JPH11289788A - Method for controlling brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain elimination of oscillation, noise and the like, and energy saving by smoothly controlling the rotation of a brushless motor. SOLUTION: A DC voltage obtained by an AC/DC converter 2 is switched by an inverter 3 and applied to a brushless motor 4 to rotate the brushless motor 4. A control circuit 10 controls the inverter 3 for switching energizing of the brushless motor 4 based on rotor position detection obtained by a position detecting circuit 5, and divides one turn of the brushless motor 4 into a plurality of sections to obtain the time of respective sections and the mean time of the sections during one turn. A time difference in respective sections and a means time difference are computed for each turn. The ratio of the means time difference to the time difference in respective sections is also computed. The variable width of applied voltages of the respective sections is adjusted in accordance with the computed ratio, so that the time difference in the respective sections are equal to the mean time difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for controlling the rotation of a sensorless DC brushless motor (hereinafter referred to as a brushless motor) used for a motor such as an air conditioner (compressor), and more particularly to each section during one rotation. The present invention relates to a method for controlling a brushless motor that suppresses fluctuations in rotation speed regardless of load by setting the rotation speed of the brushless motor to an average speed.

[0002]

2. Description of the Related Art In this type of brushless motor control method, the position of the rotor of the brushless motor is detected,
The energization of the armature winding of the brushless motor is switched based on this position detection. Therefore, for example, a control device shown in FIG. 4 is required. This control device controls the AC power supply 1 to A
The C / DC converter 2 converts the DC power into a predetermined DC power, and this DC power is used as the switching elements Ua, Va,
Switching is performed at Wa, X, Y, and Z, and the switching is applied to the armature winding of the brushless motor 4.

The position detecting circuit 5 detects the position of the rotor based on the terminal voltages of the armature windings U, V, W of the brushless motor 4, and for example, detects a half of the induced voltage included in the terminal voltage.
A point is detected, and this 1/2 point is output to the control circuit (microcomputer) 6 as position detection signals A, B, and C.
As a method of position detection, a Hall element may be arranged at a predetermined position of the brushless motor 4 and a detection signal from the Hall element may be used as a position detection signal.

The control circuit 6 includes input position detection signals A, B,
The position detection point of the rotor is obtained by C, the next energization switching time is estimated based on the current position detection time and the previous position detection time, and a predetermined drive signal for switching energization is generated at the estimated time. A chopping signal having a predetermined duty ratio is generated in accordance with the rotation speed of the brushless motor 4, and the driving signal is superimposed on the chopping signal and output to the driving circuit 7. In this way, the energization of the armature winding of the brushless motor 4 is switched, and the applied voltage of the brushless motor 4 is set to a predetermined variable width (for example, 2
Since it can be changed in step V), the rotation speed of the brushless motor 4 can be controlled to the target rotation speed.

[0005]

When the brushless motor 4 is used for a compressor motor of an air conditioner, the suction, compression and discharge of the refrigerant are repeated due to the structure of the compressor. Speed is not constant.
For example, in the case of a three-phase four-pole brushless motor, when one rotation is divided into 12 and viewed in each section, the load is light in the discharge section, so the rotation speed is temporary but fastest, and the rotation speed is the highest. Since the load becomes heavy in the section up to the compression, the rotation speed temporarily becomes the slowest.

As described above, since the rotation speed of the brushless motor 4 fluctuates during one rotation, there is a problem that the brushless motor 4 generates mechanical vibration and generates noise. In particular, in an air conditioner, in order to achieve low power consumption, it is preferable to operate at the lowest possible rotational speed. However, as the rotational speed is lower, vibration and noise tend to increase.
For this purpose, for example, there is a method using a special mechanism or the like, but there are still high costs and quality problems.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to solve the problem of vibration and noise, and to perform smooth rotation control up to a low rotation speed, thereby achieving energy saving. An object of the present invention is to provide a control method of a brushless motor which can reduce costs without using a special mechanism or the like.

[0008]

In order to achieve the above object, the position of a rotor of a brushless motor is detected by using an induced voltage included in a terminal voltage of an armature winding of the brushless motor. A brushless motor control method for controlling energization of an armature winding of the brushless motor based on position detection and controlling a rotation speed of the brushless motor by changing an applied voltage of the armature winding. While the rotation is divided into a plurality of sections, the rotation speed in each divided section is obtained, and the average rotation speed in one rotation section is obtained, and the change in the rotation speed in the same section is calculated, and the change in the average rotation speed is calculated. Then, the ratio of the change in the average rotation speed to the change in the calculated rotation speed is calculated, and the variable width of the voltage applied to the armature winding is adjusted in accordance with the calculated ratio. Is characterized in that the closer the degree of the average rotational speed.

