Control device for electric vehicle

Abstract

To provide a control device for an electric vehicle which can suppress occurrence of stop of an electric motor during travel at very low speed while suppressing burnout of the electric motor due to excess current.SOLUTION: Provided is a control device 50 for an electric vehicle 10 that drives wheels 11 by an electric motor 20. The control device comprises a motor control unit 500 which sets first target current according to accelerator opening and controls an operation of the electric motor 20 on the basis of the first target current in a state in which an accelerator operation is performed, and sets second target current so that the number of rotations of the electric motor 20 becomes the preliminarily set target number of rotations and controls the operation of the electric motor 20 on the basis of the second target current in an idle state in which the accelerator operation is not performed. The motor control unit 500 changes a limit value of the second target current according to fluctuations in the number of rotations of the electric motor 20 caused by a load.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a control device for an electric vehicle in which wheels are driven by an electric motor. [Background technology]

[0002] In recent years, various types of electric vehicles that drive wheels with electric motors have been put to practical use. Electric vehicles include not only private electric vehicles, but also, for example, electric vehicles for various competitions. Patent Document 1 describes a motorcycle for trial competitions that includes an electric motor and a clutch interposed between the electric motor and the rear wheel. Note that a trial competition is a competition in which participants compete to see how far they can ride a motorcycle through a course with complex elevation differences and inclinations. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-189539 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an electric vehicle, a limit value of the current supplied to the electric motor is sometimes set. This can prevent the electric motor from burning out due to an overcurrent. However, even if the load on the electric motor is large, a current equal to or greater than the limit value cannot be supplied to the electric motor, and the rotation speed of the electric motor may deviate significantly from the target rotation speed or the electric motor may stop.

[0005] For example, in a trial race, a motorcycle may be driven at an extremely low speed by only operating the clutch (so-called half-clutch) in an idling state, without operating the accelerator. In such a situation, the electric motor of an electric vehicle is particularly likely to stop.

[0006] On the other hand, in the case of an internal combustion engine vehicle, when the engine speed drops during extremely slow driving as described above, the vehicle behaves tenaciously to maintain the engine speed. Therefore, while the vehicle is behaving tenaciously as described above, the driver can take measures to prevent the engine from stalling, such as disengaging the clutch or operating the accelerator.

[0007] Furthermore, such differences in behavior between electric vehicles and internal combustion engine vehicles can be unnatural to riders who are accustomed to internal combustion engine vehicles, and so there is a tendency to prefer that the behavior of electric vehicles be similar to that of internal combustion engine vehicles.

[0008] It should be noted that the above-mentioned problems are not limited to motorcycles used for trial competitions, but may also exist in electric vehicles for other purposes.

[0009] One object of the present disclosure is to provide a control device for an electric vehicle that can suppress occurrences of the electric motor stopping or the like during extremely low-speed traveling while suppressing burnout of the electric motor due to overcurrent. [Means for solving the problem]

[0010] The control device for an electric vehicle disclosed herein is a control device for an electric vehicle in which wheels are driven by an electric motor, and includes a motor control unit that, when an accelerator is being operated, sets a first target current according to the accelerator opening and controls the operation of the electric motor based on the first target current, and, in an idle state in which the accelerator is not being operated, sets a second target current so that the rotation speed of the electric motor becomes a predetermined target rotation speed, and controls the operation of the electric motor based on the second target current, and is configured so that the motor control unit changes a limit value of the second target current in response to fluctuations in the rotation speed of the electric motor due to load. Effect of the Invention

