JPH0451386B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a load sensing proportioning valve (hereinafter referred to as LSPV).

In general, it is considered ideal that the braking force in a vehicle such as an automobile should be distributed between the front and rear wheels so that they lock simultaneously, and this characteristic line is called the ideal braking force distribution curve. It is known that it differs depending on the load.

LSPV is used to obtain braking force distribution lines that are as close as possible to the ideal braking force distribution curve, which differs depending on the live load, depending on the live load, and usually calculates the amount of relative change between the vehicle body and the rear axle using the link mechanism. etc., and by controlling the opening and closing of the pressure medium between the inflow and outflow channels according to the amount of displacement, the brake pressure of the rear wheels is adjusted, and each approximate control as shown in Fig. 4 is applied. It is now possible to obtain a power distribution characteristic line. The bending point (braking force adjustment starting point) shown in FIG. 4 is called a split point.

However, in conventional LSPVs of this type, the relative displacement of the vehicle body with the rear axle is extracted using a link mechanism, etc., and converted into the amount of spring deflection, and this spring force is used to create a split point at each load. Therefore, the structure tends to be complicated and the cost tends to be high.

On the other hand, changes in the bellows internal pressure (hereinafter referred to as air suspension pressure) of air suspensions equipped with vehicle height adjustment devices installed on large vehicles such as trucks and buses are approximately proportional to changes in the carrying load, so this air suspension pressure is used. It is conceivable to control the braking force by

An object of the present invention is to provide an LSPV that can obtain a braking force distribution characteristic line that approximates an ideal braking force distribution curve in response to changes in live load using air suspension pressure.

The present invention will be described below with reference to embodiments shown in the drawings.

Fig. 1 is a longitudinal sectional view showing an LSPV that is an embodiment of the present invention, Fig. 2 is a schematic circuit diagram showing an air brake device using the LSPV, Figs. 3 A, B, C,
D is a schematic sectional view for explaining the action, and FIGS. 4 and 5 are line diagrams.

First, the outline of the air brake device shown in FIG. 2 will be explained. An air tank 2 that stores air sent out from an air compressor 1 is connected to a brake valve 3 that responds to a flake pedal. The front brake chamber 4 is connected to the brake valve 3 via a quick release valve 5, and the rear brake chamber 6 is connected to the air tank 2 via a relay valve 7. The relay valve 7 is connected to the brake valve 3 via the LSPV 8, and the air suspension pressure in the air suspension 9 is guided to the LSPV 8. Air suspension 9 has frame 10a and axle 1
The bellows is interposed between the bellows and the bellows and is configured to maintain the vehicle height constant at all times by supplying pressure into the bellows in accordance with the load. Therefore, the change in the bellows pressure (air suspension pressure) in the air suspension 9 is approximately proportional to the load.

When the brake valve 3 operates, air from the air tank 2 is supplied to the front and rear brake chambers 4 and 6 via the quick release valve 5 and the relay valve 7, respectively. At this time,
In LSPV8, the pressure from brake valve 3 is reduced at a set rate, and this acts on relay valve 7, so the braking force on the rear side is suppressed more than that on the front side, thereby ensuring the desired distribution of braking force. will be done.

In this embodiment, the LSPV 8 includes a main body 11, and inside the main body 11, a first cylinder chamber 12 as a differential cylinder chamber is formed in a cylindrical hollow shape with different diameters. The first piston is a large diameter piston formed into a cylindrical shape with approximately different diameters.
A differential piston 13 consisting of a piston 14 and a second piston 30 formed to have the same diameter as the small diameter portion of the first piston 14 is fitted so as to be slidable in the vertical direction. An inflow passage 15 is bored in the upper part of the main body 11 so as to face the large diameter lower surface space of the first piston 14 in the first cylinder chamber 12.
is connected to the brake valve 3. Main body 11
An outflow passage 16 is bored in the upper part of the relay valve 7 so as to face the space above the first piston 14 in the first cylinder chamber 12.
connected to. An exhaust passage 17 is vertically bored approximately in the center of the upper part of the main body 11, and the upper end of the exhaust passage 17 is opened to the atmosphere through a filter 18. The lower end of the exhaust passage 17 is the first cylinder chamber 1
It protrudes downward from the ceiling surface of No. 2, and an exhaust valve seat 19 is formed in an annular shape at the lower end of the protrusion.

