Fuel cell system

Abstract

A fuel cell system (200) is provided with: a fuel cell stack (100); pressure detection units (51, 52) for detecting the pressure (P1) of the anode flow path (PAa) and the pressure (P2) of the cathode flow path (PAc) of the fuel cell stack (100); and a leak detection unit (50) that detects a leak of the fuel gas from the anode flow path (PAa) on the basis of the pressures (P1, P2) detected by the pressure detection units (51, 52). After the fuel cell stops operating, the leak detection unit (50) controls the fuel gas supply / discharge unit (210) and the oxidant gas supply / discharge unit (220) such that the fuel gas supply / discharge unit (210) and the oxidant gas supply / discharge unit (220) are in a flow path cut-off state in which the anode flow path (PAa) and the fuel gas supply / discharge unit (210) are cut off and the cathode flow path (PAc) and the oxidant gas supply / discharge unit (220) are cut off while the pressures (P1, P2) are respectively maintained at predetermined values (Pa). Furthermore, fuel gas leakage is detected on the basis of the amount of change or the rate of change in the pressure (P1, P2) from the flow path cut-off state.

Description

Technical Field

[0001] The present invention relates to a fuel cell system. Background Art

[0002] In recent years, in order to enable more people to use cost-effective, reliable, sustainable, and advanced energy, technological development of fuel cells that contribute to improving energy efficiency has been underway. As a technology related to such a fuel cell system, a fuel cell system that detects leakage of a fuel gas containing hydrogen after the fuel cell stops operating is known. Such a fuel cell system is described in, for example, Patent Document 1. In the fuel cell system described in Patent Document 1, the pressure of the fuel gas in the pressure retention target range of the fuel gas is detected, and when the rate of decrease in pressure is equal to or higher than a set rate, it is determined that air leakage has occurred from the pressure retention target range.

[0003] However, as in the fuel cell system described in Patent Document 1, it is difficult to detect air leakage with high accuracy using only the pressure detection value of the fuel gas.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-181263 (JP2011-181263A). Summary of the Invention

[0007] A fuel cell system according to one aspect of the present invention includes: a fuel cell stack having a cell stack in which a plurality of power generation cells are stacked in a predetermined direction, and an anode flow channel through which a fuel gas flows and a cathode flow channel through which an oxidant gas flows are provided inside the cell stack; a fuel gas supply / discharge unit that supplies a fuel gas to the anode flow channel and discharges the fuel gas from the anode flow channel; an oxidant gas supply / discharge unit that supplies an oxidant gas to the cathode flow channel and discharges the oxidant gas from the cathode flow channel; a pressure detection unit that detects the pressure of the anode flow channel and the pressure of the cathode flow channel; and a leakage detection unit that detects leakage of the fuel gas from the anode flow channel based on the pressure of the anode flow channel and the pressure of the cathode flow channel detected by the pressure detection unit. After the fuel cell stops operating, the leakage detection unit controls the fuel gas supply / discharge unit and the oxidant gas supply / discharge unit so that the anode flow channel and the fuel gas supply / discharge unit are cut off and the cathode flow channel and the oxidant gas supply / discharge unit are cut off in a state where the pressure of the anode flow channel and the pressure of the cathode flow channel are respectively maintained at a predetermined value. Further, the leakage detection unit detects leakage of the fuel gas based on the change amount or change rate of the pressure of the anode flow channel and the change amount or change rate of the pressure of the cathode flow channel from the flow channel cut-off state. Brief Description of the Drawings

[0008] The object, features, and advantages of the present invention will be further clarified by the following description of embodiments related to the accompanying drawings.

[0009] Figure 1 is a diagram schematically showing the main part structure of a fuel cell system according to an embodiment of the present invention;

[0010] Figure 2 is a schematic illustration of Figure 1 a perspective view of the overall structure of a fuel cell stack included in the fuel cell system;

[0011] Figure 3 is Figure 2 a main part cross-sectional view of a cell stack included in the fuel cell stack;

[0012] Figure 4 is a diagram showing Figure 2 a perspective view of the schematic structure of an integrated electrode assembly included in the fuel cell stack;

[0013] Figure 5 is Figure 2 a rear view of a separator included in the fuel cell stack;

[0014] Figure 6 is a cross-sectional view taken along line VI-VI of Figure 5 ;

[0015] Figure 7 is a block diagram showing the control structure of a fuel cell system according to an embodiment of the present invention;

[0016] Figure 8 is a flowchart showing an example of processing executed by the Figure 7 ECU;

[0017] Figure 9 is a diagram showing an example of an operation performed by a fuel cell system according to an embodiment of the present invention. Detailed Embodiments

[0018] Hereinafter, embodiments of the present invention will be described with reference to Figures 1 to 9 . Figure 1 is a block diagram schematically showing the main part structure of a fuel cell system 200 according to an embodiment of the present invention. The fuel cell system 200 is mounted on a vehicle, for example, and generates electric power for driving the vehicle. As Figure 1 shown, the fuel cell system 200 includes a fuel cell stack 100 formed by stacking a plurality of power generation cells, a fuel gas supply / discharge unit 210, an oxidant gas supply / discharge unit 220, and a cooling medium supply / discharge unit 230. The fuel gas and the oxidant gas may be referred to as anode gas and cathode gas, respectively.

[0019] The fuel gas supply / discharge section 210 includes a tank 211 for storing high-pressure fuel gas, an injector 212 for ejecting the fuel gas, and an ejector 213. The fuel gas in the tank 211 is supplied to the fuel cell stack 100 via the injector 212, the ejector 213, and the supply flow path 210a. The fuel gas is an anode gas containing hydrogen (e.g., hydrogen gas). The fuel gas (fuel exhaust gas) is discharged from the fuel cell stack 100 via the discharge flow path 210b.

[0020] A gas-liquid separator 214 is interposed in the discharge flow path 210b. In the gas-liquid separator 214, the moisture contained in the fuel exhaust gas is separated from the fuel exhaust gas. The separated moisture is discharged via the drain flow path 210c. In the ejector 213, a negative pressure is generated due to the flow of the fuel gas ejected from the injector 212. Due to this negative pressure, the fuel exhaust gas from which the moisture has been separated in the gas-liquid separator 214 is sucked in via the circulation flow path 210d and merged with the fuel gas ejected from the injector 212. A part of the fuel exhaust gas does not flow back to the ejector 213 but is discharged via the exhaust flow path 210e.

