JPH08214586A - Control method of brushless motor - Google Patents

Abstract

PURPOSE: To avoid a position detection error caused by noises, switch the current application to armature windings properly, reduce the vibration and noises and avoid a step out. CONSTITUTION: When a DC power supply Vdc is switched by an inverter unit 4 and is applied to the armature windings of a brushless motor 3, the inverter unit 4 is driven in accordance with the detection of the position of the rotor 3a of the brushless motor 3 to switch the current application to the armature windings. An induced voltage induced in the armature winding is compared by a comparator 5 with the half value of the reference voltage Vdc from a reference voltage generating circuit 5a and a position signal which is changed at the cross point of the comparison results is inputted to a controller 10 which decides that the position of the rotor 3a is detected when the position signal is changed a predetermined lapse of time after the switching of the current application.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation control technique for a DC brushless motor (hereinafter referred to as a brushless motor) used in a compressor of an air conditioner, and more specifically,
The present invention relates to a brushless motor control method that enables appropriate position detection in order to stabilize rotation control of a sensorless brushless motor.

[0002]

2. Description of the Related Art In this type of brushless motor, for example, when controlling the rotation of a three-phase motor, a controller shown in FIG. 5 is used.

In FIG. 5, this control apparatus has a power supply Vd obtained by converting an AC power supply 1 into a direct current by an AC / DC converter 2.
An inverter circuit 4 in which a plurality of switching elements (transistors) U, V, W, X, Y, and Z are bridge-connected to switch c to be applied to the armature winding of the brushless motor 3, and a terminal of the brushless motor 3. To detect the position signal of the rotor 3a based on the voltage (induced voltage) R, and to switch the energization of each armature winding of the brushless motor 3 in a predetermined manner based on the position signal thus obtained. And a control circuit 6 for outputting a drive signal for the inverter unit 4 and chopping a predetermined drive signal of the drive signal at a predetermined ON / OFF ratio.

The position detector 5 divides the power supply voltage Vdc of the inverter circuit 4 into halves to generate a reference voltage Vdc / 2, and a terminal voltage (induced voltage) R of one phase. And a reference voltage Vdc / 2 to output a position signal A synchronized with the rotation of the brushless motor 1 and a comparison circuit 5b.

The control circuit 6 is composed of a microcomputer, a drive circuit and the like, and outputs a drive signal to drive the transistors U, V, W, X, Y and Z of the inverter section 4.

In the control device having the above structure, when the brushless motor 3 is operated by position detection, the position detection section 5
Based on the position signal (position detection of the rotor 3a) from the motor, the energization switching timing of each armature winding is obtained at a predetermined phase angle, a drive signal is generated based on these timings, and an inverter circuit is generated by these drive signals. 4 switching elements U, V, W, X, Y, Z are driven.

In detecting the position of the rotor 3a, for example, as shown in FIG. 6 (a), the terminal voltage R of one armature winding is compared with the reference voltage Vdc / 2, and the intersection point of the comparison results is compared. A position signal (shown in FIG. 6 (b)) A that changes with is obtained.

The position signal A is input to the control circuit 6, and the control circuit 6 crosses the waveform of the induced voltage of the terminal voltage R and the reference voltage Vdc / 2, that is, the energization switching timing (for example, in FIG. 6C). The first falling edge (timing t0) of the position signal A is detected from the arrow a), and this t
The time corresponding to the predetermined phase angle is calculated from time 0. Further, based on these intersections, for example, the phase angle is 30 degrees, 90 degrees.
And a time corresponding to 150 degrees, a drive signal (shown in FIGS. 6C to 6H) for switching the conduction states of the transistors U, V, W, X, Y, and Z of the inverter unit 2 is generated. . Since the transistors U, V, W, X, Y, and Z are driven by these drive signals, the armature winding current of the brushless motor 3 is switched and the brushless motor 3 is rotationally controlled.

