Braking device

Abstract

To provide a brake device which is configured to reduce liquid pressure in a wheel cylinder when an abnormality occurs in an electric cylinder.SOLUTION: A brake device 20 comprises: a first brake part 50 which applies brake force to a wheel by adjusting liquid pressure in a wheel cylinder 11 with brake liquid supplied from a reservoir tank 24; and a brake control device 100 which controls the first brake part 50. The first brake part 50 includes an electric cylinder 51 which can supply brake liquid to the wheel cylinder 11 according to the drive of an electric motor 513. The first brake part 50 comprises: a release channel 56 which is configured to connect the reservoir tank 24 with a liquid chamber in which an output port 516 in the electric cylinder 51 is open; and a release valve 57 which is a normally closed electromagnetic valve arranged in the release channel 56. The brake control device 100 executes pressure release processing of opening the release valve 57 when an abnormality occurs in the electric cylinder 51.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a braking device including an electric cylinder that generates hydraulic pressure by driving an electric motor. In Patent Document 1, the electric cylinder is described as a "slave cylinder". The electric cylinder includes an input port to which brake fluid is supplied from a reservoir tank and an output port that discharges the brake fluid. 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.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a braking device as disclosed in Patent Document 1, when an abnormality occurs in the electric cylinder, there is a possibility that the input port cannot be opened from a state where the input port is blocked. In such a case, the flow path connecting the electric cylinder and the wheel cylinder may be blocked, and the hydraulic pressure in the flow path pressurized by the electric cylinder may not be released. Therefore, the state where the hydraulic pressure in the wheel cylinder increases may continue regardless of the target value of the hydraulic pressure.

Means for Solving the Problems

[0005] A braking device for solving the above problems comprises a reservoir tank for storing brake fluid, a braking unit capable of applying braking force to the wheels of a vehicle by adjusting the fluid pressure in the wheel cylinder with the brake fluid supplied from the reservoir tank, and a braking control device for controlling the braking unit, wherein the braking unit comprises a cylinder, a piston and an electric motor, an electric cylinder having an output port formed in the cylinder that can supply brake fluid to the wheel cylinder by the piston moving in accordance with the drive of the electric motor, a release passage configured to connect the fluid chamber of the cylinder in the electric cylinder in which the output port is open and the reservoir tank, and a release valve which is a normally closed solenoid valve disposed in the release passage, and the gist of the braking control device is to perform an abnormality determination process to determine whether or not an abnormality has occurred in the electric cylinder, and a pressure release process to open the release valve when it has been determined that an abnormality has occurred in the electric cylinder.

[0006] According to the above configuration, if an abnormality occurs in the electric cylinder, a flow path for brake fluid can be formed between the reservoir tank and the wheel cylinder via a release passage opened by the release valve. This makes it possible to reduce the hydraulic pressure inside the wheel cylinder even when an abnormality occurs in the electric cylinder. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram showing one embodiment of a vehicle braking system. [Figure 2] Figure 2 is a block diagram showing the braking control device included in the braking system. [Figure 3] Figure 3 is a flowchart showing the processing flow performed by the braking control device. [Figure 4] Figure 4 is a flowchart showing the processing flow performed by the braking control device. [Figure 5]Figure 5 is a block diagram showing the braking control device included in the modified braking system. [Modes for carrying out the invention]

[0008] A braking device 20, which is one embodiment of the braking device, will be described with reference to Figures 1 to 4. Figure 1 shows the vehicle's braking system 20. The braking system 20 includes a braking unit that can apply braking force to the vehicle's wheels. The braking system 20 also includes a braking control device 100 that can control the braking unit.

[0009] Figure 1 shows the front wheels FL, FR and rear wheels RL, RR as the wheels of the vehicle. The vehicle is equipped with a braking operation member 21. The braking operation member 21 can be operated by the driver of the vehicle. An example of the braking operation member 21 is a brake pedal.

[0010] The braking control device 100 is an example of a processing circuit provided by a vehicle. A vehicle may be equipped with other control devices, such as other processing circuits, in addition to the braking control device 100. Some of the functional components of the braking control device 100 may be provided by other control devices. Examples of other control devices include an automatic driving control device for automatically driving a vehicle. It is preferable that multiple control devices be connected in a way that allows them to send and receive information from one another. For example, a configuration can be adopted in which each processing circuit is connected to an in-vehicle network provided by the vehicle. Each processing circuit connected to the in-vehicle network can communicate with each other via the in-vehicle network.

[0011] <Brake device> The braking system 20 is equipped with a braking mechanism 10 corresponding to each of the wheels FL, FR, RL, and RR. The braking mechanism 10 can apply frictional braking force to each of the wheels FL, FR, RL, and RR. The frictional braking force applied by each braking mechanism 10 to the wheels FL, FR, RL, and RR can be adjusted by the braking system 20.

[0012] The braking system 20 is a hydraulic braking system. The braking system 20 includes a reservoir tank 24 for storing brake fluid and a hydraulic pressure generator 22. The braking system 20 includes a first braking section 50 as a braking unit. The braking system 20 may also include a second braking section 23 as a braking unit.

[0013] An example of a hydraulic pressure generator 22 is a so-called brake-by-wire type hydraulic pressure generator. The hydraulic pressure generator 22 can generate hydraulic pressure according to the amount of operation of the braking operating member 21. The hydraulic pressure generator 22 consists 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 both the master device 30 and the second braking unit 23.

[0014] <Brake mechanism> The braking mechanism 10 will now be described. The components of each braking mechanism 10 are common to all of them. The braking mechanism 10 includes 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 direction of the plate thickness of the rotating plate 12. The braking mechanism 10 is configured such that the higher the WC pressure Pwc, which is the fluid pressure inside the wheel cylinder 11, the stronger the friction braking force applied to the rotating plate 12. In other words, according to the braking mechanism 10, the higher the WC pressure Pwc, the greater the friction braking force applied to the wheels FL, FR, RL, and RR.

