JP2584427Y2 - Brake booster - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake booster, and more particularly to an improvement in a seal structure of a slave cylinder, and more particularly to a brake booster which is effective when used in a large vehicle such as a bus or a truck. .

[0002]

2. Description of the Related Art As a brake booster mounted on a vehicle such as a bus, there is a brake booster provided with a power cylinder for converting air pressure to hydraulic pressure and a slave cylinder. In this brake booster, the inside of the power cylinder is partitioned into an air pressure chamber and an atmosphere chamber by a power piston in the power cylinder, and a push rod projects from the power piston toward the atmosphere chamber. The part is connected to a slave piston in the slave cylinder.

In this brake booster, when the pedal of the brake valve is depressed, compressed air is supplied to the pneumatic chamber in the power cylinder, so that the power piston moves to the slave cylinder side, and the push rod is moved. The slave piston is made to move forward. Then, as the slave piston advances, the oil in the pressure chamber in the slave cylinder is pressure-fed into the wheel cylinder, and a braking action is performed.

[0004] In such a brake booster,
As the seal structure of the slave cylinder, a rod seal type in which the oil seal cup is fixed to the cylinder and a piston seal type in which the oil seal cup is fixed to the piston side are adopted.

[0005] Among these seal structures, the rod seal type does not slide on the inner peripheral surface of the cylinder as compared with the piston seal type. For this reason, if a seal structure of a rod seal type is adopted, precision finishing becomes unnecessary, and processing becomes easy. Further, hysteresis can be reduced by reducing the sliding resistance.
Moreover, since a light metal can be used, the weight can be reduced.

Therefore, it is desired to employ a rod seal type seal structure in the brake booster. Generally, there are a conventional type, a plunger type, and a center valve type as a rod seal type seal structure used in the field of a brake device.

[0007]

However, in conventional and plunger type rod seal type seal structures conventionally used in the field of brake devices, there is a problem that machining of a relief port is difficult. .

On the other hand, the center valve type rod seal type seal structure has a large number of parts and a complicated structure as described in, for example, Japanese Utility Model Publication No. 34-1126 and Japanese Utility Model Publication No. 53-47199. There is a problem that there is.

Further, in the conventional rod seal type seal structure, since the slave piston and the push rod are shared, there is a problem that the diameter of the seal member becomes large and it is difficult to reduce the size and weight. .

An object of the present invention is to provide a brake booster which can simplify and reduce the size of a structure while employing a rod seal type sealing structure.

[0011]

A brake booster according to the present invention comprises a power cylinder in which a power piston is slidably inserted, an input cylinder chamber and an output cylinder in which a slave piston is inserted. And a slave cylinder partitioned into a chamber and a push rod protruding from the power piston, and a tip end of the push rod is connected to the slave piston, and the power cylinder moves the slave piston forward and backward. And a cylinder-shaped holder is concentrically fitted into the slave cylinder, and the slave piston slides in the holder. Freely inserted,
An oil seal cup is accommodated in the slave cylinder in front of the holder so as to slide on the slave piston. The slave piston is formed in a cylindrical shape, and the push rod is formed in a hollow portion of the cylinder. Is inserted so as to slide within a certain range, a valve plate is fixed to the tip of the push rod in the cylindrical hollow portion of the slave piston, and the input side cylinder is attached to the tip of the push rod. Oil connecting the inlet port to the outlet port, an outlet port arranged to face the valve plate, opened and closed by sliding the push rod with respect to the slave piston within a certain range, It is characterized in that a passage is opened respectively.

[0012]

In the above-mentioned means, when the power piston is in the retracted position, the outlet port is open, so that the output side cylinder chamber communicates with the oil reservoir through the input side cylinder chamber.

In this state, when the pedal is depressed, the compressed air from the air pressure source is pressed into the pneumatic chamber of the power cylinder in accordance with the amount of depression. The compressed air pressed into the pneumatic chamber advances the power piston.

Then, the push rod is advanced with the advance of the power piston. The outlet port is closed by the advance of the push rod. Thus, the flow of oil between the input side cylinder chamber and the output side cylinder chamber is shut off.

