Adhesion joint structure and adhesion joint structure component

Abstract

To provide an adhesion joint structure for maintaining adhesive strength when shearing force is applied, while aiming at a lower cost by reducing an amount used, capable of realizing by one kind of an adhesive agent, and also to provide a component having the adhesion joint structure.SOLUTION: An adhesion joint structure bonds a laminated adherent with an adhesive agent. When a direction to which shearing force is applied is a longer direction and a direction orthogonal to the direction to which the shearing force is applied is a width direction on an adhesion target surface of the adherent, at one end and the other end in the longer direction in an adhesion target region of the adherent, an adhesion joint structure includes: a pair of first adhesion portions with a length in the longer direction of shorter than 1 / 2 a total length of the adhesion target region and continuing across an entire width of the adhesion target region; and a second adhesion portion continuing in the longer direction, with a length in the width direction of shorter than the entire width of the adhesion target region, and connecting the pair of first adhesion portions.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an adhesive joint structure and an adhesive joint structure part of overlapping and bonded joining members, and particularly to an adhesive joint structure suitable for strength members that require strong bonding strength in the automotive field. [Background technology]

[0002] From the perspective of environmental issues, the automobile industry is promoting the weight reduction of vehicle bodies in order to achieve carbon neutrality. In recent years, vehicle weight and costs have tended to increase due to the enhancement of driving assistance functions and improved comfort, so there is a demand for further weight reduction and cost reduction at the same time. Among the various efforts being made to reduce weight, one keyword that is attracting attention is multi-material. Multi-material is a method of achieving weight reduction and performance improvement by combining and using different metals and materials, and aims to use various materials in the right place at the right time. Joining technology is important in mastering the use of different materials, and in addition to spot welding, which has been widely used in the past, laser welding, adhesive joining, riveting, bolt joining, friction stir joining, etc. are adopted according to the application and material, and it is a field of technological development that is attracting attention.

[0003] Of these, adhesive bonding has been adopted in a wide range of fields due to its advantages of being a lightweight method, simple and easy to combine with other bonding methods, and other broad range of applications. Research and development is being conducted to improve performance, enhance functionality, and resolve issues related to performance and adhesive reliability, such as responding to environmental changes.

[0004] Patent document 1 presents a technology in which a soft second adhesive is applied to the adhesive end portion of a lap adhesive joint, which is the starting point of fracture when a shear stress is applied, thereby mitigating the applied stress and achieving high joint strength.

[0005] Patent Document 2 presents a technology in which, in a lap adhesive joint, by providing a recess in the adherend at the corner of the adhesive area, when a shear force is applied, the amount of adhesion is increased at the corner of the adhesive area where stress is concentrated and at the interface between the adhesive and the adherend, and by dispersing the applied stress, interfacial failure is suppressed and cohesive failure of the adhesive is promoted, thereby obtaining a stable high shear strength.

[0006] Patent Document 3 presents a technology in which, in lap adhesive joints, the strength of the adhesive interface is increased by adding anchor particles to the interface between the adhesive and the adherend, resulting in high adhesive strength and high adhesive strength reliability that can suppress a decrease in adhesive strength even when repeated stress is applied.

[0007] Patent Document 4 presents a technology for the joining structures of the outer and inner pillar lowers and side sill inners of an automobile, in which adhesive is applied in vertical stripes along the component shapes of the mating flange surfaces, which are the adhesive joints, thereby ensuring rigidity with the minimum amount of adhesive applied while achieving cost reduction by reducing the amount of adhesive used. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2020-180684 A [Patent Document 2] JP 2017-1341 A [Patent Document 3] JP 2018-69658 A [Patent Document 4] JP 2009-1084 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, when attempting to apply the above-mentioned conventional techniques to the bonding of steel sheets for automobiles, the following problems arise.

[0010] The technology described in Patent Document 1 has a cost issue due to the increased amount of adhesive used, and further has production issues such as maintenance and management of the adhesive and complicated production process due to the diversification of adhesives. The technology described in Patent Document 2 requires a process of providing depressions on the surface of the adherend, which has production and cost issues due to the increased number of steps. The technology described in Patent Document 3 has a cost issue due to the increased material cost of using anchor particles. The technology described in Patent Document 4 is a technology related to optimizing the bonding position with a focus on the rigidity of the joint. Compared to bonding the entire flange area, this technology significantly reduces the amount of adhesive used, making it difficult to prevent a decrease in adhesive strength.

