JPH036023B2 - - Google Patents

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention relates to an anti-skid device for a vehicle,
In particular, in order to selectively divide the hydraulic circuit connecting the brake master cylinder and the wheel brake cylinder of the vehicle into a brake master cylinder side hydraulic circuit section and a wheel brake cylinder side hydraulic circuit section, an interposed first valve;
a gas spring type accumulator that stores hydraulic pressure generated by a pump driven by power;
The wheel brake cylinder is moved forward from its rest position by the hydraulic pressure of the hydraulic circuit portion on the side of the wheel brake cylinder, and is moved back to the rest position by the working hydraulic pressure, and the first valve is closed and opened by the forward movement and return movement. a pressure reducing piston that increases and restores the volume of the wheel brake cylinder side hydraulic circuit portion while moving the pressure reducing piston to its rest position against the hydraulic pressure of the wheel brake cylinder side hydraulic circuit portion when the wheel rotates normally. The working hydraulic pressure is applied to the pressure reducing piston in order to position it at the wheel brake cylinder side, and when the wheels are about to lock, the pressure reducing piston is moved forward by the hydraulic pressure of the wheel brake cylinder side hydraulic circuit. The present invention relates to an anti-skid device for a vehicle that includes a second valve for eliminating hydraulic pressure.

(Prior art) As a conventional device of this kind, for example, US Pat.
There is one described in the specification of No. 3722960. As described in this U.S. patent specification, in conventional devices of this type, the high working fluid pressure in the accumulator is directly applied to the depressurizing piston when the wheels are rotating normally, and only when the wheels are about to lock. Hydraulic pressure is removed from the vacuum piston.

(Problem to be solved by the invention) By the way, when using a vehicle, if you compare the time when the brakes are applied and the time when the brakes are not applied, the former is extremely short, and most of the time when the vehicle is used is due to the latter. occupied. Therefore,
Seal members attached to the pressure reducing piston, etc., which are used to form the hydraulic circuit that guides working fluid pressure from the accumulator to the pressure reducing piston, are subjected to heavy loads, and the life of the seal members is shortened, requiring replacement in a short period of time. However, there is a problem in that maintenance of the device is time-consuming.

A method to solve this problem is to apply hydraulic pressure to the pressure reducing piston in response to the depression and release of the brake pedal in a hydraulic circuit that guides the hydraulic pressure from the accumulator to the pressure reducing piston. It is conceivable to install a third valve that isolates the hydraulic pressure chamber from the accumulator and communicates it with the drain circuit, and removes the hydraulic pressure from the pressure reducing piston when braking is not performed. This can significantly reduce the load on the sealing member and extend its life; however, if the brake pedal is released before the decompression piston has returned to its rest position during operation of the device. , the hydraulic pressure is removed from the pressure reducing piston by the third valve, and the pressure reducing piston does not move back to the rest position, and the brake master cylinder and wheel brake cylinder remain separated, resulting in a delay in operation during the next braking. Problems such as galling of the seal cup attached to the piston of the brake master cylinder can be pointed out.

