Shock absorbing material

Abstract

To provide a shock absorption member which is light, and can bend and deform at convenient points, so as to achieve high energy absorption efficiency.SOLUTION: A shock absorption member 1 includes a cylindrical body 30 and a reinforcement 40. The reinforcement 40 satisfies at least one of a first condition having a vertical plate 41 and a first plane part width-thickness ratio r1 of 10 or more and 50 or less, and a second condition having a transverse plate 42 and a second plane part width-thickness ratio r2 of 10 or more and 50 or less. The shock absorption part material has a first bend part 1B in which the cylindrical body 30 and the reinforcement 40 both bend.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an impact absorbing member.

Background Art

[0002] In recent years, fuel efficiency regulations have been tightened worldwide, and automobile manufacturers are promoting weight reduction of vehicle bodies. At the same time, collision safety of vehicle bodies has also been tightened, so it is required to achieve both weight reduction and improvement of collision performance. In addition, along with the response to fuel efficiency regulations in various countries and the trend toward carbon neutrality, electrification of automobile power sources is being advanced. With the electrification of power sources, changes have also occurred in vehicle body structures, such as an increase in vehicle body weight and a reduction in engine room size, compared to conventional vehicle body structures having internal combustion engines. One example of this is the adoption of a short nose at the front of the vehicle body. In order to maintain high collision safety while making the vehicle body a short nose, a structure that can achieve high energy absorption efficiency with a short deformation stroke is required.

[0003] In particular, for components that actively undergo plastic deformation to absorb collision energy at the time of a vehicle collision, such as front side members and rear side members, a structure capable of dramatically improving energy absorption performance is demanded. In addition, since such components have the role of minimizing the external force applied to occupants during a collision, it is ideal to have a deformation mode that can shorten the deformation stroke while suppressing rapid load fluctuations.

[0004] As deformation modes of the member, there are bellows deformation and meandering deformation. Bellows deformation refers to a deformation in which out-of-plane deformation occurs on all of the side surfaces constituting the member, but the center line in the longitudinal direction of the member hardly bends. On the other hand, meandering deformation causes bending 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 side surfaces constituting the member, and 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 will easily occur at any point in the rear frame, and the position of the bending point will become unclear. From the viewpoint of impact energy absorption, it is not acceptable for the frame 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 will not allow the advantages of bending deformation to be fully realized, nor will the reduction in deformation stroke be achieved. 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 an impact-absorbing member that is lightweight yet can bend and deform smoothly at joints to exhibit high energy absorption efficiency. [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; The hollow tube and the reinforcement both have a first bend; When the first curved portion is viewed in a cross-section along the longitudinal direction of the impact-absorbing member, The hollow tube has a first hollow tube bend that includes a first curved inner surface which is a concave surface and a first curved outer surface which is a convex surface. The reinforcement is fixedly positioned inside the first hollow tube bend and has a first reinforcement bend that is bent along the first hollow tube bend; When the first curved portion is viewed in a cross-section perpendicular to the longitudinal direction, The hollow tube has a top wall portion having the first bent inner surface and a total width dimension W1 (mm) and plate thickness t1 (mm), a pair of side wall portions provided on both sides of the top wall portion and having a total width dimension W2 (mm) and plate thickness t1 (mm), and a bottom wall portion positioned opposite the top wall portion and having the first bent outer surface, The reinforcement comprises at least one of the following: vertical plates, one end of which is joined to the top wall, 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 sections, 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 in which it has 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 a second condition in which it has 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. 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 subjected to impact energy along its longitudinal direction, a bending deformation begins at the first bent inner surface of the top wall portion of the hollow tube, with the bending starting point being the bending point. At the beginning of the bending deformation, the top wall portion attempts 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 is pre-equipped with a first bend where both the hollow tube and the reinforcement are bent, the shock-absorbing member can be deformed in a smooth manner by using the inner surface of the first bend as the starting point for bending. In addition, since the impact energy applied to the shock-absorbing member is absorbed mainly by the reinforcement as it deforms by bending, starting from its first reinforcement bend, the amount of energy absorbed can be increased. Note that "cross section along the longitudinal direction of the shock-absorbing member" means a cross section whose cutting plane is a virtual plane containing the center line of the shock-absorbing member.

[0011] (2) In the impact absorbing member described in (1) above, the minimum radius of curvature R1 of the first bent inner surface, when viewed in cross-section along the longitudinal direction, may be 1 mm to 260 mm. According to the impact-absorbing member described in (2) above, by setting the upper limit of the minimum radius of curvature R1 to 260 mm, the minimum degree of curvature can be imparted to the hollow tube so that the first inner surface of the bend functions as the bending point. On the other hand, by setting the lower limit of the minimum radius of curvature R1 to 1 mm, there is the advantage that localization of deformation during deformation of the member can be suppressed.

[0012] (3) In the impact absorbing member described in (1) or (2) above, the first hollow tube bend may have a rectangular cross-section when viewed in a cross-section perpendicular to the longitudinal direction, and the height dimension between the top wall and the bottom wall may be smaller than the total width dimension W1 (mm) of the flat section. Conversely, with the impact-absorbing member described in (3) above, compared to the case where the height dimension between the top wall and the bottom wall is larger than the total width dimension W1 (mm) of the flat section, the bending direction of the impact-absorbing member with the first bent inner surface of the top wall facing inward can be controlled with greater precision.

[0013] (4) In the impact absorbing member described in (1) or (2) above, the following may be used: The device further has a second bend, which is located adjacent to the first bend along the longitudinal direction, and in which both the hollow tube and the reinforcement bend in the opposite direction to the first bend; the second bent portion, as viewed in a cross section along the longitudinal direction, the hollow tube has a second hollow tube bent portion that includes a second bent outer side surface which is a convex curved surface and a second bent inner side surface which is a concave curved surface, and is bent in a direction opposite to the first hollow tube bent portion, the reinforce is fixedly disposed inside the second hollow tube bent portion, and has a second reinforce bent portion that is bent along the second hollow tube bent portion. According to the impact absorbing member described in the above (4), similarly to the first bent portion, also in the second bent portion, the impact absorbing member can be bent and deformed in a well-controlled manner with the second bent inner side surface as the bending start point portion. In addition, since the impact energy applied to the impact absorbing member is absorbed mainly by the reinforce while the reinforce is bent and deformed starting from the second reinforce bent portion, the energy absorption amount can be increased. At this time, the bending deformation of the first bent portion and the bending deformation of the second bent portion proceed substantially simultaneously or sequentially, and their bending directions are opposite to each other. Further, since the impact energy absorption is performed by being shared at a plurality of positions (two positions) of the first bent portion and the second bent portion, higher energy absorption efficiency can be exhibited.

