JPH0776862A - Hydraulic pressure drive device of construction machinery - Google Patents

Abstract

PURPOSE:To supply pressure oil to either an arm cylinder or a boom cylinder by giving priority. CONSTITUTION:There are provided an arm operation detector A which detects the operation of an arm cylinder 4 and a boom operation detector B which detects the operation of a boom cylinder 5 and an arm load pressure detector 60. When it is determined by means of a controller 30 that both operation signals transmitted from the arm operation detector A and the boom operation detector B are detected, an arm signal pressure and a boom signal pressure are determined based on function relations which are predetermined in conformity with the types of arm/boom composite operation configurations and which vary from each other and a signal detected with the arm load pressure detector 60. These signal pressure are given to a first solenoid valve 32 and a second solenoid valve 33, which makes it possible to output control pressures Fa1 and Fa2 whose values are different from each other, to a drive unit of an arm pressure compensation valve 7 and a drive unit of a boom pressure compensation valve 11 respectively from the first solenoid valve 32 and the second solenoid valve 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load sensing system which is provided in a construction machine such as a hydraulic excavator and which controls a flow rate of a hydraulic pump so that a pump discharge pressure is higher than a maximum load pressure of a plurality of actuators by a predetermined pressure. And a pressure compensating valve capable of controlling the differential pressure across each direction switching valve that controls the flow of pressure oil supplied to the actuator.

[0002]

2. Description of the Related Art As a hydraulic drive system for a construction machine of this type, a system shown in FIG. 10 has been conventionally proposed. Figure 10
Shows a circuit of a hydraulic drive system of the hydraulic excavator.
The conventional technique shown in FIG.
0, a swing body 51 provided on the traveling body 50, a boom 52 rotatably provided with respect to the swing body 51, and an arm 53 rotatably provided with respect to the boom 52.
Further, a bucket 54 rotatably provided at the tip of the arm 53 for performing excavation and the like is provided.

A prime mover 1, a variable displacement hydraulic pump 2 driven by the prime mover 1, a control actuator 15 for controlling a tilt angle of a swash plate of the hydraulic pump 2,
The flow control valve 14 for controlling the drive of the control actuator 15 is provided. The control actuator 15 and the flow rate control valve 14 constitute a discharge amount control means for controlling the flow rate of the hydraulic pump 2 so that the discharge pressure Ps becomes a predetermined pressure higher than the maximum load pressure Pamax of each actuator described later. .

This prior art also includes a plurality of actuators such as a traveling motor 3 for traveling the traveling body 50, a boom cylinder 5 for driving the boom 52, an arm cylinder 4 for driving the arm 53, and the like. The traveling motor 3
Although a pair is provided, only one is drawn for simplicity of explanation. Further, an arm directional control valve 6, a boom directional control valve 8, a traveling directional control valve 10, which controls the flow of pressure oil supplied from the hydraulic pump 2 to the arm cylinder 4, the boom cylinder 5, and the traveling motor 3. An arm pressure compensating valve 7 for controlling the front-rear differential pressure which is the difference between the upstream pressure and the downstream pressure of each of the arm direction switching valve 6, the boom direction switching valve 8, and the traveling direction switching valve 10, and the boom pressure compensation. A valve 9 and a traveling pressure compensating valve 11 are provided.

For example, the discharge pressure Ps of the hydraulic pump 2 and the downstream pressure P _{L1 of the} arm directional control valve 6 are applied to one driving portion 7a of the arm pressure compensating valve 7 described above, and the other driving portion 7b. Is given the maximum load pressure Pamax of the load pressures of the actuators and the upstream pressure P _{Z1 of the} arm directional control valve 6, and one drive portion 9a of the boom pressure compensating valve 9 is connected to the hydraulic pump. The discharge pressure Ps of 2 and the downstream pressure P _{L2 of the} boom directional control valve 8 are applied, and the other drive unit 9b receives the maximum load pressure Pama of the load pressures of the actuators.
x and the upstream pressure P _{Z2 of the} boom directional control valve 8 are applied. It should be noted that the above-mentioned flow control valve 14 shown in FIG.
The discharge pressure Ps of the hydraulic pump 2 is applied to one of the drive parts indicated by 0, and the maximum load pressure Pamax of the actuator is applied to the other drive part. Further, the maximum load pressure Pamax of each actuator is determined by the shuttle valves 12, 1
It is taken out via 3.

In the prior art having such a configuration, the flow control valve 14 responds to the differential pressure between the discharge pressure Ps of the hydraulic pump 2 and the maximum load pressure Pamax of the actuator, that is, the load sensing differential pressure Ls. By being controlled,
The control actuator 15 uses this load sensing (L
s) The hydraulic pump 2 discharges a flow rate that is controlled according to the differential pressure, and sets the Ls differential pressure to a predetermined differential pressure that balances the force of the spring that biases the flow rate control valve 14. In addition, each pressure compensation valve 7,
9 and 11, the differential pressure across the directional control valves 6, 8 and 10 becomes the differential pressure between the discharge pressure Ps of the hydraulic pump 2 and the maximum load pressure Pamax of the actuator, that is, Ls differential pressure, and the same differential pressure is obtained. Become. Therefore, tentatively, each directional valve 6, 8,
When performing the combined operation of traveling / arm / boom by switching 10 simultaneously, the hydraulic pump 2 adjusts the opening ratios of the directional control valves 6, 8 and 10 without being affected by the load fluctuation of other actuators. The discharged flow amount is divided into each of the arm cylinder 4, the boom cylinder 5, and the traveling motor 3, and the combined traveling / arm / boom operation can be performed. Then, when a saturation state in which the required flow rate of each actuator is greater than the flow rate discharged from the hydraulic pump 2 is reached, the flow rate supplied to each actuator becomes insufficient, so that each operating speed of the traveling / arm / boom slows down. Things happen.

