Automobile frame member and vehicle body structure

Abstract

This automobile frame member is provided within a first member made of a metal material having a tensile strength of 1,400 MPa or more, and a second member made of a metal material. The first member includes a top plate, two vertical walls, and ridge line portion sandwiched between the top plate and the vertical wall. The vertical walls each include a first wall portion connected to the ridge line portion, and a second wall portion connected to the first wall portion. The length w from the intersection of an extended surface of the top plate and an extended surface of the second wall portion to the top plate, the distance a between the two vertical walls, the length h from the top plate to the ridge line portion, and the length b of the first member satisfy 0 < w / a ≤ 0.500, 0.170 ≤ h / b ≤ 0.650, and w / h ≤ 1.750.

Description

Automotive frame components and body structures

[0001] The present invention relates to an automobile frame member and a vehicle body structure.

[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 there is a need 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, cross members, roof side rails, and center pillars. These components are required to generate a high reaction force (deformation resistance) against external forces such as collision loads and absorb collision energy in order to improve occupant safety during a collision and to improve the protection function of the battery located under the floor. Specific means for improving energy absorption performance include, for example, material improvements such as increasing the strength of the structural components or using different materials, as well as improvements to the structure and shape of the structural components.

[0004] As a conventional technology relating to an automobile frame member, Patent Document 1 discloses a vehicle bumper device including a bumper reinforcement extending in the vehicle width direction. Also, Patent Document 2 discloses a vehicle reinforcement member including a tubular main body having a cross section intersecting the longitudinal direction that exhibits a continuous closed cross section.

[0005] Japanese Patent Application Publication No. 2009-083529 International Publication No. 2020 / 027285

[0006] In the case of long automobile frame members, as the required strength level increases, the use of high-strength materials is being considered, but high-strength materials generally have lower ductility than low-strength materials. When the inventors of the present application performed a collision simulation of automobile frame members, they found that if an ultra-high-strength material with a tensile strength of 1400 MPa or more is used in the frame members, there is a concern that the material may break apart due to the propagation of cracks that occur during deformation.

[0007] If the material breaks apart when the skeletal member is deformed, the energy absorption performance will be significantly reduced. Therefore, in order to ensure the energy absorption performance of a skeletal member that includes an ultra-high strength material with a tensile strength of 1400 MPa or more, a structure in which the skeletal member does not break apart when it is deformed is desired.

[0008] However, the above-mentioned Patent Documents 1 and 2 make no mention whatsoever of the possibility that the material may be broken when a skeletal member containing an ultra-high strength material is deformed. For this reason, Patent Documents 1 and 2 do not provide any technical details necessary to prevent the skeletal member containing an ultra-high strength material from being broken.

[0009] The present invention has been made in view of the above circumstances, and has as its object to prevent the occurrence of significant fractures that lead to separation when automobile frame members containing ultra-high strength materials are deformed.

[0010] One aspect of the present invention that solves the above problem is an automobile frame member comprising: a first member made of a metal material having a tensile strength of 1400 MPa or more; a second member made of a metal material; and a hollow portion extending along the axial direction of the automobile frame member formed by joining the first member and the second member, wherein the first member has a top plate, two vertical walls facing each other, and a ridge portion extending along the axial direction of the automobile frame member and sandwiched between the top plate and the vertical walls, and the vertical walls have a first wall portion connected to the ridge portion and a second wall portion connected to the first wall portion. The automobile frame member has two wall portions, and another ridge portion sandwiched between the first wall portion and the second wall portion and extending along the axial direction of the automobile frame member, wherein the interior angle formed by the first wall portion and the second wall portion is less than 180°, and the length w from the intersection of the extended surface of the top plate and the extended surface of the second wall portion to the top plate, the spacing a between the two vertical walls, the length h from the top plate to the other ridge portion, and the length b of the first member satisfy 0<w / a≦0.500, 0.170≦h / b≦0.650, and w / h≦1.750.

[0011] When an automobile frame member containing an ultra-high strength material is deformed, the occurrence of significant fractures that could lead to separation can be avoided.

