JP2007246968A - Electrodeposition coating method for vehicle body panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrodeposition coating method for a vehicle body panel by which efficiency in a coating step is more increased through simple constitution while preventing the occurrence of paint seeds. <P>SOLUTION: The electrodeposition method for a vehicle body panel in which an outer panel and an inner panel are assembled is provided with: an outer panel coating step A20 where an outer panel is electrodeposition-coated; a vehicle body panel assembling step A50 where the outer panel electrodeposition-coated in the outer panel coating step A20 and an inner panel are joined to assemble a vehicle body panel; a vehicle body panel mounting step B20 where, in the vehicle body panel assembled in the vehicle body panel assembling step A50, the inner panel side is connected to a vehicle body; and an inner panel coating step B30 where the inner panel is electrodeposition-coated by energizing to the vehicle body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrodeposition coating method for a vehicle body panel attached to a vehicle body.

  2. Description of the Related Art Conventionally, electrodeposition coating is known as one of methods for undercoating a vehicle body such as a vehicle or an automobile. Electrodeposition coating refers to coating in which a coating is deposited on the surface of an object to be coated using electrophoresis. For example, a conductive object to be coated is immersed in an aqueous solution mixed with water-soluble, water-dispersed paint, and the paint is adsorbed on the surface of the object by energizing the object to be electroded. A film is formed.

  By the way, the body of an automobile is formed by welding and fastening various parts, and the number of parts is enormous. Therefore, in the undercoat coating process as described above, electrodeposition coating is performed in a state where many parts are assembled together. Generally, body panels such as door panels, fender panels, and trunk lid panels are fastened to the body formed by welding pressed steel sheets, and the entire vehicle body is assembled. The whole body is transported up, and the painting process proceeds with full automation. Such a coating method not only improves the efficiency of the painting process and homogenizes the coating film on the entire vehicle body, but also ensures that the welded parts and the fastening parts are primed and rust-proofed between the assembled parts. Can be done.

As a technique related to a method for painting a body panel of an automobile, there is one disclosed in Patent Document 1. That is, in the undercoating process for an automobile door composed of an outer panel and an inner panel, either one of the outer panel or the inner panel is subjected to electrodeposition coating, and before the coating film is baked, one member and the other member Are assembled and assembled, and then the electrodeposition coating is applied again to the assembled assembly, and finally the entire assembly assembly is baked. Thus, by the method of dividing the coating process for each member, an electrodeposition coating film can be formed at the joint portion between the outer panel and the inner panel, and the rust prevention property can be improved.
Japanese Patent Laid-Open No. 2-182898

(1) Occurrence of coating spots By the way, paying attention to chemical changes on the surface of the object to be coated in electrodeposition coating, the surface of the object to be coated in the case of cationic electrodeposition coating with the object to be coated as a cathode (-electrode). On the other hand, in the case of anionic electrodeposition coating in which the object to be coated is an anode (+ electrode), oxygen is generated on the surface of the object to be coated. These hydrogen and oxygen are produced by electrolyzing water (H ₂ O), but in the process of forming a coating film by electrodeposition coating, a minute pinhole is formed on the coating film surface as a path for these gases. Is known to form. This pinhole is almost closed once the coating film is melted in the baking process, and is completely blocked by the intermediate coating and the top coating after the intermediate coating process and the top coating process after the baking process.

  However, pinholes remain on the surface of the object to be coated that has not been baked, and depending on the baking conditions, pinholes may remain until intermediate coating is performed. Therefore, in the method of repeating the electrodeposition coating process twice as in the technique described in Patent Document 1 described above, the paint is granular in the second electrodeposition coating process on the pinhole generated in the first electrodeposition coating process. This may cause a poor appearance (hereinafter simply referred to as “painting”).

In particular, in the technique described in Patent Document 1, since the assembly is performed without baking after the first electrodeposition coating, pinholes on the surface of the member previously electrodeposited It is difficult to improve the appearance quality.
In addition, in FIG. 4, the cross section of the bush 8 which arises on an electrodeposition coating surface is illustrated. First, it is assumed that the pinhole 5 reaching the surface of the article 7 is formed by the first electrodeposition coating process. The protrusion 8 refers to a lump of paint that bulges out from the surface of the coating film 6 around the pinhole 5.