According to the present invention, the position of the rotor of the brushless motor is detected by using an induced voltage included in the terminal voltage of the armature winding of the brushless motor, and the brushless motor is detected based on the detected position. In a brushless motor control method for controlling energization of an armature winding and varying a voltage applied to the armature winding to control the number of rotations of the brushless motor, a method for controlling the rotation of the brushless motor based on the detection of the position of the rotor is performed. The rotation is divided into a plurality of parts, and the time of each of the divided sections is measured.
While calculating the average time during rotation, calculate the difference between the section measured during the previous rotation and the same section measured during the current rotation, and calculate the difference between the previous average time and the current average time Then, the ratio of the average time difference to the time difference in the same section is calculated, and the variable width of the applied voltage to the armature winding is adjusted according to the ratio so that the time of each section during one rotation approaches the average time. It is characterized by having.

In this case, the means for adjusting the variable width of the voltage applied to the armature winding is preferably a microcomputer of control means for the brushless motor. Preferably, the brushless motor is a compressor motor.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment 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.

According to the brushless motor control method of the present invention, for example, in the case of a three-phase four-pole brushless motor, one rotation is divided into twelve, and the average speed of the rotation speeds of the sections ta to tl is set as information of the next one rotation. By adjusting the variable width of the applied voltage, the rotation speed of each section during one rotation can be made the average speed, and regardless of the load, for example, the refrigerant suction of the compressor motor of the air conditioner, the compressor and Even if the load changes during one rotation due to the discharge, the rotation fluctuation in each section during the one rotation can be suppressed.

For this purpose, as shown in FIG. 1, a control device to which a brushless motor control method is applied divides one rotation into a plurality of sections based on position detection signals A, B, and C, and (Corresponding to the rotation speed), and the average time during one rotation (corresponding to the average rotation speed) is calculated from the calculated section time.
A control circuit (microcomputer) 10 for adjusting the variable width of the applied voltage of the brushless motor 4 is provided so that the time of each section during rotation becomes the average time. In addition,
The control circuit 10 also has the function of the control circuit 6 shown in FIG.

Next, the operation of the control device having the above configuration will be described with reference to schematic time charts shown in FIGS. 2 and 3. First, the brushless motor 4 is a three-phase four-pole motor.
The three-phase position detection signals A, B, and C are shown in FIGS.
Or (c). In addition,
2 and 3 (a) to 3 (c), the position detection signals A, B, and C are chopping waveforms because the brushless motor 4 is driven by chopping, that is, the PWM control method is employed. , But the chopping waveform is omitted. FIGS. 2 and 3 show an example in which the applied voltage is stepped up by a variable width every rotation and the number of rotations of the brushless motor 4 is increased.

Then, the control circuit 10 switches the energization of the armature winding of the brushless motor 4 based on the position detection signals A, B, and C to drive the brushless motor 4 to rotate. Or tln into 12 divisions. In the case of the PWM control method, the on / off ratio of the chopping signal superimposed on the drive signal for driving the inverter circuit 3 is changed, that is, the applied voltage of the brushless motor 4 is changed in a variable width (2 V; FIG. The rotation speed of the brushless motor 4 is set as a target rotation speed by changing the rotation speed in steps (see FIG. 4G).

At this time, the time t in the section Ta from the fall of the position detection signal A to the rise of the position detection signal C
is measured in the same manner, the times tb to tl of the 12 sections Tb to Tl are measured in the same manner, and the average time of one rotation is calculated. On the other hand, the previous time for the difference between the previous section time and the current section time is calculated. The ratio of the difference between the average time and the current average time is calculated, and the variable width of the applied voltage in each section is adjusted according to the ratio.

Here, when the brushless motor 4 is controlled at the target rotational speed, conventionally, the applied voltage of the brushless motor 4 is constant in each section T1 to T12.
For example, the voltage applied to the winding in each section is 100 V
(Variable width: 2V), the time of each section during one rotation differs due to the operation of suction, compression and discharge of the refrigerant, and the rate of change of the above-mentioned difference over time also differs. The fact that the time of each section is different and the rate of change of the difference over time is also different means that the rotation speed in each section is different,
It causes vibration and noise, and sometimes loses synchronism.

