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Institute for Commercialization

Viscous actuated ball ramp clutch having through shaft capability

Reference Number: N 04-03

Inventors: Walton, Erlen B.; Nank, Michael W.; Eybergen, William N.; Spring, James K.

Owner: NISTAC

USPTO Link:6182808

Invention Summary

Accordingly, it is an object of the present invention to provide an improved differential device which is capable of use in a "through-shaft" configuration.

It is a more specific object of the present invention to provide an improved differential device which accomplishes the above-stated object, and which includes additional features which facilitate such a through-shaft configuration.

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, an output adapted to provide driving torque to an output device, and a clutch pack including at least a first friction disc fixed to rotate with the input, and at least a second friction disc fixed to rotate with said output. The device includes means operable to move said friction discs between a disengaged position and an engaged position, said means comprising a cam ramp actuator including first and second ramp plates, and a plurality of cam members, each operably disposed between said first and second ramp plates, and in engagement with first and second ramp surfaces, respectively. The second ramp plate is disposed axially adjacent the friction discs and is operable to move the friction discs toward the engaged position. The means operable to move said friction discs further comprises a viscous coupling including an input coupling member fixed to rotate with said input, and an output coupling member.

The improved differential device is characterized by the output comprising an elongated, generally hollow shaft member extending axially through substantially the entire axial extent of the differential device. The device includes means for interconnecting one of the input coupling member and the output coupling member of the viscous coupling with the first ramp plate for common rotation.

In accordance with another aspect of the invention, the improved differential device is characterized by the output comprising a shaft member extending axially through the clutch pack and at least partially through the cam ramp actuator. A first retention means is in engagement with one of the input and the shaft member and operable to limit axial movement of the first ramp plate in a forward direction, relative to one of the input and the shaft member. As a result, substantially all axial separation forces within the clutch pack and the cam ramp actuator are taken up within either the input or the shaft member.

In accordance with yet another aspect of the invention, the improved differential device is characterized by one of the input and the output defining a plurality N of elongated cut-out portions on the periphery thereof. One of the first friction disc and the second friction disc defines a plurality N of cut-out portions cooperating with the elongated cut-out portions defined by the one of the input and the output to define a plurality N of openings. There is a plurality N of elongated members, each member being disposed in one of the openings, and operable to transmit torque between the one of the first friction disc and the second friction disc and the one of the input and the output. The openings have an axial length L1, and each of the elongated members has an axial length L2, less than L1, the difference therebetween being selected such that wear within the clutch pack will permit L1 to decrease to L2, but will prevent the cam ramp actuator from moving to an over-center condition.