JPH04110260A - Anti-skid device - Google Patents

Abstract

PURPOSE:To maintain the superior sealing performance of a sealed part and improve reliability by preventing the high pressure generation in the whole system by suppressding the kick-back phenomenon generated by the repetition of decompression and pressurization of a wheel cylinder. CONSTITUTION:As for a hydraulic adjusting valve 2, a valve body 42 opens a communication flow passage 40 in the state where brake is not applied, and a master cylinder 15 and the input flow passage 16 of a modulator communicate. In the sharp brake application, the rightward pressing force due to the brake hydraulic pressure acting into the second hydraulic chamber 38 increases larger than the leftward pressing force due to a spring 44 and both the brake hydraulic pressures acting into the first and third hydraulic pressure chambers 37 and 39, and a stepped piston 34 shifts to a small diameter part 33 side, and the valve body 42 cuts off The communication flow passage 40. Accordingly, the hydraulic pressure supplied from the input flow passage 16 of the modulator 1 is not transmitted to the master cylinder 15, and the pulsation in the master cylinder 15, i.e., the kick-back phenomenon acting on a brake pedal 49 is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an anti-skid device for a vehicle brake.

"Prior Art" An anti-skid device is installed in the middle of a path that transmits the pressure of brake fluid in a master cylinder operated by a brake pedal to seven wheel links of each wheel.
When the wheels tend to lock during sudden braking, the brake fluid in the wheel cylinders is repeatedly depressurized and repressurized to prevent the wheels from skidding, ensuring lateral stability and shortening the braking distance.

Conventionally, such anti-skid devices include, for example,
JP-A-63-287650 or JP-A-61-
There is one shown in Japanese Patent No. 33788. The former is a mechanical anti-skid device that uses the inertia of the flywheel rotated by the axle to detect locking tendency and control the brake fluid, while the latter uses a sensor that constantly detects wheel rotation. This is an electronic anti-skid device that calculates wheel speed, slip rate, deceleration, etc. based on the results, and controls brake fluid pressure based on the calculated results.

``Problems to be Solved by the Invention'' By the way, in such an electronically configured anti-skid device, when the wheel cylinder is repeatedly depressurized and re-pressurized, the pressure fluctuation is transmitted to the master link, causing a so-called problem. A kick-hack phenomenon occurs. If this kick-pack phenomenon is small, there is no problem, but if it becomes large, it causes discomfort to the driver.

In addition, during anti-skid operation, pressure fluid must be supplied to the flow path between the master cylinder and wheel cylinder using a pump to repressurize, or must be supplied against the pressure of the master ring. The entire system must be designed to withstand high pressures, the pump torque must be large, and each seal must be able to withstand high pressures. In addition, even with the above-mentioned mechanical anti-skid device, in addition to problems due to high pressure in the system, the piston of the pump is reciprocated by an eccentric cam connected to the axle.
Since this return of the piston uses the hydraulic pressure of the master cylinder, the volume change based on this causes the kick-pack phenomenon.

The present invention effectively solves the above problems, and aims to reduce the kick-pack phenomenon, prevent high pressure in the entire system, maintain good performance of each seal part, and increase its reliability. shall be.

"Means for Solving the Problem" The anti-skid device according to claim 1 is provided with a modulator between a master cylinder and a wheel cylinder, and the modulator includes a valve that opens and closes a flow path between the master cylinder and the wheel cylinder. In an anti-skid device that drains the brake fluid in the wheel cylinder to reduce the pressure and returns the brake fluid to repressurize the inside of the wheel cylinder, a fluid pressure regulating valve is installed in the flow path between the master cylinder and the modulator. The hydraulic pressure regulating valve is formed between a piston forming at least two opposing pressure receiving parts, a cylinder slidably housing the piston, and a cylinder and the piston, and having a pressure receiving part in the pressure receiving part. First and second hydraulic pressure chambers apply hydraulic pressure, a spring biases the piston in a direction to decrease the volume of the second hydraulic chamber, and the hydraulic pressure on the modulator side is higher than the hydraulic pressure on the master cylinder side. and a valve part that allows flow from the modulator to the master cylinder when the piston is high, and is closed during the movement of the piston in the direction of reducing the volume of the first hydraulic pressure chamber. 3. The anti-skid device according to claim 2, further comprising a shell connected to the flow path between the valve and the wheel cylinder, and the second hydraulic pressure chamber is connected to the flow path between the valve and the valve portion. Further, the piston is a stepped piston, and the stepped histone and the link form three hydraulic chambers, and a second hydraulic chamber including a large diameter portion of the stepped piston is connected to the valve of the modulator. One of the remaining two chambers is designated as the first hydraulic pressure chamber, and the other chamber is connected to the second hydraulic pressure chamber via a passage provided in the stepped piston, and is also connected to the master cylinder. Features.

