JP2003287002A - Hydraulic circuit in working machinery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic circuit provided with a control valve of a pilot actuation type for controlling pressure oil supply to a hydraulic actuator and a pilot valve for outputting a pilot pressure to the control valve, with improved operability in conducting fine operation. <P>SOLUTION: The hydraulic circuit is provided with an input side pressure reducing valve 11 for reducing a pressure inputted from a pilot hydraulic source 3 to the pilot valve 9, and output side pressure reducing valves 13X, 13Y for reducing a pressure outputted from the pilot valve 9 to the control valve 5, and is so structured that pressure reducing operation of these input side and output side pressure reducing valves is performed on the basis of operation of a work speed changeover switch 16. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a hydraulic circuit in a working machine provided with various hydraulic actuators such as a hydraulic excavator.

[0002]

2. Description of the Related Art Generally, working machines such as hydraulic excavators are provided with various hydraulic actuators such as hydraulic cylinders and hydraulic motors. Control of pressure oil supply to these hydraulic actuators is performed by a pilot operated control valve. On the other hand, there is a configuration in which the pilot pressure is supplied to the control valve by a pilot valve that outputs the pilot pressure based on the operation of the operation tool. As an example of such a thing, FIG. 8 shows a hydraulic circuit of a hydraulic cylinder provided in a hydraulic excavator. In FIG. 8, 1 is a hydraulic cylinder,
Reference numeral 2 is a main oil pressure source, 3 is a pilot oil pressure source, 4 is an oil tank, 5 is a control valve, and 17 is a pilot valve (see FIG. 8).
6 is a control valve for another hydraulic actuator 7 that shares a hydraulic supply source with the hydraulic cylinder 1.) In this case, the pilot pressure output from the pilot valve 17 increases as the operation amount of the operation lever 12 increases, and the control valve 5 increases the spool stroke as the supplied pilot pressure increases, thereby increasing the hydraulic pressure. The amount of pressure oil supplied to the cylinder 1 increases, and the expansion / contraction speed of the cylinder 1 increases. That is, the cylinder expansion / contraction speed is controlled in accordance with the operation amount of the operation lever, and the relationship between the operation amount (lever stroke) of the operation lever and the hydraulic cylinder expansion / contraction speed is shown by a solid line in FIG. 7, for example. The relationship is as shown. On the other hand, as the pilot valve, the one having the characteristics shown by the solid line in FIG. 4 is generally used. That is, the solid line in FIG. 4 shows the relationship between the operation amount (lever stroke) of the operation lever and the output pressure of the general-purpose pilot valve, but the output pressure is a little before the full stroke of the operation lever. Up to the stroke point S, the pressure is gradually increased substantially linearly as the lever stroke increases, but the stroke point S is set to increase at once and become equal to the input side pressure (the supply pressure PF of the pilot hydraulic pressure source). . In the above FIG. 4, P
1, P2 is the minimum control pressure of the control valve (minimum pilot pressure required to move the spool of the control valve), maximum control pressure (minimum pilot pressure required to move the spool of the control valve to the maximum stroke) ). By the way, when the hydraulic cylinder is slowly expanded and contracted to perform fine work, the maximum speed as shown in FIG. 7 is not necessary, and the cylinder is expanded and contracted in the low speed range shown as the fine operation range. become. However, the operation range of the operation lever in the fine operation range is narrow, and it is necessary to operate the operation lever while keeping the operation amount small, which requires nerves, requires skill, and reduces workability. Therefore, a pressure reducing valve capable of reducing the pilot pressure output from the pilot valve is provided, and when performing a fine operation, the pilot pressure output from the pilot valve to the control valve is reduced by the pressure reducing valve. It has been proposed that the speed of expansion and contraction of the hydraulic cylinder with respect to the operation amount of the operation lever can be slowed down, whereby the workability at the time of fine operation is improved.

