Automotive structural components

Abstract

This automotive structural member is provided with a hat-shaped first member and a hat-shaped second member. The first member has a first top plate, two first vertical walls, two first flanges, and first standing parts. The first flanges are respectively located between the first vertical walls and the first standing parts. The second member has a second top plate, two second vertical walls, and two second flanges. The second top plate is positioned between the two first vertical walls of the first member. The second vertical walls respectively face the first vertical walls of the first member. Each gap formed between the second vertical wall and the first vertical wall is 5.0 mm or less. The second flanges are respectively joined to the first flanges. The second member comprises a steel material having a tensile strength of 690 MPa or more.

Description

[Technical Field]

[0001] This invention relates to structural components for automobiles. [Background technology]

[0002] In recent years, fuel efficiency regulations have become stricter worldwide, demanding lighter vehicles. Furthermore, in response to fuel efficiency regulations in various countries and the trend toward carbon neutrality, the electrification of vehicle power sources is progressing. This necessitates the installation of heavy batteries in vehicles, further increasing the need for weight reduction. At the same time, improved crash safety is also required, necessitating a balance between vehicle weight reduction and crash safety.

[0003] Examples of structural components in automobiles that contribute to collision safety include skeletal members located around the cabin, such as bumper beams, side sills, and cross members. One of the performance requirements for these components is the ability to withstand greater collision loads (load-bearing capacity) in order to improve occupant safety during collisions and enhance the protection of batteries located under the floor.

[0004] Structural members with excellent load-bearing capacity also have excellent collision safety. Therefore, in order to achieve both collision safety and weight reduction as mentioned above, it is desirable to improve, for example, the load-bearing capacity per unit weight of the structural member (hereinafter referred to as "weight efficiency of load-bearing capacity").

[0005] To improve the weight efficiency of load-bearing performance, improvements in materials such as increasing the strength of materials, making them thinner, and applying dissimilar materials can be considered. However, improvements in the shape of each component that makes up the structural member and the joining methods between components are also required.

[0006] As a conventional technology related to automotive structural members, Patent Document 1 discloses a bumper beam in which a cover is welded to the inside of a hat-shaped profile.

[0007] Patent Document 2 discloses a bumper beam made of high-strength steel, which includes a hat-shaped profile with a cover.

[0008] Patent Document 3 discloses a bumper beam provided with a cover that closes the cross-section of a hat-shaped profile.

[0009] Patent Document 4 discloses a bumper reinforcement comprising a flat first member including two first upright portions and a hat-shaped second member including two second upright portions, wherein the first upright portions stand up toward the second member, and the first and second upright portions are not integrated.

[0010] Figure 7 of Patent Document 5 discloses a bumper beam having a main body portion with a U-shaped cross-section that opens forward and has an upper wall, side walls, a lower wall, and a pair of upper and lower joining flanges, and a pair of left and right plate-shaped closing portions that are joined to the joining flanges and form a closed cross-section.

[0011] Patent Document 6 discloses a vehicle bumper beam comprising a first member having a flat first top plate portion, two first vertical wall portions connected to each of the two sides of the first top plate portion, and two first flange portions connected to each of the two first vertical wall portions, in a cross section perpendicular to the longitudinal direction. This vehicle bumper beam further comprises a second member having a second top plate portion having a convex portion projecting toward the opposite side of the first top plate portion, two second vertical wall portions connected to each of the two sides of the second top plate portion and positioned in close proximity to each of the first vertical wall portions on the inside of the first member, and two second flange portions connected to each of the two second vertical wall portions and positioned joined to each of the first flange portions.

[0012] Patent Document 7 discloses a vehicle body structure comprising a pair of panels that constitute a vehicle body frame member, each formed in an elongated shape and having a closed cross-section when cut in a direction intersecting the longitudinal direction. This vehicle body structure comprises a concave bead formed on at least one of the pair of panels, extending in the longitudinal direction of the vehicle body frame member, recessed inward from the closed cross-section, and having a ridge line extending in the longitudinal direction of the vehicle body frame member at its open end, and a convex bead formed on at least one of the panels, extending in a direction intersecting the longitudinal direction of the vehicle body frame member, protruding from the bottom of the concave bead toward the open side of the concave bead, and having its tip located on the bottom side of the ridge line in the concave bead. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Application Publication No. 2016-509976 [Patent Document 2] Japanese Patent No. 4436322 [Patent Document 3] Japanese Patent No. 6334670 [Patent Document 4] Japanese Patent No. 6372619 [Patent Document 5] Japanese Patent Application Publication No. 2015-209024 [Patent Document 6] International Publication No. 2019 / 035185 [Patent Document 7] Japanese Patent Application Publication No. 2013-216185 [Overview of the project] [Problems that the invention aims to solve]

[0014] The bumper beams described in Patent Documents 1 to 7 all have a configuration in which a closed cross-section is formed by combining a second member with a hat-shaped first member. However, there is room for improvement from the viewpoint of suppressing excessive out-of-plane deformation in the initial stage of a collision and improving the weight efficiency of the load-bearing performance of the structural member.

