JP5280417B2 - Method for stopping operation of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation stop method of a full cell system capable of suppressing fuel cell deterioration as much as possible with a simple and compact configuration. <P>SOLUTION: An operation stop method of a fuel cell system 10 comprises: a first step of making a fuel cell stack 12 generate power while supplying a hydrogen gas and air to the fuel cell stack 12; a second step of stopping the supply of the hydrogen gas when detecting a stop command of the fuel cell stack 12, and making the fuel cell stack 12 generate power while supplying the air to the fuel cell stack 12 with an oxygen stoichiometric ratio lower than an oxygen stoichiometric ratio for normal power generation; and a third step of making the fuel cell stack 12 generate power only with a residual gas in the fuel cell stack 12 after stopping supply of an oxidant gas to the fuel cell stack 12, and supplying generated power obtained from the fuel cell stack 12 to a cooling medium supply device 15. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a method for shutting down a fuel cell system including a fuel cell that generates electricity by an electrochemical reaction between an oxidant gas and a fuel gas.

  In a fuel cell, a fuel gas (a gas mainly containing hydrogen, for example, hydrogen gas) and an oxidant gas (a gas mainly containing oxygen, for example, air) are supplied to an anode electrode and a cathode electrode to be electrochemical. It is a system that obtains direct-current electric energy by reacting with. This system is incorporated in a fuel cell vehicle for in-vehicle use as well as stationary use.

  For example, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure (MEA) provided with an anode electrode and a cathode electrode on both sides of an electrolyte membrane made of a polymer ion exchange membrane is sandwiched between a pair of separators. Yes. A fuel gas passage for supplying fuel gas to the anode electrode is formed between one separator and the electrolyte membrane / electrode structure, and between the other separator and the electrolyte membrane / electrode structure. Is formed with an oxidant gas flow path for supplying an oxidant gas to the cathode electrode.

  By the way, when the fuel cell is stopped, the supply of the fuel gas and the oxidant gas is stopped, but the fuel gas remains in the fuel gas flow channel, while the oxidant gas remains in the oxidant gas flow channel. ing. Therefore, especially when the stop period of the fuel cell becomes long, the fuel gas and the oxidant gas may permeate the electrolyte membrane, and the fuel gas and the oxidant gas may be mixed.

  Thus, for example, a fuel cell system disclosed in Patent Document 1 is known. As shown in FIG. 9, the fuel cell system includes a fuel cell 1, an anode gas supply line 2 and a cathode gas supply line 3 for supplying hydrogen gas and air to the fuel cell 1, and an anode outlet of the fuel cell 1. An anode circulation line 2a and a cathode circulation line 3a for circulating the gas and the cathode outlet gas respectively upstream; a purge line 4 for purging the fuel cell 1 and each of the lines 2, 2a, 3 and 3a with an inert gas; And a shut-off means 5 for shutting off the output electric circuit of the fuel cell 1 when the operation is stopped.

  The anode gas supply line 2 includes an inlet shutoff valve 6a and a blower 7a arranged in this order in an inlet pipe A1 connected to an anode side inlet of the fuel cell 1 from a hydrogen tank (not shown) which is a hydrogen storage device. ing. Further, a purge valve 6b and an outlet shut-off valve 6c are arranged in series in this order in an outlet line A2 connected to a fuel regeneration device (not shown) from the anode side outlet of the fuel cell 1.

  The anode gas supply line 2 opens the inlet shut-off valve 6a, the outlet shut-off valve 6c, and the purge valve 6b during the operation of the fuel cell 1, and the hydrogen gas sent from the hydrogen tank is sent to the fuel cell 1 through the blower 7a. To the anode electrode 1A.

  The cathode gas supply line 3 includes an inlet shutoff valve 6d and a blower 7b arranged in this order in an inlet pipe C1 connected to a cathode side inlet of the fuel cell 1 from an air tank (not shown) filled with compressed air. ing. In addition, an outlet shutoff valve 6e is provided in the outlet pipe C2 connected from the cathode side outlet of the fuel cell 1 to a generated water separator (not shown).

  The cathode gas supply line 3 opens the inlet shut-off valve 6d and the outlet shut-off valve 6e during the operation of the fuel cell 1, and the air sent from the air tank is supplied to the cathode 1C of the fuel cell 1 through the blower 7b. Supply.

  The anode circulation line 2a opens the circulation cutoff valve 6f when the inlet cutoff valve 6a and the outlet cutoff valve 6c of the anode gas supply line 2 are closed due to the shutdown of the fuel cell 1, and the fuel cell 1 The anode outlet gas is sucked by the blower 7 a and functions to circulate upstream of the fuel cell 1.

  On the other hand, the cathode circulation line 3 a opens the circulation cutoff valve 6 g when the inlet cutoff valve 6 d and the outlet cutoff valve 6 e of the cathode supply line 3 are closed due to the stop of the operation of the fuel cell 1. The cathode outlet gas functions to be sucked by the blower 7b and circulated upstream of the fuel cell 1.

  In this Patent Document 1, when the operation is stopped, the supply of the reaction gas to the cathode side is shut off by the inlet shut-off valve, the cathode side exhaust gas is circulated upstream via the circulation line, and the cell reaction in the fuel cell is continued. By consuming oxygen in the cathode side exhaust gas, an inert gas of nitrogen gas is used for purging the cathode side and the anode side in the fuel cell.

Japanese Patent Laid-Open No. 2004-22487

  In the above-mentioned Patent Document 1, the anode gas supply line 2 and the cathode gas supply line 3 are provided with an anode circulation line 2a and a cathode circulation line 3a for circulating the anode outlet gas and the cathode outlet gas of the fuel cell 1 respectively upstream. It has been. Furthermore, in the cathode circulation line 3a, a tank 8 which is a gas volume part is disposed in order to accumulate nitrogen gas which is an inert gas.

  Then, by continuing the cell reaction in the fuel cell 1 and consuming oxygen in the cathode side exhaust gas, an inert gas such as nitrogen gas is used for the cathode side and anode side purge in the fuel cell 1. Yes. For this reason, there exists a problem that the structure of the whole fuel cell system becomes complicated and enlarged, and cost increases.

  An object of the present invention is to solve this type of problem, and to provide a method for stopping the operation of a fuel cell system that can suppress deterioration of the fuel cell as much as possible with a simple and compact configuration. To do.

  The present invention relates to a fuel cell that generates electricity by an electrochemical reaction between an oxidant gas supplied to the cathode side and a fuel gas supplied to the anode side, and an oxidant gas supply device that supplies the oxidant gas to the fuel cell. A fuel cell system comprising: a fuel gas supply device that supplies the fuel gas to the fuel cell; a cooling medium supply device that supplies a cooling medium to the fuel cell; and a power storage device that is connectable to the fuel cell. It is about the method.

In this operation stop method, the supply of the fuel gas is stopped when the first step of generating the fuel cell while supplying the oxidant gas and the fuel gas to the fuel cell and the stop command of the fuel cell is detected. On the other hand, while supplying the oxidant gas to the fuel cell with a low oxygen stoichiometry lower than that during normal power generation, the low-oxygen stoichiometric oxidant gas and the fuel gas remaining in the fuel cell And a second step of supplying the power generated by the fuel cell to the power storage device and stopping the supply of the oxidant gas of the low oxygen stoichiometry to the fuel cell. And a third step of generating the fuel cell with only the residual gas in the fuel cell and supplying the generated electric power obtained from the fuel cell to the cooling medium supply device. That.

  In this operation stop method, it is preferable that the generated power obtained from the fuel cell is stepped down via a downverter and then supplied to the cooling medium supply device.

  Furthermore, in this operation stop method, the cooling medium supply device includes a radiator fan disposed in a radiator that cools the cooling medium and a pump that circulates the cooling medium to the fuel cell. In the third step, the radiator fan and It is preferable to supply generated power to the pump.

  Furthermore, in this operation stop method, it is preferable that the low oxygen stoichiometric oxidant gas is set to about 1.

  In the present invention, since power is generated by the fuel gas remaining in the fuel cell and the low-oxygen stoichiometric oxidant gas, an inert gas having a high nitrogen concentration is generated as exhaust gas, while the fuel gas in the fuel cell Hydrogen concentration decreases. Moreover, after the generated power is supplied to the power storage device, the generated power obtained by generating the fuel cell with only the residual gas is supplied to the cooling medium supply device.

  For this reason, the residual voltage of the fuel cell can be lowered to a lower voltage, and the oxygen concentration in the fuel cell is further reduced. Therefore, the cathode side is filled with nitrogen gas to reduce the oxygen concentration, and the fuel cell and the gas pipe can be filled with the nitrogen gas.

  On the other hand, the fuel cell is cooled under the driving action of the cooling medium supply device. Thereby, the higher the temperature, the more easily the fuel cell that is deteriorated is not exposed to a high temperature, and the deterioration during the stop and the start-up deterioration of the fuel cell are favorably suppressed. For this reason, it becomes possible to suppress deterioration of the fuel cell as much as possible with a simple and compact configuration.

1 is a schematic configuration diagram of a fuel cell system in which an operation stop method according to an embodiment of the present invention is implemented. It is circuit explanatory drawing which comprises the said fuel cell system. It is a timing chart explaining the said operation stop method. It is operation | movement explanatory drawing of the said fuel cell system. It is operation | movement explanatory drawing of the said fuel cell system. It is explanatory drawing of the nitrogen substitution state in the said fuel cell system. It is a relationship explanatory drawing of a stack voltage and oxygen concentration. It is a relationship explanatory drawing of cell temperature and film degradation. 2 is an explanatory diagram of a fuel cell system disclosed in Patent Document 1. FIG.

  As shown in FIG. 1, a fuel cell system 10 in which an operation stop method according to an embodiment of the present invention is implemented includes a fuel cell stack 12 and an oxidant gas supply device that supplies an oxidant gas to the fuel cell stack 12. 14, a cooling medium supply device 15 that supplies a cooling medium to the fuel cell stack 12, a fuel gas supply device 16 that supplies a fuel gas to the fuel cell stack 12, and a battery that can be connected to the fuel cell stack 12 ( Power storage device) 17 and a controller 18 for controlling the fuel cell system 10 as a whole. The fuel cell system 10 is mounted on a fuel cell vehicle such as a fuel cell vehicle. The battery 17 can normally travel in a fuel cell vehicle, and has a voltage of about 20 A to about 500 V, for example, and a higher voltage and a higher power capacity than a 12 V power source 98 described later.

  The fuel cell stack 12 is configured by stacking a plurality of fuel cells 20. Each fuel cell 20 includes, for example, an electrolyte membrane / electrode structure (MEA) 28 in which a solid polymer electrolyte membrane 22 in which a perfluorosulfonic acid thin film is impregnated with water is sandwiched between a cathode electrode 24 and an anode electrode 26. .

  The cathode electrode 24 and the anode electrode 26 have a gas diffusion layer made of carbon paper or the like, and porous carbon particles carrying platinum alloy (or Ru or the like) on the surface are uniformly applied to the surface of the gas diffusion layer. And an electrode catalyst layer formed. The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 22.

  The electrolyte membrane / electrode structure 28 is sandwiched between the cathode side separator 30 and the anode side separator 32. The cathode side separator 30 and the anode side separator 32 are comprised by a carbon separator or a metal separator, for example.

  An oxidant gas flow path 34 is provided between the cathode side separator 30 and the electrolyte membrane / electrode structure 28, and a fuel gas is provided between the anode side separator 32 and the electrolyte membrane / electrode structure 28. A flow path 36 is provided. A coolant flow path 37 is formed between the fuel cells 20.

  The fuel cell stack 12 communicates with each other in the stacking direction of the fuel cells 20 to supply an oxidant gas, for example, an oxidant gas inlet communication hole 38a for supplying an oxygen-containing gas (hereinafter also referred to as air), a fuel gas, For example, a fuel gas inlet communication hole 40a for supplying a hydrogen-containing gas (hereinafter also referred to as hydrogen gas), a cooling medium inlet communication hole 41a for supplying a cooling medium (for example, pure water, ethylene glycol, oil, etc.), and the oxidizing agent An oxidant gas outlet communication hole 38b for discharging gas, a fuel gas outlet communication hole 40b for discharging the fuel gas, and a cooling medium outlet communication hole 41b for discharging the cooling medium are provided.

  The oxidant gas supply device 14 includes an air pump 50 that compresses and supplies air from the atmosphere, and the air pump 50 is disposed in the air supply flow path 52. The air supply channel 52 is provided with a humidifier 54 that exchanges moisture and heat between the supply gas and the exhaust gas, and the air supply channel 52 is connected to the oxidant gas inlet of the fuel cell stack 12. It communicates with the communication hole 38a.

  The oxidant gas supply device 14 includes an air discharge channel 56 that communicates with the oxidant gas outlet communication hole 38b. The air discharge channel 56 communicates with a humidifying medium passage (not shown) of the humidifier 54, and is supplied to the fuel cell stack 12 from the air pump 50 through the air supply channel 52. A back pressure control valve 58 with an adjustable opening is provided for adjusting the pressure of the air. The back pressure control valve 58 is preferably a normally closed type (closed when not energized) back pressure valve.

  The air discharge channel 56 communicates with the dilution box 60. In the air supply flow path 52 and the air discharge flow path 56, on-off valves 61a and 61b are disposed in the vicinity of the oxidant gas inlet communication hole 38a and the oxidant gas outlet communication hole 38b.

  The fuel gas supply device 16 includes a hydrogen tank 62 that stores high-pressure hydrogen. The hydrogen tank 62 communicates with the fuel gas inlet communication hole 40 a of the fuel cell stack 12 via a hydrogen supply flow path 64. The hydrogen supply flow path 64 is provided with a shutoff valve 65 and an ejector 66. The ejector 66 supplies the hydrogen gas supplied from the hydrogen tank 62 to the fuel cell stack 12 through the hydrogen supply flow path 64 and exhaust gas containing unused hydrogen gas that has not been used in the fuel cell stack 12. Then, the gas is sucked from the hydrogen circulation path 68 and supplied again as fuel gas to the fuel cell stack 12.

  The off gas passage 70 communicates with the fuel gas outlet communication hole 40b. A hydrogen circulation path 68 communicates with the off gas flow path 70, and a dilution box 60 is connected to the off gas flow path 70 via a purge valve 72. A discharge flow path 74 is connected to the discharge port side of the dilution box 60, and a storage buffer 76 is disposed in the discharge flow path 74. An exhaust passage 78 is connected to the storage buffer 76.

  The cooling medium supply device 15 includes a cooling medium circulation path 80 that communicates with a cooling medium inlet communication hole 41 a and a cooling medium outlet communication hole 41 b provided in the fuel cell stack 12 and circulates the cooling medium to the fuel cell stack 12. A radiator 82, a thermo stud 84, and a cooling medium circulation pump 86 are disposed in the cooling medium circulation path 80, and a radiator fan 88 is disposed in the radiator 82.

  A bypass path 80 a that bypasses the radiator 82 is connected to the thermo stud 84. The thermostud 84 selectively connects the radiator 82 and the bypass path 80a to the cooling medium circulation path 80 based on the temperature of the cooling medium.

  As shown in FIG. 2, one end of a bus line 90 is connected to the fuel cell stack 12, and the other end of the bus line 90 is connected to an inverter 92. A drive motor 94 for three-phase vehicle travel is connected to the inverter 92. Note that two bus lines 90 are substantially used. However, in order to simplify the description, only one bus line 90 is used. The same applies to the other lines described below.

  An FC contactor 96 is disposed on the bus line 90 and an air pump 50 is connected to the bus line 90. One end of a power line 98 is connected to the bus line 90, and the battery 17 is connected to the power line 98 via a DC / DC converter 100 and a battery contactor 102. The power line 98 is provided with a branch power line 104, and a 12 V power source 108 is connected to the branch power line 104 via a downverter (DC / DC converter) 106. The 12V power source 108 is connected to fuel cell auxiliaries such as a radiator fan 88 and a pump 86. Note that the 12V power supply 108 may be a voltage lower than that of the battery 17 and is not limited to 12V.

  The operation of the fuel cell system 10 configured as described above will be described below.

  First, during operation of the fuel cell system 10, air is sent to the air supply passage 52 via the air pump 50 that constitutes the oxidant gas supply device 14. The air is humidified through the humidifier 54 and then supplied to the oxidant gas inlet communication hole 38 a of the fuel cell stack 12. Air is supplied to the cathode electrode 24 by moving along the oxidant gas flow path 34 provided in each fuel cell 20 in the fuel cell stack 12.