As a specific example, as shown in FIG. 2, when the current average time tva1 is compared with the time ta1 of the section Ta1, (ta1 + tb1 +... + T11) / 12 = 1.
6, the current section Ta1 is 1.36, while the variable width of the applied voltage is currently 2V. In contrast, 1
The average time tva0 before rotation is 2.0, and the section Ta0
Is 1.7. In this case, the section T before one rotation
The difference 0.34 (= 1.7-1.36) between the time ta0 of a0 and the time ta1 of the current section Ta1 is calculated, and the difference 0.4 between the average time tva0 and the average time tva1 one rotation before is calculated.
(= 2.0-1.6) is calculated. Then, the average time change (tva) with respect to the time change (ta0-ta1) of the section
0-tva1) ratio 0.85 (= 0.34 / 0.4)
Is calculated. For example, if the variable width of the applied voltage is kept constant at 2 V, that is, the applied voltage is set to 100 V, 102 V,
When stepping up in the order of 04V, the difference is increased each time the rotation is repeated, that is, the interval time tends to depart from the average time during one rotation.

Therefore, the variable width of the applied voltage in the section Ta is reduced, that is, the variable width is adjusted so as to be 85% of the calculated 2 V, so that the time change of the section approaches the average time change. That is, the rotation speed of the section is adjusted so as to be the average of the rotation speeds during one rotation. As shown in FIG. 3, the variable width of the applied voltage is 1.7 V (= 2 V) in the section Ta2.
× 85/100), that is, the applied voltage is 102
In the case of V, by setting the applied voltage to 103.7 V, the time ta2 (= 1.2) in the section Ta2 becomes substantially equal to the average time during one rotation.

Next, the section Tb will be described. The time tb1 of the current section Tb1 is 1.44 and 1
Assume that the time tb0 of the section tb0 before rotation is 1.8. Similarly to the above-described section Ta, the difference between the time Tb0 of the section Tb0 one rotation before and the current time tb1 is 0.36.
(= 1.80-1.44), and the ratio 0.90 (= 0.36 / 0.4) of the average time change (tva0-tva1) to the section time change is calculated. And
As shown in FIG. 3, the variable width of the applied voltage in the section Tb is 2 V
× 90/100 = Adjust by 1.8V, that is, when the applied voltage is 102V, the applied voltage is set to 103.8V, so that the time tb2 (1.2) of the section Tb2 becomes 1
It is almost equal to the average time of the rotation speed during rotation.

Next, the section Tc will be described. The time tc1 of the current section Tc1 is 1.52 and 1
It is assumed that the time tc0 of the section Tc0 before rotation is 1.9. As described above, the difference between the time tc0 in the section Tc0 one rotation before and the current time tc1 is 0.38 (= 1.90−1.5).
2) is calculated, and the ratio of the average time change (tva0−tva1) to this section time change is 0.95 (= 0.38 /
0.4) is calculated. Then, as shown in FIG. 3, the variable width of the applied voltage in the section Tc is set to 2V × 95/100 = 1.9.
V, that is, when the applied voltage is 102 V, the applied voltage is set to 103.9 V, so that the section Tc
The second time tc2 (1.2) is substantially equal to the average time of the rotation speed during one rotation.

Next, the section Td will be described. The time td1 of the current section Td1 is 1.60 and 1
It is assumed that the time td0 of the section Td0 before rotation is 2.0. As described above, the difference 0.4 (= 2.0−1.6) between the time td0 of the section Td0 one rotation before and the current time td1 is calculated, and the average time change (tv) with respect to this section time change is calculated.
a0-tva1) ratio 1.00 (= 0.4 / 0.4)
Is calculated. Then, as shown in FIG. 3, the variable width of the applied voltage in the section Tde is adjusted by 2V × 100/100 = 2.0V, that is, when the applied voltage is 102V, the applied voltage is set to 104V. The time td2 (1.2) of the section Td2 is substantially equal to the average time of the rotation speed during one rotation.

In the section Te, as in the section Td, the variable width of the applied voltage is set to 2V × 100/100 = 2.
To adjust only 0 V, as shown in FIG.
Is substantially equal to the average time of the rotation speed during one rotation.

Next, the section Tf will be described. The time tf1 of the current section Tf1 is 1.68 and 1
It is assumed that the time tf0 of the section Tf0 before rotation is 2.10. As described above, the time tf0 in the section Tf0 one rotation before.
0.42 (= 2.10-1.
68), and the ratio of the average time change (tva0−tva1) to the section time change is 1.05 (= 0.42).
/0.4) is calculated. Then, as shown in FIG. 3, the variable width of the applied voltage in the section Tf is set to 2V × 105/100 =
By adjusting the voltage by 2.1 V, that is, by setting the applied voltage to 104.1 V when the applied voltage is 102 V, the time tf2 (1.2) in the section Tf2 is reduced with respect to the average time of the rotation speed during one rotation. Are almost equivalent.

