JPH04339066A - Tandem brake boost apparatus - Google Patents

Abstract

PURPOSE:To prevent lowering of output of a tandem brake boost apparatus functioned as an automatic brake device. CONSTITUTION:On condition that a tandem brake boost apparatus is formed as well-known heretofore, a bellows 35 is disposed in the front side constant pressure chamber A, and one end of the bellows 35 is connected to the end portions of both constant pressure passages 21, 23. The other end of the bellows 35 is communicated with a negative pressure source through the second negative pressure introduction pipe 36, and a solenoid valve 40 for communicating the interior of the bellows 35 with the air at need is disposed in the second negative pressure introduction pipe 36. Thus, even if a brake pedal is not stepped, a solenoid valve 37 is operated to operate a tandem brake boost apparatus, thereby obtaining a function as an automatic brake. At that time, as a valve 41 is disposed in one second constant pressure passage 23 in this invention, the air introduced in the bellows 35 is checked from entering the rear side constant pressure chamber C through the second constant pressure passage 23, so that it is possible to prevent lowering of output of the tandem brake boost apparatus when it is functioned as an automatic brake.

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 the function of an automatic braking device.

2. Description of the Related Art Conventionally, a brake booster having the function of an automatic braking device is known from Japanese Patent Laid-Open No. 1-127446. This Japanese Patent Publication No. 1-12744
The brake booster disclosed in Publication No. 6 is based on the configuration of a conventionally known single type brake booster, and is provided with a bellows in a negative pressure chamber within the shell. This bellows connects the fluid passage provided in the valve body and the fluid passage provided in the shell, and by switching the solenoid valve provided in the fluid passage on the shell side, atmospheric pressure and negative pressure are removed within the bellows. It is possible to introduce it selectively. In a normal state in which the solenoid valve is not operated, negative pressure is introduced into the bellows, so in this state it can perform exactly the same function as a conventionally known brake booster. In response, when the solenoid valve is activated and atmospheric air is introduced into the bellows,
Atmospheric air is introduced to the variable pressure chamber via the fluid passage on the valve body side. Therefore, when the solenoid valve is operated in this way, the brake booster is operated even if the input shaft is not moved forward, and the brake booster functions as an automatic braking device.

[Problems to be Solved by the Invention] In recent years, there has been a desire to increase the output of brake boosters, so tandem type brake boosters are often installed on vehicles. There are cases where a tandem brake booster with the function of an automatic braking device is desired. In that case, if the technology of the brake booster disclosed in JP-A-1-127446 is applied to the tandem brake booster, the tandem brake booster can function as an automatic brake device. it is obvious. That is, most simply, the bellows or solenoid valve disclosed in the above-mentioned Japanese Patent Laid-Open No. 1-127446 may be provided in the constant pressure chamber on the front side of the tandem brake booster. However, in the case of the configuration shown in FIG. 2 of the above-mentioned Japanese Patent Application Laid-Open No. 1-127446, when the solenoid valve is operated to introduce atmospheric air into the bellows in the constant pressure chamber on the front side, the constant pressure on the front side is This results in part of the atmosphere introduced into the bellows being introduced into the rear constant pressure chamber via the constant pressure passage that communicates the chamber with the rear constant pressure chamber. Therefore, since no differential pressure is generated between the constant pressure chamber and the variable pressure chamber on the rear side, there is a drawback that the output when the tandem brake booster functions as an automatic brake is reduced. Furthermore, in the case of a configuration as shown in FIG. 3 of the above-mentioned Japanese Patent Application Laid-Open No. 1-127446, an attempt is made to connect a bellows having a flow path area sufficient to maintain responsiveness to the first constant pressure passage of the valve body. This has the disadvantage that the structure becomes complicated and the outer diameter of the valve body increases, which reduces the effective area of the power piston and reduces the output of the tandem brake booster. In view of the above-mentioned circumstances, an object of the present invention is to provide a tandem brake booster whose output does not decrease even when it functions as an automatic brake.

