JPH08218443A - Hydraulic driving device for construction machine - Google Patents

Abstract

PURPOSE: To carry out smooth earth moving work by improving the elevating speed of an earth moving plate corresponding to travel speed even in the case where the operation of high speed travel combined with the elevation of the earth moving plate is carried out in a hydraulic driving device equipped with a relatively small capacity of a pump for the earth moving plate. CONSTITUTION: Pressure oil fed from the first and second main pumps 2, 3 is supplied through right and left travel control valves 7, 6 to right and left travel motors 9, 8 for driving an earth moving plate forward and backward, and pressure oil fed from an earth moving plate pump 4a is simultaneously supplied through an earth moving plate control lever 10 to an earth moving plate cylinder 20 for elevating the earth moving plate. In this case, an changing over valve 16 is changed over by pilot pressure led through piping 17a, 17b and a shuttle valve 17c to connect a communicating pipe 14 and moreover to change over a preparatory control valve 11 through piping 27 for shutting off a center bypass line 11b.

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 construction machine, which is provided in a construction machine such as a hydraulic excavator and is capable of performing a combined operation of raising and lowering a soil discharge plate and traveling.

[0002]

2. Description of the Related Art Conventionally, for example, the following has been known as a structure of a hydraulic drive unit provided in a construction machine such as a hydraulic excavator for elevating and lowering an earth discharging plate while traveling. This is shown in FIG. That is, in FIG.
This hydraulic drive system includes a first main pump 2, a second main pump 3, a soil discharge plate pump 4a, as hydraulic pumps,
A pilot pump 4b is provided, and as a actuator driven by the pressure oil discharged from the first main pump 2, a swing motor for driving a swing body in which a driver's seat is arranged and forming a main body, and a traveling body are formed. A left traveling motor that drives the left crawler belt, and as a actuator that is driven by the pressure oil discharged from the second main pump 3, a right traveling motor that drives the right crawler belt forming the traveling body and a front drive motor. A bucket cylinder that drives a bucket to be formed, and as an actuator that is driven by the pressure oil discharged from the first main pump 2 and the pressure oil discharged from the second main pump 3,
A boom cylinder that drives the boom that forms the front, and an arm cylinder that drives the arm that forms the front are provided, and the soil discharge plate is used as an actuator that is driven by the pressure oil discharged from the soil discharge plate pump 4a. It is equipped with a cylinder 20 for a soil discharging plate to be driven.

In this hydraulic drive system, the first
A control valve group 5 for controlling the flow of pressure oil to each actuator is connected to the main pump 2 and the second main pump 3 of FIG. Control valve 21 for controlling the drive of the cylinder, a boom control valve 22 for controlling the drive of the boom cylinder, and an arm control valve 23 for controlling the drive of the arm cylinder.
And a left traveling control valve 7 for controlling the driving of the left traveling motor 9 are connected in parallel. A spare control valve 11 for controlling the drive of the cylinder for the breaker or the like when an attachment such as a breaker is mounted instead of the bucket between the arm control valve 23 and the left travel control valve 7 and is driven. Are still connected in parallel. On the other hand, the second main pump 3 includes a right travel control valve 6 that controls the drive of the right travel motor 8, a boom control valve that controls the drive of the boom cylinder, and an arm control valve that controls the drive of the arm cylinder. The control valve and the bucket control valve for controlling the drive of the bucket cylinder are connected in tandem in this order. Further, an earth removing plate control valve 10 for controlling the drive of the earth removing plate cylinder 20 is connected to the earth discharging plate pump 4b.

In the above-mentioned structure, for example, the combined operation of raising and lowering the soil discharge plate and traveling is performed by the left traveling control valve 7,
This is performed by switching between the right travel control valve 6 and the soil discharge plate control valve 10. That is, by switching the left travel control valve 7, the pressure oil of the first main pump 2 is changed to the left travel motor 9.
The pressure oil of the second main pump 3 is supplied to the right traveling motor 8 by switching the right traveling control valve 6, and the pressure oil of the soil discharging plate pump 4a is switched by switching the soil discharging plate control valve 10. Is supplied to the cylinder 20 for the earth scavenging plate, whereby the left crawler belt, the right crawler belt, and the soil shaving plate that form the running body are driven, and the combined operation of raising and lowering the soil scavenging plate and running can be performed.

