JP2006120385A - Fuel cell system and operation method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system not generating voltage shift, capable of preventing deterioration of performance when the number of stoppage is numerous, in which, hydrogen and oxygen are not mixed in a fuel gas flow passage at temporal stoppage by keeping the fuel gas flow passage in a state of sealing the fuel gas without introducing air when temporally stopping the fuel cell system for a short time. <P>SOLUTION: The fuel cell formed by interposing an electrolyte layer between a fuel electrode and an oxygen electrode comprises a fuel cell stack 20 laminated with separators interposed between them, on which fuel gas flow passages are formed along the fuel electrode; a pressure detection means detecting pressure in the fuel gas flow passage; a purging means purging the fuel gas in the fuel gas flow passage with substitution gas; and a control means stopping supply of the fuel gas to the fuel gas flow passage, selectively performing a stand-by mode performing the above purge when the pressure in the fuel gas flow passage gets to a prescribed pressure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system and an operation method thereof.

  Conventionally, since fuel cells have high power generation efficiency and do not emit harmful substances, they have been put into practical use as power generators for industrial and household use, or as power sources for artificial satellites and spacecrafts. Development is progressing as a power source for vehicles such as buses and trucks. The fuel cell may be an alkaline aqueous solution type, a phosphoric acid type, a molten carbonate type, a solid oxide type, a direct type methanol or the like, but a solid polymer type fuel cell is generally used.

  In this case, a MEA (Membrane Electrode Assembly) in which a solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes and joined together is used. When one of the gas diffusion electrodes is used as a fuel electrode (anode electrode) and hydrogen gas as a fuel is supplied to the surface of the gas diffusion electrode, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions are converted into a solid polymer electrolyte. Permeates the membrane. Further, when the other of the gas diffusion electrodes is an oxygen electrode (cathode electrode) and air as an oxidant is supplied to the surface, oxygen in the air is combined with the hydrogen ions and electrons to generate water. The An electromotive force is generated by such an electrochemical reaction.

  And when stopping a fuel cell, supply of hydrogen is stopped. In this case, if left as it is, hydrogen continues to be consumed little by little, and the pressure of the hydrogen gas on the fuel electrode side in the fuel cell gradually decreases. Here, when the pressure of the hydrogen gas becomes atmospheric pressure or less, the oxygen electrode side air passes through the MEA and moves to the fuel electrode side, so that the fuel electrode side is in a mixed state of hydrogen and air (oxygen). . When the oxygen concentration on the fuel electrode side exceeds a certain value, a potential shift occurs in the MEA, resulting in a high potential state of 1.2 [V] or more, catalyst particles are eluted, and the performance of the fuel cell is degraded. End up.

  In particular, in the case of a fuel cell used as a power source for a vehicle, the vehicle stops not only when it arrives at its destination but also when it stops at a store such as a convenience store on the way, although it temporarily stops. Therefore, the number of stops increases. Therefore, the performance of the fuel cell is deteriorated earlier.

Therefore, in order to prevent the occurrence of potential shift, purging with an inert gas such as nitrogen may be considered, but in this case, it is necessary to mount an inert gas supply source on the vehicle, and the system is complicated. And it becomes large. For this reason, a technique has been proposed in which the time required for a mixed state of hydrogen and air (oxygen) is shortened by reducing the pressure on the fuel electrode side in the fuel cell and rapidly introducing air (for example, Patent Document 1). reference.).
JP 2002-324564 A

  However, in the conventional fuel cell system, hydrogen cannot be completely discharged even if the fuel electrode side in the fuel cell is depressurized. Therefore, when air is introduced, a mixed state of hydrogen and air (oxygen) is introduced. Become.

  The present invention solves the above-mentioned conventional problems, and maintains a state in which fuel gas is sealed without introducing air into the fuel gas flow path when the fuel cell system is temporarily stopped for a short stop time. Thus, when the fuel cell is temporarily stopped, hydrogen and oxygen are not mixed, and even if the number of stops is large, a potential shift does not occur and the fuel cell system can prevent performance degradation. And an operation method thereof.

  Therefore, in the fuel cell system of the present invention, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is laminated with a separator having a fuel gas flow path formed along the fuel electrode. A fuel cell stack, a pressure detecting means for detecting the pressure in the fuel gas flow path, a purge means for purging the fuel gas in the fuel gas flow path with a replacement gas, and an operation stop command, And control means for selectively executing a standby mode in which the purge is performed when the supply of the fuel gas to the fuel gas channel is stopped and the pressure in the fuel gas channel reaches a predetermined pressure value.

  In another fuel cell system of the present invention, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is stacked with a separator having a fuel gas flow path formed along the fuel electrode. A fuel cell stack; purge means for purging the fuel gas in the fuel gas passage with a replacement gas; a timer for measuring an elapsed time since the supply of fuel gas to the fuel gas passage is stopped; And a control means for selectively executing a standby mode in which the purge is performed when the elapsed time reaches a predetermined time.

  In still another fuel cell system of the present invention, a fuel cell having an electrolyte layer sandwiched between a fuel electrode and an oxygen electrode is laminated with a separator having a fuel gas flow path formed along the fuel electrode. A fuel cell stack, pressure detection means for detecting the pressure in the fuel gas flow path, purge means for purging the fuel gas in the fuel gas flow path with a replacement gas, and fuel gas to the fuel gas flow path When the timer for measuring the elapsed time since the supply of the gas and the operation stop command are received, the supply of the fuel gas to the fuel gas channel is stopped, and the pressure in the fuel gas channel is a predetermined pressure. Or a control means for selectively executing a standby mode for performing the purge when the elapsed time reaches a predetermined time.

  In still another fuel cell system of the present invention, the predetermined pressure value is atmospheric pressure.

  In still another fuel cell system of the present invention, the predetermined pressure value is a minimum value at which the pressure in the fuel gas flow path starts from decreasing to increasing.

  In still another fuel cell system of the present invention, the predetermined time is a time during which air enters the fuel gas flow path.

  In still another fuel cell system of the present invention, the predetermined time is a time when a potential shift occurs.

  In still another fuel cell system according to the present invention, the fuel cell system further includes mode selection means for selecting the standby mode and the stop mode, and the control means receives the operation stop command and enters the fuel gas flow path. The fuel gas supply is stopped, and the stop mode in which the fuel gas in the fuel gas flow path is purged with a replacement gas is selectively executed.

  In the operation method of the fuel cell system of the present invention, the operation method of the fuel cell system is capable of purging the fuel gas in the fuel gas flow path in the fuel cell stack with the replacement gas. The supply of the fuel gas to the fuel gas channel is stopped, and the standby mode for performing the purge is selectively executed when the pressure in the fuel gas channel reaches a predetermined pressure value.

  In another fuel cell system operation method of the present invention, the fuel cell system operation method is capable of purging the fuel gas in the fuel gas flow path of the fuel cell stack with a replacement gas, and receives an operation stop command. Then, the supply of the fuel gas to the fuel gas passage is stopped, and the standby mode for performing the purge is selectively executed when the elapsed time reaches a predetermined time.

  According to still another fuel cell system operation method of the present invention, a fuel cell system operation method capable of purging the fuel gas in the fuel gas flow path of the fuel cell stack with a replacement gas, wherein the operation stop command is issued. When this is received, the supply of the fuel gas to the fuel gas passage is stopped, and the purge is performed when the pressure in the fuel gas passage becomes a predetermined pressure value or when the elapsed time reaches a predetermined time. Is selectively executed.

  In still another fuel cell system operating method of the present invention, the predetermined pressure value is atmospheric pressure.

  In still another fuel cell system operation method of the present invention, the predetermined pressure value is a minimum value at which the pressure in the fuel gas flow path starts from decreasing to increasing.