[0015] <Master device> An example of the master device 30 includes a master cylinder 31, a plurality of flow paths 331, 332, 333 connected to the master cylinder 31, a plurality of control valves 341, 342 for controlling the flow of brake fluid, and a stroke simulator 32. The stroke simulator 32 can generate a reaction force corresponding to the amount of operation of the braking operating member 21.

[0016] 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.

[0017] An example of the master cylinder 31 will be described in more detail. The main cylinder 41 included in the master cylinder 31 has a plate-shaped bottom wall 411 and a first peripheral wall 412 that extends from the bottom wall 411 along the axis of the bottom wall 411. Further, the main cylinder 41 has a second peripheral wall 413 that extends 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 that extends 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 portion 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.

[0018] In the main cylinder 41, a master chamber Rm partitioned by the bottom wall 411, the first peripheral wall 412, and the master piston 43 is formed. Hereinafter, in the master cylinder 31, the left side in FIG. 1, that is, the moving direction of the master piston 43 that reduces the volume of the master chamber Rm is defined as the front. On the other hand, the right side in FIG. 1, that is, the moving direction of the master piston 43 that increases the volume of the master chamber Rm is defined as the rear.

[0019] In the main cylinder 41, a first liquid chamber R1 partitioned by a second peripheral wall 413 and a master piston 43, and a servo chamber Rs partitioned by the second peripheral wall 413, a first annular wall 414, and the master piston 43 are formed. The master chamber Rm is formed at a position closer to the front end of the master cylinder 31. The first liquid chamber R1 is formed behind the master chamber Rm. The servo chamber Rs is formed behind the first liquid chamber R1. Inside the main cylinder 41, the master chamber Rm, the first liquid chamber R1, and the servo chamber Rs are not connected to each other. The master chamber Rm corresponds to "the liquid chamber connected to the wheel cylinder among the liquid chambers partitioned by the master piston". The servo chamber Rs corresponds to "the liquid chamber on the opposite side of the liquid chamber connected to the wheel cylinder among the liquid chambers partitioned by the master piston".

[0020] The cover cylinder 42 provided in 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 the axis thereof coincides with the second peripheral wall 413 of the main cylinder 41. The second annular wall 422 has a hole into which the rear end portion of an input piston 44 described later is inserted.

[0021] In the cover cylinder 42, a second liquid chamber R2 partitioned by the first annular wall 414 of the main cylinder 41, the third peripheral wall 421, and the input piston 44, and a third liquid chamber R3 partitioned by the third peripheral wall 421, the second annular wall 422, and the input piston 44 are formed. In the master cylinder 31, the second liquid chamber R2 is formed behind the servo chamber Rs, and the third liquid chamber R3 is formed behind the second liquid chamber R2. Inside the cover cylinder 42, the second liquid chamber R2 and the third liquid chamber R3 are not connected to each other.

[0022] The master piston 43 is housed in the master cylinder 31 in a state where it is in surface contact with the inner surfaces of the first circumferential wall 412, the second circumferential wall 413, and 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 surfaces of the first circumferential wall 412, the second circumferential wall 413, and the first annular wall 414. The rear end of the master piston 43 protrudes rearward from the first annular wall 414 and is located within the second fluid chamber R2. The master piston 43 is configured such that the pressure-receiving area that faces the master chamber Rm and receives the pressure of the master chamber Rm directed backward is equal to the pressure-receiving area that faces the servo chamber Rs and receives the pressure of the servo chamber Rs directed forward. Furthermore, the master piston 43 of this embodiment is configured such that the pressure-receiving area facing the first liquid chamber R1 and receiving the pressure from the first liquid chamber R1 directed backward is equal to the pressure-receiving area facing the second liquid chamber R2 and receiving the pressure from the second liquid chamber R2 directed forward.

[0023] The input piston 44 is housed in the master cylinder 31 in a state where it is in surface contact with the inner surface of the third circumferential wall 421 and the inner 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 against the inner surface of the third circumferential wall 421 and the inner surface of the second annular wall 422. The rear end of the input piston 44 protrudes behind the second annular wall 422 and is connected to the braking operating member 21. The input piston 44 moves in a direction approaching the master piston 43 according to the amount of operation of the braking operating member 21. In addition, a gap is formed between the input piston 44 and the master piston 43 in the second liquid chamber R2.

[0024] The master spring 45 is positioned between 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 backward. In other words, the master spring 45 is elastically compressed when the master piston 43 moves forward.

[0025] The input spring 46 is positioned between the second fluid chamber R2 of the cover cylinder 42, more 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 backward. In other words, the input spring 46 is elastically compressed when the input piston 44 moves forward.

[0026] In the master cylinder 31, the master chamber Rm is connected to the reservoir tank 24. More specifically, the rear end portion 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 Figure 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.

[0027] 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 backward, brake fluid is discharged from the third fluid chamber R3 to the reservoir tank 24.

[0028] The first flow path 331 connects the master chamber Rm and the second braking unit 23. The second flow path 332 connects the first liquid chamber R1 and the second liquid chamber R2. The third flow path 333 connects the reservoir tank 24 and the second flow path 332.

[0029] 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 between the connection point of the second flow path 332 and the third flow path 333 and the second liquid chamber R2. The second control valve 342 is located 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.

