JP2006149097A - Motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller capable of stable switching between an intermittent energization drive system and a 180° energization drive system. <P>SOLUTION: This motor controller includes: an inverter circuit 5 for supplying electric power to a motor 6; a 180°energization drive section 9 for controlling the inverter circuit 5 through a PWM preparation/each phase distribution section 11 for drive of the motor 6 by the 180° energization drive system; an intermittent conduction drive section 8 to control the inverter circuit 5 through the PWM preparation/each phase distribution section 11 for drive of the motor 6 by the 180° energization drive system; a drive system selection section 10 for selecting either of the drive systems; and a rotational-speed control PMW duty/modulation rate calculation section 12 for correcting a drive signal immediately before switching by one drive system to obtain a drive signal immediately after switching by the other drive system at the time of switching from one drive system to the other drive system. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor control device that drives and controls a synchronous motor such as a brushless motor having a rotor on which a permanent magnet is mounted.

  Conventionally, in a sensorless operation in which a motor is driven and controlled without using a position sensor that detects a rotor position of a brushless motor (hereinafter referred to as “motor”), an intermittent energization with an energization stop period and an energization angle of less than 180 degrees is performed. A drive system is generally used. In this intermittent energization drive system, when the motor coil is energized, an induced voltage generated in the motor coil due to the rotation of the motor during a certain period of energization is detected from the motor coil terminal, and the energization to the motor is detected from this induced voltage. Determine timing. As such an intermittent energization drive method, a so-called 120-degree energization drive with an energization angle of 120 degrees is common.

  As another driving method, there is a so-called 180-degree energization driving method in which the motor is driven without providing an energization stop period. A typical example of the 180-degree energization drive method is a sine wave energization drive method.

  As a method for determining energization timing when the 180-degree energization drive method is used in sensorless operation, a three-phase motor coil neutral point and a resistor are connected in parallel with the three-phase coil, and a three-phase motor coil neutral point and resistance are connected. A method of detecting the motor induced voltage by comparing the voltage with the neutral point and determining the energization timing based on the detected motor induced voltage, detecting the motor position by calculating the motor current at high speed and Examples include a method of determining, or a method of determining energization timing based on the phase difference between the motor drive voltage and the motor current.

  Generally, the 180-degree energization drive system is said to be a drive system with less torque fluctuation and rotation fluctuation because the drive waveform is smoother than the intermittent energization drive system.

A control device that controls driving of the motor by switching between both of these driving methods is disclosed in Patent Document 1. The control device disclosed in Patent Document 1 determines the energization timing based on the output of rotation pulse generating means such as an encoder when the motor is driven and controlled by the 180-degree energization drive system, and generates this rotation pulse. When the output pulse from the means cannot be detected, the 180-degree conduction drive system is switched to the 120-degree conduction drive system.
Japanese Patent Laid-Open No. 10-341594

  However, in the control device that controls driving of the motor by switching between the two driving methods disclosed in Patent Document 1, fluctuations in the number of revolutions at the time of switching the driving method and reliability of switching between energizations are not considered. For this reason, for example, the output of the motor changes due to the switching of the driving method, and as a result, the rotational speed fluctuates, which may cause noise and vibration. In the sensorless operation, in the transient state at the time of switching the drive system, the rotor position detection accuracy deteriorates due to the fluctuation of the induced voltage, the energization timing becomes unstable, and in the worst case, the step-out may occur.

  In view of the above problems, an object of the present invention is to provide a motor control device that can stably switch between an intermittent energization driving method and a 180-degree energization driving method.

  In order to achieve the above object, a motor control device according to the present invention includes a power supply unit that supplies power to a synchronous motor, and the synchronous motor that is driven by a 180-degree energization drive method that does not provide an energization pause period. 180 degree energization drive means for controlling the power supply means, intermittent energization drive means for controlling the power supply means so as to drive the synchronous motor in an intermittent energization drive system with an energization pause period, and the 180 degree energization A selection means for selecting one of the driving method and the intermittent energization driving method, and the one of the 180-degree energization driving method and the intermittent energization driving method when switching from one driving method to the other driving method. Drive signal correcting means for correcting the drive signal immediately before switching in the drive system to obtain the drive signal immediately after switching in the other drive system (hereinafter referred to as drive signal correcting means). , Is the first that the configuration).

  According to such a configuration, when switching from one drive system of the 180-degree energization drive system and the intermittent energization drive system to the other drive system, the drive signal immediately before the switch in the one drive system remains as it is. Compared with the case of using the drive signal immediately after the switching in the driving method, the fluctuation in the rotational speed before and after the switching becomes small, and the switching of the driving method can be performed stably. Specifically, when switching from the 180-degree energization driving method to the intermittent energization driving method, the drive signal immediately before switching in the 180-degree energization driving method is reduced by correction to reduce the drive signal immediately after switching in the intermittent energization driving method. And Further, the drive signal immediately before switching in the intermittent energization driving method is increased by correction to obtain the drive signal immediately after switching in the 180-degree energization driving method.

  In the motor control device having the first configuration, switching from the one drive system to the other drive system may be prohibited when the mechanical angle of the rotor of the synchronous motor is not a predetermined value. Further, even when the mechanical angle of the rotor of the synchronous motor is not a predetermined value, the driving signal immediately before switching in the one driving method is corrected using the correction value, and immediately after switching in the other driving method. And when the correction value is changed according to the mechanical angle of the rotor of the synchronous motor immediately before switching from the one drive method to the other drive method, Switching to the other driving method may not be prohibited.

  According to such a configuration, even when the motor drives a load that periodically undergoes load fluctuations, it is possible to appropriately correct the drive signal immediately before switching in the one drive method. The load fluctuation referred to here is, for example, a load fluctuation caused by suction, compression, and discharge performed during one rotation of a compressor used in a cold air cycle such as an air conditioner or a refrigerator.

