JPH08200307A - Hydraulic circuit - Google Patents

Abstract

PURPOSE: To provide a hydraulic circuit which can improve a discharge performance of a hydraulic pump and responsiveness of a directional changeover valve with a simple structure. CONSTITUTION: A hydraulic circuit is provided with directional changeover valves 9, 10 for connecting actuators 11, 12 to a hydraulic pump 2 whose discharge pressure is varied by means of a regulator, and pressure compensation valves 7, 8 on upstream or downstream sides of the valves 9, 10. Differential pressure in respect to a throttle formed by the directional changeover valves 9, 10 is kept constant based on the highest load pressure to be applied to the actuators 11, 12 selected by means of a high pressure selection circuit 23. One pressure reducing valve 33 is integrated with the directional changeover valves 9, 10. An output of the pressure reducing valve 33 serves as a maximum load pressure, and a pilot pressure of a valve part 40 of the regulator 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure oil circuit for supplying pressure oil discharged from one hydraulic pump to a plurality of actuators.

[0002]

2. Description of the Related Art A conventional hydraulic circuit is disclosed in Japanese Laid-Open Patent Publication No. 59-59.
There is one described in Japanese Patent Laid-Open No. 197603. This kind of hydraulic circuit is used for industrial construction machines and the like, and as schematically shown in FIG. 2, operation valves (direction control valves) 103, 104 are provided in a discharge passage 102 of a variable discharge hydraulic pump 101.
And circuits 107 and 108 for connecting the hydraulic valves 105 and 106 to the operation valves 103 and 104, respectively.
The pressure compensating valves 109 and 110 are installed in the pressure compensating valves 109 and 110, the load pressure of the hydraulic actuators 105 and 106 is introduced into the shuttle valve 111, and the maximum load pressure acts on the pressure compensating valves 109 and 110. Is set to a pressure commensurate with the high-pressure load pressure to make the inlet and outlet pressures of the operation valves 103 and 104 equal, and the maximum load pressure introduced into the shuttle valve 111 is transferred via the pipe line 112 to the hydraulic pump 10.
Introduced into the regulator 113 of No. 1, the hydraulic pump 111
By changing the discharge pressure of the oil actuator 10
The flow rate (load pressure) required for the operation of Nos. 5 and 106 is secured.

However, in the conventional hydraulic circuit, since the directional control valve and the hydraulic pump are separated from each other, it takes time to introduce the maximum load pressure into the regulator for adjusting the discharge capacity of the hydraulic pump. There is a problem that the responsiveness between the operation of the directional control valve and the displacement of the hydraulic pump due to the tilting of the pump is poor.

Therefore, in order to solve this problem, there is a hydraulic circuit described in Japanese Patent Laid-Open No. 4-244604. In this type of hydraulic circuit, a pressure reducing valve is provided for each actuator to improve the responsiveness with respect to the operation of the directional control valve and the discharge amount of the hydraulic pump due to tilting of the pump.

[0005]

However, in this conventional hydraulic circuit (Japanese Patent Laid-Open No. 4-244604), since a pressure reducing valve is provided for each actuator, the entire hydraulic circuit becomes complicated. was there.

The present invention has been made to solve this problem, and an object of the present invention is to provide a hydraulic circuit which can improve the responsiveness of the hydraulic pump discharge and the directional control valve with a simple structure. And

[0007]

In order to solve the above-mentioned problems, the hydraulic circuit of the present invention includes a movable discharge type hydraulic pump that changes the discharge pressure in accordance with a command from a regulator.
A plurality of directional control valves to which each actuator is connected are connected in parallel, and a pressure compensation valve is provided on each of the directional control valves on the upstream side or the downstream side of the directional control valve. A high pressure selection circuit for selecting the load pressure of the actuators, the high pressure selection circuit being connected to each of the pressure compensation valves, each pressure compensation valve selecting the maximum load pressure of the plurality of actuators. In the hydraulic circuit in which the differential pressure before and after the throttle formed by the directional control valve is maintained at a constant value based on the high pressure load pressure of the directional control valve, and the regulator operates in accordance with the output pressure of the high pressure selection circuit, the directional control is performed. One pressure reducing valve is provided integrally with the valve, and the output of this pressure reducing valve is used as the maximum load pressure and is also used as the pilot pressure of the valve portion of the regirator. That.

[0008]

According to the hydraulic circuit of the present invention, one pressure reducing valve is provided integrally with the directional control valve, and the output of this pressure reducing valve is set to the maximum load pressure and is used as the pilot pressure of the valve portion of the regirator. Therefore, the circuit configuration is simplified as compared with the conventional one, and the responsiveness of the hydraulic pump discharge and the direction switching valve can be improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydraulic circuit according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a hydraulic circuit 1 according to an embodiment of the present invention, which comprises a drive system A, an operation system B, and an operation system C.

