| 摘要 |
PURPOSE:To facilitate manufacture of a drive motor by providing a close part and a separated part between a worm provided for the armature of the drive motor and the housing of drive motor in the circumferential direction thereof, providing the housing with a magnet for forming a magnetic path, and detecting the magnetic variation by means of a magnetic sensor CONSTITUTION:An assembly 44 is fitted to the housing 34 oppositely to a worm 30. In the assembly 44, a Hall IC 38 is disposed oppositely to a magnet 40 in the radial direction of the worm 30 and a magnetic circuit 50 is formed between. When the worm 30 opposes, at the tip 52 thereof, to the Hall IC 38 and the magnet 40, they come close to each other and the magnetic force is strong at the position of the Hall IC 38 in the magnetic circuit 50. When the worm 30 opposes, at the root thereof, to the Hall IC 38 and the magnet 40, they are spaced apart from each other and the magnetic force is weak at the position of the Hall IC 38 in the magnetic path 50. The variation of magnetic force is detected by means of the Hall IC 38 and a pulse is delivered therefrom. This structure eliminates the need of magnet for armature when the rotational position of drive motor is detected. |
