JPH10217942A - Reaction mechanism of brake booster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a valve side member corresponding to the relative advancing as the part compressed by a disk spring form elastic member, increase the servo ratio smoothly and continuously, prevent to give a physical disorder feeling of the brake feeling owing to a sudden variation of the servo ratio, and facilitate the assembly. SOLUTION: A valve plunger 18 to compose the reaction mechanism of a brake booster is composed of a plunger member 35 at the front side, and a valve side member 36 at the rear side, and a disk spring form elastic member 41 is provided between the plunger member 35 and the valve side member 36. In this disk spring form elastic member 41, its compression is continued from the time the compression is started after the brake booster is operated, to the time the brake booster device is made in the full loading condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake booster used for a brake of an automobile, and more particularly to an improvement of a reaction force mechanism.

[0002]

2. Description of the Related Art Conventionally, a brake booster generally includes a valve body slidably provided in a shell, a power piston provided in the valve body, a constant pressure chamber and a variable pressure chamber formed before and after the power piston. The valve body includes a valve mechanism provided in the valve body, and an input shaft that switches a flow path of the valve mechanism by moving a valve plunger that constitutes the valve mechanism forward and backward. If you increase the servo ratio of the brake booster,
In other words, if the ratio of the brake reaction force transmitted to the brake pedal is reduced, a large brake force can be obtained with a light brake pedal depression force, but on the other hand, the brake reaction force becomes too small in a range where a small brake force is required, Brake operability becomes poor. On the other hand, when the servo ratio is reduced, a relatively large brake reaction force can be obtained in a range where a small braking force is required, so that the operability of the brake is improved in that range. Since the reaction force is too large, it is difficult for elderly people and women to easily obtain a large braking force. Therefore, conventionally, a ring-shaped outer plunger is slidably provided on the outer periphery of the valve plunger, and a coil spring is provided between the outer plunger and a step portion of the valve plunger. Although held at the forward end, when the outer plunger is retracted by a certain amount or more against the coil spring due to a brake reaction force acting on the outer plunger, the outer plunger is brought into contact with the valve body. The following is known (Japanese Utility Model Publication No. 3-57568). In the brake booster having such a configuration, in the initial stage of a brake operation in which the brake reaction force is small, the brake reaction force is transmitted from the valve plunger to the brake pedal via the input shaft, and at the same time, the coil spring is moved from the outer plunger to the coil spring. Is transmitted to the brake pedal via the valve plunger and the input shaft, so that the servo ratio is reduced and the operability of the brake in that range is improved. When the brake reaction force increases and the outer plunger is retracted by a predetermined amount or more against the coil spring, and the outer plunger comes into contact with the valve body, the brake reaction force transmitted to the brake pedal is reduced by the valve plunger. Since only the brake reaction force directly acting on the brake is applied, the servo ratio is increased, and the pedaling force in the latter half of the brake operation requiring a large braking force can be reduced.

[0003]

However, in the reaction mechanism having the above-described structure, when the outer plunger is mounted on the outer periphery of the valve plunger, the conversion point of the servo ratio is set to a predetermined point. In addition, the coil spring needs to be assembled with a required set load, and as a result, assembly workability is poor. Strictly speaking, the servo ratio continuously changes from a small servo ratio to a large servo ratio during a period from the start of compression of the coil spring by the outer plunger to the contact of the outer plunger with the valve body. However, since the outer plunger substantially starts retreating and immediately comes into contact with the valve body, the servo ratio suddenly changes from a small servo ratio to a large servo ratio. As a result, at the point where the servo ratio changes abruptly, the driver feels a sense of discomfort in the brake feeling. In view of such circumstances, the present invention provides a reaction force mechanism of a brake booster which is easy to assemble and has a smooth increase in servo ratio.

[0004]

That is, the present invention provides a valve body slidably provided in a shell, a power piston provided in the valve body, a constant pressure chamber and a variable pressure chamber formed before and after the power piston. In a brake booster provided with a valve mechanism provided in the valve body and an input shaft for switching a valve mechanism by moving a valve plunger that constitutes the valve mechanism, the valve plungers are respectively connected to the valve body. A slidable front plunger member and a rear valve side member, and a disc spring-like elastic member disposed between the plunger member and the valve side member. The compression is started after the brake booster is operated, and the compression is continued until the brake booster is fully loaded. It is intended.

