JP5321230B2 - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the shape change of an electrode even if a defect is generated in a portion relating to operation for suppressing the shape change of the electrode after the shutdown of power generation and continue the use of a fuel cell. <P>SOLUTION: A fuel cell system 10 is equipped with: a stop-time potential shutdown suppressing part conducting potential suppressing operation for suppressing voltage rising in a fuel cell 15 after the shutdown of power generation during the shutdown of a fuel cell system; a defect detection part detecting a defect in the stop-time potential shutdown suppressing part; and an electrode oxidation suppressing part conducting oxidation suppressing operation suppressing the oxidation of an electrode of a fuel cell 15 after starting on and after the next time of the fuel cell system 10 when the defect detecting part detects the defect. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a fuel cell system including a fuel cell, and a control method thereof.

  In the fuel cell system, when the fuel cell stops power generation, a special operation may be performed in order to suppress various problems that may occur in the fuel cell after power generation is stopped. For example, a configuration has been proposed in which the anode side channel and the cathode side channel of the fuel cell after power generation is stopped are scavenged with air (see, for example, Patent Document 1).

  Problems that may occur in the fuel cell after power generation is stopped include, for example, that an internal cell is formed in the fuel cell due to gas cross-leakage between the anode and the cathode, and the cathode is undesirable. There is a case in which the potential of the cathode causes a morphological change of the shape. Here, the change in the form of the cathode means that the state of the catalyst in the cathode (the particle size, specific surface area, etc. of the carbon particles supporting the catalyst metal) changes as a result of a high potential. As described above, by scavenging the anode flow path with air, it is possible to suppress the cathode from increasing in potential and to suppress the cathode shape change. Another operation performed in the fuel cell system when power generation is stopped in order to suppress the cathode shape change caused by the high potential is, for example, an operation of short-circuiting between the anode and the cathode after power generation is stopped.

JP 2006-351396 A JP 2005-129243 A JP 2008-004564 A JP 2007-328972 A

  However, in the fuel cell system, even when the above-described operation is performed when power generation is stopped, if a problem occurs in a part related to this operation, the cathode potential increases, and the cathode shape changes. Will progress. Even if a problem occurs in a portion related to the operation of suppressing the high potential of the cathode when the power generation is stopped as described above, the shape change of the cathode proceeds little by little, so that the power generation by the fuel cell is not immediately disabled. For this reason, even if a malfunction of a part related to the above-described operation is detected, it is usually desired that the fuel cell can be used for a certain period of time. However, an allowable range can be obtained by continuing to use the fuel cell. In some cases, the shape change of the cathode may proceed beyond this.

