Vehicle control devices

Abstract

To provide a vehicle control device that can achieve both regenerative braking and steering performance. [Solution] The brake ECU 22 is configured such that when the elapsed time T since the electric motor has stopped is less than a predetermined time T1, it sets the behavior control start threshold Avsc, which applies braking force and performs behavior control, to a second threshold Th2 which is smaller than the first threshold Th1 which is set when the elapsed time is greater than or equal to a predetermined time. As behavior control, it prohibits braking on the inner front wheel during a turn and applies braking force to the inner rear wheel during a turn, and as regenerative control, it adopts the wheel speed Vw of the outer rear wheel during a turn as the vehicle speed Vbr for regenerative control.

Description

Technical Field

[0001] The present disclosure relates to a vehicle control device.

Background Art

[0002] Conventionally, for example, a vehicle control system disclosed in Patent Document 1 is known. A conventional vehicle control system is configured to perform first regeneration control that performs regeneration to apply a braking force to the vehicle when the accelerator is off. Further, in a conventional vehicle control system, when the accelerator is off and a steering turning-in operation is performed, in addition to the first regeneration control, a braking force is applied to control the vehicle attitude by generating a deceleration corresponding to a steering angle. The second regeneration control is performed. Then, in the conventional vehicle control system, when the accelerator is off and the steering is turned in, if the wheel state value is equal to or greater than a second threshold smaller than the first threshold for activating ABS, the first regeneration amount and the second regeneration amount are reduced.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] By the way, in a conventional vehicle control system, the regeneration amount is reduced to ensure steerability when the steering is turned in. However, in the initial stage after the steering turning-in operation is performed, a large slip occurs on the steered wheels, so that the intended turning characteristic cannot be obtained, that is, steerability may be deteriorated.

[0005] An object of the present disclosure is to provide a vehicle control device capable of achieving both regeneration amount and steerability.

Means for Solving the Problem

[0006] The vehicle control device of this disclosure comprises an electric motor provided on the front wheels of a vehicle for driving and regenerative braking, a brake device provided on each wheel of the vehicle for applying braking force, and a controller capable of controlling the operation of the electric motor and brake device, and executing behavior control to control the behavior of the vehicle during turning and regenerative control to control the regenerative braking of the electric motor. The controller is configured such that, if the elapsed time since the electric motor has stopped driving is less than a predetermined time, the behavior control start threshold for applying braking force and executing behavior control is set to a second threshold which is smaller than the first threshold which is set when the elapsed time is predetermined or longer, and as behavior control, braking of the front wheel on the inside of the turn is prohibited and braking force is applied to the rear wheel on the inside of the turn, and as regenerative control, the wheel speed of the rear wheel on the outside of the turn is adopted as the vehicle speed for regenerative control. [Effects of the Invention]

[0007] According to this disclosure, the controller can improve the vehicle's turning ability by applying braking force to the inner rear wheel while intervening early in the behavior control by setting the behavior control initiation threshold to a small second threshold, and by adopting the wheel speed of the outer rear wheel as the vehicle speed for regenerative control, thereby preventing the vehicle speed for regenerative control from falling below the actual vehicle speed. This makes it possible to obtain a sufficient amount of regeneration and good steering ability, thus achieving a balance between regeneration and steering ability. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of the vehicle and vehicle control device according to this embodiment. [Figure 2] This diagram is intended to explain the relationship between regenerative braking and steering performance. [Figure 3] This diagram illustrates the wheel speed (magnitude of slip) of a wheel under normal behavioral control. [Figure 4]This diagram illustrates the wheel speed (magnitude of slip) required to balance regenerative braking and steering performance. [Figure 5] This is a flowchart of the control program. [Figure 6] This is a flowchart of a control program related to a modified example. [Modes for carrying out the invention]

[0009] Hereinafter, a vehicle control device, which is one embodiment of the present disclosure, will be described in detail with reference to the drawings. In addition to the embodiments described below, the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

[0010] The vehicle 1 to which the vehicle control device of this embodiment is applied comprises a vehicle body 2 and wheels 3, as shown in Figure 1. The vehicle body 2 is supported by the wheels 3 via a suspension unit (not shown). The wheels 3 consist of a right front wheel 3FR, a left front wheel 3FL, a right rear wheel 3RR, and a left rear wheel 3RL. Hereinafter, the right front wheel 3FR and the left front wheel 3FL may be collectively referred to as "front wheel 3F," and the right rear wheel 3RR and the left rear wheel 3RL may be collectively referred to as "rear wheel 3R." The vehicle 1 also includes a steering device 4. In this embodiment, the steering device 4 is configured to steer the front wheel 3F.

