Hemming structure of an automobile body

Abstract

To provide a hemming part structure of a vehicle body, capable of suppressing corrosion an outer panel and an inner panel regardless of whether adhesive used in a hemming part is conductive or non-conductive.SOLUTION: A hemming part structure of vehicle body includes: an outer panel 10; an inner panel 20; and adhesive 30 bonding the outer panel to the inner panel. An end part of the outer panel is folded to pack an end part of the inner panel, thereby constituting a hemming part. The adhesive 30 includes a thermally responsive microcapsule 31M containing a two-liquid mixed curable resin A and a thermally responsive microcapsule 32M containing a two-liquid mixed curable resin B. A resin of at least a part of an exposing area of the adhesive is covered with a coating 33 of the two-liquid mixed curable resin.SELECTED DRAWING: Figure 4

Description

【Technical Field】 【0001】 The present invention relates to a hemming portion structure of an automobile body. 【Background Art】 【0002】 Many body components such as a bonnet hood, a door, a fender, a back door, etc. are mounted on an automobile body, and inner panels and outer panels are provided on the inside and outside of the body of each of these components, respectively. As shown in FIG. 7, hemming bending is used as a method for joining the outer panel 10 and the inner panel 20. Further, a method of applying an adhesive 60 to this hemming portion to prevent displacement between the panels is widely adopted. More specifically, after press molding of each panel, hemming bending is performed after applying the adhesive, and then the adhesive is cured during painting baking. Therefore, a thermosetting type adhesive that cures by heating (about 120 to 200°C) is used for this adhesive 60. Further, both conductive and non-conductive adhesives are used for the adhesive 60. The conductive adhesive used for the hemming portion has a carbon-based conductive filler connected in a network in the adhesive to ensure conductivity. 【0003】 As such a hemming bending using an adhesive, Patent Document 1 describes a method for forming a hemming portion of an automobile body, in which a void of the hemming portion of the automobile body composed of an interior panel and an exterior panel having a bent portion covering an edge of the interior panel is filled with an adhesive containing a thermally expandable filler, and the adhesive is expanded by a heat treatment performed for curing of painting to cover an edge portion of the painting. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Patent No. 2582780 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 As shown in Figure 8, the structure of the hemming section is such that the inside 18 of the hemming bend, where the outer panel 10 is folded back, is a closed void in a bag-like structure formed by the inner panel 20 and adhesive 30. In the electrodeposition coating process, this inside 18 of the hemming bend is difficult to electrodeposit because air cannot escape and the electrodeposition solution cannot enter. One method is to fill the inside 18 of the hemming bend with adhesive 60 to prevent the void from forming, but there is a concern that the adhesive 60 may seep out during hemming and adhere to the outer panel 10 or inner panel 20, impairing the appearance or hindering electrodeposition coating and reducing corrosion resistance. 【0006】 On the other hand, the opposite side of the hemming bend interior 18, across from the adhesive 60 (upper side in Figure 8), is open and is the area where electrodeposition solution enters and electrodeposition coating is applied. If the adhesive 60 is conductive, the electrodeposition paint 40 also adheres to the surface of the adhesive 60 during the electrodeposition coating process, making it possible to form the electrodeposition paint 40 without gaps on the surfaces of the outer panel 10, the inner panel 20, and the adhesive 60, resulting in a high corrosion protection effect. However, if water penetrates the hemming bend interior 18 due to driving in the rain, the outer panel 10 and inner panel 20, which are made of steel or aluminum alloy, have a lower potential than the conductive filler in the adhesive 60, which can lead to galvanic corrosion 11 and 21 on the panels, respectively, and there is a concern that this may lead to holes. One way to counter galvanic corrosion is to reduce the amount of conductive filler in the adhesive 60, but this has the problem of reducing the electrical conductivity, which worsens the adhesion of the electrodeposition coating, and thus reduces the corrosion protection effect. 