Abstract:
A locking differential includes a housing with an interior chamber in which a two-piece split-center driver is located. The split-center driver is positioned on opposite sides of a cross-pin assembly. A pair of axially spaced output shafts extend from the interior chamber and are coupled to a pair of side gears. The split-center driver gear and a centered cam member are arranged co-axially about the adjacent ends of the output shafts, and annular clutch members are operable to disconnect an overrunning output shaft

Description:
TECHNICAL FIELD 
       [0001]    The present invention is generally directed toward a locking differential having a housing, gear members, and a set of cam members for automatically disengaging an overrunning output shaft. 
       BACKGROUND OF THE INVENTION 
       [0002]    Conventional locking differentials operate to automatically disengage an overrunning output shaft from a drive mechanism. The conventional locking differentials include a center cam for disengaging the overrunning output shaft and includes rings, commonly referred to as holdout rings, for maintaining the output shaft in a disengaged state as long as the overrun condition persists. In addition, the conventional locking differentials includes a spacer located between adjacent ends of co-axial output shafts to resist the axial forces which tend to displace the output shafts towards each other. Several types of conventional locking differentials are described in U.S. Pat. No. 4,557,158 to Dissett et al.; U.S. Pat. No. 4,644,818 to Choma et al.; U.S. Pat. No. 4,745,818 to Edwards et al.; and, U.S. Pat. No. 5,590,572 to Valente. 
       SUMMARY OF THE INVENTION 
       [0003]    In an example of the invention, a locking differential includes a two-piece split-center driver. The two-piece split-center driver was incorporated to provide an access window to allow installation or removal of any c-clips on the ends of the output shafts. The inclusion and configuration of the split-center driver may advantageously reduce unit costs and inventory costs with respect to assembling and maintaining the locking differential. In one embodiment, the locking differential includes the two-piece split-center driver positioned on opposite sides of a cross-pin assembly. 
         [0004]    In one aspect of the invention, a locking differential for driving a pair of output shafts includes a housing having a main body portion coupled to a removable end portion to define an interior chamber. The pair of output shafts extends in opposite directions from the interior chamber. The main body portion includes a radial flange extending from a periphery of the main body portion and a pair of side gears is positioned within the interior chamber. A first side gear is concentrically coupled and rotationally fixed to one of the output shafts and a second side gear is concentrically coupled and rotationally fixed to the oppositely extending output shaft. A pair of clutch gear members are slideably coupled to the side gears, such that the pair of clutch gear members are axially movable to maintain the locking differential in a disengaged state when the locking differential is in an overrunning condition, which occurs when one output shaft overruns the oppositely extending output shaft by a predetermined amount. 
         [0005]    The locking differential further includes a cross pin assembly having a cross pin extending through an opening in the main body portion of the housing and a cross pin support block positioned in a complementary shaped opening in the main body portion of the housing. Further, a two-piece split-center driver includes a first driver located on a first side of the cross pin assembly proximate the end portion of the housing and a second driver located on a second side of the cross pin assembly proximate the radial flange extending from the main body portion of the housing. A center cam member having an opening to receive the cross pin and co-axially aligned with the side gears and clutch gear members may cooperate with the pair of clutch gear members to disengage the side gears from the two-piece center driver when one of the output shafts is in the overrunning condition. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings: 
           [0007]      FIG. 1  is a cross-sectional view of a locking differential coupled to a casing and a ring gear, the locking differential having a split-center driver and a cross pin assembly according to an illustrated embodiment of the invention; 
           [0008]      FIG. 2  is a side elevational view of locking differential of  FIG. 1  having a two-piece split-center driver; 
           [0009]      FIG. 3  is a cross-sectional view the locking differential of  FIG. 2  taken along line  3 - 3  of  FIG. 2 ; 
           [0010]      FIG. 4  is an exploded, isometric view showing of the locking differential of  FIG. 2 ; 
           [0011]      FIG. 5  is a side elevational view of an output shaft extending from the locking differential of  FIG. 2  according to an illustrated embodiment of the invention; 
           [0012]      FIG. 6  is a top plan view of a clip for axially positioning the output shaft of  FIG. 5  in the locking differential of  FIG. 2  according to an illustrated embodiment of the invention; 
           [0013]      FIG. 7  is a perspective view showing one side of a two-piece split center driver used in the locking differential of  FIG. 2  according to an illustrated embodiment of the invention; and 
           [0014]      FIG. 8  is a perspective view of an opposite side of the two-piece split center driver of  FIG. 7  according to an illustrated embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIGS. 1-3  show a locking differential  100  having a housing  102  rotationally coupled to a casing  104  according to an illustrated embodiment of the invention. A pinion gear  106  drives a ring gear  108 , which in turn is coupled to the housing  102  using fasteners  109 , such as bolts  109 . In addition, the locking differential drives co-axially aligned output shafts  110 ,  112  that abut and extend outwardly from a cross pin assembly  114  located within the housing  102  and further located between a split-center driver  116 , which includes a first driver  118  that cooperates with the output shaft  110  and a second driver  120  that cooperates with the output shaft  112 . Additional details and advantages regarding the cross pin assembly  114  and the split-center driver  116  will be provided below. In the illustrated embodiments, like components retain their same reference numerals unless the components have been modified as part of an alternate embodiment in which they may then be provided with different reference numerals. 
