High-pressure tank and manufacturing process of a high-pressure tank

Abstract

High-pressure tank (100) which has the following features: a cross layer (252) comprising the first fibers (F1) wound in a cross pattern and a first resin (Re1) fixing the first fibers (F1); a circumferential layer (254) arranged outside the cross layer (252) in the high-pressure tank (100) and comprising second fibers (F2) wound in a circumferential pattern and a second resin (Re2) that fixes the second fibers (F2); and an intermediate layer (256) arranged between the cross layer (252) and the circumferential layer (254) and comprising third fibers (F31, F32) that are thinner than at least either the first fibers (F1) or the second fibers (F2), and a third resin (Re3) that fixes the third fibers (F31, F32), the first fibers (F1) of the cross layer (252) and the second fibers (F2) of the circumferential layer (254).

Description

[0001] The present invention relates to a high-pressure tank and to a manufacturing method of a high-pressure tank. Description of the state of the art

[0002] There is a common high-pressure tank filled with compressed hydrogen (see JP 2018-100768 A). The high-pressure tank of JP 2018-100768 A includes a liner, a reinforcing layer, a protective layer, and closures. The liner has a property that prevents hydrogen, etc., filled in a space within the liner from leaking out (a so-called gas barrier property). The reinforcing layer is formed to cover the entire external surface of the liner and a portion of each closure. The reinforcing layer is made of carbon fiber reinforced plastic (CFRP) and has pressure resistance. The protective layer is formed on the reinforcing layer. The protective layer is made of glass fiber reinforced plastic (GFRP) and has higher impact resistance than the reinforcing layer.

[0003] It was found that repeated gas filling and emptying of the high-pressure tank described in JP 2018-100768 A in a high-temperature and high-humidity environment causes peeling and untwisting of a portion of the protective layer. Furthermore, it was found that such peeling occurs between a layer of the protective layer in which glass fibers are wound in a crisscross pattern and a layer thereof in which glass fibers are wound in a circumferential pattern.

[0004] Further known high-pressure tanks and manufacturing methods of such high-pressure tanks are disclosed in EP 2 418 414 B1, DE 695 30 126 T2 and JP 2014 - 126 149 A. Summary of the invention

[0005] It is the object of the present invention to provide a high-pressure tank and a manufacturing method of a high-pressure tank which ensure improved temperature and humidity resistance for the high-pressure tank.

[0006] The object of the present invention is achieved by a high-pressure tank having the features of claim 1 and a manufacturing method of a high-pressure tank having the features of claim 5.

[0007] Advantageous developments of the present invention are defined in the dependent claims.

[0008] A high-pressure tank according to the invention is provided as one embodiment of the present invention. This high-pressure tank includes: a helical layer comprising first fibers wound or braided in a helical pattern and a first resin that fixes the first fibers; a hoop layer disposed outside the cross layer in the high-pressure tank and comprising second fibers wound or braided in a hoop pattern and a second resin that fixes the second fibers; an intermediate layer disposed between the cross layer and the circumferential layer and comprising third fibers that are thinner than at least one of the first fibers and the second fibers, and a third resin that fixes the third fibers, the first fibers of the cross layer, and the second fibers of the circumferential layer.

[0009] According to the present invention, the gap between the first fibers constituting the outermost layer of the cross-ply and the second fibers constituting the innermost layer of the peripheral ply is reduced by the third fibers being thinner than at least either the first fibers or the second fibers. Thus, the gap between the first fibers constituting the outermost layer of the cross-ply and the second fibers constituting the innermost layer of the peripheral ply can be filled, thereby reducing the formation of cracks in the third resin that fixes these first fibers and second fibers. As a result, the probability of the peripheral ply separating from the cross-ply can be reduced.

[0010] In the high-pressure tank of the above embodiment, the first fibers may be impregnated with the first resin, and the first resin may fix different fiber portions of the first fibers together; and the second fibers may be impregnated with the second resin, and the second resin may fix different fiber portions of the second fibers together.

[0011] In a high-pressure tank of the above embodiment, the third fibers may be impregnated with the third resin and may be arranged in a first direction and in a second direction different from the first direction to form a sheet.

[0012] This makes it possible for the gap between the outermost layer of the cross-layer, in which the first fibers are arranged in different directions, and the second fibers of the innermost layer of the circumferential layer to be reduced by the third fibers regardless of the direction of the first fibers in the outermost layer of the cross-layer.

[0013] The high-pressure tank of the above embodiment may further comprise a liner having a cylindrical part and curved parts, one of which is arranged at each end of the cylindrical part, wherein the cross-ply is formed to surround the liner, and the third fibers may form a single piece of the liner arranged to surround the cylindrical part.

[0014] This allows the circumferential layer and the cross layer to be evenly attached (connected) together around the cylindrical part.

[0015] A manufacturing method of a high-pressure tank according to the present invention is provided as another embodiment of the present invention. This manufacturing method of a high-pressure tank comprises: forming a cross-layer by winding first fibers impregnated with a first resin in a cross pattern on a semi-finished product of the high-pressure tank; forming an intermediate layer by arranging third fibers impregnated with a third resin on the cross-layer; and forming a circumferential layer by winding second fibers impregnated with a second resin in a circumferential pattern on the intermediate layer, wherein the third fibers of the intermediate layer are thinner than at least one of the first fibers of the cross-layer and the second fibers of the circumferential layer.

