Method for manufacturing a pressure vessel liner, method for manufacturing a pressure vessel liner and a pressure vessel

Abstract

To provide a method for manufacturing a pressure vessel liner, a pressure vessel liner, and a pressure vessel, which not only have high strength but can also be produced without using molds, thereby reducing manufacturing costs. [Solution] A method for manufacturing a pressure vessel liner 100 for preventing the permeation of a high-pressure fluid in a pressure vessel, wherein the pressure vessel liner 100 is formed by laminating a resin containing continuous fibers layer by layer based on the cross-sectional shape that appears when the shape of the pressure vessel liner 100 is sliced ​​into multiple layers.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a pressure vessel liner constituting a part of a pressure vessel for storing high-pressure fluid, the pressure vessel liner, and a method for manufacturing a pressure vessel using the same.

Background Art

[0002] In recent years, technological development of power systems using fuel cells as environment-friendly power has become active. Fuel cells generate electricity through a chemical reaction between hydrogen and oxygen, and are characterized in that no emissions other than water are produced. Hydrogen, which is one type of fuel, is a gas at normal temperature, and if stored at normal pressure, an extremely large-volume storage container will be required. Therefore, by pressurizing hydrogen to a high pressure of about 700 atmospheres, a sufficient amount of hydrogen can be stored in a container of limited volume.

[0003] Pressure vessels for storing such high-pressure fluids are used in various fields other than fuel cells. Examples include fire extinguishers, medical gas cylinders, industrial gas containers, and scuba diving cylinders.

[0004] As an example, pressure vessels for storing hydrogen are designed to withstand such high pressures. In general, a configuration is adopted in which a bundle of reinforcing fibers is wound around a resin liner for preventing hydrogen leakage and permeation to reinforce the liner. Since the internal pressure acts uniformly on all surfaces, the liner tends to deform in the expanding direction, and the wound bundle of reinforcing fibers receives tensile force. Since reinforcing fibers have high tensile strength, deformation of the liner can be prevented, and damage to the pressure vessel can be avoided.

[0005] For example, Patent Document 1 discloses a technology in which a liner is molded separately into both end portions and a central portion, and the respective end portions are joined and welded to form an integrated pressure vessel. This technology is characterized by setting the diameter of each liner to a predetermined condition so that sufficient welding width can be ensured even if each liner is slightly misaligned when welding the liners at both ends and the center. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-144657 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the technology described in Patent Document 1 requires each liner to be molded separately, and since multiple molds are needed to produce a single liner, there is a problem in that the cost is high. Moreover, if a product line includes pressure vessels of multiple sizes, additional molds will be required, causing costs to steadily increase.

[0008] Furthermore, in the manufacture of pressure vessels, it is necessary to apply internal pressure to the resin liner beforehand and then wind the reinforcing fibers in order to withstand the strong tightening force during the winding of the reinforcing fibers. Each pressure vessel requires the process of adding or removing internal pressure, which is inefficient and contributes to increased costs.

[0009] This invention has been made in view of the above-mentioned problems, and its objective is to provide a method for manufacturing a pressure vessel liner, a pressure vessel liner, and a pressure vessel, which not only have high strength but can also be produced without using molds and can reduce manufacturing costs. [Means for solving the problem]

[0010] The means employed by the inventors to solve the above problems are described below. The present invention relates to a method for manufacturing a pressure vessel liner for preventing the permeation of a high-pressure fluid in a pressure vessel, wherein the pressure vessel liner is formed by laminating a resin containing continuous fibers layer by layer based on the cross-sectional shape that appears when the shape of the pressure vessel liner is sliced ​​into multiple layers.

[0011] By employing a manufacturing method that involves layering the shape of pressure vessel liners one layer at a time, the use of molds is eliminated, thereby reducing initial manufacturing costs. Furthermore, even when manufacturing pressure vessel liners of different sizes, only data showing the shape of each pressure vessel liner sliced ​​into multiple layers is required, significantly reducing costs in high-mix production.

[0012] Furthermore, the strength of the molded pressure vessel liner can be improved by laminating it using a resin containing continuous fibers. When reinforcing fibers are mixed into the resin, the strength of the molded resin product is improved by the tensile strength of the reinforcing fibers themselves. In this invention, by using continuous fibers instead of short fibers for the reinforcing fibers, a certain reinforcing effect can be obtained throughout the entire laminated layer, thus achieving even higher strength.

[0013] In order to solve the aforementioned problems, the present invention employs a means in which the direction of the slice may be the longitudinal direction of the shape of the pressure vessel liner. By slicing along the longitudinal direction, a cross-sectional shape is obtained that is formed by slicing along a plane with the longitudinal direction as one axis. Based on this cross-sectional shape, by laminating resin containing continuous fibers, the continuous fibers provide a reinforcing effect against the force that tears the pressure vessel liner along the longitudinal direction, thereby achieving higher strength.

