KR20120086061A - Hydraulic system for construction machinery - Google Patents

Abstract

PURPOSE: A hydraulic system for construction equipment is provided to prevent pressure shocks by detecting the unexpected increase of load. CONSTITUTION: A hydraulic system for construction equipment comprises pressure sensors(12,42), a swash plate tilting angle adjusting unit(30) and a control part(40). The pressure sensors detect the load of a working machine. The swash plate tilting angle adjusting unit controls the discharged flow rate of a pump(10). The control part controls the swash plate tilting angle adjusting unit to increase the operation rate of an operational part according to the load of the working machine.

Description

Hydraulic system for construction machinery

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a construction machine such as an excavator, and more particularly, to a hydraulic system of a construction machine of a load sensing control method in which a discharge flow rate of a hydraulic pump increases in proportion to an operation amount of an operation unit regardless of a load of a work machine.

The work machine of the construction machine is driven by the hydraulic oil discharged from the hydraulic pump, and the discharge flow rate of the hydraulic pump is controlled according to the driving degree of the work machine. The flow rate control of these hydraulic pumps is largely negative control (also called negative control system), positive control (also known as Posicon system), and load sensing control method (Load Sensing). control).

The negative control method controls the flow rate of the hydraulic pump in accordance with the pressure of the center bypass flow path through the main control valve (MCV) that is not supplied to the working machine. Therefore, when the work machine is not driven, the hydraulic oil flow rate of the center bypass flow path becomes large, and the discharge flow rate of the hydraulic pump becomes small. Since the flow rate is divided between the work machine and the center bypass flow path when a high load is applied to the work machine, as shown in FIG. 1, the time point at which the work machine is driven is delayed and the operation amount is The driving speed of the work machine is also slowed down. The above-mentioned characteristics of the negative control method not only become an important means for the operator to sense the load acting on the work machine, but also ensure a smooth operability by preventing pressure shock from occurring even if the load suddenly increases.

On the other hand, the positive control method is a method in which the discharge flow rate of the hydraulic pump is controlled by the pilot signal pressure generated by the operation of the operation unit. In other words, when the operation amount of the operation unit increases and the pilot signal pressure increases, the discharge flow rate of the hydraulic pump increases. Since the positive control method also includes a center bypass flow path, when a high load is applied to the work machine, a phenomenon in which the driving time of the work machine is delayed with respect to the manipulation amount of the control unit occurs.

Unlike these control methods, the load sensing control method to be improved in the present invention is controlled to discharge flow rate of the hydraulic pump based on the operation amount of the operation unit irrespective of the load acting on the work machine. That is, the center bypass flow path is blocked by, for example, the center bypass cutoff valve, so that the system is maintained in a hermetic state, thereby maximizing the efficiency of the entire system.

In the construction machine to which the load sensing control method is applied, the discharge flow rate of the hydraulic pump has a substantial correspondence with the operation amount of the operation unit. For reference, FIG. 2 is a graph schematically showing a pump discharge flow rate and a work machine supply flow rate with respect to a manipulation amount of an operation unit in a construction machine of a conventional load sensing control method.

For example, as shown in FIG. 2, regardless of whether a load is applied to the work machine, the flow rate discharged from the hydraulic pump is controlled to have a linear proportional relationship with the operation amount of the control unit, for example, the angle of the joystick. The supply flow rate is also controlled to have a linearly proportional relationship with the operation amount of the control panel.

In addition, as shown in Figure 2, it can be seen that the control result of the pump flow rate in the conventional load-sensing construction equipment substantially matches the control result of the work machine supply flow rate.

Therefore, when operating a construction machine of the conventional load sensing control system, when the operator operates an operation unit such as a joystick, the load (or load feeling) acting on the work machine cannot be felt at all, As a result, the operation feeling is inferior and smooth operability cannot be secured, or when a sudden increase in load is not detected, the shock cannot be prevented from occurring.

The present invention has been made in view of the above-described point, and an object thereof is to provide a hydraulic system of a construction machine that can impart a feeling of operation in a load sensing control method.

Hydraulic system of a construction machine according to an embodiment of the present invention for achieving the above object is applied to a load sensing control method in which the discharge flow rate of the pump increases in proportion to the operation amount of the operation unit, regardless of the load of the work machine A pressure sensor for sensing a load of the work machine; A swash plate angle adjusting unit for adjusting a discharge flow rate of the pump; And a control unit controlling the swash plate angle adjusting unit so that the amount of manipulation of the operating unit increases according to the load of the working machine by adjusting the load sensing pressure provided to the swash plate angle adjusting unit based on the operation amount of the operation unit and the load of the working machine detected by the pressure sensor. Characterized in that.