[0016] According to the invention, the gap between the fibers constituting the outermost layer of the cross-ply and the fibers constituting the innermost layer of the peripheral layer can be reduced by using fibers that are thinner than at least either the fibers of the cross-ply or the fibers of the peripheral layer. Thus, the gap between the fibers constituting the outermost layer of the cross-ply and the fibers constituting the innermost layer of the peripheral layer can be filled, thereby reducing the formation of cracks in the resin that fixes these fibers. As a result, the likelihood of the peripheral layer separating from the cross-ply can be reduced.

[0017] In the manufacturing method of the high-pressure tank of the above embodiment, forming the intermediate layer may include arranging at the cross-layer of a liner in which the third fibers of the intermediate layer are arranged in a first direction and a second direction different from the first direction.

[0018] This makes it possible to arrange the fibers of the intermediate layer in a shorter time than a method of arranging the fibers of the intermediate layer by winding these fibers.

[0019] In the manufacturing method of the high-pressure tank of the above embodiment, the semi-finished product may include a liner having a cylindrical part and curved parts, one of which is arranged at each end of the cylindrical part, and arranging the liner at the cross layer may include arranging a single piece of the liner to surround the cylindrical part.

[0020] This allows the circumferential layer and the cross layer to be joined (joined) evenly around the cylindrical part. The present invention can also be implemented in various forms other than a high-pressure tank. For example, the present invention can be implemented in embodiments including a computer program implementing a manufacturing method of a high-pressure tank and a permanent recording medium storing this computer program. Brief description of the drawings

[0021] Features, advantages and technical and industrial characteristics of exemplary embodiments of the invention are described below with reference to the accompanying drawings, in which like reference numerals designate like elements and in which: Fig. 1 is a sectional view showing a schematic configuration of a high-pressure tank as an embodiment of the technology disclosed herein; Fig. Fig. 2 is an enlarged view of a portion of a protective layer 25 disposed on a cylindrical part 102; Fig. 3 is a flowchart showing a manufacturing method of a high-pressure tank 100; Fig. Fig. 4 is a view illustrating a state of glass fibers F1 of a cross-ply 252 wound around a tank main body in a step S320 of Fig. 3 be wrapped; Fig. Fig. 5 is a view illustrating a state of glass fibers F31, F32 of an intermediate layer 256 bonded to the cross layer 252 in a step S340 of Fig. 3 may be arranged; Fig. Fig. 6 is a view illustrating a state of glass fibers F2 of a peripheral layer 254 bonded to the intermediate layer 256 in a step S360 of Fig. 3 be wrapped; Fig. 7 is a photograph showing a result of repeated gas filling and emptying of a high-pressure tank 100c of a comparative mold not having the spacer 256 in a high-temperature and high-humidity environment; Fig. Fig. 8 is an enlarged view showing a part of a reinforcing layer 20 and the protective layer 25 in the structure shown in Fig. 7 is shown; Fig. Fig. 9 is a view illustrating how peeling occurs between the cross layer 252 and the circumferential layer 254 in the high-pressure tank 100c of the comparative form; and Fig. 10 is a view illustrating how the occurrence of peeling between the cross ply 252 and the circumferential ply 254 is reduced in the high-pressure tank 100 of the embodiment. Detailed description of the embodiments A. Embodiment A1. Design of the high-pressure tank

[0022] Fig. Figure 1 is a sectional view showing a schematic configuration of a high-pressure tank 100 as an embodiment of the technology disclosed herein. The high-pressure tank 100 is a gas tank that is a hollow container designed to be filled with compressed hydrogen. The high-pressure tank 100 is installed in a fuel cell vehicle to supply hydrogen to a fuel cell.

[0023] The high-pressure tank 100 has, as its main parts, a cylindrical part 102 and a pair of domed parts 104. The cylindrical part 102 of the high-pressure tank 100 has a substantially cylindrical shape. Each domed part 104 of the high-pressure tank 100 has a western hemispherical shape with a radius equal to the radius of the cylindrical part 102. One of the domed parts 104 is arranged at each end of the cylindrical part 102, with circular openings of the domed parts 104 facing the cylindrical part 102. Fig. 1, the boundaries between the cylindrical part 102 and the curved part 104 are indicated by dashed lines. The terms "cylindrical part 102" and "curved part 104" are concepts for collectively referring to the main elements, described below, of the high-pressure tank 100 by classifying these elements by the part of the high-pressure tank 100.

[0024] The high-pressure tank 100 has a liner 10, a reinforcing layer 20, a protective layer 25, a closure (lid) 30 and a closure (lid) 40.

[0025] The liner 10 forms a layer on an innermost side of the high-pressure tank 100. The liner 10 is made of a nylon resin. The liner 10 has a property that prevents hydrogen, etc., filled in a space inside the liner 10 from leaking out (a so-called gas barrier property). Main parts of the liner 10 can also be divided into a part corresponding to the cylindrical part 102 and the parts corresponding to the curved parts 104.

[0026] The closure 30 is arranged at an upper end of the portion of the liner 10 corresponding to one of the pair of curved portions 104. The "upper end" of the curved portion 104 refers to an intersection point between the curved portion 104 and a central axis CA of the high-pressure tank 100. The closure 30 has a through hole. The through hole of the closure 30 connects the interior and exterior of the high-pressure tank 100. A pipe or a valve is mounted on the high-pressure tank 100 through the closure 30.

