Brake control system

Abstract

To improve the controllability of frictional braking force just before a vehicle comes to a complete stop. [Solution] The processing circuit 71 of the braking control device 70 functions as a braking control unit 203 that executes stopping control to stop the vehicle 10 while the friction braking unit 40 is activated and friction braking force is applied to the vehicle 10, and a determination unit 202 that determines whether the total friction braking force will not exceed a predetermined value within a determination period from the start timing when the increase in friction braking force applied to the vehicle 10 by the execution of the stopping control starts until the vehicle 10 comes to a stop. If the processing circuit 71 determines that the total friction braking force will not exceed a predetermined value within the determination period, it activates the friction braking unit 40 so that friction braking force is generated on only one of the front wheels 12 and rear wheels 13.

Description

Technical Field

[0001] The present invention relates to a braking control device that controls a braking force applied to a vehicle.

Background Art

[0002] Patent Document 1 discloses a braking control device that controls regenerative braking force and frictional braking force applied to a vehicle immediately before the vehicle stops. The braking control device executes stop-time braking control for stopping the vehicle by decreasing the regenerative braking force while maintaining the frictional braking force at a predetermined value.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] A vehicle braking device includes a plurality of friction brakes provided respectively for front wheels and rear wheels. The friction brake is characterized in that when the frictional braking force generated by a corresponding wheel is relatively small, the adjustment accuracy thereof is lower than that when the frictional braking force is relatively large.

[0005] Therefore, when the above-described stop-time braking control is executed, if both the frictional braking force generated by the front wheels and the frictional braking force generated by the rear wheels are small, there is a possibility that the sum of the frictional braking force generated by the front wheels and the frictional braking force generated by the rear wheels deviates from a target frictional braking force. The target frictional braking force is a target value of the sum of the frictional braking force generated by the front wheels and the frictional braking force generated by the rear wheels. When the sum of the frictional braking force generated by the front wheels and the frictional braking force generated by the rear wheels deviates from the target frictional braking force, there is a possibility that the behavior of the vehicle at the time of stopping deviates from a desired behavior.

Means for Solving the Problem

[0006] The braking control device for solving the above problems is applied to a vehicle comprising front wheels and rear wheels, and a friction braking unit configured to adjust the friction braking force generated by the front wheels and the friction braking force generated by the rear wheels. The sum of the friction braking force generated by the front wheels and the friction braking force generated by the rear wheels is the total friction braking force of the vehicle. The braking control device comprises a braking control unit that performs stopping control to stop the vehicle while the friction braking force is applied to the vehicle by the operation of the friction braking unit, and a determination unit that determines whether the total friction braking force will not exceed a predetermined value, which is a criterion for determining whether the adjustment accuracy of the total friction braking force is low, within a determination period from a start timing, which is the timing at which the increase in the total friction braking force begins due to the execution of the stopping control, until the vehicle stops. If the determination unit determines that the total friction braking force will not exceed the predetermined value within the determination period, the braking control unit operates the friction braking unit so that the friction braking force is generated by only one of the front wheels or the rear wheels. [Effects of the Invention]

[0007] The above-described braking control device has the effect of improving the controllability of frictional braking force just before the vehicle comes to a complete stop. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing a vehicle equipped with a braking control device according to the first embodiment. [Figure 2] Figure 2 is a graph showing the characteristics of the multiple friction brakes installed in the vehicle shown in Figure 1. [Figure 3] Figure 3 is a flowchart showing the first half of the processing flow in the braking control device shown in Figure 1. [Figure 4] Figure 4 is a flowchart showing the latter half of the processing flow in the braking control device shown in Figure 1. [Figure 5]Figures 5(a) to 5(g) are timing charts showing the changes in various parameters when a smooth stop process is performed just before the vehicle comes to a complete stop in the braking control device shown in Figure 1. [Figure 6] Figure 6 is a flowchart showing the processing flow in the braking control device of the second embodiment. [Figure 7] Figures 7(a) to 7(f) are timing charts showing the changes in various parameters when regenerative braking control is performed just before the vehicle comes to a complete stop in the braking control device shown in Figure 6. [Modes for carrying out the invention]

[0009] (First Embodiment) A first embodiment of the braking control device will be described with reference to Figures 1 to 5. <Overall vehicle configuration> Figure 1 illustrates a vehicle 10 equipped with a braking control device 70. The vehicle 10 further comprises a braking operating member 11, multiple wheels, a regenerative braking unit 20, a friction braking unit 40, and multiple sensors. The braking operating member 11 is a member operated by the driver when adjusting the deceleration of the vehicle 10. An example of the braking operating member 11 is a brake pedal.

[0010] Multiple wheels include two front wheels 12 and two rear wheels 13. Figure 1 shows one front wheel 12 and one rear wheel 13. <Regenerative braking section> The regenerative braking unit 20 is configured to apply regenerative braking force to the vehicle 10. The regenerative braking unit 20 includes a motor generator 21 and a regenerative control device 30 that controls the motor generator 21. The motor generator 21 functions as a generator, thereby applying regenerative braking force to the vehicle 10. In the example shown in Figure 1, the motor generator 21 generates regenerative braking force at the rear wheels 13. The actual value of the regenerative braking force applied to the vehicle 10 by the regenerative braking unit 20 is referred to as "effective regenerative braking force FbE".

[0011] The regenerative control device 30 includes a processing circuit 31. An example of the processing circuit 31 is an electronic control device. In this case, the processing circuit 31 has a CPU and a memory that stores a control program executed by the CPU. The CPU executes the control program in the memory, enabling the processing circuit 31 to control the motor generator 21.

[0012] The regenerative control device 30 is configured to send and receive various information and commands to and from the braking control device 70 via the in-vehicle network. Therefore, when the vehicle is braking, the regenerative control device 30 can operate the motor generator 21 based on the information or commands received from the braking control device 70.

[0013] The processing circuit 31 functions as a regenerative control unit 101 when the CPU executes a memory control program. The regenerative control unit 101 adjusts the effective regenerative braking force FbE by operating the motor generator 21. In other words, the regenerative control unit 101 can adjust the effective regenerative braking force FbE by operating the motor generator 21 based on the target regenerative braking force FbETr, which is the target value of the regenerative braking force.

[0014] <Friction brake part> The friction braking unit 40 is configured to apply friction braking force to the vehicle 10. The friction braking unit 40 comprises a plurality of friction brakes individually provided for a plurality of wheels 12, 13, and a braking actuator 50.

