Fuel cell system and fault diagnosis method for fuel cell system

Abstract

Fuel cell system (10; 10d; 10e) comprising: a fuel cell (100); an air duct (210) comprising an air supply duct (211) through which air is supplied to the fuel cell (100) and an air discharge duct (212) through which the air is discharged from the fuel cell (100); an air inlet valve (240) configured to open and close the air supply channel (211); an air release valve (250) configured to open and close the air release channel (212); a hydrogen gas channel (310) comprising a hydrogen gas supply channel (311) through which hydrogen gas is supplied to the fuel cell (100) and a hydrogen gas discharge channel (312) through which the hydrogen gas is discharged from the fuel cell (100); a hydrogen gas inlet valve (330) configured to open and close the hydrogen gas supply channel (311); a hydrogen gas discharge valve (370) configured to open and close the hydrogen gas discharge channel (312); a hydrogen gas pressure sensor (340) configured to detect a pressure of a gas in the hydrogen gas channel (310) disposed downstream of the hydrogen gas inlet valve (330) and upstream of the hydrogen gas outlet valve (370); and a controller (500) configured to determine whether the air inlet valve (240) and the air outlet valve (250) are normally closed based on a state of pressure reduction obtained from the hydrogen gas pressure sensor (340) after the hydrogen gas inlet valve (330), the hydrogen gas outlet valve (370), the air inlet valve (240), and the air outlet valve (250) are caused to close.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to a fuel cell system and a failure diagnosis method for a fuel cell system.2. Description of the Prior ArtRegarding a fuel cell system, for example, JP 2008-153 079 A discloses a fuel cell system including a hydrogen gas passage, a hydrogen gas inlet shut-off valve, a hydrogen gas outlet shut-off valve, an air passage, an air inlet shut-off valve, an air outlet shut-off valve, and an air pressure sensor. In the fuel cell system, the air inlet shut-off valve and the air outlet shut-off valve are closed to seal the air passage after the fuel cell system is stopped. Next, based on a pressure obtained from an air pressure sensor disposed in the air passage, it is determined whether or not the air inlet shut-off valve or the air outlet shut-off valve is normally closed.Summary of the InventionIn the fuel cell system disclosed in JP 2008-153 079 A, the air pressure sensor is disposed in the air passage to determine whether the air inlet shut-off valve or the air outlet shut-off valve is normally closed. Therefore, the fuel cell system is complex. Further fuel cell systems and control methods for this are the subject matter of U.S. Pat. No. 2016 / 0 301 090 A1 and DE 11 2006 001 772 T5.A first aspect of the invention relates to a fuel cell system including a fuel cell, an air passage, an air inlet valve, an air outlet valve, a hydrogen gas passage, a hydrogen gas inlet valve, a hydrogen gas outlet valve, a hydrogen gas pressure sensor, and a controller. The air passage includes an air supply passage through which air is supplied to the fuel cell and an air discharge passage through which air is discharged from the fuel cell. The air inlet valve is configured to open and close the air supply passage. The air discharge valve is configured to open and close the air discharge passage. The hydrogen gas passage includes a hydrogen gas supply passage through which hydrogen gas is supplied to the fuel cell and a hydrogen gas discharge passage through which hydrogen gas is discharged from the fuel cell. The hydrogen gas inlet valve is configured to open and close the hydrogen gas supply passage. The hydrogen gas discharge valve is configured to open and close the hydrogen gas discharge passage. The hydrogen gas pressure sensor is configured to acquire a pressure of a gas in the hydrogen gas passage disposed downstream of the hydrogen gas inlet valve and upstream of the hydrogen gas discharge valve. The controller is configured to determine whether the air inlet valve and the air outlet valve are normally closed based on a state of decreasing the pressure acquired from the hydrogen gas pressure sensor after the hydrogen gas inlet valve, the hydrogen gas outlet valve, the air inlet valve, and the air outlet valve are caused to close. According to the first aspect of the invention, it can be determined whether the air inlet valve and the air outlet valve are normally closed based on a state of lowering the gas pressure in the hydrogen gas passage acquired from the hydrogen gas pressure sensor. Therefore, it can be determined whether the air intake valve and the air exhaust valve are normally closed without disposing an air pressure sensor for obtaining the gas pressure in the air passage. Thus, the structure of the fuel cell system can be simplified.In the fuel cell system according to the first aspect of the invention, when a predetermined period of time has elapsed after causing the hydrogen gas inlet valve, the hydrogen gas outlet valve, the air inlet valve, and the air outlet valve to close, the controller may be configured to determine that the air inlet valve and the air outlet valve are normally closed in a case where the decreased pressure is less than or equal to a predetermined value and determine that the air inlet valve and / or the air outlet valve is / are not normally closed in a case where the decreased pressure is not less than or equal to a predetermined value. According to the first aspect of the invention, it can be easily determined whether or not the air intake valve and the air exhaust valve are normally closed by a simple comparison operation.In the fuel cell system according to the first aspect of the invention, the predetermined value may be a value determined based on the decreased pressure when the predetermined time has elapsed in a case where the air inlet valve, the air outlet valve, the hydrogen gas inlet valve, and the hydrogen gas outlet valve are normally closed. According to the first aspect of the invention, it can be accurately determined whether the air inlet valve and the air outlet valve are normally closed based on the pressure in a case where the air inlet valve and the air outlet valve are normally closed.In the fuel cell system