WO2024204279A1 - Structural member for automobile body - Google Patents

Abstract

This structural member for an automobile body comprises: a hat-shaped member having a top plate part, a pair of side wall parts, and a pair of flange parts; and a joining member having a pair of joining parts and a top plate facing part. Two or more longitudinal-direction beads are formed on at least one of the top plate part and the top plate facing part. A plurality of height-direction beads are formed on the pair of side wall parts. Each of two outermost longitudinal-direction beads of the two or more longitudinal-direction beads includes a first bead side wall, a second bead side wall, and a bead bottom wall, and satisfies the relationships of θ3 ≥ 120 degree and w1 < w2 + w3 in a cross-section perpendicular to the longitudinal direction, where w1 is the length of the first bead side wall, w2 is the length of the second bead side wall, w3 is the length of the bead bottom wall, and θ3 is the exterior angle formed by the second bead side wall and the bead bottom wall.

Description

Automotive body structural components

The present invention relates to a structural member for an automobile body.
This application claims priority based on Japanese Patent Application No. 2023-049808 filed on March 27, 2023, the contents of which are incorporated herein by reference.

In recent years, the use of high-tensile steel plates in automotive parts has expanded with the aim of improving automobile collision safety performance and reducing vehicle weight. By using high-tensile steel plates, it is possible to obtain parts with better collision safety performance, or to achieve both collision safety performance and weight reduction through thinner parts.

However, when the thickness of the material is reduced, not only does the rigidity of the steel plate before processing decrease, but the rigidity of the parts after processing also decreases, so there are cases where a sufficient increase in strength in terms of collision safety performance cannot be obtained simply by using a high-strength, thin steel plate.

The collision safety performance of automobile body parts includes the bending crush characteristics of side sills and B-pillars in side collisions, and bumpers in frontal collisions. There is a demand for improving the three-point bending characteristics in local buckling mode to achieve higher collision safety performance even when using thin plate materials.

Patent Document 1 discloses a vehicle crashworthiness reinforcement material with excellent buckling resistance that is designed to have a recessed bead extending along the longitudinal direction of the main body portion to the center of the width of the main body portion.
Patent Document 2 discloses a metal vehicle absorber having concave or convex beads that are approximately parallel to the front-rear direction of the vehicle on one or both of an upper web and a lower web.

Japanese Patent No. 5119477 Japanese Patent No. 4330652

However, the techniques of Patent Documents 1 and 2 were unable to fully demonstrate the three-point bending characteristics of the local buckling mode of the more highly bent crushed parts that were required.

The present invention was made in consideration of the above problems, and the object of the present invention is to provide a structural member that can exhibit superior collision safety performance by improving the load-bearing capacity and impact energy absorption at the beginning of the stroke in local buckling mode deformation.

Specific aspects of the present invention are as follows:

(1) A first aspect of the present invention is a hat-shaped component having a top plate portion extending along a longitudinal direction, a pair of side wall portions extending via a pair of first ridge portions formed at both ends of the top plate portion in a width direction, and a pair of flange portions extending via a pair of second ridge portions formed at ends of the pair of side wall portions opposite the pair of first ridge portions, and a joining member having a pair of joining portions joined to the pair of flange portions of the hat-shaped component and a top plate opposing portion opposing the top plate portion of the hat-shaped component, wherein at least one of the top plate portion and the top plate opposing portion has two or more longitudinal beads extending along the longitudinal direction formed in parallel in the width direction, and a plurality of heightwise beads extending along a height direction formed in parallel in the longitudinal direction on the pair of side wall portions, and the two or more Among the longitudinal beads, each of the two longitudinal beads located on the outside comprises a first bead sidewall extending and bending inward from at least one of the top plate portion and the top plate opposing portion, a second bead sidewall extending and bending inward from at least one of the top plate portion and the top plate opposing portion at a position farther from the side wall portion than the first bead sidewall, and a bead bottom wall connecting inner ends of the first bead sidewall and the second bead sidewall, wherein, in a cross section perpendicular to the longitudinal direction, when the length of the first bead sidewall is w1, the length of the second bead sidewall is w2, the length of the bead bottom wall is w3, and the outward angle formed by the second bead sidewall and the bead bottom wall is θ3, the relationship θ3 ≧ 120 degrees and w1 < w2 + w3 is satisfied.
(2) In the structural component of the automobile body described in (1) above, when the inner angle between the first bead side wall and the top plate portion is θ1 and the inner angle between the second bead side wall and the top plate portion is θ2, the relationship θ1 < θ2 may be satisfied.
(3) In the structural component for an automobile body described in (1) or (2) above, w3 may be 0 mm or more and 18 mm or less.
(4) In a structural component of an automobile body described in any one of (1) to (3) above, at least one of the top plate portion and the top plate opposing portion, which are a central top plate portion and a central top plate opposing portion formed between the two longitudinal beads arranged on the outside, may protrude outward in the height direction more than either one of a pair of side wall portion side top plate portions and a pair of side wall portion side top plate opposing portions formed on the side wall portion side of the two longitudinal beads arranged on the outside.
(5) In the structural component of an automobile body described in any one of (1) to (4) above, the two longitudinal beads arranged on the outside may be formed on the top plate portion of the hat-shaped component.
(6) A second aspect of the present invention comprises a hat-shaped component having a top plate portion extending along the longitudinal direction, a pair of side wall portions extending via a pair of first ridge portions formed at both widthwise ends of the top plate portion, and a pair of flange portions extending via a pair of second ridge portions formed at ends of the pair of side wall portions opposite the pair of first ridge portions, and a joining member having a pair of joining portions joined to the pair of flange portions of the hat-shaped component and a top plate opposing portion opposing the top plate portion of the hat-shaped component, wherein at least one of the top plate portion and the top plate opposing portion has two or more longitudinal beads extending along the longitudinal direction formed in parallel in the width direction, and the pair of side wall portions has a plurality of heightwise beads extending along the height direction formed in parallel in the longitudinal direction, and among the two or more longitudinal beads, and each of the two longitudinal beads arranged on the outside comprises a first bead sidewall extending and bending inward from at least one of the top plate portion and the top plate opposing portion, a second bead sidewall extending and bending inward from at least one of the top plate portion and the top plate opposing portion at a position farther from the side wall portion than the first bead sidewall, and a bead bottom wall connecting inner ends of the first bead sidewall and the second bead sidewall, wherein, in a cross section perpendicular to the longitudinal direction, when the length of the first bead sidewall is w1 and the length of the second bead sidewall is w2, a relationship of w1 < w2 is satisfied, and when the inward angle formed between the first bead sidewall and the top plate portion is θ1 and the inward angle formed between the second bead sidewall and the top plate portion is θ2, a relationship of θ1 < θ2 is satisfied.
(7) In the structural component for an automobile body described in (6) above, w3 may be 0 mm or more and 18 mm or less.
(8) In the structural component of an automobile body described in (6) or (7) above, at least one of the top plate portion and the top plate opposing portion, which are the central top plate portion and the central top plate opposing portion formed between the two longitudinal beads arranged on the outside, may protrude outward in the height direction more than either one of a pair of side wall portion side top plate portions and a pair of side wall portion side top plate opposing portions formed on the side wall portion side of the two longitudinal beads arranged on the outside.
(9) In the structural component of an automobile body described in any one of (6) to (8) above, the two longitudinal beads arranged on the outside may be formed on the top plate portion of the hat-shaped component.
(10) A third aspect of the present invention includes a hat-shaped member having a top plate portion extending along the longitudinal direction, a pair of side wall portions extending via a pair of first ridge portions formed at both ends of the top plate portion in the width direction, and a pair of flange portions extending via a pair of second ridge portions formed at ends of the pair of side wall portions opposite the pair of first ridge portions, and a joining member having a pair of joining portions joined to the pair of flange portions of the hat-shaped member and a top plate opposing portion opposing the top plate portion of the hat-shaped member, wherein at least one of the top plate portion and the top plate opposing portion has two or more longitudinal beads extending along the longitudinal direction formed in parallel in the width direction, and a plurality of heightwise beads extending along the height direction formed in parallel in the longitudinal direction on the pair of side wall portions, and among the two or more longitudinal beads, each of the two longitudinal beads arranged on the outer side is a pair of longitudinal beads arranged on the top plate portion and the top plate opposing portion. a first bead side wall extending and bending inward from at least one of the top plate portion and the top plate opposing portion at a position farther from the side wall portion than the first bead side wall, and a bead bottom wall connecting the inner ends of the first bead side wall and the second bead side wall, wherein, in a cross section perpendicular to the longitudinal direction, when the length of the first bead side wall is w1 and the length of the second bead side wall is w2, a relationship of w1 < w2 is satisfied, and at least one of the central side top plate portion and the central side top plate opposing portion formed between the two longitudinal beads located on the outside, of the top plate portion and the top plate opposing portion, protrudes outward in the height direction further than either of a pair of side wall portion side top plate portions and a pair of side wall portion side top plate opposing portions formed on the side wall portion side of the two longitudinal beads located on the outside.
(11) In the structural component for an automobile body described in (10) above, w3 may be 0 mm or more and 18 mm or less.
(12) In the structural component for an automobile body described in (10) or (11) above, the two longitudinal beads arranged on the outside may be formed on the top plate portion of the hat-shaped component.

