JP2002206510A - Hydraulic control circuit for work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change the lowering speed of a boom in accordance with contents of work or technique of an operator in a hydraulic circuit provided with a boom cylinder for vertically moving a boom, a control valve for control supplying and discharging pressure oil to the boom cylinder, and a regeneration circuit for supplying a part of discharged oil from a head side oil chamber of the boom cylinder to a rod side oil chamber. SOLUTION: On the control valve 15 for a second boom, a valve passage 15a for discharge is provided to discharge oil from the head side oil chamber 8a in the boom cylinder 8 to an oil tank 13 when the boom is lowered. The valve passage for discharge is composed to be opened and closed based on selection by a boom lowering speed selecting switch 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a hydraulic control circuit of a working machine such as a hydraulic shovel used for various construction works and civil works.

[0002]

2. Description of the Related Art In general, some working machines of this type use heavy objects such as a boom cylinder for moving a boom mounted on a hydraulic excavator up and down, by supplying oil to a weight holding side oil chamber and controlling weight. There is a type provided with a hydraulic cylinder that expands and contracts so as to move upward when oil is discharged from the holding-side oil chamber, and to move downward when oil is supplied to the non-weight holding-side oil chamber and oil is discharged from the weight holding-side oil chamber. As an example of such a hydraulic control circuit for a hydraulic cylinder, a hydraulic control circuit for a boom cylinder provided in a hydraulic shovel is shown in FIG.
In the figure, 8 is a boom cylinder, 11 and 12 are first and second hydraulic pumps, 13 is an oil tank, and 14 is a hydraulic oil supply / discharge control to the boom cylinder 8 using the first hydraulic pump 11 as a hydraulic oil supply source. One boom control valve, 15 is a second boom control valve for controlling the supply of hydraulic oil to the boom cylinder 8 using the second hydraulic pump 12 as a hydraulic oil supply source, and 16 is another control valve such as a bucket cylinder provided on a hydraulic shovel. Control valves 17 for hydraulic actuators are pilot valves that output pilot pressure to the pilot lines E and F on the ascending and descending sides based on the operation of the operating lever 18 for the boom. Further, A is a head side line connecting the first boom control valve 14 and the second boom control valve 15 to the head side oil chamber 8a of the boom cylinder 8, and B is the first boom control valve 14 and the boom cylinder 8 A rod-side line connecting the rod-side oil chamber 8b to the rod-side oil chamber 8b, and a regeneration line D connecting the head-side line A and the rod-side line B, and a regeneration valve 19 is connected to the regeneration line D. And a check valve 21. In this case, when the operation lever 18 for the boom is operated on the descending side, the control valve 14 for the first boom and the valve 19 for regeneration are switched by the pilot pressure output from the pilot valve 17 to the descending pilot line F. Thereby, the pressure oil from the first hydraulic pump 11 is supplied to the rod-side oil chamber 8 of the boom cylinder 8 through the first boom control valve 14.
b, while the oil discharged from the head side oil chamber 8a is supplied to the oil tank 13 via the first boom control valve 14.
And the regeneration valve 19 and the check valve 2
1, the oil is supplied to the rod-side oil chamber 8b. That is, when the pressure of the head-side line A is higher than the pressure of the rod-side line B when the boom is lowered, the oil discharged from the head-side oil chamber 8a can be supplied as regenerated oil to the rod-side oil chamber 8b. As a result, regeneration oil is supplied to the rod-side oil chamber 8b in addition to the pressure oil of the first hydraulic pump 11 supplied from the first boom control valve 14, and Side oil chamber 8b
The operating speed of the boom cylinder 8 can be increased without reducing the pressure. In addition, during a combined operation of another hydraulic actuator (for example, a bucket cylinder) using the first hydraulic pump 11 as a pressure oil supply source and boom lowering, the surplus pump flow obtained by the regenerated oil can be supplied to the other hydraulic actuator. Therefore, it is possible to suppress a decrease in the working speed of the other hydraulic actuator during the combined operation,
Thus, it is possible to contribute to improvement of work efficiency.