A method to solve this problem is to provide a spring that moves the pressure reducing piston back to the rest position, and if the brake pedal is released while the pressure reducing piston is moving back, the hydraulic pressure is removed from the pressure reducing piston by the operation of the third valve. Even if the piston is removed, the spring moves the pressure reducing piston to its rest position, and a third valve is placed in the working hydraulic pressure chamber.
The fourth valve may be interposed between the brake master cylinder and the wheel brake cylinder in parallel with the first valve, and the fourth valve may be interposed between the brake master cylinder and the wheel brake cylinder in parallel with the first valve. The opening and closing of the valve is controlled by a piston operated by the hydraulic pressure applied to the pressure reducing piston, so that the fourth valve is opened or opened in response to the removal of the hydraulic pressure from the pressure reducing piston, and the first valve is opened and closed. It is conceivable to supply hydraulic pressure from the brake master cylinder to the wheel brake cylinder through the fourth valve even when the valve is closed. It can be pointed out that the problem remains that a large amount of water is consumed and the pump operates frequently. That is, in this type of device, the gas in the accumulator passes through the diaphragm and mixes into the hydraulic fluid, and when the brake pedal is released, the hydraulic fluid pressure is removed from the pressure reducing piston by the operation of the third valve. When the brake pedal is pressed, the mixed gas expands in the pressure reduction circuit leading from the third valve to the operating hydraulic pressure chamber, and the next time the brake pedal is depressed, the third valve is operated and the hydraulic pressure circuit is connected to the accumulator. When the mixed gas contracts, a relatively large amount of hydraulic fluid corresponding to the contracted volume is consumed from the accumulator, and a large amount of hydraulic fluid in the accumulator is consumed due to repeated depression and release of the brake pedal, which must be replenished. This is why the pump operates frequently. Furthermore, the method of providing a fourth valve is practical from the viewpoint of enabling hydraulic pressure to be supplied from the brake master cylinder to the wheel brake cylinder in the event that operating hydraulic pressure cannot be obtained due to a failure of the pump or accumulator, etc. Although it is considered necessary to provide this, if the hydraulic pressure is removed by the operation of the third valve in conjunction with the release of the brake pedal during the return movement of the pressure reducing piston and the pressure reducing piston stops, As soon as the third valve connects the hydraulic circuit to the accumulator again during the next braking operation, the pressure reducing piston is moved back to the rest position by the working hydraulic pressure, reducing the volume of the hydraulic circuit between the brake master cylinder and the wheel brake cylinder. This decrease causes the brake pedal to be pushed back, further pointing out the problem of causing discomfort to the driver.

Therefore, it is an object of the present invention to solve all of the above-mentioned problems.

[Structure of the invention]

(Means for Solving the Problems) The means taken by the present invention to achieve the above object is a one-way valve that controls communication and isolation between the hydraulic pressure chamber and the accumulator for supplying hydraulic pressure to the decompression piston. a second valve section that controls communication and isolation between the working hydraulic pressure chamber and the drain circuit; a second valve section that is actuated by hydraulic pressure generated by a brake master cylinder to connect the two valve sections from the accumulator to the working hydraulic pressure chamber; A piston that opens and closes to apply a working hydraulic pressure proportional to the hydraulic pressure generated by the master cylinder, and a piston that applies a predetermined minimum working hydraulic pressure from the accumulator to the working hydraulic pressure chamber when the piston is not in operation. and a third valve having a spring for opening and closing the valve portions.
This is because a valve was installed.

(Function) In the present invention thus constructed, when the brake pedal is released, a predetermined minimum hydraulic pressure is applied to the pressure reducing piston from the accumulator by the operation of the third valve. This minimum hydraulic pressure is
This is set to a value that satisfies both the reduction of the load on sealing members such as the sealing member attached to the decompression piston and the reduction of the expansion of gas mixed into the hydraulic fluid. Compared to the case where the pressure is directly applied to the pressure reducing piston, the life of the sealing member is significantly extended, the maintenance of the device becomes less troublesome, and the above-mentioned hydraulic pressure chamber is reduced to atmospheric pressure when the brake pedal is released. The gas expansion when the brake pedal is released is significantly reduced compared to the previous model, and the amount of hydraulic fluid consumed from the accumulator due to the operation of the third valve as the brake pedal is repeatedly depressed and released is significantly reduced. The number of operations is reduced, reducing power loss. When the device is activated, even if the brake pedal is released before the pressure reducing piston moves back to the rest position, the minimum working fluid pressure is applied to the pressure reducing piston from the accumulator by the operation of the third valve, so that the pressure reducing piston is is moved back to the rest position, and problems such as a delay in brake operation caused by the decompression piston not returning to the rest position and stopping midway, the seal cup in the brake master cylinder being scuffed, and the brake pedal being pushed back are also resolved. .

(Example) Hereinafter, the present invention will be further clarified by describing examples of the present invention based on the drawings.

