Foldable structure

Abstract

To fold cylindrical structures with a small force in a foldable structure in which at least two cylindrical structures are arranged in parallel in a direction intersecting the axial direction to ensure bending rigidity and torsional rigidity.SOLUTION: A foldable structure 102 has at least two cylindrical structures 104 arranged in parallel in a direction intersecting the axial direction, and the cylindrical structures 104 can be folded in the longitudinal direction by bending at a plurality of annular fold lines that intersect the axial direction, and the torsional characteristics of the two cylindrical structures 104 are in opposite directions. The two cylindrical structures 104 are not joined to each other on their faces, and have a joint 112 that is joined at the plurality of fold lines, and a non-joint portion 114 that is not joined to the joint 112 at a fold line adjacent to the axial direction.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present disclosure relates to a foldable structure. [Background technology]

[0002] Patent Document 1 describes a foldable structure including at least two cylindrical structures. The two cylindrical structures have a common surface row that is a series of common surfaces shared by each other, and the torsional characteristics of the common surface row of one cylindrical structure are in the opposite direction to the torsional characteristics of the common surface row of the other cylindrical structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. WO2017 / 030103 Summary of the Invention [Problem to be solved by the invention]

[0004] In a foldable structure in which two cylindrical structures face each other with their common surfaces facing each other, a relative displacement (positional shift) occurs between the facing common surfaces when the structure is folded. If the common surfaces are brought into surface contact with each other, this relative displacement cannot be tolerated, and folding cannot be performed. Even if the structure allows the relative displacement of the common surfaces, friction occurs between the common surfaces, and frictional resistance is generated against folding.

[0005] The object of the present disclosure is to provide a foldable structure in which at least two cylindrical structures are arranged in parallel in a direction intersecting an axial direction to ensure bending rigidity and torsional rigidity, and to enable folding of the cylindrical structure with a small force. It is to make it possible. [Means for solving the problem]

[0006] In the first aspect of the foldable structure, at least two cylindrical structures are arranged in parallel in a direction intersecting the axial direction of the cylindrical structures, and the cylindrical structures can be folded in the longitudinal direction by bending along a plurality of fold lines intersecting the axial direction. The two cylindrical structures arranged in parallel have opposite torsional characteristics, and the two cylindrical structures are not joined to each other by their faces, and have a joint portion that is joined to each other by the plurality of fold lines, and a non-joint portion that is not joined to each other by the fold lines adjacent to the joint portion in the axial direction.

[0007] In this foldable structure, the two cylindrical structures arranged in parallel have torsional characteristics in opposite directions. Therefore, the bending rigidity and torsional rigidity are higher than those of a configuration in which the torsional characteristics of the two cylindrical structures are in the same direction.

[0008] The two cylindrical structures are not joined to each other at their surfaces, but have a joint portion and a non-joint portion. At the joint portion, the two cylindrical structures are joined at a fold line. At the non-joint portion, the two cylindrical structures are not joined at a fold line, and the fold line of the non-joint portion is adjacent to the joint portion in the axial direction. Since the two cylindrical structures are not joined at their surfaces and the surfaces can be displaced relative to each other, relative displacement during folding is permitted, and the cylindrical structures can be folded with a small force. Furthermore, when the two cylindrical structures are folded, friction between the surfaces does not occur, so large friction does not occur when folding the cylindrical structures.

[0009] In the foldable structure of the second aspect, in the first aspect, the two cylindrical structures are arranged in a mirror image manner.

[0010] This makes it possible to obtain high bending rigidity and torsional rigidity as a foldable structure.

[0011] In the foldable structure of the third aspect, in the first aspect, the two adjacent cylindrical structures are arranged in such a manner that the other cylindrical structure is rotated around the axis from the mirror arrangement relative to one of the cylindrical structures. Is arranged.

[0012] This makes it possible to obtain high bending rigidity and torsional rigidity as a foldable structure.

