Hollow structure

Abstract

To provide a hollow structure excellent in impact resistance.SOLUTION: A hollow structure 10 includes multiple cells S arranged side by side, a hollow plate-like core layer 20 having a first main surface and a second main surface, and skin layers 30 and 40 laminated on the first main surface. The core layer 20 includes a first wall 21 forming the first main surface, a second wall 22 forming the second main surface, and standing walls 23 erected between the first wall 21 and the second wall 22 to partition the cells S. The skin layer 30 is formed from resin-impregnated fiber sheets, and a convex portion 25 is formed on the first wall 21, curving inward toward the cells S. On the outer surface of the convex portion 25, a first reinforcing portion 61 integrated with the resin forming the resin-impregnated fiber sheet is provided.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a hollow structure. [Background technology]

[0002] Hollow plate-shaped hollow structures with a plurality of cells arranged side by side inside are lightweight yet have appropriate strength, and are therefore widely used in a variety of fields, such as vehicle interior materials, furniture, and building materials. Patent Document 1 describes an invention relating to a hollow structure in which a fiber sheet and a thermoplastic resin film are bonded to both main surfaces of a honeycomb core material in which a plurality of hexagonal columnar cells are arranged side by side. By bonding the fiber sheet and the thermoplastic resin film, it is possible to suppress the occurrence of protruding wrinkles and recesses due to buckling that occurs at the bent portion when the hollow structure is bent, and a hollow structure with excellent bending rigidity can be obtained. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6301589 Summary of the Invention [Problem to be solved by the invention]

[0004] However, hollow structures used for vehicle interior materials, furniture, building materials, etc. are required to have not only flexural rigidity but also excellent impact resistance. Improved impact resistance suppresses the occurrence of cracks and fissures in the hollow structures. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention provides a hollow structure comprising a hollow plate-shaped core layer having a first main surface and a second main surface, in which a plurality of cells are arranged side by side, and a skin layer laminated on the first main surface, wherein the core layer comprises a first wall constituting the first main surface, a second wall constituting the second main surface, and a standing wall erected between the first wall and the second wall to separate the cells, the skin layer being formed from a resin-impregnated fiber sheet, the first wall having a convex portion that curves and protrudes inwardly into the cell, and the outer surface of the convex portion having a first reinforcing portion integral with the resin that constitutes the resin-impregnated fiber sheet.

[0006] In the above configuration, it is preferable that an opening is formed in the first wall, connecting the inside and outside of the cell, and a second reinforcing portion integral with the resin that constitutes the resin-impregnated fiber sheet is formed inside the cell in which the opening is formed.

[0007] In the above configuration, it is preferable that the second reinforcing portion extends to the inner surface of the first wall. In the above configuration, it is preferable that the second reinforcing portion extends to the inner surface of the second wall.

[0008] In the above configuration, it is preferable that the standing wall has a two-layer wall structure consisting of a first standing wall and a second standing wall, and a third reinforcing portion integral with the resin constituting the resin-impregnated fiber sheet is formed between the first standing wall and the second standing wall.

[0009] In the above-mentioned configuration, the fibers constituting the resin-impregnated fiber sheet are preferably glass fibers. In the above-mentioned configuration, the resin constituting the resin-impregnated fiber sheet is preferably a polyurethane resin. [Effects of the Invention]

[0010] According to the present invention, the impact resistance of the hollow structure is improved. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of a luggage board, which is a hollow structure of this embodiment. [Figure 2] FIG. 2 is a partial cross-sectional view of the luggage board, illustrating the first reinforcing portion, the second reinforcing portion, and the third reinforcing portion. [Figure 3] Fig. 3(a) is a partial cross-sectional perspective view of a core layer constituting the luggage board, Fig. 3(b) is a cross-sectional view taken along line α-α in Fig. 3(a), and Fig. 3(c) is a cross-sectional view taken along line β-β in Fig. 3(a). [Figure 4] Figure 4 is a diagram illustrating the folding process of the core layer. Figure 4(a) is a perspective view of the sheet material constituting the core layer of the hollow structure. Figure 4(b) is a perspective view showing the sheet material in the middle of being folded. Figure 4(c) is a perspective view showing the sheet material in the folded state. [Figure 5] FIG. 5 is a diagram illustrating the process of forming the luggage board. DETAILED DESCRIPTION OF THE INVENTION

[0012] A hollow structure according to one embodiment of the present invention will be described below. The hollow structure according to this embodiment is a luggage board 10 that forms the bottom surface of a luggage room provided at the rear of an automobile. Supports are provided below the periphery of the luggage room, and the luggage board 10 is placed on the supports and supported.

[0013] <About Luggage Board 10> 1, the luggage board 10 is formed in the shape of a generally rectangular plate that is symmetrical on the left and right sides. The luggage board 10 of this embodiment is approximately 800 mm x 1000 mm in size and has a thickness of approximately 30 mm.

[0014] The luggage board 10 has a shape in which a rear plate portion 11 at the rear of the vehicle and a front plate portion 12 at the front of the vehicle are integrally connected via a hinge portion 13. The hinge portion 13 is formed by reducing the thickness of the plate material that constitutes the luggage board 10. By lifting the rear plate portion 11 upward using the hinge portion 13 as a pivot axis, tools and the like stored in the space below the luggage board 10 can be taken in and out. Here, the front and rear of the luggage board 10 refer to the front and rear in the direction of travel of the vehicle, the left and right of the luggage board 10 refer to the left and right in the width direction of the vehicle as viewed forward in the direction of travel of the vehicle, and the top and bottom of the luggage board 10 refer to the top and bottom of the vehicle. For convenience, the surface located above the luggage board 10 in FIG. 1 will be referred to as the upper surface 10a, and the surface located below will be referred to as the lower surface 10b.

