Abstract:
An arrangement for securely retaining a cross pin within a differential assembly includes a cross pin having a groove positioned proximate a recess formed in a differential housing. The recess and the groove define a retention passageway at least partially filled with molten resin. Solidified resin material positioned within the retention passageway retains the cross pin in the differential housing. Another embodiment cross pin retention system includes a pair of locking clips coupled to the cross pin. Each of the pinion gears of the differential assembly is retained between one of the locking clips and the differential housing.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to differentials for use in automotive drive lines and, more particularly, to a mechanism for retaining a cross pin within a differential case. 
     Many automotive drive axles include a hypoid gear set for changing the direction of power transmission from an axis parallel to the direction of vehicle travel to an axis perpendicular thereto. The hypoid gear set includes a ring gear coupled to the differential housing and a pinion gear generally supported within the axle housing. To facilitate proper function of the drive axle assembly, the differential is mounted on a pair of adjustable differential bearings. 
     In addition, some automotive drive axles include a differential assembly including a gear set which is supported within a differential housing to facilitate relative rotation between a pair of output shafts. The gear set typically includes a pair of helical side gears that are splined to the ends of axle shafts. The helical side gears are meshed with paired sets of helical pinions generally supported on a cross pin coupled to the differential housing. In response to speed differentiation between the output shafts, torque transmitted through meshed engagement of the side gears and pinions generates thrust forces that are exerted by the gear components against the wall surface of the differential housing to frictionally limit the speed differentiation and proportionally deliver torque between the output shafts. 
     At least one known differential retains the cross pin in the differential case via a lock screw or bolt. The lock screw is threadingly engaged with a tapped hole in the differential case and further protrudes into an aperture in the differential cross pin. Another known method of retaining the differential cross pin includes positioning a snap ring within a groove in the cross pin and a corresponding groove in the differential case. Unfortunately, these mechanisms require costly machining operations to be performed on the differential case, cross pin or both. Furthermore, the torquing operation required when using a threaded fastener is undesirably time consuming and cost prohibitive. Additionally, component tolerances result in the assembled cross pin having a degree of freedom or “end play” relative to the differential housing. Elimination of the torquing or lock ring assembly steps would be beneficial to reduce the time and cost required to manufacture a differential assembly. Elimination of cross pin end play provides a robust differential assembly less apt to generate noise or prematurely wear. 
     SUMMARY OF THE INVENTION 
     The present invention provides an arrangement for securely retaining the cross pin within the differential gear assembly. The improved arrangement for retaining the cross pin permits relatively simple and rapid assembly of the differential. Additionally, the present invention provides methods for producing a reduced cost differential requiring fewer components. Accordingly, costs are further minimized by reducing the time required to handle and install a fewer number of components. 
     In one embodiment of the present invention, a differential gear assembly includes a cross pin retention system having a cross pin with a groove positioned proximate a recess within a differential housing. The recess and the groove define a retention passageway at least partially filled with resin to retain the cross pin within the differential housing. This embodiment may be serviced by simply driving the cross pin to shear the solidified resin material. A snap ring is positioned within the retention passageway during re-assembly of the serviced differential gear assembly. 
     In another aspect of the present invention, an alternate embodiment differential gear assembly includes a pair of locking clips coupled to a cross pin. Each pinion gear is retained between one of the locking clips and the differential housing. In this embodiment, the differential housing is not machined to provide a port or passageway for molten resin material nor is the housing machined to provide clearance for a locking bolt. As such, a reduced cost differential assembly may be produced. 
