JPH0481348A - Vehicle brake device and brake control valve used therefor - Google Patents

Abstract

PURPOSE:To properly control the brake pressure for each wheel by detecting the information corresponding to the ground load for each wheel, operating a brake control valve on the basis of the information, and controlling the gain of the brake pressure acting on a wheel cylinder. CONSTITUTION:A break control valve 15 is interposed in a piping 13 connecting between a master cylinder 9 and a wheel cylinder 7 of one of front wheels 1, and a piping 17 from a suspension cylinder 5 is connected to the brake control valve 15. A piping 19 is branched from the piping 13, and connected to the wheel cylinder 7 for a rear wheel 3 on the diagonal line of one front wheel 1, and the brake control valve 15 is interposed in the piping 19. The above- described piping structure is applied similarly to the wheel cylinder 7 for the other front wheel 1 and rear wheel 3. The pressure acting from a hydraulic means 24 according to the pressure supplied from the master cylinder 9 side is adjusted by each brake control valve 15, and the gain for the pressure on the master cylinder side of the brake pressure is controlled by the force corresponding to the ground load.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a vehicle braking system and a brake control valve used therein. This relates to a device that changes the rate of increase (hereinafter referred to as gain) of the wheel cylinder pressure, that is, the brake pressure.

(Prior Art) A conventional example will be described with reference to FIGS. 7 to 10. A conventional vehicle braking system is designed to change the distribution of brake pressure between the front wheels and the rear wheels depending on the axle load of the rear wheels.

FIG. 7 is a diagram showing the configuration of a conventional vehicle braking system. First, front wheels 201.201 and rear wheels 203.203 are arranged. These front wheels 201.201, rear wheels 203.2
A wheel cylinder 207 is attached to 03.

On the other hand, a master cylinder 209 is installed, and a brake pedal 211 is connected to this master cylinder 209.

And the wheel cylinder 207 of the front wheel 201.201
For the pipe 213 from the master cylinder 209,
．． Via 215, the brake pressure acts directly.

A load sensing provisioning valve (hereinafter referred to as LSPV) 225 is connected to the pipe 217, and the LSPV 225 is connected to a rear spring 247 via a main spring 245.

The LSPV 225 has a configuration as shown in FIGS. 8 and 9.

First, there is a valve body 231, and this valve body 2
A piston 233 is housed inside 31 so as to be slidable in the left and right directions in the figure. A ball 235 is accommodated in the piston 233 in a state where it is biased toward the left in the figure by a return spring 237.

On the left side of the ball 235 in the figure is a valve guide 239.
is installed in a fixed state on the valve body 231.

A lever 241 is connected to the right end of the piston 235 in the figure, and this lever 241 is rotatably supported by the valve body 231. Further, an adjustment spring 243 is stretched between the lever 241 and the valve body 231.

Further, a main spring 245 is connected to the lever 241, and a rear spring 247 is connected to the main spring 245.

The operation will be explained based on the above configuration.

First, when the brake pedal 211 is depressed, the brake pressure from the master cylinder 209 is directly applied to the front wheels 201, 201.

On the other hand, on the rear wheels 20B, 20, and 3 side, first, brake pressure from the master cylinder 209 acts on the boat 249. When the pressure on the wheel cylinder 207 side is low, the piston 233 is urged to the left in the figure by the spring force of the adjustment spring 243. Then, the ball 23 is controlled by the valve guide 239.
5 is pushed to the right in the figure, so the valve becomes open.

Therefore, the brake pressure from the master cylinder 209 is directly applied to the wheel cylinder 207 via the boat 251.
Acts on the side.

On the other hand, when the brake pedal 209 is depressed and the oil pressure reaches a specified value, the pressure from the wheel cylinder 207 side, that is, the piston 233 is urged to the right in the figure, as shown in the following equation (I). The force exerting the force is greater than the force biasing the left side.

PXA>F0PX (A-B) (I) As shown in Fig. 9, P is the pressure on the master cylinder 209 and wheel cylinder 207 side, and A and (A-B) are the pressure receiving areas. , and F is a force that urges the piston 233 to the left in the figure.

As a result, the piston 233 is urged to the right in the figure, as shown in FIG. As a result, the ball 235 is biased to the left in the figure, and the valve is closed.

At this time, the oil pressure on the master cylinder 209 side and the oil pressure on the wheel cylinder 207 side are in an equal state, and this becomes the starting point of control.

