Electromagnetic control apparatus for varying the driver steering effort of a hydraulic power steering apparatus.

摘要

A hydraulic power steering apparatus having conventional relatively rotatable valve spool (54) and valve body (64) for flow regulation, a mechanically resilient element (90) for generating a mechanical centring force in relation to the relative rotation of the valve spool and valve body which tends to restore the valve spool and valve body to a centred condition, and an integral electromagnetic mechanism (92) which variably opposes the mechanical centring force to adjust the level of operator steering input required to produce a given level of power assist. The electromagnetic mechanism comprises an exciting coil (130) and a pair of flux conducting elements (106,108) supported for rotation with the valve spool and valve body, respectively. The flux conducting elements have interleaved teeth (112,114) which are magnetically coupled to the exciting coil to define a magnetic circuit having an inter-tooth working air gap which varies with the relative rotation of the valve spool and valve body.