JP2009252552A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system for suppressing the deterioration of a fuel cell while securing the responsiveness of the system. <P>SOLUTION: A cathode circulation mechanism 60 is provided on the cathode-side construction of the fuel cell 10. The voltage of the fuel cell 10 is measured by a voltmeter 50. When the cathode potential of the fuel cell 10 is predetermined potential or higher, cathode offgas is circulated on the upstream side of the cathode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-115533, a fuel cell system that stops a gas in a cathode when the system is stopped is known. In Patent Document 1, the cathode potential is lowered by stopping the gas when the system is stopped, and the stop operation is ended when the voltage of the fuel cell becomes substantially zero.

JP 2007-115533 A Japanese Patent Laid-Open No. 2005-1000084 JP 2005-251434 A

  If the cathode potential is too high, the fuel cell may be deteriorated, which is not preferable. During power generation in a low load area of the fuel cell, or in a state where the fuel cell forms an open circuit and is ready for power generation (while waiting for power generation), the cathode of the fuel cell compared to during normal power generation The potential increases. From the viewpoint of preventing deterioration of the fuel cell, when the cathode potential is high, it is desired to lower the cathode potential as necessary.

  Patent Document 1 describes a technique for lowering the cathode potential by stopping the gas in the cathode. However, if the gas flow in the cathode is stopped, it becomes difficult to quickly respond to subsequent load fluctuations and power generation restart requests. That is, the responsiveness of the system is lowered.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel cell system that can suppress deterioration of the fuel cell while ensuring the responsiveness of the system.

In order to achieve the above object, a first invention is a fuel cell system,
An electrolyte membrane, an anode provided on one surface of the electrolyte membrane, and a cathode provided on the other surface of the electrolyte membrane, are supplied with hydrogen to the anode and supplied with oxygen to the cathode to generate power A fuel cell,
A cathode gas supply mechanism for flowing a gas containing oxygen into the cathode;
A potential detecting means for detecting a cathode potential which is the potential of the cathode;
A partial pressure reducing means for reducing the oxygen partial pressure of the gas flowing into the cathode when the cathode potential detected by the potential detecting means is equal to or higher than a predetermined potential;
It is characterized by providing.

In order to achieve the above object, a second invention is a fuel cell system,
An electrolyte membrane, an anode provided on one surface of the electrolyte membrane, and a cathode provided on the other surface of the electrolyte membrane, are supplied with hydrogen to the anode and supplied with oxygen to the cathode to generate power A fuel cell,
A cathode gas supply mechanism for flowing a gas containing oxygen into the cathode;
A partial pressure reducing means for reducing an oxygen partial pressure of a gas flowing into the cathode during power generation in a predetermined low load region of the fuel cell and / or during power generation standby of the fuel cell;
It is characterized by providing.

The third invention is the first or second invention, wherein
The partial pressure reducing means reduces the oxygen partial pressure of the gas flowing into the cathode by adding to the gas flowing upstream of the cathode a dilution gas having a lower oxygen concentration than the gas flowing upstream. It is characterized by that.

Moreover, 4th invention is set in 3rd invention,
Cathode off-gas discharged from the cathode is used as the dilution gas.

The fifth invention is the third or fourth invention, wherein
The anode off gas discharged from the anode is used as the dilution gas.

The sixth invention is the fifth invention, wherein
A reaction promoting means for promoting the reaction between hydrogen and oxygen is disposed upstream of the cathode,
The gas added with the anode off gas flows into the cathode through the reaction promoting means.

According to a seventh invention, in any one of the first to sixth inventions,
A gas inlet and outlet, further comprising an oxygen reduction mechanism capable of selectively reducing the amount of oxygen in the gas passing through the interior;
The partial pressure reducing means reduces the oxygen partial pressure of the gas flowing into the cathode by causing the gas to flow into the cathode via the oxygen reducing mechanism.

  The cathode potential can be lowered by reducing the oxygen partial pressure of the gas in the cathode.

