KR20170054624A - Hydraulic system for construction machinery - Google Patents

Hydraulic system for construction machinery Download PDF

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Publication number
KR20170054624A
KR20170054624A KR1020150156772A KR20150156772A KR20170054624A KR 20170054624 A KR20170054624 A KR 20170054624A KR 1020150156772 A KR1020150156772 A KR 1020150156772A KR 20150156772 A KR20150156772 A KR 20150156772A KR 20170054624 A KR20170054624 A KR 20170054624A
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KR
South Korea
Prior art keywords
pump
boom
arm
cylinder
valve
Prior art date
Application number
KR1020150156772A
Other languages
Korean (ko)
Inventor
강만곤
Original Assignee
현대중공업 주식회사
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Priority to KR1020150156772A priority Critical patent/KR20170054624A/en
Publication of KR20170054624A publication Critical patent/KR20170054624A/en

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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/2004—Control mechanisms, e.g. control levers
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2221—Control of flow rate; Load sensing arrangements
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2221—Control of flow rate; Load sensing arrangements
    • E02F9/2232—Control of flow rate; Load sensing arrangements using one or more variable displacement pumps
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2278—Hydraulic circuits
    • E02F9/2292—Systems with two or more pumps

Abstract

Disclosed is a hydraulic system for construction equipment. According to the present invention, when a boom is lowered, and the system is not in a jack-up state and an arm not moved; the construction equipment for construction equipment supplies a minimum quantity of operational fluid to a first cylinder reducing a capacity of a first pipe to move the boom. When the boom is lowered, and the construction equipment is not in the jack-up state and the arm moved; a pipe between the first pump and a first control valve is closed, and a capacity of the first pump is controlled to be increased or decreased. Then, provided is an effect of saving energy as the operational fluid not required to lower the boom is not supplied to the first cylinder when the boom is lowered. Moreover, the pipe between the first pump and the first control valve is closed when the boom is lowered, the construction equipment is not in the jack-up state and the arm is moved; thus operational fluid supplied to the first pump is supplied to a second cylinder to move the arm. As such, provided is an effect of increasing motion speed of the arm.

Description

Hydraulic system for construction machine {HYDRAULIC SYSTEM FOR CONSTRUCTION MACHINERY}

The present invention relates to a hydraulic system for a construction machine that reduces or blocks the working oil supplied to the cylinder to operate the boom when the boom is lowered.

Construction equipment used in civil engineering works or construction work should be suitable for movement since it should always move at construction site. In addition, the construction machine is often used in a rough place on a construction site, and it is often used in a bad weather condition or in a place that is not leveled, so that it should have low failure and excellent durability.

Excavator, which is a kind of construction machine, is composed of a traveling body that is a moving body, a turning body which is pivotally mounted on a traveling body, and a working device which is installed on a turning body. The excavating work for digging the ground, the loading work for carrying the soil, Dismantling, and dismantling the ground.

A working device of an excavator is provided with a boom installed on a revolving body so as to be able to ascend and descend with respect to a portion supported by a revolving body and a boom having one end on the boom and being stretchable or collapsible with respect to the boom And a bucket that is pivotally mounted on the other end side of the arm and operates by hydraulic pressure.

The boom of the excavator is driven by the cylinder, and the cylinder is operated by the hydraulic oil supplied to one side and the other side. At this time, when the boom descends, the boom can be lowered by its own weight even if the operating oil is not supplied to the cylinder.

Incidentally, the excavator generally has a disadvantage in that energy is wasted because the hydraulic oil is supplied to the cylinder even when the boom descends.

A hydraulic control apparatus and a construction machine equipped with the hydraulic control apparatus are disclosed in Korean Patent Laid-Open Publication No. 10-2014-0116473 (Apr. 20, 2014.02) for solving the above disadvantages.

The construction machine limits the capacity of the first pump 14 that supplies hydraulic oil to the boom cylinder 9 when the boom 6 descends and the arm 7 expands so that the power of the first pump 14 Thereby preventing loss. However, even when the boom 6 is lowered and the arm 7 is extended, the construction machine is supplied with the working oil to the boom cylinder 9, which is disadvantageous in that energy is wasted.

When the boom 6 is lowered and the arm 7 is extended, since the hydraulic oil equivalent to the operating oil supplied to the boom cylinder 9 can not be supplied to the arm cylinder 10, There is a disadvantage in that the speed of motion of the motor decreases.

It is an object of the present invention to provide a hydraulic system for a construction machine capable of solving all the problems of the prior art as described above.

It is another object of the present invention to provide a hydraulic system for a construction machine capable of reducing energy or reducing the operating oil supplied to the cylinder to operate the boom when the boom is lowered, System. ≪ / RTI >

A hydraulic system for a construction machine according to the present invention is a hydraulic system of a construction machine for moving a boom provided to be able to move up and down and an arm provided so as to extend or collapse to the boom, A first operation lever for generating a signal for moving the boom; A first pump for supplying operating oil for moving the boom according to a position of the first operation lever; A first cylinder for receiving hydraulic fluid from the first pump and moving the boom; A first control valve for switching the direction of the operating fluid supplied to the first cylinder according to the position of the first operating lever or for controlling the supply of the operating fluid to the first cylinder; A pilot operated check valve that prevents the working oil from flowing backward from the first control valve to the first pump and prevents the working oil from being supplied to the first control valve from the first pump when the boom is lowered; A second operating lever for generating a signal for moving the arm; A second pump for supplying operating oil for moving the arm according to the position of the second operating lever; A second cylinder for receiving the operating fluid from the second pump and moving the arm; And a second control valve for switching the direction of the operating fluid supplied to the second cylinder according to the position of the second operating lever or for controlling the supply of the operating fluid to the second cylinder.

The hydraulic system for a construction machine according to the present embodiment is characterized in that the boom is lowered and is not in a jack-up state, and if the arm does not move, the first cylinder, which reduces the capacity of the first pump to move the boom, Of operating fluid. When the boom is lowered and not in a jack-up state and the arm is moved, the pipeline between the first pump and the first control valve is closed and the capacity of the first pump is reduced or increased do. Then, when the boom is lowered, unnecessary operating oil for lowering the boom is not supplied to the first cylinder, so energy may be saved.

When the boom descends and is not in a jack-up state, the channel between the first pump and the first control valve is closed when the arm moves, so that the operating oil supplied from the first pump moves the arm To the second cylinder. Therefore, the movement speed of the arm may be improved.

1 is a side view of a construction machine according to an embodiment of the present invention;
2 illustrates a hydraulic system according to one embodiment of the present invention.
3 is a flowchart illustrating a method of controlling a hydraulic system according to an embodiment of the present invention.
4 shows a hydraulic system according to another embodiment of the present invention.

It should be noted that, in the specification of the present invention, the same reference numerals as in the drawings denote the same elements, but they are numbered as much as possible even if they are shown in different drawings.

Meanwhile, the meaning of the terms described in the present specification should be understood as follows.

The word " first, "" second," and the like, used to distinguish one element from another, are to be understood to include plural representations unless the context clearly dictates otherwise. The scope of the right should not be limited by these terms.

It should be understood that the terms "comprises" or "having" does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

It should be understood that the term "at least one" includes all possible combinations from one or more related items. For example, the meaning of "at least one of the first item, the second item and the third item" means not only the first item, the second item or the third item, but also the second item and the second item among the first item, Means any combination of items that can be presented from more than one.

It should be understood that the term "and / or" includes all possible combinations from one or more related items. For example, the meaning of "first item, second item and / or third item" may include not only the first item, the second item or the third item but also two of the first item, Means a combination of all items that can be presented from the above.

It is to be understood that when an element is referred to as being "connected or installed" to another element, it may be directly connected or installed with the other element, although other elements may be present in between. On the other hand, when an element is referred to as being "directly connected or installed" to another element, it should be understood that there are no other elements in between. On the other hand, other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

In each step, the identification codes (for example, S100, S110, S120, etc.) are used for convenience of explanation, and the identification codes do not describe and explain the order of each step, Unless the order is described, it may happen differently from the stated order. That is, each step may occur in the same order as described, may be performed substantially concurrently, or may be performed in reverse order.

Hereinafter, a hydraulic system for a construction machine according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings by taking an excavator as an example.

1 is a side view of a construction machine according to an embodiment of the present invention.

As shown in the figure, the construction machine according to the present embodiment includes a traveling body 110 that travels in contact with the floor of a workplace such as a ground surface, a swivel body 120 pivotally mounted on the upper surface of the traveling body 110, And a working device 130 installed in the main body 120.

The working device 130 includes a boom 131 installed at one side of the swing body 120 and capable of raising and lowering based on a portion provided on the swing body 120, An arm 133 provided so as to be stretched or folded in such a manner as to be opened or folded with respect to the arm 131 and a bucket 135 swingably provided on the other end side of the arm 133, have.

The boom 131 and the arm 133 and the bucket 135 are driven by the hydraulic system 200 and the hydraulic system 200 is controlled by the control unit 210 A second cylinder 235 for moving the arm 133 and a third cylinder 255 for moving the bucket 135.