according to the first aspect of the invention, the controller may be configured to determine that the air inlet valve and the air outlet valve are normally closed in a predetermined period in which the pressure decreases after causing the hydrogen gas inlet valve, the hydrogen gas outlet valve, the air inlet valve, and the air outlet valve to close, in a case where there is a period in which the pressure increases, and determine that the air inlet valve and the air outlet valve are normally closed in a case where there is no period in which the pressure increases. According to the first aspect of the invention, it can be easily determined whether or not the air intake valve and the air exhaust valve are normally closed based on whether or not there is an increase in pressure.The fuel cell system according to a first aspect of the invention may further include a compressor configured to supply compressed air to the fuel cell, the compressor being disposed upstream of the air inlet valve of the air passage. The controller may be configured to drive the compressor in a case where the controller determines that the air intake valve and / or the air exhaust valve is / are not normally closed. According to the first aspect of the invention, in a case where the air intake valve and / or the air exhaust valve is / are not normally closed, since foreign matter in the air (hereinafter referred to as "foreign matter") sticks therein, the foreign matter can be removed by driving the compressor.The fuel cell system according to the first aspect of the invention may further include a temperature sensor configured to acquire a gas temperature in the hydrogen gas channel. The controller may be configured to determine whether or not the air intake valve and the air exhaust valve are normally closed, based on the pressure obtained from the hydrogen gas pressure sensor in a case where the temperature obtained from the temperature sensor is equal to or lower than a predetermined value. According to the first aspect of the invention, in a case where it is determined whether the air inlet valve and the air outlet valve are normally closed using a gas pressure in the hydrogen gas passage acquired from the hydrogen gas pressure sensor, an effect of the temperature on the change in the pressure in the hydrogen gas passage can be further reduced. Therefore, it can be more appropriately determined whether the air inlet valve and the air outlet valve are normally closed.The fuel cell system according to the first aspect of the invention may further include an alarm portion configured to alarm that the air inlet valve and / or the air outlet valve is / are not normally closed. The controller may be configured to cause the alarm portion to alert about a failure in a case where the controller determines that the air intake valve and / or the air exhaust valve is / are not normally closed. According to the first aspect of the invention, in a case where the air inlet valve and the air outlet valve are not normally closed, the alarm portion alerts about the failure. Therefore, the alarm section can prompt a user to repair or check the fuel cell system.A second aspect of the invention relates to a failure diagnosis method for a fuel cell system. The fault diagnosis method includes: obtaining a pressure of a gas in a hydrogen gas passage disposed downstream of a hydrogen gas inlet valve and upstream of a hydrogen gas discharge valve after causing the hydrogen gas inlet valve, the hydrogen gas discharge valve, an air inlet valve, and an air discharge valve to be closed, wherein the hydrogen gas inlet valve is configured to open and close a hydrogen gas supply passage through which hydrogen gas is supplied to a fuel cell, wherein the hydrogen gas discharge valve is configured to open and close a hydrogen gas discharge passage through which hydrogen gas is discharged from the fuel cell, wherein the air inlet valve is configured to open and close an air supply passage through which air is supplied to the fuel cell, and wherein the air discharge valve is configured to open and close an air discharge passage through which air is discharged from the fuel cell; and determining whether the air intake valve and the air exhaust valve are normally closed based on a state of decreasing the related pressure.According to the present invention, the present invention may be implemented in various forms other than a fuel cell system. For example, the invention may be realized in the form of, for example, a fuel cell vehicle or a control method for a fuel cell system.BRIEF DESCRIPTION OF THE DRAWINGFeatures, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, wherein like numerals denote like elements, and FIG. 1 is a diagram showing the outline of a fuel cell system according to a first embodiment; FIG. 2 is a flowchart showing a failure determination process according to the first embodiment; FIG. 3 is a graph showing a change in pressure with time obtained from a hydrogen gas pressure sensor; FIG. 4 is a flowchart showing a failure determination process according to a second embodiment; FIG. 5 is a flowchart showing a failure determination process according to a third embodiment; FIG. 6 is a diagram showing the outline of a fuel cell system according to a fourth embodiment; FIG. 7 is a flowchart showing a failure determination process according to the fourth embodiment; FIG. 8 is a diagram showing the outline of a fuel cell system according to a fifth embodiment; and FIG. 9 is a flowchart showing a failure determination process according to the fifth embodiment;Detailed Description of EmbodimentsA. First EmbodimentFIG. 