Electric-motor control device

Abstract

Disclosed is a motor control device for controlling a motor. The motor control device controls a motor 2 by driving an inverter 22 in accordance with a magnetic pole position of the motor 2 detected by a position detection circuit 24. The motor control device 3 includes a position estimation unit that estimates a magnetic pole position on the basis of a phase current detected by a current detection circuit and controls the inverter 22 in accordance with the magnetic pole position estimated by the position estimation unit when the magnetic pole position cannot be acquired due to a failure of a position sensor 20. When the value of the phase current detected by the current detection circuit is small, the motor control device 3 controls a pump 6 for supplying a refrigerant to the motor 2 to increase the amount of the refrigerant supplied to the motor 2 and increase the load of the motor 2, thereby increasing the phase current to suppress a decrease in the accuracy of the detection value of the phase current.

Description

Electric motor control unit

[0001] The present invention relates to a control device for an electric motor, and more particularly to a control device for an oil-cooled electric motor used in electric vehicles.

[0002] In recent years, as a measure against climate change such as global warming, the adoption of electric vehicles, such as hybrid vehicles that use electric motors as a power source and have low carbon dioxide emissions, and electric vehicles that run solely on electric motors, has been promoted. Generally, the electric motors used to drive electric vehicles are synchronous motors that are driven by AC power converted from DC power supplied from a battery by an inverter. Synchronous motors are controlled according to the magnetic pole position obtained based on the rotation angle of the rotor detected by a position sensor built into the motor. Therefore, if the rotation angle of the rotor cannot be obtained due to a failure of the position sensor or the magnetic pole position cannot be determined, it will cause problems in the operation of the vehicle.

[0003] In relation to these technical challenges, Patent Document 1 discloses a motor drive device that, when a motor angle detector used to detect the magnetic pole position becomes unusable due to a malfunction or other reason, estimates the rotation angle of the rotor using obtainable motor current values, etc., and enables the motor to continue operating.

[0004] Japanese Patent Publication No. 2015-181345

[0005] In the technology described in Patent Document 1, when a motor angle detector cannot be used, the motor can be controlled by estimating the rotor rotation angle from the motor current value, etc., so that the motor can continue to operate even when the rotation angle can no longer be obtained from the position sensor, and the motor can be controlled based on the estimated rotor rotation angle. However, when the motor load is low, such as when driving at low speed or downhill, the motor current decreases, and the proportion of noise and error in the current detected by the current sensor increases, making it difficult to correctly estimate the motor rotation angle, i.e., the magnetic pole position.

[0006] In view of the problems in the prior art described above, the object of the present invention is to provide a control device that can suppress the decrease in the accuracy of estimating the magnetic pole position at low loads and continue the operation of the motor.

[0007] In one preferred embodiment, the electric motor control device to which the present invention is applied is a control device for controlling an electric motor mounted on a vehicle and cooled by a refrigerant circulating inside, and includes: a power conversion unit that converts DC power supplied from an external source into AC power and supplies it to the electric motor; a position detection unit that receives a detection signal from a position sensor that detects the rotational position of the electric motor's rotor and acquires the magnetic pole position of the rotor based on the detection signal; a current detection circuit that detects the load current supplied to the electric motor; a position estimation unit that estimates the magnetic pole position of the rotor based on the load current detected by the current detection circuit; a sensor failure determination unit that determines whether the position sensor is faulty; a sensor signal arbitration unit that selects and outputs the magnetic pole position detected by the position detection unit and the magnetic pole position estimated by the position estimation unit according to the determination result in the sensor failure determination unit; a drive control unit that drives the power conversion unit and controls the current supplied to the electric motor based on a torque command given from an external source and the magnetic pole position selected by the sensor signal arbitration unit; and a refrigerant adjustment unit that controls the state of the refrigerant supplied to the electric motor for cooling the electric motor so as to increase the load on the electric motor when the sensor failure determination unit determines that the position sensor is faulty.

[0008] According to the present invention, even when a vehicle is running under low load conditions in the event of a position sensor failure, it is possible to suppress a decrease in the detection accuracy of the current value used to control the electric motor without position information, and to continue controlling the electric motor. Other novel features of the present invention and the technical problems solved thereby will become apparent from the description and drawings herein.

