Braking control device

Abstract

In a braking control device 110, when a liquid pressure increase amount estimated by an estimation unit 123 is greater than or equal to an increase amount determination value during execution of regenerative cooperation control, a control unit 122 executes degeneration processing for reducing regenerative braking force to zero and opening a holding valve to end the regenerative cooperation control.

Description

Braking control device

[0001] The present invention relates to a braking control device.

[0002] Patent Document 1 describes a vehicle including a plurality of wheel cylinders corresponding to front wheels and rear wheels, a pressurizing unit that pressurizes the plurality of wheel cylinders, a hydraulic circuit that connects the plurality of wheel cylinders and the pressurizing unit, a regenerative braking unit that applies regenerative braking force to the front wheels, and a braking control device that controls the pressurizing unit, the hydraulic circuit, and the regenerative braking unit. In the hydraulic circuit, a holding valve, which is a normally-open solenoid valve, is provided in a fluid passage connecting the pressurizing unit and the wheel cylinder of the front wheel. The holding valve is closed when it is necessary to maintain the hydraulic pressure on the wheel cylinder side of the front wheel lower than the hydraulic pressure on the pressurizing unit side in the fluid passage.

[0003] The braking control device executes regenerative cooperative control that covers the required braking force demanded of the vehicle with hydraulic braking force and regenerative braking force. In the regenerative cooperative control, the braking control device calculates a target value of braking force to be applied to the front wheels and a target value of braking force to be applied to the rear wheels. Subsequently, the braking control device applies hydraulic braking force to the rear wheels based on the target value of braking force to be applied to the rear wheels. On the other hand, the braking control device applies hydraulic braking force and regenerative braking force to the front wheels based on the target value of braking force to be applied to the front wheels. In regenerative cooperative control, when it is necessary to make the hydraulic pressure of the wheel cylinder of the front wheel lower than the hydraulic pressure of the wheel cylinder of the rear wheel, the braking control device closes the holding valve.

[0004] Japanese Unexamined Patent Publication No. 2021-160418

[0005] If brake fluid leaks from the closed holding valve while the braking control device is executing regenerative cooperative control for the front wheels, brake fluid flows into the wheel cylinder of the front wheel despite the holding valve being closed. As a result, the hydraulic braking force applied to the front wheels increases in accordance with the amount of brake fluid leaking from the holding valve. In this case, the braking force applied to the vehicle may become larger than the required braking force.

[0006] A braking control device that solves the above problems is a braking control device applicable to a vehicle comprising: a pressurizing unit that applies hydraulic braking force to the first left and right wheels and the second left and right wheels by pressurizing the first wheel cylinders of the first left and right wheels, which are one of the front and rear wheels of the vehicle, and the second wheel cylinders of the second left and right wheels, which are the other of the front and rear wheels; a pressure regulating unit that has a normally open solenoid valve disposed in a fluid passage connecting the first wheel cylinder and the pressurizing unit, and has a first holding valve that maintains the fluid pressure on the first wheel cylinder side in the fluid passage at a level less than the fluid pressure on the pressurizing unit side when the valve is closed; and a regenerative braking unit that applies regenerative braking force to the first left and right wheels, wherein the The system includes a control unit that controls a retaining valve to generate the required braking force for the first left and right wheels using the regenerative braking force and the hydraulic braking force, and generates the required braking force for the second left and right wheels using the hydraulic braking force, and an estimation unit that estimates the amount of hydraulic pressure rise, which is the amount of increase in the hydraulic pressure of the first wheel cylinder from the time the first retaining valve is closed, and when the regenerative cooperative control is being performed, if the amount of hydraulic pressure rise estimated by the estimation unit is equal to or greater than the rise amount determination value, the control unit performs a degraded process to reduce the regenerative braking force to zero and open the first retaining valve to terminate the regenerative cooperative control.

[0007] The braking control device can prevent the braking force applied to the vehicle from exceeding the required braking force during vehicle braking.

[0008] Figure 1 is a schematic diagram showing the general configuration of a vehicle equipped with a braking system. Figure 2 is a schematic diagram of the pressure regulating unit of the braking system in Figure 1. Figure 3 is a flowchart explaining the processing flow when the braking control device of the braking system in Figure 1 performs regenerative cooperative control. Figures 4(a) to 4(d) are timing charts showing the changes in various variables when the braking control device of the braking system in Figure 1 performs regenerative cooperative control.

[0009] The following describes one embodiment of a vehicle equipped with a braking control device. <Configuration of this embodiment> As shown in Figures 1 and 2, the vehicle is equipped with a plurality of wheels FL, FR, RL, RR, the same number of braking mechanisms 10 as the wheels FL, FR, RL, RR, and a braking device 100. The plurality of wheels FL, FR, RL, RR consist of two front wheels FL, FR and two rear wheels RL, RR. The two front wheels FL, FR are the left front wheel FL and the right front wheel FR. The two rear wheels RL, RR are the left rear wheel RL and the right rear wheel RR. The two rear wheels RL, RR correspond to the "first left and right wheels," and the two front wheels FL, FR correspond to the "second left and right wheels."

[0010] <Braking Mechanism> Multiple braking mechanisms 10 apply braking force to the corresponding wheels FL, FR, RL, and RR. The braking mechanism 10 includes a wheel cylinder 11, a rotating body 12, and a friction material 13. The rotating body 12 is a brake rotor that rotates with the corresponding wheel, and the friction material 13 is a brake pad that does not rotate with the corresponding wheel. Therefore, by pressing the friction material 13 against the rotating body 12, braking force is applied to the corresponding wheel. The force pressing the friction material 13 against the rotating body 12 increases with increasing WC pressure, which is the hydraulic pressure of the brake fluid in the wheel cylinder 11. Therefore, the braking mechanism 10 can apply a greater braking force to the corresponding wheel as the WC pressure increases. The wheel cylinders 11 of the two rear wheels RL and RR correspond to the "first wheel cylinders," and the wheel cylinders 11 of the two front wheels FL and FR correspond to the "second wheel cylinders."

[0011] <Braking System> The braking system 100 adjusts the braking force applied to the vehicle by controlling the WC pressure of multiple wheel cylinders 11. The braking system 100 includes a hydraulic pressure generator 20, a pressure regulating unit 70, a regenerative braking system 90, and a braking control device 110.

[0012] <Hydraulic pressure generating device> The hydraulic pressure generating device 20 includes a reservoir tank 21, a braking operating member 22, a master device 30, and a pressurizing unit 50.

