Patent ID: 7459905
Filing Date: 2008-12-02
Classification: G01D

Abstract:
1. A rotation detector comprising: a sensor unit, including a sensor chip and a circuit chip, for detecting changes in a magnetic field; a magnet for supplying a biasing magnetic field to the sensor unit, the magnet being in a cylindrical shape having a hollow space therein; a holder, made of a non-magnetic material, having a holder body and an extending portion extending from the holder body, the extending portion being disposed in the hollow space in the magnet, the sensor unit being mounted on the extending portion; a reed frame held in the holder body and extending along the extending portion, the reed frame including a terminal for supplying electric power to the sensor unit and a terminal for leading out output signals from the sensor unit; a cap member for covering the magnet and the sensor unit to protect those from ambient atmosphere; and means for keeping a position of the magnet relative to the holder, wherein: the position keeping means is an engagement structure between the holder and the magnet, and the engagement structure is constituted by a projected portion formed on the holder and a depressed portion formed on the magnet, the projected portion being engaged with the depressed portion.