Joint structure of automobile frame member

Abstract

A joint structure of an automobile frame member comprises a first member and a second member. The first member includes a top plate, two vertical walls, two first ridgeline portions, and a continuous flange. The second member includes a first wall surface facing an axial end portion of the first member, a second wall surface extended from the first wall surface to the other side from the first member side, and a second ridgeline portion sandwiched between the first wall surface and the second wall surface. The continuous flange has an interval h, between the second ridgeline portion and the top plate, satisfying -10 mm ≤ h ≤ 10 mm, and angles θ formed by a surface perpendicular to the top plate and the two vertical walls, respectively, each satisfy 20° ≤ θ ≤ 45°.

Description

Joint structure of automobile frame members

[0001] The present invention relates to a joining structure for an automobile frame member.

[0002] In recent years, fuel economy regulations have become stricter around the world, requiring lighter vehicles. Furthermore, in response to fuel economy regulations in various countries and the trend toward carbon neutrality, the electrification of vehicle power sources is also progressing. This has led to the need to install heavy batteries in vehicles, further increasing the need for weight reduction. At the same time, there is also a demand for improved crashworthiness, and it is necessary to achieve both lightweight vehicles and crashworthiness.

[0003] Examples of structural components that contribute to collision safety include components arranged around the cabin, such as bumper beams, side sills, and cross members. One of the performance requirements for these components is that they must be resistant to deformation when a collision load is applied (load-bearing capacity), in order to improve the safety of occupants in the event of a collision and to improve the protection function of the battery located under the floor.

[0004] Since skeletal members with excellent load-bearing performance are also members with excellent collision safety, in order to achieve both the aforementioned collision safety and weight reduction, it is desirable to improve the load-bearing performance per unit weight of the skeletal members (hereinafter referred to as "weight efficiency of load-bearing performance").

[0005] Possible means of improving the weight efficiency of load-bearing performance include improvements in materials, such as increasing the strength of materials, thinning them, and using different materials, but improvements to the shape of each part that makes up the frame member and the joint structure between parts will also be necessary.

[0006] As a technology relating to the shape or joining structure of a conventional automobile frame member, Patent Document 1 discloses a metal frame member having a groove bottom, two ridges, and two vertical walls, in which an outward continuous flange is formed over the groove bottom, ridges, and vertical walls. Patent Documents 2 to 4 also disclose members having an outward continuous flange, similar to Patent Document 1.

[0007] Patent Document 5 discloses a joint structure including a hat-shaped first member and a hat-shaped second member whose longitudinal end is connected to the first member. In this joint structure, a flange is formed on the top surface of the second member and extends toward the first member, and the flange is joined to the vertical wall of the first member.

[0008] Patent document 6 discloses a press-molded product having a T-shaped top plate portion, a wall portion continuing from the top plate portion, and a flange portion continuing from the wall portion, in which the ridge line connecting the vertical and horizontal sides of the top plate portion is curved.

[0009] Patent document 7 discloses a floor tunnel that is laid on the floor surface inside the vehicle cabin along the fore-and-aft direction of the vehicle and has a hat-shaped open cross-section in which a cross section perpendicular to the fore-and-aft direction of the vehicle protrudes from the floor surface.

[0010] Patent Document 8 discloses a joining structure of members, which has a first member and a second member, an end of the second member abutting against a surface of the first member, and a joining portion joining the first member and the second member.

[0011] Patent Document 9 discloses a structural member for an automobile. This structural member includes a member body including a top plate extending in the longitudinal direction of the structural member and having two side portions opposing each other in the width direction of the structural member, vertical walls connected to each of the side portions via ridges, a first flange extending in the width direction from the vertical wall, and a second flange provided contiguous with an end of the member body in the longitudinal direction. It can be seen from, for example, Figure 2 of Patent Document 9 that the vertical wall of the member body is slightly inclined with respect to a plane perpendicular to the top plate, but it is clear that the angle between the plane perpendicular to the top plate and the vertical wall is less than 20°.

[0012] International Publication No. WO 2016 / 104078 Japanese Patent No. 6176046 International Publication No. WO 2013 / 154114 International Publication No. WO 2016 / 194963 Japanese Patent Application Publication No. 2020-142767 Japanese Patent No. 6690605 International Publication No. WO 2020 / 095756 International Publication No. WO 2015 / 133531 International Publication No. WO 2023 / 032953

[0013] As mentioned above, the shapes and joining structures of automobile frame members have been studied for various purposes for some time, but in order to achieve both lightweight automobiles and high levels of collision safety, further improvements in the weight efficiency of load-bearing performance are required.

[0014] The present invention has been made in view of the above circumstances, and has as its object to improve the weight efficiency of the load-bearing performance of an automobile body.

[0015] One aspect of the present invention that solves the above-mentioned problems is a joining structure for automobile frame members, comprising: a first member; and a second member to which an axial end portion of the first member is joined; the first member has a top plate, two vertical walls facing each other, two first ridge portions sandwiched between the top plate and each of the two vertical walls, and a continuous flange formed continuously across the top plate, the two vertical walls, and the two first ridge portions at an axial end portion of the first member; the second member has a first wall surface facing the axial end portion of the first member, a second wall surface extending from the first wall surface to an opposite side to the first member side, and a second ridge portion sandwiched between the first wall surface and the second wall surface; the continuous flange has a joining surface joined to the second wall surface; and a distance h between the second ridge portion and the top plate in a direction perpendicular to the top plate, based on the position of the second ridge portion, satisfies −10 mm≦h≦10 mm. The angle θ formed between a plane perpendicular to the top plate and each of the two vertical walls satisfies 20°≦θ≦45°.