[0015] Among the plurality of friction brakes, the friction brake corresponding to the front wheels 12 is referred to as "friction brake 41F", and the friction brake corresponding to the rear wheels 13 is referred to as "friction brake 41R". Each of the plurality of friction brakes 41F and 41R generates a frictional braking force at the corresponding wheels 12 and 13. The friction brakes 41F and 41R include a wheel cylinder 42, a rotating body 43, and a friction portion 44. The rotating body 43 rotates integrally with the corresponding wheels 12 and 13. Therefore, by pressing the friction portion 44 against the rotating body 43, a frictional braking force is generated at the wheels 12 and 13. The force with which the friction portion 44 is pressed against the rotating body 43 increases as the wheel pressure, which is the hydraulic pressure in the wheel cylinder 42, becomes higher. Therefore, the friction brakes 41F and 41R can generate a larger frictional braking force at the wheels 12 and 13 as the wheel pressure becomes higher.

[0016] The sum of the frictional braking forces generated by the plurality of wheels 12 and 13 is referred to as "total frictional braking force FbF of the vehicle 10". The frictional braking force generated at the front wheels 12 is referred to as "front wheel frictional braking force", and the frictional braking force generated at the rear wheels 13 is referred to as "rear wheel frictional braking force". The wheel pressure of the wheel cylinder 42 of the friction brake 41F is referred to as "front wheel pressure PwF". The wheel pressure of the wheel cylinder 42 of the friction brake 41R is referred to as "rear wheel pressure PwR".

[0017] Referring to Fig. 2, the difference in characteristics between the friction brake 41F for the front wheels 12 and the friction brake 41R for the rear wheels 13 will be described. In Fig. 2, a characteristic line LchF shows the relationship between the front wheel wheel pressure PwF and the front wheel friction braking force in the friction brake 41F. A characteristic line LchR shows the relationship between the rear wheel wheel pressure PwR and the rear wheel friction braking force in the friction brake 41R. As shown in Fig. 2, in any of the plurality of friction brakes 41F and 41R, higher wheel pressures PwF and PwR can generate a larger friction braking force. However, when the wheel pressures PwF and PwR of the plurality of wheel cylinders 42 are equal to each other, the friction brake 41F is configured to be capable of generating a larger friction braking force than the friction brake 41R. Particularly in a region where the wheel pressure is low, the increasing gradient of the friction braking force in the friction brake 41F is larger than the increasing gradient of the friction braking force in the friction brake 41R. The increasing gradient of the friction braking force refers to the increase amount of the friction braking force with respect to an increase in the wheel pressure.

[0018] The braking actuator 50 is configured to be capable of controlling the wheel pressures PwF and PwR of the plurality of wheel cylinders 42. That is, the braking actuator 50 is configured to be capable of adjusting the front wheel friction braking force and the rear wheel friction braking force. Such a braking actuator 50 has, for example, a pressure source capable of supplying brake fluid to the plurality of wheel cylinders 42. The pressure source is, for example, an electric pump or an electric cylinder. The brake fluid discharged from the braking actuator 50 is supplied to the wheel cylinders 42 via a supply flow path 51.

[0019] <Sensor> As shown in Figure 1, the multiple sensors output signals to the braking control device 70 according to the detection results. The multiple sensors include, for example, a brake sensor 61, multiple wheel speed sensors 62, and an acceleration sensor 63. The brake sensor 61 detects information related to the driver's operation of the braking control member 11. An example of the brake sensor 61 is a stroke sensor that detects the amount of operation of the driver's braking control member 11. The amount of operation based on the detection signal of the brake sensor 61 is referred to as "braking operation amount Ba". The vehicle 10 may also be equipped with a sensor that detects the operating force of the driver's braking control member 11.

[0020] Multiple wheel speed sensors 62 detect the rotational speed of the corresponding wheels 12 and 13. The rotational speed of the wheels 12 and 13 based on the detection signals from the wheel speed sensors 62 is referred to as "wheel speed VW".

[0021] The acceleration sensor 63 detects the longitudinal acceleration of the vehicle 10. The longitudinal acceleration based on the detection signal from the acceleration sensor 63 is referred to as "longitudinal acceleration GX". <Braking control device> The braking control device 70 activates the braking actuator 50 of the friction braking unit 40. The braking control device 70 is configured to send and receive various information and commands with the regenerative braking control device 30. Therefore, when the vehicle is being braked, the braking control device 70 can adjust the deceleration of the vehicle 10 by operating the braking actuator 50 and coordinating with the regenerative braking control device 30. In other words, the braking control device 70 can control the total braking force Fb of the vehicle 10 by operating the friction braking unit 40 and the regenerative braking unit 20. The total braking force Fb is the sum of the effective regenerative braking force FbE and the total friction braking force FbF.

[0022] The braking control device 70 includes a processing circuit 71. An example of the processing circuit 71 is an electronic control device. In this case, the processing circuit 71 includes a CPU 72, a first memory 73, and a second memory 74. The first memory 73 stores a control program executed by the CPU 72. The second memory 74 stores the calculation results of the CPU 72. By the CPU 72 executing the control program in the first memory 73, the processing circuit 71 can operate the friction braking unit 40 to adjust the total friction braking force FbF. The processing circuit 71 can also adjust the effective regenerative braking force FbE by transmitting instructions regarding regenerative braking force to the regenerative control device 30.

[0023] <Smooth Stop Processing> The processing circuit 71 of the braking control device 70 performs a smooth stop process just before the vehicle 10, which is decelerating by the application of braking force, comes to a complete stop. The smooth stop process is a process that reduces the change in the vehicle 10's posture when the vehicle 10 stops. In this smooth stop process, the processing circuit 71 coordinates the regenerative braking unit 20 and the friction braking unit 40.

[0024] Refer to Figure 5 to explain an example of smooth stop processing. When the vehicle 10 is decelerating due to the application of braking force, the processing circuit 71 estimates the stopping position of the vehicle 10 based on the vehicle speed VS and vehicle acceleration DVS. In this case, the processing circuit 71 should estimate the stopping position as the position of the vehicle 10 when the vehicle speed VS becomes 0 (zero) when the vehicle 10 decelerates at the current vehicle acceleration DVS. The processing circuit 71 then derives stopping-related values ​​that decrease as the vehicle 10 approaches the stopping position. For example, the processing circuit 71 derives the stopping distance DS, which is the distance from the current position of the vehicle 10 to the above-mentioned stopping position, as a stopping-related value.

[0025] As shown in Figures 5(a) to (e), the processing circuit 71 operates the friction braking unit 40 and the regenerative braking unit 20 based on the required braking force FbRq for the vehicle 10. The required braking force FbRq can also be said to be the required value of the total braking force Fb. In the example shown in Figure 5, before timing t11, the vehicle decelerates as at least the regenerative braking force, of the regenerative braking force and friction braking force, is applied to the vehicle 10. Then, at timing t11, the processing circuit 71 determines that the conditions for executing the smooth stop process have been met because the derived stopping distance DS is less than or equal to the first threshold DSth1. The first threshold DSth1 is the criterion for determining whether the vehicle 10 is about to stop or not.

