Impact absorption member and vehicle body component

Abstract

To provide an impact absorption member that can exert high energy absorption efficiency while folding and deforming properly although the member is lightweight.SOLUTION: An impact absorption member 1 comprises a cylindrical body 30 and a reinforce 40. The reinforce 40 satisfies at least either of a first condition that the reinforce has a vertical plate 41 and a width / thickness ratio r1 of a first plane part is 10 or more and 50 or less or a second condition that the reinforce has a lateral plate 42 and a width / thickness ratio r2 of a second plane part is 10 or more and 50 or less. The cylindrical body 30 has a first site R1, a second site R2 and a third site R3 arranged in this order along a longitudinal direction, and has a first bead Ba and a second bead Bb as folding starting points, in the second site R2.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an impact absorbing member and a vehicle body part. [Background technology]

[0002] In recent years, fuel efficiency regulations have become stricter around the world, and automakers are promoting the weight reduction of vehicle bodies. At the same time, vehicle crash safety standards have also become stricter, so there is a demand for both weight reduction and improved crash performance. Furthermore, in response to fuel efficiency regulations in various countries and the trend toward carbon neutrality, the electrification of automobile power sources is progressing. Compared to conventional vehicle structures with internal combustion engines, the electrification of power sources has led to changes in the vehicle body structure, such as an increase in vehicle weight and a reduction in the engine compartment. One example is the shortening of the front nose of the vehicle body. In order to maintain high collision safety while shortening the vehicle nose, a structure that can obtain high energy absorption efficiency with a short deformation stroke is required.

[0003] In particular, for parts such as front side members and rear side members that actively undergo plastic deformation to absorb collision energy during a vehicle collision, structures that can dramatically improve energy absorption performance are required. Also, because such parts play a role in minimizing the external force applied to occupants during a collision, it is ideal for them to have a deformation mode that can shorten the deformation stroke while suppressing sudden load fluctuations.

[0004] The deformation of the member includes bellows deformation and serpentine deformation. The bellows deformation refers to a deformation in which out-of-plane deformation occurs on all of the side surfaces constituting a component, but the center line in the longitudinal direction of the component hardly bends at all. On the other hand, meandering deformation occurs when bending occurs at multiple points along the longitudinal direction of a component, in which out-of-plane deformation occurs mainly on one of the side surfaces that make up the component, and the center line of the component in the longitudinal direction also bends. Comparing the above two deformation modes, it can be said that bellows deformation absorbs a greater amount of impact energy than serpentine deformation if the impact force is applied from an ideal direction. However, since the input direction of the impact force is not limited to one direction, for example, if the impact force is applied obliquely to the longitudinal direction of the component, the amount of energy absorbed by bellows deformation drops significantly. In contrast, serpentine deformation (folding deformation) can flexibly respond to the direction of the impact force to a certain extent, and therefore can stably absorb impact energy. Patent documents 1 and 2 show examples of structures that absorb impact energy by folding deformation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-174121 A [Patent Document 2] International Publication No. 2021 / 192188 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 discloses a vehicle rear structure that absorbs impact energy during a rear collision. In this vehicle rear structure, a rear frame and a tank lower frame that are disposed below the rear frame are disposed in a pair on the left and right sides of the vehicle body, and the rear frame has a displacement-load characteristic that makes the ratio of load F to displacement S (F / S) larger than that of the tank lower frame, and the tank lower frame employs a configuration in which cross-sectional deformation is suppressed so that the load does not drop suddenly after reaching the maximum bending strength.

[0007] Here, as described above, in addition to weight reduction and improved collision performance, the impact absorbing member is also required to shorten the deformation stroke. One way to reduce weight is to use light alloys such as aluminum as a material, but due to the low material strength, it is not possible to improve collision performance and shorten the deformation stroke. Therefore, an alternative solution is to use high-strength steel plates with high tensile strength and then reduce the plate thickness. However, for example, if the plate thickness is simply reduced in the rear frame disclosed in Patent Document 1, out-of-plane deformation is likely to occur at any point in the rear frame, and the position of the break point becomes unclear. From the viewpoint of impact energy absorption, it is not acceptable to break anywhere, and if the joints do not break at the designed position, the designed amount of energy absorption cannot be obtained. In that case, the original high energy absorption amount, which should be superior to bellows deformation, cannot be exhibited. In other words, simply increasing the material strength and reducing the plate thickness does not allow the advantages of the folding deformation to be expressed to a high level, and the shortening of the deformation stroke cannot be achieved. The same is true for Patent Document 2. Patent Document 2 discloses a structure including a skeletal member having a closed cross-sectional structure and a reinforcing member disposed within the skeletal member. In this structure, if the plate thickness of the skeletal member is simply reduced in order to reduce the weight, out-of-plane deformation is likely to occur at each part of the skeletal member, and the position of the breakage starting point becomes unclear. Therefore, there is room for further study to maximize the advantages of the folding deformation and further shorten the deformation stroke.

[0008] The present invention has been made in consideration of the above circumstances, and has an object to provide an impact absorbing member that is lightweight yet capable of bending and deforming at smooth joints to exhibit high energy absorption efficiency, and a vehicle body part that has this impact absorbing member. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention employs the following means. (1) One aspect of the present invention is A shock absorbing member having a hollow tube and a reinforcement fixedly disposed inside the hollow tube, the shock absorbing member being long in one direction, The hollow tube is made of a steel material having a tensile strength of 650 MPa or more and 1600 MPa or less, and the reinforcement is made of a steel material having a tensile strength of 590 MPa or more and 1600 MPa or less; A cross section perpendicular to the longitudinal direction of the impact absorbing member, The hollow tube has a top wall portion having a flat portion overall width dimension W1 (mm) and a wall thickness t1 (mm), and a pair of side wall portions provided on both sides of the top wall portion and having a flat portion overall width dimension W2 (mm) and a wall thickness t1 (mm), The reinforcement has at least one of a vertical plate having one end joined to the top wall portion, a total number of n1 sheets, and a total plate thickness of t2 (mm), and a horizontal plate connecting the pair of side wall portions, a total number of n2 sheets, and a total plate thickness of t3 (mm), The reinforcement satisfies at least one of a first condition that the reinforcement has the vertical plate and a first flat portion width-thickness ratio r1 according to the following formula 1 is 10 or more and 50 or less, and a second condition that the reinforcement has the horizontal plate and a second flat portion width-thickness ratio r2 according to the following formula 2 is 10 or more and 50 or less; The hollow tube is The insulating film has a first portion, a second portion, and a third portion aligned in the longitudinal direction, The second portion has a folding start portion. r1=((W1-t2) / (n1+1)) / t1...(Formula 1) r2=((W2-t3) / (n2+1)) / t1...(Formula 2)

[0010] According to the impact absorbing member described in (1) above, when the bending start point is set in the top wall of the hollow tube, the top wall at the start of bending deformation tends to sink inwardly into the hollow tube. When only the first condition is satisfied, the vertical plate continues to support the top wall while resisting the force that tends to sink. This prevents the top wall from sinking, and also prevents the gap between the pair of side walls that tends to occur as the top wall sinks. In this way, the hollow tube is supported by the reinforcement from the inside. Alternatively, when only the second condition is satisfied, the spacing between the pair of side walls is constrained by the horizontal plate. This constraint prevents the top wall from sinking in to expand the gap between the pair of side walls, and the top wall is indirectly supported. Therefore, in this case as well, the hollow tube is supported from the inside by the reinforcement. Alternatively, when both the first and second conditions are satisfied, in addition to suppressing sinking of the top wall, the gap between the pair of side walls is also suppressed. Therefore, due to the synergistic effect of both, the hollow tube is more firmly supported from the inside by the reinforcement. In this way, the hollow tube is reinforced at each position in the longitudinal direction by the reinforcement. In addition, the hollow tube satisfies at least one of the first condition that the first flat portion width-thickness ratio r1 is 10 or more and 50 or less, and the second condition that the second flat portion width-thickness ratio r2 is 10 or more and 50 or less. As a result, even if the thickness t1 of the hollow tube is thinned for the purpose of weight reduction, the top wall portion or the side wall portion does not easily deform out of plane. If out-of-plane deformation occurs at an unintended position, the way of compressive deformation at that portion becomes unstable, so that the out-of-plane deformed portion may be easily or difficult to break. As a result, there is a risk of bending deformation occurring at an unintended position of the hollow tube. On the other hand, in this embodiment, at least one of the first condition and the second condition is satisfied. As a result, it is possible to suppress out-of-plane deformation of the hollow tube at an unintended portion, and therefore the thickness t1 can be thinned to reduce the weight of the impact absorbing member. On the other hand, since this shock absorbing member has a folding start portion in the second portion, the bending strength of the second portion is relatively lower than the bending strength of the first portion and the bending strength of the third portion. By combining this relative strength difference with at least one of the above-mentioned first condition and second condition, the shock absorbing member can be folded and deformed smoothly at the folding start portion of the second portion. In addition, the impact energy applied to the shock absorbing member is absorbed mainly by the reinforcement while folding and deforming, so the amount of energy absorption can be increased.

[0011] (2) The impact absorbing member described in (1) above may have the following configuration: the hollow tube includes a pair of ridges connecting the top wall portion and the pair of side wall portions; The folding start portion is a first bead that crosses a boundary between one of the pair of ridge portions and the top wall portion; a second bead that crosses the boundary between the other of the pair of ridge lines and the top wall portion; has. According to the impact absorbing member described in (2) above, the first bead and the second bead, which both extend from a pair of ridges into the top wall, are provided in the second portion of the hollow tube as bending starting points, so that the bending strength of the second portion can be reliably lowered to be lower than the bending strength of the first portion and the bending strength of the third portion, even with a simple configuration. In addition, the reinforcement provided in the hollow tube suppresses out-of-plane deformation in unintended positions in the first to third portions. Therefore, while the reinforcement prevents bending deformation of the hollow tube in unintended positions, the impact absorbing member can be reliably bent and deformed smoothly with the first and second beads as bending starting points.

[0012] (3) The impact absorbing member described in (2) above may have the following configuration: the first bead crosses a boundary between one of the pair of ridge portions and one of the pair of sidewall portions; The second bead crosses the boundary between the other of the pair of ridge portions and the other of the pair of side wall portions. According to the shock absorbing member described in (3) above, by making the first and second beads extend further into the side walls, the bending strength of the second portion of the hollow tube can be more reliably reduced than the bending strength of the first portion and the bending strength of the third portion. This makes the bending starting point more distinct, and the shock absorbing member can be more reliably bent and deformed with good joints.

[0013] (4) In the impact absorbing member according to any one of the above (1) to (3), The folding start portion may have a through hole or a third bead that is long in a direction intersecting the longitudinal direction and is formed in at least one of the top wall portion and the pair of side wall portions. According to the shock absorbing member described in (4) above, by providing the through hole or the third bead as the folding start point in the second portion of the hollow tube, the bending strength of the second portion can be reliably lowered below the bending strength of the first portion and the third bending strength, even with a simple configuration. In addition, the reinforcement provided in the hollow tube suppresses out-of-plane deformation at unintended positions in the first portion to the third portion. Therefore, while the reinforcement prevents folding deformation of the hollow tube at unintended positions, the shock absorbing member can be reliably folded and deformed with good joints, with the through hole or the third bead as the folding start point.

[0014] (5) In the impact absorbing member according to any one of the above (1) to (3), The fold origin may be provided in the second portion by setting a material tensile strength ratio, obtained by dividing the material tensile strength of the second portion by the average material tensile strength of the first portion and the third portion, to 0.5 to 0.9. According to the impact absorbing member described in (5) above, by setting the material tensile strength ratio in the above range, the bending strength of the second portion can be made lower than the bending strengths of the first portion and the third portion. In addition, the reinforcement provided in the hollow tube suppresses out-of-plane deformation at unintended positions in the first portion to the third portion. Therefore, while the reinforcement prevents bending deformation of the hollow tube at unintended positions, the impact absorbing member can be reliably and smoothly bent with the second portion of the hollow tube as the bending starting point.

[0015] (6) In the impact absorbing member according to any one of the above (1) to (3), The folding origin may be provided in the second region by setting a thickness ratio, obtained by dividing the thickness of the second region by the average thickness of the first region and the third region, to 0.5 to 0.9. According to the impact absorbing member described in (6) above, by setting the plate thickness ratio within the above range, the plate thickness of the second portion is made thinner than the average plate thickness of the first portion and the third portion. As a result, the bending strength of the second portion can be made lower than the bending strength of the first portion and the third portion. In addition, the reinforcement provided in the hollow tube suppresses out-of-plane deformation at unintended positions in the first portion to the third portion. Therefore, while the reinforcement prevents bending deformation of the hollow tube at unintended positions, the impact absorbing member can be reliably and smoothly bent with the second portion of the hollow tube as the bending starting point.

[0016] (7) In the impact absorbing member according to any one of the above (1) to (3), A reinforcing portion may be provided along the longitudinal direction in each of the first region and the third region. According to the shock absorbing member described in (7) above, by providing reinforcing parts in each of the first and third parts, the bending strength of the first part and the third part can be reliably increased more than the bending strength of the second part, even with a simple configuration. That is, the bending strength of the hollow tube can be relatively lower in the second part than in the first and third parts adjacent thereto. In addition, the reinforcement provided in the hollow tube suppresses out-of-plane deformation in unintended positions in the first to third parts. Therefore, while the reinforcement prevents bending deformation of the hollow tube in unintended positions, the shock absorbing member can be more reliably and smoothly bent with the second part of the hollow tube as the bending starting point.

