JP2014143839A - Control device for motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for a motor in which, even in the case where an instantaneous interruption occurs in an AC power source, occurrence of step-out in the motor can be accurately detected and performances of the motor can be completely effectively utilized.SOLUTION: In the case where the number of times of discriminating the presence of a spike detection signal generated by using second spike voltage generation time detection means is equal to or less than the predetermined number of times when rising or falling of the spike detection signal cannot be detected, a control section 11 determines that a step-out does not occur in a brushless DC motor 200. In the case where the number of times of discriminating the presence of the spike detection signal exceeds the predetermined number of times, the control section 11 reads out a first spike voltage generation time finally detected and stored by using first spike voltage generation time detection means. When the state where the read first spike voltage generation time is equal to or longer than a predetermined time judging step-out is continued predetermined times, the control section 11 determines that a step-out occurs in the brushless DC motor 200.

Description

  The present invention relates to a motor control device, and more particularly to a motor control device driven by inverter control.

  Conventionally, a compressor mounted in an air conditioner, a refrigerator, or the like has an electric motor, and an electric motor driven by inverter control such as a sensorless three-phase brushless DC motor is applied. There are many. As a control method of the brushless DC motor, there is known a method of switching control of a switching element of an inverter circuit provided in a control device for driving the brushless DC motor by a PWM (Pulse Width Modulation) method.

  When the brushless DC motor is driven by the rectangular wave drive, an induced voltage is generated in the non-energized phase of the brushless DC motor. By supplying a voltage higher than the induced voltage from the inverter circuit, the brushless DC motor is rotated. Let it continue. However, if the induced voltage generated in the non-energized phase is higher than the supply voltage from the inverter circuit, the rotational speed of the brushless DC motor cannot be increased. In such a case, by setting the phase of the current supplied to the brushless DC motor to a phase that is advanced with respect to the induced voltage, even when the induced voltage is high, more current is supplied to the brushless DC motor and the rotational speed is increased. The drive control of the brushless DC motor is performed by using the field weakening control method (for example, Patent Document 1).

  By the way, in the brushless DC motor as described above, there is a possibility that the step-out may occur due to insufficient torque (overload) of the motor. If the step-out occurs, for example, energization of the brushless DC motor is stopped. Therefore, it is necessary to perform step-out protection control for stopping the brushless DC motor.

  In a brushless DC motor that performs rectangular wave driving, a return current flows in a non-energized phase due to energization switching, and as a result, a spike voltage is generated in each phase. The spike voltage appears as a spike-like waveform (hereinafter referred to as a spike voltage waveform) in the voltage waveform of each phase of the brushless DC motor. A method for detecting the occurrence of step-out using this spike voltage waveform has been proposed. Yes.

  When step-out occurs, the time during which the reflux current flows (circulation current time) becomes longer, and the time during which the spike voltage is generated (hereinafter referred to as the spike voltage generation time) also becomes longer. The brushless DC motor control means performs various processes related to the brushless DC motor in parallel, and the spike voltage is detected at a predetermined timing, for example, at a timing when the switching elements constituting the inverter circuit are turned on. This is done by interrupt processing.

  Therefore, if the spike voltage generation time becomes longer due to a step-out and the spike voltage waveform rises / falls after the end of the interrupt processing period for detecting the spike voltage, the spike voltage waveform rises / falls. Can no longer be detected. If this state occurs continuously for a predetermined number of times, for example, 5 times, the control means determines that a step-out has occurred in the brushless DC motor, executes step-out protection control, and stops the brushless DC motor.

  However, as described above, the control unit of the brushless DC motor performs various processes related to the brushless DC motor in parallel including the interrupt process for detecting the rising / falling edge of the spike voltage waveform. If there is a lot of processing to be executed at the same time and a large load is applied to the control means, the rise / fall of the spike voltage waveform is actually executed even when the interrupt processing for detecting the rise / fall of the spike voltage waveform is executed. The timing for detecting the may be delayed.

  When the load applied to the brushless DC motor is reduced, the spike voltage generation time may be shortened, contrary to the case where the step-out occurs in the brushless DC motor. If the timing for detecting the rise / fall of the spike voltage waveform is delayed by the control means as described above when the spike voltage generation time is shortened, before the interrupt processing for detecting the spike voltage waveform rise / fall is performed. In this case, the spike voltage waveform rises / falls and the spike voltage waveform rise / fall may not be detected.

  In the conventional brushless DC motor, if a state where the rising / falling of the spike voltage waveform cannot be detected continuously occurs a predetermined number of times, the step-out protection control is executed regardless of the cause. Therefore, when the spike voltage waveform rise / fall cannot be detected due to a delay in the interrupt processing for detecting the rise / fall of the spike voltage waveform executed by the control means, that is, when it is unlikely that a step-out has occurred. Even so, since the step-out protection control is executed and the brushless DC motor is stopped, there is a problem that the brushless DC motor is stopped unnecessarily.

  Therefore, the present applicant detects the spike voltage generated in each phase of the brushless DC motor, stores the spike voltage generation time, and generates a spike detection signal using the spike voltage waveform which is the spike voltage waveform. When the spike detection signal rise or fall cannot be detected, the spike voltage generation time that was detected and stored last is read, and the read generation time is equal to or longer than the predetermined time for determining out-of-step and the predetermined number of times. A control device that determines that the brushless DC motor has stepped out when the rising or falling edge of the spike detection signal cannot be detected has been proposed (Japanese Patent Application No. 2012-30025).