[0026] The smooth stop process includes an increase / correction process, substitution control, decrease / correction control, and degeneracy control. In this embodiment, the substitution control and decrease / correction control correspond to "stopping control" which activates the friction braking unit 40 to apply friction braking force to the vehicle 10 and stop the vehicle 10.

[0027] When the conditions for executing the smooth stop process are met at timing t11, the processing circuit 71 executes the smooth stop process's augmentation control. The augmentation control is a control that makes the total braking force Fb greater than the required braking force FbRq. In the augmentation control, the processing circuit 71 sends an instruction to the regenerative control device 30 of the regenerative braking unit 20 to increase the regenerative braking force.

[0028] When the processing circuit 31 of the regenerative control device 30 receives the instruction, it increases the target regenerative braking force FbETr. Then, the processing circuit 31 operates the motor generator 21 based on the target regenerative braking force FbETr. As a result, the effective regenerative braking force FbE increases, as shown in Figure 5(d). In the correction boosting control, the processing circuit 71 of the braking control device 70 maintains the target friction braking force FbFTr. Therefore, the processing circuit 71 can increase the effective regenerative braking force FbE while maintaining the total friction braking force FbF.

[0029] At the subsequent timing t12, the stopping distance DS becomes less than or equal to the second threshold DSth2. The second threshold DSth2 is greater than 0 (zero) and less than the first threshold DSth1. Then, the processing circuit 71 terminates the correction control and starts the substitution control. Substitution control is a control that substitutes a portion of the regenerative braking force with friction braking force. In substitution control, the processing circuit 71 sets the holding braking force FbH to the target friction braking force FbFTr and then operates the braking actuator 50 of the friction braking unit 40. As a result, the processing circuit 71 can make the total friction braking force FbF substantially equal to the holding braking force FbH.

[0030] The holding braking force FbH is the lower limit of the braking force required to maintain the vehicle 10's stop on the road surface where the vehicle 10 is located, or a braking force slightly greater than that lower limit. For example, the processing circuit 71 derives the holding braking force FbH such that its value increases as the absolute value of the road surface gradient increases.

[0031] When the processing circuit 71 operates the braking actuator 50 as described above, it sends an instruction to the regenerative control device 30 to reduce the regenerative braking force by the amount of the increase in the total friction braking force FbF. When the regenerative control device 30 receives the above instruction, the processing circuit 31 of the regenerative control device 30 reduces the target regenerative braking force FbETr by the amount of the increase in the total friction braking force FbF. Then, the processing circuit 31 operates the motor generator 21 based on the target regenerative braking force FbETr. As a result, the effective regenerative braking force FbE decreases in accordance with the increase in the total friction braking force FbF. In other words, while suppressing the increase in the total braking force Fb, a portion of the regenerative braking force is replaced with friction braking force.

[0032] The processing circuit 71 of the braking control device 70 can determine that the total friction braking force FbF has become equal to the holding braking force FbH at timing t13, and therefore terminates the substitution control. At the subsequent timing t14, the stopping distance DS becomes less than or equal to the third threshold DSth3. The third threshold DSth3 is greater than 0 (zero) and less than the second threshold DSth2. Then, the processing circuit 71 starts the reduction correction control. In the reduction correction control, the processing circuit 71 sends an instruction to the regenerative control device 30 to reduce the regenerative braking force to 0 (zero). At this time, the processing circuit 71 should send an instruction to the regenerative control device 30 to reduce the regenerative braking force at a reference reduction speed. The reference reduction speed is set so that the regenerative braking force becomes 0 (zero) before the stopping distance DS becomes 0 (zero).

[0033] When the regenerative control device 30 receives the instruction, the processing circuit 31 of the regenerative control device 30 reduces the target regenerative braking force FbETr toward 0 (zero). Then, the processing circuit 31 operates the motor generator 21 based on the target regenerative braking force FbETr. As a result, the effective regenerative braking force FbE decreases.

[0034] Furthermore, in the reduction correction control, the processing circuit 71 of the braking control device 70 maintains a state in which the target friction braking force FbFTr is equal to the held braking force FbH. Then, the processing circuit 71 operates the braking actuator 50 based on the target friction braking force FbFTr.

[0035] At timing t15, while the reduction correction control is being executed, the regenerative braking force FbE becomes 0 (zero). Since the vehicle 10 has not yet stopped at timing t15, the processing circuit 71 continues the reduction correction control. At this time, the processing circuit 71 maintains a state in which the target friction braking force FbFTr is equal to the holding braking force FbH, and then operates the braking actuator 50 based on the target friction braking force FbFTr. Therefore, if the holding braking force FbH is maintained at a constant value, the total friction braking force FbF is also maintained.

[0036] At timing t16, while the reduction correction control is being executed, the processing circuit 71 determines that the vehicle 10 has stopped. The processing circuit 71 then terminates the reduction correction control and starts the degenerate control. In the degenerate control, the processing circuit 71 increases the target friction braking force FbFTr to the required braking force FbRq. The processing circuit 71 then activates the braking actuator 50 based on the target friction braking force FbFTr. This increases the total friction braking force FbF. When the target friction braking force FbFTr reaches the required braking force FbRq at timing t17, the processing circuit 71 terminates the degenerate control. In other words, the processing circuit 71 terminates the smooth stop process.

[0037] <Functional configuration of the braking control system> Referring to Figure 1, the functional configuration of the braking control device 70 will be explained. The processing circuit 71 of the braking control device 70 functions as multiple functional units when the CPU 72 executes the control program of the first memory 73. These multiple functional units include a request setting unit 201, a determination unit 202, and a braking control unit 203.

[0038] The request setting unit 201 sets the requested braking force FbRq at predetermined control cycles. When the braking operation member 11 is operated, the request setting unit 201 sets the requested braking force FbRq such that the value increases as the braking operation amount Ba increases. When deceleration of the vehicle 10 is requested from another on-board control device, the request setting unit 201 sets the requested braking force FbRq to the braking force according to that request.

[0039] The determination unit 202 determines whether the total friction braking force FbF will be greater than a predetermined value Fbth within the determination period PDj, which is the timing from the start timing, when the increase in the total friction braking force FbF begins due to the execution of the stopping control, until the vehicle 10 comes to a stop. In other words, the determination unit 202 determines whether the total friction braking force FbF will not be greater than a predetermined value Fbth within the determination period PDj. In the example shown in Figure 5, timing t12 corresponds to the start timing. Timing t12 is the start timing of the substitution control of the smooth stop process. Timing t16 is the timing at which it is determined that the vehicle 10 has come to a stop. Therefore, the period from timing t12 to timing t16 corresponds to the "determination period PDj".

