JP2007326381A - Brake fluid pressure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake fluid pressure device enabling smooth restart by removing residual pressure when a pressure reducing valve fails. <P>SOLUTION: A wheel cylinder comprises two first wheel cylinders capable of intensifying pressure by a hydraulic actuator and a master cylinder and two second wheel cylinders capable of intensifying pressure only by the hydraulic actuator. The first wheel cylinder is directly connected to the master cylinder via a change-over valve. The brake fluid pressure device is provided with a forcedly pressure reducing means for discharging working fluid inside the second wheel cylinder in the side suffering communication failure out of the two second wheel cylinders to a reservoir without using the pressure reducing valve in the side suffering the communication failure out of the pressure reducing valves when the communication failure occurs in either one of the pressure reducing valves connected to the second wheel cylinders. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a brake control device that obtains a braking force by controlling a hydraulic pressure in a wheel cylinder.

Conventionally, the brake pedal and the wheel cylinder are disconnected, the target wheel cylinder pressure is calculated based on the detection values of the stroke sensor and the master cylinder pressure sensor, and the motor and solenoid valve connected to the pump are driven based on the target wheel cylinder pressure. A technique for obtaining a desired wheel cylinder pressure by using a so-called brake-by-wire system is disclosed. (For example, refer to Patent Document 1). In this technique, the failure location of the device is detected and notified to the driver.
JP 11-59389 A

  However, in the above-described prior art, the failure point is simply detected and notified to the driver, and the wheel cylinder residual pressure is not removed when the vehicle restarts after the failure occurs. For this reason, when the pressure reducing valve is closed, the wheel cylinder that performs pressure reduction only by the pressure reducing valve cannot release the braking force, which makes it difficult to restart.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a brake fluid pressure device that can remove a residual pressure even when a pressure reducing valve breaks down, thereby enabling a smooth restart. There is.

  In order to achieve the above object, according to the present invention, a master cylinder, a wheel cylinder provided in each wheel of the vehicle, a hydraulic actuator provided separately from the master cylinder and controlling the hydraulic pressure of the wheel cylinder, and a driver Control means for controlling the hydraulic actuator on the basis of the brake operation amount, a pressure increasing valve that is provided between the hydraulic actuator and the wheel cylinder, and controls the pressure increase of the wheel cylinder, and the wheel cylinder and the reservoir. A brake hydraulic pressure device provided between and a pressure reducing valve for pressure-reducing control of the wheel cylinder, wherein the wheel cylinder includes a first wheel cylinder capable of increasing pressure by the hydraulic actuator and the master cylinder; A second wheel cylinder that can be pressurized only by the hydraulic actuator. Each of the first and second wheel cylinders is provided with two wheels, and the first wheel cylinder is directly connected to the master cylinder via a switching valve and is connected to the second wheel cylinder. When a communication failure occurs in any one of the second wheel cylinders, the hydraulic oil in the wheel cylinder on the side where the communication failure occurs is passed through the pressure reducing valve on the side where the communication failure occurs among the pressure reducing valves. Instead, a forced pressure reducing means for discharging to the reservoir is provided.

  Therefore, it is possible to provide a brake hydraulic device that removes the residual pressure even when the pressure reducing valve breaks down and enables a smooth restart.

  Hereinafter, the best mode for carrying out the brake fluid pressure device of the present invention will be described based on the embodiments shown in the drawings.

  FIG. 1 shows a hydraulic circuit of a brake fluid pressure device. The brake fluid pressure device has a so-called tandem type master cylinder M / C, and is connected to FL and FR wheel cylinders W / C (FL, FR) by manual circuits A1, A2. The master cylinder M / C is connected to the reservoir RSV. Each electromagnetic valve is an ON / OFF valve and is driven by the control unit CU.

  On the manual circuits A1 and A2, a shut-off valve S.I. OFF / V (FL, FR) is provided to communicate / block the first and second master cylinders M / C1, M / C2 and the FL, FR wheel cylinders W / C (FL, FR), respectively.

  On the manual circuit A1, the first master cylinder M / C1 and the shutoff valve S.I. A stroke simulator S / Sim is provided between OFF / V (FL). This stroke simulator S / Sim is connected to the manual circuit A1 via a stroke simulator switching valve Sel / V which is a normally closed solenoid valve.

