JPH086663Y2 - Tandem negative pressure booster - Google Patents

Description

[Detailed Description of the Invention] A. Purpose of the Invention (1) Field of Industrial Use The present invention has a booster shell in which a partition plate for partitioning the interior into a front shell chamber and a rear shell chamber is fixedly installed. A front booster piston that partitions the partial shell chamber into a front negative pressure chamber on the front side and a front working chamber on the rear side, and an inner peripheral bead of the front diaphragm that is superposed on the rear surface of the front booster piston,
A rear booster piston that is slidably supported by the partition plate and fixed to the front end of a piston boss that is connected to the output rod, while partitioning the rear shell chamber into a front rear negative pressure chamber and a rear rear working chamber. , A rear diaphragm that overlaps with the rear surface of the rear booster piston is fixed to the rear end of the piston boss, and the piston boss projects from the rear end and is slidably supported on the rear wall of the booster shell. The cylinder is integrally connected, and a first port that communicates the inside of the valve cylinder with both negative pressure chambers and a second port that communicates the inside of the valve cylinder with both working chambers are provided. The opening to the part working chamber is not a notch that opens to the front end surface and the outer peripheral surface of the piston boss. An input rod that can be moved back and forth in the valve cylinder and a second port according to the forward and backward movement of this input rod. Control valve for switching communication between the first port and the atmosphere It was disposed, a recess for receiving a return spring for urging the piston boss to backward direction about the tandem type vacuum booster of the type that is provided on the front surface of the boss.

(2) Prior Art Negative pressure booster of the above type is disclosed in, for example, Shokai 61-45277.
It is conventionally known as disclosed in Japanese Patent Publication No. In such a negative pressure booster, the opening of the second port to the front working chamber is formed in a notch shape that opens to the front end surface and the outer peripheral surface of the piston boss. In addition to being convenient because it can be easily formed by a pair of molds that open and close, it has the following advantages.

That is, if an opening portion of the second port to the front working chamber is to be formed by making a radial hole in the peripheral wall of the piston boss, at least the thickness of the opening is required in order to secure a necessary thickness around the hole. The piston boss becomes longer in the front part only for the thickness, so there is a disadvantage that the front and rear stroke of the piston boss becomes shorter unless the booster shell is expanded forward. If the notch is opened in the surface, it is not necessary to secure the wall thickness, and the above inconvenience can be solved.
Instead of forming the radial hole in the peripheral wall of the piston boss, the opening of the second port to the front working chamber is directly opened in the front end face of the piston boss, and the rear end is fitted into the opening. It is also known that the bush is provided with a slot in the front-rear direction on the peripheral wall of the middle part (see, for example, Japanese Patent Laid-Open No. 5-5787), but in this case, in order to secure the required rigidity of the bush, A certain thickness must be ensured in the front portion of the bush of the slot, and the same inconvenience as that in the case of forming the radial hole occurs after all.

Further, instead of piercing the radial hole as described above in the peripheral wall of the piston boss, the front working chamber side opening of the second port is opened only on the front end face of the piston boss, and the opening and the front working chamber are separated from each other. It is also known that the front end of the piston boss is communicated with the front diaphragm via a predetermined gap set between the front and the rear diaphragm (see, for example, Japanese Utility Model Laid-Open No. 60-67273). However, there is a serious drawback that the front booster piston extends forward by the predetermined gap and the booster shell expands forward, and further the outer peripheral end of the piston boss front end face is set to set the predetermined gap. It cannot be a supporting point for the front booster piston, that is, the supporting point is a projection (28k) near the center of the front end face of the piston boss, so the outer portion of the front booster piston is more easily bent and deformed. Etc. Although there are drawbacks, these drawbacks can be eliminated by forming the front working chamber side opening of the second port in the notched shape as described above.