In general, when an uncoated object 7 is energized, an electric field in a direction perpendicular to the surface of the object 7 is uniformly formed along the surface of the object 7. For this reason, the coating film 6 is uniformly formed on the surface of the article 7 to be coated.
However, when power is applied to the object 7 with the pinhole 5 in the second electrodeposition coating, the coating film 6 other than the pinhole 5 formed by the first electrodeposition coating is insulated. Therefore, an electric field is formed radially from the inside to the outside of the pinhole 5. For this reason, after the second electrodeposition coating, the paint concentrates on the pinhole 5 portion and precipitates, resulting in a shape that swells along the shape of the electric field.

In addition, if it is the structure which does not divide | segment the coating process of a to-be-coated object for every member as described in patent document 1, and is electrodeposition coating collectively, it can avoid generation | occurrence | production of such coating flaws. Although it can, the rust prevention process of the junction part of an outer panel and an inner panel is needed, and the process for the work will increase in a manufacturing process.
(2) Electric corrosion Further, when the outer panel and the inner panel are made of different metal materials, it is known that metal corrosion called electric corrosion (dissimilar metal contact corrosion) occurs at the contact portion. Electrolytic corrosion is a phenomenon in which one of the two types of metals that are in electrical contact with each other has a low corrosion potential and is more likely to be oxidized than when they are not in contact with each other. Therefore, when assembling and assembling members made of different metal materials, it is necessary to insulate them from each other and prevent electrical contact in order to prevent electrolytic corrosion.

However, electrodeposition coating is a technique for forming a coating film on the surface of an object to be coated by energization. In order to perform electrodeposition coating, it is necessary to energize each member to deposit paint. For this reason, for example, if the contact portions are insulated, a complicated configuration is required in which each member is individually energized.
The present invention has been devised in view of such problems, and provides an electrodeposition coating method for a vehicle body panel that can improve the efficiency of the painting process with a simple configuration while preventing the occurrence of coating defects. With the goal.

  In order to achieve the above object, an electrodeposition coating method for a vehicle body panel according to the present invention (Claim 1) is an electrodeposition coating method for a vehicle body panel (door panel) formed by assembling an outer panel and an inner panel. An outer panel painting process to be applied, a vehicle body panel assembly process (door panel assembly process) in which the outer panel and the inner panel, which have been electrodeposited in the outer panel painting process, are joined to form the vehicle body panel, and the vehicle body panel assembly process. A vehicle body panel mounting step for connecting and mounting the inner panel side of the assembled vehicle body panel to a vehicle body (body, lower front pillar), and inner panel coating for electrodeposition coating the inner panel by energizing the vehicle body And a process.

  Further, the electrodeposition coating method for a vehicle body panel according to the present invention (Claim 2) includes an outer panel baking step of performing a baking treatment on the outer panel electrodeposited in the outer panel coating step to form a heat treatment layer on the outer panel surface. In the vehicle body panel assembling process, the outer panel and the inner panel formed with the heat treatment layer in the outer panel baking process are joined.

In addition, you may comprise so that the outer panel drying process which performs a drying process to this outer panel may be provided instead of this outer panel baking process. Even in this case, the pinhole on the outer panel surface can be closed.
Further, it is preferable that the outer panel is made of a metal material different from that of the inner panel. Further, it is preferable that the outer panel is made of an aluminum alloy and the inner panel is made of galvanized steel.

According to the electrodeposition coating method for a vehicle body panel of the present invention (Claim 1), since the outer panel and the inner panel are each electrodeposited once, it is possible to prevent the occurrence of coating flaws due to overlapping electrodeposition coating. it can.
In addition, since the outer panel is electrodeposited before the vehicle panel assembling step, it is possible to improve rust prevention at the joint between the outer panel and the inner panel. Moreover, since each panel is electrodeposited once, the coating thickness can be made uniform. Furthermore, the configuration is simple and the productivity of the vehicle panel can be improved.

