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 reinforcement 40 has a first portion R1, a second portion R2, and a third portion R3 sequentially along a longitudinal direction. In the second portion R2, a bend-start part having at least one of a plate thickness thinner than those of the first and third portions R1, R3 and tensile strength lower than those of the first and third portions R1, R3 is formed with a connection position with the cylindrical body 30 included in the bend-start part.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a shock-absorbing member.

Background Art

[0002] In recent years, fuel consumption regulations have been tightened worldwide, and automobile manufacturers are promoting the weight reduction of vehicle bodies. At the same time, since the collision safety of vehicle bodies has also been tightened, it is required to achieve both weight reduction and improvement of collision performance. In addition, along with the trend of fuel consumption regulations and carbon neutrality in each country, the electrification of the power source of automobiles is being promoted. Along with the electrification of the power source, changes have also occurred in the vehicle body structure, such as an increase in vehicle body weight and a reduction in the engine room compared to the vehicle body structure having a conventional internal combustion engine. As an example, there is the shortening of the front nose of the vehicle body. In order to maintain high collision safety while shortening the nose of the vehicle body, a structure capable of obtaining high energy absorption efficiency with a short deformation stroke is required.

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

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

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

[0006] Patent Document 1 discloses a rear vehicle structure that absorbs impact energy during a rear collision. This rear vehicle structure consists of a rear frame and a tank lower frame positioned below the rear frame, arranged in pairs on the left and right sides of the vehicle body. The rear frame has displacement-load characteristics such that the ratio of load F to displacement S (F / S) is larger than that of the tank lower frame, and the tank lower frame employs a configuration in which cross-sectional deformation is suppressed so that the load does not drop sharply after reaching the maximum bending strength.

[0007] As mentioned above, impact-absorbing members are now required to have a shorter deformation stroke in addition to being lightweight and having improved collision performance. One way to reduce weight is to use light alloys such as aluminum as the material, but due to their low material strength, improved collision performance and a shorter deformation stroke cannot be expected. Therefore, another option is to use high-strength steel plates with high tensile strength and then reduce the plate thickness. However, if the plate thickness is simply reduced in the rear frame disclosed in Patent Document 1, for example, out-of-plane deformation 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; In a cross-section perpendicular to the longitudinal direction of the impact absorbing member, The hollow tube has a top wall section having a total width W1 (mm) and a plate thickness t1 (mm), and a pair of side wall sections provided on both sides of the top wall section, each having a total width W2 (mm) and a plate thickness t1 (mm). The reinforcement comprises at least one of the following: vertical plates, one end of which is joined to the top wall, 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 aforementioned reinforcement, A first condition is that the vertical plate 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 is that the horizontal plate 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, satisfying at least one of these conditions. It has a first part, a second part, and a third part arranged in order along the longitudinal direction; In the aforementioned second area, A plate thickness thinner than both the first and third portions, Lower tensile strength than both the first and third parts, A bending point portion having at least one of the above is formed including the connection position with the hollow tube. r1=((W1-t2) / (n1+1)) / t1...(Formula 1) r2=((W2-t3) / (n2+1)) / t1...(Formula 2)

[0010] According to the impact absorbing member described in (1) above, when the bending point is set on the top wall of the hollow tube, the top wall at the beginning of the bending deformation tends to sink inward into the hollow tube. If only the first condition is met, the vertical plate continues to support the top wall while resisting the force that would cause it to sink. This suppresses the sinking of the top wall and also suppresses the gap between the pair of side walls that would occur as a result of the sinking of the top wall. In this way, the hollow tube is supported from within by reinforcement. Alternatively, if only the second condition is met, the distance between the pair of side walls is constrained by the horizontal plate. This constraint prevents the top wall from sinking in a way that pushes the space between the pair of side walls apart, thus indirectly supporting the top wall. Therefore, in this case as well, the hollow tube is supported from within by reinforcement. Alternatively, if both the first and second conditions are met, in addition to suppressing the sinking of the top wall, the gap between the pair of side walls is also suppressed. As a result, the synergistic effect of both forces further strengthens the support of the hollow tube from within. Thus, the hollow tube is reinforced at each position along its longitudinal direction by reinforcement. Furthermore, the hollow tube satisfies at least one of the following conditions: the first condition is that the width-to-thickness ratio r1 of the first planar section is 10 or more and 50 or less, and the second condition is that the width-to-thickness ratio r2 of the second planar section is 10 or more and 50 or less. As a result, even if the thickness t1 of the hollow tube is reduced for the purpose of weight reduction, the top wall or side walls will not easily deform out of plane. If out-of-plane deformation occurs at an unintended location, the way in which the compression deformation occurs at that location becomes unstable, so the out-of-plane deformed part may be more prone to breaking or less prone to breaking. As a result, there is a risk that bending deformation may occur at an unintended location of the hollow tube. On the other hand, in this embodiment, at least one of the first and second conditions is satisfied. As a result, out-of-plane deformation of the hollow tube at unintended locations can be suppressed, and the thickness t1 can be reduced to lighten the impact absorbing member. On the other hand, this shock-absorbing member has a bending point in the second part that has at least one of the following characteristics: a thinner plate thickness than both the first and third parts, and a lower tensile strength than both the first and third parts. Therefore, the bending strength of the second part is relatively lower than that of the first and third parts. This relative strength difference, combined with at least one of the first and second conditions described above, allows the shock-absorbing member to bend and deform smoothly using the second part as the bending point. In addition, the impact energy applied to the shock-absorbing member is absorbed mainly by the reinforcement bending and deforming starting from the second part, thus increasing the amount of energy absorbed.

[0011] (2) The impact absorbing member described in (1) above may be provided as follows: The tensile strength of the bending point in the second portion is equal to the tensile strengths of the first portion and the third portion; The thickness ratio obtained by dividing the total plate thickness t2 at the bending point in the second portion by the average plate thickness ta3 (mm), which is the average value of the total plate thickness t3 in the first portion and the total plate thickness t3 in the third portion, satisfies 1 / 3 ~ (ta3 - 0.2) / ta3. According to the impact-absorbing member described in (2) above, the upper limit of the plate thickness ratio at the bending point is (ta3-0.2) / ta3, which ensures the minimum plate thickness difference necessary to deform the impact-absorbing member smoothly at the bending point. Furthermore, the lower limit of the plate thickness ratio at the bending point is 1 / 3, which has the advantage of ensuring that the member can be reliably deformed at a predetermined position regardless of the load conditions in the actual usage environment.

[0012] (3) The impact absorbing member described in (1) above may be provided as follows: The total plate thickness t2 at the bending point in the second portion and the average plate thickness ta3 (mm), which is the average of the total plate thickness t3 in the first portion and the total plate thickness t3 in the third portion, are equal to each other; The tensile strength ratio obtained by dividing the tensile strength E1 (MPa) of the fold starting point in the second part by the average tensile strength Ea2 (MPa), which is the average of the tensile strength in the first part and the tensile strength in the third part, satisfies (Ea2 - 100) / Ea2 to 2. According to the impact absorbing member described in (3) above, since the upper limit value of the tensile strength ratio at the fold starting point is 2, it is possible to secure the minimum tensile strength difference required to fold and deform the impact absorbing member smoothly at the position of the fold starting point. Further, since the lower limit value of the tensile strength ratio at the fold starting point is (Ea2 - 100) / Ea2, there is an advantage that it can be surely deformed at a predetermined position regardless of the load conditions in the actual use environment.