In this embodiment, the pressure sensor for detecting the load of the work machine is characterized in that the pump pressure sensor for detecting the discharge pressure of the pump and / or the load sensing pressure sensor for detecting the load sensing pressure.

Also in this embodiment, the control unit further comprises a pressure sensor for operating the means for sensing the operation amount, the swash plate angle adjusting unit includes: a regulator for adjusting the swash plate angle of the pump; A signal line for applying a load sensing pressure to the regulator; And an electronic proportional pressure reducing valve installed in the signal line and adjusting the load sensing pressure transmitted to the regulator according to a control signal transmitted from the controller, wherein the controller is based on a pump discharge pressure or a load sensing pressure and an operation amount of the operation unit. It characterized by controlling the electromagnetic proportional pressure reducing valve.

In addition, the hydraulic system of the construction machine according to another embodiment of the present invention is an electronic load sensing control method of increasing the discharge flow rate of the pump in proportion to the operation amount of the operation unit, irrespective of the load of the work machine, for detecting the load of the work machine. A pressure sensor; A swash plate angle adjusting unit for adjusting a discharge flow rate of the pump; And a control unit controlling the swash plate angle adjusting unit to increase the amount of operation of the operating unit according to the load of the working machine by adjusting an operation amount provided to the swash plate angle adjusting unit based on the load of the working machine detected by the pressure sensor. .

Further, in this embodiment, the pressure sensor for detecting the load of the work machine is characterized in that the pump pressure sensor for detecting the discharge pressure of the pump and / or the load sensing pressure sensor for detecting the load sensing pressure.

Further, in this embodiment, the swash plate angle adjusting unit includes a regulator for adjusting the swash plate angle of the pump, wherein the control unit further comprises a sub control unit for adjusting the operation amount of the operation unit based on the discharge pressure or the load sensing pressure of the pump. It is characterized by including.

When operating the construction machine of the load sensing control method according to the present invention, when the operator operates an operation unit such as a joystick, it is possible to grasp the state of the load (or load feeling) acting on the work machine, The operation feeling is improved during operation, and smooth operation can be secured. Also, when the load is suddenly increased, it can be detected to prevent the occurrence of pressure shock.

1 is a graph showing the driving speed according to the load according to the operation amount of the operation unit in the construction machine of the negative control method;
2 is a graph schematically showing a pump discharge flow rate and a work machine supply flow rate according to a manipulation amount of an operation unit in a construction machine of a conventional load sensing control method;
3 is a view schematically showing a hydraulic system of a construction machine according to an embodiment of the present invention;
FIG. 4A is a graph schematically showing a relationship between a discharge flow rate of a pump, a discharge pressure of a pump, a load sensing pressure, and a control signal with respect to an operation unit operation amount at no load in the hydraulic system of FIG. 3; FIG.
4B is a graph schematically showing a relationship between a discharge flow rate of a pump, a discharge pressure of a pump, a load sensing pressure, and a control signal with respect to an operation unit manipulation amount under high load in the hydraulic system of FIG. 3;
5 is a schematic view of a hydraulic system of a construction machine according to another embodiment of the present invention;
FIG. 6A is a graph schematically showing the relationship between the discharge flow rate of the pump, the discharge pressure of the pump, the load sensing pressure, and the adjusted operation amount to the operation unit operation amount at no load in the hydraulic system of FIG. 5; FIG. And
FIG. 6B is a graph schematically illustrating a relationship between the discharge flow rate of the pump, the discharge pressure of the pump, the load sensing pressure, and the adjusted operation amount to the operation unit operation amount at high load in the hydraulic system of FIG. 5.

Hereinafter, a hydraulic system of a construction machine according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a view schematically showing a hydraulic system of a construction machine according to an embodiment of the present invention. 3, the hydraulic system of the construction machine according to an embodiment of the present invention is a load-sensing construction machine hydraulic pressure of the discharge flow rate of the pump 10 is increased in proportion to the operation amount of the operation unit, regardless of the load of the working machine The system includes a pump pressure sensor 12 for detecting a discharge pressure P _P of the pump 10, a load sensing pressure sensor 42 for detecting a load sensing pressure P _LS , and a pump 10. Control plate for controlling the swash plate angle adjustment unit 30 for adjusting the discharge flow rate of the control unit, the operation unit pressure sensor 24 for detecting the operation amount, for example the operating pressure (P _joystick ), and the swash plate angle adjustment unit 30 And 40.

