JP5917378B2 - Electric motor control device - Google Patents

Description

  The present invention relates to a motor control device that suppresses the occurrence of irreversible demagnetization.

  In an electric motor, when irreversible demagnetization occurs, the torque decreases, so it is desired to suppress irreversible demagnetization. As a method for suppressing the occurrence of irreversible demagnetization, for example, a high coercivity neodymium magnet having a high content of dysprosium (Dy) or a method of increasing the magnet permeance coefficient by increasing the thickness of the magnet is known. Yes.

  Also, in Patent Document 1 below, when irreversible demagnetization occurs, the phase of the current that maximizes the torque changes. Therefore, when the occurrence of irreversible demagnetization is detected, the phase of the current is adjusted so that the torque becomes maximum. It is described to do.

Japanese Patent No. 2943657

  However, the prices of rare earths such as dysprosium and neodymium (Nd) that improve the coercive force of magnets have recently increased, and in order to suppress the occurrence of irreversible demagnetization, the content of dysprosium is increased or the thickness of the magnet is decreased. If it increases, the cost of an electric motor will increase.

  The technique described in Patent Document 1 senses the occurrence of irreversible demagnetization and adjusts the phase of the current so that the torque is maximized in the irreversible demagnetization state. It does not suppress it.

  Therefore, an object of the present invention is to provide a motor control device that suppresses the occurrence of irreversible demagnetization while suppressing cost.

  The motor control device according to the present invention has the following features.

In the motor control device, comprising: a rotor including a permanent magnet; a stator around which a winding is wound; and a drive control device that supplies a drive current having a predetermined phase to the winding. When the drive current is smaller than the first threshold, the drive control device sets the phase of the drive current to a maximum torque phase at which the torque of the electric motor with respect to a predetermined drive current is maximized, and the drive current is the first When the threshold value is exceeded, the drive current phase is retarded from the maximum torque phase, and the current value of the drive current is required for the maximum torque phase so that the required torque is output. Set to a larger current value .

  Second feature: The drive control device, when the drive current is greater than or equal to the first threshold, increases a retard amount by which the phase of the drive current is retarded from the maximum torque phase as the drive current increases. Increase.

  Third feature: The drive control device retards the phase of the drive current from the maximum torque phase when the drive current is equal to or greater than the first threshold and the temperature of the permanent magnet is equal to or greater than a second threshold. Let

  4th characteristic; The said drive control apparatus makes the said 1st threshold value small, so that the temperature of the said permanent magnet is high, when the temperature of the said permanent magnet is more than the said 2nd threshold value.

  Fifth feature; the drive control device is configured such that when the temperature of the permanent magnet is equal to or higher than the second threshold, the phase of the drive current is retarded from the maximum torque phase as the temperature of the permanent magnet is higher. Increase the amount.

  According to the first feature, when the drive current is smaller than the first threshold value, the phase of the drive current is set so that the torque of the electric motor is maximized with the minimum drive current, and the drive current becomes equal to or greater than the first threshold value. Since the phase of the drive current is retarded from the maximum torque phase, when the drive current is relatively small, the motor can be driven with high efficiency, and when the drive current is relatively large, the winding received by the permanent magnet. The demagnetizing field from the wire can be reduced, and the occurrence of irreversible demagnetization of the permanent magnet can be effectively suppressed. Further, since it is not necessary to increase the content of dysprosium or the like contained in the permanent magnet or increase the thickness of the permanent magnet, it is possible to suppress the amount of expensive rare earth.

  According to the second feature, when the drive current is greater than or equal to the first threshold, the amount of retardation by which the phase of the drive current is retarded from the maximum torque phase is increased as the drive current is increased. Even so, it is possible to reduce the demagnetizing field from the winding and effectively suppress the occurrence of irreversible demagnetization of the permanent magnet.

  According to the third feature, when the driving current is equal to or higher than the first threshold and the temperature of the permanent magnet is equal to or higher than the second threshold, the phase of the driving current is retarded from the maximum torque phase. When the temperature becomes lower than a certain value, the demagnetizing field from the winding can be reduced, and the occurrence of irreversible demagnetization of the permanent magnet can be effectively suppressed.

  According to the fourth feature, when the temperature of the permanent magnet is equal to or higher than the second threshold, the higher the temperature of the permanent magnet, the smaller the first threshold, so that the coercive force decreases as the temperature of the permanent magnet increases. Even so, the occurrence of irreversible demagnetization of the permanent magnet can be effectively suppressed.