[0017] (8) In the impact absorbing member described in (7) above, Each of the reinforcing portions may have at least one of a bead, an angle member, and an embossment formed along the longitudinal direction. According to the impact absorbing member described in (8) above, the bending strength of the first portion and the third bending strength can be reliably made higher than the bending strength of the second portion.

[0018] (9) In the impact absorbing member according to any one of the above (1) to (3), the following configuration may be adopted: The hollow tube is a hat-shaped member having the top wall portion and the pair of side wall portions; a plate-shaped member joined to the hat-shaped member and facing the top wall portion; Both the first condition and the second condition are met; In a cross section perpendicular to the longitudinal direction, said n1 is 1 and said n2 is 1; The vertical plate is fixed in a spanning state between the top wall portion and the plate-like member, The horizontal plate is fixed between the pair of side wall portions in a state where it crosses the vertical plate. According to the shock absorbing member described in (9) above, when viewed in a cross section perpendicular to the longitudinal direction, the hollow tube is supported from the inside by the surface formed by the combination of the vertical and horizontal plates. Therefore, the bending strength of the reinforcement can be increased over its entire length, so that the maximum load (barrier reaction force) can be increased and the maximum load can be maintained for a long time, thereby increasing the amount of energy absorption.

[0019] (10) In the impact absorbing member according to any one of the above (1) to (3), the following configuration may be adopted: The hollow tube is a hat-shaped member having the top wall portion and the pair of side wall portions; a plate-shaped member joined to the hat-shaped member and facing the top wall portion; Both the first condition and the second condition are met; In a cross section perpendicular to the longitudinal direction, said n1 is 1 and said n2 is 1; One end of the horizontal plate is joined to one of the pair of side wall portions, and the other end of the horizontal plate is joined to the other of the pair of side wall portions, The one end of the vertical plate is joined to the top wall portion, and the other end of the vertical plate is joined to a position between the one end and the other end of the horizontal plate. According to the shock absorbing member described in (10) above, when viewed in a cross section perpendicular to the longitudinal direction, the hollow tube is supported from the inside by the surface formed by the combination of the vertical and horizontal plates. Therefore, the bending strength of the reinforcement can be increased over its entire length, so that the maximum load (barrier reaction force) can be increased and the maximum load can be maintained for a long time, thereby increasing the amount of energy absorption.

[0020] (11) A vehicle body part according to one aspect of the present invention comprises: Any one of a front side member, a rear side member, a center pillar, and a bumper beam provided on a vehicle body, The shock absorbing member includes the shock absorbing member according to any one of the above items (1) to (3). The vehicle body part described in (11) above is provided with an impact absorbing member that is lightweight yet can bend and deform smoothly at joints to achieve high energy absorption efficiency. Therefore, this vehicle body part not only bends smoothly at the joints as designed, but also absorbs the energy as designed. This meets the current needs for vehicle body parts, which are to achieve high energy absorption efficiency with a short deformation stroke. Effect of the Invention

[0021] The impact absorbing member according to each of the above aspects of the present invention is lightweight yet exhibits high energy absorption efficiency by bending and deforming at good joints. Furthermore, a vehicle body part equipped with this impact absorbing member can meet the current need for high energy absorption efficiency with a short deformation stroke. [Brief description of the drawings]

[0022] [Figure 1] 1 is a perspective view of a vehicle body in which an impact absorbing member according to each embodiment of the present invention is applied to a front side member and a rear side member. [Diagram 2] 1 is a perspective view of a shock absorbing member according to a first embodiment of the present invention; [Diagram 3] FIG. 3 is a diagram showing a bead provided on the impact absorbing member, and is an enlarged perspective view of a portion A in FIG. 2. [Figure 4]FIG. 3 is a schematic diagram for explaining dimensions of each part of the impact absorbing member, and is a cross-sectional view taken along the line BB in FIG. 2. [Diagram 5] 3(a) to (d) are diagrams showing modified examples of the impact absorbing member, respectively, and are cross-sectional views taken along the line BB in FIG. 2. [Figure 6] 5(a) to (e) are diagrams showing other modified examples of the impact absorbing member, respectively, and are cross-sectional views taken along the line BB in FIG. [Figure 7] 5(a) to (d) are diagrams showing still other modified examples of the impact absorbing member, respectively, and are cross-sectional views taken along the line BB in FIG. [Figure 8] 5(a) to (c) are diagrams showing still other modified examples of the impact absorbing member, respectively, and are cross-sectional views taken along the line BB in FIG. [Figure 9] 5(a) to (e) are diagrams showing still other modified examples of the impact absorbing member, respectively, and are cross-sectional views taken along the line BB in FIG. [Figure 10] 5(a) to (g) are diagrams showing still other modified examples of the impact absorbing member, respectively, and are cross-sectional views taken along the line BB in FIG. [Figure 11] 5(a) to (e) are diagrams showing still other modified examples of the impact absorbing member, respectively, and are cross-sectional views taken along the line BB in FIG. [Figure 12] FIG. 11 is a perspective view of a shock absorbing member according to a second embodiment of the present invention. [Figure 13] FIG. 11 is a perspective view of a shock absorbing member according to a third embodiment of the present invention. [Figure 14] FIG. 1 is a diagram showing a first embodiment of the present invention, and is a perspective view showing a shock absorbing member when no reinforcement is provided. [Figure 15] FIG. 15 is a diagram showing the state after bending deformation and the absorbed energy (kJ) at a stroke of 180 mm when the bead depth is changed in the impact absorbing member shown in FIG. 14. [Figure 16] FIG. 2 is a perspective view showing the impact absorbing member having a reinforcement, used in the first embodiment. [Figure 17]FIG. 17 is a diagram showing the state after bending deformation and the absorbed energy (kJ) at a stroke of 180 mm when the bead depth is changed in the impact absorbing member shown in FIG. 16. [Figure 18] FIG. 11 is a diagram showing a second embodiment of the present invention, and is a table showing the state of each impact absorbing member before bending deformation in the presence or absence of reinforcement, the arrangement of through holes, and when a bead is provided on the top wall portion. [Figure 19] 20 is a table showing the state of each impact absorbing member shown in FIG. 18 after bending deformation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, shock absorbing members according to embodiments of the present invention and various modified examples thereof will be described with reference to the drawings. As shown in Fig. 1, the impact absorbing member of each embodiment and each modified example can be used as a front side member FM or a rear side member RM, which are frame members of an automobile. When the impact absorbing member is used as a front side member FM, it is disposed on the vehicle front FW side relative to the passenger compartment C. On the other hand, when the impact absorbing member is used as a rear side member RM, it is disposed on the vehicle rear RW side relative to the passenger compartment C. The impact absorbing member is a hollow tube that is long in one direction, and in either case of being used as a front side member FM or a rear side member RM, it is disposed so that one end side in the longitudinal direction faces the vehicle front and the other end side in the longitudinal direction faces the vehicle rear.

[0024] Although details will be described later, the impact absorbing member has a rectangular cross section perpendicular to its longitudinal direction, and includes a hat-shaped member and a plate-shaped member. The hat-shaped member has a cross section perpendicular to the longitudinal direction that is a hat top that is a top wall portion, and a pair of side walls that are connected to both sides of the hat top. The plate-shaped member is joined to the hat-shaped member and faces the hat top. The shock absorbing member absorbs impact force by bending deformation rather than bellows deformation. Hereinafter, the area that undergoes bending deformation shown in Fig. 1 will be denoted by reference numeral 1, and will be described as shock absorbing member 1. In addition, a case where the trigger for bending deformation (the bending starting point) is set in the top wall will be described as an example.

[0025] [First embodiment] 2, the impact absorbing member 1 according to the first embodiment of the present invention is a cylindrical part that is long in the longitudinal direction along its center line CL. The impact absorbing member 1 has a rectangular cross section perpendicular to the center line CL, and includes a hat-shaped member 10, a plate-shaped member 20, and a reinforcement 40.

[0026] The hat-shaped component 10 has one top wall portion 11 , a pair of side wall portions 12 , and a pair of flange portions 13 . The top wall 11 forms the hat top of the hat-shaped member 10, which has a hat shape when viewed along the center line CL. The top wall 11 is a long plate that is long in a direction parallel to the center line CL, and the outer width dimension and plate thickness are constant at each position in the extending direction. The outer width dimension referred to here includes the ridge portions EL formed along both side edges of the top wall 11. The top wall 11 has a flat upper surface and a flat lower surface. The outer width dimension and thickness of the top wall 11 do not necessarily have to be constant at each position along the center line CL, and may be slightly changed so as to be different at each position along the center line CL according to the needs of the part design. Similarly, the upper and lower surfaces of the top wall 11 do not necessarily have to be flat, and may have some unevenness according to the needs of the part design.

[0027] The pair of side walls 12 include a left side wall 12a and a right side wall 12b. The left side wall 12a is a vertical wall integrally connected to one of both side edges of the top wall 11. In a cross section perpendicular to the center line CL, the angle between the left side wall 12a and the top wall 11 may be 90° or slightly larger than 90°. The left side wall 12a has a substantially constant width and a substantially constant thickness. The left side wall 12a has a flat outer surface and a flat inner surface. The right side wall portion 12b is a vertical wall integrally connected to the other of both side edges of the top wall portion 11. In a cross section perpendicular to the center line CL, the angle between the right side wall portion 12b and the top wall portion 11 may be 90° or an angle slightly larger than 90°. The right side wall portion 12b has a substantially constant width dimension and a substantially constant plate thickness. The right side wall portion 12b has a flat outer surface and a flat inner surface.

[0028] The left side wall portion 12a and the right side wall portion 12b are each a long plate that is long in a direction parallel to the center line CL when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1, and the outer height dimension and plate thickness at each position in the extension direction are constant. The outer height dimension referred to here also includes the portion of the ridge line portion EL formed along each upper edge of the left side wall portion 12a and the right side wall portion 12b. The left side wall portion 12a and the right side wall portion 12b have a flat outer side surface and a flat inner side surface. The outer width dimensions and thicknesses of the left side wall portion 12a and the right side wall portion 12b do not necessarily have to be constant at each position along the center line CL, and may be slightly changed so as to be different at each position along the center line CL as required for part design. Similarly, the outer and inner surfaces of the left side wall portion 12a and the right side wall portion 12b do not necessarily have to be flat, and may have some unevenness as required for part design.

[0029] The pair of flange portions 13 includes a left flange portion 13a and a right flange portion 13b. The left flange portion 13a is integrally connected to the lower edge of the left side wall portion 12a. The left flange portion 13a is a band-shaped plate having a substantially constant width and thickness, and is elongated in the direction along the center line CL. The left flange portion 13a has a flat upper surface and a flat lower surface. The right flange portion 13b is integrally connected to the lower edge of the right side wall portion 12b. The right flange portion 13b is a band-shaped plate having a substantially constant width and thickness, and is elongated in the direction along the center line CL. The right flange portion 13b has a flat upper surface and a flat lower surface. The width and thickness of the left and right flange portions 13a, 13b do not necessarily have to be constant at each position along the center line CL, and may be changed at each position along the center line CL as required for part design. Similarly, the upper and lower surfaces of the left and right flange portions 13a, 13b do not necessarily have to be flat, and may have some irregularities depending on the shape of the plate-like member 20.

[0030] The combination of the top wall portion 11, the left side wall portion 12a, and the right side wall portion 12b forms a generally trapezoidal shape in a cross section perpendicular to the center line CL. Furthermore, by combining this combination with the left flange portion 13a and the right flange portion 13b, a hat-shaped member 10 is formed, the cross section perpendicular to the longitudinal direction of which is hat-shaped. This hat-shaped member 10 is obtained by pressing a die-cut plate material. The material of the hat-shaped member 10 is a metal, and a high-strength steel plate with a tensile strength of 650 MPa or more and 1600 MPa or less can be suitably used.

[0031] 2, a ridge line EL parallel to the center line CL is formed between the top wall 11 and the left side wall 12a. A ridge line EL parallel to the center line CL is also formed between the top wall 11 and the right side wall 12b. The pair of ridge lines EL are parallel to each other and also to the center line CL.

[0032] As shown in Fig. 3, each ridge EL has a substantially constant width, and a cross section perpendicular to the longitudinal direction thereof is curved in an arc shape over the entire width. Each ridge EL has one side edge ELa that is continuous with the top wall 11, and the other side edge ELb that is continuous with the left side wall 12a or the right side wall 12b. While each ridge EL has an arc-shaped cross section, the top wall 11, the left side wall 12a, and the right side wall 12b each have a flat cross section. Therefore, when viewed from each ridge EL, the one side edge ELa and the other side edge ELb are boundaries (only a radius) where the cross section changes from an arc cross section to a flat cross section.

[0033] 2 and 3, a second bead Bb is formed at one location on the ridgeline EL connecting the top wall 11 and the right side wall 12b. The second bead Bb crosses the one side edge ELa, which is the boundary between the top wall 11 and the ridgeline EL. That is, the second bead Bb is formed so as to protrude from the ridgeline EL toward the top wall 11. Furthermore, the second bead Bb is formed so as to protrude from the ridgeline EL toward the right side wall 12b. Therefore, the second bead Bb is formed so as to extend from the top wall 11 to the right side wall 12b via the ridgeline EL.