[0007]

Even when the arm / boom combined operation is performed in the above-mentioned conventional technique, as shown in FIG. 8, when performing the aerial boom raising / arm pulling, The boom side has a high pressure and the arm has a low pressure. In such a combined operation mode, however, it is possible to move the boom 52 as much as possible by preferentially supplying pressure oil to the boom cylinder 5 rather than to the arm cylinder 4 for work efficiency. desired. In addition, as shown in FIG.
In the combined operation mode in which the bucket 54 is used to excavate the arm cylinder 4, the pressure on the arm side is higher than the pressure on the boom side. It is more efficient to supply oil preferentially.

However, in the above-mentioned conventional technique, the operating speeds of both the arm side and the boom side become slower in any of the above-mentioned two combined operation modes, and as a result, the work efficiency of the corresponding combined operation mode. There is a problem that cannot be expected to improve.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and its object is to preferentially apply pressure to either the arm cylinder or the boom cylinder depending on the type of the arm / boom combined operation mode. An object of the present invention is to provide a hydraulic drive system for a construction machine that can supply oil.

[0010]

In order to achieve this object, the present invention provides a variable displacement hydraulic pump, an arm cylinder driven by pressure oil discharged from the hydraulic pump,
And a boom cylinder, an arm directional control valve for controlling the flow of pressure oil supplied from the hydraulic pump to the arm cylinder, and a boom for controlling the flow of pressure oil supplied from the hydraulic pump to the boom cylinder. The difference is the difference between the upstream pressure and the downstream pressure of the directional switching valve, the pressure compensation valve for the arm that controls the differential pressure across the arm, which is the difference between the upstream pressure and the downstream pressure of the directional switching valve for the arm. In a hydraulic drive for a construction machine, comprising: a boom pressure compensating valve that controls a differential pressure across the arm; an arm operation detector that detects that the arm cylinder has been operated; and a boom cylinder that has been operated. Boom operation detector for detecting, arm load pressure detector for detecting load pressure applied to the arm cylinder, arm operation detector, and boom operation detection Respectively, when an arm / boom combined operation in which both the arm cylinder and the boom cylinder are operated is detected, the arm pressure compensation valve drive unit, the boom pressure compensation valve drive unit, respectively, It is possible to supply control pressures that are different from each other and are preset according to the type of complex operation mode that is performed via the arm and boom, and that correspond to the value of the detection signal detected by the arm load pressure detector. The control pressure output means is provided.

[0011]

Since the present invention is configured as described above, the arm load pressure detector detects the setting in the control pressure output means, that is, the setting made in advance corresponding to the type of the combined arm / boom operation mode. When the arm load pressure is relatively low, the flow rate is set to be preferentially supplied to the boom side, and when the arm load pressure detected by the arm load pressure detector is relatively high, the flow rate is preferentially applied to the arm side. It may be set to supply.

When the preset operation is performed in this way, the arm load pressure detected by the arm load pressure detector is relatively low when, for example, the combined operation mode of the arm and boom is the aerial arm raising / arm pulling. Depending on the setting, the control pressure output means outputs a control pressure to the drive unit of the arm pressure compensating valve to make the throttle amount of the arm pressure compensating valve relatively large, while it outputs to the drive unit of the boom pressure compensating valve. The control pressure that makes the throttle amount of the boom pressure compensation valve relatively small is output. As a result, the flow rate passing through the arm directional control valve is kept relatively low, and the operating speed of the arm cylinder is slower than in the conventional arm / boom combined operation, but the flow rate passing through the boom directional control valve is reduced. Therefore, the operating speed of the boom cylinder can be increased as compared with the conventional arm / boom combined operation.

In addition, the combined operation mode of the arm and boom is
For example, in the case of excavation performed through the force of the arm, the arm load pressure detected by the arm load pressure detector is relatively high. Therefore, the control pressure output means changes the arm pressure compensating valve according to the above setting. The control pressure that makes the throttle amount of the arm pressure compensation valve relatively small is output to the drive unit, while the control pressure that makes the throttle amount of the boom pressure compensation valve relatively large is output to the drive unit of the boom pressure compensation valve. Is output. As a result, the flow rate passing through the boom directional control valve is relatively low, and the operating speed of the boom cylinder is slower than in the conventional arm / boom combined operation, but the flow rate passing through the arm directional control valve is reduced. Since the operating speed of the arm cylinder is relatively large, the operating speed of the arm cylinder can be increased as compared with the conventional arm / boom combined operation.

