JP2694048B2 - Hydraulic drive for construction machinery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic drive system for a construction machine such as a hydraulic excavator, and in particular, a pressure compensation valve that controls a differential pressure across a flow control valve to a predetermined value. The present invention relates to a hydraulic drive system for construction machines.

BACKGROUND ART As a conventional hydraulic drive system for construction machines such as hydraulic excavators, there is a load sensing system that controls the discharge flow rate of a hydraulic pump so that the discharge pressure of the hydraulic pump is higher than a maximum load pressure of a plurality of actuators by a predetermined value. .
In this system, generally, it is called a shunt compensation valve that controls the differential pressure across the flow control valves upstream of the plurality of flow control valves that control the flow rate of pressure oil supplied from the hydraulic pump to the plurality of actuators. Place a pressure compensation valve,
When performing a combined operation of driving a plurality of actuators at the same time, the pressure oil is surely supplied to the actuator on the low load side so that a smooth combined operation can be performed.

In such a load sensing system, WO90
/ 00683 (corresponding to US Pat. No. 5,056,312) detects the differential pressure between the pump discharge pressure and the maximum load pressure, that is, the LS differential pressure,
A differential pressure sensor that outputs a corresponding differential pressure signal, a memory that stores a plurality of data patterns for individually calculating the set values of the shunt compensation valve in association with the type of actuator, and a memory that stores the data patterns from the plurality of data patterns. By providing a calculation control unit that calculates the set value corresponding to the differential pressure signal and individually controlling the set value of the shunt compensation valve based on the calculated value, the hydraulic Even in a saturation state where the discharge flow rate of the pump is insufficient, it is described that the hydraulic pressure is reliably supplied to the actuator on the low load side and the shunt ratio suitable for the type of actuator is given to improve the operability. There is.

Here, the diversion compensation valve has a first pressure-receiving chamber that operates in the closing direction to which the pressure on the upstream side of the corresponding flow control valve is guided and a second pressure-receiving chamber that operates to open the direction to which the pressure on the downstream side operates are opened. Means for applying a constant control force in the valve direction to set the target value of the differential pressure across the flow control valve, and the control pressure from the electromagnetic proportional control valve are introduced to reduce the differential pressure target value. A third pressure receiving chamber is provided, and the calculation control unit calculates a reduction target value with respect to the differential pressure target value, and outputs a corresponding control signal to the electromagnetic proportional control valve to generate a control pressure to generate the differential pressure target. The value is reduced individually.

The means for setting the differential pressure target value is usually a spring, as shown in FIG. 1 of WO90 / 00683. Further, instead of the spring, in FIG. 15 of WO90 / 00683, a pressure receiving chamber to which a constant pilot pressure is introduced is provided. Further, in FIG. 17 of WO90 / 00683, the third pressure receiving chamber operating in the closing direction is eliminated,
Instead, a pressure-receiving chamber that operates in the opening direction and that also has the function of the third pressure-receiving chamber is provided, and by controlling the control pressure guided to this pressure-receiving chamber, the function of the means for setting the differential pressure target value and the third pressure-receiving chamber. And the function of.

DISCLOSURE OF THE INVENTION However, the above-mentioned conventional techniques have the following problems.

In the prior art described in WO90 / 00683, the target differential pressures on the upstream side and the downstream side of the flow control valve are individually controlled by reducing the differential pressure target value set by the setting means of the flow shunt compensation valve, Since the differential pressure target value is constant corresponding to, for example, the initial setting of the spring, the maximum differential pressure target value is constant. Here, the maximum value of the differential pressure target value defines the maximum possible passing flow rate of the flow rate control valve, and if the maximum target differential pressure is constant, the maximum possible passing flow rate of the flow rate control valve is also constant.

By the way, in a construction machine such as a hydraulic excavator, various capacities are used for a hydraulic cylinder and a hydraulic motor that constitute a hydraulic actuator, depending on the work application. In this case, if the capacity of the hydraulic actuator becomes large and it is attempted to obtain the same drive speed with the same operation amount of the operation lever,
It is necessary to increase the supply flow rate to the hydraulic actuator with the manipulated variable. However, in the above-mentioned conventional technique, the maximum possible passing flow rate of the flow rate control valve is constant, so the supply flow rate for the same operation amount of the operation lever does not increase, and the drive speed at the same operation amount of the operation lever decreases, and It gives a feeling of strangeness. Further, even if the operation amount of the operation lever is maximized, a sufficient drive speed cannot be obtained, and proper operation becomes difficult.

Further, even when the capacity of the hydraulic actuator is not changed, there are cases where it is desired to increase the supply flow rate when the operation lever is operated to the maximum and increase the maximum drive speed of the hydraulic actuator depending on the work mode. Even in such a case, since the maximum possible passage flow rate of the flow rate control valve is constant in the above-mentioned conventional technique, the supply flow rate of the hydraulic actuator does not increase, and the maximum drive speed cannot be increased.

An object of the present invention is to make it possible to change the maximum possible passing flow rate of the flow control valve by freely changing the target value of the differential pressure across the flow control valve, which corresponds to the capacity of the hydraulic actuator used and the working mode. Accordingly, it is an object of the present invention to provide a hydraulic drive system for a construction machine capable of freely setting the maximum drive speed.