[0011] Vehicle 1 is also equipped with a front motor 11, which is an electric motor that drives the front wheels 3F. In vehicle 1, the rotation of the output shaft of the front motor 11 is transmitted to the left and right axles 13R and 13L via a differential gear 12 (including a reduction gear). As a result, the right front wheel 3FR and the left front wheel 3FL are rotationally driven in vehicle 1. In other words, vehicle 1 is a front-wheel-drive electric vehicle.

[0012] The front motor 11 is configured to be able to independently drive the vehicle 1 in the forward direction and in the reverse direction, respectively, by the power supply control of the inverter 14. Furthermore, in the vehicle 1 of this embodiment, the inverter 14 also has the function of storing regenerative energy by converting the alternating current generated by the front motor 11 into direct current and charging the battery 16 via the DC / DC converter 15. As a result, in the vehicle 1, the front motor 11 applies regenerative braking force to the front wheels 3F. In other words, the front motor 11 functions as a motor-generator.

[0013] The front motor 11 is controlled by a drive ECU 21, which is part of the controller 20. The drive ECU 21 is an electronic control unit (ECU) that primarily consists of a microcomputer. The microcomputer includes a CPU and memory devices such as ROM and RAM, and the CPU implements various functions by executing programs (instructions) stored in the ROM.

[0014] The drive ECU 21 receives detection signals from the accelerator sensor 31, which is one of the sensor group 30 that detects the amount of accelerator operation Oa (i.e., the amount of depression), accelerator opening, or accelerator pedal position by the driver, and inputs a request for acceleration (driving force) or deceleration (regenerative braking force) corresponding to the amount of accelerator operation Oa.

[0015] The drive ECU 21 then controls the front motor 11 to transmit the calculated driving force to the front wheel 3F in accordance with the requested acceleration. The drive ECU 21 also controls the front motor 11 to transmit the calculated regenerative braking force to the front wheel 3F in accordance with the requested deceleration. For example, the drive ECU 21 receives a detection signal output from the control sensor 32 of the front motor 11 and controls the operation of the inverter 14 to control the power supply to the front motor 11. Furthermore, when the drive ECU 21 performs regenerative control via the inverter 14, it obtains a detection signal Sr representing the amount of regenerative energy R recovered in accordance with the regenerative braking of the front motor 11. In addition, the drive ECU 21 is connected to an acceleration sensor 35 that detects acceleration and deceleration (acceleration when decelerating) in the left, right, front, and rear directions of the vehicle 1.

[0016] Furthermore, Vehicle 1 is equipped with a brake ECU 22 which constitutes the controller 20. Vehicle 1 is also equipped with friction braking force generating mechanisms 40FR, 40FL, 40RR, 40RL (hereinafter sometimes simply referred to as "friction braking force generating mechanism 40") provided on each wheel 3, and a brake actuator 41 which is electrically connected to the brake ECU 22. The drive ECU 21 and brake ECU 22 which form the controller 20, the front motor 11, and the friction braking force generating mechanism 40 (including the brake actuator 41) as a braking device constitute a vehicle control device.

[0017] The friction braking force generating mechanism 40 includes a brake disc 40d fixed to the wheel 3 and a brake caliper 40c fixed to the vehicle body 2. The friction braking force generating mechanism 40 operates a wheel cylinder (not shown) built into the brake caliper 40c using hydraulic pressure from the hydraulic fluid supplied from the brake actuator 41. As a result, the friction braking force generating mechanism 40 presses the brake pad 40p, which acts as a friction material, against the brake disc 40d, thereby applying a friction braking force Bf.

