Manufacturing method of high pressure tank

Abstract

To provide a method for manufacturing a high-pressure tank capable of suppressing functional deterioration of a cylindrical member having gas barrier property, and ensuring bondability between the cylindrical member and a dome member.SOLUTION: In a method for manufacturing a high-pressure tank 1, an overlapping portion 20a is formed by overlapping a cylindrical member 21 and a dome member 22. The cylindrical member 21 and the dome member 22 are bonded by irradiating the overlapping portion 20a with a laser light L to fabricate a liner 20. An outer circumferential surface 20c of the liner 20 is covered with a reinforcing layer 30. The cylindrical member 21 has: an intermediate layer 21B having a gas barrier property against a high-pressure gas; and an inner circumferential layer 21C containing an absorber that absorbs a part of the laser light L. The dome member 22 contains an absorber with a higher absorptivity of the laser light than the absorber of the inner circumferential layer 21C. By an irradiation of the laser light L, the cylindrical member 21 and the dome member 22 are welded at an interface between an end edge portion 21a of the cylindrical member 21 and an end edge portion 22a of the dome member 22.SELECTED DRAWING: Figure 6B

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a high-pressure tank. [Background technology]

[0002] For example, Patent Document 1 discloses a high-pressure tank that includes a liner that contains gas and a reinforcing layer that covers the outer surface of the liner. The liner of the high-pressure tank is made of a resin material, and the reinforcing layer is made of a fiber-reinforced resin material. The liner has a cylindrical portion and dome portions formed continuously from both ends of the cylindrical portion, and the reinforcing layer is formed by winding a bundle of reinforcing fibers impregnated with resin around the outer circumferential surface of the liner.

[0003] By the way, the liner may be produced by joining members made of a resin material, and a laser beam may be used for this joining. For example, Patent Document 2 discloses a technology for producing a resin fuel tank by attaching an extraction part to an opening formed in the tank body.

[0004] In this technology, first, a tank body composed of an intermediate layer (barrier layer) made of a fuel-permeation-resistant resin, and outer and inner layers made of polyethylene, and an extraction member for removing the fuel are prepared. Next, the extraction member is brought into contact with the tank body so as to communicate with the opening of the tank body, and the extraction member is irradiated with laser light to weld the polyethylene outer layer of the tank body and the resin of the extraction member. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-219025 A [Patent Document 2] JP 2002-160537 A Summary of the Invention [Problem to be solved by the invention]

[0006] Here, for example, when producing the liner, it is conceivable to prepare a cylindrical member corresponding to the cylindrical portion and a pair of dome members corresponding to the dome portion, and join them by irradiating them with laser light.

[0007] In this case, for example, when the joining method using laser light shown in Patent Document 2 is used, it is assumed that the edge of the cylindrical member is placed on the outside and the edge of the dome member is placed on the inside, and the laser light is irradiated to the overlapping portion where they are overlapped. Here, for example, if a resin material that absorbs laser light is used only for the dome member, the cylindrical member is indirectly melted by the heat generated by the dome member, so there is a risk that the joining strength between the cylindrical member and the dome member is not sufficient. In view of this, it is also possible to heat the dome member to a higher temperature by increasing the irradiation intensity of the laser light or lengthening the irradiation time of the laser light. However, if the cylindrical member is provided with a barrier layer having gas barrier properties, there is a risk that excessive heat will be input to this barrier layer, which may reduce the gas barrier properties.

[0008] The present invention has been made in consideration of the above-mentioned points, and aims to provide a manufacturing method for a high-pressure tank that can suppress deterioration of the functionality of a tubular member having gas barrier properties while ensuring the bonding between the tubular member and a dome member. [Means for solving the problem]