  Further, in the motor control device of the first configuration, the drive signal immediately before switching in the one driving method is corrected using a correction value to be a driving signal immediately after switching in the other driving method, The correction value may be changed according to the state of the synchronous motor immediately before switching from one drive system to the other drive system.

  According to such a configuration, fine drive control can be performed, the rotational speed fluctuation can be further reduced, and the rotational speed can be further stabilized. The state of the synchronous motor includes, for example, the energization angle of the synchronous motor, the rotational speed of the synchronous motor when the driving method is switched, the output voltage of the power supply means when the driving method is switched, and the switching method when the driving method is switched. It is at least one of the mechanical angles of the rotor of the synchronous motor.

  Further, from the viewpoint of preventing the drive signal in the intermittent energization driving method from becoming a value contrary to the definition, in the motor control device of each configuration described above, when switching from the 180-degree energization driving method to the intermittent energization driving method. If the corrected drive signal immediately before switching in the 180-degree energization drive method exceeds the maximum value of the drive signal in the intermittent energization drive method, the maximum value of the drive signal in the intermittent energization drive method is set to the intermittent energization. It may be a drive signal immediately after switching in the drive system.

  According to the present invention, it is possible to realize a motor control device that can stably switch between the intermittent energization driving method and the 180-degree energization driving method.

  An embodiment of the present invention will be described below with reference to the drawings. An example of the configuration of a motor control device according to the present invention is shown in FIG. A motor control device according to the present invention shown in FIG. 1 includes a reactor 2, a rectifier circuit 3, a smoothing capacitor 4, an inverter circuit 5, a three-phase brushless motor 6 (hereinafter referred to as “motor 6”), and a control circuit. 7, resistors R <b> 1 to R <b> 3, and rotor position detection circuits 13 and 14, and receives power from the commercial power source 1. If the rotor position detection circuits 13 and 14 are digital rotor position detection circuits, the rotor position detection circuits 13 and 14 may be built in the control circuit 7.

  An AC voltage from the commercial power source 1 is supplied to the rectifier circuit 3 via the reactor 2. The reactor 2 is provided in order to improve the power factor drop in the smoothing capacitor 4. The rectifier circuit 3 rectifies and outputs the input AC voltage to a DC voltage, and the DC voltage output from the rectifier circuit 3 is smoothed by the smoothing capacitor 4. In the present embodiment, a full-wave rectifier circuit in which four diodes are bridge-connected to the rectifier circuit 3 is used, but other rectifier circuits such as a voltage doubler rectifier circuit may be used. Further, a so-called PAM (Pulse Amplitude Modulation) method, which is a variable power supply method performed in recent years, may be employed.

  The DC voltage smoothed by the smoothing capacitor 4 is supplied to the inverter circuit 5. The inverter circuit 5 is a circuit in which driving elements which are six semiconductor switching elements are connected in a three-phase bridge shape, and the driving voltage from the inverter circuit 5 is output to the motor 6.

  The control circuit 7 is a circuit for driving and controlling the motor 6, and a microcomputer or a DSP (Digital Signal Processor) is generally used. The control circuit 7 includes an intermittent energization drive unit 8, a 180-degree energization drive unit 9, a drive method selection unit 10, a PWM creation / each phase distribution unit 11, and a rotation speed control PWM duty / modulation rate calculation unit 12. I have.

  The intermittent energization drive unit 8 sets the energization timing and sets a drive voltage (PWM duty) reference value (for example, rotation speed control) in order to drive the motor 6 by an intermittent energization drive method in which an energization angle is less than 180 degrees and an energization stop period is provided. Control such as setting of PWM duty). The 180-degree energization drive unit 9 performs control such as setting of energization timing and setting of a drive voltage (PWM duty) reference value (for example, rotation speed control modulation factor) in order to drive the motor 6 by the 180-degree energization drive method. . The drive method selection unit 10 selects a drive method and operates the intermittent energization drive unit 8 or the 180-degree energization drive unit 9. The PWM creation / each phase distribution unit 11 creates, for each drive element, a PWM drive signal for driving each drive element of the inverter circuit 5 based on the output of the intermittent conduction drive unit 8 or the 180-degree conduction drive unit 9. Output to the inverter circuit 5. The rotation speed control PWM duty / modulation rate calculation unit 12 calculates the PWM duty or the modulation rate when the drive method is switched.

  The drive method selection unit 10 selects either the intermittent energization drive method or the 180 degree energization drive method according to the state of the motor 6 or an external instruction. Here, the state of the motor 6 refers to the rotation speed, drive voltage (PWM duty), efficiency, load state, disturbance state, and the like. For example, when the driving voltage (PWM duty) supplied to the motor 6 is low, the intermittent driving method is selected by the driving method selection unit 10, and when the driving voltage (PWM duty) supplied to the motor 6 is high, the driving method is selected. The 180 degree energization driving method is selected by the selection unit 10. Further, when the rotation speed of the motor 6 is low, the intermittent drive method is selected by the drive method selection unit 10, and when the rotation number of the motor 6 is high, the 180-degree drive method is selected by the drive method selection unit 10. It may be. Also, a multiplication value of the drive voltage (PWM duty) supplied to the motor 6 and the rotation speed of the motor 6 is calculated, and when the calculated multiplication value is lower than the threshold value, the drive method selection unit 10 sets the intermittent energization drive method. When the calculated multiplication value is greater than or equal to the threshold value, the drive method selection unit 10 may select the 180-degree energization drive method. In addition, a current detection circuit for detecting the current value of the direct current supplied to the inverter circuit 5 is provided, and when the current value detected by the current detection circuit becomes equal to or greater than a predetermined value, the 180 degree conduction drive system is intermittently operated. You may make it switch to an energization drive system. Furthermore, an external switch that gives an external instruction to the driving method selection unit 10 may be provided. As a result, the driving method can be switched by the operator operating the external switch. For example, when driving at night, the motor 6 is driven by the 180-degree energization drive method with an emphasis on noise reduction, and the operator causes the drive method selection unit 10 to select the 180-degree energization drive method by operating an external switch. Can do.