[0015] The present invention has been made in view of the above circumstances, and an object thereof is to improve the weight efficiency of the load-bearing performance of an automobile structural member.

Means for Solving the Problems

[0016] One aspect of the present invention for solving the above problems is an automobile structural member, comprising a hat-shaped first member and a hat-shaped second member. A hollow portion formed by joining the first member and the second member, The first member has a first top plate, two first vertical walls facing each other, two first flanges protruding outward from each of the two first vertical walls, and a first upright portion protruding from at least one of the first flanges toward the first top plate side. One end of the first vertical wall is connected to the first top plate, the other end of the first vertical wall is connected to the first flange, the first flange is between the first vertical wall and the first upright portion, the second member has a second top plate, two second vertical walls facing each other, and two second flanges protruding outward from each of the two second vertical walls. The second top plate is located between the two first vertical walls of the first member, the second vertical wall faces the first vertical wall of the first member, a gap formed between the second vertical wall and the first vertical wall is 5.0 mm or less, the second flange is joined to the first flange, the second member is made of a steel material having a tensile strength of 690 MPa or more, and the first upright portion is continuously formed along the axial direction of the automobile structural member. The first vertical wall is formed in a straight line or convex inward toward the hollow portion in a cross section perpendicular to the axial direction of the automobile structural member. It is characterized by that.

Effects of the Invention

[0017] According to the present invention, the weight efficiency of the load-bearing performance of an automobile structural member can be improved.

Brief Description of the Drawings

[0018] [Figure 1] It is a perspective view showing a schematic configuration of an automotive structural member according to an embodiment of the present invention. [Figure 2] It is a view showing a cross-section perpendicular to the axial direction of the automotive structural member. [Figure 3] It is a view for explaining the definition of the height H of the first top plate and the height h of the second top plate. [Figure 4] It is a view for explaining the deformation behavior of the automotive structural member. [Figure 5] It is a load-stroke diagram for explaining the change over time of the reaction force generated in each structural member shown in FIG. 4. [Figure 6] It is a view showing an example of the shape of the first member. [Figure 7] It is a view showing an example of the shape of the first member. [Figure 8] It is a view showing an example of the shape of the first member. [Figure 9] It is a view showing an example of the shape of the second member. [Figure 10] It is a view showing an example of the shape of the second member. [Figure 11] It is a view for explaining the analysis model of simulation (1). [Figure 12] It is a view for explaining the analysis model of simulation (1). <000012!> [Figure 13] It is a view showing the result of simulation (1). [Figure 14] It is a view showing the result of simulation (2).

Mode for Carrying Out the Invention

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the present specification and the drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted. [

[0020] Figure 1 is a perspective view showing a schematic configuration of an automobile structural member according to an embodiment of the present invention. Figure 2 is a diagram showing a cross-section of the automobile structural member perpendicular to the axial direction.

[0021] Automotive structural member 1 (hereinafter sometimes simply referred to as "structural member 1") is applied, for example, as a skeletal member of the vehicle body, and is particularly applied to parts where bending deformation is likely to occur when a collision load is applied. Specifically, it can be applied to skeletal members such as bumper beams (front bumper beam or rear bumper beam), side sills, roof side rails, cross members (floor cross members, roof cross members, etc.), or center pillars.

[0022] In this specification and in the drawings, the X, Y, and Z directions are perpendicular to each other, and the Y direction is parallel to the axial direction of the automotive structural member 1. Furthermore, when the structural member 1 is applied to, for example, the following skeletal member, the X, Y, and Z directions correspond to the following directions. • Bumper beam, cross member X direction: vehicle height direction, Y direction: vehicle width direction, Z direction: vehicle length direction • Side sills, roof side rails 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

[0023] As shown in Figures 1 and 2, the structural member 1 comprises a first member 100 and a second member 200.

[0024] First, the general configuration of the first component 100 will be described.

[0025] The first member 100 has a first top plate 101, two first vertical walls 102 and 103, two first flanges 104 and 105, and two first upright parts 106 and 107.