"Operation" The anti-skid device of the present invention is characterized in that when the wheel cylinder is depressurized during anti-skid control, the difference between the first hydraulic chamber and the second hydraulic chamber receiving the pressure on the wheel cylinder side increases. The pressure increases and the force based on this differential pressure overcomes the spring. Then, the piston moves toward the first hydraulic pressure chamber and the valve portion blocks the flow path between the master cylinder and the modulator. In this state, the pressure between the modulator and the valve part is increased by the pump, and this pressure increase is caused by the movement of the piston in the closing direction of the valve part, and the spring force of the spring is increased against the high pressure of the master cylinder. It is relaxed according to the hydraulic pressure in the first hydraulic pressure chamber.

Therefore, the load on the pump and modulator seals of the anti-skid device is not increased, and their reliability is improved. Further, since the volume change caused by the movement of the piston is absorbed by the first hydraulic chamber side, it is usually hardly transmitted to the master cylinder side, and the kick bank phenomenon is also reduced.

"Embodiments" Hereinafter, embodiments of the anti-skid device of the present invention will be described based on the drawings.

FIRST EMBODIMENT> Fig. 1 shows a first embodiment in which the modulator is of mechanical construction. Reference numeral 1 indicates a modulator, reference numeral 2 indicates a hydraulic pressure regulating valve, and inside the modulator 1 are the wheels 3 and 3. A lock detection section 4 that detects a tendency to lock, a fluid pressure modulation section 6 that reduces the pressure of brake fluid to the wheel cylinder 5, and a pump section 7 that repressurizes the reduced pressure of the brake fluid are provided.

The lock detection unit 4 is rotated in conjunction with an axle (not shown).A flywheel 10 is attached to the shaft 8 via a ball ramp mechanism 9, and a lever 11 is provided near the flywheel 10. By moving along the flywheel 10 or the shaft 8,
A lever 11 biased by a spring 12 rotates about a shaft 13 to operate a pressure release valve 14 of the hydraulic pressure modulating section 6.

The hydraulic pressure modulation unit 6 includes a cutoff valve 18 as a modulator valve and a cylinder chamber 19 provided in series between an input flow path 16 leading to the master cylinder 15 and an output flow path 17 leading to the wheel cylinder 3. , the cylinder chamber 19 is connected to the discharge passage 20 via the pressure release valve 14, and when the pressure release valve 14 is opened by operating the flywheel 10, the pressure in the output flow passage 17 is released. The depressurizing piston 21 in the cylinder chamber 19 operates and discharges the brake fluid in the cylinder chamber 19 from the discharge path 20 to a reservoir (not shown) while the output flow path 1
7, the pressure of the brake fluid in the wheel cylinder 5 is reduced, and the cut-off valve I8, which follows the movement of the pressure reducing piston 21, cuts off the input flow path 16 and the output flow path 17.

In the pump section 7, a pump chamber 22 that communicates with the cylinder chamber 19 of the hydraulic pressure modulation section 6 is formed between the input channel 16 and the discharge channel 20, and a pump piston 23 therein is connected to the shaft 8. is provided facing the cam 24 that is integrated with the cam 24,
The discharge passage 20 and the pump chamber 1 are provided in the pump piston 23.
A ball valve 25 is provided for communication with the pump piston 9, and a lip seal 26 is provided on the outer periphery of the pump piston 23 to partition the pump chamber 22.

Then, the pump piston 23 is pressed against the cam 24 due to the pressure difference between the input flow path 16 and the cylinder chamber 19 and moves back and forth, sucking brake fluid from the discharge path 20 into the pump chamber 22 and connecting it to the rhinobu seal 26. The brake fluid is fed into the cylinder chamber 19 of the hydraulic pressure modulating section 6 through a gap, and the pressure reducing piston 21 is moved to pressurize the brake fluid in the wheel cylinder 5. Note that the space between the input channel 16 and the pump chamber 22 is sealed by a seal member 27.

