JP2011238360A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit ununiformity of water content in a cell surface of each battery cell in a fuel cell system of which fuel cell is operated without humification by supplying air without humidity.SOLUTION: A hydrogen flow path 14 and an air flow path 15 in each battery cell 10 are disposed so that a hydrogen flow direction and an air flow direction are opposed to each other. Unreacted hydrogen and water discharged from a hydrogen outlet 14b of the hydrogen flow path 14 is recirculated to a hydrogen inlet 14a, and air without humidity is supplied to an air inlet 15a of the air flow path 15. Thus a fuel cell system is operated without humidification. By water content measuring means S10, S30 and S50 for determining whether water content of the air inlet 15a in the battery cell 10 is insufficient, or not, if it is determined that the water content of the air inlet 15a is insufficient, an air stoichiometric ratio is lowered to facilitate electricity generation at the air inlet 15a.

Description

  The present invention relates to a fuel cell system including a fuel cell that generates electric energy by a chemical reaction between hydrogen and oxygen, and is effective when applied to a moving body such as a vehicle, a ship, and a portable generator.

  2. Description of the Related Art Conventionally, in a fuel cell, a solid body formed by stacking a plurality of battery cells each having a membrane electrode assembly (MEA) in which an electrolyte membrane made of a solid polymer is sandwiched between a pair of electrodes (anode and cathode). A polymer electrolyte membrane fuel cell is known.

  In this type of fuel cell, it is known that the wet state of the electrolyte membrane of the battery cell affects the internal resistance of the fuel cell. For example, when the internal moisture content of the fuel cell is small and the electrolyte membrane is dry, there is a problem that the internal resistance of the fuel cell increases and the output of the fuel cell and the power generation efficiency decrease.

  Various techniques for solving such problems have been proposed (see, for example, Patent Documents 1 and 2).

  In Patent Document 1, in a fuel cell system that performs humidified operation by supplying a humidified oxidant gas to a fuel cell, it is determined whether the moisture content in the fuel cell is excessive or insufficient, and depending on the result of the determination, The internal moisture content of the fuel cell is adjusted by adjusting the supply amount and pressure of the reaction gas supplied to the battery.

  On the other hand, in patent document 2, in the fuel cell which supplies a non-humidified oxidant gas and performs a non-humidification operation, it is set as the structure which suppresses drying of the electrolyte membrane in each battery cell. Specifically, each flow path of the fuel gas and the oxidant gas is set so that the flow direction of the fuel gas and the flow direction of the oxidant gas in the battery cell face each other, and the gas flow path outlet of the oxidant gas The water is circulated between the anode and the cathode by facilitating the flow of the water on the side to the gas channel inlet side of the fuel gas.

  In addition, in the fuel cell system that performs the non-humidifying operation of the fuel cell as in Patent Document 2, it is not necessary to use a humidifier or the like that humidifies the oxidant gas supplied to the fuel cell as in Patent Document 1, so that the fuel cell It is possible to reduce the number of system parts.

JP 2002-352827 A JP 2002-367655 A

  Here, as in Patent Document 2, in a fuel cell system in which a non-humidified oxidant gas is supplied to perform a non-humidified operation of the fuel cell, the dried oxidant gas is supplied to the gas channel inlet of the oxidant gas. Therefore, in the vicinity of the gas channel inlet of the oxidant gas, the electrolyte membrane is easily dried as compared with the gas channel outlet side. As a result, the amount of water in the cell surface of each battery cell becomes non-uniform, the area of the part contributing to power generation in the cell surface decreases, and the output of the fuel cell decreases.

  On the other hand, in Patent Document 2, water is circulated between the cathode and anode of each battery cell. However, when operating conditions such as an increase in the output of the fuel cell change, the anode side changes to the cathode side. The accompanying water increases, and moisture is biased to the downstream side of the oxidant gas on the cathode side. That is, even in the fuel cell described in Patent Document 2, the amount of water in the cell surface of each battery cell may still be uneven.

  In view of the above points, the present invention sufficiently suppresses the non-uniformity of water content in the cell plane of each battery cell in a fuel cell system that supplies a non-humidified oxidant gas to perform a non-humidified operation of the fuel cell. For the purpose.

  In order to achieve the above object, in the first aspect of the present invention, a membrane electrode assembly in which an electrolyte membrane (11) made of a solid polymer is sandwiched between a pair of electrodes (12, 13), a pair of electrodes (12, 13) A fuel gas channel (14) for supplying fuel gas to the anode side, and an oxidant gas channel (15) for supplying oxidant gas to the cathode side of the pair of electrodes (12, 13). The fuel cell (1) is configured by stacking a plurality of battery cells (10) having a fuel gas flow path (14) and an oxidant gas flow path (15), the fuel gas flow direction and the oxidant gas. The unreacted fuel gas and moisture discharged from the fuel gas outlet (14b) of the fuel gas channel (14) are supplied to the fuel gas channel (14) as fuel. Recirculate to the gas inlet (14a), A fuel cell system for supplying a humidified oxidant gas to an oxidant gas inlet (15a) of an oxidant gas flow path (15) to perform a non-humidification operation, and supplying the oxidant gas flow path (15). The oxidant gas stoichiometric ratio adjusting means (50a) for adjusting the stoichiometric ratio of the oxidant gas and the amount of water at the oxidant gas inlet (15a) of the oxidant gas flow path (15) in the battery cell (10) are insufficient. In the water content determination means (S10, S30, S50) and the water content determination means (S10, S30, S50) for determining whether or not the water content is insufficient, the water content in the oxidant gas inlet (15a) is insufficient. When it is determined that the amount of water in the oxidant gas inlet (15a) is determined not to be insufficient, power generation at the oxidant gas inlet (15a) is promoted. At least the stoichiometric ratio of oxidant gas And control means for reducing (50), characterized in that it comprises a.

  Thus, when the amount of water at the oxidant gas inlet (15a) is insufficient, the stoichiometric ratio of the oxidant gas is reduced so that power generation at the oxidant gas inlet (15a) is promoted. With this configuration, water generated by power generation and accompanying water that moves from the anode side to the cathode side increase on the oxidant gas inlet (15a) side, so that drying of the oxidant gas inlet (15a) is suppressed. be able to. And since the water | moisture content by the side of an oxidant gas inlet part (15a) is pushed away to the downstream of an oxidant gas flow path (15), a moisture content can be ensured in the cathode side whole region of a battery cell (10).