[0018] The brake actuator 41 is provided between a master cylinder (not shown) that pressurizes hydraulic oil based on a brake operation amount Ob (depression force) on a brake pedal B by a driver and a friction braking force generation mechanism 40, and is an actuator that controls the hydraulic pressure of the hydraulic oil supplied to wheel cylinders incorporated in each brake caliper 40c. Here, the brake actuator 41 can, for example, independently control the hydraulic pressure of the wheel cylinders for each of the four wheels to apply a friction braking force Bf to the wheels 3.

[0019] The operation of the brake actuator 41 is controlled by an electrically connected brake ECU 22. The brake ECU 22 is an electronic control unit mainly including a microcomputer. The brake ECU 22 is connected to a drive ECU 21 via a CAN (Controller Area Network) (not shown) so as to be capable of mutual transmission and reception.

[0020] The brake ECU 22 is connected to a hydraulic pressure sensor (not shown), various control valves, and a pump provided in the brake actuator 41. Further, among the sensor group 30, the brake ECU 22 is connected to a brake sensor 33 that detects a brake operation amount of a driver on the brake pedal B, that is, a stroke amount, an angle, a pressure, and the like, four wheel speed sensors 34 that respectively detect wheel speeds of the four wheels, and an acceleration sensor 35.

[0021] The brake ECU 22 calculates the frictional braking force Bf to be generated by the frictional braking force generation mechanism 40 so as to achieve the deceleration of the vehicle 1 required by the brake operation amount Ob of the brake pedal B performed by the driver. Then, the brake ECU 22 controls the operation of the brake actuator 41 based on the calculated frictional braking force Bf. As a result, the hydraulic pressure controlled by the brake actuator 41 is supplied to the frictional braking force generation mechanism 40, causing the frictional braking force Bf to be generated on the wheels 3. The brake ECU 22 also calculates the vehicle body speed Vb using the wheel speed Vwfr of the right front wheel 3FR, the wheel speed Vwfl of the left front wheel 3FL, the wheel speed Vwrr of the right rear wheel 3RR, and the wheel speed Vwrl of the left rear wheel 3RL respectively detected by each of the four wheel speed sensors 34.

[0022] As described above, in the front-wheel drive vehicle 1 in which the front wheels 3F are driven by the front motor 11, regenerative braking is executed when the accelerator operation amount Oa of the accelerator pedal A is operated to "0", that is, "accelerator off", and the front wheels 3F are subjected to regenerative braking. Further, in the vehicle 1, when the steering device 4 is steered, the front wheels 3F are steered.

[0023] Now, assuming a situation where the vehicle 1 is traveling on, for example, a low-μ road with reduced friction coefficient, and the driver steers immediately after releasing the accelerator, there is a possibility that steering performance may deteriorate. That is, when the vehicle 1 travels on a low-μ road, in order to avoid locking of the drive wheels due to regenerative braking, for example, the brake ECU 22 executes slip control by controlling the regenerative amount R in cooperation with the drive ECU 21. However, in this case, in order to prevent the regenerative amount R from decreasing due to frequent occurrence of slip control caused by road surface disturbances such as steps or instantaneous reduction of friction coefficient, as shown in FIG. 2, the slip control start speed threshold is lowered below the steady slip control target speed to allow larger slip than that in steady slip control. Note that the slip control reference vehicle body speed when executing regenerative slip control in a normal state is set larger than the steady slip control target speed, and the wheel speed Vw obtained by averaging the wheel speed Vwrr and wheel speed Vwrl of the driven rear wheels 3R is employed.

[0024] In other words, if a larger slip than steady-state slip control is allowed to prevent a decrease in the amount of regenerative braking R, as shown by the thick solid line in Figure 2, in period T1 (corresponding to a predetermined time T1) after period T0 in which the slip control start speed threshold is lowered from the slip control reference vehicle speed, the average wheel speeds of the front wheels 3F (Vwfr and Vwfl) decrease the most as the amount of regenerative braking R increases. As a result, in period T1 (predetermined time T1), the slip of the steering wheels, the front wheels 3F, increases, and as a result, the steering characteristics of vehicle 1 may become stronger, worsening steering performance. That is, in this case, although the amount of regenerative braking R can be increased, steering performance deteriorates, making it impossible to achieve both sufficient regenerative braking R and good steering performance.

