High-pressure tank and method for manufacturing the same

Abstract

The present invention relates to a high-pressure tank and a method for manufacturing the high-pressure tank. The high-pressure tank includes: a liner including a cylindrical body and a pair of dome portions, each of the pair of dome portions being provided at a respective end portion of the body in the axial direction; and a reinforcing layer provided on an outer peripheral surface of the liner. The reinforcing layer includes: a pair of resin rings, each of the pair of resin rings being provided to surround a respective end portion of the outer peripheral surface of the body; a circumferential layer covering a portion of the outer peripheral surface of the body between the resin rings; and a helical layer covering the resin rings, the circumferential layer, and the dome portions. The resin rings are configured to cover a portion of the body starting from a boundary portion between the body and the dome portions, and the thickness of the resin rings increases from the boundary portion toward the center of the body.

Description

Technical Field

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

[0002] There is known a high-pressure tank, such as a hydrogen tank, which includes a liner having a cylindrical body and a pair of dome portions provided at both ends in the axial direction of the body, and a reinforcing layer provided on the outer peripheral surface of the liner and having a circumferential layer and a helical layer. A high-pressure tank having such a structure is manufactured in the following manner: using a fiber-reinforced resin in which fibers are impregnated with a resin, a circumferential layer is formed on the outer peripheral surface of the body of the liner, and then a helical layer covering the circumferential layer and the dome portions is formed (for example, see Japanese Unexamined Patent Application Publication No. 2014-133304 (JP2014-133304A)). Summary of the Invention

[0003] In the circumferential layer, the fibers impregnated with the resin are oriented in the circumferential direction at an angle substantially orthogonal to the axial direction of the liner, that is, in the circumferential direction of the high-pressure tank. On the other hand, in the helical layer, the fibers impregnated with the resin are not oriented in the circumferential direction of the high-pressure tank, but are oriented in various directions intersecting the circumferential direction of the high-pressure tank. Since the orientation directions of the fibers in the circumferential layer and the helical layer are different in this way, there is a possibility that delamination will occur at the interface between the circumferential layer and the helical layer near the boundary portion between the body and the dome portions.

[0004] The present invention provides a high-pressure tank in which delamination between the circumferential layer and the helical layer can be suppressed near the boundary portion between the body and the dome portions, and the present invention also provides a method for manufacturing the high-pressure tank.

[0005] A high-pressure tank according to one aspect of the present invention includes: a liner including a cylindrical body and a pair of dome portions, each of the pair of dome portions being provided at a corresponding end of the body in the axial direction; and a reinforcing layer provided on the outer peripheral surface of the liner. The reinforcing layer includes: a pair of resin members, each of the pair of resin members being provided so as to surround a corresponding end portion of the outer peripheral surface of the body; a circumferential layer covering a part of the outer peripheral surface of the body between the resin members; and a helical layer covering the resin members, the circumferential layer, and the dome portions. The resin members are configured to cover a part of the body starting from the boundary portion between the body and the dome portions, and the thickness of the resin members increases from the boundary portion toward the center of the body.

[0006] In the autoclave according to the present invention, a structure of a resin member and a helical layer is used near the boundary portion between the body and the dome portion of the liner, instead of the conventional structure of a circumferential layer and a helical layer. This eliminates the interface formed by fibers having different orientation directions near the boundary portion as in the conventional arrangement, and accordingly, delamination of the circumferential layer and the helical layer near the boundary portion between the body and the dome portion can be suppressed.

[0007] In the autoclave according to the above aspect, the resin member can be made of annular nylon. Nylon has little difference in stiffness from the liner, and accordingly can fill the gap between the liner, the circumferential layer, and the helical layer. Moreover, nylon is relatively inexpensive, and accordingly the manufacturing cost of the autoclave can be reduced.

[0008] In the autoclave according to the above aspect, the helical layer can include a bent portion along the shape of the dome portion, and the resin member can be arranged to extend from the boundary portion in the axial direction of the body to the portion of the body corresponding to the end of the bent portion of the bent portion. In the conventional structure of the circumferential layer and the helical layer, the region from the boundary portion to the portion of the body corresponding to the end of the bent portion of the bent portion is a region where the thickness of the circumferential layer changes. By arranging the resin member in the region where the thickness changes, the effect of suppressing delamination can be sufficiently ensured, and the influence on the strength of the reinforcing layer due to the arrangement of the resin member can be suppressed.

