| 摘要 |
PURPOSE:To miniaturize a motor, and to reduce cost by mounting a gear to the outer circumferential section of a rotor yoke, transmitting a revolving output and detecting the speed of revolution by magnetic leakage from the gear. CONSTITUTION:A brushless motor is constituted of a magnet 1 for drive, a coil 2 for drive, a motor shaft 3, a rotor yoke 4, a sub-rotor 6 and a housing for a bearing 8. In this case, a gear section 4a is shaped to the outer circumferential section of the rotor yoke 4 while a ferromagnetic thin-film resistance element 5 is fitted near the gear section 4a. Consequently, since the rotor is turned, an external gear connected to the gear section 4a is rotated, thus transmitting a motor output. Since the leakage field of the magnet 1 is changed by the crest and bottom land of the gear section 4a, the leakage field is converted into an electric signal by the element 5, thus detecting the speed of revolution of the motor.
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