Abstract: A servo valve has a miniature force motor embedded in a main fluid chamber to directly operate between two nozzles to generate a differential pressure in two ports. The miniature force motor includes two disc ring-shaped magnets in opposing magnetic orientation, an armature base and poppet ends of magnetic material coupled to an armature shaft having pilot ends that interface to form the pilot stage valves at each armature shaft end. The armature shaft extends through a center hole in the magnets, armature base, and the poppet ends and engages bearing elements at each end allowing lateral armature motion. Two elastic members provide restoring forces to the armature assembly. Guide/stops have shaped magnetic surfaces to control the magnetic path and to linearize the force versus stroke and to increase the proportional stroke of the armature.

Abstract: The force motor of the present invention controls the local magnetic field through a uniquely designed mechanical structure of the internal components. The mechanical structure divides the magnetic field in the force motor into three sections. The force produced on the armature by the magnetic field in the first section increases exponentially as the armature approaches the housing. The force produced on the armature by the magnetic field in the second and the third sections, as the armature approaches the housing, counter balances the rise in the force due to the magnetic field in the first section. Thus, a flat F-S curve over a long stroke length is obtained.

Abstract: The force motor of the present invention controls the local magnetic field through a uniquely designed mechanical structure of the internal components. The mechanical structure divides the magnetic field in the force motor into three sections. The force produced on the armature by the magnetic field in the first section increases exponentially as the armature approaches the housing. The force produced on the armature by the magnetic field in the second and the third sections, as the armature approaches the housing, counter balances the rise in the force due to the magnetic field in the first section. Thus, a flat F-S curve over a long stroke length is obtained.