JP2856224B2 - Tandem brake booster - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem brake booster, and more particularly, to a tandem brake booster having a function as an automatic brake device.

2. Description of the Related Art Conventionally, a tandem brake booster having a function as an automatic brake device is disclosed in JP-A-60-25.
No. 840 discloses this. This Japanese Unexamined Patent Publication No.
In the tandem brake booster disclosed in Japanese Patent No. 25840, a front chamber and a rear chamber are separated from each other through a communication passage, and a switching valve is provided in the communication passage. ing. When the tandem brake booster functions as an automatic brake, the switching valve is switched to prevent communication between the two transformer chambers, and at the same time, air is introduced into the transformer chamber of the front chamber. By introducing the atmosphere into the variable pressure chamber of the front chamber, the tandem brake booster can be operated without depressing the brake pedal. In addition, as a brake booster having a function as an automatic brake device, in addition to the above, Japanese Patent Application Laid-Open No.
No. 25166 and JP-A-1-127446 are also known.

In the tandem brake booster disclosed in Japanese Patent Application Laid-Open No. 60-25840, when the tandem brake booster functions as an automatic brake, only the transformer chamber in the front room is used. In other words, the air was not introduced into the transformer chamber of the rear chamber when the automatic brake functioned. For this reason, there is a disadvantage that the output of the tandem brake booster when operated as an automatic brake is lower than when the normal tandem brake booster is operated. Accordingly, it is an object of the present invention to increase the output of a tandem brake booster when functioning as an automatic brake, as compared with the related art.

That is, the present invention provides a center plate for partitioning the inside of a shell into a front chamber and a rear chamber, a valve body slidably penetrating the center plate, and a position in the front chamber. A front power piston connected to the valve body, a rear power piston connected to the valve body located in the rear chamber, and a rear side of the front power piston to partition the front chamber into a constant pressure chamber and a variable pressure chamber. A front diaphragm, a rear diaphragm stretched behind the rear power piston to partition the rear chamber into a constant pressure chamber and a variable pressure chamber, and a valve formed in the valve body for switching between the constant pressure chamber of the front chamber and a fluid circuit. Mechanism and the constant pressure chamber of the front chamber through both the valve mechanism and the variable pressure passage. A first constant pressure passage for communicating the pressure chamber,
A tandem brake booster having a second constant pressure passage communicating the two constant pressure chambers, wherein one end of a flexible conduit is connected to the first constant pressure passage, and the other end is drawn out of the shell; The conduit is provided with a switching valve for selectively communicating the conduit with a negative pressure source or the atmosphere. Further, the second constant pressure passage is provided at a position of the through hole formed in the center plate and the position of the through hole. The invention provides a tandem brake booster characterized in that the tandem brake booster is provided and is constituted by an inner space of a pipe which penetrates the front diaphragm and the front power piston while maintaining airtightness.

According to the above construction, when air is introduced into the conduit by the switching valve, the air introduced into the conduit is supplied to both the first constant pressure passage and the valve mechanism and the variable pressure passage through the first constant pressure passage. Introduced into the transformer room. Therefore, in that case, the tandem brake booster can be operated even when the brake pedal is not depressed. in this way,
According to the present invention, when the tandem brake booster functions as an automatic brake, the atmosphere can be introduced into both the transformation chambers via the internal space of the conduit and the first transformation passage. Therefore, the output can be increased as compared with a conventional device in which the atmosphere is introduced into only one of the transformer chambers when functioning as an automatic brake. Further, since it is not necessary to provide the second constant pressure passage in the valve body, the second constant pressure passage is compared with the conventional one in which the second constant pressure passage is constituted by the axial hole and the radial hole formed in the valve body. Radial dimensions can be reduced. As described above, since the effective area of both diaphragms can be increased by reducing the radial dimension of the valve body, the output can be increased by that much as compared with the related art. Therefore, when the tandem brake booster functions as an automatic brake device, the output of the tandem brake booster can be increased as compared with the conventional case.