  In order to suppress torque fluctuation, vibration, noise, and improve efficiency, it is desirable to use 180-degree energization drive and sinusoidal energization that can realize a smooth change in the drive waveform. The drive waveform for intermittent energization driving may be any drive waveform as long as the energization angle is less than 180 degrees and an energization stop period is provided in the drive waveform and an induced voltage generated in the energization stop period can be detected. For example, 120-degree energization driving is complete two-phase energization, and rectangular wave energization is possible. Therefore, there is an advantage that it is easy to create a drive waveform to be supplied to each phase.

  Next, a driving waveform in the intermittent energization driving method and a driving waveform in the 180 degree energization driving method will be described. FIG. 2 shows a drive waveform in a rectangular wave 120-degree conduction drive method that is an example of the intermittent conduction drive method, and FIG. 3 shows a drive waveform in a sine wave conduction drive method that is an example of the 180-degree conduction drive method. 2 and 3 are waveform diagrams showing PWM drive signals for driving the drive elements of the inverter circuit 5 (PWM generation / output signals of the respective phase distribution units 11) as analog values for each coil terminal. The drive waveform during the energization period is PWM chopped at several to several tens of kHz, and the duty of the PWM drive signal is changed so as to reach the target rotational speed. By changing the duty of the PWM drive signal, the voltage or current applied to the motor 6 is changed, and the rotation speed and torque are controlled.

  Here, the rotational speed control performed by the control circuit 7 when the intermittent energization drive system is selected by the drive system selection unit 10 will be described with reference to the flowchart of FIG.

  When a command signal for rotating at the target rotational speed N1 is given from the outside (step S1), the intermittent energization drive unit 8 sets the rotational speed control PWM duty according to the command signal (step S2). The PWM creation / each phase distribution unit 11 creates a PWM drive signal for driving each drive element of the inverter circuit 5 based on the output of the intermittent energization drive unit 8 and outputs the PWM drive signal to the inverter circuit 5. The rotor position detection circuit 13 detects the rotor position based on the induced voltage from the motor coil terminal, and the intermittent energization drive unit 8 performs the actual rotation of the motor 6 based on the rotor position detection signal output from the position detection circuit 13. The number N is detected (step S3), and it is determined whether or not the actual rotational speed N matches the target rotational speed N1 (step S4).

  If the actual rotational speed N matches the target rotational speed N1 (YES in step S4), the process proceeds to step S2. On the other hand, if the actual rotational speed N does not coincide with the target rotational speed N1 (NO in step S4), the intermittent energization drive unit 8 determines whether the actual rotational speed N is less than or greater than the target rotational speed N1 ( Step S5).

  If the actual rotational speed N is greater than the target rotational speed N1 (NO in step S5), the intermittent energization drive unit 8 decreases the rotational speed control PWM duty (step S6), and then proceeds to step S2. On the other hand, if the actual rotational speed N is less than the target rotational speed N1 (YES in step S5), the intermittent energization drive unit 8 increases the rotational speed control PWM duty (step S7), and then proceeds to step S2. By repeating this operation, the rotational speed control PWM duty is adjusted, and rotational speed control for controlling the actual rotational speed of the motor 6 according to the target rotational speed is performed.

  FIG. 5 shows the waveform of the PWM drive signal supplied to the control terminal of the U-phase upper arm drive element of the inverter circuit 5 when the rectangular wave 120 drive method that is an example of the intermittent drive method is selected. In the rectangular wave 120-degree energization drive method, a PWM duty equal to the rotation speed control PWM duty is output from the inverter circuit 5 to the motor 6 over the entire energization section. Other sections are energized suspension periods.

  Next, the rotational speed control performed by the control circuit 7 when the 180-degree energization drive system is selected by the drive system selection unit 10 will be described with reference to the flowchart of FIG.

  When the command signal for rotating at the target rotation speed N1 is given from the outside (step S8), the 180-degree energization drive unit 9 sets the rotation speed control modulation rate according to the command signal (step S9). The PWM creation / each phase distribution unit 11 creates a PWM drive signal for driving each drive element of the inverter circuit 5 based on the output of the 180-degree energization drive unit 9 and outputs the PWM drive signal to the inverter circuit 5. . The rotor position detection circuit 14 detects the rotor position based on the voltage at the neutral point of the three-phase motor coil and the voltage at the neutral point of the resistors R1 to R3. The actual rotational speed N of the motor 6 is detected based on the rotor position detection signal output from (step S10), and it is determined whether or not the actual rotational speed N matches the target rotational speed N1 (step S11).

  If the actual rotational speed N matches the target rotational speed N1 (YES in step S11), the process proceeds to step S9. On the other hand, if the actual rotational speed N does not match the target rotational speed N1 (NO in step S11), the 180 energization drive unit 9 determines whether the actual rotational speed N is less than or greater than the target rotational speed N1 ( Step S12).

  If the actual rotational speed N is greater than the target rotational speed N1 (NO in step S12), the 180-degree energization drive unit 9 decreases the rotational speed control modulation rate (step S13), and then proceeds to step S9. On the other hand, if the actual rotational speed N is less than the target rotational speed N1 (YES in step S12), the 180-degree energization drive unit 9 increases the rotational speed control modulation rate (step S14), and then proceeds to step S9. By repeating this operation, the rotational speed control modulation rate is adjusted, and rotational speed control is performed to control the actual rotational speed of the motor 6 according to the target rotational speed.

  FIG. 7 shows the waveform of the PWM drive signal supplied to the control terminal of the U-phase upper arm drive element of the inverter circuit 5 when the sine wave drive method that is an example of the 180-degree drive method is selected. In the sine wave energization drive system, the PWM duty calculated using the rotation speed control modulation rate is output from the inverter circuit 5 to the motor 6 so that the motor current waveform becomes a sine wave shape according to the energization phase.

