How to select high pressure tanks for inspection

Abstract

To provide an inspection object selection method of a high-pressure tank which can shorten an inspection time of the high-pressure tank, and can reduce an inspection expense.SOLUTION: An inspection object selection method of a high-pressure tank comprises: an inspection step of adjusting an inner pressure of the tank so as to be raised higher than a resin pressure being a pressure of a resin material which is pressurized and charged into a resin impregnation molding metal mold by an inner pressure adjustment mechanism, and inspecting a resin hardening-start point at which the resin pressure starts lowering by the hardening of the resin material in a state that the resin material is pressurized and charged into the resin impregnation molding metal mold, and is charged into a fiber bundle; and a selection step of selecting the high-pressure tank as an inspection object when a pressure difference obtained by subtracting the resin pressure from the inner pressure within a prescribed time which is preset from the resin hardening start point which is detected in the inspection step exceeds a determination threshold which is decided in advance on the basis of a correlation between the pressure difference which has been obtained in advance and an exfoliation.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a method for selecting an inspection target for a high-pressure tank. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing a high-pressure tank by using a resin impregnation molding die to manufacture a high-pressure tank by RTM (Resin Transfer Molding). In this method for manufacturing a high-pressure tank, a tank, which is an intermediate product of a high-pressure tank in which a fiber bundle is wound on the outer peripheral surface of a liner, is placed in a die, and resin material is pressurized and filled into the die to impregnate the fiber bundle. Furthermore, a "curing process" is performed in which the impregnated resin material is thermally cured in a thermal curing oven, and a fiber-reinforced resin layer is formed on the outer peripheral surface of the liner.

[0003] When manufacturing a high-pressure tank by the above-mentioned RTM molding, peeling may occur in the fiber-reinforced resin layer after the curing process. In order to measure this peeling, non-destructive testing, for example, using X-ray CT, is carried out. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-84317 Summary of the Invention [Problem to be solved by the invention]

[0005] However, currently there is no way to identify high-pressure tanks that are likely to have large peeling that exceeds the tolerance, so all manufactured high-pressure tanks must be inspected, which creates the problem of high inspection time and costs. [Means for solving the problem]

[0006] The present disclosure can be realized in the following forms.

[0007] According to one embodiment of the present disclosure, there is provided a method for selecting an inspection target for a high-pressure tank, the method for selecting an inspection target for inspecting the presence or absence of delamination in a fiber reinforced resin layer of the high-pressure tank, the method comprising: a detection step of detecting a resin hardening start point at which the resin pressure starts to decrease as the resin material hardens in a state in which an internal pressure of a tank, which is an intermediate product of the high-pressure tank and in which a fiber bundle constituting the fiber reinforced resin layer before thermal curing is wound around an outside of a liner, is adjusted by an internal pressure adjustment mechanism so as to be greater than a resin pressure, which is a pressure of a resin material pressurized and filled into the resin impregnation molding die, and the resin material is pressurized and filled into the fiber bundle in the resin impregnation molding die, and a selection step of selecting the high-pressure tank as the inspection target when a differential pressure obtained by subtracting the resin pressure from the internal pressure within a predetermined time from the resin hardening start point detected in the detection step exceeds a judgment threshold value that is predetermined based on a correlation between the differential pressure and delamination obtained in advance. According to the above-described embodiment of the method for selecting an inspection target for a high-pressure tank, a resin hardening start point is detected in a detection step, and a high-pressure tank is selected as an inspection target for inspecting the presence or absence of delamination in a fiber-reinforced resin layer in a selection step. In the selection step, when a differential pressure obtained by subtracting the resin pressure from the internal pressure within a predetermined time period from the resin hardening start point exceeds a judgment threshold that is predetermined as a lower limit of the differential pressure at which delamination beyond an allowable level occurs based on a correlation between the differential pressure and delamination, the high-pressure tank is selected as the inspection target. Since there is a correlation between the magnitude of the differential pressure and the occurrence of peeling, for example, if the judgment threshold is determined as the lower limit of the differential pressure at which peeling above tolerance occurs, it can be inferred that there is a high possibility that significant peeling will occur in the finished high-pressure tank when the differential pressure exceeds the judgment threshold. This eliminates the need to inspect all manufactured high-pressure tanks, and allows for spot inspection of only those high-pressure tanks suspected of significant peeling, thereby reducing inspection time and costs. The present disclosure may also be realized in the form of a manufacturing method for a high-pressure tank. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a high-pressure tank manufactured by a high-pressure tank manufacturing method according to a first embodiment of the present disclosure. [Diagram 2] 4 is a flowchart showing each step of a manufacturing method for a high-pressure tank according to the first embodiment of the present disclosure. [Diagram 3] FIG. 2 is a front cross-sectional view showing a schematic diagram of a resin impregnation molding die. [Figure 4] FIG. 2 is a front cross-sectional view showing a schematic diagram of a resin impregnation molding die. [Diagram 5] 11A and 11B are diagrams for explaining an internal pressure adjustment mechanism. [Figure 6] 1 is a flowchart showing detailed steps of an RTM molding process. [Figure 7] 13 is a graph showing changes in the internal pressure and resin pressure of the tank after the start of a filling and pressurizing operation of the piston. FIG. [Figure 8] FIG. 13 is a graph showing a change in differential pressure after the start of a filling and pressurizing operation of the piston. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A. First embodiment: A1. High pressure tank 1 consists of: A first embodiment of the present disclosure will be described below with reference to Figs. 1 to 8. Fig. 1 is a cross-sectional view showing a high-pressure tank 1 that is a target of a high-pressure tank inspection target selection method according to the first embodiment of the present disclosure. The high-pressure tank 1 includes a liner 20, a fiber reinforced resin layer 30, a resin layer 40, and two nozzles 91 and 92. In this embodiment, the high-pressure tank 1 stores a high-pressure (e.g., 70 MPa) gas (e.g., hydrogen or natural gas) in an internal space 11.