[0027] The closure 40 is arranged at one end of the part of the liner 10 corresponding to the other end of the pair of bulged parts 104. The closures 30, 40 also serve as mounting portions used to mount a tank main body on a filament winding device to form the reinforcing layer 20 and the protective layer 25. In the present specification, the liner 10 with the closure 30 and the closure 40 mounted thereon is further referred to as a "tank main body." Main parts of the tank main body can also be divided (split) into a part corresponding to the cylindrical part 102 and parts corresponding to the bulged parts 104.

[0028] The reinforcement layer 20 is formed to cover an external surface of the tank main body. Specifically, the reinforcement layer 20 is formed to cover the entire external surface of the liner 10 and a part of each of the closure 30 and the closure 40. The reinforcement layer 20 serves to enhance the pressure resistance of the high-pressure tank 100. The reinforcement layer 20 is formed of a carbon fiber reinforced plastic (CFRP), which is a composite material of an epoxy resin and carbon fibers. The diameter of the carbon fibers in the reinforcement layer 20 has a constant value within the range of 2 μm to 10 μm. Main parts of the reinforcement layer 20 can also be divided into a part corresponding to the cylindrical part 102 and parts corresponding to the bulged parts 104.

[0029] The diameter of the carbon fibers in the reinforcement layer 20 is smaller than the diameter of the glass fibers in the protective layer 25, which are described below. This configuration allows the carbon fibers in the reinforcement layer 20 to be arranged more densely than the glass fibers in the protective layer 25. This improves the pressure resistance of the high-pressure tank 100 compared to a case where the diameter of the fibers in the reinforcement layer 20 is equal to or larger than the diameter of the fibers in the protective layer 25.

[0030] The protective layer 25 is formed on the reinforcement layer 20. The protective layer 25 is made of glass fiber reinforced plastic (GFRP), which is a composite material composed of a thermosetting resin and glass fibers. Thus, the protective layer 25 has higher impact resistance than the reinforcement layer 20.

[0031] Fig. 2 is an enlarged view of a portion of the protective layer 25 disposed on the cylindrical part 102. In Fig. 1 and Fig. 2, a direction from the center axis CA of the high-pressure tank 100 toward an outside is indicated by an arrow Do. Fig. Figure 2 is a view to illustrate the core of the technology and does not show the exact dimensions of each part.

[0032] The protective layer 25 has a cross-layer 252, a peripheral layer 254, and an intermediate layer 256. The cross-layer 252, the peripheral layer 254, and the intermediate layer 256 are each formed of a glass fiber reinforced plastic. The cross-layer 252, the peripheral layer 254, and the intermediate layer 256 differ from each other at least in the thickness of the glass fibers used or in the direction of the glass fiber arrangement. Thermosetting resins included in the cross-layer 252, the peripheral layer 254, and the intermediate layer 256 are the same epoxy resin.

[0033] The cross-ply 252 is formed on the reinforcement layer 20. Specifically, the cross-ply 252 is formed to cover the liner 10 below the reinforcement layer 20. The cross-ply 252 includes glass fibers F1 wound or braided in a cross pattern and an epoxy resin Re1 that fixes the glass fibers F1. Cross-pattern winding (braiding) or cross-winding is a fiber winding method by which fibers are wound in a direction intersecting a plane perpendicular to the central axis CA of the tank main body. The diameter of the glass fibers F1 in the cross-ply 252 has a constant value within a range of 10 μm to 20 μm. Main parts of the cross-ply 252 can also be divided (split) into a part belonging to the cylindrical part 102 and parts belonging to the curved parts 104.

[0034] The circumferential layer 254 is arranged outside the cross layer 252 in the high-pressure tank 100 (see arrow Do). The circumferential layer 254 is provided in the cylindrical part 102 of the high-pressure tank 100. The circumferential layer 254 comprises glass fibers F2 wound in a circumferential pattern and an epoxy resin Re2 that fixes the glass fibers F2. Circumferential pattern winding, or hoop winding, is a fiber winding method by which fibers are wound in a direction substantially parallel to a plane perpendicular to the central axis CA of the tank main body. The diameter of the glass fibers F2 in each of the circumferential layers 254 has a constant value within a range of 10 µm to 20 µm. Specifically, the diameter of the glass fibers F2 in the circumferential layer 254 is the same as the diameter of the glass fibers F1 in the cross layer 252.This configuration makes it possible to wind the glass fibers F1 of the cross layer 252 and the glass fibers F2 of the circumferential layer 254 around the tank main body using the same winding device and the same fibers.

[0035] The intermediate layer 256 is arranged between the cross layer 252 and the circumferential layer 254. The intermediate layer 256 is provided in the cylindrical part 102 of the high-pressure tank 100. The intermediate layer 256 comprises glass fibers F31, F32 arranged in two directions and an epoxy resin Re3 that fixes the glass fibers F31, F32.

[0036] The diameters of the glass fibers F31, F32 in the intermediate layer 256 have a constant value within a range of 2 µm to 10 µm. The diameters of the glass fibers F31, F32 in the intermediate layer 256 are smaller than the diameters of the glass fibers F1, F2 included in the cross layer 252 and the circumferential layer 254. The glass fibers F31, F32 in the intermediate layer 256 are oriented in a first direction D1 (see Fig. 5) and in a second direction D2 (see Fig. 5) which differs from the first direction D1, to form a non-woven fabric covering (glass fiber covering) F3. The covering F3 of the glass fibers F31, F32 in the intermediate layer 256 is a single piece of covering arranged to surround the part of the lining 10 corresponding to the cylindrical part 102 (see Fig. 1). The composition of the F3 fairing is described in detail below.