To achieve the above object, according to the present invention, one hydraulic pump; a plurality of hydraulic actuators driven by pressure oil discharged from this hydraulic pump; A plurality of flow rate control valves for controlling the flow rate of the pressure oil according to the operation amount of the operating means; a first pressure receiving chamber operating in a closing direction into which the upstream side pressure and the downstream side pressure of the corresponding flow rate control valves are introduced, respectively. A second pressure-receiving chamber that operates in the opening direction and a third pressure-receiving chamber that operates in the closing direction to reduce the target value of the differential pressure across the flow control valve to which the first control pressure is introduced; A plurality of shunt compensating valves for respectively controlling the differential pressures across the plurality of flow rate control valves; a differential pressure for detecting a differential pressure between the pressure of the pressure oil discharged from the hydraulic pump and the maximum load pressure of the plurality of hydraulic actuators. Inspection Means; first proportional control valve means for generating the first control pressure in response to a first control current; differential pressure across the plurality of flow control valves based on a detection value of the differential pressure detection means First calculation control means for calculating at least one decrease target value for subtracting the target value and outputting a corresponding first control current to the first proportional control valve means.
(A) is installed in at least one of the plurality of shunt compensation valves and guides a second control pressure to set a target value of the differential pressure across the flow control valve. A fourth pressure-receiving chamber that operates in the opening direction to be set; (b)
Second proportional control valve means for generating the second control pressure according to a second control current; and (c) signal generating means for outputting a signal relating to a target value of the differential pressure across the flow control valve. (D) A target value of the differential pressure across the corresponding flow control valve is calculated according to the signal from the signal generating means, and a corresponding second control current is output to the second proportional control valve means. And a second arithmetic control unit for controlling the hydraulic drive of the construction machine.

In the present invention configured as described above, for example, when the hydraulic actuator has a standard capacity, the signal generating means outputs a signal indicating that, and the second arithmetic control means responds in accordance with the signal. A normal target value is calculated as a target value of the differential pressure across the flow control valve, and a second control current corresponding to the second proportional control valve means is output. The second proportional control valve means generates a second control pressure in response to the second control current, and the fourth pressure receiving chamber receives the control pressure to set the differential pressure across the flow control valve as a target value. Set a normal target value. On the other hand, when the hydraulic actuator is replaced with a large-capacity actuator, a signal indicating that is output from the signal generating means, and the second arithmetic and control means responds to the signal by the differential pressure across the flow control valve. A value larger than the normal target value is calculated as the target value of, and the corresponding second control current is output to the second proportional control valve means. The second proportional control valve means generates a second control pressure in response to the second control current, and the fourth pressure receiving chamber receives the control pressure to set the differential pressure across the flow control valve as a target value. Set a target value that is larger than the normal target value. As a result, when the hydraulic actuator is at the standard capacity, the diversion compensation valve sets the maximum possible passing flow rate of the flow control valve to the standard maximum flow rate, and when the hydraulic actuator is at the capacity larger than the standard capacity,
Set the maximum possible flow rate of the flow control valve to a flow rate higher than the standard maximum flow rate. Therefore, it is possible to supply the pressure oil at a flow rate suitable for the capacity of each hydraulic actuator used, and it is possible to freely set the maximum drive speed of the actuator.

In the above hydraulic drive device, preferably, the signal generating means includes setting means for setting a type regarding a capacity of a hydraulic actuator related to the flow dividing compensation valve in which the fourth pressure receiving chamber is installed, and the second arithmetic control means. Calculates the differential pressure target value according to the signal from the setting means.

The signal generating means includes an operation detecting means for detecting an operation state of a flow rate control valve related to the diversion compensating valve in which the fourth pressure receiving chamber is installed, and the second arithmetic control means has a detection value of the operation detecting means. The target differential pressure value may be calculated from

Further, the signal generating means detects a setting means for setting a type regarding a capacity of a hydraulic actuator related to the shunt compensation valve in which the fourth pressure receiving chamber is set, and an operation state of a flow control valve related to the shunt compensation valve. The second calculation control means may include operation detection means, and may calculate the differential pressure target value from a signal from the setting device and a detection value of the operation detection means.

Further, in the hydraulic drive system, preferably, the fourth pressure receiving chamber is installed in each of the plurality of shunt compensation valves, and the second proportional control valve means is provided in each of the plurality of shunt compensation valves. Includes a common proportional control valve connected to four pressure chambers.

The fourth pressure receiving chamber is installed in each of the plurality of flow compensation valves, and the second proportional control valve means is connected to each of the fourth pressure receiving chambers of the plurality of flow compensation valves. The proportional control valve may be included.

Further, in the above hydraulic drive device, preferably, the second arithmetic control unit includes at least two target values including a normal target value of the differential pressure across the corresponding flow control valve and a target value larger than the normal target value. Is stored, means for selecting one of the two target values according to a signal from the signal generating means, and means for outputting the second control current according to the selected target value. .

The second arithmetic control means stores the initial value of the target value of the differential pressure across the flow control valve and at least two different correction values to be added to the initial value, and the signal generating means. One of the two correction values is selected according to a signal from the means, added to the initial value, and means for calculating the target value, and the second control current is output according to the calculated target value. And means for doing so.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a hydraulic drive system for a construction machine according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing details of the servo mechanism of the hydraulic pump shown in FIG.

FIG. 3 is a schematic diagram showing a hardware configuration of the control unit shown in FIG.

FIG. 4 is a flow chart for explaining the function of the control unit shown in FIG.

FIG. 5 is a diagram showing the relationship between the pressure difference between the pump discharge pressure and the maximum load pressure, and the control pressure introduced to the shunt compensation valve.

FIG. 6 is a diagram showing a functional relationship between the open side target value and the close side target value of the diversion compensation valve, and the control current value when the open side control valve is driven and the control current value when the close side control valve is driven.

FIG. 7 is a schematic diagram of a hydraulic drive system for a construction machine according to a second embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described based on illustrated embodiments. In these embodiments, the present invention is applied to a hydraulic drive system for a hydraulic excavator.