[0021] In the fuel gas supply / discharge section 210, switching valves 501 to 503 are respectively provided on the supply side for supplying the fuel gas to the fuel cell stack 100 and the discharge side for discharging the fuel gas from the fuel cell stack 100. Specifically, the switching valve 501 on the supply side is provided in the flow path 210f between the tank 211 and the injector 212, and the switching valves 502 and 503 on the discharge side are respectively provided in the drain flow path 210c and the exhaust flow path 210e.

[0022] The switching valves 501 to 503 are electromagnetic valves that are opened or closed, for example, by exciting or demagnetizing a solenoid according to an electric signal. During the operation of the fuel cell (during power generation), the switching valves 501 to 503 are opened or opened at an appropriate timing. When the switching valves 501 to 503 are closed, the flow paths 210a and 210b on the supply side and the discharge side of the fuel gas are cut off, and the fuel gas can be sealed in the fuel cell stack 100. As long as it is the supply side and the discharge side of the fuel gas, the switching valves can also be provided at other positions.

[0023] The oxidant gas supply / discharge section 220 includes a compressor 221 for compressing the oxidant gas into a high pressure and a humidifier 222 for humidifying the oxidant gas. The oxidant gas compressed by the compressor 221 is humidified in the humidifier 222 and supplied to the fuel cell stack 100 via the supply flow path 220a. The oxidant gas is a cathode gas containing oxygen (e.g., air). The oxidant gas containing moisture (oxidant exhaust gas) is discharged from the fuel cell stack 100 via the discharge flow path 220b. This oxidant gas is discharged via the humidifier 222 and the flow path 220c.

[0024] In the oxidant gas supply / discharge unit 220, on-off valves 504 and 505 are respectively provided on the supply side for supplying oxidant gas to the fuel cell stack 100 and the discharge side for discharging oxidant gas from the fuel cell stack 100. Specifically, the on-off valve 504 on the supply side is provided in the flow path 220d between the compressor 221 and the humidifier 222, and the on-off valve 505 on the discharge side is provided in the flow path 210c downstream of the humidifier 222. Sometimes, without distinguishing between fuel gas and oxidant gas, they are referred to as reaction gas.

[0025] The on-off valves 504 and 505 are, for example, electromagnetic valves that open and close by energizing or de-energizing a solenoid according to an electric signal. During fuel cell operation (power generation), the on-off valves 504 and 505 are opened or opened at an appropriate timing. When the on-off valves 504 and 505 are closed, the flow paths 220a and 220b on the supply side and the discharge side of the oxidant gas are cut off, and the oxidant gas can be sealed in the fuel cell stack 100. As long as it is the supply side and the discharge side of the oxidant gas, the on-off valves can also be provided at other positions.

[0026] The cooling medium supply / discharge unit 230 has a pump (not shown), and the cooling medium ejected from the pump is supplied to the fuel cell stack 100 via the supply flow path 230a. The cooling medium is, for example, water. The cooling medium is discharged from the fuel cell stack 100 via the discharge flow path 230b. The discharged cooling medium is cooled by heat exchange in the radiator and is supplied to the fuel cell stack 100 again via the supply flow path 230a.

[0027] A pressure sensor 51 for detecting the pressure of the fuel gas is connected to the supply flow path 210a of the fuel gas. A pressure sensor 52 for detecting the pressure of the oxidant gas is connected to the supply flow path 220a of the oxidant gas. A hydrogen sensor 53 for detecting leakage of the fuel gas into the housing of the fuel cell stack 100 is connected to the fuel cell stack 100. Although not shown, a temperature sensor for detecting the temperature of the reaction gas, etc. is also connected to the fuel cell system 200. The fuel cell system 200 controls the operation according to the signals of these sensors.

[0028] Figure 2 is a perspective view schematically showing the overall structure of the fuel cell stack 100. Hereinafter, for convenience, as shown in the figure, the three mutually orthogonal axis directions are defined as the front-rear direction, the left-right direction, and the up-down direction, and the structure of each part will be described according to this definition. Figure 2 The front-rear direction of [] is the stacking direction of the fuel cell stack 100. These directions are not necessarily the same as the front-rear direction, the left-right direction, and the up-down direction of the vehicle. For example, Figure 2 the front-rear direction of [] can be the front-rear direction of the vehicle, can also be the left-right direction, or can be the up-down direction.

[0029] As Figure 2As shown, the fuel cell stack 100 has a battery laminate 10, end units 40 disposed at the front and rear end portions of the battery laminate 10, and a housing 30 that surrounds the battery laminate 10, and is generally rectangular parallelepiped in shape.

[0030] The housing 30 has four substantially rectangular side walls 300 that face the upper surface, right surface, lower surface, and left surface of the battery laminate 10, respectively. A substantially box-shaped accommodation space SP0 with an open front surface and rear surface is formed by these four side walls 300. The housing 30 is made of a metal such as aluminum or iron. Figure 1 The hydrogen sensor 53 is provided in the accommodation space SP0 outside the battery laminate 10.

[0031] Although not shown in the figure, the end unit 40 has a plurality of plates arranged overlapping in the front-rear direction. More specifically, the end unit 40 has a terminal plate disposed adjacent to the front and rear end faces of the battery laminate 10, an insulating plate disposed outside the terminal plate in the front-rear direction, and an end plate disposed outside the insulating plate in the front-rear direction.

[0032] The terminal plate is a substantially rectangular plate-shaped member made of metal and has a terminal portion for taking out the electric power generated by the electrochemical reaction in the battery laminate 10. The insulating plate is a substantially rectangular plate-shaped member made of a non-conductive resin or rubber and electrically insulates the terminal plate and the end plate. The end plate is a plate-shaped member made of metal or a resin configured to have high strength.

[0033] At Figure 2 Part A, a part of the side wall 300 of the housing 30 is shown cut away. As shown in Figure 2 Part A, the battery laminate 10 is a laminate having a plurality of power generation cells 1 (for convenience, only a single cell 1 is shown). The power generation cell 1 has an integrated electrode assembly 2 (Unitized Electrode Assembly, hereinafter referred to as UEA) and separators 3 disposed on the front and rear sides of the UEA 2 and sandwiching the UEA 2. The UEA 2 and the separators 3 are alternately arranged in the front-rear direction. The UEA 2 can also be referred to as a membrane electrode structure or a membrane electrode member.

