Motor control device and vehicle

Abstract

The present disclosure relates to a control device for an electric motor and a vehicle. A control device (60) includes: a rotor temperature estimating unit (62a) for estimating the temperature of a rotor (14) based on stator temperature information from a first temperature sensor (17) for determining the temperature of a stator (12), refrigerant temperature information from a second temperature sensor (25) for determining the temperature of a refrigerant used for cooling an electric motor (10), and rotor (14) speed information from a rotary transformer (18) for determining the speed of the rotor (14); and a motor control unit (62d) for controlling at least one of the output characteristics and driving conditions of the electric motor (10) based on the temperature of the rotor (14) estimated by the rotor temperature estimating unit (62a).

Description

Technical Field

[0001] The present disclosure relates to a control device for controlling an electric motor mounted on a vehicle and also to a vehicle equipped with such a control device. Background Art

[0002] Japanese Patent No. 6026815 describes a conventional control device for a vehicle electric motor. This device is installed in a vehicle equipped with an electric motor cooled by cooling oil. The device controls the output of the electric motor based on the temperature of the stator coils and the temperature of the cooling oil.

[0003] Permanent magnets embedded in and fixed to the rotor of an electric motor will irreversibly demagnetize if they exceed a specified temperature, degrading the motor's performance. Furthermore, when the motor rotates at high speeds, motor losses increase, increasing the amount of heat generated and the rotor's temperature. This increases the need to suppress the motor's output during high-speed rotation.

[0004] Against this backdrop, the motor control disclosed in Japanese Patent No. 6026815 performs motor output control regardless of the motor's rotational speed. Therefore, even when the motor is rotating at a low speed, control must be performed assuming high-speed rotation. Consequently, the motor's output is likely to be excessively restricted in the motor's low-speed range, making it difficult to operate the motor efficiently in this range. Summary of the Invention

[0005] Therefore, an object of the present disclosure is to provide a vehicle control device that can easily and efficiently operate an electric motor, and a vehicle including such a control device.

[0006] In order to solve the above-mentioned problem, the control device disclosed in the present invention is a control device for controlling an electric motor mounted on a vehicle, comprising: a rotor temperature estimating unit, which estimates the temperature of the rotor based on stator temperature information from a stator temperature determining unit for determining the temperature of the stator, refrigerant temperature information from a refrigerant temperature determining unit for determining the temperature of a refrigerant used in cooling the electric motor, and speed information of the rotor from a speed determining unit for determining the speed of the rotor; and a control unit, which controls at least one of the output characteristics and driving conditions of the electric motor based on the temperature of the rotor estimated by the rotor temperature estimating unit.

[0007] It should be noted that the above-mentioned electric motor may be a structure capable of generating power but not electricity. Alternatively, the electric motor may be a so-called motor generator, or a structure capable of generating both power and electricity.

[0008] Furthermore, the various temperature determination units mentioned above can of course be temperature sensors provided at the temperature detection object, or can include: one or more temperature sensors provided at a portion other than the temperature detection object; and a control unit that estimates the temperature of the temperature detection object based on one or more temperatures detected by the one or more temperature sensors and information or a program (software) such as a mapping stored in a storage unit. Alternatively, the various temperature determination units mentioned above can also include: one or more sensors other than the temperature sensor provided at the temperature detection object, such as one or more temperature sensors, current sensors, voltage sensors, and rotation speed detection sensors that are not provided at the temperature detection object; and a control unit that estimates the temperature of the temperature detection object based on one or more physical information detected by the one or more sensors and information or a program such as a mapping stored in a storage unit. In short, the various temperature determination units mentioned above can include any configuration that can detect the temperature of the temperature detection object or estimate the temperature of the temperature detection object.

[0009] Furthermore, the rotational speed determination unit may also be comprised of a rotational speed detection sensor that directly detects the rotational speed of the rotor, such as a resolver or a rotational speed detection sensor including a pulser ring. Alternatively, the rotational speed determination unit may include: one or more sensors other than the rotational speed detection sensor, such as one or more temperature sensors, current sensors, and voltage sensors; and a control unit that estimates the rotational speed of the rotor based on one or more physical information detected by the one or more sensors and information or a program such as a map stored in a storage unit. In short, the rotational speed determination unit may include any component that can detect or estimate the rotational speed of the rotor.

[0010] According to the present disclosure, a control device controls at least one of the motor's output characteristics and driving conditions by considering not only stator temperature information and refrigerant temperature information but also the rotor's rotational speed. This prevents excessive restriction of the motor's output during low-speed rotation, enabling efficient motor operation in both low-speed and high-speed rotation conditions.

[0011] Furthermore, in the present disclosure, the rotor may include a permanent magnet, and the control unit may control at least one of the output characteristic and the driving condition of the electric motor based on a temperature of the rotor so that the permanent magnet does not demagnetize.

[0012] According to this configuration, demagnetization of the permanent magnets of the rotor can be effectively suppressed or prevented.

[0013] In addition, in the present disclosure, the control device may also include: a power cut-off time determination unit, which determines the power cut-off time at which the power of the vehicle is cut off; and a startup temperature estimation unit, which estimates the temperature of the rotor when the vehicle is powered on after the power cut-off time ends, based on the power cut-off time and the temperature of the rotor just before the power is cut off estimated by the rotor temperature estimation unit.

[0014] This configuration allows the rotor temperature to be estimated at vehicle startup. This allows the electric motor to operate efficiently and output high torque from the time the vehicle is started, thus achieving a powertrain with excellent responsiveness to operation from the time the vehicle is started.