  The present invention has been made in order to solve the above-described conventional problems, and even if a failure occurs in a portion related to an operation for suppressing the change in the shape of the electrode after the power generation is stopped, the change in the shape of the electrode is performed. It aims at enabling the use of the fuel cell to be continued while suppressing.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.
[Form 1]
A fuel cell system comprising a fuel cell,
When the fuel cell system is stopped, a stop-time potential suppression unit that performs a potential suppression operation for suppressing a voltage increase in the fuel cell after power generation is stopped;
A fault detection unit for detecting a fault in the stop potential suppression unit;
An electrode oxidation suppression unit that performs an oxidation suppression operation for suppressing oxidation of an electrode included in the fuel cell after the next startup of the fuel cell system when the failure detection unit detects the failure;
With
The fuel cell
A plurality of power generation bodies each including an electrolyte membrane and a pair of electrodes are stacked,
An in-cell fuel gas passage formed on an anode, which is one electrode of each of the power generation bodies, through which a fuel gas containing hydrogen flows, and the fuel gas with respect to each of the in-cell fuel gas passages An anode side flow path comprising a fuel gas manifold for supplying and discharging
An in-cell oxidizing gas channel formed on a cathode, which is one of the electrodes included in each of the power generators, through which an oxidizing gas containing oxygen flows, and the oxidizing gas with respect to each of the in-cell oxidizing gas channel An oxidant gas manifold for supplying and discharging gas, and a cathode side flow path comprising:
The potential control unit at the time of stop is an outflow that suppresses the inflow and outflow of air to the cathode side channel in a state where hydrogen is enclosed in the anode side channel when the fuel cell stops power generation as the potential suppression operation. Performing the first potential suppression operation to enter the input suppression state,
The defect detection unit detects a defect in which air flows into the cathode-side channel due to poor formation of the inflow / outflow suppression state in the cathode-side channel,
The electrode oxidation suppression unit includes, as the oxidation suppression operation, a first oxidation suppression operation that circulates the cooling water even after power generation of the fuel cell is stopped when the fuel cell system is restarted after the next startup. During power generation after the next startup of the fuel cell system, at least one of a second oxidation suppression operation for increasing the circulating amount of the cooling water as compared with normal power generation control is performed.
Fuel cell system.
[Form 2]
A fuel cell system comprising a fuel cell,
When the fuel cell system is stopped, a stop-time potential suppression unit that performs a potential suppression operation for suppressing a voltage increase in the fuel cell after power generation is stopped;
A fault detection unit for detecting a fault in the stop potential suppression unit;
An electrode oxidation suppression unit that performs an oxidation suppression operation for suppressing oxidation of an electrode included in the fuel cell after the next startup of the fuel cell system when the failure detection unit detects the failure;
With
The fuel cell
A plurality of power generation bodies each including an electrolyte membrane and a pair of electrodes are stacked,
An in-cell fuel gas passage formed on an anode, which is one electrode of each of the power generation bodies, through which a fuel gas containing hydrogen flows, and the fuel gas with respect to each of the in-cell fuel gas passages An anode side flow path comprising a fuel gas manifold for supplying and discharging
An in-cell oxidizing gas channel formed on a cathode, which is one of the electrodes included in each of the power generators, through which an oxidizing gas containing oxygen flows, and the oxidizing gas with respect to each of the in-cell oxidizing gas channel An oxidant gas manifold for supplying and discharging gas, and a cathode side flow path comprising:
The potential control unit at the time of stop is an outflow that suppresses the inflow and outflow of air to the cathode side channel in a state where hydrogen is enclosed in the anode side channel when the fuel cell stops power generation as the potential suppression operation. Performing the first potential suppression operation to enter the input suppression state,
The defect detection unit detects a defect in which air flows into the cathode-side channel due to poor formation of the inflow / outflow suppression state in the cathode-side channel,
The electrode oxidation suppression unit normally does not perform an oxidation suppression operation when the fuel cell system stops generating power and encloses hydrogen in the anode-side flow path when the fuel cell system is stopped as the oxidation suppression operation. A third oxidation suppression operation is performed in which hydrogen is sealed in the anode-side flow path at a pressure higher than the hydrogen charging pressure when the system is stopped.
Fuel cell system.
[Form 3]
A fuel cell system comprising a fuel cell,
When the fuel cell system is stopped, a stop-time potential suppression unit that performs a potential suppression operation for suppressing a voltage increase in the fuel cell after power generation is stopped;
A fault detection unit for detecting a fault in the stop potential suppression unit;
An electrode oxidation suppression unit that performs an oxidation suppression operation for suppressing oxidation of an electrode included in the fuel cell after the next startup of the fuel cell system when the failure detection unit detects the failure;
With
The fuel cell
A plurality of power generation bodies each including an electrolyte membrane and a pair of electrodes are stacked,
An in-cell fuel gas passage formed on an anode, which is one electrode of each of the power generation bodies, through which a fuel gas containing hydrogen flows, and the fuel gas with respect to each of the in-cell fuel gas passages An anode side flow path comprising a fuel gas manifold for supplying and discharging
An in-cell oxidizing gas channel formed on a cathode, which is one of the electrodes included in each of the power generators, through which an oxidizing gas containing oxygen flows, and the oxidizing gas with respect to each of the in-cell oxidizing gas channel An oxidant gas manifold for supplying and discharging gas, and a cathode side flow path comprising:
The potential suppression unit at the time of stop is a low potential of the reactivity on the anode as compared with hydrogen instead of the fuel gas in the anode side flow path when the power generation of the fuel cell is stopped as the potential suppression operation. Perform the second potential suppression operation to replace with active gas,
The failure detection unit detects a failure of hydrogen flowing into the anode-side flow channel due to a defect in an inflow / outflow suppression state in the anode-side flow channel,
The electrode oxidation suppression unit includes, as the oxidation suppression operation, a first oxidation suppression operation that circulates the cooling water even after power generation of the fuel cell is stopped when the fuel cell system is restarted after the next startup. During power generation after the next startup of the fuel cell system, at least one of a second oxidation suppression operation for increasing the circulating amount of the cooling water as compared with normal power generation control is performed.
Fuel cell system.
[Form 4]
A fuel cell system comprising a fuel cell,
When the fuel cell system is stopped, a stop-time potential suppression unit that performs a potential suppression operation for suppressing a voltage increase in the fuel cell after power generation is stopped;
A fault detection unit for detecting a fault in the stop potential suppression unit;
An electrode oxidation suppression unit that performs an oxidation suppression operation for suppressing oxidation of an electrode included in the fuel cell after the next startup of the fuel cell system when the failure detection unit detects the failure;
With
The fuel cell
A plurality of power generation bodies each including an electrolyte membrane and a pair of electrodes are stacked,
An in-cell fuel gas passage formed on an anode, which is one electrode of each of the power generation bodies, through which a fuel gas containing hydrogen flows, and the fuel gas with respect to each of the in-cell fuel gas passages An anode side flow path comprising a fuel gas manifold for supplying and discharging
An in-cell oxidizing gas channel formed on a cathode, which is one of the electrodes included in each of the power generators, through which an oxidizing gas containing oxygen flows, and the oxidizing gas with respect to each of the in-cell oxidizing gas channel An oxidant gas manifold for supplying and discharging gas, and a cathode side flow path comprising:
The stop-time potential suppressing unit seals the anode-side flow path after stopping the supply of the fuel gas containing hydrogen to the fuel cell when the power generation of the fuel cell is stopped as the potential suppressing operation. Short-circuiting the anode and the cathode to perform a third potential suppressing operation for consuming hydrogen in the anode-side flow path;
The defect detection unit detects a problem that the short-circuit operation is insufficient,
The electrode oxidation suppression unit includes, as the oxidation suppression operation, a first oxidation suppression operation that circulates the cooling water even after power generation of the fuel cell is stopped when the fuel cell system is restarted after the next startup. During power generation after the next startup of the fuel cell system, at least one of a second oxidation suppression operation for increasing the circulating amount of the cooling water as compared with normal power generation control is performed.
Fuel cell system.
According to the fuel cell system according to any one of the first to fourth aspects, when the malfunction detection unit detects a malfunction in the stop potential suppression unit, the electrode oxidation suppression unit starts the fuel cell system after the next time. Later, an oxidation suppression operation for suppressing the oxidation of the electrode is performed. Therefore, even when a malfunction occurs in the stop potential suppressing unit and an undesirable voltage increase occurs in the fuel cell after power generation is stopped, the oxidation of the electrode can be suppressed. Thereby, even if it is a case where a malfunction generate | occur | produces in the electric potential suppression part at the time of a stop, use of a fuel cell can be continued, suppressing electrode oxidation.