  According to the control device described above, whether or not the rise or fall of the spike detection signal can be detected is due to step-out, whether or not the spike immediately before the rise or fall of the spike detection signal can no longer be detected. Since the determination is made using the voltage generation time, the step-out protection control is not executed when there is a low possibility that step-out has occurred, so that the brushless DC motor is not stopped unnecessarily.

Japanese Patent Laid-Open No. 2003-199382 (pages 4 to 5, FIGS. 5 and 6)

  However, in the brushless DC motor control device described above, no consideration is given to a case where an instantaneous power supply interruption (hereinafter referred to as an instantaneous interruption) from an AC power supply such as a commercial power supply occurs. When a momentary interruption occurs, the brushless DC motor approaches a step-out and the time during which the return current flows increases, so the spike voltage generation time also increases. Accordingly, when the rise / fall of the spike detection signal cannot be detected due to the delay of the interrupt processing for detecting the rise / fall of the spike detection signal executed by the control device, the generation time of the spike voltage to be detected and stored last is generated. If it is longer due to a momentary interruption, there is a risk of erroneously determining that a step-out has occurred.

  The present invention solves the above-described problems, and even when a momentary interruption occurs in the AC power supply, it is possible to accurately detect the occurrence of step-out in the motor, and control the motor to fully utilize the performance of the motor. An object is to provide an apparatus.

  In order to solve the above-described problems, a motor control device of the present invention converts DC power into AC power by an inverter and supplies the AC power to the motor to perform rotation control of the motor. A spike detection signal is generated using a spike voltage waveform that is a waveform of a spike voltage generated due to a return current generated when switching energization to each phase of the motor, and energization switching to each phase of the motor is performed. The first spike voltage generation time detecting means for detecting and storing the first spike voltage generation time from the timing of the first to the rising or falling timing of the spike detection signal, and constant from the timing of switching the energization to each phase of the motor The presence or absence of the spike detection signal corresponding to the spike voltage waveform was determined at the time interval of and it was determined that this spike detection signal was present A second spike voltage generating time detecting means for computing and storing second spike voltage generating time with a number, and has a. When the number of times that the spike detection signal detected using the second spike voltage generation time detection means is less than or equal to a predetermined number, the motor control device determines that the motor has not stepped out, When the number of times that the detection signal is determined exceeds a predetermined number, the first spike voltage generation time that is detected and stored last is read using the first spike voltage generation time detection means, and the read first When the spike voltage generation time is longer than the predetermined time and the state where the spike detection signal rise or fall cannot be detected continues for a predetermined number of times, it is determined that the motor has stepped out.

  The electric motor control apparatus of the present invention configured as described above counts the number of times that the second spike voltage generation time detection means determines that there is a spike detection signal, and finally detects the first spike voltage generation time detection means. Even if the first spike voltage generation time stored in the above is longer due to a momentary interruption, if the number of times that the second spike voltage generation time detection means determines that there is a spike detection signal is less than the predetermined number, the motor will step out. Judge that it is not. Therefore, even if the first spike voltage generation time detected and stored last is longer due to a momentary interruption, it is not erroneously determined that a step-out has occurred.

It is a block diagram which shows the structure of the control apparatus of a brushless DC motor in the Example of this invention. It is a timing chart for demonstrating the behavior of the brushless DC motor in the Example of this invention when the field-weakening control is performed. It is a timing chart for demonstrating the behavior of a brushless DC motor when a step-out occurs when performing field weakening control. It is a timing chart for demonstrating the behavior of a brushless DC motor when the momentary interruption of a power supply generate | occur | produces when performing field weakening control. It is a flowchart explaining the process when the position detection of a rotor cannot be performed in the Example of this invention.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. As an embodiment, a control device that drives and controls a brushless DC motor of a compressor mounted on an outdoor unit of an air conditioner will be described as an example. The present invention is not limited to the following embodiments, and can be variously modified without departing from the gist of the present invention.

  FIG. 1 is a block diagram showing the configuration of the control device 100 of the brushless DC motor 200. The brushless DC motor 200 to be controlled by the control device 100 includes a hollow stator having three-phase (U-phase, V-phase, and W-phase) windings, and a four-pole coil disposed in the hollow interior of the stator. A three-phase, four-pole sensorless brushless DC motor including a rotor having a permanent magnet. As this brushless DC motor 200, an IPM (Interior Parmant Magnet) motor in which a permanent magnet is embedded in the rotor may be applied, or an SPM (Surface Permanent Magnet) motor in which a permanent magnet is disposed on the surface of the rotor. May be.

  The control device 100 includes a converter circuit 2 that converts AC power supplied from the AC power source 1 into DC power, a smoothing capacitor 3 that smoothes DC power converted by the converter circuit 2, and a DC that is smoothed by the smoothing capacitor 3. An inverter circuit 4 (which forms at least a part of the inverter means) that drives the brushless DC motor 200 using electric power in a rectangular wave; a zero cross detection circuit 6 that detects a zero cross point of an induced voltage of each phase of the brushless DC motor 200; A position detection circuit 8 for detecting the position of the rotor using the zero cross point detected by the zero cross detection circuit 6; a control means 10 for controlling the brushless DC motor 200 based on a signal from the position detection circuit 8; 10 drives the brushless DC motor 200 through the inverter circuit 4 based on the control signal output from the motor 10. Comprising a motor drive circuit 7 which, a.