1 is a diagram showing the outline of a fuel cell system 10 according to a first embodiment. The fuel cell system 10 according to the first embodiment is mounted in, for example, a fuel cell vehicle, and is used as a power generation device for driving a driving motor of the fuel cell vehicle. The fuel cell system 10 can be used as a stationary power generation device. The fuel cell system 10 includes a fuel cell (FC) 100, an air passage 210, a hydrogen gas passage 310, and a controller 500.The fuel cell 100 according to the first embodiment is a polymer electrolyte fuel cell. The fuel cell 100 has a stack structure in which a plurality of cells are stacked. Each of the cells includes: a membrane electrode assembly in which an electrode catalyst layer is disposed on opposite surfaces of an electrolyte membrane; and a pair of separators between which the membrane electrode assembly is interposed. In each of the cells, hydrogen gas is supplied to an anode side of the membrane electrode assembly as fuel gas, and air is supplied to a cathode side as oxidizing gas. Consequently, an electromotive force is generated by an electrochemical reaction. The respective cells are connected in series with each other. In the first embodiment, a coolant passage 410 through which a coolant for cooling the fuel cell 100 circulates is connected to the fuel cell 100. Heat in the coolant circulating through the coolant passage 410 is dissipated through a radiator 420.The air passage 210 includes: an air supply passage 211 through which air is supplied to the fuel cell 100; and an air discharge passage 212 through which air is discharged from the fuel cell 100. In the air supply passage 211, an air cleaner 220, a compressor (ACP) 230, and an air intake valve 240 are disposed in this order from the upstream side. An air discharge valve 250 is disposed in the air discharge passage 212.The air cleaner 220 removes foreign matter in air and introduces air into the air supply passage 211.The compressor 230 compresses the air introduced from the air cleaner 220 into the air supply passage 211, and supplies the compressed air to the fuel cell 100. As the compressor 230, for example, a supercharger or a Roots pump may be used. In order to cool the high temperature air compressed by the compressor 230, an intercooler may be disposed downstream of the compressor 230.The air inlet valve 240 is disposed in the air supply passage 211 between the compressor 230 and the fuel cell 100. The air inlet valve 240 is a valve for opening and closing the air supply passage 211.The air discharge valve 250 is a valve for opening and closing the air discharge passage 212. The controller 500 may adjust a pressure of air flowing through the cathode side in the fuel cell 100 by adjusting an opening degree of the air discharge valve 250.The hydrogen gas channel 310 includes: the hydrogen gas supply channel 311, through which hydrogen gas is supplied to the fuel cell 100; and the hydrogen gas discharge channel 312, through which hydrogen gas is discharged from the fuel cell 100. In the first embodiment, the hydrogen gas channel 310 includes a hydrogen gas circulation channel 313 for circulating the hydrogen gas discharged from the fuel cell 100 back into the fuel cell 100. In the hydrogen gas supply passage 311, a hydrogen gas supply portion 320, the hydrogen gas inlet valve 330, and the hydrogen gas pressure sensor (P) 340 are arranged in this order from the upstream side. In the hydrogen gas discharge passage 312, a gas-liquid separator 350 and the hydrogen gas discharge valve 370 are disposed in this order from the upstream side. In the hydrogen gas circulation channel 313, a hydrogen pump (HP) 360 is disposed.The hydrogen gas supply portion 320 supplies hydrogen gas to the hydrogen gas supply channel 311. In the first embodiment, the hydrogen gas supply section 320 includes: a hydrogen tank in which hydrogen is stored; and a main shut-off valve of the hydrogen tank. The main stop valve is a valve for opening and closing a connection portion between the hydrogen tank and the hydrogen gas supply passage 311.The hydrogen gas inlet valve 330 is disposed in the hydrogen gas supply passage 311 between the hydrogen gas supply portion 320 and the fuel cell 100. The hydrogen gas inlet valve 330 is a valve for opening and closing the hydrogen gas supply passage 311. The hydrogen gas inlet valve 330 may be configured as an injector, for example.The hydrogen gas pressure sensor 340 is disposed in the hydrogen gas passage 310 that is disposed downstream of the hydrogen gas inlet valve 330 and upstream of the hydrogen gas discharge valve 370. The hydrogen gas pressure sensor 340 is a sensor for obtaining a pressure P from a gas in the hydrogen gas passage 310. The controller 500 controls the opening degree of the hydrogen gas inlet valve 330 using the pressure P obtained from the hydrogen gas pressure sensor 340 such that the amount of hydrogen gas supplied to the fuel cell 100 can be adjusted.The gas-liquid separator 350 separates water generated by power generation of the fuel cell 100 from the hydrogen gas (anode off gas) discharged from the fuel cell 100.The hydrogen pump 360 re-introduces the hydrogen gas, from which the generated water is separated by the gas-liquid separator 350, downstream of the hydrogen gas inlet valve 330 of the hydrogen gas supply channel 311, through the hydrogen gas circulation channel 313, and circulates the hydrogen gas to the fuel cell 100.The hydrogen gas discharge valve 370 is disposed in the hydrogen gas discharge passage 312 between the gas-liquid separator 350 and the air discharge passage 212. The hydrogen gas discharge valve 370 is a valve for opening and closing the hydrogen gas discharge passage 312. The controller 500 causes the hydrogen gas discharge valve 370 to be opened so that the generated water and the anode off gas separated by the gas-liquid separator 350 can be discharged. The generated water and the anode off gas discharged from the hydrogen gas discharge valve 370 flow to the downstream side of the air discharge valve 250 in the air discharge passage 212 and are discharged from the fuel cell system 10.The controller 500 is configured as a computer including a central processing unit (CPU), a memory, and an interface circuit through which the respective components are connected. The CPU executes a control program stored in the memory such that it can be determined whether the air intake valve 240 and the air exhaust valve 250 are normally closed based on a state of lowering the pressure P of a gas in the hydrogen gas passage 310 acquired from the hydrogen gas pressure sensor 340. In the first embodiment, the controller 500 controls the opening and closing of the air inlet valve 240, the air outlet valve 250, the hydrogen gas inlet valve 330, and the hydrogen gas outlet valve 370. The controller 500, the air inlet valve 240, the air outlet valve 250, the hydrogen gas inlet valve 330, and the hydrogen gas outlet valve 370 may be operated by a battery (not