【0007】 Furthermore, as shown in Figure 9, when a non-conductive adhesive 61 is used, galvanic corrosion does not occur inside the hemming bend 18. However, on the open side, the electrodeposited paint 40 does not adhere to the surface of the non-conductive adhesive 61. As a result, a gap is created at the boundary between the non-conductive adhesive 61 and the electrodeposited paint 40 on the surfaces of the outer panel 10 and the inner panel 20, creating a weak point. If water penetrates this weak point, corrosion 12 and 22 occurs on the outer panel 10 and the inner panel 20, which is a problem. 【0008】 Patent Document 1 describes a method to solve the problems of non-conductive adhesives mentioned above by including a thermally expandable filler in the adhesive, so that the adhesive expands during paint curing to cover the weak points. However, there are concerns that thermal expansion may cause deformation of the panel, impairing its appearance or reducing the bonding strength of the hemmed areas. 【0009】 Therefore, in view of the above problems, the present invention aims to provide an automobile body hemming structure that can suppress corrosion of the outer panel and inner panel, regardless of whether the adhesive used in the hemming is conductive or non-conductive. [Means for solving the problem] 【0010】 To achieve the above objective, the present invention provides a hemming section structure for an automobile body comprising an outer panel, an inner panel, and an adhesive for joining the outer panel and the inner panel, wherein the edge of the outer panel is folded back to enclose the edge of the inner panel to form a hemming section, the adhesive comprises a thermoresponsive microcapsule containing liquid A of a two-component mixed curing resin and a thermoresponsive microcapsule containing liquid B of a two-component mixed curing resin, and at least a portion of the exposed portion of the adhesive is covered with a film of the two-component mixed curing resin. [Effects of the Invention] 【0011】 As described above, according to the present invention, the adhesive used to join the outer panel and the inner panel contains a heat-responsive microcapsule containing liquid A of a two-component curing resin and a heat-responsive microcapsule containing liquid B of a two-component curing resin. This allows the portion of the adhesive exposed from the outer and inner panels to be covered with a film of the two-component curing resin, thereby suppressing corrosion. [Brief explanation of the drawing] 【0012】 [Figure 1]This is a flowchart illustrating an example of a method for forming a hemmed section structure of an automobile body according to the present invention. [Figure 2] Figure 1 is a schematic cross-sectional view showing one embodiment of the hemming structure after electrodeposition coating. [Figure 3] Figure 1 is a schematic cross-sectional view showing one embodiment of the hemming structure immediately after paint curing. [Figure 4] Figure 3 is a schematic cross-sectional view showing the hemming structure after the two-component curing resin components A and B have been mixed. [Figure 5] This is a schematic cross-sectional view showing another embodiment of the hemming section structure of an automobile body according to the present invention. [Figure 6] This is a schematic cross-sectional view showing yet another embodiment of the hemming section structure of an automobile body according to the present invention. [Figure 7] This is a schematic diagram showing an example of the hemming structure of an automobile body. [Figure 8] This is a schematic cross-sectional view showing an example of a conventional hemming section structure. [Figure 9] This is a schematic cross-sectional view illustrating another example of a conventional hemming section structure. [Modes for carrying out the invention] 【0013】 Hereinafter, an embodiment of the hemming section structure of an automobile body according to the present invention will be described with reference to the attached drawings. Note that the drawings are illustrated in a way that is simple and clear, and are not necessarily drawn to scale. 【0014】 The hemming structure of the vehicle body according to this embodiment includes an outer panel, an inner panel, and an adhesive for joining the outer panel and the inner panel. The edge of the outer panel is folded back so as to wrap the edge of the inner panel to form a hemming portion. The adhesive includes thermally responsive microcapsules containing a liquid A of a two-component mixed-curing resin and thermally responsive microcapsules containing a liquid B of a two-component mixed-curing resin, and at least a part of the exposed area of the adhesive is covered with a film of the two-component mixed-curing resin. 