Panel bonding structure

Abstract

To suppress deformation of an outer panel.SOLUTION: An adhesive for bonding the inner panel (2) and the outer panel (3) is applied to the bottom side portion (11) and the pair of side edge portions (12) except for a partial side 11a of the bottom side portion (11) on both end sides of the bottom side portion (11), the partial side 11b being located away from a central side 11a of the bottom side portion (11) in the vehicle widthwise direction toward the both end side C2 sides.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a panel bonding structure for bonding an inner panel disposed on the inside of a vehicle to a resin outer panel disposed on the outside of the vehicle. [Background technology]

[0002] BACKGROUND ART In a manufacturing process for exterior panels used in vehicles such as automobiles, an inner panel disposed on the inside of the vehicle and an outer panel disposed on the outside are bonded together with an adhesive.

[0003] For example, Patent Document 1 (JP 2018-167697 A) discloses a technique for bonding the peripheral edges of an inner panel and an outer panel that constitute a back door for a vehicle with an adhesive. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-167697 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in a configuration such as that described above in which the peripheral edges of the inner panel and outer panel are bonded with adhesive, when the temperature of the vehicle rises, for example in the scorching sun of midsummer, the difference in thermal expansion between the inner panel and the outer panel and distortion caused by the restraining force of the adhesive between the two panels can cause the outer panel to deform, resulting in a deterioration in appearance.

[0006] Therefore, an object of the present invention is to suppress deformation of the outer panel. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a panel bonding structure for bonding an inner panel placed on the inside of a vehicle and a resin outer panel placed on the outside of the vehicle, wherein the outer panel has a bottom edge portion extending in the vehicle width direction and a pair of left and right side edge portions extending from both ends of the bottom edge toward the top of the vehicle, and the adhesive for bonding the inner panel and outer panel is attached to the bottom edge portion and the pair of side edge portions, except for portions of the bottom edge portion on both ends of the bottom edge portion that are located away from both ends on either side of the center in the vehicle width direction.

[0008] In this way, in the panel bonding structure according to the present invention, the adhesive is applied to the bottom edge of the outer panel except for the portions at both ends of the bottom edge, so the restraining force of the adhesive can be released in the portions at both ends of the bottom edge where the adhesive is not applied. This makes it possible to suppress part of the distortion (thermal stress) caused by the restraining force of the adhesive between the inner panel and the outer panel when the two panels thermally expand, thereby suppressing deformation of the outer panel. [Effects of the Invention]

[0009] According to the present invention, deformation of the outer panel can be suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is an exploded perspective view showing an example of the configuration of a back door. [Figure 2] 1 is a diagram showing an embodiment of a panel bonding structure according to the present invention. [Figure 3] 10 is a diagram showing the results of an analysis of the degree of deformation occurring in the lower portion of the outer panel when the temperature rises in the embodiment of the present invention and a comparative example. FIG. [Figure 4] 10A and 10B are diagrams showing a panel bonding structure of a back door according to a comparative example. [Figure 5] 10A and 10B are diagrams illustrating thermal stresses occurring in a lower portion of an outer panel according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, the panel bonding structure according to the present invention will be described using a back door provided at the rear of a vehicle such as a standard-sized car or a light car as an example.

[0012] <Backdoor configuration> First, the configuration of a back door to which the panel bonding structure according to the present invention is applied will be described.

[0013] FIG. 1 is an exploded perspective view showing an example of the configuration of a back door.

[0014] The back door 1 shown in FIG. 1 is a flip-up type back door that is attached to the upper rear part of the vehicle via a hinge so as to be able to open and close in the vertical direction.

[0015] The back door comprises, as its main components, a resin inner panel 2 arranged on the inside of the vehicle, a resin outer panel 3 arranged on the outside of the vehicle, and a window section 4. The inner panel 2 is provided with a window opening 2a. The outer panel 3 has an upper section 5 attached to the top of the inner panel 2, and a lower section 6 attached below the upper section 5. The center of the lower section 6 is provided with a license plate attachment section 6a that is recessed toward the inside of the vehicle. The window section 4 has a transparent area that forms the rear window, and is attached so as to cover the window opening 2a of the inner panel 2 between the upper section 5 and the lower section 6.

[0016] <Challenges in panel adhesive structures> Here, the problems associated with the panel bonding structure of a back door will be described based on a comparative example.

[0017] FIG. 4 is a diagram showing a panel bonding structure of a back door according to a comparative example.

[0018] 4, the hatched area indicates the bonding area A between the inner panel 200 and the lower part 600 of the outer panel 300. Although the outer panel 300 has an upper part in addition to the lower part 600, only the bonding area A between the lower part 600 and the inner panel 200 is shown here, and the bonding area between the upper part and the inner panel 200 is omitted.