The present invention improves the load-bearing capacity and impact energy absorption at the beginning of the stroke in local buckling mode deformation, thereby achieving better collision safety performance.

FIG. 1A is a schematic diagram for explaining three-point bending characteristics in local buckling mode, FIG. 1B is a schematic diagram for explaining three-point bending characteristics in wall buckling mode, and FIG. 1C is a schematic diagram for explaining moment bending characteristics. FIG. 2 is a perspective view showing a structural member according to the present embodiment. FIG. 2B is a schematic cross-sectional view of the structural member according to the present embodiment, showing a cross-section along A1-A1' in FIG. 2A. FIG. 2 is a plan view showing a structural member according to the present embodiment. FIG. 4 is a partially enlarged view of a portion B of FIG. 3 . FIG. 4 is a perspective view showing a state after deformation of the structural member according to the embodiment. FIG. 4 is an enlarged cross-sectional view of a longitudinal bead before deformation. 10A to 10C are enlarged cross-sectional views showing the process of deformation of a longitudinal bead. 10A to 10C are enlarged cross-sectional views showing the process of deformation of a longitudinal bead. FIG. 11 is a perspective view showing a structural member according to a first modified example. FIG. 11 is an enlarged cross-sectional view showing a structural member according to a second modified example. FIG. 11 is an enlarged cross-sectional view showing a structural member according to a third modified example. FIG. 13 is an enlarged cross-sectional view showing a structural member according to a fourth modified example. FIG. 13 is an enlarged cross-sectional view showing a structural member according to a fifth modified example. FIG. 13 is an enlarged cross-sectional view showing a structural member according to a sixth modified example. FIG. 4 is a schematic diagram for explaining three-point bending conditions.

The bending crush characteristics of automobile parts can be broadly divided into three-point bending characteristics, in which the impact of the collision is applied directly to the crushed part of the part, causing deformation, and moment bending characteristics, in which the impact of the collision is applied indirectly to the crushed part of the part, causing deformation.
Among these, the three-point bending characteristics are classified into three-point bending characteristics in a local buckling mode and three-point bending characteristics in a wall buckling mode.
The three-point bending characteristics in the local buckling mode and the three-point bending characteristics in the wall buckling mode are often evaluated based on the three-point bending characteristics obtained by conducting a three-point bending test in which an impactor directly collides with a component, as shown in (a) and (b) of Figure 1.
In the three-point bending characteristic of the local buckling mode, as shown in FIG. 1A, when the distance between the supports supporting the load in the three-point bending test is long, bending deformation occurs mainly at the position where the load is applied by the impactor.
In the three-point bending characteristics of the wall buckling mode, as shown in FIG. 1B, when the distance between the supports supporting the load in the three-point bending test is short, the main deformation is that the side wall is crushed in the part height direction, centered around the position where the load is applied by the impactor.
Furthermore, the moment bending characteristics are often evaluated based on the moment bending characteristics obtained by conducting a moment bending test in which an impactor or the like does not come into contact with the crushed portion of the part, as shown in FIG. 1(c).

The present inventors have studied component shapes for improving collision safety performance against deformation in the local buckling mode as shown in FIG. 1(a) and have obtained the following findings.
(a) In three-point bending where the crushed part comes into contact with the impactor, a combination of compressive stress along the longitudinal direction occurs on the inside of the bent part, compressive stress along the height direction occurs on the side wall of the part, and tensile stress along the longitudinal direction occurs on the outside of the bent part.
(i) Because compressive stress along the height direction occurs in the side walls, the side walls can easily buckle and deform due to compressive stress along the height direction, particularly when the material plate thickness is thin. Even in parts designed to operate in local buckling mode, the deformation state may approach that of wall buckling mode in the early stages of deformation.
(c) When the deformation state approaches the wall buckling mode, if buckling deformation of the side wall easily occurs, not only will good three-point bending characteristics for the wall buckling mode not be obtained, but the crushed side wall will reduce the height of the crushed part, and the bending rigidity in the height direction of the cross section that intersects the longitudinal direction will decrease. Therefore, even if the deformation state reaches the local buckling mode in the subsequent deformation, good three-point bending characteristics for the local buckling mode may not be obtained.
(e) Therefore, by designing a part shape that can simultaneously increase the deformation resistance to compressive stress along the longitudinal direction, the deformation resistance to compressive stress along the height direction, and the deformation resistance to tensile stress along the longitudinal direction, it is possible to improve the load-bearing capacity in deformation in local buckling mode, especially at the beginning of the stroke, and to demonstrate excellent collision safety performance.

The present invention, which was completed based on the above findings, will be described in detail below with reference to the embodiments. Note that in this specification and drawings, components having substantially the same functional configuration are designated by the same reference numerals, and duplicate explanations will be omitted.

In the following description, the axial direction of a structural member, i.e., the direction in which the axis extends, will be referred to as the longitudinal direction Z.
In addition, in a plane perpendicular to the longitudinal direction Z, a direction parallel to the top plate portion is referred to as a width direction X, and a direction perpendicular to the longitudinal direction Z and the width direction X is referred to as a height direction Y.
The direction away from the axis of the structural member is referred to as outward and the opposite direction is referred to as inward.

The following describes a structural member 100 for an automobile body according to an embodiment of the present invention (hereinafter referred to as structural member 100).

First, the schematic configuration of the structural member 100 will be described with reference to FIGS. 2A to 4. FIG.
Fig. 2A is a perspective view of the structural member 100, Fig. 2B is a cross-sectional view taken along the line A1-A1' of Fig. 2A, Fig. 3 is a plan view of the structural member 100, and Fig. 4 is an enlarged partial view of part B of Fig. 3.
2A to 4, the structural member 100 is a member with a closed cross-sectional structure constituted by a hat-shaped member 110 and a joining member 120. Application examples of the structural member 100 include B-pillars, side sills, bumper reinforcements, etc.

The structural member 100 in this embodiment is a part that is intended to be installed in an automobile with the top plate portion 111 of the hat-shaped member 110 facing the outside of the vehicle.

Therefore, when an impact load from the outside of the vehicle is input to the hat-shaped member 110 and bending deformation occurs in the structural member 100, as shown in FIG.
A compressive stress (A) along the longitudinal direction Z in the top plate portion 111 of the hat-shaped member 110;
A compressive stress (B) along the height direction Y in the side wall portion 115 of the hat-shaped component 110;
Tensile stress (C) along the longitudinal direction Z in the joining member 120;
will occur in a complex manner.
Furthermore, the "compressive stress (B) along the height direction Y in the side wall portion 115 of the hat-shaped member 110" can also be rephrased as "compressive stress (B) along a direction perpendicular to the longitudinal direction Z in the side wall portion 115 of the hat-shaped member 110."

As shown in FIGS. 2A to 4, the hat-shaped component 110 has a top plate portion 111 extending along the longitudinal direction Z, a pair of side walls 115, 115, and a pair of flange portions 119, 119.
The hat-shaped member 110 may be a member made of a metal plate such as a steel plate, an aluminum plate, an aluminum alloy plate, a stainless steel plate, or a titanium plate, or further, a resin plate or a CFRP (Carbon Fiber Reinforced Plastic) plate.

(Top plate)
The top plate portion 111 corresponds to a portion that comes into direct contact with an impactor in the three-point bending test of the local buckling mode shown in FIG.
The structural member 100 in this embodiment is installed in an automobile with the top plate portion 111 of the hat-shaped member 110 facing the outside of the vehicle, so that when an impact load from the outside of the vehicle is input to the top plate portion 111, causing bending deformation in the structural member 100, a compressive stress (A) along the longitudinal direction Z is generated in the top plate portion 111.

The width W of the top plate portion 111 may be, for example, 40 mm or more and 200 mm or less. As shown in FIG. 2B, the width W of the top plate portion 111 is the distance in the width direction X between the boundary points between the top plate portion 111 and the first ridge portions 113, 113 at both ends of the top plate portion 111 in a cross section perpendicular to the longitudinal direction Z of the structural member 100. As shown in FIG. 2B, the top plate portion 111 (more specifically, the central top plate portion 111a and the side wall portion top plate portion 111b described later) is horizontal, but may be curved. In this case, the angle at the ridge portion or R portion of the top plate portion 111 is the angle between a tangent extending from the boundary position between the ridge portion or R portion and the top plate portion 111 and another imaginary straight line, etc.

