JPH09209415A - Hydraulic driving device of construction machinery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To vary flow characteristic between actuators according to a work state in a hydraulic driving device of a construction machinery and to promote composite controllability. SOLUTION: A first hydraulic pump 25a is connected in parallel with first and second actuators 22 and 23 through flow controlling valves 30a and 31a and pressure controlling valves 33a and 34a, and a second hydraulic pump 25b is connected in parallel with first, second and third actuators 22, 23 and 24 through flow controlling valves 30b, 31b and 32b and pressure controlling valves 33b, 34b and 35b. A target differential pressure setting 81 sets target differential pressure of the hydraulic pump 25a in larger value than target differential pressure of the hydraulic pump 25b in a controlling state operating at least one of the first and second actuators 22 and 23 having comparatively low load pressure and third actuator 24 having comparatively high load pressure based on the detected result of a controlling state detector 73.

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 such as a hydraulic excavator, and more particularly to a hydraulic drive system for a construction machine suitable for combined driving of a plurality of actuators.

[0002]

2. Description of the Related Art As a conventional technique of a hydraulic drive system for a construction machine, which is suitable for a combined drive of a plurality of actuators, Japanese Patent Application Laid-Open No. Hei 4-
There are those described in Japanese Patent Laid-Open No. 194405 and Japanese Patent Laid-Open No. 5-171660. A conventional technique based on the invention described in JP-A-4-194405 will be described with reference to FIG.

In FIG. 7, the hydraulic drive system comprises a hydraulic pump 1 and 2 driven by a prime mover such as an engine (not shown), a boom driven by pressure oil discharged from the hydraulic pumps 1 and 2. Actuators 3a, 3b, 3 for work machines such as arms and buckets, turning, and traveling devices
c and 4a, 4b, 4c and directional flow control valves 5a, 5b, 5c and 6a, 6b, 6c for supplying pressure oil from the hydraulic pumps 1 and 2 to the actuators 3a, 3b, 3c and 4a, 4b, 4c. And the actuators 3a, 3b, 3
c and pressure control valves 7a, 7b, 7c and 8a, 8b, 8c for load compensating the pressure oil supply to 4a, 4b, 4c.
And a merging valve 11 that connects the discharge circuits 9 and 10 of the hydraulic pumps 1 and 2.

In the above structure, the discharge pressure oil of the hydraulic pump 1 is supplied from the discharge circuit 9 to the directional flow control valves 5a, 5b, 5c.
By operating an operation valve (not shown) corresponding to the directional flow control valves 5a, 5b, 5c, the directional flow control valve is opened, and the pressure oil is pressure control valves 7a, 7b, 7c.
Each actuator 3a, 3b, 3c is operated via c. Here, the directional flow control valves 5a, 5b, 5c and the pressure control valve 7 are connected to one of the pressure control valves 7a, 7b, 7c.
A pressure between a, 7b and 7c is applied in the opening direction, and on the other hand,
The actuator 3a, which is detected by the check valves 13a, 13b, 13c and guided to the maximum load pressure detection circuit 12,
The maximum load pressure PLmax1 of 3b and 3c is applied in the closing direction. Therefore, the respective pressures between the directional flow control valves 5a, 5b, 5c and the pressure control valves 7a, 7b, 7c are controlled to be the same as the maximum load pressure PLmax1.

On the other hand, the maximum load pressure PLmax1 and the discharge pressure of the hydraulic pump 1 are guided to the capacity control section 14 of the hydraulic pump 1, and the maximum load pressure PLmax1 has a predetermined value Δ.
The pump capacity is controlled so that the pump discharge pressure Ps1 is increased by PLS1. As a result, the differential pressure between the pump discharge pressure Ps1 and the maximum load pressure PLmax1, that is, the directional flow control valve 5a,
The differential pressure across the throttle openings of 5b, 5c is always controlled to be constant, and the flow rate according to the opening area of the directional flow control valves 5a, 5b, 5c does not depend on the load pressure, but the actuators 3a, 3
b, 3c.

Further, by the operation of the directional flow control valves 6a, 6b, 6c connected to the discharge circuit 10 of the hydraulic pump 2,
The pressure oil discharged from the hydraulic pump 2 passes through the directional flow control valve and the pressure control valves 8a, 8b, 8c, and the actuators 4a,
4b and 4c are activated. Pressure control valves 8a, 8 at this time
The operations of b and 8c and the capacity control of the hydraulic pump 2 are the same as those described for the hydraulic pump 1.

The merging valve 11 has actuators 3a, 3b, 3c as disclosed in Japanese Patent Laid-Open No. 4-194405.
And O of operation levers (not shown) of 4a, 4b, 4c
It is configured to be turned on based on the detection result by the N, OFF detection means or the discharge pressure detection means of the hydraulic pumps 1, 2. When the merging valve 11 is turned on, the discharge circuit 9 of the hydraulic pump 1 and the discharge circuit 10 of the hydraulic pump 2 are connected to each other, and the maximum load pressure detection circuit 12 and the maximum load pressure detection circuit 15 are connected to each other. The total output of 2 drives the actuator.

In this way, the hydraulic pumps 1 and 2 output excessively to waste energy, or the total output of the hydraulic pumps 1 and 2 cannot be fully utilized, and the movement of the actuator is slow. It prevents the occurrence of such problems.

In the prior art disclosed in Japanese Patent Application Laid-Open No. 5-171660, a merging valve is not provided, and a flow rate control valve connected to the first hydraulic pump and a flow rate connected to the second hydraulic pump are not provided in the valve device. A control valve is provided, and the pressure oils of the two hydraulic pumps are merged on the downstream side of the two flow rate control valves to be supplied to the actuator. The same effect can be obtained in this conventional technique.

