Abstract: A motor vehicle power steering gear has a proportional control valve with a cylindrical valve member riding rotatably on a spool shaft and connected thereto through a torsion bar. Electromagnetic apparatus for varying the magnitude of the effective restoring torque of the torsion bar comprises a stationary exciting coil, an inner pole member comprising an extension of the cylindrical valve member having a plurality of outwardly facing teeth and an outer pole member fixed on the spool shaft for rotation therewith and having an equal plurality of opposing inwardly facing teeth, the teeth defining an air gap axially beside the coil.

Abstract: A motor vehicle power steering gear has a proportional control valve with a cylindrical valve member riding rotatably on a spool shaft and connected thereto through a torsion rod. Electromagnetic apparatus for varying the magnitude of the effective restoring torque of the torsion rod comprises a stationary exciting coil, an extension of the cylindrical valve member having a plurality of outwardly facing teeth and an outer pole member fixed on the spool shaft for rotation therewith and having an equal plurality of opposing inwardly facing teeth, the teeth defining an air gap axially beside the coil. The cylindrical valve member is formed with a pair of sleeve surfaces for riding on the spool shaft surface with a small controlled clearance providing a hydraulic seal; and faces of the teeth of the cylindrical valve member and outer pole member are both machined after formation of the members for accurate control of the radial distance thereof from the spool shaft surface and thus of the air gap.