[0010] In this embodiment, the high-pressure gas stored in the high-pressure tank 1 is hydrogen. The high-pressure tank 1 is loaded onto a mobile object such as a fuel cell vehicle that is powered by a fuel cell that uses hydrogen as a fuel gas. The high-pressure tank 1 is not limited to being installed in a fuel cell vehicle, but may also be installed in a mobile object such as a ship or an airplane, or in a stationary facility such as a house or a building.

[0011] The liner 20 has a cylindrical portion and hemispherical dome portions disposed on both ends of the cylindrical portion. The liner 20 is a hollow container having an internal space 11 that is a space for filling the inside with gas. The liner 20 is used as a tank body of the high-pressure tank 1. The liner 20 is formed of a resin having low gas barrier properties, particularly low hydrogen permeability. For example, polyamide, ethylene vinyl alcohol, or fully saponified polyvinyl alcohol can be used as the resin for forming the liner 20. In this embodiment, polyamide is used.

[0012] The fiber reinforced resin layer 30 is a layer of fiber reinforced resin in which fibers are impregnated with a thermosetting resin, and is formed on the outside of the liner 20. The fiber reinforced resin layer 30 may be formed in contact with the outer surface of the liner 20, or may be formed on the outside of the liner 20 via a release agent. The fiber reinforced resin layer 30 has a carbon fiber reinforced resin layer 31 containing carbon fibers and a thermosetting resin, and a glass fiber reinforced resin layer 35 containing glass fibers and a thermosetting resin. For example, an epoxy resin or an unsaturated polyester resin can be used as the thermosetting resin. In this embodiment, an epoxy resin is used. The curing speed and strength of the epoxy resin are adjusted by a curing accelerator.

[0013] The carbon fiber reinforced resin layer 31 is formed so as to cover the entire outer surface of the liner 20 and parts of the mouthpieces 91, 92. The carbon fiber reinforced resin layer 31 is made of carbon fiber reinforced plastics (CFRP) in which carbon fibers are impregnated with a thermosetting resin, and has pressure resistance. The strength (e.g., fracture toughness) of the carbon fiber reinforced resin layer 31 contributes more to the pressure resistance of the high-pressure tank 1 than the strengths of the glass fiber reinforced resin layer 35 and the resin layer 40.

[0014] The glass fiber reinforced resin layer 35 is formed so as to cover the outer surface of the carbon fiber reinforced resin layer 31. The glass fiber reinforced resin layer 35 is made of glass fiber reinforced plastics (GFRP) in which glass fibers are impregnated with a thermosetting resin, and has higher impact resistance than the carbon fiber reinforced resin layer 31.

