Vehicle control device, vehicle, and vehicle control method

Abstract

To provide a vehicle control device or the like for suppressing the torque of a prime mover according to the state of the prime mover.SOLUTION: A storage device configured to store a torque-change rate relationship which is a relationship between a torque required for a prime mover provided in the vehicle and configured to drive wheels of the vehicle and an upper limit threshold value of a change rate of a rotation speed of the prime mover allowed for the torque required for the prime mover, the processing circuit is configured to calculate a required torque required for the prime mover based on a command to accelerate the vehicle input to the vehicle and a rotational speed of the prime mover, and perform traction control for suppressing a torque of the prime mover when it is determined that a change rate of the rotational speed of the prime mover exceeds the upper limit threshold corresponding to the required torque in the torque-change rate relationship.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a vehicle control device, a vehicle, and a vehicle control method. [Background technology]

[0002] For example, Patent Document 1 discloses an electric motorcycle that switches between a plurality of drive modes with different upper limit rotation speeds of the electric motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-23223 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, in order to suppress an increase in the rotation speed of the rear wheels due to slippage, the drive modes are switched in sequence from the first drive mode to the third drive mode, in which the upper limit rotation speed of the electric motor increases in order, as the vehicle speed increases. Control is not performed according to the state of the electric motor.

[0005] Therefore, one aspect of the present disclosure aims to provide a vehicle control device, a vehicle, and a vehicle control method that suppress the torque of a prime mover depending on the state of the prime mover.

[0006] A vehicle control device according to one aspect of the present disclosure includes a processing circuit and a memory that stores a torque-rate-of-change relationship, which is the relationship between the torque required of a prime mover provided on the vehicle and driving the wheels of the vehicle, and an upper threshold value for the rate of change of the prime mover's rotation speed that is allowable for the torque required of the prime mover, and the processing circuit is configured to calculate the required torque required of the prime mover based on a command to accelerate the vehicle input to the vehicle and the rotation speed of the prime mover, and to perform traction control that suppresses the torque of the prime mover when it is determined that the rate of change of the rotation speed of the prime mover exceeds the upper threshold value corresponding to the required torque in the torque-rate-of-change relationship. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a side view showing an example of the configuration of a vehicle according to an exemplary embodiment. [Figure 2] FIG. 2 is a schematic diagram showing an example of a power system of the vehicle of FIG. [Figure 3] FIG. 3 is a diagram showing an example of the torque-change rate relationship used in the traction control according to the embodiment. [Figure 4] FIG. 4 is a diagram showing an example of the behavior of a combination of the torque required for the electric motor and the rate of change in the rotation speed of the electric motor. [Figure 5] FIG. 5 is a flowchart illustrating an example of the operation of the ECU according to the embodiment. [Figure 6] FIG. 6 is a diagram showing an example of the torque-change rate relationship used in the traction control according to the first modification, similar to FIG. [Figure 7] FIG. 7 is a diagram similar to FIG. 4, showing an example of the behavior of a combination of the torque required for the electric motor and the rate of change in the rotation speed of the electric motor. [Figure 8] FIG. 8 is a diagram similar to FIG. 4, showing another example of the behavior of the combination of the torque required for the electric motor and the rate of change in the rotation speed of the electric motor. [Figure 9] FIG. 9 is a flowchart showing an example of the operation of the ECU according to the first modification. [Figure 10] FIG. 10 is a diagram showing an example of a comparison of the behavior of the effective torque of the electric motor between an implementation case in which the return control according to Modification 2 is implemented and a non-implementation case in which the return control according to Modification 2 is not implemented. [Figure 11] FIG. 11 is a schematic diagram showing an example of a power system of a vehicle according to the third modification. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. The embodiments described below are all comprehensive or specific examples. Among the components in the following embodiments, components that are not recited in an independent claim showing a top concept will be described as optional components. Each figure in the accompanying drawings is a schematic diagram and is not necessarily an exact drawing. In each figure, substantially identical components are assigned the same reference numerals, and duplicated descriptions may be omitted or simplified.

[0009] A vehicle 1 according to an exemplary embodiment will be described with reference to Figure 1. Figure 1 is a side view showing an example of the configuration of a vehicle 1 according to an exemplary embodiment. The vehicle 1 includes one or more wheels 10, a prime mover 20 that drives the one or more wheels 10, and a control device 30 that controls the prime mover 20. The vehicle 1 has a structure that moves by driving the one or more wheels 10 that come into contact with the ground surface.

[0010] In this embodiment, the vehicle 1 is a motorcycle and may include three or fewer wheels 10. Examples of motorcycles include saddle-ride type vehicles with foot bars on the sides of the seat and scooter-type vehicles with footrests in front of the seat. In this embodiment, the vehicle 1 is a saddle-ride type vehicle. The vehicle 1 is a lean vehicle that leans when turning.

[0011] Prime mover 20 has a structure that rotates a shaft, and generates power via the shaft. In this embodiment, prime mover 20 is a rotating electric machine that converts electrical energy into mechanical energy. Hereinafter, "prime mover 20" may also be referred to as "rotating electric machine 20." Vehicle 1 is an EV vehicle, and is equipped with one rotating electric machine 20 as a prime mover.

[0012] The rotating electric machine 20 may have any known structure. For example, the rotating electric machine 20 may have an inner rotor structure including a rotor that rotates integrally with the drive shaft and a stator, with the rotor located inside the stator, or an outer rotor structure in which the rotor is located outside the stator. The rotating electric machine 20 may rotate the rotor by receiving a supply of electric power, and generate electric power by forcibly rotating the rotor via the drive shaft. The rotating electric machine 20 transmits the rotational power of the drive shaft to the wheels 10.

[0013] The vehicle 1 includes front wheels 11 and rear wheels 12 as wheels 10, and an electronic control unit as a control device 30. The electronic control unit is also called an ECU. Hereinafter, the "control device 30" may be referred to as the "electronic control unit 30" or the "ECU 30." The ECU 30 controls various components of the vehicle 1.

[0014] Furthermore, the vehicle 1 includes a body frame 101, a handlebar 102, a steering shaft 103, a pair of left and right front forks 104, a swing arm 105, a rear suspension 106, a seat 107, a battery 108, an outer shell member 109, and a drive structure 110.

[0015] The upper part of the front fork 104 is connected to a pair of brackets 104a spaced apart in the vertical direction, and the lower part of the front fork 104 rotatably supports the front wheel 11. The bracket 104a is connected to a steering shaft 103 that supports a handlebar 102. The steering shaft 103 is supported by a head pipe 101a, which is part of the body frame 101, so as to be angularly displaceable.

[0016] The swing arm 105 supports the rear wheel 12, extends in the front-to-rear direction, and is pivotally supported by the body frame 101. The rear suspension 106 is connected to the swing arm 105 and the body frame 101. The battery 108 is disposed behind the handlebars 102 and extends downward. In this embodiment, although not limited thereto, the battery 108 is disposed at the position of the internal combustion engine and fuel tank of a motorcycle equipped with an internal combustion engine. A seat 107 on which a rider sits is disposed above the body frame 101 and behind the battery 108. The outer shell member 109 includes a front cowl that covers the front of the vehicle 1 and forms a front outer shell.

[0017] The battery 108 includes a secondary battery that can charge and discharge electric power. The battery 108 stores electric power generated by the power generation function of the rotating electric machine 20 and supplies the stored electric power to electrical components in the vehicle 1 that use the electric power. The rotating electric machine 20 is one of the electrical components that receives power from the battery 108. Examples of the secondary battery may include a lead-acid battery, a nickel-cadmium battery, a nickel-metal hydride battery, a metal lithium battery, a lithium-ion secondary battery, a lithium-ion polymer secondary battery, a sodium-sulfur battery, a sodium-ion battery, and an all-solid-state battery.

[0018] The rotating electric machine 20 is disposed between the front wheel 11 and the rear wheel 12, and is fixed to the body frame 101. The drive structure 110 transmits the rotational power generated by the rotating electric machine 20 to the rear wheel 12, which is a drive wheel. The drive structure 110 includes a power transmission member 111. Examples of the power transmission member 111 may include a chain, a belt, and a gear. In this embodiment, the drive structure 110 includes a transmission 112, but this does not have to be the case. The transmission 112 transmits the rotational power generated by the rotating electric machine 20 to the rear wheel 12 via the power transmission member 111.

[0019] Here, in this specification and claims, the upward, downward, forward, backward, leftward, and rightward directions are directions based on the vehicle 1 placed upright on a horizontally extending ground. The upward direction refers to the direction from the ground toward the vehicle 1, and the downward direction refers to the direction from the vehicle 1 toward the ground. The forward direction refers to the forward direction of the vehicle 1. The backward, leftward, and rightward directions each refer to a corresponding direction based on the driver straddling the vehicle 1 placed upright on the ground.

[0020] The vehicle 1 further includes one or more input devices 40. The input devices 40 include a first input device 41 that receives input of a command to accelerate the vehicle 1. The first input device 41 has an operable structure. In this embodiment, the first input device 41 is an operable throttle grip disposed on the handlebar 102, although this is not limited thereto. Hereinafter, the "first input device 41" may be referred to as the "throttle grip 41." The throttle grip 41 has a cylindrical shape and is rotatable around a cylindrical axis.

[0021] The vehicle 1 is equipped with a throttle position sensor 41a as an input sensor that detects the operation of the throttle grip 41. The throttle position sensor 41a detects the rotation angle of the throttle grip 41 and outputs the detection result to the ECU 30. Examples of the throttle position sensor 41a may include an electromagnetic pickup type rotation sensor, an anisotropic-magneto-resistive (AMR) rotation sensor, a Hall IC type rotation sensor, and a mechanical, optical, magnetic, or electromagnetic induction encoder.

[0022] The first input device 41 is not limited to one including a structure capable of rotating. The first input device 41 may have any structure that accepts an input of an operation by the driver. The first input device 41 may or may not include a part that operates in response to an operation input by the driver. For example, in the former case, the first input device 41 may include a linearly movable structure such as a lever, a depressible structure such as a button, a swingable structure such as a pedal, or a swiveling structure. In the latter case, the first input device 41 may be a touch panel. The location of the first input device 41 is not limited to the steering wheel 102. For example, the first input device 41 may be located in a position that can be operated by the hands or feet of the driver seated in the seat 107. For example, the first input device 41 may be located near a foot bar on which the driver's feet rest, or on a footrest on which the driver's feet rest.

[0023] The input unit 40 may include, as a second input unit, a first mode input unit 42 that receives an input specifying a driving mode to be executed by the vehicle 1. In the present embodiment, the first mode input unit 42 receives an input for selecting a sport-oriented mode or a stability-oriented mode, although this is not limited thereto. The sport-oriented mode is a driving mode in which the ECU 30 executes control to achieve high vehicle responsiveness. The stability-oriented mode is a driving mode in which the ECU 30 executes control to achieve lower vehicle responsiveness than the sport-oriented mode. The first mode input unit 42 may receive an input for selecting another driving mode in addition to, or instead of, the sport-oriented mode and the stability-oriented mode. For example, the other driving mode is an energy-saving mode in which the ECU 30 executes control to achieve driving of the vehicle 1 with reduced power consumption compared to the stability-oriented mode.

[0024] In this embodiment, first mode input device 42 is disposed on steering wheel 102, but may be disposed in a position where it can be operated by the hand or foot of a driver seated in seat 107. First mode input device 42 may have a structure that allows linear movement such as a lever, a structure that allows depressing movement such as a button, or a touch panel structure. First mode input device 42 outputs the input result to ECU 30.

[0025] The input unit 40 may include, as a third input unit, a boost input unit 43 that receives an input to execute a boost mode that temporarily improves the power performance of the vehicle 1. Upon receiving the input, the boost input unit 43 outputs a command to the ECU 30 to execute the boost mode.