[0014] To solve the aforementioned problems, other means employed by the present invention include using a polyamide resin for the resin and carbon fibers for the continuous fibers. Polyamide resins are semi-crystalline polymers with a partially crystalline structure, where molecules are densely and regularly arranged in the crystalline regions. Furthermore, because polyamides contain numerous amide groups (-CONH-) within their molecular chains, these amide groups form hydrogen bonds, causing the molecules to attract each other and resulting in a dense structure. Therefore, the crystalline regions exhibit gas barrier properties, making it difficult for gas molecules to pass through.

[0015] Furthermore, carbon fibers have a graphite structure, which consists of layers of carbon atoms arranged in a hexagonal pattern, forming very strong covalent bonds. Because this graphite structure is aligned along the longitudinal direction of the fiber, it has high strength in the tensile direction. By using a polyamide resin with high gas barrier properties and carbon fibers for the continuous fibers, it is possible to effectively prevent fluid permeation and create a liner for pressure vessels with higher strength.

[0016] As a means of solving the aforementioned problems, the present invention can also be configured as a liner for a pressure vessel. This means is a liner for a pressure vessel that stores a high-pressure fluid, which prevents the permeation of the fluid, and can employ a configuration in which multiple layers made of a resin containing continuous fibers are laminated, and the continuous fibers are continuous in each layer.

[0017] By constructing a structure in which multiple layers made of resin containing continuous fibers are laminated, it is possible to produce it at a lower initial cost compared to a product molded as a single unit using a mold, thus making it an inexpensive liner for pressure vessels. Furthermore, because the continuous fibers are continuous in each layer, higher strength can be achieved compared to cases where the reinforcing fibers are discontinuous.

[0018] Another means employed by the present invention to solve the aforementioned problems is that, in the above means, the high-pressure vessel liner can be laminated in a horizontal position. By stacking the pressure vessel liner in a laid-down state, the continuous fibers are continuous in the longitudinal direction of the pressure vessel liner. Accordingly, the continuous fibers exert a reinforcing effect against the force that tears the pressure vessel liner in the longitudinal direction, so that higher strength can be achieved.

[0019] As another measure adopted by the present invention to solve the above-described problems, a configuration as a method for manufacturing a pressure vessel may also be employed. The measure is a method for manufacturing a pressure vessel that stores high-pressure fluid, and includes a winding step of winding a fiber-reinforced plastic filament around a pressure vessel liner for preventing permeation of the fluid, and a heating step of applying heat to the pressure vessel liner around which the filament is wound to fix the fiber-reinforced plastic.

[0020] Here, the pressure vessel liner is shaped by laminating a resin containing continuous fibers layer by layer based on a cross-sectional shape that appears when the shape of the pressure vessel liner is sliced into a plurality of layers, and the air pressure inside the pressure vessel liner during winding of the filament is configured to be equivalent to the atmospheric pressure.

[0021] By adopting the manufacturing method in which the shape of the pressure vessel liner is laminated layer by layer, there is no need to use a mold, so that the initial cost during manufacturing can be reduced. In addition, by configuring the pressure vessel liner with a resin containing continuous fibers, the liner will not be damaged by the filament winding force in the winding step. Therefore, it is not necessary to increase the internal pressure of the pressure vessel liner in advance so as not to be damaged by the filament winding force.

[0022] In this way, by making the air pressure inside the pressure vessel liner equivalent to the atmospheric pressure, the fluid filling operation for increasing the internal pressure and the internal pressure removal operation are no longer required, and the production time can be shortened. Accordingly, the production cost can be reduced. Effects of the Invention

[0023] As described above, the method for manufacturing a pressure vessel liner, the pressure vessel liner, and the method for manufacturing a pressure vessel of the present invention employ a structure in which the shape of the pressure vessel liner is composed of multiple layers using a resin containing continuous fibers, and each layer is laminated. Therefore, molds are not required, and high strength can be obtained from the continuous fibers. Consequently, not only is it strong, but it can also be produced without using molds, which has the effect of reducing manufacturing costs. [Brief explanation of the drawing]

[0024] [Figure 1] This is a cross-sectional view showing a liner for a pressure vessel according to the present invention. [Figure 2] This is an explanatory diagram illustrating the method for manufacturing a pressure vessel liner according to the present invention. [Figure 3] This is an explanatory diagram illustrating the method for manufacturing a pressure vessel according to the present invention. [Modes for carrying out the invention]

[0025] Embodiments for carrying out the present invention will be described below with reference to Figures 1 to 3. Please note that each diagram is a schematic representation for explanatory purposes, and dimensions and shapes may be exaggerated or simplified in some cases.

