Fiber-reinforced resin pipe manufacturing method and high-pressure tank manufacturing method

Abstract

To provide a method for manufacturing a fiber-reinforced resin pipe capable of shortening process time.SOLUTION: A method for manufacturing a fiber-reinforced resin pipe includes: a preparation step which prepares a metallic mandrel having a first cylindrical part and two second cylindrical parts disposed at both ends in an axial direction of the first cylindrical part, and having a first thickness, which is the thinnest in the first cylindrical part, being thinner than a second thickness, which is the thinnest in the two second cylindrical parts; a fiber layer formation step which forms a fiber layer by winding fibers impregnated with thermosetting resin around the first cylindrical part; and a heating step which thermally cures the thermosetting resin of the fiber layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a fiber-reinforced resin pipe and a method for manufacturing a high-pressure tank. [Background technology]

[0002] Conventionally, a method for manufacturing carbon fiber reinforced resin is a filament winding method in which carbon fiber impregnated with a thermosetting resin is wound around a metal mandrel (for example, Patent Document 1). The fiber layer wound around the mandrel is thermoset by heating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-888 Summary of the Invention [Problem to be solved by the invention]

[0004] In the process of heating the fiber layer, the applied heat is transferred to the mandrel, so the rate of temperature rise near the inner circumferential surface of the fiber layer is slower than near the outer circumferential surface of the fiber layer. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms. According to one aspect of the present disclosure, there is provided a method for manufacturing a fiber-reinforced resin pipe, the method including: a preparation step of preparing a metal mandrel having a first cylindrical portion and two second cylindrical portions disposed at both axial ends of the first cylindrical portion, wherein a first thickness, which is the thinnest of the first cylindrical portion, is thinner than a second thickness, which is the thinnest of the two second cylindrical portions; a fiber layer formation step of winding fibers impregnated with a thermosetting resin around the first cylindrical portion to form a fiber layer; and a heating step of thermally curing the thermosetting resin in the fiber layer, wherein the amount of heat applied to the first cylindrical portion in the heating step is greater than the amount of heat applied to the second cylindrical portion.

[0006] (1) According to one aspect of the present disclosure, there is provided a method for manufacturing a fiber-reinforced resin pipe. This manufacturing method includes: a preparation step of preparing a metal mandrel having a first cylindrical portion and two second cylindrical portions disposed at both axial ends of the first cylindrical portion, the first thickness being thinner than the second thickness being thinner of the two second cylindrical portions; a fiber layer formation step of winding fibers impregnated with a thermosetting resin around the first cylindrical portion to form a fiber layer; and a heating step of thermally curing the thermosetting resin in the fiber layer. According to this aspect, the first cylindrical portion has a first thickness thinner than the second thickness, thereby reducing the heat capacity of the first cylindrical portion compared to when the first cylindrical portion has a uniform thickness and the thickness is the second thickness. Therefore, heat applied to the fiber layer in the heating step is less likely to be transferred to the mandrel, thereby suppressing a decrease in the rate of temperature rise near the inner circumferential surface of the fiber layer. This reduces the process time required for manufacturing. Furthermore, since the second cylindrical portion has a second thickness that is greater than the first thickness, the strength of the mandrel can be maintained. (2) In the manufacturing method of the above embodiment, the thickness of the first cylindrical portion may be thinner than the second thickness. According to this embodiment, the thickness of every part of the first cylindrical portion is thinner than the second thickness, so the heat capacity can be further reduced compared to when only a part of the first cylindrical portion is thinner than the second thickness. Therefore, the effect of suppressing a decrease in the temperature rise rate near the inner circumferential surface of the fiber layer can be further enhanced. (3) In the manufacturing method of the above aspect, the outer diameter of the first cylindrical portion and the outer diameter of the two second cylindrical portions may be the same. According to this aspect, a fiber-reinforced resin pipe having a uniform inner diameter can be manufactured. (4) In the manufacturing method of the above embodiment, when the thickness of the fiber layer is t1 and the first thickness is t2, 0.35≦t1 / t2≦2 According to this embodiment, distortion of the fiber-reinforced resin pipe can be suppressed and residual stress in the fiber-reinforced resin pipe can be reduced. Therefore, a fiber-reinforced resin pipe having sufficient strength can be manufactured. If the fiber layer is too thick relative to the first thickness of the mandrel, radial stress of the fiber layer may distort the mandrel during the fiber layer forming step, resulting in a risk of distortion of the shape of the fiber layer. On the other hand, since the linear expansion coefficient of the mandrel is greater than that of the fiber layer, if the fiber layer is too thin relative to the first thickness of the mandrel, the radial stress of the mandrel may cause the fiber layer to be cured in a radially expanded state during the heating step, which may result in residual stress in the fiber layer. Therefore, by setting the thickness of the fiber layer within the above range, distortion of the fiber-reinforced resin pipe can be suppressed and residual stress in the fiber-reinforced resin pipe can be reduced. (5) In the manufacturing method of the above aspect, the amount of heat applied to the first cylindrical portion may be greater than the amount of heat applied to the second cylindrical portion in the heating step. According to this aspect, the fiber layer can be thermally cured more efficiently in the heating step than when the same amount of heat as that applied to the second cylindrical portion is applied to the first cylindrical portion. (6) There is provided a method for manufacturing a high-pressure tank using the manufacturing method described in the above aspect. This manufacturing method includes, after the heating step, removing the fiber layer from the mandrel and inserting a liner inside the fiber layer. According to this aspect, the high-pressure tank is manufactured using a heat-set fiber layer manufactured in a shorter process time, so that the high-pressure tank can be manufactured in a shorter process time. The present disclosure can be realized in various forms other than the fiber-reinforced resin pipe manufacturing method, for example, a fiber-reinforced resin pipe manufacturing apparatus, a fiber-reinforced resin pipe manufacturing mandrel, etc. [Brief explanation of the drawings]