[0014] (5) In the impact absorbing member according to the above (1) or (2), when viewed in a cross section along the longitudinal direction, the minimum curvature radius R2 of the second bent inner side surface may be 1 mm to 260 mm. According to the impact absorbing member described in the above (5), by setting the upper limit value of the minimum curvature radius R2 to 260 mm, it is possible to impart the minimum degree of bending to the hollow tube for making the second bent inner side surface function as the bending start point portion. On the other hand, by setting the lower limit value of the minimum curvature radius R2 to 1 mm, there is an advantage that localization of deformation during deformation of the member can be suppressed.

[0015] (6) The impact absorbing member according to the above (1) or (2) may be configured as follows: the first condition is satisfied; when the first bent portion is viewed in a cross section perpendicular to the longitudinal direction, a flange formed at the one end of the vertical plate is spot-welded to the top wall portion. According to the impact absorbing member described in the above (6), by adopting surface joining using flanges, for example, as compared with line joining in which the plate thickness at the one end of the vertical plate is taken as a joining line, out-of-plane deformation at an unexpected location in the top wall portion can be more reliably prevented. Further, by adjusting the pitch and construction range of spot welding, fine adjustment such as changing the distribution of joining strength along the longitudinal direction of the impact absorbing member can also be performed.

[0016] (7) In the impact absorbing member described in the above (1) or (2), the following configurations may be adopted: the second condition is satisfied; When the first bent portion is viewed in a cross section perpendicular to the longitudinal direction, flanges formed at both ends of the horizontal plate are spot-welded to the respective one of the pair of side wall portions. According to the impact absorbing member described in the above (7), by adopting surface joining using flanges, for example, as compared with line joining in which the plate thickness at both ends of the horizontal plate is taken as a joining line, out-of-plane deformation at an unexpected location in the pair of side wall portions can be more reliably prevented. Further, by adjusting the pitch and construction range of spot welding, fine adjustment such as changing the distribution of joining strength along the longitudinal direction of the impact absorbing member can also be performed.

[0017] (8) In the impact absorbing member described in the above (1), the following configurations may be adopted: the hollow tube includes: a hat-shaped member having a hat top portion whose cross section perpendicular to the longitudinal direction serves as the top wall portion, and the pair of side wall portions continuous to both sides of the hat top portion; and a plate-shaped member joined to the hat-shaped member and having the bottom wall portion opposed to the hat top portion; both the first condition and the second condition are satisfied; When the first bent portion is viewed in a cross section perpendicular to the longitudinal direction, the number n1 is 1 and the number n2 is 1, the vertical plate is fixed in a state of being stretched between the hat top portion and the bottom wall portion, and the horizontal plate is fixed between the pair of side wall portions in a state of intersecting the vertical plate. According to the impact absorbing member described in (8) 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 increases the maximum load (barrier reaction force) and allows this maximum load to be maintained for a longer period, thereby increasing the amount of energy absorbed.

[0018] (9) The impact absorbing member described in (1) above may be provided as follows: The aforementioned hollow tube A hat-shaped member having a hat apex whose cross-section perpendicular to the longitudinal direction is the top wall portion and a pair of side wall portions connected to both sides of the hat apex, A plate-shaped member having a bottom wall portion opposite to the hat top portion and joined to the hat-shaped member; Satisfying both the first and second conditions; When the first curved portion is viewed in a cross-section perpendicular to the longitudinal direction, The number of sheets n1 is 1 and the number of sheets 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 of the hat, 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 (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 increases the maximum load (barrier reaction force) and allows this maximum load to be maintained for a longer period, thereby increasing the amount of energy absorbed. [Effects of the Invention]

[0019] According to the impact absorbing members of each of the above embodiments of the present invention, the members are lightweight yet can bend and deform smoothly at joints, thereby exhibiting high energy absorption efficiency. [Brief explanation of the drawing]

[0020] [Figure 1] This is a perspective view of a vehicle body in which an impact-absorbing member according to one embodiment of the present invention is applied to the front side member and the rear side member. [Figure 2] This is a perspective view of the shock-absorbing component, with a portion of it broken to show its internal structure. [Figure 3] This figure shows the external shape of the impact-absorbing member, where (a) is a side view from the -Y direction in Figure 2, and (b) is a cross-sectional view of (a) AA. [Figure 4] This is a schematic diagram illustrating the dimensions of each part of the shock-absorbing member, and is a cross-sectional view AA of Figure 3(a). [Figure 5] Figures (a) to (d) are diagrams showing modified examples of the same shock-absorbing member, and are cross-sectional views AA of Figure 3(a). [Figure 6] Figures (a) to (e) are diagrams showing other modified examples of the shock-absorbing member, and are cross-sectional views AA of Figure 3(a). [Figure 7] Figures (a) to (d) are diagrams showing yet another modified example of the same shock-absorbing member, and are cross-sectional views AA of Figure 3(a). [Figure 8] Figures (a) to (c) show yet another modified example of the same shock-absorbing member, and are cross-sectional views AA of Figure 3(a). [Figure 9] Figures (a) to (e) are diagrams showing yet another modification of the same shock-absorbing member, and are cross-sectional views AA of Figure 3(a). [Figure 10] Figures (a) to (g) are diagrams showing yet another modified example of the same shock-absorbing member, and are cross-sectional views AA of Figure 3(a). [Figure 11] Figures (a) to (e) are diagrams showing yet another modification of the same shock-absorbing member, and are cross-sectional views AA of Figure 3(a). [Figure 12] This figure illustrates the impact-absorbing member used in the first embodiment, where (a) is a side view showing the member before a load is applied along its longitudinal direction, and (b) is a side view showing the member after it has been subjected to a load and undergone out-of-plane deformation. [Figure 13]This figure illustrates the first embodiment, and is a graph in which the horizontal axis shows the ratio W / t and the vertical axis shows the out-of-plane deformation amount δ. [Figure 14] This figure illustrates the impact-absorbing member used in the second embodiment, where (a) is a cross-sectional view corresponding to Figure 4 or Figure 9(a), and (b) is a side view showing the member before and after bending deformation. [Figure 15] This figure illustrates the second embodiment, where (a) is a perspective view of the bent deformation area in the impact absorbing member of Case-A, and (b) is a perspective view of the bent deformation area in the impact absorbing member of Case-B. [Figure 16] This figure shows the impact-absorbing member used in the third embodiment, and is a cross-sectional view AA of Figure 3(a). Of these, Case000 and 005 are comparative examples. On the other hand, Case001 to Case004 are examples of inventions equipped with various reinforcements. [Figure 17] This figure shows how the load is applied in the third embodiment, with (a) being a plan view and (b) being a side view. [Figure 18] These figures show the cross-sectional dimensions of the impact-absorbing member used in the third embodiment, where (a) is a cross-sectional view of BB in Figure 17(b) and (b) is a cross-sectional view of CC in Figure 17(b). Note that the reinforcement is not shown in (a) and (b). [Figure 19] The figures show the shock-absorbing member after bending deformation in the third embodiment, where (a) shows Case 001 in Figure 16, (b) shows Case 002 in Figure 16, (c) shows Case 003 in Figure 16, (d) shows Case 004 in Figure 16, and (e) shows Case 005 in Figure 16. [Figure 20] This bar graph compares the maximum loads in the third embodiment, with the horizontal axis representing the case number and the vertical axis representing the maximum load (kN). [Figure 21] This bar graph compares the energy absorption amounts in the third embodiment, with the horizontal axis representing the case number and the vertical axis representing the energy absorption amount (kJ). [Modes for carrying out the invention]

[0021] The following describes an impact-absorbing member according to one embodiment of the present invention and various modified examples thereof, with reference to the drawings. As shown in Figure 1, the impact-absorbing member of this embodiment can be used as a front side member FM or a rear side member 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.

