Braking control device for electric vehicle

Abstract

To provide a braking control device for an electric vehicle, capable of improving regeneration efficiency while suppressing a change in behavior in a pitch direction during braking traveling.SOLUTION: A braking control device for an electric vehicle performs the followings: out of a pair of front wheels and a pair of rear wheels, identifying control target wheels having a small reaction force load against the pitching of the vehicle relative to the magnitude of braking force to be generated; determining a front-and-rear distribution ratio according to required braking force (Step S1); when the required braking force is equal to or greater than maximum regenerative braking force with which braking is enabled by each motor (Yes in Step S3), causing regenerative braking force to act on the control target wheels in the first place, and when there is surplus regenerative braking force, causing the surplus regenerative braking force to act on the other wheels (Step S6); and when the regenerative braking force of the control target wheels is not sufficient for control target braking force required for the control target wheels, causing friction braking force to act on the control target wheels in addition, and causing friction braking force to act on the other wheels (Step S7).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a braking control device for an electric vehicle in which a motor is connected to each of a pair of front wheels and a pair of rear wheels, and each wheel is provided with a friction braking mechanism. [Background technology]

[0002] An electric vehicle in which a motor is connected to each of a pair of front wheels and a pair of rear wheels, and each wheel is provided with a friction braking mechanism, can generate a braking force by making the motor function as a generator during braking driving, and can also generate a braking force by the friction braking mechanism. On the other hand, the motor and the friction braking mechanism have different points at which they generate braking force in the vehicle height direction, so that the magnitude of their contribution to the anti-dive force acting on the front side of the vehicle differs, and the magnitude of their contribution to the anti-lift force acting on the rear side of the vehicle differs. In other words, the behavior in the pitching direction differs between when a predetermined braking force is generated by the motor and when a predetermined braking force is generated by the friction braking mechanism. Patent Documents 1 and 2 disclose control devices configured to cooperatively control the braking forces of the motor and the friction braking mechanism so as to output a required braking force while suppressing such a change in behavior in the pitching direction.

[0003] The control device described in Patent Document 1 is configured to determine a front-rear braking force distribution ratio, which is the ratio of the braking force generated at the front wheels to the braking force generated at the rear wheels, based on the braking force required for the vehicle, then calculate a required pitching moment to achieve a target pitch angle, and then calculate a front-wheel friction regeneration distribution ratio, which is the frictional braking force applied to the front wheels relative to the braking force required for the front wheels, and a rear-wheel friction regeneration distribution ratio, which is the frictional braking force applied to the rear wheels relative to the braking force required for the rear wheels, based on the front-rear braking force distribution ratio, the required pitching moment, and fixed values ​​determined by the structure, such as the distance between the point of application of the braking force and the instantaneous rotation center of the wheels.

[0004] Furthermore, the control device described in Patent Document 2 is configured to adjust a regenerative front wheel ratio, which is the ratio of the front wheel regenerative braking force when the regenerative braking force applied to the vehicle is allocated to the front wheel regenerative braking force and the rear wheel regenerative braking force, and a friction front wheel ratio, which is the ratio of the front wheel friction braking force when the friction braking force applied to the vehicle is allocated to the front wheel friction braking force and the rear wheel friction braking force, according to the pitching moment so as to suppress the pitching motion of the vehicle. Patent Document 2 also describes that the vehicle is configured so that the sensitivity to the magnitude of the braking force is greater for the anti-lift force than for the anti-dive force, and that in order to efficiently generate the anti-lift force, it is preferable to reduce the regenerative front wheel ratio and the friction front wheel ratio so as to increase the rear wheel braking force. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-049858 [Patent Document 2] JP 2021-115926 A Summary of the Invention [Problem to be solved by the invention]

[0006] When the friction regeneration distribution ratio is determined after determining the front / rear braking force distribution ratio and the required pitching moment, as in the control devices described in Patent Documents 1 and 2, the pitch angle during braking can be controlled to a target pitch angle. However, since the friction regeneration distribution ratio is calculated using the required pitching moment as a parameter, only regenerative energy within the constraints of the required pitching moment is regenerated, and there is a possibility that the maximum regenerative energy of the entire braking system cannot be regenerated.