[0030] The stroke simulator 32 is positioned, 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 rear by a spring inside. When brake fluid flows into the stroke simulator 32 from the second flow path 332, causing the internal piston to displace against the spring bias, the stroke simulator 32 generates pressure in the brake fluid in proportion to the displacement of the piston. Specifically, when the input piston 44 moves forward by operating the braking operating member 21 with the first control valve 341 open and the second control valve 342 closed, 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, which are connected by the second flow path 332.

[0031] <1st braking section> The first braking unit 50 is equipped with 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 which operates according to the amount of drive of the first electric motor 513. In other words, the first braking unit 50 can generate braking force on the vehicle's wheels FL, FR, RL, and RR.

[0032] An example of the first braking unit 50 will be described below. The first braking unit 50 is equipped with an electric cylinder 51. The first braking unit 50 includes a fourth passage 54 connecting the electric cylinder 51 and the reservoir tank 24. The first braking unit 50 includes a sixth passage 58 connecting the second braking unit 23 and the electric cylinder 51. The first braking unit 50 includes a fifth passage 55 connecting the servo chamber Rs of the master cylinder 31 and the sixth passage 58.

[0033] <Electric Cylinder> The electric cylinder 51 of the first braking unit 50 is located between the fourth passage 54 and the sixth passage 58. The fourth passage 54 is connected to the input port 515 of the electric cylinder 51. The sixth passage 58 is connected to the output port 516 of the electric cylinder 51. The input port 515 and the output port 516 will be described later.

[0034] The electric cylinder 51 comprises 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 the linear motion of the piston 512.

[0035] Inside the cylinder 511, a fluid chamber Re into which brake fluid is introduced is partitioned by a piston 512. The first electric motor 513 can generate the driving force to slide the piston 512 within 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 accordance with the change in the position of the piston 512.

[0036] In the following, the direction of movement of the piston 512 that reduces the volume of the liquid chamber Re is defined as the forward direction Za. The direction of movement of the piston 512 that increases the volume of the liquid chamber Re, which is opposite to the forward direction Za, is defined as the backward direction Zb. The position of the piston 512 where the volume of the liquid chamber Re is maximum is called the "initial position". In other words, the initial position is the position when the piston 512 has moved furthest in the backward direction Zb.

[0037] 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 positioned to connect the input port 515 and the liquid chamber Re when the piston 512 is in its initial position. As a result, when the piston 512 is in its initial position, the liquid chamber Re of the cylinder 511 is connected to the fourth flow path 54 via the input port 515 and the through hole 517. In other words, the liquid chamber Re of the cylinder 511 is connected to the reservoir tank 24 via the input port 515 and the through hole 517. The input port 515 is open when the piston 512 is in its initial position and is configured to be closed by the piston 512 when the piston 512 moves a predetermined amount in the forward direction Za from the initial position. The predetermined amount is the amount by which the piston 512 moves in the forward direction Za from the initial position 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 described above corresponds to the "flow path connecting the servo chamber of the master cylinder and the output port of the electric cylinder".

[0038] As shown in Figure 1, the electric cylinder 51 of the braking device 20 does not have a spring that biases the piston 512 in the retraction direction Zb. The electric cylinder 51 may have a spring that biases the piston 512 in the retraction direction Zb.

[0039] <Release channel and release valve> The first braking unit 50 is equipped with a release passage 56. The first braking unit 50 is equipped with a release valve 57 located in the release passage 56. The release valve 57 is a normally closed solenoid valve. That is, the release passage 56 is closed when no control is being performed to open the release valve 57. The release valve 57 can be opened by control from the braking control device 100.

[0040] The release passage 56 is a passage that connects the reservoir tank 24 and the wheel cylinder 11 in a manner that bypasses the electric cylinder 51. One end of the passage is connected to the fourth passage 54, and the other end of the passage is connected to the sixth passage 58. Specifically, the release passage 56 connects the reservoir tank 24 and the input port 515 in the fourth passage 54, and the output port 516 and the second braking unit 23 in the sixth passage 58. The release passage 56 constitutes a passage that connects the liquid chamber Re of the electric cylinder 51 and the reservoir tank 24 via the output port 516, which is always open, and the sixth passage 58.

[0041] <Second braking section> The second braking unit 23 is equipped with a second electric motor 64 as a power source. The second braking unit 23 can generate braking force on the vehicle's wheels FL, FR, RL, and RR according to the amount of drive of the second electric motor 64. The second braking unit 23 is interposed between the first braking unit 50 and the wheel cylinder 11.

[0042] An example of the second braking unit 23 will be described below. The second braking unit 23 is a braking actuator that can individually adjust the WC pressure Pwc of each wheel FL, FR, RL, RR. The second braking unit 23 is equipped with pumps 631 and 632 that discharge brake fluid. Pumps 631 and 632 are driven by a second electric motor 64.

[0043] The second braking unit 23 can increase the WC pressure Pwc without increasing the hydraulic pressure of the brake fluid regulated by the first braking unit 50. The braking device 20 has a redundant configuration with the first braking unit 50 on the upstream side and the second braking unit 23 on the downstream side.

[0044] The second braking unit 23 is provided with two hydraulic circuits 611 and 612. Two wheel cylinders 11 for the front wheels FL and FR are connected to the first hydraulic circuit 611. Two wheel cylinders 11 for the rear wheels RL and RR are connected to the second hydraulic circuit 612.

[0045] 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 regulating valve 621, which is a normally open linear solenoid valve, is provided in the fluid passage connecting the connection point with the first flow path 331 and the wheel cylinder 11. The wheel cylinders 11 for the front wheels FL and FR correspond to the "wheel cylinders connected to the master chamber".

