JPH09323640A - Pneumatic pressure booster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent loss of grease a friction contact interface between a reaction disk and a valve body. SOLUTION: The reaction disk 25 is made of an elastic member, which is not impregnated with grease and aging effect of frictional force between the reaction disk and the valve body is suppressed. The constitution of a booster is such that a valve mechanism 14 comprising a plunger 15 in the valve body 8 supported by a power piston 5 is provided, atmospheric air is introduced into an actuation pressure room 7 while interlocking the plunger 15 with an input shaft 20, thereby the power piston is pushed forward under differential pressure with a negative pressure room 6, boosted output power is transmitted to an output shaft 26 in an operationally connected relation with the valve body 8 through the reaction disk 25 and a part of a reaction force is transmitted to the input shaft 20 through the reaction disk 25 and the plunger 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic booster used in a vehicle brake system.

[0002]

2. Description of the Related Art As a pneumatic booster, a shell main body is divided into a constant pressure chamber and a working pressure chamber by a power piston having a diaphragm, and the shell main body is inserted into the power piston and extended to the rear thereof. A valve mechanism including a plunger that interlocks with the input shaft is supported in the valve body, and the base end of the output shaft is operatively connected to the front end of the valve body via a reaction disc, A differential pressure is generated between the constant pressure chamber and the working pressure chamber by the operation of the valve mechanism, the thrust of the power piston is transmitted to the output shaft, and a part of the reaction force from the output shaft is used as the reaction disc. There is one that is transmitted to the input shaft via the plunger.

In such a pneumatic booster, the input / output characteristics generally increase as shown in FIG. 3 after a so-called jump-in process in which a predetermined output J is generated with a constant input. In accordance with the above, the output is increased at a predetermined boost ratio. Therefore, if a high deceleration is desired, the jump-in output J may be set high, and if a soft braking is desired, the jump-in output J may be set low.

By the way, the above jump-in output is
This is caused by the existence of a gap between the reaction disc and the plunger before the start of boosting action, and the larger this gap, the larger the jump-in output J. However, at the same time when the boosting action starts, the reaction disc elastically deforms due to the output reaction force, and a part of the reaction disc enters into the sliding hole of the plunger and acts to fill the gap. In addition to the size of the gap, the physical properties (particularly hardness) of the reaction disc and the frictional force generated on the frictional contact surface between the reaction disc and the valve body have a great influence.

[0005]

Therefore, in the past, consideration was given to applying grease to the reaction disc to improve its lubricity and to eliminate the influence of frictional force as much as possible to suppress the change in jump-in output. . However, when grease is applied in this way, while the reaction disk is repeatedly deformed and restored by the boosting action, the grease is extruded from the friction contact surface with the valve body and becomes a so-called state of running out of grease, and the friction force is increased. There has been a problem that the jump-in output, that is, the input / output characteristic changes with time and changes with time.

The present invention has been made in view of the above-mentioned conventional problems, and its object is to prevent the grease from running off from the frictional contact surface between the reaction disk and the valve body, and to improve the input / output characteristics. It is to suppress the change over time.

[0007]

According to the present invention, in order to solve the above problems, a reaction disk for transmitting a part of an output reaction force to an input shaft is formed from an elastic member impregnated with grease. Characterize. In this case, nitrile rubber can be selected as the elastic member, and silicon grease can be selected as the grease impregnated therein. In the pneumatic booster configured as described above,
The grease impregnated in the reaction disc is supplied to the friction contact surface between the reaction disc and the valve body for a long period of time, and the temporal change of the frictional force generated at the friction contact surface between the reaction disc and the valve body is suppressed.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIGS. 1 and 2, reference numeral 1 is a shell body composed of a front shell 2 and a rear shell 3, and a power piston 5 having a diaphragm 4 inside the shell body 1.
Is divided into a constant pressure chamber 6 and a working pressure chamber 7. A valve body 8 arranged on the shaft center of the shell body 1 is fitted and supported on the power piston 5. Valve body 8
Has a disc-shaped large-diameter portion 8a and a cylindrical small-diameter portion 8b connected to each other. The small-diameter portion 8b is inserted in the rear shell 3 in an airtight and slidable manner and extends rearwardly thereof. Has been done. The valve body 8 is provided with a constant pressure passage 9 which communicates the constant pressure chamber 6 with the inside of the small diameter portion 8b, and an atmosphere passage 10 which communicates the inside of the small diameter portion 8b with the working pressure chamber 7. For example, an engine negative pressure is introduced into the constant pressure chamber 6 through an introduction pipe 11 connected to the front portion of the front shell 2, while the small diameter portion 8b of the valve body 8 has a rear end opening side. A silencer 12 and a filter 13 are arranged.

