Vehicle control method and electric vehicle

Abstract

The present invention provides a vehicle control method and an electric vehicle that can provide timely notification regarding the limiting of the electric motor's output, even on uphill sections of roads. [Solution] The electric vehicle 10 calculates a moving average of the actual output torque of the electric motor 3, calculates the protection temperature corresponding to the moving average as the first temperature based on map data showing the relationship between the output torque of the electric motor 3 and the protection temperature, calculates the temperature rise of the electric motor 3 per unit time, calculates the estimated time it will take for the electric motor 3 to rise from the current temperature to the first temperature based on the temperature rise per unit time, and notifies the driver that output limiting will be applied if the calculated estimated time is less than or equal to the reference time.

Description

[Technical Field]

[0001] This invention relates to a vehicle control method and an electric vehicle. [Background technology]

[0002] Conventionally, in electric vehicles powered by electric motors, the motor load increases and generates heat when the driver operates the accelerator. In such electric vehicles, if the motor temperature rises and reaches a predetermined protection temperature, the output of the electric motor may be limited. When the output of the electric motor is limited, the vehicle will not accelerate even if the driver presses the accelerator, which may cause discomfort to the driver. In contrast, there is a known technology that calculates the remaining time until the motor temperature reaches the protection temperature and notifies the driver of the calculated remaining time via audio output or display (see, for example, Patent Document 1). In Patent Document 1, from the d-axis current command value id and the q-axis current command value iq, Ia = √(id 2 +iq 2 The current value Ia to be applied to the electric motor is determined by the following method. Data showing the relationship between the current value Ia and the electric motor's temperature rise curve is prepared in advance, and the remaining time until the electric motor reaches the protection temperature from the current temperature is calculated based on the temperature rise curve for the determined current value Ia. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2003-134609 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, while the above-mentioned conventional technology works effectively under the condition that the current value Ia is constant, on steep uphill roads, when accelerator operation is frequent or acceleration and deceleration are large, the current value Ia also changes frequently, making it difficult to calculate the remaining time until the protection temperature is reached. As a result, there is a problem that the driver may not be able to be notified about the electric motor output limit at an appropriate time.

[0005] The present invention aims to provide a vehicle control method and an electric vehicle that can provide timely notification regarding the limiting of the output of the electric motor, even on an uphill road. [Means for solving the problem]

[0006] A vehicle control method according to one aspect of this disclosure provides notification regarding the output limiting of an electric motor in an electric vehicle that is driven by the driving force of an electric motor. Specifically, it calculates a moving average value of the actual output torque of the electric motor and uses an output limiting map that shows the relationship between the output torque of the electric motor and the protection temperature to calculate the protection temperature corresponding to the moving average value as the first temperature. It also monitors the temperature of the electric motor and calculates the temperature rise per unit time, and based on this temperature rise per unit time, it calculates the estimated time it will take for the electric motor to rise from the current temperature to the first temperature. When the estimated time falls below a predetermined reference time, it notifies the driver that output limiting will be applied.

[0007] This allows the system to determine whether or not to issue an output limit notification based on a predicted temperature derived from actual motor temperature measurements. Therefore, even when the driver frequently operates the accelerator on an uphill road or when there are large accelerations and decelerations, the system can notify the driver about the electric motor's output limit at an appropriate time. [Brief explanation of the drawing]

[0008] [Figure 1] A block diagram showing the configuration of a vehicle (electric vehicle) according to one embodiment of the present disclosure. [Figure 2]Block diagram showing the functional configuration of the controller in this embodiment. [Figure 3] Diagram showing an example of fluctuations in the output torque of the electric motor when the vehicle is running, and the moving average value of the output torque. [Figure 4] Diagram showing an example of the relationship between the rotational speed and output torque of the electric motor, and the range where the first torque threshold value is exceeded. [Figure 5] Diagram showing an example of the relationship between the rotational speed and output torque of the electric motor, and another example of the range where the first torque threshold value is exceeded. [Figure 6] Diagram showing an example of the temperature of the electric motor detected by the temperature sensor in this embodiment. [Figure 7] Diagram showing an example of torque output rate map data representing the relationship between the protection temperature of the electric motor and the output limitation rate in the electric motor. [Figure 8] Flowchart showing the vehicle control method of this embodiment. [Figure 9] Flowchart showing the cancellation of the notification of output limitation in the vehicle control method of this embodiment. [Figure 10] Flowchart showing another example of the cancellation of the notification of output limitation in the vehicle control method of this embodiment. [Figure 11] (A) is a diagram showing the output limitation rate, motor temperature, moving average value of the output torque, and notification timing of output limitation when the moving average value of the output torque is 100 [Nm], and (B) is a diagram showing the output limitation rate, motor temperature, and notification timing of output limitation in the comparative example when the moving average value of the output torque is 100 [Nm]. [Figure 12] (A) is a diagram showing the output limitation rate, motor temperature, moving average value of the output torque, and notification timing of output limitation when the moving average value of the output torque is 200 [Nm] in the example, and (B) is a diagram showing the output limitation rate, motor temperature, and notification timing of output limitation in the comparative example when the moving average value of the output torque is 200 [Nm].

Mode for Carrying Out the Invention

[0009] An embodiment of this disclosure will be described below. [Electric Vehicle Configuration] Figure 1 is a block diagram showing the configuration of the vehicle 10 (electric vehicle) according to this embodiment. The vehicle 10 includes a battery 1, an inverter 2, an electric motor 3, a position detection sensor 4, a navigation device 5, a notification device 6, and a controller 7.

[0010] Battery 1 supplies power to the electric motor 3 via inverter 2. The inverter 2 converts the DC power supplied from the battery 1 into AC power suitable for driving the electric motor 3, and supplies this AC power to the electric motor 3.

