Patent ID: 8069736

Claim:
A torque sensor, comprising, a torsion bar, a first cylinder made of a non-magnetic conductor, being fixed on one end of the torsion bar, and arranged coaxially with the torsion bar, a second cylinder made of a non-magnetic conductor, being fixed on the other end of the torsion bar, and arranged coaxially with the torsion bar in the form of being inserted into the first cylinder, and a measuring part, wherein, either one of the first cylinder and the second cylinder comprises a reference slit, either one of the first cylinder and the second cylinder, the cylinder not having the reference slit provided thereon, comprises a first detection slit and a second detection slit, being placed at positions different in an axial direction, and the measuring part comprises, a drive coil arranged coaxially with the torsion bar, on one side, either of the inner circumferential side of the second cylinder, and the outer circumferential side of the first cylinder, a detection coil arranged coaxially with the torsion bar, on the other side, any side of the inner circumferential side of the second cylinder, and the outer circumferential side of the first cylinder, not having the drive coil arranged thereon, a drive circuit for subjecting the drive coil to AC driving, and a measuring circuit, wherein, the first detection slit and the second detection slit are arranged in such a manner that each position in the axial direction of the detection slits overlaps a position of the reference slit at least partially, and a position in the circumferential direction of the first detection slit with respect to a portion of the reference slit that the position in the axial direction of the first detection slit overlaps, is different from a position in the circumferential direction of the second detection slit with respect to a portion of the reference slit that the position in the axial direction of the second detection slit overlaps, the drive coil comprises a first drive coil and a second drive coil placed at positions different in the axial direction, the detection coil comprises a first detection coil and a second detection coil placed at positions different in the axial direction, the first drive coil and the first detection coil are arranged in such a manner that the positions thereof in the axial direction overlaps the first detection slit at least partially, and the second drive coil and the second detection coil are arranged in such a manner that the positions thereof in the axial direction overlaps the second detection slit at least partially, the measuring circuit detects a phase difference between a voltage signal induced by the first detection coil, and a voltage signal induced by the second detection coil, and a direction of generated magnetic flux of the first drive coil and a direction of generated magnetic flux of the second drive coil are opposite to each other.