As described above, the pressure oil can be preferentially supplied to either the arm cylinder or the boom cylinder according to the type of the arm / boom combined operation mode.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment 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 showing an embodiment of a hydraulic drive system for a construction machine of the present invention, FIG. 2 is a flow chart showing a processing procedure in a controller provided in the embodiment shown in FIG. 1, and FIG. 3 is a view showing the controller shown in FIG. 4 is a block diagram illustrating control A of the processing, FIG. 4 is a block diagram illustrating control B of the processing in the controller shown in FIG. 1, and FIG. 5 is an arm directional control valve provided in the embodiment shown in FIG. FIG. 6 is a diagram showing characteristics obtained by the arm pressure compensating valve for controlling the front-rear differential pressure of FIG. 6, and FIG. 6 is a diagram showing the characteristics of the boom directional control valve provided in the embodiment shown in FIG. It is a figure which shows the obtained characteristic.

The embodiment shown in FIG. 1 is also a hydraulic drive system for a hydraulic excavator, and like the prior art shown in FIG. 10, the traveling body 50, the revolving structure 51, the boom 52, the arm 53, and the bucket. 54, and also the prime mover 1
And a plurality of actuators such as a variable displacement hydraulic pump 2, a traveling motor 3 for traveling the traveling body 50, a boom cylinder 5 for driving the boom 52, and an arm cylinder 4 for driving the arm 53. Although a pair of traveling motors 3 are provided, only one traveling motor 3 is shown for the sake of simplicity. Further, an arm directional control valve 6, a boom directional control valve 8, a traveling directional control valve 10, which controls the flow of pressure oil supplied from the hydraulic pump 2 to the arm cylinder 4, the boom cylinder 5, and the traveling motor 3. These arm direction switching valve 6, boom direction switching valve 8, traveling direction switching valve 10
An arm pressure compensating valve 7, a boom pressure compensating valve 9, and a traveling pressure compensating valve 11 are provided for controlling the front-rear differential pressure, which is the difference between the upstream pressure and the downstream pressure. Further, the shuttle valves 12, 1 for extracting the maximum load pressure Pamax of the actuator
Equipped with 3. These configurations are the same as those shown in FIG. 10 described above.

Further, the differential pressure detector 27 for detecting the differential pressure Ls, which is the differential pressure between the discharge pressure Ps of the hydraulic pump 2 and the maximum load pressure Pamax of the actuator, and the fact that the arm cylinder 4 has been operated, that is, for the arm An arm operation detector A that detects that the direction switching valve 6 has been operated, and a boom operation detector B that detects that the boom cylinder 5 has been operated, that is, that the boom direction switching valve 8 has been operated. , And an arm load pressure detector 60 for detecting the load pressure applied to the arm cylinder 4. In addition, the pilot pressure P
s ₁ can be supplied, the pilot pressure Ps ₁ output from the pilot pump 21 is reduced to drive the arm pressure compensating valve 7 drive section 7 b, the boom pressure compensating valve 9 drive section 9 b, and travel. A first solenoid valve 32, a second solenoid valve 33, and a third solenoid valve 34 that can be supplied to each of the drive units of the pressure compensation valve 11 for use are provided. In addition, the main relief valve 2 that regulates the discharge pressure Ps from the hydraulic pump 2
2, a pilot relief valve 23 that regulates the pilot pressure Ps ₁ discharged from the pilot pump 21, and a tank 25.

A small diameter chamber 20a connected to the pilot pump 21 is provided for controlling the tilt angle of the swash plate of the hydraulic pump 2, and a small diameter chamber 20a of the control actuator 20 and a large diameter chamber. An electromagnetic switching valve 24 provided in a pipe line connecting the chamber 20b and an electromagnetic switching valve 26 provided in a pipe line connecting the large diameter chamber 20b of the control actuator 20 and the tank 25 are provided. Further, it has logical judgment, calculation, and storage functions, and inputs signals output from the differential pressure detector 27, arm operation detector A, boom operation detector B, and arm load pressure detector 60, respectively. Then
After signal processing, control means for outputting drive signals for driving the electromagnetic switching valves 24, 26 and drive signals for driving the first solenoid valve 32, the second solenoid valve 33, and the third solenoid valve 34, that is, The controller 30 described later is provided.

The control actuator 20 and the electromagnetic switching valves 24, 26 described above control the discharge amount control means for controlling the flow rate of the hydraulic pump 2 so that the discharge pressure Ps becomes a predetermined pressure higher than the maximum load pressure Pamax of each actuator. Are configured.

In particular, the arm pressure compensation valve 7 described above is used.
The pilot pressure Ps ₁ output from the pilot pump 21 and the downstream pressure P _{L1 of the} arm directional control valve 6 are applied to one drive portion 7a, and the first solenoid valve 32 is applied to the other drive portion 7b. The control pressure Fa ₁ output from the engine and the upstream pressure P _{Z1 of the} arm directional control valve 6 are given, and the pilot pressure output from the pilot pump 21 is supplied to one drive portion 9a of the boom pressure compensating valve 9 described above. Ps ₁ and the downstream pressure P _{L2 of the} boom directional control valve 8 are given, and the control pressure Fa ₂ output from the second electromagnetic valve 33 and the upstream pressure of the boom directional control valve 8 are applied to the other drive unit 9b. P _Z2 is given.