[0011] The electric motor 3 is driven by electricity supplied from the inverter 2 to move the vehicle 10. The electric motor 3 also functions as a generator, generating electricity (regenerative braking) when the vehicle 10 decelerates and outputting the generated electricity to the inverter 2. Furthermore, the electric motor 3 includes a temperature sensor 3a for detecting the temperature of the electric motor 3 (for example, the coil temperature), and a torque sensor 3b (operating state detection unit) provided on the motor shaft (not shown). In this embodiment, an example is shown in which the output torque of the electric motor 3 is detected by the torque sensor 3b, but the torque of the electric motor 3 may also be calculated based on the d-axis current command value and the q-axis current command value input from the inverter 2 to the electric motor 3.

[0012] The position detection sensor 4 is a sensor that detects the current position of the vehicle. Examples of position detection sensors 4 include receivers that receive GNSS (Global Navigation Satellite System) satellite signals to determine the current position.

[0013] The navigation device 5 obtains road information on which the vehicle 10 is traveling by referring to the current position of the vehicle 10 acquired by the position detection sensor 4 and pre-stored map information. The map information may be stored in a storage device 7a such as a memory provided in the controller 7, or it may be downloaded from a predetermined map server via the internet. Furthermore, the road information included in the map information may include, for example, road surface gradient, and the average torque when driving on an uphill road.

[0014] The notification device 6 is a device for notifying the driver of information regarding the vehicle 10, and examples include an instrument panel consisting of a liquid crystal panel for displaying image information, and a speaker for outputting audio information. For example, in this embodiment, as will be described later, the notification device 6 lights up an indicator light 6a to show the driver that the output of the electric motor 3 is being limited.

[0015] The controller 7 controls the inverter 2 to control the drive of the electric motor 3. The controller 7 also controls the notification device 6 to broadcast various information from the notification device 6. Furthermore, the controller 7 controls the navigation device 5 to acquire map information from the navigation device 5.

[0016] The controller 7 is a computer equipped with a storage device 7a such as memory, and a processor 7b such as a CPU (Central Processing Unit). The processor 7b reads and executes a program stored in the storage device 7a, thereby notifying the driver of the vehicle 10 about the output limit of the electric motor 3.

[0017] In other words, conventionally, when a vehicle is in motion, for example, when driving on a continuous uphill road, in driving conditions where the vehicle load is high and a large output torque is continuously required of the electric motor, the amount of heat generated by the electric motor increases, and the temperature of the electric motor rises. The electric motor has a preset upper temperature limit (protection temperature) that takes into account the effects of deterioration of resin parts such as insulating materials and demagnetization of permanent magnets due to the rise in temperature. In driving conditions where the temperature of the electric motor rises in this way, control is performed to limit the output torque by predicting the temperature of the electric motor so that it does not exceed the protection temperature. If the output torque of the electric motor is limited while the vehicle is in motion, the vehicle may not be able to accelerate sufficiently, causing discomfort to the driver. Furthermore, on steep uphill roads, insufficient output torque could lead to the vehicle coming to a complete stop. To prevent this, it is common practice to inform the driver in advance when limiting the output torque of the electric motor.

[0018] In driving conditions such as those described above, where the vehicle is traveling on a continuous uphill road, the driver frequently operates the accelerator pedal, causing the required torque of the electric motor to change frequently. This made it difficult to accurately predict the temperature of the electric motor. Consequently, there was a problem in being unable to provide timely notifications to the driver. In contrast, in the vehicle 10 of the embodiment of the present invention, the controller 7 is configured to predict the time until output limiting is applied based on the measured temperature of the electric motor 3, and to notify the driver of information regarding output limiting at an appropriate time.

[0019] Figure 2 is a block diagram showing the functional configuration of controller 7. In this embodiment, the controller 7 functions as an average torque calculation unit 11, a unit temperature rise calculation unit 12, a first temperature calculation unit 13, a time calculation unit 14, and a notification control unit 15, as shown in Figure 2, by having the processor 7b read and execute a program recorded in the storage device 7a.

[0020] The average torque calculation unit 11 calculates a moving average value of torque from the actual output torque of the electric motor 3 within a predetermined period. In this embodiment, the output torque of the electric motor 3 is obtained from the torque sensor 3b, but it may also be calculated from the d-axis current command value, q-axis current command value, etc., input from the inverter 2 to the electric motor 3.

[0021] Figure 3 shows an example of the fluctuation in the output torque of the electric motor 3 while the vehicle 10 is in motion, and the moving average value of said output torque. In Figure 3, the dashed line shows an example of the actual output torque of the electric motor 3, and the solid line shows the moving average value of said output torque. The average torque calculation unit 11 acquires the actual output torque of the electric motor 3 at predetermined sampling intervals (e.g., 10-millisecond intervals). Furthermore, the average torque calculation unit 11 calculates a moving average value A1 of this actual output torque. The time interval used to calculate the moving average value is not particularly limited and can be set appropriately based on experimental results. For example, a moving average value over a 60-second time interval can be used, that is, the average value of the output torque detected from the present to 60 seconds ago.

[0022] In this example, 60 seconds is used as the time interval for calculating the moving average value A1 of the output torque of the electric motor 3, but this can be changed depending on the operating state of the vehicle 10. For example, the time interval for calculating the moving average value A1 of the output torque may be changed according to the amount the driver presses the accelerator pedal. In other words, when the driver presses the accelerator pedal a large amount, the output torque of the electric motor 3 increases, and the temperature of the electric motor 3 tends to rise. In this case, the value of the moving average value A1 becomes large, and the timing of the output limit notification may become too early. Therefore, by setting the time interval for calculating the moving average value A1 to be longer the greater the amount the driver presses the accelerator pedal, the timing of the output limit notification can be made more appropriate. On the other hand, if the driver only presses the accelerator pedal a small amount, the moving average value A1 of the output torque will be small, and the timing of the output limit notification will not be earlier, so the time interval can be set to be shorter.

