JPH038982B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a pressure booster used in brake devices, clutch devices, etc. of vehicles, and more specifically, a pressure booster device in which a plurality of pistons are arranged in series in a shell. This invention relates to a tandem pressure booster.

(Prior Art) A conventional tandem type pressure booster had a general structure as shown in FIG. That is, a first diaphragm 3 and a second diaphragm are contained in a sealed container (shell) consisting of a front shell 1 and a rear shell 2.
A diaphragm 4 is stretched, and a first piston 5 and a second piston 6 are attached to both diaphragms 3 and 4, respectively. Both pistons 5 and 6 are connected by a cylindrical member 7, and a center plate (partition wall) 8 defining a small chamber on the first piston 5 side is provided between the pistons 5 and 6. The cylindrical member 7 can slide against the center plate 8 in an airtight manner.

Thus, four pressure chambers A, B, C, and D are defined in the front and rear portions of the first and second pistons 5 and 6, and among these, pressure chambers A and C are the first and second pressure chambers. The pressure chambers B and D are connected to each other through an internal passage 9 and to the negative pressure generating section of the vehicle engine through a pressure inlet 10, while the pressure chambers B and D are constant pressure chambers. The pressure chambers communicate with each other through a passage 11 of the second diaphragm 4.

12 is a driven rod that is inserted into the shaft of the cylindrical member 7 from the side of the first piston 5 and has a flange portion 13 at the rear end, the tip of which is engaged with a master cylinder (not shown). and the flange portion 1
3 is fitted into a storage body 14 fixed to the second piston 6. Reference numeral 15 denotes an operating lever that is linked to a pedal (not shown) and is engaged with the storage body 14 via a valve plunger 16. A well-known valve mechanism 17 including the valve plunger 16 is provided at the rear of the second piston 6, and the operating rod 15
It plays the role of cutting off communication between the second constant pressure chamber C and the second working pressure chamber D according to the displacement of the second constant pressure chamber C and the second working pressure chamber D.

Note that 18 is an elastic pressure deformation member interposed between the flange portion 13 of the driven rod 12 and the plunger 16, and serves as an intermediate component that transmits reaction force. Further, the first and second pistons 5 and 6 are urged to the return position by a return spring 19 interposed in front of the first piston 5.

With such a configuration, when no pedal force is applied to the pedal and the operating rod 12 is not displaced, the valve mechanism 17
communicates the second constant pressure chamber C and the second working pressure chamber D, so the pressure chambers A, B, C, and D are all kept at the same pressure, and the first and second pistons 5 and 6 are not displaced. .

On the other hand, when the operating rod 15 is displaced to the left in the figure, the valve mechanism 17 is moved between the second constant pressure chamber C and the second constant pressure chamber C.
The communication with the second working pressure chamber D is cut off, and the atmosphere is introduced into the second working pressure chamber D. As mentioned above, since the first and second constant pressure chambers A and C and the first and second working pressure chambers B and D are in communication with each other, the operation of the valve mechanism 17 prevents the introduction of atmospheric air. The first thing to be done is
A pressure difference occurs between the second working pressure chambers B, D and the first and second constant pressure chambers A, C which communicate with the negative pressure source, and this pressure difference causes the first and second constant pressure chambers A, C to communicate with the negative pressure source. 2 pistons 5 and 6 will be displaced. As a result, the first
Driven rod 12 receiving the thrust of the second pistons 5 and 6
operates the master cylinder. At this time, the reaction force is transmitted to the operating rod 15 via the driven rod 12, the pressurizing deformation member 18, and the valve plunger 16.

The input/output characteristics of the air pressure booster having the above configuration are as shown in FIG. 2.
In other words, the initial characteristic (A) is that the output Fθ jumps in when the input Fi is constant, and the output Fθ is
It has three characteristics: a medium-term characteristic (B) in which Fθ increases with a predetermined slope and tanθ, and a final characteristic (C) in which the increase in output Fθ is moderated. Here, the initial characteristic (A) occurs before the reaction force is transmitted to the operating rod 15,
Specifically, the pressurizing deformation member 18 is the valve plunger 16
represents the output required to protrude by a clearance δ from the Furthermore, the medium-term characteristic (B) occurs while the reaction force is being transmitted to the operating rod via the valve plunger 18, and is the ratio of the output Fθ and the input Fi, or
tanθ is the so-called servo ratio. Specifically, if the outer diameter of the flange portion 13 of the driven rod 12 is D ₁ and the outer diameter of the tip of the valve plunger 16 is D ₂ , then (D ₁ /D ₂ ) ²
It is expressed as