Further, the controller 30 described above has a judging means for judging whether or not an operation signal is output from both the arm operation detector A and the boom operation detector B.
When the determination means determines that the operation signals are output from both the arm operation detector A and the boom operation detector B, the operation means performs an operation to execute the control (A), and the above-described determination means. In addition, when it is determined that no operation signal is output from one of the arm operation detector A and the boom operation detector B, a calculation means for executing control (B) is provided.

As a calculation means for executing the control (A),
The value of the detection signal detected by the arm load pressure detector 60,
First arm / boom combined operation mode, for example, “arm 5
Arm pressure compensating valve 7 in order to preferentially supply pressure oil to the arm cylinder 4 based on the functional relationship set in advance corresponding to the “combined operation mode of excavating through the force of 3”.
Arm load pressure detector 60, and a first calculation means for performing a calculation for obtaining a control pressure for driving the
Corresponding to the value of the detection signal detected by the second arm / boom combined operation mode different from the above-described first arm / boom operation operation mode, for example, “in-air boom up / arm pull combined operation mode”. Second calculating means for calculating a control pressure for driving the boom pressure compensating valve 9 in order to preferentially supply pressure oil to the boom cylinder 5, that is, a boom signal pressure, based on the set functional relationship; Is included.

As shown in FIG. 3, the above-mentioned first calculating means is preset with a functional relationship of the arm pressure compensation maximum value that decreases with an increase in arm load pressure, and outputs it from the arm load pressure detector 60. The function generator 30a that outputs the maximum arm pressure compensation value corresponding to the arm load pressure and the functional relationship between the arm pressure compensation pressure that increases substantially linearly with the increase in the Ls differential pressure are set in advance. A function generator 30b that outputs an arm pressure compensation pressure corresponding to the Ls differential pressure output from the detector 27, an arm pressure compensation maximum value output from the function generator 30a, and an arm pressure output from the function generator 30b. The functional relationship between the minimum value selector 30e that selects the minimum value of the compensation pressure and outputs it as the pressure compensation pressure and the arm signal pressure that decreases substantially linearly with the increase of the pressure compensation pressure is set in advance. It is, and a function generator 30g for outputting an arm signal pressure corresponding to the pressure compensated pressure outputted from the minimum value selector 30e.

Further, as shown in FIG. 3, the second calculation means presets a functional relationship of the boom pressure compensation maximum value that increases with an increase in arm load pressure, and outputs it from the arm load pressure detector 60. The function relationship between the function generator 30d that outputs the boom pressure compensation maximum value corresponding to the arm load pressure and the boom pressure compensation pressure that increases substantially linearly as the Ls differential pressure increases is set in advance. A function generator 30c that outputs a boom pressure compensation pressure corresponding to the Ls differential pressure that is output from the detector 27, a boom pressure compensation maximum value that is output from the function generator 30d, and a boom pressure that is output from the function generator 30c. The functional relationship between the minimum value selector 30f that selects the minimum value of the compensation pressure and outputs it as the pressure compensation pressure and the boom signal pressure that decreases almost linearly as the pressure compensation pressure increases is preset. , And a function generator 30h for outputting boom signal pressure corresponding to the pressure compensated pressure outputted from the minimum value selector 30f.

Further, as a calculation means for executing the control (B), according to the Ls differential pressure detected by the differential pressure detector 27,
The boom pressure compensating valve is operated in accordance with the third computing means for computing the control pressure for driving the arm pressure compensating valve 7, that is, the arm signal pressure, and the Ls differential pressure similarly detected by the differential pressure detector 27. And a fourth calculating means for calculating the control pressure for driving the motor 9, that is, the boom signal pressure.

As shown in FIG. 4, the above-mentioned third calculation means includes a function generator 30b for outputting an arm pressure compensation pressure corresponding to the Ls differential pressure output from the differential pressure detector 27, and a pressure compensation pressure. A function relation of the arm signal pressure that decreases substantially linearly with an increase in the pressure is preset, and the function generator 30g outputs the arm signal pressure corresponding to the pressure compensation pressure output from the function generator 30b. There is.

The fourth calculation means is the differential pressure detector 27.
The function generator 30c that outputs a boom pressure compensation pressure corresponding to the differential pressure output from the function generator and the boom signal pressure that decreases substantially linearly with the increase of the pressure compensation pressure are set in advance. And a function generator 30h which outputs a boom signal pressure corresponding to the pressure compensation pressure output from 30c.

The controller 30, the pilot pump 21, the first solenoid valve 32, and the second solenoid valve 33 described above are
By the arm operation detector A and the boom operation detector B, respectively, the arm cylinder 4 and the boom cylinder 5
When an arm / boom combined operation in which both of the above are operated is detected, the arm 53 and the boom 5 are respectively provided in the drive unit of the arm pressure compensation valve 7 and the drive unit of the boom pressure compensation valve 9.
Control pressures Fa ₁ and Fa ₂ corresponding to the values of the detection signals detected by the arm load pressure detector 60, which are different from each other and are set in advance according to the type of the composite operation mode performed via It constitutes a control pressure output means capable of supplying.

