JPH09209414A - Hydraulic driving device of construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To flow hydraulic oil from a relatively small control input, by providing a changeover valve selectively connecting either one of two variable volume hydraulic pumps and either one of flow rate control valves for working or right and left traveling. SOLUTION: A changeover valve 51 is switched over to the second changeover position 55b when a boom cylinder 33 and right and left traveling motors 43a, 43b are controlled in a multiple operation way. Variable restrictors 13a, 23a of a flow rate control valve 36 for a boom are opened in sequence and then a variable restrictor 13b of the flow rate control valve 42A for right hand traveling and a variable restrictor 23b of the flow rate control valve 42B for left hand traveling are opened respectively. The hydraulic oil of a variable volume hydraulic pump 11 is supplied in a cylinder 33 through a delivery pipe 12, a main pipe 14a for working, a variable restrictor 13a, etc. And the hydraulic oil of the pump 11 is supplied in the cylinder through the main pipe 24a for working, the variable restrictor 23a, etc. And further, the hydraulic oil of the variable volume hydraulic pump 21 is supplied to right and left traveling motors 43a, 43b through the variable restrictors 13b, 23b, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises two variable displacement hydraulic pumps, a pair of traveling actuators, and a plurality of working actuators, and load sensing control and input torque limitation for the two hydraulic pumps. The present invention relates to a hydraulic drive system for a construction machine such as a hydraulic excavator that performs control.

[0002]

2. Description of the Related Art Conventionally, a two-pump load sensing system has been known which ensures independence between two variable displacement hydraulic pumps. For example, Japanese Patent Laid-Open No. 6-123123 discloses a first variable throttle for controlling the flow rate of pressure oil supplied from a first variable displacement hydraulic pump to an actuator,
A second variable throttle for controlling the flow rate of pressure oil supplied from the second variable displacement hydraulic pump to the actuator is provided, and the maximum load pressure of the actuator to which the pressure oil is supplied from the first variable displacement hydraulic pump is selected. Is supplied to the regulator of the first variable displacement hydraulic pump, and the maximum load pressure of the actuator to which the pressure oil is supplied from the second variable displacement hydraulic pump is selectively supplied to the regulator of the second variable displacement hydraulic pump. A hydraulic drive device for a construction machine is shown which is capable of ensuring independence of two pumps and combining the flow rates flowing out from the first variable throttle and the second variable throttle to supply the corresponding actuators. There is.

FIG. 7 is a circuit diagram showing the above-mentioned conventional technique. The first and second variable displacement hydraulic pumps 11 and 21 are respectively connected to the right traveling motor or the left traveling motor and the variable throttles 13a and 23a of the plurality of working actuators. In this conventional technique, the first variable diaphragm 13a is used.
And the second variable diaphragm 23a are respectively formed on one spool. The "circle symbol" drawn in the block showing each control valve indicates a variable throttle. Here in particular,
The variable diaphragm drawn with "black circles" is a variable diaphragm that belongs to the operation amount of the spool entirely and starts to open when the operation amount of the spool is relatively small. The variable diaphragm drawn with "white circles" Is a variable diaphragm that partially belongs to the operation amount of the spool and starts to open when the operation amount of the spool becomes large.

For example, in the boom flow control valve 36 for controlling the boom cylinder, when the operation amount is small, the boom cylinder is connected only to the first variable throttle 13a connected to the first variable displacement hydraulic pump 11. Pressure oil is supplied to the second variable throttle 23a when the operation amount increases, the pressure oil flowing out from the second variable throttle 23a connected to the second variable displacement hydraulic pump 21 merges, and therefore the flow rate supplied to the boom cylinder. Will increase.

Further, for example, only one "black circle" is drawn in the block of the left traveling flow control valve for controlling the left traveling motor. Therefore, the pressure oil is supplied to the left travel motor only through the second variable throttle 23a connected to the second variable displacement hydraulic pump 21. The pressure oil from the first variable displacement hydraulic pump 11 is never merged.

FIG. 9 is a circuit diagram including a vertical cross section of a work flow rate control valve, for example, a boom flow rate control valve provided in the prior art shown in FIG. When the spool 5 is operated in the direction of the arrow in FIG. 9 and reaches the position of the stroke amount S1, the first variable throttle 13a starts to open, and the amount of pressure oil of the hydraulic pump 11 proportional to the opening of the throttle 13a is released. , The first variable throttle 13a, the pressure compensating valve 2a, and the check valve 3a, and is supplied to the work actuator, that is, the boom cylinder 33. Further, when the spool 5 is operated in the direction of the arrow to reach the position of the stroke S2, the second variable throttle 23a also starts to open, and the pressure oil from the second variable displacement hydraulic pump 21 also receives the second variable throttle 23a. , The pressure compensating valve 2b, and the check valve 3b, and are supplied to the boom cylinder 33 and merged. These operations are as described above.

In this prior art, the hydraulic pumps 11 and 21
And the signal pressure for driving the regulator 4a of the first variable displacement hydraulic pump 11 (first variable throttle 1
3a side maximum load pressure) and the second variable displacement hydraulic pump 2
Since the signal pressure for driving the first regulator 4b (the maximum load pressure on the second variable throttle 23a side) is individually guided, energy loss can be suppressed and it is economical.

However, in this prior art, in the combined operation of the left and right traveling motors and the work actuators such as the boom cylinder and the arm cylinder, when the load pressure difference is remarkable, the discharge flow rate is controlled by the torque limit control of the pump. There is a problem in that the speed of the actuator forming the low load side is extremely decreased due to the decrease. For example, on a sloping road, when climbing a hydraulic shovel while scratching the ground at the front including the boom, the load pressure on the running side becomes high and the load pressure on the front side becomes low, which reduces the operating speed of the front. , It takes time to run uphill. Also, when the hydraulic excavator located on the muddy ground is to escape, the load pressure on the running side decreases and the load pressure on the front side increases because the running body, that is, the crawler track, runs idle due to the muddy condition. The speed slows down, and it takes time to escape from the muddy area.

In order to solve the above-mentioned problems in the prior art, the applicant of the present invention previously filed Japanese Patent Application No. 7-35546.
The hydraulic drive for construction machinery was proposed as the issue. FIG.
It is a circuit diagram which shows the prior art proposed by the applicant of the present application.

The prior art of the applicant of the present application is such that a plurality of operations such as a traveling control valve group 41 including left and right traveling flow control valves 42A and 42B, a boom flow control valve 36, an arm flow control valve 35, and the like. Switching valve 5 having a first switching position 54a and a second switching position 55a between which the work control valve group 31 including the work flow control valve is separated.
1a is arranged.