In FIG. 1, 1 is a brake pedal, and 2 is a brake master cylinder. The brake master cylinder 2 is operatively connected to the brake pedal 1, and when the brake pedal 1 is depressed, hydraulic pressure corresponding to the brake pedal depression force is generated, which is applied to the circuit 3-
It is applied to the valve chamber 6 in the valve seat 5 through the annular groove 5a and hole 5b of the valve seat 5, which are fluid-tightly fitted and fixed into the hole 4a of the body 4 and the cylinder hole 4b of the body 4. This valve chamber 6 has a valve seat 7 that is fluid-tightly fitted into the valve seat 5.
When the valve 8 installed in the valve chamber 6 opens the hole 5c of the valve seat 5 as shown in the drawing, the hydraulic pressure applied to the valve chamber 6 flows between the hole 5c and the cylinder hole. A decompression chamber 10 defined on the left side of the valve seat 5 by a decompression piston 9 fluid-tightly and slidably fitted into the cylinder hole 4b, a hole 5d in the valve seat 5, and a valve fluid-tightly fitted and fixed in the cylinder hole 4b. It is applied to the chamber 12 on the right side of the valve seat 10 through the holes 11a of the seat 11 in sequence. This chamber 12 includes a closing member 13 that is fluid-tightly fitted and fixed into the cylinder hole 4b, and this closing member 1.
The valve 16 is separated from the valve seat 11 by a piston 14 that is fluid-tightly and slidably fitted into the interior of the valve 16. When the hole 7a of the valve seat 7 is closed and the hole 11b of the valve seat 11 is opened as shown in the drawing, the chamber 12
The hydraulic pressure applied to the hole 11b - the valve chamber 15 - the hole 11c of the valve seat 11 - the annular groove 4 of the body 4
c and hole 4d - is applied to the wheel brake cylinder 18 via the circuit 17 in sequence.

The valves 8 and 16 are biased away from each other by a spring 19 interposed between them. In the drawing, the vacuum piston 9 occupies its rest position, lifting the valve 8 from the valve seat 5 against the spring 19 and opening the bore 5c. Also shown in the drawing is the piston 14 in its rest position and the valve 16 lifted from the valve seat 11 against the spring 19 to lift the valve 16 into the hole 11b.
is opened and brought into contact with the valve seat 7 to close the hole 7a. As will be understood from the explanation below, the valve seat 5 and valve 8 constitute the first valve, and the valve seats 7 and 11 and the valve 16 constitute the fourth valve.

A pump 23 for generating hydraulic pressure is driven by an electric motor 24, sucks liquid from a reservoir 25, and discharges it into a circuit 28 via a strainer 26 and a check valve 27. A gas spring type accumulator 29 and a pressure responsive switch 30 are connected to this circuit 28. The pressure response switch 30 and the electric motor 24 are connected to an electronic control unit 31, and the electronic control unit 31 controls the electric motor 24 based on a signal from the pressure response switch 30, and controls the hydraulic pressure in the accumulator 29 to operate the device. It is operated so that it is within the required predetermined range (175 to 200 Kg/cm ² ). The hydraulic pressure in the accumulator 29 is supplied by the circuit 28 to the circuit 34 via the regulator valve 33. This circuit 34 is for guiding hydraulic pressure to the hydraulic pressure chamber 20 on the left side of the pressure reducing piston 9.

The regulator valve 33 corresponds to the third valve, and includes a hole 35a communicating with the circuit 28,
The body 35 has a hole 35b communicating with the reservoir 25 via the drain circuit 36, a hole 35c communicating with the circuit 34, and a hole 35d communicating with the circuit 3. The valve seat 3 is inserted into the cylinder hole 35e of the body 35 from the back side (left side in the drawing).
7. The washer 38, the piston guide 39, and the closing member 40 are fitted and fixed in order, and the space between the valve seat 37, the piston guide 39, the closing member 40, and the cylinder hole 35e is made liquid-tight. An annular protrusion 37a is provided on the left side of the valve seat 37, and a filter/spring retainer 41 having numerous small holes is fitted and fixed into this protrusion 37a. A valve 42 that opens and closes the hole 37b of the valve seat 37 and a spring 43 that urges the valve 42 to contact the valve seat 37 and close the hole 37b are installed. Hole 3 of valve seat 37
A movable member 45 having a valve 47 press-fitted and fixed at its right end and a spring 46 biasing the movable member 46 toward the washer 38 are installed in the large diameter portion on the right side of the movable member 7b. The outer diameter of the right end of the movable member 45 is smaller than the inner diameter of the washer 38, and has an outer diameter larger than the inner diameter of the washer 38. A collar portion 45a that restricts rightward movement is formed on the movable member 45.