Inside the valve body 8, a valve mechanism 14 for selectively opening the constant pressure passage 9 and the atmosphere passage 10 with respect to the working pressure chamber 7 is arranged. The valve mechanism 14 includes a plunger 15 slidably fitted in a shaft hole (plunger sliding hole) 8c provided on the axis of the large diameter portion 8a of the valve body 8 and an inner surface of the small diameter portion 8b of the valve body 8. An elastically deformable valve body 17 whose base end portion is fixed using a pressing member 16, and an outer edge portion of the front end of the valve body 17 and an inner periphery of the valve body 8 are formed to include an opening edge of a constant pressure passage 9. Negative pressure valve 18 composed of a valve seat portion, an inner edge portion of the front end of the valve body 17 and the plunger 15
An atmosphere valve 19 is provided which is composed of a valve seat portion formed at the rear end of the atmosphere valve 19. An input shaft 20 interlocking with a brake pedal (not shown) is operatively connected to the rear end of the plunger 15, and the valve body 17 is constantly operated by a valve spring 21 having one end engaged with the input shaft 20. Is biased in a direction to close the negative pressure valve 18 and the atmospheric valve 19. The plunger 15 is connected to the valve body 8 by a stop key 22 which is inserted in the valve body 8 in the radial direction using the atmosphere passage 10.
The relative movement range with is restricted. Also, the input shaft 20
Is normally urged in the returning direction (on the side of the brake pedal) by a spring 23 having one end engaged with the pressing member 16.

On the other hand, at the front end portion of the large diameter portion 8a of the valve body 8, the shaft center is the same as that of the shaft hole 14 and the shaft hole 14
A larger-diameter concave hole 24 is formed, and the reaction disk 25 and the large-diameter base end portion 26a of the output shaft 26 are fitted into the concave hole 24. Large-diameter portion 2 of the proximal end of the output shaft 26
The 6a is restricted from coming off from the recessed hole 24 by a spring receiver 28 on which a return spring 28 interposed between the front shell 2 and the valve body 8 is seated. The reaction disc 25 receives an output reaction force when a boosting force is applied, which will be described later, and abuts on the bottom of the recessed hole 24. In this state, a gap 29 of a predetermined size X between the reaction disc 25 and the plunger 15 (see FIG. 2) is formed. In addition,
The front end portion of the output shaft 26 is hermetically inserted through the front shell 2 and extends to the front thereof, and is operatively connected to, for example, a master cylinder.

Here, the reaction disk 25
Is formed of an elastic member impregnated with grease. The elastic member and the grease to be impregnated into the elastic member are selected in consideration of oil resistance to gasoline and light oil. As an example, nitrile rubber is selected as the elastic member and silicon grease is selected as the grease. . In this case, the nitrile rubber may be directly impregnated with silicon grease by mixing or kneading.

