JPH0379216B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a safety device for a positive pressure brake booster that supplies positive pressure such as compressed air to a variable pressure chamber of the brake booster.

[Prior art]

Conventionally, as a brake booster, positive pressure is supplied to the variable pressure chamber of the brake booster, and negative pressure is supplied to the constant pressure chamber.
There are known devices in which a power piston is actuated by the differential pressure between the positive pressure and the negative pressure (for example, JP-A-56-167547 and JP-A-49-113077). In this type of brake booster, the pressure difference between the positive pressure and negative pressure can be made much larger than the pressure difference between normal atmosphere and negative pressure, so the power piston is made with a small diameter. There is an advantage that a large boost ratio can be obtained without increasing the size of the brake booster.

[Problem to be solved by the invention]

However, in this type of brake booster,
In the unlikely event that the passage supplying positive pressure to the valve mechanism is damaged, if the damaged part is in communication with the atmosphere, the positive pressure will escape from the damaged part to the atmosphere, so positive pressure will not be supplied to the transformer chamber. Although it will not be possible to supply
Since the atmosphere is introduced from the damaged area and supplied to the variable pressure chamber, the positive pressure brake booster functions in the same way as a normal negative pressure brake booster. However, if the damaged part is, for example, in the constant pressure chamber of the brake booster and the communication part with the negative pressure introduced into this,
Since not only positive pressure but also atmospheric pressure is no longer introduced into the variable pressure chamber, the function as a brake booster is lost. Furthermore, if the passage supplying the positive pressure becomes clogged, or if the compressor that is the source of the positive pressure breaks down, the brake booster will similarly lose its function.

In view of such circumstances, the present invention reliably supplies atmospheric air to the variable pressure chamber even if the passage supplying positive pressure to the valve mechanism is damaged or clogged, or even if the compressor malfunctions. The present invention provides a safety device for a positive pressure brake booster that can be supplied with a positive pressure brake booster.

[Means to solve the problem]

That is, the present invention includes a power piston slidably disposed in a shell, a valve mechanism housed in a valve body of the power piston shaft, and a valve mechanism formed on the front side of the power piston in the operating direction, so that negative pressure is constantly maintained. The constant pressure chamber to be introduced, the variable pressure chamber formed on the rear side of the power piston in the operating direction and supplied with positive pressure, the fluid pressure source outside the shell and the supply passage formed in the valve body are communicated, and the fluid pressure is increased. a conduit that supplies positive pressure from a source to the valve mechanism; the valve mechanism is actuated to switch the flow path, and the positive pressure supplied to the supply passage is supplied to the variable pressure chamber to advance the power piston; In a positive pressure brake booster comprising an input shaft, an atmospheric passage is provided for supplying atmospheric pressure to the valve mechanism, and when positive pressure is introduced into the supply passage, the supply passage is opened and the atmospheric passage is shut off, A control valve is provided that opens the atmospheric passage and shuts off the supply passage when positive pressure is not introduced into the supply passage.

[Effect]

According to the above configuration, when positive pressure is introduced into the supply passage, the control valve opens the supply passage and blocks the atmospheric passage, so that the positive pressure can operate the brake booster. On the other hand, when positive pressure is not introduced into the supply passage, the control valve opens the atmospheric passage and shuts off the supply passage, so that the brake booster can be operated by atmospheric pressure.

〔Example〕

The present invention will be described below with reference to the illustrated embodiments.
In FIG. 1, a power piston 2 is slidably provided in a shell 1 of a brake booster, and a diaphragm 3 is stretched on the back surface of the power piston 2. The interior of the shell 1 is divided into a constant pressure chamber 4 at the front and a variable pressure chamber 5 at the rear. A valve body 6 is integrally provided on the shaft portion of the power piston 2, and a valve mechanism 7 for switching the flow path is housed within the valve body 6.

The valve mechanism 7 has a first valve formed in the valve body 6.
A valve seat 10, a second valve seat 12 formed on the valve plunger 11, and a power piston 2 on both valve seats 10, 12.
The valve body 14 is provided with a valve body 14 that is seated from the front side, that is, from the left side in FIG. Holder 1 that forms part of
It is sealed by a sealing member 16 provided at 5. The outside of the seat portion between the first valve seat 10 and the valve body 14 is communicated with a supply passage 17 formed in the valve body 6, and this supply passage 17 is a flexible spiral conduit connected to the valve body 6. 18, a connector 19 attached to the shell 1 and an external conduit 20 communicate with a fluid pressure source such as a compressed air tank (not shown).