  Next, as an example in which the load driven by the motor periodically fluctuates, a three-phase brushless motor having four poles (two pole pairs) is used as the motor 6, and the load driven by the motor 6 is a reciprocating compressor for a refrigerator. FIG. 8 shows a drive signal when the motor 6 is driven by 120-degree energization and a load torque characteristic at one mechanical angle rotation of the rotor of the motor 6. In order to make one rotation of the rotor of the motor, a period of electrical energization angles of the number of pole pairs is required. Even if the electrical energization angle is the same, the load size is different if the mechanical angle of the rotor is different. Since the load is larger in the period P1 than in the case where the load is constant, the period becomes longer, and in the period P2, the load is smaller, so the period becomes shorter.

  When a three-phase brushless motor having four poles (two pole pairs) is used as the motor 6 and the load driven by the motor 6 is a reciprocating compressor for a refrigerator, and the motor 6 is driven by 120 degrees energization, the intermittent energization drive unit 8 Will be described with reference to the flowchart of FIG.

  The intermittent energization drive unit 8 first measures the time period P1 (step S21), and then measures the time period 2 (step S22). Thereafter, the intermittent energization drive unit 8 determines whether or not the period P1 is longer than the period P2 (step S23).

  If the period P1 is longer than the period P2 (YES in step S23), the intermittent energization drive unit 8 increments the count number T1 of the built-in period P1 counter, and counts T2 of the built-in period P2 counter. Is set to 0 (step S24), and then the process proceeds to step S26. The reason why the count T2 of the counter for period P2 is set to 0 is that the time of each period may change depending on the load state. However, in order to prevent the determination of the mechanical angle when the motor 6 drives a compressor with a small load fluctuation in one rotation of the rotor mechanical angle, the count number T2 of the counter for the period P2 is set to 0. Instead, the count number T2 of the counter for the period P2 may be decremented.

  If the period P1 is not longer than the period P2 (NO in step S23), the intermittent energization drive unit 8 increments the count number T2 of the period P2 counter and sets the count number T1 of the period P1 counter to 0. (Step S25), and then the process proceeds to Step S27. The reason why the count T1 of the counter for the period P1 is set to 0 is that the time of each period may vary depending on the load state. However, in order to prevent the determination of the mechanical angle when the motor 6 drives a compressor having a small load fluctuation in one rotation of the mechanical angle of the rotor, the count number T1 of the counter for the period P1 is set to 0. Instead, the count number T1 of the counter for the period P1 may be decremented.

  In step S26, the energization drive unit 8 determines whether or not the count number T1 of the period P1 counter is greater than a predetermined number N. If the count number T1 of the period P1 counter is not greater than the predetermined number N (NO in step S26), the process proceeds to step S21. On the other hand, if the count number T1 of the counter for the period P1 is larger than the predetermined number N (YES in step S26), the mechanical angle can be determined, and the process proceeds to step S28.

  In step S27, the energization driving unit 8 determines whether or not the count number T2 of the period P2 counter is greater than a predetermined number N. If the count number T2 of the counter for the period P2 is not greater than the predetermined number N (NO in step S27), the process proceeds to step S21. On the other hand, if the count number T2 of the counter for period P2 is larger than the predetermined number N (YES in step S27), the mechanical angle can be determined, and the process proceeds to step S28.

  In step S28, the energization drive unit 8 determines a mechanical angle of 0 degrees. For example, the switching point from the cycle P1 to the cycle P2 is set to 0 degree mechanical angle.

  The flowchart in FIG. 9 relates to the case where the motor 6 is driven by 120 degrees energization. However, when the motor 6 is driven by 180 degrees energization, the 180 degrees energization drive unit performs the same processing as the flowchart of FIG. That's fine. Further, the flowchart of FIG. 9 relates to the case where there are two types of cycles, but when the number of cycles is three or more, the count number of the counter dedicated to the longest cycle may be incremented.

  Here, as the easiest method for switching the drive system from the intermittent energization drive system to the 180-degree energization drive system, the rotation speed control PWM duty of the intermittent energization drive system is directly used as the rotation speed control modulation rate of the 180-degree energization drive system. A way to do this is conceivable. The rotational speed control PWM duty and the rotational speed control modulation factor are the same dimension. However, in this method, an imbalance occurs between the current state of the motor 6 (for example, the rotational speed and motor torque) and the inverter output. For this reason, as indicated by the characteristic line CL1 shown in FIG. 10, there are cases where the rotational speed fluctuates greatly when the driving method is switched, and it takes time until the actual rotational speed and the target rotational speed match. In addition, if the rotational speed fluctuation is large, the rotor position detection accuracy is deteriorated, and in the worst case, there is a possibility of stepping out.

  Therefore, in the motor control device according to the present invention, when switching from the intermittent energization drive method to the 180-degree energization drive method, the rotational speed control PWM duty of the intermittent energization drive method remains unchanged from the 180-degree energization drive method. Instead of the rate, the rotational speed control PWM duty / modulation rate calculation unit 12 calculates a value obtained by multiplying the rotational speed control PWM duty of the intermittent energization driving method output from the intermittent energization driving unit 8 by a predetermined value α. Thus, the rotational speed control PWM duty is corrected, and the corrected value is output to the 180 degree energization drive unit 9 as the rotational speed control modulation factor of the 180 degree energization drive system. The 180-degree energization drive unit 9 generates an energization voltage according to the energization timing based on the input rotation speed control modulation factor, and outputs it to the PWM creation / each phase distribution unit 11. The PWM creation / each phase distribution unit 11 creates a PWM drive signal for each drive element of the inverter circuit 5 based on the output of the 180-degree conduction drive unit 9 and outputs the PWM drive signal to the inverter circuit 5. Thereby, the motor 6 is rotationally driven.

