JP3117618B2 - Hydraulic drive for hydraulic excavator with loader front - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive system for a hydraulic shovel with a loader front having a structure capable of opening and closing a bucket. The present invention relates to a hydraulic drive device of a hydraulic shovel with a loader front provided with a so-called negative control, which controls a discharge capacity of a variable displacement hydraulic pump based on a pressure generated by a generator.

[0002]

2. Description of the Related Art FIG. 3 is a side view showing an external appearance of a hydraulic excavator with a loader front which is an object of the present invention. Generally, a hydraulic excavator with a loader front is provided with a traveling body 40.
A revolving body 41 disposed on the traveling body 40 and provided with a driver's cab; a boom 42 rotatably provided on the revolving body 41; and an arm 43 rotatably connected to the boom 42. Is rotatably connected to the arm 43,
In addition, a bucket 44 is provided which can be opened and closed. A loader front is formed by the boom 42, the arm 43, and the bucket 44 described above.

The left and right crawler belts forming the traveling body 40 are driven by two traveling motors, that is, a right traveling motor and a left traveling motor, and the revolving unit 41 is revolved on the traveling body 40 by the revolving motor. The boom 42 rotates in the upward direction by driving the boom cylinder 45 to extend, and rotates in the downward direction by driving the boom cylinder 45 to contract. Arm 43
Also, for example, from the state shown in FIG. 3, the arm cylinder 46 rotates in the upward direction by driving the arm cylinder 46 to extend, and rotates in the downward direction by driving the arm cylinder 46 to contract. Bucket 44 also
For example, from the state shown in FIG. 3, the bucket cylinder 47 is rotated upward by driving it to extend (tilt operation), and is rotated downward by driving the bucket cylinder 47 to contract (dump operation). ). Furthermore, the bucket 44 is divided into an open state by driving the bucket open / close cylinder to extend, and returns to a closed state by driving the bucket open / close cylinder to contract. The boom cylinder 45, the arm cylinder 46, and the bucket cylinder 47 constitute a front actuator.

In this hydraulic excavator with a loader front, as will be described in detail later, for example, the bucket 44 is closed by driving the bucket opening / closing cylinder to contract, and the boom 42, the arm 43, and the bucket 44 are appropriately rotated. As a result, earth and sand is excavated, and earth and sand are deposited on the bucket 44. Then, for example, when the boom 42 and the arm 43 are raised while the revolving body 41 is swung, the bucket 44 is positioned above the bed of a truck (not shown), and the bucket opening / closing cylinder is driven to extend in this state. When opened, the earth and sand deposited on the bucket 44 is discharged on the truck bed. In this way, excavation work of earth and sand can be performed.

FIG. 4 is a circuit diagram showing a conventional hydraulic drive device provided in a hydraulic excavator with a loader front as shown in FIG.

This prior art includes a plurality of hydraulic pumps, for example, a variable displacement hydraulic pump 1 and a variable displacement hydraulic pump 2. The discharge capacity of the hydraulic pump 1 is controlled by the discharge capacity control means 3.
The discharge capacity of the hydraulic pump 2 is controlled by the discharge capacity control means 4.

On the hydraulic pump 1 side, for example, a right running direction control valve 5 for controlling the driving of the above-described right running motor is disposed at the most upstream position, and a boom cylinder for controlling the driving of a boom cylinder 45 is disposed downstream thereof. A directional control valve 6, a directional control valve 7 that is selectively used when the bucket 44 is tilted or the bucket 44 is opened and closed, and an arm cylinder 4.
The directional control valve 8 for controlling the driving of the arm 6 is connected in tandem. Boom directional control valve 6 and directional control valve 7
The arm direction control valve 8 and the arm direction control valve 8 are connected in parallel with each other. The first switching valve to which the pressure oil from the hydraulic pump 1 is basically supplied by the above-described right traveling direction control valve 5, boom direction control valve 6, direction control valve 7, and arm direction control valve 8. Groups are composed.

On the hydraulic pump 2 side, a swing direction control valve 9 for controlling the drive of the swing motor, an arm direction control valve 10 for controlling the drive of the arm cylinder 46, and a drive of the boom cylinder 45 are controlled. A boom direction control valve 11, a bucket direction control valve 12 for expanding and contracting a bucket cylinder 47, and a left traveling direction control valve 13 for controlling driving of a left traveling motor are arranged. The turning direction control valve 9, the arm direction control valve 10, the boom direction control valve 11, the bucket direction control valve 12, and the left running direction control valve 13 are connected in parallel with each other. , And these directional control valves 9, 10, 11, 12,
13, the second pressure oil from the hydraulic pump 2 is supplied.
Are formed.

At the most downstream of the center bypass passage of the first switching valve group on the side of the hydraulic pump 1, a pressure generating means for generating a pressure for driving the discharge displacement control means 3;
That is, the fixed throttle 15 and the relief valve 17 for defining the maximum value of the pressure generated by the fixed throttle 15 are provided. Similarly, at the most downstream of the center bypass passage of the second switching valve group on the hydraulic pump 2 side, a pressure generating means for generating a pressure for driving the above-described discharge capacity control means 4, that is, a fixed throttle 16, and a fixed throttle 16 And a relief valve 18 for defining the maximum value of the pressure generated at 16.

One outlet port of the directional control valve 7 belonging to the above-described first switching valve group is connected to the bucket 44 of the bucket directional control valve 12 belonging to the second switching valve group through a pipe 14a. It is connected to an outflow port through which pressure oil flows out during operation. Further, another outflow port of the direction control valve 7 is connected to a bucket opening / closing direction control valve 31 for controlling the driving of the above-described bucket opening / closing cylinder via a pipe line 14b.

Further, an operation lever 21A for switching the bucket directional control valve 12 and the directional control valve 7 belonging to the above-described second switching valve group, and a pilot pump due to a difference in the operation direction of the operation lever 21A, respectively. 14 is reduced to the pilot pressure and the bucket directional control valve 12 is
A pilot valve 19 or a pilot valve 20 for outputting to the control room 12a or the control room 12b, and a shuttle valve 21B for selectively taking out the pilot pressure generated by the pilot valves 19 and 20 are provided. The pilot pressure extracted by the shuttle valve 21B is guided to one control chamber 7b of the direction control valve 7 via a pilot line 7d.

An operation lever 31A for switching the bucket opening / closing direction control valve 31 and a difference in the operation direction of the operation lever 31A cause the pilot pump 14
The pilot valve 27 or the pilot valve 28 which reduces the pressure and outputs the pilot pressure to the control chamber 31a or the control chamber 31b of the bucket opening / closing direction control valve 31
And a shuttle valve 31B for selectively taking out the pilot pressure generated by the pilot valves 27 and 28. The pilot pressure taken out by the shuttle valve 31B is guided to another control chamber 7a of the direction control valve 7 via the pilot line 7c, and the pilot line 32
Through c, it is led to the drive section of the switching valve 32 provided in the pilot line 7d. The upper position of the switching valve 32 shown in FIG. 4 is a switching position for bringing the pilot line 7d into a communicating state, and the lower position is a switching position for connecting the pilot line 7d to the tank 32.

In FIG. 4, a right direction control valve 5, a boom direction control valve 6, an arm direction control valve 8 belonging to a first switching valve group, and a turning belonging to a second switching valve group. An operating device including an operating lever for switching between the direction control valve 9 for use, the direction control valve 10 for the arm, the direction control valve 11 for the boom, and the direction control valve 13 for the left running is not shown.

