Impact absorbing member

Abstract

The present disclosure provides an impact absorbing member in which both load-bearing performance and weight reduction are further achieved. An impact absorbing member (3) comprises a long body part (1) having a cross section including: a top plate part (1A) having a recess (1Aa) at a position partway in the width direction; left and right vertical wall parts (1B) respectively connected to both end parts in the width (D1) direction of the top plate part (1A); and left and right flange parts (1C) connected to the lower end parts of the respective vertical wall parts (1B). An angle on an inner surface side formed by the top plate part (1A) and the vertical wall parts (1B) is less than 90°. The flange part (1C) extends upward such that the height thereof approaches the height of the top plate part (1A) toward a tip side from a root side connected to the vertical wall part (1B).

Description

Impact absorbing material

[0001] The present invention relates to a technology relating to an impact absorbing member that is attached to a vehicle door or other component that requires impact absorption. The impact absorbing member of the present invention has a cross-sectional shape that includes a top plate portion, left and right vertical wall portions, and left and right flange portions. The impact absorbing member is a member used to absorb impact from the thickness direction of the top plate portion.

[0002] An automobile door, for example, is composed of an outer panel for appearance, an inner panel that serves as a framework, and components housed between the two. One of these components is a door impact beam (an impact absorbing member). Door impact beams are used to improve the side collision performance of automobiles. The door impact beam is housed between the outer panel and the inner panel. For this reason, the door impact beam is required to have a smaller cross section. Furthermore, the door impact beam is required to efficiently absorb collision energy.

[0003] To address this issue, various cross-sectional shapes have been proposed to improve the load-bearing capacity of door impact beams. Conventionally, cross-sectional shapes have been disclosed in which a bead consisting of a concave or convex portion is provided on the top plate. For example, Patent Documents 1 and 2 disclose providing a bead on the top plate. Patent Documents 1 and 2 disclose that providing such a bead makes it easier to maintain the shape of the central portion of the cross section of the door impact beam. Patent Document 3 also discloses providing a corrugated portion with an uneven shape on the top plate. Patent Document 3 discloses that this improves the strength of the door impact beam against impact loads applied thereto. The door impact beams (impact absorbing members) described in Patent Documents 1 to 3 have a cross-sectional shape including a top plate, left and right vertical wall portions, and left and right flange portions. The cross-sectional shape is provided with an uneven shape on the top plate.

[0004] Japanese Patent Application Laid-Open No. 2011-251597 Japanese Patent No. 6304379 Japanese Patent Application Laid-Open No. 2018-052428

[0005] Here, door impact beams are required to both minimize vehicle weight and improve load-bearing performance. The structures described in Patent Documents 1 and 2 are based on the idea of ​​providing a bead to facilitate maintaining the shape of the central portion of the cross section. However, the present applicant has confirmed the following findings regarding these structures: In the above structures, a side impact load from the vehicle causes the left and right vertical wall portions to open, resulting in deformation. Therefore, the applicant has concluded that further improvements are needed to address impact absorption. Furthermore, Patent Document 3 improves strength against impact loads by providing multiple irregularities to the top plate. However, this structure increases the complexity of the cross section of the door impact beam, which may increase weight and complicate manufacturing processes. Furthermore, the applicant has also concluded that the structure described in Patent Document 3 also causes the left and right vertical wall portions to open due to a side impact load. Therefore, the applicant has concluded that further improvements are needed to address impact absorption.

[0006] The present invention has been made in light of the above-mentioned points, and an object of the present invention is to provide an impact absorbing member that achieves both further improvement in load-bearing performance and weight reduction.

[0007] The inventors have investigated various deformation modes of the door impact beam during a side collision of a vehicle, and have also studied various changes in the cross-sectional shape of the door impact beam in these deformation modes. In other words, the inventors have developed the present invention by studying deformation modes that can further improve the load-bearing performance.

[0008] In order to solve the problem, one aspect of the present invention is an impact absorbing member having a long main body portion with a cross section having a top plate portion having a recess at a mid-width position, left and right vertical wall portions connected to both widthwise ends of the top plate portion, and left and right flange portions connected to the lower ends of each vertical wall portion, wherein the angle formed by the inner surface of the top plate portion and the vertical wall portions is less than 90 degrees, and the flange portions rise in height from the base side where they connect to the vertical wall portions toward the tip side so that their height approaches that of the top plate portion.

[0009] According to the aspects of the present invention, it is possible to provide an impact absorbing member that achieves both further improvement in load-bearing capacity and weight reduction by simply changing the cross-sectional shape.

