JP5429521B2 - Electrodeposition coating apparatus, electrodeposition electrode, and electrodeposition coating method - Google Patents

Description

  In the present invention, an object to be coated is immersed in a bath of a water-based paint (electrodeposition paint) containing an electrodeposition component, and an electrodeposition component is deposited and applied by applying an electrophoretic phenomenon and electrolysis of water by energization. The present invention relates to an electrodeposition coating method and an electrodeposition coating apparatus.

  An electrodeposition coating method and apparatus are disclosed, for example, in JP-A-8-3788 (Patent Document 1). The electrodeposition coating apparatus disclosed in this publication includes an electrode member on which an object is to be mounted, a transfer head on which the electrode member is mounted so as to be movable up and down, an electrodeposition tank, a power supply unit including a DC power source, etc. With. The electrodeposition tank is filled with a coating electrodeposition solution, and a counter electrode connected to the positive electrode side of the DC power source in the power supply unit is immersed therein. At the time of electrodeposition coating, the electrode member descends and the object to be coated is immersed in the electrodeposition liquid. The electrode member is connected to the negative electrode side of the DC power source, and a predetermined voltage is applied between the electrode member and the counter electrode on the positive electrode side, and the surface of the object to be coated is subjected to cationic electrodeposition coating. In addition, when performing anion electrodeposition coating, it is set as the polarity opposite to the above.

  In the case of a battery case 30 of a non-aqueous electrolyte secondary battery having a flat rectangular parallelepiped shape as shown in FIGS. 6 and 7, electrodeposition is performed on almost the entire inner surface of the case except for the upper end region of the inner surface of the battery case 30. The insulating coating film 31 is formed by painting. In the electrodeposition coating on the inner surface of the battery case 30, it is necessary not to form an insulating coating film on the outer surface of the case and the upper end region of the inner surface of the case, and therefore, disclosed in JP-A-8-3788. When such a general electrodeposition coating method (a method of immersing an object to be coated in an electrodeposition tank) is employed, masking as described below is necessary.

  In one method, after an insulating coating is formed on the entire inner and outer surfaces of the case, masking is applied to the portion (the portion where the coating should be left) except for the upper end region on the inner surface of the case. Remove the membrane. In another method, before the electrodeposition coating, the upper surface area of the case outer surface and the case inner surface is masked, electrodeposition coating is performed in this state, and finally the mask attached to the upper surface area of the case outer surface and the case inner surface is removed.

  In the electrodeposition coating method that requires masking as described above, a step of applying a mask and a step of removing the mask are required, which is complicated.

  Japanese Unexamined Patent Application Publication No. 2007-242602 (Patent Document 2) discloses a method of performing electrodeposition coating on a predetermined region on the inner surface of the battery case without requiring masking. This publication describes the following.

  (A) Since part or all of the inner surface of the battery case is in contact with the outer surface of the power generation element, it is configured not to form a coating, so that current can be collected by contact between the outer surface and the battery case. In addition to obtaining good high-rate discharge characteristics and output characteristics, a film is formed on the other part of the inner surface of the battery case, so that a short circuit between the power generation element and the battery case is reliably prevented. .

  (B) Filling the battery case with the electrodeposition coating composition to a predetermined position, using the battery case 6 as a cathode and taking the anode into the battery case, a liquid temperature of 20 ° C., an applied voltage of 10 V, and an electrodeposition time of 3 Electrodeposition coating was performed under the conditions of minutes. As a result of curing this at 190 ° C. for 20 minutes, the coating thickness of the obtained insulating film was 0.5 μm.

  In the electrodeposition coating method disclosed in the above Japanese Patent Application Laid-Open No. 2007-242602, the battery case, which is the object to be coated, is regarded as an electrodeposition tank, up to a predetermined height position on the inner surface of the case where the electrodeposition liquid is accumulated. Since the electrodeposition is applied, masking as described above is not necessary.

JP-A-8-3788 JP 2007-242602 A

  According to the electrodeposition coating method disclosed in Japanese Patent Application Laid-Open No. 2007-242602, there is an advantage that masking is not required, but there are also points to be improved as described below.

  FIG. 8 schematically shows a state in which the electrodeposition coating is performed with the battery case 30 as an object to be coated as an electrodeposition tank. In the battery case 30, an electrodeposition coating liquid 35 is supplied through a coating material injection pipe 32. Further, the electrodeposition coating liquid 35 in the battery case 30 is sucked and discharged to the outside through the paint suction pipe 33. The paint suction pipe 33 is connected to the power supply unit 34 and functions as an electrode.

