Patent ID: 6047605
Filing Date: 2000-04-11
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 member which is unitary and of generally homogeneous chemical composition throughout, said member comprising separate magnetically active and magnetically substantially passive regions;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;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 to prevent irreversible loss of the magnitude of the circumferential polarization.