[0010] FIG. 3 is a schematic diagram showing an example of a state in which a door impact beam according to an embodiment of the present invention is provided on a vehicle door. FIG. 4 is a perspective view showing the shape of a main body of an impact absorbing member. FIG. 5 is a cross-sectional view taken along X-X in FIG. 2 , illustrating the cross-sectional shape of the main body. FIG. 6 is a diagram illustrating the cross-sectional shape of a door impact beam according to a comparative example. FIG. 7 is a schematic diagram illustrating a three-point bending test. FIG. 8 is a diagram illustrating cross-sectional deformation due to the application of a bending load in an inventive example according to the present invention. FIG. 9 is a diagram illustrating cross-sectional deformation due to the application of a bending load in a comparative example. FIG. 10 is a diagram illustrating a load-displacement curve obtained from the test results of a three-point bending test. FIG. 11 is a diagram illustrating the relationship between recess depth [%] and energy absorption amount EA in an example. FIG. 12 is a diagram illustrating the relationship between recess depth [%] and energy absorption amount per unit weight [EA / weight] in an example.

[0011] Next, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a door impact beam will be described as an example of an impact absorbing member. As shown in FIG. 1 , the door impact beam 3 is provided inside a door 4. However, the location where the impact absorbing member of the present invention is provided is not limited to an automobile door. The impact absorbing member may also be provided on the roof of a vehicle, etc. The location where the impact absorbing member is provided is not particularly limited. The impact absorbing member of the present invention may be provided inside a component that is intended to absorb energy from a collision. Furthermore, the installation location is not limited to the interior of the component.

[0012] The impact absorbing member of this embodiment is a member for absorbing loads due to impacts input from the top panel side of the impact absorbing member. Therefore, the impact absorbing member of this embodiment may be attached to the above-mentioned component in a direction in which an impact may be input. Alternatively, the impact absorbing member may be attached in a direction in which an impact force needs to be absorbed. The material of the impact absorbing member is, for example, a steel plate or other metal plate. From the viewpoints of strength and weight reduction, the material of the impact absorbing member is preferably a high-tensile steel plate having a tensile strength of 980 MPa or more. More preferably, the material of the impact absorbing member is a material having a tensile strength of 1470 MPa or more. The impact absorbing member is manufactured, for example, by press-forming a steel plate to form the cross-sectional shape described below. The impact absorbing member may also be manufactured by methods other than press-forming. In the following description, the door impact beam 3 is also referred to as the impact absorbing member 3.

[0013] (Configuration) As shown in Fig. 1, the door impact beam 3 of this embodiment is provided inside a door 4 on the side of an automobile. As shown in Fig. 1, the door impact beam 3 comprises a long main body 1 and left and right mounting portions 2. The left and right mounting portions 2 are connected to both ends of the main body 1 in the longitudinal direction.

[0014] (Mounting Portion) The mounting portion 2 constitutes a portion for connecting the door impact beam 3 to a component such as the door 4. The mounting portion 2 may have any known shape. Examples of the shape of the mounting portion 2 include those described in Patent Documents 1 to 3. Therefore, in this embodiment, detailed description of the shape of the mounting portion 2 is omitted. In the following embodiment, an impact absorbing member 3 having mounting portions 2 on both the left and right ends of the main body 1 is exemplified. However, the door impact beam 3 does not necessarily have left and right mounting portions 2. In this case, for example, mounting points for attaching the impact absorbing member 3 to the main body 1 may be set. The mounting points may be, for example, two or more locations spaced apart along the longitudinal direction of the main body 1. Furthermore, even in an impact absorbing member 3 having left and right mounting portions 2, mounting points for the component on which the impact absorbing member 3 is to be attached may be set appropriately on the main body 1.

[0015] (Main Body 1) The main body 1 is a main body portion that absorbs the impact of the door impact beam 3. As shown in FIG. 2, the main body 1 is an elongated member (longitudinal member) extending in an extension direction intersecting the cross section. In this example, the main body 1 is an elongated member extending in a direction perpendicular to the cross section. Note that the main body 1 may have a shape extending with some curvature in the up-down or left-right direction along the extension direction. As shown in FIG. 3, the cross section of the main body 1 in this embodiment includes a top plate 1A, left and right vertical wall portions 1B, and left and right flange portions 1C. Also, as shown in FIG. 3, the cross section has an M-shaped cross section. Note that the main body 1 is typically symmetrical as shown in FIG. 3. However, the cross section may also be asymmetrical. The main body 1 in this embodiment has a symmetrical cross section as shown in FIG. 3. When the main body 1 is placed on a horizontal support surface, the surface defining the top plate 1A is horizontal. In FIG. 3, the plane that defines the top panel portion 1A is located at the position indicated by the symbol k.

