JPH0823695A - Method for controlling motor - Google Patents

Abstract

PURPOSE:To obtain a proper conduction switching timing by varying a reference voltage corresponding to the number of rotations and load of a motor when obtaining a timing for switching the conduction of the coil winding of an electric motor. CONSTITUTION:A brushless motor 1 performs synchronous operation for a specific amount of time, a control circuit 12 switches a DC power supply based on the position detection of a rotor, the DC power supply is applied to the coil winding of each armature, thus successively switching the conduction of each armature. Then, when switching to the operation by position detection, a shaping circuit 10 outputs a position signal and a comparison circuit 11 compares the waveform signal with a D/A-converted voltage and then outputs a position signal which is the cross point between an induced voltage waveform and a reference voltage. In this case, the reference voltage is varied according to the number of rotations and load state of the brushless motor 1, calculates the timing of a specific phase angle delay according to the cross point between the previous induced voltage and the reference voltage, and measures a calculation time from the edge of the position signal to obtain a conduction timing, thus obtaining a proper timing of the position signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor used in an air conditioner (for example, a sensorless DC brushless motor).
The present invention relates to a rotor position detection technique, and more particularly, to a motor control method that enables a motor to operate at maximum efficiency.

[0002]

2. Description of the Related Art In order to control the rotation of this sensorless DC brushless motor (hereinafter referred to as brushless motor),
For example, a three-phase brushless motor requires the control device shown in FIG.

In FIG. 4, this control device comprises a drive unit 2 for switching and applying a DC power supply Vcc to a plurality of armature windings of a brushless motor 1, and a brushless motor 1.
Terminal voltage (shown in FIGS. 5A, 5B, and 5C); 12
Position detection circuit 3 for detecting a virtual neutral point (a shown in FIG. 5) by comparing U, V, W with voltages having different phases of 0 degrees; induced voltages) U, V, W and a predetermined reference voltage, and the detected virtual medium. Sex point a
To obtain a position detection timing with a predetermined phase delay (for example, π / 6 phase delay), obtain an energization switching timing of each armature winding based on this position detection, and output a drive signal,
Further, it is provided with a control circuit (microcomputer) 4 for chopping a drive signal for driving a switching element (lower arm switching element) of at least one arm of the drive unit 2 in accordance with the rotation speed.

In the position detecting circuit 3, 1/2 of the DC voltage Vcc applied to the brushless motor 1 is used.
Is used as a reference voltage, the induced voltage waveforms of the input terminal voltages U, V, and W are compared with the reference voltage Vcc / 2, and a virtual neutral point a
The position signal of is output.

In the control device having the above structure, the control circuit 4
Outputs a drive signal for turning on and off the switching element of the drive unit 2 at a predetermined time when the brushless motor 1 is activated to switch the energization of each armature winding of the brushless motor 1 to perform the synchronous operation of the brushless motor 1 for a predetermined time. To do.

After a lapse of a predetermined time, the synchronous operation is switched to the operation based on the position detection. At this time, the control circuit 4 detects the position of the rotor of the brushless motor 1 by three signals from the position detection circuit 3. Then, based on the position detection, the transistor of the drive unit 2 is driven on and off in a predetermined manner to switch the energization of each armature winding, and the brushless motor 1
To control the rotation.

Further, the number of revolutions is calculated based on the detected position, the calculated number of revolutions is compared with the target number of revolutions, and a drive signal for driving the switching element of the lower arm is output according to the comparison result. The chopping ratio (ON / OFF ratio) is changed to control the rotation of the brushless motor 1 to a target rotation speed (so-called PWM control method).

[0008]

In the motor control method described above, the energization switching timing of the armature winding is obtained with reference to each virtual neutral point a. The induced voltage waveform of the terminal voltage varies depending on the load (shown in FIGS. 5A to 5C), and as a result, the detection timing of the virtual neutral point a varies (the phase angle varies), and the brushless motor is operated at maximum efficiency. There is a problem that you cannot do it.

That is, since the reference voltage is constant at Vcc / 2, the phase angle is 2 in the case shown in FIG.
This is because in the case of 0 degree, the phase angle becomes 40 degrees in the case shown in FIG. 7C, which is different from the original phase angle of 30 degrees, and the energization switching timing becomes inappropriate.

Further, because the phase angles are different, adjustment is required when calculating the time until the energization switching timing, and the calculation time including this adjustment becomes long, and for example, high-speed calculation is possible in the case shown in FIG. 5 (a). If an expensive and expensive microcomputer is not used, the energization switching timing of the phase angle of 30 degrees may not be in time.

The present invention has been made in view of the above problems, and an object thereof is to obtain an appropriate energization switching timing irrespective of the number of rotations and load of the motor, and thus to operate the motor with maximum efficiency. Another object of the present invention is to provide a motor control method that can be achieved at low cost.