The operation of this embodiment is as follows.
That is, the differential pressure detector 27 detects the differential pressure Ls, which is the differential pressure between the discharge pressure Ps of the hydraulic pump 2 and the maximum load pressure Pamax of the actuator, and inputs it to the controller 30. The controller 30 responds to this Ls differential pressure, that is, to a predetermined differential pressure preset in the controller 30 (differential pressure corresponding to the force of the spring for urging the flow rate control valve 14 shown in FIG. 10 described above). So that they coincide with each other, the drive signal corresponding to the deviation between the predetermined differential pressure and the Ls differential pressure is applied to the electromagnetic switching valve 24,
26, so that the electromagnetic switching valves 24, 26 are appropriately switched and the control actuator 20 is driven.
The hydraulic pump 2 discharges a flow rate such that the differential pressure becomes a predetermined differential pressure. The control actuator 20 does not move when both the electromagnetic switching valves 24 and 26 are in the closed state shown in FIG.
The tilt angle of the hydraulic pump 2 is kept constant. When only the electromagnetic switching valve 26 is switched to the lower position, the pilot pressure Ps ₁ of the pilot pump 21 is applied to the small diameter chamber 20a of the control actuator 20, and the pressure oil of the large diameter chamber 20b is returned to the tank 25, The piston of the control actuator 20 moves to the right in FIG. 1, the tilt angle becomes smaller, and the flow rate discharged from the hydraulic pump 2 decreases. Further, when only the electromagnetic switching valve 24 is switched from the state shown in FIG. 1 to the lower position, the pilot pressure Ps ₁ of the pilot pump 21 is changed to the small diameter chamber 20 of the control actuator 20.
a and the large diameter chamber 20b, the piston of the control actuator 20 moves to the left in FIG. 1 due to the area difference between the small diameter chamber 20a and the large diameter chamber 20b, the tilt angle increases, and the hydraulic pump The flow rate discharged from 2 increases. Such a combination of the differential pressure detector 27, the control actuator 20, the electromagnetic switching valves 24 and 26, and the controller 30 is known.

Further, for example, when the arm directional switching valve 6 and the boom directional switching valve 8 are switched to drive the arm 53 or the boom 52, the arm operation detector A or the boom operation detector B is switched to these. The operation amount of the direction switching valves 6 and 8 is detected and an operation signal is output. As shown in step S1 of FIG. 2, these operation signals are input to the controller 30. The determination means of the controller 30 is the same as in FIG.
As shown in step S2 of step 1, it is determined whether the arm and the boom are simultaneously operated, that is, whether the operation signals are output from both the arm operation detector A and the boom operation detector B. Now, assuming that only one of the operation signals is input, the process proceeds to step S3 of FIG. 2 and the control (B) is executed.

Here, assuming that only the operation signal of the arm operation detector A is input, as shown in FIG. 4 exemplifying the control (B), the third arithmetic means of the controller 30 makes a difference. The function generator 30b calculates the arm pressure compensation pressure according to the Ls differential pressure output from the pressure detector 27, and the function generator 30g calculates the arm signal pressure according to the calculated arm pressure compensation pressure. . The arm signal pressure calculated in this way is output from the controller 30. This arm signal pressure is applied to the drive unit of the first solenoid valve 32 shown in FIG. 1 to drive the first solenoid valve 32. Therefore, the pilot pressure Ps ₁ of the pilot pump 21 is applied to the one drive portion 7a of the arm pressure compensating valve 7, and the pilot pressure Ps ₁ is reduced by the first solenoid valve 32 to the other control pressure Fa _1. The arm pressure compensating valve 7 is opened according to the differential pressure between the pilot pressure Ps ₁ and the control pressure Fa ₁ , that is, the throttle amount is controlled, and the flow rate discharged from the hydraulic pump 2 is controlled. Is supplied to the arm cylinder 4 via the arm pressure compensating valve 7 and the arm directional control valve 6, the arm cylinder 4 operates, and the arm cylinder 4 causes the arm 53 to move.
Can be driven.

Similarly, if only the operation signal of the boom operation detector B is input, as shown in FIG. 4, the fourth arithmetic means of the controller 30 outputs from the differential pressure detector 27. The function generator 3 according to the Ls differential pressure
The boom pressure compensation pressure is calculated by 0c, and the boom signal pressure is calculated by the function generator 30h according to the calculated boom pressure compensation pressure. The boom signal pressure calculated in this way is output from the controller 30. This boom signal pressure is given to the drive unit of the second solenoid valve 34 shown in FIG. 1, and the second solenoid valve 33 is driven. Therefore, the pilot pressure Ps ₁ of the pilot pump 21 is applied to the one drive portion 9a of the boom pressure compensation valve 9, and
As the pilot pressure Ps ₁ is applied to the second pressure-reduced by the other driving unit 9b as a control pressure Fa ₂ solenoid valve 33, the boom pressure compensation in accordance with the pressure difference between the pilot pressure Ps ₁ and the control pressure Fa ₂ The valve 9 is opened, that is, the throttle amount is controlled, and the flow rate discharged from the hydraulic pump 2 is supplied to the boom cylinder 5 via the boom pressure compensating valve 9 and the boom direction switching valve 8. The boom cylinder 5 can drive the boom 52.

