JP2020179528A - Structure and method of producing the same - Google Patents

Abstract

To provide a structure capable of preventing a core body from being transparent at a hinge part.SOLUTION: A structure including a resin mold and a core body comprises a first body part, a second body part, and a hinge part. The first and second body parts are pivotally coupled with each other at the hinge part. The resin mold includes a front wall and a back wall. The core body is arranged between the front wall and the back wall so as to step over the hinge part between the first and second body parts. The core body is not present in an end area near an end part of the hinge part in a longitudinal direction, or a thickness of the core body is smaller than a thickness of a portion other than the end area of the hinge part.SELECTED DRAWING: Figure 1

Description

The present invention relates to a structure having a resin molded body (eg, a resin panel) that can be used as a bath lid, a floor board installed in a luggage compartment of a vehicle, and the like, and a method for manufacturing the same.

Patent Document 1 discloses a structure in which a core body is arranged between a front wall and a back wall of a resin molded body. This structure is provided with a hinge portion.

Japanese Unexamined Patent Publication No. 2013-067148

In a structure like Patent Document 1, a hinge portion is formed by closing a split mold with a core material arranged between a pair of resin sheets and compressing the pair of resin sheets and the core material. ..

When the hinge portion is formed by such a method, the wall thickness of the resin molded body at the hinge portion becomes very thin, and as shown by the white circle in the photograph of FIG. 15, the hinge portion 1c is formed from the core material. The core body may show through.

The present invention has been made in view of such circumstances, and provides a structure capable of suppressing the see-through of the core body at the hinge portion.

According to the present invention, the structure has a resin molded body and a core body, the structure includes first and second main body portions and a hinge portion, and the first and second main body portions are the hinges. The resin molded body is rotatably connected to each other at a portion, the resin molded body includes a front wall and a back wall, and the core body straddles the first and second main body portions and the hinge portion. In the end region near the end of the hinge portion in the longitudinal direction, which is arranged between the back wall and the back wall, the core body is not present, or the thickness of the core body is the end of the hinge portion. A structure is provided that is thinner than the non-partial region.

In the vicinity of the end portion in the longitudinal direction of the hinge portion, the wall thickness of the front wall and the back wall of the resin molded body becomes particularly thin, and the core body tends to show through. Then, in the structure of the present invention, the core body does not exist in the end region near the end portion in the longitudinal direction of the hinge portion, or the thickness of the core body is a portion other than the end region of the hinge portion. It is thinner than. Therefore, according to the present invention, the see-through of the core body is suppressed.

Hereinafter, various embodiments of the present invention will be illustrated. The embodiments shown below can be combined with each other.
Preferably, in the structure described above, the hinge portion includes first and second thin-walled portions and a thick-walled portion, and the thick-walled portion is thicker than the first and second thin-walled portions. It is a large portion, and the first and second thin-walled portions and the thick-walled portions extend along the longitudinal direction of the hinge portion, and the thick-walled portions are the first and second thin-walled portions in the width direction of the hinge portion. It is a structure sandwiched between.
Preferably, it is a method for manufacturing a structure, wherein the structure includes a first and second main body portions and a hinge portion, and the first and second main body portions are rotatably connected to each other by the hinge portion. The method includes an extrusion step, an insert step, a shaping step, and a mold clamping step. In the extrusion step, a first and second resin sheets are inserted between the first and second molds. In the extruding and inserting step, the core material is inserted between the first and second resin sheets, and in the shaping step, the first and second resin sheets are placed along the inner surfaces of the first and second molds, respectively. In the mold clamping step, the first and second molds are molded, and the core material is the first and second main body core portions arranged in the first and second main body portions, and the above. A hinge core portion arranged in the hinge portion is provided, and the first and second main body core portions are connected to each other by the hinge core portion, and the core material is placed in an end region near the end portion of the hinge core portion. The hinge core portion has a notched portion, or the hinge core portion has a thinned portion, and in the mold clamping step, the first and second resin sheets and the hinge core portion have the hinge portion. This is a method for manufacturing a structure, which is compressed and welded by the first and second molds at a portion to be.
Preferably, in the method described above, the hinge portion includes first and second thin-walled portions and a thick-walled portion, and the thick-walled portion is thicker than the first and second thin-walled portions. The first and second thin-walled portions and the thick-walled portions extend along the longitudinal direction of the hinge portion, and the thick-walled portion is formed by the first and second thin-walled portions in the width direction of the hinge portion. It is a method that is sandwiched.
Preferably, it is the method described above, wherein the wall thickness of the hinge core portion is 3 to 10 mm.
Preferably, in the method described above, the first and second resin sheets have a wall thickness of 0.5 to 1.5 mm.
Preferably, it is the method described above, wherein the core material has the notch.