[0013] The reservoir tank 21 stores brake fluid and is open to the atmosphere. The braking operation member 22 is a member operated by the driver of the vehicle to adjust the deceleration of the vehicle when slowing it down. An example of the braking operation member 22 is the brake pedal. When the driver operates the braking operation member 22, the hydraulic pressure generator 20 applies a braking force to the vehicle corresponding to the amount of operation of the braking operation member 22 by adjusting the WC pressure of the multiple wheel cylinders 11.

[0014] <Master device> The master device 30 includes a master cylinder 31, a stroke simulator 32, a plurality of flow paths 331, 332, 333, and a plurality of control valves 341, 342.

[0015] The master cylinder 31 comprises a main cylinder 41, a cover cylinder 42, a master piston 43, and an input piston 44. The master piston 43 and the input piston 44 are each movable relative to the main cylinder 41 and the cover cylinder 42. The master cylinder 31 is equipped with a master spring 45 that biases the master piston 43 and an input spring 46 that biases the input piston 44.

[0016] The main cylinder 41 has a plate-shaped bottom wall 411, a cylindrical circumferential wall 412 extending from the bottom wall 411 along the axis of the bottom wall 411, and a first annular wall 413 extending from the rear end of the circumferential wall 412 toward the axis of the circumferential wall 412. The first annular wall 413 has a hole into which the rear end of the master piston 43, which will be described later, is inserted.

[0017] Within the main cylinder 41, the master chamber Rm is partitioned by the bottom wall 411, the peripheral wall 412, and the master piston 43. Hereafter, in the master cylinder 31, the direction in which the master piston 43 moves to reduce the volume of the master chamber Rm will be referred to as "forward." Conversely, the opposite direction to forward will be referred to as "rearward." Rearward is the direction in which the master piston 43 moves to increase the volume of the master chamber Rm.

[0018] Rearward of the master chamber Rm within the main cylinder 41, the first fluid chamber R1 is partitioned by the peripheral wall 412 and the master piston 43. Rearward of the first fluid chamber R1 within the main cylinder 41, the servo chamber Rs is partitioned by the peripheral wall 412, the first annular wall 413 and the master piston 43. Within the main cylinder 41, the master chamber Rm, the first fluid chamber R1, and the servo chamber Rs are not connected to each other.

[0019] The cover cylinder 42 has a cylindrical circumferential wall 421 and a second annular wall 422 extending from the rear end of the circumferential wall 421 toward the axis of the circumferential wall 421. The circumferential wall 421 is attached to the first annular wall 413 so that its axis coincides with that of the circumferential wall 412 of the main cylinder 41. The second annular wall 422 is provided with a hole into which the rear end of the input piston 44, which will be described later, is inserted.

[0020] Within the cover cylinder 42, the second fluid chamber R2 is partitioned by the peripheral wall 421, the second annular wall 422, and the first annular wall 413 of the main cylinder 41. In the master cylinder 31, the second fluid chamber R2 is located behind the servo chamber Rs.

[0021] The master piston 43 is housed in the master cylinder 31 in a state where it is in contact with the inner surface of the circumferential wall 412 and the inner surface of the first annular wall 413 of the main cylinder 41 via a sealing member. Therefore, when the master piston 43 moves in the axial direction, the master piston 43 slides against the sealing members provided on the circumferential wall 412 and the first annular wall 413. The rear end of the master piston 43 protrudes rearward from the first annular wall 413 and is located within the second liquid chamber R2.

[0022] The input piston 44 is housed in the master cylinder 31, in contact with the inner circumferential surface of the second annular wall 422 of the cover cylinder 42 via a sealing member. Therefore, when the input piston 44 moves axially, it slides against the sealing member provided on the second annular wall 422. The rear end of the input piston 44 protrudes rearward from the second annular wall 422. A braking operating member 22 is connected to the rear end of the input piston 44. In the second fluid chamber R2, a gap is formed between the master piston 43 and the input piston 44. When the braking operating member 22 is operated, the input piston 44 moves in a direction approaching the master piston 43.

[0023] The master spring 45 is positioned between the bottom wall 411 of the main cylinder 41 and the master piston 43. The master spring 45 biases the master piston 43 backward, so when the master piston 43 moves forward, the master spring 45 is elastically compressed.

[0024] The input spring 46 is positioned between the first annular wall 413 of the main cylinder 41 and the input piston 44. The input spring 46 biases the input piston 44 backward, so when the input piston 44 moves forward, the input spring 46 is elastically compressed.

[0025] In the master cylinder 31, the master chamber Rm is connected to the reservoir tank 21. More specifically, the rear end portion of the master chamber Rm is connected to the reservoir tank 21 via a port formed in the peripheral wall 412 of the main cylinder 41. Therefore, when the master piston 43 moves forward from the rearmost position shown in Figure 1, the connection between the master chamber Rm and the reservoir tank 21 is released. From this point onward, the hydraulic pressure in the master chamber Rm increases as the master piston 43 moves forward. For example, if the hydraulic pressure in the servo chamber Rs increases, the hydraulic pressure in the servo chamber Rs will move the master piston 43 forward. This will increase the hydraulic pressure in the master chamber Rm.

[0026] The first flow path 331 connects the second hydraulic circuit 712 of the pressure regulating unit 70 (described later) to the master chamber Rm. The second flow path 332 connects the first liquid chamber R1 to the third flow path 333. The third flow path 333 connects the second liquid chamber R2 to the reservoir tank 21.

[0027] The first control valve 341 is a normally closed solenoid valve. The second control valve 342 is a normally open solenoid valve. The first control valve 341 is located in the third flow path 333 on the side of the second liquid chamber R2 beyond the connection point with the second flow path 332. The second control valve 342 is located in the third flow path 333 on the side opposite to the first control valve 341, with the connection point with the second flow path 332 in between. When the braking control device 110 is operating, the first control valve 341 is opened and the second control valve 342 is closed.

[0028] The stroke simulator 32 generates a reaction force corresponding to the amount of operation of the braking operating member 22. The stroke simulator 32 is connected to the second flow path 332. <Pressurizing Unit> As shown in Figure 1, the pressurizing unit 50 is equipped with an electric cylinder 51. The pressurizing unit 50 can adjust the WC pressure of multiple wheel cylinders 11 by operating the electric cylinder 51.

