JPH08216867A - Hydraulic brake system - Google Patents

Abstract

PURPOSE: To enable a wheel cylinder to be fed with hydraulic pressure being higher than that generated by a master cylinder in time of an operational failure in a hydraulic servo unit. CONSTITUTION: A stepped piston 34 capable of receiving hydraulic pressure out of a master cylinder at a large diametral part 34a via a supply route 40, and being shiftable in a direction where another hydraulic pressure at the side of a wheel cylinder of both symmetrical front wheels is made to go up by a small diametral part 34b, and a pressure intensifying cylinder unit 4 having installed with a selector valve 45, closing at a time when this auxiliary power pressure is more than the specified one but opening whenever it is lowered more than the specified pressure are set up in each brake piping system of the front wheels. With this constitution, even if a hydraulic servo unit will not be normally operated, since the hydraulic pressure out of the master cylinder is received by the stepped piston 34, the hydraulic pressure intensified according to a pressure area ratio between the large diametral part 34a and the small diametral part 34b can be supplied to the wheel cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic brake system equipped in a vehicle or the like and equipped with a hydraulic booster so as to obtain a large braking force with a light operating force. The present invention relates to a device that does not cause insufficient braking force during operation.

[0002]

2. Description of the Related Art In a hydraulic brake system for a vehicle having a large weight, a boosting force higher than that of a negative pressure type as disclosed in, for example, Japanese Patent Publication No. 3700/1990 or Japanese Patent Publication No. 143762/1993. A hydraulic booster is used that provides the ratio. However, in such a hydraulic booster, a failure occurs such that no hydraulic pressure is generated in an external hydraulic pressure source (for example, a hydraulic pump), or even if the external hydraulic pressure source is normal, piping or a hydraulic booster is generated. If a failure such as a pressure leak occurs due to the damage of the seal member of itself, the desired operation by the auxiliary power pressure may not be obtained.

If the hydraulic booster becomes inoperative or malfunctions due to the above-mentioned failure, and in an extreme case, if the assisting force due to this is lost, the master cylinder is operated only by the operating force of the driver. Therefore, there is a problem that the braking force is significantly reduced with an operating force equivalent to the normal operation force, and in order to increase the braking force, the braking operation must be performed with a considerably larger operation force than the normal operation. is there.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a master cylinder is generated in a wheel cylinder so as to prevent insufficient braking force when the hydraulic booster does not operate or malfunctions. The purpose is to be able to supply a liquid pressure higher than the liquid pressure.

[0005]

[Means for Solving the Problems] The above object is to provide a hydraulic booster that operates by receiving auxiliary power pressure from an external hydraulic pressure source in response to a driver's brake operation, and a hydraulic booster. The hydraulic booster includes a master cylinder that generates a brake fluid pressure by receiving an operating force through the wheel cylinder and a wheel cylinder that is supplied with brake fluid pressure from the master cylinder to exert a braking force on wheels. In a hydraulic brake system having a servo piston slidably arranged inside a body kept liquid-tight by a member and receiving the auxiliary power pressure to transmit an operating force to the master cylinder, the large-diameter portion is provided with Having a stepped piston that receives hydraulic pressure on the master cylinder side and is movable in a direction to increase the hydraulic pressure on the wheel cylinder side by a small diameter portion,
The master cylinder side hydraulic pressure supply passage for the large diameter portion of the stepped piston is closed when the auxiliary power pressure is equal to or higher than a predetermined pressure, and is opened when the auxiliary power pressure is lower than the predetermined pressure. A hydraulic braking system comprising a pressure boosting cylinder device provided with a directional control valve.

[0006]

[Function] When the auxiliary power pressure for operating the hydraulic booster falls below a predetermined pressure, the switching valve of the pressure boosting cylinder device opens and the hydraulic pressure generated by the operation of the master cylinder in response to the brake operation is stepped. Press the large diameter part of the piston,
The stepped piston moves in a direction to increase the wheel cylinder hydraulic pressure, and the wheel cylinder is supplied with the hydraulic pressure increased according to the pressure receiving area ratio between the large diameter portion and the small diameter portion of the stepped piston.