  A shunt resistor 5 that detects a bus current of the inverter circuit 4 is connected between the smoothing capacitor 3 and the inverter circuit 4. The current detection circuit 9 detects the voltage across the shunt resistor 5. The current detection circuit 9 calculates the bus current of the inverter circuit 4 from the input voltage, and the calculated bus current is input to the CPU 11a of the control unit 11 described later via the A / D conversion unit 14 included in the control means 10. The

  The inverter circuit 4 has a total of six switching elements including three switching elements 41U1, 41V1, and 41W1 on the upper arm and three switching elements 41U2, 41V2, and 41W2 on the lower arm. A phase bridge circuit is configured. These six switching elements (hereinafter referred to as switching elements 41 unless otherwise mentioned) can be realized by, for example, an IGBT (insulated gate bipolar transistor). A free-wheeling diode 42 is connected to each switching element 41 in parallel. Specifically, an anode terminal of the free-wheeling diode 42 is connected to an emitter terminal of the switching element 41, and a free-wheeling diode 42 is connected to a collector terminal of the switching element 41. The cathode terminal is connected. The free-wheeling diode 42 has a function of flowing a free-wheeling current generated by the energy accumulated in the stator winding of the brushless DC motor 200 that becomes a non-conduction phase at the moment when the corresponding switching element 41 is turned off to the input power supply side.

  The control means 10 generates a PWM (Pulse Width Modulation) waveform based on a control unit 11 that controls the rotation speed of the brushless DC motor 200 and a command from the control unit 11, and sends the generated PWM waveform to the motor drive circuit 7. From the PWM generation unit 12 to be output, a ROM (Read Only Memory) in which a control program for executing various processes and the like are stored in advance, and a RAM (Random Access Memory) in which operation parameters and data of various processes are stored A storage unit 15, an input unit 13, and an A / D conversion unit 14.

  The control unit 11 uses a rotor position detection signal input from the input unit 13 to generate a spike detection signal, which will be described later, and a rise / fall of the spike detection signal generated by the detection signal generation unit 11b. Exchange of data with the rise / fall detection unit 11c for detecting the detection, the detection signal determination unit 11d for determining the presence or absence of the spike detection signal generated by the detection signal generation unit 11b, and the A / D conversion unit 14 or the storage unit 15 And a CPU 11a that receives an input from the rising / falling detection unit 11c and the detection value determination unit 11d and controls the PWM generation unit 12.

  Next, a method for controlling the brushless DC motor 200 realized using the control device 100 having the above-described configuration will be described. The position detection circuit 8 compares the induced voltage generated in the non-energized phase of the brushless DC motor 200 taken in via the zero-cross detection circuit 6 with a reference voltage, and detects the intersection (zero-cross point) between the two. Then, the position detection circuit 8 generates a position detection signal based on the detected zero cross point and outputs it to the control means 10.

  The CPU 11a of the control means 10 that has input the rotor position detection signal via the input unit 13 calculates the motor rotation speed (actual rotation speed) of the brushless DC motor 200 using this position detection signal. Further, the CPU 11a generates a PWM waveform from the difference between the calculated motor rotation speed and the rotation speed (frequency) target value output from the control unit of the outdoor unit, and the bus current value of the inverter circuit 4 input from the current detection circuit 9. , And outputs a rotation speed instruction signal including the calculated duty ratio to the PWM generator 12. Further, the CPU 11a uses the input position detection signal to send a commutation signal including information about the commutation timing and which switching element 41 of the inverter circuit 4 is switched on / off to the PWM generation unit 12. Output.

  The PWM generation unit 12 that receives the rotation speed instruction signal and the commutation signal from the CPU 11a generates a PWM waveform having a duty ratio included in the rotation speed instruction signal, and also includes the commutation timing and the inverter circuit 4 included in the commutation signal. An energization switching signal is generated from information about which of the switching elements 41 is switched on / off. Then, the PWM generation unit 12 generates a drive signal in which the generated PWM waveform is superimposed on the generated energization switching signal, and outputs the drive signal to the motor drive circuit 7.

The motor drive circuit 7 that has received the drive signal from the PWM generator 12 generates a motor drive signal based on the input drive signal and outputs the motor drive signal to the inverter circuit 4. The inverter circuit 4 to which the motor drive signal is input from the motor drive circuit 7 generates a three-phase rectangular wave voltage using the DC voltage smoothed by the smoothing capacitor 3 and the input motor drive signal. It is applied to the brushless DC motor 200 at a predetermined energization timing.
In the following description, the case where the drive control of the brushless DC motor 200 is performed according to the rotor position detection result as described above is referred to as normal control.

  By controlling the brushless DC motor 200 as described above, the rotation speed of the brushless DC motor 200 is controlled to be the target rotation speed. In the PWM method, as the duty ratio of the PWM control superimposed on the drive signal increases, the electrical phase (energization phase) of the energization switching timing advances and the motor rotation speed increases. In order to further increase the motor rotation speed after the duty ratio of the PWM waveform reaches 100%, the phase of the current supplied to the brushless DC motor 200 is advanced with respect to the induced voltage so that the induced voltage is reduced. Even in a high state, it becomes possible to supply more current to the brushless DC motor 200, thereby executing field-weakening control that increases the rotational speed of the brushless DC motor 200.

  Next, a step-out detection method when performing field weakening control and field weakening control of the brushless DC motor 200 realized using the control device 100 will be specifically described with reference to FIGS. 1 to 5. When the rotational speed of the brushless DC motor 200 is further increased after the duty ratio of the PWM control reaches 100%, the CPU 11a of the control means 10 causes the phase angle of the energization phase of each phase of the brushless DC motor 200 from the normal control. Shift to field-weakening control.

