Fuel cell stack inspection method

Abstract

To provide an inspection method of a fuel cell stack that can detect leakage even when a defective part of a separator through which fluid passes is minute, and can improve the detection accuracy as compared to a conventional method.SOLUTION: An inspection method of inspecting a fuel cell stack for fluid leaks includes: an encapsulating step P1 of encapsulating gas channels 50, 54 formed between a membrane electrode structure 30 and each separator 28 with a hydrogen-containing inert gas having a predetermined hydrogen concentration or less; an air filling step P2 of filling air into a cooling medium flow path 56 formed between power generation cells; and a detection step P3 of detecting fluid leakage from the separator 28 on the basis of a cell voltage.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for inspecting a fuel cell stack. [Background technology]

[0002] In recent years, research and development into fuel cell stacks has been conducted to contribute to energy efficiency, ensuring that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] A fuel cell stack contains a stack of multiple power-generating cells. Each power-generating cell has a membrane electrode assembly (MEA) and a pair of separators that sandwich the membrane electrode assembly. The membrane electrode assembly has an electrolyte membrane and a pair of electrodes (anode and cathode) arranged on either side of the electrolyte membrane.

[0004] A fuel cell stack is formed with a fuel gas flow path, an oxidant gas flow path, and a coolant flow path. The fuel gas flow path is a flow path through which fuel gas supplied to an anode electrode flows, and is formed between the anode electrode and a separator. The oxidant gas flow path is a flow path through which oxidant gas supplied to a cathode electrode flows, and is formed between the cathode electrode and a separator. The coolant flow path is a flow path through which a cooling medium for cooling the power generation cells flows, and is formed between the power generation cells.

[0005] As an inspection method for detecting fluid leaks in a fuel cell stack, the following Patent Document 1 discloses a detection method for detecting cross leaks, in which a test fluid leaks from one of a gas flow path and a cooling medium through a separator to the other of the gas flow path and the cooling medium. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-042413 Summary of the Invention [Problem to be solved by the invention]

[0007] However, if the defect in the separator through which the test fluid passes is minute, it is difficult to detect the leak of the test fluid with a detector. Therefore, a test method that can improve detection accuracy is required.

[0008] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0009] One aspect of the present invention is an inspection method for inspecting a fuel cell stack having a flow path formed therein through which the fluid flows, for leakage of the fluid, the fuel cell stack comprising a power generation cell having a membrane electrode assembly including an electrolyte membrane, an anode electrode and a cathode electrode arranged on either side of the electrolyte membrane, and a pair of separators sandwiching the membrane electrode assembly, and a cell voltage detection device for detecting the cell voltage of the power generation cell, the method including a sealing step of sealing a hydrogen-containing inert gas having a predetermined hydrogen concentration or less into a gas flow path formed between the membrane electrode assembly and each of the separators, an air filling step of filling a coolant flow path formed between the power generation cells with air, and a detection step of detecting leakage of the fluid from the separators based on the cell voltage. [Effects of the Invention]

[0010] According to the aspects of the present invention, even if the defect portion of the separator through which the fluid passes is minute, it is possible to detect the fluid leakage, and as a result, it is possible to improve the detection accuracy compared to when the fluid leakage is detected by a detector. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of a fuel cell stack. [Figure 2] FIG. 2 is an exploded perspective view of the power generating cell. [Figure 3]FIG. 3 is a flowchart showing the steps of the fuel cell stack inspection method. [Figure 4] Figure 4A is a diagram showing the power-generating cell and cell voltage when there is no defect in the separator, Figure 4B is a diagram showing the power-generating cell and cell voltage when there is a defect in the separator facing the cathode electrode, and Figure 4C is a diagram showing the power-generating cell and cell voltage when there is a defect in the separator facing the anode electrode. [Figure 5] FIG. 5A is a diagram showing a power-generating cell and cell voltage when there are defects in both the separator facing the cathode electrode and the separator facing the anode electrode in a first pressure state, and FIG. 5B is a diagram showing a power-generating cell and cell voltage when there are defects in both the separator facing the cathode electrode and the separator facing the anode electrode in a second pressure state. DETAILED DESCRIPTION OF THE INVENTION

[0012] FIG. 1 is a perspective view of a fuel cell stack 10. The fuel cell stack 10 includes a power generating cell stack 12. The power generating cell stack 12 is configured by stacking a plurality of power generating cells 14 in a stacking direction (the direction of arrow A). At one end side (the side of arrow A1) of the power generating cell stack 12 in the stacking direction, a terminal plate 18a, an insulator 20a, and an end plate 22a are arranged outward in this order. At the other end side (the side of arrow A2) of the power generating cell stack 12 in the stacking direction, a terminal plate 18b, an insulator 20b, and an end plate 22b are arranged outward in this order.

[0013] The insulators 20a and 20b are made of an insulating material such as polycarbonate (PC), phenolic resin, etc. Each of the insulators 20a and 20b may be made of a plurality of sheets (for example, two sheets) stacked in the stacking direction.

[0014] Connecting bars 24 are arranged between each side of the end plates 22a, 22b. Both ends of each connecting bar 24 are fixed to the inner surfaces of the end plates 22a, 22b via bolts or the like, and apply a compressive load (clamping load) in the stacking direction to the power generation cell stack 12. The fuel cell stack 10 may also be configured to include a housing with the end plates 22a, 22b as end plates, and to house the power generation cell stack 12 and the like inside the housing.

