JPH0868079A - Hydraulic excavator hydraulic drive with loader front - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a hydraulic drive device for a hydraulic excavator with a loader front, which can simplify a circuit configuration for driving a bucket cylinder and a bucket opening / closing cylinder. [Configuration] Bucket opening / closing direction control valve 6A on the pump 1 side
A boom directional control valve 7A and an arm directional control valve 8 are arranged, and an arm directional control valve 10, a boom directional control valve 11 and a bucket directional control valve 12 are arranged on the pump 2 side.
The most downstream arm directional control valve 8 of the switching valve group on the pump 1 side
Of the bucket control lever 21A is provided upstream of the fixed throttle 15 arranged at the most downstream of the center bypass passage on the pump 1 side, and a connecting passage 23 for connecting the downstream side of the bucket and the bucket directional control valve 12 described above. An open / close control valve for opening and closing the center bypass passage on the pump 1 side is provided in conjunction with the switching valve 35, 36 for keeping the arm directional control valve 8 in a neutral state in conjunction with the lever 21A, and a boom directional control valve. Switching valves 37 and 38 for holding 11 in the neutral position are provided.

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 excavator with a loader front having a structure in which a bucket can be opened and closed, and more particularly to a pressure provided at the most downstream side of a center bypass passage of a switching valve group. The present invention relates to a hydraulic drive device for a hydraulic excavator with a loader front, which has a so-called negative control, which controls the discharge capacity of a variable capacity hydraulic pump based on the pressure generated by a generating means.

[0002]

2. Description of the Related Art FIG. 3 is a side view showing the external appearance of a hydraulic excavator with a loader front, which is the subject of the present invention. Generally, a hydraulic excavator with a loader front is used for the traveling body 40.
And a revolving structure 41 arranged on the traveling structure 40 and provided with a driver's cab, a boom 42 rotatably mounted on the revolving structure 41, and an arm 43 rotatably connected to the boom 42. , Rotatably connected to this arm 43,
Moreover, it is provided with a bucket 44 that can be opened and closed. The boom 42, the arm 43, and the bucket 44 described above form a loader front.

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 structure 41 revolves on the traveling structure 40 by the revolving motor. The boom 42 rotates in a rising direction by driving the boom cylinder 45 to extend, and rotates in a descending direction by driving the boom cylinder 45 to contract. Arm 43
Also, for example, the arm cylinder 46 is rotated so as to extend from the state shown in FIG. Bucket 44
For example, when the bucket cylinder 47 is driven so as to extend from the state shown in FIG. 3, the bucket cylinder 47 is rotated upward (tilt operation), and when the bucket cylinder 47 is driven so as to contract, the bucket cylinder 47 is rotated downward (dump operation). ) Do. Further, the bucket 44 is divided into an open state by driving the bucket opening / closing cylinder so as to extend, and returns to the closed state by driving so as to contract the bucket opening / closing cylinder. The boom cylinder 45, the arm cylinder 46, and the bucket cylinder 47 described above form a front actuator.

In this hydraulic excavator with a loader front, which will be described in detail later, for example, the bucket opening / closing cylinder is driven to contract to close the bucket 44, and the boom 42, the arm 43, and the bucket 44 are appropriately rotated. Thus, the earth and sand are excavated, and the earth and sand are accumulated on the bucket 44. Then, for example, while rotating the revolving structure 41, the boom 42 and the arm 43 are raised to position the bucket 44 above the loading platform of the truck (not shown), and in this state, the bucket opening / closing cylinder is driven to extend, so that the bucket 44 moves. The soil that has been opened and accumulated in the bucket 44 is dumped onto the bed of the truck. Thus, excavation work of earth and sand can be performed.

FIG. 4 is a circuit diagram showing a conventional hydraulic drive system 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 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, in the uppermost stream, for example, a right traveling directional control valve 5 for controlling the drive of the above-described right traveling motor is arranged, and for the boom for controlling the drive of the boom cylinder 45 downstream thereof. The directional control valve 6, the directional control valve 7 that is selectively utilized when the bucket 44 is tilted or when the bucket 44 is opened and closed, and the arm cylinder 4
The directional control valve 8 for arm which controls the drive of 6 is tandem-connected. Boom direction control valve 6 and direction control valve 7
And the arm directional 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 right traveling directional control valve 5, the boom directional control valve 6, the directional control valve 7, and the arm directional control valve 8 described above. A group is made up.

On the hydraulic pump 2 side, the swing directional control valve 9 for controlling the drive of the swing motor, the arm directional control valve 10 for controlling the drive of the arm cylinder 46, and the drive of the boom cylinder 45 are controlled. A boom directional control valve 11, a bucket directional control valve 12 for expanding and contracting the bucket cylinder 47, and a left traveling directional control valve 13 for controlling the drive 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 traveling direction control valve 13 are connected in parallel with each other. , These directional control valves 9, 10, 11, 12,
The second hydraulic pressure pump 2 supplies the pressure oil from the second hydraulic pressure pump 13.
The switching valve group of is constituted.

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

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

The operation lever 21A for switching the directional control valve 12 for the bucket and the directional control valve 7 belonging to the above-mentioned second switching valve group and the operation direction of the operation lever 21A are different from each other. The directional control valve 12 for the bucket is reduced as the pilot pressure by reducing the pressure of 14.
The pilot valve 19 or the pilot valve 20 for outputting to the control chamber 12a or the control chamber 12b, and the shuttle valve 21B for selectively extracting the pilot pressure generated by the pilot valves 19 and 20. The pilot pressure taken out by the shuttle valve 21B is guided to one control chamber 7b of the directional control valve 7 via the pilot conduit 7d.

