JPH1032994A - Control method for brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a control method in which the responsiveness of the control operation of a speed of rotation is enhanced and in which the accuracy of the control operation of the speed of rotation is enhanced, by a method wherein the applied voltage of a brushless motor is made properly variable. SOLUTION: When the speed of rotation of a brushless motor 4 is controlled, the on-off ratio (the minimum variable width of a voltage applied to the brushless motor 4) of a chopping signal in a driving signal (containing the chopping signal) which drives an inverter part 3 is changed by a control circuit 10 according to a present speed of rotation. At this point, when the present speed of rotation is lower, a variable width is made larger, and, when the present speed of rotation is higher, the variable width is made smaller. In addition, a voltage which is applied to the brushless motor 4 at the timing of the position detection of the brushless motor 4 or at a timing synchronized with the timing of the position detection is made variable by the control circuit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for controlling the rotation of a brushless motor used for a motor such as a compressor of an air conditioner. The present invention relates to a brushless motor control method capable of performing a high speed control.

[0002]

2. Description of the Related Art To control the rotation of a brushless motor,
For example, the control device shown in FIG. 4 is required. In this figure, the control device includes an AC power supply 1 and an AC / DC converter 2
The DC power is supplied to the inverter 3 for switching, and the switched power is applied to an armature winding of a brushless motor (for example, a three-phase motor) 4.

A position detection circuit 5 compares, for example, armature winding voltages (induced voltages) R, S, T of the brushless motor 4 with a reference voltage, and outputs a position detection signal based on these comparison results to a control circuit (microcomputer) 6. Output to

The control circuit 6 outputs a drive signal of the inverter unit 3 to the drive circuit 7 in order to detect the position of the rotor from the input position detection signal and switch the supply of the armature winding current to a predetermined value. The drive circuit 7 includes transistors U, constituting the upper arm of the inverter unit 3 based on the drive signal.
V, W and transistors X, Y,
Drive Z. In the PWM control method, the control circuit 6 outputs a drive signal including a predetermined chopping signal to the drive circuit 7.

As described above, the position of the rotor is detected based on the position detection signal, and the energization of each armature winding of the brushless motor 4 is switched based on the detected position to control the rotation of the brushless motor 4. I do.

Further, the on / off ratio (on time, off time) of the chopping signal is varied, that is, the voltage applied to the brushless motor 4 is varied to control the number of revolutions of the brushless motor 4. When increasing the number, the applied voltage is increased, and when decreasing the number of revolutions, the applied voltage is decreased.

[0007]

However, in the above-described method of controlling the brushless motor, the timing for changing the rotation speed of the brushless motor 4 (timing for changing the applied voltage) is set at a predetermined time asynchronous with the position detection timing. There is a drawback that the response of the rotation speed control is poor, and the accuracy of the rotation speed control cannot be improved.

That is, the number of rotations of the brushless motor 4 is detected based on the position detection, and this position detection information is not reflected on the variation of the applied voltage. In particular, since the position detection interval increases as the rotation speed decreases, the response of the rotation speed control deteriorates, that is, the accuracy of the rotation speed control deteriorates, and as a result, the rotation speed increases and decreases.

Further, for example, when the present invention is used for a motor of a compressor of an air conditioner, the above-described deterioration of the response of the rotation speed control is not preferable. That is, it is preferable to keep the increase and decrease of the rotational speed constant in order to quickly make the room a comfortable environment.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to improve the response of the speed control by appropriately changing the applied voltage when controlling the speed of the brushless motor. It is an object of the present invention to provide a brushless motor control method capable of improving accuracy.

[0011]

In order to achieve the above object, the present invention switches a DC power supply and applies it to an armature winding of a brushless motor, while detecting a position of a rotor of the brushless motor, A brushless motor control method for switching the energization of an armature winding current of the brushless motor based on the position detection, and performing a rotation speed control by varying an applied voltage of the brushless motor,
In controlling the rotation speed of the brushless motor, the minimum variable width of the voltage applied to the brushless motor is changed according to the current rotation speed.

According to a brushless motor control method of the present invention, when controlling the rotation speed of the brushless motor, the voltage applied to the brushless motor is varied at the timing of the position detection or at a timing synchronized with the timing of the position detection. In addition, the minimum variable width of the applied voltage is changed according to the current rotational speed.

According to the brushless motor control method of the present invention, the minimum variable width for varying the voltage applied to the brushless motor in accordance with the rotation speed of the brushless motor is stored as a table in the storage means. When controlling the rotation speed of the brushless motor, the minimum variable width of the voltage applied to the brushless motor is changed with reference to the table.

According to the brushless motor control method of the present invention, the minimum variable width for varying the voltage applied to the brushless motor in accordance with the rotation speed of the brushless motor is stored as a table in the storage means. When controlling the rotation speed of the brushless motor, the voltage applied to the brushless motor at the timing of the position detection or at the timing synchronized with the timing of the position detection is varied,
Further, the minimum variable width of the applied voltage is changed with reference to the table.