The hydraulic pressure regulating valve 2 has, in its cylinder 31,
A stepped piston 34 that integrally connects a large diameter portion 32 and a small diameter portion 33 is slidably housed, so that a stepped portion 35 of the stepped piston 34 and a stepped portion 36 of the cylinder 19
and a second hydraulic pressure chamber 38 formed between the large diameter portion 32 of the stepped piston 34 and one end of the cylinder chamber 31. A first hydraulic pressure chamber 39 is defined between the small diameter portion 33 of the stepped piston 34 and the other end of the cylinder 31. The manual flow path 16 of the modulator 1 is connected to the hydraulic pressure chamber 38, and the first hydraulic pressure chamber 3
The output channels 17 of the modulator 1 are connected to the respective terminals 9 .

Further, in the stepped piston 34, a communication passage 40 is formed that connects the input hydraulic pressure chamber 37 and the second hydraulic pressure chamber 38, and a valve chamber is formed in the middle of the communication passage 40. A ball-shaped valve body 42 is housed in 41 , and the valve body 42 passes through the communication flow path 40 and connects to the rod 4 embedded in the wall of the cylinder 31 .
3 restricts movement to the left in the figure. A spring 44 is housed in the first hydraulic pressure chamber 39 and biases the stepped piston 34 toward the large diameter portion 32 . A weak spring 45 that biases the valve body 42 in the valve closing direction is housed in the valve chamber 41 . To be precise, the stepped piston 34 as a whole is biased toward the large diameter portion 32 due to the difference in the biasing forces between the springs 44 and 45, and when there is no load, the stepped piston 34 is biased toward the large diameter portion 32, as shown in FIG. The tip of the diameter portion 32 is brought into contact with the wall of the cylinder 31,
In this state, the valve body 42 opens the communication channel 41.

Note that the tip of the large diameter portion 32 of the stepped piston 34 maintains the communication state between the communication flow path 40 and the manual flow path 16 of the modulator 1 even when the large diameter portion 32 is in contact with the wall of the cylinder 31. A notch 46 is formed for maintenance.

Reference numerals 47 and 48 indicate sealing members that seal between the respective hydraulic pressure chambers 3738 and 39 on the outer periphery of the large diameter portion 32 and the small diameter portion 33.

In this embodiment, the area of the large diameter portion 32 is 7-
Subtracting the area on the g side (the area of the valve seat that is opened and closed by the valve 42), it becomes equal to the area of the small diameter portion 33, and the sliding range of the piston 34 indicates that the hydraulic pressure regulating valve 2 is l) M, 7 T. It does a great job. That is, the hydraulic pressure in the second hydraulic pressure chamber 38 is approximately maintained at a hydraulic pressure corresponding to the sum of the spring force of the spring 44 and the hydraulic pressure in the hydraulic chamber 39.

In the anti-skid device configured in this way, the hydraulic pressure regulating valve 2 is operated by either the stepped piston 34 pushed by the spring 44 or the first valve when the brake is not applied.
As shown in the figure, the tip of the large diameter portion 32 is brought into contact with the wall of the cylinder 31, and in this state, the valve body 42 is inserted into the communication channel 4.
0 is opened, and the first hydraulic pressure chamber 37 and the second hydraulic pressure chamber 38, in other words, the master cylinder 15 and the input flow path 16 of the modulator 1 are brought into communication.

During normal braking, brake fluid from the master cylinder 15 flows into the input channel 16 of the modulator 1 via the input hydraulic chamber 37 of the hydraulic pressure regulating valve 2, the communication channel 40, and the second hydraulic chamber 38. From the output flow path 17 to the wheel cylinder 5
sent to.

On the other hand, does modulator 1 tend to lock wheel 3 during sudden braking?
When the lock detection unit 4 detects this, the modulator 1 operates to discharge the brake fluid in the wheel cylinder 5 from the discharge passage 20 and reduce the pressure inside the wheel cylinder 5.

