JP3402700B2 - Operating method of brushless motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combination of stator windings that are energized based on a change in induced voltage generated in the stator windings that are not energized by the rotation of a rotor having permanent magnets having a plurality of poles. The present invention relates to a driving method of a brushless motor for changing the.

[0002]

2. Description of the Related Art In a conventional brushless motor operating method, regardless of the rotational speed of the stator and the motor operating current,
Generally, an operating method in which the intermittent energization cycle to the stator winding is constant.

[0003]

However, in the case of this operating method in which the energization period is constant, the position detection accuracy of the rotor when the rotor is rotating at high speed is the position detection accuracy at low speed rotation. It was lower than that of.

As for the motor operating current waveform, the motor operating current waveform during high speed rotation tends to be worse than the motor operating current waveform during low speed rotation.

Therefore, it is possible to improve the deterioration of the position detection accuracy and the deterioration of the motor operating current waveform at the time of high speed rotation of the rotor by increasing the intermittent energization period to the stator winding, but the induction of the motor It is difficult to reduce the minimum value of the voltage applied to the motor because it is necessary to set the lower limit of the intermittent energization time due to the relationship of the time constant of the voltage detection circuit, etc., and it is difficult to expand the low-speed operation range of the motor. .

Further, when the motor operating current is small,
As compared with the case where the motor operating current is large, the ratio of the electrical loss of the semiconductor switching element that energizes the stator windings is high, and there is a drawback that the efficiency is reduced.

As described above, according to the conventional operation method, it is difficult to satisfy both the improvement of the rotor position detection accuracy during the high speed rotation of the rotor, the improvement of the motor operating current waveform, and the expansion of the low speed operation range of the motor. In addition, it is difficult to operate the motor with high efficiency because the loss of the semiconductor switching element cannot be reduced when the motor current is small.

Therefore, the present invention has been made to solve the above problems, and improves the rotor position detection accuracy when the rotor rotates at high speed, improves the motor operating current waveform, and expands the motor low speed operating range. It is an object of the present invention to provide a method for operating a brushless motor that satisfies the above conditions, reduces loss of the semiconductor switching element when the motor operating current is small, and enables high efficiency.

[0009]

Therefore, the present invention has a rotor having permanent magnets having a plurality of poles, and a plurality of stator windings arranged to give a rotating magnetic field to the rotor when energized. Then, some of the plurality of stator windings are energized to obtain a rotating magnetic field, and the energization is fixed based on the change in the induced voltage in the stator windings that are not energized. In the brushless motor operating method in which the stator windings are intermittently energized to adjust the strength of the rotating magnetic field, the stator windings are intermittently changed by changing the combination of the child windings.
The brushless mode is used to set the energization cycle for energizing the winding.
It is a method of operating a brushless motor, which is characterized in that it is changed according to the operating current of the motor.

Further, the present invention has a rotor having permanent magnets having a plurality of poles, and a plurality of stator windings arranged to give a rotating magnetic field to the rotor when energized. Some of the child windings are energized to obtain a rotating magnetic field, and the combination of energized stator windings is selected based on the change in induced voltage that occurs in the non-energized stator windings. replaced as to intermittently perform the energization of the stator windings, the method of operating a brushless motor for adjusting the intensity of the rotating magnetic field, the power supply to intermittently stator windings carried
The energization cycle of the
Change according to the operating current of the brushless motor.
This is a method of operating a brushless motor, which is characterized in that both of them are changed together .

[0011]

When the rotation speed of the rotor is high, the intermittent energization cycle to the stator winding is reduced, and when the rotation speed of the rotor is low, the intermittent energization cycle is increased.
The intermittent energization cycle to the stator winding is changed according to the rotation speed of the rotor.

If the motor operating current is small,
The intermittent energization cycle is shortened, and the intermittent energization cycle to the stator winding is changed according to the motor operating current.

[0014]

According to the above construction, the improvement of the rotor position detection accuracy at the time of high speed operation, the improvement of the motor operating current waveform, and the expansion of the low speed operating range of the motor are both satisfied.

Further, the motor operating efficiency can be improved when the motor current is small.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

Embodiment 1 FIG. 1 shows a drive device for a brushless motor for carrying out the method for operating a brushless motor according to the present invention. FIG. 1 particularly detects the rotational speed of a rotor of a brushless motor and determines the rotational speed according to the detected rotational speed. FIG. 6 is a control block diagram for performing a method of operating a brushless motor that changes an intermittent energization cycle to a stator winding.

