JPH07315191A - Brake fluid pressure control device - Google Patents

Abstract

PURPOSE:To minimize a load against a fluid pressure pump without impairing the reliability concerning braking performance. CONSTITUTION:A constantly open first solenoid directional control valve 15 to cut off a first flow passage 3 at the time of traction control and a constantly closed second solenoid directional control valve 13 provided in the middle of a fourth flow passage 12 communicated between a reserver 7 and a master cylinder 1 and to open the fourth flow passage 12 by way of working at the time of traction control are furnished in an upstream side first flow passage 3a between a pressure intensifying valve 5a and the master cylinder 1. Additionally, a relief valve 16 provided in a fifth flow passage 14 communicated between a discharge side of a fluid pressure pump 9 in a third flow passage 8, the second solenoid directional control valve 13 in the fourth flow passage 12 and the reserver 7 and to release fluid pressure in the direction of the fourth flow passage 12 when discharged fluid pressure of the fluid pressure pump 9 exceeds specified fluid pressure and a relief pressure adjustment means 22 to energize relief pressure of the relief valve 16 in a direction to heighten it by receiving braking fluid pressure generated in the master cylinder 1 are furnished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake fluid pressure control device for a vehicle or the like, and more particularly to a device for performing antiskid control and traction control.

[0002]

2. Description of the Related Art Conventionally, as a brake fluid pressure control device for anti-skid control and traction control,
For example, the one described in Japanese Patent Application Laid-Open No. 2-18150 is known.

This conventional brake fluid pressure control device includes a master cylinder for generating a brake fluid pressure by operating a brake pedal and a wheel cylinder for braking a wheel by receiving the brake fluid pressure through a first flow path. And a hydraulic control valve that is provided in the middle of the first flow path and that opens and closes based on predetermined conditions to reduce, maintain, and increase the brake hydraulic pressure input to the wheel cylinders, and a hydraulic control valve. The brake fluid discharged from the wheel cylinder when decompressing the second
A reservoir that stores via a flow path and a hydraulic pump that sucks and pressurizes the brake fluid stored in the reservoir via a third flow path and returns it to the first flow path between the hydraulic control valve and the master cylinder. Is provided in the middle of the fourth flow path that communicates between the reservoir and the liquid storage tank of the master cylinder, and when the brake pedal is operated, it is a normally open type that operates in the direction to close the fourth flow path by receiving the brake fluid pressure. The opening / closing valve and the first flow path between the hydraulic pressure control valve and the master cylinder are activated during traction control to shut off the first flow path, while the discharge side of the hydraulic pump and the liquid storage tank of the master cylinder are connected. The fifth
An electromagnetic switching valve that communicates with each other via a flow passage, and a relief valve that is provided in the middle of the fifth flow passage and that releases the hydraulic pressure toward the liquid storage tank when the discharge hydraulic pressure of the hydraulic pump exceeds a predetermined hydraulic pressure. The structure was equipped with.

That is, in this conventional device, during normal braking in which brake fluid pressure is generated by the operation of the brake pedal, and during anti-skid control, the opening / closing valve is actuated by receiving the brake fluid pressure. By closing the four flow paths and releasing the operation of the electromagnetic switching valve to close the fifth flow path and open the first flow path, the brake fluid pressure is applied to the wheel cylinders via the fluid pressure control valve. When the traction control is performed without operating the brake pedal, the normally open on-off valve keeps the fourth flow path open and the electromagnetic switching valve. Is activated to close the first flow path and open the fifth flow path, so that the hydraulic pump is driven to suck and pressurize from the liquid storage tank of the master cylinder. When the brake fluid pressure can be supplied to the wheel cylinder via the fluid pressure control valve and the fluid pressure discharged from the fluid pressure pump exceeds a predetermined relief pressure, the relief valve of the fifth flow path is opened. The hydraulic pressure was released to the liquid storage tank of the master cylinder.

[0005]

However, in the conventional brake fluid pressure control device, as described above, the first fluid passage between the fluid pressure control valve and the master cylinder is operated during traction control to be the first fluid passage. An electromagnetic switching valve that connects the discharge side of the hydraulic pump and the liquid storage tank of the master cylinder via the fifth flow path while blocking the flow path, and is provided in the middle of the fifth flow path. It is equipped with a relief valve that releases the fluid pressure toward the liquid storage tank when the fluid pressure discharged from the fluid pressure pump exceeds a predetermined fluid pressure. Normally, the relief valve relief pressure minimizes the load on the fluid pressure pump. Since the pressure needs to be set to a value lower than the brake fluid pressure in order to hold it down, the electromagnetic switching valve is in the non-operating state and communicates with the first flow path,
During normal braking with the fifth passage blocked by the relief valve, if the fifth passage is in communication due to a failure of the electromagnetic switching valve, the relief valve opens and the master cylinder There is a problem that the brake fluid pressure generated at 1 is reduced by flowing out toward the liquid storage tank, which may reduce the braking performance of the wheels.

