JPH0541103Y2 - - Google Patents

Description

[Detailed description of the invention] A. Purpose of the invention (1) Industrial application field The present invention is a negative pressure booster mainly used for operating brake master cylinders of automobiles.
In particular, the booster shell contains a booster piston whose interior is partitioned into a negative pressure chamber on the front side and an operating chamber on the rear side, and which is urged in the backward direction by a return spring, and the booster piston is connected to the rear end of the booster piston. An input rod that can move back and forth and a control valve that communicates and switches the working chamber between the negative pressure chamber and the atmosphere inlet at the rear end of the valve cylinder are arranged in the valve cylinder. A covering cylinder that covers the valve cylinder and slidably supports its outer peripheral surface via a bearing and a seal member is provided protruding from the rear surface of the booster shell, and an input rod passes through the rear end of the covering cylinder. while forming an annular end wall;
The present invention relates to an improvement in a negative pressure booster in which the input rod is provided with a stopper plate that comes into contact with the inner surface of the end wall to restrict the retraction limit of the input rod.

(2) Conventional technology Such a negative pressure booster is known, for example, as disclosed in Japanese Utility Model Publication No.
This method is already known as disclosed in Japanese Patent Application Laid-Open No. 62-12453, respectively.

(3) Problems to be solved by the invention In such a negative pressure booster, in order to improve the responsiveness of the booster piston when the input rod moves forward, it is necessary to introduce atmospheric air into the working chamber through the atmospheric air inlet of the valve barrel. It is necessary that the introduction be smooth. By the way, in conventional models, a vent hole is bored in the stopper plate of the input rod in order to keep the atmosphere inlet of the valve barrel in constant communication with the atmosphere, but the opening area of the vent hole is enlarged to allow the introduction of the atmosphere. If an attempt is made to make the air flow smooth, a portion of the air hole will be blocked by the end wall of the covering tube, so there is a certain limit to increasing the effective opening area of the air hole.

The present invention was developed in view of these circumstances, and is designed to allow atmospheric air to be introduced smoothly into the air inlet of the valve cylinder without being interfered with by the end wall of the jacket cylinder or the stopper plate of the input rod. An object of the present invention is to provide the negative pressure booster.

B. Structure of the device (1) Means for solving the problem In order to achieve the above-mentioned purpose, the present invention involves drilling a vent hole in the peripheral wall of the covering tube to constantly communicate the atmosphere inlet of the valve tube with the atmosphere. The first feature is that the air filter covering the ventilation hole is housed and held in a cylindrical filter case that is fixed to the booster shell and surrounds the covering tube.

A second feature of the present invention is that a flange formed at one end of the filter case is sandwiched between a booster shell and a support wall that supports the shell.

(2) Effect According to the first feature above, the ventilation hole in the peripheral wall of the cladding tube creates an air passage with low ventilation resistance between the atmosphere and the atmosphere inlet of the valve cylinder. Since it is formed without any interference from the plate, when the input rod is operated, the atmosphere smoothly enters the operating chamber through the ventilation path. In addition, the air entering the cladding tube is filtered by the air filter covering the vent hole, which prevents dust in the atmosphere from adhering to the bearing and sealing members between the valve tube and the cladding tube and damaging them. obtain.

Furthermore, according to the second feature, since the flange of the filter case that holds the air filter is clamped between the booster shell and its support wall, no fixing means dedicated to the filter case is required.

(3) Embodiment An embodiment of the present invention will be described below with reference to the drawings.

First, in FIG. 1 showing a first embodiment of the present invention, a brake master cylinder M operated by the booster B is attached to the front surface of a booster shell 1 of a tandem negative pressure booster B.

The booster shell 1 includes a pair of front and rear shell halves 1a, 1b whose opposite ends are connected to each other, and is sandwiched between the two shell halves 1a, 1b so that the inside of the booster shell 1 is divided into a front shell chamber 2 and a rear shell chamber. 3, and a partition wall plate 1c that partitions the rear shell half body 1b into
is supported by a vehicle body (not shown).