[0026] The first member 100 is a member whose cross-section perpendicular to the axial direction (Y direction) is hat-shaped. More specifically, in the cross-section perpendicular to the axial direction of the first member 100, each of the two first vertical walls 102 and 103 is located between the first top plate 101 and each of the two first flanges 104 and 105, and each of the two first flanges 104 and 105 is located between each of the two first vertical walls 102 and 103 and each of the two first upright portions 106 and 107. The parts of the first member 100 will be described in more detail below.

[0027] The first top plate 101 is a plate-like portion that extends in the longitudinal direction of the structural member 1. The extension direction of the first top plate 101 is in the vehicle width direction when the structural member 1 is applied to a skeletal member such as a bumper beam or cross member, in the vehicle length direction when it is applied to a skeletal member such as a side sill or roof side rail, and in the vehicle height direction when it is applied to a skeletal member such as a center pillar.

[0028] The width of the first top plate 101 (length in the X direction in Figure 2) is appropriately changed depending on the application location of the structural member 1 in the vehicle body, but is set to, for example, 30 to 200 mm.

[0029] The two first vertical walls 102 and 103 are positioned facing each other. Each end of the two first vertical walls 102 and 103 is connected to the first top plate 101, and ridges 108 and 109 are formed between the two first vertical walls 102 and 103 and the first top plate 101, respectively. These ridges 108 and 109 extend in the axial direction (Y direction) of the structural member 1.

[0030] The first vertical walls 102 and 103 may be formed perpendicular to the first top plate 101, or they may be formed at an angle. The angle between each of the two first vertical walls 102 and 103 and the first top plate 101 is set to, for example, 90 to 110 degrees.

[0031] The first flanges 104 and 105 are connected to the ends of the first vertical walls 102 and 103 opposite to the connecting ends of the first top plate 101, and protrude outward from each of the two first vertical walls 102 and 103. A ridge portion 110 is formed between one of the two first flanges 104 and one of the two first vertical walls 102, and a ridge portion 111 is formed between the other first flange 105 and the other first vertical wall 103. These ridge portions 110 and 111 extend in the axial direction (Y direction) of the structural member 1.

[0032] Here, we will explain the "height H of the first top plate," which is the height from the first flanges 104 and 105 to the first top plate 101. First, in a cross section perpendicular to the axial direction of the structural member 1, the direction perpendicular to the straight line connecting the ridge portion 108 and the ridge portion 109 is called direction H. v And the height H of the first top plate 101 is defined as the direction H. v This is the length from ridge sections 110 and 111 to ridge sections 108 and 109. Direction H in the example shown in Figure 2. v This is in the same direction as the Z direction. The height H of this first top plate 101 is appropriately changed depending on the application location of the structural member 1 in the vehicle body, but is set to, for example, 30 to 200 mm.

[0033] Note that the hat-shaped first member 100 may also be asymmetrical, as shown in Figure 3, for example. In this case, the length from one of the first flanges 104 to the first top plate 101 and the length from the other first flange 105 to the first top plate 101 are different. In such cases, direction H v The length H1 from ridge section 110 to ridge section 108, and the direction H v The height H of the first top plate 101 is defined as the longer of the lengths H2 from ridge section 111 to ridge section 109. In the example shown in Figure 3, since length H1 is longer than length H2, length H1 is the height H of the first top plate 101.

[0034] As shown in Figure 2, the first upright portions 106 and 107 protrude toward the first top plate 101 from the tip of the first flanges 104 and 105 (the end of the first flanges 104 and 105 opposite to the side connected to the first vertical walls 102 and 103). A ridge portion 112 is formed between one of the two first upright portions 106 and one of the two first flanges 104, and a ridge portion 113 is formed between the other first upright portion 107 and the other first flange 105. These ridge portions 112 and 113 extend in the axial direction (Y direction) of the structural member 1.

[0035] Here, the length from the first flanges 104 and 105 to the tips of the first upright parts 106 and 107 in the direction perpendicular to the first top plate 101 (Z direction) is defined as the height of the first upright parts 106 and 107. The higher the height of the first upright parts 106 and 107, the greater the second moment of area of ​​the first member 100, which increases the deformation resistance of the first member 100 when an impact load is applied, and thus improves the load-bearing capacity.

[0036] The heights of the first upright sections 106 and 107 are appropriately changed depending on the application location of the structural member 1 in the vehicle body and the required load-bearing capacity, but for example, they are set to a height of 0.15 to 0.50 times the height H of the first top plate 101.

[0037] Next, the general configuration of the second member 200 will be described.

[0038] The second member 200 has a second top plate 201, two second vertical walls 202 and 203, and two second flanges 204 and 205.

[0039] The second member 200 is a member with a hat-shaped cross-section perpendicular to the axial direction (Y direction). More specifically, in the cross-section perpendicular to the axial direction of the second member 200, each of the two second vertical walls 202 and 203 is located between the second top plate 201 and each of the two second flanges 204 and 205. The following describes each part of the second member 200 in more detail.

[0040] The second top plate 201 is a plate-shaped portion facing the first top plate 101 and extends along the extending direction of the first top plate 101. Also, the second top plate 201 is located between the two first vertical walls 102 and 103 of the aforementioned first member 100.

[0041] Here, the "height h of the second top plate", which is the height from the second flanges 204 and 205 to the second top plate 201, will be described. First, in a cross-section perpendicular to the axial direction of the structural member 1, a direction perpendicular to the straight line connecting the ridge line portion 206 and the ridge line portion 207 is defined as the direction h. v And the height h of the second top plate 201 is the length from the ridge line portions 208 and 209 to the ridge line portions 206 and 207 in that direction h. In the example shown in FIG. 2, the direction h v is the same as the Z direction. The height h of this second top plate 201 is appropriately changed according to the application location of the structural member 1 in the vehicle body, but is set to, for example, 30 to 200 mm. v

[0042] Note that the hat-shaped second member 200 may be, for example, a left-right asymmetric shape as shown in FIG. 3. In this case, the length from one of the two second flanges 204 to the second top plate 201 and the length from the other second flange 205 to the second top plate 201 are different from each other. In such a case, the longer of the length h1 from the ridge line portion 208 to the ridge line portion 206 and the length h2 from the ridge line portion 209 to the ridge line portion 207 in the direction h v is taken as the height h of the second top plate 201. In the example shown in FIG. 3, since the length h1 is longer than the length h2, the length h1 is the height h of the second top plate 201. <0**********010>

[0043] ​​As shown in the embodiments described later, from the viewpoint of improving the weight efficiency of the load-bearing performance of the structural member 1, the ratio (h / H) of the height h of the second top plate 201 to the height H of the first top plate 101 is preferably 0.10 to 0.52. From the viewpoint of improving the weight efficiency of the load-bearing performance, the height ratio (h / H) is more preferably 0.15 or more, and even more preferably 0.20 or more. Furthermore, from the viewpoint of improving the weight efficiency of the load-bearing performance, the height ratio (h / H) is more preferably 0.48 or less, and even more preferably 0.45 or less.

[0044] The two second vertical walls 202 and 203 are positioned facing each other. Each end of the two second vertical walls 202 and 203 is connected to the second top plate 201, and ridges 206 and 207 are formed between the two second vertical walls 202 and 203 and the second top plate 201, respectively. These ridges 206 and 207 extend in the axial direction (Y direction) of the structural member 1.

[0045] Furthermore, as mentioned above, each of the two second vertical walls 202 and 203 is positioned opposite each of the two first vertical walls 102 and 103 because the second top plate 201 is sandwiched between the two first vertical walls 102 and 103 of the first member 100. That is, one of the two second vertical walls 202 faces the other first vertical wall 102, and the other second vertical wall 203 faces the other first vertical wall 103.

[0046] From the perspective of suppressing out-of-plane deformation of the first vertical walls 102 and 103 and improving load-bearing performance, the second vertical walls 202 and 203 need to be located near the first vertical walls 102 and 103 so that they come into contact with the first vertical walls 102 and 103 that have deformed due to the impact load. Specifically, the distance between the second vertical walls 202 and 203 and the first vertical walls 102 and 103 must be 5.0 mm or less, that is, the gap formed between the second vertical walls 202 and 203 and the first vertical walls 102 and 103 must be 5.0 mm or less. If this gap exceeds 5.0 mm, the first vertical walls 102 and 103 and the second vertical walls 202 and 203 will not come into contact when the structural members deform due to the input of the impact load, and the effect of suppressing out-of-plane deformation of the first vertical walls 102 and 103 cannot be obtained. From the viewpoint of suppressing out-of-plane deformation of the first vertical walls 102 and 103 and improving load-bearing performance, the above-mentioned gap is more preferably less than or equal to the plate thickness of the first vertical walls 102 and 103, and even more preferably 0 mm. That is, it is preferable that the second vertical walls 202 and 203 are in contact with the first vertical walls 102 and 103.

[0047] Furthermore, from the viewpoint of suppressing out-of-plane deformation of the first vertical walls 102 and 103 and improving load-bearing performance, it is preferable that one of the two second vertical walls 202 is parallel to one of the two first vertical walls 102, and the other second vertical wall 203 is parallel to the other first vertical wall 103.

[0048] The second flanges 204 and 205 are connected to the ends of the second vertical walls 202 and 203 opposite to the connecting ends of the second top plate 201, and protrude outward from each of the second vertical walls 202 and 203. A ridge portion 208 is formed between one of the two second flanges 204 and one of the two second vertical walls 202, and a ridge portion 209 is formed between the other second flange 205 and the other second vertical wall 203. These ridge portions 208 and 209 extend in the axial direction (Y direction) of the structural member 1.

[0049] Each of the first member 100 and the second member 200 described above is manufactured, for example, by press forming a flat plate made of a metal material. The metal material is, for example, steel, aluminum alloy, magnesium alloy, etc. As shown in the embodiments described later, when steel is used as the metal material, the effect of improving the weight efficiency of the load-bearing performance can be enhanced by using steel with a tensile strength of 690 MPa or more. From the viewpoint of further enhancing the effect of improving the weight efficiency of the load-bearing performance, the tensile strength is preferably 780 MPa or more, and more preferably 980 MPa or more or 1180 MPa or more. Note that the materials of the first member 100 and the second member 200 may be different from each other.

[0050] The total length (axial length) of the first member 100 and the total length of the second member 200 are appropriately changed depending on the application location of the structural member 1 in the vehicle body, but are, for example, 1000 to 3000 mm. Note that the total length of the first member 100 and the total length of the second member 200 may be different from each other.

[0051] The plate thickness of the first member 100 and the plate thickness of the second member 200 are appropriately changed according to the application location of the structural member 1 in the vehicle body and the required load-bearing capacity, but are for example 0.5 to 6.0 mm. The plate thickness of the first member 100 and the second member 200 may be, for example, 0.8 mm or more, or 1.0 mm or more. On the other hand, the plate thickness of the first member 100 and the second member 200 may be, for example, 4.0 mm or less, or 3.0 mm or less. The plate thickness of the first member 100 and the plate thickness of the second member 200 may be different from each other.

[0052] The first member 100 and the second member 200 have been described above. These first member 100 and the second member 200 are joined at the joint 300. More specifically, each of the two first flanges 104 and 105 and each of the two second flanges 204 and 205 are overlapped, and the flanges are joined to each other by known joining means. The joining means is not particularly limited, but welding means such as spot welding, laser welding, plasma welding, or bonding means using industrial adhesives may be employed.

[0053] When the first member 100 and the second member 200 are joined at the joint 300, a hollow portion 301 extending along the axial direction (Y direction) is formed in the structural member 1, and the cross section perpendicular to the axial direction becomes a closed section. In other words, the second member 200 plays a role similar to a closing plate for closing the cross section of the hat-shaped first member 100.

[0054] The general configuration of the structural member 1 according to this embodiment is as described above. Next, the deformation behavior of the structural member 1 during a collision will be explained.

[0055] Figure 4 is a diagram illustrating the deformation behavior of structural members. In addition to structural member 1 in this embodiment, Figure 4 also illustrates the deformation behavior of other structural members. The left side of Figure 4 shows the state of each structural member before deformation, and the right side shows the state after deformation.

[0056] Furthermore, as shown by the thick black arrows in Figure 4, collision loads are applied to each structural member from the second member 200 side (or the closing plate side). Even if the collision load were applied from the first member 100 side, the same deformation as described later would occur.

[0057] Figure 5 is a load-stroke diagram illustrating the time-dependent changes in the reaction forces generated in each structural member shown in Figure 4. This figure schematically shows the predicted load-stroke diagrams for each structural member when a collision simulation is performed, illustrating the relationship between the stroke amount (displacement) of the impactor and the load (i.e., the reaction force generated on the structural member side).

[0058] Normally, when a collision load is applied to a structural member, the reaction force generated in that member gradually increases, and the plastic deformation of the structural member also progresses gradually. On the other hand, if excessive out-of-plane deformation occurs in the structural member, the gradually increasing reaction force will begin to decrease, and it is unlikely that the reaction force will increase again afterward. Therefore, if excessive out-of-plane deformation that may occur in a structural member can be suppressed, the maximum reaction force of the structural member when a collision load is applied can be increased, and the load-bearing capacity can be improved.

[0059] Based on the above points, we will now explain the schematic configuration and deformation behavior of each structural member shown in Figure 4.

[0060] The structural member 800 shown in Figure 4(A) has a configuration in which a hat-shaped member 810 and a closing plate 820 are joined together. In this structural member 800, after the input of an impact load, excessive out-of-plane deformation is likely to occur first in the portions of the vertical walls 811 and 812 of the hat-shaped member 810 near the flanges 813 and 814.

[0061] The structural member 900 shown in Figure 4(B) has a configuration in which a hat-shaped member 910 and the second member 200 in this embodiment are joined together. The hat-shaped member 910 is a member in which the first upright portions 106 and 107 are not formed on the first member 100 in this embodiment.

