Abstract:
A drive system for a motor vehicle according to this invention includes a first housing that includes a first mounting surface for securing the first housing to one of an IRS housing and a beam housing. Located within the first housing and one of said IRS housing and the beam housing are a pinion, first and second drive shafts, a differential mechanism including an input for transmitting power differentially between first and second drive shafts and the pinion, and a ring gear meshing with the pinion and driveably connected to the differential mechanism.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates generally to apparatus for fixed axle and independent rear suspension (IRS) applications in a motor vehicle. More particularly, the invention pertains to a center housing containing an inter-wheel differential mechanism, the center housing being adapted for use alternately with beam housing and IRS housing.  
         [0002]     In fixed axle motor vehicle applications, a beam axle housing contains side shafts driven differentially from a driveshaft, which that driveably connects a transmission output to an inter-wheel differential mechanism. Alternatively, the vehicle may have an independent rear suspension, in which a differential case containing a differential mechanism drives right-side and left-side halfshafts that accommodate articulation and axial displacement of the drive wheels relative to the differential case. The halfshafts include a constant velocity joint, which transmits power between the differential and the drive wheels without restraining movement of the wheels relative to the suspension.  
         [0003]     It is important that the components of such systems be light weight in order to maximize fuel economy especially in light duty trucks and sports utility vehicles. Maximum use of identical components for both fixed axle and IRS applications in rear drive systems is required.  
       SUMMARY OF THE INVENTION  
       [0004]     A drive system for a motor vehicle according to this invention includes a first housing that includes a first mounting surface for securing the first housing to one of an IRS housing and a beam housing. Located within the first housing and one of said IRS housing and the beam housing are a pinion, first and second drive shafts, a differential mechanism including an input for transmitting power differentially between first and second drive shafts and the pinion, and, a ring gear meshing with the pinion and driveably connected to the differential mechanism.  
         [0005]     The first housing, sometimes called a center housing, can be secured to a light-weight stamped beam housing (also referred to as a banjo housing) or to a lightweight cast aluminum IRS housing, which is formed with mounts for IRS applications. A straddle mounted hypoid pinion and an integral hypoid ring gear help to minimize weight. The ring gear functions as a differential case cover, which eliminates an additional component and further help to reduce weight. The center housing has cast mounting bosses, which provide structural connections in IRS applications and can be used for clamp and locating devices during machining. The beam stamped housing can be formed with a cross section that is round, oval, or square, rectangular, or another suitable shape sufficient to support vehicle weight. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0006]     The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which:  
         [0007]      FIG. 1  is a perspective view showing a center housing and axle beam housing for fixed axle applications;  
         [0008]      FIG. 2  is a perspective view showing a center housing and housing for independent rear suspension applications;  
         [0009]      FIG. 3  is a partial cross section taken at a horizontal plane through the center housing and axle beam housing assembly of  FIG. 1 ; and  
         [0010]      FIG. 4  is a partial cross section taken at a horizontal plane through the center housing and IRS housing assembly of  FIG. 2 .  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0011]     Referring first to  FIG. 1 , a center or first housing  10  and beam housing  12 , when assembled together, enclose a space that contains a ring gear and its mating pinion, a differential mechanism, and shafts that transmit power between the drive wheels of a motor vehicle and the differential mechanism for vehicle applications in which the axle shafts are fixed in position within the beam housing  12 .  
         [0012]     In  FIG. 2 , the center housing  10  is shown in position for assembly to an IRS housing  14 . The center housing  10  and IRS housing  14  together provide an internal volume containing a ring gear and its mating pinion, a differential mechanism, and shafts that transmit power between the drive wheels of a motor vehicle and the differential mechanism for vehicle applications in which the axle shafts are supported for independent movement.  
         [0013]     Housing  10  is substantially identical for either application, and the arrangement of components located within the assemblies of  FIG. 1  and  2  may be either that illustrated in  FIG. 3  or  4 . Preferably housing  10  is a casting of aluminum or iron, housing  14  is an aluminum casting, and housing  12  is formed in sections of stamped or drawn steel, which are joined by welding along weld lines  16 ,  17 .  