[0046] The second hydraulic circuit 612 is connected to the reservoir tank 24 via the fourth passage 54, the electric cylinder 51, and the sixth passage 58. In the second hydraulic circuit 612, a second differential pressure regulating valve 622, which is a normally open linear solenoid valve, is provided in the fluid passage connecting the connection point with the sixth passage 58 and the wheel cylinder 11. The wheel cylinders 11 for the rear wheels RL and RR correspond to "wheel cylinders different from the wheel cylinder connected to the master chamber." The passage connecting the servo chamber Rs to the output port 516 of the electric cylinder 51 is connected to the wheel cylinders 11 for the rear wheels RL and RR via the second hydraulic circuit 612.

[0047] Pump 631 is located in the first hydraulic circuit 611. Pump 631 supplies brake fluid to the fluid passage connecting the first differential pressure regulating valve 621 and the wheel cylinder 11. Pump 632 is located in the second hydraulic circuit 612. Pump 632 supplies brake fluid to the fluid passage connecting the second differential pressure regulating valve 622 and the wheel cylinder 11.

[0048] In the hydraulic circuit 611, the same number of pathways 65a and 65b as the number of wheel cylinders 11 connected to the hydraulic circuit 611 are provided on the wheel cylinder 11 side of the first differential pressure regulating valve 621. Similarly, in the hydraulic circuit 612, the same number of pathways 65c and 65d as the number of wheel cylinders 11 connected to the hydraulic circuit 612 are provided on the wheel cylinder 11 side of the second differential pressure regulating valve 622. Each pathway 65a to 65d is provided with a retaining valve 66 that is closed when the WC pressure Pwc increases, and a pressure reducing valve 67 that is opened when the WC pressure Pwc decreases. That is, each retaining valve 66 is located in the fluid passage on the wheel cylinder 11 side of each differential pressure regulating valve 621 and 622. Each retaining valve 66 is a normally open solenoid valve, and each pressure reducing valve 67 is a normally closed solenoid valve.

[0049] The hydraulic circuits 611 and 612 are connected to reservoirs 681 and 682, which temporarily store brake fluid that flows out of the wheel cylinder 11 through the pressure reducing valve 67 when the pressure reducing valve 67 is open. Each reservoir 681 and 682 is connected to pumps 631 and 632 via suction passages 691 and 692.

[0050] Reservoir 681 is connected via tank-side passage 701 to the liquid passage connecting the first differential pressure regulating valve 621 and the master chamber Rm. Reservoir 682 is connected via tank-side passage 702 to the liquid passage connecting the connection point with the sixth passage 58 in the second hydraulic circuit 612 and the second differential pressure regulating valve 622.

[0051] Each pump 631, 632 can draw brake fluid from the reservoir tank 24 via reservoirs 681, 682. Each pump 631, 632 discharges the drawn brake fluid into the fluid passage between the differential pressure regulating valves 621, 622 and the retaining valve 66. The fluid passage between this fluid passage and pumps 631, 632 is called the intermediate fluid passage 711, 712.

[0052] <Sensor> The braking device 20 is equipped with various sensors. Figure 1 shows examples of various sensors, including multiple hydraulic sensors 351, 352, and 353, a stroke sensor SE1, and a rotation angle sensor SE2. Detection signals from these sensors are input to the braking control device 100. Based on the detection signals from these sensors, the braking control device 100 can acquire vehicle status values.

[0053] 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 installed 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 will be referred to as the "master pressure".

[0054] The input hydraulic pressure sensor 352 can detect the hydraulic pressure in the second liquid chamber R2. For example, the input hydraulic pressure sensor 352 is connected in the second flow path 332 at a position between the first control valve 341 and the second liquid chamber R2.

[0055] The control pressure sensor 353 can detect the hydraulic pressure pressurized by the electric cylinder 51. For example, the control pressure sensor 353 is located near the output port 516 of the electric cylinder 51. As an example, Figure 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 passage 56 connected to the fourth passage 54 and the sixth passage 58. Hereinafter, the hydraulic pressure detected by the control pressure sensor 353 will be referred to as the "control pressure".

[0056] The stroke sensor SE1 can detect the amount of operation of the braking 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 to the electric cylinder 51, for example. Based on the rotation angle detected by the rotation angle sensor SE2, the rotation speed of the first electric motor 513 can be calculated.

[0057] <Braking control device> The braking control device 100 will be explained using Figure 2. The braking control device 100 is composed of multiple functional units that perform various types of control. Figure 2 shows, as an example of a functional unit, the first control unit 101, the second control unit 102, and the abnormality determination unit 103. Each functional unit of the braking control device 100 is capable of sending and receiving information from each other.

[0058] 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 braking operating member 21 and is resolved when the operation of the braking operating member 21 is released. In this case, the first control unit 101 and the second control unit 102 can operate the braking device 20 using the required braking force calculated based on the amount of operation of the braking operating member 21. A braking request may also be output by the 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.

[0059] 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 for the hydraulic pressure in the wheel cylinder 11, i.e., a target value for the WC pressure Pwc. Hereinafter, the target value for the WC pressure Pwc may also be referred to as the "target WC pressure". By adjusting the WC pressure Pwc of wheels FL, FR, RL, and RR based on the target WC pressure, a braking force corresponding to the required braking force is applied to wheels FL, FR, RL, and RR.

[0060] <Adjustment of WC pressure by the first braking unit> The first control unit 101 will now be described. The first control unit 101 has the function of controlling the first braking unit 50. The first control unit 101 can activate the first braking unit 50 to generate braking force.

[0061] 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 WC pressure Pwc for each wheel FL, FR, RL, and RR that is pressurized by the first braking unit 50 is called the first braking pressure P1.

