JPH0467035B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a surge pressure absorption circuit for a hydraulic device.

(Prior Art) A well-known surge pressure absorption circuit for a hydraulic device is a device described in Japanese Patent Laid-Open No. 167502/1983. As shown in FIG. 1, this device has a variable orifice 3 interposed in a main line 2 connected to a variable pump 1, and the differential pressure across the variable orifice 3 is maintained constant using a load sensing valve 4. , on the other hand, the pilot chamber 6 of the pressure control pilot valve 5 is communicated with the main line 2, and its spring chamber 7 is communicated with the main line 2 via the throttle 8, and the spring chamber 7 of the pressure control pilot valve 5 is communicated with the main line 2 through the throttle 8. A pilot relief valve 10 is connected to a pilot line 9 branched from between the and the throttle 8,
A normally closed surge pressure absorption valve 11 is connected to the front of the variable orifice 3 of the main line 2, and the spring chamber 12 of this surge pressure absorption valve 11 is connected to the spring chamber 7 of the pressure control pilot valve 5. It consists of

In the above device, when the cylinder 13 connected to the main line 2 reaches the stroke end,
When the fluid pressure in the main line 2 reaches the set pressure of the pilot relief valve 10, the fluid is relieved from this valve 10 and the pressure loss at the throttle 8 causes the spring chamber of the pressure control pilot valve 5 to be released. As a result, the pressure control pilot valve 10 is located at the symbol position S2, and the fluid in the main line 2 is transferred to the discharge amount controller 1 of the variable pump 1.
4, the discharge amount of the variable pump 1 is reduced, and the fluid pressure in the main line 2 is maintained at the above pressure. By the way, in order to operate the pressure control pilot valve 5 as described above, it is necessary to set the spring force of the surge pressure absorption valve 11 to be larger than the spring force of the pressure control pilot valve 5. The spring force of the surge pressure absorption valve 11 is
If the spring force is set larger than the spring force of the pressure control pilot valve 5, the surge pressure absorption valve 11 will operate only after the pilot relief valve 10 and the pressure control pilot valve 5 have operated. Therefore, the above-mentioned device has a drawback in that it does not have a sufficient absorption effect against sudden surge pressure generated in the circuit.

(Object of the invention) This invention was made in view of the above, and its purpose is to effectively absorb this surge pressure even when a sudden surge pressure occurs in the circuit of a pressure reducing device, and to prevent the surge pressure from occurring. An object of the present invention is to provide a surge pressure absorption circuit that can prevent the above.

(Structure and operation of the invention) The surge pressure absorption circuit of the hydraulic device of the present invention, which meets the above object, includes a resistance valve interposed in the main line connecting the hydraulic pump and the actuator, and
A normally open surge pressure absorption valve is installed in a branch line branching from this main line, and the pilot chamber of the surge pressure absorption valve receives the fluid pressure in front of the resistance valve, and the spring chamber receives the above-mentioned fluid pressure. They each guide the fluid pressure downstream of the resistance valve.

As a result of the above, if there is fluid flow in the main line, a pressure difference will be created across the resistance valve, and this pressure difference will keep the surge pressure absorbing valve closed; When the actuator reaches its stroke end, the fluid pressure in the main line increases, and the fluid flow in the main line stops, the differential pressure across the resistance valve becomes zero, and the spring force The surge pressure absorption valve is therefore activated immediately, bypassing main line fluid to the tank. In this way, the surge pressure absorption valve operates immediately after the fluid pressure in the main line increases and the flow of fluid in the main line stops, making it possible to effectively prevent the generation of surge pressure. becomes.

(Embodiments) Next, specific embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 shows a first embodiment of the invention. In the figure, 21 is a variable pump, and an actuator 23 such as a cylinder is connected to this variable pump 21 via a main line 22, and a check valve 24 as a resistance valve is connected to the main line 22. A variable orifice 25 is provided respectively. Further, a load sensing valve 26, a pressure control pilot valve 27, an electromagnetic proportional pressure relief valve 28, and a normally open, seat-type surge pressure absorption valve 29 are connected to the main line 22 as described later. ing.

In the load sensing valve 26, the pressure between the check valve 24 and the variable orifice 25 in the main line 22 is introduced into the pilot chamber 30 via the pilot line 31, and the pressure between the check valve 24 and the variable orifice 25 is introduced into the spring chamber 32. Rear pressure is led through a pilot line 33, and the load sensing valve 26 is adapted to respond to the differential pressure across the variable orifice 25. Further, this load sensing valve 26 is provided with three ports, l, m, and n. The port n of the tank 36 is connected via a pilot line 37 to a port m of a pressure control pilot valve 27, which will be described later.