When the push rod is further advanced with the output port closed, the push rod advances the slave piston along the holder via the valve plate.

As the slave piston is pushed forward by the push rod, the pressure in the output side cylinder chamber increases. The increased pressure in the output side cylinder chamber 25 is sent to the wheel cylinder through the output port. The wheel cylinder is fixed to an anchor plate fixed to each of the front and rear axles, expands a pair of brake shoe assemblies, and applies a brake shoe to a friction surface of a brake drum provided on an outer periphery thereof to perform a braking action. . The brake shoe assembly is urged by a return spring in a direction to attract each other, and when the pressure oil is released to the wheel cylinder, the brake shoe is attracted to form a gap between the brake shoe assembly and the brake drum. , To eliminate the generation of braking force.

When the depression of the pedal is released, the compressed air in the pneumatic chamber is discharged into the atmosphere from a predetermined exhaust port by a brake valve. Then, the push rod is retracted toward the pneumatic chamber by the return spring, and the power piston is retracted.

At this time, until the push rod is moved by a predetermined distance, the push rod is relatively retracted in the slave piston so that the tip end surface is separated from the valve plate. Then, the slave piston is retracted along the holder together with the push rod.

When the slave piston is retracted in the holder together with the push rod, an outlet port 16 formed in the end face of the push rod is opened, and the input side cylinder chamber and the output side cylinder chamber are communicated with each other. The oil that has been pumped to the output side is returned to the output side cylinder chamber,
The braking action is released.

[0020]

1 is a longitudinal sectional view showing a brake booster according to an embodiment of the present invention. FIG. 2 is an enlarged partial sectional view showing the operation state.

This brake booster includes a power cylinder unit 1 for converting air pressure to hydraulic pressure, and a slave cylinder unit 2 for transmitting hydraulic pressure to a wheel cylinder (not shown). The power cylinder unit 1 includes a cylindrical power cylinder 3 and a power piston 5 fixed to one end of a push rod 4 disposed at the center of the power cylinder 3. The inside of the power cylinder 3 is divided into an air pressure chamber 6 and an atmosphere chamber 7 by the power piston 5. The distal end of the push rod 4 in the region constituting the atmosphere chamber 7 is linked to a slave piston, which will be described later, disposed in the slave cylinder unit 2 via a snap link. A spring 8 is provided on the push rod 4, and the push rod 4 is constantly urged toward the pneumatic chamber 6 by the spring 8.

An air port 9 is opened on the side of the air pressure chamber 6 of the power cylinder 3, and this air port 9 is connected to an air source via a brake valve (not shown). On the other hand, the slave cylinder 10 of the slave cylinder unit 2 is in contact with the power chamber 3 on the side of the atmosphere chamber 7 and is fastened by bolts and nuts. That is, the power cylinder 3 and the slave cylinder 10 are connected in series.

On the other hand, a push rod 4 is projected from the center of the power piston 5.
Of the slave cylinder 1 via the sealing member 11
0 is inserted along its center line. A cylindrical slave piston 12 is slidably fitted on the outer periphery of the insertion end of the push rod 4 into the slave cylinder 10, and the push rod 4 is inserted into the hollow portion 13 of the slave piston 12. It is connected to the slave piston 12 via the inserted snap ring 14 so as to be slidable within a predetermined range (described later).

Further, an inlet port 15, an outlet port 16, and an oil passage 17 connecting the inlet port 15 and the outlet port 16 are formed at the insertion end of the push rod 4 into the slave piston 12. The inlet port 15 is the slave piston 12 in the middle of the push rod 4.
The hollow portion 13 is opened at a position facing the open end side.
The inlet port 15 is connected to the slave cylinder 12 via an annular groove 18 formed on the inner peripheral surface of the hollow portion 13 of the slave piston 12 and a radial groove 19 formed on the end surface of the seal member 11 on the slave piston 12 side. 10 is connected to an input side cylinder chamber described later.

The outlet port 16 is formed on the distal end surface of the push rod 4, and a valve seat 20 is formed at the distal end surface of the push rod 4 at a position outside the outlet port 16 so as to bulge around the outlet port 16. ing.

