JPH0490954A - Hydraulic control device for air over hydraulic brake - Google Patents

Abstract

PURPOSE:To improve the control characteristics of antilock control by switching communication of a back pressure chamber to a back pressure feedback passage or a back pressure exhaust passage by means of a pressure difference between the back pressure feedback passage of a control piston and a back pressure chamber. CONSTITUTION:When there is a possibility of a wheel lock occurring during brake, a control part closes a hold valve 21 and opens a decay valve 22. As a result, a control piston 14 is moved to the air pressure side and a cut valve 10 is closed through the force of a cut spring 15 to close a brake liquid passage 5. With the decay valve 22 opened, exhaust gas from a positive pressure chamber 20 is exerted on a valve body 34 of a switch valve 27 through an exhaust gas passage 23 and a back pressure feedback passage 26. In which case, According to relations in magnitude between an exhaust gas pressure and a sum of the pressure of a back pressure chamber 28 and the spring force of a spring 33, a valve body 34 switches a passage. This constitution prevents brake control from being brought into an unstable state due to abnormal pressurization in the back pressure chamber.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hydraulic pressure control device for air-over-hydraulic brakes, and in particular to improving the hydraulic pressure responsiveness of brake hydraulic pressure during anti-lock control. Concerning techniques that are effective when applied to

[Conventional technology]

This type of prior art will be explained using FIG. 4.

That is, as a hydraulic pressure control device for air-over-hydrolink brakes, it converts the pressure from the pneumatic pressure source 3 into hydraulic pressure and supplies this hydraulic pressure to the wheel cylinder 6 via the brake fluid path 5. In addition to system 1, there is a hydraulic pressure control system 2 that controls brake hydraulic pressure by interfering with the brake hydraulic system l.
There is a known technology in which the brake fluid pressure is controlled to be reduced (anti-lock control) by the fluid pressure control system 2 when there is a risk of wheel locking.

In this device, a brake hydraulic system 1 has an air master cylinder 4 that converts air pressure from an air pressure source 3 into hydraulic pressure, and has a structure that supplies hydraulic pressure to a wheel cylinder 6 via a brake fluid path 5. It becomes.

On the other hand, a modulator 11 is connected to a pneumatic line 7 branched from the brake valve 8.

A hold valve 21 consisting of a solenoid valve is interposed on the pneumatic path 7 between the positive pressure chamber 20 of the modulator 11 and the brake valve 8. By blocking this pneumatic path 7, the air inside the pneumatic cylinder 12 is It is possible to confine it to a predetermined pressure. In addition, a decay valve 22, which is also a solenoid valve, is installed in the exhaust path 23 from the pneumatic chamber 20 to the exhaust valve 25, and is capable of reducing the pressure of the air in the pneumatic cylinder 12.

The exhaust path 23 is branched in the middle to form a back pressure return path 2.
6, which communicates with a back pressure chamber 28.

Further, a back pressure exhaust path 31 is provided from the back pressure chamber 28 to communicate with the exhaust valve 25.

In the device configuration described above, when there is a risk of wheel locking during braking, the hold valve 21 is operated, the air pressure path 7 is cut off, and the supply of air to the positive pressure chamber 20 is stopped. Then, by operating the Decay valve 22, the internal pressure in the positive pressure chamber 20 is reduced from "depressurized" to "
Hold.

When the internal pressure in the positive pressure chamber 20 drops below a certain level, the hold valve 21 is controlled again to open the air pressure path 7 and "pressurize" the inside of the positive pressure chamber 20.

In this way, the hold valve 21 and the decay valve 22
By controlling these as appropriate, the "depressurization", "holding" and "pressurization" in the positive pressure chamber 20 are reversed, the hydraulic pressure supplied to the foil cylinder 6 is controlled, and locking of the wheels is prevented.