  Further, when power generation at the oxidant gas inlet (15a) is promoted, power generation is suppressed on the downstream side of the oxidant gas inlet (15b) as compared with the oxidant gas inlet (15a). As a result, the amount of accompanying water moving from the anode side to the cathode side on the downstream side of the oxidant gas inlet (15a) is reduced, and from the cathode side (oxidant gas outlet (15b)) to the anode (fuel gas). The amount of diffusion water to the inlet (14a) increases. And since the water | moisture content by the side of a fuel gas inlet part (14a) is pushed away downstream of a fuel gas flow path (14), a moisture content can be ensured in the anode side whole region of a battery cell (10).

  Therefore, in the fuel cell system in which the non-humidified oxidant gas is supplied to perform the non-humidified operation of the fuel cell (1), it is possible to sufficiently suppress the non-uniformity of the moisture content in the cell plane of the battery cell (10). It becomes possible. As a result, it is possible to suppress a decrease in the power generation area in the cell plane of each battery cell (10).

  Here, the “stoichiometric ratio” of the oxidant gas in the present invention is the theoretical supply amount of the oxidant gas and the actual supply amount of the oxidant gas that are required when a predetermined current flows through the fuel cell (1). It means the ratio. Similarly, the “stoichiometric ratio” in the fuel gas means a ratio between the theoretical amount of fuel gas required when a predetermined current flows through the fuel cell (1) and the actual supply amount of fuel gas. For example, when the stoichiometric ratio of the oxidant gas is 1.3, it means that 1.3 times the theoretical supply amount of oxidant gas is supplied to the fuel cell (1).

  In the invention according to claim 2, in the fuel cell system according to claim 1, provided in the oxidant gas discharge path (31) for discharging the oxidant gas from the oxidant gas flow path (15). And a cathode side pressure adjusting means (34) for adjusting the pressure of the oxidant gas in the cell surface of the battery cell (10), and the control means (50) is a moisture content determining means (S10, S30, S50). Then, when it is determined that the amount of water in the oxidant gas inlet (15a) is insufficient, the pressure of the oxidant gas is increased.

  According to this, when the amount of water at the oxidant gas inlet (15a) is insufficient, the pressure of the oxidant gas is increased in addition to the decrease in the stoichiometric ratio of the oxidant gas. The amount of diffusion water moving from the cathode side to the anode side on the downstream side of the flow path (15) can be increased. For this reason, the amount of moisture on the fuel gas inlet (14a) side of the fuel gas channel (14) increases, and the increased moisture is pushed downstream of the fuel gas channel (14), so that the battery cell (10) A sufficient amount of water can be secured in the entire anode side.

  Thereby, the reduction | decrease in the electric power generation area in the cell surface of each battery cell (10) can be suppressed more effectively.

  According to a third aspect of the present invention, in the fuel cell system according to the first or second aspect, the fuel gas supply path (20) for supplying the fuel gas to the fuel gas flow path (14) is provided, An anode-side pressure adjusting means (23) for adjusting the pressure of the fuel gas in the cell surface of the battery cell (10) is provided, and the control means (50) is a moisture amount determining means (S10, S30, S50). When it is determined that the amount of water in the oxidant gas inlet (15a) is insufficient, the pressure of the fuel gas is reduced.

  According to this, when the amount of water at the oxidant gas inlet (15a) is insufficient, the pressure of the fuel gas is reduced in addition to the decrease in the stoichiometric ratio of the oxidant gas. The amount of diffusion water moving from the cathode side to the anode side on the downstream side of the path (15) can be increased. For this reason, the amount of moisture on the fuel gas inlet (14a) side of the fuel gas channel (14) increases, and the increased moisture is pushed downstream of the fuel gas channel (14), so that the battery cell (10) A sufficient amount of water can be secured in the entire anode side.

  Thereby, the reduction | decrease in the electric power generation area in the cell surface of each battery cell (10) can be suppressed more effectively.

  According to a fourth aspect of the present invention, in the fuel cell system according to any one of the first to third aspects, the fuel gas system for adjusting a stoichiometric ratio of the fuel gas supplied to the fuel gas passage (14). The stoichiometric ratio adjusting means (50a) is provided, and the control means (50) is determined by the moisture amount determination means (S10, S30, S50) that the moisture amount at the oxidant gas inlet (15a) is insufficient. In this case, the fuel gas stoichiometric ratio is increased.

  According to this, when the amount of water at the oxidant gas inlet (15a) is insufficient, the fuel gas stoichiometric ratio is increased in addition to the decrease in the oxidant gas stoichiometric ratio. The amount of accompanying water moving from the anode side to the cathode side on the downstream side of the passage (14) can be increased. For this reason, the amount of water on the oxidant gas inlet (15a) side of the oxidant gas flow path (15) increases, and the increased water is pushed down to the downstream side of the oxidant gas flow path (15). A sufficient amount of moisture can be secured in the entire cathode side of (10).

  Thereby, the reduction | decrease in the electric power generation area in the cell surface of each battery cell (10) can be suppressed more effectively.

  Here, the fuel cell (1) sets the supply amounts of the fuel gas and the oxidant gas supplied to the fuel cell (1) according to the required power generation amount from the various electric loads (2). For this reason, as the required power generation amount for the fuel cell (1) increases, the supply amount of the fuel gas and the oxidant gas increases, and the accompanying water from the anode side to the cathode side on the air outlet 15b side increases. The amount of water in the cell surface of the battery cell (10) is likely to be uneven.

  Accordingly, in the invention according to claim 5, in the fuel cell system according to claim 1, the power generation amount of the fuel cell (1) is set to a predetermined limit power generation amount lower than the required power generation amount. ), And the control means (50) has a shortage of water content at the oxidant gas inlet (15a) in the water content determination means (S10, S30, S50). When it is determined that the fuel cell (1) is in the state, the output of the fuel cell (1) is limited until a predetermined time elapses from the determination.

  According to this, when the amount of water at the oxidant gas inlet (15a) is insufficient, in addition to the decrease in the oxidant gas stoichiometric ratio, the power generation amount of the fuel cell (1) is temporarily reduced. Since the output of the fuel cell (1) is limited, an increase in the amount of fuel gas and oxidant gas supplied can be suppressed. Thereby, it becomes possible to suppress the nonuniformity of the moisture content in the cell surface in the battery cell (10).

  Further, if the state in which the stoichiometric ratio of the oxidant gas is reduced continues, the cathode side overvoltage caused by the decrease in the oxygen concentration in the oxidant gas and the moisture amount in the oxidant gas flow path (15) increase due to the cathode amount. There is a risk that the supply of the oxidant gas to the water may be hindered.

