Abstract:
A differential assembly includes a yoke, attached to a drive shaft, for driving a pinion head. The differential assembly further includes inner and outer pinion bearing assemblies, a separable mounting plate, and a cavity defined by a housing for receiving a pinion assembly. The outer pinion bearing assembly is integrally mounted to the housing, while the inner pinion bearing assembly is secured to the separable mounting plate. The pinion head is straddle mounted between the inner and outer pinion bearing assemblies. This is abstract submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to an improved pinion support for a differential assembly and in particular to a pinion support for a straddle mount single drive axle.  
       BACKGROUND OF THE INVENTION  
       [0002]     Differentials are utilized in the drive lines of many modern vehicles. Typically, a differential takes a rotating input and drives two shafts which extend in opposed directions. The differential allows the two shafts to rotate at varying speeds relative to each other.  
       SUMMARY OF THE INVENTION  
       [0003]     The present invention relates to a differential assembly comprising a yoke, attached to a drive shaft, for driving a pinion head. The differential assembly further includes inner and outer pinion bearing assemblies, a separable mounting plate, and a cavity defined by a housing for receiving a pinion assembly. The outer pinion bearing assembly is integrally mounted to the housing, while the inner pinion bearing assembly is secured to the mounting plate. The pinion head is straddle mounted between the inner and outer pinion bearing assemblies. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0005]      FIG. 1  is a perspective view of a differential assembly assembled within a vehicle in accordance with the present invention.  
         [0006]      FIG. 2  is a cross-sectional view of a differential assembly according to an embodiment of the present invention.  
         [0007]      FIG. 3  is a cross-sectional view of a differential assembly according to an alternate embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0008]     Referring to  FIG. 1 , a differential assembly  10  is shown assembled within a vehicle  11 . Focusing on  FIG. 2 , the differential assembly  10  is illustrated in accordance with the present invention. The differential assembly  10  comprises a yoke  12  attached to a drive shaft  13 , for driving a pinion head  14 . The differential assembly  10  further includes a pinion assembly  15 . Pinion assembly  15  includes gear teeth  14   a , inner and outer pinion bearing assemblies  16 ,  18  and shaft  13 . Pinion assembly  15  is received within a cavity  21  defined by a housing  22 ; housing  22  is fixed against rotation. Inner pinion bearing assembly  16  of pinion assembly  15  is secured to a separable mounting plate  20 .  
         [0009]     Pinion head  14  is straddle mounted between inner and outer bearing assemblies  16 ,  18  to achieve optimum support. Pinion head  14  is directly mounted to drive shaft  13  and supported on either side by the two axially spaced pinion bearing assemblies  16 ,  18 . Inner pinion bearing assembly  16  supports the portion of the drive shaft  13  which is located within housing  22 . Outer pinion bearing assembly  18  supports the portion of the drive shaft  13  with which the vehicle drive shaft is normally associated. Straddle mounting pinion head  14  between inner and outer pinion bearing assemblies  16 ,  18  decreases the number of bearing assemblies found in conventional differential assemblies by allowing pinion head  14  to be optimally supported. Furthermore, lubrication to the inner and outer pinion bearing assemblies  16 ,  18  is provided without the need for extra oil channels, thus reducing the complexity of the differential assembly  10 .  
         [0010]     Inner and outer pinion bearing assemblies  16 ,  18  each further comprise an inner race  24 ,  26 , an outer race  28 ,  30  and a bearing  32 ,  34 , respectively. The bearings  32 ,  34  are disposed between inner races  28 ,  30  and outer races  32 ,  34 . Inner race  24  of inner pinion bearing assembly  16  abuts a face  36  of gear teeth  14   a  of pinion head  14 . Inner race  26  of outer bearing assembly  18  abuts a face  38  of gear teeth  14   a  of pinion head  14 . Outer race  28  of inner pinion bearing  16  is mounted on the separable mounting plate  20 , while outer race  30  of outer pinion bearing assembly  18  is integrally mounted to housing  22 .  