[0025] To achieve both sufficient regenerative braking R and good steering performance, the following "Measure 1" and "Measure 2" can be cited as examples. First, "Measure 1" aims to achieve good steering performance, that is, to control the steering characteristics of the vehicle 1 during cornering. Here, the vehicle 1 is equipped with a friction braking force generation mechanism 40 on all wheels 3, and can apply independent frictional braking force to each wheel 3. Therefore, in the vehicle 1, the drive ECU 21 and the brake ECU 22 work together to control the operation of the front motor 11 and the friction braking force generation mechanism 40, and perform behavior control to control the vehicle's behavior. As an example of behavior control to control the behavior of the vehicle 1, Vehicle Stability Control (VSC), which is a behavior control that reduces slip that causes skidding during cornering, can be cited.

[0026] As a result, "Countermeasure 1" involves reducing the slip control initiation speed threshold (behavior control initiation threshold Avsc, described later) at which behavior control is initiated, that is, by intervening in behavior control earlier, as shown in Figure 3, for example, when vehicle 1 turns right, friction braking force Bf is applied to the right front wheel 3FR and right rear wheel 3RR which are on the inside of the turn (or when vehicle 1 turns left, friction braking force Bf is applied to the left front wheel 3FL and left rear wheel 3RL), thereby suppressing understeer characteristics. However, in this case, although behavior control can be intervened earlier, the friction braking force Bf is added to the front wheel 3F on the inside of the turn in addition to the regenerative braking force, causing the average wheel speed of the front wheel 3F to drop significantly during period T1, as shown by the thick solid line in Figure 3, that is, the slip increases. And when the slip of the front wheel 3F on the inside of the turn increases in this way, the effect of the bending moment in the turning direction that acts to turn vehicle 1 is canceled out.

[0027] Therefore, in addition to the early intervention of behavior control in "Countermeasure 1," as "Countermeasure 2," with the aim of obtaining good steering performance, as shown in Figure 4, the application of friction braking force Bf to the inner front wheel 3F is prohibited, and the bending moment is secured by applying friction braking force Bf only to the inner rear wheel 3R. Furthermore, as "Countermeasure 2," with the aim of obtaining a sufficient amount of regeneration R, the decrease in the amount of regeneration R is suppressed by excluding the wheel speed Vw of the inner rear wheel 3R to which friction braking force Bf is applied, and using the wheel speed Vw of the outer rear wheel 3R to determine the vehicle speed Vbr for regenerative control, which will be described later.

[0028] As shown by the solid line in Figure 4, by implementing "Countermeasure 1" and "Countermeasure 2," the decrease in the average wheel speed Vw of the front wheel 3F during period T1 is suppressed, meaning that slip is suppressed. As a result, the understeer characteristics of the vehicle 1 can be suppressed due to the effect of the bending moment in the turning direction. Furthermore, regarding the vehicle speed Vbr for regenerative control, as shown by the solid line in Figure 4, if only the wheel speed Vw of the rear wheel 3R on the outside of the turn is used, regenerative control can be performed without being affected by the wheel speed Vw of the rear wheel 3R to which frictional braking force Bf is applied, compared to when the average wheel speed Vw of the rear wheel 3R shown by the dashed line is used. Therefore, by implementing "Countermeasure 1" and "Countermeasure 2," it is possible to achieve both sufficient regeneration R and good steering performance.

[0029] Therefore, in the steering system 10 of this embodiment, the drive ECU 21 and brake ECU 22 work together to execute the control program shown in Figure 5 in order to achieve both sufficient regenerative braking R and good steering performance. Specifically, the brake ECU 22 starts executing the control program in step S10, and in the following step S11, it determines whether or not the operation state of the accelerator pedal A is not the accelerator OFF state.

[0030] Specifically, the brake ECU 22 receives a detection signal output by the accelerator sensor 31 from the drive ECU 21, and if the operation state of accelerator pedal A is not accelerator OFF, it determines "Yes" and executes the step process of step S12. On the other hand, if the operation state of accelerator pedal A is accelerator OFF, the brake ECU 22 determines "No" and executes the step process of step S13.