[0009] This is a schematic diagram showing the configuration of an electric powertrain in one embodiment. This is a schematic block diagram showing the configuration of the motor and motor control device. This is a schematic diagram showing the cross-sectional structure of the motor. This is a schematic diagram showing the cross-sectional structure at section A-A' in Figure 3. This is a schematic block diagram showing the configuration of the motor control device. This is a flowchart showing the flow of load increase control.

[0010] Hereinafter, representative embodiments of the present invention will be described with reference to the drawings. It should be noted that the embodiments and drawings described below are illustrative examples for explaining the present invention, and have been omitted and simplified as appropriate for clarity of explanation.

[0011] Figure 1 is a schematic diagram showing the configuration of an electric powertrain in one embodiment of the present invention.

[0012] The electric powertrain in this embodiment includes an electric motor (hereinafter simply referred to as "motor") 2 that serves as the power source for the vehicle 1, a motor control device 3 that controls the motor 2, and a battery 4 as a power supply source. The motor control device 3 controls the motor 2 according to drive commands sent from the vehicle electronic control unit (vehicle ECU) 5 via an in-vehicle network 13 such as a controller area network (CAN). The motor 2 drives the wheels 8 via the axle 7 to move the vehicle 1. The motor 2 can also provide braking force to the wheels 8 by functioning as a generator that generates electricity by receiving the rotational force of the wheels 8 when the vehicle 1 is being braked.

[0013] In this embodiment, an oil-cooled motor is used as the motor 2, which circulates oil as a coolant inside the motor 2 to cool the heat generated during operation. The motor control device 3 can manage the cooling state of the motor 2 by controlling the amount of cooling oil circulated to the motor 2 by controlling the electric oil pump 6.

[0014] Vehicle 1 is equipped with a grill shutter 9 and an electric fan 10 that control the inflow of air into the vehicle 1 where the electric powertrain is installed. The vehicle ECU 5 can control the drive mechanism 11 via the in-vehicle network 13 to adjust the opening degree of the grill shutter 9 and also control the amount of air flowing into the vehicle 1 by adjusting the rotation speed of the electric fan 10. If vehicle 1 is a so-called hybrid vehicle and is equipped with an engine along with the electric powertrain, the grill shutter 9 and electric fan 10 may be used to control the flow rate of air sent to the radiator 12 that cools the engine's coolant. Also, if the cooling oil that cools the motor 2 is configured to circulate through a heat exchanger (not shown) and be cooled by the heat exchanger, the grill shutter 9 and electric fan 10 may be used to send cooling air to that heat exchanger.

[0015] Figure 2 is a schematic block diagram showing the configuration of the motor 2 and the motor control device 3.

[0016] In this embodiment, the motor 2 is a brushless oil-cooled motor driven by three-phase AC power. The motor 2 operates by receiving three-phase AC power supplied from the motor control device 3. The motor 2 is equipped with a position sensor 20 that detects the rotational position of the rotor, and during operation of the motor 2, a position signal indicating the rotational position of the rotor detected by the position sensor 20 is sent to the motor control device 3.

[0017] The motor control device 3 receives drive commands from the vehicle ECU 5 via the in-vehicle network 13 at the controller 21. The controller 21 controls the inverter 22, which is a power conversion unit, according to the drive commands, and converts the DC power supplied from the battery 4 into three-phase AC power (U, V, and W) and supplies it to the motor 2. A current sensor (not shown) is provided at the output of the inverter 22, and the current detection circuit 23 detects the current flowing through each phase of the motor 2, i.e., the load current. The detected current values ​​for each phase (current detection values) are provided to the controller 21 for the control of the motor 2. The position signal sent from the position sensor 20 of the motor 2 is provided to the position detection circuit 24, and the position detection circuit 24 acquires a position detection value corresponding to the rotational position of the rotor. The position detection value is provided to the controller 21 for the control of the motor 2, similar to the current detection value.

[0018] The controller 21 can also send a rotation command to the electric oil pump 6 and control the amount of cooling oil circulated to the motor 2, thereby managing the cooling state of the motor 2.

[0019] Figure 3 is a schematic diagram showing the cross-sectional structure of motor 2, and Figure 4 is a schematic diagram showing the cross-sectional structure of section A-A' in Figure 3 as viewed in the direction of the arrow.