  In the motor control device according to the present invention, since the operation as described above is performed when switching from the intermittent energization driving method to the 180-degree energization driving method, the intermittent energization driving method from the intermittent energization driving method as shown by the characteristic line CL2 shown in FIG. Compared to the case where the rotational speed control PWM duty of the intermittent energization drive system is used as it is as the rotational speed control modulation rate of the 180 degree energization drive system, the speed after switching is increased and the rotational speed fluctuation is small. Thus, a stable drive system can be switched. Note that the predetermined value α is a value set in advance by experiment or simulation so that the fluctuation of the rotational speed at the time of switching the driving method becomes small.

  However, when the motor 6 is driving the compressor, even if the predetermined value α is determined, if the mechanical angle of the motor rotor when switching from the intermittent energization driving method to the 180 ° energization driving method is different, the compression is performed. Since the correction may not be performed properly due to machine load fluctuations, the switching from the intermittent energization driving method to the 180 degree energization driving method is performed at the same mechanical angle every time so that the correction can be performed appropriately every time. That is, when the mechanical angle is not a predetermined value, it is desirable to prohibit switching from the intermittent energization drive method to the 180-degree energization drive method. However, if it is desired to immediately switch from the intermittent energization drive method to the 180-degree energization drive method, it is preferable to store a predetermined value α corresponding to the mechanical angle of the rotor as ROM data and use it.

  Further, as the easiest method for switching the drive system from the 180-degree energization drive system to the intermittent energization drive system, the rotation speed control modulation rate of the 180-degree energization drive system is directly used as the rotation speed control PWM duty of the intermittent energization drive system. A method is conceivable. The rotational speed control PWM duty and the rotational speed control modulation factor are the same dimension. However, in this method, an imbalance occurs between the current state of the motor 6 (for example, the rotational speed and motor torque) and the inverter output. For this reason, as indicated by the characteristic line CL3 shown in FIG. 11, the rotational speed greatly varies at the time of switching the driving method, and it may take time for the actual rotational speed and the target rotational speed to coincide. In addition, if the rotational speed fluctuation is large, the rotor position detection accuracy is deteriorated, and in the worst case, there is a possibility of stepping out.

  Therefore, in the motor control device according to the present invention, when switching from the 180-degree energization drive method to the intermittent energization drive method, the rotation speed control modulation rate of the 180-degree energization drive method is directly used as the rotation speed control PWM of the intermittent energization drive method. Instead of setting the duty, the rotational speed control PWM duty / modulation rate calculation unit 12 calculates a value obtained by multiplying the rotational speed control modulation rate of the 180 ° energization drive output from the 180 ° energization drive unit 9 by a predetermined value β. Thus, the rotational speed control modulation rate is corrected, and the corrected value is output to the intermittent energization drive unit 8 as the rotational speed control PWM duty of the intermittent energization drive. The intermittent energization drive unit 8 generates an energization voltage corresponding to the energization timing based on the input rotation speed control PWM duty and outputs it to the PWM creation / each phase distribution unit 11. The PWM creation / each phase distribution unit 11 creates a PWM drive signal for each drive element of the inverter circuit 5 based on the output of the intermittent energization drive unit 8 and outputs the PWM drive signal to the inverter circuit 5. Thereby, the motor 6 is rotationally driven.

  In the motor control device according to the present invention, since the operation as described above is performed when switching from the 180-degree energization drive method to the intermittent energization drive method, as indicated by the characteristic line CL4 shown in FIG. When switching to the intermittent energization drive system, the rotational speed control modulation rate of the 180-degree energization drive system is directly used as the rotational speed control PWM duty of the intermittent energization drive system, and the rotational speed after switching is reduced, and the rotational speed fluctuation is small. Thus, a stable drive system can be switched. Note that the predetermined value β is a value set in advance by experiment or simulation so that the fluctuation in the rotational speed at the time of switching the driving method is reduced.

  However, when the motor 6 is driving the compressor, even if the predetermined value β is determined, if the mechanical angle of the motor rotor when switching from the 180 ° energization drive method to the intermittent energization drive method is different, the compression is performed. Since the correction may not be performed properly due to machine load fluctuations, the switching from the 180-degree energization driving method to the intermittent energization driving method is performed at the same mechanical angle every time so that the correction can be performed appropriately every time. That is, when the mechanical angle is not a predetermined value, it is desirable to prohibit switching from the 180-degree energization drive method to the intermittent energization drive method. However, if it is desired to immediately switch from the 180-degree energization drive method to the intermittent energization drive method, a predetermined value β corresponding to the mechanical angle of the rotor is preferably stored as ROM data and used.

  For the predetermined values α and β, α is 1 or more and β is 1 or less. Further, the predetermined values α and β may be values according to the state of the motor 6 immediately before the drive system is switched, instead of being constant values. As a result, fine drive control can be performed, fluctuations in the rotational speed can be further reduced, and the rotational speed can be further stabilized. For example, when the control for prohibiting the switching to the drive method is not performed when the mechanical angle is not a predetermined value, as shown in FIG. 12, each predetermined value α set in advance according to the electrical energization angle of the intermittent energization drive. , Β are stored as ROM data of the control circuit 7, the electrical energization angle of the intermittent energization drive is detected from the intermittent energization drive unit 8 at the time of driving system switching, and predetermined values α, β corresponding to the energization angles are detected. Should be read. Note that the mechanical angle of the rotor of the motor 6 may be used instead of the electrical energization angle of the intermittent energization drive. Further, as shown in FIG. 13, predetermined values α and β set in advance according to the number of revolutions of the motor 6 are stored as ROM data of the control circuit 7, and the intermittent energization drive unit 8 or The 180-degree energization drive unit 9 detects the rotational speed of the motor 6 based on the rotor position detection signal output from the rotor position detection circuit 13 or 14, and reads the predetermined values α and β corresponding to the rotational speed. May be.

