JP2530334Y2 - Tandem type negative pressure booster - Google Patents

Description

[Detailed description of the invention] A. Purpose of the invention (1) Industrial application field In the invention, a partition plate that partitions the inside of the booster shell into a front shell room and a rear shell room is fixed. A front booster piston that divides the lower shell chamber into a front front negative pressure chamber and a rear front working chamber, and partitions the rear shell chamber into a front rear negative pressure chamber and a rear rear working chamber. A rear booster piston is slidably supported by the partition plate and connected via a piston boss connected to the output rod. The piston boss is slidably supported on the rear wall of the booster shell protruding from the rear end. And a second port communicating the interior of the valve cylinder with both working chambers, and a second port communicating the interior of the valve cylinder with the two working chambers. The port is an axial port communicating between the front and rear working chambers, and the rear working chamber and valve. A control valve configured to include a radial port that communicates between them, a movable input rod in the valve cylinder, and a second port that switches between the first port and the atmosphere in accordance with the longitudinal movement of the input rod. A tandem-type negative pressure booster provided with a concave portion for receiving a return spring for urging a piston boss in a retreating direction, provided on a front surface of the boss.

(2) Prior Art Such a negative pressure booster is already known, for example, as disclosed in Japanese Utility Model Application Laid-Open No. 61-45277.

(3) Problems to be solved by the present invention Conventionally, in the piston boss of such a negative pressure booster, the second
The axial port of the port is formed so as to penetrate through the peripheral wall of the concave portion on the front surface of the boss.However, since the peripheral wall of the concave portion is relatively thin, the axial port has a sufficiently large cross-sectional area over the entire length. It was considered difficult to form. However, if the cross-sectional area of the axial port is not sufficient, the response of each booster piston is reduced when the control valve is switched.

The present invention has been made in view of the above-described circumstances, and has a high responsive tandem in which the axial port of the second port can be easily formed with a mold while ensuring a wide sectional area of each part. It is an object to provide a mold negative pressure booster.

B. Configuration of the Invention (1) Means for Solving the Problems According to the invention, in order to achieve the above object, the inner peripheral portion of the front booster piston is fitted into the recess on the front surface of the piston boss. A connecting cylinder whose bottom is bonded to the bottom wall of the concave portion is integrally formed, and between the bottom portion of the connecting tube and the bottom wall of the concave portion is sealed to seal the space between the first and second ports. A single annular sealing member is interposed, and an axial port of the second port has an axial groove formed on the inner peripheral surface of the concave portion at both front and rear ends of the concave portion, and an outer peripheral portion of a connecting cylinder covering the groove. A front port portion defined between the front port portion and a rear port portion formed in the piston boss so as to penetrate the bottom wall of the concave portion in the axial direction and continuing to the rear end of the front port portion. The port portion has the concave portion from the rear end of the piston boss with its long diameter directed in the circumferential direction of the piston boss. And director hole after extending to near,
The front port portion is formed so as to become wider in the circumferential direction of the piston boss toward the front and is continuous with the front end of the rear elongated hole, and the front port portion is flatter than the rear elongated hole and the piston boss is formed. It is formed of a long hole in the circumferential direction and is disposed so as to be continuous with the front end of the tapered hole.

(2) Operation If the connecting cylinder of the front booster piston is fitted into the concave portion on the front face of the piston boss, the front port portion of the axial 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, the cross-sectional area of the front port can be ensured widely without being restricted by the concave portion, while the rear port portion of the axial port is located behind the concave portion. A wide cross-sectional area can be ensured without being restricted by the recess. Therefore, the cross-sectional area of the axial port can be sufficiently secured over the entire length, so that the air flows quickly through the axial port when the control valve is switched.

Further, since the groove for defining the front port portion on the inner peripheral surface of the concave portion can be easily formed by a mold, even if the degree of flatness of the front port portion is increased, it is difficult to form (for example, metal). There is no problem in terms of the strength of the mold), and the above-mentioned groove is formed directly on the inner peripheral surface of the concave portion, so that the tubular body for defining the front port portion is specially interposed between the inner peripheral surface of the concave portion and the outer peripheral surface of the connecting cylinder. There is no need to wear it. Further, despite the fact that the inner peripheral surface of the concave portion and the outer peripheral surface of the connecting cylinder are directly fitted to each other, the first and second ports communicate with each other through the concave portion and the connecting cylinder. The structure can be prevented by a simple annular seal member interposed between the bottom of the connecting cylinder and the connecting cylinder.