The pilot chamber 38 of the pressure control pilot valve 27 is connected to the main line 22 in front of the check valve 24 via a pilot line 39, and the spring chamber 40 is connected to the check valve via a pilot line 42 provided with a throttle 41. 24 are respectively connected to the main line 22 in front. In addition, the pressure control pilot valve 27 has three ports l, m, and n.
Port l is located in front of the throttle 41 of the pilot line 42, port m is connected to port n of the load sensing valve 26, and port n is connected to the swash plate control in the variable pump 21 via the pilot line 43. Discharge amount control section 4 consisting of a cylinder
4 are connected to each other. Further, the spring chamber 40 of this pressure control pilot valve 27 is connected to the line 4.
5 to the electromagnetic proportional pressure relief valve 28.
The next side communicates with a tank 46.

On the other hand, the variable orifice 25 of the main line 22
A branch line 47 is provided at the rear position, and a surge pressure absorption valve 29 is interposed in this branch line 47, and its pilot chamber 48 is connected to the main line 22 via the pilot line 49.
The spring chamber 50 is connected to the branch line 47 at a position in front of the check valve 24. Note that the secondary side of this surge pressure absorption valve 29 is connected to the tank 51. What is particularly important to note here is that the spring force of the spring chamber 50 of the surge pressure absorption valve 29 is set smaller than the cracking pressure of the check valve 24, but the reason for this will be explained later. will be explained in detail.

A detailed structure of the surge pressure absorption valve 29 is schematically shown in FIG. This surge pressure absorption valve 29 is a normally open type seat valve, and the valve body 5
As mentioned above, the pilot chamber 48 provided in the main line 22 receives the fluid pressure in front of the check valve 24, and the spring chamber 50 receives the branch line 47,
That is, the variable orifice 25 of the main line 22
The downstream fluid pressure is guided respectively. A cylindrical sleeve 53 is fitted into the valve body 52, and a piston 54 is slidably disposed within the sleeve 53. A spring holder 55 is attached to the lower end of the sleeve 53, and a spring 56 is disposed between the spring holder 55 and the piston 54, and the piston 54 is moved toward the pilot chamber 48 by the spring 56. energized. As a result of the above,
When the fluid pressure in the pilot chamber 48 is smaller than the sum of the fluid pressure in the spring chamber 50 and the fluid pressure corresponding to the spring force, the piston 54 is pressed by the spring 56, and the piston 54 moves out of the pilot chamber 48 as shown in the figure. Open the opening 57 located on the side and provided in the sleeve 53,
The spring chamber 50, that is, the main line 22, is connected to the tank 5.
Connect to 1. On the other hand, if the fluid pressure in the pilot chamber 48 is greater than the sum of the fluid pressure in the spring chamber 50 and the fluid pressure corresponding to the spring force, the piston 54 is pressed toward the spring chamber 50 and the sleeve 53 is The opening 57 is closed to block the connection between the spring chamber 50, that is, the main line 22, and the tank 51.

Next, the operating state of the hydraulic device will be explained.

First, consider a case where, for example, the fluid pressure in the main line 22 is increasing while the actuator 23 is operating. In this case, since the pressure before and after the variable orifice 25 is introduced to the pilot chamber 30 and spring chamber 32 of the load sensing valve 26 via the pilot lines 31 and 33, respectively, the load sensing valve 26 According to the differential pressure before and after, the pressure transmitted to the discharge amount control section 44 of the variable pump 21 is controlled as shown below at the symbol position S1 or S2, and the discharge amount of the variable pump 21 is controlled between the front and rear of the variable orifice 25. (This differential pressure is the load sensing valve 26
) so that the fluid pressure corresponds to the spring force of That is, when the differential pressure before and after the variable orifice 25 becomes smaller than the fluid pressure corresponding to the spring force of the load sensing valve 26, the load sensing valve 26 is positioned at the symbol position S1 by the spring force of the spring chamber 32. , ports n and m are communicated, the discharge amount control unit 44 is communicated with the tank 36, and the swash plate is inclined toward the maximum discharge amount side to increase the discharge amount. As a result, the differential pressure before and after the variable orifice 25 increases. On the other hand, when the differential pressure before and after the variable orifice 25 becomes larger than the fluid pressure corresponding to the spring force of the load sensing valve 26, the load sensing valve 26 is located at the symbol position S2 and communicates between ports l and m, and the discharge amount The pressure of the main line 22 is transmitted to the control unit 44, and the swash plate is inclined toward the minimum discharge amount side, thereby reducing the discharge amount. As a result, the differential pressure across the variable orifice 25 decreases. The load sensing valve 26 operates as described above to maintain the differential pressure across the variable orifice 25 equal to the fluid pressure corresponding to the spring force of the load sensing valve 26.