The tilt operation, dump operation, and opening / closing operation of the bucket 44 in the prior art shown in FIG. 4 will be described below. Now, for example, it is assumed that the bucket opening / closing directional control valve 31 is in a neutral state, and the bucket 44 is closed at this time. When excavating earth and sand, a digging operation, that is, a tilt operation illustrated in FIG. 3 described above is performed.

In this case, the operation of tilting the operation lever 21A shown in FIG. 4 in the counterclockwise direction in FIG. 4 is performed. Thereby, the pilot valve 19 is operated, and the generated pilot pressure is supplied to the control chamber 12a of the bucket directional control valve 12, and the bucket directional control valve 12 is switched to the left position in FIG. At the same time, the pilot pressure generated by the pilot valve 19 is taken out from the shuttle valve 21B, guided to the pilot line 7d, and supplied to the control chamber 7b of the direction control valve 7. Thereby, the direction switching valve 7 is switched to the right position in FIG.

As described above, the bucket directional control valve 12
4 is switched to the left position in FIG. 4, the center bypass passage of the second switching valve group belonging to the hydraulic pump 2 is gradually closed, and the value of the pressure generated in the fixed throttle 16 decreases, whereby the discharge is reduced. The displacement control means 4 operates to increase the discharge displacement of the hydraulic pump 2, and the flow supplied to the second switching valve group increases. This flow rate is supplied to the outlet port of the bucket directional control valve 12 through the left position in FIG. Similarly, the center bypass passage of the first switching valve group is gradually closed in accordance with the switching operation of the directional control valve 7, and the value of the pressure generated in the fixed throttle 15 decreases, thereby controlling the discharge displacement control. The means 3 operates so as to increase the discharge capacity of the hydraulic pump 1, and the flow rate supplied to the first switching valve group increases. This flow rate is supplied to the conduit 14a via the right position of the directional control valve 7 in FIG.
It joins the outflow port of the above-described bucket directional control valve 12. Therefore, the combined pressure oil of the flow rate discharged from the second hydraulic pump 2 and the flow rate discharged from the first hydraulic pump 1 is supplied to the head side of the bucket cylinder 47 in FIG. 47 operates to extend, a desired tilt operation is performed, earth and sand are dug up, and earth and sand are piled on the bucket 44.

From such a state, the boom 4 shown in FIG.
2. An operation of selectively driving the arm 43, the revolving unit 41, the traveling unit 40, and the like as appropriate to move the bucket 44 to a predetermined dumping position is performed.

When the operation lever 31A is moved to a predetermined unloading position, the operation lever 31A is moved to unload the bucket 44 as shown in FIG.
The operation of tilting in the counterclockwise direction is performed. As a result, the pilot valve 27 operates, and the generated pilot pressure is taken out from the shuttle valve 31B. This pilot pressure is supplied to the drive unit of the switching valve 32 via the pilot line 32c, and accordingly, the switching valve 32 is switched to the lower position in FIG. 4, and the pilot line 7d communicates with the tank 29. . Further, the above-mentioned pilot pressure is supplied to the control chamber 7a of the directional control valve 7 via the pilot line 7c, and the directional control valve 7 is switched to the left position in FIG. Therefore, the outflow port at the left position of the direction control valve 7 is connected to the line 1
4b. At the same time, the pilot pressure generated by the pilot valve 27 as described above is supplied to the control chamber 31a of the bucket opening / closing direction control valve 31, and the bucket opening / closing direction control valve 31 is switched to the left position.

Thus, the pressure oil from the hydraulic pump 1 is
The directional control valve 7 is guided to the pipeline 14b through the left position, and supplied to the head side of the bucket opening / closing cylinder (not shown) via the bucket opening / closing directional control valve 31 so that the bucket opening / closing cylinder (not shown) extends. And bucket 4
4 is opened and the desired soil release is performed.

At this time, when the tilting operation or the dumping operation of the bucket 44 is performed at the same time, the operation lever 21A is operated together with the operation lever 21A.
A may be operated, and the bucket directional control valve 12 is controlled by the pilot pressure generated by the operation of the pilot valve 19.
Is switched to the left position to perform the above-described tilt operation, or the bucket directional control valve 12 is controlled by the pilot pressure generated by the operation of the pilot valve 20.
Is switched to the right position, and the dump operation is performed simultaneously.

When the above-mentioned soil release is completed, the operation lever 31A is tilted clockwise in FIG. 4 to operate the pilot valve 28, and the generated pilot pressure is transmitted via the shuttle valve 31B. Pilot line 32
c, the pipe is guided to the pilot pipe 7c, and the switching valve 32 is kept in the lower position and the directional control valve 7 is kept in the left position, as described above. The bucket opening / closing direction control valve 31 is provided to the control chamber 31b of the valve 31, and is switched to the right position in FIG. Thereby, the pressure oil from the hydraulic pump 1 is supplied to the rod side of the bucket opening / closing cylinder (not shown) through the left position of the direction control valve 7, the pipeline 14b, and the right position of the bucket opening / closing direction control valve 31. The bucket opening / closing cylinder that does not operate operates to contract, and the bucket 44 is closed. When the bucket 44 is closed as described above, an operation is performed to return the operation lever 31A to the neutral position. Thereby, the bucket opening / closing direction control valve 31 and the direction control valve 7 return to the neutral position. The switching valve 32 also returns to the upper position, which is the neutral position, and the pilot line 7d is in a communicating state.

From such a state, the boom 4 shown in FIG.
2. The operation of selectively driving the arm 43, the revolving unit 41, the traveling unit 40, and the like again and moving the bucket 44 to a predetermined excavation position is performed. At this time, the bucket 44
Is not a standby posture that is sufficiently satisfied for the next excavation operation, the dump operation of the bucket 44 is performed.

As mentioned above, the dumping operation of the bucket 44 is performed by tilting the operation lever 21A clockwise in FIG. As a result, the pilot valve 20 is operated, and the generated pilot pressure is supplied to the control chamber 12b of the bucket directional control valve 12, and the bucket directional control valve 12 is switched to the right position in FIG.
Accordingly, pressure oil from the hydraulic pump 2 is supplied to the rod side of the bucket cylinder 47 shown in FIG.
7 contracts, and a desired dump operation is performed.

At this time, the pilot pressure generated by the operation of the pilot valve 20 is guided to the pilot line 7d, the directional control valve 7 is switched to the right position, and the hydraulic oil from the hydraulic pump 1 is supplied to the line. At this time, since the bucket directional control valve 12 is switched to the right position, the pipeline 14a communicates with the tank 29, and the hydraulic oil discharged from the hydraulic pump 1 is supplied to the hydraulic pump 2a.
Without returning to the tank 29.

Normally, the pressure receiving area on the head side of the bucket cylinder 47 is set to about twice the pressure receiving area on the rod side. When the bucket 44 is tilted, the hydraulic pump 1
And the hydraulic oil of the hydraulic pump 2 are joined to form the bucket cylinder 4
7, a large excavating force can be obtained, and a relatively high operating speed equivalent to that when the hydraulic oil of the hydraulic pump 2 is supplied to the rod side of the bucket cylinder 47 can be obtained.

[0026]

By the way, in the conventional hydraulic drive system of a hydraulic shovel with a loader front having the above-described structure, a complicated circuit configuration for driving a bucket opening / closing cylinder (not shown), that is, , Bucket opening / closing direction control valve 31, shuttle valve 31B, pilot lines 7c and 32c, line 14b, and switching valve 32
Therefore, there is a problem that the number of parts is increased and the manufacturing cost is increased, and a space for arranging these circuit components is increased, so that there is a problem that the hydraulic drive device cannot be downsized.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and has as its object to simplify the circuit configuration for driving a bucket cylinder and a bucket opening / closing cylinder, and furthermore, to substantially reduce the circuit configuration. An object of the present invention is to provide a hydraulic drive device for a hydraulic shovel with a loader front, which can achieve the same function.

