JP6127376B2 - Hollow structure - Google Patents

Description

  The present invention relates to a technique for suppressing deformation of a hollow structure.

  When a hollow structure expands by absorbing moisture, if there are a portion with a large degree of expansion and a portion with a small degree of expansion, the hollow structure cannot maintain its original shape and deformation may occur. There is a technique for suppressing deformation caused in this way in a hollow structure. Patent Document 1 discloses a moisture-proof material on both surfaces of a base material serving as a base of a face material in a hollow flash door composed of a quadrilateral frame material and a face material affixed on both sides of the saddle material. The technology for providing the is described.

Japanese Patent Application No. 9-289585 JP 2010-84509 A

  By the way, in order to exhibit the intended function, there is a hollow structure provided with an opening. For example, Patent Literature 2 describes a hollow acoustic structure that scatters or absorbs sound in a specific frequency band among sounds entering from an opening. Some acoustic structures are made of a material that expands when absorbing moisture, such as wood. In such an acoustic structure, deformation may occur due to the influence of moisture entering the inside from the opening. For example, when the space closer to the opening has higher humidity and the amount of moisture absorbed by the acoustic structure varies depending on the location of the inner surface, the degree of expansion varies depending on the location, and the acoustic structure This is when the body shape changes. Since the technique of Patent Document 1 is premised on a flash door that does not have an opening, if an opening is provided, the flash door is deformed as described above due to the influence of moisture entering the inside from the opening. It is possible that this will occur.

  Then, an object of this invention is to suppress the deformation | transformation produced by the influence of the moisture which penetrate | invades into the inside of a hollow structure from an opening part.

In order to solve the above-described problems, the present invention provides a hollow structure having a hollow space surrounded by a plurality of inner surfaces and an opening connecting the hollow space and the outer space, with one of the plurality of inner surfaces. A first plate-like portion having a certain first inner surface and the opening, and a second plate-like portion having one of the plurality of inner surfaces and a second inner surface facing the first inner surface. And a connecting portion connecting the first plate-like portion and the second plate-like portion, and a moisture resistance greater than that of the first plate-like portion and provided on the first inner surface. A hollow structure characterized by comprising an expansion suppressing member.

Also, the present invention includes a hollow space surrounded by a plurality of inner surfaces, the hollow space and the hollow structure having an opening connecting the exterior space, the first inner surface is one of said plurality of inner face And a first plate-like portion having the opening, a second plate-like portion having a second inner surface that is one of the plurality of inner surfaces and faces the first inner surface, and the first A connecting portion that connects the plate-like portion and the second plate-like portion, and a first expansion suppression member that is provided in the first plate-like portion and suppresses the expansion of the first plate-like portion. A second expansion suppression member provided on the second plate-like portion for suppressing the expansion of the second plate-like portion, wherein the first plate-like portion absorbs moisture and expands. The difference between the change in the size of the inner surface of the first inner surface and the change in the size of the second inner surface when the second plate-like portion absorbs moisture and expands is reduced. Providing a hollow structure, characterized in that it comprises a tension suppressing member.
Further, the present invention provides a hollow structure having a hollow space surrounded by a plurality of inner surfaces and an opening connecting the hollow space and the outer space, the first inner surface being one of the plurality of inner surfaces, and A first plate-like portion having the opening; a first expansion suppressing member provided on the first plate-like portion to suppress expansion of the first plate-like portion; and one of the plurality of inner surfaces. A second plate-like portion having a second inner surface facing the first inner surface, the thickness or material being different from the first plate-like portion, and the first plate The second plate-like shape in which the difference between the change in the size of the first inner surface when the shape portion absorbs moisture and expands and the change in the size of the second inner surface when the shape portion absorbs moisture and expands becomes small. A hollow structure comprising: a connecting portion connecting the first plate-like portion and the second plate-like portion; Subjected to.

  According to the present invention, it is possible to suppress deformation caused by the influence of moisture entering the inside of the hollow structure from the opening as compared with the case where the expansion suppressing member is provided regardless of the change in the size of the inner surface during expansion. it can.

It is an external view of the acoustic structure in an embodiment. It is the figure which looked at the acoustic structure 1 in the Z-axis negative direction. It is a figure which shows the cross section of the acoustic structure in arrow III-III. It is a figure which shows an example of the acoustic structure which absorbed moisture and expanded. It is a figure which shows an example of another acoustic structure. It is a figure which shows an example of the acoustic structure of a modification. It is a figure which shows the example of the acoustic structure in a modification. It is a figure which shows an example of the acoustic structure of a modification. It is a figure which shows an example of the acoustic structure of a modification. It is a figure which shows the example of the acoustic structure of a modification. It is a figure which shows an example of the acoustic structure of a modification.

[Embodiment]
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an external view of an acoustic structure 1 in the embodiment. In FIG. 1, the X axis, the Y axis, and the Z axis, which are coordinate axes of a three-axis orthogonal coordinate system, are indicated by arrows. In each coordinate axis, the direction indicated by the arrow indicates the positive direction, and the opposite direction indicates the negative direction. The acoustic structure 1 includes a first plate member 10, a second plate member 20, and a connecting member 30. The acoustic structure 1 is a hollow structure having a rectangular parallelepiped shape. In FIG. 1, the acoustic structure 1 is shown so that each side of the rectangular parallelepiped is along the X, Y, and Z axis directions. In the acoustic structure 1, a hollow space (hollow space) and an external space (external space) are connected via openings 101 and 102 provided in the first plate member 10.

  The openings 101 and 102 are holes provided in the center of the first plate member 10 in the Y-axis direction, and in this embodiment, the boundary surface with the external space is a rectangle. Note that the shape of the boundary surface is not limited to a rectangle, but may be another shape. The second plate member 20, the connecting member 30, and the first plate member 10 are arranged in this order in the positive Z-axis direction, and adjacent members are connected to each other. The first plate member 10 and the second plate member 20 are both plate-like members having a rectangular outer periphery. The first plate member 10 has a reflecting surface 111 on the Z axis positive direction side. The reflection surface 111 is a surface adjacent to the openings 101 and 102 and reflects sound waves incident from the external space in a normal phase.