[0016] <Recess 1Aa of Top Plate 1A> A recess 1Aa is formed in the middle of the top plate 1A in the width direction. In this embodiment, the recess 1Aa is formed in the center of the top plate 1A in the width direction. Furthermore, the shape of the recess 1Aa in this embodiment is V-shaped as shown in FIG. 3. The cross-sectional shape of the recess 1Aa is preferably V-shaped, but is not limited to this. The shape of the recess 1Aa may be U-shaped or a conventional bead shape (see FIG. 4), provided that it satisfies the conditions of the present disclosure. For example, the V-shape may be such that the opposing distance between the left and right side walls forming the V-shape becomes smaller as it goes downward, and the lower ends of the left and right side walls are connected by, for example, a circular arc-shaped bend. Note that "downward" refers to the direction from the top plate 1A toward the bottom of the recess 1Aa.

[0017] The depth H1 of the recess 1Aa is preferably 50% or more of the cross-sectional height H0 of the door impact beam 3. More preferably, the depth H1 is 60% or more of the cross-sectional height H0. The upper limit of the depth H1 of the recess 1Aa is, for example, 100% of the cross-sectional height H0. The depth H1 of the recess 1Aa may be deeper than 100% of the cross-sectional height H0. However, if the depth H1 of the recess 1Aa exceeds 100% of the cross-sectional height H0, the bottom of the recess 1Aa will protrude downward. In this case, problems may occur when attaching the impact absorbing member 3 to a component. Furthermore, the protrusion will lead to an increase in weight. For this reason, the depth H1 of the recess 1Aa is preferably 100% or less of the cross-sectional height H0.

[0018] Here, as shown in FIG. 3 , the cross-sectional height H0 is the height-direction length from the lower end of the bent portion (ridge portion) 1E to the upper surface of the top plate portion 1A. The depth H1 of the recess 1Aa is the height-direction length from the lower end of the recess 1Aa in the height direction to the upper surface of the top plate portion 1A. A cross-sectional shape with a deeper depth H1 of the recess 1Aa increases the amount of energy absorption per unit weight. This allows the door impact beam 3 to be structured to efficiently absorb energy. In other words, by making the depth H1 of the recess 1Aa 50% or more, preferably 60% or more, of the cross-sectional height H0, collision performance can be improved.

[0019] Here, the angle formed by the bottom of the V-shaped recess 1Aa is referred to as angle α. This angle α becomes smaller as the depth H1 of the recess 1Aa increases. The angle α is, for example, 60 degrees or less, preferably 50 degrees or less. The angle α may be greater than 0 degrees. Consider a case where a high-tensile steel plate or the like is used for the door impact beam 3 to ensure strength. In this case, if the angle α is small, it becomes difficult to process the V-shaped recess 1Aa. From this perspective, the angle α is preferably 30 degrees or more. Furthermore, the ratio of the width D2 of the recess 1Aa to the width D1 of the top plate portion 1A is preferably 40% or more but less than 60%.

[0020] In this embodiment, as shown in FIG. 3 , the ridge portion 1D of the top plate portion 1A connecting the top plate portion 1A to the vertical wall portion 1B is defined as part of the top plate portion 1A to define the width D1 of the top plate portion 1A. The ridge portion 1D is also called a bent portion or ridge portion. The width D1 of the top plate portion 1A is used to define the ratio of the width D2 of the recess 1Aa. In other words, in this embodiment, the distance between the tops of the left and right vertical wall portions 1B is defined as the width D1 of the top plate portion 1A. Furthermore, in this embodiment, the bent portion transitioning to the flat portion of the top plate portion 1A on the upper side of the recess 1Aa is included in the width D2 of the recess 1Aa.

[0021] As the ratio of the width D2 of the recess 1Aa to the width D1 of the top plate portion 1A decreases, the angle α of the bottom of the recess 1Aa becomes more acute. Here, the strength and weight of the impact absorbing member 3 are taken into consideration. In this case, it is preferable to use a high-tensile steel plate with a tensile strength of 980 MPa or more as the material for the impact absorbing member 3. However, molding a high-tensile steel plate into an acute-angled shape may lead to cracks. From this perspective, the width D2 of the recess 1Aa is preferably 40% or more of the width D1 of the top plate portion 1A. However, this ratio also affects the size of the width D1 of the top plate portion 1A. Figure 3 illustrates an example in which the width D2 of the recess 1Aa is 50% of the width D1 of the top plate portion 1A. Also illustrated is an example in which the angle α is 45 degrees.