[0015] 2, the power generating cell 14 has a resin-framed MEA 26 and a separator 28. The resin-framed MEA 26 is composed of a membrane electrode assembly 30 and a resin frame member 32 that surrounds the outer periphery of the membrane electrode assembly 30.

[0016] The membrane electrode assembly 30 has an electrolyte membrane 34, an anode electrode 36 provided on one surface (the side of arrow A2) of the electrolyte membrane 34, and a cathode electrode 38 provided on the other surface (the side of arrow A1) of the electrolyte membrane 34.

[0017] The electrolyte membrane 34 is, for example, a solid polymer electrolyte membrane (cation exchange membrane) such as a thin film of perfluorosulfonic acid containing water, and is sandwiched between the anode electrode 36 and the cathode electrode 38. Note that the electrolyte membrane 34 may be made of an HC (hydrocarbon)-based electrolyte in addition to a fluorine-based electrolyte.

[0018] The anode electrode 36 has an anode electrode catalyst layer and an anode gas diffusion layer, neither of which are shown. The anode electrode catalyst layer is bonded to one surface (the side of arrow A2) of the electrolyte membrane 34. The anode gas diffusion layer is laminated on the anode electrode catalyst layer. The cathode electrode 38 has a cathode electrode catalyst layer and a cathode gas diffusion layer, neither of which are shown. The cathode electrode catalyst layer is bonded to the other surface (the side of arrow A1) of the electrolyte membrane 34. The cathode gas diffusion layer is laminated on the cathode electrode catalyst layer.

[0019] The anode electrode catalyst layer is formed, for example, by uniformly applying porous carbon particles having a platinum alloy supported on their surfaces together with an ion-conductive polymer binder onto the surface of the anode gas diffusion layer, while the cathode electrode catalyst layer is formed, for example, by uniformly applying porous carbon particles having a platinum alloy supported on their surfaces together with an ion-conductive polymer binder onto the surface of the cathode gas diffusion layer.

[0020] The cathode gas diffusion layer and the anode gas diffusion layer are formed from a conductive porous sheet such as carbon paper or carbon cloth. A porous layer (not shown) may be provided between the cathode electrode catalyst layer and the cathode gas diffusion layer or between the anode electrode catalyst layer and the anode gas diffusion layer.

[0021] A cell voltage detection device 39 is connected to the anode electrode 36 and the cathode electrode 38. The cell voltage detection device 39 detects the cell voltage of the power generation cell 14. The cell voltage is the voltage between the anode electrode 36 and the cathode electrode 38. The cell voltage detection device 39 may be a voltmeter. The cell voltage detection device 39 is attached to the separator 28, for example.

[0022] The resin frame member 32 has a frame shape, and, for example, its inner peripheral edge is joined to the outer peripheral edge of the membrane electrode assembly 30. By providing the resin frame member 32 on the outer periphery of the membrane electrode assembly 30 in this way, it becomes possible to reduce the area of ​​the relatively expensive electrolyte membrane 34 required to constitute one power generation cell 14, for example.

[0023] The joining structure between the resin frame member 32 and the membrane electrode assembly 30 is not particularly limited, but may be, for example, such that the inner peripheral edge of the resin frame member 32 is sandwiched between the outer peripheral edge of the cathode gas diffusion layer and the outer peripheral edge of the anode gas diffusion layer. In this case, the inner peripheral edge face of the resin frame member 32 may be close to, abut against, or overlap the outer peripheral edge face of the electrolyte membrane 34.

[0024] Instead of the above-described joining structure, the resin frame member 32 may be configured by causing the outer peripheral edge of the electrolyte membrane 34 to protrude outward beyond the cathode gas diffusion layer and the anode gas diffusion layer, and providing frame-shaped films on both sides of the outer peripheral edge of the electrolyte membrane 34. In other words, the resin frame member 32 may be configured by joining multiple stacked frame-shaped films with an adhesive or the like.

[0025] 1 and 2, at one end (arrow B1 side) of the long sides of the power generation cell 14, the end plates 22a, 22b, and the insulators 20a, 20b, an oxidant gas inlet manifold 40a, a coolant inlet manifold 42a, and a fuel gas outlet manifold 44b are arranged in the direction of arrow C. At the other end (arrow B2 side) of the long sides of the power generation cell 14, the end plates 22a, 22b, and the insulators 20a, 20b, an oxidant gas inlet manifold 44a, a coolant outlet manifold 42b, and an oxidant gas outlet manifold 40b are arranged in the direction of arrow C.

[0026] An oxidant gas, such as an oxygen-containing gas, is supplied to the oxidant gas inlet manifold 40a. A coolant, such as at least one of pure water, ethylene glycol, and oil, is supplied to the coolant inlet manifold 42a. A fuel gas, such as a hydrogen-containing inert gas, is discharged from the fuel gas outlet manifold 44b. A fuel gas is supplied to the fuel gas inlet manifold 44a. A coolant is discharged from the coolant outlet manifold 42b. An oxidant gas is discharged from the oxidant gas outlet manifold 40b.