  In still another fuel cell system operating method of the present invention, the predetermined time is a time during which air enters the fuel gas flow path.

  In still another fuel cell system operating method of the present invention, the predetermined time is a time at which a potential shift occurs.

  In still another fuel cell system operation method of the present invention, when the standby mode or operation stop command is received, the supply of fuel gas to the fuel gas flow path is stopped, and the fuel gas flow The stop mode in which the fuel gas in the passage is purged with the replacement gas is selectively executed.

  According to the present invention, in a fuel cell system, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is stacked with a separator having a fuel gas flow path formed along the fuel electrode. A fuel cell stack, a pressure detecting means for detecting the pressure in the fuel gas flow path, a purge means for purging the fuel gas in the fuel gas flow path with a replacement gas, and an operation stop command, And control means for selectively executing a standby mode in which the purge is performed when the supply of the fuel gas to the fuel gas channel is stopped and the pressure in the fuel gas channel reaches a predetermined pressure value.

  In this case, if the standby mode is selected when the operation of the fuel cell system is stopped, the fuel gas in the fuel gas flow path is not discharged into the atmosphere, so that the fuel gas is not wasted. Further, since the fuel gas is not discharged, there is no safety problem even if the operation of the fuel cell system is stopped in a closed place. Further, since the state in which the fuel gas is sealed in the fuel gas channel is maintained, hydrogen and oxygen are not mixed in the fuel gas channel, and the occurrence of potential shift can be prevented. Therefore, even if the number of stops is large, a potential shift does not occur, and the performance of the fuel electrode can be prevented from deteriorating. Further, since purge is performed when the pressure in the fuel gas flow path reaches a predetermined pressure value, the hydrogen gas remaining in the fuel gas flow path is rapidly replaced with air and mixed with oxygen in the air. There is no. Therefore, no potential shift occurs in the unit cell, and the catalyst particles are not eluted and the performance of the fuel cell stack is not deteriorated.

  Further, in another fuel cell system, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is stacked with a separator having a fuel gas flow path formed along the fuel electrode. A battery stack, purge means for purging the fuel gas in the fuel gas flow path with a replacement gas, a timer for measuring an elapsed time since the supply of the fuel gas to the fuel gas flow path is stopped, When the stop command is received, control means for stopping the supply of the fuel gas to the fuel gas flow path and selectively executing a standby mode for performing the purge when the elapsed time reaches a predetermined time.

  In this case, if the standby mode is selected when the operation of the fuel cell system is stopped, the fuel gas in the fuel gas flow path is not discharged into the atmosphere, so that the fuel gas is not wasted. Further, since the fuel gas is not discharged, there is no safety problem even if the operation of the fuel cell system is stopped in a closed place. Further, since the state in which the fuel gas is sealed in the fuel gas channel is maintained, hydrogen and oxygen are not mixed in the fuel gas channel, and the occurrence of potential shift can be prevented. Therefore, even if the number of stops is large, a potential shift does not occur, and the performance of the fuel electrode can be prevented from deteriorating. Furthermore, since purging is performed when the elapsed time since the supply of the fuel gas to the fuel gas passage is stopped for a predetermined time, the hydrogen gas remaining in the fuel gas passage is rapidly replaced with air, It will not be mixed with oxygen in the air. Therefore, no potential shift occurs in the unit cell, and the catalyst particles are not eluted and the performance of the fuel cell stack is not deteriorated.

  Further, in another fuel cell system, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is stacked with a separator having a fuel gas flow path formed along the fuel electrode. A battery stack; pressure detection means for detecting pressure in the fuel gas flow path; purge means for purging the fuel gas in the fuel gas flow path with a replacement gas; and supply of fuel gas to the fuel gas flow path When the timer for measuring the elapsed time since the stop and the operation stop command are received, the supply of the fuel gas to the fuel gas passage is stopped, and the pressure in the fuel gas passage becomes a predetermined pressure value. Or a control unit that selectively executes a standby mode in which the purge is performed when the elapsed time reaches a predetermined time.

  In this case, if the standby mode is selected when the operation of the fuel cell system is stopped, the fuel gas in the fuel gas flow path is not discharged into the atmosphere, so that the fuel gas is not wasted. Further, since the fuel gas is not discharged, there is no safety problem even if the operation of the fuel cell system is stopped in a closed place. Further, since the state in which the fuel gas is sealed in the fuel gas channel is maintained, hydrogen and oxygen are not mixed in the fuel gas channel, and the occurrence of potential shift can be prevented. Therefore, even if the number of stops is large, a potential shift does not occur, and the performance of the fuel electrode can be prevented from deteriorating. Further, since the purge is performed when the pressure in the fuel gas passage becomes a predetermined pressure value or the elapsed time after the supply of fuel gas to the fuel gas passage is stopped for a predetermined time, the fuel gas flow The hydrogen gas remaining in the passage is rapidly replaced with air, and is not mixed with oxygen in the air. Therefore, no potential shift occurs in the unit cell, and the catalyst particles are not eluted and the performance of the fuel cell stack is not deteriorated.

  Further, in the operation method of the fuel cell system, the operation method of the fuel cell system is capable of purging the fuel gas in the fuel gas flow path in the fuel cell stack with the replacement gas. The supply of the fuel gas to the fuel gas channel is stopped, and the standby mode for performing the purge is selectively executed when the pressure in the fuel gas channel reaches a predetermined pressure value.

  In this case, if the standby mode is selected when the operation of the fuel cell system is stopped, the fuel gas in the fuel gas flow path is not discharged into the atmosphere, so that the fuel gas is not wasted. Further, since the fuel gas is not discharged, there is no safety problem even if the operation of the fuel cell system is stopped in a closed place. Further, since the state in which the fuel gas is sealed in the fuel gas channel is maintained, hydrogen and oxygen are not mixed in the fuel gas channel, and the occurrence of potential shift can be prevented. Therefore, even if the number of stops is large, a potential shift does not occur, and the performance of the fuel electrode can be prevented from deteriorating. Further, since purge is performed when the pressure in the fuel gas flow path reaches a predetermined pressure value, the hydrogen gas remaining in the fuel gas flow path is rapidly replaced with air and mixed with oxygen in the air. There is no. Therefore, no potential shift occurs in the unit cell, and the catalyst particles are not eluted and the performance of the fuel cell stack is not deteriorated.

  Further, in another fuel cell system operation method, the fuel cell system operation method is capable of purging the fuel gas in the fuel gas flow path in the fuel cell stack with a replacement gas. Then, the supply of the fuel gas to the fuel gas passage is stopped, and when the elapsed time reaches a predetermined time, a standby mode for performing the purge is selectively executed.

  In this case, if the standby mode is selected when the operation of the fuel cell system is stopped, the fuel gas in the fuel gas flow path is not discharged into the atmosphere, so that the fuel gas is not wasted. Further, since the fuel gas is not discharged, there is no safety problem even if the operation of the fuel cell system is stopped in a closed place. Further, since the state in which the fuel gas is sealed in the fuel gas channel is maintained, hydrogen and oxygen are not mixed in the fuel gas channel, and the occurrence of potential shift can be prevented. Therefore, even if the number of stops is large, a potential shift does not occur, and the performance of the fuel electrode can be prevented from deteriorating. Furthermore, since purging is performed when the elapsed time since the supply of the fuel gas to the fuel gas passage is stopped for a predetermined time, the hydrogen gas remaining in the fuel gas passage is rapidly replaced with air, It will not be mixed with oxygen in the air. Therefore, no potential shift occurs in the unit cell, and the catalyst particles are not eluted and the performance of the fuel cell stack is not deteriorated.