  Therefore, in the invention according to claim 6, in the fuel cell system according to any one of claims 1 to 5, the control means (50) is a water content determination means (S10, S30, S50), When it is determined that the amount of water in the oxidant gas inlet (15a) is insufficient, the stoichiometric ratio of the oxidant gas is periodically reduced.

  According to this, since the stoichiometric ratio of the oxidant gas is periodically reduced, an increase in overvoltage due to a decrease in the oxygen concentration in the oxidant gas or an increase in the amount of water in the oxidant gas flow path (15). It is possible to prevent the supply of the oxidant gas to the cathode from being hindered. As a result, it is possible to suppress a decrease in the output of the fuel cell (1).

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

1 is an overall configuration diagram of a fuel cell system according to an embodiment. It is a schematic block diagram of the battery cell which concerns on embodiment. It is a flowchart which shows the stoichiometric ratio control process which concerns on embodiment. It is explanatory drawing explaining the variable stoichiometric ratio control process which concerns on embodiment. It is explanatory drawing explaining the relationship between the current density of the air inlet part at the time of performing the stoichiometric ratio control process which concerns on embodiment, and an output voltage. It is explanatory drawing explaining the moisture content in a film | membrane in the cell surface at the time of performing the stoichiometric ratio control process which concerns on embodiment, and its distribution. It is explanatory drawing explaining the amount of accompanying water in the cell surface at the time of performing the stoichiometric ratio control process which concerns on embodiment, and its distribution. It is explanatory drawing explaining the current density in the cell surface at the time of performing the stoichiometric ratio control process which concerns on embodiment, and its distribution. It is explanatory drawing explaining the temperature in a cell surface at the time of performing the stoichiometric ratio control process which concerns on embodiment, and its distribution.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In this embodiment, the fuel cell system according to the present invention is mounted on an electric vehicle (fuel cell vehicle) that travels using the fuel cell 1 as a driving source for traveling.

  FIG. 1 is an overall configuration diagram of the fuel cell system according to the first embodiment, and FIG. 2 is a schematic configuration diagram of the battery cell 10.

  As shown in FIG. 1, the fuel cell system of the present embodiment includes a fuel cell 1 that generates electric power using an electrochemical reaction between hydrogen and oxygen. The fuel cell 1 supplies power to various electric loads 2 such as a secondary battery (not shown), a driving motor (not shown), an auxiliary machine, and the like.

  The fuel cell 1 of the present embodiment employs a polymer electrolyte fuel cell (PEFC), and a plurality of battery cells 10 (hereinafter also simply referred to as cells) serving as a basic unit are stacked. They are electrically connected in series.

  Here, as shown in FIG. 2, each cell 10 includes an electrolyte membrane 11 made of a proton-conductive ion exchange membrane (solid polymer) and a pair of electrodes 12 and 13 holding the electrolyte membrane 11. It has a membrane electrode assembly and a pair of separators that sandwich the membrane electrode assembly from both sides.

  One electrode 12 of the pair of electrodes 12 and 13 is configured as a hydrogen electrode (anode) to which hydrogen as a fuel gas is supplied, and the other electrode 13 is an air electrode (to which air as an oxidant gas is supplied). Cathode). Each electrode 12 and 13 is composed of a catalyst layer and a gas diffusion layer.

  Each of the pair of separators is formed with a hydrogen flow path 14 for supplying hydrogen to the hydrogen electrode 12 on the surface facing the hydrogen electrode 12, and supplies air to the air electrode 13 on the surface facing the air electrode 13. An air flow path 15 is formed. In addition, the hydrogen flow path 14 of this embodiment corresponds to the fuel gas flow path of the present invention, and the air flow path 15 corresponds to the oxidant gas flow path of the present invention.

  In the present embodiment, the hydrogen flow path 14 and the air flow path 15 are provided so that the flow direction of hydrogen flowing through the hydrogen flow path 14 and the flow direction of air flowing through the air flow path 15 face each other. For this reason, the hydrogen inlet part (fuel gas inlet part) 14a of the hydrogen channel 14 faces the air outlet part (oxidant gas outlet part) 15b of the air channel 15 via the membrane electrode assembly, and the hydrogen channel The 14 hydrogen outlet portions (fuel gas outlet portions) 14b face the air inlet portion (oxidant gas inlet portion) 15a of the air flow path 15 through the membrane electrode assembly.

  When a reaction gas such as hydrogen and air is supplied to the fuel cell 1, each cell 10 electrochemically reacts hydrogen and oxygen to output electric energy as shown below.

(Hydrogen electrode side) H ₂ → 2H ⁺ + 2e ⁻
(Air electrode side) 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O
At this time, in the hydrogen electrode 12, hydrogen supplied to the inside is ionized into electrons (e ⁻ ) and protons (H ⁺ ) by a catalytic reaction in the catalyst layer, and the protons (H ⁺ ) are water (accompanying water). Is moved to the air electrode 13 side.

On the other hand, in the air electrode 13, protons (H ⁺ ) that have moved from the hydrogen electrode 12 side, electrons that have circulated from the outside, and oxygen (O ₂ ) in the air react to generate water (product water). The The generated water generated on the air electrode 13 side diffuses from the air electrode 13 side to the hydrogen electrode 12 side when flowing from the air flow upstream side to the downstream side. That is, water circulates between the hydrogen electrode (anode) 12 and the air electrode (cathode) 13 (see the arrow shown in the vicinity of the electrolyte membrane 11 in FIG. 2).

  The electrical energy output from the fuel cell 1 is measured by a voltage sensor 4 that detects a voltage that is output as a whole of the fuel cell 1 and a current sensor 3 that detects a current that is output as the fuel cell 1 as a whole. Note that detection signals from the voltage sensor 4 and the current sensor 3 are input to a control device 50 described later.

  Further, in the fuel cell 1 of the present embodiment, the local current measuring device 5 is arranged between the cells 10 adjacent to each other at a predetermined position, as indicated by the oblique lines in FIG. The local current measuring device 5 is configured to detect a local current value (current density) between adjacent cells 10. In the present embodiment, the local current measuring device 5 detects the current (current density) at the air inlet 15a of the air channel 15 (hydrogen outlet 14b of the hydrogen channel 14).

  Since the current flowing through the air inlet portion 15a of the air flow path 15 has a correlation such that it decreases with a decrease in the amount of water in the air inlet portion 15a of the air flow path 15, it is based on the detection value of the local current measuring device 5. Thus, it is possible to determine whether or not the air inlet portion 15a of the air flow path 15 is dry. The detection signal of the local current measuring device 5 is input to the control device 50 described later.