[0026] The boost mode may be a driving mode in which the power performance of the vehicle 1 is improved for a predetermined period of time by a single input to the boost input device 43. Upon receiving a command from the boost input device 43, the ECU 30 improves the power performance of the vehicle 1 for a predetermined period of time. The boost mode may be a driving mode in which the power performance of the vehicle 1 is improved while the boost input device 43 continues to receive an input. The ECU 30 improves the power performance of the vehicle 1 while continuing to receive a command from the boost input device 43. In this embodiment, the boost input device 43 is disposed on the steering wheel 102, but may be disposed in a position that can be operated by the hands or feet of the driver seated in the seat 107. The boost input device 43 may have a structure that can be moved linearly, such as a lever, a structure that can be pressed, such as a button, or a touch panel structure.

[0027] The input unit 40 may include, as a fourth input unit, a second mode input unit 44 that receives an input specifying a traction mode to be set for the traction control executed by the vehicle 1. In this embodiment, the second mode input unit 44 receives an input for selecting one of three traction modes, although this is not limited thereto. The traction control is a control for reducing the torque generated by the electric motor 20 to a level lower than the torque required for the electric motor 20.

[0028] The first traction mode is a mode in which traction control is least likely to be performed. The third traction mode is a mode in which traction control is most likely to be performed. The second traction mode is a mode in which traction control is more likely to be performed than the first traction mode and less likely to be performed than the third traction mode. For example, the first traction mode and the second traction mode may be modes designed to simulate the vehicle 1 traveling on a non-slip surface such as a dry road surface, and the third traction mode may be a mode designed to simulate the vehicle 1 traveling on a slippery surface such as a wet road surface. The third traction mode may be set to make traction control much easier to perform than the second traction mode.

[0029] In this embodiment, the second mode input device 44 is disposed on the steering wheel 102, but may be disposed in a position that allows it to be operated by the hand or foot of the driver seated in the seat 107. The second mode input device 44 may have a structure that allows linear movement such as a lever, a structure that allows depression such as a button, or a touch panel structure. The second mode input device 44 outputs the input result to the ECU 30.

[0030] The vehicle 1 may further include one or more wheel speed sensors 50. The vehicle 1 may include, as the wheel speed sensors 50, one or both of a front wheel speed sensor 51 that detects the rotation speed of the front wheels 11 and a rear wheel speed sensor 52 that detects the rotation speed of the rear wheels 12. The front wheel speed sensor 51 and the rear wheel speed sensor 52 output the detection results to the ECU 30.

[0031] FIG. 2 is a schematic diagram showing an example of the power system of the vehicle 1 of FIG. 1. As shown in FIG. 2, in this embodiment, the rotating electric machine 20 is a brushless DC motor. Hereinafter, the "rotating electric machine 20" may be referred to as the "electric motor 20." The electric motor 20 includes a motor shaft 20a, a rotor 20b integrally including the motor shaft 20a, and a stator 20c circumferentially surrounding the rotor 20b. The rotor 20b includes a permanent magnet, and the stator 20c includes windings that form a plurality of coils. The multiple coils are positioned to surround the rotor 20b in the circumferential direction.

[0032] The vehicle 1 further includes a rotation sensor 21 that detects the rotational position of the rotor 20b of the electric motor 20, a current control circuit 22, a voltage control circuit 23, and a power conversion circuit 24. An example of the rotation sensor 21 is similar to the example of the throttle position sensor 41a. The current control circuit 22 controls the current supplied from the battery 108 to the stator 20c of the electric motor 20 in accordance with a command received from the ECU 30. By controlling the value of the current supplied to the electric motor 20, the torque generated on the motor shaft 20a by the electric motor 20 is controlled. The voltage control circuit 23 controls the voltage applied from the battery 108 to the stator 20c of the electric motor 20 based on the command received from the ECU 30 and the detection result of the rotation sensor 21. By controlling the voltage applied to the electric motor 20, the speed at which the electric motor 20 rotates the motor shaft 20a is controlled.

[0033] The power conversion circuit 24 converts AC power generated by the windings of the stator 20c when the motor shaft 20a of the electric motor 20 is forcibly rotated into DC power and supplies it to the battery .

[0034] The motor shaft 20a of the electric motor 20 is connected to an input shaft 112a of the transmission 112 via gears so as to be able to transmit rotational power. The output shaft 112b of the transmission 112 is connected to a drive sprocket 111a so as to rotate integrally with the drive sprocket 111a. The drive sprocket 111a is connected to a driven sprocket 111b attached to the rear wheel 12 so as to rotate integrally with the drive sprocket 111a via a chain 111c so as to be able to transmit rotational driving force. The drive sprocket 111a, the driven sprocket 111b, and the chain 111c are components of the drive structure 110.

[0035] The configuration of the ECU 30 will be described in detail. The ECU 30 may include a microcomputer equipped with one or more processors P, such as a central processing unit (CPU) or a digital signal processor (DSP), and a memory M. The ECU 30 may include a clock for measuring time. The memory M may include one or more memories, one or more storages, or both. Examples of the memory may include semiconductor memories. Examples of the storage may include semiconductor memories, hard disk drives (HDDs), and solid state drives (SSDs). Examples of the semiconductor memories may include volatile memories, such as random access memories (RAMs), and non-volatile memories, such as read-only memories (ROMs). The ECU 30 may include a processing circuit. The ECU 30 may include at least a portion of the memory M in the processing circuit.

[0036] Some or all of the functions of the ECU 30 may be realized by the CPU using the RAM as a working memory and executing a program recorded in the ROM. Some or all of the functions of the ECU 30 may be realized by a dedicated hardware circuit such as an electronic circuit or an integrated circuit. Some or all of the functions of the ECU 30 may be realized by a combination of the above-mentioned software functions and hardware circuits. Communication between the ECU 30 and devices mounted on the vehicle 1, such as various actuators and various sensors, may be communication via an in-vehicle network such as a CAN (Controller Area Network).

[0037] The ECU 30 adjusts the torque output by the electric motor 20 in response to detection signals from sensors that detect the vehicle state of the vehicle 1. For example, the ECU 30 determines the torque required of the electric motor 20 using the rotation speed of the electric motor 20 detected via the rotation sensor 21 and a command value for the load of the electric motor 20. The command value for the load is related to the rotation position of the throttle grip 41 detected via the throttle position sensor 41a. The ECU 30 can determine the command value for the load based on the rotation position of the throttle grip 41. The rotation speed of the electric motor 20 corresponds to the rotation speed of the motor shaft 20a and can be expressed as the number of rotations of the motor shaft 20a per minute.

[0038] The ECU 30 stores a preset required torque map in the memory M. The required torque map is a list of graphs in which the torque required of the electric motor 20 is determined by the rotation speed of the electric motor 20 and the load on the electric motor 20. The required torque map may be set for each driving mode. The required torque map may be set for each reduction ratio of the transmission 112. The ECU 30 can determine the required torque required of the electric motor 20 using the detection results of the rotation sensor 21, the detection results of the throttle position sensor 41a, and the required torque map.

[0039] The ECU 30 performs traction control to suppress the effective torque, which is the torque generated by the electric motor 20, below the required torque, depending on the vehicle state of the vehicle 1 based on the required torque to the electric motor 20 and the rate of change of the rotation speed of the electric motor 20.

[0040] In the present embodiment, the rate of change in the rotation speed of the electric motor 20 is the amount of change in the rotation speed of the electric motor 20 per predetermined period, although this is not limited thereto. For example, the rate of change in the rotation speed of the electric motor 20 may be the ratio of the amount of change in the rotation speed of the electric motor 20 per predetermined period to the rotation speed of the electric motor 20. The predetermined period may be any period. For example, the predetermined period may be a period related to the operation of the ECU 30, or may be a period unrelated to the operation of the ECU 30. Examples of periods related to the operation of the ECU 30 may include a period during which the ECU 30 acquires detection results from the rotation sensor 21 or the throttle position sensor 41a, and a period during which the ECU 30 determines whether or not to execute traction control.

[0041] Traction control according to the embodiment will now be described. Regarding traction control, the ECU 30 stores in the memory M a torque-change rate relationship, which is a relationship between the torque required of the electric motor 20 and an upper threshold value of the allowable rate of change of the rotation speed of the electric motor 20 relative to the torque required of the electric motor 20. Examples of the torque-change rate relationship may include a set of numerical values, a relational expression, and a map.

[0042] For example, the set of numerical values ​​may be a set of the torque required for the electric motor 20 and an upper threshold value. The relational expression may be a relational expression between the torque required for the electric motor 20 and the upper threshold value. The map may be a map that lists graphs that determine whether the rate of change of the torque required for the electric motor 20 and the rotation speed of the electric motor 20 exceeds the upper threshold value based on the rate of change. The ECU 30 performs traction control using the torque-rate of change relationship.

[0043] Figure 3 is a diagram showing an example of the torque-rate-of-change relationship used in traction control according to this embodiment. In Figure 3, the horizontal axis represents the torque required of electric motor 20, with torque expressed in units of N·m. The vertical axis represents the rate of change of the rotational speed of electric motor 20 converted into the rate of change per second, with units of rpm / second, where rpm stands for revolutions per minute, or the number of rotations per minute.

[0044] An upper limit threshold for the rate of change of the rotation speed of the electric motor 20 is set for each torque required for the electric motor 20. In FIG. 3 , the relationship between the torque required for the electric motor 20 and the upper limit threshold is a linear function, but it may be another function or a relationship obtained from actual driving results of the vehicle 1. In this embodiment, the upper limit threshold is set lower than the limit rate of change of the rotation speed of the electric motor 20, but it may also be set higher than the limit rate of change. The limit rate of change is the rate of change of the rotation speed of the electric motor 20 at which the rear wheels 12 begin to slip, relative to the torque required for the electric motor 20. Like the upper limit threshold, the limit rate of change can be set for various torques required for the electric motor 20. The limit rate of change is one of the limit rates of change of the rotation speed. The difference obtained by subtracting the upper limit threshold from the limit rate of change may vary or may be constant depending on the magnitude of the torque required for the electric motor 20.

[0045] A plurality of control modes can be set for the traction control. In this embodiment, the plurality of control modes are set for one or more of the driving mode, the traction mode, and the reduction ratio of the transmission 112. The torque-rate of change relationship is set corresponding to the control mode, or is set by the ECU 30 correcting an upper limit threshold in the torque-rate of change relationship common to the plurality of control modes.

[0046] In the control mode related to the driving modes, the torque-change rate relationship may be set for each of the plurality of driving modes, or may be set commonly to the plurality of driving modes. The ECU 30 may switch the torque-change rate relationship set for each driving mode according to the driving mode currently being executed. The ECU 30 may correct the upper limit threshold in the common torque-change rate relationship according to the driving mode currently being executed. The correction of the upper limit threshold may be performed using a conversion formula between driving modes, a numerical correspondence relationship between driving modes, or the like.

[0047] For example, for the same torque value required of the electric motor 20, the upper threshold for the stability-oriented mode may be greater than the upper threshold for the energy-saving mode, the upper threshold for the sport-oriented mode may be greater than the upper threshold for the stability-oriented mode, and the upper threshold for the boost mode may be greater than the upper threshold for the sport-oriented mode. For example, the upper thresholds for the stability-oriented mode and the energy-saving mode may be lower than the limit rate of change. The upper thresholds for the boost mode and the sport-oriented mode may be equal to or greater than the limit rate of change.

[0048] The boost mode is one of the first control modes, and in this case, the sport-oriented mode, the stability-oriented mode, or the energy-saving mode is one of the second control modes. The sport-oriented mode is one of the first control modes, and in this case, the stability-oriented mode or the energy-saving mode is one of the second control modes. The stability-oriented mode is one of the first control modes, and in this case, the energy-saving mode is one of the second control modes.

