METHOD FOR MANUFACTURING A TANK

Abstract

A method of manufacturing a tank comprising: a preform placing step of placing a preform (2) into a mold (10), the preform (2) including a fiber layer (5) formed by winding fibers around an outer surface of a hollow liner (4); an adhesiveness adding step of adding an adhesiveness to an inner surface of the mold (10) to form a gap in the fiber layer (5) of the preform (2); a step of forming the gap in the fiber layer (5) of the preform (2) by means of the added adhesive; and a resin pouring step of pouring resin (6) into the mold (10) to impregnate the fiber layer (5) with the resin (6).

Description

BACKGROUNDTechnical FieldThe present disclosure relates to a method of manufacturing a tank reinforced with fibers.Related ArtJP 2020 085 199 A (Patent Literature 1) discloses a method for manufacturing a fiber-reinforced (FRP) tank (hereinafter also referred to as a high-pressure tank). This manufacturing method first performs a coating step by winding fibers around a liner, then performs an impregnation step by impregnating the fibers with resin, and then allows the resin to cure by heating the fibers impregnated with the resin.JP 2019,056,415 A (Patent Literature 2) discloses a method for manufacturing a high pressure tank using such a resin transfer molding (RTM) method. This manufacturing method places a preform in which a fiber layer is formed on an outer surface of a liner forming an inner space of a high-pressure tank in a casting mold, and rotates the preform in a circumferential direction in the casting mold about the central axis of the preform as a rotation center while injecting resin from a gate to the preform placed in the casting mold.SUMMARYThe above manufacturing method using the RTM method performs the fiber winding step and the resin soaking step separately when manufacturing the high-pressure tank. However, since a large amount of fibers are wound around the high pressure tank and a large thickness of the fiber layer (the composite) is formed by winding fibers, it may take a long time until the deep portion (innermost layer) of the fiber layer is completely impregnated with resin, resulting in incomplete impregnation.In view of the foregoing, the present disclosure provides a method of manufacturing a tank that allows the deep portion (innermost layer) of the fiber layer to be completely impregnated with resin within a short time.In view of the foregoing, according to one aspect of the present disclosure, there is disclosed herein a method of manufacturing a tank, including: a preform placing step of placing a preform in a casting mold, the preform including a fiber layer formed by winding fibers around an outer surface of a hollow liner; an adhesion adding step of adding adhesion to the inner surface of the casting mold to form a gap in the fiber layer of the preform; and a resin pouring step of pouring resin into the casting mold to soak the fiber layer with resin.In some embodiments, in the adhesion adding step, adhesion is added to the inner surface of the mold by filling liquefied nitrogen gas into the mold, coating the inner surface of the mold with resin, or charging the inner surface of the mold with static electricity.In some embodiments, in the adhesion adding step, adhesion is added to the inner surface of the mold, and a gap is formed in the fiber layer of the preform by separating a part of the mold from the preform or by subjecting a part of the mold to ultrasonic vibration relative to the preform.In some embodiments, in the adhesion adding step, adhesion is added to the inner surface of the mold, and a gap is formed in the fiber layer of the preform by subjecting a part of the mold to ultrasonic vibration relative to the preform while separating a part of the mold from the preform.In some embodiments, a gap is formed in the fiber layer of the preform in which a portion of the mold is subjected to ultrasonic vibrations in a longitudinal direction of the preform.In some embodiments, in the adhesion adding step, a gap is formed in the fiber layer of the preform by injecting inert gas in a longitudinal direction of the preform.In some embodiments, in the adhesion adding step, adhesion is added to the inner surface of the mold, and a gap is formed in the fiber layer of the preform by subjecting a part of the mold to ultrasonic vibration relative to the preform while separating a part of the mold from the preform, and injecting inert gas in a longitudinal direction of the preform.In some embodiments, the mold includes a first mold and a second mold; in the preform placement step, the preform is placed between the first mold and the second mold to define a first gap between the first mold and the preform and a second gap between the second mold and the preform, the second gap