The operation lever 31A for switching the directional control valve 31 for opening and closing the bucket and the operation direction of the operation lever 31A differ from each other in the pilot pump 14.
Of the bucket opening / closing direction control valve 31 to the control chamber 31a or the control chamber 31b of the bucket opening / closing direction control valve 31 or the pilot valve 27 or 28.
And a shuttle valve 31B that selectively takes out the pilot pressure generated by these pilot valves 27 and 28. The pilot pressure taken out by the shuttle valve 31B is guided to the other control chamber 7a of the directional control valve 7 via the pilot conduit 7c and the pilot conduit 32
It is led to the drive part of the switching valve 32 provided in the above-mentioned pilot conduit 7d via c. In the switching valve 32, the upper stage position shown in FIG. 4 is the switching position where the pilot pipe line 7d is in the communicating state, and the lower stage position is the switching position where the pilot pipe line 7d is connected to the tank 32.

In FIG. 4, the right traveling directional control valve 5, the boom directional control valve 6, the arm directional control valve 8 belonging to the first switching valve group, and the swivel belonging to the second switching valve group. An operation device including an operation lever for switching the direction control valve 9, the arm direction control valve 10, the boom direction control valve 11, and the left traveling direction control valve 13 is not shown.

The tilting operation, dumping 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 direction control valve 31 is in a neutral state and the bucket 44 is closed at this time. When excavating the earth and sand, the excavation operation, that is, the tilt operation illustrated in FIG. 3 described above is performed.

In this case, the operation lever 21A shown in FIG. 4 is tilted counterclockwise in FIG. As a result, the pilot valve 19 operates, the generated pilot pressure is applied 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 in the pilot valve 19 is taken out from the shuttle valve 21B, guided to the pilot conduit 7d, and given to the control chamber 7b of the directional control valve 7. As a result, 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 portion becomes smaller, which results in discharge. The capacity control means 4 operates to increase the discharge capacity of the hydraulic pump 2, and the flow rate supplied to the second switching valve group increases. This flow rate is supplied to the outflow port through the left position of the bucket directional control valve 12 in FIG. Similarly, the center bypass passage of the first switching valve group is gradually closed due to the switching operation of the directional control valve 7 described above, and the value of the pressure generated in the fixed throttle 15 portion is reduced, whereby the discharge capacity control is performed. 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 through the right position of the directional control valve 7 in FIG.
It joins the outflow port of the directional control valve 12 for buckets described above. 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 is operated so as to extend, a desired tilting operation is performed, the earth and sand are dug up, and the earth and sand are piled up on the bucket 44.

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

When the bucket 44 is moved to a predetermined dumping position, the operating lever 31A is moved in order to dump the bucket.
The operation of tilting counterclockwise 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 given to the drive unit of the switching valve 32 via the pilot pipe 32c, the switching valve 32 is switched to the lower position in FIG. 4 in accordance with this, and the pilot pipe 7d communicates with the tank 29. . Further, the pilot pressure described above is applied to the control chamber 7a of the directional control valve 7 via the pilot conduit 7c, and the directional control valve 7 is switched to the left position in FIG. Therefore, the outflow port on the left side of the directional control valve 7 is
Connect to 4b. At the same time, the pilot pressure generated in 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.

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

At this time, when the tilting operation or the dumping operation of the bucket 44 is simultaneously performed, the operation lever 21 is operated together with the operation of the operation lever 31A.
It suffices to operate A. Due to the pilot pressure generated by the operation of the pilot valve 19, the bucket directional control valve 12
Is switched to the left position to perform the tilting operation as described above, or the bucket directional control valve 12 is operated 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 at the same time.

Further, when the soil discharging as described above is completed, the operation lever 31A is tilted in the clockwise direction in FIG. 4, the pilot valve 28 is operated, and the generated pilot pressure is transmitted via the shuttle valve 31B. And pilot line 32
c, the switching valve 32 is guided to the pilot line 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. At the same time, the pilot pressure is controlled to open and close the bucket. The bucket 31 is provided to the control chamber 31b of the valve 31, and the bucket opening / closing direction control valve 31 is switched to the right position in FIG. As a result, the pressure oil from the hydraulic pump 1 is supplied to the rod side of the bucket opening / closing cylinder (not shown) via the left position of the directional control valve 7, the conduit 14b, and the right position of the bucket opening / closing directional control valve 31. The bucket opening / closing cylinder operates so as to contract, and the bucket 44 is closed. In this way, when the bucket 44 is closed, the operation of returning the operation lever 31A to the neutral position is performed. As a result, the bucket opening / closing direction control valve 31 and the direction control valve 7 are returned to the neutral position. The switching valve 32 also returns to the upper position, which is the neutral position, and the pilot conduit 7d is in the communicating state.

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

The dumping operation of the bucket 44 is performed by tilting the operating lever 21A in the clockwise direction in FIG. 4 as mentioned above. As a result, the pilot valve 20 operates, the generated pilot pressure is applied 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.
Along with this, pressure oil from the hydraulic pump 2 is supplied to the rod side of the bucket cylinder 47 shown in FIG. 3 via the right position of the bucket directional control valve 12, and the bucket cylinder 4
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 pipe line 7d, the directional control valve 7 is switched to the right position, and the pressure oil from the hydraulic pump 1 is piped. However, since the bucket directional control valve 12 is switched to the right position at this time, the pipeline 14a communicates with the tank 29, so that the pressure oil discharged from the hydraulic pump 1 is supplied to the hydraulic pump 2.
It is returned to the tank 29 without being joined with the pressure oil from.

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 pressure oil of the hydraulic pump 2 are merged and the bucket cylinder 4
By supplying to the head side of No. 7, a large excavation force can be obtained, and a relatively high operating speed equivalent to the case where the pressure 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 for the hydraulic excavator with the loader front configured as described above, a complicated circuit configuration for driving the 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 the hydraulic drive device cannot be made compact.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and an object thereof is to simplify the circuit configuration for driving the bucket cylinder and the bucket opening / closing cylinder, and moreover, to be almost the same as the prior art. An object of the present invention is to provide a hydraulic drive device for a hydraulic excavator with a loader front, which can obtain equivalent functions.

