JP4472982B2 - Motor drive control device - Google Patents

Description

  The present invention relates to a motor drive control device for driving a brushless DC motor of a compressor by a pulse width modulated drive signal.

  There is a brushless DC motor as a drive source of a compressor used in an air conditioner. This brushless DC motor is driven by a drive signal that is pulse width modulated (PWM) according to the air conditioning load. That is, a pulsed on / off signal is supplied as a drive signal to a switching circuit (also referred to as an inverter), and the longer the on period of the on / off signal (the larger the on / off duty), the greater the output of the switching circuit. As a result, the rotation speed of the brushless DC motor increases.

  In this brushless DC motor, torque pulsates with fluctuations in the air conditioning load. This torque pulsation appears as vibration and noise of the compressor.

In view of this, there is a type of controlling the on / off duty of the drive signal according to the drive frequency of the brushless DC motor to correct the torque pulsation to reduce the vibration and noise of the compressor (for example, Patent Document 1). ).
JP 2001-119981 A

  As described above, it is difficult to reliably suppress the torque pulsation only by controlling the on / off duty of the drive signal in accordance with the drive frequency of the brushless DC motor.

  The present invention takes the above-mentioned circumstances into consideration, and provides a motor drive control device capable of reliably suppressing torque pulsation of a brushless DC motor and thereby reliably reducing compressor vibration and noise. It is intended to provide.

According to a first aspect of the present invention, there is provided a motor drive control device for driving a brushless DC motor of a compressor in which torque pulsation is caused by driving by a pulse width modulated drive signal , and detecting a current flowing through the brushless DC motor. And a detecting means for detecting a torque current component corresponding to the torque pulsation of the brushless DC motor from the detection result of the detecting means, and a torque current component with respect to the torque of the brushless DC motor is reduced in accordance with the detected torque current component. Determining means for determining the positive torque correction amount corresponding to the period during which the torque current component is decreasing and the negative torque correction amount corresponding to the period during which the torque current component is decreasing, and the above-mentioned in accordance with the determined torque correction amount Adjusting means for adjusting the on / off duty of the drive signal.

According to the present invention, it is possible to provide a motor drive control device that can reliably suppress torque pulsation of a brushless DC motor and thereby reliably reduce the vibration and noise of the compressor.

[1] A first embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, a rectifier circuit 4 including a diode bridge 2 and a smoothing capacitor 3 is connected to a commercial AC power supply 1. A switching circuit 5 is connected to the output terminal of the rectifier circuit 4.

  The switching circuit 5 includes a series circuit of upstream switching elements and downstream switching elements for three phases. Transistors Tu + and Tu− are provided as U-phase upstream and downstream switching elements, and V Transistors Tv + and Tv− are provided as the upstream and downstream switching elements for the phase, and transistors Tw + and Tw− are provided as the upstream and downstream switching elements for the W phase. A damper diode D for preventing back electromotive force is connected in parallel to each of the transistors.

  Each phase of the stator 11 in the brushless DC motor 10 is connected to an interconnection point of the transistors Tu + and Tu−, an interconnection point of the transistors Tv + and Tv−, and an interconnection point of the transistors Tw + and Tw− of the switching circuit 12. Winding is connected. The brushless DC motor 10 is a permanent magnet type synchronous motor including a stator with each phase winding and a rotor 12 with a permanent magnet. The rotor 12 is connected to the drive shaft of the compressor 20. The brushless DC motor 10 is housed in a sealed case of the compressor 20. The compressor 20 has two cylinders 21 and 22. Of the cylinders 21 and 22, one of the cylinders 22 is connected to a bypass pipe connected between the refrigerant discharge side and the suction side. A four-way valve 23 is provided for opening and closing the bypass line, and switching between the one-cylinder operation and the two-cylinder operation of the compressor 20 is performed.

  Each transistor of the switching circuit 5 is turned on and off in a predetermined sequence by a drive signal supplied from the drive unit 6, whereby a current flows sequentially through each phase winding, and a magnetic field generated from each phase winding. The rotor 12 rotates due to the interaction between the rotor and the magnetic field generated by the permanent magnet of the rotor 12.

  The voltage generated in the energization path between the switching circuit 5 and each phase winding is supplied to the control unit 7 for detecting the rotational position of the rotor 12. In addition, current detectors 30 are provided in the series circuit of each phase in the switching circuit 5 as detection means for detecting the current flowing in the brushless DC motor 10. Outputs of these current detectors 30 are supplied to the control unit 7.

  The control unit 7 includes a CPU as a main control unit, a memory for data storage, and an interface (I / F) for data transmission / reception with an external device, and outputs the voltage and current detector 30 for detecting the rotational position. Is converted to digital data. A relay 8 for driving the four-way valve 23 is connected to the k control unit 7.