[0013] In the foldable structure of a fourth aspect, in any one of the first to third aspects, the tubular structure is bendable by a hinge provided at the folding line.

[0014] A simple structure that uses hinges can be realized that bends along a bending line.

[0015] In the foldable structure of the fifth aspect, in any one of the first to fourth aspects, each surface of the cylindrical structure is constituted by a plate body.

[0016] This allows the rigidity of each surface of the cylindrical structure to be maintained.

[0017] In the foldable structure of a sixth aspect, in any one of the first to fourth aspects, the tubular structure is constituted by a plurality of rigidly connected links.

[0018] This makes it possible to reduce the weight of the cylindrical structure. Effect of the Invention

[0019] In the disclosed technology, in a foldable structure in which at least two cylindrical structures are arranged in parallel in a direction intersecting the axial direction to ensure bending rigidity and torsional rigidity, the cylindrical structure can be folded with a small force. It is possible. [Brief description of the drawings]

[0020] [Figure 1A] FIG. 1A is a perspective view showing a foldable structure of a first embodiment. [Figure 1B] FIG. 1B is a plan view showing the foldable structure of the first embodiment. [Figure 1C] FIG. 1C is a side view showing the foldable structure of the first embodiment. [Figure 1D] FIG. 1D is a front view showing the foldable structure of the first embodiment. [Figure 2A]FIG. 2A is a perspective view showing a cylindrical structure of the foldable structure of the first embodiment. [Figure 2B] FIG. 2B is a perspective view showing a cylindrical structure of the foldable structure of the first embodiment. [Figure 2C] FIG. 2C is a perspective view showing a cylindrical structure of the foldable structure of the first embodiment. [Figure 3A] FIG. 3A is a partially enlarged plan view showing the foldable structure of the first embodiment. [Figure 3B] FIG. 3B is a partially enlarged plan view showing a foldable structure of a modified example of the first embodiment. [Figure 4A] FIG. 4A is a plan view showing a foldable structure of a reference example. [Figure 4B] FIG. 4B is a plan view showing a foldable structure of a reference example. [Figure 5A] FIG. 5A is a perspective view showing a foldable structure of a first comparative example. [Figure 5B] FIG. 5B is a plan view showing the foldable structure of the first comparative example. [Figure 5C] FIG. 5C is a side view showing the foldable structure of the first comparative example. [Figure 5D] FIG. 5D is a front view showing the foldable structure of the first comparative example. [Figure 6A] FIG. 6A is a perspective view showing a foldable structure of a second comparative example. [Figure 6B] FIG. 6B is a plan view showing a foldable structure of a second comparative example. [Figure 6C] FIG. 6C is a side view showing a foldable structure of a second comparative example. [Figure 6D] FIG. 6D is a front view showing a foldable structure of a second comparative example. [Figure 7A] FIG. 7A is a perspective view showing a foldable structure of a third comparative example. [Figure 7B] FIG. 7B is a plan view showing a foldable structure of a third comparative example. [Figure 7C] FIG. 7C is a side view showing a foldable structure of a third comparative example. [Figure 7D] FIG. 7D is a front view showing a foldable structure of a third comparative example. [Figure 8A] FIG. 8A is a perspective view showing a deformation state of a seventh deformation mode in a foldable structure of a first comparative example. [Figure 8B] 8B is a perspective view showing a deformation state of an eighth deformation mode in the foldable structure of the first comparative example. [Figure 8C] 8C is a perspective view showing a deformation state of nine deformation modes in the foldable structure of the first comparative example. [Figure 8D] 8D is a perspective view showing a deformation state of a tenth deformation mode in the foldable structure of the first comparative example. [Figure 8E] FIG. 8E is a graph showing the relationship between the deformation rate and the eigenvalue of the seventh to tenth deformation modes in the foldable structure of the first comparative example. [Figure 9A] FIG. 9A is a perspective view showing a deformation state of a seventh deformation mode in the foldable structure of the first embodiment. [Figure 9B] 9B is a perspective view showing a deformation state of an eighth deformation mode in the foldable structure of the first embodiment. [Figure 9C] 9C is a perspective view showing a deformation state of a ninth deformation mode in the foldable structure of the first embodiment. [Figure 9D] 9D is a perspective view showing a deformation state of a tenth deformation mode in the foldable structure of the first embodiment. [Figure 9E] FIG. 9E is a graph showing the relationship between the deformation rate and the eigenvalue of the seventh to tenth deformation modes in the foldable structure of the first embodiment. [Figure 10] FIG. 10 is a graph showing the relationship between the deformation rate and the eigenvalue of the seventh to tenth deformation modes in the foldable structure of the second comparative example. [Figure 11] FIG. 11 is a graph showing the relationship between the deformation rate and the eigenvalue of the seventh to tenth deformation modes in the foldable structure of the third comparative example. [Figure 12A] FIG. 12A is a perspective view showing a foldable structure of a second embodiment. [Figure 12B]FIG. 12B is a plan view showing the foldable structure of the second embodiment. [Figure 12C] FIG. 12C is a side view showing the foldable structure of the second embodiment. [Figure 12D] FIG. 12D is a front view showing the foldable structure of the second embodiment. [Figure 12E] FIG. 12E is a graph showing the relationship between the deformation rate and the eigenvalue of the seventh to tenth deformation modes in the foldable structure of the second embodiment. [Figure 12F] FIG. 12F is a graph showing the relationship between the deformation rate and the eigenvalue of the seventh to tenth deformation modes in the foldable structure of the second embodiment. [Figure 13A] FIG. 13A is a perspective view showing a foldable structure of a third embodiment. [Figure 13B] FIG. 13B is a plan view showing a foldable structure of the third embodiment. [Figure 13C] FIG. 13C is a side view showing a foldable structure of the third embodiment. [Figure 13D] FIG. 13D is a front view showing a foldable structure of a third embodiment. [Figure 14A] FIG. 14A is a perspective view showing a foldable structure of a fourth embodiment. [Figure 14B] FIG. 14B is a plan view showing a foldable structure of the fourth embodiment. [Figure 14C] FIG. 14C is a side view showing a foldable structure of the fourth embodiment. [Figure 14D] FIG. 14D is a front view showing a foldable structure of the fourth embodiment. [Figure 14E] FIG. 14E is a graph showing the relationship between the deformation rate and the eigenvalue of the seventh to tenth deformation modes in the foldable structure of the fourth embodiment. [Figure 14F] FIG. 14F is a graph showing the relationship between the deformation rate and the eigenvalue of the seventh to tenth deformation modes in the foldable structure of the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, the foldable structure 102 of the first embodiment will be described with reference to the drawings.