A piston 47 is fitted into the piston guide 39 in a liquid-tight and slidable manner, and a spring 48 that urges the piston 47 toward the washer 38 is fitted, and its left end is fitted into the piston 47 in a liquid-tight and sliding manner. A rod 49, which can be penetrated, is installed. The rod 49 has a hole 49a that is opened and closed by the valve 44 and a hole 49b that communicates with the drain chamber 51 that communicates the hole 49a with the hole 35b. The hole 49a is biased by the spring 52 such that the valve 44 closes the hole 49a.
The right end of the rod 49 is slidably fitted into a hole 53a of a piston 53 which is slidably and liquid-tightly fitted into the closing member 40. A chamber 54 defined in the closing member 40 by the piston 53 communicates with the hole 35d via the hole 40a of the closing member 40 and the annular passage 61,
4 is applied with the hydraulic pressure generated by the brake master cylinder 2. Due to the hydraulic pressure in this chamber 54, the piston 5
3 slides toward the rod 49 against the spring 50 interposed between the piston guides 39 and opens the hole 53a.
The gap 55 between the bottom surface of the rod 49 and the right end surface of the rod 49 is reduced or eliminated, the rod 49 is pushed to the left, the hole 49a is closed by the valve 44, and the valve 44 is closed.
Then, the movable member 45 is moved together with the rod 49 against the spring 46, and the valve 42 is further lifted from the valve seat 37 against the hydraulic pressure from the spring 43 and the accumulator 29, thereby opening the hole 37b. The hydraulic pressure from the accumulator 29 is introduced into the chamber 56. The hydraulic pressure in this chamber 56 acts to push the rod 49 and piston 47 to the right. Here, since the hydraulic pressure applied to the chamber 54 is low, the pushing force acting on the rod 49 is increased before the pushing force acting on the piston 47 exceeds the pushing force of the spring 48 in the process of increasing the working hydraulic pressure in the chamber 56. When the pushing force by the piston 53 and spring 52 is exceeded, the valve 43, movable member 45, valve 44, rod 49, and piston 53 move to the right together, and first the valve 44 contacts the valve seat 37 and the pressure from the accumulator 29 is removed. The introduction of hydraulic pressure is stopped, and then the flange 45a of the movable member 45 collides with the washer 38, and the movement of the movable member 45 and the valve 44 is stopped.As the rod 49 further moves, the valve 44 is inserted into the hole of the rod 49. 49a, the hydraulic pressure in chamber 56 stops increasing and begins to decrease. When the rod pushing force due to the working hydraulic pressure in the chamber 56 becomes smaller than the pushing force of the piston 53 and the spring 52 due to this decrease in the working hydraulic pressure, the valve 44 closes the hole 49a and the valve 44 closes the hole 49a.
2 from the valve seat 37 occurs. By repeating these operations, the chamber 56
The hydraulic pressure in the chamber 54 is adjusted to a value proportional to the hydraulic pressure in the chamber 54, that is, the hydraulic pressure generated by the brake master cylinder 2, at a first predetermined ratio (line B-C in FIG. 2).
reference). Moreover, the liquid pressure applied to the chamber 54 is high,
Even if the rightward pushing force of the piston 47 exceeds the pushing force of the spring 48 in the process of increasing the working fluid pressure in the chamber 56, the rightward pushing force of the rod 49 does not exceed the pushing force by the piston 53 and the spring 52. At times, the piston 47 slides to the right with respect to the rod 49, collides with the flange 49c of the rod 49, and pushes the rod 47 to the right. As a result, the hydraulic pressure in the chamber 56 is reduced to the rod 4.
9 to the right is the resultant force of the force acting on the rod 49 and the force acting on the piston 47, and this resultant force, the force of the springs 43, 46, 50, the force of the piston 53, and the force of the springs 48, 52. The piston 53, rod 49, valve 44, movable member 45, and valve 42 move left and right depending on the size, and the hydraulic pressure in the chamber 56 changes to the brake master cylinder 2.
is adjusted to a value proportional to the generated hydraulic pressure at a second predetermined ratio (see line CD in FIG. 2). Further, the force of the spring 52 is such that the valve 44, the movable member 45, and the valve 42 are moved to the left against the hydraulic pressure from the accumulator 29 and the springs 43 and 46, and the valve 42 is lifted from the valve seat 37. Therefore, when no hydraulic pressure is applied to the chamber 54, the valve 44 is
The opening/closing operation of the hole 49a by the valve 42 and the opening/closing operation of the hole 37b by the valve 42 occur, resulting in a predetermined minimum hydraulic pressure (line A-- in FIG. 2) corresponding to the force of the spring 52.
(see B) is introduced into the chamber 56 from the accumulator 29.