[0015] A plurality of recesses 14 are formed in parts of the upper surface 10a and the lower surface 10b of the luggage board 10. The recesses 14 are structures for accommodating and absorbing structures formed in the luggage room, such as protrusions on the support parts, so that the luggage board 10 can be stably supported on the support parts of the luggage room.

[0016] 2, the luggage board 10 includes a core layer 20 having a plurality of cells S arranged side by side therein, skin layers 30 and 40 bonded to the upper and lower surfaces of the core layer 20, and nonwoven fabric layers 50 and 60 bonded to the upper and lower surfaces of the skin layers 30 and 40. The skin layer 30 and the nonwoven fabric layer 50 are sheet layers bonded to the core layer 20 on the upper surface 10a side of the luggage board 10 so as to cover the entire core layer 20. The skin layer 40 and the nonwoven fabric layer 60 are sheet layers bonded to the core layer 20 on the lower surface 10b side of the luggage board 10 so as to cover the entire core layer 20.

[0017] The core layer 20 is made of a thermoplastic resin. The skin layers 30, 40 are formed of resin-impregnated fiber sheets 31, 41 (described later) in which reinforcing fibers are impregnated with a thermosetting resin or a thermoplastic resin. The nonwoven fabric layers 50, 60 are made of a thermoplastic resin.

[0018] The thermoplastic resin constituting the core layer 20 may be any conventionally known thermoplastic resin. Examples include polypropylene resin, polyamide resin, polyethylene resin, acrylonitrile-butadiene-styrene copolymer resin, acrylic resin, polybutylene terephthalate resin, etc. The core layer 20 of this embodiment is made of polypropylene resin.

[0019] The thermosetting resin impregnated in the resin-impregnated fiber sheets 31, 41 that make up the skin layers 30, 40 may be any conventionally known thermosetting resin. Examples include polyurethane resin, phenolic resin, epoxy resin, silicone resin, and melamine resin. The reinforcing fibers that make up the resin-impregnated fiber sheets 31, 41 that make up the skin layers 30, 40 may also be any conventionally known fiber. Examples include glass fiber, carbon fiber, aramid fiber, and boron fiber. The reinforcing fibers may be short or long fibers. The resin-impregnated fiber sheets 31, 41 in the skin layers 30 and 40 may be the same or different.

[0020] The skin layers 30, 40 of this embodiment are resin-impregnated fiber sheets 31, 41 in which long glass fibers are impregnated with polyurethane resin. When the resin impregnated in the resin-impregnated fiber sheets 31, 41 constituting the skin layers 30, 40 is a thermoplastic resin, it can be appropriately selected from conventionally known thermoplastic resins, as with the core layer 20.

[0021] The thermoplastic resin constituting the nonwoven fabric layers 50, 60 may be any conventionally known thermoplastic resin. It can be appropriately selected from the same resins as the thermoplastic resin constituting the core layer 20. The thermoplastic resin constituting the nonwoven fabric layers 50, 60 and the thermoplastic resin constituting the core layer 20 may be the same or different. The nonwoven fabric layers 50, 60 of this embodiment are made of polyester resin.

[0022] 2, a first reinforcing portion 61, a second reinforcing portion 62, and a third reinforcing portion 63 are formed inside the luggage board 10. The first, second, and third reinforcing portions 61, 62, and 63 are formed integrally with the resin impregnated in the resin-impregnated fiber sheets 31 and 41 that form the skin layers 30 and 40.

[0023] The first reinforcing portion 61 is formed on the upper surface of the upper wall portion 21 of the core layer 20, which will be described later, or on the lower surface of the lower wall portion 22 of the core layer 20. Specifically, the lower wall portion 22, which has a single-layer structure, which will be described later, has a convex portion 25 that curves and protrudes inward into the cell S, and the first reinforcing portion 61 is formed on the outer surface of this convex portion 25. The upper wall portion 21, which has a single-layer structure, which will be described later, also has a convex portion 25 that curves and protrudes into the interior of the cell S, and the first reinforcing portion 61 is formed on the outer surface of this convex portion 25. The convex portion 25 is formed from a position that is more inward of the cell S than the side wall portion 23, which will be described later, when the cell S is viewed from above. Furthermore, the convex portions 25 are formed independently between each cell S, and the convex portions 25 inside adjacent cells S are not connected. 2 shows a state in which the lower wall portion 22 has a single-layer structure, and shows a state in which the convex-shaped portion 25 and the first reinforcing portion 61 on the outer surface thereof are formed only on the lower wall portion 22.

