JPH0655587B2 - Brake hydraulic pressure control device for air spring automobile - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake hydraulic pressure control device for an automobile equipped with an air spring and a hydraulic brake, and more specifically, to a hydraulic pressure supplied to a brake cylinder. The present invention relates to a brake fluid pressure control device for an air spring automobile that is automatically adjusted in response to a change in load.

<Prior art> For trucks, semi-tractors, etc., in which the load fluctuates greatly depending on whether or not there is a load, the difference in the ideal braking force distribution between the front and rear brakes when the vehicle is empty and when the vehicle is loaded is large Various brake fluid pressure control devices have been used for this purpose (refer to pages 5-26, Vol. 5, "New Automotive Engineering Handbook" issued by the Society of Automotive Engineers of Japan on November 26, 1982. ).

<Problems to be Solved by the Invention> However, in the conventional brake fluid pressure control device,
The magnitude of the load is detected based on the distance between the axle and the vehicle body (hereinafter referred to as vehicle height), and the brake fluid pressure supplied to the rear brake cylinder is controlled based on the detection result. Therefore, there is a problem that the above-described brake fluid pressure control device cannot be applied to an automobile of a type in which the vehicle height is maintained at a predetermined value regardless of a change in load, such as an air spring automobile.

The present invention has been made in view of such a situation,
An object of the present invention is to provide a brake fluid pressure control device suitable for an air spring automobile having a vehicle height maintaining function.

<Means for Solving Problems> In order to achieve the above object, the present invention provides an automobile having an air spring and a hydraulic brake, in which a piston having a different diameter is provided in a pressure reducing cylinder and an input having a small pressure receiving area is provided. An output chamber having a large pressure receiving area is formed with the chamber, and both chambers are communicated with each other via a valve port provided in the deformed piston. Further, a valve facing the valve port from the input chamber side and a valve spring for biasing the valve seated on the valve port are provided, and the valve when the different diameter piston slides to the output chamber side by more than a predetermined value. A valve lifter is provided to lift the valve against the spring.

On the other hand, a control piston is slidably fitted to a control cylinder provided outside the decompression cylinder to form a control chamber, and a lever for connecting the deformed piston to the control piston is provided. An air inlet for supplying the air pressure of the air spring to the control chamber, a hydraulic pressure inlet for supplying the hydraulic pressure responsive to the stepping force of the brake pedal to the input chamber, and a hydraulic pressure for the output chamber to the brake cylinder. It is characterized by having a hydraulic outlet.

<Operation> In the brake fluid pressure control device for an air spring automobile constructed as described above, the air pressure supplied to the control chamber formed by the control cylinder and the control piston changes depending on the magnitude of the load. It changes in response to the pressure of the air spring. Further, when the air pressure in the control chamber changes due to the change in load, the urging force applied to the deformed piston via the lever changes, so that the balance pressure of the pressure reducing cylinder changes. Then, the magnitude of the hydraulic pressure supplied from the output chamber of the depressurizing cylinder to the brake cylinder (the degree of depressurization of the brake hydraulic pressure) changes.

Therefore, for example, when the air pressure in the control chamber rises as the load increases, the balance pressure of the decompression cylinder rises and the degree of reduction of the brake fluid pressure supplied to the brake cylinder decreases. For this reason, even in an air-spring vehicle whose vehicle height is maintained at a predetermined value regardless of changes in load, it is possible to always achieve ideal braking force distribution as in the case where a conventional load sensing proportional valve is provided. it can.

Also, since the control piston fitted to the control cylinder provided outside the decompression cylinder and the deformed piston fitted to the decompression cylinder are connected via a lever, the dimensions of the control cylinder are smaller than those of the decompression cylinder. The urging force acting on the deformed piston can be appropriately set to increase the degree of freedom, or the urging force acting on the deformed piston can be arbitrarily selected by changing the lever ratio. For this reason, not only when the pressure of the air spring is low, but also when the size of the control cylinder is restricted due to space, the urging force acting on the deformed piston is appropriately changed in response to the load change. be able to.

<Examples> Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of an essential part showing an embodiment of a brake fluid pressure control device according to the present invention, in which a piston 2 having a different diameter is slidably fitted inside a decompression cylinder 1 having a cylindrical shape. The inside of the decompression cylinder 1 has an input chamber 3 having a small pressure receiving area.
And the output chamber 4 having a large pressure receiving area.