[0015] Furthermore, if the last estimated rotor temperature can be determined, the rotor temperature can be estimated with high accuracy using filtering, current limiting, and other processes. However, when the vehicle is started, the last estimated rotor temperature is not available, making it impossible to estimate the rotor temperature with high accuracy. In contrast, according to this configuration, the rotor temperature at vehicle startup can be estimated even when the vehicle is started, making it easier to estimate the rotor temperature with high accuracy from the time the vehicle is started.

[0016] Furthermore, the vehicle of the present disclosure includes the control device of the present disclosure.

[0017] According to the present disclosure, it is possible to increase the torque output by the motor when the motor rotates at a low speed.

[0018] Effects of the Invention

[0019] According to the control device for the electric motor of a vehicle disclosed herein, the electric motor can be operated efficiently, and in particular, the torque output by the electric motor during low-speed rotation can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the configuration of an electric vehicle according to one embodiment of the present disclosure.

[0021] Figure 2 This is a graph explaining a method of determining the rotor temperature of a control device according to a comparative example.

[0022] Figure 3 This is a graph showing the relationship between the rotor temperature and the rotational speed of the rotor determined by the control device of the electric vehicle.

[0023] Figure 4 Graph showing the relationship between the actual temperature of the rotor when the rotor rotates at high speed, the temperature of the rotor determined by the control device, and the temperature of the rotor determined by the control device of the comparative example.

[0024] Figure 5Graph showing the relationship between the actual temperature of the rotor when the rotor rotates at a low speed, the temperature of the rotor determined by the control device, and the temperature of the rotor determined by the control device of the comparative example.

[0025] Figure 6 This is a graph showing the relationship between the rotational speed of the motor and the maximum torque that the motor is allowed to generate at each rotational speed.

[0026] Figure 7 This is a flowchart illustrating a process of estimating the temperature of a rotor in an electric vehicle.

[0027] Figure 8 Yes Figure 7 FIG. 1 is a diagram for explaining an overview of changes in the estimated temperature of the rotor before and after the temperature adjustment in step S4.

[0028] Figure 9 This is a flowchart illustrating the operation process when the control device controls the output characteristics of the electric motor.

[0029] Figure 10 This is a graph showing an example of the relationship between temperature and torque that can be used as a torque limit map, and is a graph showing the relationship between temperature and the maximum torque that can be generated at that temperature.

[0030] Figure 11 This is a graph showing the correlation between the magnet temperature and the power cutoff time at which the power supply to the motor is cut off.

[0031] Figure 12 This is a graph showing the correlation between the power off time and the temperature change values ​​of the stator and the refrigerant.

[0032] Figure 13 This is a flowchart illustrating the operation process when the control device controls the driving conditions of the electric motor. DETAILED DESCRIPTION

[0033] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be noted that, in the case where the following includes multiple embodiments, modifications, etc., it has been assumed from the beginning that their characteristic parts are appropriately combined to construct new embodiments. In addition, in the following embodiments, the same components are marked with the same figure marks in the drawings, and repeated descriptions are omitted. In addition, among the components described below, the components that are not recorded in the independent claims representing the highest concept are optional components, not required components.

[0034] Figure 1 FIG. 1 is a schematic diagram of an electric vehicle 1 according to an embodiment of the present disclosure. Figure 1As shown, the electric vehicle 1 includes: an electric motor 10 for driving the vehicle; a battery 20 as an example of a power source for the electric vehicle 1; an inverter 30 that converts DC power from the battery 20 into AC power and supplies it to the electric motor 10; a drive mechanism 40 that drives wheels 44 through the rotational power generated by the electric motor 10; a cooling device 50 that cools the electric motor 10; and a control device 60 that controls the output of the electric motor 10.

[0035] The electric motor 10 includes a housing 11; an annular stator 12 mounted within the housing 11; a rotor 14 spaced apart from the stator 12 and disposed radially inward of the stator 12; and a rotating shaft 16 having a substantially coaxial central axis with the rotor 14 and rotating synchronously with the rotor 14. A coil 13 is wound around the stator 12. A first temperature sensor 17 is mounted on the coil 13 to detect the coil temperature Tst.

[0036] The first temperature sensor 17 includes, for example, a thermistor element whose resistance depends on temperature and a resin covering that covers the thermistor element. The first temperature sensor 17 can be mounted anywhere on the stator 12, for example, on the neutral line when the coils 13 are Y-connected. It should be noted that while the first temperature sensor includes a thermistor element, the temperature sensor may also include a thermocouple, a platinum temperature measuring resistor element, or other temperature sensing elements.

[0037] The rotor 14 includes, for example, a cylindrical shape and a stacked structure formed by stacking a plurality of electromagnetic steel plates. The rotor 14 also includes a plurality of permanent magnets 15 embedded and fixed inside the outer peripheral side of the cylindrical stacked structure and arranged at intervals in the circumferential direction. A rotary transformer 18 is mounted at one end of the rotating shaft 16. The rotary transformer 18 is a speed detection sensor that detects the rotation angle θ and the speed N of the rotor 14. It should be noted that in the present disclosure, the rotary transformer 18 is used to detect the speed N of the rotor 14, but any other speed detection sensor that can detect the speed N of the rotor 14 can be used instead of the rotary transformer 18. For example, a speed detection sensor having a pulse generating ring and a magnetic force detection unit can also be used.

[0038] Battery 20 is a rechargeable secondary battery, such as a nickel-metal hydride battery or a lithium-ion battery. The positive and negative electrodes of battery 20 are electrically connected to inverter 30 via a high-voltage circuit 31 and a ground circuit 32, respectively. A voltage sensor 33 is provided between high-voltage circuit 31 and ground circuit 32 to detect voltage Vb of battery 20.