A valve chamber 20 is formed in the center of the upper part of the first piston 14, and the valve chamber 20 has a passage 21 formed on its side surface and is opened at its ceiling surface to allow the inflow of the first cylinder chamber 12. The passage 15 side and the outflow passage 16 side are communicated with each other. Therefore, the valve chamber 20 substantially constitutes a passage connecting the inflow passage 15 and the outflow passage 16.
A valve plate 22 having an air supply port 22 a formed in the center thereof is fitted into the upper part of the valve chamber 20 and fixed by a retaining ring 23 . An air supply valve seat 24 is provided at the periphery of the air supply port 22a of the valve plate 22.
is protruded concentrically with the exhaust valve seat 19.

A supply/exhaust valve 25 and a back pressure introduction valve 26 are housed in the valve chamber 20, with a compression spring 27 interposed therebetween in a stored state. The supply/exhaust valve 25 is configured to sit on the exhaust valve seat 19 and separate from the intake valve seat 24 when the first piston 14 is located at the upper limit. A cut valve holder 28 is slidably inserted into the central hole formed in the lower part of the first piston 14 so that the upper end surface protrudes from the bottom surface of the valve chamber 20 under normal conditions. The back pressure introduction path 29 is connected to the valve chamber 20 and the back pressure chamber 31 to be described later.
It is perforated to communicate with the The back pressure introduction valve 26 seats on the upper surface of the holder 28 and closes the introduction path 29 when the holder 28 protrudes from the bottom surface of the valve chamber 20, and closes the introduction path 29 when the holder 28 retracts from the bottom surface of the valve chamber 20. It is supported on the bottom surface of the chamber 20 to open the introduction path 29.

At the lower part of the small diameter part of the first cylinder 12,
The second piston 30 is fitted so as to abut against the first piston 14 so as to be able to move toward and away from the first piston 14, and both pistons 1
A back pressure chamber 31 is formed at the abutting portion of 4 and 30. A cut valve 32 is slidably fitted into a central hole formed in the second piston 30, and a T-shaped air vent passage 33 is bored in the lower part of the cut valve 32. The cut valve 32 is disposed such that its upper end abuts the lower end of the holder 28, and its lower end abuts the upper end of an inner piston 41, which will be described later. A compression spring 34 is interposed in a stored force state between the lower surface of the first piston 14 and the cut valve 32 in the back pressure chamber 31.
The cut valve 32 is configured to close the air vent passage 33 by the biasing force of the compression spring 34 when the inner piston 41 is released from support.

An atmospheric chamber 35 is formed below the second piston 30 in the main body 11, and this chamber 35 is communicated with the atmosphere through a filter 37 through a vent hole 36 formed in the lower part of the main body 11.

In the lower part of the main body 11, a second cylinder chamber 39 as a control cylinder chamber is connected to an atmospheric chamber 35 via a partition wall 38.
are formed adjacent to each other, and this cylinder chamber 3
9 has an inner piston 41 and an outer piston 42
A double structure control piston 40 consisting of the following is fitted. A ventilation hole 43 is provided in the partition wall 38 to connect the upper chamber 3 of the outer piston 42 in the second cylinder chamber 39.
It is bored so that the air chamber 9a and the atmospheric chamber 35 communicate with each other. At the bottom of the main body 11 is an air suspension pressure introduction passage 44.
is bored so as to communicate with the lower chamber 39b of the double-structured control piston 40 in the second cylinder chamber 39, and the internal pressure of the bellows (air suspension pressure) in the air suspension 9 is introduced into the introduction path 44. ing.

The inner piston 41 is slidably inserted into a central hole 45 formed in the partition wall 38, and comes into contact with the second cylinder 30 and the cut valve 32 when pushed up by the pressure of the second cylinder chamber 39. There is. An inverted T-shaped second air bleed passage 46 is connected to the cut valve 32 at the upper part of the inner piston 41.
and the atmospheric chamber 35 are formed to communicate with each other. The inner piston 41 is slidably fitted into a central hole 47 of an outer piston 42 fitted into the second cylinder chamber 39, and the central hole 47 is provided on the outer periphery of the intermediate portion.
A step portion 48 is formed which engages with the upper edge of. A compression spring 49 is interposed between the partition wall 38 and the outer piston 42 in the second cylinder chamber 39 in a stored force state, and the biasing force of the compression spring 49 is applied when the internal pressure of the second cylinder chamber 39 is below a set value. The outer piston 42 is set to be pushed down relative to the inner piston 41 when the piston is bent (details will become clear in the explanation of the operation).