A valve plate 21 is fitted to the end of the hollow portion 13 of the slave piston 12 on the inner peripheral surface thereof so as to be orthogonal, and a valve body 22 is provided on the end surface of the valve plate 21 on the push rod 4 side. Embedded. The valve body 22 relatively opens and closes the outlet port 16 by being relatively separated from and seated on the valve seat 20 as the push rod 4 advances and retreats with respect to the slave piston 12. A plurality of valve passages 23 are provided outside the valve body 22 in the valve plate 21 so as to communicate between the hollow portion 13 of the slave piston 12 and an output side cylinder chamber described later.

On the other hand, the hollow portion 13 of the slave piston 12
In the distal end opening peripheral surface of the guide 14A are Botsu設the annulus shape, the guide 14 A the snap ring 14 in the inner diameter of the is fitted slidably. When the power piston 5 is at the retracted position, the length of the guide 14A is such that the valve seat 20 and the valve body 22 on the distal end surface of the push rod 4 are separated by a predetermined distance, and the outlet port 16 is closed. When the power piston 5 is opened by the valve body 22 and extended by a certain distance from the retracted position, the outlet port 16 is closed by the valve body 22 when the valve seat 20 is pressed against the valve body 22. The slave piston 12 is set so as to move toward the output side cylinder chamber 25 along with the extension.

The interior of the slave cylinder 10 is partitioned into an input side cylinder chamber 24 and an output side cylinder chamber 25 by the push rod 4, the slave piston 12 and a holder described later. A step 26 is formed at the boundary between the steps. The slave cylinder 10 is provided with a reservoir port 27 and an output port 28, respectively, and the reservoir port 27 and the output port 28 are connected to the input cylinder chamber 24 and the output cylinder chamber 25 , respectively.

An oil seal cup 29 and a holder 30 each having a cylindrical shape are fitted into the input side cylinder chamber 24, respectively.
9 and the holder 30 are arranged in this order from the step 26 side. The seal member 11 is applied to the rear side of the holder 30, and the holder 30 and the oil seal cup 29 are positioned by the seal member 11. The slave piston 12 is slidably fitted on the inner peripheral side of the oil seal cup 29 and the holder 30.

Next, the operation will be described. As shown in FIG. 1, when the power piston 5 is in the retracted position, the valve element 22 is separated from the valve seat 20 formed on the distal end surface of the push rod 4, and the outlet port 16 is closed. Since it is in the open state, the output side cylinder chamber 25 is filled with oil from the input side cylinder chamber 24.

In this state, when a pedal (not shown) is depressed, compressed air from an air pressure source (not shown) is pressed into the pneumatic chamber 6 of the power cylinder 3 according to the amount of depression. The compressed air press-fitted into the air pressure chamber 6 advances the power piston 5 to the right in FIG. 1 against the urging force of the spring 8 .

Then, as the power piston 5 advances,
The push rod 4 is advanced rightward in FIG. As the push rod 4 advances, the push rod 4
The outlet port 16 is closed by the valve body 22 because the valve seat 20 formed on the distal end surface of the valve body is pressed against the valve body 22. Thereby, the flow of oil between the input side cylinder chamber 24 and the output side cylinder chamber 25 is shut off.

As shown in FIG. 2, when the push rod 4 is further advanced while the valve body 22 is seated, the push rod 4 moves the slave piston 12 through the valve plate 21 along the holder 30. To move forward.

As the slave piston 12 is pushed forward by the push rod 4, the pressure in the output side cylinder chamber 25 increases. The pressure of the oil in the output side cylinder chamber 25 becomes a pressure proportional to (diameter of the power piston 5) ² / (diameter of the slave piston 12) ² , and the increased pressure is output through the output port 28 to the wheel cylinder. And a braking action is performed.

When the depression of the pedal is released, the compressed air in the pneumatic chamber 6 is discharged to the atmosphere from a predetermined exhaust port (not shown) through an air port 9 by a brake valve. Thereby, the push rod 4 is retracted to the pneumatic chamber 6 side by the pressure of the oil in the output side cylinder chamber 25 together with the urging force of the spring 8, and the power piston 5 is retracted to the left side in FIG.