In addition, according to the electrodeposition coating method for a vehicle body panel of the present invention (Claim 2), the production process of the outer panel and the production process of the inner panel can be separated.
Moreover, a pinhole can be obstruct | occluded by forming the heat processing layer in the surface of an outer panel. As a result, even if the outer panel is energized when the inner panel is energized, the occurrence of coating flaws can be prevented.

Moreover, according to the electrodeposition coating method for a vehicle body panel of the present invention (Claim 3), it is possible to prevent the occurrence of electrolytic corrosion at the joint portion between the outer panel and the inner panel.
Further, according to the electrodeposition coating method for a vehicle body panel of the present invention (Claim 4), the rigidity and strength of the vehicle panel are secured while suppressing the cost by using galvanized steel having high formability as the inner panel. be able to. In addition, by using an aluminum alloy as the outer panel that is nearly flat and simpler than the inner panel, the entire vehicle panel can be reduced in weight while suppressing an increase in cost.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 3 are diagrams for explaining an electrodeposition coating method for a vehicle body panel as an embodiment of the present invention. FIG. 1 is a flowchart showing the electrodeposition coating method, and FIG. FIG. 3 is a perspective view of a vehicle to which the vehicle body panel is applied. In addition, in order to explain the state of the coating surface by electrodeposition, the reference numerals used in FIG.

[Constitution]
The vehicle body panel according to the present invention is applied as a door panel (vehicle body panel) 1 of a vehicle 4 shown in FIG. As shown in FIG. 2, the door panel 1 is composed of an outer panel 1a and an inner panel 1b.
The outer panel 1a is a member formed by processing an aluminum alloy plate, while the inner panel 1b is a member formed by processing a galvanized steel sheet. That is, the outer panel 1a and the inner panel 1b are made of different metal materials.

The outer panel 1a is subjected to hem (clinching) processing, and the end of the inner panel 1b is bent inward while sandwiching the end of the inner panel 1b. That is, both ends of the inner panel 1b are fixed by the bent outer panel 1a.
The outer panel 1a is a member that forms the exterior of the vehicle 4, and has a relatively flat shape. On the other hand, the inner panel 1b is a member that increases the rigidity and strength of the entire door panel 1 and is fixed to the body of the vehicle 4 while supporting the outer panel 1a, and has a relatively complicated uneven shape. In addition, in FIG. 2, the concrete cross-sectional shape of each outer panel 1a and the inner panel 1b is simplified and shown.

The outer panel 1 a and the inner panel 1 b are separately molded and then assembled as a door panel 1. Of these panels 1a and 1b, the outer panel 1a is subjected to electrodeposition coating as an undercoat treatment in a step prior to assembly with the inner panel 1b. On the other hand, the inner panel 1b is electrodeposited after being assembled with the outer panel 1a.
The assembled door panel 1 is fastened and fixed to a lower front pillar (vehicle body) 2 forming a part of the body via a door hinge 3 so as to be rotatable. The door hinge 3 is fastened to the inner panel 1b side of the door panel 1.

[flowchart]
The manufacturing process of the vehicle 1 will be described step by step with reference to FIG. The flow of A10 to A50 in the figure is the production flow of the door panel 1, while the flow of B10 to B50 is the main production flow of the vehicle 4.

The production flow of the door panel 1 mainly includes an outer panel production flow and an inner panel production flow. The outer panel production flow corresponds to the flow of steps A10 to A30, and the inner panel production flow corresponds to the flow of step A40.
First, in the outer panel manufacturing process of step A10, an aluminum alloy plate is press-molded to manufacture the outer panel 1a. The outer panel 1a manufactured at this time is in a state where the end side is not yet hem-processed.

  In the subsequent outer panel coating process of step A20, electrodeposition coating is performed as a primer treatment for the outer panel 1a. That is, here, the outer panel 1a alone is electrodeposited (that is, at the part stage). In this step, a uniform coating film 6 is formed on the surface of the outer panel 1a. In addition, in the formation process of the coating film 6, the pinhole 5 is also formed simultaneously.