[0062] 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 when the target WC pressure is increased. Specifically, it controls the first electric motor 513 to move the piston 512 in the forward direction Za, thereby closing the input port 515. The movement of the piston 512 supplies brake fluid from the output port 516 of the electric cylinder 51 to the fifth passage 55 via the sixth passage 58. The brake fluid in the fifth passage 55 is supplied to the servo chamber Rs of the master cylinder 31. The supply of brake fluid to the servo chamber Rs causes the master piston 43 to move forward. In other words, the master cylinder 31 can move the master piston 43 forward with the brake fluid supplied from the electric cylinder 51 to the servo chamber Rs. Subsequently, brake fluid is supplied from the master chamber Rm to the wheel cylinders 11 for the front wheels FL and 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 and FR is increased to the target WC pressure. Furthermore, 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 passage 58. That is, brake fluid is supplied from the sixth passage 58 to the wheel cylinders 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.

[0063] The first control unit 101 continues to operate the electric cylinder 51 if the target WC pressure is maintained. The first control unit 101 controls the electric cylinder 51 so that the master pressure decreases to a fluid pressure corresponding to the target WC pressure when the target WC pressure decreases. Specifically, by controlling the first electric motor 513, the piston 512 is moved in the backward direction Zb, thereby reducing the pressure of the brake fluid supplied to the servo chamber Rs. Also, when the brake is released, the piston 512 is moved to its initial position and the through hole 517 and the input port 515 are connected. That is, the input port 515 is opened and the fluid chamber Re and the reservoir tank 24 are connected. 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, brake fluid can flow from the servo chamber Rs to the fluid chamber Re. Then the master piston 43 moves backward, and brake fluid can flow from the wheel cylinder 11 for the front wheels FL and FR into 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 and FR decreases to the target WC pressure. In addition, brake fluid flows from the wheel cylinder 11 for the rear wheels RL and RR into the fluid chamber Re via the sixth passage 58. As a result, the WC pressure Pwc of the rear wheels RL and RR decreases to the target WC pressure.

[0064] <Adjustment of WC pressure by the second braking unit> The second control unit 102 will now be described. The second control unit 102 has the function of controlling the second braking unit 23. The second control unit 102 can activate the second braking unit 23 to generate braking force.

[0065] The second control unit 102 can adjust the WC pressure Pwc by operating pumps 631 and 632 according to the drive amount of the second electric motor 64. This allows the second braking unit 23 to generate braking force for the wheels FL, FR, RL, and RR. The amount of WC pressure Pwc for each wheel FL, FR, RL, and RR that is pressurized by the second braking unit 23 is called the second braking pressure P2. An example of adjusting the WC pressure Pwc by the second braking unit 23 will be described below.

[0066] When the pump 631 provided in the first hydraulic circuit 611 is activated, 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.

[0067] When the pump 632 in the second hydraulic circuit 612 is activated, brake fluid is discharged from the reservoir tank 24 to the intermediate fluid passage 712 via the fourth passage 54, fluid chamber Re, sixth passage 58, tank-side passage 702, reservoir 682, and suction passage 692. Alternatively, brake fluid is discharged from the fluid chamber Re to the intermediate fluid passage 712 via the sixth passage 58, tank-side passage 702, reservoir 682, and suction passage 692.

[0068] In the second braking unit 23, when the first differential pressure regulating valve 621 is activated and brake fluid is discharged from the pump 631, a differential pressure is generated between the brake fluid in the first flow path 331 and the brake fluid in the intermediate fluid passage 711. Furthermore, in the second braking unit 23, when the second differential pressure regulating valve 622 is activated and brake fluid is discharged from the pump 632, a differential pressure is generated between the brake fluid in the sixth flow path 58 and the brake fluid in the intermediate fluid passage 712.

[0069] The second control unit 102 generates the differential pressure in the second braking unit 23, thereby increasing the WC pressure Pwc by the differential pressure relative to the hydraulic pressure of the brake fluid regulated by the first braking unit 50. That is, this differential pressure 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.

[0070] Pump 632, second electric motor 64, and second differential pressure regulating valve 622 constitute a rear wheel pressurizing section 72 that increases the WC pressure Pwc of the rear wheels RL and RR by supplying brake fluid taken from the reservoir tank 24 into the wheel cylinders 11. The rear wheel pressurizing section 72 is connected to the reservoir tank 24 via a fourth passage 54, electric cylinder 51, sixth passage 58, tank-side passage 702, reservoir 682, and suction passage 692. Pump 631, second electric motor 64, and first differential pressure regulating valve 621 constitute a front wheel pressurizing section 73 that increases the WC pressure Pwc of the front wheels FL and FR by supplying brake fluid taken from the reservoir tank 24 into the wheel cylinders 11. The rear wheel pressurizing section 72 and the front wheel pressurizing section 73 share the second electric motor 64.

[0071] <Anomaly detection process> The abnormality detection unit 103 can execute an abnormality detection process. The abnormality detection process determines whether or not an abnormality has occurred in the electric cylinder 51.

[0072] An abnormality in the electric cylinder 51 is, for example, a condition in which the piston 512 cannot move in the retraction direction Zb when pressurization is being performed by the electric cylinder 51. In other words, it is a condition in which the input port 515 cannot be opened when the input port 515 is blocked. Possible causes of the abnormality include, for example, the sticking of the piston 512 or a malfunction in 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. That is, it may not be possible to reduce the WC pressure Pwc.

[0073] An example of an anomaly detection process will be explained. In the abnormality detection process, for example, a determination can be made based on the amount of operation of the braking operating member 21 detected by the stroke sensor SE1, the rotational speed of the first electric motor 513 which can be calculated from the value detected by the rotational angle sensor SE2, and the control pressure detected by the control pressure sensor 353. If there is no abnormality in the first electric motor 513, a predetermined correlation relationship will be established between the control pressure and the amount of operation of the braking operating member 21 and the rotational speed of the first electric motor 513. In the abnormality detection process, if the predetermined correlation relationship is not established, it can be determined that there is an abnormality in the first electric motor 513. More specifically, for example, if the value detected by the rotational angle sensor SE2 does not change even when attempting to drive the electric motor 513 to move the piston 512 in the backward direction Zb, it can be determined that there is an abnormality in the electric cylinder 51.