[0034] Similarly, a first bead Ba is formed at one location on the ridge EL connecting the top wall 11 and the left side wall 12a. The first bead Ba crosses the one side edge ELa, which is the boundary between the top wall 11 and the ridge EL. That is, the first bead Ba is formed so as to protrude from the ridge EL toward the top wall 11. Furthermore, the first bead Ba is formed so as to protrude from the ridge EL toward the left side wall 12a. Therefore, the first bead Ba is formed so as to extend from the top wall 11 to the left side wall 12a via the ridge EL.

[0035] The first bead Ba and the second bead Bb are each rhombic in front view, and the size of the diagonal length can be 11 mm to 23 mm. The depth of the outer surface of the first bead Ba and the second bead Bb can be 7 mm to 15 mm. The first bead Ba and the second bead Bb may be formed simultaneously with the press working when forming the hat-shaped member 10 from a metal plate, or may be formed by post-processing on the hat-shaped member 10 after press forming. When the first bead Ba and the second bead Bb are formed by press working, their plate thickness is slightly thinner than the surrounding plate thickness, and they are work-hardened. The first bead Ba and the second bead Bb have a concave outer surface and an indented inner surface toward the inside of the cylindrical body 30. The shape of the first bead Ba and the second bead Bb when viewed from the front is not limited to a diamond shape, but may be a circle, an ellipse, a rectangle or a polygon. It is preferable that the shape and dimensions of the first bead Ba and the second bead Bb are the same, but they may be slightly different as long as their function is not impaired. The first bead Ba and the second bead Bb are formed at approximately the same position in the longitudinal direction of the hat-shaped member 10. The pair of first bead Ba and second bead Bb form a folding start portion in the top wall portion 11.

[0036] The plate-shaped member 20 is a long metal plate along the center line CL, and a high-strength steel plate having a tensile strength of 650 MPa or more and 1600 MPa or less can be suitably used. The plate-shaped member 20 has a flat upper surface and a flat lower surface. The plate-shaped member 20 is welded to the left flange portion 13a and the right flange portion 13b at both side edges thereof. This forms a closed cross section between the hat-shaped member 10 and the plate-shaped member 20. In this manner, the hat-shaped member 10 and the plate-shaped member 20 form a cylindrical body 30. The width and thickness of the plate-like member 20 do not necessarily have to be constant at each position on the center line CL, and may vary slightly at each position along the center line CL as required for part design. Similarly, the upper and lower surfaces of the plate-like member 20 do not necessarily have to be flat, and may have some irregularities as required for part design.

[0037] In the cylindrical body 30 having the above configuration, the pair of first beads Ba and second beads Bb are formed at one location in the middle of the longitudinal direction, so that the bending strength at this location is relatively lower than the bending strength of the adjacent locations in the longitudinal direction. That is, as shown in Fig. 2, if the portion where the pair of first beads Ba and second beads Bb are formed is the second portion R2 and the adjacent portions are the first portion R1 and the third portion R3, a folding start portion is formed in the top wall portion 11 of the second portion R2. Then, when a load is applied to the impact absorbing member 1 along its axial direction, the impact absorbing member 1 can be folded and deformed smoothly at the folding start portion of the second portion R2.

[0038] Next, the reinforcement 40 will be described. As shown in FIG. 2, the reinforcement 40 has a vertical plate 41 and a horizontal plate 42. The vertical plate 41 is a strip-shaped plate having a substantially constant width and thickness, and is long in the direction along the center line CL. The vertical plate 41 has a flat left side and a flat right side. Although the vertical plate 41 is a strip-shaped plate, it is apparently divided into two by a horizontal plate 42 that intersects at the center position in the height direction when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1. The upper and lower parts of the vertical plate 41 divided into two have the same height, thickness, and length. The horizontal plate 42 is a strip-shaped plate having a substantially constant width and thickness, and is long in the direction along the center line CL. The horizontal plate 42 has a flat upper surface and a flat lower surface. Although the horizontal plate 42 is a strip-shaped plate, when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1, it is apparently divided into two by a vertical plate 41 that intersects at the center position in the width direction. The left and right portions of the two-part horizontal plate 42 have the same width, thickness, and length.

[0039] The reinforcement 40 has a "+" shape when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1. The center line CL of the impact absorbing member 1 passes through the intersection between the vertical plate 41 and the horizontal plate 42. The vertical plate 41 and the horizontal plate 42 can be joined by, for example, welding. When viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1, the vertical plate 41 has an upper end (one end) joined to the widthwise center of the lower surface of the top wall portion 11, and a lower end joined to the widthwise center of the upper surface of the plate-like member 20. In this manner, the top wall portion 11 is supported mainly by the vertical plate 41 and the plate-like member 20. The horizontal plate 42 has its left end (one end) joined to the center in the height direction of the inner surface of the left side wall portion 12a and its right end (the other end) joined to the center in the height direction of the inner surface of the right side wall portion 12b when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1. In this way, the left side wall portion 12a and the right side wall portion 12b are constrained so that the distance between them is kept constant.

[0040] A high-strength steel plate having a tensile strength of 650 MPa or more and 1600 MPa or less can be suitably used as the reinforcement 40. That is, the reinforcement 40 can be manufactured by intersecting a vertical plate 41 and a horizontal plate 42 made of the high-strength steel plate with each other and then welding them together. Furthermore, the impact absorbing member 1 can be manufactured by welding the reinforcement 40 into the cylindrical body 30. The arrangement of the reinforcement 40 inside the cylindrical body 30 at this time is as described above with reference to FIG. 2.

[0041] The impact absorbing member 1 having the reinforcement 40 and tubular body 30 described above satisfies both of the following conditions in order to prevent unintended out-of-plane deformation of the tubular body 30: (1) a first condition that the impact absorbing member 1 has a vertical plate 41 and the first planar portion width-thickness ratio r1 according to the following formula 1 is 10 or more and 50 or less; and (2) a second condition that the impact absorbing member 1 has a horizontal plate 42 and the second planar portion width-thickness ratio r2 according to the following formula 2 is 10 or more and 50 or less.

[0042] r1=((W1-t2) / (n1+1)) / t1...(Formula 1) r2=((W2-t3) / (n2+1)) / t1...(Formula 2)

[0043] These formulas 1 and 2 will be explained below with reference to FIG. 4, but before that, FIG. 4 will be explained first. Fig. 4 is a schematic diagram for explaining the dimensions of each part of the impact absorbing member 1, and corresponds to the cross-sectional view taken along line BB of the third region R3 in Fig. 2. Therefore, the first bead Ba and the second bead Bb are not shown in Fig. 4. Note that in Fig. 4, the following illustrations are used to make the following explanation easier to understand. First, the curvature of the arcuate cross section of each ridge line EL is exaggerated. Each ridge line EL is a corner that connects the top wall 11 to the left side wall 12a and the right side wall 12b, and has a predetermined radius of curvature. 4, the pair of left and right wall portions 12a, 12b are parallel to each other. The plate-like member 20 and the left and right flange portions 13a, 13b are integrated without any joints between them. The position of the vertical plate 41 in the left-right direction is slightly offset from the position of the center line CL. Similarly, the position of the horizontal plate 42 in the up-down direction is slightly offset from the position of the center line CL. The plate thickness of the vertical plate 41 and the plate thickness of the horizontal plate 42 are made different from each other.

[0044] Equations 1 and 2 will be explained with reference to FIG. First, the symbol W1 in Equation 1 is the overall flat width dimension (unit: mm) of the flat top wall 11 having an upper surface that is the inside of the bend in the rectangular cylindrical body 30. This overall flat width dimension W1 does not include the curved portion (rounded portion) including the ridge line portion EL. For example, if the width of the flat portion of the top wall 11 is w1 (mm) and w2 (mm) with respect to the joint position with the upper edge of the vertical plate 41 as the boundary, W1 = w1 + w2 + t2. Here, the thickness of the top wall 11 within the range of the overall flat width dimension W1 is t1 (mm), and the total plate thickness of the vertical plate 41 is t2 (mm).

[0045] W2 is the overall flat width dimension (unit: mm) of each of the flat left side wall portion 12a and the flat right side wall portion 12b that are connected to both sides of the top wall portion 11 via a pair of bends. This flat width dimension W2 does not include the bend (rounded portion) including the ridge line portion EL and the bend (rounded portion) formed between the left flange portion 13a and the right flange portion 13b (not shown). For example, when the flat widths of each side wall portion 12 are w3 (mm) and w4 (mm) with respect to the joint position with the horizontal plate 42 as the boundary, W2 = w3 + w4 + t3. The thickness of each of the left side wall portion 12a and the right side wall portion 12b within the range of this flat width dimension W2 is t1 (mm), which is the same as the top wall portion 11. The total plate thickness of the horizontal plate 42 is t3 (mm).

[0046] In the case of the impact absorbing member 1 of this embodiment, the symbol t2 in formula 1 is the plate thickness (total plate thickness, in mm) of the vertical plate 41 whose upper end (one end) is joined to the top wall portion 11 and whose total number is one (n1=1). The symbol t3 in formula 2 is the plate thickness (total plate thickness, in mm) of the horizontal plate 42 which connects the left side wall portion 12a and the right side wall portion 12b and whose total number is one (n2=1). As shown in FIG. 4, the total plate thickness t2 may be thicker than the total plate thickness t3, or conversely, the total plate thickness t3 may be thicker than the total plate thickness t2, or the total plate thickness t2 and the total plate thickness t3 may be equal.

[0047] The symbol n1 in the formula 1 is the total number of the vertical plates 41 in the reinforcement 40, which is one (n1=1) in the impact absorbing member 1 of this embodiment. If a configuration is provided with multiple vertical plates 41 and the plate thicknesses of the vertical plates 41 differ from one another, n1 will be the total number thereof, and the total plate thickness t2 will be the sum of the plate thicknesses of all the vertical plates 41. The symbol n2 in the formula 2 is the total number of the horizontal plates 42 in the reinforcement 40, which is 1 (n2=1) in the impact absorbing member 1 of this embodiment. If a configuration is provided with multiple horizontal plates 42 and the plate thicknesses of the horizontal plates 42 differ from one another, n2 will be the total number of the horizontal plates 42, and the total plate thickness t3 will be the total value of the plate thicknesses of all the horizontal plates 42. Therefore, the first flat portion width-thickness ratio r1 means the average flat portion width of the range of the flat portion overall width dimension W1 of the top wall portion 11 that is not supported by the vertical plates 41 divided by the plate thickness t1 of the top wall portion 11. Also, the second flat portion width-thickness ratio r2 means the average flat portion width of the range of the flat portion overall width dimension W2 of the side wall portion 12 that is not supported by the horizontal plates 42 divided by the plate thickness t1 of the side wall portion 12.

[0048] By providing the reinforcement 40 and satisfying the first condition that the first flat portion width-thickness ratio r1 obtained by Equation 1 is 10 or more and 50 or less, it is possible to prevent out-of-plane deformation at unintended locations in the top wall portion 11. Similarly, by satisfying the second condition that the second flat portion width-thickness ratio r2 obtained by Equation 2 is 10 or more and 50 or less, it is possible to prevent out-of-plane deformation at unintended locations in each side wall portion 12. It is possible to satisfy either one of the first condition and the second condition, or to satisfy both.

[0049] Here, the out-of-plane deformation will be described. Under the above-mentioned cross-sectional structure, a method for reducing the weight of the impact absorbing member 1 is to reduce the plate thickness t1 of the cylindrical body 30. In this case, in the case of a conventional structure without the reinforcement 40, the wide flat portion indicated by the flat portion overall width dimension W1 and the wide flat portion indicated by the flat portion overall width dimension W2 are not supported, so that out-of-plane deformation is likely to occur. The out-of-plane deformation here refers to a deformation in which the wall portion is undulating toward the inside and outside of the cylindrical body 30 in the cross section of FIG. 4. If the plate thickness t1 is made thin, it becomes unclear at which part of the cylindrical body 30 this out-of-plane deformation occurs. It is desirable for the impact absorbing member 1 to absorb impact energy by bending in a predetermined bending direction with a predetermined position as the bending start point. However, when out-of-plane deformation occurs in the cylindrical body 30, that part may be easily broken or, conversely, may be difficult to break. As a result, there is a risk that the desired energy absorption amount cannot be obtained because the bending deformation cannot be performed as previously set.

[0050] In contrast, in the cross section shown in FIG. 4, the inside of the cylindrical body 30, which has a single large opening cross section in the conventional configuration, is divided into multiple (four) small opening cross sections by combining the vertical plate 41 and the horizontal plate 42. Of course, it can be said that the occurrence of out-of-plane deformation of the top wall portion 11 can be suppressed more than in the conventional structure just by supporting the top wall portion 11 with the vertical plate 41. However, the impact absorbing member 1 of the present embodiment does not only that, but also divides the opening cross section into small sections by combining the vertical plate 41 and the horizontal plate 42, and further specifies the range of the first flat portion width-thickness ratio r1 according to the above formula 1 and the range of the second flat portion width-thickness ratio r2 according to the above formula 2 for each of the range of the top wall portion 11 that is not supported by the vertical plate 41 and the range of the left side wall portion 12a and the right side wall portion 12b that is not supported by the horizontal plate 42. This makes it possible to reduce the plate thickness t1 while suppressing out-of-plane deformation. Therefore, the shock absorbing member 1 can be folded and deformed at desired positions to obtain high energy absorption efficiency, while also being lightweight.

