JP3702395B2 - Pneumatic booster - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic booster used in a vehicle brake system.
[0002]
[Prior art]
Conventionally, a pneumatic booster is generally a valve in which a shell main body is partitioned into a constant pressure chamber and a variable pressure chamber by a power piston provided with a diaphragm, and the shell main body is inserted through the power piston to extend backward. A valve mechanism including a plunger that supports the body and interlocks with the input shaft is disposed in the valve body, and by operating the valve mechanism, a differential pressure is generated between the constant pressure chamber and the variable pressure chamber. The generated thrust is transmitted to the output shaft through a reaction disk mounted on the valve body, and the reaction force at that time is transmitted to the plunger and the input shaft through the reaction disk.
[0003]
[Problems to be solved by the invention]
By the way, in driving a car, sudden braking is often required. In such a case, a high output can be obtained with a small pedaling force (input), that is, a large boost ratio can be obtained. desired. However, in the conventional booster described above, the ratio of the contact area between the output shaft and the plunger (input shaft) with respect to the reaction disk is the same as the boost ratio, so the boost ratio is constant regardless of the input speed. It was impossible to obtain high output only when sudden braking was required.
If the ratio of the contact area between the output shaft and the plunger with respect to the reaction disk is set so that a large boost ratio can be obtained, sudden braking will occur even during normal braking, and deterioration of the pedal feeling is inevitable. It becomes like this.
[0004]
An object of the present invention is to provide a pneumatic booster that can obtain a large boost ratio when necessary without deteriorating pedal feeling.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a pneumatic booster that transmits an output and a reaction force via a reaction disk, and deforms a part of the reaction disk when a force of a moderate speed is applied, It is characterized in that it is replaced with a cushion material that is difficult to deform when a force of high speed is applied.
[0006]
In the pneumatic booster configured in this way, during normal braking, the input speed is low, so the cushioning material is deformed, and the contact area of the reaction disk with respect to the output shaft is reduced by the area occupied by the cushioning material. It becomes power ratio. On the other hand, when the input speed increases due to sudden braking, the cushion material is not deformed, so the total contact area of the reaction disk with respect to the output shaft contributes to output transmission, and a large boost ratio is obtained.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0008]
1 to 3 show a pneumatic booster as a first embodiment of the present invention. This pneumatic booster includes a shell body 1 composed of a front shell 2 and a rear shell 3 as shown in FIG. 3, and a constant pressure chamber 6 is provided inside the shell body 1 by a power piston 5 having a diaphragm 4. A hollow valve body 8 disposed on the axis of the shell body 1 is fitted and supported on the power pin 5. In the valve body 8, the front end side supported by the power piston 5 is configured as a large diameter portion 8a, and the rear end side following the large diameter portion 8a is configured as a small diameter portion 8b. The small diameter portion 8b is configured as the rear shell 3. Is slidably inserted and extended backward. The valve body 8 is provided with a constant pressure passage (negative pressure passage) 9 that connects the inside of the constant pressure chamber 6 to the inside of the small diameter portion 8b of the valve body 8, and an air passage that connects the inside of the small diameter portion 8b to the inside of the variable pressure chamber 7 ( (Air passage) 10 is provided. For example, 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 a silencer 12 is provided on the opening side of the small diameter portion 8 b of the valve body 8. And a filter 13 are provided.