The working fluid pressure in the chamber 56 is applied to the annular groove 35f of the body 35 and the hole 3 by the groove 38a provided in the washer 38.
5c to circuit 34.

As understood from the above, the valve seat 37
The valve 42 and the valve 42 constitute the one valve section, and the valve 44 and the rod 49 constitute the other valve section.

The hydraulic pressure applied to the circuit 34 from the regulator valve 33 is applied to the hydraulic pressure chamber 20 on the left side of the pressure reducing piston 9 from the hole 4e of the body 4 via the normally open solenoid valve 57. The solenoid valve 57 is connected to the second solenoid valve 59 which is interposed in a circuit 58 that connects the circuit 34 between the hydraulic pressure chamber 20 and the drain circuit 36.
Configure the valve. That is, these solenoid valves 57 and 59 are connected to the electronic control section 31, and the electronic control section 31 normally does not operate both solenoid valves 57 and 59, but operates the regulator valve 33.
The hydraulic pressure from the wheel rotation sensor 60 is supplied to the hydraulic pressure chamber 20 during braking.
When it is detected that the wheels are about to lock based on the signal from
7, 59 to cause the hydraulic fluid in the hydraulic pressure chamber 20 to flow out to the reservoir 25, remove the hydraulic pressure from the pressure reducing piston 9, and move the pressure reducing piston 9 into the vacuum chamber 10.
At the beginning of the forward movement of the pressure reducing piston 9, the valve 8 contacts the valve seat 5 and closes the hole 5c, and the subsequent forward movement of the pressure reducing piston 9 closes the pressure reducing chamber. 10 (constituting the wheel brake cylinder side hydraulic pressure circuit portion) is increased to lower the hydraulic pressure in the wheel brake cylinder 18 and reduce the braking force on the wheels. As a result, when the rotational speed of the wheel increases and the risk of the wheel locking is eliminated, the electronic control section 31 restores both solenoid valves 57 and 59 and again changes the hydraulic pressure from the regulator valve 33 to the hydraulic fluid. Pressure chamber 2
0, and the decompression piston 9 is moved back to open the decompression chamber 1.
Wheel brake cylinder 1 by reducing the volume of 0
8 and increases the braking force on the wheels. If the wheels are not about to lock up again even with an increase in the braking force applied to the wheels, the electronic control section 31 closes both solenoid valves 57 and 59.
is not operated, the pressure reducing piston 9 moves back to the rest position and the valve 8 is separated from the valve seat 5 again. Note that depending on the configuration of the electronic control section 31,
During the return movement of the pressure reducing piston 9, the solenoid valve 57 may be temporarily activated to stop the increase in the hydraulic pressure in the hydraulic pressure chamber 10 depending on the manner in which the rotational speed of the wheels increases.

When the brake pedal 1 is released during the return movement of the pressure reducing piston 9, a predetermined minimum operating hydraulic pressure is applied from the accumulator 29 to the circuit 34 by the operation of the regulator valve 33, and this pressure is reduced via the solenoid valve 57. Since the pressure is applied to the working hydraulic pressure chamber 20 on the left side of the piston 9, the pressure reducing piston 9 moves back to the rest position.

The hydraulic pressure applied to the circuit 34 by the regulator valve 33 is transferred from the circuit 34 to the hole 4 of the body 4.
f, the annular groove 4g, which is applied to the chamber 22 through the hole 13a of the closing member 13; If the hydraulic pressure is lost, for example, the pump 23 may be damaged or the accumulator 2 may be damaged.
9 fails and a predetermined hydraulic pressure cannot be obtained, the hydraulic pressure is not supplied to the hydraulic pressure chamber 20 on the left side of the pressure reducing piston 9. Therefore, during braking, the pressure reducing piston 9 absorbs the fluid in the pressure reducing chamber 10. The valve 8 moves forward due to the pressure and contacts the valve seat 8, closing the hole 5c. However, since hydraulic pressure is no longer applied to the chamber 22 on the right side of the piston 14, the valve 16 is moved by the spring 19. The brake master cylinder 2 is separated from the valve seat 7 to open the hole 7a, and is brought into contact with the valve seat 11 to close the hole 11b.
The applied hydraulic pressure is applied to the valve chamber 15 through the hole 7b of the valve seat 7 and applied to the wheel brake cylinder 18, thereby applying the brake. At this time, the decompression chamber 10 and chamber 12 are isolated from the valve chambers 6 and 15 by the operation of the valves 8 and 16, so that these chambers 10 and 12 will not waste fluid from the brake master cylinder 2. It's something that doesn't exist.

