JPH11107328A - Hydraulic control device for hydraulic shovel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic control device for a hydraulic shovel in which horizontal drawing works can be surely performed without requiring high grade operation techniques. SOLUTION: In a hydraulic shovel, hydraulic oil is supplied from a first hydraulic pump 8 through a boom spool valve 17 which actuates in accordance with operation of a boom operation lever 10 to a boom cylinder 5, and hydraulic oil is supplied from a second hydraulic pump 9 through an arm spool valve 23 which actuates in accordance with operation of an arm operation lever 12 to an arm cylinder 6. In this case, it is provided with a recovering passage 26 to recover a part of hydraulic oil to an operating fluid tank 19 at each changing position of the boom spool valve 23, a flow control valve 18 provided in the recovering passage 26, pressure sensors 33, 34 to detect if the boom operation lever 10 and the arm operation lever 12 are operated or not, and a controller 35 to control the flow control valve 18 in an opened condition when simultaneous operation of the boom operation lever 10 and the arm operation lever 12 is detected by the pressure sensors 33, 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a hydraulic shovel suitable for a hydraulic shovel that performs a combined operation of an arm cylinder and a boom cylinder.

[0002]

2. Description of the Related Art Conventionally, when operating a boom or an arm in a hydraulic excavator, a boom spool valve (boom directional switching valve) provided in an oil passage between a hydraulic pump and a boom cylinder or a hydraulic pump and an arm cylinder. )
Or an arm spool valve (arm directional switching valve)
Each is driven according to the operation of a boom operation lever or an arm operation lever. In particular,
By moving the spool of each spool valve in accordance with the operation amount of the operation lever, the flow and direction of the hydraulic oil supplied from the hydraulic pump to each cylinder are controlled, thereby controlling the operation amount of each operation lever. The boom cylinder and the arm cylinder are operated at the corresponding operation speed.

[0003] In a hydraulic shovel, pressure oil is usually supplied to a boom cylinder and an arm cylinder from separate hydraulic pumps, that is, a first hydraulic pump and a second hydraulic pump. As these hydraulic pumps, variable displacement hydraulic pumps are used, and the discharge flow rate of each hydraulic pump is basically controlled in accordance with the operation amount of each operation lever.

In some cases, a horizontal pulling operation is performed using a hydraulic excavator that performs such hydraulic control. Horizontal pulling is the work of leveling by pulling the bucket provided at the tip of the arm in the horizontal direction.Specifically, while raising the boom control lever slightly, move the arm control lever toward the retracted side at a low speed. Adjust the operating speed of the boom cylinder when raising the boom and the operating speed of the arm cylinder when retracting the arm so that the bottom of the bucket always keeps contact with the ground. There is a need.

[0005]

However, in the case of performing a horizontal pulling operation with a conventional hydraulic excavator, for example, if the operation amount of the operation lever for the boom is slightly increased as compared with the operation amount of the operation lever for the arm, the operation of the boom for the boom will be difficult. The operating speed of the cylinder becomes too high than the operating speed of the arm cylinder, causing a problem that the bucket floats above the ground.

On the other hand, if the operating speed of the boom cylinder is excessively suppressed, the bucket gets into the ground and receives an excessive reaction force from the ground. At this time, if the boom cylinder operates in the extending direction, cavitation may occur in the oil chamber on the head side, and the hydraulic equipment may be damaged. Therefore, horizontal pulling operations requiring advanced operation techniques have been limited exclusively to skilled operators.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems of the conventional hydraulic shovel, and hydraulic control of the hydraulic shovel capable of reliably performing a horizontal pulling operation without requiring advanced operation techniques. An apparatus is provided.

[0008]

SUMMARY OF THE INVENTION According to the present invention, pressure oil is supplied from a first hydraulic pump to a boom cylinder via a boom spool valve which operates in response to operation of a boom operation lever, and an arm operation is performed. In a hydraulic excavator that supplies hydraulic oil from a second hydraulic pump to an arm cylinder via an arm spool valve that operates in response to lever operation, a part of the hydraulic oil is operated at each switching position of the boom spool valve A recovery flow path that can be recovered in the oil tank, a flow control valve provided in the recovery flow path, detection means for detecting the presence or absence of operation of a boom operation lever and an arm operation lever, and a boom operation lever by the detection means And a control means for controlling the flow control valve to open when simultaneous operation of the arm operating lever is detected.