[0049] In the control mode related to the traction mode, the torque-rate change relationship may be set for each of the plurality of traction modes, or may be set commonly to the plurality of traction modes. The ECU 30 may switch the torque-rate change relationship set for each of the traction modes according to the currently executed traction mode. The ECU 30 may correct the upper limit threshold in the common torque-rate change relationship according to the currently executed traction mode. The correction of the upper limit threshold may be performed using a conversion formula between the traction modes, a numerical correspondence relationship between the traction modes, or the like.

[0050] For example, for the same torque required of electric motor 20, the upper threshold for the first traction mode may be greater than the upper threshold for the second traction mode, which may be greater than the upper threshold for the third traction mode. For example, the difference between the upper threshold for the second traction mode and the upper threshold for the third traction mode may be greater than the difference between the upper threshold for the first traction mode and the upper threshold for the second traction mode. For example, the upper threshold for the first traction mode may be equal to or greater than the limit rate of change. The upper thresholds for the second traction mode and the third traction mode may be less than the limit rate of change. The difference between the upper threshold for the first traction mode minus the limit rate of change may be greater than the difference between the upper threshold for the second traction mode minus the limit rate of change, and the difference between the upper threshold for the second traction mode minus the limit rate of change may be greater than the difference between the upper threshold for the third traction mode minus the limit rate of change.

[0051] The first traction mode is one of the first control modes, in which case the second traction mode or the third traction mode is one of the second control modes. The second traction mode is one of the first control modes, in which case the third traction mode is one of the second control modes.

[0052] In the control mode related to the reduction ratio of the transmission 112, the torque-change rate relationship may be set for each of the multiple reduction ratios of the transmission 112, or may be set commonly to the multiple reduction ratios. The ECU 30 may switch the torque-change rate relationship set for each reduction ratio depending on the reduction ratio selected in the transmission 112. The ECU 30 may correct the upper limit threshold in the common torque-change rate relationship depending on the reduction ratio selected in the transmission 112. For example, the upper limit threshold may be set so that the difference between the upper limit threshold and the limit rate of change increases as the reduction ratio selected in the transmission 112 decreases for the same torque required of the electric motor 20. The smaller the reduction ratio selected in the transmission 112, the greater the difference between the upper limit threshold and the limit rate of change. The smaller the reduction ratio selected in the transmission 112, the greater the high-speed driving. Furthermore, the smaller the reduction ratio selected in the transmission 112, the smaller the limit rate of change for the same torque required of the electric motor 20. Furthermore, the smaller the reduction ratio selected in the transmission 112, the less likely the rear wheels 12 will slip, even if the electric motor 20 generates the same torque. For this reason, the upper limit threshold is set so that, for the same torque, the smaller the reduction ratio, the greater the difference obtained by subtracting the limit change rate from the upper limit threshold.

[0053] The control mode at the smaller reduction ratio is one of the first control modes, and the control mode at the larger reduction ratio is one of the second control modes.

[0054] The control mode may be set for two or more combinations of the driving mode, the traction mode, and the reduction ratio of the transmission 112. In this case, the torque-change rate relationship is set for two or more combinations of the driving mode, the traction mode, and the reduction ratio of the transmission 112. The torque-change rate relationship may be set for each of the multiple combinations, or may be set commonly for the multiple combinations. The ECU 30 may switch the torque-change rate relationship set for each combination depending on the selected combination. The ECU 30 may correct the upper limit threshold in the common torque-change rate relationship depending on the selected combination. The setting of the upper limit threshold may be a combination of the methods for setting the upper limit threshold for the driving mode, the traction mode, and the reduction ratio.

[0055] The ECU 30 applies the torque required for the electric motor 20 and the rate of change in the rotation speed of the electric motor 20 to a torque-rate of change relationship to determine whether the rate of change in the rotation speed of the electric motor 20 exceeds an upper threshold value corresponding to the required torque. The ECU 30 executes traction control when the rate of change in the rotation speed of the electric motor 20 exceeds the upper threshold value.

[0056] In the traction control, the ECU 30 reduces the effective torque T generated by the electric motor 20 to be less than the required torque Tr so that the rate of change R of the rotation speed of the electric motor 20 becomes a target rate of change RT that is equal to or less than the upper threshold value Th.

[0057] The ECU 30 obtains the torque suppression amount Ts from the required torque Tr or the effective torque T after suppression based on the rate of change R of the rotation speed of the electric motor 20 and the target rate of change RT. The ECU 30 may store a suppression torque relationship, which is the relationship between the rate of change R of the rotation speed of the electric motor 20, the target rate of change RT, and the torque suppression amount Ts of the electric motor 20 or the effective torque T after suppression, in the memory M. Examples of the suppression torque relationship may include a set of numerical values, a relational expression, and a map. The ECU 30 can obtain the torque suppression amount Ts of the electric motor 20 or the effective torque T after suppression by applying the rate of change R of the rotation speed of the electric motor 20 and the target rate of change RT to the suppression torque relationship.

[0058] For example, the set of numerical values ​​may be a set of the rate of change R of the rotation speed of the electric motor 20, the target rate of change RT, and the suppression amount Ts of the torque of the electric motor 20, or a set of the rate of change R, the target rate of change RT, and the effective torque T after suppression of the electric motor 20. The relational expression may be a relational expression between the rate of change R of the rotation speed of the electric motor 20, the target rate of change RT, and the suppression amount Ts of the torque of the electric motor 20 or the effective torque T after suppression. The map may be a map in the form of a list of graphs in which the suppression amount Ts of the torque of the electric motor 20 or the effective torque T after suppression is determined by the rate of change R of the rotation speed of the electric motor 20 and the target rate of change RT.

[0059] The suppression amount Ts of the torque of the electric motor 20 is obtained using the moment of inertia J of the rear wheels 12, the rate of change R of the rotation speed of the electric motor 20, the target rate of change RT, and a coefficient C. The moment of inertia J may be the moment of inertia of only the rear wheels 12, or may be the moment of inertia of a rotating body including the rear wheels 12 and components of the vehicle 1 that rotate integrally with the rear wheels 12. Specifically, the suppression amount Ts is obtained by Ts = J × C × (R - RT). Then, the effective torque T of the electric motor 20 is obtained as torque (Tr - Ts) using the required torque Tr and the suppression amount Ts. The set of numerical values, relational expressions, and maps relating to the suppression torque may be set based on the above-mentioned formula for calculating the suppression amount Ts.

[0060] The ECU 30 outputs a command value for the effective torque T of the electric motor 20 to the current control circuit 22. This allows the vehicle 1 to run with slip of the rear wheels 12 suppressed.

[0061] For example, Fig. 4 shows an example of the behavior of a combination of the required torque Tr of the electric motor 20 and the rate of change R of the rotation speed of the electric motor 20. In Fig. 4, this behavior is indicated by a dashed arrow. In state A1, the rate of change R1 of the rotation speed of the electric motor 20 is less than the upper threshold value Th1 of the rate of change corresponding to the required torque Tr1. Therefore, the required torque Tr1 is used as the effective torque T1 of the electric motor 20.

[0062] In state B1, which is a transition state from state A1, the rate of change R2 of the rotation speed of the electric motor 20 exceeds the upper threshold value Th2 of the rate of change corresponding to the required torque Tr2. The ECU 30 executes traction control to suppress the effective torque T of the electric motor 20 below the required torque Tr2.

[0063] Specifically, the ECU 30 determines the effective torque T of the electric motor 20 so that the rate of change R of the rotation speed of the electric motor 20 becomes a target rate of change RT2 that is equal to or less than an upper threshold value Th2. In Fig. 4, the target rate of change RT2 is equal to the upper threshold value Th2. In this example, the ECU 30 calculates the torque suppression amount Ts2 from the required torque Tr2 by Ts2 = J × C × (R2 - Th2), and determines the torque (Tr2 - Ts2) as the effective torque T.

[0064] The operation of the ECU 30 in the traction control according to the embodiment will be described. Fig. 5 is a flowchart showing an example of the operation of the ECU 30 according to the embodiment. As shown in Fig. 5, in step S101, the ECU 30 acquires a command value from the throttle position sensor 41a of the throttle grip 41.

[0065] In step S102, the ECU 30 acquires the rotation speed of the electric motor 20 from the rotation sensor 21.

[0066] In step S103, the ECU 30 determines the required torque of the electric motor 20 by applying the command value of the throttle position sensor 41a and the rotation speed of the electric motor 20 to a required torque map. The ECU 30 may read and use the required torque map corresponding to the currently executed driving mode from the required torque maps set for each driving mode in the memory M.

[0067] In step S104, ECU 30 applies the required torque and the rate of change of the rotation speed of electric motor 20 to the torque-rate of change relationship to determine whether the rate of change of the rotation speed of electric motor 20 exceeds an upper threshold value corresponding to the required torque. ECU 30 may read and use the torque-rate of change relationship corresponding to the currently executed control mode from among the torque-rate of change relationships set in memory M corresponding to the control modes. ECU 30 may also read from memory M a torque-rate of change relationship set commonly to all the control modes, and correct the upper threshold value included in the torque-rate of change relationship according to the currently executed control mode, thereby correcting the torque-rate of change relationship for use.

[0068] If the rate of change of the rotation speed of the electric motor 20 exceeds the upper threshold (Yes in step S104), the ECU 30 proceeds to step S105, and if the rate of change of the rotation speed of the electric motor 20 is equal to or less than the upper threshold (No in step S104), the ECU 30 proceeds to step S106.

[0069] In step S105, the ECU 30 determines a torque suppression amount from the required torque of the electric motor 20 so that the rate of change in the rotation speed of the electric motor 20 is equal to or less than the upper threshold. Furthermore, the ECU 30 determines the effective torque to be generated by the electric motor 20 by subtracting the torque suppression amount from the required torque. The effective torque is the torque suppressed from the required torque.

[0070] In step S107, the ECU 30 controls the current control circuit 22 so as to cause the electric motor 20 to generate effective torque. That is, the ECU 30 controls the electric motor 20 in accordance with the effective torque. After step S107, the ECU 30 returns to step S101.

[0071] In step S106, the ECU 30 determines the required torque of the electric motor 20 as the effective torque of the electric motor 20. The effective torque is the torque that is not suppressed from the required torque. After step S106, the ECU 30 proceeds to step S107.

[0072] In steps S101 to S107, the ECU 30 determines whether to intervene in traction control based on the rate of change of the rotation speed of the electric motor 20 and an upper threshold value for that rate of change that corresponds to the required torque of the electric motor 20. In the traction control, the ECU 30 reduces the rate of change of the rotation speed of the electric motor 20 to equal to or lower than the upper threshold value, thereby suppressing the torque generated by the electric motor 20 and preventing slippage of the rear wheels 12. Steps S101 and S102 may be performed in the reverse order or in parallel.

[0073] The ECU 30 may execute the series of processes from step S101 to step S107 at predetermined intervals. That is, the ECU 30 may execute the determination of step S104 at predetermined intervals. For example, the predetermined interval may be set to a interval of one second or less. The predetermined interval may be set arbitrarily within one of the following ranges: greater than 0 milliseconds and less than 10 milliseconds; greater than 10 milliseconds and less than 20 milliseconds; greater than 20 milliseconds and less than 100 milliseconds; and greater than 100 milliseconds and less than 1 second.

[0074] [Variation 1] A first modification of the embodiment will be described. The first modification differs from the embodiment in that the ECU 30 performs two patterns of traction control using two upper limit thresholds. In the following, the differences between this modification and the embodiment will be described, and the same points as the embodiment will be omitted as appropriate.

[0075] The configuration of the vehicle 1 according to the first modification is the same as the configuration of the vehicle according to the embodiment shown in Figures 1 and 2. The ECU 30 stores the first torque-rate of change relationship and the second torque-rate of change relationship in a memory M.