However, as mentioned above, the servo ratio is uniquely determined only by the dimensions of the outer diameter D ₁ of the flange portion 13 of the driven rod 12 and the outer diameter D ₂ of the tip of the valve plunger 16, and for this reason, it is difficult to set a large servo ratio. Even if one wanted to, the dimensions could not be set above a certain value, and even if one wanted to arbitrarily select the servo ratio during use, it was impossible to change it. In addition, there is no other way to change the jump-in characteristic other than changing the value of δ, and furthermore, since the first and second pistons are integrally connected, it is difficult to design the jump-in characteristic with sufficient strength. Generally speaking, conventional air pressure boosters have been limited in that they require extensive design changes depending on the application, that is, the conditions of use.

(Object of the Invention) In view of the above-mentioned problems of the prior art, the present invention can obtain a large servo ratio, arbitrarily select the servo ratio, and easily change jump-in characteristics. The purpose of the present invention is to provide a pressure booster that has sufficient design margin as a whole.

(Structure of the Invention) This object is to provide a first driven rod located at the front with a first driven rod that protrudes beyond the shell, and a second piston located at the rear to have a tip of the first driven rod. A second driven rod is provided to abut the
An operating rod is connected to the rear end of the second driven rod via a reaction force mechanism, and the first working pressure chamber and the first constant pressure chamber are in communication with each other. This is achieved by a pressure booster provided with a valve mechanism that can select one of the two operating pressure chambers in communication.

(Example) Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIG. 3 shows the structure of a pressure booster according to the present invention. Note that the same components as those shown in FIG. 1 are denoted by the same reference numerals, and explanations of their functions will be omitted. In this embodiment, a cylindrical member 21 that can slide on the center plate 8 in an airtight manner is fixed only to the first piston 5. On the other hand, the driven rods that transmit the thrust include a first driven rod 22 fixed to the first piston 5 and a second driven rod 23 whose flange portion 23a is fitted into the housing 14 of the second piston 6. The tip of the second driven rod 23 is brought into contact with a recess 22a provided at the rear end of the first driven rod 22. Furthermore, the passage 11 (FIG. 1) that communicates the first and second working pressure chambers B and D in the conventional one is eliminated.

That is, the air pressure booster according to the present invention has a first piston 5 and a second piston 6 in the shell.
are arranged independently, and independent chambers B and C are defined at the rear of the first piston 5 and the rear of the second piston 6.

Therefore, the first constant pressure chamber A, the first working pressure chamber B, and the second working pressure chamber D have the first, first, and second working pressure chambers, respectively.
Second and third pressure introduction ports 24, 25, 26 are provided and connected to an external switching valve 27. Switching valve 2
7 is a state in which the first constant pressure chamber A and the first working pressure chamber B are in communication, or the first working pressure chamber B and the second working pressure chamber B are in communication with each other.
The structure is such that it is possible to arbitrarily select either the state in which the operating pressure chambers D are in communication.

With this configuration, when the switching valve 27 communicates the first constant pressure chamber A and the first working pressure chamber B, first, the operating rod 15 is not displaced because no pedal force is applied to the pedal. In this case, the valve mechanism 17 is
Since the constant pressure chamber C and the second working pressure chamber D are communicated with each other, the pressure chambers A, B, C, and D are all maintained at the same pressure, and the first and second pistons 5 and 6 are not displaced.

On the other hand, when the operating rod 15 is displaced to the left in the figure, the valve mechanism 17 is moved between the second constant pressure chamber C and the second constant pressure chamber C.
The communication with the working pressure chamber D is cut off, and the atmosphere is introduced into the working pressure chamber D. That is, pressure chamber A,
Since the atmosphere is introduced only into the second working pressure chamber D among B, C, and D, a pressure difference occurs between the second constant pressure chamber C and the second working pressure chamber D, and this pressure difference As a result of the displacement of the second piston 6, the first driven rod 22 transfers the thrust of the second piston 6 to the second driven rod 2.
3 to operate the master cylinder.
At this time, the reaction force is applied to the first and second driven rods 22, 23,
The pressure is transmitted to the operating rod 15 via the pressurizing deformation member 18 and the valve plunger 16, and therefore the servo ratio is (D ₁ /D ₂ ) ² .

