JP2003156006A - Fluid pressure circuit, and control method for it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid pressure circuit capable of solving a problem where a pressure reducing valve for prioritizing a boom cylinder may damage an operation of a bucket cylinder when simultaneously operating the boom cylinder and the bucket cylinder of a hydraulic shovel. SOLUTION: The pressure reducing valve 36 is disposed in a pilot line 35 for supplying pilot pressure to a spool 25 for a bucket for controlling the bucket cylinder 19. The pressure reducing valve 36 comprises a pressure reduction promoting characteristic part 36a for promoting reduction of the pilot pressure supplied to the spool 25 in response to increase of the pilot pressure supplied to a first spool 21 for a boom for controlling the boom cylinder 15, and a pressure reduction regulating characteristic part 36b for regulating the pressure reduction of the pilot pressure supplied to the spool 25 within a range allowing an operation of the bucket cylinder 19 even when the pilot pressure supplied to the first spool 21 is increased.

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 and a fluid pressure circuit control method.

[0002]

2. Description of the Related Art As shown in FIG. 4, 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.

[0004] Japanese Utility Model Registration No. 2579587 discloses a first boom control valve and a second boom control valve for controlling a boom cylinder, and a first stick control cylinder for a stick cylinder in the left and right pump lines of a hydraulic excavator. A control valve and a second control valve for stick are provided respectively, and a stick-in pilot pressure supplied to the second control valve for stick according to the boom raising pilot pressure supplied to the first control valve for boom is controlled by the pressure reducing valve. A hydraulic circuit of a construction machine adapted to be pressure-reduced 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. 2, a boom raising pilot which is supplied to a 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 operation of the boom operating valve, the pressure is reduced. Since the valve has a characteristic of reducing the stick-in pilot pressure to a pressure lower than the operating pressure Pc of the second stick control valve, the second stick control valve returns to the neutral position, and as a result, the second stick control is performed. The hydraulic oil flow rate supplied from the valve to the stick cylinder is reduced to 0, and correspondingly, it is supplied to the boom cylinder via the boom first control valve. The operating oil flow rate is maintained.

[0006]

[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 control valve and the stick second control valve as in the stick cylinder control system in the two-pump circuit disclosed in Japanese Patent No. 9587, the boom raising operation and the stick Even if the pressure reducing valve operates due to the boom raising pilot pressure due to the linked operation of the IN operation and the second stick control valve returns to the neutral position, the stick cylinder passes through the first stick control valve However, the present invention is directly applied to, for example, the boom raising operation and the bucket closing operation for rotating the bucket at the tip of the stick to the machine side. If you do, problems will occur.

That is, during the linked operation of the boom raising operation and the bucket closing operation, as the boom raising pilot pressure supplied to the boom first control valve rises, the pressure reducing valve having the characteristic shown in FIG. 3 increases. , The bucket close pilot pressure supplied to the bucket control valve that controls the bucket cylinder for rotating the bucket is gradually reduced, and near the full lever operation of the boom operation valve,
It has the characteristic of reducing the bucket / close pilot pressure to a pressure lower than the operating pressure Pd of the bucket control valve.

At this time, since the bucket control valve is not composed of two unlike the boom first and second control valves and the stick first and second control valves, it is composed of only one. When the boom raising pilot pressure is increased by operating the boom raising full lever, if the bucket closing pilot pressure to the bucket control valve is cut by the pressure reducing valve having the characteristics shown in Fig. 3, the only bucket control valve Returns to the neutral position, which causes a problem that the bucket cylinder is stuck.

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

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

[0011]

According to another aspect of the present invention, there is provided one pilot operated control valve for controlling one fluid pressure actuator, and another pilot operated control valve for controlling another fluid pressure actuator. Valve and a pressure reducing valve for reducing the pilot pressure supplied to another pilot operated control valve according to the pilot pressure supplied to the one pilot operated control valve. A pressure reducing acceleration characteristic part that accelerates pressure reduction of pilot pressure supplied to another pilot operated control valve according to an increase in pilot pressure supplied to the operated control valve, and one pilot operated control valve Even if the pilot pressure rises, the pressure reduction regulation characteristic that regulates the pressure reduction of the pilot pressure supplied to the other pilot operated control valve to the range where other fluid pressure actuators can be operated. When the one fluid pressure actuator and the other fluid pressure actuator are simultaneously operated, the pressure reduction promoting characteristic portion of the pressure reducing valve gives priority to the pilot pressure to the one pilot operated control valve. Supply to the one fluid pressure actuator can be preferentially operated, and even when the one fluid pressure actuator is operated to the maximum extent, the pressure reducing valve characteristic of the pressure reducing valve allows other pilot operated control By stably supplying the minimum required pilot pressure to the valve, the required operation of the other fluid pressure actuator can be stably ensured.