  FIG. 2 is a view of the acoustic structure 1 as viewed in the negative Z-axis direction. In FIG. 2, a part of the first plate member 10 is shown by being cut along a broken line. All of the first plate member 10, the second plate member 20, and the connecting member 30 have the same outer shape and size when viewed in the Z-axis direction. Specifically, the outer peripheries of these members are all in the shape of a rectangle having a length in the Y-axis direction L1 and a length in the X-axis direction L2. In FIG. 2, these outer peripheries appear to overlap. Unlike the first plate member 10, the second plate member 20 does not have an opening. The connecting member 30 includes a frame portion that forms a rectangular frame along the outer periphery of the member, and a partition portion that partitions the openings 101 and 102. By this partitioning part, the hollow space of the acoustic structure 1 is partitioned into a hollow space A1 connected to the opening 101 and a hollow space A2 connected to the opening 102. The partition portion is provided such that A1 is larger than hollow space A2. These frame portions and partition portions form a rectangular first frame portion 31 surrounding the hollow space A1 and a rectangular second frame portion 32 surrounding the hollow space A2. That is, the first plate member 10, the second plate member 20, and the first frame portion 31 form the hollow space A1, and the first plate member 10, the second plate member 20, and the second frame portion 32. Forms the hollow space A2. These hollow spaces are surrounded by the inner surface (surface facing the hollow side) of each member.

  FIG. 3 is a view showing a cross section of the acoustic structure 1 in the direction of arrows III-III in FIG. The first plate member 10 includes a first wooden board 11 and a first moisture-proof member 12. The first wooden board 11 is a plate-like part (first plate-like part) surrounding the hollow space of the acoustic structure 1. The first wood board 11 has the same shape as the first board member 10 when viewed in the Z-axis direction. That is, the length of the first wood board 11 in the Y-axis direction is L1, and the length in the X-axis direction is L2. The first wood board 11 has a thickness L3 in the Z-axis direction. In the following, when simply referring to “thickness”, the thickness in the Z-axis direction is indicated. The first wood board 11 has a hole that penetrates in the Z-axis direction to form the opening 101 and a hole that forms the opening 102 although not shown in FIG. The first wooden board 11 is a wooden board formed in such a shape and size, and is provided so as to face the external space. That is, the reflecting surface 111 shown in FIG. 1 is one of the surfaces of the first wooden board 11 and is the surface of the first wooden board 11 facing the external space in the positive direction of the Z axis. is there. The first wood board 11 has a first inner surface 112 in the negative Z-axis direction. The first inner surface 112 is a surface facing the hollow side (hollow space A1 side), and is one of a plurality of inner surfaces surrounding the hollow space of the acoustic structure 1. A first moisture-proof member 12 is provided on the first inner surface 112 side of the first wooden board 11.

  The first moisture-proof member 12 is a sheet having a synthetic resin, and is formed so that the shape when viewed in the Z-axis direction is the same as that of the first wooden board 11. The first moisture-proof member 12 is affixed to the first inner surface 112 using an adhesive or the like so as to match the outer periphery of the first wooden board 11. The first moisture-proof member 12 has a thickness L4. That is, the thickness of the first plate member 10 is L3 + L4.

  The second plate member 20 includes a second wooden board 21 and a second moisture-proof member 22. Similar to the first wooden board 11, the second wooden board 21 is a plate-like portion (second plate-like part) surrounding the hollow space of the acoustic structure 1. The second wood board 21 has the same shape as the second board member 20 when viewed in the Z-axis direction. That is, the second wooden board 21 is a wooden board having a rectangular shape whose length in the Y-axis direction is L1 and whose length in the Z-axis direction is L2. Unlike the first wood board 11, the second wood board 21 is not perforated. The second wooden board 21 has the same thickness L3 as the first wooden board 11. The second wood board 21 is provided so as to face the external space. The second wood board 21 has an outer surface 211 on the Z-axis negative direction side and a second inner surface 212 on the Z-axis positive direction side. The second inner surface 212 is a surface facing the hollow side (hollow space A2 side), and is one of a plurality of inner surfaces surrounding the hollow space of the acoustic structure 1. The second inner surface 212 faces the first inner surface 112. A second moisture-proof member 22 is provided on the second inner surface 212 side of the second wooden board 21.

The second moisture-proof member 22 is a sheet having the same synthetic resin as the first moisture-proof member 12, and is formed so that the shape when viewed in the Z-axis direction is the same as that of the second wooden board 21. The second moisture-proof member 22 is affixed to the second inner surface 212 using an adhesive or the like so as to match the outer periphery of the second wooden board 21. The second moisture-proof member 22 has a thickness L5. That is, the thickness of the second plate member 20 is L3 + L5. The thickness L5 is different from the thickness of the first moisture-proof member 12. For example, in the present embodiment, the thickness L5 is half (1/2) of L4.
The connecting member 30 (an example of a “connecting portion”) is bonded to the surface of the first moisture-proof member 12 and the second moisture-proof member 22 on the hollow space A1 side with an adhesive or the like. In this way, the connecting member 30 connects the first plate member 10 and the second plate member 20.

  In the acoustic structure 1, the opening 101 and the hollow space A1, and the opening 102 and the hollow space A2 function as Helmholtz resonators H1 and H2, respectively. In the Helmholtz resonators H1 and H2, spring mass systems are formed in which the gas present in the openings 101 and 102 is a mass component and the gas layers of the hollow spaces A1 and A2 are spring components. Hereinafter, the volumes of the hollow spaces A1 and A2 are set to Vi (i = 1, 2). As described above, since the hollow space A1 is larger than A2, V1> V2. The cross-sectional areas of the openings 101 and 102 in the XY plane are S1 and S2. In the acoustic structure 1, S1 and S2 have the same value, and this is S. The effective lengths of the openings 101 and 102 are W1 and W2. The effective length W1 is a value obtained by correcting the opening end of L3 + L4 that is the distance from the boundary surface between the opening 101 and the hollow space A1 to the boundary surface between the opening 101 and the external space. The effective length W2 is a similar value in the opening 102. In the acoustic structure 1, the effective lengths W1 and W2 have the same value, which is W. Assuming that the resonance frequencies in the Helmholtz resonators H1 and H2 are f (1) and f (2) and the sound velocity is c, these frequencies f (i) (i = 1, 2) are expressed by the following equation (1). expressed.