(Side wall portion)
The pair of side walls 115, 115 extend via first ridges 113, 113 formed at both ends of the top plate 111 in the width direction X. The first ridges 113, 113 have an R portion with a curvature radius of, for example, 1 mm to 10 mm in a cross section perpendicular to the longitudinal direction Z of the structural member 100. Note that "via A" means "without passing through any member other than A." For example, in the above example, only the first ridges 113, 113 exist between the pair of side walls 115, 115 and the top plate 111.
The structural member 100 in this embodiment is installed in an automobile with the top plate portion 111 of the hat-shaped member 110 facing the outside of the vehicle, so that when an impact load from the outside of the vehicle is input to the top plate portion 111, causing bending deformation in the structural member 100, a compressive stress (B) along the height direction Y is generated in the pair of side wall portions 115, 115.

The height H of the side wall 115 may be, for example, 20 mm or more and 150 mm or less. As shown in FIG. 2B, the height H of the side wall 115 is the distance in the height direction Y between the boundary point between the side wall 115 and the first ridge 113 and the boundary point between the side wall 115 and the second ridge 117 in a cross section perpendicular to the longitudinal direction Z of the structural member 100. The second ridges 117, 117 have an R portion with a radius of curvature of, for example, 1 mm to 10 mm in a cross section perpendicular to the longitudinal direction Z of the structural member 100.

(Flange part)
2A , second ridge portions 117, 117 are formed at ends of the pair of side wall portions 115, 115 opposite the first ridge portions 113, 113. The pair of flange portions 119, 119 extend outward via the second ridge portions 117, 117.
The flange portion 119 has spot welds 170 formed at a predetermined pitch in the longitudinal direction Z for joining to the joining member 120. Note that spot welding is one example of a joining means, and other joining methods such as laser welding and brazing may also be used.

(Longitudinal bead)
2B , two longitudinal beads 150, 150 extending along the longitudinal direction Z are formed in parallel in the width direction X on the top plate portion 111. Note that three or more longitudinal beads 150 may be formed in parallel.
2B, the longitudinal bead 150 is preferably formed so that the center of the longitudinal bead 150 in the width direction X is located in the region from the boundary point between the top plate portion 111 and the first ridge line portion 113 to a point that is a distance of 1/4 of the width W of the top plate portion 111 in the width direction X. More preferably, the longitudinal bead 150 is formed so that the boundary point between the longitudinal bead 150 and the top plate portion 111 is located in the region from the boundary point between the top plate portion 111 and the first ridge line portion 113 to a point that is a distance of 20 mm in a cross section perpendicular to the longitudinal direction.
The longitudinal bead 150 may have rounded portions 150a, 150b with a predetermined radius of curvature at the end on the top plate portion 111 side. In this case, the longitudinal bead 150 is connected to the top plate portion 111 via the rounded portion of the longitudinal bead 150.

By providing such a longitudinal bead 150, it is possible to increase the deformation resistance against the compressive stress along the longitudinal direction Z that occurs in the top plate portion 111. As a result, when bending deformation is applied to the structural member 100, the occurrence of early buckling deformation in the top plate portion 111 is suppressed, and the maximum load is increased.

The longitudinal bead 150 may be formed simultaneously using the same mold when the top plate portion 111, the side wall portion 115, and the flange portion 119 are press-molded, or may be formed using a separate mold or tool before the top plate portion 111, the side wall portion 115, and the flange portion 119 are press-molded.

As shown in FIG. 2B , the longitudinal bead 150 (in the case where three or more longitudinal beads are formed, each of the two longitudinal beads 150 arranged on the outside) is formed by a first bead side wall 151, a second bead side wall 152, and a bead bottom wall 153.
The first bead side wall 151 and the second bead side wall 152 bend and extend inward from the top plate portion 111. The second bead side wall 152 is disposed at a position farther from the side wall portion 115 than the first bead side wall 151. In the structural member 100 according to this embodiment, the inward angle θ1 between the first bead side wall 151 and the top plate portion 111 (the inclination angle of the first bead side wall 151) is approximately 90 degrees, but the angle θ1 may be greater than or equal to 90 degrees.
The bead bottom wall 153 connects the inner ends of the first bead side wall 151 and the second bead side wall 152. The first bead side wall 151 and the top plate portion 111 are connected via an R portion 150a, and the first bead side wall 151 and the bead bottom wall 153 are connected via an R portion 150c. The second bead side wall 152 and the top plate portion 111 are connected via an R portion 150b, and the second bead side wall 152 and the bead bottom wall 153 are connected via an R portion 150d.

When the length of the first bead sidewall 151 in a cross section perpendicular to the longitudinal direction Z is w1, the length of the second bead sidewall 152 is w2, and the length of the bead bottom wall 153 is w3, the relationship w1 < w2 is satisfied. Here, the length w1 of the first bead sidewall 151 is the distance in the direction along the first bead sidewall 151 between the boundary point between the R portion 150a and the first bead sidewall 151 and the boundary point between the R portion 150c and the first bead sidewall 151. The length w2 of the second bead sidewall 152 is the distance in the direction along the second bead sidewall 152 between the boundary point between the R portion 150b and the second bead sidewall 152 and the boundary point between the R portion 150d and the second bead sidewall 152. The length w3 of the bead bottom wall 153 is the distance along the bead bottom wall 153 between the boundary point between the R portion 150c and the bead bottom wall 153 and the boundary point between the R portion 150d and the bead bottom wall 153. In this embodiment, the length w3 of the bead bottom wall 153 is 0 mm or more and 18 mm or less. The relationship between w3 and w1 and w2 will be described later.

In this embodiment, the second bead side wall 152 extends in a substantially vertical direction. Furthermore, as described above, the relationship w1<w2 is satisfied. Therefore, the second bead side wall 152 is longer than the first bead side wall 151. Therefore, the center side top plate portion 111a formed between the two longitudinal beads 150 protrudes outward in the height direction Y more than the side wall side top plate portions 111b, 111b formed on the side wall portion 115 side of the two longitudinal beads 150. Note that the center side top plate portion 111a protrudes outward in the height direction Y more than both of the pair of side wall side top plate portions 111b, 111b, but may protrude outward in the height direction Y more than either one of them. It is preferable that w1 is 2 mm or more.

As shown in FIG. 2B, the longitudinal bead 150 has a predetermined depth d1 and a predetermined width w4.

The depth d1 of the longitudinal bead 150 is the distance in the height direction Y from the outer surface of the side wall portion top plate portion 111b to the outer surface of the bead bottom wall 153 in the longitudinal bead 150. If the longitudinal bead 150 has a shape whose depth changes along the longitudinal direction Z, the maximum value of the distance in the height direction Y from the top plate portion 111 to the bead bottom wall 153 is defined as the depth d1.

The greater the depth d1 of the longitudinal bead 150, the greater the deformation resistance to compressive stress along the longitudinal direction Z that occurs in the top plate portion 111, suppressing early buckling deformation in the top plate portion 111 and increasing the maximum load. Therefore, the depth d1 of the longitudinal bead 150 is preferably 5 mm or more, and more preferably 8 mm or more.

On the other hand, if the depth d1 of the longitudinal bead 150 is too large, the first bead side wall 151 and the second bead side wall 152 may easily collapse in a direction approaching each other immediately after an impact load from the outside of the vehicle is input to the top plate portion 111. If the first bead side wall 151 and the second bead side wall 152 easily collapse in a direction approaching each other, the pair of side wall portions 115, 115 may also easily collapse in a direction approaching each other. In this case, while the first bead side wall 151 and the second bead side wall 152 are collapsing in a direction approaching each other, the time when the deformation resistance against the compressive stress along the longitudinal direction Z generated in the top plate portion 111 increases may be delayed. Furthermore, if the depth d1 of the longitudinal bead 150 is too large, it may be difficult to form the longitudinal bead 150 if the width w4 of the longitudinal bead 150 is relatively small. Therefore, the depth d1 of the longitudinal bead 150 is preferably 20 mm or less, and more preferably 16 mm or less.

The width w4 of the longitudinal bead 150 is the distance in the width direction X between the intersection of a virtual line extending the first bead side wall 151 of the longitudinal bead 150 and a virtual line extending the side wall portion side top plate portion 111b, and the intersection of a virtual line extending the second bead side wall 152 of the longitudinal bead 150 and a virtual line extending the central side top plate portion 111a, in a cross section perpendicular to the longitudinal direction Z.
When the longitudinal bead 150 has a shape whose width changes along the longitudinal direction Z, the separation distance in the cross section where the separation distance is maximum is defined as width w4.

The smaller the width w4 of the longitudinal bead 150, the higher the deformation resistance against compressive stress along the longitudinal direction Z that occurs in the top plate portion 111, suppressing early buckling deformation in the top plate portion 111 and increasing the maximum load. Therefore, the width w4 of the longitudinal bead 150 is preferably 20 mm or less, and more preferably 15 mm or less.

On the other hand, if the width w4 of the longitudinal bead 150 is too small, and the depth d1 of the longitudinal bead 150 is relatively large, it may be difficult to mold the longitudinal bead 150. For this reason, the width w4 of the longitudinal bead 150 is preferably 5 mm or more, and more preferably 8 mm or more.