According to the invention described in claim 2, one pilot operated control valve and another pilot operated control valve in the fluid pressure circuit according to claim 1 supply the working fluid from a common fluid pressure source. The other fluid pressure actuator is a fluid pressure circuit that is an actuator that operates at a lower load than the one fluid pressure actuator, and when operating one fluid pressure actuator and another 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 can be secured.

According to a third aspect of the present invention, one pilot operated control valve in the fluid pressure circuit according to the first or second aspect is a control valve for controlling a boom cylinder of a hydraulic excavator, and another pilot operated control valve. The control valve is a fluid pressure circuit that is a control valve installed in a one-to-one relationship with other fluid pressure actuators of the hydraulic excavator, and simultaneously operates the boom cylinder of the hydraulic excavator and the other fluid pressure actuators. When doing so, the pressure reducing valve can reliably operate the boom cylinder that requires a sufficient amount of oil by preferentially supplying the pilot pressure to the control valve for the boom cylinder, as well as other pilot operations. Even if the control valve is a control valve installed in a one-to-one relationship with another fluid pressure actuator, the pilot pressure necessary for this control valve can be supplied. Hydraulic actuator can be prevented from stopping.

According to a fourth aspect of the present invention, when the pilot pressure supplied to the one pilot operated control valve for controlling the one fluid pressure actuator is less than a certain pressure,
In response to this increase in pilot pressure, the pilot pressure supplied to one pilot operated control valve is promoted by promoting reduction of pilot pressure supplied to another pilot operated control valve that controls another fluid pressure actuator. When the pressure rises above a certain level, it is a fluid pressure circuit control method that regulates the reduction of pilot pressure supplied to other pilot operated control valves to the range in which other fluid pressure actuators can operate. When operating the actuator and another fluid pressure actuator at the same time, if the pilot pressure supplied to one pilot operated control valve is less than a certain pressure,
One fluid pressure actuator can be operated preferentially, and when the pilot pressure supplied to one pilot operated control valve rises above a certain pressure, the other fluid pressure actuator can be operated as required. Yes, always,
A plurality of fluid pressure actuators can be smoothly operated with good balance.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the embodiment shown in FIG. This Figure 1
Shows a fluid pressure circuit of a hydraulic excavator as a construction machine. The same parts as those of the hydraulic excavator shown in FIG. 4 are designated by the same reference numerals.

As shown in FIG. 1A, this fluid pressure circuit includes a boom first spool 21 and a boom as one pilot operated control valve for controlling a boom cylinder 15 as one fluid pressure actuator. For second spool 22
And the first stick for controlling the stick cylinder 17
The spool 23 and the second stick spool 24, and the 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.
Is a pilot operated center bypass valve.

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.
It receives the supply of hydraulic oil as the working fluid from 26.

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

Bucket cylinder 19 for rotating the bucket
Is a boom cylinder that supports the load of the entire front work equipment.
The bucket spool 25 that controls the bucket cylinder 19 is an actuator that operates at a load lower than 15.
A control valve installed in a one-to-one relationship with the bucket cylinder 19.

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

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

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

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

Further, from the boom remote control valve 31 to the pilot line 32 to the pilot line 37 connected to the boom raising side pilot pressure acting portion of the boom first spool 21.
Is branched, and the branched pilot line 37 is guided to the pilot pressure acting portion of the pressure reducing valve 36.

This external pilot type pressure reducing valve 36 is a bucket remote control valve 34 according to the boom raising pilot pressure supplied from the boom remote control valve 31 to the boom raising side pilot pressure acting portion of the boom first spool 21. The bucket closing pilot pressure supplied from the bucket closing spool side pilot pressure acting portion of the bucket spool 25 to the bucket closing pilot pressure is controlled within a range in which the bucket cylinder 19 can be operated.