[0013] (4) In the impact absorbing member described in (1) above, the following may be adopted: The plate thickness ratio obtained by dividing the total plate thickness t2 at the fold starting point in the second part by the average plate thickness ta3 (mm), which is the average of the total plate thickness t3 in the first part and the total plate thickness t3 in the third part, satisfies 1 / 3 to (ta3 - 0.2) / ta3; The tensile strength ratio obtained by dividing the tensile strength E1 (MPa) of the fold starting point in the second part by the average tensile strength Ea2 (MPa), which is the average of the tensile strength in the first part and the tensile strength in the third part, satisfies (Ea2 - 100) / Ea2 to 2. According to the impact absorbing member described in (4) above, due to the synergistic effect resulting from the combination of (2) and (3) above, the bending strength difference between the fold starting point and its surroundings can be made clearer, and the impact absorbing member can be folded and deformed smoothly at the position of the fold starting point. The reasons for each upper and lower limit value are as described above.

[0014] (5) In the impact absorbing member described in any one of (1) to (4) above, In the direction along the longitudinal direction, the length dimension Lr1 (mm) of the fold starting point and the length dimension Lr2 (mm) of the reinforcement may satisfy Lr2 > Lr1 > (1 / 2)×Lr2. According to the shock absorption member described in (5) above, by setting the lower limit value of the length Lr1 of the folding start point portion as described above, the bending strength difference between the folding start point portion and its surroundings can be made clearer, and the shock absorption member can be bent and deformed smoothly at the position of the folding start point portion. Further, by setting the upper limit value of the length dimension Lr1 of the folding start point portion as described above, there is an advantage that the out-of-plane deformation region can be reduced, so that a higher energy absorption amount can be obtained.

[0015] (6) In the shock absorption member according to any one of (1) to (4) above, when the reinforcement is viewed in a cross section perpendicular to the longitudinal direction at a position including the folding start point portion, it may satisfy Wr2≧Wr1>(1 / 3)×Wr2, where Wr1 (mm) is the width dimension of the folding start point portion and Wr2 (mm) is the width dimension between the center of the reinforcement and the connection position. According to the shock absorption member described in (6) above, by setting the lower limit value of the width dimension Wr1 of the folding start point portion as described above, the bending strength difference between the folding start point portion and its surroundings can be made clearer, and the shock absorption member can be bent and deformed smoothly at the position of the folding start point portion. Further, by setting the upper limit value of the width dimension Wr1 of the folding start point portion as described above, there is an advantage that the relatively weak portion region can be reduced, so that a higher energy absorption amount can be obtained.

[0016] (7) In the shock absorption member according to any one of (1) to (4) above, the following may also be adopted: satisfy the first condition; in a cross-sectional view perpendicular to the longitudinal direction, a flange formed at one end of the vertical plate is spot-welded to the ceiling wall portion. According to the shock absorption member described in (7) above, for example, by adopting surface joining using a flange compared to line joining with the plate thickness at one end of the vertical plate as the joining line, out-of-plane deformation at an unexpected location in the ceiling wall portion can be more reliably prevented. Further, by adjusting the pitch and construction range of the spot welding, fine adjustment such as changing the distribution of the joining strength along the longitudinal direction of the shock absorption member can also be performed.

[0017] (8) In the impact absorbing member described in any one of the above items (1) to (4), the following may be used: The above second condition is met; In a cross-sectional view perpendicular to the longitudinal direction, flanges formed at both ends of the horizontal plate are spot-welded to each of the pair of side wall portions. With the impact-absorbing member described in (8) above, for example, compared to a line joint where the plate thickness at both ends of the horizontal plate is used as the joining line, adopting a surface joint using flanges makes it possible to more reliably prevent out-of-plane deformation at unexpected locations in the pair of side walls. Furthermore, fine adjustments can be made, such as changing the distribution of joint strength along the longitudinal direction of the impact-absorbing member by adjusting the pitch and construction range of the spot welds.

[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, It has a plate-shaped member joined to the hat-shaped member and facing the top of the hat; Satisfying both the first and second conditions; In the cross-section perpendicular to the longitudinal direction, The above total number of sheets n1 is 1 and the above total 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 plate-shaped member. The horizontal plate is fixed between the pair of side wall portions in a state where it intersects with the vertical plate. According to the impact absorbing member described in (9) above, the hollow tube is supported from the inside by a surface formed by the combination of vertical and horizontal plates when viewed in a cross section perpendicular to its longitudinal direction. Therefore, the bending strength of the reinforcement can be increased along its entire length, which 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.

[0019] (10) 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, It has a plate-shaped member joined to the hat-shaped member and facing the top of the hat; Satisfying both the first and second conditions; In the cross-section perpendicular to the longitudinal direction, The above total number of sheets n1 is 1 and the above total 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 (10) above, the hollow tube is supported from the inside by a surface formed by the combination of vertical and horizontal plates when viewed in a cross section perpendicular to its longitudinal direction. Therefore, the bending strength of the reinforcement can be increased along its entire length, which 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]

[0020] 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]

[0021] [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 member, with a portion of it broken to show its internal structure. Note that this diagram is intended to illustrate the basic structure of the shock-absorbing member, and the bending point is not shown. [Figure 3] This is a perspective view showing an example of the reinforcement provided in the impact-absorbing member. [Figure 4] This is a perspective view showing another example of reinforcement provided in the same impact-absorbing member. [Figure 5] This is a perspective view showing another example of reinforcement provided in the same impact-absorbing member. [Figure 6] This is a perspective view showing another example of reinforcement provided in the same impact-absorbing member. [Figure 7] This is a schematic diagram illustrating the dimensions of each part of the shock-absorbing member, and is a cross-sectional view of BB in Figure 2. [Figure 8] Figures (a) to (d) are diagrams showing modified examples of the same shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 9] (a) to (e) are diagrams showing other modified examples of the shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 10] Figures (a) to (d) are diagrams showing yet another modification of the same shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 11] (a) to (c) are diagrams showing yet another modification of the same shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 12] Figures (a) to (e) are diagrams showing yet another modification of the same shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 13] Figures (a) to (g) are diagrams showing yet another modification of the same shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 14] Figures (a) to (e) are diagrams showing yet another modification of the same shock-absorbing member, and are cross-sectional views of BB in Figure 2. [Figure 15] 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 16] 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 17]This figure illustrates the impact-absorbing member used in the second embodiment, where (a) is a cross-sectional view corresponding to Figure 7 or Figure 12(a), and (b) is a side view showing the member before and after bending deformation. [Figure 18] 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 19] This figure shows the impact-absorbing member used in the third embodiment, and is a cross-sectional view of BB in Figure 2. Of these, Case 000 and 005 are comparative examples. On the other hand, Case 001 to Case 004 are examples of inventions equipped with various reinforcements. [Figure 20] This is a perspective view showing how the load is applied in the third embodiment. (a) shows the structure before bending deformation, and (b) shows the structure after bending deformation. [Figure 21] 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 22] 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]

[0022] 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.