[0011] The present invention was developed in consideration of the above-mentioned problems associated with the conventional technology, and its purpose is to provide an adhesive joint structure that can be implemented using a single type of adhesive, and that maintains adhesive strength when subjected to a shear force load while aiming to reduce costs by reducing the amount of adhesive used, and a component having this adhesive joint structure. [Means for solving the problem]

[0012] The adhesive joint structure according to the present invention, which advantageously solves the above problems, is configured as follows.

[0013] [1] In an adhesive joint structure in which overlapping adherends are joined with an adhesive, the direction in which shear force is applied on the adhesion surface of the adherend is defined as the longitudinal direction, and the direction perpendicular to the direction in which shear force is applied is defined as the width direction, and the adhesion area of ​​the adherend has a pair of first adhesive sites at one end and the other end in the longitudinal direction, the length of which is shorter than half the total length of the adhesion area and which are continuous across the entire width of the adhesion area, and a second adhesive site which is shorter in the width direction than the entire width of the adhesion area and which is continuous in the longitudinal direction connecting the pair of first adhesive sites. [2] In the above [1], the second adhesive site is an adhesive joint structure having a plurality of second adhesive sites, the total widthwise length of which is shorter than the overall width of the adhesive target area. [3] In the above [1], the second adhesive sites are provided in pairs at both ends of the adhesive target area, and the total widthwise length of the second adhesive sites is shorter than the overall width of the adhesive target area, forming an adhesive joint structure. [4] In the above [1] to [3], the adhesive joint structure is one in which 55 to 90% of the bonding area of ​​the adherends is the bonding site.

[0014] A component having an adhesive joint structure according to the present invention, which advantageously solves the above problems, is configured as follows. [5] An adhesive joint structural component having the adhesive joint structure described in any one of [1] to [4] above. Effect of the Invention

[0015] According to the present invention, in an adhesive lap joint structure, by efficiently bonding the bonding area when a shear force is applied, it is possible to reduce the amount of adhesive used while maintaining the adhesive strength. Although the effect of reducing the amount of adhesive used is mainly cost reduction, it also contributes to weight reduction, and can be said to be an effective measure against the recent trend of increasing vehicle body weight and cost. In addition, it can be implemented with one type of adhesive, and furthermore, it can be easily applied with existing adhesives, and there is no complication of the process, so the impact on production is minor, and it is also advantageous in terms of the cost of introducing the technology. [Brief description of the drawings]

[0016] [Figure 1] 1A is a schematic diagram showing the adhesion target area and standard adhesion range of the adherend, and the longitudinal and transverse directions of the adherend, and FIG. 1B is a schematic diagram showing a pair of widthwise continuous adhesion sites (first adhesion sites) at both longitudinal ends of the adhesion target area of ​​the adherend, and a pair of longitudinally continuous adhesion sites (second adhesion sites) connecting the first adhesion sites, according to the present embodiment. [Diagram 2](a) is a schematic diagram showing the adhesion sites at the periphery of the adhesion target area. (b) is a schematic diagram showing a pair of widthwise continuous adhesion sites (first adhesion sites) at both longitudinal ends of the adhesion target area of ​​the adherend according to the present embodiment, and a pair of longitudinal continuous adhesion sites (second adhesion sites) connecting the first adhesion sites. (c) is a schematic diagram showing a pair of widthwise continuous adhesion sites (first adhesion sites) at both longitudinal ends of the adhesion target area of ​​the adherend, and a longitudinal continuous adhesion site (second adhesion site) connecting the first adhesion sites only at one widthwise end of the adhesion target area. [Diagram 3] FIG. 2 is an explanatory diagram of a tensile shear adhesive strength test method. [Figure 4] 1 is a graph showing the effect of adhesive area ratio (H-shaped and rectangular adhesive sites) on shear strength in a tensile shear adhesive strength test. [Diagram 5] 1 is a graph showing the effect of the adhesion area ratio (periphery and rectangular adhesion area) on shear strength in a tensile shear adhesion strength test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The adhesive joint structure according to this embodiment will be described below. The adhesive joint structure of this embodiment has, in the adhesive region of the adherend, a pair of first adhesive sites at one end and the other end in the longitudinal direction, the longitudinal length of which is shorter than half the total length of the adhesive region and which are continuous across the entire width of the adhesive region, and a second adhesive site which is longitudinally continuous and connects the pair of first adhesive sites and has a widthwise length shorter than the entire width of the adhesive region.