When only the left and right traveling motors are operated or only the work actuators such as the boom cylinder and the arm cylinder are operated, the control pressure from the switching control means 52 is not applied to the signal line 53, and the switching valve is operated. 51a is kept in the first switching position 54a shown in FIG.
The configuration is similar to that of the conventional technique shown in FIG.

That is, work of the first traveling main pipe line 14b connected to the traveling control valve group 41, the boom flow control valve 36, the arm flow control valve 35, etc. included in the work control valve group 31. For connecting to the first main working pipeline 14a connected to the first variable throttle 13a of the flow control valve for operation, and connected to the traveling control valve group 41
The load pressure detection path 44a of No. 1 and the first maximum load pressure detection path 34a connected to the work flow rate control valve included in the work control valve group 31 to communicate with each other, and the first main running pipeline 14
b and the first main working pipeline 14a are connected to the discharge pipeline 12 of the first variable displacement hydraulic pump 11, and the first load pressure detection passage 44a and the first maximum load pressure detection passage 34a are connected to the first The load-sensing pressure for controlling the discharge amount of the variable displacement hydraulic pump 11 is connected to the first load-sensing conduit 15 for guiding the regulator 4a.

Further, the second traveling main line 24b connected to the traveling control valve group 41 and the second variable throttle 2 of the working flow control valve included in the working control valve group 31.
A second load pressure detection path 44b connected to the traveling control valve group 41 and communicating with the second main work pipeline 24a connected to 3a, and a work flow rate included in the work control valve group 31. The second maximum load pressure detection passage 34b connected to the control valve is made to communicate with each other, and the second traveling main pipe line 24b and the second working main pipe line 24a are connected to each other by the second variable displacement hydraulic pump 2
The second load pressure detection path 44b is connected to the first discharge line 22.
And the second maximum load pressure detection path 34b are connected to the second load sensing pipeline 25 that guides the load sensing pressure for controlling the discharge amount of the second variable displacement hydraulic pump 21 to the regulator 4b.

In the combined operation of the left and right traveling motors and the working actuator, the control pressure is output to the signal line 53 by operating the switching control means 52, and the switching valve 5 is operated.
1a is switched to the second switching position 55a.

As a result, the first load pressure detection path 44a and the second load detection path 44b on the traveling side communicate with each other, and the first traveling main pipeline 14b communicates with the second traveling main pipeline 24b. , That is, the first variable diaphragm 13b and the second variable diaphragm 2
3b is connected to the second variable displacement hydraulic pump 21, and the left and right traveling motors are driven only by the pressure oil discharged from the second variable displacement hydraulic pump 21. Further, the first variable throttle 13a of the work flow control valve is the first variable displacement hydraulic pump 1.
1, the working actuator is driven only by the pressure oil discharged from the first variable displacement hydraulic pump 11.

As a result, during the combined operation of the left and right traveling motors and the work actuator, the pumps 11 and 21 connected to each other do not lead the load pressure of the actuators on the other side to each other. There will be no significant decrease in front operating speed when traveling uphill, and no significant decrease in traveling speed when exiting a muddy state.

[0017]

However, even the prior art of the applicant of the present application shown in FIG. 8 has the following problems. That is, the work flow control valve related to the actuator that needs to join the work actuator has both the variable throttles of black circles and white circles of FIG.
In the case where the variable throttle 13a is a white circle, that is, it partially belongs to the operation of the spool, for example, when the work flow rate control valve is an arm flow rate control valve for controlling the arm cylinder, it is possible to change the travel. At the time of compound operation, S2 spool
If it is not operated for more than the stroke, the pressure oil cannot be supplied to the arm cylinder, and the operability of the arm cylinder during this combined arm / travel operation tends to deteriorate. About this,
It demonstrates using 0-FIG. FIG. 10 shows the relationship between the spool operation amount of the boom flow control valve 36 shown in FIG. 8 and the opening area of the variable throttle. FIG. 10A shows the first variable throttle 13a of the boom flow control valve 36. The figure which shows an opening area characteristic, (b) is a figure which shows the opening area characteristic of the 2nd variable throttle 23a of the same flow control valve 36 for booms. The first variable aperture 13a shown in FIG. 10A, which is the "black circle" in FIG.
On the side, the opening area increases proportionally from the spool operation amount of 20% to the full operation, and the spool operation amount 60 on the second variable aperture 23a side shown in FIG. The open area increases proportionally from% to full operation.

FIG. 11 shows the relationship between the spool operation amount of the arm flow control valve 35 shown in FIG. 8 and the opening area of the variable throttle. FIG. 11A shows the first arm flow control valve 35. Showing the aperture area characteristic of the variable diaphragm 13a of FIG.
FIG. 6 is a diagram showing an opening area characteristic of a second variable diaphragm 23a of the arm flow control valve 35. On the side of the first variable aperture 13a shown in (a) of FIG. 11, which is the “white circle” of FIG. 8, the opening area increases proportionally from the spool operation amount of 60% to full operation, and the “black circle” of FIG. The second shown in FIG. 11B.
On the variable aperture 23a side, the opening area increases proportionally from the spool operation amount of 20% to full operation.

FIG. 12A is a diagram showing the flow rate characteristic of the boom flow rate control valve 36 having the above-mentioned opening area characteristic when the boom cylinder is independently operated, and FIG. 12B is a combined operation of the boom cylinder and the left and right traveling motors. Flow control valve for boom 36
It is a figure which shows the flow rate characteristic of. Further, FIG. 13A shows the arm flow control valve 35 having the above-mentioned opening area characteristic.
Of the figure showing the flow rate characteristics when the arm cylinder is operated independently.
(B) is a diagram showing a flow rate characteristic of the arm flow rate control valve 35 at the time of a combined operation of the arm cylinder and the left and right traveling motors.
As shown in (a) of FIG. 12 and (a) of FIG. 13, both of the boom flow rate control valve 36 and the arm flow rate control valve 35 proportionally increase the flow rate from the operation amount of 20% when operated independently. However, from 60%, it has a characteristic of further increasing due to merging. Then, at the time of a combined operation with traveling, FIG.
As shown in (b) of FIG. 13 and (b) of FIG. 13, since there is no merging, the flow rate during full operation is 50% of that during single operation. In this case, the flow rate of the boom flow control valve 36 increases proportionally from the operation amount of 20%, and relatively good operability is obtained, whereas the operation amount of the arm flow control valve 35 is 60%. Until the flow rate is exceeded, the flow rate cannot be output, that is, the arm cylinder cannot be driven, and the operability deteriorates as described above.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and an object thereof is to provide a flow control valve for any working actuator in a combined operation of a left and right traveling motor and a working actuator. Another object of the present invention is to provide a hydraulic drive system for a construction machine capable of outputting a flow rate from a relatively small operation amount.