  According to the first invention, when the cathode potential becomes too high, the cathode potential can be lowered while maintaining the flow of the gas in the cathode by flowing the gas having a reduced oxygen partial pressure into the cathode. it can. Thereby, when there is an output increase request or a power generation resumption request while the cathode potential is being lowered, these requests can be met promptly. As a result, deterioration of the fuel cell can be suppressed while ensuring the responsiveness of the system.

  According to the second aspect of the present invention, the gas in the cathode is caused to flow by flowing the gas having a reduced oxygen partial pressure into the cathode during low load region power generation or standby for power generation, which is likely to increase the cathode potential. The cathode potential can be lowered while maintaining the flow of. As a result, when there is an output increase request or a power generation resumption request while the cathode potential is being lowered, these requests can be met promptly. As a result, deterioration of the fuel cell can be suppressed while ensuring the responsiveness of the system.

  According to the third invention, the oxygen partial pressure of the gas flowing into the cathode can be selectively reduced by reducing the oxygen concentration of the gas flowing into the cathode.

  According to the fourth aspect of the invention, the cathode off-gas whose oxygen concentration has been reduced by the consumption of oxygen by power generation can be used as the dilution gas for diluting the oxygen concentration.

  According to the fifth invention, the anode off gas can be used as a dilution gas for diluting the oxygen concentration. In addition, in the cathode catalyst, hydrogen in the anode off gas reacts with oxygen in the gas flowing into the cathode, so that the amount of oxygen contributing to the power generation reaction can be reduced and the cathode potential can be lowered.

  According to the sixth invention, in the fourth invention, the amount of oxygen in the gas flowing into the cathode can be reduced at a stage before the cathode inflow by reacting hydrogen and oxygen in advance upstream of the cathode. it can.

  According to the seventh invention, the oxygen partial pressure of the gas flowing into the cathode can be selectively reduced by flowing the gas having a reduced oxygen concentration into the cathode via the oxygen reduction mechanism.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a configuration diagram of a fuel cell system according to a first embodiment of the present invention. The fuel cell system includes a fuel cell 10. The power generated by the fuel cell 10 can be supplied, for example, to a load such as a motor or stored in a battery (not shown). For example, in the case of a fuel cell vehicle that uses the fuel cell system in an auxiliary manner, power can be supplied from the battery to the vehicle drive motor while supplying power from the fuel cell 10 to the battery.

  In general, the fuel cell 10 is used as a fuel cell stack in which a plurality of unit fuel cells (hereinafter simply referred to as “unit cells”) are stacked. Although not shown, the unit cell has a configuration in which a membrane electrode assembly is sandwiched between a pair of current collector plates. The membrane electrode assembly is obtained by integrating a catalyst on both surfaces of a solid polymer electrolyte membrane. The current collector plate also functions as a separator that partitions between two adjacent membrane electrode assemblies. Each unit cell receives supply of hydrogen as a fuel gas to the anode, and receives supply of air to the cathode, and generates power by an electrochemical reaction between hydrogen and oxygen.

A hydrogen supply pipe 20 for supplying hydrogen from a hydrogen supply source (H _{2 in} FIG. 1) is connected to the fuel cell 10. The hydrogen supply source can be, for example, a hydrogen tank that stores high-pressure hydrogen. In the middle of the hydrogen supply pipe 20, an injector 22 capable of appropriately adjusting the supply amount of hydrogen is disposed. Hydrogen supplied to the fuel cell 10 is distributed to the anode of each unit cell by a supply manifold (not shown) formed in the fuel cell 10.

  The fuel cell 10 includes an exhaust pipe 24 for extracting anode off gas. The exhaust pipe 24 is connected to the anode of each unit cell via an exhaust manifold (not shown) formed in the fuel cell 10. A gas-liquid separator 26 and an exhaust drain valve 28 are sequentially arranged in the exhaust pipe 24.

  The fuel cell system of Embodiment 1 is a type of system that circulates gas at the anode. In Embodiment 1, the suction port of the hydrogen pump 30 is connected to the gas-liquid separator 26, the discharge port of the hydrogen pump 30 is connected to the hydrogen supply pipe 20, and the anode off gas is circulated upstream of the anode.

