JP2001341634A - Brake booster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the controllability of a brake and increase the stability and reliability of braking by switching a booster without using the relative movement of a valve body to an input rod and the stroke of a valve body. SOLUTION: A valve mechanism 16 interlocked with a plunger 19 formed integral with an input rod 23 is installed in a valve body 8 provided in a power piston 5 for dividing the inside of a shell body 1 into a negative pressure chamber 6 and an operating pressure chamber 7, and an air passage 31 provided in the plunger 19 is allowed to communicate with an air chamber 32 around the valve body 8. The air chamber 32 is allowed to communicate with a pressure storing chamber 40 at the rear of the shell body 1 through a switching device 60, and an electromagnetic valve 62 in the switching device 60 is set normally on the atmospheric side. At the beginning of the operation, the valve leads the atmosphere into the operating pressure chamber 7 to act as a normal air pressure booster. Then the valve confirms with a pressure sensor 63 that the pressure in the operating pressure chamber 7 reaches a specified pressure, switches over the electromagnetic valve 62 to the pressure storage chamber 40 side by a command from a controller to lead compressed air into the operating pressure chamber 7 so as to provide a large boosted force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake booster used in a brake system of a vehicle or the like, and more particularly, to a differential pressure between a negative pressure and an atmospheric pressure and a differential pressure between a negative pressure and a compressed air pressure. And a brake booster capable of switching the booster in two stages.

[0002]

2. Description of the Related Art In general, a brake booster generally divides a shell body into a negative pressure chamber and a working pressure chamber by a power piston having a diaphragm, and a brake pedal in a valve body provided in the power piston. A valve mechanism for introducing air into the working pressure chamber in conjunction with an input rod extending from the valve, and generating a boosted thrust on the power piston by a differential pressure between the negative pressure chamber and the working pressure chamber. It has become. In such a general brake booster, there is a certain limit in the difference between the negative pressure and the atmospheric pressure. Therefore, in order to obtain a large boost, the power piston must be formed in a large size. Inevitably increases the size of the device.

[0003] In recent years, a brake booster has been developed to further increase the boost by allowing compressed air to be introduced into the working pressure chamber. For example, Japanese Patent Application Laid-Open No. 7-89429 discloses a brake booster. Communication between the atmosphere passage and the working pressure chamber
The valve mechanism that shuts off, the communication between the compressed air passage and the working pressure chamber
A brake booster in which a valve mechanism for shutting off is disposed in series in the axial direction, and the two valve mechanisms are sequentially operated by relative movement between a valve body and an input rod to be switchable in two stages, is described. Japanese Patent Laid-Open Publication No. Hei 8-58565 discloses a valve mechanism for connecting / disconnecting an air passage and a working pressure chamber within a valve body, and compressing the air passage from the atmosphere side by moving (stroke) the valve body. A brake booster that can be switched to the air side is described.

[0004]

However, according to the brake booster described in Japanese Patent Application Laid-Open No. 7-89429, since the relative movement between the valve body and the input rod is used, the pressure from the introduction of air to the compressed air is reduced. In order to switch to the introduction, the brake pedal must be depressed large and strongly, deterioration of brake operability is unavoidable, and further, there is no temporary boost during switching from atmospheric to compressed air There is a problem that the region exists and the braking becomes unstable. Further, according to the brake booster described in Japanese Patent Application Laid-Open No. 8-58565, the stroke of the valve body is used. For example, when the negative pressure supplied to the negative pressure chamber fluctuates, In the case where the system has failed, the introduction of compressed air becomes impossible, and there is a problem that reliability is further lacked.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to switch the boosting force without using the relative movement between the valve body and the input rod or the stroke of the valve body. It is an object of the present invention to provide a brake booster that enables the brake operation and the stability of braking and contributes to the improvement of reliability.

[0006]

According to the present invention, in order to solve the above-mentioned problems, the inside of a shell body is divided into a negative pressure chamber and a working pressure chamber by a power piston having a diaphragm, and a valve provided on the power piston. In the body, a valve mechanism that introduces air or compressed air into the working pressure chamber is disposed in conjunction with an input rod extending from a brake pedal, and switching between air and compressed air supplied to the valve mechanism is performed. The operation is performed according to the pressure in the working pressure chamber. In the brake booster configured as described above,
Since the pressure is switched from the atmosphere side to the compressed air side when the pressure in the working pressure chamber exceeds a predetermined pressure, the booster can be smoothly and reliably switched at an appropriate timing.