  According to the fifth feature, when the temperature of the permanent magnet is equal to or higher than the second threshold value, the higher the temperature of the permanent magnet, the larger the amount of retardation by which the phase of the drive current is retarded from the maximum torque phase. Even if the coercive force decreases with an increase in the temperature of the magnet, the demagnetizing field from the winding can be greatly reduced, and the occurrence of irreversible demagnetization can be effectively suppressed.

It is a block diagram of a control apparatus. It is a block diagram of the electric motor shown in FIG. It is a figure which shows the relationship between a torque current and an exciting current. FIG. 4A is a diagram showing the relationship between the output torque of the electric motor and the advance angle of the phase of the drive current, and FIG. 4B shows the advance angle of the phase of the drive current whose amplitude is greater than or equal to the threshold value and the demagnetization factor of the magnetic flux of the permanent magnet. It is a figure which shows the relationship. It is a figure which shows an example of the demagnetization curve of a permanent magnet. It is a graph which shows the relationship between the output torque of an electric motor, and rotation speed. It is a figure which shows the magnetic curve of a permanent magnet according to the temperature of a permanent magnet. FIG. 8A is a diagram showing the relationship between the output torque of the motor and the advance angle of the phase of the drive current, and FIG. 8B shows the relationship between the advance angle of the phase of the drive current and the demagnetization factor of the magnetic flux of the permanent magnet. It is a figure shown according to temperature. It is a figure which shows the relationship between the temperature according to the temperature of a permanent magnet, and the phase according to the amplitude of drive current. It is a flowchart which shows operation | movement of the control apparatus shown in FIG.

  BEST MODE FOR CARRYING OUT THE INVENTION A motor control device according to the present invention will be described in detail below with reference to the accompanying drawings with preferred embodiments.

[First Embodiment]
FIG. 1 is a configuration diagram of the control device 10. The control device 10 is mounted on an electric vehicle, a hybrid vehicle, or the like, and includes a motor 12 such as a salient pole type PM motor as a drive source, a drive control device 14 that controls the drive of the motor 12, and a DC power source. A battery 16 is provided. As shown in FIG. 2, the electric motor 12 has a rotor 20, a stator 22 having a three-phase (U-phase, V-phase, W-phase) winding 22 a, and an outer peripheral surface of the rotor 20 so as to face the stator 22. And N and S permanent magnets 24 and salient pole portions 26. A rotating shaft 28 is provided at the center of the rotor 20.

  Returning to the description of FIG. 1, the drive control device 14 controls the drive of the electric motor 12, and includes a control unit 30, an inverter circuit 32, and U-phase and V-phase alternating currents (drive) output from the inverter circuit 32. Current detectors 34u and 34v for detecting currents iu and iv. The control unit 30 is composed of a computer having a CPU and a memory.

  The inverter circuit 32 has a plurality of switching elements (not shown), and the controller 30 controls the on / off of the plurality of switching elements (current conversion control is performed), so that a direct current supplied from the battery 16 is generated. The three-phase drive currents iu, iv, and iw are converted, and the converted three-phase drive currents iu, iv, and iw are supplied to the motor 12. The converted three-phase drive currents iu, iv, iw are supplied to the three-phase winding 22 a of the stator 22. As a result, the electric motor 12 is driven, and the rotor 20 rotates about the rotation shaft 28.

  Here, the control unit 30 controls the phase β of the drive currents iu, iv, and iw with respect to the position of the rotor 20 when performing current conversion control. The phase β and the amplitude I (magnitude) of the drive currents iu, iv, iw are controlled by turning on / off the plurality of switching elements of the inverter circuit 32. As shown in FIG. 2, the three-phase drive currents iu, iv, and iw are represented by a d-axis current (hereinafter referred to as excitation current) Id and a q-axis current (hereinafter referred to as torque current) Iq. And torque current Iq are combined. The three-phase drive currents iu, iv, and iw have the same amplitude I, and hereinafter, the three-phase drive currents iu, iv, and iw may be collectively referred to as a drive current i.

  FIG. 3 is a diagram illustrating the relationship between the torque current Iq and the excitation current Id. As shown in FIG. 3, the torque current Iq can be expressed as Iq = Icos β, and the excitation current Id can be expressed as Id = −Isin β. As the phase β of the drive current i is increased (advanced), the negative excitation current Id is increased, and as the phase β of the drive current i is decreased (retarded), the negative excitation current Id is decreased. To do. When the negative excitation current Id increases, the demagnetizing field from the winding 22a received by the permanent magnet 24 increases, and when the negative excitation current Id decreases, the demagnetizing field from the winding 22a received by the permanent magnet 24 decreases. It is assumed that phase β2> phase β1.

