Patent ID: 6145387
Filing Date: 2000-11-14
Classification: G01L

Abstract:
A magnetoelastic torque sensor for providing an output signal indicative of the torque applied to a member about an axially extending axis of said member, comprising:a first magnetoelastically active region in said member, said region being magnetically polarized in a single circumferential direction and possessing sufficient magnetic anisotropy to return the magnetization in said region, following the application of torque to said member, to said single cirumferential direction when the applied torque is reduced to zero, whereby said magnetoelastically active region produces a magnetic field varying with said torque;magnetic field sensor means mounted proximate to said magnetoelastically active region and oriented with respect thereto to sense the magnitude of the magnetic field at said sensor means and provide said output signal in response thereto;at least said magnetoelastically active region of said member being formed of a polycrystalline material wherein at least 50% of the distribution of local magnetizations lie within a 90.degree. quadrant symmetrically disposed around said single circular direction and having a coercivity sufficiently high that the field arising from said magnetoelastically active region does not magnetize regions of said member proximate to said magnetoelastically active region to give rise to parasitic magnetic fields which are of sufficient strength to destroy the usefulness, for torque sensing purposes, of the net magnetic field seen by said magnetic field sensor means.