  The used air is exhausted from the oxidant gas outlet communication hole 38 b to the air exhaust flow path 56 and is sent to the humidifier 54 to humidify the newly supplied air, and then through the back pressure control valve 58. Introduced into the dilution box 60. This hydrogen gas is discharged to the storage buffer 76 after the hydrogen concentration is lowered by being mixed with the air off-gas.

  On the other hand, in the fuel gas supply device 16, the shutoff valve 65 is opened so that the pressure is reduced from the hydrogen tank 62 by a pressure reducing valve (not shown), and then the hydrogen gas is supplied to the hydrogen supply flow path 64. This hydrogen gas is supplied to the fuel gas inlet communication hole 40 a of the fuel cell stack 12 through the hydrogen supply channel 64. The hydrogen gas supplied into the fuel cell stack 12 is supplied to the anode electrode 26 by moving along the fuel gas flow path 36 of each fuel cell 20.

  The used hydrogen gas is sucked into the ejector 66 from the fuel gas outlet communication hole 40b through the hydrogen circulation path 68, and is supplied again to the fuel cell stack 12 as fuel gas. Accordingly, the air supplied to the cathode electrode 24 and the hydrogen gas supplied to the anode electrode 26 react electrochemically to generate power.

  The hydrogen gas circulating through the hydrogen circulation path 68 is likely to contain impurities. For this reason, the hydrogen gas mixed with impurities is introduced into the dilution box 60 when the purge valve 72 is opened.

  Further, in the cooling medium supply device 15, the cooling medium is introduced from the cooling medium circulation path 80 into the cooling medium inlet communication hole 41 a of the fuel cell stack 12 under the action of the pump 86. The cooling medium is supplied to the cooling medium flow path 37 in the fuel cell stack 12, cools each fuel cell 20, and then is discharged from the cooling medium outlet communication hole 41 b to the cooling medium circulation path 80.

  Next, a method for stopping operation of the fuel cell system 10 will be described below along the timing chart shown in FIG.

  As described above, the fuel cell system 10 mounted on a fuel cell vehicle (not shown) performs a desired travel by performing a normal operation. Then, when an ignition switch (not shown) is turned off, the operation stop process of the fuel cell system 10 is started.

  For example, after a predetermined time including a failure detection time has elapsed after the ignition switch is turned off, the shutoff valve 65 is closed, while the back pressure control valve 58 is closed when the opening degree control is stopped ( (See FIG. 4). Further, the air pump 50 constituting the oxidant gas supply device 14 is considerably decelerated compared with that during normal operation, and supplies the oxygen stoichiometric gas in the oxidant gas at a low oxygen stoichiometry lower than that during normal power generation. To do. Specifically, the low oxygen stoichiometry is set to around 1.

  On the other hand, the fuel cell stack 12 continues to generate power, and the generated voltage (FC voltage) is set to a higher voltage than during normal power generation, and the current (FC current) extracted from the fuel cell stack 12 is: The value is set to prevent hydrogen gas, which is a fuel gas, from passing through the solid polymer electrolyte membrane 22 and moving from the anode side to the cathode side. At that time, in FIG. 2, the FC contactor 96 and the battery contactor 102 are turned on, and the electric power obtained at the time of power generation by the fuel cell stack 12 is charged to the battery 17 after the voltage is lowered by the DC / DC converter 100. The

  As described above, in the fuel cell stack 12, low oxygen stoichiometric air is required, while power generation is performed in a state where the supply of hydrogen gas is stopped due to the shutoff of the shutoff valve 65. The power generated by the fuel cell stack 12 is discharged to the battery 17 (battery DCHG in FIG. 3). Accordingly, when the power generation voltage of the fuel cell stack 12 drops to a predetermined voltage, that is, the voltage N1 (V) that cannot be supplied to the battery 17 (substantially the same voltage as the voltage of the battery 17), the power generation is supplied only to the air pump 50. The

  Thereby, in the fuel cell stack 12, the hydrogen concentration on the anode side decreases, while the oxygen concentration on the cathode side decreases. Therefore, for example, when the hydrogen pressure on the anode side becomes a predetermined pressure or less, the air pump 50 is turned off and the battery contactor 102 is turned off. The predetermined pressure is a pressure at which the voltage is reduced to such an extent that the air pump 50 cannot be driven.