At this time, the brake fluid pressure in the third hydraulic pressure chamber 39 of the hydraulic pressure regulating valve 2 is also reduced, so that the stepped piston 34 acts on both brakes acting on the first hydraulic pressure chamber 37 and the third hydraulic pressure chamber 39. The second hydraulic pressure chamber 38 is stronger than the rightward pressing force caused by the hydraulic pressure and the spring 44
The pressing force in the right direction due to the brake fluid pressure acting on the brake fluid pressure becomes larger, and the entire body moves toward the small diameter portion 33 side. and,
The movement of the stepped piston 34 causes the valve body 42 in the communication passage 40 to shut off the communication passage 40. At this time, the pressure inside the second liquid chamber 38 is determined by the spring force of the spring 44 and the first pressure chamber 39.
The pressure of the master cylinder IS is controlled to be lower than the pressure of the master cylinder IS, which is determined according to the pressure of the master cylinder IS. Therefore, master cylinder 1
5, the hydraulic pressure from the input flow path 16 of the modulator 1 is not transmitted, and only some brake fluid is pushed back due to the decrease in the volume of the ring-shaped input hydraulic pressure chamber 37. A slight kick-hack phenomenon occurs depending on the amount of brake fluid. Note that when the hydraulic pressure of the master cylinder 15 decreases in this state, that is, when the brake is released, the brake fluid on the second fluid royal family 38 side returns to the master cylinder 15 side via the valve body 42.

In addition, when repressurizing, the brake fluid is sucked from the discharge passage 20 by the action of the pump piston 23, and the pump chamber 2
2. It is supplied to the wheel cylinder 5 via the printer chamber 19 of the hydraulic pressure modulator 6. At this time, the pump piston 23
As the brake fluid moves back and forth, pulsations occur in the brake fluid pressure,
The pulsation also acts on the second hydraulic pressure chamber 38 of the hydraulic pressure regulating valve 2 via the input flow path 16 of the monulator 1. For this reason,
The stepped piston 34 may pulsate, or as described above, the movement of the stepped piston 34 toward the small diameter portion 33 blocks the communication passage 40, and the hydraulic pressure regulating valve 2 communicating with the master cylinder 15 Since the first hydraulic pressure chamber 37 is formed into a small ring-shaped volume, the pulsation of the hydraulic pressure caused by the fluctuation of the volume is small, and therefore the pulsation in the master lifter 15, that is, the kick acting on the brake pedal 49, is small. The back phenomenon becomes smaller. As shown in the graph of FIG. 2, the relationship between the hydraulic pressure of the mask-and-linda 15, the input hydraulic pressure of the modulator 1, and the output hydraulic pressure, the input of the modulator 1,
While the hydraulic pressure fluctuates to approximately the same extent in both output flow paths 16 and 17, the fluctuation in the hydraulic pressure in the master cylinder 15 is small.

On the other hand, the input hydraulic pressure of the modulator 1 is higher than the output hydraulic pressure because the output hydraulic pressure acts on the first hydraulic pressure chamber 39 of the hydraulic pressure regulating valve 2 and the spring force of the spring 44 is applied. 2
As shown in the figure, the hydraulic pressure of the master cylinder 15, the input hydraulic pressure,
A hydraulic pressure difference occurs in the order of output hydraulic pressure. Therefore, the seal member 2 that seals between the input flow path 16 and the pump chamber 22
7 is affected by the differential pressure between the input hydraulic pressure and the output hydraulic pressure. Incidentally, if there is no hydraulic pressure regulating valve 2, the input hydraulic pressure will be equal to the hydraulic pressure of the master cylinder 15, so the differential pressure acting on the sealing member 27 will increase, and its influence on the sealing performance will also increase. . In other words, by interposing the hydraulic pressure regulating valve 2 between the master cylinder 15 and the modulator 1, the differential pressure between the hydraulic pressure of the master cylinder 15 and the output hydraulic pressure is controlled by the sealing member 27 in the pump piston 23. , seal member 47 in hydraulic pressure regulating valve 2
It is a burden that should be distributed accordingly.

In addition, since the pump piston 23 is not operated at high pressure,
The load also becomes smaller.

Second embodiment> FIG. 3 shows a second embodiment of the electronic configuration.

The modulator 71 in this embodiment has a control valve 72 as a valve of the modulator, and the control valve 72 is a valve of the modulator.
2, and a hydraulic pressure relief system 76 that connects a reservoir 75 at a position downstream of the control valve 72.
A pressure release valve 77 is provided in the hydraulic pressure relief system 76 to open and close the flow path thereof, and a pressure release valve 77 is provided between the reservoir 75 and the input flow path 73 at a position upstream of the control valve 72. A hydraulic pressure return system 79 is connected to the input flow path 73 for returning the brake fluid stored in the input flow path 73 to the input flow path 73 by a pump 78. In this case, the control valve 72 is a so-called normal oven type solenoid valve, and the pressure release valve 77 is a normally closed type solenoid valve.

