JP7245500B2 - HOLLOW STRUCTURE AND METHOD FOR MANUFACTURING HOLLOW STRUCTURE - Google Patents

Description

The present invention relates to a hollow structure and a method for manufacturing the hollow structure .

Patent Literature 1 describes a hollow structure.
As shown in FIG. 4, the hollow structure 70 includes a core layer 72 in which a plurality of cells S are arranged side by side, and a pair of skin layers 73 and 74 bonded to both sides of the core layer 72. It has a plate member 71 made of It is described that a hole 76 is formed by piercing a needle member 75 so as to penetrate the skin layer 73 and the upper wall portion of the core layer 72 .

JP 2017-65026 A

In the hollow structure 70 disclosed in Patent Document 1 and the like, when the plate member 71 is pierced with the needle member 75 , the skin layer 73 and the core layer 72 are pushed apart by the needle member 75 . Therefore, the overall shape of the plate member 71 may warp such that the side where the hole 76 is formed (upper side in FIG. 4) is convex. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a hollow structure in which warping of a plate material is suppressed , and a method for manufacturing the hollow structure .

A hollow structure for solving the above-mentioned problems has a resin plate material having a core layer in which a plurality of cells are arranged side by side and a pair of skin layers bonded to both sides of the core layer. In the structure, at least one of the pair of skin layers and the core layer are provided with a plurality of holes that communicate between the inside and outside of the cells, and the inner surfaces of the holes allow the resin forming the plate material to evaporate. The gist is that it is an evaporation surface formed by

When a plate is irradiated with a laser beam to evaporate a resin forming the plate to form a hole, the inner surface of the hole becomes an evaporation surface where the resin forming the plate is evaporated. Since the holes are formed without expanding the skin layer and the core layer, warping of the hollow structure is suppressed.

In the hollow structure, it is preferable that the plate member has a curved portion, and the hole is provided in the curved portion. Since the bent portion is formed by bending a plate material, stress is likely to accumulate in the bent portion. If a needle member is used to form a hole in this curved portion, a further stress is applied to the curved portion, making the plate more likely to warp. According to the above configuration, in a configuration in which the plate member has the curved portion and the hole is provided in the curved portion, it is possible to suitably suppress warping of the plate member.

In the above-mentioned hollow structure, it is preferable that the open ends of the holes inside the cells have resin masses protruding inward of the cells. When the molten resin is solidified by the irradiation of the laser beam, a resin block is formed at the opening end inside the cell in the hole. Since the opening end portion can be reinforced by the resin mass, peeling of the skin layer from the core layer at the opening end portion can be suppressed.

In the above-described hollow structure, it is preferable that the core layer has side walls that partition the plurality of cells, and the holes penetrate the side walls in the thickness direction. According to this configuration, the cells on both sides of the side wall can be communicated between the inside and outside of the cell by the hole penetrating the side wall. As a result, it is possible to widen the range of frequencies that can be absorbed by the plate material.

According to the hollow structure and the method for manufacturing the hollow structure of the present invention, it is possible to suppress warping of the plate material.

(a) is a perspective view of a resin structure, (b) is a cross-sectional view along the α-α line of (a), and (c) is a cross-sectional view along the β-β line of (a). (a) is a perspective view of the sheet material forming the core layer of the hollow structure, (b) is a perspective view of the sheet material during folding, and (c) is a perspective view of the folded sheet material. . (a) to (c) are cross-sectional views of a hollow structure in a hole forming step. FIG. 4 shows a conventional hole formation process;

Embodiments of hollow structures are described.
As shown in FIGS. 1(a) to 1(c), the hollow structure 10 includes a core layer 20 in which a plurality of cells S are arranged side by side, and a pair of skin layers 30 bonded to both sides of the core layer 20. , 40 and made of resin. One of the pair of skin layers 30 and 40 and the core layer 20 are provided with a plurality of holes 15 communicating between the inside and outside of the cells S, and the inner surfaces of the holes 15 are formed by evaporating the resin forming the plate material 14 . It is the evaporation surface 15A.

