JPH05139272A - Brake fluid pressure control device - Google Patents

Abstract

PURPOSE:To perform stable brake fluid pressure control regardless of ambient temperature by sealing air pressure into a control chamber at the time of reaching the specified deceleration, and performing pressure reducing control of liquid pressure as well as setting a split point under the action of this air pressure. CONSTITUTION:When a brake pedal 5 is depressed, the air pressure in a tank is sent to an air over hydraulic booster 2 and the ball chamber 17 of a brake fluid pressure control device 1 through an air pressure pipe 7. The air over hydraulic booster 2 converts the air pressure into proportional fluid pressure to send it to the brake fluid pressure control device 1 through a fluid pressure pipe 8. Upon reaching the specified deceleration, a ball 18 closes a vent valve 20 communicated with a control chamber 24. With further rise of fluid pressure, a poppet valve 13 is closed by a plunger 12, and thereafter the fluid pressure becomes independent of delivery pressure. The air pressure is thus sealed into the control chamber 24 to prevent the change of a control characteristic due to ambient temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake fluid pressure control device for controlling a rear wheel brake fluid pressure, and more particularly to a so-called air for converting a pneumatic pressure used in a large truck or the like into a hydraulic pressure to perform a braking action. The present invention relates to a brake fluid pressure control device in an overhydraulic brake system.

[0002]

2. Description of the Related Art Conventionally, as a brake fluid pressure control device for a rear wheel to prevent the rear wheel from locking before the front wheel during braking of the vehicle, for example, as shown in Japanese Patent Publication No. 61-11824, a vehicle is Detecting that the predetermined deceleration has been reached,
After that, it is known that the increase in the rear wheel hydraulic pressure is suppressed to be lower than the increase in the front wheel hydraulic pressure.

In this device, the brake fluid pressure from the master cylinder is applied to the control piston to increase the spring load that presses the fluid pressure control plunger, and when a predetermined deceleration is reached, the inertial body (steel ball) is controlled. Close the liquid flow path to the piston to stop the spring load from rising. The control plunger has a surface A on which hydraulic pressure from the master cylinder acts,
There is a B side where the rear wheel hydraulic pressure acts on a smaller area,
Initially, the master cylinder side and the rear wheel side are in communication.
Since the same pressure acts on both sides of B and the thrust force generated in the plunger due to the area difference between both sides of A and B opposes the spring load, the master cylinder pressure rises before the ball closes the liquid flow path. The plunger does not move due to the increase in spring load, and the master cylinder side and the rear wheel side communicate with each other as described above.

However, as described above, when the predetermined deceleration is reached, the liquid flow path is closed and the spring load stops increasing. Therefore, the hydraulic pressure increase on the master cylinder side causes the plunger to move against the spring load. The communication between the master cylinder side and the rear wheel side is cut off by closing the poppet valve, and thereafter, the increase in the master cylinder hydraulic pressure and the rear wheel side hydraulic pressure have a relation between the area ratios of A and B surfaces.

That is, the hydraulic pressure acting on the rear wheels is controlled to be lower than the master cylinder hydraulic pressure acting on the front wheels, and the rear wheels are prevented from locking earlier than the front wheels. You can prevent skidding.

[0006]

However, in such a conventional brake fluid pressure control device, there is a ball in the brake fluid that senses the vehicle deceleration and closes the fluid flow path. There has been a problem that the operating speed and flow path resistance of the ball vary depending on the change in the viscosity of the brake fluid, and the control characteristics depend on the ambient temperature, especially during sudden braking.

The present invention has been made in view of the above conventional problems, and an object thereof is to stabilize the control characteristics and secure safer braking.

[0008]

To achieve the above object, the present invention is provided between an air-over hydraulic booster for converting an air pressure supplied by operating a brake pedal into a hydraulic pressure and a wheel brake unit. In a brake fluid pressure control device that senses the deceleration of a vehicle and controls the hydraulic pressure of the rear wheels, a control chamber in which the air pressure is enclosed when a predetermined deceleration is reached, and the action of the enclosed air pressure are It is provided with a hydraulic pressure control mechanism for receiving and setting a split point and controlling the hydraulic pressure to be reduced.

Further, the present invention is provided with an inertial body for closing a vent valve communicating with the control chamber when a predetermined deceleration is reached, and for enclosing the air pressure in the control chamber.