Further, in the PWM control system, the control circuit 6 chops the ON portion of the drive signal of the inverter unit 4 at a predetermined duty ratio (ON / OFF ratio) (FIG. 6).
(Shown in (c) to (h)).

As described above, the brushless motor 3 is rotationally controlled by obtaining the timing of switching each armature winding current of the brushless motor 3 on the basis of the position signal A, and the on / off ratio of chopping is varied to make the brushless. Motor 3
Is controlled to a predetermined rotation speed. The same effect can be obtained by chopping the drive signal of the transistor forming one arm (upper arm or lower arm) of the inverter unit 4 among the drive signals.

[0011]

By the way, in the above brushless motor control method, the terminal voltage R has a chopped waveform, and thus the induced voltage of the terminal voltage R also has a chopped waveform (see FIG. 6).

Then, for example, when the timing of t1 shown in FIG. 6 is detected, the energization switching timing (see FIG.
The arrow b in (c); the first rising edge (intersection of the induced voltage waveform and the reference voltage) of the position signal A after the timing of switching the energization from the transistor X to Y) is used as the position detection (timing t1) of the rotor 3a. to decide.
The energization switching timing of each phase is calculated based on the timing t1, and the energization of each armature winding is switched at the time of this timing.

However, a pulse (shown by a broken line in FIG. 6B) appears in the position signal A due to noise generated at the time of switching the energization shown by a broken line in FIG. 6A. The edge of this pulse will be judged to be the position detection of the rotor 3a (that is, the position detection will be advanced by x), and the erroneous position detection will advance the energization switching timing (phase) of the brushless motor 3 by x. This not only causes uneven rotation torque, increase in vibration and noise, but also may cause step out in the worst case.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to enable appropriate position detection, suppress uneven rotation, vibration and noise, and eliminate step-out and stabilize rotation control. Another object of the present invention is to provide a brushless motor control method capable of performing the above.

[0015]

In order to achieve the above-mentioned object, the present invention detects the position of a rotor of a brushless motor by switching a DC power source by an inverter means and applying it to an armature winding of the brushless motor. A method of controlling a brushless motor that drives the inverter means based on the above to switch energization of the armature winding, wherein an induced voltage generated in the armature winding is compared with a reference voltage, and the comparison result When a position signal that changes at an intersection is obtained and the position of the rotor is detected by the position signal, the change point of the position signal after a predetermined time has elapsed from the switching of energization is determined to be the position detection of the rotor. It is characterized by having done.

[0016]

According to the above-mentioned means, the time at the time of switching the energization is clocked, and thereafter, the time of the change point of the position signal (intersection point of the induced voltage and the reference voltage) is clocked, and the time of these clocked times is counted. It is determined whether the difference (time difference) is equal to or longer than the predetermined time.

When the time difference is equal to or longer than the predetermined time, the intersection of the induced voltage and the reference voltage is determined to be the correct position detection, and when the time difference is less than the predetermined time, the intersection is determined to be the incorrect position detection.

As described above, during the predetermined time after the energization switching, the change point of the position signal (the intersection of the induced voltage and the reference voltage) is ignored, and the change point of the position signal after the predetermined time elapses. Judged as detection.

Therefore, even if noise is generated at the time of switching the energization and the noise is carried on the position signal, the noise is within the predetermined time, and therefore the noise does not cause erroneous position detection. .

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A brushless motor control method according to the present invention is
DC brushless motor (hereinafter referred to as brushless motor)
Focusing on the fact that it is possible to prevent erroneous position detection due to noise that occurs when the energization is switched by not detecting the position of the rotor for a predetermined time after the energization of the armature winding is switched. The intersection of the induced voltage and the reference voltage after the passage of time (the rising edge or the falling edge of the first position signal) is determined as the rotor position detection.

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

1, in addition to the function of the control circuit 6 shown in FIG. 4, this control device calculates the difference between the time when the energization is switched and the edge time of the position signal A after the energization is switched, A control device (microcomputer) 10 having a function of determining whether or not the calculated time difference is equal to or longer than a predetermined time and determining the position detection of the rotor 3a based on the determination result is provided.