In the subsequent outer panel baking process of Step A30, the outer panel 1a is baked, and the coating film 6 on the surface of the outer panel 1a is fixed. At this stage, a coating film (heat treatment layer) 6 having almost no pinhole 5 is formed on the surface of the outer panel 1a. Thereby, the outer panel 1a is electrically insulated by the coating film 6 on the surface.
On the other hand, in the inner panel manufacturing process of Step A40, the inner panel 1b is manufactured by press-forming a galvanized steel sheet. This step is independent of the outer panel production flow. For example, the inner panel 1b is manufactured in a factory different from the factory where the outer panel 1a is manufactured. Also, in the stage of the inner panel manufacturing process, unlike the outer panel 1a, the inner panel 1b is not subjected to undercoating.

  The outer panel 1a and the inner panel 1b manufactured in this way are assembled in the door panel assembly process (vehicle body panel assembly process) in the subsequent step A50. Here, the end portion of the inner panel 1b is sandwiched between the end sides of the outer panel 1a and is hemmed. At this time, in the door panel 1, only the outer panel 1a is electrodeposited, and the inner panel 1b is not subjected to undercoating.

Subsequently, the main production flow of the vehicle 4 will be described.
In the vehicle body assembly process of step B10, the body to which the door panel 1 of the vehicle 4 is attached is assembled. For example, a side frame, a cross member, a pillar, or the like is attached as a sub frame to the monocoque body, and the structure of the vehicle 1 is formed. The lower front pillar 2 shown in FIG. 2 is a member that forms such a structure, that is, a part of the body.

  In the subsequent body panel mounting process of Step B20, the door panel 1 manufactured in the door panel production flow is mounted on the body assembled in Step B10. Here, the door hinge 3 is fastened and fixed to the inner panel 1b side of the door panel 1 using bolts and nuts, and is also fastened and fixed to the lower front pillar 2 of the body. That is, the inner panel 1b side of the door panel 1 is connected to the body.

Subsequently, in the inner panel painting process of Step B30, electrodeposition coating of the entire body to which the door panel 1 is attached is performed. For example, in a painting plant, the body is transported to a dipping carrier, and the entire body is immersed in a painting tank to energize the body.
At this time, both the outer panel 1a and the inner panel 1b are immersed in the aqueous solution of the paint. However, since the outer panel 1a has already been subjected to electrodeposition coating in the outer panel production flow and an insulating layer is formed on the surface, the outer panel 1a (that is, the inner panel of the door panel 1) is formed from the lower front pillar 2 side. Even if energized (to the 1b side), it is not energized to the outer panel 1a side rather than the joint part with the inner panel 1b. Therefore, in this flow, paint is deposited only on the inner panel 1b and the surface of the body.

  Then, in the inner panel baking process of step B40, the inner panel 1b and the body subjected to electrodeposition coating in step B30 are subjected to baking processing, and a uniform coating film is formed on the inner panel 1b and the surface of the body. Thereby, the coating film without a pinhole is formed in the surface of the inner panel 1b. When the electrodeposition coating of the body, the outer panel 1a and the inner panel 1b is completed in this way, the production flow further proceeds to the intermediate coating / priming process of step B50.

[effect]
Thus, according to the electrodeposition coating method for the vehicle body panel, since the outer panel 1a is first electrodeposited in the outer panel painting process, the outer panel 1a can be insulated in the inner panel painting process. Thereby, it is possible to energize only the inner panel 1b side of the door panel 1 in the inner panel painting process. That is, if attention is paid only to the door panel 1, since the outer panel 1a and the inner panel 1b are each electrodeposited once, it is possible to prevent the occurrence of the coating flaws 8 due to overlapping electrodeposition coating.

  Further, prior to assembling the door panel 1 in the door panel assembling process, the outer panel 1a is electrodeposited in advance in the outer panel painting process, so that the rust prevention property at the joint between the outer panel 1a and the inner panel 1b can be improved. it can. In particular, in the present embodiment, the material metal of the outer panel 1a and the inner panel 1b is different, but since it is insulated by the coating film 6 formed in advance on the surface of the outer panel 1a, galvanic corrosion occurs at the joint between the panels. There is no risk of occurrence.