[0003]

However, when the pilot pressure output from the pilot valve is reduced in order to improve the workability of the fine operation, the pilot valve having the above-mentioned characteristics is used. , Even if the pilot pressure supplied to the control valve is reduced by the pressure reducing valve, it will be increased at a stroke at the stroke point, and the expansion and contraction speed of the hydraulic cylinder will increase rapidly just before the full stroke. Therefore, there is a problem that operability is impaired, 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 circumstances in order to solve these problems, and it is a pilot operated type for controlling pressure oil supply to a hydraulic actuator. A control valve and a pilot valve for outputting a pilot pressure for operating the control valve based on an operation of an operating tool, the hydraulic circuit being input to the pilot valve from a pilot hydraulic source. The input side pressure control valve means capable of reducing the applied pressure and the output side pressure control valve means capable of reducing the pressure output from the pilot valve to the control valve are provided. 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 operating speed of the hydraulic actuator suddenly increases. Such problems can be avoided, and operability and workability are improved when performing fine operation. In this configuration, the input-side pressure control valve means and the output-side pressure control means are configured to perform depressurizing operation by an external signal output based on an operator's operation, so that the hydraulic actuator with respect to the operation amount of the operation tool can be operated. The operating speed can be arbitrarily adjusted based on the operation of the operator.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described with reference to the drawings. First, FIG. 1 shows a hydraulic circuit of a hydraulic cylinder 1 provided in a hydraulic excavator. In the hydraulic circuit diagram, 2 is a main hydraulic pressure source, 3 is a pilot hydraulic pressure source, 4 is an oil tank, 5 is a pressure of the hydraulic cylinder 1. It is a control valve that controls oil supply and discharge. In FIG. 1, 6 is a control valve for another hydraulic actuator 7 which uses the main hydraulic pressure source 2 as a hydraulic pressure supply source.

The control valve 5 is a pilot-operated three-position switching valve having first to sixth ports 5a to 5f and extension side and reduction side pilot ports 5g and 5h. 5a is the main oil pressure source 2 via the parallel oil passage A, and the second port 5b is the center bypass oil passage B.
To the main hydraulic pressure source 2, the third port 5c to the oil tank 4, and the fourth port 5d to the extension side oil chamber 1 of the hydraulic cylinder 1.
a, the fifth port 5e is in the oil tank 4, and the sixth port 5f
Are respectively connected to the reduction side oil chambers 1b of the hydraulic cylinder 1.

The control valve 5 has the first, third, fourth, and sixth ports 5a, 5c, 5d, 5d, 5d, 5h, 5h, 5h when no pilot pressure is input to the pilot ports 5g, 5h.
5f are closed, and the bypass valve passage from the second port 5b to the fifth port 5e (center bypass oil passage B
Is located at a neutral position N in which a valve passage through which the pressure oil of (1) flows to the oil tank 4 is opened.

On the other hand, when the pilot pressure is input to the extension side pilot port 5g, the control valve 5 moves to the first port 5a.
To the fourth port 5d from the supply valve passage (parallel oil passage A
Of the pressure oil of the hydraulic cylinder expansion side oil chamber 1a) and a discharge valve path from the sixth port 5f to the third port 5c (the oil of the hydraulic cylinder reduction side oil chamber 1b is discharged to the oil tank 4). To the extension side position X to open the valve path)
Thereby, the hydraulic cylinder 1 is configured to extend.

Further, when the pilot pressure is input to the reduction side pilot port 5h, the control valve 5 moves to the first port 5a.
To the sixth port 5f from the supply valve passage (parallel oil passage A
Of the pressure oil of the hydraulic cylinder contraction side oil chamber 1b) and a discharge valve path from the fourth port 5d to the third port 5c (the oil of the hydraulic cylinder extension side oil chamber 1a is discharged to the oil tank 4). Switch to the reduction side position Y which opens the valve path)
As a result, the hydraulic cylinder 1 is reduced in size.

Here, when the hydraulic cylinder 1 is expanded and contracted, the pilot port 5 on the expansion side and the contraction side is formed.
g, 5h, a characteristic diagram showing the relationship between the pilot pressure and the spool stroke of the control valve 5, and the opening areas of the bypass valve passage, the supply valve passage, and the discharge valve passage of the control valve 5,
This is shown in FIGS. 2 (A) and 2 (B). Then, as shown in the characteristic diagram, in the control valve 5, the opening areas of the supply valve passage and the discharge valve passage increase as the input pilot pressure increases, and the pressure oil to the hydraulic cylinder 1 is thereby increased. The supply amount is increased and the cylinder operating speed is increased.
2A and 2B, P1 is the minimum control pressure of the control valve 5 (minimum pilot pressure required to move the spool), and P2 is the maximum control pressure of the control valve 5 (maximum spool pressure). It is the minimum pilot pressure required to move to the stroke). PL is the maximum value of the output pressure from the output pressure reducing valves 13X and 13Y described later.

Further, in the hydraulic circuit diagram of FIG.
Reference numeral 11 denotes an input side pressure reducing valve arranged in a pilot supply path C from a pilot hydraulic pressure source 3 to a pilot valve unit 8 which will be described later. The input side pressure reducing valve 11 serves as the input side pressure control valve means of the present invention. Correspondingly, in the present embodiment, an electromagnetic proportional pressure reducing valve having a solenoid 11a is used. And this input side pressure reducing valve 11
Is in a non-operating state in which the supply pressure PF from the pilot hydraulic pressure source 3 is output to the pilot valve unit 8 without reducing the supply pressure PF when the solenoid 11a is not energized. It is configured so that the supply pressure PF from the pilot hydraulic pressure source 3 is reduced and the pilot valve unit 8 is output. In this case, as shown in the characteristic diagram of FIG.
The output pressure from the input pressure reducing valve 11 to the pilot valve unit 8 is controlled to decrease as the applied current value increases. Therefore, when the output pressure of the input side pressure reducing valve 11 is set to a limit pressure Ps (Ps <PF) described later,
The current value applied to the solenoid 11a is set to Cs as shown in FIG.

On the other hand, the pilot valve unit 8
Includes a pilot valve 9 and an output side pressure control valve device 10 which will be described later, and is connected to the pump port 8a connected to the pilot hydraulic pressure source 3 and the oil tank 4 via the input side pressure reducing valve 11 described above. Tank port 8
b, an expansion side connection port 8c connected to the expansion side pilot port 5g of the control valve 5, and a reduction side connection port 8d connected to the reduction side pilot port 5h.

The pilot valve 9 comprises an extension side pilot valve 9X and a reduction side pilot valve 9Y. These pilot valves 9X and 9Y are input ports 9ax and 9ay connected to the pump port 8a and a tank port. Drain port 9bx, 9by connected to 8b,
And output ports 9cx and 9cy connected to the output side pressure control valve device 10, respectively. The extension side and contraction side pilot valves 9X and 9Y are output ports 9cx and 9cy in a state where the operation lever 12 for the hydraulic cylinder 1 is not operated (the neutral position of the operation lever 12).
Does not output the pilot pressure because it is connected to the tank port 8b, but the pilot pressure corresponding to the operation amount is output from the output ports 9cx and 9cy based on the operation lever 12 being operated to the extension side and the contraction side. Is configured.