[0022] 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 will be denoted by reference numeral 1 as shown in Figure 1, and this will be illustrated as impact-absorbing member 1. Furthermore, an example will be given in which the triggers for folding deformation (fold triggers) are set at two locations in the longitudinal direction of impact-absorbing member 1.

[0023] As shown in Figure 1, the impact absorbing member 1 is used with its top wall facing either the left or right direction relative to the vehicle. However, in the following description, the impact absorbing member 1 may be described as a standalone component, with the top wall side being the upward direction, the plate-like member side being the downward direction, and the direction of the pair of side walls being the left-right direction. To illustrate this more specifically using Figure 2, the direction along the Z-axis is the up-down direction when describing the component as a standalone unit, and the left-right direction when it is positioned as part of the vehicle's frame. Similarly, the direction along the Y-axis in Figure 2 is the left-right direction when describing the component as a standalone unit, and the up-down direction when it is positioned as part of the vehicle's frame. On the other hand, the direction along the X-axis in Figure 2 indicates the front-back direction, both when describing the component as a standalone unit and when it is positioned as part of the vehicle's frame.

[0024] The impact-absorbing member 1 of this embodiment will be described below as a single component, using Figure 2 and other figures. As shown in Figure 2, the impact absorbing member 1 of this embodiment is a cylindrical component that is long in the longitudinal direction (X direction) along its center line CL. The center line CL is bent at two points along its extension direction, and in a side view along the -Y direction it is approximately inverted S-shape and in a plan view along the -Z direction it is straight. The impact absorbing member 1 has a hat-shaped member 10, a plate-shaped member 20, and a reinforcement 40, and the cross-sectional shape at each position along the extension direction of the center line CL is rectangular.

[0025] 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. Similar to the center line CL, the hat-shaped member 10 is bent at two points along its extending direction (X direction), and in a side view along the -Y direction it is approximately in an inverted S shape, while in a plan view along the -Z direction it is straight. 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, like the center line CL, is bent at two points along its extension direction, and is a long plate that is roughly S-shaped when viewed from the side along the -Y direction and straight when viewed from above along the -Z direction. The outer width dimension and plate thickness of the top wall portion 11 are constant at each position along its extension direction. The outer width dimension here includes the ridge line EL formed along both side edges of the top wall portion 11. The outer and inner surfaces of the top wall portion 11 are bent at two points along their extension direction, and are roughly S-shaped when viewed from the side along the -Y direction and straight when viewed from above along the -Z direction. 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 modified to differ 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 may have some irregularities as required by the component design.

[0026] 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. Like the top wall portion 11, the left side wall portion 12a is bent at two points along its extension direction, and has an outer surface and inner surface that are substantially S-shaped in a side view along the +Y direction and straight in a plan view along the -Z direction. The right side wall portion 12b is a vertical wall that is integrally connected to the other of the two side edges 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. Like the top wall portion 11, the right side wall portion 12b is bent at two points along its extension direction, and has an outer surface and inner surface that are substantially inverted S-shape in a side view along the -Y direction and straight in a plan view along the -Z direction.

[0027] The left wall portion 12a and the right wall portion 12b, respectively, have constant external dimensions and plate thickness when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1, at each position along the longitudinal direction. The external dimensions referred to here include 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, like the top wall portion 11, is bent at two points along its extension direction, and is a long plate that is roughly S-shaped in a side view along the +Y direction and straight in a plan view along the -Z direction. The right wall portion 12b, like the top wall portion 11, is bent at two points along its extension direction, and is a long plate that is roughly inverted S-shaped in a side view along the -Y direction and straight in a plan view along the -Z direction. 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 may have some irregularities as required by the part design.

[0028] 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 has a substantially constant width dimension and a substantially constant plate thickness. Like the left wall portion 12a, the left flange portion 13a is bent at two points along its extension direction, and has a surface and a back surface that are substantially S-shaped when viewed from the side along the +Y direction and straight when viewed from above along the -Z direction. The right flange portion 13b is integrally connected to the lower edge of the right side wall portion 12b. The right flange portion 13b has a substantially constant width dimension and a substantially constant plate thickness. Like the right side wall portion 12b, the right flange portion 13b is bent at two points along its extension direction, and has a surface and a back surface that are substantially inverted S-shape in a side view along the -Y direction and straight in a plan view along the -Z direction. 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 required by the part design. Similarly, the front and back surfaces of the left flange portion 13a and the right flange portion 13b may have some irregularities as required by the part design.

[0029] A ridge line EL parallel to the center line CL is formed between the top wall section 11 and the left wall section 12a. A ridge line 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 lines EL are parallel to each other. 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.

[0030] 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. Similar to the hat-shaped member 10, the plate-shaped member 20 is bent at two points along its length, and is a long plate that is approximately inverted S-shaped when viewed from the side along the -Y direction and straight when viewed from the bottom along the +Z direction. The plate-shaped member 20 is welded to the left flange portion 13a and the right flange portion 13b at both side edges. This creates a closed space 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 a cylindrical body 30 that is approximately inverted S-shaped and bent at two points along its length. 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 outer and inner surfaces of the plate-like member 20 may have some irregularities as required by the part design.

[0031] Next, let's describe the reinforcement 40. Like the cylindrical body 30, the reinforcement 40 is bent at two points along its longitudinal direction (X direction). In a side view along the -Y direction, it is roughly in an inverted S shape, and in a plan view along the -Z direction, it is straight.

[0032] 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 long along the center line CL. Like the center line CL, the vertical plate 41 is bent at two points along its length, and has a surface and back surface that are substantially inverted S-shaped when viewed from the side along the -Y direction and straight when viewed from the top or bottom along the Z direction. 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 is apparently divided into two by a horizontal plate 42 that intersects it at the center in the height direction (+Z direction). The upper and lower parts of this divided vertical plate 41 have the same height and length dimensions.

