Electric motor control device

Abstract

To provide a control device capable of suppressing demagnetization of a permanent magnet while facilitating warming-up of a permanent magnet type electric motor.SOLUTION: An electric motor control device that controls a permanent magnet type electric motor for driving vehicles, comprises: a rotor temperature acquisition device that acquires a rotor temperature of the permanent magnet type electric motor; an inverter; and a controller that calculates a current command value to the permanent magnet type electric motor to control the inverter on the basis of the current command value. The controller sets a q-axis current command value corresponding to a torque component to zero, varies a d-axis current command value corresponding to an excitation component alternately to a positive side where a magnetic flux of a permanent magnet used in the permanent magnet type electric motor is strengthened and a negative side where the magnetic flux is weakened in a predetermined cycle, calculates a warming-up current command value that the negative side current command value is determined on the basis of a temperature coefficient of magnetic coercive force of the permanent magnet and of a rotor temperature, and executes warm-up control of controlling the inverter on the basis of the warming-up current command value in a case where the rotor temperature is lower than a threshold for determining necessity of warming-up.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to an electric motor control device for controlling a permanent magnet type electric motor for vehicle drive.

Background Art

[0002] Regarding electric vehicles, there is a problem that at low temperatures, the efficiency of the electric motor decreases due to an increase in friction such as the cooling oil of the electric motor, the reduction gear, and the bearings, leading to a decrease in power consumption performance. As a countermeasure, when the vehicle is stopped, the current of the component (q-axis component) that contributes to torque is set to zero, and the current of the component (d-axis component) that does not contribute to torque is energized, so that heat generated by the loss caused by energization is used to warm up the electric motor. It is known. However, in order to increase the warm-up speed, it is necessary to increase the current value. Therefore, in the case of a permanent magnet type electric motor, there is a problem that the permanent magnet is demagnetized by the magnetic flux in the weakening direction generated by flowing the current.

[0003] Patent Document 1 discloses control for promoting warm-up while preventing demagnetization. Specifically, the d-axis current with a current advance angle of 90° and the d-axis current with a current advance angle of 270° are alternately flowed at a predetermined cycle. Then, the current value of the d-axis current with a current advance angle of 270° that generates a magnetic flux in the strengthening direction is made larger than the current value of the d-axis current with a current advance angle of 90° that generates a magnetic flux in the weakening direction, or the energization time of the d-axis current with a current advance angle of 270° is made longer than the energization time of the d-axis current with a current advance angle of 90°.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, whether to demagnetize or not and the degree of demagnetization are determined only by the magnitude of the magnetic flux in the weakening direction (d-axis magnetic flux) generated by the d-axis current at a current advance angle of 90°, and have no correlation with the current value or the energization time at a current advance angle of 270°. Therefore, in the control described in the above document, there is a possibility that the effect of preventing demagnetization cannot be obtained.

[0006] Therefore, in view of the above problems, an object of the present invention is to provide a control device that can promote the warm-up of a permanent magnet motor while suppressing the demagnetization of the permanent magnet.

Means for Solving the Problems

[0007] According to an aspect of the present invention, there is provided an electric motor control device for controlling a permanent magnet motor for vehicle drive. The device includes a rotor temperature acquisition device that directly or indirectly acquires the rotor temperature of the permanent magnet motor, an inverter that converts and supplies electric power to the permanent magnet motor, and a control unit that calculates a current command value for the permanent magnet motor and controls the inverter based on the current command value. The control unit has a current command value on the q-axis, which is the axis corresponding to the torque component of the permanent magnet motor, being zero, and the current command value on the d-axis, which is the axis corresponding to the excitation component of the permanent magnet motor, changing alternately between the positive side that strengthens the magnetic flux of the permanent magnet used in the permanent magnet motor and the negative side that weakens it at a predetermined cycle, and the current command value on the negative side calculating a warm-up current command value determined based on the temperature coefficient of the coercive force of the permanent magnet and the rotor temperature. Then, when the rotor temperature is lower than a threshold value for determining the necessity of warm-up, the control unit executes warm-up control for controlling the inverter based on the warm-up current command value. The current command value on the d-axis of the warm-up current command value is a rectangular wave, and the current command value on the positive side is a constant value or a variable value according to the temperature characteristics of the coercive force of the permanent magnet, and the current command value on the negative side becomes smaller as the rotor temperature rises.