【0015】 The hemming structure according to this embodiment can be formed, for example, by a hemming portion forming method including a press forming step S1, a hemming step S2, and an electrocoating step S3 as shown in FIG. 1. The hemming step S2 includes two sub-steps: an adhesive application S2-1 and a hemming bend S2-2, and the electrocoating step S3 includes three sub-steps: a water washing / chemical conversion treatment S3-1, an electrocoating S3-2, and a baking of the coating S3-3. 【0016】 The press forming step S1 is a step of press forming an outer panel disposed on the outside of the vehicle body and an inner panel disposed on the inside of the vehicle body into predetermined shapes such as a bonnet hood, a door, a fender, a back door, etc. As materials for the outer panel and the inner panel, for example, a steel sheet or an aluminum alloy sheet can be used. 【0017】 Next, the adhesive application S2-1 in the hemming step S2 is a sub-step of applying an adhesive to the joint between the outer panel and the inner panel. In the adhesive according to this embodiment, microcapsules are dispersed. The base adhesive may be an adhesive generally used for hemming portions, and for example, an epoxy-based adhesive, a phenolic-based adhesive, etc. can be used. The adhesive may be conductive or non-conductive. For example, in the case of conductivity, a conductivity imparting agent such as a carbon-based conductive filler can be contained in the adhesive. Also, the adhesive may be a room temperature curing type or a heat curing type. 【0018】 Microcapsules have a heat responsiveness such that melting or softening occurs upon heating to release their contents. As such heat-responsive microcapsules, for example, phenolic resin microcapsules disclosed in JP-A-7-51560, polyurethane resin microcapsules disclosed in JP-A-6-145421, etc. can be used. The size of the microcapsules is not particularly limited, but for example, those having an average diameter in the range of 50 to 500 μm are used. 【0019】 The response temperature (T3) of the heat-responsive microcapsules is preferably lower than the curing temperature (T1) of the electrodeposition paint used in the electrodeposition coating S3-2 of the electrodeposition coating process S3 described later. Thereby, the contents can be released by the baking S3-3 of the electrodeposition coating process S3. The response temperature (T3) of the heat-responsive microcapsules is preferably, for example, 15°C lower than the curing temperature (T1) of the electrodeposition paint, and more preferably 30°C lower. That is, when T1 is 200°C, T3 is preferably 185°C or lower, and more preferably 170°C or lower. 【0020】 On the other hand, when the base adhesive is a thermosetting type, the response temperature (T3) of the heat-responsive microcapsules is preferably set to a temperature higher than its curing temperature (T2). Thereby, it is possible to prevent the contents of the released microcapsules from mixing with the base adhesive. When a room temperature curing type base adhesive is used, the response temperature (T3) of the heat-responsive microcapsules is preferably higher than room temperature. However, in order to prevent the heat-responsive microcapsules from releasing their contents due to heat response before reaching the baking S3-3 of the electrodeposition coating process S3, for example, 80°C or higher is more preferable, and 120°C or higher is even more preferable. 【0021】 Each microcapsule contains separately encapsulated liquid A and liquid B of a two-component curing resin. The two-component curing resin is not particularly limited as long as it is non-conductive and hardens into a resin when liquid A and liquid B are mixed, but for example, epoxy resins, polyurethane resins, and acrylic resins can be used. Liquids A and B are also called the main component and the curing agent, for example, in the case of epoxy resins. 【0022】 The hemming bend S2-2 in the hemming process S2 is a commonly performed hemming bend, a minor step in which the edges of the outer panel are folded back to wrap around the edges of the inner panel, thereby joining them together. 【0023】 The water washing and chemical treatment S3-1 in the electrodeposition coating process S3 is a small step that involves water washing and chemical treatment, which are commonly performed as pretreatments when performing electrodeposition coating. Water washing removes dirt and oil from the surface of the outer and inner panels, and chemical treatment forms a chemical conversion film on the surface of the outer and inner panels. Examples of chemical treatments include zinc phosphate treatment. 