[0018] FIG. 1 shows the adhesive area in an adhesive joint structure according to one embodiment of the present invention. In Fig. 1(a), the shaded area indicates the bonding range (bonding site) in the bonding target area. In this conventional example, the entire bonding target area is the bonding range, and this bonding range is called the standard bonding range. In conventional adhesive joint structures, the bonding range shown in Fig. 1(a) is used. 1(b) shows an example of the adhesive application range in an adhesive joint structure according to the present embodiment, which has widthwise continuous adhesive regions at both ends in the longitudinal direction of the region to be bonded, and further has a longitudinally continuous adhesive region that is continuous from one end to the other end in the longitudinal direction at the widthwise center position of the region to be bonded. This adhesive joint structure has a pair of first adhesive regions at one end and the other end in the longitudinal direction of the region to be bonded of the adherend, whose length in the longitudinal direction is shorter than half the total length of the region to be bonded and that are continuous across the entire width of the region to be bonded. Furthermore, it has a second adhesive region that is widthwise shorter than the entire width of the region to be bonded and that is continuous in the longitudinal direction connecting the pair of first adhesive regions. In this case, the adhesion site in the adhesion target area of ​​the adherend, when viewed from directly above the adherend, is H-shaped, with the longitudinal direction being the horizontal direction of the H. Here, the direction in which shear force is applied on the adhesion target surface of the adherend is defined as the longitudinal direction, and the direction perpendicular to the direction in which shear force is applied is defined as the width direction.

[0019] Figures 2(a) to (c) show another example of an adhesive application area in an adhesive joint structure according to this embodiment, in which a pair of widthwise continuous first adhesive sites, each of which has a longitudinal length at one end and the other end that is shorter than half the total length of the area to be bonded and which is continuous across the entire width of the area to be bonded, is used as a base, and the number of longitudinally continuous adhesive sites (second adhesive sites) connecting the pair of first adhesive sites and the adhesive pattern of the bonding positions are changed. In the adhesive joint structure of FIG. 2(a), the adhesive site in the region to be bonded of the adherend is the outer periphery of the region to be bonded, and is square-shaped when viewed from directly above the adherend. The adhesive joint structure in Figure 2(b) is an example having a plurality of longitudinally continuous adhesive sites (second adhesive sites) connecting a pair of first adhesive sites, and the adhesive sites in the bonding target area of ​​the adherends form a ladder shape when viewed from directly above the adherends. The adhesive joint structure of FIG. 2(c) is an example in which a longitudinally continuous adhesive region (second adhesive region) connecting a pair of first adhesive regions is provided only at one end in the width direction of the adhesive region. <Assumptions regarding the shape of the area to be bonded> It is assumed that the adhesion target area, the first adhesion site, and the second adhesion site shown in Figures 1 and 2 are rectangular. However, the corners of these rectangular shapes may be rounded as appropriate, taking into consideration the adhesive application method and the required adhesive strength. Figures 1 and 2(a) show examples in which the corners are rounded.

[0020] <Area ratio of adhesive area> A tensile shear adhesive strength test was conducted to investigate the effect of the adhesive area ratio on the maximum load. The results are explained below. Fig. 3 is a schematic diagram of the tensile shear adhesive strength test method. Among the areas where the adherends overlap, the area indicated by reference numeral 3 is the area to be bonded. An adhesive is applied to the bonding area 3, and two adherends 2 are stacked and bonded together. Then, using a tensile tester, the adherend 2 is pulled in the direction of the arrow indicated by the symbol 4, and the tensile stroke, maximum load, etc. are evaluated. In the test method of Fig. 3, an example of a test material having an area to be bonded is 12.5 mm in the longitudinal direction and 16.0 mm in the width direction. Here, the adhesive area ratio refers to the ratio (%) of the area to which the adhesive is applied to the area to be bonded.

