Patent ID: 7051857

Claim:
A method of controlling the transmission of torque in a coupling device including an input and at least one output, the coupling device comprises a housing defining a clutch cavity; a clutch assembly disposed in said clutch cavity and including a first clutch member fixed to rotate with said input and a second clutch member fixed to rotate with said output; a clutch apply member disposed in a pressure chamber and 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 electrical input signal transmitted to an electromagnetic coil; said control valve assembly defining an inlet in fluid communication with said pressure chamber, an outlet in fluid communication with a source of low pressure fluid, and a valve seat disposed intermediate said inlet and said outlet; a poppet valve member biased toward said valve seat by a biasing means including an armature, the biasing force applied by said armature to said poppet valve member being generally proportional to said electrical input signal to said electromagnetic coil; said method comprising the steps of: (a) selecting a predetermined minimum fluid pressure in said pressure chamber, corresponding to a predetermined minimum bias torque for said clutch assembly; (b) selecting said biasing means to apply a biasing force to said poppet valve member corresponding to a fluid pressure less than said predetermined minimum fluid pressure; (c) selecting said electrical input signal to correspond to a desired fluid pressure in said pressure chamber and a desired bias torque for said clutch assembly, an increasing electrical input signal resulting in an increasing biasing force on said poppet valve member, but with no substantial movement thereof.