Limited slip differential

Details Limited slip differential Limited slip differential

2000-03-03

2002-06-11

Marmor, Charles A (Department: 3681)

Planetary gear transmission systems or components

Differential planetary gearing

Spur gear differential

C475S249000

Reexamination Certificate

active

06402656

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to differentials and more particularly to limited-slip differentials.
2. Background Art
An axle with a wheel affixed to each end may be driven by a power source to propel a vehicle in a substantially straight line. However, when making either a left or right turn, the wheel on the outer end of the axle travels a greater distance than the wheel on the inner end of the axle, causing the outer wheel to rotate faster than the inner wheel. This generally leads to twisting of the axle, and often results in wheel hop and/or axle breakage.
Differentials having a single input member, which drive two output members in a manner that permit the speeds of each of the output members to differ have been known. Differentials emerged from the need to have both output wheels of a driven axle to rotate at different speeds. Typical current day differentials still remain quite similar to the first known successful differential, invented in 1827 by Onesiphore Pecqueur, a Frenchman. Today's differentials have an input gear that meshes with a ring gear, as in the earlier differential by Pecqueur. The ring gear drives a casing that carries bevel toothed pinions, which mesh with left and right side gears that power the left and right wheels, respectively. Both wheels rotate at the same speed, when the wheels travel a straight line, causing the pinions to remain stationary in the rotating casing. When making a turn, the pinions allow the wheels to rotate at different speeds, by rotating at their respective axes in the rotatable casing.
Torque from the input gear is split into two substantially equal components, which are distributed substantially equally to the left and right wheels. Consequently, if one of the driven wheels rotates on ice or mud, the wheel on the ice or mud spins, while torque to the wheel not on the ice or mud is reduced. This condition increases the risk of a motor vehicle having such a differential of becoming immobilized on substantially slippery surfaces.
When a motor vehicle travels in a curvilinear direction, such as when the vehicle turns left or right, or travels in a direction other than a straight line, such as on dry pavement, a relatively small speed difference occurs between the left and right wheels. However, when the vehicle travels on ice, snow, or through mud, the differential speed between the left and right wheels increases substantially beyond the relatively small speed difference which occurs between the wheels on dry pavement. In this instance “slip limitation” is desirable otherwise the vehicle may become immobilized. On the other hand, slip limitation is not desirable in normal driving situations since slip limitation may adversely affect directional control of the vehicle and accelerate tire wear.
“Limited slip differentials” have been known, which limit the speed differentiation or “slip,” so that some of the torque being delivered by the input gear is transferred from the wheel that slips to the wheel that has more traction, and, therefore, aids in moving the vehicle in the preferred direction.
These limited slip differentials (LSD) have been developed to overcome the above mentioned shortcomings of a conventional differential, and work on various principles, but generally are all intended to limit the speed difference or “slip” between the left and right driven wheels. Such limited slip differentials generally limit the speed differentiation or “slip” between the driven wheels, so that some of the torque being delivered by the input gear is transferred from the wheel that slips to the wheel that has more traction, and, therefore, aids in moving the vehicle in the preferred direction. However, most of these limited slip differentials do not limit the speed difference between the driven wheels adequately at a substantially large speed differential or slip between the driven wheels. Other limited slip differentials have valves, clutches, pistons or other special components that add to the complexity and cost of production.
There is a need for a limited slip differential, which limits the speed differentiation or “slip” between the driven wheels, and gradually increases torque to the non-slipping wheel, as the rotational speed difference between the slipping wheel and the non-slipping wheel increases. The rate of increase of the torque to the non-slipping wheel should increase, as the speed difference between the slipping wheel and the non-slipping wheel increases. The rate of increase of the torque applied to the non-slipping wheel should preferably increase at a greater rate than the rate of increase of the speed difference between the wheels. Torque transfer should be substantially zero or minimal between both driven wheels, when there is substantially no speed difference or slip between the driven wheels, since such torque transfer is not required when there is substantially no speed difference or slip between the driven wheels. The rate of increase of the torque applied to the non-slipping wheel should be adjustable by modifying physical characteristics of the limited slip differential. Such limited slip differentials should be inexpensive, durable, long lasting, easy to manufacture and install, either as an original equipment item or as a retrofit, easy to maintain, and require a minimum of maintenance.
When applied to a motor vehicle, the limited-slip differential should provide slip limitation or torque transfer substantially only when speed difference between the driven wheels of the motor vehicle is beyond normal driving limits. The torque transfer should increase as the speed difference between the driven wheels increases, and aid in decreasing the probability of a vehicle becoming immobilized during slippery conditions. The rate of increase of the torque applied to the non-slipping wheel should preferably increase at a greater rate than the rate of increase of the speed difference between the driven wheels. Such limited slip differentials should be inexpensive, durable, long lasting, sturdy, easy to manufacture and install, either as an original equipment item or as a retrofit, be capable of having a substantially similar form factor and size as original equipment items, be easy to maintain, and require a minimum of maintenance. The limited slip differential should also be compatible with anti-lock braking systems, two, four, and multiple drive vehicles, and be useable in vehicle and other applications.
Different limited slip differentials have heretofore been known. However, none of the limited slip differentials adequately satisfies these aforementioned needs.
Mechanical limited slip differentials have been disclosed. U.S. Pat. No. 4,516,443 (Hamano et al) and U.S. Pat. No. 4,939,953 (Yasui) disclose mechanical limited slip differentials, each having a set of clutches connected to a casing, which alternate with another set of clutches attached to one or two side gears. The clutches are kept in contact by a preloaded spring, through which both wheels are always contacted to some extent. These limited slip differentials “bind” the wheels together, starting with a specified amount of torque, but increasing the slip limitation when the input torque increases. Therefore, there is always a certain amount of torque transfer between the left and right wheel, even in normal driving when it is not needed.
Parallel-axis limited slip differentials have been disclosed. U.S. Pat. No. 5,244,440 (Ichiki et al) discloses a parallel-axis differential having a plurality of pinions, in which friction produced by meshing and rubbing of the pinions provides slip limitation. U.S. Pat. No. 5,302,159 (Dye et al) discloses a parallel-axis differential in which friction produced by end thrust of pinions and side gears to a casing, resulting from specific helical tooth angles, provides slip limitation.
U.S. Pat. No. 3,292,456 (Saari) and U.S. Pat. No. 3,738,192 (Belansky), and European Patent No. 130806A2 (Quaife) disclose parallel-axis differentials having pinions that are co

Affiliated with

Also associated with

Rating

Limited slip differential does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Limited slip differential, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Limited slip differential will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2942922