[0026] The pressure vessel liner (hereinafter referred to as "liner") 100 of the present invention is a liner used, for example, in a hydrogen tank of a fuel cell vehicle. As shown in the cross-sectional view in Figure 1, its shape is an axisymmetric shape with a roughly rounded rectangular cross-section, and holes or structures for attaching valves B and B are provided at both ends. This liner 100 is required to prevent leakage and permeation of the high-pressure hydrogen filled inside, and to withstand the winding force caused by the filaments (not shown) wound around its outer circumference.

[0027] The liner 100 of the present invention uses a resin with high gas barrier properties to prevent hydrogen leakage and permeation. For example, polyamide, ETFE, PVDF, PEEK, etc., can be used. These resins may be used alone, or their gas barrier properties may be enhanced with fillers such as nanoclay and graphene. Furthermore, the resin should be selected from those that can be used in AM (Additive Manufacturing), such as 3D printers, as described later. In particular, polyamide or polyamide with added fillers is preferred because it can be used in the FDM (Fused Deposition Modeling) method and has a low melting temperature and low cost.

[0028] Furthermore, the above resin shall include continuous fibers. In addition to carbon fibers, various inorganic or organic fibers such as aramid fibers, nylon fibers, high-strength polyester fibers, glass fibers, boron fibers, alumina fibers, silicon nitride fibers, and basalt fibers can be used as continuous fibers, but carbon fibers are preferred from the viewpoint of strength and weight. The continuous fibers shall be continuous in the longitudinal direction of the fiber.

[0029] For continuous fibers, it is preferable to use carbon fibers that have been thinly opened. As an example of a method for thinly opening fibers, a special fiber opening device (not shown) can be used. In this fiber opening device, a fluid is passed through the conveyed fiber bundle to bend the fibers and move them in the width direction, thereby opening them. In addition, the fiber opening process includes a step of bringing a contact member into contact with the conveyed fiber bundle. Upon contact, the contact member is rotated in a direction inclined with respect to the conveying direction to push a portion of the fiber bundle into a taut state, and then the contact member is separated from the taut fiber bundle to temporarily relax the fiber bundle. By allowing fluid to pass through the fiber bundle while it is in a relaxed state, it becomes possible to open the fibers to form a thin layer. Furthermore, during the occurrence of tension and relaxation, rotating the contact member in the direction of transport and the direction of inclination can reduce the damage to the fiber bundle.

[0030] The liner 100 with the above configuration is fabricated using an FDM composite material 3D printer, as shown in Figure 2. This composite material 3D printer uses a filament manufactured by bundling a predetermined number of carbon fibers that have been thinly opened using the method described above, and coating them with a thermoplastic resin such as polyamide resin. First, as shown in Figure 2(a), the 3D data D of the liner 100 is positioned using 3D printer software so that its longitudinal direction is horizontal. Next, the 3D data D is sliced ​​into multiple layers. The thickness of the layers varies depending on the 3D printer, but the thinner the layers, the better the accuracy of the shape after printing.

[0031] In Figure 2(a), the 3D data D is placed as the entire shape of the liner 100. In this state, after printing, the shape of the liner 100 will be printed as a single, seamless piece. However, the shape of the liner 100 may be divided vertically down the middle, and each part may be printed individually and then joined together by welding or fusion.

[0032] Next, the 3D printer starts fabrication using the data obtained by slicing the 3D data D layer by layer. In the example in Figure 2(b), an FDM composite material 3D printer is used to melt a material consisting of continuous carbon fibers coated with polyamide resin at high temperature and stack it layer by layer. As mentioned above, the material to be stacked may be a filament-like material in which the surrounding area of ​​the continuous fibers is coated with thermoplastic resin beforehand, or the resin and continuous fibers may be supplied separately to the 3D printer and composited within the 3D printer.

[0033] The liner 100 thus created is kept at a high temperature for a certain period of time, as shown in Figure 2(c), in order to improve the adhesion between the layers. This allows the resins between the layers to blend together, improving adhesion and enhancing gas barrier properties and strength.

[0034] The pressure vessel 200 using the liner 100 described above can be manufactured by the method shown in Figure 3. First, as shown in Figure 3(a), valves B·B are attached to both ends of the liner 100, and the fiber-reinforced plastic filament F is wound in the winding process shown in Figure 3(b). The filament F is preferably made of high-tensile-strength fibers such as carbon fiber, glass fiber, or aramid fiber. In the example shown in Figure 3(b), a thermosetting resin is used as the matrix resin, and after winding a filament F made of carbon fiber from various directions, a glass fiber filament F' is similarly wound from various directions. The carbon fiber ensures strength against internal pressure caused by high-pressure hydrogen, and the glass fiber protects the carbon fiber from external impacts. Finally, as a heating step, the pressure vessel 200 is heated by hot air or the like to cure the matrix resin.