[0027] The oxidant gas inlet manifolds 40a provided in each of the power-generating cells 14, the end plates 22a, 22b, and the insulators 20a, 20b in the power-generating cell stack 12 are interconnected in the stacking direction. That is, the oxidant gas inlet manifold 40a penetrates the end plates 22a, 22b, the insulators 20a, 20b, and the power-generating cell stack 12 in the stacking direction. Similarly, the coolant inlet manifold 42a, the fuel gas outlet manifold 44b, the fuel gas inlet manifold 44a, the coolant outlet manifold 42b, and the oxidant gas outlet manifold 40b also penetrate the end plates 22a, 22b, the insulators 20a, 20b, and the power-generating cell stack 12 in the stacking direction.

[0028] In this embodiment, an example is shown in which each power-generating cell 14 is provided with one each of the oxidant gas inlet manifold 40a, coolant inlet manifold 42a, fuel gas outlet manifold 44b, fuel gas inlet manifold 44a, coolant outlet manifold 42b, and oxidant gas outlet manifold 40b (hereinafter, these are also collectively referred to as "manifolds"). However, the number of manifolds provided in each power-generating cell 14 is not particularly limited and may be one or more. Furthermore, the shape and arrangement of the manifolds are not limited to those of this embodiment shown in FIGS. 1 and 2 and can be set appropriately depending on the required specifications.

[0029] As shown in FIG. 2 , separator 28 is rectangular, with a pair of long sides facing each other in the direction of arrow C and a pair of short sides facing each other in the direction of arrow B. Separator 28 is formed by joining separator plates 46, 48 together at their outer peripheries. This joining is achieved by welding, brazing, crimping, or the like. Hereinafter, separator plate 46 will be referred to as the first separator plate 46, and separator plate 48 will be referred to as the second separator plate 48.

[0030] Each of the first separator plate 46 and the second separator plate 48 is formed by pressing a thin metal plate, such as a steel plate, a stainless steel plate, an aluminum plate, a plated steel plate, a titanium plate, or a metal plate whose metal surface has been treated for corrosion prevention, into a corrugated cross section. Note that an insulating resin material may be provided on the outer edge of the separator 28.

[0031] The first separator plate 46 and the second separator plate 48 incorporated into the power generation cell stack 12 as the separator 28 each have an MEA side surface 46a, 48a facing the resin-framed MEA 26, and a refrigerant side surface 46b, 48b on the reverse side.

[0032] The MEA-side surface 46a of the first separator plate 46 is provided with a plurality of ridges extending linearly in the direction of arrow B. Linear oxidant gas flow fields 50 are provided in the grooves between these ridges. The ridges and the oxidant gas flow fields 50 may also be wavy. The oxidant gas flow fields 50 face the cathode 38 of the membrane electrode assembly 30 and are fluidly connected to the oxidant gas supply passage 40a and the oxidant gas discharge passage 40b. The oxidant gas flow fields 50 allow a fluid (oxidant gas) to flow in the plane of the separator 28 (in the directions of arrows B and C).

[0033] Additionally, a bead portion 52a is integrally formed by press molding or the like on the MEA side surface 46a of the first separator plate 46. The bead portion 52a protrudes in the thickness direction of the first separator plate 46 toward the resin-framed MEA 26. Instead of the bead portion 52a, a convex elastic seal made of an elastic material such as rubber may be provided on the MEA side surface 46a.

[0034] The bead portions 52a are positioned outside the membrane electrode assembly 30. The bead portions 52a surround the oxidant gas flow field 50, the oxidant gas inlet manifold 40a, and the oxidant gas outlet manifold 40b. As a result, the bead portions 52a interconnect the oxidant gas flow field 50, the oxidant gas inlet manifold 40a, and the oxidant gas outlet manifold 40b. The bead portions 52a also surround the fuel gas inlet manifold 44a, the fuel gas outlet manifold 44b, the coolant inlet manifold 42a, and the coolant outlet manifold 42b, respectively. As a result, the bead portions 52a prevent the fuel gas and the coolant from flowing into the oxidant gas flow field 50.

[0035] The MEA-side surface 48a of the second separator plate 48 is provided with a plurality of ridges extending linearly in the direction of arrow B. Linear fuel gas channels 54 are provided in the grooves between these ridges. The ridges and fuel gas channels 54 may also be wavy. The fuel gas channels 54 face the anode 36 of the membrane electrode assembly 30 and are fluidly connected to the fuel gas inlet manifold 44a and the fuel gas outlet manifold 44b. The fuel gas channels 54 allow a fluid (fuel gas) to flow in the plane of the separator 28 (in the directions of arrows B and C).

[0036] Additionally, a bead portion 52b is integrally formed by press molding or the like on the MEA side surface 48a of the second separator plate 48. The bead portion 52b protrudes in the thickness direction of the second separator plate 48 toward the resin-framed MEA 26. Instead of the bead portion 52b, a convex elastic seal made of an elastic material such as rubber may be provided on the MEA side surface 48a.

[0037] The bead portions 52b are positioned outside the membrane electrode assembly 30. The bead portions 52b integrally surround the outer peripheries of the fuel gas flow field 54, the fuel gas inlet manifold 44a, and the fuel gas outlet manifold 44b. As a result, the bead portions 52b interconnect the fuel gas flow field 54, the fuel gas inlet manifold 44a, and the fuel gas outlet manifold 44b. The bead portions 52b also individually surround the oxidant gas inlet manifold 40a, the oxidant gas outlet manifold 40b, the coolant inlet manifold 42a, and the coolant outlet manifold 42b. As a result, the bead portions 52b prevent the oxidant gas and the coolant from flowing into the fuel gas flow field 54.

