JP2024048826A - Braking device - Google Patents

Abstract

[Problem] With regard to a braking device, a configuration is proposed for reducing the hydraulic pressure in a wheel cylinder when an abnormality occurs in the electric cylinder. [Solution] A braking device (20) has a first braking unit (50) that applies a braking force to a wheel by adjusting the hydraulic pressure in a wheel cylinder (11) with brake fluid supplied from a reservoir tank (24), and a braking control device (100) that controls the first braking unit (50). The first braking unit (50) has an electric cylinder (51) that can supply brake fluid to the wheel cylinder (11) in response to the driving of an electric motor (513). The first braking unit (50) has a release flow passage (56) that is configured to connect a fluid chamber in which an output port (516) in the electric cylinder (51) is open to the reservoir tank (24), and a release valve (57) that is a normally closed solenoid valve that is disposed in the release flow passage (56). The braking control device (100) executes a pressure release process that opens the release valve (57) when an abnormality occurs in the electric cylinder (51). [Selected Figure] FIG. 1

Description

The present invention relates to a vehicle braking system.

Patent document 1 discloses a braking device equipped with an electric cylinder that generates hydraulic pressure by driving an electric motor. In addition, patent document 1 describes the electric cylinder as a "slave cylinder." The electric cylinder has an input port to which brake fluid is supplied from a reservoir tank, and an output port from which brake fluid is discharged. The braking device is configured to increase the hydraulic pressure in the wheel cylinder by supplying brake fluid from the output port of the electric cylinder.

Patent No. 6202741

In a braking device such as that disclosed in Patent Document 1, if an abnormality occurs in the electric cylinder, it may become impossible to open the input port from its blocked state. In such a case, the flow path connecting the electric cylinder and the wheel cylinder may become blocked, and the hydraulic pressure in that flow path pressurized by the electric cylinder may not be released. As a result, the increased hydraulic pressure in the wheel cylinder may continue regardless of the target hydraulic pressure value.

The braking device for solving the above problem includes a reservoir tank for storing brake fluid, a braking unit that can apply a braking force to the wheels of a vehicle by adjusting the hydraulic pressure in a wheel cylinder with brake fluid supplied from the reservoir tank, and a braking control device that controls the braking unit. The braking unit includes an electric cylinder having a cylinder, a piston, and an electric motor, and an output port that can supply brake fluid to the wheel cylinder by the piston that moves in response to the driving of the electric motor is formed in the cylinder, a release flow path that is configured to connect a fluid chamber in the electric cylinder in which the output port is open and the reservoir tank, and a release valve that is a normally closed solenoid valve that is disposed in the release flow path. The gist of the braking control device is that it executes an abnormality determination process that determines whether an abnormality has occurred in the electric cylinder, and a pressure release process that opens the release valve when it is determined that an abnormality has occurred in the electric cylinder.

According to the above configuration, if an abnormality occurs in the electric cylinder, a flow path through which brake fluid flows between the reservoir tank and the wheel cylinder can be formed via a release flow path in which the release valve is opened. This makes it possible to reduce the hydraulic pressure in the wheel cylinder even if an abnormality occurs in the electric cylinder.

FIG. 1 is a schematic diagram showing an embodiment of a braking device for a vehicle. FIG. 2 is a block diagram showing a brake control device provided in the brake system. FIG. 3 is a flowchart showing the flow of processing executed by the brake control device. FIG. 4 is a flowchart showing the flow of processing executed by the brake control device. FIG. 5 is a block diagram showing a brake control device provided in a braking device according to a modified example.

A braking device 20, which is one embodiment of the braking device, will be described with reference to FIGS.
1 shows a vehicle braking device 20. The braking device 20 includes a braking unit capable of applying a braking force to the wheels of the vehicle. The braking device 20 includes a braking control device 100 capable of controlling the braking unit.

In FIG. 1, front wheels FL, FR and rear wheels RL, RR are shown as the wheels of the vehicle. The vehicle is equipped with a brake operating member 21. The brake operating member 21 can be operated by the driver of the vehicle. An example of the brake operating member 21 is a brake pedal.

The braking control device 100 is an example of a processing circuit equipped in a vehicle. The vehicle may be equipped with a control device that is not limited to the braking control device 100, but is another processing circuit. Some of the functional parts equipped in the braking control device 100 may be equipped in another control device. An example of the other control device is an automatic driving control device for automatically driving the vehicle. The multiple control devices may be connected so that they can send and receive information to each other. For example, a configuration can be adopted in which each processing circuit is connected to an in-vehicle network equipped in the vehicle. Each processing circuit connected to the in-vehicle network can communicate with each other via the in-vehicle network.

<Braking device>
The braking device 20 includes braking mechanisms 10 corresponding to the wheels FL, FR, RL, and RR, respectively. The braking mechanisms 10 can apply frictional braking forces to the wheels FL, FR, RL, and RR. The frictional braking forces applied by the braking mechanisms 10 to the wheels FL, FR, RL, and RR can be adjusted by the braking device 20.

The braking device 20 is a hydraulic braking device. The braking device 20 includes a reservoir tank 24 that stores brake fluid, and a hydraulic pressure generating device 22. The braking device 20 includes a first braking unit 50 as a braking unit. The braking device 20 may also include a second braking unit 23 as a braking unit.

One example of the hydraulic pressure generating device 22 is a so-called brake-by-wire type hydraulic pressure generating device. The hydraulic pressure generating device 22 can generate hydraulic pressure according to the amount of operation of the brake operating member 21. The hydraulic pressure generating device 22 is composed of a master device 30 and a first braking unit 50. The master device 30 can supply brake fluid to the second braking unit 23. The first braking unit 50 can supply brake fluid to the master device 30 and the second braking unit 23.

<Braking mechanism>
The brake mechanism 10 will be described. The components of each brake mechanism 10 are common to all of the brake mechanisms 10. The brake mechanism 10 has a wheel cylinder 11 to which brake fluid is supplied, a rotating plate 12 that rotates integrally with the wheels FL, FR, RL, and RR, and a friction material 13 that moves relative to the rotating plate 12 in the plate thickness direction of the rotating plate 12. The brake mechanism 10 is configured such that the higher the WC pressure Pwc, which is the hydraulic pressure in the wheel cylinder 11, the stronger the friction material 13 is pressed against the rotating plate 12. In other words, according to the brake mechanism 10, the higher the WC pressure Pwc, the greater the frictional braking force applied to the wheels FL, FR, RL, and RR.

<Master Device>
An example of the master device 30 includes a master cylinder 31, a plurality of flow paths 331, 332, and 333 connected to the master cylinder 31, a plurality of control valves 341 and 342 that control the flow of brake fluid, and a stroke simulator 32. The stroke simulator 32 can generate a reaction force according to the amount of operation of the brake operating member 21.