When the valve body and the plunger of the switching valve are arranged so that their moving directions coincide with each other, an unreasonable force such as a prying force is not applied to the valve body, so that the opening / closing control can be smoothly performed. There is. Further, if the plunger receives the acting force of the auxiliary power pressure and the biasing force of the spring in opposition to each other without receiving the acting force of the master cylinder by the hydraulic pressure, the biasing force of the spring (in the opening direction of the plunger). Since the biasing force can be made as small as possible, there is an effect that the opening / closing switching pressure can be easily set and the degree of freedom of setting can be increased.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a piping system diagram showing a first embodiment of the present invention, and the hydraulic brake system is designated by 1 as a whole. The hydraulic booster 2 includes a driver's brake pedal 5
It is possible to operate by receiving auxiliary power pressure according to the stepping operation of
It is connected to a hydraulic pump 8 and a liquid reservoir 7 which are shared with the power steering device 6 via pipes 13 and 14. Further, the hydraulic booster 2 is integrally connected to a tandem master cylinder 3 that generates a brake hydraulic pressure, and the piston in the master cylinder 3 can be driven by an output according to the operation of the brake pedal 5. It is located in. As is well known, the tandem type master cylinder 3 has two independent pistons which are slidable to define two independent hydraulic pressure generating chambers therein. Pipe lines 11a and 12 are connected to the respective hydraulic pressure generation chambers of the master cylinder 3, and one pipe line 11a is a pressure increasing cylinder device 4 and a pipe line 11 according to the present invention described later.
It is connected to the wheel cylinders 9a, 9b for the left and right front wheels via b, and the other conduit 12 is connected to the wheel cylinders 10a, 10b for the left and right rear wheels. . From the above, the brake fluid pressure from the master cylinder 3 is changed to the wheel cylinder 9a,
By being supplied to 9b, 10a, and 10b, a braking force is applied to each wheel.

Next, the hydraulic booster 2 will be described with reference to FIG. 2. The hydraulic booster 2 in this embodiment will be described.
Has almost the same structure as that described in Japanese Patent Publication No. 3700/1990, and therefore detailed description of its structure will be omitted.

The servo piston 17 is a seal member 19, 2
It is slidably fitted in the inner hole 16a of the main body 16 with 0 and 21 interposed. An annular wall member 29 having a seal ring attached to the inner and outer circumferences is attached to the left end side of the inner hole 16a in the figure, and the seal member 2 attached to the annular wall member 29 is attached.
The cup seal portion 28 a of No. 8 is in elastic contact with the servo piston 17. In this way, the first chamber 23 and the second chamber 24 are defined on both sides of the servo piston 17 in the inner hole 16a, and the servo piston 17 is biased in the second chamber 24 toward the non-actuated position. A return spring is installed. The hydraulic booster 2 is an open type that uses the hydraulic pump 8 of the power steering device 6. That is, by driving the hydraulic pump 8, the pipeline 13, the first chamber 2
3 , the second chamber 24 , the pipe line 14, the power steering device 6, the liquid reservoir 7, the hydraulic pump 8, and the liquid flow circulating through the pipe line 13, the servo piston of the valve 27 by the pushing of the input member 18. By restricting in accordance with the movement of 17 in the direction close to the inner hole bottom wall portion 17a, the pressure is restricted and the pressure in the first chamber 23 is made higher than the pressure in the second chamber 24 .
This is a type that obtains auxiliary power pressure. The servo piston 17 receives the auxiliary power pressure and transmits the brake operating force to the master cylinder 3. Further, the hydraulic booster 2 has an emergency electric motor drive type auxiliary pump 22 as a countermeasure against a failure of the hydraulic pump side of the power steering device 6.
Is installed. In this auxiliary pump 22, the liquid circulation by the hydraulic pump 8 is eliminated, and further, the brake pedal 5
When it is detected that the stepping-in operation has been started, the liquid is sucked from the second chamber 24 side during driving and discharged to the first chamber 23 side.

The body 16 of the hydraulic booster 2 has a first chamber
A passage 25 communicating with the passage 23 is formed.
A pipe line 26 communicating with the pressure boosting cylinder device 4 according to the present invention is connected to 5.

As described above, the hydraulic booster 2 in this embodiment is used.
After briefly describing the above, the details of the pressure boosting cylinder device 4 according to the present invention will be described with reference to FIG.