[0012] 1 is a diagram showing an example of an automobile body frame. FIG. 1 is a diagram showing a schematic configuration of an automobile frame member according to one embodiment of the present invention. FIG. 2 is a diagram showing a cross section perpendicular to the axial direction (Y direction) of the automobile frame member. FIG. 3 is a diagram for explaining the dimensional ratios (w / a, h / b, w / h) of a first member according to this embodiment. FIG. 4 is a diagram showing a schematic view of the deformation process of a conventional automobile frame member made of an ultra-high strength material. FIG. 5 is a diagram showing the direction of crack propagation when a crack occurs in a conventional automobile frame member. FIG. 6 is a diagram showing the deformation process of an automobile frame member according to this embodiment. FIG. 7 is a diagram showing the direction of crack propagation when a crack occurs in an automobile frame member according to this embodiment. FIG. 8 is a diagram showing a schematic view of an example shape and deformation process of an automobile frame member made of one part. FIG. 9 is a diagram for explaining an example shape of an automobile frame member. FIG. 10 is a diagram for explaining the dimensional ratios of an automobile frame member according to another embodiment. FIG. 11 is a diagram for explaining the dimensional ratios of an automobile frame member according to another embodiment. FIG. 12 is a diagram for explaining an example shape of an automobile frame member. FIG. 13 is a diagram for explaining an analysis model of a collision simulation. FIG. 14 is a diagram showing simulation results. FIG. 15 is a diagram showing simulation results.

[0013] 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.

[0014] FIG. 1 is a diagram showing an example of an automobile body frame. The automobile frame member according to this embodiment is used as a component such as a front bumper beam, a rear bumper beam, a side sill, a roof side rail, or a center pillar. That is, the automobile frame member is applied to a portion where bending deformation occurs when subjected to an external force such as a collision load in a frontal collision, a rear collision, or a side collision. The overall length of the frame member 1 is, for example, 1000 to 3000 mm.

[0015] Fig. 2 is a diagram showing a schematic configuration of an automobile frame member 1 (hereinafter, sometimes simply referred to as "frame member") according to this embodiment. Fig. 3 is a diagram showing a cross section perpendicular to the axial direction (Y direction) of the automobile frame member 1. Note that the X direction, Y direction, and Z direction in this specification and drawings are perpendicular to one another.

[0016] The correspondence between the components to which the framework member 1 is applied and the X, Y, and Z directions in the drawings is as follows: Bumper beam: X direction: vehicle height direction, Y direction: vehicle width direction, Z direction: vehicle length direction Side sill or roof side rail: X direction: vehicle height direction, Y direction: vehicle length direction, Z direction: vehicle width direction Center pillar: X direction: vehicle length direction, Y direction: vehicle height direction, Z direction: vehicle width direction

[0017] The framework member 1 according to this embodiment is composed of a first member 10 and a second member 30. In a vehicle body structure including the framework member 1, for example, the first member 10 is disposed facing the interior side of the vehicle (toward the cabin) shown in FIG. 1 , and the second member 30 is disposed facing the exterior side of the vehicle (opposite the cabin). For example, if the framework member 1 is a bumper beam, the first member 10 is disposed on the interior side of the vehicle in the vehicle length direction, and the second member 30 is disposed on the exterior side of the vehicle in the vehicle length direction. Furthermore, if the framework member 1 is a side sill, roof side rail, or center pillar, for example, the first member 10 is disposed on the interior side of the vehicle in the vehicle width direction, and the second member 30 is disposed on the exterior side of the vehicle in the vehicle width direction. However, it is not essential that the first member 10 be disposed on the interior side of the vehicle and the second member 30 be disposed on the exterior side of the vehicle; the first member 10 may be disposed facing the exterior side of the vehicle and the second member 30 may be disposed facing the interior side of the vehicle.

[0018] The first member 10 is a member having a hat-shaped cross section perpendicular to the axial direction (Y direction) of the first member 10 , and has a top plate 11 , two vertical walls 12 and 13 , and two flanges 14 and 15 .

[0019] The top plate 11 is a portion extending parallel to the X-Y plane. The two vertical walls 12, 13 face each other, with one vertical wall 12 located between the top plate 11 and a flange 14 and the other vertical wall 13 located between the top plate 11 and a flange 15. The flange 14 extends outward from the end of one vertical wall 12 on the negative side in the Z direction (the side opposite the top plate 11), and the flange 15 extends outward from the end of the other vertical wall 13 on the negative side in the Z direction (the side opposite the top plate 11).

[0020] The first member 10 including the top plate 11, the two vertical walls 12, 13, and the two flanges 14, 15 is formed, for example, by press working, and the top plate 11 is connected to the two vertical walls 12, 13, and the two vertical walls 12, 13 are further connected to the two flanges 14, 15. In other words, the first member 10 is composed of a single part, and the top plate 11, the two vertical walls 12, 13, and the two flanges 14, 15 are members made of a continuous material.

[0021] Therefore, first ridge portions 16, 17 are formed between the top plate 11 and the vertical walls 12, 13, one first ridge portion 16 being sandwiched between the top plate 11 and the vertical wall 12, and the other first ridge portion 17 being sandwiched between the top plate 11 and the vertical wall 13. In addition, second ridge portions 18, 19 are formed between the vertical walls 12, 13 and the flanges 14, 15, one second ridge portion 18 being sandwiched between the vertical wall 12 and the flange 14, and the other second ridge portion 19 being sandwiched between the vertical wall 13 and the flange 15. The first ridge portions 16, 17 and the second ridge portions 18, 19 all extend along the axial direction (Y direction) of the framework member 1.