[0022] On the other hand, if the width D2 of the recess 1Aa is 60% or more of the width D1 of the top plate portion 1A, the width of the surface of the top plate portion 1A to which the load is input may become too short. The collision load is input to the top plate portion 1A. Therefore, if the width of the surface of the top plate portion 1A is too short, early buckling of the top plate portion 1A may be promoted. As a result, there is a risk of leading to a decrease in collision performance. From this perspective, it is preferable that the ratio of the width D2 of the recess 1Aa be less than 60% of the width D1 of the top plate portion 1A. As described above, the ratio of the width D2 of the recess 1Aa and the associated angle α are specified for molding reasons and from the perspective of improving collision performance.

[0023] FIG. 4 illustrates a comparative door impact beam 3. For ease of understanding, the same reference numerals are used for corresponding components of the comparative example. The comparative door impact beam 3 includes a bead to facilitate maintaining the shape of the central cross-section when a collision load is applied. This bead corresponds to the recess 1Aa of the present invention. The depth of this bead tends to be shallow from the perspective of maintaining the shape. In contrast, in the present embodiment, the recess 1Aa has a deep cross-sectional shape with a depth H1. Furthermore, in the present embodiment, the recess 1Aa has a V-shaped cross-section. This facilitates deformation of the central cross-section when a collision load is applied to the door impact beam 3 (see FIG. 6 ). Specifically, the V-shape of the recess 1Aa is easily deformed when a collision load is applied, thereby contributing to improved load-bearing performance. In other words, the recess 1Aa of the present embodiment is not intended to maintain the shape of the central cross-section when a collision load is applied.

[0024] (Angle θ1 between the top plate portion 1A and the vertical wall portion 1B) The angle θ1 between the top plate portion 1A and the vertical wall portion 1B is usually set to be wider than 90 degrees, as shown in FIG. 4. In contrast, in this embodiment, the angle θ1 between the top plate portion 1A and the vertical wall portion 1B is set to be less than 90 degrees. In this specification, the angle θ1 is used as the angle on the inner surface between the top plate portion 1A and the vertical wall portion 1B. The angle on the inner surface is narrower than the angle on the outer surface. This angle θ1 is also referred to as the vertical wall angle θ1. Note that there may be shallow beads or other irregularities on the surfaces of the top plate portion 1A or the vertical wall portion 1B. However, these beads or other irregularities are ignored when specifying each angle.

[0025] In FIG. 3 , the surface defining the top panel 1A is flat, so the vertical wall angle θ1 is defined as the angle between the flat surface defining the top panel 1A and the flat surface defining the vertical wall 1B. However, the flat portion of the top panel 1A may be, for example, an inclined surface with the outer side relatively lower or higher than the center side in the width direction. In this case, the vertical wall angle θ1 may be defined as the angle on the inner side between an imaginary line connecting both ends of the top panel 1A in the width direction D1 and the vertical wall 1B. The symbol k corresponds to the position of the imaginary line. The vertical wall angle θ1 is preferably, for example, greater than or equal to 80 degrees and less than 90 degrees. This is because it improves collision performance.

[0026] Consider the case where the vertical wall angle θ1 is less than 90 degrees. In this case, the lower side of the vertical wall portion 1B is located closer to the center in the cross-sectional width direction than the upper side of the vertical wall portion 1B. As a result, the vertical wall portion 1B of this embodiment is slightly inclined so as to move inward in the cross-sectional width direction from the upper side to the lower side. That is, the opposing distance between the left and right vertical wall portions 1B is smaller at the lower side than at the upper side. Therefore, a load applied to the top plate portion 1A promotes a deformation mode in which the vertical wall portion 1B folds like an accordion (see FIG. 6). In other words, a deformation state in which the vertical wall portion 1B opens is suppressed. As a result, the load-bearing capacity of the door impact beam 3 is reduced and the load-bearing capacity is improved. Furthermore, in this embodiment, as described below, the outward opening of the flange portion 1C is also suppressed during deformation. As a result, the load-bearing capacity of the door impact beam 3 is further reduced and the load-bearing capacity is improved.