  When the torque current Iq flows through the winding 22a, magnet torque is generated by the torque current Iq and the magnetic flux φ of the permanent magnet 24. Further, when the exciting current Id flows through the winding 22a, reluctance torque is generated by the salient pole portion 26 formed of a magnetic material. Therefore, the output torque T of the electric motor 12 is a combination of the magnet torque and the reluctance torque.

  Returning to the description of FIG. 1, the electric motor 12 is assembled with a position detector 12 a for detecting the rotation angle θ of the rotor 20. The position detector 12a is a known one configured using a Hall element or an encoder. The rotation angle θ obtained by the position detector 12a generally causes an error with respect to the actual rotation position of the rotor 20 due to an assembly error of the position detector 12a, etc., but this embodiment will be described. In order to simplify the explanation, it is assumed that no error occurs.

  The control unit 30 includes a current command calculation unit 40, a current conversion unit 42, subtractors 44 and 46, a voltage command calculation unit 48, a voltage conversion unit 50, and an inverter control unit 52. The current command calculation unit 40 sets the amplitude I and the phase β of the drive current i necessary for setting the output torque T of the electric motor 12 to the command torque value T1, and the excitation current is based on the set amplitude I and phase β. The command value Idc and the torque current command value Iqc are calculated.

  The current converter 42 converts the U-phase and V-phase drive currents iu and iv detected by the current detectors 34u and 34v into an excitation current Id and a torque current Iq. Here, the electric motor 12 has three phases, and the drive current i flowing through any one phase is uniquely determined by the drive current i flowing through the other two phases. The drive currents iu and iv of the phases (U phase and V phase) are detected. Specifically, the current converter 42 calculates the excitation current Id and the torque current Iq using the following equation (1). In the equation (1), θ is the rotation angle θ of the rotor 20 detected by the position detector 12a.

  The subtractor 44 obtains a deviation by subtracting the excitation current Id converted by the current conversion unit 42 from the excitation current command value Idc calculated by the current command calculation unit 40. The subtractor 46 obtains a deviation by subtracting the torque current Iq converted by the current conversion unit 42 from the torque current command value Iqc calculated by the current command calculation unit 40.

  The voltage command calculation unit 48 determines the d-axis voltage (hereinafter referred to as excitation voltage) command value Vdc, the q-axis voltage (hereinafter referred to as “excitation voltage”) according to the deviations (Idc−Id) and (Iqc−Iq) obtained by the subtractors 44 and 46. Hereinafter, a torque voltage) command value Vqc is calculated. The voltage conversion unit 50 calculates the excitation voltage command value Vdc and the torque voltage command value Vqc based on feedback control such as PI control so that the deviations (Idc−Id) and (Iqc−Iq) become “0”, respectively. .

  The voltage conversion unit 50 converts the excitation voltage command value Vdc and the torque voltage command value Vqc calculated by the voltage command calculation unit 48 into command voltage values Vuc, Vvc, and Vwc of the applied voltage of each phase of the electric motor 12. Specifically, the voltage conversion unit 50 calculates the command voltage values Vuc, Vvc, and Vwc for each phase using the following equation (2). In the equation (2), θ is the rotation angle θ of the rotor 20 detected by the position detector 12a.

  The command voltage values Vuc, Vvc, Vwc define the magnitude and phase of the applied voltage of each phase of the electric motor 12, and the inverter control unit 52 uses the command voltage values Vuc, Vvc converted by the voltage conversion unit 50. , Vwc is sent to the inverter circuit 32 a control signal for controlling the plurality of switching elements. As a result, the amplitude I and phase β of the three-phase drive currents iu, iv, iw output from the inverter circuit 32 become the amplitude I and phase β set by the current command calculation unit 40 and are applied to each phase of the motor 12. The voltages Vu, Vv, and Vw that are applied become the command voltage values Vuc, Vvc, and Vwc. Therefore, the output torque T of the electric motor 12 becomes the command torque value T1.

  FIG. 4A is a diagram showing the relationship between the output torque T of the electric motor 12 and the advance angle (advance angle) of the phase β of the drive current i. If the phase β is changed when the amplitude I of the drive current i is constant, the output torque T of the electric motor 12 varies as shown in FIG. 4A. Therefore, the control unit 30, more specifically, the current command calculation unit 40, determines the amplitude I and the phase β of the drive current i so that the output torque T of the electric motor 12 becomes the maximum with the minimum drive current i (the amplitude I is minimum). Set. Thereby, the inverter circuit 32 is controlled so that the output torque T of the electric motor 12 becomes the phase β (the phase β at this time is called the best phase βb) with the minimum drive current i at the command torque value T1 ( Normal phase control). In FIG. 4A, the position of the best phase (maximum torque phase) βb is represented by s.

