Energy absorber

Abstract

To obtain an energy absorption body capable of effectively absorbing energy against small external force at an initial stage where external force acts, and capable of effectively absorbing energy even against large external force.SOLUTION: An energy absorption body 102 has a compressed base body 108 having a negative Poisson's ratio and compressed by external force, and a pair of plate-like elastic plate bodies 106 that sandwich the compressed base body 108 and elastically curve in a thickness direction due to the external force. When the external force is relatively small, the curvature of the elastic plate body 106 mainly absorbs the energy of the external force, and when the external force is relatively large, the compression of the compressed base body 108 mainly absorbs the energy of the external force.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to energy absorbers. [Background technology]

[0002] Patent document 1 describes a deformable auxetic structure for absorbing the energy of an impact, comprising a plurality of interconnected adjacent three-dimensional auxetic cells, where each three-dimensional auxetic cell comprises at least a surface element and a plurality of legs extending from the surface element, the plurality of legs and the surface element being configured such that a partial cross-section of the structure in at least two planes perpendicular to the surface elements follows an auxetic pattern. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-98749 Summary of the Invention [Problem to be solved by the invention]

[0004] The deformable auxetic structure described in Patent Document 1 has auxetic behavior in only one direction; for example, when compressive deformation in the impact direction is attempted, the structure can only condense in the direction perpendicular to both the impact direction and the extrusion direction.

[0005] However, while such an auxetic structure can effectively absorb energy when it is sufficiently compressed by an external force, it is desirable for it to also effectively absorb energy in a pre-compression state, such as the initial stage when an external force is applied, i.e., when the external force is small and the structure exhibits elastic behavior.

[0006] An object of the present invention is to provide an energy absorber that can effectively absorb the energy of a small external force in the initial stage when the external force acts, and can also effectively absorb the energy of a large external force. [Means for solving the problem]

[0007] In a first aspect, the energy absorber has a compressed base body that has a negative Poisson's ratio and is compressed by an external force, and a pair of plate-shaped elastic plates that sandwich the compressed base body and elastically bend in the plate thickness direction due to the external force, and when the external force is relatively small, the energy of the external force is absorbed mainly by the bending of the elastic plates, and when the external force is relatively large, the energy of the external force is absorbed mainly by the compression of the compressed base body.

[0008] In this energy absorber, a compression substrate is sandwiched between a pair of elastic plates. The compression substrate has a negative Poisson's ratio, and when an external force is applied, it is compressed in the direction of the external force and also in the direction perpendicular to the external force, thereby absorbing the energy of the external force. The pair of elastic plates also absorb the energy of the external force by bending in the thickness direction when subjected to the external force.

[0009] Therefore, when an external force acts on this energy absorber, the energy is absorbed mainly by the bending of the elastic plate when the external force is relatively small, and the energy is absorbed mainly by the compression of the compressed base when the external force is relatively large. This allows for effective energy absorption of small external forces in the early stages of application, and also allows for effective energy absorption even when the external force is large.

[0010] In a second aspect, the compression base is made compressible by folding a sheet material at a predetermined folding position.

[0011] The compression substrate can be constructed by folding a sheet material, which allows for a simplified structure and reduced costs.

[0012] In a third aspect, the device includes a holding member that holds the compressed base in a state thinner than the compressible state, a biasing member that biases the compressed base toward the compressible state, a detection member that detects the external force, and a release member that releases the holding of the compressed base by the holding member when the external force detected by the detection member exceeds a predetermined value.

[0013] The holding member holds the compression base in a state thinner than the compressible state, so there are fewer restrictions on the location of the energy absorber.

[0014] When the external force detected by the detection member exceeds a predetermined value, the release member releases the holding member from holding the compressed base, thereby allowing the compressed base to receive the biasing force of the biasing member and achieve a state in which it can be compressed by an external force.

[0015] In a fourth aspect, a plurality of the compression substrates are stacked.

[0016] Therefore, compared to a configuration with a single layer of compression substrate, energy can be absorbed more effectively by a plurality of compression substrates. [Effects of the Invention]