[0010]

In the prior art shown in FIG. 7, the hydraulic pump 1 is operated when the merging valve 11 is in the OFF state.
Actuators 3a, 3b connected to the discharge circuit 9 of
3c and the actuators 4a, 4b, 4c connected to the discharge circuit 10 of the hydraulic pump 2 have a pressure difference ΔPLS1 (= PLS1) between the discharge pressure Ps1 of the hydraulic pump 1 and the maximum load pressure PLmax1.
s1−PLmax1), the discharge pressure Ps2 of the hydraulic pump 2, the maximum load pressure PLmax2 and the differential pressure ΔPLS2 (= Ps2−PLmax2). At this time, ΔPLS1 ≒
It is controlled by ΔPLS2. With this configuration, assuming a composite operation of operating all the actuators 3a, 3b, 3c, 4a, 4b, 4c, the directional flow control valves 5a, 5b, 5c, 6a, 6b, 6c corresponding to the respective operation lever amounts. It is assumed that the opening area of is set. In this case, the actuator 3
In the work of making the operation of the actuator 4b faster than the operation of the actuator 3b during the combined operation of b, 4b, and 4c, the operation lever corresponding to the actuator 4b must be operated larger than usual. As described above, there is a problem that it is difficult to perform a composite operation depending on the work situation.

The conventional technique described in Japanese Patent Laid-Open No. 5-171660 has the same problem.

It is an object of the present invention to provide a hydraulic drive system for a construction machine which changes the flow rate characteristic between the actuators according to the work situation and is excellent in combined operability.

[0013]

[Means for Solving the Problems]

(1) In order to solve the above problems, the present invention provides at least two first and second hydraulic pumps and first, second, and third actuators driven by pressure oil supplied from these hydraulic pumps. And a plurality of valve devices including first, second, and third valve devices for controlling the operations of the first, second, and third actuators, respectively, and the first valve The device includes first and second flow control valves and first and second pressure control valves, the second valve device including third and fourth flow control valves and third and fourth pressure control valves. A valve, the third valve device includes a fifth flow control valve and a fifth pressure control valve, and the first hydraulic pump includes the first flow control valve and the first pressure control valve. Is connected to the first actuator via the third flow control valve. Through said third pressure control valve second
To the first actuator, and the second hydraulic pump is connected to the first actuator via the second flow rate control valve and the second pressure control valve. , The first and second actuators are connected in parallel with the first and second actuators via the fourth and fifth flow rate control valves and the fourth and fifth pressure control valves, and the first and second actuators are connected in parallel. The valve device is the first
And the pressure oil from the second hydraulic pump merges on the downstream side of the first and second flow rate control valves and the first and second pressure control valves, and is supplied to the first actuator. Of the second actuator, the pressure oil from the first and second hydraulic pumps merges on the downstream side of the third and fourth flow rate control valves and the third and fourth pressure control valves. And the downstream pressures of the first and third flow control valves are the same as the higher load pressure of the first and second actuators. And the second, fourth, and fifth pressure control valves control the downstream pressure of the second, fourth, and fifth flow control valves to be the loads of the first, second, and third actuators. The first hydraulic pump is controlled so as to be the same as the highest pressure, and the first hydraulic pump controls the first and second hydraulic pumps. The pump discharge pressure is controlled to be higher than the higher one of the load pressures of the actuators, and the second hydraulic pump has the highest pressure of the load pressures of the first, second, and third actuators. In a hydraulic drive system for a construction machine, which is controlled so that the pump discharge pressure is higher than the pump discharge pressure, a detection unit that detects an operation state of the plurality of actuators, and the first and second operation units based on a detection result of the operation state. Target differential pressure setting means for setting first and second target differential pressures for controlling the hydraulic pump;
First pump displacement control means for controlling the pump displacement so that the discharge pressure of the hydraulic pump is higher than the pressure having the higher load pressure of the first and second actuators by the first target differential pressure, A second pump that controls the pump displacement so that the discharge pressure of the second hydraulic pump is higher than the highest load pressure of the first, second, and third actuators by the second target differential pressure. And a capacity control means.

In the present invention configured as described above,
When the first, second, and third valve devices are operated with the intention of the combined drive of the first, second, and third actuators, the first and third pressure control valves cause the first and third flow rates. The downstream pressure of the control valve is controlled to be the same as the higher pressure of the load pressure of the first and second actuators, whereby the first and third actuators are controlled.
The differential pressure across the flow control valve is the same, and the discharge flow rate of the first hydraulic pump is the first through the first and third flow control valves.
And the second actuator, which is divided and supplied. The second, fourth and fifth pressure control valves are the second, fourth and fifth pressure control valves.
The downstream pressure of the flow control valve is controlled so that it becomes the same as the highest load pressure of the first, second, and third actuators, so that before and after the second, fourth, and fifth flow control valves. The differential pressure is the same, the discharge flow rate of the second hydraulic pump is the second,
The divided flow is supplied to the first, second, and third actuators via the fourth and fifth flow control valves. As a result, the first,
The second and third actuators are supplied with flow rates according to the manipulated variables of the first, second, and third valve devices, and the combined drive of the first, second, and third actuators is reliably performed.