[0009]
In the valve body 8, a valve mechanism 14 for selectively opening the negative pressure passage 9 and the atmospheric passage 10 with respect to the variable pressure chamber 7 is incorporated. As shown well in FIG. 1, the valve mechanism 14 includes a plunger 15 slidably fitted into the valve body 8 and an elastic deformation whose base end is fixed to the inner surface of the valve body 8 using a pressing member 16. A possible valve body (poppet valve) 17, a first valve seat 18 formed at the open end of the negative pressure passage 9 and the outer edge of the front end of the valve body 17 being separated, and formed at the rear end of the plunger 15. And a second valve seat 19 on which an inner edge portion of the front end of the valve body 17 is seated. An input shaft 20 that interlocks with a brake pedal (not shown) is operatively connected to the rear end of the plunger 15, and the valve body 17 is always fixed by a valve spring 21 that has one end locked to the input shaft 20. Is biased in the direction of seating on the first and second valve seats 18,19. Note that the relative movement range of the plunger 15 relative to the valve body 8 is restricted by a stop key 22 inserted in the radial direction with respect to the valve body 8. Further, an input shaft return spring 23 is provided between the input shaft 20 and the presser member 16 that fixes the valve body 17 to normally bias the input shaft 20 in the backward direction (brake pedal side). .
[0010]
On the other hand, a recess 8c is formed at the center of the front end of the valve body 8, and a reaction disk 24, which will be described in detail later, is accommodated in the recess 8c. In addition, in the recess 8c, a base end large diameter portion 25a of the output shaft 25 that is slidably inserted through the front shell 2 is accommodated. The base end large diameter portion 25a is formed on the entire surface of the reaction disk 24. Touching. The reaction disc 24 has a central portion that faces the plunger 15 and forms a slight gap 26 between the reaction disc 24 and the plunger 15 in the illustrated non-operating state. The constant pressure chamber 6 is provided with a return spring 27 for returning the power piston 5 from the operating position to the non-operating position via the valve body 8. A retainer 28 for restricting the base end large diameter portion 25a of the output shaft 25 from coming out of the recess 8c is pressed and fixed to the front end of the valve body 8 by the return spring 27.
[0011]
The pneumatic booster described above is assembled to the vehicle body using a plurality of stud bolts 29 planted on the rear surface of the rear shell 3, while the pneumatic booster is planted on the front shell 2. A master cylinder (not shown) is assembled using a plurality of stud bolts 30. In this assembled state, a brake pedal (not shown) is operatively connected to the rear end of the input shaft 20, A piston in the master cylinder is operatively connected to the tip of the output shaft 25.
[0012]
When the brake pedal is depressed in the above assembled state, the input shaft 20 moves forward, the plunger 15 moves to the left in the figure, the second valve seat 19 opens, and the valve body through the silencer 12 and the filter 13 is opened. Atmosphere flows into the air 8, and this air is introduced into the variable pressure chamber 7 through the air passage 10. As a result, a differential pressure is generated between the constant pressure chamber 6 where the negative pressure is introduced and the variable pressure chamber 7 where the atmosphere is introduced, and the power piston 5 is propelled and the thrust is applied to the valve body 8 and the reaction disk 24. To the output shaft 25, and a predetermined boosting action is performed. At the initial stage of this boosting action, the presence of the gap 26 between the plunger 15 and the reaction disk 24 causes a so-called jump-in phenomenon in which the output increases rapidly regardless of the input, and the gap 26 disappears. After that, the output increases as the input increases, and the reaction force is transmitted from the reaction disk 24 to the input shaft 20 via the plunger 15.
When the pedal force is lost from the brake pedal, the input shaft 20 is moved (retracted) in the right direction by the restoring force of the spring 23, the plunger 15 is also retracted, and the second valve seat 19 is closed, while the first The valve seat 18 is opened, and negative pressure is introduced into the variable pressure chamber 7 through the negative pressure passage 9 to eliminate the above-described differential pressure. Thereafter, the valve body 8 is moved in the return direction by the spring force of the return spring 27, the stop key 22 abuts against the inner surface of the rear shell 3, the backward movement of the valve body 8 is stopped, and the power piston 5 returns to the original position. .
[0014]
Here, the reaction disk 24 is composed of a disk-shaped first disk member 31 disposed in the center and a ring-shaped second disk member 32 fitted on the first disk member 31. Yes. The first disk member 31 is made of rubber in the same manner as conventionally used, while the second disk member 32 is deformed when a moderate speed force is applied and a high speed force is applied. It is made from a cushion material that is difficult to deform. As this type of cushioning material, for example, there is a reverse foam (trade name) manufactured by Shin-Etsu Chemical Co., Ltd., which has recently been used as a cushion for shoes.