[0017] In the present invention, it is possible to effectively absorb the energy of a small external force in the initial stage when the external force acts, and it is also possible to effectively absorb the energy of a large external force. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a front view showing an energy absorber of the first embodiment. [Figure 2] FIG. 2 is a perspective view showing the compression structure of the energy absorber of the first embodiment. [Figure 3A] FIG. 3A is a perspective view showing a stacked state of sheet materials constituting a compression base body of the energy absorber of the first embodiment. [Figure 3B] FIG. 3B is a perspective view showing the compressed base body of the energy absorber of the first embodiment in a half-folded state. [Figure 4A] FIG. 4A is a plan view showing a sheet material constituting a compression base body of the energy absorber of the first embodiment. [Figure 4B] FIG. 4B is a plan view B showing the sheet material constituting the compression base of the energy absorber of the first embodiment. [Figure 4C] FIG. 4C is a partially enlarged perspective view showing a folded sheet material constituting the compression base of the energy absorber of the first embodiment. [Figure 5A] FIG. 5A is an exploded perspective view showing the compression structure of the energy absorber of the first embodiment from the front side. [Figure 5B] FIG. 5B is a perspective view showing the compression structure of the energy absorber of the first embodiment from the front side. [Figure 5C] 5C is a front view showing the compression structure of the energy absorber of the first embodiment as viewed in the direction of arrow 5C in FIG. 2. FIG. [Figure 6A] FIG. 6A is an explanatory diagram showing a state in which an external force acts on the energy absorber of the first embodiment. [Figure 6B] FIG. 6B is an explanatory diagram showing a state in which an external force acts on the energy absorber of the first embodiment. [Figure 6C] FIG. 6C is an explanatory diagram showing a state in which an external force acts on the energy absorber of the first embodiment. [Figure 6D] FIG. 6D is an explanatory diagram showing a state in which an external force acts on the energy absorber of the first embodiment. [Figure 7] FIG. 7 is a graph qualitatively showing the relationship between displacement and load when an external force acts on a plate-like member and causes it to bend. [Figure 8] FIG. 8 is a graph showing the relationship between displacement and load when an external force acts on each of the energy absorbers of the first embodiment, the modified example of the first embodiment, and the first to third comparative examples. [Figure 9] FIG. 9 is a front view showing an energy absorber according to a modified example of the first embodiment. [Figure 10] FIG. 10 is a front view showing the energy absorber of the first comparative example. [Figure 11]FIG. 11 is a front view showing an energy absorber of the second comparative example. [Figure 12] FIG. 12 is a front view showing an energy absorber of a third comparative example. [Figure 13A] FIG. 13A is a perspective view showing a compressed structure of an energy absorber according to a second embodiment in a half-folded state. [Figure 13B] FIG. 13B is a side view showing the compressed structure of the energy absorber of the second embodiment in a half-folded state. [Figure 14A] FIG. 14A is a perspective view showing a compression structure of an energy absorber of a second embodiment in a fully folded state. [Figure 14B] FIG. 14B is a side view showing the compressed structure of the energy absorber of the second embodiment in a fully folded state. [Figure 15] FIG. 15 is a side view showing the energy absorber of the third embodiment in a state where the compressed base body is folded in half. [Figure 16] FIG. 16 is a side view showing the energy absorber of the third embodiment in a state in which the compressed base body is changing from a half-folded state to a fully-folded state. [Figure 17] FIG. 17 is a side view showing the energy absorber of the third embodiment in a fully folded state. [Figure 18] FIG. 18 is a perspective view showing an energy absorber according to the fourth embodiment. [Figure 19] FIG. 19 is a perspective view showing a compression base constituting the compression structure of the energy absorber of the fourth embodiment, as viewed from above. [Figure 20] FIG. 20 is a perspective view showing a compression base constituting the compression structure of the energy absorber of the fourth embodiment, as viewed from below. [Figure 21] FIG. 21 is a perspective view showing a compressed base constituting the compression structure of the energy absorber of the fourth embodiment, as viewed from above in a compressed state. [Figure 22A] FIG. 22A is a front view showing the energy absorber of the fifth embodiment in a state before being compressed. [Figure 22B] FIG. 22B is a front view showing the compressed base body constituting the compressed structure of the energy absorber of the fifth embodiment in a state before compression. [Figure 23A] FIG. 23A is a front view showing an energy absorber of the fifth embodiment in the middle of being compressed. [Figure 23B] FIG. 23B is a front view showing a state in which the compression base constituting the compression structure of the energy absorber of the fifth embodiment is being compressed. [Figure 24A] FIG. 24A is a front view showing the energy absorber of the fifth embodiment in a compressed state. [Figure 24B] FIG. 24B is a front view showing the compressed base body constituting the compressed structure of the energy absorber of the fifth embodiment in a compressed state. DETAILED DESCRIPTION OF THE INVENTION

[0019] The energy absorber 102 of the first embodiment will be described below with reference to the drawings.

[0020] 1, the energy absorber 102 has a compression structure 104 and a pair of elastic plates 106 that sandwich the compression structure 104. In the following, the direction in which the elastic plates 106 sandwich the compression structure 104 is referred to as the up-down direction of the energy absorber 102, and is indicated by arrow U. The width direction of the energy absorber 102 is indicated by arrow W, and the depth direction is indicated by arrow D.

[0021] The vertical direction of the energy absorber 102 is the direction in which the energy of an external force (i.e., an impact) acting on the energy absorber 102 is absorbed by deformation. However, this vertical direction is a direction for the convenience of explanation and does not limit the direction in which the energy absorber 102 is actually used.