being larger than the first gap; In the adhesion adding step, adhesion to the fiber layer of the preform is added to the inner surface of the mold, the fiber layer of the preform can adhere to the inner surface of the second mold by bringing the second mold close to the preform, and while the fiber layer of the preform adheres to the inner surface of the second layer, a gap is formed in the fiber layer of the preform by subjecting the second mold layer to ultrasonic vibration relative to the preform while separating the second mold from the preform; and in the resin pouring step, resin is poured into the mold after bringing the second mold close to the preform.According to an aspect of the present disclosure, since resin injection / impregnation is performed after forming a gap in the fiber layer (or between the lamina thereof) with the fibers that are raised, the deep portion (innermost layer) of the fiber layer can be fully impregnated with resin within a short time.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a vertical sectional view showing a manufacturing apparatus for a high-pressure tank according to an embodiment; FIG. 2 is a flowchart illustrating a method of manufacturing a high-pressure tank according to an embodiment; FIG. 3 is a flowchart illustrating an adhesion adding step of FIG. 2 ; FIG. 4 is a vertical sectional view of the manufacturing apparatus for a high pressure tank, showing a preform placing step and a vacuum degassing step according to an embodiment; FIG. 5 is a vertical sectional view of the manufacturing apparatus for a high pressure tank, showing a liquefied nitrogen gas filling step of the adhesion adding step according to an embodiment; FIG. 6 is a vertical sectional view of the manufacturing apparatus for a high-pressure tank, showing an upper die lowering step of the adhesion adding step according to an embodiment; FIG. 7 is a vertical sectional view of the manufacturing apparatus for a high pressure tank, showing an upper die raising step of the adhesion adding step according to an embodiment; FIG. 8 is a vertical sectional view of the manufacturing apparatus for a high pressure tank, showing a full contraction step and a resin pouring step according to an embodiment; and FIG. 9 is a vertical sectional view of the manufacturing apparatus for a high pressure tank, showing a resin pouring termination step and a resin curing step according to an embodiment.DETAILED DESCRIPTIONHereinafter, an embodiment of the present disclosure will be described with reference to the drawings.The following describes a high-pressure tank for fuel cell vehicles, which is an example of a tank. The tank to which the present disclosure relates is not limited to the high-pressure tank for fuel cell vehicles. The shape, material and the like of the liner and the preform of the tank are also not limited to the illustrated example.The RTM method wraps (wraps) carbon fibers a plurality of times around a liner (in a plurality of layers) to form a preform having a fiber layer on the outer surface of the liner, impregnates the fiber layer of the preform with epoxy resin, and cures the epoxy resin to produce a high pressure tank for fuel cell vehicles that includes a fiber reinforced resin layer including carbon fibers and epoxy resin on the outer circumferential surface of the liner. The liner is a hollow container made of resin (for example, nylon resin) defining the interior of the high-pressure tank.In such a high pressure tank for fuel cell vehicles, the carbon fibers are thickly laminated, and thus the resin hardly penetrates into the inner layer of the carbon fibers. When resin is poured at high pressure into the inner layer of the carbon fibers for resin impregnation, the quality and performance of the tank such as deformation of the tank will deteriorate. In addition, since the tank has a cylindrical shape, it is difficult to uniformly fill resin in the entire tank, which makes resin impregnation nonuniform. However, pressure tends to accumulate at the vicinity of a gate, so that its gate portion is under high pressure and a large pressure difference exists between the gate portion and the resin flow end portion (for example, a portion opposite to the gate portion).That is, the high pressure tank for fuel cell vehicles has carbon fibers laminated very thickly (about ten times as in a typical RTM molded body component) to obtain enough strength, making it difficult to soak the fibers with resin. Simple tank rotation as in Patent Literature 2 does not exert a good resin impregnation effect on the inner layer of the carbon fibers. In addition, pouring resin at high pressures into the inner layer of carbon fibers for resin impregnation may result in nonuniform pressure distribution, and the quality and performance of the tank will deteriorate, such as deformation of the resin liner inside the tank in some portions that are partially under high pressure. In addition, since the resin is less likely to flow to the opposite portion of the gate portion through a narrow gap between the mold and the tank, it is necessary to rotate the tank inside the mold at high speed as disclosed in Patent Literature 2 in order to flow the resin to the entire part of the tank before it cures. However, such high speed rotations may cause damage to the carbon fibers due to a small space inside the mold.Thereupon(s), the present embodiment employs the following configuration.