[0022] The vertical wall 12 includes a first wall portion 12a connected to the first ridge portion 16, a second wall portion 12b connected to the first wall portion 12a, and a third ridge portion 20 sandwiched between the first wall portion 12a and the second wall portion 12b. The third ridge portion 20 extends along the axial direction (Y direction) of the frame member 1. The interior angle θ formed between the first wall portion 12a and the second wall portion 12b is less than 180°. The first wall portion 12a is inclined inward in cross section from the end of the second wall portion 12b on the top plate 11 side (the upper end in FIG. 3 ), with the third ridge portion 20 as a bending point. Note that the interior angle θ formed between the first wall portion 12a and the second wall portion 12b is preferably 100° or greater. The interior angle θ is more preferably 120° or greater, and even more preferably 150° or greater.

[0023] The opening angle of the first wall portion 12a, i.e., the interior angle between the top plate 11 and the first wall portion 12a, is, for example, 90° to 120°. Also, the angle between the second wall portion 12b and the flange 14 outside the hollow portion 40 (described later) is, for example, 90° to 120°.

[0024] The other vertical wall 13 is configured similarly to the above-described vertical wall 12, and has a first wall portion 13a connected to the first ridge portion 17, a second wall portion 13b connected to the first wall portion 13a, and a third ridge portion 21 sandwiched between the first wall portion 13a and the second wall portion 13b. Note that the interior angle θ between the first wall portion 13a and the second wall portion 13b on the vertical wall 13 side, the interior angle between the top plate 11 and the first wall portion 13a, and the angle between the second wall portion 13b and the flange 15 outside the hollow portion 40 (described later) may be different from the respective angles on the vertical wall 12 side.

[0025] The first member 10 is formed of an ultra-high-strength metal material, such as steel, having a tensile strength of 1400 MPa or more. The tensile strength of the first member 10 may be greater than 1500 MPa or greater than 2000 MPa. The first member 10 may also be composed of different-strength materials having different tensile strengths in the axial direction (Y direction) of the frame member 1. However, in the axial direction of the frame member 1, for example, a member in which the tensile strengths of the top plate 11 alternate at short intervals may exhibit unstable deformation behavior when a collision load is applied to the top plate 11 or the second member 30. For this reason, it is preferable that at least the top plate 11 of the first member 10 be composed of a uniform-strength material having the same tensile strength in the axial direction of the frame member 1.

[0026] The thickness of the first member 10 is not particularly limited, but may be, for example, 1.0 mm or more, 1.5 mm or more, or 2.0 mm or more. The upper limit of the thickness of the first member 10 is also not particularly limited, but is, for example, 6.0 mm or less. Note that when the tensile strength is 1400 to 1500 MPa, the thickness of the first member 10 is preferably 2.0 mm or more.

[0027] The above has described an outline of the configuration of the first member 10. Note that a more detailed description of the shape of the first member 10 will be given later.

[0028] The second member 30 is a member that is joined to the above-described first member 10, and a hollow portion 40 is formed by joining the first member 10 and the second member 30. As a result, a cross section perpendicular to the axial direction (Y direction) of the framework member 1 becomes a closed cross section. In this embodiment, the second member 30 is a flat closing plate, and the hollow portion 40 is formed by joining the second member 30 to the flanges 14, 15 of the first member 10. The hollow portion 40 extends along the axial direction of the framework member 1.

[0029] The first ridge portions 16, 17 of the first member 10 described above extend linearly along the axial direction (Y direction) of the framework member 1, but a recess that recesses inward into the hollow portion 40 may be formed in some linearly formed portions. However, from the viewpoint of increasing strength against collision loads and improving collision performance, it is preferable not to form a recess that is excessively recessed. For the same reason, it is preferable not to form a hole that penetrates through to the hollow portion 40 in the first ridge portions 16, 17.

[0030] Furthermore, the first wall portions 12a, 13a or the second wall portions 12b, 13b of the first member 10 may have a recess formed in a portion in the axial direction (Y direction) of the framework member 1 that recesses inward into the hollow portion 40. However, from the viewpoint of making it difficult for unstable deformation to occur when a collision load is input to the top plate 11 or the second member 30, it is preferable not to form a recess with an excessively large degree of recession.

[0031] The first member 10 and the second member 30 can be joined by welding means such as spot welding, laser welding, or plasma welding, or by known joining means using an industrial adhesive.

