| 摘要 |
PURPOSE:To reduce the size of a magnet rotor by allowing the current flowing angles of drive coils to correspond to the widths (rotating angle) of detecting poles, thereby alleviating the magnetic influence of main and detecting poles. CONSTITUTION:A motor case 3 is integrally molded through a plurality of supporting legs 2 with a fan casing 1 of a cooling fan device. A bearing holding cylinder 4 is provided at the center of the case 3. A stator coil 6 radially has four salient-pole teeth 7 and interpole teeth 8, and winds 2-phase drive coils 10. A current flow controlling component 12 is mounted on a printed board 11, and a rotational shaft 14 mounted with a rotary magnet 17 is supported by a bearing 15. In this case, a main pole 22 is formed on the inner surface 21 of the cylinder of the magnet 17, and a detecting pole 23 is formed on the axial extension (the opposed surface to a Hall IC 13). Thus, the magnetic property becomes substantially sinusoidal wave shape at the pole 22 and substantially rectangular shape at the pole 23, the rotation is smooth and the varying width of the magnetic sensitivity can be narrowed. |
