Fuel cell system

Abstract

To provide a fuel cell system capable of securely detecting whether or not an entrance side sealing valve or an outlet side sealing valve is abnormal, even in the case of occurence of minute leakage.SOLUTION: A fuel cell system detects output voltage of a fuel cell 18 by using a voltage sensor 110 in the case that new fuel gas is supplied to an anode passage at the time of soaking after stop-time power generation processing in a state of driving an entrance side sealing valve 118 and an outlet side sealing valve 120 into a closed state; and determines that there exists an abnormal state of the entrance side sealing valve 118 or the outlet side sealing valve 120 being in an open state when the detected output voltage is equal to or higher than a threshold voltage.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a fuel cell system that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas.

Background Art

[0002] In recent years, research and development have been carried out on fuel cells (FCs) that contribute to energy efficiency in order to enable more people to access affordable, reliable, sustainable, and advanced energy.

[0003] For example, Japanese Unexamined Patent Application Publication No. 2008-153079 discloses an abnormality determination process for an air inlet shut-off valve (21) and an air outlet shut-off valve (22) of a fuel cell system. (See

[0045] of the same publication).

[0004] In this abnormality determination process, when the fuel cell system is stopped, both the air inlet shut-off valve (21) and the air outlet shut-off valve (22) are closed by a control signal. When deterioration of the cathode electrode is detected despite being in the closed state, it is determined that the air inlet shut-off valve (21) and the air outlet shut-off valve (22) are abnormal. (Summary of the same publication).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in the fuel cell system disclosed in the above publication, when the fuel cell system is stopped, if the air inlet shut-off valve (21) and the air outlet shut-off valve (22) are not normally closed, air enters the cathode electrode from the outside through the malfunctioning air shut-off valve.

[0007] Then, the carbon contained in the cathode electrode is oxidized, and the potential of the cathode electrode becomes higher than the potential during the operation of the fuel cell system. The above publication describes that by detecting this high potential, it is possible to reliably detect that the air shut-off valve is not in the normal closed state (

[0040] ,

[0041] of the same publication).

[0008] However, the generation of a high potential due to carbon oxidation has a problem that it is difficult to detect a minute air leakage such as being fixed in a state where the valve opening degree of the air shut-off valve is small. An object of the present invention is to solve the above-described problems.

Means for Solving the Problems

[0009] One aspect of the present invention is a fuel cell system that generates electricity by an electrochemical reaction between an oxidant gas supplied to a cathode flow path along a cathode electrode of a fuel cell through an inlet-side shut-off valve from an air compressor and a fuel gas supplied to an anode flow path along the anode electrode of the fuel cell from a fuel tank, and the oxidant off-gas after power generation flows to the outside through an outlet-side shut-off valve, comprising: a voltage sensor that detects an output voltage between the anode electrode and the cathode electrode; and a control device that, when the system stops, continues power generation, consumes the oxidant gas remaining from the outlet side of the inlet-side shut-off valve to the inlet side of the outlet-side shut-off valve, and then drives the inlet-side shut-off valve and the outlet-side shut-off valve to a closed state, and performs a stop-time power generation process for shutting off the supply of the fuel gas from the fuel tank to the anode flow path. The control device detects the output voltage with the voltage sensor when a new fuel gas is supplied to the anode flow path after the stop-time power generation process in a state where the inlet-side shut-off valve and the outlet-side shut-off valve are driven to a closed state, and when the detected output voltage is equal to or higher than a threshold voltage, determines that the inlet-side shut-off valve or the outlet-side shut-off valve is in an abnormal open state.

Advantages of the Invention

[0010] According to the present invention, during system shutdown, a power generation process during shutdown is performed, in which power generation is continued to consume the oxidant gas in the cathode flow path and the fuel gas is retained in the anode flow path. By this power generation process during shutdown, fuel gas diffuses from the anode flow path into the cathode flow path through the electrolyte membrane-electrode structure during soaking after the power generation process during shutdown.

[0011] With the inlet-side shutoff valve and the outlet-side shutoff valve driven to the closed state, and with fuel gas diffused into the cathode flow path during soaking, new fuel gas is supplied to the anode flow path. It is determined whether or not the output voltage detected by the voltage sensor becomes equal to or higher than the threshold voltage when the new fuel gas is supplied to the anode flow path. Based on this determination result, it is possible to reliably detect whether or not there is an abnormality in the inlet-side shutoff valve or the outlet-side shutoff valve even when a minute leak occurs. This contributes to energy efficiency improvement.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0013] [Embodiment] [Configuration] FIG. 1 is a schematic configuration diagram of a fuel cell vehicle 12 incorporating a fuel cell system 10 according to an embodiment of the present invention.

[0014] The fuel cell system 10 can also be incorporated into other moving bodies such as ships, aircraft and other flying bodies, and robots, etc., in addition to the fuel cell vehicle 12.

[0015] The fuel cell vehicle 12 is composed of a fuel cell system 10, an output unit 16 electrically connected to the fuel cell system 10, and a control device 15 that controls the entire fuel cell vehicle 12 (including the fuel cell system 10 and the output unit 16).

[0016] The control device 15 is not limited to one, and may be divided into two or more control devices, for example, for the fuel cell system 10 and the output unit 16.

[0017] The fuel cell system 10 is composed of a fuel cell stack (simply referred to as a fuel cell) 18, a fuel tank (hydrogen tank, fuel gas tank) 20, an oxidant gas supply device 22, a fuel gas supply device 24, and a refrigerant supply device 26.

[0018] The oxidant gas supply device 22 includes a compressor (CP) 28 which is an air compressor and a humidifier (HUM) 30.

[0019] The fuel gas supply device 24 includes an injector (INJ) 32, an ejector 34, and a gas-liquid separator 36. The injector 32 may be replaced by a pressure reducing valve.

[0020] The refrigerant supply device 26 includes a refrigerant pump (WP) 38 and a radiator 39. The output unit 16 includes a voltage conversion unit 42, a power storage unit 43, and a motor (electric motor) 46.

[0021] The voltage conversion unit 42 includes an inverter 45, a DC / DC converter (SUC) 40 which is a boost converter, and a DC / DC converter (SUDC) 41 which is a buck-boost converter.

[0022] The power storage unit 43 includes a high-voltage power storage device (high-voltage battery, HV BAT) 44, a DC / DC converter (SDC) 47 which is a buck converter, and a low-voltage power storage device (low-voltage battery, LV BAT) 48.

