JPH11278242A - Booster - Google Patents

Abstract

(57) An annular groove (5a) is formed at a position near an outer peripheral portion (5A) of a power piston (5). On the other hand, an annular projection 6a is formed on the diaphragm 6, and the annular projection 6a is engaged with the annular groove 5a. Even if the diaphragm 6 is pulled radially outward during the operation of the brake booster 1, the above-described tensile force does not act on the thin portion of the diaphragm 6 located radially inward of the annular projection 6a. . [Effect] It is possible to prevent the oil resistance of the thin portion of the diaphragm 6 at the position where the diaphragm overlaps with the power piston 5 from decreasing. Therefore, the life of the diaphragm 6 can be extended as compared with the related art.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a booster, and more particularly, to an improvement in a power piston and a diaphragm provided in a booster.

[0002]

2. Description of the Related Art Conventionally, as a booster, a substantially cylindrical valve body slidably provided in a shell, a power piston provided in the valve body, and a shell extended from the back of the power piston to form a shell It is well known that a diaphragm is provided which partitions the inside into a constant pressure chamber and a variable pressure chamber.

[0003]

By the way, conventionally, in order to save the material used for the diaphragm, there has been proposed a diaphragm in which a portion overlapping with a power piston is made thin. However, when the portion that overlaps with the power piston is made thinner, the following disadvantages occur.
That is, when the booster is activated, the entire diaphragm is pulled radially outward, so that the thin portion of the diaphragm that overlaps with the power piston is also pulled radially outward. When the thin portion of the diaphragm is pulled outward in the radial direction as described above, the oil resistance of the portion is reduced, and the output of the booster may be reduced at high temperatures. More specifically, at the time of operation of the booster at a high temperature, the outer peripheral portion of the diaphragm located radially outward from the outer peripheral portion of the power piston tends to expand, and the effective effective diameter of the diaphragm decreases. As a result, the power piston is dragged forward by the expansion part, and the output of the booster is reduced.

[0004]

In view of the above circumstances, the present invention provides a substantially cylindrical valve body slidably provided in a shell, a power piston provided in the valve body, and a power piston provided in the valve body. In a booster having a diaphragm that is stretched on the back surface and partitions the inside of the shell into a constant-pressure chamber and a variable-pressure chamber, a concave portion is formed on the outer peripheral side of the power piston, and the diaphragm is formed on the power piston.
The power piston has a thick portion that engages with the concave portion.

[0005]

According to this structure, since the concave portion of the power piston and the thick portion of the diaphragm are engaged with each other, a thin portion that overlaps with the power piston by the outer peripheral portion of the diaphragm when the booster is operated is formed. It is prevented from being pulled radially outward. Thus, it is possible to prevent the oil resistance of the thin portion of the diaphragm that overlaps with the power piston from being reduced. Therefore, the life of the diaphragm can be extended as compared with the related art. Further, when the booster is operated at a high temperature, the amount of expansion of the diaphragm located radially outward from the outer peripheral portion of the power piston can be reduced. Therefore, it is possible to prevent the output of the booster from decreasing due to the expansion of the diaphragm when the booster operates at a high temperature.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiment. In FIG. 1, a substantially cylindrical valve body 3 is slidably provided in a shell 2 of a brake booster 1. The outer peripheral portion of the shell 2 penetrates the opening 2 a on the rear side of the shell 2 and projects outside the shell 2. Outer peripheral portion on the rear side of valve body 3 and shell 2
The airtightness is maintained between the opening 2a and the annular seal member 4. An outer peripheral portion of the valve body 3 is connected to an inner peripheral portion of the substantially dish-shaped power piston 5, and a diaphragm 6 is provided on a rear surface (rear end surface) of the power piston 5.
Is stretched out. The shell 2 is formed by the diaphragm 6.
The interior is partitioned into a constant pressure chamber A on the front side and a variable pressure chamber B on the rear side. A conventionally known valve mechanism 7 for switching the communication state between the constant pressure chamber A and the variable pressure chamber B is provided in the valve body 3. The valve mechanism 7 includes an annular vacuum valve seat 8 formed on the inner periphery of the valve body 3, a valve plunger 11 slidably fitted to the valve body 3, and a rear end of the valve plunger 11. An annular atmospheric valve seat 12 formed in
Further, a valve element 14 is provided on both valve seats 8 and 12 from the rear side by a spring 13.

A vacuum valve 15 is constituted by the vacuum valve seat 8 and a seat portion of a valve body 14 which comes into contact with and separates from the vacuum valve seat 8. Through the pressure chamber A. The inside of the constant-pressure chamber A is in communication with a negative pressure source via a negative-pressure introducing pipe 17, whereby a constant negative pressure is introduced into the constant-pressure chamber A. The atmosphere valve 18 is constituted by the atmosphere valve seat 12 and the seat portion of the valve element 14 which comes in contact with and separates from the atmosphere valve seat 12. The space between the vacuum valve 15 and the atmosphere valve 18 is a valve body 3
And is communicated with the variable pressure chamber B via a radial variable pressure passage 21 formed in the second direction. Further, a space on the inner peripheral side of the atmosphere valve 18 communicates with the atmosphere via an atmosphere passage 22 formed in the valve body 3 and a filter 23 provided therein. A distal end of an input shaft 24 is connected to the rear end of the valve plunger 11. A spring 25 having a greater elastic force than the spring 13 is elastically mounted over the input shaft 24 and the valve body 3. doing. Thus, when the brake booster 1 shown in FIG. 1 is not operating, the atmospheric valve 18 is closed and the vacuum valve 15 is opened. The end of the input shaft 24 is linked to a brake pedal (not shown). In this non-operating state, the constant pressure chamber A and the variable pressure chamber B communicate with each other, and a negative pressure is introduced into each of the chambers A and B.