[0039] Inverter 30 internally includes multiple switching elements composed of field effect transistors (FETs), etc. These switching elements are turned on / off by PWM (Pulse Width Modulation) signals input from control device 60. DC power from battery 20, input from high-voltage circuit 31 and ground circuit 32, is converted into AC power, which is then supplied to motor 10 via AC circuit 35. Furthermore, inverter 30, by turning the switching elements on / off by PWM signals input from control device 60, converts AC regenerative power from motor 10, input from AC circuit 35, into DC power, which is then charged to battery 20 via high-voltage circuit 31 and ground circuit 32. AC circuit 35 consists of three circuits: U-phase circuit 35u, V-phase circuit 35v, and W-phase circuit 35w. V-phase circuit 35v is equipped with a current sensor 36 for detecting V-phase current Iv, while W-phase circuit 35w is equipped with a current sensor 37 for detecting W-phase current Iw.

[0040] The cooling device 50 includes: an oil pan 22, which is arranged below the electric motor 10 and stores a coolant 21 such as cooling oil; an electric oil pump 23, which pressurizes the coolant 21 stored in the oil pan 22; a coolant circulation pipe 24, which circulates the pressurized coolant 21 in the housing 11 of the electric motor 10; and a second temperature sensor 25, which detects the temperature Tr of the coolant 21 stored in the oil pan 22.

[0041] It should be noted that in this embodiment, the second temperature sensor 25 is mounted on the oil pan 22 to detect the temperature Tr of the coolant 21. However, the second temperature sensor 25 can be located anywhere as long as it can detect the temperature Tr of the coolant 21. For example, it can be located on the oil pump 23. The second temperature sensor 25 can include, for example, a thermistor element whose resistance depends on temperature and a resin coating covering the thermistor element. It can also include a thermocouple, a platinum temperature measuring resistor element, or other temperature sensing elements. The coolant 21 is pumped from the oil pan 22 by the oil pump 23, passes through the coolant circulation pipe 24, and then flows into the motor 10 from the upper portion of the housing 11.

[0042] After cooling the coil 13 of the stator 12, the coolant 21 returns from the lower part of the housing 11 to the oil pan 22. The coolant 21 is accumulated in the lower part of the housing 11. The lower part of the stator 12 and the lower part of the rotor 14 are immersed in the coolant 21 accumulated in the housing 11. The drive mechanism 40 includes a drive shaft 41, a differential gear 42 and a wheel 44. The drive shaft 41 is connected to the rotating shaft 16 of the motor 10 and is transmitted with the driving force of the motor 10. The differential gear 42 converts the rotational power of the drive shaft 41 into rotational power that rotates the axle 43. The wheel 44 is mounted on the axle 43 and rotates synchronously with the axle 43. The electric vehicle 1 also has a vehicle power switch 3, a timer 5 and an accelerator sensor 8. The vehicle power switch 3 outputs a signal to the control device 60 to determine whether the power of the electric vehicle 1 is turned on or off. The timer 5 exchanges information with the control device 60 in both directions. The accelerator sensor 8 outputs a signal indicating the accelerator opening to the control device 60 .

[0043] The control device 60 is composed of a computer, such as a microcomputer, and includes a control unit 62 and a storage unit 64. The control unit 62, that is, a processor, includes, for example, a CPU (Central Processing Unit). In addition, the storage unit 64 is composed of a hard disk drive (HDD), a semiconductor memory, etc., and the semiconductor memory is composed of a non-volatile memory such as a ROM (Read Only Memory) and a volatile memory such as a RAM (Random Access Memory). The storage unit 64 can be composed of only one storage medium or a plurality of different storage media. The CPU reads and executes the program, etc. pre-stored in the storage unit 64. In addition, the non-volatile memory pre-stores the control program, the specified threshold value, etc. In addition, the volatile memory temporarily stores the read program and the processed data.

[0044] The control unit 62 includes a rotor temperature estimation unit 62a, a power-off time determination unit 62b, a startup temperature estimation unit 62c, and a motor control unit 62d. The control unit 60 receives signals indicating the rotation angle θ and rotation speed N of the rotor 14, a signal indicating the voltage Vb of the battery 20, a signal indicating the V-phase current Iv, a signal indicating the W-phase current Iw, a signal indicating the coil temperature Tst, a signal indicating the temperature Tr of the coolant 21, a signal indicating the power-off time, and a signal indicating the commanded torque from the resolver 18, the voltage sensor 33, the current sensors 36 and 37, the first temperature sensor 17, the second temperature sensor 25, the vehicle power switch 3, the timer 5, and the accelerator sensor 8.

[0045] The control device 60 controls the motor 10 and other devices based on the received signals representing the plurality of physical quantities and the programs and information stored in the storage unit 64. For example, the control device 60 outputs a PWM signal to the inverter 30 based on the signals from the first and second temperature sensors 17 and 25, the signal from the resolver 18, and the programs and information stored in the storage unit 64, thereby controlling the current supplied to the motor 10 and thus controlling the torque generated by the motor 10. Figures 2 to 13 The operations of the rotor temperature estimating unit 62a, the power-off time determining unit 62b, the startup temperature estimating unit 62c, and the motor control unit 62d will be described in detail.

