JP7392971B2 - Hollow structure and its manufacturing method - Google Patents

Description

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

Hollow structures in which a plurality of cells are arranged side by side are lightweight but have appropriate strength, so they are sometimes used as structural members of various vehicles, building materials, and the like. The hollow structure described in Patent Document 1 has a sandwich panel structure in which a pair of coating layers are bonded to both main surfaces of the honeycomb structure. A plurality of hexagonal cells are arranged side by side and partitioned by side walls extending in the direction of the hexagonal shape. The honeycomb structure here is formed by vacuum forming a flat sheet material to form an uneven sheet material in which convex bulges are formed, and then folding the uneven sheet material.

Special Publication No. 2008-520456

By the way, in an uneven sheet material in which a bulging portion is formed by vacuum forming, the wall thickness of the uneven sheet material on the bulging side tends to be thinner than the wall thickness of the uneven sheet material on the non-bulging side. Therefore, in a honeycomb structure formed by folding a concavo-convex sheet material in which a bulge is formed by vacuum forming, as described in Patent Document 1, the side wall The wall thickness of the side wall tends to become thinner, and the strength of the side wall may not be maintained sufficiently. Further, on the side where the uneven sheet material on the bulging side is located, sufficient bonding strength with the covering layer may not be ensured in some cases. The problem of further improving the strength is common to hollow structures formed by methods other than vacuum forming.

The present invention was made to solve these conventional problems, and its purpose is to provide a hollow structure with excellent strength.

In order to solve the above problems, the present invention provides a hollow plate-shaped core layer in which a plurality of cells partitioned by side walls extending in the thickness direction are arranged in parallel, and a core layer bonded to at least one main surface of the core layer. The hollow structure is made of a thermoplastic resin and has a skin layer formed of a polyurethane resin, and a protrusion protruding toward the inner side of the cell is formed on the side wall portion of the core layer.

According to the above configuration, the strength of the side wall portion is improved in the portion where the protrusion is formed. A hollow structure with excellent strength can be obtained.
In the above configuration, it is preferable that the protruding portion is formed by the side wall portion compressed in the thickness direction.

According to the above configuration, the protruding portion is formed integrally with the side wall portion by compressing the side wall portion made of thermoplastic resin in the thickness direction. The strength of the side wall portion can be improved more easily than when reinforcing it using other members.

In the above configuration, it is preferable that the protruding portion protrudes along the main surface from an edge of the side wall portion on the side to which the skin layer is joined.
According to the above configuration, on the side of the skin layer joined to at least one main surface of the core layer, a protrusion is formed at the edge of the side wall of the core layer so as to protrude along the main surface of the core layer. has been done. Therefore, the bonding area of the core layer to the skin layer increases due to the protrusion. Thereby, the bonding strength of the skin layer to the core layer can be improved. Moreover, the bending strength of the hollow structure can be improved.

In the above configuration, it is preferable that the protruding portion is formed as a thick portion that partially thickens the side wall portion.
According to the above configuration, the side wall portion is thick in the portion where the protruding portion is formed. Therefore, the strength of the side wall portion is improved due to the presence of the thick wall portion.

In order to solve the above problems, the present invention provides a core layer forming step of forming a hollow plate-like core layer in which a plurality of cells partitioned by side walls extending in the thickness direction are arranged in parallel; and a skin layer bonding step of bonding a thermoplastic resin skin layer to at least one main surface, and in the core layer forming step, the side wall portion is compressed in the thickness direction in a heated state. A protrusion is formed to protrude inward of the cell.

According to the above configuration, by compressing the core layer made of thermoplastic resin in the thickness direction in a heated state, the protrusion can be integrally formed in the side wall portion. Therefore, as a protrusion for reinforcing the side wall, the strength of the side wall can be improved more easily than when other members are joined. It is easy to manufacture a hollow structure with excellent strength.

The above configuration further includes a vacuum forming step of vacuum forming a single sheet material made of thermoplastic resin to obtain an uneven sheet material in which a bulge is formed, and in the core layer forming step, the unevenness Preferably, the protrusion is formed by folding the sheet material in a heated state and compressing it in the thickness direction.

According to the above configuration, the protrusion can be formed on the side wall portion by compressing the uneven sheet material in the thickness direction while forming the core layer while heating and folding the uneven sheet material. Formation of the core layer and formation of the protrusions can be performed simultaneously. The manufacturing process of a hollow structure with excellent strength can be simplified.

According to the present invention, a hollow structure with excellent strength can be obtained.

(a) is a perspective view of the hollow structure of the first embodiment. (b) is a cross-sectional view taken along the line 1B-1B in (a), and (c) is a cross-sectional view taken along the line 1C-1C in (a). (a) is a perspective view of the uneven sheet material of the first embodiment, (b) is a perspective view showing the uneven sheet material in the middle of folding, and (c) is a perspective view showing the uneven sheet material in the folded state. FIG. 1 is a schematic diagram showing an example of a manufacturing device. (a) is a perspective view of a hollow structure of a second embodiment. (b) is a 4B-4B sectional view in (a), and (c) is a 4C-4C sectional view in (a). (a) is a perspective view of the uneven sheet material of the second embodiment, (b) is a perspective view showing the uneven sheet material in a state in the middle of folding, and (c) is a perspective view showing the uneven sheet material in the folded state.

(First embodiment)
Hereinafter, a hollow structure 10 according to a first embodiment of the present invention will be described. First, the structure of the hollow structure 10 of this embodiment will be explained based on FIG. 1.

As shown in FIG. 1(a), the hollow structure 10 of this embodiment includes a core layer 20 in which a plurality of cells S are arranged in parallel, and a skin layer 30 joined to the upper surface 20a of the core layer 20. , a skin layer 40 bonded to the lower surface 20b of the core layer 20. Note that, in the hollow structure 10 and the core layer 20, the side to which the skin layer 30 is joined is the top, and the side to which the skin layer 40 is joined is the bottom.

The core layer 20 and the skin layers 30, 40 are made of a conventionally known thermoplastic resin. Examples of the thermoplastic resin constituting the core layer 20 and the skin layers 30 and 40 include polypropylene resin, polyamide resin, polyethylene resin, acrylonitrile-butadiene-styrene copolymer resin, acrylic resin, polybutylene terephthalate resin, etc. . The core layer 20 and the skin layers 30 and 40 are preferably made of the same thermoplastic resin, and in this embodiment are made of polypropylene resin.

As shown in FIGS. 1(b) and 1(c), the core layer 20 is formed by folding a single uneven sheet material made by vacuum forming a flat sheet material made of polypropylene resin into a predetermined shape. . The core layer 20 is composed of an upper wall part 21, a lower wall part 22, and a side wall part 23 that stands between the upper wall part 21 and the lower wall part 22 and forms a hexagonal cylindrical wall part. . Hexagonal columnar cells S are defined inside the core layer 20 by the upper wall 21 , the lower wall 22 , and the side wall 23 .

As shown in FIG. 1A, 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. 1(b), the upper end of the first cell S1 is closed by the upper wall portion 21, and the lower end is open downward without being closed. At the lower end edge of the side wall portion 23 of the first cell S1, which is the opening end of the first cell S1, a protrusion portion that protrudes inward of the first cell S1 so as to extend along the lower surface 20b of the core layer 20. 24 is formed. That is, in the first cell S1, the upper surface 20a of the core layer 20 is composed of the upper wall section 21, and the lower surface 20b is composed of the lower edge of the side wall section 23 and the protruding section 24.

