JPH0495558A - Servo hydraulic pressure output unit - Google Patents

Abstract

PURPOSE:To shorten an operating stroke by interposing an on-off valve, which opens when a hydraulic pressure in an output hydraulic pressure chamber is less than the specified value, between a boost chamber, being partitioned off between a master cylinder body and a booster cylinder, and a reservoir after installing it at the outside of a booster piston. CONSTITUTION:In a hydraulic booster B having a booster piston 15, adjoining its back to an output hydraulic pressure chamber 14 and being slidably fitted in a booster cylinder 13 to be concentrically to the rear end of a cylinder body 1 of a master cylinder, and a valve piston 16 being fitted in this booster piston 15 free of slide motion while connected to an operating member 40, a front end of the booster piston 15 is formed into a larger diameter than the rear end of a master piston 6, and a boost chamber 32 is partitioned off in space between the cylinder body 1 of the master cylinder M and the booster cylinder 13 of the hydraulic booster B. Then, an on-off valve 58 to be opened according to a fact that the hydraulic pressure in the output hydraulic chamber 14 becomes less than the specified value is installed between this boost chamber 32 and a reservoir R2, and this valve 58 is installed at the outside of the booster piston 15.

Description

Detailed Description of the Invention A1 Object of the Invention (1) Industrial Application Field The present invention relates to a cylinder body and a master piston that is slidably fitted into the cylinder body with its front surface facing a hydraulic pressure chamber. a master cylinder having: a booster cylinder coaxially coupled to the rear end of the cylinder body; a booster piston slidably fitted to the booster cylinder with its back surface facing the output hydraulic pressure chamber; a valve piston slidably fitted and connected to the operating member;
an inlet valve interposed between the output hydraulic pressure chamber and the hydraulic pressure supply source to open in response to the forward motion of the valve piston relative to the booster piston; and an inlet valve that closes in response to the forward motion of the valve piston relative to the booster piston. and a hydraulic pressure booster having an outlet valve interposed between the output hydraulic pressure chamber and the reservoir.

(2) Prior Art Conventionally, such a device has been used, for example, in Japanese Patent Publication No. 63-44587
This method is already known from Japanese Patent Application Laid-open No. 62-149547 and the like.

(3) Problems to be Solved by the Invention In the conventional device described above, hydraulic pressure is applied to the output hydraulic pressure chamber in accordance with the relative movement of the valve piston in the axial direction with respect to the booster piston by the operation of the operating member, thereby causing forward movement. By directly pressing the master piston of the master cylinder with the booster piston, the master cylinder is operated with a booster force.

However, in such a structure, the working stroke of the booster piston and the working stroke of the master piston in the master cylinder are the same, and during normal operation when the hydraulic pressure supply source is operating normally, the booster piston moves only as much as the working stroke of the master piston. A piston or operating member must be operated.

The present invention has been made in view of the above circumstances, and has a simple configuration that contributes to shortening the operating stroke of the operating member by making the operating stroke of the booster piston smaller than the operating stroke of the master piston in the master cylinder during normal operation. It is an object of the present invention to provide a boosting hydraulic pressure output device that can perform the following tasks.

B0 Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, according to the present invention, the front end of the booster piston is formed to have a larger diameter than the rear end of the master piston, and the master cylinder A boost chamber is defined between the cylinder body of the hydraulic booster and the booster cylinder of the hydraulic booster, with the front end of the booster piston and the rear end of the master piston facing at both ends. An on-off valve that opens when the hydraulic pressure in the pressure chamber becomes lower than a predetermined value is disposed outside the booster piston.

(2) Effect According to the above configuration, when the valve piston is not operated by the operating member, no hydraulic pressure is acting on the output hydraulic pressure chamber, so when the on-off valve is open, the boost chamber is communicated with the reservoir. The hydraulic pressure in the boost chamber is at atmospheric pressure. Therefore, even if the working fluid in the boost chamber expands due to a rise in temperature, the pressure in the boost chamber will not increase. When the valve piston is moved forward by a certain amount, the outlet valve closes and the inlet valve opens, and the opening/closing valve opens in response to the hydraulic pressure from the hydraulic pressure supply source acting on the output hydraulic pressure chamber. As the valve closes, the booster piston moves forward, and the opening and closing operations of the inlet and outlet valves in accordance with the relative movement of the valve piston and booster piston in the axial direction increase the hydraulic pressure in the output hydraulic pressure chamber in accordance with the amount of operation of the valve piston. The booster piston is driven forward.