[0012]

To achieve the above object, according to the present invention, when controlling the rotation of a motor, the plurality of armature windings of the motor are energized based on the position detection of the rotor of the motor. In the switching motor control method, the terminal voltage of the armature winding and the reference voltage are compared to detect the time of the voltage at the intersection of the induced voltage waveform of the terminal voltage and the reference voltage, and the timing of the previous time is determined. When the energization switching timing of the armature winding is obtained, the gist is that the reference voltage is changed according to the rotation speed of the motor and the load.

Further, a brushless motor is used as the motor, the terminal voltage of the armature winding is compared with a reference voltage, and the time of the voltage at the intersection of the induced voltage waveform of the terminal voltage and the reference voltage is detected, The position signal at the timing of the previous time is input to the microcomputer, the microcomputer calculates the rotation speed of the brushless motor based on the position signal, and the chopping on for the PWM control is turned on, The load state of the brushless motor is detected by the off ratio, the reference voltage is changed according to the rotation speed and the load state, and the energization switching timing that maximizes the operation efficiency of the brushless motor is obtained based on the position signal. It is a thing.

[0014]

With the above-mentioned means, when the induced voltage waveform of the terminal voltage of the armature winding of the motor differs depending on the rotation speed and load state of the motor (including the brushless motor), a reference for comparison with this induced voltage waveform The voltage is changed.

By changing the reference voltage, the position signal, which is the intersection of the induced voltage waveform and the reference voltage, does not become improper, and the timing of the predetermined phase angle delay from the previous intersection is always optimum, that is, the energization. The switching timing that maximizes the operation efficiency can be obtained.

Further, the microcomputer calculates the time of one cycle from the position signal and the timing (energization switching timing) delayed by a predetermined phase angle (30 degrees or the like) from the edge of the position signal. At this time,
As described above, the timing of the position signal does not require any adjustment, and the time for the phase angle of 30 degrees is secured. That is, as the microcomputer, it is possible to use an inexpensive computer that does not operate at high speed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A motor control method according to the present invention, for example, when comparing a terminal voltage (induced voltage) of an armature winding of a three-phase brushless motor with a reference voltage, as shown in FIG. Note that the detection timing of the position signal can be changed by changing the reference voltage Eth according to the load or the load, that is, the predetermined phase angle delay timing can be obtained from the edge of the position signal required as the optimum energization switching timing. It was done.

Therefore, the control device to which the motor control method of the present invention is applied has, for example, the configuration shown in FIG. In the figure, the same parts as those in FIG.

In FIG. 1, this control device inputs, for example, terminal voltages (voltages having different phases of 120 degrees; induced voltages) U, V, W of three armature windings of a three-phase brushless motor 1 to input waveforms. A waveform shaping circuit 10 for shaping, a comparison circuit 11 for comparing the induced voltages of these terminal voltages U, V, W with a predetermined reference voltage Eth to detect a position signal of each phase, and a control circuit 4 shown in FIG. In addition to the functions of, brushless motor 1
The value of the predetermined reference voltage Eth is set according to the number of revolutions and the load of the control circuit (microcomputer) 12 that digitally outputs the value of the set reference voltage Eth, and the digital data from the control circuit 12 is converted into analog. D to obtain a predetermined reference voltage Eth used in the comparison circuit 11
A / A conversion circuit 13 is provided. The control circuit 12
If the D / A converter has a built-in D / A conversion function, the D / A conversion circuit 13 can be omitted.

The waveform shaping circuit 10 is composed of circuits such as a filter, a sampling and holding circuit, and a multi-vibrator. For example, a spike voltage waveform and P
A signal including the induced voltage waveform from which the chopping waveform of WM control is removed is output.

The control circuit 12 detects the period T1 of one cycle (one rotation) by the signal from the comparison circuit 11 and the rotation period detector 12a based on this detection timing (timing of the virtual neutral point a). And the energization switching timing of the brushless motor 1 (predetermined phase angle (30 degrees, 90 degrees)
Power supply switching timing generator 12b for generating a delay timing), and a PWM for varying the on / off ratio of the current chopping of the PWM control according to the difference between the current rotation speed and the target rotation speed for one rotation time T1. Among the drive signals from the control unit 12C, the drive signal generation unit 12d that generates a drive signal for turning on and off the switching elements of the drive unit 2 at the energization switching timing, and the drive signal from the drive signal generation unit 12d, for example, drive The ON portion of the drive signal for driving the lower arm switching element of the unit 2 is controlled by the PWM control unit 12c.
Based on the speed control unit 12e that chops the PWM control signal from the output and outputs the current rotation speed according to the time T1 of one rotation and the load state due to ON / OFF of the PWM control chopping. The comparison voltage generator 12f for setting the voltage Eth is provided. The control circuit 11 shown in FIG. 1 is algorithmic.