[0021] Table 1 shows the test results for the adhesive application shape when it is rectangular and when it is H-shaped according to the present invention. In Table 1, No. 1 is the case where the adhesive is applied to the entire surface of the adhesion target area. For other conditions where the adhesive shape is rectangular, the width and longitudinal application length of the adhesive were variously changed so that the adhesive area ratio becomes the value in Table 1. When the adhesive shape of No. 2 to No. 5 is H-shaped, the adhesive application length BL in the first adhesion region and the adhesive application width BW in the second adhesion region (see FIG. 1(b) for BL and BW) are adjusted to be equal lengths so that the adhesive area ratio becomes the value in Table 1.

[0022] FIG. 4 shows the effect of the adhesive area ratio on the maximum load in a tensile shear adhesive strength test. The maximum load ratio, which is the vertical axis in Figure 4, is the ratio (%) of the maximum load under each condition based on the maximum load under condition No. 1 (condition in which the adhesive was applied to the entire surface of the adhesive target area in a rectangular shape). In FIG. 4, circles (◯) indicate the case where the adhesive is applied in a rectangular shape, and black diamonds (◆) indicate the case where the adhesive is applied in an H-shape. These results show that with the same adhesive area ratio, the maximum load is higher when the adhesive is applied in an H-shape than when the adhesive is applied in a rectangular shape.

[0023] [Table 1]

[0024] Table 2 shows the test results for the adhesive application shape, when it is rectangular and when it is squared according to the present invention. In Table 2, No. 1 is the case where the adhesive is applied to the entire surface of the area to be bonded. For other conditions where the adhesive shape is rectangular, the width and longitudinal application length of the adhesive were changed in various ways so that the adhesive area ratio becomes the value in Table 1. When the adhesive shape of No. 2 to No. 5 is squared, the adhesive application length BL in the first adhesive region and the adhesive application width BW in the second adhesive region (see FIG. 1(b) for BL and BW) are adjusted to be equal lengths so that the adhesive area ratio becomes the value in Table 2.

[0025] FIG. 5 shows the effect of the adhesive area ratio on the maximum load in a tensile shear adhesive strength test. The maximum load ratio, which is the vertical axis in Figure 5, is the ratio (%) of the maximum load under each condition based on the maximum load under condition No. 1 (the condition in which the adhesive was applied to the entire surface of the adhesive target area in a rectangular shape). In FIG. 5, a circle (◯) indicates the case where the adhesive is applied in a rectangular shape, and a black square (■) indicates the case where the adhesive is applied in a square shape. These results show that, with the same adhesive area ratio, the maximum load is higher when the adhesive is applied in a square shape than when the adhesive is applied in a rectangular shape.

[0026] [Table 2]

[0027] The smaller the adhesive area of ​​the adherend to the adhesion target area, the lower the absolute value of the adhesive strength (shear stress). Therefore, in order to maintain the adhesive strength, it is preferable to allow a decrease in adhesive strength of up to 10% based on the case where the adhesive is applied to the entire adhesion target area and adhered, and to set the area ratio of the adhesive part to the adhesion target area to 55% or more. From the viewpoint of ensuring adhesive strength, the area ratio of the adhesive part to the adhesion target area is more preferably 60% or more, and even more preferably 65% ​​or more.

[0028] When the adhesive is applied in an H-shape or a square shape and the surface area of ​​the adhesive is 65% or more, it is believed that the strength will be roughly the same as when the adhesive is applied to a standard rectangular adhesive area. In order to ensure a cost reduction effect by reducing the amount of adhesive used by 10% or more, it is preferable to set the adhesion area of ​​the adhesion site to 90% or less of the standard adhesion range (area to be adhered).

[0029] In addition, if there are some parts where the width of the adhesive applied to the bonded portion is extremely narrow, the load will be concentrated at that part, which may lead to early breakage. Therefore, in order to ensure the adhesive strength, it is preferable that the adhesive application width is 1 mm or more.

[0030] In actual production, when applying adhesive using a gun on a robot, for example, it is preferable to apply the adhesive in the specified shape by shaping the nozzle tip into a specified application shape (H-shape) and extruding the adhesive, or by using a nozzle tip shaped like a normal pen tip to draw multiple lines.