[0028]

In order to achieve this object, the invention according to claim 1 of the present invention is a boom cylinder,
A front actuator including an arm cylinder and a bucket cylinder, a bucket opening / closing cylinder, and a plurality of actuators including two traveling motors, at least one
A plurality of hydraulic pumps, including one variable displacement hydraulic pump, and pressure oil from the variable displacement hydraulic pump are supplied, and the drive of one of the two traveling motors is controlled to drive the uppermost stream. A first switching valve group in which a directional control valve and a directional control valve arranged downstream of the traveling directional control valve are connected in tandem, and pressure oil is supplied from a hydraulic pump other than the variable displacement hydraulic pump. The second switching valve group, the pressure generating means provided at the most downstream side of the center bypass passage of the first switching valve group, and the 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 excavator with a loader front, which comprises a discharge capacity control means for controlling the capacity, the first switching valve group controls driving of a front actuator other than the bucket cylinder. Front directional control valve and a bucket opening / closing directional control valve that controls driving of the bucket opening / closing cylinder, and the second switching valve group controls another driving of front actuators other than the bucket cylinder. A front directional control valve and a bucket directional control valve for controlling the drive of the bucket cylinder are included, and on the center bypass passage of the first switching valve group, in the vicinity of the pressure generating means. An opening / closing control valve capable of controlling opening / closing of the center bypass passage, a downstream portion of the pressure oil supply passage of the most downstream directional control valve of the first switching valve group, and the second switching valve group. A connection passage connecting the pressure oil inflow port of the included bucket directional control valve and a connection passage provided on the connection passage and directed from the first switching valve group toward the second switching valve group To the directional control valve other than the directional control valve for the bucket, which is provided on the pressure oil supply passage of the directional control valve for the bucket of the check valve and the directional control valve for the second switching valve group. A check valve for preventing the pressure oil from flowing into the passage from the connection passage, an interlocking device for interlocking the opening / closing control valve and the bucket directional control valve, the 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 other front directional control valve included in the second switching valve group is forcibly neutralized. And a neutral holding means for holding.

[0029]

Since the invention according to claim 1 of the present invention is configured as described above, when the bucket tilting operation is performed, for example, the bucket directional control valve belonging to the second switching valve group is It suffices to switch to a predetermined switching position capable of supplying pressure oil to the head side of the cylinder.
As a result, the opening / closing control valve provided on the center bypass passage of the first switching valve group operates via the interlocking device so as to close the center bypass passage. Along with this, the value of the pressure generated by the pressure generating means arranged downstream of the opening / closing control valve becomes smaller, and the discharge capacity control means operates so as to increase the discharge capacity of the variable displacement hydraulic pump. The flow rate from the variable displacement hydraulic pump is given to the bucket directional control valve belonging to the second switching valve group via the connection passage, and the pressure oil from the variable displacement hydraulic pump on the first switching valve group side and the second
The pressure oil from the hydraulic pump on the side of the switching valve group is combined and supplied to the bucket directional control valve, and further supplied to the head side of the bucket cylinder, which extends the bucket cylinder to perform the desired tilting operation. Can be made.

When the dumping operation is performed, the bucket directional control valve belonging to the second switching valve group is
It suffices to switch to a different switching position that enables the supply of pressure oil to the rod side of the bucket cylinder. 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 of the second switching valve group are joined and supplied to the bucket directional control valve. The operation is the same as the above-described tilt operation. During this dumping operation, the pressure oil supplied to the bucket directional control valve is given to the rod side of the bucket cylinder via the different switching positions described above, and the bucket cylinder may contract to perform a desired dumping operation. it can.

In this case, if it is considered that a blocking means for blocking the inflow of the pressure oil introduced into the connection passage into the bucket directional control valve is taken into consideration, the hydraulic pressure on the second switching valve group side during this 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 almost the same as that during the tilting operation.

In addition, during the tilting operation or the like, the pressure oil supplied from the variable displacement hydraulic pump through the connection passage is on 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
The directional control valves other than the bucket directional control valve are regulated so as not to flow, so that the actuators other than the bucket cylinder are not affected.

For example, when the opening / closing operation of the bucket is performed, the bucket opening / closing directional control valve 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 is reduced, and the discharge capacity control means operates so as to increase the discharge capacity of the variable displacement hydraulic pump. To do. The flow rate from the variable displacement hydraulic pump is supplied to the bucket opening / closing cylinder via the bucket opening / closing direction control valve, and the desired bucket opening / closing operation can be performed.

When the bucket dumping operation or the tilting operation is simultaneously performed during the bucket opening / closing operation, the bucket opening / closing directional control valve belonging to the first switching valve group and the second switching valve group belonging to the first switching valve group. The bucket directional control valve 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 direction control valve, and the bucket opening / closing cylinder can be actuated accordingly, while the pressure oil on the second switching valve group side is operated. The pressure oil of the hydraulic pump is supplied to the bucket directional control valve, and the bucket cylinder can be actuated in response to this, and a desired combined operation can be performed.

Further, when the front actuator other than the bucket cylinder, for example, the combined drive of the arm cylinder and the bucket cylinder is performed, the neutral direction holding means forcibly holds the arm directional control valve included in the first switching valve group at the neutral position. It Along with this, the pressure oil of the variable displacement hydraulic pump on the first switching valve group side is transferred to the bucket direction included in the second switching valve group via the arm directional control valve in the neutral state and the connection passage. The bucket cylinder can be driven by supplying the control cylinder with the control valve, and the pressure oil of the hydraulic pump on the second switching valve group side is supplied to the arm cylinder via the arm directional control valve. It can be driven, and a desired combined operation of the arm and bucket can be realized.