[0015]
In such a pneumatic booster using the reaction disk 24, during normal braking, the forward speed (input speed) of the input shaft 20 is small, so the second disk member 32 made of the cushion material is deformed. Then, the output is transmitted to the output shaft 25 only through the first disk member 31. In this case, as shown in FIG. 2, when the contact area of the plunger 15 with respect to the reaction disk 24 is A and the surface area of the first disk member 31 is B, the boost ratio α at that time is B / A, which is a very large boost. Pedal feeling is good without a ratio. On the other hand, when the input speed increases due to sudden braking, the second disk member 32 made of the cushion material is not deformed, and therefore the reaction disk 24 including the first and second disk members 31 and 32 is not deformed. The output is transmitted to the output shaft 25 through the whole. In this case, if the total surface area of the reaction disk 24 is C (C> B) as shown in FIG. 2, the boost ratio β at that time is C / A, which is larger than the boost ratio α described above. Sudden braking is achieved. In addition, the arrangement form of the second disk member (cushion material) 32 in the reaction disk 24 is not limited to the ring shape, and can be scattered in a spotted pattern, for example.
[0016]
The first embodiment is applied to a general-purpose negative pressure booster that selectively introduces air and negative pressure into the variable pressure chamber 7, but the present invention is applied to the variable pressure chamber 7. On the other hand, the present invention can also be applied to a pressurized pneumatic booster that selectively introduces compressed air and negative pressure. FIG. 4 shows a second embodiment of the present invention applied to such a pressure type pneumatic booster. Here, the same parts as those shown in FIGS. 1 to 3 are denoted by the same reference numerals, and the description thereof is omitted. In the second embodiment, a pressure accumulating chamber 34 is formed at the rear portion of the rear shell 3 using a sub-rear shell 33, and compressed air is supplied from the air compressor 37 to the pressure accumulating chamber 34 through a port 35 and a pipe 36. It has become so. In the middle of the pipe 36, a dryer 39 is interposed with two check valves 38a and 38b interposed therebetween. Dry pressure passing through the dryer 39 is supplied to the pressure accumulating chamber 34. In addition, another pipe 40 for introducing engine negative pressure is connected to a portion of the pipe 36 between the one check valve 38a and the dryer 39, and the booster is not connected to the booster. By opening the on-off valve 41 in the pipe 40 at the time of operation, a negative pressure is introduced into the dryer 39, and the moisture absorbing material inside the dryer 39 is regenerated.
[0017]
On the other hand, the plunger 15 constituting the valve mechanism 14 is integrally provided with a long shaft portion 15a, and the shaft portion 15a is slidably inserted into a guide member 42 fitted and fixed in the valve body 8. Yes. A second valve seat 19 constituting the valve mechanism 14 is formed in the middle of the shaft portion 15a of the plunger 15. On the other hand, the base end portion of the valve body 17 that is separated from and seated on the valve seat 19 is the guide member. 42 is pressed and fixed to the inner surface of the valve body 8. The guide member 42 is formed with a plurality of compressed air passages 43 communicating from the outer periphery to the tip thereof, while the small diameter portion 8b of the valve body 8 is communicated with the compressed air passage 43 in the pressure accumulating chamber 34. A plurality of through holes 44 are formed. One end of the valve spring 21 that urges the valve body 17 in the seating direction is locked to the guide member. Further, the input shaft return spring 23 is interposed between the rear end of the shaft portion 15 a of the plunger 15 and the input shaft 20.
