JP2003232303A - Fluid pressure circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid pressure circuit which can solve a problem that a decompression valve to surely operate a boom cylinder in simultaneous operation of the boom cylinder and a bucket cylinder of a hydraulic shovel may sometimes disturb the operation of the bucket cylinder. <P>SOLUTION: Pilot pressure to a bucket spool 25 to control the bucket cylinder 19 can be depression-controlled by the decompression valve 36. The decompression valve 36 is controlled by control signal pressure branched from the pilot pressure to a first spool 21 to control the boom cylinder 15. The control signal pressure is controlled by the decompression valve 38. The decompression valve 38 outputs the pilot pressure as the control signal pressure as it is to the decompression valve 36 in the range where the pilot pressure of the first spool 21 of the boom is lower than constant pressure, and at the same time, outputs the control signal pressure decompressed to constant limit pressure to the decompression valve 36 in the range where the pilot pressure of the first spool 21 of the boom is higher than the constant pressure even if the pilot pressure is changed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid pressure circuit having a pilot operated control valve.

[0002]

2. Description of the Related Art As shown in FIG. 5, a hydraulic excavator as a construction machine includes an undercarriage 11 provided with a traveling motor.
The upper revolving structure that can be revolved by the revolving motor of the revolving unit 12.
A boom 14 of a front working machine is rotatably supported by a boom cylinder 15 on the upper swing body 13 so as to be vertically rotatable. A stick 16 is attached to the tip of the boom 14 and an inward / outward direction is applied by a stick cylinder 17. The stick 18 has a bucket 18 rotatably supported at its tip end by a bucket cylinder 19 so as to be rotatable in the opening / closing direction.

Here, the boom cylinder 15 is extended to raise the boom, the stick cylinder 17 is extended to stick-in, and the bucket cylinder 19 is extended to obtain a bucket close operation.

Japanese Utility Model Registration No. 2579587 discloses a boom first control valve and a boom second control valve for controlling a boom cylinder, a stick first control valve for controlling a stick cylinder, and a left and right pump lines of a hydraulic excavator. A second stick control valve is provided, and the stick-in pilot pressure supplied to the second stick control valve is controlled by the pressure reducing valve according to the boom raising pilot pressure supplied to the first boom control valve. The hydraulic circuit of the construction machine is shown.

The pressure reducing valve used in the hydraulic circuit of the construction machine disclosed in Japanese Utility Model Registration No. 2579587 is, as shown in FIG. 6, a boom raising pilot pressure supplied to the boom first control valve. As the pressure rises, the stick-in pilot pressure supplied to the second stick control valve is gradually reduced, and when the boom raising pilot pressure reaches the set value near the full lever operating position of the boom operating valve, the pressure reducing valve Has the characteristic of reducing the stick-in pilot pressure to 0, the stick second
The control valve returns to the neutral position, which results in the stick second
The flow rate of hydraulic oil supplied from the control valve to the stick cylinder is set to 0, and the flow rate of hydraulic oil supplied to the boom cylinder via the boom first control valve is secured accordingly.

As an application circuit using a pressure reducing valve having the characteristics as shown in FIG. 6, for example, when the boom is raised and the bucket is closed, the boom cylinder 15 having a high load is changed to the bucket cylinder 19 having a low load. Since there is a problem that the boom 14 is difficult to rise because the pump discharge oil flows easily, it is preferable to incorporate a pressure reducing valve in the bucket pilot line as shown in FIG. 7 in order to solve this problem.

Explaining the hydraulic circuit shown in FIG. 7, the boom first spool 21 for controlling the boom cylinder 15 is described.
And the boom second spool 22 and the stick cylinder 17
A stick first spool 23 and a stick second spool 24, and a bucket spool 25 that controls the bucket cylinder 19.

The boom first spool 21, the stick second spool 24, and the bucket spool 25 have one hydraulic power source 26.
And is supplied with hydraulic oil from the hydraulic pressure source 26.
On the other hand, the boom second spool 22 and the stick first spool 23 are connected to the other hydraulic pressure source 27 and receive the supply of hydraulic oil from this hydraulic pressure source 27. The respective hydraulic pressure sources 26, 27 supply hydraulic oil to the respective spools through the respective parallel passages 28, and are communicated with the tank 30 through the respective bypass passages 29 when the respective spools are in the neutral position.