[0074] <Pressure release process> The first control unit 101 can perform a pressure release process. The pressure release process is a process in which the release valve 57 is opened when it is determined that an abnormality has occurred in the electric cylinder 51.

[0075] An example of pressure release processing is explained using Figure 3. Figure 3 shows the processing flow when executing pressure release processing. This processing routine is executed repeatedly, for example, at predetermined intervals. This processing routine does not need to be executed if flag F1, which will be described later, is ON.

[0076] When this processing routine is started, in step S101, the braking control device 100 first causes the abnormality determination unit 103 to perform an 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.

[0077] In step S101, if no abnormality occurs in the electric cylinder 51, i.e., if the electric cylinder 51 is functioning normally (S101: NO), the braking control device 100 terminates this processing routine. On the other hand, if an abnormality occurs in the electric cylinder 51 (S101: YES), the braking control device 100 proceeds to step S102.

[0078] 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 remains ON until flag F1 is initialized. As an example, flag F1 can be initialized by connecting an external device such as a diagnostic tool to the braking control device 100. Once flag F1 is set to ON, the braking control device 100 proceeds to step S103.

[0079] In step S103, the braking control device 100 instructs the second control unit 102 to close the first differential pressure regulating valve 621 and the second differential pressure regulating 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. After that, the braking control device 100 proceeds to step S104.

[0080] 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 between the output port 516 in the sixth passage 58 and the wheel cylinder 11, and the portion between the input port 515 in the fourth passage 54 and the reservoir tank 24 are connected via the release passage 56. After that, the braking control device 100 proceeds to step S105.

[0081] Regarding the processing in steps S103 and S104, for example, the braking control device 100 proceeds to step S104 only after the opening degrees of the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 become "0". That is, the braking control device 100 starts opening the release valve 57 only 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 begins to open.

[0082] In step S105, the braking control device 100 instructs the second control unit 102 to start opening the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622. For example, the opening of the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 is gradually increased so that the flow rate of brake fluid passing through the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 gradually increases. As a result, brake fluid can flow out of the first hydraulic circuit 611 and the second hydraulic circuit 612. After that, the braking control device 100 terminates this processing routine.

[0083] In this embodiment, steps S103, S104, and S105 correspond to the pressure release process. The pressure release process can be performed by opening the release valve 57. In other words, it is sufficient to perform the process in step S104, and it is not essential to perform the processes in steps S103 and S105.

[0084] <Assistance> The braking control device 100 can perform an assisting process. The assisting process is a process that adjusts the WC pressure Pwc when an abnormality occurs in the electric cylinder 51. Specifically, in the assisting process, the WC pressure Pwc is adjusted by supplying brake fluid from the reservoir tank 24 to the wheel cylinder 11 via the release passage 56, which opens the release valve 57, by controlling the hydraulic circuits 611 and 612 of the second braking unit 23.

[0085] An example of assistance processing is explained using Figure 4. Figure 4 shows the processing flow when performing assistance processing. This processing routine is executed repeatedly, for example, at predetermined intervals. When this processing routine is started, in step S201, the braking control device 100 first determines whether or not a braking operation has occurred. For example, the braking control device 100 can determine that a braking operation has occurred if the target WC pressure is greater than "0".

[0086] In step S201, if there is no braking operation (S201:NO), the braking control device 100 terminates this processing routine. On the other hand, if there is a braking operation (S201:YES), the braking control device 100 proceeds to step S202.

[0087] In step S202, the braking control device 100 determines whether or not flag F1 is set to ON. If flag F1 is OFF, i.e., if the electric cylinder 51 is functioning normally (S202: NO), the braking control device 100 proceeds to step S203.

[0088] In step S203, the braking control device 100 performs normal braking control. That is, the braking control device 100 adjusts the WC pressure Pwc by operating the first braking unit 50 and the second braking unit 23 so that the sum of the first braking pressure P1 and the second braking pressure P2 satisfies the target WC pressure. After that, the braking control device 100 terminates this processing routine.

[0089] On the other hand, if flag F1 is ON during the processing of step S202, that is, if an abnormality has occurred in the electric cylinder 51 (S202: YES), the braking control device 100 proceeds to step S204.

[0090] In step S204, the braking control device 100 causes the first control unit 101 to open the release valve 57. That is, it connects the reservoir tank 24 and the second braking unit 23 via the release passage 56. After that, the braking control device 100 proceeds to step S205.

[0091] In step S205, the braking control device 100 instructs the second control unit 102 to activate the second braking unit 23 to adjust the WC pressure Pwc in response to a braking request. As a result, braking force is generated by the activation of the second braking unit 23. After that, the braking control device 100 terminates this processing routine.

[0092] <Mechanism and Effects> The operation and effects of this embodiment will now be described. According to the braking device 20, if an abnormality occurs in the electric cylinder 51, a flow path for brake fluid can be formed between the reservoir tank 24 and the wheel cylinder 11 via the release passage 56 through which the release valve 57 is opened. As a result, even if an abnormality occurs in the electric cylinder 51, the WC pressure Pwc can be reduced through the release passage 56 through which the release valve 57 is opened and the master chamber Rm.

[0093] First, let's explain the wheel cylinder 11 for the rear wheels (RL and RR). By opening the release valve 57, brake fluid from the sixth passage 58 and the fifth passage 55 can 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. As a result, brake fluid can flow from the wheel cylinders 11 for the rear wheels RL and RR, which are connected to the second hydraulic circuit 612, into the reservoir tank 24 via the sixth passage 58, the release passage 56, and the fourth passage 54. In this way, the braking device 20 can reduce the WC pressure Pwc of the rear wheels RL and RR.