In this case, it is preferable that the minimum variable width is increased in a region where the rotation speed of the brushless motor is low, and the minimum variable width is reduced in a region where the rotation speed of the brushless motor is high.

Preferably, the brushless motor is applied to a motor of a compressor of an air conditioner.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS. FIG.
The same parts as those in FIG. 4 are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 1, the control device for the brushless motor has a function of controlling the rotation speed of the brushless motor 4 in addition to the function of the control circuit 6 shown in FIG. Control circuit (microcomputer) 10 for changing the minimum variable voltage width (variable width) of the voltage
It has. Further, the control circuit 10 varies the applied voltage at a position detection timing (or at a timing synchronized with the position detection) when controlling the rotation speed of the brushless motor 4.

Next, the operation of the control device for the brushless motor will be described with reference to the timing charts of FIGS. 2 and 3. First, as in the prior art, the control circuit 10
The position of the rotor is detected based on the position detection signal from the motor, and the energization of the armature winding current of the brushless motor 4 is switched based on this position detection.

In the position detection operation mode, when the current rotation speed calculated based on the position detection when varying the applied voltage to control the rotation speed is low, the variable voltage width of the applied voltage is increased. The applied voltage is varied at the position detection timing (see FIG. 2). The control circuit 10 varies the applied voltage by changing the on / off state of the chopping signal of the output drive signal (including the chopping signal) according to the variable voltage width.

When the current rotation speed is high, the rotation speed is already close to the target rotation speed. Therefore, the variable voltage width of the applied voltage is set to a small value (for example, 1 V), and this applied voltage is This is performed at the detection timing (see FIG. 2).

As described above, the variable voltage width is increased in the low rotation speed range, and the rising and falling rates of the rotation speed are increased as compared with the conventional case. Therefore, the rotation speed increases and decreases even if the position detection interval is long. Speed, that is, the rotation speed can be quickly set to the target rotation speed, and the responsiveness of the rotation speed control can be improved, and as a result, the accuracy of the rotation speed control can be improved.

In the high rotation speed range, the variable voltage width is reduced,
For example, since the same value as in the related art is used, even if the position detection interval is short, the increase and decrease rates of the rotation speed do not become too large, and the rotation speed can be easily maintained at the target rotation speed, thereby improving the accuracy of the rotation speed control. be able to.

Further, since the timing of changing the variable voltage width is set to the position detection timing or the timing synchronized with the same position detection timing, the position detection can be reflected on the variable voltage width and the response of the rotation speed control can be improved. Is more improved.

The control method of the brushless motor according to the present invention is as follows. A minimum variable voltage width (variable width) for changing the voltage applied to the brushless motor 4 in accordance with the rotation speed of the brushless motor 4 is set in advance. It is preferable that the information is stored in the ROM (storage means) 10a of the control circuit 10 in a table format shown in Table 1 below. Note that the ROM 10a stores the control circuit 1
0 may be externally attached.

[0026]

[Table 1] As is clear from Table 1, the variable voltage width of the voltage applied to the brushless motor 4 increases as the rotation speed decreases, and the variable voltage width of the voltage applied to the brushless motor 4 decreases as the rotation speed increases. . The data in Table 1 is an example when applied to a compressor motor of an air conditioner.

As described above, when the rotational speed of the brushless motor 4 is in a low range, the variable voltage range can be increased and the variable voltage range can be changed for each rotational speed. It is effective to apply in cases,
In addition, the rotation speed control can be performed more finely, the responsiveness of the rotation speed control can be further improved, and the accuracy of the rotation speed control can be improved.

If the variable voltage width is changed at the position detection timing or at a timing synchronized with the same position detection timing, the position detection can be reflected on the variable voltage width, that is, the responsiveness of the rotation speed control can be improved. It is possible to improve the accuracy of the rotation speed control.

In the above-described embodiment, as shown by the dashed line in FIG. 3, the rotation speed of the brushless motor 4 is within the dashed line range. Add the voltage width,
Alternatively, the applied voltage may be maintained (the variable voltage width may be set to zero) when the rotation speed is within the range of the dashed line.

Then, the rotation speed of the brushless motor 4 can be raised and lowered at a constant rate, which is particularly preferable for controlling the rotation speed of the compressor motor of the air conditioner. Control becomes possible.

As a method of changing the rotation speed of the brushless motor 4, a method of changing the applied voltage by changing the duty ratio of the chopping signal has been described. However, the rotation speed is changed by changing the applied voltage by another method. The method can also be applied.

[0032]

As described above, according to the brushless motor control method of the present invention, the minimum variable width (variable voltage width) of the voltage applied to the brushless motor is changed according to the current rotational speed. As a result, the responsiveness of the rotation speed control can be improved, and the accuracy of the rotation speed control can be improved.

According to the second aspect of the present invention, the voltage applied to the brushless motor is varied at the timing of the position detection or at the timing synchronized with the timing of the position detection,
In addition, since the minimum variable width of the applied voltage is changed according to the current rotation speed, the response of the rotation speed control can be further improved, and the accuracy of the rotation speed control can be further improved. .