  The fuel cell 10 is connected to an air supply pipe 40 for supplying air to the cathode. An air pump 42 is disposed in the air supply pipe 40. By the operation of the air pump 42, air is taken into the air supply pipe 40 and supplied to the fuel cell 10. Air supplied to the fuel cell 10 is distributed to the cathode of each unit cell by a supply manifold formed in the fuel cell 10.

  The air that has passed through the cathode of each unit cell is collected in an exhaust manifold formed in the fuel cell 2 and discharged to the exhaust pipe 44. In the process of passing through the cathode, oxygen in the air is consumed for power generation. A cathode off-gas that is a gas that has passed through the cathode is discharged to the exhaust pipe 44. A pressure regulating valve 46 and a gas-liquid separator 48 are sequentially provided in the exhaust pipe 44 toward the downstream side.

  The fuel cell system of Embodiment 1 includes a cathode circulation mechanism 60. The cathode circulation mechanism 60 includes a pipe line 62 and a cathode circulation valve 64 provided in the pipe line 62. The pipe line 62 connects a portion of the exhaust pipe 44 on the downstream side of the gas-liquid separator 48 and a portion of the air supply pipe 40 on the air pump 42 suction port side. By opening and closing the cathode circulation valve 64, the cathode off gas can be appropriately circulated to the upstream side of the cathode.

  The fuel cell system of Embodiment 1 includes an ECU (Electronic Control Unit) 52 and a voltmeter 50 and an ammeter 54 for detecting the power generation state of the fuel cell 10. The output of each meter is input to the ECU 52. The ECU 52 is connected to the cathode circulation valve 64 and controls the cathode circulation valve 64.

[Operation of Embodiment 1]
Hereinafter, the operation of the fuel cell system of Embodiment 1 will be described. During power generation in the low load region of the fuel cell 10 or during power generation standby in which the fuel cell 10 forms an open circuit (Open Circuit), the potential of the cathode of the fuel cell 10 (as compared to during normal power generation) ( Hereinafter, this is referred to as “cathode potential”. If the cathode potential becomes too high, the internal structure of the fuel cell 10 may be deteriorated. For this reason, it is preferable to reduce a cathode potential as needed.

  The cathode potential can be lowered by reducing the oxygen partial pressure of the gas in the cathode. Therefore, in the first embodiment, when the cathode potential is high enough to cause deterioration of the fuel cell 10, the oxygen partial pressure of the air flowing into the cathode is lowered as compared with the normal operation. Thereby, the cathode potential can be lowered.

  By the way, it is conceivable that a load change or a request to resume power generation occurs suddenly during power generation in a low load range or during power generation standby. In order to cope with this promptly, it is important that the responsiveness of the system is good. If the gas flow is lost inside the cathode, or if the gas flow is too far from the normal operating state, it will take time to generate the necessary gas flow during normal power generation. . As a result, the return to the power generation state is delayed. From the viewpoint of keeping the responsiveness of the system high, it is desirable that the gas flow inside the cathode is sufficiently maintained.

  According to the first embodiment, the oxygen partial pressure can be reduced while the supply of air to the cathode of the fuel cell 10 is continued. Therefore, the cathode potential can be lowered while the gas flow in the cathode is maintained. Thereby, deterioration of the cathode of the fuel cell 10 can be suppressed while maintaining the responsiveness of the system.

  In particular, according to Embodiment 1, a low oxygen concentration dilution gas (hereinafter also referred to as “dilution gas”) is added to air, and the resulting low oxygen partial pressure gas is It can be supplied to the cathode of the fuel cell 10. Specifically, in the first embodiment, when the cathode potential is high, by opening the cathode circulation valve 64, the air pump 42 takes in the cathode off gas together with air and discharges it to the fuel cell 10 side. A gas having a low oxygen partial pressure obtained as a result of mixing air and the cathode off-gas can be supplied to the cathode of the fuel cell 10.