The pump pressure sensor 12 is for detecting the discharge pressure P _P of the pump, and the load sensing pressure sensor 42 is for detecting the load sensing pressure P _LS transmitted from the main control valve MCV. Substantially, the discharge pressure P _P or the load sensing pressure P _LS of the pump corresponds to a load acting on the work machine, and these pressures P _P and P _LS are transmitted to the controller 40.

The operation unit pressure sensor 24 detects an operation amount (P _joystick ), for example, pilot pressure of the operation unit 20, and detects a maximum pilot pressure among pilot pressures of the plurality of operation units 20 through the shuttle valve block 22. Done. Information of the pilot pressure sensed by the operation unit pressure sensor 24 is transmitted to the control unit 40. In the present embodiment, an example of detecting an operation unit manipulation amount from the magnitude of the pilot pressure sensed by the operation unit pressure sensor 24 is provided, but unlike the present embodiment, the operation amount of the operation unit 20 is converted into an electrical signal so that the control unit ( 40).

The swash plate angle adjusting unit 30 adjusts the discharge flow rate of the pump 10 by adjusting the swash plate angle of the pump 10 according to the control signal I output from the controller 40, and the regulator 32 And a signal line 34 and an electromagnetic proportional pressure reducing valve (EPPR) 36. In this embodiment, the swash plate angle of the pump 10 is adjusted by transmitting a load sensing pressure to the swash plate angle adjusting unit 30. However, unlike the present embodiment, only the electrical signal of the controller 40 is used to control the swash plate angle. It is obvious that the swash plate angle can be adjusted.

The regulator 32 adjusts the swash plate angle of the pump 10 according to the input load sensing pressure P _LS , more specifically, the rear pressure P ² _LS of the electromagnetic proportional pressure reducing valve EPPR 36. will be.

The signal line 34 is for transmitting the load sensing pressure to the regulator 32, one end of which is connected to the main control valve MCV and the other end of which is connected to the regulator 32.

The electromagnetic proportional pressure reducing valve 36 is provided in the above-described signal line 34 to adjust the opening amount of the signal line 34. The electromagnetic proportional pressure reducing valve 36 is adjusted according to the control signal transmitted from the controller 40. In this embodiment, the control signal is indicated by the current I.

The electromagnetic proportional pressure reducing valve 36 is in an initial state as shown in FIG. 3 and has a current I of 0 at the input terminal. In this state, that is, the control variable for varying the discharge flow rate of the pump 10 in the no-load state is the load sensing pressure (P ¹ _LS ) in front of the electromagnetic proportional pressure reducing valve. That is, the pump discharge flow rate is controlled in the same manner as the construction machine of the conventional load sensing control method.

On the other hand, when a current I exceeding zero is applied to the input of the electromagnetic proportional pressure reducing valve 36, the electromagnetic proportional pressure reducing valve 36 reduces the amount of opening of the signal line 34, whereby the electromagnetic proportional pressure reducing valve ( The back pressure P ² _LS of 36 becomes smaller than the front pressure P ¹ _LS . That is, the load sensing pressure P _LS transmitted to the regulator 32 is transmitted in a reduced pressure state on the basis of the manipulation portion operation amount generated by the manipulation unit 20 and the pump discharge pressure or the load sensing pressure, whereby the pump 10 Discharge flow rate is reduced.

That is, in a state in which a load is applied to the work machine, the pump 10 based on the discharge pressure P _P or the load sensing pressure P _LS of the pump 10 in addition to the operation amount of the operation unit 20 according to the embodiment of the present invention. Discharge flow rate can be controlled. Compared with the conventional load sensing construction machine in which the discharge flow rate of the pump 10 is controlled based only on the operation amount of the operation unit 20, the operator of the present invention further provides the discharge pressure P _P of the pump 10 or Through the configuration in which the discharge flow rate of the pump 10 is controlled based on the load sensing pressure P _LS , the load applied to the work machine may be recognized, and thus the operation may be performed based on the feeling of load.

Hereinafter, the effect of the hydraulic system of the construction machine having the configuration as described above will be described in detail.

First, when information about each pressure is transmitted from the pump pressure sensor 12, the load sensing pressure sensor 42, and the operation unit pressure sensor 24 to the control unit 40, the control unit 40 is an electronic proportional pressure reducing valve ( The magnitude of the current I to be applied to 36 is calculated. The magnitude of the applied current I may be calculated as shown in Equation 1 below.

