JP2003111473A - Dc motor control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC motor control method that makes it possible to reduce noise and abnormal vibration and to stabilize input power to a DC motor. SOLUTION: A phase difference T between a zero-crossing point of a current Iu flowing in phase winding Lu of the DC motor 1 and a pulse signal Vp that is outputted from a rotational position detector 4 in the DC motor 1 is controlled directly to an optimum value in accordance with the revolutions N of the DC motor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a DC motor used in, for example, an air conditioner.

[0002]

2. Description of the Related Art Generally, in an air conditioner, a DC motor is used as an outdoor fan motor, for example. The DC motor is composed of a stator having a plurality of phase windings and a rotor having a permanent magnet.

[0003]

When the rotation speed of the DC motor changes, resonance noise is generated at a frequency corresponding to a product of "stator pole number", "least common multiple of rotor pole number" and "rotation rate per second". (So-called cogging sound) is generated.
When the frequency of this resonance sound matches the resonance point of the outdoor fan or the outdoor unit housing, large noise or abnormal vibration occurs,
It gives the user an unpleasant feeling.

The present invention takes the above circumstances into consideration,
The purpose is to control the DC motor, which can suppress the generation of resonance noise of the DC motor, reduce noise and abnormal vibration, and stabilize the input power to the DC motor. To provide a method.

[0005]

According to a first aspect of the present invention, there is provided a method of controlling a direct current motor, which comprises a stator having a plurality of phase windings and a rotor having a permanent magnet, and a rectified alternating current power supply voltage. Rectifier circuit, and a switching circuit that converts the output voltage of this rectifier circuit into multiple-phase AC voltage by switching and outputs it as the drive voltage for each phase winding of the DC motor, and the rotation position of the rotor of the DC motor. A rotational position detector that outputs a corresponding signal, a rotational speed detection unit that detects the rotational speed N of the DC motor according to the output of the rotational position detector, and a rotational speed N that is detected by this rotational speed detection unit. In a device provided with a control means for controlling the switching circuit so as to achieve a target rotation speed, a zero cross point of a current flowing through a phase winding and an output signal of the rotation position detector. A phase difference T between the controls to an optimal value corresponding to the rotational speed N detected by the rotational speed detecting means.

According to a second aspect of the present invention, there is provided a method of controlling a direct current motor, which comprises a stator having a plurality of phase windings and a rotor having a permanent magnet, a rectifying circuit for rectifying an alternating current power supply voltage, and A switching circuit that converts the output voltage of the rectifier circuit into AC voltages of a plurality of phases by turning on / off the switching element and outputs the AC voltage as a driving voltage for each phase winding of the DC motor, and the rotation position of the rotor of the DC motor. A rotation position detector that outputs a corresponding pulse signal, a rotation speed detection unit that detects the rotation speed N of the DC motor according to the output of this rotation position detector, and a rotation speed N that is detected by this rotation speed detection unit. ON / OFF duty D of the above switching element so that becomes the target rotation speed.
And a control means for controlling stepwise,
The rotation speed N of the DC motor is changed in a plurality of stages, and the position of the zero cross point of the current flowing through the phase winding and the pulse signal output from the rotation position detector is changed for each rotation speed N1, N2, ... Nn. The optimum values T1, T2, ... Tn of the phase difference T are obtained, and these optimum values T1, T2, ...
n and the duty control values D1, D2, ... Dn of the control means corresponding to the respective rotation speeds thereof, and
When the duty control value D of the control means changes by one step, the amount of change Δ in the phase difference T between the zero cross point of the current flowing in the phase winding and the pulse signal output from the rotational position detector.
T is calculated, and the variation ΔT is the optimum value T1, T2, ...
A data table is generated in which the duty control values D1, D2, ... Dn are assigned as optimum values that sequentially increase or decrease centering on Tn. When the DC motor is actually driven, the optimum value of the phase difference T corresponding to the rotation speed N detected by the rotation speed detection means and the duty control value D of the control means is obtained by referring to the data table, The phase difference T between the zero cross point of the current flowing through the winding and the pulse signal output from the rotational position detector is controlled to the optimum value obtained by the above reference.