On the other hand, as shown in FIG. 1(c), the lower end of the second cell S2 is closed by the lower wall portion 22, and the upper end is open upward without being closed. At the upper end edge of the side wall portion 23 of the second cell S2, which is the open end of the second cell S2, a protrusion portion that protrudes inward of the second cell S2 so as to extend along the upper surface 20a of the core layer 20. 25 is formed. That is, in the second cell S2, the lower surface 20b of the core layer 20 is composed of the lower wall section 22, and the upper surface 20a is composed of the upper edge of the side wall section 23 and the protruding section 25.

The thickness of the upper wall portion 21 of the first cell S1 and the thickness of the lower wall portion 22 of the second cell S2 are approximately the same. Further, the size of the protrusion 24 formed on the lower edge of the side wall 23 of the first cell S1 is relatively larger than the size of the protrusion 25 formed on the upper edge of the side wall 23 of the second cell S2. .

Further, a protrusion 26 is formed on the upper edge of the side wall 23 opposite to the opening end of the first cell S1 so as to extend along the lower surface of the upper wall 21. The amount of protrusion of the protrusion 26 is less than that of the protrusion 24, and the size of the protrusion 26 is smaller than that of the protrusion 24. A protrusion 27 is formed at the lower edge of the side wall 23 of the second cell S2, which is opposite to the open end of the second cell S2, so as to extend along the upper surface of the lower wall 22. The amount of protrusion of protrusion 27 is less than that of protrusion 25, and the size of protrusion 27 is smaller than that of protrusion 25.

As shown in FIG. 1A, the first cells S1 and the second cells S2 are arranged so that the first cells S1 or the second cells S2 are adjacent to each other in the X direction to form a column. Further, in the Y direction perpendicular to the X direction, the rows of first cells S1 and the rows of second cells S2 are alternately arranged.

As shown in FIG. 1(b) and FIG. 1(c), between adjacent first cells S1 and between adjacent second cells S2, the upper wall portion 21 and the lower wall portion 22 are It is divided by a side wall 23 that is vertically formed and has a two-layer structure including a first side wall 23a and a second side wall 23b. In the side wall portion 23 having a two-layer structure, each of the first side wall portion 23a and the second side wall portion 23b has a curved shape in a top view, with the center in the width direction slightly curved so as to swell toward the inner side of the cell S. There is. The first side wall portion 23a and the second side wall portion 23b are thermally welded to each other at their upper and lower edges, and are not thermally welded to each other at an intermediate portion in the vertical direction except for the upper and lower edges. The adjacent first cell S1 and second cell S2 are separated by a side wall 23 having a one-layer structure and formed perpendicular to the upper wall 21 and the lower wall 22.

At the upper end edge of the side wall portion 23 of the two-layer structure in the first cell S1, a protrusion portion (not shown) that protrudes from the side wall portion 23 is formed in the heat-welded portion. The protruding portion is formed along the curved shape of the first side wall portion 23a and the second side wall portion 23b. As a result, the first side wall portion 23a and the second side wall portion 23b are connected to each other, and in the vertically intermediate portion excluding the upper and lower edges, the first side wall portion 23a and the second side wall portion 23b are not joined to each other. Further, at the lower end edge of the side wall portion 23 of the two-layer structure in the second cell S2, a protrusion portion (not shown) that protrudes from the side wall portion 23 is formed in the heat-welded portion. The protruding portion is formed along the curved shape of the first side wall portion 23a and the second side wall portion 23b. As a result, the first side wall portion 23a and the second side wall portion 23b are connected to each other, and in the vertically intermediate portion excluding the upper and lower edges, the first side wall portion 23a and the second side wall portion 23b are not joined to each other. The protrusion length of the protrusion formed between the two-layer structure side wall portions 23 of the first cell S1 and the protrusion length of the protrusion portion formed between the two-layer structure side wall portions 23 of the second cell S2 are approximately They have the same width and approximately the same size. Furthermore, these protrusions have a shorter protrusion length and smaller size than the protrusions 24, 25, 26, and 27.

The thickness of the first side wall portion 23a and the second side wall portion 23b formed between adjacent first cells S1 are approximately the same. Further, the thickness of the first side wall portion 23a and the thickness of the second side wall portion 23b formed between adjacent second cells S2 are approximately the same. On the other hand, the thickness of the first side wall portion 23a and the second side wall portion 23b formed between the adjacent first cells S1 is the same as the thickness of the first side wall portion 23a and the second side wall portion 23b formed between the adjacent second cells S2. It is relatively thinner than the thickness of the second side wall portion 23b.

Further, the thickness of the side wall portion 23 having a one-layer structure is relatively thicker than the thickness of the first side wall portion 23a or the second side wall portion 23b formed between the first cells S1, and It is relatively thinner than the thickness of the first side wall portion 23a or the second side wall portion 23b formed in the.

As shown in FIG. 1A, the skin layers 30 and 40 are bonded to the upper surface 20a and lower surface 20b of the core layer 20, respectively, via adhesive layers (not shown). The skin layer 30 is joined to the upper wall portion 21 on the upper surface of the first cell S1, and is joined to the upper end of the side wall portion 23 and the protruding portion 25 on the upper surface of the second cell S2. Further, the skin layer 40 is joined to the lower end of the side wall portion 23 and the protruding portion 24 on the lower surface of the first cell S1, and is joined to the lower wall portion 22 on the lower surface of the second cell S2. Therefore, the upper surface of the hollow structure 10 has a two-layer structure consisting of the upper wall portion 21 of the core layer 20 and the skin layer 30 in the first cell S1, and a one-layer structure consisting of only the skin layer 30 in the second cell S2. It has a two-layer structure in which the protrusion 25 is partially joined to the skin layer 30. Further, the lower surface of the hollow structure 10 has a two-layer structure consisting of the lower wall portion 22 of the core layer 20 and the skin layer 40 in the second cell S2, and a one-layer structure consisting of only the skin layer 40 in the first cell S1. It has a two-layer structure in which the protrusion 24 is partially joined to the skin layer 30.

Next, a method for manufacturing the hollow structure 10 of this embodiment will be described based on FIGS. 2 and 3.
The method for manufacturing the hollow structure 10 includes a vacuum forming process, a core layer forming process, and a skin layer bonding process. The vacuum forming process is a process of vacuum forming a concavo-convex sheet material 100 having convex bulges from a single flat sheet material made of thermoplastic resin. The core layer forming step is a step of forming the core layer 20 by folding and heating the uneven sheet material 100. The skin layer joining step is a step of joining the skin layers 30 and 40 to the upper surface 20a and lower surface 20b of the core layer 20 to form the hollow structure 10. Each process for manufacturing these hollow structures 10 is performed in a series of steps using the apparatus T shown in FIG.

First, the apparatus shown in FIG. 3 will be explained. FIG. 3 shows the device T as a schematic diagram, with the left side being the upstream side and the right side being the downstream side. The device T includes, in order from the upstream side, a sheet roll 61 wound with a flat sheet material made of thermoplastic resin, a vacuum forming drum 62 for the vacuum forming process, and a first conveyor for the core layer forming process. 63, sheet rolls 64 and 65 wound with sheets serving as raw materials for the skin layers 30 and 40, and a second conveyor 66 for the skin layer joining process.

As shown in FIG. 3, in the vacuum forming process, a flat sheet material made of thermoplastic resin wound around a sheet roll 61 is supplied to a vacuum forming drum 62. By passing through the vacuum forming drum 62, a protruding bulge is formed in the flat sheet material, and the uneven sheet material 100 having a predetermined uneven shape is formed. The vacuum forming drum 62 is rotatably supported and configured to be heated to a predetermined temperature. The rotation speed of the vacuum forming drum 62 is set to be equal to the rotation speed of the sheet roll 61. Further, a cylindrical molding die is attached to the vacuum forming drum 62, and is configured to be able to draw a vacuum through a through hole formed on the outer peripheral surface of the molding die (not shown). . The outer circumferential surface of the molding die has an uneven shape (a first bulge 110 and a second bulge, which will be described later) formed on the uneven sheet material 100 so that the X direction of the uneven sheet material 100 is along the circumferential direction. An uneven shape similar to that of the bulged portion 120) is formed. As a result, the flat sheet material conveyed along the vacuum forming drum 62 is evacuated toward the outer peripheral surface of the vacuum forming drum 62 to form a bulge.