[0022] As shown in Figures 1A to 1D, the foldable structure 102 has two cylindrical structures 104 arranged side by side. In the following, when the two cylindrical structures 104 are to be distinguished from each other, they are referred to as a cylindrical structure 104A and a cylindrical structure 104B. Here, in Figures 1A and 1D, the cylindrical structure on the left side is referred to as a cylindrical structure 104A, and the cylindrical structure on the right side is referred to as a cylindrical structure 104B.

[0023] In the drawings, an X-axis, a Y-axis, and a Z-axis are set. The X-axis direction coincides with the axial direction of the cylindrical structure 104. The Y-axis direction coincides with the arrangement direction of the two cylindrical structures 104A and 104B. The Z-axis direction coincides with the height direction of the cylindrical structure 104. These directions are for the convenience of explanation and do not limit the directions when the foldable structure 102 is actually used.

[0024] The cylindrical structure 104 has a cylindrical shape with a parallelogram cross section in a direction perpendicular to the X-axis direction (the axial direction of the cylindrical structure 104), and has a plurality of folding lines BF formed in a direction perpendicular to the axial direction. The folding lines BF are formed at regular intervals in the axial direction. Each folding line BF is formed so as to surround the cylindrical structure 104. As will be described later, the cylindrical structure 104 can be changed into a shape folded in the axial direction by folding in opposite directions at the alternating folding lines BF (see FIG. 9A).

