Patent ID: 7424829

Claim:
A torque sensor where a first rotary shaft and a second rotary shaft are disposed on a common axial line, with the first rotary shaft and the second rotary shaft being coupled together by a torsion bar, and which detects torsional torque applied between the first rotary shaft and the second rotary shaft, the torque sensor comprising: magnetic field generating means disposed in a center area along the common axial line, the magnetic field generating means includes at least one permanent magnet magnetized in a radial direction around the common axial line, the magnetic field generating means generating a magnetic field in the radial direction around the common axial line; magnetic field varying means that includes first, second, third, and fourth magnetic field varying components and two outer peripheral cylinders of magnetic material, where the first and second magnetic field varying components are disposed in the center area to surround the magnetic field generating means, the third and fourth magnetic field varying components are disposed in adjoining areas to the center area, and said magnetic field varying means varying a relative direction and magnitude of a detection portion of magnetic flux from the magnetic field generating means flowing between the outer peripheral cylinders along an axis parallel to the common axial line in response to the relative rotation between the first rotary shaft and the second rotary shaft; and magnetic sensor means that detects the detection portion of magnetic flux, wherein the magnetic sensor means generates an output signal whose polarity changes in response to the relative direction of the detection portion of magnetic flux and whose magnitude changes in response to the magnitude of the detection portion of magnetic flux.