JPH10262390A - Control of brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent power swing and stopping of a brushless motor by preventing spike voltage from hiding a position detection point in electrical switching for the brushless motor. SOLUTION: The electrical switching time of the armature winding current of a brushless motor 4 is predicted by position detection signals A, B and C which detect the rotor 4a of the brushless motor 4, and the electrical switching of the armature winding current is conducted in the predicted time. A control circuit 10 detects the maximum value of preceding variation amount, by detecting the time duration of spike voltage generated by energization-switching the armature winding current based on the position detection signals A, B, and C, and calculating the variation amount based on the detected time duration of the spike voltage and previously-detected time duration of the spike voltage. For estimation of the energization-switching time, if a value which is obtained by adding the time duration of the spike voltage detected this time to the maximum value exceeds a prescribed value, the time which is earlier than the predicted energization-switching time is set as the next energization-switching time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation control technology for a sensorless DC brushless motor (hereinafter referred to as a brushless motor) used for a compressor of an air conditioner, and more particularly to a brushless motor for preventing loss of synchronism and stoppage. It relates to a control method.

[0002]

2. Description of the Related Art In this type of rotation control of a brushless motor, a method is used in which, for example, a voltage induced in an armature winding of a brushless motor is used without using a Hall element as means for detecting the position of a rotor. is there. When the position of the rotor is detected by using the induced voltage and the energization of the armature winding current of the brushless motor is switched based on the detected position, for example, a control device shown in FIG. 4 is required.

[0003] In FIG. 4, this control device doubles voltage rectification and smoothing of an AC power supply (commercial 100 V) 1 by a voltage doubler rectifying / smoothing circuit 2 and converts the doubled voltage rectified and smoothed DC power supply Vdc into a plurality of switching signals. Element (transistor) U
a, Va, Wa, X, Y, and Z are switched by an inverter circuit 3 in a bridge connection and applied to an armature winding of a three-phase brushless motor 4. The voltage doubler rectifying / smoothing circuit 2 includes a rectifier circuit, a capacitor circuit, and a smoothing capacitor which are already known.

[0004] The armature windings U, V,
A terminal voltage of W (for example, a voltage having a phase different by 120 degrees; including an induced voltage) is input to the position detection circuit 5, and the position detection circuit 5 compares each terminal voltage with the reference voltage Vdc / 2 and obtains it. The detected position signals A, B, and C are output to a control circuit (microcomputer) 6.

For this purpose, the position detecting circuit 5 is provided with a DC power supply V
A voltage dividing circuit 5a that divides dc into １ ／ to generate a reference voltage Vdc / 2, and comparing circuits 5b and 5c that compare the terminal voltages of the armature windings U, V, and W with the reference voltage Vdc / 2. , 5
d.

[0006] The brushless motor 4 is started, synchronously operated,
After performing this synchronous operation for a predetermined time, the armature windings U, B, C are detected based on the position detection signals A, B, C from the position detection circuit 5.
The energization of V and W is switched. In the case of the PWM control (chopping drive) method, the control circuit 6 controls the switching elements (transistors) Ua, Va, Wa,
The driving circuit 7 outputs a chopping signal for turning on, off, and chopping X, Y, and Z to the drive circuit 7. In addition,
As shown in FIG. 4, when the control device is used for controlling a compressor of an air conditioner, a power factor improving reactor 8 may be provided between the AC power supply 1 and the voltage doubler rectifying / smoothing circuit 2.

The operation of the control device having the above configuration will be described with reference to the time chart of FIG. FIG. 5 shows switching elements (transistors) Ua, V of the inverter circuit 3.
This is an example in which the ON drive is chopped when a, Wa, X, Y, and Z are turned ON and OFF.

First, in the position detection operation, the control circuit 6
Detects the position of the rotor 4a based on the position detection signals A, B, and C (see black points (position detection points) in FIGS. 5A, 5B, and 5C). The conduction phase is switched after 30 degrees. Note that 30 degrees later is a time calculated by, for example, the interval time of position detection × 30/360, and adding the calculated time to the time of the position detection point to predict the time.

