Patent ID: 7891261

Claim:
A clutch actuation system for engaging and disengaging a clutch, comprising: a hydraulically-actuated piston movable in response to hydraulic pressure to an apply position in which the piston is operable to engage the clutch; an electro-mechanical actuator movable in response to electric power to contact the piston at the apply position such that the clutch is maintained in an engaged state by the actuator, thereby permitting the hydraulic pressure to be released; wherein the actuator has a self-locking feature that prevents movement of the actuator in the absence of electrical power thereto; wherein the actuator includes a self-locking lead screw and a nut threadingly engaged thereon; wherein the nut travels axially in response to rotation of the lead screw; wherein the self-locking lead screw prevents the nut from traveling axially without the motor turning the lead screw; and wherein the nut includes axial leads that contact the piston when the nut is moved toward the piston.