On the other hand, the inside of the seat portion between the second valve seat 12 and the valve body 14 is connected to the constant pressure chamber 4 through a radial passage 21 and an axial passage 22 formed in the valve body 6.
This constant pressure chamber 4 is communicated with a negative pressure source such as an engine intake manifold through a negative pressure introduction hole 23 provided in the shell 1. Furthermore, the first valve seat 10, the valve body 14, and the second valve seat 12
An intermediate portion of each seal portion between the valve body 6 and the valve body 14 communicates with the variable pressure chamber 5 via a radial passage 24 provided in the valve body 6. In addition, this transformation chamber 5 is
A seal member 25 slidably penetrates the valve body 6 to maintain airtightness from the outside.

The valve plunger 11 constituting the valve mechanism 7 is connected to an input shaft 30 that is linked to a brake pedal (not shown).
The distal end surface of the valve plunger 11 faces a reaction disk 32 housed in a recess formed at the base of the output shaft 31. The output shaft 31 passes through the seal member 33 and projects to the outside of the shell 1, and is linked to a piston of a master cylinder (not shown).

In addition, the above power piston 2 and valve body 6
etc. are normally held in the non-operating position shown in the figure by a return spring 34, and in this non-operating state, the key member 35 that prevents the valve plunger 11 from being pulled out from the valve body 6 is attached to the inner surface of the shell 1. The valve plunger 11 is brought into contact with the valve body 6 to restrict the free movement of the valve plunger 11 to the right, so that when the input shaft 30 and the valve plunger 11 are next operated, the valve mechanism 7 can immediately switch the fluid circuit. ing. Furthermore, in this example,
The valve body 6 is provided with a relief valve 36 that releases positive pressure in the variable pressure chamber 5 to the constant pressure chamber 4 when the pressure in the variable pressure chamber 5 exceeds a predetermined value.

Furthermore, in this embodiment, the valve body 6 includes:
An atmospheric passage 40 is formed, one end of which communicates with the supply passage 17 outside the seat portion of the first valve seat 10 and the valve body 14, and the other end of this atmospheric passage 40 is provided in the valve body 6. It is communicated with the atmosphere through a filter 41. A check valve 42 that allows positive pressure to flow from the fluid pressure source to the valve mechanism 7 is provided in the supply passage 17, and a check valve that allows the atmosphere to flow from the atmosphere to the valve mechanism 7 is provided in the atmosphere passage 40. There are 43.

In the above configuration, in a normal state where the passages for supplying positive pressure such as the external conduit 20 and the conduit 18 are not damaged, the positive pressure from the fluid pressure source is transferred to the external conduit 20, the connector 19, the spiral conduit, etc. 18,
and is introduced into the supply passage 17 via the check valve 42. In this state, the positive pressure supplied from the supply passage 17 into the atmosphere passage 40 closes the check valve 43 due to the pressure difference with the atmosphere, so that the atmosphere is not supplied to the valve mechanism 7. .

In this state, the brake pedal (not shown) is depressed and the input shaft 30 and valve plunger 1
1 is moved to the left, the second valve seat 12 of the valve plunger 11 seats on the valve body 14 and the radial passages 21 and 2
At the same time, the valve body 14 is removed from the first valve seat 10 and the supply passage 17 and the variable pressure chamber 5 are communicated with each other. As a result, the positive pressure introduced into the supply passage 17 is supplied into the variable pressure chamber 5,
Similar to a conventionally known brake booster, the power piston 2 is moved forward against the elastic force of the return spring 34 due to the pressure difference before and after the power piston 2 .

When the force on the brake pedal is released from this brake operating state, the valve body 14 of the valve mechanism 7 seats on the first valve seat 10 and cuts off communication between the variable pressure chamber 5 and the supply passage 17. 12 and communicates the variable pressure chamber 5 with the constant pressure chamber 4, the power piston 2 is returned to its original non-operating position by the return spring 34.

When the key member 35 comes into contact with the shell 1 due to the retraction of the power piston 2, the retraction of the valve plunger 11 that is linked to this stops, but the retraction of the power piston 2 and the valve body 6 continues, and the valve body 6 When the second valve seat 12 of the valve plunger 11 approaches the valve body 14 due to the retreat and the gap between the two becomes almost zero, the valve body 6 comes into contact with the key member 35 and stops. Therefore, the next time the input shaft 30 is moved forward again, the flow path of the valve mechanism 7 is immediately switched.

In the operating state of the brake booster described above,
Normally, the pressure within the variable pressure chamber 5 does not exceed the set value of the relief valve 36, but if the pressure exceeds the set pressure of the relief valve 36, the pressure within the variable pressure chamber 5 will exceed the set value of the relief valve 36. Open constant pressure chamber 4
This prevents the pressure inside the variable pressure chamber 5 from rising more than necessary and damaging the brake booster.