  FIG. 2 is a timing chart for explaining the behavior of the control device 100 when the CPU 11a is performing field weakening control. In FIG. 2, the drive signal indicates a signal for turning on / off each switching element 41 of the inverter circuit 4, and the drive signal (U1) is supplied to the base of the switching element 41U1, and the drive signal (V1) ) Indicates what is supplied to the base of the switching element 41V1, and the drive signal (W1) indicates what is supplied to the base of the switching element 41W1. The drive signal (U2) is supplied to the base of the switching element 41U2, the drive signal (V2) is supplied to the base of the switching element 41V2, and the drive signal (W2) is supplied to the base of the switching element 41W2. Each one is shown.

  When the CPU 11a performs field weakening control of the brushless DC motor 200, only a predetermined electrical angle (predetermined and stored in the storage unit 15) from the commutation timing when the brushless DC motor 200 is driven by normal control. The drive signals are supplied to the inverter circuit 4 so as to quickly commutate. Thereby, the field angle control is performed by advancing the phase angle of the energization phase of each phase of the brushless DC motor 200.

  In FIG. 2, the voltage waveform indicates the change in voltage of each phase (changes between 0 and the voltage Vp applied to the inverter 4) when the brushless DC motor 200 is driven by field weakening control. The UN voltage waveform is the voltage change in the U-phase coil of the brushless DC motor 200, the VN voltage waveform is the voltage change in the V-phase coil of the brushless DC motor 200, the WN voltage waveform is the voltage change in the W-phase coil of the brushless DC motor 200, Respectively.

  In the voltage waveform of each phase, a spike voltage due to the reflux current flowing in each phase when not energized appears as a spike voltage waveform as shown in FIG. The spike voltage is generated when the switching elements 41U2, 41V2, 41W2 constituting the lower arm of the inverter circuit 4 are switched from on to off, and when the switching elements 41U1, 41V1, 41W1 constituting the upper arm are switched from on to off. Each case occurs.

  Specifically, in the UN voltage waveform, the spike voltage waveform (U2) when the drive signal (U2) switches from on to off, and the spike voltage waveform when the drive signal (U1) switches from on to off. (U1) appears. Further, in the VN voltage waveform, the spike voltage waveform (V2) when the drive signal (V2) is switched from on to off, and the spike voltage waveform (V1) when the drive signal (V1) is switched from on to off. Each appears. In the WN voltage waveform, the spike voltage waveform (W2) is switched when the drive signal (W2) is switched from on to off, and the spike voltage waveform (W1) is switched when the drive signal (W1) is switched from on to off. Each appears.

  In the following description, the width of the spike voltage waveform generated in the voltage waveform of each phase, that is, the spike voltage generation time is represented by a spike angle converted to an electrical angle. In FIG. 2, the spike angle corresponding to the spike voltage waveform (U1) and the spike voltage waveform (U2) is Ru, the spike angle corresponding to the spike voltage waveform (V1) and the spike voltage waveform (V2) is Rv, and the spike voltage waveform ( The spike angle corresponding to W1) and the spike voltage waveform (W2) is Rw. The CPU 11a overwrites and stores the spike angle generated in each phase in the storage unit 15.

  The spike detection signal is generated by the detection signal generator 11b using each spike voltage waveform described above. Specifically, the detection signal generation unit 11b has spike voltage waveforms (U2), (V2), and (W2) generated when the switching elements 41U2, 41V2, and 41W2 are switched from on to off, respectively, such that Vp → 0. The spike voltage waveforms (U1), (V1), and (W1) that are generated when the switching elements 41U1, 41V1, and 41W1 are switched from on to off are changed from 0 to Vp. 2 (hereinafter referred to as “rising”) is detected, and a spike detection signal as shown in FIG. 2 is generated using these signals and output to the rising / falling detection unit 11c.

  The detection permission indicates the timing at which the rising / falling detection unit 11c detects the rise / fall of the spike detection signal generated by the detection signal generation unit 11b by the interrupt processing according to an instruction from the CPU 11a. As shown in FIG. 2, the detection permission is prohibited → permitted synchronously when the switching elements 41U1, 41V1, 41W1, and 41U2, 41V2, 41W2 are switched from OFF to ON, respectively. If rising / falling is detected, permission is changed to prohibition. It should be noted that this detection permission is also permitted → prohibited even when the rise / fall of the spike detection signal cannot be detected within a predetermined time (maximum permission time Tm shown in FIG. 3) after the prohibition → permission.

  The control unit 11 performs field weakening control by the first spike voltage generation time detection unit and the second spike voltage generation time detection unit, and detects the spike angle when the control device 100 is operating as described above. In the following description, the spike angle detected by the first spike voltage generation time detector is referred to as a first spike angle, and the spike angle detected by the second spike voltage generation time detector is referred to as a second spike angle.

  The first spike voltage generation time detection means includes a CPU 11a, a detection signal generation unit 11b, and a rising / falling detection unit 11c. The CPU 11a detects the first spike angle using the switching timing of each drive signal shown in FIG. 2 and the rising / falling timing of the spike detection signal fetched from the rising / falling detection unit 11c. .

  For example, the spike angle (Rv) of the spike voltage (V2) appearing in the VN voltage waveform shown in FIG. 2 is the spike corresponding to the timing when the drive signal (V2) switches from on to off and the fall of the spike voltage (V2). Detection can be performed using the fall timing of the detection signal. In this method, the timing of switching of each drive signal and the rise / fall timing of the spike detection signal can be accurately grasped, so that the spike angle can be detected accurately, but the rise / fall of the spike detection signal is detected. Therefore, when the rising / falling edge of the spike detection signal cannot be detected due to the occurrence of step-out, for example, the first spike voltage generation time detection unit cannot detect the first spike angle.