[Means for Solving the Problems] That is, the present invention provides a center plate that divides the inside of the shell into a front chamber and a rear chamber, a valve body that is slidably penetrated through the center plate, and a valve body that is located in the front chamber. a front power piston connected to the valve body located in the rear compartment; a rear power piston connected to the valve body located in the rear compartment; a front diaphragm that extends over the back of the rear power piston and divides the rear chamber into a constant pressure chamber and a variable pressure chamber; a first constant pressure passage that communicates both of the constant pressure chambers with both of the variable pressure chambers through a valve mechanism that opens to the valve body and switches the fluid circuit; In a tandem brake booster equipped with a second constant pressure passage whose front end opens into the constant pressure chamber of the front chamber, one end of the flexible conduit is connected to both of the constant pressure passages, and the other end is connected to the two constant pressure passages. A switching valve is provided in the conduit that is drawn out from the shell and selectively connects the conduit to a negative pressure source or the atmosphere, and the second constant pressure passage is provided with a switching valve that connects the conduit from the internal space of the conduit to the constant pressure chamber of the rear chamber. The present invention provides a tandem brake booster characterized in that it is provided with a check valve that prevents atmospheric air from entering the vehicle.

[Operation] According to such a configuration, when the atmosphere is introduced into the conduit by the switching valve, the atmosphere introduced into the conduit passes through the first constant pressure passage and the valve mechanism to both of the variable pressure chambers. will be introduced in Therefore, in that case, the tandem brake booster can be operated even if the brake pedal is not depressed. At this time, in the present invention, since a check valve is provided in the second constant pressure passage, the atmosphere introduced into the conduit is prevented from entering the constant pressure chamber side of the rear chamber via the second constant pressure passage. be done. Therefore, the air introduced into the conduit is efficiently introduced into both variable pressure chambers, which prevents a decrease in the output of the tandem brake booster when the tandem brake booster functions as an automatic braking device. be able to.