         [0011]     By mounting outer race  30  of outer bearing assembly  18  directly to housing  22 , outer bearing assembly  18  provides a more rigid structure for supporting pinion head  14  than conventional differential assemblies. In addition, the pinion head  14  mounting distance can be readily machined to tolerance through machining housing  22  where outer race  30  abuts housing  22 . Accordingly, outer pinion bearing assembly  18  can be assembled into differential assembly  10  without the use of shims or a shim pack, resulting in weight savings and cost reduction over conventional differential assemblies.  
         [0012]     Moreover, attaching outer pinion bearing assembly  18  directly to housing  22  eliminates the need for a pinion bearing cage, or external adjuster, as found in conventional differential assemblies. Typically, bearing cages create an additional path for oil to leak out of the housing  22 . Therefore, by removing the need for a bearing cage, an additional path for oil to leak through does not exists.  
         [0013]     Furthermore, removal of the bearing cage reduces the yoke standout dimension H. The reduced yoke standout dimension H decreases the amount of space required for differential assembly  10  within vehicle  11 . Additionally, the reduced yoke standout dimension H provides a significant advantage for short wheelbase vehicles drive line angles (not shown) and for tandem axle inter axle dive line angles (not shown).  
         [0014]     By way of example, and without limitation,  FIGS. 2 and 3  illustrate outer pinion bearing assembly  18  as being larger than inner pinion bearing assembly  16 . Generally, outer pinion bearing assemblies substantially bear the load of the pinion head within differential assemblies. Consequently, outer pinion bearing assemblies are normally larger than inner pinion bearing assemblies. However, it can be appreciated that inner and outer pinion bearing assemblies  16 ,  18  may be of substantially the same dimensions. Additionally, bearings  32 ,  34  may be symmetrically shaped, as shown in  FIG. 1 , or bearings  32 ,  34  may be tapered at one end.  
         [0015]     Inner pinion bearing assembly  16  is mounted on a separable mounting plate  20 .  FIGS. 2 and 3  illustrate embodiments in which mounting plate  20  may be attached and removed from housing  22  through a series of bolts  42 . It can be appreciated that the present invention can be practiced with any number of bolts to secure separable mounting plate  20  to housing  22 .  FIG. 1  depicts one method to set pinion assembly  15  bearing preload for inner and outer pinion bearing assemblies  16  and  18 . However, the present invention is not limited to the use of bolts for securing separable mounting plate  20  to housing  22 . For example, mounting plate  20  may be secured to housing  22  through an adhesive, or by a snap-fit design. To set inner and outer pinion bearings  16  and  18  preload, a shim pack  43  may be placed under the mounting plate  20  of the inner pinion bearing assembly  16 .  
         [0016]     The pinion assembly  15  may be received into cavity  21  from rear portion  40  of housing  22 . Currently, pinion assemblies are received into cavity  21  of housing  22  through an opening defined by dimension D. Therefore, dimension D must be broad enough to accommodate the widest portion of pinion assembly  15 . However, with pinion assembly  15  being assembled through rear portion  40  of housing  22 , dimension D may be decreased. The result is a more compact housing  22 . Moreover, the structural integrity of housing  22  is improved due to the reduced size of opening D. Additionally, the need for separable covers or bearing carriers is eliminated along with the associated added cost and potential for oil leakage.  
         [0017]      FIG. 3  depicts an alternate embodiment of the present invention. Differential assembly  10 ′ substantially incorporates the features of differential assembly  10  of  FIG. 1 . However, outer race  28  of inner pinion bearing assembly  16  has a threaded cup  44 . Outer race  28  of inner pinion bearing assembly  16  may be threaded to a desired position to preload inner and outer pinion bearing assemblies  16  and  18 . Consequently, threaded cup  44  removes the need for a shim pack  43  to preload inner and outer pinion bearing assemblies  16  and  18 .  
         [0018]     Furthermore, inner pinion bearing assembly  16  may include a lock ring  46  and a stake  48 . The lock ring may be riveted to threaded cup  44  and attached to the stake to prevent the threaded cup  44  from rotating once the preload has been set. It should be noted however that the present invention is not limited to a lock ring and stake to prevent the threaded cup from rotating. By way of example, and without limitation, the threaded cup  44  may be coated with an adhesive to prevent rotation once the preload has been established.  
         [0019]     While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.