Boom raising pilot lines 32 and 33 from the boom remote control valve 31 are connected to the boom raising pilot pressure acting portion of the boom first spool 21 and the boom raising pilot pressure acting portion of the boom second spool 22, respectively. A bucket / close pilot line 35 from a bucket remote control valve 34 is connected to the bucket / close pilot pressure acting part of the.

An external pilot type pressure reducing valve 36 is provided in a bucket close pilot line 35 extending from the bucket remote control valve 34 to the bucket close pilot pressure acting portion of the bucket spool 25. Further, a boom raising signal pressure line 37 is branched from a boom raising pilot line 32 connected to the boom raising pilot pressure acting portion of the boom first spool 21 from the boom remote control valve 31, and this branched boom raising signal pressure line 37 is , To the signal pressure acting portion of the pressure reducing valve 36.

This external pilot type pressure reducing valve
36 acts from the bucket remote control valve 34 to the bucket / close pilot pressure acting portion of the bucket spool 25 according to the boom raising pilot pressure acting from the boom remote control valve 31 to the boom raising pilot pressure acting portion of the boom first spool 21. Bucket close pilot pressure is reduced.

That is, when the boom is raised and the bucket is closed, the pressure reducing valve 36 is operated by the boom raising pilot pressure, and the stroke of the bucket spool 25 is limited.
The amount of oil supplied to 15 is secured and the boom 14 is raised.

[0013]

[Problems to be Solved by the Invention] Utility model registration No. 257
When the left and right pump lines are provided with the stick first spool 23 and the stick second spool 24 as in the stick cylinder control system in the two-pump circuit disclosed in Japanese Patent No. 9587, a boom raising operation and a stick-in operation are performed. In the interlocking operation of the stick cylinder, even if the pressure reducing valve (not shown in FIG. 7) for reducing the stick-in pilot pressure by the boom raising pilot pressure is operated and the second stick spool 24 returns to the neutral position, Since the hydraulic oil is supplied to the hydraulic fluid source 27 from the hydraulic pressure source 27 through the first stick spool 23, the problem that the stick cylinder 17 does not move does not occur. And if it is applied as it is to the interlocking operation of the bucket closing operation that rotates the bucket 18 to the aircraft side, there is a problem Will occur.

That is, in the hydraulic circuit shown in FIG. 7, when the boom raising operation and the bucket closing operation are interlocked, the pressure reducing valve 36 having the characteristics shown in FIG. As the boom raising pilot pressure supplied to the boom raising pilot pressure acting portion of the spool 21 increases, the bucket close pilot pressure supplied from the bucket remote control valve 34 to the bucket close pilot pressure acting portion of the bucket spool 25 is gradually increased. The characteristic is that the bucket / close pilot pressure is reduced to 0 near the full lever operation position of the boom remote control valve 31.

Moreover, the bucket spool 25 is not composed of two pieces like the boom first spool 21 and the boom second spool 22 and the stick first spool 23 and the stick second spool 24, but is composed of only one. Therefore, when the boom raising pilot pressure is increased by operating the boom raising full lever, the bucket closing pilot pressure to the bucket spool 25 is cut by the pressure reducing valve 36 having the characteristic shown in FIG. Since the spool 25 returns to the neutral position, the bucket cylinder 19 is stuck.

This problem similarly occurs not only in the bucket spool 25, but also in a swing motor control valve for controlling the swing motor, an attachment control valve for controlling an attachment such as a breaker attached in place of the bucket, and the like.

The present invention has been made in view of the above circumstances, and when a plurality of fluid pressure actuators are simultaneously operated, a pressure reducing valve for reliably operating one fluid pressure actuator is provided with another fluid pressure actuator. Therefore, it is an object of the present invention to provide a fluid pressure circuit that can solve this problem.

