JPS6341339B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a negative pressure booster used, for example, in operating a brake master cylinder of a vehicle.

Conventionally, this type of device includes a first working chamber at the front that is constantly in communication with a negative pressure source through a booster piston that can freely reciprocate back and forth within the booster shell and a piston diaphragm attached to the rear surface of the booster piston, and a control valve. It is known that the booster piston is divided into a first working chamber and a second working chamber at the rear which is alternately controlled to be communicated with the atmosphere through a booster piston, and a booster piston is provided with a valve cylinder that accommodates a control valve.

In the above device, if the valve cylinder is assembled to the booster piston, it is economical when manufacturing products with various output characteristics because the booster piston can be changed and the valve cylinder can be used in common. However, in the past, the booster piston and the valve barrel were integrally molded from synthetic resin, so the above-mentioned effects could not be obtained, and the synthetic resin was expensive.

On the other hand, if an air pocket occurs between the booster piston and the piston diaphragm, there is a problem that atmospheric pressure does not act uniformly on the entire booster piston, resulting in inaccurate operation of the booster piston.

In view of the above, the present invention has a structure in which a valve cylinder is attached to a booster piston so that the valve cylinder can be easily installed and used in common when manufacturing boosters having various output characteristics. The purpose of the present invention is to provide a booster device that improves economic efficiency, reduces the cost of the booster piston, and can reliably eliminate air between the booster piston and the piston diaphragm. The booster piston is formed from a steel plate, and is provided with a valve cylinder fitting hole located at the center of the booster piston, and a plurality of locking pawls located around the fitting hole and cut and raised toward the first working chamber. Insert the cylinder into the fitting hole from the first working chamber side, overlap the retaining flange of the valve cylinder with the booster piston, and lock the locking plate with the locking pawl to prevent the cylinder from coming out between the locking plate and the booster piston. The feature is that the flange is clamped and the booster piston and piston diaphragm are communicated with the first working chamber through an opening formed by cutting and raising the locking claw.

Hereinafter, an embodiment in which the present invention is applied to a brake master cylinder will be described with reference to the drawings.

In FIG. 1, the booster shell 1 of the negative pressure booster S consists of a pair of front and rear bowl-shaped bodies 1F and 1R made of lightweight thin-walled steel plate or synthetic resin.
A plurality of claw pieces 2 protruding from the opening of the rear bowl-shaped body 1R at equal intervals on the circumference, and a plurality of notches formed at the opening of the front bowl-shaped body 1F at equal intervals on the circumference. 3, the two bowl-shaped bodies 1F, 1R are positioned relative to each other, and the front and rear opposing walls of both the bowl-shaped bodies 1F, 1R are connected via a pair of tie rods 4. The connection structure between the booster shell 1 and the tie rod 4 will be described later.

Inside the booster shell 1, a first working chamber A at the front and a second working chamber A at the rear are formed by a booster piston 5 housed therein so as to be able to reciprocate back and forth, and a piston diaphragm 6 attached to the rear surface 5b of the booster piston 5. It is divided into a working chamber B.

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 the negative pressure introduction pipe 7, and the second working chamber B is connected to the control valve 8, which will be described later.
An atmosphere inlet 1 that opens into the first working chamber A or the end wall 10 of the rear extension tube 9 of the booster shell 1 through the
1 and communication switching is controlled alternately.

The booster piston 5 is always urged in the backward direction, that is, toward the second working chamber B, by a return spring 12 contracted in the first working chamber A, and its backward limit is reached by a protrusion 13 formed protrudingly on the back surface of the piston diaphragm 3. It is regulated by coming into contact with the inner surface of the rear wall of the booster shell 1.

The booster piston 5 is provided with a valve cylinder 14 that protrudes rearward from its center, and the valve cylinder 14 is slidably supported on a flat bearing 15 provided on the extension cylinder 9, and its rear end is connected to the atmosphere inlet. It will be open to 11.