[0005]

According to the above construction, the disc spring-like elastic member starts to be compressed when the brake booster is actuated,
Further, since the compression is continued until the brake booster reaches the full load state, the interval between the plunger member and the valve-side member from the start of operation of the brake booster to the full load state. Will decrease. In other words, on the basis of the plunger member, the valve-side member is relatively advanced by an amount corresponding to the compression of the disc spring-like elastic member, that is, it corresponds to that the brake pedal is depressed accordingly. The servo ratio will increase continuously and smoothly. Further, the above-mentioned disc spring-like elastic member may be simply disposed between the plunger member and the valve side member, and it is not necessary to assemble them so as to obtain a predetermined set load as in the related art. Becomes easier.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiment. In FIG. 1, the inside of a sealed container composed of a front shell 1 and a rear shell 2 is divided into front and rear front chambers 4 by a center plate 3 provided at the center side thereof. And a rear room 5. A substantially cylindrical valve body 6 is slidably penetrated through the shaft portions of the rear shell 2 and the center plate 3 by annular bearings 7 and 8, respectively.
Each is kept airtight. A front power piston 11 and a rear power piston 12 housed in the front chamber 4 and the rear chamber 5, respectively, are connected to the valve body 6, and each power piston 11, 1
A constant pressure chamber A and a variable pressure chamber B are provided before and after the front diaphragm 13 and a constant pressure chamber C and a variable pressure chamber B are also provided before and after the rear diaphragm 14 by extending the front diaphragm 13 and the rear diaphragm 14 respectively on the back of the second diaphragm 2. D is formed.

The valve body 6 accommodates a valve mechanism 16 for switching a fluid circuit. The valve mechanism 16 includes an annular first valve seat 17 formed on the inner peripheral portion of the valve body 6 toward the rear side. The valve plunger 1 slidably provided in the valve body 6 on the inner side of the annular first valve seat 17.
8 and a valve element 21 seated on both valve seats 17 and 19 by the resilience of a poppet return spring 20 from the right in FIG. The space on the outer peripheral side of the annular seat portion where the first valve seat 17 and the valve element 21 are in contact with each other communicates with the constant pressure chamber A through an axial constant pressure passage 22 formed in the valve body 6.
Communicates with the constant pressure chamber C through another constant pressure passage 23.
The constant-pressure chamber A communicates with an intake manifold of the engine via a negative-pressure introduction pipe 24 provided in the front shell 1, whereby negative pressure is constantly introduced into the constant-pressure chambers A and C. The first valve seat 17 and the valve body 2
The space on the inner peripheral side of the seat portion where the first valve seat 1 contacts and the outer peripheral side of the annular seat portion on which the second valve seat 19 and the valve element 21 are seated is a radial constant pressure passage 25 formed in the valve body 6. The variable pressure chamber D communicates with the variable pressure chamber B via a variable pressure passage 26 formed in the axial direction of the valve body 6. Further, a space on the inner peripheral side of the annular seat portion where the second valve seat 19 and the valve element 21 contact each other communicates with the atmosphere through an atmosphere passage 27 formed in the valve body 2. 27, a filter 28 is provided.

The input shaft 3 is provided at the right end of the valve plunger 18.
A valve return spring 31 having an elasticity greater than that of the poppet return spring 20 is elastically mounted between the input shaft 30 and the valve body 6. , Usually valve plunger 18
The valve element 21 is seated on the second valve seat 19, and the valve element 21 is separated from the first valve seat 17 of the valve body 6. The end of the input shaft 30 is linked to a brake pedal (not shown). The valve plunger 18 is prevented from being pulled out of the valve body 6 by the key member 32. The key member 32 can move forward and backward in the axial direction of the valve body 6, and when the brake booster is not operated, the key member 32 abuts on the inner surface of the rear shell 2 to hold the valve plunger 18 at a forward position with respect to the valve body 6. The loss stroke of the input shaft 30 during operation of the brake booster can be reduced.

The valve plunger 18 comprises a front side plunger member 35 and a rear side valve side member 36, and a reaction disk 37 is disposed on the left side of the plunger member 35. This reaction disk 3
7 is an output shaft 3 slidably fitted on the outer peripheral surface of the holder 38.
9, a predetermined gap is formed between the reaction disk 37 and the plunger member 35 in the non-operating state shown. The distal end of the output shaft 39 projects from the shaft of the front shell 1 to the outside while maintaining airtightness, and is linked to a piston of a master cylinder (not shown). The valve body 6 and the power pistons 11 and 12 are connected to the front shell 1.
Normally, the return spring 40 mounted between the valve body 6 and the valve body 6 is held at a non-operating position in the drawing.