[Embodiment] The present invention will be explained below with reference to the illustrated embodiment. In FIG. 1, the inside of a sealed container composed of a front shell 1 and a rear shell 2 is connected to front and rear front chambers 4 by a center plate 3 provided at the center thereof. Rear compartment 5 and 2
A generally cylindrical valve body 6 is slidably passed through the shaft portions of the rear shell 2 and center plate 3 while maintaining airtightness by annular sealing means 7 and 8, respectively. A front power piston 9 and a rear power piston 10 housed in the front chamber 4 and rear chamber 5 are connected to the valve body 6, respectively, and a front diaphragm 11 and a rear diaphragm 12 are connected to the rear surface of each power piston 9, 10. A constant pressure chamber A and a variable pressure chamber B are formed before and after the front diaphragm 11, and a constant pressure chamber C and a variable pressure chamber D are formed before and after the rear diaphragm 12, respectively. Bellows 35 described later
In the state where the above two constant pressure chambers A, C and 2 are not provided,
A valve mechanism 15 for switching the fluid circuit between the two pressure change chambers B and D is provided within the valve body 6.
5 is an annular first valve seat 16 formed on the valve body 6, and an annular first valve seat 16 formed on the right end of a valve plunger 17 slidably provided on the valve body 6 inside the annular first valve seat 16. The second valve seat 18 and both valve seats 16, 18
The valve body 20 is seated by a spring 19 from the right side in FIG.
It is equipped with A space on the outer peripheral side of the annular seat portion where the first valve seat 16 and the valve body 20 contact is communicated with the constant pressure chamber A via a first constant pressure passage 21 formed in the valve body 6 in the axial direction. There is. The constant pressure chamber A communicates with a negative pressure source via a negative pressure introduction pipe 22 attached to the front shell 1, so that negative pressure is constantly introduced into the constant pressure chamber A. Further, the constant pressure chamber A is always in communication with the constant pressure chamber C via a second constant pressure passage 23 formed in the valve body 6 in the axial direction. On the other hand, a portion on the inner circumference side of the annular seat portion where the first valve seat 16 and the valve body 20 contact, and an outer circumference side of the annular seat portion where the second valve seat 18 and the valve body 20 contact; That is, the space between the inner and outer annular seat portions is communicated with the variable pressure chamber D via the variable pressure passage 24 in the radial direction formed in the valve body 6, and further communicates the variable pressure chamber D with another axial direction formed in the valve body 6. It is communicated with the variable pressure chamber B via the variable pressure passage 25. Further, a space on the inner peripheral side of the inner annular seat portion where the second valve seat 18 and the valve body 20 contact is communicated with the atmosphere via a filter 26. Valve plunger 1 slidably provided on the valve body 6
The right end of the push rod 7 is connected to an input shaft 27 that is linked to a brake pedal (not shown), and the left end of the push rod 7 is connected to the right end surface of a reaction disc 29 housed in a recess 28a formed at the base of the push rod 28. ing. The left end of the push rod 28 is connected to the front shell 1.
It is linked to a piston of a master cylinder (not shown) through an opening 1a in the shaft portion. A seal member 30 maintains airtightness between the opening 1a and the push rod 28. Further, since a return spring 31 is elastically mounted between the valve body 6 and the front shell 1, the valve body 6 is normally held at the non-operating position shown in the figure. In this non-operating state, the second valve seat 18 is seated on the valve body 20, but a slight gap is maintained between the first valve seat 16 and the valve body 20. The configuration and operation of the tandem brake booster described above are basically the same as those of conventionally known tandem brake boosters. However, in this embodiment, a bellows 35 is attached across the reinforcing plate 34 attached to the inner wall of the front shell 1 and the outer periphery of the front end of the valve body 6, and a second bellows 35 is attached at one end to the reinforcing plate 34. The internal space A' of the bellows 35 is communicated with a negative pressure source through the negative pressure introduction pipe 36. That is, the rear end of the bellows 35 is pressed into the annular recess 9a formed on the inner peripheral edge of the front power piston 9, and then the retainer 37 attached to the outer peripheral part of the valve body 6 from the front side is inserted into the annular recess. 9a, thereby maintaining airtightness between the rear end of the bellows 35 and the annular recess 9a. On the other hand, the front end of the bellows 35 is folded inward toward a U-shape, and the retainer 38 is attached to the folded part.
The outer circumferential cylindrical portion 3 of the reinforcing plate 34 is held in a state where the outer circumferential edge of the reinforcing plate 34 is sandwiched.
4a. This maintains airtightness between the outer circumferential cylindrical portion 34a of the reinforcing plate 34 and the front end of the bellows 35. The inner peripheral portion of the retainer 38 is fitted onto the shaft portion of the front shell 1, and an O-ring 39 maintains airtightness between the front shell 1 and the reinforcing plate 34. In addition, the constant pressure chamber A outside the bellows 35
is in communication with the negative pressure source through a negative pressure introduction pipe 22 attached to the front shell 1, so that negative pressure is constantly introduced into the constant pressure chamber A. Further, a solenoid valve 40 is provided between the second negative pressure introduction pipe 36 and the negative pressure source to selectively communicate the negative pressure introduction pipe 36 with the atmosphere and the negative pressure source. This solenoid valve 40 is
It is controlled ON-OFF by a controller (not shown), and in a normal state in which it is not in operation, the second negative pressure introduction pipe 36 is communicated with the negative pressure source. Therefore, at that time, negative pressure is introduced into the internal space A' of the bellows 35 via the negative pressure introduction pipe 36. On the other hand, when the solenoid valve 40 is operated by the controller at a required time, the second negative pressure introduction pipe 36 is communicated with the atmosphere, and the atmosphere is introduced into the internal space A' of the bellows 35. There is. Therefore, by operating the solenoid valve 40 from the non-operating state of the tandem brake booster shown in FIG. It becomes possible to do so. Particularly, in this embodiment, a check valve 41 is provided in the second constant pressure passage 23, whereby the solenoid valve 40 is operated and the internal space A' of the bellows 35 is activated.
When the atmosphere is introduced into the bellows 35, the internal space A of the bellows 35
The atmosphere is prevented from entering from the internal space A' of the bellows 35 toward the constant pressure chamber C of the rear chamber 5. That is, the valve body 42 of the check valve 41 is made of rubber and has a V-shaped cross section, and on the other hand, the front end of the second constant pressure passage 23 has a valve body 42 that overlaps the front end of the second constant pressure passage 23. A recessed portion 6a is formed. The valve body 42 is
The bifurcated portion is positioned on the front side, and the other end is brought into contact with the recess 6a to fit into the recess 6a. Although not shown, the shape of the recess 6a when viewed from the front side is rectangular, and accordingly, the shape of the valve body 42 when viewed from the front side is also rectangular. Therefore, when the valve body 42 is attached to the recess 6a as described above, the tip of the bifurcated portion of the valve body 42 comes into pressure contact with both the upper and lower surfaces of the recess 6a, and at the same time, both sides of the valve body 42 (not shown) are also attached to the recess 6a. Pressed on both sides. The check valve 41 configured as described above prevents the atmosphere from entering from the internal space A' of the bellows 35 toward the constant pressure chamber C of the rear chamber 5, and at the same time prevents the air from entering the constant pressure chamber C of the rear chamber 5.
Negative pressure is allowed to be introduced from the internal space A' of the rear chamber 5 toward the constant pressure chamber C of the rear chamber 5. According to the above configuration, when the solenoid valve 40 is operated by the controller from a non-operating state in which the input shaft 27 is not advanced, the atmosphere is introduced into the internal space A' of the bellows 35, so that the tandem brake booster is activated. When activated, it can function as an automatic braking device. At this time, in this embodiment, since the check valve 41 is provided in the second constant pressure passage 23, the atmosphere flows from the internal space A' of the bellows 35 to the constant pressure chamber C on the rear side via the second constant pressure passage 23. Intrusion is prevented. Therefore, the internal space A' of the bellows 35
The atmospheric air introduced into the chambers B and D will be efficiently introduced into both the variable pressure chambers B and D. Note that even in a configuration in which the check valve 41 is omitted, the tandem brake booster can function as an automatic brake device, but in that case, the atmospheric air introduced into the internal space A' of the bellows 35 is Since a portion of the fuel enters the rear constant pressure chamber C through the second constant pressure passage 23, the output of the tandem brake booster decreases. In contrast, in this embodiment, by providing the check valve 41, the internal space A of the bellows 35 is
Since atmospheric air is prevented from entering from ' to the constant pressure chamber C on the rear side, it is possible to effectively prevent the output of the tandem brake booster from decreasing when it is used as an automatic braking device. . FIG. 2 shows the second constant pressure passage 12
3 shows a second embodiment of the check valve 141 provided in No. 3. In this second embodiment, the recess 106 of the constant pressure passage 123
The cross-sectional shape of the recess 106a is circular, the bottom of the recess 106a completely surrounds the constant pressure passage 123, and a step is formed in the axial center of the recess 106a. On the other hand, the valve body 142 is formed in a poppet shape, and after the valve body 142 is housed in the recess 106a, an annular retainer 150 is fitted into the stepped portion of the recess 106a. Retainer 150 and valve body 142
Since a spring 151 is loaded between the valve body 142 and
The valve seat is in pressure contact with the bottom of the recess 106a to form the constant pressure passage 123.
is closed, and at the same time, the distal end of the valve body 142 passes through the retainer 150. The check valve 141 of the second embodiment having such a configuration can also provide the same operation and effect as the check valve 41 shown in FIG. 1 above. It should be noted that each member shown in FIG. 2 is given a member number with 100 added to the member corresponding to that shown in FIG. 1 above. FIG. 3 shows a third embodiment of the check valve 241. In the check valve 241 shown in FIG. 3, based on the structure of the check valve 141 shown in FIG. The bottom of 206a is formed into an arc shape. The other configuration is the same as the configuration shown in FIG. The check valve 241 of the third embodiment having such a configuration can also provide the same operation and effect as the check valve shown in FIGS. 1 and 2 above. Each member shown in FIG. 3 is given a member number obtained by adding 100 to the member corresponding to that in FIG. 2 above.

