Abstract:
A differential having four pinions supported for rotation on cross pins within a differential case. The differential employs a retainer system for securing the cross pins relative to the differential case. The retainer system can include a collar and a plurality of pin members.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/237,726 filed on Sep. 25, 2008, now U.S. Pat. No. 7,901,318. This application claims the benefit of U.S. Provisional Application No. 60/975,613, filed on Sep. 27, 2007. The entire disclosures of each of the above applications are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure generally relates to vehicle drivelines and more particularly to a differential for a vehicle driveline. 
     One type of automotive differential employs a differential housing, a pair of bevel side gears and a plurality of bevel pinions. Some application employ a single pair of bevel pinions that are meshingly engaged with the bevel side gears and supported for rotation in the differential housing about an axis via a single pinion shaft. Vehicle differentials configured for heavier duty applications typically employ two pair of bevel pinions that are meshingly engaged with the bevel side gears. A first pair of the bevel pinions are supported for rotation about a first pinion axis by a first pinion shaft, while a second pair of the bevel pinions are supported about a second pinion axis by a second pinion shaft. In some heavy duty differentials, the first and second pinion shafts are part of a unitarily formed cross-shaped structure. Some other heavy duty differentials employ a configuration in which an aperture or notch is formed in one or both of the first and second pinion shafts. The aperture or notch in one of the first and second pinion shafts provides clearance for the other one of the first and second pinion shaft. Still other heavy duty differentials employ a configuration in which the second pinion shaft is formed by two shaft members that terminate proximate the first pinion shaft. Examples of this configuration include certain models of the TracRite® differential that are commercially available from American Axle &amp; Manufacturing, Inc., Detroit, Mich. and U.S. Pat. No. 7,155,997, the disclosure of which is hereby incorporated by reference as if fully set forth in detail herein. 
     While such configurations are relatively robust, the coupling of the first and second pinion shafts to the differential housing can be complex and/or costly. Accordingly, there remains a need in the art for an improved heavy duty differential having multiple pinion shafts that can be robustly secured relative to the differential housing in a relatively simple, efficient and cost-effective manner. 
     SUMMARY 
     In one form, the present teachings provide a differential for an automotive driveline. The differential includes a differential housing, first and second bevel side gears, a first pinion shaft, a first set of bevel pinions, a second set of bevel pinions and a retainer assembly. The differential housing defines an internal cavity, an axle bore and first and second pinion bores. The axle bore is disposed through the differential housing and intersects the internal cavity. The axle bore is disposed about a rotational axis of the differential housing. The first and second pinion bores are perpendicular to one another and perpendicular to the rotational axis. The first and second bevel side gears are received in the internal cavity and disposed about the rotational axis. The first pinion shaft is received in the first pinion bore and coupled to the differential housing. The first set of bevel pinions are rotatably disposed on the first pinion shaft and meshingly engaged with the first and second bevel side gears. The second set of bevel pinions is meshingly engaged with the first and second bevel side gears. The retainer assembly is received in the second pinion bore and supports the second set of bevel pinions for rotation thereon. The retainer assembly includes a collar, first and second pin portions and a plurality of pin members. The collar is an annular structure that is disposed about the rotational axis radially inwardly of the first and second sets of bevel pinions. The collar has a first set of collar apertures, a second set of collar apertures, a first pin member aperture, and a pair of second pin member apertures. The first pin member aperture is formed transverse to and intersects the first set of collar apertures. The second pair of pin member apertures are spaced apart from one another and are formed transverse to and intersect the second set of pin member apertures. The first pinion shaft is received through the first set of collar apertures. The first pin portion is received in a first side of the second pinion bore, a first one of the second set of bevel pinions and the second set of collar apertures. The second pin portion is received in a second side of the second pin bore, a second one of the second set of bevel pinions and the second set of collar apertures. The first pin member is received into the first pin member aperture and a hole formed in the first pinion shaft. The second pin members are received into respective ones of the second pin member apertures and respective holes formed in the first and second pin portions. 
