Patent ID: 8314607

Claim:
A rotation angle detector, for detecting a rotation angle of a measurable rotation body having a central axis of rotation, comprising: a magnet that is designed to be attached onto the measurable rotation body and then to be rotated as integral with the measurable rotation body, a magnetic pole of the magnet at a portion of a circumference thereof being different on one side of the magnet than on another side of the magnet, the one side and the other side opposing each other in the direction of the central axis of rotation; a magnetic detecting element, for detecting a magnetic flux density of the magnet, wherein the magnetic detecting element is arranged outside the circumference of the magnet in a radial direction of the magnet at an approximately intermediate position with respect to the thickness of the magnet in the direction of the central axis of rotation, the magnetic detecting element is thinner than the magnet in the direction of the central axis of rotation, and the magnet is movable in the direction of the central axis of rotation such that a plane containing a surface of the magnet on the one side is movable from one side of a surface of the magnet detecting element to the other side of the surface of the magnet detecting element in the direction of the central axis of rotation.