Patent ID: 7997152

Claim:
A magnetostrictive torque sensor that detects a torque of a rotating shaft and/or a stationary shaft by using a magnetostriction inverse effect that occurs on a shaft surface, the magnetostrictive torque sensor comprising: a first detection coil that is disposed so as to detect a magnetic permeability change in a first direction on the shaft surface, the first detection coil detecting the magnetic permeability change in the first direction as an inductance change of the first detection coil; a second detection coil that is disposed so as to detect a magnetic permeability change in a second direction on the shaft surface, the second detection coil detecting the magnetic permeability change in the second direction as an inductance change of the second detection coil; a first oscillation circuit that oscillates autonomously at a predetermined reference frequency and causes phase shifts in oscillating waves according to the inductance change of the first detection coil; a second oscillation circuit that oscillates autonomously at a predetermined reference frequency and causes phase shifts in oscillating waves according to the inductance change of the second detection coil; a first direction magnetic permeability detector that performs an oscillating wave counting processing and detects the magnetic permeability change in the first direction based on a time required for the oscillating wave counting processing that counts a plurality of oscillating waves that are output from the first oscillation circuit and determines whether a counted number reaches a predetermined number N; a second direction magnetic permeability detector that performs an oscillating wave counting processing and detects the magnetic permeability change in the second direction based on a time required for the oscillating wave counting processing that counts a plurality of oscillating waves that are output from the second oscillation circuit and determines whether a counted number reaches a predetermined number N; and a torque detector that detects the torque of the rotating shaft and/or the stationary shaft based on a difference between the magnetic permeability of the first and second directions.