(3) Problems to be Solved by the Invention However, the structure in which the opening of the second port to the front working chamber is a notch that opens to the front end surface and the outer peripheral surface of the piston boss has the above-mentioned advantages. On the other hand, since the inner bead of the front diaphragm, which is clamped between the front booster piston and the piston boss, directly faces the open surface on the front side of the notch, the following negative pressure booster peculiar to this kind is used. It causes inconvenience.

That is, since the inside of the intake manifold of the engine is generally used as a negative pressure source that supplies a negative pressure to each negative pressure chamber,
Some gasoline vapor flows into the booster shell from the intake manifold. Therefore, when the gasoline vapor is in contact with the inner peripheral bead of the rubber front diaphragm facing the notch for a long time, the inner peripheral bead swells and narrows the notch, that is, the opening of the second port. As a result, there is a risk that the air flow in the port will be hindered and the responsiveness of the negative pressure booster will be reduced. Incidentally, such inconvenience is that the outer peripheral portion of the front diaphragm rather than the inner peripheral bead is directly exposed to the front open surface of the notch as disclosed in, for example, Japanese Patent Laid-Open No. 58-128951 and is as much as possible from the open surface. If it is molded so that it goes away, it will be alleviated, but in this case, the outer diameter of the piston boss needs to be specially increased, which causes an increase in the weight of the piston boss. There is another problem such as becoming

The present invention has been proposed in view of the above circumstances, and the second
While clarifying that the tandem type negative pressure booster of the type in which the opening of the port to the front working chamber is a notch that opens to the front end surface and the outer peripheral surface of the piston boss has the above-mentioned specific problems, It is an object of the present invention to provide a tandem type negative pressure booster capable of solving all of its peculiar problems with a simple structure.

B. Configuration of the Invention (1) Means for Solving the Problems To achieve the above object, according to the present invention, in the tandem type negative pressure booster of the type described above, the recess is formed in the inner peripheral portion of the front booster piston. Is formed integrally with the bottom wall of the recess by fitting to the bottom wall of the recess, and an annular seal member is interposed between the bottom of the connection cylinder and the bottom wall of the recess. The front port portion of the second port, which directly communicates with the notch, is defined between an axial groove formed on the inner peripheral surface of the recess over the front and rear ends thereof and an outer peripheral surface of the connecting cylinder that covers the groove. A rigid member made of an annular plate material that closes the open surface of the notch facing the inner peripheral bead is sandwiched between the facing surfaces of the inner peripheral bead of the front diaphragm and the front end of the piston boss.

(2) Action According to the special provision of the rigid member, the front diaphragm is surely prevented from swelling to the opening of the front working chamber of the second port, and the effective opening of the opening is always kept normal. Therefore, when the control valve is switched, the air flow in the second port is always smoothly performed.

Moreover, since the rigid member is made of a plate material, it does not cause the front booster piston and the diaphragm to extend forward long even if it is sandwiched between the opposed faces of the piston boss front end and the diaphragm.

Further, when the connecting cylinder of the front booster piston is fitted in the concave portion on the front surface of the piston boss, the front port portion connected to the notch of the second port is formed between the groove on the inner peripheral surface of the concave portion and the outer end surface of the connecting cylinder. Since it can be formed with a large degree of flatness, it is possible to secure a wide passage cross-sectional area of the front side port portion without being restricted by the recessed portion, and when the control valve is switched, air quickly flows through the port portion, Further, the annular seal member can reliably prevent the air from leaking to the front negative pressure chamber side. Further, in particular, the groove on the inner peripheral surface of the recess can be easily molded by a mold together with the notch that directly communicates with the groove.

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

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

The booster shell 1 is sandwiched between a pair of front and rear shell halves 1a and 1b that connect opposite ends to each other and both shell halves 1a and 1b so that the inside of the booster shell 1 is a front shell chamber 2 and a rear shell chamber. A partition wall plate 1c for partitioning into three parts and a rear shell half 1b are supported by a vehicle body (not shown).