As shown in FIG. 2(a), the uneven sheet material 100 formed by the vacuum forming process is formed with a band-shaped first bulging portion 110 projecting upward. As a result of the first bulging part 110 being formed to bulge out from the flat sheet material, there is a second bulging part 110 that protrudes downward relative to the first bulging part 110 between the first bulging parts 110. A bulge 120 is formed. The first bulging portions 110 and the second bulging portions 120 are arranged alternately in the width direction (Y direction). Further, the first bulging portion 110 and the second bulging portion 120 are arranged to extend in the X direction. The first bulge 110 when the uneven sheet material 100 is viewed from above and the second bulge 120 when the uneven sheet material 100 is viewed from below have the same shape and are shifted by 1/2 pitch in the X direction. It is formed in the same position.

The first bulging portion 110 includes an upper surface 110a, a pair of side surfaces 110b, and a pair of end surfaces 110c, and has a trapezoidal cross-sectional shape in the Y direction obtained by dividing a regular hexagon into two by the longest diagonal. The pair of end surfaces 110c are formed at the folding line P shown in FIG. 2(a). The angle between the end surface 110c and the upper surface 110a is about 90 degrees.

On the other hand, the second bulging portion 120 is composed of a lower surface 120a, a pair of side surfaces 120b, and a pair of end surfaces 120c, and has a trapezoidal cross-sectional shape in the Y direction obtained by dividing a regular hexagon into two by the longest diagonal line. . The pair of end surfaces 120c are formed at the folding line Q shown in FIG. 2(a). The angle between the end surface 120c and the lower surface 120a is about 90 degrees. The length of the second bulging portion 120 in the X direction, that is, the length between the pair of end surfaces 120c is the same as the length of the first bulging portion 110 in the X direction, that is, the length between the pair of end surfaces 110c. be. The end surface 120c of the second bulge 120 is located at the center of the first bulge 110 in the X direction. Although the side surface 110b of the first bulging portion 110 and the side surface 120b of the second bulging portion 120 are separated for convenience of explanation, they have the same configuration.

In the vacuum forming process, the first bulging portion 110 is formed to bulge relative to the flat sheet material, so the thickness of the upper surface 110a of the first bulging portion 110 is thinner than the thickness of the flat sheet material. ing. Moreover, the thickness of the pair of side surfaces 110b is thicker than the thickness of the top surface 110a, and thinner than the thickness of the flat sheet material. Furthermore, the thickness of the pair of end surfaces 110c is also thicker than the thickness of the upper surface 110a and thinner than the thickness of the flat sheet material.

On the other hand, the thickness of the lower surface 120a of the second bulging portion 120 is equivalent to the thickness of the flat sheet material. Further, the thickness of the pair of side surfaces 120b is thinner than the thickness of the lower surface 120a, that is, the thickness of the flat sheet material. Furthermore, the thickness of the pair of end surfaces 120c is also thinner than the thickness of the lower surface 120a, that is, the thickness of the flat sheet material.

In this way, in the vacuum forming process, the first bulging portion 110 formed by partially bulging the flat sheet material upward and the first bulge An uneven sheet material 100 having a second bulging portion 120 formed as a result of bulging the portion 110 is obtained.

As shown in FIG. 3, in the core layer forming step, the uneven sheet material 100 is conveyed downstream by the first conveyor 63 while its vertical movement is restricted. At this time, the conveyance speed of the first conveyor 63 is set to be slower than the rotational speed of the sheet roll 61 and the vacuum forming drum 62, which are arranged upstream of the first conveyor 63. That is, the conveyance speed by the first conveyor 63 is set to be slower than the supply speed of the uneven sheet material 100 supplied from the upstream side. Further, the first conveyor 63 is provided with a heating device 63a for heating the temperature between the first conveyors 63 to a predetermined temperature. Therefore, when the uneven sheet material 100 is conveyed between the first conveyors 63, it is heated and folded while being compressed in the downstream direction, thereby forming the core layer 20. Then, when being transported between the first conveyors 63, the core layer 20 is heated and slightly compressed in the vertical direction.

As shown in FIGS. 2(b) and 2(c), since the conveyance speed of the first conveyor 63 is slower than the supply speed of the uneven sheet material 100 supplied from the upstream side, the uneven sheet material 100 is It is sequentially folded along folding lines P and Q. Thereby, the core layer 20 is formed. Specifically, as shown in FIG. 2(b), the uneven sheet material 100 is mountain-folded along the folding line P and valley-folded along the folding line Q.

As shown in FIG. 2(c), one first bulging portion 110 is valley-folded along a folding line Q provided at the central portion in the X direction, so that an upper surface 110a on the right side in the X direction and an upper surface on the left side in the X direction 110a abuts in an upright state. In the folded first bulging portion 110, the upper surface 110a on the right side in the X direction and the upper surface 110a on the left side in the X direction, which are in contact with each other in the upright state, form the side wall portion 23 of the two-layer structure of the core layer 20, and the side wall portion 110b As a result, the side wall portion 23 of the core layer 20 having a one-layer structure is formed. At the upper end of the side wall portion 23, an upper wall portion 21 consisting of the end surfaces 110c of the adjacent first bulging portions 110 is formed, forming the first cell S1.

In addition, one second bulging portion 120 is mountain-folded at the folding line P provided at the center of the adjacent folding lines Q in the X direction, and the lower surface 120a on the right side in the X direction and the lower surface 120a on the left side in the X direction are in an upright state. contact with. In the folded second bulging portion 120, the lower surface 120a on the right side in the X direction and the lower surface 120a on the left side in the X direction, which are in contact with each other in the upright state, form the side wall portion 23 of the two-layer structure of the core layer 20, and the side wall portion 120b As a result, 20 single-layer side wall portions 23 of the core layer are formed. At the lower end of the side wall portion 23, a lower wall portion 22 consisting of the end surfaces 120c of the adjacent second bulging portions 120 is formed, forming a second cell S2.

In the core layer forming step, the first conveyor 63 is heated by a heating device 63a. Therefore, the folded core layer 20 is heated and pressed by the first conveyor 63. As a result, the upper and lower edges of the two-layer side wall portion 23 of the folded core layer 20 are thermally welded to form a protruding portion smaller than the protruding portions 24, 25, 26, and 27, and the first side wall portion 23a and the second side wall portion 23b are in a connected state. On the other hand, the first side wall part 23a and the second side wall part 23b are joined to the vertical middle part of the two-layered side wall part 23 without being thermally welded except for the upper and lower edges. A non-bonded part is formed.

Further, when the core layer 20 is conveyed between the first conveyors 63, it is heated and slightly compressed in the vertical direction. is thermally melted and pressed vertically. As a result, the lower end edge of the side wall portion 23 is partially thermally melted, and a protrusion portion 24, which is a burr-shaped protrusion extending toward the inside of the first cell S1, is formed. Similarly, in the second cell S2 where the upper wall portion 21 is not formed, the upper end of the side wall portion 23 is thermally melted and pressed in the vertical direction. As a result, the upper end edge of the side wall portion 23 is partially thermally melted, and a protrusion portion 25, which is a burr-shaped protrusion extending toward the inside of the second cell S2, is formed.