The master cylinder 31 includes a main cylinder 41 and a cover cylinder 42. The master cylinder 31 includes a master piston 43 and an input piston 44. The master cylinder 31 includes a master spring 45 that biases the master piston 43, and an input spring 46 that biases the input piston 44. The master piston 43 and the input piston 44 can move relative to the main cylinder 41 and the cover cylinder 42.

An example of the master cylinder 31 will now be described in more detail.
The main cylinder 41 of the master cylinder 31 has a plate-shaped bottom wall 411 and a first peripheral wall 412 extending from the bottom wall 411 along the axis of the bottom wall 411. The main cylinder 41 further has a second peripheral wall 413 extending from the rear end of the first peripheral wall 412 along the axis of the first peripheral wall 412, and a first annular wall 414 extending from the rear end of the second peripheral wall 413 toward the axis of the second peripheral wall 413. The first peripheral wall 412 and the second peripheral wall 413 are cylindrical. The first annular wall 414 has a hole into which the rear end of the master piston 43 described later is inserted. The inner diameter of the first peripheral wall 412 is smaller than the inner diameter of the second peripheral wall 413.

In the main cylinder 41, a master chamber Rm is formed, which is defined by a bottom wall 411, a first peripheral wall 412, and a master piston 43. In the following, in the master cylinder 31, the leftward direction in FIG. 1, i.e., the direction in which the master piston 43 moves to reduce the volume of the master chamber Rm, is referred to as the forward direction. On the other hand, the rightward direction in FIG. 1, i.e., the direction in which the master piston 43 moves to increase the volume of the master chamber Rm, is referred to as the rearward direction.

The main cylinder 41 is formed with a first fluid chamber R1 defined by the second peripheral wall 413 and the master piston 43, and a servo chamber Rs defined by the second peripheral wall 413, the first annular wall 414, and the master piston 43. The master chamber Rm is formed at a position closer to the front end of the master cylinder 31. The first fluid chamber R1 is formed rearward of the master chamber Rm. The servo chamber Rs is formed rearward of the first fluid chamber R1. Inside the main cylinder 41, the master chamber Rm, the first fluid chamber R1, and the servo chamber Rs are not connected to each other. The master chamber Rm corresponds to the "fluid chamber connected to the wheel cylinder among the fluid chambers defined by the master piston". The servo chamber Rs corresponds to the "fluid chamber opposite to the fluid chamber connected to the wheel cylinder among the fluid chambers defined by the master piston".

The cover cylinder 42 of the master cylinder 31 has a cylindrical third peripheral wall 421 and a second annular wall 422 extending from the rear end of the third peripheral wall 421 toward the axis of the third peripheral wall 421. The third peripheral wall 421 is attached to the first annular wall 414 so that its axis coincides with that of the second peripheral wall 413 of the main cylinder 41. The second annular wall 422 has a hole into which the rear end of the input piston 44 described later is inserted.

In the cover cylinder 42, a second fluid chamber R2 is defined by the first annular wall 414 of the main cylinder 41, the third peripheral wall 421, and the input piston 44, and a third fluid chamber R3 is defined by the third peripheral wall 421, the second annular wall 422, and the input piston 44. In the master cylinder 31, the second fluid chamber R2 is formed rearward of the servo chamber Rs, and the third fluid chamber R3 is formed rearward of the second fluid chamber R2. Inside the cover cylinder 42, the second fluid chamber R2 and the third fluid chamber R3 are not connected to each other.

The master piston 43 is housed in the master cylinder 31 in surface contact with the inner circumferential surface of the first peripheral wall 412, the inner circumferential surface of the second peripheral wall 413, and the inner circumferential surface of the first annular wall 414 of the main cylinder 41. Therefore, when the master piston 43 moves in the axial direction, the master piston 43 slides against the inner circumferential surface of the first peripheral wall 412, the inner circumferential surface of the second peripheral wall 413, and the inner circumferential surface of the first annular wall 414. The rear end of the master piston 43 protrudes rearward from the first annular wall 414 and is located in the second fluid chamber R2. The master piston 43 is configured so that the pressure-receiving area facing the master chamber Rm and receiving the pressure of the master chamber Rm toward the rear is equal to the pressure-receiving area facing the servo chamber Rs and receiving the pressure of the servo chamber Rs toward the front. In addition, the master piston 43 in this embodiment is configured so that the pressure-receiving area facing the first fluid chamber R1 and receiving the pressure of the first fluid chamber R1 toward the rear is equal to the pressure-receiving area facing the second fluid chamber R2 and receiving the pressure from the second fluid chamber R2 toward the front.

The input piston 44 is housed in the master cylinder 31 in surface contact with the inner circumferential surface of the third peripheral wall 421 and the inner circumferential surface of the second annular wall 422 of the cover cylinder 42. Therefore, when the input piston 44 moves in the axial direction, the input piston 44 slides on the inner circumferential surface of the third peripheral wall 421 and the inner circumferential surface of the second annular wall 422. The rear end of the input piston 44 protrudes rearward beyond the second annular wall 422 and is connected to the brake operating member 21. The input piston 44 moves in a direction approaching the master piston 43 according to the amount of operation of the brake operating member 21. In addition, a gap is formed between the input piston 44 and the master piston 43 in the second fluid chamber R2.

The master spring 45 is disposed in the master chamber Rm of the main cylinder 41, specifically, between the bottom wall 411 of the main cylinder 41 and the master piston 43. The master spring 45 biases the master piston 43 rearward. In other words, when the master piston 43 moves forward, the master spring 45 is elastically compressed.

The input spring 46 is disposed in the second fluid chamber R2 of the cover cylinder 42, specifically, between the first annular wall 414 of the main cylinder 41 and the input piston 44. The input spring 46 biases the input piston 44 rearward. In other words, the input spring 46 is elastically compressed when the input piston 44 moves forward.

In the master cylinder 31, the master chamber Rm is connected to the reservoir tank 24. More specifically, the rear end of the master chamber Rm is connected to the reservoir tank 24 via a port formed in the first peripheral wall 412 of the main cylinder 41. Therefore, when the master piston 43 moves forward from the initial position shown in FIG. 1, the master chamber Rm and the reservoir tank 24 are no longer connected. As a result, the hydraulic pressure in the master chamber Rm increases as the master piston 43 moves forward.

The third fluid chamber R3 is connected to the reservoir tank 24 via a third flow path 333, which will be described later. Therefore, when the input piston 44 moves forward, brake fluid is supplied from the reservoir tank 24 to the third fluid chamber R3, and when the input piston 44 moves rearward, brake fluid is discharged from the third fluid chamber R3 to the reservoir tank 24.