Next, the operation of the control device will be described in detail with reference to the flow charts of FIGS. 2 and 3 and the time chart of FIG. Note that FIG. 4 corresponds to the time chart of FIG.

First, when the terminal voltage R of the brushless motor 3 is normally input to the position detecting section 5 (shown in FIG. 4A), the position detecting section 5 receives the induced voltage of the terminal voltage R and the reference voltage generating circuit 5a. Comparing circuit 5 with reference voltage Vdc / 2 of
position signal A that changes at the intersection of the comparison results
Is output (shown in FIG. 4B).

Then, the control circuit 1O detects the first edge of the input position signal A after the energization switching timing as in the conventional case, and calculates the energization switching timing (switching time) of each phase based on this edge detection. .

At this time, at the time of the edge detection (position detection), the routine shown in FIG. 2 is executed. First, when the time tU at the time of energization switching is measured and temporarily stored in the internal memory of the control circuit 10, and the first edge of the input position signal A after this energization switching is the falling edge (FIG. 4).
(Timing tdw shown in (a)), the process proceeds from step ST1 to ST2, and the time tdw of the falling edge thereof is measured and temporarily stored in the internal memory of the control circuit 10.

Then, the time td of the falling edge.
Time difference (tdw-t) between w and time tU at the time of energization switching
U) is calculated, and it is determined whether the value of this time difference (tdw-tU) is equal to or longer than a predetermined time Tn described later (step ST3). As shown in FIG. 4A, the predetermined time Tn is slightly shorter than the time from the switching of energization to the correct position detection based on the already known position detection interval (intersection of the intersections) T. The time is calculated and set, or calculated and set based on the time difference calculated last time.

The time difference (tdw-tU) is a predetermined time T.
When it is n or more, the falling edge detected this time is after the elapse of the predetermined time Tn, and therefore it is determined that the falling edge is the correct position detection.

When the time difference (tdw-tU) is less than the predetermined time Tn, the falling edge of the current detection is due to noise, and it is determined that the position detection is erroneous, and the routine is ended. Re-execute.

Then, when it is determined that the falling edge of the current detection is the correct position detection, as in the conventional case,
Each phase (U, V, W phases) from the falling edge of this time detection
The power-on switching timing time is calculated, and the calculated time is set as the value of the internal timer of the control circuit 10 to set the timer (step ST4).

When the set timer is up, the energization switching timing is set, and a drive signal for switching the energization of the armature winding of the brushless motor 3 is output at this timing.

Further, as shown in FIG. 4A, when the energization switching time is tX, the time tX is measured and temporarily stored in the internal memory of the control circuit 10. Then, since the edge of the position signal A detected this time rises, the process proceeds from step ST1 to ST5, and the time tup of the rising edge is measured and temporarily stored in the internal memory of the control circuit 10.

Then, the time difference (tup-) between the time tup of the rising edge detected this time and the energization switching time tX.
tX) is calculated, and it is determined whether or not the time difference value (tup−tX) is equal to or more than the above-described predetermined time Tn (step ST6).

When the time difference (tup-tX) is equal to or longer than the predetermined time Tn, the rising edge of this time detection is after the lapse of the predetermined time Tn. Therefore, it is determined that the rising edge is the correct position detection.

When the time difference (tup-tX) is less than the predetermined time Tn, the rising edge of this time detection is due to noise, and it is determined that the position detection is erroneous, and the routine is ended. Try again.

Subsequently, when it is determined that the rising edge of this time detection is correct position detection, as in the conventional case,
The time of energization switching timing of each phase is calculated from the rising edge of this detection, and this calculated time is calculated by the control circuit 10.
The timer is set as the value of the internal timer of (step S
T7).