When the arm cylinder and the bucket cylinder are combinedly driven as described above, another front directional control valve of the second switching valve group including the bucket cylinder by the neutral holding means, that is, another directional control valve for the arm is used. It can be forcibly held neutral. In this case, the first
By driving the front directional control valve, that is, the arm directional control valve included in the directional control valve group, the pressure oil of the variable displacement hydraulic pump on the first directional control valve side is supplied to the arm cylinder via the arm directional control valve. However, the arm cylinder can be driven, and by driving the bucket directional control valve included in the second switching valve group, the second switching valve group can be driven.
The pressure oil of the hydraulic pump on the side of the switching valve group can be supplied to the bucket cylinder via the bucket directional control valve to drive the bucket cylinder, and thus desired combined operation of the arm and bucket can be realized. . The composite drive as described above can be similarly performed even when the front actuator other than the bucket cylinder is the boom cylinder.

As described above, according to the first aspect of the present invention, the two conventional directional control valves, namely, the directional control valve for opening and closing the bucket, and the directional control valve utilized for the tilting operation and the opening / closing operation of the bucket are provided. Instead, only one bucket opening / closing direction control valve needs to be provided, and along with this, it is possible to reduce the number of pilot pipes and the like, and the circuit configuration for driving the bucket cylinder and the bucket opening / closing cylinder can be simplified.

Further, it is possible to surely realize a combined drive of the front actuator other than the bucket cylinder, that is, the arm cylinder, the boom cylinder, and the bucket cylinder, and to improve the efficiency of the work performed through these actuators. You can

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic drive system for a hydraulic excavator 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 system for a hydraulic excavator with a loader front corresponding to claims 1, 2, 3, 4, 5, and 6 of the present invention. This first embodiment is
The hydraulic excavator with a loader front as shown in FIG. 3 is provided. Further, FIG. 1 is drawn corresponding to FIG. 4 described above, and those equivalent to 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 is used.
And a variable displacement hydraulic pump 2. The discharge capacity of the hydraulic pump 1 is controlled by the discharge capacity control means 3, and 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 travel direction control valve 5 for controlling the drive of the right travel motor is arranged in the most upstream, and a bucket opening / closing direction for controlling the drive of the 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 direction control valve 6A, the boom direction control valve 7A, 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 supplied by the right traveling directional control valve 5, the bucket opening / closing directional control valve 6A, the boom directional control valve 7A, and the arm directional control valve 8 described above. A group is made up. The boom directional control valve 7A and the arm directional control valve 8 described above constitute a front directional control valve that controls the drive of the front actuator.

On the hydraulic pump 2 side, a turning direction control valve 9 for controlling the driving of the turning motor, and an arm direction control valve 10 for controlling the driving of the arm cylinder 46 shown in FIG.
A boom direction control valve 11 that controls the drive of the boom cylinder 45, a bucket direction control valve 12 that expands and contracts the bucket cylinder 47, and a left travel direction control valve 13 that controls the drive of the left travel 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 traveling 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 arm directional control valve 10, the boom directional control valve 11 and the bucket directional control valve 12 described above constitute a front directional control valve that controls the drive of the front actuator.

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

Further, the operating lever 21A for switching the bucket directional control valve 12 belonging to the above-mentioned second switching valve group.
And the pilot valve 19 or the pilot valve 20 for reducing the pressure of the pilot pump 14 and outputting it as pilot pressure to the control chamber of the bucket directional control valve 12 due to the difference in the operating direction of the operating lever 21A. A shuttle valve 21B for selectively taking out the pilot pressure generated by the pilot valves 19 and 20 is provided.

On the upstream side in the vicinity of the fixed throttle 15 provided on the most downstream side of the center bypass passage of the first switching valve group, the opening / closing control valve 22 capable of controlling the opening / closing of this center bypass passage.
Is provided. The opening / closing control valve 22 keeps the center bypass passage open when it is neutral, and is driven by the pilot pressure taken out by the shuttle valve 21B and guided by the pilot conduit 21C to close the center bypass passage. The shuttle valve 21B and the pilot conduit 21C described above constitute an interlocking device that interlocks the opening / closing control valve 22 and the bucket directional control valve 12.

Further, the most downstream directional control valve 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 bucket directional control included in the second switching valve group. A connection passage 23 that connects the pressure oil inflow port of the valve 12 and a connection passage 23 that is provided on the connection passage 23 and allows a flow in the direction from the first switching valve group to the second switching valve group.
A check valve 24 that blocks a reverse flow in the 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 directional control valve 12 are provided. The pressure oil supply passage to the direction control valve is provided with check valves 25 and 26 for preventing the pressure oil from the connection passage 23 from flowing in.

The operation lever 33A for switching the arm directional control valves 8 and 10 and the 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 it. , 33C
And an operating lever 34A for switching the boom directional control valves 7A and 11, and pilot valves 34B and 34C that operate according to the difference in the operating direction of the operating lever 34A and that can reduce the pressure of the pilot pump 14 and output. Is equipped with.

Further, a bucket is provided in the pilot line connecting the pilot valve 33B for switching the arm directional control valves 8 and 10 and the control chamber 8a of the arm directional control valve 8 included in the first switching valve group. A means for stopping the output of the signal for switching the arm directional control valve 8 to the left position in FIG. 1, in synchronism with the switching of the directional control valve 12, namely, is taken out from the shuttle valve 21B and is connected to the pilot conduit 21D. A switching valve 35 for driving the arm directional control valve 8 to switch the arm directional control valve 8 to the left position in FIG. In the neutral state in which the pilot pressure is not guided to the pilot conduit 21D, the switching valve 35 is held at a position for communicating the pilot conduit connecting the pilot valve 33B and the control chamber 8a of the arm directional control valve 8 with each other. In addition, the pilot line 21D
When the pilot pressure is guided to and switched to, the pilot line that connects the pilot valve 33B and the control chamber 8a of the arm directional control valve 8 is held at a position that connects to the tank 29.

