JPH0574504B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tandem brake booster, and more specifically, a passage means for communicating a variable pressure chamber formed on the front side and a variable pressure chamber formed on the rear side. Regarding.

``Prior Art'' In general, a tandem brake booster consists of a center plate that divides the inside of a shell into a front chamber and a rear chamber, and a valve body that is provided with a shaft inside the shell that slides through the center plate. a front power piston disposed in the front chamber and connected to the valve body; a front diaphragm stretched over the back of the front power piston to divide the front chamber into a constant pressure chamber and a variable pressure chamber; The engine is equipped with a rear power piston that is disposed on the rear power piston and connected to the valve body, and a rear diaphragm that is stretched over the rear side of the rear power piston and partitions the rear interior into a constant pressure chamber and a variable pressure chamber.

In this type of tandem brake booster, it is necessary to communicate between the two variable pressure chambers, one on the front chamber side and one on the rear chamber side, and conventionally, this passage has been constructed from a through hole formed in the valve body. It has been known.

By the way, tandem brake boosters are becoming more and more popular year by year due to the demand for higher output in vehicles, but there is a problem that some vehicles have a long overall length that makes it impossible to install them, so conventionally the overall length has been shortened. Various methods have been proposed to do this.

For example, in a tandem brake booster, a cylindrical storage part is formed inwardly protruding from the shaft of the front shell, and airtightness is maintained between the front shell and a push rod slidably penetrating the front shell. Since the sealing member is stored in the storage portion, the storage portion is relatively fitted and stored in the tip shaft portion of the valve body, and the tandem brake booster is applied only by the combined force in the axial direction of the two. I'm trying to shorten the overall length.

"Problems to be Solved by the Invention" However, when the passage is formed from a through hole formed in the valve body, the valve body is required to have a wall thickness sufficient to form the passage, and the wall thickness of the passage portion is As the valve body became thicker, the weight of the valve body increased. In particular, in the case where the storage portion and the tip shaft portion of the valve body overlap in the axial direction, it becomes difficult to provide a sufficient wall thickness for the passage portion at the overlapped portion. Increasing the wall thickness increases the diameter of the valve body, which causes problems such as increased weight and reduced boost load.

"Means for Solving the Problems" In view of such circumstances, the present invention forms a cylindrical part extending toward the rear side on the shaft part of the front power piston, so that the cylindrical part is slidable on the center plate. A part of the valve body is fitted into the cylindrical part, and a bent part formed at the rear end of the cylindrical part is engaged with the stepped part of the valve body from the rear side, and the part of the valve body is fitted into the cylindrical part. The inner peripheral part of the rear power piston fitted from the rear side is brought into contact with the bent part from the rear side to integrally connect the valve body and both power pistons, and
A first passage kept airtight by a seal member is formed between the inner peripheral surface of the cylindrical part and the outer peripheral surface of the valve body, and the first passage is connected to the first passage through a through hole bored in the cylindrical part. It communicates with the variable pressure chamber on the front chamber side, and also communicates with the variable pressure chamber on the rear chamber side via a second passage formed in the valve body.

"Operation" According to such a configuration, the first passage is formed between the inner circumferential surface of the cylindrical part and the outer circumferential surface of the valve body, so that the first passage is formed from a through hole inside the valve body. The wall thickness of the valve body can be reduced, thereby making it possible to reduce the weight of the valve body.

If the wall thickness of the valve body can be made thinner, the first passage can be easily secured in the overlapped portion even if the storage portion and the tip shaft portion of the valve body are overlapped in the axial direction. Therefore, there is no need to increase the diameter of the valve body, so there is no increase in weight or reduction in boost load.

"Example" The present invention will be described below with reference to the illustrated example.
In FIG. 1, the inside of a sealed container consisting of a front shell 1 and a rear shell 2 is divided into two chambers, a front chamber 4 and a rear chamber 5, by a center plate 3 provided in the center. , and a substantially cylindrical valve body 6 made of synthetic resin is attached to the shaft portion of the rear shell 2 and center plate 3.
The front chamber 4 and the rear chamber 5 are kept airtight by seal members 7 and 8, respectively.