According to the third aspect of the present invention, the minimum variable width for varying the voltage applied to the brushless motor corresponding to the rotation speed of the brushless motor is stored in the storage means as a table, and this table is referred to. Since the variable width of the applied voltage of the brushless motor is changed, the present invention is applied when it is known in advance, the rotation speed control can be performed more finely, and the responsiveness of the rotation speed control can be improved, There is an effect that the accuracy of rotation speed control can be improved.

According to the present invention, the voltage applied to the brushless motor is varied at the timing of position detection or at the timing synchronized with the timing of the position detection,
In addition, since the variable width of the applied voltage is changed with reference to the table of claim 3, in addition to the effect of claim 3, it is possible to further improve the response of the rotation speed control,
There is an effect that the accuracy of rotation speed control can be further improved.

According to the invention of claim 5, claims 1, 2, and
In addition to 3 or 4, the variable width is increased in a region where the rotation speed of the brushless motor is low, and the variable width is reduced in a region where the rotation speed of the brushless motor is high. In other words, at low rotation speeds, the target rotation speed can be quickly set to the target rotation speed, control responsiveness can be improved, and rotation speed control accuracy can be improved. There is an effect that it is easy to maintain the rotation speed.

According to the invention of claim 6, according to claims 1, 2, 2
Since the brushless motor of 3, 4, or 5 is applied to the motor of the compressor of the air conditioner, the air of which the rotation speed of the brushless motor is constantly increased and decreased by the effect of claim 1, 2, 3, 4 or 5. It is possible to perform rotation control preferable for the harmony machine, that is, there is an effect that a comfortable environment can be quickly established in the room.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a control device to which an embodiment of the present invention is applied, to which a control method of a brushless motor is applied.

FIG. 2 is a schematic time chart for explaining the operation of the control device shown in FIG. 1;

FIG. 3 is a schematic time chart for explaining the operation of the control device shown in FIG. 1;

FIG. 4 is a schematic block diagram of a conventional control device for a brushless motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 AC / DC converter 3 Inverter part 4 Brushless motor 5 Position detection circuit 6, 10 Control circuit (microcomputer) 10a ROM (storage means)

Claims (6)

[Claims] 1. A brushless motor according to claim 1, wherein a DC power supply is switched and applied to an armature winding of the brushless motor, and a position of a rotor of the brushless motor is detected. A method of controlling a brushless motor that switches current application, and controls the number of revolutions by varying the applied voltage of the brushless motor,
A method for controlling a brushless motor, characterized in that a minimum variable width of a voltage applied to the brushless motor is changed according to a current rotation speed when controlling the rotation speed of the brushless motor. 2. A brushless motor according to claim 1, wherein the DC power supply is switched to apply the voltage to an armature winding of the brushless motor, and a position of a rotor of the brushless motor is detected. A method of controlling a brushless motor that switches current application, and controls the number of revolutions by varying the applied voltage of the brushless motor,
When controlling the rotation speed of the brushless motor, the voltage applied to the brushless motor is varied at the timing of the position detection or at the timing synchronized with the timing of the position detection, and the minimum variable width of the applied voltage is set to the current rotation. A method for controlling a brushless motor, wherein the method is changed according to the number. 3. The brushless motor according to claim 1, wherein the DC power is switched to be applied to an armature winding of the brushless motor, and a position of a rotor of the brushless motor is detected. A method of controlling a brushless motor that switches current application, and controls the number of revolutions by varying the applied voltage of the brushless motor,
The minimum variable width for varying the voltage applied to the brushless motor corresponding to the rotation speed of the brushless motor is stored as a table in storage means, and the brushless motor is controlled when controlling the rotation speed of the brushless motor. A method for controlling a brushless motor, wherein the minimum variable width of the voltage applied to the brushless motor is changed with reference to the table. 4. A brushless motor according to claim 1, wherein the DC power supply is switched and applied to an armature winding of the brushless motor, and a position of a rotor of the brushless motor is detected. A method of controlling a brushless motor that switches current application, and controls the number of revolutions by varying the applied voltage of the brushless motor,
The minimum variable width for varying the voltage applied to the brushless motor in accordance with the rotation speed of the brushless motor is stored as a table in storage means, and the position detection is performed when controlling the rotation speed of the brushless motor. The voltage applied to the brushless motor is varied at the timing synchronized with the timing of the same or the position detection, and the minimum variable width of the applied voltage is changed with reference to the table. Control method of brushless motor. 5. The brushless motor according to claim 1, wherein the minimum variable width is increased in a region where the rotation speed of the brushless motor is low, and the minimum variable width is reduced in a region where the rotation speed of the brushless motor is high. , 3 or 4, the control method of the brushless motor. 6. The control method for a brushless motor according to claim 1, wherein said brushless motor is a motor of a compressor of an air conditioner.