     Other objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of an exemplary axle assembly equipped with the cross pin retention system of the present invention; 
     FIG. 2 is an exploded perspective view of a differential assembly having a first embodiment cross pin retention system of the present invention; 
     FIG. 3 is an end view of a differential housing constructed in accordance with the teachings of the present invention; 
     FIG. 4 is a cross-sectional side view of the differential housing depicted in FIG. 3; 
     FIG. 5 is a cross-sectional side view of a differential assembly including a first embodiment cross pin retention system of the present invention; 
     FIG. 5A is a fragmentary cross-sectional side view of the differential assembly of FIG. 5 after being reassembled using a snap ring; and 
     FIG. 6 is a cross-sectional side view of a differential assembly having a second embodiment cross pin retention system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     With reference to FIGS. 1 and 2, a cross pin retention system constructed in accordance with the teachings of an embodiment of the present invention is generally identified at reference numeral  10 . The cross pin retention system is shown operatively associated with an exemplary drive axle assembly  12 . As particularly shown in FIG. 1, drive axle assembly  12  is illustrated to generally include an axle housing  14  for rotatably mounting a hypoid gear set including a pinion gear  16  and a ring gear  18  drivingly interconnected to a differential assembly  20 . The differential assembly  20  functions to transfer power to a pair of axle shafts  22  and  23  while compensating for any difference in axle shaft speed rotation as may occur during a turn or other steering maneuver. In order to compensate for a differential in axle shaft rotational speed, differential assembly  20  includes a pair of pinion gears  24  and a pair of side gears  26  drivingly interconnected to the axle shafts. To facilitate proper function of the axle assembly  12 , differential assembly  20  is rotatably mounted on a pair of differential bearings  28 . More particularly, housing  14  includes two semi-circular journals (not shown) for supporting approximately one-half of the circumference of each of the differential bearings  28 . A pair of bearing caps  30  generally supports the remaining approximate one-half of each of the differential bearings  28 . Each bearing cap  30  is mounted to the axle housing  14  in a manner conventional in the art such as via threaded fasteners. 
     Referring to FIGS. 3-5, differential assembly  20  includes a differential case or housing  32 , a cross pin  34 , a pair of side gear washers  36  and a pair of pinion gear washers  38  as well as pinion gears  24  and side gears  26  previously introduced. Differential housing  32  includes an interior cavity  40  defined by a wall  42 . Differential housing  32  includes a pair of axially aligned openings  44  extending through wall  42  and interconnecting interior cavity  40  with an external surface  46  of differential housing  32 . Openings  44  are sized to rotatably support side gears  26 . Openings  44  also allow axle shafts  22  and  23  to be inserted within interior cavity  40  and engage internal splines  48  of side gears  26 . 
     Differential housing  32  also includes a first aperture  50  and a second aperture  52  substantially axially aligned with one another. Each of first and second apertures  50  and  52  extend through wall  42  to interconnect interior cavity  40  with external surface  46  of differential housing  32 . First aperture  50  includes a first recess  54  substantially annularly extending about a portion thereof. A first port  56  extends through wall  42  from external surface  46  to first recess  54 . Second aperture  52  includes a second recess  58 . A second port  60  extends through wall  42  and is positioned in communication with second recess  58 . 
     Cross pin  34  is a generally cylindrically-shaped member having a first end  62  and a second end  64 . First end  62  includes an annular groove  66 . Second end  64  includes an annular groove  68 . A pair of flats  70  (FIG. 2) are formed on cross pin  34  to function as lubricant reservoirs during operation. 
     FIG. 5 depicts a complete differential assembly  20  where cross pin  34  is positioned within first and second apertures  50  and  52 . Annular groove  66  is aligned with first recess  54  to define a first retention passageway  72 . Second end  64  of cross pin  34  is positioned within second aperture  52  such that an annular groove  68  is proximate second recess  58 . Second recess  58  and annular groove  68  define a second retention passageway  74 . 
     Pinion gears  24  are rotatably supported on cross pin  34 . Pinion gear washers  38  are positioned within interior cavity  40  between wall  42  and pinion gears  24 . Each of pinion gear washers  38  provide a thrust surface on which a pinion gear may bear. Similarly, side gear washers  36  are positioned between side gears  26  and differential housing  32 . 
