Planetary gear transmission systems or components – Differential planetary gearing – Bevel gear differential
Reexamination Certificate
2000-05-15
2001-11-20
Marmor, Charles A (Department: 3681)
Planetary gear transmission systems or components
Differential planetary gearing
Bevel gear differential
Reexamination Certificate
active
06319166
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE DISCLOSURE
The present invention relates generally to differential mechanisms, and more particularly, to such mechanisms of the type commonly referred to as “locking differentials”.
Differential gear mechanisms of the type to which the present invention relates are broadly referred to as “limited slip” differentials, and typically include a clutch pack which is operable to limit or retard differentiating action between the output gears (side gears). More specifically, however, the present invention is intended for use on limited slip differentials of the specific type referred to as locking differentials, and will be described in connection therewith. In a locking differential, some means is provided for engaging or locking the clutch set, rather than permitting it to slip, to reduce substantially (and perhaps even eliminate) the amount of differentiating action permitted between the side gears.
Locking differentials of various types are now generally well known in the art, including both inter-axle lockers, and inter-wheel lockers. Inter-wheel locking differentials may be applied to either conventional rear wheel drive vehicles, or to front wheel drive vehicles. Although the present invention may be utilized advantageously in any of the above-described types of locking differentials, it is especially advantageous when applied to an inter-wheel, rear axle locking differential, and will be described in connection therewith.
As is now quite well know to those skilled in the vehicle drive line art, one of the major problems involves the limited amount of space available for the various drive train components and accessories. In many vehicles, the engine and drive train have become increasingly efficient, resulting in higher output torques, but with no increase in the size of the differential or of its components. The lack of space becomes especially difficult in the case of a component such as a locking differential which replaces an earlier, standard component such as an open differential. In certain vehicle applications, a proposed locking differential can be no larger, radially, than the open differential previously used in that application, because any increase in the diameter of the differential case would necessitate a larger ring gear, which, in turn, would require substantial redesign of the entire rear axle assembly.
In a conventional locking differential of the type commercialized by the assignee of the invention, there is included a lockup means for locking up the differential gear set, and an actuating means for actuating the lockup means. Typically, the lockup means comprises a clutch pack and a cam arrangement in which, when the cam members “ramp up”, one member moves axially and applies a compressive load to the clutch pack. The actuating means includes a rotatable flyweight mechanism and a latch mechanism which is moveable between an operative position and an inoperative position. In the operative position, the latch mechanism engages the flyweight mechanism to prevent rotation thereof, and actuate the cam arrangement of the lockup means. In the inoperative position, the latch mechanism is incapable of engaging the flyweights. Typically, the inoperative condition occurs when the rotational speed of the differential gear case exceeds a predetermined limit, by way of example only, corresponding to a vehicle speed of about 20 or 25 mph.
As is well know to those skilled in the art, the performance of an actuating means of the type to which the present invention applies can be improved by increasing the size of the flyweight mechanism, and by increasing the weight of the latch mechanism. However, in prior art locking differentials which have been made commercially, the flyweight mechanism and the latch mechanism have been disposed circumferentially adjacent each other (within one of the windows of the differential case). Thus, an attempt to improve the prior art, commercially available locking differential design by increasing the size of the flyweight mechanism or by increasing the weight of the latch mechanism would be inconsistent with the need to achieve the minimum overall size of the differential mechanism.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a differential gear mechanism of the locking differential type which, in terms of size, can be a direct replacement for an open differential.
It is a more specific object of the present invention to provide a locking differential which achieves the above-stated object while still making it possible to improve the performance of the actuating means.
It is another object of the present invention to provide such an improved locking differential which achieves the above-stated objects, and in which the latch mechanism is relatively simple and inexpensive, and facilitates easy installation.
The above and other objects of the invention are accomplished by the provision of an improved differential gear mechanism comprising a gear case defining a gear chamber, a differential gear set disposed in the gear chamber, and including at least one input gear and a pair of output gears defining an axis of rotation. A lockup means for locking up the differential gear set to retard differentiating action is included and actuating means for actuating the lockup means. The lockup means includes a clutch pack operable between an engaged condition, effective to retard relative rotation between the gear case and the output gears, and a disengaged condition. The lockup means further includes cam means operable to effect the engaged condition of the clutch pack, the actuating means including retarding means operable to engage the cam means and retard a portion of the cam means. The retarding means comprises a flyweight mechanism rotatable about its axis at a speed generally proportional to the level of differentiating action, and defining a stop surface moveable from a retracted position to an extended position in response to a predetermined level of differentiating action. The actuating means further includes a latch mechanism including a latch member and means biasing the latch member toward an operative position in which the latch member is disposed to engage the stop surface when the stop surface is in the extended position. The latch mechanism further includes a weight disposed oppositely from the latch member, about the axis of rotation, the weight being operable to move the latch mechanism, in opposition to the biasing means, along a straight, generally diametrally-oriented path in response to a predetermined rotational speed of the differential gear mechanism, to move the latch member from the operative position to an inoperative position, above the predetermined rotational speed.
The improved differential gear mechanism is characterized by the latch mechanism comprising an integral, generally U-shaped member, including a bottom portion and a pair of upright leg portions. The bottom portion of the U-shaped member defines the latch member formed integrally therewith. The pair of upright leg portions of the U-shaped member extend past the axis of rotation, the weight being fixed to the leg portions.
In accordance with a more limited aspect of the invention, the differential gear mechanism is characterized by the differential gear set comprising a pair of input gears mounted for rotation about a pinion shaft fixed relative to the gear case, the pinion shaft defining an axis disposed perpendicular to the axis of rotation of the output gears. Each of the upright leg portions of the U-shaped member is itself generally U-shaped and comprises a pair of oppositely disposed individual leg portions, the individual leg portions being disposed on opposite sides of the pinion shaft.
REFERENCES:
patent: Re. 28004 (1974-05-01), Otteman
patent: 3517573 (1970-06-01), Roper
patent: 3606803 (1971-09-01), Otteman
pate
Binkley Carl R.
Holmquist Ralph E.
Konkle Phillip E.
Kyle Robert J.
Morgensai Keith E.
Eaton Corporation
Kasper L. J.
Marmor Charles A
Pang Roger
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