Furthermore, since the PWM duty changes even if the rotation speed is the same depending on the state of the driving load, the PWM duty in a certain steady load state is stored as ROM data,
γ = PWM duty at the time of switching / predetermined value γ calculated by the PWM duty of ROM data is added to the predetermined values α and β as new predetermined values α and β, and these new predetermined values α and β are By using it for correcting the rotational speed control PWM duty or the rotational speed control modulation rate, it is possible to switch the driving system stably.

  In the embodiment described above, the control described below may be added in order to further improve the stability of the rotation and the reliability of the control. In addition, each control (1st control which can be added-6th control which can be added) demonstrated below may be added independently, and may be added in arbitrary combinations.

  First, the first control that can be added will be described. In the intermittent energization driving method, the motor 6 is rotationally driven by sequentially switching energization modes according to the rotor position. An example of the energization mode in the 120-degree energization drive method which is one of the intermittent energization drive methods is shown in FIG. In the example of the energization mode shown in FIG. 14, the energization mode is sequentially switched to 0, 1,..., 5, 0, 1,.

  In the embodiment described above, at the time of switching from the intermittent energization driving method to the 180-degree energization driving method, the current energization phase is calculated from the energization mode at the time of switching, and 180-degree energization driving is performed. For example, when switching from the energization mode 1 of the 120-degree energization drive method to the sine wave waveform of the 180-degree energization drive system at the switching timing from the energization mode 1 to the energization mode 2 in the 120-degree energization drive system, the phase angle is 120 degrees. In the 180-degree energization driving method, the sine wave data is set using this phase angle of 120 degrees.

  At this time, the phase angle can be used as it is, but since the fluctuation in the rotational speed can be further reduced by adjusting the phase angle in accordance with the rotational speed, it is desirable to perform control for adjusting the phase angle in accordance with the rotational speed. . For example, 5 degrees is added to 125 degrees in the low speed range, and 5 degrees is subtracted to 115 degrees in the high speed range. Thus, when the energization phase at the time of drive switching is determined according to the rotation speed of the motor 6, the rotation speed of the motor 6 is stabilized and the reliability of switching the driving method is improved. The motor current waveform at the time of switching from the 120-degree energization drive method to the 180-degree energization drive method at this time is shown in FIG. At the time of switching the driving method, the 120 degree conduction driving method is changed from the 120 degree conduction driving method to the 180 degree conduction driving method by determining the conduction phase for starting the 180 degree conduction driving method according to the energization mode and the rotation speed of the 120 degree conduction driving method at the time of switching. The motor current changes smoothly at the time of switching. Further, instead of adjusting the energization phase for starting the 180-degree energization drive method according to the rotational speed, the energization phase for starting the 180-degree energization drive method may be adjusted according to the load state of the motor 6.

  Furthermore, when switching from the 180-degree energization drive method to the 120-degree energization drive, the energization mode of the 120-degree energization drive after the switching is determined according to the energization phase of the 180-degree energization drive at the time of switching. In other words, the energization phase of the 180-degree energization drive at the time of switching is determined according to the energization mode of the 120-degree energization drive immediately after the drive method is switched.

  For example, if the 120-degree energization drive method after switching the drive method is set to start from energization mode 1, the energization phase of the 180-degree energization drive method at the time of switching may be in the range of 60 degrees to 120 degrees. It is desirable to adjust according to the rotational speed such as 90 degrees in the low rotational speed range and 80 degrees in the high rotational speed range. As a result, the reliability of switching the driving method is improved. The motor current waveform at the time of switching from the 180-degree energization drive method to the 120-degree energization drive method at this time is shown in FIG. At the time of switching the drive method, the energization phase of the 180-degree energization drive method for switching is determined according to the number of rotations of the motor 6, so that the motor current at the time of switching from the 180-degree energization drive method to the 120-degree energization drive method is determined. The change becomes smooth. Further, instead of adjusting the energization phase of the 180-degree energization driving method at the time of switching according to the rotation speed, the energization phase of the 180-degree energization driving method at the time of switching may be adjusted according to the load state of the motor 6.

  Next, the second control that can be added will be described. If the drive system is frequently switched, the load on the control circuit 7 increases and the stress on the inverter circuit 5, the motor 6 and the like becomes excessive.

  From the viewpoint of solving such a problem, it is desirable that the control circuit 7 performs control for prohibiting the switching of the driving method until a predetermined time elapses after the switching of the driving method. For this control, for example, the control circuit 7 has a built-in timer, and measures the time until a predetermined time elapses after the switching of the driving method by the timer, so that the driving method selection unit 10 does not switch the driving method during the time counting. Can be realized.

  With this control, once the drive system is switched, the switched drive system is maintained until a predetermined time elapses after the drive system is switched, and the drive system is switched again after a predetermined time has elapsed since the drive system was switched. It becomes possible. Therefore, frequent switching of the driving method can be suppressed, the overload of the control circuit 7 can be prevented, and the stress applied to the inverter circuit 5 and the motor 6 can be reduced. As a result, the life of the motor control device can be extended and the reliability can be improved.

  Next, the third control that can be added will be described. If the drive system is switched in a transient state where acceleration or deceleration is being performed toward the target rotational speed and acceleration or deceleration is continued after the switching, the control stability may deteriorate.

  From the viewpoint of solving such a problem, it is desirable that the control circuit 7 performs control for prohibiting acceleration or deceleration of the motor 6 until a predetermined time elapses after the drive system is switched. In such control, when the drive system is switched in a transient state where acceleration or deceleration is performed toward the target rotational speed, the motor 6 is driven at the rotational speed at the time of switching for a predetermined time after the switching of the driving system, Acceleration / deceleration is performed after a predetermined time has elapsed since the switching of the drive system. For this control, for example, the control circuit 7 has a built-in timer, and the timer counts until a predetermined time elapses after switching the driving method. During the time counting, the PWM creation / each phase distribution unit 11 keeps the motor 6 constant. This can be realized by generating a PWM drive signal for maintaining the rotational speed.

