Differential unit

A differential unit comprising:

• a housing;
• a drivable differential carrier supported in the housing for rotation about an axis;
• two output elements rotatable about said axis relative to the different carrier and connected to respective output shafts;
• differential gears rotatably supported by the differential carrier and having driving connection with the output elements to permit differential rotation thereof;
• a friction assembly comprising a number of plates rotationally fast with one element of the differential rotatable about said axis, interleaved with a number of plates rotationally fast with another element of the differential rotatable about said axis, and actuating means for axially loading the plates into frictional engagement with one another to restrict said differential rotation of the output elements;
• the actuating means comprising an abutment ring fixed relative to the housing, an actuating ring movable axially and angularly relative thereto, and means for causing axial movement of the actuating ring upon said angularly movement thereof;
• said means comprising circumferentially extending cam surfaces in facing pairs, as grooves with interdisposed rolling elements operative between opposed faces of the abutment ring and actuating ring, said cam surfaces providing a relationship between the axial position of the actuating ring relative to the angular position thereof which is at least partially non-linear, such that from a starting position of the actuating ring the rate of change of axial position thereof as a function of angular movement thereof is initially high and then becomes lower so that there is no discontinuity between the non-linear cam surface phase and the subsequent linear cam surface phase.