  Since V1 ≠ V2 as described above, f (1) ≠ f (2). That is, the acoustic structure 1 has two different resonance frequencies. In the acoustic structure 1, when sound waves (incident waves) in a frequency band including the resonance frequencies f (1) and f (2) are incident on the openings 101 and 102, the Helmholtz resonators H1 and H2 resonate to generate reflected waves. Radiated from the openings 101 and 102 to the external space. At this time, the specific acoustic impedance ratio ζ≈0 at the openings 101 and 102, and a reflected wave having a phase opposite to that of the incident wave is emitted from the openings 101 and 102. Assuming that the first plate member 11 is a rigid body, the reflection surface 111 can be regarded as a complete reflection surface having a specific acoustic impedance ratio ζ = ∞, and a reflection wave having the same phase as the incident wave is emitted from the reflection surface 111. In the acoustic structure 1, the reflected wave and the reflecting surface from the openings 101 and 102 are reflected in a certain frequency band including the resonance frequencies f (1) and f (2) where the specific acoustic impedance ratio 0 ≦ ζ <1. Due to the discontinuity of the phase with the reflected wave from 111, a sound absorption effect and a scattering effect are exhibited. As described above, the acoustic structure 1 is an acoustic structure that absorbs and scatters sound waves in a frequency band corresponding to the shape of the own panel and affects the sound in the surrounding space.

  Next, the size change that occurs when the acoustic structure 1 absorbs (absorbs) moisture in the air will be described. The size here is basically a length, and hereinafter, the size is represented by the length in the X-axis direction, the Y-axis direction, and the Z-axis direction shown in FIG. Further, when the substance absorbs moisture and expands, the lengths of the substance in each direction extend at substantially the same rate. In the acoustic structure 1, since the length in the X-axis direction and the Y-axis direction is sufficiently longer than the length in the Z-axis direction, the change in the length in the Z-axis direction can be ignored.

  FIG. 4 is a diagram illustrating an example of the acoustic structure 1 that has absorbed and expanded. FIG. 4 shows a state in which the acoustic structure 1 shown in FIG. 3 has expanded, and the outer periphery of the acoustic structure 1 before expansion is indicated by a two-dot chain line. The length of the first plate member 10 in the Y-axis direction is L1 before expansion, that is, in the state shown in FIG. 3, but after expansion, it extends by L6 at both ends in the Y-axis direction (that is, becomes longer). Overall, it is L7. On the other hand, the length of the second plate member 20 in the Y-axis direction is also L1 before expansion, that is, in the state shown in FIG. ing.

  The first wooden board 11 and the second wooden board 21 which are wooden boards are greatly expanded by moisture absorption compared to the first moisture-proof member 12 and the second moisture-proof member 22 which are synthetic resins. In this example, the expansion due to moisture absorption of the first moisture-proof member 12 and the second moisture-proof member 22 is extremely small and can be ignored. In FIG. 4, these moisture-proof members also extend in the Y-axis direction because the wooden boards to which they are bonded are expanded and are pulled in the Y-axis direction by the wooden boards. is there. On the other hand, the first wooden board 11 and the second wooden board 21 receive a force in the direction opposite to the direction extending in the Y-axis direction due to the expansion by these moisture-proof members. That is, expansion of the first wooden board 11 and the second wooden board 21 is suppressed by the first moisture-proof member 12 and the second moisture-proof member 22.

  As described above, the first moisture-proof member 12 has a thickness larger than that of the second moisture-proof member 22, specifically, twice. Since these moisture-proof members have the same length in the X-axis direction, the first moisture-proof member 12 is larger than the second moisture-proof member 22 even when the cross-sectional areas in the XZ plane are compared. Specifically, it is doubled. Accordingly, the first moisture-proof member 12 is larger than the second moisture-proof member 22 in terms of elongation rigidity in the Y-axis direction. That is, the first moisture-proof member 12 has a greater force than the second moisture-proof member 22 to suppress expansion of the wooden board in the Y-axis direction.

  The first moisture-proof member 12 and the second moisture-proof member 22 have a moisture permeability resistance larger than that of the first wooden board 11 and the second wooden board 21. For this reason, compared with the case where these moisture-proof members are not provided, for example, the amount of moisture absorbed by these wooden boards is reduced. That is, the first moisture-proof member 12 and the second moisture-proof member 22 suppress the expansion of these wood boards by reducing the amount of moisture absorbed by the first wood board 11 and the second wood board 21, respectively. ing. Further, the first moisture-proof member 12 has a larger moisture resistance in the Z-axis direction than the second moisture-proof member 22 because the thickness is larger. For this reason, the first moisture-proof member 12 suppresses the expansion of the wooden board more than the second moisture-proof member 22.

  Moisture enters the hollow space A1 from the external space through the opening 101. On the other hand, in the hollow space A1, there is no outlet through which moisture that has entered from the opening 101 passes. For this reason, the invading moisture tends to stay in a space near the opening 101. As a result, the first wooden board 11 provided with the opening 101 may absorb more moisture than the second wooden board 21 provided with no opening. In this embodiment, such a case will be described as an example. In this case, the first wooden board 11 has a larger expansion force than the second wooden board 21. On the other hand, in the acoustic structure 1, as described above, the first moisture-proof member 12 greatly suppresses the expansion of the wooden board on which the member is provided in the Y-axis direction as compared with the second moisture-proof member 22. doing. As a result, in the example shown in FIG. 4, in the first plate member 10 and the second plate member 20, the sum of the force that expands in the Y-axis direction and the force that suppresses the force becomes equal. The amount of change in the size (ie, length) of these members in the Y-axis direction is also equal.

Here, it is assumed that the degree of suppressing the expansion of the first wooden board 11 in the Y-axis direction is lower than that in the example of FIG. In this case, if each wooden board expands similarly to the example of FIG. 4, the amount of change in size in the Y-axis direction of the first board member 10 and the second board member 20 will be different, and the acoustic structure will be It will be deformed. An example in which such deformation occurs will be described with reference to FIG.
FIG. 5 is a diagram illustrating an example of another acoustic structure in which the thickness of the first moisture-proof member is changed from that of the acoustic structure 1. In FIG. 5A, an acoustic structure 1x including a first plate member 10x, a second plate member 20, and a connecting member 30 is shown. The first plate member 10x includes a first moisture-proof member 12x having a thickness L5 and a first wooden board 11. That is, the acoustic structure 1x has the same configuration as the acoustic structure 1 except for the thickness of the first moisture-proof member, and the thickness of the first moisture-proof member is reduced from L4 to L5 (see FIG. 4). As shown, L5 is half the thickness of L4.