[0051] This point will be described below based on the bending deformation that occurs when an impact force is applied to the impact absorbing member 1 along its longitudinal direction. When the folding start point is set on the top wall portion 11 of the cylindrical body 30, the top wall portion 11 at the beginning of folding deformation tends to sink toward the inside of the cylindrical body 30. The vertical plate 41 continues to support the top wall portion 11 while resisting the force that tends to sink. This prevents the top wall portion 11 from sinking. In addition, the gap between the left side wall portion 12a and the right side wall portion 12b is constrained by the horizontal plate 42. This constraint prevents the top wall portion 11 from sinking so as to expand the gap between the left side wall portion 12a and the right side wall portion 12b, and indirectly supports the top wall portion 11. In this way, the cylindrical body 30 is firmly supported from the inside by the reinforcement 40 due to the synergistic effect of the support of the top wall portion 11 by the vertical plate 41 and the constraint between the left side wall portion 12a and the right side wall portion 12b by the horizontal plate 42.

[0052] In this way, the cylindrical body 30 is reinforced at each position in the longitudinal direction by the reinforcement 40. In addition, the cylindrical body 30 satisfies both the first condition that the first flat portion width-thickness ratio r1 is 10 or more and 50 or less, and the second condition that the second flat portion width-thickness ratio r2 is 10 or more and 50 or less. Here, if the first flat portion width-thickness ratio r1 or the second flat portion width-thickness ratio r2 is less than 10, the plate thickness is thick and it is difficult to obtain the weight reduction effect by the reinforcement 40. On the other hand, if the first flat portion width-thickness ratio r1 or the second flat portion width-thickness ratio r2 is more than 50, the plate thickness becomes too thin and it is difficult to obtain the effect of preventing out-of-plane deformation by the reinforcement 40.

[0053] As described above, if out-of-plane deformation occurs at an unintended position, the manner in which compressive deformation occurs at that portion becomes unstable, and the out-of-plane deformed portion may be easily or not easily broken. As a result, there is a risk of bending deformation occurring at an unintended portion of the cylindrical body 30. On the other hand, the shock absorbing member 1 satisfies both the first and second conditions, and therefore, out-of-plane deformation at an unintended portion of the cylindrical body 30 can be suppressed, and therefore the plate thickness t1 can be made thinner to reduce the weight.

[0054] 2 and 3, the shock absorbing member 1 has a bending strength of the second portion R2 that is relatively lower than the bending strength of the first portion R1 and the bending strength of the third portion R3. This allows the shock absorbing member 1 to bend and deform smoothly with the second portion R2 as the bending starting point. In addition, the impact energy applied to the shock absorbing member 1 is absorbed mainly by the reinforcement 40 while being bent and deformed with the second portion R2 as the starting point, so that the amount of energy absorption can be increased.

[0055] In the above embodiment, the reinforcement 40 having a "+" shape is fixedly disposed inside the cylindrical body 30, but other than that, various forms illustrated in Fig. 5 to Fig. 11 can also be adopted. Fig. 5 to Fig. 11 correspond to the cross-sectional view taken along line BB in Fig. 2.

[0056] In Fig. 5(a), the internal space of the cylindrical body 30 is vertically divided into two by a horizontal plate 42. That is, the vertical plate 41 is omitted, and the horizontal plate 42 restricts the distance between the left side wall portion 12a and the right side wall portion 12b. A flange is formed on one of both side edges of the horizontal plate 42, and this flange is fixed by spot welding in a state of surface contact with the left side wall portion 12a. Similarly, a flange is formed on the other of both side edges of the horizontal plate 42, and this flange is fixed by spot welding in a state of surface contact with the right side wall portion 12b. 5(b), the internal space of the cylindrical body 30 is also vertically divided into two by a horizontal plate 42. That is, the vertical plate 41 is omitted, and the horizontal plate 42 restricts the distance between the left side wall portion 12a and the right side wall portion 12b. One of both side edges of the horizontal plate 42 is fixed by laser arc welding in a state where it abuts against the left side wall portion 12a. Similarly, the other of both side edges of the horizontal plate 42 is fixed by laser arc welding in a state where it abuts against the right side wall portion 12b.

[0057] 5(c), the internal space of the cylindrical body 30 is divided into two in the left-right direction by a vertical plate 41. That is, the horizontal plate 42 is omitted, and the top wall portion 11 is supported by the vertical plate 41. A flange is formed at the upper end of the vertical plate 41, and this flange is fixed to the top wall portion 11 by spot welding while being in surface contact with the top wall portion 11. Similarly, a flange is formed at the lower end of the vertical plate 41, and this flange is fixed to the plate-like member 20 by laser arc welding while being in surface contact with the plate-like member 20. 5(d), the internal space of the cylindrical body 30 is also divided into two in the left-right direction by a vertical plate 41. That is, the horizontal plate 42 is omitted, and the top wall portion 11 is supported by the vertical plate 41. The upper end of the vertical plate 41 is fixed by laser arc welding in a state where it abuts against the top wall portion 11. Similarly, the lower end of the vertical plate 41 is also fixed by laser arc welding in a state where it abuts against the plate-like member 20.

[0058] In Fig. 6(a), the internal space of the cylindrical body 30 is vertically divided into three by two horizontal plates 42. That is, the vertical plate 41 is omitted, and the distance between the left side wall portion 12a and the right side wall portion 12b is restricted by the two horizontal plates 42. Flanges are formed on one of both side edges of each horizontal plate 42, and these flanges are fixed to the left side wall portion 12a by spot welding in a state of surface contact with the left side wall portion 12a. Similarly, flanges are formed on the other of both side edges of each horizontal plate 42, and these flanges are fixed to the right side wall portion 12b by spot welding in a state of surface contact with the right side wall portion 12b. 6(b), the internal space of the cylindrical body 30 is also vertically divided into thirds by two horizontal plates 42. That is, the vertical plate 41 is omitted, and the distance between the left side wall portion 12a and the right side wall portion 12b is restricted by two horizontal plates 42. One of both side edges of each horizontal plate 42 is fixed by laser arc welding in a state where it abuts against the left side wall portion 12a. Similarly, the other of both side edges of each horizontal plate 42 is fixed by laser arc welding in a state where it abuts against the right side wall portion 12b.

[0059] In FIG. 6(c), the internal space of the cylindrical body 30 is divided into three parts in the left-right direction by two vertical plates 41. That is, the horizontal plate 42 is omitted, and the top wall portion 11 is supported by the two vertical plates 41. The upper ends of the vertical plates 41 are connected, and the connected parts are fixed to the top wall portion 11 by spot welding in a surface-joined state. Meanwhile, flanges are formed at the lower ends of the vertical plates 41, and these flanges are fixed to the plate-like member 20 by laser arc welding in a surface-contact state. In this example, the two vertical plates 41 are formed by press-forming one steel plate into an inverted U-shaped cross section, but two separate vertical plates 41 may be used. In Fig. 6(d), the internal space of the cylindrical body 30 is also divided into three parts in the left-right direction by two vertical plates 41. That is, the horizontal plate 42 is omitted, and the top wall portion 11 is supported by the two vertical plates 41. Flanges are formed at the upper end of each vertical plate 41, and these flanges are fixed to the top wall portion 11 by spot welding in a surface-jointed state. Meanwhile, the lower ends of each vertical plate 41 are connected, and this connected portion is fixed to the plate-like member 20 by spot welding in a surface-jointed state. Note that in this example, the two vertical plates 41 are formed by press-forming one steel plate into a U-shaped cross section, but two separate vertical plates 41 may be used.

[0060] In FIG. 6(e), the internal space of the cylindrical body 30 is divided into three parts in the left-right direction by two vertical plates 41. That is, the horizontal plate 42 is omitted, and the top wall portion 11 is supported by the two vertical plates 41. The upper ends of the vertical plates 41 are connected, and the connected parts are fixed to the top wall portion 11 by spot welding in a surface-joined state. Meanwhile, a wide flange is formed at the lower end of each vertical plate 41. One of these flanges is fixed to the left flange portion 13a by spot welding, and the other is fixed to the right flange portion 13b by spot welding. Between the lower ends of the two vertical plates 41, the space formed between them is sealed by a narrow plate-like member 20. That is, the plate-like member 20 is fixed to each flange connected to the lower ends of the two vertical plates 41 by spot welding.

[0061] 7(a), the internal space of the cylindrical body 30 is divided into three by a combination of one vertical plate 41 and one horizontal plate 42. That is, one of the two side edges of the horizontal plate 42 is fixed by laser arc welding in a state where it abuts against the left side wall portion 12a. Similarly, the other of the two side edges of the horizontal plate 42 is fixed by laser arc welding in a state where it abuts against the right side wall portion 12b. 2, and its lower end is fixed by laser arc welding in a state where it abuts against the widthwise center position of the horizontal plate 42. In this way, the internal space of the cylindrical body 30 is divided into three parts: two spaces defined by the top wall 11, the left and right side walls 12a and 12b, the vertical plate 41, and the horizontal plate 42, and one space defined by the horizontal plate 42, the left and right side walls 12a and 12b, and the plate-like member 20.

[0062] 7(b), the internal space of the cylindrical body 30 is divided into three by a combination of one vertical plate 41 and one horizontal plate 42. That is, a flange is formed on one of both side edges of the horizontal plate 42, and this flange is fixed by spot welding in a state of surface contact with the left side wall portion 12a. Similarly, a flange is formed on the other of both side edges of the horizontal plate 42, and this flange is fixed by spot welding in a state of surface contact with the right side wall portion 12b. 2, and a flange is formed at its lower end, and this flange is fixed by spot welding in a state of surface contact with the horizontal plate 42 at the center position in the width direction. In this way, the internal space of the cylindrical body 30 is divided into three parts: two spaces defined by the top wall 11, the left and right side walls 12a and 12b, the vertical plate 41, and the horizontal plate 42, and one space defined by the horizontal plate 42, the left and right side walls 12a and 12b, and the plate-like member 20.

[0063] 7(c), the internal space of the cylindrical body 30 is divided into three by a combination of one vertical plate 41 and one horizontal plate 42. That is, one of the two side edges of the horizontal plate 42 is fixed by laser arc welding in a state where it abuts against the left side wall portion 12a. Similarly, the other of the two side edges of the horizontal plate 42 is fixed by laser arc welding in a state where it abuts against the right side wall portion 12b. 2, and its lower end is fixed by laser arc welding in a state where it abuts against the center position in the width direction of the plate-like member 20. In this way, the internal space of the cylindrical body 30 is divided into three spaces: one space partitioned by the top wall 11, the left and right side walls 12a and 12b, and the horizontal plate 42, and two spaces partitioned by the horizontal plate 42, the left and right side walls 12a and 12b, the vertical plate 41, and the plate-like member 20.

[0064] 7(d), the internal space of the cylindrical body 30 is divided into three by a combination of one vertical plate 41 and one horizontal plate 42. That is, a flange is formed on one of both side edges of the horizontal plate 42, and this flange is fixed by spot welding in a state of surface contact with the left side wall portion 12a. Similarly, a flange is formed on the other of both side edges of the horizontal plate 42, and this flange is fixed by spot welding in a state of surface contact with the right side wall portion 12b. 2, and a flange is formed at its lower end, and this flange is fixed by laser arc welding in a state where it is in surface contact with the center position in the width direction of the plate-like member 20. In this way, the internal space of the cylindrical body 30 is divided into three spaces: one space defined by the top wall 11, the left and right side walls 12a and 12b, and the horizontal plate 42, and two spaces defined by the horizontal plate 42, the left and right side walls 12a and 12b, the vertical plate 41, and the plate-like member 20.

[0065] 8(a), the internal space of the cylindrical body 30 is divided into four parts by a combination of two vertical plates 41 and one horizontal plate 42. In this example, the vertical plates 41 and parts of the horizontal plates 42 are integrally formed by pressing a single steel plate. A flange is formed on one of the two side edges of the horizontal plate 42, and this flange is fixed by spot welding in surface contact with the left side wall portion 12a. Similarly, a flange is formed on the other of the two side edges of the horizontal plate 42, and this flange is fixed by spot welding in surface contact with the right side wall portion 12b. The horizontal plate 42 includes a left portion joined to the left side wall portion 12a, a right portion joined to the right side wall portion 12b, and a central portion connecting the left and right portions that are arranged apart from each other. This central portion is a separate part and is fixed to the left and right portions by spot welding. The portion connecting the upper ends of the two vertical plates 41 is a flange that is surface-joined at the center position in the width direction of the top wall portion 11. This flange is joined to the top wall portion 11 by spot welding. The lower ends of the two vertical plates 41 are integral with the horizontal plate 42. In this way, the internal space of the cylindrical body 30 is divided into four spaces into three spaces partitioned by the top wall portion 11, the left side wall portion 12a and the right side wall portion 12b, two vertical plates 41, and the horizontal plate 42, and one space partitioned by the horizontal plate 42, the left side wall portion 12a and the right side wall portion 12b, and the plate-like member 20.