Next, when the pressure in the master cylinder 209 increases further from the above-mentioned starting point, the piston 233 is biased to the left in the figure due to the previously described action, and the ball 235 is biased to the right in the figure to open the valve. state.

Therefore, brake oil is supplied to the wheel cylinder 207, but as the pressure on the wheel cylinder 207 side increases thereafter, the piston 233 is urged to the right in the figure, and the ball 235 is urged to the left in the figure. The valve is energized and the valve is closed, and by repeating the same action, a balanced state is achieved with an oil pressure increase rate of (1-B/A).

Further, as shown in FIG. 10, as the load (loading amount) acting on the rear wheels 203, 203 increases, the above-mentioned starting point becomes higher.

That is, as the load increases, the rear spring 247 rises, and the spring force of the main spring 245 increases accordingly. In this way, when the spring force of the main spring 245 becomes stronger, the force (F) that pushes the piston 233 increases.

Furthermore, as described above, the load amount is detected based on the amount of deflection of the rear spring 247, in other words, based on the axle load of the rear wheels 203.203.
The control characteristics of 03 are always the same.

(Problem to be solved by the invention) The conventional configuration described above has the following problems.

Generally, the brake pressure at which the wheels 201, 203 lock depends on the friction coefficient between the ground load of the wheels 201, 203 and the road surface, as shown in FIG. Therefore, wheel 2
In order to control the brake pressure so as to prevent the wheels 201.203 from locking, it is necessary to control the brake pressure according to the ground load of the wheels 201.203.

However, as already mentioned, conventional vehicle braking systems
Since the pressure of the master cylinder 209 acts directly on the wheel cylinder 207 of the front wheels 201 and 201, depending on the amount of depression of the brake pedal 211,
There is a problem in that an unnecessarily high pressure acts on this wheel cylinder 207, and the front wheels 201 and 201 eventually lock.

Also, depending on the axle load of the rear wheels 203.203, the left and right rear wheels 20
By simply changing the brake pressure ratio of wheels 203 and 203 at the same time, it is not possible to change the brake pressure distribution due to the difference in ground load between the left and right rear wheels 203 and 203.

Therefore, there is a problem in that it is not possible to respond to changes in the driving conditions of the left and right rear wheels 203, 203, such as when one of the rear wheels 203 falls on a rough road.

The present invention has been made based on these points, and its purpose is to reduce the pressure of the wheel cylinder relative to the pressure acting from the master cylinder side on each of the four wheels according to the ground load. That is, the object of the present invention is to provide a vehicle braking system and a brake control valve that can change the gain of brake pressure.

(Means for Solving the Problems) In order to achieve the above object, a vehicle braking device according to the present invention includes wheel cylinders respectively provided on a pair of front wheels and a pair of rear wheels, a master cylinder connected to a brake pedal, Four hydraulic paths connect the master cylinder and the wheel cylinders of each wheel, and the four hydraulic paths are respectively inserted to input force and pressure from the master cylinder corresponding to the ground load of each wheel. A master cylinder that inputs hydraulic pressure from a separately provided hydraulic means and controls the brake pressure on the wheel cylinder side according to the pressure from the master cylinder, and also applies brake pressure to the wheel cylinder based on the force corresponding to the ground contact load. The brake control valve is characterized by comprising a brake control valve that controls a gain with respect to the pressure of the vehicle.

Further, the brake control valve according to the present invention includes a valve body and a valve body that is slidably accommodated in the valve body while being elastically biased in one direction, and is compressed in the other direction by pressurized oil supplied from a separately provided hydraulic means. a rod portion that generates a predetermined brake pressure by sliding on the wheel cylinder and compressing brake oil on the wheel cylinder side; and a rod portion that is slidably accommodated in the valve body with elastic bias in one direction. The rod is disposed between the rod section and the hydraulic means and slides in the other direction due to the pressure from the master cylinder side, thereby adjusting the pressure acting on the rod section from the hydraulic means, thereby responding to the pressure on the master cylinder side. A first spool that provides brake pressure, and a first spool that is slidably accommodated in the valve body while being elastically biased in the other direction and slid in one direction by the action of a force corresponding to the ground load. The second spool adjusts the pressure on the side that urges the first spool in one direction and thereby adjusts the pressure acting on the rod section from the hydraulic means and, in turn, the gain of the brake pressure with respect to the pressure on the master cylinder side. It is characterized by this.