  However, when the drive current i increases and the amplitude I of the drive current i becomes equal to or greater than the threshold (first threshold) th1, the demagnetizing field from the winding 22a (the demagnetizing field in the direction opposite to the magnetic flux φ of the permanent magnet 24) is generated. There is a risk of irreversible demagnetization. FIG. 4B is a diagram showing the relationship between the advance angle of the phase β of the drive current i having the amplitude I equal to or greater than the threshold th1 and the demagnetization factor of the magnetic flux φ of the permanent magnet 24. In FIG. 4A as well, the amplitude I of the drive current i is set to the threshold th1 or more.

  When the drive current i is greater than or equal to the threshold th1 and the phase β of the drive current i is the best phase βb, irreversible demagnetization occurs. This irreversible demagnetization has a characteristic that the demagnetization factor increases because the demagnetizing field from the winding 22a received by the permanent magnet 24 increases as the drive current i advances.

  Therefore, when the amplitude I of the set drive current i is greater than or equal to the threshold th1, the current command calculation unit 40 retards the phase β of the set drive current i from the best phase βb. Further, when the phase β is retarded, the output torque T of the electric motor 12 decreases, so the amplitude I of the drive current i is reset so that the output torque T becomes the command torque value T1 at the phase β after the retardation. To do. The amount of retardation to be retarded increases in accordance with the magnitude of the difference between the amplitude I of the drive current i and the threshold th1.

  Thus, by retarding (delaying) the phase β of the drive current i from the best phase βb, the demagnetizing field from the winding 22a received by the magnet is reduced to prevent the occurrence of irreversible demagnetization. The position of the retarded phase β is represented by t.

  The phase β of the drive current i may be continuously retarded according to the magnitude of the drive current i, or may be retarded stepwise according to the magnitude of the drive current i. Also good.

  Here, the reason why irreversible demagnetization occurs will be briefly described. FIG. 5 is a diagram illustrating an example of a demagnetization curve of the permanent magnet 24. The vertical axis in FIG. 5 indicates the magnetic flux density B [T], and the horizontal axis indicates the magnetic field −H [A / m]. As shown in FIG. 5, the operating point p of the permanent magnet 24 is on the demagnetization curve. When the amplitude I of the drive current i increases, the demagnetizing field from the winding 22a increases, so that the operating point p moves to the left on the demagnetization curve (the magnetic flux density B and the magnetic field H decrease), When the amplitude I of the drive current i exceeds a certain value, the operating point p passes through the knick point (inflection point) q and further moves to the left. In FIG. 5, the operating point p when the amplitude I of the drive current i is equal to or greater than the predetermined value is represented by p ′.

  Since the operating point p ′ that has passed the nick point q is lower than the nick point q, irreversible demagnetization occurs in the permanent magnet 24. On the other hand, when the phase β of the drive current i is retarded, the demagnetizing field from the winding 22a is reduced, so that the operating point p moves to the right on the demagnetization curve. Therefore, when the amplitude I of the drive current i becomes greater than or equal to the threshold th1, the control unit 30 controls the inverter circuit 32 to retard the phase β of the drive current i, so that the operating point p does not pass the knick point q. Like that. Here, the amount of retardation (degree of delay) by which the phase β of the drive current i is retarded increases in accordance with the magnitude (amplitude I) of the drive current i. That is, the greater the difference between the amplitude I of the drive current i and the threshold th1 (difference = amplitude I−threshold th1), the greater the amount of retardation of the phase β of the drive current i, thereby demagnetizing the magnetic field from the winding 22a. Increase the degree of reduction. The threshold th1 may be the same value as the fixed value, or may be a value lower than the fixed value.

  Next, the operation state of the electric motor 12 where the magnitude of the drive current i is equal to or greater than the threshold th1 will be described. FIG. 6 is a graph showing the relationship between the output torque T of the electric motor 12 and the rotational speed NE. When the command torque value T1 becomes higher than a predetermined value, the magnitude of the drive current i becomes equal to or greater than the threshold th1. The case where the command torque value T1 is higher than a predetermined value is limited to a specific operation state such as when climbing or suddenly accelerating, so that the efficiency of the motor 12 decreases due to the retardation of the phase β of the motor 12. That can be suppressed.