The longitudinal bead 150 does not necessarily have to be formed over the entire length of the top plate portion 111 in the longitudinal direction Z, and may be formed over a portion of the entire length of the top plate portion 111. The position at which the longitudinal bead 150 is formed may be selected to be a position where the bending crushing characteristics of the structural member 100 should be most strengthened, for example, a position where the impactor comes into contact and its vicinity. Furthermore, the longitudinal bead 150 may be formed at multiple locations in the longitudinal direction Z.
It is also preferable that the longitudinal bead 150 and the height bead 160 are located at the same position in the longitudinal direction Z. In this case, it is possible to more reliably improve the load resistance and the shock absorption energy at the beginning of the stroke.

As described above, the depth d1 and width w4 of the longitudinal bead 150 affect the deformation resistance to the compressive stress along the longitudinal direction Z that occurs in the top plate portion 111. It is preferable that the aspect ratio A1 calculated by the depth d1 relative to the width w4 of the longitudinal bead 150 (depth d1/width w4) is 0.25 or more and 4.0 or less, since this can more reliably achieve the effect of increasing the deformation resistance to the compressive stress along the longitudinal direction Z that occurs in the top plate portion 111. It is even more preferable that the aspect ratio A1 is 0.5 or more and 2.0 or less.

(Height bead)
A plurality of height direction beads 160 extending along the height direction Y are formed in parallel in the longitudinal direction Z on the side wall portion 115 .
In the example shown in Figures 3 and 4, the height direction bead 160 is formed over the entire height of the side wall portion 115 in the height direction Y, but the height direction bead 160 may be formed over only a portion of the entire height direction.
The height direction bead 160 is formed so as to protrude inward from the side wall portion 115 .
The height direction bead 160 may have an R portion with a predetermined radius of curvature at the end portion on the side wall portion 115 side. In this case, the height direction bead 160 is connected to the side wall portion 115 via the R portion of the height direction bead 160.
The provision of such height direction beads 160 can increase the deformation resistance against the compressive stress (B) along the height direction Y generated in the side wall portion 115. As a result, early buckling deformation in the side wall portion 115 is suppressed, and the maximum load is increased.

In the structural member 100 according to this embodiment, the height direction bead 160 is formed so as to extend from the first ridge portion 113 to the second ridge portion 117 .
Since the height direction bead 160 is formed to extend from the first ridge line portion 113, the height direction bead 160 also contributes to the deformation resistance of the first ridge line portion 113 against the compressive stress (B) along the height direction Y, making the first ridge line portion 113 less likely to be crushed. Since the first ridge line portion 113 is less likely to be crushed, the upper part of the side wall portion 115 connected to the first ridge line portion 113 is also less likely to be crushed. Since the first ridge line portion 113 and the side wall portion 115 are less likely to be crushed, a decrease in bending rigidity in the height direction Y of the cross section intersecting the longitudinal direction Z due to a decrease in the height of the structural member 100 is suppressed, and a decrease in the three-point bending characteristics in the local buckling mode can be prevented, which is preferable. Furthermore, in this manner, when the height-direction bead 160 is formed to extend from the first ridge portion 113, a step is formed along the longitudinal direction Z of the first ridge portion 113 between a portion of the bead bottom wall 162 of the height-direction bead 160 and a portion of the side wall portion 115 where the height-direction bead is not formed.

Furthermore, by forming the height direction bead 160 so as to extend from the first ridge portion 113 to the second ridge portion 117, the height direction bead 160 also contributes to the deformation resistance of the second ridge portion 117 against the compressive stress (B) along the height direction Y, making the second ridge portion 117 less likely to be crushed. Therefore, since the first ridge portion 113, the side wall portion 115, and the second ridge portion 117 are less likely to be crushed, the decrease in bending rigidity in the height direction Y of the cross section intersecting the longitudinal direction Z that accompanies the reduction in height of the structural member 100 is further suppressed, and the decrease in the three-point bending characteristics in the local buckling mode can be further prevented, which is preferable.

The height direction bead 160 is formed by a pair of bead side walls 161 , 161 and a bead bottom wall 162 .
The pair of bead side walls 161 , 161 extend inwardly from the side wall portion 115 while bending.
The bead bottom wall 162 connects the inner ends of the pair of bead side walls 161, 161 to each other.

As shown in FIG. 4, the vertical bead 160 has a predetermined depth d2 and a predetermined width w5.

The depth d2 of the height direction bead 160 is the distance in the width direction X from the outer surface of the side wall portion 115 to the outer surface of the bead bottom wall 162 in the height direction bead 160. If the height direction bead 160 has a shape whose depth changes along the height direction Y, the maximum value of the distance in the width direction X from the side wall portion 115 to the bead bottom wall 162 is defined as the depth d2.

The greater the depth d2 of the height direction bead 160, the greater the deformation resistance to the compressive stress (B) along the height direction Y that occurs in the side wall portion 115. Therefore, the depth d2 of the height direction bead 160 is preferably 2 mm or more, and more preferably 4 mm or more.

On the other hand, if the depth d2 of the height direction bead 160 is too large, the dimension in the width direction X of the structural member 100 becomes locally small, and the bending rigidity in the cross section intersecting the longitudinal direction Z becomes too small, so that the desired three-point bending characteristics may not be obtained. In addition, in a configuration in which the longitudinal bead 150 is formed in the portion near the end of the width direction X of the top plate portion 111, if the depth d2 of the height direction bead 160 is too large, the longitudinal bead 150 may not be formed at the desired position. Furthermore, if the depth d2 of the height direction bead 160 is too large, it may be difficult to mold the height direction bead 160 if the width w5 of the height direction bead 160 is relatively small. Therefore, the depth d2 of the height direction bead 160 is preferably 10 mm or less, and more preferably 8 mm or less.

The multiple height-direction beads 160 are preferably formed with an inter-bead distance of 50 mm or less in the longitudinal direction Z of the side wall portion 115, and more preferably with an inter-bead distance of 30 mm or less. In this case, it is possible to further increase the deformation resistance against the compressive stress (B) along the height direction Y generated in the side wall portion 115. Note that the inter-bead distance means the separation distance w6 between one end of the height-direction bead 160 (end in one direction of the longitudinal direction Z) and the other end of the adjacent height-direction bead 160 (end in the other direction of the longitudinal direction Z), as shown in FIG. 4.

The plurality of height-direction beads 160 do not need to be formed over the entire length of the side wall portion 115 in the longitudinal direction Z, but may be formed over a portion of the entire length of the side wall portion 115 in the longitudinal direction Z. The positions at which the plurality of height-direction beads 160 are formed may be selected as positions at which the bending crushing characteristics of the structural member 100 should be most strengthened, for example, the position where the impactor comes into contact and its vicinity.
Furthermore, the multiple height-direction beads 160 do not need to be formed side by side on the side wall portion 115 with equal bead-to-bead distances; for example, when three height-direction beads 160 are formed, the two bead-to-bead distances may be different values.
Furthermore, the plurality of height direction beads 160 do not necessarily have to be formed at the same position in the longitudinal direction Z on the pair of side wall portions 115, 115. For example, at the same position in the longitudinal direction Z as the height direction bead 160 formed on one side wall portion 115, the height direction bead 160 does not have to be formed on the other side wall portion 115.

The width w5 of the height-wise bead 160 is the distance between the intersection of a virtual line extending the outer surface of one bead side wall 161 of the height-wise bead 160 with a virtual line extending the outer surface of the side wall portion 115, and the intersection of a virtual line extending the outer surface of the other bead side wall 161 of the height-wise bead 160 with a virtual line extending the outer surface of the side wall portion 115, in a cross section perpendicular to the height direction Y.
When the height direction bead 160 has a shape whose width changes along a direction intersecting the longitudinal direction Z, the separation distance in the cross section where the separation distance is maximum is defined as width w5.

The smaller the width w5 of the height direction bead 160, the higher the deformation resistance against the compressive stress (B) along the height direction Y that occurs in the side wall portion 115. Therefore, the width w5 of the height direction bead 160 is preferably 60 mm or less, and more preferably 40 mm or less.

On the other hand, if the width w5 of the height direction bead 160 is too small, and the depth d2 of the height direction bead 160 is relatively large, it may be difficult to mold the height direction bead 160. Therefore, it is preferable that the width w5 of the height direction bead 160 is 10 mm or more, and it is even more preferable that it is 15 mm or more.

As described above, the depth d2 and width w5 of the height direction bead 160 affect the deformation resistance to the compressive stress (B) along the height direction Y that occurs in the side wall portion 115. When the aspect ratio A2 calculated by the depth d2 relative to the width w5 of the height direction bead 160 (depth d2/width w5) is 0.05 or more and 1.0 or less, this is preferable because it can more reliably achieve the effect of increasing the deformation resistance to the compressive stress (B) along the height direction Y that occurs in the side wall portion 115. It is even more preferable that the aspect ratio A2 is 0.1 or more and 0.5 or less.