FIG. 1B shows the characteristic of the pressure reducing valve 36. The pressure reducing valve 36 is operated from the bucket remote control valve 34 to the bucket close side in response to the rise of the boom raising pilot pressure supplied to the boom raising side pilot pressure acting portion of the boom first spool 21. spool
Supply to the decompression promotion characteristic part 36a that accelerates the decompression of the bucket / close pilot pressure that is supplied to the bucket / close side pilot pressure action part 25 and the boom up side pilot pressure action part of the boom first spool 21 Even if the boom raising pilot pressure rises above a certain value, the bucket close pilot pressure reduced to the bucket close pilot pressure acting part of the bucket spool 25 is regulated within the range in which the bucket cylinder 19 can be operated. The pressure reducing regulation characteristic portion 36b is provided.

That is, even if the boom raising pilot pressure rises above a certain value Pa near the full lever operation of the boom remote control valve 31, the pressure reducing valve 36 keeps the bucket cylinder 19 under control.
Bucket close pilot pressure Pb that can secure a certain bucket spool opening area required to operate the
I try not to lower the pressure.

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

At the same time when the boom remote control valve 31 of the hydraulic excavator is operated to the boom raising side, at the same time as the bucket remote control valve 31.
Operate 34 to the bucket / close side to move the boom cylinder
15 and the bucket cylinder 19 are extended at the same time, and when performing the bucket closing operation while raising the hydraulic excavator boom, the pilot pressure is applied to the pressure reducing valve 36 by the pilot line 37 branched from the boom pilot line 32. In operation, the pressure reducing valve 36 is controlled to have the characteristics shown in FIG.

In the characteristic shown in FIG. 1 (b), in the decompression promotion characteristic portion 36a which appears in inverse proportion, the boom remote control valve 31 is operated to the boom raising side and at the same time the bucket remote control valve 34 is closed. When operated to the side,
The pressure reducing valve 36 is a bucket / close pilot pressure supplied from the bucket remote controller valve 34 to the bucket / closer side pilot pressure acting portion of the bucket spool 25 in response to an increase in the boom raising pilot pressure from the boom remote controller valve 31. Accelerate the decompression of.

Therefore, 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 hydraulic oil supplied from the pump of the hydraulic source 26 to the bucket cylinder 19 is For spool
Since it is strongly throttled at 25 according to the boom raising pilot pressure, a large flow rate is not supplied to the low load bucket cylinder 19, and 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 rather than the bucket spool 25, so that the hydraulic oil supplied from the common hydraulic source 26 is used for the boom. Since it is configured to be sufficiently supplied to the boom cylinder 15 via the first spool 21, it is necessary for the boom cylinder 15 to have a large capacity and a sufficient amount of hydraulic oil and to support the load of the entire front working machine. The hydraulic oil can be supplied preferentially to the low load bucket cylinder 19.

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 closing operation by the bucket cylinder 19 can always be smoothly realized in a 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 near the full lever operation 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 operated with a limited hydraulic oil flow rate.

At this time, from the bucket remote control valve 34, which is fully lever-operated to the bucket close side, to the bucket
When the closed pilot primary pressure is output, this bucket / close pilot primary pressure passes through the pressure reducing valve 36 functioning in the pressure reducing regulation characteristic portion 36b shown in FIG. Reduced to a stable bucket / close pilot secondary pressure.

The bucket close pilot secondary pressure is a bucket close pilot pressure Pb which can secure a constant bucket spool opening area required for bucket closing operation of the bucket cylinder 19.

Although the bucket spool 25 is installed in a one-to-one relationship with the bucket cylinder 19, the pressure reducing valve 36 functioning in the pressure reducing regulation characteristic portion 36b acts on the bucket / close side pilot pressure acting portion. Therefore, the minimum bucket close pilot pressure Pb required to move the bucket cylinder 19 is stably supplied, so that the required bucket close operation can be stably ensured.

As described above, the pressure reducing valve 36 is incorporated in the bucket pilot line 35, and the pressure reducing valve 36 is also pilot-controlled by the boom raising pilot pressure to the boom first spool 21, and the bucket spool 25.・ When interlocking operation is performed to accelerate the pressure reduction of the closed pilot pressure, the existing pressure reducing valve shown in Fig. 3 shows that when the boom raising pilot pressure becomes high due to the boom raising full lever operation, the bucket spool 25・ Since the closed pilot pressure was completely cut off and the bucket spool 25 returned to the neutral position, there was a problem that the bucket cylinder 19 did not move.
Does not reduce the bucket close pilot pressure to the bucket spool 25 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 cylinder 19 does not get stuck.

In the illustrated embodiment, the boom raising and the bucket closing are explained, but similarly, other actuators such as a swing motor and an attachment controlled by one spool are controlled. By using this pressure reducing valve in the pilot line of the spool, the same effect can be expected.