[0029] The pressurizing unit 50 is equipped with multiple passages 54 to 56 as brake fluid passages. The fourth passage 54 is connected to the input port 515 of the electric cylinder 51 and the reservoir tank 21. The fifth passage 55 is connected to the servo chamber Rs of the master cylinder 31 and the output port 516 of the electric cylinder 51. The sixth passage 56 is connected to the first hydraulic circuit 711 of the pressure regulating unit 70 (described later) and the fifth passage 55. Therefore, the electric cylinder 51 can supply brake fluid discharged from the output port 516 to both the servo chamber Rs and the first hydraulic circuit 711.

[0030] The pressurizing unit 50 is equipped with a differential pressure regulating valve 551 located in the fifth flow path 55. The differential pressure regulating valve 551 is a normally open linear solenoid valve that adjusts the differential pressure between the portion of the fifth flow path 55 closer to the servo chamber Rs than the differential pressure regulating valve 551 and the portion of the fifth flow path 55 closer to the electric cylinder 51 than the differential pressure regulating valve 551. The pressurizing unit 50 can adjust the amount of brake fluid supplied to the servo chamber Rs, i.e., the hydraulic pressure in the servo chamber Rs, by adjusting the indicated opening degree of the differential pressure regulating valve 551.

[0031] Furthermore, a check valve 552 is provided in parallel with the differential pressure regulating valve 551 in the fifth flow path 55. The check valve 552 allows the flow of brake fluid from the servo chamber Rs towards the electric cylinder 51 through the check valve 552. On the other hand, the check valve 552 restricts the flow of brake fluid that would otherwise pass through the check valve 552 from the electric cylinder 51 towards the servo chamber Rs.

[0032] The electric cylinder 51 comprises a cylinder 511, a piston 512, an electric motor 513, and a conversion mechanism 514. The piston 512 is installed inside the cylinder 511 in a manner that allows it to slide against a sealing member provided in the cylinder 511. The electric motor 513 is the power source for the electric cylinder 51. The conversion mechanism 514 converts the rotation of the output shaft of the electric motor 513 into the linear movement of the piston 512.

[0033] Inside the cylinder 511, a hydraulic chamber Re into which brake fluid is introduced is partitioned by the cylinder 511 and the piston 512. The position of the piston 512 inside the cylinder 511 can be changed by driving the electric motor 513. Hereafter, the direction of linear movement of the piston 512 when reducing the volume of the hydraulic chamber Re will be referred to as the "forward direction Za," while the opposite direction to the forward direction Za will be referred to as the "reverse direction Zb." The reverse direction Zb is also the direction of linear movement of the piston 512 when increasing the volume of the hydraulic chamber Re.

[0034] The cylinder 511 has an input port 515 and an output port 516 formed therein, which serve as ports connecting the hydraulic chamber Re to the outside. The piston 512 has a through hole 517 formed therein. The through hole 517 is positioned so that the input port 515 and the hydraulic chamber Re can communicate when the piston 512 is in its rearmost position. As a result, when the piston 512 is in its rearmost position, the hydraulic chamber Re of the cylinder 511 communicates with the reservoir tank 21 via the through hole 517, the input port 515 and the fourth flow path 54. The input port 515 is open when the piston 512 is in its rearmost position and is configured to be closed by the piston 512 when the piston 512 moves forward in the Za direction from the rearmost position. Even after the input port 515 has been closed by the piston 512, the hydraulic pressure in the hydraulic chamber Re increases when the piston 512 moves forward in the Za direction.

[0035] The output port 516 is connected to the master cylinder 31 and the sixth flow path 56 via the fifth flow path 55. The output port 516 is always open regardless of the position of the piston 512. Therefore, when the input port 515 is blocked by the piston 512, as the rotation angle of the electric motor 513 increases, the piston 512 moves in the forward direction Za within the cylinder 511, causing the brake fluid from the hydraulic chamber Re to be discharged from the output port 516 into the fifth flow path 55. On the other hand, as the electric motor 513 is driven, the piston 512 moves in the backward direction Zb within the cylinder 511, causing the brake fluid from the fifth flow path 55 to be drawn into the hydraulic chamber Re from the output port 516.

[0036] In the hydraulic pressure generator 20, when brake fluid is discharged from the output port 516 of the electric cylinder 51, the brake fluid flows through the fifth passage 55. A portion of the brake fluid flowing through the fifth passage 55 flows towards the wheel cylinders 11 of the rear wheels RL and RR via the sixth passage 56. The remaining brake fluid flows into the servo chamber Rs of the master device 30. As a result, the hydraulic pressure in the servo chamber Rs increases, causing the master piston 43 to move forward and increasing the hydraulic pressure in the master chamber Rm. This causes the brake fluid in the master chamber Rm to flow through the first passage 331 towards the wheel cylinders 11 of the front wheels FL and FR.

[0037] On the other hand, when the electric cylinder 51 is drawing brake fluid through the output port 516, brake fluid flows out from the wheel cylinders 11 of the rear wheels RL and RR and the wheel cylinders 11 of the front wheels FL and FR. As a result, the brake fluid flows in the sixth passage 56 toward the fifth passage 55. Also, in the first passage 331, the brake fluid flows toward the master chamber Rm. As a result, the master piston 43 moves in the backward direction Zb. Consequently, the brake fluid in the servo chamber Rs flows out into the fifth passage 55. This causes the brake fluid to flow toward the electric cylinder 51 in the fifth passage 55.

[0038] <Pressure Regulating Unit> The pressure regulating unit 70 is configured to adjust the WC pressure of multiple wheel cylinders 11 individually, independently of the pressurizing unit 50. The pressure regulating unit 70 has a first hydraulic circuit 711 and a second hydraulic circuit 712. The first hydraulic circuit 711 is connected to the sixth flow path 56 and to the two wheel cylinders 11 of the rear wheels RL and RR. The second hydraulic circuit 712 is connected to the first flow path 331 and to the two wheel cylinders 11 of the front wheels FL and FR.

[0039] As shown in Figure 2, the first hydraulic circuit 711 has a connecting passage 721 connected to the sixth passage 56. The second hydraulic circuit 712 has a connecting passage 722 connected to the first passage 331. The connecting passage 721 connects the two wheel cylinders 11 of the rear wheels RL and RR to the sixth passage 56. The connecting passage 722 connects the two wheel cylinders 11 of the front wheels FL and FR to the first passage 331. Multiple differential pressure control valves 731 and 732 are provided in the multiple connecting passages 721 and 722, respectively. The differential pressure control valve 731 can adjust the differential pressure between the portion of the connecting passage 721 on the sixth passage 56 side and the portion on the wheel cylinder 11 side. The differential pressure control valve 732 can adjust the differential pressure between the portion of the connecting passage 722 on the first passage 331 side and the portion on the wheel cylinder 11 side. For example, the differential pressure control valves 731 and 732 can generate a larger differential pressure the larger the current flowing through their solenoids.