[0007] [Figure 1] 4 is a flowchart showing a method for manufacturing a fiber-reinforced resin pipe. [Figure 2] Cross section of a mandrel. [Figure 3] FIG. [Figure 4] FIG. 10 is a diagram showing the relationship between the thickness ratio and the radial stress of the mandrel. [Figure 5] FIG. 10 is a diagram showing the relationship between the thickness ratio and the radial stress of the fiber layer. [Figure 6] 10 is a flowchart showing a method for manufacturing a high-pressure tank according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. First embodiment: FIG. 1 is a flowchart of a manufacturing process for achieving a method for manufacturing a fiber-reinforced resin pipe. FIG. 2 is a cross-sectional view of a mandrel 10. FIG. 2 is a cross-sectional view of the mandrel 10, cut along a plane along the central axis CX of the mandrel 10. FIG. 3 is a schematic cross-sectional view illustrating a heating step P30. In a preparation step P10 shown in FIG. 1, the mandrel 10 is prepared. The mandrel 10 is used as a mold around which fibers impregnated with a thermosetting resin are wound in the subsequent fiber layer formation step P20. The mandrel 10 is made of metal, and in this embodiment, is made of steel. As shown in FIG. 2, the mandrel 10 has a cylindrical shape and includes a first cylindrical portion 11 and two second cylindrical portions 12. Each of the two second cylindrical portions 12 is disposed at each end of the first cylindrical portion 11 in the axial direction, which is the direction of the central axis CX. 3, in the fiber layer forming step P20, the first cylindrical portion 11 is a portion around which the fiber is wound, and the second cylindrical portion 12 is a portion around which the fiber is not wound. The outer diameter of the first cylindrical portion 11 is the same as the outer diameter of the second cylindrical portion 12. This makes it possible to manufacture a fiber-reinforced resin pipe with a uniform inner diameter.

[0009] As shown in Figure 2, in this embodiment, the thickness of the mandrel 10 is not uniform. The thickness is thinnest at the center of the mandrel 10 in the axial direction, i.e., the center of the first cylindrical portion 11, and thickest at the ends of the mandrel 10 in the axial direction, i.e., the ends of the second cylindrical portion 12. In the axial direction, the thickness of the mandrel 10 gradually increases from the center to both ends of the first cylindrical portion 11. The inner peripheral surface of the mandrel 10 has a shape that describes a circle in the circumferential direction and a curve in the axial direction.