Next, a plunger member 35 constituting the valve plunger 18 is slidably fitted in a holder 38 which is fixed to the front end of the valve body 6 while maintaining airtightness. The valve side member 36 is slidably fitted in the through hole 6A of the valve body 6 on the rear side of the plunger member 35. And plunger member 3
5, a fitting recess 35A is formed at the rear end, and a fitting projection 36A protruding from the front end surface of the valve member 36 is slidably fitted in the fitting recess 35A. The fitting projection 36A penetrates the ring-shaped disc spring-shaped elastic member 41 and is fitted in the fitting recess 35A. The disc spring-shaped elastic member 41 is a rear end of the plunger member 35. Contact portion 35B formed in the portion and the step 3 of the valve member 36
6B. This disc spring-like elastic member 41
Holds the plunger member 35 and the valve-side member 36 separated in a non-operating state of the brake booster.
There is no compression by the plunger member 35 and the valve side member 36. On the other hand, the disc spring-like elastic member 41
When the brake booster is actuated, it is compressed by the plunger member 35 and the valve-side member 36. In this embodiment, the spring constant is such that the brake booster is fully loaded. At this time, the annular contact portion 35B and the step portion 36
B and are sized so that they are completely compressed and work together.

In the above configuration, when the brake pedal is depressed to advance the input shaft 30 and the valve plunger 18, the plunger member 35 and the valve side member 36 of the valve plunger 18 are interposed via the disc spring-like elastic member 41. And move forward together. When the valve-side member 36 of the valve plunger 18 is advanced, the flow path of the valve mechanism 16 is switched and air is introduced into the variable pressure chambers B and D in the same manner as in a conventionally known brake booster. Due to the pressure difference between the chambers A and C and the transformation chambers B and D, both power pistons 11 and 12 and the valve body 6
Is advanced, whereby the output shaft 39 is advanced, so that a brake hydraulic pressure is generated in the master cylinder. The brake reaction force due to the brake fluid pressure is output shaft 39
Is transmitted to the reaction disk 37 via the holder 38 and the holder 38 and the plunger member 3 from the reaction disk 37.
The brake reaction force of the holder 38 is received by the valve body 6. On the other hand, the brake reaction force of the plunger member 35 is caused by the disc spring-like elastic member 41 and the valve side member 36.
Then, the power is transmitted to the brake pedal via the input shaft 30.

When the brake reaction force increases, the disc spring-like elastic member 41 is gradually compressed by the plunger member 35 and the valve side member 36, and accordingly, the gap between the plunger member 35 and the valve side member 36 is increased. Are gradually reduced. Then, the valve-side member 36 on the input shaft 30 side is stepped by the amount corresponding to the compression of the disc spring-like elastic member 41. Therefore, the servo ratio of the brake booster is such that the disc spring-like elastic member 41 is compressed. Gradually increase (see curve A in FIG. 2). Thereafter, when the brake booster is fully loaded (point B in FIG. 2), the disc spring-like elastic member 41 is substantially completely compressed at the same time, and the plunger member 35 and the valve-side member are substantially compressed. 36 are integrally connected via a disc spring-like elastic member 41. Thereafter, since the plunger member 35 and the valve-side member 36 are integrally advanced via the disc spring-like elastic member 41, the output of the brake booster increases as the brake pedal force increases:
It increases at a rate of 1 (straight line C in FIG. 2).

As is apparent from the above configuration, the disc spring-like elastic member 41 may be simply disposed between the plunger member 35 and the valve side member 36, and a predetermined set load can be obtained as in the conventional case. It is not necessary to assemble them so that the assembly is very easy.

[0014]

As described above, according to the present invention, the servo ratio can be continuously and smoothly increased, so that the uncomfortable feeling of the brake due to the sudden change of the servo ratio as in the prior art is eliminated. No effect is obtained, and the effect of extremely easy assembly can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram of the embodiment.

[Explanation of symbols]

 6 ... Valve body 16 ... Valve mechanism 18 ... Valve plunger 30 ... Input shaft 35 ... Plunger member 35A ... Mating recess 36 ... Valve member 36A ... Mating protrusion 37 ... Reaction disk 39 ... Output shaft 41 ... Belleville spring-like elastic member

Claims (3)

[Claims] 1. A valve body slidably provided in a shell, a power piston provided on the valve body, a constant pressure chamber and a variable pressure chamber formed before and after the power piston.
In a brake booster including a valve mechanism provided in the valve body and an input shaft for moving a valve plunger that constitutes the valve mechanism forward and backward to switch a flow path of the valve mechanism, the valve plunger is connected to the valve body. A slidable front plunger member and a rear valve side member, and a disc spring-like elastic member disposed between the plunger member and the valve side member. (2) A reaction mechanism of a brake booster, wherein compression is started after the brake booster is operated, and the compression is continued until the brake booster reaches a full load state. 2. A fitting recess is formed in one of the plunger member and the valve-side member, and a fitting protrusion slidably fitted in the fitting recess is formed in the other of the plunger member and the valve-side member. 2. The brake booster device according to claim 1, wherein the spring-like elastic member is formed in a ring shape, and the fitting projection slidably penetrates the disc spring-like elastic member. Power mechanism. 3. The disc spring-like elastic member is completely compressed by the plunger member and the valve-side member substantially simultaneously when the brake booster is fully loaded. The reaction force mechanism of the brake booster according to claim 1 or 2.