ELECTROHYDRAULIC TORQUE TRANSFER DEVICE

摘要

A power transmission device includes an actuator having an electric motor driving a pump to supply pressurized fluid to a piston acting on a friction clutch to transfer torque between rotatable input and output members. In one instance, a valve between the pump outlet and the piston selectively traps pressurized fluid acting on the piston without continued energization of the electric motor. A gerotor may be formed from a material having a first coefficient of thermal expansion and a housing formed from a material having a second lower coefficient of thermal expansion to vary pump component clearances as the viscosity of the pumped fluid changes with changes in temperature. A method of controlling the power transmission device includes defining a correlation between pump speed, fluid temperature and fluid pressure, determining fluid temperature, determining pump speed, and rotating the pump to transfer a predetermined quantity of torque.