[0005]

However, the above-mentioned conventional technique has the following problems. That is, since the earth removal plate is used in the form of raising and lowering the earth removal plate while traveling to perform earth removal work, it is usually used in a combined operation of raising and lowering the earth removal plate and running, It is rarely used as an operation. Therefore, the use frequency of the soil discharge plate is relatively low, and the displacement of the soil discharge plate pump 4a is often set relatively small originally. Therefore, when the evacuation plate is to be raised and lowered while traveling at a relatively high speed, the evacuation plate pump 4a
In some cases, the amount of oil was insufficient, and the evacuation plate's up-and-down speed did not match the running speed well, so smooth earth removal work could not be performed.

An object of the present invention is to raise and lower the soil discharge plate even in the case of performing a combined operation of high-speed traveling and raising and lowering the soil discharge plate in a hydraulic drive device equipped with a relatively small capacity pump for the soil discharge plate. It is an object of the present invention to provide a structure capable of improving speed corresponding to traveling speed and performing smooth earth unloading work.

[0007]

In order to achieve the above object, according to the present invention, driving is performed by first and second hydraulic pumps and pressure oil discharged from the first and second hydraulic pumps. Are connected to a plurality of actuators including first and second traveling motors that drive a pair of left and right traveling mechanisms, respectively, and are supplied to the first traveling motor by being connected to the discharge pipeline of the first hydraulic pump. A first valve group including a first directional control valve for traveling for controlling the flow rate of pressure oil, and a pressure supplied to the second traveling motor, the pressure being connected to the discharge pipeline of the second hydraulic pump. A second valve group including a second traveling directional control valve for controlling the flow rate of oil, a third hydraulic pump, and a cylinder for an excavator plate driven by pressure oil discharged from the third hydraulic pump. And from the third hydraulic pump to the soil plate A drainage plate directional control valve for controlling the flow of pressure oil supplied to a binder, and a hydraulic drive device for a construction machine capable of performing a combined operation of raising and lowering and traveling of the drainage plate. Detecting means for detecting whether or not the work cylinder has operated, and when the detecting means detects that the earth-draining plate cylinder has worked, the first hydraulic pump supplies the first valve group to the first valve group. At least a part of one of the pressure oil supplied to the second valve group from the second hydraulic pump to the pressure oil supply pipe of the cylinder for the earth discharging plate. If the operating means does not detect that the soil discharge plate cylinder has been activated, the pressure oil flow rate to the soil discharge plate cylinder is replenished, and the pressure oil is supplied to the soil discharge plate cylinder. And a means for replenishing pressure oil to stop. Hydraulic drive system for setting machine is provided.

Preferably, in the hydraulic drive system for the construction machine, the soil discharge plate directional control valve is a pilot operated valve driven by pilot pressure, and the detecting means is provided to the soil discharge plate directional control valve. There is provided a hydraulic drive system for a construction machine, which is a means for detecting a pilot pressure.

Further preferably, in the hydraulic drive system for the construction machine, the pressure oil replenishing means is the first and the second.
Of the traveling directional control valve, the first communication pipe communicating the pressure oil supply pipeline of the traveling directional control valve with the pressure oil supply pipeline of the soil discharge plate cylinder, and the first communication pipe. Is provided on the communicating pipe, and when the detecting means detects that the cylinder for the earth discharging plate is operated, the first communicating pipe is brought into conduction, and the detecting means operates the cylinder for the earth discharging plate. A hydraulic drive system for a construction machine is provided, which has a switching valve that shuts off the first communication pipe when it is not detected.

More preferably, in the hydraulic drive system for the construction machine, each of the directional control valves included in the first and second valve groups has a center provided with a meter-in passage, a meter-out passage, and a center bypass passage. It is a bypass type valve, and one of the first and second valve groups has an upstream side of a center bypass passage and a meter-in passage connected to the first communication pipe and a downstream side of the center bypass passage. A center bypass type valve connected to the upstream side of the center bypass passage of either one of the first and second traveling directional control valves and connectable to a spare actuator passage in which the meter-in passage and the meter-out passage can be closed. A spare directional control valve is further provided, and this spare directional control valve operates the soil discharge plate cylinder by the detection means. When it is detected, the switching to the switching position is performed to cut off the center bypass passage and to connect the meter-in passage and the meter-out passage to the spare actuator passage, and the detecting means operates the earth plate cylinder. When not detected, a hydraulic drive system for a construction machine is provided, which is switched to a neutral position to bring the center bypass passage into conduction and cut off the meter-in passage and the meter-out passage.

Further preferably, the pressure oil replenishing means is provided in the first communication pipe, and further has a flow rate adjusting valve for adjusting a flow rate of the pressure oil of the first communication pipe. A hydraulic drive for a machine is provided.