  At the time of electrodeposition coating on the inner surface of the battery case 30, many bubbles 36 are generated around the electrode 33 immersed in the electrodeposition coating liquid 35 in the case. The bubbles 36 float up to the liquid surface of the electrodeposition coating liquid 35 and are repelled. As the bubble 36 bursts, the electrodeposition coating liquid may scatter and adhere to the non-coating area. Here, the non-coating region is the upper end region of the inner surface of the case 30 and the upper end surface of the case. In a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery, a battery lid provided with electrode terminals is usually fixed to the upper end surface of the battery case by laser welding. At this time, for example, as shown in FIG. 9, if the scattered electrodeposition coating liquid residue becomes a foreign matter 37 and exists on the upper end surface of the battery case 30, the battery case 30 and the battery lid 38 are completely removed. It will not be welded, and may lead to serious problems such as battery fluid leakage and gas leakage.

  In addition, when pouring the electrodeposition paint liquid into the case, stopping the pouring when the amount of liquid matched to the coating area range is reached, and electrodeposition painting in that state causes the following problems. Arise.

  a) The amount of the insulating coating component (resin amount) contained in the electrodeposition coating liquid collected in the case does not reach an amount sufficient to form a coating film having a predetermined film thickness in a predetermined region on the inner surface of the case.

  b) Therefore, as the electrolytic treatment proceeds, the resin concentration in the liquid decreases, the liquid components fluctuate, and a sufficient film thickness cannot be ensured.

  c) The liquid resistance is increased, the generated electrolytic gas is increased, and the liquid surface is present as bubbles, so that the boundary of the coating is waved and the dimensional accuracy is deteriorated.

  d) When the electrolytic gas bubbles burst, fine droplets scatter and adhere to portions other than the coating region.

  e) The liquid resistance increases, the liquid temperature rises due to electrolytic heat, and the coating uniformity decreases.

  f) The liquid composition fluctuates drastically, resulting in poor liquid stability and a short liquid life.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electrodeposition coating apparatus that performs electrodeposition coating while assuming a non-painted case as an electrodeposition tank. An object of the present invention is to provide an apparatus capable of effectively preventing the scattering of an electrodeposition coating liquid.

  Another object of the present invention is to provide a high-quality coating film by performing a stable electrolytic treatment in an electrodeposition coating method in which a case which is an object to be coated is regarded as an electrodeposition tank for electrodeposition coating. Is to provide a method.

  An electrodeposition coating apparatus according to the present invention is for applying electrodeposition coating to the inner surface of a case, and includes a case, a paint injection portion for injecting an electrodeposition coating liquid into the case, The paint suction part for sucking and discharging the electrodeposition paint liquid, the electrode immersed in the electrodeposition paint liquid in the case, and the electrode and the case are electrically connected to generate electric power for electrodeposition coating. A power supply unit that supplies power and a gas-liquid suction unit that sucks and discharges the surface liquid of the electrodeposition coating liquid injected up to a predetermined height in the case and sucks bubbles floating on the liquid surface.

  According to the present invention having the above-described configuration, the bubbles generated around the electrodes are sucked by the gas-liquid suction part, so that it is possible to suppress the scattering of the electrodeposition coating liquid due to the burst of the bubbles.

  Since many bubbles are generated around the electrode immersed in the electrodeposition coating liquid, it is desirable to dispose the gas-liquid suction part close to the electrode. In a preferred embodiment, the electrode immersed in the electrodeposition coating liquid has an opening window that opens at a height level of the liquid surface of the electrodeposition coating liquid in the case, and the surface liquid of the electrodeposition coating liquid from the opening window. It functions as a gas-liquid suction part that sucks the air bubbles floating on the liquid surface.

  The electrodeposition coating electrode according to the present invention is immersed in the electrodeposition coating liquid accumulated in the case, and has an opening window that opens at a height position of the liquid surface of the electrodeposition coating in the case. The surface of the electrodeposition coating liquid and the air bubbles that float on the liquid surface are sucked from the opening window.