  Thus, until the amplitude I of the drive current i becomes equal to or greater than the threshold th1, the phase β of the drive current i is set to the best phase βb so that the output torque T of the electric motor 12 becomes maximum, and the drive current i When the amplitude I is greater than or equal to the threshold th1, the phase β of the drive current i is retarded from the best phase βb. Therefore, when the drive current i is relatively small, the efficiency of the motor 12 can be improved and the drive current i is compared. When it is large, the demagnetizing field from the winding 22a can be reduced, and the occurrence of irreversible demagnetization of the permanent magnet 24 can be effectively suppressed. Further, as the drive current i increases, the amount of retardation for retarding the phase β of the drive current i is increased, so that the phase β of the drive current i is not unnecessarily retarded and the efficiency of the motor 12 is increased. can do. Further, since it is not necessary to increase the content of dysprosium or the like contained in the permanent magnet 24 or increase the thickness of the permanent magnet 24, it is possible to suppress the amount of expensive rare earth.

[Second Embodiment]
Next, a second embodiment will be described. Also in the second embodiment, only the parts different from the first embodiment will be described using the control device 10 shown in FIG. In the second embodiment, as indicated by a dotted line in FIG. 1, the control device 10 further includes a temperature sensor 54, and the control unit 30 includes a temperature calculation unit 56.

  The temperature sensor 54 detects information indicating the temperature of the permanent magnet 24 and detects, for example, the temperature of the lubricating oil (oil temperature) of the electric motor 12 and the temperature of the winding 22a. When the oil temperature or the temperature of the winding 22a is detected, the temperature calculation unit 56 estimates (calculates) the temperature of the permanent magnet 24 from the detection signal of the temperature sensor 54 using a known method. Further, the temperature sensor 54 may directly detect the temperature of the permanent magnet 24.

  In the first embodiment, when the amplitude I of the drive current i is greater than or equal to the threshold th1, the phase β of the drive current i is retarded. However, in the second embodiment, the amplitude of the drive current i is When I is equal to or greater than the threshold th1 and the temperature of the permanent magnet 24 is equal to or greater than the threshold (second threshold) th2, the phase β of the drive current i is retarded.

  FIG. 7 is a diagram showing magnetic curves 60, 62, 64 of the permanent magnet 24 according to the temperature of the permanent magnet 24. A magnetic curve 60 shows a magnetic curve when the permanent magnet 24 is at the first temperature, a magnetic curve 62 shows a magnetic curve when the permanent magnet 24 is at a second temperature higher than the first temperature, and a magnetic curve 64 is The magnetic curve when the permanent magnet 24 is 3rd temperature higher than 2nd temperature is shown.

  As shown in FIG. 7, the magnetic curve of the permanent magnet 24 varies depending on the temperature of the permanent magnet 24. That is, when the temperature of the permanent magnet 24 rises, the coercive force of the permanent magnet 24 decreases, and the position of the nick point q of the magnetic curve moves to the right (the magnetic field H becomes a large value). Therefore, the higher the temperature of the permanent magnet 24, the more irreversible demagnetization occurs with a lower drive current i (small amplitude I).

  Accordingly, when the temperature of the permanent magnet 24 is lower than the threshold th2, no matter how large the demagnetizing field from the winding 22a is, the permanent magnet 24 is designed so that irreversible demagnetization does not occur. Depending on the temperature, irreversible demagnetization may occur. Therefore, in the second embodiment, when the amplitude I of the drive current i is greater than or equal to the threshold th1 and the temperature of the permanent magnet 24 is greater than or equal to the threshold (second threshold) th2, the phase β of the drive current i is best. The angle is retarded from the phase βb.

  That is, the current command calculation unit 40 sets the set drive current i when the amplitude I of the set drive current i is greater than or equal to the threshold th1 and the temperature of the permanent magnet 24 calculated by the temperature calculation unit 56 is greater than or equal to the threshold th2. Is delayed from the best phase βb. Further, when the phase β is retarded, the output torque T of the electric motor 12 decreases, so the amplitude I of the drive current i is reset so that the output torque T becomes the command torque value T1 at the phase β after the retardation. . The amount of retardation to be retarded increases in accordance with the magnitude of the difference between the amplitude I of the drive current i and the threshold th1.

  As described above, the phase β of the drive current i is set so that the output torque T of the electric motor 12 is maximized until the amplitude I of the drive current i is equal to or greater than the threshold and the temperature of the permanent magnet 24 is equal to or greater than the threshold th2. When the best phase βb is set, the amplitude I of the drive current i is greater than or equal to the threshold th1, and the temperature of the permanent magnet 24 is greater than or equal to the threshold th2, the phase β of the drive current i is retarded from the best phase βb, so that When the coercive force of the magnet 24 is lower than a certain value (when the temperature is higher than the threshold th2), the demagnetizing field from the winding 22a received by the magnet can be reduced, and irreversible demagnetization of the permanent magnet 24 can be generated. It can be effectively suppressed. Note that the amount of retardation for retarding the phase β increases in accordance with the magnitude (amplitude I) of the drive current i.