The control valve 8 is configured in the valve cylinder 14 as follows. That is, an annular first valve seat ₁₆₁ is formed on the inner wall of the front part of the valve cylinder 14, and a valve piston 18 connected to the input rod 17 and forming the front end thereof is slidably engaged with the front part of the valve cylinder 14. An annular second valve seat 16 ₂ surrounded by the first valve seat 16 ₁ is formed at the rear end of the valve piston 18 .

A base end portion 20 of a cylindrical valve body 19 with both ends open is held on the inner wall of the valve cylinder 14 via a valve body holding cylinder 21 that is fitted into the valve cylinder 14 . The valve body 19 is made of an elastic material such as rubber, and a thin diaphragm 22 extends radially inward from its base end 20, and a thick valve portion 23 is connected to the inner peripheral end thereof. The valve portion 23 is connected to the first and second
It faces the valve seats 16 ₁ and 16 ₂ . Thus, the valve portion 23 can be moved back and forth by the deformation of the diaphragm 22.
It can also come into contact with the front end surface of the valve body holding cylinder 21.

An annular reinforcing plate 24 is embedded in the valve portion 23, and a valve spring 25 is connected to this to bias the valve portion 23 toward both valve seats 16 ₁ and 16 ₂ .

The outer part of the first valve seat ₁₆₁ is the booster piston 5
into the first working chamber A through a pair of through holes 26, and into the second working chamber B through another pair of through holes 27 between the intermediate portions of the first and second valve seats 16 ₁ and 16 ₂ ; Further, the inner side of the second valve seat 16 ₂ is always in communication with the atmosphere inlet 11 via the inside of the valve body 19 .

The booster piston 5 has a large-diameter cylinder hole 28 that opens at the center of its front surface, and a small-diameter cylinder hole 29 that opens at the inner end surface of the cylinder hole 28.
An elastic piston 30 made of rubber or the like and an output piston 31 of the same diameter are sequentially slid into the large-diameter cylinder hole 28 from the back thereof, and a recoil piston with a smaller diameter than the elastic piston 30 is inserted into the small-diameter cylinder hole 29. The piston 32 is slid together. Furthermore, a small shaft 33 protruding from the front end surface of the valve piston 18 enters the small diameter cylinder hole 29 and opposes the rear end surface of the reaction piston 32 . An output rod 34 is protruded from the front surface of the output piston 31, and the output rod 34
is arranged in the first working chamber A.

The input rod 17 is always urged in the backward direction by the return spring 37, and its retreat limit is reached when the movable stopper plate 35 screwed onto the input rod 17 comes into contact with the inside of the end wall 10 of the rear extension tube 9. regulated by. When the movable stopper plate 35 is rotated, the screwing position between the movable stopper plate 35 and the input rod 17 changes, so that the retraction limit of the input rod 17 can be adjusted back and forth. After the adjustment, the movable stopper plate 35 is fixed by tightening a lockite 36 which is also screwed onto the input rod 17. A ventilation hole 38 is provided in the movable stopper plate 35 to prevent it from blocking the atmosphere inlet 11.
is formed.

Filters 39 and 40 are attached to the outer end opening of the valve cylinder 14 to purify the air introduced from the atmospheric air inlet 11 and to be deformable so as not to interfere with the operation of the input rod 17.

Next, the assembly structure of the valve cylinder 14 to the booster piston 5 will be explained. As shown in Figs. A cylinder fitting hole 41 is formed. The booster piston 5 also includes a pair of arc-shaped reinforcing ribs 42 that are arranged so as to surround the insertion hole 41 and protrude from the front surface 5a. A pair of locking claws 43 are provided. Both of the locking claws 43 are biased to one side of both of the reinforcing ribs 42 and are arranged point-symmetrically with respect to the center of the insertion hole 41 .