(Function) First, the vehicle braking system according to the present invention is intended to control the brake pressure of each of the four wheels, and also to control the gain according to the ground load.

That is, a brake control valve is provided for each wheel, and pressure from a master cylinder and a force corresponding to the ground load of the wheel are input to the brake control valve, and pressure from a separately provided hydraulic means is input to the brake control valve.

The brake control valve then adjusts the pressure applied from the hydraulic means according to the pressure from the master cylinder side.
Provides brake pressure according to the pressure on the master cylinder side.

At the same time, the gain of the brake pressure relative to the pressure on the master cylinder side is controlled by adjusting the magnitude of the force according to the ground load.

Further, there is a brake control valve according to the present invention, which is used in the above-mentioned vehicle braking device.

First, the rod portion slides in the other direction by pressure oil supplied from the hydraulic means, thereby compressing the brake oil on the wheel cylinder side and providing a predetermined brake pressure.

At that time, the first spool slides in the other direction due to the pressure from the master cylinder side, thereby adjusting the hydraulic pressure applied to the rod part from the hydraulic means, thereby adjusting the brake pressure according to the pressure on the master cylinder side. provided.

On the other hand, the second spool moves in one direction under the action of a force corresponding to the ground load, thereby adjusting the pressure on the side that urges the first spool in one direction. As a result, the amount of movement of the first spool due to the pressure from the master cylinder side changes, so the oil pressure acting on the rod section from the hydraulic means and the gain of the pressure on the wheel cylinder side, that is, the brake pressure with respect to the pressure on the master cylinder side, changes. It is something.

(Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a block diagram of a vehicle braking system according to this embodiment, which includes a front wheel 1.1 and a rear wheel 3.3. The front wheel 1.1 and the rear wheel 3.3 are provided with an active suspension cylinder (hereinafter referred to as an AS cylinder) 5 and a wheel cylinder 7, respectively.

On the other hand, a master cylinder 9 is provided, and a brake pedal 11 is connected to this master cylinder 9.

A pipe 13 serving as a hydraulic path is disposed between the master cylinder 9 and the wheel cylinder 7 of one of the front wheels 1, and a brake control valve 15 is inserted into the pipe 13. This brake control valve 15 has an AS
A pipe 17 from the cylinder 5 is connected.

A piping 19 as a hydraulic path is branched from the piping 13, and this piping 19 is connected to the wheel cylinder 7 of one of the rear wheels 3 diagonally to the one of the front wheels 1. A brake control valve 15 is also inserted into the pipe 19, and a pipe 17 from the AS cylinder 5 is connected to the brake control valve 15.

Further, a pipe 21 as a hydraulic path is arranged between the master cylinder 9 and the wheel cylinder 7 of the other front wheel 1. A brake control valve 15 is also inserted in this pipe 21, and this brake control valve 15 has an AS
A pipe 17 from the cylinder 5 is connected.

A piping 23 serving as a hydraulic path is branched from the piping 21, and this piping 23 is connected to the wheel cylinder 7 of the other rear wheel 3. A brake control valve 15 is also inserted into this pipe 23, and this brake control valve 15
A pipe 17 from the AS cylinder 5 is connected to.

Further, hydraulic means 24 is provided. That is, a hydraulic pump 25 is installed, and this hydraulic pump 25 sucks and pressurizes the hydraulic oil in the tank 27, and supplies it to each brake control valve 15 via the flow divider 29 and piping 31.3335.37. is supplied to. And between each brake control valve 15 and the tank 27, there is a pipe 39.41-4.
3.45 is arranged.

Next, referring to FIG. 2, the brake control valve 15
The configuration of is explained. First, there is a valve body 47, which includes a first boat 49 that communicates with the master cylinder 9 side, a second boat 51 that communicates with the wheel cylinder 7 side, and a third boat 53 that communicates with the AS cylinder 5 side. , the fourth boat 55 which contacts the flow divider 29
, 5th boat 57 and 6th boat 5 connecting to tank 27
9 is provided.

Spool chambers 61.63 are formed in the valve body 47, and a first spool 65 and a second spool 67 are accommodated in these spool chambers 61.63 so as to be slidable in the left and right directions in the figure. .

The first spool 65 is urged rightward (in one direction) in the figure by a compression coil spring 69 as an elastic member disposed in the X chamber. Further, the spool chamber 61 on the right side of the first spool 65 and the first boat 49 are communicated with each other via a flow path 71, and the pressure Pm on the master cylinder 9 side acts through this communication path 71. .