[0038] A coolant flow field 56 is provided between the opposing coolant side 46b of the first separator plate 46 and the coolant side 48b of the second separator plate 48. The coolant flow field 56 is fluidly connected to the coolant inlet manifold 42a and the coolant outlet manifold 42b, and allows the fluid (coolant) to flow in the plane of the separator 28 (in the directions of arrows B and C).

[0039] The coolant flow field 56 is formed by overlapping the back surface shape of the MEA side surface 46a of the first separator plate 46, in which the oxidant gas flow field 50 is formed, with the back surface shape of the MEA side surface 48a of the second separator plate 48, in which the fuel gas flow field 54 is formed. The refrigerant side surfaces 46b, 48b of the opposing first and second separator plates 46, 48 are joined together at the peripheries of the communication holes by welding, brazing, or the like.

[0040] The following describes an example of a method for inspecting the fuel cell stack 10. As shown in Fig. 3, the method for inspecting the fuel cell stack 10 includes a sealing step P1, an air filling step P2, and a detection step P3.

[0041] The filling step P1 is a step of filling the gas flow paths (the oxidant gas flow path 50 and the fuel gas flow path 54) with a hydrogen-containing inert gas having a predetermined hydrogen concentration or less. In this embodiment, the filling step P1 includes a hydrogen gas supply step P11, a waiting step P12, an inert gas supply step P13, and an inert gas filling step P14.

[0042] The hydrogen gas supply step P11 is a step of supplying hydrogen gas to the oxidant gas flow path 50 and the fuel gas flow path 54. The hydrogen gas may be supplied to the oxidant gas flow path 50 and the fuel gas flow path 54 simultaneously. Alternatively, the hydrogen gas may be first supplied to the oxidant gas flow path 50 (or the fuel gas flow path 54), and then supplied to the fuel gas flow path 54 (or the oxidant gas flow path 50). Note that in this step, hydrogen gas is not sealed in.

[0043] In this embodiment, the hydrogen gas is supplied from the oxidant gas inlet manifold 40a (or the oxidant gas outlet manifold 40b) to the oxidant gas flow field 50 by a hydrogen gas supply device. The hydrogen gas supplied to the oxidant gas flow field 50 is discharged from the oxidant gas outlet manifold 40b (or the oxidant gas inlet manifold 40a). The hydrogen gas is also supplied from the fuel gas inlet manifold 44a (or the fuel gas outlet manifold 44b) to the fuel gas flow field 54 by the hydrogen gas supply device. The hydrogen gas supplied to the fuel gas flow field 54 is discharged from the fuel gas outlet manifold 44b (or the fuel gas inlet manifold 44a).

[0044] The timing for stopping the supply of hydrogen gas is not particularly limited. For example, when the amount of hydrogen gas supplied to the oxidant gas flow path 50 and the fuel gas flow path 54 exceeds a predetermined amount, the supply of hydrogen gas by the hydrogen gas supply device is stopped.

[0045] The standby step P12 is a step of suspending the supply of inert gas until a predetermined time has elapsed since the supply of hydrogen gas to the oxidant gas flow path 50 and the fuel gas flow path 54 was stopped. This increases the permeability of hydrogen gas into the electrolyte membrane 34 in the power generation cell 14. As a result, it is possible to suppress the occurrence of differences in hydrogen concentration in the electrolyte membrane 34 among the multiple power generation cells 14.

[0046] The inert gas supply process P13 is a process of supplying an inert gas to the oxidant gas flow path 50 and the fuel gas flow path 54 to dilute the hydrogen concentration in the gas flow paths. Examples of the inert gas include nitrogen gas, helium gas, argon gas, and carbon dioxide gas. In this embodiment, the inert gas is nitrogen gas.

[0047] The inert gas may be simultaneously supplied to the oxidant gas flow path 50 and the fuel gas flow path 54. Alternatively, the inert gas may first be supplied to the oxidant gas flow path 50 (or the fuel gas flow path 54), and then supplied to the fuel gas flow path 54 (or the oxidant gas flow path 50). Note that in this step, the inert gas is not sealed in.

[0048] In this embodiment, the inert gas is supplied from the oxidant gas inlet manifold 40a (or the oxidant gas outlet manifold 40b) to the oxidant gas flow field 50 by an inert gas supply device. The inert gas supplied to the oxidant gas flow field 50 is discharged from the oxidant gas outlet manifold 40b (or the oxidant gas inlet manifold 40a). The inert gas is supplied from the fuel gas inlet manifold 44a (or the fuel gas outlet manifold 44b) to the fuel gas flow field 54 by an inert gas supply device. The inert gas supplied to the fuel gas flow field 54 is discharged from the fuel gas outlet manifold 44b (or the fuel gas inlet manifold 44a).

[0049] In this step, an inert gas may be supplied to the coolant flow field 56. In this case, the inert gas is preferably supplied to the coolant flow field 56 after the supply of the inert gas to the gas flow field has started. Note that the inert gas may be supplied to the coolant flow field 56 simultaneously with the supply of the inert gas to the gas flow field.

[0050] In this embodiment, the inert gas is supplied from the inert gas supply device through the coolant inlet manifold 42a (or the coolant outlet manifold 42b) into the coolant flow field 56. The inert gas supplied to the coolant flow field 56 is discharged through the coolant outlet manifold 42b (or the coolant inlet manifold 42a).