[0015] The resin layer 40 is formed on the outer surface of the glass fiber reinforced resin layer 35. The resin layer 40 is made of a thermosetting resin that does not contain fibers. The resin layer 40 is made of the same thermosetting resin as the thermosetting resin used in the glass fiber reinforced resin layer 35.

[0016] The nozzles 91, 92 include a first nozzle 91 and a second nozzle 92. The first nozzle 91 has a substantially cylindrical shape with a through hole communicating with the internal space 11 of the liner 20. The first nozzle 91 functions as an opening of the high-pressure tank 1 and also functions as an attachment portion for attaching piping and valves to the high-pressure tank 1. The second nozzle 92 has a substantially cylindrical shape without a through hole. The nozzles 91, 92 also function as an attachment portion for attaching the liner 20 to a filament winding device when forming the fiber reinforced resin layer 30. The nozzles 91, 92 can be made of a metal such as stainless steel or aluminum.

[0017] A2. Manufacturing method of high pressure tank 1: Next, a method for manufacturing the high-pressure tank 1 will be described. Fig. 2 is a flowchart showing each step of the method for manufacturing the high-pressure tank 1 according to the first embodiment of the present disclosure. As shown in Fig. 2, the method for manufacturing the high-pressure tank 1 includes a tank preparation step (S100), an RTM (Resin Transfer Molding) molding step (S200), and a curing step (S300), and these steps (S100, S200, S300) are performed in order.

[0018] In the tank preparation step (S100), the tank 10 is prepared. Specifically, the tank 10 is prepared by winding a fiber bundle around the outer peripheral surface of the liner 20 with a shaft attached to the nozzles 91, 92, thereby forming the tank 10 with a fiber layer formed on the outer peripheral surface of the liner 20. The "tank" prepared here corresponds to "a tank that is an intermediate product of a high-pressure tank with a fiber bundle wound around the outside of the liner." The fiber bundle constitutes the fiber reinforced resin layer 30 before thermal curing.

[0019] In the RTM molding process (S200), the fiber bundle of the tank 10 is impregnated with a thermosetting resin material (hereinafter, simply referred to as "resin") using the RTM method with a resin impregnation molding die, and the impregnated resin is hardened to a certain extent. Details of this RTM molding process (S200) will be described later, together with the configuration of the resin impregnation molding die and a method for selecting an inspection target for the high-pressure tank 1.

[0020] In the curing step (S300), the tank 10 removed from the resin impregnation molding die is heated in a heat curing oven (not shown) to completely cure the resin impregnated in the RTM molding step (S200), thereby forming the fiber reinforced resin layer 30 and the resin layer 40. The fiber reinforced resin layer 30 and the resin layer 40 are formed on the outer peripheral surface of the liner 20, and the high-pressure tank 1 is completed.

[0021] A3. Configuration of resin impregnation molding die 50: Next, the RTM molding step (S200) will be described in detail. First, the configuration of the resin impregnation molding die 50 will be described with reference to Figs. 3 to 5. Figs. 3 and 4 are front cross-sectional views that typically show the resin impregnation molding die 50. Fig. 3 shows the state before the resin material is pressurized by pistons 56, 57, which will be described later, and Fig. 4 shows the state after the resin material is pressurized by pistons 56, 57.

[0022] As shown in Fig. 3 and Fig. 4, the resin impregnation molding die 50 includes an upper die 51 and a lower die 52. An upper storage section 53 and a material flow path 54 are formed in the upper die 51. The upper storage section 53 is formed on a mating surface with the lower die 52, and is formed in substantially the same shape as the upper half of the tank 10 in the radial direction. The material flow path 54 is formed penetrating the upper die 51 in the vertical direction. One end of the material flow path 54 is connected to a resin material supply source (not shown), and the other end is connected to the upper storage section 53.

[0023] The lower mold 52 is formed with a lower storage section 55 and holding sections 58, 59. The lower storage section 55 is formed on the mating surface with the upper mold 51, and is formed in approximately the same shape as the lower half of the tank 10 in the radial direction. Therefore, when the upper mold 51 and the lower mold 52 are clamped together, the upper storage section 53 and the lower storage section 55 are united and connected to each other, forming a storage section 60 having approximately the same shape as the tank 10. The tank 10 is stored in the storage section 60 with its axial direction aligned horizontally.