  The second spike voltage generation time detection means includes a CPU 11a, a detection signal generation unit 11b, and a detection value determination unit 11d. The CPU 11a causes the detection value determination unit 11d to determine the presence or absence of the spike detection signal at a constant time interval (for example, every 5 microseconds) starting from the switching timing of each drive signal (the spike detection signal is High (5V) or Low (0V) depending on the generation condition). Then, the CPU 11a counts the number of spike detection signals from the determination result fetched from the detection value determination unit 11d, and detects the second spike angle using this number.

  For example, when detecting the spike angle (Rv) of the spike voltage (V2) appearing in the VN voltage waveform shown in FIG. 2, the CPU 11a triggers the detected value determination unit 11d at the timing when the drive signal (V2) switches from on to off. Output is started, and after that, a trigger is output to the detection value discriminating unit 11d at a constant time interval. The detection value determination unit 11d determines the presence or absence of a spike detection signal each time a trigger is input from the CPU 11a, and outputs it to the CPU 11a. If the spike detection signal is High corresponding to the voltage value Vp of the spike voltage (V2), the CPU 11a counts the number of detections: 1 using the discrimination result of the spike detection signal taken in. The CPU 11a repeats counting the number of detections until the discrimination result of the captured spike detection signal becomes Low. The CPU 11a calculates the second spike angle by multiplying the counted number of detections by the predetermined time interval.

  In the detection of the second spike angle by the second spike voltage generation time detecting means described above, the rise / fall detection unit 11c detects the spike angle even when the rise / fall of the spike detection signal cannot be detected. On the other hand, since the timing at which the discrimination result of the spike detection signal input from the detection value discrimination unit 11d becomes High to Low or Low to High cannot be grasped, the first spike voltage generation time detection unit is used. Compared to the accuracy of the spike angle detection, it is poor.

  Next, a method for determining the occurrence of step-out when the brushless DC motor 200 is driven by field weakening control will be described in detail with reference to FIGS. As shown in FIG. 2, when the brushless DC motor 200 is driven by field weakening control, if the drive control can be performed normally without step-out, the spike angle of the spike voltage generated in each phase is It is constant (Ru = Rv = Rw), and the spike detection signal repeats rising / falling at a constant cycle. Therefore, the CPU 11a can determine that the step-out has not occurred in the brushless DC motor 200 if the rising / falling detection unit 11c can detect the rising / falling of the spike detection signal.

  On the other hand, as shown in FIG. 3, when the step-out occurs in the brushless DC motor 200 and the spike angle becomes large, the width of the spike detection signal is widened, and the rise / fall detection unit 11c causes the rise of the spike detection signal. / There is a possibility that the falling cannot be detected (hereinafter referred to as a step-out state). In addition, since a large load is applied to the CPU 11a, the timing at which the rising / falling detection unit 11c detects the spike voltage waveform is delayed by an instruction from the CPU 11a, and the load applied to the brushless DC motor 200 is reduced, thereby reducing the spike angle. Even in this case, there is a possibility that the rising / falling detection unit 11c cannot detect the rising / falling of the spike detection signal (hereinafter referred to as an undetectable state).

  In the conventional brushless DC motor control device, when the out-of-step occurrence is detected by generating the spike detection signal and detecting the rise / fall as described above, the rise / fall of the spike detection signal is detected. Regardless of the cause of the failure, that is, whether it is in a step-out state or in a non-detectable state, it is determined that a step-out has occurred if the rising / falling edge of the spike detection signal cannot be detected continuously a predetermined number of times. The step-out protection control was performed.

  On the other hand, in the control device 100 for the brushless DC motor 200 of the present invention, when the rising / falling of the spike detection signal cannot be detected by the method described below, the cause is the step-out of the brushless DC motor 200. If it is determined whether or not a step-out has occurred, step-out protection control is performed.

  First, a case where step-out has occurred in the brushless DC motor 200 (step-out state) will be described with reference to FIG. In FIG. 3, detailed description of the same terms and symbols as in FIG. 2 is omitted.

  When step-out occurs in the brushless DC motor 200, the spike angle of the spike voltage that appears in the voltage waveform of each phase increases. As the spike angle increases, the width of the spike detection signal generated by the detection signal generation unit 11b increases accordingly. At this time, when the width of the spike detection signal is so wide that it cannot be detected during the maximum permission time Tm of detection permission, the rising / falling detection unit 11c cannot detect the rising edge of the spike detection signal. In FIG. 3, for example, the spike angle corresponding to the spike voltage waveform (U1a) appearing in the UN voltage waveform is increased to Rua (> Ru), and the rise / fall detection unit 11c detects the rise of the spike detection signal. Indicates that it is not possible. In FIG. 3, the rising edge of the spike detection signal that cannot be detected corresponding to the spike voltage waveform (U1a) is indicated by a broken line and “◯” is given.

  When the rising / falling edge of the spike detection signal 11c cannot be detected, the CPU 11a reads the first spike angle stored in the storage unit 15. As described above, when the rising / falling edge of the spike detection signal can be detected by the rising / falling detection unit 11c, the CPU 11a overwrites and stores the corresponding spike angle in the storage unit 15. Then, the first spike angle of the spike voltage corresponding to the falling edge of the spike detection signal immediately before the rising edge of the spike detection signal that cannot be detected with “◯” (the one with “◎”), that is, the VN detection voltage The spike angle Rvj1 corresponding to the spike voltage waveform (V2j) appearing at is read.