[0032] The second member 30 is formed of a metal material such as steel, aluminum alloy, or magnesium alloy. When the second member 30 is formed of steel, the tensile strength varies depending on the application location of the frame member 1 on the vehicle body, the required energy absorption performance, etc., but may be, for example, 590 MPa or more, or 780 MPa or more. Furthermore, the tensile strength of the second member 30 may be, for example, 1400 MPa or more, similar to the first member 10. The plate thickness of the second member 30 varies depending on the application location of the frame member 1 on the vehicle body, the required energy absorption performance, etc., but is, for example, 0.5 to 6.0 mm.

[0033] (Detailed Shape of First Member) Next, the first member 10 will be described in more detail with reference to Fig. 4. The first member 10 has a shape in which the interval a, the length w, the length b, and the length h satisfy specific relationships in a cross section perpendicular to the axial direction (Y direction) of the framework member 1 shown in Fig. 4. Note that in the following description, reference is made to the extended surfaces of the top plate 11, the first wall portions 12a, 13a, the second wall portions 12b, 13b, or the flanges 14, 15, but the "extended surface" refers to a surface extending from the surface on the opposite side to the second member 30 side in the plate thickness direction.

[0034] The interval a is the distance from the intersection P1 of the extension plane of the top plate 11 shown by the dashed line in Figure 4 and the extension plane of the second wall portion 12b of the vertical wall 12 to the intersection P2 of the extension plane of the top plate 11 and the extension plane of the second wall portion 13b of the vertical wall 13.

[0035] The length w is the distance from the intersection P1 to an intersection P5 between the extension plane of the top plate 11 and the extension plane of the first wall portion 12a of the vertical wall 12.

[0036] The length b is the distance from the intersection point P1 to an intersection point P3 between the extension plane of the flange 14 and the extension plane of the second wall portion 12b of the vertical wall 12. The definition of the length b in the case where no flange is formed on the vertical wall will be described later.

[0037] The length h is the distance from the intersection P1 to an intersection P6 between the extension plane of the first wall portion 12a and the extension plane of the second wall portion 12b.

[0038] The shape of the first member 10 in this embodiment is bilaterally symmetrical. Therefore, the distance from the intersection P2 on the vertical wall 13 side to the intersection P7 between the extended surface of the top panel 11 and the extended surface of the first wall portion 13a of the vertical wall 13 is the same as the length w on the vertical wall 12 side. Also, the distance from the intersection P2 on the vertical wall 13 side to the intersection P4 between the extended surface of the flange 15 and the extended surface of the second wall portion 13b of the vertical wall 13 is the same as the length b on the vertical wall 12 side. Also, the distance from the intersection P2 on the vertical wall 13 side to the intersection P8 between the extended surface of the first wall portion 13a and the extended surface of the second wall portion 13b is the same as the length h on the vertical wall 12 side.

[0039] In the first member 10, a, w, b, and h defined above satisfy 0<w / a≦0.500, 0.170≦h / b≦0.650, and w / h≦1.750.

[0040] The deformation process when a collision load is input to a conventional frame member 50 that does not satisfy the above-mentioned numerical range is shown in Fig. 5. Fig. 5 is a schematic diagram showing a cross section perpendicular to the axial direction of the frame member 50 when a cylindrical impactor 80 collides with the conventional frame member 50.

[0041] As shown in Figure 5, when a collision load is input to the frame member 50, the vertical walls 52, 53 first collapse outward and the top plate 11 deforms inward. As a result, tensile stress concentrates on the ridges between the top plate 11 and the vertical walls 52, 53, placing a significant load on the ridges. At this time, if a steel material with a tensile strength of 1270 MPa or less is used as the material for the frame member 50, the material at the ridges will stretch and deform, thereby absorbing the collision energy. On the other hand, if an ultra-high-strength steel material with a tensile strength of 1400 MPa or more is used as the material for the frame member 50, the material's low ductility may cause partial fracture of the material near the ridges due to the significant tensile load applied to the ridges.

[0042] The partial fractures described above propagate as cracks as deformation progresses, but because the cracks that occur in the tabletop 11 are cracks in locations where a large tensile load is applied, the direction of the crack propagation is in the direction of the dashed arrow shown in Figure 6, i.e., the width direction of the tabletop 11. For this reason, the cracks propagate across the tabletop 11, causing significant fractures that could split the tabletop 11, which could lead to a sudden decrease in energy absorption performance.