[0033] 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. Like the center line CL, the horizontal plate 42 is bent at two points along its length, and has a surface and back surface that are substantially inverted S-shape in a side view along the -Y direction and straight in a plan view or bottom view along the Z axis direction. Although the horizontal plate 42 is a single strip-shaped plate, it is apparently divided into two by a vertical plate 41 that intersects it at the center in the width direction when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1. The left and right portions of this divided horizontal plate 42 have the same width, thickness, and length.

[0034] 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.

[0035] 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 horizontal plate 42 restrains the space between the left wall portion 12a and the right wall portion 12b so that the distance between them is kept constant.

[0036] 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.

[0037] As described above, the shock-absorbing member 1 is bent at two points along its longitudinal direction. This will be explained in more detail using Figure 3 in addition to Figure 2. Figure 3 is a diagram showing the external shape of the shock-absorbing member 1, where (a) is a side view of the shock-absorbing member 1 as seen from the -Y direction in Figure 2, and (b) is a cross-sectional view AA of (a).

[0038] As shown in Figures 2 and 3, the shock-absorbing member 1 has a first curved portion 1B and a second curved portion 1C where both the cylindrical body 30 and the reinforcement 40 are curved. These first curved portion 1B and second curved portion 1C are adjacent to each other along the longitudinal direction of the shock-absorbing member 1, and as shown in Figure 3(a), their curvature directions are opposite to each other in a side view. The shock-absorbing member 1 has a straight front end portion 1A, a first curved portion 1B that is connected to the rear end of the front end portion 1A and curves gently in the +Z direction, a second curved portion 1C that is connected to the rear end of the first curved portion 1B and curves gently in the opposite direction to the first curved portion 1B, and a rear end portion 1D that is connected to the rear end of the second curved portion 1C and is substantially parallel to the front end portion 1A. In Figure 3(a), dashed lines are used to clearly indicate the extent of each of these parts.

[0039] The front end 1A is straight along the X-axis direction. The rear end 1D is also straight along the X-axis direction. Therefore, the front end 1A and the rear end 1D are straight lines along the X-axis direction in both plan view and side view. As shown in Figure 3(a), when viewed from the -Y direction, the first reinforcement bend 40B and the second reinforcement bend 40C are bent in an inverted S-shape, so the front end 1A and the rear end 1D are offset from each other in the Z-axis direction. On the other hand, when viewed from the -Z direction, the first reinforcement bend 40B and the second reinforcement bend 40C are straight and coaxial, so the front end 1A and the rear end 1D are also coaxial without their relative positions shifting in the Y-axis direction.

[0040] When the impact absorbing member 1 is viewed in cross-section with a virtual plane containing its center line CL, i.e., the XZ plane containing the center line CL, the cylindrical body 30 and the reinforcement 40 are as follows. In other words, in the cylindrical body 30, the area corresponding to the first bent portion 1B forms a first hollow tube bent portion 30B that includes a first bent inner surface 31 which is a concave curved surface and a first bent outer surface 32 which is a convex curved surface. The first bent inner surface 31 is part of the outer surface of the top wall portion 11. The first bent outer surface 32 is part of the outer surface of the plate-like member 20. The minimum radius of curvature R1 of the first bent inner surface 31 is 1 mm to 260 mm. Furthermore, in this cylindrical body 30, the area corresponding to the second bent portion 1C forms a second hollow tube bent portion 30C that includes a second bent inner surface 33 which is a concave curved surface and a second bent outer surface 34 which is a convex curved surface. The second bent inner surface 33 is part of the outer surface of the plate-like member 20 and is connected to the rear end of the first bent outer surface 32. The second bent outer surface 34 is part of the outer surface of the top wall portion 11 and is connected to the rear end of the first bent inner surface 31. The minimum radius of curvature R2 of the first bent inner surface 31 is 1 mm to 260 mm. The minimum radius of curvature R2 may be the same as the minimum radius of curvature R1, or there may be a difference between them.

[0041] The first hollow tube bend 30B has a trapezoidal (rectangular) cross-section when viewed in a cross-section perpendicular to the center line CL, and the height dimension between the top wall 11 and the plate-like member 20 forming the bottom wall is smaller than the total width dimension W1 (mm) of the flat section, which will be described later. With this configuration, conversely, compared to the case where the height dimension between the top wall 11 and the plate-like member 20 is larger than the total width dimension W1 (mm) of the flat section, the bending direction of the impact absorbing member 1, with the first bent inner surface 31 of the top wall 11 facing inward, can be controlled with greater precision. The second hollow tube bend 30C may also have a similar configuration.

[0042] On the other hand, in the reinforcement 40, the area corresponding to the first bend 1B is fixedly positioned inside the first hollow tube bend 30B, forming a first reinforcement bend 40B that is bent along the first hollow tube bend 30B. Furthermore, in this reinforcement 40, the area corresponding to the second bend 1C is fixedly positioned inside the second hollow tube bend 30C, forming a second reinforcement bend 40C that is bent along the second hollow tube bend 30C. This second reinforcement bend 40C is connected to the rear end of the first reinforcement bend 40B.

[0043] The impact-absorbing member 1, comprising the reinforcement 40 and cylindrical body 30 described above, satisfies both of the following conditions to prevent out-of-plane deformation from occurring in unintended locations: (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.

[0044] r1=((W1-t2) / (n1+1)) / t1...(Formula 1) r2=((W2-t3) / (n2+1)) / t1...(Formula 2)

[0045] Equations 1 and 2 will be explained below with reference to Figure 4, but first, let's explain Figure 4 itself. Figure 4 is a schematic diagram illustrating the dimensions of each part of the impact-absorbing member 1, and corresponds to the AA cross-sectional view in Figure 3(a). Note that in Figure 4, the following diagrams are used to make the explanation easier to understand. First, the curvature of the curved sections (rounded sections) in the ridge line EL is shown to be larger than it actually is. Each curved section 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.

[0046] 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 does not include the curved portion (rounded portion) including the ridge line EL. For example, if the widths of the flat portion of the top wall portion 11 are 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). Also, as will be described later, the total plate thickness of the vertical plate 41 is t2 (mm).

[0047] 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 line EL, or the curved section (rounded section) formed between the left flange section 13a and the right flange section 13b (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. The thickness of the top wall section 11 within the range of this total width W2 is t1 (mm), the same as the thickness of the top wall section 11. Also, as will be described later, the total plate thickness of the horizontal plate 42 is t3 (mm).

[0048] 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.

[0049] 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 dimension 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 dimension 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.

[0050] 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.

[0051] 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 of the flat portion 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 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.

[0052] 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.

[0053] 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 first bent inner surface 31 (top wall portion 11) of the cylindrical body 30, the top wall portion 11 at the beginning of 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.

[0054] 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.

[0055] 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.

[0056] On the other hand, since the shock-absorbing member 1 is pre-equipped with a first hollow tube bend 30B and a second hollow tube bend 30C in which both the cylindrical body 30 and the reinforcement 40 are bent, the shock-absorbing member 1 can be deformed into a roughly inverted S-shape in a well-defined manner, using the first bend inner surface 31 and the second bend inner surface 33, respectively, as the bending starting points. In addition, since the impact energy applied to the shock-absorbing member 1 is absorbed mainly by the reinforcement 40 as it deforms by bending, starting from the first reinforcement bend 40B and the second reinforcement bend 40C, the amount of energy absorbed can be increased.

[0057] 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. These Figures 5 to 11 correspond to the AA cross-sectional view in Figure 3(a).

[0058] 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. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D. 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 constrains 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. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D.

[0059] 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-like member 20 by laser arc welding in a state of surface contact. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end portion 1D. Figure 5(d) also shows that the internal space of the cylindrical body 30 is divided into two sections horizontally 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-like member 20 by laser arc welding while abutting against it. The cross-sectional configuration of this example is almost the same for the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end portion 1D.

[0060] 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. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D. 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. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D.

[0061] 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. The cross-sectional configuration in this example is almost the same for the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end 1D. Figure 6(d) also shows that the internal space of the cylindrical body 30 is divided into three sections in the left-right direction by two vertical plates 41. That is, the horizontal plate 42 is omitted, and the top wall portion 11 is supported by 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 portion 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, two vertical plates 41 were constructed by press-forming a single steel plate into a U-shaped cross-section, but two separate vertical plates 41 may also be used. The cross-sectional configuration in this example is almost the same at the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end portion 1D.

[0062] Figure 6(e) also shows that the internal space of the cylindrical body 30 is divided into three sections in the left-right direction by two vertical plates 41. That is, the horizontal plate 42 is omitted, and the top wall portion 11 is supported by the two vertical plates 41. The upper ends of each vertical plate 41 are connected, and this connected portion is fixed to the top wall portion 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 by spot welding to each flange connected to the lower ends of the two vertical plates 41. The cross-sectional configuration of this example is almost the same at the front end 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D.

[0063] 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. The cross-sectional configuration of this example is almost the same at the front end portion 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D.

[0064] 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. The cross-sectional configuration of this example is almost the same at the front end portion 1A, the first curved portion 1B, the second curved portion 1C and the rear end portion 1D.

[0065] 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 about 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-like 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-like member 20. The cross-sectional configuration of this example is almost the same at the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end 1D.

[0066] 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-like 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-like member 20. The cross-sectional configuration of this example is almost the same at the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end 1D.

[0067] 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. 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 wall 12a and the right wall 12b, the two vertical plates 41 and the horizontal plate 42, and one space partitioned by the horizontal plate 42, the left wall 12a and the right wall 12b and the plate-like member 20. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved section 1B, the second curved section 1C and the rear end 1D.

[0068] 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. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end 1D.

[0069] 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 wall 12a and the right wall 12b, the two vertical plates 41 and the horizontal plate 42, and one space partitioned by the horizontal plate 42, the left wall 12a and the right wall 12b and the plate-like member 20. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved section 1B, the second curved section 1C and the rear end 1D.

[0070] 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, which are partitioned by the top wall portion 11, the left side wall portion 12a and the right side wall portion 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20. The cross-sectional configuration of this example is substantially the same at the front end portion 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D.

[0071] 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, which are partitioned by the top wall portion 11, the left side wall portion 12a and the right side wall portion 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20. The cross-sectional configuration of this example is substantially the same at the front end portion 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D.

[0072] 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.

[0073] 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, which are partitioned by the top wall portion 11, the left side wall portion 12a and the right side wall portion 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20. The cross-sectional configuration of this example is substantially the same at the front end portion 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D.

[0074] 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.

[0075] 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, and flanges are 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. On the other hand, the second angle member has a roughly L-shaped cross-section perpendicular to the longitudinal direction, and flanges are 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, which are partitioned by the top wall portion 11, the left side wall portion 12a and the right side wall portion 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20. The cross-sectional configuration of this example is substantially the same at the front end portion 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D.

[0076] 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, which are partitioned by the top wall portion 11, the left side wall portion 12a and the right side wall portion 12b, the vertical plate 41, the horizontal plate 42, and the plate-like member 20. The cross-sectional configuration of this example is substantially the same at the front end portion 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D.

[0077] 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, each edge of each angle member is joined by laser arc welding while abutting against the top wall 11, the left wall 12a and 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. The cross-sectional configuration in this example is almost the same at the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end 1D.

[0078] 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. The cross-sectional configuration in this example is substantially the same at the front end 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D.

[0079] 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, each edge of each angle member is joined by laser arc welding while abutting against the top wall 11, the left wall 12a and 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. The cross-sectional configuration in this example is almost the same at the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end 1D.

[0080] 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. The cross-sectional configuration in this example is substantially the same at the front end 1A, the first curved portion 1B, the second curved portion 1C, and the rear end portion 1D.

[0081] 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.

[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, 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. The cross-sectional configuration in this example is substantially the same at the front end 1A, the first bend 1B, the second bend 1C, and the rear end 1D.

[0083] 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.

[0084] 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 surface contact to the left flange portion 13a at the lower end of the left wall portion 12a. 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. The cross-sectional configuration in this example is substantially the same at the front end 1A, the first bend portion 1B, the second bend portion 1C, and the rear end portion 1D.

[0085] 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.

[0086] 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 side wall 12a and the right side wall 12b, the two vertical plates 41 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. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved section 1B, the second curved section 1C and the rear end 1D.

[0087] 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. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end 1D.

[0088] 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.

[0089] 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. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end 1D.

[0090] 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.

[0091] 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. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end 1D.

[0092] 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.

[0093] 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. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end 1D.

[0094] 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. The cross-sectional configuration of this example is substantially the same at the front end 1A, the first curved section 1B, the second curved section 1C, and the rear end 1D. [Examples]

[0095] [First Embodiment] A rectangular cylindrical member with both ends closed with caps was used as a shock-absorbing member, and the relationship between the out-of-plane deformation δ and the width-to-thickness ratio of the flat surface W / t when a load is applied along the longitudinal direction of this shock-absorbing member was determined by numerical calculation.

[0096] First, the impact-absorbing member 1X shown in Figure 12(a) was placed vertically on the base BS. This impact-absorbing member 1X is a rectangular cylindrical member with a square cross-section perpendicular to each position in its longitudinal direction, and its upper and lower ends are closed by caps. The reason why the impact-absorbing member 1X is a straight pipe without the first bend 1B and the second bend 1C is purely to confirm the relationship between the out-of-plane deformation amount δ and the planar section width-to-plate thickness ratio W / t. This impact-absorbing member 1X was set to be placed in an upright position with its central axis perpendicular to the upper surface of the base BS. The length of the impact absorbing member 1X was set to L = 200 (mm). The width of each side in a cross-section perpendicular to the longitudinal direction of the impact absorbing member 1X was defined as W (mm), and the plate thickness as t (mm). The width W (mm) was then varied in eight stages: 5 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, and 70 mm. In addition, the plate thickness t (mm) was varied in three stages: 1.0 mm, 1.6 mm, and 2.0 mm. By combining these widths W (mm) and plate thicknesses t (mm), multiple impact absorbing members 1X with various dimensions and shapes were considered, where the width-to-thickness ratio W / t of the flat surface was varied within a range of 70 or less. The tensile strength of the material for each impact absorbing member 1X was standardized to 1180 MPa, and no reinforcement was provided.

[0097] After arranging each shock-absorbing member 1X in an upright position as shown in Figure 12(a), a compressive impact force F passing through the central axis was applied to the rigid wall, which serves as the lid at the top of each member. At this time, the downward movement speed of the rigid wall was set to 5 m / s, and the load was applied until buckling deformation began. The timing of the start of buckling was determined to be when the load supported by the shock-absorbing member 1X decreased. Then, as shown in Figure 12(b), the amount of out-of-plane deformation in the impact absorbing member 1X after being subjected to an impact force F was determined as δ (mm). This amount of out-of-plane deformation δ (mm) represents the maximum deformation of the outer surface bulge after out-of-plane deformation, with the outer surface before the impact force F was applied as the reference. In this way, the relationship between the amount of out-of-plane deformation δ and the flat surface width-to-thickness ratio W / t was determined for each impact absorbing member 1X, and these were plotted on the graph shown in Figure 13.

[0098] As a result, as shown in Figure 13, in impact-absorbing members 1X with a planar width-to-thickness ratio W / t of less than 10, the strength was too high, preventing out-of-plane deformation and thus no knots were generated, making it impossible to adequately absorb the impact force F. On the other hand, as shown in Figure 13, in the impact absorbing member 1X with a planar portion width-to-thickness ratio W / t of 10 or more and 70 or less, axial crushing occurred as a result of out-of-plane deformation. The amount of out-of-plane deformation δ (mm) at this time was kept flat or only slightly increased when the planar portion width-to-thickness ratio W / t was 50 or less, but it was confirmed that it increased sharply when the planar portion width-to-thickness ratio W / t exceeded 50. From this, it can be seen that when the planar portion width-to-thickness ratio W / t exceeds 50, the way in which out-of-plane deformation occurs becomes sharply unstable. Although the impact absorbing member 1X of this first embodiment does not fall under the examples of the invention because it does not have reinforcement, it was confirmed that in order to appropriately control the out-of-plane deformation of the impact absorbing member 1X and cause it to bend, the planar portion width-to-thickness ratio W / t should be 10 or more and 50 or less.

[0099] [Second Example] In this second embodiment, the influence of the first planar section width-to-thickness ratio r1 and the second planar section width-to-thickness ratio r2, as described in Figure 4, on the bending deformation behavior of the impact absorbing member was determined and confirmed by numerical calculation. First, we considered the impact absorbing member 1E shown in Figure 14. This impact absorbing member 1E has the same configuration as the impact absorbing member 1 shown in Figure 2, except that it does not have the first bent portion 1B and the second bent portion 1C. The reason why the impact absorbing member 1E is a straight pipe without the first bent portion 1B and the second bent portion 1C is purely to confirm the relationship between out-of-plane deformation and the dimensions of each part. The length L (mm) of the impact absorbing member 1E was set to 400 mm, the plate thickness t (mm) to 1.0 mm, the tensile strength of the material to 1180 MPa, and the bending point was set to the center of the longitudinal direction of the top wall. It was also equipped with a reinforcement 40 having the same "+" shape as in Figure 2. On the other hand, in this impact-absorbing member 1E, the width dimensions w1(mm), w2(mm), w3(mm), and w4(mm) shown in Figure 4 were set to be equal. Two cases were considered: one where the width dimension was 50 mm and another where it was 70 mm. This resulted in two cases: Case A, which is an inventive example where the width-to-thickness ratio of the first flat section r1 and the width-to-thickness ratio of the second flat section r2 are both equal to 50 (r1=50 and r2=50); and Case B, which is a comparative example where the width-to-thickness ratio of the first flat section r1 and the width-to-thickness ratio of the second flat section r2 are both equal to 70 (r1=70 and r2=70). For each of these impact-absorbing members 1E in Case A and B, an impact force F along its longitudinal direction was applied to induce bending deformation, as shown in Figure 14(b).

[0100] As a result, in Case-A (inventive example) shown in Figure 15(a), the assumed fold initiation point position coincided with the actual fold position. On the other hand, in Case-B (comparative example) shown in Figure 15(b), the actual fold occurred at a position shifted from the assumed fold initiation point position. Comparing the out-of-plane deformation of the two cases, the out-of-plane deformation was kept small in the inventive example in Figure 15(a). On the other hand, the out-of-plane deformation was large in the comparative example in Figure 15(b). It was inferred that the occurrence of this large out-of-plane deformation caused the actual fold initiation point position to shift from the assumed fold initiation point position. From the above, it was confirmed that simply providing the reinforcement 40 is insufficient to suppress out-of-plane deformation, and that it is necessary to set at least one of the first planar section width-to-thickness ratio r1 and the second planar section width-to-thickness ratio r2 within an appropriate range (10 to 50).

[0101] [Third Embodiment] A third embodiment of the present invention will be described below with reference to Figures 16 to 21. In this third embodiment, the maximum load and energy absorption amount were determined by numerical calculation when collision energy was applied to multiple impact absorbing members with different reinforcement conditions.

[0102] Specifically, six types of impact-absorbing members having various cross-sectional shapes, as shown in Figure 16, were prepared. Figure 16 is a cross-sectional view of the impact-absorbing member along line AA in Figure 3(a). Of these, Case 000 shows a comparative example without reinforcement 40. Case 005 also shows a comparative example with a different method of reinforcement. Case 001 shows an example of the invention in which only one horizontal plate 42 is provided as the reinforcement 40. Case 002 shows an example of the invention in which only one vertical plate 41 is provided as the reinforcement 40. Case 003 is an example of the invention in which one horizontal plate 42 and one vertical plate 41 are intersected in a "+" shape as the reinforcement 40, and is the same configuration as illustrated in Figures 2 and 9(a). Case 004 is an example of the invention in which one vertical plate 41, half the height of one horizontal plate 42, is joined between the center of the horizontal plate 42 in the width direction and the top wall portion 11, and is the same configuration as illustrated in Figure 7(a). Case 005 is a comparative example in which an inverted U-shaped reinforcing member 10A, whose cross-section is similar to that of the hat-shaped member 10, is joined to the inner circumferential surface of the hat-shaped member 10.

[0103] The cross-sectional shapes shown in Cases 000 to 005 above were applied to the impact absorbing member 1 having the shapes shown in Figures 17 and 18. Here, Figure 17 is a diagram showing how the load is applied in this embodiment, where (a) is a plan view and (b) is a side view. Also, in Figure 18, (a) is a BB cross-sectional view of Figure 17(b), and (b) is a CC cross-sectional view of Figure 17(b). Note that the reinforcement is not shown in Figures 18(a) and (b). As shown in these figures, the impact absorbing member 1 of this embodiment has a linear total length of 500 mm, the height dimension between the top wall portion 11 and the plate-like member 20 in the BB cross-section is 70 mm, and the height dimension between the top wall portion 11 and the plate-like member 20 in the CC cross-section is 110 mm.

[0104] As shown in Figures 17(a) and (b), a load F along the -X axis was applied to the tip of the impact absorbing member 1 as collision energy. Figures 19(a) to (e) show the shape of the shock-absorbing member 1 after it has been deformed by bending under load F. Here, Figure 19(a) shows Case 001 of Figure 16, (b) shows Case 002 of Figure 16, (c) shows Case 003 of Figure 16, (d) shows Case 004 of Figure 16, and (e) shows Case 005 of Figure 16.

[0105] Then, the maximum load and energy absorption amount were determined when the impact absorbing member 1 was subjected to a load F and deformed at two points along its longitudinal direction. The results are shown in Figures 20 and 21. Here, Figure 20 is a bar graph comparing the maximum loads, with the horizontal axis representing each case number and the vertical axis representing the maximum load (kN). Figure 21 is a bar graph comparing the energy absorption amounts, with the horizontal axis representing each case number and the vertical axis representing the energy absorption amount (kJ). Here, the energy absorption amount was assumed to be when the deformation stroke was 150 mm. Furthermore, the maximum load improvement rate and the energy absorption improvement rate were determined, taking into account the weight increase relative to Case 000. Here, the maximum load improvement efficiency is the value obtained by dividing the increase in maximum load from the standard Case 000's maximum load of 400kN by the increase in weight from Case 000's weight of 2.3kg. Similarly, the energy absorption improvement rate is the value obtained by dividing the increase in maximum load from the standard Case 000's maximum load of 400kN by the increase in weight from Case 000's weight of 2.3kg. The results above are summarized in Table 1.

[0106] [Table 1]

[0107] First, as shown in Figures 19(a) to (e), it was confirmed that in all cases, the structure bends smoothly at the joints due to the pre-positioning of the first bend 1B and the second bend 1C. Furthermore, as shown in Figure 20, Case 001 had the same maximum load as Case 000, while Cases 002 to 005 showed an increase in maximum load compared to Case 000. Also, as shown in Figure 21, it was confirmed that all of Cases 001 to 005 achieved higher energy absorption than Case 000.

[0108] Here, in order to compare while taking weight increments into consideration, looking at the maximum load improvement rate and energy absorption improvement rate shown in Table 1, it was confirmed that the inventive examples, Cases 001 to 004, achieved a significantly higher energy absorption improvement rate compared to the comparative examples, Cases 000 and 005. In particular, it was confirmed that Cases 003 and 004, in which the reinforcement 40 is equipped with both vertical plates 41 and horizontal plates 42, yielded a particularly high combination of maximum load improvement efficiency and energy absorption improvement rate. As described above, according to the present invention, the material is lightweight yet folds and deforms smoothly at its joints, exhibiting high energy absorption efficiency.

[0109] The main points of this invention are summarized below. (1) One aspect of the present invention is: An impact absorbing member 1, which is long in one direction, comprises a cylindrical body (hollow tube) 30 and a reinforcement 40 fixedly positioned inside the cylindrical body 30, 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; The cylindrical body 30 and the reinforcement 40 both have a first bent portion 1B; When the first curved portion 1B is viewed in a cross-section along the longitudinal direction of the impact absorbing member 1, The cylindrical body 30 has a first hollow tube bend 30B which includes a first bend inner surface 31 that is a concave curved surface and a first bend outer surface 32 that is a convex curved surface. The reinforcement 40 is fixedly positioned inside the first hollow tube bend 30B and has a first reinforcement bend 40B that is bent along the first hollow tube bend 30B; When the first curved portion 1B is viewed in a cross-section perpendicular to the longitudinal direction, The cylindrical body 30 has a top wall portion 11 having a first bent inner surface 31 and a flat portion with a total width dimension W1 (mm) and a plate thickness t1 (mm), a pair of side wall portions 12 provided on both sides of the top wall portion 11 and having a flat portion with a total width dimension W2 (mm) and a plate thickness t1 (mm), and a plate-like member (bottom wall portion) 20 positioned opposite the top wall portion 11 and having a first bent outer surface 32. The reinforcement 40 has at least one of the following: vertical plates 41, one end of which is joined to the top wall 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 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 in which the vertical plate 41 is present 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 a second condition in which the horizontal plate 42 is present and the second planar portion width-to-thickness ratio r2 according to the following formula 2 is 10 or more and 50 or less. r1=((W1-t2) / (n1+1)) / t1...(Formula 1) r2=((W2-t3) / (n2+1)) / t1...(Formula 2)

[0110] (2) In the impact absorbing member 1 described in (1) above, the minimum radius of curvature R1 of the first bent inner surface 31, when viewed in cross-section along the longitudinal direction, may be 1 mm to 260 mm.

[0111] (3) In the impact absorbing member 1 described in (1) or (2) above, the first hollow tube bend 30B may have a rectangular cross-section when viewed in a cross-section perpendicular to the longitudinal direction, and the height dimension between the top wall portion 11 and the plate-like member (bottom wall portion) 20 may be smaller than the total width dimension W1 (mm) of the flat portion.

[0112] (4) In the impact absorbing member 1 described in any one of the above items (1) to (3), the following may be used: The cylindrical body 30 and the reinforcement 40 further have a second curved portion 1C, which is positioned adjacent to the first curved portion 1B along the longitudinal direction and curves in the opposite direction to the first curved portion 1B; When the second curved section 1C is viewed in a cross-section along the longitudinal direction, The cylindrical body 30 includes a second bent outer surface 34 which is a convex curved surface and a second bent inner surface 33 which is a concave curved surface, and has a second hollow tube bent portion 30C which is bent in the opposite direction to the first hollow tube bent portion 30B. The reinforcement 40 is fixedly positioned inside the second hollow tube bend 30C and has a second reinforcement bend 40C that is bent along the second hollow tube bend 30C.