  Further, the CPU 11a reads out a step-out determination angle Rs (for example, 24 degrees in electrical angle) that is stored in advance in the storage unit 15 and is a threshold for determining whether or not the brushless DC motor 200 has stepped out. The out-of-step determination angle Rs and the spike angle Rvj1 are compared to determine whether or not the spike angle Rvj1 is greater than or equal to the out-of-step determination angle Rs. In FIG. 3, since the spike angle Rvj1 is equal to or greater than the step-out determination angle Rs, the CPU 11a counts the number Nx: 1 in which the rising / falling of the spike detection signal could not be detected. Specifically, in FIG. 3, when the rising edge of the spike detection signal to which “◯” is given is detected, the time is counted once when the detection permission time Tm has elapsed.

  When the brushless DC motor 200 is out of phase, since the spike angle of each phase after the spike angle of the UN voltage waveform is increased, the rising / falling detection unit 11c performs the subsequent spike in the same manner as described above. The rising / falling edge of the detection signal cannot be detected. In FIG. 3, the spike angle corresponding to the spike voltage waveform (W2a) appearing in the WN voltage waveform that is the source of generation of the spike detection signal next to the spike voltage waveform (U1a) is increased to Rwa (> Rw). The spike angle corresponding to the spike voltage waveform (V1a) appearing in the VN voltage waveform is also increased to Rva (> Rv), and the rising / falling detection unit 11c detects these spike voltage waveform (W2a) and spike voltage waveform (V1a). The spike detection signal corresponding to () cannot be detected. In FIG. 3, spike detection signals after the rising edge of the undetectable spike detection signal to which “◯” is given are indicated by broken lines, and “Δ” is given to the rising / falling edge that cannot be detected.

  If the rising / falling edge of the spike detection signal cannot be detected after the rising edge of the spike detection signal that the rising / falling edge detection unit 11c cannot detect at the beginning, the CPU 11a each time the step-out determination angle Rs is detected. Is compared with the spike angle Rvj1, and if the spike angle Rvj1 is greater than or equal to the step-out determination angle Rs, the number Nx of times when the rising / falling edge of the spike detection signal could not be detected is counted. If this number of times continues for a predetermined number of Na times, for example, 5 times, the CPU 11a determines that the brushless DC motor 200 has stepped out and stops energization of the brushless DC motor 200 to the motor drive circuit 7. The step-out protection control for stopping the brushless DC motor 200 is executed through the PWM generation unit 12.

  Next, when a large load is applied to the CPU 11a and the timing of detecting the spike voltage waveform is actually delayed (by the rising / falling detection unit 11c) and the spike angle is small (detection disabled state), A case where a momentary interruption occurs in the AC power supply 1 will be described with reference to FIG. In FIG. 4, detailed description of the same terms and symbols as in FIG. 2 is omitted.

  When the load applied to the brushless DC motor 200 is reduced, the spike angle of the spike voltage appearing in the voltage waveform of each phase may be small. Further, as described above, the rising / falling detection unit 11c detects the spike detection signal by an interrupt process according to an instruction from the CPU 11a, and when a large load is applied to the CPU 11a, as shown in FIG. Even when the switching elements 41U1, 41V1, and 41W1 are switched from OFF to ON, the timing at which the rising / falling detection unit 11c actually detects the rising / falling of the spike detection signal is determined as the switching element. 41U1, 41V1, and 41W1 may be delayed by time Tr than when switching from off to on.

  For example, as shown in FIG. 4, when the detection timing of the rise / fall of the spike detection signal is delayed by the time Tr, and the spike angle corresponding to the spike voltage waveform (U1b) appearing in the UN voltage waveform is Rub ( When the width of the spike detection signal generated by the detection signal generation unit 11b is narrowed based on this, the rise / fall detection unit 11c cannot detect the rise of the spike detection signal. In FIG. 4, the rising edge of the spike detection signal that cannot be detected corresponding to the spike voltage waveform (U1b) is indicated by a broken line and “◯” is given.

  In the motor control device (Japanese Patent Application No. 2012-30025) previously proposed by the present applicant, it is determined whether or not a step-out occurs in the brushless DC motor 200 as follows. The CPU 11a reads the first spike angle stored in the storage unit 15 when the rise / fall detection unit 11c cannot detect the rise / fall of the spike detection signal. When the rising / falling edge of the spike detection signal can be detected by the rising / falling detection unit 11c, the CPU 11a overwrites and stores the first spike angle corresponding thereto in the storage unit 15. Therefore, in the case of FIG. The first spike angle of the spike voltage corresponding to the fall of the spike detection signal immediately before the rise of the spike detection signal that cannot be detected with “O” (the one with “◎”), that is, the spike voltage that appears in the VN detection voltage A spike angle Rvj2 (in FIG. 4, the spike voltage waveform (V2j) at this time is indicated by a broken line) corresponding to the waveform (V2j) is read.

  Further, the CPU 11a reads out a step-out determination angle Rs (for example, 24 degrees in electrical angle) that is stored in advance in the storage unit 15 and is a threshold for determining whether or not the brushless DC motor 200 has stepped out. The out-of-step determination angle Rs and the spike angle Rvj2 are compared to determine whether or not the spike angle Rvj2 is greater than or equal to the out-of-step determination angle Rs. In FIG. 4, since the spike angle Rvj1 is not greater than the step-out determination angle Rs, the CPU 11a determines that the brushless DC motor 200 has not stepped out and continues the field-weakening control of the brushless DC motor 200.

  If the spike angle of each phase continues to decrease even after the spike angle of the UN voltage waveform has decreased, the rising / falling detection unit 11c also detects the subsequent rising / falling of the spike detection signal in the same manner as described above. Can not. In FIG. 4, the spike angle corresponding to the spike voltage waveform (W2b) appearing in the WN voltage waveform that is the source of generation of the spike detection signal next to the spike voltage waveform (U1b) is reduced to Rwb (<Rw). The spike angle corresponding to the spike voltage waveform (V1b) appearing in the VN voltage waveform is also reduced to Rvb (<Rv), and the rising / falling detection unit 11c uses these spike voltage waveform (W2b) and spike voltage waveform (V1b). The spike detection signal corresponding to () cannot be detected. In FIG. 4, spike detection signals after the rise of the undetectable spike detection signal to which “◯” is given are indicated by broken lines, and “Δ” is given to the rise / fall that cannot be detected.