The large diameter portion 72 of the first spool 65 and the valve body 47
The aperture part 73 is constituted by a part of. The spool chamber (β chamber) 61 on the left side in the drawing of the throttle portion 73 and the fifth boat 57 are communicated via a flow path 75.

Also, the spool chamber (α chamber) 6 on the right side in the figure of the aperture section 73
1 and the fourth boat 55 are communicated via a flow path 77.

On the other hand, regarding the second spool 67, this second spool 67 has a compression coil spring 79 as an elastic member.
is biased in the left direction (other direction) in the figure. Further, the spool chamber 63 on the left side in the figure of the second spool 67 and the third boat 53 are communicated via a flow path 81.

The large diameter portion 83 of the second spool 67 and a portion of the valve body 47 constitute a constricted portion 85 . The spool chamber (δ chamber) 63 on the left side in the figure of the throttle section 85 and the sixth boat 59 are communicated via a flow path 87. or,
The spool chamber (γ chamber) 63 on the right side in the figure of the throttle section 85 and the already mentioned flow path 77 are communicated via a flow path 89. A throttle 91 is inserted into this flow path 89 . Further, the γ chamber and the X chamber are communicated via a flow path 93.

A rod chamber 95 is formed in the valve body 47 . A piston 97 of a bushing rod 94 is accommodated in the rod chamber 95 so as to be slidable in the left-right direction in the figure.

This piston 97 is urged rightward (in one direction) in the figure by a compression coil spring 101 stretched between it and the stopper 99.

The rod chamber (chamber A) 95 on the right side in the figure of the piston 97 and the already mentioned α chamber are communicated via a flow path 98.

A piston 103 is housed in the rod chamber 95 on the left side of the stopper 99 in the figure, and the piston 103 is connected to the bushing rod 94 by a pin 105.

A ball 107 is accommodated in the piston 103, and this ball 107 is urged rightward in the figure by a compression coil spring 109.
A yoke 111 is provided between the bushing rod 94 and the ball 10.
7 to the left in the figure against the spring force of the compression coil spring 109, thereby opening the valve.Also, a chamber B is formed between the piston 103 and the stopper 99, and the left side of the piston 103 is moved to the left in the figure. Let be the α chamber.

Although only one brake control valve 15 is shown in the figure, the remaining three valves have a similar configuration.

The operation will be explained based on the above configuration.

Although FIG. 2 shows a state in which the brake pedal 11 is depressed, the state in which the brake pedal 11 is not depressed will be explained first.

In this case, since no pressure PM is generated from the master cylinder 9 side, the first spool 65 is urged to the right in the figure by the compression coil spring 69. Due to this movement of the first spool 65, the throttle portion 73 is brought into a wide open state, while hydraulic oil is supplied from the flow divider 29 into the α chamber. Since the throttle section 73 is opened so wide that the differential pressure can be ignored with respect to the flow rate (Q) of the hydraulic oil, the α chamber and the β chamber are
The pressure becomes approximately equal to the pressure of the tank 27, and the tank 27 is in an open state.

As a result, the pressure in the A chamber, which is communicated with the α chamber via the flow path 98, also becomes approximately zero. Since the pressure acting on chamber B is the pressure PM itself from the master cylinder 9 side, this is also zero.

Therefore, the piston 97 is compressed by the compression coil spring 101.
As a result, the yoke 111 comes into contact with the stopper 99 and is urged to the left in the figure, so that the ball 107 resists the urging force of the compression coil spring 109 and moves to the left in the figure. Moving. As a result, the valve is opened and the B chamber and the α chamber are communicated with each other, so that the master cylinder 9 side and the wheel cylinder 7 side are communicated with each other, and the brake pressure Pw also becomes O.

Next, the case where the brake pedal 11 is depressed will be explained. In this case, pressure PM is generated on the master cylinder side. This pressure PM causes the first spool 65 to move to the left in the figure against the spring force of the compression coil spring 69. As a result, the constriction portion 73 is constricted, and as a result, the pressure inside the α chamber increases. At that time, the pressure in the β chamber is the same as that in the tank 27, and is approximately O.

Due to the increase in the pressure in the α chamber, the pressure in the A chamber also increases, and as a result, the bushing rod 94 as well as the piston 97
moves to the left in the figure. As the bushing rod 94 moves, the piston 103 also moves in the same direction, and the yoke 111 also returns to its original position, so the ball 107 is seated and the valve is closed.