In the case of such control (B), the increasing rates of the arm pressure compensation pressure and the boom pressure compensation pressure with respect to the Ls differential pressure in the function generator 30b and the function generator 30c can be set to be substantially equal to each other. . Further, the reduction rates of the arm signal pressure and the boom signal pressure with respect to the pressure compensation pressure in the function generator 30g and the function generator 30h can be set to be substantially equal to each other, for example. Therefore, with this setting, the throttle characteristics of the arm pressure compensating valve 7 and the boom pressure compensating valve 9 equivalent to those of the conventional technique can be obtained, and the arm 53 drive and the boom 52 equivalent to those of the conventional technique can be obtained.
Can be driven.

Further, in the judgment of the step S2 of FIG. 2 which is carried out by the judgment means of the controller 30, it is judged that the operation signal is output from both the arm operation detector A and the boom operation detector B. Then, the control (A) of step S4 is executed.

At this time, as shown in FIG. 3, in the first calculation means of the controller 30, the arm load pressure detector 60 is used.
The function generator 30a according to the arm load pressure output from the
The arm pressure compensation maximum value is calculated by the function generator 3 and the function generator 3 is operated according to the Ls differential pressure output from the differential pressure detector 27.
0b calculates the arm pressure compensation pressure, and the minimum value selector 30e selects the minimum value of the arm pressure compensation maximum value and the arm pressure compensation pressure calculated by the function generators 30a and 30b as the pressure compensation pressure. The arm signal pressure is calculated by the function generator 30g according to the selected pressure compensation pressure.

In the second calculating means of the controller 30, the function generator 30d calculates the boom pressure compensation maximum value according to the arm load pressure output from the arm load pressure detector 60, and the differential pressure detection is performed. The boom pressure compensation pressure is calculated by the function generator 30c according to the Ls differential pressure output from the generator 27, and the function generator 30 is calculated by the minimum value selector 30f.
The minimum value of the boom pressure compensation maximum value and the boom pressure compensation pressure calculated by d and 30c is selected as the pressure compensation pressure, and the boom signal pressure is calculated by the function generator 30h according to the selected pressure compensation pressure. To be done.

In this way, the arm signal pressure and the boom signal pressure obtained by the first calculation means and the second calculation means are supplied from the controller 30 to the first solenoid valve 32 and the second solenoid valve 33 shown in FIG. Is output to each of the driving units.

In the above-described calculation, when the operation mode of the arm / boom combined operation is, for example, "aerial boom raising / arm pulling combined operation mode" and the load pressure of the arm cylinder 4 is relatively small, it is shown in FIG. Since the maximum arm pressure compensation value in the calculation of the function generator 30a is large and the boom pressure compensation maximum value in the calculation of the function generator 30d is small, the minimum value selector 30e of the first calculation means calculates in the function generator 30b. The selected arm pressure compensation pressure is selected, and the minimum value selector 30f of the second calculation means selects the boom pressure compensation maximum value calculated by the function generator 30d. Therefore, the arm signal pressure calculated by the function generator 30g becomes the same signal pressure as in the control (B) described above, while the boom signal pressure calculated by the function generator 30h in the control (B) described above. The signal pressure has a larger value than the signal pressure. Along with this, the second solenoid valve 33 shown in FIG. 1 operates so that the throttle amount increases from the fully open state at neutral, that is, the opening area becomes smaller,
The value of the control pressure Fa ₂ output from the second solenoid valve 33 and applied to the drive unit 9b of the boom pressure compensation valve 9 is applied to the drive unit 9a of the boom pressure compensation valve 9 as a pilot of the pilot pump 21. It is sufficiently smaller than the value of pressure Ps ₁ . As a result, the throttle amount of the boom pressure compensation valve 9 becomes smaller than the throttle amount of the arm pressure compensation valve 7. That is, the opening area of the boom pressure compensating valve 9 becomes larger than the opening area of the arm pressure compensating valve 7. Figure 5
Shows the arm pressure compensation pressure in the arm pressure compensation valve 7 obtained at this time, and FIG. 6 shows the boom pressure compensation pressure in the boom pressure compensation valve 9. As shown in FIGS. 5 and 6, when the arm load pressure is small, the arm pressure compensating valve 7 has a small arm pressure compensating pressure, and the arm pressure compensating valve 7 is free to restrict, while the boom pressure compensating valve 9 is used.
The boom pressure compensation pressure is large, and the boom pressure compensation valve 9 is open. Therefore, when the sum of the required flow rates of the boom cylinder 5 and the arm cylinder 4 becomes a saturation state in which the flow rate is larger than the flow rate discharged from the hydraulic pump 2, a relatively large flow rate can be supplied to the boom cylinder 5 side, and the boom 52 The operating speed of can be increased.

