| 摘要 |
PURPOSE:To improve the detection accuracy of a rotation detector at a low rotational speed and, at the same time, to reduce the outside diameter of an FG magnet without deteriorating the detection accuracy. CONSTITUTION:Magnetism sensitive elements 31A and 31D for outputting a rotation detecting signal P1 and magnetism sensitive elements 31B and 3C for outputting another rotation detecting signal P2 are arranged at regular intervals which are equal to 1/6 of the pole width of an FG magnet 13 and a phase difference of about 60 deg. exists between the two signals P1 and P2. When the zero-crossing points of the two signals P1 and P2 and the difference signal 3 between the signals P1 and P2 are counted, the rotating state of the FG magnet 13 can be detected. In this example, the detection accuracy of the rotating state of the magnet 13 can be improved even when the number of poles of the magnet 13 is reduced, since the number of zero-crossing points becomes larger than the conventional ones. Therefore, the rotation of a capstan motor can be easily controlled even when the motor is miniaturized by reducing the outside diameter of the magnet 13. |