[0021]

In order to achieve the above object, the present invention has the following constitution. In order to make the description easy to understand, parentheses are added to the end of each component of the present invention, and the reference numerals shown in FIGS. 1 and 2 according to the embodiment of the present invention are added to the parentheses. The present invention relates to a first variable displacement hydraulic pump (11) and a second variable displacement hydraulic pump (21) whose discharge amounts are controlled according to load sensing pressures independent of each other, and these variable displacement hydraulic pumps (11). ) (21) a plurality of work actuators (33, etc.) driven by the pressure oil discharged, left and right traveling motors (43a) (43b), and a work actuator for controlling the drive of the work actuators (33, etc.), respectively. A work control valve group (31) including a flow rate control valve, and a travel control valve group including a left and right travel flow control valves (42A) (42B) for controlling the drive of the left and right travel motors (43a) (43b) ( 41) and a work flow control valve (35) for controlling the drive of at least one of the work actuators (33, etc.), A first variable throttle (13a), which is provided so as to be connectable to the first variable displacement hydraulic pump (11) and controls the flow rate of the pressure oil supplied to the corresponding actuator, and the second variable displacement hydraulic pump (21). ), And a first variable throttle (13a) for controlling the flow rate of the pressure oil supplied to the corresponding actuator.
The flow rate supplied from the second variable throttle (23a) and the flow rate supplied from the second variable throttle (23a) are combined, and a merging circuit capable of supplying the same to the corresponding actuator is built in, and the first variable throttle (13a) and the above-mentioned In the hydraulic drive device for a construction machine, wherein the second variable throttle (23a) is a variable throttle having different opening timings when the spool of the work flow control valve is operated in the same direction, the work control valve group (31). ) And the traveling control valve group (41),
Any one of the first variable displacement hydraulic pump (11) and the second variable displacement hydraulic pump (21), a work flow control valve included in the work control valve group (31), and the traveling control valve valve. A switching valve (51) that selectively connects one of the left and right traveling flow control valves (42A) (42B) included in the group (41) is provided, and the switching valve (51) is located at the first switching position. (54b) and the second switching position (55b), the first switching position (54b)
Is a first traveling main pipeline (14b) connected to the traveling control valve group (41), and the working flow control valve (35) included in the working control valve group (31).
Of the first variable pressure restrictor (13a) to communicate with the first main working pipeline (14a), and the first load pressure detection channel (41) connected to the traveling control valve group (41). Four
4a) and the first maximum load pressure detection path (34a) connected to the work flow control valve (35) included in the work control valve group (31) are communicated with each other, and the first traveling is performed. Main pipeline (14b) and the first working main pipeline (14)
a) is connected to the discharge pipe line (12) of the first variable displacement hydraulic pump (11), and the first load pressure detection line (44) is connected.
a) and the first maximum load pressure detection path (34a), the first load sensing conduit (15) for guiding the load sensing pressure for controlling the discharge amount of the first variable displacement hydraulic pump (11). And a second traveling main pipeline (24b) connected to the traveling control valve group (41).
And the second variable throttle (23) of the work flow control valve (35) included in the work control valve group (31).
a) a second work main pipe line (24a) connected to the second work pressure control line group (41) connected to the traveling control valve group (41); and the work control line. The work flow control valve (3 included in the valve group (31)
5) The second maximum load pressure detection path (34b) connected to 5) is made to communicate, and the second running main pipe line (24b) and the second working main pipe line (24a) are connected to each other. It is connected to the discharge pipe line (22) of the variable displacement hydraulic pump (21), and the second load pressure detection passage (44b) and the second maximum load pressure detection passage (34b) are connected to the second variable displacement Hydraulic pump (2
1) is a position connected to a second load sensing conduit (25) for guiding the load sensing pressure for controlling the discharge amount, and the second switching position (55b) is the first traveling main conduit. (14b) and the second running main pipeline (2
4b) to communicate with the first load pressure detection path (44
a) and the second load pressure detection path (44b) are communicated with each other, and the first traveling main pipeline (14b) and the second traveling main pipeline (24b) are connected to the second variable displacement hydraulic pressure. The first load pressure detection path (44a) and the second load pressure detection path (44) are connected to the discharge pipe line (22) of the pump (21).
b) is connected to the second load sensing pipeline (25) so that the first main working pipeline (14a) and the second main working pipeline (24a) communicate with each other, and The maximum load pressure detection path (34a) and the second maximum load pressure detection path (34b) are connected to each other, and the first main work pipeline (1
4a) and the second main pipeline for work (24a) to the first
Connected to the discharge pipe line (12) of the variable displacement hydraulic pump (11), and connects the first maximum load pressure detection path (34a) and the second maximum load pressure detection path (34b) to the first load. It is configured to have a position connected to the sensing conduit (15).

In the present invention, when the switching valve (51) is kept in the first switching position (54b), the work flow control valve (35) included in the work control valve group (31).
The first variable throttle (13a) is connected to the first variable displacement hydraulic pump (11), and the corresponding work flow control valve (35)
Second variable throttle (23a) is connected to the second variable displacement hydraulic pump (21), and the corresponding work flow control valve (35)
The pressure oil of the first and second variable displacement hydraulic pumps (11) and (21) can be joined together and supplied to the work actuator whose flow rate is controlled by the operation actuator, and a desired single operation of the work actuator can be realized.

The left and right traveling motors (43a) (43
When the switching valve (51) is switched to the second switching position (55b) in accordance with the combined operation of (b) and the corresponding work actuator, the first variable throttle (35) of the corresponding work flow control valve (35). 13a) the first working main conduit (14)
a) and the second work main line (24a) connected to the second variable throttle (23a) of the corresponding work flow control valve (35).
Communicates with the first maximum load pressure detection path (34a) and the second
Of the first variable displacement hydraulic pump (11) is connected to the first work main pipe line (14a) and the second work main pipe line (24a). Road (1
2), the first maximum load pressure detection path (34a) and the second maximum load pressure detection path (34b) control the discharge amount of the first variable displacement hydraulic pump (11). Since it is connected to the load sensing pipe line (15) of the first variable throttle (13a) and the second variable throttle (23a) at the time of full operation of the work flow control valve (35) in this combination. Is a variable throttle that is wholly or partially belonging to the operation amount of the spool of the relevant work flow control valve (35), or is a variable throttle that partially belongs to the first variable displacement hydraulic pump (11). 2) is supplied to the corresponding work actuator through both the first variable throttle (13a) and the second variable throttle (23a), whereby the flow rate characteristic of the first variable throttle (13a) and the second variable throttle (13a) are supplied. Variable aperture (23
It is possible to obtain a predetermined flow rate characteristic by combining the flow rate characteristics of a). Therefore, of the first variable aperture (13a) and the second variable aperture (23a), from the opening timing of the variable aperture that entirely belongs to the operation amount of the spool, that is, from the relatively small operation amount of the spool. A flow rate can be supplied to the corresponding work actuator, and the corresponding work actuator can be driven together with the left and right traveling motors (43a) (43b).