[0023] As will be described in detail later, the impact-absorbing member has a rectangular cross-section perpendicular to its longitudinal direction and comprises a hat-shaped member and a plate-shaped member. The hat-shaped member has a hat apex, which is the top wall, and a pair of side walls connected to both sides of the hat apex, with the cross-section perpendicular to its longitudinal direction. The plate-shaped member is joined to the hat-shaped member and faces the hat apex. The impact-absorbing member absorbs impact force through folding deformation rather than bellows deformation. Hereafter, the area undergoing folding deformation shown in Figure 1 will be denoted by reference numeral 1 and will be illustrated as impact-absorbing member 1 in the explanation. Furthermore, an example will be given where the trigger for folding deformation (fold trigger) is located on the top wall.

[0024] As shown in Figure 2, the impact absorbing member 1 of this embodiment is a cylindrical component that is elongated in the longitudinal direction along its center line CL. The impact absorbing member 1 has a rectangular cross-section perpendicular to the center line CL and includes a hat-shaped member 10, a plate-shaped member 20, and a reinforcement 40.

[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. The top wall portion 11 forms the apex of the hat-shaped member 10, which has a hat shape when viewed along the center line CL. The top wall portion 11 is a long plate that extends in a direction parallel to the center line CL, and its outer width dimension and plate thickness are constant at each position in its extending direction. The outer width dimension here includes the portion of the ridge line EL formed along both side edges of the top wall portion 11. The top wall portion 11 has a flat top surface and a flat bottom surface. Furthermore, the outer width and thickness of the top wall portion 11 do not necessarily have to be constant at each position along the center line CL, and may be slightly varied at each position along the center line CL as required by the component design. Similarly, the upper and lower surfaces of the top wall portion 11 do not necessarily have to be flat, and may have some irregularities as required by the component design.

[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. The left side wall portion 12a has a flat outer surface and a flat inner surface. The right side wall portion 12b is a vertical wall that is integrally connected to the other side edge of the top wall portion 11. The angle between the right side wall portion 12b and the top wall portion 11 in a cross section perpendicular to the center line CL may be 90° or an angle slightly larger than 90°. The right side wall portion 12b has a substantially constant width dimension and a substantially constant plate thickness. The right side wall portion 12b has a flat outer surface and a flat inner surface.

[0027] The left wall portion 12a and the right wall portion 12b are long plates that are elongated in a direction parallel to the center line CL when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1, and their outer height dimension and plate thickness are constant at each position in their extending direction. The outer height dimension here includes the portion of the ridge line EL formed along the upper edges of the left wall portion 12a and the right wall portion 12b. The left wall portion 12a and the right wall portion 12b have a flat outer surface and a flat inner surface. Furthermore, the outer width dimensions and plate thickness of the left wall portion 12a and the right wall portion 12b do not necessarily have to be constant at each position along the center line CL, and may be slightly modified to differ at each position along the center line CL as required by the part design. Similarly, the outer and inner surfaces of the left wall portion 12a and the right wall portion 12b do not necessarily have to be flat, and may have some irregularities as required by the part design.

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

[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 and also parallel to the center line CL. 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. The plate-shaped member 20 has a flat top surface and a flat bottom surface. The plate-shaped member 20 is welded to the left flange portion 13a and the right flange portion 13b at both side edges. This forms a closed cross section between the hat-shaped member 10 and the plate-shaped member 20. In this way, the hat-shaped member 10 and the plate-shaped member 20 constitute the cylindrical body 30. Furthermore, the width and thickness of the plate-like member 20 do not necessarily have to be constant at each position along the center line CL, and may be slightly changed at each position along the center line CL as required by the part design. Similarly, the upper and lower surfaces of the plate-like member 20 do not necessarily have to be flat, and may have some irregularities as required by the part design.

[0031] Next, I will explain the reinforcement 40. The reinforcement 40 has a fold in the center of its longitudinal direction. Since there are multiple variations of the fold, I will first explain the basic structure of the reinforcement 40 itself, and then continue with the explanation of the fold.

[0032] As shown in Figure 2, the reinforcement 40 has vertical plates 41 and horizontal plates 42. The reinforcement 40 is divided into a first section R1, a second section R2, and a third section R3, which are arranged sequentially along its longitudinal direction. The vertical plate 41 is a single strip-shaped plate having a substantially constant width and substantially constant thickness, except for the second portion R2, and is elongated in the direction along the center line CL. The vertical plate 41 has a flat left side and a flat right side, except for the second portion R2. 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 position in the height direction. The upper and lower portions of this divided vertical plate 41 have the same height and length dimensions.

[0033] The lower portion of the vertical plate 41 shown in Figure 3 has the same thickness at each position along its longitudinal direction. On the other hand, in the upper portion of the vertical plate 41, at least a part of the thickness of the second portion R2 is thinner than the thickness of the first portion R1 and the third portion R3. In other words, the rectangular region in the second portion R2 of the upper portion of the vertical plate 41 is the bending point BP, which has a thinner thickness than the surrounding region. More specifically, the thickness ratio obtained by dividing the plate thickness at the bending point BP (the total plate thickness if there are multiple vertical plates 41) t2 (mm) by the average plate thickness ta3 (mm), which is the average of the plate thickness at the first part R1 (the total plate thickness if there are multiple vertical plates 41) t3 (mm) and the plate thickness at the third part R3 (the total plate thickness if there are multiple vertical plates 41) t3 (mm), satisfies 1 / 3 ~ (ta3 - 0.2) / ta3.

[0034] The bending point BP can be formed, for example, by a tailor-welded blank (TWB), which is created by preparing a plate material with a recess formed in the center of its upper end so that it is roughly U-shaped when viewed from the side, and a plate material that is joined to this recess and has a thinner thickness than the one it is joined to, and then joining these by welding to form a single vertical plate 41. In addition, a vertical plate 41 having a bending point BP can also be formed by a tailor-rolled blank (TRB).

[0035] The horizontal plate 42 is a single strip-shaped plate having a substantially constant width and substantially constant thickness, and is elongated in the direction along the center line CL. The horizontal plate 42 has a flat top surface and a flat bottom surface. Although the horizontal plate 42 is a single strip-shaped plate, when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1, it appears to be divided into two by a vertical plate 41 that intersects it at the center in the width direction. The left and right portions of this divided horizontal plate 42 have the same width, thickness, and length.

[0036] 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. At this time, the upper edges of the first portion R1 and the third portion R3 of the vertical plate 41, and the upper edge of the folding initiation point BP in the second portion R2 are directly joined to the lower surface of the top wall portion 11. In this way, the top wall portion 11 is supported mainly by the vertical plate 41 and the plate-shaped member 20. That is, the top wall portion 11 is supported by three regions: the first portion R1 and the third portion R3, which have relatively thicker plate thicknesses, and the second portion R2, which has a folding initiation point BP with a relatively thinner plate thickness.

[0037] 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.

[0038] 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. The vertical plates 41 are manufactured using either TWB or TRB, but the material of the bending point BP and the material of the other parts are the same, with only the plate thickness differing. Therefore, the tensile strength of the bending point BP in the second part R2 and the tensile strengths of the first part R1 and the third part R3 are both equal, between 650 MPa and 1600 MPa.

[0039] Next, I will explain the trigger for the breakage mentioned above. In the impact absorbing member 1 illustrated in Figure 2, the upper surface of the top wall portion 11 is set to be on the inside of the bend when it breaks, at its central position in the longitudinal direction. This setting is mainly achieved by a combination of how the impact absorbing member 1 is arranged inside the vehicle and the position setting of the bending trigger in the reinforcement 40. The arrangement of the impact-absorbing member 1 inside the vehicle can be done, for example, by shifting the point of application of the impact load to a side closer to the top wall portion 11 than the center line CL, as will be described later using Figure 16(a).

[0040] On the other hand, the position of the bending initiation point is set by dividing the reinforcement 40 into three parts, a first part R1, a second part R2, and a third part R3, which are arranged sequentially along its longitudinal direction, as shown in Figure 2. The bending strength of the second part R2 is made lower than that of the first part R1 and the third part R3. This allows the impact absorbing member 1 to be bent and deform at the position overlapping with the second part R2, with the upper surface of the top wall 11 bending inward. The relative bending strength difference described above can be obtained by the arrangement of the bending initiation point BP.

[0041] In the configuration illustrated in Figure 3, the width dimension Wr1 (mm) of the folding initiation point BP is equal to the height dimension of the upper part of the vertical plate 41. That is, the entire width dimension Wr2 (mm) of the vertical plate 41 between the center position in the width direction through which the center line CL of the reinforcement 40 passes and the upper edge position which is the connection position with the top wall 11 is made into the thin folding initiation point BP. However, the configuration is not limited to this form, and for example, as shown in Figure 4, the folding initiation point BP may be formed at a position that is 1 / 3 of the width of the upper part of the vertical plate 41 and includes the upper edge of the vertical plate 41. More specifically, the width dimension Wr1 (mm) and the width dimension Wr2 (mm) may satisfy Wr2 ≥ Wr1 > (1 / 3) × Wr2. In both Figure 3 and Figure 4, it is preferable that the folding initiation point BP is positioned so that it divides the upper edge of the vertical plate 41 at the position of the second part R2 by including the upper edge of the vertical plate 41.

[0042] As shown in Figure 5, the formation position of the bending point BP may be on the horizontal plate 42 instead of the vertical plate 41. In this case, it is preferable that the bending point BP is formed at the center of the longitudinal direction of the horizontal plate 42, with one point each on the left and right sides, with the vertical plate 41 in between. Furthermore, it is preferable that the bending point BP on the left side and the bending point BP on the right side have the same shape and size (same width, same length, same plate thickness). This makes the bending strength on the left and right sides of the center line CL of the impact absorbing member 1 equal, so that the bending direction with the upper surface of the top wall portion 11 on the inside of the bend can be controlled with precision. In the example shown in Figure 5, two fold initiation points BP are formed on the horizontal plate 42, but the total number may be two or more, or an even number. In this case as well, it is preferable that the fold initiation points BP on the left and right portions are the same size and number. Furthermore, a bending point BP may be formed on both the vertical plate 41 and the horizontal plate 42, as described above.

[0043] In the configuration illustrated in Figure 5, the width dimension Wr1 (mm) of the folding point BP is made equal to the width dimension of the left or right portion of the horizontal plate 42. That is, the entire width dimension Wr2 (mm) of the horizontal plate 42 between the widthwise center position through which the center line CL of the reinforcement 40 passes and the side edge position which is the connection point with the left wall portion 12a or the right wall portion 12b is made into the thin folding point BP. However, the configuration is not limited to this form, and for example, as shown in Figure 6, the folding point BP may be formed at a position that is 1 / 3 of the width of the left or right portion of the horizontal plate 42 and includes the side edge of the horizontal plate 42. More specifically, the width dimension Wr1 (mm) and the width dimension Wr2 (mm) may satisfy Wr2 ≥ Wr1 > (1 / 3) × Wr2. In both Figure 5 and Figure 6, it is preferable that each folding point BP is positioned such that it divides the side edges of the horizontal plate 42 at the position of the second part R2, by including both side edges of the horizontal plate 42.

[0044] The configurations shown in Figure 3 or Figure 4 described above may be combined with the configurations shown in Figure 5 or Figure 6. That is, a folding initiation point BP may be formed at the position of the second part R2 on both the vertical plate 41 and the horizontal plate 42. In this case, the width dimension Wr1 of the folding initiation point BP formed on the vertical plate 41 may be equal to the width dimension Wr1 of the folding initiation point BP formed on the horizontal plate 42, or they may be different.

[0045] Furthermore, in the above example, the bending point BP was formed by reducing the plate thickness, but instead, the bending point BP may be formed by partially lowering the tensile strength. In other words, the plate thickness t2 at the bending point BP in the second section R2 (the total plate thickness if there are multiple vertical plates 41) and the average plate thickness ta3, which is the average of the plate thickness t3 in the first section R1 (the total plate thickness if there are multiple vertical plates 41) and the plate thickness t3 in the third section R3 (the total plate thickness if there are multiple vertical plates 41), may be made equal to each other. Furthermore, the tensile strength ratio obtained by dividing the tensile strength E1 (MPa) of the bending point BP in the second section R2 by the average tensile strength Ea2 (MPa), which is the average of the tensile strengths in the first section R1 and the third section R3, may satisfy (Ea2-100) / Ea2~2. Such a difference in tensile strength can be obtained by joining the bending point BP, which is made of a different material from the material of the vertical plates 41 or horizontal plates 42, using a TWB. Furthermore, both the longitudinal plate 41 and the transverse plate 42 in the second section R2 may be provided with a bending point BP that has relatively low tensile strength.

[0046] The impact absorbing member 1, which includes the reinforcement 40 and cylindrical body 30 described above, is designed to prevent out-of-plane deformation from occurring in unintended locations. In this way, both the first portion R1 and the third portion R3 satisfy both of the following conditions: (1) they have 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) they have 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.

[0047] r1=((W1-t2) / (n1+1)) / t1...(Formula 1) r2=((W2-t3) / (n2+1)) / t1...(Formula 2)

[0048] These equations 1 and 2 will be explained below with reference to Figure 7, but first, let's explain Figure 7. Figure 7 is a schematic diagram illustrating the dimensions of each part of the impact absorbing member 1 at the location of the first part R1 or the third part R3, and corresponds to the BB cross-sectional view in Figure 2. Note that in Figure 7, 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 7, the pair of left wall sections 12a and right wall section 12b are parallel to each other. Also, the plate-shaped 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.

[0049] Equations 1 and 2 will be explained with reference to Figure 7. 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).

[0050] 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).

[0051] 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 7, 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.

[0052] 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.

[0053] 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.

[0054] Now, let's explain out-of-plane deformation. Given the above cross-sectional structure, one possible way to reduce the weight of the impact absorbing member 1 is to reduce the plate thickness t1 of the cylindrical body 30. In this case, in the case of a conventional structure without 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 7. 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.