  If the rising / falling edge of the spike detection signal cannot be detected after the rising edge of the spike detection signal that the rising / falling edge detection unit 11c cannot detect at the beginning, the CPU 11a each time the step-out determination angle Rs is detected. And spike angle Rvj2. If the spike angle Rvj2 is not equal to or greater than the step-out determination angle Rs, the CPU 11a determines that the brushless DC motor 200 has not stepped out and continues the field-weakening control of the brushless DC motor 200.

  However, as shown in FIG. 4, when the spike voltage (V2j) is generated, if a momentary interruption occurs in the AC power supply 1, the time for the return current to flow near the step-out of the brushless DC motor 200 becomes longer. The spike angle of the spike voltage (V2j) that is the first spike angle stored by the CPU 11a may be Rvj3, which is larger than Rvj2. When the spike angle Rvj3 when the instantaneous interruption occurs is equal to or greater than the step-out determination angle Rs, when the rising / falling detection unit 11c cannot detect the rising / falling of the spike detection signal, the above-described method is used. If it is determined whether or not a step-out has occurred in the DC motor 200, the CPU 11a may erroneously determine that a step-out has occurred.

Therefore, in the present invention, the second spike angle detected by the second spike voltage generation time detection means described above is used, a large load is applied to the CPU 11a, and the spike voltage waveform is actually generated by the rising / falling detector 11c. Even when a momentary interruption occurs in the AC power supply 1 when the detection timing is delayed and the spike angle is small (undetectable state), the brushless DC motor 200 is out of step. To avoid misjudging.
In the following, the second spike voltage generation time detection means detects the second spike angle, and using this detection result, the brushless DC motor 200 steps out even if a momentary interruption occurs in the AC power supply 1. A method for avoiding erroneous determination that the occurrence has occurred will be specifically described with reference to FIG.

  The CPU 11a starts trigger output to the detection value determination unit 11d at a certain time interval at a timing when each drive signal (U1, U2, V1, V2, W1, W2) is switched from on to off. The detection value determination unit 11d outputs the determination result of the spike detection signal to the CPU 11a every time a trigger is input from the CPU 11a. Then, if the discrimination result of the captured spike detection signal is a level (High or Low) corresponding to the voltage value of each spike voltage, the CPU 11a counts the number of detections Ny as a spike detection signal: Yes. The number of detection times Ny corresponds to the magnitude of the spike angle. For example, if the spike voltage (V2j): spike detection signal corresponding to Vp: High, the number of detection times Ny is 4 times (because the spike angle is large), Spike voltage (U1b): Spike detection signal corresponding to 0: If Low, the number of detections Ny is 2 (because the spike angle is small).

  The storage unit 15 stores a spike detection signal corresponding to the spike voltage waveform: a detection threshold number Nb (for example, two times) that is a threshold value of the number of detections Ny. The detection threshold number Nb is determined corresponding to the magnitude of the spike angle at which the step-out may occur in the brushless DC motor 200.

  The CPU 11a reads the number of detections Ny and the number of detection thresholds Nb from the storage unit 15. If the number of detections Ny is less than or equal to the detection threshold number Nb, the CPU 11a determines that no step-out has occurred in the brushless DC motor 200 and brushless. The field weakening control of the DC motor 200 is continued. When the detection number Ny is not equal to or less than the detection threshold number Nb, the CPU 11a reads out the first spike angle detected by the first spike voltage generation time detection unit and stored and the step-out determination angle Rs from the storage unit 15. When the first spike angle is not equal to or greater than the step-out determination angle Rs, the field-weakening control of the brushless DC motor 200 is continued. When the first spike angle is equal to or greater than the step-out determination angle Rs, the spike detection signal rises. / If the number of times Nx where the falling edge could not be detected is counted and this number of times continues for a predetermined number of times Na, it is determined that the brushless DC motor 200 has stepped out.

  As described above, in the present invention, the second spike angle detected by the second spike voltage generation time detection means is used, a large load is applied to the CPU 11a, and the timing of actually detecting the spike voltage waveform is delayed, In addition, when the spike angle is small (detection impossible state), even if a momentary interruption occurs in the AC power supply 1, it is erroneously determined that the step-out has occurred in the brushless DC motor 200. I am trying not to.

Next, the flow of processing in the control unit 11 in this embodiment will be described using the flowchart shown in FIG. The flowchart shown in FIG. 5 explains the flow of processing when the out-of-step occurrence in the brushless DC motor 200 is detected. ST represents a step and the subsequent number represents a step number.
Note that FIG. 5 mainly illustrates the processing related to the present invention, and description of other processing such as when the brushless DC motor 200 is driven by the above-described normal control is omitted.

  The control unit 11 of the control means 10 starts driving control of the brushless DC motor 200, and the rising / falling detection unit 11c resets the number Nx of the spike detection signal that cannot be detected to 0 (ST1). . Next, the control part 11 produces | generates a spike detection signal from the spike voltage waveform which appeared in each phase (ST2).