Further, between the front port portion and the rear elongated hole, since the change in cross-sectional shape can be moderated by the special provision of the tapered hole, even if the difference in the circumferential length between the front port portion and the rear elongated hole is large, The flow of air between the two is always smooth.

(3) Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

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

The booster shell 1 includes a pair of front and rear shell halves 1a and 1b for connecting opposing ends to each other, and is sandwiched between the two shell halves 1a and 1b to divide the inside of the booster shell 1 into a front shell chamber 2 and a rear shell chamber. The rear shell half 1b is supported by a vehicle body (not shown).

The front shell chamber 2 is a steel-made front booster piston 4 accommodated therein so as to be able to reciprocate back and forth, and is superposed and bonded to the rear surface thereof and is sandwiched between the front shell half 1a and the partition plate 1c. The front diaphragm 5 made of rubber is 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 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 surface by polymerization and fixed between the two shell halves 1a and 1b together with the partition plate 1c. The rear diaphragm 7 made of rubber is divided into a front 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 in an annular shape from a steel plate, and are formed at both ends of a synthetic resin piston boss 10 slidably supported on 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 the length of the boss 10 at the front end face, and a flange 12 at a position slightly forward from the rear end of the outer peripheral face.
A connecting tube 13 integrally connected to the inner peripheral end of the front booster piston 4 is fitted into the circular concave portion 11, and a rear end of the connecting tube 13 is An end wall plate 13a as a bottom of the cylinder 13 is integrally and continuously provided, and a rear surface of the end wall plate 13a is overlapped with a bottom wall of the concave portion 11. A pressing plate 14 for holding the rear booster piston 6 in cooperation with the flange 12 is placed on the rear end face 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 them. Is done.

At this time, between the front booster piston 4 and the front end face of the piston boss 10, the inner peripheral bead 5a of the front diaphragm 5 is provided.
And an annular retainer 17 made of metal covering the outer peripheral surface and the rear surface of the inner peripheral bead 5a.
14, an inner bead 7a of the rear diaphragm 7 surrounding the inner peripheral end of the rear booster piston 6 is inserted. Therefore, the front and rear booster pistons 4, 6 and the piston boss 1
Each of the three diaphragms is bound together and each diaphragm
Booster pistons 4,6 corresponding to inner peripheral beads 5a, 7a of 5,7
To be fixed.

Further, the piston boss 10 is inserted to insert the through bolt 15.
A seal member 19 is attached to the bolt hole 18 provided in the
As a result, communication between the front negative pressure chamber 2a and the rear working chamber 3b by the bolt hole 18 is prevented. Further, a seal member 20 surrounding the plurality of through bolts 15 is interposed between the end wall plate 13a and the piston boss 10, whereby the end wall plate 13a
Further, communication between the first and second ports 30 and 31 described below due to the contact surface gap of the piston boss 10 is prevented.

Each through-bolt 15 is disposed with its square head 15a facing the rear working chamber 3b, and a recess 21 (see FIG. 2) of the same shape into which the square head 15a fits in a non-rotatable manner is provided on the holding plate 14. It is formed. Therefore, when the nut 16 is screwed into the 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 the nut 16, the connecting cylinder 13
The seat plate 22 is overlap-bonded to the end wall plate 13a. This seat plate 22
Is provided with a plurality of seats 22a (see FIG. 3) raised above the height of the nut 16 between the plurality of nuts 16, and a piston boss is provided between the seat 22a and the front shell half 1a. A return spring 23 for urging the lever 10 in the backward direction is contracted. Thus, the return spring 23, together with the connecting cylinder 13, is provided in the recess on the front face of the piston boss 10.
Accepted by 11.

