| 摘要 |
<p>A device for detecting rotating positions of brushless motors comprises m-phase driving coils (L) which are energized in both the positive and negative directions; driving magnet (1) which is counterposed to the coils (L) and has driving magnetic poles of N and S alternately arranged so that the magnet (1) can rotate together with a rotating shaft; position detecting magnetic means (N+) which is provided on at least one of the magnetic poles (N and S) of the magnet (1) and has the same polarity as that of the magnetic pole; magnetic detectors (2a, 2b, and 2c) which are arranged opposed to the magnet (1) and detect the magnetic fields of both the driving magnetic poles (N and S) and magnetic means (N+); a brushless motor drive circuit (3) which supplies a driving current to the coils (L) in accordance with output signals from the detectors (2a, 2b, and 2c); and synthesizing means (20) which synthesizes a rotational position signal from the output signals of the detectors (2a, 2b, and 2c), the counter-electromotive voltage waveform of the coils (L), and reference voltage (COM). Since the device is adapted to obtain one pulse per revolution of a motor, the device does not require any conventionally used PG sensor, PG magnet, etc. The elimination of such sensors and magnets reduces the device cost. Further, since no space is required for the PG sensor and its wiring, the size of the substrate can be reduced.</p> |
