A limited-angle torque motor can be used in many applications, such as the first stage of an electrohydraulic servovalve. A torque motor converts an electrical current (e.g., on the order of tens of milliamps) into a torque or force that accomplishes mechanical work, such as positioning a flapper or jet in a servovalve. A typical torque motor of this type includes, at a minimum, an armature assembly and a field assembly. The field assembly is a fixed magnetic circuit having an arrangement of pole pieces constructed of magnetically soft material to direct flux from one or more permanent magnets into a pair of pole openings. The armature is flexibly mounted to the torque motor structure for rotation about a motor axis. Each end of the armature extends into a respective pole opening, forming respective gaps to the field pole pieces. The armature is surrounded by one or more coils of wire which are excited by the electrical current from an electronic amplifier. The armature is mechanically coupled to an object to be moved, such as a flapper or jet, with a range of motion corresponding to the limited angular travel of the armature with respect to the magnetic poles. The magnetic circuit is highly sensitive to the lengths of the gaps between the armature and the poles since imbalanced forces induced by magnetic attraction between the armature and the pole faces introduce a magnetic bias that displaces the mechanical output relative to its desired mechanical rest position.
USPTO Backgrounds
USPTO Backgrounds