[0043] On the other hand, in the frame member 1 of this embodiment, which satisfies the specific numerical range described above, when a collision load is input to the top plate 11 or the second member 30, the first wall portions 12a, 13a of the vertical walls 12, 13 are deformed so that they collapse inward and the second wall portions 12b, 13b collapse outward, as shown in Fig. 7. This causes tensile stress to concentrate at the third ridge portions 20, 21. That is, the tensile load generated at the ridge portions adjacent to the top plate in conventional frame members is generated mainly at the third ridge portions 20, 21 in the frame member 1 of this embodiment. The tensile load generated here is smaller than the tensile load generated at the ridge portions between the top plate 51 and the vertical walls 52, 53 shown in Fig. 5.

[0044] Therefore, even if a crack occurs in the third ridge portions 20, 21, the crack will propagate in the longitudinal direction (Y direction) of the skeletal member 1, not in the width direction (X direction) of the skeletal member 1, as shown by the dashed arrow in Fig. 8. In other words, a crack that may occur in the skeletal member 1 will not propagate in a direction transverse to the skeletal member 1, and therefore, the occurrence of a significant fracture in the skeletal member 1 that could lead to separation can be avoided.

[0045] The value of w / a is preferably less than 0.250. As will be shown in the examples described later, when w / a is less than 0.250, the bending strength (maximum load during bending deformation) of the skeleton member 1 can be increased to the extent that the skeleton member 1 does not break. From the viewpoint of further increasing the bending strength, w / a is preferably 0.225 or less, and more preferably 0.200 or less. Furthermore, w / a is preferably 0.050 or more, or 0.100 or more.

[0046] The above-mentioned h / b is preferably less than 0.500 from the viewpoint of increasing the bending strength of the skeleton member 1 without causing separation of the skeleton member 1. From the viewpoint of further increasing the bending strength, h / b is preferably 0.400 or less, and more preferably 0.350 or less.

[0047] The w / h is preferably 0.200 or more. For example, w / h may be 0.300 or more, or 0.500 or more. Furthermore, w / h may be, for example, 1.500 or less. From the viewpoint of increasing the bending strength of the skeletal member 1 without causing separation of the skeletal member 1, w / h is preferably less than 1.000. From the viewpoint of further increasing the bending strength, w / h is more preferably 0.950 or less.

[0048] The above has described the skeletal member 1 according to this embodiment. This skeletal member 1 includes a first member 10 that satisfies 0<w / a≦0.500, 0.170≦h / b≦0.650, and w / h≦1.750. With a skeletal member 1 that includes such a first member 10, it is possible to prevent significant fracture that would lead to separation during deformation due to the input of a collision load, even if the first member 10 is made of an ultra-high strength material.

[0049] The skeletal member 1 according to this embodiment is configured by joining a first member 10 having first wall portions 12a, 13a and second wall portions 12b, 13b to a second member 30, but a skeletal member having such a first wall portion and a second wall portion may also be configured as shown in Fig. 9. The skeletal members 60 and 70 shown in Fig. 9 are not configured by joining the first member 10 and the second member 30 as in the skeletal member 1 according to this embodiment, but are molded as a single part.

[0050] 9(A) is a member having a hollow portion 40 consisting of a top plate 61, two vertical walls 62 and 63, and a bottom plate 64, and the top plate 61, the vertical walls 62 and 63, and the bottom plate 64 are formed from a single plate. Similar to the above-described framework member 1, the two vertical walls 62 and 63 have first wall portions 62a and 63a and second wall portions 62b and 63b.

[0051] In this skeletal member 60, the bending centers of the ridges located between adjacent wall portions are all located in the inner region of the hollow portion 40. In such a skeletal member 60, when a collision load is input from, for example, the top plate 61 side or the bottom plate 64 side, the first wall portion 62a and the second wall portion 62b on the vertical wall 62 side and the first wall portion 63a and the second wall portion 63b on the vertical wall 63 side are deformed so as to move in directions away from each other. When such deformation occurs, it is difficult to increase the deformation resistance against the collision load, and there is room for improvement in terms of improving energy absorption performance.

[0052] The skeleton member 70 shown in Figure 9(B) is a member having a hollow portion 40 consisting of a top plate 71, two vertical walls 72 and 73, a bottom plate 74, and two protrusions 75 and 76. The protrusions 75 and 76 extend outward from the ends of the vertical walls 72 and 73 on the bottom plate 74 side and extend parallel to the top plate 71. The top plate 71, vertical walls 72 and 73, bottom plate 74, and protrusions 75 and 76 are formed from a single plate. Similar to the skeleton member 1 described above, the two vertical walls 72 and 73 have first wall portions 72a and 73a and second wall portions 72b and 73b.

[0053] When a collision load is applied to this frame member 70 from, for example, the top plate 71 side or the bottom plate 74 side, deformation similar to that of the frame member 1 described in Fig. 7 may occur. However, the protrusions 75 and 76 shown in Fig. 9(B) have an extremely large curvature, and there is a high concern that molding cracks may occur during molding of these portions. In other words, it is not realistic to mold the frame member 70 including these protrusions 75 and 76 as a single part.