[0023] A load is connected to the power storage unit 43 which includes the voltage conversion unit 42 connected to the fuel cell stack 18 and the high-voltage power storage device 44. The load includes a motor 46 which is the main machine, a compressor 28 which is a high-voltage auxiliary machine supplied with power from the high-voltage power storage device 44, and, excluding the compressor 28, low-voltage auxiliary machines (for example, an air conditioner and the control device 15, various sensors, various solenoid valves, an injector 32, a refrigerant pump 38, etc. which will be described later) supplied with power from the low-voltage power storage device 48.

[0024] The DC / DC converter 40 boosts the output voltage Vfc which is the generated voltage of the DC voltage from the fuel cell stack 18, and applies a driving high voltage to the DC terminal of the inverter 45 and the DC / DC converter 41.

[0025] The DC / DC converter 41 step-down converts the driving high voltage to the battery voltage Vbh of the high-voltage power storage device 44 to charge the high-voltage power storage device 44.

[0026] The DC / DC converter 47 step-down converts the high-voltage battery voltage Vbh to the low-voltage battery voltage Vbl to charge the low-voltage power storage device 48.

[0027] A high voltage obtained by boosting the battery voltage Vbh by the DC / DC converter 41 and / or a high voltage obtained by boosting the output voltage Vfc by the DC / DC converter 40 is applied to the DC terminal of the inverter 45.

[0028] The inverter 45 converts the DC high voltage into three-phase AC to drive the motor 46. The inverter 45 converts the regenerative voltage of the motor 46 into a DC high voltage. This DC high voltage is step-down converted by the DC / DC converter 41 and applied to the high-voltage power storage device 44 to charge the high-voltage power storage device 44. The fuel cell vehicle 12 travels by the driving force generated by the motor 46.

[0029] The fuel cell stack 18 has a plurality of power generation cells 50 stacked thereon. The power generation cell 50 includes an electrolyte membrane-electrode structure 52, and separators 53 and 54 sandwiching the electrolyte membrane-electrode structure 52.

[0030] The electrolyte membrane-electrode structure 52 includes, for example, a solid polymer electrolyte membrane 55 which is a thin film of perfluorosulfonic acid containing moisture, and a cathode electrode 56 and an anode electrode 57 sandwiching the solid polymer electrolyte membrane 55.

[0031] The cathode electrode 56 and the anode electrode 57 have a gas diffusion layer (not shown) made of carbon paper or the like. A porous carbon particle having a platinum alloy supported on the surface is uniformly coated on the surface of the gas diffusion layer to form an electrode catalyst layer (not shown). The electrode catalyst layer is formed on both surfaces of the solid polymer electrolyte membrane 55.

[0032] On the surface of one separator 53 facing the electrolyte membrane-electrode structure 52, an oxidant gas inlet communication port 101 and an oxidant off-gas outlet communication port 102 are communicated, and a cathode flow path (oxidant gas flow path) 58 along the cathode electrode 56 is formed.

[0033] On the surface of the other separator 54 facing the electrolyte membrane-electrode structure 52, a fuel gas inlet communication port 103 and a fuel gas outlet communication port 104 are communicated, and an anode flow path (fuel gas flow path) 59 along the anode electrode 57 is formed.

[0034] A voltage sensor 110 for detecting the output voltage Vfc of the fuel cell stack 18 is provided between the wiring connecting the positive electrode terminal 108 and the negative electrode terminal 106 to the DC / DC converter 40. Further, a current sensor 112 for detecting the generated current Ifc is provided in the wiring connecting the positive electrode terminal 108 to the DC / DC converter 40.

[0035] The voltage sensor 110 and the current sensor 112 form a power generation state acquisition unit 115 for detecting the generated power as the power generation state. The voltage sensor 110 may be provided for each power generation cell 50 or for every plurality of power generation cells 50.

[0036] The compressor 28 is composed of a mechanical supercharger or the like. The mechanical supercharger is driven by a compressor motor (not shown) whose rotation is controlled by a three-phase AC output of a compressor inverter (not shown) to which the high-voltage battery voltage Vbh of the power storage device 44 is applied.

[0037] The compressor 28 has functions such as sucking and pressurizing outside air (atmospheric air, air) from the outside air intake port 113 and supplying it to the fuel cell stack 18 through the humidifier 30.

[0038] The humidifier 30 has a flow path 31A and a flow path 31B. In the flow path 31A, air (oxidant gas) compressed, heated, and dried by the compressor 28 flows. In the flow path 31B, oxidant off-gas, which is exhaust gas discharged from the oxidant off-gas outlet communication port 102 of the fuel cell stack 18 through the oxidant off-gas outlet 92, flows.

[0039] The humidifier 30 has a function of humidifying the oxidant gas supplied from the compressor 28. That is, the humidifier 30 moves the moisture contained in the oxidant off-gas through the internal porous membrane from the flow path 31B to the supply gas (oxidant gas) flowing in the flow path 31A for humidification, and supplies the humidified oxidant gas to the fuel cell stack 18 through the oxidant gas inlet 91.

[0040] In the oxidant gas supply passage 62 (including the oxidant gas supply passages 62A and 62B) from the outside air intake 113 to the oxidant gas inlet 91, an air flow sensor (AFS: flow rate sensor) 116, a compressor 28, an inlet side shutoff valve 118, and a humidifier 30 are provided in order from the outside air intake 113. The passages such as the oxidant gas supply passage 62 drawn with double lines are formed by piping (hereinafter the same). The inlet side shutoff valve 118 has a valve opening degree that can be variably controlled by the control device 15 and opens and closes the oxidant gas supply passage 62.

[0041] In the oxidant off-gas discharge passage 63 communicating with the oxidant off-gas outlet 92, a humidifier 30 and an outlet side shutoff valve 120 that also functions as a back pressure valve are provided in order from the oxidant off-gas outlet 92. The valve opening degree of the outlet side shutoff valve 120 can be variably controlled by the control device 15 and opens and closes the oxidant off-gas discharge passage 63.

[0042] A bypass passage 66 that communicates the oxidant gas supply passage 62 and the oxidant off-gas discharge passage 63 is provided between the suction port of the inlet side shutoff valve 118 and the discharge port of the outlet side shutoff valve 120. A bypass valve 122 that opens and closes the bypass passage 66 is provided in the bypass passage 66.