In addition, since the outer panel 1a and the inner panel 1b are electrodeposited once each, the coating thickness can be made uniform.
Further, since the door panel 1 connected to the body is configured to be energized to the inner panel 1b side, for example, the electrodeposition coating can be easily performed by energizing the dipping carrier on which the body is conveyed, and the configuration is simple. Thus, the productivity of the vehicle panel can be improved. In the outer panel production flow, since not only electrodeposition coating of the outer panel 1a but also baking is performed, the pinhole 5 of the coating film 6 formed on the surface of the outer panel 1a in the outer panel coating process can be almost completely blocked. it can.

  Further, the outer panel production flow and the inner panel production flow can be separated in the process. This is particularly effective when the outer panel 1a and the inner panel 1b are manufactured in different factories. For example, when the outer panel 1a is manufactured at an overseas factory and the inner panel 1b is manufactured at a domestic factory, the outer panel 1a is preliminarily treated so that it can be transported from overseas to the domestic market. Rust prevention can be improved and product quality can be improved.

  Furthermore, since galvanized steel having high formability is used as the inner panel, the rigidity and strength of the vehicle panel can be ensured while reducing costs. In addition, by using an aluminum alloy as the outer panel that is nearly flat and simpler than the inner panel, the entire vehicle panel can be reduced in weight while suppressing an increase in cost.

[Others]
Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and various modifications can be made without departing from the spirit of the present invention.
In the above-described embodiment, the outer panel baking process is performed immediately after the outer panel painting process. However, the outer panel 1a is burned to block the pinholes on the surface in advance and is not an essential process. For example, in the outer panel painting process, if the pinhole 5 at the joint portion of the outer panel 1a with the inner panel 1b is of a level that does not hinder the insulation performance, the outer panel baking process is omitted and the outer panel 1a and inner panel are removed in the inner panel baking process. The panel 1b may be baked. That is, if no current is supplied to the outer panel 1a side in the inner panel painting process, it is possible to suppress the occurrence of bumps 8 on the outer panel 1a surface.

  Further, in the above-described embodiment, the case where the outer panel 1a and the inner panel 1b are made of different metal materials is exemplified, but the present invention can also be applied to the case of the same kind of metal.

It is a flowchart which shows the electrodeposition coating method of the vehicle body panel as one Embodiment of this invention. It is sectional drawing (AA sectional drawing of FIG. 3) which shows the vehicle body panel concerning this invention. 1 is a perspective view of a vehicle to which a vehicle panel according to the present invention is applied. It is sectional drawing for demonstrating the coating spot of an electrodeposition coating surface.

Explanation of symbols

1 Door panel 1a Outer panel 1b Inner panel 2 Lower front pillar (vehicle body)
3 Door Hinge 4 Vehicle 5 Pinhole 6 Electrodeposition Paint 7 Paint Object 8

Claims (4)

It is an electrodeposition coating method for a vehicle body panel formed by assembling an outer panel and an inner panel,
An outer panel painting process for electrodeposition coating of the outer panel;
A vehicle body panel assembling step for assembling the vehicle body panel by joining the outer panel and the inner panel that have been electrodeposition-coated in the outer panel painting step;
A vehicle body panel mounting step of connecting the inner panel side of the vehicle body panel assembled in the vehicle body panel assembly step to the vehicle body;
An electrodeposition coating method for a vehicle body panel, comprising: an inner panel coating step of electrodepositing the inner panel by energizing the vehicle body. An outer panel baking step of forming a heat treatment layer on the outer panel surface by subjecting the outer panel electrodeposition-coated in the outer panel coating step to a baking treatment;
2. The method for electrodeposition coating of a vehicle body panel according to claim 1, wherein, in the vehicle body panel assembling step, the outer panel and the inner panel formed with the heat treatment layer in the outer panel baking step are joined. The method for electrodeposition coating of a vehicle body panel according to claim 1 or 2, wherein the outer panel is made of a metal material different from the inner panel. 4. The electrodeposition coating method for a vehicle body panel according to claim 3, wherein the outer panel is made of an aluminum alloy, and the inner panel is made of galvanized steel.

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