[0028]

In order to achieve this object, a first aspect of the present invention provides a boom cylinder,
A front actuator including an arm cylinder and a bucket cylinder, a plurality of actuators including a bucket opening / closing cylinder, and two traveling motors;
A plurality of hydraulic pumps including two variable displacement hydraulic pumps, and pressure oil from the variable displacement hydraulic pump are supplied, and a drive for driving one of the two traveling motors and controlling the driving of one of the two traveling motors is arranged at the most upstream position. A first switching valve group formed by tandem-connecting a directional control valve and a directional control valve disposed downstream of the traveling directional control valve, and pressure oil supplied from a hydraulic pump other than the variable displacement hydraulic pump is supplied. A second switching valve group, a pressure generating means provided at the most downstream side of the center bypass passage of the first switching valve group, and a discharge of the variable displacement hydraulic pump according to the pressure generated by the pressure generating means. In a hydraulic drive system for a hydraulic shovel with a loader front, comprising a discharge capacity control means for controlling a capacity, the first switching valve group controls driving of a front actuator other than the bucket cylinder. A second directional control valve for controlling the driving of the bucket opening / closing cylinder, the second directional control valve group controlling the driving of a front actuator other than the bucket cylinder. A front directional control valve, and a bucket directional control valve for controlling the driving of the bucket cylinder, and on the center bypass passage of the first switching valve group and upstream of the pressure generating means near the pressure generating means. An opening / closing control valve that can control opening and closing of the center bypass passage; a downstream portion of a pressure oil supply passage of a directional control valve at the most downstream side of the first switching valve group; and a second switching valve group. A connection passage connecting the pressure oil inflow port of the included directional control valve for bucket, and a connection passage provided on the connection passage and extending from the first switching valve group to the second switching valve group. A check valve that allows flow to the directional control valve, and a pressure oil supply that is provided on a pressure oil supply passage of the bucket directional control valve of the second switching valve group, and that is supplied to a directional control valve other than the bucket directional control valve. A check valve for preventing pressure oil from flowing into the passage from the connection passage; interlocking means for interlocking the open / close control valve and the bucket direction control valve; a front actuator other than the bucket cylinder and the bucket; During combined driving with a cylinder, one of the front directional control valve included in the first switching valve group and the another front directional control valve included in the second switching valve group is forcibly neutralized. And a neutral holding means for holding the holding member.

[0029]

According to the first aspect of the present invention, since the above-described configuration is employed, for example, when the tilt operation of the bucket is performed, the bucket directional control valve belonging to the second switching valve group is set to the bucket direction control valve. What is necessary is just to switch to the predetermined switching position where the supply of the pressure oil to the head side of the cylinder is possible.
Thus, the opening / closing control valve provided on the center bypass passage of the first switching valve group operates via the interlocking means to close the center bypass passage. Along with this, the value of the pressure generated by the pressure generating means disposed downstream of the on-off control valve decreases, and the discharge displacement control means operates to increase the discharge displacement of the variable displacement hydraulic pump. The flow rate from the variable displacement hydraulic pump is supplied to the bucket directional control valve belonging to the second switching valve group via the connection passage, and the hydraulic oil from the variable displacement hydraulic pump on the first switching valve group side and the second
The hydraulic fluid from the hydraulic pump on the side of the switching valve group is joined and supplied to the bucket directional control valve, and further supplied to the head side of the bucket cylinder, whereby the bucket cylinder is extended to perform a desired tilt operation. Can be made.

When the dump operation is performed, the bucket directional control valve belonging to the second switching valve group is
What is necessary is just to switch to a different switching position where the supply of pressure oil to the rod side of the bucket cylinder is possible. At this time, the pressure oil from the variable displacement hydraulic pump of the first switching valve group and the pressure oil from the hydraulic pump on the second switching valve group side are combined and supplied to the bucket direction control valve. The operation is the same as in the above-described tilt operation. During this dumping operation, the pressure oil supplied to the bucket directional control valve is supplied to the rod side of the bucket cylinder via the above-described different switching positions, and the bucket cylinder may contract to perform a desired dumping operation. it can.

In this case, if provision is made to provide a blocking means for blocking the flow of the pressure oil guided to the connection passage into the directional control valve for the bucket, the hydraulic pressure on the second switching valve group side during the dumping operation is considered. Only the pressure oil of the pump can be supplied to the bucket cylinder, and the operating speed can be made substantially equal to that during the tilt operation.

In the above-described tilt operation and the like, the pressure oil supplied from the variable displacement hydraulic pump supplied through the connection passage is supplied to the check valve provided in the connection passage and the pressure oil supply passage of the bucket directional control valve. With the check valve provided in
It is regulated so as not to flow to the directional control valves other than the bucket directional control valve, so that the operation of the actuator other than the bucket cylinder is not affected.

For example, when the opening and closing operation of the bucket is performed, the direction control valve for opening and closing the bucket belonging to the first switching valve group may be switched. As a result, the center bypass passage of the first switching valve group is closed, the value of the pressure generated by the pressure generating means decreases, and the discharge capacity control means operates to increase the discharge capacity of the variable displacement hydraulic pump. I do. The flow rate from the variable displacement hydraulic pump is supplied to the bucket opening / closing cylinder via the bucket opening / closing directional control valve, and a desired bucket opening / closing operation can be performed.

When the bucket dumping operation or the tilting operation is simultaneously performed during the opening and closing operation of the bucket, the bucket opening / closing directional control valve belonging to the first switching valve group and the bucket switching direction control valve belonging to the second switching valve group. The directional control valve for the bucket may be switched at the same time. At this time,
The pressure oil of the variable displacement hydraulic pump on the first switching valve group side is supplied to the bucket opening / closing directional control valve, and the bucket opening / closing cylinder can be operated accordingly, while the second switching valve group side The pressure oil of the hydraulic pump is supplied to the bucket directional control valve, and the bucket cylinder can be operated in accordance with the supply, so that a desired combined operation can be performed.

Further, when a front actuator other than the bucket cylinder, for example, a combined drive of the arm cylinder and the bucket cylinder, the directional control valve for the arm included in the first switching valve group is forcibly held neutral by the neutral holding means. You. Accordingly, the pressure oil of the variable displacement hydraulic pump on the first switching valve group side is supplied to the direction control valve for the arm in the neutral state and the direction for the bucket included in the second switching valve group via the connection passage described above. The control valve is supplied to the control valve, thereby driving the bucket cylinder. The hydraulic oil of the hydraulic pump on the second switching valve group side is supplied to the arm cylinder via the directional control valve for the arm. It can be driven, and a combined operation of a desired arm and bucket can be realized.

In the combined driving of the arm cylinder and the bucket cylinder described above, another front directional control valve, that is, another arm directional control valve of the second switching valve group including the bucket cylinder is operated by the neutral holding means. It can also be kept neutral. In this case, the first
Driving the front directional control valve included in the switching valve group, that is, the arm directional control valve, supplies the pressure oil of the variable displacement hydraulic pump on the first switching valve group side to the arm cylinder via the arm directional control valve. This arm cylinder can be driven, and by driving the bucket directional control valve included in the second switching valve group, this second cylinder can be driven.
Pressure oil of the hydraulic pump on the side of the switching valve group is supplied to the bucket cylinder via the bucket directional control valve, and this bucket cylinder can be driven, thereby realizing a combined operation of the desired arm and bucket. . The above-described combined drive can be similarly performed even when the front actuator other than the bucket cylinder is a boom cylinder.