[Third Embodiment]
Next, a third embodiment will be described. Also in the third embodiment, only the parts different from the second embodiment will be described using the control device 10 shown in FIG. Also in the third embodiment, the control device 10 includes a temperature sensor 54, and the control unit 30 includes a temperature calculation unit 56.

  In the second embodiment, the phase β of the drive current i is retarded when the amplitude I of the drive current i is greater than or equal to the threshold th1 and the temperature of the permanent magnet 24 is greater than or equal to the threshold th2. In the third embodiment, the value of the threshold th1 is changed according to the temperature of the permanent magnet 24, and the retardation amount of the phase β of the drive current i is changed.

  8A is a diagram showing the relationship between the output torque T of the electric motor 12 and the advance angle of the phase β of the drive current i, and FIG. 8B shows the advance angle of the phase β of the drive current i and the magnetic flux φ of the permanent magnet 24. It is a figure which shows the relationship with a demagnetizing factor according to the temperature of the permanent magnet. In FIG. 8A, the position of the best phase βb is represented by s.

  A line 66 shows the relationship between the advance angle of the drive current i when the temperature of the permanent magnet 24 is the temperature t1 and the demagnetization factor of the magnetic flux φ of the permanent magnet 24, and a line 68 shows the temperature of the permanent magnet 24 at the temperature t2. The relationship between the advance angle of the drive current i and the demagnetization factor of the magnetic flux φ of the permanent magnet 24 is shown. A line 70 represents the advance angle of the drive current i and the permanent magnet 24 when the temperature of the permanent magnet 24 is the temperature t3. The relationship with the demagnetization factor of magnetic flux (phi) is shown. It is assumed that there is a relationship of threshold value th2 <temperature t1 <temperature t2 <temperature t3.

  8A and 8B, when the phase β of the drive current i is the best phase βb (the phase β of the drive current i is the position s), the permanent magnet 24 is used at all temperatures t1, t2, and t3. If the irreversible demagnetization occurs and the phase β of the drive current i is at the position w, the drive current i having an amplitude I that does not cause irreversible demagnetization in the permanent magnet 24 at all temperatures t1, t2, and t3 is wound. It is assumed that it is supplied to the line 22a. If the direction in which the phase β is advanced is represented by a large value, the positions s, u, v, and w have a relationship of w <v <u <s.

  When the phase β of the drive current i is a phase β (position u) delayed from the best phase βb, no irreversible demagnetization occurs when the temperature of the permanent magnet 24 is the temperature t1, but the temperature of the permanent magnet 24 is the temperature t2. , T3 causes irreversible demagnetization. When the phase β of the drive current i is further delayed (when the phase β of the drive current i reaches the position v), no irreversible demagnetization occurs when the temperature of the permanent magnet 24 is the temperature t1 or t2, but the permanent magnet 24 When the temperature is at temperature t3, irreversible demagnetization occurs. When the phase β of the permanent magnet 24 reaches the position w, irreversible demagnetization does not occur even if the temperature of the permanent magnet 24 is the temperature t1, t2, or t3.

  As shown in FIG. 8B, the higher the temperature of the permanent magnet 24, the lower the coercive force of the permanent magnet 24 and the greater the demagnetization factor of irreversible demagnetization, so that the drive current i having the same amplitude I is applied to the winding 22a. Even in the case of supplying, the higher the temperature of the permanent magnet 24, the more irreversible demagnetization occurs unless the phase β of the drive current i is retarded. Further, as described with reference to FIG. 7, the higher the temperature of the permanent magnet 24, the lower the coercive force of the permanent magnet 24, and irreversible demagnetization occurs at a lower drive current i.

  Therefore, in the third embodiment, the value of the threshold th1 is decreased as the temperature of the permanent magnet 24 becomes higher than the threshold th2, and the temperature of the permanent magnet 24 is obtained even when the amplitude I of the drive current i is the same. Is higher than the threshold value th2, the phase β of the drive current i is retarded more. Further, the amount of retardation for retarding the phase β of the drive current i increases in accordance with the magnitude of the difference (amplitude I−threshold th1) between the amplitude I of the drive current i and the threshold th1, and this threshold th1 is The higher the temperature of the permanent magnet 24 is, the lower the temperature is. Therefore, even if the amplitude I of the driving current i is the same, the amount of retardation of the phase β of the driving current i increases as the temperature of the permanent magnet 24 increases.