By the way, in the above device configuration, the exhaust pressure from the exhaust passage 23 is transferred to the back pressure return passage 2 at the time of “depressurization” in the anti-lock control.
The operational response and capacity of the control piston 14 during pressure reduction is improved by returning the air to the back pressure chamber 28 through the exhaust valve 25. A constriction part 29 is provided,
In addition to this, the exhaust pressure is efficiently returned to the back pressure chamber 28 side, and in order to suppress the air to the back pressure chamber 28 from escaping to the exhaust valve 25 side, the back pressure exhaust path 31 is also [Problem to be Solved by the Invention] However, the presence of the back pressure exhaust throttle part 30 deteriorates the efficiency of air removal from the back pressure chamber 28 during pressurization. The operational response of the control piston 14 was actually reduced when the pressure was low, and the efficiency of air removal from the back pressure chamber 28 was not good.
For example, when holding the internal pressure of the positive pressure chamber 20 at a constant level, there was a concern that the pressure balance between the front chamber 20 side and the back pressure chamber 28 would be imbalanced, resulting in unstable control.The present invention was made in view of the above problem. Its purpose is to improve the pressure relief of the back pressure chamber, improve the responsiveness of the modulator, and improve the control characteristics of anti-lock control.

[Means to solve the problem]

The present invention is an air-over-hydro motor equipped with a modulator, in which one end of the control piston is connected to a brake hydraulic system that supplies brake fluid to a wheel cylinder, and the other end is connected to a hydraulic control system operated by pneumatic pressure. In the link hydraulic control device, a back pressure side return path that returns exhaust from a positive pressure chamber on the hydraulic pressure control system side of the control piston to a back pressure chamber side of the control piston; and a back pressure side that exhausts the back pressure chamber. Due to the pressure difference between the exhaust path, the back pressure side return path, and the back pressure chamber, the
The gist of the present invention is to include a passage switching valve that controls communication between the back pressure chamber and the back pressure return path or the back pressure exhaust path.

[Effect]

According to the above-mentioned means, the passage switching valve opens the passage on the back pressure return path side by the exhaust pressure from the positive pressure chamber during "depressurization" and efficiently guides the exhaust gas to the back pressure chamber.

During "holding" and "pressurizing", the passage to the back pressure exhaust path is opened to efficiently exhaust the back pressure chamber.

As a result, the operational response of the control piston can be improved in any of the operating modes of "depressurization,""holding," and "pressurization."

〔Example〕

1 and 2 show one embodiment of the invention.

As shown in the figure, this device has a brake hydraulic pressure system 1 and a hydraulic pressure control system 2.

The brake hydraulic system 1 includes an air master cylinder 4 that converts air pressure from an air pressure source 3 into hydraulic pressure, and the air master cylinder 4 is connected to a wheel cylinder 6 via a brake fluid path 5. ing. A brake valve 8 is interposed in the pneumatic passage 7 leading from the pneumatic source 3 to the air master cylinder 4 to control the amount of air supplied.

A caputo valve IO is provided on the brake fluid path 5, and controls opening and closing of the fluid pressure path to the wheel cylinder 6.

On the other hand, a modulator 11 is arranged in a pneumatic path 7 branched from the brake valve 8. The modulator 11
has a structure in which the pneumatic cylinder [2] and the hydraulic cylinder [3] are connected by the same control piston 14, and one end of the hydraulic cylinder 13 side is connected to the brake fluid path 5 of the hydraulic control system 2. The cut valve 10 is configured as the cut valve 10 interposed therein. In a normal state, this cut valve 10 is biased by a cut spring 15 in the direction of closing the brake fluid path 5, but the internal pressure (containment pressure) 75 in the positive pressure chamber 20 resists this biasing force. Ii control piston 14
The cut valve 10 is open.

A control piston 14 inside the main body of the modulator 11 is connected to a hydraulic piston 16 constituting the cant valve 10 side.
and a pneumatic piston 17 constituting the positive pressure chamber 20 side are connected, and a cup 18 is fitted into the sliding surface of both pistons 16 and 17, respectively, to seal the peripheral end surface. ing.