The first flow path 331 connects the master chamber Rm to the second braking section 23. The second flow path 332 connects the first fluid chamber R1 to the second fluid chamber R2. The third flow path 333 connects the reservoir tank 24 to the second flow path 332.

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 provided between the connection point of the second flow path 332 with the third flow path 333 and the second fluid chamber R2. The second control valve 342 is provided in the third flow path 333. When the braking control device 100 is operating, the first control valve 341 is opened and the second control valve 342 is closed.

The stroke simulator 32 is disposed, for example, between the first fluid chamber R1 and the first control valve 341 in the second flow path 332. The stroke simulator 32 has, for example, a piston (not shown) biased from the back by a spring inside. When the internal piston is displaced against the bias of the spring by the inflow of brake fluid from the second flow path 332, the stroke simulator 32 generates pressure in the brake fluid according to the displacement of the piston. Specifically, when the input piston 44 moves forward by the operation of the brake operating member 21 with the first control valve 341 open and the second control valve 342 closed, the brake fluid flows into the stroke simulator 32. As a result, the stroke simulator 32 generates the same pressure in the second fluid chamber R2 and the first fluid chamber R1 connected by the second flow path 332.

<First Braking Section>
The first braking unit 50 includes an electric cylinder 51 having a first electric motor 513 as a power source. The first braking unit 50 can adjust the WC pressure Pwc by the electric cylinder 51 that operates according to the driving amount of the first electric motor 513. That is, the first braking unit 50 can generate braking forces on the wheels FL, FR, RL, and RR of the vehicle.

An example of the first braking portion 50 will be described.
The first braking unit 50 includes an electric cylinder 51 .
The first braking unit 50 includes a fourth flow path 54 that connects the electric cylinder 51 and the reservoir tank 24. The first braking unit 50 includes a sixth flow path 58 that connects the second braking unit 23 and the electric cylinder 51. The first braking unit 50 includes a fifth flow path 55 that connects the servo chamber Rs of the master cylinder 31 and the sixth flow path 58.

<Electric cylinder>
The electric cylinder 51 included in the first braking unit 50 is provided between the fourth flow path 54 and the sixth flow path 58. The fourth flow path 54 is connected to an input port 515 of the electric cylinder 51. The sixth flow path 58 is connected to an output port 516 of the electric cylinder 51. The input port 515 and the output port 516 will be described later.

The electric cylinder 51 includes a cylinder 511, a piston 512 that can slide within the cylinder 511, a first electric motor 513 that drives the piston 512, and a conversion mechanism 514 that converts the rotational motion of the output shaft of the first electric motor 513 into linear motion of the piston 512.

Inside the cylinder 511, a fluid chamber Re is defined by the piston 512 into which brake fluid is introduced. The first electric motor 513 is capable of generating a driving force that causes the piston 512 to slide inside the cylinder 511. The position of the piston 512 inside the cylinder 511 is changed by the first electric motor 513. The volume of the fluid chamber Re changes in response to the change in the position of the piston 512.

In the following, the direction of movement of the piston 512 that reduces the volume of the liquid chamber Re is referred to as the forward direction Za. The direction of movement of the piston 512 that is opposite the forward direction Za and increases the volume of the liquid chamber Re is referred to as the backward direction Zb. The position of the piston 512 at which the volume of the liquid chamber Re is at its maximum is referred to as the "initial position." In other words, the initial position is the position at which the piston 512 has moved the furthest in the backward direction Zb.

The cylinder 511 has two ports, an input port 515 and an output port 516, which connect the liquid chamber Re to the outside. The piston 512 has a through hole 517. The through hole 517 is formed at a position that connects the input port 515 and the liquid chamber Re when the piston 512 is located at the initial position. As a result, when the piston 512 is located at the initial position, the liquid chamber Re of the cylinder 511 is connected to the fourth flow path 54 through the input port 515 and the through hole 517. That is, the liquid chamber Re of the cylinder 511 is connected to the reservoir tank 24 through the input port 515 and the through hole 517. The input port 515 is opened when the piston 512 is located at the initial position, and is configured to be closed by the piston 512 when the piston 512 moves a predetermined amount from the initial position in the forward direction Za. The predetermined amount is the amount by which the piston 512 moves from the initial position in the forward direction Za to a position where the input port 515 and the through hole 517 are not connected. On the other hand, the output port 516 of the cylinder 511 is connected to the second braking unit 23 and the fifth flow path 55 via the sixth flow path 58. The output port 516 is always open regardless of the position of the piston 512. The fifth flow path 55 corresponds to the "flow path connecting the servo chamber of the master cylinder and the output port of the electric cylinder."

As shown in FIG. 1, the electric cylinder 51 of the braking device 20 does not include a spring that biases the piston 512 in the backward direction Zb. The electric cylinder 51 may include a spring that biases the piston 512 in the backward direction Zb.

<Release Channel and Release Valve>
The first braking unit 50 includes a release flow passage 56. The first braking unit 50 includes a release valve 57 disposed in the release flow passage 56. The release valve 57 is a normally closed solenoid valve. That is, the release flow passage 56 is closed while no control is being performed to open the release valve 57. The release valve 57 can be opened by being controlled by the braking control device 100.

The release flow passage 56 is a flow passage that connects the reservoir tank 24 and the wheel cylinder 11 so as to bypass the electric cylinder 51, and has one end connected to the fourth flow passage 54 and the other end connected to the sixth flow passage 58. Specifically, the release flow passage 56 connects between the reservoir tank 24 and the input port 515 in the fourth flow passage 54 and between the output port 516 and the second braking unit 23 in the sixth flow passage 58. The release flow passage 56 constitutes a flow passage that connects the fluid chamber Re of the electric cylinder 51 and the reservoir tank 24 via the output port 516, which is always open, and the sixth flow passage 58.

<Second Braking Section>
The second braking unit 23 includes a second electric motor 64 as a power source. The second braking unit 23 can generate braking forces on the wheels FL, FR, RL, and RR of the vehicle according to the driving amount of the second electric motor 64. The second braking unit 23 is interposed between the first braking unit 50 and the wheel cylinder 11.

An example of the second braking portion 23 will be described.
The second braking unit 23 is a braking actuator capable of individually adjusting the WC pressure Pwc of each of the wheels FL, FR, RL, and RR. The second braking unit 23 includes pumps 631 and 632 that discharge brake fluid. The pumps 631 and 632 are driven by a second electric motor 64.

The second braking section 23 can increase the WC pressure Pwc without increasing the hydraulic pressure of the brake fluid adjusted by the first braking section 50. The braking device 20 has a redundant configuration in which the first braking section 50 is on the upstream side and the second braking section 23 is on the downstream side.

The second braking unit 23 is provided with two hydraulic circuits 611, 612. The first hydraulic circuit 611 is connected to two wheel cylinders 11 for the front wheels FL, FR. The second hydraulic circuit 612 is connected to two wheel cylinders 11 for the rear wheels RL, RR.