[0031] In step S12, the brake ECU 22 resets the measurement flag F, which is used to measure the elapsed time counter T (i.e., elapsed time T) that is counted up (incremented) from the time the accelerator pedal A is turned off, that is, from the time the front motor 11 starts regenerative braking, to "0", and also resets the elapsed time counter T to "0". After resetting the measurement flag F and the elapsed time counter T to "0", the brake ECU 22 executes the step processing in step S13.

[0032] In step S13, the brake ECU 22 determines whether the operation state of accelerator pedal A was not accelerator OFF based on the determination process in step S11 during the previous execution of the control program, and whether the operation state of accelerator pedal A is accelerator OFF based on the determination process in step S11 during the current execution of the control program. That is, if the brake ECU 22 determines that the accelerator was not OFF last time and is OFF this time, it determines "Yes" and executes the step process in step S14. On the other hand, if the brake ECU 22 determines that the accelerator was OFF last time, or that the accelerator is not OFF this time, it determines "No" and executes the step process in step S15.

[0033] In step S14, the brake ECU 22 sets the measurement flag F to "1", which indicates that the elapsed time counter T is incremented, i.e., that the elapsed time is being measured. Then, the brake ECU 22 executes the step processing in step S15.

[0034] In step S15, the brake ECU 22 determines whether the measurement flag F is "1". That is, if the measurement flag F is "1", the brake ECU 22 determines "Yes" and executes the step process in step S16. On the other hand, if the measurement flag F is not "1" (i.e., if the measurement flag F is "0"), the brake ECU 22 determines "No" and executes the step process in step S22. In other words, the situation in which the step process in step S22, described later, is executed is the situation in which slip control is performed under normal conditions using the normal slip control reference vehicle speed described above.

[0035] In step S16, the brake ECU 22 increments the elapsed time counter T by "1". In other words, the brake ECU 22 sets the elapsed time T since the accelerator pedal A was turned OFF by counting up the elapsed time counter T. Then, after incrementing the elapsed time counter T by "1", the brake ECU 22 executes the step process in step S17.

[0036] In step S17, the brake ECU 22 determines whether the value of the elapsed time counter T incremented in step S16 is greater than period T0, which represents the range of values ​​of the elapsed time counter T since the behavior control start threshold Avsc, which initiates behavior control to reduce the slip that occurs in the vehicle 1 when the accelerator is turned off and stabilize the behavior, was lowered, and less than period T1, which represents the range of values ​​of the elapsed time counter T during which a large slip of the front wheel 3F continues after the elapsed period T0.

[0037] In other words, the brake ECU 22 determines "Yes" and executes the step process in step S18 if the value of the incremented elapsed time counter T is greater than period T0 and less than period T0+T1 (period T0 plus period T1), that is, if it is included in period T1 where the slip of the front wheel 3F increases. On the other hand, the brake ECU 22 determines "No" and executes the step process in step S22 if the value of the elapsed time counter T is less than or equal to the lower limit of period T0, or greater than or equal to the upper limit of period T0+T1, that is, if it is a normal period and is not included in period T1 where the slip of the front wheel 3F increases.

[0038] In step S18, the brake ECU 22 sets the behavior control initiation threshold Avsc to a second threshold Th2, which has a smaller value than the first threshold Th1 that is normally set in step S22, described later. In other words, the brake ECU 22 achieves early intervention of behavior control, which is "Countermeasure 1," by setting the behavior control initiation threshold Avsc to a second threshold Th2 that is smaller than the first threshold Th1 that is normally set. Then, after setting the behavior control initiation threshold Avsc to the second threshold Th2, the brake ECU 22 executes the step processing in step S19.

[0039] In step S19, the brake ECU 22 determines whether or not vehicle 1 is turning to the right. That is, for example, based on the steering direction of the front wheels 3F by the steering device 4, the brake ECU 22 determines "Yes" if vehicle 1 is turning to the right and executes the step process in step S20. On the other hand, if vehicle 1 is turning to the left, the brake ECU 22 determines "No" and executes the step process in step S21.