[0037] The epoxy resin Re3 in the intermediate layer 256 fixes the glass fibers F31, F32 in the intermediate layer 256, the glass fibers F1, which are included in the outermost layer (layer) of the cross layer 252, and the glass fibers F2, which are included in the innermost layer (layer) of the peripheral layer 254. In Fig. In Figure 2, to facilitate understanding of the technology, a boundary between the cross layer 252 and the intermediate layer 256 is indicated by a straight line, and a boundary between the intermediate layer 256 and the peripheral layer 254 is indicated by a straight line. In reality, however, the boundaries of the epoxy resins Re1, Re2, Re3 forming the layers are not always visually recognizable.

[0038] Fig. 3 is a flowchart showing a manufacturing method of the high-pressure tank 100. In step S100, the liner 10 is prepared. In step S200, the reinforcement layer 20 is formed on the liner 10. Specifically, carbon fibers impregnated with the epoxy resin Re1 are wound around the liner 10 by a filament winding device to form the reinforcement layer 20. At the stage of step S200, the epoxy resin Re1 included in the reinforcement layer 20 has not yet been cured.

[0039] In a step S300, the protective layer 25 is formed on the reinforcing layer 20. Step S300 includes steps S320, S340, and S360.

[0040] In step S320, the cross layer 252 is formed on the tank main body on which the reinforcement layer 20 has been formed. Specifically, the glass fibers F1 impregnated with the epoxy resin Re1 are wound on the reinforcement layer 20 in a cross pattern by the filament winding device. In this case, the glass fibers F1 are wound on the cylindrical part 102 and the curved part 104 of the tank main body (see Fig. 1). As a result, the cross-layer 252 is formed on the cylindrical part 102 and the curved parts 104 of the tank main body. At the stage of step S320, the epoxy resin Re1 included in the cross-layer 252 has not yet cured.

[0041] Fig. Fig. 4 is a view illustrating a state of the glass fibers F1 of the cross-ply 252 wound around the tank main body in step S320 of Fig. 3 be wrapped. Fig. Figure 4 is a view illustrating the core of the technology and shows the inaccurate dimensions of each part. In fact, the cross-layer 252 is formed on a curved surface. However, to facilitate understanding of the technology, Fig. 4 the state of the glass fibers F1 as if the cross layer 252 were formed on a flat surface. The same applies to Fig. 5 and Fig. 6.

[0042] The glass fibers F1 of the cross layer 252 are / are arranged in a direction which is a plane perpendicular to the central axis CA (see Fig. 1) of the tank main body. Since the tank main body is not a spherical body, when a glass fiber F1 is wound in such a winding manner and passes through the same point on the tank main body again, the glass fiber F1 is arranged on the tank main body in a direction different from that of the last time. Fig. 4, of the glass fibers F1 thus wound in a cross pattern, a portion arranged earlier is represented by a fiber portion F11, and a portion arranged later is represented by a fiber portion F12.

[0043] In step S340 of Fig. 3, the intermediate layer 256 is formed on the cross layer 252 arranged on the cylindrical part 102. In particular, a single piece of the square glass fiber cladding F3 in which the glass fibers F31, F32 are arranged in the first direction D1 (see Fig. 5) and the second direction D2 (see Fig. 5), which distinguishes them from the first direction D1. The length of one side of the fiberglass cladding F3 is substantially equal to the length of the cylindrical part 102 (see Fig. 1) along the central axis C2. The length of the other side of the fiberglass liner F3 is substantially equal to the circumferential length of the cylindrical part 102 in which the cross-layer 252 is formed. The fiberglass liner F3 is impregnated with the epoxy resin Re3, and then the fiberglass liner F3 is wound on the cross-layer 252 corresponding to the cylindrical part 102 to cover the cross-layer 252. As a result, the intermediate layer 256 is formed on the cylindrical part 102 of the tank main body. At the stage of step S340, the epoxy resin Re3 included in the intermediate layer 256 has not yet cured.

[0044] This allows the glass fibers F31, F32 of the intermediate layer 256 to be arranged in a shorter time than with a method of arranging the glass fibers of the intermediate layer 256 by winding these fibers. The high impact resistance of the protective layer 25 is primarily realized by the glass fibers F1, F2 of the cross layer 252 and the circumferential layer 254. Therefore, the impact resistance of the protective layer 25 is ensured even if the glass fibers F31, F32 of the intermediate layer 256 are arranged by winding the glass fiber cladding F3.

[0045] Fig. Fig. 5 is a view illustrating a state of the glass fibers F31, F32 of the intermediate layer 256 bonded to the cross layer 252 in step S340 of Fig. 3 can be arranged. Fig. Figure 5 is a view illustrating the core of the technology and does not show the exact dimensions of each part. Glass fibers arranged along the first direction D1 are designated F31. Glass fibers arranged along the second direction D2 are designated F32. The glass fibers F31 and F32 preform the nonwoven fabric covering F3.

[0046] In step S360 of Fig. 3, the circumferential layer 254 is formed on the intermediate layer 256 disposed on the cylindrical part 102. Specifically, the glass fibers F2 impregnated with the epoxy resin Re2 are wound on the intermediate layer 256 in a circumferential pattern by the filament winding device. As a result, the circumferential layer 254 is formed on the cylindrical part 102 of the tank main body. At the stage of step S360, the epoxy resin Re2 included in the circumferential layer 254 has not yet cured.