[0009] A manufacturing method according to another aspect of the present invention is a manufacturing method of an autoclave, the autoclave including: a liner including a cylindrical body and a pair of dome portions, each of the pair of dome portions being provided at a corresponding end portion of the body in the axial direction; and a reinforcing layer provided on the outer peripheral surface of the liner and including a pair of resin members, a circumferential layer, and a helical layer. The manufacturing method includes: a resin member manufacturing step of manufacturing a resin member such that in a state where the resin member is arranged to surround the outer peripheral surface of the body, the thickness of the resin member gradually increases from the boundary portion between the body and the dome portion toward the center of the body; a circumferential layer forming step of forming a circumferential layer on the outer peripheral surface of the body such that a part of the outer peripheral surface is covered; a resin member arranging step of arranging each of the resin members manufactured in the resin member manufacturing step on a corresponding end portion of the circumferential layer such that the thickest end portion of the resin member abuts against the end portion of the circumferential layer formed in the circumferential layer forming step; and a helical layer forming step of forming a helical layer covering the circumferential layer, the resin members provided at the corresponding ends of the circumferential layer, and the dome portions.

[0010] The manufacturing method according to the present invention includes: a resin member manufacturing step of manufacturing a resin member such that the thickness of the resin member gradually increases from a boundary portion between the body and the dome portion toward the center of the body; a circumferential layer forming step of forming a circumferential layer on an outer peripheral surface of the body such that a part of the outer peripheral surface is covered; a resin member setting step of setting each of the resin members onto a corresponding end portion of the circumferential layer such that the thickest end portion of the resin member abuts against the end portion of the circumferential layer; and a helical layer forming step of forming a helical layer covering the circumferential layer, the resin members, and the dome portion. In the pressure vessel manufactured in this way, there is no interface composed of fibers having different orientation directions near the boundary portion as in the conventional arrangement, and accordingly, delamination between the circumferential layer and the helical layer near the boundary portion between the body and the dome portion can be suppressed.

[0011] In the manufacturing method according to the above aspect, the circumferential layer forming step may be a step of inserting a liner into the circumferential layer wound around the body, which is cylindrical and pre-manufactured and hardened. Thus, the circumferential layer can be easily formed.

[0012] According to the present invention, delamination between the circumferential layer and the helical layer near the boundary portion between the body and the dome portion can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals denote like elements, and in which:

[0014] Figure 1 is a cross-sectional view of a pressure vessel according to one embodiment;

[0015] Figure 2 is Figure 1 an enlarged view of part II in

[0016] Figure 3 is a flowchart showing a method of manufacturing a pressure vessel according to the embodiment;

[0017] Figure 4A is a schematic view showing a method of manufacturing a pressure vessel according to the embodiment;

[0018] Figure 4B is another schematic view showing a method of manufacturing a pressure vessel according to the embodiment;

[0019] Figure 4C is another schematic view showing a method of manufacturing a pressure vessel according to the embodiment; and

[0020] Figure 4DIt is another schematic view showing a method of manufacturing a high-pressure tank according to this embodiment. Detailed Description

[0021] Embodiments of a high-pressure tank and a method of manufacturing the same according to the present invention will be described below with reference to the drawings. In the following description, an example will be described in which the high-pressure tank 1 is installed in a fuel cell electric vehicle and filled with high-pressure hydrogen therein. However, the high-pressure tank 1 can also be applied to other uses. Moreover, the gas that the high-pressure tank 1 can be filled with is not limited to high-pressure hydrogen, and other examples thereof include various types of compressed gases such as compressed natural gas (CNG), various liquefied gases such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG), and other gases.

[0022] High-Pressure Tank

[0023] First, reference will be made to Figure 1 and Figure 2 to describe the high-pressure tank. Figure 1 is a cross-sectional view of the high-pressure tank according to this embodiment, and Figure 2 is a schematic Figure 1 enlarged view of part II in Figure 1 As schematically shown in Figure 1 , the high-pressure tank 1 according to the present embodiment is a high-pressure gas storage container having a substantially cylindrical shape and rounded dome shapes at both ends. The high-pressure tank 1 includes a liner 2 having a gas barrier property, a reinforcing layer 3 covering the outer surface of the liner 2, and a neck 4 attached to one end of the high-pressure tank 1.