According to the present invention, a common air passage for supplying air or compressed air to a valve mechanism is provided in a valve body, and the air passage is connected to the atmosphere outside the valve body in accordance with the pressure in a working pressure chamber. It is possible to adopt a configuration in which a switching means for switching to the pressure accumulation tank connected to the compressed air source is provided. In this case, the switching means may be configured to operate electrically or mechanically. When the switching device is operated electrically, a solenoid valve for switching the air passage between the atmosphere side and the pressure accumulation tank side, a pressure sensor for detecting the pressure in the working pressure chamber, And a control device for controlling the electromagnetic valve based on a signal. Also, when this switching device is configured as a mechanical type, a piston that receives the atmospheric pressure and the pressure in the working pressure chamber at both ends, and the air passage can be switched between the atmosphere side and the pressure accumulation tank side according to the movement of the piston. Thus, a structure may be provided that always includes a valve mechanism that connects the air passage to the atmosphere.

In the present invention, the compressed air tank comprises:
The shell body may be provided integrally with the shell body on the back side thereof. In this case, when the mechanically operated switching device is used as the switching device, it is desirable to dispose the switching device in the compressed air tank. According to the present invention, the casing is surrounded by a casing around the valve body, the casing is formed as an annular air chamber communicating with an air passage in the valve body, and a switching means is connected to the air chamber. Can be.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 and FIG. 2 show a first embodiment of the present invention. In both figures, reference numeral 1 denotes a shell main body composed of a front shell 2 and a rear shell 3, and the inside thereof is divided into a negative pressure chamber 6 and a working pressure chamber 7 by a power piston 5 having a diaphragm 4. A valve body 8 is arranged on the axis of the shell main body 1. The valve body 8 has a large-diameter flange portion 9 at the front end thereof connected to the diaphragm 4 and the power piston 5. Small-diameter hollow shaft 1 following flange 11
Reference numeral 0 extends through the rear shell 3 to the rear of the shell main body 1. The hollow shaft 10 and the rear shell 3
Is sealed by a seal member 11.

The valve body 8 is provided with an axial negative pressure passage 12 for communicating the inside of the hollow shaft portion 10 with the negative pressure chamber 6, and also communicates the inside of the hollow shaft portion 10 with the working pressure chamber 7. A radial pressure change passage 13 is provided. A negative pressure source 15 such as an intake manifold of an engine is connected to the negative pressure chamber 6 through a negative pressure introducing pipe 14 connected to the front shell 2.
The negative pressure is introduced from, this negative pressure,
After being disposed in the valve body 8, it can be introduced into the working pressure chamber 7 through the negative pressure passage 12 and the air passage 13 by the operation of the valve mechanism 16 described in detail.

In the valve body 8, the front side member 1 is provided.
A plunger 19 which connects the rear member 7 and the rear member 18 is provided. Member 1 constituting plunger 19
7 and 18 are small-diameter shaft portions 1 provided on the front side member 17.
7a is press-fitted into a shaft hole 18a provided in the rear-side member 18 to be integrated.
0 is formed. The front side member 17 has a shaft hole 21 having a distal end provided in the flange portion 9 of the valve body 8.
On the other hand, the rear member 18 is slidably inserted into an annular guide member 22 fitted in the hollow shaft portion 10 of the valve body 8. An input rod 23 interlocking with a brake pedal (not shown) is connected to the rear end of the rear member 18, and the plunger 19 slides in the valve body 8 interlocking with the brake pedal. . The guide member 22 has its tip abutting on a step 10 a in the hollow shaft portion 10 to restrict the movement toward the front side, and also has a stopper pin 24 driven into the inside from the outer periphery of the hollow shaft portion 10. Movement (removal) to the rear side is regulated.