The forward movement of the booster piston is transmitted to the master piston via the hydraulic pressure in the boost chamber, and since the booster piston has a larger diameter than the master piston, the amount of forward movement of the booster piston is transmitted to the master piston through the hydraulic pressure in the boost chamber. It is possible to make it smaller than the amount. Moreover, since the on-off valve is disposed outside the booster piston, the axial length of the booster cylinder does not increase due to the provision of the on-off valve.

(3) Embodiment Hereinafter, an embodiment in which the present invention is applied to a vehicle brake system will be described with reference to the drawings.

First, in FIG. 1, a cylinder body 1 of a master cylinder M has a cylinder hole 2 with a closed front end, and a front hydraulic chamber 3 is formed between the cylinder hole 2 and the front end wall.
A front master piston 4 that defines a front master piston 4 and a rear master piston 6 that defines a rear hydraulic pressure chamber 5 between the front master piston 4 and the rear master piston 6 are slidably fitted. Moreover, the front hydraulic chamber 3
A front return spring 7 that urges the front master piston 4 in the backward direction is accommodated in the rear hydraulic pressure chamber 5, and a rear return spring 8 that urges the rear master piston 6 in the backward direction is housed in the rear hydraulic pressure chamber 5. is accommodated. Further, a reservoir R1 is attached to the upper part of the cylinder body 1.

In such a master cylinder M, when the rear master piston 6 is pushed forward, the front master piston 4 can be moved forward while compressing both the return springs 7 and 8, thereby causing each master piston 4 and 6 to move forward. Before the front faces of the rear hydraulic chambers 3.5 are faced, the volume of the rear hydraulic chambers 3.5 is reduced, and braking hydraulic pressure can be applied to the corresponding wheel brakes 10a, 10b from the output ports 9a, 9b leading to these hydraulic pressure chambers 3, 5. can.

The rear end portion of the cylinder body 1 of the master cylinder M is provided with an outwardly projecting flange 1a and a connecting cylinder portion 1b that coaxially projects toward the rear side of the flange 1a.

On the other hand, a flange 13a facing the flange 1a is provided at the front end of the booster cylinder 13 in the hydraulic booster B, and the connecting cylinder 81b is connected to the booster cylinder 13.
The booster cylinder 13 is coaxially connected to the rear end of the cylinder body I by fitting into the front end of the cylinder body I and tightening both flanges la and 13a with bolts 12.

Moreover, when the master cylinder M and the hydraulic booster B are connected, the cylinder hole 2 of the master cylinder M passes into the booster cylinder 13 at the rear end of the connecting cylinder B1b, and the inner surface of the rear end of the cylinder hole 2 is A retaining ring 11 that restricts the backward limit of the rear master piston 6 is fitted.

Referring also to FIG. 2, the hydraulic booster B includes a booster cylinder 13, a booster piston 15 that is slidably fitted into the booster cylinder 13 with its back facing the output hydraulic pressure chamber 14, and A valve piston 16 is slidably fitted into the piston 15, and a valve piston 16 is interposed between the output hydraulic pressure chamber 14 and the hydraulic pressure supply source 17 to open the valve in response to the forward motion of the valve piston 16 with respect to the booster piston 15. the inlet valve 18 and the booster piston 15 of the valve piston 16;
The output hydraulic pressure chamber 1 is closed in response to the forward movement of the output hydraulic chamber 1.
4 and an outlet valve 19 interposed between the reservoir R2.

In the booster cylinder 13, a large diameter hole 20, a medium diameter hole 21, and a small diameter hole 22 are coaxially connected in order from the front end side while forming a step between the phase tiles. The connecting cylinder portion 1b at the rear end is fitted into the front portion of the large diameter hole 20 via the seal member 23.

A guide cylinder 24 is fitted into the large-diameter hole 20 so as to be sandwiched between the step between the large-diameter hole 20 and the medium-diameter hole 21 and the rear end of the connecting cylinder part 1b. The inner diameter D1 of the cylinder hole 24 is larger than the inner diameter D2 of the cylinder hole 2 that communicates with the inside of the booster cylinder 13 at the rear end of the connecting cylinder portion 1b, and
It is set slightly larger than the inner diameter of No. 1.