The electrodeposition coating method according to the present invention is a method for applying electrodeposition coating to the inner surface of a case, and includes the following steps.
(A) The process which arrange | positions an electrode in a case and electrically connects this electrode and case through a power supply part.
(B) A step of injecting an electrodeposition paint liquid into the case from the paint injection part.
(C) A step of sucking and discharging the electrodeposition coating liquid from the liquid suction portion so that the liquid level of the electrodeposition coating liquid in the case is constant.
(D) A step of supplying power from the power supply unit to perform electrodeposition coating on the inner surface of the case.
(E) A step of continuously sucking the electrodeposition paint liquid from the liquid suction part while continuously injecting the electrodeposition paint liquid from the paint injection part while performing the above-described electrodeposition coating .
(F) A step of discharging the electrodeposition coating liquid in the case after forming a film on the inner surface of the case.

According to the above method, the electrodeposition paint liquid is continuously sucked from the liquid suction part while continuously injecting the electrodeposition paint liquid from the paint injection part. Such continuous injection and continuous suction are extremely important for quality control. That is, since the liquid state such as the component concentration of the electrodeposition coating liquid in the case can be stably maintained, a high quality coating film can be formed by performing stable electrolytic treatment.
In one embodiment, the liquid suction unit sucks and discharges the surface liquid of the electrodeposition coating liquid and the air bubbles floating on the liquid surface. According to this embodiment, since the bubbles floating on the liquid surface are continuously sucked while keeping the liquid level in the case constant, scattering of the electrodeposition coating liquid due to the burst of the bubbles can be suppressed. .

  Preferably, the electrodeposition coating method further includes a step of drying and heat-curing the coating formed on the inner surface of the case after discharging the electrodeposition coating liquid from the case.

In a preferred electrodeposition coating method, the electrode has an opening window that opens at the level of the surface of the electrodeposition coating liquid in the case so as to function as a liquid suction portion. The surface liquid of the electrodeposition coating liquid and the bubbles floating on the liquid surface are continuously sucked.
In a preferred embodiment, an electrodeposition coating liquid tube disposed in a case is used as an electrode.

It is an illustration figure which shows the electrodeposition coating apparatus which concerns on one Embodiment of this invention. It is an illustration sectional view showing the important section of a preferred form electrodeposition coating electrode. It is an illustration figure which shows the electrodeposition coating apparatus which concerns on other embodiment of this invention. It is an illustration figure which shows one form of a preferable gas-liquid inhalation part. It is an illustration which shows the other example of an electrodeposition coating apparatus . It is a perspective view which shows the battery case which is a to-be-coated object. It is a longitudinal cross-sectional view of the battery case shown in FIG. It is an illustration figure for demonstrating the problem in the conventional electrodeposition coating method and apparatus. It is a figure which shows the state in which the foreign material exists between the upper end surface of a battery case, and a battery cover.

  The present invention relates to an apparatus and a method for performing electrodeposition coating on the inner surface of a case. In the following embodiments, a power source of a portable electronic device such as a mobile computer or a cellular phone is used as a case that is an unpainted object. A battery case of a chargeable / dischargeable flat rectangular parallelepiped nonaqueous electrolyte secondary battery will be described as an example.

  FIG. 1 shows an electrodeposition coating apparatus according to an embodiment of the present invention. This electrodeposition coating apparatus forms an insulating coating film on the inner surface of a battery case, assuming that the battery case 1 which is a non-coating object is an electrodeposition tank for electrodeposition coating.

  The electrodeposition coating apparatus sucks and discharges the battery case 1, the paint injection pipe 2 that functions as a paint injection part for injecting the electrodeposition paint liquid into the battery case 1, and the electrodeposition paint liquid 10 in the battery case 1. The paint suction pipe 3 functioning as a paint suction part for the operation, the electrode pipe 7 functioning as an electrode immersed in the electrodeposition paint liquid 10 in the battery case 1, and the electrode tube 7 and the battery case 1 are electrically connected. And an electric power supply unit 9 for supplying electric power for performing electrodeposition coating.

  The paint injection pipe 2 and the paint suction pipe 3 are fixed to a lower plate 12 disposed in the vicinity of the upper opening of the battery case 1, and the electrode pipe 7 is disposed on the lower plate 12 with a shim 14 interposed therebetween. The upper plate 13 is fixed.

