Patent ID: 7141966

Claim:
Rotation detecting apparatus for detecting rotation of a magnetic rotor, the apparatus comprising: a sensor chip having a magnetoresistive device; and a bias magnet for applying bias magnetic field to the magnetoresistive device, wherein the bias magnet and the sensor chip are integrated, the magnetoresistive device is capable of detecting change of a magnetic vector near the sensor chip on the basis of resistance change of the magnetoresistive device so that the rotation detecting apparatus detects the rotation of the magnetic rotor, the change of the magnetic vector is generated by the bias magnetic field and the rotation of the magnetic rotor, the bias surrounds the sensor chip so that a deflection angle of the magnetic vector is controllable, the bias magnet includes a hollow portion having a groove, the groove has a predetermined shape for providing control of the deflection angle of the magnetic vector, the hollow portion of the bias magnet accommodates the sensor chip, and has a rectangular shape with a pair of wide sides, the wide sides of the hollow portion face the sensor chip, and are parallel to a surface of the sensor chip, the surface on which the magnetoresistive device is disposed, the groove of the hollow portion extends in a longitudinal direction of the bias magnet, and the groove is disposed on a center of the wide side of the hollow portion.