JP2856223B2 - 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 front-side transformer chamber 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; A switching valve for selectively communicating the conduit with a negative pressure source or the atmosphere is provided on the conduit, and the second constant pressure passage is located outside the conduit to directly connect the two constant pressure chambers. An object of the present invention is to provide a tandem brake booster constituted by a communication passage for communication.

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, a shell 1 has a front shell 2 formed substantially in a cup shape, and a substantially dish-shaped rear shell 3 for sealing an opening of the front shell 2. It is composed of
The cup-shaped front shell 2 has a small-diameter cylindrical portion 2A on the front side, a large-diameter cylindrical portion 2B on the rear side, and an annular wall portion 2C extending between the two in the radial direction. A larger-diameter cylindrical hooking portion 2D is formed on the opening side of the large-diameter cylindrical portion 2B. A center plate 4 formed in a substantially cup shape is fitted inside the front shell 2, and a front room 5 is defined between an end wall surface of the center plate 4 and an end wall surface of the front shell 2. Has formed. The center plate 4 includes a cylindrical portion 4A that is closely fitted in the large-diameter cylindrical portion 2B of the front shell 2, and the cylindrical portion fitted to the large-diameter cylindrical portion 2B of the front shell 2. The right end of 4A is located slightly rearward from the step end surface between the large-diameter cylindrical portion 2B and the cylindrical hooking portion 2D in the front shell 2. In this state, the flange portion 3A formed in the outer peripheral portion of the rear shell 3 in the radial direction is fitted to the cylindrical hook portion 2 of the front shell 2.
At the same time as fitting into D, the center plate 4 is in contact with the right end of the cylindrical portion 4A. The front shell 2, the center plate 4, and the rear shell 3 are integrally connected to each other by locking the rear shell 3 in this state with a plurality of engaging claws 2E formed on the cylindrical hooking portion 2D. ing. An O-ring 6 made of rubber is interposed between the flange portion 3A of the rear shell 3 connected as described above and the end face of the step portion of the front shell 2 facing the flange portion. Holding. The rear chamber 7 is located between the wall surface of the rear shell 3 connected as described above and the end wall surface of the center plate 4.
Is formed. A through hole is formed in each of the center shaft portions of the center plate 4 and the rear shell 3, and a stepped cylindrical valve body 8 is slidably penetrated into each of the through holes, and a sealing member 9 is provided. Thereby, the airtightness between each through hole and the valve body 8 is maintained. A front power piston 12 and a rear power piston 13 are disposed in the front chamber 5 and the rear chamber 7, respectively.
The inner peripheral portions of the diaphragms 2 and 13 are connected to the valve body 8, and the front diaphragms 14 and the rear diaphragms 15 are stretched on the rear side surfaces of the power pistons 12 and 13, respectively. 8. On the other hand, the above diaphragms 1
The outer bead portions 14a and 15a of the outer shells 4 and 15 are sandwiched between the front shell 2, the center plate 4 and the rear shell 3 described above. That is, the outer peripheral bead portion 14a of the front diaphragm 14 is formed by the annular wall portion 2C of the front shell 2 and the cylindrical portion 4A of the center plate 4.
Is axially sandwiched between an opposing wall portion 4B formed so as to face the annular wall portion 2C at the outer peripheral portion at the left end of the front end portion, thereby keeping the airtightness of the portion and the front chamber 5 on the front side. It is divided into a constant pressure chamber A and a rear pressure transformation chamber B. At this time, the radially inner portion of the opposed wall portion 4B is annularly protruded toward the annular wall portion 2C, so that airtightness can be maintained more reliably. The outer bead portion 1 of the rear diaphragm 15
5a is accommodated in an annular groove 3B formed radially outward on the outer peripheral portion of the rear shell 3, and the outer peripheral bead portion 15a is formed on the outer peripheral surface of the annular groove 3B and the cylindrical portion 4A of the center plate 4. Radially sandwiched by the inner peripheral surface of
Thereby, the airtightness of the portion is maintained, and the inside of the rear chamber 7 is divided into a constant pressure chamber C on the front side and a variable pressure chamber D on the rear side. Further, a valve mechanism 16 having a conventionally well-known configuration is provided in the valve body 8, and when the bellows 38 described later is not provided, this valve mechanism 1 is provided.
6, the two constant pressure chambers A and C and the two transformer chambers B,
The fluid circuit between D and D can be switched. The valve mechanism 16 is formed at the right end of an annular first valve seat 17 formed on the valve body 8 and a valve plunger 18 slidably provided on the valve body 8 inside the annular first valve seat 17. An annular second valve seat 19 and a valve element 21 seated on both valve seats 17 and 19 from the right in FIG. The first valve seat 17