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a hydraulic drive system for a construction machine according to the present invention will be described below with reference to the drawings. 1 is a circuit diagram including a main part structure of an embodiment of a hydraulic drive system for a construction machine according to the present invention, and FIG. 2 is a circuit diagram showing an overall configuration of an embodiment of the present invention including a main part structure shown in FIG. 3, FIG. 3 is a diagram showing a flow rate characteristic at a boom single operation and a flow rate characteristic at a boom / travel combined operation obtained by the embodiment of the present invention shown in FIG. 2, and FIG. 4 is a diagram showing the flow rate characteristic of the present invention shown in FIG. The figure which shows the flow-rate characteristic at the time of arm independent operation obtained by embodiment, and the flow-rate characteristic at the time of arm / travel combined operation, and FIG. 5 shows the state when the switching valve shown in FIG. 2 is hold | maintained at the 1st switching position. FIG. 6 is a circuit diagram showing a state in which the switching valve shown in FIG. 2 is kept in the second switching position.

This embodiment is provided in a hydraulic excavator, for example, and in FIG. 1 showing the structure of the main part thereof, 11 is a first variable displacement hydraulic pump, 21 is a second variable displacement hydraulic pump, and 12 is a first variable displacement hydraulic pump. Of the variable displacement hydraulic pump 11, 22 is a discharge line of the second variable displacement hydraulic pump 21,
4a is a regulator for controlling the discharge amount of the first variable displacement hydraulic pump 11, and 4b is a second variable displacement hydraulic pump 21.
, 15 is a first load sensing pipe for guiding the maximum load pressure for controlling the drive of the regulator 4a, and 25 is a second load sensing pipe for guiding the maximum load pressure for controlling the drive of the regulator 4b. It is a road.

Reference numeral 33 is a working actuator, for example, a boom cylinder, and 36 is a boom flow control valve for controlling the flow of pressure oil supplied to the boom cylinder 33. The boom flow control valve 36 is included in the work control valve group 31 forming one control valve block together with the arm flow control valve 35 illustrated in FIG. 2 and the like. The spool 5 of the boom flow control valve 36 includes the first variable throttle 1
3a and a second variable diaphragm 23a are formed. The first variable diaphragm 13a and the second variable diaphragm 23a are
It is a variable diaphragm that makes the opening timings of the spools 5 different from each other when they are operated in the same direction (the arrow direction in FIG. 1). Further, the first variable throttle 13a is connectable to the first variable displacement hydraulic pump 11 via the first working main pipe line 14a,
The second variable throttle 23a is connectable to the second variable displacement hydraulic pump 21 via the second work main pipe line 24a. That is, the first variable diaphragm 13a and the second variable diaphragm 13a
The hydraulic oil of the hydraulic pumps 11 and 21 can be supplied to the boom cylinder 33 via the variable throttle 23a, the pressure compensating valves 2a and 2b located downstream thereof, and the check valves 3a and 3b.

As shown in FIG. 2, among the other work flow rate control valves, for example, the arm flow rate control valve 35 for controlling the drive of the arm cylinder is also the first variable throttle 13.
a, the second variable throttle 23a is built in, and the first variable throttle 13a is the first main working pipeline 14 described above.
a, and the second variable throttle 23a is connected to the above-mentioned second working main pipe line 24a. The turning flow rate control valve for controlling the turning motor includes only the first variable throttle 13a.

Further, as shown in FIG.
The flow control valve 42A for right traveling which controls drive of 3a, and the flow control valve 43b for left traveling which controls drive of the left traveling motor 43b are provided. These right running flow control valves 4
2A and the left travel flow control valve 42B constitute a travel control valve group 41 as shown in FIG. The right travel flow control valve 42A incorporates the first variable throttle 13b, and the left travel flow control valve 42B includes the second variable throttle 23b.
Built-in. The first variable throttle 13b is connectable to the first variable displacement hydraulic pump 11 via the first traveling main pipeline 14b, and the second variable throttle 23b connects the second traveling main pipeline 24b. It is connectable to the second variable displacement hydraulic pump 21 via the. As shown in FIG. 1, the first load pressure detection path 44 is provided in the pressure compensating valve 2c provided downstream of the first variable throttle 13b of the right travel flow control valve 42A.
a is connected, and the first load pressure detection path 44a is connected to the above-mentioned first load sensing conduit 15 via a switching valve 51 described later. Similarly, the second load pressure detection passage 44b is connected to the pressure compensation valve 2d provided downstream of the second variable throttle 23b of the left traveling flow control valve 42B, and the second load pressure detection passage 44b is Switching valve 5 described later
It is connected to the above-mentioned second load sensing conduit 25 via 1.

As shown in FIG. 2, the maximum load pressure on the side of the first variable throttle 13a of the work flow control valve is taken out by the first maximum load pressure detection path 34a, and the above-mentioned first load sensing is performed. It is led to the pipe line 15. Further, the maximum load pressure on the second variable throttle 23a side of the work flow control valve is the second load
Is taken out by the maximum load pressure detection path 34b and is guided to the above-mentioned second load sensing conduit 25.

The first variable throttle 13a and the second variable throttle 23a included in the work flow control valve, and the first variable throttle 13 included in the left and right traveling flow control valves 42A and 42B.
Among the b and the second variable diaphragms 23b, the ones indicated by "black circles" in FIG. 2 are variable diaphragms that entirely belong to the operation amount of the spool as described above, and have a relatively small stroke S1.
Start opening with. Further, what is indicated by a "white circle" in FIG. 2 is a variable diaphragm which partially belongs to the operation amount of the spool, and starts to open at a stroke S2 larger than the stroke S1.

In this embodiment, as shown in FIG. 2, the work control valve group 31 and the traveling control valve group 4 are also used.
Between the first variable displacement hydraulic pump 11 and the second variable displacement hydraulic pump 21, and the working flow rate control valve and the traveling control valve valve group 41 included in the working control valve group 31. Left and right traveling flow control valve 42A included,
42B is provided with a switching valve 51 that is selectively connected to any one of them. The switching valve 51 has a first switching position 54b and a second switching position 55b.