Here, the side wall part 23 with a two-layer structure that partitions the first cell S1 is formed by the upper surface 110a of the first bulge part 110, and the side wall part 23 with a two-layer structure that partitions the second cell S2 is It is formed by the lower surface 120a of the second bulging portion 120. The thickness of the lower surface 120a of the second bulging portion 120 is approximately the same as the thickness of the flat sheet material, while the thickness of the upper surface 110a of the first bulging portion 110 is thinner than the thickness of the flat sheet material. Therefore, the thickness of the side wall portion 23 having a two-layer structure that partitions the first cell S1 is thinner than the thickness of the side wall portion 23 having a two-layer structure that partitions the second cell S2.

Further, the thickness of the side surface 110b of the first bulging portion 110 is thinner than the thickness of the flat sheet material, and the thickness of the side surface 120b of the second bulging portion 120 is also thinner than the thickness of the flat sheet material. Therefore, the thickness of the side wall portion 23 of the one-layer structure that partitions the first cell S1 and the second cell S2 is greater than the thickness of the first side wall portion 23a or the second side wall portion 23b formed between the first cells S1. It is relatively thick and relatively thinner than the thickness of the first side wall portion 23a or the second side wall portion 23b formed between the second cells S2.

Furthermore, the thickness of the pair of end surfaces 110c of the first bulging portion 110 is thinner than the thickness of the flat sheet material, and the thickness of the pair of end surfaces 120c of the second bulging portion 120 is also thinner than the thickness of the flat sheet material. . Therefore, the thickness of the upper wall portion 21 of the first cell S1 and the thickness of the lower wall portion 22 of the second cell S2 are approximately the same.

When the core layer 20 is conveyed between the first conveyors 63, heat from the heating device 63a is transmitted to the end portion of the core layer 20 in the thickness direction. In the first cell S1, the upper surfaces 110a of the first bulging portions 110 abut against each other to form a two-layer side wall portion 23, and the side surfaces 110b form a one-layer side wall portion 23. Therefore, more resin pools are formed on the lower edge of the side wall portion 23 in the side wall portion 23 having a two-layer structure than in the side wall portion 23 having a single layer structure. After that, when the core layer 20 is cooled and the resin pool solidifies, the resin pool becomes a protrusion 24 as a burr-like protrusion, and the single-layer side wall 23 is attached to the lower edge of the two-layer side wall 23. A protrusion 24 is formed that is relatively larger than the lower end edge. Further, the protrusion length of the protrusion 24 formed at the lower end edge of the side wall portion 23 having a two-layer structure is larger than the protrusion length of the protrusion portion 24 formed at the lower end edge of the side wall portion 23 having a single layer structure. The protruding length of the protruding part 24 formed on the lower edge of the side wall part 23 with a two-layer structure is approximately the same width depending on the part, and the protruding length of the protruding part 24 formed on the lower edge of the side wall part 23 with a one-layer structure is The width is approximately the same depending on the part.

In the second cell S2, the lower surfaces 120a of the second bulging portions 120 abut against each other to form a two-layer side wall portion 23, and the side surfaces 120b form a one-layer side wall portion 23. Therefore, more resin pools are formed on the upper edge of the side wall portion 23 in the side wall portion 23 having a two-layer structure than in the side wall portion 23 having a single layer structure. After that, when the core layer 20 is cooled and the resin pool solidifies, the resin pool becomes a protrusion 25 as a burr-like protrusion, and the single-layer side wall 23 is attached to the upper edge of the two-layer side wall 23. A protrusion 25 is formed that is relatively larger than the upper end edge. Further, the protrusion length of the protrusion 25 formed on the upper edge of the side wall portion 23 having a two-layer structure is greater than the protrusion length of the protrusion portion 25 formed on the upper edge of the side wall portion 23 having a single layer structure. The protruding length of the protruding part 25 formed on the upper edge of the side wall part 23 with a two-layer structure is approximately the same width depending on the part, and the protruding length of the protruding part 25 formed on the upper edge of the side wall part 23 with a one-layer structure is The width is approximately the same depending on the part.

Moreover, the side wall portion 23 of the two-layer structure of the first cell S1 is relatively thinner than the side wall portion 23 of the two-layer structure of the second cell S2. Therefore, it is more likely to be melted by the heat from the heating device 63a. As a result, more resin pools are formed at the lower end edge of the side wall portion 23 of the first cell S1 than at the upper end edge of the side wall portion 23 of the second cell S2. Thereafter, when the core layer 20 is cooled and the resin pool solidifies, a larger burr-shaped protrusion is formed on the lower edge of the side wall 23 of the first cell S1 than on the upper edge of the side wall 23 of the second cell S2. will be done. As a result, the size of the protrusion 24 formed on the lower edge of the side wall 23 of the first cell S1 is relatively larger than the size of the protrusion 25 formed on the upper edge of the side wall 23 of the second cell S2. growing.

A resin pool is formed on the upper end edge of the side wall portion 23 of the first cell S1 by heating and pressing the core layer 20 while being conveyed between the first conveyors 63, and as a result, a burr-like protrusion is formed. A protrusion 26 is formed. Similarly, a resin pool is formed on the lower edge of the side wall portion 23 of the second cell S2 by heating and pressing the core layer 20 while being conveyed between the first conveyors 63, and as a result, a resin pool is formed in the shape of a burr. A protrusion 27, which is a protrusion, is formed.

In the skin layer bonding step, skin layers 30 and 40 are bonded to both upper and lower surfaces of the core layer 20.
The core layer 20, which is folded and has the protrusions 24, 25 formed therein, moves toward the second conveyor 66. The conveyance speed by the second conveyor 66 is set to be equal to the conveyance speed by the first conveyor 63. Further, the second conveyor 66 is provided with a heating device 66a. Near the entrance of the second conveyor 66, sheet rolls 64 and 65, each of which is wound with a thermoplastic resin sheet that will become the skin layers 30 and 40, are arranged. An adhesive (not shown) is applied to the sheets wound around the sheet rolls 64 and 65. The adhesive here is preferably a hot melt adhesive made of a resin compatible with polypropylene resin, but the adhesive may be omitted. When the adhesive is omitted, for example, a thermoplastic resin layer having a low melting point and made of the same material as the skin layers 30 and 40 may be formed. Moreover, the adhesive and the low melting point thermoplastic resin layer can also be omitted.

As shown in FIG. 3, a thermoplastic resin sheet wound around sheet rolls 64 and 65 is supplied to the upper surface 20a and lower surface 20b of the core layer 20 passing between the second conveyor 66. The adhesive applied to the sheet is in a molten state. Since the second conveyor 66 is provided with a heating device 66a, the adhesive applied to the sheet is maintained in a molten state when passing through the second conveyor 66.

Subsequently, the core layer 20 with sheets arranged on both the upper and lower surfaces is moved downstream and cooled. As a result, the adhesive applied to the sheet is cooled and solidified, and the sheet is joined to the upper surface 20a and lower surface 20b of the core layer 20. The sheet joined to the upper surface 20a of the core layer 20 becomes the skin layer 30, and the sheet joined to the lower surface 20b of the core layer 20 becomes the skin layer 40. In this way, a hollow structure 10 is obtained in which the skin layers 30 and 40 are joined to the upper surface 20a and lower surface 20b of the core layer 20.

Next, the function of the hollow structure 10 will be explained based on FIG. 1.
As shown in FIG. 1(a), in the core layer 20 formed by folding the uneven sheet material 100, the side wall portions 23 that partition the cells S are erected in the thickness direction of the core layer 20 (hollow structure 10). The plurality of cells S are formed to extend in the thickness direction of the core layer 20 (hollow structure 10). Among the plurality of cells S, the upper surface 20a of the core layer 20 is composed of the upper wall portion 21 of the first cell S1, the upper edge of the side wall portion 23 of the second cell S2, and the protruding portion 25. , are formed to protrude so as to extend inward of the second cell S2. A skin layer 30 is bonded to the upper surface 20a of the core layer 20.