[0040] In step S20, the brake ECU 22 implements the aforementioned "Countermeasure 2" in the vehicle 1 that is turning right. Specifically, because the vehicle 1 is turning right, the brake ECU 22 prohibits the supply of hydraulic fluid from the brake actuator 41 to the friction braking force generating mechanism 40FR that applies braking force to the right front wheel 3FR on the inside of the turn, that is, it prohibits pressurization of the friction braking force generating mechanism 40FR. Also, because the vehicle 1 is turning right, the brake ECU 22 supplies hydraulic fluid from the brake actuator 41 to the friction braking force generating mechanism 40RR that applies braking force to the right rear wheel 3RR on the inside of the turn, thereby applying braking force to the right rear wheel 3RR. As a result, while the application of braking force to the right front wheel 3FR on the inside of the turn is prohibited, braking force is applied to the right rear wheel 3RR on the inside of the turn, generating a bending moment in the turning direction, which allows the vehicle 1 to easily turn right. As a result, the driver can obtain good steering control.

[0041] Furthermore, the brake ECU 22 sets the regenerative control vehicle speed Vbr, which is the slip control reference vehicle speed used by the drive ECU 21 in regenerative control, to the wheel speed Vwrl of the left rear wheel 3RL on the outside of the turn during a right turn. This prevents the regenerative control vehicle speed Vbr from falling below the actual vehicle speed Vb due to being dragged down by the drop in the wheel speed Vwrr of the right rear wheel 3RR to which braking force is applied, and ensures that a sufficient amount of regeneration R is secured by the regenerative control by the drive ECU 21. After the step processing in step S20, the brake ECU 22 temporarily terminates the execution of the control program in step S24.

[0042] In step S21, the brake ECU 22 implements the aforementioned "Countermeasure 2" for vehicle 1 that is turning left. Specifically, because vehicle 1 is turning left, the brake ECU 22 prohibits the supply of hydraulic fluid from the brake actuator 41 to the friction braking force generating mechanism 40FL that applies braking force to the left front wheel 3FL on the inside of the turn, that is, it prohibits pressurization of the friction braking force generating mechanism 40FL. Also, because vehicle 1 is turning left, the brake ECU 22 supplies hydraulic fluid from the brake actuator 41 to the friction braking force generating mechanism 40RL that applies braking force to the left rear wheel 3RL on the inside of the turn, thereby applying braking force to the left rear wheel 3RL. As a result, while the application of braking force to the left front wheel 3FL on the inside of the turn is prohibited, braking force is applied to the left rear wheel 3RL on the inside of the turn, generating a bending moment in the turning direction, which allows vehicle 1 to easily turn left. As a result, the driver can obtain good steering control.

[0043] Furthermore, the brake ECU 22 sets the vehicle speed Vbr for regenerative control to the wheel speed Vwrr of the right rear wheel 3RR on the outside of the turn during a left turn. This ensures that a sufficient amount of regeneration R is secured by the regenerative control by the drive ECU 21. After the step processing in step S21, the brake ECU 22 temporarily terminates the execution of the control program in step S24.

[0044] On the other hand, the brake ECU 22 executes the steps S22 and S23 in order according to the "No" determination in the determination processes of steps S15 and S17. In other words, the brake ECU 22 executes the steps S22 and S23 respectively when the measurement flag F is "0" and when the elapsed time T exceeds the period T1, i.e., when the elapsed time T has elapsed for a predetermined time T1.

[0045] In step S22, the brake ECU 22 sets the behavior control start threshold Avsc to the first threshold Th1, which is normally set. Then, the brake ECU 22 executes the step processing in the following step S23.

[0046] In step S23, the brake ECU 22 permits the supply of hydraulic fluid from the brake actuator 41 to the friction braking force generating mechanisms 40FR and 40FL, which apply braking force to the front wheel 3F. In other words, the brake ECU 22 permits pressurization of the friction braking force generating mechanisms 40FR and 40FL. The brake ECU 22 also sets the regenerative control vehicle speed Vbr to the average value of the wheel speed Vwrr of the right rear wheel 3RR and the wheel speed Vwrl of the left rear wheel 3RL ((Vwrr + Vwrl) / 2). After the brake ECU 22 permits pressurization of the friction braking force generating mechanisms 40FR and 40FL and sets the regenerative control vehicle speed Vbr to the average value of the wheel speed Vwrr of the right rear wheel 3RR and the wheel speed Vwrl of the left rear wheel 3RL, the execution of the control program is temporarily terminated in step S24, and after a predetermined short period of time has elapsed, the execution of the program is restarted in step S10.