[0011] According to the technique disclosed herein, it is possible to suppress the occurrence of the electric motor stopping or the like when an electric vehicle is traveling at extremely low speeds while suppressing burnout of the electric motor due to overcurrent. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram illustrating a configuration of an electric vehicle according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing a process flow in a control device for an electric vehicle according to an embodiment. [Diagram 3] 5 is a diagram showing an example of a relationship between the motor rotation speed and a limit value of a second target current in an electric vehicle according to an embodiment. FIG. [Figure 4] 5 is a timing chart showing changes in various parameters when an electric vehicle according to a comparative example is traveling at an extremely low speed. [Diagram 5] 4 is a timing chart showing changes in various parameters when the electric vehicle according to the embodiment is traveling at a very low speed. [Figure 6] 13 is a diagram showing another example of the relationship between the motor rotation speed and the limit value of the second target current in the electric vehicle according to the embodiment. FIG. [Figure 7] 13 is a diagram showing another example of the relationship between the motor rotation speed and the limit value of the second target current in the electric vehicle according to the embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the technology of the present disclosure will be described in detail with reference to the drawings. <Outline of electric vehicles> Fig. 1 is a schematic diagram showing the configuration of an electric vehicle according to one embodiment, and Fig. 2 is a diagram showing a processing flow in a control device for an electric vehicle according to one embodiment. First, the schematic configuration of an electric vehicle according to one embodiment will be described with reference to Fig. 1.

[0014] An electric vehicle 10 shown in FIG. 1 is, for example, a motorcycle for trial competitions, and includes an electric motor 20 that drives a wheel (rear wheel) 11, and a clutch 30 interposed between the electric motor 20 and the rear wheel 11, which is a drive wheel.

[0015] The electric motor 20 is typically a three-phase brushless DC motor, etc. The clutch 30 is typically a multi-plate clutch, etc. Although not shown in the drawings, a drive gear is provided on the motor shaft of the electric motor 20, and the power of the electric motor 20 is configured to be transmitted to the clutch 30 via this drive gear.

[0016] The electric vehicle 10 also includes a control device 50, which is called an ECU (Engine Control Unit) or the like and which performs comprehensive control of the electric vehicle 10.

[0017] <Description of the control device> Next, the control device 50 will be described with reference to Fig. 1 and Fig. 2. Fig. 2 is a diagram showing a process flow in a control device for an electric vehicle according to one embodiment. The control device 50 is mounted at a certain location on the electric vehicle 10, and includes a motor control unit 500 that controls the driving of the electric motor 20, and an inverter 510.

[0018] The inverter 510 is configured with, for example, a three-phase switching element, specifically, six switching elements, etc. The inverter 510 supplies three-phase AC power to the electric motor 20 by performing switching control in response to a three-phase PWM (Pulse Width Modulation) signal sent from the motor control unit 500.

[0019] The control device 50 further includes an accelerator sensor 520, a current sensor 530, a rotation angle sensor 540, and an idle volume (idle Vol.) 550. The accelerator sensor 520 detects the opening of the accelerator, in other words, the throttle. The current sensor 530 detects a phase current (also called an actual current) that actually flows through the electric motor 20. The rotation angle sensor 540 is configured with, for example, a Hall IC, a rotary encoder, a resolver, etc., and detects the rotation angle of the electric motor 20. The idle volume 550 is for setting the rotation speed of the electric motor 20 in an idle state where no accelerator operation is being performed, and is configured with, for example, a variable resistor.

[0020] 2, the motor control unit 500 controls the driving of the electric motor 20 based on the detection results of the accelerator sensor 520, the current sensor 530, and the rotation angle sensor 540, the output result of the idle volume 550, etc. More specifically, the motor control unit 500 controls the AC power supplied to the electric motor 20 via the inverter 510, for example, the motor applied voltage applied to the electric motor 20. In other words, the motor control unit 500 controls the torque to the rear wheels 11 which are the drive wheels of the electric vehicle 10, i.e., the torque of the electric motor 20.

[0021] In this embodiment, the motor control unit 500 includes a first target current determination unit 501, a target rotation speed determination unit 502, a second target current determination unit 503, a limit processing unit 504, a motor control switching processing unit 505, and a phase current control unit 506, as well as a memory unit 507 in which various information necessary for the operation of the motor control unit 500 is stored.

[0022] First target current determination unit 501 executes a process for determining a first target current value, which is a target current value (also referred to as a current command value) in a state where an accelerator operation is being performed. More specifically, as the first target current determination process, first target current determination unit 501 determines the first target current value based on an accelerator opening detected by accelerator sensor 520 and a motor rotation speed detected by rotation angle sensor 540. In this example, information defining the relationship between the accelerator opening and the target rotation speed, etc. is stored in storage unit 507.