The front shell chamber 2 includes a front booster piston 4 made of a steel plate that is housed therein so as to be able to reciprocate back and forth, and a front shell half body 1 that is superimposed and bonded to the rear surface.
A and a rubber front diaphragm 5 sandwiched between the partition wall plate 1c and the front negative pressure chamber 2a on the front side and a front working chamber 2b on the rear side. Further, the rear shell chamber 3 has a rear booster piston 6 made of a steel plate accommodated therein so as to be able to reciprocate back and forth, and is bonded to the rear face thereof, and is fixed together with the partition wall plate 1c between the two shell halves 1a and 1b. A rear diaphragm 7 made of rubber divides the chamber into a rear negative pressure chamber 3a on the front side and a rear working chamber 3b on the rear side.

The front and rear booster pistons 4 and 6 are each formed into an annular shape from a steel plate, and these are connected to the partition wall plate 1c.
It is connected to both ends of a piston boss 10 made of synthetic resin which is slidably supported via a bush 8 and a seal member 9 in the following manner.

That is, the depth of the piston boss 10 is
A circular recess 11 reaching approximately half the length of 0 is formed on the front end surface, and a flange 12 is bored at a location slightly forward from the rear end of the outer peripheral surface.
The circular recess 11 includes a front booster piston 4.
A connecting tube 1 with an end wall plate 13a connected to the inner peripheral end of the
3 are fitted together, and a presser plate 14 that cooperates with the flange 12 to clamp the rear booster piston 6 is superimposed on the rear end surface of the piston boss 10. The presser plate 14, the piston boss 10, and the end wall plate 13a are connected to a plurality of (three in the illustration) through bolts 15 surrounding the axis of the piston boss 10,
They are fixed to each other by a nut 16 screwed into them.

At that time, between the front booster piston 4 and the front end surface of the piston boss 10, there is provided an inner peripheral bead 5a of the front diaphragm 5, and a metal annular retainer 17 that covers the outer peripheral surface and rear surface of the inner peripheral bead 5a. is inserted between the flange 12 and the holding plate 14, and the inner peripheral bead 7a of the rear diaphragm 7, which wraps around the inner peripheral end of the rear booster piston 6, is inserted between the flange 12 and the holding plate 14.
Therefore, the front and rear booster pistons 4, 6 and the piston boss 10 are connected to each other, and at the same time, the inner peripheral bead 5 of each diaphragm 5, 7 is connected to each other.
a, 7a are fixed to the corresponding booster pistons 4, 6.

Further, a sealing member 19 is attached to the bolt hole 18 provided in the piston boss 10 for insertion of the through bolt 15, so that the bolt hole 18
communication between the front negative pressure chamber 2a and the rear working chamber 3b is blocked. Further, a sealing member 20 surrounding the plurality of through bolts 15 is interposed between the partition wall plate 13a and the piston boss 10. the first and second ports 30, 31 of
communication between them is blocked.

Each through bolt 15 is arranged with its square head 15a facing the rear working chamber 3b side, and its square head 15
A recess 21 (see FIG. 2) of the same shape is formed in the presser plate 14, into which the recess 21 (see FIG. 2) is fitted non-rotatably. Therefore, when the nut 16 is passed through and screwed onto the bolt 15 on the front negative pressure chamber 2a side, the bolt 15 is prevented from rotating, so that the nut 16 can be tightened reliably.

The seat plate 22 is overlappingly bonded to the end wall plate 13a of the connecting cylinder 13 using the through bolts 15 and nuts 16. This seat plate 22 has a plurality of nuts 16
It is provided with a plurality of seat parts 22a (see FIG. 3) that are raised higher than the height of the protruding part of the bolt 15 between them,
A return spring 2 that biases the piston boss 10 in the backward direction is provided between the seat portion 22a and the front shell half 1a.
3 will be reduced. In this way, the return spring 23 is received in the recess 11 on the front surface of the piston boss 10 together with the connecting cylinder 13.

The backward limit of both booster pistons 4 and 6 is regulated by a large number of protrusions 24 raised on the rear surface of rear diaphragm 6 abutting against the rear wall of booster shell 1 .

A valve cylinder 25 is integrally protruded from the rear end of the piston boss 10, and this valve cylinder 25 is connected to a cover cylinder 2 which is protruded from the rear wall of the booster shell 1 and covers the valve cylinder 25.
6 via a bearing 27 and a seal member 28 in a slidable manner.

As clearly shown in FIG.
and a locking ring 57 that engages with the inner circumferential surface of the annular rib 6 that protrudes outward in the radial direction at the intermediate portion of the covering tube 26.

