JPH0415150A - Hydraulic pressure controller for air over hydraulic brake - Google Patents

Abstract

PURPOSE:To rapidly avoid the danger of wheel locking and also avoid shortage in braking forces due to subsequent excessive pressure reduction by providing in an air pressure reducing passage a pressure reduction rate regulating means for controlling the quantity of air allowed to pass through the passage. CONSTITUTION:If wheels are in danger of being locked, a hold valve 29 is closed and a decay valve 31 is opened and air pressure within an air chamber 23 is released to atmosphere and a control piston 24 is shifted to the right in Figure. During this initial period, an air pressure reducing passage 22 is broadened by a throttle piston 36 and the air pressure within the air chamber 23 is sharply reduced and a cut valve 21 is rapidly closed. At the same time the capacity of a hydraulic pressure control chamber 25 is enlarged by movement of the control piston 24 and a hydraulic fluid in a wheel cylinder 8 is absorbed and brake fluid pressure is reduced so that locking of the wheels is avoided. Thereafter, the air pressure within the air chamber 23 is lowered and the throttle piston 36 is shifted to the left in Figure by a spring 21 so that the air pressure reducing passage 22 is narrowed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic pressure control device for air-over-hydraulic brakes, and more particularly to improving the controllability of anti-lock control.

[Conventional technology]

As a hydraulic pressure control device for air-over-hydraulic brakes, there is a brake hydraulic system that converts air pressure from a pneumatic source into hydraulic pressure and supplies it to the wheel cylinder via a brake fluid path, and this brake hydraulic pressure. A device is known that includes a hydraulic pressure control system that controls the brake hydraulic pressure by interfering with the system, and that uses the hydraulic pressure control system to reduce the brake hydraulic pressure when there is a risk of wheel locking.

Here, the hydraulic control system includes a cut valve interposed in the brake fluid path, and an air chamber that receives air pressure from the air pressure source and is opened to the atmosphere through a pneumatic pressure reduction path. The vehicle also includes a control piston that is operated in accordance with the air pressure in the air chamber to control opening and closing of the cut valve and to control brake fluid pressure applied to the wheel cylinder. When there is a risk of wheel locking, the air pressure in the air chamber is released from the pneumatic pressure reduction path to the atmosphere and the control piston is moved to close the cut valve, and the control piston moves to reduce the brake fluid pressure. After reducing the pressure and avoiding the risk of wheel locking, air pressure is applied in the air chamber and the brake fluid pressure is increased by the control piston.

[Problem to be solved by the invention] By the way, in a brake device that uses a foil cylinder to press a brake shoe against a drum to perform braking, when the brake is applied by - degrees, the brake shoe digs into the drum because the drum is rotating. Even if the brake fluid pressure is reduced due to anti-lock operation, the brake shoes do not immediately separate from the drum. Therefore, a hysteresis characteristic as shown in FIG. 3 exists between the brake fluid pressure and the brake torque.

Therefore, when the brake fluid pressure is high, that is, in the initial state of anti-lock control, the hysteresis is large, so it is necessary to quickly reduce the brake fluid pressure.

On the other hand, in the later stages of brake fluid pressure reduction, it is necessary to avoid insufficient braking force due to excessive brake fluid pressure reduction.

The present invention has been made in view of the above, and an object of the present invention is to improve the controllability of anti-lock operation.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention adopts the following means, that is, converts pneumatic pressure from a pneumatic source into hydraulic pressure, and converts the brake hydraulic pressure to the wheel cylinder via the brake fluid path. and a cut valve interposed in the brake fluid path, and an air chamber that receives air pressure from the air pressure source and is opened to the atmosphere through a pneumatic pressure reduction path. It has a control piston that operates according to the pressure to control the opening and closing of the cast valve and also controls the brake fluid pressure applied to the wheel cylinder. An air-over-hydraulic brake equipped with a hydraulic control system that closes the cut valve by releasing air pressure to the atmosphere and moving the control piston, and also reduces brake fluid pressure by moving the control piston. In the hydraulic pressure control device, the pneumatic pressure reduction path is provided with a pressure reduction rate adjustment means for controlling the amount of air passing through the pneumatic pressure reduction path, and the pressure reduction adjustment by the pressure reduction rate adjustment means is performed in the air chamber. Air over hydraulic brake fluid pressure is configured such that when the air pressure inside the air chamber is high, the pressure reduction rate is large, and when the air pressure inside the air chamber is small, the pressure reduction rate is reduced. It was used as a control device.