  The fuel cell system includes a hydrogen supply pipe 20 through which hydrogen gas supplied to the hydrogen electrode 12 side of the fuel cell 1 passes, and a hydrogen discharge pipe 21 through which exhaust gas discharged from the hydrogen electrode 12 side of the fuel cell 1 passes. Is provided. The hydrogen supply pipe 20 constitutes the fuel gas supply path of the present invention.

  A hydrogen supply device 22 for supplying hydrogen gas to the hydrogen electrode of the fuel cell 1 is provided at the most upstream portion of the hydrogen supply pipe 20. In the present embodiment, a hydrogen tank filled with high-pressure hydrogen is used as the hydrogen supply device 22.

  The hydrogen supply pipe 20 is provided with a hydrogen pressure regulating valve 23 on the downstream side of the hydrogen supply device 22. When supplying hydrogen to the fuel cell 1, the hydrogen pressure is adjusted to a desired hydrogen pressure by the hydrogen pressure regulating valve 23 and supplied to the fuel cell 1. In the present embodiment, the hydrogen pressure regulating valve 23 constitutes the anode side pressure adjusting means of the present invention.

  The hydrogen discharge pipe 21 is provided with a shut valve 24. By opening the shut valve 24 as necessary, a small amount of hydrogen, vapor (or water) and the air electrode 13 are passed through the electrolyte membrane 11 from the hydrogen electrode side of the fuel cell 1 through the hydrogen discharge pipe 21. Impurities such as nitrogen and oxygen mixed on the hydrogen electrode 12 side are discharged.

  In the hydrogen discharge pipe 21 of the present embodiment, the hydrogen circulation for recirculating unreacted hydrogen (unreacted fuel gas), moisture, etc. passing through the hydrogen discharge pipe 21 to the fuel cell 1 upstream of the shut valve 24. A pipe 25 is connected. Specifically, the hydrogen circulation pipe 25 is connected between the upstream side of the shut valve 24 of the hydrogen discharge pipe 21 and the downstream side of the hydrogen pressure regulating valve 23 of the hydrogen supply pipe 20.

  The hydrogen circulation pipe 25 is provided with a circulation pump 26 for returning unreacted hydrogen or the like in the hydrogen discharge pipe 21 to the hydrogen supply pipe 20. The circulation pump 26 is connected to a driving electric motor 26a.

  Further, the fuel cell system includes an air supply pipe 30 through which air (oxidant gas) supplied to the air electrode 13 of the fuel cell 1 passes, and air through which exhaust gas discharged from the air electrode 13 of the fuel cell 1 passes. A discharge pipe 31 is provided. The air discharge pipe 31 constitutes the oxidant gas discharge path of the present invention.

  The air supply pipe 30 is provided with an air flow sensor 32 for detecting the flow rate of air supplied to the fuel cell 1 on the upstream side of the air flow. The detection signal of the airflow sensor 32 is input to the control device 50 described later.

  The air supply pipe 30 is provided with an air supply device 33 for compressing and discharging air on the downstream side of the airflow of the airflow sensor 32. In the present embodiment, a pressure feed pump is used as the air supply device 33. The air supply device 33 is connected to an electric motor 33a for driving.

  Further, the air discharge pipe 31 is provided with a back pressure adjustment valve 34 that adjusts the pressure of the air in the air flow path 15 so as to obtain a desired pressure. The back pressure adjustment valve 34 of the present embodiment constitutes the cathode side pressure adjustment means of the present invention.

  Here, in the fuel cell system of the present embodiment, the air supply pipe 30 and the air discharge pipe 31 are not provided with a dedicated humidifying means for humidifying the air supplied to the fuel cell 1, and non-humidified air is used as fuel. It is configured to supply the battery 1 and perform a non-humidifying operation.

  By the way, the fuel cell 1 generates heat with power generation. In order to cool the heat generated by the power generation of the fuel cell 1, the fuel cell system includes a cooling that cools the fuel cell 1 so that the operating temperature becomes a temperature suitable for an electrochemical reaction (for example, about 80 ° C.). A system is provided.

  The cooling system includes a cooling water pipe 40 that circulates cooling water (heat medium) in the fuel cell 1, a water pump 41 that circulates the cooling water, an electric motor 41a that drives the water pump 41, and a fan (not shown). A radiator 42 is provided. The heat generated in the fuel cell 1 is discharged out of the system by the radiator 42 through the cooling water. A temperature sensor (not shown) for detecting the temperature of the cooling water is provided in the vicinity of the outlet side of the fuel cell 1 in the cooling water pipe 40, and the detection signal of this temperature sensor is sent to the control device 50 described later. Entered.

  Further, the fuel cell system of the present embodiment is provided with a control device (ECU) 50 as control means for performing various controls. The control device 50 controls the operation of various control devices constituting the fuel cell system based on various input signals. The control device 50 includes a well-known microcomputer including a CPU, a ROM, a RAM, an I / O, and the like. Various calculations and the like are executed in accordance with a control program stored in a storage unit such as a ROM.

  Specifically, on the input side of the control device 50, required power signals from various electric loads 2, secondary batteries (not shown), detection signals related to the amount of charge from the secondary batteries, current sensor 3, voltage sensor 4 Detection signals from the local current measuring device 5, the airflow sensor 32, and the temperature sensor are input.

  On the other hand, on the output side of the control device 50, the hydrogen pressure regulating valve 23, the shut valve 24, the electric motor 26 a of the circulation pump 26, the electric motor 33 a of the air supply device 33, the back pressure adjustment valve 34, and the electric motor 41 a of the water pump 41. Etc. are connected, and control signals are output to various control devices.

  The control device 50 of the present embodiment basically controls the stoichiometric ratio of each reaction gas (hydrogen and air) supplied to the fuel cell 1 in accordance with a required power signal from the electric load 2.

  For example, when increasing the stoichiometric ratio of hydrogen (hereinafter referred to as the hydrogen stoichiometric ratio), the control device 50 increases the number of revolutions of the electric motor 26a that drives the circulation pump 26 and decreases the stoichiometric ratio of hydrogen. In this case, the rotational speed of the electric motor 26a of the circulation pump 26 is reduced. When adjusting the hydrogen stoichiometric ratio, the shut valve 24 of the hydrogen discharge pipe 21 is closed.