The positive pressure chamber 20 on the side of the pneumatic cylinder 12 is connected to the pneumatic passage 7 via a hold valve 21 which is a normally open electromagnetic valve. Further, the positive pressure chamber 20 is connected to an exhaust path 23 via a decay valve 22 which is a normally closed electromagnetic valve. The positive pressure chamber 20 is further provided with a return valve 24 for releasing a certain amount of air in the positive pressure chamber 20 after the hold valve is closed due to the force of the flow velocity when the brake is released. It has a structure in which air above a certain level (above the containment pressure) of 20 is returned to the pneumatic path 7.

An exhaust path 23 extending from the decay valve 22 is connected to an exhaust valve 25, but is branched into a back pressure return path 26 from an intermediate portion thereof. This back pressure return path 26 is connected to the pneumatic cylinder 1 via a passage switching valve 27.
It communicates with the back pressure chamber 28 of No. 2. Further, the exhaust path 2
3, an exhaust throttle portion 29 is formed near the exhaust valve 25 for efficiently sending exhaust gas from the positive pressure chamber 20 to the back pressure return path 26 side.

A back pressure exhaust passage 31 is provided between the back pressure chamber 28 and the exhaust valve 25 to exhaust the back pressure chamber 28 via the passage switching valve 27.

The passage switching valve 27 is in the normal state, that is, the first
In the "pressurizing" and "holding" states shown in the figure, the distal end surface 35 of the valve body 34 biased by the switching spring 33 inside the switching passage 32 has a structure that blocks the entrance of the back pressure return path 26. ing. At this time, the entrance on the side of the back pressure exhaust path 31 is open to the switching path 32 . In addition,
Ring-shaped sealing members 36 are attached to the front and rear end surfaces of the valve body 34, respectively, to prevent air leakage.

Next, the operation of this embodiment will be explained.

When the brake pedal is depressed by the driver, air pressure fills the positive pressure chamber 20 of the modulator 11 via the brake valve 8 → pneumatic path 7 → hold valve 21, and presses the pneumatic piston 17 of the control piston 14. With the cant valve 10 open, hydraulic pressure is supplied from the air master cylinder 4 through the brake fluid path 5 to the wheel cylinder 6 to brake the wheels.

If the wheel speed decreases during braking and there is a risk that the wheels may lock, the hold valve 21 is closed and the decay valve 22 is opened under the control of a control section (not shown). This allows the control piston 14
The balance between the hydraulic side and the pneumatic side of the control piston 14 is lost.
moves to the pneumatic side, and the cut valve 10 is closed by the biasing force of the cut spring 15, thereby blocking the brake fluid path 5.

At this time, the decay valve 22 is opened, and the exhaust from the positive pressure chamber 20 (via the exhaust passage 23 and the back pressure return passage 26,
energize 5. If the exhaust pressure at this time is greater than the sum of the pressure in the back pressure chamber 28 and the biasing force of the switching spring 33 (at the initial stage of pressure reduction), the valve body 34 moves back against the switching spring 33. As a result, the entrance of the back pressure return path 26 is opened and exhaust gas is supplied into the back pressure chamber 28. At this time,
As shown in FIG. 2, since the entrance of the back pressure exhaust path 31 is closed by the rear end surface of the valve body 34, air leakage from the back pressure chamber 28 can be prevented, and exhaust can be efficiently carried out in the back pressure chamber 28. acts on the back pressure surface of the pneumatic piston 17.

As a result, the operational response of the control piston 4 is improved, and the pressure can be reduced at 19:00, thereby reliably preventing the wheels from locking.

Subsequently, when the exhaust pressure decreases below a certain level, the valve body 34 is moved by the biasing force of the switching spring 33 to close the mouth of the back pressure return path 26. As a result, the exhaust gas from the decay valve 22 is discharged to the exhaust valve 25 side.