[0055] In contrast, the impact-absorbing member 1 of this embodiment, as shown in the cross-section in Figure 7, 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 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.

[0056] 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 a bending point is set on the 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.

[0057] 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.

[0058] 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.

[0059] Furthermore, since the impact absorbing member 1 is equipped with a bending initiation point BP as illustrated in Figures 3 to 6, the bending strength of the second part R2 is relatively lower than that of the first part R1 and the third part R3. This allows the impact absorbing member 1 to bend and deform smoothly at the second part R2, which is the bending initiation point. In addition, since the impact energy applied to the impact absorbing member 1 is absorbed mainly by the reinforcement 40 as it bends and deforms starting from the second part R2, the amount of energy absorbed can be increased.

[0060] 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 8 to 14 can also be adopted. These Figures 8 to 14 correspond to the BB cross-sectional view in Figure 2.

[0061] In Figure 8(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 almost the same in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, a bending point BP is formed on each of the side edges of the horizontal plate 42. Figure 8(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 almost the same in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, bending points BP are formed at both positions including each side edge of the horizontal plate 42.

[0062] In Figure 8(c), 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. 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 almost the same in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, a bending point BP is formed at a position including the upper end of the vertical plate 41. Figure 8(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 11 is supported by the vertical plate 41. The upper end of the vertical plate 41 is fixed to the top wall 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 in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2 is a bending point BP formed at a position including the upper end of the vertical plate 41.

[0063] In Figure 9(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 almost the same in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, bending points BP are formed at both positions including each side edge of each horizontal plate 42. Figure 9(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 almost the same in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, bending points BP are formed at both positions including each side edge of each horizontal plate 42.

[0064] In Figure 9(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 in the first section R1, the second section R2, and the third section R3. However, only in the second section R2, a bending point BP is formed at a position including the upper edge of each vertical plate 41. Figure 9(d) also shows how the internal space of the cylindrical body 30 is divided into three sections horizontally by two vertical plates 41. That is, the horizontal plate 42 is omitted, and the top wall 11 is supported by the two vertical plates 41. A flange is formed at the upper end of each vertical plate 41, and these flanges are fixed to the top wall 11 by spot welding in a surface-jointed state. On the other hand, the lower ends of each vertical plate 41 are connected, and this connected portion is fixed to the plate-like member 20 by spot welding in a surface-jointed state. In this example, 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 in the first section R1, the second section R2, and the third section R3. However, only in the second section R2, a bending point BP is formed at a position including the upper edge of each vertical plate 41.

[0065] Figure 9(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 11 is supported by the two vertical plates 41. The upper ends of each vertical plate 41 are connected, and this connected portion is fixed to the top wall 11 by spot welding in a surface-jointed state. On the other hand, a wide flange is formed at the lower end of each vertical plate 41. One of these flanges is fixed to the left flange portion 13a by spot welding, and the other is fixed to the right flange portion 13b by spot welding. The space between the lower ends of the two vertical plates 41 is sealed by a narrow plate-like member 20. That is, the plate-like member 20 is fixed 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 in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, a bending point BP is formed at a position including the upper edge of each vertical plate 41.

[0066] In Figure 10(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 in each of the first part R1, second part R2, and third part R3. On the other hand, only in the second part R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0067] Figure 10(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 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. 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 in each of the first part R1, second part R2 and third part R3. On the other hand, only in the second part R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0068] In Figure 10(c), the internal space of the cylindrical body 30 is divided into three sections by a combination of one vertical plate 41 and one horizontal plate 42. Specifically, one side edge of the horizontal plate 42 is fixed to the left wall portion 12a by laser arc welding while abutting against it. Similarly, the other side edge of the horizontal plate 42 is fixed to the right wall portion 12b by laser arc welding while abutting against it. Furthermore, the upper end of the vertical plate 41 is fixed by laser arc welding while abutting against the center of the width direction of the horizontal plate 42. The height dimension of the vertical plate 41 is approximately half that of the configuration shown in Figure 2, and its lower end is fixed by laser arc welding while abutting against the center of the width direction of the plate-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 in each of the first part R1, second part R2, and third part R3. On the other hand, only in the second part R2, a bending point BP is formed at a position including both side edges of the horizontal plate 42.

[0069] Figure 10(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 in a position where it abuts against the widthwise center of the horizontal plate 42. The height dimension of the vertical plate 41 is approximately 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 in a position where it is in surface contact with the widthwise center 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 in each of the first part R1, second part R2, and third part R3. On the other hand, only in the second part R2, a bending point BP is formed at a position including both side edges of the horizontal plate 42.

[0070] In Figure 11(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 side wall 12a and the right side wall 12b, the two vertical plates 41 and the horizontal plate 42, and one space partitioned by the horizontal plate 42, the left side wall 12a and the right side wall 12b and the plate-like member 20. The cross-sectional configuration of this example is substantially the same in the first part R1, the second part R2 and the third part R3. On the other hand, only in the second part R2, a bending point BP is formed at at least one of the positions including the upper edge of each vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0071] Figure 11(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, left wall 12a and right wall 12b and the horizontal plate 42, and three spaces partitioned by the horizontal plate 42, left wall 12a and right wall 12b, two vertical plates 41 and the plate-like member 20. The cross-sectional configuration of this example is almost the same in the first part R1, the second part R2 and the third part R3. On the other hand, only in the second part R2, a bending point BP is formed at a position including both side edges of the horizontal plate 42.

[0072] In Figure 11(c), the internal space of the cylindrical body 30 is divided into four sections by the combination of two vertical plates 41 and one horizontal plate 42. In this example, when forming the hat-shaped member 10, the portion of the top wall 11 at the center in the width direction is press-formed so that it is recessed inward into the cylindrical body 30. Two vertical plates 41 are formed in this recessed portion. The top wall 11 includes a left portion and a right portion spaced apart from each other by the recessed portion, and a central portion connecting these left and right portions. This central portion is a separate part and is fixed to the left and right portions by spot welding. A flange is formed on one of the side edges of the horizontal plate 42, and this flange is fixed to the left side wall portion 12a by spot welding in a state of surface contact. Similarly, a flange is formed on the other side edge of the horizontal plate 42, and this flange is fixed to the right side wall portion 12b by spot welding in a state of surface contact. The lower ends of each vertical plate 41, i.e., the recessed portions, are fixed to the center of the horizontal plate 42 in the width direction by spot welding in a state of surface contact. In this way, the internal space of the cylindrical body 30 is divided into four parts: three spaces partitioned by the top wall 11, the left side wall 12a and the right side wall 12b, the two vertical plates 41 and the horizontal plate 42, and one space partitioned by the horizontal plate 42, the left side wall 12a and the right side wall 12b and the plate-like member 20. The cross-sectional configuration of this example is substantially the same in the first part R1, the second part R2 and the third part R3. On the other hand, only in the second part R2, a bending point BP is formed at at least one of the positions including the upper edge of each vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0073] In Figure 12(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 in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0074] In the example shown in Figure 12(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 in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0075] In the example shown in Figure 12(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.

[0076] 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 in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0077] In the example shown in Figure 12(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.