[0024] The liner 2 is a hollow container having a storage space 5 for storing high-pressure hydrogen and is formed of a resin material or the like having a gas barrier property with respect to hydrogen. The liner 2 has a cylindrical body 21 and a pair of dome portions 22, each of the dome portions 22 being provided on the respective left and right sides of the body 21 in the axial direction (i.e., the direction of the axis L of the high-pressure tank 1). The body 21 extends over a predetermined length in the direction of the axis L of the high-pressure tank 1. The dome portions 22 are formed to be continuous from both the right and left sides of the body 21 and each have a hemispherical shape in which the diameter decreases as it moves away from the body 21.

[0025] An opening is formed at the top of one of the dome portions 22 ( Figure 1 the dome portion 22 on the left side in Figure 1 ) of the dome portions 22, and the aforementioned neck 4 is attached to this opening. No opening is formed in the other dome portion 22.

[0026] For example, the liner 2 is integrally formed by rotational blow molding using a resin material such as polyethylene, nylon, etc. Alternatively, instead of an integral molding manufacturing method such as rotational blow molding, the liner 2 can be formed by joining a plurality of components separately obtained by injection or extrusion molding. Further, the liner 2 can be made of a metal material such as aluminum instead of a resin material.

[0027] The neck 4 is made by processing a metal material such as stainless steel, aluminum, etc. into a predetermined shape. The neck 4 has a neck body 41 having a substantially cylindrical shape and a flange portion 42 fitted between the liner 2 and the reinforcing layer 3. A valve (not shown schematically) for filling hydrogen into the storage space 5 and discharging it therefrom is attached to the neck 4.

[0028] The reinforcing layer 3 is a layer having a function of improving the mechanical strength such as stiffness and pressure resistance of the high-pressure tank 1 by reinforcing the liner 2. The reinforcing layer 3 includes a pair of resin rings 31 provided at corresponding end portions surrounding the outer peripheral surface of the body 21, a circumferential layer 32 provided between the resin rings 31 and covering a part of the body 21, and a helical layer 33 covering the resin rings 31, the circumferential layer 32, and the dome portion 22.

[0029] The resin ring 31 corresponds to the "resin component" described in the claims and is formed to cover a part of the body 21 starting from the boundary portion 23 between the body 21 and the dome portion 22. More specifically, the resin ring 31 is provided in the direction of the axis L of the high-pressure tank 1 from the boundary portion 23 to the portion of the body 21 corresponding to the end of the bent portion of the bent portion 332 (described later) of the helical layer 33. From the boundary portion 23 toward the center of the body 21, the thickness of the resin ring 31 increases.

[0030] The resin ring 31 is made of a resin material having almost no difference in stiffness compared with the liner 2. In the present embodiment, the resin ring 31 is preferably made of nylon. Nylon has almost no difference in stiffness from the liner 2, and accordingly, when thermal curing is performed after the helical layer 33 is formed later, the gap between the liner 2, the circumferential layer 32, and the helical layer 33 can be filled. Moreover, nylon is relatively inexpensive, and accordingly, the manufacturing cost of the high-pressure tank 1 can be reduced. Further, nylon does not contain fibers. The term "stiffness" here refers to the thermal expansion coefficient and Young's modulus of the liner 2.

[0031] The circumferential layer 32 is formed to cover a part between the left and right resin rings 31 on the outer peripheral surface of the main body 21. The circumferential layer 32 is formed of a fiber-reinforced resin. The fiber-reinforced resin is here obtained by impregnating fibers with a resin, and for example, an article made by bundling single filaments having a diameter of about several μm is impregnated with an uncured thermosetting resin or a thermoplastic resin. Examples of the single filaments include fibers such as glass fiber, carbon fiber, aramid fiber, alumina fiber, boron fiber, steel fiber, poly(p-phenylene-2,6-benzobisoxazole) (PBO) fiber, natural fiber, high-strength polyethylene fiber, etc., and among them, carbon fiber is preferably used from the viewpoints of weight reduction, mechanical strength, etc.