The CPU of the control unit 7 includes the following (1) to (4) as main functions.
(1) Means for driving each transistor of the switching circuit 5 to be turned on / off by a pulse width modulation (on / off duty) drive signal corresponding to the air conditioning load.
(2) Detection means for detecting a torque current component (also referred to as torque component current) Iq corresponding to the torque pulsation of the brushless DC motor 10 from the detection result of the current detector 30.
(3) Determination means for determining a correction amount for the torque of the brushless DC motor 10 according to the detected torque current component.
(4) Adjustment means for adjusting the pulse width modulation (on / off duty) of the drive signal for the switching circuit 5 in accordance with the determined correction amount.

Next, the operation of the above configuration will be described with reference to the time chart of FIG.
Each transistor of the switching circuit 5 repeats the ON / OFF operation of two cycles (energization cycle) in one rotation of the brushless DC motor 10. The current Im flows through each phase winding of the brushless DC motor 10 by this on / off operation. The level of the motor current Im varies as shown in the drawing with the torque pulsation of the brushless DC motor 10 corresponding to the air conditioning load.

  The motor current Im is detected by the current detector 30, and the torque current component Iq corresponding to the torque pulsation of the brushless DC motor 10 is detected by the calculation of the CPU according to the detection result, and the torque current component Iq An average value is obtained. Then, a correction amount for the torque of the brushless DC motor 10 (hereinafter referred to as torque correction amount) is determined according to the average value of the torque current component Iq. This torque correction amount is divided into a positive torque correction amount and a negative torque correction amount on the basis of two energization cycles of the transistor, and the positive torque correction amount is a period during which the torque current component Iq is increasing. The negative torque correction amount corresponds to a period during which the torque current component Iq is decreasing.

  As shown in FIG. 3, there is a proportional relationship between the air conditioning load and the average value of the torque current component Iq that the average value of the torque current component Iq increases as the air conditioning load increases. Further, between the average value of the torque current component Iq and the width X of the torque correction amount, as shown in FIG. 4, the correction width X of the torque correction amount increases as the average value of the torque current component Iq increases. There is a proportional relationship.

  When the torque correction amount is determined, the pulse width modulation (on / off duty) of the drive signal for the switching circuit 5 is adjusted according to the torque correction amount. Specifically, the larger the torque correction amount is on the positive side, the more the on-period of the transistor is corrected in the increasing direction, and the off-period is reduced by the increase. That is, the on / off duty is adjusted in the increasing direction. Further, as the torque correction amount is larger on the negative side, the ON period of the transistor is corrected in the reduction direction, and the OFF period is increased by the reduction amount. That is, the on / off duty is adjusted in the decreasing direction.

  Thus, the torque current component Iq is detected from the motor current Im, the torque correction amount for the torque of the brushless DC motor 10 is determined according to the torque current component Iq, and the pulse width of the drive signal is determined according to the torque correction amount. By adjusting the modulation in a feedback manner, torque pulsation of the brushless DC motor 10 can be reliably suppressed. Thereby, the vibration and noise of the compressor can be reliably reduced.

[2] A second embodiment will be described.
The second embodiment pays attention to the fact that the amplitude of the torque pulsation of the brushless DC motor 10 differs depending not only on the air conditioning load but also on the driving frequency F of the brushless DC motor 10.

  That is, a torque current component Iq is detected from the motor current Im, a torque correction amount for the torque of the brushless DC motor 10 is determined according to the torque current component Iq, and the driving frequency of the brushless DC motor 10 is determined with respect to the torque correction amount. A correction coefficient α corresponding to F (the output frequency of the switching circuit 5; also referred to as the operating frequency of the compressor) is multiplied.

  For example, as shown in FIG. 5, when the drive frequency F of the brushless DC motor 10 is 30 Hz, the correction coefficient α = “1.5” is selected, and when the drive frequency F is 40 Hz, the correction coefficient α = “1. 0 "is selected.

Then, the pulse width modulation of the drive signal is adjusted according to the torque correction amount multiplied by the correction coefficient α.
In this way, the effect of suppressing the torque pulsation of the brushless DC motor 10 is improved by adding the drive frequency F to the adjustment of the pulse width modulation of the drive signal.

  Other configurations and operational effects are the same as those of the first embodiment. Therefore, the description is omitted.

[3] A third embodiment will be described.
The third embodiment focuses on the fact that the amplitude of the torque pulsation of the brushless DC motor 10 differs depending not only on the air conditioning load, but also on whether the compressor 20 is in a one-cylinder operation or a two-cylinder operation. Specifically, when the compressor 20 is in the two-cylinder operation of the cylinders 21 and 22, the number of pulsations is twice that in the one-cylinder operation, but the cylinders 21 and 22 are half rotated (π) from each other. Since each region is canceled by operating with the phase difference, the amplitude of the torque pulsation is smaller than in the case of the single cylinder operation of the cylinder 21.

