| 摘要 |
A rotor 14 is rotatably disposed around a stator 13 that is provided with a plurality of magnetic poles 13a. The inner circumferential face of the rotor is provided with a magnet 15 on whose face opposing the stator main magnetization is performed, and on whose face opposing the substrate FG magnetization is performed. The outer circumferential ends of the magnetic poles of the stator are provided with extended portions 13b and 13c that vertically extend from the magnetic pole base 13d. A face of the substrate opposing the rotor is provided with a FG pattern 19 opposing the magnet 15. The FG pattern is disposed on an outer side in a radial direction of the outer circumferential face of the stator. When an angle formed by a straight line connecting a central position in the radial direction of the magnet and a central position in the radial direction of the FG pattern with respect to a central axis of a driving shaft is taken as &thetas;, and an angle formed by a direction of the FG magnetization with respect to the central axis of the driving shaft is taken as A, 0 degree<A≦̸&thetas; is satisfied. Accordingly, it is possible to improve the precision in detecting the rotational speed by reducing noise superimposed on the FG signal, while securing a high driving efficiency. |