[Effect]

In an initial state where there is a risk of wheel locking and the air pressure in the air chamber is released, the internal pressure in the air chamber is high, so the pressure reduction rate by the pressure reduction rate adjusting means is high. Therefore, the control piston moves quickly, and the brake fluid pressure is quickly reduced.

The internal pressure in the air chamber is reduced to a certain extent and becomes low, and the pressure reduction rate by the pressure reduction rate adjusting means becomes small.

Therefore, the movement speed of the control piston becomes slower, and the brake fluid pressure decreases more slowly than before.

As a result, the risk of wheel locking can be quickly avoided, and the subsequent lack of braking force due to excessive pressure reduction can also be avoided, and furthermore, it is possible to prevent vehicle vibrations caused by an increase in hydraulic pressure amplitude due to repeated pressure reduction and pressurization. can.

〔Example〕

Embodiments of the present invention will be described based on FIGS. 1 and 2.

As shown in FIG. 1, the device includes a brake hydraulic system 1 and a hydraulic control system 2.

The brake hydraulic system l has an air mask cylinder 6 that converts air pressure from an air pressure source 5 into hydraulic pressure.
It is connected to the. A brake valve 10 for controlling the amount of air supplied to the air mask cylinder 6 is provided in a pneumatic passage 9 that connects the air pressure source 5 and the air mask cylinder 6.

The hydraulic pressure control system 2 includes the brake fluid path 7 at the end of the main body 20.
It has a cut valve 21 interposed therein. Also, provided within the main body 20 is an air chamber 23 that receives air pressure from the air pressure source 5 and is opened to the atmosphere via an air pressure reduction path 22. Further, a control piston 24 is provided within the main body 20, which operates according to the air pressure within the air chamber 23 to control opening and closing of the cut valve 21.

Further, in the main body 20, the brake fluid path 7 is interposed,
Further, a hydraulic pressure control chamber 25 whose volume changes as the control piston 24 moves is provided.

This hydraulic pressure control chamber 25 is interposed in the brake fluid path 7 on the wheel cylinder 8 side with respect to the cut valve 21 .

The cut valve 21 is biased toward the control piston 24 by a valve spring 26 and has an abutment rod 27 that protrudes toward the control piston 24. When pushed, it moves against the valve spring 26 and opens.

Further, the air chamber 23 is connected to the brake valve 10.
It is connected via a hold valve 29 and a return valve 30 to a control pneumatic passage 28 branched from the pneumatic passage 9 between the air mask cylinder 6 and the air mask cylinder 6 .

The hold valve 29 is constituted by a solenoid valve, and confines the air pressure supplied from the air pressure source 5 through the control air pressure path 28 into the air chamber 23 during anti-lock control.

The return valve 30 is for releasing the air pressure above a certain level in the air chamber 23 after the hold pulp 29 is closed by the internal pressure (flow velocity) of the air chamber 23 when the brake is released. As described above, by leaving a certain amount of air pressure in the air chamber 23 even after the brake is released, the amount of air consumed when the brake is applied is reduced.

Further, the air pressure reducing path 22 that releases the air pressure in the air chamber 23 to the atmosphere is connected to the air chamber 23 via a decay valve 31. This decay valve 31 is also constituted by a solenoid valve. In addition, pneumatic pressure reduction path 2
2 is open to the atmosphere via an exhaust valve 32.

The control piston 24 has a small diameter portion 2 on the hydraulic pressure control chamber 25 side.
4a and a large diameter portion 24b on the air chamber 23 side.
A back pressure chamber 35 is formed between the large diameter portion 24b and the main body 20 on the side opposite to the air chamber 23.
is opened to the atmosphere via the bypass air passage 40 and the exhaust valve 32.

A throttle piston 36 that constitutes pressure reduction rate adjusting means is provided interposed in the pneumatic pressure reduction path 22. The throttle piston 36 is located within the main body 20 and is located across the pneumatic pressure reducing path 22, and is biased toward one end (to the left in the figure) by a spring 37. In addition, a pressure passage 38 from the air chamber is connected to one end surface of the throttle piston 36 so that the air pressure from the pressure passage 38 moves the throttle piston 36 to the right in the figure against the spring 37. It has become.

Furthermore, a constriction part 39 is formed at a portion where the constriction piston 36 intersects with the pneumatic pressure reduction path 22. Due to the intervention of this constriction part 39, the pneumatic pressure reduction path 22 becomes wider or narrower. . When the spring 37 positions the throttle piston 36 to the left in the figure, the pneumatic pressure reduction path 22 becomes narrow, and when the air pressure from the pressure path 38 positions the throttle piston 36 to the right in the figure. , the pneumatic pressure reduction path 22 becomes wider.