[0007] The present invention has been made with attention to the above-mentioned technical problems, and aims to provide a braking control device for an electric vehicle that can improve regenerative efficiency while suppressing changes in behavior in the pitch direction during braking. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a braking control device for an electric vehicle including a pair of front wheels, a pair of rear wheels, a front motor that generates electricity by applying a braking torque to the pair of front wheels, a front friction braking mechanism that applies a braking torque by frictionally contacting the pair of front wheels, a rear motor that generates electricity by applying a braking torque to the pair of rear wheels, and a rear friction braking mechanism that applies a braking torque by frictionally contacting the pair of rear wheels, wherein the front motor, the rear motor, the front friction braking mechanism, and a controller for controlling the rear friction braking mechanism, wherein the controller identifies a control target wheel, out of the pair of front wheels and the pair of rear wheels, which has a smaller magnitude of reaction load against pitching of the electric vehicle relative to the magnitude of braking force to be generated, determines a front-rear distribution ratio which is a ratio of braking force generated at the pair of front wheels to braking force generated at the pair of rear wheels in accordance with a required braking force of the electric vehicle, and ... whether the required braking force is equal to or greater than a maximum regenerative braking force that can be generated by the front motor and the rear motor, and whether the required braking force is equal to or greater than a maximum regenerative braking force that can be generated by the front motor and the rear motor, and the front / rear distribution ratio is equal to or greater than the maximum regenerative braking force, the torque of a motor connected to the control target wheel is set to a torque based on the maximum regenerative braking force, the torque of a friction braking mechanism provided on the control target wheel is set to a torque based on a braking force that is a difference between the control target braking force and the maximum regenerative braking force, and the torque of a friction braking mechanism provided on the other wheel of the pair of front wheels and the pair of rear wheels that is different from the control target wheel is set to a torque based on the required braking force and the front / rear distribution ratio. and a rear distribution ratio, and when the required braking force is equal to or greater than the maximum regenerative braking force and the controlled braking force is less than the maximum regenerative braking force, the torque of the motor connected to the controlled wheel is set to a torque based on the controlled braking force, the torque of the motor connected to the other wheel is set to a torque based on a braking force that is a difference between the maximum regenerative braking force and the controlled braking force, and the torque of the friction braking mechanism provided on the other wheel is set toThe torque is set based on a braking force that is a difference between the braking force required for the other wheel and the braking force generated by the motor connected to the other wheel. Effect of the Invention