illustrated) even after the fuel cell system 10 is stopped.FIG. 2 is a flowchart showing a failure determination process according to the first embodiment performed by the controller 500. In the first embodiment, the process is performed by the controller 500 after an operation for stopping the fuel cell system 10 is performed. In the first embodiment, the operation for stopping the fuel cell system 10 refers to an operation in which a start switch (SW) 510 of the fuel cell system 10 is turned off. First, the controller 500 causes the hydrogen gas inlet valve 330 and the hydrogen gas discharge valve 370 to be closed (step S 110). The controller 500 causes the air inlet valve 240 and the air outlet valve 250 to be closed (step S 120). Step S 110 or step S 120 may be performed first, or step S 110 and step S 120 may both be performed simultaneously. In the first embodiment, in step S 110, the controller 500 causes the hydrogen gas discharge valve 370 to be closed, and then controls the hydrogen gas supply portion 320 and the hydrogen gas inlet valve 330 such that the hydrogen gas passage 310 is set to a predetermined pressure. Next, the controller 500 causes the main shut-off valve of the hydrogen gas supply portion 320 and the hydrogen gas inlet valve 330 to be closed. In step S 120, the controller 500 causes the compressor 230 to be stopped and causes the air intake valve 240 and the air exhaust valve 250 to be closed. By performing step S 110 and step S 120, the power generation of the fuel cell 100 is stopped.Next, the controller 500 determines whether a predetermined time period (for example, 3 hours after the air inlet valve 240 and the air outlet valve 250 are caused to be closed) has elapsed (step S 130), "The predetermined time period" may be determined by experimentally obtaining in advance a time period used for stabilizing the pressure P of a gas in the hydrogen gas passage 310 after causing the air inlet valve 240, the air outlet valve 250, the hydrogen gas inlet valve 330, and the hydrogen gas outlet valve 370 to be closed in a case where the air inlet valve 240, the air outlet valve 250, the hydrogen gas inlet valve 330, and the hydrogen gas outlet valve 370 are normally closed. In a case where the predetermined period of time has not elapsed (step S 130: NO), the controller 500 counts the elapsed time and returns to step S 130.On the other hand, in a case where the predetermined time period has elapsed (step S 130: YES), the controller 500 determines whether the pressure P of a gas in the hydrogen gas channel 310 is equal to or lower than a predetermined value (threshold value A) (step S 140). In the first embodiment, "the threshold value A" is a value determined based on the gas pressure in the hydrogen gas passage 310 when the predetermined time period has elapsed in a case where the air inlet valve 240, the air outlet valve 250, the hydrogen gas inlet valve 330, and the hydrogen gas outlet valve 370 are normally closed. The threshold value A may be, for example, a pressure slightly lower than the atmospheric pressure. In a case where the pressure P of a gas in the hydrogen gas passage 310 is equal to or lower than the threshold value A (step S 140: YES), the controller 500 determines that the air inlet valve 240 and the air outlet valve 250 are normally closed (step S 150). On the other hand, in a case where the pressure P of a gas in the hydrogen gas passage 310 is not less than or equal to the threshold value A (step S 140: NO), the controller 500 determines that the air inlet valve 240 and / or the air outlet valve 250 are faulty (step S 160), "Faulty" refers to a state where the valve is not normally closed. In a case where the air intake valve 240 and / or the air exhaust valve 250 is / are faulty, the controller 500 records the detection of a fault on a memory in a nonvolatile manner. Thus, for example, a diagnostic device connected to the controller 500 reads the record such that a user can recognize that a fault occurs in the fuel cell system 10.FIG. 3 is a graph showing a change with time of the pressure P acquired from the hydrogen gas pressure sensor 340. The graph shows the pressure P of a gas in the hydrogen gas passage 310 over the lapse of time after causing the air inlet valve 240, the air outlet valve 250, the hydrogen gas inlet valve 330, and the hydrogen gas outlet valve 370 to be closed. In an original state (the left end of the graph), the inside of the hydrogen gas passage 310 is pressurized by the supply of the hydrogen gas from the hydrogen gas supply portion 320. This configuration is applied to further reduce deterioration of the membrane electrode assembly caused when remaining hydrogen gas and oxygen in the fuel cell 100 react with each other in a cell surface in a non-uniform state while power generation of the fuel cell system 10 is stopped. Therefore, the pressure P of a gas in the hydrogen gas passage 310 is higher than the atmospheric pressure. On the air passage 210 side, the pressure of a gas in the air supply passage 211 is the same as the atmospheric pressure because the compressor 230 is stopped when the controller 500 causes the air intake valve 240 to be closed. An outlet port of the air discharge duct 212 is connected to the outside air. Therefore, the pressure of a gas in the air discharge passage 212 is also the same as the atmospheric pressure.After the air inlet valve 240, the air outlet valve 250, the hydrogen gas inlet valve 330, and the hydrogen gas outlet valve 370 are caused to be closed, the hydrogen gas enters the hydrogen gas channel 310 from the anode side to the cathode side through the membrane electrode assembly of the fuel cell 100. Therefore, the pressure P of a gas in the hydrogen gas channel 310 decreases with time. In a case where the hydrogen gas permeates into the cathode side, the hydrogen gas reacts with oxygen included in the air in the air passage 210 and generates water. Due to the reaction, the hydrogen gas and the oxygen in the air passage 210 are consumed, so that the gas pressure in the air passage 210 decreases.In a case where the air inlet valve 240 and the air outlet valve 250 are normally closed, the air passage 210 is sealed between the air inlet valve 240 and the air outlet valve 250. Therefore, the pressure of a gas in the air passage 210 between the air inlet valve 