The first switching position 54b is connected to the first traveling control valve group 41, and the first traveling main line 14b is connected to the first traveling position 54b.
It is connected to the traveling control valve group 41 by communicating with the first working main pipe line 14a connected to the first variable throttle 13a such as the arm flow control valve 35 included in the working control valve group 31. The first load pressure detection path 44a and the arm flow control valve 35 included in the work control valve group 31.
And the like, and communicates with the first maximum load pressure detection path 34a, and connects the first traveling main pipeline 14b and the first working main pipeline 14a to the discharge pipeline of the first variable displacement hydraulic pump 11. 12 and the first load pressure detection path 44a and the first load pressure detection path 44a.
The maximum load pressure detection path 34a is connected to the first load sensing pipeline 15 that guides the load sensing pressure that controls the discharge amount of the first variable displacement hydraulic pump 11. In addition, the second traveling main pipe line 24b connected to the traveling control valve group 41 and the second variable throttle 23a connected to the arm flow control valve 35 and the like included in the working control valve group 31. The second load pressure detection path 44, which communicates with the second work main path 24a and is connected to the traveling control valve group 41.
b and the second maximum load pressure detection path 3 connected to the arm flow control valve 35 and the like included in the work control valve group 31.
4b to communicate with each other, connect the second running main pipe line 24b and the second working main pipe line 24a to the discharge pipe line 22 of the second variable displacement hydraulic pump 21, and connect the second load pressure detection line 44b. The second highest load pressure detection path 34b is connected to the second load sensing pipeline 25 that guides the load sensing pressure that controls the discharge amount of the second variable displacement hydraulic pump 21.

Then, the second switching position 55 of the switching valve 51.
b makes the first traveling main pipe line 14b and the second traveling main pipe passage 24b communicate with each other, and the first load pressure detection passage 44a and the second traveling pressure main pipe passage 24b are connected to each other.
Of the first traveling main pipe 14b and the second traveling main pipe 24b are connected to the discharge pipe 22 of the second variable displacement hydraulic pump 21, and The load pressure detection path 44a and the second load pressure detection path 44b are connected to the second load sensing pipeline 25 to connect the first work main pipeline 14a and the second work main pipeline 24a to each other, and The first maximum load pressure detection path 34a and the second maximum load pressure detection path 34b are connected to each other, and the first main work pipeline 14a
And the second work main pipe line 24a are connected to the discharge pipe line 12 of the first variable displacement hydraulic pump 11, and the first maximum load pressure detection passage 34a and the second maximum load pressure detection passage 34b are connected to each other. Connect to the load sensing line 15.

The switching valve 51 described above is switched when the control pressure output from the switching control means 52 shown in FIG. 2 is applied to the signal conduit 53. That is, when the left and right traveling motors 43a and 43b are individually operated, or when the work actuators such as the boom cylinder 33 and the arm cylinder are individually operated, the control pressure is not output from the switching control means 52, and the switching valve 51 is shown in FIG. The first switching position, which is the state, is maintained. In addition, the left and right traveling motors 43a and 43b
And a work actuator such as a boom cylinder 33 or an arm cylinder, a control pressure is output from the switching control means 52 to the signal line 53, and the switching valve 51 is moved to the left side from the state shown in FIG. It can be switched to the switching position of 2.

In the embodiment constructed as described above, when the boom cylinder 33 is independently operated, for example, the switching valve 51 is maintained at the first switching position as described above. That is, FIG.
The passage 64 is kept in the closed state by the spool 65 built in the switching valve 51 as shown in FIG. Further, since the spool 56 is kept at the left limit position in FIG. 5, the first variable throttle 13a of the boom flow rate control valve 36 is
Main working pipeline 14a, passages 66, 62 of the switching valve 51,
It becomes possible to connect to the first variable displacement hydraulic pump 11 via the discharge pipe line 12, and the second flow rate control valve 36 for the boom is in the second state.
The variable throttle 23a is in a state connectable to the second variable displacement hydraulic pump 21 via the second work main conduit 24a, the passages 61 and 63 of the switching valve 51, and the discharge conduit 22.

In such a state, when the spool 5 of the boom flow rate control valve 36 is switched in the direction of the arrow in FIG.
The first variable aperture 13a starts to open when the spool 5 moves by the stroke S1, and the second variable aperture 23a starts to open when the spool 5 moves by the stroke S2. Due to the opening of the first variable throttle 13a, the pressure oil of the first variable displacement hydraulic pump 11 is discharged into the discharge line 12, the first main working line 14a, the first variable throttle 13a, and the pressure compensation valve 2.
A is supplied to the bottom side of the boom cylinder 33 via the check valve 3a. The flow rate at this time is the first variable throttle 13a.
Proportional to the opening amount of. Further, the pressure oil of the second variable displacement hydraulic pump 21 is discharged through the opening of the second variable throttle 23a, the discharge pipeline 22, the second main working pipeline 24a, the second variable throttle 23a, the pressure compensating valve 2b, Via the check valve 3b, the pressure oil of the hydraulic pump 11 is merged and supplied to the bottom side of the boom cylinder 33. That is, when the second variable throttle 23a is opened, the boom cylinder 33 is driven by the pressure oil merged by the hydraulic pumps 11 and 21.

FIG. 3A shows that the boom cylinder 33 is supplied to the boom cylinder 33 in accordance with the flow rate characteristic when the boom cylinder 33 is independently operated, that is, the operation amount (%) of the spool of the boom flow control valve 36. The relationship of the controlled flow rate (%) is shown. As shown in FIG. 3A, the flow rate of the hydraulic pump 11 starts to be supplied to the boom cylinder 33 from the operation amount (20%) of the spool opened by the first variable throttle 13a, and the second variable throttle 23a. The flow rate supplied to the boom cylinder 33 from the operation amount (60%) of the spool that also opens increases due to the confluence of the hydraulic pumps 11 and 21.

During the combined operation of the boom cylinder 33 and the left and right traveling motors 42A and 42B, control pressure is output from the switching control means 52 shown in FIG. 2 to the signal line 53, and the switching valve 51 of FIG. It is switched to the second switching position 55b which is the left side position. That is, as shown in FIG. 6, the spool 65 built in the switching valve 51 is provided with the signal line 5
It is pressed by the control pressure guided to 3 and moves downward in the drawing, the passage 64 communicates with each other, and the first working main pipe line 14a and the second working main pipe line 24a communicate with each other through the passage 64. . Further, the spool 56 is switched to the right in FIG. 6 by the control pressure guided to the signal pipe 53, and the passage 66
And the first main working pipeline 14a are disconnected from each other, and the passage 6
The first traveling main pipeline 14b and the second traveling main pipeline 24b communicate with each other via 6, and the passage 64 and the second traveling main pipeline 24b are disconnected. As a result, the first variable throttle 13a and the second variable throttle 2 of the boom flow control valve 36 are
3a is in a state connectable to the first variable displacement hydraulic pump 11 via the first work main pipe line 14a, the second work main pipe line 24a, the passage 64 of the switching valve 51, and the discharge pipe line 12, Further, the first variable throttle 13b of the right traveling flow control valve 42A and the second variable throttle 2 of the left traveling flow control valve 42B.
3b can be connected to the second variable displacement hydraulic pump 21 via the first traveling main pipeline 14b, the second traveling main pipeline 24b, the passages 66, 61, 63 of the switching valve 51, and the discharge pipeline 22. It will be in a state.