Next, when the first working pressure chamber B and the second working pressure chamber D are communicated with each other by the switching valve 27, the operating rod 15
, the atmosphere is introduced into both the first and second working pressure chambers B and D, thereby causing the first constant pressure chamber A to
and the first working pressure chamber B and the second constant pressure chamber C and the second
A pressure difference is generated in both the working pressure chambers D, and this pressure difference causes the first and second pistons 5, 6 to be displaced.
The master cylinder is activated by receiving the thrust of 6.
The servo ratio at this time is the effective diameter of the first diaphragm 3 and the second diaphragm 4, respectively.
If d ₁ , d ₂ , approximately {(d ¹ ₂ + d ₂ ² )/d ² }(D ₁ /
D ₂ ) ² +1.

Figure 4 shows the input/output characteristics of this pressure booster.
curve A represents the result when the first working pressure chamber B and the second working pressure chamber D are communicated with each other. As a result, in this pressure booster, it is possible to switch the servo ratio into two stages, and it is also possible to obtain a higher servo ratio than ever before. In addition, in this pressure booster, the load of the return spring 19 acts on the pressurizing deformation member 18 via the first and second driven rods 22 and 23.
The jump-in characteristic A can be easily changed by changing the set load of the return spring 19.

In the above embodiment, the switching valve 27 is provided outside the shell, but instead of this,
For example, a hollow member communicating with the outside may be disposed within the shell, and an appropriate valve mechanism may be provided therein to enable the switching operation as described above.

Further, in the above embodiment, a two-piston type was described, but it is of course applicable to a structure having a larger number of pistons.

Furthermore, for example, by independently providing the first working pressure chamber B and controlling the introduction of atmospheric air into it, it is also possible to continuously change the servo ratio.

(Effects of the Invention) As described above in detail, the air pressure booster according to the present invention has two pistons arranged in series and independently in the shell, and a pressure booster defined in the shell. This allowed the rooms to be switched arbitrarily, and the following effects were obtained.

Unlike conventional air pressure generators, there is no connecting part between the two pistons, so it is possible to design with sufficient strength.

The servo ratio can be changed manually or automatically.
Furthermore, a larger servo ratio than before can be obtained. Therefore, for example, in a loaded vehicle, the same deceleration can be obtained when the vehicle is empty and loaded.

Jump-in characteristics can be easily changed by changing the set load of the turn spring.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the structure of a conventional air pressure booster, Fig. 2 is a correlation diagram showing the input/output characteristics of the conventional air pressure booster, and Fig. 3 is a pressure booster according to the present invention. FIG. 4 is a correlation diagram showing the input/output characteristics of this pressure booster. 1...Front shell, 2...Backward shell, 3,4
...Diaphragm, 5...First piston, 6...
...Second piston, 8... Center plate (bulkhead), 15... Operating rod, 16... Valve plunger,
18... Pressure deformation member, 19... Turn spring, 22... First driven rod, 23... Second driven rod, 24, 25, 26... Pressure introduction port, 27...
switching valve.

Claims (1)

[Claims] 1. In an air pressure booster comprising four pressure chambers defined in a shell by a diaphragm, two pistons attached to the diaphragm, and a partition installed between the two pistons, A first piston located at the rear is provided with a first driven rod that protrudes outside the shell, a second piston located at the rear is provided with a second driven rod whose tip abuts the first driven rod, An operating rod is connected to the rear end of the second driven rod via a reaction force mechanism, and urging means for urging the first and second pistons to return positions is provided, and The first working pressure chamber on the rear side and the first constant pressure chamber on the front side of the first piston are in communication, or the first working pressure chamber and the second constant pressure chamber on the rear side of the second piston are in communication with each other. A pressure booster characterized by being provided with a switching valve mechanism that can select either state in which the pressure booster is in communication with an operating pressure chamber.