It is a perspective view of the structure 1 of the 1st Embodiment of this invention. It is an enlarged view of the area A in FIG. 3A is a plan view of the structure 1 of FIG. 1, FIG. 3B is a sectional view taken along line II in FIG. 3A, and FIG. 3C is a sectional view taken along line II-II in FIG. 3A. 4A is an enlarged view of the region A in FIG. 3B, and FIG. 4B is an enlarged view of the region B in FIG. 4A. 5A is an enlarged view of the region A in FIG. 3C, and FIG. 5B is an enlarged view of the region B in FIG. 5A. It is a perspective view of the core material 4. It is an enlarged view of the area A in FIG. It is a block diagram (cross-sectional view of the molds 21 and 31 and the member in the vicinity) of the molding machine 10 that can be used for manufacturing the structure 1 of the 1st Embodiment of this invention. It is sectional drawing which shows the state which extruded the resin sheets 23, 33 between the molds 21, 31. It is sectional drawing which shows the state after shaping the resin sheets 23, 33 along the inner surface of the mold 21, 31 from the state of FIG. It is sectional drawing which shows the state after the core material 4 was attached to the resin sheet 23 from the state of FIG. It is sectional drawing which shows the state after mold compaction | die 21 and 31 from the state of FIG. It is a perspective view of the core material 4 used for manufacturing the structure 1 of the 2nd Embodiment of this invention. It is an enlarged view of the area A in FIG. It is a photograph which shows the state which the core body 3 is transparent in the hinge part 1c.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The various features shown in the embodiments shown below can be combined with each other. In addition, the invention is independently established for each feature.

1. 1. First Embodiment 1-1. Structure of Structure As shown in FIGS. 1 to 7, the structure 1 of the first embodiment of the present invention has a resin molded body 2 and a core body 3. The structure 1 includes first and second main body portions 1a and 1b, and a hinge portion 1c. The main body portions 1a and 1b are rotatably connected to each other by the hinge portion 1c.

In the present embodiment, the structure 1 is a resin panel, and the main bodies 1a and 1b are panel-shaped molded bodies.

The hinge portion 1c includes first and second thin-walled portions 1c1 and 1c2, and a thick-walled portion 1c3. The thick portion 1c3 is a portion having a larger wall thickness than the thin portions 1c1 and 1c2. The thin-walled portions 1c1 and 1c2 and the thick-walled portion 1c3 have an elongated shape and extend along the longitudinal direction of the hinge portion 1c. The thick portion 1c3 is sandwiched between the thin portion 1c1 and 1c2 in the width direction of the hinge portion 1c.

As shown in FIG. 2, the thick portion 1c3 has a substantially triangular cross section, and the thickness of the thick portion 1c3 gradually decreases toward the end of the thick portion 1c3 in the width direction. Therefore, the thick portion 1c3 is smoothly connected to the thin portion 1c1 and 1c2.

The thickness of the thinnest portion of the thin portion 1c1 and 1c2 is, for example, 0.001 to 0.5 mm, and specifically, for example, 0.001, 0.01, 0.1, 0.2, 0.3. , 0.4, 0.5 mm, and may be within the range between any two of the numerical values exemplified here. The thickness of the thickest portion of the thick portion 1c3 is 0.1 to 3 mm, specifically, for example, 0.1, 0.5, 1, 1.5, 2, 3 mm, which is exemplified here. It may be within the range between any two of the given numerical values.

Since the thin portion 1c1 and 1c2 have a smaller wall thickness than the thick portion 1c3, when the main body portions 1a and 1b are bent by the hinge portion 1c, the thin portion 1c1 and 1c2 are easily bent selectively. Since the thin-walled portions 1c1 and 1c2 are narrower than the entire hinge portion 1c, even if the polygonal lines formed in the thin-walled portions 1c1 and 1c2 are meandering, they are not so noticeable. Therefore, according to the present embodiment, deterioration of the appearance due to the meandering of the polygonal line formed on the hinge portion 1c is suppressed.