The first hydraulic circuit 611 is connected to the reservoir tank 24 via the first flow path 331 and the master chamber Rm. In the first hydraulic circuit 611, a first differential pressure adjustment valve 621, which is a normally open linear solenoid valve, is provided in the hydraulic path connecting the connection point with the first flow path 331 and the wheel cylinder 11. The wheel cylinder 11 for the front wheels FL, FR corresponds to the "wheel cylinder connected to the master chamber."

The second hydraulic circuit 612 is connected to the reservoir tank 24 via the fourth flow path 54, the electric cylinder 51, and the sixth flow path 58. In the second hydraulic circuit 612, a second differential pressure adjustment valve 622, which is a normally open linear solenoid valve, is provided in the hydraulic path connecting the connection point with the sixth flow path 58 and the wheel cylinder 11. The wheel cylinder 11 for the rear wheels RL and RR corresponds to a "wheel cylinder different from the wheel cylinder connected to the master chamber." The flow path connecting the servo chamber Rs to the output port 516 of the electric cylinder 51 is connected to the wheel cylinder 11 for the rear wheels RL and RR via the second hydraulic circuit 612.

The pump 631 is provided in the first hydraulic circuit 611. The pump 631 supplies brake fluid to the fluid path connecting the first differential pressure adjustment valve 621 and the wheel cylinder 11. The pump 632 is provided in the second hydraulic circuit 612. The pump 632 supplies brake fluid to the fluid path connecting the second differential pressure adjustment valve 622 and the wheel cylinder 11.

In the hydraulic circuit 611, on the wheel cylinder 11 side of the first differential pressure adjustment valve 621, there are provided paths 65a and 65b in the same number as the wheel cylinders 11 connected to the hydraulic circuit 611. Similarly, in the hydraulic circuit 612, on the wheel cylinder 11 side of the second differential pressure adjustment valve 622, there are provided paths 65c and 65d in the same number as the wheel cylinders 11 connected to the hydraulic circuit 612. Each path 65a to 65d is provided with a holding valve 66 that is closed when restricting an increase in the WC pressure Pwc, and a pressure reducing valve 67 that is opened when reducing the WC pressure Pwc. That is, each holding valve 66 is disposed in the hydraulic path on the wheel cylinder 11 side of each differential pressure adjustment valve 621, 622. Each holding valve 66 is a normally open solenoid valve, and each pressure reducing valve 67 is a normally closed solenoid valve.

Reservoirs 681, 682 are connected to the hydraulic circuits 611, 612 to temporarily store the brake fluid that flows out from the wheel cylinder 11 through the pressure reducing valve 67 when the pressure reducing valve 67 is open. Each reservoir 681, 682 is connected to a pump 631, 632 via a suction flow path 691, 692.

The reservoir 681 is connected to the fluid path connecting the first differential pressure adjustment valve 621 and the master chamber Rm via a tank-side flow path 701. The reservoir 682 is connected to the fluid path connecting the connection point with the sixth flow path 58 in the second hydraulic circuit 612 and the second differential pressure adjustment valve 622 via a tank-side flow path 702.

Each pump 631, 632 can pump brake fluid from the reservoir tank 24 via the reservoir 681, 682. Each pump 631, 632 discharges the pumped brake fluid into a fluid path between the differential pressure adjustment valve 621, 622 and the retention valve 66. The fluid path between the fluid path and the pump 631, 632 is called an intermediate fluid path 711, 712.

<Sensor>
The braking device 20 is equipped with various sensors.
1 shows a plurality of hydraulic pressure sensors 351, 352, 353, a stroke sensor SE1, and a rotation angle sensor SE2 as examples of various sensors. Detection signals from the various sensors are input to the braking control device 100. The braking control device 100 can obtain state quantities of the vehicle based on the detection signals from the various sensors.

The master hydraulic pressure sensor 351 can detect the hydraulic pressure in the master chamber Rm. For example, the master hydraulic pressure sensor 351 is provided in the first flow path 331. For example, the second braking unit 23 is equipped with the master hydraulic pressure sensor 351. Hereinafter, the hydraulic pressure detected by the master hydraulic pressure sensor 351 is referred to as the "master pressure."

The input hydraulic pressure sensor 352 can detect the hydraulic pressure in the second hydraulic chamber R2. For example, the input hydraulic pressure sensor 352 is connected to a position in the second flow path 332 between the first control valve 341 and the second hydraulic chamber R2.

The control pressure sensor 353 can detect the hydraulic pressure applied by the electric cylinder 51. For example, the control pressure sensor 353 is provided near the output port 516 of the electric cylinder 51. As an example, FIG. 1 shows a configuration in which the control pressure sensor 353 is connected between the release valve 57 and the output port 516 in the release flow path 56 connected to the fourth flow path 54 and the sixth flow path 58. Hereinafter, the hydraulic pressure detected by the control pressure sensor 353 is referred to as the "control pressure."

The stroke sensor SE 1 can detect the amount of operation of the brake operating member 21 .
The rotation angle sensor SE2 can detect the rotation angle of the first electric motor 513 of the electric cylinder 51. The rotation angle sensor SE2 is attached, for example, to the electric cylinder 51. The rotation speed of the first electric motor 513 can be calculated based on the rotation angle detected by the rotation angle sensor SE2.

<Brake control device>
The braking control device 100 will be described with reference to Fig. 2. The braking control device 100 is composed of a plurality of functional units that execute various types of control. Fig. 2 shows a first control unit 101, a second control unit 102, and an abnormality determination unit 103 as examples of the functional units. The functional units included in the braking control device 100 are capable of transmitting and receiving information to and from each other.

The first control unit 101 and the second control unit 102 can operate the braking device 20 based on a braking request. A braking request is generated, for example, by operating the brake operating member 21 and is canceled when the operation of the brake operating member 21 is canceled. In this case, the first control unit 101 and the second control unit 102 can operate the braking device 20 using a required braking force calculated based on the amount of operation of the brake operating member 21. The braking request may also be output by an automatic driving control device. In this case, the first control unit 101 and the second control unit 102 can operate the braking device 20 based on the required braking force calculated by the automatic driving control device.

The first control unit 101 and the second control unit 102 operate the braking device 20 based on a value obtained by converting the required braking force into a target value of the hydraulic pressure in the wheel cylinder 11, i.e., the target value of the WC pressure Pwc. Hereinafter, the target value of the WC pressure Pwc may be referred to as the "target WC pressure." By adjusting the WC pressure Pwc of the wheels FL, FR, RL, and RR based on the target WC pressure, a braking force corresponding to the required braking force is applied to the wheels FL, FR, RL, and RR.