[0047] As can be understood from the above explanation, the vehicle control device comprises a front motor 11, which is an electric motor provided on the front wheel 3F of the vehicle 1 to drive and regenerate brake; a friction braking force generating mechanism 40, which is a brake device provided on each wheel 3 of the vehicle 1 to apply braking force; and a drive ECU 21 and a brake ECU 22, which are controllers 20 capable of controlling the operation of the front motor 11 and the friction braking force generating mechanism 40, and performing behavior control to control the behavior of the vehicle 1 during turning and regenerative control to control the regenerative braking of the front motor 11. The brake ECU 22 is configured such that, if the elapsed time T since the front motor 11 has stopped driving is less than a predetermined time T1, it sets the behavior control start threshold Avsc, which applies braking force and executes behavior control, to a second threshold Th2 which is smaller than the first threshold Th1 which is set when the elapsed time T is greater than or equal to a predetermined time T1. As behavior control, it prohibits braking of the inner front wheel 3F and applies braking force to the inner rear wheel 3R, and as regenerative control, it adopts the wheel speed Vw of the outer rear wheel 3R as the vehicle speed Vbr for regenerative control.

[0048] According to this, the brake ECU 22 improves the turning ability of the vehicle 1 by applying braking force to the inner rear wheel 3R while intervening early in the behavior control by setting the behavior control initiation threshold Avsc to a small second threshold Th2, and by adopting the wheel speed Vw of the outer rear wheel 3R as the vehicle speed Vbr for regenerative control, it is possible to prevent the vehicle speed Vbr for regenerative control from falling below the actual vehicle speed Vb. This makes it possible to obtain a sufficient amount of regeneration R and good steering ability, thus achieving a balance between the amount of regeneration R and steering ability.

[0049] In the embodiment described above, the brake ECU 22 is shown as executing the control program shown in Figure 5. In this case, the brake ECU 22 determines whether the accelerator pedal A is in the OFF position in the determination process of step S11 and step S13. Alternatively, the brake ECU 22 may determine the magnitude of the regenerative amount R which changes according to the operation state of the accelerator pedal A. Modifications will be described below.

[0050] In the modified example, the brake ECU 22 executes the control program shown in Figure 6. Here, the control program in the modified example is indicated by adding "100" to each step number of the control program in the embodiment shown in Figure 5. In the control program in the modified example, the processing content of steps S111 and S113, which correspond to steps S11 and S13 in the control program in the embodiment, is mainly different. For this reason, the following description will mainly explain in detail the processing content of steps S111 and S113 of the control program in the modified example.

[0051] In step S110, the brake ECU 22 starts executing the control program, and in the following step S111, the brake ECU 22 determines whether the regenerative amount R is "0". That is, if the regenerative amount R is "0" corresponding to the operation state of accelerator pedal A not being accelerator OFF, the brake ECU 22 determines "Yes" and executes the step process in step S112. On the other hand, if the regenerative amount R is not "0" corresponding to the operation state of accelerator pedal A being accelerator OFF, the brake ECU 22 determines "No" and executes the step process in step S113.

[0052] In step S112, the brake ECU 22 resets the measurement flag Fr to "0" and the elapsed time counter Tr, which represents the elapsed time T since the regenerative amount R became greater than the regenerative amount reference R0, as shown in Figure 2, and also resets the elapsed time counter Tr to "0". After resetting the measurement flag Fr and the elapsed time counter Tr to "0", the brake ECU 22 executes the step processing in step S113.

[0053] In step S113, the brake ECU 22 obtains a detection signal Sr representing the regenerative amount R from the drive ECU 21 and determines whether the regenerative amount R is greater than the regenerative amount reference R0. That is, if the brake ECU 22 determines that the regenerative amount R is greater than the regenerative amount reference R0, it determines "Yes" and executes the step process in step S114. On the other hand, if the brake ECU 22 determines that the regenerative amount R is less than or equal to the regenerative amount reference R0, it determines "No" and executes the step process in step S115.