[0094] Next, we will explain the wheel cylinder 11 for the front wheels FL and FR. When the release valve 57 is opened, the brake fluid in the fifth passage 55 can flow into the reservoir tank 24 via the sixth passage 58, the release passage 56, and the fourth passage 54. As a result, the brake fluid in the servo chamber Rs can flow out into the fifth passage 55. The decrease in the hydraulic pressure in the servo chamber Rs allows the master piston 43 to move backward. This allows brake fluid to flow into the reservoir tank 24 from the wheel cylinders 11 for the front wheels FL and FR, which are connected to the first hydraulic circuit 611, via the first passage 331 and the master chamber Rm. In this way, the braking device 20 can reduce the WC pressure Pwc of the front wheels FL and FR.

[0095] Before executing the process of opening the release valve 57 (S104), the braking control device 100 closes the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 (S103). After that, it opens the release valve 57, and then opens the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 (S105).

[0096] If the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 are open when the electric cylinder 51 malfunctions, opening the release valve 57 may cause the following problems: Specifically, brake fluid that has remained between the electric cylinder 51 and the wheel cylinder 11 without being released due to the malfunction of the electric cylinder 51 may rapidly flow into the reservoir tank 24. As a result, for example, a decrease in deceleration or pedal shock may occur, potentially causing discomfort to the driver.

[0097] In contrast, with the braking device 20 equipped with the braking control device 100, the opening of the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 can be gradually increased after opening the release valve 57. This first reduces the hydraulic pressure in the liquid chamber Re, and then reduces the hydraulic pressure between the first differential pressure regulating valve 621 and the second differential pressure regulating valve 622 and the wheel cylinder 11. 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 opening the release valve 57.

[0098] According to the braking device 20, if an abnormality occurs in the electric cylinder 51, the WC pressure Pwc can be adjusted by an assisting process to generate braking force. In the assisting process, the release valve 57 is opened while the second braking unit 23 is activated. 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. Brake fluid can also be supplied from the reservoir tank 24 to the wheel cylinder 11 connected to the second hydraulic circuit 612 via the release passage 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 rapidly increased. Brake fluid can also 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. Brake fluid can also be discharged from the wheel cylinder 11 connected to the second hydraulic circuit 612 to the reservoir tank 24 via the release passage 56. Therefore, it is also possible to reduce the WC pressure Pwc.

[0099] (Example of change) This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0100] The braking control device 100 and other processing circuits, which are processing circuits, may have any of the following configurations: [a] A circuit comprising one or more processors that perform various processes according to a computer program. The processor comprises a processing unit. Examples of processing units include a CPU, DSP, and GPU. The processor comprises memory. Examples of memory include RAM, ROM, and flash memory. The memory stores program code or instructions configured to cause the processing unit to perform the processes. Memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or dedicated computer. [b] A circuit comprising one or more hardware circuits that perform various processes. Examples of hardware circuits include an ASIC (Application Specific Integrated Circuit), a CPLD (Complex Programmable Logic Device), and an FPGA (Field Programmable Gate Array). [c] A circuit comprising a processor that performs a part of the various processes according to a computer program, and hardware circuits that perform the remaining parts of the various processes.

[0101] The braking control device 100 may also be configured to reduce the WC pressure Pwc by opening the release valve 57 during the pressure release process, and then close the release valve 57. Furthermore, if the configuration to close the release valve 57 is adopted as described above, the release valve 57 is opened again in step S204 of the assisting process. On the other hand, if the configuration to close the release valve 57 is not adopted, it is preferable to leave the release valve 57 open in step S204 without operating the release valve 57.

[0102] Furthermore, when the electric cylinder 51 and the second braking unit 23 are not operated together, and braking force is generated by mechanically moving the master piston 43 forward and backward by operating the braking operating member 21, it is preferable to keep the release valve 57 open at least while operating the braking operating member 21.

[0103] Furthermore, the braking 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 during the pressure release process. For example, the braking control device 100 may, at the same time as opening the release valve 57 during the pressure release process, control the differential pressure regulating valves 621 and 622 so that the rate of decrease of the WC pressure Pwc is lower than that of the differential pressure regulating valves 621 and 622 when they are open. Alternatively, the braking control device 100 may, after opening the release valve 57 during the pressure release process, control the differential pressure regulating valves 621 and 622 so that the rate of decrease of the WC pressure Pwc is lower than that of the differential pressure regulating valves 621 and 622 when they are open. The state in which the differential pressure regulating valves 621 and 622 are open is, for example, the state in which the differential pressure regulating valves 621 and 622 are fully open. The braking control device 100 may also be configured to close the differential pressure regulating valves 621 and 622 while the release valve 57 is open during the pressure release process.

[0104] The braking control device 100 may close the release valve 57 after releasing the braking force applied by the assisting process. For example, after the process in step S205, if the braking request has been released and the WC pressure Pwc has decreased, the release valve 57 can be closed.

[0105] The braking control device 100 may perform the pressure release process when it is determined that an abnormality has occurred in the electric cylinder 51 and the braking operating member 21 is being operated by the driver.

[0106] The braking control device 100 does not need to perform assistive processing. If assistive processing is not performed, after the pressure release processing is performed, a braking force corresponding to the driver's operation is generated, for example, as follows: The driver's operating force on the braking operating member 21 is transmitted to the master piston 43 via the input piston 44 and the second fluid chamber R2, thereby generating a braking force corresponding to the driver's operation by the braking mechanism 10 of the front wheels FL and FR. Alternatively, the driver's operating force on the braking operating member 21 is transmitted directly from the input piston 44 to the master piston 43, thereby generating a braking force corresponding to the driver's operation by the braking mechanism 10 of the front wheels FL and FR.

[0107] The braking control device 100 may perform assisting processing after the pressure release processing, or it may perform assisting processing simultaneously with the pressure release processing, or delayed from the pressure release processing so as to overlap with the pressure release processing. When performing assisting processing as described above, the differential pressure regulating valves 621 and 622 may operate according to the control of the assisting processing without performing valve closing and control due to the pressure release processing. Alternatively, the differential pressure regulating valves 621 and 622 may operate according to the control of the assisting processing after partially performing valve closing and control due to the pressure release processing.

[0108] In the above embodiment, a braking control device 100 comprising a first control unit 101 and a second control unit 102 was illustrated. That is, an example was shown in which the master device 30, the first braking unit 50, and the second braking unit 23 are controlled by a single braking control device 100. As the braking control device included in the braking device, a braking control device comprising a first control device having a function corresponding to the first control unit 101 and a second control device which is a separate control device from the first control device and has a function corresponding to the second control unit 102 may be adopted.

[0109] Figure 5 illustrates a braking control system 200 comprising a first control unit 210 and a second control unit 220. The first control unit 210 includes a first control unit 101 as a functional unit. The first control unit 210 may also include an abnormality detection unit 103 as a functional unit. The second control unit 220 includes a second control unit 102 as a functional unit. The first control unit 210 and the second control unit 220 can communicate with each other, for example, via an in-vehicle network. The first control unit 210 and the second control unit 220 may be connected by signal lines to enable them to communicate with each other. [Explanation of symbols]

[0110] 10...braking mechanism 11... Wheel cylinder 12… Rotating plate 13...Friction material 20…braking device 21... Braking operating member 22...Hydraulic pressure generator 23...Second braking section 24... Reservoir Tank 30…Master device 31…Master cylinder 43...Master Piston 50...1st braking section 51…Electric Cylinder 511...Cylinder 512... Piston 513...First electric motor 515…Input port 516…Output port 517... Through hole 54…Fourth channel 55…5th channel 56…Release channel 57…Release valve 58…6th channel 611...First hydraulic circuit 612...Second hydraulic 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 section

Claims

1. A braking system comprising: a reservoir tank for storing brake fluid; a braking unit capable of applying braking force to the vehicle's wheels by adjusting the fluid pressure in the wheel cylinder using brake fluid supplied from the reservoir tank; and a braking control device for controlling the braking unit, The braking unit is, An electric cylinder having a cylinder, a piston, and an electric motor, wherein an output port is formed in the cylinder that can supply brake fluid to the wheel cylinder by the piston moving in response to the drive of the electric motor, A release channel is configured to connect the liquid chamber in the electric cylinder, in which the output port is open, and the reservoir tank, The system comprises a release valve, which is a normally closed solenoid valve, located in the aforementioned release passage, The aforementioned braking control device is An abnormality determination process for determining whether or not an abnormality has occurred in the electric cylinder, A braking device that performs a pressure release process to open the release valve when it is determined that an abnormality has occurred in the electric cylinder.

2. A master cylinder having a master piston and a fluid chamber partitioned by the master piston, wherein the master piston moves in response to the operation of a braking operating member by the vehicle driver, and the master cylinder is capable of supplying brake fluid to the wheel cylinder, The system includes a fluid chamber, which is a servo chamber located on the opposite side of the master chamber (the fluid chamber connected to the wheel cylinder) among the fluid chambers partitioned by the master piston, and a flow path connecting the servo chamber to the output port of the electric cylinder, The master cylinder is configured such that the master piston moves in a direction that reduces the volume of the master chamber in response to the supply of brake fluid to the servo chamber. The braking device according to claim 1.

3. When the braking unit is designated as the first braking unit and the electric motor as the first electric motor, The system can apply braking force to the wheel by adjusting the hydraulic pressure within the wheel cylinder, and further comprises a second braking unit interposed between the first braking unit and the wheel cylinder. The second braking unit is, It has a second electric motor as a power source and a hydraulic circuit connected to the wheel cylinder, The system includes a differential pressure regulating valve, which is a normally open solenoid valve, positioned between the flow path connecting the first braking unit and the hydraulic circuit, The braking control device can control the second braking unit, and when the release valve is opened by the pressure release process, it controls the differential pressure regulating valve so that the rate of decrease in the hydraulic pressure inside the wheel cylinder is lower than when the differential pressure regulating valve is open. The braking device according to claim 1 or 2.

4. The aforementioned braking control device is When a braking operation is detected in the aforementioned electric cylinder, By controlling the hydraulic circuit, an assisting process is performed to adjust the hydraulic pressure inside the wheel cylinder by supplying brake fluid from the reservoir tank to the wheel cylinder through the release passage, which opens the release valve. The braking device according to claim 3.

5. 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.

6. The braking device according to claim 3, wherein the braking control device closes the differential pressure adjustment valve while the release valve is open due to the pressure release process.

7. The braking device according to claim 1, wherein the pressure release process is performed when it is determined that an abnormality has occurred in the electric cylinder and the braking operating member is operated by the driver.

8. A master cylinder having a master piston and a fluid chamber partitioned by the master piston, wherein the master piston moves in response to the operation of a braking operating member by the vehicle driver, and the master cylinder is capable of supplying brake fluid to the wheel cylinder, The system includes a fluid chamber, which is a servo chamber located on the opposite side of the master chamber (the fluid chamber connected to the wheel cylinder) among the fluid chambers partitioned by the master piston, and a flow path connecting the servo chamber to the output port of the electric cylinder, The braking device 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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