A booster piston 15 is slidably fitted into the medium diameter hole 21 of the booster cylinder 13 . The front part of the booster piston 15 is formed as a small diameter piston part 15a with a smaller diameter than the rear large diameter piston part 15b, and the large diameter piston part 15b can freely slide into the medium diameter hole 21 via a sealing member 25. The small diameter piston portion 15a is slidably fitted into the guide tube 24. Further, a sealing member 2 is provided on the inner surface of the rear end of the guide tube 24, and is in sliding contact with the small diameter piston portion 15a.
6 is fitted, and a seal member 27 that slides into contact with the inner surface of the guide cylinder 24 is fitted on the front end outer surface of the small diameter piston portion 15a. Furthermore, the seal member 26 is a cup seal, and is formed to allow the flow of hydraulic fluid from the front side of the seal member 26 toward the rear side (from the left side to the right side in FIG. 2).

A rod portion 15C is coaxially protruded from the rear portion of the booster piston 15. This rod portion 15c penetrates a small-diameter hole 22 at the rear end of the booster cylinder 13 and protrudes rearward, and a sealing member 28 is fitted into the inner surface of the small-diameter hole 22 so as to be in sliding contact with the outer surface of the rod portion 15c. Ru. Furthermore, between the medium-diameter hole 21 and the small-diameter hole 22, a regulating step portion 29 is provided that can abut against the rear end surface of the large-diameter piston portion 15b in order to define the retraction limit of the booster piston 15.

By fitting the booster piston 15 into the medium-diameter hole 21 in this way, an annular input hydraulic pressure chamber 31 that faces the front surface of the large-diameter piston 15b and an annular output fluid pressure chamber that exposes the rear surface of the large-diameter piston portion 15b are created. The pressure chamber 14 and the booster piston 1
5 and the booster cylinder 13. Moreover, the pressure receiving area of the booster piston 15 facing the output hydraulic pressure chamber 14 is set larger than the pressure receiving area facing the input hydraulic pressure chamber 31.

Cylinder body 1 of master cylinder M and hydraulic booster B
A boost chamber 32 is defined between the booster cylinder 13 and the booster cylinder 13 so as to be surrounded by a guide tube 24 . Therefore, the rear end of the rear master piston 6 in the master cylinder M,
Also, the front end of the booster piston 15 is connected to the boost chamber 3.
We will face both ends of 2. A base end of an output rod 33 that can come into contact with the rear end of the rear master piston 6 is coaxially fixed to the front end of the booster piston 15 . The axial length of the output rod 33 is set such that when the booster piston 15 is in the backward limit position, there is a predetermined distance between it and the rear master piston 6 which is in the backward limit position. ing.

A supply passage 34 communicating with the manual hydraulic pressure chamber 31 is bored in the booster cylinder 13, and the supply passage 34 is connected to the hydraulic pressure supply source 1.
Connected to 7. Thus, the hydraulic pressure supply source 17 is connected to the reservoir R.
The hydraulic pump 36 is connected to a motor 35 to pump up hydraulic fluid from the hydraulic pump 2, and an accumulator 37 is connected to the hydraulic pump 36.

A reaction force mechanism 38 is provided at the front end of the booster piston 15. This reaction force mechanism 38 has one end facing a reaction force chamber 76 communicating with the boost chamber 32 and the other end facing a spring chamber 77.
A reaction force piston 75 is fitted into the front end of the booster piston 15 so as to be slidable in the axial direction, and a spring is housed in a spring chamber 77 to exert a spring force that reduces the volume of the reaction force chamber 76. 78.

On the other hand, a valve piston 16 is fitted into a sliding hole 30 provided in the booster piston 15 so as to be slidable in the axial direction.
The front end of the valve piston 16 is thrust into the spring chamber 77 so as to be able to come into contact with the reaction force piston 75 . Therefore, when the valve piston 16 is at the backward limit position with respect to the booster piston 15 and no hydraulic pressure is acting on the boost chamber 32, that is, the reaction force chamber 76, there is a gap between the front end of the valve piston 16 and the reaction force piston 75. are spaced at regular intervals.

The front end of an input rod 39 is swingably connected to the rear of the valve piston 16, and the input rod 39 is connected to a brake pedal 40 as an operating member.

A circlip 41 is fitted to the rear end of the rod portion 15c of the booster piston 15, which contacts the rear end of the valve piston 16 to restrict the backward limit of the valve piston 16. Further, a step 115d facing the rear is provided at the rear l of the booster piston 15, and this step 15d and the valve piston 16
A return spring 42 is interposed between the rear ends, and the return spring 42 urges the valve piston 16 rearward with respect to the booster piston 15. Further, a step portion 16a is provided at the rear portion of the valve piston 16 and is opposed to the step portion 15d so as to be able to come into contact with the step portion 15d.