The valve mechanism 16 includes an annular negative pressure valve seat 25 formed on the inner peripheral surface of the valve body 8 so as to include an opening edge of the negative pressure passage 12, and a front member constituting the plunger 19. 17, an annular air valve seat 26 formed at the rear end, and a rear member 18 that constitutes the plunger 19.
Is slidably fitted to the front end of the annular recess 2.
0, the valve seats 25 and 26
And a poppet valve 28 which is biased in a direction to be seated. On the other hand, the guide member 22 and the input rod 2
A return spring 29 for applying a force in a return direction (right direction in the drawing) to the input rod 23 is interposed between the brake booster 3 and the input rod 23. When the brake booster is not operated, an input is performed by the return spring 29. The plunger 19 is urged in the return direction integrally with the rod 23, and the state where the air valve seat 26 contacts the poppet valve 28 is maintained.

Here, the front side member 17 and the rear side member 18 constituting the plunger 19 are attached to the rear side member 1.
An air passage 31 is formed at one end of the annular groove 30 formed on the outer periphery of 8 and at the bottom of the annular recess 20 between the members 17 and 18 at the other end. A guide member 22 for slidingly guiding the rear member 18 of the plunger 19 and the hollow shaft portion 10 of the valve body 8 are provided with an air passage 31 in the plunger 19 around the valve body 8 as described later. Radial holes 33, 34 are formed to communicate with the annular air chamber 32 of FIG. That is, inside the poppet valve 28 (primary side), air flows from the air chamber 32 around the valve body 8 through the valve body 8, the radial holes 34 and 33 of the guide member 22, and the air passage 31 in the plunger 19. It is being supplied. Thus, the negative pressure valve seat 25 and the annular portion near the outer diameter of the poppet valve 28 connect the negative pressure valve A to the air valve seat 2.
6 and the annular portion near the inner diameter of the poppet valve 28
The negative pressure or the air pressure is selectively introduced into the working pressure chamber 7 according to the opening of the negative pressure valve A and the air valve B.

On the other hand, an output rod 36 is connected to the front end of the valve body 8 via a rubber reaction disk 35.
Is operatively connected. The distal end of the output shaft 36 extends airtightly through the front shell 2 to the front of the shell main body 1, to which a master cylinder (not shown) is operatively connected. Also, the valve body 8
Is urged rearward by a return spring 37 disposed in the negative pressure chamber 6. Further, the plunger 19
An annular groove 38 is formed in the (front side member 17), and a distal end of a stop key 39 inserted into the variable pressure passage 13 from outside the valve body 8 is engaged with the annular groove 38. The base end of the stop key 39 can be brought into contact with the inner surface of the rear shell 3, and the valve body 8 and the plunger 19 are located at the positions where the stop key 39 comes into contact with the inner surface of the rear shell 3 as the retreating end. The stop key 39 has a slight play in the axial direction in the annular groove 38 of the plunger 19, and the plunger 19 can move relative to the valve body 8 within the range of the play.

An air chamber 32 around the valve body 8
Is a casing 41 that forms a pressure accumulation chamber (pressure accumulation tank) 40 on the rear side of the shell body 1 in cooperation with the rear shell 3.
Is formed in common. The casing 41 is integrated with the shell main body 1 by hermetically coupling the distal end of an outer cylindrical portion 42 having substantially the same diameter as the shell main body 1 to the outer peripheral edge of the rear shell 3. The casing 41 also has small-diameter cylindrical portions 43 and 44 extending at the center thereof on the front side and the rear side. The small-diameter cylindrical portions 43 and 44 are connected to the small-diameter portion of the rear shell 3 and the hollow shaft portion 10 of the valve body 8 via sealing members 45 and 46, respectively, so that the air chamber 32 and the pressure accumulating chamber 40 are sealed. It is partitioned as a room. In addition, a pipe joint 47 that connects the air chamber 32 and the pressure accumulating chamber 40 is mounted on the small-diameter cylindrical portion 43 on the front side. At the rear end of the small-diameter cylindrical portion 44 on the rear side, a dust boot 48 that covers the exposed portion and the opening of the hollow shaft portion 10 of the valve body 8 is mounted.