[0003]

By the way, in order to improve work efficiency as much as possible in the above-mentioned conventional one,
Although the amount of reclaimed oil from the cylinder-head-side oil chamber to the rod-side oil chamber is increased to increase the cylinder speed, this setting can be used when performing operations that require fine operation, If the operator is a beginner, there is a problem that the speed is too fast to operate. On the other hand, if the setting is made such that the amount of the regenerated oil is reduced so that the fine operation or the beginner can easily operate, there is a problem that the effect of providing the regenerating circuit is reduced and the working efficiency is reduced. There was a problem to be solved by the present invention.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present invention has been made for the purpose of solving these problems. Oil pressure that moves up and down when oil is supplied to the chamber and oil is discharged from the non-weight holding oil chamber, and is lowered when oil is supplied to the non-weight holding oil chamber and oil is discharged from the weight holding oil chamber. A cylinder, a control valve for controlling supply and discharge of pressurized oil to and from the weight holding side oil chamber and the weight non-holding side oil chamber of the hydraulic cylinder, and supplying oil discharged from the weight holding side oil chamber to the weight non-holding side oil chamber. A hydraulic control circuit for a working machine comprising a regeneration circuit, wherein the hydraulic control circuit includes a discharge oil passage for flowing discharge oil from a weight holding side oil chamber to an oil tank without passing through the control valve. And a valve means arranged in the oil passage for discharge. The closing control is obtained by a structure capable of decreasing the oil discharge flow to the oil tank from the weight holding side oil chamber. In this way, by increasing or decreasing the oil discharge flow rate from the weight holding side oil chamber to the oil tank, it is possible to change the descending speed of the heavy object in accordance with the work content, the skill of the operator, and the like. As a result, workability and operability are improved. The present invention also provides a vertically movable heavy object,
The oil supply to the weight holding side oil chamber and the oil discharge from the weight non-holding side oil chamber are raised, and the oil supply to the weight non-holding side oil chamber and the oil discharge from the weight holding side oil chamber are lowered. A hydraulic cylinder that expands and contracts, a first control valve that performs pressure oil supply and discharge control to the weight holding side oil chamber and the weight non-holding side oil chamber of the hydraulic cylinder using the first hydraulic pump as a pressure oil supply source,
A second control valve that controls the supply of pressure oil to the weight holding side oil chamber of the hydraulic cylinder using the second hydraulic pump as a source of pressure oil, and supplies oil discharged from the weight holding side oil chamber to the non-weight holding side oil chamber. A hydraulic control circuit for a working machine comprising a regeneration circuit for performing the above-described operation, wherein the second control valve is provided with a discharge valve path for flowing discharge oil from the weight holding side oil chamber to an oil tank, The configuration is such that the flow rate of oil discharge from the oil chamber on the weight holding side to the oil tank can be increased or decreased by controlling the opening and closing of the valve path. In this manner, the second control valve is used to increase or decrease the oil discharge flow rate from the weight holding side oil chamber to the oil tank, so that the weight of heavy objects can be adjusted according to the work content, the skill of the operator, and the like. Since the descending speed can be changed, workability and operability are improved, and the members can be shared.

[0005]

Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 denotes a hydraulic excavator. The hydraulic excavator 1 includes a lower traveling body 2 of a crawler type, an upper rotating body 3 rotatably supported by the lower traveling body 2, and a front portion of the upper rotating body 3. And a boom 5 supported by the upper swing body 3 so as to be vertically swingable, and a front end of the boom 5 swingable back and forth. , A bucket 7 supported at the tip of the stick 6 to be able to swing back and forth, a boom cylinder 8, a stick cylinder 9 for swinging the boom 5, the stick 6, and the bucket 7 respectively.
The basic configuration such as the configuration of the member devices such as the bucket cylinder 10 is the same as the conventional one.