  Further, in another fuel cell system operation method, the fuel cell system operation method is capable of purging the fuel gas in the fuel gas flow path in the fuel cell stack with a replacement gas. The fuel gas supply to the fuel gas channel is stopped, and the standby mode for performing the purge when the pressure in the fuel gas channel reaches a predetermined pressure value or when the elapsed time reaches a predetermined time is selected. Run it.

  In this case, if the standby mode is selected when the operation of the fuel cell system is stopped, the fuel gas in the fuel gas flow path is not discharged into the atmosphere, so that the fuel gas is not wasted. Further, since the fuel gas is not discharged, there is no safety problem even if the operation of the fuel cell system is stopped in a closed place. Further, since the state in which the fuel gas is sealed in the fuel gas channel is maintained, hydrogen and oxygen are not mixed in the fuel gas channel, and the occurrence of potential shift can be prevented. Therefore, even if the number of stops is large, a potential shift does not occur, and the performance of the fuel electrode can be prevented from deteriorating. Further, since the purge is performed when the pressure in the fuel gas passage becomes a predetermined pressure value or the elapsed time after the supply of fuel gas to the fuel gas passage is stopped for a predetermined time, the fuel gas flow The hydrogen gas remaining in the passage is rapidly replaced with air, and is not mixed with oxygen in the air. Therefore, no potential shift occurs in the unit cell, and the catalyst particles are not eluted and the performance of the fuel cell stack is not deteriorated.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a fuel cell system according to an embodiment of the present invention.

  In the figure, reference numeral 20 denotes a fuel cell stack as a fuel cell (FC), which is used as a power source for vehicles such as passenger cars, buses, trucks, passenger carts, and luggage carts. Here, the vehicle is equipped with a large number of auxiliary devices that consume electricity, such as lighting devices, radios, and power windows, which are used even when the vehicle is stopped. Since the output range is extremely wide, it is desirable to use the fuel cell stack 20 as a power source and a secondary battery as a power storage means (not shown) in combination.

  The fuel cell stack 20 is of an alkaline aqueous solution type (AFC), phosphoric acid type (PAFC), molten carbonate type (MCFC), solid oxide type (SOFC), direct methanol (DMFC), or the like. However, a polymer electrolyte fuel cell (PEMFC) is desirable.

  More preferably, it is called a PEMFC (Proton Exchange Membrane Fuel Cell) type fuel cell or PEM (Proton Exchange Membrane) type fuel cell using hydrogen gas as fuel and oxygen or air as oxidant. Here, the PEM fuel cell is generally a fuel cell in which a catalyst, an electrode, and a separator are combined on both sides of a solid polymer electrolyte membrane as an electrolyte layer that transmits ions such as protons. Are composed of a plurality of stacks connected in series.

  In this case, the solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes and integrated to join. Then, when one of the gas diffusion electrodes is used as a fuel electrode, and fuel gas, that is, hydrogen gas as anode gas, is supplied to the fuel electrode through a fuel gas flow channel in contact with the surface of the fuel electrode, hydrogen is converted into hydrogen ions (protons). ) And electrons, and hydrogen ions permeate the solid polymer electrolyte membrane. Further, when the other of the gas diffusion electrodes is an oxygen electrode and an oxidizing gas, that is, air as a cathode gas, is supplied to the oxygen electrode through an air flow channel in contact with the surface of the oxygen electrode, oxygen in the air, the hydrogen ions And the electrons combine to produce water. An electromotive force is generated by such an electrochemical reaction.

  In the figure, an apparatus for supplying hydrogen gas as fuel gas to the fuel cell stack 20 is shown. Although hydrogen gas, which is fuel taken out by reforming methanol, gasoline, or the like by a reformer (not shown), can be directly supplied to the fuel cell stack 20, it is stable and sufficient even during high-load operation of the vehicle. In order to be able to supply an amount of hydrogen gas, it is desirable to supply the hydrogen gas stored in the fuel storage means 73. Accordingly, hydrogen gas is always sufficiently supplied at a substantially constant pressure, so that the fuel cell stack 20 can follow the fluctuation of the load on the vehicle and supply a necessary current. In this case, the output impedance of the fuel cell stack 20 is extremely low and can be approximated to zero.

  Hydrogen gas is stored in a container containing a hydrogen storage alloy, a container containing a hydrogen storage liquid such as decalin, a fuel storage means 73 such as a hydrogen gas cylinder, a first fuel supply line 21 as a fuel supply line, and The fuel is supplied to the inlet of the fuel gas flow path of the fuel cell stack 20 through a second fuel supply pipe 33 as a fuel supply pipe connected to the first fuel supply pipe 21. The first fuel supply pipe 21 is provided with a fuel supply electromagnetic valve 26 as a hydrogen supply electromagnetic valve. The second fuel supply line 33 is provided with a pressure sensor 78 as pressure detecting means for detecting the pressure in the fuel gas flow path. The fuel storage means 73 has a sufficiently large capacity and always has a capability of supplying hydrogen gas at a sufficiently high pressure. In addition, the said fuel storage means 73 may be single, may be plural, and may be any number in the case of plural.

  The hydrogen gas discharged as an unreacted component from the outlet of the fuel gas flow path of the fuel cell stack 20 is discharged to the outside of the fuel cell stack 20 through the fuel discharge pipe 31. A water recovery drain tank 60 as a recovery container is disposed in the fuel discharge line 31. The water recovery drain tank 60 is connected to a fuel discharge line 30 for discharging water and separated hydrogen gas. The fuel discharge line 30 is provided with a suction circulation pump 36 as a hydrogen circulation pump. Has been. In addition, a hydrogen circulation solenoid valve 34 as a hydrogen circulation switching solenoid valve is disposed in the fuel discharge pipe 30. The end of the fuel discharge line 30 opposite to the water recovery drain tank 60 is connected to the second fuel supply line 33. Thereby, the hydrogen gas led out of the fuel cell stack 20 can be recovered and supplied to the fuel gas flow path of the fuel cell stack 20 for reuse.

  The water recovery drain tank 60 also functions as a suction tank for storing the hydrogen gas discharged from the fuel gas passage when the operation of the fuel cell system is stopped. Therefore, the capacity of the water recovery drain tank 60 is such that when air as a replacement gas is introduced into the fuel gas flow path and hydrogen gas as the fuel gas is purged, the capacity of the water recovery drain tank 60 is increased. The remaining hydrogen gas is rapidly driven into the water recovery drain tank 60, and is set so as to be large enough not to remain in the fuel gas flow path. That is, at the time when air is introduced into the fuel cell stack 20, the hydrogen gas remaining in the fuel gas flow path is rapidly removed even if the fuel gas flow path of the fuel cell stack 20 is not evacuated. The water recovery drain tank 60 has a sufficiently large capacity so that it does not move into the water recovery drain tank 60 and become mixed with oxygen in the air introduced in the fuel cell stack 20. Is.

  Further, a fuel discharge line 56 as an anode gas discharge pipe is connected between the suction circulation pump 36 and the hydrogen circulation solenoid valve 34 in the fuel discharge pipe 30, and the fuel discharge pipe 56 has a hydrogen exhaust gas. A hydrogen start / stop electromagnetic valve 56a as an electromagnetic valve is provided. Thereby, hydrogen gas can be discharged at the end of the operation of the fuel cell stack 20.

  Further, the second fuel supply line 33 is connected to an outside air introduction line 28 as a purge means. The outside air introduction conduit 28 is provided with an outside air introduction solenoid valve 28a and an air filter 28b as air introduction solenoid valves, and the outside air as a replacement gas flows into the fuel gas flow when the operation of the fuel cell stack 20 ends. It can introduce | transduce into a path | route and can purge the hydrogen gas as fuel gas.