In the present invention, the control means preferably reduces the opening area of the flow control valve when the pressure in the head side oil chamber of the boom cylinder decreases.

In the present invention, it is preferable that the control means be configured to switch the flow control valve to the shut-off side when the independent operation of the boom operation lever is detected by the detection means.

According to the present invention, the operating lever for the boom and the operating lever for the arm are operated, and when the pilot pressures generated in proportion to the operation amounts of the respective operating levers become respectively equal to or higher than predetermined pressures, the detecting means detects the pilot pressures. When the simultaneous operation of the boom operation lever and the arm operation lever is detected, the control means determines that the operation is the horizontal pulling operation, and controls the flow control valve to the open state. The flow rate sent from the first hydraulic pump and flowing through the boom spool valve to the head side oil chamber of the boom cylinder is reduced for the amount that flows from the bleed-off of the boom spool valve to the hydraulic oil tank. Response of the boom cylinder that operates in response to operation of the operating lever is slow. Therefore, the operation lever for the boom can be operated in a wider operation range than before.

When the resistance of the bucket increases due to insufficient lifting of the boom cylinder, the control means reduces the opening area of the flow control valve to reduce bleed-off. Can be raised.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings. FIG. 1 shows an embodiment of a hydraulic shovel to which a hydraulic control device of the present invention is applied.

Referring to FIG. 1, a boom 2 is attached to a front portion of a vehicle body 1 of a hydraulic shovel so that the hydraulic shovel can swing freely in a vertical direction (direction of arrow A or direction B). An arm 3 is attached to a tip end of the boom 2 so that the arm 3 can swing freely in the front-rear direction (the direction of the arrow C or the direction of the arrow D). Further, a bucket 4 is attached to the tip of the arm 3, and can be moved in the front-rear direction (arrow E).
(Or F direction).

The swinging operation of the boom 2 is performed by the expansion and contraction of a boom cylinder 5 provided between the boom 2 and the front part of the vehicle body 1. The swing operation of the arm 3 is performed by expansion and contraction of an arm cylinder 6 provided between the rear end and the boom 2. The bucket 4 is formed by expansion and contraction of a bucket cylinder 7 provided between the bucket 4 and the arm 3.

When leveling the ground G, that is, performing a so-called horizontal pulling operation with the front attachment having such a configuration, the direction in which the bucket 4 approaches the vehicle body 1 while keeping the bucket 4 in contact with the ground G. To move horizontally. At this time, an operation of simultaneously extending the arm cylinder 6 while raising the boom 2 by extending the boom cylinder 5 is performed (from the arm position indicated by the imaginary line in FIG. 1 to the arm position indicated by the solid line). Move). The pressure oil supplied to each of the cylinders 5 and 6 is controlled by a hydraulic control device mounted on the vehicle body 1.

As shown in FIG. 2, the hydraulic control device has two variable displacement hydraulic pumps 8 and 9, and the first hydraulic pump 8 supplies pressure oil to the boom cylinder 5. The second hydraulic pump 9 supplies pressure oil to the arm cylinder 6.

A pipe line 14 extending from the discharge port of the first hydraulic pump 8 is connected to a head side oil chamber 5a of the boom cylinder 5 through a boom spool valve 17.
And a pipe 16 communicating with the rod-side oil chamber 5b of the boom cylinder 5 so that when the boom spool valve 17 is at the position B, the hydraulic fluid is sucked from the hydraulic oil tank 19. Supplying the pressurized oil to the head-side oil chamber 5a,
When the boom spool valve 17 is at the C position,
The pressure oil sucked from the hydraulic oil tank 19 is supplied to the rod-side oil chamber 5b.
To be supplied.

Similarly, a pipe 20 led out from the discharge port of the second hydraulic pump 9 is connected to a pipe 21 communicating with the head side oil chamber 6a of the arm cylinder 6 via an arm spool valve 23, and an arm 21. When the arm spool valve 23 is at the position E, the pressure oil sucked from the hydraulic oil tank 19 is selectively connected to the pipe line 22 communicating with the rod-side oil chamber 6 b of the cylinder 6. When the arm spool valve 23 is at the F position, the pressure oil sucked from the hydraulic oil tank 19 is supplied to the rod-side oil chamber 6b.

The first hydraulic pump 8 and the second hydraulic pump 9 adjust their tilt angles by the regulator devices 24, 2
The discharge flow rate can be controlled by adjusting the flow rate through the nozzle 5. In addition, each regulator device 2
Numerals 4 and 25 adjust the tilt angles of the hydraulic pumps 8 and 9 by hydraulic pressure according to a discharge flow rate instruction signal given from a controller 34 described later.

The boom spool valve 17 is provided with two pilot ports 17a and 17b. When no pilot pressure is applied to the pilot ports 17a and 17b, the spool is held at the position A (neutral position). ing. Also, set the pilot pressure to pilot port 1
When applied to either 7a or 17b, the spool moves to the B position side or the C position side.

At the position A as the neutral position, the flow path between the hydraulic pump 8 and the boom cylinder 5 is shut off to keep the boom cylinder 5 in a stopped state. At the position B, pressure oil is supplied to the head-side oil chamber 5a by connecting the hydraulic pump 8 to the head-side oil chamber 5a of the boom cylinder 5,
The boom cylinder 5 is extended and the boom 2 is raised. At the C position, the hydraulic pump 8 is connected to the boom cylinder 5.
The pressure oil is supplied to the rod side oil chamber 5b by communicating with the rod side oil chamber 5b, and the boom cylinder 5 is shortened and the boom 2 is lowered. In the A position (neutral position), the boom spool valve 17 is connected to a pipe 26 serving as a recovery flow path communicating with the hydraulic oil tank 19 in order to recover the discharge pressure oil of the hydraulic pump 8 to the hydraulic oil tank 19. The road 14 is communicated.

FIG. 3 shows the opening area characteristics of the boom spool valve 17. In the figure, meter-in L ₁ , meter-out L ₂ , and bleed-off L ₃ , for example, when the boom spool valve 17 is at the position B, the boom spool valve 17 communicates with the conduits 15, 16, 26 respectively. 3 shows a variable opening of an oil passage. In addition, when it is at the position C, it indicates a variable opening of the oil passage communicating with the conduits 16, 15, 26. The bleed-off opening area of the boom spool valve 17 is opened to some extent even at the full lever position. A flow control valve 18 is provided between the bleed offline 26 of the boom spool valve 17 and the hydraulic oil tank 19. FIG. 4 shows a basic characteristic L of the flow control valve 18.
₄ is shown.

On the other hand, the arm spool valve 23 is provided with two pilot ports 23a and 23b. When no pilot pressure is applied to these pilot ports 23a and 23b, the spool is in the D position (neutral position).
Is held in. When the pilot pressure is applied to one of the pilot ports 23a and 23b,
The spool moves to the E position side or the F position side. On the E position side or the F position side, the pilot port 23
By the displacement of the spool corresponding to the pilot pressure applied to the a and 23b, hydraulic oil having a flow rate corresponding to the pilot pressure is supplied from the hydraulic pump 9 to the head-side oil chamber 6a or the rod-side oil chamber 6b of the arm cylinder 6. I can do it. At the position D (neutral position), the arm spool valve 23 connects the pipe 20 to a pipe 27 communicating with the hydraulic oil tank 19 in order to recover the discharge pressure oil of the hydraulic pump 9 to the hydraulic oil tank 19. .

FIG. 5 shows the opening area characteristic of the arm spool valve 23. In the figure, meter-in L ₅ , meter-out L ₆ , and bleed-off L ₇ are such that, for example, when the arm spool valve 23 is at the E position, the boom spool valve 23 communicates with the pipelines 21, 22, 27, respectively. 3 shows a variable opening of an oil passage. Incidentally, the bleed-off L ₇ is cut off as switches to E position from the D position. Also,
When in the F position, it indicates a variable opening of the oil passage communicating with the pipelines 22, 21, 27.

The remote control valve device 11 having the boom operation lever 10 generates a pilot pressure for driving the boom spool valve 17 in accordance with the operation direction and the operation amount of the boom operation lever 10. , Are connected to pilot ports 17a, 17b of the boom spool valve 17 via pilot lines 28, 29, respectively. In this case, the boom operation lever 10 is operated, for example, in the direction of arrow a when raising the boom 2, and is operated in the direction of arrow b when lowering the boom 2. When the boom operation lever 10 is operated on the rising side of the boom 2, the remote control valve device 11 generates a pilot pressure proportional to the operation amount in the pilot line 28, while the boom 2 is moved downward on the boom 2. When the operation lever 10 is operated,
The pilot pressure proportional to the manipulated variable is applied to pilot line 2
9 is generated.