More preferably, in the hydraulic drive system for the construction machine, the meter-in passage of one of the first and second traveling direction control valves and the other traveling direction control valve. A second communication pipe that connects the second communication pipe to the first communication pipe, and inflow prevention means that prevents the pressure oil from flowing into the first communication pipe from the second communication pipe. A hydraulic drive system for a construction machine is provided.

[0013]

In the present invention constructed as described above, it is intended that the operator raises and lowers the earth discharging plate while traveling to perform the earth discharging work, and the first and second directional control valves for traveling and the earth discharging operation. When the plate directional control valve is operated, pressure oil from the first and second hydraulic pumps is supplied to the first and second traveling motors via the first and second traveling directional control valves, respectively.
The left and right traveling mechanisms are driven to drive the construction machine. At the same time, pressure oil from the third hydraulic pump for the soil discharge plate is supplied to the soil discharge plate cylinder via the soil discharge plate directional control valve, and the soil discharge plate moves up and down. At this time, the operation of the soil discharge plate cylinder is detected by the detection means, and accordingly, the pressure oil supplied from the first hydraulic pump to the first valve group by the pressure oil supply means or the second hydraulic pump is supplied. At least a part of the pressure oil supplied to the second valve group is supplied to the soil discharge plate cylinder. Therefore, both the pressure oil from the third hydraulic pump and the pressure oil guided through the pressure oil replenishing means are supplied to the soil discharge plate cylinder. Therefore, even when performing a composite operation of raising and lowering the earth removing plate while traveling at a relatively high speed when the third hydraulic pump for the earth removing plate is set to a relatively small capacity, the cylinder for the earth removing plate is moved. Since the flow rate of the pressure oil is sufficiently high and the movement of the soil discharge plate becomes faster, it is possible to make the soil discharge plate elevating speed and the traveling speed match well. Further, when the operator does not intend to raise or lower the soil discharge plate and does not operate the soil discharge plate directional control valve, replenishment to the soil discharge cylinder by the pressure oil replenishing means is stopped, and the first and second Since the pressure oil from the hydraulic pump is guided only to the first and second valve groups, respectively, it is possible to prevent the operating speed of the actuator whose pressure oil flow rate is controlled by these first and second valve groups from decreasing. . That is, for example, in the case of traveling alone operation, it is possible to prevent the traveling speeds of the first and second traveling motors whose pressure oil flow rates are controlled by the first and second traveling direction control valves from decreasing.

Further, since the earth discharging plate directional control valve is a pilot operated valve driven by pilot pressure, and the detecting means is a means for detecting the pilot pressure applied to the earth discharging plate directional control valve, A means for detecting whether or not the earth plate cylinder has operated can be realized.

Further, the pressure oil replenishing means is constituted by a pressure oil supply pipe line of one of the first and second traveling direction control valves and a pressure oil supply pipe of the soil plate cylinder. A first communication pipe communicating with the passage and a first communication pipe provided on the first communication pipe, and when the detecting means detects that the cylinder for the earth discharging plate is activated, the first communication pipe is brought into conduction and detection is performed. If the means does not detect the operation of the cylinder for the dump plate, the first
And a switching valve for shutting off the communication pipe of the first and second hydraulic pumps, the at least part of the pressure oil from the first and second hydraulic pumps to the first or second valve group is discharged. A means for replenishing the plate cylinder and for stopping the replenishment plate cylinder when it is not operating can be realized.

The first communication pipe is connected to the center bypass passage of the first or second traveling directional control valve on the downstream side through the center bypass passage of the preliminary directional control valve, and the preliminary directional control is also provided. It is connectable to a closable spare actuator passage via a meter-in passage and a meter-out passage of the valve. As a result, the standby directional control valve is switched to the switching position and shuts off the center bypass passage when the soil discharge plate cylinder operates, so that the first communication pipe is
It will be connected to the spare actuator passage and the pressure oil supply pipeline of the first or second traveling directional control valve. Here, if the spare actuator passage is closed in advance by, for example, a rod or the like, the first communication pipe will be connected only to the pressure oil supply pipe passage of the first or second traveling direction control valve. Therefore, it is possible to realize a configuration in which a part of the pressure oil supplied to the first or second traveling motor via the first or second traveling direction control valve is guided to the soil discharge plate cylinder.

Further, the pressure oil replenishing means further includes a flow rate adjusting valve for adjusting the flow rate of the pressure oil in the first communication pipe, so that the pressure oil to be merged into the pressure oil supply pipe line of the soil discharge plate cylinder can be supplied. The flow rate can be adjusted.