A stepped hole 31 having a large diameter hole portion 31a and a small diameter hole portion 31b is formed in the casing 30 of the pressure boosting cylinder device 4 and corresponds to the large diameter hole portion 31a and the small diameter hole portion 31b. Large diameter portion 34a and small diameter portion 34
The stepped piston 34 in which b is formed is
2, 33 are mounted and slidably fitted in the stepped holes 31. A supply passage 40 is formed in the casing 30 so that the large diameter portion 34a of the stepped piston 34 receives the hydraulic pressure from the master cylinder 3 transmitted through the pipe passage 11a. Here, the supply passage 40 is connected to the first passage 66 that connects the pipe passage 11a and a second hole 46b of the valve hole 46, which will be described later, to the second hole 46b and the large diameter portion 34a of the stepped piston 34. Second passage 6 that communicates with the facing pressure chamber 68
7 and 7. A communication passage 41 is formed so that the hydraulic pressure from the master cylinder 3 communicates with the small diameter hole portion 31b of the stepped hole 31. Further, the small diameter hole portion 31b has an outlet communicating with the conduit 11b. A passage 39 is provided. From this outlet passage 39, the hydraulic pressure from the master cylinder 3 is supplied to the wheel cylinders 9a, 9b for the left and right front wheels.

In the small diameter hole portion 31b of the stepped hole 31, a spring 35 is stretched between the spring receivers 36 and 37, of which the spring receiver 37 is a suitable means for the small diameter portion 34b of the stepped piston 34. Installed by. An axial cut valve 38 having a valve portion 38a at its tip is supported between the two spring bearings 36, 37, and the stepped piston 34
By moving to the left in the figure, the small diameter hole portion 31b of the stepped hole 31
The valve seat 43 is composed of a stepped portion of the communication path 41 and the communication passage 41, and can be seated on and off. Incidentally, chamber 42 formed between the large diameter portion 34a and the small-diameter portion 34b of the stepped piston 34 has a pressure-free is open to the atmosphere through a small hole h, to this chamber 42,
A return spring 90 for urging the stepped piston 34 toward the non-actuated position (the pressure chamber 68 side) is provided.

In the middle of the supply path 40, that is, the above-mentioned first
A second hole 46b of the valve hole 46 that accommodates the poppet valve body 48 of the switching valve 45 is formed between the passage 66 and the second passage 67. The switching valve 45 is configured to close when the auxiliary power pressure from the hydraulic booster 2 is equal to or higher than a predetermined pressure, and to open when the auxiliary power pressure becomes lower than the predetermined pressure.
Hereinafter, the details of the switching valve 45 will be described.

A plunger 49, which receives the auxiliary power pressure from the hydraulic booster 2 through the conduit 26, is fitted with the seal rings 51, 52, 53, and the second hole of the valve hole 46.
Is slidably fitted in a first hole 46a formed in parallel with the hole 46b of the flange 49a of the plunger 49.
Is urged to the left side in the drawing by a spring 54 that engages with. The first hole 46 is defined by the plunger 49.
The chamber 71 formed on the right side of the drawing a communicates with the atmosphere through the small hole k. Further, a poppet valve element 48 biased rightward in the drawing by a valve spring 55 is in contact with a flange portion 49a of a plunger 49 extending vertically toward the second hole 46b. That is, the plunger 49 is configured so as to control the seating / seating of the poppet valve body 48 with respect to the valve seat 47 provided in the second hole 46 b of the valve hole 46, and the poppet valve body 48. Also, the plungers 49 are arranged so that the moving directions thereof coincide with each other. Further, the plunger 49 is configured to receive the acting force of the auxiliary power pressure from the hydraulic booster 2 and the urging force of the spring 54 so as to face each other without receiving the acting force of the master cylinder 3 caused by the hydraulic pressure. ing. The valve seat 47 of the poppet valve body 48
The maximum stroke amount of the plunger 49 is greater than the lift amount of the poppet valve body 48 from the valve seat 47 (the distance from the state where the poppet valve body 48 is seated on the valve seat 47 to the seated state) in order to ensure the seating on the valve seat 47. Is also set to be large.

Hydraulic brake system 1 in this embodiment
Is configured as described above, and its operation will be described below.

When the brake is not operated, the hydraulic booster 2 is used.
Is not operating, no auxiliary power pressure is generated, and no hydraulic pressure is generated in the master cylinder 3. Therefore, the switching valve 45 in the pressure boosting cylinder device 4 is open because the plunger 49 is at the position shown in FIG. The stepped piston 34 is also at the position shown, and the cut valve 38 is also open. That is, the master cylinder 3
The left and right front wheel cylinders 9a, 9b are maintained in direct communication with each other.