The remote control valve device 13 having the arm operation lever 12 generates a pilot pressure for driving the arm spool valve 23 in accordance with the operation direction and the operation amount of the arm operation lever 12. And the arm spool valve 23 through the pilot lines 30 and 31.
Are connected to the pilot ports 23a and 23b, respectively. In this case, when operating the arm 3 to the retracted side (the side approaching the vehicle body 1), the arm operation lever 12 is operated, for example, in the direction of arrow c to push the arm 3 to the pushed side (from the vehicle body 1 in FIG. 1). In the case of operating in the direction (separation side), the operation is performed in the direction of arrow d. When the arm operation lever 12 is operated on the retracted side of the arm 3, the remote control valve device 13 generates a pilot pressure in proportion to the operation amount in the pilot line 30, and on the other hand, the arm When the operation lever 12 is operated, a pilot pressure proportional to the operation amount is generated in the pilot line 31.

In this embodiment, the pilot pressure Pb generated by the remote control valve device 11 when the boom operation lever 10 is operated to the boom raising side is detected by the boom side pressure sensor 33 as a detecting means. I have.
Further, the pilot pressure Pa generated by the remote control valve device 13 when the arm operation lever 12 is operated to the arm retracting side is detected by the arm side pressure sensor 3 as a detecting means.
4. The pressure Ph of the head side oil chamber 5a of the boom cylinder 5 is detected by the pressure sensor 32.

The outputs of these pressure sensors 32, 33, 34 are given to a controller 35 as control means. The controller 35 includes a boom-side pump controller 35a.
, Arm-side pump controller 35b and flow control valve controller 35
c.

The boom-side pump control unit 35a controls the discharge flow rate of the first hydraulic pump 8 via the regulator device 24.
According discharge flow rate characteristics L ₈ shown in, to control the first hydraulic pump 8 so that the discharge flow rate corresponding to the operation amount of the boom operation lever 10. When the boom 2 is lowered, the boom-side pump control unit 35a
According discharge flow rate characteristic L ₈ shown in, to control the first hydraulic pump 8 so that the discharge flow rate corresponding to the operation amount of the boom operation lever 10.

The arm-side pump control unit 35b controls the discharge flow rate of the second hydraulic pump 9 via the regulator device 25, and basically performs the same control as the boom-side pump control unit 35a. It has become. In other words, when the arm operation lever 12 is operated, the second hydraulic pressure is adjusted so that the discharge flow rate is in accordance with the operation amount of the arm operation lever 12 according to the same discharge flow rate characteristic L ₉ (see FIG. 7) as in FIG. The pump 9 is controlled.

Next, the controller 35 having the above configuration will be described.
Will be described with reference to the flowchart shown in FIG.

First, a case where only the boom operation lever 10 is operated to the boom 2 ascending side will be described.

When the boom operation lever 10 is operated in the direction of arrow a in FIG. 2 to raise the boom 2, a pilot pressure Pb proportional to the operation amount is generated from the remote control valve device 11 in the pilot line 28, and the pilot pressure Pb is generated. Pressure Pb
Is provided to the pilot port 17a of the boom spool valve 17. At this time, the spool of the boom spool valve 17 is switched to the position B by being displaced in accordance with the pilot pressure Pb, and the pipeline 14 extending from the first hydraulic pump 8 is connected to the boom spool valve. 17 is connected to the head side oil chamber 5a of the boom cylinder 5 through the pipe line 15.
Communicate with

At this time, the controller 35 monitoring the operation amount of the boom operation lever 10 and the operation of the arm operation lever 12 generates the pilot pressure Pb generated from the remote control valve device 11 and the pilot pressure Pb generated from the remote control valve device 13. The pilot pressure Pa to be read is read (step S1), and it is determined whether or not the operation is a horizontal pulling operation (step S2). In this case, since only the pilot pressure Pb is detected, it is determined that the operation is “boom independent operation”, and FIG. Is output to the flow control valve 18 according to the mapping shown in FIG.
3).

[0036] Therefore, meter L ₁ of the boom spool valve 17 as shown in FIG. 3, the bleed-off L ₄ acting as bleed-off L ₃ acting simultaneously meter-out L _2, are configured in the flow control valve 18 independently The boom cylinder 5 is operated in accordance with the bleed-off equivalent opening L ₃ ′ (see FIG. 9) in combination with the boom-off opening (see FIG. 9) (step S4).