240 and the air outlet valve 250 decreases to a pressure (negative pressure) lower than the atmospheric pressure because the hydrogen gas permeating from the anode side and the oxygen included in the air react with each other and consume. The pressure P of a gas in the hydrogen gas channel 310 also decreases to a negative pressure due to the penetration of the hydrogen gas to the cathode side.On the other hand, in a case where the air inlet valve 240 and / or the air outlet valve 250 is / are faulty, the air passage 210 between the air inlet valve 240 and the air outlet valve 250 is not sealed. Therefore, since air flows into the air duct 210, the pressure of a gas in the air duct 210 between the air inlet valve 240 and the air outlet valve 250 is higher than that in a case where the air inlet valve 240 and the air outlet valve 250 are normally closed (is the same as the atmospheric pressure). Accordingly, the amount of hydrogen gas permeating into the anode side is smaller than in a case where the air inlet valve 240 and the air outlet valve 250 are normally closed. Therefore, the pressure P of a gas in the hydrogen gas passage 310 is also higher than that in a case where the air inlet valve 240 and the air outlet valve 250 are normally closed (is the same as the atmospheric pressure). Accordingly, in the first embodiment, it can be determined whether the air inlet valve 240 and the air outlet valve 250 disposed on the air passage 210 side are faulty by measuring the pressure P of the hydrogen gas passage 310.In the fuel cell system 10 according to the first embodiment, it can be determined whether the air inlet valve 240 and the air outlet valve 250 are normally closed by using the hydrogen gas pressure sensor 340 to adjust the amount of hydrogen gas supplied to the fuel cell 100 from the hydrogen gas inlet valve 330 without disposing an air pressure sensor for obtaining the pressure of a gas in the air passage 210. Accordingly, the structure of the fuel cell system 10 can be simplified and the cost can be further reduced.According to the first embodiment, whether the air inlet valve 240 and the air outlet valve 250 are normally closed may be determined based on whether the pressure P of the gas in the hydrogen gas passage 310 acquired from the hydrogen gas pressure sensor 340 is equal to or lower than the predetermined value (threshold A). Therefore, it may be determined whether the air intake valve 240 and the air exhaust valve 250 are faulty based on a state of lowering the pressure P. According to the first embodiment, whether or not the air intake valve 240 and the air exhaust valve 250 are normally closed can be easily determined by a simple comparison operation between the pressure P and the threshold value A.According to the first embodiment, whether the air inlet valve 240 and the air outlet valve 250 are normally closed may be determined based on whether the pressure P of a gas in the hydrogen gas passage 310 acquired from the hydrogen gas pressure sensor 340 is equal to or less than the pressure of a gas in the hydrogen gas passage 310 when the predetermined period of time has elapsed in a case where the air inlet valve 240, the air outlet valve 250, the hydrogen gas inlet valve 330, and the hydrogen gas outlet valve 370 are normally closed. Therefore, it can be accurately determined whether the air intake valve 240 and the air exhaust valve 250 are normally closed based on the pressure in a case where the air intake valve 240 and the air exhaust valve 250 are normally closed.B. Second EmbodimentFIG. 4 is a flowchart showing a failure determination process according to a second embodiment. In the second embodiment, the configuration of the fuel cell system 10 is the same as that of the first embodiment (FIG. 1 ). The content of the fault determination process according to the second embodiment is different from that of the first embodiment (FIG. 2 ). In FIG. 4, the same contents of the process as those of FIG. 2 are described using the same step numbers as those of FIG. 2.In the fuel cell system 10 according to the second embodiment, the controller 500 causes the hydrogen gas inlet valve 330 and the hydrogen gas discharge valve 370 to be closed (step S 110), and causes the air inlet valve 240 and the air discharge valve 250 to be closed (step S 120). Next, the controller 500 determines whether a period in which the pressure P of a gas in the hydrogen gas passage 310 acquired by the hydrogen gas pressure sensor 340 increases is present in a predetermined period in which the pressure of a gas in the hydrogen gas passage 310 decreases (step S 140 b). In a case where the period in which the pressure P of a gas in the hydrogen gas passage 310 increases is not present (step S 140 B: NO), the controller 500 determines that the air inlet valve 240 and the air outlet valve 250 are normally closed (step S 150). On the other hand, in a case where the period in which the pressure P of a gas in the hydrogen gas passage 310 increases is present (step S 140 b:YES), the air passage 210 between the air inlet valve 240 and the air outlet valve 250 is not sealed, and air can flow into the air passage 210. Therefore, the controller 500 determines that the air intake valve 240 and / or the air exhaust valve 250 is / are faulty (step S 160). In the second embodiment, "the predetermined period" is the same as "the predetermined period" in the first embodiment, for example.In the fuel cell system 10 according to the second embodiment, whether the air inlet valve 240 and the air outlet valve 250 are normally closed may be determined based on whether the period in which the pressure P of a gas in the hydrogen gas passage 310 obtained by the hydrogen gas pressure sensor 340 increases exists in the predetermined period in which the pressure of a gas in the hydrogen gas passage 310 decreases. Therefore, in the second embodiment, it can be determined whether the air intake valve 240 and the air exhaust valve 250 are faulty based on a state of lowering the pressure P. According to the second embodiment, it can be easily determined whether the air intake valve 240 and the air exhaust valve 250 are normally closed based on whether there is an increase in the pressure P.C. Third EmbodimentFIG. 