Here, a compressed air source 50 is connected to the accumulator 40 by an air pipe 51. The compressed air source 50 includes a compressor 52 connected to an end of the air pipe 51, an air dryer 53 provided in the middle of the air pipe 51, and two check valves 54 provided before and after the air dryer 53. , 55. A negative pressure pipe 56 extending from the negative pressure source 15 is connected between the two check valves 54 and 55 of the air pipe 51, and an electromagnetic valve 57 is provided in the middle of the negative pressure pipe 56. Is interposed. The solenoid valve 57 normally connects the air dryer 53 to the negative pressure source 1.
5 is maintained at a position communicating with the air dryer 5.
3, a negative pressure for drying is always introduced. When the compressor 52 operates, the solenoid valve 57 is connected to the air dryer 5.
The position where the pressure 3 and the negative pressure source 15 are shut off is maintained, whereby the compressed air generated by the compressor 52 is supplied to the pressure accumulating chamber 40 through the air pipe 51. The operation of the compressor 52 is controlled by control means (not shown).

On the other hand, the small-diameter cylindrical portion 43 of the casing 41
A switching device (switching means) 6
0 is connected by a communication pipe 61. The communication pipe 61
The leading end of the pressure accumulating chamber 40 bypasses the outside of the casing 41.
The switching device 60 is connected to the communication pipe 61.
Is provided with an electromagnetic valve 62 interposed therebetween. The switching device 60 further includes a pressure switch (pressure sensor) 63 for detecting the pressure in the working pressure chamber 7, and a control device 64 for controlling the electromagnetic valve 62 based on a signal from the pressure switch 63. . The electromagnetic valve 62 always maintains a position where the air chamber 32 communicates with the atmosphere side, whereby the atmosphere is always introduced into the air chamber 32. When the pressure in the working pressure chamber 7 detected by the pressure switch 63 exceeds a predetermined value (set value), the control device 64 outputs a switching signal to the solenoid valve 62, whereby the solenoid valve 62 and the air chamber 32 accumulate pressure. Room 40
And the air chamber 32 is connected to the pressure accumulating chamber 4.
The compressed air stored at 0 is supplied. In addition, this control device 64 is installed in the vehicle interior of the vehicle as an example,
The set value can be arbitrarily changed.

Hereinafter, the operation of the brake booster configured as described above will be described. The brake booster is mounted on a vehicle body using stud bolts 49 (FIG. 1) erected in a casing 41 forming the air chamber 32 and the pressure accumulating chamber 40. Is connected. In the non-operating state shown in FIGS. 1 and 2, the brake booster has a negative pressure in the negative pressure chamber 6 and the operating pressure chamber 7. When the brake pedal is depressed from this state, the input rod 23 , The plunger 19 moves to the front side, the air valve seat 26 is separated from the poppet valve 28, and the air valve B is opened. The air is supplied from the air chamber 32 to the primary side of the poppet valve 28 through the valve body 8, the radial holes 34 and 33 of the guide member 22, and the air passage 31 in the plunger 19. The atmosphere is introduced into the working pressure chamber 7 through the variable pressure passage 13 by the valve. As a result, a differential pressure is generated between the working pressure chamber 7 and the negative pressure chamber 6 in which the negative pressure is introduced, whereby the power piston 5 is propelled, and the thrust is applied to the valve body 8 and the output rod 36. The braking force is transmitted to a master cylinder (not shown) via the controller, and braking is started.

On the other hand, the output rod 36
Is transmitted to the input rod 23 via the reaction disk 35 and the plunger 19. When the magnitude of the reaction force from the output rod 36 generated by the advancement of the valve body 8 becomes equal to the magnitude of the pedaling force applied to the brake pedal, the air valve B is closed, and a constant boost (a booster output) is obtained. ) Is retained. From this state, the magnitude of the pedaling force applied to the brake pedal is increased or decreased, and when an imbalance occurs between the magnitude of the reaction force based on the differential pressure and the magnitude of the pedaling force applied to the brake pedal, the air valve B opens again or negative pressure valve A
Is opened in place of the air valve B, so that the magnitude of the reaction force based on the differential pressure is equal to the magnitude of the pedaling force applied to the brake pedal, between the negative pressure chamber 6 and the working pressure chamber 7. Is adjusted. Therefore, the magnitude of the pedaling force applied to the brake pedal is boosted at a predetermined boosting ratio,
The brake booster operates as a normal pneumatic booster.