In addition, a check valve 80 is installed in the middle of the hydraulic pressure discharge system 74 to allow only flow from the wheel cylinder 5 to the input flow path 73, and a check valve 80 is installed in front of and behind the pump 78 in the hydraulic pressure return system 79 to prevent back flow to the reservoir 75. A reverse valve 81 is provided for preventing the above. Then, the second hydraulic pressure chamber 38 of the hydraulic pressure regulating valve 2
is connected to the input flow path 73 of the control valve 72, and the first hydraulic pressure chamber 39 is connected to the wheel cylinder 5 at a downstream position of the control valve 72.

In this anti-skid device, when a locking tendency is detected, the control valve 72 and the pressure release valve 77 are opened/closed or the third
By switching from the state shown in the figure, the connection between the master cylinder 15 and the wheel/linda 5 is cut off, and the brake fluid of the wheel/linda 5 is discharged into the reservoir 75, thereby reducing its fluid pressure. At this time, the pump 78 is started at a predetermined time and the brake fluid in the reservoir 75 is returned to the upstream side of the control valve 72, but since the control valve 72 is closed, the wheel cylinder 5 is in a depressurized state. It is maintained. In addition, the first hydraulic pressure chamber 39 of the hydraulic pressure control valve 2 is depressurized and the second hydraulic pressure chamber 38 is pressurized, so that the stepped piston 34 moves toward the small diameter portion 33 and the valve body 42 allows communication flow. The passage 40 is blocked, and a change in hydraulic pressure corresponding to a change in the volume of the first hydraulic chamber 37 occurs in the master cylinder 15. When the wheel 3 recovers to a predetermined deceleration, the pressure release valve 77 is switched between opening and closing, and the flow path of the hydraulic pressure relief system 76 is shut off, thereby temporarily maintaining the pressure inside the wheel cylinder 5. When the rear lock is released several times, the control valve 72 opens and the hydraulic pressure in the wheel cylinder 5 increases again. At this time, the hydraulic pressure regulating valve 2 also moves toward the large diameter portion 32 side.

Such control is repeated to prevent gaps and gaps, and during this control, as in the first embodiment, the master cylinder 15 is provided with a small amount of air in the first hydraulic pressure chamber 37 of the hydraulic pressure regulating valve 2. Only fluid pressure fluctuations associated with volume changes are transmitted. Furthermore, when the pump 78 sends brake fluid to the flow path 73, the pressure in the flow path 73 is reduced to the master cylinder 15.
Since the pressure can be suppressed to be low compared to the pressure of

In addition, the reference numeral 83 in FIG.
The valve opening pressure in No. 3 is made equal to the maximum setting pressure between the second hydraulic pressure chamber 38 and the valve 72, and when the piston 34 moves to the leftward sliding limit and the pressure in the flow path 73 rises roughly. In addition, this is released to the wheel cylinder 5 side to prevent the motor of the pump 7B from seizing.

<Other Embodiments of Hydraulic Pressure Control Valve> FIG. 4 shows an embodiment of a hydraulic pressure control valve. 37 is formed, and a second hydraulic pressure chamber 3 is formed on the large diameter portion 32 side.
B. A first hydraulic chamber 39 is formed in the intermediate portion. Then, the seat area (valve 4
The area of the valve seat opened and closed by 2) is smaller than the value obtained by subtracting the area of the valve seat opened and closed by
The pressure on the side increases.

Other Modifications> In the above embodiments, a stepped piston is used, but a piston in which the large diameter portion 32 and the small diameter portion 33 have the same diameter may also be used. In this case, it is necessary to provide an annular groove for forming an input hydraulic pressure chamber in the intermediate portion of the piston and to increase the spring force of the spring 44.

Therefore, manufacturing is relatively easy, but since the spring force of the spring 44 is large, the pressure in the second hydraulic chamber must also be set relatively high.

In addition, although the valve part is provided inside the stepped piston, it may be provided outside the stepped piston.Furthermore, the valve part is only connected to the spool valve that is opened and closed by the stepped piston, and from the modulator side to the master cylinder side. It may also consist of a check valve that allows flow.