[0009] In consideration of the above-mentioned problems, a method for manufacturing a high-pressure tank according to the present invention is a method for manufacturing a high-pressure tank including a liner made of a resin material, in which a pair of dome members are joined to both ends of a cylindrical member so as to form a storage space for storing high-pressure gas, and a reinforcing layer made of a fiber-reinforced resin material coated on an outer peripheral surface of the liner, the method for manufacturing the high-pressure tank comprising the steps of: preparing the cylindrical member and the pair of dome members; forming an overlapping portion in which an edge portion of the cylindrical member and an edge portion of the dome member are overlapped in a radial direction of the cylindrical member such that an edge portion of the cylindrical member is on the radial outside of the cylindrical member; irradiating a laser beam along the edge portion of the cylindrical member from the radial outside to join the cylindrical member and the dome member to produce the liner; and a step of covering a surface of the cylindrical member with the reinforcing layer. In the preparing step, a cylindrical member is prepared in which at least a barrier layer made of a first resin material that has gas barrier properties against high-pressure gas and transmits the laser light, and an inner peripheral layer made of a second resin material that is arranged radially inward from the barrier layer and contains an absorbent that absorbs a portion of the laser light, is prepared as the dome member, and a dome member is prepared made of a third resin material that contains an absorbent that has a higher absorption property for the laser light than the absorbent of the second resin material. In the fabricating step, the laser light is irradiated to melt the second resin material and the third resin material while heating them at the interface between the edge portion of the cylindrical member and the edge portion of the dome member, thereby fusing the cylindrical member and the dome member.

[0010] According to the present invention, first, a cylindrical member and a dome member are prepared as described below. Specifically, as the cylindrical member, a member is prepared in which a barrier layer having gas barrier properties against high pressure gas and transmitting laser light, and an inner peripheral layer arranged inside the barrier layer and transmitting the laser light while absorbing a part of the laser light, are laminated. An outer peripheral layer transmitting the laser light may be further provided on the outside of the barrier layer of this cylindrical member. Furthermore, as the dome member, a dome member having a higher laser light absorption than the inner peripheral layer is prepared. Specifically, the absorbent contained in the third resin material of the dome member has a higher laser light absorption than the absorbent contained in the second resin material.

[0011] Next, the edge of the cylindrical member and the edge of the dome member are overlapped in the radial direction of the cylindrical member to form an overlapping portion, so that the edge of the cylindrical member is on the radially outer side, whereby the inner peripheral layer of the cylindrical member abuts against the dome member, and the inner peripheral layer can be brought into contact with the dome member.

[0012] In this state, the overlapping portion is irradiated with laser light from the radial outside of the cylindrical member along the edge of the cylindrical member to join the cylindrical member and create a liner. Specifically, the laser light is transmitted through the barrier layer by the irradiation of the laser light. A portion of the laser light that has transmitted through the barrier layer is absorbed by the inner circumferential layer. The laser light that has not been absorbed by the inner circumferential layer and has transmitted through the inner circumferential layer is ultimately absorbed by the dome member.

[0013] As a result, the inner circumferential layer and the dome member generate heat almost simultaneously due to the absorption of the laser light, and since the absorbent contained in the third resin material of the dome member has a higher absorption of the laser light than the absorbent contained in the second resin material, the temperature of the dome member rises faster than that of the inner circumferential layer. This allows the inner circumferential layer and the dome member to melt simultaneously at the interface between the edge of the cylindrical member and the edge of the dome member, and the cylindrical member and the dome member can be fused together. As a result, the dome member and the cylindrical member can be fused together at their respective edge portions without transmitting excessive heat from the dome member to the barrier layer, and they can be joined together.

[0014] In a more preferred embodiment, in the preparing step, a cylindrical member is prepared in which the melting point of the second resin material is higher than the melting point of the first resin material, and in the fabricating step, the irradiation of the laser light is terminated before the second resin material of the inner circumferential layer located at the interface between the inner circumferential layer and the barrier layer melts.

[0015] When the melting point of the second resin material is higher than that of the first resin material, the barrier layer made of the first resin material is likely to melt when the second resin material melts. However, according to this embodiment, the irradiation of the laser light is terminated before the second resin material of the inner circumferential layer located at the interface of the barrier layer melts, so that the melting of the first resin material of the barrier layer can be suppressed.