[0010] The first thickness t2, which is the thinnest thickness of the first cylindrical portion 11, is thinner than the second thickness t3, which is the thinnest thickness of the second cylindrical portion 12. This makes it difficult for heat applied to the fiber layer 20 in the heating step P30 to be transferred to the mandrel 10. This is because the heat capacity of the first cylindrical portion 11 can be reduced compared to when the first cylindrical portion 11 has a uniform thickness and the thickness is the second thickness t3. Furthermore, because the second cylindrical portion 12 has a second thickness t3 that is thicker than the first thickness t2, the mandrel 10 can maintain sufficient strength. Furthermore, the thickness of the first cylindrical portion 11 is thinner than the second thickness t3 at every portion. This makes it possible to reduce the heat capacity of the first cylindrical portion 11 compared to when only a portion of the first cylindrical portion 11 is thinner than the second thickness t3. Furthermore, because the first thickness t2 is thinner than the second thickness t3, the weight of the mandrel 10 can be reduced compared to when the first cylindrical portion 11 has a uniform thickness and the thickness is the second thickness t3. Therefore, the mandrel 10 can be easily transported.

[0011] In the fiber layer forming step P20 shown in FIG. 1 , fibers impregnated with a thermosetting resin are wound around the first cylindrical portion 11 of the mandrel 10 to form a fiber layer 20. In the following description, the "fibers impregnated with a thermosetting resin" may be simply referred to as "fibers." In this embodiment, the thermosetting resin is an epoxy resin, but is not limited to epoxy resin and may be a phenolic resin, melamine resin, urea resin, or the like. Furthermore, in this embodiment, the fiber material is a carbon fiber, but is not limited to carbon fiber and may be, for example, glass fiber, aramid fiber, boron fiber, or the like.

[0012] Specifically, the mandrel 10 shown in Figure 3 rotates about the central axis CX while winding the fiber delivered from a yarn feeder (not shown), thereby winding the fiber onto the mandrel 10. The yarn feeder moves along the axial direction, thereby adjusting the position on the mandrel 10 where the fiber is wound. The fiber is wound in a hoop winding manner at an angle of approximately 90 degrees with respect to the central axis CX of the mandrel 10. The fiber layer 20 is formed in multiple layers by winding additional fiber on top of the layer formed by winding the fiber.

[0013] The fiber layer thickness t1, which is the thickness of the fiber layer 20 shown in FIG. 3, and the first thickness t2 satisfy the following formula (1). 0.35≦t1 / t2≦2...Equation (1) This makes it possible to suppress distortion of the fiber-reinforced resin pipe and to suppress the occurrence of residual stress in the fiber-reinforced resin pipe.

[0014] If the fiber layer 20 is too thick relative to the first thickness t2 of the mandrel 10, in the fiber layer forming step P20, the mandrel 10 will be subjected to a force from the fiber layer 20 that reduces its radial diameter, which could result in the cross-sectional shape of the mandrel 10 in the radial direction being distorted from a perfect circle. On the other hand, since the linear expansion coefficient of the mandrel 10 is greater than that of the fiber layer 20, if the fiber layer 20 is too thin relative to the first thickness t2 of the mandrel 10, the mandrel 10 will expand radially due to heat in the heating step P30, causing the fiber layer 20 to harden in a radially expanded state, which could result in residual stress being generated in the fiber layer 20. The inventors have studied the fiber layer thickness t1 and the first thickness t2 and have found that when the range defined by formula (1) is satisfied, distortion of the fiber-reinforced resin pipe and the generation of residual stress in the fiber-reinforced resin pipe can be suppressed.

[0015] 4 and 5 show the results of the inventors' study on the fiber layer thickness t1 and the first thickness t2. Specifically, FIG. 4 is a diagram showing the relationship between the thickness ratio, which is the ratio of the fiber layer thickness t1 to the first thickness t2, and the radial stress of the mandrel 10 when the fiber layer 20 is formed. FIG. 5 is a diagram showing the relationship between the thickness ratio and the radial stress of the fiber layer 20 when the fiber layer 20 is formed. FIGS. 4 and 5 show the relationship between the thickness ratio and the radial stress of the fiber layer 20 when the outer diameter of the mandrel 10 is 300 mm and the linear expansion coefficient of the fiber layer 20 is 2×10 -6 The linear expansion coefficient of the mandrel 10 is 10.5 × 10, which is the linear expansion coefficient of general steel. -6 4 and 5 plot the calculation results of stress when the fiber layer thickness t1 is set to 2 mm, 5 mm, and 10 mm and the ratio of the fiber layer thickness t1 to the first thickness t2 is set to various values.