  That is, the current command calculation unit 40 sets the set drive current i when the amplitude I of the set drive current i is greater than or equal to the threshold th1 and the temperature of the permanent magnet 24 calculated by the temperature calculation unit 56 is greater than or equal to the threshold th2. Is delayed from the best phase βb. Here, when the temperature of the permanent magnet 24 calculated by the temperature calculation unit 56 is equal to or higher than the threshold th2, the current command calculation unit 40 sets the threshold th1 that is smaller as the temperature of the permanent magnet 24 increases. Further, when the phase β is retarded, the output torque T of the electric motor 12 decreases, so the amplitude I of the drive current i is reset so that the output torque T becomes the command torque value T1 at the phase β after the retardation. . The retardation amount that retards the phase β of the drive current i from the best phase βb increases in accordance with the difference between the amplitude I of the drive current i and the threshold th1.

  Note that the value of the threshold th1 may be continuously changed according to the temperature of the permanent magnet 24, or may be changed stepwise according to the temperature of the permanent magnet 24.

  FIG. 9 is a diagram showing the relationship between the temperature of the permanent magnet 24 and the phase β set according to the magnitude of the drive current i. A dotted line 72 is a curve showing the best phase βb corresponding to the magnitude of the drive current i, and is drawn such that the position of the best phase βb is higher as the drive current i is larger. As shown in FIG. 9, the best phase βb varies depending on the magnitude of the drive current i. The line 74 represents the phase β of the drive current i set by the control unit 30 when the temperature of the permanent magnet 24 is the temperature t1, and the line 76 is set by the control unit 30 when the temperature of the permanent magnet 24 is the temperature t2. The phase β of the drive current i that is set is represented, and a line 78 represents the phase β of the drive current i that is set by the control unit 30 when the temperature of the permanent magnet 24 is the temperature t3.

  In any case of the temperatures t1, t2, and t3 of the permanent magnet 24, the phase β of the drive current i is set to the best phase βb until the magnitude of the drive current i is equal to or greater than the threshold th1, and is equal to or greater than the threshold th1. Then, the phase β is set so as to be retarded from the best phase βb. Since the threshold value th1 decreases as the temperature of the permanent magnet 24 increases, as shown in FIG. 9, when the temperature of the permanent magnet 24 is the temperature t3, as compared with the case of the temperatures t1 and t2. The retardation of the phase β is started from the time when the driving current i is small. Further, when the temperature of the permanent magnet 24 is the temperature t2, the retardation of the phase β is started from the time when the driving current i is smaller than that at the temperature t1.

As shown in FIG. 9, when the command torque value T1 is a predetermined value and the temperature of the permanent magnet 24 is the temperature t3, the phase β of the drive current i is the phase β ₃ and the amplitude of the drive current i ( The size is set by the control unit 30 so that I becomes the amplitude I ₃ . Further, when the temperature of the permanent magnet 24 is the temperature t2, the controller 30 sets the phase β of the drive current i to the phase β ₂ and the amplitude I of the drive current i to the amplitude I ₂ . When the temperature of the permanent magnet 24 is the temperature t1, the control unit 30 sets the phase β of the drive current i to be the phase β ₁ and the amplitude I of the drive current i to be the amplitude I ₁ .

When the direction in which the phase β is advanced is represented by a large value, the best phase βb, the phase β ₁ , the phase β ₂ , and the phase β ₃ have a relationship of β ₃ <β ₂ <β ₁ <βb. That is, as the temperature of the permanent magnet 24 becomes higher, the retard amount to be retarded is increased. Further, the amplitudes I ₁ , I ₂ , and I ₃ satisfy the relational expression of threshold value th1 <I ₁ <I ₂ <I ₃ . That is, as the temperature of the permanent magnet 24 becomes higher, the retard amount to be retarded becomes larger and the output torque T becomes smaller. Therefore, by increasing the amplitude I of the drive current i accordingly, the output torque of the electric motor 12 is increased. T is set to the command torque value T1.

  As described above, when the temperature of the permanent magnet 24 is equal to or higher than the threshold th2, the value of the threshold th1 is decreased as the temperature of the permanent magnet 24 is increased. Therefore, the coercive force is decreased as the temperature of the permanent magnet 24 is increased. However, the occurrence of irreversible demagnetization of the permanent magnet 24 can be effectively suppressed, and the efficiency of the electric motor 12 can be increased without unnecessarily retarding the phase β of the drive current i. When the temperature of the permanent magnet 24 is equal to or higher than the threshold th2, the phase β of the drive current i is retarded from the best phase βb as the temperature of the permanent magnet 24 increases, so that the temperature of the permanent magnet 24 increases. Even if the coercive force is reduced, the demagnetizing field from the winding 22a can be greatly reduced to effectively suppress the occurrence of irreversible demagnetization, and the phase β of the drive current i can be retarded unnecessarily. In addition, the efficiency of the electric motor 12 can be increased.