[0018]

According to a first aspect of the present invention, there is provided one pilot operated control valve for controlling one fluid pressure actuator, and another fluid pressure operated simultaneously with the one fluid pressure actuator. Another pilot operated control valve for controlling the actuator and the pilot pressure supplied to the other pilot operated control valve are reduced by the control signal pressure branched from the pilot pressure supplied to one pilot operated control valve. A fluid pressure circuit having a possible pressure reducing valve and pressure reducing valve control means for limiting the pressure reducing control function of the pressure reducing valve when the pilot pressure supplied to one pilot operated control valve is higher than a certain pressure, When simultaneously operating one fluid pressure actuator and another fluid pressure actuator, the pressure reducing valve preferentially supplies pilot pressure to the one pilot operated control valve. Therefore, the one fluid pressure actuator that requires a sufficient amount of fluid can be operated reliably, and when the pilot pressure supplied to the one pilot operated control valve is higher than a certain pressure, the pressure reduction is performed. Since the pressure reducing control function of the pressure reducing valve is limited by the valve control means so that the pilot pressure for securing the opening area required for the other pilot operated control valve can be supplied, it is necessary to use other fluid pressure actuators. Stable operation can be secured.

According to a second aspect of the present invention, in the pressure reducing valve control means in the fluid pressure circuit according to the first aspect, when the pilot pressure supplied to one pilot operated control valve is lower than a certain pressure, The direct control characteristic part that outputs the pilot pressure as it is to the pressure reducing valve as the control signal pressure and the constant pilot pressure supplied to one pilot operated control valve are constant even if the pilot pressure changes. It is equipped with a constant pressure control characteristic part that outputs the control signal pressure reduced to the limit pressure to the pressure reducing valve.When the pilot pressure supplied to one pilot operated control valve is lower than a certain pressure, the pressure is reduced. The direct pressure control characteristic portion of the valve control means allows the pressure reducing valve to exert its original pressure reducing control function to ensure reliable operation of the fluid pressure actuator. In the range in which the pilot pressure supplied to the control valve is higher than a fixed pressure, the pressure reducing control function of the pressure reducing valve is limited by the constant pressure control characteristic portion of the pressure reducing valve control means, so that other fluid pressure actuators need to operate. Stable operation can be secured.

According to a third aspect of the present invention, the one pilot operated control valve and the other pilot operated control valve in the fluid pressure circuit according to the first or second aspect of the present invention operate from a common fluid pressure source. In response to the supply, the other fluid pressure actuator is a fluid pressure circuit that is a lower load actuator than the one fluid pressure actuator, and when operating one fluid pressure actuator and the other fluid pressure actuator at the same time, The pressure reducing valve suppresses the flow of the working fluid supplied from the fluid pressure source to the other fluid pressure actuator with a low load through the other pilot operated control valve, and thus the operation supplied from the common fluid pressure source. Since the fluid is supplied sufficiently to one fluid pressure actuator via one pilot operated control valve, it is installed with a low load fluid pressure actuator. Also necessary operations with a fluid pressure actuator of a high load can be secured.

In the invention described in claim 4, one pilot operated control valve in the fluid pressure circuit according to any one of claims 1 to 3 is a control valve for controlling a boom cylinder of a hydraulic excavator, and The pilot operated control valve of
A fluid pressure circuit that is a control valve installed in a one-to-one relationship with other fluid pressure actuators of a hydraulic excavator,
When operating the boom cylinder of a hydraulic excavator and other fluid pressure actuators at the same time, the pressure reducing valve preferentially supplies pilot pressure to the control valve for the boom cylinder so that the boom that requires a sufficient amount of oil can be used. The pressure reducing valve control means functions as a pressure reducing valve even if the cylinder can be operated reliably and the other pilot operated control valve is a control valve installed in a one-to-one relationship with another fluid pressure actuator. Therefore, the pilot pressure for ensuring the opening area required for the other pilot operated control valve can be supplied, and the stop of the other fluid pressure actuator by the pressure reducing valve can be prevented.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail with reference to the embodiment shown in FIGS. Figure 1
Shows a hydraulic circuit as a fluid pressure circuit installed in a hydraulic excavator as a construction machine. The same parts as those of the hydraulic excavator shown in FIG. 5 are designated by the same reference numerals.