The valve cylinder 14 is molded from thermosetting synthetic resin such as phenolic resin, and has a cylindrical main body 44 and a retaining flange 45 protruding from the outer peripheral surface of one end of the main body 44. , retaining flange 4
The outer circumferential surface of the connecting portion with 5 is formed into a tapered surface 46 with the flange 45 side being the larger diameter side. The retaining flange 45 has the large-diameter cylinder hole 28 on its end face, and has a concentric truncated conical short cylindrical portion 47 of the main body 44, and a flat top surface 48 disposed to sandwich the short cylindrical portion 47. The first through hole 26 has a pair of protrusions 49 having a top surface 48 thereof. Further, the other through hole 27 is opened on the small diameter side of the tapered surface 46.

The locking plate 50 includes a flat plate part 52 having a truncated conical cap part 51 into which the short cylindrical part 47 can be loosely fitted, and a flat plate part 52 that is bent diagonally from both ends of the flat plate part 52 in a direction opposite to the protruding direction of the cap part 51. A pair of legs 3
5, and a pair of locking portions 54 extending further outward from both ends of both leg portions 53. Flat plate part 5
2 and the leg portion 53 are connected in an arc shape along the outer periphery of the retaining flange 45, and the connection portion between the leg portion 53 and the locking portion 5
The connecting portions with the reinforcing ribs 42 are each formed in an arc shape along the outer peripheral edge of the reinforcing rib 42.

Reinforcing edges 55 are formed on both side edges of the locking plate 50 by bending, except for one end of both locking portions 54 which are point symmetrical with respect to the center of the cap portion 51.

The output piston 31 is mounted on the top wall of the cap portion 51.
A through hole 56 having a smaller diameter and a larger diameter than the output rod 34 is formed, and a pair of communication holes 57 communicating with the through hole 26 are formed on the base end side of the cap portion 51 of the flat plate portion 52.

When assembling the valve cylinder 14 to the booster piston 5, the main body 44 of the valve cylinder 14 is attached to the booster piston 5.
The booster piston 5 is inserted into the insertion hole 41 from the front surface 5a side, and the retaining flange 45 is positioned inside both reinforcing ribs 42 to overlap with the booster piston 5. Then, as shown in FIG. 4, the cap portion 51 of the locking plate 50 is loosely fitted into the short tube portion 47, and the connecting portion between the flat plate portion 52 and the leg portion 53 is connected at a position where it is removed from the locking claw 43. At the outer peripheral edge of the retaining flange 45, there are also a leg portion 53 and a locking portion 5.
4 are aligned with the outer peripheral edge of the reinforcing rib 42, and from this state, the locking plate 50 is attached to the leg portion 5.
3 and the locking portion 54 are brought into contact with the reinforcing rib 42, and the reinforcing rib 42 is used as a guide to move the connecting portion of the arrow a in FIG.
When rotated in the direction, the locking portion 54 locks on the locking pawl 43, and at the same time, the flat plate portion 52 engages the top surface 4 of the protruding portion 49.
8, thereby the retaining flange 45 is clamped between the locking plate 50 and the booster piston 5, and the valve cylinder 14 is assembled to the booster piston 5. In this case, the reinforcing edge 55 located at one end of the locking part 54 abuts against the edge of the locking pawl 43, and the rotation angle of the locking plate 50 is regulated. The holes 26 match. The movable end of the return spring 12 engages with the cap portion 51 of the locking plate 50, and the elastic force of the return spring 12 prevents the locking plate 50 from rotating.

The output rod 34 is loosely inserted into the through hole 56 of the cap portion 51, but since the diameter of the through hole 56 is smaller than that of the output piston 31, the through hole 56
The surrounding top wall 51a of the cap portion faces the opening of the cylinder hole 28 and functions as a stopper piece facing the output piston 31, so that the output piston 31 and the output rod 34 are stopped when the booster piston 5 is assembled.
This prevents problems such as falling from the valve cylinder 14.