When the brake pedal is further depressed, the pressure in the working pressure chamber 7 increases. When the pressure reaches a predetermined pressure, the solenoid valve 62 is operated by the command from the control device 64 in the switching device 60 to cause the pressure accumulating chamber 40 to move. Switch to the side. Thereby, the air chamber 32
Is supplied to the primary side of the poppet valve 28 through the air passage 31 and is introduced into the working pressure chamber 7 through the atmospheric valve B as it is. As a result, a large differential pressure is generated between the working pressure chamber 7 and the negative pressure chamber 6 in which the negative pressure is introduced, thereby generating a large thrust on the power piston 5 and further promoting braking.

Since the switching from the atmosphere to the compressed air is performed irrespective of the relative movement between the valve body 8 and the plunger 19, ie, the input rod 23, the switching is performed only by the pressure in the working pressure chamber 7, so that the brake is applied. There is no deterioration in operability or unstable braking. In addition, since it is performed independently of the stroke of the valve body 8, for example,
Even if the negative pressure supplied to the negative pressure chamber 6 fluctuates or the negative pressure system fails, the compressed air is reliably introduced into the working pressure chamber 7, greatly contributing to improvement in reliability. It will be. In particular, in the first embodiment, since the electromagnetic valve 62 is electrically controlled by a command from the control device 64 to switch from the atmosphere to the compressed air, for example, the brake operation speed, the brake operation force, the master It is also possible to change the set value set in the control device 64 by adding information such as the cylinder fluid pressure and the like, thereby improving the responsiveness at the time of emergency braking. In addition, accumulator (accumulator tank)
Since 40 is provided integrally with the rear shell 3 on the back side of the shell main body 1, the trouble of separately installing a pressure accumulation tank is not required, and the assembling property to the vehicle is improved. Also,
Since the annular air chamber 32 is provided around the valve body 8, it is easy to switch between the atmosphere and the compressed air to the common air passage 31 in the valve body 8 via the air chamber 32. Moreover, since the air chamber 32 and the pressure accumulating chamber 40 are formed by sharing one casing 41, there is a great cost advantage.

When the pedaling force from the brake pedal is lost, the plunger 19 is retracted by the spring force of the return spring 29, and the air valve seat 26 of the plunger 19 pushes the poppet valve 28 up from the negative pressure valve seat 25. Thereby, the negative pressure valve A
Is opened, the negative pressure in the negative pressure chamber 6 is introduced into the working pressure chamber 7 through the negative pressure passage 12 and the air pressure passage 13, and then the valve body 8 returns to the original position by the spring force of the return spring 37. Then, the poppet valve 28 is seated again on the two valve seats 25, 26.

FIGS. 3 and 4 show a second embodiment of the present invention. Since the overall configuration of the second embodiment is the same as that of the first embodiment, the same portions are denoted by the same reference numerals and the description thereof will be omitted. The feature of the second embodiment is that a mechanical switching device 70 is used instead of the electric switching device 60 in the first embodiment, and the switching device 70 It is located at the point.

The switching device 70 includes a cylinder body 71 extending between the rear shell 3 and the casing 41 in the axial direction of the valve body 8 and hermetically interposed therebetween. One end of the cylinder body 71 communicates with the working pressure chamber 7 through an opening 72 provided in the rear shell 3, and the other end communicates with the outside of the casing through an opening 73 provided in the casing 41. I have. The cylinder body 71 itself has two ports 74, 75 at different positions in the axial direction on the wall thereof. Of these ports, one of the ports 74 closer to the rear shell 3 side is provided in the pressure accumulating chamber 40. The other port 75, which is directly connected to the casing 41, is connected to the pipe 75 via a hose 77 which connects a pipe joint 76 attached to the port 75 to a pipe joint 47 provided in the small-diameter cylindrical portion 43. It communicates with the chamber 32.

