JPH0569035B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brake booster, and more specifically, to a brake booster that transmits the reaction force of an output applied to a push rod to an input shaft via a reaction disk and a valve plunger. The present invention relates to a reaction force transmission mechanism for a brake booster.

``Prior Art'' Conventionally, the reaction force transmission mechanism of a brake booster generally includes a valve plunger that is connected to an input shaft and is slidably provided on a valve body, and a push rod that is slidably provided on the valve plunger and the valve body. An elastic reaction disk is interposed between the two, one end surface of the reaction disk is opposed to the push rod, and the other end surface is opposed to the valve body and the valve plunger, and the reaction force transmitted from the push rod to the reaction disk is is received by the valve body and the valve plunger, and the reaction force transmitted to the valve plunger is further transmitted to the input shaft.

"Problems to be Solved by the Invention" However, in recent years, the output of brake boosters has increased, and as a result, it has become necessary to increase the reaction force ratio. In order to increase the reaction force ratio in the reaction force transmission mechanism having the above configuration, the area ratio between the valve body and the valve plunger facing the reaction disk is increased on the valve body side,
Or it is necessary to make the valve plunger side smaller,
Increasing the size of the reaction disk in order to increase the size of the valve body increases the size of the brake booster, so there are certain limitations.

On the other hand, if the diameter of the valve plunger is made smaller in order to make the valve plunger side smaller, problems arise with the strength of the valve plunger itself, and the contact pressure between the reaction disk and the valve plunger increases, causing damage to the reaction disk. Durability becomes a problem. For this reason, conventionally, the reaction force ratio has generally been limited to 5 to 6 times.

"Means for Solving the Problems" In view of such circumstances, the present invention provides a reaction force transmission mechanism of the brake booster described above, in which between the reaction disk, that is, the first reaction disk and the push rod, A reaction force transmitting member slidably provided on the valve body and a second elastic reaction disk are sequentially arranged, one end surface of the second reaction disk is opposed to the push rod, and the other end surface is opposite to the push rod. One end surface of the reaction force transmission member is opposed to the valve body, and the other end surface of the reaction force transmission member is opposed to the first reaction disk, and the reaction force transmission member and the second reaction disk are brought into contact with each other. The area of contact between the push rod and the second reaction disk is set to be smaller than the area of contact between the valve plunger and the first reaction disk, and the area of contact between the valve plunger and the first reaction disk is set to be smaller than the area of contact between the reaction force transmitting member and the first reaction disk. It is set small.

"Operation" According to such a configuration, the reaction force transmitted from the push rod to the input shaft 17 can be reduced at a predetermined ratio by the two reaction disks, so the reaction force ratio can be reduced to about 2 compared to the conventional one. It becomes possible to increase the size to the extent of multiplication.

``Example'' Below, an example in which the present invention is applied to a tandem brake booster will be described. In FIG. 3: front and rear front chambers 4 and rear chambers 5
A generally cylindrical valve body 6 made of synthetic resin is slidably penetrated through the shaft portions of the rear shell 2 and center plate 3, and the front chamber 4 and the rear chamber are divided into two chambers. 5 and 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 6 between the step 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). A first reaction disk 18, a reaction force transmitting member 19, a second reaction disk 20, and a push rod 21 are arranged in this order at the left end of the cylinder 16.

The diameters of the first reaction disk 18 and the second reaction disk 20 are set to be substantially the same, and their diameters are set larger than the diameter of the valve plunger 16. The first reaction disk 18 has a right end surface center portion facing the left end surface of the valve plunger 16, and an outer peripheral portion of the right end surface of the first reaction disk 18 is a stepped end surface 6b formed in the valve body 6.
When a reaction force is transmitted to the first reaction disk 18, the reaction force can be received by the valve body 6 and the valve plunger 16.

Further, the reaction force transmitting member 19 has a large diameter portion 19a at its right end and a small diameter portion 19b at its left end.
The left end portion 19b is made to match the diameter of the reaction disk 18, and is slidably fitted into the small diameter portion 22a of the hub 22 attached to the valve body 6.

The hub 22 constitutes a part of the valve body 6, and includes a flange portion 22b extending radially outward from the right end to the left end, an annular groove 22c, and a large diameter portion 22d. With the right end surface of the flange 22b in contact with the valve body 6, the bifurcated key member 23 inserted into the valve body 6 from the outside in the radial direction is engaged with the annular groove 22c.
It is fixed in one piece. And the key member 23
is the cylindrical portion 9a of the front power piston 9
This prevents it from falling off from the valve body 6.

Further, the right end portions of the second reaction disk 20 and the push rod 21 are connected to the hub 2.
It is slidably fitted into the large diameter portion 22d of No. 2,
The center portion of the right end surface of the second reaction disk 20 is opposed to the left end surface of the reaction force transmission member 19, and the outer peripheral portion of the right end surface is connected to the stepped end surface of the hub 22.
2e, so that when a reaction force is transmitted to the second reaction disk 20, the reaction force can be received by the valve plunger 16 and the hub 22, and therefore by the valve body 6.

The diameter of the right end of the output shaft 21 is set equal to the diameter of the second reaction disk 20 so that both end surfaces face each other, and the left end of the push rod 21 is connected to the front shell 1 through the seal member 24. It is slidably protruded from the shaft portion of the cylinder and is interlocked with a piston of a master cylinder (not shown).

