Patent ID: 6422095
Filing Date: 2002-07-23
Classification: G01L

Abstract:
An electric power steering apparatus comprising:a one-piece, cylindrical, rotational shaft operationally connected to a steering wheel; a torque sensor for detecting a steering torque transmitted to said rotational shaft by means of the steering wheel; an electric motor for causing an assisting torque on the basis of the steering torque detected by the torque sensor; and a transmission means for transmitting the assisting torque to said rotational shaft; said torque sensor including: a magnetostrictive film having a predetermined width, said magnetostrictive film being configured to be provided along a circumference of a portion of the rotational shaft, said magnetostrictive film having a magnetic path passing therethrough; a substantially U-shaped excitation core disposed in opposed relation to said magnetostrictive film, said excitation core extending through an excitation coil; a substantially U-shaped detection core disposed in opposed relation to said magnetostrictive film, said detection core extending through a detection coil, said detection core being disposed on said excitation core at right angles thereto; a magnetic circuit provided by said magnetic path, said excitation coil, and said detection coil; and a bridge circuit provided by said excitation coil and said detection coil, wherein said magnetostrictive film causes magnetostriction in correspondence to the steering torque applied to the rotational shaft, and the magnetostriction is electrically detected by said bridge circuit.