In the method for controlling a DC motor according to the invention of claim 3, in the invention of claim 2, conditions are set for controlling the optimum value. That is, the control of the optimum value is within the change amount ΔT for one change with respect to the change of the duty control value D.

According to a fourth aspect of the present invention, in the method of controlling a direct-current motor according to the second aspect, conditions are set for controlling the optimum value. That is, the optimum value is controlled by the rotation speed N.
For one change, the amount of change is within a predetermined multiple of the change amount ΔT.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a direct current motor (DC motor), which has a plurality of phase windings Lu, Lv, L.
A stator 2 having w, a rotor 3 having a permanent magnet, and a rotational position detector 4 are provided. Rotational position detector 4
Outputs a pulse signal (voltage signal) Vp according to the rotational position of the rotor 3.

The AC power supply voltage of the commercial AC power supply 10 is rectified by the rectifier circuit 11, and the output voltage (DC voltage) of the rectifier circuit 11 is supplied to the switching circuit 12. The switching circuit 12 converts the output voltage of the rectifier circuit 11 into AC voltages of a plurality of phases by turning on / off the switching elements according to a command from the control unit 20, and converts the output voltage into phase windings Lu, Lv of the DC motor 1. , Lw are output as drive voltages.

The control section 20 has the following (1) to (3) as main functions. (1) Rotation speed detecting means for detecting the rotation speed N of the DC motor 1 according to the output of the rotation position detector 4. (2) Control means for stepwise controlling the ON / OFF duty D of the switching element in the switching circuit 12 so that the rotation speed N detected by the rotation speed detection means becomes the target rotation speed. (3) When actually driving the DC motor 1, the optimum value of the phase difference T corresponding to the rotation speed N detected by the rotation speed detection means and the duty control value D of the control means is referred to by a data table described later. Means for controlling the phase difference T between the zero crossing point of the current flowing through the phase winding of the DC motor 1 and the pulse signal Vp output from the position detector 4 to the optimum value determined by the above reference.

On the other hand, the control unit 20 has a ROM as a storage means.
(Eg EEPROM) 21 is connected and its ROM 2
The data table of FIG. 2 is stored in 0. This data table is generated as follows.

First, as shown in the experimental data of FIG. 3, the rotation speed N of the DC motor 1 is set to a plurality of stages (low rotation speed, middle rotation speed,
High rotation speed), and the rotation speed N1, N2, ... Nn
Optimum values T1, T2, ... Tn of the phase difference T between the zero cross point of the current Iu flowing through the phase winding Lu (or Lv, Lw) and the pulse signal Vp output from the rotational position detector 4 for each time.
Then, these optimum values T1, T2, ...
, Nn, and duty control values D1, D2, ... Dn corresponding to their respective rotation speeds.

The waveform of the current Iu, the waveform of the pulse signal Vp,
The relationship of the phase difference T is shown in FIG. The zero crossing point of the current Iu can be obtained by calculation based on the pulse signal Vp at the time of starting. The phase difference T changes as the rotation speed N changes.

The experimental data shown in FIG. 3 will be described in detail.
A large number of phase differences T are detected for the rotation speed N1, and among these phase differences T, the average value of the phase differences T when the input power to the DC motor 1 is flat and stable (the midpoint of the flat region) is , And is selected as the optimum value T1. Similarly, a large number of phase differences T are detected with respect to the rotation speed N5, and among these phase differences T, the average value of each phase difference T when the input power to the DC motor 1 is flat and stable (the middle of the flat region). point)
Is selected as the optimum value T5. Similarly, the rotation speed Nn
A large number of phase differences T are detected, and the average value (the midpoint of the flat area) of each phase difference T when the input power to the DC motor 1 is flat and stable among these phase differences T is the optimum value. Selected as Tn.