[0019] As shown in Figure 4, in the comparative example, adhesive is applied to the outer peripheral edges A1 of the inner panel 200 and the lower portion 600, as well as to the lower edge A2 of the window opening 200a and a portion A3 around the center of the lower portion 600, thereby bonding the inner panel 200 and the lower portion 600 together.

[0020] In a panel bonding structure in which two panels, such as an inner panel and an outer panel, are bonded together, a temperature rise between the inner panel and the outer panel generally results in a difference in thermal expansion between the two panels. This difference in thermal expansion and the binding force of the adhesive between the two panels cause thermal stress in the two panels. For example, in the case of a back door, if a vehicle is left in the scorching sun for a long period of time in midsummer, the outer panel located on the outside of the vehicle is likely to become hotter than the inner panel located on the inside of the vehicle, resulting in a difference in thermal expansion between the inner panel and the outer panel. Meanwhile, because the inner panel and the outer panel are bound by an adhesive, a shear force due to the difference in thermal expansion between the two panels and the binding force of the adhesive cause thermal stress in the two panels.

[0021] Some of the strain caused by such thermal stress is absorbed by misalignment between the panels, etc. However, any strain that is not absorbed by misalignment between the panels manifests itself as deformation of the panels.

[0022] In this regard, in the back door according to the comparative example, thermal stress caused by a temperature rise sometimes caused deformation, such as a large dent near the center of the lower part of the lower part 600. Therefore, an analysis of the thermal stress occurring in the lower part 600 according to the comparative example revealed that the deformation occurs due to the following mechanism.

[0023] FIG. 5 is a diagram showing thermal stress occurring in the lower portion of the outer panel according to the comparative example.

[0024] When the temperature of the rear door according to the comparative example rises, thermal stresses (compressive stresses and expansion stresses) F1 to F3, as indicated by the arrows in FIG. 5, are generated in the lower portion of the lower portion 600. First, when the temperature of the rear door rises, compressive stress F1 is generated in the portion B1 at both ends of the lower portion of the lower portion 600. Along with this compressive stress F1, expansion stress F2 is generated in the opposite direction to the compressive stress F1, toward the portion B3 at the lower center. Furthermore, expansion stress F3 is generated from the bonding points B2 at both ends of the lower portion of the lower portion 600 toward the top of the vehicle, and this expansion stress F3 increases the expansion stress F2 toward the portion B3 at the lower center. The increased expansion stress F2 then acts on the portion B3 at the lower center of the lower portion 600 from both sides, causing the portion B3 to be compressed and significantly dented, resulting in a concave deformation.

[0025] As described above, in the back door according to the comparative example, the thermal stress generated when the temperature rises causes a large depression in the lower central portion B3 of the lower portion 600, resulting in a poor appearance.

[0026] Therefore, in order to suppress deformation of the outer panel due to temperature rise, the present invention proposes the following panel bonding structure. Hereinafter, one embodiment of the panel bonding structure according to the present invention will be described using the bonding structure between the inner panel and the outer panel that constitute a back door as an example.

[0027] <One embodiment of the panel bonding structure according to the present invention> FIG. 2 is a diagram showing an embodiment of a panel bonding structure according to the present invention.

[0028] 2, the hatched area indicates a bonding location A between the inner panel 2 and the lower portion 6 of the outer panel 3 in the embodiment of the present invention. Note that the upper portion of the outer panel 3 is omitted in FIG.

[0029] As shown in Figure 2, in this embodiment of the present invention, a location A2 on the upper edge of the lower portion 6, a location A3 around the center of the lower portion 6, and predetermined locations A4 and A5 on the outer periphery of the lower portion 6 are bonded to the inner panel 2 with an adhesive.

[0030] Here, the lower edge portion of the outer periphery of the lower portion 6 extending in the vehicle width direction of the lower portion 6 is referred to as the "bottom portion 11," and a pair of left and right portions extending upward from both ends 11a of the bottom portion 11 are referred to as the "side portions 12." The adhesive is applied to the entirety of each side portion 12 and a portion of the bottom portion 11. Specifically, the adhesive is applied only to a central portion C1 of the bottom portion 11, including the center 11b in the vehicle width direction, and not to portions C2 on both ends of the bottom portion 11, which are located away from the center 11b toward the both ends 11a. That is, in the embodiment of the present invention, the adhesive is applied continuously over the entirety of the central portion C1 of the bottom portion 11 and the pair of side portions 12, except for the portions C2 on both ends of the bottom portion. Note that the adhesive may be applied intermittently (discontinuously) rather than continuously to at least one of the central portion C1 of the bottom portion 11 and the pair of side portions 12. However, the adhesive needs to be discontinued to such an extent that the adhesive strength between the lower portion 6 and the inner panel 2 is ensured.