[0027] On the other hand, if the vertical wall angle θ1 is less than 80 degrees, the vertical wall portion 1B may easily collapse inward during deformation, which may lead to a decrease in collision performance. Therefore, the vertical wall angle θ1 is preferably, for example, greater than or equal to 80 degrees and less than 90 degrees. In the impact absorbing member 3 of this example, when formed by press working, the angle between the ridgeline of the top plate portion 1A and the vertical wall portion 1B is set to a negative angle less than 90 degrees. The ridgeline of the top plate portion 1A and the vertical wall portion 1B corresponds to the shoulder of the top plate portion 1A. The angle of this ridgeline corresponds to the vertical wall angle θ1. This vertical wall angle θ1 can be set to less than 90 degrees, for example, by utilizing a cam mechanism. Here, in the present disclosure, the conditions for the recess 1Aa formed in the top plate portion 1A do not necessarily need to satisfy the conditions described in this embodiment. However, it is more preferable to satisfy the above conditions.

[0028] (Flange Portion 1C) The flange portion 1C is a portion that continues from the lower end of the vertical wall portion 1B and extends outward in the width direction of the cross section. In this embodiment, the flange portion 1C extends so that its height approaches that of the top plate portion 1A as it moves from the base portion 1Ca, where the flange portion 1C connects to the vertical wall portion 1B, toward the tip portion 1Cb. That is, the flange portion 1C extends outward in the width direction of the cross section in a raised shape. Therefore, in this embodiment, when the main body 1 is placed on a horizontal mounting surface, as shown in FIG. 3, the flange portion 1C contacts the mounting surface only at the base portion. The flange portion 1C has a raised shape that forms an angle θ2 with respect to the mounting surface. This angle θ2 is also referred to as the raised angle.

[0029] In this case, the angle of the flange portion 1C relative to the outer surface of the vertical wall portion 1B is an acute angle. Furthermore, the jump angle θ2 is, for example, greater than (90 degrees - vertical wall angle θ1). Here, the vertical wall portion 1B connects to the flange portion 1C via a bent portion 1E (ridge portion 1E) having a predetermined R. The transition portion from the bent portion 1E forms the above-mentioned base portion. Furthermore, the length of the flange portion 1C may be short. The amount of overhang D3 of the flange portion 1C outward in the cross-sectional width direction relative to the end portion of the top plate portion 1A in the width D1 direction is, for example, less than 20% of the overall cross-sectional width D0. The smaller the amount of overhang D3 of the flange portion 1C, the more it contributes to weight reduction. The length of the flange portion 1C may be greater than 0, but it is preferable for it to have at least a bent portion 1E.

[0030] As described above, in this embodiment, the flange portion 1C is short and has a cross-sectional shape that protrudes toward the top plate. Note that if the protrusion amount D3 of the flange portion 1C is 20% or more of the overall cross-sectional width, the flange portion 1C is less likely to fold like an accordion during collision deformation. In this case, there is a possibility that the cross-section may open. The reason the flange portion 1C protrudes toward the top plate is to promote the flange portion 1C's foldable deformation mode, rather than the accordion-like deformation mode. In other words, by making the angle between the outer surface of the vertical wall portion 1B and the flange portion 1C an acute angle, the flange portion 1C is more likely to displace toward the vertical wall portion 1B during deformation.

[0031] (Operation and Others) The door impact beam 3 of this embodiment has a cross-sectional shape that achieves both improved load-bearing performance and reduced weight. As a comparative example, a cross-section of a conventional door impact beam 3 having an M-shaped open cross-section is illustrated as shown in FIG. 4 . As mentioned above, for ease of comparison, the same reference numerals as those in FIG. 3 are used for the reference numerals of the components in FIG. 4 . In the comparative example, a bead-shaped recess 1Aa is provided in the top plate 1A to increase the rigidity of the top plate 1A. Furthermore, the vertical wall angle θ1, which is the angle of the vertical wall 1B relative to the top plate 1A, is molded to be 90 degrees or slightly wider than 90 degrees.

[0032] Consider a vehicle equipped with a door impact beam 3 like this comparative example inside the door. In a side collision, the door impact beam 3 absorbs the collision energy and buckles. During this buckling, the cross section of the beam 3 deforms outward. This may significantly reduce the load-bearing capacity of the comparative example. Specifically, when the door impact beam 3 of the comparative example buckles in response to an impact force, it may induce deformation in the left and right vertical wall portions 1B and flange portions 1C that open outward in the width direction (see FIG. 7 ). If the left and right vertical wall portions 1B deform outward in the width direction, the load capacity after the maximum load is significantly reduced. As a result, the comparative example may experience a reduction in collision performance. The cross section subjected to the load buckles and deforms to absorb the collision energy after the maximum load.