[0016] According to the present invention, it is possible to improve the weight efficiency of the load-bearing performance of an automobile body.

[0017] 10. FIG. 11 is a perspective view showing a schematic configuration of a joining structure of an automobile frame member according to an embodiment of the present invention. FIG. 12 is a view showing a cross section perpendicular to the axial direction of a first member. FIG. 13 is a view showing the A-A cross section in FIG. 1. FIG. 14 is a view for explaining the definition of a continuous flange. FIG. 15 is a view showing an example of a discontinuous flange. FIG. 16 is a perspective view showing an example of a joining structure where h<0. FIG. 17 is a view showing the B-B cross section in FIG. 6. FIG. 18 is a view showing an example of a hardness measurement position of a first member. FIG. 19 is a view showing an example of a joining structure where a first ridge line portion is composed of straight and curved portions. FIG. 19 is a view showing a schematic diagram of the straight and curved portions of the first ridge line portion when the joining structure of FIG. 9 is viewed from above. FIG. 11 is an example of the shape of a hat member having a longer distance d than the hat member of FIG. 10. FIG. 12 is a view showing an example of the configuration of a first member. FIG. 13 is a view for explaining an analytical model of simulation (1). FIG. 14 is a view showing the results of simulation (1). FIG. 15 is a view showing an analytical model of simulation (2). FIG. 16 is a view showing the results of simulation (2). FIG. 17 is a view showing an analytical model of simulation (3). FIG. 18 is a view showing the results of simulation (3). FIG. 19 is a view showing an analytical model of simulation (4).

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configuration are designated by the same reference numerals, and redundant description will be omitted.

[0019] FIG. 1 is a perspective view showing a schematic configuration of a joining structure 1 for an automobile frame member according to this embodiment. FIG. 2 is a view showing a cross section perpendicular to the axial direction of a first member 100. FIG. 3 is a view showing a cross section taken along line A-A in FIG. 1. Note that the X direction, Y direction, and Z direction in this specification and the drawings are perpendicular to one another. In this specification, the axial direction of the first member 100 refers to the direction in which the ridge line between the top plate and the vertical wall (described later) continues, and the axial direction of the second member 200 refers to the direction in which the ridge line between the first wall surface and the second wall surface (described later) continues.

[0020] The joint structure 1 includes a first member 100 and a second member 200 .

[0021] The first member 100 and the second member 200 are members extending in different directions, and an axial end of the first member 100 is joined to the second member 200. There are no particular limitations on the means for joining the two members 100, 200, and any known joining means, such as spot welding, laser welding, or plasma welding, or an industrial adhesive, may be used.

[0022] The first member 100 has a hat member 110 whose cross section perpendicular to the axial direction (Y direction) is hat-shaped, and a closing plate 120. The first member 100 is a hollow member whose cross section perpendicular to the axial direction is a closed cross section formed by joining the hat member 110 and the closing plate 120. A detailed description of the hat member 110 will be given later.

[0023] The second member 200 is a hollow member having a rectangular cylindrical shape, and has a first wall surface 201 and a second wall surface 202. The first wall surface 201 is a wall surface that faces the end of the first member 100 in the axial direction (Y direction). The second wall surface 202 is a wall surface that extends from the first wall surface 201 to the side opposite the first member 100. The first wall surface 201 and the second wall surface 202 are connected to each other, and a ridge portion 203 is formed between the first wall surface 201 and the second wall surface 202. The ridge portion 203 extends along the axial direction (X direction) of the second member 200.

[0024] The first member 100 and the second member 200 described above are both skeletal members of an automobile body, and the joining structure 1 is applied to a location where each skeletal member of the automobile body is joined in a roughly T-shape.

[0025] For example, if the first member 100 is a floor cross member or a center pillar, the second member 200 is a side sill, and if the first member 100 is a roof cross member, the second member 200 is a roof side rail. Also, for example, if the first member 100 is a side member (front side member or rear side member), the second member 200 is a bumper beam (front bumper beam or rear bumper beam).

[0026] Furthermore, when the joining structure 1 is one of the following joining structures, the X direction, Y direction, and Z direction respectively indicate the following directions: Joining structure between floor cross member and side sill X direction: vehicle length direction, Y direction: vehicle width direction, Z direction: vehicle height direction Joining structure between center pillar and side sill X direction: vehicle length direction, Y direction: vehicle height direction, Z direction: vehicle width direction Joining structure between roof cross member and roof side rail X direction: vehicle length direction, Y direction: vehicle width direction, Z direction: vehicle height direction Joining structure between side member and bumper beam X direction: vehicle width direction, Y direction: vehicle length direction, Z direction: vehicle height direction

[0027] For example, if the first member 100 is a floor cross member and the second member 200 is a side sill, the first wall surface 201 facing the axial end of the first member 100 is the vehicle-interior-side wall surface of the side sill in the vehicle width direction. In this case, the second wall surface 202 extending from the first wall surface 201 to the side opposite the first member 100 side is the wall surface extending from the vehicle-interior-side wall surface of the side sill in the vehicle width direction toward the vehicle-exterior side in the vehicle width direction, and corresponds to the upper or lower surface of the side sill.