From the viewpoint of reducing weight, the hat-shaped component 110 is preferably formed from a steel plate having a thickness of 1.2 mm or less, and more preferably from a steel plate having a thickness of 1.0 mm or less.
The lower limit of the thickness of the hat-shaped component 110 is not particularly limited, and may be 0.3 mm or more.
Furthermore, from the viewpoint of collision safety performance, the hat-shaped member 110 is preferably formed from a steel plate having a tensile strength of 980 MPa or more, and more preferably from a steel plate having a tensile strength of 1470 MPa or more.

The hat-shaped member 110 can be formed, for example, by subjecting a plate material to cold pressing or warm pressing.
The hat-shaped member 110 may also be formed by hot stamping, in which a steel plate is heated to a high temperature in the austenite region, and then press-formed in a die, and simultaneously quenched in the die by a method such as heat extraction into the die or water cooling in the die. Thus, the hat-shaped member 110 may be a quenched member.

(Joining member)
The joining member 120 will be described below.
The joining member 120 is a member that is joined to the hat-shaped member 110. The structural member 100 according to this embodiment is installed in an automobile with the joining member 120 facing the inside of the vehicle. Therefore, when an impact load from the outside of the vehicle is input to the top plate portion 111 and bending deformation occurs in the structural member 100, a tensile stress (C) along the longitudinal direction Z is generated in the joining member 120.
Therefore, by joining the joining member 120 to the hat-shaped member 110, it is possible to increase the deformation resistance against the tensile stress (C) along the longitudinal direction Z. This makes it possible to improve the load resistance at the beginning of the stroke.
Furthermore, by being joined to the hat-shaped member 110, the joining member 120 can prevent the side wall portion 115 from opening in the width direction X when bending deformation occurs in the structural member 100. Therefore, it is possible to sufficiently increase the deformation resistance of the side wall portion 115 against the compressive stress (B) along the height direction Y, and to improve the load resistance at the beginning of the stroke.

2A and 2B, in the structural member 100 according to this embodiment, a single flat plate material is used as the joining member 120. However, instead of the flat plate material, for example, a hat-shaped member may be used.
The joining member 120 may be a member made of a metal plate such as a steel plate, an aluminum plate, an aluminum alloy plate, a stainless steel plate, or a titanium plate, or further, a resin plate or a CFRP (Carbon Fiber Reinforced Plastic) plate.
The tensile strength and thickness of the joining member 120 are not particularly limited. As described above, when an impact load from the outside of the vehicle is input to the top plate portion 111 and bending deformation occurs in the structural member 100, a tensile stress (C) along the longitudinal direction Z occurs in the joining member 120. If compressive stress occurs, the plate thickness and strength of the member greatly affect the buckling deformation due to the compressive stress, but in the case of tensile stress, a material with a thin plate thickness or low strength can be used within a range in which the member does not break due to tensile deformation. Therefore, for example, the tensile strength and thickness of the joining member 120 may be lower than those of the hat-shaped member 110, or may be thinner than those of the hat-shaped member 110.
The joining member 120 may also be a hardened member.

As shown in FIG. 2B , the joint member 120 has a pair of joint portions 121, 121 provided at both ends in the width direction X, and a top plate facing portion 123 provided in the center in the width direction X.
The pair of joint portions 121, 121 are locations where the pair of flange portions 119, 119 of the hat-shaped component 110 are joined by spot welding or the like.
The top plate facing portion 123 is a portion of the joining member 120 excluding the joint portion 121 , and is a portion facing the top plate portion 111 of the hat-shaped member 110 .
In the structural member 100 according to this embodiment, the joint member 120 is formed from a single flat steel plate, so that the joint portion 121 and the top plate facing portion 123 are adjacent regions on the same plane.

The width of the top plate facing portion 123 may be 40 mm or more and 200 mm or less. It is preferable that the width of the top plate facing portion 123 is greater than the width W of the top plate portion 111. In this case, the pair of side wall portions 115, 115 are inclined in a direction that spreads outward from the first ridge portion 113, 113 to the second ridge portion 117, 117. When an impact load from the outside of the vehicle is input to the top plate portion 111, the pair of side wall portions 115, 115 are likely to collapse in a direction in which the first ridge portions 113, 113 approach each other. As a result, the first bead side walls 151, 151 of the two longitudinal beads 150, 150 are also likely to collapse inward, but the collapse of the first bead side walls 151, 151 is suppressed by the second bead side walls 152, 152 (details will be described later). As a result, the collapse of the cross-sectional shape of the hat-shaped member 110 can be suppressed, and the impact absorption energy can be further improved. In addition, because the pair of side walls 115, 115 are inclined in a direction that spreads outward from the first ridge line portion 113, 113 to the second ridge line portion 117, 117, when the hat-shaped component 110 is press-molded, a negative angle can be eliminated when the height direction Y is the press direction, which makes molding easier.

(Longitudinal bead deformation)
5 to 7, the deformation of the longitudinal bead 150 when an impact load from the outside of the vehicle is input to the hat-shaped member 110. When an impact load from the outside of the vehicle is input to the hat-shaped member 110 and bending deformation occurs in the structural member 100, a compressive stress (A) along the longitudinal direction Z in the top plate portion 111 of the hat-shaped member 110, a compressive stress (B) along the height direction Y in the side wall portion 115 of the hat-shaped member 110, and a tensile stress (C) along the longitudinal direction Z in the joining member 120 are generated in a composite manner, as shown in FIG.

In the initial stage of the stroke, as shown in FIG. 7A, the side wall portion 115 starts to collapse inward from the pre-deformation state shown in FIG. 6, and the first bead side wall 151 collapses inward. Then, as shown in FIG. 7B, the first bead side wall 151 (more specifically, the R portion 150a, which is the boundary portion between the first bead side wall 151 and the side wall portion top plate portion 111b) comes into contact with the second bead side wall 152. After that, the collapsed first bead side wall 151 can be held by the second bead side wall 152. That is, the collapse of the first bead side walls 151, 151 is suppressed by the second bead side walls 152, 152. As a result, the collapse of the side wall portion 115 is also suppressed, and the collapse of the cross-sectional shape of the hat-shaped member 110 can be suppressed, so that the impact absorption energy can be further improved.

According to the structural member 100 of this embodiment, when an impact load from outside the vehicle is input to the top plate portion 111 and bending deformation occurs in the structural member 100, it is possible to exert a combination of deformation resistance to compressive stress (A) along the longitudinal direction Z, deformation resistance to compressive stress (B) along the height direction Y, and deformation resistance to tensile stress (C) along the longitudinal direction Z.
In particular, since the relationship w1 < w2 is satisfied and the central top plate portion 111a protrudes outward in the height direction Y more than the side wall side top plate portion 111b, the collapse of the first bead side wall 151 can be suppressed by the second bead side wall 152, and the collapse of the side wall portion 115 is also suppressed, and the deformation of the cross-sectional shape of the hat-shaped member 110 can be suppressed, thereby improving the load-bearing capacity and impact absorption energy at the beginning of the stroke in the local buckling mode deformation.
Incidentally, it is preferable that the relationship w1×1.2<w2 is satisfied, since the above-mentioned effects can be obtained more stably.

Since the thinner the plate material, the lower the deformation resistance, the conventional method has been one of the barriers to weight reduction by using thin, high-strength materials. That is, even if the deformation resistance of the top plate 111 against the compressive stress (A) along the longitudinal direction Z is increased by increasing the strength or designing the part shape, the structural member 100 cannot exhibit good three-point bending characteristics if the side wall 115 is easily buckled due to bending deformation or the like due to the thinning. Conversely, even if the deformation resistance of the side wall 115 against the compressive stress (B) in the direction intersecting the longitudinal direction Z is increased by increasing the strength or designing the part shape, the structural member cannot exhibit good three-point bending characteristics if the top plate 111 is easily buckled due to bending deformation or the like due to the thinning.
As described above, the structural member 100 of this embodiment can exert a composite deformation resistance at each portion, making it possible to exert excellent collision safety performance even when using a thin-walled, high-strength material.

(First Modification)
Next, a first modified example (structural member 100A) of the structural member 100 will be described with reference to FIG. 8. The second to sixth modified examples described later may be applied to the first modified example. FIG. 8 is a perspective view of the structural member 100A according to the first modified example. In the above-mentioned structural member 100, the longitudinal bead 150 is formed on the top plate portion 111 of the hat-shaped member 110. However, in this structural member 100A, the longitudinal bead 150 is not formed on the top plate portion 111 of the hat-shaped member 110, but is formed on the top plate facing portion 123 of the joining member 120. Therefore, the top plate facing portion 123 is divided into a central top plate facing portion 123a formed between the two longitudinal beads 150, and side wall side top plate facing portions 123b, 123b formed on the side wall portion 115 side from the two longitudinal beads 150. The central top plate facing portion 123a protrudes outward in the height direction Y further than the side wall top plate facing portions 123b, 123b.