Similarly, a pilot valve 33C for switching the arm directional control valves 8 and 10 and a pilot line connecting the control chamber 8b of the arm directional control valve 8 included in the first switching valve group are connected to each other. A means for stopping the output of the signal for switching the arm directional control valve 8 to the right position in FIG. 1 in synchronism with the switching of the bucket directional control valve 12, that is, taken out from the shuttle valve 21B, is connected to the pilot line. A switching valve 36 that drives the arm directional control valve 8 to the right position in FIG. 1 and that blocks the output of pilot pressure that is driven by the pressure introduced via 21D is provided. In the neutral state where the pilot pressure is not guided to the pilot conduit 21D, the switching valve 36 is held at a position for communicating the pilot conduit connecting the pilot valve 33C with the control chamber 8b of the arm directional control valve 8, In addition, the pilot line 21D
When the pilot pressure is guided to and switched to, the pilot line that connects the pilot valve 33C and the control chamber 8b of the arm directional control valve 8 is held at a position that connects to the tank 29.

In addition, a bucket is provided in a pilot line connecting the pilot valve 34B for switching the boom directional control valves 7A and 11 and the control chamber 11a of the boom directional control valve 11 included in the second switching valve group. A means for stopping the output of the signal for switching the boom directional control valve 11 to the left position in FIG. 1, in synchronism with the switching of the directional control valve 12, namely, is taken out from the shuttle valve 21B and is connected to the pilot conduit 21D. , 21E to drive the boom directional control valve 11 to the left position in FIG. 1 and to prevent the pilot pressure from being output. The switching valve 37 is provided with the pilot valve 3 in the neutral state where the pilot pressure is not guided to the pilot conduit 21E.
4B and the control chamber 11a of the boom directional control valve 11 are held in a position for communicating with each other, and when pilot pressure is guided to the pilot line 21E and switched, the pilot valve 34B and boom The pilot conduit connecting the control chamber 11a of the directional control valve 11 is held at a position where it connects to the tank 29.

Similarly, a pilot valve 34C for switching the boom directional control valves 7A and 11 and a pilot conduit connecting the control chamber 11b of the boom directional control valve 11 included in the second switching valve group are connected to each other. In connection with the switching of the bucket directional control valve 12, the boom directional control valve 11 is set in the same manner as in FIG.
1 means for stopping the output of the signal for switching to the right position, that is, the boom directional control valve 11 is driven by the pressure taken out from the shuttle valve 21B and guided through the pilot conduits 21D and 21E. A switching valve 38 for blocking the output of the pilot pressure for switching to the right position is provided. The switching valve 38 operates in the neutral state where the pilot pressure is not guided to the pilot conduit 21E.
4C and the control chamber 11b of the boom directional control valve 11 are held at a position for communicating with each other, and when the pilot pressure is guided to the pilot conduit 21E and switched, the pilot valve 34C and the boom The pilot line connecting the directional control valve 11 and the control chamber 11b is held at a position where it connects to the tank 29.

A pilot conduit 21D connected to the above-mentioned shuttle valve 21B, a pilot conduit 21E connected to this pilot conduit 21D, and switching valves 35, 36,
The output stopping means including 37 and 38 is the bucket cylinder 4
Front actuators other than 7 (arm cylinder 4
6. When the boom cylinder 45) and the bucket cylinder 47 are combinedly driven, the front directional control valve (the arm directional control valve 8, the boom directional control valve 7A) included in the first switching valve group, and the second directional control valve. Neutral holding means for forcibly holding one of the corresponding front directional control valves of the other front directional control valves (arm directional control valve 10, boom directional control valve 11) included in the switching valve group at the neutral position. Are configured.

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

Even in the first embodiment shown in FIG. 1, the right traveling directional control valve 5 belonging to the first switching valve group and the turning directional control valve belonging to the second switching valve group. 9. An operation device including an operation lever for switching the left traveling directional control valve 13 is not shown. Further, in FIG. 1, 2
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 the bucket 44 is tilted, the operation lever 21A is tilted counterclockwise in FIG. 1 to operate the pilot valve 19 to operate the bucket valve belonging to the second switching valve group. Control valve 12
Should be switched to the left position in FIG. 1 where 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 becomes small, and the discharge capacity control means 4 operates so as to increase the discharge capacity of the hydraulic pump 2. However, the flow rate thus increased is applied to the bucket directional control valve 12. At the same time, the pilot pressure generated along with the operation of the pilot valve 19 is taken out from the shuttle valve 21B, guided to the pilot conduit 21C, and given 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. Along with this, 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 so as to increase the discharge capacity of the hydraulic pump 1. The flow rate of the hydraulic pump 1 thus increased 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 pressure oil merged between 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.

Further, for example, when the dumping operation of the bucket 44 is performed, the operation lever 21A is operated so as to be tilted clockwise in FIG. 1 to operate the pilot valve 20, and for the bucket belonging to the second switching valve group. It is sufficient to switch the direction control valve 12 to the right position in FIG. 1 in which pressure oil can be supplied to the rod side of the bucket cylinder 47. As a result, the center bypass passage of the second switching valve group on the hydraulic pump 2 side is closed, the value of the pressure generated at the fixed throttle 16 becomes small as described above, and the discharge capacity control means 4 causes the discharge of the hydraulic pump 2 to be reduced. It operates to increase the capacity, and the increased flow rate is given to the bucket directional control valve 12. At this time, at the same time, the pilot pressure generated by the operation of the pilot valve 20 is taken out from the shuttle valve 21B, guided to the pilot pipe 21C, and the switching valve 22 is switched to the closed position. Along with this, the center bypass passage of the first switching valve group on the hydraulic pump 1 side is closed, and the fixed throttle 15
The value of the pressure generated in the discharge capacity control means 3 becomes small.
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 joins 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 tilt operation and dump operation,
The pressure oil supplied from the hydraulic pump 1 through the connection passage 23 is supplied to the check valve 24 provided in the connection passage 23 and the check valves 25 and 26 provided on the pressure oil supply passage of the bucket directional control valve 12. Is regulated so as not to flow to the directional control valves other than the bucket directional control valve, so that the actuators other than the bucket cylinder 47 are not affected.