[Application Example 1]
A fuel cell system comprising a fuel cell,
When the fuel cell system is stopped, a stop-time potential suppression unit that performs a potential suppression operation for suppressing a voltage increase in the fuel cell after power generation is stopped;
A fault detection unit for detecting a fault in the stop potential suppression unit;
A fuel cell comprising: an electrode oxidation suppression unit that performs an oxidation suppression operation for suppressing oxidation of an electrode included in the fuel cell after the next activation of the fuel cell system when the failure detection unit detects the failure. system.

  According to the fuel cell system described in Application Example 1, when the malfunction detection unit detects a malfunction in the stop potential suppression unit, the electrode oxidation suppression unit suppresses electrode oxidation after the next startup of the fuel cell system. An oxidation suppression operation is performed. Therefore, even when a malfunction occurs in the stop potential suppressing unit and an undesirable voltage increase occurs in the fuel cell after power generation is stopped, the oxidation of the electrode can be suppressed. Thereby, even if it is a case where a malfunction generate | occur | produces in the electric potential suppression part at the time of a stop, use of a fuel cell can be continued, suppressing electrode oxidation.

[Application Example 2]
The fuel cell system according to Application Example 1, wherein the electrode oxidation suppression unit performs the oxidation suppression operation when the fuel cell system is restarted after the next startup. According to the fuel cell system described in Application Example 2, since the oxidation suppression operation is performed at the time of re-stop after the next start-up, the oxidation suppression operation is performed even when a malfunction occurs in the stop potential suppression unit. By doing so, the fuel cell during power generation is not affected.