In such a state, when the flow control valves 42A, 42B for left and right traveling are switched and the spool 5 of the boom flow control valve 36 is switched in the direction of the arrow in FIG. 1, as described above, the boom flow control is performed. When the spool 5 of the valve 36 moves by the stroke S1, the first variable throttle 13a starts to open, and the spool 5 moves by the stroke S1.
The second variable diaphragm 23a starts to open when it moves by 2. At this time, the pressure oil of the first variable displacement hydraulic pump 11 is discharged by the opening of the first variable throttle 13a, the discharge pipeline 12, the first main working pipeline 14a, the first variable throttle 13a, and the pressure compensation valve 2a. , The boom cylinder 33 via the check valve 3a.
Is supplied to the bottom side of. In addition, the second variable diaphragm 23a
The same pressure oil of the first variable displacement hydraulic pump 11 is supplied to the second main working pipeline 24a and the second variable throttle 23 by the opening of
It is supplied to the bottom side of the boom cylinder 33 via a, the pressure compensating valve 2b, and the check valve 3b. This drives the boom cylinder 33. The supply flow rate of the boom cylinder 33 at the full operation at this time is the flow rate of the first variable displacement hydraulic pump 11, that is, the flow rate of [1/2] when the boom cylinder 33 is individually operated.

The opening of the first variable throttle 13b of the right traveling flow control valve 42A and the left traveling flow control valve 42B.
Of the second variable diaphragm 23b,
First traveling main pipeline 14b and second traveling main pipeline 24
Via b, the pressure oil of the second variable displacement hydraulic pump 21 is supplied to both the right traveling motor 43a and the left traveling motor 43b, so that traveling straight ahead can be realized.

FIG. 3 (b) shows the flow characteristic of the boom cylinder 33 during combined operation with the traveling of the boom cylinder 33, that is, the boom cylinder corresponding to the operation amount (%) of the spool of the boom flow control valve 36. The relationship of the control flow rate (%) supplied to 33 is shown. As shown in FIG. 3B, the operation amount of the spool (20
%), The flow rate of the first variable displacement hydraulic pump 11 starts to be supplied to the boom cylinder 33 from the operation amount (60%) of the spool that also opens the second variable throttle 23a.
The pressure oil of No. 1 is increased and supplied to the boom cylinder 33.
The control flow rate when the boom flow control valve 36 is fully operated is 50%, which is the flow rate of only the hydraulic pump 11, as described above.

As described above, the boom cylinder 33 can be operated independently and the boom cylinder 33 and the left and right traveling motors 43a and 43b can be combined.

Next, as shown in FIG. 2, the first variable aperture 13a is made up of a "white circle" variable aperture which partially belongs to the operation amount of the spool, and the second variable aperture 23a is the operation amount of the spool. Single operation of the arm cylinder controlled by the arm flow control valve 35 consisting of the variable throttle of "black circle" which belongs to the whole, this arm cylinder and the left and right traveling motors 42A,
A composite operation with 42B will be described. Although the detailed structure of the arm flow control valve is omitted, in the structure of the boom flow control valve 36 of FIG. 1, the variable throttle that opens at the stroke S2 is provided as the first variable throttle 13a.
This corresponds to a variable diaphragm that opens at 1 as the second variable diaphragm 23a.

In the following, referring to FIG. 2, for example, when the arm cylinder is operated independently, the switching valve 51 is kept at the first switching position, and the first variable throttle 13a of the arm flow control valve 35 is moved to the first switching position. Main working pipeline 14a, discharge pipeline 1
The second variable throttle 23a of the arm flow control valve 35 is connected to the first variable displacement hydraulic pump 11 via the second main hydraulic line 24a for operation, the switching valve 51, and the discharge line. The second variable displacement hydraulic pump 21 can be connected via 22.

In such a state, when the spool 5 of the arm flow control valve 35 is switched in the same direction as the spool 5 switching direction of the boom flow control valve 36 shown in FIG. 1, the arm flow control valve is switched. When the spool (not shown) of 35 moves by the stroke S1, the second variable aperture 23
a starts to open, and when the spool moves by stroke S2, the first variable aperture 13a starts to open. Second
Of the variable throttle 23a causes the pressure oil of the second variable displacement hydraulic pump 21 to pass through the discharge pipe 22, the switching valve 51, the second working main pipe 24a, and the second variable throttle 23a. Is supplied to. In addition, the second variable diaphragm 23
Due to the opening of the first variable throttle 13a whose opening time is later than that of a, the pressure oil of the first variable displacement hydraulic pump 11 is discharged to the discharge pipeline 12, the first main working pipeline 14a, and the first variable throttle 13a. Via the, is joined to the pressure oil of the hydraulic pump 21 and supplied to the arm cylinder. That is, when the first variable throttle 13a is opened, the arm cylinders are driven by the pressure oil merged by the hydraulic pumps 11 and 21.

In FIG. 4 (a), the flow rate characteristic of the above-described arm cylinder during independent operation, that is, the operation amount (%) of the spool of the arm flow control valve 35 is supplied to the arm cylinder. The relationship of control flow rate (%) is shown. As shown in FIG. 4A, the second variable diaphragm 2
The flow rate of the hydraulic pump 21 starts to be supplied to the arm cylinder from the operation amount (20%) of the spool having the opening 3a.
The operating amount of the spool (60
%) To the arm cylinder increases due to the merging of the hydraulic pumps 11 and 21. That is, in the arm flow control valve 35, the built-in first variable throttle 13a is
The variable throttle that partially belongs to the operation amount of the spool, and the second variable throttle 23a is the variable throttle that entirely belongs to the operation amount of the spool. On the contrary, the boom flow control valve 36 described above is , The built-in first variable diaphragm 13a
The variable throttle that entirely belongs to the operation amount of the spool and the second variable aperture 23a is the variable throttle that partially belongs to the operation amount of the spool. The obtained flow rate characteristic is as shown in FIG. As shown in FIG. 4A, the boom flow rate control valve 36 and the arm flow rate control valve 35 are the same, for example.