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

Referring to FIG. 1, the hydraulic drive system according to the present embodiment is a variable displacement main hydraulic pump 1a including a displacement volume changing mechanism 2.
Pilot pump 1b, pump control servo mechanism 3 that drives displacement volume variable mechanism 2, relief valve 4 that regulates the maximum pressure of pressure oil discharged from main hydraulic pump 1a, hydraulic cylinder 5a, hydraulic motor 5b, hydraulic cylinder 5a. The flow rate and the flow direction of the pressure oil to be supplied are controlled according to the operation amount and the operation direction of the operation lever device 50, and the first flow rate control valve 6a for driving the hydraulic cylinder 5a and the pressure oil to be supplied to the hydraulic motor 5b are controlled. The second flow rate control valve 6b, which controls the flow rate and the flow direction according to the operation amount and the operation direction of the operation lever device 51, controls the drive of the hydraulic motor 5b, and the differential pressure across the flow rate control valves 6a and 6b. It is provided with first and second pressure compensating valves, that is, shunt compensating valves 7a and 7b, which are operated so as to maintain a specified value.

The first diversion compensation valve 7a includes a first pressure-receiving chamber 52a that operates in the closing direction to which the pressure on the upstream side of the first flow control valve 6a is guided and a second pressure receiving chamber that operates in the opening direction to guide the pressure on the downstream side. Chamber 53
a and the first control pressure P _C1 are introduced, and the first flow control valve 6a
The third pressure-receiving chamber 54a, which is operated in the closing direction to reduce the target value of the differential pressure between the front and rear, and the second control pressure _PCT, are introduced to set the target value of the differential pressure across the first flow control valve 6a. Directionally actuated fourth
The second diversion compensation valve 7b has a pressure receiving chamber 55a of the second flow control valve 6b, and a second pressure compensation chamber 7a of the second flow control valve 6b. The second pressure-receiving chamber 53b operated in the opening direction and the third pressure-receiving chamber 54b operated in the closing direction for guiding the first control pressure P _C2 to reduce the target value of the differential pressure across the second flow control valve 6b. And the second control pressure P
_It is provided with a fourth pressure receiving chamber 55b which is operated in the opening direction and which is guided by _CT and sets a target value of the differential pressure across the second flow control valve 6b.

The hydraulic drive system of the present embodiment also detects the differential pressure between the discharge pressure from the main hydraulic pump 1a and the maximum load pressure of the hydraulic cylinder 5a and hydraulic motor 5b, and outputs a differential pressure signal ΔP _LS. And a first electromagnetic proportional control valve 56 for generating a pump control pressure P _P guided to the pump control servomechanism 3,
The third pressure receiving chamber 54a, which is operated in the closing direction of the first flow compensation valve 7a.
The second electromagnetic proportional control valve 9a for generating the first control pressure P _C1 and the first control pressure P introduced to the third pressure receiving chamber 54b which is operated in the closing direction of the second diversion compensation valve 7b. _From the third electromagnetic proportional control valve 9b for generating _C2 and the operation lever device 50 to the first
The pilot pressure introduced to the flow control valve 6a of the
Of the second flow rate control valve 6 from the operation lever device 51 and the operation detectors 20 and 21 that detect the operation status of the flow rate control valve 6a, that is, whether or not the hydraulic cylinder 5a is driven and output the operation signals a1 and a2.
The second flow control valve 6 which detects the pilot pressure guided to b
The operation status of b, that is, the operation detectors 22 and 23 that detect the presence or absence of driving of the hydraulic motor 5b and output the operation signals b1 and b2, and the opening direction operation of the first and second diversion compensation valves 7a and 7b. a fourth solenoid proportional control valve 24 for generating a fourth pressure receiving chamber 55a, the second control pressure P _CT guided to 55b, and set the type relating to capacity of the hydraulic actuators used to output the type signal F And a type setting device 25. The type signal F is a signal indicating whether the capacity set by the type setting device 25 is a standard capacity or another capacity.

Further, the hydraulic drive system according to the present embodiment further includes a differential pressure signal ΔP _LS from the differential pressure detector 8 and operation signals a ₁ , a ₂ , b ₁ , b from the operation detectors 20, 21, 22, 23. _2. Control currents I _C0 , I _C1 , I _C2 for driving the first to fourth electromagnetic proportional control valves 56, 9a, 9b, 24 by fetching the type signal F from the type setting device 25 and performing a predetermined calculation , I _T is provided as a control unit 26.

In the figure, 11a and 11b are check valves, 12 is a shuttle valve for selecting the maximum load pressure, and 13 is a crossover relief valve.

As shown in FIG. 2, the pump control servomechanism 3 responds to the piston / cylinder device 31 for driving the displacement volume variable mechanism 2 of the hydraulic pump 1a and the pump control pressure P _P from the aforementioned electromagnetic proportional control valve 56. The first servo valve 32 for adjusting the flow rate of the pressure oil supplied to the piston / cylinder device 31 to control the displacement of the hydraulic pump 1a and the piston / cylinder device 31 in response to the pump discharge pressure. The flow rate of the pressure oil is adjusted to control the displacement of the hydraulic pump 1a. And a second servo valve 33 for limiting the input torque.

The control unit 26 is composed of a microcomputer,
As shown in FIG. 3, the differential pressure detector 8 outputs a differential pressure signal ΔP _LS ,
Operation signal a ₁ from the operation detector _{20,21,22,23, a 2, b 1,} b 2, and A / D converter 26a for converting an input digital signal a type signal F from the type setting unit 25, A central processing unit (CPU) 26b that performs a predetermined calculation, a read-only memory (ROM) 26c that stores a program for performing the predetermined calculation, and a random access memory (RA that temporarily stores a numerical value during the calculation.
M) 26d, the output I / O interface 26e, and the above-mentioned electromagnetic proportional control valves 56, 9a, 9b, 24, and the control current I
Amplifiers 26f, 26g, 26h and 26i for outputting _C0 , I _C1 , I _C2 and I _T are provided.

