Electricity: motive power systems – Switched reluctance motor commutation control
Patent
1989-06-22
1990-11-13
Ro, Bentsu
Electricity: motive power systems
Switched reluctance motor commutation control
318138, H02P 602
Patent
active
049704451
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNOLOGY
The present invention relates to a brushless motor drive device which does not make use of a position detector for detecting the position of a movable element of an electric motor.
BACKGROUND ART
As a means trend of improving motor durability and reliability, a brushless motor is being largely employed for various drive motors. In general, the brushless motor requires the use of a position detector for detecting the position of a movable element. However, in order to further reduce the price and the size, a brushless motor which does not require the use of the position detector is necessary. A conventional example of a drive device for such a brushless motor is disclosed in, for example, the Japanese Laid-open Patent Publication No. 52-80415.
Hereinafter, the above described conventional drive device for the brushless motor will be discussed with reference to the drawings.
FIG. 4 is a circuit diagram of the conventional brushless motor drive circuit. In FIG. 4, driving coils 1 to 3 are connected at their one end with each other. The driving coil 1 is connected at the other end to the anode of a diode 4, the cathode of a diode 5 and the respective collectors of driving transistors 10 and 13. The driving coil 2 is connected at the other end to the anode of a diode 6, the cathode of a diode 7 and the respective collectors of driving transistors 11 and 14. The driving coil 3 is connected at the other end to the anode of a diode 8, the cathode of a diode 9 and the respective collectors of driving transistors 12 and 15. The respective cathodes of the diodes 4, 6 and 8 and the respective emitters of the driving transistors 10, 11 and 13 are connected to a positive power supply line, and the respective anodes of the diodes 5, 7 and 9 and the respective emitters of the transistors 13, 14 and 15 are connected to earth. The other ends of the driving coils 1 to 3 are also connected with a filtering circuit 16 which generates an output to a power supply switching circuit 17. An output from the power supply switching circuit 17 is supplied to the respective bases of the driving transistors 10 to 15.
FIG. 5 is a diagram used to explain the operation of FIG. 4, wherein Uo, Vo and Wo represent respective waveforms of electric power signals supplied to the driving coils 1, 2 and 3. The power supply waveforms Uo, Vo and Wo have their high harmonic components removed by the filtering circuit 16 and are respectively converted by the filtering circuit 16 into output signals F1, F2 and F3 which are delayed 90.degree. in phase. It is to be noted that the filtering circuit 16 is a primary filter and is constituted by, for example, a RC passive filter, a primary Miller integrator, etc., the cut-off frequency of which is set to a sufficiently low region as compared with the frequencies of the power supply waveforms of the coils. The output signals F1, F2 and F3 are inputted to the power supply switching circuit 17. The power supply switching circuit 17 is constituted by a logic circuit and is adapted to generate control signals U.sub.H, U.sub.L, V.sub.H, V.sub.L, W.sub.H and W.sub.L in response to the output signals F1, F2 and F3, respectively. These control signals U.sub.H, U.sub.L, V.sub.H, V.sub.L, W.sub.H and W.sub.L are supplied to the bases of the driving transistors 10 to 15 to cause the latter to perform respective switching operations. At this time, the switching operations are carried out so that a motor driving torque can generate in a constant direction at all times for driving a motor.
In the prior art construction, it is necessary to use the filtering circuit having a cut-off frequency characteristic for each a phase of the driving coils and, accordingly, a number of capacitors of high capacitance is required.
Also, where the inductance of the driving coils is high, the power supply current to be passed through the coils tends to be delayed in time after the driving transistors are switched on and permanent magnetic fields tends of be degaussed by magnetic fields generated by the driving coils.
REFERENCES:
patent: 4250435 (1981-02-01), Alley et al.
patent: 4603283 (1986-07-01), Oltendorf
patent: 4608527 (1986-08-01), Glennon et al.
patent: 4651068 (1987-03-01), Meshkat-Razavi
patent: 4900993 (1990-02-01), Yasohara et al.
Kimura Yoshitsugu
Nakano Hiromitsu
Yasohara Masahiro
Matsushita Electric - Industrial Co., Ltd.
Ro Bentsu
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