The above-described pneumatic booster is mounted on the vehicle body by using a plurality of stud bolts 30 (FIG. 1) erected on the rear surface of the rear shell 3, and a brake (not shown) is attached to the input shaft 20 in this mounted state. The pedal is connected. Then, when the brake pedal is depressed in this mounted state and the pedaling force (input) becomes larger than the set load of the spring 23,
When pushed by the input shaft 20, the plunger 15 moves to the position shown in FIGS.
To the left, the atmospheric valve 19 opens, and the silencer 1
Atmosphere flows into the valve body 8 through the filter 2 and the filter 13, and this atmosphere passes through the atmosphere passage 10 and the working pressure chamber 7
Will be introduced. As a result, a differential pressure is generated between the constant pressure chamber 6 into which the negative pressure is introduced and the working pressure chamber 7, and the power piston 5 advances and the boosted output is output via the valve body 8 to the output shaft 26. Is transmitted to the booster. And
A part of the reaction force at this time is transmitted to the input shaft 20 via the reaction disc 25 and the plunger 15.

The input / output characteristics during the above-mentioned boosting action are shown in FIG.
Is the same as that shown in the above, and the predetermined jump-in output J
After the occurrence of, the output increases at a predetermined boost ratio according to the increase of the input. Then, at the same time when the boosting action is started, the reaction disc 25 is filled by the output reaction force with the plunger sliding hole (shaft hole) 8 so as to fill the gap 29 with the plunger 15.
It bulges and deforms in c. At this time, reaction disk 2
The grease that had been impregnated in No. 5 is not the same as the concave hole 2 in the valve body 8.
4 bottom surface and inner surface of the plunger sliding hole 8c (friction contact surface)
To ensure sufficient lubricity and even if the surface roughness of the reaction disk 25 and the valve body 8 varies, the frictional force generated on the frictional contact surface becomes negligibly small. As a result, if the size X of the gap 29 and the physical properties of the reaction disk 25 are constant before the boosting action is started, the jump-in output J is constant and the input / output characteristics are also constant. Particularly in the present invention, since the reaction disc 25 is impregnated with grease, the grease is supplied to the friction contact surface between the reaction disc 25 and the valve body 8 for a long period of time, and the frictional force generated on the friction contact surface between the reaction disc 25 and the valve body 8 elapses with time. Change is suppressed, and the input / output characteristics are stable over the long term.

After that, when the pedal force from the brake pedal disappears, the reaction disc 25 pushes the plunger 15 back, and the atmospheric valve 19 closes, while the negative pressure valve 18 opens and a negative pressure is applied to the working pressure chamber 7. The introduced differential pressure is eliminated, and as a result, the spring force of the return spring 27 causes the valve body 8 to return to its original state.

[0016]

According to the pneumatic booster of the present invention,
Since the grease impregnated in the reaction disc is supplied to the friction contact surface between the reaction disc and the valve body for a long period of time, the friction contact surface does not run out of grease and the change in friction force over time is suppressed. The input / output characteristics are stable over the long term.

[Brief description of drawings]

FIG. 1 is a sectional view showing the overall structure of a pneumatic booster according to the present invention.

FIG. 2 is a cross-sectional view showing the main structure of the present pneumatic booster.

FIG. 3 is a cross-sectional view showing the input / output characteristics of the present pneumatic booster.

[Explanation of symbols]

 1 Shell Body 4 Diaphragm 5 Power Piston 6 Constant Pressure Chamber 7 Working Pressure Chamber 8 Valve Body 10 Valve Mechanism 15 Plunger 20 Input Shaft 25 Reaction Disc 26 Output Shaft

Claims (2)

[Claims] 1. A shell body is partitioned into a constant pressure chamber and a working pressure chamber by a power piston provided with a diaphragm, and a valve body extending through the shell body through the shell body is supported by the power piston. A valve mechanism including a plunger that interlocks with an input shaft is provided in the valve body, and the base end of the output shaft is operatively connected to the front end of the valve body via a reaction disc, and the constant pressure chamber is operated by the operation of the valve mechanism. And a differential pressure between the working pressure chamber,
A pneumatic booster configured to transmit a thrust force of a power piston to the output shaft, and transmit a part of a reaction force from the output shaft to the input shaft via the reaction disc and the plunger, A pneumatic booster, characterized in that the reaction disk is formed from an elastic member impregnated with grease. 2. The pneumatic booster according to claim 1, wherein the elastic member is nitrile rubber, and the grease impregnated in the elastic member is silicon grease.