  That is, a torque current component Iq is detected from the motor current Im, a torque correction amount for the torque of the brushless DC motor 10 is determined according to the torque current component Iq, and the compressor 20 operates for one cylinder with respect to the torque correction amount. Then, for example, “1” is multiplied as the correction coefficient, and for example, “0.5” is multiplied as the correction coefficient if the compressor 20 is operating in two cylinders.

Then, the pulse width modulation of the drive signal is adjusted according to the torque correction amount multiplied by the correction coefficient.
As described above, the effect of suppressing the torque pulsation of the brushless DC motor 10 is improved by adding the number of cylinder operations to the adjustment of the pulse width modulation of the drive signal.

  Moreover, as shown in FIG. 6, when switching from 2-cylinder operation to 1-cylinder operation, the correction factor should be immediately switched from “0.5” for 2-cylinder operation to “1” for 1-cylinder operation. Without delay, a delay of a certain time t is ensured for switching. When switching from the one-cylinder operation to the two-cylinder operation, a delay of a predetermined time t is ensured in the same manner for switching the correction coefficient.

Switching between 2-cylinder operation and 1-cylinder operation is originally performed in accordance with fluctuations in the air-conditioning load, etc., and when the air-conditioning load fluctuates, a delay of a fixed time t is ensured in switching the correction coefficient, The torque of the brushless DC motor 10 can be stabilized.
Other configurations and operational effects are the same as those of the first embodiment. Therefore, the description is omitted.

[4] A fourth embodiment will be described.
In the fourth embodiment, the CPU of the control unit 7 determines whether or not the one-cylinder operation and the two-cylinder operation of the brushless DC motor 10 are normally performed.

  That is, when the brushless DC motor 10 is operating in one cylinder, it is determined whether the mechanical angle (rotation angle) of the rotor 12 of the brushless DC motor 10 corresponds to the one cylinder operation. If this determination result is affirmative, the one-cylinder operation is continued as it is under the judgment that the one-cylinder operation is normal.

  When the mechanical angle (rotation angle) of the rotor 12 does not correspond to the one-cylinder operation, the brushless DC motor 10 is restarted based on the determination that the one-cylinder operation is abnormal.

  When the brushless DC motor 10 is operating in two cylinders, a difference ΔIq between the maximum value and the minimum value of the torque current component is detected as shown in FIG. 2, and the difference ΔIq is less than a set value, for example, 0.9A. If it is smaller, the two-cylinder operation is continued as it is under the judgment that the two-cylinder operation is normal.

When the difference ΔIq is as large as 0.9 A or more, the brushless DC motor 10 is restarted based on the determination that the two-cylinder operation is abnormal.
Other configurations and operational effects are the same as those of the first embodiment. Therefore, the description is omitted.

  [5] It should be noted that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine the component covering different embodiment suitably.

The block diagram which shows the structure of each embodiment of this invention. The time chart for demonstrating the effect | action of each embodiment. The figure which shows the relationship between the air-conditioning load and average value of the torque current component Iq in each embodiment. The figure which shows the relationship between the average value of the torque current component Iq in each embodiment, and the width | variety X of torque correction amount. The figure which shows the relationship between the drive frequency F and correction coefficient (alpha) in 2nd Embodiment. The figure which shows the change of the correction coefficient accompanying switching of 1 cylinder operation and 2 cylinder operation in 3rd Embodiment. The flowchart for demonstrating the effect | action of 4th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Commercial AC power supply, 4 ... Rectification circuit, 5 ... Switching circuit, 6 ... Drive part, 7 ... Control part, 10 ... Brushless DC motor, 11 ... Stator, 12 ... Rotor, 20 ... Compressor, 21, 22 ... Cylinder , 23 ... Four-way valve

Claims (2)

In a motor drive control device for driving a brushless DC motor of a compressor in which torque pulsation is generated by driving with a drive signal obtained by pulse width modulation ,
Detecting means for detecting a current flowing in the brushless DC motor;
Detecting means for detecting a torque current component corresponding to torque pulsation of the brushless DC motor from a detection result of the detecting means;
Corresponds to the positive torque correction amount corresponding to the period in which the torque current component with respect to the torque of the brushless DC motor is decreasing according to the average value of the detected torque current component and the period in which the torque current component is decreasing. Determining means for determining the negative torque correction amount,
Adjusting means for adjusting the on / off duty of the drive signal in accordance with the determined torque correction amount;
A motor drive control device comprising: The motor drive control device according to claim 1, further comprising a control unit that corrects the torque correction amount determined by the determination unit according to a drive frequency of the brushless DC motor.

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