  Therefore, as shown in FIG. 5, the fuel cell stack 12 is generated by the hydrogen gas and air remaining inside. The electric power generated by the power generation of the fuel cell stack 12 is stepped down via the downverter 106 and then charged to the 12V power source 108 (D / V DCHG), and from the 12V power source 108 to the cooling medium supply device 15. Specifically, electric power is supplied to the radiator fan 88 and the pump 86.

  In the cooling medium supply device 15, since the pump 86 is driven, the cooling medium circulates through the cooling medium circulation path 80 and the fuel cell stack 12, and the cooling medium is sent to the radiator 82. When the cooling medium passes through the radiator 82, the cooling medium is cooled under the blowing action of the radiator fan 88, and the fuel cell stack 12 can be cooled to near the outside air temperature.

  Further, when the power generation voltage of the fuel cell stack 12 decreases to the vicinity of the operation limit voltage of the downverter 106, the back pressure control valve 58 is once opened (atmospheric pressure) and the FC contactor 96 is turned off.

  In this case, in this embodiment, when the ignition switch is turned off, the back pressure control valve 58, the air pump 50, and the shutoff valve 65 are operated. Accordingly, in the fuel cell stack 12, power is generated by the hydrogen gas remaining in the fuel cell stack 12 and the low-oxygen stoichiometric air, and the generated power is supplied to the battery 17 and discharged.

  As a result, the hydrogen concentration decreases on the anode side in the fuel cell stack 12, and the oxygen concentration decreases and the nitrogen concentration increases on the cathode side. Therefore, high concentration nitrogen gas is generated on the cathode side as exhaust gas, and the nitrogen gas is supplied to the dilution box 60 and the storage buffer 76. On the other hand, on the anode side, a negative pressure state occurs due to a decrease in hydrogen concentration, and nitrogen gas permeates from the cathode side to the anode side. Accordingly, the fuel cell stack 12 and the gas piping connected to the fuel cell stack 12 can be filled with nitrogen gas which is an inert gas.

  Moreover, when the power generation voltage at the time of power generation of the fuel cell stack 12 drops below the set voltage value N1 (V), the supply of the generated power to the battery 17 is stopped, while the generated power is supplied only to the air pump 50. Has been. For this reason, even after the supply of power to the battery 17 becomes impossible, the supply of power to the air pump 50 is performed, and power generation can be continued.

  Further, in the present embodiment, the fuel cell stack 12 is generated with hydrogen and oxygen remaining in the fuel cell stack 12 in a state in which the supply of air is stopped by turning off the air pump 50. (D / V DCHG in FIG. 3).

  Therefore, as shown in FIG. 6, when the fuel cell stack 12 is generated while supplying air through the air pump 50, the nitrogen replacement range in the system is up to the range B and the range C. On the other hand, when the power generation of the fuel cell stack 12 is performed after the air pump 50 is stopped, the replacement range by the nitrogen gas is expanded to the range A on the inlet side of the fuel cell stack 12. Thereby, even if the fuel cell system 10 is stopped for a relatively long period of time, there is an advantage that deterioration of the fuel cell 20 can be prevented as much as possible.

  Furthermore, in the fuel cell stack 12, power is supplied from the fuel cell stack 12 to the 12V power source 108 when power generation is performed after the supply of air is stopped. Therefore, the voltage is supplied from the 12V power source 108 to the fuel cell auxiliary machines, for example, the radiator fan 88 and the pump 86, and the consumption (discharge) of the generated power is reliably performed.

  For this reason, as shown in FIG. 7, the voltage (stack voltage) of the fuel cell stack 12 can be lowered to a lower voltage, and the oxygen concentration in the fuel cell stack 12 is further reduced. Thereby, while the fuel cell stack 12 is stopped, the deterioration of the solid polymer electrolyte membrane 22 due to the mixture of hydrogen and oxygen is suppressed, while the corrosion current is blocked due to the lack of oxygen at the time of start-up, thereby suppressing the start-up deterioration. It becomes possible.

  Further, the fuel cell stack 12 is cooled under the driving action of the cooling medium supply device 15 during the discharge process. Therefore, as shown in FIG. 8, generally, the higher the temperature, the more easily deteriorated fuel cell 20 is not exposed to a high temperature, and the deterioration during stoppage or start-up of the fuel cell is better. It is suppressed.