[0022] As also shown in Fig. 2, the compressed structure 104 has one or more layers of compressed substrates 108. In the example shown in Figs. 1 and 2, the compressed substrate 108 has four layers, with the first and third layers from the top, compressed substrates 108A, and the second and fourth layers from the top, having different shapes. The compressed substrates 108A and 108B have different structures so as to ensure a wide mutual contact area when stacked as shown in Figs. 2 and 5B, but there is no essential difference between them in terms of physical properties.

[0023] As shown in FIG. 3A, the compressed substrate 108A and the compressed substrate 108B are respectively constituted by a sheet material 110A and a sheet material 110B formed into a rectangular sheet shape.

[0024] 4A, the sheet material 110A is divided into a plurality of unit cells 112 by dividing lines D1 and D2. Each unit cell 112 is further divided into four portions 114 by a horizontal center line CL1 and a vertical center line CL2.

[0025] The unit cell 112 is formed with mountain fold lines MF1 and valley fold lines VF1 that are inclined at a predetermined inclination angle α with respect to the center line CL1. If we consider a quadrant CL2 located further in the center of the portion 114, the portions separated by the mountain fold line MF1 and valley fold line VF1 at the position of this quadrant CL2 have lengths of m, l, and m, respectively. The mountain fold line MF1 and valley fold line VF1 are formed symmetrically with respect to the center line CL1 and center line CL2. The mountain fold line MF1 and valley fold line VF1 are examples of "fold positions" according to the technology of the present disclosure.

[0026] The center line CL1 is also divided into a mountain fold line MF2 portion and a valley fold line VF2 portion. The mountain fold line MF2 and the valley fold line VF2 are also examples of the "fold position" according to the technique of the present disclosure.

[0027] In the sheet material 110A, mountain folds along mountain fold lines MF1 and MF2 and valley folds along valley fold lines VF1 and VF2 are made at a predetermined folding angle β in the unit cells 112 to obtain the three-dimensional cell structure 116 shown in Fig. 4C. Note that Fig. 4C shows the shaded portion of the unit cells 112 in Fig. 4A.

[0028] 4B, the sheet material 110B is divided into a plurality of unit cells 112 by dividing lines D1 and D2, and mountain fold lines MF1 and MF2 and valley fold lines VF1 and VF2 are formed in each unit cell 112. However, in the sheet material 110B, the inclination direction of the mountain fold lines MF1 and valley fold lines VF1 is opposite to that of the sheet material 110A, and the positions of the mountain fold lines MF1 and valley fold lines VF1 are swapped.

[0029] In the sheet material 110B, a three-dimensional cell structure is obtained by performing mountain folds along mountain fold lines MF1 and MF2 and valley folds along valley fold lines VF1 and VF2 at a predetermined folding angle β in the unit cells 112. The cell structure obtained from the sheet material 110B is symmetrical to the three-dimensional cell structure 116 shown in FIG. 4C.

[0030] The method of forming the compressed substrate 108A and the compressed substrate 108B by folding the sheet material 110A and the sheet material 110B is one method of manufacturing the compressed substrate 108. The compressed substrate 108 can be formed by folding the sheet material 110A and the sheet material 110B, which simplifies the structure of the compressed substrate 108 and allows the compressed substrate 108 to be manufactured at low cost.

[0031] As shown in Fig. 5A, the compressed substrate 108A formed from the sheet material 110A has upper portions 108AU and lower portions 108AL that alternate in the width direction. The compressed substrate 108B formed from the sheet material 110B has lower portions 108BL and upper portions 108BU that alternate in the width direction. The compressed structure 104 is constructed by alternately stacking the compressed substrates 108A and 108B having such shapes. By stacking the compressed substrates 108A and 108B, the compressed structure 104 has a three-dimensional structure with a hollow portion 118.

[0032] As shown in FIG. 5B, in the compressed structure 104, the compressed substrates 108A and 108B are alternately stacked, with the lower portion 108AL of the compressed substrate 108A in contact with the upper portion 108AU of the compressed substrate 108B, and the lower portion 108BL of the compressed substrate 108B in contact with the upper portion 108AU of the compressed substrate 108A.

[0033] 2 to form compressed structure 104, but for example, as shown in Fig. 3B, sheet materials 110A and 110B may be laminated in a state in which the mountain folds along mountain fold lines MF1 and MF2 and the valley folds along valley fold lines VF1 and VF2 are not completely interwoven (a half-folded state, which will be described later). In this case, for example, after installation in a predetermined installation position, further mountain folds along mountain fold lines MF1 and MF2 and valley folds along valley fold lines VF1 and VF2 may be applied to form the fully folded state shown in Fig. 2.

[0034] The compression structure 104 thus constructed is a member having a negative Poisson's ratio with respect to deformation in the vertical direction. Here, when stress acts on the compression structure 104 in the vertical direction, the strain in the vertical direction is expressed as ε U , strain in the width direction is ε W , the strain in the depth direction is ε D Poisson's ratio in the width direction ν W teeth, ν W =-(ε W / ε U ) is defined as the Poisson's ratio in the depth direction, ν D teeth ν D =-(ε D / ε U ) It is defined as follows.