[0076] The first torque-change rate relationship is the relationship between the torque required of the electric motor 20 and a first threshold value that is a first upper limit threshold value for the allowable rate of change in the rotation speed of the electric motor 20 relative to the torque required of the electric motor 20. The first threshold value may be the same as the upper limit threshold value according to the embodiment. In this modification, the first threshold value is set lower than the limit rate of change in the rotation speed of the electric motor 20, but may also be set higher than the limit rate of change. The first threshold value may be a threshold value that allows a typical driver or a novice driver to safely tolerate the driving state of the vehicle 1.

[0077] The second torque-rate of change relationship is the relationship between the torque required of the electric motor 20 and a second threshold value that is a second upper limit threshold for the allowable rate of change of the rotational speed of the electric motor 20 relative to the torque required of the electric motor 20. The second threshold value is greater than the first threshold value. For example, the second threshold value may be a threshold value such that, when the rate of change of the rotational speed of the electric motor 20 exceeds the second threshold value, generating a torque corresponding to the rate of change in the electric motor 20 would result in an excessive amount of slip of the rear wheels 12. In this modification, the second threshold value is set higher than the limit rate of change. For example, the difference obtained by subtracting the limit rate of change from the second threshold value is greater than the difference obtained by subtracting the first threshold value from the limit rate of change. The difference obtained by subtracting the limit rate of change from the second threshold value may vary or may be constant depending on the magnitude of the torque required of the electric motor 20. The difference obtained by subtracting the first threshold value from the limit rate of change may vary or may be constant depending on the magnitude of the torque required of the electric motor 20.

[0078] The first torque-rate change relationship and the second torque-rate change relationship may be stored separately in the memory M, or both may be stored together in the memory M. The ECU 30 performs traction control according to this modification using the first and second torque-rate change relationships.

[0079] FIG. 6 is a diagram similar to FIG. 3 , illustrating an example of the torque-rate-of-change relationship used in traction control according to Modification 1. As shown in FIG. 6 , a first threshold value and a second threshold value for the rate of change of the rotation speed of the electric motor 20 are set for each torque required for the electric motor 20. In FIG. 6 , the relationship between the torque required for the electric motor 20 and the first threshold value and the relationship between the torque required for the electric motor 20 and the second threshold value are both linear functions. However, they may be other functional relationships or may be relationships obtained from actual driving results of the vehicle 1. The linear function related to the first threshold value and the linear function related to the second threshold value are parallel to each other, but this is not limiting. For example, the difference between the first threshold value and the second threshold value may change depending on the magnitude of the torque required for the electric motor 20.

[0080] The torque-change rate relationship according to this modification may be set for each of the plurality of control modes, as in the embodiment, or may be set commonly to the plurality of control modes.

[0081] The ECU 30 determines whether the rate of change in the rotation speed of the electric motor 20 exceeds a first threshold value and is equal to or smaller than a second threshold value, each corresponding to a required torque, and whether the rate of change in the rotation speed of the electric motor 20 exceeds the second threshold value, corresponding to the required torque. The ECU 30 executes traction control when the rate of change in the rotation speed of the electric motor 20 exceeds the first threshold value.

[0082] When the rate of change R of the rotation speed of the electric motor 20 exceeds a first threshold Tha and is equal to or smaller than a second threshold Thb corresponding to the required torque Tr, the ECU 30 executes first traction control, which is a first case of traction control. In the first traction control, the ECU 30 suppresses the effective torque T generated by the electric motor 20 to be less than the required torque Tr so that the rate of change R of the rotation speed of the electric motor 20 becomes a first target rate of change RTa that is equal to or smaller than the first threshold Tha.

[0083] The ECU 30 obtains the torque suppression amount Tsa from the required torque Tr or the effective torque T after suppression based on the rate of change R of the rotation speed of the electric motor 20 and the first target rate of change RTa. As in the embodiment, the ECU 30 may store in the memory M a first suppression torque relationship, which is the relationship between the rate of change R of the rotation speed of the electric motor 20, the first target rate of change RTa, and the torque suppression amount Tsa of the electric motor 20 or the effective torque T after suppression. Examples of the first suppression torque relationship may include a set of numerical values, a relational expression, and a map. The ECU 30 can obtain the torque suppression amount Tsa of the electric motor 20 or the effective torque T after suppression by applying the rate of change R of the rotation speed of the electric motor 20 and the first target rate of change RTa to the first suppression torque relationship.

[0084] For example, the torque suppression amount Tsa of the electric motor 20 is obtained by Tsa=J×C×(R−RTa). The effective torque T of the electric motor 20 is obtained by using the required torque Tr and the suppression amount Tsa as torque (Tr−Tsa). The set of numerical values, the relational expression, and the map of the first suppression torque relationship may be set based on the above-mentioned formula for calculating the suppression amount Tsa.

[0085] When the rate of change R of the rotation speed of the electric motor 20 exceeds a second threshold value Thb corresponding to the required torque Tr, the ECU 30 executes second traction control, which is a second case of traction control.

[0086] In the second traction control, the ECU 30 may suppress the effective torque T of the electric motor 20 to be less than the required torque Tr so that the rate of change R of the rotation speed of the electric motor 20 becomes a second target rate of change RTb that is less than the first threshold value Tha. The second target rate of change RTb may be smaller than the first target rate of change RTa.

[0087] Alternatively, in the second traction control, the ECU 30 may determine the effective torque T of the electric motor 20 to be a preset fixed torque Tf, regardless of changes in the rate of change R of the rotational speed of the electric motor 20. The fixed torque Tf does not correspond to changes in the rate of change R of the rotational speed of the electric motor 20 after the second traction control is started. The fixed torque Tf is a constant value regardless of changes in the rate of change R after the second traction control is started. For example, the fixed torque Tf is smaller than a limit torque, which is the torque of the electric motor 20 that causes the rear wheels 12 to slip. The limit torque is determined based on the effective torque of the electric motor 20 at the start of the traction control or the timing when the rear wheels 12 slip, and the angular acceleration of the rear wheels 12 or the rate of change in the rotational speed of the electric motor 20. The fixed torque Tf may be preset to correspond to the limit torque determined as described above and to be smaller than the limit torque. In this modification, the effective torque T after suppression is the fixed torque Tf.

[0088] When the effective torque T after suppression corresponds to the second target change rate RTb, the ECU 30 acquires the torque suppression amount Tsb from the required torque Tr or the effective torque T after suppression based on the rate of change R of the rotation speed of the electric motor 20 and the second target change rate RTb. As in the embodiment, the ECU 30 may store in the memory M a second suppression torque relationship which is the relationship between the rate of change R of the rotation speed of the electric motor 20, the second target change rate RTb, and the torque suppression amount Tsb of the electric motor 20 or the effective torque T after suppression. Examples of the second suppression torque relationship may include a set of numerical values, a relational expression, and a map.

[0089] For example, the torque suppression amount Tsb of the electric motor 20 is obtained by Tsb=J×C×(R−RTb). The effective torque T of the electric motor 20 is obtained by using the required torque Tr and the suppression amount Tsb as torque (Tr−Tsb). The set of numerical values, relational expression, and map of the second suppression torque relationship may be set based on the above-mentioned formula for calculating the suppression amount Tsb.

[0090] The ECU 30 outputs a command value for the effective torque T of the electric motor 20 determined by the first traction control or the second traction control to the current control circuit 22. This allows the vehicle 1 to travel with slippage of the rear wheels 12 suppressed according to the rate of change of the rotation speed of the electric motor 20.

[0091] For example, Fig. 7 shows an example of the behavior of a combination of the torque demand Tr for the electric motor 20 and the rate of change R of the rotation speed of the electric motor 20, similar to Fig. 4. The behavior is indicated by the dashed arrow. In this example, the effective torque after the electric motor 20 is suppressed in the second traction control is a fixed torque Tf.

[0092] 4, the rate of change R1 of the rotation speed of the electric motor 20 is less than the first threshold value Tha1 of the rate of change corresponding to the required torque Tr1. The required torque Tr1 is used as the effective torque T1 of the electric motor 20.

[0093] In state B2, the rate of change R2 of the rotation speed of the electric motor 20 exceeds the first threshold value Tha2 and is equal to or less than the second threshold value Thb2, where Tha2 and Thb2 correspond to the required torque Tr2. State B2 is similar to state B1 in FIG. 4. The ECU 30 determines the effective torque T of the electric motor 20 so that the rate of change R of the rotation speed of the electric motor 20 becomes a target rate of change RT2 that is equal to or less than the first threshold value Tha2. In FIG. 7, the target rate of change RT2 is equal to the first threshold value Tha2. In this example, the ECU 30 calculates the torque suppression amount Ts2 from the required torque Tr2 by Ts2 = J × C × (R2 - Tha2), and determines the effective torque T2 to be (Tr2 - Ts2).

[0094] In state C2, the rate of change R3 of the rotation speed of the electric motor 20 exceeds the first threshold value Tha3 and the second threshold value Thb3 corresponding to the required torque Tr3. The ECU 30 determines the effective torque T3 to be the fixed torque Tf.

[0095] For example, Fig. 8 shows another example of the behavior of a combination of the torque demand Tr for the electric motor 20 and the rate of change R of the rotation speed of the electric motor 20, similar to Fig. 4. This behavior is indicated by the dashed arrow. In this example, the effective torque after the electric motor 20 is restricted in the second traction control corresponds to the second target rate of change RTb.

[0096] 7, the rate of change R1 of the rotation speed of the electric motor 20 is less than the first threshold Tha1 corresponding to the required torque Tr1. The required torque Tr1 is used as the effective torque T1 of the electric motor 20.

[0097] 7, where the rate of change R2 of the rotation speed of the electric motor 20 exceeds the first threshold Tha2 and is equal to or smaller than the second threshold Thb2 corresponding to the required torque Tr1. In this example, the ECU 30 calculates the torque suppression amount Ts2 by Ts2=J×C×(R2−Tha2) so that the rate of change R of the rotation speed of the electric motor 20 becomes the target rate of change RT2, and determines the effective torque T2 to be the torque (Tr2−Ts2).

[0098] In state C3, the rate of change R3 of the rotation speed of the electric motor 20 exceeds the first threshold value Tha3 and the second threshold value Thb3 corresponding to the required torque Tr3. The ECU 30 determines the effective torque T of the electric motor 20 so that the rate of change R of the rotation speed of the electric motor 20 becomes a target rate of change RT3 that is less than the first threshold value Tha3. In this example, the ECU 30 calculates the torque suppression amount Ts3 from the required torque Tr3 by Ts3 = J × C × (R3 - RT3), and determines the effective torque T3 to be the torque (Tr3 - Ts3).

[0099] The following describes the operation of the ECU 30 in the traction control according to Modification 1. Fig. 9 is a flowchart showing an example of the operation of the ECU 30 according to Modification 1. As shown in Fig. 9, in step S201, the ECU 30 acquires a command value from the throttle position sensor 41a of the throttle grip 41.

[0100] In step S202, the ECU 30 acquires the rotation speed of the electric motor 20 from the rotation sensor 21.

[0101] In step S203, the ECU 30 determines the required torque of the electric motor 20, similarly to step S103 in FIG.

[0102] In step S204, the ECU 30 applies the required torque and the rate of change of the rotation speed of the electric motor 20 to the second torque-rate of change relationship to determine whether the rate of change of the rotation speed of the electric motor 20 exceeds a second threshold value corresponding to the required torque. The ECU 30 may read and use the second torque-rate of change relationship corresponding to the currently executed control mode from the second torque-rate of change relationships set for each control mode in the memory M. The ECU 30 may read from the memory M the second torque-rate of change relationship set commonly to all the control modes, and use the second torque-rate of change relationship by correcting the second threshold value according to the currently executed control mode.

[0103] If the rate of change of the rotation speed of the electric motor 20 exceeds the second threshold (Yes in step S204), the ECU 30 proceeds to step S205, and if the rate of change of the rotation speed of the electric motor 20 is equal to or less than the second threshold (No in step S204), the ECU 30 proceeds to step S206.