  Here, the fuel supply solenoid valve 26, the outside air introduction solenoid valve 28a, the hydrogen circulation solenoid valve 34, and the hydrogen start / stop solenoid valve 56a are so-called on-off type, such as an electric motor, a pulse motor, and an electromagnet. Actuated by an actuator consisting of Further, the suction circulation pump 36 may be of any type as long as it can forcibly discharge the reverse diffusion water together with the hydrogen gas and can bring the inside of the fuel gas passage into a negative pressure state. Good. The air filter 28b removes dust, impurities, harmful gases and the like contained in the air.

  On the other hand, air as an oxidant is supplied to an air flow path of the fuel cell stack 20 from an oxidant supply source such as an air supply fan, an air cylinder, and an air tank (not shown) through an intake manifold and the like. Note that oxygen can be used as the oxidizing agent instead of air. And the air discharged | emitted from an air flow path is discharged | emitted in air | atmosphere through an exhaust manifold, a condenser, etc. which are not shown in figure.

  The intake manifold is provided with a water supply nozzle for spraying water to maintain the oxygen electrode (cathode electrode) of the fuel cell stack 20 in a wet state. Further, the oxygen electrode and the fuel electrode can be cooled by the sprayed water. Further, the condenser is for condensing and removing moisture contained in the air discharged from the fuel cell stack 20, and the water condensed by the condenser is collected in a water tank (not shown) Supplied to the supply nozzle.

  The secondary battery as the power storage means is a so-called battery (storage battery), and a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, a lithium ion battery, a sodium sulfur battery, and the like are generally used. The power storage means does not necessarily have to be a battery, and electrically stores and discharges energy, such as a capacitor (capacitor) such as an electric double layer capacitor, a flywheel, a superconducting coil, and a pressure accumulator. Any form may be used as long as it has a function. Furthermore, any of these may be used alone, or a plurality of them may be used in combination.

  The fuel cell stack 20 is connected to a load (not shown) and supplies the generated current to the load. Here, the load is generally an inverter device that is a drive control device, and converts a direct current from the fuel cell stack 20 or the power storage means into an alternating current to rotate a vehicle wheel. To supply. Here, the drive motor also functions as a generator, and generates a so-called regenerative current when the vehicle is decelerated. In this case, since the drive motor is rotated by the wheel to generate electric power, the wheel is braked, that is, functions as a vehicle braking device (brake). Then, the regenerative current is supplied to the power storage means, and the power storage means is charged.

  In the present embodiment, the fuel cell system has control means (not shown). The control means includes arithmetic means such as a CPU and MPU, storage means such as a magnetic disk and a semiconductor memory, an input / output interface and the like, and is supplied from various sensors to the fuel gas flow path and the air flow path of the fuel cell stack 20. The flow rate of hydrogen, oxygen, air, etc., temperature, output voltage, etc. are detected and the oxidant supply source, fuel supply solenoid valve 26, outside air introduction solenoid valve 28a, hydrogen circulation solenoid valve 34, suction circulation pump 36, The operation of the hydrogen start / stop solenoid valve 56a and the like is controlled. The control means also includes a timer for measuring the elapsed time since the supply of hydrogen gas to the fuel gas flow path of the fuel cell stack 20 is stopped. Then, the control means selectively executes a standby mode or a stop mode, as will be described later. Furthermore, the control means controls the operation of all the devices that supply fuel and oxidant to the fuel cell stack 20 in cooperation with other sensors and other control devices.

  Next, the configuration of the main switch of the vehicle will be described in detail.

  FIG. 2 is a diagram showing a configuration of a main switch of the vehicle in the embodiment of the present invention. 2A is a front view of the main switch, and FIG. 2B is a perspective view of the main switch with a key attached.

  In FIG. 2, reference numeral 11 denotes a main switch of a vehicle on which the fuel cell stack 20 is mounted as a power source, and the driver inserts the key 12 into the key insertion slot 11 a and operates. The basic internal structure of the main switch 11 is the same as that of a main switch in a vehicle such as a general passenger car, and a detailed description thereof will be omitted. Further, the basic operation method of the main switch 11 is almost the same as that of a main switch in a vehicle such as a general passenger car. The key 12 is rotated with the key 12 inserted into the key insertion slot 11a. The vehicle and the fuel cell system are configured to perform an operation corresponding to the rotational position.

  In this embodiment, the rotational position of the key 12 is set in five stages as shown in FIG. 2A, and corresponds to the operations of OFF, IDOL, ACC, ON, and START, respectively. Here, OFF is a stop of the fuel cell system, IDOL is a temporary stop of the fuel cell system, ACC is a power on of an auxiliary device such as a radio and a headlight mounted on the vehicle, and ON is a fuel This is the operation of the battery system, and START is the start of operation of the fuel cell system. At the ACC, ON, and START positions, the key 12 cannot be extracted from the key insertion slot 11a, but at the OFF position, the key 12 can be extracted from the key insertion slot 11a. Further, at the IDOL position, the key 12 can be removed from the key insertion slot 11a by depressing the idling button 13.

  In the present embodiment, for example, when the vehicle is temporarily stopped, such as when stopping at a store such as a convenience store, the idling button 13 is pushed down so that the key 12 is removed from the key insertion slot 11a at the IDOL position. It has become. As a result, a standby mode command is transmitted to the control means of the fuel cell system, and the control means executes the standby mode. Therefore, the fuel cell system is temporarily stopped to stop operation for a short period of time equal to or less than a predetermined time. Done. In addition, although the said predetermined time can be determined arbitrarily, it is about 10 minutes-2 hours, for example. In the fuel cell system according to the present embodiment, hydrogen gas is discharged from the fuel gas flow path of the fuel cell stack 20 and air is introduced when performing a normal stop, whereas when performing a temporary stop. In order to prevent hydrogen and oxygen from being mixed in the fuel gas channel by maintaining the state in which hydrogen gas is sealed without introducing air into the fuel gas channel of the fuel cell stack 20. It has become.

  Furthermore, the main switch 11 can be provided with a selection means for selecting to re-enclose the hydrogen gas when the suspension is performed. If you choose to re-enclose the hydrogen gas, when the hydrogen gas pressure in the fuel gas flow path becomes less than atmospheric pressure during the temporary stop, the hydrogen gas is supplied again into the fuel gas flow path. Thus, refilling of hydrogen gas is performed. This prevents the air in the air flow path from flowing into the fuel gas flow path through the solid polymer electrolyte membrane or the gas diffusion electrode, and prevents hydrogen and oxygen from mixing in the fuel gas flow path. Can do.

  Next, the operation of the fuel cell system having the above configuration will be described. First, the operation in steady operation will be described.

  During steady operation in the fuel cell system according to the present embodiment, the hydrogen gas flowing out from the outlet of the fuel storage unit 73 is adjusted after the pressure of the hydrogen gas flowing out from the outlet of the fuel storage unit 73 is set to a predetermined pressure. The pressure is not adjusted during the operation of the fuel cell system, and is maintained as it is. Further, the oxidant supply source always operates to supply a constant amount of air to the air flow path of the fuel cell stack 20. In this case, the amount of air supplied is an amount sufficiently larger than the amount of air necessary for the output of the fuel cell stack 20 to be maximized. During steady operation in the fuel cell system, the rotational position of the key 12 inserted into the key insertion slot 11a of the main switch 11 is the ON position.

  When the fuel cell stack 20 starts operation, reverse diffusion water is generated in each unit cell constituting the fuel cell stack 20, and the reverse diffusion water permeates the solid polymer electrolyte membrane and enters the fuel gas flow path. And the fuel electrode side of the solid polymer electrolyte membrane is humidified. As a result, the fuel electrode side of the solid polymer electrolyte membrane becomes wet, and hydrogen ions generated from hydrogen by the electrochemical reaction can move smoothly in the solid polymer electrolyte membrane.