The front negative pressure chamber 2a is connected to a negative pressure source (not shown, for example, inside an intake manifold of an internal combustion engine) via a negative pressure introduction pipe 29. Further, both the front and rear negative pressure chambers 2a, 3a communicate with the inside of the valve cylinder 25 via a bifurcated first port 30 formed in the piston boss 10, and both the front and rear working chambers 2b, 3b are connected in the same way. A pair of second ports 3 formed in the piston boss 10
It communicates with the inside of the valve cylinder 25 via 1 and 31. The second ports 31 and 31 are connected to the first port 30 and the atmosphere inlet 33 at the rear end of the valve cylinder 25 by the control valve 32.
Communication is switched alternately.

Inside the valve cylinder 25, an input rod 35 connected to the brake pedal 34 and the control valve 32 controlled by the input rod 35 are provided as follows. That is, a valve piston 38 is slid into the front part of the valve cylinder 25, and the front end of an input rod 35 passing through the air inlet 33 is swingably connected to the valve piston 38. Further, an annular first valve seat 40 ₁ is protruded from the inner circumferential surface of the valve cylinder 25 , and an annular second valve seat 40 surrounded by the annular first valve seat 40 1 is provided.
₂ is formed on the rear end surface of the valve piston 38, and a valve body 41 that cooperates with these valve seats 40 ₁ and 40 ₂ is attached to the valve cylinder 25.
located within. The valve body 41 is made of rubber and has a cylindrical shape with both front and rear ends open, and the rear end, that is, the base end 41a, is held by a holding cylinder 42 fitted to the inner circumferential surface of the valve cylinder 25. It is maintained in close contact with the inner peripheral surface of the cylinder 25. The valve body 41 includes a thin flexible portion 41b bent radially inward from the base end 41a, and a thick valve portion 41c continuous to the front end of the flexible portion 41b. 41c is arranged opposite to the first and second valve seats 40 ₁ and 40 ₂ .

The valve part 41c can be moved back and forth by deforming the flexible part 41b, and is seated on the first and second valve seats 40 ₁ and 40 ₂ when moving forward, and is received at the front end of the holding cylinder 42 when retreating. It can be stopped.

An annular reinforcing plate 43 is embedded in the valve portion 41c,
A valve spring 44 is compressed between this and the input rod 35 and urges the valve portion 41c toward both valve seats 40 ₁ and 40 ₂ .

On the inner surface of the valve cylinder 25, one end of the first port 30 is located outside the first valve seat 40 ₁ , and one end of the first port 30 is located outside the first valve seat 40 ₁ .
One end of each of the second ports 31 opens inside the second port 31 .

Further, the inside of the second valve seat 40 ₂ communicates with the atmosphere inlet 33 through the hollow portion of the valve body 41 and the holding cylinder 42 .

Thus, the valve body 41, the valve spring 44, and the first valve seat 40
_{The first} and second valve seats 40 ₂ constitute the control valve 32 .

Between the input rod 35 and the holding cylinder 42, the input rod 35
A return spring 45 is provided that urges the return spring 45 toward its retraction limit.

An annular end wall 26a is integrally formed at the rear end of the covering tube 26, and a stopper plate 4 abuts against the inner surface of the end wall 26a to restrict the backward limit of the input rod 35.
6 is screwed to the input rod 35 so that it can be adjusted forward and backward. Therefore, if the stopper plate 46 is turned, the stopper plate 46
Since the screwing position between the input rod 35 and the input rod 35 changes, the retraction limit of the input rod 35 can be adjusted back and forth. After this adjustment, the stopper plate 46 is fixed by tightening a lock nut 47 which is also screwed onto the input rod 35.

In order to constantly communicate the atmosphere inlet 33 of the valve cylinder 25 with the atmosphere, the stopper plate 46 and the covering cylinder 26
A plurality of ventilation holes 48 and 54 are provided in each of the peripheral walls (see FIGS. 1 and 6). The ventilation hole 54 is
It is disposed on the covering tube 26 at the rear of the annular stepped portion 55 (on the brake pedal 34 side).

A filter case 5 is provided around the outer periphery of the covering tube 26 to surround it from the base to the vicinity of the ventilation hole 54.
8 are arranged.