An annular chamber 43 is defined between the outer surface of the guide tube 24 at an approximately central portion in the axial direction and the inner surface of the small diameter hole 20, and the small diameter hole 20 is formed on the outer surface of the guide tube 24 at a position sandwiching the annular chamber 43 from both sides. Sealing members 44 and 45 are fitted in contact with the inner surface. Further, the booster cylinder 13 is provided with a passage 46 that communicates the annular chamber 43 with the reservoir R2. Further, the guide tube 24 is provided with a passage 72 that communicates with the annular chamber 43 and opens on the inner surface of the guide tube 24 between the seal members 26 and 27, and the booster piston 15 has a passage 47 that communicates with the passage 72 at all times. drilled.

An annular groove 48 is provided on the outer surface of the valve piston 16, which communicates with the output hydraulic pressure chamber 14 at all times, and which communicates with the input hydraulic pressure chamber 31 and opens into the inner surface of the sliding hole 30, and which is connected to the valve provided in the booster piston 15. The hole 49 and the annular groove 48 constitute the inlet valve 18.

Further, an annular groove 52 communicating with the annular groove 48 via a communication passage 51 is provided on the outer surface of the valve piston 16.
7, a valve hole 53 opened on the inner surface of the sliding hole 3o, and provided in the booster piston 15, and the annular groove 5.
2 constitute an outlet valve 19.

The inlet valve 18 is closed when the valve piston 16 is at the maximum retraction position relative to the booster piston 15, and the outlet valve 19 is closed when the valve piston 16 is at the maximum retraction position relative to the booster piston 15. The valve is in an open state at a certain time, and when the forward movement of the valve piston 16 relative to the booster piston 15 is started, the valve is closed before the inlet valve 18 opens.

A passage 57 communicating with the boost chamber 32 is bored in the booster cylinder 13, and the passage 57 and the reservoir R are connected to each other.
An opening/closing valve 58 that switches between a closed state that cuts off communication between the passage 57 and the reservoir R2 and an open state that communicates between the passage 57 and the reservoir R2 according to the hydraulic pressure in the output hydraulic pressure chamber 14 is connected to the booster piston 15.
The booster cylinder 13 is disposed on the outside of the booster cylinder 13.

The valve surface 59 of this on-off valve 58 is configured in the shape of a bottomed cylinder with one end open, and is fitted and fixed into a bottomed hole 60 provided in the booster cylinder 13 with the closed end side in the outer position. Ru. Moreover, on the inner surface of the axially intermediate portion of the valve surface 59, a crocodile portion 63 whose inner edge forms a valve hole 62 is provided to protrude radially inward. A liquid chamber 64 communicating with the valve hole 62 is formed between the closed end of the valve surface 59 and the flange 63, and the liquid chamber 64 communicates with the passage 57.

A piston 65 is slidably fitted into the valve surface 59 between the flange portion 63 and the bottom of the bottomed hole 60, and a spherical valve body 67 capable of closing the valve hole 62 is attached to one end of the piston 65.
is fixed.

Thus, a hydraulic pressure chamber 68 is defined between the piston 65 and the bottom of the bottomed hole 60, and the hydraulic pressure chamber 68 is communicated with the output hydraulic pressure chamber 14 via a passage 66 provided in the booster cylinder 13. . A reservoir R2 is provided between the piston 65 and the flange 63.
A release chamber 69 is defined which leads to the. Further, a press rod 70 that gently passes through the valve hole 62 and comes into contact with the valve body 67 is housed in the liquid chamber 64 so as to be movable in the axial direction. A spring 71 that biases the pressing rod 70 toward the piston 65 is provided in between.

In such an on-off valve 58, when the hydraulic pressure in the output hydraulic pressure chamber 14 exceeds a predetermined value, the piston 65 resists the spring force of the spring 71 and closes the valve hole 62 with the valve body 67 due to the hydraulic pressure in the hydraulic pressure chamber 68. is moving in the direction of closing the passage 57, that is, the boost chamber 32 and the reservoir R2,
When the hydraulic pressure in the output hydraulic pressure chamber 14 falls below a predetermined value, the piston 65 moves toward the hydraulic pressure chamber 68 by the spring force of the spring 71.
In this state, since the valve hole 62 is open, the passage 57, that is, the boost chamber 32 and the reservoir R2 are communicated with each other.