Next, the operation of the rotor position detecting method to which the motor control device having the above-mentioned structure is applied will be described in detail with reference to the time charts of FIGS.

First, when the brushless motor 1 is started, the control circuit 12 outputs a drive signal to synchronously operate the brushless motor 1 and turns on and off a plurality of switching elements of the drive unit 2 in a predetermined manner as in the conventional case. DC power supply V
cc is switched and applied to each armature winding of the brushless motor 1, and the energization of each armature winding is sequentially switched.

After the synchronous operation has been performed for a predetermined time, the control circuit 12 switches the DC power supply Vcc based on the position detection of the rotor of the brushless motor 1 and applies it to each armature winding. The energization is switched sequentially.

When switching to the operation based on the position detection, the terminal voltages U, V, W of the armature windings of the brushless motor 1 are input to the waveform shaping circuit 10. This waveform shaping circuit 10 is shown in FIG. The position signals shown in a), (c) and (d) are output.

The comparison circuit 11 compares the waveform signal with the D / A converted voltage, and the induced voltage waveform and the reference voltage Eth.
A position signal, which is the intersection of and, is output (see FIG. 3B).

The position signal of the comparison result is input to the control circuit 12, and the rotation cycle detecting section 12 of the control circuit 12 is inputted.
a detects the time T1 of one cycle of the position signal.

The energization switching timing generator 12b calculates timings (time T2, T3) delayed by a predetermined phase angle (30 degrees, 90 degrees) on the basis of the detection time T1, and at the time T2 from the edge of the position signal. , T3 are measured to generate the energization switching timing. The drive signal generation unit 12d generates a drive signal at the energization switching timing.

Further, the PWM control unit 12c determines the PW according to the difference between the number of revolutions at the time T1 of one cycle and the target number of revolutions.
The on / off ratio of the current chopping for M control is changed. The speed control unit 12e chops the ON portion of the drive signal for driving the lower arm switching element of the drive unit 2 by the chopping. As a result, the voltage applied to the brushless motor 1 is changed, and the rotation speed of the brushless motor 1 is maintained at the target rotation speed.

At the time of the above rotation control, the comparison voltage generator 12f includes the rotation cycle detector 12a and the PWM controller 12.
The value of the reference voltage Eth of the comparison circuit 11 is set according to the information from c, that is, the rotation speed and the load state of the brushless motor 1. The load state can be determined based on the on / off ratio of the current chopping during PWM control, for example. The value of the reference voltage Eth set above may be calculated according to the number of revolutions or the load state, and when the load of the brushless motor 1 is determined, the reference voltage Et obtained in advance is obtained.
The value of h may be stored in the ROM.

In this case, the reference voltage Eth is set according to the current rotation speed and the load state, that is, the value of the reference voltage Eth is changed so that the energization switching timing that maximizes the operating efficiency of the brushless motor 1 can be obtained. To do. The value of the set reference voltage Eth is converted into an analog value by the D / A conversion circuit 13, and the analog-converted reference voltage Eth is obtained.
Is input to the comparison circuit 11.

As a result, even if the induced voltage waveforms of the terminal voltages U, V, W differ depending on the rotation speed and the load condition of the brushless motor 1, as shown in FIGS. By changing Eth,
The angle from the intersection of the reference voltage Eth and the induced voltage waveform to the next energization switching is always constant.

When the position signal thus obtained is input to the control circuit 12, the energization switching timing section 12b of the control circuit 12 is based on the detection time (1 cycle time) T1 in the rotation cycle detection section 12a. Virtual neutral point a
From the timing of the predetermined phase angle delay from T1 / 12
(T2 = 30 degrees) and T1 / 4 (T3 = 90 degrees) are calculated.

Further, as described above, the energization switching timing section 12b generates the energization switching timing by measuring the calculation times T2 and T3 from the edge of the position signal from the comparison circuit 11. Therefore, the energization switching timing does not vary depending on the rotation speed, and the optimum timing (timing of maximum operation efficiency) can always be obtained.

In the above embodiment, the conduction switching timing is obtained using the induced voltage waveforms of the three terminal voltages U, V, W of the three-phase brushless motor 1, but the induced voltage waveform of one terminal voltage is obtained. It is also possible to obtain the energization switching timing of each phase by using. In this case, T1 / 12 (3
0 degree), T1 / 4 (90 degree), 5T1 / 12 (1 degree
50 degrees), 7T1 / 12 (210 degrees), 3T1 / 12
(290 degrees) and 11T1 / 12 (330 degrees) are calculated, and these times are measured to generate the energization switching timing.