[0104] In step S205, the ECU 30 determines the effective torque of the electric motor 20, which is reduced from the required torque. In this example, the effective torque is a fixed torque Tf. The ECU 30 may determine the effective torque of the electric motor 20 so that the rate of change in the rotation speed of the electric motor 20 becomes a target rate of change that is less than the first threshold value. Therefore, the ECU 30 executes the second traction control.

[0105] In step S207, the ECU 30 controls the current control circuit 22 so as to cause the electric motor 20 to generate effective torque. After step S207, the ECU 30 returns to step S201.

[0106] In step S206, the ECU 30 applies the required torque and the rate of change of the rotation speed of the electric motor 20 to the first torque-rate-of-change relationship to determine whether the rate of change of the rotation speed of the electric motor 20 exceeds a first threshold value corresponding to the required torque. That is, based on the result of step S204, the ECU 30 determines whether the rate of change of the rotation speed of the electric motor 20 exceeds a first threshold value and is equal to or less than a second threshold value corresponding to the required torque. The ECU 30 may read and use the first torque-rate-of-change relationship corresponding to the currently executed control mode from the first torque-rate-of-change relationships set for each control mode in the memory M. The ECU 30 may read from the memory M the first torque-rate-of-change relationship set commonly to all the control modes, and use the first torque-rate-of-change relationship by correcting the first threshold value according to the currently executed control mode.

[0107] If the rate of change of the rotation speed of the electric motor 20 exceeds the first threshold and is equal to or less than the second threshold (Yes in step S206), the ECU 30 proceeds to step S208, and if the rate of change of the rotation speed of the electric motor 20 is equal to or less than the first threshold (No in step S206), the ECU 30 proceeds to step S209.

[0108] In step S208, the ECU 30 determines a torque suppression amount from the required torque of the electric motor 20 so that the rate of change of the rotation speed of the electric motor 20 becomes the first threshold value. Furthermore, the ECU 30 determines the effective torque of the electric motor 20 by subtracting the torque suppression amount from the required torque. Therefore, the ECU 30 executes the first traction control. After step S208, the ECU 30 proceeds to step S207.

[0109] In step S209, the ECU 30 determines the required torque of the electric motor 20 as the effective torque of the electric motor 20. After step S209, the ECU 30 proceeds to step S207.

[0110] In steps S201 to S209, when the rate of change of the rotation speed of the electric motor 20 exceeds the first threshold value and is equal to or less than the second threshold value, the ECU 30 reduces the rate of change of the rotation speed of the electric motor 20 to the first threshold value. This can prevent slippage of the rear wheels 12. When the rate of change of the rotation speed of the electric motor 20 exceeds the second threshold value, the ECU 30 reduces the torque of the electric motor 20 to a fixed torque Tf or reduces the rate of change of the rotation speed of the electric motor 20 to less than the first threshold value. This can prevent excessive increase in slippage of the rear wheels 12.

[0111] The rear wheels 12 in the second state where the rate of change of the rotation speed of the electric motor 20 exceeds the second threshold value may be slipping more than the rear wheels 12 in the first state where the rate of change of the rotation speed of the electric motor 20 exceeds the first threshold value but is equal to or less than the second threshold value. Since the effective torque of the electric motor 20 is reduced to the fixed torque Tf or a torque that makes the rate of change of the rotation speed of the electric motor 20 less than the first threshold value, slip of the rear wheels 12 is suppressed and the behavior of the vehicle 1 may be stabilized.

[0112] In the first state, the rear wheels 12 may not yet be slipping or may be slightly slipping. The effective torque of the electric motor 20 is suppressed to a torque greater than the torque suppressed in the second state, so that changes in the driving sensation, such as excessive deceleration felt by the driver due to the intervention of traction control, are suppressed.

[0113] The ECU 30 may execute the series of processes from step S201 to step S209 at predetermined intervals. That is, the ECU 30 may execute the determination of step S204 or S206 at predetermined intervals. For example, the predetermined interval may be set to a interval of one second or less. The predetermined interval may be set arbitrarily within one of the following ranges: greater than 0 milliseconds and less than 10 milliseconds; greater than 10 milliseconds and less than 20 milliseconds; greater than 20 milliseconds and less than 100 milliseconds; and greater than 100 milliseconds and less than 1 second.

[0114] Steps S201 and S202 may be performed in the reverse order or in parallel, and steps S204 and S206 may be performed in the reverse order or in parallel.

[0115] [Variation 2] A second modification of the embodiment will be described. The second modification differs from the embodiment and the first modification in that the ECU 30 is configured to execute return control to return the effective torque of the electric motor 20, which has been reduced so that the rate of change of the rotation speed of the electric motor 20 becomes a target rate of change that is less than an upper threshold, toward the torque required for the electric motor 20. Below, the differences between this modification and the embodiment or the first modification will be described, and descriptions of the similarities between the embodiment or the first modification will be omitted as appropriate.

[0116] The configuration of vehicle 1 according to Modification 2 is the same as the configuration of the vehicle according to the embodiment shown in Figures 1 and 2. ECU 30 executes return control to return the effective torque of electric motor 20, which was suppressed in the traction control according to the embodiment or Modification 1, toward the required torque for electric motor 20 commanded by throttle position sensor 41a.

[0117] When traction control is initiated, the ECU 30 acquires the limit torque of the electric motor 20 that causes the rear wheels 12 to slip. The ECU 30 acquires the limit torque based on the rate of change of the rotation speed of the electric motor 20 and the effective torque generated by the electric motor 20. The ECU 30 may store a limit torque relationship, which is the relationship between the rate of change of the rotation speed of the electric motor 20, the effective torque generated by the electric motor 20, and the limit torque of the electric motor 20, in the memory M. Examples of the limit torque relationship may include a set of numerical values, a relational expression, and a map. The ECU 30 can acquire the limit torque of the electric motor 20 by applying the rate of change of the rotation speed of the electric motor 20 and the effective torque of the electric motor 20 to the limit torque relationship.

[0118] For example, the set of numerical values ​​may be a set of the rate of change of the rotation speed of the electric motor 20, the effective torque of the electric motor 20, and the limit torque of the electric motor 20. The relational expression may be a relational expression (to be described later) between the rate of change of the rotation speed of the electric motor 20, the effective torque of the electric motor 20, and the limit torque of the electric motor 20. The map may be a map that lists graphs in which the limit torque of the electric motor 20 is determined by the rate of change of the rotation speed of the electric motor 20 and the effective torque of the electric motor 20.

[0119] The ECU 30 may use the rate of change in the rotation speed of the electric motor 20 and the effective torque of the electric motor 20 at the start of traction control to obtain the limit torque. Alternatively, the ECU 30 may detect the timing at which the rear wheels 12 slip based on the detection results of the front wheel speed sensor 51 and the rear wheel speed sensor 52 provided in the vehicle 1. The ECU 30 may use the rate of change in the rotation speed of the electric motor 20 and the effective torque of the electric motor 20 at that timing to obtain the limit torque. The ECU 30 may detect the peak value of the rate of change in the rotation speed at and around the detection timing of the element used to obtain the limit torque as the rate of change in the rotation speed of the electric motor 20.

[0120] As described above, the limit torque is obtained using the angular acceleration of the rear wheels 12, the effective torque T of the electric motor 20, and the moment of inertia J of the rear wheels 12. Alternatively, the limit torque is obtained using the rate of change R of the rotation speed of the electric motor 20, the effective torque T of the electric motor 20, and the rotational inertia of the rear wheels 12. In this modified example, the latter is used. The rotational inertia can be expressed using the moment of inertia J of the rear wheels 12 and a coefficient C. The limit torque TL is obtained by TL = TJ × C × R. The set of numerical values, relational expressions, and maps related to the limit torque may be set based on the above-mentioned formula for calculating the limit torque TL.

[0121] The ECU 30 starts the return control after causing the electric motor 20 to generate an effective torque that is reduced from the required torque. For example, the start timing of the return control may be the timing when the ECU 30 outputs an effective torque command to the current control circuit 22, the timing when the slip of the rear wheels 12 has converged, or the timing when the electric motor 20 has output the effective torque. The timing when the slip of the rear wheels 12 has converged may be estimated by the ECU 30 based on the detection results of the front wheel speed sensor 51 and the rear wheel speed sensor 52. The timing when the electric motor 20 has output the effective torque may be estimated by the ECU 30 based on feedback information of the current value received from the current control circuit 22.

[0122] After starting the return control, the ECU 30 outputs a first return command to the current control circuit 22 to increase the effective torque to be generated by the electric motor 20 at a predetermined first return speed toward the required torque calculated from the detection result of the throttle position sensor 41a. The ECU 30 may determine the first return speed to be a speed corresponding to the rate of change R of the rotation speed of the electric motor 20. For example, the first return speed may be increased as the rate of change R increases. The ECU 30 may use the rate of change of the rotation speed at the start timing of the return control or the rate of change of the rotation speed used to obtain the limit torque to determine the first return speed.

[0123] The first return speed may vary depending on the control mode. For example, in a control mode related to a driving mode, the first return speed in the stability-oriented mode may be higher than the first return speed in the energy-saving mode, the first return speed in the sport-oriented mode may be higher than the first return speed in the stability-oriented mode, and the first return speed in the boost mode may be higher than the first return speed in the sport-oriented mode. In a control mode related to a traction mode, the first return speed in the second traction mode may be higher than the first return speed in the third traction mode, and the first return speed in the first traction mode may be higher than the first return speed in the second traction mode. In a control mode related to a reduction ratio selected in transmission 112, the first return speed may be higher as the reduction ratio selected in transmission 112 becomes smaller.

[0124] When the ECU 30 detects that the effective torque of the electric motor 20 has reached the limit torque, the ECU 30 outputs a second return command to the current control circuit 22 to increase the effective torque generated by the electric motor 20 toward the required torque at a predetermined second return speed. The magnitude of the second return speed is smaller than the magnitude of the first return speed. The required torque is greater than the limit torque.

[0125] The second return speed may vary depending on the control mode. For example, in a control mode related to a driving mode, the second return speed in the stability-oriented mode may be higher than the second return speed in the energy-saving mode, the second return speed in the sport-oriented mode may be higher than the second return speed in the stability-oriented mode, and the second return speed in the boost mode may be higher than the second return speed in the sport-oriented mode. In a control mode related to a traction mode, the second return speed in the second traction mode may be higher than the second return speed in the third traction mode, and the second return speed in the first traction mode may be higher than the second return speed in the second traction mode. In a control mode related to a reduction ratio selected in transmission 112, the second return speed may be higher as the reduction ratio selected in transmission 112 becomes smaller.

[0126] Because the effective torque of the electric motor 20 exceeds the limit torque, slippage may occur at the rear wheels 12. As a result, the rate of change of the rotation speed of the electric motor 20 exceeds the upper limit threshold or the first threshold corresponding to the torque required of the electric motor 20. Therefore, the ECU 30 executes traction control. The traction control is executed when the effective torque of the electric motor 20 is close to the limit torque.

[0127] During traction control, the ECU 30 determines the effective torque of the electric motor 20 so that the rate of change of the rotational speed of the electric motor 20 becomes an upper limit threshold or a first threshold corresponding to the limit torque. The upper limit threshold or the first threshold corresponding to the limit torque is the upper limit threshold or the first threshold when the limit torque is set to the torque required of the electric motor 20. Immediately before the start of traction control, the effective torque of the electric motor 20 returns at the second return speed, and therefore the rate of change of the rotational speed of the electric motor 20 is small. For this reason, during traction control, the effective torque of the electric motor 20 decreases at a gentle rate.

[0128] When the ECU 30 determines that the rate of change of the rotation speed of the electric motor 20 has fallen below the upper limit threshold or the first threshold corresponding to the limit torque due to a decrease in the effective torque of the electric motor 20, the ECU 30 starts return control to increase the effective torque of the electric motor 20 at a second return speed toward the required torque. The required torque is greater than the effective torque. The return control is performed when the effective torque of the electric motor 20 is close to the limit torque.