The outline of the arithmetic function of the control unit 26 will be described. First, the control unit 26 controls the differential pressure signal Δ from the differential pressure detector 8.
The target displacement of the hydraulic pump 1a for keeping the differential pressure between the pump discharge pressure and the maximum load pressure constant based on P _LS is calculated, and the control current I _C0 corresponding to this target displacement is calculated by the first electromagnetic proportional control. Output to valve 56. Thus, the discharge flow rate of the hydraulic pump 1a is controlled so that the discharge pressure of the hydraulic pump 1a becomes higher than the maximum load pressure by a constant value. Details of this are described in, for example, the aforementioned WO90 / 00683.

Further, the control unit 26, based on the differential pressure signal ΔP _LS from the differential pressure detector 8, decreases the target value ΔP _C1 for reducing the target value of the differential pressure across the first and second flow control valves 6a, 6b. , ΔP _C2
Are calculated individually, and the control currents I _C1 and I _C2 corresponding to the reduction target values ΔP _C1 and ΔP _C2 are calculated as the second and third electromagnetic example control valves 9a and 9b.
Output to

Further, the control unit 26 determines the operating conditions of the hydraulic cylinder 5a and the hydraulic motor 5b based on the operation signals a ₁ , a ₂ , b ₁ , b ₂ from the operation detectors 20, 21, 22, 23, and the hydraulic cylinders The first target value ΔP _T0 of the differential pressure across the first and second flow rate control valves 6a and 6b is calculated from the operating states of the hydraulic actuator 5a and the hydraulic motor 5b, and the hydraulic actuator based on the type signal F from the type setter 25.
The type of 5a, 5b is determined, and the first target value ΔP _T0 is determined from the type.
Is corrected to calculate the second target value ΔP _T , and finally the control current I _T corresponding to the second target value ΔP _T is output to the fourth solenoid proportional control valve 24.

The calculation procedure in the control unit 26 until the control currents I _C1 , I _C2 and the control current I _T are output will be described in detail with reference to the flowchart shown in FIG.

First, the control unit 26 initializes the microcomputer (step 201), and then the differential pressure signal ΔP _LS from the differential pressure detector 8 and the operation signals from the operation detectors 20, 21, 22, 23.
A ₁ , a ₂ , b ₁ , b ₂ and the type signal F from the type setting device 25 are read (step 202). Subsequently, the control unit 26 uses the first calculation function to reduce the target value of the differential pressure across the first and second flow rate control valves 6a, 6b from the differential pressure signal ΔP _LS by using the decrease target value ΔP _C1 , ΔP _C2 is individually calculated from a predetermined functional relationship. FIG. 5 shows an example of the functional relationship, in which the horizontal axis represents the differential pressure signal ΔP _LS and the vertical axis represents the reduction target values ΔP _C1 and ΔP _C2 . The characteristics of ΔP _C1 and ΔP _C2 shown in the figure can be arbitrarily set in consideration of the characteristics during the combined operation of the cylinder 5a and the hydraulic motor 5b. This function is the differential pressure signal ΔP
_As the value of _LS increases, the reduction target values ΔP _C1 and ΔP _C2 are reduced. That is, when the differential pressure between the pump discharge pressure and the maximum load pressure decreases, the decrease target value Δ
By increasing P _C1 and ΔP _C2 , the first and second flow control valves 6a, 6b
The target value of the differential pressure across the flow control valve 6a, 6
The maximum possible flow rate of b is reduced (step 203).

The control unit 26 subsequently determines the operating states of the hydraulic cylinder 5a and the hydraulic motor 5b from the operation signals a ₁ , a ₂ , b ₁ , b _{2 by the second} arithmetic function, and further by the third arithmetic function. Based on the determination result, the first target value ΔP _T0 is calculated as the initial value of the differential pressure target value ΔP _T set in the fourth pressure receiving chambers 55a and 55b. That is, when the operation signals are a ₁ > a ₁₁ or a ₂ > a ₂₂ and b ₁ > b ₁₁ or b ₂ > b ₂₂ (steps 204, 205), both the hydraulic cylinder 5a and the hydraulic motor 5b are Since it is driven, the first target value ΔP _T0
= ΔP _i1 (step 207) and the operation signal is a ₁ >
When a ₁₁ or a ₂ > a ₂₂ and b ₁ > b ₁₁ or b ₂ > b ₂₂ are not satisfied (steps 204, 205), the hydraulic cylinder 5a
Since it is only driving, the first target value ΔP _T0 = ΔP _i2 is set (step 208), and the operation signal is a ₁ > a ₁₁ or a ₂ >.
In a ₂₂ rather than, and b _1> b ₁₁ or b _2> is when a b ₂₂ (step 204, 206), set to a first target value ΔP _T0 = ΔP _i3 from being driven only hydraulic motor 5b ( Step
209), when the operation signal is neither a ₁ > a ₁₁ or a ₂ > a ₂₂ nor b ₁ > b ₁₁ or b ₂ > b ₂₂ (step
204, 206), the first target value _ΔT0 = ΔP _i4 is set because the hydraulic cylinder 5a and the hydraulic motor 5b are not driven (step 210). Here, a ₁₁ , a ₂₂ , b ₁₁ and b ₂₂ are values slightly larger than the dead zones of the operating lever devices 50 and 51. Further, ΔP _i1 , ΔP _i2 , ΔP _i3 , and ΔP _i4 are determined from the functional relationship of FIG. That is, ΔP _i1 = ΔP _i4 , ΔP _i2 = ΔP _i3 , and ΔP _i1 and ΔP _i4 are the values in the normal mode for setting the target value of the differential pressure _across the first and second flow rate control valves 6a, 6b to the normal level. And ΔP _i2 and ΔP _i3 are the first and second flow control valves 6
This is the value in the high speed mode in which the target value of the differential pressure across the a and 6b is set relatively large.