[0024] The first reinforcing portion 61 formed on the upper surface of the upper wall portion 21 of the core layer 20 is thinner than the thickness of the resin-impregnated fiber sheet 31 that constitutes the skin layer 30. It is also thinner than the combined thickness of the resin-impregnated fiber sheet 31 and the nonwoven fabric layer 50 that constitute the skin layer 30. The first reinforcing portion 61 formed on the lower surface of the lower wall portion 22 of the core layer 20 is thinner than the thickness of the resin-impregnated fiber sheet 41 that constitutes the skin layer 40. It is also thinner than the combined thickness of the resin-impregnated fiber sheet 41 and the nonwoven fabric layer 60 that constitute the skin layer 40. When the cell S is viewed from above, the first reinforcing portion 61 is thicker in the thickness direction of the core layer 20 at the center of the cell S than at the side wall portion 23 side.

[0025] The second reinforcing portion 62 is formed inside the cell S in a shape that penetrates into the cell S from an opening 24 described below. The second reinforcing portion 62 is in a highly foamed state with respect to the polyurethane resin impregnated in the resin-impregnated fiber sheet 31 that constitutes the skin layer 30.

[0026] The second reinforcing portion 62 formed on the upper wall portion 21 side of the core layer 20, specifically, the second reinforcing portion 62 formed in the cell S (first cell S1) where the opening 24 is formed on the upper wall portion 21 side, is thicker than the resin-impregnated fiber sheet 31 constituting the skin layer 30 and is formed in a triangular shape in side view. It extends downward along the inner surface of the side wall portion 23. Furthermore, the second reinforcing portion 62 located in the portion where the opening 24 is formed is formed with a thickness greater than the depth of the opening 24.

[0027] The second reinforcing portion 62 formed on the lower wall portion 22 side of the core layer 20, specifically, the second reinforcing portion 62 formed in the cell S (second cell S2) in which the opening 24 is formed on the lower wall portion 22 side, has a different volume from the second reinforcing portion 62 formed in the first cell S1. The second reinforcing portion 62 formed in the first cell S1 has a larger volume than the second reinforcing portion 62 formed in the second cell S2.

[0028] The third reinforcing portion 63 is formed between a first side wall portion 23a and a second side wall portion 23b having a two-layer structure, which will be described later. The thickness of the third reinforcing portion 63 in a direction perpendicular to the thickness direction (vertical direction) of the luggage board 10 is thicker than the thickness of the first reinforcing portion 61 in the vertical direction. The thickness of the third reinforcing portion 63 in the direction perpendicular to the vertical direction is thicker at the middle part in the vertical direction than at the upper and lower parts. In addition, the thickness of the third reinforcing portion 63 in the direction perpendicular to the vertical direction is thicker than the thickness of a sheet material 100 (described later) that constitutes the core layer 20.

[0029] By forming the first reinforcing portion 61, the second reinforcing portion 62, and the third reinforcing portion 63, the impact resistance of the luggage board 10 is improved. <About the core layer 20> First, we will explain the hollow plate-shaped core layer 20 that constitutes the luggage board 10. In the following explanation, the side of the core layer 20 to which the skin layer 30 is joined may be referred to as the upper side of the core layer 20, and the side to which the skin layer 40 is joined may be referred to as the lower side of the core layer 20.

[0030] As shown in Figures 3(a) to 3(c), the core layer 20 is formed by folding a single 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 that is erected between the upper wall portion 21 and the lower wall portion 22 and divides the cells S into a hexagonal columnar shape. One of the upper wall portion 21 and the lower wall portion 22 is a first wall defined in the claims, and the other is a second wall defined in the claims. The side wall portion 23 is a standing wall defined in the claims.

[0031] As shown in Figures 3(b) and 3(c), the cells S formed within the core layer 20 include a first cell S1 and a second cell S2, which have different structures. As shown in Figure 3(b), the first cell S1 has a two-layer upper wall portion 21 provided on the upper part of the side wall portion 23. The layers of this two-layer upper wall portion 21 are joined to each other. Furthermore, the first cell S1 has a single-layer lower wall portion 22 provided below the side wall portion 23.

[0032] On the other hand, as shown in FIG. 3(c), in the second cell S2, a single-layer upper wall portion 21 is provided on the upper part of the side wall portion 23. In addition, in the second cell S2, a two-layer lower wall portion 22 is provided on the lower part of the side wall portion 23. The layers of this two-layer lower wall portion 22 are bonded to each other. As shown in FIGS. 3(b) and 3(c), adjacent first cells S1 and adjacent second cells S2 are separated by two-layer side wall portions 23 each consisting of a first side wall portion 23a and a second side wall portion 23b. Note that in FIG. 3(a), the upper wall portion 21 and the lower wall portion 22 of the core layer 20 are shown as having a single-layer structure.

[0033] As shown in FIG. 3(a), the first cells S1 are arranged in rows along the X direction, and when viewed from above, two adjacent first cells S1 share one side of a hexagon. 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 a hexagon. The rows of first cells S1 and the rows of second cells S2 are alternately arranged in the Y direction, which is perpendicular to the X direction. The first cells S1 and second cells S2 form a honeycomb structure as a whole in the core layer 20.

[0034] 3(a), in the upper wall portion 21 and the lower wall portion 22 of the core layer 20, a substantially spindle-shaped opening 24 is formed at the position of the longest diagonal of the regular hexagon, which is the cross-sectional shape of the cell S, so as to bisect the upper wall portion 21 and the lower wall portion 22. The opening 24 is formed only in the upper wall portion 21 in the first cell S1, and only in the lower wall portion 22 in the second cell S2. That is, in each cell S, the opening 24 is formed only in the upper wall portion 21 and the lower wall portion 22 of the two-layer structure.