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 comprising a front shell 1 and a rear shell 2 is separated from a front and rear front chamber 4 by a center plate 3 provided at the center thereof. A substantially cylindrical valve body 6 is partitioned into two chambers, a rear chamber 5 and a shaft portion of the rear shell 2 and the center plate 3.
Are slidably penetrated by the annular sealing means 7 and 8 while maintaining airtightness. In the valve body 6,
The front power piston 11 and the inner peripheral portion of the rear power piston 12 disposed in the front chamber 5 and the rear chamber 7 are connected to each other, and a front diaphragm 13 and a rear diaphragm 14 are provided on the back of the power pistons 11 and 12. And each diaphragm 1
The inner peripheral portions of the pressure chambers 3 and 14 are also connected to the valve body 6.
A constant-pressure chamber C and a variable-pressure chamber D are formed before and after the rear diaphragm 14. A valve mechanism 15 having a conventionally well-known configuration is provided in the valve body 6, and in a state where a bellows 37 described later is not provided, the two constant pressure chambers A and C and the two variable pressure chambers B and The fluid circuit between D and D can be switched. The valve mechanism 15 is formed at the right end of an annular first valve seat 16 formed on the valve body 6 and a valve plunger 17 slidably provided on the valve body 6 inside the annular first valve seat 16. An annular second valve seat 18;
Further, a valve body 20 is provided on both valve seats 16 and 18 from the right side in FIG. The space on the outer peripheral side of the annular seat portion where the first valve seat 16 and the valve body 20 are in contact with each other is provided with an axial first constant pressure passage 23 formed in the valve body 6 in a state where a bellows 37 described later is not provided. The chamber is communicated with the constant pressure chamber A through the above. Constant pressure chamber A
Is connected to a negative pressure source via a negative pressure introducing pipe 24 attached to the front shell 1, so that a negative pressure is always introduced into the constant pressure chamber A. The constant pressure chamber A is always in communication with a constant pressure chamber C via a second constant pressure passage 25 provided in the center plate 3 and described later. Therefore, a negative pressure is always introduced into both the constant pressure chambers A and C.
On the other hand, on the inner peripheral side of the annular seat portion where the first valve seat 16 and the valve body 20 are in contact, and on the outer peripheral side of the annular seat portion where the second valve seat 18 and the valve body 20 are in contact, That is, the space in the middle portion between the inner and outer annular seat portions is the valve body 6.
The variable pressure chamber D is communicated with a variable pressure chamber D via a radial variable pressure passage 26 formed in the valve body 6, and the variable pressure chamber D is further connected to a variable pressure chamber B via another axial variable pressure passage 27 formed in the valve body 6. Further, a space on the inner peripheral side of the inner annular seat portion where the second valve seat 18 and the valve element 20 are in contact with each other is communicated with the atmosphere via the filter 28. The right end of the valve plunger 17 slidably provided on the valve body 6 is connected to an input shaft 29 interlocked with a brake pedal (not shown).
The reaction disk 31 accommodated in the recess 30a formed at the base of the “0” is opposed to the right end surface. The left end of the push rod 30 is linked to a piston of a master cylinder (not shown) through an opening 1a of a shaft in the front shell 1. Airtightness is maintained between the opening 1 a and the push rod 30 by a seal member 32. Since the return spring 33 is mounted between the valve body 6 and the front shell 1, the valve body 6 is normally held at a non-operating position in the drawing. In this non-operating state, the valve body 20 is seated on the second valve seat 18, but a slight gap is maintained between the first valve seat 16 and the valve body 20. However, in the present embodiment, the reinforcing plate 36 attached to the inner wall of the front shell 1 is provided.
The bellows 37 is attached to the outer periphery of the front end of the valve body 6 and the front shell 1.
The internal space A ′ of the bellows 37 is communicated with a negative pressure source by a second negative pressure introducing pipe 38 that penetrates through the reinforcing plate 36 and has one end connected to the reinforcing plate 36. That is, the rear end of the bellows 37 is pressed into the annular concave portion 11 a formed on the inner peripheral edge of the front power piston 11, and then the retainer 39 fitted to the outer peripheral portion of the valve body 6 from the front side. The bellows 37 is locked in the annular recess 11a, thereby maintaining the airtightness between the rear end of the bellows 37 and the annular recess 11a. On the other hand, the front end of the bellows 37 is folded in a U-shape toward the inward side, and the outer cylindrical portion 36a of the reinforcing plate 36 is sandwiched between the folded portions by the outer peripheral edge of the second retainer 40. To fit. Thus, the airtightness between the outer peripheral cylindrical portion 36a of the reinforcing plate 36 and the front end of the bellows 37 is maintained. The inner periphery of the second retainer 40 is fitted to the shaft of the front shell 1, and the airtightness between the shaft of the front shell 1 and the reinforcing plate 36 is maintained by a rubber O-ring 41. . The constant-pressure chamber A outside the bellows 37 thus arranged communicates with the negative pressure source through the negative pressure introducing pipe 24 attached to the front shell 1 as described above, so that a negative pressure is always introduced. Have been.
