KR102169318B1 - Swing control apparatus and hydraulic system for construction machinery - Google Patents

Abstract

The swing control device is a pressure sensor that detects a pressure difference at the inlet and outlet ports of the swing motor for rotating the upper swing body, and a pressure control valve for controlling the pilot pressure provided as an input value of the regulator that adjusts the swash plate angle of the swing pump. And a control unit for receiving the detection signal from the pressure sensor and outputting a control signal for changing the pilot pressure to the pressure control valve when the pilot pressure is within a range that causes hunting of the upper rotating body. can do.

Description

Slewing control device and hydraulic system of construction machine having same {SWING CONTROL APPARATUS AND HYDRAULIC SYSTEM FOR CONSTRUCTION MACHINERY}

The present invention relates to a swing control device and a hydraulic system of a construction machine having the same, and more particularly, to a swing control device for an upper swing body and a hydraulic system of a construction machine having the same.

In general, a negative flow control (NFC) system is known as a hydraulic system for construction machinery. The negative flow control hydraulic system may cause a pressure loss of a pump by driving a plurality of actuators with a main pump. In particular, when implementing the complex operation of the actuators, there is a problem in that the operating speed of each actuator is slowed down because hydraulic pressure is distributed to each actuator.

In order to improve the problems of the negative flow control hydraulic system as described above, a swing independent hydraulic system having a configuration to independently swing an upper swing body has been developed.

The swing independent hydraulic system has an open loop type and a closed loop type. The open-circuit turning independent hydraulic system may be provided with a dedicated turning motor and a dedicated main pump for implementing the turning operation of the turning upper body. In the closed-circuit swing independent hydraulic system, there is no separate control valve between the swing pump and the swing motor, and the pilot pressure generated when operating the joystick can be used as an input value to directly control the swash angle of the swing pump.

Since the closed-circuit independent swing system is connected by a high-pressure hose without a control valve between the swing motor and the swing pump, it is possible to reduce pressure loss, and since it does not pass through the control valve, it is possible to improve fuel economy by reducing meter-in and meter-out losses. have.

However, the closed loop turning independent system basically has a characteristic that fine manipulation hunting can occur at a specific frequency due to the characteristic of the system. This is due to a system structure different from the existing negative flow control system, and this hunting phenomenon acts as a fatal disadvantage that it is difficult for customers to fine-tune the equipment when using the equipment, and control performance may also be degraded.

An object of the present invention is to provide a turning control device capable of preventing a hunting phenomenon in a closed loop turning independent system.

Another object of the present invention is to provide a hydraulic system for a construction machine having the above-described turning control device.

In order to achieve one object of the present invention, a swing control device according to exemplary embodiments of the present invention includes a pressure sensor for detecting a pressure difference at an inlet port of a swing motor for rotating an upper swing body, and a swing pump. A pressure control valve for controlling a pilot pressure provided as an input value of a regulator for adjusting the swash plate angle of, and within a range in which the detection signal from the pressure sensor is received and the pilot pressure causes hunting of the upper rotating body If present, a control unit for outputting a control signal for changing the pilot pressure to the pressure control valve may be included.

In example embodiments, the pressure control valve may include a drain valve for reducing the pilot pressure of the pilot line.

In example embodiments, the drain valve may be connected to the pilot line between the manipulator generating the pilot pressure and the regulator.

In example embodiments, the drain valve may be configured as an electronic proportional control valve.

In example embodiments, the control unit includes a matching unit that outputs a control gain value for changing a pilot pressure that may cause hunting of the upper rotating body, and calculates the detection signal and the control gain value. It may include an output unit for outputting the control signal.

In example embodiments, the matching unit may perform matching with a specific range of the input RPM and a controller gain value corresponding to the specific range of the pilot pressure.

In example embodiments, the pilot line may include a pair of first and second pilot lines.

In exemplary embodiments, the turning control device further includes a shuttle valve installed between the first and second pilot lines to select a line having a higher pilot pressure among the first and second pilot lines. can do.

In example embodiments, the swing pump and the swing motor may be connected in a closed loop form.

