A power transmission device includes a rotary input member receiving drive
torque from a source of torque, a rotary output member for providing
drive torque to an output device and a torque transfer mechanism for
transferring drive torque between the input member and the output member.
The torque transfer mechanism includes a friction clutch assembly
operably disposed between the input member and the output member and a
hydraulic clutch actuation system operable for applying a clutch
engagement force to the friction clutch assembly. The hydraulic clutch
actuation system includes an electromagnet and a piston operable to
supply pressurized fluid and provide the clutch engagement force.