A valve port 5 that connects the input chamber 3 and the output chamber 4 is formed in the deformed piston 2. A ball valve 6 is opposed to the valve port 5 from the input chamber 3 side, and the ball valve 6 is seated and biased by the valve spring 7 on the valve port 5. And
The valve lifter 8 facing the valve port 5 is connected to the output chamber 4
The ball valve 6 is opened against the valve spring 7 when the different diameter piston 2 slides toward the output chamber 4 by more than a predetermined amount.

On the other hand, a control cylinder 9 is provided outside the decompression cylinder 1,
The rod of the control piston 10 fitted in the control cylinder 9
11 is projected to the outside of the control cylinder 9. And
By connecting the small diameter end of the deformed piston 2 protruding to the outside of the decompression cylinder 1 and the tip of the rod 11 of the control piston 10 via the lever 12, the pressure of the control chamber 13 formed on the upper surface of the control piston 10 Is increased to increase the moving force (output) of the control piston 10 toward the lower side in the drawing, the pressing urging force to the output chamber 4 side transmitted to the deformed piston 2 via the lever 12 is increased. . 14, 1
5 and 16 are piston seals, 17 is a return spring, and a hydraulic pressure inlet 18 is provided in the input chamber 3, and
The output chamber 4 is provided with a hydraulic outlet 19. Reference numeral 20 is an air inlet provided in the control cylinder 9.

The hydraulic pressure control device (pressure reducing valve) configured in this way is
The brake control system is connected as shown in the figure. That is, the output hydraulic pressure of the air booster 23 that increases the hydraulic pressure output from the master cylinder 22 operated by the brake pedal 21 is supplied to the front brake cylinder 25 and the hydraulic pressure inlet 18 of the pressure reducing valve 26 via the safety cylinder 24. is doing. Further, the rear air tank 29 connected to the air tank 28 via the rear leveling valve 27 and the air inlet 20 of the control cylinder 9 are connected.
And the hydraulic pressure outlet 19 of the pressure reducing valve 26 is connected to the rear brake cylinder 30. 31 is an air compressor, 32 is a check valve, 33 is a protection valve,
34 is a front leveling valve, 35 is a front air tank, 36 is a front air spring, and 37 is a rear air spring.

In the brake fluid pressure control device having such a configuration, when the brake pedal 21 is not depressed and the depression force is sufficiently small, the pressure at the fluid pressure inlet 18 (input chamber 3) of the pressure reducing valve 26 is sufficiently low. Therefore, the different-diameter piston 2 receives a pressing force from the control piston 10 and moves downward in the drawing to open the ball valve 6.

The brake pedal's 21 stepping force increases and the hydraulic pressure inlet 18
When the pressure in the (input chamber 3) rises, the different diameter piston 2 moves upward in the figure due to the difference in pressure receiving area, and the ball valve 6 is closed. Further, when the depression force of the brake pedal 21 increases, the pressure of the hydraulic pressure inlet 18 (input chamber 3) further increases. However, at this time, the pressure of the hydraulic pressure outlet 19 (output chamber 4) maintains the previous state, and this time the different diameter piston 2 moves largely downward in the figure, so the valve lifter 8 moves the ball valve 6 The valve port 5 is opened by lifting. Then, the pressure of the input chamber 3 is introduced into the output chamber 4 through the valve port 5 and the pressure of the output chamber 4 (fluid pressure outlet 19) rises, so that the different diameter piston 2 is again caused by the difference in pressure receiving area. The ball valve 6 is pushed back to the input chamber 3 side, and the ball valve 6 is closed and balanced.

On the other hand, when the load changes, the pressures of the air springs 36 and 37 are adjusted by the action of the leveling valves 27 and 34, and the vehicle height is maintained at a predetermined value. Therefore, there is a correlation between the load and the sizes of the air springs 36 and 37, and the pressure of the air springs 36 and 37 increases as the load increases. Further, when the pressure of the air supplied to the control chamber 13 rises, the output of the control piston 10 increases and the urging force that presses the different diameter piston 2 toward the output chamber 4 increases, and the pressure reducing valve 26 accordingly. The balance pressure of becomes high.

As described above, since the pressure of the air springs 36 and 37, which increases as the load increases, is supplied to the control chamber 10, the degree of pressure reduction of the hydraulic pressure at the hydraulic pressure outlet 19 decreases as the load increases (pressure reduction). The output pressure of valve 26 rises). Therefore, the ratio of the brake fluid pressure supplied to the front brake cylinder 25 and the brake fluid pressure supplied to the rear brake cylinder 30 is optimally controlled according to the magnitude of the load, and the ratio between the front brake and the rear brake is controlled. The distribution of braking force is maintained in an ideal state.

