| 摘要 |
PURPOSE:To decrease leakage flux by providing an annular signal magnet magnetized in fewer poles than those of a driving magnet within a magnetic rotor case and by detecting a boundary portion between said adjacent magnetic poles with a detection coil. CONSTITUTION:In a brushless motor, a rotor shaft 13 is rotatably journaled by a bearing 12 fitted to an apparatus case 11. Also, the apparatus case 11 is fitted with a stator magnetic core 15 via a support plate 14. Said magnetic core 15 has a plurality of salient pole teeth 16 and a driving coil 18 for rotating a rotor 17 is divided and wound round each tooth 16. Then, a printed board 19 is fitted to the support plate 14 and the rotor 17 is fitted with a driving magnet 24. In this case, the driving magnet 24 is magnetized diametrally and fitted with an annular signal magnet 25 circumferentially so that they overlap each other, while the stator 20 is provided with a detection coil 26 in opposition to said magnets. As a result, any change of magnetic flux from the signal magnet 25 can be readily detected by the detection coil 26. |
