Two position flow control valve assembly with position sensing

Abstract

A flow control valve assembly including a valve having open and closed positions and a limited angle torque motor having two angular rotor positions corresponding to the open and closed valve positions that are stable in the absence of an applied electrical signal. The valve motor includes magnetic pole pieces forming a concentric shell around the motor shaft that include air gaps, disposed generally parallel to the axis of rotation of the shaft. Pole blades adjacent the rotor are magnetically linked to the pole pieces by flanges disposed at the rotor ends. Two alternative minimum reluctance flux paths are provided for a permanent magnet that is mounted on the rotor with its poles transverse to the axis of rotation. The two minimum reluctance paths provide the stable rotor positions. A magnetic flux sensor disposed in or proximate one of the air gaps is employed with a relatively high frequency electrical signal to determine relative rotor and valve positon. A current signal is applied to the stator coil of the motor to actuate the valve. The interaction of the magnetic field of the permanent magnet with the fields produced by the low and higher frequency electrical signals generate the actuation and rotor position responses, respectively.