[0035] <Method of manufacturing the core layer 20> Next, a method for manufacturing the hollow plate-shaped core layer 20 will be described with reference to FIG. The method for manufacturing the core layer 20 comprises a folding step and a heating step.

[0036] The folding process is a process of folding and molding the sheet material 100 that has been vacuum-formed into a predetermined uneven shape to form a hollow plate-like core layer 20 without openings 24. The heating process is a process of heating the upper and lower surfaces of the core layer 20 to bond the two-layer structure of the upper wall portion 21 and the lower wall portion 22 together and form the openings 24.

[0037] As shown in FIG. 4(a), a sheet material 100 having a predetermined uneven shape is used to form the core layer 20. The sheet material 100 has strip-shaped flat regions 110 and bulging regions 120 alternately arranged in the longitudinal direction (X direction) of the sheet material 100. In the bulging region 120, a first bulging portion 121 having a downward groove-like cross section and consisting of an upper surface and a pair of side surfaces is formed over the entire extending direction (Y direction) of the bulging region 120. Note that the angle between the upper surface and the side surface of the first bulging portion 121 is preferably 90 degrees, so that the cross section of the first bulging portion 121 has a downward U-shape. The width of the first bulging portion 121 (the length in the short direction of the upper surface) is set to be equal to the width of the flat region 110 and to be twice the bulging height of the first bulging portion 121 (the length in the short direction of the side surfaces).

[0038] In addition, in the bulging region 120, a plurality of second bulging portions 122, each of which has a cross-sectional shape that is a trapezoid obtained by bisecting a regular hexagon along its longest diagonal, are formed so as to be perpendicular to the first bulging portions 121. The bulging height of the second bulging portions 122 is set to be equal to the bulging height of the first bulging portions 121. The interval between adjacent second bulging portions 122 is equal to the width of the upper surface of the second bulging portions 122.

[0039] The first bulging portion 121 and the second bulging portion 122 are formed by partially bulging the sheet upwards by utilizing the plasticity of the sheet. As shown in FIG. 4(a), the sheet material 100 is folded sequentially along boundary lines P and Q. Specifically, the sheet material 100 is folded in the X direction by making a valley fold at the boundary line P between the flat region 110 and the bulging region 120 and a mountain fold at the boundary line Q between the top surface and side surface of the first bulging portion 121. Then, as shown in FIGS. 4(b) and 4(c), the top surface and side surface of the first bulging portion 121 are folded over, and the end surface of the second bulging portion 122 is folded over on the flat region 110, thereby forming one rectangular columnar partition 130 extending in the Y direction for one bulging region 120. The core layer 20 is formed by continuously forming such partitions 130 in the X direction.

[0040] When the sheet material 100 is folded as described above, the upper wall portion 21 of the core layer 20 is formed by the upper surface and side surface of the first bulge portion 121, and the lower wall portion 22 of the core layer 20 is formed by the end surface of the second bulge portion 122 and the flat region 110. As shown in Fig. 4(c), the portion of the upper wall portion 21 where the upper surface and side surface of the first bulge portion 121 are folded over to form a two-layer structure, and the portion of the lower wall portion 22 where the end surface of the second bulge portion 122 and the flat region 110 are folded over to form a two-layer structure, respectively, become overlapping portions 131.

[0041] Furthermore, a hexagonal columnar region formed by folding the second bulging portion 122 becomes the second cell S2, and a hexagonal columnar region formed between a pair of adjacent partitions 130 becomes the first cell S1. In this embodiment, the upper and side surfaces of the second bulging portion 122 form the side wall portion 23 of the second cell S2, and the side surfaces of the second bulging portion 122 and flat portions located between the second bulging portions 122 in the bulging region 120 form the side wall portion 23 of the first cell S1. The contact areas between the upper surfaces of the second bulging portions 122 and the contact areas between the flat portions in the bulging region 120 form the side wall portion 23 having a two-layer structure.

[0042] Subsequently, in the heating step, the upper wall portion 21 and the lower wall portion 22 of the core layer 20 formed by folding the sheet material 100 are heated. The core layer 20 may be heated, for example, in a heating device, or by placing a heating plate on the upper wall portion 21 and the lower wall portion 22 of the core layer 20.

[0043] Heating the core layer 20 causes the thermoplastic resin that constitutes the core layer 20 to thermally melt. As a result, the upper and lower edges of the two-layer side wall portion 23 are thermally welded, while the middle portion is not thermally welded and remains unbonded.

[0044] The thermoplastic resin constituting the core layer 20 is thermally melted and thermally shrunk, resulting in the formation of openings 24 in the two-layered upper wall portion 21 of the first cell S1 and the two-layered lower wall portion 22 of the second cell S2, as shown in FIG.

[0045] As shown in Figure 4(c), the upper wall 21 of the first cell S1 has a two-layer structure with an overlapping portion 131 formed by folding the top surface and side surface of the first bulge portion 121 over, and the two-layer upper wall portions 21 of adjacent compartments 130 are abutted together to form the upper wall portion 21 of one first cell S1. Therefore, the opening 24 formed in the two-layer upper wall portion 21 of the first cell S1 is formed by thermal shrinkage of the abutted portion, and is formed into a roughly spindle shape that divides the hexagonal upper wall portion 21 of the first cell S1 in half. On the other hand, the upper wall 21 of the second cell S2, which is formed by folding the second bulge portion 122, has a single-layer structure formed by the first bulge portion 121, and no opening 24 is formed therein.