[0034] Figure 3 is a main part cross-sectional view of the battery laminate 10. As shown in Figure 3As shown, the separator 3 has a front plate 3F and a rear plate 3R which are a pair of front and rear metal thin plates with a corrugated plate shape in cross section. The front plate 3F extends in the vertical, horizontal, and lateral directions and has a front surface 3Fa and a rear surface 3Fb. The rear plate 3R extends in the vertical, horizontal, and lateral directions and has a front surface 3Ra and a rear surface 3Rb. The rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R facing each other are joined between the outer peripheral edges by welding or the like. Thus, the front plate 3F and the rear plate 3R are integrally joined to form the separator 3. The separator 3 is made of a material with good corrosion resistance and conductivity, and for example, stainless steel, titanium, titanium alloy, etc. can be used.

[0035] Inside the separator 3 enclosed by the front plate 3F and the rear plate 3R, that is, between the rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R, a cooling flow path PAw for the cooling medium to flow is formed. The power generation surface of the power generation cell 1 is cooled by the flow of the cooling medium.

[0036] The surfaces of the separator 3 facing the UEA2, that is, the front surface 3Fa of the front plate 3F and the rear surface 3Rb of the rear plate 3R, are formed into concave and convex shapes by stamping or the like, so as to form a gas flow path between the separator 3 and the UEA2. More specifically, the separator 3 has a pair of front and rear rib portions 3A protruding toward the UEA2 and a pair of front and rear concave portions 3B connected to the pair of front and rear rib portions 3A and formed into a concave shape.

[0037] The pair of front and rear rib portions 3A are in contact with the front surface 2a and the rear surface 2b of the UEA2. When assembling the fuel cell stack 100, a compressive load F is applied to the battery laminate 10 in the front and rear directions, and after the assembly of the fuel cell stack 100 is completed, the compressive load F is maintained. Therefore, a specified surface pressure caused by the compressive load F acts on the UEA2 in the front and rear directions via the rib portions 3A.

[0038] An anode flow path PAa for the fuel gas to flow is formed by using the concave portion 3B between the front surface 2a of the UEA2 and the rear plate 3R of the separator 3 facing the front surface 2a. A cathode flow path PAc for the oxidant gas to flow is formed by using the concave portion 3B between the rear surface 2b of the UEA2 and the front plate 3F of the separator 3 facing the rear surface 2b.

[0039] Figure 4 is a perspective view showing a schematic structure of the UEA2. As Figure 4 shown, the UEA2 has a membrane electrode assembly 20 (Membrane Electrode Assembly, hereinafter referred to as MEA) having a substantially rectangular shape and a frame 21 supporting the MEA20. As Figure 3 shown in the detailed view of part A of , the MEA20 has an electrolyte membrane 23, an anode electrode 24 provided on the front surface 23f of the electrolyte membrane 23, and a cathode electrode 25 provided on the rear surface 23r of the electrolyte membrane 23.

[0040] The electrolyte membrane 23 is, for example, a solid polymer electrolyte membrane, and a thin film of a perfluorosulfonic acid polymer containing moisture can be used. Not limited to fluorine-based electrolyte membranes, hydrocarbon-based electrolyte membranes can also be used.

[0041] The anode electrode 24 has an electrode catalyst layer 241 formed on the front surface 23f of the electrolyte membrane 23 and serving as a reaction field for the electrode reaction, and a gas diffusion layer 242 provided on the front surface of the electrode catalyst layer 241 and diffusing and supplying the fuel gas. The cathode electrode 25 has an electrode catalyst layer 251 formed on the rear surface 23r of the electrolyte membrane 23 and serving as a reaction field for the electrode reaction, and a gas diffusion layer 252 provided on the rear surface of the electrode catalyst layer 251 and diffusing and supplying the oxidant gas. An intermediate layer (base layer) may be provided between the electrode catalyst layers 241, 251 and the gas diffusion layers 242, 252.

[0042] The electrode catalyst layers 241, 251 include a catalyst metal that promotes the electrochemical reaction between hydrogen contained in the fuel gas and oxygen contained in the oxidant gas, an electrolyte (ionomer, etc.) having proton conductivity, and carbon particles having electron conductivity, etc. The gas diffusion layers 242, 252 are composed of a conductive member having air permeability, such as a carbon porous body.

[0043] At the anode electrode 24, the fuel gas (hydrogen) supplied via the anode flow channel PAa is ionized by the action of the catalyst and moves to the cathode electrode side through the electrolyte membrane 23. The electrons generated at this time pass through the external circuit and are taken out as electric energy. At the cathode electrode 25, the oxidant gas (oxygen) supplied via the cathode flow channel PAc reacts with the hydrogen ions introduced from the anode electrode 24 and the electrons moving from the anode electrode 24 to generate water. The generated water gives appropriate humidity to the electrolyte membrane 23, and the remaining water is discharged to the outside of the UEA2 along with the flow of the gas.

[0044] As Figure 4 shown, the frame 21 is a thin plate having a substantially rectangular shape and is made of an insulating resin, rubber, etc. A substantially rectangular opening 21a is provided in the central portion of the frame 21. The MEA 20 is provided so as to cover the entire opening 21a, and the peripheral portion of the MEA 20 is supported by the frame 21. On the left side of the opening 21a of the frame 21, three through holes 201 to 203 are arranged and opened in the vertical direction, and the through holes 201 to 203 penetrate the frame 21 in the front-rear direction. On the right side of the opening 21a, three through holes 204 to 206 are arranged and opened in the vertical direction, and the through holes 204 to 206 penetrate the frame 21 in the front-rear direction.

[0045] Figure 5This is a rear view of the separator 3 disposed in front of the UEA2 (a view observed from the rear), showing the rear surface 3Rb of the rear plate 3R ( Figure 3 ). As Figure 5 shown, although part of the illustration is omitted, at the central portion in the left-right direction of the rear surface 3Rb, a plurality of ribs 3A extending in the up-down direction are provided for the MEA20 facing the UEA2 by stamping. Recesses 3B are provided between the adjacent ribs 3A in the up-down direction. An anode flow channel PAa is formed between the recess 3B and the front surface 2a of the MEA20. Although the illustration is omitted, ribs 3A and recesses 3B are similarly formed on the front surface of the front plate 3F of the separator 3, and a cathode flow channel PAc is formed between the recess 3B and the rear surface 2b of the MEA20.

[0046] In the separator 3, through holes 301 to 306 penetrating the separator 3 in the front-rear direction are respectively provided at positions corresponding to the through holes 201 to 206 ( Figure 4 ) of the frame 21. The through holes 301 to 306 are respectively in communication with the through holes 201 to 206 of the frame 21. Through the collection of these mutually communicating through holes 201 to 206, 301 to 306, a plurality of flow channels penetrating the battery stack 10 and extending in the front-rear direction are formed.