In the cylinder body 71, from the rear shell 3 side to the casing 41 side, a piston 78,
A cup-shaped valve member 79, a cup-shaped guide member 80 and a filter 81 are arranged in this order. The piston 78 and the valve member 79 are integrated by pressing a part of the piston 78 into a cup portion of the valve member 79. Further, the piston 78 is slidably fitted to the cylinder body 71 via the seal member 82, and the valve member 79 is slidably fitted to the guide member 80 via the seal member 83. The piston 78 and the valve member 79 are Cylinder body 71
The inside slides integrally. The sliding diameter of the piston 78 (the diameter of the seal member 82) and the sliding diameter of the valve member 79 (the diameter of the seal member 83) are the same.
A space Sa having a predetermined size is formed between the piston 78 and the valve member 70, and the valve member 79 is formed in the space Sa.
And an axial hole 79 formed in the bottom of the guide member 80
The atmosphere is introduced through a and 80 a and the opening 73 of the casing 41. One end of the piston 78 is connected to the opening 72 provided in the rear shell 3 as described above.
Thus, the piston 78 is subjected to a differential pressure between the pressure in the working pressure chamber 7 and the atmospheric pressure. A spring 84 is interposed between the rear shell 3 and the piston 78.
The spring 8 is normally biased rearward by the spring 84.

A space Sa between the piston 78 and the valve member 79 is formed with a plurality of radial holes 79b formed in the peripheral wall of the valve member 79 to form an annular gap Sb around the valve member 79.
The annular space Sb is in communication with the air chamber 32.
Is open to a port 75. Thus, an annular valve seat 85 is provided on the inner periphery of the cylinder body 71 between the two ports 74 and 75, and a distal end of the valve member 79 is attached to and detached from the valve seat 85. Possible valve part 8
6 are provided. The valve seat 85 and the valve portion 86 are connected to a port (first port) 74 communicating with the pressure accumulating chamber 40 and the air chamber 3.
A compressed air valve C for shutting off communication with a port (second port) 75 communicating with the valve member 2 is formed. When the compressed air valve C is opened, compressed air flows from the annular gap Sb through the valve member 79.
Through the radial hole 79b provided in
Also flows into. On the other hand, in this empty space Sa, a check valve 87 is provided.
Is arranged. The check valve 87 allows the air to flow into the space Sa from the axial hole 79a of the valve member 79, but restricts the air from flowing from the space Sa to the axial hole 79a. As a result, when the compressed air valve C is opened and compressed air flows into the space Sa, the check valve 87 is closed.

In the second embodiment, when the brake booster is not operated, the pressure in the working pressure chamber 7 is a negative pressure. When the pressure is large, the piston 78 moves toward the front side (toward the rear shell 3) against the urging force of the spring 84, whereby the valve portion 86 of the valve member 79 is seated on the valve seat 85 and the compressed air valve C is opened. The valve is kept closed. Therefore, the brake pedal is depressed from this state, and the valve body 8
When the air valve B is opened, the atmosphere is opened from the opening 73 of the casing 41 through the filter 81, the guide member 80 and the axial holes 80a, 79a of the valve member 79, and opens the check valve 87 to enter the space Sa. Then, it flows into the air chamber 32 around the valve body 8 from the second port 75 of the cylinder body 71 via the hose 77. That is, the air is supplied to the primary side of the poppet valve 28 in the valve body 8, whereby the air is introduced into the working pressure chamber 7, and a pressure difference from the negative pressure chamber 6 into which the negative pressure is introduced is generated. Then, the power piston 5 is propelled to operate as a normal pneumatic booster.

On the other hand, when the pressure in the working pressure chamber 7 rises and reaches a predetermined pressure, the differential pressure acting on the piston 78 in the switching device 70 decreases, so that the piston 78 receives the urging force of the spring 84. Move to the rear side. Then, the valve member 79
The compressed air valve C is opened by separating the valve portion 86 from the valve seat 85, and the compressed air in the pressure accumulating chamber 40
From the port 74 through the annular gap Sb and the radial hole 79b of the valve member 79 into the space Sa therein, thereby closing the check valve 87. As a result, the compressed air flows from the second port 75 of the cylinder body 71 through the hose 77 into the air chamber 32 around the valve body 8. Therefore, in this case, the compressed air is supplied to the primary side of the poppet valve 28 and is introduced into the working pressure chamber 7 through the atmosphere valve B as it is, whereby the compressed air is supplied to the negative pressure chamber 6 where the negative pressure is introduced. , A large thrust is generated in the power piston 5.