  FIG. 5B shows a case where the first wooden board 11 and the second wooden board 21 are hygroscopically expanded with the same degree as the example shown in FIG. Since the second plate member 20 has the same configuration as that shown in FIG. 4, it extends in the Y-axis direction to the same extent as in the case shown in FIG. On the other hand, in the first plate member 10x, as described above, the first moisture-proof member 12x having a thickness smaller than that of the first moisture-proof member 12 shown in FIG. For this reason, the degree to which the expansion of the first wooden board 11 in the Y-axis direction is small, and as a result, the size of the first board member 10x in the Y-axis direction is smaller than that of the first board member 10 shown in FIG. Is getting bigger. At this time, in the acoustic structure 1x, the first plate member 10x and the second plate member 20 are bonded to each other without peeling off the portion where the end in the Y-axis direction and the connecting member 30 are bonded. To maintain. Therefore, the first plate member 10x and the second plate member 20 are deformed so that the center in the Y-axis direction is warped in the positive direction of the Z-axis as shown in FIG. It has a trapezoidal shape. In addition, in the state shown in FIG.4 and FIG.5 (b), although the connection member 30 also expand | swells by moisture absorption, since the change of a size is small compared with expansion | swelling of each plate member, it shall be disregardable.

  Since the first plate member 10x and the second plate member 20 are deformed as described above, the size in the Y-axis direction differs between the inner surface side and the outer surface side. In the following, the sizes in the Y-axis direction on the respective inner surfaces will be compared. In other words, the sizes of the first inner surface 112 and the second inner surface 212 in the Y-axis direction are compared. In FIG. 5B, the size of the first inner surface 112 in the Y-axis direction is L8, and the size of the second inner surface 212 in the Y-axis direction is L9, which is smaller than L8. In addition, the first inner surface 112 is longer at both ends in the Y-axis direction by a length L10 than the second inner surface 212. That is, the difference between the size (L8) in the Y-axis direction after the deformation of the first inner surface 112 and the size (L9) in the Y-axis direction after the deformation of the second inner surface 212 is 2 × L10.

  Since the first inner surface 112 and the second inner surface 212 are deformed to warp, they are curved surfaces. The size in the Y-axis direction along the surface of the first inner surface 112 is L11 and is longer than L8. The size in the Y-axis direction along the second inner surface 212 is L12, which is longer than L9. In the acoustic structure 1x, the surface of the connecting member 30 on the hollow space A1 side and the surfaces of the first moisture-proof member 12x and the second moisture-proof member 22 on the hollow space A1 side all maintain 90 degrees. As a result, the inclinations of the first inner surface 112 and the second inner surface 212 with respect to the Y-axis direction on the end side in the Y-axis direction are substantially the same, and the warpage of both inner surfaces is substantially the same. For this reason, the sizes L11 and L12 do not change in size from the sizes L8 and L9. That is, the size L12 along the surface of the second inner surface 212 is smaller than the size L11 along the surface of the first inner surface 112. As described above, the first inner surface 112 and the second inner surface 212 do not change in size even when the sizes in the Y-axis direction are compared or the sizes in the Y-axis direction along the inner surfaces are compared. . Although the size in the Y-axis direction has been described with reference to FIG. 5, the second inner surface 212 is smaller than the first inner surface 112 because the deformation method of each plate member does not change with respect to the size in the X-axis direction. Become.

  In the acoustic structure 1 according to the present embodiment, as described above, the first moisture absorbing member 12 and the second moisture absorbing member 22 cause the first wooden board 11 or the second wooden board 21 provided with the own member to expand. It functions as an expansion suppression member that suppresses each. The first hygroscopic member 12 and the second hygroscopic member 22 differ between the change in the size of the first inner surface 112 and the change in the size of the second inner surface 212 in this case (hereinafter referred to as “inner surface size difference”). It is provided to make it smaller. In this case, the first inner surface 112 is an inner surface closer to the opening 101 out of the first inner surface 112 and the second inner surface 212. Specifically, in the acoustic structure 1, the first moisture absorbing member 12 having a thickness larger than that of the second moisture absorbing member 22 provided on the second wooden board 21, that is, having a large moisture permeability resistance in the Z-axis direction, is provided. It is provided on the first wooden board 11. In other words, in the acoustic structure 1, the expansion suppressing member is provided in consideration of the influence of moisture entering from the opening.

  On the other hand, in the acoustic structure 1x, the first wooden board 11 having the first inner surface 112 closer to the opening 101 also has the second wooden board 21 having the second inner surface 212 far from the opening 101. Also, a moisture absorbing member having the same thickness, that is, moisture permeability resistance in the Z-axis direction, is provided. That is, in the acoustic structure 1x, the influence of moisture entering from the opening 101 is not considered, and the expansion suppressing member is provided regardless of the distance from the opening 101. And in the acoustic structure 1, as shown in FIG. 4, the deformation | transformation is suppressed compared with the acoustic structure 1x shown in FIG. As described above, according to the present embodiment, when the expansion suppressing member is provided without considering the influence of moisture entering from the opening as in the acoustic structure 1x, specifically, it is related to the distance from the opening. As compared with the case where the expansion suppressing member is provided, deformation caused by the influence of moisture entering the hollow structure, that is, the acoustic structure from the opening can be suppressed.

[Modification]
The above-described embodiment is merely an example of implementation of the present invention, and may be modified as follows. Moreover, you may implement combining embodiment mentioned above and each modification shown below as needed.

(Modification 1)
In the embodiment described above, the acoustic structure includes the first moisture absorbing member having the thickness L4 and the second moisture absorbing member having the thickness L5 that is half of the thickness L4. A hygroscopic member may be provided. In the acoustic structure, for example, the thickness of the first moisture absorbing member may be 1.5 times that of the second moisture absorbing member, or may be greater than twice. In short, in the acoustic structure, it is only necessary that the thickness of the first hygroscopic member is larger than that of the second hygroscopic member. Thereby, compared with the case where an expansion | extension suppression member is provided irrespective of the distance with an opening part like the acoustic structure 1x shown in FIG. 5, the inner surface size difference mentioned above becomes small. Therefore, also in this modification, the deformation | transformation which arises by the influence of the moisture which penetrates into the inside of an acoustic structure can be suppressed like embodiment. Moreover, when deformation | transformation can be suppressed by sufficient moisture-permeable resistance, both thickness may be equivalent, or the thickness of a 1st moisture absorption member may be less than the thickness of a 2nd moisture absorption member. Moreover, although the 1st moisture absorption member and the 2nd moisture absorption member were made the same, the member from which moisture permeability resistance differs may be sufficient.