Further, 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 this first switching valve group is closed, the value of the pressure generated in the fixed throttle 15 becomes small, and the discharge capacity control means 3 operates so as to increase the discharge capacity of the hydraulic pump 1. To 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 the desired opening / closing operation of the bucket 44 can be performed.

Further, when the dumping operation or the tilting operation of the bucket 44 is simultaneously performed during the opening / closing operation of the bucket 44, the bucket opening / closing directional 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 pressure 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 pressure oil of the hydraulic pump 1 on the first switching valve group side is not supplied. Is supplied to the bucket opening / closing direction control valve 6A,
In response to this, the bucket opening / closing cylinder can be operated, while the pressure 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. The desired composite operation can be performed.

In the case of a relatively frequent combined operation of the swing motor and the bucket opening / closing cylinder, the swing directional 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. No, since the bucket opening / closing directional control valve 6A for controlling the drive of the bucket opening / closing cylinder is included in the first switching valve group on the hydraulic pump 1 side, pressure oil of the hydraulic pump 2 is supplied to the swing motor. The bucket opening / closing cylinder can be driven by supplying the hydraulic oil of the hydraulic pump 1 to the bucket opening / closing cylinder, whereby a desired combined operation of the 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.
One of the pilot valves 19 and 20 is operated in accordance with the operation of 1A, 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 It is switched to the left position or the right position in FIG. In addition, the operation lever 33
Along with the operation of A, one of the pilot valves 33B and 33C is activated and pilot pressure is generated.

At this time, the pilot pressure generated by the operation of the operation lever 21A is taken out from the shuttle valve 21B and given to the drive section of the opening / closing control valve 22 via the pilot conduit 21C. 22 is switched to the closed position. At the same time, pilot pressure is introduced from the shuttle valve 21B to the pilot conduits 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.
With the switching valves 35 and 36, the control chambers 8a and 8b of the arm directional control valve 8 included in the first switching valve group are connected to the tank 2.
9 for which the directional control valve 8 for the arm is kept neutral.

Therefore, the pilot pressure generated by the operation of the operation lever 33A is applied to any one of the control chambers 10a and 10b of the arm directional control valve 10 included in the second switching valve group. The arm directional 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 in the fixed throttle 16 becomes small as described above, and the hydraulic pump 2
The flow rate increased from is discharged to the arm cylinder 46 through the arm directional 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 in the fixed throttle 15 becomes small as described above, and the 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 of each directional control valve of the first switching valve group, the connection passage 23, and the check valve 24. The bucket cylinder 47 is supplied from the valve 12 and can be driven.

In this way, the bucket cylinder 47 is driven by the pressure oil from the hydraulic pump 1, and the arm cylinder 46
Can be driven by the pressure oil from the hydraulic pump 2, and the desired combined driving of the arm cylinder 46 and the bucket cylinder 47 can be reliably performed.

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 operating lever 21A and the operating lever 34A are simultaneously operated, but first, one of the pilot valves 19 and 20 is operated in accordance with the operation of the operating lever 21A, and the generated pilot pressure causes the bucket directional control valve to operate. It is supplied to the control chamber 12a or the control chamber 12b of 12 and this directional control valve 12 for buckets is switched to the left position or the right position of FIG. In addition, the operating lever 3
With the operation of 4A, one of the pilot valves 34B and 34C is activated and pilot pressure is generated.

At this time, the pilot pressure generated by the operation of the operation lever 21A is taken out from the shuttle valve 21B and given to the drive unit of the opening / closing control valve 22 via the pilot conduit 21C. 22 is switched to the closed position. At the same time, pilot pressure is introduced 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.
By the switching valves 37 and 38, the control chambers 11a and 11b of the arm directional control valve 11 included in the second switching valve group are connected to the tank 29, so that the boom directional control valve 11 is kept neutral. .

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

By switching the directional control valve 12 for buckets described above, the pressure generated in the fixed throttle 16 becomes small,
The 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, and the bucket cylinder 47 can be driven.

Further, by switching the opening / closing control valve 22 described above, the pressure generated in the fixed throttle 15 becomes small, and the increased flow rate is discharged from the hydraulic pump 1, and this flow rate is the first
It is supplied to the boom directional control valve 7A of the switching valve group, and further supplied to the boom cylinder 45, and the boom cylinder 45 can be driven.

In this way, the bucket cylinder 47 is driven by the pressure oil from the hydraulic pump 2, and the boom cylinder 45 is driven.
Can be driven by the pressure oil from the hydraulic pump 1, and the desired combined driving of the boom cylinder 45 and the bucket cylinder 47 can be reliably performed.

In the first embodiment thus constructed, the conventional two directional control valves shown in FIG. 4, that is, the bucket opening / closing directional control valve 31 and the tilting and opening / closing operations of the bucket 44 are utilized. A circuit for driving the bucket cylinder 47 and the bucket opening / closing cylinder can be achieved by only providing one bucket opening / closing directional control valve 7A instead of the directional control valve 7. The configuration can be simplified. As a result, the manufacturing cost can be reduced, and the space required for arranging the above-mentioned circuit components can be small, so that the hydraulic drive device can be made compact.