The hydraulic system of a construction machine for achieving another object of the present invention described above includes a swing motor for rotating an upper swing body, a swing pump connected to the swing motor in a closed loop form to supply hydraulic oil to the swing motor, A regulator for adjusting the swash plate angle of the swing pump, a pressure sensor for detecting a pressure difference at the inlet and outlet ports of the swing motor, a pressure control valve for controlling a pilot pressure of a pilot line provided as an input value of the regulator, and the And a controller configured to output a control signal for changing the pilot pressure to the pressure control valve when the detection signal is received from the pressure sensor and the pilot pressure is within a range in which hunting of the upper rotating body occurs.

In example embodiments, the pressure control valve may include a drain valve for reducing the pilot pressure of the pilot line.

In exemplary embodiments, the drain valve is composed of an electronic proportional control valve, and the control unit includes a matching unit that outputs a control gain value for changing the pilot pressure so that hunting of the upper rotating body does not occur, and It may include an output unit that calculates the detection signal and the control gain value and outputs the control signal.

In example embodiments, the matching unit may perform matching with a specific range of the input RPM and a controller gain value corresponding to the specific range of the pilot pressure.

In example embodiments, the hydraulic system may further include a main pump for driving a boom cylinder, an arm cylinder, and a bucket cylinder.

According to exemplary embodiments, the turning control device changes the pilot pressure Pi in the input frequency range that generates resonance of the upper turning body to a new input frequency for normal turning motion, thereby hunting the upper turning body. It can prevent the phenomenon. The pressure difference between the inlet and outlet ports of the turning motor may be received as a detection signal, and a control signal may be output by calculating a controller gain value matched by the detection signal and the control map. The pilot pressure is changed according to the control signal and the newly changed pilot pressure is used as an input value of the regulator to adjust the swash plate angle of the swing pump, thereby improving the hunting problem.

However, the effects of the present invention are not limited to the above-mentioned effects, and may be variously extended without departing from the spirit and scope of the present invention.

1 is a block diagram showing a hydraulic system of a construction machine according to exemplary embodiments.
2 is a hydraulic circuit diagram showing a turning control device of the hydraulic system of FIG. 1.
3A is a diagram illustrating a modeling system of an upper swing body of FIG. 1.
3B is a graph showing an input of the modeling system of FIG. 3A.
3C is a graph showing the output of the modeling system of 3A.
4 is a block diagram showing a control unit of the turning control device of FIG. 2.
5 is a hydraulic circuit diagram showing a turning control device according to exemplary embodiments.

With respect to the embodiments of the present invention disclosed in the text, specific structural or functional descriptions have been exemplified only for the purpose of describing the embodiments of the present invention, and the embodiments of the present invention may be implemented in various forms. It should not be construed as being limited to the embodiments described in.

Since the present invention can apply various changes and have various forms, specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific form of disclosure, it is to be understood as including all changes, equivalents, or substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various elements, but the elements should not be limited by the terms. The terms may be used for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component.

When a component is referred to as being "connected" or "connected" to another component, it is understood that it may be directly connected or connected to the other component, but other components may exist in the middle. Should be. On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in the middle. Other expressions describing the relationship between components, such as "between" and "just between" or "adjacent to" and "directly adjacent to" should be interpreted as well.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate the presence of a set feature, number, step, action, component, part, or combination thereof, and one or more other features or numbers It is to be understood that the possibility of addition or presence of, steps, actions, components, parts, or combinations thereof is not preliminarily excluded.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms as defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning of the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in this application. .

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. The same reference numerals are used for the same elements in the drawings, and duplicate descriptions for the same elements are omitted.

1 is a block diagram showing a hydraulic system of a construction machine according to exemplary embodiments. 2 is a hydraulic circuit diagram showing a turning control device of the hydraulic system of FIG. 1. FIG. 3A is a diagram illustrating the modeling system of the upper swing body of FIG. 1, FIG. 3B is a graph showing an input of the modeling system of FIG. 3A, and FIG. 3C is a graph showing an output of the modeling system of 3A. 4 is a block diagram showing a control unit of the turning control device of FIG. 2.

1 to 4, the hydraulic system 10 of a construction machine is connected to a swing motor 40 for rotating the upper swing body 45, a swing motor 40 and a closed loop, and the swing motor 40 ), the slewing pump 20 for supplying hydraulic oil to the slewing pump 20, the regulator 30 for adjusting the swash plate angle of the slewing pump 20, and the input value of the regulator 30 to suppress vibration of the upper slewing body 45. It may include a swing control device for controlling the pilot pressure provided.