[0062] When an impact load is applied to structural member 900, the second vertical walls 202 and 203 of the second member 200 tilt outward, causing deformation such that the second top plate 201, the second vertical walls 202 and 203, and the second flanges 204 and 205 become a single flat plate. During this process of flattening the hat-shaped second member 200, a deformation resistance force against the impact load is generated. Therefore, although out-of-plane deformation occurs in the vertical walls 911 and 912 of the hat-shaped member 910 of structural member 900, the deformation resistance force generated due to the flattening of the second member 200 results in a maximum input load to structural member 900 that is greater than that of structural member 800, as shown in Figure 5. In other words, structural member 900 has superior load-bearing capacity compared to structural member 800.

[0063] Figure 4(C) shows the structural member 1 in this embodiment. When a collision load is applied to the structural member 1, a deformation resistance force is generated as the hat-shaped second member 200 flattens, similar to the structural member 900 shown in Figure 4(B). In addition, the first upright portions 106 and 107 of the first member 100 deform to open outwards, and a deformation resistance force is also generated during this deformation process. In other words, in the structural member 1, both the deformation resistance force generated by the first upright portions 106 and 107 of the first member 100 and the deformation resistance force generated by the hat-shaped second member 200 act on it, and the simultaneous generation of these deformation resistance forces creates a synergistic effect, making it difficult for excessive out-of-plane deformation of the first vertical walls 102 and 103 to occur. Furthermore, because the second vertical walls 202 and 203 are located near the first vertical walls 102 and 103, when a collision load is applied, the second vertical walls 202 and 203 come into contact with the first vertical walls 102 and 103, thereby suppressing out-of-plane deformation of the first vertical walls 102 and 103.

[0064] These effects allow structural member 1 to withstand greater impact loads, and as shown in Figure 5, the maximum input load on structural member 1 (in other words, the maximum reaction force generated on structural member 1) is greater than that of structural member 900. In other words, structural member 1 has superior load-bearing capacity compared to structural member 900.

[0065] Furthermore, as will be shown in the embodiments described later, structural member 1 is superior to the other structural members 800 and 900 in terms of weight efficiency of load-bearing performance.

[0066] Furthermore, as shown in Figure 5, structural member 1 has a larger maximum input load than the other structural members 800 and 900. As a result, even after the input load has been attenuated, its input load remains higher than the attenuated input load of the other structural members 800 and 900. Consequently, structural member 1 absorbs more collision energy than the other structural members 800 and 900. In other words, structural member 1 according to this embodiment excels not only in weight efficiency of load-bearing performance but also in energy absorption performance.

[0067] The automotive structural member 1 according to this embodiment has been described above. Next, an example of the shape of the first member 100 will be described with reference to Figures 6 to 8, and an example of the shape of the second member 200 will be described with reference to Figures 9 and 10. Note that the structural member 1 may be constructed by arbitrarily combining the shapes of the first member 100 and the second member 200 as exemplified below.

[0068] In the example shown in Figure 6, the first member 100 is provided with inflection sections 102a and 103a in each of the two first vertical walls 102 and 103, where the inclination angle changes slightly. Even with a structural member 1 having a first member 100 of this shape, the deformation resistance force generated by the first upright sections 106 and 107 and the deformation resistance force generated by the hat-shaped second member 200 result in deformation behavior similar to that shown in Figure 4(C) when an impact load is applied. Therefore, a structural member 1 with excellent weight efficiency in load-bearing performance can be obtained.

[0069] In the example shown in Figure 7, one of the two first upright portions 106 and 107 is not provided in the first member 100, and only the first upright portion 107 is provided. Even with such a structural member 1, deformation resistance force is obtained from the first upright portion 107 when an impact load is applied, resulting in an improvement in the weight efficiency of the load-bearing performance. In other words, the structural member 1 only needs to have at least one first upright portion.

[0070] In the example shown in Figure 8, the first member 100 is provided with a first groove 114 that recesses from the first top plate 101 toward the inside of the closed cross-section of the structural member 1, that is, toward the inside of the hollow portion 301. In other words, the first groove 114 is formed to recess from the first top plate 101 toward the second top plate 201. Furthermore, the first groove 114 extends along the axial direction (Y direction) of the structural member 1, and it is preferable that the first groove 114 extends, for example, from one end to the other end of the first top plate 101 in the axial direction. In this structural member 1, the deformation resistance is increased by the first groove 114, and the load-bearing capacity is improved.