In contrast to the above-mentioned normal operation, when the conduit 18 is broken, the positive pressure from the fluid pressure source escapes from the broken part into the constant pressure chamber 4, and normally the introduction of negative pressure is greater than the ability to supply positive pressure. Since the capacity is far superior, even if the input shaft 30 is moved forward and the flow path of the valve mechanism 7 is switched as described above, positive pressure cannot be introduced into the variable pressure chamber 5. However, in this embodiment, when the input shaft 30 is moved forward and the flow path of the valve mechanism 7 is switched, the atmosphere flows through the filter 4.
1 and the atmospheric passage 40 to push open the check valve 43 and supply it to the valve mechanism 7.
Since it is introduced into the variable pressure chamber 5 from above, it operates in the same manner as a normal negative pressure type brake booster.
At this time, the atmosphere is removed from the check valve 42 provided in the supply passage 17.
Since the air is prevented from flowing to the conduit 18 side, the atmosphere will not escape into the constant pressure chamber 4 from the damaged part of the conduit 18.

In addition, when the external conduit 20 is damaged, the atmosphere is supplied from the damaged part via the conduit 18 and the supply passage 17, or (and) from the atmosphere passage 40, so it is also possible to use a normal negative pressure brake booster. Therefore, the valve mechanism 7
Even if damage occurs at any point in the passage that supplies positive pressure to the variable pressure chamber 5, atmospheric air can be reliably supplied to the variable voltage chamber 5, thereby improving safety.

Furthermore, if the external conduit 22 or the conduit 18 becomes clogged, or if the compressor supplying positive pressure to the compressed air tank fails, the valve mechanism 7 will no longer be supplied with positive pressure. However, when the input shaft 30 is advanced and the flow path of the valve mechanism 7 is switched, the variable pressure chamber 5 and the supply passage 17 communicate with each other, and the supply passage 17
Since the pressure becomes negative, the atmosphere pushes open the check valve 43 through the filter 41 and the atmosphere passage 40 and is supplied to the valve mechanism 7 and further to the variable pressure chamber 5.
Therefore, it operates in the same manner as a normal negative pressure brake booster, and safety can be improved.

Next, in the above embodiment, two check valves 42 and 43 are used.
Although the control valve is configured from the above, it is of course possible to use a single control valve. FIG. 2 shows such an embodiment. In this embodiment, the supply passage 17 and the atmosphere passage 40 are communicated with each other on a straight passage 44, and the passage 44
An intermediate portion of the first valve seat 10 and the valve body 14 communicate with the outside of the seat portions of the first valve seat 10 and the valve body 14 via a passage 45.
On the other hand, a pair of valve seats 46, 47 facing each other is formed on both sides of the passage 44, and a valve seat 46, 47 is provided between the valve seats 46, 47 by sliding left and right within the passage 44. Valve body 4 selectively seated
There are 8.

According to such a configuration, when positive pressure is being supplied from the conduit 18 to the supply passage 17, the valve body 48
is seated on the valve seat 46 due to the positive pressure, and the atmospheric passage 4
0 is shut off and the supply passage 17 is communicated with the passage 45, so that positive pressure is supplied to the valve mechanism 7.

On the other hand, when the conduit 18 is damaged,
Since the valve element 48 is seated on the valve seat 47 by atmospheric pressure, the supply passage 17 is blocked and the atmospheric passage 40 is communicated with the valve mechanism 7 via the passage 45. It is clear that the same effects as in the above-mentioned embodiments can be obtained also in this embodiment.

〔Effect of the invention〕

As described above, according to the present invention, even if positive pressure is not supplied to the valve mechanism due to damage or clogging of the passage supplying positive pressure, or failure of the compressor, atmospheric air can be reliably supplied to the variable pressure chamber. Therefore, the effect of improving safety can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
The figure is a sectional view of essential parts showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Shell, 2... Power piston, 4... Constant pressure chamber, 5... Variable pressure chamber, 6... Valve body, 7... Valve mechanism, 17... Supply passage, 18, 20... Conduit, 30...
Input shaft, 40... Atmospheric passage, 42, 43... Check valve,
46, 47...valve seat, 48...valve body.

Claims (1)

[Claims] 1. A power piston slidably disposed within the shell, a valve mechanism housed within the valve body of the shaft of the power piston, and a constant pressure system formed on the front side of the power piston in the operating direction, to which negative pressure is constantly introduced. The variable pressure chamber is formed on the rear side of the power piston in the operating direction and receives a supply of positive pressure, and the fluid pressure source outside the shell and the supply passage formed in the valve body are communicated with each other. a conduit that supplies pressure to the valve mechanism; and an input shaft that operates the valve mechanism to switch the flow path and supply the positive pressure supplied to the supply passage to the variable pressure chamber to advance the power piston. In the positive pressure brake booster, an atmospheric passage is provided for supplying atmospheric pressure to the valve mechanism, and when positive pressure is introduced into the supply passage, the supply passage is opened and the atmospheric passage is shut off, and the supply passage is closed. A safety device for a positive pressure brake booster, characterized in that a control valve is provided that opens an atmospheric passage and shuts off a supply passage when positive pressure is not introduced.