[0051] By supplying an inert gas to the coolant flow field 56, hydrogen gas that leaks from the oxidant gas flow field 50 or the fuel gas flow field 54 into the coolant flow field 56 when there is a defect in the separator 28 can be discharged to the outside.

[0052] The inert gas injection step P14 is a step of injecting the inert gas into the gas flow paths after the hydrogen concentration in the inert gas discharged from the oxidant gas flow path 50 and the fuel gas flow path 54 has fallen below a predetermined concentration.

[0053] In this embodiment, a hydrogen concentration meter measures the hydrogen concentration in the inert gas discharged from at least one of the oxidant gas flow field 50 and the fuel gas flow field 54. When the hydrogen concentration measured by the hydrogen concentration meter falls below a predetermined concentration, sealing members are attached to the oxidant gas outlet manifold 40b (or the oxidant gas inlet manifold 40a) and the fuel gas outlet manifold 44b (or the fuel gas inlet manifold 44a).

[0054] The sealing members are members that seal the holes and are configured to be detachable from any of the oxygen-containing gas inlet manifold 40a, the oxygen-containing gas outlet manifold 40b, the coolant inlet manifold 42a, the coolant outlet manifold 42b, the fuel gas inlet manifold 44a, and the fuel gas outlet manifold 44b.

[0055] Thereafter, the pressure gauges measure the internal flow channel pressure, which is the pressure of the inert gas in the oxidant gas flow channel 50 and the fuel gas flow channel 54. When the internal flow channel pressure measured by the pressure gauges reaches a predetermined pressure, the inert gas supply device stops supplying the inert gas, and sealing members are attached to the oxidant gas inlet manifold 40a (or the oxidant gas outlet manifold 40b) and the fuel gas inlet manifold 44a (or the fuel gas outlet manifold 44b). As a result, the oxidant gas flow channel 50 and the fuel gas flow channel 54 are filled with a hydrogen-containing inert gas having a predetermined hydrogen concentration or less.

[0056] The air filling step P2 is a step of filling air into the coolant flow field 56. In this step, the pressure of the air filled into the coolant flow field 56 is set higher than the pressure of the hydrogen-containing inert gas sealed in the oxidant gas flow field 50 and the fuel gas flow field 54.

[0057] In this embodiment, first, an orifice member is attached to the coolant outlet manifold 42b (or the coolant inlet manifold 42a). The orifice member narrows the flow path and is configured to be detachable from the coolant outlet manifold 42b (or the coolant inlet manifold 42a). The orifice member includes an orifice plate having holes with diameters smaller than those of the coolant inlet manifold 42a and the coolant outlet manifold 42b.

[0058] Once the orifice member is attached, the air supply device supplies air from the coolant inlet manifold 42a (or the coolant outlet manifold 42b) into the coolant flow field 56. The air supply device continues to supply air to the coolant flow field 56. When the coolant flow field 56 is filled with air, the pressure of the air becomes higher than the pressure of the hydrogen-containing inert gas sealed in the oxidant gas flow field 50 and the fuel gas flow field 54.

[0059] Instead of the orifice member, a sealing member may be attached to the coolant outlet manifold 42b (or the coolant inlet manifold 42a). In this case, after the air supply device starts supplying air to the coolant flow field 56, the filling pressure of the air in the coolant flow field 56 is measured with a pressure gauge. When the filling pressure measured with the pressure gauge reaches a predetermined filling pressure, the air supply device stops supplying air to the coolant flow field 56, and a sealing member is attached to the coolant inlet manifold 42a (or the coolant outlet manifold 42b). The predetermined filling pressure is set higher than the pressure of the hydrogen-containing inert gas sealed in the oxidant gas flow field 50 and the fuel gas flow field 54.

[0060] The detection step P3 is a step of detecting fluid leakage from the separator 28 based on the cell voltage of the power generating cell 14. There is a correlation between the presence or absence of defects in the separator 28 and the cell voltage (FIGS. 4A to 4C).

[0061] If the separator 28 is not defective (FIG. 4A), the hydrogen-containing inert gas sealed in the oxidant gas flow path 50 and the fuel gas flow path 54 is separated from the air filled in the coolant flow path 56 by the separator 28. Therefore, a combustion reaction between the hydrogen in the hydrogen-containing inert gas and the oxygen in the air does not occur in the membrane electrode assembly 30. In this case, the cell voltage detected by the cell voltage detection device 39 is substantially 0 V. In other words, no fluid leakage from the separator 28 is detected.

[0062] On the other hand, if the separator 28 facing the cathode electrode 38 has a defect ( FIG. 4B ), the air filling the coolant flow field 56 will flow into the oxidant gas flow field 50 through the defect. This is because the pressure of the air filling the coolant flow field 56 is higher than the pressure of the hydrogen-containing inert gas sealed in the oxidant gas flow field 50. When the air filling the coolant flow field 56 flows into the oxidant gas flow field 50, a combustion reaction occurs at the cathode electrode 38 between the hydrogen in the hydrogen-containing inert gas and the oxygen in the air. In this case, the cell voltage detected by the cell voltage detector 39 changes to a positive sign (+ side). In other words, a fluid leak from the separator 28 facing the cathode electrode 38 is detected.