In exemplary embodiments, the swing pump 20 may be independently connected to the engine 12 as a drive source via the power transmission device 14. The engine 12 can also be connected to the main pump 16 and the auxiliary pump 18 via a power train 14. Accordingly, the power from the engine 12 can be transmitted to the main pump 16, the auxiliary pump 18, and the swing pump 20, respectively.

Construction machinery such as an excavator may include an upper swing body 45 mounted on a lower traveling body (not shown), a cab installed on the upper swing body 45, and a working device having a boom, an arm, and a bucket. . Although not shown in the drawing, the main pump 16 is connected to a control valve (MCV) through a high pressure hydraulic line, and the control valve is a plurality of actuators including a boom cylinder, an arm cylinder, and a bucket cylinder through a high pressure hydraulic line. Each can be connected to the field. Accordingly, each of the actuators such as the boom cylinder, the arm cylinder and the bucket cylinder can be driven by the hydraulic pressure of the hydraulic oil discharged from the main pump 16.

In an exemplary embodiment, the slewing pump 20 is directly connected to the slewing motor 40 through a hydraulic line without interposing a separate control valve, and the pilot pressure generated when operating the joystick 50 as a control unit By being used as an input value for directly adjusting the swash plate angle of the slewing pump 20, a closed-circuit slewing independent hydraulic system can be implemented.

1 and 2, the swing pump 20 may be a two-way pump capable of discharging hydraulic oil in both directions. The swing pump 20 may be connected to the A port of the swing motor 40 by the first hydraulic line 42 and to the B port of the swing motor 40 by the second hydraulic line 44. The swing motor 40 may be connected to the upper swing body 45 through a swing mechanism.

The hydraulic oil discharged from the slewing pump 20 is supplied to the A port of the slewing motor 40 through the first hydraulic line 42, and after driving the slewing motor 40, the second hydraulic line 44 becomes low pressure. Can be recovered to the tank through. Accordingly, by driving the turning motor 40, the upper turning body 45 turns. For example, when hydraulic pressure is supplied to the A port of the turning motor 40, the upper turning body 45 can turn to the right.

The hydraulic oil discharged from the slewing pump 20 is supplied to the B port of the slewing motor 40 through the second hydraulic line 44 and is driven to a low pressure by driving the slewing motor 40 through the first hydraulic line 42. Can be recovered to the tank. Accordingly, the turning motor 40 is driven so that the upper turning body 45 turns. For example, when hydraulic pressure is supplied to the B port of the turning motor 40, the upper turning body 45 can turn to the left.

When the operator manipulates the joystick 50, a pilot pressure Pi corresponding to the operating displacement is formed, and the pilot pressure Pi may be used as an input value for adjusting the swash plate angle of the orbiting pump 20.

Specifically, the pilot pressure Pi may be provided as an input value of the regulator 30 through the pilot line 51 connected to the joystick 50. The pilot line 51 may include a first pilot line 52 and a second pilot line 54. The output terminal of the joystick 50 may be connected to the first pilot line 52 and the second pilot line 54. When the joystick 50 is operated in one direction, the pilot pressure Pi may be formed in one of the first and second pilot lines 52 and 54. Alternatively, the pilot pressure Pi may be provided to the regulator 30 through one pilot line connected to the joystick 50.

The first pilot line 52 may be connected to the first control valve 56, and the second pilot line 54 may be connected to the second control valve 58. The first control valve 56 may be connected to the first chamber 32 of the regulator 30, and the second control valve 58 may be connected to the second chamber 34 of the regulator 30.

The sub pump 22 may be directly connected to the swing pump 20. Alternatively, the sub pump 22 may be connected to the engine 12 separately from the orbiting pump 20. The sub pump 22 may discharge pilot hydraulic oil. The surf pump 22 may be connected to the first and second control valves 56 and 58 to supply pilot hydraulic oil to each. Accordingly, the pilot hydraulic oil from the sub-pump 22 waits at the input terminals of the first and second control valves 56 and 58, respectively.

When the operator manipulates the joystick 50 according to the desired turning direction and turning speed, a pilot pressure Pi corresponding to the operating displacement is formed in one of the first pilot line 52 and the second pilot line 54, The pilot hydraulic oil corresponding to the pilot pressure Pi may open a corresponding one of the first and second control valves 56 and 58.