[Production Apparatus for High Pressure Tank]FIG. 1 is a vertical sectional view showing a manufacturing apparatus for a high-pressure tank according to an embodiment.A preform 2 as an intermediate body of a high-pressure tank to be manufactured in the present embodiment includes a liner 4 and a fiber layer 5 formed on the outer surface of the liner 4 to be integrated with the liner 4. The liner 4 is a hollow resin container having a gas barrier property and defining the interior of the high-pressure tank. In one example, the hollow (e.g., tubular) liner 4 has a thickness of about 0.5 mm to 1 mm. In one example, the fiber layer 5 has a thickness of about 15 mm to 30 mm. The fiber layer 5 is formed by winding fibers around the outer surface of the liner 4 a plurality of times by the filament winding method.Examples of the fibers wound around the liner 4 include carbon fibers, glass fibers, and aramid fibers. The fibers may include continuous fibers or may include long fibers or short fibers. As described later, fibers (the layer) wound around the liner 4 are impregnated with resin and cured to form a fiber-reinforced resin layer that coats the circumferential surface of the liner 4. Examples of the resin include thermosetting resins such as epoxy resins, unsaturated polyester resins and polyamide resins, and thermoplastic resins such as polyethylene resins and polyester resins.A manufacturing apparatus 1 is configured to manufacture a high-pressure tank by the resin transfer molding (RTM) method, impregnates the fiber layer 5 of the preform 2 with a resin 6 (the reference sign is illustrated in FIG. 8 ), and cures the impregnated resin 6.In an example, the manufacturing apparatus 1 includes a mold 10 composed of a plurality of molds, such as a lower mold 11 as a fixed mold and an upper mold 12 as a moving mold. Closing these lower mold 11 and upper mold 12 (this may be referred to as mold clamps) defines a cavity for the fiber reinforced resin layer. In order to place the preform 2 including laminated fibers in the mold 10, the cavity of the mold 10 is made larger by the tolerance of the preform 2, for example.Note that this example includes the lower mold 11 as a fixed mold, and the upper mold 12 as a moving mold (a mold movable relative to the fixed mold). In another example, the upper mold 12 may be a fixed mold and the lower mold 11 may be a moving mold, or both the lower mold 11 and the upper mold 12 may be movable. The mold 10 in this example includes two parts, the lower mold 11 and the upper mold 12, which may be three or more parts.In the mould 10, the preform 2 is supported by means of a hollow shaft 25 arranged along the axis of the liner 4. That is, the shaft 25 constitutes a support mechanism that supports the preform 2 in the mold 10 (into the cavity).A vacuum degassing pipe 15 is integrated into the mold 10 (in the lower mold 11 in the illustrated example). The vacuum degassing pipe 15 is connected to a vacuum pump 50. The vacuum pump 50 is driven to vacuum-degas (exhaust) the mold 10 (cavity) by means of the vacuum degassing pipe 15.A resin pouring pipe 16 forming a gate (resin inlet) 14 opened to the cavity is integrated in the mold 10 (in the upper mold 12 in the illustrated example). The gate 14 is disposed at a position facing a central portion (in the axial direction) of the preform 2 in this example. The resin pouring pipe 16 is connected to a resin injector 60. The resin injector 60 can pour (supply) the resin into the mold 10 (cavity) via the gate 14 through the resin pouring pipe 16. In one example, the resin 6 is a two-component thermosetting epoxy resin composed of a base resin and a curing agent. The resin injector 60 includes a printing device 66, a resin reservoir 64 that stores the resin 6, which is a mixture of the base resin and the curing agent, and a valve 62 for supplying the resin 6 to the resin pouring pipe 16.In this example, a liquefied nitrogen gas supply pipe 18 is inserted into the mold 10 (in the upper mold 12 in the illustrated example). The liquefied nitrogen gas supply pipe 18 is connected to a liquefied nitrogen gas supply device 80 including a liquefied nitrogen gas tank 84 