[0025] In the cylindrical structure 104, the boundary lines EF along the axial direction are each formed in a zigzag shape. That is, as shown in Fig. 1B and Fig. 1C, the boundary lines EF extend in the X-axis direction and have a mountain-valley shape that linearly swings at regular intervals (periods) in the Y-axis direction or Z-axis direction.

[0026] Each plate constituting the cylindrical structure 104 is referred to as a cylindrical constituent plate 106. The cylindrical constituent plate 106 is a parallelogram. In particular, in the example shown in Figures 1A to 1D, the cylindrical constituent plate 106 is a rhombus. In the cylindrical structure 104, such a shape having the cylindrical constituent plates 106 is a so-called Miura-folded cylindrical structure.

[0027] 2A to 2C show an example of a specific structure of a cylindrical structure 104. The example shown here is a so-called Miura-folded cylindrical structure. The example shown on the left side of FIG. 2A shows a Miura-folded unit cell 108 composed of four cylindrical constituent plates 106. Note that thickness T1 (see FIG. 3A) of cylindrical constituent plates 106 is omitted in FIG. 2A to 2C.

[0028] The plate constituting the unit cell 108 is formed with a mountain fold line MF1 extending from the center of the center line CL1 to one side and a valley fold line VF1 extending to the other side. Furthermore, the mountain fold line MF1 is formed symmetrically with respect to the center line CL1 and inclined at a predetermined inclination angle α. The mountain fold line MF1 is a mountain fold and the valley fold line VF1 is a valley fold, resulting in a unit cell 108 having a three-dimensional shape as shown on the right side of FIG. 2A. In reality, the unit cells 108 are arranged in a certain direction as shown in FIG. 2B to form a semi-cylindrical structure 104H, which can be folded in the arranged direction. The numerical values ​​(%) shown in FIG. 2B are approximate values ​​of the expansion and contraction rate based on the shape of the semi-cylindrical structure 104H stretched without folding.

[0029] In the example shown in Fig. 2C, two semi-cylindrical structures 104H are joined vertically so as to face each other, thereby forming a cylindrical structure 104 having a parallelogram-shaped cross section. Note that the example shown in Fig. 2C is a configuration example for convenience in forming the shape of the cylindrical structure 104. In practice, the cylindrical structure 104 can be formed, for example, by connecting a plurality of cylindrical constituent plates 106 with hinges 110 as described below.

[0030] As shown in FIGS. 1A to 1D, in the foldable structure 102 of the first embodiment, the two cylindrical structures 104A and 104B arranged side by side are arranged in a mirror image. That is, when a mirror surface is assumed between the cylindrical structures 104A and 104B, one cylindrical structure 104 coincides with a mirror image of the other cylindrical structure 104. When folding deformation occurs, the cylindrical structure 104 is twisted in the circumferential direction (rotation direction around the central axis CA1 in the axial direction). Here, if the direction in which the cylindrical structure 104 is twisted in a specific direction during deformation is called the "torsion characteristic," the torsion characteristics are inverted directions with positive and negative. For this reason, the torsion generated during deformation of the foldable structure 102 is canceled out by the cylindrical structure 104A and the cylindrical structure 104B. As a result, the torsion of the foldable structure 102 is suppressed, and structural stiffness (rigidity) is generated.

[0031] By configuring the cylindrical structure 104 in this way, deformation (folding) in the X-axis direction can be caused by a relatively small force, whereas deformation (bending and twisting) in a direction intersecting the X-axis direction requires a large force. In other words, it is a structure that can achieve both a folding mode (small eigenvalue of deformation) in which it is required to be easy to fold and deform in the X-axis direction, and an elastic mode (large eigenvalue of deformation) in which it is required to be difficult to deform except in the X-axis direction. The "eigenvalue" of this deformation is one of the indicators that indicates the ease of deformation in a foldable structure or a cylindrical structure, and the smaller this value (lower eigenvalue), the easier it is to deform.