[0040] As described above, during substitution control and reduction correction control, the total friction braking force FbF is maintained by the holding braking force FbH. Similarly, during reduction correction control, the total friction braking force FbF is maintained by the holding braking force FbH. Therefore, the holding braking force FbH corresponds to the predicted increase in the total friction braking force during the execution of reduction correction control.

[0041] Therefore, the determination unit 202 determines that if the holding braking force FbH at the start timing of the substitution control is greater than a predetermined value Fbth, the total friction braking force FbF will be greater than a predetermined value Fbth within the determination period PDj. On the other hand, the determination unit 202 determines that if the holding braking force FbH at the start timing of the substitution control is less than or equal to the predetermined value Fbth, the total friction braking force FbF will not be greater than a predetermined value Fbth within the determination period PDj, that is, it can be determined that the total friction braking force FbF will be maintained at or below the predetermined value Fbth within the determination period PDj.

[0042] Hydraulic control that makes the front wheel pressure PwF and the rear wheel pressure PwR equal is described as "equal pressure control." When equal pressure control is performed under conditions where the target friction braking force FbFTr is relatively small, the pressing force, which is the force that presses the friction part 44 against the rotating body 43, is relatively small for both the friction brake 41F for the front wheel 12 and the friction brake 41R for the rear wheel 13. Due to the characteristics of friction brakes, when controlling the pressing force under such small conditions, the adjustment accuracy of the pressing force is lower compared to when controlling the pressing force under large conditions. Low adjustment accuracy of the pressing force means that the adjustment accuracy of the friction braking force generated by the wheels 12 and 13 is low. If the adjustment accuracy of the friction braking force generated by the wheels 12 and 13 is low, the total friction braking force FbF is likely to deviate from the target friction braking force FbFTr. Therefore, a braking force that serves as a criterion for determining whether the adjustment accuracy of the friction braking force generated by the wheels 12 and 13 is low is set to a predetermined value Fbth. An example of a specified value Fbth is 0.5 MPa.

[0043] When a braking request is received, the braking control unit 203 adjusts the total braking force Fb by coordinating the regenerative braking unit 20 and the friction braking unit 40. For example, the braking control unit 203 transmits information regarding the requested braking force FbRq to the regenerative control unit 30.

[0044] The regenerative control unit 101 of the regenerative control device 30 derives a target regenerative braking force FbETr based on the requested braking force FbRq indicated by the received information. For example, the regenerative control unit 101 sets the target regenerative braking force FbETr to the smaller of the regenerative braking force limit value and the requested braking force FbRq. The regenerative braking force limit value is the upper limit of the regenerative braking force that can be applied to the vehicle 10, or a regenerative braking force slightly smaller than that upper limit value. The regenerative control unit 101 operates the motor generator 21 based on the target regenerative braking force FbETr.

[0045] The braking control unit 203 sets the target friction braking force FbFTr based on the effective regenerative braking force FbE and the required braking force FbRq. If the effective regenerative braking force FbE is equal to the required braking force FbRq, the braking control unit 203 sets the target friction braking force FbFTr to 0 (zero). On the other hand, if the effective regenerative braking force FbE is less than the required braking force FbRq, the braking control unit 203 sets the target friction braking force FbFTr to the difference between the required braking force FbRq and the effective regenerative braking force FbE. Then, the braking control unit 203 operates the braking actuator 50 based on the target friction braking force FbFTr. If the conditions for executing the smooth stop process are met while this control is being executed, the braking control unit 203 starts the smooth stop process.

[0046] At the timing when the braking control unit 203 starts the substitution control for the smooth stop process, the determination unit 202 may determine that the total friction braking force FbF will not exceed a predetermined value Fbth within the determination period PDj. The braking control unit 203 switches the content of the substitution control depending on whether or not the total friction braking force FbF will exceed a predetermined value Fbth within the determination period PDj. For example, if the braking control unit 203 determines that the total friction braking force FbF will exceed a predetermined value Fbth within the determination period PDj, it executes a first substitution control as the substitution control. On the other hand, if the braking control unit 203 determines that the total friction braking force FbF will not exceed a predetermined value Fbth within the determination period PDj, it executes a second substitution control as the substitution control.

[0047] In the first substitution control, the braking control unit 203 operates the braking actuator 50 of the friction braking unit 40 so that the front wheel pressure PwF and the rear wheel pressure PwR are equal to each other. Even in this case, the braking control unit 203 operates the braking actuator 50 so that the sum of the front wheel friction braking force and the rear wheel friction braking force is substantially equal to the holding braking force FbH.

[0048] In the second substitution control, the braking control unit 203 operates the braking actuator 50 so that frictional braking force is generated on only one of the front wheels 12 and the rear wheels 13. For example, the braking control unit 203 operates the braking actuator 50 so that only the rear wheel pressure PwR increases, out of the front wheel pressure PwF and the rear wheel pressure PwR. In this case, the braking control unit 203 operates the braking actuator 50 so that the rear wheel frictional braking force becomes substantially equal to the holding braking force FbH.

[0049] If the braking control unit 203 determines that the vehicle 10 has stopped during the execution of the subsequent reduction correction control, the braking control unit 203 executes degenerate control. In degenerate control, the braking control unit 203 increases the total friction braking force FbF to the required braking force FbRq while satisfying the condition that the front wheel pressure PwF and the rear wheel pressure PwR are equal to each other.

[0050] <Processing flow in the braking control system> Referring to Figures 3 and 4, the process flow when performing a smooth stop during vehicle braking will be explained.

[0051] When the vehicle 10 is decelerating due to the application of braking force, the processing circuit 71 of the braking control device 70 sequentially executes a number of processes according to the processing flow shown in Figures 3 and 4. In step S11 of Figure 3, the processing circuit 71 determines whether the conditions for executing the smooth stop process have been met. For example, if the stopping distance DS is less than or equal to the first threshold DSth1, it indicates that the conditions for executing the smooth stop process have been met. If the conditions for execution have not yet been met (S11: NO), the processing circuit 71 repeatedly performs the determination in step S11 until the conditions for execution are met. On the other hand, if the conditions for execution are met (S11: YES), the processing circuit 71 proceeds to step S13.

[0052] In step S13, the processing circuit 71 performs augmentation control by functioning as a braking control unit 203. In augmentation control, the processing circuit 71 increases the effective regenerative braking force FbE by instructing the regenerative control device 30 to increase the regenerative braking force.

[0053] In the following step S15, the processing circuit 71 determines whether or not the boost compensation control has been completed. For example, if the increase in regenerative braking force in accordance with the above instruction has been completed, the processing circuit 71 can determine that the boost compensation control has been completed. If the boost compensation control has not been completed (S15: NO), the processing circuit 71 continues the execution of the boost compensation control by moving the process to step S13. On the other hand, if the boost compensation control has been completed (S15: YES), the processing circuit 71 moves the process to step S17.