In this way, when the pressure inside the positive pressure chamber 20 is reduced to a constant pressure value, the decay valve 22 is closed, the movement of the control piston 14 is stopped, and the hydraulic pressure to the foil cylinder 6 is also maintained constant.

Next, when the brake braking force decreases and repressurization is to be performed, the hold valve 21 is opened while the decay valve 22 remains closed, and air pressure is supplied into the positive pressure chamber 20. As a result, the control piston 14 moves in the direction of the hydraulic piston 16 and supplies the brake fluid pressure absorbed by the movement of the control piston to the wheel cylinder 6. In this embodiment, even in this repressurization operation mode, the back pressure chamber 2
8 is efficiently exhausted through the back pressure exhaust path 31, the operational response of the control piston 14 can be maintained at a high level.

FIGS. 3(a) to 3(c) graph the control response characteristics described above. That is, FIG. 3(a) shows the wheel speed,
The state of the wheel cylinder 6 hydraulic pressure and the valve signals to the hold valve 21 and decay valve 22 is shown. In the figure, the solid line represents the control characteristics of the device of this example.
The broken line shows the control characteristics in the prior art device structure as explained in FIG. As is clear from the figure,
"Holding" is performed by closing the hold valve 21 and reducing the pressure to a predetermined value with the decay valve 22 open, and then once closing the decay valve 22.
When the mode is set, the air in the back pressure chamber 28 is delayed and exhausted due to the influence of the back pressure exhaust throttle part 30 (FIG. 4), and the control piston 14 moves in the direction of the hydraulic piston 16. . Therefore, the hydraulic pressure in the wheel cylinder 6 temporarily increases and the wheel speed rapidly decreases. When the control section (not shown) detects this state, it is necessary to close the decay valve 22 again to stabilize the control.In contrast, in this embodiment, as described above, "depressurization j" and "holding go mode" Since abnormal pressurization of the back pressure chamber 28 does not occur during operation, the position of the control piston 14 during "holding" is stabilized, and there is no need to perform unnecessary operations of the decay valve 22.

FIG. 3(b) shows the pressure change in the positive pressure chamber 20 of the modulator 11, and FIG. 3(c) shows the pressure change in the back pressure chamber 28. As is clear from the figure, in this embodiment, pressurization and depressurization of the back pressure chamber 28 can be reliably controlled by operating the passage switching valve 27, so braking control with extremely good response characteristics to valve signals is achieved. do.

〔Effect of the invention〕

According to the present invention, since the pressurization and depressurization of the back pressure chamber is controlled by the operation of the passage switching valve, it is possible to prevent the braking control from becoming unstable due to abnormal pressurization of the back pressure chamber.

[Brief explanation of drawings]

1 to 3 show one embodiment of the present invention, and the first
2 and 2 are schematic diagrams showing a hydraulic pressure control device for air-over-hydraulic brakes. FIG. 3 is a diagram showing control characteristics and timing diagrams. FIG. 4 is a schematic diagram illustrating a prior art. ] 6 ・ 14 ・ 27 ・ Brake hydraulic system, wheel cylinder, control piston, passage switching valve, back pressure chamber, 2 ・ 11 ・ Hydraulic pressure control system, modulator, positive pressure chamber, back pressure return path, back pressure exhaust system

Claims (1)

[Claims] (1) The control piston is equipped with a modulator in which a brake hydraulic system for supplying brake fluid to the wheel cylinder is connected to one end of the control piston, and a hydraulic control system operated by pneumatic pressure is connected to the other end of the control piston. a back pressure side return path that returns exhaust from the positive pressure chamber on the hydraulic pressure control system side to the back pressure chamber side of the control piston; a back pressure exhaust path that exhausts the back pressure chamber; and the back pressure side return path. Operated by the pressure difference with the back pressure chamber,
A hydraulic pressure control device for an air over hydraulic brake, comprising a passage switching valve that controls communication between the back pressure chamber and the back pressure return path or the back pressure exhaust path.