[0023] Alternatively, the time interval may be set shorter if the current output torque of the electric motor 3 is high, or the predetermined period may be set shorter if the current temperature of the electric motor 3 is high. When the output torque of the electric motor 3 is high, or when the temperature of the electric motor 3 is high, the load on the electric motor 3 is high, and it is considered that the time until the electric motor 3 reaches the protection temperature is short. In such cases, by setting a shorter time interval for calculating the moving average value of the output torque, the driver can be notified of the output limit earlier. On the other hand, if the output torque of the electric motor 3 is low, or if the temperature of the electric motor 3 is low, the load on the electric motor 3 is low, and by setting a longer time interval for calculating the moving average value of the torque, unnecessary output limiting notifications can be prevented.

[0024] Furthermore, in this embodiment, the moving average value A1 of the output torque calculated by the average torque calculation unit 11 is a predetermined first torque threshold A R If the above conditions are met, the unit temperature rise calculation unit 12, the first temperature calculation unit 13, the time calculation unit 14, and the notification control unit 15 perform calculation processing. In other words, if the output torque of the electric motor 3 is small and the temperature of the electric motor 3 is low (there is a low possibility of reaching the protection temperature), the processing related to notification regarding the output limit of the electric motor 3 is omitted, thereby reducing the processing load on the controller 7.

[0025] Figure 4 shows an example of the relationship between the rotational speed and output torque of the electric motor 3, and the first torque threshold A. R This figure shows the range that exceeds the specified limit. In FIG. 4, line L1 shows the relationship between the rotational speed that can be output from the electric motor 3 and the maximum torque with respect to the rotational speed of the electric motor 3. The maximum torque is constant up to a predetermined first rotational speed R1, and when the rotational speed becomes higher than the first rotational speed R1, the maximum torque that can be output gradually decreases. Also, line L2 shows the 5-minute rated torque in the electric motor 3, and line L3 shows the continuous rated torque. That is, line L2 shows the relationship between the rotational speed and torque that do not reach the protection temperature when continuously operated for 5 minutes, and line L3 shows the relationship between the rotational speed and torque that do not reach the protection temperature when continuously operated indefinitely. In the 5-minute rating and continuous rating, in the range where the rotational speed is low, the torque that does not reach the protection temperature is a constant value, but it gradually decreases after a predetermined rotational speed R2. Here, in the example of FIG. 4, the maximum value (fixed value) of the 5-minute rated torque is set as the first torque threshold A R Thus, when the moving average value A1 of the output torque of the electric motor 3 calculated by the average torque calculation unit 11 is included in the range Q1 in FIG. 4, the controller 7 performs the arithmetic processing of the unit temperature rise calculation unit 12, the first temperature calculation unit 13, the time calculation unit 14, and the notification control unit 15. In the example of FIG. 4, the maximum torque of the 5-minute rating is set as the first torque threshold A R However, the maximum torque of the continuous rating or the maximum torque of other time ratings (for example, 10-minute rating) may be used as the first torque threshold A R

[0026] Also, in the example shown in FIG. 4, an example where the first torque threshold A R is a fixed value is shown, but the first torque threshold A R may be changed with respect to the rotational speed of the electric motor 3. FIG. 5 is a diagram showing an example of the relationship between the rotational speed and output torque of the electric motor 3 and another example of the range that is above the first torque threshold. For example, in FIG. 5, the first torque threshold A R is set to the same value as the 5-minute rated torque. In this case, when the moving average value A1 of the output torque of the electric motor 3 is included in the range Q2 sandwiched between line L1 and line L2, the controller 7 performs the arithmetic processing of the unit temperature rise calculation unit 12, the first temperature calculation unit 13, the time calculation unit 14, and the notification control unit 15.

[0027] The unit temperature rise calculation unit 12 calculates the temperature rise of the electric motor 3 per unit time. Figure 6 shows an example of the temperature of the electric motor 3 detected by the temperature sensor 3a. As described above, when a load is applied to the electric motor 3, the temperature of the electric motor 3 rises, and the greater the output torque of the electric motor 3, the greater the temperature rise. The unit temperature rise calculation unit 12 monitors the temperature change over a predetermined period detected by the temperature sensor 3a, thereby obtaining the temperature change of the electric motor 3 as shown in Figure 6, and calculates the temperature rise ΔB of the electric motor 3 per unit time from the amount of temperature rise over the predetermined period. For example, in the example shown in Figure 6, the current temperature is 170°C, and the temperature 10 seconds ago was 165°C. In this case, the unit temperature rise calculation unit 12 calculates ΔB as (170[°C]-165[°C]) / 10[seconds], resulting in ΔB = 0.5[°C / second]. The predetermined period may be the same time as the moving division when calculating the moving average value of the torque, or it may be a shorter time (for example, 10 seconds).

[0028] The first temperature calculation unit 13 calculates the protection temperature of the electric motor 3, which is subject to output limiting when the vehicle 10 continues to run at the moving average value A1, as the first temperature. Figure 7 shows an example of torque output rate map data representing the relationship between the protection temperature of the electric motor 3 and the output limiting rate of the electric motor 3. Specifically, the first temperature calculation unit 13 calculates the maximum torque A of the electric motor 3. M The ratio of the moving average value A1 of the torque to (first limiting factor A1 / A M The first temperature calculation unit 13 uses the torque output rate map data shown in Figure 7 to calculate the first limiting rate A1 / A. M The corresponding protection temperature is detected as the first temperature B1. This map data shows the correspondence between the torque of the electric motor 3 and the protection temperature of the electric motor 3 at that torque, and is pre-recorded, for example, in the memory device 7a of the controller 7. The correspondence between torque and protection temperature is determined in advance through experiments or simulations based on the characteristics of the electric motor 3. In the example shown in Figure 7, the maximum torque A that the electric motor 3 can output is... M In this case, the protection temperature is set to B0, and the map is such that the protection temperature increases as the torque decreases. In the example shown in Figure 7, the vertical axis represents the maximum torque A. M This shows the ratio of the torque of the electric motor 3 when the ratio is set to 100%, but the torque value may be used instead of the ratio.