[0054] In step S17, the processing circuit 71 determines whether the conditions for executing the substitution control have been met. For example, if the stopping distance DS is less than or equal to the second threshold DSth2, it indicates that the conditions for executing the substitution control have been met. If the conditions for execution have not yet been met (S17: NO), the processing circuit 71 repeatedly performs the determination in step S17 until the conditions for execution are met. On the other hand, if the conditions for execution are met (S17: YES), the processing circuit 71 proceeds to step S19.

[0055] In step S19 of Figure 4, the processing circuit 71 functions as a determination unit 202 to determine whether the holding braking force FbH is greater than a predetermined value Fbth. If the holding braking force FbH is greater than the predetermined value Fbth, it can be assumed that the total friction braking force FbF will be greater than the predetermined value Fbth within the determination period PDj. On the other hand, if the holding braking force FbH is less than or equal to the predetermined value Fbth, it can be assumed that the total friction braking force FbF will not be greater than the predetermined value Fbth within the determination period PDj. If the holding braking force FbH is greater than the predetermined value Fbth (S19: YES), the processing circuit 71 proceeds to step S21. On the other hand, if the holding braking force FbH is less than or equal to the predetermined value Fbth (S19: NO), the processing circuit 71 proceeds to step S23.

[0056] In step S21, the processing circuit 71 performs the first substitution control by functioning as a braking control unit 203. In the first substitution control, the processing circuit 71 increases the total friction braking force FbF so that the front wheel pressure PwF and the rear wheel pressure PwR are equal to each other. The processing circuit 71 also decreases the active regenerative braking force FbE by instructing the regenerative control device 30 to decrease the regenerative braking force by the amount of the increase in the total friction braking force FbF. Then, the processing circuit 71 proceeds to step S25.

[0057] In step S23, the processing circuit 71 performs a second substitution control by functioning as a braking control unit 203. In the second substitution control, the processing circuit 71 increases the total friction braking force FbF so that only the rear wheel pressure PwR increases, out of the front wheel pressure PwF and rear wheel pressure PwR. The processing circuit 71 also decreases the effective regenerative braking force FbE by instructing the regenerative control device 30 to decrease the regenerative braking force by the amount of the increase in the total friction braking force FbF. Then, the processing circuit 71 proceeds to step S25.

[0058] In step S25, the processing circuit 71 determines whether the substitution control has finished. If the total friction braking force FbF reaches the holding braking force FbH, the processing circuit 71 can determine that the substitution control has finished (S25: YES). In this case, the processing circuit 71 proceeds to step S27. On the other hand, if the substitution control has not yet finished (S25: NO), the processing circuit 71 proceeds to step S19. That is, the processing circuit 71 continues to execute either the first substitution control or the second substitution control.

[0059] In step S27, the processing circuit 71 determines whether the execution conditions for the undercorrection control have been met. For example, if the stopping distance DS is less than or equal to the third threshold DSth3, it indicates that the execution conditions for the undercorrection control have been met. If the execution conditions have not yet been met (S27: NO), the processing circuit 71 repeatedly performs the determination in step S27 until the execution conditions are met. On the other hand, if the execution conditions have been met (S27: YES), the processing circuit 71 proceeds to step S29.

[0060] In step S29, the processing circuit 71 performs reduction correction control by functioning as a braking control unit 203. In reduction correction control, the processing circuit 71 reduces the effective regenerative braking force FbE to 0 (zero) by activating the regenerative braking unit 20, and maintains the total friction braking force FbF at the retained braking force FbH by activating the friction braking unit 40.

[0061] During the execution of the attenuation correction control, in step S31, the processing circuit 71 determines whether or not the vehicle 10 has stopped. If the processing circuit 71 determines that the vehicle 10 has not stopped (S31: NO), the processing circuit 71 continues the execution of the attenuation correction control by moving the process to step S29. On the other hand, if the processing circuit 71 determines that the vehicle 10 has stopped (S31: YES), the processing circuit 71 moves the process to step S33.

[0062] In step S33, the processing circuit 71 performs degenerate control by functioning as a braking control unit 203. In degenerate control, the processing circuit 71 increases the total friction braking force FbF toward the required braking force FbRq by activating the friction braking unit 40. At this time, the processing circuit 71 increases the total friction braking force FbF toward the required braking force FbRq so that the front wheel pressure PwF and the rear wheel pressure PwR become equal to each other.

[0063] In the following step S35, the processing circuit 71 determines whether the total friction braking force FbF is substantially equal to the required braking force FbRq. For example, the processing circuit 71 only needs to determine that the total friction braking force FbF is substantially equal to the required braking force FbRq if the target friction braking force FbFTr is equal to or greater than the required braking force FbRq. If the processing circuit 71 determines that the total friction braking force FbF is less than the required braking force FbRq (S35: NO), the processing circuit 71 continues the execution of the degenerate control by moving the process to step S33. On the other hand, if the processing circuit 71 determines that the total friction braking force FbF is substantially equal to the required braking force FbRq (S35: YES), the processing circuit 71 terminates the degenerate control. That is, the processing circuit 71 terminates the smooth stop process.

[0064] <Operation and Effects of This Embodiment> (1-1) The processing circuit 71 determines whether the total friction braking force FbF is greater than a predetermined value Fbth within the determination period PDj. Even if the total friction braking force FbF is not greater than the predetermined value Fbth within the determination period PDj, if friction braking force is generated in either the front wheel 12 or the rear wheel 13, the adjustment accuracy of the friction braking force generated by the wheels 12 and 13 is low. As a result, the behavior of the vehicle 10 when the vehicle is stopped may deviate from the desired behavior due to the total friction braking force FbF deviating from the target friction braking force FbFTr.

[0065] Therefore, as shown in the example in Figure 5, if the processing circuit 71 determines that the total friction braking force FbF will not exceed a predetermined value Fbth within the determination period PDj, the processing circuit 71 operates the braking actuator 50 of the friction braking unit 40 so that friction braking force is generated on only one of the front wheels 12 and rear wheels 13. As a result, the friction braking force generated on one wheel is greater than when friction braking force is generated on all of the wheels 12 and 13. Consequently, the processing circuit 71 can adjust the friction braking force generated on one wheel with relatively high precision. This suppresses the total friction braking force FbF from deviating from the target friction braking force FbFTr.

[0066] Therefore, the braking control device 70 can improve the controllability of the total friction braking force FbF just before the vehicle 10 comes to a stop. As a result, the braking control device 70 can suppress the deviation of the vehicle 10's behavior from the desired behavior when the vehicle 10 is stopped.