As shown in FIGS. 1 and 3, the piston diaphragm 6 has annular inner and outer beads 5.
8, 59 are formed, and the outer peripheral bead 59
is sandwiched between both bowl-shaped bodies 1F and 1R by fitting positioning protrusions 60 protruding from its end faces into respective positioning holes 61 formed on the outer circumference of the rear bowl-shaped body 1R.

The inner circumferential bead 58 is fitted into the opening edge of the fitting hole 41 of the booster piston 5, but in the free state, the inner circumferential bead 58 is attached to the front surface 5a side of the booster piston 5 and the fitting hole as shown by the chain line in FIG. 41, a series of bulges 58a are formed that protrude inward. As described above, this bulging portion 58a connects the retaining flange 45 of the valve cylinder 14 to the locking plate 50 and the booster piston 5.
When clamped between them, the retaining flange 45 is used to move in the direction of the center line of the fitting hole 41 as shown by arrow b, and the tapered surface 46 of the valve barrel 14 is used to move radially outward of the fitting hole 41 as shown by arrow c. It is strongly pressurized and compressed into the annular recess 62 around the fitting hole 41, thereby reliably sealing the space between the valve cylinder 14 and the booster piston 5.

The pressure receiving part 63 of the piston diaphragm 6 is in close contact with the rear surface of the booster piston 5 and projects toward the first working chamber A between the outer peripheral surface of the booster piston 5 and the inner peripheral surface of the front bowl-shaped body 1F. U
The U-shaped bent portion is bent to allow the booster piston 5 to move forward and rearward by rolling.

As shown in FIGS. 1 and 5, an opening 64 is formed in the portion of the booster piston 5 where the locking claw 43 is cut and raised.
is formed, and the booster piston 5 and piston diaphragm 6 are communicated with the first working chamber A through the opening 64, so that no air pocket is generated between the two. Further, the portion of the piston diaphragm 6 facing the opening 64 is formed into a thick wall portion 65, whereby the atmosphere is introduced into the second working section B, and the air pressure in the second working chamber B is changed to the first working chamber A.
Even if the thick part 65 is higher than that of the opening 64
There is no inward bulge, and therefore damage caused by the opening 64 of the piston diaphragm 6 can be prevented.

Next, the connection structure between the tie rod 4 and the booster shell 1 will be explained.

As shown in FIG. 1, the tie rod 4 is integrally formed with a mounting bolt 66 that penetrates the front wall of the booster shell 1 and projects forward thereof, and also has a spring receiving plate that comes into contact with the inner surface of the front wall of the booster shell 1. 67 is fixed. And the mounting flange 68 of the brake master cylinder M stacked on the front of the booster shell 1
The tie rod 4,
The spring receiving plate 67, the front wall of the booster shell 1, and the mounting flange 68 are integrally connected. At this time, an annular seal member 71 for sealing the tie rod through hole in the front wall of the booster shell 1 is fitted into an annular groove 70 formed on the front surface of the spring receiving plate 67 so as to surround the bolt 66. The spring receiving plate 67 supports the fixed end of the return spring 12, and allows the tie rod 4 to bear the elastic force of the return spring 12, thereby removing the load on the booster shell 1.

Furthermore, tie rod 4 has booster shell 1.
A mounting bolt 7 that penetrates the rear wall and projects rearward therefrom.
2 and a stepped flange 73 that abuts the inner surface of the rear wall of the booster shell 1 are integrally formed. The stepped flange 73 is fitted into a support tube 74 that is welded and fixed to the inner surface of the rear wall of the booster shell 1, and its retaining ring 75 is locked to the support tube 74, thereby connecting the tie rod 4 and the rear wall of the booster shell 1. connected together. At this time, an annular seal member 77 for sealing the tie rod through hole in the rear wall of the booster shell 1 is fitted into the annular groove 76 between the small diameter portion of the stepped flange 73 and the support tube 74.

The mounting bolt 72 is passed through the front wall W of the vehicle compartment, and the tie rod 4 is fixed to the front wall W of the vehicle compartment by screwing and tightening a nut 78 at its tip.