[0037] That is, the boom spool valve 17, since the opening area of the bleed-off L ₃ be set to the maximum operation amount of the boom operation lever 10 is configured so as not to zero, the boom spool valve 17 By shutting off the flow control valve 18 communicating with the center bypass, the bleed-off opening area is substantially reduced to zero. Thereby, a sufficient operating pressure can be obtained at the time of the independent operation of the boom.

The boom-side pump controller 35a of the controller 35 controls the pilot pressure P detected by the pressure sensor 33.
b, the operation amount of the boom operation lever 10 is grasped,
According to the discharge flow rate characteristic L ₈ shown in FIG. 6, the discharge flow rate of the first hydraulic pump 8 is controlled to a discharge flow rate corresponding to the operation amount of the boom operation lever 10. As a result, pressure oil having a flow rate corresponding to the operation amount of the boom operation lever 10 is supplied from the first hydraulic pump 8 to the head-side oil chamber 5a of the boom cylinder 5 at an operation speed corresponding to the operation amount. The boom cylinder 5 is extended, and the raising operation of the boom 2 is started.

Next, a control operation for performing the horizontal pulling operation will be described. When performing the horizontal pulling operation, the operator moves the boom operation lever 10 and the arm operation lever 12 with the bucket 4 in contact with the ground G, and moves the boom 2 upward (in the direction of arrow a in FIG. 2) and the arm 3 respectively. Simultaneous operation is performed on the retraction side (the direction of arrow c in FIG. 2).

In this case, first, it is determined that the horizontal pulling operation is being performed because the pilot pressures Pb and Pa detected by the pressure sensors 33 and 34 are both present (step S2).

The boom-side pump control unit 35a of the controller 35, the discharge flow rate of the first hydraulic pump 8 in accordance with the discharge flow rate characteristics L ₈ shown in FIG. 6, the boom operation lever 10
Is controlled to the discharge flow rate corresponding to the operation amount of. Similarly, the arm-side pump control unit 35b controls the discharge flow rate of the second hydraulic pump 9 to a discharge flow rate corresponding to the operation amount of the arm operation lever 12 according to the discharge flow rate characteristic shown in FIG.

At the same time, the pilot port 17a of the boom spool valve 17 and the pilot port 23a of the arm spool valve 23 are controlled by the remote control valve devices 11 and 13 to control the operation amounts of the operation levers 10 and 12, respectively. Proportional pilot pressures Pb and Pa are applied.
Thus, the first hydraulic pump supplies the first hydraulic pump with a flow rate corresponding to the operation amount of each of the operation levers 10 and 12 to the head-side oil chamber 5a of the boom cylinder 5 and the head-side oil chamber 6a of the arm cylinder 6. 8 and the second hydraulic pump 9 respectively. As a result, the boom spool valve 17 is switched to the position B and the arm spool valve 23 is switched to the position E.

When the pressure Ph of the head side oil chamber 5a of the boom cylinder 5 is equal to or higher than a certain pressure Ph '(step S5), it indicates that the horizontal pulling is normally performed. In this case, the flow control valve controller 35c of the controller 35 does not output a command signal to the flow control valve 18 (Step S6). That is, the flow control valve 18
Is opened (step S7), and substantially only the bleed-off of the boom spool valve 17 follows the boom operation lever 10 to control the operation speed of the boom cylinder 5. As a result, the flow rate sent from the first hydraulic pump 8 and flowing through the meter-in of the boom spool valve 17 to the head side oil chamber 5a of the boom cylinder 5 changes from the bleed-off of the boom spool valve 17 to the operation tank 19 It decreases about the part which goes out. Thus, even if the operation amount of the boom operation lever 10 slightly changes, the operation speed of the boom cylinder 5 to the rising side of the boom is unlikely to change suddenly. Therefore, it is possible to operate the boom operation lever 10 in a wide operation range without being restricted to a narrow operation range as in the related art. In other words, in performing the horizontal pulling operation, it becomes easy to match the operating speed of the boom cylinder 5 when raising the boom with the operating speed of the arm cylinder 6 when retracting the arm.