[0067] (1-2) By generating frictional braking force at the front wheels 12, an anti-dive force acts on the front of the vehicle 10. The anti-dive force is a force that suppresses the downward displacement of the front of the vehicle 10. By generating frictional braking force at the rear wheels 13, an anti-lift force acts on the rear of the vehicle 10. The anti-lift force is a force that suppresses the upward displacement of the rear of the vehicle 10. In a typical vehicle 10, the suspension geometry is set such that when the frictional braking force of the front wheels and the frictional braking force of the rear wheels are equal, the anti-lift force is greater than the anti-dive force.

[0068] In the braking control device 70 of this embodiment, if it is determined that the total friction braking force FbF will not exceed a predetermined value Fbth within the determination period PDj, friction braking force is generated only on the rear wheels 13 of the front wheels 12 and rear wheels 13. As a result, the braking control device 70 can achieve a higher suppression effect on the pitching motion of the vehicle 10 compared to the case where friction braking force is generated only on the front wheels 12 of the front wheels 12 and rear wheels 13.

[0069] (1-3) In a friction brake having a wheel cylinder, the pressing force and, consequently, the friction braking force can be controlled by adjusting the wheel pressure. In this case, the lower the wheel pressure, the lower the precision of the wheel pressure adjustment. The lower the precision of the wheel pressure adjustment, the lower the precision of the friction braking force adjustment.

[0070] As explained using Figure 2, the gradient of increase in frictional braking force in the friction brake 41F for the front wheel 12 is greater than the gradient of increase in frictional braking force in the friction brake 41R for the rear wheel 13. In other words, the amount of increase in frictional braking force when increasing wheel pressure is greater in the friction brake 41F compared to the friction brake 41R.

[0071] In this regard, in the braking control device 70 of this embodiment, if it is determined that the total friction braking force FbF will not exceed a predetermined value Fbth within the determination period PDj, only the rear wheel pressure PwR is increased among the front wheel pressure PwF and the rear wheel pressure PwR, as shown in Figures 5(f) and (g). As a result, the braking control device 70 can achieve a higher effect in suppressing the deviation of the total friction braking force FbF from the target friction braking force FbFTr compared to the case where only the front wheel pressure PwF is increased among the front wheel pressure PwF and the rear wheel pressure PwR.

[0072] (1-4) The higher the wheel pressure while vehicle 10 is stopped, the more likely a delay will occur when vehicle 10 starts again. This is because the higher the wheel pressure, the longer it takes for the wheel pressure to become 0 (zero).

[0073] In this regard, in the braking control device 70 of this embodiment, the braking actuator 50 is operated in degraded control so that the front wheel pressure PwF and the rear wheel pressure PwR become equal to each other. As a result, the braking control device 70 can reduce the delay in the next start of the vehicle 10 compared to the case where only one of the front wheel pressure PwF and the rear wheel pressure PwR is generated even when the vehicle 10 is stopped.

[0074] (Second Embodiment) A second embodiment of the braking control device will be described with reference to Figures 6 and 7. The second embodiment differs from the first embodiment in that the smooth stop process is not performed just before the vehicle comes to a complete stop. In the following description, the differences from the first embodiment will be mainly described, and the same reference numerals will be used for components identical to those in the first embodiment to avoid redundant explanations.

[0075] If smooth stop processing is not performed just before vehicle 10 comes to a complete stop, the braking control device 70 performs regenerative substitution control just before vehicle 10 comes to a complete stop. Regenerative substitution control is a control that reduces the effective regenerative braking force FbE to 0 (zero) while suppressing the total braking force Fb from deviating from the required braking force FbRq, and increases the total friction braking force FbF to the required braking force FbRq. In this embodiment, regenerative substitution control corresponds to "stopping control".

[0076] <Processing flow in the braking control system> Referring to Figure 6, the processing flow when regenerative braking is performed will be explained.

[0077] When the vehicle 10 is decelerating due to the application of braking force, the processing circuit 71 of the braking control device 70 sequentially executes a number of processes according to the processing flow shown in Figure 6. In step S51, the processing circuit 71 determines whether the execution conditions for regenerative switching control have been met. For example, the processing circuit 71 determines that the execution conditions have been met when the vehicle speed VS of the vehicle 10 becomes less than or equal to the start determination speed VSth. In this case, the vehicle speed that serves as the criterion for determining whether the vehicle 10 has started to travel at a low speed is set to the start determination speed VSth. If the execution conditions have not yet been met (S51: NO), the processing circuit 71 repeatedly performs the determination in step S51 until the execution conditions are met. On the other hand, if the execution conditions are met (S51: YES), the processing circuit 71 proceeds to step S53.

[0078] In step S53, the processing circuit 71, functioning as a determination unit 202, determines whether the requested braking force FbRq is greater than the predetermined value Fbth. If the requested braking force FbRq is greater than the predetermined value Fbth, it can be assumed that the total friction braking force FbF will be greater than the predetermined value Fbth within the determination period PDj from the start timing of regenerative switching control until the vehicle 10 comes to a stop. On the other hand, if the requested braking force FbRq is less than or equal to the predetermined value Fbth, it can be assumed that the total friction braking force FbF will not be greater than the predetermined value Fbth within the determination period PDj. If the requested braking force FbRq is greater than or equal to the predetermined value Fbth (S53: YES), the processing circuit 71 proceeds to step S55. On the other hand, if the requested braking force FbRq is less than or equal to the predetermined value Fbth (S53: NO), the processing circuit 71 proceeds to step S61.

[0079] In step S55, the processing circuit 71 performs the first regenerative substitution control by functioning as a braking control unit 203. In the first regenerative substitution control, the processing circuit 71 transmits an instruction to the regenerative control device 30 of the regenerative braking unit 20 to reduce the regenerative braking force to 0 (zero).

[0080] When the processing circuit 31 of the regenerative control device 30 receives the above instruction, it functions as a regenerative control unit 101 and reduces the target regenerative braking force FbETr toward 0 (zero). Then, the processing circuit 31 operates the motor generator 21 based on the target regenerative braking force FbETr.

[0081] Furthermore, in the first regenerative braking substitution control, the processing circuit 71 sets the difference between the required braking force FbRq and the actual regenerative braking force FbE as the target friction braking force FbFTr. Then, the processing circuit 71 operates the braking actuator 50 based on this target friction braking force FbFTr. At this time, the processing circuit 71 increases the total friction braking force FbF so that the front wheel pressure PwF and the rear wheel pressure PwR remain equal. As a result, the processing circuit 71 can substitute the actual regenerative braking force FbE with the total friction braking force FbF.