[0043] The valve opening degree of the bypass valve 122 can be variably controlled by the control device 15. The bypass valve 122 adjusts the flow rate of the oxidant gas that bypasses the fuel cell stack 18. The confluence passage of the bypass passage 66 and the oxidant off-gas discharge passage 63 communicates with the discharge passage 64.

[0044] The fuel tank 20 is a container that includes an electromagnetic hydrogen shutoff valve 21 and stores high-purity hydrogen compressed at a high pressure.

[0045] The fuel gas (hydrogen) discharged from the fuel tank 20 is supplied to the inlet of the anode passage 59 through the injector 32 and the ejector 34 provided in the fuel gas supply passage 72 and via the fuel gas inlet 93 and the fuel gas inlet communication port 103 of the fuel cell stack 18.

[0046] In this case, a pressure sensor 73 for detecting (measuring) the gas pressure (anode pressure, fuel gas pressure) Pa of the fuel gas in the fuel gas supply passage 72 is provided in the fuel gas supply passage 72.

[0047] The outlet of the anode passage 59 communicates with the inlet 151 of the gas-liquid separator 36 through the fuel gas outlet communication port 104, the fuel off-gas outlet 94, and the fuel off-gas discharge passage 74 for the fuel off-gas, and the fuel off-gas, which is a hydrogen-containing gas from the anode passage 59, is supplied to the gas-liquid separator 36.

[0048] Actually, a part of the water generated by the power generation of the fuel cell stack 18 moves by reverse diffusion (permeation) from the cathode passage 58 through the electrolyte membrane / electrode structure 52 into the anode passage 59.

[0049] If this reverse-diffused water cannot be appropriately drained from the fuel off-gas discharge passage 74 or the circulation passage 77, water will penetrate into the anode electrode 57 of the fuel cell stack 18 and block the anode passage (fuel gas passage) 59, causing deterioration of the power generation stability of the fuel cell stack 18.

[0050] To prevent this inconvenience, the gas-liquid separator 36 for temporarily storing water separates the fuel off-gas into a gas component and a liquid component (liquid water).

[0051] The gas component (fuel off-gas) of the fuel off-gas is discharged from the gas discharge port 152 of the gas-liquid separator 36 and supplied to the suction port of the ejector 34 through the circulation passage 77.

[0052] The liquid component (liquid water) of the fuel off-gas, which consists of reverse-diffused water, passes through the drain passage 162 provided with the drain valve 164 from the liquid discharge port 160 of the gas-liquid separator 36, is mixed with the exhaust gas discharged from the discharge passage 64, and is discharged to the outside air through the discharge passage 99 and the exhaust gas exhaust port 168.

[0053] In the drain passage 162, a part of the fuel off-gas (hydrogen-containing gas) is discharged together with the liquid water. Further, only the fuel off-gas (hydrogen-containing gas) will be discharged from the drain passage 162 after the discharge of the liquid water is completed.

[0054] In order to dilute the hydrogen gas in the fuel off-gas and discharge it to the outside, a part of the oxidant gas discharged from the compressor 28 is supplied to the discharge passage 64 through the bypass passage 66.

[0055] If the drain valve 164 is continuously opened even after the water has drained from the drain passage 162, hydrogen will be wasted. Therefore, after the water has drained from the gas-liquid separator 36, it is necessary to appropriately close the drain valve 164.

[0056] The oxidant gas supplied through the bypass passage 66 of the oxidant gas is mixed with the oxidant off-gas (including the remaining fuel off-gas that did not react) flowing through the oxidant off-gas discharge passage 63 and flows through the discharge passage 64. The discharge passage 64 communicates with the drain passage 162 and merges to communicate with the discharge passage 99.

[0057] In the discharge passage 99, the fuel gas in the mixed fluid of the liquid water and the fuel off-gas discharged from the drain passage 162 is diluted by the oxidant off-gas from the discharge passage 64 and discharged to the outside (atmosphere) of the fuel cell vehicle 12 through the exhaust gas outlet 168.

[0058] The refrigerant supply device 26 of the fuel cell system 10 has a refrigerant passage 138 through which a refrigerant (coolant), which is a heat medium, flows. The refrigerant passage 138 has a refrigerant supply passage 140 and a refrigerant discharge passage 142. The refrigerant supply passage 140 supplies the refrigerant to the refrigerant passage 60 of the fuel cell stack 18, and the refrigerant discharge passage 142 discharges the refrigerant from the refrigerant passage 60 of the fuel cell stack 18. A radiator 39 is connected to the refrigerant supply passage 140 and the refrigerant discharge passage 142.

[0059] The radiator 39 cools the refrigerant. A refrigerant pump 38 is provided in the refrigerant supply passage 140. The refrigerant pump 38 circulates the refrigerant within the refrigerant circulation circuit. The refrigerant circulation circuit includes the refrigerant supply passage 140, the internal refrigerant passage of the fuel cell stack 18, the refrigerant discharge passage 142, and the radiator 39. A temperature sensor 76 is provided in the refrigerant discharge passage 142. The temperature of the cooling medium (refrigerant outlet temperature) detected by the temperature sensor 76 is detected (measured) as being the (internal) temperature of the fuel cell stack 18. Each component of the fuel cell system 10 described above is comprehensively controlled by the control device 15.

[0060] Note that the inlet side shutoff valve 118, the outlet side shutoff valve 120, and the drain valve 164 are flow control valves whose valve opening degrees are controlled by the control device 15, but electromagnetic control type on-off valves may be used for duty control.

[0061] The control device 15 is constituted by an ECU (Electronic Control Unit). The ECU is constituted by a computer having one or more processors (CPUs), a memory, an input / output interface, and electronic circuits. The one or more processors (CPUs) execute a program (computer-executable instructions) not shown, stored in the memory.

[0062] The processor of the control device 15 performs operation control of the fuel cell vehicle 12 and the fuel cell system 10 by executing calculations according to the program.

[0063] A power switch (power SW) 71 of the fuel cell vehicle 12 is connected to the control device 15. The power switch 71 is operated by the user to start or continue (ON) or end (OFF) the power generation operation of the fuel cell stack 18 of the fuel cell system 10. An accelerator opening sensor, a vehicle speed sensor, and an SOC sensor of the power storage device 44 (not shown respectively) are also connected to the control device 15. The power SW 71 can use the timer 70 to perform so-called RTC startup (automatic on / off) of the fuel cell system 10.

[0064] [Operation] The fuel cell system 10 according to this embodiment is basically configured as described above. Hereinafter, with reference to the flowchart of FIG. 2, the operation of the fuel cell system 10 related to the detection and determination of abnormalities (valve failures) in the sealing functions of the inlet side sealing valve 118 and the outlet side sealing valve 120 will be described.

[0065] For the sake of simplicity of explanation and convenience of understanding, the processing according to the flowchart of FIG. 2 starts from the state where the fuel cell stack 18 is generating power during the running or idling stop of the fuel cell vehicle 12.

[0066] During power generation in step S1, in the fuel gas supply device 24, fuel gas is discharged from the fuel tank 20 through the shut-off valve 21, via the injector 32, to the drive port nozzle of the ejector 34. Note that the injector 32 can adjust the discharge amount of the fuel gas by being, for example, PWM-driven under the control of the control device 15. As is well known, PWM drive is a power control method that creates a constant cycle of on and off of a pulse train and changes the time width (ON duty) of on.

[0067] The fuel gas is introduced from the drive port nozzle of the ejector 34 through the diffuser of the ejector 34, and via the fuel gas inlet 93 and the fuel gas inlet communication port 103, into the anode flow path 59.

[0068] As the fuel gas moves along the anode flow path 59, the fuel gas is supplied to the anode electrode 57 of the electrolyte membrane / electrode structure 52.

[0069] In the oxidant gas supply device 22, oxidant gas that has been pressurized, compressed, and heated by the compressor 28 is supplied to the oxidant gas inlet 91 via the inlet side sealing valve 118 and the humidifier 30.

[0070] The oxidant gas is introduced into the cathode flow path 58 via the oxidant gas inlet 91 and the oxidant gas inlet communication port 101.

[0071] As the oxidant gas moves along the cathode flow path 58, the oxidant gas is supplied to the cathode electrode 56 of the electrolyte membrane / electrode structure 52.

[0072] In each electrolyte membrane / electrode structure 52, the fuel gas supplied to the anode electrode 57 and oxygen in the oxidant gas supplied to the cathode electrode 56 are consumed by an electrochemical reaction in the electrode catalyst layer to generate electricity.

[0073] At the anode electrode 57, when the fuel gas (hydrogen) is supplied, hydrogen ions are generated from hydrogen molecules by an electrode reaction using a catalyst. While the hydrogen ions permeate through the solid polymer electrolyte membrane 55 and move to the cathode electrode 56, electrons are released from the hydrogen molecules.

[0074] The electrons released from the hydrogen molecules move from the negative terminal 106 through the DC / DC converter 40 and the inverter 45, through the motor 46, and to the cathode electrode 56 through the positive terminal 108. In addition to moving to the cathode electrode 56 through the main motor 46, the electrons also move to the cathode electrode 56 through various auxiliary machines.

[0075] At the cathode electrode 56, the hydrogen ions, the electrons, and oxygen contained in the supplied oxidant gas react under the action of the catalyst to generate water.

[0076] The generated water (product water) penetrates through the solid polymer electrolyte membrane 55 and also reaches the anode electrode 57. Therefore, product water is generated in the fuel cell stack 18.

[0077] In the refrigerant supply device 26, under the operation of the refrigerant pump 38, the refrigerant is supplied from the refrigerant supply flow path 140 to the refrigerant flow path 60 of the fuel cell stack 18. The refrigerant flows along the refrigerant flow path 60, cools the power generation cell 50, and then is discharged to the refrigerant discharge flow path 142.

[0078] The fuel gas supplied to the anode electrode 57 and partially consumed is discharged as fuel off-gas from the fuel gas outlet communication port 104 and the fuel off-gas outlet 94 into the fuel off-gas discharge channel 74. The fuel off-gas is introduced from the fuel off-gas discharge channel 74 into the suction port of the ejector 34 via the gas-liquid separator 36 and the circulation channel 77.

[0079] The fuel off-gas introduced from the suction port is sucked into the ejector 34 and mixed with the fuel gas by the action of the negative pressure generated by the fuel gas introduced from the drive port nozzle, and is discharged from the discharge port of the ejector 34 into the fuel gas supply channel 72.

[0080] The fuel gas mixed with the fuel off-gas discharged into the fuel gas supply channel 72 flows into the anode channel 59 in the fuel cell stack 18 via the fuel gas inlet 93 and the fuel gas inlet communication port 103.

[0081] The fuel off-gas discharged into the fuel off-gas discharge channel 74 is discharged (purged) to the outside under the opening action of the drain valve 164 as required. Similarly, the oxidant gas supplied to the cathode electrode 56 and partially consumed is discharged as oxidant off-gas from the oxidant off-gas outlet communication port 102 and the oxidant off-gas outlet 92 into the oxidant off-gas discharge channel 63.

[0082] The oxidant off-gas discharged into the oxidant off-gas discharge channel 63 is discharged to the outside (outside air, atmosphere) through the humidifier 30, the outlet side sealing valve 120, the discharge channel 64, the discharge channel 99, and the exhaust gas exhaust port 168.

[0083] In step S2, it is determined whether the power switch 71 has transitioned from the on state to the off state. If it has not transitioned to the off state (step S1: NO), the power generation process in step S1 is continued. If it has transitioned to the off state (step S1: YES), the process proceeds to step S3. In step S3, the control device 15 performs a stop-time process.

[0084] FIG. 3 is a timing chart used to explain an example of the stop-time process. At time t0 in FIG. 3, when the control device 15 detects a stop instruction by the user in which the power switch 71 transitions from the on state to the off state (corresponding to the determination of YES in step S2), the ON duty of the injector 32 is increased until time t1 to increase the anode pressure Pa. The anode pressure Pa is detected by the pressure sensor 73 and acquired by the control device 15.

[0085] On the other hand, at time t0, the control device 15 reduces the rotational speed of the compressor 28 to continue rotation (the supply of the oxidant gas is continued).

[0086] At time t2, the bypass valve 122 is switched from the closed state to a partially open state (a predetermined open state between the closed state and the fully open state), and at time t3, the outlet-side sealing valve 120 is switched from the fully open state to a partially open state.