In this way, in the above device, the discharge amount of the variable pump 21 is controlled according to the load requirements, and no excess fluid is discharged, so that energy can be saved.

In addition, in this state, the surge pressure absorption valve 29
is held closed, as explained below. Now, the pressure at the discharge part of the variable pump 21 is
If P0, this pressure P0 is introduced into the pilot chamber 48 of the surge pressure absorption valve 29. On the other hand, the fluid pressure downstream of the variable orifice 25 guided to the spring chamber 50 of the surge pressure absorption valve 29 is the pressure P0
, the cracking pressure P1 of the check valve 24 and the differential pressure before and after the variable orifice 25, that is, the fluid pressure corresponding to the spring force of the load sensing valve 26.
The fluid pressure P0-(P1+P2) is lower by P2. Therefore, the pilot chamber 4 of the surge pressure absorption valve 29
The pressure at No. 8 is higher than the pressure introduced into the spring chamber 32 by (P1 + P2). By the way, in this spring chamber 32, the above (P1+P2)
A spring force P4 acts against this, but as described above, this spring force P4 is set to be smaller than the cracking pressure of the check valve 24 (P4<P1). Therefore, the pressure in the pilot chamber 48 becomes higher than the pressure in the spring chamber 50, and as a result, the piston 54 of the surge pressure absorption valve 29 is pushed downward and moves to the opening 57 of the sleeve 53. is kept closed. In this way, the surge pressure absorbing valve 29 is maintained in the closed state during operation of the actuator 23, for example when the fluid pressure in the main line 22 is increasing.

On the other hand, when the actuator 23 reaches the stroke end, the surge pressure absorption valve 29 operates as follows to prevent the generation of surge pressure. That is, in this case, the flow of fluid in the main line 22 is eliminated, so that the pressure on the discharge side of the variable pump 21 and the pressure downstream of the variable orifice 25 become equal. As a result, in the surge pressure absorption valve 29, the fluid pressure guided to the pilot chamber 48 and the fluid pressure guided to the spring chamber 50 become equal, and the piston 54 of the surge pressure absorption valve 29 is pushed upward by the spring 56 and moves. Open opening 57 in sleeve 53. Then, the fluid in the main line 22 is released to the tank 51 via the surge pressure absorption valve 29. At this time, the fluid pressure in the main line 22 is
Since the pressure exceeds the set pressure of the electromagnetic proportional pressure relief valve 28, after the surge pressure absorption valve 29 is activated as described above, the electromagnetic proportional pressure relief valve 28 opens and the fluid in the main line 22 is sent to the tank via the pilot line 42. and open it. As a result, a pressure loss occurs in the fluid flowing in the pilot line 42 when it passes through the throttle 41, but for this reason, the pressure in the spring chamber 40 of the pressure control pilot valve 27 is guided by the pressure in the main line 22. The pressure becomes lower than the pressure in the pilot chamber 38, and the pressure control pilot valve 27 is switched to the symbol position S2 by the fluid pressure in the main line 22, and the fluid in the main line 22 is passed through ports l and n to the discharge amount control unit 44. The swash plate is tilted toward the minimum discharge amount, thereby reducing the discharge amount. As a result, the discharge amount of the variable pump 21 becomes almost zero, and the device shifts from the flow rate control state to the pressure control state where almost no flow rate is required.

In the above, when the surge pressure absorption valve 29 opens and the fluid in the main line 22 is released to the tank 51, a fluid flow is generated in the main line 22 again, and as a result, the main line 2
2, the surge pressure absorption valve 29 closes again. However, when the surge pressure absorption valve 29 closes, until the electromagnetic proportional pressure relief valve 28 opens, the surge pressure absorption valve 29 closes again. Since there is no fluid flow again, the surge pressure absorbing valve 29 will open again. In this way, the surge pressure absorption valve 29 repeats opening and closing until the electromagnetic proportional pressure relief valve 28 operates. While the electromagnetic proportional pressure relief valve 28 is opening and closing repeatedly in this way, the actuator 2
Since the fluid in the main line 22 is already released to the tank 51 immediately after the stroke end of the main line 22 reaches the stroke end, it is possible to effectively prevent the generation of surge pressure.