[0040] Of the connecting passage 721, the portion on the wheel cylinder 11 side of the differential pressure control valve 731 branches into two fluid passages 72a and 72b. Fluid passage 72a is connected to the wheel cylinder 11 of the rear wheel RL, while fluid passage 72b is connected to the wheel cylinder 11 of the right rear wheel RR. Of the connecting passage 722, the portion on the wheel cylinder 11 side of the differential pressure control valve 732 branches into two fluid passages 72c and 72d. Fluid passage 72c is connected to the wheel cylinder 11 of the left front wheel FL, while fluid passage 72d is connected to the wheel cylinder 11 of the right front wheel FR.

[0041] Multiple fluid passages 72a to 72d are each provided with multiple retaining valves 74a to 74d, which are normally open solenoid valves. The retaining valves 74a to 74d are closed when restricting the supply of brake fluid to the corresponding wheel cylinder 11. In other words, when closed, the retaining valves 74a to 74d maintain the fluid pressure on the wheel cylinder 11 side in the corresponding fluid passages 72a to 72d below the fluid pressure on the pressurizing unit 50 side. Retaining valves 74a and 74b correspond to the "first retaining valves".

[0042] The first hydraulic circuit 711 includes a pressure reducing reservoir 751 for storing brake fluid and a pressure reducing passage 761 connected to the pressure reducing reservoir 751. The second hydraulic circuit 712 includes a pressure reducing reservoir 752 for storing brake fluid and a pressure reducing passage 762 connected to the pressure reducing reservoir 752. The pressure reducing passage 761 connects the portion of the fluid passage 72a closer to the wheel cylinder 11 than the retaining valve 74a and the portion of the fluid passage 72b closer to the wheel cylinder 11 than the retaining valve 74b to the pressure reducing reservoir 751. The pressure reducing passage 762 connects the portion of the fluid passage 72c closer to the wheel cylinder 11 than the retaining valve 74c and the portion of the fluid passage 72d closer to the wheel cylinder 11 than the retaining valve 74d to the pressure reducing reservoir 752.

[0043] A plurality of pressure reducing valves 77a to 77d are respectively provided in a portion of the pressure reducing flow path 761 connected to the liquid path 72a, a portion of the pressure reducing flow path 761 connected to the liquid path 72b, a portion of the pressure reducing flow path 762 connected to the liquid path 72c, and a portion of the pressure reducing flow path 762 connected to the liquid path 72d. The plurality of pressure reducing valves 77a to 77d are normally closed solenoid valves. When the pressure reducing valves 77a and 77b are opened, the brake fluid in the wheel cylinder 11 flows into the pressure reducing reservoir 751 via the pressure reducing flow path 761. Further, when the pressure reducing valves 77c and 77d are opened, the brake fluid in the wheel cylinder 11 flows into the pressure reducing reservoir 752 via the pressure reducing flow path 762. That is, the plurality of pressure reducing valves 77a to 77d are opened when allowing the brake fluid to flow out from the corresponding wheel cylinders 11 to the pressure reducing reservoirs 751 and 752.

[0044] The first hydraulic circuit 711 has a pump 791. The second hydraulic circuit 712 has a pump 792. The plurality of pumps 791 and 792 are electric pumps that use an electric motor 78 as a power source. The pump 791 pumps up the brake fluid in the pressure reducing reservoir 751, and discharges the brake fluid to a portion of the connection flow path 721 between the differential pressure control valve 731 and the holding valves 74a and 74b. The pump 792 pumps up the brake fluid in the pressure reducing reservoir 752, and discharges the brake fluid to a portion of the connection flow path 722 between the differential pressure control valve 732 and the holding valves 74c and 74d.

[0045] The first hydraulic circuit 711 includes a return passage 801 and a pressure regulating valve 811. The return passage 801 connects the portion of the connecting passage 721 on the sixth passage 56 side of the differential pressure control valve 731 to the pressure reducing reservoir 751. The pressure regulating valve 811 is integrated with the pressure reducing reservoir 751. The pressure regulating valve 811 allows the flow of brake fluid from the pressure reducing reservoir 751 to the return passage 801, while restricting the flow of brake fluid from the return passage 801 to the pressure reducing reservoir 751. Specifically, the pressure regulating valve 811 allows the flow of brake fluid from the pressure reducing reservoir 751 to the return passage 801 when the fluid pressure of the brake fluid in the pressure reducing reservoir 751 is higher than the fluid pressure of the brake fluid in the return passage 801. On the other hand, if the pump 791 is not operating and hydraulic pressure is generated in the recirculation passage 801 by the pressurizing unit 50, the pressure regulating valve 811 restricts the flow of brake fluid from the recirculation passage 801 to the depressurizing reservoir 751. However, if the pump 791 is operating while the depressurizing reservoir 751 is empty, the pressure regulating valve 811 allows the flow of brake fluid from the recirculation passage 801 to the depressurizing reservoir 751.

[0046] The second hydraulic circuit 712 has a recirculation passage 802 and a pressure regulating valve 812. The recirculation passage 802 connects the portion of the connecting passage 722 that is on the side of the first passage 331 to the differential pressure control valve 732 to the pressure reducing reservoir 752. The pressure regulating valve 812 is integrated with the pressure reducing reservoir 752. The pressure regulating valve 812 allows the flow of brake fluid from the pressure reducing reservoir 752 to the recirculation passage 802, while restricting the flow of brake fluid from the recirculation passage 802 to the pressure reducing reservoir 752. Specifically, the pressure regulating valve 812 allows the flow of brake fluid from the pressure reducing reservoir 752 to the recirculation passage 802 when the fluid pressure of the brake fluid in the pressure reducing reservoir 752 is higher than the fluid pressure of the brake fluid in the recirculation passage 802. On the other hand, if the pump 792 is not operating and hydraulic pressure is generated in the recirculation passage 802 by the pressurizing unit 50, the pressure regulating valve 812 restricts the flow of brake fluid from the recirculation passage 802 to the depressurizing reservoir 752. However, if the pump 792 is operating while the depressurizing reservoir 752 is empty, the pressure regulating valve 812 allows the flow of brake fluid from the recirculation passage 802 to the depressurizing reservoir 752.