In the other embodiment shown in FIG. 3, a part of the regulator valve 33 of the embodiment shown in FIG.
Instead, a spring 152 is provided to urge the piston 53 toward the rod 49. The regulator valve 133 of this embodiment also has the characteristics shown in FIG. 2.

Further, the spring 50 in FIG. 1 can be omitted by interposing a spring 52 between the rod 49 and the piston 53.

〔Effect of the invention〕

As described in detail above, according to the present invention, the load on the sealing member used to configure the hydraulic circuit for applying hydraulic pressure from the accumulator to the decompression piston is reduced and the life of the sealing member is extended. The device can be maintained easily, and the decompression piston can be reliably returned to its rest position at the end of the device's operation, which prevents delays in braking and galling of the seal cup in the brake master cylinder. Excellent effects such as being able to prevent the brake pedal from being pushed back, reducing the consumption of hydraulic fluid in the accumulator, reducing the number of pump operations, and reducing power consumption can be obtained.

[Brief explanation of drawings]

Figure 1 is a system diagram of an embodiment of the present invention, Figure 2 is a characteristic diagram of the regulator valve in Figure 1, and Figure 3 is a diagram of the characteristics of the regulator valve in Figure 1.
The figure is a system diagram of another embodiment. Explanation of symbols, 2...Brake master cylinder,
8...Valve (constituting the first valve together with the valve seat 5), 9...Decompression piston, 10...Decompression chamber, 18...Wheel brake cylinder, 20...
... Working hydraulic pressure chamber, 21 ... Spring, 23 ... Pump, 24 ... Electric motor, 29 ... Accumulator, 33, 133 ... Regulator valve (third
valve), 37... Valve seat, 42... Valve (constituting one valve part of the valve seat 37 and the third valve), 44... Valve (Rod 4
9 constitutes the other valve part of the third valve and also constitutes a relief valve), 51...drain chamber, 52, 152... spring for applying the minimum working hydraulic pressure in the third valve, 53
... Piston in the third valve, 57, 59
...Solenoid valve that constitutes the second valve.

Claims (1)

[Claims] 1 In order to selectively separate the hydraulic pressure circuit connecting the brake master cylinder and the wheel brake cylinder of the vehicle into a brake master cylinder side hydraulic pressure circuit portion and a wheel brake cylinder side hydraulic pressure circuit portion, an intervening device is installed in the hydraulic pressure circuit. A gas spring type accumulator that stores hydraulic pressure generated by a pump driven by power, and a hydraulic pressure in the hydraulic circuit on the side of the wheel brake cylinder are used to move the brake cylinder from its rest position. and is moved back to its rest position by the working hydraulic pressure, and the forward and backward movements close and open the first valve and increase and restore the volume of the wheel brake cylinder side hydraulic circuit portion. When the pressure reducing piston and the wheels rotate normally, the working hydraulic pressure is applied to the pressure reducing piston to position the pressure reducing piston in its rest position against the hydraulic pressure of the wheel brake cylinder side hydraulic circuit portion, and the wheel is An anti skid for a vehicle is provided with a second valve for removing the working hydraulic pressure from the pressure reducing piston in order to move the pressure reducing piston forward by using the hydraulic pressure of the wheel brake cylinder side hydraulic circuit portion when the wheel brake cylinder is about to lock. In the apparatus, one valve section controls communication/blocking between the working hydraulic pressure chamber for supplying the working hydraulic pressure to the decompression piston and the accumulator, and the other controls communicating/blocking the working hydraulic pressure chamber and the drain circuit. A valve portion is actuated by hydraulic pressure generated by the brake master cylinder to apply a hydraulic pressure proportional to the hydraulic pressure generated by the brake master cylinder to both valve portions from the accumulator to the hydraulic pressure chamber. a third valve having a piston that opens and closes the valve portion, and a spring that opens and closes both valve portions so as to apply a predetermined minimum hydraulic pressure from the accumulator to the hydraulic pressure chamber when the piston is not in operation;
An anti-skid device for a vehicle comprising a valve.