Here, the symbol is as follows.

I: Current applied to the electromagnetic proportional pressure reducing valve 36 (control signal)

P _LS : Load sensing pressure

P _Joystick : Control amount of control panel (operating pressure)

Although not specifically described in [Equation 1], for example, the applied current is proportional to the load sensing pressure P _LS , or the discharge pressure P _P of the pump, and the manipulation amount (operation pressure, P _joystick ) of the operation unit 20. Must be calculated with specific conditions inversely proportional to

On the other hand, the front end pressure and the rear end pressure of the electromagnetic proportional pressure reducing valve 36 has a relationship as in the following [Equation 2].

Here, P ² _LS is the pressure after the electromagnetic proportional pressure reducing valve 36, P ¹ _LS is the pressure before the electromagnetic proportional pressure reducing valve 36, I is the applied current as calculated in [Equation 1], α is the proportional constant of pressure reduction valve.

4A and 4B are graphs schematically showing the relationship between the discharge flow rate of the pump, the discharge pressure of the pump, the load sensing pressure, and the control signal with respect to the operation unit operation amount in the hydraulic system of FIG. 3 in the no-load state and the high load state, respectively. .

In the no-load state of FIG. 4A, the graph shows the discharge flow rate of the pump 10 corresponding to the operation unit operation amount P _joystick linearly as in the case of the construction machine of the conventional load sensing control method, and the operation unit operation amount P _joystick . Is applied to the electromagnetic proportional pressure reducing valve 36 irrespective of the pump discharge pressure and the load sensing pressure (for example, the magnitudes of the pressures at the front and rear ends of the electromagnetic proportional pressure reducing valve are the same) and the operation amount (P _joystick ) of the operation unit. It can be seen that the value of the current to be continued to zero. That is, in the no-load state, the hydraulic system of the construction machine according to the embodiment of the present invention shows substantially the same results as the construction machine of the conventional load sensing control method.

Next, in the high load state of FIG. 4B, the graph shows that the discharge flow rate of the pump 10 is relatively decreased with respect to the operation unit manipulation amount P _joystick , which is different from the case of the construction machine of the conventional load sensing control method. Load feeling), and the pump discharge pressure and the load sensing pressure increase with a constant slope with respect to the manipulation amount of the control unit (P _joystick ) (for example, the pressure (P ² _LS ) at the rear of the electromagnetic proportional pressure reducing valve is proportional to the electronic proportion). It can be seen that the value of the current applied to the electromagnetic proportional pressure reducing valve 36 decreases with a constant slope as the pressure (P ¹ _LS ) of the front of the pressure reducing valve is lower) and the operation amount (P _joystick ) of the operation unit increases.

That is, under the high load state, the hydraulic system of the construction machine according to the embodiment of the present invention is different from the case of the construction machine of the conventional load sensing control method, by recognizing the feeling of the load according to the load of the working machine to allow the operator to improve the operation feeling and Ensure smooth operation.

In addition, by ensuring a feeling of operation can be prepared in advance when the load suddenly increases, it is possible to prepare in advance for problems such as a pressure shock occurs.

Next, Figure 5 is a view schematically showing a hydraulic system of a construction machine according to another embodiment of the present invention. For reference, the hydraulic system according to this embodiment uses a mechanical main control valve (MCV) driven by pressure in the above-described embodiment, so-called using an electronic MCV for receiving an electronic signal to drive a spool, for example. Note that it is shown based on the 'electronic load sensing control method'.

Referring to FIG. 5, in the hydraulic system of a construction machine according to another embodiment of the present invention, the discharge flow rate of the pump 110 increases in proportion to the operation amount of the operation unit 120 regardless of the load of the work machine 134. A construction machine hydraulic system using a load sensing control method, comprising: a pump pressure sensor 112 for detecting a discharge pressure P _{P of} a pump 110 and a load sensing pressure sensor for detecting a load sensing pressure P _LS ( 132, the swash plate angle adjusting unit 140 for adjusting the discharge flow rate of the pump 10, and the swash plate angle adjusting unit 140 and the electronic MCV (based on the operation amount of the operating unit 120, for example, the operating angle θ). And a control unit 150 for controlling the driving of the swash plate angle adjusting unit 140 and the electronic MCV 130 by outputting a control signal (eg, current).

The pump pressure sensor 112 is for detecting the discharge pressure of the pump, the load sensing pressure sensor 132 is for detecting the load sensing pressure transmitted from the main control valve (MCV), the discharge pressure of the pump ( P _P ) or the load sensing pressure P _LS corresponds to the load acting on the work machine, and these pressures P _P and P _LS are transmitted to the controller 150.