[0035] The compressed structure 104 of this embodiment has negative Poisson's ratios in both the width and depth directions. Therefore, the compressed structure 104 exhibits auxetic behavior, in that when compressed in the vertical direction due to an external force (impact) acting in the vertical direction, it is also compressed in the width and depth directions. By exhibiting this deformation behavior in response to an external force acting in the vertical direction, the compressed structure 104 condenses internally as the stress in the vertical direction increases, increasing its geometric rigidity and absorbing the energy of the impact. In contrast, a member with a positive Poisson's ratio expands in the width and depth directions as it is compressed in the vertical direction, resulting in little internal condensation and being disadvantageous in terms of absorbing the energy of the impact.

[0036] 1, the compression structure 104 is sandwiched between a pair of elastic plates 106. Hereinafter, the upper elastic plate 106 will be referred to as an elastic upper plate 106U, and the lower elastic plate 106 will be referred to as an elastic lower plate 106L, as appropriate.

[0037] The elastic lower plate 106L has a width greater than that of the compression structure 104. Portions of the elastic lower plate 106L that extend beyond the compression structure 104 on both sides in the width direction are supported by the support members 120. In other words, the central portion of the elastic lower plate 106L in the width direction is not supported by the support members 120. Therefore, when a downward force is applied to the central portion in the width direction, the elastic lower plate 106L elastically curves in a direction that convexly curves downward.

[0038] 1, the elastic upper plate 106U has a width substantially equal to that of the compression structure 104. The elastic upper plate 106U may have a width wider than that of the compression structure 104, as long as it can bend downwardly convexly in response to an external force acting from above and apply a load to the upper surface of the compression structure 104.

[0039] In the energy absorber 102 of this embodiment, as shown in FIG. 1, when an external force (impact) in the vertical direction is applied to the central part of the elastic upper plate 106U by the collision body 100, the structure of the elastic plate 106 and the compression structure 104 is set so that different deformation states are assumed in a stage where the value of the external force is relatively small and a stage where the value of the external force is relatively large.

[0040] Specifically, when the external force is relatively small, the elastic upper plate 106U, the compression structure 104, and the elastic lower plate 106L are all curved downward in a convex shape. However, because the compression structure 104 exhibits the auxetic behavior described above, the geometric rigidity at this stage is relatively low. Therefore, at this stage, the energy of the impact is mainly absorbed by the bending of the elastic plate 106. In other words, the bending moduli of the elastic upper plate 106U and the elastic lower plate 106L are set so that, in the initial stage when an external force is applied, even a relatively small external force will cause the elastic upper plate 106U and the elastic lower plate 106L to bend without providing resistance to energy absorption.

[0041] As the value of the external force increases, the elastic upper plate 106U, the compression structure 104, and the elastic lower plate 106L are further curved downwardly, and the compression structure 104 is also curved and compressed vertically.

[0042] When the external force becomes stronger, the elastic force of the elastic upper plate 106U and the elastic lower plate 106L increases, making it gradually more difficult for them to bend, but the compression structure 104 is compressed in the up-down direction. As a result, the energy of the impact is absorbed mainly by the compression of the compression structure 104. In practice, the rate at which the energy of the external force is absorbed continuously shifts from the bending of the elastic plate 106 to the compression of the compression structure 104. That is, there is a stage in which the energy of the external force is absorbed mainly by the bending of the elastic plate 106, followed by a stage in which the energy of the external force is absorbed mainly by the compression of the compression structure 104. The boundary value (threshold value) of the external force that separates these two stages can be set arbitrarily, for example, by adjusting the shape of the elastic plate 106 and the structure of the compression structure 104 in accordance with the magnitude of the expected external force.

[0043] 1, the elastic upper plate 106U and the elastic lower plate 106L are in contact with and sandwich the compression structure 104, but either or both of the elastic upper plate 106U and the elastic lower plate 106L may be disposed apart from the compression structure 104. For example, even in a structure in which both the elastic upper plate 106U and the elastic lower plate 106L are separated from the compression structure 104, it is sufficient that when an external force is applied, the elastic upper plate 106U moves towards and comes into contact with the compression structure 104 due to the external force, and the compression structure 104 moves towards the elastic lower plate 106L, thereby realizing a structure in which the compression structure 104 is sandwiched between the elastic upper plate 106U and the elastic lower plate 106L.

[0044] Next, the operation of the first embodiment will be described.

[0045] 6A to 6D show the results of a simulation of the deformation state when the energy absorber 102 of the first embodiment is hit from above by a collision body 100. In Fig. 6A to 6D, the upper figures show the energy absorber 102 as viewed from the front, and the lower figures show the energy absorber 102 as viewed from the side.