[0071] In the example shown in Figure 9, the second member 200 is provided with two second upright portions 210 and 211 projecting toward the second top plate 201 from each of the two second flanges 204 and 205. With this structural member 1, the second moment of area is increased by the second upright portions 210 and 211, so the deformation resistance force is increased when an impact load is applied, and the load-bearing capacity is improved. Note that the effect of increasing deformation resistance force can be obtained by providing at least one second upright portion 210 or 211. Furthermore, from the viewpoint of improving load-bearing capacity, it is preferable that the gap between the second upright portions 210 and 211 and the first upright portions 106 and 107 is 5.0 mm or less, it is more preferable that they are in contact with the first upright portions 106 and 107, and it is even more preferable that they are joined.

[0072] In the example shown in Figure 10, the second member 200 is provided with a second groove 212 that recesses from the second top plate 201 toward the outside of the closed cross-section of the structural member 1, i.e., toward the outside of the hollow portion 301. Furthermore, the second groove 212 extends along the axial direction (Y direction) of the structural member 1, and it is preferable that the second groove 212 extends, for example, from one end to the other end of the second top plate 201 in the axial direction. In this structural member 1, the deformation resistance is increased by the second groove 212, and the load-bearing capacity is improved.

[0073] Although an example of an embodiment of the present invention has been described above, the present invention is not limited to such example. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these will naturally also fall within the technical scope of the present invention.

[0074] For example, the constituent elements of the above embodiments can be combined in any way. From such any combination, the functions and effects of each constituent element in the combination will naturally be obtained, as well as other functions and effects that will be obvious to those skilled in the art from the description herein.

[0075] Furthermore, the effects described herein are merely descriptive or illustrative and not limiting. In other words, the technology relating to this disclosure may produce other effects that are obvious to those skilled in the art from the description herein, in addition to or instead of the effects described herein. [Examples]

[0076] <Simulation (1)> Using the analysis models shown in Figures 11 and 12, a collision simulation simulating a four-point bending test was conducted.

[0077] The model of Example 1 corresponds to a structural member 1 having a hat-shaped first member 100 and a hat-shaped second member 200, as shown in Figure 2. In the simulation of Example 1, as shown in Figure 11, the first top plate of the first member 100 was supported by two support points 302 placed 700 mm apart. Then, two impactors 303, placed approximately 233 mm apart between the two support points 302, were brought into contact with the second member 200, and the simulation was performed by moving these impactors 303 toward the first member 100 at a speed of 1000 mm / s.

[0078] The analysis conditions for the model in Example 1 are as follows: Software name: LS-Dyna Version: R9.3.1 • Mesh size: 3mm • Element type: Shell element developed by Belytschko-Wong-Chiang • Coefficient of friction: 0.12 • Total length of structural member: 900mm • Structural member width: 125mm • Material of the first component: Steel plate (thickness 1.6 mm, tensile strength 1470 MPa) • Width of the first tabletop: 70mm • Height of the first tabletop: 48mm • Height of the first upright section: 10mm • Material for the second component: Steel plate (thickness 1.2 mm, tensile strength 590-1470 MPa) • Height of the second tabletop: 20mm • Spot welding pitch: 30mm • Gap formed between the second vertical wall and the first vertical wall: 0 mm

[0079] The model of Comparative Example 1 shown in Figure 12 corresponds to the structural member 800 shown in Figure 4(A), in which a hat-shaped member and a closing plate are joined. The model of Comparative Example 2 corresponds to the structural member 900 shown in Figure 4(B), in which two hat-shaped members without a first upright portion are joined. The model of Comparative Example 3 is a model in which a hat-shaped member having a first upright portion is joined to a closing plate.

[0080] The simulation conditions in the models of Comparative Examples 1 to 3 are the same as those in Example 1, except for the shape of the structural members. The simulation was performed multiple times, with the tensile strength of the second member or closing plate set to a value within the range of 590 MPa to 1470 MPa.

[0081] In the simulation conducted under the above conditions, the maximum reaction force of the structural member generated in conjunction with the movement (displacement) of the impactor 303 was evaluated. The results are shown in Figure 13. In Figure 13, the vertical axis shows the value obtained by dividing the maximum reaction force by the weight per unit length in the axial direction of the structural member. The larger this value, the better the weight efficiency of the load-bearing performance.

[0082] As is clear from the results shown in Figure 13, the model of Example 1 has superior weight efficiency in load-bearing performance compared to the models of Comparative Examples 1 to 3. In particular, the greater the tensile strength of the steel plate used as the material for the second member, the greater the difference in the effect of weight efficiency in load-bearing performance between Example 1 and Comparative Examples 1 to 3, and the greater the effect of improving weight efficiency.