  Further, the control device 50 increases the rotational speed of the electric motor 33a that drives the air supply device 33 and decreases the air stoichiometric ratio when increasing the stoichiometric ratio of air (hereinafter referred to as the air stoichiometric ratio). Then, the rotational speed of the electric motor 33a of the air supply device 33 is decreased.

  Note that the control device 50 of the present embodiment is configured integrally with control means for controlling various control devices. In the present embodiment, in particular, the stoichiometric ratio of hydrogen supplied to the fuel cell 1 is controlled. The configuration (hardware and software) is the fuel gas stoichiometric ratio adjusting means 50a. In addition, the configuration (hardware and software) for controlling the stoichiometric ratio of the air supplied to the fuel cell 1 is the oxidant gas stoichiometric ratio adjusting means 50b.

  Here, when supplying non-humidified air to the fuel cell 1 as in this embodiment, the dry air is supplied to the air inlet portion 15a of the air flow path 15 of each cell 10, so The electrolyte membrane 11 on the air inlet portion 15a side (hydrogen outlet portion 14b side) becomes easy to dry.

  When the electrolyte membrane 11 on the air inlet 15a side is dry, the stoichiometric ratio of each reaction gas (hydrogen and air) supplied to the fuel cell 1 is controlled according to the required power signal from the electric load 2, Power generation in the vicinity of the air inlet 15a in the cell plane is hindered. As a result, the area of the part contributing to power generation in the cell plane is reduced, and the output of the fuel cell 1 as a whole is reduced.

  Therefore, in the present embodiment, when the air inlet portion 15a is dry, a stoichiometric ratio control process is performed to control the air stoichiometric ratio and the like so that power generation near the air inlet portion 15a is promoted. Thereby, the water circulation between the hydrogen electrode (anode) 12 and the air electrode (cathode) 13 in the cell surface is efficiently performed (see the arrow shown in the vicinity of the electrolyte membrane 11 in FIG. 2).

  Hereinafter, the stoichiometric ratio control process performed by the control device 50 will be described based on the flowchart of FIG. The control flow shown in FIG. 3 is executed in a state where hydrogen and air are supplied to the fuel cell 1 and electric energy can be output from the fuel cell 1.

  As shown in FIG. 3, first, it is determined whether or not the air inlet portion 15a of the air flow path 15 is dry, that is, whether or not the moisture content of the air inlet portion 15a is insufficient (S10). This determination process is performed based on the detection value of the local current measuring device 5 that measures the local current flowing through the air inlet 15a of the air flow path 15.

  Specifically, when the detected value of the local current measuring device 5 is equal to or lower than a preset reference current density, the air inlet portion 15a is dried (the amount of water in the air inlet portion 15a is insufficient). (S10: YES), and when it is larger than the reference current density, it is determined that the air inlet portion 15a is not dried (the water content of the air inlet portion 15a is not insufficient) (S10: NO).

  As a result of the determination process of S10, when it is determined that the air inlet portion 15a is not dry (S10: NO), the stoichiometric ratio control process is terminated, and it is determined that the air inlet portion 15a is dry. In the case (S10: YES), an air inlet power generation promotion process is performed (S20).

  In this air inlet portion power generation promotion process, the air stoichiometric ratio St can be set in accordance with the required generated power for the fuel cell 1 so as to promote power generation near the air inlet portion 15a (for example, 1.3. ˜1.6) is set to a low stoichiometric ratio Ast (for example, 1.0 to 1.1).

  Specifically, the rotational speed of the electric motor 33a of the air supply device 33 is decreased so that the air stoichiometric ratio becomes the low stoichiometric ratio Ast. The rotation speed of the electric motor 33a of the air supply device 33 is determined based on a control map that defines the relationship between the air stoichiometric ratio and the rotation speed of the electric motor 33a. The control map is stored in advance in a storage unit such as a ROM of the control device 50.

  As described above, by setting the air stoichiometric ratio St to the low stoichiometric ratio ASt, air is sufficiently supplied to the air inlet 15a side of the air flow path 15, and from the generated water and hydrogen electrode 12 side by the power generation in the air inlet 15a. Since the accompanying water that moves to the air electrode 13 side increases, drying of the air inlet portion 15a can be suppressed. And since the water | moisture content of the air inlet part 15a is swept away toward the air outlet part 15b of an air flow downstream, the moisture content can be ensured in the air electrode 13 side whole region of the cell 10. FIG.

  Further, when the power generation at the air inlet portion 15a is promoted by the decrease in the air stoichiometric ratio St, the power generation is suppressed on the downstream side of the air inlet portion 15a as compared with the air inlet portion 15a. For this reason, the amount of accompanying water moving from the anode side to the cathode side on the downstream side of the air inlet portion 15a is reduced, and from the vicinity of the air outlet portion 15b on the air electrode 13 side to the vicinity of the hydrogen inlet portion 14a on the hydrogen electrode 12 side. The amount of diffusion water increases. And since the water | moisture content by the side of the hydrogen inlet part 14a is swept away to the downstream of the hydrogen flow path 14, the water | moisture content can be ensured in the hydrogen electrode 12 side whole region in the cell 10. FIG.

  After executing the air inlet power generation promotion process (S20), it is determined again whether or not the air inlet 15a of the air flow path 15 is dry (S30). In addition, since the determination process of S30 is a process equivalent to the determination process of S10, description is abbreviate | omitted.

  As a result of the determination process of S30, when it is determined that the air inlet 15a is not dry (S30: NO), the process proceeds to S60 described later, and it is determined that the air inlet 15a is dry. If this is the case (S30: YES), a water circulation amount increasing process is performed (S40).

  This water circulation amount increasing process is a control process for increasing the amount of water circulation between the hydrogen electrode 12 and the air electrode 13. Specifically, in the water circulation amount increasing process, the air pressure increasing process for increasing the air pressure in the air flow path 15, the hydrogen pressure decreasing process for decreasing the hydrogen pressure in the hydrogen flow path 14, and the fuel cell 1 are supplied. At least one of the hydrogen stoichiometric ratio control processes for increasing the hydrogen stoichiometric ratio is executed.

  In the air pressure increase process, the back pressure adjustment valve 34 is controlled so that the passage opening degree of the air discharge pipe 31 is reduced, and the pressure of the air in the air flow path 15 is increased. The amount of diffusion water moving (diffusing) from the air electrode 13 side to the hydrogen electrode 12 side is increased. As a result, the amount of water on the hydrogen inlet 14a side of the hydrogen channel 14 is increased, and the increased moisture is swept away to the hydrogen outlet 14b side on the downstream side of the hydrogen channel 14, and is spread throughout the hydrogen electrode 12 side of the cell 10. Moisture spreads.