As shown in FIGS. 1(b) and 1(c), the core layer 20 is formed by folding one thermoplastic resin sheet material molded into a predetermined shape. The core layer 20 is composed of an upper wall portion 21, a lower wall portion 22, and a side wall portion 23 erected between the upper wall portion 21 and the lower wall portion 22 to divide the cells S into a hexagonal prism shape. It is

As shown in FIGS. 1B and 1C, the cells S defined inside the core layer 20 include a first cell S1 and a second cell S2 having different configurations. As shown in FIG. 1B, in the first cell S1, the upper wall portion 21 having a two-layer structure is provided above the side wall portion 23. As shown in FIG. Each layer of the upper wall portion 21 having the two-layer structure is joined to each other. In addition, in the first cell S1, a lower wall portion 22 having a one-layer structure is provided below the side wall portion 23 . On the other hand, as shown in FIG. 1C, in the second cell S2, the upper wall portion 21 having a one-layer structure is provided above the side wall portion 23 . Further, in the second cell S2, a lower wall portion 22 having a two-layer structure is provided below the side wall portion 23 . Each layer of the lower wall portion 22 having the two-layer structure is joined to each other. The two-layer structure upper wall portion 21 provided on the upper portion of the side wall portion 23 and the two-layer structure lower wall portion 22 provided on the lower end portion of the side wall portion 23 may be joined over the entire surface of each layer. and may be partially joined.

As shown in FIGS. 1B and 1C, adjacent first cells S1 and adjacent second cells S2 are partitioned by side wall portions 23 having a two-layer structure. Each layer constituting the side wall portion 23 of the two-layer structure is joined at the upper wall portion 21 side and the lower wall portion 22 side, and is not joined at the center side.

As shown in FIG. 1A, the first cells S1 are arranged in rows along the X direction. share an edge. Similarly, the second cells S2 are arranged in rows along the X direction, and when viewed from above, two adjacent second cells S2 share one side of the hexagon. The columns of the first cells S1 and the columns of the second cells S2 are alternately arranged in the Y direction orthogonal to the X direction. The core layer 20 as a whole has a honeycomb structure with these first cells S1 and second cells S2.

As shown in FIGS. 1(a) to 1(c), a skin layer 30, which is a thermoplastic resin sheet material, is bonded to the upper surface of the core layer 20 configured as described above. A skin layer 40 that is a thermoplastic resin sheet material is joined to the lower surface of the core layer 20 . In this embodiment, the upper portion of the first cell S1 in the core layer 20 is closed by the upper wall portion 21 of the core layer 20 and the skin layer 30 . Therefore, the upper wall portion 21 of the core layer 20 and the skin layer 30 form a blocking wall that blocks the upper portion of the first cell S1. Similarly, the lower portion of the second cell S2 in the core layer 20 is closed by the lower wall portion 22 of the core layer 20 and the skin layer 40 . Therefore, the lower wall portion 22 of the core layer 20 and the skin layer 40 constitute a blocking wall that blocks the lower portion of the second cell S2. In FIGS. 1(b) and 1(c), of the three cells S shown, the cell S on the leftmost side is represented by a symbol, but the same applies to the other cells S. .

The skin layers 30, 40 and the core layer 20 are made of thermoplastic resin. The thermoplastic resins forming the skin layers 30 and 40 and the core layer 20 are conventionally known ones, and the materials thereof are not particularly limited. Examples thereof include polypropylene resin, polyamide resin, polyethylene resin, acrylonitrile-butadiene-styrene copolymer resin, acrylic resin, polybutylene terephthalate resin and the like. The thermoplastic resins forming the skin layers 30, 40 and the core layer 20 are preferably the same material. In this embodiment, both are made of polypropylene resin.

Although the thickness of the plate member 14 is not particularly limited, it is preferably 3 mm to 40 mm.
Each thickness of the upper wall portion 21, the lower wall portion 22, and the side wall portion 23 constituting the core layer 20 is preferably 0.1 mm to 0.5 mm.

The thickness of the skin layers 30, 40 is preferably 0.3 mm to 2.0 mm. The skin layers 30 and 40 are preferably thicker than the core layer 20 . For example, the skin layers 30 and 40 are preferably 1.5 to 2.5 times as thick as the core layer 20 . By making the thickness of the skin layers 30, 40 thicker than the thickness of the core layer 20, the weight of the plate material 14 can be relatively reduced compared to a mode in which the thicknesses of the skin layers 30, 40 and the core layer 20 are equal. and the bending strength of the plate material 14 can be increased.