As shown in FIG. 1, this hydraulic circuit is
A boom first spool 21 and a boom second spool 22 as one pilot operated control valve for controlling the boom cylinder 15 as one fluid pressure actuator, and a stick first spool 23 and a stick second spool 22 for controlling the stick cylinder 17. A spool 24 and a bucket spool 25 as another pilot operated control valve for controlling the bucket cylinder 19 as another fluid pressure actuator are provided.

The boom first spool 21, the boom second spool 22, the stick first spool 23, the stick second spool 24, and the bucket spool 25 are pilot-operated center bypass valves.

The boom first spool 21, the stick second spool 24, and the bucket spool 25 are connected to one hydraulic pressure source 26 as a common fluid pressure source, from which hydraulic oil as a working fluid is supplied. receive.

On the other hand, the boom second spool 22 and the stick first spool 23 are connected to the other hydraulic pressure source 27 and receive the supply of hydraulic oil from this hydraulic pressure source 27.

The respective hydraulic pressure sources 26, 27 supply hydraulic oil to the respective spools through the respective parallel passages 28, and when the respective spools are in the neutral position, they are communicated with the tank 30 through the respective bypass passages 29. ing.

Bucket cylinder 19 for rotating the bucket
Is a lower load actuator than the high load boom cylinder 15 that bears the load of the entire front work machine. The bucket spool 25 that controls this bucket cylinder 19 is installed in a one-to-one relationship with the bucket cylinder 19. It is a valve.

A boom remote control valve as a boom operating valve is provided in the boom raising pilot pressure acting portion of the boom first spool 21 and the pilot pressure acting portion of the boom second spool 22.
Boom raising pilot lines 32 and 33 from 31 are connected respectively, and a bucket close pilot line 35 from a bucket remote control valve 34 as a bucket operating valve is connected to the bucket close pilot pressure acting part of the bucket spool 25. There is.

A boom lowering pilot line (not shown) from the boom remote control valve 31 is connected to the boom lowering pilot pressure acting portion of the boom first spool 21, and the bucket open pilot pressure acting portion of the bucket spool 25 is connected to the boom lowering pilot pressure acting portion. , A bucket open pilot line (not shown) from the bucket remote control valve 34 is connected, and the stick in pilot pressure acting portion and the stick out pilot pressure acting portion of the stick first spool 23 and the stick second spool 24 are connected to , A stick-in pilot line (not shown) and a stick-out pilot line (not shown) from a stick operation valve (not shown) are connected.

For the boom remote control valve 31, the operation in the arrow direction shown in FIG. 1 is the boom raising operation, and for the bucket remote control valve 34, the operation in the arrow direction is the bucket close operation.

An external pilot type pressure reducing valve 36 is provided in the bucket close pilot line 35 extending from the bucket remote control valve 34 to the bucket close pilot pressure acting portion of the bucket spool 25.

Further, a boom raising signal line 37 is branched from a boom raising pilot line 32 connected from the boom remote control valve 31 to a boom raising pilot pressure acting portion of the boom first spool 21. The line 37 is connected to the primary side of the pressure reducing valve 38 as the pressure reducing valve control means, and the control signal pressure line 39 drawn from the secondary side of the pressure reducing valve 38 is connected to the control signal pressure acting portion of the pressure reducing valve 36. It is connected.

The pressure reducing valve 38 has the characteristics shown in FIG. In FIG. 2, the horizontal axis is the boom-up pilot pressure on the primary side input to the pressure reducing valve 38, and the vertical axis is the secondary pressure controlled by the pressure reducing valve 38, that is, the control signal pressure to the pressure reducing valve 36. It is shown that the control signal pressure does not exceed Pa even if the boom raising pilot pressure exceeds Pa.

That is, the pressure reducing valve 38 is a direct passage control for outputting the boom raising pilot pressure as it is to the pressure reducing valve 36 as a control signal pressure in a range where the boom raising pilot pressure supplied to the boom first spool 21 is lower than a certain pressure. Characteristic part 38
In addition, the control signal pressure is reduced to a certain limit pressure even if the boom raising pilot pressure changes while the boom raising pilot pressure supplied to the boom first spool 21 is higher than a certain pressure. It has a constant pressure control characteristic portion 38b for outputting to the pressure reducing valve 36 and functions as a limiter for the external pilot control signal of the pressure reducing valve 36.