FIG. 2 shows a hydraulic control circuit of the boom cylinder 8. In FIG. 2, reference numerals 11 and 12 denote first and second hydraulic pumps, reference numeral 13 denotes an oil tank, and reference numerals 14 and 15 denote later described hydraulic pumps. First and second boom control valves. Also, 1
Reference numeral 6 denotes a bucket control valve, and the bucket control valve 16 is provided in parallel with the first boom control valve 14. A number of control valves provided in parallel with the first and second boom control valves 14 and 15 correspond to various hydraulic actuators provided in the hydraulic excavator 1 in addition to the bucket control valve 16. However, they are omitted in FIG. Further, in FIG. 2, A is a head-side line connecting the first boom control valve 14 and the second boom control valve 15 to the head-side oil chamber 8a of the boom cylinder 8, and B is the first boom control valve 14. And a rod-side line D connecting the rod-side oil chamber 8b of the boom cylinder 8, and a regeneration line D connecting the head-side line A and the rod-side line B.

The boom cylinder 8 includes a head-side oil chamber 8.
and the boom 5 is extended by the supply of pressurized oil to the cylinder a and the oil discharge from the rod-side oil chamber 8b.
The boom 5 is configured to move down by moving the boom 5 down by supplying the pressurized oil to the head and discharging the oil from the head-side oil chamber 8a. In this case, the head-side oil chamber 8a holds the weight of the front attachment 4. Thus, the rod side oil chamber 8b corresponds to the weight non-holding side oil chamber of the present invention.

The first boom control valve 14
Are pilot ports 14a, 14b on the ascending and descending sides.
And a supply / discharge valve path 1 to be described later by the pilot pressure input to the pilot ports 14a and 14b.
It is constituted by a spool valve whose opening amount is adjusted from 4c to 14f. In other words, the first boom control valve 14 is located at the neutral position N and does not supply or discharge the pressurized oil to the boom cylinder 8 when the pilot pressure is not input to both the pilot ports 14a and 14b. When the pilot pressure is input to the pilot port 14a, the first hydraulic pump 11 is displaced to the ascending side position X.
Valve line 1 for supplying pressurized oil from the head to the head-side oil chamber 8a of the boom cylinder 8 via the head-side line A
4c is opened, and a discharge valve path 14d for flowing the oil discharged from the rod-side oil chamber 8b to the oil tank 13 via the rod-side line B is opened. Further, the first boom control valve 14 is displaced to the descending position Y by inputting a pilot pressure to the descending pilot port 14b, and pressurized oil from the first hydraulic pump 11 passes through the rod side line B. To open the supply valve passage 14e for supplying the oil to the rod-side oil chamber 8b, and to discharge the oil discharged from the head-side oil chamber 8a to the head-side line A to the oil tank 13 via the throttle 14g. It is configured to open the valve path 14f. Here, the oil discharge from the head side oil chamber 8a of the first boom control valve 14 to the oil tank 13 at the descending side position Y is performed in a state where the flow rate is adjusted by a throttle 14g provided in a discharge valve path 14f. However, the oil discharge flow rate of the discharge valve path 14f is set to a flow rate necessary to obtain a slow boom lowering speed suitable for performing a fine operation.

On the other hand, the second boom control valve 15
Are the pilot ports 15a, 15b on the ascending side and the descending side.
And a supply / discharge valve path 1 described later by the pilot pressure input to the pilot ports 15a and 15b.
It is composed of a spool valve whose opening amount is adjusted to 5c and 15d. That is, the second boom control valve 15 is located at the neutral position N and does not supply or discharge the pressurized oil to the boom cylinder 8 in a state where the pilot pressure is not input to both the pilot ports 15a and 15b. When the pilot pressure is input to the pilot port 15a, it is displaced to the ascending side position X to open the supply valve path 15c, so that the pressure oil from the second hydraulic pump 12 passes through the head side line A. The oil is supplied to the head-side oil chamber 8a of the boom cylinder 8 via the air passage.
Further, the second boom control valve 15 is displaced to the descending position Y by opening a pilot pressure to the descending pilot port 15b to open the discharge valve passage 15d, thereby providing the head side oil. The oil discharged from the chamber 8a is configured to flow through the head side line A to the oil tank 13 via the throttle 15e provided in the discharge valve path 15d.