[0033] On the other hand, the door impact beam 3 of this embodiment has a deep valley-shaped recess 1Aa in the center of the top plate 1A. In addition, in this embodiment, the angle between the top plate 1A and the vertical wall 1B is less than 90 degrees. Furthermore, in this embodiment, the flange 1C has a cross-sectional shape that rises toward the top plate. This cross-sectional shape was primarily determined by CAE analysis of door impact beams 3 with various cross-sectional shapes. Specifically, this cross-sectional shape was arrived at by gaining knowledge of the load-displacement curve and deformation mode.

[0034] Consider the case where a load is applied to the door impact beam 3 of this embodiment in a side collision of a vehicle from a direction perpendicular to the longitudinal direction of the door impact beam 3. In this case, as shown in FIG. 6 , during deformation after the maximum load, a deformation mode in which the top panel 1A and the vertical wall 1B and the vertical wall 1B and the flange 1C are folded like bellows is promoted. As a result, the cross section deforms into a shape that promotes deformation inward rather than outward. In other words, by suppressing the outward opening of the vertical wall 1B and the flange 1C, the decrease in the load-bearing value during cross-sectional deformation is suppressed. Therefore, a high load value can be maintained even after deformation of the door impact beam 3 begins. In other words, the decrease in the load-bearing capacity of the door impact beam 3 is reduced, and the load-bearing capacity is improved.

[0035] In the deformation shown in FIG. 6 , due to buckling of the top plate portion 1A, the position of the bent portion between the top plate portion 1A and the vertical wall portion 1B deforms while moving toward the vertical wall portion 1B. Furthermore, along with this deformation, the lower portion of the vertical wall portion 1B deforms so that it bites inward without opening. In this case, the recess 1Aa in this embodiment has a deep V-shape and a narrow bottom angle α. Therefore, when the top plate portion 1A buckles, the bent portion at the boundary between the approximately flat portion of the top plate portion 1A and the recess 1Aa deforms so that it moves toward the recess 1Aa. Furthermore, the bottom angle α narrows with this deformation. Note that in FIG. 6 , the bent portion at the boundary between the approximately horizontal portion of the top plate portion 1A and the recess 1Aa is raised upward. This is because the collision load bends the main body portion 1 at the longitudinal load input position, displacing the load input position longitudinally of the main body portion 1 from the cross-sectional position shown in FIG. 6 .

[0036] Furthermore, during the deformation of the cross section, the position of the bent portion 1E between the vertical wall portion 1B and the flange portion 1C also moves toward the vertical wall portion 1B on the flange portion 1C side. Along with this deformation, the flange portion 1C also deforms toward the vertical wall portion 1B. This also suppresses the decrease in the load value when the cross section deforms. As described above, the impact absorbing member 3 of this embodiment can more efficiently improve the load-bearing capacity by controlling the deformation mode while suppressing an increase in the weight of the impact absorbing member 3.

[0037] (Other) The present disclosure may also have the following configurations. (1) Disclosure 1 describes an impact absorbing member having a long main body with a cross section including a top plate having a recess midway in the width direction, left and right vertical wall portions connected to both widthwise ends of the top plate, and left and right flange portions connected to the lower ends of each vertical wall portion, wherein the angle between the inner surfaces of the top plate and the vertical wall portions is less than 90 degrees, and the flange portions rise in height from the base end connected to the vertical wall portions toward the tip end so that the height approaches that of the top plate. (2) Disclosure 2 describes an impact absorbing member in which the depth of the recess is 60% or more of the height of the cross section. (3) Disclosure 3 describes an impact absorbing member in which the width of the recess is 40% or more and 60% or less of the width of the top plate. (4) Disclosure 4 describes an impact absorbing member in which the cross section of the recess is V-shaped. (5) Disclosure 5 is a shock absorbing member that is attached to a part that needs to absorb shock, the shock absorbing member having attachment portions at both ends of the elongated main body for attaching to the part.

[0038] Next, examples of this embodiment will be described. (Example 1) The cross-sectional shape of the door impact beam 3 (impact absorbing member 3) of an inventive example based on this embodiment was the cross-sectional shape shown in FIG. 3. The cross-sectional shape of the door impact beam 3 of the comparative example was the cross-sectional shape shown in FIG. 4. However, both longitudinal dimensions were 830 mm. The cross-sectional dimensions of the door impact beam 3 of this inventive example were as follows: The width D1 of the top plate portion 1A was 80 mm, and the width D2 of the recessed portion 1Aa was 40 mm. That is, the proportion of the width D2 of the recessed portion 1Aa was 50%. The height H0 of the cross-section was 41.2 mm, and the depth H1 of the recessed portion 1Aa was 38.7 mm. The angle α of the bottom of the V-shaped recessed portion 1Aa was 45 degrees. The overall width D0 of the cross-section was 122 mm, and the protrusion amount D3 of the flange portion 1C was 21 mm. The radius of curvature of the connection (bent portion) between the flat portion of the top plate 1A and the recess 1Aa, and the radius of curvature of the connection (bent portion) between the top plate 1A and the vertical wall portion 1B were each 6.7 mm. The radius of curvature of the bottom (tip) of the V-shaped recess 1Aa was also 6.7 mm. The radius of curvature of the connection (bent portion) between the vertical wall portion 1B and the flange portion 1C was 6.9 mm. In this example, the vertical wall angle θ1 was 88 degrees.