[0010]

In the present invention, when the predetermined deceleration is reached,
The inertial body closes the vent valve that leads to the control chamber to trap air pressure in the control chamber and act the trapped air pressure on the hydraulic control mechanism. This sets the split point. When the hydraulic pressure from the air over hydraulic booster exceeds the split point, the hydraulic pressure control mechanism reduces the hydraulic pressure supplied to the rear wheel brake unit with a predetermined reducing ratio as the hydraulic pressure increases, and brakes. Prevents rear wheel lock immediately before stopping.

As described above, since the ventilation valve is closed by the inertial body and the air pressure is made to act on the hydraulic pressure control mechanism, it is possible to solve the problem that the control characteristic is influenced by the ambient temperature, and the control characteristic is improved. Can be stabilized.
As a result, safer braking can be ensured.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are views showing an embodiment of the present invention. In this embodiment, the air-over hydraulic brake system used in a large truck or the like (for example, “New Edition Automotive Engineering Handbook”, Vol. 5, Chapter 2, page 23, published by the Society of Automotive Engineers of Japan in November 1982, FIG. -92)).

In FIG. 1, a brake fluid pressure control device 1 according to an embodiment is provided between an air over hydraulic booster 2 and a wheel brake unit, and is installed so as to be inclined with respect to a vehicle as shown in the drawing. Yes (the front side of the vehicle is raised). Reference numeral 3 is a compressor. The compressor 3 compresses air to create air pressure, and the created air pressure is stored in the tank 4.

When the driver operates the brake pedal 5,
The brake valve 6 opens according to the pedaling force, and the air pressure in the tank 4 is supplied to the brake fluid pressure control device 1 and the air over hydraulic booster 2 via the air pressure pipe 7. Air over hydraulic booster 2
Converts the air pressure into a hydraulic pressure (brake hydraulic pressure) and supplies it to a liquid inlet 10 formed in a valve housing 9 of the brake hydraulic pressure control device 1 via a hydraulic pressure pipe 8.

A valve hole 11 communicating with the liquid inlet 10 is formed in the valve housing 9, and a plunger 12 is slidably accommodated in the valve hole 11. A poppet valve 13 is incorporated in the internal flow path of the plunger 12, and a valve seat 14 is fixed to the plunger 12 on the outlet side of the internal flow path. These constitute a hydraulic pressure control mechanism for controlling the hydraulic pressure supplied to the rear wheel brake unit.

Liquid pressure is supplied from the air-over-hydraulic booster 2 to the internal flow passage of the plunger 12, and is guided to the rear wheel brake unit from the liquid outlet 15 through the internal flow passage. That is, as shown in the figure, the poppet valve 13 is pressed by the valve spring 16, but initially the plunger 12 is pressed against the bottom of the valve hole 11 with a force stronger than the pressing force of the valve spring 16. The valve is open.

The valve housing 9 below the hydraulic control mechanism
A ball chamber 17 is formed in the ball chamber 17, and a ball (steel ball) 18 as an inertial body is rotatably accommodated in the ball chamber 17. Air pressure is supplied to the ball chamber 17 from the tank 4 via the brake valve 6, the air pressure pipe 7, and the plug 19. A vent valve 20 is provided on the end surface of the ball chamber 17 facing the ball 18, and the vent valve 20 rolls on the inclined surface to the upper left in the figure due to inertia due to deceleration of the vehicle.
The ball 18 closes the valve.

A cover 21 is provided at the opening of the valve hole 11 of the valve housing 9, and the inside of the cover 21 is controlled by a diaphragm 23 in which the cover 21 is superposed on the valve housing 9 and fixed by bolts 22. A chamber 24 and an atmospheric chamber 25 are defined respectively. The atmosphere chamber 25 communicates with the atmosphere through the atmosphere opening hole 26, and the control chamber 24 communicates with the ball chamber 17 through the ventilation valve 20.

The diaphragm 23 has plates 27 and 28.
Is fixed via a pin 29, and the plate 27 and the cover 2
A valve-opening spring 30 for setting a split point is interposed between 1 and 1. Plunger 1
An oil seal 31 and an O ring 32 seal between the valve housing 2 and the valve housing 9. Next, the operation will be described.

When the driver steps on the brake pedal 5, the brake valve 6 operates in conjunction with the brake pedal 5,
The air pressure of the tank 4 is sent to the ball chamber 17 of the air over hydraulic booster 2 and the brake fluid pressure control device 1 via the air pressure pipe 7. The air over hydraulic booster 2 converts air pressure into proportional hydraulic pressure,
It is sent to the fluid inlet 10 of the brake fluid pressure control device 1 via the fluid pressure pipe 8.