[0023] The first target current determination unit 501 refers to the information stored in the storage unit 507 and determines a first target current value so that the actual rotation speed of the electric motor 20 (hereinafter referred to as the motor rotation speed) becomes the target rotation speed according to the accelerator opening. In other words, the first target current determination unit 501 calculates the difference between the motor rotation speed detected by the rotation angle sensor 540 and the target rotation speed calculated from the accelerator opening, and determines the first target current value so that this difference approaches zero. The determined first target current value is sent to the motor control switching processing unit 505.

[0024] The target rotation speed determination unit 502 executes a process (target rotation speed determination process) for determining a target rotation speed in an idle state where no accelerator operation is performed, based on the output of the idle volume (idle Vol.) 550. The output of the idle volume 550 is adjusted in advance by a rider of the electric vehicle 10, which is a two-wheeled vehicle. In other words, the target rotation speed in the idle state can be arbitrarily set according to the rider's preference.

[0025] The second target current determination unit 503 executes a process of determining a second target current value, which is a target current value in an idle state. More specifically, as the second target current value determination process, the second target current determination unit 503 determines the second target current value based on the motor rotation speed detected by the rotation angle sensor 540 and the target rotation speed determined by the target rotation speed determination unit 502. As an example, the second target current determination unit 503 calculates the difference between the motor rotation speed detected by the rotation angle sensor 540 and the target rotation speed determined by the target rotation speed determination unit 502, and determines the second target current value so that this difference becomes zero. It can also be said that the second target current determination unit 503 performs a feedback process of the motor rotation speed.

[0026] The limit processing unit 504 performs limit processing on the second target current value determined by the second target current determination unit 503. A limit value that is an upper limit value is set in advance for the second target current value. In the limit processing, the second target current value is compared with the limit value, and if the second target current value is equal to or greater than the limit value, the second target current value determined by the second target current determination unit 503 is replaced with the limit value. If the second target current value is smaller than the limit value, replacement with the limit value is not performed. Then, the second target current value that has been subjected to the limit processing is sent to the motor control switching processing unit 505.

[0027] Furthermore, as will be described in detail later, the limit processing unit 504 changes the limit value of the second target current value determined by the second target current determination unit 503 in response to fluctuations in the rotation speed of the electric motor 20 due to the load. In other words, the limit value of the second target current value is set to change in response to fluctuations in the motor rotation speed due to the load.

[0028] The motor control switching processing unit 505 switches the control of the electric motor 20 in response to the accelerator opening detected by the accelerator sensor 520. As described above, the first target current value determined by the first target current determination unit 501 and the second target current value determined by the second target current determination unit 503 are sent to the motor control switching processing unit 505. The motor control switching processing unit 505 switches the control of the electric motor 20 between control based on the first target current value and control based on the second target current value. In other words, the motor control switching processing unit 505 selects one of the first target current value or the second target current value as the target current value used for controlling the electric motor 20 in response to the accelerator opening.

[0029] Specifically, when the accelerator opening is greater than zero, that is, when the accelerator is being operated, the motor control switching processing unit 505 selects a first target current value and sends the first target current value to the phase current control unit 506. When the accelerator opening is zero, that is, when the accelerator is not being operated, the motor control switching processing unit 505 selects a second target current value and sends the second target current value to the phase current control unit 506.

[0030] Based on the difference between the target current value sent from the motor control switching processing unit 505, that is, one of the first target current value and the second target current value, and the actual current value detected by the current sensor 530, the phase current control unit 506 calculates a duty ratio command value for bringing this difference closer to zero using proportional-integral control (PI control) or the like. Then, based on the calculated duty ratio command value, the phase current control unit 506 outputs a three-phase PWM signal to the inverter 510. That is, the phase current control unit 506 feedback-controls the phase currents flowing through the electric motor 20 based on the three-phase PWM signal. In other words, the phase current control unit 506 appropriately controls the motor applied voltage applied to the electric motor 20 via the inverter 510 based on the three-phase PWM signal.