The present invention has been made in view of the above-mentioned conventional problems, and brake hydraulic pressure control capable of suppressing the load on the hydraulic pump to a minimum without impairing the reliability of the braking performance. The purpose is to provide a device.

[0007]

In order to achieve the above object, in a brake fluid pressure control device of the present invention, a brake fluid pressure is generated by operating a brake pedal, and a brake is provided via a first flow path. A wheel cylinder that brakes the wheels by receiving hydraulic pressure and a predetermined condition for reducing, holding, and increasing the brake hydraulic pressure that is provided in the middle of the first passage and is input to the wheel cylinder. A hydraulic pressure control valve that opens and closes based on the hydraulic pressure control valve; a normally open first cut valve that is provided in the first flow passage between the hydraulic pressure control valve and the master cylinder and that operates during traction control to shut off the first flow passage; When the hydraulic pressure control valve is depressurized, the brake fluid discharged from the wheel cylinder is stored through the second flow path, and the brake fluid stored in the reservoir is suctioned and pressurized through the third flow path. First between the control valve and the first cut valve
A normally closed valve that is provided in the middle of the fourth flow path that connects the hydraulic pump that recirculates to the flow path and the reservoir and the liquid storage tank of the master cylinder and that operates during traction control to open the fourth flow path. The second cut valve, the discharge side of the hydraulic pump in the third flow path, and the discharge path of the hydraulic pump provided in the fifth flow path communicating between the second cut valve and the reservoir in the fourth flow path. 4th when the pressure exceeds a predetermined relief pressure
A means provided with a relief valve for releasing hydraulic pressure in the flow path direction and a relief pressure adjusting means for urging in a direction to increase the relief pressure of the relief valve by receiving the brake hydraulic pressure generated in the master cylinder. .

[0008]

Since the brake fluid pressure control apparatus according to the embodiment of the present invention is configured as described above, during the traction control performed in the state where the master cylinder brake fluid pressure is not generated, the first cut valve is energized. By turning on, the flow between the master cylinder and the hydraulic control valve is stopped, while the first pump is driven by the hydraulic pump.
By supplying the hydraulic pressure to the first flow path between the cut valve and the hydraulic pressure control valve, the second cut valve is turned on so that the brake fluid in the liquid storage tank of the master cylinder is changed to the fourth hydraulic fluid.
It is supplied to the hydraulic pump via the flow path.

Therefore, at the time of increasing the pressure of the hydraulic pressure control valve, the hydraulic pressure generated by the hydraulic pressure pump is supplied to the wheel cylinders via the hydraulic pressure control valve, so that there is no brake operation. Regardless of this, the braking force of the wheels is generated, and as a result, the control is performed in the direction in which the rotational speed of the wheels is reduced and the drive slip state is eliminated.

When the discharge hydraulic pressure exceeds a predetermined relief pressure due to the driving of the hydraulic pump, the relief valve operates to open the fifth flow path, and the hydraulic pressure supplied to the hydraulic pressure control valve is changed to the second pressure. The pressure is reduced by letting it escape to the side of the fourth flow path between the cut valve and the reservoir. At this time, in the relief pressure adjusting means, since the brake fluid pressure is not received, the relief pressure of the relief valve is maintained at a predetermined low value, which can minimize the load on the hydraulic pump. it can.

During normal braking, the first cut valve and the second cut valve are de-energized to open the first flow path between the master cylinder and the hydraulic control valve. In addition, the fourth flow path between the reservoir (the suction side of the hydraulic pump) and the liquid storage tank of the master cylinder is closed, and the hydraulic control valve is in the increased pressure state, The generated brake fluid pressure can be supplied to the wheel cylinder via the first flow path.

During the normal braking and the anti-skid control in which the brake fluid pressure is generated in the master cylinder as described above, the relief pressure adjusting means receives the brake fluid pressure so that the relief pressure of the relief valve is reduced. In this state, the relief valve can be maintained in a closed state.