[0046] Next, use Figures 2 to 4 A method of estimating the rotor temperature by the control device 60 of the present disclosure will be described. Figure 2 This is a graph explaining a method of determining the rotor temperature of a control device of a comparative example. Figure 3 : is a graph showing the relationship between the rotor temperature determined by the control device 60 and the rotational speed of the rotor 14. The control device of the comparative example estimates Tro based on the following equation (1) when A0, B0, and C0 are set as constants, Tro is set as the rotor temperature estimated by the control device of the comparative example, Tst is set as the detected temperature of the coil 13 detected by the first temperature sensor 17, and Tr is set as the refrigerant temperature (coolant temperature) detected by the second temperature sensor 25.

[0047] Tro=A0·Tr+B0·Tst+C0……(1)

[0048] That is, Figure 2 As shown, in the control device of the comparative example, Tro is located on a plane in a three-dimensional space with Tro as the Z axis, Tst as the X axis, and Tr as the Y axis. If Tst and Tr are determined, Tro is uniquely determined.

[0049] In contrast, the control device 60 of the present disclosure estimates Tro based on the following equation (2), assuming that A1, B1, and C1 are constants, Tro is the rotor temperature estimated by the control device 60, Tst is the temperature of the coil 13 detected by the first temperature sensor 17, Tr is the refrigerant temperature (coolant temperature) detected by the second temperature sensor 25, and N is the rotational speed N of the rotor 14 detected by the resolver 18. It should be noted that C1 is a positive constant, satisfying C1>0.

[0050] Tro=A1·Tr+B1·Tst+C1·N……(2)

[0051] That is, Figure 3As shown, in the control device 60 of the present disclosure, Tro is not located only on a stationary plane in the three-dimensional space with Tro as the Z axis, Tst as the X axis, and Tr as the Y axis. When the rotational speed N becomes a large value, the plane where Tro is located will move toward the upper side indicated by the arrow A in the three-dimensional space, and the estimated temperature of the rotor 14 will become higher. Conversely, when the rotational speed N becomes a small value, the plane where Tro is located will move downward in the three-dimensional space, and the estimated temperature of the rotor 14 will become lower.

[0052] Figure 4 : is a graph showing the relationship between the actual temperature of the rotor 14 when the rotor 14 rotates at high speed, the estimated temperature of the rotor 14 estimated by the control device 60, and the estimated temperature of the rotor 14 estimated by the control device of the comparative example. Figure 5 This is a graph showing the relationship between the actual temperature of the rotor 14 when the rotor 14 rotates at a low speed, the estimated temperature of the rotor 14 estimated by the control device 60 , and the estimated temperature of the rotor 14 estimated by a control device of a comparative example.

[0053] like Figure 4 As shown, in the high rotation speed range, during the initial period from the measurement start time, the estimated temperature of rotor 14 estimated using the method of the present disclosure is substantially consistent with the actual temperature of rotor 14. On the other hand, the estimated temperature of rotor 14 estimated using the method of the comparative example is somewhat higher than the actual temperature of rotor 14. Therefore, during the initial period from the measurement start time in the high rotation speed range, the method of the present disclosure can estimate the actual temperature of rotor 14 with higher accuracy than the method of the comparative example. Furthermore, as time elapses from the measurement start time, the estimated temperature of rotor 14 using the method of the present disclosure and the estimated temperature of rotor 14 using the method of the comparative example are substantially consistent, and the estimated temperature tends to increase by the same degree as the actual temperature of rotor 14.

[0054] In contrast, Figure 5 As shown, in the low rotation speed range, the estimated temperature of rotor 14 estimated using the comparative example method significantly increases compared to the actual temperature of rotor 14 throughout all periods from the start of measurement. On the other hand, the estimated temperature of rotor 14 estimated using the method of the present disclosure increases compared to the actual temperature of rotor 14 throughout all periods from the start of measurement, but the magnitude of this increase is significantly reduced to approximately half the magnitude of the increase using the comparative example method. Therefore, in the low rotation speed range, using the method of the present disclosure to estimate the temperature of rotor 14 can more accurately estimate the temperature of rotor 14 than using the comparative example method.

[0055] Next, the reason why the method of the present disclosure has superior performance in estimating the temperature of the rotor 14 in the low rotation speed range compared to the method of the comparative example will be described. Figure 6 is a graph showing the relationship between the rotational speed of the motor 10 and the maximum torque that the motor 10 is allowed to generate at each rotational speed. Figure 6 In FIG. 1 , the dotted line shows the relationship between the rotational speed and the maximum torque when the temperature of the rotor 14 is Tα° C., and the solid line shows the relationship between the rotational speed and the maximum torque when the temperature of the rotor 14 is Tβ° C. (Tβ>Tα).

[0056] It is known that when motor 10 is driven at high temperatures or when it generates a torque exceeding the allowable torque, the magnetic flux decreases due to fluctuations and reversals in the magnetic moment caused by thermal vibrations, resulting in demagnetization, in which the magnetic flux does not return to its previous state. The solid line is positioned below the dashed line because demagnetization occurs at a lower generated torque when the temperature of motor 10 is high.

[0057] like Figure 6 As shown, the torque allowed to be generated decreases as the rotation speed of the motor 10 increases. That is, when the rotation speed of the motor 10 increases, the maximum value of the torque generated by the motor 10 needs to be limited. In this context, in the comparative example method, that is, the method of estimating the temperature of the rotor 14 without considering the rotation speed of the motor 10, in order to avoid demagnetization, even when the rotation speed is low, it is assumed that the rotation speed is high, and thus the torque generated by the motor 10 needs to be limited. As a result, in the comparative example method, even in the low rotation speed range where high torque is allowed, the generated torque is excessively limited, so that the performance of the motor 10 cannot be fully utilized in the low rotation speed range, and the motor 10 cannot be driven efficiently in the low rotation speed range.