[0078] Then, within the closed cross-sectional space, a pair of smaller first and second angle members are combined in a "+" shape to form a vertical plate 41 and a horizontal plate 42. The first angle member has a roughly L-shaped cross-section perpendicular to the longitudinal direction, with flanges formed on each of its end edges. One of these flanges is fixed to the top wall 11 in surface contact by spot welding, and the other is fixed to the right side wall 12b in surface contact by spot welding. The second angle member also has a roughly L-shaped cross-section perpendicular to the longitudinal direction, with flanges formed on each of its end edges. One of these flanges is fixed to the left side wall 12a in surface contact by spot welding, and the other is fixed to the plate-like member 20 in surface contact by spot welding. In addition, a recess is formed in the corner of the second angle member, and the corner of the first angle member is fixed to this recess by adhesive. Therefore, in this example, one vertical board 41 is formed by combining the vertical wall of the first angle member and the vertical wall of the second angle member. In addition, one horizontal board 42 is formed by combining the horizontal wall of the first angle member and the horizontal wall of the second angle member. In this way, the internal space of the cylindrical body 30 is divided into four spaces, 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 in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0079] In the example shown in Figure 12(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 in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0080] In the example shown in Figure 13(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 of this example is almost the same in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0081] In the example shown in Figure 13(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 each other. 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 of the first section R1, the second section R2, and the third section R3 are almost the same. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0082] In the example shown in Figure 13(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 of this example is almost the same in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0083] In the example shown in Figure 13(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 each other. 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 of the first section R1, the second section R2, and the third section R3 are almost the same. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0084] In the example shown in Figure 13(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, 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.

[0085] 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 side of the press-formed plate that is not joined to the angle material at the center of the width direction, in contact with the other side. 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 of this example is almost the same in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper end edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0086] In the example shown in Figure 13(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.

[0087] The side surfaces near the corners of the angle material and the side surfaces near the corners of the pressed sheet are joined by laser arc welding while in surface contact with each other. As a result, the wall portion of the angle material and the wall portion of the pressed sheet become parallel to each other, forming a vertical plate 41. Similarly, the other wall portions of the angle material and the other wall portions of the pressed sheet become parallel to each other, forming a horizontal plate 42. Then, one flange of the angle material is joined to the top wall portion 11 by spot welding while in surface contact, and the other flange is joined to the right side wall portion 12b by spot welding while in surface contact. In addition, the flange of the press-formed plate is joined to the left side wall portion 12a by spot welding while in surface contact, and the flangeless edge of the press-formed plate is joined to the right flange portion 13b at the lower end of the right side wall portion 12b by spot welding while in surface contact. Next, a plate-shaped member 20 is prepared that is narrower than the lower opening width of the hat-shaped member 10. Then, one edge of the plate-shaped member 20 is joined by laser arc welding with the press-formed plate in contact with the one of the two bends that is not joined to the angle material. Furthermore, the other edge of the plate-shaped member 20 is joined by spot welding with the left flange portion 13a at the lower end of the left side wall portion 12a in surface contact. As a result, the internal space of the cylindrical body 30 is divided into four spaces by the vertical plate 41 and the horizontal plate 42. The cross-sectional configuration of this example is substantially the same in the first section R1, the second section R2, and the third section R3. On the other hand, only in the second section R2, a bend initiation point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0088] In Figure 13(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.

[0089] 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 almost the same in the first part R1, the second part R2 and the third part R3. On the other hand, only in the second part R2, a bending point BP is formed at at least one of the positions including the upper edge of each vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0090] In Figure 14(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. 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 the first section R1, the second section R2, and the third section R3 are substantially the same. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0091] In Figure 14(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.

[0092] 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 the first section R1, the second section R2, and the third section R3 are substantially the same. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0093] Figure 14(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.

[0094] 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 the first section R1, the second section R2, and the third section R3 are substantially the same. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0095] Figure 14(d) also shows how 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.

[0096] 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 the first section R1, the second section R2, and the third section R3 are substantially the same. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42.

[0097] Figure 14(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 the first section R1, the second section R2, and the third section R3 are substantially the same. On the other hand, only in the second section R2, a bending point BP is formed at at least one of the positions including the upper edge of the vertical plate 41 and the positions including both side edges of the horizontal plate 42. [Examples]

[0098] [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.

[0099] First, the shock-absorbing member 1A shown in Figure 15(a) was placed vertically on the base BS. This shock-absorbing member 1A 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 lids. This shock-absorbing member 1A was positioned in an upright state with its central axis perpendicular to the upper surface of the base BS. The length of the impact absorbing member 1A 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 1A 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 1A 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 1A was standardized to 1180 MPa, and no reinforcement was provided.

[0100] After arranging each shock-absorbing member 1A in an upright position as shown in Figure 15(a), a compressive impact force F passing through the central axis was applied to the rigid wall, which is the lid at the top of each member. At this time, the downward movement speed of the rigid wall in the plane of the paper 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 1A decreased. Then, as shown in Figure 15(b), the amount of out-of-plane deformation in the impact absorbing member 1A 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 1A, and these were plotted on the graph shown in Figure 16.

[0101] As a result, as shown in Figure 16, in the impact-absorbing member 1A with a planar portion 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 16, in the impact absorbing member 1A with a flat section 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 flat section width-to-thickness ratio W / t was 50 or less, but it was confirmed that it increased sharply when the flat section width-to-thickness ratio W / t exceeded 50. From this, it can be seen that when the flat section 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 1A 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 1A and cause it to bend, the flat section width-to-thickness ratio W / t should be 10 or more and 50 or less.

[0102] [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 7, on the bending deformation behavior of the impact-absorbing member was determined and confirmed by numerical calculation. First, as shown in Figure 17, we assumed an impact absorbing member 1B having the same configuration as the impact absorbing member 1 shown in Figure 2. Then, we set the length L (mm) of the impact absorbing member 1B 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 to the center of the longitudinal direction of the top wall. In addition, we assumed that it is equipped with a reinforcement 40 having the same "+" shape as in Figure 2. On the other hand, in this impact-absorbing member 1B, the width dimensions w1(mm), w2(mm), w3(mm), and w4(mm) shown in Figure 7 were set to be equal. Two cases were considered: one where the width dimension is 50 mm and another where it is 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 1B in Case A and B, an impact force F along its longitudinal direction was applied to induce bending deformation, as shown in Figure 17(b).

[0103] As a result, in Case-A (inventive example) shown in Figure 18(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 18(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 18(a). On the other hand, the out-of-plane deformation was large in the comparative example in Figure 18(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).

[0104] [Third Embodiment] A third embodiment of the present invention will be described below with reference to Figures 19 to 22. In this third embodiment, the maximum load and energy absorption amount were numerically calculated when collision energy was applied to multiple impact absorbing members with different reinforcement conditions.