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

The front negative pressure chamber 2a is connected to a negative pressure source (not shown) (for example, the inside of an intake manifold of an internal combustion engine) via a negative pressure introducing pipe 29. The front and rear negative pressure chambers 2a and 3a are
The front and rear working chambers 2b, 3b communicate with the inside of the valve cylinder 25 via a bifurcated first port 39 formed at 0, and a pair of second ports 31, 31 also formed at the piston boss 10. Through the valve cylinder 25. The second port 31, 31 is 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 with the air introduction port 33 opening to a.

An input rod 35 connected to the brake pedal 34 is provided in the valve cylinder 25.
The control valve 32 controlled thereby is provided as follows. That is, a valve piston 38 is slidably fitted to a front portion in the valve cylinder 25, and a front end of an input rod 35 penetrating through the air introduction port 33 is swingably connected to the valve piston 38. Also on the inner peripheral surface of the valve cylinder 25 first valve seat 40 _first annular is projected, the second valve seat 40 _second annular, surrounded thereto is formed on the rear end face of the valve piston 38, these valve seats Valve element 41 cooperating with 40 ₁ , 40 ₂
Is disposed in the valve cylinder 25. The valve body 41 is made of rubber and has a cylindrical shape with both front and rear ends open.The rear end, that is, the base end 41a, is opened by a holding cylinder 42 fitted on 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
41 includes a thin flexible portion 41b bent inward in the radial direction from the base end portion 41a, and a thick valve portion 41c connected to the front end of the flexible portion 41b. First and second
It is arranged to face the valve seats 40 ₁ and 40 ₂ .

And Thus, the valve portion 41c be capable of moving back and forth by the deformation of the flexible portion 41b, it is seated on the first and second valve seat 40 _1, 40 ₂ at the time of forward movement, received at the front end of the holding cylinder 42 during retraction Can be stopped.

The valve portion 41c is embedded annular reinforcement plate 43, between the input rod 35 and this, a valve spring 44 which biases the valve portion 41c to both valve seat 40 _1, 40 ₂ are compressed state You.

The inner surface of the valve cylinder 25, one end of the first port 30 on the outside of the first valve seat 40 _1, One end of the second port 31 on the inside of the valve seat 40 ₁ is opened, respectively.

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

And Thus, the valve element 41, the control valve 32 is constituted by a valve spring 44, first valve seat 40 ₁ and the second valve seat 40 _2.

A return spring 45 for urging the input rod 35 toward the retreat limit is contracted between the input rod 35 and the holding cylinder 42.

The retraction limit of the input rod 35 is regulated by the stopper plate 46 screwed to the input rod 35 so as to be able to advance and retreat, in contact with the inner surface of the end wall 26a of the rear extension cylinder 26. Therefore, the stopper plate 46
By turning, the screwing position between the stopper plate 46 and the input rod 35 changes, so that the retraction limit of the input rod 35 can be adjusted back and forth. After the adjustment, the stopper plate 46 is fixed by the input
This is performed by tightening a lock nut 47 screwed to 35. A vent hole 48 is formed in the stopper plate 46 so that the stopper plate 46 does not block the air inlet 33.

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

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 opening at both ends in the large cylinder hole 37 and the valve cylinder 25. A reaction piston 52 integral with or in contact with the valve piston 38 is slid into the small cylinder 36, and an elastic piston 50 opposed to the reaction piston 52 is fitted into the large cylinder hole 37.
The output piston 51 superposed on the front surface of the elastic piston 50 is slid. Large cylinder hole of this output piston 51
The inner peripheral edge of the end wall plate 13a extends to the opening of the large cylinder hole 37 in order to prevent the end wall plate 13a from being pulled out.

An output rod 53 projects from the front surface of the output piston 51. The output rod 53 is a piston 55 of the brake master cylinder M.
It will be installed continuously.

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

The axial port 31A is located on the side of the recess 11 and extends across the front and rear ends of the recess 11.
the concave portion 11 contiguous with _f, the rear end of the front ports 31A _f
A rear port portion 31A _r penetrates the bottom wall in the axial direction, and the rear port portion 31A _r has a rear elongated hole c extending from the rear end of the piston boss 10 to near the concave portion 11, and a rear elongated hole. It is composed of a taper hole b for continuously connecting between the rear end of the c and the front port portion 31A _f, the tapered hole b is formed wider in the piston boss 10 circumferential direction toward the front. The rear elongated hole c and the front port portion 31A _f are both arranged with the longer diameter directed in the circumferential direction of the piston boss 10, but in particular, the front port portion 31A _f is flatter and longer than the rear elongated hole c. It is formed largely.