[0066] 8(b), the internal space of the cylindrical body 30 is also divided into four parts by combining two vertical plates 41 and one horizontal plate 42. In this example, the vertical plates 41 and parts of the horizontal plates 42 are also integrally formed by pressing a single steel plate. A flange is formed on one of the two side edges of the horizontal plate 42, and this flange is fixed by spot welding in surface contact with the left side wall portion 12a. Similarly, a flange is formed on the other of the two side edges of the horizontal plate 42, and this flange is fixed by spot welding in surface contact with the right side wall portion 12b. The horizontal plate 42 includes a left portion joined to the left side wall portion 12a, a right portion joined to the right side wall portion 12b, and a central portion connecting the left and right portions that are arranged apart from each other. This central portion is a separate part and is fixed to the left and right portions by spot welding. The portion connecting the lower ends of the two vertical plates 41 is a flange that is surface-joined at the center position in the width direction of the plate-shaped member 20. This flange is joined to the plate-shaped member 20 by spot welding. The upper ends of the two vertical plates 41 are integral with the horizontal plate 42. In this way, the internal space of the cylindrical body 30 is divided into four spaces: one space partitioned by the top wall portion 11, the left side wall portion 12a and the right side wall portion 12b, and the horizontal plate 42, and three spaces partitioned by the horizontal plate 42, the left side wall portion 12a and the right side wall portion 12b, the two vertical plates 41, and the plate-like member 20.

[0067] In Fig. 8(c), the internal space of the cylindrical body 30 is divided into four parts by a combination of two vertical plates 41 and one horizontal plate 42. In this example, when forming the hat-shaped member 10, the central portion of the top wall portion 11 in the width direction is press-molded so as to be recessed toward the inside of the cylindrical body 30. Two vertical plates 41 are formed in this recessed portion. The top wall portion 11 also includes a left portion and a right portion spaced apart from each other by the recessed portion, and a central portion connecting the left portion and the right portion. This central portion is a separate part and is fixed to each of the left portion and the right portion by spot welding. A flange is formed on one of the two side edges of the horizontal plate 42, and this flange is fixed by spot welding in surface contact with the left side wall portion 12a. Similarly, a flange is formed on the other of the two side edges of the horizontal plate 42, and this flange is fixed by spot welding in surface contact with the right side wall portion 12b. The lower ends of each vertical plate 41, i.e., the recessed portions, are fixed by spot welding in surface contact with the center position of the horizontal plate 42 in the width direction. In this way, the internal space of the cylindrical body 30 is divided into four spaces into three spaces partitioned by the top wall portion 11, the left side wall portion 12a and the right side wall portion 12b, two vertical plates 41, and the horizontal plate 42, and one space partitioned by the horizontal plate 42, the left side wall portion 12a and the right side wall portion 12b, and the plate-like member 20.

[0068] 9(a), the internal space of the cylindrical body 30 is divided into four parts by a combination of one vertical plate 41 and one horizontal plate 42. That is, one of the two side edges of the horizontal plate 42 is fixed by laser arc welding in a state where it abuts against the left side wall portion 12a. Similarly, the other of the two side edges of the horizontal plate 42 is fixed by laser arc welding in a state where it abuts against the right side wall portion 12b. The upper end of the vertical plate 41 is fixed by laser arc welding in abutment against the top wall portion 11. Similarly, the lower end of the vertical plate 41 is fixed by laser arc welding in abutment against the plate-like member 20. The vertical plate 41 is joined by laser arc welding at a center position in the height direction to a center position in the width direction of the horizontal plate 42 in a state intersecting (orthogonal) thereto. In this manner, the internal space of the cylindrical body 30 is divided into four spaces by the top wall portion 11, the left side wall portion 12a, the right side wall portion 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20.

[0069] 9(b), the internal space of the cylindrical body 30 is also divided into four parts by combining one vertical plate 41 and one horizontal plate 42. That is, a flange is formed on one of both side edges of the horizontal plate 42, and this flange is fixed by spot welding in a state of surface contact with the left side wall portion 12a. Similarly, a flange is formed on the other of both side edges of the horizontal plate 42, and this flange is fixed by spot welding in a state of surface contact with the right side wall portion 12b. A flange is formed at the upper end of the vertical plate 41, and this flange is fixed by laser arc welding in a state of surface contact with the top wall portion 11. Similarly, a flange is formed at the lower end of the vertical plate 41, and this flange is fixed by laser arc welding in a state of surface contact with the plate-like member 20. In this manner, the internal space of the cylindrical body 30 is divided into four spaces by the top wall portion 11, the left side wall portion 12a, the right side wall portion 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20.

[0070] In the example of FIG. 9(c), the internal space of the cylindrical body 30 is also divided into four by a combination of one vertical plate 41 and one horizontal plate . In this example, the hat-shaped member 10 is formed by combining a first member having a cross-sectional shape perpendicular to the longitudinal direction that is generally inverted U-shape (or narrow hat-shape) with a second member that is L-shaped. Of this first member, an upper wall portion forms part of the ceiling wall portion 11. Furthermore, one of a pair of vertical wall portions provided in the first member is a vertical plate 41, and the other is the right side wall portion 12b. Flanges are formed at the lower end of the vertical plate 41 and at the lower end of the right side wall portion 12b. Of these, the flange formed at the lower end of the vertical plate 41 is fixed by laser arc welding in a state of surface contact with the plate-shaped member 20. On the other hand, the flange formed at the lower end of the right side wall portion 12b is fixed by spot welding in a state of surface contact with the plate-shaped member 20.

[0071] Of the second member, the upper wall portion forms part of the top wall portion 11, and the vertical wall portion forms the left side wall portion 12a. A small flange is formed on the edge of the upper wall portion of the second member, and this flange is fixed by laser arc welding in a state of surface contact with the upper end of the vertical wall portion of the first member. In addition, a flange is formed on the lower end of the second member, and this flange is fixed by spot welding in a state of surface contact with the plate-like member 20. A flange is formed on one of the opposite side edges of the horizontal plate 42, and this flange is fixed by spot welding in surface contact with the left side wall portion 12a. Similarly, a flange is formed on the other opposite side edge of the horizontal plate 42, and this flange is fixed by spot welding in surface contact with the right side wall portion 12b. The vertical plate 41 is joined at its height center position by laser arc welding in a state where it intersects (orthogonally) with the width center position of the horizontal plate 42. In this manner, the internal space of the cylindrical body 30 is divided into four spaces by the top wall portion 11, the left side wall portion 12a, the right side wall portion 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20.

[0072] In the example of FIG. 9(d), the internal space of the cylindrical body 30 is also divided into four parts by a combination of one vertical plate 41 and one horizontal plate . In this example, a cylindrical body 30 is combined with a pair of angle bars each having an L-shaped cross section perpendicular to the longitudinal direction to form a rectangular closed cross-sectional space. That is, a flange is formed on only one of the two end edges of each angle bar. These flanges are then fixed by spot welding to the other angle bar, which is the connecting partner, in a face-to-face contact state. By fixing these two flange portions to the other, the closed cross-sectional space is formed between the two angle bars.

[0073] A pair of smaller first and second angle members are combined in the closed cross-sectional space in a "+" shape to form a vertical plate 41 and a horizontal plate 42. The first angle member has a substantially L-shaped cross section perpendicular to the longitudinal direction, and flanges are formed at both ends. One of these flanges is fixed by spot welding in a surface-contact state to the top wall portion 11, and the other is fixed by spot welding in a surface-contact state to the right side wall portion 12b. On the other hand, the second angle member has a substantially L-shaped cross section perpendicular to the longitudinal direction, and flanges are formed at both ends. One of these flanges is fixed by spot welding in a surface-contact state to the left side wall portion 12a, and the other is fixed by spot welding in a surface-contact state to the plate-shaped member 20. In addition, a recess is formed at the corner of the second angle member, and the corner of the first angle member is fixed by adhesion into this recess. Therefore, in this example, the vertical wall of the first angle iron and the vertical wall of the second angle iron are combined to form one vertical plate 41. Furthermore, the horizontal wall of the first angle iron and the horizontal wall of the second angle iron are combined to form one horizontal plate 42. In this manner, the internal space of the cylindrical body 30 is divided into four spaces by the top wall portion 11, the left side wall portion 12a, the right side wall portion 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20.

[0074] In the example of FIG. 9(e), the internal space of the cylindrical body 30 is also divided into four parts by a combination of one vertical plate 41 and one horizontal plate . In this embodiment, the cylindrical body 30 is formed by combining four angle bars, each having an L-shaped cross section perpendicular to the longitudinal direction. Flanges are formed on both end edges of each angle bar. Furthermore, two flat plate-like plates are fixed by laser arc welding in a state where they are crossed (orthogonal) at the center position in the width direction, thereby forming a reinforcement 40 including a vertical plate 41 and a horizontal plate 42. Then, the upper and lower ends of the vertical plate 41 and the left and right ends of the horizontal plate 42 are spot welded in a state where they are sandwiched between the flanges of the four angle irons so that the reinforcement 40 is disposed in the center, thereby forming a cylindrical body 30 including a top wall portion 11, a left side wall portion 12a, a right side wall portion 12b, and a plate-like member 20. In this manner, the internal space of the cylindrical body 30 is divided into four spaces by the top wall portion 11, the left side wall portion 12a, the right side wall portion 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20.

[0075] In the example of FIG. 10(a), the internal space of the cylindrical body 30 is also divided into four parts by a combination of one vertical plate 41 and one horizontal plate . In this example, the reinforcement 40, which includes a vertical plate 41 and a horizontal plate 42, is formed by joining two angle bars by spot welding at their respective corners. That is, two angle bars are prepared, each of which has a substantially L-shaped cross section perpendicular to the longitudinal direction and has chamfered corners. Then, these angle bars are joined by spot welding with their chamfers in surface contact with each other. As a result, the wall of one angle bar and the wall of the other angle bar become parallel to each other, forming the vertical plate 41. Similarly, the other wall of one angle bar and the other wall of the other angle bar become parallel to each other, forming the horizontal plate 42. Then, the edges of each angle bar are butted against the top wall 11, the left side wall 12a, the right side wall 12b, and the plate-like member 20, and are joined by laser arc welding. As a result, the internal space of the cylindrical body 30 is divided into four spaces by the vertical plates 41 and the horizontal plates 42.

[0076] In the example of FIG. 10(b), the internal space of the cylindrical body 30 is also divided into four by a combination of one vertical plate 41 and one horizontal plate . In this example, the corners of two angle bars are joined by spot welding to form the reinforcement 40 having a vertical plate 41 and a horizontal plate 42. That is, two angle bars are prepared, each of which has a substantially L-shaped cross section perpendicular to the longitudinal direction and has chamfered corners. A flange is formed on one of a pair of edges of each angle bar. The chamfers of these angles are in surface contact with each other and spot welded together, so that the wall of one angle and the wall of the other angle are parallel to each other to form a vertical plate 41. Similarly, the other wall of one angle and the other wall of the other angle are parallel to each other to form a horizontal plate 42. The reinforcement 40 formed as described above is joined by spot welding with each flange in surface contact with the left side wall 12a and the right side wall 12b. In addition, the edge of the reinforcement 40 where the flange is not formed is joined by laser arc welding with the edge abutted against the top wall 11 and the plate-like member 20. As a result, the internal space of the cylindrical body 30 is divided into four spaces by the vertical plates 41 and the horizontal plates 42.

[0077] In the example of FIG. 10(c), the internal space of the cylindrical body 30 is also divided into four parts by a combination of one vertical plate 41 and one horizontal plate . In this example, the reinforcement 40 including the vertical plate 41 and the horizontal plate 42 is formed by spot welding the side surfaces near the corners of two angle irons. That is, two angle irons having a substantially L-shaped cross section perpendicular to the longitudinal direction are prepared. Then, these angle irons are joined by spot welding with the side surfaces near the corners of each of them overlapping and in surface contact with each other. As a result, the wall portion of one angle iron and the wall portion of the other angle iron become parallel to each other, forming the vertical plate 41. Similarly, the other wall portion of one angle iron and the other wall portion of the other angle iron become parallel to each other, forming the horizontal plate 42. Then, the edges of each angle bar are butted against the top wall 11, the left side wall 12a, the right side wall 12b, and the plate-like member 20, and are joined by laser arc welding. As a result, the internal space of the cylindrical body 30 is divided into four spaces by the vertical plates 41 and the horizontal plates 42.

[0078] In the example of FIG. 10(d), the internal space of the cylindrical body 30 is also divided into four parts by a combination of one vertical plate 41 and one horizontal plate . In this example, the corners of two angle bars are joined together by spot welding to form the reinforcement 40, which includes a vertical plate 41 and a horizontal plate 42. That is, two angle bars having a substantially L-shaped cross section perpendicular to the longitudinal direction are prepared. A flange is formed on one of a pair of edges of each angle bar. Then, these angle bars are joined by spot welding with the sides near the corners of each angle bar overlapping and in surface contact with each other. As a result, the wall of one angle bar and the wall of the other angle bar are parallel to each other, forming the vertical plate 41. Similarly, the other wall of one angle bar and the other wall of the other angle bar are parallel to each other, forming the horizontal plate 42. The reinforcement 40 formed as described above is joined by spot welding with each flange in surface contact with the left side wall 12a and the right side wall 12b. In addition, the edge of the reinforcement 40 where the flange is not formed is joined by laser arc welding with the edge abutted against the top wall 11 and the plate-like member 20. As a result, the internal space of the cylindrical body 30 is divided into four spaces by the vertical plates 41 and the horizontal plates 42.