[0046] The displacement of the elastic upper plate 106U is 10 mm in Figure 6A, 20 mm in Figure 6B, 30 mm in Figure 6C, and 40 mm in Figure 6D. This "displacement" is the downward displacement length at the center of the width of the elastic plate 106 from the state before bending.

[0047] As shown in Figure 6A, at a displacement of 10 mm, the upper elastic plate 106U and the lower elastic plate 106L are curved downward in a convex shape. The compression structure 104 is slightly compressed in the vertical direction and is curved as a whole. Because the compression structure 104 exhibits auxetic behavior as described above, at this stage, the energy of the external force is absorbed mainly by the bending of the elastic plate 106.

[0048] 6B, at the stage where the displacement is 20 mm, the elastic upper plate 106U and the elastic lower plate 106L are further curved compared to the state shown in Fig. 6A, and the compression structure 104 is compressed in the up-down direction. Therefore, although some of the impact energy is absorbed by the curvature of the elastic upper plate 106U and the elastic lower plate 106L, a larger proportion is absorbed by the compression of the compression structure 104.

[0049] 6C, at the stage where the displacement is 30 mm, the elastic upper plate 106U and the elastic lower plate 106L are further bent compared to the state shown in FIG. 6B, and the compression structure 104 is further compressed in the vertical direction. At this stage, the energy of the external force is mainly absorbed by the compression of the compression structure 104.

[0050] As shown in Fig. 6D, at a displacement of 40 mm, the compression structure 104 is further compressed in the vertical direction compared to the state shown in Fig. 6C. At this stage, the rate at which the compression structure 104 absorbs the energy of the external force is even higher than in the state shown in Fig. 6C.

[0051] Here, Fig. 7 qualitatively shows an example of the relationship between displacement and load when a typical plate-like member elastically bends due to an external force and absorbs energy. The horizontal axis of the graph in Fig. 7 represents displacement from the position at the center of the plate-like member before bending, as in the case shown in Figs. 6A to 6D of this embodiment.

[0052] As shown by the two-dot chain line in FIG. 7, the plate-like member in question behaves elastically up to a predetermined critical point P1, so that displacement and load are roughly proportional. Beyond critical point P1, the rate at which load increases relative to displacement decreases. In order to more effectively absorb energy in a plate-like member with such deformation characteristics, it is conceivable to increase the elastic constant (flexural modulus) by, for example, increasing the plate thickness. However, as shown by the one-dot chain line and two-dot chain line in FIG. 7, simply increasing the flexural modulus results in a sudden rise in load in the range up to when displacement reaches critical point P1, resulting in a greater force being applied from the plate-like member to the impactor 100.

[0053] FIG. 8 shows an example of the relationship between displacement and load in the energy absorber 102 of the first embodiment, an energy absorber of a modified example of the first embodiment, and the energy absorbers of the first to third comparative examples.

[0054] In the graph shown in FIG. 8, the curve L11 corresponds to the energy absorber 102 of the first embodiment, and the curve L12 corresponds to the energy absorber 152 of the modified example of the first embodiment.

[0055] 9, the energy absorber 152 of this modified example has the sheet materials 110A and 110B constituting the compressed structure 104 each having a thickness (plate thickness) that is 1.5 times that of the energy absorber 102 of the first embodiment, but otherwise has the same structure as the energy absorber 102 of the first embodiment. Note that even if the thicknesses of the sheet materials 110A and 110B are increased in this manner, there is no need to significantly change the shape of the compressed base body 108.

[0056] In the graph shown in FIG. 8, curve C11 corresponds to the energy absorber 52 of the first comparative example, curve C12 corresponds to the energy absorber 62 of the second comparative example, and curve C13 corresponds to the energy absorber 72 of the third comparative example.

[0057] As shown in Fig. 10, the energy absorber 52 of the first comparative example does not have a compression structure 104 (see Fig. 1), and is composed of only one elastic plate 106. The thickness of the elastic plate 106 of the first comparative example is adjusted compared to the elastic plate 106 of the first embodiment.

[0058] As shown in Fig. 11, the energy absorber 62 of the second comparative example has a compression structure 104, an elastic upper plate 106U, and an elastic lower plate 106L that are the same as those of the energy absorber 102 of the first embodiment, but the elastic lower plate 106L is structured so as not to bend. Note that a structure in which the elastic plate 106 does not bend can also be achieved by, for example, increasing the thickness of the elastic lower plate 106L, but in the example shown in Fig. 11, this is achieved by supporting the entire lower surface side of the elastic lower plate 106L with a support member 120.

[0059] As shown in Figure 12, the energy absorber 72 of the third comparative example has a compression structure 104, an elastic upper plate 106U, and an elastic lower plate 106L that are the same in structure as the energy absorber 152 of the modified example of the first embodiment, but by supporting the entire lower surface side of the elastic lower plate 106L with a support member 120, the elastic lower plate 106L does not bend, similar to the energy absorber 62 of the second comparative example.