[0031] The control device 50 is configured by, for example, a wiring board on which various parts including a microcontroller and switching elements are mounted. The first target current determination unit 501, the target rotation speed determination unit 502, the second target current determination unit 503, the limit processing unit 504, the motor control switching processing unit 505, the phase current control unit 506, and the like are realized by, for example, program processing using a processor in a microcontroller. However, some or all of them may be realized by hardware such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC) without being limited to program processing.

[0032] As described above, when the accelerator is being operated, the motor control unit 500 constituting the control device 50 sets a first target current value according to the accelerator opening degree, and controls the operation of the electric motor 20 based on the first target current value (phase current feedback control). On the other hand, when the vehicle is in an idling state where the accelerator is not being operated, the motor control unit 500 sets a second target current value so that the rotation speed of the electric motor 20 becomes a preset target rotation speed, and controls the operation of the electric motor 20 based on this second target current value (rotation speed feedback control).

[0033] This allows the operation of the electric motor 20 to be appropriately controlled even in an idling state where the accelerator is not being operated, making it easier to drive the vehicle by operating only the clutch without operating the accelerator, for example. Also, by rotating the electric motor 20 at an appropriate rotation speed with the clutch 30 disengaged, it is expected that the gyro effect will make it easier to maintain a stopped state (standing) without the feet touching the ground.

[0034] Furthermore, in the technology disclosed herein, the limit value of the second target current value in an idle state is changed according to fluctuations in the rotation speed of the electric motor 20 caused by the load. In other words, the limit value of the second target current value is set to change according to fluctuations in the motor rotation speed caused by the load. This makes it possible to prevent the electric motor 20 from burning out due to an overcurrent, while also preventing the electric motor 20 from stopping or otherwise occurring during extremely low-speed driving.

[0035] <Limit value change processing> The process of changing the limit value of the second target current value will be described in detail below.

[0036] As described above, the limit processing unit 504 changes the limit value of the second target current value determined by the second target current determination unit 503 in response to fluctuations in the rotation speed of the electric motor 20 due to the load. As an example, the storage unit 507 stores information such as a map that defines the relationship between the rotation speed of the electric motor 20 and the limit value of the second target current value. The limit processing unit 504 refers to the information stored in the storage unit 507 and appropriately changes the limit value of the second target current value.

[0037] More specifically, the limit processing unit 504 has a first threshold value that defines the range of the rotation speed of the electric motor 20, and changes the limit value of the second target current value in a first rotation range in which the rotation speed of the electric motor 20 is lower than the first threshold value to a value higher than the limit value of the second target current value in a second rotation range in which the rotation speed is equal to or higher than the first threshold value.

[0038] 3, for example, in the information stored in the storage unit 507, in the second region A2 where the rotation speed of the electric motor 20 is equal to or higher than the first threshold value Nth1, the limit value Li of the second target current value is set to the first limit value Li1. Also, in the first region A1 where the rotation speed of the electric motor 20 is lower than the first threshold value Nth1, the limit value Li of the second target current value is set to a value higher than the first threshold value Li1.

[0039] As a result, when the rotation speed of the electric motor 20 is lower than the first threshold value Nth1, the limit processing unit 504 changes the limit value Li of the second target current value to a higher value than when the rotation speed of the electric motor 20 is equal to or higher than the first threshold value Nth1.

[0040] 3, the limit value Li of the second target current value in the related art was set to a constant value (for example, the first limit value Li1) regardless of the rotation speed of the electric motor 20. In other words, the limit processing unit 504 set the limit value Li of the second target current value to a constant value (for example, the first limit value Li1) regardless of fluctuations in the rotation speed of the electric motor 20 due to the load.

[0041] In this embodiment, the limit value Li of the second target current value in the first rotation region A1 is set to a stepwise higher value as the rotation speed of the electric motor 20 decreases. As an example, when the rotation speed of the electric motor 20 is equal to or higher than a first threshold value Nth1 (e.g., 500 [rpm]), the limit value Li of the second target current value is set to a first limit value Li1 (e.g., 50 [A]). When the rotation speed of the electric motor 20 is equal to or higher than a second threshold value Nth2 and is lower than the first threshold value Nth1, the limit value Li of the second target current value is set to a second limit value Li2. Furthermore, when the rotation speed of the electric motor 20 is lower than the second threshold value Nth2, the limit value Li of the second target current value is set to a third limit value Li3.