Effects of the Invention

[0008] According to the above aspect, it is possible to provide a control device that can promote the warm-up of a permanent magnet motor while suppressing the demagnetization of the permanent magnet.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of a vehicle system equipped with an electric motor control device according to the present embodiment. Hereinafter, an example in which the electric motor control device of this example is applied to an electric vehicle will be described. However, the electric motor control device of this example can also be applied to vehicles other than electric vehicles such as hybrid electric vehicles (HEVs).

[0011] As shown in FIG. 1, the vehicle including the electric motor control device of this example includes a battery 1, an inverter 2, a drive motor 3, a reduction gear 4, a drive shaft 5, drive wheels 6, 7, a voltage sensor 8, a current sensor 9, a rotation sensor 10, a temperature sensor 11, a charger 12, a charging port 13, a motor controller 20, and a battery controller 30.

[0012] The battery 1 is a drive source of the vehicle and is configured by connecting a plurality of secondary batteries in series or in parallel. The inverter 2 has a power conversion circuit in which a plurality of switching elements such as IGBTs and MOSFETs are connected for each phase. The inverter 2 switches on and off the switching elements according to a drive signal from the motor controller 20 as a control unit, converts the direct current output from the battery 1 into an alternating current, outputs it to the drive motor 3, and drives the drive motor 3. Further, the inverter 2 reversely converts the alternating current power output by the regeneration of the drive motor 3 and outputs it to the battery 1. The inverter 2 has a connection circuit in which two switching elements per phase are connected in a bridge shape with three phases.

[0013] The drive motor 3 (hereinafter referred to as the motor 3) is a drive source of the vehicle and transmits a driving force to the drive wheels 6 and 7 via the reduction gear 4 and the drive shaft 5 during power running. Further, the motor 3 is rotated while being carried around by the drive wheels 6 and 7 during deceleration of the vehicle or the like, and generates a regenerative driving force to recover the kinetic energy of the vehicle as electrical energy. As a result, the battery 1 is discharged by the power running of the motor 3 and charged by the regeneration of the motor 3. A permanent magnet synchronous motor is used for the motor 3.

[0014] In addition, the vehicle of this example includes a cooling mechanism that cools the motor 3 using a refrigerant. The cooling mechanism is configured such that the refrigerant circulates through the motor 3 and the battery 1, and during warm-up control described later, the refrigerant whose temperature has risen by exchanging heat with the motor 3 warms the battery 1.

[0015] The voltage sensor 8 is a sensor that detects the voltage of the battery 1 and is connected between the battery 1 and the inverter 2. The detected value of the voltage sensor 8 is output to the motor controller 20 and the battery controller 30. The current sensor 9 is a sensor for detecting the current of the drive motor and is connected between the inverter 2 and the drive motor 3. The detected current of the current sensor 9 is output to the motor controller 20. The rotation sensor 10 is a sensor for detecting the rotational speed of the drive motor 3 and is composed of a resolver or the like. The detected value of the rotation sensor 10 is output to the motor controller 20.

[0016] The temperature sensor 11 is a sensor for detecting the stator temperature of the motor 3. The temperature sensor 11 is provided on the motor 3.

[0017] The charger 12 converts the power supplied from an external charging device via a charging plug connected to the charging port 13 into power suitable for charging the battery 1 and supplies it to the battery 1 to charge the battery 1. The output side of the charger 12 is electrically connected to the wiring connecting the battery 1 and the inverter 2. Therefore, the power output from the charger 12 can be supplied not only to the battery 1 but also to the inverter 2.

[0018] The charging port 13 is provided on the surface of the vehicle and has a connection port for connecting the charging plug. The charging plug is provided at the tip of a charging cable connected to an external charging device. When the charging plug is inserted into the charging port 13, power can be supplied from the external charging device to the battery 1 or the inverter 2.

[0019] The motor controller 20 receives the vehicle speed (V), the accelerator opening (APO), and the rotor phase (θ of the motor 3 re) Based on the current of the motor 3, the voltage of the battery 1, etc., a PWM control signal for operating the inverter 2 is created, and the PWM control signal is output to a driver circuit (not shown) that operates the inverter 2. Then, based on the PWM control signal, the driver circuit generates a drive signal for the switching element of the inverter 2 and outputs it to the inverter 2. Thereby, the motor controller 20 drives the motor 3 by operating the inverter 2.