[0039] On the other hand, the cross-sectional dimensions of the door impact beam 3 in the comparative example were as follows: the width D1 of the top plate portion 1A was 82 mm, and the width D2 of the recessed portion 1Aa was 40 mm. The height H0 of the cross section was 41.4 mm, and the depth H1 of the recessed portion 1Aa was 14.4 mm. The angle α at the bottom of the recessed portion 1Aa was 45 degrees. The overall width D0 of the cross section was 127 mm, and the protrusion D3 of the flange portion 1C was 22 mm. The radius of the connection (bent portion) between the flat portion of the top plate portion 1A and the recessed portion 1Aa and the radius of the connection (bent portion) between the top plate portion 1A and the vertical wall portion 1B were each 6.7 mm. The radius of each bent portion of the recessed portion 1Aa was also 6.7 mm. The radius of the connection (bent portion) between the vertical wall portion 1B and the flange portion 1C was also 6.7 mm. In this comparative example, the vertical wall angle θ1 was 95 degrees. In the comparative example, the depth H1 of the recess 1Aa is about 1 / 3 of the height of the entire cross section.

[0040] In the example, a door impact beam was manufactured by cold pressing a high-tensile steel plate having a thickness of 1.2 mm and a tensile strength of 1.7 GPa into the shape shown in FIG. 3 . In the comparative example, a door impact beam was manufactured by cold pressing a high-tensile steel plate having a thickness of 1.4 mm and a tensile strength of 1.7 GPa into the shape shown in FIG. 4 . The cross-sectional shapes of the example and the comparative example differ in the vertical wall angle θ1 and the depth H1 of the recess 1Aa. Furthermore, the cross-sectional shapes of the two examples differ in the rise angle θ2 of the flange portion 1C. In particular, the depth H1 of the recess 1Aa of the example of the present invention is deeper, at 38.7 mm. Therefore, the cross-sectional area of ​​the example of the present invention appears to be larger. However, by setting the thickness of the example of the present invention to 1.2 mm and the thickness of the comparative example to 1.4 mm, the cross-sectional areas of the two examples are the same.

[0041] (Evaluation) A three-point bending test was conducted to verify the deformation mode of the cross section. The three-point bending test was performed under the following conditions: Specifically, as shown in FIG. 5 , a door impact beam 3 to be evaluated was placed on left and right supports 10. The longitudinal center of the door impact beam 3 was pressed with a punch 11 of radius 100. The reaction force generated between the support 10 and the test piece door impact beam 3 was measured as a load value. The punch was pressed in at a constant speed of 0.01 km / min. The stroke amount was a downward stroke of 100 mm from the state shown in FIG. 5 . The distance between the left and right supports 10 was 720 mm. The load value and stroke amount were measured for each of the three-point bending test equipment for multiple stroke amounts. Using these measurements, load-displacement curves for the inventive example and the comparative example were created. The results are shown in FIG. 8 . The area surrounded by the curve and the x-axis in FIG. 8 indicates the energy absorption amount. A larger amount of energy absorption indicates that more energy is absorbed.

[0042] As can be seen from Figure 8, even when the cross-sectional area of ​​the door impact beam is the same, the example of the present invention exhibits a greater energy absorption capacity than the comparative example. In other words, the cross-sectional shape based on the present invention exhibits better collision performance. This result demonstrates that a deformation mode that suppresses outward opening of the cross section is effective. Furthermore, the deformation modes of the example of the present invention and the comparative example at a stroke of 100 mm were confirmed. In the example of the present invention, the vertical wall portion 1B and flange portion 1C were in a folded-like deformation state, as shown in Figure 6. In the comparative example, the vertical wall portion 1B and flange portion 1C were in a deformed state that opened outward, as shown in Figure 7.