At this time, until the push rod 4 is moved by a predetermined distance, the push rod 4 is moved so that its tip end surface is separated from the valve plate 21.
2 is relatively retracted. And snap ring 1
When the abutment 4 comes into contact with the wall surface of the guide 14A, the slave piston 12 together with the push rod 4 is retracted to the left in FIG.

When the slave piston 12 is retracted in the holder 30 together with the push rod 4, the push rod 4
The valve seat 20 formed on the front end side of the valve body is separated from the valve body 22. For this reason, the outlet port 16 is opened, the input side cylinder chamber 24 and the output side cylinder chamber 25 are communicated, the oil that has been pressure-fed to the wheel cylinder is returned to the output side cylinder chamber 25, and the braking action is released. .

[0038]

[Effects of the Invention] As described above, according to the present invention,
The following effects are obtained. Since the seal structure in the slave cylinder is configured as a rod seal structure, sliding on the inner peripheral surface of the cylinder is eliminated as compared with the piston seal type seal structure.

As described above, the precision finishing of the slave cylinder can be omitted, and the processing is facilitated. Further, hysteresis can be reduced by reducing the sliding resistance. Moreover, since a light metal can be used, the weight can be reduced.

In spite of the rod seal type seal structure, the input side cylinder chamber and the output side cylinder chamber of the slave cylinder are connected to each other via the input port, the output port and the oil passage formed in the push rod. With this configuration, it is not necessary to open a relief port in the slave cylinder, and it is possible to avoid difficulties in processing the relief port.

Since the holder is interposed between the slave cylinder and the slave piston, the inner diameter of the slave cylinder required to reliably seal the atmosphere with the slave cylinder is determined by the amount of the holder. In addition to being able to be set large, an increase in the inner diameter of the push rod can be suppressed. As a result, in spite of the rod seal type seal structure, it is possible to improve the sealing performance with the atmosphere side while suppressing an increase in the diameter of the seal member.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a brake booster according to an embodiment of the present invention.

FIG. 2 is an enlarged partial sectional view showing an operation state thereof.

[Explanation of symbols]

1. Power cylinder part 2. Slave cylinder part 3.
Power cylinder, 4 ... Push rod, 5 ... Power piston, 6 ... Pneumatic chamber, 7 ... Atmosphere chamber, 8 ... Spring, 9
... Airport, 10 ... slave cylinder, 11 ... sealing member, 12 ... slave piston, 13 ... middle empty section, 14 ...
Snap ring, 14A ... guide, 15 ... input mouth port,
16 ... outlet port, 17 ... oil passage, 18 ... annular groove,
19 ... radial groove, 20 ... valve seat, 21 ... valve plate,
22: valve element, 23: valve passage, 24: input side cylinder chamber,
25: output side cylinder chamber, 26: stepped portion, 27: reservoir port, 28: output port, 29: oil seal cup, 30: holder.

Claims (1)

(57) [Scope of request for utility model registration] 1. A power cylinder having a power piston slidably fitted therein and a slave cylinder having a slave piston fitted therein and partitioned into an input cylinder chamber and an output cylinder chamber. A push rod protrudes from the power piston, and a tip end of the push rod is connected to the slave piston. The power cylinder moves the slave piston forward and backward to pump oil to the brake actuator. In the brake booster, a cylindrical holder is concentrically fitted in the slave cylinder, the slave piston is slidably fitted in the holder, and the holder in the slave cylinder is provided. The oil seal cup is housed so as to be in sliding contact with the slave piston. The slave piston is formed in a cylindrical shape, and the push rod is fitted into the hollow portion of the cylinder so as to slide within a certain range. A valve plate is fixed on the front side, and at the tip end of the push rod, an inlet port communicating with the input side cylinder chamber, and disposed so as to face the valve plate, and this push rod is slightly opposed to the slave piston. A brake booster characterized by having an outlet port opened and closed by sliding in the range of, and an oil passage connecting the inlet port and the outlet port.