  Further, the surplus hydrogen gas supplied to the fuel gas flow channel is mixed with the back-diffused water that has permeated into the fuel gas flow channel and becomes surplus to form a gas-liquid mixture. The hydrogen gas that has become the gas-liquid mixture is sucked by the suction circulation pump 36 and led out of the fuel cell stack 20 through the fuel discharge pipe 31 connected to the fuel cell stack 20. The gas-liquid mixture passes through the fuel discharge pipe 31 and is introduced into the water recovery drain tank 60. Then, by staying in the water recovery drain tank 60 having a relatively wide space, heavy moisture falls downward due to gravity, and the reverse diffusion water is separated from the hydrogen gas. The hydrogen gas in a state where the reverse diffusion water is separated and dried is discharged out of the water recovery drain tank 60 from the fuel discharge pipe 30.

  In steady operation, the hydrogen gas discharged from the fuel discharge line 30 passes through the open hydrogen circulation electromagnetic valve 34, is introduced into the second fuel supply line 33, and again. Then, it is supplied to the fuel gas flow path of the fuel cell stack 20 and reused. Since the hydrogen start / stop solenoid valve 56a is in a closed state, the hydrogen gas discharged from the suction circulation pump 36 is not discharged into the atmosphere through the fuel discharge pipe 56, but the second fuel. It is introduced into the supply line 33. Further, since the outside air introduction electromagnetic valve 28 a is also closed, the atmosphere is not introduced into the second fuel supply conduit 33.

  Here, since the fuel discharge line 30 is connected to the side wall of the upper part of the water recovery drain tank 60, only hydrogen gas in a state where the reverse diffusion water is separated and becomes lightweight is removed from the fuel discharge line 30. It is discharged and no water is discharged. Further, since the fuel discharge pipe 31 and the fuel discharge pipe 30 are connected to the side wall of the upper part of the water recovery drain tank 60 at a position apart from each other, they are introduced from the fuel discharge pipe 31 into the water recovery drain tank 60. The gas-liquid mixture thus made does not flow out of the fuel discharge line 30 as it is. Thereby, it is possible to appropriately trap excess reverse diffusion water that has permeated into the fuel gas flow path, and it is possible to collect and reuse the excess hydrogen gas.

  On the other hand, the reverse diffusion water that has been separated from the gas-liquid mixture and dropped is stored as stored water in the lower portion of the water recovery drain tank 60. Since the capacity of the water recovery drain tank 60 is set to be large, the vehicle on which the fuel cell stack 20 is mounted once travels after filling the fuel storage means 73 with hydrogen gas as fuel. It is not necessary to discharge water from the water recovery drain tank 60 until the next time hydrogen gas is filled into the fuel storage means 73.

  Next, the operation when stopping the operation of the fuel cell system will be described. First, the timing of potential shift that occurs when the operation of the fuel cell system is stopped will be described.

  FIG. 3 is a graph showing the relationship between the pressure in the fuel gas flow path and the potential shift timing when the operation of the fuel cell system in the embodiment of the present invention is stopped, and FIG. 4 is the fuel in the embodiment of the present invention. FIG. 5 is a graph showing the relationship between the output voltage and the pressure in the fuel gas passage when the operation of the battery system is stopped. FIG. 5 shows the standby time in the standby mode and the pressure in the fuel gas passage in the embodiment of the present invention. It is a graph which shows the relationship with electric potential shift time.

  In FIG. 3, the vertical axis represents the pressure in the fuel gas flow path, the horizontal axis represents time, and the line 41 represents the relationship between the pressure in the fuel gas flow path and time. A line 42 indicates the timing at which air starts to enter the fuel gas flow path, a line 43 indicates the timing at which the output voltage of the fuel cell stack 20 starts to decrease, and a line 44 causes a potential shift. The line 45 indicates the timing when the voltage drop and the potential shift are completed. From FIG. 3, when the pressure in the fuel gas flow path becomes atmospheric pressure, the mixing of air into the fuel gas flow path is started, and when the pressure in the fuel gas flow path reaches a limit value, the output of the fuel cell stack 20 It can be seen that the voltage drop starts.

  FIG. 4 is a graph showing experimental results using the fuel cell stack 20 actually manufactured by the inventors of the present invention. In FIG. 4, the vertical axis represents the pressure in the fuel gas flow path and the output voltage of the fuel cell stack 20, and the horizontal axis represents time, and the line 51 represents the relationship between the output voltage of the fuel cell stack 20 and time. A line 52 indicates the relationship between the pressure in the fuel gas flow path and time. Point 53 is a point at which the pressure in the fuel gas flow path becomes negative, and 54 is a time when occurrence of a potential shift is predicted. In addition, since it was an experiment using the fuel cell stack 20 that was actually prototyped, the occurrence of potential shift could not be measured.

  Further, FIG. 5 is a graph in the standby mode, in which the vertical axis represents the pressure and potential shift time in the fuel gas flow path, and the horizontal axis represents the standby time. A line 61 indicates the relationship between the potential shift time and the standby time, and a line 62 indicates the relationship between the pressure in the fuel gas flow path and the standby time. Note that the potential shift time is proportional to the degree of deterioration. A line 63 indicates the timing when the pressure in the fuel gas flow path becomes atmospheric pressure, a line 64 indicates a timing when the potential shift starts, and a line 65 indicates a timing when the potential shift ends. If the timing indicated by the line 64 is exceeded, the potential shift time increases, so that the deterioration reaction easily proceeds.

  Next, the operation when the stop mode is selected will be described.

  FIG. 6 is a flowchart showing the operation when stopping the operation of the fuel cell system according to the embodiment of the present invention.

  First, when the vehicle driver rotates the key 12 inserted in the key insertion slot 11a of the main switch 11 and turns the rotation position to OFF, a stop command for operation is transmitted to the control means of the fuel cell system (step S1). Then, the operation for stopping the operation of the fuel cell system is started. In this case, the stop mode is selected by turning off the rotational position of the key 12. When the control means receives an operation stop command, the control means stops the supply of hydrogen gas to the fuel gas flow path, and executes a stop mode for purging the hydrogen gas in the fuel gas flow path with air. First, the control means executes a hydrogen supply electromagnetic valve CLOSE (step S2), closes the fuel supply electromagnetic valve 26, and shuts off the supply of hydrogen gas from the fuel storage means 73. Subsequently, the control means executes the hydrogen circulation switching electromagnetic valve OFF (step S3), closes the hydrogen circulation electromagnetic valve 34, and stops the hydrogen gas circulation. Thereby, the supply of hydrogen gas to the fuel gas flow path of the fuel cell stack 20 is interrupted.

  Subsequently, the control means executes the hydrogen exhaust solenoid valve OPEN (step S4), opens the hydrogen start / stop solenoid valve 56a, and discharges the hydrogen gas in the fuel gas passage from the fuel discharge passage 56 to the atmosphere. Let In this case, since the suction circulation pump 36 is operating, pressure reduction is started, and the fuel cell stack 20, the water recovery drain tank 60, the second fuel supply line 33, the fuel discharge line 30, and the fuel discharge line 31 are entered. The remaining hydrogen gas is sucked by the suction circulation pump 36 and discharged from the fuel discharge pipe 56 to the atmosphere. And since the inside of a fuel gas flow path becomes a negative pressure, hydrogen gas is reliably removed from the fuel gas flow path quickly and discharged. When a hydrogen combustor is provided in the fuel discharge pipe 56, the hydrogen gas discharged into the atmosphere is burned, combined with oxygen, and discharged as water.