[0020] The motor 2 has a hollow cylindrical stator coil 31 fixed inside the motor casing 30, and a rotor 33 that is rotatably positioned inside the stator coil 31 with a small gap between it and the stator coil 31, and has magnetic poles formed on its surface. Stator coil end portions 32 are formed at both ends of the stator coil 31 in the rotation axis direction of the rotor 33, where the stator coil is exposed. An output shaft 34 is provided at the center of the rotor 33, extending in one direction in the rotation axis direction of the rotor 33, and the rotational force of the rotor 33 is transmitted via the output shaft 34. The output shaft 34 is rotatably supported by a bearing 35 fixed to the motor casing 30. In this embodiment, the bearing 35 located on the extending side of the output shaft 34 is held by a bearing retainer 37 fixed to the motor casing 30 by bolts 36.

[0021] The motor casing 30 has a coolant passage 38 formed inside it for guiding cooling oil into the motor casing 30. The cooling oil guided into the motor casing 30 flows from top to bottom, as shown by the dashed arrow in the figure, and cools the stator coil 31. The cooling oil that has cooled the motor 2 is discharged from the bottom of the motor casing 30 in the figure and returned to the electric oil pump 6, where it is used again to cool the motor 2.

[0022] When the amount of cooling oil supplied to the motor 2 increases, the amount of cooling oil that falls directly onto the rotor 33 and output shaft 34 without passing over the outer circumference of the stator coil 31 also increases, and the amount of cooling oil adhering to the rotor 33 and output shaft 34 also increases. When the amount of cooling oil adhering to the rotor 33 and output shaft 34 increases, the viscous friction torque increases, and the load torque of the motor 2 increases. In this embodiment, this is utilized to increase the load torque of the motor 2 when, as will be described later, the position of the rotor 33 cannot be detected due to a failure of the position sensor 20, the motor 2 becomes low load, the load current decreases, and sensorless control of the motor 2 becomes difficult. In addition to a failure of the position sensor 20, the magnetic pole position cannot be acquired in the event of a break in the wiring between the position sensor 20 and the controller 21, a short circuit, or a failure of the position detection circuit 24. In this specification, the state in which the magnetic pole position cannot be acquired based on the position signal output by the position sensor 20, including these abnormalities, will be treated as a failure of the position sensor 20. Furthermore, the term "magnetic pole position" is sometimes used collectively to refer to the electrical angle and electrical angular rotation speed used in the control of motor 2.

[0023] FIG. 5 is a schematic block diagram showing a logical configuration of a controller 21 included in the motor control device 3. In the present embodiment, the controller 21 can be configured to include, for example, a microcontroller unit (MCU) provided with a processor and a memory. The functions of each part described below can be realized by the processor of the MCU executing a program stored in the memory. Instead of realizing all functions software-wise by program execution, part or all of them can also be realized by a hardware circuit using an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or the like.

[0024] When the controller 21 receives a torque command sent from the vehicle ECU 5, in the current command calculation unit 40, a d-axis current command value (I ｄ ,

[0026] , , ｑ , ｑ , ｄ , ｑ , ｄ , ｑ , ｄ command), and a q-axis current command value (I ｑ command) are calculated. The torque command is calculated in the vehicle ECU 5 based on, for example, the accelerator opening degree and the brake demand amount. I ｄ command, I ｑ command may be obtained by calculation from the operating point at which the torque of the motor 2 is maximized with respect to the effective value of the same-phase current, or a map created based on a previously calculated result may be held and obtained from the map.

[0025] The I ｄ command and I ｑ command obtained by the current command calculation unit 40 are given to the current control unit 41. The current control unit 41, in addition to the I ｄ command and I ｑ command, based on the d-axis current (I ｄ ), q-axis current (I ｑ ), and electrical angular rotation speed obtained from the motor current value detected by the current detection circuit 23, calculates a d-axis voltage command value (V ｄ ), q-axis voltage command value (V ｑ ), and the deviation between I ｄ command, I ｑ command. At this time, non-interference control may be used as necessary. <000021​​​​V obtained by the current control unit 41 ｄ Directive, V ｑ The command is given to the dq / UVW conversion unit 42. The dq / UVW conversion unit 42 is V ｄ Directive, V ｑ In addition to the command, information on the electrical angle of motor 2 is acquired, and V is activated according to the electrical angle. ｄ Directive, V ｑ The command is the phase voltage command value for each of the U, V, and W phases of the three-phase AC power. ｕ Directive, V ｖ Directive, V ｗ Converts into a three-phase voltage command including the command.