[0032] Examples of the thermosetting resin for the fiber-reinforced resin include phenolic resin, melamine resin, urea resin, epoxy resin, etc., and among them, epoxy resin is preferably used from the viewpoints of mechanical strength, etc. Generally, epoxy resin is a resin obtained by mixing a prepolymer which is a copolymer of bisphenol A and epichlorohydrin, etc. with a curing agent such as polyamine, etc. and thermally curing the resin. Epoxy resin has fluidity in the uncured state and forms a strong crosslinked structure after thermal curing. On the other hand, examples of the thermoplastic resin for the fiber-reinforced resin include polyetheretherketone, polyphenylene sulfide, polyacrylate, polyimide, polyamide, etc.

[0033] The circumferential layer 32 can be formed, for example, by directly performing circumferential winding of fibers impregnated with a resin on the outer peripheral surface of the main body 21. Circumferential winding is a form in which the fibers are wound in the circumferential direction of the liner 2 such that the angle (so-called winding angle) between the axis of the liner 2 (i.e., the axis L of the autoclave 1) and the winding direction of the fibers is substantially perpendicular. The term "substantially perpendicular" as used here includes both 90° and an angle of about 90° that can be formed by winding the fibers while shifting the winding position so that the fibers do not overlap each other.

[0034] In addition, the circumferential layer 32 can be formed, for example, by winding fibers impregnated with a resin around the outer peripheral surface of a cylindrical mold by using circumferential winding to manufacture a circumferential layer-wound main body, hardening the manufactured circumferential layer-wound main body, and then inserting the liner into the circumferential layer-wound main body.

[0035] Note that the thickness of the circumferential layer 32 is preferably the same as the maximum thickness of the resin ring 31. Therefore, when the helical layer 33 is formed on the outer sides of the resin ring 31 and the circumferential layer 32, the formation of a gap due to the thickness difference can be suppressed.

[0036] The helical layer 33 is formed of a fiber-reinforced resin so as to cover the resin ring 31, the circumferential layer 32, and the dome portion 22. The fiber-reinforced resin for the helical layer 33 can be the same as or different from the fiber-reinforced resin for the circumferential layer 32, but is preferably the same from the viewpoint of cost reduction.

[0037] The helical layer 33 is formed by, for example, helically winding fibers impregnated with resin so as to cover the resin ring 31, the circumferential layer 32, and the dome portion 22. Note that helical winding is a form in which the fibers are helically wound such that the angle (winding angle) between the axis of the liner 2 and the winding direction of the fibers is greater than 0° and less than 90°. Depending on the winding angle, such helical winding is further divided into low-angle helical winding and high-angle helical winding.

[0038] Low-angle helical winding is a form of helical winding when the winding angle is small (for example, greater than 0° and not greater than 30°) and the winding direction of the fibers is reversed at the dome portion 22 before the fibers make one full turn around the axis of the liner 2. High-angle helical winding is a form of helical winding when the winding angle is large (for example, greater than 30° and less than 90°), and the fibers are wound around the axis of the liner 2 on the body 21 for at least one full turn until the winding direction of the fibers is reversed at the dome portion 22.

[0039] The helical layer 33 has a pair of left and right curved portions 332 formed in the form along the dome portion 22 of the liner 2 and a straight cylindrical portion 331 connecting the left and right curved portions 332.

[0040] In the autoclave 1 according to the present embodiment, the structure of the resin ring 31 and the helical layer 33 is used near the boundary portion 23 between the body 21 and the dome portion 22, instead of the conventional structure of the circumferential layer and the helical layer. This eliminates the interface formed by fibers having different orientation directions near the boundary portion as in the conventional arrangement, and thus delamination between the circumferential layer 32 and the helical layer 33 near the boundary portion 23 can be suppressed. As a result, compared with the conventional structure, the strain experienced by the fibers of the helical layer 33 can be reduced, and fiber wear can be suppressed.

[0041] Note that in the present embodiment, the term "near the boundary portion" does not mean the side toward the dome portion 22 from the boundary portion 23 between the body 21 and the dome portion 22, but actually means a partial region of the body 21 toward the center of the body 21 from the boundary portion 23.