Since the skin layer 30 is joined to the upper edge of the upper wall portion 21 of the first cell S1 and the side wall portion 23 of the second cell S2 and the protruding portion 25, the skin layer 30 is bonded to the upper edge of the upper wall portion 21 of the first cell S1 and the side wall portion 23 of the second cell S2, and to the protruding portion 25. , the bond strength becomes stronger.

Further, the lower surface 20b of the core layer 20 is composed of the lower edge and protrusion 24 of the side wall 23 of the first cell S1 and the lower wall 22 of the second cell S2. It is formed to protrude so as to extend inwardly. A skin layer 40 is bonded to the lower surface 20b of the core layer 20.

Since the skin layer 40 is joined to the lower edge of the lower wall portion 22 of the second cell S2, the lower edge of the side wall portion 23 of the first cell S1, and the protruding portion 24, the skin layer 40 is different from the case where the protruding portion 24 is not formed. , the bond strength becomes stronger.

Furthermore, the first side wall 23a or the second side wall 23b, which has a two-layer structure that partitions the first cells S1, is relative to the side wall 23 that has a one-layer structure that partitions the first cell S1 and the second cell S2. The first side wall portion 23a or the second side wall portion 23b having a two-layer structure that partitions the second cells S2 is relatively thick. Then, due to the heat from the heating device 63a of the first conveyor 63, the side wall portion 23 of the two-layer structure between the first cells S1 is more easily melted than the side wall portion 23 of the two-layer structure between the second cells S2. As a result, since the protrusion 24 formed in the first cell S1 is larger than the protrusion 25 formed in the second cell S2, the lower surface 20b of the core layer 20 where the protrusion 24 is formed is larger than the upper surface 20a The bonding strength of the skin layer 40 becomes relatively strong.

According to the hollow structure 10 of this embodiment and its manufacturing method, the following effects can be obtained.
(1) The hollow structure 10 of the present embodiment includes a core layer 20 in which a plurality of cells S are arranged in parallel and partitioned by sidewall portions 23 extending in the thickness direction. In the first cell S1 of the core layer 20, a protrusion 24 that protrudes inward of the first cell S1 is formed at the lower edge of the side wall 23, and a protrusion 24 is formed in the first cell S1 of the core layer 20. Here, a protrusion 25 that protrudes inward of the second cell S2 is formed on the upper edge of the side wall 23.

Therefore, in the portions where the protrusions 24 and 25 are formed, the side wall portion 23 is reinforced and the strength of the core layer 20 is improved. A hollow structure with excellent strength can be obtained.
(2) The hollow structure 10 of this embodiment includes a core layer 20 and skin layers 30 and 40 joined to the upper surface 20a and lower surface 20b of the core layer 20. The protruding portion 24 protrudes along the lower surface 20b of the core layer 20 at the lower end edge of the side wall portion 23 on the side to which the skin layer 40 is joined. Further, the protruding portion 25 protrudes along the upper surface 20a of the core layer 20 at the upper end edge of the side wall portion 23 on the side to which the skin layer 30 is joined.

Therefore, on the lower surface 20b of the core layer 20, the bonding area of the core layer 20 to the skin layer 40 increases due to the protrusion 24, and on the upper surface 20a of the core layer 20, the bonding area of the core layer 20 to the skin layer 30 due to the protrusion 25. increases. Thereby, the bonding strength of the skin layers 30 and 40 to the core layer 20 can be improved.

(3) In the manufacturing method of the hollow structure 10, in the core layer forming step, the core layer 20 is heated and compressed in its thickness direction, so that the side wall portion 23 protrudes toward the inner side of the cell S. Projections 24 and 25 are formed.

Therefore, the protruding parts 24 and 25 can be formed integrally with the side wall part 23 by compressing the thermoplastic resin core layer 20 in its thickness direction in a heated state and thermally melting the side wall part 23. As the protrusions 24 and 25 for reinforcing the side wall 23, the strength of the side wall 23 can be improved more easily than when other members are joined.

(4) In the core layer forming step, the core layer 20 is formed by folding a single uneven sheet material 100 made of vacuum-formed thermoplastic resin, and the core layer 20 is compressed in the thickness direction in a heated state. .

Therefore, the formation of the core layer 20 and the formation of the protrusions 24 and 25 can be performed in the same process. The manufacturing process of the hollow structure 10 having excellent strength can be simplified.
Furthermore, the formation of the core layer 20 and the thermal welding of the upper and lower edges of the two-layered side wall portion 23 of the core layer 20 can be performed simultaneously.

(5) The hollow structure 10 of this embodiment is manufactured through a vacuum forming process, a core layer forming process, and a skin layer bonding process, and each process is performed in a series of steps by the apparatus T.
Therefore, the hollow structure 10 can be manufactured with excellent productivity and mass production, and at an advantageous cost.

(6) The conveyance speed by the first conveyor 63 that constitutes the core layer forming step is set to be slower than the rotational speed of the sheet roll 61 and the vacuum forming drum 62 that are arranged upstream of the first conveyor 63. It is set. That is, the conveyance speed by the first conveyor 63 is slower than the supply speed of the uneven sheet material 100 that has passed through the vacuum forming drum 62.

Therefore, the uneven sheet material 100 is sequentially folded along the folding lines P and Q. By moving the uneven sheet material 100, the core layer forming step can be easily performed.
(Second embodiment)
Next, a hollow structure 11 according to a second embodiment of the present invention will be described. In the hollow structure 11 of the second embodiment, the structure of the uneven sheet material 200 for forming the core layer 50 of the hollow structure 11 is different from the structure of the uneven sheet material 100 of the first embodiment. Therefore, the configurations of the upper wall portion 51, lower wall portion 52, and side wall portion 53 of the core layer 50 are different from the core layer 20 of the first embodiment. Here, parts that are different from the first embodiment will be mainly described.

As shown in FIGS. 4(a) to 4(c), the core layer 50 of the second embodiment is formed by folding a single uneven sheet material made of thermoplastic resin molded into a predetermined shape. The cells S defined inside the core layer 50 include a third cell S3 and a fourth cell S4 having different configurations. As shown in FIG. 4(b), in the third cell S3, an upper wall portion 51 having a two-layer structure is provided above the side wall portion 53. Each layer of the upper wall portion 51 of this two-layer structure is joined to each other. Further, in the third cell S3, a lower wall portion 52 having a one-layer structure is provided below the side wall portion 53. On the other hand, as shown in FIG. 4C, in the fourth cell S4, an upper wall portion 51 having a one-layer structure is provided above the side wall portion 53. Further, in the fourth cell S4, a lower wall portion 52 having a two-layer structure is provided below the side wall portion 53. Each layer of the lower wall portion 52 of this two-layer structure is joined to each other.

As shown in FIG. 4(a), the third cells S3 are arranged in a row along the X direction. Similarly, the fourth cells S4 are arranged in a row along the X direction. The rows of third cells S3 and the rows of fourth cells S4 are arranged alternately in the Y direction orthogonal to the X direction. The core layer 50 has a honeycomb structure as a whole due to these third cells S3 and fourth cells S4. Note that in FIG. 4A, illustration of the upper wall portion 51 and lower wall portion 52 of the two-layer structure is omitted.

As shown in FIGS. 4(b) and 4(c), the adjacent third cells S3 and the adjacent fourth cells S4 are each partitioned by side wall portions 53 having a two-layer structure. In the third cell S3 and the fourth cell S4, the side wall portions 53 of the two-layer structure are thermally welded to each other at both the upper and lower end portions, but are not thermally welded to each other at the central portion in the thickness direction of the core layer 50. It has a part. The adjacent third cell S3 and fourth cell S4 are separated by a side wall portion 53 having a one-layer structure and formed perpendicularly to the upper wall portion 51 and the lower wall portion 52.