         [0016]    The housing  102  includes a main body portion  102   a  and a removable end cap portion  102   b . The main body portion  102   a  is coupled to the end cap portion  102   b , for example with bolts  103 , to define an interior chamber  122 . In addition, a pair of side gears  124 ,  126  are rotationally fixed to portions of the output shafts  110 ,  112 , as illustrated. In one embodiment, the side gears  124 ,  126  are rotationally fixed to the portions of the output shafts  110 ,  112  with complementary splines located on the side gears  124 ,  126  and on the portions of the output shafts  110 ,  112 , respectively. By way of example, output shaft splines  127  are best shown in  FIG. 6  on output shaft  110 . A pair of clutch gear members  128 ,  130  are slideably coupled to the side gears  124 ,  126 .  FIG. 2  shows the cross pin assembly  114  having a cross pin  132  and a cross pin support block  134 . Holdout rings  133  are used to hold clutch gear members  128 ,  130  in a disengaged state. 
         [0017]    Now referring to  FIG. 4 , the cross pin  132  extends diametrically through an opening  136  in the housing  102  and through an opening  138  in the cross pin support block  134  to secure the assembled components within the interior chamber  122  of the housing  102 . In turn, the cross pin support block  134  is sized to be received into a complementary shaped opening  140  formed in the housing  102 . In one embodiment, the cross pin assembly  114  is coupled to the housing  102  with an elongated fastener  141  (also shown in  FIG. 1 ). As noted above, the cross pin assembly  114  prevents the output shafts  110 ,  112  from being axially displaced in the same direction. The cross pin  132  may have a cylindrical body portion that abuts an end surface  135  of the output shaft  110  ( FIG. 6 ) and abuts an end surface (not shown) of the output shaft  112 . By configuring the cross pin assembly  114  as separate components, instead of a conventional one-piece pin with an integrally attached head (re: U.S. Pat. No. 5,590,572), which has been reported as being more difficult to manufacture and more costly to replace, the cross pin assembly  114  may be manufactured and provided as an interchangeable component. 
         [0018]    The locking differential  100  further includes a center cam member  142  having a key  144 , which may take the form of a protuberance or a recess formed in the cam member  142 . One purpose of the key  144  is to limit an amount of angular movement of the cam member  142  relative to the split-center driver  116  by cooperation between complementary keys  146  (as best shown in  FIG. 9  with respect to the second driver  120 ) formed on both the first driver  118  (not shown) and the second driver  120 . In one embodiment, the key  144  on the cam member  142  takes the form of a recess and the keys  146  on the first and second drivers  118 ,  120  take the form of a protruding, complementarily shaped member. In another embodiment, the key  144  on the cam member  132  protrudes while the keys  146  on the first and second drivers  118 ,  120  take the form of recesses. In addition, the center cam member  142  may be coupled to the first and/or second drivers  118 ,  120  with snap rings  148 ,  150  to prevent relative axial movement therebetween. Referring back to  FIGS. 3 and 4 , springs  152 ,  154  may be used to re-engage the clutch gear members  128 ,  130  with the drivers  118 ,  120  when the locking differential  100  is not in an overrunning condition. 
         [0019]    Referring now to  FIGS. 6 and 7 , the output shaft  110  may be restrained from axial displacement (i.e., axial means along a rotational or centerline axis  156  of the locking differential  100 ) with a clip  158 , which may take the form of c-clip, snap ring, or some equivalent coupling mechanism. In the illustrated embodiment, the clip  158  is a c-clip located within a groove  162  formed in the output shafts  110 . Although not shown in  FIG. 6 , the output shaft  112  may be restrained in a similar fashion using a clip identical to clip  158 . Accordingly, one purpose of the clip  158  is to prevent relative axial motion between the output shafts  110 ,  112  and the side gears  124 ,  126 , respectively. 
         [0020]      FIGS. 8 and 9  show the split-center driver  116 , where  FIG. 8  shows the first driver  118  and  FIG. 9  shows the second driver  120 . In the illustrated embodiment, the split center driver  116  is a two-piece component and as noted above, the first driver  118  is positioned on one side of the cross-pin assembly  114  and the second driver  120  is positioned on the other side of the cross-pin assembly  114 . The first and second drivers  118 ,  120  each include external splines  166 , laterally projecting members  168  for engaging the clutch gear members  128 ,  130 , a substantially planar surface  170  located on an opposite side of the driver from the laterally projecting members  168 , and a clearance recess  172  formed in the substantially planar surface  170 . In one embodiment, the clearance recess  172  is configured to permit access to the clip  158  ( FIG. 7 ) located in a central portion of the locking differential  100  ( FIG. 1 ). Advantageously, the two-piece split-center driver  116  permits easier access and assembly of the locking differential  100  ( FIG. 1 ). In addition, the first and second drivers  118 ,  120  are less complex to manufacture and may be interchangeable, and thus less costly to maintain in inventory. Consequently, the locking differential  100 , as described herein and claimed hereinafter, may operate to eliminate the need for a single or one-piece center driver. 
         [0021]    While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.