[0029] The time calculation unit 14 uses the temperature rise ΔB of the electric motor 3 per unit time, calculated as described above, to calculate the expected time T1 for the electric motor 3 to reach the first temperature B1 from the current motor temperature B0, using the formula T1 = (B1 - B0) / ΔB.

[0030] The notification control unit 15 determines that the predicted time T1 calculated by the time calculation unit 14 is equal to a predetermined reference time T R In the following cases, the notification device 6 is controlled to notify the driver that there is a risk of the output of the electric motor 3 being limited. Here, the reference time T R This refers to the time sufficient for the driver to take appropriate action (such as changing lanes or stopping on the shoulder) after receiving a notification from the warning device 6, and is set to, for example, 10 seconds. In this embodiment, the indicator light 6a provided on the instrument panel is illuminated as a notification of the output limit of the notification control unit 15.

[0031] Furthermore, the notification control unit 15 terminates the output limit notification (turns off the indicator light 6a) when it detects that the vehicle 10 has finished climbing the uphill road (has reached the top of the uphill road) or has stopped moving (e.g., has stopped on the shoulder of the road) or has completed a retreat. The completion of the vehicle 10's ascent of the uphill road can be detected, for example, by using the vehicle 10's current position detected by the position detection sensor 4 and map information. Furthermore, the completion of the vehicle 10's retreat can be detected by a sensor signal from a wheel speed sensor (not shown) installed on the vehicle 10.

[0032] Specifically, the notification control unit 15 terminates the output limit notification after a predetermined waiting time T2 has elapsed following detection of the end of the climb or the completion of the evacuation. Here, the waiting time T2 may be a time (e.g., 60 seconds) during which the driver does not feel dissatisfied with the time interval until the next output limit notification, or it may be set to the time it takes for the vehicle 10 to reach the top of the climb. Alternatively, if the vehicle 10 has completed its climb up the climb, a fixed time may be set as the waiting time T2, and if the vehicle 10 has completed its evacuation, the time it takes for the vehicle to reach the top of the climb may be set as the waiting time T2. If the waiting time T2 is defined as the time it takes to climb the uphill road, the distance L from the vehicle 10's current position to the end of the uphill road is calculated based on map information. Additionally, the vehicle speed V of the vehicle 10 on the uphill road is calculated by detecting the vehicle speed on the uphill road using the wheel speed sensor. This allows the approximate waiting time T2 until the vehicle 10 completes the uphill road to be calculated using the formula T2 = L / V.

[0033] Alternatively, the notification control unit 15 may terminate the output limit notification after detecting the end of the operation or completion of the retraction, and when the temperature of the electric motor 3 drops to a predetermined target temperature. The target temperature B3 is calculated, for example, using the first temperature B1, the temperature rise ΔB of the electric motor 3 per unit time calculated by the unit temperature rise calculation unit 12, and the waiting time T2, by the formula B3 = B1 - ΔB·T2. In this case, it is preferable that the waiting time T2 is calculated from the distance from the vehicle 10's current position to the end of the climb based on map information, and the average speed of the vehicle 10. In this case, a target temperature B3 can be set such that the temperature of the electric motor 3 does not exceed the output limit by the time the vehicle 10 has climbed the uphill road.

[0034] [Vehicle control methods for electric vehicles] Next, we will explain the vehicle control method for vehicle 10 as described above. Figure 8 is a flowchart illustrating the vehicle control method of this embodiment, which determines whether or not to notify the driver regarding the output limit of the electric motor 3. In this embodiment, the controller 7 executes the flowchart shown in Figure 8 at a predetermined cycle (for example, 10 milliseconds). First, the average torque calculation unit 11 of the controller 7 calculates a moving average value A1 from the actual output torque of the electric motor 3 within a predetermined period (Step S1: Average Torque Calculation Step). For example, the average torque calculation unit 11 calculates a moving average value A1 for a predetermined time interval (e.g., 60 seconds) from the actual torque of the electric motor 3 as shown in Figure 3.

[0035] Next, the controller 7 determines that the calculated moving average value A1 is equal to the first torque threshold A R Determine whether the above is true or not (Step S2). First torque threshold A R As described above, a fixed value as shown in Figure 3 may be used, or a value that changes according to the rotational speed of the electric motor 3 may be used as shown in Figure 4. The first torque threshold A changes according to the rotational speed of the electric motor 3. R When using this method, in step S1, in addition to the moving average value A1, the average value (moving average) of the rotational speed of the electric motor 3 is calculated.

[0036] If the result in step S2 is NO, the notification process regarding the output limit of the electric motor 3 is terminated because it is unlikely that the temperature of the electric motor 3 will reach the protection temperature. If YES is determined in step S2, the first temperature calculation unit 13 calculates the maximum torque A of the electric motor 3. M The ratio of the moving average value A1 of the torque to the first limiting factor A1 / A M ) is calculated, and the first limiting ratio A1 / A is calculated using the torque output rate map data shown in Figure 5 stored in the memory device 7a. M The corresponding protection temperature is calculated as the first temperature B1 (Step S3: First temperature calculation step). As mentioned above, the relationship between the output torque of the electric motor 3 and the protection temperature may be stored as torque output ratio map data. In this case, the protection temperature relative to the moving average value A1 of the torque can be calculated as the first temperature B1. The calculated first temperature B1 is then stored, for example, in a memory device 7a provided in the controller 7.

