Planetary gear transmission systems or components – Differential planetary gearing – Bevel gear differential
Reexamination Certificate
2003-02-17
2004-10-12
Pang, Roger (Department: 3681)
Planetary gear transmission systems or components
Differential planetary gearing
Bevel gear differential
Reexamination Certificate
active
06802793
ABSTRACT:
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.
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Endreszl Joseph M.
Zink Frederick E.
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