     After the pinion gears and the side gears are positioned in meshing engagement with one another as shown in FIG. 5, a molten resin material  76  is introduced to retain cross pin  34  within differential housing  32 . Specifically, molten resin is injected within first port  56  and into first retention passageway  72 . The molten resin flows to fill first recess  54  and annular groove  66  thereby fixing the axial position of cross pin  34  relative to differential housing  32  once the resin solidifies. As a redundant retention measure, additional molten resin is injected within second port  60  and into second retention passageway  74 . The molten resin is injected to substantially fill second recess  58  and annular groove  68  to further couple cross pin  34  to differential housing  32 . As described above, cross pin  34  may be retained within differential. housing  32  without the use of a lock pin in a threaded bore. Additionally, cross pin  34  need not be cross drilled to accept a locking bolt. 
     It should be appreciated that differential assembly  20  is a serviceable assembly should the need arise. Because solidified resin material  76  exhibits substantially lower mechanical properties than cross pin  34  or differential housing  32 , differential assembly  20  may be disassembled by shearing solidified resin positioned within the retention passageways by driving cross pin  34  along its longitudinal axis. Once disassembled, the differential assembly may be serviced and reassembled by using a pair of standard snap rings  80  positioned within first retention passageway  72  (FIG. 5A) and second retention passageway  74 . 
     With reference to FIG. 6, a second embodiment cross pin retention system is depicted at reference numeral  100 . Second embodiment cross pin retention  100  is useful within a differential assembly including components very similar to those previously described. For clarity, like components are identified with the previously introduced reference numerals. 
     Cross pin retention system  100  includes a simplified differential housing  102  operating in conjunction with a modified cross pin  104  having locking rings  106  coupling cross pin  104  and differential housing  102 . Differential housing  102  is similar to previously described differential housing  32  as having a wall  107  defining an interior cavity  108 . Differential housing  102  includes a first aperture  109  interconnecting interior cavity  108  with an exterior surface.  110  of differential housing  102 . A second aperture  112  is aligned with first aperture  109 . Second aperture  112  also interconnects interior cavity  108  with exterior surface  110 . Based on the location of locking rings  106 , first aperture  109  and second aperture  112  need not include further geometrical features such as first recess  54  and second recess  58  of the previous embodiment. It should be appreciated that ports  56  and  60  may also be eliminated. Accordingly, the cost and time required to machine differential housing  102  is substantially reduced. 
     Cross pin  104  is a substantially solid cylindrical member having a first end  114  and a second end  116 . A first ring groove  118  and a second ring groove  120  are formed on cross pin  104  between first end  114  and second end  116 . An intermediate portion  122  of cross pin  104  is located between first ring groove  118  and second ring groove  120 . One skilled in the art will note that first end  114  and second end  116  of cross pin  104  are no longer cross-drilled for receipt of a lock bolt. As such, the cost of producing cross pin  104  is reduced. 
     To assemble the differential assembly equipped with cross pin retention system  100 , each of side gears  26  and side gear washers  36  are positioned as shown in FIG.  6 . Similarly, pinion gears  24  and pinion gear washers  38  are positioned within interior cavity  108  of differential housing  102 . At this time, cross pin  104  is slidingly disposed through first aperture  109 , apertures extending through pinion gears  24  and second aperture  112 . Locking rings  106  are coupled to cross pin  104 . One locking ring  106  is positioned within first ring groove  118 . Another locking ring  106  is positioned within second ring groove  120 . Each pinion gear  24  includes an end face  124  which abuts an outboard face  126  of each locking ring  106 . Based on the location of each of the components previously described, each pinion gear  24  is axially restrained on one side by locking ring  106 . Each pinion gear  24  is restrained from axially sliding away from locking ring  106  by pinion gear washer  38 , differential housing  102  and side gears  26 . Locking rings  106  also function to limit the axial movement of cross pin  104  by trapping intermediate portion  122  between each of pinion gears  24 . 
     The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations may be made therein without department from the spirit and scope of the invention as defined in the following claims.