Abstract:
A support structure for a differential assembly comprising: a support ring having a peripheral wall extending between a first face and a second face, the support ring having a non-hollow center; a bore in the peripheral wall sized and shaped to receive a pinion shaft; and an aperture in the first face, the second aperture in fluid communication with the first aperture.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit from U.S. Provisional Patent Application No. 60/961,250, entitled “Support Structure for Differential,” filed on Jul. 19, 2007, which is hereby incorporated in its entirety by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to mechanical differentials, and more particularly to a support structure for supporting one or more pinion shafts in a mechanical differential. 
       BACKGROUND OF THE INVENTION 
       [0003]    Differential assemblies are known in the automotive industry as devices that split engine torque two ways, allowing each output to spin at a different speed. Generally, differential assemblies have three primary tasks: to aim the engine power at the wheels; to act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one final time before transmission to the wheels; and to transmit the power to the wheels while allowing them to rotate at different speeds. 
         [0004]    A typical mechanical differential contains a housing (or carrier), two side gears, and several pinion gears. A rotating driveshaft of the vehicle engages a ring gear, which is mounted onto the differential housing. The driveshaft drives the ring gear, which in turn rotates the differential housing. Pinion shafts attach the pinion gears to the housing so that, as the housing rotates, the pinion gears are driven. The pinion gears drive the two side gears, which in turn drive the axle (or half shafts) attached thereto. 
         [0005]    The pinion shafts of the differential assembly typically have a support ring that secures to the inward ends of pinion shafts so that the torque of the housing can be transmitted to the pinion shafts and thereby drive the pinion gears. The pinion gears spin upon the pinion shafts and rotate about the axis of the housing. 
         [0006]    The conventional support ring is typically a ring-type component having a hollow center with a plurality of apertures provided through the wall of the support ring for receiving the ends of the pinion shafts. This type of support ring is usually made from a hollow tube or pipe. In some cases, the required size of the support ring does not correspond to the size of the standardized tube material supplied in the market. In such cases, manufacturers have been forced to use solid bars that correspond to the required size of the support ring. However, solid bars generally have to be substantially machined to create rings. As such, a large amount of material has to be machined to form a hollow support ring having the required dimensional characteristics. 
         [0007]    With reference to  FIGS. 1A and 1B , typical mechanical differentials contain a housing  1 , two side gears  3 , and several pinion gears  4 . The pinion gears  4  are fixed to the housing  1  by a pinion shaft  5  so that the pinion gears  4  may be driven by the housing  1  to rotate around the housing  1  while spinning on the pinion shafts  5 . Typically, the pinion shafts  5  are rigidly secured to the housing  1  at their respective distal ends, and supported by a support ring  6  at their respective proximal ends. Torque is transmitted to the housing  1 , and the housing  1  drives the pinion shafts  5  which in turn drives the pinion gears  4 . As the pinion gears  4  move, the pinion gears  4  drive the side gears  3  so that torque may be transmitted to the side gears  3 . 
         [0008]      FIGS. 2A-2E  illustrates a conventional support ring  6  having an outer surface  11  and inner surface  13 , with the inner surface  13  defining a hollow center. Typically, three apertures  10  are machined through the outer surface  11  and the inner surface  13  of the support ring  6  to provide connections for the pinion shafts. 
         [0009]    During operation of the differential assembly, friction and heat are generated as components within the differential housing are engaging and contacting one another. This friction and heat reduces the durability and load carrying capacity of the differential assembly, such as by causing scoring damage to the contact surfaces. Consequently, in most applications, the differential assembly must guide lubricant to the various frictional surfaces to relieve friction and minimize the generation of heat. 
         [0010]    For example, the contact surfaces of the pinion gear bore and pinion shaft  5  are among the important surfaces that require significant lubrication. In many applications, the lubricant for lubricating these surfaces is supplied to the differential through shaft bores  17  and corresponding splined bores  18  of the side gears  3 . Under the effect of centrifugal force generated when the differential is rotating, the lubricant flows inwardly thru the shaft bores  17  and splined bores  18 , and the lubricant is collected by the inner surface  13  of support ring  6 . The lubricant then flows through the clearance between the bores  10  of the support ring  6  and flat features  19  of each pinion shaft  5  to a corresponding interface of the contact pair of the pinion gear bore and pinion shaft  5 . 