In the second embodiment, as in the first embodiment, the switching from the atmosphere to the compressed air is performed according to the relative movement between the valve body 8 and the input rod 23 or the stroke of the valve body 8. Since it is performed irrelevantly, the same effects as those of the first embodiment, which contribute to the improvement of the brake operability and the braking stability and the reliability, can be obtained. Thus, in the second embodiment, the switching device 70 mechanically switches between the atmosphere and the compressed air by the movement of the piston 78 operated by the differential pressure between the working pressure chamber 7 and the atmosphere. This eliminates the need for wiring for connecting the control device 64 with the solenoid valve 62 and the pressure sensor 63 as in the switching device 60 in the first embodiment, and improves the reliability of the device accordingly. . In the second embodiment, the switching device 7
Since 0 is arranged in the accumulator 40, the overall structure is simpler than in the first embodiment, and the mountability on the vehicle is improved. In addition, in the first embodiment, when the switching device 60 is installed in the vehicle interior, the suction sound of the atmosphere is generated. In the second embodiment, however, such a suction sound is not generated. . Furthermore, since the sliding diameter of the piston 78 and the sliding diameter of the valve member 79 are the same, the sliding between the piston 78 and the valve member 79 is stabilized even when compressed air acts.

FIG. 5 shows a third embodiment of the present invention. The feature of the third embodiment is that the same mechanical switching device 90 is used instead of the switching device 70 in the second embodiment. The overall structure of the switching device 90 is the same as that of the switching device 70.
Therefore, here, the same parts as those shown in FIG. 4 are denoted by the same reference numerals.

The switching device 90 includes the cylinder body 71
From inside, the valve member 79 and the guide member 80 (FIG. 4) used in the second embodiment are omitted, the piston 78 is provided independently, and the piston 78 is provided with the check valve 87 and newly added. A support member 91 having a cylindrical portion 91a on the front end side (front side) is fitted via a seal member 92, and a double-structured poppet valve 93 can slide on the cylindrical portion 91a of the support member 91. It is fitted in. The piston 78 is provided with a radial hole 78a that opens on the back side of the check valve 87, and the support member 91 has an opening 73 of the casing 41.
Is provided with an axial hole 91b that communicates with the shaft.

In the switching device 90, the cylinder body 7
The first port 74 and the second port 7 provided on the first wall
5 is set by reversing the axial position of the second embodiment. The compressed air valve C is formed by the annular valve seat 85 provided on the inner surface of the cylinder body 71 and an annular portion near the outer diameter of the poppet valve 93, while the rear end of the piston 78 is provided at the rear end of the piston 78. Is provided with an annular valve seat 94 forming an atmospheric valve D between the poppet valve 93 and an annular portion near the inner diameter of the poppet valve 93. Thus, the poppet valve 93 is normally urged by the valve spring 95 whose one end is locked to the front end of the support member 91 in a direction in which the poppet valve 93 is seated on the compressed air valve seat 85. The valve is kept closed. On the other hand, the atmospheric valve D is kept open when the piston 78 is displaced toward the rear shell 3.

In the third embodiment, when the brake booster is not operated, the pressure in the working pressure chamber 7 is a negative pressure. When the pressure is large, the piston 78 moves to the front side against the urging force of the spring 84, thereby
8, the valve seat 94 is separated from the poppet valve 93,
The atmosphere valve D maintains the open state. Accordingly, when the brake pedal is depressed from this state and the air valve B in the valve body 8 is opened, the atmosphere flows from the opening 73 of the casing 41 through the filter 81 and the axial hole 91 of the support member 91.
a, the air flows into the air chamber 32 around the valve body 8 through the atmosphere valve D, and further from the second port 75 of the cylinder body 71 through the hose 77. That is, the air is supplied to the primary side of the poppet valve 28 in the valve body 8, whereby the air is introduced into the working pressure chamber 7, and a pressure difference from the negative pressure chamber 6 into which the negative pressure is introduced is generated. Then, the power piston 5 is propelled to operate as a normal pneumatic booster.

