JP2003090302A - Hydraulic control circuit of construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic control circuit of a construction machine which can uniformly perform a boom hoisting operation and an arm drawing operation even when the boom hoisting operation and the arm drawing operation are performed in a compound manner. SOLUTION: In the hydraulic control circuit of the construction machine in which a pressurized oil is fed from common hydraulic pumps 2 and 3 to an arm cylinder 11 and a boom cylinder 8 to actuate an arm 12 and a boom 9 constituting an attachment, a sub spool 17 to limit the flow rate of the arm cylinder 11 by receiving a signal output when the boom hoisting operation is performed is provided on an arm control valve 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control circuit provided in a construction machine such as a hydraulic excavator.

[0002]

2. Description of the Related Art Conventionally, a hydraulic excavator has oscillated a boom with a mounting portion provided on a floor plate of an upper swing body as a fulcrum, and drives an arm connected to a tip portion of the boom in a pushing direction or a pulling direction. , Excavating by swinging the bucket equipped to that arm,
We are dumping the excavated earth and sand.

The boom cylinder for driving the boom and the arm cylinder for driving the arm are usually arranged in different hydraulic pump circuits. When operating the boom, the pressure oils from both hydraulic pumps are combined. Then, it is supplied to the boom cylinder to increase the boom speed.

The boom merging valve for merging the pressure oil is connected in parallel with the arm control valve for controlling the arm cylinder. Therefore, when the arm pulling operation and the boom raising operation are performed in combination, the pressure oil, which has been separately provided to the boom merging valve and the arm control valve from one hydraulic pump, is taken to the arm control valve side, and the boom raising speed becomes slow. This is because the arm pulling causes a lighter load than the boom raising because the arm operates in the direction in which the arm descends by its own weight.

[0005]

Particularly, in a special machine such as a telescopic crumb or a long arm machine having a heavy attachment, when the boom raising and the arm pulling are combined and operated, the boom raising speed becomes slow and the work does not progress.

The present invention has been made in consideration of the problems in the conventional hydraulic control circuit as described above. Even when the boom raising and the arm pulling are combined, the boom raising operation and the arm pulling operation are performed. An object of the present invention is to provide a hydraulic control circuit for a construction machine that can be operated without excess or deficiency.

[0007]

SUMMARY OF THE INVENTION The present invention provides a hydraulic control circuit for a construction machine, which supplies pressure oil from a common hydraulic pump to an arm cylinder and a boom cylinder that operate an arm and a boom that form an attachment. ,
A hydraulic control circuit for a construction machine, comprising flow rate limiting means for limiting a flow rate of the arm cylinder in response to a signal output when a boom raising operation is performed.

In the present invention, the flow rate control means may be configured to limit the flow rate of the meter-in circuit of the arm cylinder. The flow rate control means is preferably configured to limit the flow rate when the control valve for supplying the controlled pressure oil to the arm cylinder is switched to the arm pulling side.

Further, it is preferable that the flow rate limiting means limits the flow rate of both the meter-in circuit and the meter-out circuit of the arm cylinder. Thereby,
It is possible to prevent cavitation from occurring on the head side of the arm cylinder during the arm pulling operation.

Further, in the present invention, it is possible to provide a control means for controlling the ratio of the flow rate limited by the flow rate limiting means in accordance with the boom raising operation amount. According to this configuration,
When combined operation of raising the boom and pulling the arm is performed, the flow rate on the arm side can be limited according to the amount of boom operation.

As a specific example of the flow rate limiting means, a sub-spool incorporated in the arm spool of the control valve of the arm cylinder is shown. This sub-spool is configured to reduce the passing flow rate when the boom raising operation is performed. According to this configuration, the circuit configuration is simplified and the space can be saved.

When a hydraulic pilot type valve controlled by a remote control valve is used as the control valve of the boom cylinder, the pilot pressure output from the remote control valve when the boom is raised is applied to the pilot port of the sub spool. be able to.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the drawings.

FIG. 1 shows an embodiment of a hydraulic control circuit for a construction machine according to the present invention.

The hydraulic control circuit shown in the figure is applied to a hydraulic excavator, and when the engine 1 is driven, the first hydraulic pump 2, the second hydraulic pump 3 and the pilot pump 4 rotate respectively.

The first and second hydraulic pumps 2 and 3 are variable displacement hydraulic pumps, and are composed of swash plate type axial piston pumps whose discharge flow rate changes according to the inclination angle displacement of the swash plate.