A front power piston 9 and a rear power piston 10 housed in the front chamber 4 and rear chamber 5 are connected to the valve body 6, respectively, and a front diaphragm 11 and a rear diaphragm are connected to the back of each power piston 9, 10. 12, respectively, and the front chamber 4 and rear chamber 5 are separated by the diaphragms 11 and 12.
and are divided into two rooms each, making a total of four rooms A,
B, C, and D are formed.

The front power piston 9 has a cylindrical portion 9a fitted on the outer periphery of the valve body 6 on its shaft portion, and this cylindrical portion 9a is kept airtight by the seal member 7 described above and slides on the center plate 3. It passes through freely. And the cylindrical part 9a
A radially inward bent portion 9 formed at the right end of the
b is brought into contact with the stepped portion 6a formed on the outer circumferential surface of the valve body 6, and the rear power piston 10 is brought into contact with the right end surface of the bent portion 9b. By biasing the fitted rear diaphragm 12 in the direction of the stepped portion 6a,
Both power pistons 9 and 10 are integrally connected to the valve body between the stepped portion 6a and the rear diaphragm 12.

A valve mechanism 15 is housed inside the valve body 6, and the right end of a valve plunger 16 constituting the valve mechanism 15 is connected to an input shaft 17 that is linked to a brake pedal (not shown), and the left end surface is connected to an input shaft 17 that is linked to a brake pedal (not shown). It is opposed to the right end surface of the reaction disk 18.

The reaction disk 18 is housed in a push rod 19 whose base is slidably attached to the valve body 6, and the left end of the push rod 19 slides from the shaft of the front shell 1 via a seal member 20. freely protrude to the outside,
It is linked to a piston of a master cylinder (not shown). This push rod 19 is prevented from falling off from the valve body 6 by a return spring 21 which is loaded between the front shell 1 and the valve body 6 and has a small diameter only by one turn at its right end. There is.

Further, the valve plunger 16 is connected to the valve body 6.
A key member 25 that prevents the key member 25 from slipping out is inserted in the radial direction of the valve body 6 and interlocked with the valve plunger 16, and the key member 25 is interlocked with the valve plunger 16.
6 prevents it from falling off from the valve body 6.

The key member 25 is provided to be slidable in the axial direction of the valve body 6, and when the valve body 6, power pistons 9, 10, etc. are held in the non-operating position shown in the figure by the return spring 21, , the key member 25 is brought into contact with the inner wall surface of the rear shell 2 to advance the valve plunger 16 and the input shaft 17 from their freely retreated positions, and the valve body 27 of the valve mechanism 15 is formed on the valve body 6. The ineffective stroke of the input shaft 17 at the initial stage of operation is reduced.

Further, the aforementioned chamber A is a constant pressure chamber into which negative pressure is constantly introduced, and communicates with an intake manifold (not shown) via a negative pressure introducing pipe 35 attached to the front shell 1. Also, this constant pressure chamber A
is the axial passage 3 formed in the valve body 6.
6. It is constantly communicated with the constant pressure chamber C via a radial passage 37, an annular groove 38 formed on the outer peripheral surface of the valve body 6, and a through hole 39 bored in the cylindrical portion 9a.

When the brake booster is not in operation, these constant pressure chambers A and C are connected to the above-mentioned axial passage 36 formed in the valve body 6 and the valve body 27 of the valve mechanism 15.
The variable pressure chamber D is communicated with a variable pressure chamber D through a gap between the valve seat 28 and the valve seat 28 and a radial passage 40 formed in the valve body 6, and further, this variable pressure chamber D is constantly changed in pressure via a passage means 41 according to the present invention formed in the valve body 6. It communicates with room B.

The passage means 41 includes a first passage 46 which is kept airtight by a seal member 45 between the inner peripheral surface of the cylindrical portion 9a of the front power piston 9 and the outer peripheral surface of the valve body 6. 1 aisle 4
6 is communicated with the variable pressure chamber B on the front chamber 4 side through a through hole 47 bored in the cylindrical portion 9a, and communicated with the rear chamber 5 side through a second passage 48 formed by penetrating the valve body 6. It communicates with the pressure change room D.