[0047] Fig. Fig. 6 is a view illustrating a state of the glass fibers F2 of the peripheral layer 254 bonded to the intermediate layer 256 in step S360 of Fig. 3 are / are wound. Fig. Figure 6 is a view illustrating the core of the technology and does not show the exact dimensions of each part. The glass fibers F2 of the circumferential layer 254 are formed in a direction substantially parallel to the plane perpendicular to the central axis CA of the tank main body (see Fig. 1) wound. In order to wind the glass fibers F2 so that they cover the cylindrical part 102 of the tank main body, the glass fibers F2 are wound on the intermediate layer 256, while the position of the glass fiber F2 being wound is gradually shifted along the direction of the central axis CA. In Fig. 6, different fiber sections of the glass fibers F2, which are wound in a circumferential pattern in this way, are designated F21, F22, F23.

[0048] In a step S400 of Fig. 3, the epoxy resins comprised in the reinforcement layer 20 and the protective layer 25 are heated, thereby curing these epoxy resins comprised in the reinforcement layer 20 and the protective layer 25. As a result, the glass fibers F1 of the cross-layer 252 are fixed to one another by the epoxy resin Re1. The glass fibers F2 of the peripheral layer 254 are fixed to one another by the epoxy resin Re2. The glass fibers F31, F32 of the intermediate layer 256 are fixed to one another by the epoxy resin Re3. Furthermore, the glass fibers F1 in the outermost layer of the cross-layer 252 and the glass fibers F2 in the innermost layer of the peripheral layer 254 are fixed to the glass fibers F31, F32 of the intermediate layer 256 by the epoxy resin Re3.

[0049] The high pressure tank 100 is manufactured by the process as described above.

[0050] Fig. 7 is a photograph showing a result of repeated gas filling and emptying of a high-pressure tank 100c of a comparative mold not having the spacer 256 in a high-temperature and high-humidity environment. Fig. Figure 7 shows a portion of the high-pressure tank 100c of the comparative form in a plane including a central axis (see Fig. 1) of the high-pressure tank 100c of the comparative mold. The design of the high-pressure tank 100c of the comparative mold is the same as the design of the high-pressure tank 100 of the exemplary embodiment, except that the comparative mold uses the intermediate layer 256 (see Fig. 2 and Fig. 6) does not have. It can be Fig. 7 that repeated gas filling and emptying in a high-temperature and high-humidity environment causes peeling and twisting of the protective layer 25. Such peeling occurred in the cylindrical part 102 of the high-pressure tank 100c, but not in the domed part 104 thereof.

[0051] Fig. Figure 8 is an enlarged view showing a part of the reinforcing layer 20 and the protective layer 25 of the structure shown in Fig. 7 is shown. In Fig. 8, the circumferential layer 254, in which glass fibers are wound in a circumferential pattern, comprises regions of the glass fibers with shapes of almost perfect circles (see also Fig. 6). The cross-layer 252, in which glass fibers are wound in a cross pattern, has portions of the glass fibers with shapes that are elongated in a lateral direction. It may be Fig. 8 it can be seen that a detachment has occurred between the cross layer 252 and the circumferential layer 254 of the protective layer 25.

[0052] Fig. 9 is a view illustrating how the peeling occurs between the cross layer 252 and the circumferential layer 254 in the high-pressure tank 100c of the comparative example. Fig. Figure 9 shows a portion of the high-pressure tank 100c of the comparative form in a plane including the central axis (see Fig. 1) of the high-pressure tank 100c of the comparative form. As further shown in Fig. 6, in the circumferential layer 254, the sections F21, F22, F23 of the glass fibers F2 are arranged substantially parallel to each other, while in the cross layer 252, the sections F11, F12 of the glass fibers F1 are arranged in different directions. For this reason, in the high-pressure tank 100c in which the circumferential layer 254 is arranged at the cross layer 252 without the intermediate layer 256 being arranged therebetween, there is a large distance between contact points of the glass fibers F1 in the outermost layer of the cross layer 252 and the glass fibers F2 in the innermost layer of the circumferential layer 254, and thus there is a large gap IS between the glass fibers F1 of the cross layer 252 and the glass fibers F2 of the circumferential layer 254. Since the glass fibers F2 of the circumferential layer 254 are arranged substantially parallel to each other (see also Fig. 6), the space IS, which is in Fig. 9, is continuously present along an outer circumferential direction of the cylindrical part 102 in the high-pressure tank 100c of the comparative example. The gap IS between the glass fibers F1 of the cross-layer 252 and the glass fibers F2 of the peripheral layer 254 is filled with the epoxy resin Re1 or the epoxy resin Re2.

[0053] A stress applied to the protective layer 25 at a location between the glass fibers F1, which form the outermost layer of the cross-layer 252, and the glass fibers F2, which form the innermost layer of the peripheral layer 254, is absorbed by the epoxy resins Re1, Re2, which fill the gap IS and fix these fibers. The crack resistance (breaking strength) of the epoxy resin is significantly lower than that of the glass fibers. The epoxy resin swells (swells) in a high-temperature and high-humidity environment. When the epoxy resin masses Re1, Re2 have large volumes, a large difference in dimensions occurs between the glass fibers F2, F3 and the epoxy resins Re1, Re2 due to the swelling of the epoxy resins Re1, Re2, so that the epoxy resins Re1, Re2 easily detach from the glass fibers F2, F3.Thus, upon repeated gas filling and emptying in a high-temperature and high-humidity environment, cracks are likely to form between the glass fibers F1 of the cross-layer 252 and the glass fibers F2 of the circumferential layer 254 within portions formed of the epoxy resins Re1, Re2 or at interfaces between the epoxy resins Re1, Re2 and the glass fibers F1, F2.

