Patent ID: 7661324

Claim:
A magnetostrictive torque sensor comprising: a rotating shaft that is used to rotate according to an input torque and that is provided with a magnetostrictive film, an excitation coil that applies an alternating magnetic field to the magnetic film, and a detection coil that detects a change in a magnetic characteristic of the magnetostrictive film, wherein a bias magnetic field is added to the alternating magnetic field so as to satisfy the following conditions: H m <H in <H n ; and −H m >−H in >−H n where H m (> 0 ) is an applied magnetic field corresponding to a maximum magnetic permeability obtained according to a magnetic hysteresis curve of the magnetostrictive film, which shows magnetization caused by the alternating magnetic field, H n (> 0 ) is an applied magnetic field corresponding to an end of a range in which a discontinuous magnetization is performed, and H in (> 0 ) is an applied magnetic field that determines a sensitivity range to be set on a magnetostrictive sensitivity curve representing a magnetostrictive sensitivity exhibited by the magnetostrictive film.