[0047] <Detection System> As shown in Figures 1 and 2, the detection system of the braking device has a plurality of sensors that output signals corresponding to detection results to the braking control device 110. The plurality of sensors include a master pressure sensor 351, an input pressure sensor 352, a servo pressure sensor 353, and a stroke sensor 23. The master pressure sensor 351 detects the hydraulic pressure in the master chamber Rm. The master pressure sensor 351 is connected to a portion of the connection flow path 722 between the connection portion with the first flow path 331 and the differential pressure control valve 732. That is, the master pressure sensor 351 is provided in the second hydraulic circuit 712. The hydraulic pressure in the master chamber Rm based on the detection signal of the master pressure sensor 351 is referred to as "master pressure". The input pressure sensor 352 detects the hydraulic pressure in the second liquid chamber R2. For example, the input pressure sensor 352 is connected to a position in the second flow path 332 between the first control valve 341 and the second liquid chamber R2. The servo pressure sensor 353 detects the servo pressure, which is the hydraulic pressure of the brake fluid discharged from the electric cylinder 51 to the fifth flow path 55. For example, the servo pressure sensor 353 is provided in a portion of the fifth flow path 55 between the connection portion with the sixth flow path 56 and the output port 516. The discharge hydraulic pressure of the electric cylinder 51 based on the detection signal of the servo pressure sensor 353 is referred to as "servo pressure". The stroke sensor 23 detects the operation amount of the brake operation member 22.

[0048] <Regenerative Braking Device> The regenerative braking device 90 includes a motor generator 91 and a regenerative control unit 92. By causing the motor generator 91 to function as an electric motor, driving force is transmitted from the motor generator 91 to the rear wheels RL and RR. On the other hand, by causing the motor generator 91 to function as a generator, a regenerative braking force FBE corresponding to the power generation amount of the motor generator 91 is applied to the rear wheels RL and RR. The motor generator 91 corresponds to a "regenerative braking unit".

[0049] The regenerative control unit 92 controls the motor generator 91. The regenerative control unit 92 derives the maximum regenerative braking force FBEM, which is the maximum value of the regenerative braking force FBE that the motor generator 91 can currently apply to the rear wheels RL and RR. For example, the regenerative control unit 92 derives the maximum regenerative braking force FBEM based on the rotational speed of the rear wheels RL and RR, the amount of charge stored in the on-board battery that supplies power to the motor generator 91, and its temperature. When the regenerative control unit 92 receives information from the braking control device 110 regarding the rear wheel required braking force FBRr, which is the braking force required for the rear wheels RL and RR, it compares the rear wheel required braking force FBRr with the maximum regenerative braking force FBEM. When the rear wheel required braking force FBRr is less than or equal to the maximum regenerative braking force FBEM, the regenerative control unit 92 controls the amount of power generated by the motor generator 91 so that the regenerative braking force FBE becomes equal to the rear wheel required braking force FBRr. On the other hand, when the rear wheel requested braking force FBRr is greater than the maximum regenerative braking force FBEM, the regenerative control unit 92 controls the amount of power generated by the motor generator 91 so that the regenerative braking force FBE becomes equal to the maximum regenerative braking force FBEM. The regenerative control unit 92 transmits information regarding the actual regenerative braking force FBEA to be applied to the rear wheels RL and RR to the braking control device 110.

[0050] <Braking Control Device> The braking control device 110 operates the hydraulic pressure generator 20 and the pressure regulating unit 70 based on detection signals from a plurality of sensors 351 to 353 and 23. The braking control device 110 is a processing circuit 111 having a CPU 112 and a memory 113. By executing a control program with the CPU 112, the braking control device 110 functions as a derivation unit 121, a control unit 122, and an estimation unit 123.

[0051] <Derivation Section> The derivation section 121 derives the required braking force FBR, which is the braking force required for the vehicle. When the braking operation member 22 is operated, the derivation section 121 derives a value corresponding to the amount of operation of the braking operation member 22 as the required braking force FBR. The derivation section 121 also derives the required braking force FBR when deceleration is required for the vehicle in a situation where no braking operation is being performed. Subsequently, the derivation section 121 derives the front wheel required braking force FBRf and the rear wheel required braking force FBRr based on the required braking force FBR and a predetermined distribution ratio. The front wheel required braking force FBRf is the target value of the braking force to be applied to the front wheels FL and FR, and the rear wheel required braking force FBRr is the target value of the braking force to be applied to the rear wheels RL and RR. The sum of the front wheel required braking force FBRf and the rear wheel required braking force FBRr is equal to the required braking force FBR.

[0052] In this embodiment, the braking force that can be applied to the front wheels FL and FR is the hydraulic braking force FBPf. Therefore, the target hydraulic braking force for the front wheels, which is the target value of the hydraulic braking force FBPf for the front wheels FL and FR, is equal to the required braking force for the front wheels FBRf. On the other hand, the braking force that can be applied to the rear wheels RL and RR is the hydraulic braking force FBPr and the regenerative braking force FBE. Therefore, the target hydraulic braking force for the rear wheels, which is the target value of the hydraulic braking force FBPr for the rear wheels RR and RL, is not necessarily equal to the required braking force for the front wheels FBRf.

[0053] The derivation unit 121 then transmits the rear wheel requested braking force FBRr to the regenerative braking device 90. The derivation unit 121 receives the actual regenerative braking force FBEA that the regenerative braking device 90 actually applies to the rear wheels RL and RR from the regenerative braking device 90. Based on the rear wheel requested braking force FBRr and the actual regenerative braking force FBEA, the derivation unit 121 derives the rear wheel target hydraulic braking force. Specifically, the derivation unit 121 sets the value obtained by subtracting the actual regenerative braking force FBEA from the rear wheel requested braking force FBRr as the rear wheel target hydraulic braking force. For example, if the rear wheel requested braking force FBRr can be covered by the regenerative braking force FBE alone, the rear wheel target hydraulic braking force will be "0".

[0054] <Regenerative Coordination Control by the Control Unit> The control unit 122 calculates the target front wheel hydraulic pressure, which is the target value of the WC pressure of the front wheels FL and FR, based on the target front wheel hydraulic braking force. The control unit 122 also calculates the target rear wheel hydraulic pressure, which is the target value of the WC pressure of the rear wheels RL and RR, based on the target rear wheel hydraulic braking force. Subsequently, the control unit 122 performs regenerative coordination control to generate the required braking force FBR using the hydraulic braking force FBP and the regenerative braking force FBE. In regenerative coordination control, the control unit 122 controls the electric cylinder 51 so that the servo pressure becomes the target front wheel hydraulic pressure. Specifically, the control unit 122 drives the electric motor 513 of the electric cylinder 51. At this time, the control unit 122 drives the electric motor 513 so that the greater the target front wheel hydraulic braking force, the greater the amount of movement of the piston 512 in the forward direction Za relative to the initial position.

