Abstract: The shortcomings inherent in prior art coupling fluids are eliminated by combining 1) a polyorganosiloxane fluid as the base oil with 2) sulfur or certain sulfur compounds and 3) at least one cyclic organosiloxane. These three ingredients form a suitable coupling fluid for use in viscous coupling systems.

Abstract: A viscous coupling has an operating chamber in which: first and second (resistance) plates for transmitting torque therebetween are so arranged to be rotatable relative to each other, while spaced alternately with each other; and a viscous fluid is filled in the operating chamber, so that the resistance of the viscous fluid to rotation of the plates contributes to transmitting of torque between the first and the second plates. The coupling further comprises a plurality of spacer rings each of which is interposed between adjacent ones of the first or the second plates, each of which spacer rings is provided with an annular groove in which a peripheral portion of each of the second or the first plates is fitted, so that the first plates are surely spaced apart from the second plates through the spacer rings, whereby the hump torque is prevented from being produced in the coupling even when a difference in rotational speed between the first plates and second plate increases.

Abstract: A differential apparatus comprises first and second rotary devices rotatable with respect to each other, a viscous clutch having a chamber filled with a viscous fluid and restricting a differential operation generated between the first and second rotary devices by the resistance of the viscous fluid, a friction clutch separated from the viscous clutch and restricting the differential operation, and a device for preventing the seal of the chamber from being reduced by an increase in pressure within the chamber and actuating the friction clutch in accordance with an input torque.

Abstract: There is provided a power transmission unit comprising an input member for receiving a torque input from a ring gear connected to a drive pinion which is connected to a propeller shaft, first and second output members supported by the input member in a freely rotatable manner and engaged with right and left rear wheels, and first and second clutches arranged between the input member and the first and second output members respectively to release the connections between the input member and the first and second output members respectively with the help of the actions of cam devices for releasing clutches when the angular speed of the input member becomes smaller than those of the first and second output members.

Abstract: A hydraulic power transmission device of the viscous shear type provides a rotatable driving connection between first and second shaft assemblies. A centrifugal clutch is interposed between the shaft assemblies to provide an overriding rotatable driving connection therebetween when the angular velocity of the first shaft assembly exceeds a predetermined level.