The thickness of the first side wall portion 53a and the second side wall portion 53b, which constitute the two-layered side wall portion 53 formed between adjacent third cells S3, are approximately the same. Moreover, the thickness of the first side wall part 53a and the thickness of the second side wall part 53b, which constitute the two-layered side wall part 53 formed between adjacent fourth cells S4, are approximately the same. On the other hand, the thickness of the first side wall part 53a and the second side wall part 53b formed between the adjacent third cells S3 is the same as the thickness of the first side wall part 53a and the second side wall part 53b formed between the adjacent fourth cells S4. It is relatively thinner than the thickness of the second side wall portion 53b.

Further, the thickness of the side wall portion 53 having a one-layer structure is relatively thicker than the thickness of the first side wall portion 53a or the second side wall portion 53b formed between the third cells S3, and It is relatively thinner than the thickness of the first side wall portion 53a or the second side wall portion 53b formed in the.

As shown in FIG. 4(b), at the upper end of the side wall portion 53 of the third cell S3, a thick portion 54 in which the side wall portion 53 is partially thickened extends toward the inner side of the third cell S3. It is formed protrudingly. The thick portion 54 is formed at the upper edge of the side wall portion 53 so as to be integrated with the lower surface of the upper wall portion 51 . Further, as shown in FIG. 4(c), at the upper end of the side wall portion 53 of the fourth cell S4, a thick portion 55 in which the side wall portion 53 is partially thickened is provided inside the fourth cell S4. It is formed to protrude to the side. The thick portion 55 is formed at the upper end edge of the side wall portion 53 so as to be integrated with the lower surface of the upper wall portion 51 . The size of the thick part 54 formed at the upper end of the side wall part 53 of the third cell S3 is relatively smaller than the size of the thick part 55 formed at the upper end of the side wall part 53 of the fourth cell S4. .

Next, a method for manufacturing the hollow structure 11 according to the present embodiment will be described with reference to FIG. 5, focusing on the differences from the first embodiment. The hollow structure 11 of the second embodiment is also manufactured using the apparatus T used to manufacture the hollow structure 10 of the first embodiment. Here, the shape of the uneven sheet material 200 formed in the vacuum forming process is different from that of the first embodiment. That is, the shape of the outer peripheral surface of the molding die attached to the vacuum forming drum 62 in the vacuum forming process is different from that of the first embodiment.

As shown in FIG. 5(a), a convex bulging region 220 is formed from a flat sheet material made of thermoplastic resin wound around a sheet roll 61 by vacuuming with a vacuum forming drum 62. A sheet material 200 is obtained. The core layer 50 of the hollow structure 11 is formed by folding the uneven sheet material 200.

In the uneven sheet material 200, band-shaped planar regions 210 and bulging regions 220 are arranged alternately in the longitudinal direction (X direction) of the uneven sheet material 200. In the bulging region 220, a first bulging portion 221 having a downward groove shape in cross section and consisting of an upper surface 221a and a pair of side surfaces 221b is formed over the entire length of the bulging region 220 in the extending direction (Y direction). Note that the angle between the upper surface 221a and the side surface 221b of the first bulging portion 221 is preferably 90 degrees, and as a result, the cross-sectional shape of the first bulging portion 221 has a downward U-shape. Further, the width of the first bulging portion 221 (the length in the lateral direction of the upper surface 221a) is equal to the width of the plane area 210, and the bulging height of the first bulging portion 221 (the length in the lateral direction of the side surface 221b) is equal to the width of the plane area 210. length) is set to be twice the length.

Further, in the bulging region 220, a plurality of second bulging portions 222 having a trapezoidal cross-sectional shape obtained by bisecting a regular hexagon by the longest diagonal line are arranged so as to be perpendicular to the first bulging portion 221. It is formed. The height of the second bulge 222 (the height of the upper surface 222a) is set to be equal to the height of the first bulge 221 (the height of the upper surface 221a). Further, the interval between adjacent second bulging parts 222 is equal to the width of the upper surface 222a of the second bulging parts 222.

Note that the first bulging portion 221 and the second bulging portion 222 are formed by partially bulging a flat sheet material upward by vacuum forming using the plasticity of the sheet.
In the vacuum forming process, the first bulging part 221 and the second bulging part 222 are formed to bulge relative to the flat sheet material, so the thickness of the upper surface 221a of the first bulging part 221 is flat. It is thinner than the thickness of the sheet material. Moreover, the thickness of the pair of side surfaces 221b is thicker than the thickness of the upper surface 221a, and thinner than the thickness of the flat sheet material. Further, the thickness of the upper surface 222a of the second bulging portion 222 is thinner than the thickness of the flat sheet material, and is approximately the same as the thickness of the upper surface 221a of the first bulging portion 221. The thickness of the side surface 222b and end surface 222c of the second bulging portion 222 is thicker than the thickness of the upper surface 222a, and thinner than the thickness of the flat sheet material.

As shown in FIGS. 4(b) and 4(c), in the core layer forming step, the uneven sheet material 200 is conveyed downstream by the first conveyor 63 while its vertical movement is restricted. Folded. The uneven sheet material 200 is folded along the folding lines P and Q to form the core layer 50. Specifically, the uneven sheet material 200 is valley-folded along the folding line P between the plane region 210 and the bulging region 220, and at the folding line Q between the upper surface 221a and the side surface 221b of the first bulging portion 221. Fold in a mountain and compress in the X direction. Then, the upper surface 221a and the side surface 221b of the first bulging portion 221 overlap, and the end surface 222c of the second bulging portion 222 and the plane area 210 overlap, so that one Y A prismatic partition body 230 extending in the direction is formed. A hollow plate-shaped core layer 50 is formed by continuously forming such partitions 230 in the X direction.

When compressing the uneven sheet material 200 as described above, the upper wall 51 of the core layer 50 is formed by the upper surface 221a and the side surface 221b of the first bulge 221, and the end surface 222c of the second bulge 222 and the plane region 210 form the lower wall portion 52 of the core layer 50 . As shown in FIG. 4C, a portion of the upper wall portion 51 where the upper surface 221a and the side surface 221b of the first bulging portion 221 overlap to form a two-layer structure, and a portion of the lower wall portion 52 where the upper surface 221a and the side surface 221b of the first bulging portion 221 overlap to form a two-layer structure. The portions where the end surface 222c of the protruding portion 222 and the plane region 210 are folded to form a two-layer structure serve as overlapping portions 231, respectively.

Further, the hexagonal column-shaped area formed by folding the second bulging portion 222 becomes the fourth cell S4, and the hexagonal column-shaped area partitioned and formed between the pair of adjacent partition bodies 230 becomes the fourth cell S4. It becomes 3 cells S3. Therefore, the upper wall part 51 of the third cell S3 is formed by the upper surface 221a and the side surface 221b of the first bulging part 221, and the upper wall part 51 of the fourth cell S4 is formed by the upper surface 221a of the first bulging part 221. It is formed. On the other hand, the lower wall portion 52 of the third cell S3 is formed by a plane region 210, and the lower wall portion 52 of the fourth cell S4 is formed by the end surface 222c of the second bulging portion 222 and the plane region 210. In other words, the upper wall portion 51 formed by the bulged portion is relatively thinner than the lower wall portion 52 formed by including the portion where the planar sheet material is not bulged. In addition, in the side wall portion 53 having a two-layer structure, the side wall portion 53 of the fourth cell S4, which is formed by the upper surfaces 222a of the second bulging portions 222 being in contact with each other, is a portion of the bulging region 220 that is not bulged. It is thinner than the side wall portion 53 of the third cell S3, which is formed by contacting each other.