As described above, according to the first aspect of the present invention, two conventional directional control valves, namely, a directional control valve for opening and closing a bucket and a directional control valve used for tilting operation and opening and closing operation of a bucket are used. Instead, only one bucket opening / closing directional control valve is required, and accordingly, the number of pilot lines and the like can be reduced, and the circuit configuration for driving the bucket cylinder and the bucket opening / closing cylinder can be simplified.

Further, it is possible to reliably realize a combined drive of front actuators other than the bucket cylinder, that is, the arm cylinder, the boom cylinder, and the bucket cylinder, and to improve the efficiency of work performed via these actuators. Can be.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic drive system for a hydraulic shovel with a loader front according to the present invention will be described below with reference to the drawings.
FIG. 1 is a circuit diagram showing a first embodiment of a hydraulic drive device for a hydraulic shovel with a loader front according to claims 1, 2, 3, 4, 5, and 6 of the present invention. This first embodiment is:
It is provided in a hydraulic excavator with a loader front as shown in FIG. FIG. 1 is drawn corresponding to FIG. 4 described above, and the same components as those shown in FIG. 4 are denoted by the same reference numerals.

That is, even in the first embodiment shown in FIG. 1, a plurality of hydraulic pumps, for example, the variable displacement hydraulic pump 1
And a variable displacement hydraulic pump 2. The discharge capacity of the hydraulic pump 1 is controlled by a discharge capacity control means 3, and the discharge capacity of the hydraulic pump 2 is controlled by a discharge capacity control means 4.

On the hydraulic pump 1 side, for example, a right running direction control valve 5 for controlling the driving of a right running motor is arranged at the most upstream, and a bucket opening / closing direction for controlling the driving of a bucket opening / closing cylinder is provided downstream thereof. The control valve 6A, the boom directional control valve 7A for controlling the drive of the boom cylinder 45 shown in FIG. 3, and the arm directional control valve 8 for controlling the drive of the arm cylinder 46 are connected in tandem. The bucket opening / closing directional control valve 6A, the boom directional control valve 7A, and the arm directional control valve 8 are connected in parallel with each other. A first switching valve to which the pressure oil from the hydraulic pump 1 is supplied by the above-described right traveling direction control valve 5, bucket opening / closing direction control valve 6A, boom direction control valve 7A, and arm direction control valve 8. Groups are composed. The boom direction control valve 7A and the arm direction control valve 8 constitute a front direction control valve for controlling the driving of the front actuator.

On the hydraulic pump 2 side, a turning direction control valve 9 for controlling the driving of the turning motor, an arm direction control valve 10 for controlling the driving of the arm cylinder 46 shown in FIG.
A boom direction control valve 11 for controlling the driving of the boom cylinder 45, a bucket direction control valve 12 for expanding and contracting the bucket cylinder 47, and a left traveling direction control valve 13 for controlling the driving of the left traveling motor are arranged. . The turning direction control valve 9, the arm direction control valve 10, the boom direction control valve 11, the bucket direction control valve 12, and the left running direction control valve 13 are connected in parallel with each other. These directional control valves 9, 10, 11, 1
A second switching valve group to which the pressure oil from the hydraulic pump 2 is supplied is constituted by 2 and 13. The above-described arm direction control valve 10, boom direction control valve 11, and bucket direction control valve 12 constitute a front direction control valve for controlling driving of a front actuator.

At the most downstream of the center bypass passage of the first switching valve group on the hydraulic pump 1 side, there is provided a pressure generating means for generating a pressure for driving the discharge capacity control means 3, that is, a fixed throttle 15, A relief valve 17 that regulates the maximum value of the pressure generated by the throttle 15 is provided. Similarly, at the most downstream of the center bypass passage of the second switching valve group on the hydraulic pump 2 side, a pressure generating means for generating a pressure for driving the above-described discharge capacity control means 4, that is, a fixed throttle 16, and a fixed throttle 16 And a relief valve 18 for defining the maximum value of the pressure generated at 16.

An operating lever 21A for switching the bucket directional control valve 12 belonging to the above-described second switching valve group.
And a pilot valve 19 or a pilot valve 20 for reducing the pressure of the pilot pump 14 and outputting it as a pilot pressure to the control chamber of the bucket directional control valve 12 due to a difference in the operation direction of the operation lever 21A. A shuttle valve 21B for selectively extracting pilot pressure generated by the pilot valves 19 and 20;

An opening / closing control valve 22 capable of controlling the opening and closing of the center bypass passage is provided upstream of the fixed throttle 15 provided at the most downstream side of the center bypass passage of the first switching valve group.
Is provided. The opening / closing control valve 22 keeps the center bypass passage open when neutral, and is driven by the pilot pressure taken out by the shuttle valve 21B and guided through the pilot line 21C to operate to close the center bypass passage. The shuttle valve 21B and the pilot line 21C described above constitute interlocking means for interlocking the opening / closing control valve 22 and the bucket direction control valve 12.

Further, the directional control valve at the most downstream of the first switching valve group, that is, the downstream portion of the pressure oil supply passage of the arm directional control valve 8, and the directional control for the bucket included in the second switching valve group. A connection passage 23 connecting the pressure oil inflow port of the valve 12 to the pressure passage, and a connection passage 23 provided on the connection passage 23 to allow a flow in a direction from the first switching valve group to the second switching valve group;
A check valve 24 for preventing backflow in a direction from the second switching valve group to the first switching valve group; and a check valve 24 provided on the pressure oil supply passage of the second switching valve group, other than the bucket direction control valve 12. Check valves 25 and 26 are provided to prevent pressure oil from flowing from the connection passage 23 into the pressure oil supply passage to the direction control valve.

An operation lever 33A for switching between the arm direction control valves 8 and 10 and a pilot valve 33B which operates according to the difference in the operation direction of the operation lever 33A to reduce the pressure of the pilot pump 14 and output the pressure. , 33C
An operation lever 34A for switching between the boom direction control valves 7A and 11; and pilot valves 34B and 34C that operate according to the difference in the operation direction of the operation lever 34A and that can output the pressure of the pilot pump 14 by reducing the pressure. It has.

Further, a bucket pipe is provided in a pilot pipe connecting the pilot valve 33B for switching the arm direction control valves 8 and 10 and the control chamber 8a of the arm direction control valve 8 included in the first switching valve group. A means for stopping the output of a signal for switching the arm direction control valve 8 to the left position in FIG. 1 in interlocking with the switching of the direction control valve 12, that is, taken out from the shuttle valve 21 B and taken out of the pilot line 21 D And a switching valve 35 which is driven by the pressure guided through the valve and blocks the output of the pilot pressure for switching the arm direction control valve 8 to the left position in FIG. In a neutral state in which pilot pressure is not guided to the pilot line 21D, the switching valve 35 is held at a position for communicating the pilot line connecting the pilot valve 33B and the control chamber 8a of the arm direction control valve 8, In addition, pilot line 21D
When the pilot pressure is guided and switched, the pilot line connecting the pilot valve 33B and the control chamber 8a of the arm direction control valve 8 is held at the position connecting the tank 29.