[0060] In the energy absorber 52 of the first comparative example, the load increases rapidly until the displacement reaches approximately 5 mm. That is, in the initial stage of the collision of the impactor 100, a large force is applied from the energy absorber 52 to the impactor 100.

[0061] In the energy absorber 62 of the second comparative example, the elastic lower plate 106L does not bend, so the energy of the external force is absorbed by the bending of the elastic upper plate 106U and local compression at the central portion of the compression structure 104. However, the degree of bending of the elastic upper plate 106U is smaller in the second comparative example than in the first embodiment. Furthermore, the load increases rapidly as the displacement increases up to a displacement of approximately 10 mm.

[0062] In the energy absorber 72 of the third comparative example, the thickness of the compression structure 104 is 1.5 times that of the second comparative example, so the load increases even more rapidly than in the second comparative example up to a displacement of approximately 10 mm.

[0063] In this way, both the energy absorber 62 of the second comparative example and the energy absorber 72 of the third comparative example may apply a large force to the impactor 100 in the initial stage of the impact of the impactor 100.

[0064] In contrast, the load of the energy absorber 102 of the first embodiment is smaller in the range up to when the displacement reaches 15 mm than that of any of the energy absorbers of the first to third comparative examples. In other words, the energy absorber 102 does not apply a large force to the impact body 100 in the initial stage of the collision of the impact body 100. Furthermore, in the range of displacement from approximately 15 mm to 40 mm, the load gradually increases as the displacement increases, and it can be seen that the energy of the external force can be effectively absorbed.

[0065] Furthermore, the energy absorber 152 of the modified example of the first embodiment has a smaller load in the range up to when the displacement reaches 15 mm than any of the energy absorbers of the first to third comparative examples. That is, similar to the energy absorber 102 of the first embodiment, it does not exert a large reaction force on the impactor 100 in the initial stage of the collision of the impactor 100, and further, in the range of displacement from approximately 15 mm to 40 mm, the value of the load that accompanies an increase in displacement is larger than that of the first embodiment. That is, it can be seen that the energy absorber 152 of the modified example of the first embodiment can more effectively absorb the energy of an external force.

[0066] In this way, the energy absorber 102 of the first embodiment and the energy absorber 152 of the modified example of the first embodiment can effectively absorb energy in response to small external forces in the initial stage of the external force application, and can also effectively absorb energy in response to large external forces.

[0067] In particular, since the compression structure 104 is constructed by stacking multiple compression substrates 108, energy can be absorbed more effectively by compression of the multiple compression substrates 108 compared to, for example, a case in which the compression structure 104 is constructed by a single layer of compression substrates 108.

[0068] Next, a second embodiment will be described. In the second embodiment, the same elements, members, etc. as those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted.

[0069] 13A and 13B, the energy absorber 202 of the second embodiment has a compression structure 104 similar to the energy absorber 102 of the first embodiment. Although not shown in FIGS. 13A and 13B, an elastic upper plate 106U and an elastic lower plate 106L (see FIG. 1) are disposed above and below the compression structure 104.

[0070] However, in the second embodiment, sheet material 110A and sheet material 110B are stacked in a state prior to forming the three-dimensional structure shown in FIG. 2, i.e., in a state where the folding angles of mountain fold line MF1 and valley fold line VF1 (see FIGS. 4A and 4B) do not reach the predetermined angle β.

[0071] 13A and 13B will be referred to as a "half-folded state" for the sake of convenience. The thicknesses of the sheet materials 110A and 110B in the half-folded state are thinner than the thicknesses of the compressed substrates 108A and 108B.

[0072] In the second embodiment, as shown in Fig. 13B, sheet material 110A and sheet material 110B are provided with a plurality of springs 204. The elasticity of these springs 204 acts on sheet material 110A and sheet material 110B to deform them into the fully folded state shown in Fig. 14A and Fig. 14B. The length of springs 204 is set so that they become their natural length when sheet material 110A and sheet material 110B are in the fully folded state.

[0073] 13B, the second embodiment further includes a pin 206, a release member 208, and an impact sensor 210. The pin 206 holds the sheet materials 110A and 110B at predetermined positions of the sheet materials 110A and 110B so that the half-folded state is maintained against the elastic force of the spring 204. When the impact force detected by the impact sensor 210 exceeds a predetermined value, the release member 208 releases the holding by the pin 206. The pin 206 is an example of a "holding member" according to the technology of the present disclosure, and the impact sensor 210 is an example of a "detection member" according to the technology of the present disclosure. The release member 208 is an example of a "release member" according to the technology of the present disclosure.

[0074] In the second embodiment configured as described above, the sheet materials 110A and 110B are maintained in a half-folded state by the pins 206. In the half-folded state, the sheet materials 110A and 110B are thinner than in the fully folded state, and therefore the energy absorber 202 can be made smaller.