During the combined operation of the arm cylinder and the left and right traveling motors 42A and 42B, the control pressure is output from the switching control means 52 shown in FIG. 2 to the signal line 53, and the switching valve 51 is moved to the left side in FIG. Second switching position 5 which is the position
It is switched to 5b. That is, the first work main pipe line 14a and the second work main pipe line 24a communicate with each other via the switching valve 51, and these work main pipe lines 14a and 24a have the first work pipe line 14a.
The variable displacement hydraulic pump 11 of FIG. Further, the first traveling main pipeline 14b and the second traveling main pipeline 24b communicate with each other via the switching valve 51, whereby the traveling main pipelines 14b and 24b are connected to the second variable displacement hydraulic pump 2.
1 can be connected.

In such a state, when the flow control valves 42A, 42B for left and right traveling are switched and the spool of the arm flow control valve 35 is switched in the same direction as the arrow in FIG. 1 as described above, the arm flow control is performed. When the spool of the valve 35 moves by the stroke S1, the second variable throttle 2
3a starts to open, and when the spool moves by stroke S2, the first variable aperture 13a starts to open. At this time, due to the opening of the second variable throttle 23a, the pressure oil of the first variable displacement hydraulic pump 11 passes through the discharge pipeline 12, the second main working pipeline 14b, and the second variable throttle 23a, and then the arm cylinder. Is supplied to. In addition, the first variable diaphragm 13a
The same pressure oil of the first variable displacement hydraulic pump 11 is applied to the first main working pipeline 14a and the first variable throttle 13
It is supplied to the arm cylinder via a. This drives the arm cylinder. The supply flow rate of the arm cylinder at the time of full operation at this time is the flow rate of the first variable displacement hydraulic pump 11, that is, the flow rate of [1/2] when the arm cylinder is independently operated as described above.

The first variable throttle 13b of the right travel flow control valve 42A and the second variable throttle 13B of the left travel flow control valve 42B.
Due to the opening of the variable throttle 23b, the pressure oil of the second variable displacement hydraulic pump 21 is transferred to the right traveling motor 43a via the discharge pipeline 22, the first traveling main pipeline 14b and the second traveling main pipeline 24b. , The left traveling motor 43b is both supplied, and traveling straight ahead can be realized. This point is the same as that when combined with the boom cylinder 33 described above.

FIG. 4B shows the flow characteristics of the combined operation of the arm cylinder and traveling, that is, the arm cylinder corresponding to the operation amount (%) of the spool of the arm flow control valve 35. The relationship of the control flow rate (%) supplied is shown. As shown in FIG. 4B, the flow rate of the first variable displacement hydraulic pump 11 starts to be supplied to the arm cylinder from the operation amount (20%) of the spool opened by the second variable throttle 23a, and The pressure oil of the hydraulic pump 11 is increased from the operation amount (60%) of the spool that also opens the variable throttle 13a, and is supplied to the arm cylinder. The control flow rate when the arm flow control valve is fully operated is as described above.
The flow rate of only the hydraulic pump 11 is 50%. The flow rate characteristic of the arm flow rate control valve 35 obtained at this time is also shown in FIG.
As is clear from (b) of FIG. 4 and (b) of FIG. 4, it is equivalent to the boom flow control valve 36.

As described above, the arm cylinder is independently operated, and the arm cylinder and the left and right traveling motors 43a,
A composite operation with 43b can be performed.

In the embodiment thus constructed, the switching valve 51 is switched to the second switching position 55b during the combined operation of the left and right traveling motors 43a and 43b and the work actuators such as the boom cylinder 33 and the arm cylinder. Detects the maximum load pressure of the work actuator.
Maximum load pressure detection path 34a, second maximum load pressure detection path 3
4b is connected to a first load sensing conduit 15 communicating with the regulator 4a of the first variable displacement hydraulic pump 11, and a first load pressure detection conduit for detecting the load pressure of the left and right traveling motors 43a, 43b. 44 a and the second load pressure detection path 44 b are connected to the second load sensing conduit 25 that communicates with the regulator 4 b of the second variable displacement hydraulic pump 21. As a result, the hydraulic pumps 11 and 21 are not affected by the load pressures of the opposite sides during this combined operation, and the front operating speed during climbing is increased, as in the prior art of the applicant shown in FIG. 8 described above. It does not cause a significant decrease or a significant decrease in running speed when escaping a muddy area.

Further, the boom flow rate control valve 36, the arm flow rate control valve 35, and the switching valve in which the forms of the variable throttles constituting the first variable throttle 13a and the second variable throttle 23a are set to be opposite to each other. As is clear from the connection relationship between 51 and the hydraulic pumps 11 and 21, a working actuator,
When performing a combined operation with the left and right traveling motors 43a and 43b,
When the corresponding work flow rate control valve is fully operated, whether the first variable throttle 13a and the second variable throttle 23a are variable throttles wholly belong to the operation amount of the spool of the work flow control valve. Regardless of whether it is a variable throttle that partially belongs, the pressure oil of the first variable displacement hydraulic pump 11 is supplied to the corresponding work actuator via both the first variable throttle 13a and the second variable throttle 23a. Therefore, the flow rate characteristic of the first variable throttle 13a and the second variable throttle 2
It is possible to obtain a predetermined flow rate characteristic that is a combination of the flow rate characteristics of 3a. Therefore, the first variable aperture 13a and the second variable aperture 13a
Among the variable throttles 23a, the flow rate can be supplied to the corresponding work actuator from the opening timing of the variable throttle that entirely belongs to the operation amount of the spool, that is, from the relatively small operation amount of the spool. It can be driven together with the traveling motors 43a and 43b. As a result, it is possible to ensure good operability of the corresponding work actuator during this composite operation.

The turning flow control valve for driving the turning motor is the first variable displacement hydraulic pump 11 connected to the first variable displacement hydraulic pump 11.
Is equipped with a first variable throttle 13a which can always communicate with the main working pipeline 14a, and the first variable throttle 13a is composed of a variable throttle indicated by a "black circle" which entirely belongs to the operation amount of the spool. When operating the swing motor independently and
In any of the traveling complex operations, the hydraulic oil is driven by the pressure oil from the first variable displacement hydraulic pump 11. This point is equivalent to the prior art of the applicant of the present invention shown in FIG. 8, and the control flow rate equivalent to that of the prior art of FIG. 8 is output to the swing motor from a relatively small operation amount.

[0055]

According to the first aspect of the present invention,
In the combined operation of the left and right traveling motors and work actuators, the flow control valve for any work actuator can output the flow rate from a comparatively small operation amount, which makes the work actuator suitable. It is possible to obtain excellent operability.

[Brief description of drawings]

FIG. 1 is a circuit diagram including a main structure of an embodiment of a hydraulic drive system for a construction machine according to the present invention.