【0024】 Electrodeposition coating S3-2 in electrodeposition coating process S3 is a commonly performed electrodeposition coating process, a small step in which the outer and inner panels are immersed in an electrodeposition tank filled with electrodeposition solution, and an electric current is applied to adhere the electrodeposition paint to the exposed surfaces of the outer and inner panels. For example, cationic electrodeposition paint can be used as the electrodeposition paint. The electrodeposition paint has a curing temperature (T1) of, for example, 120 to 200°C. Figure 2 shows the hemming area when electrodeposition coating S3-2 is performed in this manner. Note that Figure 2 shows the case when a conductive adhesive is used as the adhesive. 【0025】 As shown in Figure 2, in the hemming section, the edge of the outer panel 10 is folded back to enclose the edge of the inner panel 20, and a conductive adhesive 30 is applied between the outer panel 10 and the inner panel 20. The inside 18 of the hemming bend where the outer panel 10 is folded back forms a closed void with a bag-like structure due to the inner panel 20 and the adhesive 30. Dispersed in the adhesive 30 are thermally responsive microcapsules 31M containing liquid A of a two-component mixed curing resin and thermally responsive microcapsules 32M containing liquid B of a two-component mixed curing resin. 【0026】 Electrodeposition paint 40 is applied to the exposed surfaces of the outer panel 10 and the inner panel 20. In Figure 2, since the adhesive 30 is a conductive adhesive, the electrodeposition paint 40 is also applied to the exposed surface of the adhesive 30 by electrodeposition painting S3-2. However, the exposed surface of the adhesive 30 on the inside 18 side of the hemming bend is not coated with electrodeposition paint 40 because the inside 18 is a closed bag structure and the electrodeposition solution does not penetrate it. Then, paint baking S3-3 is performed to cure the electrodeposition paint 40 on the exposed surfaces. 【0027】 The paint baking S3-3 step in the electrodeposition coating process S3 is a standard paint baking step in which the outer panel 10 and inner panel 20 are heated to the curing temperature (T1) of the electrodeposition paint 40 to cure the electrodeposition paint 40 and form an electrodeposition coating film 40C. Figure 3 shows the hemmed section immediately after the paint baking S3-3 step. 【0028】 As shown in Figure 3, when the hemming portion is heated by the paint baking S3-3 and reaches the response temperature (T2) of the heat-responsive microcapsules 31M and 32M, the heat-responsive microcapsules 31M and 32M release their contained contents, liquid A 31 and liquid B 32 of the two-component curable resin, through melting or other means. Then, liquid A 31 and liquid B 32 of the two-component curable resin from the microcapsules near the exposed surface of the adhesive 30 flow out onto the exposed surface of the adhesive 30, leaving the microcapsule cavities 31E and 32E in the adhesive 30. 【0029】 Since the two-component mixed curing resin components A 31 and B 32 do not heat-cur on their own and maintain fluidity, as shown in Figure 4, they mix on the exposed surface of the adhesive 30, undergo a chemical reaction, and harden, forming a resin film 33. In this way, the exposed surface of the adhesive 30 inside the hemming bend 18 is covered with a non-conductive resin film 33, so that even if water penetrates inside the hemming bend 18, the water does not come into contact with the conductive filler in the conductive adhesive 30, thus preventing galvanic corrosion from occurring on the outer panel 10 and inner panel 20. It is not necessary for the entire exposed surface of the adhesive 30 inside the hemming bend 18 to be covered with the resin film 33; even if only a part of the surface is exposed, sufficient protection against galvanic corrosion can be obtained. 【0030】 On the other hand, the exposed surface of the adhesive 30 on the open side, opposite to the inside 18 of the hemming bend, is completely covered with the electrodeposited coating 40C because the adhesive 30 is conductive and the surface is open, thus preventing corrosion. Furthermore, when the electrodeposited coating 40 is attached to the surface of the adhesive 30, the two-component mixed curing resin components A 31 and B 32 cannot pass through the electrodeposited coating 40, so no resin film is formed on the exposed surface of the adhesive 30 on the open side. 【0031】 In this way, galvanic corrosion inside the hemming bend 18 can be prevented, making it possible to increase the amount of conductive filler in the adhesive 30 and increase the electrical conductivity. This improves the adhesion of the electrodeposited paint 40 to the adhesive 30 on the open side, thereby increasing the corrosion protection effect. Furthermore, even with the dispersion of microcapsules 31M and 32M, the volume change of the adhesive 30 is equivalent to that of adhesives generally used in hemming sections, and therefore there is no risk of panel deformation or adhesive overflow. 