[0054] On the other hand, the skeletal member 1 according to this embodiment, which is composed of the first member 10 and the second member 30, is much easier to form than the skeletal member 70 shown in Fig. 9(B) . In other words, the skeletal member 1 according to this embodiment is a member that can avoid the occurrence of significant fractures that lead to separation during deformation and also has excellent formability.

[0055] (Examples of Shape of Skeleton Member) Next, examples of shapes of the skeleton member 1 including the first member 10 having a bilaterally symmetrical shape will be described with reference to FIG.

[0056] Fig. 10(A) shows an example in which a groove 11a is formed in the top plate 11 of the first member 10. Fig. 10(B) shows an example in which the second member 30 is a hat-shaped member rather than a flat plate. This second member 30 has a top plate 31, two vertical walls 32, 33, and two flanges 34, 35, and the flanges 34, 35 are joined to the flanges 14, 15 of the first member 10. Fig. 10(C) shows an example in which a groove 31a is formed in the top plate 31 shown in Fig. 10(B).

[0057] Fig. 10(D) shows an example in which the vertical walls 32, 33 of the hat-shaped second member 30 are arranged to face the inner surfaces of the second wall portions 12b, 13b of the vertical walls 12, 13 of the first member 10. Fig. 10(E) shows an example in which a groove portion 31a is formed in the top plate 31 shown in Fig. 10(D). Fig. 10(F) shows an example in which the flange is removed from the hat-shaped second member 30 shown in Fig. 10(D) and the second member 30 is formed into a U-shape. In this example, the vertical walls 32, 33 of the second member and the second wall portions 12b, 13b of the first member 10 are joined to each other.

[0058] As described above, there are various examples of shapes of the skeleton member 1 including the first member 10 that satisfies the above-described numerical range. Furthermore, although the first wall portions 12a, 13a of the skeleton member 1 described above each have a symmetrical shape when viewed in the axial direction (Y direction), they may also have an asymmetrical shape, for example, as shown in FIG.

[0059] 11, the length w defined on the vertical wall 12 side is the distance w1 from the intersection P1 to the intersection P5, and the length h is the distance h1 from the intersection P1 to the intersection P6. Also, the length w defined on the vertical wall 13 side is the distance w2 from the intersection P2 to the intersection P7, and the length h is the distance h2 from the intersection P2 to the intersection P8.

[0060] Furthermore, by satisfying 0<w / a≦0.500, 0.170≦h / b≦0.650, and w / h≦1.750 on both the vertical wall 12 side and the vertical wall 13 side, it is possible to avoid the occurrence of significant fractures that could lead to separation when deformation occurs due to the input of a collision load.

[0061] In the skeletal member 1 described above, the flanges 14, 15 are formed on the two vertical walls 12, 13, but the flanges 14, 15 do not have to be formed on at least one of the two vertical walls 12, 13. Fig. 12 shows an example in which the flange 14 is formed on the vertical wall 12 and the flange is not formed on the vertical wall 13. In addition, in the skeletal member 1 shown in Fig. 12, a groove 11a is formed in the top plate of the first member 10, and top plates 11b, 11c are formed to sandwich the groove 11a. These top plates 11b, 11c do not extend in the same plane and are non-parallel to the flange 14.

[0062] The second member 30 is an L-shaped plate consisting of a flat top plate 31 and a vertical wall 33 extending from an end of the top plate 31 toward the side opposite the top plate 11 of the first member 10 (the negative side in the Z direction). A ridge portion 36 is formed between the top plate 31 and the vertical wall 33, and the ridge portion 36 extends along the axial direction (Y direction) of the first member 10. The top plate 31 of the second member 30 is joined to the flange 14 of the first member 10, and the vertical wall 33 of the second member 30 is joined to the inner surface of the second wall portion 13b of the vertical wall 13 of the first member 10. In this way, the first member 10 and the second member 30 are joined to form the framework member 1.

[0063] The aforementioned lengths w, b, and h of such a skeletal member 1 are defined as follows. First, the lengths w, b, and h of the vertical wall 12 on which the flange 14 is formed are defined in the same manner as described above. More specifically, the length w of the vertical wall 12 is the distance w from the intersection P of the extended surface of the top plate 11b and the extended surface of the second wall portion 12b to the intersection P of the extended surface of the top plate 11b and the extended surface of the first wall portion 12a. The length b of the vertical wall 12 is the distance b from the intersection P to the intersection P of the extended surface of the flange 14 and the extended surface of the second wall portion 12b. The length h of the vertical wall 12 is the distance h from the intersection P to the intersection P of the first wall portion 12a and the second wall portion 12b.

