Torque coupling device

Abstract

A torque coupling device for use as, for example, a so-called center differential provided between front and rear road wheel axles of a four-wheeled vehicle comprises a cup-shape front housing, a rear housing closing an open end of the front housing, a rotational shaft co-axially rotatably supported by the front and rear housings therewithin, and a clutch disc assembly interposed within the front housing between an axial inner end of the front housing and an axial inner end of the rear housing. The initial clearance in axial direction between the clutch assembly and the inner ends of the front and rear housings is tuned so that when the relative rotation between the housings and said rotational shaft causes a certain temperature difference between the housing and the clutch assembly, the difference in thermal expansion between the front housing and the clutch assembly brings clutch discs of the clutch assembly into friction contact to transmit a rotational torque between the housings and the rotational shaft. In a modified form of the coupling device, a piston axially movable relative to, but rotatable bodily with the front housing is interposed between one end of the clutch assembly and the inner end of the rear housing and defines an axially narrow annular spacing between itself and the rear housing. An impeller with radially extending blades is received within the spacing for generating a pressure acting on the piston, through the agency of a high viscous fluid.