In the core layer forming step, the first conveyor 63 is heated by a heating device 63a. Therefore, the folded core layer 50 is heated and pressed by the first conveyor 63. As a result, the upper and lower edges of the two-layered side wall portion 53 of the folded core layer 50 are thermally welded, while the portions other than the upper and lower edges are not thermally welded.

Further, when the core layer 20 is conveyed between the first conveyors 63, it is heated and slightly compressed in the vertical direction, so that the heat from the heated upper wall portion 51 or the lower wall portion 52 is transferred to the side wall portion 53. As a result, the thermoplastic resin is thermally melted, and thick portions 54 and 55 are partially formed in the side wall portion 53. At this time, since the upper wall part 51 of the core layer 50 is relatively thinner than the lower wall part 52, the heat from the heating device 63a is transmitted through the upper wall part 51 more than through the lower wall part 52. This is easily transmitted to the side wall portion 53. As a result, in the core layer forming step, a resin pool is likely to be formed at the upper end portion of the side wall portion 53 due to thermal melting of the side wall portion 53 . By subsequent cooling, the formed resin pools become thick parts 54, 55, and the upper end of the side wall part 53 has a thick part 54, which protrudes inward of the third cell S3 and the fourth cell S4. 55 will be formed.

Further, the side wall portion 53 having a two-layer structure that partitions the fourth cells S4 from each other is thinner than the side wall portion 53 having a two-layer structure that partitions the third cells S3 from each other. Therefore, the heat from the heating device 63a is more easily transmitted to the two-layered side wall portion 53 that partitions the fourth cells S4 than to the two-layered side wall portion 53 that partitions the third cells S3. As a result, in the core layer forming step, larger resin pools are more likely to form on the two-layer side wall portions 53 that partition the fourth cells S4 than on the two-layer side wall portions 53 that partition the third cells S3. . As a result, the size of the thick portion 55 formed at the upper end of the side wall portion 53 of the fourth cell S4 is relatively larger than the size of the thick portion 54 formed at the upper end portion of the side wall portion 53 of the third cell S3. becomes smaller.

According to the hollow structure 11 of this embodiment and its manufacturing method, in addition to (5) and (6) in the first embodiment, the following effects can be obtained.
(7) Thick parts 54 and 55 are formed on the side wall part 53 of the core layer 50.

Therefore, the strength of the side wall portion 53 is improved due to the presence of the thick portions 54 and 55.
(8) In the manufacturing method of the hollow structure 11, in the core layer forming step, the core layer 50 is heated and compressed in its thickness direction, so that the side wall portion 53 protrudes toward the inner side of the cell S. Thick wall portions 54 and 55 are formed.

Therefore, the thick portions 54 and 55 can be formed integrally with the side wall portion 53 by compressing the thermoplastic resin core layer 50 in its thickness direction in a heated state and thermally melting the side wall portion 53. As the thick parts 54 and 55 for reinforcing the side wall part 53, the strength of the side wall part 53 can be improved more easily than when other members are joined.

(9) In the core layer forming step, the core layer 50 is formed by folding a single uneven sheet material 200 made of vacuum-formed thermoplastic resin, and the core layer 50 is compressed in the thickness direction in a heated state. .

Therefore, the formation of the core layer 50 and the formation of the thick portions 54 and 55 can be performed in the same process. The manufacturing process of the hollow structure 11 having excellent strength can be simplified.
Furthermore, the formation of the core layer 50 and the thermal welding of the upper and lower edges of the two-layered side wall portion 53 of the core layer 50 can be performed simultaneously.

The above embodiment can be modified as follows. Note that the above embodiment and the following modification examples can be applied in combination with each other within a technically consistent range.
- The core layer 20 is not limited to one formed by folding an uneven sheet material. For example, it may be an uneven sheet material in which a cylindrical or truncated conical bulge is formed by vacuum forming a single sheet material.

- The core layer 20 is not limited to one in which columnar cells S are partitioned. For example, sheet layers may be bonded to both upper and lower surfaces of a core layer having a predetermined uneven shape. Examples of the core layer having such a configuration include the one described in JP-A No. 2014-205341. Alternatively, a plastic cardboard or the like having a harmonica-shaped cross section may be used.

- The core layer 20 does not need to be formed from a vacuum-formed uneven sheet material. For example, it may be formed from an uneven sheet material in which the side walls of the cell are formed by bending and arranging a plurality of belt-shaped sheets at predetermined intervals.

- Although hexagonal columnar cells S are arranged in parallel inside the core layer 20, the shape of the cells S is not limited to this. For example, a polygonal prism shape such as a quadrangular prism shape or an octagonal prism shape may be used. Further, the cells do not need to be adjacent to each other, and a gap (space) may exist between the cells.

- The core layer 20 may include a mixture of cells having different shapes.
- In the hollow structure 10 of the first embodiment, the thickness of the uneven sheet material 100 forming the core layer 20 does not have to be different depending on the region. Further, the thickness of each portion may be different from that of the core layer 20 of the first embodiment. Similarly, in the hollow structure 11 of the second embodiment, the thickness of the uneven sheet material 200 forming the core layer 50 does not have to be different depending on the region. Further, the thickness of each portion may be different from that of the core layer 50 of the second embodiment.

- In the uneven sheet material 100 forming the core layer 20 of the hollow structure 10 of the first embodiment, the thickness of the upper surface 110a of the first bulging portion 110 is thinner than the thickness of the flat sheet material. Moreover, the thickness of the pair of side surfaces 110b is thicker than the thickness of the upper surface 110a, and thinner than the thickness of the flat sheet material. Furthermore, the thickness of the pair of end surfaces 110c is also thicker than the thickness of the upper surface 110a and thinner than the thickness of the flat sheet material. The thicknesses of the top surface 110a, side surface 110b, and end surface 110c are not limited to these. For example, the thickness of the end surface 110c may be thinner than the thickness of the upper surface 110a. This is because when the uneven sheet material 100 is vacuum formed from the flat sheet material wound around the sheet roll 61, the corner where the upper surface 110a and the end surface 110c are connected becomes the most drawn part, and the end surface 110c is This is because it may become thinner. Moreover, each of the top surface 110a, side surface 110b, and end surface 110c may not have a uniform thickness, but may gradually become thinner toward the corner.

In the uneven sheet material 100 forming the core layer 20 of the hollow structure 10 of the first embodiment, the thickness of the lower surface 120a of the second bulging portion 120 is equivalent to the thickness of the flat sheet material. Further, the thickness of the pair of side surfaces 120b is thinner than the thickness of the lower surface 120a, that is, the thickness of the flat sheet material. Furthermore, the thickness of the pair of end surfaces 120c is also thinner than the thickness of the lower surface 120a, that is, the thickness of the flat sheet material. The thicknesses of the top surface 110a, side surface 110b, and end surface 110c are not limited to these. For example, the thickness of the lower surface 120a may be thinner than the thickness of the flat sheet material. This is because the flat sheet material may be stretched while being heated by the vacuum forming drum 62.

In either case, in the core layer 20 folded in the folding process, the two-layer structure side wall portion 23 of the first cell S1 is relatively thinner than the two-layer structure side wall portion 23 of the second cell S2. , is more easily melted by the heat from the heating device 63a. As a result, more resin pools are formed at the lower end edge of the side wall portion 23 of the first cell S1 than at the upper end edge of the side wall portion 23 of the second cell S2.

- In the core layer 20 of the hollow structure 10 of the first embodiment, a case has been described in which the thickness of the upper wall portion 21 of the first cell S1 and the thickness of the lower wall portion 22 of the second cell S2 are approximately the same. The present invention is not limited to this, and for example, the thickness of the upper wall portion 21 of the first cell S1 may be thinner than the thickness of the lower wall portion of the second cell S2.