Further, as shown in the experimental data of FIG.
Phase winding Lu when the duty control value D changes by one step
A change amount ΔT of the phase difference T between the zero cross point of the current Iu flowing in and the pulse signal Vp output from the position detector 4 is obtained, and the change amount ΔT is centered on the optimum values T1, T2, ... Tn. Values that sequentially increase or decrease are assigned to the duty control values D1, D2, ... Dn as optimum values.

That is, the optimum value T1 is associated with the rotation speed N1 and the duty control value D1, and the optimum value T2 is associated with the rotation speed N2 and the duty control value D2.
The optimum value T3 is associated with 3 and the duty control value D3, and finally, the optimum value Tn is associated with the rotation speed Nn and the duty control value Dn. In the row of rotation speed N1,
The optimum value (T1 + Δt) is assigned to the duty control value D2, and the optimum value (T1 + 2 · Δ) is assigned to the duty control value D3.
t) is assigned, the optimum value (T1 + 3 · Δt) is assigned to the duty control value D4, and finally the optimum value (T1 + n · Δt) is assigned to the duty control value Dn. In the column of the rotation speed N2, the duty control value D
The optimum value (T2-Δt) is assigned to 1, the optimum value (T2 + Δt) is assigned to the duty control value D3, the optimum value (T2 + 2 · Δt) is assigned to the duty control value D4, and finally the duty control value is set. The optimum value (T2 + n · Δt) is assigned to Dn. Similarly, in the column of the rotation speed N3, the optimum value (T
3-2 · Δt) is assigned and the duty control value D2
Is assigned the optimum value (T3−Δt), the duty control value D4 is assigned the optimum value (T3 + Δt), and finally the duty control value Dn is set to the optimum value (T3 + n · Δ).
t) is assigned.

The operation will be described. When the DC motor 1 is actually driven, the optimum value of the phase difference T corresponding to the current rotation speed N and the current duty control value D of the DC motor 1 is obtained by referring to the data table in the ROM 21,
The phase difference T between the zero cross point of the current Iu flowing through the phase winding Lu of the DC motor 1 and the pulse signal Vp output from the position detector 4 is controlled to the optimum value obtained by the above reference.

As described above, by directly controlling the phase difference T toward the optimum value, the current Iu flowing through the phase winding Lu has the maximum and minimum peak values A as shown in FIG. The difference B decreases to an optimum waveform. FIG. 7 shows the current Iu in the related art, and the difference B between the maximum value and the minimum value of the peak value A is large, and the waveform is not optimal.

By obtaining the current Iu having the optimum waveform, it is possible to suppress the generation of resonance noise of the DC motor 1. This suppression can reduce large noise and abnormal vibrations in the outdoor fan and the outdoor unit housing. The relationship between the noise and the phase difference T is shown in FIG.

Further, by obtaining the current Iu having the optimum waveform, the input power to the DC motor 1 can be stabilized.

Moreover, when the specifications of the outdoor fan or the outdoor unit housing are changed, only the ROM 21 is replaced, and the optimum control according to the specifications becomes possible.

In the control of the optimum value based on the reference of the data table, one change with respect to the change of the duty control value D is suppressed within the change amount ΔT and the number of revolutions N
With respect to the change of, the amount of one change is suppressed within a predetermined multiple of the change ΔT, for example, within 10 times. By setting these conditions,
The phase winding current can have a smoother waveform.

The present invention is not limited to the above-described embodiment, but can be variously modified without departing from the scope of the invention.

[0025]

As described above, according to the present invention, it is possible to provide a method of controlling a DC motor which can reduce noise and abnormal vibration and can stabilize the input power to the DC motor.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a DC motor and a drive control circuit thereof according to an embodiment.

FIG. 2 is a diagram showing a format of a data table in the same embodiment.

FIG. 3 is a diagram showing experimental data for obtaining the optimum value of the phase difference in the same embodiment.

