A torque coupling for use in a power transfer device. The torque coupling
includes a friction clutch and a clutch actuator. The clutch actuator
controls engagement of the friction clutch and has a first actuator plate
rotatable about an axis, a second actuator plate adjacent to the first
actuator plate, and a ballramp unit disposed between the first and second
actuator plates. A piston assembly acts to induce rotation of the first
actuator plate relative to the second actuator plate. Relative rotation
between the first actuator plate and the second actuator plate induces
linear movement of one of the first and second actuator plates along the
axis to regulate engagement of the friction clutch.