| 摘要 |
PURPOSE:To control the phase of a cylinder motor, by detecting a signal produced in accordance with the difference between a detected output influenced by a magnetized magnetic pole and that influenced by a non-magnetized magnetic pole and dividing in frequency a detected output by using the signal as a reference. CONSTITUTION:A multi-pole magnet 4 for driving to which the 1st magnetization is performed, the 2nd magnetization of magnetized parts 4a, etc., installed to one specific magnetic pole of the magnet 4 and having the opposite polarity of that of the magnetic pole, and detecting means of a Hall element 10 for detecting the rotating phase angle of the magnet 4 are provided. A signal produced in accordance with the difference between an output influenced by the magnetic pole of the magnet 4 with the 2nd magnetization and another output influenced by the magnetic pole without the 2nd magnetization is detected and one obtained by dividing in frequency an output detected by the detecting means by using the signal as a reference is used as the switching pulse of a rotary head. Therefore, a Hall element to be used for detecting the change in a magnetic flux caused by a PG magnet when a motor is rotated can be eliminated and, as a result, the motor can be miniaturized and the cost of the motor can be reduced.
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