Coupling device and improved method of controlling torque transmission

Abstract

A method of controlling a pressure control valve assembly () to control a control pressure () in a system () including a source () of pressurized fluid. The control valve assembly is operable to vary the control pressure in response to variations in an electrical input signal () to an electromagnetic coil (). The control valve assembly defines an inlet () in communication with the control pressure, an outlet () in communication with the low pressure, and a valve seat () disposed intermediate the inlet () and the outlet (). A poppet valve member () is biased toward the valve seat by a biasing means including an armature (), the biasing force being generally proportional to the input signal to the coil. The method comprises the steps of selecting a predetermined, minimum pressure for the control pressure corresponding to a minimum condition of the system. Next is selecting the biasing means to apply a biasing force to the poppet valve () corresponding to a fluid pressure less than the predetermined minimum pressure for the control pressure. The last step is selecting the electrical input signal () to correspond to the desired control pressure, an increasing input signal resulting in an increasing biasing force on the poppet valve member (), but with no substantial movement thereof.