<Adjustment of WC pressure by first braking unit>
The following describes the first control unit 101. The first control unit 101 has a function of controlling the first braking unit 50. The first control unit 101 can operate the first braking unit 50 to generate a braking force.

The first control unit 101 can adjust the WC pressure Pwc by operating the electric cylinder 51. This allows the first braking unit 50 to generate braking force on the vehicle's wheels FL, FR, RL, and RR. The amount of the WC pressure Pwc applied to each wheel FL, FR, RL, and RR by the first braking unit 50 is referred to as the first braking pressure P1.

When the target WC pressure is increased, the first control unit 101 controls the electric cylinder 51 so that the master pressure increases to a hydraulic pressure corresponding to the target WC pressure. Specifically, the first electric motor 513 is controlled to move the piston 512 in the forward direction Za to close the input port 515. The movement of the piston 512 causes brake fluid to be supplied from the output port 516 of the electric cylinder 51 to the fifth flow path 55 via the sixth flow path 58. The brake fluid in the fifth flow path 55 is supplied to the servo chamber Rs of the master cylinder 31. The brake fluid is supplied to the servo chamber Rs, so that the master piston 43 moves forward. That is, the master cylinder 31 can move the master piston 43 forward by the brake fluid supplied from the electric cylinder 51 to the servo chamber Rs. Next, brake fluid is supplied from the master chamber Rm to the wheel cylinder 11 for the front wheels FL, FR via the first hydraulic circuit 611 of the second braking unit 23. As a result, the WC pressure Pwc of the front wheels FL, FR is increased to the target WC pressure. In addition, brake fluid is supplied from the output port 516 of the electric cylinder 51 to the second hydraulic circuit 612 of the second braking unit 23 via the sixth flow path 58. That is, brake fluid is supplied from the sixth flow path 58 to the wheel cylinder 11 for the rear wheels RL and RR via the second hydraulic circuit 612 of the second braking unit 23. As a result, the WC pressure Pwc of the rear wheels RL and RR is increased to the target WC pressure.

When the target WC pressure is maintained, the first control unit 101 continues the operation of the electric cylinder 51 .
When the target WC pressure is reduced, the first control unit 101 controls the electric cylinder 51 so that the master pressure is reduced to a hydraulic pressure corresponding to the target WC pressure. Specifically, the first electric motor 513 is controlled to move the piston 512 in the backward direction Zb, thereby reducing the pressure of the brake fluid supplied to the servo chamber Rs. When the brake is released, the piston 512 is moved to the initial position to connect the through hole 517 and the input port 515. That is, the input port 515 is opened to connect the fluid chamber Re and the reservoir tank 24. As described above, by moving the piston 512 in the backward direction Zb or by connecting the through hole 517 and the input port 515, the brake fluid can flow from the servo chamber Rs to the fluid chamber Re. Then, the master piston 43 moves rearward, and the brake fluid can flow from the wheel cylinder 11 for the front wheels FL, FR to the master chamber Rm via the first hydraulic circuit 611 of the second braking unit 23. As a result, the WC pressure Pwc of the front wheels FL, FR decreases to the target WC pressure. Also, the brake fluid flows from the wheel cylinder 11 for the rear wheels RL, RR into the fluid chamber Re through the sixth flow passage 58. As a result, the WC pressure Pwc of the rear wheels RL, RR decreases to the target WC pressure.

<Adjustment of WC pressure by second braking section>
The second control unit 102 will be described. The second control unit 102 has a function of controlling the second braking unit 23. The second control unit 102 can operate the second braking unit 23 to generate a braking force.

The second control unit 102 can adjust the WC pressure Pwc by operating the pumps 631, 632 according to the drive amount of the second electric motor 64. This allows the second braking unit 23 to generate a braking force on the wheels FL, FR, RL, and RR. The amount of the WC pressure Pwc applied to each wheel FL, FR, RL, and RR by the second braking unit 23 is referred to as the second braking pressure P2. An example of adjusting the WC pressure Pwc by the second braking unit 23 will be described below.

When the pump 631 provided in the first hydraulic circuit 611 is operated, brake fluid is discharged from the reservoir tank 24 to the intermediate fluid passage 711 via the master chamber Rm, the first flow path 331, the tank side flow path 701, the reservoir 681, and the suction flow path 691. Alternatively, brake fluid is discharged from the master chamber Rm to the intermediate fluid passage 711 via the first flow path 331, the tank side flow path 701, the reservoir 681, and the suction flow path 691.

When the pump 632 provided in the second hydraulic circuit 612 is operated, brake fluid is discharged from the reservoir tank 24 to the intermediate fluid passage 712 via the fourth passage 54, the fluid chamber Re, the sixth passage 58, the tank side passage 702, the reservoir 682, and the suction passage 692. Alternatively, brake fluid is discharged from the fluid chamber Re to the intermediate fluid passage 712 via the sixth passage 58, the tank side passage 702, the reservoir 682, and the suction passage 692.

In the second braking section 23, when the first differential pressure adjustment valve 621 is operated and brake fluid is discharged from the pump 631, a pressure difference occurs between the brake fluid in the first flow path 331 and the brake fluid in the intermediate fluid path 711. In addition, in the second braking section 23, when the second differential pressure adjustment valve 622 is operated and brake fluid is discharged from the pump 632, a pressure difference occurs between the brake fluid in the sixth flow path 58 and the brake fluid in the intermediate fluid path 712.

The second control unit 102 generates the above-mentioned pressure difference in the second braking unit 23, thereby increasing the WC pressure Pwc by the pressure difference with respect to the hydraulic pressure of the brake fluid adjusted by the first braking unit 50. In other words, the pressure difference corresponds to the second braking pressure P2. The sum of the first braking pressure P1 and the second braking pressure P2 corresponds to the WC pressure Pwc.

The pump 632, the second electric motor 64, and the second differential pressure adjustment valve 622 constitute a rear wheel pressurizing unit 72 that increases the WC pressure Pwc of the rear wheels RL and RR by supplying the brake fluid taken from the reservoir tank 24 into the wheel cylinder 11. The rear wheel pressurizing unit 72 is connected to the reservoir tank 24 via the fourth flow path 54, the electric cylinder 51, the sixth flow path 58, the tank side flow path 702, the reservoir 682, and the intake flow path 692. The pump 631, the second electric motor 64, and the first differential pressure adjustment valve 621 constitute a front wheel pressurizing unit 73 that increases the WC pressure Pwc of the front wheels FL and FR by supplying the brake fluid taken from the reservoir tank 24 into the wheel cylinder 11. The rear wheel pressurizing unit 72 and the front wheel pressurizing unit 73 share the second electric motor 64.

<Abnormality Judgment Processing>
The abnormality determination unit 103 can execute an abnormality determination process. The abnormality determination process is a process for determining whether or not an abnormality has occurred in the electric cylinder 51.

