JPS5826667A - Vacuum booster - Google Patents

Abstract

PURPOSE:To increase the rigidity of the shell of a vacuum booster and to reduce the wall thickness of the shell for making the booster light-weight by forming the front peripheral wall of the front shell having a diameter smaller than that of the rear peripheral wall of the front shell on which a diaphragm rolls so that an annular step part is provided in the middle part of the front shell. CONSTITUTION:The front shell 1A of a booster comprises a rear peripheral wall 1Ab on which a diaphragm 3 rolls and a front peripheral wall 1Aa. Further, the front peripheral wall 1Aa has a diameter smaller than that of the rear peripheral wall 1Ab so that an annular step part 1Ac is provided in the middle part of the front shell 1A. However, the inner diameter of the front peripheral wall 1Aa is made larger than the outer diameter of a booster piston 2 in order to avoid interference with the booster piston 2 which is advancing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a negative pressure booster used for operating mask cylinders such as brakes and clutches of automobiles.

As such a booster, the booster shell is composed of a front shell and a rear shell whose open ends are joined to each other, and the booster shell has a booster piston housed therein so as to be able to move back and forth, and an inner circumference of the booster shell. A rolling diaphragm whose ends are tied and whose outer peripheral end is clamped between the front and rear shells divides the booster piston into two chambers, and the booster piston is moved forward by the pressure difference generated between the two chambers. What has been done is already known.

Generally, the interior of the front shell is a negative chamber that is constantly connected to a negative pressure source and is the main operating space for the booster piston, so the front shell is formed to have a longer axial length than the rear shell. Therefore, if the thickness of the shells is the same, the peripheral wall of the front shell will have lower rigidity than the peripheral wall of the rear shell.

Therefore, conventionally, both the front and rear shells are made of sufficiently thick material for reasons of production control, but this inevitably increases the weight of the booster shell.

The present invention has been proposed in view of the above, and focuses on the fact that the transfer stroke of the rolling diaphragm is approximately half of the operating stroke of the booster piston, The front peripheral wall in front of the rear peripheral wall is formed to have a smaller diameter so as not to interfere with the booster piston, and an annular step is provided in the middle of the front shell, and this annular step increases the rigidity of the front shell. However, it is an object of the present invention to provide the above-mentioned booster, which can reduce its plate thickness and, by extension, its weight.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. The booster shell 1 is composed of a front shell 1A and a rear shell 1B that are joined by abutting their open ends against each other.
Inside, there is a booster piston 2 housed therein so as to be able to move back and forth, and an inner peripheral bead 3a on the rear surface of the piston 2.
are tied together and the outer peripheral bead 3b is attached to the front and rear shells 1.
, 4.18 rolling type diaphragm 3 sandwiched between
It is divided into a first working chamber A at the front and a second working chamber B at the rear.

The diaphragm 3 covers the outer peripheral surface of the booster piston 1 and allows the convex surface of the U-shaped bent portion 3C to face the first working chamber A. Therefore, when the booster piston 2 moves forward from the retracted position shown in FIG. 2, the diaphragm 3 moves the bent portion 3C forward while rolling on the inner peripheral surface of the front shell 1A. That is, the displacement iLd of the bent portion 3C becomes one half of the operating stroke Lp of the booster piston 2.

In the front shell 1A, the part where the diaphragm 3 rolls is the rear wall IAb, and the front part thereof is the front peripheral wall iAa.
The front peripheral wall 1Aα is formed to have a smaller diameter than the rear peripheral wall 1Ab, and an annular stepped portion 1Ac is provided in the middle of the front shell 1A. However, it goes without saying that the inner diameter of the front peripheral wall 1Aα is formed to be larger than the outer diameter of the booster piston 2 so as not to interfere with the advancing booster piston 2.

The first working chamber A is always in communication with the intake manifold (not shown) of the internal combustion engine, which is a negative pressure source, through a connecting pipe 4, and the second working chamber B is in communication with the first working chamber through a control valve 5. A, or the lower atmosphere introducing lower part of the valve body holding cylinder 6, which will be described later, is controlled to be communicated with AC.