[0129] The ECU 30 repeats the return control and the traction control until the effective torque of the electric motor 20 and the required torque converge to each other and become the same. At this time, the effective torque of the electric motor 20 fluctuates within a small fluctuation range near the limit torque. This allows the vehicle 1 to exhibit stable behavior.

[0130] For example, FIG. 10 shows an example comparing the behavior of the effective torque of the electric motor 20 between an implementation case in which the return control according to Modification 2 is implemented and a non-implementation case in which the return control according to Modification 2 is not implemented. FIG. 10 shows an example in which the second traction control according to Modification 1 is implemented. In FIG. 10, the horizontal axis represents elapsed time, and the vertical axis represents the torque of the electric motor 20. The behavior of the torque required for the electric motor 20 is shown by a dashed line. The behavior of the effective torque of the electric motor 20 in the implementation case is shown by a solid line. The behavior of the effective torque of the electric motor 20 in the non-implementation case is shown by a dashed line. In the non-implementation case, the return speed of the effective torque of the electric motor 20 is maintained at the first return speed even if the effective torque exceeds the limit torque.

[0131] The ECU 30 starts the traction control at time t1, stops the traction control at a subsequent time t2, and starts the return control. After time t2, in both the implementation case and the non-implementation case, the ECU 30 increases the effective torque of the electric motor 20 at a first return speed.

[0132] In this embodiment, the ECU 30 reduces the increase rate of the effective torque of the electric motor 20 to a second return speed at time t11 when the effective torque reaches the limit torque. At a subsequent time t12, the ECU 30 initiates traction control, reducing the effective torque of the electric motor 20. At a subsequent time t13, the ECU 30 increases the effective torque of the electric motor 20 at the second return speed. Thereafter, the ECU 30 repeats the traction control and the return of the effective torque of the electric motor 20 at the second return speed until the required torque decreases to the limit torque. During this repetitive process, the fluctuation range of the effective torque is kept small.

[0133] In the non-exemplary case, the ECU 30 stops the return control at time t21 when the effective torque of the electric motor 20 reaches the required torque, and immediately thereafter starts traction control. During traction control, the effective torque of the electric motor 20 behaves similarly to the traction control from time t1 to time t2. At a subsequent time t22, the ECU 30 starts return control at the first return speed. When the effective torque of the electric motor 20 reaches the required torque, the ECU 30 performs traction control similar to the traction control from time t1 to time t2. Thereafter, the ECU 30 may repeat the return of the effective torque of the electric motor 20 at the first return speed and the traction control until the required torque drops to the limit torque. During this repetitive process, the effective torque repeatedly fluctuates over a range significantly larger than in the exemplary case.

[0134] Therefore, the vehicle 1 exhibits more stable behavior in the implemented case than in the non-implemented case, and the driver can safely operate the vehicle 1. The return control according to this modification may be applied to the traction control of the embodiment, or may be applied to the first traction control of the first modification.

[0135] [Variation 3] Modification 3 of the embodiment will be described. Modification 3 differs from the embodiment, Modification 1, and Modification 2 in that the ECU 30 uses a torque-rate-of-change relationship that reflects the state of the vehicle 1A in traction control. Below, the differences between this modification and the embodiment, Modification 1, or Modification 2 will be described, and descriptions of the similarities with the embodiment, Modification 1, or Modification 2 will be omitted as appropriate.

[0136] The configuration of vehicle 1A according to Modification 3 is the same as the configuration of vehicle 1 according to the embodiment shown in Fig. 1. Fig. 11 is a schematic diagram showing an example of the power system of vehicle 1A according to Modification 3. As shown in Fig. 11, vehicle 1A includes inertial force sensor 60 in addition to the components included in vehicle 1 according to the embodiment.

[0137] Inertial force sensor 60 is used to detect the attitude of vehicle 1A and control the behavior of vehicle 1A, and outputs the detection results to ECU 30. Inertial force sensor 60 includes an acceleration sensor and may further include a gyro sensor. The acceleration sensor detects acceleration in two or three mutually intersecting detection axis directions, and in this embodiment, detects acceleration in the three detection axis directions of vehicle 1A: left-right, up-down, and front-rear directions. The gyro sensor detects angular velocity or angular acceleration around two or three mutually intersecting detection axes. The detection axes of the gyro sensor may be the same as the detection axes of the acceleration sensor.

[0138] The control content of the ECU 30 according to this modification will be described in detail. The ECU 30 determines a torque-rate change relationship in which the upper limit threshold is increased or decreased from a reference upper limit threshold based on one or more of the vehicle 1A conditions, including the speed of the vehicle 1A, the attitude of the vehicle 1A, the slip ratio of the vehicle 1A, the difference between the front and rear wheel speeds of the vehicle 1A, and the change in torque required for the electric motor 20. The reference upper limit threshold is the upper limit threshold of the torque-rate change relationship according to the embodiment, modification 1, or modification 2. The reference upper limit threshold may also be the upper limit threshold of the torque-rate change relationship in each control mode. The ECU 30 may correct the reference upper limit threshold. The ECU 30 may store in advance in the memory M a map of the torque-rate change relationship in which an increase or decrease processing has been performed with respect to the reference upper limit threshold, and switch the map to be used depending on the state of the vehicle 1A.

[0139] When the speed of the vehicle 1A is used, the ECU 30 may acquire detection results from the front wheel speed sensor 51 or the rear wheel speed sensor 52 and detect the speed of the vehicle 1A based on the results. The ECU 30 may decrease the upper limit threshold as the speed of the vehicle 1A increases. As the speed of the vehicle 1A increases, the critical rate of change in the rotation speed of the electric motor 20 that causes slip of the rear wheels 12 may decrease even if the electric motor 20 generates the same torque. The ECU 30 determines a torque-rate-of-change relationship that includes an upper limit threshold that varies from a reference upper limit threshold depending on the speed of the vehicle 1A. The amount of variation of the upper limit threshold from the reference upper limit threshold corresponding to a specific speed of the vehicle 1A may be constant regardless of the torque required of the electric motor 20, or may vary depending on the torque required of the electric motor 20. For example, the amount of variation of the upper limit threshold from the reference upper limit threshold may increase as the torque required of the electric motor 20 increases.

[0140] When the attitude of vehicle 1A is used, ECU 30 may obtain a detection result from inertial force sensor 60 and detect the attitude of vehicle 1A based on the result. ECU 30 may increase the upper limit threshold as the amount of tilt of vehicle 1A in the forward tilt direction increases, and may decrease the upper limit threshold as the amount of tilt of vehicle 1A in the backward tilt direction increases.

[0141] For example, vehicle 1A tilts forward when descending a slope. The ratio of rear wheel load to front wheel load of vehicle 1A in a forward-leaning posture is smaller than that of vehicle 1A in a horizontal posture, and therefore the torque of electric motor 20 that causes rear wheels 12 of vehicle 1A in a forward-leaning posture to begin slipping is smaller than that of vehicle 1A in a horizontal posture. Furthermore, vehicle 1A in a forward-leaning posture is more likely to increase in speed due to the effect of gravity, and the torque generated by electric motor 20 is more likely to accelerate vehicle 1A in a forward-leaning posture. Therefore, the rate of change of the rotation speed of electric motor 20 in a forward-leaning posture is affected differently from that in a horizontal posture by the torque of electric motor 20 and the effect of gravity. For example, even if the torque generated by electric motor 20 is the same in both the forward-leaning posture and the horizontal posture, the rate of change of the rotation speed of electric motor 20 in a forward-leaning posture may be greater than the rate of change of the rotation speed of electric motor 20 in a horizontal posture. For this reason, if the same upper limit threshold is used for both the forward tilted posture and the horizontal posture, the rate of change in the rotation speed of the electric motor 20 may exceed the upper limit threshold even if the rear wheels 12 of the vehicle 1A in the forward tilted posture are not slipping. Furthermore, the greater the amount of forward tilt of the vehicle 1A, the greater the possibility that the rear wheels 12 are not slipping even if the rate of change in the rotation speed of the electric motor 20 exceeds the upper limit threshold. Therefore, the greater the amount of forward tilt of the vehicle 1A, the greater the upper limit threshold may be corrected to be larger.

[0142] For example, when the vehicle 1A climbs a slope, it tilts backward. The ratio of the rear wheel load to the front wheel load of the vehicle 1A in a backward tilted position is greater than that of the vehicle 1A in a horizontal position. Therefore, the torque of the electric motor 20 that causes the rear wheels 12 of the vehicle 1A in a backward tilted position to begin to slip is greater than that of the vehicle 1A in a horizontal position. Furthermore, the vehicle 1A in a backward tilted position is less likely to increase its speed due to the effect of gravity, and the torque generated by the electric motor 20 is less likely to accelerate the vehicle 1A in a backward tilted position. Therefore, the rate of change of the rotation speed of the electric motor 20 in a backward tilted position is affected differently from that in a horizontal position by the torque of the electric motor 20 and the effect of gravity. For example, even if the torque generated by the electric motor 20 is the same in both the backward tilted position and the horizontal position, the rate of change of the rotation speed of the electric motor 20 in a backward tilted position may be smaller than the rate of change of the rotation speed of the electric motor 20 in a horizontal position. For this reason, if the same upper limit threshold is used for both the backward tilted posture and the horizontal posture, there is a possibility that the rate of change in the rotation speed of the electric motor 20 will be equal to or less than the upper limit threshold even if the rear wheels 12 of the vehicle 1A in the backward tilted posture are slipping. Furthermore, the greater the amount of backward tilt of the vehicle 1A, the greater the possibility that the rate of change in the rotation speed of the electric motor 20 will be equal to or less than the upper limit threshold even if the amount of slip of the rear wheels 12 is increasing. Therefore, the greater the amount of backward tilt of the vehicle 1A, the smaller the upper limit threshold may be corrected.

[0143] The ECU 30 may set a smaller upper limit threshold value as the bank angle, which is the amount of inclination of the vehicle 1A to the left or right, increases. The vehicle 1A turns at a larger bank angle as the centrifugal force acting on the vehicle 1A increases. The larger the bank angle, the lower the slip tolerance of the rear wheels 12 becomes, so the upper limit threshold value may be set smaller.

[0144] The ECU 30 determines a torque-rate-change relationship that includes an upper threshold that varies from the reference upper threshold in accordance with the amount of tilt of the vehicle 1A in various directions. The amount of variation of the upper threshold from the reference upper threshold that corresponds to a particular tilt direction and amount of tilt of the vehicle 1A may be constant regardless of the torque required of the electric motor 20, or may vary depending on the torque required of the electric motor 20. For example, the greater the torque required of the electric motor 20, the greater the amount of variation of the upper threshold from the reference upper threshold.

[0145] When the slip ratio of the vehicle 1A is used, the ECU 30 may acquire detection results from the front wheel speed sensor 51 and the rear wheel speed sensor 52 and detect the slip ratio of the vehicle 1A based on the results. The slip ratio may be expressed as "(front wheel traveling speed - rear wheel traveling speed) / rear wheel traveling speed." The front wheel traveling speed is the traveling speed in the rotation direction of the front wheels 11 and corresponds to the rotation speed of the front wheels 11. The rear wheel traveling speed is the traveling speed in the rotation direction of the rear wheels 12 and corresponds to the rotation speed of the rear wheels 12. The ECU 30 may reduce the upper limit threshold as the absolute value of the slip ratio increases. The absolute value of the slip ratio increases as the difference between the front wheel traveling speed and the rear wheel traveling speed increases, and increases as the rear wheel traveling speed decreases. The larger the absolute value of the slip ratio, the more likely it is that the rear wheels 12 are slipping with a large amount of slip. Therefore, the larger the slip ratio, the smaller the upper limit threshold may be.