[0047] As Figure 2 shown, in the rear end unit (wet side end unit) 40, a plurality of through holes 401 to 406 penetrating the end unit 40 in the front-rear direction are provided at positions corresponding to the through holes 201 to 206, 301 to 306. No through holes 401 to 406 are provided in the front end unit (dry side end unit) 40.

[0048] The through holes 401 and 406 are respectively a fuel gas supply port and a discharge port. Supply flow channels 210a and discharge flow channels 210b are respectively connected to the through holes 401 and 406. As Figure 1 shown by the solid arrows in Figure 2 , fuel gas is supplied to the fuel cell stack 100 via the through hole 401, and fuel gas is discharged from the fuel cell stack 100 via the through hole 406.

[0049] The through holes 404 and 403 are respectively an oxidant gas supply port and a discharge port. Supply flow channels 220a and discharge flow channels 220b are respectively connected to the through holes 404 and 403. As Figure 1 shown by the dashed arrows in Figure 2 , oxidant gas is supplied to the fuel cell stack 100 via the through hole 404, and oxidant gas is discharged from the fuel cell stack 100 via the through hole 403.

[0050] The through holes 405 and 402 are respectively a cooling medium supply port and a discharge port. Supply flow channels are respectively connected to the through holes 405 and 402.Figure 1 The supply flow path 230a and the discharge flow path 230b. As Figure 2 shown by the single-dot chain line, the cooling medium is supplied to the fuel cell stack 100 via the through hole 405, and the cooling medium is discharged from the fuel cell stack 100 via the through hole 402.

[0051] As Figure 5 shown, at the outer peripheral edge portion of the separator 3, a welding portion WP1 (dotted line) is provided over the entire circumference, and the rear plate 3R and the front plate 3F are joined together integrally by the welding portion WP1. Further, around the through holes 301, 303, 304, 306 for gas supply and discharge, a welding portion WP2 (dotted line) is provided so as to individually surround the through holes 301, 303, 304, 306 over the entire circumference. Thereby, a cooling medium flow space SPw that closes the outer peripheral edge portion of the separator 3 and the through holes 301, 303, 304, 306 is formed inside the separator 3 (between the rear plate 3R and the front plate 3F), and the cooling medium is supplied to the cooling medium flow space SPw and discharged from the cooling medium flow space SPw via the through holes 302, 305.

[0052] On the rear surface 3Rb of the rear plate 3R, a sealing projection 31 that protrudes rearward toward the frame 21 of the UEA2 is provided outside the anode flow path PAa. The projection 31 has an outer projection 311, an inner projection 312, and individual projections 313 that extend without crossing each other.

[0053] The outer projection 311 extends along the outer peripheral edge of the rear plate 3R in a substantially rectangular shape so as to surround all the through holes 301 to 306. The inner projection 312 extends in a substantially rectangular shape so as to surround the anode flow path PAa, and extends partly near the outer projection 311 so as to surround the through holes 301, 306 for supply and discharge of fuel gas. A plurality of individual projections 313 are provided between the outer projection 311 and the inner projection 312 so as to individually surround the through holes 302 to 305.

[0054] Although not shown, a sealing projection 31 that protrudes forward toward the frame 21 of the UEA2 is similarly provided on the front surface 3Fa of the front plate 3F. However, the inner projection 312 on the front surface 3Fa of the front plate 3F is different from the inner projection 312 on the rear surface 3Rb of the rear plate 3R, and extends in a substantially rectangular shape so as to surround the cathode flow path PAc, and extends partly near the outer projection 311 so as to surround the through holes 304, 303 for supply and discharge of oxidant gas. Further, a plurality of individual projections 313 on the front surface 3Fa of the front plate 3F are provided between the outer projection 311 and the inner projection 312 so as to individually surround the through holes 301, 302, 305, 306.

[0055] Thus, by providing the convex portion 31 on the rear surface 3Rb of the rear plate 3R, a gas flow space SPa surrounded by a seal is formed from the through hole 301 to the anode flow path PAa and the through hole 306. Thereby, in the sealed state, the fuel gas flows in the gas flow space SPa along the rear surface 3Rb of the rear plate 3R. In addition, by providing the convex portion 31 on the front surface 3Fa of the front plate 3F, a gas flow space (not shown) surrounded by a seal is formed from the through hole 304 to the cathode flow path PAc and the through hole 303. Thereby, in the sealed state, the oxidant gas flows in the gas flow space (not shown) along the front surface 3Fa of the front plate 3F.

[0056] Figure 6 is a main part cross-sectional view of the separator 3 showing the structure of the seal portion 33 (a cross-sectional view taken along the Figure 5 VI-VI line shown). As Figure 6 shown, a sealing material 32 made of a rubber material or a resin material is fixed to the surface of the convex portion 31 (the inner convex portion 312 in Figure 6 ), thereby forming the seal portion 33. The convex portion 31 is in close contact with the front and rear surfaces of the frame 21 by means of the sealing material 32. The sealing material 32 can also be omitted, and the convex portion 31 can be in close contact with the front and rear surfaces of the frame 21.

[0057] However, due to the deflection of the separator 3, the deterioration of the sealing material 32, etc., sometimes poor sealing occurs. In this case, as Figure 6 shown by the arrow L1 in, sometimes the fuel gas leaks to the outside of the gas flow space SPa via the convex portion 31 or the sealing material 32, and further leaks to the outside of the battery stack 10. That is, sometimes external leakage of the fuel gas to the outside of the battery stack 10 occurs. In addition, due to welding defects, damages, etc. such as welding defects occurring at the welding portions WP1 and WP2 where the front plate 3F and the rear plate 3R are joined, as Figure 6 shown by the arrow L2 in, sometimes the fuel gas leaks from the gas flow space SPa to the cooling medium flow space SPw. That is, sometimes cross leakage of the fuel gas to other flow paths occurs.

[0058] In order to be able to detect such leakage of the fuel gas with high precision, the fuel cell system 200 is configured as follows in the present embodiment. Not only the fuel gas, but also the oxidant gas may leak, but for convenience hereinafter, it is treated as if there is no leakage of the oxidant gas.