[0037] Furthermore, the unit temperature rise calculation unit 12 of the controller 7 detects (monitors) the temperature of the electric motor 3 detected by the temperature sensor 3a at a predetermined sampling period, and calculates the temperature rise ΔB of the electric motor 3 per unit time based on the obtained change in the temperature of the electric motor 3 over time (step S4: unit temperature rise calculation step). In other words, in this embodiment, the temperature rise ΔB per unit time is calculated from the actual temperature detected by the temperature sensor 3a of the electric motor 3. The calculated temperature rise ΔB per unit time is stored in the storage device 7a as appropriate.

[0038] Subsequently, the time calculation unit 14 uses the temperature rise ΔB per unit time, the first temperature B1, and the current motor temperature B0 detected by the temperature sensor 3a to calculate the estimated time T1 until the electric motor 3 reaches the first temperature B1 using the formula T1 = (B1 - B0) / ΔB (Step S5: Time calculation step). In other words, it calculates the estimated time T1 until the output limit of the electric motor 3 is reached, assuming that the vehicle continues to run at the current moving average value A1 of torque.

[0039] Then, the notification control unit 15 determines that the calculated predicted time T1 is equal to the reference time T R Determine whether the following conditions are met (Step S6). If the result in step S6 is NO, the notification control unit 15 terminates the processing according to this flowchart without issuing a notification regarding the output limit of the electric motor 3.

[0040] On the other hand, if the result in step S6 is determined to be YES, the notification control unit 15 causes the notification device 6 to notify that the output of the electric motor 3 will be limited (step S7). For example, in this embodiment, the notification control unit 15 notifies the driver that the output of the electric motor 3 will be limited by lighting up the indicator light 6a. After that, the process according to this flowchart is terminated.

[0041] Next, we will explain how the notification related to the output limit of the electric motor 3 by the notification control unit 15 is released. Figure 9 is a flowchart showing the release of the output limit notification in the vehicle control method of this embodiment. The notification control unit 15 of the controller 7 determines whether the vehicle 10 has finished climbing the uphill road (step S11). The determination of whether the vehicle 10 has finished climbing the uphill road is made by identifying the end position of the uphill road on which the vehicle 10 is traveling from the map information, and determining that the vehicle 10 has finished climbing the uphill road (has reached the top of the uphill road) when the current position of the vehicle 10 detected by the position detection sensor 4 reaches the end position of the uphill road. If the result in step S11 is YES, the notification control unit 15 counts the time since the end of the pitching shift and determines whether a predetermined waiting time T2 has elapsed (step S12). The waiting time T2 is the amount of time until the next power limit notification that the driver will not be dissatisfied with, and is set to, for example, 60 seconds. If the result in step S12 is NO, the process returns to step S12 and continues counting the waiting time. If the result in step S12 is determined to be YES, the notification control unit 15 cancels the notification related to the output limit of the electric motor 3, that is, in this embodiment, turns off the indicator light 6a (step S13).

[0042] If the result in step S11 is NO, the notification control unit 15 determines whether the vehicle 10 has taken an evasive action (step S14). Whether the evasive action has been completed is determined, for example, by whether the vehicle speed of the vehicle 10 obtained from the wheel speed sensor has become 0. The controller 7 may further detect the stopping position of the vehicle 10 using sensors such as an on-board camera or LiDAR mounted on the vehicle 10. In this case, the controller may determine that the evasive action is complete when the vehicle stops at a predetermined evasive position such as the shoulder of the road or a parking lot, and may not determine that the evasive action is complete when the vehicle 10 temporarily stops at a traffic light or railroad crossing.

[0043] If the result in step S14 is determined to be YES, the notification control unit 15 determines whether a predetermined waiting time T2 has elapsed since the completion of the evacuation action (step S15). The waiting time T2 used in step S15 may be the same as in step S12, a time at which the driver does not feel dissatisfied with the time interval until the next power limit notification, but it is preferable that the waiting time T2 be the time until the vehicle 10 finishes climbing the uphill road. When the waiting time T2 is the time until the vehicle finishes climbing the road, the distance L from the vehicle 10's current position (evacuation position) to the end of the uphill road is calculated based on map information. In addition, the speed of the vehicle 10 while it is traveling on the uphill road is measured in advance, and the average speed V of the vehicle 10 is calculated. Then, using these distance L and average speed V, the waiting time T2 is calculated by T2 = L / V.

[0044] If the result in step S15 is NO, the process returns to step S15 and continues counting the waiting time. If the result in step S15 is YES, the same process as in step S13 is performed, and the notification control unit 15 cancels the notification related to the output limit of the electric motor 3. Furthermore, if the result is NO in both step S11 and step S14, the process returns to step S11. In other words, if vehicle 10 is ascending the uphill road and has not taken any evasive action, the notification regarding the output limit of the electric motor 3 continues.

[0045] By the way, in the flowchart shown in Figure 9, the notification control unit 15 cancels the notification related to the output limit of the electric motor 3 after the waiting time T2 has elapsed. However, as mentioned above, the notification control unit 15 may also cancel the output limit notification when the temperature of the electric motor 3 drops to a predetermined target temperature. Figure 10 is a flowchart showing another example of the release of output limit notification in the vehicle control method of this embodiment. In the process shown in Figure 10, the notification control unit 15 determines whether the vehicle 10 has finished climbing the uphill road, similar to step S11 (step S21). If the result in step S21 is determined to be YES, the notification control unit 15 calculates the target temperature B3 using the first temperature B1 calculated in step S3, the temperature rise ΔB of the electric motor 3 per unit time calculated in step S4, and the waiting time T2, using the formula B3 = B1 - ΔB·T2 (step S22). The waiting time T2 can be the same as the waiting time T2 used in step S12, for example, by setting a time interval until the next output limit notification that the driver will not be dissatisfied with.