An abnormality in the electric cylinder 51 is, for example, a state in which the piston 512 cannot move in the backward direction Zb when pressure is being applied by the electric cylinder 51. In other words, a state in which the input port 515 cannot be opened when the input port 515 is blocked. Causes of the abnormality include, for example, sticking of the piston 512 and a malfunction of the mechanism that transmits the driving force of the first electric motor 513. When the above abnormality occurs, it may not be possible to release the hydraulic pressure between the electric cylinder 51 and the wheel cylinder 11. In other words, it may not be possible to reduce the WC pressure Pwc.

An example of the abnormality determination process will be described.
In the abnormality determination process, for example, a determination can be made based on the operation amount of the brake operating member 21 detected by the stroke sensor SE1, the rotation speed of the first electric motor 513 that can be calculated from the detection value of the rotation angle sensor SE2, and the control pressure detected by the control pressure sensor 353. When no abnormality occurs in the first electric motor 513, a prescribed correlation is established between the control pressure and the operation amount of the brake operating member 21 and the rotation speed of the first electric motor 513. In the abnormality determination process, when the prescribed correlation is not established, it can be determined that an abnormality occurs in the first electric motor 513. More specifically, for example, when the detection value of the rotation angle sensor SE2 does not change even if the electric motor 513 is driven to move the piston 512 in the backward direction Zb, it can be determined that an abnormality occurs in the electric cylinder 51.

<Pressure release process>
The first control unit 101 can execute a pressure release process.
The pressure release process is a process of opening the release valve 57 when it is determined that an abnormality has occurred in the electric cylinder 51 .

An example of the pressure release process will be described with reference to FIG. 3. FIG. 3 shows the flow of the process when the pressure release process is executed. This process routine is executed repeatedly at a predetermined cycle, for example. This process routine does not need to be executed if flag F1, which will be described later, is ON.

When this processing routine is started, first, in step S101, the braking control device 100 causes the abnormality determination unit 103 to execute the abnormality determination process. Then, as a result of the abnormality determination process, the braking control device 100 determines whether or not an abnormality has occurred in the electric cylinder 51.

In step S101, if no abnormality has occurred in the electric cylinder 51, i.e., if the electric cylinder 51 is normal (S101: NO), the brake control device 100 temporarily ends this processing routine. On the other hand, if an abnormality has occurred in the electric cylinder 51 (S101: YES), the brake control device 100 transitions to step S102.

In step S102, the braking control device 100 sets flag F1 to ON. The initial value of flag F1 is OFF. Flag F1 being ON indicates that an abnormality has occurred in the electric cylinder 51. For example, once flag F1 is set to ON, it will remain set to ON unless flag F1 is initialized. As an example, flag F1 can be initialized by connecting a device outside the vehicle, such as a diagnostic machine, to the braking control device 100. When flag F1 is set to ON, the braking control device 100 transitions to step S103.

In step S103, the braking control device 100 causes the second control unit 102 to close the first differential pressure adjustment valve 621 and the second differential pressure adjustment valve 622. As a result, the first hydraulic circuit 611 and the second hydraulic circuit 612 of the second braking unit 23 are disconnected from the first braking unit 50. The braking control device 100 then transitions to step S104.

In step S104, the braking control device 100 causes the first control unit 101 to open the release valve 57. As a result, the portion of the sixth flow path 58 between the output port 516 and the wheel cylinder 11 is connected to the portion of the fourth flow path 54 between the input port 515 and the reservoir tank 24 via the release flow path 56. The braking control device 100 then transitions to step S105.

Regarding the processing of steps S103 and S104, for example, the braking control device 100 transitions the processing to step S104 after the opening degree of the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 becomes "0". That is, the braking control device 100 starts to open the release valve 57 after the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 have finished closing. In other words, the braking control device 100 closes the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 before the release valve 57 starts to open.

In step S105, the braking control device 100 causes the second control unit 102 to start opening the first differential pressure adjustment valve 621 and the second differential pressure adjustment valve 622. For example, the opening degree of the first differential pressure adjustment valve 621 and the second differential pressure adjustment valve 622 is gradually increased so that the flow rate of brake fluid passing through the first differential pressure adjustment valve 621 and the second differential pressure adjustment valve 622 gradually increases. As a result, brake fluid can flow out from the first hydraulic pressure circuit 611 and the second hydraulic pressure circuit 612. The braking control device 100 then ends this processing routine.

In this embodiment, the processes of steps S103, S104, and S105 correspond to the pressure release process. The pressure release process can be carried out by opening the release valve 57. In other words, it is sufficient to carry out the process of step S104, and it is not essential to carry out the processes of steps S103 and S105.

<Assistance Processing>
The brake control device 100 can execute an assist process. The assist process is a process for adjusting the WC pressure Pwc when an abnormality occurs in the electric cylinder 51. Specifically, in the assist process, the hydraulic circuits 611, 612 of the second braking unit 23 are controlled to supply brake fluid from the reservoir tank 24 to the wheel cylinder 11 via the release flow path 56 in which the release valve 57 is in an open state, thereby adjusting the WC pressure Pwc.

An example of the assisting process will be described with reference to Fig. 4. Fig. 4 shows a process flow when the assisting process is executed. This process routine is executed repeatedly at predetermined intervals, for example.
When this processing routine is started, first, in step S201, the brake control device 100 determines whether or not a braking operation is being performed. For example, the brake control device 100 can determine that a braking operation is being performed when the target WC pressure is greater than "0".

In step S201, if there is no braking operation (S201: NO), the brake control device 100 temporarily ends this processing routine. On the other hand, if there is a braking operation (S201: YES), the brake control device 100 transitions to step S202.

In step S202, the braking control device 100 determines whether or not the flag F1 is set to ON.
If the flag F1 is OFF, that is, if the electric cylinder 51 is normal (S202: NO), the brake control device 100 transitions the process to step S203.

In step S203, the brake control device 100 performs normal brake control. That is, the brake control device 100 operates the first brake unit 50 and the second brake unit 23 to adjust the WC pressure Pwc so that the sum of the first brake pressure P1 and the second brake pressure P2 satisfies the target WC pressure. Thereafter, the brake control device 100 ends this processing routine.

On the other hand, if flag F1 is ON in the processing of step S202, i.e., if an abnormality has occurred in the electric cylinder 51 (S202: YES), the braking control device 100 transitions to the processing of step S204.

In step S204, the braking control device 100 causes the first control unit 101 to open the release valve 57. In other words, the first control unit 101 causes the reservoir tank 24 and the second braking unit 23 to be connected via the release flow path 56. After that, the braking control device 100 proceeds to step S205.