The pressure oil supplied from one of the first and second hydraulic pumps to one of the first and second traveling direction control valves is discharged through the first communication pipe. The portion guided to the pressure oil supply pipe of the soil plate cylinder is compensated from the other hydraulic pump through the second communication pipe, and at this time, the inflow prevention means causes the second hydraulic pump to communicate with the second communication pipe. The pressure oil guided via the first communication pipe is prevented from entering the soil discharge plate cylinder. Therefore, since it is possible to prevent the traveling speed of one traveling motor from decreasing, it is possible to sufficiently ensure the uniform speed of the two traveling motors even during the combined operation.

[0019]

Embodiments of the present invention will be described below with reference to FIGS. A first embodiment of the present invention will be described with reference to FIGS. This embodiment is an embodiment applied to a hydraulic drive system for a hydraulic excavator. FIG. 2 shows an example of a hydraulic excavator to which the hydraulic drive system according to this embodiment is applied. In FIG. 2, a hydraulic excavator 100 includes a right crawler belt 120 and a left crawler belt (not shown) that form a running body, and a revolving structure 12 that forms a main body on which the running seat is provided.
1 and a boom 122 that is rotatably provided in a front position of the revolving structure 121 and is driven by a boom cylinder 105.
An arm 123 rotatably provided on the boom 122 and driven by an arm cylinder 108; and a bucket cylinder 106 rotatably provided on the arm 123.
It has a bucket 124 driven by and a soil discharging plate 125 rotatably provided on the traveling body and driven by the soil discharging cylinder 20.

FIG. 1 shows a hydraulic circuit of the hydraulic drive system of the present embodiment provided in the hydraulic excavator having the above-mentioned structure.
1 and 2, the hydraulic drive system according to the present embodiment includes a first main pump 2, a second main pump 3, an earth plate pump 4a, and a pilot pump 4b as hydraulic pumps driven by the engine 1. And the boom cylinder 105 and the arm cylinder 108 described above are provided as actuators driven by the pressure oil discharged from the first main pump 2 and the pressure oil discharged from the second main pump 3. , As an actuator driven by the pressure oil discharged from the first main pump 2,
A turning motor (not shown) for driving the turning body 121 and a left traveling motor 9 for driving a left crawler belt (not shown) are provided and driven by pressure oil discharged from the second main pump 3. The right traveling motor 8 that drives the right crawler belt 120 as an actuator and the above-described bucket cylinder 106 are provided, and as an actuator that is driven by the pressure oil discharged from the soil discharge plate pump 4a, A cylinder 20 is provided.

A control valve group 5 for controlling the flow of pressure oil to each actuator is connected to the first main pump 2 and the second main pump 3. This will be described in detail below. First, in the first main pump 2, a swing control valve 21 that controls the drive of a swing motor (not shown), a boom control valve 22 that controls the drive of the boom cylinder 105, and a drive of the arm cylinder 108. The arm control valve 23 for controlling the control of the left traveling motor 9 and the left control valve 7 for controlling the driving of the left traveling motor 9 are connected in parallel. All of these control valves are pilot operated valves driven by pilot pressure, and are center bypass type valves having a meter-in passage, a meter-out passage, and a center bypass passage. As shown in FIG. 1, a swing control valve 21, a boom control valve 22, an arm control valve 23, a spare control valve 1
1 (described later) and the left traveling control valve 7 are connected in this order. The turning control valve 21, the boom control valve 22, and the arm control valve 23 do not form an essential part of this embodiment and have known configurations, so some of them are not shown.

Next, in the second main pump 3, the right travel control valve 6 for controlling the drive of the right travel motor 8, the boom control valve 24 for controlling the drive of the boom cylinder 105, and the arm cylinder 108. The arm control valve 25 for controlling the drive of the bucket cylinder and the bucket control valve 26 for controlling the drive of the bucket cylinder 106 are connected in tandem in this order. In other words, these control valves are all center bypass type pilot operated valves as well,
As shown in FIG. 1, the center bypass passage is connected to the right travel control valve 6, the boom control valve 24, the arm control valve 25, and the bucket control valve 26 in this order. The boom control valve 24, the arm control valve 25, and the bucket control valve 26 do not form an essential part of this embodiment.
Moreover, since a known configuration is sufficient, a part of the illustration is omitted.

