JP6607016B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device that can determine whether or not a motor is idling.

  Conventionally, a motor has been used as one of techniques for obtaining power by electric energy. Such a motor may be in an idling state depending on a load state. For example, Patent Document 1 discloses a technique for detecting such an idle state.

  The control device for the electric oil pump described in Patent Document 1 sets the rotation speed of the electric oil pump to a predetermined determination target rotation speed according to the temperature of the oil, and sets the actual rotation speed and the determination target rotation speed. Whether or not the motor is idling is determined based on the difference. At this time, if the oil temperature is below a predetermined value, control is performed to increase the difference in motor speed between normal operation and idling, and if the oil temperature is higher than the predetermined value, normal operation is performed. And control so that the difference between the motor phase current and the idling motor is increased. As a result, at low temperatures when the oil viscosity increases, the pump load is normally prevented from increasing, and the actual rotational speed does not follow the target rotational speed, increasing the difference from the target rotational speed. Therefore, the occurrence of idling can be determined. On the other hand, when the temperature is high, the phase current differs between the normal time and the idling time according to the difference in the output torque. Therefore, it is possible to determine the occurrence of idling by controlling the difference to be significant.

JP 2012-197715 A

  The technique described in Patent Document 1 determines whether or not the motor is idling based on the rotational speed of the motor and the phase current of the motor. Become.

  Therefore, there is a need for a motor control device that can determine whether or not the motor is idling with an inexpensive configuration.

  A characteristic configuration of the motor control device according to the present invention includes a switching information acquisition unit that acquires switching information that defines a phase switching timing from a control unit that performs DUTY control of a switching element of an inverter that drives a three-phase motor, and the switching information. Based on the above, a regenerative time calculation unit that calculates a time during which the energy stored in the coil of the three-phase motor is released as a regenerative time, and DUTY information that defines the on-duty related to the DUTY control is acquired from the control unit A DUTY information acquisition unit that performs, and an idle state determination unit that determines whether or not the three-phase motor is in an idle state based on a determination threshold set by the regeneration time and the on-duty. It is in.

  When the three-phase motor is idling, the number of revolutions suddenly increases compared to the previous number of revolutions, but the number of revolutions may also increase when the load suddenly decreases regardless of the idling state. is there. For this reason, it is not easy to determine whether or not the three-phase motor is idling based only on the rotational speed. Therefore, with this configuration, it is determined whether or not the three-phase motor is idling based on the regeneration time that is calculated when the switching information that defines the phase switching timing is acquired and the on-duty that is indicated by the DUTY information. Since the determination threshold value used at the time is set and it is determined whether or not the idling state is based on the determination threshold value, it is possible to easily and inexpensively determine.

  In addition, it is preferable that the regeneration time calculation unit calculates the regeneration time when the time differential value of the induced voltage of the three-phase motor is positive.

  With such a configuration, the regeneration time can be calculated based on the on-duty. Therefore, the regeneration time can be accurately calculated based on the phase switching timing.

  In addition, it is preferable that the regeneration time calculation unit calculates the regeneration time when the time differential value of the induced voltage of the three-phase motor is negative.

  With such a configuration, the regeneration time can be calculated with reference to off-duty. Therefore, for example, when the on-duty is small, the regeneration time can be calculated at the phase switching timing based on the large off-duty, so that the regeneration time can be appropriately calculated.

  In addition, it is preferable that a temperature detection unit that detects an environmental temperature of a substrate on which the switching element is mounted is provided, and the determination threshold is set based on the environmental temperature.

  Switching elements have different allowable currents and electrical characteristics depending on the environmental temperature. Therefore, with such a configuration, it can be determined whether or not the three-phase motor is idling according to the temperature of the switching element.

It is a block diagram which shows typically the structure of a motor control apparatus. It is a figure which shows an induced electric power waveform. It is a figure which shows a phase voltage waveform and a phase current waveform. It is a figure which shows an example of a determination threshold value. It is a figure which shows an example of a determination threshold value.

