JP2002081405A - Hydraulic circuit in work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve operability when an interlocking operation or a fine operation is performed for a plurality of hydraulic actuators in a hydraulic circuit provided with a pilot operating type control valve for performing pressure oil supply controls for the hydraulic actuators and a pilot valve for outputting pilot pressure corresponding to operating tool manipulated variable. SOLUTION: A pilot pressure control valve device 16 constituted of a pressure reduction valve 18 for reducing pilot pressure and a selector valve 19 switching by an external signal is provided in a pilot oil passage D from a pilot valve 14B to a control valve 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a hydraulic circuit in a working machine having various hydraulic actuators such as a hydraulic shovel.

[0002]

2. Description of the Related Art In general, a working machine such as a hydraulic shovel is provided with various hydraulic actuators. The hydraulic oil supply to these hydraulic actuators is controlled by a pilot-operated control valve. There is a configuration in which the supply of the pilot pressure to the valve is performed by a pilot valve that outputs the pilot pressure based on the operation of the operating tool. As an example of such a thing, a hydraulic circuit of a boom cylinder and a bucket cylinder provided in a hydraulic shovel is shown in FIG.
6, 21 is a hydraulic pump, 22 is an oil tank, 23 is a boom cylinder, 24 is a bucket cylinder, 25 is a boom control valve, 26 is a bucket control valve, and 27 is a boom pilot valve. (Note that the bucket pilot valve is omitted). In this one,
The pilot pressure output from the boom pilot valve 27 increases as the operation amount of the boom operation lever 28 increases, and the opening amount of the boom control valve 25 increases as the supplied pilot pressure increases. Therefore, the amount of pressurized oil supplied to the boom cylinder 23 increases, and the operation speed of the boom cylinder 23 increases. That is, the operation speed of the cylinder is controlled in accordance with the operation amount of the operation tool. By the way, in the hydraulic circuit, for example, when it is desired to sufficiently open the bucket by lowering the boom lowering speed during the interlocking operation of the boom lowering and the bucket open, the lowering speed of the boom with respect to the operation amount of the boom operating lever is usually If it is later than the time, operability is improved. Therefore, when it is desired to reduce the operating speed of the hydraulic actuator with respect to the operation amount of the operating tool, conventionally, a stopper is provided in the control valve to limit the maximum movement amount of the spool of the control valve, or a pilot supplied to the control valve. The maximum speed of the hydraulic actuator can be limited as necessary by limiting the upper limit value of the pressure.

[0003]

However, in the prior art, although the maximum speed of the hydraulic actuator can be limited, the hydraulic actuator cannot be controlled so as to reduce the speed of the hydraulic actuator in an intermediate operation range of the operating tool. There is a problem that the operability in the intermediate operation region cannot be improved only by reducing the stroke region in which the speed of the operation tool can be controlled. On the other hand, in an electrically controlled type configured to electrically detect the operation amount of the operating tool and output a pilot pressure corresponding to the detected value from the pilot valve to the control valve, the pilot valve corresponding to the operation amount detection value is used. Attempts are made to electrically control the output pressure of the control valve so as to be changed as necessary. However, this control requires a control unit that outputs a command to a manipulated variable detector and a pilot valve. This cannot be adopted if no such device is provided, and there is a problem to be solved by the present invention.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has been made for the purpose of solving these problems. A hydraulic actuator and a hydraulic oil supply control for the hydraulic actuator are provided. In a hydraulic circuit configured to include a pilot-operated control valve that performs a pilot operation and a pilot valve that outputs a pilot pressure corresponding to the operation amount of an operating tool, an external signal is supplied to a pilot oil passage from the pilot valve to the control valve. And a pressure control valve device for reducing the pilot pressure output from the pilot valve and supplying the reduced pressure to the control valve. By doing so, the operating speed of the hydraulic actuator with respect to the operation amount of the operating tool can be reduced over the entire operating range of the operating tool, and the stroke range in which the speed of the operating tool can be controlled can be sufficiently widened. As a result, operability is improved when a plurality of hydraulic actuators are operated in conjunction with each other or when performing fine operations. The pressure control valve device includes a pressure reducing valve that reduces the pilot pressure from the pilot valve and outputs the reduced pressure to the control valve, and a switching valve that switches between the first position and the second position based on an external signal. Further, the switching valve is operable to supply the pilot pressure from the pilot valve to the control valve without passing through the pressure reducing valve in the first position, and to supply the pilot pressure from the pilot valve to the control valve through the pressure reducing valve in the second position. By doing so, it is possible to select between a case where the pilot pressure is reduced and a case where the pilot pressure is not reduced by switching the switching valve by an external signal. Further, the pressure control valve device is provided with a pressure reducing valve that can be switched between a non-operating state in which the pilot pressure from the pilot valve is output to the control valve without reducing the pressure and an operating state in which the pilot pressure is reduced and output. A switching valve for switching between a position and a second position, the switching valve being operative to deactivate the pressure reducing valve in a first position and to activate the depressurizing valve in a second position. You can also.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to FIGS. In FIG. 1, 1
Is a hydraulic excavator. The hydraulic excavator 1 includes a lower traveling body 2 of a crawler type, an upper revolving body 3 rotatably supported by the lower traveling body 2, and a vertically swingable supported by the upper revolving body 3. And a hydraulic operating portion such as a boom 4, an arm 5 supported at the tip of the boom 4 so as to be able to swing back and forth, and a bucket 6 supported at the tip of the arm 5 so as to be swingable back and forth. Further, as hydraulic actuators for operating these hydraulic operating portions, a traveling motor (not shown), a turning motor (not shown), a boom cylinder 7,
The basic configuration such as the provision of various hydraulic actuators such as the arm cylinder 8 and the bucket cylinder 9 is the same as the conventional one.