[0016] In a more preferred embodiment, the second resin material is nylon 6. According to this embodiment, since the inner peripheral layer of the cylindrical member is made of nylon 6, heat resistance against the temperature rise that occurs when the cylindrical member is filled with high-pressure gas can be ensured. Effect of the Invention

[0017] According to the present invention, it is possible to manufacture a high-pressure tank that can suppress deterioration of the function of a cylindrical member having gas barrier properties and ensure the bond between the cylindrical member and the dome member. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic perspective view of a high-pressure tank according to an embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view of the high-pressure tank of FIG. 1 taken along line AA. [Diagram 3] FIG. 3 is an enlarged view of part B shown in FIG. [Figure 4] 2 is a flow diagram for illustrating a method for manufacturing the high-pressure tank shown in FIG. [Figure 5A] 13A to 13C are schematic perspective views for illustrating a step of preparing a cylindrical member and a pair of dome members, and a step of forming overlapping portions. [Figure 5B]FIG. 5B is an enlarged view of a main part of FIG. 5A. [Figure 6A] FIG. 2 is a schematic perspective view for explaining a process for producing a liner. [Figure 6B] FIG. 6B is an enlarged view of a main part of FIG. 6A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a method for manufacturing a high-pressure tank according to an embodiment of the present invention will be described with reference to the drawings.

[0020] 1. High pressure tank 1 First, the high-pressure tank 1 will be described. Fig. 1 is a schematic perspective view of a high-pressure tank according to an embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line AA of the high-pressure tank in Fig. 1. Fig. 3 is an enlarged view of part B shown in Fig. 2. The high-pressure tank 1 has a cylindrical portion 11 and a pair of dome portions 12 formed on both sides of the cylindrical portion 11, and the overall shape of the high-pressure tank 1 is approximately ellipsoidal.

[0021] The cylindrical portion 11 and each dome portion 12 are composed of a liner 20 made of a resin material and a reinforcing layer 30 made of a fiber-reinforced resin material coated on the outer circumferential surface of the liner 20. A pair of metal nozzles 41, 42 are formed on both ends of the high-pressure tank 1. One nozzle 41 of the pair of nozzles 41, 42 forms a fluid path by connecting a valve or the like when supplying the fluid stored inside the high-pressure tank 1 to the outside. The other nozzle 42 of the pair of nozzles 41, 42 generally plays a role as a holding part that holds the tank when the reinforcing layer 30 is formed. The other nozzle 42 is not an essential component for the function of the tank.

[0022] The reinforcing layer 30 is a layer in which fiber bundles in which reinforcing fibers such as carbon fibers are impregnated with resin are wound, and in the reinforcing layer 30, hoop layers wound by hoop winding and helical layers wound by helical winding are alternately formed in the layer thickness direction. In the high-pressure tank 1 shown in FIG. 1, the outermost layer is formed by a helical layer. In this embodiment, the reinforcing layer 30 is formed by a generally known hoop layer and a helical layer, but for example, the reinforcing layer 30 may be formed by joining a cylindrical body portion and a dome-shaped side end portion so as to cover the liner 20.

[0023] An example of an application of such a high-pressure tank 1 is a hydrogen tank that stores hydrogen gas used as a reactant gas in a fuel cell. Hydrogen tanks can be used for a variety of purposes, including fuel cell vehicles and emergency power sources using fuel cells. In addition, the high-pressure tank can store not only hydrogen gas, but also any other fluid, such as other gases or liquids.

[0024] Next, the structure of the high-pressure tank 1 will be described in detail with reference to Fig. 2. Fig. 2 is a cross-sectional view of the high-pressure tank 1 in Fig. 1 taken along line AA. In this embodiment, the liner 20 is formed with a storage space 14 in which high-pressure gas is stored. The liner 20 has a cylindrical tubular member 21 and a pair of dome members 22, 22 joined to both ends of the tubular member 21. In this embodiment, the material of the liner 20 contains a resin material having a property (gas barrier property) that does not allow the fluid (high-pressure gas) trapped in the storage space 14 to pass through.

[0025] In this embodiment, specifically, the tubular member 21 has a laminated structure in which three resin layers are formed in the thickness direction. As shown in Fig. 3, the tubular member 21 has an overlapping portion 20a in which the end edge 21a of the tubular member 21 and the end edge 22a of the dome member 22 are overlapped in the radial direction of the tubular member 21 so that the end edge 21a of the tubular member 21 faces outward. In this embodiment, a welded portion 29 is formed in the overlapping portion 20a.