[0075] For example, even if the space for arranging the energy absorber is narrow, the energy absorber 202 can be arranged in a compact size, and there are fewer restrictions on the arrangement location.

[0076] Then, if the external force (impact) acting on the energy absorber 202 exceeds a predetermined value, the release member 208 releases the holding of the sheet materials 110A and 110B by the pins 206. The elastic force of the springs 204 causes the sheet materials 110A and 110B to be in a fully folded state, i.e., to form the compressed substrates 108A and 108B, and thereafter, similar to the energy absorber 102 of the first embodiment, it is possible to effectively absorb energy in the initial stage of the external force, even when the external force is small, and also to effectively absorb energy even when the external force is large.

[0077] In the second embodiment, the length of spring 204 is set so that it becomes its natural length when sheet materials 110A and 110B are fully folded. Therefore, when sheet materials 110A and 110B are fully folded, the elasticity of spring 204 does not have an effect, or has a small effect, on absorbing energy due to compression when an external force is applied.

[0078] Next, a third embodiment will be described. In the third embodiment, the same elements, members, etc. as those in the first or second embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0079] The energy absorber 302 of the third embodiment includes a bag member 304, an exhaust device 306, and an impact sensor 210. The bag member 304 is formed into a bag shape using a thin film, and maintains an expanded bag-like state by sealing air inside. A half-folded sheet material 110A or sheet material 110B is accommodated inside the expanded bag member 304. While Figures 15 to 17 show a state in which the sheet material 110A is accommodated in the bag member 304, the same applies to a structure in which the sheet material 110B is accommodated.

[0080] An adhesive portion 110C is set in a part of the sheet material 110A, and is adhered to the inner surface of the bag member 304 by adhesive or the like.

[0081] An exhaust port 304V is formed in a part of the bag member 304. The exhaust device 306 is provided at the exhaust port 304V and is a device that can exhaust air from the bag member 304.

[0082] The elasticity of the mountain fold line MF1 and the valley fold line VF1 (see FIG. 4A) causes stress to act on the sheet material 110A, moving it from the half-folded state to the fully folded state. However, as shown in FIG. 15, when the sheet material 110A is housed inside the bag member 304, a part of the sheet material 110A comes into contact with the bag member 304, and a force is applied from the bag member 304 to the sheet material 110A to keep it in the half-folded state, preventing it from deforming to the fully folded state.

[0083] In the third embodiment, when the impact detected by the impact sensor 210 exceeds a predetermined value, the exhaust device 306 is activated, and the air inside the bag member 304 is exhausted as shown in FIG. 16. Then, as shown in FIG. 17, the bag member 304 comes into close contact with the sheet material 110A. In this state, the force from the bag member 304 to the sheet material 110A to hold it in a half-folded state is no longer applied. As a result, the sheet material 110A is unfolded into a fully-folded state as shown in FIG. 17.

[0084] In the third embodiment configured as described above, when the bag member 304 is not evacuated, the sheet material 110A is maintained in a half-folded state by the bag member 304, so that the energy absorber 302 can be made smaller.

[0085] If the external force (impact) acting on the energy absorber 302 exceeds a predetermined value, the exhaust device 306 exhausts the air inside the bag member 304. As a result, the sheet materials 110A and 110B are unfolded into a fully folded state, i.e., into a state in which the compressed substrates 108A and 108B are formed. Thereafter, similar to the energy absorber 102 of the first embodiment, it is possible to effectively absorb energy in the initial stage of application of a small external force, and also to effectively absorb energy even when the external force is large.

[0086] In the third embodiment, although one sheet material 110A is shown in Figures 15 to 17, a structure may be adopted in which a plurality of sheet materials 110A or 110B are housed one by one in the bag member 304 and stacked in the thickness direction.

[0087] Next, a fourth embodiment will be described. In the fourth embodiment, the same elements, members, etc. as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0088] In the energy absorber 402 of the fourth embodiment, multiple compression substrates 406 having the structure shown in Figures 19 and 20 are arranged in the front-to-back, left-to-right, and up-to-down directions, and as a whole, a compression structure 404 shown in Figure 18 is formed.

[0089] The compressed substrate 406 has a rectangular (including a square) shape when viewed from above (in the direction of arrow A), and is symmetrical in the up-down, left-right, and front-rear directions.

[0090] The unit cell 112 has one first pillar 408 located in the center and four second pillars 410 located at the four corners. Outer beams 412 connecting the second pillars 410 are formed at positions along each side of the square when viewed in the direction of arrow A. The outer beams 412 are inclined so that the center is convex upward in the upper part of the compressed substrate 406 and convex downward in the lower part.

[0091] Each of the four sides of the first pillar 408 is also connected to the center of the corresponding outer beam 412 by an inner beam 414 .