As a result, the master cylinder 9 side and the wheel cylinder 7 side are cut off, and the brake oil on the wheel cylinder 7 side is compressed by the movement of the piston 103, so that a predetermined brake pressure Pw is generated.

Also, as the piston 103 moves to the left in the figure, the volume of the B chamber increases, so the pressure P on the master cylinder 9 side increases.
, decreases. As a result, the first spool 65 is pushed back to the right side in the figure, and the throttle portion 73 is opened.

As a result, the pressure in the α chamber and A chamber decreases,
The piston 97 is pushed back to the right in the figure, thereby
Balance is achieved.

If the above-mentioned balance is expressed as a formula, it will be as shown in the following formula (I[).

Pw −Am =Px −Ax +kA−XA −(
II) However, PM: Pressure on the master cylinder 9 side PX: Pressure in the X chamber on the left side in the figure of the first spool 65 AM:
Pressure receiving area AX on the right side of the figure of the first spool 65: Pressure receiving area kA of the first spool 65 on the left side of the figure: Spring constant xA of the compression coil spring 69: Displacement of the first spool 65 Next, the pressure on the AS cylinder 5 side Brake pressure P due to P^
Gain control of w will be explained. FIG. 2 shows a case where the pressure PA on the AS cylinder 5 side is high, that is, a case where the ground load is high.

Due to the action of the pressure PA on the AS cylinder 5 side, the second spool 67 moves rightward in the figure against the spring force of the compression coil spring 79.

As a result, the constricted portion 85 is opened wide, and the pressure inside the γ chamber is reduced.

Since the γ chamber and the X chamber are communicated with each other via the flow path 93, the pressure inside the X chamber also decreases. This pressure drop in the X chamber causes the first spool 65 to further move to the left in the figure.

Due to this movement of the first spool 65, the constriction portion 73 is further constricted, so that the pressure in the α chamber and eventually in the A chamber increases.

As a result, the piston 97 moves to the left side in the figure, so the brake pressure Pw increases. In other words, as the ground load increases, the pressure PA of the AS cylinder 5 increases, and thereby the wheel cylinder 7 side , that is, the gain of the brake pressure P1 increases.

On the contrary, when the ground load decreases and the pressure PA on the AS cylinder 5 side decreases, the gain of the brake pressure pw decreases due to the opposite effect to the above.

In this way, in the case of this embodiment, as shown in FIG.
The brake pressure Pw is increased as M increases, and the gain of the brake pressure Pw is increased as the ground load increases.

By the way, if the hydraulic system breaks down for some reason, in this case the bushing rod 94 and the piston 103 move to the right end in the figure, and the ball 107 is pushed up by the yoke 111 to open the valve. In other words, the master cylinder 9 side and the wheel cylinder 7 side are in communication with each other.

Therefore, when the brake pedal 11 is depressed, the brake oil is swept away from the master cylinder 9 side to the wheel cylinder 7 side, and the pressure PW on the wheel cylinder 7 side increases.
The predetermined braking function is performed. Further, at this time, since the pressure in the A chamber does not increase, the state of communication between the master cylinder 9 side and the wheel cylinder 7 side is maintained.

Regarding the throttle 91 inserted in the flow path 89,
This is to prevent the pressure in the α chamber from decreasing when the pressure in the γ chamber decreases. Also, flow path 7
7 also has a restriction 90, which is for preventing the pressure in the γ chamber from decreasing when the pressure in the α chamber decreases.

According to this embodiment, the following effects can be achieved.

First, it is possible to control the gain of the brake pressure P acting on the wheel cylinder 7 for the front wheels 1.1 and rear wheels 3.3 individually depending on the ground load.
1. Brake pressure can be appropriately controlled within a range where the rear wheels 3.3 do not lock.

In addition, since the cylinder pressure of the AS cylinder 5 located close to the wheel is taken out as information corresponding to the ground load of the wheel 1.1.3.3, information approximately equivalent to the ground load can be input. , Thereby, the upper limit value of the brake pressure can be controlled with high precision.

Next, a second embodiment will be described with reference to FIGS. 4 to 6. In the case of the first embodiment, the pressure information from the AS cylinder 5 was configured as information corresponding to the ground load of the wheel, but in the case of this embodiment, the present invention is applied to the conventional suspension 121. It was applied.