On the other hand, a solenoid valve 42 for selectively communicating the negative pressure introducing pipe 38 with the atmosphere and the negative pressure source is provided midway between the second negative pressure introducing pipe 38 and the negative pressure source. The solenoid valve 42 is ON / OFF controlled by a controller (not shown), and connects the second negative pressure introducing pipe 38 to the negative pressure source in a normal state where the solenoid valve 42 is not operated. Therefore, at that time, a negative pressure is introduced into the internal space A ′ of the bellows 37 via the second negative pressure introducing pipe 38. On the other hand, when the solenoid valve 42 is operated by the controller when necessary, the atmosphere is introduced into the internal space A 'of the bellows 37 via the second negative pressure introducing pipe 38, and thereafter, , The air introduced into the internal space A ′ of the bellows 37 passes through the first constant-pressure passage 23, the variable-pressure passage 26, and the variable-pressure passage 27 to both of the variable pressure chambers B
Introduced in D. As described above, in the present embodiment, by operating the solenoid valve 42 from the inoperative state of the tandem brake booster shown in FIG. 1, even if the brake pedal (not shown) linked to the input shaft 29 is not depressed. The tandem brake booster can be operated. Further, in the present embodiment, the second constant pressure passage 25 that connects the two constant pressure chambers A and C is configured as follows. That is, a through hole 3a is formed at one location on the wall surface of the center plate 3, and one end of a steel pipe 43 is connected to a wall surface on the front side of the through hole 3a. On the other hand, the tip of the pipe 43 is loosely fitted and penetrated into each of the through holes formed in the front diaphragm 13 and the front power piston 11 in a superposed state, and is then positioned in the constant pressure chamber A. An extendable bellows 44 is attached between the front end of the pipe 43 located in the constant pressure chamber A and the through holes of the front diaphragm 13 and the front power piston 11. The airtightness between the section and the through hole of the front diaphragm 13 is maintained. Note that a plurality of the second constant pressure passages 25 may be provided. As described above, in the present embodiment, the second constant pressure passage 25 is formed by the through hole 3 a formed in the center plate 3 and the internal space of the pipe 43.
Therefore, a negative pressure is always introduced into both the constant-pressure chambers A and C via the second constant-pressure passage 25. In the above configuration, since the solenoid valve 42 is not normally operated as shown in FIG. 1, the negative pressure is also introduced into the internal space A ′ of the bellows 37 through the second negative pressure introducing pipe 38. Therefore, a negative pressure is introduced into all the chambers A, B, C, D, and A '.
When the brake pedal (not shown) is depressed from the inoperative state shown in FIG. 1, the input shaft 29 moves forward (leftward), and accordingly, the fluid circuit is switched by the valve mechanism 15, so that the fluid chambers B and D are moved into the two variable pressure chambers B and D. Atmosphere is introduced. As a result, similarly to the conventionally known tandem brake booster,
An output having a predetermined servo ratio can be obtained from the push rod 30. In order to make the tandem brake booster function as an automatic brake device with respect to the time of the normal brake operation, when the input shaft 29 shown in FIG.
2 can be activated. As a result, the air is introduced into the internal space A 'of the bellows 37, and the air introduced into the internal space A' of the bellows 37 is supplied to the first constant pressure passage 23 and the variable pressure passage 26 communicating therewith. It is introduced into both of the transformation chambers B and D via the transformation passage 27.
As a result, a pressure difference is generated between the two constant pressure chambers A, C and the two variable pressure chambers B, D, so that a predetermined output can be obtained from the push rod 30 even when the brake pedal is not depressed. In the present embodiment, when the tandem brake booster functions as an automatic brake device in this manner, the atmosphere can be introduced into both the transformation chambers B and D. Therefore, according to the present embodiment, when the tandem brake booster is operated as an automatic brake device, as compared with a conventional device in which the atmosphere is introduced into only one of the transformer chambers to function as an automatic brake device, The output of the tandem brake booster can be increased. further,
In the present embodiment, since the second constant pressure passage 25 is constituted by the through hole 3a of the center plate 3 and the pipe 43 attached at that position instead of providing the second constant pressure passage 25 in the valve body 6,
Compared to the conventional device in which the second constant pressure passage 25 is constituted by the axial hole formed in the valve body 6 and the radial hole continuously opening on the outer peripheral surface of the valve body 6 from the axial hole, Can be increased in strength. Further, by configuring the second constant pressure passage 25 as described above,
When the tandem brake booster is caused to function as an automatic brake, the output can be further increased as compared with the related art. That is, there is no need to provide an axial hole and a radial hole for forming the second constant pressure passage 25 in the valve body 6. Dimensions can be reduced. Thereby, the effective area of both diaphragms 13 and 14 connected to valve body 6 can be increased. Therefore, also in this sense, when the tandem brake booster is caused to function as an automatic brake, the output can be increased as compared with the conventional case. FIG. 2 shows a second embodiment of the second constant pressure passage 25. In the second embodiment, an annular seal member 144 is used instead of the bellows 44 of the first embodiment. That is, an annular seal member 144 is attached to each through hole of the front diaphragm 113 and the front power piston 111, and the pipe 143 is slidably penetrated through the seal member 144 while maintaining airtightness. Other configurations are the same as those of the first embodiment. Members corresponding to those of the first embodiment are denoted by member numbers obtained by adding 100. Even with the second constant pressure passage 125 of the second embodiment, the same operation and effect as those of the first embodiment can be obtained.