Further, an earth discharging plate control valve 10 for controlling the driving of the earth discharging plate cylinder 20 is connected to the earth discharging plate pump 4a. Similarly to the above, the soil discharge plate control valve 10 is also a center bypass type valve having a meter-in passage, a meter-out passage, and a center bypass passage, and is a pilot operated valve driven by pilot pressure. That is, after the pilot pressure generated by the pilot pump 4b is guided to the pilot valve 13 via a pipe line (not shown) and reduced in pressure, the pilot pressure is discharged via the pipe 13a or 13b depending on the operating direction of the operating lever 13A of the pilot valve 13. It is configured to be guided to the signal port 10A or 10B of the earth plate control valve 10.

Further, in the hydraulic drive system according to the present embodiment, the auxiliary control valve 11 connected in parallel between the arm control valve 23 on the downstream side of the first main pump 2 and the left traveling control valve 7.
And a communication pipe 14 that connects the pressure oil supply pipelines of the preliminary control valve 11 and the left traveling control valve 7 to the pressure oil supply pipeline of the soil plate cylinder 11.

The spare control valve 11 is for controlling the drive of the cylinder for the breaker when the attachment such as a breaker is mounted instead of the bucket and is driven, and the center bypass passage 11 is provided.
The upstream side of b and the meter-in passage 11a are connected to the communication pipe 14, the downstream side of the center bypass passage 11b is connected to the upstream side of the center bypass passage 7b of the left traveling control valve 7, and the meter-in passage 11a and the meter-out passage The tip of the passage 11c is closed (in Fig. 1, x
(Indicated by a mark)
It can be connected to a and b. Further, the spare control valve 11 is the operation lever 13A of the pilot valve 13.
Is operated to generate pilot pressure in either of the pipes 13a, 13b, this pilot pressure is
b, the shuttle valve 17c, and the pipe 27, it is guided to the signal port 11A and switched to the left position in FIG. As a result, the center bypass passage 11b is blocked and the meter-in passage 11a and the meter-out passage 11 are cut off.
c is electrically connected to the spare actuator passages 12a and 12b. When the pilot valve 13 is not operated, it is switched to the neutral position (the position shown in FIG. 1) to bring the center bypass passage 11b into conduction and to block the meter-in passage 11a and the meter-out passage 11c.

A flow rate adjusting valve 15 for adjusting the flow rate of the pressure oil passing through the communication pipe 14 and a switching valve 16 are provided on the communication pipe 14. When the operation lever 13A of the pilot valve 13 is operated and pilot pressure is generated in any of the pipes 13a and 13b, this switching valve 16 is supplied to the signal port 16A via the pipelines 17a and 17b and the shuttle valve 17c. It is switched to the right position in FIG. 1 by being guided, and the communication pipe 14 is made conductive by connecting the inlet side 16a and the outlet 16b. When the operation lever 13A is not operated and the pilot pressure is not guided, it is switched to the neutral position (the position shown in FIG. 1) and the communication pipe 14 is shut off.

In the above, the control valves 21, 22, 23, 11, 7 constitute the first valve group,
The control valves 6, 24, 25, 26 constitute a second valve group, and the pipes 17a, b, the shuttle valve 17c, and the pipe 27 serve as detection means for detecting whether or not the cylinder 20 for the dump plate has operated. The communication pipe 14, the flow rate adjusting valve 15, and the switching valve 16 constitute pressure oil replenishing means.

Next, the operation of this embodiment will be described. As a comparative example of this embodiment, a hydraulic circuit of a conventional hydraulic drive device of this type is shown in FIG. The same members as those in FIG. 1 showing the present embodiment are designated by the same reference numerals. In FIG. 3, a main point different from the hydraulic circuit of the present embodiment of FIG. 1 is that the communication pipe 14 is not provided, and accordingly, the flow rate adjusting valve 15, the switching valve 16, the pipes 17 a, 17 b, The shuttle valve 17c is omitted, and the connection of the left traveling control valve 7 near the meter-in passage 7a is slightly different. Other configurations are almost the same as the hydraulic circuit of FIG.