[0042] Moreover, the resin ring 31 is provided in the direction of the axis L of the autoclave 1 from the boundary portion 23 to the portion of the body 21 corresponding to the end of the curved portion of the curved portion 332 of the helical layer 33. In the conventional structure of the circumferential layer and the helical layer, the region from the boundary portion to the portion of the body corresponding to the end of the curved portion of the curved portion is a region where the thickness of the circumferential layer changes. By providing the resin ring 31 in the region where the thickness changes, the effect of suppressing delamination can be sufficiently ensured, and the influence on the strength of the reinforcing layer 3 due to the provision of the resin ring 31 can be suppressed.

[0043] That is, when the position where the resin ring 31 is provided is a position closer to the boundary portion 23 side than the end of the bent portion of the bent portion 332, a portion where the thickness of the circumferential layer 32 changes is formed, and accordingly, there is a possibility that the delamination suppression effect will be insufficient. On the other hand, when the position where the resin ring 31 is provided exceeds the end of the bent portion of the bent portion (that is, when these positions are closer to the center of the main body 21), the provision of the resin ring 31 may affect the strength of the reinforcing layer 3. Considering the above, the resin ring 31 is preferably provided in the region from the boundary portion 23 to the portion corresponding to the end of the bent portion of the bent portion 332 of the spiral layer 33 in the main body 21.

[0044] Method for manufacturing autoclave

[0045] Next, reference will be made to Figures 3 to 4D describe the manufacturing method of the autoclave 1 according to the present embodiment. Figure 3 is a flowchart showing the manufacturing method of the autoclave according to this embodiment, and Figures 4A to 4D is a schematic view schematically showing the manufacturing method of the autoclave according to this embodiment. The manufacturing method of the autoclave 1 includes a liner manufacturing step S1, a circumferential layer winding body manufacturing step S2, a resin ring manufacturing step S3, a circumferential layer forming step S4, a resin ring setting step S5, and a spiral layer forming step S6. Note that the liner manufacturing step S1, the circumferential layer winding body manufacturing step S2, and the resin ring manufacturing step S3 are independent steps from each other, and accordingly, they can be executed in parallel, and any one of these steps can be executed first.

[0046] In the liner manufacturing step S1, a liner 2 is manufactured. The liner 2 has a cylindrical main body 21 and dome portions 22 provided at both ends of the main body 21 in the axial direction. Specifically, first, the liner 2 is integrally formed by rotational blow molding using resin components such as polyethylene, nylon, etc. Next, a neck 4 is attached to one end of the formed liner 2 (see Figure 4A ).

[0047] In the circumferential layer winding body manufacturing step S2, first, a sheet made of a fiber-reinforced resin is wound around the outer peripheral surface of a drum-shaped mandrel such that the fibers are oriented in the circumferential direction of the mandrel, thereby forming a circumferential layer winding body 30 having a cylindrical shape and being an intermediate form of the circumferential layer 32. Next, the formed circumferential layer winding body 30 is removed from the mandrel and hardened (see Figure 4A ).

[0048] The method for hardening the circumferential layer winding body 30 (in other words, the resin in which the fibers are impregnated) is not particularly limited. However, when the resin used for impregnation is a thermosetting resin, the resin can be pre-cured. The pre-curing conditions (temperature and time) vary depending on the type of resin used for impregnation, but the viscosity of the resin is set to be higher than the viscosity when it is wound around a predetermined mold (the viscosity before pre-curing). Here, the pre-curing is performed until the resin used for impregnation loses its fluidity. On the other hand, when the resin used for impregnation is a thermoplastic resin, the resin can be hardened by cooling the fibers in a state where the resin has fluidity.

[0049] In addition, in this circumferential layer winding body manufacturing step S2, the circumferential layer winding body 30 can be formed by a centrifugal winding (CW) method, in which a fiber sheet impregnated with resin is attached to the inner surface of a rotating cylindrical mold. The fiber sheet used at this time has, for example, fibers oriented in the circumferential direction of the cylindrical mold.

[0050] In the resin ring manufacturing step S3, a resin ring 31 is manufactured by injection molding using nylon such that in a state where the manufactured resin ring 31 is later set to surround the outer peripheral surface of the main body 21 of the lining 2, its thickness gradually increases from the boundary portion 23 between the main body 21 and the dome portion 22 toward the center of the main body 21 (see Figure 4A ).