A space on the outer peripheral side of the annular seat portion where the valve body 21 contacts the first constant-pressure passage 2 formed in the valve body 8 in the axial direction when the bellows 38 described later is not provided.
4 communicates with the constant pressure chamber A. Constant pressure chamber A
Is connected to a negative pressure source via a negative pressure introducing pipe 25 attached to the front shell 2, so that a negative pressure is always introduced into the constant pressure chamber A. The constant-pressure chamber A is always in communication with the constant-pressure chamber C via a second constant-pressure passage 26, which will be described later, provided in the annular wall 2C of the front shell 2. 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 17 and the valve body 21 are in contact, and on the outer peripheral side of the annular seat portion where the second valve seat 19 and the valve body 21 are in contact, That is, the space in the middle of the inner and outer annular seats is
A radially variable pressure passage 27 formed in the valve body 8 communicates with the variable pressure chamber D, and the variable pressure chamber D communicates with a variable pressure chamber B through another axially variable pressure passage 28 formed in the valve body 8. I have. Further, a space on the inner peripheral side of the inner annular seat portion where the second valve seat 19 and the valve element 21 are in contact with each other is communicated with the atmosphere via a filter 29. The right end of the valve plunger 18 slidably provided on the valve body 8 is connected to an input shaft 30 linked to a brake pedal (not shown).
The reaction disk 32 accommodated in a concave portion 31 a formed at the base of the push rod 31 is opposed to the right end surface. The left end of the push rod 31 is linked to a piston of a master cylinder (not shown) through an opening 2a of a shaft in the front shell 2. Open above
A seal member 33 is provided between the port 2a and the push rod 31.
Keeps her tight. A return spring 34 extends between the valve body 8 and the front shell 2.
, The valve body 8 is normally held at the non-operating position shown in the figure. In this inactive state,
Although the valve element 21 is seated on the second valve seat 19, the first valve seat 1
A slight gap is maintained between 7 and the valve element 21. However, in this embodiment, the bellows 38 is attached to the reinforcing plate 37 attached to the inner wall of the front shell 2 and the outer periphery of the front end of the valve body 8, and the bellows 38 penetrates the front shell 2 and the reinforcing plate 37. By the second negative pressure introducing pipe 39 having one end connected to the reinforcing plate 37,
The internal space A 'of the bellows 38 communicates with a negative pressure source. That is, the rear end of the bellows 38 is formed in the annular recess 12 formed in the inner peripheral edge of the front power piston 12.
After being pressed into the inside of the valve body 8, it is locked in the annular recess 12 a by a retainer 40 fitted from the front side to the outer peripheral portion of the valve body 8, whereby the rear end of the bellows 38 is The airtightness with the annular recess 12a is maintained. On the other hand, the front end of the bellows 38 is folded in a U-shape toward the inward side, and the outer peripheral cylindrical portion 37a of the reinforcing plate 37 is sandwiched between the folded portions by the outer peripheral edge of the second retainer 41. To fit. Thereby, airtightness between the outer peripheral cylindrical portion 37a of the reinforcing plate 37 and the front end of the bellows 38 is maintained.
The inner peripheral portion of the second retainer 41 is fitted on the shaft of the front shell 2, and the airtightness between the shaft of the front shell 2 and the reinforcing plate 37 is maintained by a rubber O-ring 42. . The constant pressure chamber A outside the bellows 38 arranged in this way communicates with the negative pressure source via the negative pressure introducing pipe 25 attached to the front shell 2 as described above, so that a negative pressure is always introduced. Have been. Further, a solenoid valve 43 for selectively communicating the negative pressure introducing pipe 39 with the atmosphere and the negative pressure source is provided midway between the second negative pressure introducing pipe 39 and the negative pressure source. The solenoid valve 43 is ON / OFF controlled by a controller (not shown), and connects the second negative pressure introducing pipe 39 to the negative pressure source in a normal state where the solenoid valve 43 is not operated. Therefore, at that time, a negative pressure is introduced into the internal space A ′ of the bellows 38 via the second negative pressure introducing pipe 39. On the contrary,
When the solenoid valve 43 is actuated by the controller when required, the atmosphere is introduced into the internal space A 'of the bellows 38 through the second negative pressure introducing pipe 39. The air introduced into the space A 'is introduced into both the transformation chambers B and D via the first constant pressure passage 24, the radial transformation passage 27 and the axial transformation passage 28. As described above, in the present embodiment, by operating the solenoid valve 43 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 30 is not depressed. The tandem brake booster can be operated. Further, in the present embodiment, the second constant pressure passage 26 that connects the two constant pressure chambers A and C is configured as follows.