[0031] As described above, in the embodiment of the present invention, the adhesive is applied to the outer peripheral edge of the lower portion 600 except for the portions C2 on both ends of the bottom side. Therefore, the restraining force of the adhesive is released in the portions C2 on both ends of the bottom side where the adhesive is not applied. As a result, in the embodiment of the present invention, it is possible to suppress the occurrence of expansion stress that promotes concave deformation of the lower portion, as occurs in the comparative example. That is, in the comparative example of FIG. 5, the adhesive is applied along the entire outer peripheral edge of the lower portion 600, so that when the temperature of the back door rises, expansion stress F3 is generated that originates from adhesion points B2 on both ends of the lower part of the lower portion 600 and moves upward toward the vehicle. However, in the embodiment of the present invention, adhesive is not applied to the locations (portions C2 on both ends of the bottom side) that are the origin of such expansion stress F3, so it is possible to suppress the occurrence of expansion stress F3 that promotes concave deformation of the lower portion.

[0032] Fig. 3 shows the results of an analysis of the degree of deformation that occurs in the lower portion of the outer panel when the temperature rises, in an embodiment of the present invention and a comparative example. In Fig. 3, (a) shows the analysis result according to the embodiment of the present invention, (b) shows the analysis result according to the first comparative example, (c) shows the analysis result according to the second comparative example, and (d) shows the analysis result according to the third comparative example. In Figs. 3(a) to (d), the same hatched areas indicate areas that are concavely or convexly deformed to the same degree. In each of Figs. 3(a) to (d), the areas marked with white lines and labeled A are all bonding locations where adhesive is applied.

[0033] First, the first comparative example shown in Fig. 3(b) will be described. Similar to the comparative example shown in Fig. 5, the first comparative example is an example in which adhesive is applied over the entire outer peripheral edge A1 of the lower portion 600. In this case, adhesive is applied over the entire outer peripheral edge A1 of the lower portion 600, causing a large concave deformation in portion B4 of the lower central portion of the lower portion 600, as shown in Fig. 3(b). Furthermore, in this case, portions B5 and B6 of the lower end portions of the lower portion 600 are convexly deformed, protruding outward from the vehicle, in contrast to portion B4 of the lower central portion. This makes the difference in concave and convex shape between the central portion and the end portions in the vehicle width direction more noticeable, deteriorating the appearance.

[0034] In contrast, the embodiment of the present invention shown in FIG. 3(a) can suppress the occurrence of expansion stress that promotes concave deformation of the lower portion 6. That is, in the embodiment of the present invention, as described above, adhesive is not applied to the origin of the expansion stress that promotes concave deformation of the lower portion 6 (portions C2 on both ends of the bottom edge of the lower portion 6), so the occurrence of expansion stress that promotes concave deformation of the lower portion 6 can be suppressed. This makes it possible to suppress concave deformation of portion B7 on the lower center side of the lower portion 6. In particular, in this case, as shown in FIG. 3(a), portion B7 on the lower center side of the lower portion 6 becomes convex in accordance with the convex deformation of portions B8 on both ends of the lower portion, so that the unevenness of the lower portion 6 is less noticeable than in the first comparative example, and deterioration of the appearance is reduced.

[0035] Next, the second comparative example shown in FIG. 3(c) is an example in which adhesive is not applied to the entire lower edge C3 of the outer peripheral edge of the lower portion 600. That is, in the second comparative example, adhesive is applied to portions A6 of both side edges of the outer peripheral edge of the lower portion 600, excluding the entire lower edge C3. In this case, because adhesive is not applied to the entire lower edge C3 of the lower portion 600, when thermal stress occurs due to an increase in the temperature of the back door, as shown in FIG. 3(c), the unadhesive lower edge peripheral portion B9 of the lower portion 600 undergoes a large overall convex deformation across the vehicle width, deteriorating the appearance. Therefore, the second comparative example is not a desirable measure for suppressing deformation of the lower portion.