Similarly, a pilot pipe connecting the pilot valve 33C for switching the arm directional control valves 8 and 10 and the control chamber 8b of the arm directional control valve 8 included in the first switching valve group includes: A means for stopping output of a signal for switching the arm directional control valve 8 to the right position in FIG. 1 in cooperation with the switching of the bucket directional control valve 12, that is, taken out from the shuttle valve 21B, A switching valve 36, which is driven by the pressure guided through 21D and prevents the output of the pilot pressure for switching the arm direction control valve 8 to the right position in FIG. 1, is provided. In a neutral state in which pilot pressure is not guided to the pilot line 21D, the switching valve 36 is held at a position for communicating the pilot line connecting the pilot valve 33C with the control chamber 8b of the arm direction control valve 8, In addition, pilot line 21D
When the pilot pressure is guided to the tank 29 and the switching is performed, the pilot line connecting the pilot valve 33 </ b> C and the control chamber 8 b of the arm direction control valve 8 is held at the position connecting the tank 29.

The pilot valve 34B for switching between the boom directional control valves 7A and 11 and the pilot pipe connecting the control chamber 11a of the boom directional control valve 11 included in the second switching valve group include a bucket. A means for stopping the output of the signal for switching the boom direction control valve 11 to the left position in FIG. 1 in cooperation with the switching of the direction control valve 12 for the boom, that is, taken out from the shuttle valve 21B and taken out of the pilot line 21D , 21E, and is provided with a switching valve 37 for preventing the output of the pilot pressure for switching the boom direction control valve 11 to the left position in FIG. In the neutral state where the pilot pressure is not guided to the pilot line 21E, the switching valve 37
4B and the control line 11a of the boom directional control valve 11, the pilot line is held at a position where the pilot line communicates with the control room. When the pilot pressure is guided to the pilot line 21E for switching, the pilot valve 34B and the boom The pilot pipe connecting the directional control valve 11 to the control chamber 11 a is held at a position connecting to the tank 29.

Similarly, a pilot pipe which connects the pilot valve 34C for switching the boom directional control valves 7A and 11 and the control chamber 11b of the boom directional control valve 11 included in the second switching valve group includes: In conjunction with the switching of the bucket directional control valve 12, the boom directional control valve 11 is moved in FIG.
Means for stopping the output of the signal for switching to the right position of the boom, that is, driven by the pressure taken out from the shuttle valve 21B and guided through the pilot pipes 21D and 21E, and the boom direction control valve 11 is And a switching valve 38 for preventing the output of the pilot pressure for switching to the right position of. In the neutral state where the pilot pressure is not guided to the pilot line 21E, the switching valve 38
4C is held at a position where a pilot pipe connecting the control chamber 11b of the boom directional control valve 11 is communicated. When the pilot pressure is guided to the pilot pipe 21E and switched, the pilot valve 34C and the boom The pilot pipe connecting the directional control valve 11 to the control chamber 11b is held at a position connecting to the tank 29.

The pilot line 21D connected to the shuttle valve 21B, the pilot line 21E connected to the pilot line 21D, and the switching valves 35, 36,
The output stopping means including 37, 38
Front actuators other than 7 (arm cylinder 4
6, the boom cylinder 45) and the bucket cylinder 47 during combined driving, the front directional control valves (arm directional control valve 8, boom directional control valve 7A) and the second directional control valve included in the first switching valve group. Neutral holding means for forcibly holding one corresponding front directional control valve of another front directional control valve (arm directional control valve 10, boom directional control valve 11) included in the switching valve group. Is composed.

On the pressure oil supply passage of the arm direction control valve 8, a fixed throttle 8A for realizing a combined operation of the arm cylinder 46 and the bucket opening / closing cylinder is provided.

Incidentally, even in the first embodiment shown in FIG. 1, the right traveling direction control valve 5 belonging to the first switching valve group and the turning direction control valve belonging to the second switching valve group. 9. An operating device including an operating lever for switching the left traveling direction control valve 13 is not shown. Also, in FIG.
9 is a tank.

The tilting operation, dumping operation, and opening / closing operation of the bucket 44 in the first embodiment will be described below.

For example, when performing the tilting operation of the bucket 44, the pilot valve 19 is operated by operating the operation lever 21A so as to be tilted in the counterclockwise direction in FIG. 1, and the bucket direction belonging to the second switching valve group is operated. Control valve 12
May be switched to the left position in FIG. 1 where the pressure oil can be supplied to the head side of the bucket cylinder 47. This allows
The center bypass passage of the second switching valve group on the hydraulic pump 2 side is closed, the value of the pressure generated in the fixed throttle 16 decreases, and the discharge displacement control means 4 operates to increase the discharge displacement of the hydraulic pump 2. The increased flow rate is supplied to the bucket directional control valve 12. At the same time, the pilot pressure generated by the operation of the pilot valve 19 is taken out from the shuttle valve 21B, guided to the pilot line 21C, and supplied to the drive unit of the switching valve 22. As a result, the switching valve 22 is switched to the right position, that is, the closed position. Accordingly, the hydraulic pump 1
The center bypass passage of the first switching valve group on the side is closed,
The value of the pressure generated in the fixed throttle 15 decreases, and the discharge capacity control means 3 operates to increase the discharge capacity of the hydraulic pump 1. The increased flow rate of the hydraulic pump 1 is supplied to the inflow port of the bucket directional control valve 12 of the second switching valve group via the connection passage 23 and the check valve 24. That is, the combined pressure oil of the hydraulic pump 1 and the hydraulic pump 2 is supplied to the bucket directional control valve 12 and further supplied to the head side of the bucket cylinder 47, and the bucket cylinder 47 extends to perform a desired tilt operation. Can be made.

For example, when the dumping operation of the bucket 44 is performed, the pilot valve 20 is operated by operating the operating lever 21A so as to be tilted clockwise in FIG. 1 to operate the bucket valve belonging to the second switching valve group. The directional control valve 12 may be switched to the right position in FIG. 1 where the supply of pressure oil to the rod side of the bucket cylinder 47 is possible. As a result, the center bypass passage of the second switching valve group on the hydraulic pump 2 side is closed, and the value of the pressure generated in the fixed throttle 16 is reduced as described above, and the discharge displacement control means 4 discharges the hydraulic pump 2 Acting to increase the capacity, the increased flow is provided to the bucket directional control valve 12. At this time, at the same time, the pilot pressure generated due to the operation of the pilot valve 20 is taken out from the shuttle valve 21B, guided to the pilot line 21C, and switched so that the switching valve 22 is brought to the closed position. Accordingly, the center bypass passage of the first switching valve group on the hydraulic pump 1 side is closed, and the fixed throttle 15 is closed.
Discharge pressure control means 3
Operates to increase the discharge capacity of the hydraulic pump 1. The increased flow rate of the hydraulic pump 1 is supplied to the inflow port of the bucket directional control valve 12 of the second switching valve group via the connection passage 23 and the check valve 24, and merges with the pressure oil from the hydraulic pump 2. The combined pressure oil is supplied to the bucket directional control valve 12 and further supplied to the rod side of the bucket cylinder 47, and the bucket cylinder 47 contracts to perform a desired dumping operation.

In the above-described tilt operation and dump operation,
The pressure oil supplied from the hydraulic pump 1 through the connection passage 23 is supplied to a check valve 24 provided in the connection passage 23 and check valves 25 and 26 provided on the pressure oil supply passage of the bucket directional control valve 12. This restricts the flow to the directional control valves other than the bucket directional control valve, so that other actuators other than the bucket cylinder 47 are not affected.

