Abstract:
The present invention relates to a transfer case or gearbox used in a motor vehicle that is capable of transferring power to both the front and rear wheels of the vehicle. The transfer case uses two or more chains for transferring power the various outputs of the transfer case. The use of two or more chains allows the transfer case housing to be curved so that is can be positioned around other underbody components.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a transfer case arrangement for overcoming packaging constraints on an all-wheel drive vehicle.  
       BACKGROUND OF THE INVENTION  
       [0002]     Traditionally, four-wheel drive and all-wheel vehicles enable transfer of drive torque, produced by an engine and supplied through a gear reducing transmission to front and rear wheel assemblies. A transfer case is generally provided for enabling the split of drive torque between the front and rear wheel assemblies. The transfer case includes an input, operably connected to an output of the transmission, a first output shaft and a second output shaft, respectively connected with the wheel assemblies. A transfer mechanism is provided therein for selectively engaging the first and second output shafts, enabling the transfer of drive torque therebetween. The transfer case must be conveniently packaged within a vehicles underbody, avoiding interference with other vehicle components including drive shafts, exhaust systems, suspension, vehicle frame and the like. Packaging of the transfer case within a vehicle underbody has become more difficult in recent years as automakers seek to implement four-wheel and all-wheel drive systems in smaller vehicle applications. In view of the above, it is desirable in the industry to provide an improved transfer case design that overcomes packaging constraint issues.  
       SUMMARY OF THE INVENTION  
       [0003]     The present invention relates to a transfer case or gearbox used in a motor vehicle that is capable of transferring power to both the front and rear wheels of the vehicle. An input shaft is coupled to a source of power on one end, such as a transmission and extends into the housing of the gearbox. A first output shaft is operably connected to one or more of the rear wheels of the vehicle. The first output shaft is driven by the input shaft. A second output shaft is connected to one or more of the front wheels of the vehicle and is also driven by the input shaft. Two or more linkage assemblies are connected between the first output shaft and the second output shaft in order to transfer power between the first and second output shafts. The two or more linkage assemblies allow for the first and second output shafts to be positioned in different planes with respect to one another in order to provide a gearbox that will overcome some of the packaging limitations present in certain vehicle applications.  
         [0004]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0006]      FIG. 1  is a plan view of the undercarriage of a motor vehicle incorporating the present invention;  
         [0007]      FIG. 2  shows a front cross-section plan view of the present invention demonstrating the possible positioning of the various components, and how interference with other vehicle components is avoided; and  
         [0008]      FIG. 3  is side-view cross-section plan view of the present invention, showing in detail the various shafts, sprockets, and linkage assemblies. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0009]     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0010]     Referring to  FIG. 1 , an all-wheel vehicle drivetrain is diagrammatically illustrated as shown generally as  10 . The all-wheel drivetrain  10  includes a prime mover  12  coupled to and driving a transmission  14 . The transmission  14  can be an automatic or manual type transmission. The output of the transmission  14  drives a gearbox or transfer case assembly  16  that provides power to a primary or rear drive line  20 , including a primary or rear output shaft  22 , a primary or rear differential  24 , a pair of live primary or rear axles  26  and a respective pair of primary or rear tire wheel assemblies  28 .  
         [0011]     The transfer case assembly  16  also selectively provides power to a secondary or front driveline  30  including a secondary or front output shaft  32 , a secondary or front differential assembly  34 , a pair of secondary or front axles  36  and a respective pair of secondary or front tire wheel assemblies  38 . The front tire wheel assemblies  38  can be directly coupled to the front axles  36 . Both the primary driveline  20  and the secondary driveline  30  may include suitable and appropriately disposed universal joints  40  that function in a conventional fashion to allow static and dynamic offset and misalignments between the various shafts and components.  
         [0012]     While disclosed herein as front and rear drivelines  20 ,  30  the invention disclosed and claimed may be readily utilized in transmissions and transfer cases wherein the primary driveline  20  is disposed at the front of the vehicle and the secondary driveline  30  is disposed at the rear of the vehicle. Specifically, in those vehicles wherein the front driveline is engaged in operating substantially all of the time, i.e., a front wheel drive vehicle.  