Unlike the structural member 100, this structural member 100A is a part that is assumed to be installed in an automobile with the hat-shaped member 110 facing the inside of the vehicle and the joining member 120 facing the outside of the vehicle.
According to this structural member 100, when it is installed in an automobile with the hat-shaped member 110 facing the inside of the automobile and the joining member 120 facing the outside of the automobile, it is possible to obtain the same effects as those of the structural member 100.
In this modified example, it is preferable that the following conditions are satisfied.
(1) In a cross section perpendicular to the longitudinal direction Z, the longitudinal bead 150 is formed so that the center of the longitudinal bead 150 in the width direction X is located in the region from the inner end of the joint 121 of the joint member 120 to a point that is spaced apart in the width direction X by 1/4 of the width of the top plate opposing portion 123.
(2) In a cross section perpendicular to the longitudinal direction Z, the longitudinal bead 150 is formed so that the boundary point between the longitudinal bead 150 and the joining member 120 is located in the region from the inner end of the joining portion 121 of the joining member 120 to a point that is 20 mm away.

Moreover, it is preferable that the joint member 120 is formed from a steel plate having a thickness of 1.2 mm or less.
Moreover, it is preferable that the joining members 120 are formed from a steel plate having a tensile strength of 980 MPa or more.
The joining member 120 is preferably a hardened member.

(Second Modification)
Next, a second modified example of the structural member 100 (structural member 100B) will be described with reference to FIG. 9. FIG. 9 is an enlarged cross-sectional view showing a longitudinal bead 150 according to the second modified example. In the second modified example, the shape of the longitudinal bead 150 is substantially triangular in a cross section perpendicular to the longitudinal direction Z of the structural member 100B. More specifically, the first bead side wall 151 and the second bead side wall 152 are connected via the R portion 150e. That is, in the second modified example, w3=0. The second bead side wall 152 is longer than the first bead side wall 151, and the relationship w1<w2 is satisfied. It is preferable that the relationship w1×1.4≦w2 is satisfied. It is preferable that the upper limit of w2 is equal to or less than w1×2.5. Furthermore, when the inner angle between the first bead side wall 151 and the top plate portion 111 is θ1 and the inner angle between the second bead side wall 152 and the top plate portion 111 is θ2, the relationship θ1<θ2 is satisfied. Here, the angle θ1 is the inner angle between a virtual line extending the outer surface of the top plate portion 111 and a virtual line extending the outer surface of the first bead side wall 151. The angle θ2 is the inner angle between a virtual line extending the outer surface of the top plate portion 111 and a virtual line extending the outer surface of the second bead side wall 152. The specific ranges of the angles θ1 and θ2 are not particularly limited and may be set appropriately according to the required characteristics, etc. Furthermore, the angle between the first bead side wall 151 and the second bead side wall 152 (the outward angle between an imaginary line extending the outer surface of the first bead side wall 151 and an imaginary line extending the outer surface of the second bead side wall 152) is an acute angle. In the second modified example, the height of the center side top plate portion 111a is approximately the same as the height of the side wall side top plate portion 111b.
It is more preferable that θ1 and θ2 satisfy the relationship θ1×1.1<θ2. It is preferable that θ1 is 90° or more. In this case, in order to satisfy the relationship θ1<θ2, it is preferable that θ2 is more than 90°, and more preferably more than 99°.
It is preferable that θ2 is equal to or smaller than 135°. In this case, in order to satisfy the relationship θ1<θ2, it is preferable that θ1 is less than 135°, and more preferably less than 122°.

Next, the deformation of the longitudinal bead 150 will be described. At the beginning of the stroke, first, as the side wall portion 115 starts to collapse inward, the first bead side wall 151 also starts to collapse inward. However, there is no bead bottom wall 153 between the first bead side wall 151 and the second bead side wall 152, and the angle between them is an acute angle. Furthermore, the overall length of the longitudinal bead 150 in a cross section perpendicular to the longitudinal direction Z is short, and the number of sides constituting the longitudinal bead 150 is small. Therefore, the degree of deformation freedom of the cross-sectional shape perpendicular to the longitudinal direction Z of the longitudinal bead 150 is small. In other words, the deformation of the cross-sectional shape perpendicular to the longitudinal direction Z of the longitudinal bead 150 is kept small. Therefore, the collapse of the cross-sectional shape of the hat-shaped member 110 can be suppressed, and the impact absorption energy can be further improved.

(Third Modification)
Next, a third modified example of the structural member 100 (structural member 100C) will be described with reference to Fig. 10. Fig. 10 is an enlarged cross-sectional view showing a longitudinal bead 150 according to the third modified example. In the third modified example, in addition to the shape of the second modified example, the central top plate portion 111a further protrudes outward in the height direction Y beyond the side wall top plate portions 111b, 111b.

Next, the deformation of the longitudinal bead 150 will be described. At the beginning of the stroke, first, as the side wall portion 115 starts to collapse inward, the first bead side wall 151 collapses inward. Then, the first bead side wall 151 (more specifically, the R portion 150a which is the boundary portion between the first bead side wall 151 and the side wall portion side top plate portion 111b) comes into contact with the second bead side wall 152. Then, the collapsed first bead side wall 151 can be held by the second bead side wall 152. That is, the collapse of the first bead side walls 151, 151 is suppressed by the second bead side walls 152, 152. As a result, the collapse of the side wall portion 115 is also suppressed. Furthermore, there is no bead bottom wall 153 between the first bead side wall 151 and the second bead side wall 152, and the angle between them is an acute angle. Furthermore, the overall length of the longitudinal bead 150 in a cross section perpendicular to the longitudinal direction Z is short, and the number of sides constituting the longitudinal bead 150 is small. Therefore, the degree of freedom of deformation of the cross-sectional shape perpendicular to the longitudinal direction Z of the longitudinal bead 150 is small. In other words, deformation of the cross-sectional shape perpendicular to the longitudinal direction Z of the longitudinal bead 150 is kept small. Therefore, the collapse of the cross-sectional shape of the hat-shaped member 110 can be suppressed, and the impact absorption energy can be further improved.
The second bead side wall 152 is longer than the first bead side wall 151, and the relationship w1<w2 is satisfied. It is preferable that the relationship w1×1.8≦w2 is satisfied. The upper limit of w2 is preferably equal to or less than w1×4.0.

(Fourth Modification)
Next, a fourth modified example of the structural member 100 (structural member 100D) will be described with reference to FIG. 11. FIG. 11 is an enlarged cross-sectional view showing a longitudinal bead 150 according to the fourth modified example. In the fourth modified example, the longitudinal bead 150 has a substantially triangular shape in a cross section perpendicular to the longitudinal direction Z of the structural member 100D. More specifically, the first bead side wall 151 and the second bead side wall 152 are connected via the R portion 150e. That is, in the fourth modified example, w3=0. The second bead side wall 152 is longer than the first bead side wall 151, and the relationship w1<w2 is satisfied. Furthermore, the angle between the first bead side wall 151 and the second bead side wall 152 (the angle on the outer side between the imaginary line extending the outer surface of the first bead side wall 151 and the imaginary line extending the outer surface of the second bead side wall 152) is an acute angle. Furthermore, the central top plate portion 111a protrudes outward in the height direction Y more than the side wall top plate portion 111b. The angles θ1 and θ2 are arbitrary and may be determined appropriately depending on the required characteristics, etc. As an example, θ2=90 degrees, θ1>θ2 may be given.

Next, the deformation of the longitudinal bead 150 will be described. At the beginning of the stroke, first, as the side wall portion 115 begins to collapse inward, the first bead side wall 151 collapses inward. Then, the first bead side wall 151 (more specifically, the R portion 150a, which is the boundary portion between the first bead side wall 151 and the side wall portion side top plate portion 111b) comes into contact with the second bead side wall 152. Then, the collapsed first bead side wall 151 can be held by the second bead side wall 152. That is, the collapse of the first bead side walls 151, 151 is suppressed by the second bead side walls 152, 152. As a result, the collapse of the side wall portion 115 is also suppressed. Furthermore, there is no bead bottom wall 153 between the first bead side wall 151 and the second bead side wall 152, and the angle they form is an acute angle. Furthermore, the overall length of the longitudinal bead 150 in a cross section perpendicular to the longitudinal direction Z is short, and the number of sides constituting the longitudinal bead 150 is small. Therefore, the degree of freedom of deformation of the cross-sectional shape perpendicular to the longitudinal direction Z of the longitudinal bead 150 is small. In other words, deformation of the cross-sectional shape perpendicular to the longitudinal direction Z of the longitudinal bead 150 is kept small. Therefore, the collapse of the cross-sectional shape of the hat-shaped member 110 can be suppressed, and the impact absorption energy can be further improved.