The hydraulic system 200 according to the present embodiment will be described with reference to Figs. 1 and 2. Fig. 2 is a view showing a hydraulic system according to an embodiment of the present invention.

As shown, the hydraulic system 200 according to the present embodiment may include a first operation lever 221 for generating a signal for moving the boom 131. [ The first operation lever 221 is located at a predetermined position by the user's operation and is operated by the operation of the boom 131 in accordance with the position of the first operation lever 221 A signal may be generated.

The control unit 210 may receive a signal corresponding to the position of the first operation lever 221 and may drive a first pump 223 for supplying operating oil for operating the boom 131. [ The first pump 223 is provided in a variable capacity type and its capacity can be varied by the first regulator 223a controlled by the controller 210. [

The operating fluid supplied from the first pump 223 may be supplied to the first cylinder 225 and the piston of the first cylinder 225 may be supplied to the first cylinder 225, Or the bottom dead center. Then, the boom 131 is raised or lowered by the piston.

The operating fluid supplied from the first pump 223 may be supplied to the first cylinder 225 through the first control valve 227. The first control valve 227 can switch the direction of the operating oil supplied to the first cylinder 225 or control the supply of the operating oil to the first cylinder 225 depending on the position of the first operating lever 221 have.

That is, when the first operating lever 221 is located at the neutral position, the operating fluid pressurized by the first pump 223 can be supplied to the tank through the first control valve 227. When the first operating lever 221 is in the raised position or the lowered position, the operating fluid pressurized by the first pump 223 is supplied to the first cylinder 224 by the switching of the spool of the first control valve 227 One side or the other side.

The hydraulic system 200 according to the present embodiment may include a second operation lever 231 for generating a signal for moving the arm 133. [ The second operation lever 231 is positioned at a predetermined position by the user's operation and is moved in the direction of the arm 133 in accordance with the position of the second operation lever 231 A signal may be generated.

The control unit 210 may receive a signal corresponding to the position of the second operation lever 231 and may drive a second pump 233 for supplying operating oil for operating the arm 133. The second pump 233 is provided in a variable capacity type and its capacity can be varied by a second regulator 233a controlled by the control unit 210. [

The operating fluid supplied from the second pump 233 can be supplied to the second cylinder 235 and the piston of the second cylinder 235 can be supplied to the first cylinder 235, Or the bottom dead center. Then, the arm 133 is raised or lowered by the piston.

The hydraulic fluid supplied from the second pump 233 may be supplied to the second cylinder 235 through the second control valve 237. The second control valve 237 can control the direction of the operating oil supplied to the second cylinder 235 or control the supply of the operating oil to the second cylinder 235 depending on the position of the second operating lever 231 have.

That is, when the second operation lever 231 is located at the neutral position, the hydraulic fluid pressurized by the second pump 233 can be supplied to the tank through the second control valve 237. [ When the second operating lever 231 is positioned at the raised or lowered position, the operating fluid pressurized by the second pump 233 is supplied to the second cylinder 235 by switching the spool of the second control valve 237 One side or the other side.

Two of the second control valves 237 may be connected in parallel and the hydraulic fluid supplied from the first pump 223 may be supplied to the second cylinder 235 through any one of the second control valves 237 .

When the boom 131 descends, the boom 131 can be lowered by its own weight even if the operating oil is not supplied to the first cylinder 225. [ Therefore, when the boom 131 descends, it is possible to save energy by preventing the hydraulic fluid from being supplied to the first cylinder 225.

The hydraulic system 200 according to the present embodiment is provided with a pilot operation type check valve 231 that prevents the hydraulic fluid from being supplied from the first pump 223 to the first cylinder 225 under a separate control when the boom 131 descends, And may include a valve 241. The pilot operated check valve 241 may prevent the hydraulic oil from flowing back to the first pump 223 from the first control valve 227. [

The pilot operated check valve 241 is provided between the first pump 223 and the first control valve 227 when the boom 131 descends and is not in a jack-up state and the arm 133 does not move, Can be opened. At this time, it is not necessary to open the channel between the first pump 223 and the first control valve 227 because the boom 131 descends. However, since the arm 133 does not move, the pressure of the first pump 223 It is necessary to discharge the working oil. The pilot operated check valve 241 may open a channel between the first pump 223 and the first control valve 227 and the first regulator 223a may open the channel between the first pump 223 and the first control valve 227, Can be minimized.

When the arm 133 is moved, the first pump 223 and the first control valve 227 are closed when the boom 131 is lowered and not in a jack-up state. Can be closed. When the boom 131 descends and the pipeline between the first pump 223 and the first control valve 227 is closed, the pressurized hydraulic fluid of the first pump 223 flows through the second control valve 237 2 cylinder 235 as shown in FIG. Then, the moving speed of the arm 133 can be improved.