[0087] Between time t3 and time t4, the operating state of the injector 32, the low rotational speed state of the compressor 28, the fully open state of the inlet-side sealing valve 118, the partially open state of the bypass valve 122, and the partially open state of the outlet-side sealing valve 120 are continued.

[0088] At time t4, the outlet-side sealing valve 120 is switched from the partially open state to the closed state. At time t5, the bypass valve 122 is switched to the fully open state. At time t6, the inlet-side sealing valve 118 is switched from the fully open state to the closed state.

[0089] Between time t0 and time t6, so-called power generation during stop is continued, oxygen in the cathode channel 58 is consumed, and as a result, the cathode channel 58 is filled with an oxidant gas rich in nitrogen N2.

[0090] Note that the surplus generated power of the fuel cell system 10 during power generation during stop is charged to the power storage device 44 through the DC / DC converter 40 and the DC / DC converter 41.

[0091] From time point t6 after the end of power generation at stop to time point t7 (which will be described as time point ta later), the control device 15 increases the ON duty of the injector 32 again and boosts the anode pressure (fuel gas pressure) Pa in the anode flow path 59 to be equal to or higher than a predetermined threshold pressure (threshold gas pressure) Pth.

[0092] When the control device 15 detects that the pressure has been boosted to Pa≧Pth (fuel gas pressure≧threshold gas pressure), at time point t7 (time point ta), it stops the operations of the injector 32 and the compressor 28.

[0093] At time point t7, the fuel cell system 10 (fuel cell vehicle 12) starts soak. In the soak state after time point t7, the inlet side seal valve 118 and the outlet side seal valve 120 continue to be in the closed state, and the bypass valve 122 is maintained in the fully open state. Also, the shut-off valve 21 and the drain valve 164 are maintained in the closed state.

[0094] In this soak state, the fuel gas (hydrogen H2) gradually permeates (diffuses) from the anode flow path 59 through the electrolyte membrane / electrode structure 52 to the cathode flow path 58.

[0095] Returning to the flowchart of FIG. 2, from the system stop at time point t7 (ta) after the stop-time processing in step S3, in step S4, the control device 15 starts counting the first threshold time T1 and the second threshold time T2 by the timer 70 and proceeds with the process to step S5. Here, the counting time by the timer 70 until the first threshold time T1 is defined as the soak time Ts = Ts1, and the counting time by the timer 70 until the second threshold time T2 is defined as the soak time Ts = Ts2.

[0096] Here, the second threshold time T2 is a time shorter than the first threshold time T1 (T2 < T1) and can be arbitrarily set. Also, the first threshold time T1 only needs to be set to a time longer than the second threshold time T2 (T1 > T2) and can be arbitrarily set according to the second threshold time T2.

[0097] In step S5, the control device 15 determines whether the power switch 71 has been transitioned from the off state to the on state (user-activated) by the user.

[0098] When the control device 15 detects that the power switch 71 has been transitioned from the off state to the on state (user activation) (step S5: YES), the process proceeds to step S6. When not detected (step S5: NO), the process proceeds to step S8.

[0099] In step S6, the control device 15 opens the shut-off valve 21, drives the injector 32, and injects fuel gas (H2) from the fuel tank 20 into the fuel cell stack 18, and the process proceeds to step S7. Note that the injection of fuel gas in step S6 by the control device 15 is performed while maintaining the inlet-side seal valve 118 and the outlet-side seal valve 120 in the fully closed state.

[0100] In step S7, the control device 15 determines whether the soak time Ts2 at the time of user activation in step S5 is equal to or longer than the second threshold time T2. When Ts2 ≥ T2 (step S7: YES), in order to perform the abnormality determination process (fault detection process, fault determination process) of the inlet-side seal valve 118 and the outlet-side seal valve 120, the process proceeds to step S10.

[0101] In step S7, when the soak time Ts2 at the time of user activation performed in step S5 is less than the second threshold time T2 (Ts2 < T2) (step S7: NO), the process ends without performing the abnormality determination process.

[0102] On the other hand, when user activation has not been detected (step S5: NO), in step S8, the control device 15 determines whether the soak time Ts1 is equal to or longer than the first threshold time T1. When Ts1 ≥ T1 (step S8: YES) during the continuation of the determination of step S8: NO → step S5: NO, the process proceeds to step S9.

[0103] In step S9, while maintaining the inlet-side shutoff valve 118 and the outlet-side shutoff valve 120 in the fully closed state in the same manner as the (H2) charging process in step S6, the control device 15 opens the cutoff valve 21 and drives the injector 32. As a result, fuel gas (H2) is charged from the fuel tank 20 into the fuel cell stack 18 (automatic hydrogen charging process).

[0104] After the fuel gas (H2) is charged into the fuel cell stack 18, the control device 15 proceeds with the process to step S10 in order to perform the abnormality determination process for the inlet-side shutoff valve 118 and the outlet-side shutoff valve 120.

[0105] In the abnormality determination process of step S10, the control device 15 determines whether the output voltage Vfc detected by the voltage sensor 110 is a voltage exceeding a predetermined threshold voltage Vth (Vfc > Vth).

[0106] Note that as shown in FIG. 4, the threshold voltage Vth is preset to a voltage between the normal power generation voltage Vn and the open circuit voltage Vocv on the current-voltage characteristic 200 of the fuel cell stack 18.

[0107] FIG. 5 is a schematic operation explanatory diagram in the case where the soak time Ts has elapsed for a time longer than the second threshold time T2 (Ts ≧ T2 < T1) and it is determined that both the inlet-side shutoff valve 118 and the outlet-side shutoff valve 120 are normal (sealing function normal) (in the closed state).

[0108] FIG. 6 is a schematic operation explanatory diagram in the case where the soak time Ts has elapsed for a time longer than the second threshold time T2 (Ts ≧ T2 < T1) and it is determined that either the inlet-side shutoff valve 118 or the outlet-side shutoff valve 120 is abnormal (sealing function abnormal).

[0109] As shown in the upper diagram of FIG. 5, when the soak time Ts has elapsed the second threshold time T2 and the inlet-side shutoff valve 118 and the outlet-side shutoff valve 120 are in the normal sealed state (closed state), hydrogen H2 that has permeated through the electrolyte membrane / electrode structure 52 from the anode flow path 59 enters the cathode flow path 58 of the fuel cell stack 18.