As shown in FIGS. 1(b) and 1(c), one surface of the hollow structure 10 (upper surface side in FIG. 1) is provided with a hole 15 that communicates the inside and outside of the cell S with each other. Specifically, as shown in FIG. 1B, in the first cell S1, the hole 15 is provided so as to penetrate the skin layer 30 on the upper surface side and the upper wall portion 21 of the two-layer structure. Further, as shown in FIG. 1(c), in the second cell S2, the hole 15 is provided so as to penetrate the skin layer 30 on the upper surface side and the upper wall portion 21 of the one-layer structure. That is, the hole 15 is provided in one of the closing walls of each cell S that closes the upper portion of the side wall portion 23 .

The hole 15 is formed by irradiating the plate member 14 with a laser beam 17 in a hole forming process, which will be described later, and the inner surface of the hole 15 is an evaporation surface 15A formed by evaporating the resin.
In the conventional method in which a needle member is pierced to form a hole, a plurality of groove-like marks are formed on the inner surface of the hole as the needle member is inserted, and a large curved surface is formed at the open end of the hole. On the other hand, the hole 15 formed by irradiating the laser beam 17 is likely to have a smooth surface without forming groove-like traces on the evaporation surface 15A which is the inner surface of the hole 15 . In addition, it is easy to increase the precision of the holes, and stress is less likely to remain. The evaporation surface 15A can be identified by observing the inner surface of the hole 15 using a microscope or the like.

As shown in FIG. 1A, the holes 15 are provided at regular intervals along the X direction, which is the direction in which the cells S are arranged side by side. As shown in FIGS. 1B and 1C, the interval P2 between the holes 15 adjacent to each other in the X direction is shorter than the pitch P1 of each cell S. As shown in FIG. In this embodiment, the spacing P2 of the holes 15 is 0.9 times the pitch P1 of each cell S.

As shown in FIG. 1A, a plurality of rows of holes 15 are provided at predetermined intervals so as to be parallel to each other. Specifically, when the hollow structural body 10 is viewed from above, the first cells S1 in a row are adjacent to the second cells S2 in the adjacent row while sharing one side of the hexagon. The spacing between the rows of the holes 15 is adjusted so that the spacing between the adjacent holes 15 of the first cell S1 and the adjacent holes 15 of the second cell S2 is the same as the spacing P2 between the adjacent holes 15 in the same row. is set.

A method for manufacturing the hollow structure 10 will be described.
A method for manufacturing the hollow structure 10 includes a plate forming step of forming a hollow plate 14 having a pair of skin layers 30 and 40 and a core layer 20 sandwiched between the pair of skin layers 30 and 40, and a plate forming step. and a hole forming step of forming holes 15 in the plate material 14 obtained in .

(plate material forming process)
As shown in FIG. 2(a), the first sheet material 100 is formed by molding one thermoplastic resin sheet into a predetermined shape. In the first sheet material 100 , strip-shaped flat areas 110 and swollen areas 120 are alternately arranged in the longitudinal direction (X direction) of the first sheet material 100 . In the bulging region 120 , a first bulging portion 121 having a downward groove shape in cross section and having an upper surface and a pair of side surfaces is formed over the entirety of the extending direction (Y direction) of the bulging region 120 . The angle between the upper surface and the side surface of the first bulging portion 121 is preferably 90 degrees. Moreover, the width of the first bulging portion 121 (the length of the upper surface in the short direction) is equal to the width of the planar region 110, and the bulging height of the first bulging portion 121 (the length of the side surface in the short direction) ) is set to be twice as long.

In the bulging region 120 , a plurality of second bulging portions 122 each having a trapezoidal cross-sectional shape obtained by bisected a regular hexagon along the longest diagonal line are arranged so as to be perpendicular to the first bulging portions 121 . formed. The bulging height of the second bulging portion 122 is set to be equal to the bulging height of the first bulging portion 121 . Also, the interval between adjacent second bulging portions 122 is equal to the width of the upper surfaces of the second bulging portions 122 .

The first swelling portion 121 and the second swelling portion 122 are formed by partially swelling the sheet upward using the plasticity of the sheet. Also, the first sheet material 100 can be formed from one sheet by a well-known forming method such as a vacuum forming method or a compression forming method.