(Modification 2)
In the embodiment described above, the first and second hygroscopic members are provided on the entire first inner surface 112 and the second inner surface 212, respectively, but may be provided on a part of these inner surfaces. .
FIG. 6 is a diagram illustrating an example of an acoustic structure in the present modification. The acoustic structure 1a shown in FIG. 6A includes a first moisture absorbing member 12a and a second moisture absorbing member 22a. The first hygroscopic member 12 a has a thickness L <b> 5 and is provided on the entire first inner surface 112. That is, the first hygroscopic member 12a has a size L1 in the Y-axis direction. The second moisture absorbing member 22a has the same thickness L5 as the first moisture absorbing member 12a, and the size in the Y-axis direction is L13, which is half of L1. Therefore, a part of the second inner surface 112 is exposed in the hollow space A1. That is, the acoustic structure 1a has the same configuration as the acoustic structure 1x shown in FIG. 5 except for the second moisture absorbing member 22a.

  In the acoustic structure 1a, since the second wooden board 21 absorbs moisture from the exposed portion without passing through the second moisture absorbing member 22a, it is larger in the Y-axis direction than the second wooden board 21 shown in FIG. Inflate. FIG. 6B shows an example of the acoustic structure 1a that has expanded due to moisture absorption. In this example, the first wood board 11 expands as in the example shown in FIG. 5, and the size along the surface of the first inner surface 112 is L11. Further, the second wooden board 21 expands more than the example shown in FIG. 5, and the size along the surface of the second inner surface 212 is L11 larger than L12 shown in FIG. Thus, for example, in the case where the first and second moisture absorbing members having the same thickness are provided, one of the moisture absorbing members provided on the inner surface closer to the opening 101 (that is, the first inner surface) (the first inner surface). Compared to the first inner surface, the area of the far inner surface (that is, the second inner surface) is smaller than the first inner surface, and the second inner surface is compared to the first inner surface. It is preferable to increase the area of the portion exposed to the hollow space A1. Thereby, compared with the case where an expansion | extension suppression member is provided irrespective of the distance with an opening part like the acoustic structure 1x shown in FIG. 5, said inner surface size difference becomes small. Therefore, also in this modification, the deformation | transformation which arises by the influence of the moisture which penetrate | invades into the inside of an acoustic structure can be suppressed like embodiment.

(Modification 3)
In the first and second modifications, the acoustic structure includes the first and second hygroscopic members having either the same thickness or the same area and the other being different from each other, but both the thickness and the area are different. Each hygroscopic member may be provided. For example, the thickness of the first hygroscopic member 12 included in the acoustic structure 1 of the embodiment is smaller than L4 and larger than L5, and the size of the second hygroscopic member 22 in the Y-axis direction is smaller than L1 and smaller than L13. Also make it bigger. In this case, the degree of expansion of both the first wooden board 11 and the second wooden board 21 increases. By providing the first and second hygroscopic members with the same thickness and area on each wooden board so that the degree of expansion is the same, the distance from the opening as in the acoustic structure 1x shown in FIG. Regardless of the case where the expansion suppressing member is provided, the inner surface size difference can be reduced. Further, the inner surface size difference may be reduced by merely providing the first hygroscopic member without providing the second hygroscopic member. In short, the above-described expansion suppressing member (the hygroscopic member such as the first and second hygroscopic members) is the first wooden plate closer to the opening of the first and second wooden plates (both the first example in the above example). It is sufficient that the difference in the inner surface size is made smaller than in the case where the expansion suppressing member is provided at least on the wood board regardless of the distance from the opening.

(Modification 4)
In the embodiment described above, the first and second wood boards are both formed to have the same thickness (L3), but this is not a limitation. For example, the thickness of the first wooden board 11 included in the acoustic structure 1 of the embodiment may be smaller than or larger than L3. Different wood may be used for the first and second wooden boards.
FIG. 7 is a diagram illustrating an example of an acoustic structure in the present modification. FIG. 7A shows an acoustic structure 1b including a first wood board 11b having a thickness greater than L3. The acoustic structure 1b includes a first moisture absorbing member 12b having a thickness smaller than that of the first moisture absorbing member 12 shown in FIG. In this case, since the expansion coefficients of the first and second wood boards are different from each other, the above-described inner surface size difference may be reduced by adopting a structure in which either the first or second moisture absorbing member is omitted.

(Modification 5)
The acoustic structure may be provided with a plate-like portion in which a material other than wood is formed in a plate shape instead of the wood plates such as the first and second wood boards. For example, the acoustic structure has a plate shape made of a synthetic resin such as polyvinyl chloride, plastic, metal, etc. (both examples of “material” of “second plate-like portion” of claim 3 of the present invention). A part. FIG. 7B shows an acoustic structure 1c including a second plate-like portion 21c formed of a metal as a material. The second plate-like portion 21c absorbs moisture and expands less than the second wood plate 21, and hardly expands. The acoustic structure 1 c includes a first moisture absorbing member 12 c that is not provided with a moisture absorbing member on the second plate-like portion 21 c and is thicker than the first moisture absorbing member 12. Thereby, in the acoustic structure 1c, the degree to which the expansion of the first wooden board 11b in the Y-axis direction is made larger than the degree to which the expansion of the first wooden board 11 of the acoustic structure 1 is suppressed. . That is, the acoustic structure 1c includes the first moisture absorbing member 12c, so that the inner surface size difference is smaller than when the first moisture absorbing member 12 is provided.

(Modification 6)
In the above-described embodiment, the first and second wood boards have a larger surface than the other surfaces among the six surfaces of the rectangular parallelepiped represented by the acoustic structure (the reflective surface 111 and the outer surface 211 in the embodiment). Although it had, the other surface may be larger. For example, in the acoustic structure 1 shown in FIG. 2, the length of the connecting member in the Z-axis direction is longer than L1 or L2. In this case, when the inner surface size difference becomes large, the connecting member may be deformed, or the portion where the first and second inner surfaces are bonded to the connecting member may be peeled away. Such deformation is also suppressed as compared with the case where the hygroscopic member reduces the inner surface size difference as described above, and the expansion suppressing member is provided regardless of the distance from the opening. In this case, deformation may occur due to expansion of the connecting member. In that case, an expansion suppressing member may be provided on the connecting member to suppress deformation.

(Modification 7)
In the above-described embodiment, nothing is provided on the external space side of the first wooden board 11 and the second wooden board 21, and the reflection surface 111 and the outer surface 211 of these wooden boards are exposed to the external space. Some members may be provided on these surfaces. For example, a decorative member may be provided on the reflective surface 111. A decorative member is a member provided in order to improve the appearance of an acoustic structure. For example, the decorative member is formed of cloth, synthetic fiber, or the like. This decorative member may be made of a material having a moisture permeability resistance larger than that of wood and function as a moisture-proof member, or may be bonded to the reflecting surface 111 to suppress the expansion of the first wood board. Further, the outer surface 211 may be provided with a moisture-proof member such as the first and second moisture-proof members.

