JP2000055004A - Hydraulic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To release the peak pressure of multiple actuators into a tank by a single safety valve. SOLUTION: Individual control valves 3 and individual actuators 4 are connected through a first circuit 5 and a second circuit 6 respectively, pressurized oil with the highest pressure in the first circuit 5 and the second circuit 6 is selected by multiple shuttle valves 30, and the selected pressurized oil is supplied to a circuit 10 on the higher pressure side of a safety valve 7 to release the highest peak pressure into a tank through the single safety valve 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydraulic circuit for supplying hydraulic pressure discharged from a hydraulic pump to a plurality of actuators by a plurality of operation valves.

[0002]

2. Description of the Related Art A hydraulic circuit shown in FIG. 3 is known. A plurality of operation valves 3 are provided in the discharge path 2 of the hydraulic pump 1. The respective operation valves 3 are connected to the first chamber 4A and the second chamber 4B of the plurality of actuators 4 by the first circuit 5 and the second circuit 6, respectively. By operating the operation valve 3 from the neutral position A to one of the left and right pressure oil supply positions B, a hydraulic circuit that supplies the discharge pressure oil of the hydraulic pump 1 to the first chamber 4A or the second chamber 4B of the plurality of actuators 4 is formed. Are known. In this hydraulic circuit, when an external force acts on the actuator 4 when the operation valve 3 is in the pressure oil supply position B and in the neutral position A, the first circuit 5 or the second circuit
A peak pressure occurs in the circuit 6. For this purpose, each operating valve 3
The safety valve 7 is provided in each of the first circuit 5 and the second circuit 6 connecting the actuator 4 and each of the actuators 4, and the above-mentioned peak pressure flows to the tank 8 to prevent the actuator and the circuit from being damaged. That is, the set pressure of the safety valve 7 is
The discharge pressure oil of the hydraulic pump 1 is supplied to the actuator 4 at a pressure higher than the relief set pressure of the main relief valve 9 (that is, the maximum discharge pressure of the hydraulic pump 1) that regulates the maximum discharge pressure provided in the discharge path 2. The safety valve 7 does not operate. The safety valve 7 is activated when a peak pressure is generated.

[0003]

In such a hydraulic circuit, since two safety valves are required for one actuator, the number of safety valves is twice the number of actuators, so that the number of safety valves is large. . This safety valve has a complicated structure, is expensive, and is large in comparison with a check valve or a suction valve. For this reason, the hydraulic circuit described above requires a very high overall cost and a large mounting space.

Therefore, the present invention solves the above-mentioned problems,
It is an object of the present invention to provide a hydraulic circuit in which the overall cost is low and the mounting space can be reduced.

[0005]

The present invention provides a plurality of closed center type operation valves 3 connected to a discharge path 2 of a hydraulic pump 1 and a first circuit 5 for each of the operation valves 3. A plurality of actuators 4 respectively connected by a second circuit 6, a means for selecting the maximum pressure oil among the pressures of the first circuit 5 and the second circuit 6, and a circuit on the output side of the selection means And a means for detecting a pressure corresponding to the highest load pressure among the load pressures of the actuators 4, and a safety valve 7 provided in the discharge path 2 of the hydraulic pump 1 so as to be opened by the pump discharge pressure. And a force in the closing direction acts at a pressure corresponding to the detected highest load pressure to increase the discharge pressure of the hydraulic pump 1 by a predetermined pressure higher than the pressure corresponding to the highest load pressure. Unload valve 33 A hydraulic circuit, characterized in that it comprises.

According to the present invention, a plurality of actuators 4
Is selected by the selection means.
The selected maximum peak pressure flows out of the tank at the safety valve 7. Therefore, the peak pressure generated in a plurality of actuators can flow out to the tank with one safety valve 7, and only one expensive and large safety valve 7 needs to be provided, so that the whole can be made inexpensive and the mounting space can be reduced.