Further, in FIG. 2, reference numeral 17 denotes a pilot valve for a boom, which is an ascending pilot valve 17A and a descending pilot valve 17B.
The pilot valves 17A and 17B on the ascending and descending sides are connected to the operating lever 1 for the boom.
The pilot pressure corresponding to the operation amount is output based on operating the boom 8 on the boom raising side and the boom lowering side. Then, the pilot pressure output from the ascending pilot valve 17A is inputted to the ascending pilot ports 14a, 15a of the first and second boom control valves 14, 15 via the ascending pilot line E. Further, the pilot pressure output from the descending pilot valve 17B is input to the descending pilot port 14b of the first boom control valve 14 and the pilot port 19a of the regeneration valve 19 described later via the descending pilot line F. At the same time, it is supplied to a speed switching valve 20 described later.

The regeneration valve 19 has a regeneration line D
, But this is the pilot port 19a
And a spool valve provided with a spool valve. When the pilot pressure is not input to the pilot port 19a, the regeneration valve 19 is located at the closed position X that closes the regeneration line D.
When the pilot pressure is input to a, the reproduction line D is switched to the open position Y that opens through the throttle 19b. Reference numeral 21 denotes a check valve disposed on the regeneration line D. The check valve 21 is connected to the head-side line A to the rod-side line while the pressure of the head-side line A is higher than that of the rod-side line B. The flow of oil to B is allowed, but the flow in the reverse direction is prevented. Thus, when the regeneration valve 19 is in the open position Y
When the pressure of the head side line A is higher than that of the rod side line B, the oil of the head side line A flows to the lot side line B via the regeneration line D.

The speed switching valve 20 is an electromagnetic two-position switching valve having a solenoid 20a.
When the solenoid 20a is not energized, the lower pilot port 15b of the second boom control valve 15
Is located at the first position X where the fluid flows into the oil tank 13, and the pressure of the descending pilot line F is not input to the descending pilot port 15b of the second boom control valve 15, but the solenoid 20a is energized. , The pressure in the descending pilot line F to the second boom control valve 1
5 is switched to the second position Y input to the descending pilot port 15b.

On the other hand, reference numeral 22 denotes a boom lowering speed selection switch provided on the driver's seat. The boom lowering speed selection switch 22 is electrically connected to a solenoid 20a of the speed switching valve 20. Then, the boom lowering speed selection switch 22 switches between “LOW” and “HIG”.
H "can be arbitrarily selected, but the solenoid 20a of the speed switching valve 20 is not energized when the boom lowering speed selection switch 22 is set to" LOW ", and is set to" HIGH ". ”Is set to be energized.

When the boom 5 is raised in the above-described configuration, when the boom operation lever 18 is operated to the up side, the pilot pressure output from the up side pilot valve 17A causes the pilot pressure output from the first and second booms to rise. Pilot ports 14a, 15a of the control valves 14, 15
To the first and second boom control valves 14, 1
5 is switched to the ascending side position X. Thereby, the pressure oil of both the first and second hydraulic pumps 11 and 12 is supplied to the head-side oil chamber 8a of the boom cylinder 8 via the first and second boom control valves 14 and 15. As a result, the lifting operation of the boom 5 against the weight of the front attachment 4 can be performed strongly.