[Application Example 3]
The fuel cell system according to Application Example 1, wherein the electrode oxidation suppression unit performs the oxidation suppression operation during power generation after the next startup of the fuel cell system. According to the fuel cell system described in Application Example 3, since the oxidation suppression operation is performed during power generation after detecting the malfunction of the stop potential suppression unit, the oxidation suppression operation is performed in the stop potential suppression unit. The fuel cell before the failure occurs is not affected.

[Application Example 4]
4. The fuel cell system according to any one of application examples 1 to 3, wherein the electrode oxidation suppression unit performs an operation of improving cooling efficiency of the fuel cell as the oxidation suppression operation. According to the fuel cell system described in Application Example 4, by improving the cooling efficiency of the fuel cell, a malfunction occurs in the stop potential suppressing unit, and the voltage rises to an undesirable level in the fuel cell after power generation is stopped. Even in this case, the progress of the oxidation reaction of the electrode can be suppressed.

[Application Example 5]
The fuel cell system according to Application Example 4, wherein the electrode oxidation suppression unit performs the operation of improving the cooling efficiency of the fuel cell, so that when the fuel cell system is restarted after the next startup, When it is determined that the temperature of the fuel cell can be lowered when a voltage increase due to a malfunction occurs, an operation for improving the cooling efficiency of the fuel cell is performed, and the fuel cell By performing the operation to improve the cooling efficiency, the temperature of the fuel cell cannot be lowered when the voltage rise due to the malfunction occurs at the time of re-stop after the next startup of the fuel cell system. A fuel cell system that does not perform an operation of improving the cooling efficiency of the fuel cell. According to the fuel cell system described in Application Example 5, when it is determined that the effect of lowering the temperature of the fuel cell at the time of voltage increase due to a malfunction cannot be obtained, an operation for improving the cooling efficiency of the fuel cell is performed. Therefore, it is possible to suppress a decrease in system efficiency due to an operation for improving the cooling efficiency of the fuel cell.

[Application Example 6]
The fuel cell system according to Application Example 4 or 5, further including a stop time learning unit that learns by actually measuring a stop time in which the fuel cell system is stopped, and the electrode oxidation suppression unit includes the stop A fuel cell system that performs an operation of improving the cooling efficiency of the fuel cell when it is determined that a voltage increase due to a malfunction occurs within a stop time based on a learning result in a time learning unit. According to the fuel cell system described in Application Example 6, since it is possible to suppress the operation for improving the cooling efficiency of the fuel cell when the voltage increase due to the malfunction does not occur within the stop time, the fuel cell system can be suppressed. It is possible to suppress a decrease in system efficiency due to an operation for improving the cooling efficiency of the battery.

[Application Example 7]
The fuel cell system according to any one of Application Examples 4 to 6, wherein the fuel cell is formed by stacking a plurality of power generation bodies each including an electrolyte membrane and a pair of electrodes, and each of the power generation bodies includes the fuel cell. An in-cell fuel gas channel formed on an anode, which is one of the electrodes, through which hydrogen-containing fuel gas flows, and a fuel gas for supplying and discharging the fuel gas to and from each in-cell fuel gas channel An anode-side flow path including a manifold, an in-cell oxidizing gas flow path that is formed on a cathode that is one electrode of each of the power generators, and in which an oxidizing gas containing oxygen flows, and each of the cells A cathode-side flow path that includes an oxidizing gas manifold that supplies and discharges the oxidizing gas to and from the inner oxidizing gas flow path, and the stop-time potential suppressing unit performs the anode-side flow path as the potential suppressing operation. Wherein the fuel gas while enclosing the fuel cell system for operation of the inflow and outflow suppression while suppressing the inflow and outflow of air to the cathode side flow path. According to the fuel cell system described in Application Example 7, by suppressing the inflow and outflow of air with respect to the cathode side flow path, even when fuel gas is sealed in the anode side flow path, an internal battery is formed in the power generator. It is possible to prevent the cathode from becoming a high potential and the voltage of the fuel cell from being raised to an undesirable level.