[0016] As shown in Fig. 4, the greater the fiber layer thickness t1 is relative to the first thickness t2, that is, the greater the thickness ratio, the greater the stress that reduces the radial diameter of the mandrel 10. On the other hand, as shown in Fig. 5, the greater the first thickness t2 is relative to the fiber layer thickness t1, that is, the smaller the thickness ratio, the greater the stress that expands the radial diameter of the fiber layer 20.

[0017] To prevent distortion of the mandrel 10 due to the formation of the fiber layer 20, the radial stress shown in FIG. 4 is preferably less than 190 MPa. Therefore, the thickness ratio is preferably 2.0 or less. On the other hand, to sufficiently reduce the residual stress generated in the fiber layer 20 due to the thermal expansion of the mandrel 10 in the heating step P30, the radial stress shown in FIG. 5 is preferably less than 250 MPa. Therefore, the thickness ratio is preferably 0.35 or more. As described above, by satisfying the above formula (1), distortion of the fiber-reinforced resin pipe and the generation of residual stress in the fiber-reinforced resin pipe can be suppressed. Furthermore, a thinner first thickness t2 of the mandrel 10 can more effectively suppress the transfer of heat to the mandrel 10 in the heating step P30, so a thickness ratio of 2.0 is even more preferable.

[0018] In the heating step P30 shown in FIG. 1 , the thermosetting resin contained in the fiber layer 20 is thermally cured using a heating furnace. Specifically, the fiber layer 20 is heated until the temperature of the fiber layer 20 reaches a target temperature at which the thermosetting resin contained in the fiber layer 20 is thermally cured. As shown in FIG. 3 , both ends of the mandrel 10 on which the fiber layer 20 is formed are held by a pair of collets 50. The mandrel 10 held by the pair of collets 50 is rotated around the central axis CX. In this embodiment, the heating furnace includes a heater and a fan (not shown), and blows hot air toward the mandrel 10 in the direction of the arrows shown in FIG. 3 . In this embodiment, the amount of heat applied per unit time to the first cylindrical portion 11 is adjusted to be greater than the amount of heat applied per unit time to the second cylindrical portion 12. Specifically, the hot air is sent more densely to the first cylindrical portion 11 than to the second cylindrical portion 12. Hot air is densely delivered by at least one of adjusting the direction and position of the fan, or making the airflow speed of the fan that mainly delivers air to the first cylindrical portion 11 faster than the airflow speed of the fan that mainly delivers air to the second cylindrical portion 12. By adjusting the amount of heat applied to the first cylindrical portion 11 to be greater than the amount of heat applied to the second cylindrical portion 12, the amount of heat received by the first cylindrical portion 11 is greater than the amount of heat received by the second cylindrical portion 12. Therefore, when the total amount of heat applied in the heating step P30 is the same, the fiber layer 20 can be thermally cured more efficiently than when a heat amount with no gradient is applied to the mandrel 10.

[0019] In the heating step P30, the mandrel 10 is heated from the outside, so the rate of temperature rise on the inner peripheral surface of the fiber layer 20 is slower than the rate of temperature rise on the outer peripheral surface. Here, as described above, the first thickness t2 is thinner than the second thickness t3, and the heat capacity of the first cylindrical portion 11 is small, so the heat applied to the fiber layer 20 in the heating step P30 is less likely to be transferred to the mandrel 10. This makes it possible to suppress a decrease in the rate of temperature rise on the inner peripheral surface of the fiber layer 20, and shorten the time required to reach the target temperature required for thermal curing. This therefore shortens the process time required for manufacturing.

[0020] Furthermore, by reducing the difference in the temperature rise rate between the outer peripheral surface and the inner peripheral surface of the fiber layer 20, it is possible to suppress a decrease in the strength of the fiber layer 20 after thermal curing. If the temperature rise rate in the fiber layer 20 varies, the timing of thermal curing will vary, and residual stress may occur in the fiber layer 20 after thermal curing due to shrinkage caused by thermal curing. Here, by reducing the difference in the temperature rise rate between the outer peripheral surface and the inner peripheral surface of the fiber layer 20, it is possible to reduce the variation in the timing of thermal curing. Therefore, it is possible to suppress the occurrence of residual stress and suppress a decrease in the strength of the fiber layer 20 after thermal curing.