  Further, in the hydrogen pressure lowering process, the hydrogen pressure regulating valve 23 is controlled so that the passage opening degree of the hydrogen supply pipe 20 becomes smaller, the hydrogen pressure in the hydrogen flow path 14 is lowered, and the downstream side of the air flow path 15 The amount of diffusion water that moves (diffuses) from the air electrode 13 side to the hydrogen electrode 12 side is increased. Thereby, like the air back pressure control process, moisture spreads over the entire region of the cell 10 on the hydrogen electrode 12 side.

  Further, in the hydrogen stoichiometric ratio control process, control is performed to increase the rotation speed of the electric motor 26a of the circulation pump 26, the hydrogen stoichiometric ratio is increased, the flow rate of hydrogen flowing through the hydrogen passage 14 is increased, and the hydrogen passage 14, the accompanying water moving from the hydrogen electrode 12 side to the air electrode 13 side on the hydrogen outlet portion 14 b side is increased. As a result, the amount of moisture on the air inlet 15a side of the air channel 15 is increased, and the increased moisture is swept away to the air outlet 15b side on the downstream side of the air channel 15 to reach the entire area of the cell 10 on the air electrode 13 side. Moisture spreads.

  After executing the water circulation amount increasing process in S40, it is determined again whether or not the air inlet portion 15a of the air flow path 15 is dried (S50). Since the determination process in S50 is the same as the determination process in S10 and S30, description thereof is omitted. Note that the determination processing of S10, S30, and S50 corresponds to the moisture content determination means of the present invention.

  As a result of the determination process of S50, when it is determined that the air inlet 15a is dry (S50: YES), the water circulation amount increase process is performed again (S40). In this water circulation amount increasing process, it can be determined that the degree of drying of the air inlet portion 15a is high. Therefore, two or more control processes among the air pressure increasing process, the hydrogen pressure decreasing process, and the hydrogen stoichiometric ratio control process are executed in combination. Also good.

  On the other hand, when it is determined that the air inlet 15a is not dry as a result of the determination process of S50 (S50: NO), a variable stoichiometric ratio control process is executed (S60).

  In this variable stoichiometric ratio control process, if the state in which the air stoichiometric ratio is lowered is continued, supply of air to the air electrode 13 side due to a decrease in the oxygen concentration in the air flow path 15 or an increase in the amount of moisture in the air flow path 15. In order to suppress the hindrance from being inhibited, control for periodically reducing the air stoichiometric ratio is executed.

  Specifically, as shown in FIG. 4, the air stoichiometric ratio is gradually increased from the low stoichiometric ratio Ast to the reference stoichiometric ratio St higher than the low stoichiometric ratio ASt, and then gradually decreased from the reference stoichiometric ratio St. The process of decreasing to the ratio Ast is continuously repeated. As the reference stoichiometric ratio St, a stoichiometric ratio St set according to the required generated power for the fuel cell 1 can be adopted.

  Here, in FIG. 4, the time T1 when increasing from the low stoichiometric ratio Ast to the reference stoichiometric ratio St and the time T2 required when decreasing from the standard stoichiometric ratio St to the low stoichiometric ratio Ast are different times. The same time may be set. In FIG. 4, the air stoichiometric ratio is varied in a triangular wave shape. However, the present invention is not limited to this. For example, the air stoichiometric ratio may be varied in a sine wave shape.

  Here, the operation when the stoichiometric ratio control process of the present embodiment is executed when the air inlet portion 15a of the air flow path 15 is dry will be described based on the experimental data shown in FIGS.

FIG. 5 is an explanatory diagram for explaining the relationship between the current density [A / cm ² ] of the air inlet 15a and the output voltage [V] in the predetermined cell 10 when the stoichiometric ratio control process of the present embodiment is executed. is there. The solid line in FIG. 5 represents experimental data at the time of execution of the stoichiometric ratio control process (reference stoichiometric ratio = 1.5, low stoichiometric ratio = 1.1, back pressure (air pressure) = 180 kPa) according to the present embodiment. Show. 5 indicates experimental data when the stoichiometric ratio control process without the variable stoichiometric ratio control process (S60 in FIG. 4) is performed, and the alternate long and short dash line indicates the stoichiometric ratio according to the required generated power of the fuel cell 1. (= 1.5, back pressure (air pressure) = 140 kPa) is shown experimental data, the two-dot chain line is the control of the stoichiometric ratio (= 1.5) corresponding to the required power generation of the fuel cell 1 In addition to the above, experimental data is shown when the water content increasing process (back pressure (air pressure) = 180 kPa) is executed.

As shown by the one-dot chain line in FIG. 5, when the stoichiometric ratio (= 1.5) is controlled according to the required generated power of the fuel cell 1, power generation occurs when the current density exceeds about 0.6 [A / cm ² ]. It turns out that it becomes impossible. In addition to the control of the stoichiometric ratio (= 1.5) corresponding to the required generated power of the fuel cell 1, as shown by the two-dot chain line in FIG. 5, the moisture amount increasing process (back pressure (air pressure)) = Even when 180 kPa) is executed, it is understood that power generation cannot be performed when the current density exceeds about 1.3 [A / cm ² ].

On the other hand, as shown by the broken line in FIG. 5, the stoichiometric ratio control process (low stoichiometric ratio = 1.1, back pressure (air pressure) = 180 kPa) without the variable stoichiometric ratio control process (S60 in FIG. 4). ), The output voltage decreases as the current density increases, but it can be seen that power generation is possible even when the current density exceeds about 2.0 [A / cm ² ].

  Further, as shown by the solid line in FIG. 5, when the stoichiometric ratio control process accompanied by the variable stoichiometric ratio control process is executed, the output voltage slightly decreases as the current density increases, but the broken line in FIG. It can be seen that the output voltage is maintained higher than the experimental data shown. 5 shows the state when the portion protruding upward (shown by a black triangle in the figure) in the solid line is raised to the reference stoichiometric ratio, and the portion protruding downward (the part indicated by a black circle in the drawing) ) Shows the state when it is lowered to a low stoichiometric ratio.

  Next, FIG. 6 shows the amount of water (the amount of water in the membrane) of the electrolyte membrane 11 and the distribution of the amount of water (film) in the cell plane (on the air flow path 15 side) when the stoichiometric ratio control process of the present embodiment is executed. FIG. 7 shows the water content of the accompanying water moving from the hydrogen electrode 12 side to the air electrode 13 side in the cell plane, and the water content distribution (water content distribution in the film). FIG. FIG. 8 shows the current density and current density distribution in the cell plane when the stoichiometric ratio control process of this embodiment is executed, and FIG. 9 shows the temperature and temperature distribution in the cell plane.