[0020] The motor controller 20 switches between a normal motor control mode (normal control mode) for controlling the motor 3 to drive in response to a torque request due to a user's accelerator operation or the like, and a warm-up control mode for warming up the motor in a low-temperature state, and controls the inverter 2 and the motor 3. The motor controller 20 has a motor torque control unit 21 and a current control unit 22.

[0021] Based on a signal of vehicle information indicating vehicle variables input to the motor controller 20, the motor torque control unit 21 calculates a torque command value (T m1 * ) for causing the drive motor 3 to output a required torque due to a user's operation or a required torque on the system.

[0022] A torque map (not shown) indicating the correlation between the motor speed and the torque command value, which is set for each accelerator opening, is stored in advance in the motor torque control unit 21. The torque map is set with a torque command value for efficiently outputting torque from the motor 3 with respect to the accelerator opening and the motor speed.

[0023] The motor speed is calculated based on the detection value of the rotation sensor 10. The accelerator opening is detected by an accelerator opening sensor (not shown). Then, the motor torque control unit 21 refers to the torque map and calculates a torque command value (T m1 * ) corresponding to the input accelerator opening (APO) and the motor speed.

[0024] Further, the motor torque control unit 21 restricts the torque command value (T m1 * ) to calculate the torque command value (T m2 * ) and outputs it to the current control unit 22. When the temperature of the motor 3 increases, for example, when the stator temperature increases, the insulation performance of the coil 34 may deteriorate, and when the rotor temperature increases, there is a risk of demagnetization due to the heat of the permanent magnet. Therefore, when the temperature of the motor 3 is high, the motor torque control unit 21 restricts the torque command value (T m1 * ) to keep the torque command value below the limit value.

[0025] The current control unit 22 is a control unit that calculates a command value for the current flowing through the motor 3 based on the torque command value (T m2 * ) and controls the inverter 2 based on the command value. The current control unit 22 calculates a current command value for warm-up, which will be described later, during the warm-up mode.

[0026] The battery controller 30 manages the state of the battery 1 by calculating the state of charge (SOC) of the battery 1 based on the detected voltage of the voltage sensor 8. The battery controller 30 also controls the charger 12 to control the charging of the battery 1 by an external charging device.

[0027] When the battery controller 30 detects that the charging plug is inserted into the charging port 13, it calculates a voltage or current suitable for charging the battery 1 according to the state of the battery 1. Then, when power is supplied from an external charging device to the charger 12, the battery controller 30 controls the charger 12 to convert the input power to the charger 12 into the charging power of the battery 1 and supply power to the battery 1. When the SOC of the battery 1 reaches the target SOC, the battery controller 30 controls the charger 12 to stop the power supply from the charger 12 to the battery 1, and outputs a stop signal indicating the stop of charging to the external charging device via the charging cable.

[0028] Also, when a charging plug is inserted into the charging port 13, the battery controller 30 outputs a signal indicating that the power of an external charging device can be used to the motor controller 20. By receiving this signal, the motor controller 20 recognizes that it is possible to pass a current through the motor 3 using the power of the external charging device.

[0029] Note that based on the torque command value (T m1 * ) output from the motor torque control unit 21, a vibration damping control unit that calculates a torque command value (T m3 * ) for vibration damping the drive motor 3 to suppress the torsional vibration of the drive shaft 5 may be provided. In this case, the torque command value (T m3 * ) for vibration damping the drive motor 3 is input to the current control unit 22.

[0030] Next, the necessity of warm-up when driving the vehicle and the warm-up control by the motor controller 20 will be described.

[0031] First, the necessity of warm-up will be described. At low temperatures, the friction of the motor 3, the cooling oil of the speed reducer 4, and the bearings of each part increases, and the efficiency of the motor 3 decreases, so the power consumption performance of the vehicle deteriorates. Therefore, warm-up is necessary. As a warm-up method, it is known to energize a current (d-axis current) of a component that does not contribute to torque when the vehicle is stopped. In order to increase the warm-up speed by this method, the current value may be increased. However, in the permanent magnet type motor 3, there is a problem that the magnet is demagnetized by the weakening magnetic flux caused by the negative d-axis current described later. That is, simply increasing the d-axis current will demagnetize the permanent magnet. On the other hand, if the d-axis current is decreased to suppress demagnetization, it will take a long time for warm-up.

