Rotation angle detecting device

摘要

A rotation angle detecting device for a rotation object includes a rotor and a pair of permanent magnets and a magnetic detector disposed at the rotation axis of the rotation object. One of the permanent magnets has a circumferentially extending rut-shape concavity around the magnet detector or an axially extending elliptic columnar surface having a central portion thicker than others to make magnetic flux density in the vicinity of said magnetic detector constant in an axial or a diametrical direction.