When one of the first and second control valves 56 and 58 is opened, the pilot hydraulic oil may be provided to any one of the first and second chambers 32 and 34 of the regulator 30. have. The pilot hydraulic oil introduced into one of the first and second chambers 32 and 34 may control the discharge direction and flow rate of the hydraulic oil by adjusting the swash plate of the swing pump 20.

As shown in FIG. 3A, in the closed-loop swing independent system, the upper swing body 45 may be modeled as a mass-spring system. The first and second hydraulic lines 42 and 44 connected to the AB ports of the swing motor 40 may be represented by a spring, and the upper swing body 45 may be represented by a mass.

For example, when the user manipulates the joystick 50 to the right in order to turn the upper swing body 45 to the right, the high pressure hydraulic oil discharged from the swing pump 20 turns through the first hydraulic line 42 It is supplied to the A port of the motor 40 so that the upper swing body 45 rotates to the right. Since the upper swing body system in the closed loop swing independent system consists of a mass and a spring, an unstable characteristic, that is, a hunting phenomenon at a specific frequency, for example, a low RPM of the engine 12, a joystick pilot pressure (Pi) in a specific range. Can occur. In this hunting phenomenon, when the joystick pilot pressure Pi is kept constant, the turning upper body 45 rotates and stops repeatedly.

3B and 3C, when a step input (f(t)) is applied to the upper swing body 45 system, the upper swing body 45 has an output (x1(t)) for attenuating motion. )). However, when the frequency of the input value matches the natural frequency of the system, a hunting phenomenon may occur and a resonant output (x2(t)) may be expressed.

In exemplary embodiments, the hydraulic system 10 of a construction machine is used to control a pilot pressure provided as an input value of the regulator 30 in order to prevent unstable swing motion such as vibration of the upper swing body 45. It may include a turning control device. The swing control device can act as a damper in the system by changing the range of the input frequency where resonance occurs to a new input frequency for normal swing motion in order to stabilize the upper swing body system.

The swing control device includes pressure sensors 62 and 64 for detecting a pressure difference at the inlet and outlet ports of the swing motor 40, a pressure control valve for controlling a pilot pressure provided as an input value of the regulator 30, and When the detection signal from the pressure sensors 62 and 64 is received and the pilot pressure is within a range that causes hunting of the upper rotating body 45, a control signal for changing the pilot pressure is output to the pressure control valve. It may include a control unit 60.

The pressure sensor may include a first pressure sensor 62 and a second pressure sensor 64. The first pressure sensor 62 measures the pressure PA of hydraulic oil flowing into and out of the A port of the turning motor 40 through the first hydraulic line 42, and the second pressure sensor 64 is a second hydraulic line. The pressure (PB) of the hydraulic oil flowing into and out of the B port of the turning motor 40 can be measured through (44).

The controller 60 may be connected to the first and second pressure sensors 62 and 64 to receive a pressure difference between the inlet and outlet ports of the turning motor 40 as a detection signal. The controller 60 may receive the rotation speed RPM of the engine 12 and the joystick pilot pressure Pi as input signals. For example, the control unit 60 may receive a signal regarding the RPM of the engine 12 and the joystick pilot pressure Pi from the hydraulic control system EPOS.

In exemplary embodiments, the control unit 60 includes a matching unit 61 outputting a controller gain value for changing an input frequency range that causes hunting of the upper rotating body 45, and the detection signal and the controller. It may include an operation unit 63 that calculates a gain value and outputs a control signal. The pressure control valve may receive the control signal from the operation unit 63 and change the pilot pressure based on the control signal.

The pressure control valve may include a drain valve 70 for reducing the pilot pressure formed by the joystick 50. The drain valve 70 may be configured as an electronic proportional control valve (EPPRV). The drain valve 70 may form a secondary pressure according to the input current applied as the control signal.

The matching unit 61 receives the RPM of the engine 12 and the joystick pilot pressure Pi, and can match the controller gain value corresponding to the received pilot pressure Pi value based on the gain control map versus the pilot pressure. have. The zone in which hunting of the upper swing body occurs may be determined according to the input RPM of the engine and the joystick pilot pressure Pi. When the joystick pilot pressure Pi is, for example, about 6 bar or more, the upper swing body 45 may start to rotate. Hunting of the upper swing body 45 may occur in a range in which the RPM of the engine 12 is between 850 and 1266 and the joystick pilot pressure Pi is between 0 and 25 bar.