On the other hand, at this time, the operation states of the first, second, and third actuators are detected by the operation detecting means, and the target differential pressure setting means is based on the detection result of the operation state. The first and second target differential pressures for controlling the hydraulic pump are set, and the first pump displacement control means determines whether the discharge pressure of the first hydraulic pump is higher than the load pressure of the first and second actuators. The pump displacement is controlled so as to be higher than the pressure by the first target differential pressure, and the second pump displacement control means controls the discharge pressure of the second hydraulic pump to the load pressure of the first, second and third actuators. The pump displacement is controlled so as to be higher than the highest pressure by the second target differential pressure. Thus the first
By controlling the capacities of the first and second hydraulic pumps, the differential pressure across the first and third flow rate control valves becomes a differential pressure corresponding to the first target differential pressure, and the second, fourth, and fifth differential pressures are obtained. The differential pressure across the flow control valve becomes a differential pressure corresponding to the second target differential pressure,
Flow rate from the first hydraulic pump to the first and second actuators and / or
Alternatively, the supply flow rate from the second hydraulic pump to the first, second, and third actuators can be made different from the normal flow rate. For example, if the second target differential pressure is set to be equal to the normal target differential pressure and the first target differential pressure is set to be larger than the normal target differential pressure, then the first hydraulic pump can be set to the first and second actuators. The supply flow rate to is higher than usual. As a result, the flow rate characteristics between the actuators change according to the work situation, the composite operability is improved, and the work efficiency is improved.

(2) In the above (1), preferably,
The third actuator is an actuator having a higher load pressure than the first and second actuators, and the target differential pressure setting means is configured to perform a combined operation of the first, second and third actuators by the detection means. Once detected,
The first target differential pressure is set higher than the second target differential pressure by a predetermined value.

When the third actuator is an actuator having a higher load pressure than the first and second actuators, the discharge pressure of the second hydraulic pump is set to be higher than the load pressure of the third actuator by the first pump displacement control means. The discharge pressure of the first hydraulic pump is controlled to be higher by the second target differential pressure, whereas the discharge pressure of the first hydraulic pump is higher than the load pressure of the first and second actuators by the second pump displacement control means. Since the pressure is controlled to be higher than the above pressure by the first target differential pressure, a relatively low discharge pressure, which is slightly higher than the higher load pressure of the first and second actuators, is sufficient.
For this reason, when the first and second hydraulic pumps are subjected to horsepower limitation control, the second hydraulic pump having a high discharge pressure has a reduced discharge amount and is divided and supplied to the first, second and third actuators. Although the flow rate of the pressure oil to be reduced decreases, the second hydraulic pump having a low discharge pressure has a horsepower margin in the discharge amount. Therefore, the target differential pressure setting means sets the first target differential pressure to the second target differential pressure. By setting the pressure higher than the pressure by a predetermined value, the discharge amount of the first hydraulic pump increases, and the increased discharge amount increases the first and second discharge amounts.
Is divided and supplied to the actuator. Therefore, the flow rate supplied to the first and second actuators is
And the second target differential pressure are both increased as compared with the case where they are set equal to the normal target differential pressure, and the composite operability is improved. In addition, the discharge amounts of the first and second hydraulic pumps are effectively set to the first,
It can be supplied to the second and third actuators, and the output of the prime mover can be effectively utilized.

(3) Further, in the above (1), preferably, the target differential pressure setting means is a combined operation of the first, second and third actuators by the detecting means, and the third differential pressure setting means. When it is detected that the load pressure of the actuator is higher than the load pressures of the first and second actuators, the first target differential pressure is set higher than the second target differential pressure by a predetermined value.

By adding the load pressure of the actuator to the target differential pressure setting condition in the target differential pressure setting means in this way, even when the magnitude relationship among the load pressures of the first, second and third actuators changes, the work can be performed. Depending on the situation, the flow rate characteristics between the actuators change, the composite operability improves, and the work efficiency improves.

(4) Further, in the above (2) or (3), preferably, the detecting means is the first, second, or third.
The target differential pressure setting means includes means for detecting operation amounts of the first, second and third operation means for operating the valve device, and the target differential pressure setting means is responsive to the operation amounts of the first and second operation means. The predetermined value is increased.

In this way, the second target differential pressure is set equal to the normal target differential pressure by increasing the predetermined value according to the operation amount of the first and second operating means, and the first target differential pressure is set. When the pressure is set higher than the normal target differential pressure, the increase amount of the supply flow rate from the first hydraulic pump to the first and second actuators increases in accordance with the operation amounts of the first and second operating means. Therefore, better composite operability can be obtained.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, the hydraulic drive system of the present embodiment has a first hydraulic pump 25a and a second hydraulic pump 2 which are a plurality of hydraulic pumps driven by a prime mover (not shown).
5b, a plurality of actuators driven by pressure oil supplied from these hydraulic pumps, for example, first and second actuators 22 and 23 having a relatively low load pressure and a third actuator 24 having a relatively high load pressure. , A first valve device 50 provided between the first and second hydraulic pumps 25a and 25b and the first actuator 22, and the first and second hydraulic pumps 25a and 25b and the second actuator 23. A second valve device 51 provided between the
The third valve device 52 provided between the hydraulic pump 25b and the third actuator 24 and the second and third valve devices 51 and 52 are operated to operate the second and third actuators 23 and 24. An operating lever device 71 for operating,
The first valve device 50 is operated to operate the first actuator 22.
Based on the detection result of the operation lever device 72 for activating the operation lever, the operation state detector 73 for detecting the ON / OFF state and the operation amount of the operation of the operation lever devices 71, 72, and the detection result of the operation state detector 73. First and second hydraulic pumps 25,
Target differential pressure setting device 81 for setting first and second target differential pressures for controlling 25b, and pump discharge pressure detector 79a for detecting pump discharge pressures of the first and second hydraulic pumps 25, 25b. , 79b, a first maximum load pressure detector 78a for detecting the maximum load pressure of the first and second actuators 22, 23, and the first, second and third actuators 2
The second maximum load pressure detector 78b for detecting the maximum load pressure of 2, 23, 24, the first and second target differential pressures set by the target differential pressure setting unit 81, and the pump discharge pressure detector 79a, 7
9b and first and second maximum load pressure detectors 78a, 78
first and second pump displacement controllers 75a and 75b that generate control signals for controlling the displacements of the first and second hydraulic pumps 25 and 25b based on the detection result of b;
The control signal is sent to the first and second hydraulic pumps 25,
First and second regulator 7 for controlling the capacity of 25b
6a and 76b.