  FL shut-off valve When OFF / V (FL) is closed and the stroke simulator switching valve Sel / V is opened, the hydraulic oil in the first master cylinder M / C1 is moved to the stroke simulator S / when the brake pedal BP is depressed. Introduced into Sim to ensure pedal stroke.

  The pump P is driven by the motor M, and the discharge pressure is accumulated in the accumulator ACC. The discharge side of the pump P and the accumulator ACC are connected to the pressure increasing circuit C, and are connected to each wheel cylinder W / C (FL to RR) at the connection point I (FL to RR). On the other hand, the suction side of the pump P is connected to the pressure reducing circuit B.

  The pressure increasing circuit C is provided with a pressure increasing valve IN / V (FL to RR), which is a normally closed electromagnetic valve, for communicating / blocking the accumulator ACC and the pump P with each wheel cylinder W / C (FL to RR). Switch.

  Each wheel cylinder W / C (FL to RR) is connected to the decompression circuit B at the connection point I (FL to RR). On this pressure reducing circuit B, a pressure reducing valve OUT / V (FL to RR), which is a normally closed electromagnetic valve, is provided to switch communication / blocking between each wheel cylinder W / C (FL to RR) and the reservoir RSV.

  Check valves C / V are provided on the suction side and the discharge side of the pump P, respectively, to prevent the hydraulic fluid from flowing backward from the pressure increasing circuit C to the pressure reducing circuit B via the pump P. Further, the pressure increasing circuit C and the pressure reducing circuit B are connected via a relief valve Ref / V, and when the pressure in the pressure increasing circuit C becomes equal to or higher than a specified value, hydraulic oil is released to the pressure reducing circuit B.

  On the manual circuits A1 and A2, the shutoff valve S.I. Between the OFF / V (FL, FR) and the master cylinder M / C, first and second master cylinder pressure sensors MC / Sen 1 and 2 are provided, respectively, and each wheel cylinder W / C (FL to RR). Is provided with a wheel cylinder pressure sensor WC / Sen (FL to RR).

  The detected first and second master cylinder pressures Pm1 and Pm2, the wheel cylinder pressures P (FL to RR), and the detected value of the stroke sensor S / Sen that detects the stroke of the brake pedal BP are input to the control unit CU. Is done.

  Based on these detected values, the control unit CU calculates the target wheel cylinder pressure P * (FL to RR) of each wheel FL to RR, and the pump P and pressure increase, pressure reducing valves IN / V (FL to RR, OUT / V (FL to RR) is driven, and during normal braking, the shut-off valve S.OFF/V (FL, FR) is closed and the stroke simulator switching valve Sel / V is opened.

  Further, the control unit CU compares the target hydraulic pressure P * (FL to RR) and the actual hydraulic pressure P (FL to RR) of each wheel cylinder W / C (FL to RR) to When the hydraulic pressure shows an abnormal response, an abnormal signal is output to the warning lamp WL. In addition, the wheel speed VSP is input to the control unit CU to determine whether the vehicle is running / stopped.

[Brake control]
(Normal pressure increase: Electric pressure increase mode)
During normal pressure increase (electric pressure increase mode), the stroke simulator switching valve Sel / V is opened and the shutoff valve S.I. OFF / V (FL, FR) is cut off, and the depression of the brake pedal BP by the driver is detected by the stroke sensor S / Sen, and each wheel cylinder W / C (FL to RR) is detected in the control unit CU based on the detected value. Target hydraulic pressure P * (FL to RR) is calculated.

  Further, the control unit CU drives the pump P by the motor M to accumulate pressure in the accumulator ACC, and causes the constant pressure of the accumulator ACC to act on the pressure increasing circuit C. Further, each pressure increasing valve IN / V (FL to RR) is driven according to the calculated target hydraulic pressure P * (FL to RR), and hydraulic oil is supplied to each wheel cylinder W / C (FL to RR). Get braking force.

(Decompression mode)
At the time of depressurization, each pressure reducing valve OUT / V (FL to RR) is driven by the control unit CU, and the hydraulic oil is discharged from each wheel cylinder W / C (FL to RR) to the reservoir RSV via the pressure reducing circuit B. .

(Retention mode)
At the time of holding, each pressure increasing valve IN / V (FL to RR) and each pressure reducing valve OUT / V (FL to RR) are closed, each wheel cylinder W / C (FL to RR) and pressure increasing, pressure reducing circuit C , B are cut off.