A conventionally known key member 26 is inserted through the valve body 3 from the outside in the radial direction, and the key member 26 is engaged with the valve plunger 11. This prevents the valve plunger 11 from dropping from the valve body 3 to the rear side. Output shaft 2 in constant pressure chamber A
7, a disk-shaped reaction disk 28 is accommodated in a recess 27a formed at the base of the output shaft 27. Then, the concave portion 27 of the output shaft 27 in that state
a is slidably fitted to the annular projection 3a of the valve body 3, and the reaction disk 28 is attached to the annular projection 3a.
Abutting against the end face. As a result, the reaction disc 28 and the front end face of the valve plunger 11 located on the rear side adjacent to the reaction disc 28 face each other at a close position.
A retainer 31 is provided on the outer periphery of the output shaft 27 from the front side.
The retainer 31 is in contact with the step end surface of the valve body 3. A return spring 32 is elastically mounted on the retainer 31 and the wall surface on the front side of the shell 1 so that the valve body 6 and the like are normally held at a non-operating position in the drawing. The front end of the output shaft 27 is linked to a piston of a master cylinder (not shown). The above configuration and the operation based on it are the same as those of the conventionally known brake booster.

In this embodiment, the power piston 5
By improving the diaphragm 6, the service life of the diaphragm 6 is made longer than in the prior art. That is, in the power piston 5 of the present embodiment, an annular groove 5a as a concave portion that is continuous in the circumferential direction is formed on the radially inner side near the outer peripheral portion 5A. On the other hand, the diaphragm 6 is formed so as to be thin as a whole in a region overlapping with the back surface of the power piston 5, and a portion of the thinned portion facing the annular groove 5 a of the power piston 5 bulges toward the front side. The annular projection 6a is a thick portion to be formed. Therefore, the portion of the diaphragm 5 that overlaps with the back surface of the power piston 5 is thick only in the portion of the inner peripheral bead portion 6b and the portion of the annular protrusion 6a. The annular projection 6a of the diaphragm 6 is engaged with the annular groove 5a of the power piston 5.

In this embodiment, since the power piston 5 and the diaphragm 6 are configured as described above, when the brake booster 1 is actuated, the diaphragm is located on the outer peripheral side of the outer peripheral portion 5A of the power piston 5. Even if the thin portion of the diaphragm 6, which is the overlapping portion with the power piston 5 on the inner side thereof, is pulled radially outward by the elastically deforming portion 6A, the elastically deforming portion 6A radially inward from the annular projection 6a. Such a thin portion of the diaphragm 6 does not receive such a radially pulling force. As a result, the diaphragm 6 at the position where it overlaps with the power piston 5
It is possible to prevent the oil resistance of the thin portion from being reduced. Therefore, the life of the diaphragm 6 can be extended as compared with the related art. Moreover, when the brake booster 1 is operated at a high temperature, the annular projection 6a is engaged with the annular groove 5a, so that the thin portion of the diaphragm 6 outside the annular projection 6a is radially outward. It is hard to be pulled by. Thereby, the amount by which the elastic deformation 6A of the diaphragm 6 expands can be reduced. As described above, since the elastic deformation 6A can be prevented from being excessively expanded, it is possible to suppress the resistance from being applied to the advancement of the power piston by the expanded portion. Therefore,
When the brake booster 1 is operated under high temperature,
It is possible to prevent the output of the brake booster 1 from decreasing due to the expansion of the elastic deformation 6A of the diaphragm 6.

In the above embodiment, the case where the present invention is applied to a single type brake booster has been described.
The present invention is also applicable to a tandem brake booster or a triple type brake booster including a plurality of pairs of constant pressure chambers and variable pressure chambers. In the above-described embodiment, the case where the present invention is applied to the brake booster has been described. However, it is needless to say that the present invention can be applied to the clutch booster.

[0012]

As described above, according to the present invention, there is obtained an effect that the life of the diaphragm can be extended as compared with the conventional art. Further, when the brake booster is operated at a high temperature, it is possible to prevent the output of the brake booster from being reduced due to the expanded portion of the diaphragm.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Brake booster 2 Shell 3 Valve body 5 Power piston 5a Annular groove (recess) 6 Diaphragm 6A Annular protrusion (thick part) A Constant pressure chamber B Transformation chamber

Claims (2)

[Claims] 1. A substantially cylindrical valve body slidably provided in a shell, a power piston provided in the valve body, and a constant-pressure chamber which is stretched on a back surface of the power piston to form a constant-pressure chamber and a variable-pressure chamber. A booster provided with a diaphragm partitioned into a chamber and a diaphragm, wherein a concave portion is formed on an outer peripheral side of the power piston, and a thick portion that engages with the concave portion of the power piston is formed on the diaphragm. Features booster. 2. The power piston according to claim 1, wherein the concave portion of the power piston comprises an annular groove continuous in the circumferential direction, and the thick portion of the diaphragm comprises an annular protrusion continuous in the circumferential direction. Booster.