  The paint injection pipe 2 is connected to a discharge pump 4. The electrodeposition paint liquid sent from the electrodeposition paint liquid storage tank to the paint injection pipe 2 via the pump 4 is sent from the lower end opening of the paint injection pipe 2 and poured into the battery case 1. The paint suction pipe 3 is connected to the suction pump 5 via the decompression chamber 6. In order to suck the entire amount of the electrodeposition paint liquid 10 in the battery case 1, the lower end opening of the paint suction pipe 3 is positioned close to the bottom wall of the battery case 1. The suction pump 5 sucks the air in the decompression chamber 6 to bring the decompression chamber 6 into a decompressed state. As a result, the electrodeposition paint liquid in the battery case 1 is sucked from the lower end opening of the paint suction pipe 3 and led to the decompression chamber 6. Although not shown, an open / close valve that opens and closes the flow path leading to the paint injection pipe 2 and an open / close valve that opens and closes the flow path between the paint suction pipe 3 and the decompression chamber 6 are provided.

  In the illustrated embodiment, the electrode tube 7 has an opening window 8 that opens at the level of the liquid level of the electrodeposition coating liquid 10 in the battery case 1. Since the lower end of the electrode tube 7 is also an opening, the electrodeposition coating liquid 10 enters the electrode tube 7 as shown in FIG. The electrode tube 7 is connected to the power supply unit 9 and serves as an anode, and the battery case 1 serves as a cathode. The electrode tube 7 is connected to the suction pump 5 via the decompression chamber 6. Although not shown, an open / close valve for opening and closing the flow path is provided between the electrode tube 7 and the decompression chamber 6. When the pump 5 is operated in a state where the flow path leading to the paint suction pipe 3 is closed and the flow path leading to the electrode pipe 7 is opened, a portion located on the surface of the electrodeposition paint liquid 10 is opened from the opening window 8 of the electrode pipe 7. It is sucked and guided to the decompression chamber 6. At the time of electrodeposition coating, bubbles 11 are generated around the electrode tube 7, but the bubbles 11 floating on the surface of the electrodeposition coating liquid 10 are sucked from the opening window 8 together with the liquid on the surface of the electrodeposition coating liquid 10.

  Electrodeposition coating on the inner surface of the battery case 1 is performed through the following steps.

  First, a plate unit including the lower plate 12, the shim 14, and the upper plate 13 is disposed so as to cover the upper opening of the battery case 1. A paint injection pipe 2 that has been connected to the pump 5 and a paint suction pipe 3 that has been connected to the decompression chamber 6 are fixed to the lower plate 12 in advance. An electrode tube 7 that has been connected to the decompression chamber 6 and connected to the power supply unit 9 is fixed to the upper plate 13 in advance. The position of the opening window 8 of the electrode tube 7 determines the liquid level of the electrodeposition coating liquid 10 accumulated in the battery case 1, and the insulating property formed on the inner surface of the battery case 1 when the electrodeposition coating is completed. It determines the upper end position of the coating film. The height position of the opening window 8 is adjusted by changing the thickness and the number of shims 14 disposed between the lower plate 12 and the upper plate 13.

  Next, the discharge pump 4 is operated to feed the electrodeposition paint liquid into the battery case 1 from the lower end opening of the paint injection pipe 2. During the electrodeposition coating, the flow path between the paint suction pipe 3 and the decompression chamber 6 is closed, and the flow path between the electrode tube 7 and the decompression chamber 6 is kept open.

  When the liquid level of the electrodeposition coating liquid 10 in the battery case 1 reaches a predetermined height position, electric power is supplied from the power supply unit 9 to perform electrodeposition coating. The opening window 8 of the electrode tube 7 opens at the height position of the liquid surface of the electrodeposition coating liquid 10 in the battery case 1.

  While electrodeposition coating was being performed, the electrodeposition paint liquid was continuously injected from the paint injection pipe 2 and floated from the opening window 8 of the electrode pipe 7 to the surface liquid and liquid surface of the electrodeposition paint liquid 10. Aspirate bubbles continuously. By such continuous injection and suction, the concentration and liquid level of the electrodeposition coating liquid 10 in the battery case 1 can be kept constant, and the scattering of the electrodeposition coating liquid due to the burst of bubbles is suppressed. be able to.

  After a predetermined insulating coating film is formed on the inner surface of the battery case 1, the injection of the electrodeposition paint liquid through the paint injection pipe 2 is stopped, and the flow path between the electrode pipe 7 and the decompression chamber 6 is closed. . Further, the supply of power by the power supply unit 9 is stopped.