Further, during normal braking and anti-skid control as described above, the second cut valve operates normally even if the fifth flow path is in a communication state due to a failure of the relief valve. The closed circuit is formed as long as it is, and conversely, even when the fourth flow path is in the communication state due to the failure of the second cut valve, the closed circuit is formed as long as the relief valve is normally operating. Therefore, the brake fluid pressure generated in the master cylinder can be maintained, and a sufficient braking force for the wheels can be secured.

As described above, in the brake fluid pressure control device of the present invention, the reliability of the braking performance is not impaired,
The load on the hydraulic pump can be minimized.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is an overall view showing a brake fluid pressure control device according to an embodiment of the present invention, in which reference numeral 1 is a master cylinder.

The master cylinder 1 generates a brake fluid pressure by operating the brake pedal 2. The brake fluid pressure generated in the master cylinder 1 is the first flow passage 3
It is transmitted to the wheel cylinder 4 of the brake device via the, so that the braking of the wheel is performed.

In the middle of the first flow path 3, a normally open pressure increasing valve for controlling (decompressing / holding / increasing) the brake fluid pressure of the wheel cylinder 4 in order to prevent wheel locking. (Hydraulic pressure control valve) 5a is provided, and the downstream side first flow path 3b between the pressure increasing valve 5a and the wheel cylinder 4 and the second flow path 6 communicating with the reservoir 7 are always provided. A closed pressure reducing valve (fluid pressure control valve) 5b is provided.
That is, when the valves 5a and 5b are closed, the hydraulic pressure of the wheel cylinder 4 is held, and when the pressure increasing valve 5a is closed and the pressure reducing valve 5b is opened, the hydraulic pressure of the wheel cylinder 4 is drained to the reservoir 7 and reduced. When the pressure reducing valve 5b is closed and the pressure increasing valve 5a is opened, the brake fluid pressure is supplied to the wheel cylinder 4 to increase the pressure. Both valves 5a and 5b are controlled by the brake controller 17 under predetermined conditions. The switching is controlled based on

In the figure, 20 is a pressure increasing valve 5a.
A return check valve that bypasses the above and permits only the flow from the wheel cylinder 4 to the master cylinder 1 direction is shown.

Next, reference numeral 9 in the drawing denotes a hydraulic pump, which allows the brake fluid stored in the reservoir 7 to pass through the third flow path 8 so as to be upstream between the master cylinder 1 and the pressure increasing valve 5a. And a damper chamber 10 as a pulse pressure damping means in the third flow path 8 on the discharge side.
Is provided. In the figure, 9a and 9b are hydraulic pumps 9.
Are an inlet check valve and an outlet check valve provided on the suction side and the discharge side, respectively.

The third flow path 8 communicating with the reservoir 7 and the liquid storage tank 11 of the master cylinder 1 are connected by a fourth flow path 12, and in the middle of the fourth flow path 12. , 4th channel 1 opened during traction control
No. 2 normally closed in 2 port 2 position with 2 communicating
An electromagnetic switching valve (second cut valve) 13 is provided. That is, the second electromagnetic switching valve 13 is
The fourth flow path 12 is closed, and the fourth flow path is opened when the energization is on.

Further, a first electromagnetic switching valve (first cut valve) 15 that is normally open at the 2-port 2-position is provided upstream of the confluence point P with the third flow passage 8 in the upstream first flow passage 3a. Is provided. That is, the first electromagnetic switching valve 15 is provided with the master cylinder 1 and the pressure increasing valve 5a when the energization is off.
The flow between the master cylinder 1 and the pressure increasing valve 5a is stopped when the energization is on. The first electromagnetic switching valve 15 and the second electromagnetic switching valve 13 are switched and controlled by the brake controller 17 based on predetermined conditions.
In the figure, 21 is a return check valve.

Further, the discharge side of the hydraulic pump 9 and the damper chamber 1
There is provided a fifth flow path 14 that connects the third flow path 8 between the first flow path 0 and the second flow path 12 between the second electromagnetic switching valve 13 in the fourth flow path 12 and the reservoir 7. In the middle of the fifth flow path 14, when the discharge hydraulic pressure of the hydraulic pump 9 exceeds a predetermined hydraulic pressure, the valve is opened to the direction of the fourth flow path 12 (the liquid storage tank 11 passing through the second electromagnetic switching valve 13). Direction and the reservoir 7 direction) is provided with a relief valve 16 for releasing hydraulic pressure.