[0079] In the example of FIG. 10(e), the internal space of the cylindrical body 30 is also divided into four parts by a combination of one vertical plate 41 and one horizontal plate . In this example, the corners of one angle bar and one pressed plate are joined together by spot welding to form the reinforcement 40 including a vertical plate 41 and a horizontal plate 42. That is, one angle bar having a substantially L-shaped cross section perpendicular to the longitudinal direction and one pressed plate having a substantially S-shaped cross section by bending at right angles at two locations in the width direction are prepared. Flanges are formed on both of a pair of edges of the angle bar. Also, flanges are formed on both of a pair of edges of the pressed plate.

[0080] The side surface of the angle bar near the corner and the side surface of the pressed plate near the corner are joined by laser arc welding while being in surface contact with each other. As a result, the wall of the angle bar and the wall of the pressed plate become parallel to each other to form a vertical plate 41. Similarly, the other wall of the angle bar and the other wall of the pressed plate become parallel to each other to form a horizontal plate 42. One flange of the angle iron is spot welded to the top wall 11 in surface contact, and the other flange is spot welded to the right side wall 12b in surface contact. In addition, one flange of the pressed plate is spot welded to the left side wall 12a in surface contact, and the other flange of the pressed plate is spot welded to the lower part of the right side wall 12b in surface contact. Furthermore, a plate-shaped member 20 having flanges formed on both end edges is prepared, and each flange is joined to the hat-shaped member 10 by spot welding. In addition, one of two bent portions of the pressed plate that is not joined to the angle bar is brought into contact with the center position of the plate-shaped member 20 in the width direction and joined by laser arc welding. As a result, the internal space of the cylindrical body 30 is divided into four spaces by the vertical plates 41 and horizontal plates 42.

[0081] In the example of FIG. 10(f), the internal space of the cylindrical body 30 is also divided into four by a combination of one vertical plate 41 and one horizontal plate . In this example, the corners of one angle bar and one pressed plate are joined together by spot welding to form a reinforcement 40 including a vertical plate 41 and a horizontal plate 42. That is, one angle bar having a substantially L-shaped cross section perpendicular to the longitudinal direction and one pressed plate having a substantially S-shaped cross section by bending at right angles at two locations in the width direction are prepared. Flanges are formed on both of a pair of edges of the angle bar. Also, a flange is formed on one of a pair of edges of the pressed plate.

[0082] The side surface of the angle bar near the corner and the side surface of the pressed plate near the corner are joined by laser arc welding while being in surface contact with each other. As a result, the wall of the angle bar and the wall of the pressed plate become parallel to each other to form a vertical plate 41. Similarly, the other wall of the angle bar and the other wall of the pressed plate become parallel to each other to form a horizontal plate 42. One flange of the angle iron is spot welded to the top wall 11 in surface contact, and the other flange is spot welded to the right side wall 12b in surface contact. In addition, the flange of the pressed plate is spot welded to the left side wall 12a in surface contact, and the flange-free edge of the pressed plate is spot welded to the right flange 13b at the lower end of the right side wall 12b in surface contact. Then, a plate-like member 20 narrower than the lower opening width of the hat-shaped member 10 is prepared. One edge of the plate-like member 20 is brought into contact with one of the two bent portions of the pressed plate that is not joined to the angle bar, and joined by laser arc welding. Furthermore, the other edge of the plate-like member 20 is brought into surface contact with the left flange portion 13a at the lower end of the left wall portion 12a, and joined by spot welding. As a result, the internal space of the cylindrical body 30 is divided into four spaces by the vertical plate 41 and the horizontal plate 42.

[0083] In FIG. 10(g), the internal space of the cylindrical body 30 is divided into six parts by a combination of two vertical plates 41 and one horizontal plate . In this example, a first press-processed plate formed in two stages by press processing and a second press-processed plate formed in one stage by press processing are prepared. Then, both corners of the upper stage of the second press-processed plate are joined by laser arc welding to both corners of the lower stage of the first press-processed plate in face contact. As a result, the first press-processed plate and the second press-processed plate are integrated to form a reinforcement 40. In this reinforcement 40, two vertical walls of the first press-processed plate and two vertical walls of the second press-processed plate are connected to form two vertical plates 41. Also, two horizontal walls of the first stage of the first press-processed plate and one horizontal wall of the second press-processed plate are connected to form one horizontal plate 42.

[0084] Then, this reinforcement 40 is incorporated and fixed in the hat-shaped member 10. That is, the higher step (upper end) of the first press-processed plate is joined by spot welding in a state where it is in surface contact with the top wall portion 11. Furthermore, each side wall of the lower step of the first press-processed plate is joined by spot welding in a state where it is in surface contact with the left side wall portion 12a and the right side wall portion 12b. Finally, both side edges of the second press-processed plate are joined by spot welding in a state where it is sandwiched between the left flange portion 13a, the right flange portion 13b, and the plate-like member 20. In this way, the internal space of the cylindrical body 30 is divided into six spaces: three spaces partitioned by the top wall portion 11, the left side wall portion 12a and the right side wall portion 12b, the two vertical plates 41, and the horizontal plate 42, and three spaces partitioned by the horizontal plate 42, the left side wall portion 12a and the right side wall portion 12b, the two vertical plates 41, and the plate-like member 20.

[0085] In FIG. 11(a), one vertical plate 41 and one horizontal plate 42 are combined to divide the internal space of the cylindrical body 30 into four parts. In this example, two hollow tubes are prepared, each of which has a cross section that is roughly shaped like the letter "9" with the left and right reversed. A flange is formed on the edge of the open part of the "9" shape. The two hollow tubes are assembled so that their cross-sectional shapes perpendicular to the longitudinal direction are rotationally symmetrical to each other. Then, the flange of one hollow tube is joined to the other hollow tube by laser arc welding in a face-to-face contact state. This joining is performed at two places. As a result, the outer peripheral parts of both hollow tubes are assembled to each other to form a cylindrical body 30. That is, an outer shape part corresponding to the top wall 11, the left side wall 12a, the right side wall 12b, and the plate-like member 20 is formed. At the same time, the vertical wall of one hollow tube and the vertical wall of the other hollow tube are connected to each other in the cylindrical body 30 to form a vertical plate 41. Similarly, the horizontal wall of one hollow tube and the horizontal wall of the other hollow tube are connected to each other in the cylindrical body 30 to form a horizontal plate 42. In this manner, the internal space of the cylindrical body 30 is divided into four spaces by the vertical plates 41 and the horizontal plates 42.

[0086] In FIG. 11(b), one vertical plate 41 and one horizontal plate 42 are combined to divide the internal space of the cylindrical body 30 into four parts. In this example, two hollow tubes with a cross section shaped like the letter "8" are prepared. These hollow tubes are formed by bending a single plate material at right angles in various places, and both ends of the material are machined into flanges. Next, the flanges of each hollow tube are pre-joined by laser arc welding.

[0087] The two hollow tubes thus prepared are stacked and bonded together, one of which is the lower stage and the other being the upper stage. The side walls of the two hollow tubes are then joined together by laser arc welding, so that the two hollow tubes are integrated into one. As a result, the outer peripheries of both hollow tubes are combined with each other to form a cylindrical body 30. That is, an outer shape portion corresponding to the top wall portion 11, the left side wall portion 12a, the right side wall portion 12b, and the plate-like member 20 is formed. At the same time, the vertical wall of one hollow tube and the vertical wall of the other hollow tube are connected to each other within the cylindrical body 30 to form a vertical plate 41. Similarly, the horizontal wall of one hollow tube and the horizontal wall of the other hollow tube are connected to each other within the cylindrical body 30 to form a horizontal plate 42. In this manner, the internal space of the cylindrical body 30 is divided into four spaces by the vertical plates 41 and the horizontal plates 42.

[0088] In FIG. 11(c), the internal space of the cylindrical body 30 is also divided into four by a combination of one vertical plate 41 and one horizontal plate . In this example, a hollow tube is formed by bending a single plate material at multiple points to form three rectangular spaces. These three rectangular spaces are arranged in an inverted L shape, with the lower left corner of the page open. Flanges are formed on both side edges of the plate material that forms the hollow tube. These flanges are joined by laser arc welding in an overlapping state to the wall portion that forms the adjacent rectangular space.

[0089] Then, a generally L-shaped angle bar is attached to the corner of the hollow tube so as to cover the corner and form a fourth rectangular space. Flanges are formed on both side edges of the angle bar. These two flanges are then joined by laser arc welding in a state of surface contact with the side wall surface of the hollow tube. In this way, by combining the hollow tube material and the angle bar, the outer peripheries of both are combined with each other to form a cylindrical body 30 having a rectangular outer shape. That is, the outer shape parts corresponding to the top wall 11, the left side wall 12a, the right side wall 12b, and the plate-like member 20 are formed. At the same time, within this cylindrical body 30, a part of the hollow tube material forms a vertical plate 41, and another part forms a horizontal plate 42. In this manner, the internal space of the cylindrical body 30 is divided into four spaces by the vertical plates 41 and the horizontal plates 42.

[0090] In FIG. 11(d), the internal space of the cylindrical body 30 is also divided into four by a combination of one vertical plate 41 and one horizontal plate . In this example, two molded bodies approximately shaped like the letter "9" are obtained by roll forming. A flange is formed on the edge of only one of these molded bodies. Then, this flange is brought into surface contact with the edge of the other molded body and joined by laser arc welding. In addition, the corners of each molded body are butted against each other and joined by laser arc welding. This joint portion becomes the center position of the cylindrical body 30. In this way, an intermediate body having three rectangular spaces arranged in an L-shape is obtained by using a pair of molded bodies. The intermediate body has an open corner at the top right corner of the page.

[0091] Then, a substantially L-shaped angle bar is attached to the corner of the intermediate body so as to cover the corner and form a fourth rectangular space. Flanges are formed on both side edges of the angle bar. These two flanges are then joined by laser arc welding in a state of surface contact with the side wall surface of the intermediate body. In this way, by combining the formed body and the angle bar, the outer peripheries of both are combined with each other to form a cylindrical body 30 having a rectangular outer shape. That is, the outer shape parts corresponding to the top wall 11, the left side wall 12a, the right side wall 12b, and the plate-like member 20 are formed. At the same time, within this cylindrical body 30, a part of the intermediate body forms a vertical plate 41, and another part forms a horizontal plate 42. In this manner, the internal space of the cylindrical body 30 is divided into four spaces by the vertical plates 41 and the horizontal plates 42.

[0092] In FIG. 11(e), the internal space of the cylindrical body 30 is also divided into four by a combination of one vertical plate 41 and one horizontal plate . In this example, four hollow tubes with rectangular cross sections are prepared. These hollow tubes are then glued together in two vertical rows and two horizontal rows. The joints on the outer circumference are then firmly joined by laser arc welding. In this manner, by combining the four hollow tubular materials, the outer peripheries of each material are combined with each other to form a cylindrical body 30 having a rectangular outer shape. That is, the outer shape parts corresponding to the top wall 11, the left side wall 12a, the right side wall 12b, and the plate-like member 20 are formed. At the same time, within this cylindrical body 30, parts of each hollow tubular material are combined with each other to form a vertical plate 41 and a horizontal plate 42. In this manner, the internal space of the cylindrical body 30 is divided into four spaces by the vertical plates 41 and the horizontal plates 42.

[0093] [Second embodiment] Next, a second embodiment of the present invention will be described below with reference to Fig. 12. In the following description, differences from the first embodiment will be mainly described, and other configurations will be the same as those of the first embodiment, and therefore repeated description will be omitted. This embodiment is different in that a third bead Bc shown in FIG. 12 is formed on the top wall portion 11 as a folding base portion instead of the first bead Ba and the second bead Bb in the first embodiment.

[0094] The third bead Bc is a single recess formed in the top wall portion 11, and is long in a direction intersecting the longitudinal direction of the impact absorbing member 1. The third bead Bc is formed between a pair of ridge lines EL forming both side edges of the top wall portion 11. More specifically, when the top wall portion 11 is viewed from the front, the third bead Bc is formed long along the width direction of the top wall portion 11 between a pair of side edges ELa that are the boundaries between the top wall portion 11 and each ridge line EL. Therefore, the third bead Bc is formed only on the top wall portion 11, which is a flat portion, and does not reach the inside between the pair of ridge lines EL.

[0095] The third bead Bc has a rectangular central portion in the longitudinal direction and semicircular ends. The width of the third bead Bc can be 20 mm to 40 mm. The length of the outer surface of the third bead Bc can be 50 mm to 80 mm. The depth of the outer surface of the third bead Bc can be 4 mm to 15 mm. The third bead Bc may be formed at the same time as the press working when forming the hat-shaped member 10 from the metal plate, or may be formed by applying press working to the hat-shaped member 10 in a post-process. When the third bead Bc is formed by press working, the plate thickness is slightly thinner than the surrounding plate thickness and is work-hardened. The inner surface of the third bead Bc is recessed toward the inside of the cylindrical body 30, just as the outer surface is recessed. The number of the third bead Bc is not limited to one, but may be two or more. In addition, although FIG. 12 illustrates an example in which the longitudinal direction of the third bead Bc is perpendicular to the longitudinal direction of the impact absorbing member 1, the longitudinal direction of the third bead Bc may be at a slight angle to the perpendicular direction.