[0055] When the servo pressure changes, the hydraulic pressure in the servo chamber Rs changes. Therefore, in the master cylinder 31, the master piston 43 moves in response to the change in the hydraulic pressure in the servo chamber Rs. As a result, the hydraulic pressure in the master chamber Rm connected to the wheel cylinders 11 of the front wheels FL and FR changes.

[0056] When the servo pressure is changing toward the front wheel target hydraulic pressure, the control unit 122 closes the holding valves 74a and 74b of the first hydraulic circuit 711 when the servo pressure reaches the rear wheel target hydraulic pressure. In other words, the control unit 122 maintains the hydraulic pressure of the wheel cylinders 11 of the rear wheels RL and RR at the rear wheel target hydraulic pressure. In this way, the control unit 122 makes the hydraulic braking force FBPr applied to the rear wheels RL and RR match the rear wheel target hydraulic braking force. After the holding valves 74a and 74b of the first hydraulic circuit 711 are closed, even if the servo pressure increases, the hydraulic braking force FBPr applied to the rear wheels RL and RR will no longer increase beyond the rear wheel target hydraulic braking force.

[0057] <Estimated Section> When regenerative cooperative control is performed with the retaining valve 74a of the first hydraulic circuit 711 closed, the hydraulic pressure on the pressurizing unit 50 side of the retaining valve 74a in the fluid passage 72a of the first hydraulic circuit 711 is higher than the hydraulic pressure on the wheel cylinder 11 side of the left rear wheel RL. Similarly, the hydraulic pressure on the pressurizing unit 50 side of the retaining valve 74b in the fluid passage 72b of the first hydraulic circuit 711 is higher than the hydraulic pressure on the wheel cylinder 11 side of the right rear wheel RR.

[0058] In this case, if regenerative braking coordinated control is performed with the retaining valves 74a and 74b closed, there is a possibility that brake fluid leakage may occur from the retaining valves 74a and 74b, which should be closed. If brake fluid leakage occurs from the retaining valves 74a and 74b, which should be closed, brake fluid will flow into the wheel cylinders 11 of the rear wheels RL and RR. As a result, the hydraulic braking force FBPr applied to the rear wheels RL and RR will increase in proportion to the amount of brake fluid leakage from the retaining valves 74a and 74b. In this case, the braking force applied to the vehicle may become greater than the required braking force FBR.

[0059] Depending on the structure of the retaining valve 74a, the leakage pattern of the retaining valve 74a changes depending on the magnitude of the pressure difference between the hydraulic pressure on the pressurizing unit side of the retaining valve 74a in the fluid passage 72a and the hydraulic pressure on the wheel cylinder 11 side of the left rear wheel RL. Therefore, the estimation unit 123 estimates the hydraulic pressure rise ΔPWr according to the pressure difference between the hydraulic pressure on the pressurizing unit 50 side of the retaining valves 74a and 74b in the fluid passages 72a and 72b and the hydraulic pressure on the wheel cylinder 11 side of the retaining valves 74a and 74b in the fluid passages 72a and 72b. Here, the above pressure difference can also be rephrased as the pressure difference between the servo pressure and the WC pressure of the rear wheels RL and RR, or the pressure difference between the WC pressure of the front wheels FL and FR and the WC pressure of the rear wheels RL and RR. Note that the WC pressure of the rear wheels RL and RR is not a hydraulic pressure that can be directly measured by a hydraulic pressure sensor. Therefore, the above differential pressure only needs to be the differential pressure between the servo pressure and the target hydraulic pressure of the rear wheels.

[0060] Furthermore, in regenerative cooperative control, the estimation unit 123 estimates the hydraulic pressure rise amount ΔPWr, which is the amount of increase in the WC pressure of the rear wheels RL and RR from the time when the retaining valves 74a and 74b of the first hydraulic circuit 711 are closed. The estimation unit 123 estimates the hydraulic pressure rise amount ΔPWr based on the elapsed time since the retaining valves 74a and 74b of the first hydraulic circuit 711 were closed. Specifically, the estimation unit 123 estimates that the hydraulic pressure rise amount ΔPWr is greater when the elapsed time since the retaining valves 74a and 74b of the first hydraulic circuit 711 were opened is longer than when the elapsed time is shorter.

[0061] Furthermore, it is preferable that the pattern of increase in the hydraulic pressure rise ΔPWr with respect to elapsed time be determined in advance based on experiments and simulations. For example, the estimation unit 123 may estimate the hydraulic pressure rise ΔPWr by inputting the elapsed time and the differential pressure into a map or formula in the memory 113. However, it is preferable that such maps and formulas are determined assuming the case in which liquid leakage is most likely to occur in the multiple retaining valves 74a and 74b that are manufactured.

[0062] <Degradation Processing of the Control Unit> When the control unit 122 is performing regenerative cooperative control, if the hydraulic pressure rise amount ΔPWr estimated by the estimation unit 123 is equal to or greater than the rise amount determination value ΔPWth, it reduces the regenerative braking force FBE to zero and performs a degradation process that opens the holding valves 74a and 74b of the first hydraulic circuit 711. In other words, if there is a discrepancy between the requested braking force FBR and the braking force actually applied to the vehicle, the control unit 122 transitions from a state in which at least a portion of the rear wheel requested braking force FBRr is generated by the regenerative braking force FBE to a state in which it is generated only by the hydraulic braking force FBPr. As a result, the control unit 122 terminates the regenerative cooperative control.

[0063] Furthermore, it is preferable that the pressure rise determination value ΔPWth is determined based on experiments and simulations, along with the estimation method for the hydraulic pressure rise ΔPWr described above. The pressure rise determination value ΔPWth may be a variable value corresponding to the magnitude of the required braking force FBR, the rear wheel required braking force FBRr, and the rear wheel target hydraulic braking force. In addition, the pressure rise determination value ΔPWth may be a variable value corresponding to the magnitude of the vehicle speed.

[0064] <Processing flow executed by the braking control device> Referring to Figure 3, the processing flow when the braking control device 110 performs regenerative cooperative control will be explained. This process is executed when a braking request occurs. In addition, it is assumed that in a separate process, the braking force applied to the front wheels FL, FR and the rear wheels RL, RR is adjusted based on the requested braking force FBR.