Further, the operation mode of the arm / boom combined operation is, for example, "a combined operation mode of excavating through the force of the arm 53", and when the load pressure of the arm cylinder 4 is relatively large, it is shown in FIG. Since the arm pressure compensation maximum value in the calculation of the function generator 30a is small and the boom pressure compensation maximum value in the calculation of the function generator 30d is large, the function generator 30 is the minimum value selector 30e of the first calculation means.
The arm pressure compensation maximum value calculated in a is selected, and the second
In the minimum value selector 30f of the calculation means, the function generator 30c
The boom pressure compensation pressure calculated in step 1 is selected. Therefore, while the boom signal pressure calculated by the function generator 30h becomes the same signal pressure as in the control (B) described above,
The arm signal pressure calculated by the function generator 30g has a larger value than the signal pressure in the control (B) described above. Along with this, the first solenoid valve 32 shown in FIG. 1 operates so as to increase the throttle amount from the fully open state at the time of neutral, that is, to reduce the opening area, and output from the first solenoid valve 32. , Drive unit 7 of arm pressure compensating valve 7
The value of the control pressure Fa ₁ given to b is sufficiently smaller than the value of the pilot pressure Ps ₁ of the pilot pump 21 given to the drive portion 7a of the arm pressure compensation valve 7. As a result, the throttle amount of the arm pressure compensation valve 7 becomes smaller than the throttle amount of the boom pressure compensation valve 9. That is, the opening area of the arm pressure compensation valve 7 is equal to the boom pressure compensation valve 9
Is larger than the opening area. As shown in FIGS. 5 and 6, when the arm load pressure is large, the arm pressure compensating valve 7 has a large arm pressure compensating pressure, and the arm pressure compensating valve 7 is free to open, while the boom pressure compensating valve 9 is used. The boom pressure compensation pressure is low, and the boom pressure compensation valve 9 is free to throttle. Therefore, when the sum of the required flow rates of the boom cylinder 5 and the arm cylinder 4 becomes a saturation state in which the flow rate is greater than the flow rate discharged from the hydraulic pump 2, a relatively large flow rate can be supplied to the arm cylinder 4 side, and the arm 53 can be supplied. The operating speed of can be increased.

As described above, in this embodiment, when the arm / boom combined operation mode is the "aerial boom raising / arm pull combined operation mode", the pressure oil can be automatically supplied preferentially to the boom side. In the "combined operation mode of excavating through the force of the arm 53", the pressure oil can be automatically supplied preferentially to the arm side, whereby the work efficiency can be improved.

In the above embodiment, the controller 3
Although the first computing means included in 0 has the minimum value selector 30e and the second computing means has the minimum value selector 30f, the present invention is not limited to the above configuration. For example, the function generator 30a forming the first calculation means shown in FIG.
Instead of the above, a function generator 30i shown in FIG. 7A, that is, a function generator 30i in which a function relationship in which the maximum arm pressure compensation value increases as the arm load pressure increases is set, is provided. Function generator 3 constituting the calculation means of
Instead of 0d, the function generator 30j shown in FIG. 7B, that is, the function generator 30j in which a functional relationship in which the boom pressure compensation maximum value decreases as the arm load pressure increases is set.
And an unillustrated adder for adding the arm pressure compensation maximum value output from the function generator 30i and the arm pressure compensation pressure output from the function generator 30b, and the boom pressure output from the function generator 30j. An unillustrated adder for adding the compensation maximum value and the boom pressure compensation pressure output from the function generator 30c is provided, and the first solenoid valve 32 shown in FIG. 1 is provided according to the signals output from these adders. The second solenoid valve 33 may be driven.

With this arrangement, when the arm load pressure detected by the arm load pressure detector 60 is small, the maximum arm pressure compensation value calculated by the function generator 30i is small and calculated by the function generator 30j. Since the maximum boom pressure compensation value is large, the value of the signal given to the first solenoid valve 32 is small and the value of the signal given to the second solenoid valve 33 is large. Along with this, the control pressure Fa ₁ output from the first solenoid valve 32 shown in FIG.
When the control pressure Fa ₂ output from the second solenoid valve 33 becomes small, the arm pressure compensating valve 7 is controlled to throttle freely, and the boom pressure compensating valve 9 is controlled to open freely. As in the embodiment described above, a relatively large flow rate can be supplied to the boom cylinder 5 side, and the boom 52
The operating speed of can be increased.

When the arm load pressure detected by the arm load pressure detector 60 is large, the arm pressure compensation maximum value calculated by the function generator 30i is large, and the boom pressure compensation maximum calculated by the function generator 30j is large. Since the value is small, the value of the signal given to the first solenoid valve 32 is large, and the value of the signal given to the second solenoid valve 33 is small. Accordingly, the first solenoid valve shown in FIG. The control pressure Fa ₁ output from the valve 32 is low, the control pressure Fa ₂ output from the second solenoid valve 33 is high, the arm pressure compensating valve 7 opens freely, and the boom pressure compensating valve 9 throttles. When it is controlled freely and becomes saturated,
Also in this case, a relatively large flow rate can be supplied to the arm cylinder 4 side similarly to the embodiment described above, and the operating speed of the arm 53 can be increased.

Therefore, also in the case of such a configuration, similarly to the above-described embodiment, when the combined arm / boom operation mode is the "in-air boom up / arm pull combined operation mode", the boom side is automatically prioritized. In addition to being able to supply the pressure oil with pressure, the pressure oil can be automatically supplied preferentially to the arm side in the case of the "complex operation mode of excavating through the force of the arm 53", thereby improving work efficiency. it can.