     In another form, the present teachings provide a method for assembling an automotive differential. The method includes: providing a differential case having an internal cavity; installing a first bevel side gear into the internal cavity for rotation about a rotational axis; meshingly engaging a first set of bevel pinions to the first bevel side gear for rotation about a first pinion axis; meshingly engaging a second set of bevel pinions to the first bevel side gear for rotation about a second pinion axis; positioning a collar in the internal cavity radially inwardly of the first and second sets of bevel pinions; installing first and second pin portions to the first set of bevel pinions, each of the first and second pin portions extending through the collar, through an associated one of the first set of bevel pinions and engaging the differential case; installing a first pinion shaft to the second set of bevel pinions, the first pinion shaft extending through the collar and the second set of bevel pinions, the first pinion shaft having opposite ends that engage the differential case; installing a first pin member through the collar and the first pinion shaft; installing a second pin member through the collar and the first pin portion; and installing a third pin member through the collar and the second pin portion. 
     In a further form, the present teachings provide a differential for an automotive driveline. The differential can include a differential housing, first and second side gears, which are received in the differential housing and disposed about a rotational axis, a first pinion shaft, which is received through the differential housing, first and second sets of bevel pinions and a retainer assembly. The first set of bevel pinions is rotatably disposed on the first pinion shaft and are meshingly engaged with the first and second bevel side gears. The second set of bevel pinions are meshingly engaged with the first and second bevel side gears. The retainer assembly includes a retainer structure, first and second pin portions and a plurality of pin members. The retainer structure is disposed radially inwardly of the first and second sets of bevel pinions. The first and second pin portions and the first pinion shaft cooperate to non-rotatably couple the retainer structure to the differential housing. The pin members are received longitudinally into a wall of the retainer structure. 
     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. 
    
    
     
       DRAWINGS 
       Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a schematic illustration of an exemplary vehicle having a differential unit constructed in accordance with the teachings of the present disclosure; 
         FIG. 2  is a partially broken away perspective view of a portion of the vehicle of  FIG. 1  illustrating the rear axle assembly in more detail; 
         FIG. 3  is a sectional view of a portion of the vehicle of  FIG. 1 , illustrating the differential unit in longitudinal cross section; 
         FIG. 4  is a sectional view taken along the line  4 - 4 ; 
         FIG. 5  is an enlarged portion of  FIG. 4 , illustrating a portion of the differential unit where the first and second pin portions abut the first pinion shaft. 
         FIGS. 6 and 7  are similar to  FIG. 5  but illustrate different end conditions of the first and second pin portions; 
         FIG. 8  is a sectional view similar to  FIG. 3 , but illustrating another differential unit constructed in accordance with the teachings of the present disclosure; 
         FIG. 9  is a perspective view of a portion of the differential unit of  FIG. 8 ; and 
         FIG. 10  is a sectional view of a portion of another differential constructed in accordance with the teachings of the present disclosure, the sectional view being taken longitudinally through the first and second pin portions and the first pinion shaft. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1  of the drawings, a vehicle having a differential assembly that is constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral  10 . The vehicle  10  can include a driveline  12  that is drivable via a connection to a power train  14 . The power train  14  can include an engine  16  and a transmission  18 . The driveline  12  can include a drive shaft  20 , a rear axle  22  and a plurality of wheels  24 . The engine  16  can be mounted in an in-line or longitudinal orientation along the axis of the vehicle  10  and its output can be selectively coupled via a conventional clutch to the input of the transmission  18  to transmit rotary power (i.e., drive torque) therebetween. The input of the transmission  18  can be commonly aligned with the output of the engine  16  for rotation about a rotary axis. The transmission  18  can also include an output and a gear reduction unit. The gear reduction unit can be operable for coupling the transmission input to the transmission output at a predetermined gear speed ratio. The drive shaft  20  can be coupled for rotation with the output of the transmission  18 . Drive torque can be transmitted through the drive shaft  20  to the rear axle  22  where it can be selectively apportion in a predetermined manner to the left and right rear wheels  24   a  and  24   b , respectively. 
     With additional reference to  FIG. 2 , the rear axle  22  can include a differential assembly  30 , a left axle shaft assembly  32  and a right axle shaft assembly  34 . The differential assembly  30  can include a housing  40 , a differential unit  42 , an input pinion  44  and a ring gear  46 . The housing  40  can support the differential unit  42  for rotation about a first axis  48  and can further support the input pinion  44  for rotation about a second axis  50  that can be perpendicular to the first axis  48 . 
     The housing  40  can be initially formed in a suitable casting process and thereafter machined as required. The housing  40  can include a wall member  52  that can define a central cavity  54  having a left axle aperture  56 , a right axle aperture  58 , and an input shaft aperture  60 . 