5 is a flowchart illustrating a failure determination process according to a third embodiment. In the third embodiment, the configuration of the fuel cell system 10 is the same as that of the first embodiment (FIG. 1 ). The content of the fault determination process according to the third embodiment is different from that of the first embodiment (FIG. 2 ). In FIG. 5, the same contents of the process as those of FIG. 2 are described using the same step numbers as those of FIG. 2.Regarding the fault determination process, points different from the first embodiment will be described. In the fuel cell system 10 according to the third embodiment, in a case where the controller 500 determines that the air inlet valve 240 and / or the air outlet valve 250 is faulty (step S 160), the controller 500 causes the compressor 230 disposed upstream of the air inlet valve 240 of the air passage 210 to be driven (step S 170 c). By driving the compressor 230, air is blown to the air inlet valve 240 and the air outlet valve 250. Therefore, in a case where the air inlet valve 240 and / or the air outlet valve 250 is / are not normally closed by foreign matter stuck therein, the foreign matter can be removed by inflating air on the foreign matter. After driving the compressor 230, the controller 500 returns to step S 110 and performs the failure determination process. The driving of the compressor 230 is not particularly limited, and is preferably performed after the air inlet valve 240 and the air outlet valve 250 are caused to open. In a case where the failure is not corrected even after the driving of the compressor 230 is performed three times, for example, the controller 500 may end the process without returning to step S 110.In the fuel cell system 10 according to the third embodiment, in a case where the air inlet valve 240 and / or the air outlet valve 250 is / are not normally closed by foreign matter stuck therein, the foreign matter can be removed by driving the compressor 230. Consequently, the error caused by the sticking of foreign matter into the air intake valve 240 or the air exhaust valve 250 can be solved.In the above description, the third embodiment is combined with the first embodiment. However, the third embodiment may be combined with the second embodiment. In this case, the controller 500 performs step S 170 cafter step S 160 shown in FIG. 4.D. Fourth EmbodimentFIG. 6 is a diagram showing the outline of a fuel cell system 10 daccording to a fourth embodiment. FIG. 7 is a flowchart illustrating a failure determination process according to a fourth embodiment. The fuel cell system 10 daccording to the fourth embodiment is different from that according to the first embodiment (FIG. 1 ) in that a temperature sensor 430 is disposed in the coolant passage 410. The fault determination process according to the fourth embodiment is different from that of the first embodiment (FIG. 2 ).The temperature sensor 430 is disposed in the coolant passage 410 on a side where the coolant is discharged from the fuel cell 100. The controller 500 indirectly acquires (detects) a temperature of a gas in the hydrogen gas channel 310 by causing the temperature sensor 430 to acquire a temperature T of the coolant flowing through the coolant channel 410. For example, instead of disposing the temperature sensor 430 in the coolant passage 410, the temperature sensor 430 may be attached to the fuel cell 100 or the hydrogen gas passage 310 to acquire (determine) a temperature of a gas in the hydrogen gas passage 310 based on the measured temperature.In the fuel cell system 10 daccording to the fourth embodiment, the controller 500 causes the hydrogen gas inlet valve 330 and the hydrogen gas discharge valve 370 to be closed (step S 110), and causes the air inlet valve 240 and the air discharge valve 250 to be closed (step S 120). Next, the controller 500 determines whether the temperature T acquired from the temperature sensor 430 is equal to or lower than a predetermined value (threshold B) (step S 130 d). "The threshold B" refers to, for example, a normal temperature (35 degrees Celsius). In a case where the temperature T is not equal to or less than the threshold B (step S 130 d: NO), the controller 500 repeats the process of step S 130 duntil the temperature T becomes equal to or less than the threshold B (step S 130 d: YES). On the other hand, in a case where the temperature T is equal to or lower than the threshold B (step S 130 D: YES), the controller 500 determines whether the pressure P of a gas in the hydrogen gas passage 310 is equal to or lower than the threshold A (step S 140). In a case where the pressure P of a gas in the hydrogen gas passage 310 is equal to or lower than the threshold value A (step S 140: YES), the controller 500 determines that the air inlet valve 240 and the air outlet valve 250 are normally closed (step S 150). On the other hand, in a case where the pressure P of a gas in the hydrogen gas passage 310 is not less than or equal to the threshold value A (step S 140: NO), the controller 500 determines that the air intake valve 240 and / or the air exhaust valve 250 are faulty (step S 160). Instead of a fixed value such as a normal temperature, the threshold value B may be an ambient temperature at this time measured by an ambient temperature sensor.In the fuel cell system 10 daccording to the fourth embodiment, in a case where it is determined whether the air inlet valve 240 and the air outlet valve 250 are normally closed using a pressure P obtained from the hydrogen gas pressure sensor 340 from a gas in the hydrogen gas passage 310, an effect of the temperature on the change in the pressure in the hydrogen gas passage can be further reduced. Therefore, it can be more appropriately determined whether the air inlet valve 240 and the air outlet valve 250 are normally closed.In the above description, the fourth embodiment is combined with the first embodiment. However, the fourth embodiment may be combined with the second embodiment. In this case, the controller 500 performs step S 140 bafter step S 130 dshown in FIG. 4.By combining the fourth embodiment with the third embodiment, in a case where the controller 500 determines that the air intake valve 240 and / or the air exhaust valve 250 is / are faulty (step S 160), the controller 500 may perform driving of the compressor 230 (FIG. 5, step S 170 c).E. Fifth EmbodimentFIG. 