As shown in detail in FIG. 2, the relief valve 16 includes a discharge side of the hydraulic pump 9 in the third flow passage 8 and a second electromagnetic switching valve 13 in the fourth flow passage 12 and the reservoir 7. A valve seat 16a provided in the middle of the fifth flow path 14 connecting the space, and a ball valve 16b provided in a state where the valve seat 16a can be opened and closed from the fourth flow path 12 side,
The ball valve 16b is abutted against the valve seat 16a and is urged in the closing direction of the fifth flow passage 14 to press and urge the spring 16c to determine the relief pressure. , Relief pressure adjusting means 2
2 is incorporated. That is, the relief pressure adjusting means 22 has a cylindrical piston 22b slidably provided in the cylinder 22a, and is generated in the master cylinder 1 at one end surface thereof via the control flow passage 22c. It receives the brake fluid pressure and slides to press the ball valve 16b in the direction of abutting against the valve seat 16a. By adding this pressing force to the pressing force of the spring 16c, the relief valve 16 The relief pressure can be increased. In the figure, 22d is a seal member.

The brake controller 17 is provided with an ABS control section for performing anti-skid control and a TCS control section for performing traction control, and receives a vehicle speed signal from a vehicle speed sensor 18 and a wheel speed signal from a wheel speed sensor 19. To be done.

Next, the operation of the embodiment will be described. (a) During normal brake operation FIG. 1 shows a normal brake state in which the brake controller 17 is not operating. In this state, the first electromagnetic switching valve 15, the second electromagnetic switching valve 13, the pressure increasing valve 5a. And with the pressure reducing valve 5b all inactive (energization off),
In the state where the flow between the master cylinder 1 and the pressure increasing valve 5a is allowed and the fourth flow path 12 is closed,
The normally open pressure increasing valve 5a is open and the normally closed pressure reducing valve 5b is closed, so that the brake fluid pressure generated in the master cylinder 1 is released when the brake pedal 2 is depressed in this state. , Is transmitted to the wheel cylinder 4 via the pressure increasing valve 5a of the first flow path 3, whereby braking of the wheel is performed according to the pedaling force of the brake pedal 2.

During normal braking when the brake fluid pressure is generated in the master cylinder 1 as described above, the relief pressure adjusting means 22 receives the brake fluid pressure via the control flow path 22c. The piston 22b slides to press the ball valve 16 in the direction of contacting the valve seat 16a. By adding this pressing force to the pressing force of the spring 16c, the relief pressure of the relief valve 16 is increased. It is in a state of Therefore, the relief valve 16 can be maintained in the closed state even when the brake fluid pressure is applied.

Further, during normal braking as described above, even when the fifth flow path 14 is in a communication state due to the failure of the relief valve 16, as long as the second electromagnetic switching valve 13 operates normally. A closed circuit is formed, and conversely, even if the fourth flow passage 12 is in a communication state due to the failure of the second electromagnetic switching valve 13, as long as the relief valve 16 is operating normally, the closed circuit is closed. Since it is formed, the brake fluid pressure generated in the master cylinder 1 can be maintained,
As a result, normal braking force of the wheels can be secured.

(B) At the time of anti-skid control When the brake pedal 2 is operated as described above and the wheels are likely to lock, the ABS control section of the brake controller 17 performs anti-skid control. That is, in the ABS control section of the brake controller 17, when the tire slip state is detected from the vehicle speed detected by the vehicle speed sensor 18 and the wheel rotation speed detected by the wheel speed sensor 19, the pressure increasing valve 5a and the pressure increasing valve 5a are detected. The depressurization valve 5b is operated to depressurize, hold, and reincrease the brake fluid pressure until the slip amount decreases to a predetermined value. First, switching to depressurization operation is performed.

That is, during the depressurizing operation, by turning on the energization, the pressure increasing valve 5a is closed and the pressure reducing valve 5b is opened, so that the brake fluid in the wheel cylinder 4 becomes the second pressure. The pressure is reduced by draining to the reservoir 7 via the pressure reducing valve 5b of the flow path 6,
The braking force of the wheels is reduced, and the slip amount can be reduced. The brake fluid once stored in the reservoir 7 is returned to the upstream side first flow path 3 a via the third flow path 8 by driving the hydraulic pump 9.

Further, during anti-skid control,
The fourth flow passage 12 is maintained in a closed state by the non-operation of the second electromagnetic switching valve 13, and therefore, even if the hydraulic pressure of the wheel cylinder 4 becomes a negative pressure, the liquid storage tank 11 of the master cylinder 1 There is no suction of the brake fluid inside, and therefore a normal decompression operation can be ensured.