As described above, according to the present invention, it is possible to prevent a decrease in the output of the tandem brake booster when the tandem brake booster functions as an automatic braking device. It will be done.

[Brief explanation of drawings]

[Fig. 1] Cross-sectional view showing one embodiment of the present invention

[Fig. 2] A sectional view showing another embodiment of the main part in Fig. 1.

[Fig. 3] A sectional view showing another embodiment of the main part in Fig. 1.

[Explanation of symbols]

23 Second constant pressure passage 35 Bellows 36 Second negative pressure introduction pipe 40 Solenoid valve 41 Check valve

Claims (1)

[Claims] 1. A center plate that divides the interior of the 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 the valve body located in the rear compartment, a front diaphragm stretched over the back of the front power piston and dividing the front compartment into a constant pressure chamber and a variable pressure chamber, and the back of the rear power piston. a rear diaphragm stretched across the rear diaphragm to partition the rear chamber into a constant pressure chamber and a variable pressure chamber, and a valve mechanism formed in the valve body whose front end opens into the constant pressure chamber of the front chamber and switches the fluid circuit. a first constant pressure passage that communicates both of the constant pressure chambers with both of the variable pressure chambers, and a first constant pressure passage that is formed in the valve body and communicates between the two constant pressure chambers, and whose front end portion communicates with the constant pressure of the front chamber. In a tandem brake booster equipped with a second constant pressure passage opening into the chamber, one end of a flexible conduit is connected to both of the constant pressure passages, the other end is pulled out to the outside of the shell, and the other end is connected to the conduit. A switching valve is provided to selectively connect the conduit to a negative pressure source or the atmosphere, and further prevents atmospheric air from entering the second constant pressure passage from the internal space of the conduit toward the constant pressure chamber of the rear chamber. A tandem brake booster characterized by being equipped with a check valve.