[0059] Figure 7 is a block diagram showing the control structure of the fuel cell system 200 related to the detection of the leakage of the fuel gas. As Figure 1 、 7As shown, the fuel cell system 200 includes an ECU 50 as a leak detection unit, a pressure sensor 51 that detects the pressure P1 (referred to as the anode pressure) of the fuel gas in the anode flow channel PAa, a pressure sensor 52 that detects the pressure P2 (referred to as the cathode pressure) of the oxidant gas in the cathode flow channel PAc, a hydrogen sensor 53 that detects hydrogen outside the battery stack 10 and inside the housing, a fuel gas supply / discharge unit 210, and an oxidant gas supply / discharge unit 220. The fuel gas supply / discharge unit 210 includes an injector 212 and switching valves 501 to 503, and the oxidant gas supply / discharge unit 220 includes a compressor 221 and switching valves 504 and 505.

[0060] The ECU 50 is composed of a computer having an arithmetic unit such as a CPU, a storage unit such as a ROM (read only memory) and a RAM (random access memory), and other peripheral circuits. The arithmetic unit functions as a gas flow control unit 50A and a leak determination unit 50B by executing a program pre-stored in the storage unit.

[0061] Figure 8 is a flowchart showing an example of the processing executed by the arithmetic unit of the ECU. The processing shown in this flowchart starts when the operation (power generation) of the fuel cell stops due to the disconnection of the vehicle's power switch or ignition switch. For example, it is executed every time the fuel cell stops operating. It can also be executed every time the fuel cell performs a specified number of operations or every time a specified period has elapsed. Figure 8 At the start point of the processing, the anode pressure P1 and the cathode pressure P2 detected by the pressure sensors 51 and 52 are the initial pressure P0 that is sufficiently lower than during power generation.

[0062] As Figure 8 shown, first, in S1 (S: processing step), the fuel gas supply / discharge unit 210 and the oxidant gas supply / discharge unit 220 are controlled to increase the pressure of the fuel gas in the anode flow channel PAa and the oxidant gas in the cathode flow channel PAc in the fuel cell stack 100. Specifically, control signals are output to the switching valves 501 to 503 of the fuel gas supply / discharge unit 210 to open the switching valve 501 and close the switching valves 502 and 503. In this state, a control signal is output to the injector 212 to supply fuel gas to the anode flow channel PAa. At the same time, control signals are output to the switching valves 504 and 505 of the oxidant gas supply / discharge unit 220 to open the switching valve 504 and close the switching valve 505. In this state, a control signal is output to the compressor 22 to supply oxidant gas to the cathode flow channel PAc. In this case, the supply amount of the gas is adjusted so that the anode pressure P1 and the cathode pressure P2 increase in the same proportion.

[0063] Next, in S2, it is determined whether the anode pressure P1 and the cathode pressure P2 detected by the pressure sensors 51 and 52 have reached a predetermined value Pa stored in advance. The predetermined value Pa is a value of the pressure difference such that symptoms of easy fuel gas leakage occur when there is a sealing defect in the sealing portion 33 or a welding defect in the welding portions WP1 and WP2. When S2 is negative (S2: No), the process returns to S1 and the gas pressure continues to rise. When S2 is positive (S2: Yes), the process proceeds to S3.

[0064] In S3, a control signal is output to the switching valve 501 to close the switching valve 501, and a control signal is output to the injector 212 to stop the supply of the fuel gas. As a result, the pressure rise in the anode flow path PAa stops, the fuel gas is sealed in the anode flow path PAa, and the anode pressure P1 is maintained at the predetermined value Pa. At the same time, a control signal is output to the switching valve 504 to close the switching valve 504, and a control signal is output to the compressor 221 to stop the supply of the oxidant gas. As a result, the pressure rise in the cathode flow path PAc stops, the oxidant gas is sealed in the cathode flow path PAc, and the cathode pressure P2 is maintained at the predetermined value Pa.

[0065] The above is Figure 7 the process performed by the gas flow control unit 50A. The gas flow control unit 50A controls the flow of the reaction gas to a flow path cut-off state in which the anode flow path PAa and the cathode flow path PAc are cut off while maintaining the anode pressure P1 and the cathode pressure P2 at the predetermined value Pa, respectively. In the flow path cut-off state, the fuel gas and the oxidant gas face each other via the MEA 20. Therefore, even in the absence of fuel gas leakage, the reaction gas is consumed due to the electrochemical reaction, and the pressures P1 and P2 decrease. The amount of pressure decrease in this case is the normal amount of pressure decrease, and the normal amount of pressure decrease can be obtained in advance through experiments, analysis, etc.

[0066] Figure 7 The leakage determination unit 50B performs the processes after S4. In S4, only a predetermined time T1 is waited in the flow path cut-off state. The predetermined time T1 is the time required for a significant pressure drop of the fuel gas when there is a sealing defect or a welding defect. The predetermined time T1 is grasped in advance through experiments, analysis, etc. and stored in the storage unit.

[0067] Next, in S5, it is determined whether the anode pressure P1 is equal to or lower than the predetermined value Pb and whether the cathode pressure P2 is higher than the predetermined value Pb. The predetermined value Pb is a value lower than the predetermined value Pa by a predetermined pressure drop ΔP. The predetermined value Pb is a threshold value for determining the occurrence of fuel gas leakage, and is grasped in advance through experiments, analysis, etc. and stored in the storage unit.

[0068] In S5, it is determined not only whether P1 ≤ Pb holds, but also whether P2 > Pb holds. Therefore, it is determined whether the anode pressure P1 has decreased significantly compared to the cathode pressure P2 on the premise of no leakage, thereby improving the accuracy of leakage determination. Alternatively, in place of the process of S5, it can be determined whether the anode pressure P1 is smaller than the cathode pressure P2 by a specified value or more.

[0069] When S5 is negative, it proceeds to S6. In this case, it is determined that there is no leakage of fuel gas, and the process ends. On the other hand, when S5 is positive (S5: yes), it proceeds to S7, and it is determined whether hydrogen is detected in the accommodation space SP0 outside the battery laminate 10 and inside the housing 30 based on the signal from the hydrogen sensor 53. For example, when the hydrogen sensor 53 detects hydrogen in an amount equal to or more than a specified amount, it is determined that hydrogen is detected.

[0070] When S7 is positive (S7: yes), it proceeds to S8. In this case, it is determined that fuel gas has leaked (oozed out) outside the battery laminate 10, and the process ends. On the other hand, when S7 is negative (S7: no), it proceeds to S9. In this case, it is determined that fuel gas has leaked (cross-leaked) in the coolant flow path PAw (coolant flow space SPw), and the process ends. Through the above, the process related to the detection of fuel gas leakage ends. After the Figure 8 process ends, the ECU 50 can also output the determination result. For example, the determination result can also be output to a monitor for display or output to a memory for storage. After the Figure 8 process ends, the oxidant gas accumulated in the cathode flow path PAc continues to be consumed by the electrochemical reaction with the fuel gas.

