JPS5951237B2 - DC brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has a permanent magnet rotor or equivalent magnetic pole rotor, and controls the excitation of individual stator windings using a semiconductor switching element controlled by a rotor position detection signal. This invention relates to DC brushless motors that are rotationally driven by electromagnetic force, and is aimed specifically at improving their efficiency.

A principle diagram of a brushless motor in which semiconductor switching elements are normally converted into transistors is shown in FIG.

In the figure, E is a DC power supply, Wa, Wb, Wc are stator wires, Qa, Qb, Qc are transistors as semiconductor switching elements, and the collectors thereof include the stator winding Wa,
Wb, Wc and surge absorption circuits Ba, Sb, Sc are connected in parallel.

D is a rotor position detection circuit that detects the position of the rotor using light, magnetic field, magnetic permeability, capacitance, etc., and the voltage in the mode shown in FIG.
, Qb, and Qc. With this application, the transistors Qa, Qb, and Qc are turned on and off in sequence.
The stator windings Va, Wb, and Wc are energized and controlled accordingly, and a unidirectional torque is always generated by the winding current and the electromagnetic force between the rotor, and the rotor is rotationally driven. Each stator winding Wa, Wb, Wc is connected to a transistor Qa, Qb.
, Qc, a large transient voltage is generated in the stator winding Wa, for example, when the transistor Qa is turned off.

Therefore, in order to prevent transistor breakdown, dielectric breakdown of stator windings, and radio interference, each stator winding Wa, W
b, Wc are equipped with surge absorption circuits Ba, Sb,
Sc is provided for husband and wife. This surge absorption circuit generally has a constant voltage diode node ZD inserted between the emitter and collector of the transistor Qa as shown in Fig. 3A, and the surge energy is consumed within the Zener diode, and a capacitor Ca is connected to the stator winding Wa. When the surge energy is connected to both ends of the capacitor and the winding, it becomes vibrational energy and is dissipated as a resistance component in Wa or Ca. This inserted into the stator winding Wa
There are some devices that supply surge energy through a diode Da, store this energy in a capacitor Ca, and then gradually discharge it through a resistor Ra, but in both cases, all of the surge energy becomes heat loss. Considering the amount of surge energy here, if the inductance of one stator winding is L, and the current just before the transistor turns OFF is I, the energy stored in the winding when the transistor turns OFF is It is LI2/2 (Juyur).

If the number of poles of the motor is P, the number of phases is m, and the number of rotations when the current is I (A) is N (Rpm), then the number of switching operations per second is, and the surge power PL is.

In a motor with a low power supply voltage, the current is relatively large.Moreover, the current when the stator winding conducts is not the same at the beginning of conduction and at the end of conduction, but the current at the end of conduction is large, and the average current flowing through the motor It may be 2 to 3 times as large.

In this way, surge power is proportional to the square of the current, and because the current when the surge is generated is larger than the average input current of the motor, the surge power can reach several percent or more of the motor's input power.

The present invention has been made in view of the above points, and one embodiment thereof will be described below with reference to FIG.

E is the power supply, Ma, Wb, Wc are the stator windings, Qa, Qb
, Qc are switching transistors, D is a rotor position detection circuit, and Sa, Sb, and Sc are surge absorption circuits.

Since the first-stage surge absorption circuits Sc, Sb, and Sc all have the same configuration, the configuration of Sa will be explained. A series circuit consisting of a capacitor C that is charged by the surge voltage generated in the stator winding Wa when the transistor Qa is turned off, and a polarity diode D that allows the charging current to flow between both ends of the stator winding Wa. will be established. Also, a capacitor C is placed between both ends of the capacitor C. and a resistor R, and the emitter-collector of a transistor Q, which discharges the charge of a capacitor C to a stator winding Wa, is connected between both ends of a diode D. The emitter and base of the transistor are capacitor C. connected to both ends of the In the above configuration, when the switching transistor Qa is turned off, the collector potential rises rapidly due to the transient voltage of the stator winding Wa, and this potential charges the capacitor C through the diode D. Then R,C. After a minute time determined by the time constant of the capacitor C
. When the voltage across the transistor Q exceeds the cut-off voltage of the transistor Q, and the base current flows, the transistor Q,
starts conducting, current flows in the closed circuit of capacitor C, transistor Q, and individual stator winding Wa, and the power stored in capacitor C is returned to individual stator winding Wa. FIG. 5 shows the collector voltage V of the transistor Qa.
The waveform of the cathode voltage VDI of the l diode D is expressed with the rotation angle taken on the horizontal axis. Cathode voltage VD
” waveform is shown by a solid line, and the waveform of the collector voltage Vcl is shown by a broken line. In the figure, time T is the time when the transistor Qa turns ON, T2 is the time when this transistor turns OFF, T,
T indicates the time when transistor Q is turned ON, and T is the time when transistor Qa is turned ON again. Collector voltage V. ”
Focusing on , the period (T.-T,) is the transistor Qa
is 0N, indicating the saturation voltage of this transistor about IV. Time T. Transistor Qa(7)0FF
When a surge voltage occurs, the collector voltage Vc'' takes on a pulse-like waveform.
is 0FF, so the collector voltage V. " is the electromotive voltage waveform generated in the stator winding Wa. Regarding the cathode voltage VD of the diode D1," the period (T.