The drive system A includes a variable discharge hydraulic pump 2 for sucking and pressurizing hydraulic oil from a tank 3, and a discharge conduit 4 for supplying pressure oil from the hydraulic pump 2 to an operating system B.
The discharge pressure (hereinafter referred to as pump pressure) of the hydraulic pump 2 is input, and the side opposite to the discharge pressure is connected to a maximum load pressure circuit 24, which will be described later, and the maximum load pressure circuit 24 is also connected.
On the side where is connected, a valve portion 40 of a regulator 50 having a spring 41 and an adjusting cylinder 42 that controls the tilt angle of the swash plate 2a of the hydraulic pump 2 by the output from the valve portion 40 are configured. ing. The valve portion 40 includes a spring 41
The pump pressure is higher than the maximum load pressure circuit 24 by the spring force.

The operating system B is a pressure compensating valve 7 having branch conduits 5a and 5b branching from the discharge conduit 4, and connecting positions 7a and 8a and shut-off positions 7b and 8b, which are connected to the branch conduits 5a and 5b. , 8 and the pressure compensating valves 7, 8 respectively, and are connected to the intermediate positions 9a, 10a and the supply / discharge position 9
b, 10b, 9c, 10c and directional control valves 9, 1
0, the load detection circuits 21 and 22 for detecting the load pressure of the actuators 11 and 12 of the operating system C, and the actuators 11 and 1 detected by the load detection circuits 21 and 22.
High pressure selection circuit 23 for selecting the highest load pressure of 2
And the input side is connected to the branch conduit 5b, and the output side is the valve unit 4
The pressure reducing valve 33 is connected to the 0 switching position 40c and uses the pressure of the maximum load pressure circuit 24 as the pilot pressure.

The pressure reducing valve 33 is provided with a switching position 33a and a switching position 33b, and normally, a switching position 33 is provided by a spring 35.
The pressure reducing signal 34 (output from the pressure reducing valve 33) from the pressure reducing valve 33 from a position opposed to the spring force of the spring 35 is switched to the switching 33b, and the output from the pressure reducing valve 33 is , Becomes the same as the pilot pressure, and this pressure is output to the maximum load pressure circuit 24. The maximum load pressure circuit 24 is provided in the pressure chamber 31 of the differential pressure piston 31, 32.
b, 32b, and the other pressure chamber 31
a and 32a are connected to the load detection circuits 21 and 22, the pressure chambers 31b and 32b are in the direction of closing the pressure compensation valves 7 and 8, and the other pressure chambers 31a and 32a are the pressure compensation valves 7 and 8. , 8 are operated in the direction of opening. Furthermore,
The opening degree of the pressure compensating valves 7 and 8 is determined by the pressure difference between the upstream side and the downstream side of the pressure compensating valves 7 and 8 and the pressing direction of the pressure compensating valves 7 and 8 by the differential pressure pistons 31 and 32.

The working system C includes actuators 11 and 12 which are operated by supplying pressure oil by operating the directional control valves 9 and 10, and directions of the pressure chambers 11a, 11b, 12a and 12b of the actuators 11 and 12, respectively. Switching valve 9,
A supply / discharge passage 13a connected to the output side port of 10;
It is formed by 14a, 13b and 14b.

The hydraulic circuit 1 in this embodiment is constructed as described above. Next, the operation of the hydraulic circuit 1 will be described. For convenience of explanation, in FIG. 1, the engine (not shown) is started and the hydraulic pump 2 is in the idling operation. In this state, the direction switching valves 9 and 10 are in the neutral positions 9a and 10a. And

In this state, the pump pressure is supplied to the upstream side of the directional control valves 9, 10 via the pressure compensating valves 7, 8, but the directional control valves 9, 10 are in the neutral positions 9a, 10.
Since the load pressure detection circuits 21 and 22 of the actuators 11 and 12 are in communication with the tank 3, the pressure is not generated in the load pressure detection circuits 21 and 22, and the pressure is also applied to the high pressure selection circuit 23. Does not occur. Therefore, the opening degree of the pressure compensating valves 7 and 8 is determined by the pump pressure and the pressure (branch conduits 6a and 6b) between the pressure compensating valves 7 and 8 and the direction switching valves 9 and 10. When this pressure becomes equal to the pump pressure, the valve is closed.

The pump pressure is applied to the pressure chamber 4 of the valve section 40.
0B, and is also introduced into the pressure chamber 40C of the valve portion 40 provided with the spring 41 that presses to the left side in FIG. 1 via the branch conduit 5b and the pressure reducing valve 33. Since the spring 41 is disposed on the side of the pressure chamber 40C in the valve portion 40, the force pressing the left side in FIG. 1 is larger than the force pressing the right side in FIG. 1 by the spring force of the spring 41. And
As a result, the pump pressure generates a discharge pressure higher than the maximum load pressure by an amount corresponding to the spring force.

Next, when the direction switching valves 9 and 10 are simultaneously switched and the switching positions of the direction switching valves 9 and 10 are switched, the pressure oil that has been transmitted to the upstream side of the direction switching valves 9 and 10 is released. Pressure chambers 11a, 12a of actuators 11, 12 via supply / discharge passages 13a, 14a, 13b, 14b
Alternatively, they are introduced into the pressure chambers 11b and 12b and driven.