When the driver depresses the brake pedal 5 to operate the brake, the hydraulic booster 2 is moved to the first chamber 23 by the throttling action of the valve 26 which moves with the pushing of the input member 18. A pressure difference is generated between the servo chamber 17 and the second chamber 24, and the servo piston 17 receives a predetermined auxiliary power pressure. Then, as the servo piston 17 moves forward, hydraulic pressure is generated in the master cylinder 3. At this time, the switching valve 45 in the pressure boosting cylinder device 4 has the plunger 49
3 receives the auxiliary power pressure from the hydraulic booster 2 via the pipe line 26, thereby resisting the biasing force of the spring 54.
Moving from the state shown in (1) to the right, the poppet valve element 48 is seated on the valve seat 47 and the valve is closed. As a result, the first passage 66
And the second passage 67 are cut off, and the stepped piston 34 stops at the position shown in FIG. Therefore, since the cut valve 38 remains open, the hydraulic pressure generated by the master cylinder 3 is applied to the pipe line 11a, the communication passage 41 in the pressure boosting cylinder device 4, the small diameter hole portion 31b of the stepped hole 31, and the outlet passage. 39, the wheel cylinders 9a, 9 for the left and right front wheels via the conduit 11b.
b.

When the hydraulic booster 2 operates normally, the pressure boosting cylinder device 4 operates as described above, but the hydraulic pump 8 or the auxiliary pump 22, which is an external hydraulic pressure source, fails. , Or the seal member 19 mounted on the outer circumference of the servo piston 17, or the seal members 20 and 21 mounted on the main body 16 side to keep the first chamber 23 liquid-tight to the outside due to pressure leakage due to damage. The operation of the pressure boosting cylinder device 4 when the pressure booster 2 does not operate normally will be described below.

When the hydraulic booster 2 malfunctions, the auxiliary power pressure drops below a predetermined pressure (in extreme cases, the auxiliary power pressure is 0).
Takes the valve open state shown in FIG. The hydraulic pressure generated in the master cylinder 3 in response to the operation of the brake pedal 5 is
It is supplied to the pressurizing chamber 68 through the passage and the second passage.
As a result, the stepped piston 34 moves to the left in the figure, and by the movement of the stepped piston 34, the cut valve 38 is first seated on the valve seat 43 to close the valve, and the communication passage 41 and the outlet passage 39 are shut off. To be done. And then, the stepped piston 3
As the volume of the small diameter hole portion 31b is reduced in accordance with the further movement of 4, the increased hydraulic pressure determined by the pressure receiving area ratio between the large diameter portion 34a and the small diameter portion 34b of the stepped piston 34 is increased between the left and right front wheels. It is supplied to the wheel cylinders 9a and 9b.

Hydraulic brake system 1 in this embodiment
Operates as described above, but the hydraulic pump 8 or the auxiliary pump 22 which is an external hydraulic pressure source fails, or pressure leakage occurs due to damage of the seal members 19 or 21, and the hydraulic booster 2 Is not working properly,
Since the hydraulic pressure generated in the master cylinder 3 can be increased and supplied to the wheel cylinders 9, the braking force can be increased without a large braking operation force.

Next, as a second embodiment of the present invention, as a modified example of the pressure boosting cylinder device 4 described in the first embodiment, a pressure boosting cylinder device 4'shown in FIG. Will be described.

This pressure boosting cylinder device 4'has almost the same structure as the pressure boosting cylinder device 4 described in the first embodiment.
The structure of the switching valve is different. That is, in the switching valve 60 of the pressure boosting cylinder device 4'in the present embodiment, the arrangement relationship between the plunger and the valve body is arranged in parallel in the first embodiment, but in the present embodiment, as shown in FIG. Is to be placed in. The plunger 59 is fitted with a seal ring 61 and slidably fitted in an inner hole 62 formed in the casing 30 ', and is urged to the left in the drawing by a spring 63. The spring chamber 72 in which the spring 63 is stretched communicates with the atmosphere through the small hole m. The shaft 59a of the plunger 59 is sealed by the seal rings 75 and 76 and faces the valve chamber 80 , and the tip end of the shaft 59a is urged rightward in the figure by the valve spring 64. 58 is pressed. At this time, the valve body 58 is separated from the valve seat 65, and thus the switching valve 60 is in the open state. With this switching valve 60, the first and second passages 66 of the supply passage 40 'are provided.
The hydraulic pressure from the master cylinder 3 can be supplied to the pressurizing chamber 68 ′ by performing the communication and blocking action of ′ and 67 ′.
In this embodiment, the valve element 58 of the switching valve 60 is also similarly provided.
Of the plunger 59 to ensure the seating of the
Is set to be larger than the lift amount of the valve element 58 from the valve seat 65. Further, since the cut valve 38 of the stepped piston 34 'has the same structure as the pressure boosting cylinder device 4 described in the first embodiment, the description thereof will be omitted.