  Further, in the first embodiment, a cathode off gas is used as the dilution gas. The cathode off gas is a low oxygen concentration gas in which oxygen is consumed by power generation. In the first embodiment, this cathode off gas can be used effectively.

[Specific Processing in First Embodiment]
Hereinafter, specific processing of the fuel cell system of Embodiment 1 will be described with reference to FIG. FIG. 2 is a flowchart of a routine executed by ECU 52 in the first embodiment. In the first embodiment, it is assumed that the cathode circulation valve 64 is closed first.

  In the first embodiment, it is determined whether the cathode potential is high enough to cause deterioration of the fuel cell 10 using the voltage value indicated by the voltmeter 50. When the anode is filled with hydrogen, the voltage value of the fuel cell can be used as an indicator of the cathode potential. However, the cathode potential may be grasped with higher accuracy by performing calculation based on the voltage value of the voltmeter 50.

  In the routine shown in FIG. 2, first, the voltage value of the fuel cell 10 is acquired (step S100). Specifically, the ECU 52 acquires the output value of the voltmeter 50. In the first embodiment, it is assumed that the process of step S100 is continuously executed and the voltage of the fuel cell 10 is constantly monitored.

  Next, it is determined whether or not the voltage value acquired in step S100 is equal to or higher than a predetermined voltage (step S102). By this step, it is determined whether or not the current cathode potential of the fuel cell 10 is high enough to cause deterioration of the fuel cell 10. The predetermined voltage to be used for the determination may be determined in advance through experiments or simulations.

  When the condition of step S102 is satisfied, a process for opening the cathode circulation valve 64 is executed (step S104). In this step, the ECU 52 issues a control signal, the cathode circulation valve 64 is opened, and as a result, the cathode off gas is added to the suction port side of the air pump 42. As a result, a mixed gas of air and cathode off gas is supplied to the cathode of the fuel cell 10, and a gas having a reduced oxygen partial pressure as compared with air flows into the cathode. Thereafter, the current routine ends, and the process returns to step S100.

  When the condition of step S102 is not satisfied, a process for closing the cathode circulation valve 64 is executed (step S106). In this step, when the cathode circulation valve 64 is currently opened, the cathode circulation valve 64 is closed, and when the cathode circulation valve 64 is currently closed, the closed state is maintained as it is. As a result, the measure for reducing the oxygen partial pressure is released, and only air is supplied to the cathode as usual. After execution of step S106, the current routine ends, and the process returns to step S100.

  According to the above processing, the situation where the cathode of the fuel cell 10 is at a high potential can be reliably detected, and the cathode circulation valve 64 can be accurately opened and closed. The fuel cell system can be operated while suppressing deterioration of the fuel cell 10 and ensuring the responsiveness of the system. Further, according to the first embodiment, it is possible to immediately switch between execution and stop of the oxygen partial pressure reduction as the cathode circulation valve 64 is opened and closed, so that the responsiveness of the system can be maintained high.

  In the first embodiment described above, the fuel cell 10 corresponds to the “fuel cell” in the first invention, and the voltmeter 50 corresponds to the “potential detection means” in the first invention. Further, in the first embodiment, the “cathode gas supply mechanism” in the first invention is realized by the air supply pipe 40 and the air pump 42, and the cathode circulation mechanism 60 is configured in accordance with the processes in steps S 102 and S 104 of the routine of FIG. By being controlled, the “partial pressure reducing means” in the first aspect of the present invention is realized.

[Modification of Embodiment 1]
(First modification)
In the first embodiment, a fuel cell system of a type in which a gas (hydrogen) is circulated through an anode is targeted. However, the present invention is not limited to this. Unlike Embodiment 1, a so-called circulation-less fuel cell system is known in which gas is not circulated via an anode. For such a circulation-less fuel cell system, the cathode circulation mechanism 60 (that is, the pipe line 62 and the cathode circulation valve 64) can be provided to perform the same processing as in the first embodiment.