On the other hand, when lowering the boom 5, when performing a fine operation or when the operator is a beginner, the boom lowering speed selection switch 22 is set to "LOW". When the boom lowering speed selection switch 22 is set to "LOW", the solenoid 20a of the speed switching valve 20 is not energized as described above. Is not input to the descending pilot port 15b of the second boom control valve 15 at the first position X. When the operation lever 18 for the boom is operated downward in this state, the pilot pressure output from the lower pilot valve 17B is applied to the lower pilot port 14b of the first boom control valve 14 and the pilot port 19a of the regeneration valve 19. And switches the first boom control valve 14 to the lower position Y, and the regeneration valve 1
9 is switched to the open position Y. On the other hand, the second boom control valve 15 is held at the neutral position N. Thereby, the pressure oil from the first hydraulic pump 11 is supplied to the rod-side oil chamber 8b of the boom cylinder 8 via the first boom control valve 14, and the pressure of the head-side line A is reduced to the rod-side line. While the pressure is higher than B, a part of the oil discharged from the head side oil chamber 8a is regenerated by the regeneration valve 19 and the check valve 21.
Is supplied to the rod-side oil chamber 8b as regenerated oil.
The remaining oil discharged from the head-side oil chamber 8a is discharged to the oil tank 13 via the first boom control valve 14. In other words, in the state where it is set to "LOW", oil discharge from the head side oil chamber 8a of the boom cylinder 8 to the oil tank 13 is performed only through the discharge valve passage 14f of the first boom control valve 14. As a result, the oil discharge flow rate of the discharge valve path 14f is set to a flow rate at which a slow boom descent speed is obtained. Operability is improved when the operator is a beginner.

On the other hand, when lowering the boom 5, it is necessary to improve the working efficiency or to perform a work requiring a fast boom descent such as an excavation loading operation. 22 as "HIG
H ”. Thereby, the speed switching valve 20
Is turned on, the speed switching valve 20 changes the pressure of the descending pilot line F to the descending pilot port 15b of the second boom control valve 15.
Is switched to the second position Y to be input to. In this state, when the operation lever 18 for the boom is operated to the descending side, the pilot pressure output from the descending pilot valve 17B causes the descending pilot ports 14b, 15b of the first and second boom control valves 14, 15 and The signal is input to the pilot port 19a of the regeneration valve 19, and the first and second boom control valves 14, 15 are switched to the lower position Y, and the regeneration valve 19 is switched to the open position Y. Thereby, the pressure oil from the first hydraulic pump 11 is supplied to the rod-side oil chamber 8b of the boom cylinder 8 via the first boom control valve 14, and the pressure of the head-side line A is reduced to the rod-side line. While the pressure is higher than B, a part of the oil discharged from the head-side oil chamber 8a is supplied to the rod-side oil chamber 8b via the regeneration valve 19 and the check valve 21 as regenerated oil. The remaining oil discharged from the head-side oil chamber 8a is discharged to the oil tank 13 via the first boom control valve 14 and the second boom control valve 15. That is, in the state where the control valve 1 is set to “HIGH”, the oil discharge from the head side oil chamber 8 a of the boom cylinder 8 to the oil tank 13 is performed by the first and second boom control valves 1.
This is performed via the discharge valve passages 14f, 15d of the first and second booms.
The amount of oil discharge increases by the amount of the second boom control valve 15 as compared with the case of only the case, so that the oil discharge from the head side oil chamber 8a is performed quickly, and the lowering operation of the boom 5 is performed. Can be performed at high speed.