  If a temperature drop occurs while the fuel cell stack 12 is stopped, air is sucked from outside the system, and the concentration of the oxidant gas in the fuel cell stack 12 increases. For this reason, by performing the stop process while cooling the fuel cell stack 12, there is almost no temperature decrease while the fuel cell stack 12 is stopped, the amount of air sucked is reduced, and the rate of increase in oxygen concentration is reduced. . Thereby, it is possible to obtain an effect that it is possible to suppress deterioration of the fuel cell stack 12 as much as possible with a simple and compact configuration.

  Furthermore, the oxygen gas has a low oxygen stoichiometric value of around 1. Accordingly, during power generation, oxygen can be consumed almost completely to effectively increase the nitrogen gas concentration, and hydrogen permeation from the anode side to the cathode side due to insufficient oxygen supply can be suppressed.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 12 ... Fuel cell stack 14 ... Oxidant gas supply device 16 ... Fuel gas supply device 17 ... Battery 18 ... Controller 20 ... Fuel cell 22 ... Solid polymer electrolyte membrane 24 ... Cathode electrode 26 ... Anode electrode 28 ... Electrolyte membrane / electrode structure 30, 32 ... Separator 34 ... Oxidant gas flow path 36 ... Fuel gas flow path 37 ... Cooling medium flow path 38a ... Oxidant gas inlet communication hole 38b ... Oxidant gas outlet communication hole 40a ... Fuel gas Inlet communication hole 40b ... Fuel gas outlet communication hole 41a ... Cooling medium inlet communication hole 41b ... Cooling medium outlet communication hole 50 ... Air pump 52 ... Air supply flow channel 54 ... Humidifier 56 ... Air discharge flow channel 58 ... Back pressure control valve 60 Dilution boxes 61a and 61b Open / close valve 62 Hydrogen tank 64 Hydrogen supply flow path 65 Shut-off valve 66 Ejector 68 Hydrogen circulation path DESCRIPTION OF SYMBOLS 70 ... Off gas flow path 72 ... Purge valve 74 ... Discharge flow path 76 ... Storage buffer 78 ... Exhaust flow path 80 ... Cooling medium circulation path 80a ... Bypass path 82 ... Radiator 84 ... Thermo stud 86 ... Pump 88 ... Radiator fan 96 ... FC contactor DESCRIPTION OF SYMBOLS 100 ... DC / DC converter 102 ... Battery contactor 106 ... Downverter 108 ... 12V power supply

Claims (4)

A fuel cell that generates electricity by an electrochemical reaction of an oxidant gas supplied to the cathode side and a fuel gas supplied to the anode side;
An oxidant gas supply device for supplying the oxidant gas to the fuel cell;
A fuel gas supply device for supplying the fuel gas to the fuel cell;
A cooling medium supply device for supplying a cooling medium to the fuel cell;
A power storage device connectable to the fuel cell;
A method for stopping operation of a fuel cell system comprising:
A first step of generating electricity in the fuel cell while supplying the oxidant gas and the fuel gas to the fuel cell;
Upon detecting a stop command of the fuel cell, while stopping supply of the fuel gas, the oxidant gas, while supplying to the fuel cell at a low hypoxic stoichiometric than the oxygen stoichiometry of the normal power generation, the low A second step of generating the fuel cell with the oxidant gas of oxygen stoichiometry and the fuel gas remaining in the fuel cell , and supplying generated electric power obtained from the fuel cell to the power storage device;
After the supply of the oxidant gas of the low oxygen stoichiometry to the fuel cell is stopped, the fuel cell is caused to generate power only with the residual gas in the fuel cell, and the generated power obtained from the fuel cell is supplied to the cooling medium. A third step of supplying to the supply device;
A method for stopping the operation of the fuel cell system.   2. The operation stopping method according to claim 1, wherein generated power obtained from the fuel cell is stepped down through a downverter and then supplied to the cooling medium supply device. 3. The operation stop method according to claim 1, wherein the cooling medium supply device includes a radiator fan disposed in a radiator that cools the cooling medium, and a pump that circulates the cooling medium to the fuel cell,
In the third step, the generated electric power is supplied to the radiator fan and the pump.   4. The operation of a fuel cell system according to claim 1, wherein the oxidant gas of the low oxygen stoichiometry is set to about 1 in the low oxygen stoichiometry. 5. How to stop.

Images