[0046] The bottom wall 22 of the second cell S2 has a two-layer structure with an overlapping portion 131 formed by folding the end face of the second bulge portion 122 and the flat region 110, and this overlapping portion 131 is butted together to form the bottom wall 22 of one second cell S2. Therefore, the opening 24 formed in the two-layer bottom wall 22 of the second cell S2 is formed by thermal contraction of the butted overlapping portion 131, and is formed into a roughly spindle shape that divides the hexagonal bottom wall 22 of the second cell S2 in half. On the other hand, the bottom wall 22 of the first cell S1 has a single-layer structure formed by the flat region 110, and no opening 24 is formed therein.

[0047] <About the manufacturing method of the luggage board 10> Next, a method for manufacturing the luggage board 10 will be described together with the function of the luggage board 10.

[0048] The method for manufacturing the luggage board 10 includes a molding process and a post-processing process. The molding process is a process of joining the core layer 20 and the skin layers 30, 40 together and forming a shaped body into the shape of the luggage board 10. The post-processing process is a process of treating the edges of the shaped body and joining the nonwoven fabric layers 50, 60 to the shaped body after the edge treatment.

[0049] 5, in the molding process, first, the core layer 20 is prepared by cutting it to a predetermined size. Then, resin-impregnated fiber sheets 31 and 41 that will become the skin layers 30 and 40 are prepared by cutting them to a predetermined size. The core layer 20 and the resin-impregnated fiber sheets 31 and 41 are both cut to a size that is approximately 100 mm larger than the size of the luggage board 10.

[0050] In the molding process, a mold consisting of an upper mold 71 and a lower mold 72 having an internal structure of a predetermined shape is used. A cavity of the size and shape of the luggage board 10 is formed in the upper mold 71 and the lower mold 72 by clamping them together. The upper mold 71 is formed with a protrusion 71a for forming the hinge portion 13 of the luggage board 10 and a protrusion 71b for forming the recess 14 on the upper surface 10a side. The lower mold 72 is formed with protrusions 72a and 72b for forming the recess 14 on the lower surface 10b side. Note that in Figure 5, the shapes and sizes of the upper mold 71 and the lower mold 72, and the sizes and thicknesses of the core layer 20 and the resin-impregnated fiber sheets 31 and 41 placed in the upper mold 71 and the lower mold 72 are exaggerated to make the molding process easier to understand.

[0051] In the molding process, the upper mold 71 and the lower mold 72 are heated to a predetermined temperature. The heating temperature may be set depending on the resin materials constituting the core layer 20 and the resin-impregnated fiber sheets 31 and 41. In this embodiment, which uses a core layer 20 made of polypropylene resin and resin-impregnated fiber sheets 31 and 41 impregnated with polyurethane resin, the heating temperature is set to approximately 80 to 120°C.

[0052] Next, the cut core layer 20 and resin-impregnated fiber sheets 31 and 41 are placed on the lower mold 72. From the bottom, the resin-impregnated fiber sheet 41 that will become the skin layer 40, the core layer 20, and the resin-impregnated fiber sheet 31 that will become the skin layer 30 are placed in this order. The core layer 20 is placed so that the lower surface 10b faces the lower mold 72. At this time, the core layer 20 and the resin-impregnated fiber sheets 31 and 41 are kept at room temperature without being heated.

[0053] In this state, the upper mold 71 is moved toward the lower mold 72 and clamped. The resin-impregnated fiber sheets 31 and 41 are bonded to the top and bottom surfaces of the core layer 20 in a positioned state by the adhesive force of the polyurethane resin.

[0054] By heating the upper mold 71 and the lower mold 72, the shape of the hinge portion 13 is formed in the protrusion 71a of the upper mold 71, and the recess 14 on the upper surface 10a side is formed in the protrusion 71b. Furthermore, the recess 14 on the lower surface 10b side is formed in the protrusions 72a and 72b formed on the lower mold 72. Furthermore, in the peripheral portions of the core layer 20 and the resin-impregnated fiber sheets 31 and 41, portions cut out larger than the size of the luggage board 10 are compressed in the thickness direction to form compressed portions.

[0055] In this way, by clamping the mold, a shaped body is formed in which a compressed portion is formed on the peripheral portion of the luggage board 10. In the shaped body, the resin-impregnated fiber sheet 31 becomes the skin layer 30, and the resin-impregnated fiber sheet 41 becomes the skin layer 40.

[0056] In the molding process, the thermosetting resin impregnated into the resin-impregnated fiber sheets 31, 41 is in a high-viscosity state before being thermally cured. The thermosetting resin impregnated into the resin-impregnated fiber sheets 31, 41 in this embodiment is a polyurethane resin. Therefore, when the mold is closed, the pressure of the highly viscous thermosetting resin and the foaming pressure of the polyurethane press the upper wall 21 and the lower wall 22 of the core layer 20 toward the inside of the cells S. This pressure forms convex portions 25 on the single-layered upper wall 21 and lower wall 22, which curve and protrude toward the inside of the cells S. The outer surfaces of the convex portions 25, i.e., the upper surface of the single-layered upper wall 21 on which the convex portions 25 are formed, and the lower surface of the single-layered lower wall 22 on which the convex portions 25 are formed, form resin portions integral with the thermosetting resin impregnated into the resin-impregnated fiber sheets 31, 41, and are bonded to the core layer 20.

[0057] Furthermore, the highly viscous thermosetting resin penetrates into the cells S through the openings 24 formed in the two-layer upper wall portion 21 and the lower wall portion 22, forming a resin portion integral with the thermosetting resin impregnated in the resin-impregnated fiber sheets 31 and 41. Because the thermosetting resin is a polyurethane resin, its volume increases due to foaming. Therefore, part of the resin that penetrates into the cells S through the openings 24 formed in the upper wall portion 21 penetrates along the inner surface of the two-layer upper wall portion 21 and bonds to it. Another part of the resin reaches the inner surface of the lower wall portion 22 in the same cell S and bonds to it. Similarly, part of the resin that penetrates into the cells S through the openings 24 formed in the lower wall portion 22 penetrates along the inner surface of the two-layer lower wall portion 22 and bonds to it. Another part of the resin reaches the inner surface of the upper wall portion 21 in the same cell S and bonds to it.

[0058] Furthermore, the highly viscous thermosetting resin penetrates between the two-layer sidewalls 23, forming a resin portion integral with the thermosetting resin impregnated in the resin-impregnated fiber sheets 31, 41. Because the thermosetting resin is polyurethane resin, its volume increases due to foaming. The resin portion integral with the thermosetting resin is formed by the pressure of the highly viscous thermosetting resin and the foaming pressure of the polyurethane resin, which pushes and expands the first and second sidewalls 23a, 23b, which are not joined at the middle of the thickness direction of the two-layer sidewalls 23. The first and second sidewalls 23a, 23b are joined by the portion that penetrates between the two-layer sidewalls 23.

[0059] The highly viscous thermosetting resin is gradually thermally cured by the heated upper mold 71 and lower mold 72. The resin portion that is integral with the thermosetting resin impregnated in the resin-impregnated fiber sheets 31, 41 and that is formed on the outer surface of the convex portion 25 becomes the first reinforcing portion 61. The portion that extends from the opening 24 into the cell S becomes the second reinforcing portion 62. The portion that extends between the two-layered side wall portions 23 becomes the third reinforcing portion 63.

[0060] The first reinforcing portion 61, the second reinforcing portion 62, and the third reinforcing portion 63 are formed as resin portions integral with the thermosetting resin impregnated in the resin-impregnated fiber sheets 31, 41, but may also include reinforcing fibers contained in the resin-impregnated fiber sheets 31, 41. This is because the pressure of the highly viscous thermosetting resin or the foaming pressure of the polyurethane resin causes the reinforcing fibers to push against the upper wall portion 21 and the lower wall portion 22 together with the resin, or the reinforcing fibers to enter through the openings 24 together with the resin, or to enter between the two-layered side wall portions 23.

[0061] In the post-processing step, the compressed portion formed on the peripheral portion of the shaped body is removed, and the removed portion is polished, etc. Thereafter, a nonwoven fabric layer 50 is bonded to the entirety of one main surface of the shaped body from which the compressed portion has been removed, and a nonwoven fabric layer 60 is bonded to the entirety of the other main surface.

[0062] Through the above steps, the luggage board 10 is obtained. Next, the effects of the luggage board 10 of the above embodiment will be described. (1) The luggage board 10 has a structure in which skin layers 30, 40 and nonwoven fabric layers 50, 60 are joined to a core layer 20. A convex portion 25, which has a curved shape and protrudes inward of the cell S, is formed on the single-layer upper wall portion 21 of the core layer 20 or the single-layer lower wall portion 22. A first reinforcing portion 61, which is integral with the resin constituting the resin-impregnated fiber sheets 31, 41 that form the skin layers 30, 40, is formed on the outer surface of the convex portion 25.

[0063] Therefore, compared to when the convex portions 25 are not formed, the bonding area between the resin constituting the resin-impregnated fiber sheets 31, 41 and the upper wall portion 21 or the lower wall portion 22 is larger. This improves the bonding strength between the upper wall portion 21 or the lower wall portion 22 and the skin layer 30, 40, improving the rigidity of the luggage board 10. Furthermore, although cracks and fractures may occur in normal hollow structures when subjected to impact, the improved bonding strength suppresses the occurrence of cracks and fractures, improving impact resistance.

[0064] (2) An opening 24 that connects the inside and outside of the cell S is formed in the two-layer upper wall portion 21 or the two-layer lower wall portion 22 of the core layer 20. Inside the cell S where the opening 24 is formed, a second reinforcing portion 62 is formed that is integral with the resin that constitutes the resin-impregnated fiber sheets 31, 41 that form the skin layers 30, 40. Since the second reinforcing portion 62 that is integral with the resin that constitutes the resin-impregnated fiber sheets 31, 41 extends into the inside of the cell S, the rigidity of the luggage board 10 is improved and the impact resistance is also improved.

[0065] (3) The second reinforcing portion 62 that enters through the opening 24 extends to the inner surface of the upper wall portion 21 or the lower wall portion 22. Therefore, the upper wall portion 21 or the lower wall portion 22 is sandwiched between the skin layer 30, 40 joined to the outer surface of the upper wall portion 21 or the lower wall portion 22 and the second reinforcing portion 62 that is integral with the resin that constitutes the resin-impregnated fiber sheet 31, 41. This allows the second reinforcing portion 62 to exert an anchoring effect. This further improves the rigidity of the luggage board 10 and its impact resistance.

[0066] (4) The second reinforcing portion 62 extending from the opening 24 of the two-layered upper wall portion 21 extends to the inner surface of the single-layered lower wall portion 22 that faces it within the same cell S. Furthermore, the second reinforcing portion 62 extending from the opening 24 of the two-layered lower wall portion 22 also extends to the inner surface of the single-layered upper wall portion 21 that faces it within the same cell S. Therefore, the second reinforcing portion 62 is formed in a columnar shape between the upper wall portion 21 and the lower wall portion 22. The shape of the cell S is well maintained, and resistance to bending and impact is improved.

[0067] (5) Between the first side wall portion 23a and the second side wall portion 23b of the two-layered side wall portion 23, a third reinforcing portion 63 is formed that is integral with the resin that constitutes the resin-impregnated fiber sheets 31, 41 that form the skin layers 30, 40. Therefore, the first side wall portion 23a and the second side wall portion 23b are joined by the third reinforcing portion 63. In the side wall portion 23 in which the third reinforcing portion 63 is formed, cracks in the luggage board 10 that originate from peeling between the first side wall portion 23a and the second side wall portion 23b are suppressed. Resistance to bending and impact is improved.

[0068] (6) The resin impregnated in the resin-impregnated fiber sheets 31, 41 used in the skin layers 30, 40 of this embodiment is polyurethane resin. Therefore, when thermally cured during the molding process, foaming occurs, which easily generates resin pressure. This makes it easy to form the first reinforcing portion 61, the second reinforcing portion 62, and the third reinforcing portion 63.

[0069] (7) In this embodiment, the reinforcing fibers in the resin-impregnated fiber sheets 31, 41 used in the skin layers 30, 40 are long glass fibers. This results in a luggage board 10 with high strength and excellent impact resistance.

[0070] (8) In the manufacturing method of the luggage board 10 of this embodiment, the first reinforcing portion 61, the second reinforcing portion 62, and the third reinforcing portion 63 are formed simultaneously with molding of the luggage board 10 through a molding process using the upper mold 71 and the lower mold 72. Therefore, it is possible to easily manufacture a luggage board 10 that has excellent rigidity and impact resistance.

[0071] The above-described embodiments can be modified as follows: The above-described embodiments and the following modifications can be applied in combination with each other within the scope of technical compatibility. The first reinforcing portion 61 does not have to be formed on the entire upper surface of the single-layered upper wall portion 21 or the entire lower surface of the single-layered lower wall portion 22 in each cell S. In other words, the convex portion 25 does not have to be formed on the entire single-layered upper wall portion 21 or the entire single-layered lower wall portion 22 in each cell S. There may be a mixture of cells S in which the convex portion 25 and the first reinforcing portion 61 are formed and cells S in which they are not formed. Even in this case, the rigidity and impact resistance of the luggage board 10 are improved by forming the first reinforcing portion 61 in part of the cells S.

[0072] The first reinforcing portion 61 may be formed on the upper surface of the two-layered upper wall portion 21 or the lower surface of the two-layered lower wall portion 22 of each cell S. In other words, the convex portion 25 may be formed on the two-layered upper wall portion 21 or the two-layered lower wall portion 22 of each cell S.

[0073] The second reinforcing portions 62 do not have to be formed in a manner that they penetrate into all of the openings 24. There may be some openings 24 in which the second reinforcing portions 62 are not formed. The second reinforcing portion 62 does not have to extend to the inner surface of the two-layered upper wall portion 21 or the two-layered lower wall portion 22.

[0074] The second reinforcing portion 62 does not have to extend to the upper wall portion 21 having a single layer structure or the lower wall portion 22 having a single layer structure that faces the opening 24 in the cell S. The third reinforcing portion 63 does not have to be formed on all of the two-layer side wall portions 23. There may be a mixture of two-layer side wall portions 23 with the third reinforcing portion 63 and two-layer side wall portions 23 without the third reinforcing portion 63.

[0075] Neither the second reinforcing portion 62 nor the third reinforcing portion 63 may be necessary. The rigidity and impact resistance are improved simply by forming the first reinforcing portion 61. The openings 24 do not have to be formed in all the upper wall portions 21 of the first cell S1, and do not have to be formed in all the lower wall portions 22 of the second cell S2. The first cell S1 may have a mixture of upper wall portions 21 with and without openings 24, and the second cell S2 may have a mixture of lower wall portions 22 with and without openings 24.

[0076] The shape of the opening 24 does not have to be substantially spindle-shaped. There are no particular limitations on the shape as long as the two-layer structure of the upper wall portion 21 and the lower wall portion 22 is formed by thermal shrinkage. The opening 24 does not have to be formed by thermal shrinkage of the two-layer structure of the upper wall portion 21 and the lower wall portion 22. After the core layer 20 is formed, the opening 24 may be formed in the core layer 20 using a communication jig or the like.

[0077] The shape of the cells formed in the hollow plate is not limited to a hexagonal prism. For example, they may be cylindrical, or may be polygonal prisms such as square or octagonal prisms. Furthermore, the shape of the cells S may be, for example, a frustum shape or a shape in which the top faces of two frustum shapes are butted together. In other words, any shape that forms a columnar shape as a whole may be used. Furthermore, cells of different shapes may be mixed within the core layer 20, and spaces (gaps) may be formed between the cells.