[0045]

According to the present invention having the above-described structure, it is possible to preferentially supply the pressure oil to either the arm cylinder or the boom cylinder depending on the type of the arm / boom combined operation mode. As a result, the corresponding arm
It is possible to improve the work efficiency of the boom combined operation mode as compared with the related art.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing a processing procedure in a controller provided in the embodiment shown in FIG.

FIG. 3 is a block diagram illustrating control A of processing in the controller shown in FIG.

FIG. 4 is a block diagram illustrating control B of processing in the controller shown in FIG.

5 is a diagram showing characteristics obtained by the arm pressure compensation valve for controlling the differential pressure across the arm directional control valve provided in the embodiment shown in FIG. 1;

6 is a diagram showing characteristics obtained by a boom pressure compensating valve for controlling the differential pressure across the boom directional control valve provided in the embodiment shown in FIG. 1;

FIG. 7 is a diagram for explaining another embodiment of the present invention, (a) is a diagram showing a function generator which is provided in the controller and sets a functional relationship between arm load pressure and arm pressure compensation maximum value;
(B) is a figure which is provided in the controller and shows a function generator for setting a functional relationship between arm load pressure and boom pressure compensation maximum value.

FIG. 8 is a side view showing an example of an operation performed in the hydraulic excavator.

FIG. 9 is a side view showing another example of the operation performed in the hydraulic excavator.

FIG. 10 is a circuit diagram showing a conventional hydraulic drive system for a construction machine.

[Explanation of symbols]

 2 Hydraulic pump 3 Traveling motor 4 Arm cylinder 6 Directional switching valve for arm 7 Pressure compensating valve for arm 8 Boom direction switching valve 9 Boom pressure compensating valve 20 Control actuator 21 Pilot pump (control pressure output means) 24 Electromagnetic switching valve 25 tank 26 electromagnetic switching valve 27 differential pressure detector 30 controller (control pressure output means) 30a function generator 30b function generator 30c function generator 30d function generator 30e minimum value selector 30f minimum value selector 30g function generator 30h Function generator 30i Function generator 30j Function generator 32 First solenoid valve (control pressure output means) 33 Second solenoid valve (control pressure output means) 50 Traveling body 51 Revolving body 52 Boom 53 Arm 54 Bucket 60 Arm load Pressure detector A Arm operation detector B Boom operation detector

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area F15B 11/16

Claims (2)

[Claims] 1. A variable displacement hydraulic pump, and an arm cylinder driven by pressure oil discharged from the hydraulic pump,
And a boom cylinder, an arm directional control valve for controlling the flow of pressure oil supplied from the hydraulic pump to the arm cylinder, and a boom for controlling the flow of pressure oil supplied from the hydraulic pump to the boom cylinder. The difference is the difference between the upstream pressure and the downstream pressure of the directional switching valve, the pressure compensation valve for the arm that controls the differential pressure across the arm, which is the difference between the upstream pressure and the downstream pressure of the directional switching valve for the arm. In a hydraulic drive system for a construction machine, comprising: a boom pressure compensating valve that controls a differential pressure across the arm; an arm operation detector that detects that the arm cylinder has been operated; and a boom cylinder that has been operated. The boom operation detector for detecting, the arm load pressure detector for detecting the load pressure applied to the arm cylinder, the arm operation detector, and the boom operation detector. When an arm / boom combined operation in which both the arm cylinder and the boom cylinder are operated is detected by each of the devices, the drive unit of the arm pressure compensation valve and the drive unit of the boom pressure compensation valve are respectively detected. , Supplying control pressure corresponding to the value of the detection signal detected by the arm load pressure detector, which are different from each other and set in advance according to the type of the combined operation mode performed via the arm and boom. A hydraulic drive system for a construction machine, comprising a control pressure output means capable of performing the control pressure output. 2. The control pressure output means can reduce the pilot pressure of the pilot pump and the pilot pressure of the pilot pump and supply the reduced pressure to the drive unit of the arm pressure compensation valve and the boom pressure compensation valve. First solenoid valve, second
Solenoid valve and control means having logical judgment, calculation, and storage functions, and the control means outputs operation signals from both the arm operation detector and the boom operation detector. If it is determined that the operation signal is output from both the arm operation detector and the boom operation detector, the arm load pressure detector detects the operation signal. The pressure compensating valve for the arm so that the pressure oil is preferentially supplied to the arm cylinder based on the value of the detected signal and the functional relationship preset corresponding to the first arm / boom combined operation mode. It is determined by the first calculating means for calculating the control pressure for driving the control unit and the determining means that the operation signals are being output from both the arm operation detector and the boom operation detector. In this case, the value of the detection signal detected by the arm load pressure detector and the functional relationship preset in correspondence with the second arm / boom combined operation mode different from the first arm / boom combined operation mode. 2. The second calculation means capable of calculating a control pressure for driving the boom pressure compensation valve so as to preferentially supply pressure oil to the boom cylinder based on the above. Hydraulic drive for construction machinery.