[0058] In contrast, in the method disclosed herein, the temperature of the rotor 14 is estimated by taking into account the rotational speed of the motor 10. Figure 5 As shown, in the low-speed rotation area, the estimated temperature of the rotor 14 can be made to be a temperature that is significantly lower than the estimated temperature of the comparative example method and higher than the actual temperature of the rotor 14. As a result, the maximum torque that can be generated in the low-speed rotation area can be significantly increased, thereby enabling the motor 10 to be driven particularly efficiently.

[0059] In the electric vehicle 1, the motor 10 is operated at a high speed in limited situations such as highway driving, and is mostly operated at a low speed during normal driving, i.e., street driving. Therefore, if the control device 60 of the present disclosure is installed in a vehicle (not limited to the electric vehicle 1, but also a hybrid vehicle), the maximum torque that can be generated in the low-speed rotation range that accounts for the majority of driving can be significantly increased, and the motor 10 can be driven extremely efficiently, thereby achieving significant operational effects.

[0060] Figure 7 This is a flowchart for explaining the process of estimating the temperature of the rotor 14 in the electric vehicle 1. Figure 7 When the electric vehicle 1 is started and power is supplied to the motor 10, the process begins. In step S1, the resolver 18 detects the rotational speed N of the rotor 14. In the following step S2, the first temperature sensor 17 detects the coil temperature Tst, and the second temperature sensor 25 detects the refrigerant temperature Tr. In the following step S3, the rotor temperature estimating unit 62a of the control device 60 calculates the temperature Tro of the rotor 14 (which is consistent with the temperature of the permanent magnet 15) based on the rotational speed N, the coil temperature Tst, the refrigerant temperature Tr, and the above-mentioned formula (2) stored in the storage unit 64. In the following step S4, the rotor temperature estimating unit 62a adjusts the temperature change amount to a temperature change amount based on the physical quantity based on the previously estimated temperature Tro, that is, Tro in the previous control cycle, and the temperature Tro calculated in step S3, thereby determining the current estimated temperature Tro of the rotor 14.

[0061] This adjustment can be performed using, for example, filtering, current limiting, or moving average processing. This adjustment suppresses a sharp increase in the rotor 14 temperature Tro from the previous estimated value. When filtering, for example, a known Kalman filter can be used to determine the final estimated rotor 14 temperature Tro based on the temperature Tro calculated in step S3 and the previously estimated rotor 14 temperature Tro.

[0062] Furthermore, when current limiting is performed, a linear function is defined. If the rate of change of the temperature Tro calculated in step S3 relative to the previous estimated temperature Tro exceeds the rate of change of this linear function, the rate of change of the final estimated temperature Tro relative to the previous estimated temperature Tro is replaced by the rate of change of this linear function. Furthermore, the moving average process estimates the final estimated temperature Tro by calculating the average of not only the previous temperature Tro but also the temperature Tro calculated in step S3 for multiple times before the current one.

[0063] This adjustment requires at least the last estimated temperature Tro. However, the last estimated temperature Tro is not available for the initial temperature estimation after the electric vehicle 1 is driven. In such a case, for example, the coil temperature detected by the first temperature sensor 17 can be used as the estimated temperature Tro during driving (when the power is turned on), or the refrigerant temperature detected by the second temperature sensor 25 can be used as the estimated temperature Tro during driving. However, it is also possible to estimate the estimated temperature Tro during driving with high accuracy. The method for estimating the estimated temperature Tro during driving will be described in detail later.

[0064] This temperature change adjustment is performed for the following reasons. For example, if the driver accidentally over-accelerates, causing wheel spin, the rotational speed can increase dramatically for a moment, and the estimated temperature of the rotor 14 can also increase momentarily. However, if the rotational speed of the rotor 14 increases only momentarily, the actual temperature of the rotor 14 will not increase. This temperature change adjustment is performed to eliminate such situations.

[0065] Figure 8 This is a diagram for explaining the summary of the change in estimated temperature before and after the temperature adjustment in step S4. Figure 8 In FIG, the dotted line indicates the estimated temperature before the temperature adjustment in step S4, and the solid line indicates the estimated temperature after the temperature adjustment in step S4. Figure 8 As shown, by performing step S4 , local unevenness in the graph representing the fluctuation of the estimated temperature with respect to time can be reduced, the graph can be smoothed, and the accuracy of the estimated temperature can be improved.

[0066] Next, control of the electric motor 10 by the control device 60 will be described. Figure 9 This is a flowchart for explaining the operation process when the control device 60 controls the output characteristics of the motor 10. Figure 9 When the electric vehicle 1 is started and electric power is supplied to the motor 10, the process starts. In step S11, the motor control unit 62d controls the accelerator sensor 8 (see FIG. Figure 1 ) signal to obtain the command torque Tra. In the next step S12, the rotor temperature estimation unit 62a uses Figure 7 The temperature of the rotor 14 is estimated according to the process described above, and the process proceeds to step S13.

[0067] In step S13, the motor control unit 62d determines whether the temperature Tro of the rotor 14 estimated by the rotor temperature estimating unit 62a is higher than the temperature threshold T1 stored in the storage unit 64. If a negative determination is made in step S13, and the motor control unit 62d determines that the temperature Tro is lower than the temperature threshold T1, the process proceeds to step S14, where the motor control unit 62d outputs a PWM signal for generating torque Tra to the inverter 30, causing the motor 10 to generate torque Tra. Control then returns to step S11 and the steps following it are repeated.