As shown in FIG. 3, the pressure reducing valve 36 in the bucket / close pilot line 35 is controlled by the bucket remote control valve 34 in response to the control signal pressure output from the pressure reducing valve 38 in the boom raising signal pressure line 37. The bucket / close pilot pressure supplied to the bucket / close pilot pressure acting portion of the bucket spool 25 is controlled to be reduced.

Therefore, in the combination of the pressure reducing valve 36 and the pressure reducing valve 38, as shown in FIG. 4, the boom raising pilot pressure rises above a certain pressure Pa near the full lever operating position of the boom remote control valve 31. Also, the bucket close pilot pressure supplied to the bucket close pilot pressure acting portion of the bucket spool 25 is the bucket cylinder 19
The bucket close pilot pressure Pb is not lower than the bucket close pilot pressure Pb that can secure a constant bucket spool opening area required to operate the.

That is, according to the characteristics of the pressure reducing valve 36 shown in FIG. 3, the bucket area which can secure the opening area of the bucket spool 25 necessary for operating the bucket cylinder 19
The closing pilot pressure is Pb, and the pressure reducing valve at that time 36
Assuming that the control signal pressure of No. is Pa, the control signal pressure from the pressure reducing valve 38 to the pressure reducing valve 36 will not exceed Pa as shown in FIG. As shown in FIG. 4, the bucket close pilot pressure, which is the secondary pressure of the pressure reducing valve 36, does not fall below Pb.

Next, the function and effect of this embodiment will be described.

When the boom remote control valve 31 of the hydraulic excavator is operated to the boom raising side and at the same time the bucket remote control valve 34 is operated to the bucket close side, the boom cylinder 15 and the bucket cylinder 19 are simultaneously extended, and the hydraulic excavator is operated. When performing the bucket closing operation while performing the boom raising operation, the boom raising pilot pressure acts on the pressure reducing valve 38 by the boom raising signal pressure line 37 branched from the boom raising pilot line 32, and the pressure reducing valve 38 moves to the position shown in FIG. The control signal pressure having the characteristic shown in is output.

In the characteristic shown in FIG. 2, in the direct passage control characteristic portion 38a, the pressure reducing valve 38 uses the boom raising pilot pressure from the boom remote control valve 31 as it is as the control signal pressure to control the pressure control valve 36. As shown in FIG. 4, the bucket close pilot pressure supplied from the bucket remote control valve 34 through the pressure reducing valve 36 to the bucket close pilot pressure acting portion of the bucket spool 25 is reduced as shown in FIG. Appears as it is.

For this reason, the spool opening of the bucket spool 25 is controlled to be smaller than the opening commanded by the bucket remote control valve 34, and the pump of the hydraulic power source 26 moves to the bucket cylinder.
Since the hydraulic oil supplied to 19 is throttled by the bucket spool 25 according to the boom raising pilot pressure, a large flow rate is not supplied to the bucket cylinder 19 with a low load,
Only the bucket cylinder 19 does not perform the bucket closing operation at high speed.

In other words, the pressure reducing valve 36 preferentially supplies the pilot pressure to the boom first spool 21 from the bucket spool 25 so that the hydraulic oil supplied from the common hydraulic power source 26 is supplied to the boom first spool 21. Through 21, the required amount of hydraulic oil can be reliably supplied to the boom cylinder 15 that has a capacity larger than that of the bucket cylinder 19 and needs a sufficient amount of hydraulic oil and that supports the load of the entire front working machine.

In short, even in the hydraulic circuit in which the low load bucket cylinder 19 and the high load boom cylinder 15 are provided side by side, the boom cylinder 15 ensures reliable boom raising operation,
The bucket cylinder 19 and the bucket closing operation can be smoothly achieved in a well-balanced manner, and the necessary operation can be secured.

On the other hand, when the boom remote control valve 31 is operated to the boom raising side to the vicinity of the full lever operation position and the boom first spool 21 and the boom second spool 22 are operated to near the full stroke, the boom cylinder 15 is maximized. The boom can be raised with the hydraulic oil flow rate.