         [0011]    Consequently there exists a significant need for a pinion shaft support structure that is capable of providing lubrication pathways to the interface of the pinion gear bores and pinion shafts, while also capable of reducing the time and expense in machining the support structure thereby resulting in reduced manufacturing costs. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0012]    Objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustrations, wherein like numerals indicate like elements throughout, and wherein: 
           [0013]      FIG. 1A  illustrates a differential housing assembly which is generally known in the art; 
           [0014]      FIG. 1B  illustrates a cross-sectional view of the differential housing assembly of  FIG. 1A  taken along line A-A; 
           [0015]      FIG. 2A  is a perspective view of a support ring generally known in the art; 
           [0016]      FIG. 2B  is a top view of the support ring of  FIG. 2A ; 
           [0017]      FIG. 2C  is a cross-sectional view of the support ring of  FIG. 2B  taken generally along line B-B; 
           [0018]      FIG. 2D  is a side view of the support ring of  FIG. 2A ; 
           [0019]      FIG. 2E  is a cross-sectional view of the support ring of  FIG. 2D  taken generally along line C-C; 
           [0020]      FIG. 3A  is a perspective view of a support ring in an embodiment of the present invention; 
           [0021]      FIG. 3B  is a top view of the support ring of  FIG. 3A ; 
           [0022]      FIG. 3C  is a cross-sectional view of the support ring of  FIG. 3B  taken generally along line D-D; 
           [0023]      FIG. 3D  is a side view of the support ring of  FIG. 3A ; 
           [0024]      FIG. 3E  is a cross-sectional view of the support ring of  FIG. 3D  taken generally along line E-E; 
           [0025]      FIG. 4A  illustrates the support ring of  FIG. 3A  incorporated into a mechanical differential assembly in an embodiment of the present invention; 
           [0026]      FIG. 4B  is a cross-sectional view of the differential assembly of  FIG. 4A  taken generally along line F-F; 
           [0027]      FIG. 5A  is a perspective view of a support ring in another embodiment of the present invention; 
           [0028]      FIG. 5B  is a top view of the support ring of  FIG. 5A ; 
           [0029]      FIG. 5C  is a cross-sectional view of the support ring of  FIG. 5B  taken generally along line G-G; 
           [0030]      FIG. 5D  is a side view of the support ring of  FIG. 5A ; 
           [0031]      FIG. 5E  is a cross-sectional view of the support ring of  FIG. 5D  taken generally along line H-H; 
           [0032]      FIG. 6A  illustrates the support ring of  FIG. 5A  incorporated into a mechanical differential assembly in an embodiment of the present invention; and 
           [0033]      FIG. 6B  is a cross-sectional view of the differential assembly of  FIG. 4A  taken generally along line I-I. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    While the present support structure is described with reference to several embodiments described herein, it should be clear that the present invention should not be limited to such embodiments. Therefore, the description of the embodiments provided herein are illustrative of the present invention and should not limit the scope of the invention as claimed. 
         [0035]    Reference will now be made in detail to an embodiment of the invention as illustrated in accompanying  FIGS. 3A-3E . In accordance with the embodiment, a support structure  20  is generally illustrated. For example, the support structure  20  may consist of a support ring  22  capable of use in a differential assembly. The shape of the support ring  22  should not be deemed as limited to any specific shape. The support ring  22  may correspond to the shape of the differential housing, for example. 
         [0036]    In an embodiment, the support ring  22  may generally be manufactured from a rod material, such as a non-hollow bodied metal rod material. Use of the non-hollow rod material can provide manufacturing cost savings, especially when used to manufacture the support rings  22  having required dimensions different from typical hollow, rod dimensions and similar to the dimensions of non-hollow rod dimensions. In such an embodiment, the present invention permits a reduced amount of machining and, as a result, a cost savings. 
         [0037]    As shown in  FIGS. 3A-3E , the support ring  22  may comprise an outer wall  24  and an inner wall  25  extending between faces  28  of the sidewalls  26 . In an embodiment, the support ring  22  may be annular and cylindrical. The faces  28  may be recessed, such as by machining the faces  28  a predetermined distance within the sidewalls  26 . For example, a non-hollow tube material may be cut into sections to form the support ring  22 , and the faces  28  may be machined into the sidewalls  26 . One of ordinary skill in the art will appreciate other methods for forming the recessed sidewalls  26 , including but not limited to casting, such as die casting. 