[0021] Furthermore, because the first thickness t2 of the first cylindrical portion 11 is thinner than the second thickness t3, a decrease in the strength of the fiber layer 20 after thermal curing can be suppressed. Because the first thickness t2 is thinner than the second thickness t3, the rigidity of the first cylindrical portion 11 can be lower than when the first cylindrical portion 11 has a uniform thickness and the thickness is the second thickness t3. As described above, due to the difference in the linear expansion coefficients of the fiber layer 20 and the mandrel 10, the mandrel 10 is likely to expand radially in the heating step P30. If the fiber layer 20 expands radially and is cured in a state in which tensile stress is generated in the fiber layer 20, residual stress may be generated in the fiber layer 20. Here, by thinning the first cylindrical portion 11 and reducing the rigidity of the first cylindrical portion 11, the expansion of the mandrel 10 in the heating step P30 can be suppressed. Therefore, the generation of residual stress in the fiber layer 20 after thermal curing can be suppressed, and a decrease in strength can be suppressed.

[0022] By carrying out the heating step P30, a fiber reinforced resin pipe, which is the thermally cured fiber layer 20, in this embodiment, a CFRP (Carbon Fiber Reinforced Plastics) pipe is completed. The fiber reinforced resin pipe is removed from the mandrel 10, and this manufacturing process is completed.

[0023] The manufacturing method according to the first embodiment described above includes a preparation step P10 for preparing a metal mandrel 10 having a first cylindrical portion 11 and two second cylindrical portions 12, a fiber layer formation step P20 for forming a fiber layer 20, and a heating step P30 for thermally curing the thermosetting resin of the fiber layer 20. Therefore, the first cylindrical portion 11 has a first thickness t2 that is thinner than the second thickness t3, thereby reducing the heat capacity compared to when the first cylindrical portion 11 has a uniform thickness equal to the second thickness t3. Therefore, heat applied to the fiber layer 20 in the heating step P30 is less likely to be transferred to the mandrel 10, thereby suppressing a decrease in the rate of temperature rise near the inner surface of the fiber layer 20. This reduces the process time. Furthermore, the second cylindrical portion 12 has a second thickness t3 that is thicker than the first thickness t2, thereby maintaining the strength of the mandrel 10.

[0024] Furthermore, the thickness of the first cylindrical portion 11 is thinner than the second thickness t3. Therefore, the thickness of every portion of the first cylindrical portion 11 is thinner than the second thickness t3, and the heat capacity can be further reduced compared to when only a portion of the first cylindrical portion 11 is thinner than the second thickness t3. This further enhances the effect of suppressing a decrease in the rate of temperature rise near the inner circumferential surface of the fiber layer 20.

[0025] Furthermore, the outer diameter of the first cylindrical portion 11 is the same as the outer diameter of the two second cylindrical portions 12. Therefore, a fiber reinforced resin pipe with a uniform inner diameter can be manufactured.

[0026] Furthermore, the fiber layer thickness t1 and the first thickness t2 satisfy the above formula (1). This suppresses distortion of the fiber-reinforced resin pipe and reduces residual stress in the fiber-reinforced resin pipe. Therefore, a fiber-reinforced resin pipe with sufficient strength can be manufactured.

[0027] Furthermore, in the heating step P30, the amount of heat applied to the first cylindrical portion 11 is greater than the amount of heat applied to the second cylindrical portion 12. Therefore, the fiber layer 20 can be thermally cured more efficiently in the heating step P30 than when the same amount of heat as that applied to the second cylindrical portion 12 is applied to the first cylindrical portion 11.

[0028] B. Second embodiment: 6 is a flowchart of the manufacturing process for achieving the manufacturing method of the high-pressure tank according to the second embodiment. The high-pressure tank is manufactured using a fiber-reinforced resin pipe manufactured using the method according to the first embodiment. The same steps as those in the first embodiment are designated by the same reference numerals, and detailed explanations will be omitted where appropriate.

[0029] The high-pressure tank is mounted on, for example, a fuel cell vehicle and used to store fuel gas to be supplied to the fuel cell. The high-pressure tank has a cylindrical portion and two hemispherical dome portions located at both axial ends of the cylindrical portion and tapering toward the axial ends. An annular nozzle is attached to the dome portion to allow fuel gas to flow between the inside and outside of the high-pressure tank.