In the above structure, for example, when performing a combined operation of raising and lowering the soil discharging plate 125 and traveling, the left traveling control valve 7, the right traveling control valve 6, and the soil discharging plate control valve 10 are respectively set. , The operator switches. That is, when the operator operates the operation means of the pressure reducing valve (not shown),
The pilot pressure from the pilot pump 4b is reduced and supplied to the signal port 7A (or 7B) of the left traveling control valve 7, and the left traveling control valve 7 is switched to the left position (or right position) in the figure. As a result, the pressure oil of the first main pump 2 is supplied to the left traveling motor 9 and the left crawler belt (not shown) is driven in the forward direction (or reverse direction). Similarly, when the operating means of the pressure reducing valve (not shown) is operated, the pilot pressure from the pilot pump 4b is reduced and supplied to the signal port 6A (or 6B) of the right traveling control valve 6, and the right traveling control valve 6 is shown. It is switched to the left position (or the right position). As a result, the pressure oil of the second main pump 3 is supplied to the right traveling motor 8 and the right crawler belt 120 (see FIG. 2) is driven in the forward direction (or reverse direction). At the same time, the operator operates the pilot valve 13
The pilot pressure generated from the dump plate pump 4a is shown by operating the operation lever 13A of FIG. 1 to the right side (or left side) of the drawing to switch the dump plate control valve 10 to the left position (or right position) of the drawing. The pilot pressure is guided to the pilot valve 13 via a pipe line and reduced in pressure, and this pilot pressure is further reduced via the pipe 13b (or the pipe 13a) to the bottom side 20a (or the rod side 20) of the soil discharge plate cylinder 20.
By being supplied to b), the earth discharging plate 125 performs a lowering operation (or a raising operation). In this way, the soil discharging plate 12
It is possible to perform a combined operation of raising and lowering 5 and traveling.

Here, since the soil discharging plate 125 is used in the form of raising and lowering while traveling to perform the soil discharging work, it is rarely used as a single operation of the soil discharging plate 125 in general. . Therefore, the dump plate 12
5 is used relatively infrequently, and the displacement plate pump 4a is often set to have a relatively small capacity.
Therefore, when trying to move up and down the soil discharge plate 125 while traveling at a relatively high speed, the amount of pressure oil from the soil discharge plate pump 4a is insufficient, and the vertical speed of the soil discharge plate 125 does not affect the traveling speed. It may not be possible to perform smooth soil removal work without matching.

On the other hand, also in the hydraulic circuit shown in FIG. 1 of the hydraulic drive system of the present embodiment, the operator intends to perform the earth removing work by moving up and down the earth removing plate 125 while traveling,
When the left traveling control lever 7, the right traveling control lever 6, and the soil discharging plate control lever 10 are switched in the same manner as described above, pressure oil from the first main pump 2 and the second main pump 3 is changed in the same manner as above. Are supplied to the left traveling motor 9 and the right traveling motor 8 via the left traveling control lever 7 and the right traveling control lever 6, respectively, and the left crawler belt (not shown) and the right crawler belt 120 are driven forward and backward. And at the same time, the pump 4
The pressure oil from a is supplied to the cylinder 20 for the earth discharging plate via the control lever 10 for the earth discharging plate, and the earth discharging plate 125 moves up and down.

However, in the hydraulic circuit of the present embodiment, at this time, the pilot pressure for operating the soil discharge plate control lever 10 is guided to the signal port 16A of the switching valve 16 via the pipes 17a and 17b and the shuttle valve 17c. As a result, the switching valve 16 is switched to the right side position in FIG. 1 to bring the communication pipe 14 into conduction. At the same time, this pilot pressure is introduced to the signal port 11A of the auxiliary control valve 11 via the pipe 27 to switch the auxiliary control valve 11 to the left position in FIG. 1 and shut off the center bypass line 11b. As a result, the communication pipe 1
4 is connected only to the spare actuator passages 12a and 12b and the meter-in passage 7a of the left traveling control valve 7. However, since the tip of the spare actuator passage is closed, as a result,
Since the communication pipe 14 is connected only to the meter-in passage 7a of the left travel control valve 7, the pressure oil supplied from the first main pump 2 to the left travel motor 9 via the left travel control valve 7 is not supplied. A part of it can be guided to the soil discharge plate cylinder 20.

That is, both the pressure oil from the soil discharge plate pump 4a and the pressure oil introduced from the communication pipe 14 are supplied to the soil discharge plate cylinder 20. Therefore, when the displacement plate pump 4a is set to a comparatively small capacity, even when performing a combined operation of raising and lowering the displacement plate while traveling at a relatively high speed, the pressure to the displacement plate cylinder 20 is increased. Since the oil flow rate is sufficiently high and the movement of the soil discharge plate 125 becomes fast, the up-and-down speed of the soil discharge plate 125 and the traveling speed can be matched well. On the other hand, when the operator does not operate the operation lever 13A unintentionally to raise or lower the soil discharge plate 125, the switching valve 16
1 is switched to the left side position in FIG. 1 to shut off the communication pipe 14, and the auxiliary control valve 11 is switched to the neutral position shown in FIG. 1, thereby stopping the supply of pressure oil to the soil plate cylinder 20. To be done. That is, since the pressure oils from the first and second main pumps 2 and 3 are guided only to the control valves 21, 22, 23, 11, 7 and the control valves 6, 24, 25, 26, respectively, these pressure oils are used. It is possible to prevent the operating speed of the actuator whose flow rate is controlled from decreasing. That is, for example, in the case of independent traveling operation, the left / right traveling control valve 1
It is possible to prevent the traveling speeds of the left and right traveling motors 9 and 8 whose pressure oil flow rates are controlled by 1 and 6 from decreasing.