Here, the expansion side and contraction side pilot valves 9X and 9Y have characteristics as shown in FIG.
That is, FIG. 4 shows the relationship between the operation amount (lever stroke) of the operation lever 12 and the output pressure of the pilot valves 9X and 9Y. First, the input ports 9ax and 9a are shown.
The pressure input to y is the supply pressure P of the pilot hydraulic pressure source 3.
At F, the output pressures of the pilot valves 9X and 9Y gradually increase substantially linearly as the lever stroke increases until a stroke point S slightly before the full stroke of the operating lever 12, as shown by the solid line in FIG. However, it suddenly increases at the stroke point S and becomes equal to the supply pressure PF of the pilot hydraulic pressure source 3. On the other hand, input ports 9ax and 9ay
When the input pressure to the pilot pressure source 3 is lower than the supply pressure PF of the pilot hydraulic pressure source 3, for example, the limiting pressure Ps described later, the relationship between the output pressure of the pilot valves 9X and 9Y and the lever stroke is that the output pressure is the limiting pressure Ps. Until reaching, it is the same as the case shown by the solid line in FIG. 4, but the output pressure is the limiting pressure Ps.
After that, as shown by the broken line in FIG.
Even if 2 is operated to the full stroke, the output pressure is limited so as not to exceed the limit pressure Ps. Here, the limit pressure Ps is a pressure set to limit the input pressure of the pilot valves 9X and 9Y in order to prevent the output pressure of the pilot valves 9X and 9Y from suddenly increasing at the stroke point S. In the present embodiment, the output pressure immediately before the stroke point S is set as the limiting pressure Ps.
Further, in FIG. 4, P1 and P2 are the control valves 5 described above.
Is the minimum control pressure and the maximum control pressure.

Further, the output side pressure control valve device 10 is provided.
Is composed of expansion side and contraction side output pressure reducing valves 13X and 13Y, an electromagnetic switching valve 14, and a shuttle valve 15. The inlet side of the shuttle valve 15 is an output port of the expansion side pilot valve 9X. 9cx and reduction side pilot valve 9
It is connected to the Y output port 9cy, and the outlet side is connected to the first port 14a of the electromagnetic switching valve 14 described later. The shuttle valve 15 is configured to select the high pressure side of the pressure input from the inlet side and output the high pressure side from the outlet side, and thus, the extension side pilot valve 9X or the contraction side pilot valve 9Y is selected. Output port 9c
When the pilot pressure is output from x and 9 cy, the pilot pressure passes through the shuttle valve 15 and the electromagnetic switching valve 14
Is input to the first port 14a.

The electromagnetic switching valve 14 is a two-position switching valve having first to third ports 14a to 14c,
The first port 14a is on the exit side of the shuttle valve 15, the second port 14b is on the tank port 8b, and the third port 14 is on.
c is an output-side pressure reducing valve 13X on the extension side and a reduction side, which will be described later.
3Y 2nd pistons 13ex and 13ey are connected, respectively.

The solenoid operated directional control valve 14 has the first port 14a when the solenoid 14d is not energized.
Is located at the first position X, which opens the valve path from the first port to the third port 14c and closes the second port 14b. When the electromagnetic switching valve 14 is in the first position X,
The outlet side pressure of the shuttle valve 15, that is, the output port 9 of the extension side pilot 9X or the contraction side pilot valve 9Y.
The pilot pressures output from cx and 9cy are output side pressure reducing valves 13X and 1X via the electromagnetic switching valve 14 at the first position X.
It is adapted to be applied to the 3Y second pistons 13ex and 13ey.

On the other hand, when the solenoid 14d is energized, the electromagnetic switching valve 14 closes the first port 14a and switches to the second position Y where the second port 14b and the third port 14c communicate with each other. When the electromagnetic switching valve 14 is in the second position Y, the output pressure reducing valve 13
The application lines of the X and 13Y to the second pistons 13ex and 13ey are electrically connected to the tank port 8b via the electromagnetic switching valve 14 at the second position Y.

The output side pressure reducing valves 13X and 13Y on the expansion side and the contraction side are input ports 13ax and 13ay, drain ports 13bx and 13by, and an output port 13cx.
13cy, the first piston 13dx, 13dy, the second piston 13ex, 13ey, the third piston 13fx, 13
fy and ammo 13gx, 13gy,
The output side pressure reducing valve 13X on the extension side has an input port 13ax at the output port 9cx of the extension side pilot valve 9X, a drain port 13bx at the tank port 8b, and an output port 13x.
cx is connected to each of the extension side connection ports 8c. The output side pressure reducing valve 13Y on the reduction side is the input port 1
3ay is the output port 9cy of the reduction side pilot valve 9Y.
The drain port 13by is connected to the tank port 8b, and the output port 13cy is connected to the reduction side connection port 8d. Furthermore, the output side pressure reducing valve 1 on the extension side and the contraction side
For the 3X and 13Y first pistons 13dx and 13dy,
Output pressures from the output ports 9cx and 9cy of the extension side and contraction side pilot valves 9X and 9Y are respectively applied, and the extension side pilot valve 9X or the contraction side pilot valve 9Y is applied to the second pistons 13ex and 13ey as described above. Output pressure from the output ports 9cx, 9cy is applied via the electromagnetic switching valve 14 at the first position X, and the third piston 13fx,
Output pressure from the output ports 13cx and 13cy is applied to 13fy.