[0046] Next, the notification control unit 15 determines whether the temperature of the electric motor 3 has fallen below the target temperature B3 calculated in step S22 (step S23). If the result in step S23 is NO, the process returns to step S23 and continues monitoring the temperature of the electric motor 3. If the result in step S23 is determined to be YES, the notification control unit 15 cancels the notification related to the output limit of the electric motor 3 (turns off the indicator light 6a) (step S24).

[0047] If the result in step S21 is NO, the notification control unit 15 determines whether or not the vehicle 10 has taken an evasive action, similar to step S14 (step S25). If the result in step S25 is determined to be YES, the notification control unit 15 calculates the target temperature B3 using the first temperature B1 calculated in step S3, the temperature rise ΔB of the electric motor 3 per unit time calculated in step S4, and the waiting time T2, similar to step S22 (step S26). The waiting time T2 used here may be the same as in step S22, a time at which the driver does not feel dissatisfied with the time interval until the next output limit notification, but it is preferable that the waiting time T2 be the time until the vehicle 10 finishes climbing the uphill road.

[0048] After this, the notification control unit 15 determines whether the temperature of the electric motor 3 has fallen below the target temperature B3 calculated in step S26 (step S27). If the result in step S27 is NO, the process returns to step S27 and continues monitoring the temperature of the electric motor 3. If the result in step S27 is determined to be YES, the notification control unit 15 cancels the notification related to the output limit of the electric motor 3, similar to step S24. Furthermore, if the result is NO in both step S21 and step S25, the process returns to step S21. In other words, if vehicle 10 is ascending the uphill road and has not taken any evasive action, the notification regarding the output limit of the electric motor 3 continues to be provided.

[0049] [Example of notification timing related to output limiting] Next, we will explain the difference in notification timing between the case in which notification regarding the output limiting of the electric motor 3 is provided according to this embodiment (Example) and the case in which notification regarding the output limiting is provided when the output limiting rate of the electric motor begins to decrease using the conventional method (Comparative Example). Here, it is assumed that the vehicle 10 in the embodiment and the vehicle in the comparative example are equipped with the same electric motor 3, and that the maximum torque of the electric motor 3 is 300 [Nm].

[0050] Figure 11(A) shows the output limiting rate, motor temperature, moving average value of output torque, and output limiting notification timing (timing of illumination of indicator light 6a) when the moving average value A1 of the output torque is 100 [Nm] in the embodiment. Figure 11(B) shows the output limiting rate, motor temperature, and output limiting notification timing (indicator light 6a lighting timing) when the moving average value A1 of the output torque is 100 [Nm] in the comparative example.

[0051] In the comparative example shown in Figure 11(B), the timing at which the output limiting rate decreases is 582 seconds, and at that timing, a notification is issued indicating that there is a risk of output limiting.

[0052] In the embodiment, the protection temperature (first temperature B1) when the output limiting ratio is 33.3% (=100[Nm] / 300[Nm]) was calculated based on the torque output ratio map data, and B1 = 176.7°C was obtained. From the temperature change of the electric motor, the temperature rise ΔB per unit time was calculated, and ΔB = 0.33[°C / sec] was obtained. In the embodiment, the expected time T1 until the temperature of the electric motor 3 reaches the first temperature B1 was the reference time T R (T R If the time interval falls below 10 seconds, a notification is issued indicating that output limitations may be imposed. Therefore, as shown in Figure 11, a notification indicating that output limitations may be imposed was issued at 592 seconds, which is 10 seconds before the output limitation rate reaches 33.3%, that is, at the time when the motor temperature reaches 173.4°C.

[0053] As described above, when the moving average value of the output torque of the electric motor 3 is 100 [Nm], in the comparative example, the notification regarding the output limit is given 10 [seconds] earlier than in the embodiment. In this case, since the notification regarding the output limit is given early on uphill roads, there is a possibility that the notification regarding the output limit will be given frequently, which may cause dissatisfaction to the driver. In contrast, in the embodiment, it can be seen that the notification regarding the output limit is not given unnecessarily early, and the notification is given at an appropriate timing.

[0054] Figure 12(A) shows the output limiting rate, motor temperature, moving average value of output torque, and output limiting notification timing when the moving average value A1 of the output torque is 200 [Nm] in the embodiment. Figure 12(B) shows the output limiting rate, motor temperature, and output limiting notification timing when the moving average value A1 of the output torque is 200 [Nm] in the comparative example.

[0055] In the comparative example shown in Figure 12(B), the timing at which the output limiting rate decreases is 591 seconds, and at that timing, a notification is issued indicating that there is a risk of output limiting.

[0056] In the embodiment, the protection temperature (first temperature B1) when the output limiting ratio is 66.7% (=200[Nm] / 300[Nm]) was calculated based on the torque output rate map data, and B1 = 173.3°C was obtained. From the temperature change of the electric motor 3, the temperature rise ΔB per unit time was calculated, and ΔB = 0.67[°C / sec] was obtained. In the embodiment, the expected time T1 until the temperature of the electric motor 3 reaches the first temperature B1 was set to the reference time T R (T R If the time interval falls below 10 seconds, a notification is issued indicating that output limitations may be imposed. Therefore, as shown in Figure 12(A), a notification indicating that output limitations may be imposed was issued at 586 seconds, which is 10 seconds before the output limitation rate reaches 66.7%, that is, at the timing when the motor temperature reaches 166.6°C.

[0057] As described above, when the moving average value of the output torque of the electric motor 3 is 200 [Nm], in the comparative example, the notification regarding the output limit is given 5 [seconds] later than in the embodiment. In this case, on an uphill road, the time between the notification regarding the output limit and the driver moving the vehicle to an escape position is shortened, which may cause dissatisfaction to the driver. In contrast, in the embodiment, it can be seen that the notification is given at an appropriate timing that takes into account the time required for the driver to take escape action.