"Effects of the Invention" As is clear from the above description, the anti-skid device of the present invention can provide the following effects.

(i) During anti-skid control, almost no fluid pressure fluctuations are transmitted to the modulator by the fluid pressure regulating valve, so the kick-pack phenomenon can be reduced.

(11) While the input hydraulic pressure of the modulator acts on the second hydraulic pressure chamber of the hydraulic pressure regulating valve, the hydraulic pressure of the wheel cylinder acts on the first hydraulic pressure chamber, so the hydraulic pressure of the master cylinder and the modulator When a hydraulic pressure difference occurs in the order of input hydraulic pressure and wheel cylinder hydraulic pressure, and the master cylinder hydraulic pressure acts directly as input hydraulic pressure, the differential pressure acting on the sealing member of the modulator is reduced. It is possible to maintain good sealing performance and improve reliability and durability.

Moreover, the pump can also be made smaller.

[Brief explanation of the drawing]

Fig. 1 is a piping system diagram showing a first embodiment of the anti-skid device of the present invention, and Fig. 2 shows the changes over time of the master cylinder hydraulic pressure, input hydraulic pressure of the modulator, and output hydraulic pressure in Fig. 1. 3 is a piping system diagram showing a second embodiment of the present invention, and FIG. 4 is a sectional view showing another embodiment of the hydraulic pressure control valve. l...Modulator, 2...Liquid pressure adjustment valve, 40tsukku detection section, 5...Wheel cylinder,
6...Liquid pressure modulation section, 7...Pump section, 16...
...Input flow path, 17 ・Output flow path, 27...
- Seal member, 32 large diameter part, 33... small diameter part,
34...Stepped piston, 3S 36...Stepped part,
37... Input hydraulic pressure chamber, 38... Second hydraulic pressure chamber, 39
...First hydraulic chamber, 40...Communication flow path, 41.
... Valve chamber, 42 ... Valve body, 44, 45 ・
・・Spring, 47.4B・・・・Role member, 49・・
...Prequibetal, 51...Modulator,
52... Control valve, 53... Hydraulic pressure relief system, 54...
・Accumulator, 55... Aluminum drive system, 56 Reservoir 60 ・ Pressure accumulation system, 61... Pressure system, 62
63... Valve, 64... Pump, 65...
...Input channel, 71... Modulator, 72...
Control valve, 73... Input flow path, 76... Hydraulic pressure relief system, 77... Pressure release valve, 75... Reservoir
78... Pump, 90... Liquid pressure control valve, 9
1... Piston.

Claims (2)

[Claims] (1) A modulator is provided between the master cylinder and the wheel cylinder, and the modulator is equipped with a valve that opens and closes the flow path between the master cylinder and the wheel cylinder, and discharges the brake fluid in the wheel cylinder to reduce the pressure. In an anti-skid device that returns brake fluid to repressurize the inside of a wheel cylinder, a fluid pressure regulating valve is provided in a flow path between a master cylinder and a modulator, and the fluid pressure regulating valve has at least two opposing pressure receiving parts. a formed piston, a cylinder that slidably accommodates the piston, first and second hydraulic pressure chambers that are formed between the cylinder and the piston and apply hydraulic pressure to the pressure receiving portion, and the piston. a spring that biases the second hydraulic pressure chamber in a direction that reduces the volume of the second hydraulic chamber;
When the hydraulic pressure on the modulator side is higher than the hydraulic pressure on the master cylinder side, a valve that allows flow from the modulator to the master cylinder and closes while the piston is moving in the direction of reducing the volume of the first hydraulic chamber. The first hydraulic pressure chamber is connected to the flow path between the valve and the wheel cylinder, and the second hydraulic pressure chamber is connected to the flow path between the valve and the valve portion. An anti-skid device featuring: (2) The piston is a stepped piston, and the stepped piston and the cylinder form three hydraulic chambers, and the second hydraulic chamber containing the large diameter portion of the stepped piston is controlled by the valve of the modulator. One of the remaining two chambers is connected to the first hydraulic pressure chamber, and the other chamber is connected to the second hydraulic pressure chamber via a flow path provided in the stepped piston, and is also connected to the master cylinder. The anti-skid device according to claim 1, characterized in that: