Impact absorbing members and vehicle body parts

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 a shock-absorbing member and a vehicle body part.

Background Art

[0002] In recent years, fuel consumption regulations have been tightened worldwide, and automobile manufacturers are promoting the weight reduction of vehicle bodies. At the same time, since the collision safety of vehicle bodies has also been tightened, it is required to achieve both weight reduction and improvement of collision performance. In addition, along with fuel consumption regulation countermeasures in each country and the trend toward carbon neutrality, the electrification of the power source of automobiles is being promoted. Along with the electrification of the power source, changes have also occurred in the vehicle body structure, such as an increase in vehicle body weight and a reduction in the engine room compared to the vehicle body structure having a conventional internal combustion engine. As an example, there is the shortening of the short nose at the front of the vehicle body. In order to maintain high collision safety while shortening the short nose of the vehicle body, a structure capable of obtaining 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 plastically deform during a vehicle collision to absorb collision energy, a structure capable of dramatically improving the energy absorption performance is required. In addition, since such parts also have the role of minimizing the external force applied to the occupants during a collision, it is ideal to have a deformation mode that can suppress rapid load fluctuations and shorten the deformation stroke.

[0004] The deformation modes of the member include bellows deformation and meandering deformation. Bellows deformation refers to deformation in which out-of-plane deformation occurs on all of the respective side surfaces constituting the member, but the center line in the longitudinal direction of the member hardly bends. On the other hand, meandering deformation is deformation in which bending occurs at a plurality of locations in the longitudinal direction of the member, and at that time, out-of-plane deformation occurs mainly on one of the respective side surfaces constituting the member, and moreover, the center line in the longitudinal direction of the member also bends. When comparing the two deformation modes described above, if the impact force is applied from an ideal direction, bellows deformation can be said to absorb more impact energy than meandering deformation. However, the direction of impact force input is not fixed to only one direction, so for example, if the impact force is applied obliquely to the longitudinal direction of the member, the amount of energy absorbed by bellows deformation decreases significantly. In contrast, meandering deformation (folding deformation) can respond to the direction of application of impact force to a certain extent, and can stably absorb impact energy. An example of a structure that absorbs impact energy by folding deformation is shown in Patent Documents 1 and 2. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-174121 [Patent Document 2] International Publication No. 2021 / 192188 [Overview of the project] [Problems that the invention aims to solve]

[0006] Patent Document 1 discloses a rear vehicle structure that absorbs impact energy during a rear collision. This rear vehicle structure consists of a rear frame and a tank lower frame positioned below the rear frame, arranged in pairs on the left and right sides of the vehicle body. The rear frame has displacement-load characteristics such that the ratio of load F to displacement S (F / S) is 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 sharply after reaching the maximum bending strength.

[0007] As mentioned above, impact-absorbing members are now required to have a shorter deformation stroke in addition to being lightweight and having improved collision performance. One way to reduce weight is to use light alloys such as aluminum as the material, but due to their low material strength, improved collision performance and a shorter deformation stroke cannot be expected. Therefore, another option is to use high-strength steel plates with high tensile strength and then reduce the plate thickness. However, if the plate thickness is simply reduced in the rear frame disclosed in Patent Document 1, for example, out-of-plane deformation is likely to occur at any point in the rear frame, and the position of the bending point becomes unclear. From the viewpoint of impact energy absorption, it is not acceptable for the plate to break anywhere; if it does not break cleanly at the designed position, the amount of energy absorbed as designed cannot be obtained. In that case, the inherently high energy absorption capacity, which should be superior to bellows deformation, cannot be realized. In other words, simply increasing the material strength and reducing the plate thickness does not allow the advantages of bending deformation to be fully realized, nor does it achieve a shorter deformation stroke. The same applies to Patent Document 2. Patent Document 2 discloses a structure comprising a skeletal member having a closed cross-section structure and a reinforcing member disposed within the skeletal member. In this structure, if the plate thickness of the skeletal member is simply reduced for the purpose of weight reduction, out-of-plane deformation is more likely to occur in each part of the skeletal member, and the position of the bending initiation point becomes unclear. Therefore, there is room for consideration in order to fully realize the advantages of bending deformation and to achieve further shortening of the deformation stroke.

[0008] This invention has been made in view of the above circumstances, and aims to provide a shock-absorbing member that is lightweight yet can bend and deform smoothly at joints to exhibit high energy absorption efficiency, and a vehicle body part having this shock-absorbing member. [Means for solving the problem]

[0009] To solve the aforementioned problems, the present invention employs the following means. (1) One aspect of the present invention is: An impact absorbing member comprising a hollow tube and a reinforcement fixedly positioned inside the hollow tube, wherein the member is long in one direction, The hollow tube is made of steel with a tensile strength of 650 MPa to 1600 MPa, and the reinforcement is made of steel with a tensile strength of 590 MPa to 1600 MPa; In a cross-section perpendicular to the longitudinal direction of the impact absorbing member, The hollow tube has a top wall section having a total width W1 (mm) and a plate thickness t1 (mm), and a pair of side wall sections provided on both sides of the top wall section, each having a total width W2 (mm) and a plate thickness t1 (mm). The reinforcement comprises at least one of the following: vertical plates, one end of which is joined to the top wall portion, with a total number of n1 plates and a total plate thickness of t2 (mm); and horizontal plates, the other half of which connects the pair of side wall portions, with a total number of n2 plates and a total plate thickness of t3 (mm). The reinforcement satisfies at least one of the following conditions: a first condition having the vertical plate and the first planar portion width-to-thickness ratio r1 according to the following formula 1 being 10 or more and 50 or less; and a second condition having the horizontal plate and the second planar portion width-to-thickness ratio r2 according to the following formula 2 being 10 or more and 50 or less; The aforementioned hollow tube It has a first part, a second part, and a third part that are arranged in order along the longitudinal direction, The second portion has a bending point. 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 point is set on the top wall of the hollow tube, the top wall at the beginning of the bending deformation tends to sink inward into the hollow tube. If only the first condition is met, the vertical plate continues to support the top wall while resisting the force that would cause it to sink. This suppresses the sinking of the top wall and also suppresses the gap between the pair of side walls that would occur as a result of the sinking of the top wall. In this way, the hollow tube is supported from within by reinforcement. Alternatively, if only the second condition is met, the distance between the pair of side walls is constrained by the horizontal plate. This constraint prevents the top wall from sinking in a way that pushes the space between the pair of side walls apart, thus indirectly supporting the top wall. Therefore, in this case as well, the hollow tube is supported from within by reinforcement. Alternatively, if both the first and second conditions are met, in addition to suppressing the sinking of the top wall, the gap between the pair of side walls is also suppressed. As a result, the synergistic effect of both forces further strengthens the support of the hollow tube from within. Thus, the hollow tube is reinforced at each position along its longitudinal direction by reinforcement. Furthermore, the hollow tube satisfies at least one of the following conditions: the first condition is that the width-to-thickness ratio r1 of the first planar section is 10 or more and 50 or less, and the second condition is that the width-to-thickness ratio r2 of the second planar section is 10 or more and 50 or less. As a result, even if the thickness t1 of the hollow tube is reduced for the purpose of weight reduction, the top wall or side walls will not easily deform out of plane. If out-of-plane deformation occurs at an unintended location, the way in which the compression deformation occurs at that location becomes unstable, so the out-of-plane deformed part may be more prone to breaking or less prone to breaking. As a result, there is a risk that bending deformation may occur at an unintended location of the hollow tube. On the other hand, in this embodiment, at least one of the first and second conditions is satisfied. As a result, out-of-plane deformation of the hollow tube at unintended locations can be suppressed, and the thickness t1 can be reduced to lighten the impact absorbing member. On the other hand, since this shock-absorbing member has a bending point in the second section, the bending strength of the second section is relatively lower than that of the first section and the third section. This relative strength difference, combined with at least one of the first and second conditions described above, allows the shock-absorbing member to bend and deform smoothly at the bending point of the second section. In addition, since the impact energy applied to the shock-absorbing member is absorbed mainly by the reinforcing member as it bends and deforms, the amount of energy absorbed can be increased.

[0011] (2) The impact absorbing member described in (1) above may have the following configuration: The hollow tube comprises a pair of ridges connecting the top wall and the pair of side wall sections; The aforementioned bending point is, A first bead that crosses the boundary between one of the pair of ridge sections and the top wall section, A second bead that crosses the boundary between the other of the pair of ridge sections and the top wall section, It holds. According to the impact absorbing member described in (2) above, by providing the first and second beads, which extend from a pair of ridge sections into the top wall section, as bending initiation points in the second section of the hollow tube, the bending strength of the second section can be reliably reduced compared to the bending strength of the first and third sections, despite the simple configuration. In addition, out-of-plane deformation at unintended locations of the first to third sections is suppressed by the reinforcement provided inside the hollow tube. Therefore, while preventing bending deformation of the hollow tube at unintended locations with the reinforcement, the impact absorbing member can be reliably and smoothly bent using the first and second beads as bending initiation points.

[0012] (3) The impact absorbing member described in (2) above may have the following configuration: The first bead crosses the boundary between one of the pair of ridge portions and one of the pair of side wall portions; The second bead crosses the boundary between the other of the pair of ridge sections and the other of the pair of side wall sections. According to the impact-absorbing member described in (3) above, by extending the first and second beads further into the side walls, the bending strength of the second portion of the hollow tube can be reduced even more reliably than that of the first portion and the third portion. Therefore, the point of fold can be made clearer, and the impact-absorbing member can be deformed by folding more reliably and smoothly.

[0013] (4) In the impact absorbing member described in any one of the above items (1) to (3), The bending point portion may have a through hole or a third bead that is elongated in a direction intersecting the longitudinal direction, formed in at least one of the top wall portion and the pair of side wall portions. According to the shock absorption member described in (4) above, by providing the through hole or the third bead as the starting point of bending in the second part of the hollow tube, the bending strength of the second part can be reliably reduced compared to the bending strength of the first part and the third bending strength while having a simple structure. In addition, out-of-plane deformation at unintended positions in the first to third parts is suppressed by the reinforcement provided in the hollow tube. Therefore, while preventing the bending deformation of the hollow tube at unintended positions by the reinforcement, the shock absorption member can be reliably bent and deformed in a stepped manner with the through hole or the third bead as the starting point of bending.

[0014] (5) In the shock absorption member according to any one of (1) to (3) above, By setting the material tensile strength ratio obtained by dividing the material tensile strength of the second part by the average material tensile strength of the first part and the third part to be 0.5 to 0.9, the starting point of bending may be provided in the second part. According to the shock absorption member described in (5) above, by setting the material tensile strength ratio within the above range, the bending strength of the second part can be made lower than the bending strengths of the first part and the third part. In addition, out-of-plane deformation at unintended positions in the first to third parts is suppressed by the reinforcement provided in the hollow tube. Therefore, while preventing the bending deformation of the hollow tube at unintended positions by the reinforcement, the shock absorption member can be reliably bent and deformed in a stepped manner with the second part of the hollow tube as the starting point of bending.

[0015] (6) In the shock absorption member according to any one of (1) to (3) above, By setting the plate thickness ratio obtained by dividing the plate thickness of the second part by the average plate thickness of the first part and the third part to be 0.5 to 0.9, the starting point of bending may be provided in the second part. 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 and third portions. As a result, the bending strength of the second portion can be made lower than the bending strength of the first and third portions. In addition, out-of-plane deformation at unintended locations of the first to third portions is suppressed by the reinforcement provided inside the hollow tube. Therefore, while preventing bending deformation of the hollow tube at unintended locations with the reinforcement, the impact absorbing member can be reliably and smoothly bent using the second portion of the hollow tube as the bending starting point.

[0016] (7) In the impact absorbing member described in any one of the above items (1) to (3), Each of the first and third portions may be provided with a reinforcing portion along the longitudinal direction. According to the impact-absorbing member described in (7) above, by providing reinforcing parts to both the first and third parts, the bending strength of the first and third parts can be reliably increased compared to the bending strength of the second part, even with a simple configuration. In other words, the bending strength of the hollow tube can be reduced relative to the first and third parts adjacent to it at the second part. Furthermore, out-of-plane deformation at unintended locations of the first to third parts is suppressed by the reinforcement provided inside the hollow tube. Therefore, while preventing bending deformation of the hollow tube at unintended locations with the reinforcement, the impact-absorbing member can be more reliably and smoothly bent using 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 material, or an emboss formed along the longitudinal direction. According to the impact-absorbing member described in (8) above, the bending strength of the first part and the third part can be reliably increased compared to the bending strength of the second part.

[0018] (9) In any one of the above items (1) to (3), the following configuration may be adopted for the impact absorbing member: The aforementioned hollow tube A hat-shaped member having the top wall portion and the pair of side wall portions, It has a plate-shaped member joined to the hat-shaped member and facing the top wall portion; Satisfying both the first and second conditions; In the cross-section perpendicular to the longitudinal direction, The above n1 is 1 and the above n2 is 1, The vertical plate is fixed in a state where it is stretched between the top wall portion and the plate-shaped member. The horizontal plate is fixed between the pair of side wall portions in a state where it intersects with the vertical plate. According to the impact absorbing member described in (9) above, the hollow tube is supported from the inside by a surface formed by the combination of vertical and horizontal plates when viewed in a cross section perpendicular to its longitudinal direction. Therefore, the bending strength of the reinforcement can be increased along its entire length, which not only increases the maximum load (barrier reaction force) but also allows the maximum load to be maintained for a longer period, thereby increasing the amount of energy absorbed.

[0019] (10) In any one of the above items (1) to (3), the following configuration may be adopted for the shock-absorbing member: The aforementioned hollow tube A hat-shaped member having the top wall portion and the pair of side wall portions, It has a plate-shaped member joined to the hat-shaped member and facing the top wall portion; Satisfying both the first and second conditions; In the cross-section perpendicular to the longitudinal direction, The above n1 is 1 and the above n2 is 1, One end of the horizontal plate is joined to one of the pair of side wall sections, and the other end of the horizontal plate is joined to the other of the pair of side wall sections. One end of the vertical plate is joined to the top wall, and the other end of the vertical plate is joined to the horizontal plate at a position between the one end and the other end. According to the impact absorbing member described in (10) above, the hollow tube is supported from the inside by a surface formed by the combination of vertical and horizontal plates when viewed in a cross section perpendicular to its longitudinal direction. Therefore, the bending strength of the reinforcement can be increased along its entire length, which not only increases the maximum load (barrier reaction force) but also allows the maximum load to be maintained for a longer period, thereby increasing the amount of energy absorbed.

[0020] (11) A vehicle body part according to one aspect of the present invention is It is one of the following components on the vehicle body: front side member, rear side member, center pillar, or bumper beam. It has an impact-absorbing member as described in any one of the above items (1) to (3). The body part described in (11) above is equipped with an impact-absorbing member that is lightweight yet folds and deforms smoothly at the desired joints, exhibiting high energy absorption efficiency. Therefore, with this body part, it folds smoothly at the designated joints and achieves the designed amount of energy absorption. Thus, it can meet the current demand for body parts that achieve high energy absorption efficiency with a short deformation stroke. [Effects of the Invention]

[0021] According to the impact-absorbing members of each of the above embodiments of the present invention, they are lightweight yet can bend and deform smoothly, exhibiting high energy absorption efficiency. Furthermore, a vehicle body component equipped with this impact-absorbing member can meet the current need for high energy absorption efficiency with a short deformation stroke. [Brief explanation of the drawing]

[0022] [Figure 1] This is a perspective view of a vehicle body in which impact-absorbing members according to each embodiment of the present invention are applied to the front side member and the rear side member. [Figure 2] This is a perspective view of an impact-absorbing member according to the first embodiment of the present invention. [Figure 3] This figure shows a bead provided on the shock-absorbing member, and is an enlarged perspective view of part A in Figure 2. [Figure 4]This is a schematic diagram illustrating the dimensions of each part of the shock-absorbing member, and is a cross-sectional view of BB in Figure 2. [Figure 5] Figures (a) to (d) are diagrams showing modified examples of the same shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 6] (a) to (e) are diagrams showing other modified examples of the shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 7] Figures (a) to (d) are diagrams showing yet another modification of the same shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 8] (a) to (c) are diagrams showing yet another modification of the same shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 9] Figures (a) to (e) are diagrams showing yet another modification of the same shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 10] Figures (a) to (g) are diagrams showing yet another modification of the same shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 11] Figures (a) to (e) are diagrams showing yet another modification of the same shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 12] This is a perspective view of an impact-absorbing member according to a second embodiment of the present invention. [Figure 13] This is a perspective view of an impact-absorbing member according to a third embodiment of the present invention. [Figure 14] This figure shows a first embodiment of the present invention, and is a perspective view showing an impact absorbing member without reinforcement. [Figure 15] Figure 14 shows the state after bending deformation and the absorbed energy (kJ) at a 180 mm stroke for the impact absorbing member shown, when the bead depth is changed. [Figure 16] This is a perspective view showing the impact absorbing member with reinforcement used in the first embodiment. [Figure 17]Figure 16 shows the state after bending deformation and the absorbed energy (kJ) at a 180 mm stroke for the impact absorbing member shown, when the bead depth is changed. [Figure 18] This figure shows a second embodiment of the present invention, and is a table showing the state of each impact absorbing member before bending deformation, with and without reinforcement, with and without through holes, and with beads provided on the top wall. [Figure 19] Figure 18 is a table showing the state of each impact-absorbing member after bending deformation. [Modes for carrying out the invention]

[0023] The impact-absorbing members according to each embodiment of the present invention and various modified examples thereof will be described below with reference to the drawings. As shown in Figure 1, the impact-absorbing members of each embodiment and each modified example can be used as front side members FM or rear side members RM, which are structural members of an automobile. When the impact-absorbing member is used as a front side member FM, it is positioned on the vehicle forward side FW from the passenger compartment C. On the other hand, when the impact-absorbing member is used as a rear side member RM, it is positioned on the vehicle rear side RW from the passenger compartment C. The impact-absorbing member is a long hollow tube in one direction, and in both cases, whether used as a front side member FM or a rear side member RM, it is positioned so that one end in the longitudinal direction faces the front of the vehicle and the other end in the longitudinal direction faces the rear of the vehicle.

[0024] As will be described in detail later, the impact-absorbing member has a rectangular cross-section perpendicular to its longitudinal direction and comprises a hat-shaped member and a plate-shaped member. The hat-shaped member has a hat apex, which is the top wall, and a pair of side walls connected to both sides of the hat apex, with the cross-section perpendicular to its longitudinal direction. The plate-shaped member is joined to the hat-shaped member and faces the hat apex. The impact-absorbing member absorbs impact force through folding deformation rather than bellows deformation. Hereafter, the area undergoing folding deformation shown in Figure 1 will be denoted by reference numeral 1 and will be illustrated and described as impact-absorbing member 1. Furthermore, the explanation will be illustrated using the case where the trigger for folding deformation (folding initiation point) is set on the top wall.

[0025] [First Embodiment] As shown in Figure 2, the impact absorbing member 1 according to the first embodiment of the present invention is a cylindrical component that is elongated 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 member 10 has a top wall portion 11, a pair of side wall portions 12, and a pair of flange portions 13. The top wall portion 11 forms the apex of the hat-shaped member 10, which has a hat shape when viewed along the center line CL. The top wall portion 11 is a long plate that is elongated in the direction parallel to the center line CL, and its outer width dimension and plate thickness are constant at each position in its extending direction. The outer width dimension here includes the ridge portion EL formed along both side edges of the top wall portion 11. The top wall portion 11 has a flat top surface and a flat bottom surface. Furthermore, the outer width and thickness of the top wall portion 11 do not necessarily have to be constant at each position along the center line CL, and may be slightly varied at each position along the center line CL as required by the component design. Similarly, the upper and lower surfaces of the top wall portion 11 do not necessarily have to be flat, and may have some irregularities as required by the component design.

[0027] The pair of side wall portions 12 have a left wall portion 12a and a right wall portion 12b. The left side wall portion 12a is a vertical wall that is integrally connected to one of the side edges of the top wall portion 11. The angle between the left side wall portion 12a and the top wall portion 11 in a cross section perpendicular to the center line CL may be 90° or an angle slightly larger than 90°. The left side wall portion 12a has a substantially constant width dimension and a substantially constant plate thickness. The left side wall portion 12a has a flat outer surface and a flat inner surface. The right side wall portion 12b is a vertical wall that is integrally connected to the other side edge of the top wall portion 11. The angle between the right side wall portion 12b and the top wall portion 11 in a cross section perpendicular to the center line CL 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 wall portion 12a and the right wall portion 12b are long plates that are elongated 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 their outer height dimension and plate thickness are constant at each position in their extending direction. The outer height dimension here includes the portion of the ridge line EL formed along the upper edges of the left wall portion 12a and the right wall portion 12b. The left wall portion 12a and the right wall portion 12b have a flat outer surface and a flat inner surface. Furthermore, the outer width dimensions and plate thickness of the left wall portion 12a and the right wall portion 12b do not necessarily have to be constant at each position along the center line CL, and may be slightly modified to differ at each position along the center line CL as required by the part design. Similarly, the outer and inner surfaces of the left wall portion 12a and the right wall portion 12b do not necessarily have to be flat, and may have some irregularities as required by the part design.

[0029] The pair of flange portions 13 have 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 wall portion 12a. The left flange portion 13a is a strip-shaped plate having a substantially constant width and substantially constant 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 strip-shaped plate having a substantially constant width and substantially constant 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. Furthermore, the width and thickness of the left flange portion 13a and the right flange portion 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 necessary for the part design. Similarly, the upper and lower surfaces of the left flange portion 13a and the right flange portion 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 wall portion 12a, and the right wall portion 12b results in a roughly trapezoidal shape in the cross-section perpendicular to the center line CL. Furthermore, by combining the left flange portion 13a and the right flange portion 13b with this combination, a hat-shaped member 10 is constructed in which the cross-section perpendicular to the longitudinal direction is hat-shaped. This hat-shaped member 10 is obtained by press-forming a die-cut sheet metal. The material of the hat-shaped member 10 is metal, and high-strength steel plate with a tensile strength of 650 MPa to 1600 MPa can be suitably used.

[0031] As shown in Figure 2, a ridge section EL parallel to the center line CL is formed between the top wall section 11 and the left wall section 12a. A ridge section EL parallel to the center line CL is also formed between the top wall section 11 and the right wall section 12b. These pairs of ridge sections EL are parallel to each other and also parallel to the center line CL.

[0032] As shown in Figure 3, each ridge section EL has a substantially constant width dimension, and its cross-section perpendicular to its longitudinal direction is curved in an arc shape across its entire width. Each ridge section EL has one side edge ELa connected to the top wall section 11 and the other side edge ELb connected to the left wall section 12a or the right wall section 12b. While each ridge section EL has an arc-shaped cross-section, the top wall section 11, the left wall section 12a, and the right wall section 12b each have a flat cross-sectional shape. Therefore, from the perspective of each ridge section EL, one side edge ELa and the other side edge ELb are the boundaries (end of the arc) where the cross-sectional shape changes from an arc to a flat cross-section.

[0033] As shown in Figures 2 and 3, a second bead Bb is formed at one point on the ridge line EL connecting the top wall 11 and the right side wall 12b. The second bead Bb crosses one of the side edges ELa, which is the boundary between the top wall 11 and the ridge line EL. In other words, the second bead Bb is formed to protrude from the ridge line EL toward the top wall 11. Furthermore, the second bead Bb is formed to protrude from the ridge line EL toward the right side wall 12b. Therefore, the second bead Bb is formed to extend from the top wall 11 through the ridge line EL to the right side wall 12b.

[0034] Similarly, a first bead Ba is formed at one location on the ridge EL connecting the top wall portion 11 and the left side wall portion 12a. The first bead Ba traverses one of the side edges ELa, which is the boundary between the top wall portion 11 and the ridge EL. That is, the first bead Ba is formed to protrude outwards from the ridge EL toward the top wall portion 11. Furthermore, the first bead Ba is formed to protrude outwards from the ridge EL toward the left side wall portion 12a. Therefore, the first bead Ba is formed to extend from the top wall portion 11 through the ridge EL toward the left side wall portion 12a.

[0035] The first bead Ba and the second bead Bb are rhombic in front view, and their diagonal length can be exemplified as 11 mm to 23 mm. The depth of the outer surface of the first bead Ba and the second bead Bb can be exemplified as 7 mm to 15 mm. The first bead Ba and the second bead Bb may be formed simultaneously during press working when forming the hat-shaped member 10 from a metal sheet, or they may be formed as a post-processing step 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 thickness is slightly thinner than the surrounding thickness and they are work-hardened. The inner surfaces of the first bead Ba and the second bead Bb are also concave towards the inside of the cylindrical body 30, just as their outer surfaces are concave. The shapes of the first bead Ba and the second bead Bb in a front view are not limited to rhombuses, but may also be circular, elliptical, rectangular, or polygonal. The shapes and dimensions of the first bead Ba and the second bead Bb are preferably the same, but they may differ slightly 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. These two beads form a bending point on 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 with a tensile strength of 650 MPa to 1600 MPa can be suitably used. The plate-shaped member 20 has a flat top surface and a flat bottom surface. The plate-shaped member 20 is welded to the left flange portion 13a and the right flange portion 13b at both side edges. This forms a closed cross section between the hat-shaped member 10 and the plate-shaped member 20. In this way, the hat-shaped member 10 and the plate-shaped member 20 constitute the cylindrical body 30. Furthermore, the width and thickness of the plate-like member 20 do not necessarily have to be constant at each position along the center line CL, and may be slightly changed at each position along the center line CL as required by the 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 by the 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 point along its longitudinal direction, so the bending strength at this position is relatively lower than the bending strength of the adjacent points along its longitudinal direction. That is, as shown in Figure 2, if the part where the pair of first beads Ba and second beads Bb are formed is designated as the second part R2, and the parts on either side of it are designated as the first part R1 and the third part R3, then a bending initiation point is formed on the top wall portion 11 of the second part R2. When a load is applied to the impact absorbing member 1 along its axial direction, the impact absorbing member 1 can be deformed in a smooth, segmented manner at the bending initiation point of the second part R2.

[0038] Next, I will explain Reinforce 40. As shown in Figure 2, the reinforcement 40 has vertical plates 41 and horizontal plates 42. The vertical plate 41 is a single strip-shaped plate having a substantially constant width and substantially constant thickness, and is elongated 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 single strip-shaped plate, when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1, it appears to be divided into two by a horizontal plate 42 that intersects it at the center position in the height direction. The upper and lower parts of this divided vertical plate 41 have the same height, thickness, and length dimensions. The horizontal plate 42 is a single strip-shaped plate having a substantially constant width and substantially constant thickness, and is elongated in the direction along the center line CL. The horizontal plate 42 has a flat top surface and a flat bottom surface. Although the horizontal plate 42 is a single strip-shaped plate, when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1, it appears to be divided into two by a vertical plate 41 that intersects it at the center in the width direction. The left and right portions of this divided 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 joining of the vertical plate 41 and the horizontal plate 42 can be done, for example, by welding. When viewed in a cross-section perpendicular to the longitudinal direction of the impact-absorbing member 1, the upper end (one end) of the vertical plate 41 is joined to the center of the width direction of the lower surface of the top wall portion 11, and the lower end is joined to the center of the width direction of the upper surface of the plate-shaped member 20. In this way, the top wall portion 11 is supported mainly by the vertical plate 41 and the plate-shaped member 20. When viewed in a cross-section perpendicular to the longitudinal direction of the impact-absorbing member 1, the left end (one end) of the horizontal plate 42 is joined to the center of the height direction on the inner surface of the left wall portion 12a, and the right end (the other end) is joined to the center of the height direction on the inner surface of the right wall portion 12b. In this way, the space between the left wall portion 12a and the right wall portion 12b is restrained so that their distance from each other remains constant.

[0040] As the reinforcement 40, a high-strength steel plate with a tensile strength of 650 MPa to 1600 MPa can be suitably used. That is, the reinforcement 40 can be manufactured by arranging a vertical plate 41 and a horizontal plate 42 made of the high-strength steel plate in a crisscross pattern and then welding them together. Furthermore, the impact absorbing member 1 can be manufactured by welding this reinforcement 40 inside 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 Figure 2.

[0041] The impact absorbing member 1, comprising the reinforcement 40 and cylindrical body 30 described above, satisfies both of the following conditions to prevent unintended out-of-plane deformation of the cylindrical body 30: (1) it has a vertical plate 41 and the first planar portion width-to-thickness ratio r1 according to the following formula 1 is 10 or more and 50 or less; and (2) it has a horizontal plate 42 and the second planar portion width-to-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] Equations 1 and 2 will be explained below with reference to Figure 4, but first, let's explain Figure 4. Figure 4 is a schematic diagram illustrating the dimensions of each part of the impact absorbing member 1, and corresponds to the BB cross-section of the third part R3 in Figure 2. Therefore, the first bead Ba and the second bead Bb are not shown in Figure 4. In addition, Figure 4 is illustrated as follows to make the following explanation easier to understand. First, the curvature of the circular arc section formed by each ridge section EL is shown to be large. Each ridge section EL is a corner connecting the top wall section 11 with the left wall section 12a and the right wall section 12b, respectively, and has a predetermined radius of curvature. Furthermore, in Figure 4, the pair of left-side wall sections 12a and right-side wall sections 12b are parallel to each other. Also, the plate-like member 20 and the left flange section 13a and right flange section 13b are integrated by omitting the joint. Furthermore, the position of the vertical board 41 in the left-right direction is slightly offset from the position of the center line CL. Similarly, the position of the horizontal board 42 in the up-down direction is slightly offset from the position of the center line CL. In addition, the thickness of the vertical board 41 and the thickness of the horizontal board 42 are different from each other.

[0044] Equations 1 and 2 will be explained with reference to Figure 4. First, the symbol W1 in Equation 1 is the total width dimension (in mm) of the flat top wall portion 11, which has an upper surface that is on the inside of the bend in the rectangular cylindrical body 30. This total width dimension W1 of the flat portion does not include the curved portion (rounded portion) including the ridge portion EL. For example, if the width of the flat portion of the top wall portion 11 is w1 (mm) and w2 (mm) with respect to the joint position with the upper edge of the vertical plate 41, then W1 = w1 + w2 + t2. Here, the thickness of the top wall portion 11 within the range of the total width dimension W1 is t1 (mm), and the total plate thickness of the vertical plate 41 is t2 (mm).

[0045] The symbol W2 represents the total width (in mm) of the flat left wall section 12a and the flat right wall section 12b, which are connected to both sides of the top wall section 11 via a pair of curved sections. This total width W2 of the flat section does not include the curved section (rounded section) including the ridge section EL, or the curved section (rounded section) formed between the left flange section 13a and the right flange section 13b, which are not shown. For example, if the width of the flat section of each side wall section 12 is w3 (mm) and w4 (mm) with respect to the joint position with the horizontal plate 42, then W2 = w3 + w4 + t3. Within the range of this total width W2 of the flat section, the thickness of the left wall section 12a and the right wall section 12b is t1 (mm), the same as that of the top wall section 11. The total thickness of the horizontal plate 42 is t3 (mm).

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

[0047] The reference numeral n1 in Equation 1 represents the total number of vertical plates 41 in the reinforcement 40, which is 1 in the impact absorbing member 1 of this embodiment (n1=1). If there are multiple vertical plates 41 and the thickness of each vertical plate 41 differs from that of the others, then n1 will be the total number of such plates, and the total plate thickness t2 will be the sum of the thicknesses of all the vertical plates 41. The symbol n2 in Equation 2 represents the total number of horizontal plates 42 in the reinforcement 40, which is 1 (n2=1) in the impact absorbing member 1 of this embodiment. If there are multiple horizontal plates 42 and the thickness of each horizontal plate 42 differs from that of the others, then n2 will be the total number of such plates, and the total plate thickness t3 will be the sum of the thicknesses of all the horizontal plates 42. Therefore, the first flat section width-to-thickness ratio r1 means the average flat section width of the top wall section 11 in the area not supported by the vertical plates 41, divided by the thickness t1 of the top wall section 11. Also, the second flat section width-to-thickness ratio r2 means the average flat section width of the side wall section 12 in the area not supported by the horizontal plates 42, divided by the thickness t1 of the side wall section 12.

[0048] By providing the reinforcement 40 and satisfying the first condition that the first planar section width-to-thickness ratio r1, determined by Equation 1, is between 10 and 50, out-of-plane deformation at unintended locations can be prevented in the top wall section 11. Similarly, by satisfying the second condition that the second planar section width-to-thickness ratio r2, determined by Equation 2, is between 10 and 50, out-of-plane deformation at unintended locations can be prevented in each side wall section 12. Either one of these first and second conditions may be satisfied, or both may be satisfied.

[0049] Now, let's explain out-of-plane deformation. Under the above cross-sectional structure, one possible means of 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 conventional structure without reinforcement 40, the wide flat portion shown in the overall width dimension W1 and the wide flat portion shown in the overall width dimension W2 are not supported, making them prone to out-of-plane deformation. Out-of-plane deformation here refers to a type of deformation in which the wall portion undulates inward and outward from the cylindrical body 30 in the cross-section shown in Figure 4. When the plate thickness t1 is reduced, it becomes unclear at what point in 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 bending point as the bending starting point. However, if out-of-plane deformation occurs in the cylindrical body 30, that part may become easier or harder to break. As a result, there is a risk that the desired amount of energy absorption cannot be obtained because the bending deformation cannot be performed as predetermined.

[0050] In contrast, the impact-absorbing member 1 of this embodiment, as shown in the cross-section in Figure 4, divides the inside of the cylindrical body 30, which in the conventional configuration had a single large opening cross-section, into multiple (four) small opening cross-sections by a combination of vertical plates 41 and horizontal plates 42. Of course, even just the fact that the top wall portion 11 is supported by the vertical plates 41 can be said to suppress out-of-plane deformation of the top wall portion 11 more than in the conventional structure. However, the impact-absorbing member 1 of this embodiment does more than that; after dividing its opening cross-section into small sections by a combination of vertical plates 41 and horizontal plates 42, it further defines the range of the first planar portion width-to-thickness ratio r1 according to Equation 1 and the range of the second planar portion width-to-thickness ratio r2 according to Equation 2 for the area of ​​the top wall portion 11 that is not supported by the vertical plates 41 and the area of ​​the left wall portion 12a and the right wall portion 12b that is not supported by the horizontal plates 42, respectively. This makes it possible to reduce the thickness t1 of the plate while suppressing out-of-plane deformation. Therefore, while the impact absorbing member 1 can be deformed in a precise manner at the desired position to achieve high energy absorption efficiency, it is also possible to reduce its weight.

[0051] This point will be explained 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 bending point is set on the top wall portion 11 of the cylindrical body 30, the top wall portion 11 at the beginning of the bending deformation tends to sink inward into the cylindrical body 30. The vertical plate 41 continues to support the top wall portion 11 while resisting this sinking force. This suppresses the sinking of the top wall portion 11. In addition, the gap between the left wall portion 12a and the right wall portion 12b is constrained by the horizontal plate 42. This constraint prevents the top wall portion 11 from sinking in a way that pushes the gap between the left wall portion 12a and the right wall portion 12b apart, thus indirectly supporting the top wall portion 11. In this way, the synergistic effect of the support of the top wall portion 11 by the vertical plate 41 and the constraint between the left wall portion 12a and the right wall portion 12b by the horizontal plate 42 results in the cylindrical body 30 being firmly supported from the inside by the reinforcement 40.

[0052] Thus, the cylindrical body 30 is reinforced at each position along its longitudinal direction by the reinforcement 40. Furthermore, the cylindrical body 30 satisfies both of the following conditions: the first condition is that the width-to-thickness ratio r1 of the first planar section is 10 or more and 50 or less, and the second condition is that the width-to-thickness ratio r2 of the second planar section is 10 or more and 50 or less. Here, if the width-to-thickness ratio r1 of the first planar section or the width-to-thickness ratio r2 of the second planar section is less than 10, the plate thickness is too thick, and the weight reduction effect of the reinforcement 40 is difficult to obtain. On the other hand, if the width-to-thickness ratio r1 of the first planar section or the width-to-thickness ratio r2 of the second planar section is greater than 50, the plate thickness becomes too thin, and the effect of preventing out-of-plane deformation by the reinforcement 40 is difficult to obtain.

[0053] As described above, if out-of-plane deformation occurs at an unintended location, the way in which compressive deformation occurs at that location becomes unstable, making the out-of-plane deformed area more prone to breaking or less prone to breaking. As a result, there is a risk that bending deformation may occur at an unintended location in the cylindrical body 30. On the other hand, by satisfying both the first and second conditions above, the impact absorbing member 1 can suppress out-of-plane deformation of the cylindrical body 30 at an unintended location, thus allowing for a reduction in plate thickness t1 and weight reduction.

[0054] Furthermore, since the impact absorbing member 1 is equipped with the bending initiation points shown in Figures 2 and 3, the bending strength of the second portion R2 is relatively lower than that of the first portion R1 and the third portion R3. This allows the impact absorbing member 1 to bend and deform smoothly, with the second portion R2 as the bending initiation point. In addition, since the impact energy applied to the impact absorbing member 1 is absorbed mainly by the reinforcement 40 as it bends and deforms, starting from the second portion R2, the amount of energy absorbed can be increased.

[0055] In the above embodiment, an example was given in which a reinforcement 40 having a "+" shape is fixedly placed inside the cylindrical body 30. However, various other configurations illustrated in Figures 5 to 11 can also be adopted. Figures 5 to 11 correspond to the BB cross-sectional view in Figure 2.

[0056] In Figure 5(a), the horizontal plate 42 divides the internal space of the cylindrical body 30 into two sections vertically. That is, the vertical plate 41 is omitted, and the horizontal plate 42 constrains the distance between the left wall portion 12a and the right wall portion 12b. A flange is formed on one of the side edges of the horizontal plate 42, and this flange is fixed to the left wall portion 12a by spot welding in a state of surface contact. Similarly, a flange is formed on the other side edge of the horizontal plate 42, and this flange is fixed to the right wall portion 12b by spot welding in a state of surface contact. Figure 5(b) also shows that the internal space of the cylindrical body 30 is divided vertically into two sections by the horizontal plate 42. That is, the vertical plate 41 is omitted, and the horizontal plate 42 restrains the distance between the left wall portion 12a and the right wall portion 12b. One side edge of the horizontal plate 42 is fixed to the left wall portion 12a by laser arc welding while abutting against it. Similarly, the other side edge of the horizontal plate 42 is fixed to the right wall portion 12b by laser arc welding while abutting against it.

[0057] In Figure 5(c), the vertical plate 41 divides the internal space of the cylindrical body 30 into two sections in the left-right direction. 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 in a state of surface contact. Similarly, a flange is formed at the lower end of the vertical plate 41, and this flange is fixed to the plate-shaped member 20 by laser arc welding in a state of surface contact. Figure 5(d) also shows that the internal space of the cylindrical body 30 is divided into two halves by the 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 to the top wall portion 11 by laser arc welding while abutting against it. Similarly, the lower end of the vertical plate 41 is fixed to the plate-shaped member 20 by laser arc welding while abutting against it.

[0058] In Figure 6(a), the internal space of the cylindrical body 30 is divided into three sections vertically by two horizontal plates 42. That is, the vertical plate 41 is omitted, and the distance between the left wall portion 12a and the right wall portion 12b is constrained by the two horizontal plates 42. A flange is formed on one side edge of each horizontal plate 42, and these flanges are fixed to the left wall portion 12a by spot welding while in surface contact. Similarly, a flange is formed on the other side edge of each horizontal plate 42, and these flanges are fixed to the right wall portion 12b by spot welding while in surface contact. Figure 6(b) also shows how the internal space of the cylindrical body 30 is divided into three sections vertically by two horizontal plates 42. That is, the vertical plate 41 is omitted, and the distance between the left wall portion 12a and the right wall portion 12b is constrained by the two horizontal plates 42. One side edge of each horizontal plate 42 is fixed to the left wall portion 12a by laser arc welding while abutting against it. Similarly, the other side edge of each horizontal plate 42 is fixed to the right wall portion 12b by laser arc welding while abutting against it.

[0059] In Figure 6(c), the internal space of the cylindrical body 30 is divided into three sections horizontally by two vertical plates 41. That is, the horizontal plate 42 is omitted, and the top wall 11 is supported by the two vertical plates 41. The upper ends of each vertical plate 41 are connected, and this connected portion is fixed to the top wall 11 by spot welding in a surface-jointed state. On the other hand, flanges are formed at the lower ends of each vertical plate 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 were constructed by press-forming a single steel plate into an inverted U-shape in cross-section, but two separate vertical plates 41 may also be used. Figure 6(d) also shows how the internal space of the cylindrical body 30 is divided into three sections horizontally by two vertical plates 41. That is, the horizontal plate 42 is omitted, and the top wall 11 is supported by the two vertical plates 41. A flange is formed at the upper end of each vertical plate 41, and these flanges are fixed to the top wall 11 by spot welding in a surface-jointed state. On the other hand, 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. In this example, the two vertical plates 41 were constructed by press-forming a single steel plate into a U-shape in cross-section, but two separate vertical plates 41 may also be used.

[0060] Figure 6(e) also shows that the internal space of the cylindrical body 30 is divided into three sections horizontally by two vertical plates 41. That is, the horizontal plate 42 is omitted, and the top wall 11 is supported by the two vertical plates 41. The upper ends of each vertical plate 41 are connected, and this connected portion is fixed to the top wall 11 by spot welding in a surface-jointed state. On the other hand, 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. The space between the lower ends of the two vertical plates 41 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] In Figure 7(a), the internal space of the cylindrical body 30 is divided into three sections by a combination of one vertical plate 41 and one horizontal plate 42. Specifically, one side edge of the horizontal plate 42 is fixed to the left wall portion 12a by laser arc welding while abutting against it. Similarly, the other side edge of the horizontal plate 42 is fixed to the right wall portion 12b by laser arc welding while abutting against it. Furthermore, the upper end of the vertical plate 41 is fixed by laser arc welding while abutting against the top wall portion 11. The height dimension of the vertical plate 41 is approximately half that of the configuration shown in Figure 2, and its lower end is fixed by laser arc welding while abutting against the center of the width direction of the horizontal plate 42. In this way, the internal space of the cylindrical body 30 is divided into three parts: two spaces partitioned by the top wall portion 11, the left side wall portion 12a and the right side wall portion 12b, the vertical plate 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.

[0062] Figure 7(b) also shows how the internal space of the cylindrical body 30 is divided into three sections by a combination of one vertical plate 41 and one horizontal plate 42. Specifically, a flange is formed on one of the side edges of the horizontal plate 42, and this flange is fixed to the left side wall portion 12a by spot welding in a state of surface contact. Similarly, a flange is formed on the other side edge of the horizontal plate 42, and this flange is fixed to the right side wall portion 12b by spot welding in a state of surface contact. Furthermore, 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 laser arc welding while in surface contact with it. The height dimension of the vertical plate 41 is about half that of the form shown in Figure 2, and a flange is formed at its lower end, and this flange is fixed to the horizontal plate 42 by spot welding while in surface contact with the widthwise center position. In this way, the internal space of the cylindrical body 30 is divided into three parts: two spaces partitioned by the top wall portion 11, the left side wall portion 12a and the right side wall portion 12b, the vertical plate 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.

[0063] In Figure 7(c), the internal space of the cylindrical body 30 is divided into three sections by a combination of one vertical plate 41 and one horizontal plate 42. Specifically, one side edge of the horizontal plate 42 is fixed to the left wall portion 12a by laser arc welding while abutting against it. Similarly, the other side edge of the horizontal plate 42 is fixed to the right wall portion 12b by laser arc welding while abutting against it. Furthermore, the upper end of the vertical plate 41 is fixed by laser arc welding while abutting against the center of the width direction of the horizontal plate 42. The height dimension of the vertical plate 41 is approximately half that of the configuration shown in Figure 2, and its lower end is fixed by laser arc welding while abutting against the center of the width direction of the plate-shaped member 20. In this way, the internal space of the cylindrical body 30 is divided into three parts: one space partitioned by the top wall 11, the left side wall 12a and the right side wall 12b and the horizontal plate 42, and two spaces partitioned by the horizontal plate 42, the left side wall 12a and the right side wall 12b, the vertical plate 41 and the plate-shaped member 20.

[0064] Figure 7(d) also shows how the internal space of the cylindrical body 30 is divided into three sections by a combination of one vertical plate 41 and one horizontal plate 42. Specifically, a flange is formed on one of the side edges of the horizontal plate 42, and this flange is fixed to the left side wall portion 12a by spot welding in a state of surface contact. Similarly, a flange is formed on the other side edge of the horizontal plate 42, and this flange is fixed to the right side wall portion 12b by spot welding in a state of surface contact. Furthermore, a flange is formed at the upper end of the vertical plate 41, and this flange is fixed by spot welding while abutting against the center of the width direction of the horizontal plate 42. The height dimension of the vertical plate 41 is about half that of the form shown in Figure 2, and a flange is formed at its lower end, and this flange is fixed by laser arc welding while in surface contact with the center of the width direction of the plate-shaped member 20. In this way, the internal space of the cylindrical body 30 is divided into three parts: one space partitioned by the top wall 11, the left side wall 12a and the right side wall 12b and the horizontal plate 42, and two spaces partitioned by the horizontal plate 42, the left side wall 12a and the right side wall 12b, the vertical plate 41 and the plate-shaped member 20.

[0065] In Figure 8(a), the internal space of the cylindrical body 30 is divided into four sections by the combination of two vertical plates 41 and one horizontal plate 42. In this example, the vertical plates 41 and a portion of the horizontal plate 42 are integrally formed by press-forming a single steel plate. A flange is formed on one of the side edges of the horizontal plate 42, and this flange is fixed to the left side wall portion 12a by spot welding in surface contact with it. Similarly, a flange is formed on the other side edge of the horizontal plate 42, and this flange is fixed to the right side wall portion 12b by spot welding in surface contact with it. The horizontal plate 42 includes a left portion joined to the left side wall portion 12a and a right portion joined to the right side wall portion 12b, as well as a central portion that connects these left and right portions which are spaced apart from each other. This central portion is a separate part and is fixed to the left and right portions by spot welding, respectively. The upper ends of the two vertical plates 41 are joined to a flange that is surface-jointed to the center of the top wall 11 in the width direction. This flange is joined to the top wall 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 parts: three spaces partitioned by the top wall 11, the left side wall 12a and the right side wall 12b, two vertical plates 41 and a horizontal plate 42, and one space partitioned by the horizontal plate 42, the left side wall 12a and the right side wall 12b and a plate-like member 20.

[0066] Figure 8(b) also shows how the internal space of the cylindrical body 30 is divided into four sections by the combination of two vertical plates 41 and one horizontal plate 42. In this example as well, the vertical plates 41 and a portion of the horizontal plate 42 are integrally formed by press-forming a single steel plate. A flange is formed on one of the side edges of the horizontal plate 42, and this flange is fixed to the left side wall portion 12a by spot welding in surface contact with it. Similarly, a flange is formed on the other side edge of the horizontal plate 42, and this flange is fixed to the right side wall portion 12b by spot welding in surface contact with it. The horizontal plate 42 includes a left portion joined to the left side wall portion 12a and a right portion joined to the right side wall portion 12b, as well as a central portion that connects these left and right portions which are spaced apart from each other. This central portion is a separate part and is fixed to the left and right portions by spot welding, respectively. The lower ends of the two vertical plates 41 are joined to a flange that is surface-jointed to the center of the plate-shaped member 20 in the width direction. 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 parts: one space partitioned by the top wall 11, the left side wall 12a and the right side wall 12b and the horizontal plate 42, and three spaces partitioned by the horizontal plate 42, the left side wall 12a and the right side wall 12b, the two vertical plates 41 and the plate-like member 20.

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

[0068] In Figure 9(a), the internal space of the cylindrical body 30 is divided into four sections by a combination of one vertical plate 41 and one horizontal plate 42. Specifically, one side edge of the horizontal plate 42 is fixed to the left wall portion 12a by laser arc welding while abutting against it. Similarly, the other side edge of the horizontal plate 42 is fixed to the right wall portion 12b by laser arc welding while abutting against it. Furthermore, the upper end of the vertical plate 41 is fixed to the top wall portion 11 by laser arc welding while abutting against it. Similarly, the lower end of the vertical plate 41 is fixed to the plate-shaped member 20 by laser arc welding while abutting against it. The vertical plate 41 is joined to the horizontal plate 42 by laser arc welding at a position that intersects (orthogonal to) the horizontal plate 42 at its center in the width direction. In this way, the internal space of the cylindrical body 30 is divided into four spaces, each partitioned by the top wall 11, the left side wall 12a and the right side wall 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20.

[0069] In the example shown in Figure 9(b), the internal space of the cylindrical body 30 is divided into four sections by a combination of one vertical plate 41 and one horizontal plate 42. Specifically, a flange is formed on one of the side edges of the horizontal plate 42, and this flange is fixed to the left side wall portion 12a by spot welding while in surface contact with it. Similarly, a flange is formed on the other side edge of the horizontal plate 42, and this flange is fixed to the right side wall portion 12b by spot welding while in surface contact with it. Furthermore, 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 laser arc welding while in surface contact with it. Similarly, a flange is formed at the lower end of the vertical plate 41, and this flange is fixed to the plate-shaped member 20 by laser arc welding while in surface contact with it. In this way, the internal space of the cylindrical body 30 is divided into four spaces, each partitioned by the top wall 11, the left side wall 12a and the right side wall 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20.

[0070] In the example shown in Figure 9(c), the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, the hat-shaped member 10 is formed by combining a first member whose cross-sectional shape perpendicular to its longitudinal direction is substantially inverted U-shaped (or narrow hat-shaped), and a second member which is L-shaped. Of this first member, the upper wall portion forms part of the top wall portion 11. Furthermore, of the pair of vertical wall portions provided in the first member, one is a vertical plate 41 and the other is a right-side wall portion 12b. Flanges are formed at the lower ends of both the vertical plate 41 and the right-side wall portion 12b. The flange formed at the lower end of the vertical plate 41 is fixed to the plate-like member 20 by laser arc welding while in surface contact. On the other hand, the flange formed at the lower end of the right-side wall portion 12b is fixed to the plate-like member 20 by spot welding while in surface contact.

[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 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 to the upper end of the vertical wall portion of the first member by laser arc welding in a state of surface contact. In addition, a flange is formed on the lower end of the second member, and this flange is fixed to the plate-shaped member 20 by spot welding in a state of surface contact. A flange is formed on one of the side edges of the horizontal plate 42, and this flange is fixed to the left side wall portion 12a by spot welding in a surface contact state. Similarly, a flange is formed on the other side edge of the horizontal plate 42, and this flange is fixed to the right side wall portion 12b by spot welding in a surface contact state. The vertical plate 41 is joined to the horizontal plate 42 by laser arc welding at a position that intersects (orthogonal to) the horizontal plate 42 at its widthwise center position. In this way, the internal space of the cylindrical body 30 is divided into four spaces, each partitioned by the top wall 11, the left side wall 12a and the right side wall 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20.

[0072] In the example shown in Figure 9(d), the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, the cylindrical body 30 is formed by combining a pair of angle members, each having an L-shaped cross-section perpendicular to its longitudinal direction, to create a rectangular closed cross-sectional space. Specifically, a flange is formed on only one of the two end edges of each angle member. These flanges are then fixed to the other angle member, which is the connection partner, by spot welding while in surface contact. By fixing these two flange portions to the other, the closed cross-sectional space is formed between the two angle members.

[0073] Then, within the closed cross-sectional space, a pair of smaller first and second angle members are combined in a "+" shape to form a vertical plate 41 and a horizontal plate 42. The first angle member has a roughly L-shaped cross-section perpendicular to the longitudinal direction, with flanges formed on each of its end edges. One of these flanges is fixed to the top wall 11 in surface contact by spot welding, and the other is fixed to the right side wall 12b in surface contact by spot welding. The second angle member also has a roughly L-shaped cross-section perpendicular to the longitudinal direction, with flanges formed on each of its end edges. One of these flanges is fixed to the left side wall 12a in surface contact by spot welding, and the other is fixed to the plate-like member 20 in surface contact by spot welding. In addition, a recess is formed in the corner of the second angle member, and the corner of the first angle member is fixed to this recess by adhesive. Therefore, in this example, one vertical board 41 is formed by combining the vertical wall of the first angle member and the vertical wall of the second angle member. In addition, one horizontal board 42 is formed by combining the horizontal wall of the first angle member and the horizontal wall of the second angle member. In this way, the internal space of the cylindrical body 30 is divided into four spaces, each partitioned by the top wall 11, the left side wall 12a and the right side wall 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20.

[0074] In the example shown in Figure 9(e), the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, the cylindrical body 30 is formed by combining four angle members, each having an L-shaped cross-section perpendicular to its longitudinal direction. Flanges are formed on both ends of each angle member. Furthermore, a reinforcement 40 comprising a vertical plate 41 and a horizontal plate 42 is formed by laser arc welding to fix two flat plate materials in a position where they intersect (orthogonally) at their widthwise center. Then, a cylindrical body 30 comprising a top wall 11, a left side wall 12a, a right side wall 12b, and a plate-like member 20 is formed by spot welding the upper and lower ends of the vertical plate 41 and the left and right ends of the horizontal plate 42 while sandwiched between the flanges of the four angle materials, so that the reinforcement 40 is positioned in the center. In this way, the internal space of the cylindrical body 30 is divided into four spaces, each partitioned by the top wall 11, the left side wall 12a and the right side wall 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20.

[0075] In the example shown in Figure 10(a), the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, a reinforcement 40 comprising a vertical plate 41 and a horizontal plate 42 is formed by joining two angle members at their respective corners using spot welding. Specifically, two angle members are prepared, each having a roughly L-shaped cross-section perpendicular to the longitudinal direction and chamfered corners. These angle members are then joined by spot welding with their chamfered edges in surface contact. As a result, the wall portion of one angle member and the wall portion of the other angle member become parallel to each other, forming the vertical plate 41. Similarly, the other wall portion of one angle member and the other wall portion of the other angle member become parallel to each other, forming the horizontal plate 42. Then, the edges of each angle member are joined by laser arc welding while abutting them against the top wall 11, the left wall 12a, the right wall 12b, and the plate-like member 20, respectively. 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.

[0076] In the example shown in Figure 10(b), the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, a reinforcement 40 comprising a vertical plate 41 and a horizontal plate 42 is formed by spot welding the corners of two angle members. Specifically, two angle members are prepared, each having a roughly L-shaped cross-section perpendicular to the longitudinal direction and chamfered corners. A flange is formed on one of the pair of edges of each angle member. These angle members are joined by spot welding with their chamfered edges in surface contact. As a result, the wall portion of one angle member and the wall portion of the other angle member become parallel to each other, forming a vertical plate 41. Similarly, the other wall portion of one angle member and the other wall portion of the other angle member become parallel to each other, forming 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 wall portion 12a and the right wall portion 12b. In addition, the edges of the reinforcement 40 that do not have flanges are joined by laser arc welding with the top wall portion 11 and the plate-like member 20 abutted against them. 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.

[0077] In the example shown in Figure 10(c), the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, a reinforcement 40 comprising a vertical plate 41 and a horizontal plate 42 is formed by spot welding the nearby side surfaces of the corners of two angle members. Specifically, two angle members with a roughly L-shaped cross-section perpendicular to the longitudinal direction are prepared. These angle members are then joined by spot welding with the nearby side surfaces of their corners overlapping and in surface contact. As a result, the wall of one angle member and the wall of the other angle member become parallel to each other, forming the vertical plate 41. Similarly, the other wall of one angle member and the other wall of the other angle member become parallel to each other, forming the horizontal plate 42. Then, the edges of each angle member are joined by laser arc welding while abutting them against the top wall 11, the left wall 12a, the right wall 12b, and the plate-like member 20, respectively. 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.

[0078] In the example shown in Figure 10(d), the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, a reinforcement 40 comprising a vertical plate 41 and a horizontal plate 42 is formed by spot welding the corners of two angle members together. Specifically, two angle members are prepared, each having a roughly L-shaped cross-section perpendicular to the longitudinal direction. A flange is formed on one of the pair of edges of each angle member. These angle members are then joined by spot welding with their sides near each other's corners overlapping and in surface contact. As a result, the wall of one angle member and the wall of the other angle member become parallel to each other, forming the vertical plate 41. Similarly, the other wall of one angle member and the other wall of the other angle member become 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 wall portion 12a and the right wall portion 12b. In addition, the edges of the reinforcement 40 that do not have flanges are joined by laser arc welding with the top wall portion 11 and the plate-like member 20 abutted against them. 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.

[0079] In the example shown in Figure 10(e), the internal space of the cylindrical body 30 is divided into four sections by combining one vertical plate 41 and one horizontal plate 42. In this example, a reinforcement 40 comprising vertical plates 41 and horizontal plates 42 is formed by spot welding the corners of one angle material and one pressed sheet metal to each other. Specifically, one angle material has a roughly L-shaped cross-section perpendicular to the longitudinal direction, and one pressed sheet metal has a roughly S-shaped cross-section due to being bent at right angles at two points in the width direction. Flanges are formed on both of the pair of edges of the angle material. Similarly, flanges are formed on both of the pair of edges of the pressed sheet metal.

[0080] The side surfaces near the corners of the angle material and the side surfaces near the corners of the pressed sheet are joined by laser arc welding while in surface contact with each other. As a result, the wall portion of the angle material and the wall portion of the pressed sheet become parallel to each other, forming a vertical plate 41. Similarly, the other wall portions of the angle material and the other wall portions of the pressed sheet become parallel to each other, forming a horizontal plate 42. Then, one flange of the angle material is joined to the top wall portion 11 by spot welding while in surface contact, and the other flange is joined to the right side wall portion 12b by spot welding while in surface contact. In addition, one flange of the press-formed plate is joined to the left side wall portion 12a by spot welding while in surface contact, and the other flange of the press-formed plate is joined to the lower part of the right side wall portion 12b by spot welding while in surface contact. Furthermore, a plate-shaped member 20 with flanges formed on both ends is prepared, and each flange is joined to the hat-shaped member 10 by spot welding. In addition, the plate-shaped member 20 is joined by laser arc welding with the press-formed plate at the center in the width direction, with the side of the two bends that is not joined to the angle material in contact with it. 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.

[0081] In the example shown in Figure 10(f), the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, a reinforcement 40 comprising vertical plates 41 and horizontal plates 42 is formed by spot welding the corners of one angle material and one pressed sheet metal to each other. Specifically, one angle material has a roughly L-shaped cross-section perpendicular to the longitudinal direction, and one pressed sheet metal has a roughly S-shaped cross-section due to being bent at right angles at two points in the width direction. Flanges are formed on both of the pair of edges of the angle material. Also, a flange is formed on one of the pair of edges of the pressed sheet metal.

[0082] The side surfaces near the corners of the angle material and the side surfaces near the corners of the pressed sheet are joined by laser arc welding while in surface contact with each other. As a result, the wall portion of the angle material and the wall portion of the pressed sheet become parallel to each other, forming a vertical plate 41. Similarly, the other wall portions of the angle material and the other wall portions of the pressed sheet become parallel to each other, forming a horizontal plate 42. Then, one flange of the angle material is joined to the top wall portion 11 by spot welding while in surface contact, and the other flange is joined to the right side wall portion 12b by spot welding while in surface contact. In addition, the flange of the press-formed plate is joined to the left side wall portion 12a by spot welding while in surface contact, and the flangeless edge of the press-formed plate is joined to the right flange portion 13b at the lower end of the right side wall portion 12b by spot welding while in surface contact. Next, a plate-shaped member 20 is prepared that is narrower than the lower opening width of the hat-shaped member 10. Then, one edge of the plate-shaped member 20 is joined by laser arc welding with the press-formed plate in contact with the one of the two bends that is not joined to the angle material. Furthermore, the other edge of the plate-shaped member 20 is joined by spot welding with the left flange portion 13a at the lower end of the left wall portion 12a in surface contact. 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 Figure 10(g), the internal space of the cylindrical body 30 is divided into six sections by the combination of two vertical plates 41 and one horizontal plate 42. In this example, a first press-formed plate, which is formed in two heights by press forming, and a second press-formed plate, which is formed in one height by press forming, are prepared. Then, the two corners of the upper section of the second press-formed plate are joined to the lower section of the first press-formed plate by laser arc welding, with the upper section of the second press-formed plate in surface contact. As a result, the first press-formed plate and the second press-formed plate become one unit and form a reinforcement 40. In this reinforcement 40, two vertical walls on the first press-formed plate and two vertical walls on the second press-formed plate are joined together to form two vertical plates 41. Also, two horizontal walls on the first section of the first press-formed plate and one horizontal wall on the second press-formed plate are joined together to form one horizontal plate 42.

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

[0085] In Figure 11(a), the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, two hollow pipes are prepared, each with a roughly "9" shape formed by reversing the cross-section horizontally. Flanges are formed at the ends of the open sections of the "9" shape. The two hollow tubes described above are combined such that their cross-sectional shapes perpendicular to their longitudinal directions are rotationally symmetrical. Then, the flange of one hollow tube is joined to the other hollow tube by laser arc welding with surface contact between them. This joining is performed in two places. As a result, the outer periphery portions of both hollow tubes are combined to form a cylindrical body 30. That is, the top wall portion 11, the left wall portion 12a and the right wall portion 12b, and the outer shape portions corresponding to the plate-like member 20 are formed. At the same time, within this cylindrical body 30, the vertical wall of one hollow tube and the vertical wall of the other hollow tube connect to form a vertical plate 41. Similarly, within this cylindrical body 30, the horizontal wall of one hollow tube and the horizontal wall of the other hollow tube connect to form a horizontal plate 42. In this way, the internal space of the cylindrical body 30 is divided into four spaces partitioned by the vertical plate 41 and the horizontal plate 42.

[0086] In Figure 11(b), the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, two hollow pipes with a roughly figure-eight cross-section are prepared. These hollow pipes are formed by bending a single sheet of material at right angles in various places, and the edges of both ends of the material are processed into flanges. Next, the flange portions of each hollow pipe are joined together in advance by laser arc welding.

[0087] One of the two hollow tubes prepared in this way is placed on top of the other as the upper section and glued together. Then, the side walls of the two hollow tubes are joined together by laser arc welding, so that they become one. As a result, the outer circumferences of both hollow tubes are combined to form a cylindrical body 30. That is, the top wall 11, the left side wall 12a and the right side wall 12b, and the outer shape corresponding to the plate-like member 20 are formed. At the same time, within this cylindrical body 30, the vertical wall of one hollow tube and the vertical wall of the other hollow tube connect to form a vertical plate 41. Similarly, within this cylindrical body 30, the horizontal wall of one hollow tube and the horizontal wall of the other hollow tube connect to form a horizontal plate 42. In this way, the internal space of the cylindrical body 30 is divided into four spaces partitioned by the vertical plate 41 and the horizontal plate 42.

[0088] Figure 11(c) also shows that the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, a hollow tube is formed by bending a single sheet of material in multiple places, creating three rectangular spaces. These three rectangular spaces are arranged in an inverted L-shape, with the lower left corner of the paper being open. Flanges are formed on each of the edges of the sheet material that forms the hollow tube. These flanges are joined to the walls forming the adjacent rectangular spaces by laser arc welding, overlapping each other.

[0089] Then, an L-shaped angle member is attached to the corner of the hollow pipe to cover the aforementioned corner and form a fourth rectangular space. Flanges are formed on both side edges of this angle member. These two flanges are then joined to the side wall surface of the hollow pipe by laser arc welding. In this way, by combining the hollow pipe material and the angle material, the outer periphery portions of both materials combine with each other to form a cylindrical body 30 with a rectangular outer shape. Specifically, the top wall portion 11, the left wall portion 12a and the right wall portion 12b, and the outer shape portions corresponding to the plate-like member 20 are formed. At the same time, within this cylindrical body 30, a part of the hollow pipe material forms a vertical plate 41, and another part forms a horizontal plate 42. In this way, the internal space of the cylindrical body 30 is divided into four spaces partitioned by the vertical plate 41 and the horizontal plate 42.

[0090] Figure 11(d) also shows that the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, two roughly "9" shaped molded bodies are obtained by roll forming. A flange is formed on the edge of only one of these molded bodies. This flange is then joined to the edge of the other molded body by laser arc welding while in surface contact with it. In addition, the corners of each molded body are joined to each other by laser arc welding while butting them together. This joined portion becomes the center of the cylindrical body 30. In this way, an intermediate body is obtained from the pair of molded bodies, in which three rectangular spaces are arranged in an L-shape. The upper right corner of this intermediate body is open.

[0091] Then, a roughly L-shaped angle material is attached to the corner of the intermediate body so as to cover the aforementioned corner and form a fourth rectangular space. Flanges are formed on both side edges of this angle material. These two flanges are then joined by laser arc welding while in surface contact with the side wall surface of the intermediate body. In this way, by combining the molded body and the angle material, the outer periphery portions of both are combined to form a cylindrical body 30 with a rectangular outer shape. That is, the top wall portion 11, the left wall portion 12a and the right wall portion 12b, and the outer shape portions corresponding to 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 way, the internal space of the cylindrical body 30 is divided into four spaces partitioned by the vertical plate 41 and the horizontal plate 42.

[0092] Figure 11(e) also shows that the internal space of the cylindrical body 30 is divided into four sections by the combination of one vertical plate 41 and one horizontal plate 42. In this example, four hollow pipes with rectangular cross-sections are prepared. These hollow pipes are then glued together and stacked in two vertical and two horizontal rows. Finally, the joints that appear on the outer circumference are firmly joined using laser arc welding. In this way, by combining the four hollow tubes, their outer periphery parts combine with each other to form a cylindrical body 30 with a rectangular outer shape. Specifically, the top wall portion 11, the left wall portion 12a and the right wall portion 12b, and the outer shape portions corresponding to the plate-like member 20 are formed. At the same time, within this cylindrical body 30, parts of each hollow tube combine with each other to form vertical plates 41 and horizontal plates 42. In this way, the internal space of the cylindrical body 30 is divided into four spaces partitioned by the vertical plate 41 and the horizontal plate 42.

[0093] [Second Embodiment] Next, a second embodiment of the present invention will be described below with reference to Figure 12. In the following description, the differences from the first embodiment will be the main focus, and other configurations will be assumed to be the same as in the first embodiment, thus omitting redundant explanations. In this embodiment, the difference is that, instead of the first bead Ba and the second bead Bb in the first embodiment described above, a third bead Bc, shown in Figure 12, is formed on the top wall portion 11 as the bending point.

[0094] The third bead Bc is a single recess formed in the top wall portion 11, and is elongated in a direction intersecting the longitudinal direction of the impact absorbing member 1. The third bead Bc is formed between a pair of ridge portions EL that form 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 elongated 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 portion EL. Therefore, the third bead Bc is formed only on the flat portion of the top wall portion 11 and does not extend to the inside between the pair of ridge portions EL.

[0095] The third bead Bc has a rectangular shape in its longitudinal center and semicircular shapes at both ends. The width of the third bead Bc can be exemplified as 20 mm to 40 mm. The length of the outer surface of the third bead Bc can be exemplified as 50 mm to 80 mm. The depth of the outer surface of the third bead Bc can be exemplified as 4 mm to 15 mm. The third bead Bc may be formed simultaneously during the press working process when forming the hat-shaped member 10 from the metal sheet, or it may be formed by applying a press to the hat-shaped member 10 as a post-processing step. When the third bead Bc is formed by press working, its thickness is slightly thinner than the surrounding thickness and it is work-hardened. The inner surface of the third bead Bc is also concave towards the inside of the cylindrical body 30, just as the outer surface is concave. The number of third beads Bc is not limited to one, but may be two or more. Furthermore, while Figure 12 illustrates a configuration in which the longitudinal direction of the third bead Bc is perpendicular to the longitudinal direction of the impact absorbing member 1, it may have a slight angle with respect to the perpendicular direction.

[0096] In the impact absorbing member 1 of this embodiment, the portion of the third bead Bc described above forms the second portion R2, and the portions adjacent to it in the longitudinal direction are the first portion R1 and the third portion R3. Therefore, when a load along the center line CL is applied to this impact absorbing member 1, it bends with the third bead Bc of the second portion R2 as the bending starting point. And during this bending, the reinforcement 40 also bends and absorbs the impact energy.

[0097] [Third Embodiment] Next, a third embodiment of the present invention will be described below with reference to Figure 13. In the following description, the differences from the first embodiment will be the main focus, and other configurations will be assumed to be the same as in the first embodiment, and redundant explanations will be omitted. In this embodiment, instead of the first bead Ba and 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 wall portion 12a and the right wall portion 12b, and these through holes Ta and Tb are used as bending points.

[0098] The through holes Ta and Tb are both circular and have the same inner diameter, with specific inner diameter dimensions ranging from 20 mm to 40 mm. The through holes Ta and Tb are formed only on the flat wall surface of the hat-shaped member 10 and do not overlap with the pair of ridge sections EL. The through holes Ta and Tb are formed at the same position along the longitudinal direction of the impact absorbing member 1. In this embodiment of the impact absorbing member 1, the portion where the through holes Ta and Tb are formed constitutes the second portion R2, and the portions adjacent to it in the longitudinal direction are 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 second portion R2 bends with the through holes Ta and Tb as the bending starting point. During this bending, the reinforcement 40 also bends, absorbing the impact energy. The shapes of the through holes Ta and Tb are not limited to circles; other shapes such as ellipses may also be used. Furthermore, the sizes of the through holes Ta and Tb may differ. Multiple through holes Ta and Tb may be formed on each plane of the hat-shaped member 10. Alternatively, only one of the through holes Ta or Tb may be formed. However, if the through hole Ta is omitted and only the through hole Tb is formed, it is preferable to form it in both the left wall portion 12a and the right wall portion 12b.

[0099] Although the embodiments of the present invention have been described above, the present invention is not limited to these forms, and the following modifications may also be adopted. Furthermore, each embodiment and each modification may be combined as appropriate. [Example 1] A material strength distribution may be intentionally applied between the first part R1 and the third part R3. Specifically, the material tensile strength ratio obtained by dividing the material tensile strength of the second part R2 by the average material tensile strength of the first part R1 and the third part R3 may be set to 0.5 to 0.9. Such a material tensile strength ratio can be obtained by using a tailored blank prepared by preparing a flat plate material with relatively low tensile strength and a pair of flat plate materials with relatively high tensile strength, and then welding the flat plate material with relatively low tensile strength between the flat plate materials with relatively high tensile strength. Such a material tensile strength ratio may be applied to the first to third embodiments described above. By creating such a difference in material tensile strength, the relative bending strength of the second part R2 compared to the first part R1 and the third part R3 can be further reduced, thus ensuring that the position of the second part R2 functions reliably as the bending initiation point.

[0100] [Differentiation 2] A thickness distribution may be intentionally applied between the first part R1 and the third part R3. Specifically, the thickness ratio obtained by dividing the thickness of the second part R2 by the average thickness of the first part R1 and the third part R3 may be set to 0.5 to 0.9. Such a thickness ratio can be obtained by using a tailored blank, which is made by preparing a relatively thin flat plate material and a pair of relatively thick flat plate materials, and then welding the relatively thin flat plate material between the relatively thick flat plate materials. Furthermore, such a thickness difference may be applied to the first to third embodiments or the modified example 1 described above. By providing such a plate thickness distribution, the relative bending strength of the second part R2 compared to the first part R1 and the third part R3 can be reduced, thus ensuring that the position of the second part R2 functions reliably as the bending initiation point.

[0101] [Difference 3] Except for the second part R2, the first part R1 and the third part R3 may each be provided with a reinforcing portion (not shown) along the longitudinal direction. This reinforcing portion may be at least one of a bead, an angle material, or an emboss formed along the longitudinal direction. Such a reinforcing portion may also be applied to the first to third embodiments or the modified examples 1 and 2 described above. By providing such a reinforcement, the relative bending strength of the first part R1 and the third part R3 with respect to the second part R2 can be further increased, allowing the second part R2 to function more reliably as a bending point. [Examples]

[0102] [First Embodiment] A first embodiment of the present invention will be described below with reference to Figures 14 to 17. In this embodiment, the bending deformation and energy absorption amount were determined by numerical calculation when a load was applied to the impact absorbing member 1 (hereinafter referred to as the "inventive example") described with reference to Figure 2 and the impact absorbing member 1 (hereinafter referred to as the "comparative example") 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.

[0103] Figure 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. The hat-shaped member 10 has a first bead Ba and a second bead Bb formed on it. Both the first bead Ba and the second bead Bb are rhombic in shape, and three cases are set for their depths of 6 mm, 8 mm, and 10 mm, as shown in Figure 15. In the case of a depth of 6 mm, the first bead Ba and the second bead Bb are contained within the ridge line EL and do not protrude beyond the side edges ELa and ELb. In the case of a depth of 8 mm, the first bead Ba and the second bead Bb protrude beyond the side edges ELa and ELb and outside the ridge line EL. The hat-shaped member 10 was made of a material with a tensile strength of 780 MPa and a plate thickness of 2.0 mm. The plate-shaped member 20 was made of a material with a tensile strength of 690 MPa and a plate thickness of 1.2 mm.

[0104] Figure 16 shows the same impact-absorbing member 1 as described in Figure 2, and comprises a hat-shaped member 10, a plate-shaped member 20, and a reinforcement 40. The hat-shaped member 10 has a first bead Ba and a second bead Bb formed on it. Both the first bead Ba and the second bead Bb are rhombic in shape. As shown in Figure 17, three cases were set up: when the depth is 6 mm, 8 mm, and 10 mm. Of these, the case with a depth of 6 mm is a comparative example because both the first bead Ba and the second bead Bb are contained within the ridge portion EL and do not protrude beyond the side edge ELa into the top wall portion 11. On the other hand, in the cases with depths of 8 mm and 10 mm, both the first bead Ba and the second bead Bb protrude beyond the side edge ELa into the top wall portion 11, so these are examples of the invention. In the cases with depths of 8 mm and 10 mm, the first bead Ba and the second bead Bb extend beyond the side edge ELb, reaching the left wall portion 12a and the right 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-shaped 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 inventive example thinner than that of the comparative example is to evaluate the inventive example and the comparative example under weight equivalent conditions, taking into account the weight difference due to the presence or absence of the reinforcement 40.

[0106] As shown in Figure 15, when the depth of the first bead Ba and the second bead Bb was 6 mm, the hat-shaped member 10 underwent out-of-plane deformation at an unintended position due to the absence of reinforcement 40. As a result, proper bending could not be obtained at the positions of the first bead Ba and the second bead Bb. Furthermore, when the depths of the first bead Ba and the second bead Bb were 8 mm, bending occurred at the positions of the first bead Ba and the second bead Bb. However, due to the absence of reinforcement 40, the range of out-of-plane deformation was wide, and it was not possible to cause a clean bending deformation. The energy absorbed during a 180 mm stroke was 4.74 kJ. Furthermore, 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, due to the absence of reinforcement 40, the range of out-of-plane deformation was wide, and it was not possible to cause a clean bending deformation. The energy absorbed during a 180 mm stroke was 4.63 kJ.

[0107] Next, as shown in Figure 17, when the depth of the first bead Ba and the second bead Bb was 6 mm, these first bead Ba and the second bead Bb could not function as a trigger for folding the top wall portion 11, and the hat-shaped member 10 underwent out-of-plane deformation at an unintended position. As a result, proper bending at the positions of the first bead Ba and the second bead Bb could not be 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 reinforcement 40 suppressed out-of-plane deformation at unintended locations, and the pair of first beads Ba and second beads Bb that had penetrated to the top wall portion 11 were deformed in a smooth manner, with the bending starting point. Moreover, since the reinforcement 40 absorbed the load while bending during the bending deformation, the energy absorption amount for a 180 mm stroke was 7.47 kJ, which is higher than the energy absorption amount (4.74 kJ) of the comparative example with a depth of 8 mm for the first bead Ba and the second bead Bb shown in Figure 15. Furthermore, even 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 as well, the inclusion of the reinforcement 40 suppressed out-of-plane deformation at unintended locations. As a result, the pair of first beads Ba and second beads Bb, which were firmly embedded up to the top wall 11, were able to bend and deform smoothly using the bending initiation point as the bending point. In addition, because the reinforcement 40 bent and absorbed the load during bending deformation, the energy absorption amount for a 180 mm stroke was 7.94 kJ, which is higher than the energy absorption amount (4.63 kJ) of the comparative example shown in Figure 15, where the diameters of the first bead Ba and the second bead Bb were 10 mm.

[0108] From the above results, it was confirmed that it is important to include the reinforcement 40 and to enlarge the first bead Ba and the second bead Bb to a certain extent so that they protrude into the top wall portion 11 at least beyond the side edge ELa. By including both of these, it was confirmed that the amount of energy absorbed can be increased while the impact absorbing member 1 is deformed in a smooth manner.

[0109] [Second Example] A second embodiment of the present invention will be described below with reference to Figures 18 to 19. In this embodiment, various cases were set up in which 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 were modified in terms of the presence or absence of the reinforcement 40 and the presence or absence of the formation of through holes Ta and Tb. Then, the manner of bending deformation and the amount of energy absorbed when a load is applied coaxially with the center line CL were determined by numerical calculation.

[0110] First, let's explain Figure 18. Figure 18 is a perspective view showing the shock-absorbing member 1 for each case (a) to (l) before the load is applied. Cases (a) to (c) represent the case where one third bead Bc, as shown in Figure 12, is formed on the top wall portion 11. Cases (a) and (c) do not have a reinforcement 40, while case (b) does have a reinforcement 40. In order to make cases (a) and (b) equivalent in mass, the thickness of the hat-shaped member 10 in case (b) is made thinner than that of the hat-shaped member 10 in case (a) due to the inclusion of the reinforcement 40. On the other hand, the thickness of the hat-shaped member 10 in case (c) is the same as that of case (b).

[0111] Cases (d) to (f) are those in which through holes Tb, as shown in Figure 13, are formed in the side wall portion 12. Specifically, 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 holes Ta are formed in the top wall portion 11, and it is left flat. Cases (d) and (f) do not have the reinforcement 40, while case (e) does have the reinforcement 40. In order to make cases (d) and (e) equivalent in mass, the thickness of the hat-shaped member 10 in case (e) is made thinner than that of the hat-shaped member 10 in case (d) due to the inclusion of the reinforcement 40. On the other hand, the thickness of the hat-shaped member 10 in case (f) is the same as that of case (e).

[0112] Cases (g) to (i) are those in which a through-hole Ta, as shown in Figure 13, is formed in one location in the top wall portion 11. However, no through-hole Tb is formed in the side wall portion 12, and it is left flat. Cases (g) and (i) do not have the reinforcement 40, while case (h) does have the reinforcement 40. In order to make cases (h) and (i) equivalent in mass, the thickness of the hat-shaped member 10 in case (h) is made thinner than that of the hat-shaped member 10 in case (g) due to the inclusion of the reinforcement 40. On the other hand, the thickness of the hat-shaped member 10 in case (i) is the same as that of case (h).

[0113] Cases (j) to (l) are those in which a through-hole Ta, as shown in Figure 13, is formed in one location in the top wall portion 11, and a through-hole Tb, as shown in Figure 13, is also 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. Cases (j) and (l) do not have the reinforcement 40, while case (k) does have the reinforcement 40. In order to make cases (j) and (k) equivalent in mass, the thickness of the hat-shaped member 10 in case (k) is made thinner than that of the hat-shaped member 10 in case (j) due to the inclusion of the reinforcement 40. On the other hand, the thickness of the hat-shaped member 10 in case (l) is the same as that of case (k).

[0114] For each of the cases (a) to (l) described above, a load coaxial with the center line CL was applied to the shock-absorbing member 1 to cause bending deformation. The state after bending deformation is shown in Figure 19. First, in cases (a) to (c), where a third bead Bc was formed on the top wall portion 11, the material broke at the position of the third bead Bc. However, in comparative cases (a) and (c), the lack of reinforcement 40 resulted in a wider bending range, making it impossible to achieve a clean, sharp break. Furthermore, the lack of reinforcement 40 in cases (a) and (c) resulted in lower energy absorption. On the other hand, in the inventive example case (b), the material broke cleanly at the position of the third bead Bc and also exhibited high energy absorption.

[0115] Next, in cases (d) to (f), in which through holes Tb are formed in the side wall portion 12, case (f) lacked a reinforcement 40, resulting in out-of-plane deformation at unintended locations. Consequently, in case (f), bending deformation occurred at unintended positions, and the energy absorption was also low. In case (d), although it broke at the through-hole Tb, the bending range was wider due to the lack of reinforcement 40, and it was not possible to break and deform it cleanly at a single joint. Also, in case (d), the amount of energy absorbed was lower due to the lack of reinforcement 40. On the other hand, in the inventive example case (e), it broke cleanly at the through-hole Tb and also had a higher amount of energy absorbed.

[0116] Next, in cases (g) to (i) in which through holes Ta were formed in the top wall portion 11, cases (g) and (i) lacked reinforcement 40, resulting in out-of-plane deformation at unintended locations. Furthermore, the energy absorption was low. On the other hand, in the inventive example case (h), the joints broke cleanly at the location of the through holes Ta, and the energy absorption was also higher.

[0117] Next, in cases (j) to (l), in which through holes Ta are formed in the top wall portion 11 and through holes Tb are formed in the side wall portion 12, cases (j) and (l) lacked the reinforcement 40, resulting in a wider range of bending and making it impossible to bend and deform smoothly at the joints. In addition, the energy absorption amount was lower in cases (j) and (l). On the other hand, in the inventive example case (k), bending smoothly at the positions of the through holes Ta and Tb was achieved, and the energy absorption amount was also higher. Based on the above results, it was confirmed that in the inventive examples (b), (e), (h), and (k), which have appropriate bending initiation points and reinforcement 40, the impact absorbing member 1 can be deformed smoothly at the intended positions and a high amount of energy can be absorbed.

[0118] The main points of this invention are summarized below. (1) One aspect of the present invention is: An impact absorbing member 1 comprises a cylindrical body 30 and a reinforcement 40 fixedly positioned inside the cylindrical body 30, and is long in one direction, The cylindrical body 30 is made of steel with a tensile strength of 650 MPa to 1600 MPa, and the reinforcement 40 is made of steel with a tensile strength of 590 MPa to 1600 MPa; In a cross-section perpendicular to the longitudinal direction of the impact absorbing member 1, The cylindrical body 30 has a top wall portion 11 having a total width 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, each having a total width W2 (mm) and a plate thickness t1 (mm). The reinforcement 40 has at least one of the following: vertical plates 41, one end of which is joined to the top wall portion 11, with a total number of n1 plates and a total plate thickness of t2 (mm); and horizontal plates 42, which connect the pair of side wall portions 12, with a total number of n2 plates and a total plate thickness of t3 (mm). The reinforcement 40 satisfies at least one of the following conditions: a first condition having a vertical plate 41 and a first planar portion width-to-thickness ratio r1 according to the following formula 1 being 10 or more and 50 or less; and a second condition having a horizontal plate 42 and a second planar portion width-to-thickness ratio r2 according to the following formula 2 being 10 or more and 50 or less; The cylindrical body 30 It has a first part R1, a second part R2, and a third part R3 arranged in order along the longitudinal direction, The second part, R2, has a bending 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 is provided with a pair of ridge sections EL that connect the top wall section 11 and the pair of side wall sections 12; The aforementioned bending point is, A first bead Ba crosses the side edge ELa which is the boundary between one of the pair of ridge sections EL and the top wall section 11, A second bead Bb crosses the side edge ELb, which is the boundary between the other of the pair of ridge sections EL and the top wall section 11, It holds.

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

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

[0122] (5) In the impact absorbing member 1 described in any one of the above items (1) to (4), The tensile strength ratio obtained by dividing the tensile strength of the material at the second part R2 by the average tensile strength of the material at the first part R1 and the third part R3 is set to 0.5 to 0.9, thereby providing the aforementioned bending point at the second part R2.

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

[0124] (7) In the impact absorbing member 1 described in any one of the above items (1) to (6), Each of the first part R1 and the third part 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 material, or an emboss formed along the longitudinal direction.

[0126] (9) The impact absorbing member 1 described in any one of the above items (1) to (8) may have the following configuration: The cylindrical body 30 A hat-shaped member 10 having a top wall portion 11 and a pair of side wall portions 12, It has a hat-shaped member 10 joined to a plate-shaped member 20 that faces the top wall portion 11; Satisfying both the first and second conditions; In the cross-section perpendicular to the longitudinal direction, The above n1 is 1 and the above n2 is 1, The vertical plate 41 is fixed in a state where it is stretched between the top wall portion 11 and the plate-shaped member 20. The horizontal plate 42 is fixed between the pair of side wall sections 12 in a state where it intersects with the vertical plate 41.

[0127] (10) The impact absorbing member 1 described in any one of the above items (1) to (8) may have the following configuration: The cylindrical body 30 A hat-shaped member 10 having a top wall portion 11 and a pair of side wall portions 12, It has a hat-shaped member 10 joined to a plate-shaped member 20 that faces the top wall portion 11; Satisfying both the first and second conditions; In the cross-section perpendicular to the longitudinal direction, The above n1 is 1 and the above 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. 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 the horizontal plate 42 at a position between the one end and the other end.

[0128] (11) A vehicle body part according to one aspect of the present invention is It is one of the following components on the vehicle body: front side member, rear side member, center pillar, or bumper beam. It has an impact-absorbing member 1 as described in any one of the above items (1) to (10). [Explanation of Symbols]

[0129] 1. Impact absorbing member 10 Hat-shaped member 11 Top wall section, hat top section 12 Side wall section 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 boards 42 Horizontal board Ba First bead (starting point of the bend) Bb Second bead (starting point of the bend) Bc Third bead (starting point of the bend) EL ridge section ELa, ELb lateral edge (boundary) Ta,Tb through hole R1 Part 1 R2 2nd part R3 3rd part

Claims

1. An impact absorbing member comprising a hollow tube and a reinforcement fixedly positioned inside the hollow tube, wherein the member is long in one direction, The hollow tube is made of steel with a tensile strength of 650 MPa to 1600 MPa, and the reinforcement is made of steel with a tensile strength of 590 MPa to 1600 MPa; The aforementioned hollow tube A hat-shaped member having a top wall and a pair of side walls, It has a plate-shaped member joined to the hat-shaped member and facing the top wall portion; In a cross-section perpendicular to the longitudinal direction of the impact absorbing member, The hollow tube has a top wall portion having a total width W1 (mm) and a plate thickness t1 (mm), and a pair of side wall portions provided on both sides of the top wall portion, each having a total width W2 (mm) and a plate thickness t1 (mm). The reinforcement comprises a vertical plate having one end joined to the top wall and consisting of one plate with a thickness of t2 (mm), and a horizontal plate having one plate with a thickness of t3 (mm) connecting the pair of side wall sections. The vertical plate is fixed in a state where it is stretched between the top wall portion and the plate-shaped member. The horizontal plate is fixed between the pair of side walls in a state where it intersects with the vertical plate; The reinforcement satisfies the following conditions: firstly, it has the vertical plates and the first planar portion width-to-thickness ratio r1 according to the following formula 1 is 10 or more and 50 or less; and secondly, it has the horizontal plates and the second planar portion width-to-thickness ratio r2 according to the following formula 2 is 10 or more and 50 or less; The aforementioned hollow tube It has a first part, a second part, and a third part that are arranged in order along the longitudinal direction, The second portion has a bending point; A shock-absorbing member characterized by the following features. r1=((W1-t2) / 2) / t1...(Formula 1) r2=((W2-t3) / 2) / t1...(Formula 2)

2. The hollow tube comprises a pair of ridges connecting the top wall and the pair of side wall portions; The aforementioned bending point is, A first bead that crosses the boundary between one of the pair of ridge sections and the top wall section, A second bead that crosses the boundary between the other of the pair of ridge sections and the top wall section, Having; The impact absorbing member according to feature 1.

3. The first bead crosses the boundary between one of the pair of ridge portions and one of the pair of side wall portions; The second bead crosses the boundary between the other of the pair of ridge sections and the other of the pair of side wall sections; The impact absorbing member according to feature 2.

4. The aforementioned bending point portion has a through hole or a third bead that is elongated in a direction intersecting the longitudinal direction, formed in at least one of the top wall portion and the pair of side wall portions. The shock-absorbing member according to any one of claims 1 to 3.

5. The material tensile strength ratio obtained by dividing the material tensile strength of the second portion by the average material tensile strength of the first and third portions is set to 0.5 to 0.9, thereby providing the bending point in the second portion; The shock-absorbing member according to any one of claims 1 to 3.

6. The impact absorbing member according to any one of claims 1 to 3, characterized in that the second portion is provided with the bending point by making the thickness ratio obtained by dividing the thickness of the second portion by the average thickness of the first portion and the third portion 0.5 to 0.

9.

7. Each of the first and third portions is provided with a reinforcing portion along the longitudinal direction. The shock-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 material, or an emboss formed along the longitudinal direction. The shock-absorbing member according to feature 7.

9. It is one of the following components on the vehicle body: front side member, rear side member, center pillar, or bumper beam. Having an impact absorbing member as described in any one of claims 1 to 3 A vehicle body part characterized by the following features.

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