[0058] [Effects of this embodiment] The vehicle 10 (electric vehicle) of this embodiment is driven by the driving force of an electric motor 3 and includes a temperature sensor 3a for detecting the temperature of the electric motor 3, a torque sensor 3b for detecting the output torque of the electric motor 3, a notification device 6, and a controller 7. The controller 7 performs the following steps by having the processor 7b read and execute a program recorded in the storage device 7a: an average torque calculation step (step S1), a first temperature calculation step (step S3), a unit temperature rise calculation step (step S4), a time calculation step (step S5), and a notification step (steps S6 to S7). In the average torque calculation step, the moving average value A1 of the actual output torque of the electric motor 23 is calculated. In the first temperature calculation step, the protection temperature of the electric motor 3 corresponding to the moving average value is calculated as the first temperature B1 based on the torque output rate map data. In the unit temperature rise calculation step, the temperature of the electric motor 3 is monitored and the temperature rise ΔB per unit time is calculated. In the time calculation step, the estimated time T1 for the electric motor 3 to rise from its current temperature to the first temperature B1 is calculated based on the temperature rise ΔB per unit time of the electric motor 3. In the notification step, the estimated time T1 is set to a predetermined reference time T R The driver will be notified that output limitations will be applied in the following cases:

[0059] In this embodiment, the expected time T1 until the electric motor 3 reaches the protection temperature is calculated based on the moving average value A1 of the actual output torque of the electric motor 3 and the operating temperature of the electric motor 3, and this expected time T1 is set to the reference time T R The driver will be notified that the output of the electric motor 3 will be limited if the following conditions are met. This ensures that even when the vehicle 10 is traveling uphill and the driver is frequently operating the accelerator pedal, resulting in large accelerations and decelerations, the driver will be notified that the output of the electric motor 3 will be limited at an appropriate timing based on the actual output torque and temperature of the electric motor 3.

[0060] In this embodiment, during the notification step, when the end of the vehicle 10's uphill driving on the uphill road or the cessation of driving (completion of retreat) is detected, a notification is given that the output restriction has been released after a predetermined waiting time T2 has elapsed from the time the uphill driving or retreat is completed. This allows the driver to cancel the output limit notification at a time when they will not feel dissatisfied with the interval until the next output limit notification. In other words, if the output limit notification is canceled earlier than the waiting time T2, there is a possibility that the driver will receive a notification regarding the output limit of the electric motor 3 too early when they resume driving the vehicle 10 after receiving the cancellation, or that the driver will receive another notification regarding the output limit of the electric motor 3 before the vehicle 10 has finished climbing the uphill road, which will cause dissatisfaction to the driver. In contrast, in this embodiment, by setting the waiting time T2 to the time when the driver will not feel dissatisfied with the interval until the next output limit notification, or the time when the vehicle 10 has finished climbing the uphill road, the inconvenience of causing driver dissatisfaction can be suppressed.

[0061] In this embodiment, during the notification step, when the vehicle 10 has finished climbing the uphill road or has completed its retreat, the target temperature B3 is calculated using the formula B3 = B1 - ΔB·T2, based on the first temperature B1, the temperature rise ΔB per unit time, and the waiting time T2. The notification control unit 15 may then notify that the output restriction has been released after the temperature of the electric motor 3 has dropped to or below the target temperature B3. In this case as well, the power limit notification can be canceled at a time when the driver is not dissatisfied with the interval until the next power limit notification.

[0062] In this embodiment, the time until the vehicle 10 finishes climbing the slope may be calculated based on the average speed V of the vehicle 10 on the uphill slope and the distance L from the current position to the end of the uphill slope, and this time may be used as the waiting time T2. As a result, after the power limit notification is lifted, when vehicle 10 travels uphill, the likelihood of another power limit notification being issued midway through the uphill climb is reduced, and the power limit notification can be lifted at a time that does not cause driver dissatisfaction.

[0063] In this embodiment, the moving average value A1 calculated in step S1 is the first torque threshold A R If the above conditions are met, the first limiting rate calculation step, the unit temperature rise calculation step, the first temperature calculation step, the time calculation step, and the notification step are performed. As a result, when the moving average value A1 is low and the likelihood of the electric motor 3 reaching the protection temperature is low, the first limiting factor calculation step, the unit temperature rise calculation step, the first temperature calculation step, the time calculation step, and the notification step are not performed, thereby reducing the processing load associated with these processes.

[0064] In this embodiment, the first torque threshold A R This value may vary depending on the rotational speed of the electric motor 3. In this case, it is possible to determine with greater accuracy whether or not to provide notification regarding the output limit based on the rotational speed of the electric motor 3 and the moving average value A1 of the output torque. Furthermore, in addition to uphill sections on ordinary roads, notification regarding the output limit can also be provided at an appropriate timing when driving on expressways, etc.

[0065] In this embodiment, the first torque threshold A R This may be the rated torque of the electric motor 3. This allows you to determine whether or not the electric motor 3 will reach the protection temperature using only the moving average value A1 of the output torque, thereby simplifying the process.

[0066] [Differentiation] The present invention is not limited to the embodiments described above, but also includes the following modifications to the extent that the objectives of the present invention can be achieved.

[0067] [Example 1] In the above embodiment, the reference time T RA fixed value is used, but it may be set to change according to the vehicle speed of vehicle 10. For example, on a steep uphill road, the vehicle speed is low, so the time required for the driver to take appropriate action (e.g., the time to take evasive action) is shorter. On the other hand, when the vehicle speed is high, such as on an uphill road on a highway, the time required for the driver to take appropriate action is longer. Thus, to allow the driver to take appropriate action, the reference time T should be set to change as the vehicle speed increases. R You may also want to set it to a larger value. Furthermore, drivers can adjust the standard time T according to their own driving skills. R It may be possible to allow this to be changed.