Next, the operation of this embodiment will be explained. When the brake pedal 40 is not operated, the valve piston 16 is held at the retracting limit by the spring force of the return spring 42, and the booster piston 15 is held in place by the hydraulic pressure acting on the input hydraulic pressure chamber 31. It is held at the backward limit by pressure. Moreover, in this state, the inlet valve 18 is closed and the outlet valve 19 is open, so the output hydraulic pressure chamber 14
Since no hydraulic pressure is acting on the boost chamber 32 and the on-off valve 58 is open, the hydraulic pressure in the boost chamber 32 is at atmospheric pressure.

Therefore, even if the working fluid in the boost chamber 32 expands due to a rise in temperature, the pressure in the boost chamber 32 will not increase.

When the brake pedal 40 is depressed in this state, the valve piston 16 is pushed forward, first the outlet valve 19 is closed, and then the inlet valve 18 is opened. Therefore, hydraulic pressure is introduced into the output hydraulic pressure chamber 14 from the input hydraulic pressure chamber 31, and the booster piston 15 receives hydraulic pressure on its back surface and moves forward, while hydraulic pressure acts on the hydraulic pressure chamber 68 of the on-off valve 58. Then, the on-off valve 58 is closed.

By closing the on-off valve 58, the boost chamber 32 is placed in a sealed state, and the hydraulic pressure in the boost chamber 32 increases in accordance with the forward movement of the booster piston 15. Also, when the booster piston 15 moves forward due to the hydraulic pressure in the output hydraulic pressure chamber 14, the valve piston 16
moves backward with respect to the booster piston 15, and the outlet valve 19 opens and the inlet valve 18 closes.However, as the valve piston 16 is further moved forward, the valve piston 16 moves back toward the booster piston 15. By repeating this operation, the booster piston 15 moves forward.

The boost chamber 3 is opened in response to the forward movement of the booster piston 15.
2 increases, and as this hydraulic pressure acts on the rear end surface of the rear master piston 6 in the master cylinder M, the rear master piston 6 moves forward, and the output capos 9a, 9
Braking fluid pressure is output from b.

Moreover, the area of the front end surface of the booster piston 15 facing the boost chamber 32 is larger than the area of the rear end surface of the rear master piston 6 facing the boost chamber 32, so the amount of forward movement of the booster piston 15 is greater than the amount of forward movement of the rear master piston 6. The booster piston 1 in the hydraulic booster B can reduce the amount of operation and operate the master cylinder M with boost, and the booster piston 1 in the hydraulic booster B can operate normally when the hydraulic pressure supply source 17 is operating normally.
5, that is, the operating stroke of the brake pedal 40.

Furthermore, when the hydraulic pressure generated in the boost chamber 32 exceeds a certain value, the hydraulic pressure in the reaction chamber 76 communicating with the boost chamber 32 causes the reaction piston 75 to move against the spring force of the spring 78. When the piston 75 comes into contact with the front end of the valve piston 16, the actuation reaction force is applied to the valve piston 16 and the input rod 39.
This allows the operator of the brake pedal 40 to feel the output of the master cylinder M. Moreover, the reaction force piston 75 comes into contact with the valve piston 16 after the valve piston 16 is moved forward by a predetermined amount or more and the hydraulic pressure in the boost chamber 32 reaches a predetermined value or more, and the reaction force piston 75 comes into contact with the valve piston 16 after the hydraulic pressure in the boost chamber 32 reaches a predetermined value or more. The load can remain low.

Brake pedal 4 to release the operation of master cylinder M
When 0 is released, the valve piston 16 also retreats as the brake pedal 40 returns, and as a result, the inlet valve 18 closes and the outlet valve 19 opens, so that the output hydraulic pressure chamber I4
The hydraulic pressure is quickly discharged, and the booster piston 15 also quickly returns to the backward limit position.

Incidentally, the above-mentioned operation is performed when the hydraulic pressure supply source 17 is operating normally, but next, let us assume a case where the output hydraulic pressure from the hydraulic pressure supply source 17 decreases due to a failure or the like. In this case, as the hydraulic pressure in the output hydraulic pressure chamber 14 decreases in accordance with the decrease in the output hydraulic pressure of the hydraulic pressure supply source 17, the on-off valve 58 opens to communicate between the boost chamber 32 and the reservoir R2. For this reason,
Valve piston 1 in response to depression operation of brake pedal 40
The forward actuation of step 1 after the return spring 42 is compressed
6a contacts the stepped portion 15d, the power is transmitted to the booster piston 15, and the output rod 33 provided at the front end of the booster piston 15 directly presses the rear master piston 6 of the master cylinder M, causing the rear master piston 6 to move forward. Accordingly, braking fluid pressure is output from the output boats 9a and 9b.