FIG. 2 is a circuit diagram showing an overall configuration of an embodiment of the present invention including a main part structure shown in FIG.

FIG. 3 is a diagram showing a flow rate characteristic during a boom single operation and a flow rate characteristic during a boom / travel combined operation, which are obtained according to the embodiment of the present invention shown in FIG.

FIG. 4 is a diagram showing a flow rate characteristic at the time of single arm operation and a flow rate characteristic at the time of arm / travel combined operation, which are obtained by the embodiment of the present invention shown in FIG.

FIG. 5 is a circuit diagram showing a state in which the switching valve shown in FIG. 2 is maintained in a first switching position.

FIG. 6 is a circuit diagram showing a state in which the switching valve shown in FIG. 2 is maintained in a second switching position.

FIG. 7 is a circuit diagram showing a conventional hydraulic drive system for a construction machine.

FIG. 8 is a circuit diagram showing a hydraulic drive system for a construction machine previously proposed by the applicant of the present application.

9 is a circuit diagram including a vertical cross section of a flow control valve provided in the conventional technique shown in FIG. 7. FIG.

10 is a diagram showing opening area characteristics of the first variable throttle and the second variable throttle of the boom flow control valve obtained by the applicant's prior art shown in FIG.

11 is a diagram showing opening area characteristics of the first variable throttle and the second variable throttle of the arm flow control valve shown in FIG. 8 obtained by the applicant's prior art.

FIG. 12 is a diagram showing a flow rate characteristic during a boom single operation and a flow rate characteristic during a boom / travel combined operation, which are obtained by the applicant's prior art shown in FIG. 8;

FIG. 13 is a diagram showing a flow rate characteristic at the time of the arm alone operation and a flow rate characteristic at the time of the arm / travel combined operation, which are obtained by the applicant's prior art shown in FIG. 8;

[Explanation of symbols]

 2a Pressure compensating valve 2b Pressure compensating valve 2c Pressure compensating valve 2d Pressure compensating valve 3a Check valve 3b Check valve 4a Regulator 4b Regulator 5 Spool 11 First variable displacement hydraulic pump 12 Discharge pipe line 13a First variable throttle 13b First Variable throttle 14a First working main pipeline 14b First traveling main pipeline 15 First load sensing pipeline 21 Second variable displacement hydraulic pump 22 Discharge pipeline 23a Second variable throttle 23b Second variable throttle 24a Second main pipeline for work 24b Second main pipeline for travel 25 Second load sensing pipeline 31 Work control valve group 33 Boom cylinder (work actuator) 34a First maximum load pressure detection pathway 34b Second Maximum load pressure detection path 35 Arm flow control valve (work flow control valve) 36 Arm flow control valve Flow control valve for work) 41 Travel control valve group 42A Flow control valve for right travel 42B Flow control valve for left travel 43a Right travel motor 43b Left travel motor 44a First load pressure detection path 44b Second load pressure detection path 51 switching valve 52 switching control means 53 signal line 54b first switching position 55b second switching position 56 spool 61 passage 62 passage 63 passage 64 passage 65 spool 66 passage

Claims (1)

[Claims] 1. A first variable displacement hydraulic pump and a second variable displacement hydraulic pump, the discharge amounts of which are controlled independently of each other according to load sensing pressure, and the first and second variable displacement hydraulic pumps. A plurality of work actuators and left and right traveling motors driven by the discharged pressure oil, a work control valve group including work flow control valves for controlling the driving of the work actuators, and a drive of the left and right traveling motors. A traveling control valve group including a left and right traveling flow control valve for controlling, wherein the working flow control valve for controlling driving of at least one of the working actuators is the first variable displacement hydraulic pump. Is provided so that it can be connected to
A first variable throttle that controls the flow rate of pressure oil supplied to the corresponding actuator, and a first variable throttle that is connected to the second variable displacement hydraulic pump and that controls the flow rate of pressure oil supplied to the corresponding actuator. A second variable throttle, and a converging circuit capable of converging the flow rate supplied from the first variable throttle and the flow rate supplied from the second variable throttle and supplying the combined flow rate to the corresponding actuator. A hydraulic drive device for a construction machine, wherein the first variable throttle and the second variable throttle are variable throttles whose opening timings are different from each other when the spools of the work flow control valve are operated in the same direction. Which is arranged between the group and the traveling control valve group, and which is included in the working control valve group and either of the first variable displacement hydraulic pump or the second variable displacement hydraulic pump. A switching valve that selectively connects either the industrial flow control valve or the left and right traveling flow control valves included in the traveling control valve valve group is provided, and the switching valve is provided at the first switching position and the second switching position. The switching position of the working flow control valve included in the working control valve group and the first running main pipe line connected to the running control valve group. A first load pressure detection path communicating with the first main working pipeline connected to the first variable throttle and connected to the traveling control valve group, and included in the work control valve group. The first maximum load pressure detection path connected to the work flow control valve is communicated, and the first traveling main pipeline and the first working main pipeline are connected to the first variable displacement hydraulic pump. Connected to the discharge pipe line, and connected to the first load pressure detection line and the first load pressure detection line. Connected to the first load sensing pipeline for guiding the load sensing pressure that controls the discharge amount of the first variable displacement hydraulic pump, and connected to the traveling control valve group. The second main working pipeline connected to the second variable throttle of the work flow control valve included in the work control valve group is connected to the second main working pipeline, and the travel control is performed. The second load pressure detection path connected to the valve group and the second highest load pressure detection path connected to the work flow control valve included in the work control valve group are communicated with each other, and Of the main pipeline for traveling and the second main pipeline for work are connected to the discharge pipeline of the second variable displacement hydraulic pump to connect the second load pressure detection path and the second maximum load pressure detection path. , Controlling the discharge rate of the second variable displacement hydraulic pump Is a position connected to a second load sensing pipeline for guiding the load sensing pressure, and the second switching position connects the first traveling main pipeline and the second traveling main pipeline. The first load pressure detection path and the second load pressure detection path are communicated with each other, and the first traveling main pipeline and the second traveling main pipeline are connected to the second variable displacement hydraulic pump. Connected to the discharge pipe line, the first load pressure detection line and the second load pressure detection line are connected to the second load sensing pipe line, and the first work main line and the second work line. The main working pipeline is communicated with the first maximum load pressure detection channel and the second maximum load pressure sensing channel are communicated with each other, and the first working main pipeline and the second working main pipeline are connected. Is connected to the discharge line of the first variable displacement hydraulic pump, and is connected to the first maximum load pressure detection line. Hydraulic drive system for a construction machine, characterized in that the serial second highest load pressure Detchi a position connecting to the first load-sensing line above.