Thus, the booster shell 1 is attached to the front wall W of the passenger compartment via the tie rod 4, and the brake master cylinder M is connected to the booster shell 1 via the tie rod 4.

Next, the sealing structure between the tie rod 4, booster piston 5, and piston diaphragm 6 will be explained.

As shown in FIGS. 1 and 3, a pair of tie rod penetration holes 79 are formed in the booster piston 5 between the reinforcing ribs 42, and a plurality of through holes 79, three in the illustrated example, are formed on the rim of the booster piston 5. Notches 80 are provided at equal intervals on the circumference. Also, the piston diaphragm 6
Through-holes 81 corresponding to the through-holes 79 are formed in each of the through-holes 79, and a thick portion 82 is formed at the edge of each through-hole 81.

As shown in FIGS. 3 and 6, three locking claws 84 corresponding to the notches 80 are provided at one end of the outer peripheral surface of the two seal mounting tubes 83, and four locking claws 84 are provided at the other end. A retaining flange 86 having a tool engaging recess 85 is provided in a protruding manner. The top surface 84a of each locking pawl 84 is formed with a fitting guide inclined surface 84b that slopes downward from the intermediate portion toward the end surface of the seal mounting tube 83, and the rising surface 84c is formed from the intermediate portion toward one end. A rotation guiding inclined surface 84d having a downward slope is formed. Rotation guiding inclined surface 84 in each locking pawl 84
The direction of inclination of d is the same.

Each seal mounting tube 8 for the booster piston 5
3 is performed before assembling the valve cylinder 14 to the booster piston 5. The seal mounting cylinder 83 is assembled by aligning each locking pawl 84 with each notch 80 from the rear surface 5b side of the booster piston 5. The piston diaphragm 6 and the through hole 8 of the booster piston 5
It is inserted into 1,79. In this case, each locking claw 84
The fitting guide slope 84b of the top surface 84a allows the seal mounting cylinder 83 to fit smoothly into the through hole 79 of the booster piston 5. Then, as shown in FIGS. 6 and 7, the short cylindrical portion 88 of the tool 87 is attached to the seal mounting tube 83, and the short cylindrical portion 88 is attached to the seal mounting tube 83.
Each engagement protrusion 89 on the outer circumferential surface is engaged with each tool engagement recess 85, and a receiver 90 is applied to the front surface 5a of the booster piston 5 to press the tool 87 and the thick part 82 of the booster piston 5 is pressed. Rotate the handle 91 in the direction of arrow d in FIG. 7 while compressing. As a result, each locking pawl 84 is misaligned with each notch 80, and the rising surface 84c of each locking pawl 84 and the retaining flange 8
The booster piston 5 and the edges of the through holes 79 and 81 of the piston diaphragm 6 are sandwiched between the booster piston 5 and the seal mounting cylinder 83, and the space between the booster piston 5 and the seal mounting cylinder 83 is sealed. In this case, the rising surface 84 of each locking claw 84
Each locking pawl 84 is
smoothly enters the opening edge of the through hole 79 of the booster piston 5, and the clamping is reliably performed.

As shown in FIGS. 2 and 3, the retaining flange 45 of the valve barrel 14 has a cutout having a concave arc-shaped inner circumferential surface that can match the outer circumferential surface between the adjacent locking claws 84 on both seal mounting tubes 83. The notches 92 are formed, and when the valve cylinder 14 is fitted into the insertion hole 41 of the booster piston 5 as described above and each notch 92 and each seal mounting tube 83 are fitted with the convexes and convexes, each notch in the retaining flange 45 is formed. Locking claws 84 whose outer peripheral surfaces near both ends of 92 are adjacent to each other
The valve cylinder 14 and the seal mounting cylinder 83 are mutually prevented from rotating. As another rotation preventing means, as shown in FIG. 8, a groove 93 which can be engaged with one locking pawl 84 may be formed in the notch 92 of the retaining flange 45 in the valve cylinder 14. good.