At the same time, the load detection circuits 21 and 22 detect the load pressures of the actuators 11 and 12, and the highest load pressure among the load pressures of the actuators 11 and 12 is selected by the high pressure selection circuit 23. The selected pressure acts on the pressure reducing valve 33 (pilot pressure). Since the pressure reducing valve 33 is switched to the switching position 33a by the highest load pressure of the actuators 11 and 12 selected by the high pressure selecting circuit 23 acting on the pressure reducing valve 33, the discharge conduit 4 and the branch conduit 5b are used. The supplied pump pressure is introduced and transmitted to the maximum load pressure circuit 24. When the pressure in the maximum load pressure circuit 24 becomes higher than the maximum load pressure acting on the pressure reducing valve 33, the pressure reducing signal 34 switches the pressure reducing valve 33 to the switching position 33b. Therefore, the pressure on the output side of the pressure reducing valve 33 (the maximum load pressure circuit 2
(Pressure in 4) generates pressure oil having the same pressure as the maximum load pressure acting on the pressure reducing valve 33.

The pressure on the outlet side of the pressure reducing valve 33 is
It is introduced into the pressure chamber 40C on the side of the switching position 40c of the valve portion 40 of the regulator 50. Therefore, this pressure and spring 4
The switching position of the valve portion 40 is determined by the balance between the sum of the spring force of 1 and the pump pressure introduced into the pressure chamber 40A on the switching position 40a side of the valve portion 40 via the discharge conduit 4. , The hydraulic pump 2 by the action of the adjusting cylinder 42
The tilting angle of the swash plate 2a is adjusted to control the discharge pressure from the hydraulic pump 2. Further, the pressure on the outlet side of the pressure reducing valve 33 pushes the pressure compensating valves 7 and 8 of the differential pressure pistons 31 and 32 integrally provided with the pressure compensating valves 8 and 7 in a direction to close the pressure chamber 31b, The pressure chambers 31a, 32a acting on the pressure chamber 32b and facing the pressure chambers 31b, 32b.
The pressure in the load pressure detection circuits 21 and 22 acts on the pump pressure and the load pressure of the actuators 11 and 12 (the pressure in the load pressure detection circuits 21 and 22). Pressure) and the pressure downstream of the pressure compensating valves 7 and 8 (branch conduits 6a and 6b) and the sum of the maximum load pressure circuit 24. And the directional control valve 9,
The pressure difference before and after 10 is compensated. By determining the opening of the pressure compensating valves 7 and 8, the actuators 11 and 12 are supplied with a pressure commensurate with the actuators 11 and 12, and the malfunction of the actuators 11 and 12 is prevented. .

In the hydraulic circuit of this embodiment, the hydraulic circuit having the structure in which the direction switching valves 9 and 10 are provided between the actuators 11 and 12 and the pressure compensating valves 7 and 8 has been described, but the present invention is not limited to this. Instead of this, a hydraulic circuit having a structure in which a pressure compensating valve is provided between the actuator and the directional control valve (Japanese Patent Laid-Open No. 59-197603 shown in the prior art) is integrated with this directional control valve. Even if the pressure reducing valve 50 in the example is provided, the same effect as this embodiment can be obtained.

[0022]

As described above, according to the hydraulic circuit of the present invention,
Since one pressure reducing valve is provided integrally with the direction switching valve, and the output of this pressure reducing valve is set to the maximum load pressure, and the pilot pressure of the valve portion of the regulator is used, the maximum load pressure of the actuator is generated by this pressure reducing valve. , The distance to the directional control valve is shortened compared to the conventional one, and the transmission to the hydraulic pump is faster than the conventional one, and the responsiveness between the operation of the directional control valve and the pump discharge amount due to the pump tilting is reduced. It is possible to make a defect and simplify the hydraulic circuit.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing a conventional hydraulic circuit.

[Explanation of symbols]

 1 Hydraulic Circuit 2 Hydraulic Pump 7, 8 Pressure Compensation Valve 9, 10 Directional Switching Valve 11, 12 Actuator 23 High Pressure Selection Circuit 33 Pressure Reduction Valve 50 Regulator

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area F15B 11/16

Claims (1)

[Claims] 1. A plurality of directional switching valves each having an actuator connected thereto are connected in parallel to a discharge side of a movable discharge hydraulic pump that changes a discharge pressure according to a command from a regulator. A pressure compensation valve is provided on the upstream side or the downstream side, and a high pressure selection circuit that selects the highest load pressure acting on the actuator is connected to the plurality of actuators. Connected to each of them, the pressure compensating valve selects a maximum load pressure of the plurality of actuators, and the differential pressure before and after the throttle formed by the directional control valve is set to a constant value based on the high pressure load pressure of a high pressure selection circuit. And in the hydraulic circuit in which the regulator operates according to the output pressure of the high pressure selection circuit, one pressure reducing valve is provided integrally with the direction switching valve, While the output of the pressure reducing valve and the maximum load pressure, the hydraulic circuit, characterized in that the pilot pressure of the valve portion of the Regyereta.