Piston assembly for hydraulically actuated friction coupling

A hydraulically actuated friction coupling in a limited slip differential assembly, said differential assembly comprising:

• a differential case rotatably supported in a differential housing and defining an axis of rotation;
• two output shafts outwardly extending from said case in an axial direction and drivingly connected to said case;
• a frictional clutch pack for selectively engaging and disengaging said case and said output shafts, said clutch pack comprising at least one first member coupled to rotate with one of said output shafts and at least one second member coupled to rotate with said case, said members being frictionally engageable with one another;
• a hydraulic clutch actuator for selectively frictionally loading said clutch pack, said actuator comprising:
• a hydraulic pump located within said differential case for generating a hydraulic pressure in response to relative rotation between said differential case and one of said output shafts to frictionally load said clutch pack;
• a piston assembly disposed within said case between said pump and said clutch pack, said piston assembly including a substantially annular pressure plate adjacent to said pump and a substantially annular thrust plate axially spaced from said pressure plate and adjacent to said clutch pack, said plates fixed to each other through a pair of concentric radially spaced resilient annular seal members so as to define an annular cavity within said piston assembly,
• wherein said annular cavity is in fluid communication with an outlet port of said hydraulic pump.

A hydraulically actuated friction coupling in a limited slip differential assembly, said differential assembly comprising:

• a differential case rotatably supported in a differential housing and defining an axis of rotation;
• two output shafts outwardly extending from said case in an axial direction and drivingly connected to said case;
• a friction clutch pack for selectively engaging and disengaging said case and said output shafts, said clutch pack comprising a number of alternating inner friction plates non-rotatably coupled to one of said output shafts and outer friction plates non-rotatably coupled to said differential case, said friction plates being frictionally engageable with one another;
• a hydraulic clutch actuator for selectively frictionally loading said clutch pack, said actuator comprising:
• a gerotor pump located within said differential case for generating a hydraulic pressure in response to relative rotation between said differential case and one of said output shafts to frictionally load said clutch pack;
• a piston assembly non-rotatably disposed within said case between said pump and said clutch pack, said piston assembly including a substantially annular pressure plate abutting said pump and a substantially annular thrust plate axially spaced from said pressure plate and abutting said clutch pack, said plates fixed to each other through a pair of concentric radially spaced resilient annular seal members so as to define an annular cavity within said piston assembly, said piston assembly is provided for frictionally loading said friction clutch pack to cause a frictional restriction of rotation of said output shafts relative to said differential case,
• wherein said pressure plate has at least one opening therethough disposed adjacent to an output port of said hydraulic pump for providing a fluid communication between said outlet port of said hydraulic pump and said annular cavity within said piston assembly, and
• wherein said piston assembly is non-rotatably coupled to said differential case.