[0042] Therefore, when the rotation speed of the electric motor 20 is equal to or greater than the first threshold value Nth1, the limit processing unit 504 sets the limit value Li of the second target current value to the first limit value Li1, and when the rotation speed of the electric motor 20 is equal to or greater than the second threshold value Nth2 and less than the first threshold value Nth1, the limit processing unit 504 sets the limit value Li of the second target current value to the second limit value Li2. Furthermore, when the rotation speed of the electric motor 20 is less than the second threshold value Nth2, the limit processing unit 504 sets the limit value Li of the second target current value to the third limit value Li3.

[0043] As a result, even if the load on the electric motor 20 increases when the electric vehicle 10 is traveling at an extremely low speed, the rotation speed of the electric motor 20 can be prevented from deviating significantly from the target rotation speed, and the electric motor 20 can be prevented from stopping.

[0044] Moreover, the control device 50 can appropriately change various pieces of information stored in the storage unit 507 in accordance with the preferences of the occupant. As an example, the control device 50 can appropriately change the relationship between the rotation speed of the electric motor 20 and the limit value Li of the second target current value in accordance with the preferences of the occupant of the electric vehicle 10. For example, the first threshold value Nth1, the second threshold value Nth2, the first limit value Li1, the second limit value Li2, the third limit value Li3, etc. can be appropriately changed. In this example, the control device 50 is configured to be connectable to an input device 100, which is an external terminal, and various pieces of information are input by the input device 100.

[0045] Next, an example of changes in motor rotation speed when the electric vehicle 10 is traveling at extremely low speed will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a timing chart showing changes in various parameters when the electric vehicle according to the comparative example is traveling at extremely low speed, and Fig. 5 is a timing chart showing changes in various parameters when the electric vehicle according to the embodiment is traveling at extremely low speed.

[0046] In an electric vehicle according to a comparative example (conventional example), for example, when extremely low speed traveling is started by only clutch operation, the second target current value is determined so that the motor rotation speed becomes the target rotation speed determined according to the output of the idle volume. In the example shown in Fig. 4, the target rotation speed at the start of extremely low speed traveling is determined to be the first rotation speed N1 which is larger than the first threshold value Nth1, and the second target current value is determined to be the first current value I1.

[0047] Until time T1, the load on the electric motor is constant, so the second target current value is maintained at the first current value I1. When the load on the electric motor starts to increase at time T1, the second target current value is changed so that the motor rotation speed is maintained at the target rotation speed, the first rotation speed N1. Specifically, when the load on the electric motor starts to increase, the second target current value also increases from the first current value I1 accordingly.

[0048] Then, when the second target current value reaches the first limit value Li1 at time T12, the second target current value is maintained at the first limit value Li1 without any further increase. Accordingly, the motor rotation speed gradually decreases. After time T3, when the load on the electric motor becomes constant, the motor rotation speed is also maintained at a constant value, for example, the second rotation speed N2.

[0049] In this way, in the control device for an electric vehicle according to the comparative example, when the load on the electric motor increases during extremely low-speed driving, the rotation speed of the electric motor deviates significantly from the target rotation speed. For example, in the example shown in Fig. 4, the difference between the first rotation speed N1 and the second rotation speed N2, which are the target rotation speeds, becomes large. This may cause the electric vehicle to run in a manner not intended by the driver.

[0050] In the case of the electric vehicle 10 according to the embodiment, for example, when very low speed traveling is started by only clutch operation, the second target current value is determined so that the motor rotation speed becomes the target rotation speed determined according to the output of the idle volume 550. In the example shown in Fig. 5, the target rotation speed at the start of very low speed traveling is determined to be the first rotation speed N1 that is larger than the first threshold value Nth1, and the second target current value is determined to be the first current value I1 that is smaller than the first limit value Li1.