The first and second pistons 13dx,
13dy, 13ex, 13ey and ammo 13gx, 1
3 gy presses the valve elements of the output side pressure reducing valves 13X and 13Y to the non-operating state side where the pressures input to the input ports 13ax and 13ay are output from the output ports 13cx and 13cy without reducing the pressure, and the third piston 13fx, 13
The fy is configured to press the valve elements of the output pressure reducing valves 13X and 13Y toward the operating state where the pressure input to the input ports 13ax and 13ay is reduced and the pressure is output from the output ports 13cx and 13cy.

Here, the operating lever 12 is operated to the extension side or the contraction side, and the pilot valve 9 on the extension side or the contraction side.
When the pilot pressure is output from the X and 9Y output ports 9cx and 9cy, the output pressure reducing valve 13
The relationship between the force F1 that presses the X and 13Y toward the non-operating state side and the force F2 that presses the output side pressure reducing valves 13X and 13Y toward the operating state side is set as follows. That is, the electromagnetic switching valve 14 is located at the first position X and the second piston 13
When the output pressure from the output ports 9cx, 9cy of the expansion side pilot valve 9X or the contraction side pilot valve 9Y is applied to ex and 13ey, the output side pressure reducing valve 13X,
The force F1 that presses 13Y toward the non-operating state side is greater than the force F2 that presses toward the operating state side (F1> F2), and the electromagnetic switching valve 14 is located at the second position Y and the second piston 13ex, Tank port 8 is applied to 13ey
In the state where it is conducted to b, the force F that pushes to the operating state side
2 is larger than the force F1 that pushes it toward the non-operating state (F2
> F1).

The output pressure reducing valves 13X and 13Y are provided.
When the force F1 that pushes the valve to the non-operating state side is larger than the force F2 that pushes the valve to the operating state side (F1> F2), the output pressure reducing valves 13X and 13Y are connected to the input ports 13ax and 13a
Output port 13 without reducing the pressure input to y
It is held in a non-operating state that outputs from cx and 13cy.
Thus, the pilot pressure output from the expansion side or contraction side pilot valves 9X, 9Y is expanded without being decompressed via the expansion side or contraction side output side pressure reducing valves 13X, 13Y in the non-operating state. Side or reduced side connection port 8c,
8d, and is supplied to the expansion side or contraction side pilot ports 5g, 5h of the control valve 5.

Further, the force F2 for pressing the output pressure reducing valves 13X and 13Y toward the operating state side is the force F2 for pressing toward the non-operating state side.
When it is larger than 1 (F2> F1), the output side pressure reducing valves 13X and 13Y reduce the pressure input to the input ports 13ax and 13ay to reduce the output ports 13cx and 13cy.
It will be in the operating state that is output from. Thus, the pilot pressure output from the extension side or reduction side pilot valves 9X, 9Y is reduced by the output side pressure reducing valves 13X, 13Y in the operating state, and the extension side or reduction side connection ports 8c, 8 are provided.
It is output from d and supplied to the expansion side or contraction side pilot ports 5g, 5h of the control valve 5.