[0068] [Differentiation 2] In the above embodiment, the notification control unit 15 is shown to cancel the notification regarding the output limit of the electric motor 3 after a predetermined waiting time T2 has elapsed since the vehicle 10 finished climbing the uphill road or completed moving away. Here, the waiting time T2 is shown as an example of a time during which the driver does not feel dissatisfied with the time interval until the next output limit notification; however, this time may be set individually by each driver.

[0069] [Difference 3] In the above embodiment, after calculating the moving average value A1 of the output torque of the electric motor 3, the moving average value A1 is set to the first torque threshold A R An example is shown in which the unit temperature rise calculation step, time calculation step, and notification step are performed when the above conditions are met. In contrast, the moving average value A1 of the output torque of the electric motor 3 is set to the first torque threshold A for a predetermined period of time. R If the above occurs, the unit temperature rise calculation step, time calculation step, and notification step may be performed. In other words, the moving average value A1 temporarily becomes the first torque threshold A R If the temperature only exceeds a certain threshold and there is little probability that the temperature of the electric motor 3 will reach the protection temperature, the unit temperature rise calculation step, the time calculation step, and the notification step may be omitted.

[0070] Alternatively, the average torque on an uphill section may be recorded as road information to be included in the map data. In this case, the average torque recorded in the road information of the road on which the vehicle 10 travels is the first torque threshold A. R If the above is true, the average torque calculation step, the unit temperature rise calculation step, the time calculation step, and the notification step are performed, and the average torque recorded in the road information is the first torque threshold A R If the value is less than the specified value, the average torque calculation step, the unit temperature rise calculation step, the time calculation step, and the notification step may be omitted.

[0071] Furthermore, the unit temperature rise calculation step, time calculation step, and notification step may be performed not only based on the moving average value A1, but also in other ways.

[0072] [Difference 5] In the above embodiment, the notification device 6 notifies that there is a risk of the output of the electric motor 3 being limited by illuminating the indicator light 6a, but it is not limited to this. For example, notification regarding the output limiting of the electric motor 3 may be provided by displaying an image or text on a liquid crystal panel. Alternatively, the notification device 6 may be equipped with a speaker and provide notification regarding the output limiting by voice from the speaker. Furthermore, when releasing the notification of the output limiting, the speaker may provide voice notification that there is no longer a risk of the output limiting being applied. [Explanation of Symbols]

[0073] 3...Electric motor, 3a...Temperature sensor, 3b...Torque sensor, 6...Notification device, 6a...Indicator light, 7...Controller, 7a...Memory device, 7b...Processor, 10...Vehicle, 11...Average torque calculation unit, 12...Unit temperature rise calculation unit, 13...First temperature calculation unit, 14...Time calculation unit, 15...Notification control unit, 23...Electric motor.

Claims

1. A vehicle control method for an electric vehicle that is driven by the driving force of an electric motor, The average torque calculation step involves calculating the moving average value of the actual output torque of the electric motor from the operating state of the electric motor, A first temperature calculation step in which, based on torque output rate map data showing the relationship between the output torque of the electric motor and the protection temperature of the electric motor, the protection temperature of the electric motor corresponding to the moving average value is calculated as the first temperature, A unit temperature rise calculation step involves monitoring the temperature of the electric motor and calculating the temperature rise per unit time, A time calculation step of calculating the estimated time it takes for the electric motor to rise from its current temperature to the first temperature, based on the temperature rise of the electric motor per unit time, A vehicle control method that includes a notification step of notifying the driver that output limitations will be applied when the predicted time is less than or equal to a predetermined reference time.

2. In the notification step, if the completion of the electric vehicle's ascent on the uphill path or the cessation of the electric vehicle's movement is detected, a notification is given that the output restriction has been released after a predetermined waiting time has elapsed since the completion of the ascent or the cessation of the movement. The vehicle control method according to claim 1.

3. In the notification step, if it is detected that the electric vehicle has finished climbing the uphill road or that the electric vehicle has stopped moving, The target temperature is calculated by subtracting the temperature obtained by multiplying the temperature rise per unit time by a predetermined waiting time from the first temperature. The system notifies that the output limit has been released after the temperature of the electric motor has dropped below the target temperature. The vehicle control method according to claim 1.

4. The waiting time is calculated based on the electric vehicle's speed on the uphill path and the distance from its current position to the end of the uphill section of the path, and is the time until the electric vehicle finishes its ascent. The vehicle control method according to claim 2 or claim 3.

5. The first temperature calculation step, the unit temperature rise calculation step, the time calculation step, and the notification step are performed when the moving average value is equal to or greater than a predetermined first torque threshold. The vehicle control method according to claim 1.

6. The first torque threshold is a different value depending on the rotational speed of the electric motor. The first temperature calculation step, the unit temperature rise calculation step, the time calculation step, and the notification step are performed when the value of the moving average is equal to or greater than the first torque threshold corresponding to the rotational speed of the electric motor. The vehicle control method according to claim 5.

7. The first torque threshold is the rated torque of the electric motor. The vehicle control method according to claim 5 or claim 6.

8. An electric vehicle that is driven by the power of an electric motor, A temperature sensor for detecting the temperature of the electric motor, An operating state detection unit for detecting the operating state of the electric motor, A notification device that provides notification regarding the output limit of the electric motor, Equipped with a computer, The aforementioned computer, From the operating state of the electric motor, the moving average value of the actual output torque of the electric motor is calculated. Based on torque output rate map data showing the relationship between the output torque of the electric motor and the protection temperature of the electric motor, the protection temperature of the electric motor corresponding to the moving average value is calculated as the first temperature. The temperature of the electric motor is monitored, and the temperature rise per unit time is calculated. Based on the temperature rise of the electric motor per unit time, the estimated time it takes for the electric motor to rise from its current temperature to the first temperature is calculated. An electric vehicle that, when the predicted time falls below a predetermined reference time, notifies the driver from the notification device that output limitations will be imposed.

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