[0009] According to this invention, of the pair of front wheels and the pair of rear wheels, a wheel to be controlled that has a small magnitude of anti-reaction load against the pitching of the electric vehicle relative to the magnitude of the braking force to be generated is identified. In other words, a wheel that has a low contribution rate to suppressing pitching of the electric vehicle when a braking force is output during braking travel is identified. Then, when the required braking force is equal to or greater than the maximum regenerative braking force that can be generated by the front motor and the rear motor, and the controlled braking force required for the controlled wheel is equal to or greater than the maximum regenerative braking force, the torque of the motor connected to the controlled wheel is set to a torque based on the maximum regenerative braking force, the torque of the friction braking mechanism provided for the controlled wheel is set to a torque based on a braking force that is a difference between the controlled braking force and the maximum regenerative braking force, and the torque of the friction braking mechanism provided for the other wheel is set to a torque based on the braking force required for the other wheel. Also, when the required braking force is equal to or greater than the maximum regenerative braking force and the controlled braking force is less than the maximum regenerative braking force, the torque of the motor connected to the controlled wheel is set to a torque based on the controlled braking force, the torque of the motor connected to the other wheel is set to a torque based on a braking force that is the difference between the maximum regenerative braking force and the controlled braking force, and the torque of the friction braking mechanism provided on the other wheel is set to a torque based on a braking force that is the difference between the braking force required for the other wheel and the braking force generated by the motor connected to the other wheel. That is, when the required braking force is equal to or greater than the maximum regenerative braking force, first, the motor connected to the controlled wheel is controlled to generate the maximum regenerative braking force at the controlled wheel, and the other motors and friction braking mechanisms are controlled to output a braking torque according to the braking force shortage. Therefore, the maximum regenerative energy can be regenerated at the controlled wheel. Also, the controlled wheel has a small reaction load against the pitching of the electric vehicle relative to the magnitude of the braking force generated. Therefore, by performing regenerative braking on the controlled wheel, friction braking is performed on the other wheel by the friction braking mechanism.As a result, even if the maximum regenerative energy is regenerated on the controlled wheel, the reaction load against the pitching of the electric vehicle can be prevented from decreasing, and changes in the behavior of the electric vehicle in the pitch direction when braking can be suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram for explaining an example of an electric vehicle. [Diagram 2] 4 is a flowchart for explaining an example of control executed by a brake control device according to an embodiment of the present invention. [Diagram 3] FIG. 4 is a diagram showing an example of a map for determining front / rear braking force distribution. [Figure 4] 3 is a diagram showing a distribution of the magnitude of braking force generated by each braking mechanism when the control example shown in FIG. 2 is executed. FIG. [Diagram 5] 11 is a waterfall graph comparing the magnitude of the pitch angle when the front / rear braking force distribution is fixed, when the front / rear braking force distribution is varied, and when the front / rear braking force distribution and the regenerative distribution are varied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Fig. 1 shows a schematic left side view of an electric vehicle according to an embodiment of the present invention. The electric vehicle (hereinafter simply referred to as vehicle) Ve shown in Fig. 1 includes a pair of front wheels 1, a pair of rear wheels 2, a front motor (not shown) connected to the pair of front wheels 1 so as to be able to transmit torque, and a rear motor (not shown) connected to the pair of rear wheels 2 so as to be able to transmit torque. In other words, the vehicle is configured to be four-wheel drive by controlling the motors.

[0012] These motors can be configured in the same manner as motors provided as driving force sources for conventional electric vehicles and hybrid vehicles. That is, in addition to the function of a motor that outputs a driving torque that increases the rotation speed of the connected wheels 1, 2 by receiving power from a power storage device (not shown), the motors also have the function of a generator that generates electric power by being rotated by the connected wheels 1, 2. When the motor functions as a generator in this way, a braking torque according to the generated power acts on the wheels 1, 2. That is, each motor can function as a braking device. These motors can be configured, for example, by AC motors such as permanent magnet synchronous motors and induction motors. In the following description, the braking force generated by making the motor function as a generator is referred to as a regenerative braking force.

[0013] Each of the wheels 1 and 2 is provided with a friction braking mechanism (not shown) that generates a braking torque by frictional contact. This friction braking mechanism can be configured similarly to friction braking mechanisms such as disc brakes and drum brakes provided in conventional vehicles. That is, a braking torque is applied to the wheels 1 and 2 by contacting a fixed member provided on the vehicle body based on the driver's brake operation with a rotating member that rotates integrally with the wheels 1 and 2. In the following description, the braking force generated by operating the friction braking mechanism is referred to as the friction braking force.

[0014] Furthermore, suspensions 3, 4 are provided to support the wheels 1, 2 and to dampen vertical vibrations of the wheels 1, 2. These suspensions 3, 4 can be configured in the same manner as suspensions provided on conventional vehicles, such as strut suspensions or multi-link suspensions.

[0015] The vehicle Ve configured as described above generates at least one of a regenerative braking force and a friction braking force when there is a braking request such as depression of the brake pedal during driving. Specifically, the total value of the regenerative braking force of the front motor (hereinafter referred to as the front regenerative braking force) and the braking force of the front friction braking mechanism (hereinafter referred to as the front friction braking force) is controlled so that it matches the braking force required for the pair of front wheels 1, and the total value of the regenerative braking force of the rear motor (hereinafter referred to as the rear regenerative braking force) and the braking force of the rear friction braking mechanism (hereinafter referred to as the rear friction braking force) matches the braking force required for the pair of rear wheels 2. Note that, since there is a correlation based on specifications such as tire radius between the braking torque applied to the axle by the motor and the braking torque applied to the wheels 1 and 2 by the friction braking mechanism, and the braking force generated by these braking torques, the braking torque and the braking force are referred to as braking force without distinction.

