Patent ID: 7497132

Claim:
A magnetostrictive torque sensor comprising: a rotating shaft that is rotated by application of a torque; a first magnetostrictive film formed around an entire circumferential periphery of a surface of the rotating shaft; a second magnetostrictive film formed around an entire circumferential periphery of the surface of the rotating shaft; a third magnetostrictive film having a different alloy composition than the first magnetostrictive film and the second magnetostrictive film and being formed around an entire circumferential periphery of the surface of the rotating shaft; a first sensor coil for sensing impedance of the first magnetostrictive film; a second sensor coil for sensing impedance of the second magnetostrictive film; a third sensor coil for sensing impedance of the third magnetostrictive film; torque calculating means for outputting a signal according to a change in impedance outputted from the first through third sensor coils, and calculating the torque applied to the rotating shaft on the basis of an output signal of the first sensor coil and an output signal of the second sensor coil; and failure sensing means for comparing the output signals of the first through third sensor coils and detecting failures in the first magnetostrictive film or the second magnetostrictive film.