(Manual mode)
When the system fails, etc., the normally open shutoff valve OFF / V (FL, FR) is opened, and normally closed pressure increasing valves IN / V (FL to RR) and pressure reducing valves OUT / V (FL to RR) are closed. As a result, the master cylinder M / C communicates with the FL and FR wheel cylinders (FL, FR), and a manual brake is secured.

[Scratch prevention control when pressure reducing valve is closed]
When the pressure reducing valve OUT / V (FL to RR) is fixedly closed, hydraulic oil cannot be discharged from each wheel cylinder W / C to the reservoir RSV via the pressure reducing valve OUT / V (FL to RR). Residual pressure is generated in the cylinder W / C.

  Since the FL and FR wheel cylinders W / C (FL, FR) are connected to the master cylinder M / C via the manual circuits A1 and A2, the shut-off valve S.F. The residual pressure can be discharged to the master cylinder M / C by opening OFF / V (FL, FR), but the RL and RR wheels are only activated by opening the pressure reducing valve OUT / V (RL, RR). Since the oil can be discharged, the residual pressure of the RL and RR wheels cannot be released and the brake is dragged.

  Therefore, when the driver re-starts after stopping the vehicle based on the warning accompanying the failure of the pressure reducing valve OUT / V, there is a possibility that the driver may feel uncomfortable due to the drag of the brake.

  Therefore, in the first embodiment of the present application, when it is determined that at least one of the RL and RR wheel pressure reducing valves OUT / V (RL, RR) is fixedly closed, the pressure reducing valve which is fixedly closed after issuing a warning to the driver. The residual pressure is discharged via the other pressure reducing valve OUT / V and the pressure increasing valve IN / V without going through OUT / V.

  Specifically, when the RR wheel pressure reducing valve OUT / V (RR) is fixedly closed, the RR wheel pressure increasing valve IN / V (RR) → RL wheel pressure increasing valve IN / V (RL) → RL wheel pressure reducing valve OUT / The residual pressure in the RR wheel wheel cylinder W / C is discharged to the pressure reducing circuit B via V (RL). When the RL wheel pressure reducing valve OUT / V (RL) is fixed, the same is true except that RL and RR are reversed.

  Therefore, even if the driver restarts after stopping the vehicle based on the warning, the residual pressure is discharged through the normal side of the RL and RR wheel pressure reducing valves OUT / V (RL, RR). Prevent brake dragging.

[Scratch prevention control process when RR wheel pressure reducing valve is closed]
FIG. 2 is a flowchart showing the flow of the brake drag prevention control process when the RR wheel pressure reducing valve OUT / V (RR) is fixedly closed. The same applies to the RL wheel. Hereinafter, description will be given based on each step.

  In step S101, the ignition is turned on, and the process proceeds to step S102.

  In step S102, braking by the driver is started, and the process proceeds to step S103.

  In step S103, the electric pressure increasing mode is executed, and the process proceeds to step S104.

  In step S104, it is determined whether or not braking by the driver is finished. If YES, the process proceeds to step S015, and if NO, the determination is repeated until braking by the driver is finished.

  In step S105, the RL and RR wheel pressure reducing valves OUT / V (RL, RR) are opened, and the process proceeds to step S106.

  In step S106, it is determined whether or not the RR wheel actual wheel cylinder pressure P (RR) is substantially zero. If YES, the control is terminated, and if NO, the process proceeds to step S107.

  In step S107, it is determined that the RR wheel pressure reducing valve OUT / V (RR) has failed, the warning lamp WL is turned on, and the process proceeds to step S108.

  In step S108, it is determined whether or not the vehicle is stopped based on the wheel speed VSP. If YES, the process proceeds to step S109. If NO, stop determination is repeated until the vehicle stops.

  In step S109, the mode is switched to the manual mode, and the process proceeds to step S110.

  In step S110, the RL wheel pressure increase, pressure reducing valves IN / V (RL), OUT / V (RL) are opened, the accumulator pressure Pacc is discharged to the reservoir RSV, and the process proceeds to step S111.

  In step S111, it is determined whether or not the accumulator pressure Pacc ≦ RR wheel actual wheel cylinder pressure P (RR). If YES, the process proceeds to step S112, and if NO, the process returns to step S110.