Furthermore the front port unit 31A _f is recess in the inner peripheral surface of the concave portion 11
An axial groove 56 formed over both front and rear ends of the groove 11;
Defined between the coupling tube 13 outer peripheral surface which covers the, also the front end of the front port portion 31A _f is a notch 57 that opens in the front end surface and the outer peripheral surface of the piston boss 10. In this manner, when the piston boss 10 is formed, the front port portion 31A _{f having} a large flatness is formed.
Can be easily formed by a mold.

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 retreat limit, and the control valve 32 moves the valve portion 41c to the first and second valve seats 40 ₁ and 40 ₂ . It is 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 air introduction port 33 after being seated, and the negative pressure chambers 2a, 2a, Three
In a, the negative pressure of the negative pressure source supplied through the negative pressure introducing pipe 29 is stored, and the negative pressure appropriately diluted by the atmosphere is held in both working chambers 2b and 3b. Thus, a slight forward force is applied to the front and rear booster pistons 4 and 6 by the pressure difference between the front negative pressure chamber 2a and the working chamber 2b and between the rear negative pressure chamber 3a and the working chamber 3b. When these forward forces and the resilient force of the return spring 23 are balanced, the booster pistons 4 and 6 stop when they slightly advance from the retreat limit.

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, the booster pistons 4, 6 move forward with good response against the force of the return spring 23 by obtaining a large forward force based on the pressure difference between them, and move the piston 55 of the brake master cylinder M forward through the output rod 53. Drive to In this manner, the brake master cylinder M can be operated without delay when the brake pedal 34 is depressed, and the vehicle can be braked.

During such braking, the valve piston 38 moves forward together with the input rod 35 and abuts on the elastic piston 50 via the reaction force piston 52.
Receiving the operation reaction force, swells and deforms toward the small cylinder hole 36 to cause a part of the reaction force to act on the reaction force piston 52, and the force is applied to the brake pedal via the valve piston 38 and the input rod 35.
Feedback to the 34 side. The operator can sense the output of the output rod 53, that is, the magnitude of the braking force by the reaction force.

When the output of the output rod 53 exceeds the boosting limit point due to the increase in the input force of the input rod 35, the pedaling force on the brake pedal 34,
Since the front surface of the valve piston 38 is in contact with 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 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 pedaling force on the brake pedal 34 is released,
First, the input rod 35 is moved by the spring force of the return spring 45 to the valve piston 38.
Retracted together, so to separate larger second valve seat 40 ₂ from the first valve portion 40 ₁ of the valve portion 41c with is seated on the valve portion 41c of the valve body 41, both working chambers 2b, 3b are first and second By communicating with the two negative pressure chambers 2a and 3a via the ports 30 and 31, the pressure difference between the booster pistons 4 and 6 immediately disappears, and therefore, the booster pistons 4 and 6 retreat with the elastic force of the return spring 23. Then, the operation of the brake master cylinder M is released. When the input rod 35 returns to the retreat limit where the stopper plate 46 contacts the partition 26a of the extension cylinder 26, the rear booster piston 6 moves to the sixth position.
As shown, once return the protrusion 24 of the rear diaphragm 7 to the retracted limit to abut the rear wall of the booster shell 1, the valve portion 41c with turn to seat the first valve seat 40 ₁ in the valve seat 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 Then, the control valve 32 is returned to the initial neutral state. In this way, the working chambers 2b and 3b hold the negative pressure diluted with the atmosphere,
The negative pressure booster B enters the rest state shown in FIG.