FIG. 2 shows a hydraulic circuit of the boom cylinder 7 and the bucket cylinder 9. In the hydraulic circuit diagram, 10 is a hydraulic pump, 11 is an oil tank, and 12 is a supply of pressurized oil to the boom cylinder 7. A boom control valve 13 for performing control is a bucket control valve for controlling supply of pressurized oil to the bucket cylinder 9.

The boom control valve 12 is a pilot-operated three-position switching valve, and includes first to sixth ports 12a.
~ 12f and expansion side, reduction side pilot port 12
g, 12h, the first port 12a is connected to the hydraulic pump 10 through the parallel oil passage A and the second port 12b
To the hydraulic pump 10 via the center bypass oil passage B,
The third port 12c is connected to the oil tank 11 and the fourth port 12d
The fifth port 1 is connected to the extension-side oil chamber 7a of the boom cylinder 7.
2e is connected to the oil tank 11, and the sixth port 12f is connected to the reduction side oil chamber 7b of the boom cylinder 7.

When the pilot pressure is not input to both pilot ports 12g and 12h, the control valve 12 controls the first, third, fourth and sixth ports 12a and 12h.
c, 12d and 12f are closed respectively, and the second port 1
A bypass valve passage from 2b to the fifth port 12e (a valve passage for flowing the pressure oil of the center bypass oil passage B to the oil tank 11).
Is located at the neutral position N to open.

On the other hand, when the pilot pressure is input to the expansion-side pilot port 12g, the control valve 12 controls the supply valve path (the pressure oil in the parallel oil path A from the boom cylinder) to the fourth port 12d from the first port 12a. A valve path for supplying to the extension-side oil chamber 7a), and from the sixth port 12f to the third port 1
2c (the boom cylinder reduction side oil chamber 7b)
Is switched to the extension side position X for opening the valve path for discharging the oil to the oil tank 11), whereby the boom cylinder 7 is extended and the boom 4 is raised.

When a pilot pressure is input to the reduction-side pilot port 12h, the control valve 12 controls the supply valve passage (the pressure oil in the parallel oil passage A from the boom cylinder 12b) from the first port 12a to the sixth port 12f. A valve path for supplying to the reduction side oil chamber 7b), and the fourth port 12d to the third port 1
2c (the boom cylinder extension side oil chamber 7a)
The boom cylinder 7 is contracted and the boom 4 is lowered by switching to the contraction side position Y for opening the valve path for discharging the oil to the oil tank 11).

Here, the pilot pressure input to the extension side pilot port 12g and the spool stroke of the boom control valve 12, and the opening areas of the bypass valve passage, the supply valve passage, and the discharge valve passage of the control valve 12 are shown. FIG. 3 is a characteristic diagram showing the relationship. And, as shown in the characteristic diagram,
The control valve 12 increases the opening area of the supply valve path and the discharge valve path as the input pilot pressure increases,
As a result, the amount of pressurized oil supplied to the boom cylinder 7 increases,
The cylinder operating speed is designed to increase. Note that the bucket control valve 13 has the same structure as the boom control valve 12 described above, and a description thereof will be omitted.