[0032] 3A, each of the cylindrical constituent plates 106 in the cylindrical structure 104 has a constant thickness T1. Since each of the cylindrical constituent plates 106 has the thickness T1, the cylindrical constituent plates 106 have a predetermined bending rigidity and torsional rigidity.

[0033] In each of the cylindrical structures 104, the cylindrical constituent plates 106 are connected to each other by hinges 110. The hinges 110 realize a structure in which the cylindrical constituent plates 106 do not interfere with each other in both the folded state (see FIG. 9A) and the unfolded state (see FIG. 1A). Since the cylindrical constituent plates 106 do not interfere with each other, a sufficient range of contraction (expansion / contraction length) is ensured when the cylindrical structure 104 is folded, and excessive resistance to expansion and contraction is not generated.

[0034] 1A to 1D showing the foldable structure 102, the hinge 110 is omitted in FIG. 1A and FIG. 1D, and is simplified in FIG. 1B and FIG. 1C.

[0035] As a structure in which the cylindrical constituent plates 106 do not interfere with each other when the cylindrical structure 104 is folded, the structure shown in Fig. 3B can also be adopted. In the structure shown in Fig. 3B, a tapered portion 106T in which the plate thickness gradually decreases is formed around the periphery of the cylindrical constituent plates 106. The cylindrical constituent plates 106 are connected by hinges 110 at each side (the tip of the tapered portion 106T). In other words, by forming the tapered portion 106T, the cylindrical constituent plates 106 do not interfere with each other in both the folded and unfolded states.

[0036] 1B, the two cylindrical structural bodies 104A and 104B arranged side by side are not joined to each other by their cylindrical constituent plates 106 at their surfaces, but are connected by joining them at a plurality of joints 112 formed by hinges 110. In the X-axis direction, joints 112 joined at the positions of the fold lines BF and non-joints 114 not joined at the positions of the fold lines BF are present alternately. In other words, when considering a specific joint 112 joined at the fold line BF, this joint 112 and non-joints 114 not joined at the fold lines BF on both sides adjacent to each other in the X-axis direction are configured.

[0037] Next, the operation of this embodiment will be described.

[0038] 4A shows a joint structure of a reference example. In the joint structure of the reference example, the cylindrical constituent plates 106 constituting the cylindrical structure 104 are connected by a hinge 110, and further, the two cylindrical structures 104 are joined at the surfaces of the cylindrical constituent plates 106 (joint surfaces 106S).

[0039] In the joint structure of the reference example, when the cylindrical structure 104 is folded as shown in Fig. 4B, the cylindrical constituent plates 106 that are in surface contact with each other at the joint surfaces 106S are displaced from each other. However, since the cylindrical constituent plates 106 are actually joined by surfaces, a resistance force acts against this displacement. In other words, the joint structure of the reference example generates a large resistance to folding.

[0040] In contrast, in the foldable structure 102 of this embodiment, the two cylindrical constituent plates 106 are linearly joined at the folding line BF, and a non-jointed portion 114 is present adjacent to the joint portion 112. That is, in the foldable structure 102 of this embodiment, the two cylindrical constituent plates 106 are not joined at the surface, and there is no part that resists folding as in the case where they are joined at the surface. As a result, the foldable structure 102 of this embodiment has a structure that allows folding in the X-axis direction to occur with less force.

[0041] In describing the action of the foldable structure 102 of this embodiment, first, the foldable structures 12, 22, and 32 of the first to third comparative examples will be described. In the first to third comparative examples, the same elements, members, etc. as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0042] 5A to 5D show the foldable structure 12 of the first comparative example. In the foldable structure 12 of the first comparative example, the foldable structure 12 is configured by one cylindrical structure 104. In the illustrated example, the one cylindrical structure 104 has a cylindrical structure 104A.