[0028] When the first member 100 is a center pillar and the second member 200 is a side sill, the first wall surface 201 is the upper surface of the side sill. In this case, the second wall surface 202 is a wall surface extending downward from the upper surface of the side sill, and corresponds to the wall surface of the side sill on the outer or inner side of the vehicle in the vehicle width direction.

[0029] When the first member 100 is a roof cross member and the second member 200 is a roof side rail, the first wall surface 201 is the inner wall surface of the roof side rail in the vehicle width direction. In this case, the second wall surface 202 is a wall surface that extends from the inner wall surface of the roof side rail in the vehicle width direction toward the outer side of the vehicle in the vehicle width direction, and corresponds to the upper or lower surface of the roof side rail.

[0030] When the first member 100 is a side member and the second member 200 is a bumper beam, the first wall surface 201 is the vehicle-interior wall surface of the bumper beam in the vehicle length direction. In this case, the second wall surface 202 is the wall surface extending from the vehicle-interior wall surface of the bumper beam in the vehicle length direction toward the vehicle exterior in the vehicle length direction, and corresponds to the upper or lower surface of the bumper beam.

[0031] The overall length of the first member 100 and the overall length of the second member may be changed as appropriate depending on the location of application of the joining structure 1 to the vehicle body, and may be, for example, 1000 to 3000 mm.

[0032] The plate thickness of the first member 100 and the plate thickness of the second member 200 are changed as appropriate depending on the application location of the joining structure 1 on the vehicle body, the required load-bearing performance, etc., and are, for example, 0.5 to 6.0 mm. The plate thickness of each member 100, 200 may be, for example, 0.8 mm or more, or 1.0 mm or more. Furthermore, the plate thickness of each member 100, 200 may be, for example, 4.0 mm or less, or 3.0 mm or less. The plate thicknesses of each member 100, 200 may be different from each other.

[0033] The first member 100 and the second member 200 are made of a metal material such as steel, an aluminum alloy member, a magnesium alloy member, etc. The materials of the members 100 and 200 may be different from each other.

[0034] Next, a detailed description will be given of the hat member 110 of the first member 100. The hat member 110 has a top plate 111, two vertical walls 112, 113, and two flanges 114, 115.

[0035] The top plate 111 is a plate-like portion extending in the longitudinal direction of the first member 100. The extending direction of the top plate 111 is the vehicle width direction when the first member 100 is applied to a frame member such as a cross member, the vehicle height direction when the first member 100 is applied to a frame member such as a center pillar, and the vehicle length direction when the first member 100 is applied to a frame member such as a side member.

[0036] The two vertical walls 112, 113 are disposed opposite each other and are located between the top plate 111 and each of the two flanges 114, 115. Each of the two vertical walls 112, 113 is connected to the top plate 111, and ridges 116, 117 are formed between the two vertical walls 112, 113 and the top plate 111, respectively.

[0037] The two ridge portions 116, 117 are formed linearly along the axial direction (Y direction) of the first member 100, and extend to the axial end portion (the end portion on the second member 200 side) of the first member 100. In this specification, the two ridge portions 116, 117 sandwiched between the top plate 111 and the two vertical walls 112, 113 may be referred to as "first ridge portions," and the ridge portion 203 of the second member 200 described above may be referred to as "second ridge portion."

[0038] The flanges 114 and 115 are connected to the vertical walls 112 and 113 at their ends opposite the connecting end of the top plate 111 , and extend outward from each of the two vertical walls 112 and 113 .

[0039] In the first member 100 described above, the length from the flanges 114, 115 to the top plate 111 in the direction perpendicular to the top plate 111 (the Z-direction length in FIG. 2) is changed as appropriate depending on the application location of the first member 100 on the vehicle body, but is set to, for example, 30 to 200 mm. In addition, the width of the top plate 111 (the X-direction length in FIG. 2) is changed as appropriate depending on the application location of the joining structure 1 on the vehicle body, but is set to, for example, 30 to 250 mm.

[0040] A continuous flange 130 is formed at the axial end (end on the second member 200 side) of the first member 100, extending outward with respect to the hollow portion from the top plate 111, two first ridge portions 116, 117, and two vertical walls 112, 113 of the hat member 110. This continuous flange 130 is formed continuously over the entire area from one of the two vertical walls 112 to the ridge portion 116, the top plate 111, the ridge portion 117, and the other vertical wall 113.

[0041] The continuous flange 130 is a flange in which a top plate extension 141 extending from the top plate 111 and vertical wall extensions 142 and 143 extending from the two vertical walls 112 and 113 are continuous.

[0042] More specifically, as shown in FIG. 4( a), at the axial end of the first member 100, a corner R of the first ridge portion 116 exists between the top plate 111 and the vertical wall 112. Furthermore, if there is a portion (corresponding to the connecting portion 144 in the figure) that connects the top plate extension portion 141 and the vertical wall extension portion 142 and that includes the above-mentioned corner R, the top plate extension portion 141 and the vertical wall extension portion 142 are continuous via the connecting portion 144. Therefore, in this case, the flange including the top plate extension portion 141, the vertical wall extension portion 142, and the connecting portion 144 is a continuous flange. That is, in the example shown in FIG. 4( a), the top plate extension portion 141, the vertical wall extension portion 142, and the connecting portion 144 form the continuous flange 130.