[0063] On the other hand, if the separator 28 facing the anode 36 has a defect (FIG. 4C), the air filling the coolant flow field 56 will flow into the fuel gas flow field 54 through the defect. This is because the pressure of the air filling the coolant flow field 56 is higher than the pressure of the hydrogen-containing inert gas sealed in the fuel gas flow field 54. When the air filling the coolant flow field 56 flows into the fuel gas flow field 54, a combustion reaction occurs at the anode 36 between the hydrogen in the hydrogen-containing inert gas and the oxygen in the air. In this case, the cell voltage detected by the cell voltage detector 39 becomes negative (- side). In other words, a fluid leak from the separator 28 facing the anode 36 is detected.

[0064] In this way, by detecting fluid leakage from separator 28 based on the cell voltage, fluid leakage can be detected even if there is a minute defect in separator 28 through which the fluid passes. As a result, detection accuracy can be improved compared to when fluid leakage is detected by a detector.

[0065] The pressure of the air filling the coolant flow field 56 is higher than the pressure of the hydrogen-containing inert gas filled in the oxidant gas flow field 50 and the fuel gas flow field 54. As a result, if the separator 28 facing the anode 36 or the cathode 38 is defective, the air filling the coolant flow field 56 can be guided to the fuel gas flow field 54 or the oxidant gas flow field 50. This allows a combustion reaction between hydrogen in the hydrogen-containing inert gas and oxygen in the air to be induced at the anode 36 or the cathode 38. As a result, it is possible to determine from a change in cell voltage whether the separator 28 facing the anode 36 or the separator 28 facing the cathode 38 is defective.

[0066] Furthermore, the hydrogen concentration of the hydrogen-containing inert gas in the oxidant gas flow field 50 and the fuel gas flow field 54 is diluted to a predetermined concentration or less. This reduces the amount of heat generated by a combustion reaction between hydrogen in the hydrogen-containing inert gas and oxygen in the air, even if the combustion reaction is induced at the anode electrode 36 or the cathode electrode 38. As a result, deterioration of the electrolyte membrane 34 due to heat generation can be suppressed.

[0067] The above embodiment may be modified as follows.

[0068] (Variation 1) In the detection step P3, leakage of fluid from the separator 28 may be detected based on the cell voltage in the first pressure state and the cell voltage in the second pressure state.

[0069] The first pressure state is a state in which the first pressure is higher than the second pressure, and the second pressure is higher than the third pressure. The first pressure is the pressure of the hydrogen-containing inert gas sealed in the gas flow passage (fuel gas flow passage 54) facing the anode electrode 36. The second pressure is the pressure of the air filled in the coolant flow passage 56. The third pressure is the pressure of the hydrogen-containing inert gas sealed in the gas flow passage (oxidant gas flow passage 50) facing the cathode electrode 38.

[0070] In the first pressure state, if both the separator 28 facing the cathode 38 and the separator 28 facing the anode 36 are defective (FIG. 5A), the hydrogen-containing inert gas sealed in the fuel gas flow field 54 flows into the coolant flow field 56 facing the anode 36. This is because the first pressure is higher than the second pressure. In this case, no combustion reaction occurs at the anode 36.

[0071] On the other hand, the air filling the coolant flow field 56 facing the cathode electrode 38 flows into the oxidant gas flow field 50. This is because the second pressure is higher than the third pressure. In this case, a combustion reaction occurs at the cathode electrode 38 between the hydrogen in the hydrogen-containing inert gas and the oxygen in the air. Therefore, the cell voltage detected by the cell voltage detection device 39 changes to a positive sign (+ side). In other words, it is detected that a fluid is leaking from the separator 28 facing the cathode electrode 38.

[0072] To obtain the cell voltage in the first pressure state, the hydrogen gas supply step P11, the waiting step P12, the inert gas supply step P13, the inert gas charging step P14, and the air charging step P2 are performed in this order.

[0073] In this case, in the inert gas supply step P13, the pressure (first pressure) of the hydrogen-containing inert gas sealed in the fuel gas flow field 54 is set higher than the pressure (third pressure) of the hydrogen-containing inert gas sealed in the oxidant gas flow field 50. In addition, in the inert gas sealing step P14, the pressure (second pressure) of the air filled in the coolant flow field 56 is set lower than the first pressure and higher than the third pressure.

[0074] The second pressure state is a state in which the third pressure is higher than the second pressure and the second pressure is higher than the first pressure. In the second pressure state, if both the separator 28 facing the cathode 38 and the separator 28 facing the anode 36 are defective (FIG. 5B), the hydrogen-containing inert gas sealed in the oxidant gas flow field 50 flows into the coolant flow field 56 facing the cathode 38. This is because the third pressure is higher than the second pressure. In this case, no combustion reaction occurs at the cathode 38.

[0075] On the other hand, the air filling the coolant flow field 56 facing the anode electrode 36 flows into the fuel gas flow field 54. This is because the second pressure is higher than the first pressure. In this case, a combustion reaction occurs at the anode electrode 36 between the hydrogen in the hydrogen-containing inert gas and the oxygen in the air. Therefore, the cell voltage detected by the cell voltage detection device 39 changes to a negative sign (- side). In other words, it is detected that a fluid is leaking from the separator 28 facing the anode electrode 36.

[0076] To obtain the cell voltage in the second pressure state, the hydrogen gas supply step P11, the waiting step P12, the inert gas supply step P13, the inert gas charging step P14, and the air charging step P2 are performed in this order.

[0077] In this case, in the inert gas supply step P13, the pressure (third pressure) of the hydrogen-containing inert gas sealed in the oxidant gas flow field 50 is set higher than the pressure (first pressure) of the hydrogen-containing inert gas sealed in the fuel gas flow field 54. In addition, in the inert gas sealing step P14, the pressure (second pressure) of the air filled in the coolant flow field 56 is set lower than the third pressure and higher than the first pressure.