[0051] In the circumferential layer forming step S4, the lining 2 manufactured in the lining manufacturing step S1 is inserted into the circumferential layer winding body 30 manufactured and hardened in the circumferential layer winding body manufacturing step S2, thereby forming a circumferential layer 32 (see Figure 4B ).

[0052] In the resin ring setting step S5, the resin ring 31 manufactured in the resin ring manufacturing step S3 is set at both end portions of the circumferential layer 32 formed in the circumferential layer forming step S4. At this time, the resin ring 31 is assembled onto the outer peripheral surface of the main body 21 such that the thickest end portion of the resin ring 31 abuts against the end portion of the circumferential layer 32 (see Figure 4B and Figure 4C ). In addition, the end portions of the resin ring 31 and the end portions of the circumferential layer 32 are preferably fixed with an adhesive so as to suppress the positional deviation of the resin ring 31.

[0053] In the helical layer forming step S6, a helical layer is formed which covers the circumferential layer 32, the resin rings 31 provided at both ends of the circumferential layer 32, and the dome portion 22 of the liner 2. Specifically, first, fibers impregnated with resin are wound by helical winding so as to cover the entire circumferential layer 32, the resin rings 31, and the dome portion 22, thereby forming a winding body for the helical layer. Next, the winding body for the helical layer, the circumferential layer 32, and the liner 2 on which the resin rings 31 are formed are conveyed into a thermosetting furnace, and the fibers impregnated with resin are thermoset, for example, by heating in the thermosetting furnace at 160° C. for 10 minutes. Thus, the pressure vessel 1 is manufactured.

[0054] In the pressure vessel 1 manufactured by the above manufacturing method, there is no interface formed by fibers having different orientation directions near the boundary portion as in the conventional arrangement, and accordingly, delamination between the circumferential layer 32 and the helical layer 33 near the boundary portion 23 between the body 21 and the dome portion 22 can be suppressed.

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

[0056] For example, in the above embodiments, the resin member has been described as a resin ring, but in addition to the resin ring, for example, a C-shaped resin member or a combination of a plurality of arc-shaped resin members can also be used.

Claims

1. A manufacturing method of a high-pressure tank, the high-pressure tank comprising: A lining, the lining including a cylindrical-shaped body and a pair of dome portions, each of the pair of dome portions being provided at a respective end of the body in the axial direction, wherein the lining is formed of nylon; and a reinforcing layer, the reinforcing layer being provided on the outer peripheral surface of the lining, and the reinforcing layer including a pair of resin members, a circumferential layer, and a helical layer, the manufacturing method being characterized by including: A resin member manufacturing step: manufacturing the resin members by injection molding using nylon such that in a state where the resin members are arranged to surround the outer peripheral surface of the body, the thickness of the resin members gradually increases from a boundary portion between the body and the dome portions toward the center of the body, wherein the nylon for manufacturing the resin members does not contain fibers; A circumferential layer forming step: winding a sheet made of fiber-reinforced resin around the outer peripheral surface of a drum-shaped mandrel such that the fibers are oriented in the circumferential direction of the mandrel, thereby forming the circumferential layer on the outer peripheral surface of the body such that a part of the outer peripheral surface is covered, wherein the thickness of the circumferential layer is the same as the maximum thickness of the resin members; A resin member setting step: setting each of the resin members manufactured in the resin member manufacturing step on a respective end portion of the circumferential layer such that the thickest end portion of the resin members abuts against the end portion of the circumferential layer formed in the circumferential layer forming step; and A helical layer forming step: forming the helical layer by helically winding fibers impregnated with resin, the helical layer covering and contacting the circumferential layer, the resin members provided at respective ends of the circumferential layer, and the dome portions.

2. The manufacturing method according to claim 1, wherein The circumferential layer forming step is a step in which the lining is inserted into a circumferential layer winding body, the circumferential layer winding body being cylindrical-shaped and pre-manufactured and hardened.

3. The manufacturing method according to claim 1 or 2, wherein The resin members are resin rings.

4. The manufacturing method according to claim 1 or 2, wherein The helical layer includes a bent portion along the shape of the dome portions, and The resin members are arranged in the axial direction of the body from the boundary portion to a portion of the body corresponding to the end of the bent portion of the bent portion.

5. The manufacturing method according to claim 1 or 2, wherein The end portions of the resin members and the end portions of the circumferential layer are fixed with an adhesive.

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