[0082] In the following step S57, the processing circuit 71 determines whether the substitution of the effective regenerative braking force FbE with the total friction braking force FbF has been completed. For example, the processing circuit 71 can determine that the substitution is complete if the effective regenerative braking force FbE becomes 0 (zero). If the processing circuit 71 determines that the substitution is not complete (S57: NO), the processing circuit 71 continues the execution of the first regenerative substitution control by moving the process to step S55. On the other hand, if the processing circuit 71 determines that the substitution is complete (S57: YES), the processing circuit 71 terminates the first regenerative substitution control.

[0083] In step S61, the processing circuit 71 performs the second regenerative substitution control by functioning as a braking control unit 203. In the second regenerative substitution control, the processing circuit 71 transmits an instruction to the regenerative control device 30 of the regenerative braking unit 20 to reduce the regenerative braking force to 0 (zero), similar to the case of the first regenerative substitution control.

[0084] When the processing circuit 31 of the regenerative control device 30 receives the above instruction, it functions as a regenerative control unit 101 and reduces the target regenerative braking force FbETr toward 0 (zero). Then, the processing circuit 31 operates the motor generator 21 based on the target regenerative braking force FbETr.

[0085] Furthermore, in the second regenerative braking substitution control, the processing circuit 71 sets the difference between the requested braking force FbRq and the actual regenerative braking force FbE as the target friction braking force FbFTr. Then, the processing circuit 71 operates the braking actuator 50 based on this target friction braking force FbFTr. At this time, the processing circuit 71 increases the total friction braking force FbF such that only one of the front wheel pressure PwF and the rear wheel pressure PwR increases. For example, the processing circuit 71 increases only the rear wheel pressure PwR of the front wheel pressure PwF and the rear wheel pressure PwR. Even in this case, the processing circuit 71 can substitute the actual regenerative braking force FbE with the total friction braking force FbF.

[0086] In the following step S63, the processing circuit 71 determines whether the substitution has been completed, similar to the determination process in step S57. If the processing circuit 71 determines that the substitution has not been completed (S63: NO), the processing circuit 71 continues the execution of the second-generation substitution control by returning to step S61. On the other hand, if the processing circuit 71 determines that the substitution has been completed (S63: YES), the processing circuit 71 terminates the second-generation substitution control.

[0087] Then, in step S65, the processing circuit 71 determines whether or not the vehicle 10 has stopped. For example, the processing circuit 71 may determine that the vehicle 10 has stopped if the state in which the vehicle speed VS is 0 (zero) continues for longer than the determination time. If the processing circuit 71 determines that the vehicle 10 has not yet stopped (S65: NO), the processing circuit 71 repeatedly performs the determination in step S65 until it can determine that the vehicle 10 has stopped. On the other hand, if the processing circuit 71 determines that the vehicle 10 has stopped (S65: YES), the processing circuit 71 proceeds to step S67.

[0088] In step S67, the processing circuit 71 performs equal pressure control by functioning as a braking control unit 203. In equal pressure control, the processing circuit 71 activates the braking actuator 50 to maintain a state in which the total friction braking force FbF is equal to the required braking force FbRq, and to make the front wheel pressure PwF and the rear wheel pressure PwR equal to each other.

[0089] Then, in step S69, the processing circuit 71 determines whether the front wheel pressure PwF and the rear wheel pressure PwR are equal to each other. For example, if the difference between the front wheel pressure PwF and the rear wheel pressure PwR is within a predetermined allowable range, the processing circuit 71 determines that the front wheel pressure PwF and the rear wheel pressure PwR are equal to each other. If the processing circuit 71 determines that the front wheel pressure PwF is different from the rear wheel pressure PwR (S69: NO), the processing circuit 71 continues the equalization control by moving the process to step S67. On the other hand, if the processing circuit 71 determines that the front wheel pressure PwF and the rear wheel pressure PwR are equal to each other (S69: YES), the processing circuit 71 terminates the equalization control.

[0090] <Operation and Effects of This Embodiment> The operation and effects of this embodiment will be explained with reference to Figure 7. As shown in Figures 7(a) to (f), at timing t21, while the vehicle 10 is decelerating due to the application of regenerative braking force, the processing circuit 71 of the braking control device 70 determines that the conditions for executing regenerative switching control have been met. In the example shown in Figure 7, timing t21 corresponds to the "start timing". Timing t23 is the timing when the vehicle 10 comes to a stop. Therefore, the period from timing t21 to timing t23 corresponds to the "determination period PDj".

[0091] At timing t21, which corresponds to the start timing, the required braking force FbRq is less than or equal to a predetermined value Fbth. In this case, the processing circuit 71 can determine that the total friction braking force FbF will not exceed the predetermined value Fbth within the determination period PDj. Therefore, the processing circuit 71 starts the second-generation replacement control.

[0092] When the second regenerative braking substitution control is performed by the braking control device 70, the regenerative braking unit 20 operates to reduce the effective regenerative braking force FbE to 0 (zero). Specifically, the processing circuit 31 of the regenerative control device 30 reduces the target regenerative braking force FbETr at a speed that allows the regenerative braking force to be reduced to 0 (zero) before the vehicle speed VS becomes 0 (zero). Then, the processing circuit 31 operates the motor generator 21 based on the target regenerative braking force FbETr.

[0093] As the effective regenerative braking force FbE decreases in this way, the processing circuit 71 of the braking control device 70 increases the total friction braking force FbF to compensate for the decrease in the effective regenerative braking force FbE. In the second regenerative switching control, as shown in Figures 7(e) and (f), the processing circuit 71 increases only the rear wheel pressure PwR out of the front wheel pressure PwF and rear wheel pressure PwR.

[0094] Figures 7(e) and (f) show the changes in wheel pressures PwF and PwR when the first wheel swap control is performed even though the required braking force FbRq is less than or equal to a predetermined value Fbth at timing t21, as illustrated by the dashed lines. In this case, both wheel pressures PwF and PwR are low. As a result, the total friction braking force FbF tends to deviate from the required braking force FbRq due to the low adjustment accuracy of wheel pressures PwF and PwR.

[0095] In this regard, in the braking control device 70 of this embodiment, by performing a second wheel substitution control, only the rear wheel pressure PwR is increased among the front wheel pressure PwF and rear wheel pressure PwR. As a result, the rear wheel friction braking force becomes larger compared to the case where friction braking force is generated in all of the multiple wheels 12 and 13. Consequently, the processing circuit 71 can adjust the rear wheel friction braking force with greater precision compared to the case where friction braking force is generated in all of the multiple wheels 12 and 13. This allows the processing circuit 71 to suppress the total friction braking force FbF from deviating from the required braking force FbRq. Therefore, the braking control device 70 can improve the controllability of the total friction braking force FbF just before the vehicle 10 comes to a stop.