In step S205, the brake control device 100 causes the second control unit 102 to operate the second brake unit 23 to adjust the WC pressure Pwc in response to the braking request. As a result, a braking force is generated by the operation of the second brake unit 23. Thereafter, the brake control device 100 ends this processing routine.

<Action and Effects>
The operation and effects of this embodiment will be described.
According to the braking device 20, when an abnormality occurs in the electric cylinder 51, a flow path through which the brake fluid flows between the reservoir tank 24 and the wheel cylinder 11 can be formed via the release flow path 56 with the release valve 57 open. As a result, even when an abnormality occurs in the electric cylinder 51, the WC pressure Pwc can be reduced via the release flow path 56 with the release valve 57 open and the master chamber Rm.

First, the wheel cylinder 11 for the rear wheels RL, RR will be described.
Opening the release valve 57 allows the brake fluid in the sixth flow path 58 and the fifth flow path 55 to flow into the reservoir tank 24. At this time, even if the input port 515 is closed, the hydraulic pressure in the fluid chamber Re decreases. This allows the brake fluid to flow from the wheel cylinders 11 for the rear wheels RL, RR connected to the second hydraulic pressure circuit 612 into the reservoir tank 24 via the sixth flow path 58, the release flow path 56, and the fourth flow path 54. In this manner, the braking device 20 can reduce the WC pressure Pwc of the rear wheels RL, RR.

Next, the wheel cylinder 11 for the front wheels FL, FR will be described.
By opening the release valve 57, the brake fluid in the fifth flow path 55 can flow into the reservoir tank 24 via the sixth flow path 58, the release flow path 56, and the fourth flow path 54. This allows the brake fluid in the servo chamber Rs to flow out to the fifth flow path 55. The reduction in the hydraulic pressure in the servo chamber Rs allows the master piston 43 to move rearward. This allows the brake fluid to flow from the wheel cylinders 11 for the front wheels FL, FR connected to the first hydraulic pressure circuit 611 into the reservoir tank 24 via the first flow path 331 and the master chamber Rm. In this way, the braking device 20 can reduce the WC pressure Pwc of the front wheels FL, FR.

Before executing the process of opening the release valve 57 (S104), the braking control device 100 closes the first differential pressure adjustment valve 621 and the second differential pressure adjustment valve 622 (S103). After that, it opens the release valve 57, and then opens the first differential pressure adjustment valve 621 and the second differential pressure adjustment valve 622 (S105).

If the release valve 57 is opened while the first differential pressure adjustment valve 621 and the second differential pressure adjustment valve 622 are open when an abnormality occurs in the electric cylinder 51, the following may occur. That is, the brake fluid that has been trapped between the electric cylinder 51 and the wheel cylinder 11 without being released due to the abnormality in the electric cylinder 51 may suddenly flow into the reservoir tank 24. This may result in, for example, a decrease in deceleration or pedal shock, causing the driver to feel uncomfortable.

In contrast, with the braking device 20 equipped with the braking control device 100, the opening degree of the first differential pressure adjustment valve 621 and the second differential pressure adjustment valve 622 can be gradually increased after the release valve 57 is opened. This allows the hydraulic pressure in the hydraulic chamber Re to be reduced first, and then the hydraulic pressure between the first differential pressure adjustment valve 621 and the second differential pressure adjustment valve 622 and the wheel cylinder 11 to be reduced. With the braking device 20 configured in this way, it is possible to suppress a decrease in deceleration and the occurrence of pedal shock when the release valve 57 is opened.

According to the braking device 20, when an abnormality occurs in the electric cylinder 51, the WC pressure Pwc can be adjusted by the assist process to generate a braking force. In the assist process, the second braking unit 23 is operated while the release valve 57 is in an open state. This allows brake fluid to be supplied from the reservoir tank 24 to the wheel cylinder 11 connected to the first hydraulic circuit 611 via the master chamber Rm of the master cylinder 31. In addition, brake fluid can be supplied from the reservoir tank 24 to the wheel cylinder 11 connected to the second hydraulic circuit 612 via the release flow path 56 that bypasses the electric cylinder 51. In other words, even if an abnormality occurs in the electric cylinder 51, the WC pressure Pwc can be quickly increased. In addition, brake fluid can be discharged from the wheel cylinder 11 connected to the first hydraulic circuit 611 to the reservoir tank 24 via the master chamber Rm of the master cylinder 31. In addition, brake fluid can be discharged from the wheel cylinder 11 connected to the second hydraulic circuit 612 to the reservoir tank 24 via the release flow path 56. This allows the WC pressure Pwc to be reduced.

(Example of change)
This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

・The brake control device 100 and other processing circuits, which are processing circuits, may have any of the following configurations [a] to [c]. [a] Equipped with one or more processors that execute various processes according to a computer program. The processor includes a processing device. Examples of the processing device include a CPU, a DSP, and a GPU. The processor includes a memory. Examples of the memory include a RAM, a ROM, and a flash memory. The memory stores program code or instructions configured to cause the processing device to execute the processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. [b] Equipped with one or more hardware circuits that execute various processes. Examples of the hardware circuit include an ASIC (Application Specific Integrated Circuit), a CPLD (Complex Programmable Logic Device), and an FPGA (Field Programmable Gate Array). [c] A circuit that includes a processor that executes some of the various processes according to a computer program and a hardware circuit that executes the remaining processes of the various processes.

The brake control device 100 may open the release valve 57 in the pressure release process to reduce the WC pressure Pwc, and then close the release valve 57 .
When the above-described configuration for closing the release valve 57 is adopted, the release valve 57 is opened again in the process of step S204 of the assist process. On the other hand, when the configuration for closing the release valve 57 is not adopted, the release valve 57 may be left open without being operated in the process of step S204.

In addition, when neither the electric cylinder 51 nor the second braking unit 23 is operated, and the master piston 43 is moved forward and backward mechanically by operating the brake operating member 21 to generate a braking force, it is advisable to keep the release valve 57 open at least while the brake operating member 21 is being operated.

In addition, the brake control device 100 does not necessarily have to close the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 before opening the release valve 57 in the pressure release process. For example, the brake control device 100 may open the release valve 57 in the pressure release process and simultaneously control the differential pressure regulating valves 621 and 622 so that the rate of decrease of the WC pressure Pwc is lower than the state in which the differential pressure regulating valves 621 and 622 are released. Alternatively, the brake control device 100 may control the differential pressure regulating valves 621 and 622 so that the rate of decrease of the WC pressure Pwc is lower than the state in which the differential pressure regulating valves 621 and 622 are released after opening the release valve 57 in the pressure release process. The state in which the differential pressure regulating valves 621 and 622 are released is, for example, a state in which the differential pressure regulating valves 621 and 622 are fully open. During the pressure release process, the braking control device 100 may close the differential pressure adjustment valves 621 and 622 while keeping the release valve 57 open.