As shown in FIG. 1, sealing means is provided between the seal mounting tube 83 and the tie rod 4 to allow the booster piston 5 to operate. The sealing means is composed of a bellows-shaped telescopic boot 94 made of an elastic material such as rubber. , and the rear ends 94b are fitted into the openings of the seal mounting tube 83, respectively.

In the vehicle interior, a brake pedal 98 that is pivotally supported 97 on a fixed bracket 96 is connected to the rear end of the input rod 17 of the booster S via a connecting fitting 99. 100 is a return spring that biases the brake pedal 98 rearward.

Cylinder body 10 of brake master cylinder M
The rear end of booster shell 1 passes through the front wall of booster shell 1 and connects to the first
It has entered the working chamber A, and the cylinder body 1
Booster S at the rear end of the working piston 102 in 01
The output rods 34 of the two are opposed to each other.

Next, to explain the operation of this embodiment, the state shown in FIG. 1 shows the non-operating state. Spring 37 returns to a predetermined retracted position abutting 10
is held by a spring force of and the valve piston 18
presses the front face of the valve part 23 via the second valve seat 16 ₂ and moves it back until it lightly contacts the front face of the valve body holding cylinder 21 , thereby pressing the front face of the valve part 23 through the second valve seat 16 ₂ .
A slight gap g is formed between the valve portion 23 and the valve portion 23. Such a state can be easily obtained by adjusting the movable stopper plate 35 described above.

As described above, during engine operation, the first working chamber A, which always stores negative pressure, communicates with the second working chamber B through the through hole 26, the gap g, and the through hole 27, and also through the front opening of the valve part 23. is closed by the second valve seat ₁₆₂ , the negative pressure in the first working chamber A is transmitted to the second working chamber B, and the air pressures in both working chambers A and B are balanced. Therefore, the booster piston 5 also returns the spring 1.
It assumes the illustrated retracted position with a spring force of 2.

Now, if the brake pedal 98 is depressed to brake the vehicle and the input rod 17 and the valve piston 18 are moved forward, the valve portion 23, which is urged forward by the valve spring 25, will move forward following the valve piston 18. ,
Since the gap g between the first valve seat 16 ₁ and the valve part 23 is extremely narrow as described above, the valve part 23 immediately seats on the first valve seat 16 ₁ and blocks communication between the working chambers A and B. At the same time, the second valve seat 16 ₂ separates from the valve portion 23 and communicates the second working chamber B with the atmosphere inlet 11 via the through hole 27 and the inside of the valve body 19 . Therefore, the atmosphere is quickly introduced into the second working chamber B, and the second working chamber B
has a higher pressure than the first working chamber A, and due to the pressure difference created between the two chambers A and B, the booster piston 5 moves forward against the return spring 12, and moves the output rod 34 forward via the elastic piston 30. The actuating piston 102 of the brake master cylinder M is driven forward, and the vehicle is braked.

When the actuating piston 102 is driven, a forward thrust load is applied to the cylinder body 101, and this load is transmitted to the vehicle body, that is, the front wall W of the vehicle interior, through the tie rod 4 and is supported. Therefore, the above-mentioned load does not act on the booster shell 1.

On the other hand, due to its advancement, the small shaft 33 of the valve piston 18 passes through the reaction piston 32 to the elastic piston 30.
, a part of the reaction force is fed back to the brake pedal 98 side via the valve piston 18 due to the bulging deformation of the elastic piston 30 toward the reaction piston 32 side due to the actuation reaction force of the output rod 34. The driver can sense the output of the output rod 34, that is, the braking force.