  Even when the degree of moisture absorption and expansion of the first wooden board 11 and the second wooden board 21 is suppressed by providing these decorative members and moisture-proof members, the first wooden board 11 and the second wooden board 21 are controlled according to the degree of suppression. And the 2nd moisture absorption member or the 1st moisture absorption member should just be provided. For example, as a result of providing a decorative member on the reflective surface 111 of the acoustic structure 1 of the embodiment, in addition to the first moisture-proof member 12, the decorative member suppresses the expansion of the first wooden board 11 in the Y-axis direction. Suppose. Then, when the second plate member 20 expands as shown in FIG. 4, the size of the first wooden board 11 in the Y-axis direction is smaller than L7 shown in FIG. It will be deformed to warp in the opposite direction to the example shown in (b). In this case, for example, by providing a moisture-proof member having a thickness smaller than that of the first moisture-proof member 12 on the first inner surface 112, the degree of suppressing the expansion of the first wooden board 11 in the Y-axis direction is reduced. The inner surface size difference may be reduced.

(Modification 8)
In the embodiment described above, the acoustic structure includes the first moisture-proof member 12 and the second moisture-proof member 22 as the expansion suppression member that suppresses the expansion of the first and second wooden boards. A member may be provided.
FIG. 8 is a diagram illustrating an acoustic structure 1d that is an example of the acoustic structure according to the present modification. FIG. 8A shows the acoustic structure 1d viewed in the negative Z-axis direction, and FIG. 8B shows a cross section of the acoustic structure 1d in the direction of arrows VIII-VIII in FIG. 8A. It is shown. The acoustic structure 1 d includes a first plate member 10 d, and the first plate member 10 d includes a first wooden board 11 and a plurality of ribs 13. The rib 13 is a metal (an example of a “material” of the “expansion suppressing member” of the present invention ) formed in a rod shape (an example of a “shape” of the “expansion suppressing member” of the present invention) , and the first inner surface 112. Is provided. Specifically, the first inner surface 112 is provided with a total of eight ribs 13 in which four sets of two ribs 13 intersecting each other are arranged in the X-axis direction. Since the rib 13 is made of metal, the degree of expansion due to moisture absorption is smaller than that of the first wooden board 11, that is, the tree. Therefore, the rib 13 suppresses expansion of the first wooden board 11 in the X-axis direction and the Y-axis direction. In this way, the rib 13 functions as an expansion suppressing member that suppresses an increase in the size of the first inner surface 112 of the first wooden board 11.

  The plurality of ribs 13 are all provided so as not to contact the boundary surface between the opening 101 and the hollow space A1 and the boundary surface between the opening 102 and the hollow space A2. These ribs 13 have a predetermined ratio with respect to the distance L15 between the first inner surface 112 and the second inner surface 212, in the size in the Z-axis direction, that is, the height L14 from the first inner surface 112. (For example, 20%) or less. In the acoustic structure 1d, the rib 13 is provided, so that the acoustic structure 1d functions as the above-described Helmholtz resonator when compared with a structure without the rib 13 (for example, the acoustic structure 1 of the embodiment). The resonance frequency is less likely to fluctuate.

FIG. 9 is a diagram illustrating an acoustic structure 1e that is an example of the acoustic structure according to the present modification. FIG. 9A shows the acoustic structure 1e viewed in the negative Z-axis direction, and FIG. 9B shows the acoustic structure 1e in section IX-IX in FIG. 9A. It is shown. The acoustic structure 1e includes a first plate member 10e. The first plate member 10 e includes a first wooden board 11 and a frame 14. The frame 14 is made of a metal (an example of a “material” of the “expansion suppressing member” of the present invention ) provided along the outer periphery of the first wood board 11 (the “shape” of the “expansion suppressing member” of the present invention ) . An example) . Since the frame 14 is made of metal, the degree of expansion due to moisture absorption is smaller than that of the first wooden board 11, that is, the tree. Therefore, the frame 14 suppresses expansion of the first wooden board 11 in the X-axis direction and the Y-axis direction. Thereby, the frame 14 functions as an expansion suppressing member that suppresses an increase in the size of the first inner surface 112 of the first wooden board 11.

  In addition, the rib 13 and the frame 14 may be formed of a material other than a metal, and in short, both of them are only required to have a smaller degree of expansion due to moisture absorption than the first wooden board 11. Ribs and frames such as the rib 13 and the frame 14 may also be provided in the second plate member. Here, when the first and second plate members are provided with the same rib and frame, if the degree of suppressing the expansion is not sufficient, that is, if the strength of the rib and the frame is not sufficient, the openings 101 and 102 are used. The acoustic structure may be deformed as in the example shown in FIG. 5 due to the influence of entering moisture. The rib and the frame in this modification may be provided so that the above-mentioned inner surface size difference is smaller than in such a case. Further, the rib and the frame may be provided at positions other than the positions shown in FIGS. For example, in the case of ribs, two sets of crossing two ribs 13 may be provided side by side in the X-axis direction and two sets in the Y-axis direction. Moreover, if it is a flame | frame, you may provide not along the outer periphery in the edge part of the outer peripheral side of the 1st inner surface 112 instead of the outer periphery of the 1st wooden board 11. In short, the ribs and the frame are rod-shaped members provided along the surfaces of the first and second wooden boards, and the ribs and the frames are intended to suppress expansion of these board members in the X-axis direction and the Y-axis direction. That's fine. In other words, the rib and the frame may be anything that suppresses an increase in the size of the inner surface (first or second inner surface) of the wooden board on which the member is provided. In addition, an acoustic structure is not restricted to what is provided with any one of a moisture-proof member, a rib, and a flame | frame, You may provide it in combination of these two or more.