At this time, the volume of the output hydraulic pressure chamber 14 increases, but the hydraulic fluid in the passage 72 communicating with the reservoir R3 flows into the input hydraulic pressure chamber 31 via the sealing member 26, and the inlet is in an open state. Since it flows into the output hydraulic pressure chamber 14 via the valve 18, the output hydraulic pressure chamber 14 will not be in a reduced pressure state.

Further, the on-off valve 58 is provided in the booster cylinder 13 on the outside of the booster piston 15, and by providing the on-off valve 58, the axial length of the booster piston 15, that is, the axial length of the booster cylinder cylinder 3 is reduced. It won't be long.

The present invention can be used not only to obtain brake hydraulic pressure as in the above-mentioned embodiments, but also to obtain hydraulic pressure for clutch operation.

C1 Effects of the invention As described above, according to the invention, the front end of the booster piston is formed to have a larger diameter than the rear end of the master piston, and there is a space between the cylinder body of the master cylinder and the booster cylinder of the hydraulic booster. A boost chamber is defined in which the front end of the booster piston and the rear end of the master piston are exposed at both ends, and is interposed between the boost chamber and the reservoir. The on-off valve, which opens when
During normal operation when the hydraulic pressure supply source is operating normally, the on-off valve is opened before the operating member starts operating, and the hydraulic pressure in the boost chamber is brought to atmospheric pressure, and the valve piston moves forward by operating the operating member. In response to the increase in hydraulic pressure in the output hydraulic pressure chamber due to the operation, the on-off valve is closed to seal the boost chamber, and the forward movement of the booster piston in response to the hydraulic pressure action on the output hydraulic pressure chamber is performed via the hydraulic pressure in the boost chamber. This can contribute to shortening the operating stroke of the booster piston, that is, the operating stroke of the operating member, by making the amount of forward movement of the booster piston smaller than the amount of forward movement of the master piston. Moreover, since the on-off valve is arranged outside the booster piston, the axial length of the booster cylinder does not increase due to the provision of the on-off valve, and an increase in the axial length of the booster cylinder can be avoided. can.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a longitudinal sectional side view, and FIG. 2 is an enlarged view of the main part of FIG. 1. DESCRIPTION OF SYMBOLS 1... Cylinder body, 5... Hydraulic pressure chamber, 6... Master piston, 13-... Booster cylinder, 14...
Output hydraulic pressure chamber, 15... Booster piston, 16-...
Valve piston, 17... Hydraulic pressure supply source, 18... Inlet valve, 19... Outlet valve, 32... Boost chamber, 40...
- Brake pedal as an operating member, 58... Opening/closing valve, B... Hydraulic pressure booster, M... Master cylinder, R
2...Reservoir

Claims (1)

[Claims] a master cylinder (M) having a cylinder body (1) and a master piston (6) slidably fitted into the cylinder body (1) with its front surface facing the hydraulic pressure chamber (5);
A booster cylinder (13) coaxially coupled to the rear end of the cylinder body (1), and a booster piston slidably fitted into the booster cylinder (13) with its back facing the output hydraulic pressure chamber (14). (15) and booster piston (1
5) and is slidably fitted into the operating member (40).
a valve piston (16) connected to the valve piston (16);
6) an inlet valve (18) interposed between the output hydraulic pressure chamber (14) and the hydraulic pressure supply source (17) to open in response to the forward movement of the booster piston (15); and the valve piston. A hydraulic booster (16) having an outlet valve (19) interposed between the output hydraulic pressure chamber (14) and the reservoir (R_2) to close in response to the forward movement of the booster piston (15). In the booster hydraulic pressure output device including B) and;, the front end of the booster piston (15) is formed to have a larger diameter than the rear end of the master piston (6), and ) and the booster cylinder (13) of the hydraulic booster (B), there is a front end of the booster piston (15) and a master piston (6).
A boost chamber (32) is defined with the rear end facing both ends, and is interposed between the boost chamber (32) and the reservoir (R_2), and the hydraulic pressure in the output hydraulic pressure chamber (14) is below a predetermined value. A booster hydraulic pressure output device characterized in that an on-off valve (58) that opens in response to the above is disposed outside the booster piston (15).