The hydraulic pressure sent to the brake hydraulic pressure control device 1 is sent to the rear wheel brake unit through the internal flow path of the plunger 12. Here, the hydraulic pressure acting on the plunger 12 is the A surface (O ring 32) of the plunger 12.
Area equivalent to outer diameter) and B side (from A side to oil seal 3
1) The area corresponding to the inner diameter is subtracted) to push the plunger 12 to the upper left from the area difference between the two surfaces, but the effective diameter of the diaphragm 23 is set so as to balance with the air pressure acting on the diaphragm 23. Therefore, the plunger 12 is pressed against the bottom of the valve hole 11 by the tension of the valve opening spring 30.

Therefore, when the brake pedal 5 is depressed to increase the air pressure and the hydraulic pressure,
The brake works and deceleration occurs. Then, when a predetermined deceleration is reached, the ball 18 rolls due to inertia and the ventilation valve 2
Close 0. Therefore, the increase in the air pressure acting on the diaphragm 23 stops, and when the hydraulic pressure further increases, the plunger 12 overcomes the force generated in the diaphragm 23 and the tension of the valve opening spring 30 and moves to the upper left side, and the poppet valve 13 closes. After that, the hydraulic pressure sent to the rear wheel brake unit becomes independent of the discharge pressure from the air over hydraulic booster 2.

Since the air pressure acting on the diaphragm 23 is constant, the poppet valve 13 is repeatedly opened and closed due to the balance of the forces acting on the plunger 12.
A hydraulic characteristic as shown in FIG. 2 is shown. The rise in the hydraulic pressure sent to the rear wheel brake unit rises gently with respect to the rise in the discharge pressure from the air over hydraulic booster 2 at the ratio of the area ratio of the A surface to the B surface. You can prevent the rear wheel from locking.

That is, thereafter, by repeatedly opening and closing the poppet valve 13 by the reciprocating movement of the plunger 12 in response to the increase of the hydraulic pressure, the hydraulic pressure is reduced at a predetermined reducing ratio, and the rear wheel lock immediately before the braking is stopped. Therefore, the braking stability of the vehicle can be secured. In addition, in FIG.
Indicates a split point at which the predetermined deceleration has been reached in full loading, and B indicates a split point at which the predetermined deceleration has been reached in light loading.

As described above, when the predetermined deceleration is reached, the air pressure is confined in the control chamber 24, and the confined air pressure is made to act on the plunger 12 having the poppet valve 13 built therein. It is possible to prevent the control characteristic from changing, and secure safer braking.

[0026]

As described above, according to the present invention, it is possible to solve the problem that the control characteristics are affected by the ambient temperature, and it is possible to perform stable brake fluid pressure control. , Can improve safety.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the discharge pressure of the air over hydraulic booster and the rear wheel brake pressure.

[Explanation of symbols]

 1: Brake fluid pressure control device 2: Air over hydraulic booster 3: Compressor 4: Tank 5: Brake pedal 6: Brake valve 7: Pneumatic pipe 8: Hydraulic pipe 9: Valve housing 10: Liquid inlet 11: Valve hole 12 : Plunger 13: Poppet valve 14: Valve seat 15: Liquid outlet 16: Valve spring 17: Ball chamber 18: Ball (inertia) 19: Plug 20: Vent valve 21: Cover 22: Bolt 23: Diaphragm 24: Control chamber 25: Atmosphere chamber 26: Atmosphere opening hole 27, 28: Plate 29: Pin 30: Valve opening spring 31: Oil seal 32: O-ring

Claims (2)

[Claims] 1. A wheel brake unit, which is provided between an air-over hydraulic booster for converting air pressure supplied by operating a brake pedal into a hydraulic pressure, and senses deceleration of a vehicle to control hydraulic pressure of rear wheels. In a brake fluid pressure control device for performing, a control chamber in which the air pressure is enclosed when a predetermined deceleration is reached, and a fluid which controls the fluid pressure by setting a split point under the action of the enclosed air pressure. A brake fluid pressure control device comprising a pressure control mechanism. 2. An inertial body for closing a ventilation valve communicating with the control chamber when a predetermined deceleration is reached, and the air pressure is contained in the control chamber. Brake fluid pressure control device.