  Next, operation | movement of the control apparatus 10 of 3rd Embodiment is demonstrated according to the flowchart of FIG. In principle, the control unit 30 controls the inverter circuit 32 so that the phase β of the drive current i becomes the best phase βb.

  In step S1, the temperature calculation unit 56 calculates the temperature of the permanent magnet 24 based on the detection signal detected by the temperature sensor 54. In step S2, the current command calculation unit 40 calculates the permanent magnet 24 calculated in step S1. A threshold th1 corresponding to the temperature is set. As the calculated temperature of the permanent magnet 24 is higher, a threshold value th1 that is smaller is set.

  In step S3, the current command calculation unit 40 determines whether or not the amplitude I of the drive current i is greater than or equal to the threshold th1, and if it is determined in step S3 that the amplitude I is greater than or equal to the threshold th1, the process proceeds to step S4. It is determined whether or not the temperature of the permanent magnet 24 calculated in step S1 is equal to or higher than a threshold th2.

  If it is determined in step S4 that the temperature of the permanent magnet 24 is equal to or higher than the threshold th2, the process proceeds to step S5, where the current command calculation unit 40 retards the phase β of the drive current i from the best phase βb. This retardation amount increases in accordance with the difference between the amplitude I of the drive current i and the threshold value th1. Further, the current command calculation unit 40 resets the amplitude I of the drive current i so that the output torque T of the electric motor 12 becomes the command torque value T1 in the phase β after being retarded.

  On the other hand, if it is determined in step S3 that the amplitude I of the drive current i is not equal to or greater than the threshold th1, or if it is determined in step S4 that the temperature of the permanent magnet 24 is not equal to or greater than the threshold th2, the process proceeds to step S6. The current command calculation unit 40 sets the phase β of the drive current i to the best phase βb. That is, the amplitude I and the phase β of the drive current i are set so that the output torque T of the electric motor 12 becomes the maximum with the minimum drive current i (the amplitude I is minimum).

  In the first to third embodiments, when the magnitude of the drive current i is equal to or less than the threshold th1 (normal phase control), the phase β of the drive current i so that the output torque T of the electric motor 12 is maximized. Although it is controlled, it may not be the maximum. That is, the phase β of the drive current i may be controlled so that the output torque T of the electric motor 12 is large (the output torque T of the electric motor 12 is greater than a certain value). However, the phase β at this time is preferably a phase delayed from the best phase βb.

  As described above, the present invention has been described using the preferred embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the description of the scope of claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus 12 ... Electric motor 12a ... Position detector 14 ... Drive control apparatus 16 ... Battery 20 ... Rotor 22 ... Stator 22a ... Winding 24 ... Permanent magnet 26 ... Salient pole part 28 ... Rotating shaft 30 ... Control part 32 ... Inverter Circuit 34u, 34v ... Current detector 40 ... Current command calculation unit 42 ... Current conversion unit 44, 46 ... Subtractor 48 ... Voltage command calculation unit 50 ... Voltage conversion unit 52 ... Inverter control unit 54 ... Temperature sensor 56 ... Temperature calculation unit

Claims (5)

A rotor with permanent magnets;
A stator wound with windings;
A drive control device for supplying a drive current of a predetermined phase to the winding;
In an electric motor control device comprising:
The drive control device sets the phase of the drive current to a maximum torque phase at which the torque of the electric motor with respect to a predetermined drive current is maximized when the drive current is smaller than a first threshold, and the drive current is When the threshold value is greater than or equal to one threshold, the current value of the drive current is set to the current required for the maximum torque phase so that the phase of the drive current is retarded from the maximum torque phase and the required torque is output. A control device for an electric motor, wherein the current value is set to be larger than the current value . The motor control device according to claim 1,
When the drive current is equal to or greater than the first threshold, the drive control device increases the amount of retardation by which the phase of the drive current is retarded from the maximum torque phase as the drive current increases. An electric motor control device. In the control apparatus for the electric motor according to claim 1 or 2,
The drive control device retards the phase of the drive current from the maximum torque phase when the drive current is greater than or equal to the first threshold and the temperature of the permanent magnet is greater than or equal to a second threshold. The motor control device. In the motor control device according to claim 3,
When the temperature of the permanent magnet is equal to or higher than the second threshold value, the drive control device reduces the first threshold value as the temperature of the permanent magnet is higher. In the motor control apparatus according to claim 4,
When the temperature of the permanent magnet is equal to or higher than the second threshold, the drive control device increases the amount of retardation by which the phase of the drive current is retarded from the maximum torque phase as the temperature of the permanent magnet is higher. An electric motor control device.

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