[0110] In this state, as shown in the lower diagram of FIG. 5, even if hydrogen H2 is introduced into the anode flow path 59 of the fuel cell stack 18 by user activation (step S5: YES) or automatic hydrogen supply processing (step S8: YES), since hydrogen H2 exists in both the cathode flow path 58 and the anode flow path 59, an electrochemical reaction between hydrogen H2 and oxygen O2 does not occur. That is, the fuel cell stack 18 cannot generate an output voltage Vfc which is the electromotive force (Vfc = 0 [V]). This output voltage Vfc = 0 is detected by the voltage sensor 110 and acquired by the control device 15.

[0111] In this case, since the output voltage Vfc is Vfc = 0, the determination in step S10 is negative (step S10: NO).

[0112] In step S11, when the control device 15 determines that this negative determination time has been measured by the timer 70 for a predetermined minute time ΔTp, in step S12, it is determined that the inlet side sealing valve 118 and the outlet side sealing valve 120 are normal, and the process ends.

[0113] On the other hand, as shown in the upper diagram of FIG. 6, when the inlet side sealing valve 118 or the outlet side sealing valve 120 is in an open failure state (any state from a state where the valve is slightly open to a fully open state), for example, even in a slightly open open failure state, since a soak time Ts of equal to or longer than the second threshold time T2 (T1 > T2) has elapsed, oxygen O2 has entered the cathode flow path 58.

[0114] In this state, as shown in the lower diagram of FIG. 6, when hydrogen H2 is introduced into the anode flow path 59 of the fuel cell stack 18 by user activation (step S5: YES) or automatic hydrogen supply processing (step S8: YES), since oxygen O2 exists in the cathode flow path 58 and hydrogen H2 exists in the anode flow path 59, the fuel cell stack 18 generates an open circuit voltage Vocv which is the electromotive force when no power generation current Ifc is drawn (Ifc = 0 when no load is connected) (Vfc = Vocv > Vth). This output voltage Vfc = Vocv is detected by the voltage sensor 110 and acquired by the control device 15.

[0115] In this case, since the output voltage Vfc is Vfc = Vocv ≥ Vth, the control device 15 makes an affirmative determination in step S10 (step S10: YES).

[0116] In step S13, when the control device 15 determines that this affirmative determination time has been measured by the timer 70 for a predetermined time ΔTq, in step S14, it is determined that the inlet side shutoff valve 118 or the outlet side shutoff valve 120 is abnormal, and the process ends.

[0117] FIG. 7 shows a time chart as an operation example for explaining the determination processes in steps S7 and S8 and the like when the control device 15 detects the introduction of hydrogen H2 during the soak time Ts from the start time ta of the soak state (refer to time t7 in FIG. 3) when the system stops.

[0118] In FIG. 7, in operation example (i), after the start of the soak state, from time tg when the first threshold time T1 has elapsed to time th, hydrogen H2 is automatically introduced from the fuel tank 20 through the injector 32 for the detection processing time Tdet, and then the injector 32 is stopped. As a result, hydrogen H2 is sealed in the anode flow path 59 of the fuel cell stack 18, and the anode pressure Pa is increased.

[0119] In the case of operation example (i), the control device 15 executes the abnormality determination process in step S10 based on the result of its own automatic pressure increase (step S9). Note that in FIG. 7, the execution of the abnormality determination process is indicated by the hatched section.

[0120] In Fig. 7, in operation example (ii), after the soak state starts, at time td after time tc when the second threshold time T2 has elapsed, user activation is performed by the user operating the power switch 71 to the on state, and hydrogen H2 is introduced before power generation starts at time te (opening of the inlet-side sealing valve 118 and the outlet-side sealing valve 120). As a result, hydrogen H2 is enclosed in the anode flow path 59 of the fuel cell stack 18, and the anode pressure Pa is increased. Thereafter, the oxidant gas is supplied into the fuel cell stack 18 to start power generation.

[0121] In the case of operation example (ii), the control device 15 executes the abnormality determination process of step S10 based on the determination result of step S7: YES.

[0122] In Fig. 7, in operation example (iii), after the soak state starts, at time tb before the second threshold time T2 elapses, user manual activation is performed by the user operating the power switch 71 to the on state, and the oxidant gas is introduced and hydrogen H2 is introduced.

[0123] In the case of operation example (iii), the control device 15 ends the process without executing the abnormality determination process of step S10.

[0124] In Fig. 7, in operation example (iv), after the soak state starts, from time tg to time th when the first threshold time T1 has elapsed, hydrogen H2 is automatically introduced from the fuel tank 20 through the injector 32 for the detection processing time Tdet, and then the injector 32 is stopped. As a result, hydrogen H2 is enclosed in the anode flow path 59 of the fuel cell stack 18, and the anode pressure Pa is increased.

[0125] Thereafter, at time ti, user activation is performed by the user operating the power switch 71 to the on state, and hydrogen H2 is introduced before power generation starts at time tk (opening of the inlet-side sealing valve 118 and the outlet-side sealing valve 120). As a result, hydrogen H2 is enclosed in the anode flow path 59 of the fuel cell stack 18, and the anode pressure Pa is increased. Thereafter, the oxidant gas is supplied into the fuel cell stack 18 to start power generation.

[0126] In the case of operation example (iv), the control device 15 executes the abnormality determination process by time th. Also, when the user activates the device at time ti, since the second threshold time T2 has not elapsed since the start time th of soaking, the process ends without executing the abnormality determination process, and power generation starts after time tk.

[0127] In FIG. 7, in the case of operation example (v), when the anode pressure Pa increases from time tg to time th, for the same reason as in operation example (iv), the abnormality determination process in step S10 is executed. Further, when the user activates the device at time tk after the soaking time Ts (Ts = (tk - th) ≥ T2) has elapsed, the abnormality determination process is also executed between time tk and time tl.

[0128] In FIG. 7, in the case of operation example (vi), when the anode pressure Pa increases from time tg to time th, for the same reason as in operation example (iv), the abnormality determination process in step S10 is executed.

[0129] In the abnormality determination process of this step S10 (in this case, from time tg to time th), if at least one of the inlet side shut-off valve 118 or the outlet side shut-off valve 120 is determined to be abnormal (valve open state with abnormal sealing function), the abnormality determination process of step S10 is not performed when the user activates the device at time tk after the soaking time Ts (Ts = (tk - th) ≥ T2) has elapsed. This is because it is already determined to be abnormal between time tg and time th, and it is more accurate to re - determine after re - driving the valves of the inlet side shut-off valve 118 or the outlet side shut-off valve 120.