By the way, when the main body portions 1a and 1b are bent by the hinge portion 1c, the thin-walled portions 1c1 and 1c2 are not always bent evenly, and the thin-walled portions 1c1 and 1c2 may be bent unevenly. In such a case, there is a problem that cracks are likely to occur in the thin portion 1c1 and 1c2. In order to prevent the occurrence of such cracks, in the present embodiment, as shown in FIG. 2, the thick portion 1c3 is provided so as not to reach the end portion in the longitudinal direction of the hinge portion 1c.

As shown in FIG. 3B, the resin molded body 2 includes a front wall 2f and a back wall 2r. The front wall 2f and the back wall 2r face each other with a gap. The periphery of the front wall 2f and the back wall 2r is connected by the peripheral wall 2s.

As shown in FIGS. 3 to 5, a core body 3 is provided between the front wall 2f and the back wall 2r. The core body 3 is provided so as to straddle the main body portions 1a and 1b and the hinge portion 1c. The core body 3 is a member arranged for the purpose of securing a space between the front wall 2f and the back wall 2r and increasing the strength and heat insulating properties of the structure 1, and is preferably made of a foam. To.

By the way, as shown in FIG. 4, in the hinge portion 1c, the wall thickness of the back wall 2r is very thin. This is because, as will be described later, the resin sheet 33 is stretched and then compressed when the hinge portion 1c is formed. In the vicinity of the longitudinal end of the hinge portion 1c, the resin sheet 33 is stretched not only for the formation of the hinge portion 1c but also for the formation of the peripheral wall 2s. Therefore, in the vicinity of the end portion in the longitudinal direction of the hinge portion 1c, the wall thickness of the back wall 2r becomes particularly thin, and as shown in FIG. 15, the core body 3 is transparent and the appearance tends to be deteriorated. Further, when the hinge portion 1c has the thin-walled portions 1c1, 1c2 and the thick-walled portion 1c3 as in the present embodiment, the wall thickness of the back wall 2r tends to be particularly thin in the thin-walled portions 1c1, 1c2, so that the core body 3 The sheer is particularly likely to occur, and the technical significance of applying the present invention is remarkable.

In order to solve such a problem, in the present embodiment, as shown in FIGS. 3 and 5, the core body 3 does not exist in the end region R near the longitudinal end of the hinge portion 1c, and the table is shown. The wall 2f and the back wall 2r are welded together so as to be integrated. As described above, since the core body 3 is configured so as not to exist in the region where the core body 3 is likely to show through, the see-through of the core body 3 is suppressed.

As will be described later, in the structure 1, the core material 4 shown in FIGS. 6 to 7 is sandwiched between the resin sheets 23 and 33 shown in FIG. 8, and the resin sheets 23 and 33 and the core material 4 are placed in the hinge portion 1c. It can be formed by compressing.

As shown in FIGS. 6 to 7, the core material 4 includes first and second main body core portions 4a and 4b and a hinge core portion 4c connecting them. The main body core portions 4a and 4b are arranged in the main body portions 1a and 1b, and the hinge core portion 4c is arranged in the hinge portion 1c. The core material 4 has a cutout portion 4d in which the hinge core portion 4c is cut out in an end region near the end portion of the hinge core portion 4c. By using such a core material 4, a configuration in which the core material 4 does not exist in the end region R of the hinge portion 1c is realized. The wall thickness of the hinge core portion 4c is, for example, 3 to 10 mm. If the wall thickness is too thin, the core material 4 is likely to crack at the hinge core portion 4c, and if the wall thickness is too thick, the core body 3 is likely to show through at the hinge portion 1c. Specifically, the wall thickness is, for example, 3, 4, 5, 6, 7, 8, 9, and 10 mm, and may be within the range between any two of the numerical values exemplified here. The value of (thickness of the hinge core portion 4c) / (thickness of the first and second main body core portions) is preferably 0.1 to 0.6, specifically, for example, 0.1, 0.2, It is 0.3, 0.4, 0.5, 0.6, and may be within the range between any two of the numerical values exemplified here. If this value is too small, the core material 4 is likely to crack at the hinge core portion 4c, and if this value is too large, the core body 3 is likely to show through at the hinge portion 1c.