(Second modification)
In the first embodiment, the cathode off-gas is used as a dilution gas for reducing the oxygen partial pressure. However, the present invention is not limited to this. A gas having a sufficiently low or almost zero oxygen concentration can be used as the dilution gas as compared with the gas (air in the first embodiment) supplied to the cathode during normal operation of the fuel cell 10. Such a gas may be used, for example, separately stored in a tank.

(Third Modification)
In the first embodiment, the cathode potential is detected based on the voltage value indicated by the voltmeter 50, and the cathode circulation valve 64 is opened and closed in accordance with the detected voltage value. However, the present invention is not limited to this. Instead of (or with) the actual measurement of the voltage value, the cathode circulation valve 64 may be controlled according to the following method.

(i) Determination by detection of load state When the fuel cell 10 is generating power at a low load, the cathode potential of the fuel cell 10 is usually high. Therefore, in the third modification, based on the load state of the fuel cell 10, it is indirectly determined whether or not the cathode potential is high enough to cause deterioration of the fuel cell 10.

  First, by measuring the cathode potential while generating power in the low load state of the fuel cell 10, a low load region that becomes high enough to cause deterioration of the fuel cell 10 is grasped in advance. What is necessary is just to monitor continuously whether the present load of a fuel cell system exists in the specified low load region.

  Specifically, in the third modification, it is determined whether or not the current value measured by the ammeter 54 is equal to or less than a predetermined value in the system configuration of the first embodiment. When the current value is less than or equal to the predetermined value, it is determined that the fuel cell 10 is operated in a low load region where there is a risk of deterioration, and the operation of step S104 may be executed as in the first embodiment. As a result, the gas with a reduced oxygen partial pressure can be caused to flow into the cathode during low load region power generation, which is a situation where the cathode potential is likely to increase.

(ii) Judgment based on whether or not power generation is on standby Normally, hydrogen is present at the anode and air is present at the cathode inside the fuel cell 10, and the fuel cell 10 forms an open circuit for power generation. In the equipped state (hereinafter also referred to as “power generation standby”), the cathode potential is around 1V. In such a state, the fuel cell 10 may be deteriorated.

  Therefore, in the third modified example, if the fuel cell 10 is on standby for power generation, it is determined that the cathode potential is high enough to cause deterioration of the fuel cell 10. Specifically, in the third modification, when the load on the fuel cell 10 is zero, the operation of step S104 is executed as in the first embodiment. As a result, the gas having a reduced oxygen partial pressure can flow into the cathode, and the cathode potential can be lowered.

  In a complex system that uses a fuel cell as an auxiliary power source and a battery as the main power source, the state where power is taken out of the battery and power generation of the fuel cell is stopped included.

  In the above-described third modification, the low load region in which the cathode potential is high enough to cause deterioration of the fuel cell 10 is equivalent to the “predetermined low load region” in the second invention. is doing. In the above-described third modification, the state in which the fuel cell 10 forms an open circuit (OC) corresponds to “power generation standby” in the second invention.

Embodiment 2. FIG.
[Configuration of Embodiment 2]
FIG. 3 is a configuration diagram of the fuel cell system according to the second embodiment. The second embodiment is different from the first embodiment in that a pipe line 160 and a return valve 162 are provided instead of the cathode circulation mechanism 60. The second embodiment is different from the first embodiment in that a combustion reaction chamber 142 is provided between the air pump 42 and the fuel cell 10. In addition, in Embodiment 2, the same structure as Embodiment 1 is attached | subjected with the same code | symbol, and description is abbreviate | omitted.

  As shown in FIG. 3, in the second embodiment, the pipe line 160 connects a portion of the exhaust pipe 24 downstream of the exhaust drain valve 28 and the suction port side of the air pump 42. The anode off gas discharged from the anode of the fuel cell 10 can be supplied to the upstream side of the cathode of the fuel cell 10 via the pipe line 160. By appropriately opening and closing the return valve 162, the anode off gas can be supplied at a desired timing.

  Note that the return valve 162 is controlled by a control signal from the ECU 52, similarly to the cathode circulation valve 64. When the exhaust / drain valve 28 is closed during normal operation, the exhaust / drain valve 28 is also opened when the return valve 162 is opened / closed. When hydrogen and oxygen flow into the combustion reaction chamber 142, the reaction between the hydrogen and oxygen can be promoted.