The control unit 26 subsequently determines the type of the hydraulic actuators 5a, 5b from the type signal F by the fourth calculation function, and further determines the type of the hydraulic actuators 5a, 5b by the fifth calculation function according to the type of each hydraulic actuator 5a, 5b. The first target value ΔP _T0 is corrected to calculate the second target value ΔP _T. That is, the type signal F
To detect the hydraulic cylinder 5a and the hydraulic motor.
When it is determined that both 5b are in the standard capacity (step 21
1,212), the second target value ΔP _T = ΔP _T0 + P _S1 is set (step 214), and when it is determined that the hydraulic cylinder 5a is the standard displacement and the hydraulic motor 5b is not the standard displacement (step 211,
212), the second target value ΔP _T = ΔP _T + P _S2 is set (step 215), and when it is determined that the hydraulic cylinder 5a is not at the standard displacement but the hydraulic motor 5b is at the standard displacement (step 211,
213), when the second target value ΔP _T = ΔP _T0 + P _S3 is set (step 216) and it is determined that neither the hydraulic cylinder 5a nor the hydraulic motor 5b has the standard displacement (steps 211, 21).
In 3), the second target value ΔP _T = ΔP _T0 + P _S4 is set (step 217). Here, P _{S1 to} P _S4 are correction values determined according to the type signal F, and have a relationship of at least P _S1 <S _S2 and P _S3 <P _S4 .

Finally, the control unit 26 uses the second target value ΔP _T and the above-described decrease target value ΔP _C1 ,
The control currents I _T , I _C1 , I _C2 corresponding to ΔP _C2 are output. FIG.
The horizontal axis represents the control pressures ΔP _T , ΔP _C1 and ΔP _C2 , and the vertical axis represents the control currents I _T , I _C1 and I _C2 . This function is for each control current if each control pressure ΔP _T , ΔP _C1 , and ΔP _C2 rises.
I _T , I _C1 and I _C2 also have a relationship of increasing in proportion to them. Thus, the control current I _T, by outputting the I _C1, I _C2 (step 218), first, second diverted compensating valves 7a, 7b
Solenoid proportional control valves 9a, 9b, 24 for controlling the
Is performed, and the process returns to step 2.

In the present embodiment configured as described above, the first flow control valve 6a and / or 51
Or when the second flow control valve 6b is operated, the main hydraulic pump
The pressure oil discharged from 1a is the first flow control valve 6a and / or
Or, via the second flow control valve 6b, the hydraulic cylinder 5a and / or
Alternatively, it is supplied to the hydraulic motor 5b. At this time, the differential pressure across the first flow control valve 6a and / or the second flow control valve 6b is the same as that of the first flow compensation valve 7a and / or the second flow compensation valve 7b.
The pressure control chambers 54a and 54b and the fourth pressure control chambers 55a and 55b are controlled to be equal to the target values. Hereinafter, this will be described in detail.

Now, for example, when the hydraulic pressure of the hydraulic motor 5b is independently driven and the load pressure rises according to the work mode, the differential pressure across the second flow control valve 6b tends to decrease, but the load pressure is the second shunt compensation valve. Second pressure receiving chamber 53b operated in the opening direction of 7b
As a result, the second branch flow compensation valve 7b increases the opening degree. At this time, the differential pressure between the discharge pressure of the main hydraulic pump 1a and the maximum load pressure also tries to decrease, but this decrease in differential pressure is detected by the differential pressure detector 8 as a differential pressure signal ΔP _LS ,
The control unit 26 drives the first electromagnetic proportional control valve 56 and the pump control servomechanism 3 by the control current I _C0 to increase the discharge flow rate of the hydraulic pump 1a. By this operation, the pressure of the pressure oil supplied to the second flow rate control valve 6b is increased, so that the differential pressure across the second flow rate control valve 6b is kept constant and the hydraulic motor 5b operates. The driving force is increased.

On the other hand, during combined operation of the hydraulic cylinder 5a and the hydraulic motor 5b, when the pressure oil supply amount of the hydraulic pump 1a is insufficient, that is, when saturation occurs, most of the pressure oil is left in the low pressure side actuator as it is. Supplied, no combined motion. In this case, the control unit 26 is shown in FIG.
In step 203 shown in, the reduction target values ΔP _C1 and ΔP _C2 are calculated,
In step 218, the corresponding control currents I _C1 and I _C2 are set to the second and third values.
Output to the electromagnetic proportional control valves 9a, 9b, and the first control pressures P _C1 , P _C2 are supplied from the control valves 9a, 9b to the third pressure receiving chambers 54a, 54b of the flow dividing compensation valves 7a, 7b to divide the flow. The compensating valves 7a and 7b are biased in the closing direction. As a result, the fourth pressure receiving chamber 55 of the diversion compensation valve 7a, 7b
The target value of the differential pressure across the flow control valves 6a, 6b set by a, 55b is individually reduced to eliminate the saturation state during the above combined operation, and to ensure the combined operation, and the actuator type. To improve the operability by providing a split flow ratio suitable for. The details are described in the aforementioned WO90 / 00683.