  The pressure of hydrogen gas in the fuel gas flow path is detected by a pressure sensor 78. In this case, since the pressure of the hydrogen gas can be considered to be the same in the range from the fuel supply solenoid valve 26 to the suction circulation pump 36 in the path through which the hydrogen gas flows, the pressure sensor 78 is disposed within the range. Then, the pressure detected by the pressure sensor 78 is equal to the pressure of the fuel gas flow path of the fuel cell stack 20.

  Subsequently, the control means determines in this state whether or not the pressure of the hydrogen gas in the fuel gas channel has become less than a preset threshold value, for example, −70 [kPaG]. (Step S5). In this case, since the threshold value represents a considerable negative pressure, the state where the pressure is less than the threshold value is a state where hydrogen gas does not substantially remain in the fuel passage in the fuel gas passage. In addition, the said control means repeats the said determination until the pressure of the hydrogen gas in a fuel gas flow path becomes less than a threshold value.

  When the pressure of the hydrogen gas in the fuel gas flow path becomes less than the threshold, the control means executes the air introduction solenoid valve ON (step S6), opens the outside air introduction solenoid valve 28a, and fuels the air. Introduce into the gas flow path. In this case, since the fuel supply electromagnetic valve 26 is in a closed state, the introduced air does not flow toward the fuel storage means 73. Thereby, the fuel gas flow path of the fuel cell stack 20 is filled with air. Since the air passes through the air filter 28b and is filtered, it does not contain dust, impurities, harmful gases, etc. present in the atmosphere. Therefore, a member such as a catalyst in the fuel gas passage is not contaminated or altered by the dust, impurities, harmful gas, or the like.

  In the present embodiment, since the water recovery drain tank 60 that also functions as a suction tank is connected to the fuel cell stack 20, when air is introduced into the fuel cell stack 20, the fuel gas of the fuel cell stack 20 The hydrogen gas remaining in the flow path is rapidly driven into the water recovery drain tank 60. Therefore, when air is introduced into the fuel cell stack 20, the hydrogen gas remaining in the fuel gas channel is introduced even if the fuel gas channel of the fuel cell stack 20 is not evacuated. It will not be mixed with oxygen in the air. Therefore, no potential shift occurs in the unit cell, so that the catalyst particles are not eluted and the performance of the fuel cell stack 20 is not deteriorated.

  In this case, the larger the volume of the water recovery drain tank 60 is, the shorter the time required for the hydrogen gas remaining in the fuel cell stack 20 to move into the water recovery drain tank 60 is. If the value is too large, the entire fuel cell system will be enlarged. Before introducing air into the fuel gas flow path of the fuel cell stack 20, the suction circulation pump 36 functions as a decompression pump and sucks the hydrogen gas remaining in the fuel gas flow path of the fuel cell stack 20. To do. In this case, since the suction circulation pump 36 also functions as a decompression pump, it is not necessary to provide the decompression pump independently, and the entire fuel cell system can be made compact.

  Subsequently, the control means determines whether or not the voltage output from the fuel cell stack 20 in this state has become a preset threshold, for example, 5 [V] or less (step S7). Here, the threshold value is an output corresponding to a state in which no hydrogen gas remains in the fuel gas flow path, the air is filled, and a potential difference is not substantially generated between the fuel electrode and the oxygen electrode. This is the voltage value. In addition, the said control means repeats the said determination until the voltage which the fuel cell stack 20 outputs becomes less than a threshold value.

  When the output of the fuel cell stack 20 becomes equal to or lower than the predetermined voltage, the control means stops all the auxiliary machines (step S8) and ends the process. The control means stops the suction circulation pump 36, closes the outside air introduction electromagnetic valve 28a, and finally stops the oxidant supply source. As a result, the operation of the fuel cell stack 20 is stopped.

  Next, an operation when the operation of the fuel cell system is temporarily stopped will be described. Here, a case where the standby mode is selected will be described.

  FIG. 7 is a first flowchart showing an operation when the operation of the fuel cell system in the embodiment of the present invention is temporarily stopped.

  First, when the driver of the vehicle rotates the key 12 inserted into the key insertion slot 11a of the main switch 11 while pushing down the idling button 13, and sets the rotation position to IDOL, the control means of the fuel cell system stops the operation. A standby mode command as a command is transmitted (step S11), and a pause operation for stopping the operation of the fuel cell system for a short period of time equal to or less than a predetermined time is started. In this case, the standby mode is selected by setting the rotational position of the key 12 to IDOL. When the control means receives an operation stop command, the control means stops the supply of hydrogen gas to the fuel gas flow path, and the pressure in the fuel gas flow path reaches a predetermined pressure value or the progress When the time reaches a predetermined time, a standby mode for purging the hydrogen gas in the fuel gas passage with air is executed. Then, the control means executes the hydrogen supply electromagnetic valve CLOSE (step S12), closes the fuel supply electromagnetic valve 26, and shuts off the supply of hydrogen gas from the fuel storage means 73.

  Subsequently, the control means executes the hydrogen circulation pump OFF (step S13) and stops the suction circulation pump 36. As a result, the discharge of hydrogen gas from the fuel gas flow path of the fuel cell stack 20 is stopped. Subsequently, the control means executes a hydrogen circulation switching electromagnetic valve CLOSE (step S14), closes the hydrogen circulation electromagnetic valve 34, and stops the hydrogen gas circulation. As a result, the supply of hydrogen gas to the fuel gas flow path of the fuel cell stack 20 is shut off, and a state in which hydrogen gas is sealed in the fuel gas flow path of the fuel cell stack 20 is started. In this case, both the outside air introduction electromagnetic valve 28a and the hydrogen start / stop electromagnetic valve 56a remain closed, so that the state in which the hydrogen gas is sealed in the fuel gas flow path of the fuel cell stack 20 is maintained.

  Subsequently, in this state, the control means determines that the pressure of the hydrogen gas in the fuel gas flow path has become a predetermined pressure value of 0 [kPaG], that is, atmospheric pressure, or the standby time, that is, the fuel It is determined whether or not an elapsed time from the start of the state in which the hydrogen gas is sealed in the fuel gas flow path of the battery stack 20 has reached a threshold as a predetermined time, for example, 10 minutes to 2 hours (step S15). . In this case, strictly speaking, it is determined whether or not the pressure of the hydrogen gas in the fuel gas flow path has become less than atmospheric pressure, or whether or not the elapsed time has exceeded a threshold value. Note that the control means sets the threshold value for the elapsed time after the hydrogen gas pressure in the fuel gas flow path becomes lower than the atmospheric pressure or when the hydrogen gas is sealed in the fuel gas flow path. The above determination is repeated until it exceeds. Further, when the pressure of the hydrogen gas in the fuel gas passage becomes less than atmospheric pressure, the air in the air passage enters the fuel gas passage through the solid polymer electrolyte membrane or the gas diffusion electrode, and the fuel gas passage in the fuel gas passage Pressure turns from decreasing to increasing. Further, the threshold value as the predetermined time is preferably a time during which air enters the fuel gas flow path.

  When the pressure of the hydrogen gas in the fuel gas flow path becomes less than atmospheric pressure or the elapsed time from the start of the state in which the hydrogen gas is sealed in the fuel gas flow path exceeds the threshold value, the control The means shifts to the stop mode (step S16) and ends the process. When the mode is shifted to the stop mode, the operations of steps S1 to S8 in FIG. 3 described above are executed, and the operation of the fuel cell stack 20 is stopped, as in the case of performing a normal stop.

  As described above, when the fuel cell system is temporarily stopped for a short time, the hydrogen gas in the fuel gas passage is not discharged into the atmosphere, so that the hydrogen gas is not wasted. Further, since hydrogen gas is not discharged from the vehicle, there is no safety problem even if the vehicle is temporarily stopped in a closed place such as an indoor parking lot. Furthermore, since the state in which the hydrogen gas is sealed in the fuel gas channel is maintained, the hydrogen and oxygen are not mixed in the fuel gas channel, and the occurrence of a potential shift can be prevented.