[0071] The main operations of this embodiment are summarized as follows. Figure 9 is a diagram showing changes in the anode pressure P1 and the cathode pressure P2 over time from the initial time point t0 when the operation of the fuel cell stops. The characteristic f1 in the figure shows the change in the anode pressure P1, and the characteristic f2 shows the change in the cathode pressure P2. At the time point t0, with the discharge-side switching valves 502, 503, and 505 closed, fuel gas and oxidant gas are simultaneously supplied to the anode flow path PAa and the cathode flow path PAc (S1). As a result, as shown by the characteristics f1 and f2, the anode pressure P1 and the cathode pressure Pc gradually increase from the initial pressure P0.

[0072] At time point t1, when the anode pressure P1 and the cathode pressure P2 rise to the specified value Pa, the supply of fuel gas and oxidant gas is stopped (S3). As a result, the anode flow channel PAa and the cathode flow channel PAc in the fuel cell stack are maintained in a flow channel cut-off state in which the fuel gas and the oxidant gas with the specified pressure Pa are respectively sealed. At time point t1, since the anode pressure P1 is equal to the cathode pressure P2, gas cross-leakage does not occur between the anode flow channel PAa and the cathode flow channel PAc.

[0073] When there are sealing defects or welding defects in the separator 3 on the anode flow channel PAa side, fuel gas leaks from the anode flow channel PAa. As Figure 9 shown, from time point t1, the anode pressure P1 gradually decreases over time. In contrast, since there is no leakage of oxidant gas from the cathode flow channel PAc, the cathode pressure P2 is constant. In fact, the fuel gas and the oxidant gas are consumed due to mutual reaction, and accordingly, the anode pressure P1 and the cathode pressure P2 decrease. However, in Figure 6 for convenience, characteristics f1 and f2 are assumed to ignore this point.

[0074] At time point t2, which is after the specified time T1 has elapsed from time point t1, when the anode pressure P1 is higher than the specified value Pb and the cathode pressure P2 is higher than the specified value Pb, it is determined that there is no leakage of fuel gas (S6). On the other hand, as Figure 9 shown, although the cathode pressure P2 is higher than the specified value Pb, when the anode pressure P1 reaches below the specified value Pb, it is determined that the pressure reduction is caused by leakage rather than by reaction. That is, it is determined that cross-leakage from the anode flow channel PAa to the cooling medium flow channel PAw or exosmosis to the outside of the battery laminate 10 has occurred.

[0075] Furthermore, when hydrogen is detected by the hydrogen sensor 53, it is determined that there is exosmosis of fuel gas, and when hydrogen is not detected, it is determined that there is cross-leakage of fuel gas (S8, S9). Thus, it is possible to not only determine whether there is leakage of fuel gas but also determine the leakage mode.

[0076] The following effects can be achieved by adopting this embodiment.

[0077] (1) The fuel cell system 200 includes: a fuel cell stack 100 having a cell stack 10 formed by laminating a plurality of power generation cells 1, and an anode flow channel PAa for fuel gas to flow and a cathode flow channel PAc for oxidant gas to flow are provided inside the cell stack 10; a fuel gas supply / discharge unit 210 that supplies fuel gas to the anode flow channel PAa and discharges fuel gas from the anode flow channel PAa; an oxidant gas supply / discharge unit 220 that supplies oxidant gas to the cathode flow channel PAc and discharges oxidant gas from the cathode flow channel PAc; pressure sensors 51 and 52 that detect the pressure P1 of the anode flow channel PAa and the pressure P2 of the cathode flow channel PAc; and an ECU 50 that, as a leakage detection unit, detects the leakage of fuel gas from the anode flow channel PAa based on the anode pressure P1 and the cathode pressure P2 detected by the pressure sensors 51 and 52 ( Figure 1 , Figure 2 , Figure 7 ). After the fuel cell stops operating, the ECU 50 controls the fuel gas supply / discharge unit 210 and the oxidant gas supply / discharge unit 220 so that the anode flow channel PAa is cut off from the fuel gas supply / discharge unit 210 and the cathode flow channel PAc is cut off from the oxidant gas supply / discharge unit 220 while the anode pressure P1 and the cathode pressure P2 are respectively maintained at a specified value Pa, and further detects the leakage of fuel gas based on the change amount of the anode pressure P1 and the change amount of the cathode pressure P2 from the flow channel cut-off state ( Figure 8 ).

[0078] In this way, after the fuel cell stops operating, fuel gas and oxidant gas are respectively supplied to the anode flow channel PAa and the cathode flow channel PAc to detect the leakage of fuel gas. Therefore, there is no need to add a dedicated flow channel for leakage detection, etc., and leakage detection can be performed with a simple structure. In addition, not only based on the change amount of the anode pressure P1, but also based on the change amount of the cathode pressure P2 to determine the leakage of fuel gas. Therefore, even when the fuel gas reacts with the oxidant gas and the anode pressure P1 decreases, the occurrence of fuel gas leakage can be determined with high accuracy.

[0079] (2) The ECU 50 determines that leakage has occurred in the anode flow channel PAa based on the ratio of the change amount of the anode pressure P1 to the change amount of the cathode pressure P2 from the flow channel cut-off state, that is, when the cathode pressure P2 is higher than the specified value Pb but the anode pressure P1 is below the specified value Pb ( Figure 8 ). Thereby, it is possible to accurately determine whether there is leakage of fuel gas.

[0080] (3) The fuel cell system 200 further includes a cooling medium supply / discharge unit 230 that supplies a cooling medium to a cooling medium flow path PAw adjacent to the anode flow path PAa via a rear plate 3R (partition wall) and discharges the cooling medium from the cooling medium flow path PAw ( Figure 1 , Figure 2 ). When the degree of decrease in the anode pressure P1 is greater than the degree of decrease in the cathode pressure P2 over time starting from the flow path cut-off state, the ECU 50 determines that fuel gas has leaked from the anode flow path PAa to the outside of the battery stack 10 or from the anode flow path PAa to the cooling medium flow path PAw ( Figure 8 ). Thus, it can be determined that the mode of fuel gas leakage is either external leakage to the outside of the battery stack 10 or cross-leakage to the cooling medium flow path PAw.