[0065] As shown in Figure 3, the braking control device 110 determines whether or not regenerative cooperative control is being performed (S11). If regenerative cooperative control is not being performed (S11: NO), the braking control device 110 terminates this process. On the other hand, if regenerative cooperative control is being performed (S11: YES), the braking control device 110 obtains the elapsed time since the holding valves 74a and 74b of the first hydraulic circuit 711 were closed in the regenerative cooperative control (S12). Subsequently, the braking control device 110 obtains the differential pressure between the WC pressure (= servo pressure) of the front wheels FL and FR and the WC pressure (= rear wheel target hydraulic pressure) of the rear wheels RL and RR (S13). After that, the braking control device 110 estimates the hydraulic pressure rise amount ΔPWr of the WC pressure of the rear wheels RL and RR based on the elapsed time obtained in step S12 and the differential pressure obtained in step S13 (S14). Next, the braking control device 110 determines whether the hydraulic pressure rise ΔPWr is greater than or equal to the rise determination value ΔPWth (S15). If the hydraulic pressure rise ΔPWr is less than the rise determination value ΔPWth (S15: NO), the braking control device 110 determines whether the regenerative cooperative control has finished (S16). If the regenerative cooperative control has finished (S16: YES), the braking control device 110 terminates this process. On the other hand, if the regenerative cooperative control has not finished (S16: NO), the braking control device 110 proceeds to step S12.

[0066] In step S15, if the hydraulic pressure rise ΔPWr is equal to or greater than the rise determination value ΔPWth (S15: YES), the braking control device 110 reduces the regenerative braking force FBE applied to the rear wheels RL and RR to "0" (S17). Subsequently, the braking control device 110 opens the retaining valves 74a and 74b of the first hydraulic circuit 711 by ending the energization of the retaining valves 74a and 74b of the first hydraulic circuit 711 (S18). Once the regenerative coordinated control is finished in this way, the braking control device 110 terminates this process.

[0067] <Operation and Effects of this Embodiment> The operation and effects of this embodiment will be explained with reference to the flowcharts shown in Figures 4(a) to 4(d). Figures 4(a) to 4(d) show the changes in the requested braking force FBR, regenerative braking force FBE, WC pressure of wheels FL, FR, RL, RR, and the open / closed state of the retaining valves 74a and 74b of the first hydraulic circuit 711 when a braking request occurs. In Figure 4(c), "PWf" shows the changes in the WC pressure of the front wheels FL and FR, and "PWr" shows the changes in the WC pressure of the rear wheels RL and RR.

[0068] Timing t11 is the timing when a braking request is generated and regenerative braking control is initiated. During the period from timing t11 to the next timing t12, the requested braking force FBR gradually increases. Therefore, from timing t11, the regenerative braking force FBE applied to the rear wheels RL and RR gradually increases. Also, as the WC pressure of the front wheels FL and FR increases, the hydraulic braking force FBPf applied to the front wheels FL and FR gradually increases. Furthermore, from timing t11 onward, the rear wheel requested braking force FBRr is supplied solely by the regenerative braking force FBE. Therefore, the hydraulic braking force FBPr applied to the rear wheels RL and RR is "0".

[0069] In the example shown in Figure 4, the retaining valves 74a and 74b of the first hydraulic circuit 711 are closed at timing t11. As a result, a differential pressure is generated between the servo pressure and the WC pressure of the rear wheels RL and RR after timing t11. In other words, a differential pressure is generated between the WC pressure of the front wheels FL and FR and the WC pressure of the rear wheels RL and RR. Therefore, after timing t11, there is a possibility that fluid leakage may occur in the retaining valves 74a and 74b of the first hydraulic circuit 711. If fluid leakage occurs in the retaining valves 74a and 74b, as shown by the dashed line in Figure 4(c), the WC pressure of the rear wheels RL and RR gradually increases, and the hydraulic braking force FBPr applied to the rear wheels RL and RR gradually increases. In Figure 4(c), the WC pressure in the rear wheels RL and RR increases at a constant rate over time. However, the pattern of increase in the WC pressure in the rear wheels RL and RR varies depending on the fluid leakage pattern in the retaining valves 74a and 74b. For example, the gradient of change in the WC pressure in the rear wheels RL and RR may gradually decrease or gradually increase over time.

[0070] At timing t12, the required braking force FBR is maintained at a constant level. Therefore, at timing t12, the regenerative braking force FBE applied to the rear wheels RL and RR is maintained at a constant level. Also, by maintaining a constant WC pressure at the front wheels FL and FR, the hydraulic braking force FBPf applied to the front wheels FL and FR is maintained at a constant level. On the other hand, if brake fluid continues to leak from the retaining valves 74a and 74b of the first hydraulic circuit 711, the WC pressure at the rear wheels RL and RR will continue to increase, and therefore the hydraulic braking force FBPr applied to the rear wheels RL and RR will continue to increase.

[0071] At timing t13, the estimated hydraulic pressure rise ΔPWr of the rear wheels RL and RR, relative to timing t11 when regenerative cooperative control is started, becomes equal to the rise determination value ΔPWth. Therefore, at timing t13, the degraded processing is started. Specifically, the regenerative braking force FBE is reduced toward "0", and the holding valves 74a and 74b of the first hydraulic circuit 711 are opened. As a result, the WC pressure of the rear wheels RL and RR increases, and the hydraulic braking force FBPr applied to the rear wheels RL and RR also increases.

[0072] At timing t14, the regenerative braking force FBE becomes "0". Also, the WC pressure of the rear wheels RL and RR becomes equal to the WC pressure of the front wheels FL and FR, and the sum of the hydraulic braking force FBPr applied to the rear wheels RL and RR and the hydraulic braking force FBPf applied to the front wheels FL and FR becomes equal to the required braking force FBR. Then, the regenerative cooperative control is terminated.

[0073] Note that the example shown in Figure 4 assumes the case where brake fluid leakage is most significant in the retaining valves 74a and 74b of the first hydraulic circuit 711. Therefore, the actual WC pressure of the rear wheels RL and RR at timing t13 is likely to be lower than the WC pressure of the rear wheels RL and RR shown by the dashed line.