[0105] Specifically, six types of impact-absorbing members having various cross-sectional shapes, as shown in Figure 19, were prepared. Figure 19 is a cross-sectional view of the impact-absorbing member along the line BB in Figure 2. Of these, Case 000 shows a comparative example without the reinforcement 40. Case 005 also shows a comparative example with a different reinforcement method. Case 001 shows an example of the invention in which only one horizontal plate 42 is provided as the reinforcement 40. This horizontal plate 42 is provided with folding initiation points BP on both sides of the second part R2 shown in Figure 2. Case 002 shows an example of the invention in which only one vertical plate 41 is provided as the reinforcement 40. This vertical plate 41 has a bending point BP at the upper edge of the second part R2 shown in Figure 2. Case 003 is an example of the invention in which one horizontal plate 42 and one vertical plate 41 intersect in a "+" shape as the reinforcement 40, and is the same configuration as illustrated in Figures 2 and 12(a). These vertical plate 41 and horizontal plate 42 are provided with bending points BP on both side edges and the upper edge at the position of the second part R2 shown in Figure 2. 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 width direction of one horizontal plate 42 and the top wall portion 11, and is the same configuration as illustrated in Figure 10(a). These vertical plate 41 and horizontal plate 42 are provided with folding points BP on both side edges and the top edge at the position of the second portion R2 shown in Figure 2. Case 005 is a comparative example in which a 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.

[0106] For each of the impact absorbing members shown in Cases 000 to 005 above, a load F parallel to the longitudinal direction of the impact absorbing member was applied as collision energy while both ends were held rotatably around a horizontal axis, as shown in Figure 20(a). At this time, the position of the center line of the impact absorbing member was offset in the height direction relative to the input position of the collision energy before the collision energy was applied. More specifically, the position where the load F was applied was closer to the top wall than the center line of the impact absorbing member and applied horizontally. As a result, the member was deformed from the state shown in Figure 20(a) before bending deformation to the state shown in Figure 20(b) after bending deformation, with the top wall 11 as the bending starting point.

[0107] The results for the maximum load in each case are shown in Table 1 and Figure 21 below. In Figure 21, the horizontal axis represents the case number and the vertical axis represents the maximum load (kN). Similarly, the results for the energy absorption in each case are shown in Table 1 and Figure 22 below. In Figure 22, the horizontal axis represents the case number and the vertical axis represents the energy absorption (kJ).

[0108] [Table 1]

[0109] As shown in Figure 22, Cases 001 to 004, which belong to the inventive examples, all achieved higher energy absorption compared to Case 000 without reinforcement. The same was true for the comparative example Case 005, but as shown in Table 1, it was significantly heavier than Case 000. On the other hand, the weight increase compared to Case 000 was kept to a minimum for all of the inventive examples Cases 001 to 004. Therefore, it is possible to reduce the overall weight of the parts in Cases 001 to 004 by either thinning the plate thickness to the same energy absorption as Case 000 or by shortening the deformation stroke. Thus, it was confirmed that the configuration of the inventive examples can exhibit high energy absorption efficiency by bending and deforming smoothly at joints while remaining lightweight.

[0110] The main points of this invention are summarized below. (1) One aspect of the present invention is an impact absorbing member 1 that is long in one direction and comprises a cylindrical body (hollow tube) 30 and a reinforcement 40 fixedly arranged inside the cylindrical body 30, wherein the cylindrical body 30 is made of steel material having a tensile strength of 650 MPa or more and 1600 MPa or less, and the reinforcement 40 is made of steel material having a tensile strength of 590 MPa or more and 1600 MPa or less. Furthermore, when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1, the cylindrical body 30 has a top wall portion 11 having a total width dimension W1 (mm) and a plate thickness t1 (mm), and a pair of side wall portions 12 provided on both sides of the top wall portion 11, having a total width dimension W2 (mm) and a plate thickness t1 (mm). Furthermore, when viewed in a cross section perpendicular to the longitudinal direction of the impact absorbing member 1, the reinforcement 40 has at least one of the following: vertical plates 41 with one end joined to the top wall portion 11 and a total number of n1 plates (n1 is an integer of 1 or more) and a total plate thickness t2 (mm), and horizontal plates 42 connecting the pair of side wall portions 12 and a total number of n2 plates (n2 is an integer of 1 or more) and a total plate thickness t3 (mm). Furthermore, the reinforcement 40 satisfies at least one of the following conditions: a first condition in which the width-to-thickness ratio r1 of the first planar section according to the following formula 1 is 10 or more and 50 or less; and a second condition in which the width-to-thickness ratio r2 of the second planar section according to the following formula 2 is 10 or more and 50 or less. Furthermore, the reinforcement 40 has a first portion R1, a second portion R2, and a third portion R3 arranged in order along the longitudinal direction. Furthermore, the reinforcement 40 has a bending point BP formed at the second part R2, including the connection point with the cylindrical body 30, which has at least one of the following characteristics: a plate thickness that is thinner than both the first part R1 and the third part R3, and a tensile strength that is lower than both the first part R1 and the third part R3. r1=((W1-t2) / (n1+1)) / t1...(Formula 1) r2=((W2-t3) / (n2+1)) / t1...(Formula 2)

[0111] (2) The impact absorbing member 1 described in (1) above may be made as follows: In other words, the tensile strength of the bending point BP in the second section R2 may be equal to the tensile strengths of the first section R1 and the third section R3. Furthermore, the thickness ratio obtained by dividing the total plate thickness t2 at the bending point BP in the second section R2 by the average plate thickness ta3 (mm), which is the average value of the total plate thickness t3 in the first section R1 and the total plate thickness t3 in the third section R3, may be such that it satisfies 1 / 3 ~ (ta3 - 0.2) / ta3.

[0112] (3) The impact absorbing member 1 described in (1) above may be made as follows: In other words, the total plate thickness t2 at the bending point BP in the second part R2 and the average plate thickness ta3 (mm), which is the average of the total plate thickness t3 in the first part R1 and the total plate thickness t3 in the third part R3, may be made equal to each other. Furthermore, the tensile strength ratio obtained by dividing the tensile strength E1 (MPa) at the bending point BP in the second part R2 by the average tensile strength Ea2 (MPa), which is the average of the tensile strengths in the first part R1 and the third part R3, may be made such that it satisfies (Ea2-100) / Ea2~2.

[0113] (4) The impact absorbing member 1 described in (1) above may be made as follows: In other words, the thickness ratio obtained by dividing the total plate thickness t2 at the bending initiation point BP in the second part R2 by the average plate thickness ta3 (mm), which is the average value of the total plate thickness t3 in the first part R1 and the total plate thickness t3 in the third part R3, may satisfy 1 / 3 ~ (ta3 - 0.2) / ta3. Furthermore, the tensile strength ratio obtained by dividing the tensile strength E1 (MPa) at the bending initiation point BP in the second part R2 by the average tensile strength Ea2 (MPa), which is the average value of the tensile strength in the first part R1 and the tensile strength in the third part R3, may satisfy (Ea2 - 100) / Ea2 ~ 2.

[0114] (5) In the impact absorbing member 1 described in any one of the above items (1) to (4), the length dimension Lr1 (mm) of the bending point BP and the length dimension Lr2 (mm) of the reinforcement 40 in the direction along the longitudinal direction may satisfy Lr2 > Lr1 > (1 / 2) × Lr2.

[0115] (6) In the impact absorbing member 1 described in any one of the above items (1) to (5), when the reinforcement 40 is viewed in a cross section perpendicular to the longitudinal direction at a position including the bending point BP, the width dimension Wr1 (mm) of the bending point BP and the width dimension Wr2 (mm) between the center and connection position of the reinforcement 40 may satisfy Wr2 ≥ Wr1 > (1 / 3) × Wr2.

[0116] (7) In the impact absorbing member 1 described in any one of the above items (1) to (6), the flange formed at one end of the vertical plate 41 may be spot welded to the top wall portion 11 in a cross-sectional view perpendicular to the longitudinal direction, provided that the first condition is met.

[0117] (8) In the impact absorbing member 1 described in any one of the above items (1) to (7), the flanges formed at both ends of the horizontal plate 42 in a cross-sectional view perpendicular to the longitudinal direction may be spot welded to each of the pair of side wall portions 12, provided that the second condition is met.

[0118] (9) The impact absorbing member described in (1) above may be made as follows: In other words, the cylindrical body 30 may have a hat-shaped member 10 having a hat-top portion whose cross-section perpendicular to the longitudinal direction is the top wall portion 11 and a pair of side wall portions 12 connected to both sides of the hat-top portion, and a plate-shaped member 20 joined to the hat-shaped member 10 and facing the hat-top portion. Furthermore, both the first and second conditions may be satisfied. In addition, when viewed in a cross-section perpendicular to the longitudinal direction, the total number of plates n1 is 1 and the total number of plates n2 is 1, and the vertical plate 41 may be fixed in a state where it is stretched between the hat-top portion and the plate-shaped member 20. In addition, the horizontal plate 42 may be fixed between the pair of side wall portions 12 in a state where it intersects with the vertical plate 41.

[0119] (10) The impact absorbing member 1 described in (1) above may be made as follows: In other words, the cylindrical body 30 may have a hat-shaped member 10 having a hat-shaped apex with a top wall portion 11 and a pair of side wall portions 12 connected to both sides of the hat-shaped apex, and a plate-shaped member 20 joined to the hat-shaped member 10 and facing the hat-shaped apex. Furthermore, both the first and second conditions may be satisfied. In addition, when viewed in a cross section perpendicular to the longitudinal direction, the total number of plates n1 is 1 and the total number of plates n2 is 1, and one end of the horizontal plate 42 may be joined to one of the pair of side wall portions 12, and the other end of the horizontal plate 42 may be joined to the other of the pair of side wall portions 12. Moreover, one end of the vertical plate 41 may be joined to the hat-shaped apex, and the other end of the vertical plate 41 may be joined to a position between the one and other ends of the horizontal plate 42. [Explanation of Symbols]

[0120] 1. Impact absorbing member 10 Hat-shaped member 11 Top wall section, hat top section 12 Side wall section 12a Left side wall (side wall) 12b Right side wall (side wall) 20 Plate-shaped member 30. Cylindrical body (hollow tube) 40 Reinforce 41 vertical boards 42 Horizontal board BP bending point R1 Part 1 R2 2nd part R3 3rd part

Claims

1. An impact absorbing member comprising a hollow tube and a reinforcement fixedly positioned inside the hollow tube, wherein the member is long in one direction, The hollow tube is made of steel with a tensile strength of 650 MPa to 1600 MPa, and the reinforcement is made of steel with a tensile strength of 590 MPa to 1600 MPa; In a cross-section perpendicular to the longitudinal direction of the impact absorbing member, The hollow tube has a top wall portion having a total width W1 (mm) and a plate thickness t1 (mm), and a pair of side wall portions provided on both sides of the top wall portion, each having a total width W2 (mm) and a plate thickness t1 (mm). The reinforcement comprises 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 aforementioned reinforcement, A first condition is that the vertical plate 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 is that the horizontal plate 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, satisfying at least one of these conditions. It has a first portion, a second portion, and a third portion arranged in order along the longitudinal direction; In the aforementioned second part, A plate thickness thinner than both the first and third portions, Lower tensile strength than both the first and third parts, A bending point having at least one of the above is formed including the connection point with the hollow tube; 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. The tensile strength of the bending point in the second portion is equal to the tensile strengths of the first portion and the third portion; The thickness ratio obtained by dividing the total plate thickness t2 at the bending point in the second portion by the average plate thickness ta3 (mm), which is the average of the total plate thickness t3 in the first portion and the total plate thickness t3 in the third portion, satisfies 1 / 3 to (ta3 - 0.2) / ta3; The impact absorbing member according to feature 1.

3. The total plate thickness t2 at the bending point in the second portion and the average plate thickness ta3 (mm), which is the average of the total plate thickness t3 in the first portion and the total plate thickness t3 in the third portion, are equal to each other; The tensile strength ratio obtained by dividing the tensile strength E1 (MPa) of the bending point in the second portion by the average tensile strength Ea2 (MPa), which is the average of the tensile strengths in the first portion and the third portion, satisfies (Ea2 - 100) / Ea2 to 2; The impact absorbing member according to feature 1.

4. The thickness ratio obtained by dividing the total plate thickness t2 at the bending point in the second portion by the average plate thickness ta3 (mm), which is the average of the total plate thickness t3 in the first portion and the total plate thickness t3 in the third portion, satisfies 1 / 3 to (ta3 - 0.2) / ta3; The tensile strength ratio obtained by dividing the tensile strength E1 (MPa) of the bending point in the second portion by the average tensile strength Ea2 (MPa), which is the average of the tensile strengths in the first portion and the third portion, satisfies (Ea2 - 100) / Ea2 to 2; The impact absorbing member according to feature 1.

5. In the direction along the longitudinal direction, The length dimension Lr1 (mm) of the bending point and the length dimension Lr2 (mm) of the reinforcement satisfy Lr2 > Lr1 > (1 / 2) × Lr2. The shock-absorbing member according to any one of claims 1 to 4.

6. When the reinforcement is viewed in a cross-section perpendicular to the longitudinal direction at a position including the bending point, The width dimension Wr1 (mm) of the bending point and the width dimension Wr2 (mm) between the center of the reinforcement and the connection point satisfy Wr2 ≥ Wr1 > (1 / 3) × Wr2. The shock-absorbing member according to any one of claims 1 to 4.

7. The above first condition is met; In a cross-sectional view perpendicular to the longitudinal direction, the flange formed at one end of the vertical plate is spot-welded to the top wall; The shock-absorbing member according to any one of claims 1 to 4.

8. The above second condition is met; In a cross-sectional view perpendicular to the longitudinal direction, flanges formed at both ends of the horizontal plate are spot-welded to each of the pair of side wall portions; The shock-absorbing member according to any one of claims 1 to 4.

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-shaped member joined to the hat-shaped member and facing the top of the hat; Satisfying both the first and second conditions; In the cross-section perpendicular to the longitudinal direction, The total number of sheets n1 is 1 and the total 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 plate-shaped member. The horizontal plate is fixed between the pair of side walls in a state where it intersects with the vertical plate; The impact absorbing member according to feature 1.

10. 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-shaped member joined to the hat-shaped member and facing the top of the hat; Satisfying both the first and second conditions; In the cross-section perpendicular to the longitudinal direction, The total number of sheets n1 is 1 and the total 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