(Fifth Modification)
Next, a fifth modified example of the structural member 100 (structural member 100E) will be described with reference to Fig. 12. Fig. 12 is an enlarged cross-sectional view showing a longitudinal bead 150 according to the fifth modified example. In the fifth modified example, a step S is formed in the second bead side wall 152. The size of the step S (the length in the width direction in Fig. 12) is not particularly limited, and may be, for example, about 5 mm. The other configurations are the same as those of the above-mentioned embodiment.
The length w2 of the second bead side wall 152 is the distance in a direction along the second bead side wall 152 between the boundary point between the R portion 150b and the second bead side wall 152 and the boundary point between the R portion 150d and the second bead side wall 152. More precisely, it is the distance between a perpendicular line dropped from the boundary point between the R portion 150b and the second bead side wall 152 and a perpendicular line dropped from the boundary point between the R portion 150d and the second bead side wall 152.

Next, the deformation of the longitudinal bead 150 will be described. At the beginning of the stroke, first, as the deformation of the structural member 100E progresses due to the impact load from the outside of the vehicle, the side wall portion 115 begins to collapse inward, and the first bead side wall 151 collapses inward. Then, the first bead side wall 151 (more specifically, the R portion 150a, which is the boundary portion between the first bead side wall 151 and the side wall portion top plate portion 111b) comes into contact with the second bead side wall 152. Then, the collapsed first bead side wall 151 can be held by the second bead side wall 152. That is, the collapse of the first bead side walls 151, 151 is suppressed by the second bead side walls 152, 152. As a result, the collapse of the side wall portion 115 is also suppressed, and the collapse of the cross-sectional shape of the hat-shaped member 110 can be suppressed, so that the impact absorption energy can be further improved.

(Sixth Modification)
Next, a sixth modified example of the structural member 100 (structural member 100F) will be described based on FIG. 13. FIG. 13 is an enlarged cross-sectional view showing a longitudinal bead 150 according to the sixth modified example. In the sixth modified example, the bead bottom wall 153 is inclined, the R portion 150c is disposed at a lower position than the R portion 150d, and the angle θ3 is 120 degrees or more. The angle θ3 is an outer angle formed by the second bead side wall 152 and the bead bottom wall 153, and more specifically, is an angle formed by an imaginary line extending the outer surface of the second bead side wall 152 and an imaginary line extending the outer surface of the bead bottom wall 153. In this modified example, w1<w2+w3 is satisfied. The other configurations are the same as those of the above-mentioned embodiment. It is preferable that the angle θ3 is less than 180 degrees.

Next, the deformation of the longitudinal bead 150 will be described. In the initial stage of the stroke, first, as the deformation of the structural member 100F progresses due to the impact load from the vehicle exterior, the side wall portion 115 starts to collapse inward, and the first bead side wall 151 collapses inward. Then, the first bead side wall 151 (more specifically, the R portion 150a which is the boundary portion between the first bead side wall 151 and the side wall portion side top plate portion 111b) comes into contact with the second bead side wall 152 or the bead bottom wall 153. Then, the collapsed first bead side wall 151 can be held by the second bead side wall 152 or the bead bottom wall 153. That is, the collapse of the first bead side walls 151, 151 is suppressed by the second bead side walls 152, 152 or the bead bottom walls 153, 153. As a result, the side wall portion 115 is prevented from collapsing, and the cross-sectional shape of the hat-shaped member 110 is prevented from collapsing, thereby further improving the impact absorption energy. Note that, when the relationship w1×1.5<w2+w3 is satisfied, the above-mentioned effect can be obtained more stably, which is preferable.
The upper limit of w2+w3 is preferably equal to or less than w1×3.5.

In the above-described embodiment and each modified example, the top plate portion 111, the top plate opposing portion 123, the side wall portion 115, and the bead bottom wall 162 are straight in a cross section perpendicular to the longitudinal direction Z, but they may be curved. The curved shape here is not limited to the cross section perpendicular to the longitudinal direction Z, but also includes curvature in the longitudinal direction of the member, i.e., curvature in the height direction (up and down) and width direction (left and right). In this case, the shape of the top plate portion 111, the top plate facing portion 123, the side wall portion 115, and the bead bottom wall 162 in a cross section perpendicular to the longitudinal direction Z is a straight line connecting both ends of the length direction of each part in the cross section (for example, a straight line is drawn connecting both ends of the width direction (length direction of the top plate portion 111) of the top plate portion 111 in a cross section perpendicular to the longitudinal direction Z, and this straight line is assumed to be the top plate portion 111), and the above-mentioned parameters (for example, the length w1 of the first bead side wall 151, the length w2 of the second bead side wall 152, the length w3 of the bead bottom wall 153, etc.) may be defined. In addition, the first modified example may be applied to the above-mentioned embodiment and the second to sixth modified examples. In other words, the longitudinal bead 150 may be formed on both the top plate portion 111 and the top plate facing portion 123.

(Example)
The effects of the present invention will be specifically described below with reference to examples. Note that the examples described below are merely examples of the present invention and do not limit the present invention.

A simulation model of a structural member was prepared, which was composed of a hat-shaped member made of steel plate with a thickness of 0.8 mm and a tensile strength of 2.5 GPa, and a joining member made of steel plate with a thickness of 0.8 mm and a tensile strength of 270 MPa.
A simulation model of the structural member was appropriately given longitudinal and vertical beads, and a simulation was performed assuming three-point bending to evaluate the maximum load at the beginning of the stroke and the impact absorption energy up to a stroke of 100 mm. In addition, a three-point bending simulation was also performed on a structural member that did not have longitudinal and vertical beads as a reference or comparative example. The basic conditions, the conditions of the comparative example, and the conditions of each invention example are as follows.
(Basic conditions)
Angle between side wall and top plate = 95 degrees Width of top plate W = 70 mm
Side wall height H = 50 mm
Radius of curvature of first ridge (inner bend) = 5 mm
Radius of curvature of the second ridge (inner bend) = 5 mm
Total length of structural member L = 800 mm
Bead depth in the vertical direction d2 = 4 mm
Height direction bead width w5 = 24 mm
Distance between beads in the height direction = 16 mm
(Comparative Example 1)
No longitudinal bead or height bead (Comparative Example 2)
Shape of the longitudinal bead in a cross section perpendicular to the longitudinal direction Z: Approximately rectangular (w1 = w2 = 5.6 mm, w3 = 4.6 mm)
(Corresponding to Example 1: embodiment)
Shape of the longitudinal bead in a cross section perpendicular to the longitudinal direction Z: Approximately rectangular (w1 = 5.6 mm, w2 = 10.6 mm (= w1 + 5 mm), w3 = 4.6 mm)
(Example 2: Corresponding to the second modified example)
Shape of the longitudinal bead in a cross section perpendicular to the longitudinal direction Z: Approximately triangular (w1 = 5.2 mm, w2 = 9.7 mm, w3 = 0 mm)
θ1=90 degrees, θ2=124.8 degrees (Example 3: corresponds to the fourth modified example)
Shape of the longitudinal bead in a cross section perpendicular to the longitudinal direction Z: Approximately triangular (w1 = 9.7 mm, w2 = 10.2 mm, w3 = 0 mm)
θ1 = 124.8 degrees, θ2 = 90 degrees (Example 4: corresponds to the third modified example)
Shape of the longitudinal bead in a cross section perpendicular to the longitudinal direction Z: Approximately triangular (w1 = 5.2 mm, w2 = 15.8 mm, w3 = 0 mm)
θ1=90 degrees, θ2=124.8 degrees