Further, in the hydraulic circuit diagram of FIG.
Reference numeral 14 denotes a boom pilot valve, which includes an extension-side pilot valve 14A and a reduction-side pilot valve 14B. The extension side and reduction side pilot valves 14A and 14B move the boom operation lever 15 to the extension side,
The pilot pressure is output based on the operation toward the reduction side, and the output pilot pressure is set to increase as the operation amount of the boom operation lever 15 increases.

The pilot pressure output from the extension-side pilot valve 14A passes through the extension-side pilot oil passage C and extends to the extension-side pilot port 1 of the boom control valve 12.
2g. The pilot pressure output from the reducing pilot valve 14B is equal to the reducing pilot oil passage D
Is input to the reduction-side pilot port 12h of the boom control valve 12 via the
Further, a pilot pressure control valve device 16 according to the present invention is arranged. In FIG. 2, the pilot valve for the bucket is omitted.

The pilot pressure control valve device 16 has an inlet port 16 connected to the reducing pilot valve 14B.
a, an outlet port 16b connected to the boom control valve reduction side pilot port 12h, an external signal port 1 connected to an external signal pilot pressure output means 17 described later.
6c, a drain port 16d connected to the oil tank 11 and a pressure reducing valve 18 and a switching valve 19
Is incorporated.

The pressure reducing valve 18 is a pilot operated type having an input port 18a, an output port 18b and a pilot port 18c.
a is connected to the inlet port 16a, and the output port 18b is connected to the outlet port 16b. When the pilot pressure is not input to the pilot port 18c, the pressure reducing valve 18 is connected to the input port 18a.
Is in a non-operating state in which the valve path from the port to the output port 18b is closed, but is activated by the input of pilot pressure to the pilot port 18c to reduce the pilot pressure input to the input port 18a to reduce the output pressure. 18b.

The switching valve 19 is a two-position switching valve having first to fourth ports 19a to 19d and a pilot port 19e, and the first port 19a is an inlet of the pilot pressure control valve device 16. Side port 16a, second port 19b to drain port 16d, third port 1
9c is connected to the pilot port 18c of the pressure reducing valve 18, the fourth port 19d is connected to the outlet port 16b, and the pilot port 19e is connected to the external signal port 16c.

When the pilot pressure is not input to the pilot port 19e, the switching valve 19
It is located at a first position X where a valve path from the first port 19a to the fourth port 19d is opened and a valve path connecting the second port 19b and the third port 19c is opened. When the switching valve 19 is located at the first position X, the pilot pressure input from the inlet port 16a of the pilot pressure control valve device 16 passes through the switching valve 19 at the first position X. While output to the outlet port 16b, the pressure reducing valve pilot port 18c communicates with the drain port 16d via the switching valve 19 at the first position X.

On the other hand, when the pilot pressure is input to the pilot port 19e, the switching valve 19 switches to the first port 19a.
To the third position 19c, and switch to the second position Y in which the second port 19b and the fourth port 19d are closed. When the switching valve 19 is located at the second position Y, the pilot pressure input from the inlet port 16a of the pilot pressure control valve device 16 passes through the switching valve 19 at the second position Y. The pressure is supplied to the pressure reducing valve pilot port 18c.

The external signal pilot pressure output means 17 is constituted by, for example, an electromagnetic valve. The external signal pilot pressure output means 17 is provided with a work mode selection switch 20 provided at the driver's seat or the like of the excavator 1. Based on turning on,
External signal port 16c of pilot pressure control valve device 16
To output the pilot pressure. The pilot pressure output to the external signal port 16c is input to the pilot port 19e of the switching valve 19.