[0081] (4) The fuel cell system 200 further includes a hydrogen sensor 53 that detects fuel gas outside the battery stack 10 ( Figure 1 ). When, starting from the flow path cut-off state, the degree of decrease in the anode pressure P1 is greater than the degree of decrease in the cathode pressure P2 over time and the hydrogen sensor 53 detects fuel gas, the ECU 50 determines that fuel gas has leaked from the anode flow path PAa to the outside of the battery stack 10. When the hydrogen sensor 53 does not detect fuel gas, the ECU 50 determines that fuel gas has leaked from the anode flow path PAa to the cooling medium flow path PAw ( Figure 8 ). Thus, with a simple structure, the mode of fuel gas leakage can be determined. Since the hydrogen sensor 53 is provided in the accommodation space SP0 within the housing instead of in the cooling medium flow path PAw, it is also easy to install the hydrogen sensor 53.

[0082] (5) After the fuel cell stops operating, the ECU 50 controls the fuel gas supply / discharge unit 210 and the oxidant gas supply / discharge unit 220 to simultaneously increase the anode pressure P1 and the cathode pressure P2 to a specified value Pa ( Figure 8 ). Thus, it is possible to quickly transfer to the flow path cut-off state where the gas pressure has risen to the specified value Pa, and the leakage detection process can be completed in a short time. In addition, since the anode pressure P1 and the cathode pressure P2 are simultaneously increased to equal values, cross-leakage caused by the pressure difference between the anode pressure P1 and the cathode pressure P2 can be suppressed.

[0083] The above fuel cell system 200 can also be used as a method for detecting air leakage in a fuel cell. That is, the method for detecting air leakage in a fuel cell includes: a step (S1 to S3) of increasing the anode pressure P1 and the cathode pressure P2 to a specified value Pa after the fuel cell stops operating, so as to enter a flow path cut-off state; a step (S4) of maintaining the flow path cut-off state unchanged and waiting for a specified time T1; and a step (S5 to S9) of detecting leakage of fuel gas based on the change amount of the anode pressure P1 and the change amount of the cathode pressure P2 after the specified time T1 has elapsed.

[0084] The above-described embodiment can be deformed into various forms. Hereinafter, several modification examples will be described. In the above-described embodiment, the pressure sensors 51 and 52 as the pressure detection units are connected to the flow paths 210f and 220a. However, as long as the pressures P1 and P2 in the anode flow path and the cathode flow path are detected, the position where the pressure detection unit is provided is not limited to the above. The anode pressure P1 and the cathode pressure P2 can also be calculated by using the detection values of other sensors. Other sensors detect other physical quantities that have a correlation with these pressures P1 and P2, and the configuration of the pressure detection unit is not limited to the above. The pressure difference between the anode pressure P1 and the cathode pressure P2 can also be detected, and leakage detection can be performed by determining whether the anode pressure P1 is lower than the cathode pressure P2 and whether the pressure difference is equal to or greater than a specified value. In the above-described embodiment, the specified values Pa and Pb are used as constant values, but the specified values Pa and Pb can also be changed according to, for example, the temperature detection value.

[0085] In the above-described embodiment, the ECU 50 as the leakage detection unit detects the leakage of fuel gas by determining whether the pressures P1 and P2 have decreased by more than a specified amount after the flow path cut-off state has been reached and after the specified time T1 has elapsed. However, it is also possible to detect the leakage of fuel gas without waiting for the specified time T1, by determining whether the pressures P1 and P2 have decreased by more than a specified amount within a specified time (for example, at the time when P1 ≤ Pb and P2 > Pb are satisfied). In the above-described embodiment, the leakage of fuel gas is detected based on the change amount (decrease amount) of the pressures P1 and P2. However, it is also possible to detect the leakage of fuel gas based on the change rate of the pressures P1 and P2 (for example, the change rate of the pressures P1 and P2 per unit time, more specifically, the decrease rate), that is, by determining whether the ratio of the pressure decrease is equal to or greater than a specified value. Therefore, the configuration of the leakage detection unit for determining whether the degree of decrease in the anode pressure P1 over time from the flow path cut-off state is greater than the degree of decrease in the cathode pressure P2 is not limited to the above.

[0086] In the above embodiment, whether leakage from the anode flow channel PAa occurs is determined by whether P1≤Pb and P2>Pb are established after a predetermined time T1 has passed from the flow channel closed state, but in other ways, whether leakage occurs in the anode flow channel PAa can be determined based on the change amount or change rate of the anode pressure P1 relative to the change amount or change rate of the cathode pressure P2 from the flow channel closed state. For example, it is also possible to divide the reduction amount of the cathode pressure P2 by the reduction amount of the anode pressure P1 (reduction amount of the anode pressure P1 / reduction amount of the cathode pressure P2) to obtain the ratio of the pressure reduction amount, and determine whether the ratio is greater than a predetermined value to determine whether leakage occurs in the anode flow channel PAa. In the above embodiment, the hydrogen sensor 53 as a gas detection unit is provided in the housing space SP0 in the housing, but the gas detection unit can also be provided in other locations such as in the motor housing.

[0087] In the above embodiment, after the fuel cell stops operating, the fuel gas and the oxidant gas are supplied to the anode flow channel PAa and the cathode flow channel PAc respectively to detect the gas leakage, but it is also possible to supply either the fuel gas or the oxidant gas to the anode flow channel PAa and the cathode flow channel PAc respectively to detect the gas leakage. Figure 1 A connecting flow channel is provided to connect the fuel gas supply flow channel 210a and the oxidant gas supply flow channel 220a, and a switch valve is provided on the connecting flow channel. When leakage detection is performed after the fuel cell stops operating, the switch valve is opened to supply either the fuel gas or the oxidant gas to the anode flow channel PAa and the cathode flow channel PAc, respectively, as a flow channel cut-off state for maintaining the gas pressure of each flow channel PAa, PAc at a specified value Pa.

[0088] In the above embodiment, an example in which the fuel cell system 200 is applied to a vehicle is described. However, the fuel cell system of the present invention can also be applied to mobile objects other than vehicles such as aircraft and ships, robots, and various industrial machines.

[0089] One or more of the above-described embodiments and modifications may be arbitrarily combined, and modifications may be combined with each other.

[0090] According to the present invention, leakage of fuel gas can be detected with high accuracy.

[0091] The present invention has been described above in conjunction with preferred embodiments, but it should be understood by those skilled in the art that various modifications and changes can be made without departing from the scope of the claims.

