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Institute for Commercialization

Viscous actuated ball ramp clutch having one-way clutch

Reference Number: N 04-03

Inventors: Walton, Erlen B.; Preston, David M.

Owner: NISTAC

USPTO Link:6237735

Invention Summary

Accordingly, it is an object of the present invention to provide an improved differential device for use in a driveline of a vehicle which enables the driveline system to overcome the above disadvantages of the prior art driveline systems.

It is a more specific object of the present invention to provide an improved center differential device for use in a four-wheel drive driveline system wherein the center differential includes a one-way clutch to prevent the transmission of negative torque, but without adding substantial weight and cost to the driveline system.

It is a more specific object of the present invention to provide an improved center differential which accomplishes the above-stated objects, in which the differential includes a means to bypass or override the one-way clutch.

It is an even more specific object of the present invention to provide an improved center differential which accomplishes the above-stated objects, wherein the one-way clutch and the mechanism for overriding the one-way clutch are required to transmit only a relatively small portion of the entire driveline torque.

The above and other objects of the invention are accomplished by the provision of an improved differential device of the type including an input adapted to receive input torque from a source of torque, an output adapted to provide driving torque to an output device and a clutch pack including at least a first friction disk fixed to rotate with the input and at least a second friction disk fixed to rotate with the output. The device includes means operable to move the friction disks between a disengaged position and an engaged position, and comprises a cam ramp actuator including first and second ramp plates, and a plurality of cam members, each operably disposed between the first and second ramp plates. The second ramp plate is disposed axially adjacent the friction disks and is operable to move the friction disks toward the engaged position. The means operable to move the friction disks further comprises a viscous coupling including an input coupling member fixed to rotate with the input, and an output coupling assembly.

The improved differential device is characterized by one-way clutch means disposed in series between the output coupling assembly and the first ramp plate. The one-way clutch means is configured such that positive torque is transmitted from the input through the viscous coupling, through the one-way clutch means to the first ramp plate during operation in a forward direction, whereas negative torques are not transmitted through the one-way clutch means during operation in the forward direction.

In accordance with another aspect of the invention, the improved differential device is characterized by the device further comprising an override mechanism operably associated with the output coupling assembly and the first ramp plate. The override mechanism is configured such that positive torque is transmitted from the input to the first ramp plate during operation in a reverse direction below a predetermined speed of rotation.