[0036] Next, a third comparative example shown in FIG. 3(d) is an example in which, contrary to the embodiment of the present invention, adhesive is applied to the outer peripheral edge of the lower portion 600 except for the portion C1 at the center of the lower edge (portion A7 including the portion C2 at both ends). In this case, because adhesive is applied to the portions C2 at both ends of the lower edge of the lower portion 600, expansion stress is generated starting from these adhesive locations (portions C2 at both ends), which promotes concave deformation of the lower portion 600. Therefore, in the third comparative example, a portion B10 at the lower center of the lower portion 600 is significantly depressed and concavely deformed. Furthermore, because no adhesive is applied to the portion C1 at the center of the lower edge, the constricting force of the adhesive is not obtained in the portion B10 at the lower center, and therefore concave deformation occurs significantly. Moreover, in the third comparative example, both portions B11 at both ends of the lower portion of the lower portion 600 are convexly deformed, which makes the difference in concave and convex deformation between the portion B10 at the lower center and the portion B10 at the lower center, which is concavely deformed, even more noticeable, resulting in a worsened appearance.

[0037] From the above, it can be said that in order to effectively suppress deformation of the lower portion of the outer panel and reduce deterioration of the appearance, it is effective to identify the locations that will be the origin of the expansion stress that promotes concave deformation of the lower portion 6 and avoid bonding at those locations, as in the embodiment of the present invention. In this way, with the panel bonding structure of the present invention, by making the locations that will be the origin of the thermal stress that promotes deformation non-bonded, it is possible to suppress the generation of thermal stress that promotes deformation of the outer panel and improve the appearance.

[0038] In the non-bonded areas (portions C2 on both ends of the bottom edge) between the lower portion 6 and the inner panel 2 shown in Figure 2, the lower portion 6 and the inner panel 2 are simply in contact with each other (without being bonded), but if there is a risk of foreign matter such as water entering through the non-bonded areas, a sealing material such as a sponge may be interposed in the non-bonded areas.

[0039] Furthermore, the range of the non-bonded areas (portions C2 on both ends of the bottom side) between the lower portion 6 and the inner panel 2 can be changed as appropriate depending on the shape or rigidity of the tailgate. In the embodiment of Fig. 2, the non-bonded areas start from both ends 11a of the bottom side 11, but the non-bonded areas may start from a position closer to the center 11b than both ends 11a of the bottom side 11.

[0040] Furthermore, in a back door having a symmetrical shape as shown in Fig. 2, thermal stress generally occurs symmetrically, so it is preferable that the non-bonded portions (portions C2 on both ends of the bottom portion) provided on the bottom portion 11 of the outer panel 3 are also symmetrical. That is, as shown in Fig. 2, by setting the left and right non-bonded portions on the lower edge (bottom portion 11) of the outer panel 3 at symmetrical positions with the same width based on the center 11b of the bottom portion 11, the effect on thermal stress is also symmetrical, making it possible to suppress variations in appearance between the left and right sides.

[0041] While the panel bonding structure according to the present invention has been described above using the embodiment shown in Figures 1 and 2 as an example, the panel bonding structure according to the present invention is not limited to being applied to a tailgate having the shape shown in Figures 1 and 2. Even in the case of a tailgate having another shape, as long as the outer panel has a shape that has a bottom edge extending in the vehicle width direction and a pair of left and right side edge portions extending upward from both ends of the bottom edge toward the vehicle, and the outer peripheral edge of the outer panel is bonded to the inner panel, by applying adhesive to only the bottom edge of the outer panel except for the portions on both ends of the bottom edge that are located apart from each other across the center in the vehicle width direction, it becomes possible to suppress deformation of the outer panel due to temperature rise, as in the above embodiment.

[0042] Furthermore, by employing a method similar to that of the present invention, it is possible to similarly suppress deformation of outer panels when temperatures rise in other panel bonding structures. That is, by analyzing the thermal stresses that occur when temperatures rise in the panel bonding structure in question and identifying the bonded locations that are the origins of the thermal stresses that promote deformation, it is possible to suppress the occurrence of thermal stresses that promote deformation by making those bonded locations non-bonded. Therefore, the method of the present invention can be widely applied to a variety of panel bonding structures. [Explanation of symbols]

[0043] 1. Backdoor 2 Inner Panel 3 Outer panel 5 Upper part 6 Lower part 11 Bottom 11a both ends 11b center 12 Side part C1 Central part C2 Bottom end parts

Claims

[Claim 1] A panel bonding structure for bonding an inner panel disposed on the inside of a vehicle to a resin outer panel disposed on the outside of the vehicle, The outer panel has a bottom edge portion extending in the vehicle width direction and a pair of left and right side edge portions extending upward from both ends of the bottom edge portion of the vehicle, A panel bonding structure characterized in that the adhesive that bonds the inner panel and the outer panel is attached to the bottom edge portion and the pair of side edge portions, except for the portions of the bottom edge portion that are located at both ends and separated from each other across the center of the vehicle width direction.

Images