[Operation of Embodiment 2]
The contents of the anode off-gas are non-power generation-related gases such as nitrogen that have permeated to the anode due to so-called cross leak, and hydrogen that has passed through the anode without being consumed in power generation. In the second embodiment, the role of the dilution gas that the cathode offgas has played in the first embodiment is replaced with the anode offgas. As a result, as in the first embodiment, the cathode potential can be lowered by supplying a gas having a low oxygen partial pressure to the cathode of the fuel cell 10. Therefore, as in the first embodiment, it is possible to suppress the deterioration of the fuel cell 10 while ensuring the responsiveness of the system.

  In the second embodiment, hydrogen contained in the anode off gas reacts with oxygen in the air by the combustion reaction chamber 142 or the catalyst layer on the cathode of the fuel cell 10. Thereby, the amount of oxygen contributing to the power generation reaction can be reduced, and the cathode potential can be effectively reduced. In particular, in the second embodiment, by providing the combustion reaction chamber 142, hydrogen in the anode off gas and oxygen in the air can be reacted at a stage before flowing into the fuel cell 10.

[Specific Processing of Embodiment 2]
Hereinafter, specific processing of the fuel cell system of Embodiment 2 will be described with reference to FIG. FIG. 4 is a flowchart of a routine executed by the ECU 52 in the second embodiment. In the flowchart of FIG. 4, the processes in steps S100 and S102 are the same as those in the flowchart of FIG.

  When the condition of step S102 is established in the flowchart of FIG. 4, the return valve 162 is opened (step S204). As a result, the anode off gas is added to the air, and the air pump 42 discharges the mixed gas downstream. Hydrogen and oxygen react with each other in the combustion reaction chamber 142, and finally a gas having a low oxygen partial pressure flows into the fuel cell 10. Thereafter, the current routine ends.

  If the condition of step S102 is not satisfied, the return valve 162 is set to the closed state (step S206). Thereby, the measure for reducing the oxygen partial pressure is released, and only air is supplied to the cathode as usual. Thereafter, the current routine ends.

  According to the above processing, as in the first embodiment, it is possible to operate the fuel cell system while suppressing deterioration of the fuel cell 10 and maintaining good responsiveness of the system.

  In the second embodiment described above, the “partial pressure reducing means” according to the first aspect of the present invention is realized by controlling the return valve 162 according to the processes of steps S102 and S204 of the routine of FIG. .

[Modification of Embodiment 2]
(First modification)
The fuel cell system according to Embodiment 2 includes a combustion reaction chamber 142. However, the present invention is not limited to this, and the combustion reaction chamber 142 may not be provided. In this case, the catalyst layer at the cathode of the fuel cell 10 can cause a reaction between hydrogen contained in the anode off gas and oxygen in the air.

(Second modification)
As described in the modification of the first embodiment, the second embodiment can be applied to a circulation-less fuel cell system. The circulation-less fuel cell system can be further classified into a dead-end type system and a small exhaust type system. The dead-end system is a system that generates power with the downstream of the anode of the fuel cell closed. The small amount exhaust type system is a system that generates power while discharging a very small amount of gas from the downstream of the anode of the fuel cell. In these systems, similarly to the second embodiment, the anode downstream and the cathode upstream are connected via a return valve 162 via a conduit, and the return valve 162 may be appropriately opened and closed.

(Third Modification)
In the second embodiment as well, as described in the modification of the first embodiment, (i) determination based on detection of a load state and (ii) determination based on whether or not power generation is on standby can be performed.

Embodiment 3 FIG.
In Embodiments 1 and 2, the oxygen partial pressure of the gas flowing into the cathode is reduced by adding a dilution gas such as a cathode off gas or an anode off gas as necessary. On the other hand, in the third embodiment, a mechanism for selectively removing oxygen is added to the system, and if necessary, air is allowed to flow into the cathode via this mechanism, whereby the oxygen partial pressure of the gas flowing into the cathode is increased. Reduce.

