Differential containing rheological fluid

Details Differential containing rheological fluid Differential containing rheological fluid

1996-12-27

2001-02-06

Ta, Khoi Q. (Department: 3681)

Planetary gear transmission systems or components

Fluid drive or control of planetary gearing

Control of differential planetary gearing

C475S086000, C192S021500

Reexamination Certificate

active

06183386

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a differentials for vehicles and in particular to an improved structure for a vehicle differential which uses a rheological fluid to control the operation of the differential during use.
Differential gear mechanisms, commonly referred to as differentials, are well known devices which are used in the drive train systems of most vehicles. The differential is usually connected between an input driving shaft (typically a drive shaft assembly which is rotated by an engine of the vehicle) and a pair of output driven shafts (typically a pair of axles connected to the wheels of the vehicle). The differential is designed to distribute torque from the input shaft to the two output shafts, while permitting the two output shafts to rotate at different speeds under certain conditions. When the vehicle is operated in a straight line, the wheels of the vehicle turn at the same speed, and torque is distributed equally by the differential to the two wheels. When the vehicle negotiates a turn, the outside wheel rotates at a somewhat faster speed than the inside wheel. As a result, although torque is continued to be supplied to both wheels, a somewhat greater amount of torque is supplied to the inside wheel than to the outside wheel.
A conventional differential employs a number of meshing gears to accomplish the function described above. However, one of the drawbacks of conventional mechanical differentials is that when the vehicle is operated on a slippery surface, most or all of the torque will be distributed to a slipping wheel. For example, when one wheel of the vehicle is on a slippery surface, most or all of the torque will be delivered to that slipping wheel. As a result, the vehicle will become immobilized. To overcome this problem, it is known to provide mechanical differentials with additional mechanisms for limited or selectively preventing differentiation of speed between the two driven wheels. A number of such mechanically actuated limited slip and non-slip differential structures are known, most of which include a friction clutch structure of some type. Unfortunately, such structures are relatively complex and expensive in structure and operation. It would, therefore, be desirable to provide an improved structure for a differential which can be adjusted in accordance with the changing operating conditions of the vehicle.
SUMMARY OF THE INVENTION
This invention relates to an improved structure for a vehicle differential. The differential includes a case which is rotatably supported within an axle housing. The case is formed having a center wall which divides the interior of thereof into first and second fluid chambers. The ends of a pair of axle shafts extend into the case and respectively within the fluid chambers. Each of the fluid chambers is filled with a rheological fluid. Respective electromagnetic coils are disposed within or adjacent to each of the fluid chambers. An electronic controller is provided for supplying electrical current to each of the electromagnetic coils in response to sensed operating conditions of the vehicle, such as rotational speed and torque of the axle shafts. By varying the magnitude of the electrical current supplied to the electromagnetic coils, the strength of the magnetic field applied to the rheological fluid contained in each of fluid chambers can be varied. As a result, the resistance to flow or shear of the rheological fluid, which affects the amount of torque which is transmitted from the rotatably driven case to each of the axle shafts, can be varied in response to the operating conditions of the vehicle.
Various objects and advantages of this 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.


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