[0027] The three-phase voltage command output from the dq / UVW conversion unit 42 is supplied to the PWM conversion unit 43. In addition to the three-phase voltage command, the PWM conversion unit 43 is also supplied with the power supply voltage detected by the PWM voltage detection circuit 44. Based on the three-phase voltage command, the power supply voltage, and the carrier signal used for pulse width modulation, the PWM conversion unit 43 converts the PWM pulse width D ｕ , D ｖ , D ｗ The following is calculated. In this case, in order to improve the voltage utilization rate, a modulation method that adds a third harmonic component may be used, or a two-phase modulation method may be used and a modulation offset signal may be added. Furthermore, if the modulation rate reaches the upper limit, the modulation rate may be corrected so that the effective values ​​of the modulation rate are equal.

[0028] The PWM pulse width D obtained by the PWM conversion unit 43 ｕ , D ｖ , D ｗ This is supplied to the dead time compensation unit 45. The dead time compensation unit 45 controls the PWM pulse width D ｕ , D ｖ , D ｗ A compensation amount is added to each of these to compensate for the effects of dead time. If the phase current is positive, a positive compensation amount is added to the PWM pulse width; if the phase current is negative, a negative compensation amount is added to the PWM pulse width. Compensation amount D for each phase ｘ dt is dead time T ｄ , the carrier frequency is F ｓ The phase current of each phase is I ｘ The current threshold used to calculate the compensation amount is I ｔｈIn that case, D ｘ dt = -T ｄ × f ｓ (I ｘ ≤ -I ｔｈ ) D ｘ dt = T ｄ × f ｓ × I ｘ / I ｔｈ (-I ｔｈ < I ｘ < I ｔｈ ) D ｘ dt = T ｄ × f ｓ (I ｘ ≥I ｔｈ ) is obtained as follows. Note that the suffix x represents the respective phases U, V, and W. Also, generally, the current threshold I ｔｈ A value roughly equivalent to the ripple included in the phase current is set for this value.

[0029] The PWM pulse width of each phase after adding the compensation amount is D'. ｕ = D ｕ +D ｕ dt D' ｖ = D ｖ +D ｖ dt D' ｗ = D ｗ +D ｗ This is obtained as dt. The inverter 22 has a PWM pulse width D' with the compensation amount added. ｕ , D' ｖ , D' ｗ The power elements of the upper and lower arms are switched based on this, and as a result, the current of each phase supplied to the motor 2 is controlled.

[0030] The current of each phase flowing from the inverter 22 to the motor 2 is detected by the current detection circuit 23, and the current value is provided to the UVW / dq conversion unit 46. The UVW / dq conversion unit 46 acquires information on the electrical angle of the motor 2 and, according to the electrical angle, converts the current values ​​of each phase U, V, and W, and I ｕ , I ｖ , I ｗ Current values ​​I for the d-axis current and q-axis current. ｄ , I ｑ Convert to the obtained I ｄ, I ｑ is given to the current control unit 41 and is used for calculating the V ｄ command and the V ｑ command.

[0031] A drive control unit is configured to control the current supplied to the motor 2 by driving the inverter 22 by the respective parts described above.

[0032] The I ｄ , I ｑ obtained by the UVW / dq conversion unit 46 is also input to the shaft error estimation value calculation unit 47 and is used for estimating the magnetic pole position and the electrical angle rotation speed when the magnetic pole position cannot be obtained due to a failure of the position sensor of the motor 2. The shaft error estimation value calculation unit 47 uses, in addition to I ｄ , I ｑ , the V ｄ command and the V ｑ command output from the current control unit 41 and the information on the electrical angle rotation speed given to the current control unit 41 to calculate the shaft error estimation value Δθ ＊ ｃ . If the electrical angle rotation speed is ω ｅ , the winding resistance of the motor 2 is R, the d-axis inductance is L ｄ , and the q-axis inductance is L ｑ , the shaft error estimation value Δθ ＊ ｃ is obtained as Δθ ＊ ｃ = tan -1 {(V ｄ command - R × I ｄ + ω ｅ × L ｄ × I ｑ ) / (V ｑ command - R × I ｑ - ω ｅ × L ｄ × I ｄ )}. [[ID=...]]