[0026] 3, the tubular member 21 has a three-layer structure including an outer peripheral layer (outer layer) 21A formed on the radially outer side of the tubular member 21, an intermediate layer 21B formed on the inner side of the outer peripheral layer 21A, and an inner peripheral layer (inner layer) 21C formed on the inner side of the intermediate layer 21B. The outer peripheral layer 21A, the intermediate layer 21B, and the inner peripheral layer 21C are layered to form a coaxial cylindrical shape centered on the axis of the tubular member 21. Such a tubular member 21 can be formed by extrusion molding.

[0027] The outer peripheral layer 21A is the layer located at the outermost position of the cylindrical member 21, and is a layer for ensuring the shape retention of the liner 20 and for ensuring adhesion with the reinforcing layer 30. If the intermediate layer 21B and the inner peripheral layer 21C described later can ensure these functions, the outer peripheral layer 21A may be omitted, and the cylindrical member 21 may have a structure in which the intermediate layer 21B and the inner peripheral layer 21C are laminated. The outer peripheral layer 21A is made of a resin material that does not contain an absorbent that absorbs laser light. Therefore, the outer peripheral layer 21A has a higher transmittance of laser light than the inner peripheral layer 21C and the dome member 22 described later.

[0028] Here, the resin material of the outer peripheral layer 21A may be any of the thermoplastic resins exemplified for the inner peripheral layer 21C described later, or may be the same type of resin material as that of the inner peripheral layer 21C described later. However, unlike the resin material of the inner peripheral layer 21C described later, the resin material of the outer peripheral layer 21A does not contain an absorbent that absorbs laser light.

[0029] Examples of resin materials for the outer peripheral layer 21A include thermoplastic resins such as nylon 6 (PA6), nylon 66 (PA66), polyethylene terephthalate (PET), polyvinylidene chloride (PVDC), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyetherimide (PEI), or polytetrafluoroethylene (PTFE).

[0030] Here, by selecting a resin material for the outer peripheral layer 21A having a melting point higher than that of the intermediate layer 21B (described later), it is possible to prevent the intermediate layer 21B from being deformed by heating during molding of the reinforcing layer 30. In particular, by setting the melting points of the resin materials constituting the outer peripheral layer 21A and the inner peripheral layer 21C higher than that of the resin material constituting the intermediate layer 21B, it is possible to prevent thermal deformation of the intermediate layer 21B.

[0031] The intermediate layer 21B is a layer made of a resin material having a barrier property (permeation resistance) against high pressure gas, and this resin material transmits laser light. In this embodiment, the intermediate layer 21B is a layer that does not absorb the energy of laser light and does not generate heat, since it does not contain an absorbent that absorbs laser light, similar to the outer peripheral layer 21A. The resin having gas barrier property that constitutes the intermediate layer 21B is a resin that has permeation resistance against the high pressure gas (e.g. hydrogen gas) filled in the high pressure tank 1, and specifically, is a resin that is less permeable to hydrogen gas than the resin that constitutes the inner peripheral layer 21C.

[0032] Examples of the resin material of the intermediate layer 21B include thermoplastic resins such as ethylene vinyl alcohol copolymer (EVOH), polyethylene (PE), polypropylene (PP), acrylonitrile-styrene copolymer (AS), acrylonitrile-butadiene-styrene copolymer (ABS), acrylic resin (PMMA), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), nylon 12 (PA12), polyacetal (POM), polycarbonate (PC), acetyl cellulose (CA), cast nylon (CN), etc. When the high-pressure gas filled in the high-pressure tank 1 is hydrogen gas, it is particularly preferable that the resin material of the intermediate layer 21B is ethylene vinyl alcohol copolymer (EVOH).

[0033] Here, the intermediate layer 21B corresponds to the "barrier layer" of the present invention, and the resin constituting the intermediate layer 21B corresponds to the "first resin material" of the present invention.

[0034] The inner circumferential layer 21C is a layer located at the innermost side of the cylindrical member 21. An edge portion of the inner circumferential layer 21C contacts and overlaps with the dome member 22, and at this overlapping portion, forms a welded portion 29 together with the resin material of the dome member 22. The inner circumferential layer 21C is made of a second resin material containing an absorbent that absorbs a portion of the laser light.