[0032] In order to solve the above problems, in this example, the rotor warm-up control is performed as described below. The motor controller 20 manages the temperature of the rotor of the motor 3 while the vehicle is stopped. The motor controller 20 uses the temperature sensor 11 to detect the stator temperature at a predetermined cycle, and calculates the rotor temperature based on this. Alternatively, when the vehicle is stopped, the motor controller 20 detects the stator temperature with the temperature sensor 11, calculates the current stator temperature from the elapsed time since the vehicle stopped and the outside air temperature, and obtains the rotor temperature by calculating the rotor temperature based on this.

[0033] Figure 2 is an example of a cross-sectional view of the motor 3 used in this example. Specifically, it shows a part (one pole portion) of the cross-section of an 8-pole distributed winding motor. As shown in the figure, the stator (stator core) 32 has six slots 32A per pole, and a coil 34 is arranged in each slot 32A. The rotor (rotor core) 31 has one permanent magnet (hereinafter also simply referred to as "magnet") 33 per pole. Note that the number of slots 32A and magnets 33 and the arrangement of the magnets 33 are not limited to this.

[0034] In the warm-up control of this example, the current command value of the axis (q-axis) corresponding to the torque component of the motor 3 is set to zero. For the axis (d-axis) corresponding to the excitation component, the current command value is alternately switched between the magnetization direction with respect to the magnetic flux direction of the magnet 33, that is, the current advance angle β = 270° (hereinafter also referred to as the positive side), and the demagnetization direction, that is, the current advance angle β = 90° (hereinafter also referred to as the negative side) at a predetermined cycle. As a result, an exciting current flows alternately in the positive and negative directions through the stator 32 of the motor 3, so that magnetic flux is generated, and eddy currents flow through the rotor 31, causing the rotor to generate heat. Also, since the current flows alternately in the positive and negative directions, hysteresis loss occurs, and eddy currents continuously flow through the rotor 31. As a result, the rotor 31 is warmed up without generating torque.

[0035] As shown in Figure 2, it is known that when the current command value is in the magnetization direction, magnetic flux in the same direction as the magnetic flux of the magnet 33 is generated, and when it is in the demagnetization direction, magnetic flux in the opposite direction to the magnetic flux of the magnet 33 is generated, demagnetizing the magnet 33.

[0036] Therefore, in this example, the d-axis current command value in the weakening direction is set based on the temperature coefficient of the coercive force of the magnet 33 used in the motor 3 and the detected temperature. Thereby, the d-axis current command value corresponding to the rotor temperature can be set. For example, as the warm-up progresses, the d-axis current command value can be decreased or stopped, and the warm-up can be efficiently performed while suppressing demagnetization.

[0037] Furthermore, while decreasing the d-axis current command value as the warm-up progresses, the energization time and the d-axis current command value in the strengthening direction are increased. Since the d-axis current in the strengthening direction has no influence on demagnetization, by increasing the d-axis current command value in the strengthening direction, the generated loss can be increased and the warm-up efficiency can be further improved.

[0038] Also, it is known that the coercive force of the magnet 33 increases as the rotor temperature decreases, that is, it is difficult to demagnetize. Therefore, for example, by controlling the d-axis current based on the temperature coefficient of the coercive force such that a larger d-axis current command value is set as the rotor temperature is lower and the d-axis current command value is smaller as the rotor temperature rises, the motor 3 can be warmed up without causing irreversible demagnetization.

[0039] Next, the control of the inverter 2 by the motor controller 20 will be described with reference to FIGS. 3 and 4. FIG. 3 is a flowchart showing a control flow for determining the necessity of warm-up control executed by the motor controller 20. FIG. 4 is a flowchart showing a control flow of warm-up control executed by the motor controller 20. Hereinafter, the description will be made according to the steps of each flowchart.

[0040] First, the control flow of FIG. 3 will be described.