  Next, the flow path between the paint suction pipe 3 and the decompression chamber 6 is opened, and the entire amount of the electrodeposition paint liquid 10 in the battery case 1 is sucked from the paint suction pipe 3 and led to the decompression chamber 6.

  Thereafter, the battery case 1 is released from the plate unit and moved to the post-processing station. In the post-processing station, the insulating coating film (film) formed on the inner surface of the battery case 1 is dried and heat-cured.

Preferably, an electrodeposition coating liquid tube disposed in the case is used as the electrode. In the embodiment shown in FIG. 1, in addition to the original function as an electrode, the electrode tube 7 also has a function as a gas-liquid suction part that sucks the surface liquid of the electrodeposition coating liquid and bubbles floating on the liquid surface. I played. As another embodiment, a member that functions as a gas-liquid suction part may be provided separately from the electrodes. FIG. 3 shows such an embodiment. In the embodiment shown in FIG. 3, the same reference numerals as those in the embodiment of FIG. 1 indicate the same or equivalent elements, and thus the duplicate description thereof is omitted.

  In the embodiment shown in FIG. 3, the electrode 17 immersed in the electrodeposition coating liquid 10 in the battery case 1 serves only as an electrode and does not function as a gas-liquid suction part. Instead, a gas-liquid suction pipe 18 having a lower end opening disposed at a predetermined liquid level of the electrodeposition coating liquid 10 is disposed. The gas-liquid suction pipe 18 is connected to the decompression chamber 6. Since many bubbles are generated around the electrode 17 during electrodeposition coating, it is preferable to dispose the gas-liquid suction pipe 18 close to the electrode 17.

  In the electrodeposition coating method in the embodiment shown in FIG. 3, when the liquid level of the electrodeposition coating liquid 10 reaches the lower end opening of the gas-liquid suction pipe 18, the surface liquid and bubbles of the electrodeposition coating liquid 10 become the gas-liquid suction pipe. 18 is inhaled. Immediately after the surface liquid is sucked from the gas-liquid suction pipe 18, the liquid level of the electrodeposition paint liquid 10 slightly falls from the lower end opening of the gas-liquid suction pipe 18, but the supply of the electrodeposition paint liquid from the paint injection pipe 2 continues. Therefore, the liquid level of the electrodeposition coating liquid 10 reaches the lower end opening of the gas-liquid suction pipe 18 again, and the same operation as described above is repeated.

  FIG. 4 is another example of the gas-liquid suction pipe. The illustrated gas-liquid suction pipe 19 has a notch 20 at the lower end, and the lowermost end portion is always immersed in the electrodeposition coating liquid 10 in the battery case 1. According to this embodiment, since the notch 20 is always located at the level of the liquid level, unlike the embodiment shown in FIG. 3, the surface liquid and bubbles of the electrodeposition coating liquid 10 are continuously sucked. can do.

In order to confirm the effect of the present invention, the inventor of the present application compared and observed the scattering state of the electrodeposition coating liquid. As a preferred example , the apparatus shown in FIG. 1 was used. For comparison, the apparatus shown in FIG. 5 was also used. In the apparatus shown in FIG. 5, the paint suction pipe 3 whose lower end opening is close to the bottom wall of the battery case 1 also functions as an electrode connected to the power supply unit 9. As with the embodiment shown in FIG. 3, the gas-liquid suction pipe 18 has a lower end opening positioned at a predetermined level of the electrodeposition coating liquid.

  Electrodeposition coating was actually performed, and the adhesion state of the scattered paint in the non-coating formation region at the upper end of the battery case 1 was visually observed.

  In the case of the apparatus shown in FIG. 5, out of the total number 73,041 visually inspected, it was determined that 3,191 were scattered paint on the inner surface of the battery case. The ratio is 4.4%.

  On the other hand, in the case of the apparatus shown in FIG. 1, out of the total number 49,180 visually inspected, it was determined that 948 scattered paint adhered to the inner surface of the battery case. The ratio was 1.9%, and the adhesion rate of the scattered paint was greatly reduced as compared with the apparatus shown in FIG.

  From the above results, the following can be considered. In the apparatus shown in FIG. 5, since the electrode 3 and the gas-liquid suction pipe 18 are located apart from each other, many of the bubbles generated around the electrode 3 are not sucked into the gas-liquid suction pipe 3. It is thought that the remaining parts burst and scattered the electrodeposition paint. Further, since the surface liquid and the bubbles are sucked intermittently by the gas-liquid suction pipe 18, it is considered that the bubble sucking effect is inferior.

