Helical gear differential with geared lube pump

Details Helical gear differential with geared lube pump Helical gear differential with geared lube pump

2000-03-22

2001-12-04

Wright, Dirk (Department: 3681)

Planetary gear transmission systems or components

With lubricaton

For differential planetary gearing

C475S252000

Reexamination Certificate

active

06325737

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to differentials for use in automotive drivelines and, more particularly, to a lubricating system for a helical gear differential.
BACKGROUND OF THE INVENTION
Differentials of the type used in automotive drivelines generally include a planetary gearset supported within a differential casing to facilitate relative rotation (i.e., speed differentiation) between a pair of output shafts. The planetary gearset typically includes helical side gears fixed to the end of the output shafts, which are meshed with paired sets of helical pinion gears. Each pair of pinion gears is disposed in pinion bores formed in the differential casing. Since the pinion bores are parallel to the rotary axis of the differential casing, the pinion gears rotate on axes parallel to the common axis of the output shafts and the side gears. This type of differential is known as a parallel gear type differential. In response to speed differentiation between the output shafts, the torque transmitted through meshed engagement of the side gears and pinion gears generates thrust forces. These thrust forces are exerted against the wall surface of the gear pockets and other thrust surfaces within the differential casing by the gear components to frictionally limit speed differentiation and proportion torque between the output shafts.
In order to reduce friction and provide wear protection between the pinion gears and other contacting surfaces of the differential system, various lubrication methods have been developed. One such method, as disclosed in U.S. Pat. No. 5,310,389, employs radial lubrication orifices disposed in the differential casing. The radial lubrication orifices are formed radially outward from the pinion gear meshing sections. Lubrication oil is then introduced through the radial orifices of the differential casing to the pinion gears to provide lubrication. However, due to the size of the lubrication holes, this method may not provide sufficient lubricant flow to the pinion gears. Alternatively, another lubrication method, as disclosed in U.S. Pat. No. 5,711,737, employs a plurality of lubrication holes formed in an end of the differential casing to introduce lubrication oil into the differential casing. Each lubrication hole is positioned so that its center is positioned near the pinion gear meshing point. In operation, lubrication oil is introduced through the lubrication hole and into the meshing portion of the pinion gears due to the gear pumping effect of the pinion gears. However, due to the restriction of hole size and position, it is expected that this method may not provide an optimal lubrication system.
Accordingly, there exists a need in the relevant art to provide a lubrication system for a helical gear differential capable of maximizing the gear pumping effect for improved wear protection and reduced friction of the differential system. Furthermore, there exists a need in the relevant art to provide a simplified and cost effective method of manufacturing differentials.
SUMMARY OF THE INVENTION
In accordance with the broad teachings of this invention, a helical gear differential having an advantageous construction is provided.
It is an object of the present invention to provide a lubrication system for a helical gear differential capable of maximizing the gear pumping effect for improved wear protection and reduced friction and heat, which is superior to conventional differential lubrication systems in terms of function and simplified manufacture.
According to a preferred embodiment of the present invention, a differential casing is provided which is rotatable about an axis. The differential casing is generally cylindrically shaped and defines a first end surface and a second end surface. A pair of side gears is disposed within the differential casing and is individually rotatable about the axis. At least one pair of pinion bores are also formed in the differential casing and extend substantially through the second end surface of the differential casing. Pinion gears are slidably and rotatably disposed in the pinion bores for transmitting power from the engine to the pair of side gears. The pinion gears have rotational axes that are fixed in relation to the differential casing and are engaged with the pair of side gears. Each pair of pinion gears further include a mutually meshing portion, which extends beyond the second end surface of the differential casing. Such arrangement enables a gear pumping effect, caused by rotation of the meshing pinion gears, to pump lubricant from outside the differential casing into the casing for improved wear protection and reduced heat and friction. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.


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