[Application Example 8]
The fuel cell system according to any one of Application Examples 4 to 6, wherein the fuel cell is formed by stacking a plurality of power generation bodies each including an electrolyte membrane and a pair of electrodes, and each of the power generation bodies includes the fuel cell. An in-cell fuel gas channel formed on an anode, which is one of the electrodes, through which hydrogen-containing fuel gas flows, and a fuel gas for supplying and discharging the fuel gas to and from each in-cell fuel gas channel An anode-side flow path including a manifold, an in-cell oxidizing gas flow path that is formed on a cathode that is one electrode of each of the power generators, and in which an oxidizing gas containing oxygen flows, and each of the cells A cathode-side flow path that includes an oxidizing gas manifold that supplies and discharges the oxidizing gas to and from the inner oxidizing gas flow path, and the stop-time potential suppressing unit performs the anode-side flow path as the potential suppressing operation. And the place of the fuel gas, a fuel cell system reactive performs an operation to replace a low inert gas as compared to the hydrogen on the anode. According to the fuel cell system described in Application Example 8, by replacing the inside of the anode side flow path with an inert gas, the formation of the internal cell in the power generator is suppressed, and the cathode becomes a high potential and the fuel cell. Can be prevented from rising to an undesirable level.

[Application Example 9]
7. The fuel cell system according to any one of Application Examples 4 to 6, wherein the stop-time potential suppressing unit stops the supply of fuel gas containing hydrogen to the fuel cell as the potential suppressing operation, and then stops the fuel cell. A fuel cell system that operates to short circuit According to the fuel cell system described in Application Example 9, hydrogen is consumed inside the fuel cell by reducing the amount of hydrogen remaining in the fuel cell by short-circuiting the fuel cell after the supply of the fuel gas is stopped. be able to. Thereby, it is possible to suppress the formation of the internal battery in the power generation body, and to suppress the cathode from becoming a high potential and the voltage of the fuel cell from rising to an undesirable level.

[Application Example 10]
The fuel cell system according to Application Example 2, wherein the fuel cell is formed by stacking a plurality of power generation bodies each including an electrolyte membrane and a pair of electrodes, and the fuel cell includes one electrode included in each power generation body. An in-cell fuel gas passage formed on the anode, through which a fuel gas containing hydrogen flows, and a fuel gas manifold for supplying and discharging the fuel gas to and from each of the in-cell fuel gas passages. An anode-side flow path provided, an in-cell oxidizing gas flow path through which an oxidizing gas containing oxygen flows, formed on a cathode that is one electrode of each of the power generators, and the in-cell oxidizing gas flow A cathode-side flow path provided with an oxidizing gas manifold that supplies and discharges the oxidizing gas to and from the passage, and the fuel cell system is configured to stop power generation of the fuel cell when the system is stopped. Previous The fuel gas is sealed in the anode-side flow path, and the electrode oxidation suppression unit operates as the oxidation suppression operation in the anode-side flow path during the normal system stop when the oxidation suppression operation is not performed. A fuel cell system that performs an operation of sealing the fuel gas in the anode-side flow path at a pressure higher than a sealing pressure when the gas is sealed. According to the fuel cell system described in Application Example 10, even when a malfunction occurs in the stop-time potential suppressing unit by increasing the fuel gas sealing pressure in the anode-side flow path when the system is stopped. The timing of the fuel cell voltage increase can be delayed. As a result, the frequency at which the voltage rise actually occurs during the stop of the fuel cell system can be reduced, whereby the oxidation of the electrodes provided in the fuel cell can be suppressed.

[Application Example 11]
In the fuel cell system according to Application Example 10, when the electrode oxidation suppression unit seals the fuel gas in the anode-side flow path at a pressure higher than the sealing pressure when the normal system is stopped, A fuel cell system that performs an operation of increasing the sealing pressure when it is determined that a voltage increase due to the malfunction does not occur within a reference stop time set for the fuel cell system. According to the fuel cell system of Application Example 11, if it is determined that the voltage rises even if the sealing pressure for sealing the fuel gas in the anode-side flow path is increased, the fuel gas sealing pressure is not increased. When the voltage rise due to the malfunction occurs, the time during which the voltage is raised can be suppressed.

[Application Example 12]
The fuel cell system according to Application Example 10 or 11, wherein the potential suppression unit at the time of stop is the potential suppression operation with respect to the cathode-side flow channel in a state where the fuel gas is sealed in the anode-side flow channel. A fuel cell system that performs an operation to suppress an inflow / outflow of air while suppressing the inflow / outflow of air. According to the fuel cell system described in Application Example 12, the internal battery is formed in the power generation body even if fuel gas is sealed in the anode-side flow path by suppressing the inflow and outflow of air to the cathode-side flow path. It is possible to prevent the cathode from becoming a high potential and the voltage of the fuel cell from being raised to an undesirable level.