  With this control, once the drive system is switched, acceleration or deceleration is prohibited until a predetermined time has elapsed after switching the drive system, so that the load on the control circuit 7 is reduced and the control reliability can be improved. .

  Next, the fourth control that can be added will be described. Since the intermittent energization drive method has an energization suspension period, the maximum power supplied to the motor 6 is smaller than the 180-degree energization drive method without the energization suspension period, and the maximum rotation speed of the motor 6 is also higher than that of the 180-degree energization drive method. Lower. Therefore, when switching from the 180-degree energization drive method to the intermittent energization drive method at a rotation speed that is equal to or higher than the maximum rotation number of the intermittent energization drive method, the actual rotation speed after the change decreases to the maximum rotation number of the intermittent energization drive method. As a result, the difference between the actual rotational speed and the target rotational speed increases. In this case, if the value obtained by multiplying the rotational speed control modulation rate in the 180-degree energization drive system immediately before switching by the predetermined value β is directly used as the rotational speed control PWM duty in the intermittent energization drive system immediately after switching, intermittent energization immediately after switching. Since the rotational speed control PWM duty in the drive system exceeds 100%, the intermittent energization drive system immediately after switching regardless of the value obtained by multiplying the rotational speed control modulation rate in the 180-degree energization drive system immediately before switching by a predetermined value β. The rotation speed control PWM duty at is set to 100%.

  From the viewpoint of solving such a problem, when the control circuit 7 switches from the 180-degree energization drive method to the intermittent energization drive method, the rotation speed of the motor 6 after the switching is lower than the rotation speed before the switching. When the deviation between the actual rotational speed and the target rotational speed is greater than or equal to a predetermined value, it is desirable to perform control to change the target rotational speed low. In such control, for example, the actual rotational speed of the motor 6 immediately after switching from the 180-degree energization driving system to the intermittent energization driving system is reduced as compared with the actual rotational speed immediately before switching, and a deviation of more than a predetermined value from the target rotational speed occurs. If this happens, the target rotational speed is once changed to the actual rotational speed after the transition to the intermittent energization drive method. As a result, there is no difference between the target rotational speed and the actual rotational speed, fluctuations in the rotational speed are quickly settled, and control is stabilized. Note that when the decrease in the actual rotational speed of the motor 6 after switching is smaller than a predetermined value, the target rotational speed is not changed.

  Next, a fifth control that can be added will be described. Here, representative examples of loads driven by the motor 6 include compressors such as an air conditioner and a refrigerator. Since the motor 6 is a synchronous motor unlike an induction motor, it is necessary to accurately detect the rotor position and output a drive voltage from the inverter circuit 5 to the motor 6 in accordance with the position state. However, when the load driven by the motor 6 is a compressor such as an air conditioner or a refrigerator, the inside of the compressor is high temperature and high pressure, and a sensor cannot be built in. Therefore, the rotor equipped with a permanent magnet rotates. A sensorless rotor position detection circuit that detects a rotor position by detecting an induced voltage generated in a motor coil is generally used. Note that the rotor position detection circuits 13 and 14 in FIG. 1 are sensorless rotor position detection circuits.

  The sensorless rotor position detection circuit is roughly divided into two methods: an analog method and a digital method.

  In the analog method, in the case of the intermittent energization drive method, an analog filter circuit consisting of a capacitor and a resistor is inserted in the position detection input part that inputs the motor terminal voltage, and the motor terminal voltage is shaped into a sine wave and then input to the comparator Then, the rotor position detection signal is generated based on the comparison result with the virtual neutral point potential. Because of this filter circuit, the detected voltage waveform is 90 degrees out of phase with the actual induced voltage waveform.

  In the digital method, the induced voltage waveform of the motor 6 is input to the comparator as a pulse-shaped waveform PWM-switched, and compared with a reference voltage that is ½ of the DC voltage received by the inverter circuit 5, the rotor position detection signal is Generate. However, when the PWM waveform is turned off as in the intermittent energization driving method, the induced voltage waveform does not appear when the PWM waveform is turned off. Therefore, processing is performed so that the rotor position can be detected from the induced voltage waveform only when the PWM waveform is turned on. Based on the generated rotor position detection signal, timing for outputting an actual PWM waveform is determined, and advance angle (field weakening) control is performed. Advance angle control enables high-efficiency operation and expansion of high-speed ranges. In addition, since there is no filter circuit, detection accuracy is high, there is no phase delay, and advance (field weakening) control becomes easy. Further, the rotor position can be detected even at a low speed when the induced voltage is low, and the operation can be performed at a low rotational speed at the time of startup. As a result, the starting current can be reduced, and the drive element of the inverter circuit 5 can be prevented from being damaged by the overcurrent, so that the reliability can be improved.

  As described above, the digital method has many advantages over the analog method, but as described above, the digital method has a disadvantage that position detection can be performed only when the PWM waveform is on. Further, the ON time of the PWM waveform changes if the PWM carrier frequency changes even if the PWM duty is the same, and becomes longer as the PWM carrier frequency is lower. For this reason, the control circuit 7 uses a 180-degree energization drive type PWM carrier so as to ensure the minimum on-time of the PWM waveform that can detect the rotor position in consideration of the signal transmission delay time, the rotor position detection processing time, and the like. It is desirable to perform control to set the PWM carrier frequency of the intermittent energization drive method lower than the frequency. In such control, since the PWM carrier frequency of the intermittent energization drive method is set lower than the PWM carrier frequency of the 180 degree energization drive method, the on time of the PWM waveform in the intermittent energization drive method becomes longer, and the time during which the rotor position can be detected Becomes longer. Therefore, when the digital rotor position detection circuit is used, the reliability of rotor position detection can be ensured.