[0051] Until time T11, the load on the electric motor 20 is constant, and therefore the second target current value is maintained at the first current value I1. When the load on the electric motor 20 starts to increase at time T11, the second target current value is changed so that the motor rotation speed is maintained at the target rotation speed, the first rotation speed N1. Specifically, when the load on the electric motor 20 starts to increase, the second target current value also increases from the first current value I1 accordingly.

[0052] Then, when the second target current value reaches the first limit value Li1 at time T12, the second target current value is maintained at the first limit value Li1 without any further increase. Accordingly, the motor rotation speed gradually decreases. However, when the motor rotation speed decreases to the first threshold value Nth1 at time T13, the limit value Li of the second target current value is changed from the first limit value Li1 to the second limit value Li2. As a result, the second target current value increases to a value corresponding to the target rotation speed, and accordingly, the motor rotation speed also increases slightly (time T13-T14). In addition, the motor rotation speed also decreases between times T14-T15 thereafter, but the rate of decrease in the motor rotation speed during that time is suppressed compared to the rate of decrease in the motor rotation speed between times T12-T13.

[0053] At time T15, when the second target current value reaches the second limit value Li2, the second target current value is not increased any more and is maintained at the second limit value Li2. Accordingly, the motor rotation speed gradually decreases (times T15-T16). Then, at time T16, when the motor rotation speed decreases to the second threshold value Nth2, the limit value Li of the second target current value is changed from the first limit value Li1 to the second limit value Li2.

[0054] As a result, the second target current value increases again to a value corresponding to the target rotation speed, and the motor rotation speed also increases slightly (time T16-T17). During the subsequent period, the motor rotation speed is maintained at a substantially constant value (e.g., third rotation speed N3) without decreasing. Between times T17-T18, although the load on electric motor 20 increases, the motor rotation speed is maintained at a substantially constant value without decreasing.

[0055] In this way, the control device 50 for an electric vehicle according to the embodiment can suppress a large deviation of the rotation speed of the electric motor 20 from the target rotation speed even when the load on the electric motor increases during extremely low speed driving. For example, in the example shown in Fig. 5, it is possible to suppress a deviation between the first rotation speed N1 and the third rotation speed N3, which are the target rotation speeds. Therefore, it becomes easier to drive the electric vehicle 10 as intended by the occupant, even during extremely low speed driving.

[0056] It should be noted that the fluctuation in motor rotation speed over time shown in Fig. 5 is merely one example. How the motor rotation speed fluctuates over time varies depending on the set conditions, such as the characteristics of electric motor 20 (e.g., torque constant, rotor inertia, etc.), motor rotation speed thresholds (Nth1, Nth2 in this example), and second target current limit values ​​(Li1, Li2, Li3 in this example). In particular, the fluctuation in motor rotation speed in the section from time T12 to time T18 where the second target current value increases varies depending on the various set conditions.

[0057] However, in the control device 10 for an electric vehicle according to the embodiment, in either case, it is possible to suppress the deviation between the first rotation speed N1 and the third rotation speed N3, which are the target rotation speeds. In other words, compared to the control device for an electric vehicle according to the conventional example, it is possible to suppress the rotation speed of the electric motor 20 from deviating greatly from the target rotation speed.

[0058] Furthermore, by changing the limit value of the second target current value in the idle state according to the fluctuation in the rotation speed of the electric motor 20 caused by the load, it is possible to cause the electric vehicle 10 to behave in a manner similar to that occurring during so-called knocking when the rotation speed of the electric motor 20 caused by the load decreases. This makes it easier for the occupant of the electric vehicle 10 to recognize that the electric motor 20 is about to stop. Therefore, when the electric motor 20 is about to stop, it becomes easier to take measures, such as operating the accelerator.

[0059] In this embodiment, an example has been described in which the limit value Li of the second target current in the first rotation region A1 is set to a stepwise higher value as the rotation speed of the electric motor 20 becomes lower, but the setting of the limit value Li of the second target current in the first rotation region A1 is not limited to this.