[0024] The holding parts 58, 59 are formed penetrating the lower mold 52 in the vertical direction, and hold the pistons 56, 57 therein so that they can move up and down. The holding parts 58, 59 and the pistons 56, 57 are formed in a substantially elliptical shape in a plan view, and are provided substantially symmetrically on both radial sides of the tank 10 in a front view. The upper surfaces of the pistons 56, 57 and the inner peripheral surfaces of the holding parts 58, 59 define a material storage part 61. A sealing member (not shown) is provided around the entire outer peripheral surface of each piston 56, 57 to prevent the resin stored in the material storage part 61 from leaking into the space below.

[0025] The material storage section 61 communicates with the material flow path 54 when the mold is closed, and is capable of storing the resin material supplied from the material flow path 54. The material storage section 61 communicates with the storage section 60, and when the material is stored in the material storage section 61, the storage section 60 is also filled with the resin material.

[0026] Furthermore, the upper storage section 53 is provided with a pressure sensor 63. In this embodiment, four pressure sensors 63 are provided at different positions on the inner wall surface of the upper storage section 53. The pressure sensors 63 function as part of the inner wall of the storage section 60, and can detect the pressure of the resin material filled in the storage section 60 (hereinafter, also simply referred to as "resin pressure"). In this embodiment, the detection result of the pressure sensor 63 is treated as the pressure of the resin material pressure-fed to the storage section 61 by the pistons 56, 57 (i.e., "resin pressure").

[0027] Fig. 5 is a diagram for explaining an internal pressure adjustment mechanism 70 that adjusts the internal pressure of the tank 10 during RTM molding. Note that Fig. 5 illustrates the tank 10 in a similar manner to the high-pressure tank 1 as a finished product shown in Fig. 1, but strictly speaking, at the start of RTM molding, the resin has not yet been impregnated and cured, and the fiber reinforced resin layer 30 and the resin layer 40 are not yet complete.

[0028] 5, the internal pressure adjustment mechanism 70 includes a supply flow path 71 through which nitrogen gas flows to be sealed into the internal space 11 of the tank 10 via the first nozzle 91, and a recovery flow path 77 that recovers gas discharged from the tank 10. The internal pressure adjustment mechanism 70 adjusts the pressure inside the liner 20 by pressurizing the tank 10 by sealing a gas (e.g., nitrogen gas) in the tank 10 and reducing the pressure by recovering the sealed gas.

[0029] A pressure pump 72 that pressure-feeds gas toward the tank 10 is disposed in the supply flow path 71. An on-off valve 75 is disposed in the supply flow path 71 between the pressure pump 72 and the tank 10. The on-off valve 75 switches the pressure pump 72 side and the tank side of the supply flow path 71, across the on-off valve 75, between either a non-communicating state or a communicating state.

[0030] A pressure reducing pump 78 is disposed in the recovery passage 77 to assist in the recovery of the gas sealed in the liner 20. A pressure adjusting valve 79 is disposed in the recovery passage 77 between the pressure reducing pump 78 and the tank 10. The pressure adjusting valve 79 is a valve mechanism that can adjust the flow path width of the recovery passage 77 in stages. A pressure sensor 81 is disposed in the recovery passage 77 to measure the pressure in the space between the tank 10 and the pressure adjusting valve 79.

[0031] The internal pressure adjustment mechanism 70 and the resin impregnation molding die 50 are connected to a control unit 82 that manages a series of controls in the RTM molding process (S200). The control unit 82 is a microcomputer having a central processing unit (CPU) and a storage device (not shown). The storage device is, for example, a RAM, a ROM, or a hard disk drive (HDD). The HDD or ROM stores various programs for implementing the method provided in this embodiment, and the various programs read from the HDD or ROM are expanded on the RAM and executed by the CPU. The detection results of the pressure sensors 63, 81 described above are stored in the storage device. Pressure information measured by the pressure sensors 63, 81 is transmitted to the control unit 82.

[0032] The control unit 82 adjusts the pressure inside the liner 20 by controlling the pressure booster pump 72, the on-off valve 75, the pressure regulator valve 79, and the pressure reducer pump 78 in accordance with the received pressure information. In this manner, the control unit 82 uses the detection results of the sensors 63, 81 to control the internal pressure adjustment mechanism 70 as well as to control the elevation of the pistons 56, 57. Furthermore, the control unit 82 executes an inspection object selection method for the high-pressure tank 1, which will be described later.