For example, when the opening / closing operation of the bucket 44 is performed, the bucket opening / closing directional control valve 6A belonging to the first switching valve group may be switched. As a result, the center bypass passage of the first switching valve group is closed, the value of the pressure generated in the fixed throttle 15 decreases, and the discharge displacement control means 3 operates to increase the discharge displacement of the hydraulic pump 1. I do. The flow rate from the hydraulic pump 1 is supplied to a bucket opening / closing cylinder (not shown) via the bucket opening / closing direction control valve 6A, and a desired bucket 44 can be opened / closed.

When the bucket 44 is to be simultaneously opened and closed during the dumping operation or the tilting operation of the bucket 44, the bucket opening and closing direction control valve 6A and the second switching valve belonging to the first switching valve group. The bucket directional control valves 12 belonging to the group may be simultaneously switched. During such simultaneous operation, the hydraulic oil of the hydraulic pump 1 on the first switching valve group side is not supplied to the bucket cylinder 47 via the connection passage 23, and the hydraulic oil of the hydraulic pump 1 on the first switching valve group side is supplied. Is supplied to the bucket opening / closing directional control valve 6A,
Accordingly, the bucket opening / closing cylinder can be operated, while the hydraulic oil of the hydraulic pump 2 on the second switching valve group side is supplied to the bucket directional control valve 12, and the bucket cylinder 47 is operated accordingly. And a desired composite operation can be performed.

In the case of a relatively frequently combined operation of the swing motor and the bucket opening / closing cylinder, the swing direction control valve 9 for controlling the drive of the swing motor is included in the second switching valve group on the hydraulic pump 2 side. However, since the bucket opening / closing direction control valve 6A for controlling the driving of the bucket opening / closing cylinder is included in the first switching valve group on the hydraulic pump 1 side, the hydraulic oil of the hydraulic pump 2 is supplied to the swing motor. The bucket opening / closing cylinder can be driven by supplying the pressure oil of the hydraulic pump 1 to the bucket opening / closing cylinder, whereby a combined operation of a desired swing motor and the bucket opening / closing cylinder can be realized.

Further, for example, the combined operation of the arm cylinder 46 and the bucket cylinder 47 is performed as follows. That is, at this time, the operation lever 21A and the operation lever 33A are simultaneously operated.
1A, one of the pilot valves 19 and 20 is operated, and the generated pilot pressure is supplied to the control chamber 12a or the control chamber 12b of the bucket directional control valve 12, and the bucket directional control valve 12 is operated. The position is switched to the left position or the right position in FIG. The operation lever 33
With the operation of A, one of the pilot valves 33B and 33C is operated, and a pilot pressure is generated.

At this time, the pilot pressure generated due to the operation of the operation lever 21A is taken out from the shuttle valve 21B and supplied to the drive unit of the opening / closing control valve 22 through the pilot line 21C. 22 is switched to the closed position. At the same time, pilot pressure is guided from the shuttle valve 21B to the pilot lines 21D and 21E, whereby the switching valve 35 is switched to the right position in FIG. 1 and the switching valve 36 is switched to the left position in FIG.
The control valves 8a and 8b of the arm direction control valve 8 included in the first switching valve group are connected to the tank 2 by the switching valves 35 and 36.
9 so that the arm directional control valve 8 is held neutral.

Accordingly, the pilot pressure generated by the operation of the operation lever 33A is given to one of the control chambers 10a and 10b of the arm direction control valve 10 included in the second switching valve group. The arm direction control valve 10 is switched to the left position or the right position in FIG.

By switching between the bucket directional control valve 12 and the arm directional control valve 10 as described above, the pressure generated at the fixed throttle 16 is reduced as described above, and the hydraulic pump 2
And the increased flow rate is discharged, and this flow rate is supplied to the arm cylinder 46 via the arm direction control valve 10 of the second switching valve group, and the arm cylinder 46 can be driven.

Further, by switching the opening / closing control valve 22 described above, the pressure generated at the fixed throttle 15 is reduced as described above, and an increased flow rate is discharged from the hydraulic pump 1.
This flow rate is supplied to the inflow port of the bucket directional control valve 12 via the center bypass passage, the connection passage 23, and the check valve 24 of each directional control valve of the first switching valve group. The bucket cylinder 47 is supplied from the valve 12 and can be driven.

As described above, the bucket cylinder 47 is driven by the pressure oil from the hydraulic pump 1 and the arm cylinder 46 is driven.
Can be driven by the pressure oil from the hydraulic pump 2 to reliably perform the desired combined drive of the arm cylinder 46 and the bucket cylinder 47.

Further, for example, the combined operation of the boom cylinder 45 and the bucket cylinder 47 is performed as follows. That is, at this time, the operation lever 21A and the operation lever 34A are simultaneously operated. First, one of the pilot valves 19 and 20 is operated in accordance with the operation of the operation lever 21A, and the generated pilot pressure is applied to the bucket direction control valve. The control valve 12 is supplied to the control room 12a or the control room 12b, and the direction control valve 12 for the bucket is switched to the left position or the right position in FIG. The operation lever 3
Along with the operation of 4A, one of the pilot valves 34B and 34C operates to generate a pilot pressure.

At this time, the pilot pressure generated due to the operation of the operation lever 21A is taken out from the shuttle valve 21B and supplied to the drive section of the opening / closing control valve 22 through the pilot line 21C. 22 is switched to the closed position. At the same time, pilot pressure is guided from the shuttle valve 21B to the pilot lines 21D and 21E, whereby the switching valve 37 is switched to the right position in FIG. 1 and the switching valve 38 is switched to the left position in FIG.
The control valves 11a and 11b of the directional control valve 11 for the arm included in the second switching valve group are connected to the tank 29 by the switching valves 37 and 38, so that the boom directional control valve 11 is held neutral. .

Therefore, the pilot pressure generated by the operation of the operation lever 34A is given to one of the control chambers 7e and 7f of the boom directional control valve 7A included in the first switching valve group. This boom directional control valve 7
A is switched to the left position or the right position in FIG.

By the switching of the bucket directional control valve 12 described above, the pressure generated at the fixed throttle 16 is reduced,
An increased flow rate is discharged from the hydraulic pump 2, and this flow rate is supplied to the bucket cylinder 47 via the bucket directional control valve 12 of the second switching valve group, so that the bucket cylinder 47 can be driven.

Further, by the switching of the opening / closing control valve 22 described above, the pressure generated in the fixed throttle 15 is reduced, and an increased flow rate is discharged from the hydraulic pump 1.
Is supplied to the boom direction control valve 7A of the switching valve group, and is further supplied to the boom cylinder 45 to drive the boom cylinder 45.

As described above, the bucket cylinder 47 is driven by the pressure oil from the hydraulic pump 2 and the boom cylinder 45
Of the boom cylinder 45 and the bucket cylinder 47 can be reliably driven.

In the first embodiment configured as described above, the two conventional directional control valves shown in FIG. 4, that is, the directional control valve 31 for opening and closing the bucket and the tilting and opening and closing operations of the bucket 44 are utilized. It is only necessary to provide one bucket opening / closing direction control valve 7A in place of the direction control valve 7, so that the number of pipelines and the like can be reduced, and a circuit for driving the bucket cylinder 47 and the bucket opening / closing cylinder is provided. The configuration can be simplified. As a result, the manufacturing cost can be reduced, and the space required for arranging the circuit components described above can be reduced, and the hydraulic drive device can be made more compact.