The pressure oil discharged from the first hydraulic pump 2 is
It is supplied to a plurality of control valves arranged in the center bypass line LCB on the left side of the drawing.

In this center bypass line LCB,
Although control valves for controlling the right traveling motor, the bucket cylinder, the boom cylinder, etc. are arranged, only the boom control valve 5 related to the present invention is shown in the present embodiment for simplicity of explanation.

On the other hand, control valves for controlling the left traveling motor, the swing motor, the arm cylinder, etc. are arranged on the center bypass line RCB on the right side in the drawing in which the pressure oil from the second hydraulic pump 3 flows. Similarly, only the arm control valve 6 relevant to the present invention is shown.

The pilot pressure discharged from the pilot pump 4 is used as a pressure source Pa for various controls.

The boom control valve 5 is connected to the head side oil chamber 8a and the rod side oil chamber 8b of the boom cylinder 8 through the supply / discharge passage 7, and the boom 9 is connected to the rod 8c of the boom cylinder 8. There is.

The boom 9 has a fulcrum portion 9a at the bottom thereof.
It is possible to swing in the up-down direction, that is, in the boom raising direction or the boom lowering direction around the rotation center (connected to the mounting portion provided on the floor plate of the upper swing body).

The boom control valve 5 has a neutral position a, a boom lowering position b, and a boom raising position c. When the boom control valve 5 is switched from the neutral position a to the boom lowering position b, the pressure oil from the first hydraulic pump 2 is changed. Is supplied to the rod-side oil chamber 8b through the rod-side supply / discharge passage 7b, while the head-side oil chamber 8b
The pressure oil discharged from a is discharged to the tank T via the head side supply / discharge passage 7a. As a result, the boom cylinder 8 is contracted and the boom 9 is lowered.

On the contrary, when the boom control valve 5 is switched from the neutral position a to the boom raising position c,
Pressure oil is supplied to the head side oil chamber 8a of the boom cylinder 8 through the head side supply / discharge passage 7a, while the rod side oil chamber 8b is supplied.
The pressure oil discharged from the tank is discharged to the tank T via the rod side supply / discharge passage 7b. As a result, the boom cylinder 8 extends and the boom 9 operates to raise the boom.

Next, the arm control valve 6 is connected to the head side oil chamber 11a of the arm cylinder 11 through the supply / discharge passage 10.
And the rod-side oil chamber 11b, and the arm 12 is connected to the rod 11c of the arm cylinder 11.

The arm 12 can be swung in the front-rear direction, that is, in the arm pushing direction or the arm pulling direction around the fulcrum portion 12a (connected to the boom tip portion 9b) as a rotation center.

The arm control valve 6 has a neutral position d, an arm pushing position e, and an arm pulling position f. When the arm position is switched from the neutral position a to the arm pushing position e, the pressure oil passes through the rod side supply / discharge passage 10b. The pressure oil supplied to the rod side oil chamber 11b and discharged from the head side oil chamber 11a is discharged to the tank T via the head side supply / discharge passage 10a. At this time, the arm cylinder 11 shrinks and the arm 12
Moves the arm.

On the contrary, when the arm control valve 6 is switched from the neutral position d to the arm pulling position f,
The pressure oil is supplied to the head side oil chamber 11 through the head side supply / discharge passage 10a.
On the other hand, the pressure oil that is supplied to a and is discharged from the rod side oil chamber 11b is discharged to the tank T via the rod side supply / discharge passage 10b. As a result, the arm cylinder 11 extends and the arm 12 performs an arm pulling operation.

A pilot pressure P _a1 derived from the boom remote control valve 13 is applied to the pilot port 5a of the boom control valve 5 described above through a pilot line 14, and this pilot pressure P _a1 is simultaneously applied to the boom merging valve 15. It is also given to the pilot port 15a.

Therefore, when the boom operating lever 13a is operated in the boom raising direction, the boom merging valve 15 opens at the shutoff position g.
To the communication position h.

As a result, the pressure oil from the second hydraulic pump 3 flows through the oil passage 16a → the oil passage 16b → the communicating position h → the oil passage 16c →
It flows to the head side supply / discharge passage 7a and is supplied to the head side oil chamber 8a of the boom cylinder 8. As a result, the first hydraulic pump 2
Also, the pressure oil from the second hydraulic pump 3 joins and is supplied to the boom cylinder 8, so that the operation of the boom 9 can be accelerated.