As described above, in the present embodiment, when the boom 5 is lowered, the boom lowering speed selection switch 2
2 is set to "HIGH", the oil discharge flow from the head side oil chamber 8a of the boom cylinder 8 to the oil tank 13 is increased, the descent speed of the boom 5 is increased, and the boom descent speed selection switch 22 is set to " If it is set to “LOW”, the oil discharge flow rate from the head side oil chamber 8a to the oil tank 13 decreases, and the lowering speed of the boom 5 decreases. As a result, the lowering speed of the boom 5 can be arbitrarily selected according to the work content and the skill of the operator, and the operability and workability are improved. Moreover, in this case, the head-side oil chamber 8
The flow rate of the oil discharged from a to the oil tank 13 is increased or decreased by using the second boom control valve 15, which is controlled by the second hydraulic pump 12 when the boom 5 is raised. Is operated to supply the pressurized oil to the boom cylinder head side oil chamber 8a, so that one valve has two functions, so that the members can be shared and the cost can be reduced. Further, since the second boom control valve 15 is a spool valve whose opening is adjusted by an input pilot pressure, good operability corresponding to the amount of operation of the boom operation lever 18 can be obtained.

The present invention is, of course, not limited to the above-described embodiment, and the hydraulic cylinder for moving a heavy object up and down is not limited to a boom cylinder provided on a hydraulic shovel, but may be various working machines. The present invention can be appropriately carried out as needed for the hydraulic cylinder provided in the first embodiment.

[Brief description of the drawings]

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

FIG. 2 is a hydraulic control circuit diagram showing an embodiment of the present invention.

FIG. 3 is a hydraulic control circuit diagram showing a conventional example.

[Explanation of symbols]

 Reference Signs List 5 boom 8 boom cylinder 8a head side oil chamber 8b rod side oil chamber 11 first hydraulic pump 12 second hydraulic pump 13 oil tank 14 first boom control valve 15 second boom control valve 19 regeneration valve 20 speed switching Valve 22 Boom lowering speed selection switch D Reproduction line

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2D003 AA01 AB03 AC09 BA01 BA05 BB02 CA04 DA03 3H089 AA32 AA33 BB04 CC01 DA06 DB46 DB49 DB63 GG02 JJ02

Claims (2)

[Claims] An oil supply to the weight holding side oil chamber and an oil discharge from the weight non-holding side oil chamber move up and down the vertically movable heavy object to supply the oil to the weight non-holding side oil chamber and weight. A hydraulic cylinder that expands and contracts so as to move downward by oil discharge from the holding oil chamber, a control valve that controls supply and discharge of pressurized oil to the weight holding oil chamber and the weight non-holding oil chamber of the hydraulic cylinder,
And a regeneration circuit for supplying the oil discharged from the weight holding side oil chamber to the weight non-holding side oil chamber. A discharge oil passage for flowing the discharged oil to the oil tank without passing through the control valve is provided, and by controlling the opening and closing of a valve means arranged in the discharge oil passage, the oil discharge flow rate from the weight holding side oil chamber to the oil tank is controlled. A hydraulic control circuit for a work machine, wherein the hydraulic pressure control circuit is configured to be capable of increasing or decreasing. 2. A vertically movable movable heavy object is moved upward by oil supply to the weight holding side oil chamber and oil discharge from the weight non-holding side oil chamber, and oil supply and weight to the weight non-holding side oil chamber. Hydraulic cylinder that expands and contracts so as to move down when oil is discharged from the holding oil chamber, and pressurized oil supply to the weight holding side oil chamber and weight non-holding side oil chamber of the hydraulic cylinder using the first hydraulic pump as a pressure oil supply source A first control valve for controlling discharge, a second control valve for controlling supply of pressure oil to the weight holding side oil chamber of the hydraulic cylinder using the second hydraulic pump as a pressure oil supply source, and discharge from the weight holding side oil chamber. In a hydraulic control circuit of a working machine comprising a regeneration circuit for supplying oil to the non-weight holding oil chamber, the drainage oil from the weight holding oil chamber is supplied to the oil tank through the second control valve. A discharge valve path is provided, and the opening and closing of the discharge valve path is controlled. A hydraulic control circuit for a working machine, characterized in that the flow rate of oil discharge from a weight holding side oil chamber to an oil tank can be increased or decreased.