Further, the above-mentioned first valve device 50 includes the first and second flow rate control valves 30a and 30b and the first directional control valve 30 connected via the rods 54 and 55, and the first flow rate. It includes a first pressure control valve 33a for controlling the downstream pressure of the control valve 30a and a second pressure control valve 33b for controlling the downstream pressure of the second flow rate control valve 30b. Downstream of the first pressure control valve 33a and the second pressure control valve 33b,
A confluence point 61 of pressure oils of the first and second hydraulic pumps 25 and 25b is provided, and a first direction control valve 30 is connected to the confluence point 61, and the first direction control valve 30 is a first actuator. It is connected to 22.

The above-mentioned second valve device 51 includes the rod 5
Third and fourth flow control valves 3 connected via 6, 57
1a, 31b and the second directional control valve 31, and the third pressure control valve 34 for controlling the downstream pressure of the third flow rate control valve 31a.
a, and a fourth pressure control valve 34b for controlling the downstream pressure of the fourth flow rate control valve 31b. Downstream of the third pressure control valve 34a and the fourth pressure control valve 34b, the first pressure control valve 34a
And the confluence point 62 of the pressure oils of the second hydraulic pumps 25, 25b.
The second directional control valve 31 is connected to the confluence 62, and the second directional control valve 31 is connected to the second actuator 23.

The above-described third valve device 52 includes a rod 57.
It includes a fifth flow rate control valve 32b and a third directional control valve 32, which are connected via a valve, and a fifth pressure control valve 35b for controlling the downstream pressure of the fifth flow rate control valve 32b. The third directional control valve 32 is provided downstream of the fifth pressure control valve 35b.
And the third directional control valve 32 is connected to the third actuator 24.

The first hydraulic pump 25a is connected to the first actuator 22 via the first flow control valve 30a, and is connected to the second actuator 23 via the third flow control valve 31a. No. 1 actuator 22 is connected in parallel. The second hydraulic pump 25b is the second
Of the first actuator 22 via the flow control valve 30b of
Is connected to the second actuator 23 via the fourth flow control valve 31b and the fifth flow control valve 32.
to the third actuator 24 via b
The actuator 22 is connected in parallel.

One drive portion of the first pressure control valve 33a is connected to a pipe portion between the first flow control valve 30a and the first pressure control valve 33a, and the pressure of the portion is applied in the opening direction. The other drive unit sets the higher load pressure (hereinafter referred to as the maximum load pressure) of the load pressure of the first actuator 22 and the load pressure of the second actuator 23 detected by the check valves 37a and 38a. It is connected to a first pressure signal transmission line 83 that leads as a first pressure signal,
Is applied in the closing direction.

One drive portion of the second pressure control valve 33b is connected to a pipe portion between the second flow control valve 30b and the second pressure control valve 33b, and the pressure of the portion is applied in the opening direction. , The other drive unit has check valves 37b, 38b, 39
The highest load pressure (hereinafter referred to as the maximum load pressure) of the load pressure of the first actuator 22, the load pressure of the second actuator 23, and the load pressure of the third actuator 24 detected by b is set as the second load pressure. It is connected to a second pressure signal transmission line 84 which is guided as a pressure signal, and the second pressure signal is given in the closing direction.

One drive portion of the third pressure control valve 34a is connected to a pipe line portion between the third flow control valve 31a and the third pressure control valve 34a, and the pressure of the portion is applied in the opening direction. The other drive unit is connected to the first pressure signal transmission line 83, and the first pressure signal (maximum load pressure of the first and second actuators 22 and 23) is applied in the closing direction.

One of the driving parts of the fourth pressure control valve 34b is connected to the pipe portion between the fourth flow control valve 31b and the fourth pressure control valve 34b, and the pressure of the portion is applied in the opening direction. , The other drive unit is connected to the second pressure signal transmission line 84, and the second pressure signal (maximum load pressure of the first, second and third actuators 22, 23, 24) is applied in the closing direction. It

One of the driving parts of the fifth pressure control valve 35b is connected to a pipe portion between the fifth flow control valve 32b and the fifth pressure control valve 35b, and the pressure of the portion is applied in the opening direction. , The other drive unit is connected to the second pressure signal transmission line 84, and the second pressure signal (maximum load pressure of the first, second and third actuators 22, 23, 24) is applied in the closing direction. It

The first maximum load pressure detector 78a is connected to the conduit 36.
is connected to the first pressure signal transmission line 83 via a,
The maximum load pressure of the first and second actuators 22 and 23 is detected, and the second maximum load pressure detector 78b is connected to the conduit 36b.
Is connected to the second pressure signal transmission line 84 to detect the maximum load pressure of the first, second and third actuators 22, 23, 24.

An unload valve 26a for controlling the pressure difference between the pump discharge pressure and the first pressure signal so as not to exceed a predetermined value is connected to the discharge line of the first hydraulic pump 25a. An unload valve 26b for controlling the differential pressure between the pump discharge pressure and the first pressure signal so as not to exceed a predetermined value is connected to the discharge line of the second hydraulic pump 25b.