Further, since the rod 11 of the control piston 10 fitted to the control cylinder provided outside the decompression cylinder 1 and the small diameter end of the different diameter piston 2 are connected via the lever 12, the decompression cylinder 1 is compared with the decompression cylinder 1. As a result, the dimensional freedom of the control cylinder 9 is increased, and the biasing force acting on the odd-shaped piston 2 can be appropriately selected. Also, the modified piston 2 and the control piston
By changing the lever ratio of the lever 12 connecting the 10 members, the biasing force acting on the odd-shaped piston 2 can be arbitrarily selected. For this reason, not only when the pressure of the air springs 36, 37 is low, but also when the size of the control cylinder 9 is restricted due to the space, the biasing force acting on the deformed piston 2 is made to respond to the variation of the load. Can be changed accurately.

Furthermore, in the embodiment, only the pressure reduction degree of the brake hydraulic pressure supplied to the rear brake cylinder 30 is variably controlled according to the load, but a similar mechanism is also provided in the hydraulic pressure control path of the front brake cylinder 25, for example. It is also possible to further improve the braking performance of the air spring automobile by optimally controlling the brake fluid pressure (braking force) of the plurality of axles according to the load of each axle, such as by interposing.

<Effects of the Invention> As described above, according to the present invention, even in an air spring automobile whose vehicle height is maintained at a predetermined value, the degree of pressure reduction of the brake fluid pressure supplied to the brake cylinder is automatically adjusted according to the load. Can be changed. Further, since the rod of the control piston fitted to the control cylinder provided outside the decompression cylinder and the piston of different diameter are connected via the lever,
A control cylinder of arbitrary size can be provided for the decompression cylinder to set the urging force acting on the deformed piston appropriately, or if the size of the control cylinder is restricted, the deformed piston can be simply changed by changing the lever ratio. It is possible to arbitrarily select the urging force acting on. Therefore, not only when the pressure of the air spring is low, but also when the size of the control cylinder is restricted due to space restrictions, the biasing force that acts on the deformed piston can be changed accurately in response to load fluctuations. It is possible to improve the braking characteristics of an air spring automobile.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an essential part showing an embodiment of the present invention, and FIG. 2 is a brake control system diagram of an air spring automobile showing an application example of the present invention. 1 ... Pressure reducing cylinder, 2 ... Pressure reducing piston, 3 ... Input chamber, 4 ... Output chamber, 5 ... Valve port, 6 ... Valve, 7 ... Valve spring, 8 ... Valve lifter, 9 ... Control cylinder, 10 ... Control piston 11 …… rod, 12 …… lever 13 …… control chamber, 14,15,16 …… piston seal 17 …… return spring, 18 …… hydraulic inlet 19 …… hydraulic outlet, 20 …… air inlet 21 …… Brake pedal, 22 …… Master cylinder 23 …… Air booster, 24 …… Safety cylinder 25 …… Front brake cylinder, 26 …… Reducing valve 27 …… Rear leveling valve, 28 …… Air tank 29 …… Rear air Tank, 30 …… rear brake cylinder 31 …… air compressor, 32 …… check valve 33 …… protection valve, 34 …… front leveling valve 35 …… front air tank, 36 …… front air spring 37 ...... Rear air spring

Claims (1)

[Claims] 1. A vehicle having an air spring and a hydraulic brake, wherein the decompression cylinder is divided into an input chamber having a small pressure receiving area and an output chamber having a large pressure receiving area, and a different diameter piston, and the input chamber. A valve port provided on the different diameter piston for communicating with the output chamber, a valve facing the valve port from the input chamber side, a valve spring for biasing the valve to seat on the valve port, and the different A valve lifter that lifts the valve against the valve spring when the diameter piston slides to the output chamber side more than a predetermined value, and a control slidably fitted to a control cylinder provided outside the decompression cylinder. A piston, a lever connecting the modified piston to a control piston, and a control cylinder by the control piston An air inlet for supplying the air pressure of the air spring to the formed control chamber, a hydraulic pressure inlet for supplying the hydraulic pressure in response to the stepping force of the brake pedal to the input chamber, and a hydraulic pressure for the output chamber to the brake cylinder. Brake fluid pressure control device for an air spring automobile, comprising: