Apparatus for removing progressive bubbles in slurry during coating of secondary battery

Abstract

Since the air bubbles in the slurry should be counted, separate equipment for counting the air bubbles is required, and the mixer should be operated, it is complicated and it takes a lot of time to remove fine air bubbles in the slurry.SOLUTION: The present invention relates to an apparatus for preventing introduction of foreign substances such as bubbles, fine particles, and bubble pockets having various sizes when coating slurry for a secondary battery is coated, and more particularly, to an apparatus for removing foreign substances such as bubbles in the supplied slurry by discharging the foreign substances including bubbles, which progress from a place where the bubbles gather, in various forms and apparatuses when the coating slurry for a secondary battery is supplied.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] [Cross-reference to related application] This application claims priority to Korean Patent Application No. 10-2024-0096689, filed with the Korean Intellectual Property Office on July 22, 2024, the disclosure of which is incorporated herein by reference.

[0002] The present invention relates to an apparatus for preventing the inflow of foreign matter such as air bubbles, fine particles, and air pockets of various sizes when coating a secondary battery coating slurry, and in particular to an apparatus for removing foreign matter such as air bubbles from supplied slurry by discharging the air bubbles and other foreign matter that advance from the areas where the air bubbles accumulate in various forms and devices when supplying a coating slurry for secondary batteries. [Background technology]

[0003] In today's world where electronic technology is rapidly developing, the popularity and popularity of electric vehicles and the growing interest in energy storage technology have led to an expansion of the application field of secondary batteries to medium and large sized batteries in addition to conventional batteries used in common devices such as mobile phones, video cameras and laptops.

[0004] However, there is a need for high energy density not only in batteries used in general electronic devices but also in medium- to large-sized batteries used as power sources for electric vehicles, and lithium secondary batteries have been developed and commercialized to meet this need.

[0005] Secondary batteries undergo several manufacturing processes, where the positive and negative electrodes are coated and dried, then an electrode assembly is formed with a separator sandwiched between the positive and negative electrodes. The battery is then inserted into a battery case of various shapes, and a charge-discharge process is carried out to activate the electrode assembly through multiple charge-discharge cycles.

[0006] In the process of checking electrode quality through charging and discharging, the three major factors that cause electrode defects such as peeling and pinholes on the surfaces of negative and positive electrodes are the progression of large particles, the progression of air bubbles, and the inclusion of foreign matter such as oil, which cause problems in secondary battery electrode products.

[0007] In secondary battery electrode products, it is one of the three major causes of battery fires that occurs in the slurry during secondary battery coating, and it is necessary to remove the bubbles.

[0008] Progressive bubbles can occur in piping connections, such as pumps, supply pipes, elbows, and T-shaped pipes, that mix and supply coating slurry during the electrode coating process. Bubbles can occur during the slurry mixing process, and cavitation in the pumps that supply the slurry can also cause progressive bubbles. Furthermore, due to the nature of coating slurry production and supply, the piping must be thoroughly cleaned before supplying the coating slurry after each electrode production batch, requiring the evacuation of any air remaining in the piping. During this process, bubbles and bubble pockets form in fittings, filters, and storage tanks. These tiny bubbles and bubble pockets in the corners of piping fittings and accessories are then supplied in small amounts along with the slurry, often resulting in defects during the electrode coating process.

[0009] These bubbles can lead to electrode peeling, pinholes, reduced performance, and fires, resulting in serious damage to both manufacturers and consumers.

[0010] Therefore, in order to improve the quality of the electrode, it is essential to remove bubbles generated in the coating slurry. Whether or not bubbles are removed has a significant impact on the production yield and quality of secondary batteries.

[0011] Due to the above-mentioned needs, efforts and research have been made to remove foreign matter such as air bubbles from the slurry used in the production of batteries.

[0012] As an example of the above-mentioned related technology, Korean Patent No. 10-2254336 (registered on May 14, 2021) discloses a method for manufacturing electrode slurry for secondary batteries, which includes an atmospheric pressure degassing process including a process of mixing raw materials for the electrode slurry and storing and transporting the mixed electrode slurry, a process of centrifuging the electrode slurry at atmospheric pressure to remove air bubbles in the electrode slurry as gas components and transferring the degassed electrode slurry to a coater die, and a process of circulating the electrode slurry remaining in the coating process from the coater die to a centrifuge.

[0013] However, the registered patent uses a degassing device including a cylindrical chamber, a raw material supply section, a rotating section, a slurry discharge section, and a degassing gas discharge section. However, the rotating unit requires a separate rotating means, which causes problems such as an economical burden and a complicated device.

[0014] Meanwhile, Korean Patent Publication No. 10-2023-0143049 (published on October 11, 2023) discloses a method for manufacturing electrode slurry, other devices, and electrodes for secondary batteries, which include a step of producing a mixture by mixing raw materials inside a mixer, a step of counting bubbles when transferring the mixture to a storage tank, a step of transferring the mixture from the storage tank to the mixer if the bubble count value is greater than a reference value, and a step of removing bubbles inside the mixer.

[0015] The above-mentioned publication has problems in that it is necessary to count the bubbles in the slurry, which requires separate equipment for counting, and it is cumbersome because it requires operating a mixer, and it takes a long time to remove the fine bubbles in the slurry. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] Korean Patent No. 10-2254336 [Patent Document 2] Korean Patent Publication No. 10-2023-0143049 Summary of the Invention

[0017] The present disclosure aims to separate and discharge bubbles and progressive bubbles that occur in the upper part of any type of device (hereinafter referred to as a "recovery device") equipped with a filter that collects progressive bubbles, large particles, oil bubbles, etc. (hereinafter referred to as "bubbles") in slurry when supplying slurry for manufacturing secondary batteries.Unlike conventional technology, the present disclosure aims to provide a bubble removal device that can guide bubbles upward using the retention speed of a commonly used recovery device and discharge the guided bubbles to the outside without having a separate power source, and also aims to provide a bubble removal device equipped with technology that can open the upper air vent in an emergency, such as when the pressure in the filter suddenly rises during electrode processing or when the bubble removal device does not work.

[0018] According to one aspect of the present invention, there is provided an air bubble removal device that collects air bubbles generated in a slurry during the production of a secondary battery by retaining them in a recovery device when the slurry is supplied and collecting them on the top of a filter. A certain amount of the collected air bubbles (the amount not discharged during the electrode production) is periodically discharged to the outside and removed. The device includes an air bubble discharge unit formed with a plurality of air bubble discharge holes for discharging the air bubbles and preventing the discharge holes from being blocked by progressively large particles or various foreign matter, an air bubble vent hole that opens and closes the upper air bubble discharge hole according to specific gravity and discharges only the accumulated air bubbles, an upper emergency valve that forcibly lowers the air bubble vent hole to urgently release pressure if the air bubble vent hole is closed due to a sudden pressure rise of unknown cause during the production of an electrode coating, and a stopper that maintains the correct position of the emergency valve so that it does not interfere with the vent hole.

[0019] Furthermore, the bubble removal device may include a bubble removal main body portion consisting of a lower fastening portion that fits into the upper nozzle of the recovery device and is housed in the upper portion, and a fastening portion that is fastened to the location at the bottom where the bubbles are recovered, as well as an upper fixing portion that is fixed to the bubble removal main body of the bubble removal main body portion.

[0020] According to the present invention, it is possible to provide an air bubble removal device that can remove air bubbles using only the force of the inflowing slurry, and is economical as it does not require any additional parts or devices. The use of balls with a specific gravity of 1 or less prevents the slurry from scattering outside, thereby preventing potential risks and ensuring stability. The use of a stopper makes it possible to control the pressure of the inflowing slurry and the pressure of the outflowing slurry during filtration, allowing for stable slurry supply with effective electrode coating while removing progressing air bubbles. Furthermore, it reduces labor and is economical compared to conventional methods, and is able to remove air bubbles that have accumulated in the slurry when coating secondary batteries. [Brief explanation of the drawings]

[0021] The above and other aspects, features, and advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings.

[0022] [Figure 1] 1A and 1B are diagrams illustrating a general manufacturing process of a secondary battery and the position of a fixed filter. [Figure 2] 1 is a schematic diagram of an air bubble removal device of the present invention. [Figure 3] FIG. 3 is an exploded perspective view of FIG. 2. [Figure 3A] FIG. 4 is a cross-sectional view taken along line A in FIG. 3. [Figure 3B] FIG. 4 is a cross-sectional view taken along line B in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will now be described in more detail with reference to the accompanying drawings.

[0024] The following description is provided to aid in the understanding and implementation of the present invention, but is not intended to limit the present invention.

[0025] Those skilled in the art will appreciate that various modifications, changes or variations can be made within the scope of the present invention, as set forth in the claims that follow.

[0026] First, in order to understand the reason and necessity for using the present invention in the production of a secondary battery, before describing the present invention in detail, a brief description will be given of the steps from slurry production to coating in the production of a secondary battery.

[0027] FIG. 1 is a schematic diagram showing the arrangement of various recovery devices for removing foreign matter in a slurry preparation step and an electrode coating step as an example of a general secondary battery manufacturing process.

[0028] In addition to the description of FIG. 1 above, in the description of the present invention, detailed descriptions of known components that can be easily understood by a person having ordinary skill in the field to which the technology of the present invention belongs will be omitted.

[0029] Known components include components of slurries used in the manufacture of secondary batteries, and configurations of filters and collection devices used to exhaust gases in slurries common in secondary battery technology.

[0030] To explain the manufacturing process of the secondary battery illustrated in FIG. 1 , the binder 10 prepared in FIG. 1 is continuously mixed through a solution mixer supply pump: Solumix 11 and transferred to a PD mixer 55, in which a foreign matter removal filter is provided.

[0031] In the above, the arrow pointing to the right from the binder 10 indicates forward movement.

[0032] In the binder mixer 20 of FIG. 1, the dotted arrows pointing toward the Solmix 11 below the binder 10 (opposite to the forward direction) indicate mixing lines within the binder mixer 20 where mixing is poor.

[0033] Necessary materials such as solvents are stored in an NMP tank 30 and are simultaneously transferred to the PD mixer 55, and are sent to the binder mixer 20 and pre-dispersion mixer (not shown) as required.

[0034] Conductive material 41, which is a conductive material storage tank necessary for manufacturing secondary batteries, is weighed from weighing hopper 43 through storage hopper 42, transferred to conductive material storage tank 40, and supplied when transferred to PD mixer 55 via foreign matter removal filter F.

[0035] Furthermore, another material, an active material, is transferred from a storage tank 51 to a PD mixer 55 via a weighing hopper 50 and a storage hopper 52 .

[0036] As described above, the PD mixer 55 mixes the raw materials collected in the PD mixer 55 to produce a slurry for a secondary battery, and the produced slurry is transferred to the slurry storage tank 61 or the slurry tank 60. Thereafter, the slurry is circulated by a foreign matter removal filter to remove air bubbles, foreign matter, and metals, and then returned to the coating slurry storage tanks 70 and 70′.

[0037] In the above, if air bubbles, foreign matter, or metals are present in the slurry in the slurry storage tanks 60 and 61, the slurry is repeatedly circulated through the mesh filter F and the magnetic filter. When the slurry dispersion is complete, the slurry is transferred to the coating storage tanks 70 and 70' and supplied through the foreign matter removal filter F.

[0038] Of course, the filters F can be installed in the respective supply pipes or the like.

[0039] The slurry transferred to the coating storage tanks 70, 70' passes through a head tank 80, a coating supply pump, and a foreign matter removal filter F, and is coated with electrodes in a die 90. Thereafter, the slurry is dried to produce negative and positive electrode rolls for secondary batteries, and then transferred to other processes.

[0040] This step is an example and may be performed in other ways, but in any method, filtering is typically performed using a filter F to remove foreign matter such as gas.

[0041] The filtration and collection of bubbles can be performed using various devices including a filter F.

[0042] If air bubbles are present in the slurry passing through the head tank 80 and mold 90, they are continuously degassed by reverse circulation as shown in the figure, but air pockets in piping elbows, valves, fittings, etc. and fine bubbles in the slurry pose a risk of progression.

[0043] The circle indicated by black dots in FIG. 1 represents a recovery device, which is a filter F used to remove foreign matter and metals in the general manufacturing process of secondary batteries.

[0044] In this recovery device, depending on the residence time of the slurry, fine bubbles in the slurry and bubbles generated by cavitation in the pump or air pockets are recovered at the top of the filter, and the recovered bubbles are supplied through piping together with the slurry.

[0045] In the above, when using a general recovery device to remove gas in the slurry by opening the cap on the top of the device to remove bubbles, there is a problem that the operator must wait until the bubbles are removed, and there is also a risk that the slurry inside will spray out from the open hole when removing foreign matter.

[0046] When operating for long periods of time, there may be times when workers are not present. In such situations, air bubbles in the slurry may not be properly discharged, and may migrate along with the slurry, causing defects in electrode production and potentially causing performance degradation or fire during future use of the secondary battery electrode battery.

[0047] Therefore, it is important and absolutely necessary to remove air bubbles, which are foreign matter, from the slurry supplied during secondary battery manufacturing. However, if the slurry supplied to the foreign matter removal filter F and the slurry discharged after filtering to remove air bubbles are successively coated, the internal pressure of the foreign matter removal filter F may change due to the large particles moving forward, which may change the coating density in the direction of movement during electrode coating and adversely affect the quality of the electrode coating.

[0048] One possible method for avoiding the adverse effects on product quality as described above is to maintain a constant pressure within the foreign matter removal filter F so that the supply pressure of the slurry flowing into the foreign matter removal filter F and the supply pressure at which the slurry is filtered and supplied to the mold 90 are constant.

[0049] The inventors have discovered that in the normal manufacturing process of secondary batteries, instead of using the normal filter and upper cap of the recovery device to discharge foreign matter such as air bubbles in the slurry to the outside, air bubbles that are discharged when the inflowing slurry is filtered through the filter and move upward due to the residence time (this is also used to discharge air bubbles in normal methods), can be naturally guided through guide holes and discharged upward.By replacing the upper cap of the normally used filter with a separate component that utilizes the rising air bubbles to prevent the slurry from being discharged to the outside, it is possible to solve the problems with the normally used filter and recovery device.

[0050] FIG. 2 is a schematic diagram of an air bubble removal device 1000 of the present invention.

[0051] In Figure 2, the bubble removal device 1000 comprises a bubble discharge unit 100 that is positioned on the upper side and discharges bubbles, and a bubble removal main body 200 to which the bubble discharge unit 100 is attached and which can house and control the bubble discharge unit 100.

[0052] The bubble discharge unit 100 comprises a bubble discharge hole 120 extending from the top to the bottom, and a bubble discharge pipe 110 formed so as to prevent the bubble discharge hole 120 from being blocked when a bubble removal ball 300 for discharging bubbles in an emergency, as will be described later, is forcibly lowered. A bubble safety discharge vent 130 is connected to the top of the bubble discharge hole 120, communicating with at least both sides, to prevent danger from occurring during the upper discharge operation if a malfunction occurs and slurry is discharged. The bubble discharge hole 120 and the bubble vent 130 are connected to the outside.

[0053] Furthermore, the air bubble removal main body 200 includes an air bubble removal main body 210 and a fastening portion 250, an upper fastening portion 251 of the fastening portion 250 being fastened to the underside of the air bubble removal main body 210, and a lower fastening portion 252 being fastened to the foreign matter removal filter F.

[0054] The bubble removal ball 300 is installed between the upper fastening part 251 of the bubble removal main body 210 and the bubble discharge pipe 110 of the bubble discharge unit 100. When a viscous slurry flows into the bubble removal device 1000, the bubble removal ball 300 utilizes specific gravity to discharge only the air bubbles. The bubble removal ball 300 moves upward and blocks the bubble discharge hole 120 of the bubble discharge pipe 110, preventing the slurry from being discharged. When air bubbles are collected upward due to the residence time of the slurry supplied to the foreign matter removal filter F or the recovery device, the air bubbles are collected below the bubble removal ball 300 via the lower fastening part 252. When the specific gravity is low, the bubble removal ball 300 descends, and only the collected air bubbles are discharged from the bubble discharge unit 100 to the outside.

[0055] FIG. 3 is a detailed view of FIG. 2, and is a perspective view showing the state before the bubble removing device 1000 of the present invention is assembled.

[0056] In FIG. 3, the air bubble discharge unit 100 includes an air bubble discharge pipe 110 extending from above to below as described above, and an air bubble discharge hole 120 for discharging air bubbles is formed inside the air bubble discharge pipe 110.

[0057] Air bubble vents 130 communicating with the air bubble discharge holes 120 are formed on at least both sides of the upper side of the air bubble discharge holes 120, and air bubbles rising from below are discharged upward through the air bubble discharge holes 120 of the air bubble discharge pipe 110, and the air bubbles are discharged to the outside through the air bubble vents 130 communicating with the air bubble discharge holes 120.

[0058] It is preferable that at least two bubble vent holes 130 communicating with the bubble discharge holes 120 are formed in order to smoothly discharge bubbles.

[0059] Furthermore, an O-ring 115 is provided on the underside of the bubble discharge pipe 110, so that the bubble discharge pipe 110 can be more effectively and completely fitted into the opening 220 of the bubble removal main body 200.

[0060] Furthermore, it is preferable to form at least two recesses 121 around the bubble discharge hole 120 at the bottom of the bubble discharge pipe 110, as shown by guideline A in Fig. 4A. When the entire bubble removal device 1000 of the present invention is assembled, a situation arises in which the bubble removal ball 300 may come into contact with the bubble discharge pipe 110. In this case, there is a risk that the bubble removal ball 300 may become clogged in the bubble discharge hole 120 of the bubble discharge pipe 110. Therefore, it is preferable to form two or more recesses 121 to prevent the bubble removal ball 300 from becoming clogged.

[0061] The bubble removal main body 200 of FIG. 3 will now be described in more detail.

[0062] The bubble removal body 200 has an opening 220 formed in the top of the bubble removal body 210 to accommodate the bubble discharge unit 100 .

[0063] The opening 220 is formed to a size that allows the bubble discharge pipe 110 of the bubble discharge unit 100 to fit snugly inside. In this case, the bubble discharge unit 100 is completely housed within the opening 220 of the bubble removal main body 200 via the O-ring 115 attached to the lower part of the bubble discharge pipe 110, and the bubble discharge unit 100 is properly housed and fastened via the upper fastening part 251 of the fastening part 250.

[0064] An O-ring 230 is provided on the vent side where the ends of the bubble discharge pipe 110 housed in the upper part of the bubble removal main body 210 of the bubble removal main body 200 join to form a ball seat 231, and the bubble removal ball 300 is housed within the bubble removal main body 210.

[0065] Therefore, the air bubble removal ball 300 is accommodated and positioned between the end of the upper fastening portion 251 of the fastening portion 250 of the air bubble removal main body 200 and the end of the air bubble discharge pipe 110 .

[0066] The fastening part 250 can be divided into an upper fastening part 251 that is fastened to the lower part of the bubble removal body 210, and a lower fastening part 252 that is fastened to the foreign matter removal filter F or the collection device. A protrusion 253 is formed between the upper fastening part 251 and the lower fastening part 252, and when fastened, the outside of the protrusion 253 is aligned with the bubble removal body 210. An O-ring 254 is provided inside the protrusion 253 to ensure more stable fastening between the fastening part 250 and the bubble removal body 210.

[0067] The fastening part 250 is provided with a bubble guide hole 260 that penetrates the upper fastening part 251 and the lower fastening part 252, and fine guide holes 261 are formed around the bubble guide hole 260 (see FIG. 3B).

[0068] The fine guide holes 261 are formed in a shape that does not come into direct contact with the air bubble removal balls 300, so that the air bubble removal balls 300 do not block the air bubble guide holes 260 to create a vacuum, and the fine guide holes 261 play an auxiliary role in guiding air bubbles upward inside while preventing a vacuum.

[0069] The air bubble removal ball 300 has a specific gravity of less than 1, and therefore can easily move up and down within the ball attachment portion 231 in response to air bubbles generated from the foreign matter removal filter F and the collection device.

[0070] Furthermore, the stopper 400 in Figures 2 and 3 is intended to ensure that when the bubble discharge unit 100 is attached to the bubble removal body 210, the bubble discharge unit 100 and the bubble removal body 210 are not tightly fastened together, but are fastened together at a constant width to control the pressure.This ensures that the inflow pressure and outflow pressure are constant, and the bubble discharge unit 100 can be fastened tightly or slightly loosely via the stopper 400.

[0071] Therefore, the air bubble discharge unit 100 and the air bubble removal body 210 may be made of an elastic material.

[0072] Furthermore, in order to discharge the internal pressure if the pressure inside the foreign matter removal filter F or the recovery device suddenly rises during electrode coating, the stopper 400 is removed, the bubble discharge unit 100 is closed, and the bubble removal ball 300 blocking the bubble discharge hole 120 is forcibly lowered, thereby suppressing the rising pressure.

[0073] Therefore, the air bubble removing device 1000 of the present invention, which is constructed and operates as described above, can be used by being mounted in combination on top of a commonly used foreign matter removing filter F or collection device.

[0074] According to the present invention as described above, the bubble removal device 1000 of the present invention can be used instead of the conventional upper cap to discharge bubbles collected upward in the foreign matter removal filter F or collection device to the outside.

[0075] As described above, according to the bubble removal device 1000 of the present invention, when the slurry flows into the foreign matter removal filter F or the recovery device, is filtered, and is discharged from the slurry discharge port, the air bubbles separated from the slurry move upward along the air bubble guide holes 260 and fine guide holes 261 formed in the fastening portion 250 of FIG. 2, rise via the air bubble removal ball 300 along the air bubble discharge holes 120 formed in the air bubble discharge pipe 110 of the air bubble discharge unit 100 attached to the opening 220 formed in the upper part of the air bubble removal main body 210, and are discharged to the outside through the air bubble vent holes 130.

[0076] Normally, the slurry that flows into the foreign matter removal filter F from the slurry inlet and the recovery device is filtered and discharged from the slurry outlet, and the fine air bubbles that are recovered at this time are discharged from the upper cap.

[0077] When the bubble removal ball 300 is filled with the inflowing slurry, the specific gravity of the bubble removal ball 300 is less than 1, so it easily rises toward the bubble discharge pipe 110 of the bubble discharge unit 100 (dotted line 300 in Figure 2), eliminating the risk of slurry leaking out. The rising bubbles rise along the bubble discharge holes 120 formed in the recess 121 of the bubble discharge pipe 110 and pass through the bubble vent holes 130, so even if the bubble removal ball 300 rises due to the inflow of slurry, there is no problem in discharging the bubbles.

[0078] Furthermore, the bubble discharge unit 100 of the bubble removal device 1000 of the present invention further includes a stopper 400, and by controlling the adhesive strength between the bubble discharge unit 100 and the bubble removal main body 200, the pressure between the slurry inlet and the slurry outlet can be precisely adjusted, and by controlling the shape of the lower fastening part 252 of the fastening part 250, it can be applied to any filter.

[0079] Furthermore, the bubble removal device 1000 of the present invention can remove bubbles using only the force of the slurry supplied during electrode coating, making it an efficient product that does not require any additional unnecessary devices or equipment to remove bubbles from the slurry. [Explanation of symbols]

[0080] 10. Binder 11 Solution mixer supply pump, Solmix 20 Binder Mixer 30 NMP tank 40, 51 Storage tank 41 Conductive materials 42 Storage Hopper 43 Weighing hopper 55 PD Mixer 60, 61 Slurry storage tank 70, 70' Coating Slurry Storage Tank 80 Head Tank 90 Die 100 Air bubble discharge unit 110 Bubble discharge pipe 115 O-ring 120 Bubble discharge hole 121 recess 130 Bubble Vent 200 Air bubble removal main body 210 Air bubble removal unit 220 Opening 231 Ball seat, ball mounting part 250 Fastening part 251 Upper fastening section 252 Lower fastening part 253 Protrusion 260 Bubble guide hole 261 Micro guide hole 300 Air Bubble Removal Balls 400 Stopper 1000 Air bubble remover F Foreign matter removal filter

Claims

1. An apparatus for removing bubbles accumulated in a slurry during coating of a secondary battery, a gas discharge unit having a bubble discharge pipe forming a bubble discharge hole and a bubble vent hole communicating with the bubble discharge hole; an air bubble removal body having an air vent formed on the upper side and configured to accommodate and fit a gas discharge pipe; and an air bubble removal body including a fastening part having an upper fastening part that fits onto the air bubble removal body and a lower fastening part that fits onto a filter or a recovery device on the lower side; an air bubble removal ball located between the air bubble removal pipe of the air bubble removal unit and the upper fastening part of the air bubble removal main body; An apparatus comprising:

2. The device according to claim 1 , wherein a recess is formed around the bubble discharge hole of the bubble discharge unit.

3. The device according to claim 2 , wherein the recess is formed outside the bubble discharge hole.

4. The device according to claim 1 , wherein the fastening portion is formed with a bubble guide hole extending in the vertical direction.

5. The device according to claim 4 , wherein fine guide holes extending vertically are formed around the bubble guide hole.

6. The device of claim 1 , wherein the bubble removal ball is arranged to move up and down.

7. The device according to claim 1 or 6, wherein the bubble removal ball is made to have a specific gravity of 1 or less.

8. The device according to claim 1 , wherein a stopper is attached between the bubble discharge unit and the bubble removal body.

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