  Various mechanisms such as a filter that selectively captures oxygen and an adsorbent that adsorbs oxygen molecules can be used as the mechanism that selectively removes oxygen. In a situation where the cathode is recognized as having a high potential, air may be passed through such a filter, and during normal power generation, air may be passed without bypassing (bypassing) such a filter.

  In the system configuration of the second embodiment, hydrogen may be supplied to the combustion reaction chamber 142, and hydrogen may be added as necessary. In this case, the combustion reaction chamber 142 functions as a mechanism for selectively removing oxygen only during a period in which hydrogen is added.

  Also in the third embodiment, as in the first and second embodiments, the oxygen partial pressure of the gas flowing into the cathode is selectively reduced to suppress deterioration of the fuel cell while ensuring the responsiveness of the system. Can do.

  In the third embodiment described above, the filter, the adsorbent, and the combustion reaction chamber 142 are cited as the “oxygen reducing mechanism” in the seventh aspect of the invention.

  The first to third embodiments described above can be used not only individually but also in combination of two or more.

1 is a configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. FIG. 3 is a flowchart illustrating specific processing executed in the first embodiment. 3 is a configuration diagram of a fuel cell system according to Embodiment 2. FIG. 10 is a flowchart illustrating specific processing executed in the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 20 Hydrogen supply pipe 22 Injector 24 Exhaust pipe 26 Gas-liquid separator 28 Exhaust drain valve 30 Hydrogen pump 40 Air supply pipe 42 Air pump 44 Exhaust pipe 46 Pressure regulating valve 48 Gas-liquid separator 50 Voltmeter 54 Ammeter 60 Cathode circulation Mechanism 62 Pipe line 64 Cathode circulation valve 142 Combustion reaction chamber 160 Pipe line 162 Return valve

Claims (7)

An electrolyte membrane, an anode provided on one surface of the electrolyte membrane, and a cathode provided on the other surface of the electrolyte membrane, are supplied with hydrogen to the anode and supplied with oxygen to the cathode to generate power A fuel cell,
A cathode gas supply mechanism for flowing a gas containing oxygen into the cathode;
A potential detecting means for detecting a cathode potential which is the potential of the cathode;
A partial pressure reducing means for reducing the oxygen partial pressure of the gas flowing into the cathode when the cathode potential detected by the potential detecting means is equal to or higher than a predetermined potential;
A fuel cell system comprising: An electrolyte membrane, an anode provided on one surface of the electrolyte membrane, and a cathode provided on the other surface of the electrolyte membrane, are supplied with hydrogen to the anode and supplied with oxygen to the cathode to generate power A fuel cell,
A cathode gas supply mechanism for flowing a gas containing oxygen into the cathode;
A partial pressure reducing means for reducing an oxygen partial pressure of a gas flowing into the cathode during power generation in a predetermined low load region of the fuel cell and / or during power generation standby of the fuel cell;
A fuel cell system comprising:   The partial pressure reducing means reduces the oxygen partial pressure of the gas flowing into the cathode by adding to the gas flowing upstream of the cathode a dilution gas having a lower oxygen concentration than the gas flowing upstream. The fuel cell system according to claim 1 or 2, wherein   The fuel cell system according to claim 3, wherein the cathode off-gas discharged from the cathode is used as the dilution gas.   The fuel cell system according to claim 3 or 4, wherein the anode off-gas discharged from the anode is used as the dilution gas. A reaction promoting means for promoting the reaction between hydrogen and oxygen is disposed upstream of the cathode,
6. The fuel cell system according to claim 5, wherein the gas to which the anode off gas is added flows into the cathode via the reaction promoting means. The fuel cell system according to any one of claims 1 to 6,
A gas inlet and outlet, further comprising an oxygen reduction mechanism capable of selectively reducing the amount of oxygen in the gas passing through the interior;
The fuel cell system, wherein the partial pressure reducing means reduces the oxygen partial pressure of the gas flowing into the cathode by causing the gas to flow into the cathode via the oxygen reducing mechanism.

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