[0054] If there is a large gap IS between the glass fibers F1 of the cross-layer 252 and the glass fibers F2 of the peripheral layer 254, a void BD that is not filled with the epoxy resins Re1, Re2 is likely to be formed. A crack CR is likely to develop (form) from such a void BD as a result of repeated gas filling and emptying.

[0055] No peeling occurs between the reinforcement layer 20 and the innermost layer of the cross-layer 252 in the high-pressure tank 100c of the comparative form (see Fig. 8). The epoxy resin of the reinforcement layer 20, the epoxy resin Re1 of the cross-layer 252, and the epoxy resin Re2 of the peripheral layer 254 are resins with the same composition. On the other hand, the diameter of the carbon fibers in the reinforcement layer 20 is smaller than the diameters of the glass fibers F1, F2 in the cross-layer 252 and the peripheral layer 254. It appears that, due to the smaller diameter of the carbon fibers in the reinforcement layer 20, the above-described problem associated with the large gap IS between the cross-layer 252 and the peripheral layer 254 did not occur, and therefore, no peeling occurred between the reinforcement layer 20 and the cross-layer 252.

[0056] Fig. 10 is a view illustrating how the occurrence of peeling between the cross ply 252 and the circumferential ply 254 is reduced in the high-pressure tank 100 of the embodiment. Fig. Figure 10 shows a portion of the high-pressure tank 100 of the embodiment in a plane including the central axis CA (see Fig. 1) of the high-pressure tank 100 of the embodiment. As further shown in Fig. 6, in this embodiment, the glass fibers F31, F32, which are thinner than the glass fibers F2 of the peripheral layer 254 and the glass fibers F1 of the cross-layer 252, are arranged between the portions F21, F22, F23 of the glass fibers F2 and the portions F11, F12 of the glass fibers F1. Thus, the distance between contact points of the glass fibers F1 of the cross-layer 252 and the glass fibers F31, F32 of the intermediate layer 256 and the distance between contact points of the glass fibers F31, F32 of the intermediate layer 256 and the glass fibers F2 of the peripheral layer 254 are narrower than the distance between the contact points in the high-pressure tank 100c of the comparative form. In other words, the gap between the glass fibers F1, F2, F31, F32 is smaller than the gap between the glass fibers F1, F2 in the high-pressure tank 100c of the comparative form.Thus, the main part where the stress (strain) applied to the protective layer 25 is absorbed by the epoxy resin Re3 is reduced, and a void from which a crack may develop (propagate) is less likely to form. Therefore, the formation of cracks in the epoxy resin Re3, which fills such a gap and fills the glass fibers F1 constituting the outermost layer of the cross-layer 252 and the glass fibers F2 constituting the innermost layer of the peripheral layer 254, is reduced. As a result, the peripheral layer 254 is less likely to detach from the cross-layer 252 compared to the high-pressure tank 100c of the comparative example.

[0057] In this embodiment, the glass fibers F31, F32 of the intermediate layer 256 are arranged in the first direction D1 and in the second direction D2, which is different from the first direction D1, in order to form the cladding F3 (see Fig. 6). Thus, the gap between the outermost layer of the cross-layer 252, in which the glass fibers F1 are arranged in different directions, and the glass fibers F2 of the innermost layer of the peripheral layer 254 can be reduced regardless of the direction of the glass fibers F1 in the outermost layer of the cross-layer 252.

[0058] In this embodiment, the glass fibers F31, F32 of the intermediate layer 256 form the single piece of the cladding F3 arranged to surround the cylindrical part 102 of the liner 10 in which the reinforcement layer 20 and the cross-layer 252 are formed (see S340 of Fig. 3 and Fig. 5). Thus, the circumferential layer 254 and the cross layer 252 can be evenly joined to each other around the cylindrical part 102.

[0059] The following method is also suitable as a method for arranging a structure smaller in size than the glass fibers F1 included in the outermost layer of the cross-layer 252 and the glass fibers F2 included in the innermost layer of the peripheral layer 254, to change the distance between contact points of the glass fibers F1, F2 and this additional structure, thereby reducing the gap. Applying a thermosetting resin comprising particles with a diameter smaller than the diameters of the glass fibers F1, F2 to an upper side of the cross-layer 252 and providing the peripheral layer 254 at the upper end of this thermosetting resin can theoretically narrow the distance between the contact points of the structures.However, in this case, a difficulty arises in obtaining the resin containing particles over the entire cross-layer 252 of the cylindrical part 102 in an environment subject to gravity. That is, the resin containing particles drips from the surface of the cross-layer 252 of the cylindrical part 102 under the influence of gravity.

[0060] Instead, in this embodiment, the glass fiber cladding F3 impregnated with the resin is wound onto the cross-layer 252 of the cylindrical part 102. Thus, the glass fibers F31, F32, as structures smaller than the glass fibers F1, F2, and the thermosetting resin for fixing the glass fibers F1, F2, F31, F32, can be easily arranged on the cross-layer 252 of the cylindrical part 102. Therefore, the intermediate layer 256 can be easily formed.