The front shell chamber 2 is formed of a steel plate front booster piston 4 housed therein so as to be reciprocally movable back and forth, and is superposed on the rear surface of the front booster piston 4 and is sandwiched between the front shell half body 1a and the partition plate 1c. The front diaphragm 5 made of rubber and partitioned into a front negative pressure chamber 2a on the front side and a front working chamber 2b on the rear side. The rear shell chamber 3 is made of a steel plate rear booster piston 6 housed therein so as to be capable of reciprocating back and forth, and a rubber which is superposed on the rear surface thereof and is fixed between the shell halves 1a and 1b together with the partition plate 1c. The manufactured rear diaphragm 7 divides the front rear negative pressure chamber 3a and the rear rear working chamber 3b.

The front and rear booster pistons 4 and 6 are each formed into an annular shape by a steel plate, and these are mounted on both ends of a synthetic resin piston boss 10 which is slidably supported by a partition plate 1c via a bush 8 and a seal member 9. It is bound as follows.

That is, the piston boss 10 is formed with a circular recess 11 whose depth reaches approximately half of the length of the boss 10 on the front end face, and a flange 12 at a position slightly forward from the rear end of the outer peripheral face thereof.
The connecting cylinder 13 integrally connected to the inner peripheral end of the front booster piston 4 is fitted in the circular recess 11, and the rear end of the connecting cylinder 13 is An end wall plate 13a serving as a bottom portion of the cylinder 13 is integrally and continuously provided, and a rear surface of the end wall plate 13a is superposed on the bottom wall of the recess 11. Further, a holding plate 14 for holding the rear booster piston 6 in cooperation with the flange 12 is laid on the rear end surface of the piston boss 10. And
The holding plate 14, the piston boss 10 and the end wall plate 13a are fixed to each other by a plurality of (three in the figure) through bolts 15 surrounding the axis of the piston boss 10 and a nut 16 screwed to these. To be done.

At that time, between the front booster piston 4 and the front end face of the piston boss 10, an inner peripheral bead 5a of the front diaphragm 5 is provided.
And an annular retainer 17 formed of a metal plate so as to cover the outer peripheral surface and the rear surface of the inner peripheral bead 5a, and the rear booster piston 6 is interposed between the flange 12 and the pressing plate 14.
The inner peripheral bead 7a of the rear diaphragm 7 that wraps the inner peripheral end of the is inserted. Therefore, the front and rear booster pistons 4,6
At the same time that the piston boss 10 and the piston boss 10 are bonded to each other, the inner peripheral beads 5a and 7a of the diaphragms 5 and 7 are fixed to the corresponding booster pistons 4 and 6.

Furthermore, to insert the through bolt 15, the piston boss 10
A seal member 19 is attached to the bolt hole 18 provided in
This prevents the bolt hole 18 from communicating between the front negative pressure chamber 2a and the rear working chamber 3b. Further, a seal member 20 surrounding a plurality of through bolts 15 is interposed between the end wall plate 13a and the piston boss 10, whereby the end wall plate 13a is formed.
Also, communication between the first and second ports 30 and 31, which will be described later, is prevented by the contact surface gap of the piston boss 10.

Each through bolt 15 is arranged with its square head portion 15a facing the rear working chamber 3b side, and a concave portion 21 (see FIG. 2) of the same shape in which the square head portion 15a is non-rotatably fitted is provided on the holding plate 14. It is formed. Therefore, when the nut 16 is screwed into the through bolt 15 on the front negative pressure chamber 2a side, the rotation of the bolt 15 is prevented, so that the nut 16 can be securely tightened.

Using the through bolt 15 and nut 16 described above, the connecting cylinder 13
The seat plate 22 is superposed and bonded to the end wall plate 13a. This seat 22
Is provided with a plurality of seat portions 22a (see FIG. 3) raised between the plurality of nuts 16 and higher than the height of the nuts 16, and the piston boss is provided between the seat portions 22a and the front shell half body 1a. A return spring 23 that biases 10 in the backward direction is contracted. In this way, the return spring 23 together with the connecting cylinder 13 is a recess on the front surface of the piston boss 10.
Accepted by 11.