[0074] Based on the above, the braking control device 110 performs a degraded process if the estimated hydraulic pressure rise ΔPWr of the rear wheels RL and RR becomes greater than or equal to the rise determination value ΔPWth while regenerative cooperative control is being executed. That is, the braking control device 110 terminates the regenerative cooperative control and generates the rear wheel required braking force FBRr using only the hydraulic braking force FBP. As a result, the continuous increase in the hydraulic braking force FBPr applied to the rear wheels RL and RR due to continued fluid leakage in the retaining valves 74a and 74b of the first hydraulic circuit 711 is suppressed. In other words, the braking control device 110 can predict fluid leakage in the retaining valves 74a and 74b even without a hydraulic pressure sensor to detect the WC pressure of the rear wheels RL and RR and a fluid leakage sensor to detect fluid leakage in the retaining valves 74a and 74b.

[0075] <Examples of Modifications> This embodiment can be implemented with the following modifications. This embodiment and the following examples of modifications can be combined with each other to the extent that they do not contradict each other technically.

[0076] - In regenerative braking coordinated control, if there is a parameter that affects the amount of brake fluid leakage in the retaining valves 74a and 74b that are closed, the estimation unit 123 may estimate the hydraulic pressure rise ΔPWr of the rear wheels RL and RR based on that parameter. For example, the parameter may be the oil temperature of the brake fluid, which affects the viscosity of the brake fluid. Alternatively, the parameter may be a value indicating the degree of deterioration of the retaining valves 74a and 74b over time, such as the mileage since the vehicle was manufactured.

[0077] - In regenerative braking coordinated control, the effective regenerative braking force may be less than the rear wheel required braking force FBRr. In this case, both the regenerative braking force FBE and the hydraulic braking force FBP are applied to the rear wheels RL and RR.

[0078] - The vehicle may be equipped with motor generators 91 corresponding to the front wheels FL and FR instead of the motor generators 91 corresponding to the rear wheels RL and RR. In this case, the braking control device 110 may restrict the increase in WC pressure of the front wheels FL and FR by closing the retaining valves 74c and 74d of the second hydraulic circuit 712. Alternatively, the braking control device 110 may restrict the increase in WC pressure of the front wheels FL and FR by closing the differential pressure adjustment valve 551.

[0079] - The vehicle may be equipped with motor generators 91 corresponding to the front wheels FL and FR, in addition to the motor generators 91 corresponding to the rear wheels RL and RR. - In the above embodiment, the distribution ratio of the front wheel required braking force FBRf and the rear wheel required braking force FBRr was fixed at a predetermined value, but it is not limited to this. That is, the braking control device 110 may vary the distribution ratio within a single braking period. For example, when the required braking force FBR is small, the braking control device 110 sets the distribution ratio so that the rear wheel braking force is equal to the required braking force FBR. Then, as the required braking force FBR increases, the braking control device 110 sets the distribution ratio so that the difference between the required braking force FBR and the rear wheel braking force increases. Furthermore, when the distribution ratio is varied, the differential pressure between the hydraulic pressure on the pressurizing unit 50 side of the retaining valves 74a and 74b in the hydraulic passages 72a and 72b, and the differential pressure between the hydraulic pressure on the wheel cylinder 11 side of the retaining valves 74a and 74b in the hydraulic passages 72a and 72b also changes during the execution of regenerative cooperative control. Therefore, the estimation unit 123 may estimate the amount of fluid leakage in the retaining valves 74a and 74b per unit time according to the above differential pressure, and estimate the amount of fluid leakage per unit time by accumulating the amount of fluid leakage per unit time.

[0080] The braking control device 110 may include an upstream control device that controls the hydraulic pressure generator 20 and a downstream control device that controls the pressure regulating unit 70. In this case, it is preferable that the upstream control device and the downstream control device are configured to send and receive various types of information via an in-vehicle network.

[0081] The configurations of the hydraulic pressure generator 20, the pressurizing unit 50, and the pressure regulating unit 70 are examples. The configurations of the hydraulic pressure generator 20, the pressurizing unit 50, and the pressure regulating unit 70 can be appropriately changed within the range in which they can perform their functions.

[0082] The braking control device 110 is not limited to a processing circuit 111 that includes a CPU 112 and a memory 113 and executes software processing. For example, the braking control device 110 may include a dedicated hardware circuit that executes at least a part of the various processes performed in the above embodiment. An example of a dedicated hardware circuit is an ASIC. ASIC is an abbreviation for "Application Specific Integrated Circuit". In other words, the braking control device 110 may have any of the following configurations (a) to (c).

[0083] (a) A processing circuit comprising a processing unit that executes all of the above processes according to a program, and a program storage device such as a ROM that stores the program. (b) A processing circuit comprising a processing unit and a program storage device that execute a part of the above processes according to a program, and a dedicated hardware circuit that executes the remaining processes.

[0084] (c) A processing circuit equipped with dedicated hardware circuits to perform all of the above processing. Here, there may be multiple software execution devices equipped with processing units and program storage devices, and multiple dedicated hardware circuits.

Claims

1. A braking control device applicable to a vehicle comprising: a pressurizing unit that applies hydraulic braking force to the first left and right wheels and the second left and right wheels by pressurizing the first wheel cylinders of the first left and right wheels, which are one of the front and rear wheels of the vehicle, and the second wheel cylinders of the second left and right wheels, which are the other of the front and rear wheels; a pressure regulating unit having a normally open solenoid valve disposed in a fluid passage connecting the first wheel cylinder and the pressurizing unit, which has a first holding valve that, when the valve is closed, maintains the fluid pressure on the first wheel cylinder side in the fluid passage at a level lower than the fluid pressure on the pressurizing unit side; and a regenerative braking unit that applies regenerative braking force to the first left and right wheels, wherein the control unit performs regenerative coordinated control that controls the first holding valve to generate the required braking force for the first left and right wheels using the regenerative braking force and the hydraulic braking force, and generates the required braking force for the second left and right wheels using the hydraulic braking force; A braking control device comprising: an estimation unit that estimates a hydraulic pressure rise amount, which is the amount of increase in the hydraulic pressure of the first wheel cylinder from the time the first retaining valve is closed, wherein the control unit, while the regenerative cooperative control is being executed, if the hydraulic pressure rise amount estimated by the estimation unit is greater than or equal to a rise amount determination value, performs a degraded process to reduce the regenerative braking force to zero and open the first retaining valve to terminate the regenerative cooperative control.

2. The braking control device according to claim 1, wherein the control unit reduces the hydraulic braking force applied to the first left and right wheels to zero in the regenerative cooperative control.

3. The braking control device according to claim 1 or 2, wherein the estimation unit estimates the amount of hydraulic pressure rise based on the differential pressure between the hydraulic pressure of the first wheel cylinder and the hydraulic pressure of the second wheel cylinder, and the elapsed time since the first retaining valve was closed.

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