[0043] (Example 2) Next, the depth H1 of the recess 1Aa provided in the top panel 1A was evaluated. Specifically, multiple door impact beams 3 were fabricated with the cross-sectional shapes and dimensions shown in the first embodiment, except for the angle α between the depth H1 of the recess 1Aa and the bottom of the recess 1Aa. The three-point bending test described above was then performed on each door impact beam 3 to determine the energy absorption amount EA for each cross-sectional shape. Six types of door impact beams 3 were fabricated and evaluated. Each of the six types of door impact beams 3 had a different ratio of the depth H1 of the recess 1Aa to the cross-sectional height H0. The six ratios were 50.0%, 60.0%, 62.5%, 75.0%, 87.5%, and 93.8%.

[0044] FIG. 9 shows the relationship between the depth H1 of the recess 1Aa and the energy absorption amount EA. As can be seen from FIG. 9, by setting the depth H1 of the recess 1Aa to 50% or more, the energy absorption amount EA increases compared to the comparative example. Furthermore, the energy absorption amount EA increases as the depth H1 of the recess 1Aa increases. The case where the depth H1 of the recess 1Aa is 50% corresponds to the invention example in Example 1. We also considered a case where the dimensions of the top panel portion 1A and the vertical wall portion 1B are kept constant while the depth H1 of the recess 1Aa is varied. In this case, the mass of the door impact beam 3 increases as the depth H1 of the recess 1Aa increases. Therefore, we calculated the relationship between the depth H1 of the recess 1Aa and the energy absorption amount per unit weight [EA / weight]. The results are shown in FIG. 10.

[0045] As can be seen from Figure 10, the greater the proportion of the depth H1 of the recess 1Aa, the greater the energy absorption amount EA per unit weight (= mass). Also, as can be seen from Figure 10, by setting the proportion of the depth H1 of the recess 1Aa to 60% or more, the energy absorption amount EA per unit weight (= mass) can be stably achieved to be 1.2 times or more that of the comparative example (conventional structure). The dashed-dotted lines in Figures 9 and 10 are examples of threshold values ​​for evaluation in this example. In Figures 9 and 10, the example threshold value is indicated by a line drawn at a position 1.2 times the value of the comparative example.

[0046] From the above, the following was found. That is, as can be seen from Fig. 9, when the ratio of the depth H1 of the recess 1Aa is 50% or more, the energy absorption amount EA can be reliably increased compared to the comparative example. Furthermore, as can be seen from Fig. 10, by setting the ratio of the depth H1 of the recess 1Aa to 60% or more, the energy absorption amount per unit weight [EA / weight] can be more stably ensured. In other words, it was found that the load-bearing performance can be improved compared to the conventional case without increasing the mass of the door impact beam 3.

[0047] The entire contents of Japanese Patent Application No. 2024-115895 (filed July 19, 2024), from which this application claims priority, are incorporated herein by reference. While the present application has described a limited number of embodiments, the scope of the invention is not limited thereto, and modifications of each embodiment based on the above disclosure would be obvious to one skilled in the art.

[0048] DESCRIPTION OF SYMBOLS 1 Main body 1A Top plate 1Aa Recess 1B Vertical wall 1C Flange 1Ca Root 1Cb Tip 1D Ridge 1E Bent portion (ridge) 3 Impact absorbing member (door impact beam) 4 Door (part to be installed) D0 Width of cross section D1 Width of top plate D2 Width of recess D3 Projection amount of flange H0 Height of cross section H1 Depth of recess α Angle at bottom of recess θ1 Vertical wall angle θ2 Bounce angle

Claims

1. An impact absorbing member having a long main body having a cross section that includes a top plate portion having a recess at a position midway in the width direction, left and right vertical wall portions connected to both ends of the top plate portion in the width direction, and left and right flange portions connected to the lower ends of each of the vertical wall portions, The angle between the top plate and the vertical wall on the inner side is less than 90 degrees. The flange portion described above is curved upwards from the base where it connects to the vertical wall towards the tip, so that its height approaches the height of the top plate. Shock-absorbing material.

2. The depth of the recess is 60% or more of the height of the cross-section. The impact absorbing member described in claim 1.

3. The width of the above-mentioned recess is 40% to 60% of the width of the above-mentioned top plate. The impact absorbing member described in claim 1.

4. The cross-sectional shape of the above recess is V-shaped. An impact absorbing member as described in any one of claims 1 to 3.

5. An impact-absorbing member that is attached to a component whose impact needs to be mitigated, The long main body section described above is provided with mounting parts at both ends for attaching to the above-mentioned components. An impact absorbing member as described in any one of claims 1 to 3.