The retreat limit of both booster pistons 4 and 6 is regulated by a large number of protrusions 24 protruding on the rear surface of the rear diaphragm 6 contacting the rear wall of the booster shell 1.

The front negative pressure chamber 2a is connected via a negative pressure introducing pipe 29 to a negative pressure source (not shown) (for example, inside the intake manifold of the internal combustion engine). The front and rear negative pressure chambers 2a and 3a are connected to the piston boss 1
The first and second bifurcated first ports 39 are connected to the inside of the valve cylinder 25, and the front and rear working chambers 2b, 3b are also formed in the piston boss 10 by a pair of second ports 31, 31. Through the valve cylinder 25. The second ports 31 and 31 are connected to the first port 30 by the control valve 32 and the end wall 26 of the rear extension cylinder 26.
The communication is alternately switched to the air inlet 33 opening at a.

An input rod 35 connected to the brake pedal 34 is provided in the valve cylinder 25.
And the control valve 32 controlled thereby is provided as follows. That is, the valve piston 38 is slidably fitted to the front portion of the valve cylinder 25, and the front end of the input rod 35 penetrating the atmosphere introduction port 33 is swingably coupled to the valve piston 38. An annular first valve seat 40 ₁ is provided on the inner peripheral surface of the valve cylinder 25 so as to project, and an annular second valve seat 40 ₂ surrounded by the annular first valve seat 40 ₁ is formed on the rear end surface of the valve piston 38. Valve body 41 cooperating with 40 ₁ and 40 ₂
Are arranged in the valve cylinder 25. The valve body 41 is made of rubber and has a tubular shape with its front and rear ends open, and its rear end portion, that is, the base end portion 41a, is provided with a holding cylinder 42 fitted to the inner peripheral surface of the valve cylinder 25. It is held in close contact with the inner peripheral surface of the cylinder 25. This valve body
41 is provided with a thin flexible portion 41b bent inward in the radial direction from the base end portion 41a, and a thick valve portion 41c continuous to the front end of the flexible portion 41b, the valve portion 41c is the First and second
It is arranged to face the valve seats 40 ₁ and 40 ₂ .

Thus, the valve portion 41c can be moved back and forth due to the deformation of the flexible portion 41b, is seated on the first and second valve seats 40 ₁ and 40 ₂ when moving forward, and is received by the front end of the holding cylinder 42 when moving backward. Can be stopped.

An annular reinforcing plate 43 is embedded in the valve portion 41c, and this and the input rod 3
A valve spring 44 that urges the valve portion 41c toward both valve seats 40 ₁ and 40 ₂ is contracted between the valve spring 44 and the valve 5.

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

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

Thus, the valve body 41, the valve spring 44, the first valve seat 40 ₁ and the second valve seat 40 ₂ constitute the control valve 32.

Between the input rod 35 and the holding cylinder 42, a return spring 45 for urging the input rod 35 toward the backward limit thereof is contracted.

The backward limit of the input rod 35 is regulated by a stopper plate 46 screwed to the input rod 35 so as to be adjustable forward and backward, and brought into contact with the inner surface of the end wall 26a of the rear extension cylinder 26. Therefore, the stopper plate 46
When is turned, the screwing position of the stopper plate 46 and the input rod 35 is changed, so that the backward limit of the input rod 35 can be adjusted back and forth. After the adjustment, the stopper plate 46 is fixed in the same manner as the input rod.
It is performed by tightening a lock nut 47 screwed to 35. The stopper plate 46 is provided with a vent hole 48 so that the stopper plate 46 does not block the atmosphere introduction port 33.

An air filter 49 for filtering the air taken into the valve cylinder 25 from the air introduction port 33 is attached to the valve cylinder 25 around the input rod 35. The air filter 49 includes an input rod 35 and a valve cylinder 25.
It has appropriate flexibility so as not to interfere with relative displacement with.