  The motor control device according to the present invention can determine whether or not the three-phase motor is idling. Hereinafter, the motor control apparatus 1 of this embodiment is demonstrated.

  FIG. 1 is a block diagram showing a configuration of a motor control device 1 of the present embodiment. As shown in FIG. 1, the motor control device 1 includes functions of a switching information acquisition unit 11, a regeneration time calculation unit 12, a DUTY information acquisition unit 13, an idling state determination unit 14, a temperature detection unit 15, and a map storage unit 16. These functional units are constructed by hardware and / or software with the CPU as a core member in order to perform processing related to determination as to whether or not the three-phase motor M is in an idling state. ing.

  First, the driving of the three-phase motor M that determines whether or not the motor control device 1 is idling will be described. The three-phase motor M is driven by an inverter 3 that is PWM-controlled by the control unit 2.

  The inverter 3 converts DC power output from the DC power supply 4 into AC power and supplies the AC power to the three-phase motor M. The DC power supply 4 outputs DC power consisting of DC voltage (VDC) and DC current. The inverter 3 is provided between the DC power supply 4 and the three-phase motor M. The three-phase motor M is used as a power source for the water pump P in the present embodiment, and includes a rotor including a permanent magnet and a stator that generates a magnetic field for applying a rotational force to the rotor. The stator includes a U-phase, V-phase, and W-phase three-phase coil (hereinafter referred to as “stator coil”) SC. Each stator coil SC may be a star connection or a delta connection. FIG. 1 shows an example of delta connection. The inverter 3 controls such a three-phase motor M.

  The inverter 3 includes a plurality of switching elements Q. In the present embodiment, as the switching element Q, high-side transistors Q1, Q3, Q5 connected to the positive terminal side of the DC power supply 4 and low-side transistors Q2, Q4, connected to the negative terminal side of the DC power supply 4, A total of six transistors Q1 to Q6, Q6, are used. Diodes D1 to D6 are disposed between the source terminals and drain terminals of the transistors Q1 to Q6, respectively.

  The transistors Q1 to Q6 are PWM controlled by the control unit 2 with a predetermined duty ratio. Since the PWM control is a known pulse width modulation control, the description thereof is omitted.

  The switching information acquisition unit 11 acquires switching information that defines the timing of phase switching from the control unit 2 that performs DUTY control of the switching element Q of the inverter 3. As described above, the control unit 2 performs PWM control on the transistors Q1 to Q6 which are the switching elements Q. At this time, the DUTY ratio is adjusted according to the output torque required for the three-phase motor M. Therefore, the control unit 2 performs DUTY control of the switching element Q.

  The control unit 2 sequentially switches the switching elements Q to be controlled in order to sequentially switch the current flowing through the stator coil SC of the three-phase motor M. As is well known, the three phases of the three-phase motor M are the U phase, the V phase, and the W phase, and such switching is referred to as “phase switching”. When such phase switching is performed, the control unit 2 transmits switching information that defines the timing of phase switching to the switching information acquisition unit 11. The switching information acquisition unit 11 transmits the acquired switching information to a regeneration time calculation unit 12 described later.

  Based on the switching information, the regeneration time calculation unit 12 calculates the time during which the energy stored in the coil of the three-phase motor M is released as the regeneration time. The switching information is transmitted from the switching information acquisition unit 11 described above. Here, the three-phase motor M is driven according to the attractive force and repulsive force between the permanent magnet provided in the rotor and the stator coil SC provided in the stator. At this time, the current flowing through the stator coil SC is switched and energy is stored, but the energy stored in the stator coil SC may remain even after the attraction and repulsion are generated. Such energy corresponds to the “energy stored in the coil of the three-phase motor M”. Further, in the three-phase energization, when the phase is switched, the stator coil SC that has been energized so far continues to flow current, and regenerative energy is generated. The time during which such regenerative energy is generated is called “regeneration time”. Since the regeneration time calculation unit 12 can specify that the control unit 2 has switched the phase based on the acquired switching information, the regeneration time calculation unit 12 calculates the regeneration time based on the switching information. Specifically, for example, a timer may be used to count the time from when phase switching is performed until regeneration (generation of regenerative energy) ends.