The booster piston 2 is always urged in the backward direction, that is, toward the second working chamber B, by a coil-type return spring 8 contracted in the first working chamber A, and its backward limit is reached by a protrusion 3d formed protrudingly on the back surface of the diaphragm 3. is regulated by contacting the rear wall of the booster shell 1.

The booster piston 2 is integrally formed with a valve cylinder 9 that projects in the axial direction from the rear surface of its central portion, and the rear end thereof is open to the atmosphere. This valve cylinder 9 is slidably supported by a flat bearing 10 fixed to a rear extension cylinder 1Bα of the rear shell 1B.

The control valve 5 is configured in the valve cylinder 9 as follows.

That is, an annular first valve seat 11° is formed on the front inner wall of the valve cylinder 9, and a valve piston 13 connected to the input rod 12 and forming the front end thereof is slidably connected to the front part of the valve cylinder 9. An annular second valve seat 112 surrounded by the first valve seat 111 is formed at the rear end of the valve piston 13 .

A base end portion 14α of a cylindrical valve body 14 with both ends open is held on the inner wall of the valve cylinder 9 via a valve body holding cylinder 6 fitted into the valve cylinder 9. The rear end of the valve body holding cylinder 6 is open as an atmosphere introduction lower part. The valve body 14 is made of an elastic material such as rubber, and extends from its base end 14α to a thin intermediate portion 14.
b extends radially inward, and a thick valve portion 14C is connected to the inner peripheral end of the intermediate portion 14bΩ.
are opposed to the first and second valve seats 1j, -11x. Thus, the valve portion 14C can be moved back and forth by deforming the intermediate portion 14b.

An annular reinforcing plate 15 is embedded in the valve portion 14C, and a valve spring 16 acts on this to bias the valve portion 14C toward both valve seats Tlr-112.

The outer part of the first valve seat 111 is the through hole 1 of the booster piston 2.
7 to the first working chamber A, and the first and second valve seats 1
1. ．． The middle part of the second valve seat 112 is always connected to the second working chamber B- through another through hole 18, and the inner part of the second valve seat 112 is always connected to the atmosphere introducing lower part through the valve body 14 and the inside of the valve body holding cylinder 6. communicate.

Further, a boss 21 having a stepped cylinder hole 2o for accommodating the reaction mechanism 19 is raised on the front surface of the central portion of the booster piston 2. The stepped cylinder hole 2o consists of a large diameter hole 22 that opens on the front surface of the boss 21, and a small diameter hole 23 connected to the back of the large diameter hole 22.
6 and the large diameter hole 22, the elastic piston 24 and the reaction piston 25 are sequentially slid together, so that the elastic piston 24 is interposed between the other two pistons 25 and 26. Then,
The reaction mechanism 1 is made up of the three pistons 24, 25, and 26.
9 is composed.

An output rod 27 is attached to the front surface of the reaction histone 25 via a spring pin 28. This output rod 27 passes through the front wall of the front shell IA and is connected to the rear end of an actuating piston 29 that slides into the cylinder body 30 of the brake mask cylinder M attached to the front wall.

A return spring 32 that springs the input rod 12 in the backward direction is compressed between the valve body holding cylinder 6 fixed to the valve cylinder 9 and the spring seat body 31 fixed to the input rod 12. A stopper 33 for regulating the limit is inserted into the small diameter hole 23 of the valve piston 1.
It is fixed to the small shaft 13α of No. 3.

A retractable dustproof boot 34 that covers the valve cylinder 9 is stretched between the rear extension cylinder 1Bα of the rear shell 1B and the valve body holding cylinder 6. An air filter 3 is installed at the air inlet T of the valve body holding cylinder 6.
5. Attach 36 respectively.

Note that 37 in the figure is a brake pedal connected to the input rod 12.

Next, to explain the operation of this embodiment, FIG. 2 shows the booster in the non-operating state, in which the input rod 12 and the booster piston 2 are moved to a predetermined retracted position by the elastic force of the return spring 8.32. is retained.