The target differential pressure setting device 81 activates at least one of the first and second actuators 22 and 23 having a relatively low load pressure, and simultaneously operates the third actuator 24 having a relatively high load pressure. When actuated, the first target differential pressure of the first hydraulic pump 25a is set to a value larger than the second target differential pressure of the second hydraulic pump 25b. FIG. 2 shows an example of the processing procedure.

In FIG. 2, the operating states of the first, second and third actuators 22, 23 and 24 are checked (steps 100, 110 and 120) and at least one of the first and second actuators 22 and 23 is checked. If it is not in the operating state in which the third actuator 24 is operated, the first target differential pressure ΔPLS1 and the second target differential pressure ΔPLS2 are equal, and ΔPLS1 = ΔPLS, ΔPLS2 =
Set to ΔPLS (step 150). In the operation state in which at least one of the first and second actuators 22 and 23 is operated and the third actuator 24 is operated, the operation amount of the operation lever device 71 of the third actuator 24 and the first operation amount The ratio ε of the operation amounts of the operation lever device 71 of the actuator 22 and / or the operation lever device 72 of the second actuator 23 is calculated (step 130). In the target differential pressure setting device 81, the relationship between the increase amount α of the target differential pressure ΔPLS and ε is stored in advance.
The increase amount α is determined from the ratio ε at that time (step 14
0). Based on this result, the first target differential pressure ΔPLS1 of the first hydraulic pump 25a and the second target differential pressure ΔPLS1 of the second hydraulic pump 25b.
The target differential pressure ΔPLS2 of ΔPLS1 = ΔPLS + α ΔPLS2 = ΔPLS is determined and output to the regulators 75a and 75b (step 160).

The operation of the first embodiment thus configured is as follows.

First, a case where the three first, second and third actuators 22, 23 and 24 are simultaneously driven will be described.

The first, second and third actuators 22,
The operation lever device 7 is intended for the combined drive of 23 and 24.
When rods 1 and 72 are operated, rods 54 and 55, rod 5
6, 57 and the rod 58 are operated, and the first and second flow rate control valves 30a, 30 are operated by operating the rods 54, 55.
b, the first directional control valve 30 is switched, the rod 5
The third and fourth flow control valves 3 are operated by the operations of 6, 57.
1a, 31b, the second directional control valve 31 is switched,
By operating the rod 58, the fifth flow control valve 32b and the third directional control valve 32 are switched. Accordingly, the higher load pressure PLmax1 of the first and second actuators 22 and 23 drives the first and third pressure control valves 33a and 34a in the closing direction via the first pressure signal transmission line 83. To the first, second, and third actuators 22,
The highest load pressure of 23 and 24, that is, the load pressure PLmax2 of the third actuator 24 is transmitted through the second pressure signal transmission line 84 to the second, fourth and fifth pressure control valves 33.
It is guided to the drive unit in the closing direction of b, 34b, 35b. Accordingly, the first to fifth pressure control valves 33a, 33b, 34
a, 34b, 35b are driven, and the upstream pressures of the first and third pressure control valves 33a, 34a, that is, the downstream pressures of the first and third flow rate control valves 30a, 31a are the first and second actuators 22. , 23, which has the higher load pressure PLmax
1 and the first and third flow rate control valves 30a, 31
The upstream pressure of a becomes the discharge pressure of the first hydraulic pump 25a,
In addition, the second, fourth and fifth pressure control valves 33b, 34b,
The upstream pressure of 35b, that is, the downstream pressure of the second, fourth, and fifth flow control valves 30b, 31b, 32b becomes equal to the load pressure PLmax2 of the third actuator 24. The upstream pressure of the flow rate control valves 30b, 31b, 32b becomes the discharge pressure of the second hydraulic pump 25b. As a result, the differential pressure across the first and third flow rate control valves 30a and 31a becomes the same, and the discharge flow rate of the first hydraulic pump 25a becomes the first differential pressure.
And the third flow rate control valves 30a and 31a are branched and supplied to the first and second actuators 22 and 23, respectively, and the second, fourth and fifth flow rate control valves 30b, 31b and 3 are supplied.
The differential pressure across 2b is also the same, and the second hydraulic pump 25b
The discharge flow rate of the second, fourth, and fifth flow rate control valves 30b, 3
It is divided into 1b and 32b and supplied to the first, second and third actuators 22, 23 and 24. As a result, the first,
The second and third actuators 22, 23, 24 are supplied with flow rates according to the operation amounts of the operating lever devices 71, 72, and the first, second, third actuators 22, 23, 2
The composite drive of 4 is surely performed.

On the other hand, at this time, the higher load pressure PLmax1 of the first and second actuators 22 and 23 is detected by the first maximum load pressure detector 78a, and the load pressure PLmax2 of the third actuator 24 is 2 maximum load pressure detector 7
Detected by 8b.

The operating state of the operating lever devices 71, 72 is detected by the operating state detector 73, and the target differential pressure setting device 8 is set.
As described above, the first target differential pressure ΔPLS1 of the first hydraulic pump 25a and the second target pressure of the second hydraulic pump 25b are set to 1.
ΔPLS1 = ΔPLS + α, ΔP as the target differential pressure ΔPLS2 of
Set LS2 = ΔPLS. As a result, the discharge pressure Ps1 of the first hydraulic pump 25a is ΔPLS + from the maximum load pressure PLmax1 detected by the first maximum load pressure detector 78a.
The pump displacement is controlled so as to be increased by α, and the discharge pressure Ps2 of the second hydraulic pump 25b is ΔPL from the maximum load pressure PLmax2 detected by the second maximum load pressure detector 78b.
The pump capacity is controlled so as to be higher by S. As a result, the differential pressure across the first and third flow control valves 30a, 31a is approximately ΔPLS + α, and the differential pressure across the second, fourth, and fifth flow control valves 30b, 31b, 32b is approximately ΔPLS.
Is controlled. Therefore, when ΔPLS is a normal target differential pressure, the first and third flow rate control valves 30a and 31a are
Compared with the case where the first and second target differential pressures ΔPLS1 and ΔPLS2 are both set equal to the normal target differential pressure ΔPLS, a larger flow rate is passed by an amount corresponding to the increase amount α of the target differential pressure. First and second actuators 22, 23
The flow rate supplied to the is increased.