8 is a diagram showing the outline of a fuel cell system 10 eaccording to a fifth embodiment. FIG. 9 is a flowchart showing a failure determination process according to the fifth embodiment. The fuel cell system 10 eaccording to the fifth embodiment is different from that according to the first embodiment (FIG. 1 ) in that the fuel cell system 10 eincludes an alarm portion 600. The fault determination process according to the fifth embodiment is different from that of the first embodiment (FIG. 2 ).The alarm section 600 alarms that the air inlet valve 240 and / or the air outlet valve 250 is / are faulty. For example, in a case where the fuel cell system 10 eis mounted in a fuel cell vehicle, the alarm section 600 may display a warning or the like about a failure on a dashboard of the fuel cell vehicle. The alarm section 600 may alert about an error using a warning sound generated by a buzzer.Regarding the fault determination process, points different from the first embodiment will be described. In the fuel cell system 10 eaccording to the fifth embodiment, in a case where the controller 500 determines that the air inlet valve 240 and / or the air outlet valve 250 is / are faulty (step S 160), the controller 500 causes the alarm portion 600 to alert that the air inlet valve 240 and / or the air outlet valve 250 is / are abnormal (step S 180 e).In the fuel cell system 10 eaccording to the fifth embodiment, the alarm section 600 alarms a failure in a case where the air inlet valve 240 and the air outlet valve 250 are not normally closed. Therefore, the alarm section 600 can cause a user to repair or check the fuel cell system 10 e. Consequently, deterioration of the membrane electrode assembly of the fuel cell 100 caused when exposed to the air for a long period of time can be further reduced.In the above description, the fifth embodiment is combined with the first embodiment. However, the fifth embodiment may be combined with any one of the embodiments two to four. For example, by combining the fifth embodiment with the third embodiment, in a case where the failure is not resolved even after the driving of the compressor 230 is performed (FIG. 5, step S 170 c), the controller 500 may cause the alarm section 600 to alert that the air inlet valve 240 and / or the air outlet valve 250 is / are faulty (FIG. 9, step S 180 e).F. Other Embodiment 1In step S 140 of the fault determination process shown in FIG. 2, the controller 500 determines whether the pressure P of a gas in the hydrogen gas passage 310 is equal to or lower than the threshold value A. On the other hand, the controller 500 may determine whether the air intake valve 240 and the air exhaust valve 250 are normally closed based on an average change rate Q of the pressure P of a gas in the hydrogen gas passage 310 in the predetermined period. As shown in the following expression (1), the average change rate Q may be obtained using the pressure P 1 of a gas in the hydrogen gas channel 310 at time t 1, and a pressure P 2 of a gas in the hydrogen gas channel 310 at time t 2 after time t 1.In this case, the controller 500 may determine that the air inlet valve 240 and the air outlet valve 250 are faulty in a case where the average change rate Q is equal to or greater than a threshold C. The threshold C may be determined based on the expression (1) by experimentally obtaining in advance the pressure P 1 of a gas in the hydrogen gas passage 310 at the time t 1 and the pressure P 2 of a gas in the hydrogen gas passage 310 at the time t 2 after the time t 1 in a case where the air inlet valve 240, the air outlet valve 250, the hydrogen gas inlet valve 330, and the hydrogen gas outlet valve 370 are normally closed. Even in a case where the failure determination process using the average change rate Q of the pressure P is used, it can be determined whether the air inlet valve 240 and the air outlet valve 250 are faulty based on a state of lowering the pressure P from a gas in the hydrogen gas passage 310.G. Other Embodiment 2In a case where the controller 500 determines that the air intake valve 240 and / or the air exhaust valve 250 is / are faulty, the controller 500 causes the compressor 230 to be driven in step S 170 cof the fault determination process shown in FIG. 5. On the other hand, the controller 500 may cause not only the compressor 230 but also the hydrogen gas supply portion 320 to be driven. "Cause the hydrogen gas supply portion 320 to be driven" means that the controller 500 causes the main shut-off valve of the hydrogen tank to be open. By driving the hydrogen gas supply portion 320, the hydrogen gas can be blown to the hydrogen gas inlet valve 330 and the hydrogen gas discharge valve 370. Consequently, both a failure caused by the sticking of foreign matter in the air inlet valve 240 or the air outlet valve 250 and a failure caused by the sticking of foreign matter in the hydrogen gas inlet valve 330 or the hydrogen gas outlet valve 370 can be solved. Although there are no particular restrictions on this, it is preferable that the controller 500 causes the hydrogen gas inlet valve 330 and the hydrogen gas outlet valve 370 to be open before causing the hydrogen gas supply portion 320 to be driven. Instead of causing the compressor 230 and the hydrogen gas supply portion 320 to be driven, the controller 500 may cause the hydrogen gas supply portion 320 to be driven in a case where a failure is not recovered even after the driving of the compressor 230 is performed a plurality of times. In this case, the consumption of the hydrogen gas can be further reduced as compared with a case where not only the compressor 230 but also the hydrogen gas supply portion 320 is driven.The invention is not limited to the above-described embodiments, and various configurations can be realized within a scope not deviating from the scope of the invention. In order to solve some or all of the problems described above, or in order to achieve some or all of the effects described above, for example, the technical features in the embodiments corresponding to the technical features in the respective aspects described in the "Summary of the Invention" may be appropriately replaced or combined with each other. The technical features may be appropriately removed unless they are referred to as indispensable features in this specification.