[0043] 4(b), the shape of the top plate extension portion 141 is different from that of FIG. 4(a), but in this example as well, a connecting portion 144 including the corner R of the first ridge portion 116 is present between the top plate extension portion 141 and the vertical wall extension portion 142, and the connecting portion 144 connects the top plate extension portion 141 and the vertical wall extension portion 142. That is, in the example shown in FIG. 4(b), the top plate extension portion 141, the vertical wall extension portion 142, and the connecting portion 144 form the continuous flange 130.

[0044] 5, there is no portion that connects the top plate extension portion 141 and the vertical wall extension portion 142, including the corner R of the first ridge portion 116, and there is a discontinuous portion between the top plate extension portion 141 and the vertical wall extension portion 142. For this reason, in the example shown in FIG. 5, the top plate extension portion 141 and the vertical wall extension portion 142 are each provided as independent flanges, and therefore the continuous flange 130 is not formed.

[0045] As shown in FIG. 1 , the continuous flange 130 has a first flat surface 140 joined to the first wall surface 201 of the second member 200 and a second flat surface 150 joined to the second wall surface 202 .

[0046] The first plane 140 is a surface that contacts the first wall surface 201. In the continuous flange 130 shown in FIG. 1 , the first plane 140 is formed by a top plate extension portion 141 extending from the top plate 111, vertical wall extension portions 142 and 143 extending from the two vertical walls 112 and 113, and connecting portions 144 and 145 that connect each of the two vertical wall extension portions 142 and 143 to the top plate extension portion 141.

[0047] The second plane 150 is a surface that comes into contact with the second wall surface 202 and extends from the upper ends of the top plate extension 141 and the two connecting portions 144 and 145 toward the second member 200 .

[0048] The first member 100 having the continuous flange 130 is formed so that the angle θ ( FIG. 2 ) formed between a plane perpendicular to the top plate 111 and each of the two vertical walls 112, 113 when viewed in a cross section perpendicular to the axial direction of the first member 100 satisfies 20°≦θ≦45°. In the following description, the angle θ will be referred to as the vertical wall angle θ.

[0049] When a continuous flange 130 is provided that is continuously formed across the top plate 111, the first ridge portions 116, 117, and the vertical walls 112, 113, if the vertical wall angle θ is less than 20°, excessive stress is generated in the first ridge portions 116, 117 when a collision load is input from the second member 200 side, making it easy for cracks to occur in the first member 100 starting from the first ridge portions 116, 117. On the other hand, if the vertical wall angle θ is 20° or more, stress concentration generated in the first ridge portions 116, 117 when a collision load is input from the second member 200 side is alleviated, making it difficult for distortion to occur in the first ridge portions 116, 117. As a result, cracks in the first member 100 are less likely to occur when a collision load is input.

[0050] If the vertical wall angle θ is greater than 45°, there is a risk that the first member 100 will buckle early before it can fully exert its deformation resistance against the collision load from the second member 200. On the other hand, if the vertical wall angle θ is 45° or less, the occurrence of such early buckling of the first member 100 can be suppressed, thereby increasing the deformation resistance against the collision load from the second member 200 and improving the load-bearing performance.

[0051] Therefore, as will be shown in the examples described later, a joining structure 1 having a first member 100 whose vertical wall angle θ satisfies 20°≦θ≦45° can suppress the occurrence of cracks in the first member 100 and can obtain excellent load-bearing performance.

[0052] If the vertical wall angle θ is less than 20°, there is a risk that the connecting portions 144, 145 may break during the molding process of the continuous flange 130. Therefore, by setting the vertical wall angle θ to 20° or more, molding of the continuous flange 130 becomes easier, and the first member 100 can be manufactured more easily.

[0053] Furthermore, as will be shown in the examples below, in order to improve the load-bearing performance in a small overlap collision, the vertical wall angle θ is preferably 25° or more.

[0054] 2, the hat member 110 has a bilaterally symmetrical shape, and the angle between one of the two vertical walls 112 and the top plate 111 and the angle between the other vertical wall 113 and the top plate 111 are equal to each other, but the two vertical wall angles may be different from each other. However, in order to obtain the effects of suppressing cracking and excellent load-bearing performance described above, each vertical wall angle θ needs to satisfy 20°≦θ≦45°.

[0055] In the joint structure 1, the distance h ( FIG. 3 ) between the second ridge line 203 and the top plate 111 of the first member 100 in the direction perpendicular to the top plate 111 (Z direction), with the position of the second ridge line 203 of the second member 200 as the reference (origin), satisfies −10 mm≦h≦10 mm. In other words, the joint structure 1 is configured so that the absolute value of the length from the second ridge line 203 to the top plate 111 in the direction perpendicular to the top plate 111 (Z direction length) is within 10 mm. Note that when the value of the distance h has a positive sign, it indicates that the top plate 111 is located on the negative side of the Z direction relative to the second ridge line 203, and when the value of the distance h has a negative sign, it indicates that the top plate 111 is located on the positive side of the Z direction relative to the second ridge line 203.

[0056] When the distance h satisfies the above range, the rigidity of the joint structure 1 is increased, and as shown in the examples described later, the load-bearing performance can be improved. From the viewpoint of further improving the load-bearing performance, the distance h is preferably −7 mm or more, and more preferably −5 mm or more. From the same viewpoint, the distance h is preferably 7 mm or less, and more preferably 5 mm or less.