[0078] Functional resins may be added to the thermoplastic resin that constitutes the core layer 20 and the thermosetting or thermoplastic resin that constitutes the skin layers 30, 40, for example, by adding a flame-retardant resin to enhance flame retardancy. Furthermore, inorganic substances such as wood flour or talc may be added to improve bending strength. This allows the luggage board 10 to be endowed with different functions, thereby improving its versatility.

[0079] The core layer 20 may be formed not only by folding a single sheet material 100 but also by using multiple sheets. For example, the core layer may be formed by bending a strip-shaped sheet material at predetermined intervals and arranging multiple sheets side by side. In this modification, the bent portions of each sheet material form the standing walls of the cells.

[0080] The skin layers 30, 40 may be joined by an adhesive. The nonwoven fabric layers 50 and 60 may be omitted. Other sheet materials may be bonded to the outer surface of at least one of the nonwoven fabric layers 50, 60. The other sheet materials do not have to be synthetic resin nonwoven fabric sheets, but may be, for example, metal sheets (metal foils, steel plates), paper, cloth, woven fabric sheets, knitted fabric sheets, or printed resin sheets such as melamine resin sheets.

[0081] The hollow structure is not limited to the luggage board 10. It may be any structure that is a hollow plate material in which a plurality of cells S are arranged side by side and in which a resin sheet that serves as a skin layer is joined to the main surface side. The technical concepts that can be understood from the above embodiment and each modification will be described below.

[0082] (i) A hollow structure comprising a hollow plate-shaped core layer having a plurality of cells arranged side by side and having a first main surface and a second main surface, and a skin layer laminated on the first main surface, wherein the core layer comprises a first wall constituting the first main surface, a second wall constituting the second main surface, and a standing wall erected between the first wall and the second wall to separate the cells, the skin layer being formed from a resin-impregnated fiber sheet, the first wall having a convex portion that curves and protrudes inwardly into the cells, and the outer surface of the convex portion having a first reinforcing portion integral with the resin that constitutes the resin-impregnated fiber sheet.

[0083] (ii) A hollow structure as described in (i) above, in which an opening is formed in the first wall, connecting the inside and outside of the cell, and a second reinforcing part is formed inside the cell in which the opening is formed, which is integral with the resin that constitutes the resin-impregnated fiber sheet.

[0084] (C) The hollow structural body according to (B), wherein the second reinforcing portion extends to the inner surface of the first wall. (iv) The hollow structural body according to claim (ii) or (iii), wherein the second reinforcing portion extends to the inner surface of the second wall.

[0085] (e) A hollow structure described in any one of (a) to (d), wherein the standing wall has a two-layer wall structure consisting of a first standing wall and a second standing wall, and a third reinforcing portion integral with the resin constituting the resin-impregnated fiber sheet is formed between the first standing wall and the second standing wall.

[0086] (vi) The hollow structural body according to any one of (a) to (e), wherein the fibers constituting the resin-impregnated fiber sheet are glass fibers. (g) The hollow structural body according to any one of (a) to (f), wherein the resin constituting the resin-impregnated fiber sheet is a polyurethane resin. [Explanation of symbols]

[0087] S, S1, S2...cells 10...Luggage board (hollow structure) 20...Core layer 21...Top wall part (1st wall, 2nd wall) 22…Lower wall part (2nd wall, 1st wall) 23, 23a, 23b...Side wall part (standing wall) 24...Opening 25...Convex shaped part 30, 40...skin layer 61...First reinforcement part 62...Second reinforcement part 63...Third reinforcement part

Claims

1. A hollow structure including a hollow plate-shaped core layer having a plurality of cells arranged side by side and a first main surface and a second main surface, and a skin layer laminated on the first main surface, the core layer includes a first wall constituting the first main surface, a second wall constituting the second main surface, and a standing wall provided between the first wall and the second wall to partition the cells, the skin layer is formed of a resin-impregnated fiber sheet, The first wall has a convex portion that is curved and protrudes inward of the cell, A hollow structure characterized in that a first reinforcing portion integral with the resin constituting the resin-impregnated fiber sheet is formed on the outer surface of the convex portion.

2. An opening communicating the inside and outside of the cell is formed in the first wall, 2. The hollow structural body according to claim 1, wherein a second reinforcing portion is formed inside the cell in which the opening is formed, the second reinforcing portion being integral with the resin constituting the resin-impregnated fiber sheet.

3. The hollow structural body according to claim 2 , wherein the second reinforcing portion extends to an inner surface of the first wall.

4. The hollow structural body according to claim 2 , wherein the second reinforcing portion extends to an inner surface of the second wall.

5. the standing wall has a two-layer wall structure consisting of a first standing wall and a second standing wall, 2. The hollow structure according to claim 1, wherein a third reinforcing portion is formed between the first standing wall and the second standing wall, the third reinforcing portion being integral with the resin constituting the resin-impregnated fiber sheet.

6. 6. The hollow structure according to claim 1, wherein the fibers constituting the resin-impregnated fiber sheet are glass fibers.

7. 7. The hollow structure according to claim 6, wherein the resin constituting the resin-impregnated fiber sheet is a polyurethane resin.

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