When a large resistance force acts on the bucket 4 due to insufficient lifting of the boom during the horizontal pulling operation, the pressure in the head side oil chamber 5a of the boom cylinder 5 starts to decrease. Therefore, during the horizontal pulling operation, the pressure Ph of the head side oil chamber 5a of the boom cylinder 5 becomes a constant pressure P.
If it is less than h '(step S5), the controller 35
The flow control valve controller 35c outputs a command signal to the flow control valve 18 so as to gradually reduce the opening area (step S8). As a result, the bleed-off of the entire hydraulic circuit is reduced (step S9), and the pressure oil that has flowed from the bleed-off of the boom spool valve 17 to the working tank 19 until then passes through the meter-in of the boom spool valve 17, and
Since it flows into the head side oil chamber 5a of the boom cylinder 5,
Outlet output of first hydraulic pump 8 and boom cylinder 5
, The pressure in the head side oil chamber 5a rises, and the occurrence of cavitation is suppressed.

When the pressure Ph of the head side oil chamber 5a of the boom cylinder 5 rises to a constant pressure Ph ', the flow control valve control unit 37 of the controller 35 sets the opening area of the flow control valve 18 to be smaller. It outputs a command signal that gradually increases.

In the present invention, the detecting means is constituted by the pressure sensor in the above embodiment. However, the present invention is not limited to this. For example, the detecting means may be constituted by a potentiometer for electrically detecting the operation amount of the operation lever.

Further, in the present embodiment, the recovery passage in the present invention uses the center bypass inside the boom spool valve. However, the present invention is not limited to this, and a bypass passage may be provided outside the boom spool valve.

[0048]

As is apparent from the above description,
ADVANTAGE OF THE INVENTION According to the hydraulic control apparatus of the hydraulic shovel of this invention, the simultaneous operation of the boom operation lever and the arm operation lever performed at the time of performing the horizontal pulling operation of pulling the bucket in the horizontal direction to perform leveling is performed by an advanced operation. It can be done easily and smoothly without the need for technology.

[Brief description of the drawings]

FIG. 1 is an overall external view showing an embodiment of a hydraulic shovel of the present invention.

FIG. 2 is a hydraulic circuit diagram of the hydraulic shovel of the present invention.

FIG. 3 is an opening area characteristic diagram of the boom spool valve shown in FIG. 2;

FIG. 4 is a basic characteristic diagram of the boom spool valve shown in FIG. 2;

FIG. 5 is an opening area characteristic diagram of the arm spool valve shown in FIG. 2;

6 is a discharge flow rate characteristic diagram of the first hydraulic pump shown in FIG.

FIG. 7 is a discharge flow rate characteristic diagram of the second hydraulic pump shown in FIG.

8 is a flowchart illustrating the operation of the hydraulic control circuit shown in FIG.

FIG. 9 is an opening area characteristic diagram of the boom spool valve at the time of independent operation of the boom of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body 2 Boom 3 Arm 4 Bucket 5 Boom cylinder 6 Arm cylinder 7 Bucket cylinder 8 First hydraulic pump 9 Second hydraulic pump 10 Boom operating lever 12 Arm operating lever 17 Boom spool valve 19 Hydraulic oil Tank 23 Spool valve for arm 26 Bleed offline

Claims (3)

[Claims] 1. A pressure oil is supplied from a first hydraulic pump to a boom cylinder via a boom spool valve that operates in response to an operation of a boom operation lever, and operates in response to an operation of an arm operation lever. In a hydraulic shovel that supplies hydraulic oil from a second hydraulic pump to an arm cylinder via an arm spool valve, a part of the hydraulic oil can be collected in a hydraulic oil tank at each switching position of the boom spool valve. A recovery flow path; a flow control valve provided in the recovery flow path; detection means for detecting presence or absence of operation of the boom operation lever and the arm operation lever; and the boom operation lever and the arm by the detection means. And a control means for controlling the flow control valve to be in an open state when simultaneous operation of the operating levers is detected. 2. The control device according to claim 1, wherein said control means reduces an opening area of said flow control valve when a pressure in a head side oil chamber of said boom cylinder decreases.
A hydraulic control device for the hydraulic shovel according to the above. 3. The control device according to claim 1, wherein the single operation of the boom operation lever is detected by the detection device.
The hydraulic control device for a hydraulic shovel according to claim 1, wherein the hydraulic control device is configured to switch the flow control valve to a shut-off side.