  Next, the control unit 11 resets the number of detections Ny of the spike detection signal: existence corresponding to the spike voltage waveform to 0 (ST3). Next, the control unit 11 determines whether the spike detection signal is at a level (High or Low) corresponding to the voltage value of each spike voltage based on the discrimination result of the spike detection signal output from the detection value discrimination unit 11d. The presence or absence is determined (ST4). If the spike detection signal is present (ST4-Yes), the control unit 11 counts the number of detections Ny, that is, adds 1 to the previous number of detections Ny (ST12), and stores the new number of detections Ny. Store in unit 15.

  Next, the control unit 11 determines whether or not a predetermined time has elapsed (ST13). As described above, the predetermined time is a trigger period (5 microseconds in this embodiment) output from the CPU 11a to the detection value determination unit 11d. If the predetermined time has not elapsed (ST13-No), the control unit 11 returns the process to ST13, and if the predetermined time has elapsed (ST13-Yes), the control unit 11 returns the process to ST4. Note that the routine from ST4 (-Yes) to ST13 described above is a routine related to the second spike voltage generation time detection means.

  In ST4, when the spike detection signal is not present (ST4-No), the control unit 11 determines whether or not the rising / falling detection unit 11c has detected the rising / falling of the spike detection signal ( ST5).

  If the rise / fall of the spike detection signal can be detected (ST5-Yes), the control unit 11 stores the spike angle Rj of the spike voltage of the phase corresponding to the detected rise / fall in the storage unit 15 (ST14), Return the process to ST1. Note that the spike angle Rj in ST14 is the first spike angle detected by the control unit 11 by the first spike voltage generation time detection means, and the control unit 11 stores the spike angle Rj in the storage unit 15.

  If the rise / fall of the spike detection signal cannot be detected (ST5-No), the control unit 11 reads the number of detections Ny and the number of detection thresholds Nb of the spike detection signal corresponding to the spike voltage waveform from the storage unit 15, It is determined whether or not the number of detections Ny is greater than the detection threshold number Nb (ST6). If the detection count Ny is not greater than the detection threshold count Nb (ST6-No), the control unit 11 returns the process to ST1.

  If the detection number Ny is larger than the detection threshold number Nb (ST6-Yes), the control unit 11 reads the spike angle Rj (Rvj1 in the present embodiment) and the step-out determination angle Rs (24 degrees in the present embodiment) from the storage unit 15. Are read (ST7). Next, the control unit 11 compares the step-out determination angle Rs with the spike angle Rj, and determines whether or not the spike angle Rj is greater than or equal to the step-out determination angle Rs (ST8).

  If the spike angle Rj is not greater than the step-out determination angle Rs (ST8-No), the control unit 11 returns the process to ST1. If the spike angle Rj is equal to or greater than the step-out determination angle Rs (ST8-Yes), the control unit 11 counts the number Nx of times when the spike detection signal rise / fall was not detected, that is, the number Nx up to the previous time. 1 is added (ST9).

  Next, the control unit 11 determines whether or not the number Nx of times when the rising / falling of the spike detection signal could not be detected has reached a predetermined number Na (5 times in this embodiment) (ST10). If the number of times Nx is not Na (ST10-No), the control unit 11 returns the process to ST2. If the number of times Nx is Na (ST10-Yes), the control unit 11 performs step-out protection control for stopping energization of the brushless DC motor 200 (ST11), and ends the process.

  As described above, the motor control device according to the present invention counts the number of times the second spike voltage generation time detection means determines that there is a spike detection signal, and finally detects the spike signal generation time detection means. Even if the first spike voltage generation time stored in the above is longer due to a momentary interruption, if the number of times that the second spike voltage generation time detection means determines that there is a spike detection signal is less than the predetermined number, the motor will step out. Judge that it is not. Therefore, even if the first spike voltage generation time detected and stored last is longer due to a momentary interruption, it is not erroneously determined that a step-out has occurred.

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Converter circuit 3 Smoothing capacitor 4 Inverter circuit 5 Shunt resistance 6 Zero cross detection circuit 7 Motor drive circuit 8 Position detection circuit 9 Current detection circuit 10 Control means 11 Control part 11a CPU
11b Detection signal generation unit 11c Rising / falling detection unit 11d Detection signal determination unit 12 PWM generation unit 13 Input unit 14 A / D conversion unit 41U1, 41U2 Switching element 41V1, 41V2 Switching element 41W1, 41W2 Switching element 42 Free-wheeling diode 100 Control Equipment 200 Brushless DC motor

Claims (2)

A control device for an electric motor that converts direct current power into alternating current power by an inverter and supplies it to an electric motor, and performs rotation control of the electric motor,
The motor control device generates a spike detection signal using a spike voltage waveform that is a waveform of a spike voltage generated due to a return current generated when energization switching to each phase of the motor is performed, and First spike voltage generation time detection means for detecting and storing a first spike voltage generation time from the timing of switching the energization to each phase of the motor to the rise or fall timing of the spike detection signal; and The second spike voltage generation time is determined by determining the presence or absence of the spike detection signal corresponding to the spike voltage waveform at a certain time interval from the timing of switching the energization to each phase, and using the number of times the spike detection signal is determined to be present. Second spike voltage generation time detection means for calculating and storing
The motor control device determines that the motor has not stepped out when the number of times that the spike detection signal detected using the second spike voltage generation time detection means is less than a predetermined number. When the number of times that the spike detection signal is determined exceeds a predetermined number, the first spike voltage generation time that is detected and stored last using the first spike voltage generation time detection means is read out, It is determined that the motor has stepped out when the read first spike voltage generation time is a predetermined time or longer and the rise or fall of the spike detection signal cannot be detected a predetermined number of times. Electric motor control device.   2. The motor control device according to claim 1, wherein when it is determined that the motor has stepped out, step-out protection control is performed to stop the motor. 3.

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