The discharge pressure of the hydraulic pump 1 is controlled to a predetermined pressure higher than the pressure corresponding to the highest load pressure. Therefore, the discharge pressure is low when the highest load pressure is low, and high when the highest load pressure is high. . Therefore, the discharge pressure of the hydraulic pump 1 does not become unnecessarily high. Further, in a hydraulic circuit in which a plurality of closed center type operation valves 3 are connected to the discharge path 2 of the hydraulic pump 1, the discharge pressure of the hydraulic pump 1 can be maintained at a predetermined pressure when each of the operation valves 3 is in the neutral position.

[0008]

FIG. 1 shows a first embodiment of the present invention.
It will be described based on. The same members as those in the related art have the same reference numerals. The discharge path 2 of the hydraulic pump 1 includes a plurality of operation valves 3
Pump port 3A. Thereby, the plurality of operation valves 3 are provided in the discharge path 2 of the hydraulic pump 1 in parallel. Each of the operation valves 3 is a closed center type operation valve that closes the pump port 3A at the neutral position A.

The operation valves 3 will be specifically described. Each of the operation valves 3 has a pump port 3A, a tank port 3B, a first actuator port 3C, a second actuator port 3D, and a load pressure detection port 3E. When in the neutral position A, the operation valve 3 shuts off the pump port 3A, the first actuator port 3C, and the second actuator port 3D, respectively, and communicates the tank port 3B with the load pressure detection port 3E. When the operation valve 3 is at the first pressure oil supply position B on the right side in FIG. 1, the pump valve 3A communicates with the first actuator port 3C and the second actuator port 3C.
D and tank port 3B, and load pressure detection port 3E
Communicates with the pump port 3A. When the operation valve 3 is at the second pressure oil supply position B on the left side in FIG. 1, the pump port 3A communicates with the second actuator port 3D, and the first actuator port 3C communicates with the tank port 3B.
The load pressure detection port 3E communicates with the pump port 3A.

The output pressure of the operation valve 3, that is, the load pressure of the actuator 4 is output to the load pressure detection port 3E of each operation valve 3. The load pressure detection port 3E of each of the operation valves 3
Are output from the shuttle valve 31, and the highest load pressure is introduced into the load pressure detection path 32. The highest load pressure introduced into the load pressure detection path 32 makes the unload pressure of the unload valve 33 provided in the discharge path 2 of the hydraulic pump 1 variable.

The unload valve 33 includes a first pressure receiving portion 33.
A force is applied in the direction of opening (the direction connecting the inlet and the outlet) by the pump discharge pressure acting on A, and the direction of closing by the highest load pressure acting on the second pressure receiving portion 33B and the spring force of the spring 33C (the inlet (The direction to shut off the outlet) acts.
Thus, the discharge pressure of the hydraulic pump 1 is set to a pressure higher than the highest load pressure by a predetermined pressure corresponding to the spring force of the spring 33C. A relief valve 34 is provided in the load pressure detection path 32. The highest pressure acting on the second pressure receiving portion 33B of the unload valve 33 is the set pressure of the relief valve 34. Thus, the maximum discharge pressure of the hydraulic pump 1 is regulated by the set force of the relief valve 34 and the spring force of the spring 33C. Note that a main relief valve may be provided in the discharge path 2 to regulate the maximum discharge pressure of the hydraulic pump 1.

A high pressure side circuit 10 is connected to the high pressure side port 7A of the safety valve 7. The low-pressure side circuit 11 is in contact with the low-pressure side port 7B of the safety valve 7. This low pressure side circuit 11 is connected to the tank 8. The set pressure of the safety valve 7 is higher than the maximum discharge pressure of the hydraulic pump 1 described above. Each of the first circuits 5
And each second circuit 6 is connected to the tank 8 by a suction valve 13.

