Patent ID: 7063198

Claim:
A coupling device including a rotatable housing defining a clutch cavity; a clutch assembly disposed in said clutch cavity and including a first clutch member fixed to rotate with said housing, and a second clutch member fixed to rotate with an output; said housing defining a pressure chamber, and a clutch apply member disposed in said pressure chamber and being operable to bias said first and second clutch members into torque-transmitting relationship in response to the presence of pressurized fluid in said pressure chamber; said coupling device including a source of said pressurized fluid, and a control valve assembly operable to vary the fluid pressure in said pressure chamber in response to variations in an input; said housing defining a hub portion defining an outer cylindrical surface, said housing defining a high pressure fluid passage providing fluid communication from said pressure chamber to a first port formed in said outer cylindrical surface; characterized by: (a) a stationary plenum member defining an inner cylindrical surface disposed in a surrounding relationship about said outer cylindrical surface defined by said hub portion; (b) said plenum member defining a high pressure fluid passage providing fluid communication from a second port formed in said inner cylindrical surface, in fluid communication with said first port formed in said outer cylindrical surface, to said control valve assembly; and (c) first and second annular seal members disposed within said inner cylindrical surface on axially opposite sides of said second port, to define an annular pressure region; and (d) said hub portion of said housing comprising a member in which at least said outer cylindrical surface is substantially free of graphite porosity.