In such a tandem type negative pressure booster B, the connecting cylinder 13 connected to the piston boss 10 and the front booster piston 4
A plurality of through bolts 15 arranged around the axis of the piston boss 10 by pressing the three end plates 13a and the holding plate 14 which sandwiches the rear booster piston 6 in cooperation with the piston boss 10;
The nut is screwed to these, and the nut is screwed together. Further, an inner circumferential bead 5a of the front diaphragm 5 is provided between the front booster piston 4 and the piston boss 10, and a rear diaphragm 7 is provided between the rear booster piston 6 and the holding plate 14. Inner bead 7a
The front and rear pistons 4 and 6 and the front and rear diaphragms 5 and 7 can be connected to the piston boss 10 without dividing the piston boss 10, and the end wall plate 13a Since the rotation of the holding plate 14 is restricted by the plurality of through bolts 15, the holding plate 14 does not rotate even when the nut 16 is tightened, so that the front and rear diaphragms 5, 7 can be prevented from being twisted.

By in particular the front port portion 31A _f of the axial port 31A of the second port 31, the fitting of the connecting tube 13 of the piston boss 10 front of the recess 11 and the front booster piston 4, the recess 11
Since the degree of flatness can be increased between the groove 56 on the inner peripheral surface and the outer end surface of the connecting cylinder 13, the cross-sectional area of the front port 31 _Af is secured widely without being restricted by the recess 11. it is possible to, while it is possible to side port portion 31A _r after the axial port 31A to secure a wide cross-sectional area without the constraint recess 11 lies at the rear than the recess 11. Therefore, since the cross-sectional area of the axial port 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 front and rear booster pistons 4, 6 Responsiveness is improved. Moreover, the front port 3
Since the tapered hole b gradually changes the cross-sectional shape between _1Af and the rear elongated hole c, the flow of air in the axial port 31A is performed smoothly, and no noise is generated.

C. Effects of the Invention As described above, according to the present invention, the connecting cylinder in which the inner periphery of the front booster piston is fitted into the recess on the front surface of the piston boss and the bottom is overlapped and bonded to the bottom wall of the recess. Is formed integrally, and between the bottom of the connecting cylinder and the bottom wall of the concave portion, an annular sealing member for sealing therebetween is interposed, and the axial port of the second port is provided on the inner peripheral surface of the concave portion. A front port portion defined between an axial groove formed over both front and rear ends of the concave portion and an outer peripheral surface of the connecting cylinder covering the groove, and a piston boss penetrating the concave bottom wall in an axial direction. A rear elongated port extending from the rear end of the piston boss to the vicinity of the concave portion with a longer diameter in the circumferential direction of the piston boss. The front end of the rear slot is formed to be wider in the direction The front port portion is formed of a continuous tapered hole, the front port portion is formed to be flatter than the rear long hole and is formed of a long hole extending in the circumferential direction of the piston boss, and is disposed so as to be continuous with the front end of the tapered hole. By simply fitting the recess on the front surface of the boss and the connecting cylinder of the front booster piston, the front port portion of the axial port is increased between the groove on the inner peripheral surface of the recess and the outer end face of the connecting cylinder to increase the degree of flatness. Since the cross-sectional area of the front port can be widely secured without being restricted by the concave portion,
Along with the rear port portion of the axial port being located behind the concave portion and the effect of being able to secure a wide cross-sectional area without being restricted by the concave portion, the cross-sectional area of the axial port can be sufficiently extended over the entire length. As a result, the response of the front and rear booster pistons at the time of control valve switching can be improved.

Further, since the groove for defining the front port portion on the inner peripheral surface of the concave portion can be easily formed with a mold, there is no problem in forming even if the flatness of the front port portion is increased. In addition, since the groove is formed directly on the inner peripheral surface of the concave portion, it is not necessary to specially interpose the cylindrical body for defining the front port portion between the inner peripheral surface of the concave portion and the outer peripheral surface of the connection cylinder. Simplification is achieved. Further, despite the fact that the inner peripheral surface of the concave portion and the outer peripheral surface of the connecting cylinder are directly fitted to each other, the first and second ports communicate with each other through the concave portion and the connecting cylinder. Since the structure can be reliably prevented by a single annular seal member interposed between the and the connecting cylinder bottom, the structure can be further simplified.

Further, between the front port portion and the rear elongated hole, since the change in cross-sectional shape can be moderated by the special provision of the tapered hole, even if the difference in the circumferential length between the front port portion and the rear elongated hole is large, The flow of air between the two is always smoothly performed, and generation of abnormal noise due to turbulence of the air flow in the axial port is effectively suppressed.