[0057] The second ridge portion 203 is a curved surface portion between the first wall surface 201 and the second wall surface 202, and the position of the second ridge portion 203 in a direction perpendicular to the top plate 111 when calculating the distance h is the position of the intersection between an imaginary plane extending the first wall surface 201 and an imaginary plane extending the second wall surface 202.

[0058] Furthermore, if the second ridge 203 and the top plate 111 are not parallel, for example, if either the top plate 111 or the second ridge 203 is inclined with respect to the horizontal plane, the distance (length in the Z direction) between the second ridge 203 and the top plate 111 will vary depending on the measurement location. In this case, the above-mentioned distance h means the minimum distance between the second ridge 203 and the top plate 111.

[0059] 6 and 7 are diagrams showing an example of the joining structure 1 when h<0. The continuous flange 130 in this example also has extensions 141-143 extending from the top plate 111 and the two vertical walls 112, 113, and is shaped so that there are no discontinuous portions across the top plate 111, the two vertical walls 112, 113, and the two ridge portions 116, 117. The first plane 140 is formed by the two vertical wall extensions 142, 143.

[0060] The above has described the joining structure 1 for automobile frame members according to this embodiment. As described above, this joining structure 1 is provided with a continuous flange 130 formed continuously from the vertical walls 112, 113 to the top plate 111 at the axial end of the first member 100. The vertical wall angle θ satisfies 20°≦θ≦45°, and the distance h between the second ridge portion 203 and the top plate 111 satisfies −10 mm≦h≦10 mm.

[0061] According to this joint structure 1, distortion of the first ridge portions 116, 117 is unlikely to occur when a collision load is applied, making it possible to achieve a highly rigid structure with excellent load-bearing performance. Furthermore, the joint structure 1 is equivalent in weight to or lighter than a structure whose vertical wall angle θ and spacing h do not satisfy the above ranges, and therefore is also excellent in weight efficiency of load-bearing performance.

[0062] As will be shown in the examples described later, when a steel material is used for the hat member 110 of the first member 100, the tensile strength of the steel material is preferably 980 MPa or more. In the joint structure 1 having the continuous flange 130, when the tensile strength is 980 MPa or more, the effect of suppressing early yielding of the material is enhanced, and the load-bearing performance can be effectively improved.

[0063] This effect increases dramatically as the tensile strength increases. In other words, the joint structure 1 is well-suited to high-strength steel plates, and is a useful structure for electric vehicles, for example, where the use of high-strength steel plates is being considered to improve battery protection functions. From the perspective of further improving load-bearing performance, the tensile strength of the steel material is more preferably 1180 MPa or more, and even more preferably 1270 MPa or more.

[0064] In this specification, the tensile strength of the material constituting the hat member 110 is determined by converting the hardness of the top plate 111 measured in accordance with JIS Z 2244 at a test force F of 49.03 N or greater using a hardness conversion table (SAE J 417). The hardness of the top plate 111 is measured as follows: First, a portion of the top plate 111, as shown by the dashed-dotted line in FIG. 1 , is cut out, and the hardness is measured at 10 arbitrary points designated as hardness measurement points, as shown in FIG. 8( a) or 8(b), for example. Note that the hardness measurement points must be at least 3 mm apart. The average Vickers hardness measured under these conditions is defined as the hardness of the top plate 111, and the tensile strength corresponding to the hardness of the top plate 111 is calculated using the hardness conversion table (SAE J 417). The tensile strength calculated here is the tensile strength of the material constituting the hat member 110. For example, according to a hardness conversion table, if the hardness of the top plate 111 is 310 HV or more, the hat member 110 can be considered to be made of a material with a tensile strength of 980 MPa or more.

[0065] The first ridge portions 116, 117 of the first member 100 described above are formed linearly up to the first wall surface 201 of the second member 200, but the first ridge portions 116, 117 may also be composed of straight portions 116a, 117a and curved portions 116b, 117b, as shown in Figures 9 and 10. Note that Figure 10 is a top view of the joint structure 1 in Figure 9, and is a schematic diagram focusing on the straight portions and curved portions of the first ridge portions 116, 117. For this reason, part of the member shape is omitted from the illustration.

[0066] 9 , curved portions 116b, 117b are located between the straight portions 116a, 117a of the two first ridge portions 116, 117 and the continuous flange 130. These curved portions 116b, 117b are curved so as to be convex toward the inside of the top plate 111. Therefore, the width of the top plate 111 gradually increases toward the second member 200 at the axial end of the first member 100.

[0067] When a collision load is input from the second member 200 side toward the first member 100, the collision load is transmitted to the straight line portions 116a, 117a of the first ridge portions 116, 117, thereby increasing the deformation resistance of the first member 100. Therefore, in order to transmit the load to the straight line portions 116a, 117a early when the collision load is input and to obtain high deformation resistance from the initial stage of the collision, it is preferable that the distance d ( FIG. 10 ) between the straight line portions 116a, 117a in the axial direction (Y direction) of the first member 100 and the second ridge portion 203 of the second member 200 is not excessively large.

[0068] Specifically, the distance d preferably satisfies the relationship 0≦d≦20 mm. When the distance d satisfies this range, high deformation resistance can be obtained from the initial stage of a collision, thereby increasing the amount of collision energy absorption. From the viewpoint of enhancing this effect, the distance d is preferably 17 mm or less, and more preferably 15 mm or less.