FIG. 4 shows the strokes of the rods 54 and 55 of the first valve device 50 and the first actuator 2 at that time.
2 shows the relationship between the supply flow rates of the two. The first flow rate control valve 30a when both the first hydraulic pump 25a and the second hydraulic pump 25b are controlled by the same target differential pressure ΔPLS
When the characteristic of No. 2 is "a" and the characteristic of the second flow rate control valve 30b is "B", the supply flow rate characteristic of the first actuator 22 is the sum of "A" and "B", as in "C". It becomes a characteristic. Here, if only the target differential pressure of the first hydraulic pump 25a is set to ΔPLS + α, only the flow amount corresponding to α becomes
The flow rate supplied from the flow control valve 30a to the first actuator 22 increases, and the supply flow rate characteristic of the first actuator 22 is the sum of “b” and “c”, and a characteristic like “d” is obtained. To be That is, the first actuator 2
The total flow rate supplied to 2 increases. Second valve device 51
The same applies to the third and fourth flow rate control valves 31a and 31b.

As described above, the flow rate characteristics between the actuators change according to the combined operation of the first, second and third actuators 22, 23 and 24, which improves the operability and the work efficiency. .

Next, the first and second hydraulic pumps 25a,
When 25b is horsepower controlled, the third actuator 24 is further driven from the state in which the two first and second actuators 22 and 23 are combinedly driven, and the three first,
A case of shifting to the combined drive of the second and third actuators 22, 23, 24 will be described.

First, when the operating lever devices 71 and 72 are operated with the intention of operating the first and second actuators 22 and 23 having relatively low load pressures, the rods 54 and 55 and the rods 56 and 57 are operated. It By operating the rods 54 and 55, the first and second flow control valves 30a and 30b,
The first directional control valve 30 is switched and the rods 56, 5
By operating 7, the third and fourth flow control valves 31a,
31b, the second directional control valve 31 is switched. Along with this, the higher load pressure of the first and second actuators 22, 23 causes the first and second pressure signal transmission lines 83,
You are led to 84. At this time, the operation state is detected by the operation state detector 73, and the target differential pressure setting unit 81, as described above, receives the first target differential pressure ΔP of the first hydraulic pump 25a.
LS1, second target differential pressure ΔPLS1 of second hydraulic pump 25b
To set the same value ΔPLS. As a result, both the first hydraulic pump 25a and the second hydraulic pump 25b have a higher load pressure PLmax of the first and second actuators 22 and 23.
The pump displacement is controlled so that the pump discharge pressure becomes higher than ΔPLS by 1. As a result, the differential pressure across the first to fourth flow control valves 30a, 30b, 31a, 31b is approximately ΔPLS, and the flow rate determined by this differential pressure and the opening area of each flow control valve is the first. And the second actuator 22,
23.

Here, the operation lever device 71 is operated with the intention of driving the third actuator 24 having a relatively high load pressure. As a result, the rod 58 is operated and the fifth flow rate control valve 32b and the third directional control valve 32 are switched. Along with this, the first with relatively low load pressure
And the higher load pressure of the second actuators 22 and 23 is passed through the first pressure signal transmission line 83 to the first and third load signals.
The load pressure PLmax1 is detected by the first maximum load pressure detector 78a while being guided to the drive section of the pressure control valves 33a and 34a in the closing direction. In addition, the maximum load pressure of the first, second, and third actuators 22, 23, 24, that is, the load pressure of the third actuator 24, is transmitted through the second pressure signal transmission line 84 to the second, fourth, and fourth pressure signal transmission lines 84. 5 pressure control valve 3
The load pressure PLmax2 is guided to the drive units 3b, 34b, 35b in the closing direction, and the load pressure PLmax2 is the second maximum load pressure detector 7
Detected by 8b.

On the other hand, at this time, the operating lever devices 71, 72
The operation state of the first hydraulic pump 2 is detected by the operation state detector 73, and the target differential pressure setter 81 detects the operation state of the first hydraulic pump 2 as described above.
5a first target differential pressure ΔPLS1, second hydraulic pump 25
As the second target differential pressure ΔPLS1 of b, ΔPLS1 = ΔPLS +
Set α and ΔPLS2 = ΔPLS. As a result, the pump displacement is controlled so that the discharge pressure Ps1 of the first hydraulic pump 25a is higher than the maximum load pressure PLmax1 detected by the first maximum load pressure detector 78a by ΔPLS + α, and the second maximum pressure PLs1 is higher than the maximum load pressure PLmax1. The discharge pressure Ps2 of the hydraulic pump 25b is the maximum load pressure PLmax detected by the second maximum load pressure detector 78b.
The pump displacement is controlled to be higher than 2 by ΔPLS. As a result, the first and third flow control valves 30a, 3
The upstream and downstream differential pressure of 1a becomes approximately ΔPLS + α,
The upstream and downstream differential pressures of the fourth and fifth flow control valves 30b, 31b, 32b are controlled to approximately ΔPLS. Therefore, the first and third flow control valves 30a and 31a are the same as the first
In comparison with the case where only the second actuators 22 and 23 are operated and the same operation amount of the operation lever device is compared, a large amount of flow amount is passed by an amount corresponding to the increase amount α of the target differential pressure.