FIG. 4 is a diagram showing experimental data for obtaining the amount of change in phase difference in the same embodiment.

FIG. 5 is a diagram showing a relationship between noise and phase difference in the same embodiment.

FIG. 6 is a diagram showing a waveform of a phase winding current in the same embodiment.

FIG. 7 is a diagram showing a waveform of a conventional phase winding current.

[Explanation of symbols]

1 ... DC motor, 2 ... Stator, 3 ... Rotor, 4 ... Rotation position detector, 10 ... Commercial AC power supply, 11 ... Rectifier circuit, 1
2 ... Switching circuit, 20 ... Control unit, 21 ... ROM
(Memory means)

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3L060 AA08 CC19 DD08 EE06                 5H560 AA01 BB04 BB12 DA01 DA14                       DC02 DC12 HA03 RR01 SS07                       TT12 XB09

Claims (4)

[Claims] 1. A DC motor composed of a stator having a plurality of phase windings and a rotor having a permanent magnet, a rectifier circuit for rectifying an AC power supply voltage, and an AC voltage of a plurality of phases by switching an output voltage of the rectifier circuit. A switching circuit that converts the voltage into a voltage and outputs the voltage as a drive voltage for each phase winding of the DC motor; a rotational position detector that outputs a signal corresponding to the rotational position of the rotor of the DC motor; Speed detection means for detecting the rotation speed N of the DC motor according to the output of the DC motor, and control means for controlling the switching circuit so that the rotation speed N detected by the rotation speed detection means becomes a target rotation speed. And a phase difference T between the zero crossing point of the current flowing through the phase winding and the output signal of the rotational position detector, The method of the direct current motor and controlling the optimum value corresponding to the rotational speed N detected. 2. A DC motor composed of a stator having a plurality of phase windings and a rotor having a permanent magnet, a rectifier circuit for rectifying an AC power supply voltage, and an output voltage of the rectifier circuit for turning on / off a switching element. A switching circuit for converting the voltage into a plurality of phases of AC voltage and outputting it as a drive voltage for each phase winding of the DC motor; and a rotational position detector for outputting a pulse signal according to the rotational position of the rotor of the DC motor. A rotation speed detecting means for detecting a rotation speed N of the DC motor according to an output of the rotation position detector; and the switching so that the rotation speed N detected by the rotation speed detecting means becomes a target rotation speed. A control means for controlling the on / off duty D of the element in a stepwise manner, wherein the rotation speed N of the DC motor is changed in a plurality of stages, , Nn, the optimum values T1, T2, ... Tn of the phase difference T between the zero crossing point of the current flowing through the phase winding and the pulse signal output from the rotational position detector. Then, these optimum values T1, T2, ...
2, ... Nn and the duty control values D1, D2, ... Dn of the control means corresponding to the respective rotation speeds thereof, and the phase winding when the duty control value D of the control means changes by one step. A change amount ΔT of the phase difference T between the zero crossing point of the flowing current and the pulse signal output from the rotational position detector is obtained, and the change amount ΔT is the optimum value T.
1, T2, ... Tn, the duty control values D1, D are set to have optimum values that increase or decrease sequentially.
2, ..., Dn are allocated to the data table, and the phase difference corresponding to the rotation speed N detected by the rotation speed detection means and the duty control value D of the control means when the DC motor is actually driven. The optimum value of T is obtained by referring to the data table, and the phase difference T between the zero cross point of the current flowing in the phase winding and the pulse signal output from the rotational position detector is set to the optimum value obtained by referring to A method for controlling a DC motor, comprising: controlling. 3. The method of controlling a DC motor according to claim 2, wherein the control of the optimum value is performed within one change amount ΔT with respect to a change of the duty control value D. Control method of DC motor. 4. The method for controlling a DC motor according to claim 2, wherein the optimum value control is within a predetermined multiple of the change amount ΔT with respect to a change in the rotation speed N. DC motor control method.