[0078] In this manner, in this modification, leakage of fluid from the separator 28 is detected based on the cell voltage in the first pressure state and the cell voltage in the second pressure state. This makes it possible to identify, from changes in cell voltage, whether both the separator 28 facing the anode electrode 36 and the separator 28 facing the cathode electrode 38 are missing.

[0079] (Variation 2) A hydrogen-containing inert gas having a predetermined hydrogen concentration or less may be sealed into the oxidant gas flow path 50 and the fuel gas flow path 54 without performing the hydrogen gas supply process P11, the waiting process P12, the inert gas supply process P13, and the inert gas sealing process P14 in this order.

[0080] In this case, in the sealing step P1, first, sealing members are attached to the oxidant gas outlet manifold 40b (or the oxidant gas inlet manifold 40a) and the fuel gas outlet manifold 44b (or the fuel gas inlet manifold 44a). After the sealing members are attached, the gas supply device introduces a hydrogen-containing inert gas having a predetermined hydrogen concentration or less from a tank or the like into the oxidant gas flow field 50 via the oxidant gas inlet manifold 40a (or the oxidant gas outlet manifold 40b). The gas supply device also introduces a hydrogen-containing inert gas having a predetermined hydrogen concentration or less from a tank or the like into the fuel gas flow field 54 via the fuel gas inlet manifold 44a (or the fuel gas outlet manifold 44b).

[0081] Thereafter, the pressure gauges measure the internal flow channel pressure, which is the pressure of the hydrogen-containing inert gas in the oxidant gas flow channel 50 and the fuel gas flow channel 54. When the internal flow channel pressure measured by the pressure gauges reaches a predetermined pressure, the supply of hydrogen-containing inert gas by the gas supply device is stopped, and sealing members are attached to the oxidant gas inlet manifold 40a (or the oxidant gas outlet manifold 40b) and the fuel gas inlet manifold 44a (or the fuel gas outlet manifold 44b). As a result, the oxidant gas flow channel 50 and the fuel gas flow channel 54 are filled with hydrogen-containing inert gas having a predetermined hydrogen concentration or less.

[0082] The inventions and effects that can be understood from the above-described embodiments and modifications will be described below.

[0083] (1) The present invention provides a method for inspecting a fuel cell stack (10), the method being for inspecting a fuel cell stack having a flow path formed therein through which the fluid flows, for leakage of the fluid, the fuel cell stack comprising: a membrane electrode assembly (30) including an electrolyte membrane (34), an anode electrode (36) and a cathode electrode (38) arranged on either side of the electrolyte membrane; a power generation cell (14) having a pair of separators (28) sandwiching the membrane electrode assembly; and a cell voltage detection device (39) for detecting a cell voltage of the power generation cell, the method including: a sealing step (P1) of sealing a hydrogen-containing inert gas having a predetermined hydrogen concentration or less into gas flow paths (50, 52) formed between the membrane electrode assembly and each of the separators; an air filling step (P2) of filling air into coolant flow paths (56) formed between the power generation cells; and a detection step (P3) of detecting leakage of the fluid from the separators based on the cell voltage.

[0084] This makes it possible to detect fluid leakage even if the defect in the separator through which the fluid passes is minute, resulting in higher detection accuracy compared to when fluid leakage is detected by a detector.

[0085] (2) The present invention is a method for inspecting a fuel cell stack, and the sealing step may include a hydrogen gas supply step (P11) of supplying hydrogen gas to the gas flow path, and an inert gas supply step (P13) of supplying an inert gas to the gas flow path after the hydrogen gas supply step to dilute the hydrogen concentration in the gas flow path. This reduces the amount of heat generated by a combustion reaction between hydrogen in the hydrogen-containing inert gas and oxygen in the air, even if the combustion reaction is induced at the anode electrode or the cathode electrode. As a result, deterioration of the electrolyte membrane due to heat generation can be suppressed.

[0086] (3) The present invention may be a fuel cell stack inspection method that further includes a waiting step (P12) between the hydrogen gas supply step and the inert gas supply step, in which the supply of the inert gas is stopped until a predetermined time has elapsed since the supply of the hydrogen gas to the gas flow path was stopped. This increases the permeability of hydrogen gas into the electrolyte membrane in the power-generating cell. As a result, it is possible to suppress the occurrence of differences in hydrogen concentration among multiple power-generating cells.

[0087] (4) In the fuel cell stack inspection method, the inert gas may be supplied to both the gas flow path and the coolant flow path in the inert gas supply step. This allows hydrogen gas leaking from the gas flow path to the coolant flow path when a separator is damaged to be discharged to the outside. As a result, the occurrence of differences in hydrogen concentration among multiple power-generating cells can be suppressed compared to when hydrogen gas leaking remains in the coolant flow path.

[0088] (5) The present invention may be a fuel cell stack inspection method that further includes an inert gas injection step (P14) of injecting the inert gas into the gas flow path after the hydrogen concentration in the inert gas discharged from the gas flow path becomes equal to or lower than a predetermined concentration. This reduces the amount of heat generated by a combustion reaction between hydrogen in the hydrogen-containing inert gas and oxygen in the air, even if the combustion reaction is induced at the anode or cathode. As a result, deterioration of the electrolyte membrane due to heat generation can be suppressed.