[0031] In the case of a method in which the tip nozzle is shaped to a predetermined application shape and extruded, various adhesion ranges can be accommodated by changing the size of the nozzle. In addition, when the adhesion range is wider, for example, when the adhesion range is linear, such as when the flange portion of a hat-shaped joint is adhesively joined, it is also possible to adopt a method of dividing the adhesion range into multiple areas and extruding a predetermined shape into each area to apply the adhesive, for example, a method of continuously stamping a seal. Alternatively, when a normal tip nozzle is used, it is possible to deal with a wide adhesion range by drawing a predetermined shape without any restrictions on shape or size. EXAMPLES

[0032] The effects of this embodiment will be specifically described below based on examples, but the present invention is not limited to these examples. Steel plate used in the test The type is cold-rolled steel sheet, with a strength level of 590MPa TS. The thickness is 1.4mm, the width is 16.0mm, and the longitudinal length of the bonding area is 12.5mm. Adhesion conditions The adhesive used was a one-part heat-curing epoxy adhesive (manufactured by Cemedine, model number EP138). The adhesive was applied to a thickness of 0.5 mm. Tensile shear bond strength test pieces were prepared with adhesive joint structures that correspond to the adhesive application ranges shown in Figure 1(b) and Figure 2(a). Test piece No. 1 is the example of Figure 1(b), with BL (thickness of the adhesive area that continues in the width direction) = 3.9 mm, BW (thickness of the adhesive area that continues in the length direction) = 3.9 mm, and adhesive area ratio = 72%. Test piece No. 2 is the example of Figure 2(a), with BL (thickness of the adhesive area that continues in the width direction) = 3.1 mm, and BW (thickness of the adhesive area that continues in the length direction) = 3.1 mm. Adhesive area ratio = 69%. For comparison, test pieces with rectangular bonded areas of 100% (test piece No. 3) and 70% (longitudinal bonded length of 8.8 mm, test piece No. 4) were also prepared.

[0033] For each test piece, a tensile shear bond strength test shown in FIG. 3 was carried out to measure the maximum load.

[0034] The maximum load in the tensile shear bond strength test was 4.5 kN for the H-shaped bond in Figure 1(b) of the invention example (test piece No. 1), 4.4 kN for the square-shaped bond in Figure 2(a) of the invention example (test piece No. 2), 4.4 kN for the 100% rectangular bond of the comparative example (test piece No. 3), and 4.0 kN for the 70% rectangular bond (test piece No. 4). Therefore, for the same adhesive area ratio, the H-shaped and L-shaped adhesives had higher maximum loads than the rectangular adhesive, and the maximum shear stress load was the same as that of the 100% rectangular adhesive. [Explanation of symbols]

[0035] 1. Tensile shear adhesive strength test method 2 Adherent material 3. Area to be glued 4 Tensile Load

Claims

1. In an adhesive joint structure in which overlapping adherends are joined with an adhesive, On the surface of the material to be bonded, The direction in which the shear force is applied is called the longitudinal direction. The direction perpendicular to the direction in which the shear force is applied is called the width direction. year, On the area to be bonded of the adherend, A pair of first adhesive regions each having a length in the longitudinal direction shorter than half the total length of the adhesive target region at one end and the other end, the length being continuous across the entire width of the adhesive target region; a second adhesive region having a widthwise length shorter than the overall width of the adhesive target region and continuous in the longitudinal direction connecting the pair of first adhesive regions; An adhesive joint structure having the above structure.

2. The second adhesive region is made up of a plurality of second adhesive regions, and the sum of the widthwise lengths of the second adhesive regions is shorter than the total width of the adhesive target region. The adhesive joint structure according to claim 1.

3. The second adhesive regions are provided in pairs at both ends of the adhesive target region, and the sum of the widthwise lengths is shorter than the entire width of the adhesive target region. The adhesive joint structure according to claim 1.

4. The adhesion area is 55 to 90% of the area to be bonded of the adherend. An adhesive joint structure according to any one of claims 1 to 3.

5. A bonded joint structural component having the bonded joint structure according to any one of claims 1 to 3.

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