  In step S112, the RR wheel pressure increasing valve IN / V (RR) is opened, and the residual pressure in the RR wheel wheel cylinder W / C (RR) is increased to the RL wheel pressure increasing and pressure reducing valves IN / V (RL), OUT / V. (RL) is discharged to the reservoir RSV and the process proceeds to step S113.

  In step S113, it is determined whether or not the RR wheel actual wheel cylinder pressure P (RR) is approximately zero. If YES, the control is terminated, and if NO, the process returns to step S112.

[Effect of Example 1]
(1) The master cylinder M / C, the wheel cylinders W / C (FL to RR) provided on the vehicle wheels FL to RR, and the master cylinder M / C are provided separately, and the wheel cylinders W / C (FL To RR) provided between the pump P for controlling the hydraulic pressure, the control unit CU for controlling the pump P based on the brake operation amount of the driver, and the wheel cylinder W / C (FL to RR). And a pressure increasing valve IN / V (FL to RR) for increasing the pressure of the wheel cylinder W / C (FL to RR), and a wheel provided between the wheel cylinder W / C (FL to RR) and the reservoir RSV. A brake hydraulic pressure device including a pressure reducing valve OUT / V (FL to RR) for pressure reducing control of the cylinder W / C (FL to RR), wherein the wheel cylinder W / C (FL to RR) is a pump P And mastercilin A first wheel cylinder (front wheel wheel cylinder W / C (FL, FR)) that can be pressurized by M / C and a second wheel cylinder (rear wheel wheel cylinder W / C ( RL, RR)), and each of the first and second wheel cylinders is provided with two wheels, and the front wheel cylinder W / C (FL, FR) is provided with a shut-off valve S.R. Directly connected to the master cylinder M / C via OFF / V (FL, FR) and connected to one of the pressure reducing valves OUT / V (RL, RR) connected to the rear wheel cylinder W / C (RL, RR) When the communication failure occurs, the hydraulic oil in the wheel cylinder W / C on the side of the rear wheel wheel cylinder W / C (RL, RR) where the communication failure has occurred is reduced to the pressure reducing valve OUT / V (RL, RR). Among them, a forced pressure reducing means for discharging to the reservoir RSV is provided without passing through the pressure reducing valve OUT / V (RL, RR) on the side where the communication failure occurs.

  As a result, after issuing a warning to the driver, it is possible to discharge the residual pressure via the other pressure reducing valve OUT / V and the pressure increasing valve IN / V without going through the pressure reducing valve OUT / V that is fixedly closed. Even when the driver restarts after stopping the vehicle based on the warning, it is possible to prevent the brake from being dragged.

  Also, even in situations where braking force is required while discharging residual pressure, such as on slopes, the front wheels FL and FR are in manual mode, so residual pressure is discharged while ensuring braking force. It can be performed.

  (2) The forced pressure reducing means supplies the hydraulic oil in the wheel cylinder W / C on the side of the rear wheel wheel cylinder W / C (RL, RR) where the communication failure has occurred to the pressure reducing valve OUT / V (RL, RR). ) On the side where the poor communication occurs, and the booster valves IN / V (RL, RR) and the decompression valves OUT / V (RL, RR) on the side where no poor communication occurs. ) To the reservoir RSV.

  Thereby, since the residual pressure can be eliminated only by the control in the control unit CU, dragging can be prevented without adding other components.

  A second embodiment will be described with reference to FIGS. 3 and 4. The basic configuration is the same as that of the first embodiment. In the first embodiment, the residual pressure is discharged through the pressure increasing valve IN / V connected to the wheel to which the pressure reducing valve OUT / V is fixedly closed, but in the second embodiment, the rear wheel pressure increasing valves IN / V (RL, RR) and A difference is that a check valve C / V (RL, RR) is provided in parallel, and the residual pressure is discharged through the check valve C / V (RL, RR).

[Hydraulic circuit of Example 2]
FIG. 3 is a hydraulic circuit diagram according to the second embodiment. A check valve C / V (RL, RR) that allows only the flow from the pressure increasing circuit C to the rear wheel wheel cylinder W / C (RL, RR) side in parallel with the rear wheel pressure increasing valve IN / V (RL, RR). ) Is provided.