Next, 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 by the return spring 27, The key member 25 is brought into contact with the inner wall surface of the rear shell 2, and the valve plunger 16 and the input shaft 17 are
is advanced from its freely retracted position, and the valve element 28 of the valve mechanism 15 is brought close to the valve seat 29 formed in the valve body 6, thereby reducing the invalid stroke of the input shaft 17 at the initial stage of operation.

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 33 attached to the front shell 1. Also, this constant pressure chamber A
is a gap 34 between the bifurcated portions of the key member 23;
Slit 3 provided in the flange portion 22b of the hub 22
5. It is constantly communicated with the constant pressure chamber C through a radial passage 36 formed in the valve body 6, an annular groove 37 formed in 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 an axial passage 39 formed in the valve body 6, a gap between the valve body 28 and the valve seat 29 of the valve mechanism 15, and a radius formed in the valve body 6. It communicates with a variable pressure chamber D via a directional passage 40, and further, this variable pressure chamber D is connected to an axial passage 41 formed in the valve body 6 and the front power piston 9.
The front chamber is connected to the front chamber through a passage 43 kept airtight by a seal member 42 between the inner circumferential surface of the cylindrical portion 9a and the outer circumferential surface of the valve body 6, and a through hole 44 formed in the cylindrical portion 9a. It communicates with transformer room B on the 4th side.

The seal member 42, as shown in FIG.
In this embodiment, the annular seal member 42 is composed of an annular seal member having a required width in the axial direction.
An opening 45 of a required size is bored within the width of the opening 45, and the inside of the opening 45 is used as the passage 43, and the contour portion 42a forming the opening 45 is thick and has a circular cross section, so that a reliable seal can be achieved. That's what I do.

In the above configuration, when the brake pedal (not shown) is depressed and the input shaft 17 and the valve plunger 16 are moved forward, the valve body 28 of the valve mechanism 15 is seated on the valve seat 29, and the variable pressure chambers B and D are connected to the constant pressure chamber. A,
At the same time, the valve body 28 is separated from the valve plunger 16 to allow the atmosphere to communicate with the variable pressure chambers B and D. As a result, the atmosphere is transferred to the pressure change chamber B,
Similarly to the conventionally known tandem brake booster, each power piston 9, 10 moves forward against the elastic force of the return spring 27 due to the pressure difference between the two power pistons 9, 10. , a braking action is performed.

At this time, the reaction force transmitted from the push rod 21 to the second reaction disk 20 is transferred to the step end surface 22e of the hub 22 and the reaction force transmission member 1.
9, so that the reaction force is transmitted to the reaction force transmission member 19 in a magnitude corresponding to the area ratio between the step end surface 22e and the end surface of the reaction force transmission member 19. Become.

The reaction force transmitted to the reaction force transmission member 19 is then transmitted to the first reaction disk 18, and the reaction force transmitted to the first reaction disk 18 is transmitted to the step section 6b of the housing 6 and the valve plunger. 16, a reaction force corresponding to the area ratio between the step end surface 6b and the end surface of the valve plunger 16 is transmitted to the valve plunger 16.

In this way, the reaction force transmitted from the push rod 21 to the input shaft 17 via the valve plunger 16 can be reduced at a predetermined rate by the two reaction disks 20 and 18, compared to the conventional one. This makes it possible to increase the reaction force ratio.

``Effects of the Invention'' As described above, according to the present invention, it is possible to increase the reaction force ratio and lower the surface pressure of the reaction disk compared to the conventional method, so that the reaction force of the reaction disk and valve body can be reduced. This has the effect of improving durability.

[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 seal member 42 shown in FIG. 1. 1...Front shell, 2...Rear shell, 6
...Valve body, 6b...Step end face, 15...
Valve mechanism, 16... Valve plunger, 17... Input shaft, 18... First reaction disk, 19...
...Reaction force transmission member, 20... Second reaction disk, 21... Push rod, A, C... Constant pressure chamber, B, D... Variable pressure chamber.

Claims (1)

[Claims] 1. A valve plunger interlocked with an input shaft is slidably provided on a valve body, and a first reaction having elasticity is provided between the valve plunger and a push rod slidably provided on the valve body. A disk is interposed, one end surface of the first reaction disk faces the push rod, and the other end surface faces the valve body and the valve plunger, so that the reaction force transmitted from the push rod to the first reaction disk is transferred to the valve body. In the reaction force transmission mechanism of the brake booster, the reaction force received by the valve plunger and further transmitted to the valve plunger is transmitted to the input shaft, between the first reaction disk and the push rod, A reaction force transmitting member slidably provided on the valve body and a second elastic reaction disk are sequentially arranged, one end surface of the second reaction disk is opposed to the push rod, and the other end surface is opposite to the push rod. One end surface of the reaction force transmission member is opposed to the valve body, the other end surface of the reaction force transmission member is opposed to the first reaction disk, and further the reaction force transmission member and the second
The contact area with the reaction disk is set to be smaller than the contact area between the push rod and the second reaction disk, and the contact area between the valve plunger and the first reaction disk is set to be smaller than the contact area between the reaction force transmitting member and the first reaction disk. A reaction force transmission mechanism for a brake booster, characterized in that the area is set smaller than the contact area with the brake booster.