At this time, even if the boom raising pilot pressure from the boom remote control valve 31 rises, the control signal pressure action of the pressure reducing valve 36 is passed through the pressure reducing valve 38 functioning in the constant pressure control characteristic portion 38b shown in FIG. Since the control signal pressure limited to a certain limit pressure acts on the portion, the bucket / close pilot pressure supplied from the bucket remote control valve 34 to the bucket / close pilot pressure acting portion of the bucket spool 25 via the pressure reducing valve 36 is As shown in FIG. 4, it does not drop below a certain pressure Pb.

This bucket / close pilot pressure Pb
Is a pilot pressure that can secure a constant bucket spool opening area required for the bucket cylinder 19 to perform a bucket closing operation.

Although the bucket spool 25 is installed in a one-to-one relationship with the bucket cylinder 19, the pressure reducing valve 38 is provided to the bucket / close pilot pressure acting portion.
Since the minimum bucket closing pilot pressure Pb necessary for the bucket closing operation of the bucket cylinder 19 can be supplied from the pressure reducing valve 36 whose pressure is regulated by the constant pressure control characteristic unit 38b, the required bucket closing operation Can be secured stably.

Thus, the pressure reducing valve 36 having the pressure reducing characteristic as shown in FIG. 3 is incorporated in the bucket / close pilot line 35, and the pressure reducing valve 36 is further moved by the boom raising pilot pressure to the boom first spool 21. Even if you perform a linked operation such as pilot control to reduce the bucket / close pilot pressure to the bucket spool 25,
Since the pressure reducing valve 38 having the characteristics shown in FIG. 2 is incorporated in the boom raising signal pressure line 37, the control signal pressure to the pressure reducing valve 36 is
As shown in FIG. 2, since it does not exceed Pa, even if the boom raising pilot pressure is increased by operating the boom raising full lever, as shown in FIG.
Since the bucket close pilot pressure to 25 is not reduced to a pressure lower than the bucket close pilot pressure Pb that can secure a constant bucket spool opening area required to operate the bucket cylinder 19, the pressure reducing valve 36 as in the conventional case is used. Completely cuts the bucket close pilot pressure to the bucket spool 25,
25 does not return to the neutral position, and the bucket cylinder 19 does not get stuck.

In the illustrated embodiment, the boom raising and the bucket closing are described, but similarly, other actuators such as a swing motor and an attachment controlled by one spool are controlled. When the same pressure reducing valve 36 is used in the spool pilot line, the same effect can be expected by installing the pressure reducing valve 38 as shown in FIG. 2 in the control signal pressure line of the pressure reducing valve 36. it can.

Further, the present fluid pressure circuit is not limited to construction machines such as hydraulic excavators, but in short, when a plurality of fluid pressure actuators are simultaneously operated, a pressure reducing valve for reliably operating one fluid pressure actuator is provided. In the case of impairing the operation of other fluid pressure actuators, it can be widely applied to solve the problem.

[0052]

According to the first aspect of the present invention, when the one fluid pressure actuator and the other fluid pressure actuator are simultaneously operated, the pressure reducing valve gives priority to the pilot pressure to the one pilot operated control valve. Since it is supplied in a stable manner, it is possible to reliably operate one fluid pressure actuator that requires a sufficient amount of fluid, and when the pilot pressure supplied to one pilot operated control valve is higher than a certain pressure. Since the pressure reducing valve control means limits the pressure reducing control function of the pressure reducing valve so that the pilot pressure for securing the opening area required for the other pilot operated control valve can be supplied, another fluid pressure actuator The required operation can be stably secured.

According to the second aspect of the present invention, in the range where the pilot pressure supplied to one pilot operated control valve is lower than a certain pressure, the direct pressure control characteristic portion of the pressure reducing valve control means causes the pressure reducing valve to be the original one. The pressure reducing control function can be exerted to surely operate the one fluid pressure actuator, and in the range where the pilot pressure supplied to the one pilot operated control valve is higher than a certain pressure, the pressure reducing valve control means The constant pressure control characteristic portion limits the pressure reducing control function of the pressure reducing valve, and the required operation of other fluid pressure actuators can be stably ensured.