The first regulator 233a and the pilot operated check valve 241 can be controlled by a first electronic proportional pressure reducing valve 243a and a second electron proportional pressure reducing valve 243b, The first electromagnetic proportional pressure reducing valve 243a, and the second electromagnetic proportional pressure reducing valve 243b may be controlled by the control unit 210, respectively.

The first electromagnetic proportional pressure reducing valve 243a controls the first regulator 223a to stop the first pump 223a when the boom 131 descends and is not in a jack-up state and the arm 133 does not move, 223 can be reduced. At this time, the second electromagnetic proportional control valve 243b does nothing.

When the arm 133 is moved, the first electromagnetic proportional pressure reducing valve 243a controls the first regulator 223a to move the first pump 223a to the first pump 223a, The capacity of the battery 223 may be reduced or increased. At this time, the second electromagnetic proportional pressure reducing valve 243b may control the pilot operation type check valve 241 to close the channel between the first pump 223 and the first control valve 227. [

The jack-up mentioned above means that the bucket 135 is connected to the floor of the work place while lifting the boom 131 and lifting one side of the traveling body 110 from the floor of the work place or lowering the boom 131, Refers to a state in which one side of the traveling body 110 lifted from the floor is brought into contact with the floor of the workplace.

A control method of the hydraulic system 200 according to the present embodiment will be described with reference to Figs. 3 is a flowchart illustrating a method of controlling a hydraulic system according to an embodiment of the present invention.

As shown in the figure, in step S110, it is possible to determine whether the boom 131 has been lowered. If the boom 131 does not descend, the hydraulic system 200 operates in a predetermined normal state. That is, when the boom 131 does not descend but is stopped, the operating oil is not supplied to the first cylinder 225. When the boom 131 rises without falling, the predetermined normal The hydraulic system 200 operates.

When the boom 131 descends, it can be determined whether or not the boom 131 is in the jack-up state in step S120. In the jack-up state, the hydraulic fluid pumped by the first pump 223 must be supplied to the first cylinder 225, so that no action is taken. Then, the hydraulic system 200 operates in a normal state.

If it is determined that the arm 133 is not in the jack-up state, it is determined whether or not the arm 133 is exercised in step S130.

Therefore, when the arm 133 does not move, only the boom 131 is lowered. Therefore, the first regulator 223a is controlled by the first electromagnetic proportional pressure reducing valve 243a so that the capacity of the first pump 223 is minimized (S140). At this time, the second electromagnetic proportional control valve 243b does nothing. Then, the minimum operating fluid pressurized by the first pump 223 may be supplied to the first cylinder 225 side through the pilot operated check valve 241 → the first control valve 227. The operating oil supplied to the first cylinder 225 is for discharging the pressurized operating oil of the first pump 223 and prevents the first pump 223 from being damaged by the hydraulic pressure.

When the arm 133 moves, the boom 131 descends and the arm 133 moves. Therefore, the pilot operation type check valve 241 is controlled by the second electromagnetic proportional pressure reducing valve 243b, The pipe between the pump 223 and the first control valve 227 is closed. The first regulator 223a is controlled by the first proportional pressure reducing valve 243a so that the capacity of the first pump 223 is reduced or increased (S150). Then, the operating fluid pressurized by the first pump 223 is supplied to the second cylinder 235 for moving the arm 133, so that the moving speed of the arm 133 is improved.

The hydraulic system for a construction machine and the control method thereof according to the present embodiment are configured such that when the boom 131 descends and is not in a jack-up state and the arm 133 does not move, So that the first cylinder 225 is supplied with the minimum operating fluid. When the boom 131 descends and is not in the jack-up state and the arm 133 moves, the channel between the first pump 223 and the first control valve 227 is closed, 1 < / RTI > pump 223 is reduced or increased. Then, when the boom 131 is lowered, unnecessary operating oil for lowering the boom 131 is not supplied to the first cylinder 225, so that energy can be saved.

Since the pipeline between the first pump 223 and the first control valve 227 is closed when the boom 131 descends and is not in a jack-up state and the arm 133 moves, Since the operating fluid supplied from the first pump 223 is supplied to the second cylinder 235 for moving the arm 133, the moving speed of the arm 133 can be improved.

4 is a view showing a hydraulic system according to another embodiment of the present invention, and only differences from FIG. 2 are described.

As shown in the figure, the hydraulic system 300 according to another embodiment of the present invention includes, instead of the first electromagnetic proportional pressure reducing valve 243a and the second electromagnetic proportional pressure reducing valve 243b shown in FIG. 2, A second hydraulic pressure valve 343a and a second hydraulic pressure valve 343b.