provided with a pressure control valve 82. The liquid nitrogen gas supply device 80 may pressurize the liquid nitrogen gas and fill liquid nitrogen gas into the casting mold 10 (for example, outside the preform 2 placed in the casting mold 10) through the liquid nitrogen gas supply pipe 18.The manufacturing apparatus 1 includes a transfer mechanism 20 for transferring the preform 2 to the predetermined position; a drive mechanism 30 for driving the mold 10 (specifically, the upper mold 12) in the direction to open and close the mold 10 (vertical direction) or in the axial direction (lateral direction); a temperature control unit 40 for controlling the temperature of the mold 10 (the lower mold 11, the upper mold 12); and a control device 90 as a control unit for controlling the operation state of the entire manufacturing apparatus 1 (specifically, the operation state of the transfer mechanism 20, the drive mechanism 30, the temperature control unit 40, the vacuum pump 50, the pressurizing device 66, and the valve 62 of the resin injector 60, and the pressure control valve 82 of the liquefied nitrogen gas supply device 80)).[Method for Manufacturing a High Pressure Tank]FIG. 2 is a flowchart illustrating a method of manufacturing a high-pressure tank according to an embodiment. FIG. 3 is a flowchart illustrating an adhesion adding step of FIG. 2. FIGS. 4 to 9 are vertical sectional views each illustrating a preform placing step and a vacuum degassing step; a liquefied nitrogen gas filling step of the adhesion adding step; an upper die lowering step of the adhesion adding step; an upper die raising step of the adhesion adding step; a full contraction step and a resin pouring step; and a resin pouring terminating step and a resin curing step.(Mold Preparation Step: S 201)First, the method prepares the mold 10 including the lower mold 11 and the upper mold 12 having the above-described structure.(Preform preparation step: S 202)As previously described, the method prepares the preform 2 which includes the fiber layer 5 formed by angles (curling) of fibers around the outer surface of the hollow liner 4.(Mold Temperature Obtaining Step: S 203)Subsequently, the controller 90 controls the temperature control unit 40 to maintain the mold 10 (the lower mold 11, the upper mold 12) at a predetermined temperature. When the resin 6 is a thermosetting resin, this predetermined temperature is equal to or higher than the curing temperature of the resin 6.Note that herein, the method initially maintains the mold 10 at a temperature equal to or higher than the curing temperature of the resin 6. In another example, the method may initially hold the mold 10 at a temperature below the curing temperature of the resin 6, and then, at an appropriate time, in a step described later (for example, after the resin 6 is poured and the composite is completely impregnated with the resin 6, for example), hold the mold 10 at a temperature equal to or higher than the curing temperature of the resin 6.(Preform placing step: S 204)Subsequently, the control device 90 controls the transmission mechanism 20 and the drive mechanism 30 to place the preform 2 in the mold 10 (i.e., between the lower mold 11 and the upper mold 12) (FIGS. 1, 4 ). Specifically, during an opening of the upper die 12, the transfer mechanism 20 places the preform 2 on the lower die 11 under the control of the controller 90 At this time, the shaft 25 supports the preform 2. Temporary contraction is an intermediate state between the state in which the upper die 12 is open and the fully contracted state, and the lower die 11 and the upper die 12 have a gap therebetween in the temporary contracted state. As shown in FIG. 4, the upper mold 12 moves to a position having a gap (second gap) of several millimeters with the preform 2. This gap (second gap) between the upper mold 12 and the preform 2 is larger than a gap (first gap) between the lower mold 12 and the preform 2.(Vacuum degassing step: S 205)Subsequently, the controller 90 controls the vacuum pump 50 during the aforementioned temporary contraction state (for example, before completion of die clamping) to vacuum-degas the die 10 (FIG. 4 ).(Adhesion addition step: S 206)After completion (or completion) of the aforementioned vacuum degassing, the process adds adhesion to the fiber layer 5 (or the fibers thereof) of the preform 2 to the inner surface (cavity surface) of the casting mold 10, and forms a gap in the fiber layer 5 (or between the lamina thereof) using such adhesion. As used herein, the term "forms a gap in the fiber layer 5" includes extending a gap in the fiber layer 5.In this example, the aforementioned adhesion addition step (S 206) includes a liquefied nitrogen gas filling step (S 2061), an upper die lowering step (S 2062), and an upper die raising step (S 2063) as illustrated in FIG. 3.