[0035] Specifically, the resin material of the inner circumferential layer 21C is different from the resin material of the outer circumferential layer 21A described later, and is a resin material containing an absorbent that absorbs a part of the laser light. The resin material of the inner circumferential layer 21C is a thermoplastic resin, which is the resin material exemplified for the outer circumferential layer 21A, and the abbreviated names include thermoplastic resins such as PA6, PA66, PET, PVDC, PBT, PPS, PEI, and PTFE. The resin material of the inner circumferential layer 21C is preferably nylon 6 (PA6). Since the inner circumferential layer 21C of the cylindrical member 21 is formed of nylon 6, even if the temperature of the inner circumferential layer 21C rises due to adiabatic compression when filling with high-pressure gas (hydrogen gas), the heat resistance of the cylindrical member 21 against this temperature rise can be ensured.

[0036] Further, examples of the absorbent contained in the resin material of the inner circumferential layer 21C include nigrosine, aniline black, phthalocyanine, naphthalocyanine, porphyrin, perylene, quaterrylene, azo dye, anthraquinone, squaric acid derivative, and immonium dye. The resin material of the inner circumferential layer 21C corresponds to the "second resin material" in the present invention. These absorbents are not particularly limited as long as they can absorb the laser light.

[0037] Here, the melting point of the resin material of the inner circumferential layer 21C is higher than that of the intermediate layer 21B. Here, the inner circumferential layer 21C and the dome member 22 described later contain an absorbent, but since the absorbent only needs to exhibit the laser light absorption property, generally, the resin material contains very little of it. Therefore, the melting point of the resin material of the inner circumferential layer 21C is almost the same as that of the resin (absorbent) which is the main material thereof.

[0038] For example, when the resin material of the intermediate layer 21B is an ethylene vinyl alcohol copolymer (EVOH), its melting point is 195° C., and therefore the resin material of the inner circumferential layer 21C has a higher melting point than the resin material of the intermediate layer 21B, as shown below: The abbreviations of the resins of the inner circumferential layer 21C, followed by the melting points in parentheses, are PA6 (220° C.), PA66 (265° C.), PET (260° C.), PVDC (210° C.), PBT (240° C.), PPS (290° C.), PEI (215° C.), or PTFE (330° C.).

[0039] The dome member 22 is made of a resin material (third resin material) containing an absorbent having higher laser light absorption than the absorbent of the resin (second resin material) of the inner circumferential layer 21C. Here, high laser light absorption means that a larger amount of heat is generated when a sample made of only the absorbent is irradiated with laser light under the same conditions. Therefore, the absorbent contained in the dome member 22 is an absorbent that generates a larger amount of heat when irradiated with laser light under the same conditions than the absorbent contained in the inner circumferential layer 21C.

[0040] Here, the resin constituting the dome member 22 may be the resin materials exemplified for the outer peripheral layer 21A and the inner peripheral layer 21C, and may be, in abbreviated form, thermoplastic resins such as PA6, PA66, PET, PVDC, PBT, PPS, PEI, or PTFE. It is more preferable that the resin material of the inner peripheral layer 21C and the dome member 22 are made of the same type of resin material. This can improve the fusion property of the inner peripheral layer 21C and the dome member 22 by the laser beam. The dome member 22 can be molded from such a resin material containing an absorbent by, for example, injection molding.

[0041] 2. Manufacturing method of high pressure tank 1 Next, a method for manufacturing the high-pressure tank 1 according to this embodiment will be described. Fig. 4 is a flow diagram for explaining a method for manufacturing the high-pressure tank shown in Fig. 1. Fig. 5A is a schematic perspective view for explaining a process for preparing a cylindrical member and a pair of dome members, and a process for forming an overlapping portion, and Fig. 5B is an enlarged view of a main part of Fig. 5A. Fig. 6A is a schematic perspective view for explaining a process for producing a liner, and Fig. 6B is an enlarged view of a main part of Fig. 6A.