Claims

1. A fuel cell system, characterized in that, Comprising: A fuel cell stack (100) having a cell stack body (10) formed by laminating a plurality of power generation cells (1) in a specified direction, and an anode flow channel (PAa) for fuel gas flow and a cathode flow channel (PAc) for oxidant gas flow provided inside the cell stack body (10); A fuel gas supply / discharge unit (210) that supplies fuel gas to the anode flow channel (PAa) and discharges fuel gas from the anode flow channel (PAa); An oxidant gas supply / discharge unit (220) that supplies oxidant gas to the cathode flow channel (PAc) and discharges oxidant gas from the cathode flow channel (PAc); Pressure detection units (51, 52) that detect the pressure (P1) of the anode flow channel (PAa) and the pressure (P2) of the cathode flow channel (PAc); and A leakage detection unit (50) that detects leakage of fuel gas from the anode flow channel (PAa) based on the pressure (P1) of the anode flow channel (PAa) and the pressure (P2) of the cathode flow channel (PAc) detected by the pressure detection units (51, 52), After the fuel cell stops operating, the leakage detection unit (50) controls the fuel gas supply / discharge unit (210) and the oxidant gas supply / discharge unit (220) so that the anode flow channel (PAa) and the fuel gas supply / discharge unit (210) are cut off and the cathode flow channel (PAc) and the oxidant gas supply / discharge unit (220) are cut off while the pressure (P1) of the anode flow channel (PAa) and the pressure (P2) of the cathode flow channel (PAc) are respectively maintained at a specified value (Pa), and further, based on the change amount or change rate of the pressure (P1) of the anode flow channel (PAa) and the change amount or change rate of the pressure (P2) of the cathode flow channel (PAc) from the flow channel cut-off state, detects leakage of fuel gas.

2. The fuel cell system according to claim 1, wherein The leakage detection unit (50) determines whether leakage has occurred in the anode flow channel (PAa) based on the change amount or change rate of the pressure (P1) of the anode flow channel (PAa) relative to the change amount or change rate of the pressure (P2) of the cathode flow channel (PAc) from the flow channel cut-off state.

3. The fuel cell system according to claim 1, wherein The specified value is a first specified value (Pa), The leakage detection unit (50) determines whether the pressure (P1) of the anode flow channel (PAa) and the pressure (P2) of the cathode flow channel (PAc) after a specified time has elapsed from the flow channel cut-off state are equal to or lower than a second specified value (Pb) that is lower than the first specified value (Pa). When the pressure (P1) of the anode flow channel (PAa) is equal to or lower than the second specified value (Pb) and the pressure (P2) of the cathode flow channel (PAc) is greater than the second specified value (Pb), it is determined that leakage of fuel gas has occurred.

4. The fuel cell system according to claim 2, characterized in that, Further comprising: A cooling medium supply / discharge section (230) that supplies a cooling medium to a cooling medium flow channel (PAw) adjacent to the anode flow channel (PAa) via a partition wall (3R) and discharges the cooling medium from the cooling medium flow channel (PAw). When, over time from the flow channel cut-off state, the degree of pressure (P1) reduction in the anode flow channel (PAa) is greater than the degree of pressure (P2) reduction in the cathode flow channel (PAc), the leakage detection section (50) determines that fuel gas has leaked from the anode flow channel (PAa) to the outside of the fuel cell stack (10) or from the anode flow channel (PAa) to the cooling medium flow channel (PAw).

5. The fuel cell system according to claim 4, characterized in that Further provided with: A gas detection section (53) that detects fuel gas outside the fuel cell stack (10). When fuel gas is detected by the gas detection section (53) in a state where, over time from the flow channel cut-off state, the degree of pressure (P1) reduction in the anode flow channel (PAa) is greater than the degree of pressure (P2) reduction in the cathode flow channel (PAc), the leakage detection section (50) determines that fuel gas has leaked from the anode flow channel (PAa) to the outside of the fuel cell stack (10). When fuel gas is not detected by the gas detection section (53), the leakage detection section (50) determines that fuel gas has leaked from the anode flow channel (PAa) to the cooling medium flow channel (PAw).

6. The fuel cell system according to any one of claims 1 to 5, characterized in that: After the fuel cell stops operating, the leakage detection section (50) controls the fuel gas supply / discharge section (210) and the oxidant gas supply / discharge section (220) so that the pressure (P1) in the anode flow channel (PAa) and the pressure (P2) in the cathode flow channel (PAc) simultaneously rise to the specified value (Pa).

7. The fuel cell system according to claim 1, characterized in that: The power generation cell (1) has an integrated electrode assembly (2) and a pair of separator plates (3, 3). The integrated electrode assembly (2) has a membrane electrode assembly (20) including an electrolyte membrane (23) and electrodes (24, 25) and a frame (21) that supports the membrane electrode assembly (20). The pair of separator plates (3, 3) are arranged on both sides in the specified direction of the integrated electrode assembly (2). A sealing portion (33) is provided on the contact surface where the pair of separator plates (3, 3) contact the frame (21). The anode flow channel (PAa) is provided between one of the pair of separator plates (3, 3) and the integrated electrode assembly (2) in a state sealed by the sealing portion (33).

8. The fuel cell system according to claim 7, characterized in that: Each of the pair of separator plates (3, 3) is composed of a pair of plates (3F, 3R) integrated by welding. A cooling medium flow channel (PAw) for the flow of a cooling medium is formed inside the pair of plates (3F, 3R).

9. A method for detecting air leakage in a fuel cell, characterized in that: The fuel cell has a cell stack (10) formed by laminating a plurality of power generation cells (1) in a specified direction, and an anode flow channel (PAa) for allowing a fuel gas to flow and a cathode flow channel (PAc) for allowing an oxidant gas to flow are provided inside the cell stack (10). The air leakage detection method includes: a step of raising the pressure (P1) of the anode flow channel (PAa) and the pressure (P2) of the cathode flow channel (PAc) to a specified value (Pa) respectively after the fuel cell stops operating; a step of cutting off the anode flow channel (PAa) and the cathode flow channel (PAc) to set them in a flow channel cut-off state while maintaining the pressure (P1) of the anode flow channel (PAa) and the pressure (P2) of the cathode flow channel (PAc) at the specified value (Pa); and a step of detecting leakage of the fuel gas based on the change amount or change rate of the pressure (P1) of the anode flow channel (PAa) and the change amount or change rate of the pressure (P2) of the cathode flow channel (PAc) from the flow channel cut-off state.

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