Next, when the amount of slip of the tire is reduced to a predetermined value by the pressure reducing operation as described above, the pressure increasing valve 5a and the pressure reducing valve 5b are switched to the holding operation and the brake fluid pressure of the wheel cylinder 4 is changed. When the tire slip amount falls below a predetermined value, both valves 5a and 5b are switched to the pressure increasing operation to reincrease the brake fluid pressure of the wheel cylinder 4.

When the brake fluid in the reservoir 7 is exhausted during this pressure boosting operation, a negative pressure is created between the reservoir 7 and the second electromagnetic switching valve 13. However, as described above, during antiskid control. Does not suck the brake fluid in the liquid storage tank 11 of the master cylinder 1 because the fourth flow path 12 is kept closed.

(C) During traction control When a tire slip phenomenon occurs due to a sudden increase in engine torque, such as when the vehicle suddenly starts or accelerates, the TCS control section of the brake controller 17 performs traction control. That is, the brake controller 1
In the TCS control unit of No. 7, when the slip state of the tire is detected from the vehicle speed detected by the vehicle speed sensor 18 and the wheel rotation speed detected by the wheel speed sensor 19, the hydraulic pump 9 and the electromagnetic switching valve 15 are detected. By operating the pressure increasing valve 5a and the pressure reducing valve 5b, the brake fluid pressure of the wheel cylinder 4 is increased / maintained / reduced until the slip amount decreases to a predetermined value to brake the wheel.

That is, by turning on the energization of the first electromagnetic switching valve 15, the master cylinder 1 and the pressure increasing valve 5 are turned on.
While the flow between the first and second electromagnetic switching valves 15 and 5a is stopped, the hydraulic pressure is supplied to the upstream first flow path 3a between the first electromagnetic switching valve 15 and the pressure increasing valve 5a. On the other hand, by turning on the energization of the second electromagnetic switching valve 13,
Since the flow passage 12 is opened, the master cylinder 1
The brake fluid in the liquid storage tank 11 is supplied to the hydraulic pump 9 via the fourth flow path 12.

Therefore, first, the pressure increasing valve 5a is opened and the pressure reducing valve 5b is closed to switch to the pressure increasing operation. During this pressure increasing operation, the hydraulic pressure generated by the hydraulic pressure pump 9 is changed. By being supplied to the wheel cylinder 4 via the pressure boosting valve 5a, a braking force of the wheel is generated despite no braking operation, thereby reducing the rotational speed of the wheel and eliminating the slip state. The direction is controlled.

When the discharge hydraulic pressure exceeds the relief pressure due to the driving of the hydraulic pump 9, the relief valve 16 operates to open the fifth flow path 14 to change the supply hydraulic pressure to the pressure increasing valve 5a to the first level. It is designed to escape to the side of the four channels 12. At this time, during traction control when the brake fluid pressure of the master cylinder 1 is not generated, there is no brake fluid pressure received by the piston 22b of the relief pressure adjusting means 22, so the relief pressure of the relief valve 16 is the spring. The state is set to be low based only on the pressing force of 16c, so that the load on the hydraulic pump 9 can be suppressed to the minimum.

Next, when the slip amount of the tire is reduced to a predetermined value by the pressure increasing operation as described above, both valves 5a and 5b are switched to the holding operation to hold the brake fluid pressure of the wheel cylinder 4. If the slip amount of the tire falls below a predetermined value, the depressurization operation is switched to re-depressurize the brake fluid pressure of the wheel cylinder 4. Since the operation of the reservoir 7 during the depressurization operation is the same as that during the antiskid control, the description thereof will be omitted.

As described above, in this embodiment, the relief pressure of the relief valve 16 can be arbitrarily set by the relief pressure adjusting means 22 depending on whether or not the brake fluid pressure is generated. It is possible to obtain the effect that the load on the hydraulic pump 9 can be suppressed to a minimum without impairing the reliability of the performance.

Further, as long as both the relief valve 16 and the second electromagnetic switching valve fail at the same time, the closed circuit state can be maintained, so that the reliability of the braking performance can be further enhanced. To be

Next, another embodiment of the relief pressure adjusting means shown in FIG. 3 will be described.

The relief pressure adjusting means 23 of this embodiment is
The structure is such that the pressure receiving end area of the piston 23b that receives the brake fluid pressure is increased and the spring 23e that pushes back in the direction of separating from the ball valve 16b is provided.
In the figure, 23a is a cylinder and 23d is a seal member.