A second embodiment of the present invention will be described with reference to FIG. This embodiment is also an embodiment when applied to a hydraulic drive device of a hydraulic excavator. The hydraulic circuit of the hydraulic drive system according to this embodiment is shown in FIG. 4, the hydraulic drive system according to the present embodiment is different from the hydraulic drive system according to the first embodiment shown in FIG. 1 mainly in that the pressure oil supply pipeline of the right travel control valve 6 and the left travel control valve 6 are used. The communication pipe 28 connecting the pressure oil supply pipe line of the control valve 7 is provided. The communication pipe 28 is provided with a check valve 28a, and also has a check valve 29a, which is connected to the meter-in passage 7a of the left travel control valve 7 and a check valve 29a of the pipe 30.
It is connected to the downstream side of 30a.

The other structure is almost the same as that of the first embodiment. The check valves 29a and 30a are connected to the communication pipe 28.
To constitute an inflow prevention means for preventing the inflow of pressure oil into the communication pipe 14.

In the present embodiment, a portion of the pressure oil supplied from the first main pump 2 to the left traveling control valve 7 to the soil discharge plate cylinder 20 via the communication pipe 14 is divided into the second portion. The main pump 3 of the above is supplemented via the communication pipe 28, and at this time, the check valves 29a, 30a
Thus, the pressure oil guided from the second main pump 3 through the communication pipe 28 passes through the communication pipe 14 and the cylinder 20 for the earth discharging plate.
To prevent contamination with Therefore, the left traveling motor 9
Since it is possible to prevent the traveling speed of
Even during the combined operation, it is possible to sufficiently ensure the constant velocity of the left and right traveling motors 9 and 8.

In the first and second embodiments, the case where the present invention is applied to the small hydraulic excavator as shown in FIG. 2 has been described as an example, but the present invention is not limited to this, and other It can also be applied to the hydraulic excavator, and the same effect can be obtained in this case as well.

[0038]

According to the present invention, both the pressure oil from the third hydraulic pump and the pressure oil guided through the pressure oil replenishing means are supplied to the soil discharge plate cylinder, so that the soil discharge plate cylinder is discharged. When the third hydraulic pump for the plate is set to have a relatively small capacity, the movement of the earth removing plate is improved even when performing a combined operation of moving the earth removing plate up and down while traveling at a relatively high speed. The board ascending / descending speed and the traveling speed can be matched well. Therefore, it is possible to improve the operability of the soil discharging plate during traveling. In addition, the lifting speed when operating the soil shaving plate alone will be faster. Further, when the soil discharge plate is not operated, the pressure oil from the first and second hydraulic pumps does not flow into the soil discharge plate cylinder and can be effectively used. Further, since the portion guided from one hydraulic pump to the pressure oil supply pipeline of the cylinder for the soil discharge plate via the first communication pipe is compensated from the other hydraulic pump via the second communication pipe, It is possible to prevent the traveling speed of the traveling motor from decreasing. Therefore,
Even during the combined operation, it is possible to sufficiently ensure the constant velocity of the two traveling motors.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a hydraulic drive system according to a first embodiment of the present invention.

FIG. 2 is a side view showing an example of a hydraulic excavator to which the hydraulic drive system shown in FIG. 1 is applied.

FIG. 3 is a hydraulic circuit diagram of a conventional hydraulic drive system according to a comparative example of the first embodiment.

FIG. 4 is a hydraulic circuit diagram of a hydraulic drive system according to a second embodiment of the present invention.