[0069] 11 shows an example of the shape of the hat member 110 in which the distance d is longer than that of the hat member 110 in Fig. 10. When the distance d is increased as in Fig. 11, due to processing constraints, it is necessary to form the continuous flange 130 so that the width of the second flat surface 150 also increases. In this case, the space for joining the second flat surface 150 to the second member 200 also increases, which may require changes to the vehicle body structure around the joining space, or may make joining itself difficult because the joining space cannot be secured.

[0070] Therefore, from the viewpoint of facilitating the joining of the continuous flange 130 and the second member 200, it is preferable that the distance d satisfies 0≦d≦20 mm.

[0071] In addition, when calculating the distance d, the position of the second ridge portion 203 in the axial direction (Y direction) of the first member 100 is the position of the intersection between an imaginary plane extending the first wall surface 201 and an imaginary plane extending the second wall surface 202.

[0072] The outline and preferred configuration of the joint structure 1 have been described above.

[0073] In the above-described joint structure 1, the continuous flange 130 has the first flat surface 140 and the second flat surface 150, but at least a portion of the first flat surface 140 and the first wall surface 201 do not have to be joined to each other. Even in this case, as long as the second flat surface 150 and the second wall surface 202 are joined, it is possible to obtain the joint structure 1 with excellent weight efficiency in load-bearing performance described in the above embodiment. In other words, it is sufficient for the continuous flange 130 to have a joining surface that is joined to the second wall surface 202 of the second member 200.

[0074] Furthermore, the first member 100 described above is configured by the hat member 110 and the closing plate 120, but the configuration of the first member 100 may be, for example, as shown in FIG.

[0075] Fig. 12(a) shows a configuration example in which a groove 118 is provided in the top plate 111 of the hat member 110. Fig. 12(b) shows a configuration example in which an inflection portion 119 is provided in the vertical walls 112 and 113 of the hat member 110. Fig. 12(c) shows a configuration example in which the hat member 110 and another hat member 121 are joined by a flange. Fig. 12(d) shows another configuration example in which two hat members 110 and 122 are used.

[0076] Furthermore, the second member 200 is not limited to the rectangular cylindrical member described above, and may be configured, for example, by a combination of a hat member and a closing plate, or a combination of two hat members.

[0077] While one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the technical ideas set forth in the claims, and it is understood that such modifications also fall within the technical scope of the present invention.

[0078] For example, the components of the above-described embodiments can be combined in any manner, and such combinations will naturally provide the functions and effects of the individual components involved in the combination, as well as other functions and effects that will be apparent to those skilled in the art from the description herein.

[0079] Furthermore, the effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that would be apparent to a person skilled in the art from the description of this specification, in addition to or in place of the above-described effects.

[0080] <Simulation (1)> A simulation was performed using the analytical model shown in FIG. 13 . This simulation assumed that a collision load was input in the axial direction of the second member 200, such as in a small overlap collision. FIG. 13( a) schematically shows the first member 100, and FIG. 13( b) shows a specific configuration of the first member 100. Although not shown in FIG. 13( a), a continuous flange 130 such as that shown in FIG. 1 is formed at the end of the first member 100 on the second member 200 side, and the continuous flange 130 is joined to the first wall surface 201 and the second wall surface 202 of the second member 200.

[0081] In this simulation, multiple models were used in which the distance h between the second ridge line portion 203 and the top plate 111 was changed within a range of -10 to 40 mm, and the vertical wall angle θ was changed within a range of 0 to 60. Then, the relationship between the distance h and the load-bearing performance was evaluated based on the maximum reaction force of the first member 100 generated in each model.

[0082] The main simulation conditions are set as follows: Software name: LS-Dyna Version: R9.3.1 Mesh size: 2 mm Element type: Shell element developed by Belytschko-Wong-Chiang Material of hat member 110: Steel plate (tensile strength 1180 MPa, plate thickness 1.6 mm) Material of plate 120: Steel plate (tensile strength 270 MPa, plate thickness 0.8 mm) Material of second member 200: Steel plate (tensile strength 1180 MPa, plate thickness 1.2 mm) Vertical wall angle θ: 0 to 60° Spacing h: -10 to 40 mm Spacing d: 0 mm Boundary conditions: Both axial end faces of second member 200 are fully restrained, and the axial end face of first member 100 (the end face opposite to the second member side) is forcibly displaced 2 mm in the direction of the arrow.

[0083] Figure 14 shows the results of simulation (1), showing the change in maximum reaction force with changes in the gap h and the vertical wall angle θ. As shown in Figure 14, the joint structure that satisfies -10 mm ≦ h ≦ 10 mm has a larger maximum reaction force and better load-bearing performance than structures that fall outside this range.

[0084] Furthermore, the smaller the absolute value of the interval h, the less material is used to form the continuous flange, and the lighter the weight of the joined structure becomes. That is, a joined structure that satisfies -10 mm ≦ h ≦ 10 mm is lighter than a structure with an absolute value of the interval h of 20 mm or more, yet has improved load-bearing performance, and is therefore a structure with excellent weight efficiency in terms of load-bearing performance.