More specifically, an intersection a between the terminal voltage (induced voltage) of the armature winding U and the reference voltage Vdc / 2 (FIG. 5A)
30), the current is switched from the energization of the Wa phase (transistor Wa) to the energization of the Ua phase (transistor Ua) 30 degrees later (see (d) and (f) in the same figure).

When an intersection (see FIG. 5 (c)) between the terminal voltage (induced voltage) of the armature winding W and the reference voltage Vdc / 2 is detected, 30 degrees later, the Z-phase from the energization of the Y-phase (transistor Y) is turned off.
The phase (transistor Z) is switched to energization (see (h) and (i) in the figure).

When an intersection (see FIG. 5B) between the terminal voltage (induced voltage) of the armature winding V and the reference voltage Vdc / 2 is detected, after 30 degrees, the Ua phase (transistor Ua) is turned on and the Ya phase is turned on. (Transistor Ya) is switched to the energized state (see FIGS. 3D and 3E).

When an intersection (see FIG. 5 (a)) between the terminal voltage (induced voltage) of the armature winding U and the reference voltage Vdc / 2 is detected, after 30 degrees, the Z-phase (transistor Z) is de-energized by X.
The current is switched to the energization of the phase (transistor X) (see (g) and (i) in the figure).

When an intersection (see FIG. 5 (c)) between the terminal voltage (induced voltage) of the armature winding W and the reference voltage Vdc / 2 is detected, after 30 degrees, the Va phase (transistor Va) is turned on from the energization of the Va phase (transistor Va). (Transistor Wa) is switched to the energized state (see (e) and (f) in the figure).

When an intersection (see FIG. 5 (b)) between the terminal voltage (induced voltage) of the armature winding Y and the reference voltage Vdc / 2 is detected, after 30 degrees, the X-phase (transistor X) is turned off from the energization of the X-phase (transistor X).
The current is switched to the energization of the phase (transistor Y) (see (g) and (h) in the same figure).

Hereinafter, the rotation of the brushless motor 4 can be controlled by repeating the switching of the energized phase. Further, the voltage of the brushless motor 4 can be varied by varying the width of the ON time (see FIG. 5) when each transistor is driven by chopping, that is, the brushless motor 4 can be controlled to a predetermined rotation speed. it can.

[0016]

However, in the above-described method of controlling a brushless motor, the spike voltage k generated by energization switching is large, and if that state continues, the spike voltage k can be applied to the position detection point. 5 is extremely high, and is applied to any position detection point (the intersection of the induced voltage and the reference voltage Vdc / 2) (FIG. 5).
(See the wavy line in (a)). In other words, since the position detection point is hidden, the energization switching is delayed, and as a result, a problem occurs in which the brushless motor 4 loses synchronism and stops.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to make it possible to change the energization switching time in accordance with the amount of change in the time width of the spike voltage so that the spike voltage does not reach the position detection point. In other words, it is an object of the present invention to provide a brushless motor control method capable of reliably detecting the position of the rotor and preventing step-out and stop of the brushless motor.

[0018]

In order to achieve the above object, the present invention compares a terminal voltage of an armature winding of a brushless motor with a reference voltage, and uses the position detection signal of the comparison result to determine the position of the brushless motor. Control of a brushless motor that detects a position of a rotor, predicts a switching time of energization of the armature winding current based on the position detection, and switches energization of the armature winding current at the predicted energization switching time. A method for detecting a time width of a spike voltage generated by switching the energization of the armature winding current based on the position detection signal, and detecting the time width of the detected spike voltage and the previously detected spike voltage. The amount of change is calculated based on the time width of the signal, and the maximum value of the amount of change is detected while the value obtained by adding the time width of the spike voltage detected this time and the maximum value exceeds a predetermined value. Is characterized in that sometimes have to switch the energization of the armature winding earlier than the predicted energization switching time.