As shown in FIGS. 2A and 2B, the core layer 20 is formed by folding the first sheet material 100 configured as described above along the boundary lines P and Q. As shown in FIGS. Specifically, the first sheet material 100 is valley-folded along the boundary line P between the plane region 110 and the bulging region 120, and is folded along the boundary line Q between the top surface and the side surface of the first bulging portion 121. Fold and compress in the X direction. Then, as shown in FIGS. 2B and 2C, the upper surface and the side surface of the first bulging portion 121 are folded over, and the end surface of the second bulging portion 122 and the plane region 110 are folded over, thereby forming one A prismatic partition 130 extending in the Y direction is formed for one bulging region 120 . The core layer 20 in the form of a hollow plate is formed by continuously forming such division bodies 130 in the X direction. In this embodiment, the direction in which the first sheet member 100 is compressed for folding is the direction in which the cells S are arranged side by side (the X direction).

When the first sheet material 100 is compressed as described above, the upper wall portion 21 of the core layer 20 is formed by the upper surface and the side surface of the first bulging portion 121, and the end surface and the plane surface of the second bulging portion 122 are formed. The region 110 forms the lower wall portion 22 of the core layer 20 . In addition, as shown in FIG. 2C, a portion of the upper wall portion 21 where the upper surface and the side surface of the first bulging portion 121 are folded to form a two-layer structure, and a second bulging portion of the lower wall portion 22 A portion where the end surface of 122 and the planar region 110 are folded to form a two-layer structure becomes an overlapping portion 131 .

In addition, the hexagonal prism-shaped regions partitioned by folding the second bulging portion 122 become the second cells S2, and the hexagonal prism-shaped regions partitioned and formed between the pair of adjacent partitions 130 are the second cells S2. 1 cell S1. In the present embodiment, the upper surface and the side surface of the second bulging portion 122 constitute the side wall portion 23 of the second cell S2, and the side surface of the second bulging portion 122 and the second bulging portion 122 in the bulging region 120 The planar portion located therebetween constitutes the side wall portion 23 of the first cell S1. A side wall portion 23 having a two-layer structure is formed by the contact portion between the upper surfaces of the second bulging portion 122 and the contact portion between the planar portions of the bulging region 120 . The upper portion of the first cell S1 is defined by the pair of overlapping portions 131, and the lower portion of the second cell S2 is defined by the pair of overlapping portions 131. As shown in FIG. It is preferable that the first sheet material 100 be heated and softened before performing such a folding process.

The hollow structure 10 is formed by thermally welding the second sheet material made of thermoplastic resin to the upper and lower surfaces of the core layer 20 thus obtained. The second sheet material joined to the upper surface of the core layer 20 becomes the skin layer 30 and closes the upper portion of the side wall portion 23 together with the upper wall portion 21 of the core layer 20 . The second sheet material joined to the lower surface of the core layer 20 becomes the skin layer 40 and closes the lower portion of the side wall portion 23 together with the lower wall portion 22 of the core layer 20 . Therefore, in this embodiment, the folding step of folding the first sheet material 100 to form the core layer 20, and the second sheet material are joined to the top surface and the bottom surface of the core layer 20 to form the skin layers 30 and 40, respectively. A step including the step of forming the plate corresponds to the step of forming the plate material.

When the second sheet material (skin layers 30 and 40) is heat-sealed to the core layer 20, the two-layer upper wall portion 21 (superposed portion 131) of the first cell S1 is heat-sealed to each other. . Similarly, the lower wall portion 22 (overlapping portion 131) of the two-layer structure in the second cell S2 is thermally welded to each other.

Through the above steps, the hollow plate material 14 including the pair of skin layers 30 and 40 and the core layer 20 sandwiched between the pair of skin layers 30 and 40 is formed.
The plate forming step may include a shaping step of shaping the formed plate 14 into a predetermined shape. For example, a predetermined shape can be imparted to the plate material 14 by press-molding the plate material 14 in a vacuumed state. An example of the predetermined shape is a curved portion obtained by curving the plate member 14 with a constant curvature. In the shaping step, the plate material 14 may be partially shaped to have a curved portion, or the entire plate material 14 may be shaped to have a curved portion.