However, the oil passage 16a is branched into an oil passage 16d in addition to the oil passage 16b, and this oil passage 16d is connected to the arm control valve 6. Therefore, when the arm pulling operation is performed even when the pressure oil supplied to the boom cylinder 8 is being merged by the boom merging valve 15, the pressure oil from the second hydraulic pump 3 as a common hydraulic pump is loaded as compared with the boom 9. Is taken by the lower arm side, and the operation speed of the boom 9 becomes slower.

Therefore, in this embodiment, the sub spool 17 having a throttle is provided inside the arm control valve 6 independently of the arm spool, and the meter-in circuit of the arm cylinder 11 is throttled.

The arm control valve 6 is switched by the pilot pressure P _a2 derived from the arm remote control valve 18 as in the conventional case, but the sub spool 17 is used.
Is the pilot pressure P derived from the boom remote control valve 13.
It is independently switched in the arm pulling position f by _a1 , and the communication position i is switched to the diaphragm position j.

The sub spool 17 which is switched by the boom operating pressure functions as a flow rate control means.

The throttle amount at the throttle position j is determined by testing, for example, the speed balance of the boom and the arm in the attachment, and is appropriately set according to the class of construction machine and the type of attachment.

Next, the operation of the hydraulic control circuit having the above configuration will be described.

In the hydraulic control circuit shown in FIG. 1, when the arm pulling operation and the boom raising operation are combined, the boom remote control valve 13 is operated.
Based on the pilot pressure P _a1 derived from switched from the neutral position a boom control valve 5 to the boom up position c, the neutral position the arm control valve 6 based on the pilot pressure P _a2 derived from the arm remote control valve 18 Switch from d to arm pull position f.

Since the pilot pressure P _a1 derived from the boom remote control valve 13 is also supplied to the pilot port 15a of the boom merging valve 15, the boom merging valve 15 is also switched from the shutoff position g to the communication position h. As a result, the pressure oil discharged from the first hydraulic pump 2 and the second hydraulic pump 3 merges via the boom merging valve 15 and is supplied to the head side oil chamber 8a of the boom cylinder 8.

Further, the pilot pressure P _a1 derived from the boom remote control valve 13 is supplied to the port 6a of the arm control valve 6 and given to the pilot port 17a of the sub spool 17. As a result, sub spool 1
7 is an arm pulling position f from the communication position i to the diaphragm position j.
Is switched to.

When the meter-in circuit of the arm cylinder 11 is throttled in this way, the flow rate of the pressure oil flowing through the oil passage 16d is limited, so that the pump pressure of the second hydraulic pump 3 increases and the increased pump pressure is increased by the boom. It is supplied to the cylinder 8.

As a result, the required amount of pressure oil can be supplied to the boom side having a high load pressure, and the delay of the boom speed is eliminated even when the arm pulling and the boom raising are combined. be able to.

In the hydraulic control circuit described above, when the sub spool 17 is switched to the throttle position j, less pressure oil is introduced to the head side oil chamber 11a of the arm cylinder 11, but the arm control valve 6 moves to the arm pulling position. Since it is switched to f, the meter-out circuit of the arm cylinder 11 is open. Therefore, the pump flow rate may be insufficient on the head side of the arm cylinder 11 and cavitation may occur.

The hydraulic control circuit shown in FIG. 2 is for eliminating the occurrence of cavitation. In the following description, the same components as those in FIG. 1 will be assigned the same reference numerals and the description thereof will be omitted.

In the hydraulic control circuit shown in FIG. 2, the meter-out circuit of the arm cylinder 11 is narrowed.

In this circuit, the regeneration switching valve 21 is connected to the oil passage 20 which returns from the rod side oil chamber 11b of the arm cylinder 11 to the tank T. This regeneration switching valve 21 is normally k
Although it is in the position, it returns to the tank T while giving a certain negative pressure to the return oil, but when the boom is raised, the pilot pressure derived from the boom remote control valve 13 is supplied to the pilot port 21a through the pilot line 22. By being given, the k position is switched to the l position.

When switched to the l position, the arm cylinder 1
The return oil discharged from the rod side oil chamber 11b of No. 1 is
It is introduced into the head side supply / discharge passage 10a via the position and reproduced. As a result, the pump flow rate does not become insufficient in the head-side oil chamber 11a, and cavitation can be prevented.

FIG. 3 shows a second embodiment of the present invention, in which the stroke of the sub spool 17 is electrically controlled according to the operation amount of the boom operating lever 13a.

In the circuit shown in FIG. 3, the boom remote control valve 1
A pressure sensor 24 is provided in a pilot line 23 that leads from 3 to the pilot port 15 a of the boom merging valve 15.

The boom operation pressure signal detected by the pressure sensor 24 is supplied to the controller 25 as a control means.
Given to. The controller 25 gives a proportional valve command value according to the boom operating pressure to the proportional control valve 26, and the sub spool 17 strokes based on the secondary pressure of the proportional control valve 26, and as a result, the meter-in circuit of the arm cylinder 11 Is narrowed down.

If the controller 25 is used to control the stroke of the sub-spool 17 as described above, the controller 25 is normally provided with detection results such as pump pressure and engine speed from the sensor. It becomes possible to perform more accurate control by using them as parameters.

A detailed description will be given below. In the present embodiment, the meter-in circuit of the arm cylinder 11 is throttled by making the sub-spool 17 stroke, but this throttling effect changes depending on the inflow flow rate. For example, if the engine speed decreases and the pump discharge amount decreases, the throttling effect decreases.

Even in such a case, if the controller 25 calculates the proportional valve command value using the engine speed as a parameter, an appropriate throttling effect can be obtained.

FIG. 4 shows the proportional valve 2 depending on the engine speed.
6 is a characteristic diagram for setting the secondary pressure characteristic of No. 6 in FIG.

When the boom remote control valve 13 is operated to change the remote control pressure P _{a1, the} secondary pressure of the proportional control valve 26 is changed according to the engine speed. Specifically, the secondary pressure is set to the characteristic M ₅ when the engine is in rated operation, but the throttle effect is increased stepwise as the engine speed decreases. Refer to characteristics M ₅ → M ₄ → M ₃ . When the engine speed is the lowest, the characteristic M ₁ is selected. In this case, the secondary pressure becomes maximum.

With this configuration, it is possible to obtain a constant diaphragm effect even when the engine speed changes.

When considering the pump pressure as a parameter, it is determined that the load is large when the pump pressure is high and the throttling effect by the sub spool 17 is enhanced, and that the load is small when the pump pressure is low. Sub spool 17
It is also possible to control such that the diaphragm effect due to is reduced.

Next, FIG. 5 shows the regeneration switching valve 2 shown in FIG.
The switching operation of No. 1 is electrically controlled.

In the circuit shown in FIG. 5, the detection signal from the pressure sensor 24 is input to the controller 28, and the detection signal from the pressure sensor 29 that detects the arm operating pressure is also input.

Upon receiving both detection signals, the controller 28 performs the following control.

First, in FIG. 6 (a), based on the secondary pressure characteristic of the proportional control valve 27 with respect to the boom raising operation pressure, the proportion of the boom raising operation pressure during work when the operation pressure P _a1 is “A” The secondary pressure P _iA of the control valve 27 is _calculated . The secondary pressure P _iA is a secondary pressure P _iA upon full lever operation and arm pulling.

When the amount of arm pulling operation of the arm operating lever 18a increases, the amount of oil flowing into the head side oil chamber 11a of the arm cylinder 11 increases, so that cavitation hardly occurs. Therefore, the characteristic N shown in FIG.
By setting, the secondary pressure of the proportional control valve 27 decreases according to the arm pulling operation amount, and the regeneration flow rate decreases, so that the operability of the arm pulling operation can be improved.

The controller 28 can control the flow rates of both the meter-in circuit and the meter-out circuit by combining the meter-in circuit shown in FIG. 3 and the meter-out circuit shown in FIG. .

Further, the hydraulic control circuit of the present invention has been described by taking the hydraulic excavator as an example in the above-mentioned embodiment, but the present invention is not limited to this, and is applied to any construction machine having a boom and an arm and operating them in combination. In particular, it is suitable for a special machine such as a telescolum or a long arm machine with a heavy attachment.

[0065]

As is apparent from the above description,
According to the present invention of claims 1 and 2, in a hydraulic control circuit of a construction machine, which supplies pressure oil from a common hydraulic pump to an arm cylinder and a boom cylinder that operate an arm and a boom that constitute an attachment, Even when the boom raising and arm pulling operations are combined, the boom raising operation and the arm pulling operation are performed because the flow rate limiting device that receives the signal output when the boom raising operation is performed limits the flow rate of the arm cylinder. The pulling operation can be performed just enough.

According to the third aspect of the present invention, since the control valve for supplying the controlled pressure oil to the arm cylinder is configured to limit the flow rate when it is switched to the arm pulling side, the load is low. It is possible to prevent pressure oil from being supplied to the arm cylinder.

According to the present invention of claim 4, since the flow rate of both the meter-in circuit and the meter-out circuit of the arm cylinder is limited, cavitation can be prevented even when the arm is lowered by its own weight. be able to.

According to the fifth aspect of the present invention, the control means for controlling the rate of the flow rate restricted by the flow rate limiting means is provided according to the magnitude of the signal corresponding to the boom raising operation amount.
When performing a combined boom raising and arm pulling operation, more accurate flow rate control can be performed in consideration of the engine speed and pump pressure.

According to the sixth aspect of the present invention, since the sub spool is built in the arm spool of the control valve of the arm cylinder, it is not necessary to significantly change the circuit design.
Moreover, since the circuit configuration is simple, it is possible to save space.

According to the present invention of claim 7, a hydraulic pilot type valve is used as the control valve of the boom cylinder, and the pilot pressure output from the remote control valve is applied to the pilot port of the sub-spool during boom raising operation. Since it is configured, the present invention can be realized with a simple circuit configuration.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram in which a meter-out circuit of an arm cylinder is also throttled in the hydraulic circuit of FIG.

FIG. 3 is a hydraulic circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a graph showing a characteristic of narrowing a meter-in circuit according to an engine speed.

FIG. 5 is a circuit diagram in which a meter-out circuit is also narrowed down in the second embodiment.

6A and 6B are graphs showing the secondary pressure characteristic of the proportional control valve 27.

[Explanation of symbols] 1 engine 2 first hydraulic pump 3 second hydraulic pump 4 Pilot pump 5 Control valve for boom cylinder Control valve for 6-arm cylinder 7 supply and discharge routes 8 boom cylinders 9 boom 10 supply and discharge routes 11 arm cylinder 12 arms 13a Boom control lever 13 Remote control valve for boom operation 15 Boom confluence valve 17 sub spool 18 Arm operation remote control valve 21 Regeneration switching valve 24 Pressure sensor 25 controller 26 Proportional control valve 27 Proportional control valve

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2D003 AA01 AB03 AC07 BA01 BA02                       BB02 CA02 DA03 DA04 DB02                       DB03 DC01 FA02                 3H089 AA22 AA23 AA60 AA72 BB11                       BB20 BB27 CC01 CC12 DA03                       DA07 DB13 DB44 DB47 DB48                       DB49 DB55 DB75 EE02 EE22                       EE36 FF05 GG02 HH05 JJ02

Claims (7)

[Claims] 1. A boom raising operation is performed in a hydraulic control circuit of a construction machine that supplies pressure oil from a common hydraulic pump to an arm cylinder and a boom cylinder that operate an arm and a boom that constitute an attachment. A hydraulic control circuit for a construction machine, comprising a flow rate restricting means for restricting a flow rate of the arm cylinder in response to a signal output at times. 2. The hydraulic control circuit for a construction machine according to claim 1, wherein the flow rate control means limits a flow rate of a meter-in circuit of the arm cylinder. 3. The flow rate control means is configured to limit the flow rate when a control valve for supplying controlled pressure oil to the arm cylinder is switched to the arm pulling side. The hydraulic control circuit for a construction machine as described in 1 or 2. 4. The hydraulic control circuit for a construction machine according to claim 1, wherein the flow rate limiting means is configured to limit a flow rate of both the meter-in circuit and the meter-out circuit of the arm cylinder. . 5. A hydraulic control circuit for a construction machine according to claim 4, further comprising control means for controlling a rate of a flow rate limited by said flow rate limiting means in accordance with a magnitude of a signal corresponding to a boom raising operation amount. . 6. The sub-spool is built in the arm spool of the control valve of the arm cylinder as the flow rate limiting means, and the sub-spool is configured to reduce the passing flow rate when the boom raising operation is performed. A hydraulic control circuit for a construction machine according to claim 1. 7. A control valve for the boom cylinder is a hydraulic pilot type controlled by a remote control valve, and the pilot pressure output from the remote control valve during boom raising operation is applied to the pilot port of the sub spool. A hydraulic control circuit for a construction machine according to claim 6, configured as described above.