[0096] Furthermore, the execution of the second regenerative substitution control causes the effective regenerative braking force FbE to become 0 (zero) at timing t22. At this point, the processing circuit 71 terminates the second regenerative substitution control. At the subsequent timing t23, the processing circuit 71 can determine that the vehicle 10 has stopped. At this point, the processing circuit 71 executes equal pressure control. As a result, when the vehicle 10 is stopped, the front wheel pressure PwF and the rear wheel pressure PwR can be kept equal to each other. Therefore, the braking control device 70 of this embodiment can obtain effects equivalent to (1-4) in the first embodiment described above.

[0097] (Example of change) The above embodiments can be implemented with the following modifications. The above embodiments and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0098] In the first embodiment, the processing circuit 71, i.e., the braking control unit 203, may increase the total friction braking force FbF toward the required braking force FbRq in order to maintain a state in which the front wheel pressure PwF and the rear wheel pressure PwR are separated during degraded control.

[0099] In the second embodiment, the processing circuit 71, i.e., the braking control unit 203, does not need to perform equal pressure control after the vehicle has stopped following the execution of the second regenerative substitution control. In the first embodiment, the processing circuit 71, i.e., the braking control unit 203, may increase only the front wheel pressure PwF among the front wheel pressure PwF and rear wheel pressure PwR in the second substitution control.

[0100] In the second embodiment, the processing circuit 71, i.e., the braking control unit 203, may increase only the front wheel pressure PwF among the front wheel pressure PwF and rear wheel pressure PwR in the second regenerative switching control.

[0101] The friction braking section may be configured to include an electric braking device as a friction brake that generates a pressing force corresponding to the drive amount of the electric motor. An example of an electric braking device is the device disclosed in "Japanese Patent Application Publication No. 2024-143525".

[0102] The regenerative braking unit may be configured to include a power unit comprising at least one motor generator and an engine, provided that it can provide regenerative braking force to the vehicle 10.

[0103] The braking control device 70 may be configured to include multiple processing circuits. For example, among the multiple processing circuits, the first processing circuit executes some of the multiple functional units 201 to 203. The functional unit realized by the first processing circuit is the first functional unit. In this case, a second processing circuit, separate from the first processing circuit, functions as a functional unit other than the first functional unit among the multiple functional units 201 to 203.

[0104] The processing circuit 71 may be configured as a circuit including one or more processors that operate according to a computer program, one or more dedicated hardware circuits such as dedicated hardware that performs at least some of the various processes, or a combination thereof. Examples of dedicated hardware include application-specific integrated circuits (ASICs). The processor includes a CPU and memory such as RAM and ROM, where the memory stores program code or instructions configured to cause the CPU to perform the processes. The memory, i.e., storage medium, includes any available medium that can be accessed by a general-purpose or dedicated computer.

[0105] (Other technological ideas) This section describes the technical concepts that can be understood from the above-mentioned multiple embodiments and modifications. [Note 1] After the vehicle has come to a stop, it is preferable that the braking control unit generates the frictional braking force on both the front and rear wheels so that the total frictional braking force is equal to the required braking force.

[0106] [Note 2] The friction braking unit comprises a friction brake provided for the front wheel, a friction brake provided for the rear wheel, and a braking actuator. The multiple friction brakes each have wheel cylinders to which brake fluid is supplied, and are configured to generate a greater friction braking force the higher the hydraulic pressure of the wheel cylinders. The braking actuator is configured to allow individual adjustment of the hydraulic pressure of the wheel cylinders of the plurality of friction brakes. It is preferable that, after the vehicle has stopped, the braking control unit operates the braking actuators such that the hydraulic pressure of the wheel cylinders of the plurality of friction brakes is equal to each other, and the total friction braking force is equal to the required braking force, thereby generating the friction braking force on both the front and rear wheels.

[0107] [Note 3] The braking force that can maintain the vehicle in a stopped state is the holding braking force. In the reduction correction control, it is preferable that the braking control unit operates the friction braking unit so that the total friction braking force becomes equal to the holding braking force, while also operating the regenerative braking unit so that the regenerative braking force decreases to 0 (zero).

[0108] [Note 4] Preferably, the braking control unit operates the friction braking unit so that the friction braking force is generated in both the front wheel and the rear wheel when the determination unit determines that the total friction braking force is greater than the predetermined value within the determination period.

[0109] In this specification, the expression "at least one" means "one or more" of the desired options. For example, if there are two options, the expression "at least one" means "only one option" or "both of the two options." As another example, if there are three or more options, the expression "at least one" means "only one option" or "a combination of two or more arbitrary options." [Explanation of symbols]

[0110] 10... Vehicles 12…Front wheel 13... Rear wheel 20...Regenerative braking section 21…Motor Generator 30…Regenerative braking control device 40...Friction brake part 41F, 41R… Friction brakes 42... Wheel cylinder 50... Brake actuator 70... Brake control device 71…Processing circuit 101...Regenerative Control Unit 202…Judgment section 203... Brake Control Unit

Claims

1. This invention is applied to a vehicle comprising front wheels and rear wheels, and a friction braking unit configured to allow adjustment of the friction braking force generated by the front wheels and the friction braking force generated by the rear wheels. The sum of the frictional braking force generated by the front wheels and the frictional braking force generated by the rear wheels constitutes the total frictional braking force of the vehicle. A braking control unit that performs stopping control to bring the vehicle to a stop while the friction braking force is applied to the vehicle by the operation of the friction braking unit, The system includes a determination unit that determines whether the total friction braking force does not exceed a predetermined value, which is a criterion for determining whether the adjustment accuracy of the total friction braking force is low, within a determination period from the start timing, which is the timing at which the increase in the total friction braking force begins due to the execution of the aforementioned stopping control, until the vehicle comes to a stop. If the determination unit determines that the total friction braking force will not exceed the predetermined value within the determination period, the braking control unit operates the friction braking unit so that the friction braking force is generated on only one of the front or rear wheels. Brake control device.

2. The aforementioned vehicle is equipped with a regenerative braking unit that provides regenerative braking force, The braking control unit, as the stopping control, performs control to stop the vehicle while the sum of the total friction braking force and the regenerative braking force is less than the required braking force for the vehicle. The determination unit determines, based on the predicted value of the increase in the total friction braking force during the execution of the stopping control, whether or not the total friction braking force will exceed the predetermined value within the determination period. The braking control device according to claim 1.

3. The aforementioned vehicle is equipped with a regenerative braking unit that provides regenerative braking force, The braking control unit, as part of the stopping control, suppresses the sum of the total friction braking force and the regenerative braking force from deviating from the required braking force for the vehicle, while reducing the regenerative braking force to 0 (zero) and increasing the total friction braking force. The determination unit determines, based on the requested braking force and the regenerative braking force at the start timing, whether or not the total friction braking force will exceed the predetermined value within the determination period. The braking control device according to claim 1.

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