The pilot pressure vs. gain map may be matched with a controller gain value corresponding to a specific range of the input RPM and a specific range of the pilot pressure Pi. For example, when the engine RPM is in the range of 850 to 1052, the controller gain value is A in the range of 0 to 10 bar, and the controller gain value is B in the range of the pilot pressure 10 to 15 bar. , When the pilot pressure is between 15 and 20 bar, the controller gain value may be mapped to C, and when the pilot pressure is in the range of 20 bar or more, the controller gain may be mapped to 0.

The calculation unit 63 may output a specific voltage signal Vout by multiplying the absolute value of the pressure difference (|PA-PB|) from the pressure sensors 62 and 64 by the controller gain value. The output signal may be converted into a current signal (mA) through an EPPRV driver and then input to the drain valve 70.

Referring again to FIG. 2, the shuttle valve 55 may be connected between the first and second pilot lines 52 and 54. The shuttle valve 55 may be connected to the drain valve 70. When the joystick 50 is operated, a pilot pressure Pi may be formed in any one of the first and second pilot lines 52 and 54. The pilot line in which the pilot pressure Pi is formed may be connected to the drain valve 70 via the shuttle valve 55.

The drain valve 70 may be opened when a pilot pressure Pi greater than its set opening pressure is input. The opening pressure of the drain valve 70 may be changed and set according to the input current. Accordingly, the set pressure of the drain valve 70 can be tuned by the control unit 60.

When the pilot pressure Pi acts on the drain valve 70, when the pilot pressure Pi is greater than the set pressure of the drain valve 70, the pilot hydraulic oil is opened and forms the pilot pressure Pi may be discharged. Accordingly, the pilot pressure Pi may be changed to have the same size as the set pressure, and then may be provided as an input value of the regulator 30 through the first and second pilot lines 52 and 54.

As described above, the swing control device changes the pilot pressure Pi in the input frequency range for generating resonance of the upper swing body 45 to a new input frequency for the normal swing movement, so that the upper swing body 45 ) Can prevent hunting phenomenon. The pressure difference between the inlet and outlet ports of the turning motor 40 may be received as a detection signal, and a control signal may be output by calculating a controller gain value matched by the detection signal and the control map. The pilot pressure is changed according to the control signal and the newly changed pilot pressure is used as an input value of the regulator 30 to adjust the swash plate angle of the swing pump 20, thereby improving the hunting problem.

5 is a hydraulic circuit diagram showing a turning control device according to exemplary embodiments. The hydraulic system is substantially the same as or similar to the hydraulic system described with reference to FIGS. 1 and 2 except for the configuration of the pilot line and the addition of a pilot pressure sensor. Accordingly, the same components are denoted by the same reference numerals, and repeated descriptions of the same components are omitted.

5, the slewing pump 20 is connected to the A port of the slewing motor 40 by a first hydraulic line 42 and to the B port of the slewing motor 40 by the second hydraulic line 44. Can be connected. The swing motor 40 may be connected to the upper swing body 45 through a swing mechanism. The hydraulic oil discharged from the swing motor 40 may be supplied to the swing motor 40 through the first and second hydraulic lines 42 and 44 to rotate the swing motor 40 in a forward or reverse direction.

The joystick 50 may be connected to the sub pump 22 through a pilot hydraulic oil line to receive pilot hydraulic oil from the sub pump 22. The output terminal of the joystick 50 may be connected to the first pilot line 52 and the second pilot line 54. have. The first pilot line 52 may be connected to the first chamber 32 of the regulator 30, and the second pilot line 54 may be connected to the second chamber 34 of the regulator 30. The shuttle valve 55 may be connected between the first and second pilot lines 52 and 54. The shuttle valve 55 may be connected to the drain valve 70.

When the joystick 50 is operated, a pilot pressure Pi may be formed in any one of the first and second pilot lines 52 and 54. The line in which the pilot pressure Pi is formed may be connected to the drain valve 70 via the shuttle valve 55. After the pilot pressure Pi is changed to have the same size as the set pressure of the drain valve 70, it may be provided as an input value of the regulator 30 through the first and second pilot lines 52 and 54.

In example embodiments, the first pressure sensor 62 measures the pressure PA of the hydraulic oil flowing into and out of the A port of the turning motor 40 through the first hydraulic line 42, and the second pressure sensor Reference numeral 64 may measure the pressure PB of the hydraulic oil flowing into and out of the B port of the turning motor 40 through the second hydraulic line 44.

The first pilot pressure sensor 66 may be installed on the first pilot line 52, and the second pilot pressure sensor 68 may be installed on the second pilot line 54. The pilot pressure Pi formed by the joystick 50 may be detected by the pilot pressure sensors.

The controller 60 may be connected to the first and second pressure sensors 62 and 64 to receive a pressure difference between the inlet and outlet ports of the turning motor 40 as a detection signal. The controller 60 may be connected to the first and second pilot pressure sensors 66 and 68 to receive the pilot pressure Pi formed by the joystick 50 as a detection signal. The controller 60 may receive the rotational speed (RPM) of the engine 12 as an input signal. For example, the control unit 60 may receive a signal related to the RPM of the engine 12 from the hydraulic control system (EPOS).

Although the above has been described with reference to embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the present invention described in the following claims. You will understand that you can.

10: hydraulic system of construction machinery 12: engine
14: power train 16: main pump
18: auxiliary pump 20: slewing pump
22: sub pump 30: regulator
32: first chamber 34: second chamber
40: swing motor 42: first hydraulic line
44: second hydraulic line 45: upper pivot
50: joystick 51: pilot line
52: first pilot line 54: second pilot line
55: shuttle valve 56: first control valve 58: second control valve
60: control unit 61: matching unit
62: first pressure sensor 63: calculation unit
64: second pressure sensor 66: first pilot pressure sensor
68: second pilot pressure sensor 70: drain valve

Claims (14)

A pressure sensor for detecting a pressure difference at the inlet and outlet ports of the turning motor for turning the upper turning body;
A pressure control valve for controlling a pilot pressure provided as an input value of a regulator for adjusting an angle of the swash plate of the swing pump; And
The detection signal as the pressure difference from the pressure sensor, engine RPM, and pilot pressure are received, and a control signal for changing the pilot pressure is transmitted when the pilot pressure is within a range that causes hunting of the upper swing body. Includes a control unit outputting to the pressure control valve,
The swing pump and the swing motor are connected in a closed loop type,
The range for generating hunting of the upper swing body is within the range of the engine RPM between 850 and 1266 and the pilot pressure between 0 and 25 bar,
The control unit
A matching unit for outputting a controller gain value corresponding to a specific range of the engine RPM and a specific range of the pilot pressure; And
And an output unit for outputting the control signal proportional to a value obtained by multiplying the pressure difference by the controller gain. The swing control apparatus of claim 1, wherein the pressure control valve comprises a drain valve for reducing the pilot pressure of the pilot line. The swing control apparatus of claim 2, wherein the drain valve is connected to the pilot line between the regulator and the control unit generating the pilot pressure. The swing control device of claim 2, wherein the drain valve is configured as an electronic proportional control valve. delete delete The apparatus of claim 1, wherein the pilot line includes a pair of first and second pilot lines. The construction machine according to claim 7, further comprising a shuttle valve installed between the first and second pilot lines to select a line having a higher pilot pressure among the first and second pilot lines. Turning control device. delete A swing motor for rotating the upper swing body;
A swing pump connected to the swing motor in a closed loop form to supply hydraulic oil to the swing motor;
A regulator adjusting the swash plate angle of the swing pump;
A pressure sensor detecting a pressure difference at the inlet and outlet ports of the turning motor;
A pressure control valve for controlling a pilot pressure of a pilot line provided as an input value of the regulator; And
The detection signal as the pressure difference from the pressure sensor, engine RPM, and pilot pressure are received, and a control signal for changing the pilot pressure is transmitted when the pilot pressure is within a range in which hunting of the upper swing body occurs. Includes a control unit outputting to the pressure control valve,
The range for generating hunting of the upper swing body is within the range of the engine RPM between 850 and 1266 and the pilot pressure between 0 and 25 bar,
The control unit
A matching unit for outputting a controller gain value corresponding to a specific range of the engine RPM and a specific range of the pilot pressure; And
And an output unit for outputting the control signal proportional to a value obtained by multiplying the pressure difference by the controller gain value. 11. The hydraulic system of claim 10, wherein the pressure control valve comprises a drain valve for reducing the pilot pressure of the pilot line. 12. The hydraulic system of claim 11, wherein the drain valve is configured as an electronic proportional control valve. delete The hydraulic system according to claim 10, further comprising a main pump for driving a boom cylinder, an arm cylinder and a bucket cylinder.

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