  Next, the sixth control that can be added will be described. If a sensorless rotor position detection circuit that detects the rotor position by detecting the induced voltage generated in the motor coil by the rotation of the rotor equipped with the permanent magnet is used, after switching the drive system to some extent When the induced voltage cannot be detected even after the elapse of time, it is considered that the rotor position with respect to the phase of the drive voltage is greatly shifted. In the worst case, there is a possibility that the motor 6 is locked, an excessive current flows through the drive element of the inverter circuit 5, and the drive element is destroyed.

  From the viewpoint of solving such problems, for this reason, if the control circuit 7 cannot detect the induced voltage even after a predetermined time has elapsed after switching the drive system, control is performed to stop energization of the motor 6. It is desirable to make it. For this control, for example, the control circuit 7 has a built-in timer, starts counting by the timer from the switching point of the driving system, continues counting by the timer until the induced voltage is detected, and the measured time of the timer is a predetermined time. If it exceeds, it can be realized by stopping energization of the motor 6.

  As a result, when the induced voltage cannot be detected even after a predetermined time has elapsed after switching the drive system, the energization of the motor 6 is stopped. Therefore, even if the induced voltage cannot be detected after a lapse of a predetermined time after switching the driving method, an excessive current does not flow to the inverter circuit 5, and it is possible to prevent damage to driving elements such as transistors and to improve the reliability of driving control. Can be improved.

  In addition, this invention is not limited to the said embodiment, Of course, many corrections and changes can be added to the said embodiment within the scope of the present invention. For example, as the intermittent energization drive method, an energization drive with an energization angle other than 120 degrees is also adopted, and the drive method is switched between a plurality of intermittent energization drive methods and a 180 degree energization drive method. Good. A position sensor that detects the rotor position can also be used depending on the type of load driven by the motor.

These are figures which show the example of 1 structure of the motor control apparatus which concerns on this invention. These are figures which show the drive waveform in a rectangular wave 120 degree | times energization drive system. These are figures which show the drive waveform in a sine wave energization drive system. These are the flowcharts of rotation speed control performed when the intermittent energization drive system is selected. These are figures which show the waveform of the signal supplied to the control terminal of the U-phase upper arm drive element of an inverter circuit, when a 120 electricity supply drive system is selected. These are the flowcharts of rotation speed control performed when the 180 degree | times energization drive system is selected. These are figures which show the waveform of the signal supplied to the control terminal of the U-phase upper arm drive element of an inverter circuit, when a sine wave energization drive system is selected. These are a figure which shows the load torque characteristic in one rotation of the mechanical angle of the rotor of a motor, and a drive signal when the load which a motor drives changes periodically. These are flowcharts of the mechanical angle determination process. These are figures which show the rotation speed change at the time of switching from an intermittent energization drive system to a 180 degree | times energization drive system. These are figures which show the rotation speed change at the time of switching from a 180 degree | times energization drive system to an intermittent energization drive system. These are the figures which show the correspondence data table of the electrical energization angle of intermittent energization drive, and each predetermined value. These are figures which show the corresponding | compatible data table of the rotation speed of a motor, and each predetermined value. These are figures which show an example of the electricity supply mode in a 120 degree | times electricity supply drive system. These are figures which show a motor current waveform at the time of switching from a 120 degree | times energization drive system to a 180 degree | times energization drive system. These are figures which show a motor current waveform at the time of switching from a 180 degree | times energization drive system to a 120 degree | times energization drive system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Commercial power supply 2 Reactor 3 Rectifier circuit 4 Smoothing capacitor 5 Inverter circuit 6 Three-phase brushless motor 7 Control circuit 8 Intermittent energization drive part 9 180 degree energization drive part 10 Drive system selection part 11 PWM creation / each phase distribution part 12 Rotation speed control PWM duty / modulation rate calculation unit 13, 14 Rotor position detection circuit R1-R3 Resistance

Claims (5)

Power supply means for supplying power to the synchronous motor;
180 degree energization drive means for controlling the power supply means so that the synchronous motor is driven by a 180 degree energization drive method without providing an energization pause period;
Intermittent energization drive means for controlling the power supply means so that the synchronous motor is driven by an intermittent energization drive method providing an energization pause period;
Selecting means for selecting one of the 180-degree energization driving method and the intermittent energization driving method;
When switching from one of the 180-degree energization drive system and the intermittent energization drive system to the other drive system, the drive signal immediately before the switch in the one drive system is corrected to correct the drive signal in the other drive system. A motor control device comprising drive signal correction means for making a drive signal immediately after switching.   The motor control device according to claim 1, wherein when the mechanical angle of the rotor of the synchronous motor is not a predetermined value, switching from the one drive system to the other drive system is prohibited. Even when the mechanical angle of the rotor of the synchronous motor is not a predetermined value,
The driving signal immediately before switching in the one driving method is corrected using a correction value to become a driving signal immediately after switching in the other driving method, and switching from the one driving method to the other driving method. 3. The motor control device according to claim 2, wherein when the correction value is changed according to a mechanical angle of a rotor of the immediately preceding synchronous motor, switching from the one drive system to the other drive system is not prohibited. The driving signal immediately before switching in the one driving method is corrected using a correction value, and becomes a driving signal immediately after switching in the other driving method,
The motor control device according to claim 1, wherein the correction value is changed in accordance with a state of the synchronous motor immediately before switching from the one driving method to the other driving method.   When switching from the 180-degree energization driving method to the intermittent energization driving method, the correction of the drive signal immediately before the switching in the 180-degree energization driving method exceeds the maximum value of the drive signal in the intermittent energization driving method. 5. The motor control device according to claim 1, wherein the maximum value of the drive signal in the intermittent energization drive method is a drive signal immediately after switching in the intermittent energization drive method.

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