Although the embodiment of the present invention has been described above with reference to the drawings, the specific configuration is not limited to this embodiment. For example, in the embodiment, the case where the fluid pressure control valve is composed of the pressure increasing valve and the pressure reducing valve which are separate bodies is shown.
It is also possible to configure with one hydraulic pressure control valve having three switching positions of holding and depressurizing.

[0043]

As described above, in the brake fluid pressure control device of the present invention, the brake fluid pressure control device is provided in the middle of the first flow path that communicates between the master cylinder and the wheel cylinder, and is input to the wheel cylinder. Reduced brake fluid pressure
A hydraulic control valve that opens and closes based on a predetermined condition for holding and boosting pressure, and a normally open first valve that is provided in the first flow path and operates during traction control to shut off the first flow path.
A cut valve, a reservoir that stores the brake fluid discharged from the wheel cylinders when the hydraulic pressure control valve is depressurized through the second flow path, and a brake fluid that is stored in the reservoir through the third flow path is sucked and pressurized. Is provided in the middle of the fourth flow path that connects the hydraulic pump that recirculates to the first flow path between the hydraulic pressure control valve and the first cut valve and the reservoir and the liquid storage tank of the master cylinder. Normally closed second cut valve that operates during traction control to open the fourth flow path, and connects the discharge side of the hydraulic pump in the third flow path, the second cut valve in the fourth flow path, and the reservoir. A relief valve provided in the fifth flow passage for releasing the hydraulic pressure in the direction of the fourth flow passage when the discharge hydraulic pressure of the hydraulic pump exceeds a predetermined relief pressure, and a brake hydraulic pressure generated in the master cylinder. That is the relief pressure of the relief valve By providing the relief pressure adjusting means for urging in the increasing direction, it is possible to minimize the load on the hydraulic pump without impairing the reliability of the braking performance. Is obtained.

[Brief description of drawings]

FIG. 1 is an overall view showing a brake fluid pressure control device of an embodiment.

FIG. 2 is an enlarged cross-sectional view showing details of a relief valve incorporating a relief pressure adjusting means in the brake fluid pressure control device of the embodiment.

FIG. 3 is an enlarged sectional view showing another embodiment of the relief pressure adjusting means.

[Explanation of symbols]

 1 master cylinder 2 brake pedal 3 first flow path 4 wheel cylinder 5a pressure increasing valve (hydraulic pressure control valve) 5b pressure reducing valve (hydraulic pressure control valve) 6 second flow passage 7 reservoir 8 third flow passage 9 hydraulic pump 11 Liquid storage tank 12 Fourth flow path 13 Second electromagnetic switching valve (second cut valve) 14 Fifth flow path 15 First electromagnetic switching valve (first cut valve) 16 Relief valve 22 Relief pressure adjusting means 23 Relief pressure adjusting means

Claims (1)

[Claims] 1. A master cylinder for generating a brake fluid pressure by operating a brake pedal, a wheel cylinder for braking a wheel by receiving the brake fluid pressure via a first flow passage, and a middle of the first flow passage. The hydraulic pressure control valve that is installed in the wheel cylinder and that opens and closes based on predetermined conditions to reduce, maintain, and increase the brake hydraulic pressure that is input to the wheel cylinder, and the first flow between the hydraulic pressure control valve and the master cylinder. A normally open first cut valve that is installed in the road and operates during traction control to shut off the first flow path, and brake fluid discharged from the wheel cylinder when the hydraulic pressure control valve is depressurized through the second flow path. And a hydraulic pump for sucking and pressurizing the brake fluid stored in the reservoir via the third flow path and returning it to the first flow path between the hydraulic control valve and the first cut valve. Reservoir A normally closed second cut valve that is provided in the middle of the fourth flow path that communicates between the liquid storage tank of the master cylinder and the fluid storage tank of the master cylinder to open the fourth flow path during traction control; It is provided in the fifth flow passage that connects the discharge side of the hydraulic pump and the second cut valve and the reservoir in the fourth flow passage, and when the discharge hydraulic pressure of the hydraulic pump exceeds a predetermined relief pressure, the fourth It is provided with a relief valve for releasing hydraulic pressure in the flow path direction, and a relief pressure adjusting means for urging in a direction to increase the relief pressure of the relief valve by receiving the brake hydraulic pressure generated in the master cylinder. Brake fluid pressure control device.