At this time, the first regulator 323a and the pilot operation type check valve 341 may be controlled by the first hydraulic valve 343a and the second hydraulic valve 343b, respectively, and the first hydraulic valve 343a may be controlled by the first hydraulic valve 343a 1 operation lever 321 and the second hydraulic valve 343b can be controlled by the first operation lever 321 and the second operation lever 331. [

Thus, when the boom 131 (see Fig. 1) is lowered and is not in the jack-up state and the arm 133 (see Fig. 1) is not moved, the first hydraulic valve 343a, The capacity of the first pump 323 can be reduced by controlling the pump 323a. At this time, the second hydraulic pressure valve 343b does not perform any operation.

When the arm 133 moves, the second hydraulic pressure valve 343a controls the first regulator 323a to control the first pump 223a to operate in a state where the boom 131 descends and is not in a jack- ) Can be regulated in such a manner as to reduce or increase the capacity of the patient. At this time, the second hydraulic pressure valve 343b may control the pilot operated check valve 341 to close the channel between the first pump 323 and the first control valve 327.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Will be clear to those who have knowledge of. Therefore, the scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention.

210:
221: first operation lever
223: First pump
225: first cylinder
227: first control valve
241: Pilot operated check valve
243a, 243b: first and second electronic proportional pressure reducing valves

Claims (6)

1. A hydraulic system for a construction machine for moving a boom capable of being raised and lowered and an arm provided so as to extend or collapse against the boom,
A first operation lever for generating a signal for moving the boom;
A first pump for supplying operating oil for moving the boom according to a position of the first operation lever;
A first cylinder for receiving hydraulic fluid from the first pump and moving the boom;
A first control valve for switching the direction of the operating fluid supplied to the first cylinder according to the position of the first operating lever or for controlling the supply of the operating fluid to the first cylinder;
A pilot operated check valve that prevents the working oil from flowing backward from the first control valve to the first pump and prevents the working oil from being supplied to the first control valve from the first pump when the boom is lowered;
A second operating lever for generating a signal for moving the arm;
A second pump for supplying operating oil for moving the arm according to the position of the second operating lever;
A second cylinder for receiving the operating fluid from the second pump and moving the arm;
And a second control valve for switching the direction of the operating oil supplied to the second cylinder according to the position of the second operating lever or controlling the supply of the operating oil to the second cylinder, system. The method according to claim 1,
Wherein the pilot operated check valve opens the channel between the first pump and the first control valve when the boom is lowered and not in a jack-up state and the arm does not move, Is closed and the pipeline between the first pump and the first control valve is closed when the arm is in the non-jack-up state. The method according to claim 1,
A first regulator for regulating the capacity of the first pump;
Further comprising a first electromagnetic proportional pressure reducing valve and a second electromagnetic proportional pressure reducing valve for respectively controlling the first regulator and the pilot operated check valve. The method of claim 3,
The capacity of the first pump is decreased by the first electromagnetic proportional pressure reducing valve when the boom is lowered and not in a jack-up state and the arm is not moved,
When the boom is lowered and not in a jack-up state and the arm is moved, the capacity of the first pump is regulated by the first electromagnetic proportional pressure reducing valve, and by the second electromagnetic proportional pressure reducing valve Wherein the pilot operated check valve closes a conduit between the first pump and the first control valve. The method according to claim 1,
A first regulator for regulating the capacity of the first pump;
Further comprising a first hydraulic valve and a second hydraulic valve for controlling the first regulator and the pilot operated check valve, respectively. 6. The method of claim 5,
If the boom is lowered and not in a jack-up state and the arm does not move, the capacity of the first pump is reduced by the first hydraulic valve,
The capacity of the first pump is regulated by the first hydraulic valve when the boom descends and is not in a jack-up state and the arm moves, and the capacity of the pilot operated type And the check valve closes the conduit between the first pump and the first control valve.
KR1020150156772A 2015-11-09 2015-11-09 Hydraulic system for construction machinery KR20170054624A (en)

Priority Applications (1)

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KR1020150156772A KR20170054624A (en) 2015-11-09 2015-11-09 Hydraulic system for construction machinery

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
KR1020150156772A KR20170054624A (en) 2015-11-09 2015-11-09 Hydraulic system for construction machinery

Publications (1)

Publication Number Publication Date
KR20170054624A true KR20170054624A (en) 2017-05-18

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KR1020150156772A KR20170054624A (en) 2015-11-09 2015-11-09 Hydraulic system for construction machinery

Country Status (1)

Country Link
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