[0092] The first pillar 408, the second pillar 410, the outer beam 412, and the inner beam 414 are provided symmetrically in the vertical direction on the compression base 406. The centers of the corresponding outer beams 412 on the vertical direction are connected by a connecting pillar 416.

[0093] 18, compression base bodies 406 having such a structure are arranged in a line in the front-rear, left-right, and up-down directions to form a compression structure 404. The compression structure 404 is then sandwiched between an elastic upper plate 106U and an elastic lower plate 106L to form an energy absorber 402 of the fourth embodiment.

[0094] In the energy absorber 402 of the fourth embodiment, when an external force acts in the vertical direction on a pair of upper and lower first pillars 408 and second pillars 410 of the compression base 406, the inclination angle of the outer beam 412 and the inner beam 414 increases. The compression base 406 is then compressed vertically, as well as horizontally and longitudinally. In other words, a compression structure 404 in which multiple compression bases 406 are connected achieves a structure with a negative Poisson's ratio.

[0095] Therefore, in the energy absorber 402 of the fourth embodiment, the compression structure 404 exhibits auxetic behavior, similar to the energy absorber 102 of the first embodiment. The energy absorber 402 of the fourth embodiment can effectively absorb energy in response to a small external force in the initial stage of the external force application, and can also effectively absorb energy in response to a large external force.

[0096] Next, a fifth embodiment will be described. In the fourth embodiment, the same elements, members, etc. as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0097] In the energy absorber 502 of the fifth embodiment, multiple compression substrates 506 having the structure shown in Figure 22B are arranged in the front-to-back, left-to-right, and up-to-down directions, and as a whole, a compression structure 504 shown in Figure 22A is formed.

[0098] The compression substrate 506 has a plurality of substantially cubic blocks 508, which are arranged in a line in the vertical, horizontal, and front-to-rear directions. The blocks 508 are connected by thin connecting pieces 510. The area surrounded by four blocks 508 forms a gap 512.

[0099] As shown in Fig. 22A, compressed substrates 506 having such a structure are arranged in the front-rear, left-right, and up-down directions to form a compressed structure 504. Gaps 512 are also formed between the compressed substrates 506. The energy absorber 502 of the fifth embodiment is formed by sandwiching the compressed structure 504 between the elastic upper plate 106U and the elastic lower plate 106L. In practice, more compressed substrates 506 than those shown in Fig. 22A may be arranged in the up-down, width, and depth directions.

[0100] In the energy absorber 502 of the fifth embodiment, when an external force acts in the vertical direction on the compression structure 504, as shown in Figures 23A and 23B, in each of the compression substrates 506, the blocks 508 rotate around the connecting pieces 510, and the voids 512 are gradually crushed. Then, as shown in Figures 24A and 24B, as the voids 512 are crushed, the compression substrate 506 is compressed vertically, as well as horizontally and longitudinally. In other words, the compression structure 504 in which multiple compression substrates 506 are connected achieves a structure having a negative Poisson's ratio.

[0101] Therefore, in the energy absorber 502 of the fifth embodiment, the compression structure 504 exhibits auxetic behavior, similar to the energy absorber 102 of the first embodiment. The energy absorber 502 of the fifth embodiment can effectively absorb energy in response to a small external force in the initial stage of the external force, and can also effectively absorb energy in response to a large external force. [Explanation of symbols]

[0102] 100 Collider 102 Energy absorber 104 Compressed Structure 106 Elastic Plate 108 Compressed substrate 110A, 110B sheet material 120 Support member 152 Energy absorber 202 Energy absorber 204 Spring 206 pins 208 Release member 210 Impact Sensor 302 Energy absorber 304 Bag parts 304V exhaust port 306 Exhaust system 402 Energy Absorber 404 Compressed Structure 406 Compressed substrate 408 Pillar 1 410 Second Pillar 412 Outside beam 414 Inside beam 416 Connecting column 502 Compressed Structure 502 Energy Absorber 504 Compressed Structure 506 Compressed substrate 508 Block 510 Connecting piece 512 void

Claims

1. a compression substrate having a negative Poisson's ratio and compressed by an external force; a pair of elastic plates that sandwich the compression base and are elastically curved in the plate thickness direction by the external force; and An energy absorber that absorbs the energy of the external force mainly by bending the elastic plate when the external force is relatively small, and absorbs the energy of the external force mainly by compressing the compression base when the external force is relatively large.

2. 2. The energy absorber according to claim 1, wherein the compressible substrate is made compressible by folding the sheet material at a predetermined folding position.

3. a holding member that holds the compression substrate in a state thinner than the compressible state; a biasing member that biases the compressible substrate toward the compressible state; a detection member that detects the external force; a release member that releases the holding of the compressed base by the holding member when the external force detected by the detection member exceeds a predetermined value; 3. The energy absorber of claim 2, wherein

4. The energy absorber according to any one of claims 1 to 3, wherein a plurality of the compression substrates are stacked.

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