The swash plate angle adjusting unit 140 adjusts the discharge flow rate of the pump 110 by adjusting the swash plate angle of the pump 110 according to the control signal I output from the controller 150, and controls the regulator and the signal line. Include. In this embodiment, the swash plate angle control unit 140 transmits a control signal of the controller 150 to adjust the swash plate angle of the pump 110.

The swash plate angle adjusting unit 140 is for adjusting the swash plate angle of the pump 110 according to an input manipulation unit manipulation amount, for example, the manipulation angle θ.

According to the feature of this embodiment, the sub control unit 152 is formed in the control unit to adjust the operation amount (eg, the operation angle) of the operation unit. For example, based on the discharge pressure P _P or the load sensing pressure P _LS of the pump, the operation amount (operation angle, θ) of the operation unit 120 transmitted to the swash plate angle adjusting unit 140 such as a regulator is reduced. Is transmitted, whereby the discharge flow rate of the pump 110 is reduced.

For example, in a state in which a load is applied to the work machine, the amount of manipulation of the manipulation unit 120 is adjusted based on the discharge pressure P _P or the load sensing pressure P _LS of the pump 110 according to an embodiment of the present invention. As a result, the discharge flow rate of the pump 110 can be controlled. Compared with the conventional electronic load sensing type construction machine in which the discharge flow rate of the pump 110 is controlled based only on the operation amount of the operation unit 120, the operator of the present invention uses the discharge pressure P _P or the rod of the pump 110. Through the configuration in which the discharge flow rate of the pump 110 is controlled based on the sensing pressure P _LS , the load applied to the work machine may be recognized, and thus the operation may be performed based on the feeling of load.

Hereinafter, the effect of the hydraulic system of the construction machine having the configuration as described above will be described in detail.

First, when information about each pressure is transmitted from the pump pressure sensor 112 and the load sensing pressure sensor 132 to the control unit 150, the control unit 150 controls the input amount of the manipulation unit 120 (for example, an operation angle). , θ1) is adjusted based on these information, and then output to the adjusted operating portion manipulated amount (eg, operating angle, θ2) and transmitted to the swash plate angle adjusting unit 140. At this time, the size of the manipulation amount of the manipulation unit 120 can be defined through the following [Equation 3].

Here, θ ₁ is the actual operation amount (operation angle) of the operating part, θ ₂ is the operation amount (operation angle) of the adjusted operation part, P _LS is the load sensing pressure, and P _P means the discharge pressure of the pump.

Although not specifically described in [Equation 3], for example, the operation unit manipulation amount should be calculated under specific conditions based on the load sensing pressure P _LS or the discharge pressure P _P of the pump.

On the other hand, the manipulated amount θ ₁ before being adjusted through the control unit 150 and the manipulated amount θ ₂ after the adjustment specifically have a relationship as shown in Equation 4 below.

Where a is any constant.

On the other hand, [Equation 4] illustrates a relationship in which the manipulation amount of the operation unit is adjusted based on the load sensing pressure P _LS , but this also applies to replacing the load sensing pressure with the discharge pressure P _P of the pump. Can be.

Figures 6a and 6b the discharge flow rate and discharge pressure of the pump (P _P), the load sensing pressure of the pump for the operation manipulation amount (θ ₁₎ in the unloaded state and in the high load state, the hydraulic system of Figure 5, respectively (P _LS), And a graph schematically showing the relationship between control signals of the adjusted operation unit operation amount θ ₂ .

In the no-load state of FIG. 6A, the graph shows the discharge flow rate of the pump 110 corresponding to the operation unit operation amount θ ₁ linearly as in the case of the construction machine of the conventional electronic load sensing control method, and the operation unit operation amount θ _1. ), The pump discharge pressure and the load sensing pressure (for example, the magnitude of the manipulation amount in the front and rear ends of the control unit 150 are the same), and the manipulation amount of the operation portion is maintained without any adjustment (θ ₂ = θ ₁ ). It can be seen that it is output to each control unit. That is, in the no-load state, the hydraulic system of the construction machine according to the embodiment of the present invention shows substantially the same results as the construction machine of the conventional electronic load sensing control method.