The pressure boosting cylinder device 4'in the second embodiment of the present invention is constructed as described above, and its operation will be described below.

When the brake is not operated, for the same reason as in the first embodiment, the switching valve 60 and the stepped piston 34 'in the pressure boosting cylinder device 4'have the states shown in FIG. 4, respectively. Both the cut valves 38 are open. When a brake operation is performed by the driver depressing the brake pedal 5, the hydraulic booster 2
At, an auxiliary power pressure is generated, and this auxiliary power pressure is supplied to the plunger 59 via the pipe line 26. At this time, the plunger 59 moves to the right in the drawing against the spring force of the spring 63, and the valve body 58 moves to the right in the drawing due to the urging of the valve spring 64 accordingly. When the valve element 58 is seated on the valve seat 65 provided in the chamber 80 , the switching valve 60 is closed. By closing the switching valve 60, the supply of hydraulic pressure from the master cylinder 3 to the pressurizing chamber 68 ′ is cut off, so that the stepped piston 34 ′ remains in the state shown in the figure, and thus the cut valve 38 is also opened. The valve remains open, and the hydraulic pressure from the master cylinder is used for the communication passage 41 and the small diameter hole portion 31b of the stepped hole 31 '.
′ Through the outlet passage 39, and is supplied to the wheel cylinders 9a and 9b of the left and right front wheels via the pipe line 11b.

When the hydraulic booster 2 does not operate normally due to a failure of the external hydraulic pressure source or a defective seal,
Since the auxiliary power pressure cannot be obtained, the switching valve 60 of the pressure boosting cylinder device 4'is opened as shown in the figure. As a result, the hydraulic pressure from the master cylinder 3 is supplied to the pressurizing chamber 68 'through the supply passage 40', and the stepped piston 34 'moves leftward in the drawing. Then, first, the cut valve 38 is seated on the valve seat 43 to close the valve, and the communication between the communication passage 41 and the outlet passage 39 is cut off. However, the large diameter portion 34a ′ corresponds to the movement of the stepped piston 34 ′. The increased hydraulic pressure determined by the pressure receiving area ratio between the small diameter portion 34b 'and the small diameter portion 34b' is supplied to the wheel cylinders 9a, 9b of the left and right front wheels via the outlet passage and the pipe passage 11b.

As described above, the pressure boosting cylinder device 4'in this embodiment performs the same operation as the pressure boosting cylinder device 4 in the first embodiment, and the effect is also the same as the effect by the first embodiment. In addition, the pressure boosting cylinder device 4'of the second embodiment.
In the above, in the plunger 59 of the switching valve 60, the shaft portion 59a has a diameter as small as possible than the pressure receiving portion of the auxiliary power pressure (the mounting portion of the seal ring 61), but the tip end of the shaft portion 59a is the supply passage 40 '(valve Since it is designed to receive the hydraulic pressure generated by the master cylinder 3 toward the chamber 80 ) in the same valve closing direction as the auxiliary power pressure, it is difficult to set the opening / closing switching pressure as compared with the first embodiment. Becomes

Although the respective embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications can be made based on the technical idea of the present invention.

For example, in each of the above-described embodiments, the pressure increasing cylinder devices 4 and 4'are installed only in the brake system for the front wheels, but as shown by the alternate long and short dash line in FIG. It is also possible to install pressure boosting cylinder devices 4 and 4'to further enhance the braking force of all wheels.

The hydraulic booster 2 is not limited to the open type, but may be a closed type in which the pump pressure or accumulator pressure is adjusted by opening and closing a valve, as described in JP-A-3-143762. Is.