That is, the work mode selection switch 20
Is turned on, the pilot port 19e of the switching valve 19
, The switching valve 19 is switched to the second position Y. In this state, the boom operation lever 15
When the pilot pressure is output from the reduction side pilot valve 14B based on the lowering operation of the pilot pressure, the pilot pressure is input to the inlet side port 16a of the pilot pressure control valve device 16 and passes through the switching valve 19 at the second position Y. The pressure is supplied to the pilot port 18c of the pressure reducing valve 18. As a result, the pressure reducing valve 18 opens a valve path from the input port 18a to the output port 18b, so that the pilot pressure input to the inlet port 16a is reduced from the outlet port 16b by the pressure reducing valve 18. The output is supplied to the boom control valve reduction side pilot port 12h. Here, the pressure reducing operation of the pressure reducing valve 18 is shown in the characteristic diagram of FIG. 4. In FIG. 4, the minimum value Po1 of the output pilot pressure Po output from the outlet port 16b is input to the inlet port 16a. The input pilot pressure Pi becomes equal to or less than the minimum value Pi1 (Po1 ≦ Pi1), and the maximum value Po2 of the output pilot pressure Po becomes smaller than the maximum value Pi2 of the input pilot pressure Pi (Po1 <Pi1).
In FIG. 4, the output pilot pressure Po is controlled to be reduced in a linear relationship (proportional relationship) with respect to the input pilot pressure Pi. However, a non-linear relationship may be employed.

On the other hand, when the work mode selection switch 20 is OFF, the pilot port 19 of the switching valve 19 is turned off.
No pilot pressure is input to e, and the switching valve 19 is located at the first position X. In this state, the pilot pressure input to the inlet port 16a of the pilot pressure control valve device 16 is output to the outlet port 16b via the switching valve 19 at the first position X. On the other hand, the pressure reducing valve 18 is inactive because the pilot port 18c communicates with the oil tank 11 via the switching valve 19 at the first position X and the drain port 16d. Thus, the boom operation lever 15
When the pilot pressure is output from the reduction side pilot valve 14B based on the descending operation of the pilot pressure, the pilot pressure is input to the inlet side port 16a of the pilot pressure control valve device 16 and passes through the switching valve 19 at the first position X. Exit port 1
6b, and is supplied to the boom control valve reduction side pilot port 12h.

In the first embodiment constructed as described above, a work mode selection switch 20 is provided in a pilot oil passage extending from the boom reduction side pilot valve 14B to the boom control valve reduction side pilot port 12h. O
Based on the N operation, the pilot pressure output from the reduction side pilot valve 14B is reduced to reduce the reduction side pilot port 1B.
A pilot pressure control valve device 16 for supplying 2h is provided. As a result, for example, when the interlocking operation of the boom lowering and the bucket opening is performed, if the work mode selection switch 20 is turned on, the supply amount of the pressurized oil to the boom cylinder 7 with respect to the operation amount of the boom operation lever 15 is reduced. As a result, the boom lowering speed becomes slow while the boom cylinder 7
The amount of pressurized oil supplied to the bucket cylinder 9 is increased by an amount corresponding to the reduced amount of pressurized oil supplied to the bucket 6, so that the bucket 6 can be sufficiently opened. Moreover, in this case, not only does the maximum speed of the boom lowering when the boom operation lever 15 is fully operated become slow, but also the stroke range in which the speed of the boom operation lever 15 can be controlled can be made sufficiently wide, and the entire operation region is covered. As a result, the boom lowering speed can be reduced, so that good operability can be obtained.

Next, a second embodiment of the present invention will be described with reference to FIG.
The second embodiment is different from the first embodiment except that a pilot pressure control valve device 30 is used instead of the pilot pressure control valve device 16 of the first embodiment. Since the configuration is the same as that of the embodiment, the components other than the pilot pressure control valve device 30 are denoted by the same reference numerals and description thereof is omitted. 1, 3, and 4 share the first embodiment.

The pilot pressure control valve device 30 used in the second embodiment is a
B, the outlet port 30b connected to the boom control valve reduction side pilot port 12h, the external signal port 30c connected to the external signal pilot pressure output means 17, and the oil tank 11. A switching port 31 and a pressure reducing valve 32 are incorporated in each of the drain ports 30d to be connected.

The switching valve 31 includes first to third ports 31
a to 31c and a pilot port 31d, the first port 31a being an inlet port 30a of the pilot pressure control valve device 30, the second port 31b being a drain port 30d, and the third port being a third port. The port 31c is connected to a first piston 32c of the pressure reducing valve 32 described later, and the pilot port 31d is connected to the external signal port 30c.