The three-point bending conditions were set as follows: the radius of curvature of the impactor was 50 mm, and the distance between the support stands was 700 mm, as shown in Fig. 14. The maximum load at the beginning of the stroke and the impact absorption energy up to a stroke of 100 mm are shown in Table 1. The reference ratios in Table 1 are values expressed as percentages relative to the values of Comparative Example 1 (maximum load and impact energy absorption amount).
In Comparative Example 1, the side wall portion buckled from the early stage of the stroke, and the structural members were significantly deformed, so that the maximum load and the impact absorption energy at the early stage of the stroke were low.
In Comparative Example 2, the maximum load and impact absorption energy at the beginning of the stroke were improved by the longitudinal bead, but the improvement in the reference ratio was greater in Invention Examples 1 to 4.
In Examples 1 to 4, the maximum load at the beginning of the stroke was large, and the shock absorption energy was also large.
In Example 1, the central top plate portion protrudes outward in the height direction Y more than the side wall top plate portion. At the beginning of the stroke, the side wall portion starts to collapse, and accordingly, the first bead side wall also starts to collapse. As the deformation of the structural member progresses further, the first bead side wall collapses further inward, but because the central top plate portion protrudes outward in the height direction Y more than the side wall top plate portion, the first bead side wall can be held by the second bead side wall. It is therefore believed that the maximum load at the beginning of the stroke becomes larger, and the impact absorption energy also becomes larger.
In Example 2, the cross section of the longitudinal bead perpendicular to the longitudinal direction Z is triangular, and the relationship θ1<θ2 is satisfied. At the beginning of the stroke, the side wall starts to collapse, and the first bead side wall also starts to collapse. However, since the cross section of the longitudinal bead perpendicular to the longitudinal direction Z is triangular, the degree of deformation of the cross section of the longitudinal bead is small. Therefore, it is considered that the maximum load at the beginning of the stroke is large, and the impact absorption energy is also large.
In the third example of the invention, the cross section of the longitudinal bead perpendicular to the longitudinal direction Z is triangular, and the central top plate portion protrudes outward in the height direction Y more than the side wall top plate portion. At the beginning of the stroke, the side wall portion starts to collapse, and the first bead side wall also starts to collapse accordingly. As the deformation of the structural member progresses further, the first bead side wall collapses further inward, but since the central top plate portion protrudes outward in the height direction Y more than the side wall top plate portion, the first bead side wall can be held by the second bead side wall. Furthermore, since the cross section of the longitudinal bead perpendicular to the longitudinal direction Z is triangular, the degree of freedom of deformation of the cross-sectional shape of the longitudinal bead is small. Therefore, it is considered that the maximum load at the beginning of the stroke is large, and the impact absorption energy is also large.
In Example 4, in addition to the shape of Example 2, the central top plate portion protrudes outward in the height direction Y more than the side wall top plate portion. At the beginning of the stroke, the side wall portion starts to collapse, and the first bead side wall also starts to collapse accordingly. As the deformation of the structural member progresses further, the first bead side wall collapses further inward, but since the central top plate portion protrudes outward in the height direction Y more than the side wall top plate portion, the first bead side wall can be held by the second bead side wall. Furthermore, since the cross-sectional shape perpendicular to the longitudinal direction Z of the longitudinal bead is triangular, the degree of freedom of deformation of the cross-sectional shape of the longitudinal bead is small. Therefore, it is considered that the maximum load at the beginning of the stroke is large, and the impact absorption energy is also large.

The present invention provides a structural member that can provide superior collision safety performance by improving the load-bearing capacity and impact energy absorption at the beginning of the stroke in local buckling mode deformation.

100, 100A, 100B, 100C, 100D, 100E, 100F Structural member 110 Hat-shaped member 111 Top plate portion 111a Central top plate portion 111b Side wall portion side top plate portion 113 First ridge portion 115 Side wall portion

Claims (12)

1. A top plate portion extending along a longitudinal direction;
   A pair of side walls extending through a pair of first ridges formed at both ends of the top plate in a width direction;
   a pair of flange portions extending via a pair of second ridge portions formed at ends of the pair of side wall portions opposite to the pair of first ridge portions;
   A hat-shaped member having
   A pair of joints joined to the pair of flange portions of the hat-shaped member;
   a top plate facing portion facing the top plate portion of the hat-shaped member;
   A joining member having
   Equipped with
   At least two or more longitudinal beads extending along the longitudinal direction are formed in parallel in the width direction on at least one of the top plate portion and the top plate opposing portion,
   A plurality of height-direction beads extending along a height direction are formed in the pair of side wall portions and are arranged in parallel in the longitudinal direction,
   Among the two or more longitudinal beads, each of the two longitudinal beads arranged on the outside is
   a first bead side wall extending inwardly from at least one of the top plate portion and the top plate opposing portion;
   a second bead side wall that is bent and extends inward from at least one of the top plate portion and the top plate opposing portion at a position farther from the side wall portion than the first bead side wall;
   a bead bottom wall connecting inner ends of the first bead side wall and the second bead side wall;
   Equipped with
   In a cross section perpendicular to the longitudinal direction,
   The length of the first bead side wall is w1,
   The length of the second bead side wall is w2,
   The length of the bead bottom wall is w3,
   The outer angle between the second bead side wall and the bead bottom wall is θ3
   and w1<w2+w3.
2. The inner angle between the first bead side wall and the top plate portion is θ1.
   The inner angle between the second bead side wall and the top plate portion is θ2.
   2. The structural member of an automobile body according to claim 1, wherein the relationship θ1<θ2 is satisfied.
3. 3. The structural member of an automobile body according to claim 1, wherein the width w3 is equal to or greater than 0 mm and equal to or less than 18 mm.
4. Among the top plate portion and the top plate opposing portion,
   At least one of the central top plate portion and the central top plate opposing portion formed between the two longitudinal beads arranged on the outer side is
   A structural member of an automobile body as described in claim 1 or 2, characterized in that it protrudes outward in the height direction from either a pair of side wall portion side top plate portions or a pair of side wall portion side top plate opposing portions formed on the side wall portion side of the two longitudinal beads arranged on the outside.
5. 3. The structural member of an automobile body according to claim 1, wherein the two outer longitudinal beads are formed on the top plate portion of the hat-shaped member.
6. A top plate portion extending along a longitudinal direction;
   A pair of side walls extending through a pair of first ridges formed at both ends of the top plate in a width direction;
   a pair of flange portions extending via a pair of second ridge portions formed at ends of the pair of side wall portions opposite to the pair of first ridge portions;
   A hat-shaped member having
   A pair of joints joined to the pair of flange portions of the hat-shaped member;
   a top plate facing portion facing the top plate portion of the hat-shaped member;
   A joining member having
   Equipped with
   At least two or more longitudinal beads extending along the longitudinal direction are formed in parallel in the width direction on at least one of the top plate portion and the top plate opposing portion,
   A plurality of height-direction beads extending along a height direction are formed in the pair of side wall portions and are arranged in parallel in the longitudinal direction,
   Among the two or more longitudinal beads, each of the two longitudinal beads arranged on the outside is
   a first bead side wall extending inwardly from at least one of the top plate portion and the top plate opposing portion;
   a second bead side wall that is bent and extends inward from at least one of the top plate portion and the top plate opposing portion at a position farther from the side wall portion than the first bead side wall;
   a bead bottom wall connecting inner ends of the first bead side wall and the second bead side wall;
   Equipped with
   In a cross section perpendicular to the longitudinal direction,
   The length of the first bead side wall is w1,
   The length of the second bead side wall is w2,
   Then, the relationship w1 < w2 is satisfied.
   The inner angle between the first bead side wall and the top plate portion is θ1.
   The inner angle between the second bead side wall and the top plate portion is θ2.
   θ1<θ2.
7. 7. The structural member of an automobile body according to claim 6, wherein the width w3 is equal to or greater than 0 mm and equal to or less than 18 mm.
8. Among the top plate portion and the top plate opposing portion,
   At least one of the central top plate portion and the central top plate opposing portion formed between the two longitudinal beads arranged on the outer side is
   A structural member of an automobile body as described in claim 6 or 7, characterized in that it protrudes outward in the height direction from either a pair of side wall portion side top plate portions or a pair of side wall portion side top plate opposing portions formed on the side wall portion side of the two longitudinal beads arranged on the outside.
9. 8. A structural member for an automobile body according to claim 6, wherein the two outer longitudinal beads are formed on the top plate portion of the hat-shaped member.
10. A top plate portion extending along a longitudinal direction;
    A pair of side walls extending through a pair of first ridges formed at both ends of the top plate in a width direction;
    a pair of flange portions extending via a pair of second ridge portions formed at ends of the pair of side wall portions opposite to the pair of first ridge portions;
    A hat-shaped member having
    A pair of joints joined to the pair of flange portions of the hat-shaped member;
    a top plate facing portion facing the top plate portion of the hat-shaped member;
    A joining member having
    Equipped with
    At least two or more longitudinal beads extending along the longitudinal direction are formed in parallel in the width direction on at least one of the top plate portion and the top plate opposing portion,
    A plurality of height-direction beads extending along a height direction are formed in the pair of side wall portions and are arranged in parallel in the longitudinal direction,
    Among the two or more longitudinal beads, each of the two longitudinal beads arranged on the outside is
    a first bead side wall extending inwardly from at least one of the top plate portion and the top plate opposing portion;
    a second bead side wall that is bent and extends inward from at least one of the top plate portion and the top plate opposing portion at a position farther from the side wall portion than the first bead side wall;
    a bead bottom wall connecting inner ends of the first bead side wall and the second bead side wall;
    Equipped with
    In a cross section perpendicular to the longitudinal direction,
    The length of the first bead side wall is w1,
    The length of the second bead side wall is w2,
    Then, the relationship w1 < w2 is satisfied.
    Among the top plate portion and the top plate facing portion,
    At least one of the central top plate portion and the central top plate opposing portion formed between the two longitudinal beads arranged on the outer side is
    A structural member of an automobile body, characterized in that it protrudes outward in the height direction more than either of a pair of side wall portion side top plate portions or a pair of side wall portion side top plate opposing portions formed on the side wall portion side of the two longitudinal beads arranged on the outside.
11. 11. The structural member of an automobile body according to claim 10, wherein the width w3 is equal to or greater than 0 mm and equal to or less than 18 mm.
12. 12. The structural member of an automobile body according to claim 10 or 11, wherein the two longitudinal beads arranged on the outside are formed on the top plate portion of the hat-shaped member.

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