[Brief description of the drawings]

1 shows an embodiment of the present invention. FIG. 1 is a vertical sectional side view of a tandem type negative pressure booster in a rest state, and FIGS. 2 and 3 are lines II-II and III-II in FIG. III section view, 4th
FIG. 5 is a plan view of the piston boss, FIG. 5 is a cross-sectional view taken along the line VV of FIG. 4, and FIG. 6 is a partial vertical sectional side view showing a state immediately before the negative pressure booster finishes its operation and returns to a rest state. is there. B: negative pressure booster, b: tapered hole, c: rear elongated hole, 1 ... booster shell, 1a, 1b ... half shell, 1c
... partition wall 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 bead, 10… Piston boss, 11… Recess, 13
…… Connection tube, 13a …… End wall plate as bottom of connection tube, 14…
… Presser plate, 15… Through bolt, 16 …… Nut, 25 …… Valve cylinder, 30 …… First port, 31 …… Second port, 31A …… Axial port, 31A _f …… Front port 31A _r … Rear port, 31R… Radial port, 32… Control valve, 33…
Atmospheric inlet, 35 …… Input rod, 53 …… Output rod

Continuation of the front page (56) References JP-A 60-108582 (JP, U) JP-A 60-125271 (JP, U) JP-A 60-157361 (JP, U)

Claims (1)

(57) [Scope of request for utility model registration] 1. A partition plate (1c) for partitioning the inside of a booster shell (1) into a front shell chamber (2) and a rear shell chamber (3) is fixed, and the front shell chamber (2) is fixed. A front booster piston (4) partitioning a front front negative pressure chamber (2a) and a rear front working chamber (2b), and a rear shell chamber (3) into a front rear negative pressure chamber (3a). And a rear booster piston (6) partitioned into a rear working chamber (3b) on the rear side and the partition plate (1c).
The piston boss (10), which is slidably supported by and is connected to the output rod (53) via a piston boss (10).
In addition, a valve cylinder (25) projecting from the rear end and 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). , 3a), and a first port (30) communicating with both working chambers (2
b, 3b) and a second port (31) communicating with the second port (31).
The port (31) has an axial port (31A) communicating between the front and rear working chambers (2b, 3b), the rear working chamber (3b) and the valve cylinder (2
5) a radial port (31R) communicating between them, and an input rod (35) that can move back and forth in the valve cylinder (25); Control valve (32) for switching the port (31) between the first port (30) and the atmosphere
And a recess (11) for receiving a return spring (23) for urging the piston boss (10) in the backward direction is provided on the front surface of the boss (10). A connecting cylinder (13) is integrally formed on the inner peripheral portion of the booster piston (4), the bottom (13a) being fitted into the concave portion (11) and being bonded to the bottom wall of the concave portion (11). , Its connecting tube (13)
A single annular seal member (20) is provided between the bottom portion (13a) of the recess and the bottom wall of the concave portion (11) to seal the space therebetween and to block between the first and second ports (30, 31). The axial port (31A) of the second port (31) is provided with an axial groove (56) formed on the inner peripheral surface of the concave portion (11) over both front and rear ends of the concave portion (11). A front port portion (31A _f ) defined between an outer peripheral surface of the connection cylinder (13) covering the groove (56) and a piston boss (10) extending axially through the bottom wall of the concave portion (11).
And a rear port portion (31A _r ) formed in the front port portion (31A _f ) and connected to the rear end of the rear port portion (31A _f ).
A _r ) has a rear elongated hole (c) extending from the rear end of the piston boss (10) to the vicinity of the concave portion (11) with the major axis directed in the circumferential direction of the piston boss (10). A) a tapered hole (b) formed to be wide in the circumferential direction and continuous with the front end of the rear slot (c), and the front port portion (31A _f ) is formed of the rear slot (c). A tandem-type negative pressure booster characterized by being formed with an elongated hole which is flatter than that of the piston boss (10) in the circumferential direction and is disposed so as to be continuous with the front end of the tapered hole (b).