[0041] In step S10, it is determined whether or not charging is in progress. If charging is in progress, the process of step S11 is executed, and if charging is not in progress, the process of step S16 is executed. In step S16, the remaining amount C0 of the battery 1 is compared with a preset threshold value C TDetermine whether it is more, and if it is more, execute the process of step S13. On the other hand, for the threshold value C T In the following cases, end this control flow. For the threshold value C T is a threshold value for determining whether warm-up is possible even without external power supply, and is determined according to the capacity of the battery 1 to be used, the power required for warm-up of the motor 3 to be used, etc. Note that in step S10, in addition to the determination of whether or not charging is in progress as described above, it may be determined whether or not to start charging from now on. In this case, even if it is not charging, if charging is to be started from now on, the process of step S11 is executed. However, the processes after step S11 are executed after starting charging. Also, when it is not charging and charging is not to be started from now on, the process of step S16 is executed. Whether or not to start charging from now on is determined based on, for example, the charging history recorded in the battery controller 30 or the like. For example, in light of the history of the charging start time so far, if it is estimated that charging will start several minutes from the current time, it is determined that charging will start from now on.

[0042] In step S11, based on the detection signal of a temperature sensor (not shown) that detects the temperature of the battery 1, the current battery temperature T B0 is determined to be lower than a preset threshold value T BT or not. If it is lower, the process of step S12 is executed, and if not, this control flow is ended. The determination in step S11 is for protecting the battery 1. When the motor 3 is warmed up, the battery 1 is also warmed up via the refrigerant. Therefore, if warm-up control of the motor 3 is performed in a state where the battery temperature is close to the allowable temperature, the battery temperature may exceed the allowable temperature. Therefore, in step S11, it is determined whether or not the battery temperature exceeds the allowable temperature by performing warm-up control of the motor 3. Therefore, the threshold value T BT is the battery temperature at which the temperature rise due to the warm-up control of the motor 3 does not exceed the allowable temperature, and is a value determined by the heat capacity of the battery 1 to be used, etc.

[0043] In step S12, based on the detection signal of a temperature sensor (not shown) that detects the temperature of the refrigerant, the current refrigerant temperature TW0 is lower than a preset threshold value T WT If it is lower, the process of step S13 is executed; otherwise, this control flow ends.

[0044] In step S13, the current stator temperature T S0 is lower than a preset threshold value T ST If it is lower, the process of step S14 is executed; otherwise, this control flow ends. The determination in step S13 is for the protection of the stator 32. An insulating material for insulating the coil 34 is used for the stator 32, but the insulating material has an upper limit temperature at which the insulating performance can be maintained. Therefore, if the warm-up control of the motor 3 is performed when the temperature of the stator 32 is close to the upper limit temperature, there is a risk of exceeding the upper limit temperature. Therefore, it is determined in step S13 whether the stator temperature exceeds the upper limit temperature by performing the warm-up control of the motor 3. Therefore, the threshold value T ST is the stator temperature at which the temperature rise due to the warm-up control of the motor 3 does not exceed the upper limit temperature, and is a value determined by the insulating material used.

[0045] Note that all or part of the determinations in steps S10 to S13 above may be omitted.

[0046] In step S14, the current rotor temperature T detected by the temperature sensor 11 R0 is lower than a preset threshold value T RT If it is lower, the process of step S15 is executed; otherwise, this control flow ends. The threshold value T RT is a determination threshold value for starting the warm-up control. The motor controller 20 determines that the rotor 31 is in a low-temperature state and requires warm-up when the current rotor temperature T R0 is lower than the threshold value T RT On the other hand, when the current rotor temperature T R0 is higher than the threshold value T RTIf it is higher, it is determined that the rotor 31 is not in a low-temperature state and does not require warm-up. Note that the rotor temperature may be estimated from the temperature of the stator 32 detected by the temperature sensor 11 or from the refrigerant temperature.

[0047] In step S15, warm-up control described later is executed.

[0048] Next, the control flow of FIG. 4 will be described. This control flow is executed when it is determined to execute warm-up control in the control flow of FIG. 3.

[0049] In step S20, the temperature difference ΔT between the target temperature (threshold value T RT ) and the current rotor temperature T R0 is calculated.