[0016] On the other hand, when braking force is generated as described above, a reaction load is generated against the nose-down direction in which the front of the vehicle Ve is tilted vertically downward. The magnitude of the reaction load depends on the braking force to be generated. Specifically, the magnitude of the reaction load relative to the magnitude of the braking force to be generated differs depending on the geometry of the suspensions 3, 4, and differs between regenerative braking force and friction braking force. More specifically, the direction and magnitude of the reaction load differ depending on the angle between the horizontal line and the line connecting the instantaneous rotation centers O1, O2 of the suspensions 3, 4 (or wheels 1, 2) when braking force is generated and the point of application of the braking force.

[0017] In the example shown in Fig. 1, when a front regenerative braking force or a front frictional braking force is generated, an anti-dive force is generated in the anti-dive direction (upward in the vertical direction), and when a rear regenerative braking force or a rear frictional braking force is generated, an anti-lift force is generated in the anti-lift direction (downward in the vertical direction). Furthermore, the magnitude of the anti-dive force and the anti-lift force relative to the magnitude of the generated braking force increases in the following order: when a front regenerative braking force is generated, when a front frictional braking force is generated, when a rear regenerative braking force is generated, and when a rear frictional braking force is generated. Therefore, the pair of front wheels 1 correspond to the "wheels to be controlled" in the embodiment of the present invention, and the pair of rear wheels 2 correspond to the "other wheel" in the embodiment of the present invention.

[0018] Equation (1) shows a calculation formula for determining the pitch angle when the vehicle Ve shown in FIG. 1 is braking.

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[0019] Here, h in Equation 1 is the height from the road surface to the center of gravity G of the vehicle Ve, and W B is the wheelbase distance, k f is the spring constant of the front suspension, k r is the spring constant of the rear suspension, α is the front braking distribution, which is the braking force applied to the pair of front wheels 1 in relation to the braking force of the vehicle Ve, β is the front regenerative distribution, which is the front regenerative braking force in relation to the braking force of the pair of front wheels 1, AntiDive1 is the friction anti-dive coefficient, which is the magnitude of the anti-dive force in relation to the magnitude of the front friction braking force, AntiDive2 is the regenerative anti-dive coefficient, which is the magnitude of the anti-dive force in relation to the magnitude of the front regenerative braking force, γ is the rear regenerative distribution, which is the rear regenerative braking force in relation to the braking force of the pair of rear wheels, AntiLift1 is the friction anti-lift coefficient, which is the magnitude of the anti-lift force in relation to the magnitude of the rear friction braking force, AntiLift2 is the regenerative anti-lift coefficient, which is the magnitude of the anti-dive force in relation to the magnitude of the front regenerative braking force, and F is the braking force of the vehicle Ve.

[0020] As shown in formula (1), the direction and magnitude of the reaction load (anti-dive force and anti-lift force) acting in the pitch direction of the vehicle Ve varies depending on the type of braking force to be generated, so that the behavior of the vehicle Ve in the pitch direction changes depending on the braking force. Therefore, the vehicle Ve shown in FIG. 1 is configured to appropriately control each regenerative braking force and each friction braking force during braking running, thereby increasing the generated power by generating the regenerative braking force and suppressing the change in the behavior of the vehicle Ve in the pitch direction. That is, an electronic control unit (hereinafter, referred to as ECU) 5 for controlling the regenerative braking force and the friction braking force is provided. This ECU 5 is mainly configured with a microcomputer like a conventional ECU, and is configured to input data from various sensors provided in the vehicle Ve, and to determine signals to be output to each motor and each friction braking mechanism based on the input data and a map or an arithmetic expression stored in advance. The ECU 5 corresponds to the "controller" in the embodiment of the present invention.