[0085] FIG. 15 shows the rate of increase in maximum reaction force (i.e., the rate of improvement in load-bearing performance) when the spacing h is 0 mm, relative to the maximum reaction force when the spacing h is 40 mm. The values ​​on the vertical axis in FIG. 15 are calculated by dividing the maximum reaction force when the spacing h is 0 mm by the maximum reaction force when the spacing h is 40 mm. As shown in FIG. 15, when the vertical wall angle is 20° or greater, the rate of improvement in load-bearing performance increases dramatically. That is, according to the results shown in FIGS. 14 and 15, when the relationship -10 mm≦h≦10 mm is satisfied, a vertical wall angle of 20° or greater effectively increases the maximum reaction force and enhances the improvement in load-bearing performance. Furthermore, because the improvement in load-bearing performance is further enhanced when the vertical wall angle is 25° or greater, a vertical wall angle of 25° or greater is preferred.

[0086] <Simulation (2)> Next, a simulation was performed using the analytical model shown in FIG. 16 . This simulation assumed that a collision load was input in the axial direction of the first member 100, such as in a side collision. FIG. 16( a) schematically shows the first member 100, and FIG. 16( b) shows a specific configuration of the first member 100. Although not shown in FIG. 16( a), a continuous flange 130 such as that shown in FIG. 1 is formed at the end of the first member 100 on the side of the second member 200, and the continuous flange 130 is joined to the first wall surface 201 and the second wall surface 202 of the second member 200.

[0087] In this simulation, multiple models were used in which the vertical wall angle θ was changed within a range of 0° to 60°. Then, the relationship between the vertical wall angle θ and the load-bearing performance was evaluated based on the maximum reaction force of the first member 100 generated in each model.

[0088] In addition, in this simulation, a reference model was also used, which had a discontinuous flange in which a notch was formed in the continuous flange 130. A discontinuous flange is a flange in which the top plate extension 141 and the two vertical wall extensions 142 and 143 are not connected to each other, without the connecting portions 144 and 145 as shown in FIG.

[0089] The main simulation conditions are set as follows: Software name: LS-Dyna Version: R9.3.1 Mesh size: 2 mm Element type: Shell element developed by Belytschko-Wong-Chiang Material of hat member 110: Steel plate (tensile strength 1180 MPa, plate thickness 1.6 mm) Material of plate 120: Steel plate (tensile strength 270 MPa, plate thickness 0.8 mm) Material of second member 200: Steel plate (tensile strength 1180 MPa, plate thickness 1.2 mm) Vertical wall angle θ: 0° to 60° Spacing h: 5 mm Spacing d: 0 mm Boundary conditions: The axial end face of the first member 100 (the end face opposite to the second member side) is completely restrained, and the second member 200 is forcibly displaced 40 mm in the direction of the arrow.

[0090] Fig. 17 is a diagram showing the results of simulation (2). The presence or absence of "cracks" shown in Fig. 17 refers to the presence or absence of a location where the thickness of the first member 100 has decreased by 15% or more compared to the initial thickness, and if the simulation shows that there is a location where the thickness has decreased by 15% or more, it is determined that "cracks have occurred."

[0091] 17, when the vertical wall angle θ satisfies 20°≦θ≦45°, high load-bearing performance can be obtained within a range where cracks do not occur. Since cracks are more likely to occur as a higher strength material is used, when a high strength material is used for the hat member 110, the technical significance of satisfying 20°≦θ≦45° becomes even greater.

[0092] Furthermore, a joint structure that satisfies 20°≦θ≦45° has improved load-bearing performance despite having the same weight as a joint structure when the vertical wall angle θ is 60°, and is therefore a structure with excellent weight efficiency in terms of load-bearing performance.

[0093] According to the results of the above simulations (1) and (2), a joint structure that satisfies -10 mm≦h≦10 mm and 20°≦θ≦45° exhibits high load-bearing performance against both collision loads input in the axial direction of the first member 100 and collision loads input in the axial direction of the second member 200. For example, a joint structure in which the first member 100 is a floor cross member and the second member 200 is a side sill exhibits excellent load-bearing performance against both small overlap collisions and side collisions by having the distance h and vertical wall angle θ satisfy the above ranges.

[0094] <Simulation (3)> Next, a simulation was performed using the analytical model shown in FIG. 18 . This simulation assumed that a collision load was input in the axial direction of the second member 200, such as in a small overlap collision. FIG. 18( a) schematically shows the first member 100, and FIG. 18( b) shows a specific configuration of the first member 100. Although not shown in FIG. 18( a), a continuous flange 130 such as that shown in FIG. 1 is formed at the end of the first member 100 on the second member 200 side, and the continuous flange 130 is joined to the first wall surface 201 and the second wall surface 202 of the second member 200.

[0095] In this simulation, a plurality of models were used in which the tensile strength of the hat member 110 was changed within a range of 270 to 2000 MPa. Then, the relationship between the tensile strength and the load-bearing performance was evaluated based on the maximum reaction force of the first member 100 generated in each model.

[0096] The main simulation conditions were set as follows: Software name: LS-Dyna Version: R9.3.1 Mesh size: 2 mm Element type: Shell element developed by Belytschko-Wong-Chiang Material of hat member 110: Steel plate (tensile strength 270 to 2000 MPa, plate thickness 1.6 mm) Material of plate 120: Steel plate (tensile strength 270 MPa, plate thickness 0.8 mm) Material of second member 200: Steel plate (tensile strength 1180 MPa, plate thickness 1.2 mm) Vertical wall angle θ: 30° Spacing h: 0 mm Spacing d: 0 mm Boundary conditions: Both axial end faces of second member 200 are fully restrained, and the axial end face of first member 100 (the end face opposite to the second member side) is forcibly displaced 2 mm in the direction of the arrow.