As described above, when the terminal voltage (induced voltage) of the armature winding of the brushless motor 1 is compared with the reference voltage Eth, the reference voltage Eth is changed according to the rotation speed and the load state of the brushless motor 1. Variable, calculates the timing of a predetermined phase angle delay (so-called energization switching timing) from the intersection point of the induced voltage and the reference voltage, and measures the calculated time from the edge of the position signal. To obtain the energization timing.

Therefore, when the induced voltage waveform of the terminal voltage varies depending on the rotational speed or the load state, and the timing of the intersection of the induced voltage waveform and the reference voltage changes,
Since the reference voltage is variable, it is possible to obtain the appropriate timing of the position signal, and also to adjust the phase required from the edge of the position signal without adjusting the time measurement for generating the energization switching timing. It is possible to obtain an energization switching timing with an angular delay and also obtain an energization switching timing that maximizes operation efficiency.

Moreover, when the time from the edge of the position signal from the comparison circuit 11 to the required phase angle is calculated, the time for the phase angle of 30 degrees is surely secured, that is, the time required for the calculation is short. Therefore, the microcomputer of the control circuit 12 does not have to have a high-speed operation function, that is, an inexpensive microcomputer having a low-speed operation function can be used.

[0039]

As described above, according to the motor control method of the present invention, when controlling the rotation of the motor, the plurality of armature windings of the motor are energized to detect the position of the rotor of the motor. In the method of controlling the motor that is switched based on the reference voltage, when the position signal timing is obtained by comparing the terminal voltage (induced voltage) of the motor armature winding with the reference voltage, the reference voltage is used to determine the motor rotation speed and the load state. The timing of the predetermined phase angle delay from the edge of the position signal (so-called energization switching timing) is calculated based on the time of one cycle. Therefore, the intersection of the induced voltage waveform and the reference voltage is calculated. When the timing of the position signal changes, the reference voltage is changed, so that the appropriate timing of the position signal can be obtained, and the energization switching timing is generated. It is possible to obtain the energization switching timing that is delayed by the required phase angle (for example, 30 degrees, 90 degrees, etc.) from the edge of the position signal without adjusting the measurement of the time for the operation, and maximize the operation efficiency. It is possible to obtain the energization switching timing.

Further, according to the present invention, the timing of the position signal is input to the microcomputer, and the microcomputer calculates the rotation speed of the motor based on the position signal and performs PWM control. The load condition of the motor is detected by the on / off ratio of the chopping, the reference voltage is changed according to the rotation speed and the load condition, and the energization switching that maximizes the operating efficiency of the brushless motor is performed based on the position signal. Since the timing is obtained, the same effect as described above can be obtained, and the time for the phase angle of 30 degrees can be surely secured from the edge of the position signal. There is a useful effect that it can be used and the cost can be reduced as a result.

[Brief description of drawings]

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

FIG. 2 is a schematic time chart diagram explaining the operation of the motor control device shown in FIG.

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

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

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 brushless motor (sensorless DC brushless motor) 2 drive part 3 position detection circuit 4,12 control circuit (microcomputer) 10 waveform shaping circuit 11 comparison circuit 12a rotation period detection part 12b energization switching timing generation part 12c PWM control part 12d drive signal Generator 12e Speed controller 12f Comparison voltage generator 13 D / A conversion circuit a Virtual neutral point Eth Reference voltage U, V, W Terminal voltage of armature winding

Claims (2)

[Claims] 1. A method for controlling a motor, wherein when energizing a motor, the energization of a plurality of armature windings of the motor is switched based on position detection of a rotor of the motor. And the reference voltage are compared to detect the time of the voltage at the intersection of the induced voltage waveform of the same terminal voltage and the reference voltage, and the energization switching timing of the armature winding is obtained based on the timing of the previous time. At this time, the motor control method is characterized in that the reference voltage is varied according to the rotation speed of the motor and the load. 2. A motor control method for switching the energization of a plurality of armature windings of the brushless motor based on position detection of the rotor of the brushless motor when controlling the rotation of the brushless motor by a PWM control method. The terminal voltage of the armature winding is compared with the reference voltage to detect the time of the voltage at the intersection of the induced voltage waveform of the terminal voltage and the reference voltage, and the position signal at the timing of the previous time is input to the microcomputer. The microcomputer calculates the rotation speed of the brushless motor based on the position signal, and detects the load state of the brushless motor by the on / off ratio of chopping for the PWM control. The reference voltage is varied according to the rotation speed and the load state, and the operating efficiency of the brushless motor is maximized based on the position signal. A motor control method being characterized in that to obtain the energization switching timing.