Further, in the present fluid pressure circuit, not only construction machinery such as a hydraulic excavator, but in short, a pressure reducing valve for giving priority to one fluid pressure actuator when simultaneously operating a plurality of fluid pressure actuators is used. When the operation of the fluid pressure actuator is impaired, it can be widely applied to solve the problem.

[0042]

According to the invention described in claim 1, when the one fluid pressure actuator and the other fluid pressure actuator are simultaneously operated, the pressure reduction promoting characteristic portion of the pressure reducing valve allows
By preferentially supplying pilot pressure to one pilot operated control valve, it is possible to operate one fluid pressure actuator with priority, and even when one fluid pressure actuator is operated to the maximum, a pressure reducing valve By stably supplying the minimum required pilot pressure to the other pilot-operated control valve by means of the pressure-reducing restriction characteristic part, the necessary operation of the other fluid pressure actuator can be stably ensured.

According to the second 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 it is supplied, the required operation can be ensured even in the fluid pressure actuator provided with the low load fluid pressure actuator.

According to the third aspect of the invention, when simultaneously operating the boom cylinder of the hydraulic excavator and the other fluid pressure actuator, 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 necessary pilot pressure can be supplied to this control valve, so that it is possible to prevent other fluid pressure actuators from stopping.

According to the fourth aspect of the present invention, when one fluid pressure actuator and another fluid pressure actuator are simultaneously operated, the pilot pressure supplied to the one pilot operated control valve satisfies a constant pressure. If not, the one fluid pressure actuator can be operated with priority, and if the pilot pressure supplied to the one pilot operated control valve rises above a certain pressure, the other fluid pressure actuator is required. It is possible to secure various operations, and it is possible to always smoothly operate a plurality of fluid pressure actuators in good balance.

[Brief description of drawings]

FIG. 1A is a circuit diagram showing an embodiment of a fluid pressure circuit according to the present invention, and FIG. 1B is a characteristic diagram showing a pressure reducing characteristic of a pressure reducing valve used in this fluid pressure circuit.

FIG. 2 is a characteristic diagram showing characteristics of stick-in pilot pressure with respect to boom raising pilot pressure of a pressure reducing valve used in a conventional fluid pressure circuit.

FIG. 3 is a characteristic diagram showing characteristics of bucket / close pilot pressure with respect to boom-up pilot pressure of a pressure reducing valve analogically applied to a conventional fluid pressure circuit.

FIG. 4 is a side view of the hydraulic excavator.

[Explanation of symbols]

15 Boom cylinder as one fluid pressure actuator 19 Bucket cylinder as another fluid pressure actuator 21 Boom first spool as one pilot operated control valve 25 Bucket spool as another pilot operated control valve 26 Fluid Hydraulic pressure source as pressure source 36 Pressure reducing valve 36a Pressure reduction promoting characteristic portion 36b Pressure reduction regulating characteristic portion

Claims (4)

[Claims] 1. A pilot operated control valve for controlling one fluid pressure actuator, another pilot operated control valve for controlling another fluid pressure actuator, and a pilot operated control valve supplied to one pilot operated control valve A pressure reducing valve for reducing the pressure of the pilot pressure supplied to another pilot operated control valve according to the pilot pressure is provided, and the pressure reducing valve responds to an increase in the pilot pressure supplied to one pilot operated control valve. Pressure reducing characteristic part for promoting the pressure reduction of the pilot pressure supplied to another pilot operated control valve, and another pilot operated control valve even if the pilot pressure supplied to one pilot operated control valve rises. And a depressurization regulating characteristic part for regulating depressurization of the pilot pressure supplied to the valve within a range in which another fluid pressure actuator can be operated. 2. The one pilot operated control valve and the other pilot operated control valve are supplied with 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, wherein the fluid pressure circuit is an actuator that operates in accordance with (1). 3. 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 claim 1 or 2, wherein the fluid pressure circuit is a control valve installed in (3). 4. When the pilot pressure supplied to one pilot operated control valve for controlling one fluid pressure actuator is less than a certain pressure, another fluid pressure actuator is activated in response to the increase in pilot pressure. When the pilot pressure supplied to one pilot operated control valve rises above a certain pressure, the other pilot operated control valve is controlled. A method for controlling a fluid pressure circuit, characterized in that the reduction of pilot pressure supplied to a valve is regulated within a range in which another fluid pressure actuator can be operated.