[0043] 6A to 6D show the foldable structure 22 of the second comparative example. The foldable structure 22 of the second comparative example has two cylindrical structures 104, and these cylindrical structures 104 have the same shape. In the illustrated example, two cylindrical structures 104A are adjacent to each other in the Y-axis direction (one cylindrical structure 104 is arranged at a position where the other cylindrical structure 104 is moved in parallel) and joined. In other words, two cylindrical structures 104 having the same directional torsional characteristics are arranged side by side. In the two cylindrical structures 104A, the hinges 110 adjacent to each other in the X-axis direction constitute the joint portion 112. For this reason, the cylindrical structures 104A are substantially joined at the surface of the cylindrical constituent plate 106.

[0044] 7A to 7D show the foldable structure 32 of the third comparative example. The foldable structure 32 of the third comparative example has two cylindrical structures 104. One cylindrical structure 104 is a cylindrical structure 104A, and the other cylindrical structure 104 is a cylindrical structure 104B. In the cylindrical structures 104A and 104B, the hinges 110 adjacent to each other in the X-axis direction form a joint portion 112. Therefore, the cylindrical structures 104A and 104B are substantially joined at the surface of the cylindrical constituent plate 106.

[0045] The foldable structure of the technology disclosed herein and the foldable structures of the first to third comparative examples have multiple deformation modes. For example, in the X-axis direction, the Y-axis direction, and the Z-axis direction, there are three-component translational deformation modes (1st to 3rd orders). In addition, around the X-axis, the Y-axis, and the Z-axis, there are three rotational deformation modes (4th to 6th orders).

[0046] Furthermore, each of these foldable structures has seventh to tenth deformation modes. Figures 8A to 8D show the deformation states of the seventh to tenth deformation modes in the case of the first comparative example, and Figures 9A to 9D show the deformation states of the first embodiment.

[0047] The seventh deformation mode is a deformation mode related to folding in the X-axis direction as shown in FIG. 8A and FIG. 9A. The eighth deformation mode is a deformation mode related to bending in the Y-axis direction as shown in FIG. 8B and FIG. 9B. The ninth deformation mode is a deformation mode related to twisting around the X-axis as shown in FIG. 8C and FIG. 9C. The tenth deformation mode is a deformation mode related to bending in the Z-axis direction as shown in FIG. 8D and FIG. 9D. Of the seventh to tenth deformation modes, it is desirable that the seventh deformation mode is easy to deform in response to an input (low eigenvalue of deformation), and the eighth to tenth deformation modes are desirable to be more difficult to deform in response to an input than the seventh deformation mode (high eigenvalue of deformation). In particular, it is preferable that the eighth and ninth deformation modes have eigenvalues ​​similar to those of the tenth deformation mode.

[0048] FIG. 8E shows the relationship between the deformation ratio and the eigenvalue in the foldable structure 12 of the first comparative example. FIG. 10 shows the relationship between the deformation ratio and the eigenvalue in the foldable structure 22 of the second comparative example. In both the foldable structure 12 of the first comparative example and the foldable structure 22 of the second comparative example, a low eigenvalue is obtained in the seventh deformation mode, and a high eigenvalue is obtained in the tenth deformation mode. However, the eigenvalues ​​of the eighth and ninth deformation modes are lower than the eigenvalue of the tenth deformation mode. In particular, the eigenvalue of the eighth deformation mode is lower than the eigenvalue of the ninth deformation mode.

[0049] FIG. 11 shows the relationship between the deformation ratio and the eigenvalue in the foldable structure 32 of the third comparative example. In the foldable structure 32 of the third comparative example, a high eigenvalue is obtained in the 10th deformation mode. In addition, in the 8th and 9th deformation modes, eigenvalues ​​close to the 10th deformation mode are obtained. However, the eigenvalue of the 7th deformation mode is higher than that of the foldable structure 12 of the first comparative example, for example.