As described above, according to the present invention, the output of the tandem brake booster when the tandem brake booster functions as the automatic brake device can be increased as compared with the conventional one. The effect is obtained.

[Brief description of the drawings]

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

FIG. 2 is a sectional view showing another embodiment of a main part of the present invention.

[Explanation of symbols]

 6 Valve body 23 First constant pressure passage 25 Second constant pressure passage 37 Bellows (conduit) 38 Second negative pressure introduction pipe 42 Solenoid valve 43 Pipe 125 Second constant pressure passage 143 Pipe A, C Constant pressure chamber A 'Inner space of bellows B , D Transformer room

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B60T 13/52-13/577

Claims (1)

(57) [Claims] 1. A center plate for partitioning a shell into a front chamber and a rear chamber, a valve body slidably penetrating the center plate, and a front power piston connected to the valve body located in the front chamber. A rear power piston connected to a valve body located in the rear chamber, a front diaphragm stretched on the back of the front power piston to partition the front chamber into a constant pressure chamber and a variable pressure chamber, and a rear diaphragm on the rear power piston. A rear diaphragm which is stretched and partitions the rear chamber into a constant pressure chamber and a variable pressure chamber, and a valve mechanism formed in the valve body for switching a fluid circuit with the constant pressure chamber of the front chamber communicates with the valve mechanism. A first constant-pressure passage for communicating the constant-pressure chamber of the front chamber with the two pressure-changing chambers via the variable-pressure passage; A tandem brake booster comprising a second constant pressure passage communicating the two constant pressure chambers,
One end of a flexible conduit is connected to the first constant pressure passage, the other end is pulled out of the shell, and the conduit is provided with a switching valve for selectively communicating the conduit with a negative pressure source or the atmosphere. Further, a pipe is provided in which the second constant-pressure passage is provided at a position of the through-hole formed in the center plate and the through-hole, and penetrates the front diaphragm and the front power piston in an airtight manner. A tandem brake booster characterized by comprising an internal space.