         [0013]      FIG. 3  depicts a cross-sectional plan view of the transfer case  16 . The transfer case or gearbox has a housing  42  that rotatably receives an input shaft  44  from the transmission  14 . The input shaft  44  is coupled to a first output shaft  46 . The first output shaft  46  transmits power to one or more of the rear wheels  28  of the vehicle. The first output shaft  46  is coupled to the rear drive shaft  22  by the constant velocity joint  40 . This allows power to transfer from the transfer case  16  to one or more the rear wheels  28  of the vehicle.  
         [0014]     A sprocket  48  is connected to the first output shaft  46  and is configured to rotate with respect to the first output shaft  46 . A first linkage assembly  50  is connected to the sprocket  48  and extends to a second sprocket  52  that is rotatably connected to an intermediate shaft  54  that is rotatably contained within the housing  42  of the transfer case  16 . A third sprocket  56  is also rotatably connected to the intermediate shaft  54  and has a second linkage assembly  58  that extends to a fourth sprocket  60  that is rotatably connected to a second output shaft  62 . The second output shaft  62  is connected via the constant velocity joint  40  to a front output shaft  32 . This allows the second output shaft  62  to transfer power to one or more of the front wheels  38  of the vehicle. The linkage assemblies  50 ,  58  in a preferred embodiment of the invention are chains, however the linkage assembly can consist of other suitable components for transferring power such as belts or gears.  
         [0015]     The transfer case  16  operates by having torque introduced to the housing  42  by the input shaft  44 . The input shaft  44  is rotatably disposed on roller bearings  64 . The first output shaft  46  is also rotatably connected to a pair of roller bearings  66 . The first output shaft  46  is connectable or splined to the input shaft  44  so that when the input shaft  44  rotates the first output shaft  46  will also rotate. The sprocket  48  is connecting to the first output shaft  46  so that it will also rotate with the movement of the first output shaft  46 . As the sprocket  48  rotates the first linkage assembly  50  will also rotate and cause torque to be transmitted to the intermediate shaft  54  through the sprocket  52 . Bearings  68  allow rotation of the intermediate shaft  54 . Two pairs of roller bearings  70  allow the second output shaft  62  to rotate freely in the housing. Although  FIG. 2  only depicts sets of roller bearings  64 ,  66 ,  68 ,  70  it is within the scope of this invention to use a greater or lesser number of roller bearings depending on the type of transfer case being used. As the sprocket  52  rotates the intermediate shaft  54  will rotate and subsequently cause the third sprocket  56  to rotate.  
         [0016]     As the third sprocket  56  rotates the second linkage assembly  58  will rotate and cause torque to be transmitted to the fourth sprocket  60 . The fourth sprocket  60  is connected to the second output shaft  62  which transmit power to the front output shaft  32 .  
         [0017]      FIG. 2  depicts a cross-sectional schematic plan view of the transfer case and its orientation with respect to a vehicle floorboard  72 . As shown in  FIG. 2  the transfer case housing  42  is configured so that the input shaft  44  and the second output shaft  62  are not in the same plane. The use of two linkage assemblies  50 ,  58  allows for the transfer case  16  to have a modified shape so that it will fit neatly with the contours of the floorboard  72 . The intermediate shaft  54  is used as a vertex of the angle a formed between the input shaft  44  and the front output shaft  62 . It should be understood that the angle a can be greater or lesser depending upon the particular design requirements or angle of the floorboard  72 . This allows the transfer case  16  to be neatly packaged within the vehicle underbody so that it will not interfere with other components of the vehicle. Additionally, it is possible to use more than two linkage assemblies in order to add additional shapes to the transfer case  16 . For example, an alternate embodiment can include additional intermediate shafts and linkage assembly in order to give the transfer case  16  a general U-shape. It is also within the scope of the present invention to use even more intermediate shafts and linkage assemblies as desired or necessary, depending upon the design criteria of the vehicle underbody.  
         [0018]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.