[0033] The obtained shaft error estimation value is given to the estimated speed calculation unit 48, and the electrical angle rotation speed is estimated. The estimated value ω １ ＊ of the electrical angle rotation speed is the proportional gain of the PI control that makes the shaft error estimation value Δθ ＊ ｃ zero, and is Kｐ , the integral gain is K ｉ When this is the case, using the Laplace operator s, ω １ ＊ = Δθ ＊ ｃ (K Ｐ +K ｉ It can be obtained as / s).

[0034] The estimated electrical angular rotation speed ω calculated by the estimated speed calculation unit 48 １ ＊ This is provided to the angle estimation unit 49, and the angle estimation value θ of the electrical angle ＊ ｄｃ The angle estimate θ is calculated. ＊ ｄｃ This uses the Laplace operator s, θ ＊ ｄｃ = ω １ ＊ It can be obtained as ×1 / s.

[0035] Thus, the axis error estimation unit 47, the estimated speed calculation unit 48, and the angle estimation unit 49 calculate I based on the current values ​​of each phase of the motor 2. ｄ , I ｑ and the command values ​​(V) to control them. ｄ , V ｑ It functions as a position estimation unit that estimates the magnetic pole position based on ).

[0036] Meanwhile, the rotational position of the rotor 33 detected by the position detection circuit 24 is provided to the electrical angle calculation unit 50, and the electrical angle θ is calculated based on the mechanical rotational angle of the rotor 33. ｅ The following is calculated: Electric angle θ ｅ Furthermore, this is provided to the electrical angular rotation speed calculation unit 51, and the electrical angular rotation speed calculation unit 51 calculates the electrical angular rotation speed ω ｅ The following is obtained. The electrical angle calculation unit 50 and the electrical angle rotation speed calculation unit 51 function as position detection units that acquire the magnetic pole position based on the rotation position of the rotor 33 detected by the position detection circuit 24.

[0037] The rotational position detected by the position detection circuit 24 is also provided to the sensor failure determination unit 52. Based on the provided rotational position information, the sensor failure determination unit 52 determines whether there is an abnormality in the value detected by the position detection circuit 24 and detects a sensor failure. For example, the amount of change in the rotational position detected by the position detection circuit 24 over a predetermined time is monitored, and if the amount of change deviates from a predetermined range, a sensor failure can be determined. If information indicating a failure state, such as an abnormality in the detected value, is obtained from the position sensor 20, the sensor failure determination unit 52 can also be configured to detect a sensor failure based on this information.

[0038] The estimated electrical angular rotation speed ω obtained by the estimated speed calculation unit 48 １ ＊ , the angle estimate θ obtained by the angle estimate calculation unit 49 ＊ ｄｃ , the electrical angle θ obtained by the electrical angle calculation unit 50 ｅ , and the electrical angular rotation speed ω obtained in the electrical angular rotation speed calculation unit 51 ｅ The signal is provided to the sensor signal arbitration unit 53. The sensor signal arbitration unit 53 arbitrates between these signals based on the fault determination result from the sensor fault determination unit 52. If no sensor fault is detected, the sensor signal arbitration unit 53 uses the electrical angle θ obtained by the electrical angle calculation unit 50. ｅ Information of magnetic pole position θ ｅ_ａｒｂ The dq / UVW conversion unit 42 and the UVW / dq conversion unit 46 receive the electrical angular rotation number ω obtained by the electrical angular rotation number calculation unit 51. ｅ The information of the electrical angular rotation ω ｅ_ａｒｂ This is then provided to the current control unit 41 and the axis error estimation unit 47, respectively. On the other hand, if a sensor malfunction is detected, the sensor signal arbitration unit 53 uses the electrical angle estimation value θ obtained by the angle estimation unit 49. ＊ ｄｃ Information of magnetic pole position θ ｅ_ａｒｂ The dq / UVW conversion unit 42 and the UVW / dq conversion unit 46 receive the estimated electrical angular rotation value ω obtained by the estimated speed calculation unit 48. １ ＊ The information of the electrical angular rotation ω ｅ_ａｒｂ This is then provided to the current control unit 41 and the axis error estimation unit 47, respectively.