Here, the output side pressure reducing valve 13 in the operating state is
The depressurization operation of X and 13Y is shown in the characteristic diagram of FIG.
In, the minimum value Pc1 of the output pressure Pc from the output ports 13cx, 13cy is equal to the input port 13ax, 13ay.
Equal to the minimum value Pa1 of the input pressure Pa input to (Pc
1 = Pa1), and the maximum value Pc2 of the output pressure Pc is smaller than the maximum value Pa2 of the input pressure Pa (Pc2 <Pa
2) In FIG. 5, the output pressure Pc is reduced in a linear relationship (proportional relationship) with respect to the input pressure Pa, but a non-linear relationship is also possible.

On the other hand, the solenoid 11a of the input side pressure reducing valve 11 and the solenoid 14d of the electromagnetic switching valve 14 are electrically connected to a work speed switching switch 16 provided on the driver's seat of the hydraulic excavator 1 or the like. When the work speed changeover switch 16 is off, the solenoids 11a and 14d are not energized, but when the work speed changeover switch 16 is turned on, the solenoids 11a and 14d are energized.

When working at a normal work speed, the work speed changeover switch 16 is turned off.
To In this state, the solenoids 11a and 14d of the input side pressure reducing valve 11 and the electromagnetic switching valve 14 are not energized, and thus the input side pressure reducing valve 11 and the output side pressure reducing valves 13X and 13D.
Both Y are in a non-operating state in which the pressure reducing operation is not performed. In this way, the input side pressure reducing valve 11 and the output side pressure reducing valve 13
When X and 13Y are inactive, the supply pressure PF from the pilot hydraulic pressure source 3 is input to the pilot valve 9 and the output pressure from the pilot valve 9 is not reduced and the control valve 5, the control valve 5 is supplied with the pilot pressure equivalent to the output pressure of the pilot valve 9 shown by the solid line in FIG. 4, as shown by the solid line in FIG. On the other hand, when the hydraulic cylinder 1 does not require the maximum speed and is slowly expanded and contracted for fine work, the work speed changeover switch 16 is turned on.
Set to N. In this state, the solenoids 11a and 14d of the input side pressure reducing valve 11 and the electromagnetic switching valve 14 are energized, so that the input side pressure reducing valve 11 and the output side pressure reducing valves 13X and 13X.
Both Y are in an operating state in which the pressure reducing operation is performed. In this way, when the input pressure reducing valve 11 and the output pressure reducing valves 13X and 13Y are in the operating state, the pilot valve 9 receives the pressure reduced to the limiting pressure Ps by the input pressure reducing valve 11. At the same time, the output pressure from the pilot valve 9 is reduced by the expansion-side and reduction-side output-side pressure reducing valves 13X and 13Y and supplied to the control valve 5. In this case, the maximum value of the output pressure from the pilot valve 9 becomes the limiting pressure Ps as shown by the broken line in FIG. 4, but the pressure obtained by reducing the limiting pressure Ps by the output pressure reducing valves 13X and 13Y, that is, The maximum value PL of the output pressure from the output pressure reducing valves 13X and 13Y is
It is smaller than the maximum control pressure P2 of the control valve 5 described above (PL
<P2). Thus, as shown by the broken line in FIG. 6, even if the operating lever 12 is operated to the full stroke side from the stroke point S, the control valve 5
The pilot pressure supplied to the pump never exceeds the maximum value PL.

Further, the relationship between the lever stroke of the operating lever 12 and the expansion / contraction speed of the hydraulic cylinder 1 when the work speed changeover switch 16 is OFF and ON is shown in FIG. 7. As shown in FIG. When the speed changeover switch 16 is turned on, the expansion / contraction speed of the hydraulic cylinder 1 decreases over the entire lever stroke, and the expansion / contraction speed becomes constant after the stroke point S, which is slightly before the full stroke, and the operation is performed up to the full stroke. However, the expansion / contraction speed does not suddenly increase. Also,
The range of the lever stroke in the low speed region of the hydraulic cylinder 1 shown as the fine operation region in FIG. 7 is wider by X when the work speed changeover switch 16 is ON than when it is OFF.