[0113] (5) In the impact absorbing member 1 described in any one of the above items (1) to (4), the minimum radius of curvature R2 of the second bent inner surface 33, when viewed in cross-section along the longitudinal direction, may be 1 mm to 260 mm.

[0114] (6) In the impact absorbing member 1 described in any one of the above items (1) to (5), the following may be used: The above first condition is met; When the first curved section 1B is viewed in a cross-section perpendicular to the longitudinal direction, the flange formed at one end of the vertical plate 41 is spot-welded to the top wall.

[0115] (7) In the impact absorbing member 1 described in any one of the above items (1) to (6), the following may be used: The above second condition is met; When the first curved section 1B is viewed in a cross-section perpendicular to the longitudinal direction, the flanges formed at both ends of the horizontal plate 42 are spot-welded to each of the pair of side wall sections 12.

[0116] (8) The impact absorbing member 1 described in (1) above may be provided as follows: The cylindrical body 30 A hat-shaped member 10 having a hat top portion whose cross-section perpendicular to the longitudinal direction is a top wall portion 11 and a pair of side wall portions 12 connected to both sides of the hat top portion, It comprises a plate-shaped member 20 joined to a hat-shaped member 10 and having a bottom wall portion facing the top of the hat; Satisfying both the first and second conditions; When the first curved portion 1B is viewed in a cross-section perpendicular to the longitudinal direction, The number of sheets n1 is 1 and the number of sheets n2 is 1, The vertical plate 41 is fixed in a state where it is stretched between the top of the hat and the bottom wall. 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.

[0117] (9) The impact absorbing member 1 described in (1) above may be provided as follows: The cylindrical body 30 A hat-shaped member 10 having a hat top portion whose cross-section perpendicular to the longitudinal direction is a top wall portion 11 and a pair of side wall portions 12 connected to both sides of the hat top portion, The plate-shaped member 20 has a bottom wall portion opposite to the hat top portion and is joined to the hat-shaped member 10; Satisfying both the first and second conditions; When the first curved portion 1B is viewed in a cross-section perpendicular to the longitudinal direction, The number of sheets n1 is 1 and the number of sheets 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 of the hat, and the other end of the vertical plate 41 is joined to the position between one end and the other end of the horizontal plate 42. [Explanation of Symbols]

[0118] 1. Impact absorbing member 1B First curve 1C Second curve 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) 30B First hollow pipe bend 30C Second hollow pipe bend 31 First bend inner surface 32 First bend outer surface 33. Inner surface of the second bend 34. Outer surface of the second bend 40 Reinforce 40B First Reinforcement Curve 40C Second Reinforcement Curve 41 vertical boards 42 Horizontal board

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 hollow tube and the reinforcement both have a first bend; When the first curved portion is viewed in a cross-section along the longitudinal direction of the impact-absorbing member, The hollow tube has a first hollow tube bend that includes a first curved inner surface which is a concave surface and a first curved outer surface which is a convex surface. The reinforcement is fixedly positioned inside the first hollow tube bend and has a first reinforcement bend that is bent along the first hollow tube bend; When the first curved portion is viewed in a cross-section perpendicular to the longitudinal direction, The hollow tube has a top wall portion having the first bent inner surface and a total width dimension W1 (mm) and plate thickness t1 (mm), a pair of side wall portions provided on both sides of the top wall portion and having a total width dimension W2 (mm) and plate thickness t1 (mm), and a bottom wall portion positioned opposite the top wall portion and having the first bent outer surface, The reinforcement comprises at least one of the following: vertical plates, one end of which is joined to the top wall, 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 sections, 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; A shock-absorbing member characterized by the following features. r1=((W1-t2) / (n1+1)) / t1...(Formula 1) r2=((W2-t3) / (n2+1)) / t1...(Formula 2)

2. When viewed in a cross-section along the longitudinal direction, the minimum radius of curvature R1 of the inner surface of the first bend is between 1 mm and 260 mm. The impact absorbing member according to feature 1.

3. The first hollow tube bend, when viewed in a cross-section perpendicular to the longitudinal direction, Having a rectangular cross-section, The height dimension between the top wall and the bottom wall is smaller than the total width dimension W1 (mm) of the flat section. The impact absorbing member according to feature 1 or 2.

4. The device further has a second bend, which is located adjacent to the first bend along the longitudinal direction, and both the hollow tube and the reinforcement bend in the opposite direction to the first bend; When the second curved portion is viewed in a cross-section along the longitudinal direction, The hollow tube has a second hollow tube bend that includes a second curved outer surface which is a convex curved surface and a second curved inner surface which is a concave curved surface, and is bent in the opposite direction to the first hollow tube bend. The reinforcement is fixedly positioned inside the second hollow tube bend and has a second reinforcement bend that is bent along the second hollow tube bend; The impact absorbing member according to feature 1 or 2.

5. When viewed in a cross-section along the longitudinal direction, the minimum radius of curvature R2 of the inner surface of the second bend is between 1 mm and 260 mm. The impact absorbing member according to feature 4.

6. The above first condition is met; When the first curved portion is viewed in a cross-section perpendicular to the longitudinal direction, the flange formed at one end of the vertical plate is spot-welded to the top wall; The impact absorbing member according to feature 1 or 2.

7. The above second condition is met; When the first curved portion is viewed in a cross section perpendicular to the longitudinal direction, the flanges formed at both ends of the horizontal plate are spot-welded to each of the pair of side wall portions; The impact absorbing member according to feature 1 or 2.

8. The aforementioned hollow tube A hat-shaped member having a hat apex whose cross-section perpendicular to the longitudinal direction is the top wall portion and a pair of side wall portions connected to both sides of the hat apex, It comprises a plate-shaped member joined to the hat-shaped member and having a bottom wall portion facing the top of the hat; Satisfying both the first and second conditions; When the first curved portion is viewed in a cross-section perpendicular to the longitudinal direction, The number of sheets n1 is 1 and the number of sheets n2 is 1, The vertical plate is fixed in a state where it is stretched between the top of the hat and the bottom wall. The horizontal plate is fixed between the pair of side walls in a state where it intersects with the vertical plate; The impact absorbing member according to feature 1.

9. The aforementioned hollow tube A hat-shaped member having a hat apex whose cross-section perpendicular to the longitudinal direction is the top wall portion and a pair of side wall portions connected to both sides of the hat apex, It has a plate-like member having a bottom wall portion opposite to the hat top portion and joined to the hat-shaped member; Satisfying both the first and second conditions; When the first curved portion is viewed in a cross-section perpendicular to the longitudinal direction, The number of sheets n1 is 1 and the number of sheets 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 hat apex, and the other end of the vertical plate is joined to the horizontal plate at a position between the one and the other end; The impact absorbing member according to feature 1.

Images