Next, the operation of the device of the present invention will be explained.

When the brake pedal is depressed, the brake valve 10 opens and air pressure from the air pressure source 5 is supplied to the air mask cylinder 6, where it is converted into hydraulic pressure and output.

At this time, the air pressure from the air pressure source 5 is supplied to the air chamber 23 through the open hold valve 29, so the control piston 24 is located on the left side of the figure as shown in FIG. The cut valve 21 pressed by this is held in an open state. Therefore, the brake fluid pressure from the air mask cylinder 6 is supplied to the foil cylinder 8, and braking is performed.

At this time, since the air pressure in the air chamber is high, the air pressure applied through the pressurizing path 38 moves the throttle piston 36 to the right in the figure, widening the air pressure reducing path 22.

When there is a risk of wheel locking, the hold valve 29 closes and the decay valve 31 opens in response to a command from an electronic control device (not shown), and the air pressure in the air chamber 23 is released to the atmosphere Pk. Start moving to the right.

In this initial state, the pneumatic pressure reduction path 22 is widened by the throttle piston 36, so the pressure reduction rate is large;
The air pressure in the air chamber 23 is rapidly reduced, and at the same time as the cut valve 21 is quickly closed, the control piston 24 moves, and the volume of the hydraulic control chamber 25 expands.
The pressure fluid in the wheel cylinder 8 is absorbed here, and the brake fluid pressure is reduced, thereby avoiding the risk of wheel locking.

After that, the air pressure inside the air chamber 23 becomes low, so
As the spring 37 moves the throttle piston 36 to the left in the figure, the pneumatic pressure reduction path 22 becomes narrower, and the pressure reduction rate becomes smaller. Therefore, insufficient braking force due to excessive reduction of brake fluid pressure can be avoided.

If it becomes necessary to apply the brakes again,
Decay valve 31 closes, hold valve 29 opens, and air pressure is supplied to air chamber 23. Control piston 2
4 moves to the left, the volume of the hydraulic pressure control chamber 25 becomes smaller, and the internal brake fluid is pressurized. It will be done. When the operating characteristics during this period are compared with the characteristics of a conventional device without the throttle piston 36, the results are as shown in FIG. In this figure, the operating characteristics of the embodiment are shown by solid lines,
Characteristics of the conventional device are shown by broken lines.In this example, the operation of the throttle piston was mechanically linked to the air chamber internal pressure via the pressure passage, but a solenoid valve whose passage can be varied was used as a pressure reduction rate adjustment means. The internal pressure within the air chamber may be detected by a pressure sensor, and the opening degree may be adjusted by a solenoid valve in accordance with the internal pressure.

〔Effect of the invention〕

According to the present invention, brake fluid pressure can be quickly reduced in the initial state of anti-lock operation,
After that, it is possible to prevent excessive pressure reduction and perform effective anti-lock control.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment of the present invention. Figure 1 shows the concept of the entire device. Figure 2 shows operating characteristics in comparison with a conventional device. Figure 3 shows brake fluid pressure and brake torque. It is a graph diagram showing the relationship between. Hydraulic pressure control system, brake fluid path, cut valve, air chamber, brake fluid pressure system, 2 pneumatic source, 7 wheel cylinder, 21 pneumatic pressure reduction path, 23 control piston, throttle piston as pressure reduction rate adjusting means.

Claims (1)

[Claims] (1) A brake hydraulic system that converts pneumatic pressure from a pneumatic source into hydraulic pressure and supplies it to the wheel cylinder via a brake fluid path, and a cut valve interposed in the brake fluid path, and It has an air chamber that receives air pressure from an air pressure source and is opened to the atmosphere through a pneumatic pressure reduction path, and operates according to the air pressure in the air chamber to control the opening and closing of the cut valve. It has a control piston that controls the brake fluid pressure applied to the wheel cylinder, and when there is a risk of wheel locking, the air pressure in the air chamber is removed from the air pressure reduction path to the atmosphere and the control piston is moved. A hydraulic pressure control system for an air-over-hydraulic brake, comprising: a hydraulic pressure control system that closes a cut valve and reduces brake fluid pressure by moving a control piston; A pressure reduction rate adjustment means is provided for controlling the amount of air passing through the pressure reduction path, and the pressure reduction adjustment by the pressure reduction rate adjustment means is made to depend on the internal pressure in the air chamber, and when the air pressure in the air chamber is large, A hydraulic pressure control device for air over hydraulic brakes that has a large pressure reduction rate and is configured to reduce the pressure reduction rate when the air pressure in the air chamber becomes small.