[0050] That is, in any of the first to third foldable structures, the difference between the eigenvalue of the seventh deformation mode and the eigenvalue of the eighth deformation mode is small. In practice, it is desirable to increase this difference.

[0051] FIG. 9E shows the relationship between the deformation ratio and the eigenvalue in the foldable structure 102 of the first embodiment. In the foldable structure 102 of this embodiment, the eigenvalue of the 10th deformation mode is high, and the eigenvalues ​​of the 8th and 9th deformation modes are also close to the eigenvalue of the 10th deformation mode. In addition, the eigenvalue of the 7th deformation mode is approximately the same as or lower than the foldable structure 12 of the first comparative example. As a result, in the foldable structure 102 of this embodiment, a large difference occurs between the eigenvalue of the 7th deformation mode (mode related to folding) and the eigenvalues ​​of the 8th to 10th deformation modes (modes related to elastic deformation), and ideal deformation characteristics are obtained.

[0052] 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 description thereof will be omitted.

[0053] As shown in Figures 12A to 12D, the foldable structure 202 of the second embodiment has two cylindrical structures 104, but one cylindrical structure 104A is offset from the other cylindrical structure 104B in the Z-axis direction (Z+ direction in the illustrated example). In addition, in the joint 112, the joint portion by the folding line BF also generates a shift of a predetermined length L2 with respect to the length L1 of the folding line BF. Here, if the shift rate R is defined as R = L2 / L1, R can be set to a range of, for example, 0.8 or less.

[0054] 12E and 12F show the relationship between the deformation ratio and the eigenvalue in the foldable structure 202 of the second embodiment. FIG. 12E shows the case where the displacement ratio R is 0.5, and FIG. 12F shows the case where the displacement ratio R is 0.8. In either case, a large difference occurs between the eigenvalue of the seventh deformation mode and the eigenvalues ​​of the eighth to tenth deformation modes, and ideal deformation characteristics are obtained.

[0055] Next, a third embodiment will be described. In the third 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.

[0056] As shown in Figures 13A to 13D, the foldable structure 302 of the third embodiment has two cylindrical structures 104, but the other cylindrical structure 104B is rotated 180 degrees around the central axis CA of the cylindrical shape with respect to one cylindrical structure 104A. In the third embodiment, as in the second embodiment, the deviation rate is defined as R = L2 / L1. In the third embodiment, R = 0 (zero).

[0057] In the foldable structure 302 of the third embodiment as well, a large difference occurs between the eigenvalue of the seventh deformation mode and the eigenvalues ​​of the eighth to tenth deformation modes.

[0058] 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.

[0059] 14A to 14D, the foldable structure 402 of the fourth embodiment has two cylindrical structures 104, but the other cylindrical structure 104B is rotated 180 degrees around the central axis CA of the cylindrical shape relative to one cylindrical structure 104A, and is offset in the Z-axis direction (Z+ direction in the illustrated example). In the fourth embodiment, when the deviation rate R is defined as R=L2 / L1, R can be set to a range of, for example, 0.8 or less.

[0060] 14E and 14F show the relationship between the deformation ratio and the eigenvalue in the foldable structure 402 of the fourth embodiment. FIG. 14E shows the case where the displacement ratio R is 0.5, and FIG. 14F shows the case where the displacement ratio R is 0.8. In either case, a large difference occurs between the eigenvalue of the seventh deformation mode and the eigenvalues ​​of the eighth to tenth deformation modes, and ideal deformation characteristics are obtained.