- In the hollow structure 11 of the second embodiment, the thick parts 54 and 55 are formed at the upper edge of the side wall part 53 so as to be integrated with the lower surface of the upper wall part 51. The formation positions of 54 and 55 are not limited to this. The side wall portion 53 may be located at a position that does not touch the upper wall portion 51. In this case, the upper wall portion 51 is relatively thinner than the lower wall portion 52, and the heat from the heating device 63a is more easily transmitted to the side wall portion 53 through the upper wall portion 51 than through the lower wall portion 52. Therefore, the thick portions 54 and 55 are likely to be formed at the upper end of the side wall portion 53.

- In addition to the thick portions 54 and 55, protrusions similar to the protrusions 24 and 25 of the first embodiment may be formed on the side wall portion 23 of the hollow structure 11 of the second embodiment. In other words, the protruding portion formed on the upper end edge of the side wall portion 53 and the thick portions 54 and 55 formed on the upper end portion of the side wall portion 53 may coexist. Also in the core layer 50 of the second embodiment, the side wall portion 53 has a two-layer structure such that each of the first side wall portion 53a and the second side wall portion 53b swells inward in the cell S at the center in the width direction. It may have a slightly curved shape when viewed from above. The protrusion on the upper edge of the side wall 53 in this case is also formed along the curved shapes of the first side wall 53a and the second side wall 53b, similarly to the protrusions 24 and 25 of the first embodiment. Note that the side wall portion 53 having a two-layer structure has a curved shape in a top view such that the distance from both ends of the first side wall portion 53a and the second side wall portion 53b becomes wider toward the center when viewed from above. There is.

- In the hollow structure 10 of the first embodiment, the protrusion 25 may be larger than the protrusion 24. Alternatively, they may be of approximately the same size.
- In the hollow structure 11 of the second embodiment, the thick portion 55 may be smaller than the thick portion 54. Alternatively, they may be of approximately the same size.

- The thick portions 54 and 55 may be formed in a portion other than the upper end portion of the side wall portion 53. It may be at the lower end or at the middle. Moreover, they may be formed at multiple locations from the upper end to the lower end.

- In order to reinforce the hollow structure 10, the cells S may be filled with a filler such as foamed resin, a steel plate may be bonded to any part of the main surface of the core layer 20, or a metal rod may be placed within the cells S. You may insert a reinforcing member such as.

- The skin layers 30 and 40 joined to the hollow structure 10 do not have a single layer structure, and at least one of them may have a multilayer structure. For example, it may have a multilayer structure including a low melting point film layer, a decorative layer printed with a pattern, a nonwoven fabric layer, and the like.

- At least one of the skin layers 30 and 40 may be omitted.
- As the thermoplastic resin constituting the core layer 20 and the skin layers 30 and 40, one to which various functional resins are added may be used. For example, flame retardancy can be increased by adding a flame retardant resin to a thermoplastic resin. It is also possible to use a material to which various functional resins are added to all of the core layer 20 and skin layers 30 and 40, and it is also possible to use a material to which various functional resins are added to at least one of the core layer 20 and the skin layers 30 and 40. It is also possible to use

- Although the skin layers 30 and 40 are bonded to the core layer 20 with an adhesive, they may also be bonded to the core layer 20 by heat welding. In this case, the temperature of the heating device 66a of the second conveyor 66 may be adjusted in consideration of the thermal melting temperature of the thermoplastic resin forming the core layer 20 and the skin layers 30, 40.

- In each of the above embodiments, the flat hollow structures 10 and 11 have been described, but the hollow structures 10 and 11 do not have to be flat. For example, it may be formed into a curved plate shape by press molding or the like. In this case, since the peel strength of the hollow structures 10 and 11 is high, even if formed into a curved plate shape, the surface thereof can be formed flat.

DESCRIPTION OF SYMBOLS 10, 11...Hollow structure, 20, 50...Core layer, 20a, 20b...Main surface, 21, 51...Top wall part, 22, 52...Bottom wall part, 23, 53...Side wall part, 24, 25...Protrusion Part, 30... skin layer, 40... skin layer, 54, 55... thick wall part, 100, 200... uneven sheet material, S... cell, S1... first cell, S2... second cell.

Claims (6)

A thermoplastic resin material comprising a hollow plate-shaped core layer formed by a plurality of cells arranged in parallel and partitioned by side walls extending in the thickness direction, and a skin layer bonded to at least one main surface of the core layer. A hollow structure,
A protrusion protruding toward the inner side of the cell is formed on the side wall portion of the core layer,
A part of the side wall part is formed as a side wall part with a two-layer structure consisting of a first side wall part and a second side wall part,
An inter-side wall protrusion having a shape that connects the first side wall portion and the second side wall portion is formed between the first side wall portion and the second side wall portion,
The protrusion length of the protrusion is longer than the protrusion length of the inter-side wall protrusion,
The hollow structure is characterized in that the protruding portion protrudes along the main surface at an edge of the side wall portion on the side to which the skin layer is bonded, and is bonded to the skin layer. The protruding portion is formed by the side wall portion compressed in the thickness direction ,
The hollow structure according to claim 1 , wherein the protrusion has a thickness smaller than that of the side wall . In the core layer, the cells are partitioned by an upper wall part, a lower wall part, and the side wall part standing between the upper wall part and the lower wall part,
The protruding portion is formed as a thick portion that partially thickens the side wall portion at an upper end portion of the side wall portion ,
The hollow structure according to claim 1 or 2 , wherein the thick portion is formed so as to be located below an intersection between the side wall portion and the lower surface of the upper wall portion . A thermoplastic resin material comprising a hollow plate-shaped core layer formed by a plurality of cells arranged in parallel and partitioned by side walls extending in the thickness direction, and a skin layer bonded to at least one main surface of the core layer. A hollow structure,
The core layer includes a first cell whose upper end is closed by the upper wall and whose lower end is open downward without being closed, and a first cell whose lower end is closed by the lower wall and whose upper end is open downward. and a second cell that is open upward without being blocked,
A protrusion protruding toward the inner side of the cell is formed on the side wall portion of the core layer,
The protruding portion protrudes along the main surface at an edge of the side wall portion on the side to which the skin layer is bonded, and is bonded to the skin layer;
A hollow structure characterized in that the size of the protrusion formed on the lower edge of the side wall of the first cell is larger than the size of the protrusion formed on the upper edge of the side wall of the second cell. body. a core layer forming step of forming a hollow plate-shaped core layer in which a plurality of cells partitioned by side walls extending in the thickness direction are arranged in parallel;
a skin layer bonding step of bonding a thermoplastic resin skin layer to at least one main surface of the core layer,
In the core layer forming step, a hollow plate-shaped core layer is formed in which a plurality of cells partitioned by sidewalls extending in the thickness direction are arranged in parallel, and a part of the sidewall is formed as a first sidewall. Formed as a side wall part with a two-layer structure consisting of a second side wall part,
In the core layer forming step, the core layer is compressed in the thickness direction in a heated state, so that an edge of the side wall portion on the side to which the skin layer is bonded protrudes toward the inner side of the cell. forming an inter-side wall protrusion having a shape that connects each other between the side wall parts of the two-layer structure;
The method for manufacturing a hollow structure , wherein in the skin layer joining step, the skin layer is joined to the main surface including the protrusion . Further comprising a vacuum forming step of vacuum forming a single sheet material made of thermoplastic resin to obtain an uneven sheet material in which a bulge is formed,
6. The method for manufacturing a hollow structure according to claim 5, wherein in the core layer forming step, the protrusion is formed by folding the uneven sheet material in a heated state and compressing it in the thickness direction.