(Hole forming step)
In the hole forming step, the plate member 14 is irradiated with a laser beam 17 to form holes 15 at predetermined positions in the plate member 14 . Although the type of the laser beam 17 is not particularly limited, for example, a YAG laser (laser generated from a solid having a crystal structure of yttrium-gallium-garnet doped with neodymium ions as a light-emitting element, wavelength of 1.064 μm) can be mentioned. be done. In addition, YVO ₄ laser (laser generated from a solid having a crystal structure of yttrium vanadate doped with neodymium ions as a light emitting element, wavelength 1.064 μm), carbon dioxide laser (carbon dioxide, nitrogen and helium) Laser, wavelength 10.6 .mu.m, etc., whose source is an oscillation tube in which a specified amount is enclosed. Of these, the carbon dioxide laser is preferable because it is easily absorbed by a transparent resin to melt and evaporate the resin, and because it is possible to provide small-diameter through holes with a relatively small irradiation area.

As shown in FIG. 3A, in the hole forming step, the position of the laser beam irradiation device 16 is adjusted so that the hole 15 can be formed at a predetermined position in the plate member 14 .
As shown in FIGS. 3B and 3C, a plurality of holes 15 are formed by irradiating the laser beam 17 while changing the position of the laser beam irradiation device 16 . The hole 15 is formed with a substantially circular cross-sectional shape. The inner surface of the hole 15 becomes an evaporation surface 15A by evaporating the resin forming the plate member 14 .

A hemispherical resin lump 18 protruding inward of the cell S is attached to the open end portion 15B of the hole 15 inside the cell S. As shown in FIG. Similarly, a hemispherical resin mass 18 protruding outward from the cell S is attached to the open end portion 15C on the outside of the cell S as well. The resin mass 18 is formed by condensing part of the evaporated resin when the plate member 14 is irradiated with the laser beam 17 . It is also formed by solidifying a melted resin when irradiated with the laser beam 17 . The shape of the resin mass 18 is not limited to a hemispherical shape, and may be annular around the hole 15 . It may be configured such that the resin mass 18 is not formed by controlling the conditions for irradiating the laser beam 17 . The resin lumps 18 protruding outward from the cells S can be easily removed by wiping. In rare cases, traces may remain after wiping, but the diameter of the holes 15 is not affected.

By going through the manufacturing process described above, a resin plate member 14 having a core layer 20 in which a plurality of cells S are arranged side by side and a pair of skin layers 30 and 40 bonded to both sides of the core layer 20 is obtained. is obtained. One of the pair of skin layers 30 and 40 and the core layer 20 are provided with a plurality of holes 15 communicating between the inside and outside of the cells S, and the inner surfaces of the holes 15 are formed by evaporating the resin forming the plate material 14. It becomes 15 A of evaporation surfaces.

Applications of the hollow structure 10 are not particularly limited. Since the hollow structural body 10 is configured such that a plurality of cells S form a honeycomb structure, it is lightweight and has excellent bending strength. It also has excellent heat insulating properties. Moreover, since a plurality of holes 15 are provided to communicate the inside and outside of the cell S, the sound absorption is excellent. Specifically, since the precision of the holes is high, the sound absorption coefficient of a specific frequency can be increased. Therefore, it can be appropriately used for applications requiring these properties. Applications of the hollow structure 10 include, for example, conference room walls and vehicle interior materials.

The action and effect of this embodiment will be described.
(1) One of the pair of skin layers 30 and 40 and the core layer 20 are provided with a plurality of holes 15 communicating between the inside and outside of the cells S, and the inner surfaces of the holes 15 allow the resin forming the plate member 14 to evaporate. The evaporation surface 15A is formed by

When the plate member 14 is irradiated with the laser beam 17 to evaporate the resin forming the plate member 14 to form the hole 15, the inner surface of the hole 15 becomes an evaporation surface where the resin forming the plate member 14 is evaporated. Since the holes 15 are formed without expanding the skin layers 30 and 40 and the core layer 20, warping of the hollow structure 10 is suppressed. That is, the holes 15 can be formed without applying stress to the plate member 14 . Moreover, since the evaporation surface 15A is a smooth surface, concentration of stress on the inner surface of the hole 15 can be suppressed as compared with an aspect in which the inner surface of the hole 15 is configured with a rough surface.

(2) The plate member 14 has a curved portion, and the hole 15 is provided in the curved portion. Since the bent portion is formed by bending the plate member 14, stress is likely to accumulate in the bent portion. If the hole 15 is formed in this curved portion with a needle member, further stress is applied to the curved portion and the plate member 14 is likely to warp. Therefore, in a configuration in which the plate member 14 has a curved portion and the hole 15 is provided in the curved portion, warping of the plate member 14 can be suitably suppressed.