  When either one of the RL and RR wheel pressure reducing valves OUT / V (RL, RR) is fixedly closed, the remaining in the wheel cylinder W / C on the side fixed via this check valve C / V (RL, RR) The pressure is introduced into the pressure-increasing circuit C and discharged to the pressure-reducing circuit B through pressure-increasing and pressure-reducing valves IN / V and OUT / V on the side where no sticking occurs.

[RR wheel drag prevention control processing in embodiment 2]
FIG. 4 is a flowchart illustrating the flow of the RR wheel drag prevention control process according to the second embodiment. Steps S201 to S209 are the same as steps S101 to S109 in the first embodiment.

  In step S210, the RL wheel pressure increasing and pressure reducing valves IN / V (RL) and OUT / V (RL) are opened, the accumulator pressure Pacc is discharged to the reservoir RSV, and the control is terminated.

[Effect of Example 2]
(3) The forced pressure reducing means uses the hydraulic oil in the wheel cylinder W / C on the side of the rear wheel cylinder W / C (RL, RR) where the communication failure has occurred, as a pressure reducing valve OUT / V (RL, RR). ) Of the pressure-increasing valve IN / V (RL, RR) on the side where the poor communication occurs and the one-way valve C / V (RL, RR) provided in parallel with the pressure-increasing valve IN / V (RL, RR) on the side where the poor communication occurs / V (RL, RR) and means for discharging to the reservoir RSV via the pressure reducing valve OUT / V (RL, RR).

  As a result, even when the pressure increasing valve IN / V and the pressure reducing valve OUT / V cause a communication failure at the same time in one of the RL and RR wheels, the residual pressure is surely discharged to prevent dragging at the time of restart. be able to.

  Example 3 will be described with reference to FIG. The basic configuration is the same as that of the first embodiment. In the third embodiment, the wheel cylinder W / C pressure in which the residual pressure Pr is generated is detected from the RL and RR wheels, and the target wheel cylinder pressure P * on the side where no residual pressure is generated is set to the residual pressure Pr.

  Thus, by making the wheel cylinder pressure on the side where the residual pressure Pr is generated equal to the wheel cylinder pressure on which the residual pressure Pr is not generated, the braking force of the left and right rear wheels RL and RR is made equal to stabilize the vehicle behavior.

  In particular, when the pressure reducing valve OUT / V is stuck closed during traveling, the braking force remains generated on one of the left and right rear wheels, and the braking operation until the vehicle stops is worsened. In this case, braking is performed without deteriorating the vehicle behavior by equalizing the braking forces of the left and right rear wheels RL and RR.

[RR wheel drag prevention control processing in Embodiment 3]
FIG. 5 is a flowchart illustrating the flow of the RR wheel drag prevention control process according to the third embodiment.

  Steps S301 to S307 are the same as steps S101 to S107 of the first embodiment.

  In step S308, it is determined whether the vehicle is stopped based on the wheel speed VSP. If YES, the process proceeds to step S309, and if NO, the process proceeds to step S314.

  Steps S309 to S313 are the same as steps S109 to S113 of the first embodiment.

  In step S314, RR wheel actual wheel cylinder pressure P (RR) is detected, and the process proceeds to step S315.

  In step S315, RL wheel target wheel cylinder pressure P * (RL) = RR wheel actual wheel cylinder pressure P (RR) is set, and the process proceeds to step S316.

  In step S316, it is determined whether or not the vehicle is stopped. If YES, the process proceeds to step S309, and if NO, the determination is repeated until the vehicle stops.

[Effect of Example 3]
(4) The control unit CU is connected to the rear wheel wheel cylinder W / C (RL, RR) when the communication failure occurs in any of the pressure reducing valves OUT / V (RL, RR). The rear wheel wheel cylinder W / C pressure was detected, and this detected value was set as the target hydraulic pressure of the rear wheel wheel cylinder W / C on the side where no communication failure occurred.

  Accordingly, by making the wheel cylinder pressures on the side where the residual pressure is generated and the side where the residual pressure is not generated equivalent, the braking force of the left and right rear wheels RL and RR can be made equivalent and the vehicle behavior can be stabilized. In particular, when the pressure-reducing valve OUT / V is stuck closed during traveling, the braking force remains generated on one of the left and right rear wheels, and the braking operation until the vehicle stops is worsened. By making the braking forces of the left and right rear wheels RL and RR equal, the operational effect of the third embodiment that performs braking without deteriorating the vehicle behavior is more effective.

