30被连接到用于提供电源的前驱动桥28之上。第二齿轮78刚性地安装在轴80上的，在本发明的优选实施例中，包括一个装置，用于有选择地将动力传递到前驱动桥28。这是通过以知的方式进行的动力传递。如上所述，离合器84安装在向外延伸的齿85的轴80，可以有选择地，向后定位成接合向外延伸的齿86刚性连接第二齿轮78的轴80的动力传递到第二齿轮78上，当前驱动桥28，6×6的运作模式是随意的。前列位置将重新定位离合器84脱开第二齿轮78到轴80上，并允许自由运行的惰齿轮72和第二齿轮78，在没有任何的动力传递到前驱动桥28之上，从而返回车辆到6×4的操作模式。

然而，在本发明中使用的配置，如果车辆再次与差速器“锁定”，在最坏的情况下操作，功率将被传输到轴28和20之间，将不再被集中在一个在输出齿轮54上。基本上，在啮合的输出齿轮54与惰齿轮72中，剩下的一半的输出转矩的驱动向前定位后轴20被提供给的一半将被传送发送到正向驱动桥28的负载上，因为它接触在不同的周向位置与输出齿轮54的第一齿轮56上。输出齿轮54的齿的磨损和应力显著降低，以改善整体可靠性。如这样描述的，本发明以公开在美国专利号为405053相同的方式提供电源，一般地但包括装置，用于保证在最坏的情况中驱动桥系统的可靠性。此外，还有一些设计上的限制，在美国专利号4050534中公开的驱动桥系统预先确定的轴的相对位置是从差速器壳体提供电力以使各车轴延伸。由于提供电力，在该现有技术的驱动轮轴系统上前驱动桥齿轮啮合的齿轮，其提供电源的向前定位的后轴向前延伸的输出轴相对的位置，在一个有限的范围内接收到输入轴电源的功率。然而，一个惰轮的使用中，所提供的前驱动桥提供动力的轴，该轴可以被重新定位，而不必是一个预定的距离，在垂直或水平方向相对于所述轴驱动的向前定位的后轴相比。它甚至是可能的，如果要重定位不同分离的第一齿轮的横向平面的轴向向前将会比第二齿轮惰齿轮的横向平面长。在这个位置上，第二齿轮可以调整的部分“叠置”从正面观察时，各自的轴向前和向后到可以延伸的第一齿轮上。因此，通过包括在空转齿轮72，本发明的驱动桥系统能提供一个更好的从输出齿轮54的功率分布，并允许更大的灵活性，从差速器壳体18的轴延伸的设计位置的正向驱动桥28和向前定位的后轴20的操作。

英文原文：Tandemdriveaxlesystem摘要Animprovedtandemdriveaxlesystemisofthetypewhichiscapableofsupplyinginputtorquefromavehiclepowersourcetofirstandsecondreardriveaxlesandafrontdriveaxle.Theinputtorqueisdividedthroughadifferentialgearsettoallowpowertobetransmittedfromoneofthesidegearsthereoftothesecondreardriveaxle.Anoutputgearassociatedwiththeothersidegeariscapableoftransmittingatleastaportionoftheoutputtorquetherefromtoafirstgearwhichisoperablycoupledtothefirstreardriveaxle.Anidlergearisalsoindrivingengagementwiththeoutputgearand,inturn,drivesasecondgearwhichisselectivelycoupledtothefrontdriveaxletotransmittheremainderoftheoutputtorquefromtheoutputgear.Ifthesecondgearisselectivelyuncoupledfromtheforwarddriveaxle.FieldoftheInvention.Thisinventionrelatestoatandemdriveaxlesystemand,morespecifically,toanimprovementthereinrelatingtothemeansforselectivelytransmittingpowertothefrontdriveaxleofavehiclehavingafrontdriveaxleandfirstandsecondreardriveaxles.DescriptionofthePriorArt.Thisinventionrelatestoatandemdriveaxlesystemforavehiclewhichiscommonlyknownasa6x6vehicle.Specifically,a6x6vehicleisonewhichincludessixwheelsonthegroundwhichareallbeingdrivenbythevehiclepowersource.Typically,undernormaldrivingconditions,thedrivesystemofa6x6vehicleiscapableofbeingselectivelyalteredtoeliminatetheapplicationofpowertothefrontdriveaxlesothatinfactonlypowerisbeingsuppliedtothetworearaxles.Inthissituation,thevehiclewouldbeappropriatelydescribedasa6x4vehicle.Atonetime,itwascommonpracticetodividepowerbetweenthefrontdriveaxleandthepairofreardriveaxlesthroughatransfercase.AsshowninU.S.PatentNumbers2,770,150;3,095,758;3,191,708and3,495,477,suchtransfercasescanbeutilizedtoreceiveaninputtorquefromthevehiclepowersourceortransmissionandtosupplyoutputtorquetoaforwardlyextendingshaftfordrivingthefrontdriveaxleandarearwardextendingshaftwhichiscapableofdrivingoneortworeardriveaxles.Whilesuchconfigurationshavebeensatisfactorilyemployedinthepast,theuseofatransfercaseinvolvesadditionalgearingandsubstantiallyincreasestheweightandcostofsuchadrivesystem.Accordingly,inordertoeliminatesomeoftheobjectionsofthistypeofdrivesysteminwhichatransfercaseisrequired,U.S.PatentNumber4,050,434disclosesavehicledriveaxlesystemwhichiscapableofbeingutilizedon6x6vehicleswhichcanbeselectivelyoperatedinthe6x4modeasmentionedhereinabove.Specifically,thevehicledrivesystemdisclosedthereinutilizesaninputshaftfromthevehiclepowerortransmissionsystemtoainteraxledifferentialconfigurationtodriveadifferentialgearsethavingfirstandsecondsidegearmeans.Thefirstsidegearmeansincludesanoutputgearwhilethesecondsidegearmeansincludesashaftwhichextendsrearwardlytotherearwardreardriveaxletoprovidepowerthereto.Afirstgearisindrivingengagementwiththeoutputgearassociatedwiththefirstdifferentialsidegeartobecapableofdrivingashaftwhichisoperablycoupledtotheforwardlypositionedreardriveaxle.Asecondgearmeansisindrivingengagementwiththefirstgearmeanstoprovidepowertoashaftwhichextendsforwardlyfordrivingthefrontdriveaxle.Thereisincludedmeansforselectivelycouplinganduncouplingtheforwardlyextendingshaftfordrivingthefrontdriveaxlefromthesecondgearmeanstoselectivelyallowthedrivesystemtobeoperatedineitherthe6x6orthe6x4mode.U.S.PatentNumber4,050,534includesaexplanationofhowthedriveaxlesystemdisclosedthereinwilloperateundera"idealoperatingcondition".Inthis"idealoperatingcondition",theinputpowerwouldbeequallydividedinthedifferentialgearsettoprovideapproximatelyfiftypercentofpowertoeachofthedifferentialside-gears.Withoneofthedifferentialsidegearsbeingutilizedtoprovidepowertoboththefrontdriveaxleandoneofthereardriveaxles,theoverallpowerdistributionunderthis"idealoperatingcondition"wouldresultinthefrontdriveaxleprovidingapproximatelytwenty-fivepercentofthepowerneededtodrivethevehiclewhiletheforwardlypositionedreardriveaxleprovidedapproximatelytwenty-fivepercentandtherearwardreardriveaxletheremainingfiftypercent.Whilethis"idealoperatingcondition"mightreasonablyconformtomostloadingconditionsforthevehicle,therearesome"worstcase"situationswhichcastdoubtontheacceptabilityandreliabilityoftheconfigurationdisclosedthereinTheexplanationofthepowerloadingforthedriveaxlesystemisbasicallyaccurateforthe"idealoperatingcondition"inwhichtheloadisrelativelyevenlydistributed,thevehicleisoperatingonalevelsurface,andeachofthewheelsismakingnon-slipping,frictionalcontactwiththedrivingsurface.However,ifthecontactwiththedrivingsurfaceisunsatisfactoryforoneormoreoftheaxles,asexplainedinU.S.PatentNumber4,050,534,itisnotuncommonforsuchadriveaxlesystemtoincludeameansfor"lockingout"theinteraxledifferentialtopreventawheelorpairofwheelsonaslipperysurfacefromreceivingallofthetorquefromtheinteraxledifferentialandpreventingeffectivemovementofthevehicle.Insuchacondition,itwouldbepossiblefortheoutputgeartobereceivingsubstantiallyalloftheinputtorqueiftherearwardrearaxleassociatedwiththeseconddifferentialsidegearwerenotmakinggoodcontactwiththedrivingsurfaceand,therefore,incapableofactuallyprovidingpowerformovingthevehicle.Withtheoutputgearreceivingsubstantiallyalloftheinputtorque,itwouldallbetransmittedtotheremainingtwoaxles.TheresultingloadontheoutputgearintheconfigurationastaughtinU.S.PatentNumber4,050,534wouldbesignificantandmightunnecessarilystrainorweakentheteeththereon.WhilethedriveaxlesystemdisclosedinU.S.PatentNumber4,050,534mightbesatisfactoryforanumberofvehicleinstallations,thedirectcouplingofthesecondgearwhichdrivesthefrontdriveaxletothefirstgearwhichdrivestheforwardlypositionedrearaxledoespresentaconfigurationwhichlimitsthepossibledesignlocationoftheforwardlyextendingoutputshaftfordrivingthefrontdriveaxle.Thelocationoftheoutputshaftfordrivingthefrontdriveaxlecanbesignificantinsomevehicleswherehighergroundclearanceisdesiredorwherethereisaneedtoavoidtheengineortransmissionandprovideclearancebetweentheengineortransmissionandtheoutputshaftextendingforwardlytopowerthefrontdriveaxle.SummaryoftheInventionItis,therefore,anobjectofthisinventiontoprovideanimprovedtandemdriveaxlesystemwhichisreliableandcapableofbeingdesignedtoaccommodatespecialvehicleconfigurations.Theseandotherobjectsoftheinventionareprovidedinapreferredembodimentthereofwhichincludesanimprovedtandemdriveaxlesystemofthetypewhichiscapableofreceivinginputtorquefromavehiclepowersourceandtransmittingthetorquetofirstandsecondreardriveaxlesandafrontdriveaxle.Thereisalsoincludedmeansfordividingtheinputtorquethroughadifferentialgearsethavingfirstandseconddifferentialsidegears.Eachofthesidegearstransmitsoutputtorqueofamagnitudewhichissubstantiallyone-halfoftheinputtorqueunderidealoperatingconditions.Thefirstdifferentialsidegearincludesanoutputgearindrivingengagementwithafirstgearmeansfortransmittingatleastaportionoftheoutputtorquefromthefirstdifferentialsidegeartothefirstreardriveaxle.Theseconddifferentialsidegearisoperablycoupledtothesecondreardriveaxlefortransmissionoftheoutputtorquefromtheseconddifferentialsidegear.Theimprovementincludesanidlergearmeansindrivingengagementwiththeoutputgearandasecondgearmeansindrivingengagementwiththeidlergearmeanstobecapableoftransmittingaremainderoftheoutputtorqueofthefirstdifferentialsidegearfromtheoutputgearthroughtheidlergearmeanstotheforwarddriveaxleshaft.Thereisalsoincludedmeansforselectivelycouplingthesecondgearmeanstothefrontdriveaxlefortransmittingtheremainderoftheoutputtorquetheretoandforuncouplingthesecondgearmeansfromthefrontdriveaxletoallowfreerunningoftheidlergearmeansandsecondgearmeans.BriefDescriptionoftheDrawingsFigure1isaschematictopplanviewshowingthedriveaxlesystemofthepresentinventionasitwouldappearina6x6vehicle.Figure2isaschematicviewofthedriveaxlesystemasitwouldgenerallyappearalongtheline2-2ofFigure1.Figure3isaviewpartiallyinsectionofapreferredembodimentoftheinventionaswouldgenerallybeseenalongline3-3ofFigure2.DescriptionofthePreferredEmbodimentAsseeninFigure1,aschematicviewofa6x6vehicle10includesvariousfeaturesofthedriveaxlesystemofthepresentinvention.Thevehiclepowersource12includesanengineandtransmissionandhasadriveshaft16whichextendsrearwardlytherefrom.Thedriveshaft16iscoupledtoashaftwithinainteraxledifferentialhousing18whichisphysicallyassociatedwiththeforwardlypositionedrearaxle20ofapairoftandemreardriveaxles20,22.Inthepreferredembodiment,theinteraxledifferentialhousing18basicallyincludesthecomponentswhichareutilizedtodivideandtransferthepowertothevariousmembersofthedriveaxlesystem.Theinteraxledifferentialwithinthehousing18dividesasingleinputtorqueandsuppliesaportionofitsoutputpowerthroughanaxledifferentialtotheforwardlypositionedrearaxle20.Aseconddriveshaft24receivestheremainingoutputtorqueandextendsrearwardlyfromtheinteraxledifferentialwithinthehousing18todriveanotheraxledifferential26oftherearwardlypositionedrearaxle22.Toprovidepowertoafrontsteering,driveaxle28forthevehicle10,athirddriveshaft30extendsforwardlyfromtheinteraxledifferentialhousing18tobecoupledwithyetanotheraxledifferential32oftheforwarddriveaxle28.Asthusdescribed,powercanbeprovidedfromthepowersource12totheinteraxledifferentialwithinthehousing18which,aswillbeexplainedindetailhereinbelow,iscapableofdividingtheinputpowertoprovideanoutputpowertoeachoftheaxles20,22and28whenthevehicleisbeingoperatedina6x6mode.Aswillalsobeseen,thereisincludedmeansassociatedwiththevehicledrivesystemofthepresentinventionforuncouplingthethirddriveshaft30topreventpowerfrombeingappliedtothefrontdriveaxle28sothatthevehiclecouldbeoperatedina6x4mode.AsseeninFigures2and3,theinteraxledifferentialhousing18includesthemajorelementsofthepresentinventionwhichdivideandtransmitpowertothevariousaxles.Specifically,aninputshaft34ismountedforrotationwithintheinteraxledifferentialhousing18atbearings36andincludesacoupling38towhichthedriveshaft16(notshown)isjoined.Aninteraxledifferentialgearset40ismountedattherearwardendoftheinputshaft34andincludesadifferentialcageandspider42whichisrigidlycoupledtotheshaft34.Thedifferentialcageandspider42includespiniongears44whicharecapableoftransmittingpowertoafirstdifferentialsidegear46andaseconddifferentialsidegear48.Thedifferentialsidegear46ismountedontheinputshaft34andiscapableofindependentrelativerotationthereon.Similarly,theseconddifferentialsidegear48ismountedontheinputshaft34tobecapableofindependentrelativerotationthereonandisbasicallysupportedbybearings50whichalsoservetosupporttherearendoftheinputshaft32becauseofthemannerinwhichthesidegear48receivestherearendoftheinputshaft34therein.Theseconddifferentialsidegear48isrigidlyjoinedtoarearwardlyextendingshaftmeans48whichextendsfromtherearoftheinteraxledifferentialhousing18tobetherecoupledwiththesecondrearwardlyextendingdriveshaft24(notshown).Accordingly,powerreceivedattheseconddifferentialsidegear48iscapableofprovidingpowertotherearwardlypositionedrearaxle22inthemannerdescribedhereinabove.Thefirstdifferentialsidegear46includesatitsforwardendanoutputgear54whichiscapableoftransmittingtheoutputpowerreceivedbythefirstdifferentialsidegear46.Totransmitaportionoftheoutputpowerfromthefirstdifferentialsidegear46tobytheforwardlypositionedrearaxle20,afirstgear56.isalignedwithandinengagingcontactwiththeoutputgear54.Thefirstgear56isrigidlymountedonashaft58whichis,inturn,mountedforrotationatbearings60withintheinterioroftheinteraxledifferentialhousing18.Aninputpinion62ismountedattherearwardendoftheshaft58andisinengagingcontactwithadifferentialringgear64whichdrivesanaxledifferentialmechanism(notshown)forprovidingtheoutputtorquetotheforwardlypositionedreardriveaxle20.Asthusdescribed,theinputtorquefromthepowersource12iscapableofbeingsuppliedtotherearaxles20and22asitisbeingdividedbytheinteraxledifferentialgearset40.Specifically,underanidealoperatingconditioninwhichthevehicleisoperatingonarelativelylevelsurfacewithagenerallyevenlydistributedloadonthevariousaxles,theoutputtorqueateachofthedifferentialsidegear46,48wouldbeaboutone-halfoftheinputtorquereceivedfromthepowersource12.Ifthevehicleweretobeoperatingina6x4mode,thedriveaxlesystemasthusdescribedwouldbeoperatinginamannerwellknownintheartwiththeinteraxledifferential40basicallydividingalloftheloadbetweenthetworeartandemaxles20and22.Theinteraxledifferential40isconsiderednecessarybecauseoftherealpossibilitythattheloadinactualoperationwouldnotbeevenlydistributedbetweenthetwoaxlesandtheinteraxledifferentialwouldstillenablethevehicletooperatewhileallowingsomeslippageorvaryingtactionconditionsbetweenthetwoaxles20,22.However,asisalsowellknowninthedriveaxleart,thereareoccasionswhenthedifferentiationprovidedbytheinteraxledifferential40isnotdesired.Sinceitispossibleforthewheelsassociatedwithoneoftheaxles20,22tobeinsuchanon-tractionconditionthatnopowercouldbeappliedtothedrivingsurfaceforthemovementofthevehicle,thereisquiteoftenincludedmeansfor"lockingout"thedifferentialtoinsurethatbothaxlesmovesimultaneouslyandthateitheraxlemakingsufficientcontactwiththedrivingsurfacewouldbecapableofpropellingthevehicle.Toaccomplishthis,aclutchmeans66ismountedontheinputshaft34onasetofoutwardlyextendingteeth67thereof.AsshowninFigure3,theclutchmeans66isforwardlypositionedsothatitis,infact,notaffectingthedifferentiationwhichisprovidedbytheinteraxledifferential40.However,inordertoachievethe"lockout"conditiontopreventdifferentiation,thereismeansintheformofashiftrodandfork(notshown)whichcanactonthecircumferentialgroove68oftheclutchmeans66tocauseittobemovedaxiallyrearwardlyontheteeth67oftheinputshaft34.Whentheclutchmeans66ismovedsufficientlyrearwardly,itisbroughtintoalignmentwithandengagesasetofgearteeth70ontheforwardendofthefirstdifferentialsidegear46tocouplethefirstdifferentialsidegear46directlytotheinputshaft34.Whenthefirstdifferentialsidegear46issocoupledtotheinputshaft34,therewouldbenofurtherdifferentiationandtheinputtorquewouldthenbetransmittedeitherthroughtheoutputgear54ortherearwardlyextendingshaft52accordingtotheresistancecreatedbyeachrearaxle20,22aseachmakescontactwiththedrivingsurface.Asmentionedhereinabove,thepresentinventionandthedriveaxlesystemdisclosedinU.S.PatentNumber4,050,534bothincludemeanswithinthedifferentialhousing18forprovidingoutputtothefrontdriveaxle28.InU.S.PatentNumber4,050,534thisisaccomplishedbytherebeinganadditionalgearindrivingengagementwiththefirstgear56sothattheoutputtorquereceivedattheoutputgear54willbecapableofprovidingpowertoboththefrontdriveaxle28andtheforwardlypositionedreardriveaxle20.Asaresult,allofthepowerwhichistransmittedtothesetwoaxleswillbespecificallytransmittedatasingleengagingcontactpointbetweentheoutputgear54andthefirstgear58.However,inaworstcasesituation,therecouldbesufficientslippageintherearwardlypositionedrearaxle22fortheoperatorofthevehicletocausetheclutchmeans66tobeutilizedtopreventdifferentiationbytheinteraxledifferential40.Ifthevehicleisheavilyloadedandthereisexcellentroadtractionforthefrontdriveaxle28andtheforwardlypositionedrearaxle20,alloftheinputpowerfromthepowersourcewouldbetransmittedtothesetwoaxlesthroughthesingleoutputgear54.Althoughthiswouldnotbeanormaloperatingcondition,itwouldnotbeunusualforthishighloadingsituationtoperiodicallyoccur.Theresultingstressandwearontheteethoftheoutputgear54attheirsingleengagingcontactpointwiththefirstgear56couldbesignificantandadverselytoaffecttheoverallreliabilityandlifeofthedriveaxlesystemAccordingly,inthepreferredembodiment,toprovidepowertothefrontdriveaxle28thereisincludedaidlergear72whichisinengagingcontactwiththeoutputgear54butatalocationthereonwhichiscircumferentiallyspacedfromthepointofengagementwiththefirstgear56.Theidlergear72isrigidlymountedonanidlershaft74whichismountedforrotationonbearings76withintheinteraxledifferentialhousing18.Toprovidepowerforthefrontdriveaxle28,thereisincludedasecondgear78whichengagestheidlergear72sothatbothgears72,78willrotateinresponsetorotationoftheoutputgear54.Thesecondgear78ismountedonashaft80andiscapableofindependentrelativerotationthereon.Theshaft80ismountedwithintheinteraxledifferentialhousing18atbearings82andincludesaforwardendwhichiscapableofbeingcoupledtotheforwardlyextendingdriveshaft30forprovidingpowertothefrontdriveaxle28.Thesecondgear78isnotrigidlymountedontheshaft80inthepreferredembodimentoftheinventioninordertoincludeameansforselectivelytransmittingpowertothefrontdriveaxle28.Thisisaccomplishedinamannerwellknowninthepowertransmittingartintheformofaclutch84whichissimilarinfunctionandoperationtotheclutchmeans66describedhereinabove.Theclutch84ismountedonoutwardlyextendingteeth85oftheshaft80andcanbeselectively,rearwardlypositionedtoengageoutwardlyextendingteeth86onthesecondgear78torigidlycouplethesecondgear78totheshaft80forthetransmissionofpowertothefrontdriveaxle28whenthe6x6modeofoperationisdesired.Relocatingtheclutch84toaforwardpositionwoulduncouplethesecondgear78fromtheshaft80andallowtheidlergear72andthesecondgear78torunfreelywithoutanytransmissionofpowertothefrontdriveaxle28andthusreturnthevehicletothe6x4modeofoperation.However,withtheconfigurationutilizedinthepresentinvention,ifthevehicleweretoagainbeoperatinginaworstcasesituationwiththeinteraxledifferential"lockedout",thepowerbeingtransmittedtotheaxle28a