[0097] Fig. 19 is a diagram showing the results of simulation (3). As shown in Fig. 19, when the tensile strength is 980 MPa or more, the effect of improving the load-bearing performance is greater than when the tensile strength is less than 980 MPa.

[0098] <Simulation (4)> Next, a simulation was performed using the analytical model shown in FIG. 20 . This simulation assumed that a collision load was input in the axial direction of the first member 100, such as in a side collision. FIG. 20( a) schematically shows the first member 100, and FIG. 20( b) shows a specific configuration of the first member 100. Although not shown in FIG. 20( a), a continuous flange 130 such as that shown in FIG. 1 is formed at the end of the first member 100 on the side of the second member 200, and the continuous flange 130 is joined to the first wall surface 201 and the second wall surface 202 of the second member 200.

[0099] Although not shown in the figures, this simulation uses a model in which first ridges 116, 117 are configured with straight line portions 116a, 117a and curved line portions 116b, 117b as shown in Fig. 10. Simulations were performed using multiple models in which the distance d between straight line portions 116a, 117a and second ridge 203 was changed within a range of 5 to 60 mm.

[0100] The main simulation conditions are set as follows: Software name: LS-Dyna Version: R9.3.1 Mesh size: 2 mm Element type: Shell element developed by Belytschko-Wong-Chiang Material of hat member 110: Steel plate (tensile strength 1180 MPa, plate thickness 1.6 mm) Material of plate 120: Steel plate (tensile strength 270 MPa, plate thickness 0.8 mm) Material of second member 200: Steel plate (tensile strength 1180 MPa, plate thickness 1.2 mm) Vertical wall angle θ: 30° Spacing h: 5 mm Spacing d: 5 to 60 mm Boundary conditions: The axial end face of the first member 100 (the end face opposite to the second member side) is completely restrained, and the second member 200 is forcibly displaced 40 mm in the direction of the arrow.

[0101] Fig. 21 shows the results of simulation (4). The average reaction force shown on the vertical axis of Fig. 21 is the average value of the reaction force generated in the first member 100 until the second member 200 is displaced 40 mm, and the higher this average reaction force, the higher the energy absorption capacity of the structure.

[0102] 21, when the distance d satisfies 0≦d≦20 mm, the average reaction force increases dramatically compared to when the distance d exceeds 20 mm. Therefore, in a joint structure that satisfies the above-mentioned conditions of −10 mm≦h≦10 mm and 20°≦θ≦45°, if the condition also satisfies 0≦d≦20 mm, a joint structure that is excellent not only in weight efficiency of load-bearing performance but also in energy absorption performance can be obtained.

[0103] The present invention can be applied to the body structure of an automobile.

[0104] DESCRIPTION OF SYMBOLS 1 Joint structure 100 First member 110 Hat member 111 Top plate 112, 113 Vertical wall 114, 115 Flange 116, 117 First ridge portion 116a, 117a Straight portion 116b, 117b Curved portion 118 Groove portion 119 Inflection portion 120 Closing plate 121 Hat member 122 Hat member 130 Continuous flange 140 First plane 141 Top plate extension portion 142, 143 Vertical wall extension portion 144, 145 Connecting portion 150 Second plane 200 Second member 201 First wall surface 202 Second wall surface 203 Second ridge portion d Distance in Y direction between straight portion of first ridge portion and second ridge portion h Distance in Z direction between second ridge portion and top plate θ Angle between the plane perpendicular to the top and the vertical wall

Claims

1. A joining structure for an automobile frame member, comprising: a first member; and a second member to which an axial end portion of the first member is joined; the first member has: a top plate; two vertical walls opposing each other; two first ridge portions sandwiched between the top plate and each of the two vertical walls; and a continuous flange formed continuously across the top plate, the two vertical walls and the two first ridge portions at the axial end portion of the first member; the second member has: a first wall surface facing the axial end portion of the first member; a second wall surface extending from the first wall surface to the opposite side to the first member side; and a second ridge portion sandwiched between the first wall surface and the second wall surface; the continuous flange has a joining surface joined to the second wall surface; and a distance h between the second ridge portion and the top plate in a direction perpendicular to the top plate, based on the position of the second ridge portion, satisfies -10 mm≦h≦10 mm. A joint structure in which an angle θ between a plane perpendicular to the top plate and each of the two vertical walls satisfies 20°≦θ≦45°.

2. A joining structure as described in claim 1, wherein the first ridge portion has a straight portion and a curved portion that is curved so as to be convex toward the inside of the top plate between the straight portion and the continuous flange, and the distance d between the straight portion and the second ridge portion in the axial direction of the first member satisfies 0≦d≦20 mm.

3. A joint structure as described in claim 1 or 2, wherein the top plate, the two vertical walls and the two first ridge portions are made of steel having a tensile strength of 980 MPa or more.

4. A joint structure as described in any one of claims 1 to 3, wherein the first member is a floor cross member, and the second member is a side sill.

5. A joint structure as described in any one of claims 1 to 3, wherein the first member is a roof cross member, and the second member is a roof side rail.

6. A joint structure as claimed in any one of claims 1 to 3, wherein the first member is a center pillar, and the second member is a side sill.

7. A joint structure as claimed in any one of claims 1 to 3, wherein the first member is a side member, and the second member is a bumper beam.

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