[0042] First, as shown in Figures 5A and 5B, step S1 is performed to prepare a cylindrical member 21 and a pair of dome members 22, 22. Specifically, the cylindrical member 21 is prepared by laminating the above-mentioned outer peripheral layer 21A, intermediate layer (barrier layer) 21B, and inner peripheral layer 21C in the radial direction of the cylindrical member 21. A recess 22b having a depth D corresponding to the thickness T of the cylindrical member 21 is formed in the edge portion 22a of the dome member 22 along the circumferential direction. The resin materials constituting each of the outer peripheral layer 21A, intermediate layer (barrier layer) 21B, and inner peripheral layer 21C and the resin material constituting the dome member 22 are made of the materials as shown above.

[0043] Next, as shown in Figures 5A and 5B, step S2 of forming overlapping portion 20a is performed. In this step, overlapping portion 20a (Figure 6B) is formed by overlapping edge portion 21a of tubular member 21 and edge portion 22a of dome member 22 in the radial direction of tubular member 21 so that edge portion 21a of tubular member 21 is on the radial outside of tubular member 21. Specifically, in this embodiment, tubular member 21 and dome member 22 are brought close to each other along the direction of axis C, and edge portion 21a of tubular member 21 is fitted into recess 22b formed in edge portion 22a of dome member 22.

[0044] Here, the depth of the recess 22b of the dome member 22 is a depth D corresponding to the thickness T of the end edge portion 21a of the tubular member 21, so when the end edge portion 21a of the tubular member 21 is fitted into the recess 22b of the dome member 22, an outer peripheral surface 20c of the liner 20 without any steps is formed between the outer peripheral surface 21c of the tubular member 21 and the outer peripheral surface 22c of the dome member 22.

[0045] Next, as shown in Figures 6A and 6B, a step S3 of producing the liner 20 is performed. Specifically, the overlapping portion 20a is irradiated with laser light L along the edge portion 21a of the tubular member 21 from the radial outside of the tubular member 21, thereby joining the tubular member 21 and the dome member 22 to produce the liner 20. In this embodiment, as shown in Figure 6A, the overlapping portion 20a is irradiated with laser light L while rotating the tubular member 21 and the dome member 22 around the axis C.

[0046] More specifically, as shown in FIG. 6B, by irradiating laser light L, the resin material of the inner circumferential layer 21C and the resin material of the dome member 22 are melted while generating heat at the interface between each edge portion 21a of the tubular member 21 and each edge portion 22a of the dome member 22, thereby fusing the tubular member 21 and the dome member 22.

[0047] In this embodiment, the irradiation of the laser light L is terminated before the resin material of the inner circumferential layer 21C located at the interface between the inner circumferential layer 21C and the intermediate layer 22B melts, so that the irradiation time of the laser light L is set to satisfy such a condition. Specifically, the irradiation time of the laser light L can be set by adjusting the rotation speed of the cylindrical member 21 and the dome member 22.

[0048] By irradiating the laser light L in this manner, the laser light L passes through the outer circumferential layer 21A and the intermediate layer 21B. A portion of the laser light L that passes through the outer circumferential layer 21A and the intermediate layer 21B is absorbed by the absorbent of the inner circumferential layer 21C. The laser light L that is not absorbed by the inner circumferential layer 21C and passes through the inner circumferential layer 21C is finally absorbed by the absorbent of the dome member 22.

[0049] As a result, the inner circumferential layer 21C and the dome member 22 generate heat almost simultaneously due to absorption of the laser light L, and since the absorbent contained in the resin material of the dome member 22 has a higher absorption capacity for the laser light L than the absorbent contained in the resin material of the inner circumferential layer 21C, the temperature of the dome member 22 rises more quickly than that of the inner circumferential layer 21C.

[0050] This allows the inner circumferential layer 21C and the dome member 22 to melt simultaneously at the interface between the edge portion 21a of the tubular member 21 and the edge portion 22a of the dome member 22, thereby fusing the tubular member 21 and the dome member 22. As a result, the tubular member 21 and the dome member 22 can be fused and joined at their respective edge portions 21a, 22a without transmitting excessive heat from the dome member 22 to the intermediate layer 21B.

