| 摘要 |
An electric fan comprises a rotary shaft supported on a mounting base plate. The rotary shaft is extended through a cylindrical stator and on a tip of the rotary shaft, the bottom of a cup-shaped rotor yoke as well as an impeller are secured. The stator is enclosed in the rotor yoke, on whose inner wall an anisotropic rotor magnet magnetized in the reverse polarity alternately in its circumferential direction is secured. The stator and the rotor form a DC brushless motor, whereby the impeller is rotated through the rotation of the rotor and the rotary shaft. In the proximity of the rotor magnet, there is provided a hall integrated circuit (IC), through which a rotating position of the rotor may be detected. On the basis of the rotating position signal from the hall IC, a microcomputer controls the current flowing period in such a manner that the current flowing through the stator coil will partly overlap between each phase. A separate microcomputer adjusts the voltage applied to the DC brushless motor and controls the wind velocity.
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