[0089] (6) The present invention provides a fuel cell stack inspection method, wherein in the air filling step, the coolant flow path may be filled with air at a pressure higher than the pressure of the hydrogen-containing inert gas sealed in the gas flow path. This allows the air filling the coolant flow path to be guided to the gas flow path when a separator is defective. Therefore, a combustion reaction between hydrogen in the hydrogen-containing inert gas and oxygen in the air can be induced at the anode or cathode. As a result, it is possible to determine whether the separator facing the anode or the separator facing the cathode is defective based on a change in cell voltage.

[0090] (7) The present invention may provide a fuel cell stack inspection method, wherein the detection step detects leakage of the fluid from the separator based on the cell voltage in a first pressure state and the cell voltage in a second pressure state, the first pressure state being a state in which the first pressure is higher than the second pressure and the second pressure is higher than the third pressure, the second pressure state being a state in which the third pressure is higher than the second pressure and the second pressure is higher than the first pressure, the first pressure being the pressure of the hydrogen-containing inert gas sealed in the gas flow path facing the anode, the second pressure being the pressure of the air filling the coolant flow path, and the third pressure being the pressure of the hydrogen-containing inert gas sealed in the gas flow path facing the cathode. This allows defects in both the separator facing the anode and the separator facing the cathode to be identified from changes in cell voltage.

[0091] (8) The present invention may be a fuel cell stack inspection method, wherein the detection step detects whether the fluid is leaking from the separator facing the anode electrode or the separator facing the cathode electrode based on a change in the cell voltage to a positive or negative sign. This improves detection accuracy compared to when fluid leakage is detected by a detector. [Explanation of symbols]

[0092] 10... fuel cell stack 12... power generation cell stack 14...Power generating cell 28...Separator 30...Membrane electrode structure 34...Electrolyte membrane 36...Anode electrode 38...Cathode electrode 39... Cell voltage detection device 50... Oxidant gas flow path 54... fuel gas flow path 56... cooling medium flow path P1: Sealing process P2: Air filling process P3: Detection process P11: Hydrogen gas supply process P12: Standby process P13: Inert gas supply process P14...Inert gas sealing process

Claims

1. 1. A method for inspecting a fuel cell stack having a fluid flow path formed therein for leakage of the fluid, the method comprising: The fuel cell stack comprises: a power generation cell including a membrane electrode assembly including an electrolyte membrane, an anode electrode and a cathode electrode disposed on either side of the electrolyte membrane, and a pair of separators sandwiching the membrane electrode assembly; a cell voltage detection device for detecting a cell voltage of the power generation cell; Equipped with a sealing step of sealing a hydrogen-containing inert gas having a predetermined hydrogen concentration or less into gas flow paths formed between the membrane electrode assembly and each of the separators; an air filling step of filling a coolant flow field formed between the power generation cells with air, thereby increasing the pressure of the air filled in the coolant flow field compared to the pressure of the hydrogen-containing inert gas sealed in the gas flow field; a detecting step of detecting leakage of the fluid from the separator based on the cell voltage; Including, The method for inspecting a fuel cell stack, wherein the hydrogen concentration is low enough to prevent deterioration of the electrolyte membrane due to heat generated by a combustion reaction between hydrogen in the hydrogen-containing inert gas and oxygen in the air.

2. 2. The fuel cell stack inspection method according to claim 1, The encapsulation step includes: a hydrogen gas supplying step of supplying hydrogen gas to the gas flow channel; an inert gas supplying step of supplying an inert gas to the gas flow path after the hydrogen gas supplying step to dilute the hydrogen concentration in the gas flow path; A method for inspecting a fuel cell stack, comprising:

3. 3. The fuel cell stack inspection method according to claim 2, further comprising: The fuel cell stack inspection method further includes, between the hydrogen gas supply step and the inert gas supply step, a waiting step of waiting for the supply of the inert gas to be stopped until a predetermined time has elapsed since the supply of the hydrogen gas to the gas flow path was stopped.

4. 4. The fuel cell stack inspection method according to claim 2 or 3, In the inert gas supplying step, the inert gas is supplied to both the gas flow path and the coolant flow path.

5. The fuel cell stack inspection method according to any one of claims 2 to 4, comprising: A fuel cell stack inspection method, further comprising an inert gas sealing step of sealing the inert gas into the gas flow path after the hydrogen concentration in the inert gas discharged from the gas flow path becomes equal to or lower than a predetermined concentration.

6. The fuel cell stack inspection method according to any one of claims 1 to 5, In the detecting step, leakage of the fluid from the separator is detected based on the cell voltage in a first pressure state and the cell voltage in a second pressure state; the first pressure state is a state in which the first pressure is higher than the second pressure and the second pressure is higher than the third pressure, and the second pressure state is a state in which the third pressure is higher than the second pressure and the second pressure is higher than the first pressure, a first pressure being a pressure of the hydrogen-containing inert gas sealed in the gas flow path facing the anode electrode, a second pressure being a pressure of the air filled in the coolant flow path, and a third pressure being a pressure of the hydrogen-containing inert gas sealed in the gas flow path facing the cathode electrode.

7. The fuel cell stack inspection method according to any one of claims 1 to 6, comprising: In the detection step, it is detected whether the fluid is leaking from the separator facing the anode electrode or the separator facing the cathode electrode based on a change in the cell voltage to a positive or negative sign.

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