In FIG. 1, an AC power supply 1 is connected to a brushless motor 4 via a rectifier circuit 2 and a semiconductor switching element group 3.

The switching element drive signal forming section 9 of the control circuit section 100 is connected to the semiconductor switching element group 3. The rotor position detecting unit 5 is connected to the switching element drive signal forming unit 9 via the energization winding switching unit 6. The rotation speed detection unit 7 is connected to the switching element drive signal formation unit 9 via the intermittent energization cycle determination unit 8.

The induced voltage 1a generated in the stator winding of the brushless motor 4 is input to the rotor position detection unit 5, and the detection result is input to the energization winding switching unit 6 to energize the stator winding. In order to control, energization winding information 1b is given to the switching drive signal forming unit 9.

At the same time, the induced voltage 1a is input to the rotor rotation speed detection unit 7, and the detection speed result is input to the intermittent energization cycle determination unit 8. In the intermittent energization cycle determining unit 8, for example, FIG.
As shown in (b), the relationship between the rotation speed N and the intermittent energization period T is defined, and the intermittent energization period is determined according to the detected rotation speed.

Returning to FIG. 1, the energization winding information 1b of the stator and the intermittent energization period information 1c to the stator winding thus obtained are input to the switching element drive signal forming section 9. Then, the drive signal 1d is formed. The drive signal 1d is input to the semiconductor switching element group 3 and the brushless motor 4 is rotated.

The relationship between the rotation speed N and the intermittent energization period T shown in FIG. 5 (a) or FIG. 5 (b) is only one example,
If the intermittent energization cycle is set to decrease with the increase of the rotation speed, another relationship may be adopted.

FIG. 3 shows the relationship between the motor terminal voltage waveform, the motor operating current waveform, and the intermittent energization cycle Ta.

Ta in FIG. 3 indicates an intermittent energization period, and Ton
Indicates the period of energization to the stator winding, Toff indicates the period of de-energization of the stator winding, and i indicates the pulsating flow due to intermittent energization of the motor operating current waveform.

FIG. 4 shows a case where the intermittent energization period is set to Ta / 2 and the rotor speed is the same as that in FIG.

With the method of detecting the rotor position by the induced voltage of the stator winding, it is impossible to detect the rotor position during the period in which the stator winding is de-energized, that is, during the Toff period.

This means that the position detection accuracy is determined as it is during the Toff period, and the smaller the Toff period, the higher the position detection accuracy. Therefore, as in the example shown in FIG. 4, the Toff period becomes shorter when the intermittent energization period is set smaller than in the example shown in FIG. 3, and the position detection accuracy is improved at the same speed.

Similarly, in the example of FIG. 4, since the intermittent energization cycle becomes short, the pulsating component i1 of the current decreases and the motor current waveform can be improved.

Further, the lower limit value of the energization period Ton to the stator winding is a constant value irrespective of the intermittent energization cycle Ta due to the time constant of the detection circuit of the induced voltage.

Therefore, the number of intermittent energization periods per unit time indicates the low-speed operation cycle of the motor, and the example of FIG. 3 having a smaller number of energization periods than the example of FIG. 4 operates at a lower speed of the motor. Is possible.

From the above, when the rotation speed of the rotor is high, the intermittent energization cycle can be shortened to improve the rotor position detection accuracy and the motor operating current (see FIG. 4). On the other hand, when the rotation speed of the rotor is low, the intermittent energization period is increased, the motor average applied voltage is decreased, and the low-speed motor operation range can be expanded (FIG. 3).
reference).

However, the maximum value of the intermittent energization cycle needs to be set within a range where good position detection accuracy can be obtained.

Embodiment 2 FIG. 2 shows a brushless motor drive circuit for carrying out the method for operating a brushless motor according to the present invention. In particular, the motor operating current is detected and the stator is detected according to the current value. It is a control block diagram of the operating method of the brushless motor which changes the intermittent electrification cycle to a winding.

In FIG. 2, the AC power supply 10 is connected to a brushless motor 14 via a rectifier circuit 11, a current detector 12 and a semiconductor switching element group 13.

The switching element drive signal forming section 17 of the control circuit section 200 includes a semiconductor switching element group 13
It is connected to the. The rotor position detection unit 15 is connected to the switching element drive signal forming unit 17 via the energization winding switching unit 16. The current detector 12 is connected to the switching element drive signal forming unit 17 via the intermittent energization period unit 18.

The induced voltage 2a of the brushless motor 14 is
It is input to the rotor position detection unit 15 and the energization winding switching unit 16
The energization winding information 2b is formed via. Current detector 12
The current information 2c obtained by the
8 and the predetermined current value I and energization interruption period T as shown in FIG. 6 (a) or 6 (b).
The appropriate intermittent energization period information 2d shown in FIG.

Current-carrying winding information 2b thus obtained
The brushless motor 14 is operated based on the energization period information 2d.

When the brushless motor 14 is operated at the same number of revolutions, the ON / OFF frequency of the semiconductor switching element decreases as the intermittent energization period increases, so that the electric current of the semiconductor switching element per unit time is reduced. The loss is reduced and the efficiency of the brushless motor 14 is improved.

Especially when the motor operating current is small,
Since the ratio of the loss of the switching element increases, as shown in FIG. 6, the loss of the switching element is reduced by increasing the intermittent energization cycle with the decrease of the motor operating current, and the highly efficient operation of the motor can be achieved. It is possible.

In the second embodiment, the current detector 12
Is provided between the rectifier circuit 11 and the semiconductor switching element group 13, but between the AC power supply 10 and the rectifier circuit 11, or between the semiconductor switching element group 13 and the brushless motor 14.
It may be provided between.

[0042]

As described above, according to the present invention, since the intermittent energization period to the stator winding is changed according to the rotation speed of the rotor, the accuracy of position detection in the high speed rotation range and the motor are improved. The operating current waveform can be improved, and at the same time, the low speed rotation range can be expanded.

Furthermore, since the intermittent energization cycle to the stator winding is changed according to the motor operating current, the loss of the semiconductor switching element can be reduced especially when the motor operating current is small, and efficient operation can be achieved. .

[0044]

[Brief description of drawings]

FIG. 1 is a diagram showing a brushless motor driving apparatus for carrying out a method for operating a brushless motor according to the present invention.

FIG. 2 is a diagram showing another brushless motor drive device for carrying out the method for operating a brushless motor according to the present invention.

FIG. 3 is a diagram showing a motor terminal voltage waveform and a motor operating current waveform when the intermittent energization cycle is Ta.

FIG. 4 is a diagram showing motor terminal voltage waveforms and motor operating current waveforms when the intermittent energization cycle is Ta / 2.

FIG. 5 is a diagram showing a relationship between a rotation speed of a rotor and an intermittent energization cycle.

FIG. 6 is a diagram showing a relationship between a motor operating current and an intermittent energization cycle.

[Explanation of symbols]

4 brushless motor 5 Rotor position detector 7 Rotation speed detector 8 Intermittent energization cycle determination unit Ta Intermittent energization cycle Ton Energization period to stator winding Toff Stabilizer winding energization pause period

Claims (2)

(57) [Claims] 1. A rotor having a permanent magnet having a plurality of poles, and a plurality of stator windings arranged to give a rotating magnetic field to the rotor when energized. While energizing some of the stator windings to obtain a rotating magnetic field, the combination of energized stator windings is changed based on the change in the induced voltage generated in the non-energized stator windings. In a brushless motor operating method in which the stator winding is energized intermittently to adjust the strength of the rotating magnetic field, the energizing cycle in which the stator winding is energized intermittently
Of the brushless motor according to the operating current of the brushless motor. 2. A rotor having a plurality of permanent magnets and a plurality of stator windings arranged to give a rotating magnetic field to the rotor when energized. While energizing some of the stator windings to obtain a rotating magnetic field, the combination of energized stator windings is changed based on the change in the induced voltage generated in the non-energized stator windings. In a brushless motor operating method in which the stator winding is energized intermittently to adjust the strength of the rotating magnetic field, the energizing cycle in which the stator winding is energized intermittently
Can be changed according to the rotation speed of the rotor, including starting.
, And can be changed according to the operating current of the brushless motor.
A method of operating a brushless motor, characterized in that and are used together .