[0039] The controller 21 also receives detection signals acquired by temperature sensors (not shown) provided on the motor 2 and inverter 22, respectively. The detection signals from the temperature sensors are input to the temperature detection circuit 54, where the temperature information of the motor 2 and inverter 22 is acquired.

[0040] The acquired temperature information is provided to the cooling flow rate calculation unit 55, which calculates the flow rate of the cooling oil to be circulated to the motor 2 and inverter 22. For example, a MAP or calculation formula obtained from the results of analysis or experimentation can be used to calculate the cooling oil flow rate. The acquired cooling oil flow rate is provided to the pump rotation speed command calculation unit 56, which calculates the rotation speed of the electric oil pump 6 to obtain the acquired flow rate. The pump rotation speed command calculation unit 56 issues a rotation speed command to the electric oil pump 6 so that the rotation speed of the electric oil pump 6 becomes the calculated rotation speed. In this embodiment, the rotation speed of the electric oil pump 6 is calculated based on the cooling oil flow rate, but it is also possible to directly acquire the rotation speed of the electric oil pump 6 from the temperature information detected by the temperature detection circuit 54 using a MAP or calculation formula. This makes it possible to reduce the amount of calculation in the controller 21.

[0041] In this embodiment, if the position sensor 20 fails or the position sensor 20 fails to acquire the magnetic pole position of the motor 2, the motor 2 is controlled based on the magnetic pole position (magnetic pole position and electrical angular rotation speed) estimated by the position estimation unit (axis error estimation value calculation unit 47, estimated speed calculation unit 48, angle estimation value calculation unit 49). As described above, the magnetic pole position is estimated based on the current value detected by the current detection circuit 23. In the region where the load current value detected by the current detection circuit 23 is small, the I obtained by the UVW / dq conversion unit 46 ｄ , I ｑ The proportion of noise and errors included increases, ｄ , I ｑThe accuracy of the measurement decreases. As a result, the accuracy of estimating the magnetic pole position and electrical angular rotation speed also decreases, making it difficult to control the motor 2 accurately. In addition, as the proportion of noise and error increases, the polarity of the detected current value switches frequently, causing hunting in the compensation amount in the dead time compensation unit 45, which makes it easier for noise and vibration due to torque pulsation to occur. In this embodiment, in such cases, the viscous resistance of the cooling oil is used to increase the load on the motor 2 and increase the load current to I ｄ , I ｑ This suppresses the decrease in detection accuracy.

[0042] For this purpose, in this embodiment, the controller 21 is provided with a refrigerant adjustment unit that adjusts the state of the cooling oil supplied to the motor 2. In this embodiment, the refrigerant adjustment unit adjusts the I obtained by the UVW / dq conversion unit 46. ｄ , I ｑ The system includes a load state determination unit 57 that receives input and determines the load state of the motor 2, and a load increase control unit 58 that outputs a request to increase the load on the motor 2 based on the determination result of the load state determination unit 57 and the determination result of the sensor failure determination unit 52.

[0043] The load state determination unit 57 receives I from the UVW / dq conversion unit 46. ｄ , I ｑ Obtain these values ​​and use them to determine the phase current of motor 2 and the load current I load The load current is obtained as follows. The current value obtained here may be obtained from either the peak value or the RMS value. The load state determination unit 57 compares the obtained load current with a preset first threshold value, and determines that it is a low load state if the load current is below the first threshold value. The first threshold value can be set by obtaining a load current value at a level where hunting does not occur through experiments or the like in advance. Load current I load After the load current I falls below the first threshold, the load state determination unit 57 maintains the low load state determination result. Alternatively, the load state determination unit 57 determines that the load current I load After the load current I falls below the first threshold, the low load state determination result is maintained, and the load current I loadThe system may be configured to release the low-load condition determination when the load current I, which is greater than the first threshold, exceeds a second threshold. The second threshold is, for example, the load current I due to the adjustment of the refrigerant state, which is greater than the first threshold. load It can be determined by taking into account the increase.