The piston boss 10 is provided with a large cylinder hole 37 opening at the center of the front surface thereof and a small cylinder hole 36 having both ends open inside the large cylinder hole 37 and the valve cylinder 25. The small cylinder 36 is slidably fitted with a reaction force piston 52 that is in contact with the valve piston 38 or is in contact with the valve piston 38, and the large cylinder hole 37 has an elastic piston 50 that faces the reaction piston 52.
Further, the output piston 51 which is superposed on the front surface of the elastic piston 50 is slidably fitted. Large cylinder hole of this output piston 51
In order to prevent the end wall plate 13a from being pulled out, 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 on the front surface of the output piston 51, and the output rod 53 is a piston 55 of the brake master cylinder M.
Will be serialized.

In FIGS. 1, 4, and 5, each of the second ports 31 is an axial port 31A that communicates between the working chambers 2b and 3b.
And a radial port 31R that communicates between the rear working chamber 3b and the valve cylinder 25.

The axial port 31A is located on the side of the concave portion 11 and extends to the front and rear ends of the concave portion 11 at the front port portion 31A.
_f and the front side port portion 31A _f , which is connected to the rear end of the recess 11
The rear port portion 31A _r axially penetrates the bottom wall, and the rear port portion 31A _r has a rear elongated hole c extending from the rear end of the piston boss 10 to the vicinity of the recess 11 and a rear elongated hole. It is composed of a tapered hole b which continuously connects between c and the rear end of the front port portion 31A _f , and the tapered hole b is formed so as to be wider in the circumferential direction of the piston boss 10 as it goes forward. Both the rear elongated hole c and the front port portion 31A _f are arranged with their major diameters oriented in the circumferential direction of the piston boss 10, and in particular, the front port portion 31A _f is flatter and has a larger diameter than the rear elongated hole c. It is made large.

In the illustrated example, the front port portion 31A _f has an axial groove 56 formed in the inner peripheral surface of the recess 11 over the front and rear ends of the recess 11.
And a front end of the front port portion 31A _f directly communicates with the front end surface of the piston boss 10 and a notch 57 opening in the outer peripheral surface. With this configuration, when the piston boss 10 is molded, the front port portion 31A _f having a large flatness can be easily formed together with the notch 57 by the mold. The retainer 17 is arranged so as to close the open surface of the notch 57 that faces the inner peripheral bead 5a of the front diaphragm 5. Thus, the retainer 17 functions as a rigid member that restrains the swelling of the inner peripheral bead 5a into the notch 57.

Next, the operation of this embodiment will be described. First, in the rest state of the negative pressure booster B, as shown in FIG. 1, the input rod 35 is located at the backward limit, and the control valve 32 moves the valve portion 41c to the first and second valve seats 40 ₁ and 40 ₂ . After being seated, both the front and rear working chambers 2b, 3b are in a neutral state in which both the negative pressure chambers 2a, 3a and the atmosphere introduction port 33 are in communication with each other.
The negative pressure of the negative pressure source supplied through the negative pressure introduction pipe 29 is stored in a and 3a, and the negative pressure appropriately diluted by the atmosphere is held in both working chambers 2b and 3b. In this way, a slight forward force is applied to the front and rear booster pistons 4 and 6 due to the difference in atmospheric pressure between the front negative pressure chamber 2a and the working chamber 2b and the rear negative pressure chamber 3a and the working chamber 3b. , These forward force and return spring 23
The booster pistons 4 and 6 are stopped at a position slightly advanced from the backward limit, in balance with the elastic force of.

Now, depress the brake pedal 34 to brake the vehicle,
If caused to advance the input rod 35 and the valve piston 38, initially, since both booster pistons 4 and 6 are stationary, the second valve seat 40 ₂ immediately away both working chambers 2b from the valve portion 41c, the 3b atmosphere introduction Connect to mouth 33. As a result, the atmosphere is both operating chambers 2b through the second valve seat 40 ₂ and the second port 31 from the air inlet 33, is quickly introduced into 3b, the chamber 2b, 3b and Ryomake chamber 2a, to a high pressure from 3a Therefore, a large forward force based on the pressure difference between them is obtained, and both booster pistons 4 and 6 advance forward with good response against the force of the return spring 23, and the piston 55 of the brake master cylinder M is moved forward through the output rod 53. Drive to. In this way, the brake master cylinder M can be operated without delay when the brake pedal 34 is depressed to brake the vehicle.