[Application Example 13]
12. The fuel cell system according to application example 10 or 11, wherein the stop-time potential suppression unit short-circuits the fuel cell after stopping supply of fuel gas containing hydrogen to the fuel cell as the potential suppression operation. A fuel cell system that performs the operation. According to the fuel cell system described in the application example 13, the fuel cell is short-circuited after the supply of the fuel gas is stopped, thereby consuming hydrogen inside the fuel cell and reducing the amount of hydrogen remaining in the fuel cell. be able to. Thereby, it is possible to suppress the formation of the internal battery in the power generation body, and to suppress the cathode from becoming a high potential and the voltage of the fuel cell from rising to an undesirable level.

  The present invention can be realized in various forms other than those described above. For example, the present invention can be realized in the form of a control method for a fuel cell system.

1 is a block diagram showing a configuration of a fuel cell system 10. FIG. 2 is an exploded perspective view showing a single cell 70. FIG. It is explanatory drawing showing the mode of the voltage transition at the time of a stop of a fuel cell. It is a flowchart showing a control processing routine at the time of system stop. It is a flowchart showing a malfunction detection processing routine. It is a flowchart showing a malfunction detection processing routine. It is a flowchart showing a malfunction detection processing routine. It is explanatory drawing which shows the result of having investigated the relationship between electrode potential, oxidation amount, and fuel cell temperature. It is a flowchart showing the process routine at the time of a stop after malfunction detection. It is a figure showing the relationship between hydrogen filling pressure and time until a voltage rises again. It is a flowchart showing a control processing routine at the time of system stop. It is a flowchart showing an oxidation suppression operation necessity determination processing routine. 2 is a block diagram illustrating a schematic configuration of a fuel cell system 110. FIG. 2 is a block diagram illustrating a schematic configuration of a fuel cell system 210. FIG. It is explanatory drawing showing the mode of the voltage transition at the time of a stop of a fuel cell.

A. Overall configuration of the fuel cell system 10:
FIG. 1 is a block diagram showing a configuration of a fuel cell system 10 as a first embodiment of the present invention. The fuel cell system 10 of the present embodiment includes a fuel cell 15, a hydrogen tank 20, a compressor 30, a hydrogen shut-off valve 40, a modulatable pressure valve 42, a hydrogen circulation pump 44, a purge valve 46, a first valve A cathode sealing valve 48, a load connection unit 51, a voltage sensor 52, a notification device 54, an environmental temperature sensor 55, a refrigerant circulation pump 60, a radiator 61, a refrigerant temperature sensor 63, a control unit 50, It has.

  The fuel cell 15 is a solid polymer type fuel cell, and has a stack structure in which a plurality of single cells 70 as power generation bodies are stacked. FIG. 2 is an exploded perspective view showing the single cell 70 constituting the fuel cell 15. The unit cell 70 includes an MEA (Membrane Electrode Assembly) 71, gas diffusion layers 72 and 73, and gas separators 74 and 75. Here, the MEA 71 includes an electrolyte membrane and an anode and a cathode that are electrodes formed on each surface of the electrolyte membrane. The MEA 71 is sandwiched between the gas diffusion layers 72 and 73, and the sandwich structure composed of the MEA 71 and the gas diffusion layers 72 and 73 is sandwiched between the gas separators 74 and 75 from both sides (however, the gas diffusion layer 72 is provided). (It is not shown in FIG. 2 because it is disposed on the back surface of the surface on which the gas diffusion layer 73 is disposed).

  The electrolyte membrane constituting the MEA 71 is a proton conductive ion exchange membrane formed of a solid polymer material, for example, a fluororesin, and exhibits good electrical conductivity in a wet state. The cathode and the anode are layers formed on the electrolyte membrane, and include carbon particles supporting a catalytic metal (for example, platinum) that progresses an electrochemical reaction, and a polymer electrolyte having proton conductivity. The gas diffusion layers 72 and 73 are made of a member having gas permeability and electron conductivity, and are formed of, for example, a metal member such as foam metal or metal mesh, or a carbon member such as carbon cloth or carbon paper. can do.