As shown in FIGS. 5 and 7, the filter case 58 is made of synthetic resin and has a cylindrical shape, and has an outward flange 58a at its front end and an inward end wall 58b at its rear end. Each is bent.
This filter case 58 has the same number of ventilation holes 59 at positions corresponding to the plurality of ventilation holes 54 of the covering tube 26.
is bored, and an annular rib 6 protrudes radially outward at a position corresponding to the annular rib 56 of the covering tube 26.
0 is formed, and a plurality of slits 61 extending from the flange 58a to the rear of the annular rib 60 are provided.

The filter case 58 is temporarily fixed to the covering tube 26 by fitting the inner circumferential surface of the annular rib 60 to the outer circumferential surface of the rib 56 of the covering tube 26 while opening the plurality of slits 61. At this time, the flange 58a comes into contact with the rear wall of the booster shell 1. Further, an air filter 63 that covers the ventilation hole 54 is housed in a filtration chamber 62 defined between the end wall 58a of the filter case 58 and the annular step 55 of the covering tube 26.

Referring again to FIG. 1, the booster shell 1 is supported by a dash board 64 of the vehicle body, which serves as a support wall located on the rear side, with a gasket 65 in between. That is, a plurality of mounting bolts 66 (one of which is shown in FIG. 1) is fixed to the rear wall of the booster shell 1 by welding so as to protrude rearward therefrom.
After this mounting bolt 66 passes through the gasket 65 and dash board 66, it is screwed with a nut 67.

At that time, the flange 58a of the filter case 58
is the rear wall of booster shell 1 and dart board 64
The gasket 65 is sandwiched between the two.

The control valve 32 is connected to the valve cylinder 25 from the atmosphere inlet 33.
An air filter 49 is mounted around the input rod 35 to filter the air taken in to the side. This air filter 49 has appropriate flexibility so as not to impede relative displacement between the input rod 35 and the valve cylinder 25.

The piston boss 10 has a large cylinder hole 37 that opens at the center of its front surface, and a large cylinder hole 37 that opens at the center of the front surface.
and a small cylinder hole 3 whose both ends are open inside the valve cylinder 25.
6 is provided. And in the small cylinder 36,
Integral with the valve piston 38 or valve piston 38
A reaction piston 52 that comes into contact with the large cylinder hole 37 is slidably fitted with an elastic piston 50 that faces the reaction piston 52 and an output piston 51 that is superimposed on the front surface of the elastic piston 50.
In order to prevent the output piston 51 from being pulled out of the large cylinder hole 37, the inner peripheral edge of the end wall plate 13a is extended to the opening of the large cylinder hole 37.

An output rod 53 is provided protruding from the front surface of the output piston 51, and this output rod 53 is connected to the piston 55 of the brake master cylinder M.

Next, the operation of this embodiment will be explained. First, in the boosting rest state of the negative pressure booster B, as shown in FIG.
The valve part 41c is connected to the first and second valve seats 40 ₁ , 40 ₂
The control valve 3 is seated in a neutral state in which the front and rear working chambers 2b, 3b are disconnected from both the negative pressure chambers 2a, 3a and the atmosphere inlet 33.
2, negative pressure from a negative pressure source supplied through the negative pressure introduction pipe 29 is stored in both negative pressure chambers 2a and 3a, and negative pressure appropriately diluted with the atmosphere is stored in both working chambers 2b and 3b. That is, the atmospheric pressure is maintained slightly higher than the pressure in the negative pressure chambers 2a and 3a. In this way, the front and rear booster pistons 4 and 6 have a front negative pressure chamber 2a.
A slight forward force is applied due to the pressure difference between the rear negative pressure chamber 3a and the working chamber 2b, and the rear negative pressure chamber 3a and the working chamber 3b, but these forward forces are balanced by the elastic force of the return spring 23, Both booster pistons 4 and 6 are stopped after being slightly advanced from the retraction limit.

Now, when the brake pedal 34 is depressed to brake the vehicle and the input rod 35 and the valve piston 38 are moved forward, since both the booster pistons 4 and 6 are initially immovable, the second valve seat ₄₀₂ is moved to the valve portion 41c. Immediately move away from the air intake port 33 and connect both working chambers 2b, 3b to the atmosphere inlet 33.
communicate with.

As a result, the atmosphere is removed from the vent hole 48 of the stopper plate 46.
The valve cylinder passes through a first path from the air inlet 33 to the air inlet 33, and a second path from the air hole 59 of the filter case 58 to the air inlet 33 via the filtration chamber 62 and the air hole 48 of the covering tube 26. 25, and then introduced into both working chambers 2b, 3b through the second valve seat ₄₀₂ and the second port 31.