[0083] Furthermore, when the tensile strength of the second member is 690 MPa or higher, the increase in weight efficiency of Example 1 compared to Comparative Example 1 is even greater than the sum of the increase in weight efficiency of Comparative Example 2 compared to the model of Comparative Example 1 and the increase in weight efficiency of Comparative Example 3 compared to the model of Comparative Example 1. In other words, when the tensile strength of the second member is 690 MPa or higher, the weight efficiency of the load-bearing performance of an automobile structural member that combines (1) providing a first upright portion to a hat-shaped first member and (2) making the second member hat-shaped and bringing the vertical walls of the second member and the vertical walls of the first member close together increases significantly to an extent that cannot be predicted from the results of the weight efficiency obtained with an automobile structural member having only the feature of (1) above and the weight efficiency obtained with an automobile structural member having only the feature of (2) above.

[0084] In electric vehicles, whose development has been accelerating in recent years, it is expected that higher-strength steel plates will be increasingly used as structural material to improve battery protection. For this reason, structural material like the model in Example 1 will be particularly useful in future automobile development.

[0085] <Simulation (2)> In the model of Example 1, multiple models were created by changing the ratio (h / H) of the height of the second tabletop (h) to the height of the first tabletop (H) by changing the height h of the second tabletop, and simulations were performed.

[0086] In this simulation, the material for the first member is set to a steel plate with a thickness of 1.6 mm and a tensile strength of 1470 MPa, and the material for the second member is set to a steel plate with a thickness of 1.2 mm and a tensile strength of 1470 MPa. Other simulation conditions are the same as those in simulation (1) described above.

[0087] According to the simulation results shown in Figure 14, when the ratio of the height of the second tabletop to the height of the first tabletop (h / H) is within the range of 0.10 to 0.52, it can be seen that there is a high effect in improving the weight efficiency of the load-bearing capacity. [Industrial applicability]

[0088] This invention can be applied to structural components for automobiles. [Explanation of Symbols]

[0089] 1. Automotive structural components 100 First Member 101 First top plate 102, 103 First vertical wall 104, 105 First flange 106, 107 1st standing part 108-113 Ridge section 114 First trench section 200 Second Member 201 Second top plate 202, 203 Second Vertical Wall 204, 205 Second flange 206-209 Ridge section 210, 211 2nd standing section 212 Second groove 300 joint 301 Hollow part 302 Support points 303 Impactor 800 Automotive structural components (conventional structure) 810 Hat-shaped member 820 Closing Plate 900 Automotive structural components (reference structure) 910 Hat-shaped member H Height of the first top plate h Height of the second tabletop

Claims

1. Automotive structural member, A hat-shaped first member, A hat-shaped second member, It comprises a hollow portion formed by joining the first member and the second member, The first member is, The first top panel and, Two first vertical walls facing each other, Two first flanges projecting outward from each of the two aforementioned first vertical walls, It has at least one first flange and a first upright portion that protrudes toward the first top plate side, One end of the first vertical wall is connected to the first top plate, and the other end of the first vertical wall is connected to the first flange. The first flange is located between the first vertical wall and the first upright portion. The second member is, The second top panel and Two second vertical walls facing each other, It has two second flanges projecting outward from each of the two aforementioned second vertical walls, The second top plate is located between the two first vertical walls of the first member, The second vertical wall faces the first vertical wall of the first member, The gap formed between the second vertical wall and the first vertical wall is 5.0 mm or less. The second flange is joined to the first flange, The second member is made of steel with a tensile strength of 690 MPa or more. The first upright portion is formed continuously along the axial direction of the automobile structural member, The first vertical wall is formed in a straight line or convex inward toward the hollow portion in a cross section perpendicular to the axial direction of the automobile structural member, the automobile structural member.

2. The automotive structural member according to claim 1, wherein the ratio (h / H) of the height h of the second top plate to the height H of the first top plate is 0.10 to 0.

52.

3. The automobile structural member according to claim 1 or 2, wherein the first upright portion is provided on each of the two first flanges.

4. The automobile structural member according to claim 1 or 2, wherein the first member has a groove that is recessed toward the second top plate from the first top plate.

5. The automotive structural member according to claim 1 or 2, wherein the second member has a second upright portion that protrudes from at least one of the second flanges toward the second top plate.

6. The automotive structural member according to claim 1 or 2, wherein the second member has a groove that is recessed from the second top plate toward the side opposite to the first top plate.

7. The automotive structural member according to claim 1 or 2, wherein the automotive structural member is an automotive frame member.

8. The automotive structural member according to claim 7, wherein the automotive frame member is a bumper beam, a side sill, a roof side rail, a cross member, or a center pillar.

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