(Other examples)
As mentioned above, although the brake hydraulic device of the present invention has been described based on the embodiments, the specific configuration is not limited to the embodiments, and departs from the gist of the invention according to each claim of the claims. Unless otherwise, design changes and additions are permitted.

1 is a hydraulic circuit of a brake fluid pressure device according to a first embodiment. It is a flowchart which shows the flow of the brake drag prevention control process at the time of the RR wheel pressure reducing valve of Example 1 adhering to valve closing. FIG. 3 is a hydraulic circuit diagram according to a second embodiment. 12 is a flowchart illustrating a flow of RR wheel drag prevention control processing in the second embodiment. 12 is a flowchart illustrating a flow of RR wheel drag prevention control processing in the third embodiment.

Explanation of symbols

A1, A2 Manual circuit ACC Accumulator B Pressure reducing circuit BP Brake pedal C Pressure increasing circuit C / V Check valve C / V (RL, RR) One-way valve CU Control unit FL to RR Wheel I (FL to RR) Connection point IN / V (FL to RR) Booster valve M Motor M / C Master cylinder M / C1 Master cylinder M / C1, M / C2 First, second master cylinder MC / Sen1, 2, First, second master cylinder pressure sensor OUT / V (FL to RR) Pressure reducing valve P Pump Ref / V Relief valve RSV Reservoir OFF / V (FL to RR) Shut-off valve S / Sen Stroke sensor S / Sim Stroke simulator Sel / V Stroke simulator switching valve W / C (FL to RR) Wheel cylinder WC / Sen (FL to RR) Wheel cylinder pressure sensor WL warning lamp

Claims (4)

A master cylinder,
A wheel cylinder provided on each vehicle wheel;
A hydraulic actuator that is provided separately from the master cylinder and controls the hydraulic pressure of the wheel cylinder;
Control means for controlling the hydraulic actuator based on the brake operation amount of the driver;
A pressure increasing valve provided between the hydraulic actuator and the wheel cylinder for controlling pressure increase of the wheel cylinder;
A pressure reducing valve provided between the wheel cylinder and the reservoir for controlling the pressure reduction of the wheel cylinder;
A brake hydraulic device comprising:
The wheel cylinder has a first wheel cylinder that can be increased by the hydraulic actuator and the master cylinder, and a second wheel cylinder that can be increased only by the hydraulic actuator,
Each of the first and second wheel cylinders is provided with two wheels,
The first wheel cylinder is directly connected to the master cylinder via a switching valve;
When a communication failure occurs in any of the pressure reducing valves connected to the second wheel cylinder, the hydraulic oil in the wheel cylinder on the side of the second wheel cylinder where the communication failure occurs is supplied to the pressure reducing valve. A brake fluid pressure device comprising a forced pressure reducing means for discharging to the reservoir without passing through a pressure reducing valve on a side where a communication failure has occurred. The brake hydraulic device according to claim 1,
The forced pressure reducing means includes the hydraulic oil in the wheel cylinder on the side where the communication failure has occurred in the second wheel cylinder, the pressure increasing valve on the side where the communication failure of the pressure reducing valve occurs, and the communication failure occurs. A brake fluid pressure device characterized by being a means for discharging to the reservoir via the pressure-increasing valve and the pressure-reducing valve on the non-acting side. The brake hydraulic device according to claim 1,
The forcible pressure reducing means is provided such that the hydraulic oil in the wheel cylinder on the side where the communication failure has occurred in the second wheel cylinder is provided in parallel with the pressure increasing valve on the side where the communication failure of the pressure reducing valve occurs. A brake hydraulic device, characterized by being a means for discharging to a reservoir via a direction valve and the pressure increasing valve and the pressure reducing valve on the side where the communication failure has not occurred. The brake hydraulic device according to any one of claims 1 to 3,
When the communication failure occurs in any of the pressure reducing valves connected to the second wheel cylinder, the control means detects the second wheel cylinder pressure on the side where the communication failure occurs, and this detected value is used as the communication value. A brake fluid pressure control device characterized in that a target fluid pressure of the second wheel cylinder on the side where no defect has occurred is used.

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