At that time, especially the covering tube 26 and the filter case 5
The ventilation holes 54 and 59 provided in the hole 8 allow the air inlet 33 to communicate with the atmosphere at all times without being interfered with by the opposing end wall 26a and the stopper plate 46. By forming them with a large diameter or increasing their number, it is possible to form a ventilation path with extremely low ventilation resistance between the atmosphere and the atmosphere introduction port 33. Therefore, the atmospheric air can be introduced smoothly into both working chambers 2b and 3b. Moreover, since the air flowing into the filter chamber 62 from the vent hole 59 of the filter case 58 is filtered by the air filter 63, dust in the air is prevented from entering the sliding part of the valve cylinder 25, and the bearing 27 And the service life of the seal member 28 can be extended.

When the working chambers 2b and 3b become higher in pressure than the negative pressure chambers 2a and 3a due to the introduction of atmospheric air, the booster pistons 4 and 6 gain a large forward force based on the pressure difference between them, resisting the force of the return spring 23. The piston 55 of the brake master cylinder M is driven forward via the output rod 53. thus,
Brake master cylinder M to brake pedal 34
It can be activated without delay when the driver depresses the brake pedal, and the brakes can be applied to the vehicle.

During such braking, the valve piston 38 also advances together with the input rod 35 and comes into contact with the elastic piston 50 via the reaction piston 52.
0 bulges and deforms toward the small cylinder hole 36 side in response to the actuation reaction force of both booster pistons 4 and 6, and a part of the reaction force acts on the reaction force piston 52, so that force is applied to the valve piston 38 and Feedback is provided to the brake pedal 34 via the input rod 35. Due to such a reaction force, the driver can sense the output of the output rod 53, that is, the magnitude of the braking force.

When the output of the output rod 53 exceeds the boosting limit point due to an increase in the pedal force on the brake pedal 34, that is, the input to the input rod 35, the front surface of the valve piston 38 comes into contact with the piston boss 10, so that the entire input is applied to the valve piston. 38, the output rod 53 via the piston boss 10, the elastic piston 50 and the output piston 51
As a result, the sum of the forward force due to the pressure difference between the booster pistons 4 and 6 and the forward force due to the input is output from the output rod 53.

Next, when the pedal force on the brake pedal 34 is released, the input rod 35 moves back together with the valve piston 38 due to the elastic force of the return spring 45, and the second valve seat 4
0 ₂ is seated on the valve portion 41c of the valve body 41, and the valve portion 41c is separated from the first valve portion 40 ₁ by a large distance. Communicating with the negative pressure chambers 2a, 3a, the pressure difference between the front and rear of each booster piston 4, 6 is immediately eliminated, and therefore both booster pistons 4, 6 retreat with the elastic force of the return spring 23.
The operation of the brake master cylinder M is released. Then, when the input rod 35 returns to the retraction limit where the stopper plate 46 comes into contact with the partition wall 26a of the extension tube 26, the rear booster piston 6 temporarily pushes the protrusion 24 of the rear diaphragm 7 into the booster shell, as shown in FIG. The second port 31 is returned to the retraction limit where it comes into contact with the rear wall of 1, and this time the first valve seat 40 ₁ is seated on the valve seat 41c and the valve portion 41c is slightly separated from the second valve seat 40 ₂ . Atmospheric air is again introduced into both the working chambers 2b, 3b through the valve, and if the booster pistons 4, 6 move forward a little due to the resulting pressure difference, the small gap between the second valve seat ₄₀₂ and the valve part 41c disappears. The control valve 32 is brought to its initial neutral state. In this way both working chambers 2b, 3
A negative pressure diluted with the atmosphere is maintained at point b, and the negative pressure booster B enters the boosting rest state as shown in FIG.

FIG. 8 shows a second embodiment of the present invention, except that both ends of a synthetic resin flow regulating member 70 are locked to the end wall 26a of the covering tube 26 and the end wall 58b of the filter case 58. It has the same configuration as the previous embodiment.
The above-mentioned flow regulating member 70 has a tapered flow regulating surface 70a continuous to the inner peripheral edge of the end wall 26a of the covering tube 26, thereby rectifying the air flowing into the ventilation hole 48 of the stopper plate 46 and preventing the generation of wind noise. can do.