Further, in the brushless motor control method according to the present invention, the time width of the spike voltage generated by switching the energization of the armature winding current is detected based on the position detection signal, and the detected spike voltage is detected. The amount of fluctuation is calculated based on the time width of the spike voltage and the time width of the previously detected spike voltage, and a value obtained by adding the time width of the spike voltage and the maximum value while detecting the maximum value of the fluctuation amount so far. When the value exceeds a predetermined value ΔT, a value (predetermined value ΔTsp) is calculated by subtracting the predetermined value from the value obtained by the addition (the predetermined value ΔTsp). The time is set, and then the predetermined value ΔTsp is changed to a smaller value.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS. In the figure,
The same parts as those in FIG.

In FIG. 1, a control device to which the brushless motor control method is applied includes a control circuit 6 shown in FIG.
In addition to the above function, the time width of the spike voltage k generated by the energization switching is detected based on the position detection signal, and the difference (fluctuation amount) between the previous and current time widths is calculated, and the maximum value of the fluctuation amount so far Is detected (stored and updated), and a value obtained by adding the maximum value and the time width of the current spike voltage k is a predetermined value (a value smaller than 30 degrees in the case of a three-phase four-pole motor;
For example, a control circuit (microcomputer) 10 is provided which, when it exceeds (eg, 29 degrees), makes at least the next energization switching earlier than the predicted time.

Next, the operation of the control device will be described in detail with reference to flowcharts shown in FIGS. 2 and 3. First, it is assumed that the rotation control of the brushless motor 4 is in a position detection operation mode. It is assumed that the position detection operation described in the example is being performed. For details of the position detection operation, see FIG.

At this time, the control circuit 10 stores (stores and updates) the energization switching time tk of the armature winding current. Further, the rotor 4a is controlled by the position detection signals A, B, and C.
Is detected (the black point shown in FIG. 5), the time difference ts between the previous position detection time and the current position detection time is calculated,
Using this time difference ts, a predetermined value ΔT (= ts × θ / 36)
0) is calculated and stored internally. When the ideal angle from the energization switching to the position detection is 30 degrees, θ may be a value smaller than 30 degrees, for example, 29 degrees.

When the end of the spike voltage k is detected by the position detection signal A or B or C, the routine shown in FIG. 2 is executed. In this case, the routine of FIG. 2 is executed each time the end of the spike voltage k is detected. The end of the spike voltage k is determined by the first edge of the position detection signal A or B or C after energization switching (falling edge when the next induced voltage is rising, rising edge when the next induced voltage is falling). To detect.

Further, each time the position of the rotor 4a is detected by the position detection signals A, B and C, a routine shown in FIG. 3 is executed. The position is detected at the first edge of the position detection signals A, B, and C after the energization switching (a rising edge when the induced voltage is rising, and a falling edge when the induced voltage is falling).

First, when the end of the spike voltage k generated by the energization switching is detected, the end time tse is stored (step ST1), and the previously stored previous energization switching time tk is read (step ST2). The magnitude (time width) tsp of the spike voltage k is calculated and stored by subtracting the previous energization switching time tk from the time tse (step ST3).

Subsequently, the time width ts of the previous spike voltage
pp is read (step ST4), and a difference from the current spike voltage time width tsp, that is, a fluctuation amount Tsp is calculated (step ST5). Subsequently, the maximum value Tspmx is read out of the fluctuation amounts so far (step ST6), and the fluctuation amount Tsp calculated this time is compared with the maximum value Tspmx (step ST7).

The fluctuation amount Tsp calculated this time is the maximum value Tspm.
If it is larger, the process proceeds from step ST7 to ST8, and the variation Tsp calculated this time is set to the maximum value Tspmx of the variation thus far. That is, the maximum value Tsp of the fluctuation amount
Update mx. If the fluctuation amount Tsp for calculating the current time is equal to or less than the maximum value Tspm, the existing maximum value Tspmx is held as it is. That is, there is no need to update.

Subsequently, the maximum value Tspmx is added to the time width tsp of the spike voltage calculated this time, and it is determined whether or not the added value exceeds a predetermined value ΔT (step ST9). If the sum exceeds the predetermined value ΔT, it is determined that there is a high possibility that the current spike voltage will hide the current position detection point, and a value (predetermined value) ΔTsp that makes the energization switching time described later earlier than the predicted time is set to ( tsp +
tspmx) -ΔT (step ST1)
0).