[0068] On the other hand, if an affirmative determination is made in step S13 and the motor control unit 62d determines that the temperature Tro exceeds the temperature threshold T1, the process proceeds to step S15 to calculate the permissible torque Trb at the estimated temperature Tro of the rotor 14. Specifically, the permissible torque Trb is calculated using a torque limit map. Figure 10 This is a graph showing an example of the relationship between temperature and torque that can be used as a torque limit map, and is a graph showing the relationship between temperature and the maximum torque that can be generated at that temperature. Figure 10 Here, TrA is the maximum torque that can be generated by the motor 10, and TrB is the limit torque when the estimated temperature of the rotor 14 is T2. In addition, T1 is the torque limit start temperature.

[0069] exist Figure 10 In the example shown, the maximum torque generated by the motor 10, TrA, represents the maximum torque that the motor 10 can generate until the temperature of the rotor 14 reaches the temperature threshold T1. On the other hand, when the temperature of the rotor 14 exceeds the temperature threshold T1, the maximum torque generated by the motor 10 decreases as a linear function as the temperature increases. Using this torque limit map, the maximum torque that can be generated in the region where the estimated temperature of the rotor 14 is high can be limited through simple control, while also reliably preventing demagnetization of the permanent magnets 15 embedded and fixed to the rotor 14.

[0070] It should be noted that the description above describes a case where the maximum value of the torque generated by the motor 10 decreases as the temperature increases, following a linear function, when the temperature of the rotor 14 exceeds the temperature threshold T1. However, the maximum value of the torque generated by the motor 10 may decrease as the temperature increases, following any function other than a linear function. For example, the maximum value of the torque generated by the motor 10 may decrease as the temperature increases, following a function that has a plateau, such as a broken line, or according to a higher-order function, such as a quadratic function, when the temperature of the rotor 14 exceeds the temperature threshold T1.

[0071] Return to Figure 9In the flowchart shown, in step S16 following step S15, the motor control unit 62d outputs a PWM signal for generating the torque Trb calculated in step S15 to the inverter 30, and the motor 10 generates the torque Trb. After that, the control is returned to repeat the steps from step S11 onwards. For example, when the electric vehicle 1 reaches the destination and the power to the motor 10 is cut off, Figure 9 The control of the illustrated electric motor 10 is completed.

[0072] Next, we will describe the control of the electric motor 10 during the first cycle of starting the electric vehicle 1 after the electric vehicle 1 is powered off (after the power supply from the battery 20 to the electric motor 10 is cut off). As mentioned above, when smoothing the estimated temperature of the rotor 14 and performing filtering and current limiting, it is necessary to refer to the estimated temperature of the previous control cycle. However, in the first cycle of starting the electric vehicle 1, there is no initial temperature to refer to, so an initial temperature estimation is required.

[0073] In the control device 60, the startup temperature estimating unit 62c estimates the initial temperature of the rotor 14 as follows. Figure 11 , that is, the relationship between the magnet temperature of the permanent magnets 15 of the rotor 14 and the power-off time at which the power to the motor 10 is cut off. The magnet temperature and the power-off time are correlated. The startup temperature estimating unit 62c estimates the initial temperature of the rotor 14 to be used as a reference when restarting the electric vehicle 11 based on information about the estimated temperature Tro of the rotor 14 immediately before power-off, information about the power-off time from the timer 5, and mapping information pre-stored in the storage unit 64 that defines the correlation between the magnet temperature and the power-off time.

[0074] According to the technology disclosed in the present invention, the initial temperature of the rotor 14 to be referred to when restarting the electric vehicle 1 can be accurately estimated by the startup temperature estimating unit 62c. Figure 11 Unlike the case where the initial temperature of the permanent magnet is not estimated and the previous value is maintained as shown by the line a in FIG, the estimated temperature of the permanent magnet 15 does not exceed the actual temperature excessively, and the motor 10 can be easily operated efficiently from the time of restarting the motor 10. Figure 11 Unlike the case where the initial temperature of the permanent magnet is not estimated but is set to a constant temperature as shown by the line b in the figure, the estimated temperature of the permanent magnet 15 can be prevented from falling below the actual temperature, and the magnetic force of the permanent magnet 15 can be protected.

[0075] It should be noted that, although the power-off time is estimated using the timer 5, the power-off time may be estimated based on the temperature change of the first temperature sensor 17 that detects the temperature of the stator 12, the second temperature sensor 25 that detects the temperature of the refrigerant, or other temperature sensors mounted on the electric vehicle 1. As an example, the case of using the detection value of the first temperature sensor 17 or the second temperature sensor 25 will be described. Figure 12 As shown, the power-off time is correlated with the temperature changes of stator 12 and the refrigerant. Therefore, the power-off time can be estimated by detecting these temperature changes with first temperature sensor 17 or second temperature sensor 25. This allows the initial temperature to be estimated without using timer 5, thus eliminating the need for timer 5 and reducing manufacturing costs.

[0076] It should be noted that the initial temperature of the rotor 14 may be estimated using only one of the temperatures detected by the first temperature sensor 17 and the second temperature sensor 25. However, by calculating the average of the multiple initial temperatures of the rotor 14 estimated based on the detection values ​​of the multiple sensors and setting this average as the initial temperature, the difference between the initial temperature and the actual temperature of the rotor 14 when the power is restarted can be easily reduced, and the initial temperature of the rotor 14 can be estimated with high accuracy.