The seal member 45, as shown in FIG.
In this embodiment, the annular seal member 45 is composed of an annular seal member having a required width in the axial direction.
An opening 49 of a required size is bored within the width of the opening 49, and the inside of the opening 49 is used as the first passage 46.
As shown in FIGS. 4A and 4B, a contoured portion 45a forming the opening 49 is thick and circular in cross section to ensure reliable sealing.

In this embodiment having the above configuration, the first passage 46 is formed between the inner peripheral surface of the cylindrical portion 9a and the outer peripheral surface of the valve body 6, so that the first passage 46 is connected to the through hole inside the valve body. It is clear that the wall thickness of the valve body 6 at the first passage 46 can be made thinner than when the second passage 48 is extended to form the first passage. 6 can be made lighter.

Furthermore, when the second passage 48 is extended to form the first passage, it is possible to fit the storage part of the front shell 1 that stores the seal member 20 into the tip shaft part of the valve body 6 when the valve body 6 moves forward. Therefore, it is necessary to lengthen the overall length of the tandem brake booster or increase the diameter of the valve body 6 even at the expense of the boost load. However, in this embodiment, as described above, the thickness of the valve body 6 is Since the thickness can be reduced, such problems can be solved.

"Effects of the Invention" As described above, according to the present invention, it is possible to achieve the effect that the weight of the valve body can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
The figure is a perspective view of the sealing member 45 shown in FIG.
Figure 4 shows the - line and - line of Figure 2, respectively.
It is a sectional view along a line. 1...Front shell, 2...Rear shell, 3
...Center plate, 4...Front chamber, 5...
... Rear chamber, 6 ... Valve body, 9 ... Front power piston, 9a ... Cylindrical part, 10 ... Rear power piston, 41 ... Passage means, 11 ... Front diaphragm, 45 ... Seal member, 12
...Rear diaphragm, 45a...Outline part, 4
6...First passage, 47...Through hole, 48...Second passage, 49...Opening, A, C...Constant pressure chamber, B, D
...Transformation room.

Claims (1)

[Scope of Claims] 1. A center plate that divides the inside of the shell into a front chamber and a rear chamber, a valve body provided with the center plate slidably passing through a shaft portion in the shell, and a valve body provided in the front chamber. a front power piston disposed and connected to the valve body; a front diaphragm stretched over the back of the front power piston to divide the front chamber into a constant pressure chamber and a variable pressure chamber; In a tandem brake booster equipped with a rear power piston connected to a valve body and a rear diaphragm stretched over the back of the rear power piston and dividing the rear interior into a constant pressure chamber and a variable pressure chamber, the front power piston is A cylindrical part extending toward the rear side is formed on the shaft part, and this part is slidably passed through the center plate, and a part of the valve body is fitted into the cylindrical part, and the rear side of the cylindrical part is fitted into the cylindrical part. The bent portion formed at the end is engaged with the stepped portion of the valve body from the rear side, and the inner peripheral portion of the rear power piston fitted into the valve body from the rear side is brought into contact with the bent portion from the rear side. The valve body and both power pistons are integrally connected, and a first passage is formed between the inner circumferential surface of the cylindrical portion and the outer circumferential surface of the valve body, the first passage being kept airtight by a sealing member. One passage is communicated with the variable pressure chamber on the front chamber side through a through hole bored in the cylindrical part, and communicated with the variable pressure chamber on the rear chamber side via a second passage formed in the valve body. Passage means for a tandem brake booster characterized by: 2. A patent claim characterized in that the sealing member is an annular sealing member having a required width in the axial direction, and an opening is bored within the width of the annular sealing member, and the inside thereof is used as the first passage. The passage means of the tandem brake booster according to item 1. 3. The passage means for a tandem brake booster according to claim 2, wherein the contour portion forming the opening has a thick wall.