[0021] The data input to the ECU 5 are, for example, values ​​detected by a brake sensor that detects the amount of operation of the brake pedal operated by the driver and the force of the brake pedal, a vehicle speed sensor that detects the vehicle speed, an SOC sensor that detects the remaining charge of the power storage device, etc. The ECU 5 also stores data on the specifications of the vehicle Ve. Specifically, the data stored include the mass of the vehicle Ve, the height of the center of gravity of the vehicle Ve, the wheelbase, the spring constant of the front suspension 3, the spring constant of the rear suspension 4, the regenerative anti-dive coefficient, the friction anti-dive coefficient, the regenerative anti-lift coefficient, the friction anti-lift coefficient, etc.

[0022] 2 shows a flowchart for explaining an example of control executed by the ECU 5 when the driver requests braking force, i.e., when the brake pedal is depressed by more than a predetermined amount or with more than a predetermined force, or when the vehicle is shifted to the brake range (B range). In the control example shown in FIG. 2, first, an optimal front / rear braking force distribution is calculated (step S1). This step S1 is a step for distributing the required braking force to a braking force generated by a pair of front wheels 1 and a braking force generated by a pair of rear wheels 2, and can be determined according to, for example, a distribution ratio at which the pair of front wheels 1 and the pair of rear wheels 2 are locked simultaneously.

[0023] Fig. 3 shows an example of a map for determining front / rear braking force distribution, with the horizontal axis representing the braking force generated by the pair of front wheels 1 and the vertical axis representing the braking force generated by the pair of rear wheels 2, with the dashed line representing the deceleration determined according to the required braking force and the solid line representing a line connecting the plots of predetermined optimum distributions such as when the pair of front wheels 1 and the pair of rear wheels 2 lock simultaneously. As shown in Fig. 3, the front / rear braking force distribution is calculated so that the braking force generated by the pair of front wheels 1 is greater than the braking force generated by the pair of rear wheels 2, regardless of the required deceleration.

[0024] In parallel with the above step S1, the magnitude of the regenerative braking force is calculated (step S2). This step S2 can be calculated based on, for example, the vehicle speed or the state of charge of the power storage device. In other words, it can be calculated based on the power that can be input to the power storage device. Note that the power that can be input to the power storage device varies depending on various parameters such as the remaining charge of the power storage device and the temperature of the power storage device, so the magnitude of the regenerative braking force may be calculated taking these parameters into consideration.

[0025] Following steps S1 and S2, it is determined whether the required braking force (required total braking force) is equal to or greater than the regenerative braking force (step S3). In other words, it is determined whether it is necessary to use the friction braking mechanism to generate the required braking force.

[0026] If the required braking force is less than the regenerative braking force and thus the negative determination is made in step S3, the required braking force can be generated only by the regenerative braking force. Therefore, if the negative determination is made in step S3, the braking force acting on the pair of front wheels 1 and the braking force acting on the pair of rear wheels 2 are set to the regenerative braking force (step S4). That is, the braking torque of the front motor is determined so that the regenerative braking force is the same as the braking force of the pair of front wheels 1 allocated by the front / rear braking force distribution calculated in step S1, and the braking torque of the rear motor is determined so that the regenerative braking force is the same as the braking force of the pair of rear wheels 2. Then, the control value of the braking torque determined in step S4 is commanded to each motor (step S5), and this routine is temporarily terminated.