[0077] Next, a method for the control device 60 to control the driving conditions of the motor 10 using the estimated rotor temperature will be described. The method for the control device 60 to control the output characteristics of the motor 10 using the estimated rotor temperature is described above. Figure 9 However, the control device 60 may control the driving conditions of the electric motor 10 using the estimated rotor temperature.

[0078] In detail, Figure 13 As shown in the flowchart illustrating the operational process of control device 60 controlling the driving conditions of motor 10, when electric vehicle 1 is started and power is supplied to motor 10, thereby initiating the process, control device 60 may also obtain a requested performance value C1 in step S21. Requested performance value C1 may include, for example, one or more of the voltage applied to motor 10, the carrier frequency that determines the pulse width modulation cycle in PWM control, the amount of oil circulated by turning the start switch of oil pump 23 on / off, the amount of cooling air flowing based on the duty cycle of the radiator fan, the amount of cooling water circulating based on the duty cycle of the water pump, or the amount of air passing through the vehicle based on the opening and closing of the grille shutter.

[0079] In the next step S22, the rotor temperature estimation unit 62a uses Figure 7The temperature of the rotor 14 is estimated using the previously described process, and the process proceeds to step S23. In step S23, the control device 60 determines whether the temperature Tro of the rotor 14 estimated by the rotor temperature estimating unit 62a is higher than the temperature threshold T2 stored in the storage unit 64. If a negative determination is made in step S23, and the control device 60 determines that the temperature Tro is lower than the temperature threshold T2, the process proceeds to step S24, where the control device 60 performs control to achieve the requested performance value C1. Afterward, control returns to repeat the steps following step S21.

[0080] On the other hand, if a positive determination is made in step S23, indicating that temperature Tro exceeds temperature threshold T2, the control device proceeds to step S25, where it calculates an allowable performance value C2 for the estimated rotor 14 temperature Tro. Specifically, the control device calculates or determines the allowable voltage value, allowable carrier frequency, whether to drive the oil pump 23, the allowable duty cycle of the radiator fan, the allowable duty cycle of the water pump, and whether to open the grille shutter using at least one of a program, data, and map stored in the storage unit 64. Following step S25, in step S26, the control device performs control to achieve allowable performance value C2. After this, control returns to repeat the steps from step S21 onward.

[0081] Reducing the voltage applied to motor 10 reduces the Joule heat generated in motor 10, thereby lowering the temperature of motor 10. Furthermore, the temperature of motor 10 can be lowered by changing the permissible carrier frequency, driving oil pump 23, increasing the permissible duty cycle of the radiator fan, increasing the permissible duty cycle of the water pump, or opening the grille shutter. This control increases the maximum torque value that motor 10 can generate, particularly in the low-speed rotation range, enabling efficient operation of motor 10.

[0082] As described above, the control device 60 of the present disclosure controls the electric motor 10 mounted on the electric vehicle 1. Furthermore, the control device 60 includes: a rotor temperature estimating unit 62a for estimating the temperature of the rotor 14 based on stator temperature information from a first temperature sensor (stator temperature determining unit) 17 for determining the temperature of the stator 12, refrigerant temperature information from a second temperature sensor (refrigerant temperature determining unit) 25 for determining the temperature of the refrigerant used to cool the electric motor 10, and rotor 14 speed information from a resolver (speed determining unit) 18 for determining the speed of the rotor 14; and a motor control unit 62d for controlling at least one of the output characteristics and driving conditions of the electric motor 10 based on the temperature of the rotor 14 estimated by the rotor temperature estimating unit 62a.

[0083] According to the present disclosure, control device 60 controls at least one of the output characteristics and driving conditions of motor 10 by taking into account the rotational speed of rotor 14 in addition to stator temperature information and refrigerant temperature information. This prevents excessive restriction of the output of motor 10 during low-speed rotation, and enables efficient operation of motor 10 in both low-speed and high-speed rotation conditions.

[0084] In addition, the rotor 14 may include a permanent magnet 15. Also, it may be possible to use Figure 9 and Figure 13 As described above, the control unit 62 controls at least one of the output characteristics and the driving conditions of the electric motor 10 based on the temperature of the rotor 14 so that the permanent magnets 15 are not demagnetized.

[0085] According to this configuration, demagnetization of the permanent magnets 15 of the rotor 14 can be effectively suppressed or prevented.

[0086] In addition, the control device 60 may also include: a power cut-off time determination unit 62b, which determines the power cut-off time at which the power of the electric vehicle 1 is cut off; and a startup temperature estimation unit 62c, which estimates the temperature of the rotor 14 when the electric vehicle 1 is powered on after the power cut-off time ends based on the power cut-off time and the temperature of the rotor 14 just before the power is cut off estimated by the rotor temperature estimation unit 62a.

[0087] This configuration allows the temperature of the rotor 14 to be estimated at vehicle startup. This allows the motor 10 to operate efficiently and output high torque from the time the vehicle is started, thus achieving a powertrain with excellent responsiveness to operation from the time the vehicle is started.

[0088] Furthermore, if the last estimated temperature of rotor 14 can be determined, the temperature of rotor 14 can be estimated with high accuracy using filtering, current limiting, and the like. However, the last estimated temperature of rotor 14 does not exist at vehicle startup, making it impossible to estimate the temperature of rotor 14 with high accuracy. In contrast, according to this configuration, the temperature of rotor 14 at vehicle startup can be estimated even at vehicle startup, making it easier to estimate the temperature of rotor 14 with high accuracy from the time the vehicle is started.

[0089] It should be noted that the present disclosure is not limited to the above-described embodiment and its modifications, and various improvements and changes are possible within the scope of the claims of the present application and their equivalents.