【0032】 Figures 3 and 4 illustrate the case where the adhesive 30 is conductive, but the present invention is not limited to this, and the adhesive can also exhibit a similarly excellent corrosion prevention effect even if it is non-conductive. The case where a non-conductive adhesive is used will be explained with reference to Figure 5. Figure 5 shows the hemmed portion after paint baking S3-3 has been performed, and the same reference numerals are used for components as in Figures 3 and 4. 【0033】 As shown in Figure 5, on the exposed surface of the adhesive 34 on the open side opposite the hemming bend interior 18, the electrodeposited paint 40 does not adhere during electrodeposition coating S3-2 because the adhesive 34 is non-conductive. Therefore, during paint baking S3-3, on both the hemming bend interior 18 side and the open side, liquid A 31 and liquid B 32 of the two-component mixed curing resin released from the thermally responsive microcapsules 31M and 32M near the exposed surface of the adhesive 34 flow out onto the exposed surface of the adhesive 34, leaving the microcapsule cavities 31E and 32E in the adhesive 34. Since liquid A 31 and liquid B 32 of the two-component mixed curing resin do not heat-cur on their own and maintain their fluidity, they mix and harden on the exposed surface of the adhesive 34, forming a resin film 33 on both the hemming bend interior 18 side and the open side. Therefore, galvanic corrosion inside the hemming bend 18 can be prevented, and even on the open side, the gap that occurs at the boundary between the electrodeposited coating 40C on the surface of the outer panel 10 and the inner panel 20 and the non-conductive adhesive 34 can be sealed with the resin coating 33, thus preventing corrosion from occurring on the panel. 【0034】 Furthermore, while Figures 2 to 5 have described the case in which adhesives 30 and 34 are applied to the outer panel 10 and inner panel 20, the present invention is not limited to this, and for example, as shown in Figure 6, a sheet-shaped adhesive 50 may be used and attached between the outer panel 10 and the inner panel 20. The sheet-shaped adhesive 50 has heat-responsive microcapsules 31M containing liquid A of a two-component mixed curing resin and heat-responsive microcapsules 32M containing liquid B of a two-component mixed curing resin embedded on its sheet surface. 【0035】 As mentioned above, the microcapsules containing the two-component mixed curing resin that forms a resin film through thermal response are located near the exposed surface of the adhesive. Therefore, as shown in Figure 6, the microcapsules can be effectively utilized by providing the thermally responsive microcapsules 31M and 32M only on the surface of the sheet-like adhesive. For even more effective utilization, the thermally responsive microcapsules 31M and 32M may be embedded at both ends of the sheet-like adhesive 50. [Explanation of Symbols] 【0036】 10 Outer Panel 18 Hemming bend inside 20 Inner Panel 30 Conductive adhesive 31, 32 Two-component curing resin: Part A and Part B 31M, 32M thermally responsive microcapsules 33 Resin coating 34 Non-conductive adhesives 40 Electrodeposition paint 50 Sheet-type adhesives 60 Conductive adhesive 61 Non-conductive adhesives

Claims

[Claim 1] A hemming section structure for an automobile body comprising an outer panel, an inner panel, and an adhesive for joining the outer panel and the inner panel, The edge of the outer panel is folded back to enclose the edge of the inner panel, forming a hemmed portion. The adhesive comprises a heat-responsive microcapsule containing liquid A of a two-component curing resin and a heat-responsive microcapsule containing liquid B of a two-component curing resin. The adhesive is a thermosetting adhesive, and its curing temperature is lower than the response temperature of the thermally responsive microcapsules. A hemmed portion structure in which at least a portion of the exposed area of ​​the adhesive is covered with a coating of the two-component mixed curing resin. [Claim 2] The hemming structure according to claim 1, wherein the adhesive contains a conductivity imparting agent, and another portion of the exposed portion of the adhesive is covered with an electrodeposited coating. [Claim 3] The hemming structure according to claim 1 or 2, wherein the adhesive is a thermosetting adhesive sheet, and a thermoresponsive microcapsule containing liquid A of the two-component mixed curing resin and a thermoresponsive microcapsule containing liquid B of the two-component mixed curing resin are embedded on the surface of the thermosetting adhesive sheet.

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