     The left axle shaft assembly  32  can include a first axle tube  62  fixed to the left axle aperture  56  and a first axle half-shaft  64  that can be supported for rotation in the first axle tube  62  about the first axis  48 . Similarly, the right axle shaft assembly  34  can include a second axle tube  66  that can be fixed to the right axle aperture  58  and which can support a second axle half-shaft  68  for rotation about the first axis  48 . 
     The input pinion  44  can be disposed in the input shaft aperture  60  and can meshingly engage the ring gear  46 , which can be fixedly but removably coupled to the differential unit  42 . It will be appreciated that rotary power transmitted to the input pinion  44  from the drive shaft  20  is employed to drive the differential unit  42  about the first axis  48  via the ring gear  46  in a conventional manner. The differential unit  42  can transmit drive torque to the first and second axle half-shafts  64  and  68  in a predetermined manner. 
     With additional reference to  FIGS. 3 and 4 , the differential unit  42  can be disposed within the central cavity  54  of the housing  40  and can include a differential housing  100 , first and second bevel side gears  102  and  104 , respectively, a first set of bevel pinions  106 , a second set of bevel pinions  108 , a first pinion shaft  110  and a retainer system  112 . 
     The differential housing  100  can include a differential case  120  and a differential cover  122 . The differential case  120  can have a body  126  and a flange  128  that can be disposed generally perpendicular to the rotational axis  48   a  of the differential unit  42 . The body  126  can define an internal cavity  130 , a first axle bore  132 , a first pinion shaft bore  134  and a second pinion shaft bore  136 . The first axle bore  132  can be disposed about the rotational axis  48   a  of the differential unit  42  and can intersect the internal cavity  130  on an end of the body  126  opposite the flange  128 . The first pinion shaft bore  134  can extend through the body  126  along a first pinion axis  144  that is generally perpendicular to the rotational axis  48   a  of the differential unit  42 . The second pinion shaft bore  136  can extend through the body  126  along a second pinion axis  146  that is generally perpendicular to both the rotational axis  48   a  of the differential unit  42  and the first pinion axis  144 . The differential cover  122  can be coupled to the differential case  120  to substantially close an end of the differential case  120  opposite the first axle bore  132 . The differential cover  122  can define a second axle bore  152  that can be arranged about the rotational axis  48   a  of the differential unit  42 . The first and second axle bores  132  and  152  can be sized and shaped to engage an end of an associated one of the first and second axle half-shafts  64  and  68  ( FIG. 2 ) in a conventional manner that permits drive torque to be transmitted between the differential housing  100  and the first and second axle half shafts  64  and  68  ( FIG. 2 ). 
     The first and second bevel side gears  102  and  104  can be conventional in their construction and as such, need not be discussed in significant detail herein. Briefly, the first and second bevel side gears  102  and  104  can include a plurality of gear teeth  160  and a central splined aperture  162  that is configured to non-rotatably but axially silde-ably engage a corresponding one of the first and second axle half shafts  64  and  68  ( FIG. 2 ) to permit drive torque to be transmitted between the first and second bevel side gears  102  and  104  and the first and second axle half shafts  64  and  68  ( FIG. 2 ). The first and second bevel side gears  102  and  104  can be received in the internal cavity  130  on opposite sides of the differential case  120  such that they are aligned about the rotational axis  48   a  of the differential unit  42  and abutted against the differential case  120  and the differential cover  122 , respectively. 
     The first and second sets of bevel pinions  106  and  108  can be can be conventional in their construction and as such, need not be discussed in significant detail herein. Briefly, the first and second sets of bevel pinions  106  and  108  can include gear teeth  170  that can meshingly engage the first and second bevel side gears  102  and  104 , a surface  172  opposite the gear teeth  170  that can be configured to engage the differential case  120 , and a through bore  174 . In the particular example provided, the opposite surface  172  is arcuate in shape and conforms to the arcuate recesses  176  that are formed in the internal cavity  130  of the differential case  120  at the locations where the first and second pinion shaft bores  134  and  136  intersect the interior side of the wall of the differential case  120 . The first set of bevel pinions  106  can include a first pinion  106   a  and a second pinion  106   b  that can be received in the arcuate recesses  176  that are associated with the first pinion shaft bore  134 . The second set of bevel pinions  108  can include a first pinion  108   a  and a second pinion  108   b  that can be received in the arcuate recesses  176  that are associated with the second pinion shaft bore  136 . 