(3) The opening end 15B inside the cell S of the hole 15 has a resin mass 18 protruding inward of the cell S. As shown in FIG. As the molten resin is solidified by the irradiation of the laser beam 17, a resin block 18 is formed at the opening end portion 15B inside the cell S in the hole 15. As shown in FIG. Since the opening end portion 15B can be reinforced by the resin mass 18, peeling of the skin layer 30 from the core layer 20 at the opening end portion 15B can be suppressed.

(4) By forming the hole 15 by irradiating the laser beam 17, the precision of the hole 15 can be improved. In addition, formation of a curved surface at the opening edge of the hole 15 can be suppressed, and the opening edge can be made sharper.

This embodiment can be implemented with the following modifications. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
- Although the holes 15 are provided in one of the pair of skin layers 30 and 40 and the core layer 20 in the present embodiment, the present invention is not limited to this aspect. The holes 15 may be provided in both the pair of skin layers 30 and 40 and the core layer 20 . In the embodiment in which the holes 15 are provided in both the pair of skin layers 30 and 40, the holes 15 may be formed in both the pair of skin layers 30 and 40 at the same time by irradiating the laser beam 17 once.

In the present embodiment, the interval between the holes 15 adjacent in the direction in which the cells S are arranged is configured to be shorter than the average value of the intervals between the cells S adjacent in the direction in which the cells S are arranged. , is not limited to this aspect. The interval between the holes 15 adjacent in the direction in which the cells S are arranged may be equal to or longer than the average value of the intervals between the cells S adjacent in the direction in which the cells S are arranged. good.

- In this embodiment, the holes 15 are provided at regular intervals along the direction in which the cells S are arranged, but the holes 15 may be provided at random. Also, a certain number of holes 15 may be formed in each cell S. For example, a fixed number of holes 15 can be formed in each cell S by recognizing each cell S with a camera. It may be configured such that one hole 15 is opened at a predetermined position of each cell S, for example, at the center of the cell S.

- In the present embodiment, the hole 15 is provided only in the blocking wall that blocks the upper part of the cell S among the blocking walls of each cell S, but it is not limited to this aspect. For example, the hole 15 may be provided across the closing wall that closes the upper portion of the cell S and the side wall portion 23 of the core layer 20 . By adjusting the side wall portion 23 to be positioned at the position where the hole 15 is formed by irradiating the laser beam 17, the hole 15 is formed so as to pass through the blocking wall and the side wall portion 23 in the thickness direction. can do. Both the cells S on both sides of the side wall portion 23 can be brought into communication between the inside and the outside of the cell S by the holes 15 penetrating the side wall portion 23 . Therefore, it is possible to efficiently form the holes 15 communicating between the inside and the outside of the cell S and reduce the number of the holes 15 . Alternatively, a hole penetrating through the side wall portion 23 in the thickness direction may be formed by irradiating the side wall portion 23 with the laser beam 17 from an oblique direction. Further, in the present embodiment, the side wall portions 23 of the core layer 20 are provided so as to be orthogonal to the skin layers 30 and 40, but the side wall portions 23 of the core layer 20 are provided so as to be oblique to the skin layers 30 and 40. Side walls 23 may be provided. This makes it easy to form a hole through the side wall portion 23 with the laser beam 17 in the thickness direction. It becomes easier to provide

- The shape of the hole 15 is not limited to a circular shape. For example, the shape of the hole 15 can be appropriately selected from a triangular shape, a square shape, an elongated shape, and the like. By narrowing the shape of the hole 15 such as an elongated shape, it is possible to make it difficult for insects, dust, and the like to enter the core layer 20 . Alternatively, holes 15 of different shapes may be mixed. Mixture of holes 15 with different shapes makes it possible to absorb sounds of a wide range of frequencies.