Next, in the high load state of FIG. 6B, unlike the case of the construction machine of the conventional electronic load sensing control method (indicated by the dotted line), the discharge flow rate of the pump 110 is relatively relatively to the operation unit operation amount θ ₁ . It shows the result of delay (indicated by the solid line) (load feeling occurs), and also shows a state in which the pump discharge pressure and the load sensing pressure have increased (high load state acting on the work machine) with respect to the operation unit operation amount θ ₁ , respectively. As the operation amount θ ₁ of the operation unit increases, the operation unit operation amount θ ₂ adjusted and outputted through the control unit 150 is relatively delayed, thereby decreasing the flow rate discharged from the pump 110, thereby delaying the work machine. It can be seen that it is driven. That is, by adjusting the operation unit operation amount in accordance with an embodiment of the present invention, the operator can perform the operation based on the feeling of load.

That is, under a high load state, the hydraulic system of the construction machine according to the embodiment of the present invention is different from the case of the construction machine of the conventional electronic load sensing control method, and the operator recognizes the load according to the load of the work machine and improves the operator's feeling of operation. And to ensure smooth operability.

In addition, by ensuring a feeling of operation can be prepared in advance when the load suddenly increases, it is possible to prepare in advance for problems such as a pressure shock occurs.

10, 110: hydraulic pump
12, 112: pump pressure sensor
20, 120: control panel (joystick)
22: Shuttle Valve Block
24: pressure sensor
30, 140: swash plate adjustment unit
32: regulator
34: signal line
36: Electronic proportional pressure reducing valve
40, 150: control unit
42, 132: load sensing pressure sensor
130: main control valve (MCV)
134: working machine
152: sub control unit
P _P : discharge pressure of pump
P _LS : Load sensing pressure

Claims (6)

In the hydraulic system of a construction machine of a load sensing control system in which the discharge flow rate of the pump 10 increases in proportion to the operation amount of the operation unit 20, regardless of the load of the work machine,
Pressure sensors 12 and 42 for sensing the load of the work machine;
A swash plate angle adjusting unit 30 for adjusting the discharge flow rate of the pump 10; And
The load sensing pressure provided to the swash plate angle adjusting unit 30 is adjusted based on the manipulation amount of the manipulation unit 20 and the load of the work machine sensed by the pressure sensors 12 and 42, so that the load sensing pressure is adjusted according to the load of the work machine. Hydraulic system of a construction machine, characterized in that it comprises a control unit (40) for controlling the swash plate angle control unit (30) so that the operation amount of the operation unit 20 is increased. The pressure sensor for detecting the load of the work machine includes a pump pressure sensor 12 for detecting the discharge pressure of the pump 10 and / or a load sensing pressure sensor for detecting the load sensing pressure. Hydraulic system of a construction machine, characterized in that 42). The apparatus of claim 1, further comprising an operation unit pressure sensor 24 as a means for sensing an operation amount of the operation unit 20,
The swash plate adjustment unit 30 is:
A regulator 32 for adjusting the swash plate angle of the pump;
A signal line (34) for applying the load sensing pressure to the regulator (32); And
An electronic proportional pressure reducing valve (EPPR) 36 installed in the signal line 34 to adjust the load sensing pressure transmitted to the regulator 32 according to a control signal transmitted from the controller 40; ,
The control unit (40) controls the electromagnetic proportional pressure reducing valve (36) based on the pump discharge pressure or the load sensing pressure and the operation amount of the operation unit. In the hydraulic system of the construction machine of the electronic load sensing control system in which the discharge flow rate of the pump 110 increases in proportion to the operation amount of the operation unit 120, regardless of the load of the work machine,
Pressure sensors 112 and 132 for detecting a load of the work machine 134;
A swash plate angle adjusting unit 140 for adjusting the discharge flow rate of the pump 110; And
The manipulation amount provided by the swash plate angle control unit 140 is adjusted based on the load of the work machine 134 sensed by the pressure sensors 112 and 132, thereby controlling the manipulation amount of the manipulation part 120 according to the load of the work machine. Hydraulic system of a construction machine, characterized in that it comprises a control unit 150 for controlling the swash plate angle control unit 140 to be larger. The pressure sensor for detecting a load of the work machine 134 is a pump pressure sensor 112 for detecting a discharge pressure of the pump 110 and / or a load sensing for detecting a load sensing pressure. Hydraulic system of a construction machine, characterized in that the pressure sensor (132). According to claim 4, The swash plate angle adjusting unit 140 includes a regulator for adjusting the swash plate angle of the pump 110,
The control unit 150 further includes a sub-control unit 152 for adjusting the operation amount of the operation unit 120 based on the discharge pressure or the load sensing pressure of the pump 110. .

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