FIELD OF THE INVENTION
The present disclosure relates to a clutch and a clutch actuator. More particularly  a clutch actuator includes a dual input force mechanism including a biasing member and an incline plane such that torque transferred by the clutch provides a majority of the clutch actuation input force. The clutch is deactuated by an electro-magnet.

BACKGROUND OF THE INVENTION
Electromagnetic clutches have been utilized commercially in a variety of applications  including automobiles. Typically  an electromagnetic clutch includes a rotor having an inner annular bearing portion  a clutch portion extending generally radially outwardly from one end of the inner portion and an outer annular portion extending from the clutch portion in a generally overlying spaced relation with respect to the inner portion. The spacing between the inner and outer annular portions receives an electromagnetic coil that may be energized to create a flux field in the rotor. A floating plate mounted to the annular portion may be attracted by the magnetic field for selective coupling to the rotor when the electromagnetic coil is energized.

Another friction clutch has been configured as a normally closed clutch having a number of springs biasedly urging a floating plate into engagement with a friction plate. The entire clutch actuation force is provided by the springs. To disengage the clutch and cease torque transfer from the friction plate to the floating plate  an electromagnet is energized to overcome the force of the biasing springs and translate the floating plate away from the friction plate. While these prior electromagnetic clutches may have served a purpose  a need for improvement exists. In particular  to disengage the floating plate from the friction plate  a relatively large quantity of energy is required to overcome the biasing force of the springs. Accordingly  it may be desirable to provide an energy efficient electro-magnetic clutch.

SUMMARY OF THE INVENTION
This section provides a general summary of the disclosure  and is not a comprehensive disclosure of its full scope or all of its features.

An electromagnetic clutch includes a rotatable input member and a rotatable output member. A clutch plate is fixed for rotation with one of the input member and the output member. An armature plate is axially moveable relative to the other of the input member and the output member. A self-energizing actuator converts rotary motion of the input member to linear movement of the armature plate. The actuator includes a biasing member urging relative rotation between the one of the input member and the output member and the armature plate to initially engage the armature plate and the clutch plate. The self-energizing actuator provides an additional clutch engagement force once the input member is driven and also includes an electromagnet to axially translate the armature plate and disengage the armature plate and the clutch plate.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.