[0054] Each step from S114 to S117 corresponds to each step from S14 to S17 in the control program of the embodiment described above. For this reason, in step S114, the brake ECU 22 sets the measurement flag Fr to "1" in the same way as in step S14, in step S115, it determines whether the measurement flag Fr is "1" in the same way as in step S15, in step S116, it increments the elapsed time counter Tr by "1" in the same way as in step S16, and in step S117, it determines whether the elapsed time counter Tr (i.e., elapsed time T) is smaller than the period T1 (see Figure 2, etc.) corresponding to a predetermined time T1 during which large slip continues in the right front wheel 3FR and the left front wheel 3FL.

[0055] The brake ECU 22 then executes the steps S118 to S124, similar to steps S18 to S24 in the control program of the embodiment described above. Therefore, the same effects as in the embodiment described above can be obtained in this modified example as well.

[0056] Furthermore, the present invention is not limited to the embodiments and modifications described above, and various modifications are possible. For example, the vehicle 1 is not limited to an electric vehicle (EV) equipped only with a front motor 11, but may also be a front-wheel-drive hybrid vehicle (HEV, PHEV) equipped with an internal combustion engine. Moreover, in the embodiments and modifications described above, the friction braking force generating mechanism 40 is exemplified as being composed of a disc brake, but it may also be composed of a drum brake. [Explanation of Symbols]

[0057] 1...Vehicle, 3...Wheel, 3F...Front wheel, 3R...Rear wheel, 11...Front motor, 20...Controller, 21...Drive ECU, 22...Brake ECU, 40...Friction braking force generation mechanism, 41...Brake actuator, Avsc...Behavior control start threshold, Th1...First threshold, Th2...Second threshold, Vw...Wheel speed, Bf...Friction braking force, R...Regenerative braking amount

Claims

1. An electric motor is installed on the front wheels of the vehicle to drive and regenerate braking, A braking device provided on each wheel of the vehicle to apply braking force, The system includes a controller capable of controlling the operation of the electric motor and the brake device, performing behavior control to control the vehicle's behavior during turning, and regenerative control to control the regenerative braking of the electric motor, The aforementioned controller If the elapsed time since the electric motor stopped is less than a predetermined time, the behavior control start threshold for applying braking force and executing the behavior control is set to a second threshold that is smaller than the first threshold set when the elapsed time is equal to or greater than the predetermined time. A vehicle control device configured to, as behavior control, prohibit braking of the front wheel on the inside of the turn and apply braking force to the rear wheel on the inside of the turn, and as regenerative control, adopt the wheel speed of the rear wheel on the outside of the turn as the vehicle speed for regenerative control.

2. The aforementioned controller The vehicle control device according to claim 1, wherein if the elapsed time is greater than or equal to a predetermined time, the behavior control start threshold is set to the first threshold, and braking of the inner and outer front wheels is permitted as the behavior control, and the average wheel speed of the inner and outer rear wheels is adopted as the regenerative control vehicle speed.

3. The elapsed time is The vehicle control device according to claim 1 or 2, wherein the electric motor has started the regenerative braking.

4. The elapsed time is The vehicle control device according to claim 1 or 2, wherein the amount of regenerative energy recovered in connection with the regenerative braking is the amount of time elapsed since the amount of regenerative energy recovered became greater than a predetermined reference amount.

5. The aforementioned controller If the elapsed time is less than the predetermined time, the behavior control start threshold is set to the second threshold. In the behavior control when the vehicle turns right, the braking system is prohibited from generating braking force on the right front wheel and instead generates braking force on the right rear wheel, and in the regenerative control, the wheel speed of the left rear wheel is adopted as the vehicle speed for regenerative control, or In the behavior control when the vehicle turns left, the braking system is prohibited from generating braking force on the left front wheel and instead generates braking force on the left rear wheel, and in the regenerative control, the wheel speed of the right rear wheel is adopted as the vehicle speed for regenerative control. If the elapsed time is equal to or greater than the predetermined time, the behavior control start threshold is set to the first threshold. The vehicle control device according to claim 1, wherein the behavior control involves generating braking force on each of the front wheels on the inside and outside of the turn, and adopting the average wheel speed of each of the rear wheels on the inside and outside of the turn as the vehicle body speed for regenerative control.

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