As shown in FIG. 4, an axial force sensor 125 is attached to the cylinder rod 123 of the suspension 121. Further, a displacement sensor 129 is attached to the cylinder 127. The ground load (W) is calculated based on the detected values detected by the axial force sensor 125 and the displacement sensor 129. That is,
The ground load (W) is as shown in the following equation (1).

W = FD + k - (x + xo ) - (III) However, FD Axial force of two lots k: Spring constant X: Sprung upper unsprung relative displacement xo: Initial value of sprung upper unsprung relative displacement , a solenoid 131 is connected to the brake control valve 15, and a rod 133 is connected to the brake control valve 15.
The configuration is such that an arbitrary thrust force (F5) is applied to the second spool 67 via the solenoid 131. The current (i) is as shown in the following equation (IV).

i=1 ・W... (IV) where 1: proportional constant Further, the above actions can be summarized as shown in the functional block diagram shown in FIG. 6.

Therefore, even with such a configuration, the same effects as in each of the embodiments described above can be achieved.

Note that the present invention is not limited to the above embodiments.

Where and how information equivalent to the ground contact load of each wheel is detected and applied to the brake control valve is arbitrary.

(Effects of the Invention) As detailed above, according to the vehicle braking device and brake control valve according to the present invention, information corresponding to the ground load of each wheel is detected, and the brake is applied based on this information. Since the control valve is operated to thereby control the gain of the brake pressure acting on the wheel cylinders, the brake pressure can be appropriately controlled within a range where each wheel does not lock.

[Brief explanation of the drawing]

1 to 3 are diagrams showing a first embodiment of the present invention,
Figure 1 is a configuration diagram of the vehicle braking system, Figure 2 is a sectional view of the brake control valve, Figure 3 is a characteristic diagram showing how the wheel cylinder pressure gain changes depending on the ground load, and Figures 4 to 6. 4 is a diagram showing the structure of the wheel suspension and its vicinity, FIG. 5 is a sectional view of the brake control valve, and FIG. 6 is a functional block diagram.
Figures 7 to 11 are diagrams showing conventional examples, where Figure 7 is a configuration diagram of a vehicle braking system, Figure 8 is a sectional view of a load sensing provisioning valve, and Figure 9 is a load sensing provisioning valve. Cross-sectional view showing the effect of
FIG. 0 is a characteristic diagram showing the relationship between front wheel brake force and rear wheel brake force, and FIG. 11 is a characteristic diagram showing the relationship between lock brake pressure and ground contact load. 1...Front wheel, 3...Rear wheel, 5...AS cylinder,
7...Wheel cylinder, 9...Master cylinder,
13,19.21.23...Piping (hydraulic route), 15
...Brake control valve, 24...Hydraulic means, 47
... Valve body, 5... First spool, 67... Second spool, 94... Rod section.

Claims (2)

[Claims] (1) wheel cylinders provided on a pair of front wheels and a pair of rear wheels, a master cylinder connected to a brake pedal, and four hydraulic paths connecting the master cylinder and the wheel cylinder of each wheel; The four hydraulic circuits are inserted into the four hydraulic paths, respectively, and input the force corresponding to the ground load of each wheel and the pressure from the master cylinder, as well as input the hydraulic pressure from a separately provided hydraulic means, and input the hydraulic pressure according to the pressure from the master cylinder. A brake control valve that controls the brake pressure on the wheel cylinder side and controls the gain of the brake pressure applied to the wheel cylinder based on the force corresponding to the ground load with respect to the pressure from the master cylinder. Vehicle braking system. (2) A valve body and a wheel cylinder that is slidably accommodated in the valve body while being elastically biased in one direction and is slid in the other direction by pressure oil supplied from a separately provided hydraulic means. a rod portion that generates a predetermined brake pressure by compressing brake fluid on the side; and a rod portion that is slidably accommodated in the valve body while being elastically biased in one direction, and that the rod portion and the hydraulic means are connected to each other. A first member disposed between the cylinders and slidable in the other direction by pressure from the master cylinder side to adjust the pressure acting on the rod portion from the hydraulic means, thereby providing brake pressure in accordance with the pressure from the master cylinder side. The spool is slidably accommodated in the valve body while being elastically biased in the other direction, and is slid in one direction by the action of a force corresponding to the ground load, thereby urging the first spool in one direction. A second spool that adjusts the pressure on the applying side and thereby adjusts the pressure acting on the rod section from the hydraulic means and thus the gain of the brake pressure with respect to the pressure on the master cylinder side. valve.