[0061] In the above, an example was given in which each surface of the cylindrical structure 104 is constituted by the cylindrical constituent plate 106, but each surface of the cylindrical structure 104 may be constituted by, for example, a suitable combination of a plurality of links, i.e., rod-shaped members. Specifically, since each surface of the cylindrical structure 104 is a parallelogram, links may be arranged on each side and diagonal of this parallelogram, and the ends of the links may be rigidly joined to each other. If each surface of the cylindrical structure 104 is constituted by a plurality of rigidly joined links, it is possible to achieve weight reduction compared to the case where the cylindrical constituent plate 106 is used. In contrast, in the configuration using the cylindrical constituent plate 106, each surface of the cylindrical structure 104 is covered with the cylindrical constituent plate 106, and it is possible to ensure higher rigidity.

[0062] Furthermore, the configuration for connecting the cylindrical structures in a bendable manner is not limited to the above-mentioned hinge 110. For example, the thickness of the cylindrical constituent plate 106 may be thin at the hinge 110 portion to make it bendable (so-called thin-walled hinge). By using a thin-walled hinge, an increase in the number of parts can be suppressed. Furthermore, the parallelogram cylindrical constituent plates 106 may be joined to each other by thermal welding, adhesion, adhesive tape, or the like to make the joints bendable. In such a joint structure, since the hinge 110 is not used, the structure can be simplified.

[0063] In addition, the following notes are disclosed: (Appendix 1) A foldable structure in which at least two cylindrical structures are arranged in parallel in a direction intersecting the axial direction of the cylindrical structures, The cylindrical structure can be folded in a longitudinal direction by bending along a plurality of bending lines intersecting an axial direction, and the two cylindrical structures arranged in parallel have torsional characteristics in opposite directions; The two cylindrical structures have a joint portion that is not joined to each other by a surface and is joined to each other at a plurality of the fold lines, and a non-joint portion that is not joined to each other at the fold lines adjacent to the joint portion in the axial direction. A foldable structure. (Appendix 2) The foldable structure according to claim 1, wherein the two cylindrical structures are arranged in a mirror-image manner. (Appendix 3) The foldable structure described in Appendix 1, wherein the two adjacent cylindrical structures are arranged in such a manner that the other cylindrical structure is rotated around an axis from a mirror image arrangement relative to one of the cylindrical structures. (Appendix 4) The foldable structure according to any one of claims 1 to 3, wherein the cylindrical structure is bendable by a hinge provided at the folding line. (Appendix 5) 5. The foldable structure according to any one of claims 1 to 4, wherein each surface of the cylindrical structure is constituted by a plate body. (Appendix 6) The foldable structure according to any one of claims 1 to 4, wherein the cylindrical structure is constituted by a plurality of links rigidly connected to each other. [Explanation of symbols]

[0064] 102 Foldable structures 104 Cylindrical structure 106 Cylindrical component plate 106T Tapered section 108 unit cells 110 Hinge 112 Joint 114 Non-joint part 202 Foldable structures 302 Foldable structures 402 Foldable structures

Claims

1. A foldable structure in which at least two cylindrical structures are arranged in parallel in a direction intersecting the axial direction of the cylindrical structures, The cylindrical structure can be folded in a longitudinal direction by bending along a plurality of bending lines intersecting an axial direction, and the two cylindrical structures arranged in parallel have torsional characteristics in opposite directions; The two cylindrical structures have a joint portion that is not joined to each other by a surface and is joined to each other at a plurality of the fold lines, and a non-joint portion that is not joined to each other at the fold lines adjacent to the joint portion in the axial direction. A foldable structure.

2. The foldable structure according to claim 1, wherein the two cylindrical structures are arranged in a mirror image manner.

3. The foldable structure according to claim 1, wherein the two adjacent cylindrical structures are arranged in such a manner that the other cylindrical structure is rotated around an axis from a mirror arrangement with respect to one of the cylindrical structures.

4. The foldable structure according to claim 1, wherein the cylindrical structure is bendable by a hinge provided at the fold line.

5. The foldable structure according to claim 1, wherein each surface of the cylindrical structure is constituted by a plate body.

6. The foldable structure according to claim 1, wherein the cylindrical structure is composed of a plurality of links rigidly connected to each other.

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