[0090] For example, in the above embodiment, the above formula (2) is used to estimate the temperature of the rotor 14, and a term proportional to the rotational speed N is added to the formula for calculating the provisional Tro. However, the formula for calculating the provisional Tro may be a formula in which a constant is added to the above formula (2). Alternatively, the formula for calculating the provisional Tro may include a function F(N) that is defined by the rotational speed N and is not a linear function. For example, F(N) may include a higher-order function of quadratic or higher, or may include one or more functions selected from trigonometric functions, exponential functions, logarithmic functions, and special functions.

[0091] In addition, use Figure 9 The case where the output characteristics of the motor 10 are controlled based on the temperature of the rotor 14 estimated by the rotor temperature estimating unit 62a has been described. Figure 13 The driving conditions of the motor 10 are controlled based on the temperature of the rotor 14 estimated by the rotor temperature estimating unit 62a. However, the control device of the present disclosure may control both the output characteristics and the driving conditions of the motor based on the rotor temperature estimated by the rotor temperature estimating unit.

[0092] Furthermore, the description above illustrates a case where the stator temperature determination unit is the first temperature sensor 17, the refrigerant temperature determination unit is the second temperature sensor 25, and the rotational speed determination unit is the resolver 18. However, the stator temperature determination unit, the refrigerant temperature determination unit, and the rotational speed determination unit may also estimate one or more of the stator temperature, the refrigerant temperature, and the rotor rotational speed based on one or more physical information related to the electric motor, such as the voltage applied to the electric motor, the power supplied by the electric motor, the current supplied to the electric motor, the duty cycle of the radiator fan, and the duty cycle of the water pump, and software. Furthermore, the description above illustrates an electric vehicle 1, but the vehicle may also be a hybrid vehicle equipped with an internal combustion engine in addition to the electric motor.

[0093] In addition, the case where the electric motor 10 has permanent magnets 15 has been described. However, the electric motor may also be an electric motor without permanent magnets, such as an induction motor, an SR (Switched Reluctance) motor, etc. In electric motors, it is generally known that the efficiency decreases as the temperature of the conductor in the rotor increases. Therefore, by using the technology disclosed in the present invention, for example, even in an electric motor without permanent magnets, by estimating the temperature of the rotor and operating the cooling pump when the temperature exceeds a certain temperature, the efficiency decrease of the electric motor can be effectively suppressed or prevented. The rotor of the electric motor increases in temperature due to iron loss caused by rotation and heat from the stator. By using the technology disclosed in the present invention, regardless of whether the electric motor has permanent magnets, the components of the electric motor can be reliably protected from thermal damage, and the strength decrease caused by the temperature characteristics of the steel plate can be reliably prevented.

[0094] This application claims priority from Japanese Patent Application No. 2021-073551 filed on April 23, 2021, the entire contents of which including the specification, claims, drawings, and abstract are incorporated herein by reference.

Claims

1. A control device (60) for controlling an electric motor (10) mounted on a vehicle (1), the control device (60) comprising: a rotor temperature estimating unit (62a) for estimating the temperature of the rotor (14) based on stator temperature information from a stator temperature determining unit (17) for determining the temperature of the stator (12), refrigerant temperature information from a refrigerant temperature determining unit (25) for determining the temperature of a refrigerant used for cooling the electric motor (10), and rotational speed information of the rotor (14) from a rotational speed determining unit (18) for determining the rotational speed of the rotor (14); a control unit (62) for controlling at least one of an output characteristic and a driving condition of the electric motor (10) based on the temperature of the rotor (14) estimated by the rotor temperature estimating unit (62a); a power-off time determining unit (62b) for determining a power-off time at which a power source (20) of the vehicle (1) is cut off; as well as A startup temperature estimating unit (62c) estimates the temperature of the rotor (14) when the vehicle (1) is powered on after the power-off time ends, based on the power-off time and the temperature of the rotor (14) immediately before the power (20) is shut off, estimated by the rotor temperature estimating unit (62a). The rotor temperature estimating unit (62a) determines the estimated temperature of the rotor (14) by adjusting the temperature change amount to the temperature change amount based on the physical quantity based on the temperature of the rotor (14) estimated last time, that is, the temperature of the rotor (14) in the previous control cycle, the stator temperature information, the refrigerant temperature information, and the rotation speed information. The adjustment of the temperature change is performed using filtering, current limiting or moving average processing. The temperature of the rotor (14) in the previous control cycle in the first cycle when starting the vehicle (1) is the temperature of the rotor (14) when the vehicle (1) is powered on, estimated by the startup temperature estimating unit (62c).

2. The control device (60) according to claim 1, wherein: The rotor (14) includes permanent magnets (15), The control unit (62) controls at least one of the output characteristics and the driving conditions of the motor (10) based on the temperature of the rotor (14) so ​​that the permanent magnet (15) is not demagnetized.

3. The control device (60) according to claim 1 or 2, comprising: Before the temperature of the rotor (14) estimated by the rotor temperature estimating unit (62a) reaches a temperature threshold, the control unit (62) controls at least one of the output characteristics and the driving conditions of the motor (10) so that the maximum value of the generated torque of the motor (10) becomes the maximum torque that can be generated by the motor (10). When the temperature of the rotor (14) estimated by the rotor temperature estimation unit (62a) exceeds the temperature threshold, the control unit (62) controls at least one of the output characteristics and the driving conditions of the motor (10) so that the maximum value of the generated torque of the motor (10) decreases as the estimated temperature of the rotor (14) increases.

4. A vehicle (1) comprising the control device (60) according to any one of claims 1 to 3.

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