Further, the switching valves 35 and 36 which operate to hold the arm directional control valve 8 of the first switching valve group in a neutral state are interlocked with the operation of the operation lever 21A for switching the bucket directional control valve 12. Since it is provided, the boom direction control valve 11 of the second switching valve group is also linked to the operation of the operation lever 21A that switches the bucket direction control valve 12.
Since the switching valves 37 and 38 that operate so as to maintain the neutral state of the bucket cylinder 47 and the arm cylinder 4 are provided.
The combined drive of 6 and the combined drive of the bucket cylinder 47 and the boom cylinder 45 can be reliably performed,
The work efficiency can be improved.

FIG. 2 is a circuit diagram showing a second embodiment corresponding to claims 4 and 5 of the present invention. In the second embodiment, a blocking means is provided for blocking the merging of the pressure oil from the hydraulic pump 1 guided through the connection passage 23 into the bucket cylinder 47 during the dumping operation of the bucket 44. The blocking means has a switching position structure of the bucket directional control valve 12A. That is, in this second embodiment, the bucket directional control valve 12 has four ports, and the right position in FIG. 2 is the switching position for preventing the pressure oil from merging from the hydraulic pump 1 and the bucket 44. The switch is in the switching position for the dump operation. The left position in FIG. 2 is the hydraulic pump 1.
It is a switching position that allows the merging of the pressure oil from the above, 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. 1 described above.

In the second embodiment thus constructed, the pressure oil obtained by merging the hydraulic pump 1 and the hydraulic pump 2 is supplied to the head side of the bucket cylinder 47 during the tilting operation, and the bucket cylinder 47 moves during the dumping operation. Since the pressure oil of only the hydraulic pump 2 is supplied to the rod side having a pressure receiving area of about 1/2 that of the head side, the operating speeds during the tilting operation and the dumping operation can be made substantially the same.
Other operational effects are the same as those of the first embodiment described above.

In each of the above embodiments, the hydraulic pump 1,
The discharge volume control means 3 and 4 for controlling the discharge volume of No. 2 are hydraulic drive type discharge volume control means which operate in accordance with 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, and the discharge volume control means 3 and 4 are configured by electrically driven discharge volume control means. A configuration may be adopted in which the corresponding discharge volume control means is driven according to the output signal.

Further, in the above embodiment, the pilot valve 19 or the pilot valve 2 is operated as an operating device for the bucket directional control valves 12, 12A in accordance with the operation of the operating lever 21A.
0 is operated to generate a pilot pressure, and a hydraulic operating device is provided, and the opening / closing control valve 22 is switched according to the pilot pressure output from the hydraulic operating device. However, the present invention is configured in this way. It is not limited to that.
That is, the operation device described above is configured by an electric operation device having an electric lever, the opening / closing control valve 22 is formed by a solenoid 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, the opening / closing control valve 22 is configured by a hydraulic drive type opening / closing control valve, and between the electric operating device and the opening / closing control valve 22, An electric / hydraulic pressure converting means 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 outputted from the electric / hydraulic converting means.

Similarly, in the above embodiment, the switching valves 35, 36, 37, 38 are switched according to the pilot pressure, but the present invention is not limited to such a configuration. That is, the operation device described above is configured by an electric operation device having an electric lever, and the switching valves 35, 3 are provided.
6, 37, 38 are solenoid valves, and the switching valves 35, 36, 3 are selected according to signals output from the electric operating device.
A configuration in which 7, 38 can be switched may be used.

Further, particularly in the above-described first embodiment, the switching valve 35 is connected to the pilot line connecting the pilot valve 33B for operating the arm and the control chamber 8a of the arm directional control valve 8 of the first switching valve group. Is provided and a switching valve 36 is provided in a pilot line that connects the pilot valve 33C and the control chamber 8b of the arm directional control valve 8 described above.
Although the arm directional control valve 8 of the first switching valve group is forcibly held in the neutral position when 1A is operated, the present invention is not limited to this structure. That is, the switching valve 3 is connected to the pilot line connecting the pilot valve 33B and the control chamber 8a of the arm directional control valve 8 of the first switching valve group.
5 is not provided, and the switching valve 36 is not provided in the pilot line that connects the pilot valve 33C and the control chamber 8b of the directional control valve 8 for arm, and the pilot valve 33B and the direction for arm of the second switching valve group are not provided. A switching valve 35 is provided in a pilot line that connects the control valve 10 to the control chamber 10a, and the pilot valve 3
3C and the control chamber 10b of the arm directional control valve 10 is provided with a switching valve 36, and when the bucket operating lever 21A is operated, the arm directional control of the second switching valve group is performed. The valve 10 may be forcibly held in the neutral position.

With this structure, during the combined operation of the arm cylinder 46 and the bucket cylinder 47, the arm directional control valve 10 of the second switching valve group is forcibly driven by the operation of the bucket operation lever 21A. 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 by driving the arm directional control valve 8 of the first switching valve group. ,
This 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 transferred to the bucket cylinder 47 via the bucket directional control valve 12. Can be driven to drive the bucket cylinder 47, whereby a desired combined operation of the arm and the bucket can be realized.

Similarly, in the first embodiment described above, the switching valve 37 is connected to the pilot line connecting the boom operating pilot valve 34B and the control chamber 11a of the boom directional control valve 11 of the first switching valve group. Is provided 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 described above, and the second switching is performed when the bucket operation lever 21A is operated. Although the boom direction control valve 11 of the valve group is forcibly held in the neutral position, the present invention is not limited to this structure. 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 connecting the control chamber 11b of the
A switching valve 37 is provided in a pilot line that connects B and the control chamber 7e of the boom directional 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 directional control valve 7A.
The boom directional control valve 7A of the second switching valve group may be forcibly held neutral when the bucket operating lever 21A is operated.