[0033] A4.Details of RTM molding process (S200) and inspection object selection method: Next, the details of the RTM molding step (S200) and the method of selecting an inspection target for the high-pressure tank 1 will be described. The "inspection" here refers to inspecting the presence or absence of delamination in the fiber reinforced resin layer 30 of the high-pressure tank 1, and specifically, is a non-destructive inspection using X-ray CT. The presence or absence of delamination is determined by checking a tomographic image of the high-pressure tank 1 taken by a well-known non-destructive inspection device (not shown). The method of selecting an inspection target for the high-pressure tank 1 in the first embodiment selects the high-pressure tank 1 to be subjected to the non-destructive inspection during its manufacturing process, and selects the high-pressure tank 1 that is likely to have delamination due to the differential pressure during the manufacturing process. This will be described in detail below.

[0034] Fig. 6 is a flow chart showing the detailed steps of the RTM molding process (S200). As shown in Fig. 6, the RTM molding process (S200) includes a housing process (S201), a resin injection process (S202), a filling process (S203), a detection process (S204), a selection process (S205), and a mold opening process (S206), and these processes (S201, S202, S203, S204, S205, S206) are performed in order. The method for selecting an inspection target for the high-pressure tank 1 includes a detection process (S204) and a selection process (S205).

[0035] In the accommodation step (S201), the tank 10 is accommodated in the lower accommodation section 55 of the lower mold 52 with the upper mold 51 in an open state, and then the upper mold 51 is clamped. As a result, the tank 10 is accommodated in the accommodation section 60. In the resin injection step (S202), as shown by the arrow A1 in Fig. 3, the resin material is supplied from the material flow path 54 of the resin impregnation molding mold 50 to the material storage section 61.

[0036] In the filling step (S203), as shown in Fig. 4, the resin material is filled into the pressurized fiber bundle by pistons 56, 57. The resin material stored in the material storage section 61 is pressurized and filled into the tank 10 at a set resin pressure by the pressing action of the pistons 56, 57, as shown by arrow A2 in Fig. 4. At this time, the internal pressure of the tank 10 is adjusted by the internal pressure adjustment mechanism 70 so that it is greater than the resin pressure. This is to prevent the tank 10 from collapsing due to the resin pressure.

[0037] FIG. 7 is a graph showing changes in the internal pressure and resin pressure of the tank 10 after the start of the filling and pressurizing operation of the pistons 56 and 57. In FIG. 7, the change in the internal pressure of the tank 10 is shown by a solid line, and the change in the resin pressure is shown by a dashed line. In FIG. 7, the resin pressures detected by the four pressure sensors 63 are shown by four dashed lines. As shown in FIG. 7, pressing by the pistons 56 and 57 is performed from time 0 to T1. At time T1, the pistons 56 and 57 are in the state shown in FIG. 4. During the time from time 0 to T1, the resin pressure is affected by the pressing by the pistons 56 and 57, so it repeatedly rises and falls in a short time. For this reason, the graph of the resin pressure shows a waveform that zigzags finely up and down.

[0038] Thereafter, the positions of pistons 56, 57 are maintained, and the resin pressure gradually increases from time T1 to time T2. Then, from time T2 when the resin impregnated in the fibers begins to harden and restrain the fibers, the resin pressure gradually decreases. The point at time T2 when the resin begins to harden is called the "resin hardening start point P." In the detection step (S204), the resin hardening start point P, at which the resin pressure begins to decrease as the resin material hardens, is detected. The resin hardening start point P is detected by control unit 82 through sensing by pressure sensor 63.

[0039] The period from time 0 to time T1 corresponds to the filling step (S203). In the selection step (S205), after the resin hardening start point P is detected, if the differential pressure D obtained by subtracting the resin pressure from the internal pressure in a judgment region S set from the resin hardening start point P until a predetermined time (in this embodiment, time T2 to time T3) exceeds a judgment threshold, the high-pressure tank 1 is selected as an inspection target. In this embodiment, this selection is performed by the control unit 82. The judgment threshold is determined based on the correlation between the differential pressure D and the state of peeling obtained by a previous test, and is determined to be, for example, the lower limit of the differential pressure D at which peeling occurs that is beyond the allowable limit of the standard. The differential pressure D and the judgment threshold are positive values.