[0027] On the other hand, if the required braking force is equal to or greater than the regenerative braking force and therefore the answer is affirmative in step S3, it is determined whether the braking force of the pair of front wheels 1 (front wheel braking force) assigned in step S1 is equal to or greater than the regenerative braking force (step S6), and if the answer is negative in step S6 because the front wheel braking force is less than the regenerative braking force, the braking force applied to the pair of front wheels 1 is set to the regenerative braking force, and the braking force applied to the pair of rear wheels 2 is set to the regenerative braking force and the friction braking force (step S7). That is, the braking torque of the front motor is determined so that the regenerative braking force is the same as the braking force of the pair of front wheels 1 assigned by the front / rear braking force distribution calculated in step S1, the braking torque of the rear motor is determined so that the surplus regenerative braking force, which is the difference between the regenerative braking force and the regenerative braking force acting on the pair of front wheels 1, is applied to the pair of rear wheels 2, and the braking torque of the rear friction braking mechanism is determined so that the braking force, which is the difference between the braking force of the pair of rear wheels 2 assigned in step S1 and the surplus regenerative braking force, is applied to the pair of rear wheels 2. Then, the control value of the braking torque determined in step S7 is commanded to each motor and the rear friction braking mechanism (step S5), and this routine is temporarily terminated. The braking force of the pair of front wheels 1 assigned in step S1 corresponds to the "braking force to be controlled" in the embodiment of this invention.

[0028] On the other hand, if the front wheel braking force is equal to or greater than the regenerative braking force and thus the answer is YES in step S6, the braking force acting on the pair of front wheels 1 is set to the regenerative braking force and the friction braking force, and the braking force acting on the pair of rear wheels 2 is set to the friction braking force (step S8). That is, the braking torque of the front motor is determined so that a braking force of the same magnitude as the regenerative braking force acts on the pair of front wheels 1, and the braking torque of the front friction braking mechanism is determined so that a deficient braking force, which is the difference between the braking force of the pair of front wheels 1 and the regenerative braking force allocated by the front / rear braking force distribution calculated in step S1, acts on the pair of front wheels 1, and further, the braking torque of the rear friction braking mechanism is determined so that a braking force of the same magnitude as the braking force of the pair of rear wheels 2 allocated in step S1 acts on the pair of front wheels 2. Then, the control value of the braking torque determined in step S8 is commanded to each motor and the front friction braking mechanism (step S5), and this routine is temporarily terminated.

[0029] Fig. 4 shows the magnitude of each regenerative braking force and each frictional braking force that is set when the control example shown in Fig. 2 is executed. Note that the solid lines in Fig. 4 show the magnitude of each regenerative braking force and each frictional braking force that is set when a braking force is required to cause a deceleration of 0.1 G to act on the vehicle Ve, the dashed lines show the magnitude of each regenerative braking force and each frictional braking force that is set when a braking force is required to cause a deceleration of 0.2 G to act on the vehicle Ve, and the dashed dotted lines show the magnitude of each regenerative braking force and each frictional braking force that is set when a braking force is required to cause a deceleration of 0.3 G to act on the vehicle Ve.

[0030] In the example shown in Fig. 4, when a braking force is requested to cause a deceleration of 0.1 G to act on the vehicle Ve, a negative determination is made in step S3, and thus a braking force is generated by a front regenerative braking force and a rear regenerative braking force. Also, when a braking force is requested to cause a deceleration of 0.2 G to act on the vehicle Ve, a negative determination is made in step S5, and thus a braking force is generated by a front regenerative braking force, a rear regenerative braking force, and a rear friction braking force. Furthermore, when a braking force is requested to cause a deceleration of 0.3 G to act on the vehicle Ve, a positive determination is made in step S5, and thus a braking force is generated by a front regenerative braking force, a front friction braking force, and a rear friction braking force.

[0031] In other words, regenerative braking force is generated on wheels with a small reaction load that contributes to preventing the vehicle Ve from tilting in the nose-down direction during braking - in other words, wheels with small anti-dive and anti-lift coefficients and a small reaction load against the braking force - and surplus regenerative braking force or any shortfall in the required braking force is generated on the other wheels.

[0032] Fig. 5 shows a waterfall chart comparing the magnitude of the pitch angle when the vehicle decelerates at a predetermined deceleration while traveling at a predetermined vehicle speed. That is, Fig. 5 shows the reduction amount of the pitch angle when the distribution of the braking force generated at the front and rear wheels is set based on the required braking force, tire capacity, and front and rear load distribution, i.e., the distribution of the braking force generated at the front and rear wheels is determined based on the map shown in Fig. 3 (ideal front and rear distribution), using the pitch angle when the distribution of the braking force generated at the front and rear wheels is set based on the required braking force, tire capacity, and front and rear load distribution (fixed distribution) as a reference, and the reduction amount of the pitch angle when the control example shown in Fig. 2 is executed based on the pitch angle when the distribution of the braking force generated at the front and rear wheels is set based on the required braking force, tire capacity, and front and rear load distribution (optimized regenerative distribution).