With such a configuration, during the combined operation of the boom cylinder 45 and the bucket cylinder 47, the boom directional control valve 7A of the second switching valve group is forced along with the operation of the bucket operation lever 21A. Of the second switching valve group, the pressure oil of the hydraulic pump 2 is supplied to the boom cylinder 46 via the boom direction control valve 11 by driving the boom direction control valve 11 of the second switching valve group. The boom 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 1 is controlled by the boom directional control valve 7A and the arm directional control. Bucket cylinder 47 via valve 8, connecting passage 23, and bucket directional control valve 12
The bucket cylinder 47 can be driven and the desired combined boom and bucket operation can be realized.

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

[0086]

According to the invention described in claim 1 of the present invention, since it has the above-mentioned structure, two conventional directional control valves, that is, a directional control valve for opening and closing a bucket, and a tilting operation and an opening and closing operation of the bucket are realized. 1 instead of the directional control valve used
It is only necessary to provide two bucket directional control valves for opening and closing, and along with this, it is possible to reduce the number of pipe lines, etc., and it is possible to simplify the circuit configuration for driving the bucket cylinder and the bucket opening and closing cylinder. The manufacturing cost can be reduced, the space required for arranging the circuit components can be small, and the hydraulic drive device can be made compact. Further, the combined drive of the front actuator other than the bucket cylinder and the bucket cylinder can be reliably performed, and the work efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a hydraulic drive system for a hydraulic excavator 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 an external appearance of a hydraulic excavator with a loader front, which is a target of the present invention.

FIG. 4 is a circuit diagram showing a conventional hydraulic drive system for a hydraulic excavator with a loader front.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Variable capacity hydraulic pump 2 Variable capacity hydraulic pump 3 Discharge capacity control means 4 Discharge capacity control means 5 Right travel directional control valve (first switching valve group) 6A Bucket opening / closing cylinder (first switching valve group) 7e Control chamber 7f Control room 7A Boom directional control valve (front directional control valve)
(First switching valve group) 8 Arm directional control valve (front directional control valve)
(First switching valve group) 8a Control chamber 8b Control chamber 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 chamber 10b Control chamber 11 Boom directional control valve (front directional control valve)
(Second switching valve group) 11a Control chamber 11b Control chamber 12 Bucket directional control valve (front directional control valve)
(Second switching valve group) 12a Control chamber 12b Control chamber 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 stop means) (neutral holding means) 21E Pilot line (output stop means) (neutral holding means) 22 Open / close control valve 23 Connection passage 24 Check valve 25 Check valve 26 Check valve 29 Tank 33A Operation lever 33B Pilot Valve 33C Pilot valve 34A Operating 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 Traveling body 41 Revolving structure 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)

Front Page Continuation (72) Inventor Tomohiko Yasuda 650 Kazunachi-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura Plant

Claims (8)

[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, and a plurality of hydraulic pumps including at least one variable displacement hydraulic pump. A directional control valve for traveling which is supplied with pressure oil from the variable displacement hydraulic pump and which controls driving of one of the two traveling motors and is arranged at the most upstream side, and a downstream of this directional control valve for traveling. A directional control valve arranged in tandem, a first switching valve group, a second switching valve group to which pressure oil is supplied from a hydraulic pump other than the variable displacement hydraulic pump, and the first switching valve group. Pressure generating means provided on 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. In a hydraulic drive system for a hydraulic excavator with a loader front, which comprises a discharge capacity control means for controlling a discharge capacity, the first directional control valve controls the 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, and 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 directional control valve for controlling the drive of the bucket cylinder, and is provided on the center bypass passage of the first switching valve group in the vicinity of the pressure generating means and upstream of the center. An opening / closing control valve that can control opening / closing of the bypass passage, and a pressure oil supply for the most downstream directional control valve of the first switching valve group. A connection passage that connects a downstream portion of the passage and a pressure oil inflow port of the bucket directional control valve included in the second switching valve group, and a connection passage that is provided on the connection passage and is connected to the first switching valve group. A check valve that allows a flow in the direction toward the second switching valve group, and a check valve that is provided on the pressure oil supply passage of the bucket directional control valve of the second switching valve group and is provided in the bucket directional control valve. Check valve for preventing pressure oil from flowing from the connection passage to the pressure oil supply passage to the directional control valve other than the above, interlocking means for interlocking the opening / closing control valve and the bucket directional control valve, When the front actuator other than the bucket cylinder and the bucket cylinder are driven in combination, 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 the output of a signal for switching one of the front directional control valve and the other front directional control valve in conjunction with the switching of the bucket directional control valve. The hydraulic drive system for a hydraulic excavator with a loader front according to claim 1, which is an output stop means. 3. The output stop means includes a switching valve that blocks the output of pilot pressure that drives one of the front directional control valve and the other front directional control valve. 2. A hydraulic drive system for a hydraulic excavator with a loader front according to 2. 4. The 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 and a boom directional control valve to be controlled, and the other front directional control valve included in the second switching valve group is a separate one that controls driving of the corresponding front actuator. 4. The hydraulic drive system for a hydraulic excavator with a loader front according to claim 1, wherein the hydraulic drive system comprises at least one of the arm directional control valve and another boom directional control valve. 5. The hydraulic drive system for a hydraulic excavator with a loader front according to claim 1, wherein the pressure generating means is a fixed throttle. 6. The hydraulic drive system for a hydraulic excavator with a loader front according to claim 1, wherein the second switching valve group includes a swing motor. 7. A blocking means for blocking the merger of the pressure oil from the variable displacement hydraulic pump, which is guided through the connecting passage, into the bucket cylinder during the dumping operation of the bucket. A hydraulic drive system for a hydraulic excavator with a loader front according to any one of 1 to 6. 8. The blocking mechanism 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 blocking the merging of the pressure oil from the variable displacement hydraulic pump. Hydraulic drive for hydraulic excavator with loader front.