[0035] In the winding process of filament F·F', the air pressure inside the liner 100 is kept equal to atmospheric pressure. Generally, filament F·F' is wound with strong winding force. Therefore, to prevent the liner 100 from being crushed by this winding force, a gas at a high pressure is sealed inside the liner 100 beforehand to increase the internal pressure before winding. However, in the manufacturing method of the pressure vessel 200 of the present invention, since the liner 100 is made of a resin containing carbon fibers, which are continuous fibers, it will not be crushed by winding force even without increasing the internal pressure.

[0036] For filament F·F', it is preferable to use thin-layer opened fibers. One example of a thin-layer opening method is to use a special opening device (not shown) to open the fibers. In this opening device, a fluid is passed through the conveyed fiber bundle to bend the fibers and move them in the width direction, thereby opening them. In addition, the opening process includes a step of bringing a contact member into contact with the conveyed fiber bundle. Upon contact, the contact member is rotated in a direction inclined with respect to the conveying direction to push a portion of the fiber bundle into a taut state, and then the contact member is separated from the taut fiber bundle to temporarily relax the fiber bundle. By allowing fluid to pass through the fiber bundle while it is in a relaxed state, it becomes possible to open the fibers to form a thin layer. Furthermore, during the occurrence of tension and relaxation, rotating the contact member in the direction of transport and the direction of inclination can reduce the damage to the fiber bundle.

[0037] For opened fibers, for example, if a 12K carbon fiber bundle is opened to a width of 20 mm, it is estimated that there are approximately 2,000 to 2,500 fibers in the width direction and approximately 4 to 6 fibers in the thickness direction. If it is opened to a width of 40 mm, it is estimated that there are approximately 5,000 to 5,500 fibers in the width direction and approximately 2 to 3 fibers in the thickness direction. Furthermore, if a 50K carbon fiber bundle is opened to a width of 42 mm, it is estimated that there are approximately 8 to 10 fibers in the thickness direction. In this way, a film of matrix resin is placed between bundles of thinly separated fibers, and the mixture is heated and then sandwiched between rollers.

[0038] As described above, the manufacturing method for the liner 100 of the present invention allows for fabrication by additive manufacturing (AM) without the use of a mold, thus reducing initial costs and enabling production at a low cost. Furthermore, in the manufacturing of the pressure vessel 200, the liner 100 can be manufactured using a pre-fabricated liner 100, through a winding process and a heating process. In this case, since the liner 100 contains continuous fibers, there is no need to increase the internal pressure, and the amount of filament F·F' can also be reduced. As a result, the manufacturing time can be shortened by several tens of minutes.

[0039] The present invention is not limited to the embodiments described above, and can be modified as appropriate within the scope of the claims of the present invention. For example, the liner can be sliced ​​not only longitudinally but also radially. Furthermore, it is possible to create a multi-layered liner using multiple materials. Furthermore, liners and pressure vessels can be used not only for hydrogen tanks in fuel cell vehicles, but also for various industrial gas cylinders, aerospace cylinders, and the like. [Explanation of Symbols]

[0040] 100 Pressure vessel liners 200 pressure vessels B valve D 3D data F filament

Claims

1. A method for manufacturing a pressure vessel liner for preventing permeation of a high-pressure fluid in a pressure vessel storing the fluid, A method for manufacturing a pressure vessel liner, characterized by forming it by laminating a resin containing continuous fibers layer by layer based on the cross-sectional shape that appears when the shape of the pressure vessel liner is sliced ​​into multiple layers.

2. The method for manufacturing a pressure vessel liner according to claim 1, characterized in that the direction of the slice is the longitudinal direction in the shape of the pressure vessel liner.

3. A method for manufacturing a pressure vessel liner according to claim 1 or claim 2, characterized in that the resin is a polyamide resin and the continuous fibers are carbon fibers.

4. A pressure vessel liner for preventing permeation of a high-pressure fluid in a pressure vessel for storing the fluid, Multiple layers are laminated, each composed of a resin containing continuous fibers. A liner for high-pressure vessels, characterized in that the continuous fibers are continuous in each layer.

5. The high-pressure vessel liner according to claim 4, characterized in that the shape of the high-pressure vessel liner is stacked in a horizontal position.

6. A method for manufacturing a pressure vessel for storing high-pressure fluids, A winding step of winding fiber-reinforced plastic filaments around a liner for a pressure vessel to prevent the permeation of the aforementioned fluid, The process includes a heating step of applying heat to the liner for a pressure vessel around which the filament is wound to fix the fiber-reinforced plastic, The pressure vessel liner is manufactured by laminating a resin containing continuous fibers layer by layer, based on the cross-sectional shape that appears when the shape of the pressure vessel liner is sliced ​​into multiple layers. A method for manufacturing a pressure vessel, characterized in that the air pressure inside the pressure vessel liner during the winding of the filament is equivalent to atmospheric pressure.

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