| 摘要 |
PURPOSE:To contrive to miniaturize and lighten an apparatus by providing a PG magnet and its detector on the inside of an FG magnet and by arranging a PG detecting element in a position where said element can directly detect a magnetic flux from the PG magnet. CONSTITUTION:A PG magnet 12 is fixed on a rotor yoke 4 on the inside of an FG magnet 9 and a PG detecting element 13 is fixed on an FG board 10 opposed to the FG magnet 9 so as to be opposed to the PG magnet 12. Then, if a magnetic-field detecting element 8 detects a pole face field of a driving magnet 5 and passes its signal to a driving coil 6, the driving magnet 5 is driven to rotation. With said rotation, the FG magnet 9 revolves and an FG signal is outputted from an FG coil pattern not shown in the drawing. Said FG signal controls an electric current supplied to the driving coil 6 and a rotational speed of the driving magnet 5 to a constant value. In this manner, a cylinder motor can be miniaturized axially and also lightened because a magnetic material piece and its holder become useless.
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