         [0038]    A plurality of bores  30  may be machined into the outer wall  24  so that the inner ends of a plurality of pinion shafts, such as pinion shafts  5  shown in  FIGS. 4A and 4B , may be supported therein. The bores  30  are machined such that the bores  30  extend a predetermined distance within the support ring  22 , such as a predetermined distance toward the center of the support ring  22 . The dimensions of the bores  30  may correspond to and/or may be substantially similar to the pinion shafts that may be supported therein. For example, in order to support cylindrical pinion shafts, the bores  30  may be circular and have at least a diameter equal to the pinion shafts  5 . 
         [0039]    Windows (or apertures)  32  may be formed in the faces  38  of the support ring  22 . The windows  32  may permit fluid communication with the faces  28  and the bores  30 . The windows  32  may be smaller in size than the bores  30 . It should be realized that the configuration of the support structure  20 , or any features thereof, may be machined from a solid or non-hollow body of any suitable shape or material; alternatively, the support structure  20 , or any features thereof, may be molded from powdered metal, a durable polymer, a composite material, or the like. Additionally, while the illustrative embodiment shows three bores  30  for supporting three pinion shafts  5 , it will be appreciated that any number of apertures for supporting any number of pinion shafts may be utilized. 
         [0040]    The windows  32  may be cut into or otherwise formed into the faces  28  of the support ring  22  such that lubricant coming from the center holes of the side gears  3  may flow into the faces  28  and into the bores  30  to reach the pinion shafts  5 . For example, if the support ring  22  is incorporated into the differential housing  1  of  FIGS. 4A and 4B , centrifugal force of the components of the differential housing  1  along with the surface tension of the lubricant may aid in permits lubricant to flow through the bores  30  and on the pinion shafts  5 . Lubrication of the pinion shafts  5  is typically needed or at least desirable between the inner bore of the pinion gears and pinion shafts  5 . The windows  32  may be used to aid in removing or assembling the pinion shafts  5  from or into the support structure  20 . 
         [0041]    One of ordinary skill in the art will appreciate various methods for manufacturing the support ring  22 . For example, one method may involve providing a non-hollow material, cutting the material into a desired thickness defined between the sidewalls  26 , and machining the faces  28  into the sidewalls  26 . In another embodiment, the support ring  22  may be cast into the desired thickness as a non-hollow material. In such an embodiment, if it is desired to have the faces  28  recessed into the sidewalls  26 , recesses may be machined into the sidewalls  26  or the faces  28  may be cast in such a manner. One or more of the bores  60  and one or more of the windows  32  may be machined, cast or otherwise formed into the outer wall  24  of the support ring  22 . 
         [0042]      FIGS. 5 and 6  illustrate an alternative embodiment of a support structure  100 . The support structure  100  comprises a generally non-hollow body  105  having side walls  120  extending between an inner wall  135  and an outer wall  110 . The side walls  120  may have faces  130 , which may be recessed toward the opposing sidewall  120 . The outer wall  110  may include one or more bores  140 , each capable of supporting the proximal end of a corresponding pinion shaft  5 . 
         [0043]    The faces  130  may have one or more apertures (or windows)  150  for providing fluid communication to the bores  140 . While the apertures  150  are illustrated as having circular cross-sections, it should be appreciated that any suitable cross-sectional shape may be employed, including but not limited to triangular, square, rectangular, hexagonal, octagonal, or the like. A hole  160  may also be included in the faces  130  to assist in the assembly and disassembly of the differential. In an embodiment, the hole  160  may be used similar to the apertures  150 , preferably only if the hole  150  terminates within the body of the support structure  100 . 
         [0044]    It should be realized that the configuration of the support structure  100 , or any features thereof, may be machined from a non-hollow body of any suitable shape or material; alternatively, the support structure  100 , or any features thereof, may be molded from powdered metal, a durable polymer, a composite material, or the like. Additionally, while the illustrative embodiment shows three bores  140  for supporting three pinion shafts  5 , it will be appreciated that any number of apertures for supporting any number of pinion shafts may be utilized. 
         [0045]    Referring again to  FIGS. 5 and 6 , the apertures  150  permit lubrication coming from the center holes of the side gears  3  to flow from the annular pockets  130  to the pinion shafts  5 . With the help of centrifugal force and surface tension, the lubricant may flow along the pinion shafts  5  into the interface between the inner bore of the pinion gears and pinion shafts to improve lubrication therebetween. 
         [0046]    The invention has been described above and, obviously, modifications and alternations will occur to others upon a reading and understanding of this specification. The claims as follows are intended to include all modifications and alterations insofar as they come within the scope of the claims or the equivalent thereof.