[0018]
In the second embodiment, when the input shaft 20 and the plunger 15 move forward in response to the depression of the brake pedal, the second valve seat 19 opens and the compressed air in the pressure accumulating chamber 34 passes through the valve body 8. The pressure is introduced into the variable pressure chamber 7 through the hole 44 and the compressed air passage 43 of the guide member 42 and the air passage 10, and as a result, a large differential pressure is generated between the constant pressure chamber 6 and the negative pressure. The piston 5 is propelled and the thrust is transmitted to the output shaft 25 via the valve body 8 and the reaction disk 24, and a boosting action is performed.
[0019]
Here, during normal braking, since the forward speed (input speed) of the input shaft 20 is small, the second disk member (cushion material) 32 of the reaction disk 24 is deformed, and only the first disk member 31 is used. Accordingly, the output is transmitted to the output shaft 25, and the contact area of the plunger 15 with respect to the reaction disk 24 is reduced, so that the boost ratio is reduced. On the other hand, when the input speed increases due to sudden braking, the second disk member 32 is not deformed, so that the output is transmitted to the output shaft 25 through the entire reaction disk 24, and the boost at that time The ratio is significantly increased. That is, in this type of pressure-type pneumatic booster in which compressed air is introduced into the variable pressure chamber 7 to perform a large boost action, the boost ratio becomes low during normal braking, and the pedal feeling is reduced. Will be improved.
[0020]
In this type of pressure type pneumatic booster, a large differential pressure is generated between the constant pressure chamber 6 and the variable pressure chamber 7, so that the cylindrical expansion and contraction portion of the valve body 17 constituting the valve mechanism 14 is provided. There is a risk of swelling to the outside, impeding adhesion to the valve seats 18 and 19, and reducing the durability of the valve body itself. Therefore, for example, as shown in FIG. 5, a coil spring 45 is embedded or joined to the outer periphery of the expandable portion 14a, or a bead 46 is provided on the outer periphery of the expandable portion 14a as shown in FIG. It is desirable to do. As shown in FIG. 5, when reinforced by the coil spring 45, the existing valve spring 21 can be omitted, and the assemblability can be improved by reducing the number of parts.
[0021]
【The invention's effect】
As described above, according to the pneumatic booster according to the present invention, a good pedal feeling can be ensured during normal braking, while a high output can be obtained when sudden braking is required. Improves. In addition, since only a part of the material of the reaction disk is changed, the reaction disk can be applied without changing the basics of the conventional booster, and the utility value is high.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the main structure of a pneumatic booster according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a part of the pneumatic booster shown in FIG. 1 further enlarged.
3 is a cross-sectional view showing the overall structure of the pneumatic booster shown in FIG. 1. FIG.
FIG. 4 is a cross-sectional view showing the overall structure of a pneumatic booster that is a second embodiment of the present invention.
5 is a cross-sectional view showing a structure of a valve body used in the pneumatic booster shown in FIG.
6 is a cross-sectional view showing another structure of the valve body used in the pneumatic booster shown in FIG. 4;
[Explanation of symbols]
1 Shell body 4 Diaphragm 5 Power piston 6 Constant pressure chamber 7 Transformer chamber 8 Valve body
14 Valve mechanism
15 Plunger
20 Input shaft
24 reaction discs
31 First disc member
32 Second disc member (cushion material)

Claims (1)

The inside of the shell body is partitioned into a constant pressure chamber and a variable pressure chamber by a power piston equipped with a diaphragm, and the valve body that extends through the shell body through the power piston is supported and input to the valve body. A reaction disk in which a valve mechanism including a plunger interlocking with a shaft is disposed, a differential pressure is generated between the constant pressure chamber and the variable pressure chamber by the operation of the valve mechanism, and a thrust generated in a power piston is mounted on the valve body In the pneumatic pressure booster that transmits the reaction force to the output shaft via the reaction disk and the plunger and the input shaft via the reaction disk, a part of the reaction disk is moved at a gentle speed. It is deformed when a force is applied, and is replaced with a cushion material that is difficult to deform when a force of high speed is applied. Pneumatic booster.

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