Next, when the depressing force of the brake pedal 98 is released, the input rod 17 is moved backward due to the reaction force applied to the valve piston 18 and the _elastic force of the return spring 37. Since the valve portion 23 is seated on the valve body and the valve portion 23 is brought into contact with the front surface of the valve body holding cylinder 21, the valve portion 23 receives the retreating force of the input rod 17 and is compressively deformed in the axial direction. As a result, a gap larger than the initial gap g is formed between the first valve seat 16 ₁ and the valve part 23, so that the air pressures in both working chambers A and B are quickly balanced with each other through this large gap. When the pressure difference between them disappears, the booster piston 5 moves back due to the elastic force of the return spring 12, and the projection 13 of the piston diaphragm 6 comes into contact with the inner surface of the rear wall of the booster shell 1 and stops. When the input rod 17 comes into contact with the end wall 10, the valve part 23 is released from the retreating force of the input rod 17 and returns to its original shape, so that the gap with the first valve seat ₁₆₁ is reduced to the small gap g again. It can be narrowed down.

As described above, according to the present invention, since the booster piston is formed from a steel plate, its cost can be reduced, and the booster piston is The valve cylinder can be assembled to the piston very easily, and furthermore, the valve cylinder can be commonly used in boosters having various output characteristics, so that economical efficiency can be improved. Moreover, the air between the booster piston and the piston diaphragm can be expelled into the first working chamber through the opening of the booster piston, so that the booster piston can always be operated accurately. Since there is no need to perform this process, the number of processing steps can be reduced.

Furthermore, if the portion of the piston diaphragm that faces the booster piston opening is made thicker, in addition to the above-mentioned effects, even if the pressure in the second working chamber becomes higher than that in the first working chamber, the piston diaphragm will remain in the opening. Therefore, the piston diaphragm can be prevented from being damaged by the opening, and its durability can be improved.

[Brief explanation of the drawing]

1 to 7 show one embodiment of the present invention, and FIG. 1 is a longitudinal sectional front view of the entire body taken along the line 2-- in FIG. 2, and FIG. , a side view showing the attachment relationship between the locking plate and the seal mounting tube, FIG. 3 is an exploded perspective view of the booster piston, piston diaphragm, valve tube, locking plate, and seal mounting tube, and FIG. 4 is the valve tube relative to the booster piston. Fig. 5 is a partially enlarged longitudinal sectional front view showing the seal structure of the booster piston and valve cylinder, Fig. 6 is a perspective view showing the relationship between the seal mounting cylinder and tools, and Fig. 7 is the booster piston. FIG. 8 is a sectional view showing how to attach the seal mounting cylinder to the valve cylinder, and FIG. 8 is a partial side view of a modified side showing the relationship between the valve cylinder and the seal mounting cylinder. A, B...First and second working chambers, 1...Booster shell, 5...Booster piston, 6...Piston diaphragm, 8...Control valve, 14...Valve cylinder,
41... Fitting hole, 43... Locking claw, 45... Removal prevention flange, 50... Locking plate, 64... Opening.

Claims (1)

[Scope of Claims] 1. A first working chamber at the front part which is constantly communicated with a negative pressure source by a booster piston that can freely reciprocate back and forth within the booster shell and a piston diaphragm attached to the rear surface of the booster piston; In a negative pressure booster, the booster piston is divided into the first working chamber and a rear second working chamber which is alternately controlled to communicate with the atmosphere via a valve, and is provided with a valve cylinder for accommodating the booster piston and the control valve. , the booster piston is formed from a steel plate, and the booster piston includes:
A fitting hole for the valve cylinder located at the center thereof and a plurality of locking claws located around the fitting hole and cut and raised toward the first working chamber are provided, and the valve cylinder is inserted into the first working chamber. The locking plate is fitted into the fitting hole from the side so that the locking flange of the valve cylinder overlaps the booster piston, and the locking plate is locked to the locking pawl, so that the locking plate is inserted between the locking plate and the booster piston. A negative pressure doubler, characterized in that a flange is clamped, and the booster piston and the piston diaphragm are communicated with the first working chamber through an opening formed by cutting and raising the locking claw. power device. 2. In what is stated in claim 1,
A negative pressure booster in which a portion of the piston diaphragm facing the opening is made thicker.