Further, during the combined operation of the hydraulic cylinder 5a and the hydraulic motor 5b, the control unit 26 determines that the operation signal is a ₁ > a ₁₁ or a ₂ > a ₂₂ and b ₁ > in steps 204 and 205 shown in FIG.
It is determined that b ₁₁ or b ₂ > b ₂₂ and the first step is performed in step 207.
The target value ΔP _T 0 of is set to the normal value ΔP _i1 . For this reason,
In steps 214 to 217, the second target value ΔP _T is determined with its normal value ΔP _i1 as an initial value, and in step 218, the corresponding control current I _T is output to the fourth solenoid proportional control valve 24. As a result, the target value of the differential pressure across the flow control valves 6a, 6b set in the fourth pressure receiving chambers 55a, 55b of the diversion compensation valves 7a, 7b becomes a normal value, and as described above, depending on this target value. The usual maximum possible throughflow is obtained.

On the other hand, when a single driving of the hydraulic cylinder 5a or the hydraulic motor 5b, the control unit 26 an operation signal in step 204 to 206 shown in FIG. 4 is a _1> a ₁₁ or a _2> a _22, and b ₁
> B ₁₁ or b ₂ > b ₂₂ or not a ₁ > a ₁₁ or a ₂ > a ₂₂ and b ₁ > b ₁₁ or b ₂ > b ₂₂ and step 208 or At 209, the first target value ΔP _T0 is set to ΔP _i2 or ΔP _i3 larger than usual. For this reason,
In steps 214 to 217, the second target value ΔP _T is determined by using the value ΔP _i2 or ΔP _i3 larger than usual as the initial value, and in step 218, the corresponding control current I _{T is set} to the fourth solenoid proportional control valve 2.
Output to 4. As a result, the target value of the differential pressure across the flow control valves 6a, 6b set in the fourth pressure receiving chambers 55a, 55b of the diversion compensation valves 7a, 7b becomes a larger value than usual, and the maximum value of the corresponding flow control valves is possible. Change the flow rate to a large value. By greatly changing the maximum possible passing flow rate in this way, the supply flow rate for the same operation amount of the operation lever device increases during single drive, and efficient work can be performed by increasing the drive speed of the actuator.

When both the hydraulic cylinder 5a and the hydraulic motor 5b have the standard displacements, the type setting device 25 sets the type signal F for setting the hydraulic cylinders 5a and the hydraulic motors 5b to the standard displacements by setting the type setting device 25 by the operator. Output. The control unit 26 determines in Steps 211 and 212 shown in FIG. 4 from the type signal F that the hydraulic cylinder 5a and the hydraulic motor 5b are in the standard capacity, and in Step 214, sets the second target value to ΔP _T = ΔP _T0 + P _S1 . After setting, the corresponding control current I _T is output to the fourth solenoid proportional control valve 24 in step 218. As a result, the target value of the differential pressure across the flow control valves 6a, 6b set in the fourth pressure receiving chambers 55a, 55b of the flow compensation valves 7a, 7b becomes a standard value, and the first and second flow control valves The maximum possible flow rate of 6a and 6b is also the standard value.

Furthermore, when one of the hydraulic cylinder 5a and the hydraulic motor 5b is replaced with an actuator having a capacity larger than the standard capacity, one of the hydraulic cylinder 5a and the hydraulic motor 5b is changed from the type setting device 25 to the standard by setting the type setting device 25 by the operator. A type signal F for setting a capacity other than the capacity is output. The control unit 26 executes steps 211,212 or 211,2 shown in FIG.
At 13, the hydraulic cylinder 5a and the hydraulic motor 5b from the type signal F
It is determined that one of the two is in a capacity other than the standard capacity, and the second target value is set to ΔP _T = ΔP _T0 + P _S2 or ΔP _T = ΔP _T0 + P _S3 in step 215 or 216, and it is handled in step 218. The control current I _T is output to the fourth solenoid proportional control valve 24. As a result, the target value of the differential pressure across the flow control valves 6a, 6b set in the fourth pressure receiving chambers 55a, 55b of the flow compensation valves 7a, 7b is ΔP _T = ΔP
_The value becomes larger than that at the time of _T0 + P _S1 , and the maximum possible passing flow rate of the first and second flow rate control valves 6a, 6b is also changed to a large value. That is, the supply flow rate with respect to the same operation amount of the operation lever device increases, and the drive speed of the operation lever device with the same operation amount slightly increases for an actuator of standard capacity and slightly decreases for an actuator other than the standard capacity. The operator's discomfort is reduced and operability is improved.

When both the hydraulic cylinder 5a and the hydraulic motor 5b are replaced with actuators having a larger capacity than the standard capacity, the operator sets the type setter 25 to change the hydraulic cylinder 5a and the hydraulic motor 5b from the type setter 25 to a value other than the standard capacity. The type signal F for setting the capacity is output. Controller unit
In step 211, 213 shown in FIG. 4, it is determined from the type signal F that both the hydraulic cylinder 5a and the hydraulic motor 5b are in capacities other than the standard capacity, and in step 217, the second target value is ΔP _T = ΔP _T0 + P _S4 is set, and the control current I _T is output to the corresponding fourth electromagnetic proportional control valve 24 in step 218. As a result, the target value of the differential pressure across the flow control valves 6a, 6b set in the fourth pressure receiving chambers 55a, 55b of the flow compensation valves 7a, 7b is ΔP _T = ΔP
_The value becomes even larger than that at the time of _T0 + P _S1 , and the maximum possible passing flow rate of the first and second flow rate control valves 6a, 6b is also changed to a larger value. That is, the supply flow rate for the same operation amount of the operation lever device is further increased, the driving speed at the same operation amount of the operation lever device is not reduced, the discomfort given to the operator is reduced, and the operation amount of the operation lever device is maximized. If so, a sufficient driving speed can be obtained and an appropriate operation can be performed.