When the set timer is up, the energization switching timing is set, and a drive signal for switching the energization of the armature winding of the brushless motor 3 is output at this timing.

On the other hand, the times tU, t when the energization is switched
To store X, the waveform output interrupt routine shown in FIG. 3 is executed. First, the control circuit 10 outputs a drive signal for performing energization switching for switching the drive waveform of the brushless motor 3 from on to off by the time-up of the energization switching timer that has already been calculated (step ST1).
0).

Next, if the energization switching this time turns the U-phase drive waveform from ON to OFF, step ST
From 11 to ST12, the energization switching time tU
(See FIG. 4A) is temporarily stored in the internal memory of the control circuit 10.

Next, if the energization switching this time is to switch the X-phase drive waveform from ON to OFF, step ST
11, the process proceeds from ST13 to ST14, and the energization switching time tX (see FIG. 4A) is temporarily stored in the internal memory of the control circuit 10.

The execution of the routines shown in FIGS. 2 and 3 will be described in detail with reference to FIG. 4. For example, as shown by the broken line in FIG. When it occurs after the arrow b) in (c), the position signal A includes a pulse corresponding to the noise (indicated by a broken line in (b) of the figure). Then, in the conventional case, an erroneous position detection is determined by the edge of the pulse.

However, as described above, the predetermined time T
Since n covers the noise, the control circuit 10 does not regard the edge of the pulse as the position detection timing, but determines the edge after the predetermined time Tn has elapsed (FIG. 4).
Timing tup shown in (a).

Therefore, the control circuit 10 can determine the correct position detection without causing an error in the position detection due to the noise generated when the energization is switched. As described above, since the correct position detection can be obtained, the energization switching timing of each armature winding becomes appropriate, the rotational torque unevenness, the generation of vibration and noise are suppressed, and the worst step out is eliminated.

[0044]

As described above, according to the control method of the brushless motor of the present invention, the induced voltage after switching the energization is compared with the reference voltage, and the rotor is changed by the position signal which changes at the intersection of the comparison results. When detecting the position of
Since the change point of the position signal after a lapse of a predetermined time from the energization switching is judged to be the position detection, even if noise occurs during the energization switching, it is possible to always judge the correct position detection. It is possible to appropriately switch the energization, to suppress uneven rotation, vibration and noise, prevent out-of-step, and stabilize rotation control, which is a useful effect.

[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 brushless motor control method is applied.

FIG. 2 is a schematic flowchart for explaining the operation of the brushless motor control device shown in FIG.

3 is a schematic flowchart for explaining the operation of the brushless motor control device shown in FIG. 1. FIG.

FIG. 4 is a schematic time chart diagram for explaining the operation of the brushless motor control device shown in FIG. 1.

FIG. 5 is a schematic block diagram of a conventional brushless motor control device.

FIG. 6 is a schematic time chart diagram for explaining the operation of the brushless motor control device shown in FIG. 5.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 AC power supply 2 AC / DC converter 3 Brushless motor (DC brushless motor) 3a Rotor (of brushless motor 1) 4 Inverter section 5 Position detection section 5a Reference voltage generation circuit 5b Comparison circuit 6,10 Control circuit (microcomputer) R Terminal voltage of armature winding A Position signal U, V, W Switching element (upper arm transistor) X, Y, Z Switching element (lower arm transistor)

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[Procedure amendment]

[Submission date] March 13, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

FIG.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (1)

[Claims] 1. A DC power source is switched by an inverter means to be applied to an armature winding of a brushless motor, and the inverter means is driven based on position detection of a rotor of the brushless motor to drive the armature winding. A control method for a brushless motor that switches between energizations, wherein an induced voltage generated in the armature winding is compared with a reference voltage, a position signal that changes at an intersection of the comparison results is obtained, and the rotor is generated by the position signal. The method for controlling a brushless motor is characterized in that, when the position is detected, a change point of the position signal after a lapse of a predetermined time from the switching of energization is determined as the position detection of the rotor.