The pressure of the first and second circuits 5 and 6 of the first actuator 4 (the upper actuator 4 in FIG. 1) is increased to the first pressure.
Of the second actuator 4 (the upper and lower middle actuator 4 in FIG. 1) and the pressure of the second circuit 6 of the second actuator 4 (the upper and lower middle actuator 4 in FIG. 1). The pressure oil of the higher pressure is taken out and compared with the pressure of the first circuit 5 by the third shuttle valve 3.
Take out the pressure oil of the higher pressure as compared with 0. This pressure is compared with the pressure of the second circuit 6 of the third actuator 4 (the lower actuator 4 in FIG. 1) by the fourth shuttle valve 30 to take out the higher pressure oil, and the pressure and the first oil are taken out.
The pressure of the circuit 5 is compared with the fifth shuttle valve 30 to extract the higher pressure oil. The pressure oil (that is, the pressure oil having the maximum pressure) is output to the high-pressure side circuit 10 of the safety valve 7. That is, a means for sequentially comparing the pressures of the first and second circuits 5 and 6 with the shuttle valve 30 and selecting the pressure oil having the maximum pressure is formed.

Because of this, each actuator 4
The pressure oil of the highest pressure in the first circuit 5 and the second circuit 6 acts on the high pressure side port 7A of the safety valve 7 to reduce the peak pressure generated in a plurality of actuators to one safety valve 7
Can flow out to the tank 8.

FIG. 2 shows a second embodiment of the present invention.
Each operation valve 3 is the same as that of the first embodiment,
Is supplied from each operation valve 3 to each actuator 4 via the first and second circuits 5 and 6, respectively. The maximum discharge pressure of the hydraulic pump 1 is defined by the unload valve 33 and the relief valve 34 as in the first embodiment. The first circuit 5 and the second circuit 6 are respectively connected to the inlet side of a check valve 12 that allows the flow of pressure oil from the inlet to the outlet. The output side of each check valve 12 is connected to the high-pressure side circuit 10, respectively. Thereby, the pressure oil of the maximum pressure among the pressures of the first circuit 5 and the second circuit 6 flows into the high-pressure side circuit 10. That is,
Instead of the shuttle valves 30 described above, a plurality of check valves 12 may be used.
And means for selecting the pressure oil having the maximum pressure among the pressures of the first circuit 5 and the second circuit 6 is formed. The hydraulic pump 1 is a variable displacement hydraulic pump.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a conventional hydraulic circuit diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Hydraulic pump 2 ... Discharge path 3 ... Operating valve 3E ... Load pressure detection port 4 ... Actuator 5 ... 1st circuit 6 ... 2nd circuit 7 ... Safety valve 8 ... Tank 12 ... Check valve 30 ... Shuttle valve 31 ... Shuttle valve 33 ... Unload valve

Claims (5)

[Claims] A plurality of closed center type operation valves (3) connected to a discharge path (2) of a hydraulic pump (1), a first circuit (5) and a second circuit (5) for each of the operation valves (3). A plurality of actuators (4) each connected by a circuit (6)
Means for selecting the maximum pressure oil out of the pressures of the first circuit (5) and the second circuit (6); and one safety valve (7) provided in a circuit on the output side of the selection means. ), Means for detecting a pressure corresponding to the highest load pressure among the load pressures of the actuators (4), provided in the discharge path (2) of the hydraulic pump (1), in a direction to open with the pump discharge pressure And the force in the closing direction acts at a pressure corresponding to the detected highest load pressure to make the discharge pressure of the hydraulic pump (1) higher by a predetermined pressure than the highest load pressure. Unload valve (3
A hydraulic circuit comprising: 3). 2. The hydraulic circuit according to claim 1, wherein a set pressure of the safety valve is higher than a maximum discharge pressure of the hydraulic pump. 3. The selecting means connects all circuits of each first circuit (5) and each second circuit (6) in sequence via a shuttle valve (30), so that the hydraulic oil having the maximum pressure is provided. 3. The hydraulic circuit according to claim 1, wherein said hydraulic circuit is selected. 4. The selecting means connects an output side pipeline of a check valve (12) provided in each first circuit (5) and each second circuit (6) to the same high pressure side circuit (10). 3. The hydraulic circuit according to claim 1, wherein said means selects a pressure oil having a maximum pressure. 5. Each of the operation valves (3) has a shape having a load pressure detection port (3E) for detecting its output pressure, and the pressures of the respective load pressure detection ports (3E) are compared with each other. The hydraulic circuit according to claim 1, wherein a plurality of shuttle valves (31) for outputting a high pressure as a load pressure are provided as the load pressure detecting means.