[0050] In step S21, the d-axis current command value I d is set by the method described below. First, the d-axis current command value I d with a current advance angle β of 270° is set. Here, it is set to the maximum allowable current I lim of the inverter SW element as a constant value. The d-axis current command value I d with a current advance angle β of 90° is set from the temperature coefficient of the preset coercive force H cj of the magnet, the allowable current I dem that does not demagnetize when the rotor temperature is the threshold value TRT, and ΔT. The coercive force H cj becomes larger as the magnet temperature is lower. Therefore, as shown in FIG. 5, the coercive force H cj for each magnet temperature is plotted, and the temperature coefficient is set by linear approximation (solid line L1 in the figure) or quadratic function approximation (dashed-dotted line L2 in the figure).

[0051] In the case of linear approximation, the coercive force H cj is expressed by the following formula (1) using the temperature coefficient a. H cj =aΔT + 1 ···(1) When this temperature coefficient a is used, the d-axis current command value Id increases linearly as the rotor temperature increases as shown by the solid line L3 in FIG. 6. Expressing this by a formula gives the following formula (2). Id =I dem {1+a(T RT -T R0 )} ···(2) On the other hand, in the case of quadratic function approximation, the coercive force H cj is expressed by the following equation (3) using temperature coefficients b and c. H cj =bΔT 2 +cΔT+1 (3) When these temperature coefficients b and c are used, the d-axis current command value Id increases in a quadratic curve as the rotor temperature increases, as shown by the dashed line L4 in Figure 6. This can be expressed as the following equation (4). I d =I dem {1+b(T RT -T R0 ) 2 +c(T RT -T R0 )} ···(4) As shown above, the d-axis current command value I d After setting, in step S22, the current advance angle β = 90° current conduction time t 90 and current advance angle β = 270° current conduction time t 270 Here, it is set to a constant value set in advance.

[0052] In step S23, the current is applied for the time period set in step S22.

[0053] In step S24, the current rotor temperature T R0 is the threshold T RT If it is lower, the process of step S25 is executed. On the other hand, if the current rotor temperature T R0 is the threshold T RT In the above cases, it is assumed that the warm-up has been completed and this control flow ends.

[0054] In step S25, the current stator temperature T S0 is the threshold T ST If it is lower, the process returns to step S20 to continue warming up. S0 is the threshold T STIn the above case, this control flow is terminated for stator protection.

[0055] FIG. 7 is a diagram showing the d-axis current when the above-described warm-up control is performed. The solid line in the figure is the d-axis current with a current advance angle β = 270° (positive side), the broken line is the d-axis current command value with a current advance angle β = 90° (negative side), and the one-dot chain line indicates the rotor temperature.

[0056] As shown in FIG. 7, the positive d-axis current is constant, but the absolute value of the negative d-axis current decreases as the rotor temperature rises. That is, the negative d-axis current that causes demagnetization gradually decreases. Thereby, demagnetization due to the warm-up of the motor 3 can be suppressed.

[0057] Next, a modified example of the warm-up control will be described with reference to FIGS. 8 to 10. Note that each of the modified examples described below also belongs to the scope of the present invention in the same manner as the above-described embodiment.

[0058] [First Modified Example] In this modified example, the setting of the energization time t 270 in step S22 of FIG. 4 is different from that in the above embodiment.

[0059] FIG. 8 is a diagram showing the d-axis current when the warm-up control according to the first modified example is performed. As shown, in this modified example, as the negative d-axis current decreases, the negative energization time t 270 is lengthened. This is to compensate for the decrease in copper loss due to the decrease in the negative d-axis current by extending the energization time t 270 . When using the motor 3 in which the ratio of the copper loss in the total loss is larger than the iron loss, the warm-up can be efficiently performed by suppressing the decrease in the copper loss as in this modified example.

[0060] However, since the period in which the positive and negative of the d-axis current are reversed becomes longer, the iron loss decreases. Therefore, it is not suitable when using the motor 3 in which the ratio of the iron loss in the total loss is larger than the copper loss. In this case, the period in which the positive and negative are reversed remains constant, that is, the positive energization time t 270 and the negative energization time t 90Keep the total constant and vary the ratio of the energization time t 270 and t 90 to suppress the reduction of iron loss.

[0061] [Second Modification Example] In this modification example, the setting of the positive d-axis current command value in step S21 of FIG. 4 is different from that in the above embodiment.