Claims

A fuel cell system (10; 10d; 10e) comprising: a fuel cell (100); an air duct (210) including an air supply duct (211) through which air is supplied to the fuel cell (100), and an air discharge duct (212) through which the air is discharged from the fuel cell (100); an air inlet valve (240) configured to open and close the air supply duct (211); an air discharge valve (250) configured to open and close the air discharge duct (212); a hydrogen gas duct (310) including a hydrogen gas supply duct (311) through which hydrogen gas is supplied to the fuel cell (100), and a hydrogen gas discharge duct (312) through which the hydrogen gas is discharged from the fuel cell (100); a hydrogen gas inlet valve (330) configured to open and close the hydrogen gas supply duct (311); a hydrogen gas discharge valve (370) configured to open and close the hydrogen gas discharge passage (312); a hydrogen gas pressure sensor (340) configured to acquire a pressure of a gas in the hydrogen gas passage (310), which is disposed downstream of the hydrogen gas inlet valve (330) and upstream of the hydrogen gas discharge valve (370); and a controller (500) configured to determine whether the air inlet valve (240) and the air discharge valve (250) are normally closed based on a state of lowering the pressure acquired by the hydrogen gas pressure sensor (340) after the hydrogen gas inlet valve (330), the hydrogen gas discharge valve (370), the air inlet valve (240) and the air discharge valve (250) are caused to close.The fuel cell system (10; 10d; 10e) according to claim 1, wherein, when a predetermined period of time has elapsed after causing the hydrogen gas inlet valve (330), the hydrogen gas outlet valve (370), the air inlet valve (240), and the air outlet valve (250) to be closed, the controller (500) is configured to determine that the air inlet valve (240), the air outlet valve (250) are normally closed in a case where the decreased pressure is less than or equal to a predetermined value, and determine that the air inlet valve (240) and / or the air outlet valve (250) is / are not normally closed in a case where the decreased pressure is not less than or equal to a predetermined value.The fuel cell system (10; 10d; 10e) according to claim 2, wherein the predetermined value is a value determined based on the decreased pressure when the predetermined time period has elapsed in a case where the air inlet valve (240), the air outlet valve (250), the hydrogen gas inlet valve (330), and the hydrogen gas outlet valve (370) are normally closed.The fuel cell system (10; 10d; 10e) according to claim 1, wherein the controller (500) is configured to determine that the air inlet valve (240) and / or the air outlet valve (250) is / are not normally closed in a predetermined period in which the pressure decreases after the hydrogen gas inlet valve (330), the hydrogen gas outlet valve (370), the air inlet valve (240) and the air outlet valve (250) are caused to close, in a case where a period in which the pressure increases is present, and determine that the air inlet valve (240) and the air outlet valve (250) are normally closed in a case where the period in which the pressure increases is not present.The fuel cell system (10; 10d; 10e) according to any one of claims 1 to 4, further comprising a compressor (230) configured to supply compressed air to the fuel cell (100), the compressor (230) being disposed upstream of the air inlet valve (240) of the air duct (210), wherein the controller (500) is configured to drive the compressor (230) in a case where the controller (500) determines that the air inlet valve (240) and / or the air outlet valve (250) is / are not normally closed.The fuel cell system (10; 10d; 10e) according to any one of claims 1 to 5, further comprising a temperature sensor (430) configured to acquire a temperature of a gas in the hydrogen gas channel (310), wherein the controller (500) is configured to determine whether the air inlet valve (240) and the air outlet valve (250) are normally closed based on the pressure acquired from the hydrogen gas pressure sensor (340) in a case where the temperature acquired from the temperature sensor (430) is equal to or lower than a predetermined value.The fuel cell system (10; 10d; 10e) according to any one of claims 1 to 6, further comprising an alarm section (600) configured to alarm that the air inlet valve (240) and / or the air outlet valve (250) is / are not normally closed, wherein the controller (500) is configured to cause the alarm section (600) to alarm about a failure in a case where the controller (500) determines that the air inlet valve (240) and / or the air outlet valve (250) is / are not normally closed.A failure diagnosis method for a fuel cell system, the failure diagnosis method comprising: obtaining a pressure of a gas in a hydrogen gas passage (310) disposed downstream of a hydrogen gas inlet valve (330) and upstream of a hydrogen gas discharge valve (370) after causing the hydrogen gas inlet valve (330), the hydrogen gas discharge valve (370), an air inlet valve (240), and an air discharge valve (250) to be closed, wherein the hydrogen gas inlet valve (330) is configured to open and close a hydrogen gas supply passage (311) through which hydrogen gas is supplied to a fuel cell (100), wherein the hydrogen gas discharge valve (370) is configured to open and close a hydrogen gas discharge passage (312) through which hydrogen gas is discharged from the fuel cell (100), wherein the air inlet valve (240) is configured to open and close, an air supply passage (211) through which air is supplied to the fuel cell (100), and wherein the air discharge valve (250) is configured to open and close an air discharge passage (212) through which air is discharged from the fuel cell (100); and determining, based on a state of lowering the related pressure, whether the air inlet valve (240) and the air discharge valve (250) are normally closed.

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