Further, in conjunction with the operation of the operation lever 21A for switching the bucket direction control valve 12, the switching valves 35 and 36 which operate so as to neutralize the arm direction control valve 8 of the first switching valve group are provided. Because of this, the boom direction control valve 11 of the second switching valve group is operated in conjunction with the operation of the operation lever 21A that switches the bucket direction control valve 12.
The switching valves 37 and 38 that operate so as to maintain the neutral position of the bucket cylinder 47 and the arm cylinder 4 are provided.
6 and the combined drive of the bucket cylinder 47 and the boom cylinder 45 can be reliably performed.
Work efficiency can be improved.

FIG. 2 is a circuit diagram showing a second embodiment according to the fourth and fifth aspects of the present invention. In the second embodiment, a blocking means is provided for preventing the pressure oil from the hydraulic pump 1 guided through the connection passage 23 from joining the bucket cylinder 47 during the dumping operation of the bucket 44. This blocking means comprises a switching position structure of the bucket direction control valve 12A. That is, in the second embodiment, the port of the bucket directional control valve 12 has four ports, and the right position in FIG. 2 is a switching position for preventing the joining of the hydraulic oil from the hydraulic pump 1, and the bucket 44 Is the switching position at the time of the dump operation. The left position in FIG.
This is a switching position at which the joining of the pressure oil is permitted, and is a switching position when the bucket 44 is tilted. Other configurations are the same as those of the first embodiment shown in FIG.

In the second embodiment constructed as described above, the combined hydraulic oil of the hydraulic pump 1 and the hydraulic pump 2 is supplied to the head side of the bucket cylinder 47 at the time of tilt operation, and the pressure oil of the bucket cylinder 47 is supplied at the time of dump operation. Since the pressure oil of only the hydraulic pump 2 is supplied to the rod side having a pressure receiving area of approximately 比 べ as compared with the head side, the operation speeds during the tilt operation and the dump operation can be made substantially the same.
Other functions and effects are the same as those of the first embodiment.

In each of the above embodiments, the hydraulic pump 1
The discharge capacity control means 3 and 4 for controlling the discharge capacity 2 comprise a hydraulically driven discharge capacity control means which operates according to the pressure generated in the fixed throttles 15 and 16, but the present invention is not limited to this. I can't. For example, a differential pressure sensor for detecting the differential pressure generated by the fixed throttles 15 and 16 is provided, respectively, and the discharge capacity control means 3 and 4 are configured by an electric drive type discharge capacity control means. The discharge capacity control means may be driven in accordance with the output signal.

Further, in the above embodiment, the pilot valve 19 or the pilot valve 2 is operated as the operation device of the bucket direction control valves 12 and 12A in accordance with the operation of the operation lever 21A.
0 is operated to generate a pilot pressure, and an open / close control valve 22 is switched according to the pilot pressure output from the hydraulic operation device. The present invention is configured in this manner. It is not limited.
That is, the above-mentioned operation device is constituted by an electric operation device having an electric lever, the opening / closing control valve 22 is constituted by an electromagnetic valve, and the opening / closing control valve 22 is switched according to a signal output from the electric operation device. It may be configured.
In addition, the above-described operating device is configured by an electric operating device having an electric lever, and the opening / closing control valve 22 is configured as a hydraulically driven opening / closing control valve, and between the electric operating device and the opening / closing control valve 22, An electro-hydraulic converter such as an electromagnetic proportional pressure reducing valve for converting an electric signal into a hydraulic signal may be provided, and the opening / closing control valve 22 may be driven by a hydraulic output output from the electric-hydraulic converter.

Similarly, in the above embodiment, the switching valves 35, 36, 37, and 38 are switched according to the pilot pressure, but the present invention is not limited to this configuration. That is, the above-mentioned operation device is constituted by an electric operation device having an electric lever, and the switching valves 35, 3
6, 37, 38 are constituted by solenoid valves, and the switching valves 35, 36, 3 are set in accordance with signals output from the electric operation device.
A configuration in which 7, 38 can be switched may be adopted.

In the first embodiment, the switching valve 35 is connected to the pilot line for connecting the pilot valve 33B for operating the arm and the control chamber 8a of the directional control valve 8 for the arm of the first switching valve group. And a switching valve 36 is provided in a pilot line connecting the pilot valve 33C and the control chamber 8b of the above-described directional control valve 8 for an arm.
Although the directional control valve 8 for the arm of the first switching valve group is forcibly held neutral when 1A is operated, the present invention is not limited to this configuration. In other words, the switching valve 3B is connected to the pilot line connecting the pilot valve 33B and the control chamber 8a of the arm direction control valve 8 of the first switching valve group.
5, the switching valve 36 is not provided in the pilot line connecting the pilot valve 33C and the control chamber 8b of the arm direction control valve 8, and the pilot valve 33B and the arm direction of the second switching valve group are not provided. A switching valve 35 is provided in a pilot pipe communicating with the control chamber 10a of the control valve 10, and a pilot valve 3 is provided.
A switching valve 36 is provided in a pilot pipe connecting the 3C and the control chamber 10b of the arm direction control valve 10, and when the bucket operating lever 21A is operated, the arm direction control of the second switching valve group is performed. A configuration may be adopted in which the valve 10 is forcibly held neutral.

With this configuration, during the combined operation of the arm cylinder 46 and the bucket cylinder 47, the arm direction control valve 10 of the second switching valve group is forcibly operated in accordance with the operation of the bucket operation lever 21A. By driving the arm directional control valve 8 of the first switching valve group, the pressure oil of the hydraulic pump 1 is supplied to the arm cylinder 46 via the arm directional control valve 8. ,
The arm cylinder 46 can be driven, and by driving the bucket directional control valve 12 included in the second switching valve group, the pressure oil of the hydraulic pump 2 is supplied to the bucket cylinder 47 via the bucket directional control valve 12. And the bucket cylinder 47 can be driven, thereby realizing a desired combined operation of the arm and the bucket.

Similarly, in the first embodiment, the switching valve 37 is connected to the pilot line for connecting the boom operation pilot valve 34B and the control chamber 11a of the boom directional control valve 11 of the first switching valve group. And a switching valve 38 is provided in a pilot line connecting the pilot valve 34C and the control chamber 11b of the boom directional control valve 11, and the second switching is performed when the bucket operating lever 21A is operated. Although the boom direction control valve 11 of the valve group is forcibly held neutral, the present invention is not limited to this configuration. That is, the switching valve 37 is not provided in the pilot line connecting the pilot valve 34B and the control chamber 11a of the boom directional control valve 11 of the second switching valve group, and the pilot valve 34C and the boom directional control valve 11 are not provided. The switching valve 38 is not provided in the pilot line communicating with the control room 11b of the
A switching valve 37 is provided in a pilot line connecting B and the control chamber 7e of the boom direction control valve 7A of the second switching valve group,
A switching valve 38 is provided in a pilot line connecting the pilot valve 34C and the control chamber 7f of the boom direction control valve 7A,
When the operation lever 21A for the bucket is operated, the boom direction control valve 7A of the second switching valve group may be forcibly held neutral.

With this configuration, during the combined operation of the boom cylinder 45 and the bucket cylinder 47, the boom direction control valve 7A of the second switching valve group is forcibly operated with the operation of the bucket operating lever 21A. The pressure oil of the hydraulic pump 2 is supplied to the boom cylinder 46 via the boom directional control valve 11 by driving the boom directional control valve 11 of the second switching valve group. By driving the boom cylinder 46 and driving the bucket directional control valve 12 included in the second switching valve group, the pressure oil of the hydraulic pump 1 allows the boom directional control valve 7A and the arm directional control The bucket cylinder 47 is provided via the valve 8, the connection passage 23, and the bucket directional control valve 12.
And the bucket cylinder 47 can be driven, whereby a desired combined operation of the boom and the bucket can be realized.