[0062] FIG. 9 is a diagram showing the d-axis current when the warm-up control according to the second modification example is performed. As shown in the figure, in this modification example, the positive d-axis current command value is increased by the amount by which the negative d-axis current command value is decreased. As a result, without causing a reduction in iron loss, it is possible to compensate for the reduction in copper loss due to the decrease in the negative d-axis current, so that the motor 3 can be warmed up in a shorter time. However, when the positive d-axis current command value at the start of the warm-up control is set to the maximum allowable current I lim of the inverter SW element, a current exceeding the maximum allowable current I lim will flow, so it is necessary to monitor the temperature of the inverter 2 and end the warm-up control when the allowable upper limit temperature is reached.

[0063] [Third Modification Example] In this modification example, the setting of the positive d-axis current command value in step S21 of FIG. 4 is different from that in the above embodiment.

[0064] FIG. 10 is a diagram showing the d-axis current when the warm-up control according to the third modification example is performed. As shown in the figure, in this modification example, as the rotor temperature rises, the positive and negative d-axis current command values are decreased. As a result, compared with the above embodiment and each modification example, the time required to warm up the motor 3 becomes longer, but in a configuration in which the battery 1 is heated using the refrigerant whose temperature has risen due to the warm-up of the motor 3, it is effective for warming up the battery 1. This effect will be described below.

[0065] Since the battery 1 has a larger heat capacity than the motor 3, if the motor 3 is efficiently warmed up, a situation may occur where the battery 1 has not warmed up sufficiently when the warm-up control of the motor 3 ends. To avoid this, it is desirable to continue the warm-up control of the motor 3 until the battery 1 warms up. However, even if the warm-up control is continued with the refrigerant at a low temperature, the temperature of the battery 1 does not rise.

[0066] Therefore, at the start of the warm-up control, a relatively large d-axis current is passed to raise the temperature of the refrigerant, and then the d-axis current is gradually decreased to bring the temperature of the refrigerant to a temperature suitable for warming up the battery 1, and then the duration of the warm-up control is extended to raise the temperature of the battery 1.

[0067] As described above, according to the present embodiment, there is provided an electric motor control device that controls a permanent magnet type electric motor (motor 3) for vehicle drive. This electric motor control device includes a rotor temperature acquisition device (temperature sensor 11) that directly or indirectly acquires the rotor temperature of the permanent magnet type electric motor, an inverter 2 that converts and supplies electric power to the permanent magnet type electric motor, and a control unit (motor controller 20) that calculates a current command value for the permanent magnet type electric motor and controls the inverter 2 based on the current command value. The control unit has a current command value of the q-axis, which is the axis corresponding to the torque component of the permanent magnet type electric motor, being zero, and the current command value of the d-axis, which is the axis corresponding to the excitation component of the permanent magnet type electric motor, changing alternately between the positive side that strengthens the magnetic flux direction of the permanent magnet 33 used in the permanent magnet type electric motor and the negative side that weakens it at a predetermined cycle, and the current command value on the negative side calculates a warm-up current command value determined based on the temperature coefficient of the coercive force of the permanent magnet 33 and the rotor temperature. Then, when the rotor temperature is lower than a threshold value for determining the necessity of warm-up, the control unit executes warm-up control for controlling the inverter 2 based on the warm-up current command value. Thereby, while suppressing the demagnetization by the d-axis current on the negative side, the motor 3 can be efficiently warmed up.

[0068] According to this embodiment, the current command value on the d-axis is a rectangular wave, and the current command values on the positive and negative sides are constant values or variable values according to the temperature characteristics of the coercive force of the permanent magnet 33. Even if the d-axis current is not a rectangular wave but is in a form such as a so-called sine wave, warming up can be performed while suppressing demagnetization by setting it to a constant value or a variable value according to the temperature characteristics of the coercive force of the permanent magnet 33. However, by making it a rectangular wave, a current containing more high-frequency components can be passed through the motor 3, so the warm-up time can be made shorter.

[0069] In this embodiment (second modification), the predetermined period determined by the energization time on the positive side and the energization time on the negative side is constant or variable according to the current command value, and the side with the smaller current command value among the positive and negative sides has a longer energization time. Thereby, it is possible to compensate for the reduction in copper loss due to reducing the d-axis current on the negative side.