(Liquid nitrogen gas filling step: S2601)In the adhesion adding step (S 206) described above, the controller 90 first opens the pressure control valve 82 of the liquefied nitrogen gas supplier 80 to compress and fill the liquefied nitrogen gas from the liquefied nitrogen gas tank 84 into the casting mold 10 (FIG. 5 ). Since the upper mold 12 is temporarily contracted, the liquefied nitrogen gas is injected (compressed and filled) into the gap (second gap) between the upper mold 12 and the preform 2 (or the upper surface thereof). Accordingly, the method adds adhesion to the fiber layer 5 of the preform 2 to the inner surface of the mold 10.(Upper die lowering step: S 2062)Subsequently, the control device 90 controls the drive mechanism 30 to lower the upper die 12 to the lower end (for example, bring it close to the preform 2) and close the die 10 (the upper die 12 and the lower die 11) (FIG. 6 ). Accordingly, the method brings the fiber layer 5 of the preform 2 into contact with the inner surface of the mold 10 and allows it to adhere to the inner surface of the mold 10.(Upper die raising step: S 2063)Subsequently, the controller 90 controls the drive mechanism 30 to lift the upper mold 12 (e.g., until it is temporarily drawn (close)) (e.g., to separate it from the preform 2) while the fiber layer 5 of the preform 2 adheres to the inner surface of the mold 10. At this time, the controller 90 controls the drive mechanism 30 to subject the upper die 12 to ultrasonic vibrations in the axial direction (for example, in the longitudinal direction of the preform 2) (FIG. 7 ). Accordingly, the method forms a gap in the fiber layer 5 (or between the lamina thereof) of the preform 2 adhering to the inner surface of the casting mold 10.Note that at this time, in addition to or instead of the longitudinal direction of the preform 2, the method may subject the upper mold 12 to ultrasonic vibrations in the transverse direction of the preform 2 (for example, in the laminating direction and the thickness direction of the fiber layer).In addition, the method may also provide an inert gas supply pipe (not shown) for forming (expanding) a gap in the fiber layer 5 (or between the lamina thereof) of the preform 2 adhering to the inner surface of the casting mold 10 by injecting inert gas such as nitrogen gas in the longitudinal direction of the preform 2.It should be noted that the fiber layer 5 of the preform 2 does not have to be held adhered to the inner surface of the mold 10 until the upper mold 12 is completely raised. As long as the method can form a gap in the fiber layer 5 of the preform 2 (or between the lamina thereof) with the fibers being raised, the fiber layer 5 of the preform 2 need only adhere to the inner layer of the mold 10 until the upper mold 12 is raised to a predetermined position (in other words, the fiber layer 5 of the preform 2 may be peeled from the inner surface of the mold 10 when the upper mold 12 is raised to a predetermined position).(Full Contraction Step: S 207)Subsequently, the control device 90 controls the drive mechanism 30 to lower the upper die 12 to the lower end to complete closing of the upper die 12 (for example, to bring it close to the preform 2) and completely close (completely contract) the upper die 12 and the lower die 11 (FIG. 8 ).(Resin Pouring Step: S 208)Thereafter, the method injects / pours the resin into the mold 10 (FIG. 8 ). Specifically, the controller 90 opens the valve 62 and pressurizes the resin 6 stored in the resin reservoir 64 by the pressurizing device 66. causing the (uncured) resin 6 to flow through the resin pouring pipe 16 provided in the upper mold 12 so that the resin 6 is injected / poured from the gate (in the illustrated example, the gate 14 provided at the central portion of the preform 2) to the preform 2, and the composite of the fiber layer 5 of the preform 2 is impregnated with the resin 6.(Harzeingießbeendigungsschritt: S209)After the composite of the fiber layer 5 of the preform 2 is completely impregnated with the resin 6 and the curing and heat generation of the resin 6 end, the method ends the pouring of the resin 6 (FIG. 9 ).(Resin Curing Step: S 210)After the resin 6 is finished to be poured as mentioned above, the method cures the resin 6 (FIG. 9 ).