[0033] As shown in FIG. 5, when the control example shown in FIG. 2 is executed, the maximum pitch angle during braking can be reduced compared to the case of fixed distribution or ideal front / rear distribution.

[0034] As described above, when the required braking force is equal to or greater than the regenerative braking force, the front motor is first controlled to generate the regenerative braking force at the front wheels, and the rear motor, the front friction braking mechanism, and the rear friction braking mechanism are controlled to generate the insufficient braking force. Therefore, the maximum regenerative energy can be regenerated at the front wheels. In addition, the front wheels have a small reaction load against the pitching of the vehicle Ve relative to the magnitude of the braking force to be generated. Therefore, by generating a regenerative braking force at the front wheels, a friction braking force is generated at the rear wheels. As a result, even if the maximum regenerative energy is regenerated at the front wheels, the reaction load against the pitching of the vehicle Ve can be suppressed from decreasing, and therefore, the change in the behavior of the vehicle Ve in the pitch direction during braking can be suppressed.

[0035] In addition, the above-mentioned vehicle Ve is configured to generate regenerative braking force at the front wheels 1 because the anti-dive coefficient is smaller than the anti-lift coefficient, but if the anti-lift coefficient is smaller than the anti-dive coefficient, the vehicle Ve may be configured to generate regenerative braking force at the rear wheels 2. [Explanation of symbols]

[0036] 1 Front wheel 2 Rear wheels 3,4 Suspension 5 Electronic Control Unit (ECU) Vehicle

Claims

[Claim 1] A braking control device for an electric vehicle including a pair of front wheels, a pair of rear wheels, a front motor that generates electricity by applying a braking torque to the pair of front wheels, a front friction braking mechanism that applies a braking torque by frictionally contacting the pair of front wheels, a rear motor that generates electricity by applying a braking torque to the pair of rear wheels, and a rear friction braking mechanism that applies a braking torque by frictionally contacting the pair of rear wheels, a controller that controls the front motor, the rear motor, the front friction braking mechanism, and the rear friction braking mechanism; The controller: identifying a control target wheel, among the pair of front wheels and the pair of rear wheels, which has a smaller magnitude of a reaction load acting against the pitching of the electric vehicle relative to a magnitude of a braking force to be generated; determining a front-rear distribution ratio that is a ratio of a braking force generated at the pair of front wheels to a braking force generated at the pair of rear wheels in accordance with a required braking force of the electric vehicle; when the required braking force is equal to or greater than a maximum regenerative braking force that can be applied by the front motor and the rear motor, and a controlled braking force required for the controlled wheel in accordance with the required braking force and the front-rear distribution ratio is equal to or greater than the maximum regenerative braking force, the torque of the motor connected to the controlled wheel is set to a torque based on the maximum regenerative braking force, the torque of a friction braking mechanism provided on the controlled wheel is set to a torque based on a braking force that is a difference between the controlled braking force and the maximum regenerative braking force, and the torque of a friction braking mechanism provided on the other wheel of the pair of front wheels and the pair of rear wheels that is different from the controlled wheel is set to a torque based on the braking force required for the other wheel in accordance with the required braking force and the front-rear distribution ratio, When the required braking force is equal to or greater than the maximum regenerative braking force and the controlled braking force is less than the maximum regenerative braking force, the torque of the motor connected to the controlled wheel is set to a torque based on the controlled braking force, the torque of the motor connected to the other wheel is set to a torque based on a braking force that is a difference between the maximum regenerative braking force and the controlled braking force, and the torque of the friction braking mechanism provided on the other wheel is set to a torque based on a braking force that is a difference between the braking force required for the other wheel and the braking force generated by the motor connected to the other wheel. A braking control device for an electric vehicle.

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