[0064] The lengths w and h of the vertical wall 13 on which no flange is formed are defined in the same manner as described above. Specifically, the length w of the vertical wall 13 is the distance w from the intersection P2 of the extension of the top plate 11c and the extension of the second wall portion 13b to the intersection P7 of the extension of the top plate 11c and the extension of the first wall portion 13a. The length h of the vertical wall 12 is the distance h2 from the intersection P2 to the intersection P8 of the first wall portion 13a and the second wall portion 13b. Meanwhile, the length b of the vertical wall 13 is defined differently from the above because no flange is formed on the vertical wall 13. Specifically, the length b of the vertical wall 13 is the distance b2 from the intersection P2 to the intersection P4 of the extension of the top plate 31 of the second member 30 and the extension of the vertical wall 33 of the second member 30.

[0065] In this way, by satisfying 0<w / a≦0.500, 0.170≦h / b≦0.650, and w / h≦1.750 for the lengths w, b, and h defined on the vertical wall 12 side and the vertical wall 13 side, respectively, it is possible to avoid the occurrence of significant fractures that lead to separation when deformation occurs due to the input of a collision load.

[0066] 13A and 13B are diagrams showing examples of the shape of a frame member in which a flange is not formed on at least one of the two vertical walls 12, 13. Fig. 13A shows an example in which a first member 10 is composed of a top plate 11, two vertical walls 12, 13, and one flange 15. The second member 30 in this example is formed in an L-shape and has a top plate 31 and a vertical wall 32 extending from one end of the top plate 31 toward the outside of the hollow portion 40. The top plate 31 of the second member 30 is joined to the flange 15 of the first member 10, and the vertical wall 32 of the second member 30 is joined to the second wall portion 12b of the vertical wall 12 of the first member 10.

[0067] 13(B) shows an example in which the first member 10 is composed of a top plate 11 and two vertical walls 12, 13, and neither of the vertical walls 12, 13 has a flange. The second member 30 in this example is formed in a U-shape and has a top plate 31 and two vertical walls 32, 33 extending from each end of the top plate 31 toward the outside of the hollow portion 40. The vertical wall 32 of the second member 30 is joined to the second wall portion 12b of the vertical wall 12 of the first member 10, and the vertical wall 33 of the second member 30 is joined to the second wall portion 13b of the vertical wall 13 of the first member 10.

[0068] While the embodiments of the present invention have been described above, the present invention is not limited to these examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the technical ideas described in the claims, and it is understood that these modifications also fall within the technical scope of the present invention.

[0069] For example, the components of the above-described embodiments can be combined in any manner, and such combinations will naturally provide the functions and advantages of the individual components involved in the combination, as well as other functions and advantages that will be apparent to those skilled in the art from the description herein.

[0070] A collision simulation was carried out using the finite element method to simulate deformation of an automobile frame member during a collision using the analytical model shown in Fig. 14. This simulation was a three-point bending analysis in which the top plate 11 of the first member 10 was supported by two cylindrical supports 81 with a diameter of 60 mm, and an impactor 80 with a diameter of 100 mm was inserted from the second member 30 side. The analytical model shown in Fig. 14 is a model in which the first member 10 is arranged on the inside of the vehicle and the second member 30 is arranged on the outside of the vehicle. The input from the impactor 80 corresponds to a collision load input from outside the vehicle body.

[0071] The framework member of the analytical model is formed by joining a first member 10 having a bilaterally symmetrical shape and a flat plate-like second member 30 as shown in Fig. 4. In this simulation, multiple models are used in which the lengths of a, b, w, and h shown in Fig. 4, the tensile strength and plate thickness of the first member 10, etc. are changed.

[0072] This simulation also evaluated whether or not the framework member would break during the displacement of the impactor 80 from its initial position to 250 mm. In this simulation, "break" refers to a state in which the material of the tabletop becomes discontinuous in the longitudinal direction of the framework member due to the propagation of a crack, causing the material to break across the tabletop. The common concept of forming limit diagrams (FLDs) was used to determine whether a break occurred, and elements determined to be broken were deleted from the finite element model.

[0073] The simulation conditions and the evaluation results regarding whether or not the skeletal members were separated are shown in Table 1. The first member 10 and the second member 30 were made of steel, and the tensile strength of the second member 30 was 1470 MPa and the plate thickness was 1.8 mm.

[0074]

[0075] The models in Cases 1 to 3 are models using the general hat member shown in Figure 6, and both w and h are 0. The results of Cases 1 to 3 show that separation occurs when the tensile strength is 1400 MPa or more, w / a = 0, and h / b = 0.