[0096] In the impact absorbing member 1 of this embodiment, the above-described third bead Bc constitutes the second region R2, and its adjacent longitudinal sides are the first region R1 and the third region R3. Therefore, when a load is applied to the impact absorbing member 1 along the center line CL, the impact absorbing member 1 bends with the third bead Bc of the second region R2 as the bending starting point. During this bending, the reinforcement 40 also bends to absorb the collision energy.

[0097] [Third embodiment] Next, a third embodiment of the present invention will be described below with reference to Fig. 13. In the following description, differences from the first embodiment will be mainly described, and other configurations will be the same as those of the first embodiment, and therefore repeated description will be omitted. In this embodiment, instead of the first bead Ba and the second bead Bb in the first embodiment, one through hole Ta is formed in the top wall portion 11, and one through hole Tb is formed in each of the left side wall portion 12a and the right side wall portion 12b, and these through holes Ta, Tb are used as the folding starting points.

[0098] The through holes Ta, Tb are both circular and have the same inner diameter, with a specific inner diameter dimension being, for example, 20 mm to 40 mm. The through holes Ta, Tb are formed only in the flat wall surface of the hat-shaped component 10 and do not overlap a pair of ridge portions EL. The through holes Ta, Tb are formed at the same position along the longitudinal direction of the impact absorbing member 1. In the impact absorbing member 1 of this embodiment, the portion where the through holes Ta, Tb are formed forms the second portion R2, and the adjacent portions in the longitudinal direction form the first portion R1 and the third portion R3. Therefore, when a load is applied to the impact absorbing member 1 along the center line CL, the impact absorbing member 1 bends with the through holes Ta, Tb in the second portion R2 as bending starting points. During this bending, the reinforcement 40 also bends to absorb the collision energy. The shape of the through holes Ta, Tb is not limited to a circle, and other shapes such as an ellipse may be adopted. The sizes of the through holes Ta, Tb may be different from each other. The number of the through holes Ta, Tb may be multiple for each flat surface of the hat-shaped member 10. Only one of the through holes Ta, Tb may be formed. However, when the through hole Ta is omitted and only the through hole Tb is formed, it is preferable to form it in both the left side wall portion 12a and the right side wall portion 12b.

[0099] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and the following modifications may be adopted. Furthermore, the embodiments and modifications may be combined as appropriate. [Variation 1] A material strength distribution may be intentionally provided between the first region R1 and the third region R3. Specifically, a material tensile strength ratio obtained by dividing the material tensile strength of the second region R2 by the average material tensile strength of the first region R1 and the third region R3 may be set to 0.5 to 0.9. Such a material tensile strength ratio is obtained by preparing a pair of flat plate materials, one of which has a relatively low tensile strength and the other of which has a relatively high tensile strength, and then using a tailored blank in which the flat plate material with the relatively low tensile strength is disposed between the flat plate materials with the relatively high tensile strength and welded. Such a material tensile strength ratio may be applied to the first embodiment to the third embodiment. By providing such a material tensile strength difference, the relative bending strength of the second portion R2 with respect to the first portion R1 and the third portion R3 can be further reduced, thereby ensuring that the position of the second portion R2 functions as a folding start point.

[0100] [Variation 2] A thickness distribution may be intentionally provided between the first region R1 and the third region R3. Specifically, a thickness ratio obtained by dividing the thickness of the second region R2 by the average thickness of the first region R1 and the third region R3 may be set to 0.5 to 0.9. Such a thickness ratio is obtained by preparing a flat plate material having a relatively thin thickness and a pair of flat plate materials having a relatively thick thickness, and then using a tailored blank in which the flat plate material having a relatively thin thickness is disposed between the flat plate materials having a relatively thick thickness and welded. In addition, such a thickness difference may be applied to the first embodiment to the third embodiment or the first modified example. When such a plate thickness distribution is provided, the relative bending strength of the second portion R2 with respect to the first portion R1 and the third portion R3 can be reduced, thereby ensuring that the position of the second portion R2 functions as the position of the break start point.

[0101] [Variation 3] Except for the second region R2, the first region R1 and the third region R3 may each be provided with a reinforcing portion (not shown) along the longitudinal direction. As this reinforcing portion, at least one of a bead, an angle member, and an embossment formed along the longitudinal direction may be provided. In addition, such a reinforcing portion may be applied to the first to third embodiments or the first and second modifications. When such a reinforcing portion is provided, the relative bending strength of the first portion R1 and the third portion R3 with respect to the second portion R2 can be further increased, so that the position of the second portion R2 can function more reliably as a folding start portion. EXAMPLES

[0102] [First Example] A first embodiment of the present invention will be described below with reference to Figures 14 to 17. In this embodiment, the manner of bending deformation and the amount of energy absorption were obtained by numerical calculation when a load was applied to the impact absorbing member 1 described with reference to Figure 2 (hereinafter, "invention example") and an impact absorbing member 1 in which the reinforcement 40 is omitted or the first bead Ba and the second bead Bb do not extend beyond the side edge ELa to the top wall portion 11 (hereinafter, "comparative example").

[0103] FIG. 14 shows a perspective view of a comparative example, which includes a hat-shaped member 10 and a plate-shaped member 20 but does not include a reinforcement 40. A first bead Ba and a second bead Bb are formed on the hat-shaped member 10. Both the first bead Ba and the second bead Bb are diamond-shaped, and three cases of their depths, 6 mm, 8 mm, and 10 mm, are set as shown in FIG. 15. Here, when the depth is 6 mm, the first bead Ba and the second bead Bb are contained within the ridge portion EL and do not protrude beyond the side edges ELa, ELb. When the depth is 8 mm, the first bead Ba and the second bead Bb protrude beyond the ridge portion EL beyond the side edges ELa, ELb. The material used for the hat-shaped member 10 had a tensile strength of 780 MPa and a plate thickness of 2.0 mm. The material used for the plate-like member 20 had a tensile strength of 690 MPa and a plate thickness of 1.2 mm.

[0104] FIG. 16 is the same as the impact absorbing member 1 described in FIG. 2, and includes a hat-shaped member 10, a plate-shaped member 20, and a reinforcement 40. The hat-shaped member 10 is formed with a first bead Ba and a second bead Bb. Both the first bead Ba and the second bead Bb are rhombic. As shown in FIG. 17, three cases were set: a case where the depth is 6 mm, a case where the depth is 8 mm, and a case where the depth is 10 mm. Of these, the case where the depth is 6 mm is a comparative example because both the first bead Ba and the second bead Bb are contained within the ridge line portion EL and do not protrude beyond the side edge ELa into the top wall portion 11. On the other hand, the cases where the depth is 8 mm and 10 mm are examples of the invention because both the first bead Ba and the second bead Bb protrude beyond the side edge ELa into the top wall portion 11. In addition, in the cases where the depth is 8 mm and 10 mm, the first bead Ba and the second bead Bb extend beyond the side edge ELb and onto the left side wall portion 12a and the right side wall portion 12b.

[0105] The material used for the hat-shaped member 10 had a tensile strength of 780 MPa and a plate thickness of 1.6 mm. The material used for the plate-like member 20 had a tensile strength of 690 MPa and a plate thickness of 1.2 mm. The reason for making the plate thickness of the hat-shaped member 10 in the example thinner than that in the comparative example is to evaluate the example and the comparative example in a state of equivalent weight, taking into account the weight difference depending on whether or not the reinforcement 40 is present.

[0106] 15, when the depth of the first bead Ba and the second bead Bb was 6 mm, the hat-shaped component 10 underwent out-of-plane deformation at an unintended position due to the absence of the reinforcement 40. Therefore, appropriate bending was not obtained at the positions of the first bead Ba and the second bead Bb. In addition, when the depth of the first bead Ba and the second bead Bb was 8 mm, bending occurred at the positions of the first bead Ba and the second bead Bb. However, because there was no reinforcement 40, the range of out-of-plane deformation was wide, and it was not possible to cause bending deformation at the joints. The amount of energy absorption at a stroke of 180 mm was 4.74 kJ. In addition, when the depth of the first bead Ba and the second bead Bb was 10 mm, bending occurred at the positions of the first bead Ba and the second bead Bb. However, because there was no reinforcement 40, the range of out-of-plane deformation was wide, and it was not possible to cause bending deformation at the joints. The amount of energy absorption at a stroke of 180 mm was 4.63 kJ.

[0107] 17, when the depth of the first bead Ba and the second bead Bb was 6 mm, the first bead Ba and the second bead Bb could not function as a folding trigger for folding the top wall portion 11, and the hat-shaped member 10 underwent out-of-plane deformation at an unintended position. Therefore, appropriate folding at the positions of the first bead Ba and the second bead Bb was not obtained. Furthermore, when the depth of the first bead Ba and the second bead Bb was 8 mm, bending occurred at the positions of the first bead Ba and the second bead Bb. This is because the provision of the reinforcement 40 suppresses out-of-plane deformation at unintended locations, and the pair of first beads Ba and second beads Bb that have penetrated into the top wall portion 11 are used as bending starting points to cause bending deformation at good joints. Furthermore, since the reinforcement 40 absorbed the load while bending during bending deformation, the amount of energy absorption at a stroke of 180 mm was 7.47 kJ, which was higher than the amount of energy absorption (4.74 kJ) of the comparative example in which the depth of the first bead Ba and the second bead Bb shown in FIG. 15 was 8 mm. In addition, when the depth of the first bead Ba and the second bead Bb was 10 mm, bending occurred at the positions of the first bead Ba and the second bead Bb. In this case, the provision of the reinforcement 40 also suppressed out-of-plane deformation at unintended locations. In addition, the pair of first beads Ba and second beads Bb, which were firmly inserted into the top wall portion 11, served as the bending starting points, allowing for good bending deformation at joints. In addition, since the reinforcement 40 absorbed the load while bending during bending deformation, the energy absorption amount at a stroke of 180 mm was 7.94 kJ, which was higher than the energy absorption amount (4.63 kJ) of the comparative example in which the diameters of the first bead Ba and the second bead Bb shown in FIG. 15 were 10 mm.

[0108] From the above results, it was confirmed that it is important to provide a reinforcement 40 and to make the first bead Ba and the second bead Bb larger to a certain extent so that they extend at least beyond the side edge ELa into the top wall portion 11, and that by providing both of these, the amount of energy absorption can be increased while the impact absorbing member 1 is bent and deformed at good joints.

[0109] [Second Example] A second embodiment of the present invention will be described below with reference to Figures 18 and 19. In this embodiment, various cases were set in which the presence or absence of reinforcements 40 and the presence or absence of through holes Ta, Tb were changed for each of the impact absorbing member 1 of the second embodiment described with reference to Figure 12 and the impact absorbing member 1 of the third embodiment described with reference to Figure 13. Then, the manner of bending deformation and the amount of energy absorption when a load was applied coaxially with the center line CL were obtained by numerical calculation.

[0110] First, a description will be given of Fig. 18. Fig. 18 is a perspective view showing the impact absorbing members 1 of the cases (a) to (l) before a load is applied. Cases (a) to (c) are cases where one third bead Bc shown in FIG. 12 is formed on the top wall portion 11. Cases (a) and (c) are not provided with the reinforcement 40, while case (b) is provided with the reinforcement 40. In order to make cases (a) and (b) equivalent in mass to each other, the plate thickness of the hat-shaped member 10 in case (b) is made thinner than that of the hat-shaped member 10 in case (a) by the amount of the reinforcement 40 provided. On the other hand, the plate thickness of the hat-shaped member 10 in case (c) is made the same as that of case (b).

[0111] Cases (d) to (f) are cases where the through hole Tb shown in Fig. 13 is formed in the side wall portion 12. That is, one through hole Tb is formed in the left side wall portion 12a, and one through hole Tb is also formed in the side wall portion 12. However, no through hole Ta is formed in the top wall portion 11, which is left flat. Cases (d) and (f) do not include the reinforcement 40, while case (e) includes the reinforcement 40. In order to make cases (d) and (e) equivalent in mass to each other, the plate thickness of the hat-shaped member 10 in case (e) is made thinner than that of the hat-shaped member 10 in case (d) by the amount of the reinforcement 40 provided. On the other hand, the plate thickness of the hat-shaped member 10 in case (f) is made the same as that in case (e).

[0112] Cases (g) to (i) are cases where a through hole Ta shown in Fig. 13 is formed in one location of the top wall portion 11. However, no through hole Tb is formed in the side wall portion 12, which is left flat. Cases (g) and (i) were not provided with the reinforcement 40, while case (h) was provided with the reinforcement 40. In order to make cases (h) and (i) equivalent in mass to each other, the plate thickness of the hat-shaped member 10 in case (h) was made thinner than that of the hat-shaped member 10 in case (g) by the amount of the reinforcement 40 provided. On the other hand, the plate thickness of the hat-shaped member 10 in case (i) was made the same as that of case (h).