During such braking, the valve rod 38 moves forward together with the input rod 35 and contacts the elastic piston 50 via the reaction force piston 52.
Of the brake pedal through the valve piston 38 and the input rod 35 because the reaction piston 52 bulges and deforms toward the small cylinder hole 36 side to act a part of the reaction force on the reaction piston 52.
Feedback is given to the 34 side. By such a reaction force action, the operator can detect 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 boost limit point due to an increase in the pedaling force on the brake pedal 34, that is, the input of the input rod 35,
Since the front surface of the valve piston 38 abuts on the piston boss 10, the entire input is transmitted to the output rod 53 via the valve piston 38, the piston boss 10, the elastic piston 50 and the output piston 51. The sum of the forward force due to the atmospheric pressure difference between the booster pistons 4 and 6 and the forward force due to the input is the output rod 53
Output from

Next, when the pedal force on the brake pedal 34 is released,
First, the input rod 35 is moved by the elastic force of the return spring 45 to the valve piston 38.
With this, the second valve seat 40 ₂ is seated on the valve portion 41c of the valve body 41, and the valve portion 41c is largely separated from the first valve portion 40 _1, so that both working chambers 2b and 3b have the first and second working chambers 2b and 3b. By communicating with both negative pressure chambers 2a and 3a via ports 30 and 31, the pressure difference between the booster pistons 4 and 6 immediately disappears, so that both booster pistons 4 and 6 are retracted by 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 retracted limit at which the stopper plate 46 contacts the partition wall 26a of the extension cylinder 26, the rear booster piston 6 moves to the sixth position.
As shown in the figure, the protrusion 24 of the rear diaphragm 7 is temporarily returned to the retracted limit where it abuts the rear wall of the booster shell 1, and this time the first valve seat 40 ₁ is seated on the valve seat 41c and the valve portion 41c.
Since slightly moved away from the second valve seat 40 _2, the second port 3
Both working chambers 2b again through 1, but the air is introduced into 3b, it small clearance between the second valve seat 40 ₂ and the valve portion 41c when the forward both booster pistons 4 and 6 Sukoshiku by pressure difference caused by the eliminated , The control valve 32 is brought to the initial neutral state. In this way, the negative pressure diluted in the atmosphere is held in both working chambers 2b, 3b,
The negative pressure booster B is in the rest state shown in FIG.

In such a tandem type negative pressure booster B, of the axial port 31A of the second port 31, especially the front port portion 31A _f
By fitting the recess 11 on the front surface of the piston boss 10 and the connecting cylinder 13 of the front booster piston 4, the groove 56 on the inner peripheral surface of the recess 11 is formed.
Since it can be formed with a large degree of flatness between it and the outer end surface of the connecting cylinder 13, it is possible to secure a wide cross-sectional area of the front port portion 31A _f without being restricted by the recess 11. On the other hand, the rear port portion 31A _{f of the} axial port 31A
Is located behind the concave portion 11 and a wide cross-sectional area can be secured without being restricted by the concave portion 11. Therefore axial port
Since the cross-sectional area of 31 can be sufficiently secured over the entire length, a large amount of air can flow through the axial port 31A when the control valve 32 is switched, and the responsiveness of the front and rear booth pistons 4 and 6 can be improved. It will be good. Moreover, between the front port portion 31A _f and the rear elongated hole c, the change in the cross-sectional shape is moderated by the tapered hole b, so that the air flow in the axial port 31A is smoothly performed and an abnormal noise is generated. There is no.