When the pilot pressure is not input to the pilot port 31d, the switching valve 31
It is located at a first position X where a valve path from the first port 31a to the third port 31c is opened and the second port 31b is closed. When the switching valve 31 is located at the first position X, the pilot pressure input from the inlet port 30a of the pilot pressure control valve device 30 passes through the switching valve 31 at the first position X. The pressure is applied to the first piston 32 c of the pressure reducing valve 32.

On the other hand, when the pilot pressure is input to the pilot port 31d, the switching valve 31 sets the first port 31a.
And switch to the second position Y where the second port 31b and the third port 31c communicate. Thus, when the switching valve 31 is located at the second position Y, the application line to the first piston 32c of the pressure reducing valve 32 is changed to the switching valve 31 at the second position Y.
Through the oil tank 11.

The pilot port 31d of the switching valve 31 is output from the external signal pilot pressure output means 17 based on the ON operation of the work mode selection switch 20, as in the first embodiment. The pilot pressure is input via an external signal port 30c of the pilot pressure control valve device 30.

The pressure reducing valve 32 is connected to an input port 32.
a, output port 32b, first, second, third piston 32
c, 32d, 32e, and an ammunition 32f, and the input port 32a is connected to the pilot pressure control valve device 3.
0 is connected to the inlet port 30a, and the output port 3
2b is connected to the outlet side port 30b. further,
As described above, the input pressure from the inlet port 30a via the switching valve 31 at the first position X is applied to the first piston 32c, and the inlet port 30 is applied to the second piston 32d.
The input pressure from a is applied, and the output pressure from the output port 32b is applied to the third piston 32e.

The first and second pistons 32c, 3c
The 2d and the ammunition 32f press the valve body of the pressure reducing valve 32 to the non-operating state where the input pressure from the input port 32a is output to the output port 32b without reducing the pressure, and the third piston 32e is connected to the pressure reducing valve. 32 valve bodies are connected to the input port 32a.
It is configured to depress the input pressure from the output port 32b and to push the input pressure to the operation state side where the pressure is output to the output port 32b. Here, the relationship between the force F1 for pressing the pressure reducing valve 32 toward the non-operating state and the force F2 for pressing the pressure reducing valve 32 toward the operating state is such that the switching valve 31 is located at the first position X and One piston 32c
In the state where the input pressure from the inlet port 30a is applied, the force F1 pressing toward the non-operation state becomes larger than the force F2 pressing toward the operation state (F1> F2), and the switching valve 31 The first piston 3 located at the second position Y
In a state where the application line 2c is in conduction with the oil tank 11, the force F2 pressing toward the operating state is set to be larger than the force F1 pressing toward the non-operating state (F2> F1). .

That is, the work mode selection switch 20
Is OFF, the pilot port 31d of the switching valve 31
No pilot pressure is input to the switch, and the switching valve 31 is moved to the first position X.
It is located in. Then, the pilot pressure input to the inlet side port 30 a of the pilot pressure control valve device 30 via the switching valve 31 at the first position X is applied to the first piston 32 c of the pressure reducing valve 32. In this state, as described above, the force F1 for pressing the pressure reducing valve 32 toward the non-operation state is greater than the force F2 for pressing the pressure reduction valve 32 toward the operation state, so that the pressure reduction valve 32 reduces the input pressure from the input port 32a. The non-operating state of outputting to the output port 32b without reducing the pressure is maintained. When the pilot pressure is output from the reduction side pilot valve 14B based on the lowering operation of the boom operation lever 15, the pilot pressure is input to the inlet port 30a of the pilot pressure control valve device 30, and The pressure is output from the outlet side port 30b without being depressurized by the pressure reducing valve 32 in the operating state, and is supplied to the boom control valve reducing side pilot port 12h.