[0030] By performing the steps from the preparation step P10 to the heating step P30, a fiber-reinforced resin pipe is manufactured, which is a heat-cured fiber layer 20. In the insertion step P40, the heat-cured fiber layer 20 is removed from the mandrel 10, and a liner is inserted into the heat-cured fiber layer 20. The liner is a hollow container having a cylindrical portion and two dome portions provided at both ends of the cylindrical portion. The dome portions are hemispherical portions whose diameter decreases toward the axial ends. The liner is formed from a resin that has gas barrier properties against hydrogen gas, such as polyethylene, nylon, polypropylene, or polyester. Specifically, in the insertion step P40, the heat-cured fiber layer 20 is placed on the outside of the cylindrical portion of the liner. The liner may be made of metal instead of resin.

[0031] In step P50, fibers impregnated with a thermosetting resin are wound around the dome portion of the liner. Specifically, the fibers impregnated with a thermosetting resin are wound helically so that the orientation angle of the fibers relative to the central axis of the liner is greater than 0 degrees and less than or equal to 45 degrees, for example, less than or equal to 20 degrees. Thereafter, similar to the heating step P30, the fibers are heated to thermally cure the thermosetting resin in the fibers wound around the dome portion. This completes the high-pressure tank, and this step ends.

[0032] The manufacturing method of the second embodiment described above includes, after the heating step P30, an insertion step P40 in which the fiber layer 20 is removed from the mandrel 10 and a liner is inserted inside the fiber layer 20. This allows the high-pressure tank to be manufactured using the heat-set fiber layer 20 manufactured in a shorter process time, thereby shortening the manufacturing process and enabling the high-pressure tank to be manufactured.

[0033] C. Other Embodiments: (C1) The mandrel 10 according to the first embodiment has a curved inner circumferential surface. However, the shape of the mandrel 10 is not limited to the above. For example, the first cylindrical portion 11 and the second cylindrical portion 12 may each have a uniform thickness. Furthermore, the inner circumferential surface of the mandrel 10 may have a shape that describes a straight line in the axial direction, or a shape that has steps. Regardless of the shape of the mandrel 10, by having the first cylindrical portion 11 have a first thickness t2 that is thinner than the second thickness t3, it is possible to make it difficult for heat applied to the fiber layer 20 in the heating step P30 to be transferred to the mandrel 10.

[0034] (C2) The heating furnace used in the heating step P30 according to the first embodiment is equipped with a fan, and hot air is blown onto the mandrel 10. The heating furnace used in the heating step P30 may be configured not to blow hot air onto the mandrel 10. In other words, a heating furnace in which the temperature inside the heating furnace is set to the target temperature by a heat source may be used in the heating step P30.

[0035] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features of the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0036] 10... mandrel, 11... first cylindrical portion, 12... second cylindrical portion, 20... fiber layer, 50... collet, CX... center axis, P10... preparation step, P20... fiber layer forming step, P30... heating step, P40... insertion step, P50... step, t1... fiber layer thickness, t2... first thickness, t3... second thickness

Claims

1. A method for manufacturing a fiber-reinforced resin pipe, a preparation step of preparing a metal mandrel having a first cylindrical portion and two second cylindrical portions disposed at both axial ends of the first cylindrical portion, wherein a first thickness, which is the thinnest of the thicknesses of the first cylindrical portion, is thinner than a second thickness, which is the thinnest of the thicknesses of the two second cylindrical portions; a fiber layer forming step of winding a fiber impregnated with a thermosetting resin around the first cylindrical portion to form a fiber layer; a heating step of thermally curing the thermosetting resin in the fiber layer, In the heating step, the amount of heat applied to the first cylindrical portion is greater than the amount of heat applied to the second cylindrical portion.

2. The method of claim 1, The method of manufacturing, wherein the thickness of the first cylindrical portion is less than the second thickness.

3. The manufacturing method according to claim 1 or 2, The manufacturing method, wherein the outer diameter of the first cylindrical portion and the outer diameters of the two second cylindrical portions are the same.

4. The method according to any one of claims 1 to 3, When the thickness of the fiber layer is t1 and the first thickness is t2, 0.35≦t1 / t2≦2 Manufacturing method that meets the above requirements.

5. A method for manufacturing a high-pressure tank using the manufacturing method according to any one of claims 1 to 4, After the heating step, the method for manufacturing a high-pressure tank includes an inserting step of removing the fiber layer from the mandrel and inserting a liner inside the fiber layer.

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