Patent ID: 8405388

Claim:
A rotation angle sensor, comprising: a rotation shaft; a yoke which is made from a magnetic permeable material and includes a first disk portion, a second disk portion, and a connection portion magnetically connecting the first disk portion and the second disk portion, the first disk portion and the second disk portion being provided on the rotation shaft and separated from each other in an axial direction of the rotation shaft except where they are connected by the connection portion; a permanent magnet which is provided between the first disk portion and the second disk portion, and has an annular shape; and a magnetic field detection section which generates an output signal in response to an intensity of a magnetic field formed by the permanent magnet during a rotation of the rotation shaft, wherein a center of the permanent magnet is deviated from a center of the rotation shaft so that a distance between the magnetic field detection section and an outer circumference of the permanent magnet in a direction perpendicular to the axial direction of the rotation shaft is gradually changed in accordance with the rotation of the shaft.