[0044] Based on the determination results from the sensor failure determination unit 52 and the load state determination unit 57, the load increase control unit 58 outputs a load increase request signal requesting an increase in the torque of the motor 2 when it determines that a sensor failure has occurred and the load state of the motor 2 is in a low load state.

[0045] The load increase request signal output from the load increase control unit 58 is provided to the pump rotation speed command calculation unit 56. When the load increase request signal is input from the load increase control unit 58, the pump rotation speed command calculation unit 56 increases the rotation speed command of the electric oil pump 6 in order to increase the amount of cooling oil supplied to the motor 2. The rotation speed command output in response to the load increase request signal may, for example, indicate the maximum rotation speed regardless of the cooling flow rate calculated by the cooling flow rate calculation unit 55. Alternatively, a cooling oil flow rate that can reduce the effects of noise and errors at low load currents may be obtained in advance through experiments, etc., and the unit may be set to indicate any rotation speed that supplies cooling oil at or above that flow rate. By increasing the rotation speed of the electric oil pump 6, the amount of cooling oil supplied to the motor 2 increases, the viscous resistance increases, the load torque of the motor 2 increases, and the load current of the motor 2 can be increased.

[0046] The load increase request signal output from the load increase control unit 58 may be sent to the vehicle ECU 5 via the in-vehicle network 13. In the vehicle ECU 5, the load increase request signal is treated as a signal requesting an increase in the airflow rate taken into the vehicle 1 on which the electric powertrain is installed. When the vehicle ECU 5 receives the load increase request signal, it controls either or both of the drive mechanism 11 of the grill shutter 9 and the electric fan 10 to increase the airflow rate introduced into the vehicle 1 on which the electric powertrain is installed. The airflow rate introduced into the vehicle 1 can be increased by increasing the opening of the grill shutter 9, or by increasing the rotation speed of the electric fan 10. The increased airflow rate can be maximized, for example, within a range that does not adversely affect other equipment inside the vehicle 1. Alternatively, a control value that results in an arbitrary airflow rate obtained in advance through experiments may be set, and the grill shutter 9 and electric fan 10 may be controlled according to that control value. By increasing the airflow rate introduced into the vehicle 1, the cooling of the cooling oil used to cool the motor 2 is promoted, and the temperature of the cooling oil decreases. This increases the viscous resistance, similar to when the viscosity of the cooling oil increases and the flow rate of the cooling oil is increased, thereby increasing the load torque of motor 2 and increasing the load current.

[0047] Figure 6 shows a flowchart illustrating the flow of load increase control performed by the motor control device 3 in this embodiment.

[0048] The motor control device 3 monitors the position detection value output from the position detection circuit 24 and the phase current value detected by the current detection circuit 23 (step S100). The motor control device checks whether the position detection value output from the position detection circuit 24 is a normal value and determines whether there is an abnormality in the position sensor 20 or the position detection circuit 24 (step S110). If there is an abnormality in the position detection value and it is determined that there is an abnormality in the position sensor 20 or the position detection circuit 24, the motor control device 3 further determines whether the motor 2 is in a low-load state based on the phase current value (step S120).

[0049] If it is determined in step S120 that motor 2 is in a low-load state, the motor control device 3 controls the state of the cooling oil to increase the torque of motor 2. Specifically, the maximum or a preset arbitrary rotation command value is sent to the electric oil pump 6. The motor control device 3 also sends a load increase request to the in-vehicle network 13, which requests an increase in the airflow rate taken into the vehicle 1. The request sent to the in-vehicle network 13 is received by the vehicle ECU 5 and used to control the grill shutter 9 and electric fan 10 via the vehicle ECU 5 to increase the airflow rate taken into the vehicle 1 (step S130).

[0050] On the other hand, if the result of the determination in steps S110 and S120 is negative, that is, if the position detection value is normal, or if the motor 2 is not in a low-load state even if the position detection value is abnormal, the motor control device 3 performs normal control of the electric oil pump 6 based on temperature information. No load increase request is sent to the in-vehicle network 13. In this case, the motor control device 3 may, instead of a load increase request, send information to the in-vehicle network 13 indicating, for example, that an increase in airflow rate is not required (step S140).