     The first pinion shaft  110  can be received in the first pinion shaft bore  134  and through the through bores  174  in the first and second pinions  106   a  and  106   b  of the first set of bevel pinions  106 . 
     The retainer system  112  can include a second pinion shaft  200 , a collar  202  and a plurality of pin members  204 . The second pinion shaft  200  can support the second set of bevel pinions  108  for rotation in the internal cavity  130  about the second pinion axis  146 . The second pinion shaft  200  can include a first pin portion  210  on which the first pinion  108   a  is rotatably disposed, and a second pin portion  212  on which the second pinion  108   b  is rotatably disposed. The first and second pin portions  210  and  212  can be received in the second pinion shaft bore  136  along the second pinion axis  146 . In the particular example provided, the first and second pin portions  210  and  212  are discrete cylindrically-shaped members having inner ends  214  that are generally flat and orthorgonal to the second pinion axis  146  as shown in  FIG. 5 . It will be appreciated, however, that the first and second pin portions  210  and  212  could have inner ends  214  that conform to a shape of at least a portion of the first pinion shaft  110 , an example of which is shown in  FIG. 6  or engage one or more holes  216  that can be formed in the first pinion shaft  110  as shown in  FIG. 7 . 
     Returning to  FIGS. 3 and 4 , the collar  202  can be disposed in the internal cavity  130  radially inward of the first and second sets of bevel pinions  106  and  108 . The collar  202  can be an annular structure having a first set of apertures  230 , which can be sized to receive the first pinion shaft  110  therethrough, and a second set of apertures  232  that are sized to receive the first and second pin portions  210  and  212  therethough. Accordingly, it will be appreciated that the collar  202  supports the first and second pin portions  210  and  212  on a side opposite the wall of the differential case  120 . The collar  202  can have a width that can be sufficient to fully support the first pinion shaft  110  and/or the first and second pin portions  210  and  212  (i.e., the outer ends of the first pinion shaft  110  and/or the outer ends of the first and second pin portions  210  and  212  need not engage the differential case  120 ). 
     The pin members  204  can include a first set of pin members  260  and a second set of pin members  262 . While the first and second sets of pin members  260  and  262  can be any type of pins, roll pins are employed in the example illustrated. The first set of pin members  260  can be received through holes  270  formed through the collar  202  and holes  272  formed through the first pinion shaft  110 . In the example provided, the first set of pin members  260  includes a pair of pin members, but it will be appreciated that the first set of pin members  260  could include a single pin member. The second set of pin members  262  can be received through holes  274  formed through the collar  202  and holes  276  formed through the first and second pin portions  210  and  212 . 
     The first and second sets of pin members  260  and  262  can be installed to the holes  270  and  274 , respectively, and the holes  272  and  276 , respectively, in a direction that can be generally parallel to the rotational axis  48   a  of the differential unit  42 . Accordingly, it will be appreciated that the first and second pinion shafts  110  and  200  can be secured to one another in a cost-efficient manner. 
     While the retainer system  112  has been illustrated and described herein as including a plurality of discrete pin members, it will be appreciated that a differential constructed in accordance with the teachings of the present disclosure could be constructed somewhat differently. For example, the retainer system  112   a  could include a plate member  320  to which one or more of the pin members  204   a  can be coupled as shown in  FIGS. 8 and 9 . The pin members  204   a  can be coupled to the plate member  320  in any appropriate manner, such as press-fit, welded (e.g., friction welded, resistance welded) or integrally formed with the plate member  320 . One or more of the pin members  204   a  can include a protrusion, such as a tab or circumferentially-extending rib or bead  322  that can be sized to frictionally engage the collar  202   a  on a side opposite the first pinion shaft  110  and/or the first and second pin portions  210  and  212  to thereby resist withdrawal of the pin member(s)  204   a  from the collar  202   a.    
     In the example of  FIG. 10 , the first pinion shaft  110   b  is relatively larger in diameter than the second pinion shaft  200   b . An aperture  400  can be formed through the first pinion shaft  110   b  through which the second pinion shaft  200   b  can extend. Configuration in this manner permits the first and second pin portions (not specifically shown) to be a part of a unitary structure. 
     While the invention has been described in the specification and illustrated in the drawings with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined in the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the invention will include any embodiments falling within the foregoing description and the appended claims.