Subsequently, in order to execute the routine by detecting the end of the next spike voltage, the time width tsp of the current spike voltage is replaced with tspp, and the routine ends (step ST11).

On the other hand, each time the position of the rotor 4a is detected by the position detection signals A, B and C, the routine shown in FIG. 3 is executed. Note that the above-described calculation processing of the limited angle time Δtsp or the like may be executed in this routine. First, the position detection time ti is detected (step ST20), and the time tsk (= ti-tin) of the position detection interval is calculated by subtracting the previous position detection time tin from this time ti (step ST21).

Subsequently, if the point delayed by 30 degrees from the position detection point is an ideal energization switching point, の of the previous position detection interval time tsk is added to the position detection time ti, and this added value is calculated. The next value (the predetermined value) ΔTsp obtained in the routine of FIG.
k is calculated (step ST22), and the calculated time tk is set as the energization switching time (step ST2).
3). That is, the next energization switching time is equal to the predicted energization switching time (the position detection interval time ts before the position detection time ti).
(a time obtained by adding よ り of k)) by a predetermined value ΔTsp.

Subsequently, the position detection time ti is set to tin (step ST24), and a predetermined value Δ for preparing the later energization switching time and for accelerating the energization switching calculated this time.
Tsp is set to １ ／ and stored (step ST25).
That is, in step ST9 of the routine shown in FIG. 2, when it is determined that the value obtained by adding the maximum value Tspmx to the time width tsp of the spike voltage calculated this time does not exceed the predetermined value ΔT, the predetermined value ΔTsp for speeding up the energization switching is provided.
Is not calculated. Therefore, the value ΔTsp calculated and stored in step ST25 is used in the routine shown in FIG. If the time width of the spike voltage does not increase, the process of step ST10 is not performed, while the predetermined value ΔTsp is reduced to １ ／ each time.
When the processing of (1) is not continuously performed a predetermined number of times, the predetermined value ΔTsp may be temporarily cleared to zero.

As described above, the variation of the time width of the spike voltage k is calculated, and the maximum value of the variation is detected, and the maximum value and the time width of the current spike voltage k are added. The value is a predetermined value (3 for a three-phase four-pole motor
When it exceeds (a value smaller than 0 degrees; for example, 29 degrees), at least the next energization switching is advanced earlier than the predicted time. Therefore, when the possibility that the spike voltage k is applied to the position detection point increases, the next energization switching time is advanced by the predetermined value ΔTsp, and the end of the spike voltage k generated by the energization switching is earlier, so that FIG. In other words, the position indicated by the dashed line is not reached, that is, the spike voltage k does not reach the next position detection point, and the position can be reliably detected. As a result, the step-out and stop of the brushless motor 4 are eliminated.

Further, in the routine shown in FIG. 3, since the predetermined value ΔTsp is set to １ ／ and the processing is terminated, the value obtained by adding the maximum value of the fluctuation amount and the time width of the current spike voltage k becomes the predetermined value (3 Less than 30 degrees for phase quadrupole motor;
(For example, 29 degrees) When the value does not exceed ΔT, the predetermined value Δ
Tsp becomes the former half. Therefore, if the value obtained by adding the maximum value of the fluctuation amount and the time width of the current spike voltage k does not exceed the predetermined value ΔT after at least once the energization switching time is advanced, the predetermined value ΔTsp is halved each time. Therefore, the next energization switching time approaches the predicted energization switching time by that amount, and is set to 1/2 each time, so that the energization switching time becomes an almost optimal predicted energization switching time.