[0076] On the other hand, even when the tensile strength is 1400 MPa or more, no separation occurs in any of the cases where the conditions 0<w / a≦0.500, 0.170≦h / b≦0.650, and w / h≦1.750 are simultaneously satisfied. In other words, in the frame members according to the examples of the present invention, significant fractures that lead to separation do not occur when deformation occurs due to the input of a collision load.

[0077] Figure 15 shows the simulation results for CASE with a tensile strength of 2000 MPa and a plate thickness of 1.6 mm. The vertical axis represents the bending strength (maximum load during bending deformation) and the horizontal axis represents w / a. As shown in Figure 15, when w / a is less than 0.250, the bending strength increases and the collision performance is further improved. Note that although splitting occurred in the frame member with w / a = 0, the bending strength immediately before splitting was high. However, when splitting occurs, the energy absorption performance is significantly reduced, and the collision performance of the frame member is low.

[0078] Fig. 16 shows the simulation results for CASE with a tensile strength of 2000 MPa and a plate thickness of 1.6 mm, and is a graph with the bending strength (maximum load during bending deformation) on the vertical axis and the h / b on the horizontal axis. As shown in Fig. 16, when the h / b ratio is less than 0.500, the bending strength increases and the collision performance is further improved.

[0079] Fig. 17 shows the simulation results for CASE with a tensile strength of 2000 MPa and a plate thickness of 1.6 mm, and is a graph with the bending strength (maximum load during bending deformation) on the vertical axis and w / h on the horizontal axis. As shown in Fig. 17, when w / h is less than 1.000, the bending strength increases and the collision performance is further improved.

[0080] The above describes the embodiments of the present invention. The effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology disclosed herein may achieve other effects that will be apparent to those skilled in the art from the description of this specification, in addition to or in place of the above effects.

[0081] The present invention can be applied to automobile frame members.

[0082] DESCRIPTION OF SYMBOLS 1 Automobile frame member 10 First member 11 Top plate 11a Groove portion 11b Top plate 11c Top plate 12, 13 Vertical walls 12a, 13a First wall portion 12b, 13b Second wall portion 14, 15 Flange 16, 17 First ridge portion 18, 19 Second ridge portion 20, 21 Third ridge portion 30 Second member 31 Top plate 31a Groove portion 32, 33 Vertical walls 34, 35 Flange 36 Ridge portion 40 Hollow portion 50 Conventional automobile frame member 51 Top plate 52, 53 Vertical walls 60 Automobile frame member 61 Top plate 62, 63 Vertical walls 62a, 63a First wall portion 62b, 63b Second wall portion 64 Bottom plate 70 Automobile frame member 71 Top plate 72, 73 Vertical walls 72a, 73a First wall portion 72b, 73b Second wall portion 74 Bottom plate 75, 76 Protruding portion 80 Impactor 81 Support

Claims

1. Automotive frame component, A first member made of a metal material with a tensile strength of 1400 MPa or more, A second member made of a metal material, The first member and the second member are joined together to form a hollow portion extending along the axial direction of the automobile frame member, The first member is, The tabletop and Two vertical walls facing each other, It has a ridge portion that extends along the axial direction of the automobile frame member, sandwiched between the top plate and the vertical wall, The aforementioned vertical wall is The first wall portion connected to the aforementioned ridge portion, A second wall portion connected to the first wall portion, It has, sandwiched between the first wall portion and the second wall portion, another ridge portion extending along the axial direction of the automobile frame member, The interior angle between the first wall portion and the second wall portion is less than 180°. An automobile frame member wherein the length w from the intersection of the extended surface of the top plate and the extended surface of the second wall to the top plate, the distance a between the two vertical walls, the length h from the top plate to the other ridge portion, and the length b of the first member satisfy 0 < w / a ≤ 0.500, 0.170 ≤ h / b ≤ 0.650, and w / h ≤ 1.

750.

2. The first member is made of a metal material having a tensile strength of 1500 MPa or less and a plate thickness of 2.0 mm or more, as described in claim 1.

3. The first member is made of a metal material having a tensile strength greater than 1500 MPa, as described in claim 1.

4. The automobile frame member according to claim 1 or 2, wherein the w / a is less than 0.

250.

5. The automobile frame member according to claim 1 or 2, wherein the w / a is 0.050 or more.

6. The automobile frame member according to claim 1 or 2, wherein the h / b ratio is less than 0.

500.

7. The automobile frame member according to claim 1 or 2, wherein the w / h is less than 1.

000.

8. A vehicle body structure comprising an automobile frame member according to claim 1 or 2, A vehicle body structure in which the first member is located on the inside of the vehicle and the second member is located on the outside of the vehicle.