The length of the end region R is appropriately set so that the core body 3 does not show through, but the value of (length of end region R) / (thickness of main body portions 1a and 1b) is 0. 5 to 5.0 is preferable, and 1.0 to 3.0 is more preferable. If this value is too small, the suppression of see-through of the core body 3 may be insufficient, and if this value is too large, the core material 4 is likely to break at the hinge core portion 4c. Specifically, this value is, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0. Yes, it may be within the range between any two of the numerical values exemplified here. The thickness of the main bodies 1a and 1b is, for example, 5 to 30 mm, preferably 10 to 25 mm, specifically, for example, 5, 10, 15, 20, 25, 30 mm, and any of the numerical values exemplified here. It may be within the range between the two. If this thickness is too thin, the strength of the structure 1 may be insufficient, and if this thickness is too thick, the structure 1 may become too heavy. In addition, the hinge portion 1c at the time of manufacture may be insufficient. The elongation of the resin sheets 23 and 33 in the vicinity becomes too large, and the core body 3 becomes easily transparent at the hinge portion 1c.

1-2. Molding machine 10
Next, the molding machine 10 that can be used for carrying out the method for manufacturing the structure according to the first embodiment of the present invention will be described with reference to FIGS. 8 to 12. The molding machine 10 includes a pair of resin sheet forming devices 20 and first and second molds 21 and 31. Each resin sheet forming device 20 includes a hopper 12, an extruder 13, an accumulator 17, and a T-die 18. The extruder 13 and the accumulator 17 are connected via a connecting pipe 25. The accumulator 17 and the T-die 18 are connected via a connecting pipe 27.
Hereinafter, each configuration will be described in detail.

<Hopper 12, extruder 13>
The hopper 12 is used to put the raw material resin 11 into the cylinder 13a of the extruder 13. The form of the raw material resin 11 is not particularly limited, but is usually in the form of pellets. The raw material resin is, for example, a thermoplastic resin such as polyolefin, and examples of the polyolefin include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymer and a mixture thereof. The raw material resin 11 is charged into the cylinder 13a from the hopper 12 and then melted by being heated in the cylinder 13a to become the molten resin 11a. Further, it is conveyed toward the tip of the cylinder 13a by the rotation of the screw arranged in the cylinder 13a. The screw is arranged in the cylinder 13a, and the molten resin is kneaded and conveyed by its rotation. A gear device is provided at the base end of the screw, and the screw is rotationally driven by the gear device.

<Accumulator 17, T-die 18>
The molten resin 11a is extruded from the resin extrusion port of the cylinder 13a and injected into the accumulator 17 through the connecting pipe 25. The accumulator 17 includes a cylinder 17a and a piston 17b slidable inside the cylinder 17a, so that molten resin can be stored in the cylinder 17a. Then, by moving the piston 17b after a predetermined amount of the molten resin 11a is stored in the cylinder 17a, the molten resin 11a is pushed out from the slit provided in the T die 18 through the connecting pipe 27, and the first and the molten resin 11a The second resin sheets 23 and 33 are formed.

<Molds 21, 31>
The resin sheets 23 and 33 are extruded between the molds 21 and 31. As shown in FIG. 9, the molds 21 and 31 have cavities 21a and 31a, and pinch-off portions 21b and 31b are provided so as to surround the cavities 21a and 31a. Decompression suction holes (not shown) are provided in the cavities 21a and 31a, and the resin sheets 23 and 33 are decompressed and sucked through the decompression suction holes to form a shape along the inner surfaces of the molds 21 and 31. It is possible to do. The decompression suction hole is a very small hole, one end of which is communicated to the inner surface of the cavities 21a and 31a through the inside of the molds 21 and 31, and the other end is connected to the decompression device.

The mold 31 is provided with a ridge 31c that forms the hinge portion 1c. The ridge 31c is an elongated protrusion, and is preferably configured so that the longitudinal direction of the ridge 31c is not parallel to the extrusion direction of the resin sheets 23 and 33, and the longitudinal direction of the ridge 31c is the resin sheet 23. , 33 are more preferably configured to be orthogonal to the extrusion direction. In this case, the change in the thickness of the resin sheets 23 and 33 along the longitudinal direction of the hinge portion 1c is suppressed. As shown in FIG. 9, the tip of the ridge 31c is provided with a tip surface 31c1 corresponding to the thin portion 1c1 and 1c2 and a groove 31c2 corresponding to the thick portion 1c3.