  Even if the state in which the hydrogen gas is sealed in the fuel gas channel is maintained, the hydrogen gas in the fuel gas channel decreases with the passage of time. When the pressure of the hydrogen gas in the fuel gas channel becomes less than atmospheric pressure, the air in the air channel flows into the fuel gas channel through the solid polymer electrolyte membrane or the gas diffusion electrode, and hydrogen and oxygen are mixed. Resulting in. Therefore, when the pressure of the hydrogen gas in the fuel gas flow path becomes less than atmospheric pressure or the elapsed time after the start of the state in which the hydrogen gas is sealed in the fuel gas flow path exceeds the threshold value, the stop mode Then, the hydrogen gas in the fuel gas channel is discharged, and the fuel gas channel is filled with air.

  Next, the operation when resealing hydrogen gas will be described.

  FIG. 8 is a second flowchart showing an operation when the operation of the fuel cell system in the embodiment of the present invention is temporarily stopped.

  First, when the driver of the vehicle rotates the key 12 inserted in the key insertion slot 11a of the main switch 11, presses down the idling button 13, and sets the rotation position to IDOL, the control means of the fuel cell system is instructed to stop the operation. The standby mode command is transmitted (step S21), and a pause operation for stopping the operation of the fuel cell system for a short period of time equal to or shorter than a predetermined time is started. In this case, the standby mode is selected by setting the rotational position of the key 12 to IDOL. When the control means receives an operation stop command, the control means stops the supply of hydrogen gas to the fuel gas flow path and executes a standby mode. In addition, the said driver | operator shall operate the selection means for selecting performing re-encapsulation of hydrogen gas, and shall select re-encapsulation of hydrogen gas. Then, the control means executes the hydrogen supply electromagnetic valve CLOSE (step S22), closes the fuel supply electromagnetic valve 26, and shuts off the supply of hydrogen gas from the fuel storage means 73.

  Subsequently, the control means executes the hydrogen circulation pump OFF (step S23), and stops the suction circulation pump 36. As a result, the discharge of hydrogen gas from the fuel gas flow path of the fuel cell stack 20 is stopped. Subsequently, the control means executes the hydrogen circulation switching electromagnetic valve CLOSE (step S24), closes the hydrogen circulation electromagnetic valve 34, and stops the hydrogen gas circulation. As a result, the supply of hydrogen gas to the fuel gas flow path of the fuel cell stack 20 is shut off, and a state in which hydrogen gas is sealed in the fuel gas flow path of the fuel cell stack 20 is started. In this case, both the outside air introduction electromagnetic valve 28a and the hydrogen start / stop electromagnetic valve 56a remain closed, so that the state in which the hydrogen gas is sealed in the fuel gas flow path of the fuel cell stack 20 is maintained.

  Subsequently, the control means determines in this state whether or not the pressure of the hydrogen gas in the fuel gas flow path has become 0 [kPaG] as a predetermined pressure value, that is, less than atmospheric pressure (step S25). . When the pressure of the hydrogen gas in the fuel gas flow path becomes less than atmospheric pressure, the control means executes a hydrogen supply electromagnetic valve constant time OPEN (step S26), and opens the fuel supply electromagnetic valve 26 to provide fuel. The hydrogen gas is resupplied from the storage means 73 for a predetermined time. Thereby, hydrogen re-encapsulation is performed in which the hydrogen gas is re-encapsulated in the fuel gas flow path of the fuel cell stack 20. In addition, when the pressure of the hydrogen gas in the fuel gas channel is not less than atmospheric pressure, hydrogen re-encapsulation is not performed.

  Subsequently, the control means determines that the standby time, that is, the elapsed time from the start of the state in which the hydrogen gas is sealed in the fuel gas flow path of the fuel cell stack 20 exceeds a threshold, for example, 10 minutes to 2 hours. It is determined whether or not (step S27). When the elapsed time from the start of the state in which the hydrogen gas is sealed in the fuel gas flow path exceeds the threshold value, the control means shifts to the stop mode (step S28) and ends the process. When the mode is shifted to the stop mode, the operations of steps S1 to S8 in FIG. 3 described above are executed, and the operation of the fuel cell stack 20 is stopped, as in the case of performing a normal stop. In addition, when the elapsed time since the start of the state in which the hydrogen gas is sealed in the fuel gas flow path does not exceed the threshold, the control means again determines whether or not the pressure is less than atmospheric pressure, The above operation is repeated.

  As described above, when hydrogen gas is re-enclosed, when the pressure of the hydrogen gas in the fuel gas flow path becomes lower than the atmospheric pressure, the fuel supply electromagnetic valve 26 is opened and the hydrogen gas from the fuel storage means 73 is supplied to the fuel gas flow. The gas is supplied again into the passage and refilled with hydrogen gas. For this reason, since the pressure of the hydrogen gas in the fuel gas channel does not become less than atmospheric pressure, the air in the air channel does not flow into the fuel gas channel through the solid polymer electrolyte membrane or the gas diffusion electrode. Hydrogen and oxygen are not mixed in the road.

  Note that if re-encapsulation of hydrogen gas is repeated many times, a large amount of hydrogen gas is consumed. Therefore, when the elapsed time since the start of the state in which the hydrogen gas is sealed in the fuel gas flow path exceeds the threshold value, the mode shifts to the stop mode, the hydrogen gas in the fuel gas flow path is discharged, and the fuel gas flow The road is filled with air.

  Next, the operation when starting the operation of the fuel cell system will be described. In this case, when the driver of the vehicle rotates the key 12 inserted in the key insertion slot 11a of the main switch 11 and sets the rotation position to START, the control means first starts the fuel supply electromagnetic valve 26 and the hydrogen circulation electromagnetic valve 34. Then, the outside air introduction electromagnetic valve 28a is closed to shut off the supply of hydrogen gas and air to the fuel gas flow path. Then, the hydrogen start / stop electromagnetic valve 56a is opened, and the air in the fuel gas flow path is discharged from the fuel discharge pipe 56 to the atmosphere.

  Thereafter, the control means opens the fuel supply electromagnetic valve 26 and introduces hydrogen gas into the fuel gas flow path. In this case, since the outside air introduction electromagnetic valve 28a is in a closed state, air does not flow in. As a result, the fuel gas flow path of the fuel cell stack 20 is filled with hydrogen gas, and it is possible to shift to steady operation.

  In the present embodiment, since the water recovery drain tank 60 is connected to the fuel cell stack 20, when hydrogen gas is introduced into the fuel cell stack 20, it remains in the fuel gas flow path of the fuel cell stack 20. The air that has been removed is rapidly driven into the water recovery drain tank 60. Therefore, even when the hydrogen gas is introduced into the fuel cell stack 20, even if the fuel gas flow path of the fuel cell stack 20 is not evacuated, it remains in the air remaining in the fuel gas flow path. There is no mixing with hydrogen gas into which oxygen has been introduced. Therefore, no potential shift occurs in the unit cell, so that the catalyst particles are not eluted and the performance of the fuel cell stack 20 is not deteriorated.

  Thus, in the present embodiment, the fuel cell system can select the standby mode in order to perform a temporary stop with a short stop time of the fuel cell system. For example, it can be selected when the operation of the fuel cell system is stopped for a short period of time, such as when visiting a store such as a convenience store. When performing the temporary stop, if the standby mode is selected, the hydrogen gas in the fuel gas passage is not discharged into the atmosphere, so that the hydrogen gas is not consumed wastefully. Further, since hydrogen gas is not discharged from the vehicle, there is no safety problem even if the vehicle is temporarily stopped in a closed place such as an indoor parking lot. Furthermore, since the state in which the hydrogen gas is sealed in the fuel gas channel is maintained, the hydrogen and oxygen are not mixed in the fuel gas channel, and the occurrence of a potential shift can be prevented. Therefore, even if the number of stops is large, a potential shift does not occur, and the performance of the fuel electrode in the fuel gas flow path of the fuel cell stack 20 can be prevented from being deteriorated.

