COMPOSITE INJECTION DEVICE FOR MANUFACTURING ULTRAFINE METALLIC POWDER

Abstract

An objective of the present disclosure is to provide an injection device that can manufacture spherical and defect-minimized powder. In accordance with the objective, the present disclosure provides an EIGA-type composite injection device that can inject both of gas and water. That is, the composite injection device of the present disclosure manufactures amorphous spherical powder by forming fine spherical pre-powder by injecting high-temperature gas at high pressure to a stream of liquid metal melted through an injector coil and then by inject water immediately before the pre-powder solidifies.

Claims

1. A composite injection device for manufacturing ultrafine metallic powder, the composite injection device comprising: a metal melter configured to heat and melt a metal bar by surrounding the metal bar with an induction coil and configured to continuously supply the metal bar without an orifice; a first injector disposed under the metal melter; and a second injector disposed under the first injector at a distance at which the molten metal drops by predicting time for which a melting point of the molten metal is reached, wherein the first injector and the second injector are configured in a variable type such that heights thereof can be adjusted in accordance with the melting point of the molten metal, and the higher the melting point of the molten metal, the larger the disposition gap corresponding to a height difference of the first injector and the second injector is adjusted; injection of the second injector is performed before a melting point of a molten metal film is reached; the metal bar includes high melting-point metal having a melting point of 1500 C. or more or a highly reactive material; the first injector injects high-temperature gas; the second injector injects water, or coolant gas, or a mixture of water and coolant gas, thereby manufacturing spherical amorphous fine powder; a stream of the molten metal is dispersed in a film shape by primarily injecting high-temperature gas at 300 to 400 C. at gas pressure of 60 to 100 bar to the molten metal through the first injector and spherical fine powder with less defects is formed by increasing a cooling rate of the molten metal and increasing impulse; and spherical fine power is manufactured in an amorphous type by changing the cooling rate to be high by secondarily injecting water or coolant gas at 20 C. to room temperature or a mixture of water and coolant gas at 20 C. to room temperature through the second injector before the molten metal film solidifies.

2. The composite injection device of claim 1, wherein pressure of water that is injected from the second injector is 100 to 1000 bar.

3. The composite injection device of claim 1, wherein when coolant gas is injected from the second injector, pressure of the coolant gas is 20 to 200 bar.

4. The composite injection device of claim 1, wherein as the temperature of gas becomes high, the gas is supplied at low supply amount and pressure from the first injector.

5. A composite injection device for manufacturing ultrafine metallic powder, the composite injection device comprising: a metal melter configured to heat and melt a metal bar by surrounding the metal bar with an induction coil and configured to continuously supply the metal bar without an orifice; a first injector disposed under the metal melter; and a second injector disposed close to the firs injector, wherein the first injector and the second injector are operated with a time difference by operating the second injector later than the first injector, the higher the melting point of molten metal, the longer the time difference of the operation time of the first injector and the second injector is adjusted, and the higher the melting point of the molten metal, the longer the time for which the molten metal is exposed to gas injection from the first injector is made, and then the molten metal is exposed to injection from the second injector; the metal bar includes high melting-point metal having a melting point of 1,600 C. or more or a highly reactive material; the first injector injects high-temperature gas; the second injector injects water, or coolant gas, or a mixture of water and coolant gas, thereby manufacturing spherical amorphous fine powder; a stream of the molten metal is widely dispersed in a film shape by primarily injecting high-temperature gas at 300 to 400 C. at gas pressure of 60 to 100 bar to the molten metal through the first injector and spherical fine powder with less defects is formed by increasing a cooling rate of the molten metal and increasing impulse; and spherical fine power is manufactured in an amorphous type by changing the cooling rate to be high by secondarily injecting water or coolant gas at 20 C. to room temperature or a mixture of water and coolant gas at 20 C. to room temperature through the second injector before the molten metal film solidifies.

6. A device for manufacturing metallic powder, the device comprising: a chamber; an induction coil disposed in the chamber and configured to melt a metal bar; a guide having a hole through which molten metal melted by the induction coil passes, and configured to guide the molten metal; a gas injector disposed at the guide and configured to inject gas at 300 C. or more toward the molten metal that has passed through the hole; and a water injector configured to inject water at room temperature or less at a downstream side further than the gas injector in a flow direction of the molten metal, wherein amorphous spherical metallic powder is manufactured after the molten metal passes through the gas injector and the water injector; and some of gas that is supplied to the gas injector is diverted and supplied to the molten metal flowing from the induction coil to the guide.

7. The device of claim 6, wherein some of gas that is supplied to the gas injector is diverted, passes through a pressure relief valve, and is then supplied to the molten metal flowing from the induction coil to the guide.

8. The device of claim 6, further comprising: a heater configured to heat gas to temperature of 300 C. or more; and a pressurizer configured to pressurize the gas heated through the heater to 60 bar or more, wherein the gas pressurized by the pressurizer is supplied to the gas injector, and some of the gas heated by the heater is diverted and supplied to the molten metal flowing from the induction coil to the guide.

9. The device of claim 8, wherein temperature of gas that is injected from the gas injector is 300 C. to 400 C. and pressure of the gas is 60 bar to 100 bar.

10. The device of claim 6, wherein temperature of water that is injected from the water injector is 5 C. or less and pressure of the water is 100 bar to 1000 bar, and a coolant is mixed in the water that is injected from the water injector.

11. The device of claim 6, further comprising a gas barrier installed in the chamber to at least surround molten metal flowing from the induction coil to the guide, wherein some of gas that is supplied to the gas injector is diverted and supplied into the gas barrier.

12. The device of claim 11, wherein the gas that is supplied into the gas barrier is supplied at an angle in a flow direction of the molten metal.

13. The device of claim 11, wherein an anti-outflow portion is formed at an end of the gas barrier to prevent gas from flowing out of the gas barrier in an opposite direction to a flow direction of the molten metal.

14. The device of claim 11, further comprising a separation plate installed in the chamber to divide the chamber into a first chamber in which the induction coil is disposed and a second chamber in which the gas injector is disposed, and having a hole through which the molten metal passes, wherein the gas barrier is installed on the separation plate.

15. The device of claim 6, further comprising a separation plate installed in the chamber to divide the chamber into a first chamber in which the induction coil is disposed and a second chamber in which the gas injector is disposed, and having a hole through which the molten metal passes, wherein some of gas that is supplied to the gas injector is diverted and supplied into the first chamber, and pressure of the first chamber is higher than pressure of the second chamber.

16. The device of claim 6, wherein the water injector can be moved in the flow direction of the molten metal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a graph showing application fields according to particle sizes;

[0031] FIG. 2 is a cross-sectional configuration view showing a VIGA-type moisture injection device using a crucible;

[0032] FIG. 3 is a cross-sectional configuration view showing a composite injection device;

[0033] FIG. 4 is a cross-sectional configuration view showing an EIGA-type composite injection device according to the present disclosure;

[0034] FIG. 5 is a cross-sectional view illustrating the difference in phenomenon when coolant gas and high-temperature gas are injected;

[0035] FIG. 6 is a schematic cross-sectional view illustrating the advantages of a composite injection device using high-temperature gas and water;

[0036] FIG. 7 is a TTT (time-temperature transition) of an Fe-based amorphous alloy;

[0037] FIG. 8 is an XRD result graph examining whether there is an amorphous structure in powder manufactured by high-temperature gas injection and a composite injection device of high-temperature gas and water;

[0038] FIG. 9 is a view showing a device for manufacturing metallic powder according to another embodiment of the present disclosure;

[0039] FIG. 10 is a view showing from above a guide and a gas injector of FIG. 9;

[0040] FIG. 11 is a view showing another embodiment of the device for manufacturing metallic powder of FIG. 9;

[0041] FIG. 12 is a view showing a device for manufacturing metallic powder according to another embodiment of the present disclosure; and

[0042] FIG. 13 is a view showing another embodiment of the device for manufacturing metallic powder of FIG. 12.

DETAILED DESCRIPTION

[0043] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0044] The present disclosure proposes a composite gas/water atomizing that combines gas atomizing and water atomizing to manufacture spherical fine powder. In detail, the present disclosure relates to a device for manufacturing spherical fine powder by injecting a medium of gas or water through two stages.

[0045] A stream is dispersed in a film shape by injecting gas to a metal stream molten at a first state of the composite injection device. The molten metal film is finely crushed and cooled by injecting gas, water, or a mixture of gas and water at a second stage, whereby fine powder is manufactured. This method facilitates mass production of fine powder and is advantageous for amorphization due to a high cooling rate.

[0046] Spherical powder by water injection (see FIG. 2) has the following limitations in manufacturing.

[0047] It is difficult to manufacture fine powder of 20 m or less through a free-fall type. Accordingly, there is a need for a high-pressure water pump. Such a water injection type requires a reduction facility due to oxidation. The oxygen content is still relatively high even though there is such a reduction facility.

[0048] Further, there is a problem that it is impossible to manufacture fine powder when high melting-point metal having a melting point of 1500 or 1600 C. or more is contained or by using highly reactive materials.

[0049] Meanwhile, it is difficult to manufacture spherical powder or fine powder of a nanometer size in manufacturing by gas injection. That is, when the diameter of an orifice is 3 mm or less, there is a limitation in manufacturing due to clogging of a nozzle, and there is the danger of an increase in diameter of the orifice and damage to the orifice when injection is performed for a long period of time.

[0050] Further, it is also a problem that amorphization is difficult due to deficit of a cooling rate. That is, it is impossible to manufacture amorphous spherical powder using metal with a high melting point of 1600 C. or more and highly reactive materials.

[0051] FIG. 3 shows a VIGA gas-water composite injection device (free-fall type/close coupled type). This makes it possible to manufacture spherical powder and is advantageous for amorphization due to a high cooling rate. However, it is difficult to manufacture fine powder. That is, when the diameter of an orifice is 3 mm or less, there is a limitation in manufacturing due to clogging of a nozzle, and there is the danger of an increase in diameter of the orifice and damage to the orifice when injection is performed for a long period of time. Further, when metal having a melting point of 1600 C. or more is contained or highly reactive materials are used, it is impossible to manufacture fine powder.

[0052] FIG. 4 is a cross-sectional configuration view showing an EIGA-type composite injection device according to the present disclosure.

[0053] In the composite injection device, a metal electrode 10 is heated and molten by surrounding it with an induction coil 200, and a first injector 400-1 and a second injector 500-1 are disposed under the induction coil 200, whereby high-temperature gas (gas heated at 300 to 400 C.) is injected from the first injector 400-1, and water, gas, or a mixture of water and gas is injected from the second injector 500-1.

[0054] High-temperature gas is injected to a metal stream primarily molten by the first injector 400-1, whereby the stream is dispersed in a film shape. Molten metal film is finely crushed and cooled by injecting gas, water, or a mixture of gas and water by the second injector 500-1, whereby fine powder is manufactured. This method facilitates mass production of fine powder and is advantageous for amorphization due to a high cooling rate. The first injector makes a temperature range in which molten metal can be maintained in a liquid state, a thin film shape is formed by widely dispersing a molten material by applying high pressure while maintaining a liquid state through high-temperature gas, and the liquid-state film has surface tension, so it is easy to form fine powder without a defect.

[0055] That is, since high-temperature gas is injected at high pressure, fine powder shows a spherical shape and is manufactured into powder with defects minimized. When water injection is applied, the cooling rate is high, which is advantageous for amorphization. This can be replaced by using cooling gas.

[0056] Injection of gas at high temperature and high pressure and water at high pressure or a gas mixture forms a strong jet stream around an injection nozzle, so fine powder can be manufactured. In particular, since high-temperature gas is injected from the first injector 400-1, high pressure can be maintained, whereby the size of molten metal is reduced.

[0057] FIG. 5 is a cross-sectional view illustrating the difference in phenomenon when coolant gas and high-temperature gas are injected. When coolant gas is injected, the cooling rate is high, but the power that is manufactured has large particles and contains satellite powder, and the particle size distribution is not uniform. When high-temperature gas is injected, the cooling rate is low, but the gas injection speed is high, so the impulse is large and the size of particles decreases. The solidification speed is low, so spherical powder is manufactured with less defects. This resultant difference can be seen through pictures.

[0058] FIG. 6 is a schematic cross-sectional view illustrating the advantages of a composite injection device using high-temperature gas and water.

[0059] Since high-temperature gas is injected, as described above, the cooling rate and solidification speed are low and the gas injection speed is high, so the impulse is large and the size of the particles is small, whereby spherical fine powder is manufacture and has the advantage of less defects. Further, since water is injected before solidification while a film shape is formed, the cooling rate is changed to be high and amorphization is achieved. Accordingly, amorphous spherical fine powder can be obtained.

[0060] That is, gas that is injected from the first injector slowly solidifies a metal stream melted at high temperature of 300 to 400 C. and widely disperses it in a film shape. Water, gas, or a mixture of water and gas is injected to the stream of the film-shaped molten material, so the metal film is finely crushed and rapidly cooled, whereby amorphous fine powder is formed in a spherical shape.

[0061] The second injector injects water in this embodiment. The molten metal film formed by injection of high-temperature gas from the first injector makes a situation that is advantageous for formation of spherical powder, and water is injected from the second injector immediately before the molten metal film solidifies, whereby amorphous fine powder can be obtained. Injection from the second injector should be performed before the molten metal film reaches a melting point, and to this end, the time at which the molten metal reaches a melting point is expected and the second injector is disposed in accordance with the falling distance for the time.

[0062] When the first injector and the second injector are disposed at the same height, the second injector may be operated later than the first injector. That is, the first injector and the second injector are operated with a time difference. However, it is preferable to adjust the height for each sequential operation.

[0063] For this, it is possible to refer to the TTT (time-temperature transition) curve of an Fe-based amorphous alloy shown in FIG. 7. It shows entering an amorphous region by changing the path by rapidly increasing the cooling rate by operating the second injector immediately before the cooling line by injector of high-temperature gas and the molting point of metal cross each other.

[0064] The pressure of the gas that is injected from the first injector can be maintained at a high level of 60 to 100 bar due to high temperature and the pressure of water that is injected from the second injector is 100 to 1000 bar. These pressures are maintained almost at the same level even though a mixture of gas and water is injected from the second injector. When only gas is injected from the second injector, gas at low temperature, that is, 20 degrees to the room temperature is injected and the gas pressure is maintained at 20 to 200 bar.

[0065] Meanwhile, control is performed such that the higher the temperature of the gas that is injected from the first injector, the lower the gas supply amount and the gas pressure.

[0066] Further, the higher the melting point of molten metal, the longer the exposure time to the gas that is injected from the first injector, and then it is exposed to injection (water injection, gas injection, or injection of a mixture of water and gas) from the second injector. For example, the disposition gap or the injection time difference that is the height difference of the first injector and the second injector may be large for metal with a high melting point. That is, the first injector and the second injector may be configured in a variable type so that the heights thereof can be adjusted in accordance with the melting point of molten metal, and when they are configured in a fixed type, they can be adjusted through an injection time difference.

[0067] The composite injection device of the present disclosure can continuously supply a metal electrode because there is no orifice, and the injectors can perform injection for a long time. Further, since an orifice is not clogged or a material is not rapidly solidified immediately after it is melted, it is possible to manufacture spherical amorphous fine powder using even materials containing molten metal with a high melting point over 1600 C. or highly reactive materials.

[0068] Fine powder of 20 m or less is obtained over 30% in the powder that is manufactured by this embodiment, so it shows a high yield.

[0069] The gas that is used in the above description is inert gas, nitrogen gas, a gas mixture of inert gas and nitrogen gas, etc. such as Ar.

[0070] FIG. 8 is an XRD result graph examining whether there is an amorphous structure in powder manufactured by high-temperature gas injection and a composite injection device of high-temperature gas and water;

[0071] Powders manufactured by only high-temperature gas show peaks with the characteristics of crystals. Only powder of 20 m or less was found as being amorphous, and an Fcc-Al phase was observed as the size of the powder was increased.

[0072] When high-temperature gas and water were compositely injected in accordance with this embodiment, all of powders of 150 m or less were found as being amorphous.

[0073] FIG. 9 is another embodiment of the present disclosure.

[0074] The device for manufacturing metallic powder of this embodiment includes a chamber 100, an induction coil 200, a guide 300, a gas injector 400, a water injector 500, a separation plate 600, a gas barrier 700, a heater 800, and a pressurizer 900. That is, high-temperature gas of the gas injector 400 corresponding to a first injector is supplied even to a space in which a metal electrode is melted by the induction coil by modifying the embodiment described above. This configuration makes a high-temperature atmosphere in the melting space, so a molten material flows thinly and quickly, thereby increasing the powder manufacturing efficiency.

[0075] The chamber 100 forms a sealed inside. The inside of the chamber 100 is divided into a first chamber 102 at the upper portion and a second chamber 104 at the lower portion by the separation plate 600. In order to make an environment for manufacturing metallic powder, the inside of the chamber is first made into a high vacuum state by taking out the air in the chamber 100 and then the first chamber 102 and the second chamber 104 are filled with inert gas. To this end, first and second gas injection pipes 120 and 140 for injecting inert gas are installed at the first chamber 102 and the second chamber 104, respectively. For example, argon (Ar) may be used as inert gas and nitrogen gas may be used instead of inert gas.

[0076] The induction coil 200 for melting the metal electrode 10 is disposed in the chamber 100, specifically, the first chamber 102.

[0077] Depending on embodiments, two or more induction coils for preheating and melting the metal electrode 10 may be provided to continuously and stably produce molten metal from metal having a high melting point over 1500 C. or 1600 C.

[0078] The metal electrode 10 is moved in the height direction of the chamber 100 by a feeder 200, whereby it can be supplied into the induction coil 200. The feeder 20 may be installed on the chamber 100 to be able to clamp and move the metal electrode 10 in the height direction. In this case, the feeding speed of the metal electrode 10 that is supplied into the induction coil 200 can be adjusted by the feeder 20.

[0079] A first hole 620 through which molten metal M melted by the induction coil 200 passes is formed at the separation plate 600. Further, a second hole 320 through which molten metal M melted by the induction coil 200 passes is formed also at the guide 300 installed under the separation plate 600, and the guide 300 serves to guide molten metal M. Accordingly, molten metal M sequentially passes through the first hole 620 of the separation plate 600 and the second hole 320 of the guide 300 from the induction coil 200.

[0080] As shown in FIG. 10, for example, the guide may be formed in a disc shape and the second hole 320 may be formed at the center of the guide 300.

[0081] The guide 300 has the gas injector 400 that injects high-temperature gas toward molten metal M that has passed through the second hole 320. The temperature of gas that is injected from the gas injector 400 is over 300 C., and particularly, it is preferable that the temperature is in the range of 300 C. to 400 C. Further, it is preferable that the pressure of the gas that is injected from the gas injector 400 is in the range of 60 bar to 100 bar. The gas that is injected from the gas injector 400 may be inert gas such as argon (Ar) or may be nitrogen gas.

[0082] The gas injector 400 may be formed in a ring shape around the second hole 320. Accordingly, high-temperature gas can be injected in all directions of molten metal M.

[0083] The water injector 500 that injects water under the room temperature is disposed at the downstream side further than the gas injector 400 in the flow direction of molten metal M. It is preferable that the pressure of the water that is injected from the water injector 500 is in the range of 100 bar to 1000 bar. When water is mixed with a low-temperature coolant such as ethanol, the temperature of water that is injected from the water injector may be under 5 C. Depending on cases, not only a low-temperature coolant such as ethanol, but an antioxidant, etc. may be mixed with water.

[0084] The effect of forming amorphous spherical fine powder by injecting high-temperature gas and water was described above. In this embodiment, some of the gas that is supplied to the gas injector 400 is diverted and supplied to molten metal M flowing to the guide 300 from the induction coil 200, whereby the manufacturing efficiency is increased. To this end, as shown in FIG. 9, the gas barrier 700 installed in the chamber 100 to surround molten metal M flowing from the induction coil 200 to the guide 300 is provided. The gas barrier 700 may be formed in a cylindrical shape with both open ends and may be installed on the separation plate 600. The gas barrier 700 has a height that can at least surround molten metal M.

[0085] The gas barrier 700 has one or more through-holes 720 for supplying gas. However, the present disclosure is not limited thereto and gas may be supplied though one open end of the gas barrier 700. Accordingly, high-temperature gas makes a high-temperature atmosphere around the induction coil 200, whereby it is possible to prevent molten metal M melted at the induction coil 200 from rapidly solidifying before reaching the guide 300.

[0086] Gas flows in the same direction as the flow direction of molten metal M inside the gas barrier 700, whereby molten metal M can more thinly and quickly flow. That is, flowability of molten metal M toward the guide 300 is improved. Accordingly, even though the size of the metal bar 100 is increased or the metal bar 10 is more quickly supplied into the induction coil 200, it can be processed, so it is possible to more quickly manufacture a large amount of metallic powder.

[0087] The through-hole 720 is formed to be inclined in the flow direction of molten metal M.

[0088] An anti-outflow portion 740 may be further formed at the end of the gas barrier 700 to prevent gas from flowing out of the gas barrier 700 in the opposite direction to the flow direction of molten metal M. In this embodiment, the anti-outflow portion 740 is formed along the edge of the end of the gas barrier 700 and is inclined in the flow direction of molten metal M. Accordingly, gas supplied inside the gas barrier 700 more surely flows in the same direction as the flow direction of molten metal M, whereby molten metal M can more thinly and quickly flow.

[0089] Since high-temperature gas over 300 C. is injected at high pressure from the gas injector 400, the device may further include the heater 800 that heats gas over 300 C. and the pressurizer 900 that pressurizes the heated gas over 60 bar.

[0090] That is, gas is supplied to the gas injector 400 after passing through the heater 800 and the pressurizer 900.

[0091] When some of gas is diverted at the rear end of the pressurizer 800, the gas can be supplied into the gas barrier 700 after passing through a pressure relief valve 1000. Since high-temperature gas that is supplied into the gas barrier 700 makes a high-temperature atmosphere, improves flowability of molten metal M, and makes a water stream thin, gas does not need to be supplied at high pressure, and this is because when gas is supplied at high pressure, the gas may interfere with a uniform stream of a molten material or may damage the induction coil 200.

[0092] However, the present disclosure is not limited thereto, and, as shown in FIG. 11, some of gas heated by the heater 800 may be diverted and supplied into the gas barrier 700. In this case, since the gas is diverted before it is pressurized, the gas is supplied into the gas barrier 700 with only temperature increased. However, even in this case, pressure may be increased over a predetermined level due to an increase in temperature and expansion of the gas, so the pressure relief valve 1000 may be further provided.

[0093] FIG. 12 is another embodiment of the present disclosure.

[0094] This embodiment is characterized in that some of the gas that is supplied to the gas injector 400 is diverted and supplied to molten metal M flowing to the guide 300 from the induction coil 200. However, diverging gas is supplied into the first chamber 102 without the gas barrier 700. The diverging gas can be supplied to the first gas injection pipe 120 connected to the first chamber 102.

[0095] Since some of the gas that is supplied to the gas injector 400 is diverted and supplied into the first chamber 102, the pressure of the first chamber 102 is increased over the pressure of the second chamber 104. Accordingly, high-temperature gas can make a high-temperature atmosphere around the induction coil 200, which enables molten metal M melted at the induction coil 200 to flow well toward the guide 300. For example, the pressure of the second chamber may be a value within the range of 0.010.1 Torr and the pressure of the first chamber 102 may be set as a value that is within the range of 0.021 Torr and lager than the pressure of the second chamber 104. Diverging gas can be supplied to the first chamber 102 without passing through the pressurizer 900 (FIG. 12).

[0096] FIG. 13 shows a configuration in which the water injector 500 is installed in a movable type in the embodiment of FIG. 12. Position can be adjusted by a moving unit such as a rail 510 on the inner wall of the chamber 100. The higher the melting point of molten metal M, the farther the water injector 500 can be adjusted from the gas injector 400. The water injector 500 may be adjusted to be close to the gas injector 400 to obtain fine metallic powder.

[0097] The position adjustment of the water injector 500 may be applied to the embodiment of FIG. 11.

[0098] Unless specifically defined in the above description, all of technological and scientific terms used herein have the same meanings as those that are generally understood by those skilled in the art. Further, terms defined in common dictionaries are not construed ideally or excessively unless specifically clearly defined. Throughout the present specification, unless explicitly described otherwise, comprising or having any components will be understood to imply the inclusion of other components rather than the exclusion of any other components. Further, a singular form may include a plural form by the context.

[0099] Further, in the specification, the term under or beneath includes not only the case when a corresponding object is directly disposed under a target object, but the case when another object exists therebetween.

[0100] Further, in the specification, the term over, on, at the upper portion of, under, or at the lower portion of means that an object is positioned over or under a target object and does not means that the object is necessarily positioned over and under the target object in the gravitational direction.

[0101] Further, in components that are referred to as unit throughout the specification, two or more components may be combined into a single component or a single component may be divided into two or more by detailed functions. Further, each of components to be described hereafter may additionally perform some or all of the function of another component in addition to its main function, and some functions of the main function of each component may be performed exclusively by another component.

[0102] The present disclosure is not limited to the exemplary embodiments described above and defined by claims, and it is apparent to those skilled in the art that the present disclosure may be modified in various ways without departing from the scope of the present disclosure described in claims.