         [0014]     Housing  10  is cast with several mounting bosses  18 ,  20  for use in the IRS applications. Beam housing  12  includes a beam arm  22  extending rightward from center housing  10 , and a beam arm  24  extending leftward from the center housing  10 . The laterally extending arms  22 ,  24  of the beam housing  12  have a cross section that is round, oval, square, or rectangular, as required to support the vehicle weight and operating loads.  
         [0015]     Center housing  10  is secured by a series of bolt holes  26 , located on a bolt circle and passing through a rearward-facing mounting flange  28 , to the beam housing  12 , which includes a forward-facing mounting flange  30  and bolt holes aligned with the bolt holes  26 . Alternatively, housing  10  is secured by a series of holes  26 , located on a bolt circle and passing through a rearward-facing mounting flange  28 , to the IRS housing  14 , which includes a forward-facing mounting flange  32  and bolt holes aligned with the bolt holes  26 . In each case bolts, inserted in the aligned bolt holes, engage nuts or threads formed in the housing  12  or  14 .  
         [0016]     Turning now to  FIG. 3 , a rear driveshaft  40 , which driveably connects a transmission output shaft to an inter-wheel differential mechanism  42 , is supported on housing  10  by bearings  44 . Driveshaft  40  is driveably secured to a bevel pinion  52 , which is supported on housing  10  by pinion support bearings  46 ,  48 . The rearward bearing  48  is straddle mounted on an arm  50 , which extends radially toward the pinion shaft  44 . Pinion  52 , preferably a hypoid pinion, is in meshing engagement with a ring gear  54 . Center bevel gears  58 , secured to ring gear  54 , are in continuous meshing engagement with a right-side bevel gear  60  and left-side bevel gear  62 .  
         [0017]     A right-hand axle shaft  64 , secured to side bevel gear  60  and located in arm  22  of beam housing  12 , extends rightward toward the right side drive wheel and is supported on housing  10  by a bearing  65 . A left-hand axle shaft  66 , secured to side bevel gear  62  and located in arm  24  of beam housing  12 , extends leftward toward the left side drive wheel and is supported on housing  10  by a bearing  67 . A mounting plate  68 , secured to the outer surface of housing arm  24 , provides support for a component of the vehicle suspension system.  
         [0018]     In the embodiment illustrated in  FIG. 4 , the axle beam housing  12  is replaced by the IRS housing  14 , and the rear-facing mounting flange  28  of the first housing  10  is secured to the front-facing mounting flange  32  of housing  14 . A flange  70  secured to a rear driveshaft, driveably connects the transmission output to an inter-wheel differential mechanism  72  though a pinion shaft  74 , which is rotatably supported on housing  10  by pinion shaft bearings  76 ,  78 . The teeth of a hypoid pinion  80  mesh with the teeth  82  of a ring gear  84 .  
         [0019]     A differential shaft  86 , secured by bolts  88  to the pinion  84 , passes through center bevel pinions  90 ,  92  causing them to rotate as a unit with ring gear  84 . Right-side bevel gear  94  and left-side bevel gear  96  mesh with center bevel gears  90 ,  92 .  
         [0020]     A left side differential output shaft or halfshaft  98 , driveably connected to side bevel gear  92  and supported on housing  14  on bearings  100 , extends leftward from the differential  72  toward the left-hand drive wheel (not shown). Halfshaft  98  includes a constant velocity joint  102 , which articulates to accommodate movement of the left drive wheel relative to the differential  72  and may also displace axially to accommodate relative axial displacement. The constant velocity joint  102  transmits power between the inboard shaft component  104  of halfshaft  98  and the outboard shaft component  106 . A boot  108  seals the constant velocity joint  102  against entry of dirt and other foreign matter.  
         [0021]     Similarly a right-hand differential output shaft or halfshaft  110 , driveably connected to side bevel gear  94 , extends rightward from the differential  72  toward the right drive wheel (not shown). Halfshaft  110  also includes a constant velocity joint, which articulates to accommodate movement of the right drive wheel relative to the differential  72  and may also displace axially to accommodate relative axial displacement. The constant velocity joint and halfshaft  110  transmit power between the inboard shaft component  112  of halfshaft  110  and an outboard shaft component (not shown).  
         [0022]     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.