[0113] 13 is formed in one location on the top wall portion 11, and further, a through hole Tb shown in Fig. 13 is formed in the side wall portion 12. That is, one through hole Tb is formed in the left side wall portion 12a, and one through hole Tb is formed in the side wall portion 12. Cases (j) and (l) do not include the reinforcement 40, while case (k) includes the reinforcement 40. In order to make cases (j) and (k) equivalent in mass to each other, the plate thickness of the hat-shaped member 10 in case (k) is made thinner than that of the hat-shaped member 10 in case (j) by the amount of the reinforcement 40 provided. On the other hand, the plate thickness of the hat-shaped member 10 in case (l) is made the same as that in case (k).

[0114] A load was applied coaxially with the center line CL to the impact absorbing member 1 of each of the above-described cases (a) to (l) to cause bending deformation. The state after bending deformation is as shown in FIG. First, in cases (a) to (c) in which the third bead Bc was formed in the top wall portion 11, each broke at the position of the third bead Bc, but in the comparative examples (a) and (c), the bending range was wide because the reinforcement 40 was not provided, and the joints could not be broken smoothly. In addition, in cases (a) and (c), the amount of energy absorption was low because the reinforcement 40 was not provided. On the other hand, in case (b), which is an example of the invention, the joints broke smoothly at the position of the third bead Bc and the amount of energy absorption was high.

[0115] Next, among cases (d) to (f) in which through holes Tb were formed in the side wall portion 12, in case (f), out-of-plane deformation occurred at an unintended location because the reinforcement 40 was not provided. Therefore, in case (f), bending deformation occurred at an unintended location, and the amount of energy absorption was also low. In case (d), although it broke at the position of the through hole Tb, the bending range was wide because there was no reinforcement 40, and it was not possible to break and deform the joints smoothly. In addition, in case (d), the amount of energy absorption was low because there was no reinforcement 40. On the other hand, in case (e), which is an example of the invention, it broke at the position of the through hole Tb smoothly and also had a high amount of energy absorption.

[0116] Next, among cases (g) to (i) in which the through hole Ta was formed in the top wall portion 11, in cases (g) and (i), out-of-plane deformation occurred at unintended locations because the reinforcement 40 was not provided. The amount of energy absorption was also low. On the other hand, in case (h), which is an example of the invention, the joint broke smoothly at the position of the through hole Ta, and the amount of energy absorption was also high.

[0117] Next, among cases (j) to (l) in which a through hole Ta was formed in the top wall portion 11 and a through hole Tb was formed in the side wall portion 12, cases (j) and (l) did not have the reinforcement 40, so the bending range was wide and it was not possible to bend smoothly at the joints. Also, the energy absorption amount was low in cases (j) and (l). On the other hand, in case (k), which is an example of the invention, the joints were bent smoothly at the positions of the through holes Ta and Tb, and the energy absorption amount was high. From the above results, it was confirmed that in cases (b), (e), (h), and (k), which are examples of the invention equipped with appropriate bending points and reinforcements 40, the impact absorbing member 1 can be bent and deformed at the intended positions with good joints, and a high amount of energy absorption can be obtained.

[0118] The gist of the present invention is summarized below. (1) One aspect of the present invention is In the impact absorbing member 1, which includes a cylindrical body 30 and a reinforcement 40 fixedly disposed inside the cylindrical body 30 and is long along one direction, The cylindrical body 30 is made of a steel material having a tensile strength of 650 MPa or more and 1600 MPa or less, and the reinforcement 40 is made of a steel material having a tensile strength of 590 MPa or more and 1600 MPa or less; In a cross section perpendicular to the longitudinal direction of the shock absorbing member 1, The cylindrical body 30 has a top wall portion 11 having a flat portion overall width dimension W1 (mm) and a plate thickness t1 (mm), and a pair of side wall portions 12 provided on both sides of the top wall portion 11 and having a flat portion overall width dimension W2 (mm) and a plate thickness t1 (mm), The reinforcement 40 has at least one of a vertical plate 41 having one end joined to the top wall portion 11, a total number of n1 plates, and a total plate thickness of t2 (mm), and a horizontal plate 42 connecting a pair of side wall portions 12, a total number of n2 plates, and a total plate thickness of t3 (mm), The reinforcement 40 satisfies at least one of a first condition that the reinforcement 40 has a vertical plate 41 and a first flat surface portion width-thickness ratio r1 according to the following formula 1 is 10 or more and 50 or less, and a second condition that the reinforcement 40 has a horizontal plate 42 and a second flat surface portion width-thickness ratio r2 according to the following formula 2 is 10 or more and 50 or less; The cylindrical body 30 is The first portion R1, the second portion R2, and the third portion R3 are arranged in this order along the longitudinal direction, The second region R2 has a folding start point. r1=((W1-t2) / (n1+1)) / t1...(Formula 1) r2=((W2-t3) / (n2+1)) / t1...(Formula 2)

[0119] (2) The impact absorbing member 1 described in (1) above may have the following configuration: The cylindrical body 30 has a pair of ridge lines EL connecting the top wall portion 11 and the pair of side wall portions 12; The folding start portion is a first bead Ba that crosses a side edge ELa that is a boundary between one of the pair of ridge lines EL and the top wall portion 11; a second bead Bb that crosses a side edge ELb that is a boundary between the other of the pair of ridge lines EL and the top wall portion 11; has.

[0120] (3) The impact absorbing member 1 described in (2) above may have the following configuration: The first bead Ba crosses a side edge ELa which is a boundary between one of the pair of ridge portions EL and one of the pair of side wall portions 12; The second bead Bb crosses the side edge ELb which is the boundary between the other of the pair of ridge portions EL and the other of the pair of side wall portions 12.

[0121] (4) In the impact absorbing member 1 described in any one of (1) to (3) above, The folding start portion may have a through hole Ta, Tb or a third bead Bc that is formed in at least one of the top wall portion 11 and the pair of side wall portions 12 and is long in a direction intersecting the longitudinal direction.

[0122] (5) In the impact absorbing member 1 described in any one of (1) to (4) above, The folding origin may be provided in the second region R2 by setting a material tensile strength ratio, obtained by dividing the material tensile strength of the second region R2 by the average material tensile strength of the first region R1 and the third region R3, to 0.5 to 0.9.

[0123] (6) In the impact absorbing member 1 described in any one of (1) to (5) above, The folding start point may be provided in the second region R2 by setting a thickness ratio, obtained by dividing the thickness of the second region R2 by the average thickness of the first region R1 and the third region R3, to 0.5 to 0.9.

[0124] (7) In the impact absorbing member 1 described in any one of (1) to (6) above, Each of the first region R1 and the third region R3 may be provided with a reinforcing portion along the longitudinal direction.

[0125] (8) In the impact absorbing member 1 described in (7) above, Each of the reinforcing portions may have at least one of a bead, an angle member, and an embossment formed along the longitudinal direction.

[0126] (9) The impact absorbing member 1 according to any one of the above (1) to (8) may have the following configuration: The cylindrical body 30 is A hat-shaped member 10 having a top wall portion 11 and a pair of side wall portions 12; a plate-like member 20 joined to the hat-shaped member 10 and facing the top wall portion 11; Both the first condition and the second condition are met; In a cross section perpendicular to the longitudinal direction, said n1 is 1 and said n2 is 1; The vertical plate 41 is fixed in a spanning state between the top wall portion 11 and the plate-like member 20, The horizontal plate 42 is fixed between the pair of side wall portions 12 in a state in which it crosses the vertical plate 41 .

[0127] (10) The impact absorbing member 1 according to any one of the above (1) to (8) may have the following configuration: The cylindrical body 30 is A hat-shaped member 10 having a top wall portion 11 and a pair of side wall portions 12; a plate-like member 20 joined to the hat-shaped member 10 and facing the top wall portion 11; Both the first condition and the second condition are met; In a cross section perpendicular to the longitudinal direction, said n1 is 1 and said n2 is 1; One end of the horizontal plate 42 is joined to one of the pair of side wall portions 12, and the other end of the horizontal plate 42 is joined to the other of the pair of side wall portions 12, The one end of the vertical plate 41 is joined to the top wall portion 11, and the other end of the vertical plate 41 is joined to a position between the one end and the other end of the horizontal plate .

[0128] (11) A vehicle body part according to one aspect of the present invention comprises: Any one of a front side member, a rear side member, a center pillar, and a bumper beam provided on a vehicle body, The shock absorbing member has the shock absorbing member 1 according to any one of the above items (1) to (10). [Explanation of symbols]

[0129] 1. Shock absorbing material 10 Hat-shaped member 11 Ceiling wall, hat top 12 Side wall 12a Left side wall (side wall) 12b Right side wall (side wall) 20 Plate-shaped member 30 Cylindrical body (hollow tube) 40 Reinforce 41 Vertical Board 42 Horizontal board Ba First bead (starting point of break) Bb Second bead (starting point of break) Bc 3rd bead (starting point of break) EL Ridge ELa,ELb Side edge (border) Ta,Tb through hole R1 1st part R2 2nd part R3 3rd part

Claims

1. A shock absorbing member having a hollow tube and a reinforcement fixedly disposed inside the hollow tube, the shock absorbing member being long in one direction, The hollow tube is made of a steel material having a tensile strength of 650 MPa or more and 1600 MPa or less, and the reinforcement is made of a steel material having a tensile strength of 590 MPa or more and 1600 MPa or less; A cross section perpendicular to the longitudinal direction of the impact absorbing member, The hollow tube has a top wall portion having a flat portion overall width dimension W1 (mm) and a wall thickness t1 (mm), and a pair of side wall portions provided on both sides of the top wall portion and having a flat portion overall width dimension W2 (mm) and a wall thickness t1 (mm), The reinforcement has at least one of a vertical plate having one end joined to the top wall portion, a total number of n1 sheets, and a total plate thickness of t2 (mm), and a horizontal plate connecting the pair of side wall portions, a total number of n2 sheets, and a total plate thickness of t3 (mm), The reinforcement satisfies at least one of the following conditions: a first condition that the reinforcement has the vertical plate and the first flat portion width-thickness ratio r1 according to the following formula 1 is 10 or more and 50 or less; and a second condition that the reinforcement has the horizontal plate and the second flat portion width-thickness ratio r2 according to the following formula 2 is 10 or more and 50 or less; The hollow tube is The insulating film has a first portion, a second portion, and a third portion aligned in the longitudinal direction, The second portion has a folding origin portion; A shock absorbing member characterized by: r1=((W1-t2) / (n1+1)) / t1...(Formula 1) r2=((W2-t3) / (n2+1)) / t1...(Formula 2)

2. The hollow tube includes a pair of ridges connecting the top wall portion and the pair of side wall portions; The folding start portion is a first bead that crosses a boundary between one of the pair of ridge portions and the top wall portion; a second bead that crosses the boundary between the other of the pair of ridge lines and the top wall portion; having The impact absorbing member according to claim 1 .

3. the first bead crosses a boundary between one of the pair of ridge portions and one of the pair of sidewall portions; the second bead crosses a boundary between the other of the pair of ridge portions and the other of the pair of side wall portions; The shock absorbing member according to claim 2 .

4. The folding start portion has a through hole or a third bead that is long in a direction intersecting the longitudinal direction and is formed in at least one of the top wall portion and the pair of side wall portions. The impact absorbing member according to any one of claims 1 to 3.

5. a material tensile strength ratio obtained by dividing a material tensile strength of the second portion by an average material tensile strength of the first portion and the third portion is set to 0.5 to 0.9, thereby providing the folding origin portion in the second portion; The impact absorbing member according to any one of claims 1 to 3.

6. The folding origin portion is provided in the second portion by setting a plate thickness ratio obtained by dividing the plate thickness of the second portion by an average plate thickness of the first portion and the third portion to 0.5 to 0.9; The impact absorbing member according to any one of claims 1 to 3.

7. Each of the first portion and the third portion is provided with a reinforcing portion along the longitudinal direction. The impact absorbing member according to any one of claims 1 to 3.

8. Each of the reinforcing portions has at least one of a bead, an angle member, and an embossment formed along the longitudinal direction. The shock absorbing member according to claim 7 .

9. The hollow tube is a hat-shaped member having the top wall portion and the pair of side wall portions; a plate-shaped member joined to the hat-shaped member and facing the top wall portion; Both the first condition and the second condition are satisfied; In a cross section perpendicular to the longitudinal direction, said n1 is 1 and said n2 is 1; The vertical plate is fixed in a spanning state between the top wall portion and the plate-like member, The horizontal plate is fixed between the pair of side wall portions in a state where the horizontal plate crosses the vertical plate; The impact absorbing member according to any one of claims 1 to 3.

10. The hollow tube is a hat-shaped member having the top wall portion and the pair of side wall portions; a plate-shaped member joined to the hat-shaped member and facing the top wall portion; Both the first condition and the second condition are satisfied; In a cross section perpendicular to the longitudinal direction, said n1 is 1 and said n2 is 1; One end of the horizontal plate is joined to one of the pair of side wall portions, and the other end of the horizontal plate is joined to the other of the pair of side wall portions, The one end of the vertical plate is joined to the top wall portion, and the other end of the vertical plate is joined to a position between the one end and the other end of the horizontal plate; The impact absorbing member according to any one of claims 1 to 3.

11. Any one of a front side member, a rear side member, a center pillar, and a bumper beam provided on a vehicle body, The shock absorbing member according to any one of claims 1 to 3 is included. A vehicle body part characterized by:

Images