The brake control device 100 may close the release valve 57 after the braking force applied by the assist process is released. For example, after the process of step S205, if the braking request is released and the WC pressure Pwc has decreased, the release valve 57 may be closed.

The brake control device 100 may execute the pressure release process when it is determined that an abnormality has occurred in the electric cylinder 51 and the brake operating member 21 is being operated by the driver.

- The brake control device 100 does not need to perform the assist process. When the assist process is not performed, after the pressure release process is performed, a braking force is generated according to the driver's operation, for example, as described below. The driver's operating force on the brake operating member 21 is transmitted to the master piston 43 via the input piston 44 and the second fluid chamber R2, and the braking mechanism 10 of the front wheels FL and FR generates a braking force according to the driver's operation. Alternatively, the driver's operating force on the brake operating member 21 is transmitted directly from the input piston 44 to the master piston 43, and the braking mechanism 10 of the front wheels FL and FR generates a braking force according to the driver's operation.

The braking control device 100 may perform the assist process after the pressure release process, or may perform the assist process simultaneously with the pressure release process, or may perform the assist process delayed from the pressure release process so as to overlap with the pressure release process. When performing the assist process as described above, the differential pressure regulating valves 621, 622 may operate according to the control of the assist process without performing the valve closing and control due to the pressure release process. Alternatively, the differential pressure regulating valves 621, 622 may operate according to the control of the assist process after performing some of the valve closing and control due to the pressure release process.

- In the above embodiment, a braking control device 100 including a first control unit 101 and a second control unit 102 is exemplified. That is, an example is shown in which a single braking control device 100 controls the master device 30, the first braking unit 50, and the second braking unit 23. As a braking control device included in the braking device, a braking control device including a first control device having a function equivalent to the first control unit 101, and a second control device that is a control device separate from the first control device and has a function equivalent to the second control unit 102 may be used.

FIG. 5 illustrates a braking control device 200 that is composed of a first control device 210 and a second control device 220. The first control device 210 includes a first control unit 101 as a functional unit. The first control device 210 may include an abnormality determination unit 103 as a functional unit. The second control device 220 includes a second control unit 102 as a functional unit. The first control device 210 and the second control device 220 can communicate with each other, for example, via an in-vehicle network. The first control device 210 and the second control device 220 may be connected by a signal line so that they can communicate with each other.

LIST OF SYMBOLS 10... Brake mechanism 11... Wheel cylinder 12... Rotating plate 13... Friction material 20... Brake device 21... Brake operation member 22... Fluid pressure generating device 23... Second braking section 24... Reservoir tank 30... Master device 31... Master cylinder 43... Master piston 50... First braking section 51... Electric cylinder 511... Cylinder 512... Piston 513... First electric motor 515... Input port 516... Output port 517... Through hole 54... Fourth flow path 55... Fifth flow path 56... Release flow path 57... Release valve 58... Sixth flow path 611... First hydraulic pressure circuit 612... Second hydraulic pressure circuit 621... First differential pressure regulating valve 622... Second differential pressure regulating valve 100... Brake control device 101... First control unit 102... Second control unit 103... Abnormality determination unit

Claims (8)

A braking device having a reservoir tank for storing brake fluid, a braking unit capable of applying a braking force to a wheel of a vehicle by adjusting a fluid pressure in a wheel cylinder by the brake fluid supplied from the reservoir tank, and a brake control device for controlling the braking unit,
The braking portion includes:
an electric cylinder having a cylinder, a piston, and an electric motor, the cylinder being formed with an output port capable of supplying brake fluid to the wheel cylinder by the piston that moves in response to driving of the electric motor;
a release flow passage configured to connect the reservoir tank to a fluid chamber in the cylinder of the electric cylinder, the fluid chamber being in a state where the output port is open;
A release valve which is a normally closed solenoid valve arranged in the release flow path,
The braking control device includes:
an abnormality determination process for determining whether or not an abnormality has occurred in the electric cylinder;
a pressure release process for opening the release valve when it is determined that an abnormality has occurred in the electric cylinder. a master cylinder having a master piston and a fluid chamber defined by the master piston, the master piston moving in response to an operation of a brake operating member by a driver of the vehicle, capable of supplying brake fluid to the wheel cylinders;
a flow passage connecting a servo chamber, which is a fluid chamber on the opposite side of a master chamber, which is a fluid chamber connected to the wheel cylinder, among the fluid chambers partitioned by the master piston, to the output port of the electric cylinder,
2. The braking device according to claim 1, wherein the master cylinder is configured such that the master piston moves in a direction in which the volume of the master chamber decreases in response to brake fluid being supplied to the servo chamber. When the braking unit is a first braking unit and the electric motor is a first electric motor,
a second brake unit disposed between the first brake unit and the wheel cylinder, the second brake unit being capable of applying a braking force to the wheel by adjusting a hydraulic pressure in the wheel cylinder;
The second braking portion is
a hydraulic circuit having a second electric motor as a power source and connected to the wheel cylinder;
a differential pressure regulating valve which is a normally open solenoid valve arranged in a flow path connecting the first braking unit and the hydraulic circuit,
3. The braking device according to claim 1, wherein the brake control device is capable of controlling the second braking unit, and when the release valve is opened by the pressure release process, the brake control device controls the differential pressure regulating valve so that a rate of decrease in the hydraulic pressure in the wheel cylinder is slower than a state in which the differential pressure regulating valve is released. The braking control device includes:
When a braking operation is detected while an abnormality occurs in the electric cylinder,
4. The braking device according to claim 3, further comprising: a brake fluid supply circuit for supplying brake fluid from the reservoir tank to the wheel cylinder through the release flow passage with the release valve in an open state, thereby adjusting the hydraulic pressure in the wheel cylinder. The braking device according to claim 2, wherein the flow path connecting the servo chamber to the output port of the electric cylinder is connected to a wheel cylinder different from the wheel cylinder connected to the master chamber. The braking device according to claim 3, wherein the braking control device closes the differential pressure adjustment valve while the pressure release process opens the release valve. The braking device according to claim 1, wherein the pressure release process is executed when it is determined that an abnormality has occurred in the electric cylinder and the driver is operating the brake operating member. a master cylinder having a master piston and a fluid chamber defined by the master piston, the master piston moving in response to an operation of a brake operating member by a driver of the vehicle, capable of supplying brake fluid to the wheel cylinders;
a flow passage connecting a servo chamber, which is a fluid chamber on the opposite side of a master chamber, which is a fluid chamber connected to the wheel cylinder, among the fluid chambers partitioned by the master piston, to the output port of the electric cylinder,
5. The braking system according to claim 4, wherein in the assisting process, brake fluid is supplied from the master chamber to the wheel cylinder connected to the master chamber.

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