On the other hand, the work mode selection switch 20 is turned on.
When operated, the pilot pressure is input to the pilot port 31d of the switching valve 31, and the switching valve 31 is moved to the second position Y.
Switch to. In this state, since the application line of the pressure reducing valve 32 to the first piston 32c is connected to the oil tank 11, as described above, the force F2 pressing the pressure reducing valve 32 toward the operating state is shifted toward the non-operating state. The pressing force F1 is larger than the pressing force F1, so that the pressure reducing valve 32 enters an operating state in which the input pressure from the input port 32a is reduced and output to the output port 32b. When the pilot pressure is output from the reduction side pilot valve 14B based on the lowering operation of the boom operation lever 15, the pilot pressure is input to the inlet side port 30a of the pilot pressure control valve device 30, and is activated. The outlet port 30 is depressurized by the pressure reducing valve 32 in the state.
b, and is supplied to the boom control valve reduction side pilot port 12h. Here, the pressure reducing operation of the pressure reducing valve 32 is the same as the pressure reducing operation of the pressure reducing valve 18 of the first embodiment, and as shown in the characteristic diagram of FIG. Although the pilot pressure Po is reduced in a linear relationship (proportional relationship), it may be a non-linear relationship.

Also in the second embodiment, the pilot pressure control valve device 30 provided in the pilot oil passage extending from the boom reduction side pilot valve 14B to the boom control valve reduction side pilot port 12h. Accordingly, the same operation and effect as those of the first embodiment can be obtained, which can contribute to improvement of operability.

The present invention is, of course, not limited to the above-described first and second embodiments. As means for outputting an external signal for performing the pressure reducing operation of the pilot pressure control valve device, The operation mode selection switch 20 and the external signal pilot pressure output means 17 are not limited to the above and may be any as long as they can output an external signal to the pilot pressure control valve device as needed. Further, in the pilot pressure control valve device of the above-described embodiment, the pressure reducing valve and the switching valve are incorporated as one unit, but they may be provided separately. Further, in the above embodiment, the pilot pressure control valve device is provided in the hydraulic circuit for the boom cylinder of the hydraulic shovel, but the hydraulic pressure of other hydraulic actuators such as a traveling motor, a turning motor, an arm cylinder, and a bucket cylinder is provided. It can also be provided in a circuit, and by doing so, it is possible to improve the operability when various hydraulic actuators are interlocked. Further, even when the hydraulic actuator is operated alone, the present invention can be applied to a case where the operating speed of the hydraulic actuator is to be reduced with respect to the operation amount of the operating tool, such as when performing a fine operation. Furthermore, the present invention can be applied not only to a hydraulic shovel but also to various working machines provided with a hydraulic actuator.

[Brief description of the drawings]

FIG. 1 is a perspective view of a hydraulic shovel.

FIG. 2 is a hydraulic circuit diagram of the first embodiment.

FIG. 3 is a diagram showing opening characteristics of a boom control valve.

FIG. 4 is a diagram showing characteristics of a pressure reducing valve.

FIG. 5 is a hydraulic circuit diagram of a second embodiment.

FIG. 6 is a conventional hydraulic circuit diagram.

[Explanation of symbols]

 7 Boom cylinder 12 Boom control valve 14B Reduction side pilot valve 15 Boom operation lever 16 Pilot pressure control valve device 17 External signal pilot pressure output means 18 Pressure reducing valve 19 Switching valve 20 Work mode selection switch 30 Pilot pressure control valve device 31 Switching valve 32 Pressure reducing valve

Claims (3)

[Claims] 1. A hydraulic circuit comprising a hydraulic actuator, a pilot-operated control valve for controlling hydraulic oil supply to the hydraulic actuator, and a pilot valve for outputting a pilot pressure corresponding to an operation amount of an operating tool. A pressure control valve device for reducing the pilot pressure output from the pilot valve based on an external signal and supplying the reduced pressure to the control valve in a pilot oil passage extending from the pilot valve to the control valve. Hydraulic circuit in machine. 2. The pressure control valve device according to claim 1,
A pressure reducing valve that reduces the pilot pressure from the pilot valve and outputs the reduced pressure to the control valve; and a switching valve that switches between the first position and the second position based on an external signal. In the working machine, a pilot pressure from the pilot valve is supplied to the control valve without passing through the pressure reducing valve in the position, and the pilot pressure is supplied to the control valve through the pressure reducing valve in the second position. Hydraulic circuit. 3. The pressure control valve device according to claim 1,
A pressure reducing valve that can be switched between a non-operating state in which the pilot pressure from the pilot valve is output to the control valve without reducing the pressure and an operating state in which the pilot pressure is reduced and output, and switching between the first position and the second position based on an external signal. A hydraulic pressure circuit for a working machine, wherein the hydraulic pressure circuit is configured to operate the pressure reducing valve in a non-operating state in a first position and to activate the pressure reducing valve in a second position. .