[0130] Thus, in the case of operation example (vi) where an abnormality is detected between time tg and time th, the abnormality determination process is not performed between time tk and time tl. In the case of operation example (vi), at time tl, both the inlet side shut-off valve 118 and the outlet side shut-off valve 120 are driven to the fully open state, and power generation in the fuel cell stack 18 starts.

[0131] When the control device 15 drives the inlet-side sealing valve 118 and the outlet-side sealing valve 120 to open once at time point t1 in operation example (vi), and the fuel cell stack 18 starts power generation, then, as described with reference to FIG. 3, the power-off transition of the power switch 71 causes the power generation process at shutdown to be performed, and the soak state starts at time point t7 (time point ta).

[0132] In this case, after determining an abnormality between time points tg and th in operation example (vi), the abnormality determination process is performed again between time points tg and th in operation example (i) or between time points td and te in operation example (ii).

[0133] In the determination process of this abnormal state, when the control device 15 determines an abnormal state continuously a plurality of times with valve driving in between (operation example (vi) and operation example (i), or operation example (vi) and operation example (ii)), it is determined that at least one of the inlet-side sealing valve 118 and the outlet-side sealing valve 120 is faulty.

[0134] In this way, it is possible to avoid performing continuous abnormal determination processing in the same driving state of the inlet-side sealing valve 118 and the outlet-side sealing valve 120. That is, in the case of operation example (vi), it is possible to prevent misjudgment caused by performing continuous abnormal determination processing without valve driving when at least one of the sealing functions of the inlet-side sealing valve 118 or the outlet-side sealing valve 120 is in an abnormal state.

[0135] In the abnormal determination process, after determining an abnormal state, it may be possible to perform the abnormal detection after step S10 again only after driving at least one of the inlet-side sealing valve 118 or the outlet-side sealing valve 120 to the open state.

[0136] [Modification Example] The above embodiment can also be modified as follows.

[0137] In FIG. 1, a temperature sensor (ambient temperature sensor) is provided at the outside air intake 113. In operation example (i) of FIG. 7, after the soak start time point ta, when the outside air temperature approaches the freezing point, the control device 15 detects the outside air temperature with the temperature sensor at predetermined time intervals.

[0138] When the outside air temperature reaches the freezing point, the fuel cell system 10 is automatically started to perform a drying power generation process for a certain period of time in order to dry the fuel cell stack 18, the cathode flow path 58 and the anode flow path 59 of the fuel cell stack 18, and the flow paths communicating with these cathode flow path 58 and anode flow path 59.

[0139] During this automatic start-up and drying power generation process, when the soaking time (duration) from the soaking start time ta exceeds the second threshold time T2, the abnormality determination process of the shut-off valve in step S10 may be performed.

[0140] [Invention understandable from the embodiment] Here, the invention understandable from the above embodiment and the modification example will be described below. For the convenience of understanding, some of the components are labeled with the reference numerals used in the above embodiment, but the components are not limited to those with the reference numerals attached.

[0141] (1) The fuel cell system 10 according to the present invention generates electricity through an electrochemical reaction between an oxidant gas supplied from an air compressor 28 through an inlet side shutoff valve 118 to a cathode flow path 58 along a cathode electrode 56 of a fuel cell (50 or 18), and a fuel gas supplied from a fuel tank 20 to an anode flow path 59 along an anode electrode 57 of the fuel cell, and the oxidant off-gas after power generation flows to the outside through an outlet side shutoff valve 120. The fuel cell system includes a voltage sensor 110 that detects an output voltage between the anode electrode and the cathode electrode, and a control device 15 that, when the system stops, continues power generation, consumes the oxidant gas remaining from the outlet side of the inlet side shutoff valve to the inlet side of the outlet side shutoff valve, then drives the inlet side shutoff valve and the outlet side shutoff valve to a closed state, and performs a stop-time power generation process of shutting off the supply of the fuel gas from the fuel tank to the anode flow path. The control device, in a state where the inlet side shutoff valve and the outlet side shutoff valve are driven to a closed state, after the stop-time power generation process, when new fuel gas is supplied to the anode flow path, detects the output voltage with the voltage sensor, and when the detected output voltage is equal to or higher than a threshold voltage, determines that the inlet side shutoff valve or the outlet side shutoff valve is in an abnormal open state.

[0142] When the system stops, a stop-time power generation process is performed in which power generation is continued to consume the oxidant gas in the cathode flow path and the fuel gas is retained in the anode flow path, and during the soak time after the stop-time power generation process, the fuel gas diffuses from the anode flow path into the cathode flow path through the electrolyte membrane / electrode structure.

[0143] Thereby, in a state where the inlet side shutoff valve and the outlet side shutoff valve are driven to a closed state, it is determined whether or not the output voltage detected by the voltage sensor becomes equal to or higher than the threshold voltage when new fuel gas is supplied to the anode flow path. Based on this determination result, it is possible to reliably detect whether or not the inlet side shutoff valve or the outlet side shutoff valve is abnormal even when a minute leak occurs. This contributes to improving energy efficiency.

[0144] (2) Also, in the fuel cell system, a pressure sensor 73 for detecting the fuel gas pressure is provided in the anode flow path, and when the fuel gas pressure detected by the pressure sensor has increased to the threshold gas pressure, the control device stops the supply of the fuel gas and ends the power generation process at the time of stop.

[0145] In this way, during the power generation process at the time of stop, the supply of the fuel gas is continued, and when the fuel gas pressure has increased to the threshold gas pressure, the supply of the fuel gas is stopped. Therefore, the oxidant gas in the cathode flow path can be surely consumed. As a result, it is possible to accurately detect whether the inlet side shutoff valve and the outlet side shutoff valve are abnormal when the fuel gas is supplied next time.

[0146] (3) Further, in the fuel cell system, a timer 70 is further provided. When new fuel gas is supplied to the anode flow path after the power generation process at the time of stop, it is at the time of user startup when the fuel cell system after system stop in which the inlet side shutoff valve and the outlet side shutoff valve are driven to the closed state is started by the user or at the time of automatic anode pressure increase by the timer.

[0147] Thereby, it is possible to detect whether the inlet side shutoff valve and the outlet side shutoff valve are abnormal when the fuel cell system is started by the user or automatically started by the timer.