Note that such a configuration is similar to the second configuration shown in FIG.
Can be provided also in the embodiment.

[0086]

According to the first aspect of the present invention having the above-described structure, two conventional directional control valves, that is, a directional control valve for opening and closing a bucket, and a tilt operation and an opening and closing operation of a bucket are used. Instead of the directional control valve used, 1
It is only necessary to provide two bucket opening / closing directional control valves, and accordingly, the number of pipelines and the like can be reduced, and the circuit configuration for driving the bucket cylinder and the bucket opening / closing cylinder can be simplified. The manufacturing cost can be reduced, and the space required for arranging circuit components can be reduced, and the hydraulic drive device can be made compact. In addition, it is possible to reliably perform a combined drive of the front cylinder other than the bucket cylinder and the bucket cylinder, and it is possible to improve work efficiency.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a hydraulic drive device of a hydraulic shovel with a loader front according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a side view showing the appearance of a hydraulic excavator with a loader front, which is an object of the present invention.

FIG. 4 is a circuit diagram showing a conventional hydraulic drive device of a hydraulic shovel with a loader front.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Variable displacement hydraulic pump 2 Variable displacement hydraulic pump 3 Discharge displacement control means 4 Discharge displacement control means 5 Right running direction control valve (first switching valve group) 6A Bucket opening / closing cylinder (first switching valve group) 7e Control room 7f Control room 7A Directional control valve for boom (directional control valve for front)
(First switching valve group) 8 Direction control valve for arm (Direction control valve for front)
(First switching valve group) 8a Control room 8b Control room 8A Fixed throttle 9 Turning direction control valve (second switching valve group) 10 Arm direction control valve (Front direction control valve)
(Second switching valve group) 10a Control room 10b Control room 11 Boom directional control valve (front directional control valve)
(Second switching valve group) 11a Control room 11b Control room 12 Bucket directional control valve (front directional control valve)
(Second switching valve group) 12a Control room 12b Control room 12A Bucket directional control valve (front directional control valve) (second switching valve group) 13 Left traveling directional control valve (second switching valve group) 14 Pilot pump 15 Fixed throttle (pressure generating means) 16 Fixed throttle (pressure generating means) 17 Relief valve 18 Relief valve 19 Pilot valve 20 Pilot valve 21A Operation lever 21B Shuttle valve (Interlocking means) 21C Pilot line (Interlocking means) 21D Pilot line (output stopping means) (neutral holding means) 21E Pilot line (output stopping means) (neutral holding means) 22 on-off control valve 23 connection passage 24 check valve 25 check valve 26 check valve 29 tank 33A operating lever 33B pilot Valve 33C Pilot valve 34A Operation lever 34B Pilot valve 34C Pilot valve 35 Switching valve (output stopping means) (neutral holding means) 36 Switching valve (output stopping means) (neutral holding means) 37 Switching valve (output stopping means) (neutral holding means) 38 Switching valve (output stopping means) (Neutral holding means) 40 Running body 41 Revolving body 42 Boom (loader front) 43 Arm (loader front) 44 Bucket (loader front) 45 Boom cylinder (front actuator) 46 Arm cylinder (front actuator) 47 Bucket cylinder (front actuator)

Continuing from the front page (72) Inventor Tomohiko Yasuda 650, Kandachi-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura Plant (56) References JP-A-4-31630 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) E02F 9/22 F15B 11/00 F15B 11/17

Claims (8)

(57) [Claims] 1. A front actuator including a boom cylinder, an arm cylinder, and a bucket cylinder, a plurality of actuators including a bucket opening / closing cylinder, and two traveling motors, a plurality of hydraulic pumps including at least one variable displacement hydraulic pump, The traveling direction control valve which is supplied with the pressure oil from the variable displacement hydraulic pump and controls the driving of one of the two traveling motors and is arranged at the most upstream position, and the downstream of the traveling direction control valve. A first switching valve group configured by tandem-connecting a directional control valve disposed in the first switching valve group; a second switching valve group supplied with hydraulic oil from a hydraulic pump other than the variable displacement hydraulic pump; Pressure generating means provided at the most downstream side of the center bypass passage of the switching valve group, and the variable displacement hydraulic pump according to the pressure generated by the pressure generating means. A hydraulic drive device for a hydraulic shovel with a loader front, comprising: a discharge displacement control unit that controls a discharge displacement; wherein the first switching valve group controls a drive of a front actuator other than the bucket cylinder. And a bucket opening / closing directional control valve for controlling the driving of the bucket opening / closing cylinder, wherein the second switching valve group includes another front directional control valve for controlling the driving of a front actuator other than the bucket cylinder. A bucket direction control valve for controlling the driving of the bucket cylinder, the bucket being provided on the center bypass passage of the first switching valve group and upstream in the vicinity of the pressure generating means; An opening / closing control valve capable of controlling opening / closing of a bypass passage; A connection passage connecting a downstream portion of the passage and a pressure oil inflow port of a bucket directional control valve included in the second switching valve group; provided on the connection passage; A check valve that permits flow in a direction toward the second switching valve group; and a bucket direction control valve provided on a pressure oil supply passage of the bucket direction control valve of the second switching valve group. A check valve for preventing pressure oil from flowing from the connection passage into the pressure oil supply passage to the other directional control valve; an interlocking means for interlocking the open / close control valve and the bucket directional control valve; During combined driving of the front actuator other than the bucket cylinder and the bucket cylinder, the front directional control valve included in the first switching valve group, and the another front included in the second switching valve group. Hydraulic drive system for a hydraulic excavator with a loader front, characterized in that a neutral holding means for holding the force-neutral one of the directional control valve. 2. The neutral holding means stops output of a signal for switching one of the front directional control valve and the another front directional control valve in conjunction with the switching of the bucket directional control valve. The hydraulic drive device for a hydraulic shovel with a loader front according to claim 1, wherein the hydraulic drive device is an output stop unit. 3. The output stop means includes a switching valve for preventing output of pilot pressure for driving one of the front directional control valve and the another front directional control valve. 2. A hydraulic drive device for a hydraulic excavator with a loader front according to 2. 4. A front actuator other than the bucket cylinder is at least one of an arm cylinder and a boom cylinder, and the front directional control valve included in the first switching valve group drives the corresponding front actuator. At least one of an arm directional control valve to be controlled and a boom directional control valve, wherein the another front directional control valve included in the second switching valve group controls driving of a corresponding front actuator. The hydraulic drive device for a hydraulic shovel with a loader front according to any one of claims 1 to 3, wherein the hydraulic shovel is at least one of an arm directional control valve and another boom directional control valve. 5. The hydraulic drive device for a hydraulic shovel with a loader front according to claim 1, wherein said pressure generating means is a fixed throttle. 6. The hydraulic drive device for a hydraulic shovel with a loader front according to claim 1, wherein the second switching valve group includes a swing motor. 7. A device according to claim 1, further comprising a blocking means for preventing the hydraulic oil guided from said variable displacement hydraulic pump, which is guided through said connection passage, from flowing into said bucket cylinder during a dumping operation of the bucket. The hydraulic drive device for a hydraulic shovel with a loader front according to any one of claims 1 to 6. 8. The switch according to claim 7, wherein the blocking means is formed in the directional control valve for the bucket and has a switching position structure for preventing the joining of the pressure oil from the variable displacement hydraulic pump. Hydraulic drive for hydraulic excavator with loader front.