The inner peripheral bead 5a of the front diaphragm 5 which is clamped between the booster piston 4 and the front end surface of the piston boss 10 is covered with an annular retainer 17 on the outer peripheral surface and the rear surface of the bead 5a to retain its shape. Therefore, even if the tensile force acts on the front diaphragm 5 due to the pressure difference between the negative pressure chamber 2a and the working chamber 2b,
The diameter of the inner peripheral bead 5a does not increase, and therefore the inner peripheral bead 5a can be reliably prevented from being separated from between the front booster piston 4 and the piston boss 10.

Moreover, since the retainer 17 is arranged so as to close the opening of the second port 31 to the front working chamber 2b, that is, the front open surface of the cutout 57, the swelling of the inner peripheral bead 5a into the cutout 57 is prevented. Therefore, even if the inner peripheral beads 5a come into contact with the evaporated gasoline in the atmosphere, the narrowing of the opening due to the swelling can be prevented.

C. Effect of the Invention As described above, according to the present invention, the tandem negative pressure type in which the opening of the second port to the front working chamber is a notch that opens to the front end surface and the outer peripheral surface of the piston boss. In the booster, a rigid member made of an annular plate material that closes an open surface of the notch that faces the inner peripheral bead is sandwiched between the inner peripheral bead of the front diaphragm and the front end of the piston boss to which the bead is fixed. The rigid member reliably prevents the inner peripheral bead of the front diaphragm from swelling to the opening to the front working chamber of the second port, so that the effective opening of the opening is always kept normal. Therefore, when the control valve is switched, air is always smoothly circulated in the second port, and good responsiveness of the negative pressure booster can be secured. Moreover, since the rigid member is made of an annular plate material,
Even if it is sandwiched between the opposed surfaces of the piston boss front end and the diaphragm, it does not cause the front booster piston and the diaphragm to extend forward long, and therefore the opening of the second port to the front working chamber The front and back stroke of the piston boss is regulated in combination with the effect that the front and rear length of the piston boss itself can be shortened as much as possible by preventing the flesh from being formed at the front side by making the part above the notch It can be secured as long as possible within the booster shell of the size.

In addition, the rigid member is sandwiched between the inner peripheral bead of the front diaphragm and the front surface of the piston boss front end to which the bead is fixed, so that the rigid member can be easily and securely fixed in place without using a dedicated fixing means. The fixing structure is simple and can contribute to cost reduction and assembling. Further, since the notch can be arranged at a position facing the inner peripheral bead located at the inner peripheral end edge of the front diaphragm, the piston boss in which the notch is formed does not need to have a particularly large diameter. The notch can be arranged at an appropriate position. Furthermore, the outer peripheral end of the piston boss front end surface,
Since it can be used as a support point for the front booster piston, it is advantageous in suppressing flexural deformation of a portion outside the support point of the front booster piston.