[0148] (4) Furthermore, in the fuel cell system, when the automatic anode pressure increase by the timer is performed after the elapse of the first threshold time from the time of system stop or the start of soak, the control device performs the determination process for the abnormal state, and also performs the determination process for the abnormal state when the system is started by the user after the elapse of the second threshold time shorter than the first threshold time from the time of system stop or the start of soak.

[0149] With this configuration, for example, the determination process for the abnormal state is performed after the first threshold time, and then, when the user activates the system before the elapse of the second threshold time, which is shorter than the first threshold time, the determination process for the abnormal state is not performed. Therefore, the abnormal detection timing is appropriately set, and it is possible to surely detect whether the inlet-side sealing valve and the outlet-side sealing valve are abnormal.

[0150] (5) Furthermore, in the fuel cell system, in the determination process for the abnormal state, the control device determines that at least one of the inlet-side sealing valve and the outlet-side sealing valve has failed when the abnormal state is continuously determined a plurality of times.

[0151] With this configuration, it is possible to accurately determine the failure of the sealing valve.

[0152] (6) Furthermore, in the fuel cell system, in the determination process for the abnormal state, after determining the abnormal state, the control device drives at least one of the inlet-side sealing valve or the outlet-side sealing valve to the open state, and then performs the determination process for the abnormal state. When it is determined to be in the abnormal state again, the control device determines that at least one of the inlet-side sealing valve and the outlet-side sealing valve has failed.

[0153] With this configuration, it is possible to avoid performing consecutive abnormal determination processes in the same driving state of the inlet-side sealing valve and the outlet-side sealing valve.

[0154] (7) Furthermore, in the fuel cell system, in the determination process for the abnormal state, after determining the abnormal state, the control device drives at least one of the inlet-side sealing valve or the outlet-side sealing valve to the open state, and then, when the anode pressure is automatically increased by the timer after the elapse of the first threshold time from the next system stop or the start of soak, the control device performs the determination process for the abnormal state. Also, when the system is activated by the user after the elapse of the second threshold time, which is shorter than the first threshold time, from the next system stop or the start of soak, the control device performs the determination process for the abnormal state.

[0155] With this configuration, it is possible to avoid performing continuous abnormality determination processing in the same driving state of the inlet-side sealing valve and the outlet-side sealing valve.

[0156] Note that the present invention is not limited to the above-described disclosure, and various configurations can be adopted without departing from the gist of the present invention.

Explanation of Reference Numerals

[0157] 10…Fuel cell system 12…Fuel cell vehicle 15…Control device 16…Output unit 18…Fuel cell stack (fuel cell) 20…Fuel tank 21…Cut-off valve 22…Oxidant gas supply device 24…Fuel gas supply device 26…Refrigerant supply device 28…Air compressor 56…Cathode electrode 57…Anode electrode 58…Cathode flow path 59…Anode flow path 70…Timer 71…Power switch 110…Voltage sensor 118…Inlet-side sealing valve 120…Outlet-side sealing valve T1…First threshold time T2…Second threshold time

Claims

1. A fuel cell system in which electricity is generated by an electrochemical reaction between an oxidant gas supplied from an air compressor through an inlet sealing valve to a cathode flow path along a cathode electrode of a fuel cell and a fuel gas supplied from a fuel tank to an anode flow path along an anode electrode of the fuel cell, and the oxidant off-gas generated after the electricity generation is circulated to the outside through an outlet sealing valve, a voltage sensor that detects an output voltage between the anode electrode and the cathode electrode; a control device that performs a power generation process during a system shutdown by continuing power generation and consuming the oxidant gas remaining from the outlet side of the inlet side sealing valve to the inlet side of the outlet side sealing valve, and then driving the inlet side sealing valve and the outlet side sealing valve to a closed state and cutting off the supply of the fuel gas from the fuel tank to the anode flow path, The control device includes: When the inlet side sealing valve and the outlet side sealing valve are driven to a closed state and new fuel gas is supplied to the anode flow path after the shutdown power generation process, the output voltage is detected by the voltage sensor, and when the detected output voltage is equal to or higher than a threshold voltage, it is determined that the inlet side sealing valve or the outlet side sealing valve is in an open abnormal state. Fuel cell system.

2. 2. The fuel cell system according to claim 1, a pressure sensor for detecting a fuel gas pressure is provided in the anode flow channel; The control device includes: When the fuel gas pressure detected by the pressure sensor is increased to a threshold gas pressure, the supply of the fuel gas is stopped and the stop-time power generation process is terminated. Fuel cell system.

3. 3. The fuel cell system according to claim 1, Further, a timer is provided, The time when the fuel gas is newly supplied to the anode flow path after the shutdown power generation process is the time when the fuel cell system is started by a user after the system shutdown in which the inlet side sealing valve and the outlet side sealing valve are driven to the closed state, or the time when the anode pressure is automatically increased by the timer. Fuel cell system.

4. 4. The fuel cell system according to claim 3, The control device includes: When the anode pressure is automatically increased by the timer after a first threshold time has elapsed since the system was stopped or the soak was started, the abnormal state determination process is performed. Also, when the timer is activated by the user after a second threshold time, which is shorter than the first threshold time, has elapsed since the system was stopped or the soak was started, the abnormal state determination process is performed. Fuel cell system.

5. 5. The fuel cell system according to claim 4, The control device includes: In the abnormal state determination process, when the abnormal state is determined to be present a number of times in succession, it is determined that at least one of the inlet side seal valve and the outlet side seal valve is broken. Fuel cell system.

6. 6. The fuel cell system according to claim 5, The control device includes: In the abnormal state determination process, after determining that an abnormal state exists, at least one of the inlet side sealing valve and the outlet side sealing valve is driven to an open state, and then the abnormal state determination process is performed. If an abnormal state is determined again, it is determined that at least one of the inlet side sealing valve and the outlet side sealing valve has a failure. Fuel cell system.

7. 5. The fuel cell system according to claim 4, The control device includes: In the abnormal state determination process, after determining that an abnormal state exists, if at least one of the inlet side sealing valve or the outlet side sealing valve is driven to an open state and then the timer automatically increases the anode pressure after a first threshold time has elapsed since the next system shutdown or the start of a soak, the abnormal state determination process is performed; and also when activated by the user after the second threshold time, which is shorter than the first threshold time, has elapsed since the next system shutdown or the start of a soak. Fuel cell system.

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