[0146] The ECU 30 determines a torque-rate-of-change relationship that includes an upper threshold that varies from a reference upper threshold depending on the slip ratio. The amount of variation of the upper threshold from the reference upper threshold corresponding to a particular slip ratio may be constant regardless of the torque required of the electric motor 20, or may vary depending on the torque required of the electric motor 20. For example, the amount of variation of the upper threshold from the reference upper threshold may increase as the torque required of the electric motor 20 increases.

[0147] When the front and rear wheel speed difference of the vehicle 1A is used, the ECU 30 may acquire detection results from the front wheel speed sensor 51 and the rear wheel speed sensor 52, and may detect the front and rear wheel speed difference, which is the difference between the traveling speed of the front wheels and the traveling speed of the rear wheels of the vehicle 1A, based on the detection results. The ECU 30 may set a smaller upper threshold value as the absolute value of the front and rear wheel speed difference increases. The larger the absolute value of the front and rear wheel speed difference, the more likely it is that the rear wheels 12 are slipping with a large amount of slip. For this reason, the larger the absolute value of the front and rear wheel speed difference, the smaller the upper threshold value may be.

[0148] The ECU 30 determines a torque-rate-change relationship that includes an upper threshold that varies from the reference upper threshold depending on the front / rear wheel speed difference. The amount of variation of the upper threshold from the reference upper threshold corresponding to a specific front / rear wheel speed difference may be constant regardless of the torque required for the electric motor 20, or may vary depending on the torque required for the electric motor 20. For example, the amount of variation of the upper threshold from the reference upper threshold may increase as the torque required for the electric motor 20 increases.

[0149] When using the amount of change in the required torque, the ECU 30 may decrease the upper limit threshold value as the amount of change in the required torque to the electric motor 20 increases. The greater the amount of change in the required torque to the electric motor 20, the greater the amount of change in the torque that the electric motor 20 generates at the rear wheels 12. Sudden torque fluctuations are likely to cause the rear wheels 12 to slip. For this reason, the greater the amount of change in the required torque to the electric motor 20, the smaller the upper limit threshold value may be.

[0150] The ECU 30 determines a torque-rate-change relationship that includes an upper threshold that varies from the reference upper threshold in accordance with the amount of change in the torque required for the electric motor 20. The amount of variation of the upper threshold from the reference upper threshold that corresponds to a particular amount of change in the required torque may be constant regardless of the torque required for the electric motor 20, or may vary in accordance with the torque required for the electric motor 20. For example, the amount of variation of the upper threshold from the reference upper threshold may increase as the torque required for the electric motor 20 increases.

[0151] The ECU 30 may be configured to determine a torque-rate change relationship in which the upper limit threshold is increased or decreased from the reference upper limit threshold based on the state of the vehicle 1A for any of the torque-rate change relationships according to the embodiment, Modification 1, and Modification 2. This allows the ECU 30 to perform highly accurate traction control adapted to the state of the vehicle 1A.

[0152] [others] Although exemplary embodiments and modifications of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and modifications. In other words, various modifications and improvements are possible within the scope of the present disclosure. For example, various modifications made to the embodiments or modifications, and forms constructed by combining components of different embodiments and modifications, are also included within the scope of the present disclosure.

[0153] For example, in the embodiment and modified examples, vehicles 1 and 1A are saddle-ride type vehicles, but may also be scooter type vehicles. Regardless of the type of vehicle, vehicles 1 and 1A may be arranged between seat 107 and front wheel 11, or may be arranged in another position. For example, as is often seen in scooter type vehicles, motor 20 may have an arrangement structure in which it swings together with a swing arm. Vehicles 1 and 1A are sports-oriented vehicles that include a cowl as outer shell member 109, but may also be naked type vehicles that do not include a cowl.

[0154] In the embodiment and the modified example, the vehicles 1 and 1A include a transmission 112, but may not include one. In this case, for example, the motor shaft 20a of the electric motor 20 may be connected to the drive sprocket 111a so as to rotate integrally with the drive sprocket 111a, or may be connected to the drive sprocket 111a via a reducer.

[0155] In the embodiment and modified examples, the vehicles 1 and 1A are motorcycles, but are not limited to this. The vehicles 1 and 1A may have a structure that can carry one or more people, or may have a structure that cannot carry people. The vehicles 1 and 1A may be operated by a person on board, or may be remotely controlled from outside the vehicles 1 and 1A. Examples of the vehicles 1 and 1A may include motorcycles, automobiles, mopeds, and various other mobility vehicles. The automobiles may include three or more wheels 10. Examples of the automobiles may include passenger cars, freight cars, public buses, all-terrain vehicles, and utility vehicles.

[0156] In the embodiment and modified examples, the prime mover 20 is a rotating electric machine 20 that is an electric motor, but is not limited to this. The prime mover 20 may also be an internal combustion engine that converts thermal energy into mechanical energy. The vehicles 1 and 1A may include one prime mover 20, or two or more prime movers 20. The two or more prime movers 20 may drive one wheel 10, or may drive separate wheels 10. One prime mover 20 of the two or more prime movers 20 may drive another prime mover 20. For example, the prime mover 20 as an internal combustion engine may drive the prime mover 20 as a rotating electric machine, causing the rotating electric machine to generate electrical energy.

[0157] The internal combustion engine may have any known structure. The internal combustion engine operates by receiving a supply of fuel. The fuel used by the internal combustion engine may be any fuel, such as fuels containing hydrocarbon compounds such as gasoline, ethanol, propane gas, and methane, fuels derived from animals and plants such as biofuels, or non-carbon fuels such as hydrogen.

[0158] For example, the cylinder structure of the internal combustion engine may be either a single-cylinder or a multi-cylinder structure. The internal combustion engine may be either a four-stroke engine or a two-stroke engine. The internal combustion engine generates power by repeatedly burning and exploding a mixture of fuel and air in the cylinder. The internal combustion engine converts the reciprocating motion of the piston caused by the burning and exploding into the rotational motion of the crankshaft and transmits the rotational power of the crankshaft to the outside. The internal combustion engine may transmit the rotational power to wheels 10, a rotating electric machine, or both.

[0159] Therefore, the vehicles 1 and 1A may be a vehicle that includes only an internal combustion engine as the prime mover 20, an EV vehicle that includes only a rotating electric machine as the prime mover 20, or a hybrid vehicle that includes an internal combustion engine and a rotating electric machine as the prime mover 20. Regardless of the type of vehicle the vehicles 1 and 1A are, the ECU 30 uses the rotation speed of the prime mover 20 that drives the wheels 10 and the detection result of the input sensor 41a of the first input device 41 to calculate the required torque for the prime mover 20 and use it for traction control.

[0160] A description will be given of examples of aspects of the present disclosure. A control device for a vehicle according to a first aspect of the present disclosure includes a processing circuit and a memory device that stores a torque-rate-of-change relationship, which is a relationship between a torque required of a prime mover provided on the vehicle and driving wheels of the vehicle and an upper threshold value for a rate of change in the rotation speed of the prime mover that is allowable for the torque required of the prime mover, and the processing circuit is configured to calculate a required torque required of the prime mover based on a command input to the vehicle to accelerate the vehicle and the rotation speed of the prime mover, and to perform traction control that suppresses the torque of the prime mover when it is determined that the rate of change in the rotation speed of the prime mover exceeds the upper threshold value corresponding to the required torque in the torque-rate-of-change relationship.

[0161] According to the first aspect, the intervention of traction control is determined based on the rate of change of the rotational speed of the prime mover and the upper threshold of the rate of change corresponding to the required torque of the prime mover. Thus, traction control that suppresses the torque of the prime mover is initiated according to the state of the prime mover relative to the required torque.

[0162] In the first aspect above, in the control device according to the second aspect of the present disclosure, the processing circuit may, in the traction control, reduce the rate of change of the rotation speed of the prime mover to below the upper limit threshold value corresponding to the required torque in the torque-rate of change relationship.

[0163] According to the second aspect, in traction control, the rate of change of the rotation speed of the prime mover is reduced to an upper limit threshold or less, thereby making it possible to suppress an increase in slip of the wheels driven by the prime mover.

[0164] In the first or second aspect described above, in a control device according to a third aspect of the present disclosure, the memory may store, as the torque-rate-of-change relationship, a first relationship between the torque required of the prime mover and a first threshold that is a first upper limit threshold for the rate of change of the rotational speed of the prime mover allowed for the torque required of the prime mover, and a second relationship between the torque required of the prime mover and a second threshold that is a second upper limit threshold for the rate of change of the rotational speed of the prime mover allowed for the torque required of the prime mover and that is greater than the first threshold, and the processing circuit may perform first traction control when it determines that the rate of change of the rotational speed of the prime mover exceeds the first threshold corresponding to the required torque and is equal to or less than the second threshold corresponding to the required torque, and may perform second traction control when it determines that the rate of change of the rotational speed of the prime mover exceeds the second threshold corresponding to the required torque.

[0165] According to the third aspect, the increase in slip of the wheels driven by the prime mover can be suppressed by two traction controls. During the second traction control, the wheels driven by the prime mover may slip more than during the first traction control. Therefore, the second traction control can stabilize the vehicle by suppressing the prime mover in a state with lower torque than during the first traction control. The first traction control can suppress the change in the driving sensation experienced by the driver due to the intervention of suppression by suppressing the prime mover in a state with higher torque.

[0166] In any of the first to third aspects described above, in a control device according to a fourth aspect of the present disclosure, the processing circuit determines the torque-rate-of-change relationship by increasing or decreasing the upper limit threshold corresponding to the torque required of the prime mover based on one or more of the speed of the vehicle, the attitude of the vehicle, the slip ratio of the vehicle, the amount of change in the required torque, the running driving mode, the running traction mode, and the reduction ratio selected in the transmission equipped in the vehicle, and the slip ratio may be the slip ratio between a wheel driven by the prime mover and a wheel not driven by the prime mover.

[0167] According to the fourth aspect, traction control suitable for the state of the vehicle is possible.

[0168] In any of the first to fourth aspects described above, in a control device according to a fifth aspect of the present disclosure, the processing circuit includes a first control mode and a second control mode in the traction control, and the processing circuit determines the torque-rate-of-change relationship by varying the upper limit threshold according to the control mode currently being executed so that the upper limit threshold in the first control mode is greater than the upper limit threshold in the second control mode, or so that the difference between the upper limit threshold and the limit rate of change of rotational speed in the first control mode is greater than the difference between the upper limit threshold and the limit rate of change of rotational speed in the second control mode, and the limit rate of change of rotational speed may be a rate of change of the rotational speed of the prime mover that corresponds to the torque required of the prime mover and causes a wheel driven by the prime mover to slip.

[0169] According to the fifth aspect, traction control can be performed in a plurality of control modes having mutually different control contents.

[0170] In any of the first to fifth aspects described above, in a control device according to a sixth aspect of the present disclosure, the processing circuit may further perform the following in the traction control: obtaining a limit torque of the prime mover that causes a wheel driven by the prime mover to slip based on the rate of change of the rotation speed of the prime mover and the torque generated by the prime mover; and restoring the torque of the prime mover, which has been suppressed to less than the limit torque in the traction control, toward the required torque; and the processing circuit may change the rate of return of the torque of the prime mover toward the required torque using the limit torque as a threshold value.

[0171] According to the sixth aspect, it is possible to restore the torque of the prime mover in accordance with the state of the wheels driven by the prime mover.

[0172] In the sixth aspect above, in a control device according to a seventh aspect of the present disclosure, when the processing circuit determines that the required torque is greater than the limit torque, the processing circuit may change the recovery speed of the torque of the prime mover between a first period in which the torque of the prime mover is equal to or less than the limit torque and a second period in which the torque of the prime mover is greater than the limit torque.

[0173] According to the seventh aspect, it is possible to restore the torque of the prime mover depending on whether the torque acting on the wheels driven by the prime mover is equal to or less than the limit torque or greater than the limit torque.

