JPH0542866A - Brake booster - Google Patents

Abstract

PURPOSE:To favorably prevent a bellows from expanding owing to a ring even if the bellows tends to expand when atmospheric air is introduced in the bellows by providing the ring for reinforcing at a position of the bellows whose cross section is like V. CONSTITUTION:In functioning a tandem brake booster as an automatic braking device, a solenoid valve 42 is actuated by a controller, and atmospheric air instead of negative air is introduced into the internal space A' of a bellows 17. Then, since the atmospheric air is introduced into variable pressure chambers B and D through passages 23, 27, and 28, pressure difference is produced between constant pressure chambers A and C and the variable pressure chambers B and D, specified pressure can be obtained from a push rod. Together with the actuation mentioned above, the bellows 17 tends to be expanded, but a reinforcing ring 45 is fitted in the root 17c whose cross section is a V shape at the center of the bellows 17 excellently preventing the bellows 17 expanding. This obviates the necessity to enlarge the volume of the constant pressure chamber A.

Description

Detailed Description of the Invention

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

2. Description of the Related Art Conventionally, as a brake booster having a function as an automatic brake device, a valve body slidably provided in a shell, a power piston provided in the valve body, and a power piston formed before and after the power piston are formed. A constant pressure chamber, a variable pressure chamber, and a constant pressure passage formed in the valve body for communicating with the constant pressure chamber and a valve mechanism for switching a fluid circuit, and a constant pressure passage for communicating the constant pressure chamber with the variable pressure chamber through the valve mechanism and the variable pressure passage. A bellows provided in the constant pressure chamber, having a rear end connected to the constant pressure passage and a front end connected to a shell, and a negative pressure or an atmosphere is selectively supplied to the inner space of the bellows. It is known to be able to supply the same (for example, JP-A-1-127446 and JP-A-60-25840). In the above-described conventional brake booster, the atmosphere is introduced into the variable pressure chamber by supplying the atmosphere into the bellows when required, thereby operating the brake booster without depressing the brake pedal. it can.

By the way, in the above-mentioned conventional brake booster, since the bellows is manufactured only from rubber and no special reinforcing member is used, the atmosphere is introduced into the bellows as described above. However, there was a drawback that the bellows expanded due to atmospheric pressure.

In view of the above-mentioned circumstances, the present invention provides a valve body slidably provided in a shell,
The power piston provided in the valve body, the constant pressure chamber and the variable pressure chamber formed before and after the power piston, and the valve mechanism formed in the valve body for switching the constant pressure chamber and the fluid circuit are communicated with each other, and the valve mechanism and the variable pressure chamber are connected to each other. A constant pressure passage that communicates the constant pressure chamber with the variable pressure chamber via a passage, and the constant pressure passage is provided in the constant pressure chamber and connects the rear end to the constant pressure passage.
In a brake booster having a bellows having a front end connected to a shell and capable of selectively supplying negative pressure or atmosphere to the inner space of the bellows, the bellows is reinforced at a position having a V-shaped cross section. It is provided with a ring for.