[0060] For example, as shown in Fig. 6, the limit value Li of the second target current value in the first rotation region A1 may be set to a value that increases linearly as the rotation speed of the electric motor 20 decreases. Alternatively, as shown in Fig. 7, the limit value Li of the second target current value in the first rotation region A1 may be set to a value that increases non-linearly as the rotation speed of the electric motor 20 decreases.

[0061] Even when the limit value Li of the second target current value is set to such a value, it is possible to prevent the electric motor 20 from burning out due to overcurrent while preventing the electric motor 20 from stopping or the like during extremely low speed driving.

[0062] Furthermore, the control device 50 for an electric vehicle according to the embodiment can suppress the occurrence of the electric motor 20 stopping or the like during extremely low-speed driving while suppressing burnout of the electric motor 20 due to the above-mentioned current, thereby reducing the load on the electric motor 20 and extending the life of the electric motor 20. This makes it possible to contribute to the Sustainable Development Goals (SDGs) established by the United Nations, particularly Goal 7 (Ensure access to affordable, reliable, sustainable and modern energy for all) and Goal 13 (Take urgent action to combat climate change and its impacts).

[0063] Although one embodiment of the technology of the present disclosure has been described above, it goes without saying that the technology of the present disclosure is not limited to the above embodiment and can be modified in various ways without departing from the spirit of the technology. In addition, the material, shape, size, number, installation location, etc. of each component in the above embodiment are arbitrary as long as the technology of the present disclosure can be achieved, and are not particularly limited.

[0064] For example, in the above embodiment, a motorcycle for trial racing is illustrated as an example of an electric vehicle, but the electric vehicle according to the technology of the present disclosure is not limited to this. The technology of the present disclosure is applicable to control devices of various electric vehicles that drive wheels with electric motors. [Explanation of symbols]

[0065] 10: electric vehicle, 11: wheel (rear wheel), 20: electric motor, 30: clutch, 50: control device, 100: input device, 500: motor control unit, 501: first target current determination unit, 502: target rotation speed determination unit, 503: second target current determination unit, 504: limit processing unit, 505: motor control switching processing unit, 506: phase current control unit, 507: memory unit, 510: inverter, 520: accelerator sensor, 530: current sensor, 540: rotation angle sensor, 550: idle volume (idle Vol.)

Claims

1. A control device for an electric vehicle in which wheels are driven by an electric motor, When the accelerator is operated, a first target current is set according to an accelerator opening degree, and the operation of the electric motor is controlled based on the first target current. a motor control unit that sets a second target current so that the rotation speed of the electric motor becomes a preset target rotation speed in an idling state where an accelerator operation is not performed, and controls an operation of the electric motor based on the second target current; The motor control unit changes a limit value of the second target current in response to a fluctuation in the rotation speed of the electric motor due to a load. A control device for an electric vehicle.

2. The motor control unit includes: a first threshold value that defines a range of rotation speeds of the electric motor; changing a limit value of the second target current in a first rotation region in which the rotation speed of the electric motor is lower than the first threshold value to a value higher than a limit value of the second target current in a second rotation region in which the rotation speed of the electric motor is equal to or higher than the first threshold value; The control device for an electric vehicle according to claim 1.

3. The motor control unit includes: the limit value of the second target current in the first rotation region is changed to a higher value as the rotation speed of the electric motor decreases; The control device for an electric vehicle according to claim 2.

4. The motor control unit includes: a limit value of the second target current in the first rotation region is changed linearly to a higher value as the rotation speed of the electric motor decreases; The control device for an electric vehicle according to claim 2.

5. The motor control unit includes: a limit value of the second target current in the first rotation region is changed nonlinearly to a higher value as the rotation speed of the electric motor decreases; The control device for an electric vehicle according to claim 2.

6. The motor control unit includes: the limit value of the second target current in the first rotation region is changed in a stepwise manner to a higher value as the rotation speed of the electric motor decreases; The control device for an electric vehicle according to claim 2.

7. The electric vehicle includes a clutch for transmitting the power of the electric motor to the wheels. The control device for an electric vehicle according to claim 1.

8. The electric vehicle is a motorcycle for trial racing. The control device for an electric vehicle according to claim 7.

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