[0036]

As described above, according to the first aspect of the brushless motor control method, the energization switching time is predicted by detecting the position of the rotor of the brushless motor. The time width of the spike voltage generated by the energization switching is detected based on the position detection signal, and the fluctuation amount is calculated based on the time width of the detected spike voltage and the time width of the previously detected spike voltage. While detecting the maximum value of the fluctuation amount so far, when the value obtained by adding the time width of the spike voltage detected this time and the maximum value exceeds a predetermined value, the armature winding is earlier than the predicted energization switching time. Since the energization of the wire is switched, the larger the amount of change in the time width of the spike voltage, the earlier the energization switching time can be. You can not expose the 置検 out point, that it is possible to reliably detect the position of the rotor, out-of the brushless motor, there is an effect that it is possible to prevent the stop.

According to the second aspect of the present invention, the energization switching time is predicted by detecting the position of the rotor of the brushless motor. The time width of the spike voltage generated by the energization switching of the armature winding current is determined by the position detection. Based on the signal, the amount of fluctuation is calculated based on the time width of the detected spike voltage and the time width of the previously detected spike voltage, and the maximum value of the fluctuation amount is detected,
When a value obtained by adding the time width of the spike voltage and the maximum value exceeds a predetermined value ΔT, a value (predetermined value ΔTsp) obtained by subtracting the predetermined value from the added value is calculated. In the prediction, the time earlier by the predetermined value ΔTsp is set as the next energization switching time, and then the predetermined value ΔTsp is changed to a smaller value, so that the same effect as in claim 1 is obtained, and the fluctuation amount is changed. When the value obtained by adding the maximum value of .times. And the time width of the current spike voltage k does not exceed a predetermined value (a value smaller than 30 degrees in the case of a three-phase quadrupole motor; for example, 29 degrees) .DELTA.T, the predetermined value .DELTA. In order to make the value smaller (（), the next energization switching time approaches the predicted energization switching time, and it is possible to finally set the almost optimal predicted energization switching time. There is a cormorant effect.

[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 flowchart for explaining the operation of the control device shown in FIG. 1;

FIG. 3 is a schematic flowchart 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.

FIG. 5 is a schematic time chart for explaining the operation of the control device shown in FIG. 3;

[Explanation of symbols]

Reference Signs List 1 AC power supply 2 times voltage rectifier circuit 3 Inverter circuit 4 Brushless motor (sensorless DC brushless motor) 4a Rotor (of brushless motor 4) 5 Position detection circuit 6, 10 Control circuit (microcomputer) A, B, C Position detection signal k Spike voltage ΔT predetermined value (a value smaller than 30 degrees; for example, 29 degrees) ΔTsp predetermined value (a value that advances the energization switching time)

Claims (2)

[Claims] 1. A terminal voltage of an armature winding of a brushless motor is compared with a reference voltage, a position of a rotor of the brushless motor is detected based on a position detection signal of the comparison result, and based on the position detection. A brushless motor control method for switching the energization of the armature winding current at the predicted energization switching time, wherein the energization of the armature winding current is switched. The time width of the generated spike voltage is detected based on the position detection signal, and the amount of fluctuation is calculated based on the time width of the detected spike voltage and the time width of the previously detected spike voltage. While the maximum value of the fluctuation amount is detected, when the value obtained by adding the time width of the spike voltage detected this time and the maximum value exceeds a predetermined value, the electric power supply is switched earlier than the predicted energization switching time. A method for controlling a brushless motor, characterized in that energization of a child winding is switched. 2. A terminal voltage of an armature winding of a brushless motor is compared with a reference voltage, and a position of a rotor of the brushless motor is detected based on a position detection signal of the comparison result. A brushless motor control method for switching the energization of the armature winding current at the predicted energization switching time, wherein the energization of the armature winding current is switched. The time width of the generated spike voltage is detected based on the position detection signal, and the amount of fluctuation is calculated based on the time width of the detected spike voltage and the time width of the previously detected spike voltage. While detecting the maximum value of the fluctuation amount, when the value obtained by adding the time width of the spike voltage and the maximum value exceeds a predetermined value ΔT, a value obtained by subtracting the predetermined value from the added value (the predetermined value ΔT) sp) is calculated, and a time earlier by a predetermined value ΔTsp is set as the next energization switching time when the energization switching time is predicted, and then the predetermined value ΔTsp is changed to a smaller value. Control method of a brushless motor.