According to the above structure, even if the bellows is expanded when the atmosphere is introduced into the bellows, the expansion of the bellows itself can be effectively prevented by the ring.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. In FIG. 1, a shell 1 of a tandem brake booster is constructed by connecting a front shell 2 and a rear shell 3, and the inside of the shell 1 is a center. The plate 4 divides the front chamber 5 on the front side and the rear chamber 6 on the rear side. Through holes are formed in the shaft portion of the center plate 4 and the shaft portion of the rear shell 3, respectively, and the stepped cylindrical valve body 7 is slidably penetrated into each of the through holes, and the seal member Airtightness is maintained between each through hole and the valve body 7 by means of 8. The front power piston 9 and the rear power piston 10 are arranged in the front chamber 5 and the rear chamber 6, respectively, and the inner peripheral portions of the power pistons 9 and 10 are connected to the outer peripheral portion of the valve body 7, respectively. 9,
A front diaphragm 11 and a rear diaphragm 12 are stretched on the rear side surface of the diaphragm 10, respectively.
The inner peripheral bead portions 11 a and 12 a of the first and the second peripheral portions 12 are also connected to the outer peripheral portion of the valve body 7. On the other hand, the outer peripheral bead portion 11b of the front diaphragm 11 is axially sandwiched by the annular wall portion 2a of the front shell 2 and the opposing wall portion 4a of the center plate 4, and the front diaphragm 11 keeps the front chamber 5 inside. Front side constant pressure chamber A
And a transformer room B on the rear side. Further, the outer peripheral bead portion 12b of the rear diaphragm 12 is sandwiched between the connecting portions of the front shell 2 and the rear shell 3, and the rear diaphragm 12 allows the inside of the rear chamber 6 to be a constant pressure chamber C on the front side and a variable pressure chamber on the rear side. It is partitioned with D. A conventionally well-known valve mechanism 16 is provided in the valve body 7, and the two constant pressure chambers A and C are provided by the valve mechanism 16 in a state where a bellows 17 described later is not provided.
And the fluid circuit between the two variable pressure chambers B and D can be switched. That is, the valve mechanism 1
6 is an annular first valve seat 18 formed on the valve body 7.
And an annular second valve seat 20 formed at the right end of a valve plunger 19 slidably provided on the valve body 7 inside the annular first valve seat 18, and further on both valve seats 18, 20 as shown in FIG. 1 and the valve element 22 seated by the spring 21 from the right side. In the space on the outer peripheral side of the annular first seat portion where the first valve seat 18 and the valve body 22 contact each other, the axial first constant pressure passage 23 formed in the valve body 7 is formed without the bellows 17. It is made to communicate with the above-mentioned constant pressure room A via. In the constant pressure chamber A, a negative pressure is introduced from a negative pressure source via a first negative pressure introducing pipe 24 connected to the front shell 2, and the negative pressure is introduced between the first negative pressure introducing pipe 24 and the negative pressure source. Is provided with a check valve 25 to allow only negative pressure to flow from the negative pressure source to the constant pressure chamber A. The constant pressure chamber A is always in communication with the constant pressure chamber C of the rear chamber via the second constant pressure passage 26 formed on the outer side of the outer peripheral bead portion 11b of the front diaphragm 11, and therefore both constant pressure chambers A and C are connected. Negative pressure is always introduced inside. On the other hand, on the inner peripheral side of the annular first seat portion where the first valve seat 18 and the valve body 22 are in contact with each other, rather than the annular second seat portion where the second valve seat 20 and the valve body 22 are in contact with each other. The space on the outer peripheral side, that is, the space between the inner and outer annular seat portions, is connected to the variable pressure chamber D via the first radial variable pressure passage 27 formed in the valve body 7.
The variable pressure chamber D is communicated with the variable pressure chamber B through the axial second variable pressure passage 28 formed in the valve body 7. Further, the space on the inner peripheral side of the inner second annular seat portion where the second valve seat 20 and the valve body 22 come into contact with each other is provided with a pressure passage 29 formed in the valve body 7 and a filter 30 provided therein. It is in communication with the atmosphere. A right end portion of the valve plunger 19 slidably provided on the valve body 7 is connected to an input shaft 34 interlocked with a brake pedal (not shown), and a left end portion thereof is a reaction housed in a recess 35a of the push rod 35. Disc 36
Facing the right end surface of. The left end portion of the push rod 35 is interlocked with the piston 37a of the master cylinder 37 that penetrates the shaft opening 2b of the front shell 2. Between the opening 2b and the piston 37a,
Airtightness is maintained by the seal member 38. Since the return spring 39 is elastically mounted over the valve body 7 and the front shell 2, the valve body 7 is normally held in the inoperative position shown in the drawing. A rubber bellows 17 is provided over the wall surface of the front shell 2 and the outer peripheral portion on the front side of the valve body 7. An inner space A ′ of the bellows 17 is formed in the reinforcing plate 40 and the wall surface of the front shell 2. The respective through holes are communicated with the negative pressure source by the second negative pressure introducing pipe 41 attached to the wall surface of the front shell 2. In this embodiment, the second negative pressure introducing pipe 41 is not directly connected to the negative pressure source,
It is connected to the first negative pressure introducing pipe 24 which is located downstream of the check valve 25. A solenoid valve 42 that selectively connects the second negative pressure introducing pipe 41 to the atmosphere and the negative pressure source (first negative pressure introducing pipe 24) is provided in the middle of the second negative pressure introducing pipe 41. The solenoid valve 42 is ON / OFF controlled by a controller (not shown).
In the non-operating state shown in (2), the second negative pressure introducing pipe 41 is communicated with the negative pressure source. Therefore, negative pressure is introduced into the internal space A ′ of the bellows 17 via the second negative pressure introducing pipe 41. (Operation) Normally, the tandem brake booster configured as described above has a solenoid valve 42 as shown in FIG.