As described above, according to the present embodiment, the first and second flow dividing compensation valves 7a, 7b are provided with the fourth pressure receiving chambers 55a, 55b which are operated in the opening direction, and are set by the fourth pressure receiving chambers 55a, 55b. Since the target values of the front and rear pressure applied to the first and second flow rate control valves 6a, 6b are calculated by the control unit 26 according to the operation amount of the hydraulic actuator and the type of the hydraulic actuator, It is possible to freely set the maximum drive speed of the actuator by changing the maximum possible passing flow rate of the flow rate control valves 6a and 6b according to the type of capacity or the operating condition of the hydraulic actuator. As a result, even if the hydraulic actuator is replaced with a hydraulic actuator having a capacity other than the standard capacity, the operator can operate with the same feeling as that for the hydraulic actuator having the standard capacity.
It is possible to obtain excellent operability without lowering the maximum driving speed.

Another embodiment of the present invention will be described with reference to FIG. The first
In the embodiment described above, the second control pressure introduced to the fourth pressure receiving chamber that operates in the opening direction of each shunt compensation valve is generated by the common electromagnetic proportional control valve. A control valve is provided to individually set the differential pressure target value. In the figure, the same reference numerals are given to members equivalent to the members shown in FIG.

That is, referring to FIG. 7, the hydraulic drive system according to the present embodiment has a fourth pressure receiving chamber that operates in the opening direction of the first flow compensation valve 7a.
The electromagnetic proportional control valve 24a for generating the second control pressure P _CT1 guided to 55a and the second control pressure P _CT2 guided to the fourth pressure receiving chamber 55b of the opening direction operation of the second diversion compensation valve 7b are An electromagnetic proportional control valve 24b for generating is provided.

Further, the control unit 26A determines the operating conditions of the hydraulic cylinder 5a and the hydraulic motor 5b based on the operation signals a ₁ , a ₂ , b ₁ , b ₂ from the operation detectors 20, 21, 22, 23, and the hydraulic cylinders 5a and the hydraulic motor 5b operating state from the first and second flow control valve
The first target values ΔP _T01 and ΔP _T02 of the differential pressure across 6a and 6b are individually calculated, and the type of the hydraulic actuators 5a and 5b is determined based on the type signal F from the type setter 25. 1
Calculated second target value [Delta] P _T1, the [Delta] P _T2 individually corrects the target value, the second target value [Delta] P _T1, the control current I _T1 corresponding to [Delta] P _T2, I
_T2 is output to the solenoid proportional control valves 24a and 24b.

According to this embodiment, the first and second diversion compensation valves 7a, 7b
Since the target values set in the fourth pressure receiving chambers 55a and 55b can be individually changed, for example, the shunt compensation valve related to the hydraulic actuator in the standard capacity controls the maximum flow rate to the standard maximum flow rate, and The shunt compensation valve related to the large capacity hydraulic actuator controls the maximum flow rate to a flow rate larger than the standard maximum flow rate, and the first and second flow rate control valves.
The maximum possible flow rate of 6a and 6b can be set individually, and the operability can be further improved.

In the above embodiment, the case where the differential pressure target value is changed according to the type relating to the capacity of the hydraulic actuator has been described, but even with hydraulic actuators of the same capacity, the operator consciously sets the maximum flow rate according to the work mode. It may be desired to change, and the present invention can be applied to such a case. That is, in this case, a maximum flow rate setting device similar to the type setting device described above may be provided, and the maximum flow amount obtained by changing the target pressure value may be changed by a signal from this setting device. Accordingly, the maximum drive speed of the actuator when the operation lever is operated to the maximum can be freely set according to the work mode, and the work efficiency can be improved.

Further, in the above embodiments, the first and second diversion compensation valves
Separate electromagnetic proportional control valves 9a and 9b are provided for the third pressure receiving chambers 54a and 55b of 7a and 7b, and the first control pressures introduced to these pressure receiving chambers are individually generated. When the valves may reduce the target differential pressure value at the same rate, a common electromagnetic proportional control valve may be provided to guide the same first control pressure to the third pressure receiving chamber.

Further, in the flowchart shown in FIG. 4, the operation status of the hydraulic actuator is identified and then the type of the hydraulic actuator is determined, but it goes without saying that the order may be reversed.

Further, for a specific hydraulic actuator, the differential pressure target value may be set simply by setting by the type setting device regardless of the detection value of the operation detector, and in this case, the control content can be simplified.

Further, in the above-described embodiment, the reduction of the differential pressure target value when the pump pressure oil supply amount is insufficient is performed only by increasing the reduction target value set in the pressure receiving chamber of the closing direction drive, but the same difference The target pressure value can be reduced also by reducing the target differential pressure value itself set in the pressure receiving chamber driven in the opening direction, or both of them may be performed together.

When simultaneously driving an actuator with an extremely high pressure load and an actuator with an extremely low pressure load, the differential pressure set in the pressure-receiving chamber of the light-dividing compensating valve operating in the opening direction By setting a larger target value for reducing the differential pressure set in the pressure-receiving chamber that operates in the closing direction than the target value, the flow rate to the light load side is suppressed and control in a wider range becomes possible.

INDUSTRIAL APPLICABILITY As described above, according to the present invention, the maximum possible passing flow rate of the flow control valve can be changed by freely changing the target value of the differential pressure across the flow control valve. The maximum drive speed can be freely set according to the capacity of the actuator and the work mode.