A detour path 50 is formed in the upper part of the main body 11 so as to bypass the air supply port 22a formed in the valve plate 22 and communicate the inflow path 15 and the outflow path 16. A check valve chamber 51 is formed. A check valve 52 is installed inside the check valve chamber 51 and is biased by a compression spring 53 and plugged with a plug 54 .
Flow is allowed only in the direction from to the inflow path 15.

Next, the action will be explained.

Operation of the load detection device The air suspension pressure introduced into the second cylinder chamber 39 is applied to the inner piston 41 and the outer piston 42.
The compression spring 49 acts on the outer piston 42 in a direction opposite to the air suspension pressure. That is, the inner piston 41 and the outer piston 42
The second force is obtained by subtracting the force of the spring 49 from the force generated by the air suspension pressure acting on the effective area of
It acts on the first piston 14 via the piston 30.

Here, since the force of the compression spring 49 in a balanced state, which will be described later, is constant, the higher the air suspension pressure is, the greater the force acting on the first piston 14 is. That is, as described above, the vehicle's live load and air suspension pressure are proportional, and the larger the live load is, the higher the air suspension pressure is. Therefore, as the load increases, the force acting on the first piston 14 increases.

In this way, by detecting the vehicle's live load as a force acting on the first piston 14, the LSPV characteristics are created to match the characteristics of the vehicle, but the relationship between the air suspension pressure and the splint point is Since each characteristic is different, characteristic lines a, b, and c as shown in FIG. 5 are considered necessary.

All of these characteristics can be satisfied by appropriately selecting the effective areas of the inner piston 41 and outer piston 42 of the control piston 40 and the force of the compression spring 49. The structure of the LSPV according to this embodiment satisfies the relationship shown by straight line b in FIG. If it is desired to satisfy the relationship shown by straight line a, the compression spring 49 may be omitted, and if it is desired to satisfy the relationship shown by straight line C, a compression spring may be set below the outer piston 42.

Proportioning Operation in Normal Conditions In any braking condition, as described above, a force corresponding to the load at that time acts on the first piston 14, so the operation will be explained assuming that this is constant.

The pressure from the inflow passage 15 (hereinafter sometimes referred to as inlet pressure Pi) is applied to the passage 21 and the air supply port 22a.
and is sent to the outflow path 16. At this time, the first piston 14 is gradually pushed up when the pressure acting on the effective area of the small diameter portion overcomes the upward force caused by the air suspension pressure. When the air supply valve seat 24 comes into contact with the air supply/exhaust valve 25, the supply from the inflow path 15 to the outflow path 16 is cut off. This point becomes the splitting point. When the inlet pressure Pi further increases from this state, the piston 14 is pushed up and the air supply valve seat 24 opens, so that pressure is again supplied from the inflow path 15 to the outflow path 16. As a result, when pressure corresponding to the ratio of the large-diameter lower effective area and upper effective area of the piston 14 is supplied, the piston 14 is pushed down again and closes the air intake valve seat 24 (such an air intake valve seat The state in which both the exhaust valve seat 24 and the exhaust valve seat 19 are closed is called a balanced state (see Fig. 3A).

From this state, as the inlet pressure Pi increases, the pressure in the outflow path 16 (hereinafter sometimes referred to as the outlet pressure Po) increases with a predetermined pressure reduction ratio to the inlet pressure Pi. (See Figure 4).

Furthermore, when the inlet pressure Pi is lowered from the balanced state, the first piston 14 is pushed down together with the supply and exhaust valve 25, and the exhaust valve seat 19 opens (the third
(See Figure B), the outlet pressure Po is exhausted, so the original balance state is restored. This allows the outlet pressure Po
is reduced at a predetermined pressure reduction ratio relative to the inlet pressure Pi.

Note that when the air suspension pressure changes in accordance with the load, as described above, the force acting upward on the first piston 14 changes accordingly, so a corresponding splint point is created, as shown in FIG. Each characteristic line shown in is obtained.