This situation will be described with reference to FIG. In FIG. 4, FIG. 4A shows the relationship between the pump discharge pressure Ps1 of the first hydraulic pump 25a and the pump discharge flow rate, and FIG. 4B shows the pump discharge pressure Ps2 of the second hydraulic pump 25b and the pump discharge pressure. The relationship with the flow rate is shown.

The above-mentioned first and second actuators 2
When only 2 and 23 are operated, the first hydraulic pump 2
In both 5a and the second hydraulic pump 25b, the pump discharge pressures Ps1 and Ps2 are increased by ΔPLS with respect to the higher load pressure of the first and second actuators 22 and 23.
Since the pump capacity is controlled, the pump discharge pressures Ps1 and Ps2
Is approximately the same value Pso1, the first and second hydraulic pumps 25 and 25b operate at points a and b in FIG. 4, respectively, and the first to fourth flow rate control valves 30a and 30b, 31
The flow rates corresponding to the openings of a and 31b are supplied to the first and second actuators 22 and 23. That is, the discharge flow rate A of the first hydraulic pump 25a is distributed by the first and third flow rate control valves 30a and 31a and supplied to the first and second actuators 22 and 23, and the second hydraulic pump 25b.
Of the second flow rate control valve 30b, 3
1b to distribute the first and second actuators 22,
23.

Here, as described above, when the third actuator 24 having a relatively high load pressure is operated, the discharge pressure Ps2 of the second hydraulic pump 25b becomes the load pressure (maximum load) of the third actuator 24. The pressure is controlled to a pressure Pso3 which is higher than the pressure PLmax2 by ΔPLS, and the operating point shifts to a point c near the pump horsepower limit. At this time, the second hydraulic pump 25b
The discharge flow rate of B is reduced from B to C, and the reduced flow rate is distributed by the second, fourth and fifth flow control valves 30b, 31b and 32b, and the first, second and third actuators 2 are
2, 23, 24 are supplied. As a result, from the second hydraulic pump 25b to the first and second actuators 22, 2
The flow rate supplied to 3 is reduced. However, the first hydraulic pump 25a is operated by the first and second actuators 22,2.
Since the pump discharge pressure Ps1 is controlled to be the higher load pressure PLmax1 + ΔPLS + α of 3, the pump discharge pressure Ps1
Shifts to Pso2, which is slightly higher than the pump discharge pressure Pso1 described above. With this pump discharge pressure Pso1, the first hydraulic pump 25a has a margin in terms of horsepower as well, and the pump discharge flow rate can be increased up to Dmax, which is a point d1 near the pump horsepower limit, and the operating point of the first hydraulic pump 25a. Moves to point d2. Therefore, the discharge flow rate of the first hydraulic pump increases from A to D, and the increased discharge flow rate is distributed by the first and third flow rate control valves 30a and 31a, and the first and second actuators 22, 23.
As a result, the flow rate supplied from the first hydraulic pump 25a to the first and second actuators 22 and 23 increases,
A sudden change in the operating speed of the first and second actuators 22 and 23 is prevented, and operability is improved. In addition, the first and second
The discharge amounts of the hydraulic pumps 25a, 25b can be effectively supplied to the first, second, and third actuators 22, 23, 24, and the output of the prime mover can be effectively utilized.

As described above, according to the present embodiment, it is possible to change the flow rate characteristic between the actuators according to the work situation, improve the composite operability, and improve the work efficiency. In addition, the first and second hydraulic pumps 25a and 25b
The discharge flow rate of can be effectively supplied to the actuator, and the output of the prime mover can be effectively utilized.

A second embodiment of the present invention will be described with reference to FIGS. In the figure, the same members and parts as those shown in the above drawings are designated by the same reference numerals.

In FIG. 5, the target differential pressure setting device 81A according to the present embodiment includes the first and second maximum load pressure detectors 78a and 78b in addition to the detection result of the operation state detector 73.
Of the first and second hydraulic pumps 25a, 2 based on the detection result of
The first and second target differential pressures for controlling 5b are set. FIG. 6 shows an example of the processing procedure.

In FIG. 6, the operating states of the first, second and third actuators 22, 23, 24 and the first,
The magnitude relationship between the load pressures of the second and third actuators 22, 23, 24 is checked (steps 100, 110, 1
20, 170), the first and second actuators 22,
If at least one of the actuators 23 is not operated and the third actuator 24 is not operated, or if the load pressure of the first and second actuators 22, 23 is the third
If it is not lower than the load pressure of the actuator 24, the first target differential pressure ΔPLS1 and the second target differential pressure ΔPLS2 are set to be equal and ΔPLS1 = ΔPLS and ΔPLS2 = ΔPLS are set (step 150). First and second actuator 2
In the operation state in which at least one of 2, 2 and 23 is operated and the third actuator 24 is operated,
When the load pressure of the first and second actuators 22 and 23 is lower than the load pressure of the third actuator 24,
The operation amount of the operation lever device 71 of the third actuator 24 and the operation lever device 71 of the first actuator 22 and / or the operation lever device 7 of the second actuator 23.
The ratio ε of the manipulated variables of 2 is calculated (step 130). In the target differential pressure setting device 81, the target differential pressure ΔPLS for ε is preset.
Is stored, and the increase amount α is determined from the ratio ε at that time (step 140). Based on this result, the first target differential pressure ΔPLS of the first hydraulic pump 25a
1, the second target differential pressure ΔPLS2 of the second hydraulic pump 25b
Is determined to be ΔPLS1 = ΔPLS + α ΔPLS2 = ΔPLS and output to the regulators 75a and 75b (step 160).