  Further, when the standby mode is selected, it is possible to further select to re-enclose hydrogen gas. When the hydrogen gas is re-enclosed, when the hydrogen gas pressure in the fuel gas channel becomes less than atmospheric pressure with the hydrogen gas sealed in the fuel gas channel of the fuel cell stack 20, the fuel gas Hydrogen gas is again sealed in the flow path. Therefore, the hydrogen gas pressure in the fuel gas channel does not become less than atmospheric pressure until the elapsed time exceeds the threshold value, so that the air in the air channel flows into the fuel gas channel through the solid polymer electrolyte membrane or the gas diffusion electrode. There is no inflow. Accordingly, since hydrogen and oxygen are not mixed in the fuel gas flow path, the occurrence of a potential shift can be prevented.

  Further, when the operation of the fuel cell stack 20 is not resumed even after the standby mode is ended, the same operation as that in the case of performing the normal stop by selecting the stop mode is performed, and the fuel gas of the fuel cell stack 20 is The air is discharged from the flow path and introduced. Therefore, it does not become mixed with oxygen in the air introduced in the fuel cell stack 20. In this case, the hydrogen gas discharged from the fuel gas flow path of the fuel cell stack 20 is accommodated in the water recovery drain tank 60. Therefore, when air is introduced into the fuel cell stack 20, even if the fuel gas flow path of the fuel cell stack 20 is not evacuated, the hydrogen gas remaining in the fuel gas flow path rapidly It moves into the water recovery drain tank 60 and is not mixed with the oxygen in the air introduced in the fuel cell stack 20.

  In addition, the air discharged from the fuel gas flow path of the fuel cell stack 20 when the operation of the fuel cell system is started is accommodated in the water recovery drain tank 60. Therefore, when hydrogen gas is introduced into the fuel cell stack 20, even if the fuel gas flow path of the fuel cell stack 20 is not evacuated, the remaining air in the fuel gas flow path rapidly The hydrogen gas that has moved into the water recovery drain tank 60 and introduced into the fuel cell stack 20 is not mixed with the remaining oxygen in the air.

  In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.

It is a figure which shows the structure of the fuel cell system in embodiment of this invention. It is a figure which shows the structure of the main switch of the vehicle in embodiment of this invention. It is a graph which shows the relationship between the pressure in a fuel gas flow path when stopping the driving | operation of the fuel cell system in embodiment of this invention, and the timing of a potential shift. It is a graph which shows the relationship between the output voltage at the time of stopping the driving | operation of the fuel cell system in embodiment of this invention, and the pressure in a fuel gas flow path. It is a graph which shows the relationship between the standby time in the standby mode in embodiment of this invention, the pressure in a fuel gas flow path, and electric potential shift time. It is a flowchart which shows the operation | movement at the time of stopping the driving | operation of the fuel cell system in embodiment of this invention. It is a 1st flowchart which shows the operation | movement at the time of stopping operation | movement of the fuel cell system in embodiment of this invention. It is a 2nd flowchart which shows the operation | movement at the time of stopping operation | movement of the fuel cell system in embodiment of this invention.

Explanation of symbols

20 Fuel cell stack 28 Outside air introduction line 78 Pressure sensor

Claims (16)

A fuel cell stack in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode, and is stacked with a separator having a fuel gas flow path formed along the fuel electrode;
Pressure detecting means for detecting the pressure in the fuel gas flow path;
Purge means for purging the fuel gas in the fuel gas flow path with a replacement gas;
Control for selectively executing a standby mode in which the purge is performed when the fuel gas passage is stopped when an operation stop command is received and the pressure in the fuel gas passage reaches a predetermined pressure value And a fuel cell system. A fuel cell stack in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode, and is stacked with a separator having a fuel gas flow path formed along the fuel electrode;
Purge means for purging the fuel gas in the fuel gas flow path with a replacement gas;
A timer for measuring an elapsed time after stopping the supply of fuel gas to the fuel gas flow path;
A control means for stopping the supply of the fuel gas to the fuel gas flow path when receiving an operation stop command, and selectively executing a standby mode for performing the purge when the elapsed time reaches a predetermined time. A fuel cell system. A fuel cell stack in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode, and is stacked with a separator having a fuel gas flow path formed along the fuel electrode;
Pressure detecting means for detecting the pressure in the fuel gas flow path;
Purge means for purging the fuel gas in the fuel gas flow path with a replacement gas;
A timer for measuring an elapsed time after stopping the supply of fuel gas to the fuel gas flow path;
When the operation stop command is received, the supply of the fuel gas to the fuel gas passage is stopped, and when the pressure in the fuel gas passage becomes a predetermined pressure value or the elapsed time reaches a predetermined time, And a control means for selectively executing a standby mode for purging.   The fuel cell system according to claim 1 or 3, wherein the predetermined pressure value is atmospheric pressure.   4. The fuel cell system according to claim 1, wherein the predetermined pressure value is a minimum value at which the pressure in the fuel gas flow path starts from decreasing to increasing. 5.   4. The fuel cell system according to claim 2, wherein the predetermined time is a time during which air enters the fuel gas flow path.   The fuel cell system according to claim 2 or 3, wherein the predetermined time is a time at which a potential shift occurs. Mode selection means for selecting the standby mode and the stop mode;
Upon receiving an operation stop command, the control means selectively stops the supply of the fuel gas to the fuel gas flow path and purges the fuel gas in the fuel gas flow path with a replacement gas. The fuel cell system according to claim 1, which is executed. An operation method of a fuel cell system capable of purging a fuel gas in a fuel gas flow path in a fuel cell stack with a replacement gas,
When the operation stop command is received, the supply of the fuel gas to the fuel gas passage is stopped, and the standby mode for performing the purge is selectively executed when the pressure in the fuel gas passage reaches a predetermined pressure value. A method for operating a fuel cell system. An operation method of a fuel cell system capable of purging a fuel gas in a fuel gas flow path in a fuel cell stack with a replacement gas,
When the operation stop command is received, the supply of the fuel gas to the fuel gas flow path is stopped, and the standby mode for performing the purge is selectively executed when the elapsed time reaches a predetermined time. How to operate the system. An operation method of a fuel cell system capable of purging a fuel gas in a fuel gas flow path in a fuel cell stack with a replacement gas,
When the operation stop command is received, the supply of the fuel gas to the fuel gas passage is stopped, and when the pressure in the fuel gas passage becomes a predetermined pressure value or the elapsed time reaches a predetermined time, A method for operating a fuel cell system, wherein a standby mode for purging is selectively executed.   The method of operating a fuel cell system according to claim 9 or 11, wherein the predetermined pressure value is atmospheric pressure.   12. The method of operating a fuel cell system according to claim 9, wherein the predetermined pressure value is a minimum value at which the pressure in the fuel gas flow path starts from decreasing to increasing.   The method of operating a fuel cell system according to claim 10 or 11, wherein the predetermined time is a time during which air enters the fuel gas flow path.   The method of operating a fuel cell system according to claim 10 or 11, wherein the predetermined time is a time at which a potential shift occurs.   Upon receipt of the standby mode or an operation stop command, the supply of the fuel gas to the fuel gas passage is stopped, and the stop mode in which the fuel gas in the fuel gas passage is purged with a replacement gas is selectively used. The method of operating a fuel cell system according to any one of claims 9 to 15, wherein the method is executed.

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