-T,), the transistor Q, is turned off, the diode D, is in a reverse bias state, and the cathode voltage VDI
is approximately equal to the power supply voltage VR. Time T. Due to the surge voltage at , the diode D becomes forward biased, and the capacitor C is charged via this diode. After that, the time constant determined by the resistor R of the delay circuit DE and the time constant of the capacitor C, T, - T.), that is, at time T., the transistor Q becomes conductive, and the charge in the capacitor C is discharged to the stator winding Wa through this transistor.From time T. to time 2π. is almost equal to the waveform of the collector voltage V.l. In this case, the collector voltage V.l becomes slightly larger than the electromotive force waveform of the stator winding Wa at time T3 due to the discharge current of the capacitor C1. .The discharge current that started flowing from time T3 flows through the transistor Q.
The excitation current flows in the stator winding Wa in the opposite direction to the excitation current in the stator winding Wa due to a(7)0N, and since the rotor magnetic poles at this time are also reversed, the current flows in the same direction as the rotation direction of the rotor. That is, torque in the normal rotation direction is generated. In addition, surge absorption circuit Sb
, Sc.

As described above, the present invention has a permanent magnet rotor or a corresponding magnetic pole rotor, and controls the excitation of the stator winding using a semiconductor switching element controlled by a rotor position detection signal to generate a stator winding current. In a DC brushless motor that obtains rotational force by electromagnetic force between rotors, a capacitor is charged with a surge voltage generated in a stator winding when the semiconductor switching element is turned OFF, and the surge voltage is stored in the capacitor when the switching element is turned OFF. This electric charge is discharged into the stator winding, and this current is used to generate rotor torque in the normal rotational direction, so a part of the surge energy is converted into motor output, resulting in an efficient brushless motor. Motors can be provided.

[Brief explanation of drawings]

FIG. 1 is a principle diagram of a DC brushless motor, FIG. 2 is an output diagram of a rotor position detection circuit, and FIG.
FIG. 4 is an electric circuit diagram of a brushless motor according to the present invention;
FIG. 5 is an operational characteristic diagram of the surge absorption circuit in FIG. 4. E...DC power supply, Qa, Qb, Qc...
・Switching transistors, Wa, Wb, Wc...
...Stator winding, D...Rotor position detection circuit, Sa, Sb, Sc...Surge absorption circuit, R
1...Resistor, D1...Diode, Q
1...Transistor, Cl, C2...
capacitor.

Claims (1)

[Claims] 1 Having a permanent magnet rotor or equivalent magnetic pole rotor, the stator winding is excited and controlled by a semiconductor switching element controlled by a rotor position detection signal, and the stator winding current and the electromagnetic force between the rotor are controlled. In a DC brushless motor that obtains rotational force, a capacitor is provided between both ends of the stator winding, and is charged with a surge voltage generated in the stator winding when the excitation semiconductor switching element is turned off, and its charging current A series circuit is provided with a diode having a polarity that allows the current to flow, and a delay circuit is provided between both ends of the capacitor, and after the delay time of the delay circuit is provided between both ends of the diode,
A discharging semiconductor switching element is provided for discharging the charged charge of the capacitor to the stator winding, and the discharging semiconductor switching element discharges the charged charge to the stator winding during an OFF period of the excitation semiconductor switching element. A DC brushless motor characterized in that a lever current generates torque in a rotor in the normal rotation direction.