Abstract: An electronically controlled locking differential assembly including a friction clutch assembly provided within a differential case for selectively restricting differential action. The friction clutch assembly is actuated by a selectively controllable actuator including an electrical motor externally mounted to an axle housing, a reduction gearing and a drive screw adapted to axially displace a pusher block when the drive motor is actuated. The pusher block is integrally secured to a clutch actuating sleeve adapted to slide within a differential case trunnion coaxially to the side gear. The actuating sleeve is provided to apply a clutch loading force to an actuator plate. When the drive motor is actuated by a signal from a control unit, the rotary motion of the drive screw is transmitted to the actuator plate via the pusher block and the actuating sleeve, thereby actuating the friction clutch assembly and locking the differential.

Abstract: A control system for actuating various types of clutches includes a first piston which contacts a clutch disc associated with a first shaft. The first piston forces the first shaft clutch disc into a corresponding clutch disc associated with a second shaft. A second piston is received within a fluid chamber, and is reciprocated by a motor to force fluid outwardly of the fluid chamber and against the first piston. In this way, the position of the second piston controls the force of the first piston against the clutch disc of the first shaft. An electronic control for the second piston motor accurately controls the position of the second piston to control the force of the first piston on the clutch discs. The first and second pistons, the ball screw motor, the fluid chambers and the fluid paths are all received in a casing for the shafts. In this way, the size of the clutch is reduced over prior art assemblies which typically required a separate pump removed from the casing.