That is, the second constant pressure passage 26 is connected to the front shell 2.
Outer peripheral bead portion 14 of front diaphragm 14 formed by annular wall portion 2C and opposed wall portion 4B of center plate 4
a first passage 44 formed between the inner peripheral surface of the large-diameter cylindrical portion 2B of the front shell 2 and the outer peripheral surface of the outer peripheral bead portion 14a at a position radially outward of the holding portion a. The end of the first passage 44 on the rear side in the axial direction is communicated with the constant pressure chamber C of the rear chamber through a through hole 4C formed in the center plate 4 at a position radially outward of the holding portion. I have. On the other hand, the end of the first passage 44 on the axial front side is the small-diameter cylindrical portion 2 of the front shell 2.
A through a second passage 45 in a bulging portion 2F formed by bulging a part of A and a part of an annular wall portion 2C radially outward,
It communicates with the constant pressure chamber A in the front room. Therefore,
In the present embodiment, both the constant pressure chambers A,
C communicates directly, and a negative pressure is always introduced into both the constant pressure chambers A and C. In the above configuration, since the solenoid valve 43 is not normally operated as shown in FIG. 1, the negative pressure is also introduced into the internal space A ′ of the bellows 38 via the second negative pressure introducing pipe 39. 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 30 moves forward (leftward), and the fluid circuit is switched by the valve mechanism 16 in accordance with the depression, so that the two pressure change chambers B, D Atmosphere is introduced. As a result, an output having a predetermined servo ratio can be obtained from the push rod 31 in the same manner as in a conventionally known tandem brake booster. When the tandem brake booster is to function as an automatic brake device with respect to the normal brake operation, the solenoid valve 43 may be operated by the controller from a non-operating state in which the input shaft 30 shown in FIG. 1 is not advanced. . As a result, the air is introduced into the internal space A 'of the bellows 38, and the air introduced into the internal space A' of the bellows 38 is connected to the first constant pressure passage 24 and the radial variable pressure passage communicating therewith. 27 and are introduced into both transformation chambers B, D via an axial transformation passage 28. This causes a pressure difference between the two constant pressure chambers A and C and the two variable pressure chambers B and D.
A predetermined output can be obtained from the push rod 31 even when the brake pedal is not depressed. And
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. for that reason,
According to the present embodiment, the tandem brake booster is operated as an automatic brake device in comparison 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 brake booster can be increased. Further, in this embodiment,
Since the second constant pressure passage 26 is provided on the outer side of the outer peripheral bead portion 14a of the front diaphragm 14 instead of being provided in the valve body 8, the axial hole formed in the valve body 8 is continuously connected to the axial hole. According to the present embodiment, the strength of the valve body 8 can be increased as compared with the conventional device in which the second constant pressure passage 26 is constituted by the radial holes that open on the outer peripheral surface. In addition, by configuring the second constant pressure passage 26 as described above, when the tandem brake booster functions 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 26 in the valve body 8. Dimensions can be reduced. Thereby, the effective area of both diaphragms 14 and 15 connected to valve body 8 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. In the present embodiment, the second constant pressure passage 26 is configured as described above, but instead of such a configuration, the two constant pressure chambers A and C are directly communicated with each other by a conduit, and the internal space of the conduit is formed. May be used as the second constant pressure passage 26.

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.

[Explanation of symbols]

 8 Valve body 24 First constant pressure passage 26 Second constant pressure passage 38 Bellows (conduit) 39 Second negative pressure introduction pipe 43 Solenoid valve A, C Constant pressure chamber A 'Inner space of bellows B, D Transformer chamber

──────────────────────────────────────────────────続 き Continued from the front page (56) References JP-A-60-64058 (JP, A) JP-A-60-64057 (JP, A) JP-A-61-50863 (JP, A) JP-A-60-640 99761 (JP, A) JP-A-48-18667 (JP, A) JP-A-61-60360 (JP, A) JP-A-61-60361 (JP, A) JP-A-61-253254 (JP, A) Japanese Utility Model Showa 61-88863 (JP, U) Japanese Utility Model Showa 60-118555 (JP, U) (58) Fields investigated (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 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. A switching valve for selectively communicating the conduit with a negative pressure source or the atmosphere is disposed on the conduit, and the second constant pressure passage is located outside the conduit to directly connect the two constant pressure chambers. A tandem brake booster comprising a communication passage for communication.