[0051] In this embodiment, if the melting point of the resin material of the inner circumferential layer 21C is higher than that of the intermediate layer 21B, the resin material of the intermediate layer 21B is likely to melt when the resin material of the inner circumferential layer 21C melts. However, in this embodiment, the irradiation of the laser light L is terminated before the resin material of the inner circumferential layer 21C located at the interface with the intermediate layer 21B melts, so that the resin material of the intermediate layer 21B can be prevented from melting. This reduces thermal damage to the resin material constituting the intermediate layer 21B and ensures the gas barrier properties of the intermediate layer 21B.

[0052] In particular, when ethylene vinyl alcohol copolymer (EVOH) is used for intermediate layer 21B, EVOH has a higher gas barrier property against hydrogen gas than other thermoplastic resins, but has a lower melting point than other thermoplastic resins. Therefore, for example, when EVOH is used for intermediate layer 21B and a thermoplastic resin such as nylon 6 (PA6) is used for inner circumferential layer 21C, only PA6 is melted, reducing thermal damage to the EVOH of intermediate layer 21B and ensuring the gas barrier property of EVOH.

[0053] In this embodiment, the resin material of the inner circumferential layer 21C and the resin material of the dome member 22 are melted while being heated, and the cylindrical member 21 and the dome member 22 are fused together, so that a welded portion 29 can be formed between the inner circumferential layer 21C of the cylindrical member 21 and the dome member 22. As a result, there is no fused portion on the outer circumferential surface 20c of the liner 20, and the outer circumferential surface 20c of the liner 20 can be maintained as a smooth surface without any steps between the outer circumferential surface 21c of the cylindrical member 21 and the outer circumferential surface 22c of the dome member 22.

[0054] Finally, a step S4 of covering the reinforcing layer 30 is performed. In this step, after the nozzles 41, 42 are attached to the manufactured liner 20, a fiber bundle impregnated with resin is wound around the liner 20 by a filament winding method. Specifically, the fiber bundle is wound around the outer circumferential surface of the cylindrical member 21 of the liner 20 by hoop winding, and then the fiber bundle is wound around the dome members 22, 22 by helical winding. By alternately repeating such winding, the reinforcing layer 30 is formed on the outer circumferential surface of the liner 20. In this manner, the high-pressure tank 1 shown in Figs. 1 and 2 can be manufactured.

[0055] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit of the present invention as described in the claims. [Explanation of symbols]

[0056] 1: high pressure tank, 20: liner, 20a: overlapping portion, 21: cylindrical member, 21B: intermediate layer (barrier layer), 21C: inner peripheral layer, 22: dome member, L: laser light

Claims

1. a liner made of a resin material, the liner including a cylindrical member and a pair of dome members joined to both ends of the cylindrical member so as to form a storage space for storing high-pressure gas; a reinforcing layer made of a fiber-reinforced resin material and covering an outer peripheral surface of the liner, The method for manufacturing the high-pressure tank includes the steps of: preparing the cylindrical member and the pair of dome members; forming an overlapping portion by overlapping an edge portion of the cylindrical member and an edge portion of the dome member in a radial direction of the cylindrical member such that the edge portion of the cylindrical member is on the radial outside of the cylindrical member; a step of irradiating a laser beam from the radially outer side along an edge portion of the cylindrical member to the overlapping portion, thereby joining the cylindrical member and the dome member to produce the liner; and covering the outer peripheral surface of the prepared liner with the reinforcing layer. As the cylindrical member, a cylindrical member is prepared in which at least a barrier layer made of a first resin material having gas barrier properties against high-pressure gas and transmitting the laser light, and an inner peripheral layer made of a second resin material containing an absorbent that absorbs a part of the laser light and disposed radially inward of the barrier layer, the second resin material having a melting point higher than the melting point of the first resin material, As the dome member, a dome member made of a third resin material containing an absorbent having a higher laser light absorption property than the absorbent of the second resin material is prepared; In the step of fabricating the liner, the second resin material and the third resin material are melted while being heated at an interface between an edge portion of the cylindrical member and an edge portion of the dome member by the irradiation of the laser light, thereby fusing the cylindrical member and the dome member; a step of terminating the irradiation of the laser light before the second resin material of the inner circumferential layer located at the interface between the inner circumferential layer and the barrier layer melts.

2. The method for manufacturing a high-pressure tank according to claim 1, wherein the second resin material is nylon 6.

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