In the embodiment configured as described above, the control valve 5 for controlling the pressure oil supply and discharge of the hydraulic cylinder 1 is controlled by the pilot pressure output from the pilot valve 9 based on the operation of the operation lever 12. While operating, the input side pressure reducing valve 11 capable of reducing the input pressure input from the pilot hydraulic pressure source 3 to the pilot valve 9 is provided on the input side of the pilot valve 9, while the pilot valve 9 Output side pressure reducing valves 13X and 13Y capable of reducing the pilot pressure output from the pilot valve 9 are provided on the output side of. Then, in the case where the hydraulic cylinder 1 is slowly expanded and contracted without requiring the maximum speed and fine work is performed, the work speed changeover switch 16 is turned on to turn on the input side pressure reducing valve 11
And the pressure reducing operation of the output side pressure reducing valves 13X and 13Y is performed, and as described above, the expansion / contraction speed of the hydraulic cylinder 1 with respect to the operation amount of the operation lever 12 becomes slow over the entire lever stroke. Thus, when performing a fine operation of the hydraulic cylinder 1, it is not necessary to operate the lever as in the prior art, which requires skill to perform a fine operation while keeping the operation amount small, and even if the hydraulic cylinder 1 is operated up to a full stroke. The operability and workability are improved without the problem that the expansion and contraction speed of the is suddenly increased. Moreover, in this device, the pilot valve unit 8 includes a pilot valve 9 for outputting a pilot pressure corresponding to the operation amount of the operating lever 12, and an output side pressure for reducing the pilot pressure output from the pilot valve 9. Since the control valve device 10 is integrally incorporated, the control valve device 10 can be easily installed on a working machine such as a hydraulic excavator, and the pilot valve unit 8 can be replaced with, for example, an existing pilot valve. In such a case, there is an advantage that the replacement work is easy.

The present invention is of course not limited to the above-mentioned embodiment, but means for outputting an external signal for performing a pressure reducing operation to the input side pressure control valve means and the output side pressure control valve means. Not only the work speed changeover switch 16 but also any device capable of outputting an external signal to each of the pressure control valve means on the input side and the output side as required. Further, the present invention can be implemented in a hydraulic circuit of a traveling motor, a turning motor, or the like provided in a hydraulic excavator, or a hydraulic circuit of another hydraulic actuator such as a hydraulic actuator for attachment, or only the hydraulic excavator. Instead, it can be applied to various working machines provided with hydraulic actuators.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a hydraulic cylinder.

FIG. 2A is a diagram showing opening characteristics of the control valve when the hydraulic cylinder is extended and FIG. 2B is when the hydraulic cylinder is contracted.

FIG. 3 is a diagram showing characteristics of an input side pressure reducing valve.

FIG. 4 is a diagram showing characteristics of a pilot valve.

FIG. 5 is a diagram showing characteristics of an output pressure reducing valve.

FIG. 6 is a diagram showing a relationship between a lever stroke and a pilot pressure supplied to a control valve.

FIG. 7 is a diagram showing a relationship between a lever stroke and an expansion / contraction speed of a hydraulic cylinder.

FIG. 8 is a hydraulic circuit diagram showing a conventional example.

[Explanation of symbols]

1 hydraulic cylinder 3 Pilot hydraulic power source 5 control valve 9 Pilot valve 11 Input side pressure reducing valve 12 Operation lever 13X Output side pressure reducing valve on extension side 13Y Reduction side output pressure reducing valve 16 Working speed switch

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Claims (2)

[Claims] 1. A pilot operated control valve for controlling pressure oil supply to a hydraulic actuator, and a pilot valve for outputting pilot pressure for operating the control valve based on operation of an operating tool. In the hydraulic circuit, the input side pressure control valve means capable of reducing the pressure input to the pilot valve from the pilot hydraulic source and the pressure output from the pilot valve to the control valve can be reduced in the hydraulic circuit. An output side pressure control valve means is provided to provide a hydraulic circuit in a working machine. 2. An input side pressure control valve means and an output side pressure control means according to claim 1, wherein the pressure reducing operation is performed by an external signal output based on an operation of an operator. Hydraulic circuit in working machinery.