Regarding the pressure boosting cylinder devices 4 and 4'in each of the above-mentioned embodiments, the stepped holes 31 and 31 ', and the large diameter portions 34a and 34a' and the small diameter portion 34b of the stepped pistons 34 and 34 ', Chambers 42, 4 defined between 34b 'and
Although 2'is opened to the atmosphere so as to have no pressure, the chambers 42, 42 'may be fluidly connected to the reservoir 70 of the master cylinder 3 instead. In this case, cup seals can be attached instead of the seal rings 32, 32 'attached to the small diameter portions 34b, 34b'.

Further, the front wheel cylinders 9a, 9a
Even if the hydraulic pressure supplied to b can be increased, the pressure-increasing cylinder devices 4, 4'change the pipe connection relationship so that the hydraulic pressure of the master cylinder 3 supplied to the brake system of the front wheels is not changed. Instead, it can be operated by the hydraulic pressure of the master cylinder 3 supplied to the brake system of the rear wheels.
That is, the first passages 66, 66 'of the supply passages 40, 40'.
Instead of being connected to the conduit 11a, a conduit branched from the conduit 12 so that the large-diameter portions 34a, 34a 'of the stepped pistons 34, 34' can act on the hydraulic pressure of the rear wheel brake system. And the cutoff valve 38
Through the small diameter holes 31b, 31b of the stepped holes 31, 31 '
It is also possible to adopt a piping system that connects only to ‘ Even if this piping system is applied, the same effects as those of the above-described respective embodiments can be obtained.

[0035]

As described above, according to the hydraulic brake system of the present invention, the hydraulic brake system is broken due to the failure of the external hydraulic pressure source, the damage of the piping, the breakage of the seal member of the hydraulic booster itself, or the like. Even when the force device does not operate normally, a hydraulic pressure higher than the hydraulic pressure generated in the master cylinder can be supplied to the wheel cylinders, and the braking force can be increased without a large operating force.

[Brief description of drawings]

FIG. 1 is a piping system diagram in an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the hydraulic booster in FIG.

FIG. 3 is an enlarged sectional view of a pressure boosting cylinder device as a first embodiment in FIG.

FIG. 4 is an enlarged cross-sectional view showing a modified example of the pressure boosting cylinder device as a second embodiment.

[Explanation of symbols] 1 hydraulic brake system 2 hydraulic booster 3 master cylinder 4 booster cylinder device 4'pressure booster cylinder device 8 hydraulic pump 9a wheel cylinder (front wheel) 9b wheel cylinder (front wheel) 17 servo piston 34 Stepped piston 34 'Stepped piston 34a Large diameter part 34a' Large diameter part 34b Small diameter part 34b 'Small diameter part 40 Supply path 40' Supply path 45 Switching valve 48 Poppet valve body 49 Plunger 58 Valve body 59 Plunger 60 Switching valve

Claims (4)

[Claims] 1. A hydraulic booster that operates by receiving an auxiliary power pressure from an external hydraulic pressure source in response to a driver's brake operation, and a brake fluid that receives an operating force via the hydraulic booster. A master cylinder that generates pressure and a wheel cylinder that is supplied with brake fluid pressure from this master cylinder to exert a braking force on the wheels, wherein the hydraulic booster is inside the body that is kept liquid-tight by a seal member. In a hydraulic brake system having a servo piston that is slidably disposed on the master cylinder and transmits the operating force to the master cylinder, the large-diameter portion receives the hydraulic pressure on the master cylinder side. , A stepped piston movable in a direction in which the hydraulic pressure on the wheel cylinder side is increased by a small diameter portion, and the master cylinder for the large diameter portion of the stepped piston. A pressure increasing cylinder device is provided in the hydraulic pressure supply passage on the side of the vehicle, which is provided with a switching valve that closes when the auxiliary power pressure is equal to or higher than a predetermined pressure and opens when the auxiliary power pressure becomes lower than the predetermined pressure. Hydraulic brake system equipped with. 2. A valve body in which the switching valve is seated on and off a valve seat provided in the supply passage, and a plunger for receiving the auxiliary power pressure so as to control the seating on and off of the valve body. The hydraulic brake system according to claim 1, which includes: 3. The hydraulic brake system according to claim 2, wherein the valve element and the plunger of the switching valve are arranged such that their moving directions coincide with each other. 4. The plunger according to claim 2 or 3, wherein the plunger receives the acting force of the auxiliary power pressure and the biasing force of the spring in opposition to each other without receiving the acting force of the hydraulic pressure of the master cylinder. Hydraulic brake system.