- The position where the resin mass 18 adheres is not limited to the aspect of this embodiment. That is, in the present embodiment, only the opening ends 15B inside the cells S in the holes 15 have the resin lumps 18 protruding inward of the cells S, but the opening ends outside the cells S in the holes 15 The portion 15</b>C may have a resin block 18 protruding outward from the cell S. Since the skin layers 30 and 40 are thick, the outer peripheral side of the hole 15 does not melt when the hole 15 is made, so the resin mass 18 is just placed on the skin layer. Therefore, the resin mass 18 can be easily wiped off. The thickness of the skin layers 30 and 40 can be 1.5 times, 2.0 times, or 2.5 times the thickness of the core layer 20 . When the thickness of the skin layers 30 and 40 is the above multiple, the plate member 14 is lightweight and has a high bending strength.

- In the present embodiment, after the core layer 20 is formed, the second sheet material is joined to the upper and lower surfaces of the core layer 20 to form the skin layers 30 and 40, thereby making the thickness of the plate material 14 substantially constant. However, it is not limited to this aspect. That is, the thickness of the plate member 14 may be changed. For example, after forming the core layer 20 , the thickness of the plate member 14 may be changed by forming the skin layers 30 and 40 after changing the thickness of the core layer 20 . As a method for changing the thickness of the core layer 20, for example, a method of partially cutting the core layer 20 or a method of compressing and crushing the core layer 20 can be employed. As a change in the thickness of the plate material 14, for example, the thickness of the plate material 14 gradually decreases from one end to the other end. 40 may be configured to be in an inclined state.

- At least one of the skin layers 30 and 40 may be attached with another material such as non-woven fabric or leather. For example, another material such as non-woven fabric or leather may be applied and then irradiated with the laser beam 17 to form the holes together with the skin layers 30 and 40 . By attaching other materials such as non-woven fabric and leather, it becomes possible to suitably use it as a deck board for a luggage compartment, which is an interior material of a vehicle. Also, the skin layers 30 and 40 may be made of other materials such as non-woven fabric and leather.

- The shape of the core layer 20 is not limited to the honeycomb shape of this embodiment. As for the shape of the core layer 20, for example, a plurality of cells S are configured to have a cylindrical shape, a conical shape, a prefixed conical shape, a shape combining the prefixes of the prefixed conical shapes, a triangular prism shape, a harmonica shape, or the like. good too.

Next, technical ideas that can be grasped from the above embodiment and another example will be described below.
(a) Plate forming step of forming a resin plate 14 having a core layer 20 in which a plurality of cells S are arranged side by side and a pair of skin layers 30 and 40 bonded to both sides of the core layer 20. Then, the plate material 14 obtained in the plate material forming step is irradiated with a laser beam 17 to form a plurality of holes 15 communicating between the inside and outside of the cells S in at least one of the pair of skin layers 30 and 40 and the core layer 20. A method for manufacturing a hollow structure, comprising the steps of:

By forming the hole 15 by irradiating the plate material 14 with the laser beam 17, the warp of the plate material 14 when forming the hole 15 can be suppressed.
(b) The plate forming step includes a shaping step of shaping the formed plate 14 into a predetermined shape.

Forming the plate material 14 into a predetermined shape before forming the holes 15 in the plate material 14 facilitates shaping the plate material 14 . Further, by forming the hole 15 by irradiating the laser beam 17, even if the plate material 14 has a predetermined shape, the hole 15 can be formed while suppressing warping.

S... Cell, 10... Hollow structure, 14... Plate material, 15... Hole, 15A... Evaporation surface, 20... Core layer, 30... Skin layer, 40... Skin layer.

Claims (2)

A hollow structure having a resin plate material comprising a core layer in which a plurality of cells are arranged side by side and a pair of skin layers bonded to both sides of the core layer,
At least one of the pair of skin layers and the core layer are provided with a plurality of holes communicating between the inside and outside of the cells,
the inner surface of the hole is an evaporation surface formed by evaporation of the resin forming the plate;
The plate material has a curved portion,
The hole is provided in the curved portion,
At the opening end inside the cell of the hole, there is a resin lump projecting inward of the cell,
The core layer has sidewalls that partition the plurality of cells,
The hole penetrates the side wall in the thickness direction,
an interval between adjacent holes of the plurality of holes is shorter than a pitch of the plurality of cells;
The plurality of holes are mixed with holes of different shapes,
A hollow structure , wherein the thickness of the skin layer is thicker than the thickness of the core layer . A method for manufacturing a hollow structure according to claim 1,
2. The method for manufacturing a hollow structural body according to claim 1, wherein said hole is formed by irradiating said plate with a laser beam.

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