1-3. Method for Manufacturing a Structure Here, a method for manufacturing a structure according to an embodiment of the present invention will be described with reference to FIGS. 8 to 12. The method of this embodiment includes an extrusion step, a shaping step, an insert step, and a mold clamping step. The details will be described below.

(1) Extrusion Step In the extrusion step, as shown in FIGS. 8 to 9, the resin sheets 23 and 33 are extruded between the dies 21 and 31. The wall thickness of the resin sheets 23 and 33 is not particularly limited, but is preferably 0.5 to 1.5 mm. When the wall thickness is small as described above, the core body 3 is likely to show through, so that the technical significance of applying the present invention is remarkable. Specifically, the wall thickness is, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4. , 1.5 mm, and may be within the range between any two of the numerical values exemplified here.

(2) Shaped step In the shaping step, as shown in FIGS. 9 to 10, the resin sheets 23 and 33 are sucked under reduced pressure by the dies 21 and 31, and the resin sheets 23 and 33 are transferred to the dies 21 and 31. Shaped into a shape along the inner surface. In the present embodiment, since another member such as a skin material is not arranged between the resin sheet 23 and the mold 21 and between the resin sheet 33 and the mold 31, the resin sheets 23 and 33 are respectively. , Is shaped so as to be in direct contact with the molds 21 and 31. The skin material may be integrally molded on the resin sheet 23 side. In this case, the resin sheet 23 is shaped with the skin material arranged between the mold 21 and the resin sheet 23.

(3) Insert step In the insert step, as shown in FIGS. 10 to 11, the core material 4 is welded to the resin sheet 23. When the core material 4 is made of a foam, one surface 4f of the core material 4 is welded to the resin sheet 23 by melting the foam by the heat of the resin sheet 23. The other surface 4r of the core material 4 is welded to the resin sheet 33 at the time of mold clamping shown in FIG.

(4) Die-clamping step In the mold-clamping step, the molds 21 and 31 are clamped as shown in FIGS. 11 to 12. As a result, the resin sheets 23 and 33 are welded to each other along the pinch-off portions 21b and 31b, and a structure 1 having a shape along the inner surface of the cavity formed by the pair of molds 21 and 31 is obtained. The resin molded body 2 is formed by the resin sheets 23 and 33, and the core body 3 is formed by the core material 4. The resin sheets 23 and 33 and the hinge core portion 4c are compressed and welded between the ridge 31c and the mold 21 to form the hinge portion 1c. The portion compressed by the tip surface 31c1 of the ridge 31c becomes the thin-walled portion 1c1 and 1c2, and the portion facing the groove 31c2 becomes the thick-walled portion 1c3. The outside of the pinch-off portions 21b and 31b is the burr 41.

As shown in FIG. 4, the hinge portion 1c formed from the portion where the hinge core portion 4c is sandwiched between the resin sheets 23 and 33 has a structure in which the core body 3 is sandwiched between the front wall 2f and the back wall 2r. On the other hand, as shown in FIG. 5, the hinge portion 1c formed from the portion corresponding to the notch portion 4d has a structure in which the front wall 2f and the back wall 2r are directly welded and integrated. This portion becomes the end region R.

After that, the structure 1 shown in FIG. 1 is obtained by opening the molds 21 and 31 to take out the structure 1 and removing the burr 41.

2. Second Embodiment The second embodiment of the present invention will be described with reference to FIGS. 13 to 14. This embodiment is similar to the first embodiment, and the main difference is the difference in the configuration of the core material 4. Hereinafter, the differences will be mainly described.

In the present embodiment, the core material 4 includes a thin-walled portion 4e in which the hinge core portion 4c is thinned instead of the notch portion 4d. By thinning the hinge core portion 4c in the vicinity of the end portion of the hinge core portion 4c, it is possible to suppress see-through of the core body 3. Further, if the notch portion 4d is provided, the strength of the hinge core portion 4c may become too low, but the decrease in strength is suppressed by providing the thin-walled portion 4e instead of the notch portion 4d.