(Modification 9)
In the above-described embodiment, the acoustic structure has two hollow spaces connected to the external space through the opening, but may have one, or may have three or more. . In the above-described embodiment, the acoustic structure functions as a Helmholtz resonator. However, the acoustic structure may function as a resonator that resonates on a principle different from that.
FIG. 10 is a diagram illustrating an acoustic structure 1f that is an example of the acoustic structure according to the present modification. FIG. 10A shows the acoustic structure 1f viewed in the negative Z-axis direction, and FIG. 10B shows a cross section of the acoustic structure 1f taken along the line XX in FIG. 10A. . The acoustic structure 1f includes a first plate member 10f, a second plate member 20, and a connecting member 30f. The first plate member 10f has four openings 103, 104, 105, and 106 arranged in the X-axis direction. These openings have different positions in the Y-axis direction. The connecting member 30f connects the first plate member 10f and the second plate member 20, and partitions the space between these plate members into hollow spaces A3, A4, A5, and A6. The hollow spaces A3, A4, A5, and A6 are connected to the external space through the openings 103, 104, 105, and 106, respectively.

  FIG. 10B shows a cross section of a portion where the hollow space A4 is connected to the external space through the opening 104. FIG. Of the portion forming the hollow space A4 in the acoustic structure 1f, the portion on the Y axis positive direction side from the opening 104 forms the first resonator 41. The length of the hollow space inside the first resonator 41 in the Y-axis direction is L16. Similarly, the portion on the Y-axis negative direction side of the opening 104 forms a second resonator 42. The length of the hollow space inside the second resonator 42 in the Y-axis direction is L17. The first resonator 41 and the second resonator 42 are so-called closed tubes having a hollow space with one end closed and the other end open. These resonance tubes resonate at a frequency (resonance frequency) corresponding to the length (L16 and L17) of each hollow space in the Y-axis direction. The acoustic structure 1f includes, in addition to the first resonance body 41 and the second resonance body 42, a resonance body corresponding to the position where the openings 103, 105, and 106 are provided. Resonance occurs at a resonance frequency corresponding to the length of the space in the Y-axis direction. The acoustic structure 1f exhibits a sound absorption effect of absorbing sound waves in a certain frequency band including these resonance frequencies, and also exhibits a scattering effect of scattering sound waves in the same frequency band.

  The first plate member 10f includes a first wooden board 11f and a first moisture absorbing member 12f. The first wood board 11f is the same size as the first wood board 11 except that it has four openings. The first hygroscopic member 12f has a thickness L18, which is larger than L4 shown in FIG. That is, the first hygroscopic member 12 f is formed to be thicker than the first hygroscopic member 12. Since the acoustic structure 1f has a larger number of openings than the acoustic structure 1, the moisture that enters the hollow spaces through the openings also increases. On the other hand, in the acoustic structure 1f, expansion of the first and second plate members in the Y-axis direction is suppressed by the portion of the connecting member 30f that partitions each hollow space, as compared with the acoustic structure 1. However, expansion in the X-axis direction is hardly suppressed. In the acoustic structure 1f, the first hygroscopic member 12f is provided to suppress the expansion of the first plate member 10f in the X-axis direction as compared with the acoustic structure 1. Thereby, in the acoustic structure 1f, it is suppressed that the edge part of a X-axis direction deform | transforms so that it may warp in a Z-axis negative direction. The acoustic structure may have an open tube resonator instead of the closed tube resonator as described above. In this case as well, each resonator resonates at a resonance frequency corresponding to the length of each hollow space in the Y-axis direction, and the acoustic structure responds to sound waves in a certain range of frequency bands including these resonance frequencies. Thus, the same sound absorbing effect and scattering effect are exhibited. In short, the acoustic structure may be an acoustic structure that absorbs and scatters sound waves in the frequency band corresponding to the shape of the panel itself and affects the sound in the surrounding space.

(Modification 10)
In the embodiment described above, the acoustic structure has a rectangular parallelepiped shape having only a flat surface, but may have a curved surface shape.
FIG. 11 is a diagram illustrating an acoustic structure 1g that is an example of the acoustic structure according to the present modification. FIG. 11A shows the appearance of the acoustic structure 1g, and FIG. 11B shows a cross section of the acoustic structure 1g. The acoustic structure 1g includes a first curved plate member 10g, a second curved plate member 20g, and a connecting member 30g. Each of the first curved plate member 10g and the second curved plate member 20g has a shape in which a cylinder is cut in half. The first curved plate member 10g and the second curved plate member 20g are connected to each other with an adhesive or the like to form a cylinder having both ends opened. That is, the first curved plate member 10g and the second curved plate member 20g are plate-like portions formed in the shape of a plate having a curved surface. The connecting member 30g has a disk shape and is provided so as to close the opening portions at both ends of the cylinder. The first curved plate member 10g, the second curved plate member 20g, and the connecting member 30g form a hollow space A7 having a cylindrical shape inside. The first curved plate member 10 g has an opening 107. The hollow space A7 is connected to the external space through the opening 107.

  The first curved plate member 10g includes a first wooden board 11g and a first moisture-proof member 12g. The first wood board 11g has a shape in which a cylinder is cut in half, and an opening 107 is provided. The first moisture-proof member 12g is provided on the first inner surface 112g on the hollow space A7 side of the first wood board 11g. The second curved plate member 20g includes a second wooden board 21g and a second moisture-proof member 22g. The second wood board 21g has a shape in which a cylinder is cut in half. The second moisture-proof member 22g is provided on the second inner surface 212g of the second wood board 21g on the hollow space A7 side. Even such an acoustic structure 1g is an acoustic structure that absorbs and scatters sound waves in a frequency band corresponding to the shape of the panel itself and affects the sound in the surrounding space.

  The first moisture-proof member 12g is formed to be thicker than the second moisture-proof member 22g. Thereby, also in the acoustic structure 1g, said inner surface size difference becomes small. In the acoustic structure 1g, since the first curved plate member 10g and the second curved plate member 20g are directly connected, these curved plate members are different due to the influence of moisture entering the hollow space A7 from the opening 107. When it expands to a certain degree, for example, the parts connected to each other may be displaced in the X-axis direction, and thus a deformation may occur such that a gap is formed between the connecting member 30g. However, since the acoustic structure 1g is provided with the first moisture-proof member 12g that is thicker than the second moisture-proof member 22g, the above-described inner surface size difference is reduced and such deformation is suppressed.

(Modification 11)
In the embodiment described above, the acoustic structure is formed by a plurality of members (first and second plate members and a connecting member), but may be formed by one member. In this case, the acoustic structure includes a plurality of plate-like portions each having a plurality of inner surfaces surrounding the hollow space. In this acoustic structure, for example, an expansion suppressing member such as a moisture-proof member is provided on the inner surface of the plate-like portion provided with the opening. Further, if it is difficult to provide the expansion suppressing member on the inner surface, a frame such as the frame 14 shown in FIG. 9 may be provided so as to surround the outer periphery of the plate-like portion provided with the opening.