(Demolding step: S 211)After the resin 6 is cured, the controller 90 controls the drive mechanism 30 to open the upper mold 12. When the curing of the resin 6 ends, a high-pressure tank 8 including the fiber-reinforced resin layer formed on the outer circumferential surface of the liner is obtained.Note that the method of adding the adhesion to the inner surface of the mold 10 in the adhesion adding step (S 206) is not limited to the above-described method. For example, instead of the liquid nitrogen gas, the method may add adhesion to the inner surface of the mold 10, by coating the inner surface of the mold 10 with a resin (for example, epoxy resin) that is the same as the resin 6, or by charging the inner surface of the mold 10 with static electricity. If the method adds adhesion by charging the inner surface of the mold 10 with static electricity, the steps of lowering and raising the upper mold 12 may be omitted.The above-described method pressurizes and fills the mold 10 with liquefied nitrogen gas in the temporary contraction state in which a gap (second gap) of several mm is formed between the upper mold 12 and the preform 2. This helps to supply the liquid nitrogen gas substantially uniformly over (or the top surface of) the preform 2. However, as long as the method can supply the liquefied nitrogen gas over (or the surface of) the preform 2 (as a whole), for example, by adjusting the pressure of the liquefied nitrogen gas, there is no need to provide a gap (second gap) of several mm in advance between the upper mold 12 and the preform 2. For example, the method may pressurize the mold 10 and fill it with liquefied nitrogen gas in a state where the mold 10 (the lower mold 11 and the upper mold 12) is closed.As described above, when a high-pressure tank for fuel cell vehicles is manufactured by the RTM soaking technology, it is difficult to perform charging, soaking and curing of the epoxy resin entirely on the thick laminated large tank (having thick wound carbon fibers) while uniformly applying a resin pressure, and a reduction in performance and deterioration in tank performance may occur. In addition, since the carbon fibers are laminated thickly on the tank, the resin is difficult to penetrate into the innermost layer of the composite unless the resin is filled at high pressure. This may cause an excessively high pressure in the portion immediately below the sprue terminal and the like, resulting in critical quality problems leading to a reduction in performance and a deterioration in tank performance, such as deformation of the resin liner, inside the tank, or misalignment of the fibers.The present embodiment is directed to a substantial improvement in resin flowability in a compound tank and adds adhesion (liquid nitrogen gas filling, epoxy resin application, static electricity or the like) to the surface of the mold after mold closing and before resin pouring so that the carbon fibers wound around the preform 2 may adhere to the surface of the mold and are raised in the laminating direction to form a gap between the laminas. At the same time, the present embodiment forms a gap between the lamina by subjecting the upper die 12 to ultrasonic vibrations (in a direction perpendicular or parallel to the longitudinal direction of the tank (the preform 2)) and by injecting inert gas such as nitrogen gas in the longitudinal direction of the tank (the preform 2).Since the following embodiment allows the carbon fibers to adhere to the surface of the mold to form a gap before the resin is poured, the inner layer of the fiber layer is likely to be impregnated with the resin. Since the present embodiment forms a gap between the laminas by subjecting the upper die 12 to ultrasonic vibrations (in a direction perpendicular or parallel to the longitudinal direction of the tank (the preform 2)) and by injecting inert gas such as nitrogen gas in the longitudinal direction of the tank (the preform 2), the inner layer of the fiber layer is more likely to be impregnated with the resin. When the upper mold 12 is subjected to ultrasonic vibrations, vibrations in a direction parallel to the longitudinal direction of the tank help ensure a sealing property of the RTM mold more easily than vibrations in a direction perpendicular to the longitudinal direction of the tank.Therefore, in the epoxy resin soaking using the RTM soaking technology, since the present embodiment can soak the entire tank with epoxy resin uniformly and at a low pressure in both the compound extension direction (a direction parallel to the longitudinal direction of the tank) and the thickness direction (a direction perpendicular to the longitudinal direction of the tank), it is possible to achieve improved performance and reliable quality of the high-pressure tank. That is, since the present embodiment can achieve low pressurization and uniform resin impregnation during epoxy resin casting, it is possible to obtain a high-pressure tank that can achieve improved resin impregnation property, tank performance, and excellent surface quality. This also allows high speed resin filling that can achieve significantly shorter casting cycles of the high pressure tank.As described above, according to the present embodiment, since the pouring / soaking of the resin 6 is performed