In the above device, if the response speed of the check valve 24 is extremely fast, the actuator 2
Strictly speaking, when 3 reaches the stroke end,
There is a pressure difference in the main line 22 that is equal to the cracking pressure of the check valve 24, and it is possible that the pressure difference in the main line 22 does not become zero, but in reality, the response of the check valve 24 may vary slightly. Because of the delay, the pressure inside the main line 22 is maintained at approximately the same pressure, and the surge pressure absorption valve 29 operates as described above. Furthermore, after the electromagnetic proportional pressure relief valve 28 operates and begins to release the fluid in the main line 22 to the tank as described above, there is no flow of fluid in the main line 22, and surge pressure Although the absorption valve 29 should remain open,
In reality, there is some fluid leakage between the main line 22 and the actuator 23, and this leakage causes a pressure difference in the main line 22 equal to the cracking pressure of the check valve 24. Therefore, the surge pressure absorption valve 29 is kept closed.

In the above device, the check valve 24 is used as a resistance valve to generate a differential pressure when fluid flows into the main line 22, but a simple throttle may be used instead of the check valve 24. can. However, in this case, if the flow rate in the main line 22 is low, for example, if there is a leak in the main line 22 or the actuator 23 in the pressure control state after the electromagnetic proportional pressure relief valve 28 opens as described above, , the surge pressure absorption valve 29 will remain open due to insufficient differential pressure within the main line 22, resulting in leakage to the tank 51, so it is necessary to consider its usage condition. . It is of course possible to use a check valve with a throttle instead of the check valve 24 as the resistance valve. Furthermore, the position where the resistance valve 24 is provided is not limited to that shown in the drawings, and may be provided within the main line 22 between the pilot line 31 leading to the load sensing valve 26 and the variable orifice 25.

The first embodiment of this invention has been described above, but
In this device, immediately after the actuator 23 reaches the stroke end, the fluid in the main line 22 is passed through the surge pressure absorption valve 29 to the tank 51.
Since the actuator 23 is opened to the
During operation, only the flow rate required by the actuator 23 is discharged from the variable pump 21 by the load sensing valve 26, thereby making it possible to save energy.

FIG. 4 shows a second embodiment of the present invention, in which the differential pressure between the check valve 24 and the variable orifice 25 in the main line 22 is kept constant by a pressure reducing type pressure compensating valve 61. This is what I did. That is, the pressure in front of the check valve 24 is introduced into the pilot chamber 62 of the pressure reducing type pressure compensation valve 61, and the pressure in the rear of the variable orifice 25 is introduced into the spring chamber 63 through the pilot line 64 and the throttle 65. The pressure reducing type pressure compensating valve 61 is made to respond to the differential pressure before and after the check valve 24 and the variable orifice 25. In this case, the electromagnetic proportional pressure relief valve 28 is connected to the main line 22 via the pilot line 64.

In the above device, similarly to the above embodiment, when the actuator 23 reaches the stroke end and there is no fluid flow in the main line 22, the surge pressure absorption valve 29 opens and the main line 22
It becomes possible to release the fluid in the tank 51 to the tank 51 and prevent the generation of surge pressure.

Although the embodiments of the present invention have been described above, the surge pressure absorption circuit of the pressure reducing device of the present invention is not limited to the above, and can be implemented with various modifications. For example, the resistance valve for generating a pressure difference in the main line 22 that is higher than the fluid pressure corresponding to the spring force of the surge pressure absorption valve 29 is not limited to the above-described check valve 24, a check valve with a throttle, or a throttle. Various means can be used, as long as they generate a pressure loss due to the flow of fluid. Further, although the above example uses the electromagnetic proportional pressure relief valve 28 as the relief valve, it is of course possible to use other types of relief valves, or this relief valve may be omitted. It is also possible.

(Effect of the invention) The surge pressure absorption circuit of the hydraulic device of the present invention is configured as described above. Therefore, in this circuit, when the actuator reaches the stroke end, the pressure in the main line increases. At the same time, immediately after the flow ceases, the surge pressure absorption valve opens and releases the fluid in the main line to the tank, making it possible to effectively prevent surge pressure from occurring within the circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional device, FIG. 2 is a circuit diagram showing an embodiment of the present invention, FIG. FIG. 3 is a circuit diagram showing another embodiment of the invention. 21...variable pump, 22...main line,
23...actuator, 24...resistance valve, 29
... Surge pressure absorption valve, 47 ... Branch line, 48
...Pilot room, 50...Spring room.

Claims (1)

[Claims] 1. A resistance valve 24 is interposed in the main line 22 connecting the hydraulic pump 21 and the actuator 23, and a normally open surge pressure absorption valve 29 is interposed in a branch line 47 branching from the main line 22. A hydraulic device is constructed in which the pilot chamber 48 of the surge pressure absorption valve 29 receives the fluid pressure before the resistance valve 24, and the fluid pressure after the resistance valve 24 enters the spring chamber 50. Surge pressure absorption circuit.