(Modification 12)
In the acoustic structure, in the embodiment described above, the opening is provided in the first wooden board, but it may be provided in the second wooden board instead of the first wooden board. As described above, when an opening is provided in one of the first and second wooden boards, an expansion suppressing member such as a moisture-proof member is provided at least for the one provided with the opening. It only has to be. Moreover, the connection member may be provided with an opening. For example, it is assumed that an opening is provided in a position closer to the first wooden board than the second wooden board, and no opening is provided in the first and second wooden boards. In this case, an expansion suppression member should just be provided in the direction of the wooden board which has an inner surface near at least an opening part among the 1st and 2nd wooden boards. As a result, the wooden board that has a larger degree of expansion due to the influence of moisture entering from the opening, that is, the first wooden board having the first inner surface closer to the opening is more than the other (second wooden board). Also, the expansion is suppressed, the inner surface size difference is reduced, and the deformation is suppressed. In short, in the acoustic structure, an opening may be provided in at least one of the first wooden board, the second wooden board, and the connecting member.

(Modification 13)
In the acoustic structure, in the above-described embodiment, the opening is provided only in the first wooden board, but it may be provided in the second wooden board (that is, both wooden boards). In this case, for example, if the shape of the cross section in the XY plane (hereinafter referred to as “XY cross section”) of the opening provided in each wooden board is the same, the opening having the larger area of the XY cross section is provided. It is good to provide a moisture proof member only on the wooden board currently provided, or to provide the moisture proof member with a larger thickness on the wooden board. In addition, when the XY cross section has a different shape, for example, the wood board (the former) having an opening having a longer outer periphery of the XY cross section is closer to the opening than the other wood board (the latter). In some cases, the area of the inner surface is large, and the influence of moisture that penetrates is large. In this case, it is preferable to provide the moisture-proof member only on the former wooden board or to provide the moisture-proof member having a larger thickness on the former wooden board.

  In addition, the size difference may occur due to other factors such as the shape and material of the acoustic structure itself, regardless of the position of the opening and the shape of the opening. In such a case, in the acoustic structure, the size of each wooden board that actually absorbs moisture and expands is measured.For example, an expansion suppressing member is provided only on the wooden board that is greatly expanded as a result, or both wooden boards are provided with An expansion suppression member may be provided, and the expansion suppression member having a greater degree of suppression of expansion may be provided on the wooden plate that has expanded more. In short, in the acoustic structure, an expansion suppressing member such as a moisture proof member is provided at least on one of the first and second wooden boards, and thereby, due to the influence of moisture entering from the opening. It is only necessary that the wood plate having a larger degree of expansion (that is, the one having the larger cross-sectional area) is suppressed in expansion than the other wood plate and the inner surface size difference is reduced.

(Modification 14)
In addition to the acoustic structures described in the above embodiments and modifications, the present invention can also be applied to, for example, acoustic structures that constitute musical instruments, acoustic devices, and the like. Some of these acoustic structures have a hollow space connected to an external space through an opening, like the acoustic structure, in order to absorb and scatter sound. In these acoustic structures, the present invention is applied to the case where a material having a degree of moisture absorption and expansion that causes deformation as described in FIG. The inner surface size difference is reduced and deformation is suppressed. Thus, the present invention can be applied to various hollow acoustic structures having openings.

(Modification 15)
In addition to the above-described acoustic structure, the present invention can also be applied to a hollow structure constituting, for example, a soundproof room or a wall, door, or ceiling of an acoustic room. Some of these structures have a hollow space connected to an external space through an opening. In these hollow structures, the present invention is applied to the case where a material having a degree of moisture absorption and expansion that causes deformation as described in FIG. The inner surface size difference is reduced and deformation is suppressed. Thus, the present invention can be applied to various hollow structures having openings.

DESCRIPTION OF SYMBOLS 1 ... Acoustic structure, 10 ... 1st board member, 11 ... 1st wooden board, 12 ... 1st moisture-proof member, 13 ... Rib, 14 ... Frame, 20 ... 2nd board member, 21 ... 2nd Wood board, 22 ... second moisture-proof member, 30 ... connecting member, 31 ... first frame, 32 ... second frame, 101 ... first opening, 102 ... second opening, 111 ... reflection Surface 112 112 first inner surface 211 second outer surface 212 second inner surface

Claims (3)

In a hollow structure having a hollow space surrounded by a plurality of inner surfaces and an opening connecting the hollow space and the external space,
A first plate-like portion having a first inner surface that is one of the plurality of inner surfaces and the opening;
A second plate-like portion having a second inner surface which is one of the plurality of inner surfaces and faces the first inner surface;
A connecting portion connecting the first plate-like portion and the second plate-like portion;
An expansion suppression member having a moisture resistance greater than that of the first plate-like portion, provided on the first inner surface, and not provided on the second inner surface. Structure. In a hollow structure having a hollow space surrounded by a plurality of inner surfaces and an opening connecting the hollow space and the external space,
A first plate-like portion having a first inner surface that is one of the plurality of inner surfaces and the opening;
A second plate-like portion having a second inner surface which is one of the plurality of inner surfaces and faces the first inner surface;
A connecting portion connecting the first plate-like portion and the second plate-like portion;
A first expansion suppression member that is provided on the first plate-shaped portion and suppresses expansion of the first plate-shaped portion;
A second expansion suppression member that is provided on the second plate-shaped portion and suppresses expansion of the second plate-shaped portion, and is different in thickness, area, shape, or material from the first expansion suppression member. And the change in the size of the first inner surface when the first plate-like portion absorbs moisture and expands, and the second inner surface when the second plate-like portion absorbs moisture and expands. A hollow structure, comprising: a second expansion suppression member that reduces a difference from a change in size. In a hollow structure having a hollow space surrounded by a plurality of inner surfaces and an opening connecting the hollow space and the external space,
A first plate-like portion having a first inner surface that is one of the plurality of inner surfaces and the opening;
A first expansion suppression member that is provided on the first plate-shaped portion and suppresses expansion of the first plate-shaped portion;
One of the plurality of inner surfaces, a second plate-like portion having a second inner surface facing the first inner surface, wherein the thickness or material is different from the first plate-like portion, In addition, the difference between the change in the size of the first inner surface when the first plate-like portion absorbs moisture and expands and the change in the size of the second inner surface when the first plate-like portion expands by absorbing moisture is obtained. A second plate-like portion that becomes smaller;
A hollow structure comprising: the first plate-like portion and a connecting portion that connects the second plate-like portion.

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