According to the third aspect of the invention, when the one fluid pressure actuator and the other fluid pressure actuator are simultaneously operated, the pressure reducing valve causes the working fluid supplied from the fluid pressure source to operate in another pilot operation. Suppresses the flow of hydraulic fluid to another fluid pressure actuator with a low load via the control valve, so that the working fluid supplied from the common fluid pressure source is sufficient for one fluid pressure actuator via one pilot operated control valve. Since the fluid pressure is supplied, the required operation can be ensured even in the high load fluid pressure actuator that is installed together with the low load fluid pressure actuator.

According to the fourth aspect of the present invention, when the boom cylinder of the hydraulic excavator and the other fluid pressure actuator are simultaneously operated, the pressure reducing valve preferentially supplies the pilot pressure to the control valve for the boom cylinder. By doing so, the boom cylinder that requires a sufficient amount of oil can be operated reliably, and another pilot operated control valve is a control valve installed in a one-to-one relationship with another fluid pressure actuator. Even if there is, the pressure reducing valve control means limits the function of the pressure reducing valve, so it is possible to supply pilot pressure to secure the opening area required for other pilot operated control valves, and other fluid pressure actuators can be operated by the pressure reducing valve. It can be prevented from stopping.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a fluid pressure circuit according to the present invention.

FIG. 2 is a characteristic diagram showing control characteristics of a pressure reducing valve control means used in the fluid pressure circuit of the above.

FIG. 3 is a characteristic diagram showing a pressure reducing characteristic of a pressure reducing valve used alone in the fluid pressure circuit.

FIG. 4 is a characteristic diagram showing a combined characteristic of the pressure reducing valve control means and the pressure reducing valve.

FIG. 5 is a side view of the hydraulic excavator.

FIG. 6 is a characteristic diagram showing a pressure reducing characteristic of stick-in pilot pressure with respect to a boom raising pilot pressure of a pressure reducing valve used in a conventional hydraulic circuit.

FIG. 7 is a circuit diagram showing a hydraulic circuit using a pressure reducing valve in a bucket pilot line, which is a premise of the present invention.

[Explanation of symbols]

15 Boom cylinder as one fluid pressure actuator 19 Bucket cylinder as another fluid pressure actuator 21 Boom as one pilot operated control valve No. 1
Spool 25 Bucket spool as another pilot operated control valve 26 Hydraulic pressure source as fluid pressure source 36 Pressure reducing valve 38 Pressure reducing valve as pressure reducing valve control means 38a Direct control characteristic part 38b Constant pressure control characteristic part

Claims (4)

[Claims] 1. A pilot operated control valve for controlling one fluid pressure actuator, and another pilot operated control valve for controlling another fluid pressure actuator that is simultaneously operated with one fluid pressure actuator, The pilot pressure supplied to the other pilot operated control valve is controlled by the control signal pressure branched from the pilot pressure supplied to the other pilot operated control valve. A pressure reducing valve control means for limiting the pressure reducing control function of the pressure reducing valve when the supplied pilot pressure is higher than a predetermined pressure. 2. The direct pressure control characteristic unit, wherein the pressure reducing valve control means outputs the pilot pressure as it is to the pressure reducing valve as a control signal pressure in a range where the pilot pressure supplied to one pilot operated control valve is lower than a certain pressure. In the range where the pilot pressure supplied to one pilot operated control valve is higher than a certain pressure, even if the pilot pressure changes, a constant pressure control that reduces the control signal pressure to a certain limit pressure to the pressure reducing valve. The fluid pressure circuit according to claim 1, further comprising a characteristic portion. 3. The one pilot operated control valve and the other pilot operated control valve are supplied with a working fluid from a common fluid pressure source, and the other fluid pressure actuator has a lower load than the one fluid pressure actuator. The fluid pressure circuit according to claim 1 or 2, wherein the fluid pressure circuit is an actuator. 4. One pilot operated control valve is a control valve for controlling a boom cylinder of a hydraulic excavator, and another pilot operated control valve has a one-to-one relationship with another fluid pressure actuator of the hydraulic excavator. The fluid pressure circuit according to any one of claims 1 to 3, wherein the fluid pressure circuit is a control valve installed in (4).