  Here, a solid line (thick solid line, thin solid line) in FIGS. 6 to 9 shows experimental data when the stoichiometric ratio control process of the present embodiment is executed, and a broken line (thick broken line, thin broken line) indicates the fuel cell 1. Experimental data when the stoichiometric ratio (= 1.5) is controlled according to the required generated power is shown. Also, as indicated by the arrows in each figure, the bold line in the solid line and the broken line corresponds to the left vertical axis, and the thin line corresponds to the right vertical axis.

  As shown by the broken line in FIG. 6, when the stoichiometric ratio (= 1.5) is controlled in accordance with the required generated power of the fuel cell 1, the amount of moisture in the film and its distribution are determined by the air outlet portion in the air flow path 15. It can be seen that the electrolyte membrane 11 on the side of the air inlet 15a is dry.

  Further, as shown by the broken line in FIG. 7, the accompanying water moving from the hydrogen electrode 12 side to the air electrode 13 side and the distribution thereof are biased toward the air outlet 15b side in the air flow path 15 and increase in the air inlet. On the part 15a side, the water content of the accompanying water can hardly be confirmed, and it can be seen that water circulation is not established in part between the hydrogen electrode 12 and the air electrode 13.

  Furthermore, as shown in FIGS. 8 and 9, the current density and temperature in the cell plane are biased toward the air outlet 15b side, and the power generation area contributing to power generation in the cell plane is significantly reduced. I understand that.

  On the other hand, as shown by the solid line in FIG. 6, when the stoichiometric ratio control process is executed, the amount of moisture in the film and its distribution are more on the air inlet 15a side in the air flow path 15, and on the air inlet 15a side. It can be seen that the electrolyte membrane 11 is not dried. It can also be seen that there is a predetermined amount or more of moisture in the film over a wide range from the air inlet portion 15a side to the air outlet portion 15b side, and the film moisture amount is secured over the entire area in the cell plane.

  In addition, as shown by the solid line in FIG. 7, the accompanying water moving from the hydrogen electrode 12 side to the air electrode 13 side and the distribution thereof are more on the air inlet portion 15a side in the air flow path 15, and on the air inlet portion 15a side. It can be seen that power generation is promoted. Further, since the accompanying water is squeezed from the air inlet portion 15a side toward the air outlet portion 15b side, the generated water generated on the air electrode 13 side is likely to diffuse from the air electrode 13 side to the hydrogen electrode 12 side. It turns out that it is.

  Furthermore, as shown by the solid line in FIG. 8, it can be seen that the current density in the cell plane and the distribution thereof are higher on the air inlet portion 15a side, and power generation is possible at the air inlet portion 15a. Further, it can be seen that a current density of a predetermined amount or more exists over a wide range from the air inlet portion 15a side to the air outlet portion 15b side, and the power generation area contributing to power generation is substantially the entire area of the cell surface.

  Furthermore, as shown by the solid line in FIG. 9, the temperature in the cell surface and its distribution are higher than the temperature in the cell surface and its distribution shown by the broken line in FIG. 9 from the air inlet 15a side to the air outlet 15b side. It can be seen that the temperature difference between and is reduced.

  As described above, in the present embodiment described above, when the amount of water in the air inlet portion 15a of the air flow path 15 is insufficient, the air stoichiometric ratio is set to a normal air stoichiometric ratio so that power generation on the air inlet portion 15a side is promoted. Lower to a low stoichiometric ratio Ast lower than the ratio setting range.

  As a result, the drying of the electrolyte membrane 11 on the air inlet portion 15a side in the cell plane of each cell 10 can be sufficiently suppressed, so that the fuel that performs the non-humidifying operation by supplying non-humidified air to the fuel cell 1 is provided. In the battery system, it becomes possible to suppress the non-uniformity of moisture in the cell surface.

  Even if the air stoichiometric ratio is reduced to the low stoichiometric ratio Ast, if the amount of water at the air inlet 15a is insufficient, in addition to the reduction in the air stoichiometric ratio, the water between the hydrogen electrode 12 and the air electrode 13 Since the water circulation amount increasing process for increasing the circulation amount is executed, the circulation amount of water between the hydrogen electrode 12 and the air electrode 13 can be increased.

  Thereby, it is possible to sufficiently suppress the drying of the electrolyte membrane 11 in the entire area of the cell surface of each cell 10 and to more effectively suppress the non-uniformity of moisture in the cell surface.

  Further, since the variable stoichiometric ratio control process for periodically lowering the air stoichiometric ratio is executed, an increase in overvoltage on the air electrode 13 side due to a decrease in oxygen concentration in the air in the air passage 15, or in the air passage 15. Inhibition of the supply of air to the air electrode 13 due to an increase in the amount of water can be suppressed. As a result, it is possible to suppress a decrease in the output of the fuel cell 1.

(Other embodiments)
As mentioned above, although embodiment of this invention was described, this invention is not limited to this, Unless it deviates from the range described in each claim, it is not limited to the wording of each claim, and those skilled in the art Improvements based on the knowledge that a person skilled in the art normally has can be added as appropriate to the extent that they can be easily replaced. For example, various modifications are possible as follows.

  (1) In the above embodiment, in the stoichiometric ratio control process, after the air inlet part power generation promotion process is performed, when the air inlet part 15a is dry, the water circulation amount increasing process is executed. Instead of the amount increasing process, an output limiting process for temporarily reducing the required generated power of the fuel cell 1 may be performed.

  Specifically, in the stoichiometric ratio control process, when the air inlet portion 15a is dry after performing the air inlet portion power generation promotion processing, the power generation amount of the fuel cell 1 until the predetermined time elapses after the determination. Is set to a predetermined limited power generation amount lower than the required power generation amount, and the output of the fuel cell 1 may be limited. Note that the limited power generation amount may be a fixed value or a variable value that varies depending on the required power generation amount of the fuel cell 1.

  According to this, when the amount of water in the air inlet portion 15a is insufficient, in addition to the reduction in the air stoichiometric ratio, the power generation amount of the fuel cell 1 is temporarily reduced to limit the output of the fuel cell 1. Therefore, an increase in the supply amount of hydrogen and air can be suppressed. As a result, it is possible to temporarily suppress an increase in accompanying water from the hydrogen electrode 12 side to the air electrode 13 side, and it is possible to suppress nonuniformity in the amount of water in the cell surface. Note that the control device 50 that executes the output voltage processing constitutes the output limiting means of the present invention.