On the other hand, in the apparatus shown in FIG. 1, since the electrode 7 itself is provided with the opening window 8 to function as a gas-liquid suction part, most of the bubbles generated around the electrode are removed from the opening window 8. It is thought that it can be sucked. Furthermore, since the surface liquid and the air bubbles are continuously sucked through the opening window 8 without interruption, it is considered that the air bubble sucking effect is good. Note that the apparatus shown in FIG. 5 also has the advantage that the liquid state such as the component concentration of the electrodeposition coating liquid in the case can be stably maintained.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be advantageously used as an apparatus and method that can efficiently and cleanly apply electrodeposition to the inner surface of a case.

DESCRIPTION OF SYMBOLS 1 Battery case, 2 Paint injection pipe, 3 Paint suction pipe, 4 Discharge pump, 5 Suction pump, 6 Decompression chamber, 7 Electrode pipe, 8 Open window, 9 Power supply part, 10 Electrodeposition coating liquid, 11 Bubble, 12 Lower part Plate, 13 Upper plate, 14 Shim, 17 Electrode, 18 Gas-liquid suction pipe, 19 Gas-liquid suction pipe, 20 Notch, 30 Battery case, 31 Insulating coating, 32 Paint injection pipe, 33 Paint suction pipe, 34 Electric power Supply part, 35 Electrodeposition coating liquid, 36 Air bubbles, 37 Foreign matter, 38 Battery cover.

Claims (9)

An electrodeposition coating apparatus for applying electrodeposition coating to the inner surface of a case,
Case and
A paint injection part for injecting an electrodeposition paint liquid into the case;
A paint suction part for sucking and discharging the electrodeposition paint liquid in the case;
An electrode immersed in the electrodeposition coating liquid in the case;
A power supply unit that electrically connects the electrode and the case and supplies power for electrodeposition coating;
An electrodeposition coating apparatus comprising: a gas-liquid suction unit that sucks and discharges the surface liquid of the electrodeposition coating liquid injected to a predetermined height in the case and sucks bubbles floating on the liquid surface.   The electrodeposition coating apparatus according to claim 1, wherein the gas-liquid suction part is positioned in proximity to the electrode.   The electrode has an opening window that opens at a height position of the surface of the electrodeposition coating liquid in the case, and sucks the surface liquid of the electrodeposition coating liquid and bubbles floating on the liquid surface from the opening window. The electrodeposition coating apparatus according to claim 1, which functions as the gas-liquid suction unit. An electrodeposited electrode immersed in an electrodeposition coating liquid collected in the case,
As an air-liquid suction part that has an opening window that opens at the level of the liquid level of the electrodeposition paint liquid in the case, and sucks the surface liquid of the electrodeposition paint liquid and the bubbles floating on the liquid surface from this opening window Electrodeposition electrode that fulfills the functions of An electrodeposition coating method for applying electrodeposition coating to the inner surface of a case,
Disposing an electrode in the case, and electrically connecting the electrode and the case via a power supply unit;
Injecting the electrodeposition paint liquid from the paint injection part into the case;
Sucking and discharging the electrodeposition coating liquid from the liquid suction portion so that the liquid level of the electrodeposition coating liquid in the case is constant;
Supplying electric power from the power supply unit and performing electrodeposition coating on the inner surface of the case;
A step of continuously sucking the electrodeposition paint liquid from the liquid suction part while continuously injecting the electrodeposition paint liquid from the paint injection part while performing the electrodeposition coating;
And a step of discharging the electrodeposition coating liquid in the case after forming a coating on the inner surface of the case. The electrodeposition coating method according to claim 5, further comprising a step of drying and heat-curing a film formed on the inner surface of the case after discharging the electrodeposition coating liquid.   The electrodeposition coating method according to claim 5 or 6, wherein the liquid suction unit sucks and discharges the surface liquid of the electrodeposition coating liquid and the bubbles floating on the liquid surface.   The electrode has an opening window that opens at the level of the liquid surface of the electrodeposition coating liquid in the case so as to function as the liquid suction portion. The electrodeposition coating method according to claim 7, wherein the surface liquid and the bubbles floating on the liquid surface are continuously sucked. The electrodeposition coating method according to claim 5, wherein the electrode disposed in the case functions as a tube for sucking an electrodeposition coating liquid .

Images