Further, in particular, on the inner peripheral portion of the front booster piston, there is integrally formed a connecting cylinder which is fitted in the concave portion of the front surface of the piston boss and whose bottom portion is superposed and bonded to the concave bottom wall. An annular seal member is interposed between the bottom wall and the bottom wall, and the front port portion of the second port that directly communicates with the cutout is formed in the inner peripheral surface of the recess over the front and rear ends thereof in the axial direction. Between the groove on the inner peripheral surface of the concave portion and the outer peripheral surface of the connecting cylinder that covers the groove, the concave portion on the front surface of the piston boss and the connecting cylinder of the front booster piston are connected to the groove on the inner peripheral surface of the concave portion. The front port part of the second port between the outer peripheral surface of the cylinder,
It can be formed with a large degree of flatness, whereby the passage cross-sectional area of the front-side port portion can be widely ensured without being restricted by the concave portion, and the front-side port portion at the time of switching of the control valve can be assured. The air can be smoothly circulated, and the leakage of the circulated air to the front negative pressure chamber side can be reliably prevented by the annular seal member. Further, the groove on the inner peripheral surface of the recess can be molded extremely easily by a mold together with the notch directly communicating with the groove.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a vertical side view of a tandem type negative pressure booster in a rest state, and FIGS. 2 and 3 are II-II and III- lines in FIG. III line sectional view, FIG. 4 is a plan view of the piston boss, FIG. 5 is VV of FIG.
FIG. 6 is a partial vertical sectional side view showing a state immediately before the negative pressure booster finishes its operation and returns to the rest state. B ... Negative pressure booster, 1 ... Booster shell, 1a, 1b ...
… Shell half, 1c …… Partition plate, 2 …… Front shell chamber, 2a
... front negative pressure chamber, 2b ... front working chamber, 3 ... rear shell chamber, 3a ... rear negative pressure chamber, 3b ... rear working chamber, 4 ... front booster piston, 5 ... front Diaphragm, 5a ... Inner circumference bead, 6 ... Rear booster piston, 7 ... Rear diaphragm, 7a ... Inner circumference bead, 10 ... Piston boss,
11 ... Recess, 13 ... Connection tube, 13a ... End wall plate as bottom of connection tube, 20 ... Seal member, 25 ... Valve tube, 30 ... First
Port, 31 …… Second port, 31A _f …… Front port part, 32
...... Control valve, 33 …… Atmosphere inlet, 35 …… Input rod, 53 ……
Output rod, 57 ... Notch

Continuation of front page (56) Reference JP-A-58-128951 (JP, A) Actually open 60-67273 (JP, U) Actually open 58-106266 (JP, U)

Claims (1)

[Scope of utility model registration request] A partition plate (1c) for partitioning the interior of the booster shell (1) into a front shell chamber (2) and a rear shell chamber (3) is fixed to the front shell chamber (2). A front booster piston (4) partitioned into a front negative pressure chamber (2a) and a rear front working chamber (2b), and a front diaphragm superposed on the rear surface of the front booster piston (4). The inner peripheral bead (5a) of (5) is slidably supported by the partition plate (1c) and fixed to the front end of the piston boss (10) connected to the output rod (53), while the rear shell chamber is formed. A rear booster piston (6) partitioning (3) into a front rear negative pressure chamber (3a) and a rear rear working chamber (3b), and a rear diaphragm (6) superposed on the rear surface of the rear booster piston (6). 7) and are fixed to the rear end of the same piston boss (10), and the piston boss (10) is A valve cylinder (25) that projects and is slidably supported on the rear wall of the booster shell (1) is integrally connected, and the inside of the valve cylinder (25) is connected to both negative pressure chambers (2a, 3).
The first port (30) communicating with a) and the second port (31) communicating with both working chambers (2b, 3b) in the valve cylinder (25) are provided, and the second port (31) The opening to the front working chamber (2b) is a notch (57) opening to the front end surface and the outer peripheral surface of the piston boss (10), and the valve rod (25) has a forward and backward movable input rod ( 35) and a control valve (32) for switching the second port (31) to communicate with the first port (30) and the atmosphere according to the forward and backward movement of the input rod (35). The recess (1) that receives the return spring (23) that biases the (10) backward
In the tandem type negative pressure booster in which 1) is provided on the front surface of the boss (10), the inner peripheral portion of the booster piston (4) is fitted into the concave portion (11) so that the bottom portion (13a) is the concave portion. (1
1) A connecting cylinder (13) integrally formed on the bottom wall is integrally formed, and the bottom (13a) of the connecting cylinder (13) and the recess (11) are formed.
An annular seal member (2
0) is interposed, and the cutout (57) of the second port (31) is provided.
The front side port portion (31A _f ) that directly communicates with the concave portion (11)
Axial groove (56) formed on the inner peripheral surface over the front and rear ends
Between the inner peripheral bead (5a) of the front diaphragm (5) and the front end of the piston boss (10), and the outer peripheral surface of the connecting cylinder (13) covering the groove (56). A tandem-type negative pressure booster, characterized in that a rigid member (17) made of an annular plate material that closes the open surface of the notch (57) facing the inner peripheral bead (5a) is sandwiched.