  (2) In the above embodiment, in the stoichiometric ratio control process, after the air inlet part power generation promotion process is performed, when the air inlet part 15a is dry, the water circulation amount increasing process is executed. For example, the air inlet power generation promotion process and the water circulation amount increase process may be executed simultaneously.

  (3) In the above-described embodiment, the variable stoichiometric ratio control process is always executed after the air inlet power generation promotion process is performed in the stoichiometric ratio control process. However, the present invention is not limited to this. For example, when the period during which the air stoichiometric ratio is set to the low stoichiometric ratio is short and an increase in overvoltage on the air electrode 13 side does not occur, the variable stoichiometric ratio control process may not be executed in the stoichiometric ratio control process.

  (4) In the above embodiment, the air inlet portion 15a measured by the local current measuring device 5 in the moisture amount determination process (see S10, S30, S50 in FIG. 3) as to whether or not the air inlet portion 15a is dry. However, the present invention is not limited to this.

  For example, when a sensor for detecting the membrane resistance of the electrolyte membrane 11 facing the air inlet portion 15a is provided, and the detected value of the sensor is equal to or higher than a preset reference value, the air inlet portion 15a is dry. You may judge.

  In addition, when a sensor for detecting one of the moisture content and the membrane conductivity of the electrolyte membrane 11 facing the air inlet portion 15a is provided, and the detected value of the sensor is equal to or lower than a preset reference value, the air inlet You may determine with the part 15a being dry.

  In addition, a humidity sensor that detects humidity at the air inlet portion 15a may be provided, and when the detected value of the humidity sensor is equal to or less than a preset reference value, it may be determined that the air inlet portion 15a is dry. .

  (5) In the above embodiment, the fuel cell system of the present invention is applied to a vehicle. However, the present invention is not limited to this, and the present invention is applied to mobile objects such as ships and portable generators, and installation types for home use and factories. May be.

1 Fuel cell 10 Battery cell
11 Electrolyte membrane 12 Hydrogen electrode (anode)
13 Air electrode (cathode)
14 Hydrogen channel (fuel gas channel)
14a Hydrogen inlet (fuel gas inlet)
14b Hydrogen outlet (fuel gas outlet)
15 Air channel (oxidant gas channel)
15a Air inlet (oxidant gas inlet)
15b Air outlet (oxidant gas outlet)
20 Hydrogen supply piping (fuel gas supply route)
23 Hydrogen pressure regulating valve (Anode side pressure adjusting means)
31 Air discharge piping (oxidant gas discharge route)
34 Back pressure adjusting valve (Cathode pressure adjusting means)
50 Control device (control means)
50a Fuel gas stoichiometric ratio adjusting means 50b Oxidant gas stoichiometric ratio adjusting means

Claims (6)

A membrane electrode assembly in which an electrolyte membrane (11) made of a solid polymer is sandwiched between a pair of electrodes (12, 13), and a fuel gas for supplying fuel gas to the anode side of the pair of electrodes (12, 13) A plurality of battery cells (10) having a channel (14) and an oxidant gas channel (15) for supplying an oxidant gas to the cathode side of the pair of electrodes (12, 13) are laminated. The fuel gas channel (14) and the oxidant gas channel (15) are arranged such that the flow direction of the fuel gas and the flow direction of the oxidant gas are opposed to each other. The unreacted fuel gas and moisture discharged from the fuel gas outlet (14b) of the fuel gas channel (14) are re-applied to the fuel gas inlet (14a) of the fuel gas channel (14). Circulating and non-humidified oxidizing agent The scan A fuel cell system oxidant gas inlet portion is supplied to (15a) performs a non-humidified operation of the oxidizing gas channel (15),
Oxidant gas stoichiometric ratio adjusting means (50b) for adjusting the stoichiometric ratio of the oxidant gas supplied to the oxidant gas flow path (15);
Moisture amount determination means (S10, S30, S50) for determining whether or not the amount of moisture in the oxidant gas inlet (15a) of the oxidant gas flow path (15) in the battery cell (10) is insufficient. ,
When the moisture amount determination means (S10, S30, S50) determines that the amount of moisture in the oxidant gas inlet (15a) is insufficient, the moisture in the oxidant gas inlet (15a) Control means (50) for reducing at least the stoichiometric ratio of the oxidant gas so that power generation at the oxidant gas inlet (15a) is promoted compared to a case where it is determined that the amount is not insufficient. ,
A fuel cell system comprising: Provided in the oxidant gas discharge path (31) for discharging the oxidant gas from the oxidant gas flow path (15), and adjusts the pressure of the oxidant gas in the cell plane of the battery cell (10). Cathode side pressure adjusting means (34) for
The control means (50) determines the oxidant when the water content determination means (S10, S30, S50) determines that the water content in the oxidant gas inlet (15a) is insufficient. The fuel cell system according to claim 1, wherein the pressure of the gas is increased. An anode for adjusting the pressure of the fuel gas in the cell plane of the battery cell (10) provided in the fuel gas supply path (20) for supplying the fuel gas to the fuel gas flow path (14) Side pressure adjusting means (23),
The control means (50) determines the fuel gas when the water content determination means (S10, S30, S50) determines that the water content in the oxidant gas inlet (15a) is insufficient. The fuel cell system according to claim 1, wherein the pressure of the fuel cell is reduced. A fuel gas stoichiometric ratio adjusting means (50a) for adjusting a stoichiometric ratio of the fuel gas supplied to the fuel gas flow path (14);
The control means (50) determines the fuel gas when the water content determination means (S10, S30, S50) determines that the water content in the oxidant gas inlet (15a) is insufficient. The fuel cell system according to any one of claims 1 to 3, wherein the stoichiometric ratio is increased. Output limiting means (50) for limiting the output of the fuel cell (1) by setting the power generation amount of the fuel cell (1) to a predetermined limit power generation amount lower than the required power generation amount;
The control means (50) determines from the determination when the water content determination means (S10, S30, S50) determines that the water content in the oxidant gas inlet (15a) is insufficient. The fuel cell system according to claim 1, wherein the output of the fuel cell (1) is limited until a predetermined time elapses.   The control means (50) determines the oxidant when the water content determination means (S10, S30, S50) determines that the water content in the oxidant gas inlet (15a) is insufficient. 6. The fuel cell system according to claim 1, wherein the stoichiometric ratio of the gas is periodically decreased.

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