Is not operated, negative pressure is introduced into the internal space A ′ of the bellows 17 via the second negative pressure introducing pipe 41. In addition, the constant pressure chamber A is provided via the other first negative pressure introducing pipe 24.
Negative pressure is also introduced into the chambers A, B, C, D, and A ′. When the brake pedal (not shown) is depressed from this non-operating state, the input shaft 34 is moved forward (leftward), and the fluid circuit is switched by the valve mechanism 16 accordingly, so that the atmosphere is introduced into both the variable pressure chambers B and D. To be done. As a result, similar to a conventionally known tandem brake booster, it is possible to obtain an output of a predetermined servo ratio from the push rod 35. When the tandem brake booster is to function as an automatic brake device as compared with the normal brake operation, the solenoid valve 42 may be operated by the controller from the non-operation state in which the input shaft 34 shown in FIG. 1 is not advanced. .. As a result, the atmosphere is introduced into the internal space A ′ of the bellows 17 instead of the negative pressure. Therefore, the atmosphere introduced into the internal space A ′ of the bellows 17 is introduced into both the variable pressure chambers B and D through the first constant pressure passage 23 and the first variable pressure passage 27 and the second variable pressure passage 28 which are in communication therewith. be introduced. Therefore, a pressure difference is generated between the constant pressure chambers A and C and the variable pressure chambers B and D, so that the push rod 35 is pushed even though the brake pedal is not depressed.
To obtain the desired output. Thus, in the bellows 17 of this embodiment, the front side end portion is made thicker to form the front bead portion 17a, and the rear side end portion is also made to be the rear bead portion 17b. Then, the front bead portion 17a is held by the inner peripheral portion of the support member 43 provided in the constant pressure chamber A, and the front shell 2 is held.
It is pressed against the wall surface of and keeps its airtightness.
The front bead portion 17a is prevented from being displaced. The outer peripheral portion of the support member 43 is sandwiched by the annular wall portion 2a of the front shell 2 and the opposing wall portion 4a of the center plate 4 in a state of being overlapped with the outer peripheral bead portion 11b of the front diaphragm 11. In addition, a plurality of through holes (not shown) are provided at required positions of the support member 43 so that negative pressure can be introduced from the first negative pressure introducing pipe 24 into the constant pressure chamber A. On the other hand, the rear bead portion 17b of the bellows 17 is fitted on the outer peripheral portion of the valve body 7 from the front side, and then is pressed to the annular recess 9a of the inner peripheral portion of the front power piston 9 to the outer peripheral portion of the valve body 7. An annular retainer 44 press-fitted from the front side is used to prevent the retainer from falling off. Further, in the central portion of the bellows 17 which is expanded and contracted in the axial direction, as shown in an enlarged view in FIG. 2, a valley portion 17c having a V-shaped cross-section located on the radially inner side is provided with a reinforcing member made of steel material. The rings 45 are respectively fitted. Further, a notch 17d having an arcuate cross-section in the circumferential direction is provided at the front and rear positions that are continuous from the valley portion 17c in which the ring 45 is fitted and are adjacent to each other. Further, notches 17e continuous in the circumferential direction are also provided at the positions on the back surface of each notch 17d, that is, at the side facing the internal space A ', and the valley portion on the bellows 17 on the radially outer side is provided. 17f
A notch 17g continuous in the circumferential direction is also provided in the inner peripheral portion of the. In addition, in the present embodiment, the thickness of each valley 17c, 17f is made thicker than the thickness of the intermediate portion connecting them, so that the notches 17d, 17e, 17g as described above are formed.
Even if the groove is provided, the durability of the valleys 17c and 17f does not decrease. As described above, in this embodiment, since the reinforcing ring 45 is provided in the central portion of the bellows 17, even if the entire bellows 17 is expanded when the atmosphere is introduced into the internal space A ′ of the bellows 17. The expansion of the bellows 17 can be effectively prevented by the reinforcing rings 45. Further, when the valve body 7 is advanced to the forward end position shown by the phantom line in FIG. 1, the bellows 1
7 is folded to the most contracted state in the axial direction. As shown in FIG. 3, at this time, the adjacent valleys 17c and 17f of the bellows 17 and their intermediate portions are superposed on each other. At this time, in this embodiment, since the notches 17d and 17e are provided at the positions adjacent to the ring 45 in each valley 17c, the rings 45 are housed in the notches 17d at the adjacent positions. Therefore, despite the provision of the ring 45, the axial dimension when the bellows 17 is folded does not increase. Therefore, the ring 45 is attached to the bellows 17.
It is not necessary to increase the volume of the constant pressure chamber A by providing the above, and the tandem brake booster does not increase in size.

As described above, according to the present invention, it is possible to effectively prevent the expansion of the bellows itself by the ring.

[Brief description of drawings]

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

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a cross-sectional view showing a different state of FIG.

[Explanation of symbols]

1 Shell 7 Valve Body 9 Front Power Piston 10 Rear Power Piston 16 Valve Mechanism 17 Bellows 17c Valley 23 First Constant Pressure Passage 27, 28 Variable Pressure Passage 45 Ring A, C Constant Pressure Chamber A'Bellows 17 Internal Space B, D Variable Pressure Chamber

Claims (1)

[Claims] 1. A valve body slidably provided in a shell, a power piston provided on the valve body, a constant pressure chamber and a variable pressure chamber formed before and after the power piston, and the constant pressure chamber formed on the valve body. And a valve mechanism for switching the fluid circuit, and a constant pressure passage for communicating the constant pressure chamber with the variable pressure chamber via the valve mechanism and the variable pressure passage; A bellows connecting to a passage and having a bellows whose front end is connected to a shell, capable of selectively supplying negative pressure or atmosphere to the inner space of the bellows, wherein the bellows has a V-shaped cross section. A brake booster characterized in that a reinforcing ring is provided at the position where