According to this embodiment, since the load pressure of the actuator is added to the setting condition of the target differential pressure, the first, second, and
Even in a hydraulic drive device in which the magnitude relationship of the load pressures of the third actuators 22, 23, 24 changes, the flow rate characteristics between the actuators are changed according to the work situation,
The same effect as the first embodiment can be obtained.

[0057]

According to the present invention, the flow rate characteristics between the actuators can be changed according to the work situation, the composite operability can be improved, and the work efficiency can be improved.

Further, the discharge flow rate of the hydraulic pump can be effectively supplied to the actuator, and the output of the prime mover can be effectively utilized.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the processing contents of a target differential pressure setting device.

FIG. 3 is a diagram showing characteristics of a valve device.

FIG. 4 is an explanatory diagram showing flow rate characteristics of a hydraulic pump.

FIG. 5 is a hydraulic circuit diagram showing a hydraulic drive system for a construction machine according to another embodiment of the present invention.

FIG. 6 is a flowchart showing the processing contents of a target differential pressure setting device.

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

[Explanation of symbols]

 22 1st actuator 23 2nd actuator 24 3rd actuator 25a 1st hydraulic pump 25b 2nd hydraulic pump 30 1st directional control valve 30a 1st flow control valve 30b 2nd flow control valve 31 3rd 2 directional control valve 31a 3rd flow control valve 31b 4th flow control valve 32 3rd directional control valve 32b 5th flow control valve 33a 1st pressure control valve 33b 2nd pressure control valve 34a 3rd Pressure control valve 34b Fourth pressure control valve 35b Fifth pressure control valve 50 First valve device 51 Second valve device 52 Third valve device 71,72 Operation lever device 73 Operation state detector 75a, 75b Pump dose controller 76a, 76b Regulator 78a, 78b Maximum load pressure detector 79a, 79b Pump discharge pressure detector 81 Target differential pressure setting device

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Genroku Sugiyama 650, Kazunachi-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura Plant

Claims (4)

[Claims] 1. At least two first and second hydraulic pumps, a plurality of actuators including first, second, and third actuators driven by pressure oil supplied from these hydraulic pumps, and said first and second hydraulic pumps. A plurality of valve devices including first, second, and third valve devices for controlling the operations of the first, second, and third actuators, respectively, wherein the first valve device has first and second flow rates. A control valve and first and second pressure control valves, and the second valve device includes third and fourth flow control valves and third and fourth pressure control valves, and the third The valve device includes a fifth flow control valve and a fifth pressure control valve,
The first hydraulic pump includes the first flow control valve and the first flow control valve.
Is connected to the first actuator via a pressure control valve of the first actuator, and is connected to the second actuator via the third flow rate control valve and a third pressure control valve to the first actuator.
Is connected in parallel, the second hydraulic pump is connected to the first actuator via the second flow rate control valve and the second pressure control valve, and the fourth and fifth actuators are connected. Through the flow control valve and the fourth and fifth pressure control valves, the second and third actuators are connected in parallel with the first actuator, and the first valve device includes the first and second actuators. The pressure oil from the second hydraulic pump is supplied to the first and second flow control valves and the first and second flow control valves.
Of the pressure control valve and supplies the pressure oil to the first actuator, and the second valve device controls the pressure oil from the first and second hydraulic pumps to control the third and fourth flow rates. The valves and the third and fourth pressure control valves on the downstream side, and joins the second pressure control valve to supply the second actuator, and the first and third pressure control valves.
The pressure control valve controls the downstream pressure of the first and third flow control valves to be the same as the higher pressure of the load pressure of the first and second actuators, and also controls the second and the second flow control valves. The fourth and fifth pressure control valves are arranged so that the downstream pressures of the second, fourth and fifth flow control valves are the same as the highest load pressures of the first, second and third actuators. The first hydraulic pump is controlled so that the pump discharge pressure is higher than the higher one of the load pressures of the first and second actuators, and the second hydraulic pump is controlled by the first hydraulic pump. In a hydraulic drive device for a construction machine, which is controlled so that a pump discharge pressure is higher than a highest pressure among load pressures of the second and third actuators, a detection unit that detects an operation state of the plurality of actuators, , The detection result of the operation state Target differential pressure setting means for setting first and second target differential pressures for controlling the first and second hydraulic pumps based on the first and second hydraulic pumps. First pump displacement control means for controlling the pump displacement so as to be higher than the higher load pressure of the actuator by the first target differential pressure, and the discharge pressure of the second hydraulic pump is the first displacement. , Second, third
From the highest load pressure of the actuator
And a second pump displacement control means for controlling the pump displacement so as to increase by the target differential pressure. 2. The hydraulic drive system for a construction machine according to claim 1, wherein the third actuator is the first and second actuators.
When the combined operation of the first, second and third actuators is detected by the detection means, the target differential pressure setting means is an actuator having a higher load pressure than the first target differential pressure setting means. Is set to be higher than the second target differential pressure by a predetermined value. 3. The hydraulic drive system for a construction machine according to claim 1, wherein the target differential pressure setting means is a combined operation of the first, second and third actuators by the detecting means, and the third differential pressure setting means. When it is detected that the load pressure of the actuator is higher than the load pressures of the first and second actuators, the first target differential pressure is set higher than the second target differential pressure by a predetermined value. A hydraulic drive system for a construction machine, which is characterized in that 4. A hydraulic drive system for a construction machine according to claim 2 or 3, wherein said detection means operates first, second and third operation means for operating said first, second and third valve devices. Means for detecting the operation amount of the means, wherein the target differential pressure setting means increases the predetermined value according to the operation amounts of the first and second operation means. .