[0174] In the seventh aspect above, in a control device according to an eighth aspect of the present disclosure, the processing circuit may make the torque recovery rate of the prime mover in the second period lower than the torque recovery rate of the prime mover in the first period.

[0175] According to the eighth aspect, in the second period, the torque acting on the wheel driven by the prime mover is greater than the limit torque, which may cause slippage in the wheel. Since the return speed in the second period is low, slippage in the wheel can be moderated.

[0176] In any of the sixth to eighth aspects described above, in a control device according to a ninth aspect of the present disclosure, the memory stores, as the torque-change rate relationship, a first relationship between the torque required of the prime mover and a first threshold value that is a first upper limit threshold value for a rate of change in the rotation speed of the prime mover that is allowable for the torque required of the prime mover, and a second relationship between the torque required of the prime mover and a second threshold value that is a second upper limit threshold value for a rate of change in the rotation speed of the prime mover that is allowable for the torque required of the prime mover and that is greater than the first threshold value, and the processing circuit stores, when the rate of change in the rotation speed of the prime mover is, When it is determined that the rotational speed of the prime mover exceeds the first threshold corresponding to the required torque and is equal to or less than the second threshold corresponding to the required torque, a first traction control is performed to reduce the rate of change of the rotational speed of the prime mover to the first threshold corresponding to the required torque, and when it is determined that the rate of change of the rotational speed of the prime mover exceeds the second threshold corresponding to the required torque, a second traction control is performed to reduce the rate of change of the rotational speed of the prime mover to less than the first threshold corresponding to the required torque, and in the second traction control, the torque of the prime mover is returned toward the required torque.

[0177] According to the above ninth aspect, the second traction control can suppress the torque of the prime mover to a low level, and by restoring the torque of the prime mover toward the required torque, it is possible to suppress a decrease in driving performance, such as the vehicle not accelerating.

[0178] In the above ninth aspect, in a control device according to a tenth aspect of the present disclosure, when the processing circuit determines that the rate of change of the rotation speed of the prime mover exceeds the first threshold value corresponding to the required torque during the process of returning the torque of the prime mover toward the required torque, the processing circuit may reduce the rate of change of the rotation speed of the prime mover to the first threshold value corresponding to the limit torque.

[0179] According to the tenth aspect, the torque of the prime mover transitions toward the limit torque without causing excessive slip of the wheels driven by the prime mover. The torque of the prime mover can be maintained near the limit torque or at or above the limit torque. This makes it possible to suppress a decrease in the vehicle's running performance and changes in vehicle behavior due to the occurrence and resolution of slip.

[0180] In the above-mentioned tenth aspect, in a control device according to an eleventh aspect of the present disclosure, when the processing circuit determines that the rate of change of the rotation speed of the prime mover has decreased to the first threshold value corresponding to the limit torque, the processing circuit may return the torque of the prime mover toward the required torque.

[0181] According to the eleventh aspect, the torque of the prime mover can be transitioned toward the required torque while being maintained near the limit torque or at or above the limit torque.

[0182] A vehicle according to a twelfth aspect of the present disclosure comprises a prime mover that drives the wheels of the vehicle, an input device that accepts input of a command to accelerate the vehicle, and a control device according to any of the first to eleventh aspects described above, and the processing circuit calculates the required torque required of the prime mover based on the command input to the input device and the rotation speed of the prime mover.

[0183] According to the twelfth aspect, the same effects as those of the control device according to the one aspect of the present disclosure can be obtained.

[0184] A control method according to a thirteenth aspect of the present disclosure is a vehicle control method, which includes maintaining a torque-rate-of-change relationship that is a relationship between the torque required of a prime mover provided on the vehicle and driving wheels of the vehicle and an upper threshold value of the rate of change of the prime mover's rotation speed that is allowable for the torque required of the prime mover, calculating a required torque required of the prime mover based on a command to accelerate the vehicle and the prime mover's rotation speed, and suppressing the torque of the prime mover when it is determined that the rate of change of the prime mover's rotation speed exceeds the upper threshold value corresponding to the required torque in the torque-rate-of-change relationship.

[0185] According to the thirteenth aspect, the same effect as that of the control device according to one aspect of the present disclosure can be obtained. A part or all of the control method of the present disclosure may be realized, for example, by a circuit such as a CPU or an LSI, an IC card, or a standalone module. Multiple elements included in the control method of the present disclosure may be realized by one device, or may be realized by two or more devices sharing the same functions.

[0186] The functions of the elements disclosed herein can be performed using circuits or processing circuitry, including general-purpose processors, special-purpose processors, integrated circuits, ASICs, conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuitry because it includes transistors and other circuitry. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0187] All numbers such as ordinal numbers and quantities used in this specification are provided as examples to specifically explain the technology of the present disclosure, and the present disclosure is not limited to the illustrated numbers. The connection relationships between components are provided as examples to specifically explain the technology of the present disclosure, and the connection relationships that realize the functions of the present disclosure are not limited to these.

[0188] Because the present disclosure may be embodied in various forms without departing from the scope of its essential characteristics, the scope of the present disclosure is defined by the appended claims rather than the description in the specification, and therefore the exemplary embodiments and modifications are intended to be illustrative and not limiting. All modifications within the scope of the claims and their equivalents are intended to be embraced by the claims. [Explanation of symbols]

[0189] 1, 1A vehicle 10 wheels 11 Front wheel 12 rear wheels 20 Prime movers, rotating electrical machines, electric motors 30 Control device, electronic control unit (ECU) 40 Input Device 41 First input device, throttle grip

Claims

1. A control device for a vehicle, a processing circuit; a memory that stores a torque-change rate relationship that is a relationship between a torque required for a prime mover that is provided on the vehicle and drives wheels of the vehicle and an upper limit threshold of a change rate of a rotation speed of the prime mover that is allowable with respect to the torque required for the prime mover, The processing circuitry Calculating a required torque required of the prime mover based on a command to accelerate the vehicle input to the vehicle and a rotation speed of the prime mover; When it is determined that the rate of change in the rotation speed of the prime mover exceeds the upper limit threshold value corresponding to the required torque in the torque-rate of change relationship, traction control is performed to suppress the torque of the prime mover. A control device configured to execute the

2. The processing circuit, in the traction control, reduces the rate of change of the rotation speed of the prime mover to or below the upper limit threshold value corresponding to the required torque in the torque-rate of change relationship. The control device according to claim 1 .

3. the storage device stores, as the torque-rate-of-change relationship, a first relationship between the torque required of the prime mover and a first threshold value that is a first upper limit threshold value for a rate of change in the rotation speed of the prime mover that is allowable with respect to the torque required of the prime mover, and a second relationship between the torque required of the prime mover and a second threshold value that is a second upper limit threshold value for a rate of change in the rotation speed of the prime mover that is allowable with respect to the torque required of the prime mover and that is greater than the first threshold value; The processing circuitry when it is determined that the rate of change of the rotation speed of the prime mover exceeds the first threshold value corresponding to the required torque and is equal to or less than the second threshold value corresponding to the required torque, a first traction control is performed to reduce the rate of change of the rotation speed of the prime mover to the first threshold value corresponding to the required torque; When it is determined that the rate of change in the rotation speed of the prime mover exceeds the second threshold value corresponding to the required torque, a second traction control is performed to reduce the rate of change in the rotation speed of the prime mover to less than the first threshold value corresponding to the required torque. The control device according to claim 1 .

4. the processing circuit determines the torque-rate-of-change relationship by increasing or decreasing the upper limit threshold corresponding to the torque required of the prime mover, based on one or more of the speed of the vehicle, the attitude of the vehicle, the slip ratio of the vehicle, the amount of change in the required torque, the running driving mode, the running traction mode, and the reduction ratio selected in a transmission provided in the vehicle; The slip ratio is the slip ratio between the wheels driven by the prime mover and the wheels not driven by the prime mover. The control device according to claim 1 .

5. the processing circuit includes a first control mode and a second control mode for the traction control; the processing circuit determines the torque-rate-of-change relationship by varying the upper limit threshold in accordance with the control mode currently being executed so that the upper limit threshold in the first control mode is greater than the upper limit threshold in the second control mode, or so that a difference between the upper limit threshold and the limit rotational speed change rate in the first control mode is greater than a difference between the upper limit threshold and the limit rotational speed change rate in the second control mode; The limiting rate of change of rotational speed is a rate of change of the rotational speed of the prime mover that corresponds to the torque required for the prime mover and causes the wheels driven by the prime mover to slip. The control device according to claim 1 .

6. The processing circuitry In the traction control, a limit torque of the prime mover that causes a wheel driven by the prime mover to slip is obtained based on a rate of change of a rotation speed of the prime mover and a torque generated in the prime mover; and returning the torque of the prime mover, which has been suppressed to less than the limit torque in the traction control, toward the required torque, The processing circuit changes the speed at which the torque of the prime mover returns to the required torque, using the limit torque as a threshold. The control device according to claim 1 .

7. When the processing circuit determines that the required torque is greater than the limit torque, the processing circuit changes the return speed of the torque of the prime mover between a first period in which the torque of the prime mover is equal to or less than the limit torque and a second period in which the torque of the prime mover is greater than the limit torque. The control device according to claim 6.

8. The processing circuit reduces the rate of return of the torque of the prime mover during the second period to a rate that is lower than the rate of return of the torque of the prime mover during the first period. The control device according to claim 7.

9. The storage device a first relationship between a torque required of the prime mover and a first threshold value that is a first upper limit threshold value of a rate of change in a rotation speed of the prime mover that is allowed with respect to the torque required of the prime mover; a second relationship between a torque required of the prime mover and a second threshold value that is a second upper limit threshold value of a rate of change in the rotation speed of the prime mover that is allowed with respect to the torque required of the prime mover and that is greater than the first threshold value; is stored as the torque-change rate relationship, The processing circuitry when it is determined that the rate of change of the rotation speed of the prime mover exceeds the first threshold value corresponding to the required torque and is equal to or less than the second threshold value corresponding to the required torque, a first traction control is performed to reduce the rate of change of the rotation speed of the prime mover to the first threshold value corresponding to the required torque; When it is determined that the rate of change in the rotation speed of the prime mover exceeds the second threshold value corresponding to the required torque, a second traction control is performed to reduce the rate of change in the rotation speed of the prime mover to less than the first threshold value corresponding to the required torque; In the second traction control, the torque of the prime mover is returned toward the required torque. A control device according to any one of claims 6 to 8.

10. When the processing circuit determines that the rate of change in the rotation speed of the prime mover exceeds the first threshold value corresponding to the required torque during the process of returning the torque of the prime mover toward the required torque, the processing circuit reduces the rate of change in the rotation speed of the prime mover to the first threshold value corresponding to the limit torque. The control device according to claim 9.

11. When the processing circuit determines that the rate of change of the rotation speed of the prime mover has decreased to the first threshold value corresponding to the limit torque, the processing circuit returns the torque of the prime mover toward the required torque. The control device according to claim 10.

12. A vehicle, the prime mover that drives the wheels of the vehicle; an input device that receives an input of a command to accelerate the vehicle; The control device according to claim 1, The processing circuit calculates a required torque required of the prime mover based on the command input to the input device and the rotation speed of the prime mover. vehicle.

13. A vehicle control method, comprising: Maintaining a torque-rate-of-change relationship that is a relationship between a torque required of a prime mover provided in the vehicle and driving wheels of the vehicle and an upper limit threshold of a rate of change of a rotation speed of the prime mover that is allowed with respect to the torque required of the prime mover; Calculating a required torque required of the prime mover based on a command to accelerate the vehicle and a rotation speed of the prime mover; suppressing the torque of the prime mover when it is determined that the rate of change of the rotation speed of the prime mover exceeds the upper limit threshold corresponding to the required torque in the torque-rate of change relationship; A control method comprising:

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