after a gap is formed in the fiber layer 5 (or between the lamina thereof) with the fibers that are raised, the deep portion (the innermost layer) of the fiber layer 5 can be fully soaked with the resin 6 within a short time.Although the embodiment of the present disclosure has been described above in detail with reference to the drawings, the specific configurations are not limited thereto, and any configuration change that falls within the spirit and scope of the present disclosure is included in the scope of the present disclosure.DESCRIPTION OF THE REFERENCE NUMERALS1 Manufacturing Apparatus for High Pressure Tank (Tank) 2 Preform 4 Liner 5 Fiber Layer 6 Resin 8 High Pressure Tank (Tank) 10 Mold 11 Lower Mold (First Mold) 12 Upper Mold (Second Mold) 14 Pouring Opening (Resin Inlet) 15 Vacuum degassing pipe 16 Resin Pouring pipe 18 Liquefied nitrogen gas supply pipe 20 Transmission mechanism 25 Shaft 30 Drive mechanism 40 Temperature control unit 50 Vacuum pump 60 Resin injector 80 Liquefied nitrogen gas supply device 90 Control device

Claims

A method for manufacturing a tank, comprising: a preform placing step of placing a preform (2) in a mold (10), the preform (2) including a fiber layer (5) formed by winding fibers around an outer surface of a hollow liner (4); an adhesion adding step of adding adhesion to an inner surface of the mold (10) to form a gap in the fiber layer (5) of the preform (2); a step of forming the gap in the fiber layer (5) of the preform (2) by the added adhesion; and a resin pouring step of pouring resin (6) into the mold (10) to impregnate the fiber layer (5) with the resin (6).The method for manufacturing a tank according to claim 1, wherein in the adhesion adding step, the adhesion is added to the inner surface of the mold (10) by filling liquefied nitrogen gas into the mold (10), coating the inner surface of the mold (10) with resin (6), or charging the inner surface of the mold (10) with static electricity.The method for manufacturing a tank according to claim 1, wherein in the adhesion adding step, the adhesion is added to the inner surface of the mold (10) and the gap is formed in the fiber layer (5) of the preform (2), by separating a part of the mold (10) from the preform (2), or by subjecting a part of the mold (10) to ultrasonic vibrations relative to the preform (2).The method for manufacturing a tank according to claim 1, wherein in the adhesion adding step, the adhesion is added to the inner surface of the mold (10), and the gap is formed in the fiber layer (5) of the preform (2) by subjecting a part of the mold (10) to ultrasonic vibrations relative to the preform (2) while separating a part of the mold (10) from the preform.The method for manufacturing a tank according to claim 4, wherein the gap is formed in the fiber layer (5) of the preform (2) by subjecting a part of the casting mold (10) to ultrasonic vibrations in a longitudinal direction.The method for manufacturing a tank according to claim 3, wherein in the adhesion addition step, the gap is formed in the fiber layer (5) of the preform (2) by injecting inert gas in a longitudinal direction of the preform (2).The method for manufacturing a tank according to claim 1, wherein in the adhesion adding step, the adhesion is added to the inner surface of the mold (10), and the gap is formed in the fiber layer (5) of the preform (2) by subjecting a part of the mold (10) to ultrasonic vibration relative to the preform (2) while separating a part of the mold (10) from the preform (2) and injecting an inert gas in a longitudinal direction of the preform (2).The method for manufacturing a tank according to claim 1, wherein the mold (10) includes a first mold (11) and a second mold (12); in the preform placing step, the preform (2) is placed between the first mold (11) and the second mold (12) to define a first gap between the first mold (11) and the preform (2) and define a second gap between the second mold (12) and the preform (2), the second gap being larger than the first gap; in the adhesion adding step of adding adhesion to the fiber layer (5) of the preform (2) to the inner surface of the mold (10), the fiber layer (5) of the preform (2) can adhere to the inner surface of the second mold (12) by bringing the second mold (12) close to the preform (2), and while the fiber layer (5) of the preform (2) adheres to the inner surface of the second mold (12), a gap is formed between the fiber layer (5) of the preform (2) by subjecting the second mold (12) to ultrasonic vibration relative to the preform (2) while separating the second mold (12) from the preform (2); and in the resin pouring step, pouring the resin (6) into the mold (10) after bringing the second mold (12) close to the preform (2).

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