[0040] A large pressure difference D causes a part of the fiber reinforced resin layer 30 of the finished high-pressure tank 1 to peel off after the curing step (S300). This is presumably because, during RTM molding, the pressure difference D between the internal pressure and the resin pressure acts on the fibers as an expansion force, and this expansion force remains as residual stress. In this state, when the tank 10 is heated during the curing step (S300), the shear strength between the resin and the fibers decreases, and the residual stress exceeds the shear strength.

[0041] In the selection process (S205), high-pressure tanks 1 that are likely to experience peeling and require precise inspection by non-destructive testing are selected. In this embodiment, only the high-pressure tanks 1 selected in the selection process (S205) are subjected to non-destructive testing.

[0042] The resin pressure can be an average value of pressure values ​​obtained from the multiple pressure sensors 63. The judgment region S (times T2 to T3) is, for example, 60 seconds, and the differential pressure D may be calculated at multiple points in the judgment region S, and the average value may be compared with the judgment threshold. Alternatively, the differential pressure D at one point in the judgment region S (for example, 60 seconds after the resin hardening start point P) may be compared with the judgment threshold.

[0043] The inventors of the present application conducted a test to see the extent to which peeling occurs in the high-pressure tank 1 as a finished product by adjusting the internal pressure and changing the setting of the differential pressure D in various ways. FIG. 8 is a graph showing the change in the differential pressure D after the start of the filling and pressurizing operation of the pistons 56 and 57 in the test. In FIG. 8, the graphs are labeled W1, W2, W3, W4, W5, W6, and W7 in order of the relative magnitude of the differential pressure D, and are illustrated with different selections. The resin pressure was set to 5 MPa. The set temperature of the tank 10 in the curing process (S300) was 110° C., and the time left after the set temperature was reached was 20 minutes.

[0044] As a result, the effect of suppressing peeling was higher as the differential pressure D was smaller. In other words, the high-pressure tank 1 shown in W1 had the most peeling, occurring over a wide area, and the high-pressure tank 1 shown in W7 had the least peeling. Thus, there is a correlation between the differential pressure D within a specified time (judgment region) from the resin hardening start point P and the occurrence of peeling. In this test example, generally, when the differential pressure D was 1.0 MPa or less, the occurrence of peeling was low and the product standard was met. From this result, under the above test conditions, for example, the judgment threshold can be set to 1.0 MPa.

[0045] As described above, it can be assumed that the greater the differential pressure D, the higher the possibility of peeling occurring. The occurrence of peeling varies depending on various set conditions such as the set temperature and heating time of the work (tank 10) in the curing process (S300) and the type of resin to be impregnated, so it is preferable to set the judgment threshold of the differential pressure D at which peeling is predicted to occur by conducting a test at a stage when various processing conditions have been decided and checking against the specifications of the finished product. Also, the appropriate setting range for the judgment region S differs depending on the resin used, and it is preferable to set it short for resins that harden faster. It is preferable to set the judgment region S until the resin has hardened to a certain extent and the expansion force acting on the fibers is determined as described above.

[0046] When a predetermined time has elapsed since the start of the supply of the material, it is determined that the resin has hardened to a certain extent, and the process proceeds to the mold opening process (S206). In the mold opening process (S206), the upper mold 51 is removed, and the tank 10 is taken out of the storage section 60. Thereafter, the above-mentioned curing process (S300) is performed.

[0047] According to the inspection object selection method for the high-pressure tank 1 of the first embodiment, when the differential pressure D obtained by subtracting the resin pressure from the internal pressure in the judgment area S after the resin hardening start point P is detected exceeds a judgment threshold determined based on a correlation between the differential pressure D and the state of peeling obtained in advance by a test, the high-pressure tank 1 is selected as an inspection object. That is, in the selection step (S205), the high-pressure tank 1 that is likely to have large peeling or a large number of peelings over a wide area in the finished high-pressure tank 1 and that is considered to require precise inspection by non-destructive inspection is selected. Therefore, it is not necessary to inspect all the manufactured high-pressure tanks 1, and only the high-pressure tanks 1 suspected of having large peeling can be randomly inspected, thereby reducing the inspection time and inspection costs.