By the way, when the inlet pressure Pi is lowered, the outlet pressure Po is also gradually lowered, but the inlet pressure Pi
Even if becomes zero, the outlet pressure Po that balances only the force acting upward on the first piston 14 remains on the outflow path 16 side.

A check valve 52 is provided to prevent this, and when the inlet pressure Pi is below the splint point, the inlet pressure Pi and the outlet pressure Po are 1:1.
The pressure is starting to drop. That is, during pressure reduction, since the inlet pressure Pi is acting on the check valve chamber 52, the check valve 52 has an inlet pressure Pi and an outlet pressure Po.
The opening leading to the outlet 16 is closed by the force caused by the difference between the
2 is opened and the outlet pressure Po flows backward, reducing the pressure on the outflow path 16 side. Due to this action, the balance state in the first piston 14 is disrupted, the first piston 14 is pushed down, the air supply valve seat 24 is opened, and the initial state is returned to the inlet pressure Pi and the outlet pressure Po.
That means the ratio is 1:1.

Operation in case of failure (see Figure 3C).

When the air suspension pressure becomes zero due to damage to piping or the like in the air suspension, the outer piston 42 is pushed down by the compression spring 49. At the same time, the compression spring 34 causes the cut valve 3 to
2. Since the inner piston 41 is pushed down and the seat portion of the cut valve 32 comes into contact with the second piston 30, the back pressure chamber 31 is blocked from the air vent path 33. Further, the cut valve holder 28 is also pushed down by the inlet pressure Pi and the spring 27, and the seat portion of the back pressure introduction valve 26 opens, so that the inlet pressure Pi is introduced into the back pressure chamber 31 through the back pressure introduction path 29. Since this introduction pressure acts on the back surface of the first piston 14, the ratio of the effective areas of the upper surface and the lower surface of the first piston 14 is approximately 1:1. Therefore,
The ratio between the inlet pressure Pi and the outlet pressure Po is also 1:1.

Operation when Air Suspension Pressure is Low If the control piston 40 has an integral structure, if there is no longer enough air suspension pressure to push the outer piston 42 down to the balanced position against the compression spring 49, the above-mentioned Due to the failure operation, the decompression effect is canceled.

However, if the air suspension side is normal, a pressure reducing action is necessary even if the air suspension pressure is low.

Therefore, by configuring the control piston 40 in a divided structure into an inner piston 41 and an outer piston 42, even if the outer piston 42 is pushed down, the air suspension pressure acting on the inner piston 41 applies force to the first piston 14. This allows the decompression effect to be performed in the same way as under normal conditions.

According to this embodiment, the load sensing proportioning function can be demonstrated using air suspension pressure, so the structure can be simplified.
The risks of wear, failure and malfunction in the link material structure are eliminated, and it is economically advantageous.

Since the control piston that receives the air suspension pressure has a double structure, the necessary proportioning function can be ensured even when the air suspension pressure is low.

The differential piston that operates to close the passage between the inflow path and the outflow path has a composite structure of a first piston and a second piston, and in an unexpected situation where the air suspension pressure becomes 0, the pressure in the inflow path is By introducing the air into the back of the piston, it is possible to leave the air supply port between the inflow and outflow channels open and stop the decompression operation, which is a braking force distribution function, so that it can be used in case of unexpected situations. Concerns about insufficient braking power can be eliminated and safety can be ensured.

It goes without saying that the present invention is not limited to the embodiments described above, and that various changes can be made without departing from the spirit thereof.

For example, the composite structure of the control piston is not limited to a double structure, and any structure may be used as long as one of the pistons cooperates with the operating piston except in a fail-safe situation. Furthermore, the control piston may be of monolithic construction.