  Hereinafter, a specific example will be described. FIG. 2 shows a waveform of induced power per predetermined phase (induced power waveform) in the three-phase motor M. As shown in FIG. 2, the induced power has an electrical angle of 0 ° as a positive zero cross point and 180 ° as a negative zero cross point.

  FIG. 3 shows a phase voltage waveform (phase voltage waveform) and a phase current waveform (phase current waveform) per predetermined phase in the three-phase motor M. As shown in FIG. 3, the voltage component of PWM control is superimposed on the phase voltage waveform and the phase current waveform.

  On the other hand, regenerative energy is generated at the timing of phase switching in the three-phase motor M, and can be confirmed, for example, in a phase voltage waveform or a phase current waveform. Assuming that the timing of regeneration time is T1 and T2, W-U phase energization, regeneration T1, W-V phase energization, U-V phase energization, U-W phase energization, regeneration T2, V-W phase energization, V- It occurs in the form of U-phase energization, W-U phase energization,.

  In the example of FIG. 3, regenerative energy is generated between T11 and T12, and a period T1 from T11 to T12 corresponds to the regenerative time. Regenerative energy is also generated between T21 and T22, and a period T2 from T21 to T22 corresponds to the regeneration time. The timing (T11 or T12) at which such regeneration time occurs corresponds to the phase switching timing and can be specified based on the switching information. Therefore, the regeneration time calculation unit 12 may count with a timer from the timing of T11 or the timing of T12 until the next voltage rise or fall.

  The DUTY information acquisition unit 13 acquires from the control unit 2 DUTY information that defines on-DUTY related to DUTY control. “On DUTY related to DUTY control” is a ratio of a period during which the switching element Q is in a driving state to a period of one cycle related to the DUTY control. Such on-duty is indicated by DUTY information, and is transmitted from the control unit 2 to the DUTY information acquisition unit 13.

  The idling state determination unit 14 determines whether or not the three-phase motor M is in the idling state based on a determination threshold set by the regeneration time and the on-duty. Here, if the three-phase motor M is in the idling state, the number of revolutions increases. However, even when the load on the three-phase motor M is too light, the number of revolutions may increase regardless of whether the three-phase motor M is idling. is there. For this reason, it is not easy to determine whether or not the three-phase motor M is in the idling state only by the rotation speed.

  On the other hand, since the load of the three-phase motor M is light in the idling state, the current (current consumption) flowing through the three-phase motor M is reduced. Therefore, by detecting the current flowing through the three-phase motor M, it can be determined whether or not the three-phase motor M is idling. However, a separate current sensor must be provided, and in such a case, the cost It becomes a factor of up.

  Therefore, in this embodiment, it is determined whether or not the three-phase motor M is idling by using a correlation between the regeneration time and the on-duty. Here, when the three-phase motor M is not in the idling state, the regeneration time has a unique relationship with the on-duty. However, when the three-phase motor M is in an idling state, the energy stored in the stator coil SC is reduced even if the control unit 2 is controlled at a predetermined on-duty, so that the regeneration time is reduced. Therefore, whether or not the three-phase motor M is in the idling state easily and inexpensively by setting a determination threshold value for determining whether or not the three-phase motor M is in the idling state based on the regeneration time and the on-duty. It becomes possible to determine whether or not.

  Such a determination threshold value is defined by a map and may be stored in the map storage unit 16 in advance. Thereby, the idling state determination unit 14 can read and use the map from the map storage unit 16 when determining.

