ELECTROMAGNETIC CONTROL APPARATUS FOR VARYING THE FORMING METHOD FOR ENGAGING PART IN MANUFACTURE OFDRIVER STEERING EFFORT OF A HYDRAULIC POWER STEERI ELEMENT FOR SLIDE FASTENER NG SYSTEM

摘要

A hydraulic power steering apparatus having conventional relatively rotatable valve spool (54) and valve body (64) elements for flow regulation, and an integral electromagnetic mechanism (92) which effectively varies the centring force between the valve spool and valve body to adjust the level of steering assist provided for a given operator steering input. The electromagnetic mechanism includes a rotary magnetic circuit (100) and a stationary magnetic circuit (102). The rotary magnetic circuit comprises a pair of axially displaced magnetic pole pieces (106,108) which rotate with the pinion shaft (28) and a permanent magnet disk element (104) which is disposed between the pole pieces and which rotates with the input shaft (18). The stationary magnetic circuit includes an annular exciting coil (130) disposed about the rotary magnetic circuit and ferromagnetic pole elements (134-139) adjacent each of the rotary pole pieces. The exciting coil is energized so as to vary the valve body/valve spool centring force, and hence the driver steering effort, with vehicle speed.