Claims (8)

(57) [Claims] 1. A hydraulic pump (1a); a plurality of hydraulic actuators (5a, 5b) driven by pressure oil discharged from the hydraulic pump; and a hydraulic pump supplying each of these hydraulic actuators. A plurality of flow rate control valves (6a, 6b) for controlling the flow rate of the pressure oil according to the operation amount of the operation means (50, 51) respectively; the upstream side pressure and the downstream side pressure of the corresponding flow rate control valves are respectively introduced. The first pressure receiving chamber (52a, 52b) operated in the closing direction and the second pressure receiving chamber (5 operated in the opening direction
3a, 53b) and the first control pressure (PC1, PC2) is introduced, and the third pressure receiving chamber (54a, 54b) in the closing direction operation that reduces the target value of the differential pressure across the corresponding flow control valve is reduced. A plurality of shunt compensation valves (7a, 7b), each of which controls the differential pressure across the plurality of flow control valves; and a pressure of pressure oil discharged from the hydraulic pump and a maximum load of the plurality of hydraulic actuators. A pressure difference detecting means (8) for detecting a pressure difference from the pressure;
According to the control current (IC1, IC2) of the first control pressure (P
C1, PC2) first proportional control valve means (9a, 9b)
And; calculating at least one reduction target value (ΔPC1, ΔPC2) for reducing the target value of the differential pressure across the flow control valves based on the detection value (ΔPLS) of the differential pressure detection means, and corresponding to the first Operation control means (26, 203, 218) for outputting the control current (IC1, IC2) of the above to the first comparison control valve means
A hydraulic drive for a construction machine comprising: (a) at least one of the plurality of shunt compensation valves (7a, 7b)
Target value (ΔPT) of the differential pressure across the flow control valve (6a, 6b) that is installed in one of the flow control valves (6a, 6b) to which the second control pressure (PCT) is introduced.
Pressure receiving chamber (55a, 55b) that operates in the opening direction
(B) second proportional control valve means (24) for generating the second control pressure (PCT) according to the second control current (IT); and (c) the corresponding flow control valve (). 6a, 6b) a signal generating means (25, 20-23) for outputting a signal (F, a1, a2, b1, b2) relating to the target value (ΔPT) of the differential pressure across the front and back; (d) From the signal generating means A target value (ΔPT) of the differential pressure across the corresponding flow control valve is calculated according to the signal of the above, and a corresponding second control current (IT) is output to the second proportional control valve means (24). Second arithmetic control means (26,204-21
8) and; are provided as hydraulic drive devices for construction machines. 2. The hydraulic drive system for a construction machine according to claim 1, wherein the signal generating means is provided in the flow dividing compensation valve (7a, 7b) in which the fourth pressure receiving chamber (55a, 55b) is installed. The second calculation control means (26, 211-217) includes a setting means (25) for setting a type relating to the capacity of the hydraulic actuators (5a, 5b) concerned, and the second calculation control means (26, 211-217) is responsive to the signal (F) from the setting means. A hydraulic drive system for a construction machine, which is characterized by calculating a pressure target value (ΔPT). 3. The hydraulic drive system for a construction machine according to claim 1, wherein the signal generating means is provided in the shunt compensation valve (7a, 7b) in which the fourth pressure receiving chamber (55a, 55b) is installed. The second arithmetic control means (26,204) includes an operation detecting means (20-23) for detecting an operation state of the flow control valves (6a, 6b) concerned.
-210) calculates the differential pressure target value (ΔPT) from the detection values (a1, a2, b1, b2) of the operation detecting means, and is a hydraulic drive system for construction machinery. 4. The hydraulic drive system for a construction machine according to claim 1, wherein the signal generating means is a shunt compensation valve (7a, 7b) in which the fourth pressure receiving chamber (55a, 55b) is set. Setting means (25) for setting the type of capacity of the related hydraulic actuators (5a, 5b), and operation detecting means (20) for detecting the operating state of the flow control valves (6a, 6b) related to the shunt compensation valve.
-23) and the second operation control means (26, 20-21).
7) is the differential pressure target value (ΔP) from the signal (F) from the setting device and the detection values (a1, a2, b1, b2) of the operation detecting means.
A hydraulic drive system for a construction machine, characterized by calculating T). 5. The hydraulic drive system for a construction machine according to claim 1, wherein the fourth pressure receiving chamber (55a, 55b) is installed in each of the plurality of flow compensation valves (7a, 7b). The hydraulic drive system for a construction machine, wherein the second proportional control valve means includes a common proportional control valve (24) connected to the fourth pressure receiving chamber of each of the plurality of flow compensation valves. 6. The hydraulic drive system for a construction machine according to claim 1, wherein the fourth pressure receiving chamber (55a, 55b) is installed in each of the plurality of shunt compensation valves (7a, 7b). The second proportional control valve means includes a plurality of proportional control valves (24a, 24b) individually connected to the respective fourth pressure receiving chambers of the plurality of shunt compensation valves. Hydraulic drive. 7. The hydraulic drive system for a construction machine according to claim 1, wherein the second arithmetic control means (26) is a normal differential pressure across the flow control valve (6a, 6b). Target values (Δpi1, Δpi4) and larger target values (Δpi
2, Δpi3) means for storing at least two target values, and the two target values according to the signals (a1, a2, b1, b2) from the signal generating means (20-23). Means for selecting one of the two (204-210) and means for outputting the second control current (IT) according to the selected target value (218)
A hydraulic drive system for a construction machine, comprising: 8. The hydraulic drive system for a construction machine according to claim 1, wherein the second arithmetic control means (26) targets the differential pressure across the corresponding flow control valve (6a, 6b). Initial value (ΔPTO) and at least 2 to add to this initial value
Means for storing two different correction values (PS1-PS4) (26
c) and a means (211) for selecting one of the two correction values according to the signal (F) from the signal generating means (25), adding it to the initial value, and calculating the target value (ΔPT). −217)
And a means (218) for outputting the second control current (IT) in accordance with the calculated target value, a hydraulic drive system for a construction machine.