C. Effects of the invention As described above, according to the first feature of the invention, a ventilation hole is provided in the peripheral wall of the covering cylinder to constantly communicate the atmosphere inlet of the valve cylinder with the atmosphere, and an air filter is installed to cover this ventilation hole. is housed and held in a cylindrical filter case that surrounds the sheathing tube fixed to the booster shell, so there is no interference between the opposing end walls of the sheathing tube and the stopper plate of the input rod, and there is no interference between the valve and the atmosphere. An air passage with low ventilation resistance can be formed between the cylinder and the air inlet port. Therefore, when the input rod is operated, air can be smoothly introduced into the working chamber through the air passage, which improves the response of the booster piston. In addition to contributing to improved performance, noise caused by airflow can also be reduced by reducing ventilation resistance. Furthermore, the air filter that covers the ventilation hole can filter the air that enters the covering cylinder.
It is possible to prevent dust in the atmosphere from adhering to the bearing and sealing member between the covered cylinder and the valve cylinder and damaging them, thereby contributing to improving the durability of the bearing and sealing member. can. Furthermore, the air filter is housed and held in a cylindrical filter case fixed to the booster shell and is effectively protected from collision with other objects, which can also contribute to improving the durability of the filter itself. .

According to the second feature of the present invention, the flange formed at one end of the filter case is sandwiched between the booster shell and the support wall that supports the shell, so there is no need for a special fixing means for the filter case. Therefore, it can contribute to the simplification of the structure.

[Brief explanation of the drawing]

1 to 7 show the first embodiment of the present invention, in which FIG. 1 is a vertical cross-sectional side view of the tandem negative pressure booster in the boosting rest state, and FIGS. 2 and 3 are the first embodiment of the present invention. 4 is a partial vertical sectional side view showing the state of the negative pressure booster immediately before it returns to a resting state after completing its operation; FIG. 5 is an enlarged view of the main part of FIG. 1; 6 is a sectional view taken along the line -- in FIG. 1, FIG. 7 is a perspective view of the filter case, and FIG. 8 is a longitudinal sectional view of the essential parts of a negative pressure booster showing a second embodiment of the present invention. B...Negative pressure booster, 1...Booster shell,
2a, 3a... negative pressure chamber, 2b, 3b... working chamber,
4, 6...Booster piston, 25...Valve cylinder, 2
6... Covering tube, 26a... End wall, 32... Control valve, 33... Atmospheric inlet, 35... Input rod, 46
...stopper plate, 54...ventilation hole, 58...filter case, 58a...flange, 62...filtration chamber, 63...air filter, 64...support wall.

Claims (1)

[Claims for Utility Model Registration] (1) The interior of the booster shell 1 is divided into negative pressure chambers 2a, 3a on the front side and working chambers 2b, 3b on the rear side, and is biased in the backward direction by a return spring 23. The booster pistons 4 and 6 are accommodated in the valve cylinder 25 connected to the rear ends of the booster pistons 4 and 6, and an input rod 35 that can move back and forth is provided, and the input rod 35 is actuated in response to the back and forth movement of the input rod 35. Room 2b, 3b
A control valve 32 is provided to communicate and switch the negative pressure chambers 2a, 3a and the atmosphere inlet 33 at the rear end of the valve cylinder 25, and covers the valve cylinder 25 and covers its outer peripheral surface with a bearing 27 and a seal member 28. A covering tube 26 that is slidably supported through the booster shell 1 is protruded from the rear surface of the booster shell 1, and an annular end wall 26a through which the input rod 35 passes is formed at the rear end of the covering tube 26. In a negative pressure booster in which the input rod 35 is provided with a stopper plate 46 that contacts the inner surface of the input rod 26a and restricts the retraction limit of the input rod 35, the atmosphere inlet 33 of the valve cylinder 25 is connected to the surrounding wall of the covering cylinder 26 to the atmosphere. It is characterized in that a ventilation hole 54 is provided for continuous communication, and an air filter 63 covering the ventilation hole 54 is housed and held in a cylindrical filter case 58 that is fixed to the booster shell 1 and surrounds the covering tube 26. , negative pressure booster. (2) According to claim (1), the flange 58a formed at one end of the filter case 58 is sandwiched between the booster shell 1 and a support wall 64 that supports the shell 1. negative pressure booster.