[0070] According to this embodiment, a stator temperature acquisition device (temperature sensor 11) for directly or indirectly acquiring the stator temperature of the permanent magnet motor is provided, and the control unit stops the warm-up control when the stator temperature exceeds a predetermined temperature. Thereby, the motor 3 can be warmed up while protecting the stator 32. Note that the stator temperature acquisition device may be the temperature sensor 11 that directly detects the stator temperature as described above, or the motor controller 20 that is arranged to detect the rotor temperature by the temperature sensor 11 and estimates the stator temperature based on the detected rotor temperature, or estimates it from the refrigerant temperature.

[0071] According to this embodiment, a refrigerant temperature acquisition device for directly or indirectly acquiring the temperature of the refrigerant used for cooling the permanent magnet motor is provided, and the control unit stops the warm-up control when the refrigerant temperature exceeds a predetermined temperature. Thereby, an excessive rise in the refrigerant temperature can be prevented. Note that the refrigerant temperature acquisition device may be a sensor that detects the temperature of the refrigerant, or the motor controller 20 that estimates it from the rotor temperature, the stator temperature, or the like.

[0072] According to this embodiment, the control unit executes warm-up control when the vehicle is stopped. This is because, when the vehicle is stopped, the q-axis current that does not contribute to the torque of the motor 3 can be set to zero.

[0073] Needless to say, the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the technical idea described in the claims.

Explanation of Reference Numerals

[0074] 1 Battery, 2 Inverter, 3 Drive Motor, 4 Reducer, 4 Drive Shaft, 8 Voltage Sensor, 9 Current Sensor, 10 Rotation Sensor, 11 Temperature Sensor, 12 Charger, 13 Charge Port, 20 Motor Controller, 21 Motor Torque Control Unit, 22 Current Control Unit, 30 Battery Controller, 31 Rotor, 32 Stator, 32A Slot, 33 Permanent Magnet, 34 Coil

Claims

1. In a motor control device for controlling a permanent magnet type motor for vehicle drive, a rotor temperature acquisition device for directly or indirectly acquiring the rotor temperature of the permanent magnet type motor; an inverter for converting and supplying electric power to the permanent magnet type motor; a control unit for calculating a current command value for the permanent magnet type motor and controlling the inverter based on the current command value; comprising: the control unit: the current command value of the q-axis, which is the axis corresponding to the torque component of the permanent magnet type motor, is zero, and the current command value of the d-axis, which is the axis corresponding to the excitation component of the permanent magnet type motor, changes alternately between the positive side for strengthening the magnetic flux of the permanent magnet used in the permanent magnet type motor and the negative side for weakening it at a predetermined period, and the current command value on the negative side is determined based on the temperature coefficient of the coercive force of the permanent magnet and the rotor temperature, calculates a warm-up current command value; when the rotor temperature is lower than a threshold value for determining the necessity of warm-up, executes warm-up control for controlling the inverter based on the warm-up current command value; regarding the warm-up current command value, the current command value of the d-axis is a rectangular wave, the current command value on the positive side is a constant value or a variable value according to the temperature characteristics of the coercive force of the permanent magnet, the current command value on the negative side becomes smaller as the rotor temperature rises. A motor control device characterized by this.

2. In the motor control device according to Claim 1, the predetermined period determined by the energization time on the positive side and the energization time on the negative side is constant or variable according to the current command value, and the one with the smaller current command value among the positive side and the negative side has a longer energization time. A motor control device.

3. In the motor control device according to Claim 1 or 2, it is provided with a stator temperature acquisition device for directly or indirectly acquiring the stator temperature of the permanent magnet type motor; The control unit is a motor control device that stops the warm-up control when the stator temperature exceeds a predetermined temperature.

4. In the motor control device according to any one of claims 1 to 3, it is provided with a refrigerant temperature acquisition device that directly or indirectly acquires the temperature of the refrigerant used for cooling the permanent magnet motor, and the control unit is a motor control device that stops the warm-up control when the temperature of the refrigerant exceeds a predetermined temperature.

5. In the motor control device according to any one of claims 1 to 4, the control unit is a motor control device that executes the warm-up control when the motor is stopped.

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