[0061] The glass fibers F1 of the cross-layer 252 in this embodiment are further referred to as "first fibers." The epoxy resin Re1 of the cross-layer 252 is further referred to as a "first resin." The glass fibers F2 of the peripheral layer 254 are further referred to as "second fibers." The epoxy resin Re2 of the peripheral layer 254 is further referred to as a "second resin." The glass fibers F31, F32 of the intermediate layer 256 are further referred to as "third fibers." The epoxy resin Re3 of the intermediate layer 256 is further referred to as a "third resin." The tank main body, which is the liner 10 with the closure 30 and the closure 40 mounted thereon, is further referred to as a "semi-finished product of a high-pressure tank." B. Further embodimentsB1. Further embodiment 1

[0062] In the above embodiment, the liner 10 is formed of a nylon resin. However, another synthetic resin having a gas barrier property, such as a polyethylene-based resin, or a metal such as stainless steel may also be used to manufacture (provide) the liner.

[0063] In the above embodiment, the diameter of the glass fibers F1 in the cross layer 252 has a constant value within a range of 10 µm to 20 µm. The diameter of the glass fibers F2 in the peripheral layer 254 has a constant value within a range of 10 µm to 20 µm. In particular, the diameter of the glass fibers F2 in the peripheral layer 254 is the same as the diameter of the glass fibers F1 in the cross layer 252. The diameter of the glass fibers F31, F32 in the intermediate layer 256 has a constant value within a range of 2 µm to 10 µm.

[0064] However, the diameter of the fibers in the cross layer can have a value that is less than 10 µm, such as 5 µm or 8 µm. The diameter of the fibers in the cross layer can have a value that is greater than 20 µm, such as 25 µm or 38 µm. The diameter of the fibers in the circumferential layer can have a value that is less than 10 µm, such as 5 µm or 8 µm. The diameter of the fibers in the circumferential layer can have a value that is greater than 20 µm, such as 25 µm or 38 µm. The diameter of the fibers in the intermediate layer can have a value that is less than 2 µm, such as 0.5 µm or 1.0 µm. The diameter of the fibers in the intermediate layer may be greater than 10 µm, such as 12 µm or 15 µm. In short, the diameters of the fibers contained in the respective layers may have different values.The fibers comprised in the cross layer and the fibers comprised in the circumferential layer may have different thicknesses from each other.

[0065] The fibers comprised in the intermediate layer may have any diameter that is smaller than the diameter of either the fibers comprised in the cross-ply or the fibers comprised in the circumferential layer. The diameter of the fibers comprised in the intermediate layer is preferably no greater than half, more preferably no greater than one-third, and even more preferably no greater than one-fifth of the smaller diameter of the diameters of the fibers in the cross-ply and the diameter of the fibers in the circumferential layer. The fibers comprised in the intermediate layer may have fibers that are thicker than either the fibers comprised in the cross-ply or the fibers comprised in the circumferential layer.

[0066] In the above embodiment, the glass fibers F1, F2, F31, F32 are used as the fibers included in the cross layer 252, the fibers included in the circumferential layer 254, and the fibers included in the intermediate layer 256. However, other fibers that differ in material or composition, such as carbon fibers, may also be used as the fibers included in the cross layer, the fibers included in the circumferential layer, and the fibers included in the intermediate layer. However, it is preferable that the fibers included in each layer withstand temperatures of 200°C to 300°C. Furthermore, it is preferable that the fibers included in each layer be flexible and easy to stretch (elongate). The cross layer, the circumferential layer, and the intermediate layer may comprise different fibers, or two or all three of these layers may comprise the same fibers.

[0067] In the above embodiment, the epoxy resin is used as the resin included in the cross-layer 252, the resin included in the circumferential layer 254, and the resin included in the intermediate layer 256. However, another thermosetting resin, such as an unsaturated polyester resin, may also be used as the resin included in the cross-layer, the resin included in the circumferential layer, and the resin included in the intermediate layer. The cross-layer, the circumferential layer, and the intermediate layer may comprise different resins, or two or all three of these layers may comprise the same resin.

[0068] However, it is preferable that the combination of the fiber material and the resin material used in each layer be such that a contact angle of the resin used relative to the fibers used is not greater than 50° in each layer. The contact angle of the fiber material is measured by the following procedure: The fibers are arranged parallel to each other without a gap and fixed to a glass panel, and then the resin is dropped onto these fibers. The contact angle is a contact angle measured 60 seconds after the resin is dropped from a direction perpendicular to a longitudinal direction of the fibers.

[0069] In the above embodiment, neither the first direction D1 of the glass fibers F31 nor the second direction D2 of the glass fibers F32 in the intermediate layer 256 is parallel to the direction of the glass fibers F2 included in the peripheral layer 254. However, the direction of at least some fibers in the intermediate layer may coincide with the direction of the fibers of the peripheral layer.

[0070] In the above embodiment, the high-pressure tank 100 is filled with compressed hydrogen and is installed in a fuel cell vehicle. However, the high-pressure tank may be installed in another vehicle, such as an electric vehicle or a hybrid vehicle, or may be installed in another moving object, such as a ship, an aircraft, or a robot. Alternatively, the high-pressure tank may be installed in a stationary facility, such as a house or building. The high-pressure tank may be filled with a gas other than hydrogen, for example, nitrogen or helium. B2. Further embodiment 2

[0071] In the above embodiment, the glass fibers F31, F32 are arranged in the intermediate layer 256 in the first direction D1 and the second direction D2, which is different from the first direction D1, to form the nonwoven fabric covering F3 (see Fig. 5 and Fig. 6). However, the directions of the fibers included in the intermediate layer may be parallel to each other, and the covering may be a nonwoven fabric in which parallel fibers are fixed to each other with an adhesive (adhesive).