[Explanation of symbols]

2 1st main pump (1st hydraulic pump) 3 2nd main pump (2nd hydraulic pump) 4a Excavator pump (3rd hydraulic pump) 4b Pilot pump 5 Control valve group 6 Right traveling Control valve (second traveling direction control valve) 7 Left traveling control valve (first traveling direction control valve) 7a Meter-in passage 7b Center bypass passage 8 Right traveling motor (second traveling motor) 9 Left traveling motor (1st traveling motor) 10 control valve for soil discharge plate 11 spare control valve 11a meter-in passage 11b center bypass passage 11c meter-out passage 12a, b spare actuator passage 14 communication pipe (first communication pipe) 15 flow control valve 16 Switching Valve 20 Cutter for Exhaust Plate 28 Communication Pipe (Second Communication Pipe) 29a Reverse The valve (inflow preventing means) 30a check valve (inflow preventing means) 100 hydraulic excavator 120 the right track (traveling mechanism)

Claims (6)

[Claims] 1. A first hydraulic pump and a second hydraulic pump, and the first hydraulic pump.
And a plurality of actuators including first and second traveling motors, which are driven by pressure oil discharged from the second hydraulic pump and respectively drive a pair of left and right traveling mechanisms, and a discharge pipe of the first hydraulic pump. A first valve group including a first traveling directional control valve connected to a first passage and controlling a flow rate of pressure oil supplied to the first traveling motor; and a discharge pipe passage of the second hydraulic pump. A second valve group that is connected and that includes a second traveling directional control valve that controls the flow rate of pressure oil supplied to the second traveling motor; and a third hydraulic pump,
An earth-discharging plate cylinder driven by pressure oil discharged from the third hydraulic pump, and a soil-discharging plate controlling the flow of pressure oil supplied from the third hydraulic pump to the earth discharging plate cylinder. In a hydraulic drive of a construction machine, which has a direction control valve and is capable of a combined operation of raising and lowering the soil discharge plate and traveling, a detection unit that detects whether or not the cylinder for the soil discharge plate has operated, When it is detected by the means that the soil discharge plate cylinder has operated, the first hydraulic pump causes the first hydraulic pump to operate.
Of at least one of the pressure oil supplied to the second valve group and the pressure oil supplied to the second valve group from the second hydraulic pump. When the operating means does not detect the operation of the soil discharge plate cylinder, the pressure oil flow rate is supplied to the soil discharge plate cylinder by merging into the oil supply pipe line. A hydraulic drive device for a construction machine, comprising: a pressure oil supply unit that stops supply of pressure oil. 2. The hydraulic drive system for a construction machine according to claim 1, wherein the earth discharge plate directional control valve is a pilot operated valve driven by pilot pressure, and the detection means is the earth discharge plate directional control. A hydraulic drive system for a construction machine, which is means for detecting a pilot pressure applied to a valve. 3. The hydraulic drive system for a construction machine according to claim 1, wherein the pressure oil replenishing means controls the pressure of one of the first and second traveling directional control valves. A first communication pipe that connects the oil supply pipe line and the pressure oil supply pipe line of the soil discharge plate cylinder, and the first discharge pipe provided on the first communication pipe. When the operation is detected, the first communication pipe is brought into conduction,
A hydraulic drive device for a construction machine, comprising: a switching valve that shuts off the first communication pipe when the detection means does not detect that the cylinder for the soil discharge plate is operating. 4. The hydraulic drive system for a construction machine according to claim 3, wherein each of the directional control valves included in the first and second valve groups includes a meter-in passage, a meter-out passage, and a center bypass passage. One of the first and second valve groups is a center bypass type valve in which the upstream side of the center bypass passage and the meter-in passage are connected to the first communication pipe and A center bypass whose downstream side is connected to the upstream side of the center bypass passage of either one of the first and second traveling directional control valves and which is connectable to a spare actuator passage in which the meter-in passage and the meter-out passage can be closed. A spare directional control valve of a type, wherein the spare directional control valve has the detection means for operating the cylinder for the dump plate. Is detected, the center bypass passage is switched to the switching position, the meter-in passage and the meter-out passage are electrically connected to the spare actuator passage, and the earth discharging cylinder is operated by the detecting means. When not detected, a hydraulic drive system for a construction machine, characterized in that it is switched to a neutral position to bring a center bypass passage into conduction and cut off a meter-in passage and a meter-out passage. 5. The hydraulic drive system for a construction machine according to claim 3, wherein the pressure oil replenishing means is provided in the first communication pipe, and adjusts a flow rate of the pressure oil in the first communication pipe. A hydraulic drive system for a construction machine, further comprising a regulating valve. 6. The hydraulic drive system for a construction machine according to claim 3, wherein the meter-in passage of the traveling directional control valve of any one of the first and second traveling directional control valves and the other traveling direction of the traveling directional control valve. Second connecting the pressure oil supply line of the control valve
And a flow-in prevention means for preventing pressure oil from flowing into the first communication pipe from the second communication pipe.