[0048] Furthermore, since the inspection target can be selected simply by monitoring the pressure difference D for a predetermined time after the resin hardening start point P is detected, there is no need for complicated control.

[0049] B. Other embodiments: (B1) In the method for selecting an inspection target for a high-pressure tank 1 according to the first embodiment, the resin impregnation molding die 50 for manufacturing the high-pressure tank 1 to be selected has pistons 56, 57, and the resin is filled and pressurized by the pistons 56, 57, but this does not have to be the case. The shape of each piston 56, 57 is not limited to a circular shape in a plan view. The shape of each piston 56, 57 may be, for example, a substantially rectangular shape with arc-shaped corners in a plan view.

[0050] (B2) In the inspection object selection method for the high-pressure tank 1 of the first embodiment, the resin pressure is detected from a plurality of (four) pressure sensors 63, but the number of pressure sensors 63 is not limited to four and may be one, or may be any number other than four. The pressure sensor 63 may be provided on the inner wall surface of the lower storage section 55 instead of the inner wall surface of the upper storage section 53. The pressure sensor 63 is not limited to the storage section 60, and may be disposed at any position in the internal space of the mold 50, such as the material flow path 54 or the material storage section 61. The pressure sensor 63 may be omitted, for example, in a case where the pressurizing mechanism includes a sensor for detecting the pressure of the resin material pumped by the pistons 56 and 57 constituting the pressurizing mechanism.

[0051] (B3) In the method for selecting an inspection target for the high-pressure tank 1 of the first embodiment, up to the selection step (S205) is performed in the manufacturing process of the high-pressure tank 1, but the selection step (S205) may be performed after the completion of manufacturing of the high-pressure tank 1. In this case, for example, in the manufacturing process, the resin hardening start point P is detected by the detection step (S204), and data on the resin pressure and internal pressure for calculating the differential pressure D in the judgment region S is acquired, and the calculation of the differential pressure D based on the acquired data, the comparison with the judgment threshold, and the selection of the inspection target may be performed in a step separate from the manufacturing process.

[0052] The present disclosure is not limited to the above-mentioned embodiments, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in each embodiment corresponding to the technical features in each form described in the Summary of the Invention column can be appropriately replaced or combined in order to solve some or all of the above-mentioned problems or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0053] 1...High pressure tank, 10...Tank, 11...Internal space, 20...Liner, 30...Fiber reinforced resin layer, 31...Carbon fiber reinforced resin layer, 35...Glass fiber reinforced resin layer, 40...Resin layer, 50...Resin impregnation molding die, 51...Upper die, 52...Lower die, 53...Upper storage section, 54...Material flow path, 55...Lower storage section, 56, 57...Piston, 58, 59...Holding section, 60...Storage section, 61...Material storage section, 63...Pressure sensor, 70...Internal pressure adjustment mechanism, 71...Supply flow path, 72...Pressure pump, 75...Opening and closing valve, 77...Recovery flow path, 78...Decompression pump, 79...Pressure adjustment valve, 81...Pressure sensor, 82...Control section, 91...First nozzle, 92...Second nozzle

Claims

[Claim 1] 1. A method for selecting a high-pressure tank as an inspection target for inspecting for the presence or absence of delamination in a fiber-reinforced resin layer of the high-pressure tank, comprising: a detection process for detecting a resin hardening start point at which the resin pressure starts to decrease as the resin material hardens, in a state in which the internal pressure of the tank, which is an intermediate product of the high-pressure tank in which the fiber bundle constituting the fiber reinforced resin layer before thermal hardening is contained in a resin impregnation molding die and wound around the outside of a liner, is adjusted by an internal pressure adjustment mechanism so that the internal pressure of the tank is greater than the resin pressure, which is the pressure of the resin material pressurized and filled into the resin impregnation molding die, and the resin material is pressurized and filled into the fiber bundle in the resin impregnation molding die; a selection process for selecting the high-pressure tank as the inspection target when a pressure difference, obtained by subtracting the resin pressure from the internal pressure, within a predetermined time period from the resin hardening start point detected in the detection process exceeds a judgment threshold that is predetermined based on a correlation between the pressure difference and peeling obtained in advance; A method for selecting an inspection target for a high-pressure tank, comprising:

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