Patent ID: 7671584
Filing Date: 2010-03-02
Classification: G01D

Abstract:
1. A rotation angle detection device comprising: a cylindrical magnetic circuit mounted to a rotary member; and a non-contact sensor provided in an inner void of the magnetic circuit, wherein the magnetic circuit is composed of a yoke formed of a magnetic material and having a pair of flat portions parallel and opposed to each other, and a pair of permanent magnets whose magnetic poles are aligned in a same direction so that magnetic fields whose magnetic fluxes are parallel to each other are generated in a void between the flat portions, and wherein the non-contact sensor detects a rotation angle of the rotary member by detecting a change in the direction of the magnetic fluxes; wherein the yoke is of a cylindrical configuration with a pair of cutouts into which the permanent magnets are fitted with each of the permanent magnets being fitted in curved portions of the magnetic circuit; wherein each of the flat portions of the yoke is disposed between the curved portions of the yoke; wherein a cross-sectional area of the flat portions within the yoke is smaller than a cross-sectional area of the curved portions of the yoke; and wherein each flat portion comprises a straight, non-curved portion.