Electro-hydrostatic actuator for construction machinery

Abstract

Disclosed is an electro-hydrostatic actuator for construction machinery. According to the embodiment, a valve unit and an accumulator are built-in to achieve a compact design and stable operation.

Description

Electric hydrostatic actuator for construction machinery

[0001] The present embodiment relates to an electric hydrostatic actuator for construction equipment having a compact configuration by housing components necessary for the operation of the hydraulic actuator within the internal space of a hydraulic cylinder.

[0002] Generally, an EHA (Electro-Hydrostatic Actuator) consists of an electric motor, a bidirectional hydraulic pump, an integrated manifold block, a reservoir, and a hydraulic cylinder acting as a hydraulic actuator.

[0003] A conventional electric hydrostatic actuator is described with reference to the drawings.

[0004] Referring to the attached FIG. 1, a conventional electro-hydrostatic actuator comprises a hydraulic cylinder (10), a hydraulic pump (20) that supplies working fluid to the hydraulic cylinder (10), a motor unit (30) coupled to the hydraulic pump (20), a valve block (40) provided on the outside of the hydraulic cylinder (10), and an accumulator (50) connected to the valve block (40).

[0005] A plurality of relief valves (R1, R2) are installed in the valve block (40), and a plurality of pilot check valves (C1, C2) are installed as shown in the drawing. The pilot check valves (C1, C2) perform the function of connecting and blocking the flow path leading to the accumulator (50) according to the direction of the load to compensate for the volume imbalance of oil supplied to and discharged to both chambers of the hydraulic cylinder (10).

[0006] If the size of the above valve block (40) and accumulator (50) increases, it has an adverse effect on the layout of the location where the electro-hydrostatic actuator is installed. In addition, if the weight of the above valve block (40) and accumulator (50) increases, it has an adverse effect on the durability of the hydraulic cylinder (10), so countermeasures are required.

[0007] Embodiments of the present invention aim to provide an electric hydrostatic actuator for construction machinery in which a valve unit and an accumulator are built in by utilizing the internal structure of a cylinder unit and a piston rod.

[0008] An electric hydrostatic actuator for construction machinery according to one embodiment of the present invention comprises: a cylinder unit (100) having a chamber portion (110) formed of a predetermined size; a piston (300) equipped with a valve unit (200) that operates according to the state of oil supplied to the chamber portion (110); a piston rod (500) connected to the piston unit (300) and having an accumulator (400) built into which oil passing through the valve unit (200) flows in or out; and a hydraulic pump unit (600) that supplies oil to the cylinder unit (100).

[0009] The above chamber section (110) includes a first chamber section (112) formed on one side relative to the piston (300); and a second chamber section (114) formed on the other side relative to the piston (300), and the first chamber section (112) and the second chamber section (114) are characterized in that oil can move between them via the valve unit (200).

[0010] The valve unit (200) includes a first relief valve (210) which operates to bypass oil to the second chamber (114) when oil is supplied to the first chamber (114) by the hydraulic pump unit (600) at a preset pressure or higher; and a second relief valve (220) which operates to bypass oil to the first chamber (112) when oil is supplied to the second chamber (114) at a preset pressure or higher.

[0011] The valve unit (200) further includes a first pilot check valve (230) positioned adjacent to the first relief valve (210); and a second pilot check valve (240) positioned adjacent to the second relief valve (220).

[0012] When the first chamber (112) is in a high-pressure state compared to the second chamber (114) and the piston rod (500) is extended to the outside of the cylinder unit (100), the oil stored in the accumulator (400) moves to the second chamber (114) via the first pilot check valve (230).

[0013] When the first chamber (112) is in a high-pressure state compared to the second chamber (114) and the piston rod (500) is retracted into the cylinder unit (100), the oil in the second chamber (114) moves to the accumulator (400) via the first pilot check valve (230).

[0014] When the second chamber (114) is in a high-pressure state compared to the first chamber (112) and the piston rod (500) is extended to the outside of the cylinder unit (100), the oil stored in the accumulator (400) is moved to the first chamber (112) via the second pilot check valve (240).

[0015] When the second chamber (114) is in a high-pressure state compared to the first chamber (112) and the piston rod (500) is retracted into the cylinder unit (100), the oil of the first chamber (112) moves to the accumulator (400) via the second pilot check valve (240).

[0016] The above accumulator (400) is maintained in a state coupled with the piston unit (300) so that oil moves into the inside of the piston unit (300).

[0017] The first pilot check valve (230) is operated by receiving pressure from the first chamber (112), and the second pilot check valve (240) is operated by receiving pressure from the second chamber (114).

[0018] The first and second relief valves (210, 220) and the first and second pilot check valves (230, 240) are positioned on the inner side of the piston (300) at a 90-degree interval from each other. The interval between them is set to 90 degrees to maximize the distance between the valves, but in some cases, it does not necessarily have to be 90 degrees.

[0019] A gas section (700) is formed in the piston rod (500) on the inside, partitioned by a sealing member (S) that seals the oil stored in the accumulator (400).

[0020] The above gas section (700) is filled with an inert gas, and in most cases, is filled with nitrogen.

[0021] The above gas section (700) is compressed when the piston rod (500) contracts.

[0022] Embodiments of the present invention allow for a compact design by embedding a valve unit in a piston provided inside a cylinder unit and filling the piston rod with an accumulator and nitrogen gas.

[0023] The embodiments of the present invention enable stable operation by allowing oil to move stably according to pressure fluctuations in the first and second chambers constituting the chamber section.

[0024] FIG. 1 is a simplified drawing of a conventional electric hydrostatic actuator.

[0025] FIG. 2 is a drawing illustrating an electric hydrostatic actuator for construction machinery according to the present embodiment.

[0026] FIG. 3 is a drawing showing the arrangement of a valve unit according to the present embodiment.

[0027] FIGS. 4 to 6 are operating state diagrams of an electric hydrostatic actuator for construction machinery according to the present embodiment.

[0028] FIGS. 7 and 8 are operating state diagrams of the first and second relief valves according to the present embodiment.

[0029] The advantages and features of the present disclosure and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present disclosure is complete and to fully inform those skilled in the art of the scope of the disclosure, and the present disclosure is defined only by the scope of the claims. Throughout the specification, like reference numerals refer to like components.

[0030] When one component is referred to as being "connected to" or "coupled to" another component, it includes cases where it is directly connected or coupled to the other component, or cases where another component is interposed. Conversely, when one component is referred to as being "directly connected to" or "directly coupled to" another component, it indicates that no other component is interposed. "And / or" includes each of the mentioned items and all combinations of one or more of them.

[0031] The terms used herein are for describing embodiments and are not intended to limit the disclosure. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, actions, and / or elements to the mentioned components, steps, actions, and / or elements.

[0032] Although terms such as "first," "second," etc., are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used merely to distinguish one component from another.

[0033]

[0034] An electric hydrostatic actuator for construction machinery according to one embodiment of the present invention will be described with reference to the drawings. Attached FIG. 2 is a drawing illustrating an electric hydrostatic actuator for construction machinery according to the present embodiment, and FIG. 3 is a drawing illustrating the arrangement of a valve unit according to the present embodiment.

[0035]

[0036] Referring to the attached FIGS. 2 and 3, the electric hydrostatic actuator for construction machinery according to the present embodiment is configured such that a valve unit (200) is embedded in a piston (300) provided inside a cylinder unit (100), and an accumulator (400) is embedded in the longitudinal direction of a piston rod (500).

[0037] To this end, the present embodiment includes a piston (300) having a chamber portion (110) of a predetermined size formed inside the cylinder unit (100) and a valve unit (200) that operates according to the state of the oil supplied to the chamber portion (110), a piston rod (500) connected to the piston unit (300) and having an accumulator (400) built in which oil passing through the valve unit (200) flows in or out, and a hydraulic pump unit (600) that supplies oil to the cylinder unit (100).

[0038] The chamber section (110) includes a first chamber section (112) formed on one side relative to the piston (300) and a second chamber section (114) formed on the other side relative to the piston (300). Since the volume corresponding to the volume of the piston rod (500) is excluded from the second chamber section (114), the first chamber section (112) is formed with a larger volume than the second chamber section (114).

[0039] The first chamber (112) and the second chamber (114) can extend or compress the piston rod (500) by moving oil between them via the valve unit (200) to be described later.

[0040]

[0041] The valve unit (200) includes a first relief valve (210) which operates to bypass oil to the second chamber (114) when oil is supplied to the first chamber (112) by the hydraulic pump unit (600) at a preset pressure or higher, and a second relief valve (220) which operates to bypass oil to the first chamber (112) when oil is supplied to the second chamber (114) at a preset pressure or higher.

[0042] And the valve unit (200) further includes a first pilot check valve (230) positioned adjacent to the first relief valve (210) and a second pilot check valve (240) positioned adjacent to the second relief valve (220).

[0043] The first and second relief valves (210, 220) are arranged facing each other in the vertical direction according to the drawing, and the first and second pilot check valves (230, 240) are arranged facing each other in the horizontal direction according to the drawing. The vertical or horizontal directions may be installed by changing them in various ways inside the piston (300) in the directions defined according to the drawing.

[0044] The first relief valve (210) and the first pilot check valve (230) are spaced apart at a 90-degree angle, and the first pilot check valve (230) and the second relief valve (220) are also spaced apart at a 90-degree angle. When arranged in this way, the degree of freedom for the placement of the first and second relief valves (210, 220) and the first and second pilot check valves (230, 240) is improved, and the phenomenon of layouts overlapping between them is prevented, thereby ensuring stable operation. However, if there is no problem with the layout, it is not necessary to maintain a 90-degree angle.

[0045] The first relief valve (210) is operated to open only when the pressure of the first chamber (112) is above a preset maximum pressure, and remains closed when the pressure is below the maximum pressure.

[0046] When the first relief valve (210) is opened, the oil from the first chamber (112) is transferred to the second chamber (114). The maximum pressure can be defined as, for example, 350 bar, but this can be changed.

[0047] The second relief valve (220) is operated to open when the pressure in the second chamber (114) is above the maximum pressure, and the oil in the second chamber (114) is moved to the first chamber (112).

[0048] The first pilot check valve (230) is opened by receiving pressure from the first chamber section (112), and the second pilot check valve (240) is opened by receiving pressure from the second chamber section (114).

[0049]

[0050] The above accumulator (400) is maintained in a state coupled with the piston unit (300) so that oil moves into the inside of the piston unit (300).

[0051] A gas section (700) is formed in the piston rod (500) on the inside, partitioned by a sealing member (S) that seals the oil stored in the accumulator (400). The gas section (700) is filled with an inert gas, for example, nitrogen gas, but it may be changed to another non-flammable gas.

[0052] The above gas section (700) is prevented from leaking by the sealing member (S), and the oil stored in the accumulator (400) is also prevented from leaking to the outside.

[0053] The above gas section (700) is compressed when the piston rod (500) contracts, and the compression state changes according to the operation of the hydraulic pump unit (600) and the movement of oil to the first chamber section (112) or the second chamber section (114).

[0054] The above gas portion (700) expands or compresses inside the piston rod (500) like a coil spring.

[0055]

[0056] The operating state of the electric hydrostatic actuator for construction machinery according to the present embodiment is described with reference to the drawings.

[0057] Referring to the attached FIG. 2, in this embodiment, the first chamber section (112) is in a high-pressure state compared to the second chamber section (114), and when the piston rod (500) is extended to the outside of the cylinder unit (100), the oil stored in the accumulator (400) is moved to the second chamber section (114) via the first pilot check valve (230).

[0058] A separately provided control unit controls the flow rate of oil supplied to the first chamber (112) by the hydraulic pump unit (600) for the extension speed and stable operation of the piston rod (500).

[0059] The control unit controls the suction flow rate of the oil stored in the second chamber (114) and the discharge flow rate discharged to the first chamber (112) to be equal when the hydraulic pump unit (600) discharges oil to the first chamber (112). For reference, the flow rate of oil supplied to the first chamber (112) is calculated by multiplying the area of ​​the first chamber (112) by the movement speed of the piston rod (500).

[0060] The second chamber (114) has a smaller volume than the first chamber (112), so when the hydraulic pump unit (600) is operated to supply oil to the first chamber (112), the amount of oil in the second chamber (114) may be insufficient.

[0061] In this embodiment, to prevent this, the first pilot check valve (230) detects the pressure in the first chamber section (112) and operates to open, and the oil stored in the accumulator (400) is moved to the second chamber section (114) through the first pilot check valve (230) as shown by the arrow in the drawing.

[0062] In this case, the second chamber (114) can be operated stably so that problems caused by a lack of oil are prevented even when the hydraulic pump unit (600) sucks in oil to supply it to the first chamber (112).

[0063] When the above piston rod (500) is extended, the nitrogen gas expands, causing the sealing member (S) to move toward the first chamber section (112) according to the drawing, and the oil stored in the accumulator (400) moves.

[0064]

[0065] Referring to the attached FIG. 4, this embodiment corresponds to the case where the piston rod (500) is operated to contract into the cylinder unit (100) while the pressure of the first chamber (112) is still high.

[0066] In this case, the control unit controls the flow rate of oil flowing out of the first chamber (112) for the hydraulic pump unit (600) to control the retraction speed of the piston rod (500) and stable operation.

[0067] When the control unit controls the outflow rate of the first chamber (112) of the hydraulic pump unit (600), the suction rate of the oil stored in the first chamber (112) and the discharge rate discharged to the second chamber (114) are controlled to be the same. For reference, the flow rate of oil supplied to the second chamber (114) is calculated by multiplying the area of ​​the second chamber (112) by the movement speed of the piston rod (500).

[0068] The second chamber (114) has a smaller volume than the first chamber (112), so when the hydraulic pump unit (600) is operated to supply oil to the second chamber (114), the amount of oil in the second chamber (114) can be greater than the volume.

[0069] In this embodiment, to prevent this, the first pilot check valve (230) detects the pressure of the first chamber (112) and operates to open, and the remaining oil after filling the second chamber (114) is transferred to the accumulator (400) as shown by the arrow in the drawing.

[0070] In this case, the second chamber (114) can prevent the pressure from rising to the maximum pressure of the second relief valve (220), thereby maintaining stable operation.

[0071]

[0072] Referring to the attached FIG. 5, this embodiment corresponds to a case where the second chamber (114) is in a high-pressure state compared to the first chamber (112) and the piston rod (500) is extended outward from the cylinder unit (100).

[0073] In this case, the control unit controls the flow rate of oil so that the hydraulic pump unit (600) moves the oil stored in the second chamber (114), which is maintained in a high-pressure state for the extension speed and stable operation of the piston rod (500), to the first chamber (112).

[0074] The control unit controls the suction flow rate of the oil stored in the second chamber (114) and the discharge flow rate discharged to the first chamber (112) to be equal when the hydraulic pump unit (600) discharges oil to the first chamber (112). For reference, the flow rate of oil supplied to the first chamber (112) is calculated by multiplying the area of ​​the second chamber (114) by the movement speed of the piston rod (500).

[0075] The second chamber (114) has a smaller volume than the first chamber (112), so when the hydraulic pump unit (600) is operated to supply oil to the first chamber (112), the amount of oil in the first chamber (112) may be insufficient.

[0076] In this embodiment, to prevent this, the second pilot check valve (240) detects the pressure in the second chamber (114) and operates to open, and the oil stored in the accumulator (400) is moved to the first chamber (112) through the second pilot check valve (240) as shown by the arrow in the drawing.

[0077] In this case, the first chamber (112) can operate stably by preventing problems caused by a lack of oil when the hydraulic pump unit (600) supplies oil.

[0078] When the above piston rod (500) is extended, the nitrogen gas expands.

[0079]

[0080] Referring to the attached FIG. 6, this embodiment corresponds to a case where the second chamber (114) is in a high-pressure state compared to the first chamber (112) and the piston rod (500) is retracted into the inside of the cylinder unit (100).

[0081] In this case, the control unit controls the flow rate of oil supplied to the second chamber (114) by the hydraulic pump unit (600) for the retraction speed and stable operation of the piston rod (500).

[0082] The control unit controls the suction flow rate of the oil stored in the first chamber (112) and the discharge flow rate discharged to the second chamber (114) to be equal when the hydraulic pump unit (600) discharges oil to the second chamber (114). For reference, the flow rate of oil supplied to the second chamber (114) is calculated by multiplying the area of ​​the second chamber (112) by the movement speed of the piston rod (500).

[0083] The second chamber (114) has a smaller volume than the first chamber (112), so when the hydraulic pump unit (600) is operated to supply oil to the second chamber (114), the amount of oil in the first chamber (112) can be greater than the volume.

[0084] In this embodiment, to prevent this, the second pilot check valve (240) detects the pressure of the second chamber section (114) and operates to open, and the oil from the first chamber section (112) is moved to the accumulator (400) via the second pilot check valve (240) as shown by the arrow in the drawing.

[0085] In this case, the first chamber (112) can prevent the pressure from rising to the maximum pressure of the first relief valve (210), thereby maintaining stable operation.

[0086]

[0087] Referring to the attached FIG. 7, the present embodiment illustrates the operating state of a first relief valve (210) for preventing overload of a cylinder unit (100). When the first chamber (112) is in a high-pressure state compared to the second chamber (114), and the hydraulic pump unit (600) supplies oil stored in the second chamber (114) to the first chamber (112), if the pressure increases above a set pressure, the first relief valve (210) is operated to open.

[0088] In this case, overloading of the first chamber (112) formed in the cylinder unit (100) is prevented, so stable operation can always be maintained.

[0089]

[0090] Referring to the attached FIG. 8, the present embodiment illustrates the operating state of a second relief valve (220) to prevent overload of the cylinder unit (100). When the second chamber (114) is in a high-pressure state compared to the first chamber (112) and the hydraulic pump unit (600) supplies oil stored in the first chamber (112) to the second chamber (114), if the pressure increases above the set pressure, the second relief valve (220) is operated to open.

[0091] In this case, overloading of the second chamber (114) formed in the cylinder unit (100) is prevented, so stable operation can be maintained at all times.

[0092]

[0093] Although an embodiment of the present invention has been described above, those skilled in the art may modify and change the present invention in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of the present invention as described in the claims, and such modifications and changes are also to be included within the scope of the rights of the present invention.

[0094] These embodiments allow the oil flowing inside a hydrostatic actuator to be operated along an optimal path.

Claims

1. A cylinder unit (100) having a chamber portion (110) formed of a predetermined size; A piston (300) equipped with a valve unit (200) that operates according to the state of the oil supplied to the chamber (110); A piston rod (500) having an accumulator (400) built into it, which is connected to the piston unit (300) and through which oil passing through the valve unit (200) flows in or out; and An electric hydrostatic actuator for construction machinery comprising a hydraulic pump unit (600) that supplies oil to the cylinder unit (100).

2. In Paragraph 1, The above chamber section (110) is a first chamber section (112) formed on one side relative to the piston (300); An electric hydrostatic actuator for construction machinery, characterized by including a second chamber section (114) formed on the other side relative to the piston (300), wherein oil can move between the first chamber section (112) and the second chamber section (114) via the valve unit (200).

3. In Paragraph 2, The above valve unit (200) is a first relief valve (210) that operates to bypass oil to the second chamber (114) when oil is supplied to the first chamber (114) by the hydraulic pump unit (600) at a preset pressure or higher; The above valve unit (200) is an electric hydrostatic actuator for construction machinery that includes a second relief valve (220) which operates to bypass oil to the first chamber (112) when oil is supplied to the second chamber (114) at a preset pressure or higher.

4. In Paragraph 3, The above valve unit (200) includes a first pilot check valve (230) positioned adjacent to the first relief valve (210); An electric hydrostatic actuator for construction machinery further comprising a second pilot check valve (240) positioned adjacent to the second relief valve (220).

5. In Paragraph 4, An electric hydrostatic actuator for construction machinery in which the first chamber (112) is in a high-pressure state compared to the second chamber (114), and when the rod (500) is extended to the outside of the cylinder unit (100), the oil stored in the accumulator (400) is moved to the second chamber (114) via the first pilot check valve (230).

6. In Paragraph 1, An electric hydrostatic actuator for construction machinery in which the first chamber (112) is in a high-pressure state compared to the second chamber (114), and when the piston rod (500) is retracted into the cylinder unit (100), the oil in the second chamber (114) moves to the accumulator (400) via the first pilot check valve (230).

7. In Paragraph 1, An electric hydrostatic actuator for construction machinery in which, when the second chamber (114) is in a high-pressure state compared to the first chamber (112) and the piston rod (500) is extended to the outside of the cylinder unit (100), the oil stored in the accumulator (400) is moved to the first chamber (112) via the second pilot check valve (240).

8. In Paragraph 1, An electric hydrostatic actuator for construction machinery in which, when the second chamber (114) is in a high-pressure state compared to the first chamber (112) and the piston rod (500) is retracted into the cylinder unit (100), the oil of the first chamber (112) moves to the accumulator (400) via the second pilot check valve (240).

9. In Paragraph 1, The above accumulator (400) is an electric hydrostatic actuator for construction machinery that is maintained in a state coupled with the piston unit (300) so that oil moves into the inside of the piston unit (300).

10. In Paragraph 5, An electric hydrostatic actuator for construction machinery, wherein the first pilot check valve (230) is operated by receiving pressure from the first chamber section (112), and the second pilot check valve (240) is operated by receiving pressure from the second chamber section (114).

11. In Paragraph 4, The first and second relief valves (210, 220) and the first and second pilot check valves (230, 240) are electric hydrostatic actuators for construction machinery arranged inside the piston (300) at 90-degree intervals from each other.

12. In Paragraph 9, An electric hydrostatic actuator for construction machinery, wherein the piston rod (500) has a gas section (700) formed on the inside through a sealing member (S) that seals the oil stored in the accumulator (400).

13. In Paragraph 12, The above gas section (700) is an electric hydrostatic actuator for construction machinery that is filled with inert gas.

14. In Paragraph 13, The above gas section (700) is an electric hydrostatic actuator for construction machinery in which compression occurs when the above piston rod (500) contracts.

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