Next, the section Tg will be described. The time tg1 of the current section Tg1 is 1.76 and 1
It is assumed that the time tg0 of the section Tg0 before rotation is 2.20. As described above, the time tg0 of the section Tg0 one rotation before.
0.44 (= 2.20-1.) Between the time tg1 and the current time tg1.
76) is calculated, and the ratio of the average time change (tva0−tva1) to the section time change is 1.10 (= 0.44).
/0.4) is calculated. Then, as shown in FIG. 3, the variable width of the applied voltage in the section Tg is 2V × 110/100 =
By adjusting by 2.2 V, that is, when the applied voltage is 102 V, the applied voltage is set to 104.2 V, so that the time tg2 (1.2) of the section Tg2 is smaller than the average time of the rotation speed during one rotation. Are almost equivalent.

Next, the section Th will be described. The time th1 of the current section Th1 is 1.84 and 1
It is assumed that the time th0 of the section Th0 before rotation is 2.30. Similarly to the above, the time th0 of the section Th0 one rotation before.
0.46 (= 2.30-1.
84) is calculated, and the ratio of the average time change (tva0−tva1) to this section time change is 1.15 (= 0.46).
/0.4) is calculated. Then, as shown in FIG. 3, the variable width of the applied voltage in the section Th is 2V × 115/100 =
By adjusting by 2.3 V, that is, when the applied voltage is 102 V, the applied voltage is set to 104.3 V, so that the time th2 (1.2) of the section Th2 is equal to the average time of the rotation speed during one rotation. Are almost equivalent.

Next, the section Ti will be described. The time ti1 of the current section Ti1 is 1.92 and 1
Assume that the time ti0 of the section Ti0 before rotation is 2.4. As described above, the difference between the time td0 in the section Td0 one rotation before and the current time td1 is 0.48 (= 2.4−1.9).
2) is calculated, and the ratio of the average time change (tva0−tva1) to this section time change is 1.20 (= 0.48 /
0.4) is calculated. Then, as shown in FIG. 3, the variable width of the applied voltage in the sections Td and Te is set to 2V × 120/1.
00 = 2.4V, that is, the applied voltage is 102V
In this case, by setting the applied voltage to 104.4 V, the time td2 (1.2) in the section Td2 becomes substantially equal to the average time of the rotation speed during one rotation.

Also, in the section Tj, as in the section Ti, the variable width of the applied voltage is set to 2V × 120/100 = 2.
To adjust only 4V, as shown in FIG.
Is substantially equal to the average time of the rotation speed during one rotation.

Next, the section Tk will be described. The time tk1 of the current section Tk1 is 1.28 and 1
It is assumed that the time tk0 of the section Tk0 before rotation is 1.60. As described above, the time tk0 of the section Tk0 one rotation before.
0.32 (= 1.60-1.
28) is calculated, and the ratio of the average time change (tva0−tva1) to the section time change is 0.80 (= 0.32).
/0.4) is calculated. Then, as shown in FIG. 3, the variable width of the applied voltage in the sections Td and Te is set to 2V × 80/1.
00 = 1.6 V is adjusted, that is, the applied voltage is 102 V
In this case, by setting the applied voltage to 103.6 V, the time tk2 (1.2) in the section Tk2 becomes substantially equal to the average time of the rotation speed during one rotation.

Also, in the section Tl, similarly to the section Tk, the variable width of the applied voltage is set to 2V × 80/100 = 1.6.
Since only V is adjusted, as shown in FIG. 3, the time t12 (1.2) in the section T12 becomes substantially equal to the average time of the rotation speed during one rotation.

Similarly, by repeating the above-described processing for each rotation, the time in each section is set to the average time of the rotation speed during one rotation, that is, the rotation speed in each section is averaged for the rotation speed during one rotation. To speed.

As described above, the ratio of the average time change to the time change in each section is added to the applied voltage so that the time (rotation speed) of each section is equal to the average time (average rotation speed). In other words, since the variable width of the applied voltage is adjusted (variable) according to the load state during one rotation, regardless of the rotation speed and the load state at that time,
The applied voltage in each section can be optimized. For example, when there is a load fluctuation during one rotation with a compressor or the like, smooth rotation control can be performed, thereby eliminating the problem of vibration and noise. In addition, smooth rotation control can be performed up to a low rotation speed, and energy saving can be achieved. Further, since the control circuit 10 can be executed by software of a microcomputer without using a special mechanism or the like, the cost can be reduced.