The value of (thickness of the thin-walled portion 4e) / (thickness of the hinge core portion 4c other than the thin-walled portion 4e) is, for example, 0.1 to 0.9, preferably 0.2 to 0.8. Specifically, this value is, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, where It may be in the range between any two of the illustrated values. If this value is too small, the thin portion 4e is easily damaged, and if this value is too large, the see-through of the core body 3 may not be suppressed.

In the structure 1 obtained by using the core material 4 having such a structure, in the end region R near the end portion in the longitudinal direction of the hinge portion 1c, the thickness of the core body 3 is the end region R of the hinge portion 1c. It becomes thinner than other parts.

1: Structure 1a: 1st main body 1b: 2nd main body 1c: Hinge 1c1: 1st thin part 1c2: 2nd thin part 1c3: Thick part 2: Resin molded body 2f: Outer wall 2r: Back wall 2s: Peripheral wall 3: Core body 4: Core material 4a: First main body core part 4b: Second main body core part 4c: Hinge core part 4d: Notch part 4e: Thin-walled part 4f: Surface 4r: Surface 10: Molding machine 11: Raw resin 12: Hopper 13: Extruder 13a: Cylinder 17: Accumulator 17a: Cylinder 17b: Piston 18: T die 20: Resin sheet forming device 21: First mold 21a: Cavity 21b: Pinch-off portion 23: First resin sheet 25: Connecting pipe 27: Connecting pipe 31: Second mold 31a: Cavity 31b: Pinch-off portion 31c: Convex 31c1: Tip surface 31c2: Groove 33: Second resin sheet 41: Burr

Claims (7)

A structure having a resin molded body and a core body.
The structure includes first and second main body portions and a hinge portion.
The first and second main body portions are rotatably connected to each other by the hinge portion.
The resin molded body includes a front wall and a back wall, and has a front wall and a back wall.
The core body is arranged between the front wall and the back wall so as to straddle the first and second main body portions and the hinge portion.
In the end region near the end portion in the longitudinal direction of the hinge portion, the core body is not present, or the thickness of the core body becomes thinner than the portion other than the end region of the hinge portion. There is a structure. The structure according to claim 1.
The hinge portion includes first and second thin-walled portions and a thick-walled portion.
The thick portion is a portion having a larger wall thickness than the first and second thin portions.
The first and second thin-walled portions and thick-walled portions extend along the longitudinal direction of the hinge portion.
The thick portion is a structure sandwiched between the first and second thin portions in the width direction of the hinge portion. It is a method of manufacturing a structure.
The structure includes first and second main body portions and a hinge portion.
The first and second main body portions are rotatably connected to each other by the hinge portion.
The method includes an extrusion step, an insert step, a shaping step, and a mold clamping step.
In the extrusion process, the first and second resin sheets are extruded between the first and second dies.
In the insert step, the core material is inserted between the first and second resin sheets, and the core material is inserted.
In the shaping step, the first and second resin sheets are shaped along the inner surfaces of the first and second molds, respectively.
In the mold clamping step, the first and second molds are molded and molded.
The core material includes first and second main body core portions arranged in the first and second main body portions, and a hinge core portion arranged in the hinge portion.
The first and second main body core portions are connected to each other by the hinge core portion.
The core material has a notch portion in which the hinge core portion is cut out, or has a thin wall portion in which the hinge core portion is thinned, in an end region near the end portion of the hinge core portion.
A method for manufacturing a structure, in which in the mold clamping step, the first and second resin sheets and the hinge core portion are compressed and welded by the first and second molds at a portion to be the hinge portion. The method according to claim 3.
The hinge portion includes first and second thin-walled portions and a thick-walled portion.
The thick portion is a portion having a larger wall thickness than the first and second thin portions.
The first and second thin-walled portions and thick-walled portions extend along the longitudinal direction of the hinge portion.
A method in which the thick portion is sandwiched between the first and second thin portions in the width direction of the hinge portion. The method according to claim 3 or 4.
The method in which the wall thickness of the hinge core portion is 3 to 10 mm. The method according to any one of claims 3 to 5.
The method in which the first and second resin sheets have a wall thickness of 0.5 to 1.5 mm. The method according to any one of claims 3 to 6.
A method in which the core material has the notch.