Also, the valve piston 13 is moved to the second position by the elastic force of the return spring 32.
The valve seat 112 is seated on the front surface of the valve portion 14C, and the valve seat 112 is seated on the front surface of the first valve seat 11. with a gap l between them.
is formed. Therefore, the first working chamber A, which constantly stores negative pressure, communicates with the second working chamber B via the through hole 17, the gap y, and the through hole 18, and the front opening of the valve portion 14C is connected to the second valve seat. 112, the negative pressure in the first working chamber A is transmitted to the second working chamber B, the air pressure in both working chambers A and H is balanced, and the booster piston 2 is under the control of the return spring 8. It is placed.

Now, step on the brake pedal 37 to brake the vehicle,
When the input rod 12 and the valve piston 13 are moved forward, the valve portion 14C, which is urged forward by the valve spring 16, moves forward following the valve piston 13 and immediately moves forward to the first valve seat 11. seated on the second valve seat 1, cutting off the communication between both working chambers A and B, and at the same time
12 is separated from the valve portion 14C and communicates the second working chamber B with the atmosphere introduction lower via the through hole 18 and the inside of the valve body 14.

Therefore, the atmosphere is quickly introduced into the second working chamber B, and the pressure in the second working chamber B becomes higher than that in the first working chamber A. The pressure difference between the two chambers A and B causes the booster piston 2 to resist the return spring 8. As the output rod 2T moves forward via the elastic piston 24 and the reaction piston 25, the actuating piston 29 of the brake mask cylinder M is driven and the vehicle is braked.

On the other hand, when the small shaft 13α of the valve piston 13 comes into contact with the elastic piston 24 via the pressure receiving piston 26 due to its advancement, a part of the elastic piston 24 is pushed into the small diameter hole 24 by the actuation reaction force transmitted from the output rod 2T to the reaction piston 25. A bulging deformation occurs on the side, and as a result, part of the reaction force is transferred to the pressure receiving piston 26.
It is fed back to the brake pedal 37 side via the valve piston 13, so that the driver can sense the output of the output rod 27, that is, the braking force.

Next, when the depression force of the brake pedal 37 is released, first the reaction force applied to the valve piston 13 and the return spring 32 are released.
The input rod 12 retreats due to the elastic force of , thereby seating the second valve seat 112 on the valve portion 14C and
4C from the first valve seat 111 and a gap is again formed between them, both working chambers A are
, H quickly balance each other, and if there is no difference between them, the booster piston 2 will retreat with the elastic force of the return spring 80.

As described above, according to the present invention, the front circumferential wall in front of the rear circumferential wall of the front shell is formed to have a smaller diameter than the rear circumferential wall of the front shell where the rolling diaphragm moves as the booster piston operates, and Since the front shell is provided with an annular step, the rigidity of the front shell can be significantly increased by the annular step.

As a result, the thickness of the front shell can be reduced, and the weight of the booster shell can be reduced.

Further, by forming the front wall of the front shell to have a small diameter, the front shell can be made compact, and the booster can be easily installed in a narrow space such as an engine room of an automobile.

[Brief explanation of the drawing]

Fig. 1 is a front view of one embodiment of the negative pressure booster of the present invention, and Fig. 2 is a view of Fig. 1 in the state of connection with a mask cylinder.
It is a sectional view taken along the line -■. A...First working chamber, B...Second working chamber, 1A...
Front shell, 1B... Rear shell, 1Aα... Front circumferential wall, 1Ab... Rear circumferential wall, IAC... Annular step,
1... Booster shell, 2°... Booster piston,
3゛°・Diaphragm, 3a...Inner peripheral bead, 3b・
...Outer bead. 3c...Bending portion patent applicant Nissin Kogyo Co., Ltd.

Claims (1)

[Claims] The booster shell is composed of a front shell and a rear shell whose open ends are joined to each other, and a booster piston is housed inside the booster shell so as to be able to move back and forth;
The booster piston is divided into two chambers by a rolling diaphragm whose inner peripheral end is connected to the piston and whose outer peripheral end is clamped between the front and rear shells. In a negative pressure booster configured to operate the booster piston forward, the diaphragm is formed to have a small diameter at a front local wall in front of the rear circumferential wall of the front shell on which the diaphragm rolls as the booster piston is operated; A negative pressure booster, characterized in that an annular step is provided in the middle of the front shell.