As described above, according to the present invention, the braking force can be distributed according to the vehicle load using the air suspension pressure.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view showing an LSPV that is an embodiment of the present invention, Fig. 2 is a schematic circuit diagram showing an air brake device using the LSPV, and Figs. 3 A, B, C, and D explain the operation. The schematic cross-sectional views, FIGS. 4 and 5, are also line diagrams. 1...Air compressor, 2...Air tank,
3...Brake valve, 4...Front brake chamber, 5...Quick release valve, 6...
...Rear brake chamber, 7...Relay valve,
8...LSPV, 9...Air suspension, 11
... Main body, 12 ... First cylinder chamber (differential cylinder chamber), 13 ... Differential piston, 14 ... First piston (large diameter piston), 15 ... Inflow path, 16
...Outflow path, 17...Exhaust path, 18...Filter, 19...Exhaust valve seat, 20...Valve seat, 21...
Passage, 22... Valve plate, 22a... Air supply port, 23... Stop ring, 24... Air supply valve seat, 2
5... Supply and exhaust valve, 26... Back pressure introduction valve, 27...
Compression spring, 28...Cut valve holder, 29...Back pressure introduction path, 30...Second piston, 31...Back pressure chamber, 32...Cut valve, 33...Air vent path, 3
4... Compression spring, 35... Atmospheric chamber, 36... Ventilation path, 37... Filter, 38... Partition wall, 39...
Second cylinder chamber (control cylinder chamber), 40... Control piston, 41... Inner piston, 42...
Outer piston, 43...Vent hole, 44...Air suspension pressure introduction path, 45...Central hole, 46...Air vent path, 47...Central hole, 48...Step part, 49...
Compression spring, 50...Detour, 52...Check valve.

Claims (1)

[Claims] 1. A differential piston 13 slidably fitted into a differential cylinder chamber 12 formed in the main body 11;
An inlet passage 15 is provided in the small diameter chamber of the differential cylinder chamber 12 so as to face the end face space of the large diameter piston 14 of the differential piston 13, and an inlet passage 15 is provided in the small diameter chamber of the differential cylinder chamber 12 so as to face the end surface space of the large diameter piston 14 of the differential piston 13; An outflow passage 16 opened to face the end space of the large-diameter piston 14 of the piston 13, and a valve chamber 20 opened to the differential piston 13 so as to communicate the inflow passage 15 and the outflow passage 16. an exhaust passage 17 that protrudes from the main body 11 and is inserted into the valve chamber 20 and has an exhaust valve seat 19 formed at its insertion end; Air valve seat 2
4 is formed in the air supply port 22a, and the exhaust valve seat 19 and the air supply valve seat 24 are disposed in the valve chamber 20, and as the differential piston 13 reciprocates, the exhaust valve seat 19 and the air supply valve seat 24 are disposed in the valve chamber 20.
The load sensing proportioning valve is provided with an air supply/exhaust valve 25 that opens and closes the exhaust passage 17 and the air supply port 22a by seating and leaving the main body 11 adjacent to the differential cylinder chamber 12. A control cylinder chamber 39 is formed, and a control piston 40 is slidably fitted into this control cylinder chamber 39, and this control piston 40 connects the differential piston 13 to the supply/exhaust valve 25 and the intake valve seat. The control cylinder chamber 39 has an air suspension pressure introduction path 4 connected to the air suspension 9.
4 is opened to always urge the control piston 40 in the direction, and the control piston 40 has an outer piston 42 slidably fitted in the control cylinder chamber 39; It consists of an inner piston 41 that is slidably fitted into the outer piston 43 and is engaged so as to move integrally only in the direction of the differential piston 13; is equipped with a second piston 30 separated from the large-diameter piston 14, and this second piston 30 is fitted into the differential cylinder chamber 12 so as to abut against the large-diameter piston 14 so as to be able to move toward and away from the large-diameter piston 14. At the same time, a back pressure chamber 31 is formed at the abutting portion of the large diameter piston 14 and the second piston 30, and a cut valve 32 is provided in the second piston 30.
The cut valve 32 and the inner piston 41 are slidably fitted in a state in which they are urged to abut against the inner piston 41 by a spring 34 interposed between the cut valve 32 and the inner piston 41. A first air bleed passage 33 and a second air bleed passage 46 are respectively opened at the abutting portion of the large diameter piston 14 so as to communicate the back pressure chamber 31 and the atmospheric chamber 35. A valve holder 28 is disposed so as to abut against the cut valve 32 and is slidably inserted therein, and a back pressure introducing passage 29 is provided in the cut valve holder 28 to connect the valve chamber 20 and the back pressure chamber 31. Furthermore, a back pressure introduction valve 26 is arranged in the valve chamber 20 so as to approach and separate from the cut valve holder 28 at the position of the back pressure introduction path 29. , a load sensing proportioning valve characterized in that the back pressure introduction valve 26 is always biased by a spring 27 in a direction to close the back pressure introduction path 29.