[0033]

As described above, according to the first aspect of the present invention, the brushless motor is controlled by using the induced voltage included in the terminal voltage of the armature winding of the brushless motor. The position of the rotor is detected, and based on this position detection, the energization of the armature winding of the brushless motor is switched, and the voltage applied to the armature winding is varied to change the rotation speed of the brushless motor. In the control method of the brushless motor to be controlled, one rotation is divided into a plurality of parts, a rotation speed in each divided section is obtained, and an average rotation speed in one rotation section is obtained, and a change in the rotation speed in the same section is calculated. At the same time, the change in the average rotation speed is calculated, the ratio of the change in the average rotation speed to the change in the calculated rotation speed is calculated, and the mark of the armature winding is marked according to this ratio. The variable width of the voltage is adjusted so that the rotation speed of each section during one rotation is close to the average rotation speed, so that the rotation speed of each section is averaged, eliminating problems of vibration and noise, and There is an effect that smooth rotation control can be performed up to a low rotation speed and energy saving can be achieved.

According to the second aspect of the present invention, the position of the rotor of the brushless motor is detected by using the induced voltage included in the terminal voltage of the armature winding of the brushless motor.
A brushless motor control method for controlling energization of an armature winding of the brushless motor based on the position detection and controlling a rotation speed of the brushless motor by changing an applied voltage of the armature winding, One rotation is divided into a plurality of parts based on the position detection of the rotor, the time of each divided section is measured, and the average time during one rotation is calculated based on the measured time of each section. Calculates the difference between the section measured during the previous rotation and the time of the same section measured during the current rotation, calculates the difference between the previous average time and the current average time, and calculates the average for the time difference of the same section. The ratio of the time difference was calculated, and the variable width of the applied voltage to the armature winding was adjusted in accordance with the ratio, so that the time of each section during one rotation was made closer to the average time. By close to the average time of one rotation, since the optimum applied voltage of each section, it is smooth rotation control even when there is a load variation during one rotation,
Thereby, the problem of vibration and noise can be solved.
In addition, since smooth rotation control can be performed up to a low rotation speed, there is an effect that energy can be saved.

According to the third aspect of the present invention, the means for adjusting the variable width of the voltage applied to the armature winding in the first or second aspect is a microcomputer of the control means of the brushless motor. In addition to the effect of item 1 or 2, there is an effect that it can be executed by the software of the microcomputer of the control means, that is, without using a special mechanism or the like and without increasing the cost.

According to the fourth aspect of the present invention, the brushless motor according to the first or second aspect is used for a compressor motor. Therefore, in addition to the effect of the first or second aspect, for example, in the case of a compressor of an air conditioner, one rotation Although there is a load fluctuation in the air conditioner, this load fluctuation can be dealt with, and there is an effect that the smooth operation and energy saving of the air conditioner can be achieved.

[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]

3 Inverter unit 4 Brushless motor (sensorless DC brushless motor) 5 Position detection circuit 6, 10 Control circuit (microcomputer)

Claims (4)

[Claims] 1. A brushless motor according to claim 1, wherein a position of a rotor of the brushless motor is detected using an induced voltage included in a terminal voltage of an armature winding of the brushless motor, and the motor of the brushless motor is detected based on the detected position. In the brushless motor control method of controlling the rotation of the brushless motor by switching the energization of the armature winding and changing the voltage applied to the armature winding, a single rotation is divided into a plurality of sections. , And the average rotation speed in one section of rotation is calculated, and the change in rotation speed in the same section is calculated, and the change in average rotation speed is calculated. The average rotation speed with respect to the change in the calculated rotation speed is calculated. And the variable width of the voltage applied to the armature winding is adjusted in accordance with the calculated ratio, so that the rotation speed of each section during one rotation approaches the average rotation speed. A method for controlling a brushless motor, comprising: 2. The brushless motor according to claim 1, further comprising: detecting a position of a rotor of the brushless motor using an induced voltage included in a terminal voltage of an armature winding of the brushless motor; A brushless motor control method for controlling the rotation speed of the brushless motor by switching the energization of the armature winding and changing the voltage applied to the armature winding. While dividing the inside into a plurality, measuring the time of each divided section and calculating the average time during one rotation based on the measured time of each section, the time measured during the previous rotation and the time measured during the current rotation are calculated. The difference between the measured time of the same section is calculated, the difference between the previous average time and the current average time is calculated, and the ratio of the average time difference to the time difference of the same section is calculated. A method for controlling a brushless motor, characterized in that the variable width of the voltage applied to the armature winding is adjusted accordingly so that the time of each section during one rotation approaches the average time. 3. The brushless motor control method according to claim 1, wherein the means for adjusting the variable width of the voltage applied to the armature winding is a microcomputer for controlling the brushless motor. 4. The brushless motor control method according to claim 1, wherein said brushless motor is a compressor motor.