[0051] According to the embodiment described above, even if the motor load decreases when a motor position sensor or the like fails and the motor's rotational position cannot be obtained, the state of the refrigerant cooling the motor is controlled to increase the motor load. This suppresses a large decrease in the phase current used to estimate the motor's rotational position, prevents a decrease in the accuracy of rotational position estimation due to the effects of noise and detection errors of the phase current, maintains the controllability of the motor, and reduces the generation of unpleasant noise and vibration.

[0052] The present invention has been described above using representative embodiments as examples, but the present invention is not limited thereto and can be implemented in various ways without departing from the spirit of the invention as described in the claims. Furthermore, the embodiments described above are described in detail to make the present invention easy to understand and are not necessarily limited to those having all the configurations described. For example, in the embodiments described above, both the amount of cooling oil supplied to the motor 2 is controlled and the cooling state of the cooling oil is controlled by the grill shutter and electric fan, but only one of these may be performed. The control of the refrigerant state is performed when the motor is under low load and the load current is small, but the refrigerant state can also be controlled so that the motor load increases regardless of the magnitude of the load current when the rotational position of the motor can no longer be detected by the position sensor. In this case, power consumption will increase, but the increase in processing load due to the processing related to the control of the refrigerant state can be suppressed. Furthermore, in the embodiments described above, cooling oil is used as the refrigerant to cool the motor, but the refrigerant is not limited to oil, and any fluid other than oil may be used as long as it can directly cool the rotor and has viscous resistance that can increase the motor load.

[0053] 1: Vehicle, 2: Motor, 3: Motor control device, 4: Battery, 5: Vehicle electronic control unit (vehicle ECU), 6: Electric oil pump, 9: Grill shutter, 10: Electric fan, 11: Grill shutter drive mechanism, 20: Position sensor, 21: Controller, 22: Inverter, 23: Current detection circuit, 24: Position detection circuit

Claims

A control device for controlling an electric motor mounted in a vehicle and cooled by a refrigerant circulating inside, A power conversion unit that converts DC power supplied from an external source into AC power and supplies it to the motor, A position detection unit receives a detection signal from a position sensor that detects the rotational position of the rotor of the electric motor, and acquires the magnetic pole position of the rotor based on the detection signal. A current detection circuit for detecting the load current supplied to the electric motor, A position estimation unit that estimates the magnetic pole position of the rotor based on the load current detected by the current detection circuit, A sensor failure determination unit for determining a failure of the position sensor, A sensor signal arbitration unit selects and outputs the magnetic pole position detected by the position detection unit and the magnetic pole position estimated by the position estimation unit according to the determination result in the sensor fault determination unit, A drive control unit drives the power conversion unit and controls the current supplied to the electric motor based on a torque command provided from an external source and the magnetic pole position selected by the sensor signal arbitration unit, When the sensor failure determination unit determines that the position sensor is faulty, the refrigerant adjustment unit controls the state of the refrigerant supplied to the motor for cooling the motor so that the load on the motor increases. A control device for an electric motor. 　 The motor control device according to claim 1, characterized in that the refrigerant adjustment unit controls the state of the refrigerant when the load current of the motor becomes smaller than a predetermined threshold. 　 The control device for an electric motor according to claim 1, wherein the control of the state of the refrigerant by the refrigerant adjustment unit includes increasing the amount of refrigerant supplied to the electric motor. 　 The control device for an electric motor according to claim 1, wherein the control of the state of the refrigerant by the refrigerant adjustment unit includes control of the cooling of the refrigerant. 　 The control device for an electric motor according to claim 4, wherein the control of the cooling of the refrigerant includes controlling the flow rate of air flowing into the space inside the vehicle in which the electric motor is located. 　 The control of the airflow rate includes sending information to another control device provided in the vehicle and connected via an in-vehicle network requesting an increase in the airflow rate, thereby controlling the airflow rate by the other control device, as described in claim 5. 　 The control device for an electric motor according to claim 6, characterized in that the control of the airflow rate is performed by controlling the opening degree of a grill shutter provided on the vehicle. 　 The control device for an electric motor according to claim 6, characterized in that the control of the airflow rate is performed by controlling the rotation speed of a fan provided in the vehicle that takes in air into the interior of the vehicle.

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