On the other hand, when the pressure in the working pressure chamber 7 rises and reaches a predetermined pressure, the differential pressure acting on the piston 78 in the switching device 90 becomes smaller, so that the piston 78 receives the urging force of the spring 84. Move to the rear side. Then, piston 7
The valve seat 94 of No. 8 contacts the poppet valve 93 to close the atmosphere valve D, and at the same time, the check valve 87 opens, and the atmosphere flows out of the radial hole 78 a of the piston 78 to the second port 75, The introduction of the atmosphere into the working pressure chamber 7 is continued. Then, when the pressure in the working pressure chamber 7 further increases, the piston 78 moves further rearward, the poppet valve 93 is lifted, and the compressed air valve C opens. At this time, the poppet valve 93
Is a double structure of the cylindrical portion 91a of the support member 91.
Since it slides in contact with both outer surfaces, it can be lifted smoothly even if compressed air acts. As a result, the compressed air in the accumulator 40 passes from the first port 74 of the cylinder body 71 through the compressed air valve C, the radial hole 78a of the piston 78, and the second air.
From the port 75 through the hose 77 into the air chamber 32 around the valve body 8. So, in this case,
The compressed air is supplied to the primary side of the poppet valve 28 and is introduced into the working pressure chamber 7 through the atmospheric valve B as it is, and a large pressure difference is generated between the compressed pressure chamber 6 and the negative pressure chamber 6. Occurs. Thus, the third embodiment also has the same effect as the second embodiment.

[0035]

As described above in detail, according to the brake booster of the present invention, boosting can be performed without using the relative movement between the valve body and the input rod or the stroke of the valve body. Since switching is possible, there is an effect that greatly contributes to improvement in brake operability and braking stability and reliability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an overall structure of a brake booster according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a main part of the brake booster shown in FIG.

FIG. 3 is a sectional view showing the overall structure of a brake booster according to a second embodiment of the present invention.

FIG. 4 is an enlarged sectional view showing a main part of the brake booster shown in FIG. 3;

FIG. 5 is a cross-sectional view showing a main structure of a brake booster according to a second embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 shell main body, 4 diaphragm, 5 power piston 6 negative pressure chamber, 7 operating pressure chamber 8 valve body, 16 valve mechanism, 19 plunger 31 air passage, 32 air chamber 40 pressure accumulation chamber, 50 compressed air source 60 switching device, 62 electromagnetic Valve, 63 pressure sensor, 64 control device 70 switching device, 78 piston 90 switching device, 93 poppet valve A negative pressure valve (valve mechanism 16), B air valve (valve mechanism 1)
6) C compressed air valve (switching device 70, 90) D atmospheric valve (switching device 90)

Continued on the front page (72) Inventor Shuzo Watanabe Nakakoma-gun, Yamanashi Prefecture ▲ 1000, Yoshida, Kata-machi, Tokiko Co., Ltd.Yamanashi Plant 3D048 BB07 BB21 BB33 CC33 EE02 EE10 HH04 HH06 HH27 HH37 HH38 HH66 RR06

Claims (7)

[Claims] 1. The interior of a shell body is divided into a negative pressure chamber and a working pressure chamber by a power piston having a diaphragm, and is interlocked with an input rod extending from a brake pedal in a valve body provided in the power piston. A valve mechanism for introducing air or compressed air into the working pressure chamber, and switching between air and compressed air supplied to the valve mechanism is performed according to the pressure in the working pressure chamber. Features a brake booster. 2. A common air passage for supplying air or compressed air to a valve mechanism is provided in the valve body, and the air passage is connected to the atmosphere side and the compressed air outside the valve body according to a pressure in a working pressure chamber. 2. A brake booster according to claim 1, further comprising switching means for switching between a pressure accumulating tank connected to the power source and the pressure accumulating tank. 3. The brake booster according to claim 2, wherein the pressure accumulating tank is provided integrally with the shell main body on the back side of the shell main body. A switching means for switching an air passage between an atmosphere side and a pressure storage tank side; a pressure sensor for detecting a pressure in the working pressure chamber; and a solenoid valve based on a signal from the pressure sensor. The brake booster according to claim 2 or 3, further comprising a control device for controlling, and operating electrically. 5. A switching means for switching between an air passage and an accumulator tank in accordance with the movement of the piston.
The brake booster according to claim 2 or 3, further comprising a valve mechanism that normally connects the air passage to the atmosphere side, and operates mechanically. 6. The brake booster according to claim 5, wherein switching means is provided in the pressure accumulating tank. 7. The valve body is surrounded by a casing, the casing is formed as an annular air chamber communicating with an air passage in the valve body, and a switching means is connected to the air chamber. The brake booster according to any one of claims 2 to 6.