[0072] In a preceding embodiment, the glass fibers F31, F32 are arranged in the intermediate layer 256 in the first direction D1 and the second direction D2, which is different from the first direction D1, to form the nonwoven fabric covering F3 (see Fig. 5). However, the fibers of the intermediate layer may form a covering, which is a woven fabric formed by interweaving the fibers together. It is preferable that the fibers of the intermediate layer be arranged such that a plurality of fibers form a surface.

[0073] In the above embodiment, in order to form the intermediate layer 256, the glass fiber cladding F3 is impregnated with the epoxy resin Re3, and then the glass fiber cladding F3 is wound on the cross layer 252 corresponding to the cylindrical part 102 to cover the cross layer 252 (see S340 of Fig. 3 and Fig. 5). However, an intermediate layer in which the fibers are not impregnated with the resin can also be used. B3. Further embodiment 3

[0074] In the above embodiment, the glass fibers F31, F32 of the intermediate layer 256 form a single piece of the cladding F3, which is arranged to surround the cylindrical part 102 of the liner 10 in which the reinforcement layer 20 and the cross-layer 252 are formed (see S340 of Fig. 3 and Fig. 5). However, more than one facing, for example two, three, or five facings of the third fibers, may be used to form the intermediate layer.

[0075] The present invention is not limited to the above embodiments, but can be realized within the scope of the invention as defined in the appended claims.

[0076] A high-pressure tank (100) is provided, comprising: a cross layer (252) comprising first fibers (F1) wound in a cross pattern and a first resin (Re1) that fixes the first fibers (F1); a circumferential layer (254) arranged outside the cross layer (252) in the high-pressure tank (100) and comprising second fibers (F2) wound in a circumferential pattern and a second resin (Re2) that fixes the second fibers (F2); and an intermediate layer (256) disposed between the cross layer (252) and the peripheral layer (254) and comprising third fibers (F31, F32) that are thinner than at least one of the first fibers (F1) and the second fibers (F2), and a third resin (Re3) that fixes the third fibers (F31, F32), the first fibers (F1) of the cross layer (252) and the second fibers (F2) of the peripheral layer (254).

Claims

[1] High-pressure tank (100) comprising: a cross layer (252) comprising first fibers (F1) wound in a cross pattern and a first resin (Re1) fixing the first fibers (F1); a circumferential layer (254) disposed outside the cross layer (252) in the high-pressure tank (100) and comprising second fibers (F2) wound in a circumferential pattern and a second resin (Re2) fixing the second fibers (F2); and an intermediate layer (256) arranged between the cross layer (252) and the peripheral layer (254) and comprising third fibers (F31, F32) which are thinner than at least one of the first fibers (F1) and the second fibers (F2), and a third resin (Re3) which fixes the third fibers (F31, F32), the first fibers (F1) of the cross layer (252) and the second fibers (F2) of the peripheral layer (254). [2] High pressure tank (100) according to claim 1, wherein: the first fibers (F1) are impregnated with the first resin (Re1), and the first resin (Re1) fixes different fiber sections (F11, F12) of the first fibers (F1) together; and the second fibers (F2) are impregnated with the second resin (Re2), and the second resin (Re2) fixes different fiber sections (F21, F22, F23) of the second fibers (F2) together. [3] High-pressure tank (100) according to claim 1 or 2, wherein the third fibers (F31, F32) are impregnated with the third resin (Re3) and are arranged in a first direction (D1) and in a second direction (D2) different from the first direction (D1) to form a cladding (F3). [4] High-pressure tank (100) according to claim 3, further comprising a liner (10) having a cylindrical part (102) and curved parts (104), one of which is arranged at each end of the cylindrical part (102), the cross-ply (252) being formed to surround the liner (10), the third fibers (F31, F32) forming a single piece of the liner (F3) arranged to surround the cylindrical part (102). [5] A method of manufacturing a high-pressure tank (100), the method comprising: Forming a cross layer (252) by winding first fibers (F1) impregnated with a first resin (Re1) in a cross pattern on a semi-finished product of the high-pressure tank (100); Forming an intermediate layer (256) by arranging third fibers (F31, F32) impregnated with a third resin (Re3) on the cross layer (252); and Forming a circumferential layer (254) by winding second fibers (F2) impregnated with a second resin (Re2) in a circumferential pattern on the intermediate layer (256), wherein the third fibers (F31, F32) of the intermediate layer (256) are thinner than at least either the first fibers (F1) of the cross layer (252) or the second fibers (F2) of the peripheral layer (254). [6] The manufacturing method of the high-pressure tank (100) according to claim 5, wherein forming the intermediate layer (256) comprises arranging on the cross layer (252) of a liner (F3) in which the third fibers (F31, F32) of the intermediate layer (256) are arranged in a first direction (D1) and a second direction (D2) different from a first direction (D1). [7] A manufacturing method of the high-pressure tank (100) according to claim 6, wherein: the semi-finished product comprises a lining (10) with a cylindrical part (102) and curved parts (104), one of which is arranged at each end of the cylindrical part (102); and disposing the cladding (F3) on the cross layer (252) comprises disposing a single piece of the cladding (F3) to surround the cylindrical part (102).

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