  An example of such a map is shown in FIGS. FIG. 4 is a map that defines the relationship between the regeneration time at the positive zero cross point and the on-duty, and FIG. 5 is a map that defines the relationship between the regeneration time at the negative zero-cross point and the on-duty. Therefore, when the regenerative time calculation unit 12 calculates the regenerative time when the time differential value of the induced voltage of the three-phase motor M is positive, the idling state determination unit 14 uses the map of FIG. It is good to determine whether or not M is in the idling state. When the regeneration time calculating unit 12 calculates the regeneration time when the time differential value of the induced voltage of the three-phase motor M is negative, the idling state determining unit 14 may determine whether or not the three-phase motor M is idling using the map of FIG.

  The idling state determination unit 14 plots the transmitted regeneration time and the on-duty indicated in the DUTY information on the map shown in FIGS. 4 and 5, and when the plot is located in the area A indicated by hatching, It is determined that the three-phase motor M is idling. On the other hand, when the plot is located outside the area indicated by hatching, it is determined that the three-phase motor M is not idling. Incidentally, the hatching in FIGS. 4 and 5 shows the case where the temperature of the semiconductor described later is 25 ° C.

  Here, the semiconductor (semiconductor element: switching element Q) generates heat when it operates, and the mobility decreases as the temperature increases. Therefore, the resistivity of the semiconductor varies with the environmental temperature. That is, since the current flows more easily as the temperature of the semiconductor element becomes lower, the determination threshold is preferably set based on the environmental temperature. Specifically, as shown in FIGS. 4 and 5, the determination threshold is set to be smaller as the environmental temperature of the substrate is higher, and the determination threshold is set to be higher as the environmental temperature of the substrate is lower. . A map may be provided for each temperature, and may be used depending on the detection result of the temperature detector 15.

  In order to properly use such a determination threshold according to the environmental temperature, the temperature detection unit 15 detects the environmental temperature of the substrate on which the switching element Q is mounted. The “substrate on which the switching element Q is mounted” is a substrate constituting the inverter 3. Accordingly, for example, as shown in FIGS. 4 and 5, when the predetermined on-duty state is set, the determination threshold is set so that the regeneration time becomes longer as the environmental temperature detected by the temperature detection unit 15 is lower. During the regeneration time, the determination threshold value may be set so that the on-duty becomes smaller as the environmental temperature detected by the temperature detection unit 15 is lower.

  Note that the idling state determination unit 14 may determine based on the regeneration time at the time when the time differential value of the induced voltage of the three-phase motor M is positive, or the time differential value of the induced voltage of the three-phase motor M is negative. You may determine based on the regeneration time of a certain time. Of course, you may determine using both.

[Other Embodiments]
In the above-described embodiment, the determination threshold is set based on the environmental temperature. However, a uniform determination threshold can be set regardless of the environmental temperature.

  The present invention can be used for a motor control device capable of determining whether or not a motor is idling.

1: Motor control device 2: Control unit 3: Inverter 11: Switching information acquisition unit 12: Regeneration time calculation unit 13: DUTY information acquisition unit 14: Idling state determination unit 15: Temperature detection unit M: Three-phase motor Q: Switching element SC: Stator coil (coil)

Claims (4)

A switching information acquisition unit that acquires switching information that defines the timing of phase switching from a control unit that performs DUTY control of a switching element of an inverter that drives a three-phase motor;
Based on the switching information, a regeneration time calculation unit that calculates the time during which energy stored in the coil of the three-phase motor is released as the regeneration time;
A DUTY information acquisition unit for acquiring DUTY information defining on-DUTY related to the DUTY control from the control unit;
An idling state determination unit that determines whether or not the three-phase motor is in an idling state based on a determination threshold set by the regeneration time and the on-duty;
A motor control device comprising:   The motor control device according to claim 1, wherein the regenerative time calculation unit calculates the regenerative time when the time differential value of the induced voltage of the three-phase motor is positive.   The motor control device according to claim 1, wherein the regenerative time calculation unit calculates the regenerative time when the time differential value of the induced voltage of the three-phase motor is negative. A temperature detection unit for detecting an environmental temperature of a substrate on which the switching element is mounted;
The motor control device according to any one of claims 1 to 3, wherein the determination threshold is set based on the environmental temperature.

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