  The gas separators 74 and 75 are formed of a gas-impermeable conductive member, for example, a carbon-made member such as dense carbon that has been made to be gas-impermeable by compressing carbon, or a metal member such as press-formed stainless steel. ing. The gas separators 74 and 75 are members that form walls of a flow path of a reaction gas (a fuel gas containing hydrogen or an oxidizing gas containing oxygen) formed between the gas separators 74 and 75. An uneven shape for forming the flow path is formed. Between the gas separator 74 having the groove 88 formed on the surface and the MEA 71, an in-cell oxidizing gas flow path that is a flow path for the oxidizing gas is formed. In addition, an in-cell fuel gas flow path, which is a flow path for the fuel gas, is formed between the gas separator 75 having a groove 89 formed on the surface and the MEA 71. When assembling the single cell 70, a seal portion (not shown) is arranged on the outer periphery of the MEA 71, and the gas separators 74 and 75 are joined together while ensuring the sealing performance of the gas flow path in the single cell 70. .

  Here, in the gas separators 74 and 75, a recess 87 is formed on the back surface of the surface provided with the grooves 88 and 89 for forming the in-cell gas flow path (however, formed on the back surface of the gas separator 74). The recessed portion 87 is not shown). These recesses 87 are formed over a range that overlaps the entire region where the gas diffusion layers 72 and 73 are arranged on the gas separators 74 and 75, and between the adjacent single cells 70 between the cells that are the flow paths of the refrigerant. A refrigerant flow path is formed. Note that the inter-cell refrigerant flow path is not provided between the single cells 70 but may be provided, for example, every time a predetermined number of single cells 70 are stacked.

  The gas separators 74 and 75 are provided with a plurality of holes at positions corresponding to each other near the outer periphery thereof. When a fuel cell is assembled by stacking a plurality of single cells 70, holes provided at corresponding positions of the separators overlap each other to form a flow path that penetrates the fuel cell in the stacking direction of the gas separators. Specifically, the hole 83 forms an oxidant gas supply manifold that distributes the oxidant gas to each in-cell oxidant gas flow path, and the hole 84 oxidizes the oxidant gas that collects from each in-cell oxidant gas flow path. A gas exhaust manifold is formed. The hole 85 forms a fuel gas supply manifold that distributes the fuel gas to each in-cell fuel gas flow path, and the hole 86 forms a fuel gas discharge manifold that collects the fuel gas from each in-cell fuel gas flow path. Form. Moreover, the hole 81 forms a refrigerant supply manifold that distributes the refrigerant to the inter-cell refrigerant flow path, and the hole 82 forms a refrigerant discharge manifold that collects the refrigerant from the inter-cell refrigerant flow path.

  In the fuel cell 15 of the present embodiment, a current collector plate (terminal) 78 having an output terminal, an insulating plate (insulator) 77, and an end plate 76 are sequentially arranged on both ends of a laminated body formed by laminating a plurality of single cells 70. Formed by. The fuel cell 15 is held in a state where fastening pressure is applied in the stacking direction of the single cells 70 by a holding member (not shown) (for example, a tension plate coupled to both end plates 76 by bolts).

  Returning to FIG. 1, the hydrogen tank 20 is a storage device that stores hydrogen gas as a fuel gas, and is connected to a hydrogen supply manifold of the fuel cell 15 via a hydrogen supply channel 22. On the hydrogen supply flow path 22, a hydrogen cutoff valve 40 and a modulatable pressure valve 42 are provided in order from the hydrogen tank 20. The adjustable pressure valve 42 is a pressure regulating valve capable of adjusting the hydrogen pressure (hydrogen amount) supplied from the hydrogen tank 20 to the fuel cell 15. The hydrogen tank 20 may be a hydrogen cylinder that stores high-pressure hydrogen gas, or may be a tank that includes a hydrogen storage alloy and stores hydrogen by storing the hydrogen in the hydrogen storage alloy.

  A hydrogen discharge passage 24 is connected to the hydrogen discharge manifold of the fuel cell 15. A purge valve 46 is provided in the hydrogen discharge channel 24. Further, a connection flow path 25 is provided by connecting the hydrogen supply flow path 22 and the hydrogen discharge flow path 24. The connection channel 25 is connected to the hydrogen supply channel 22 on the downstream side of the adjustable pressure valve 42 and is connected to the hydrogen discharge channel 24 on the upstream side of the purge valve 46. The connection channel 25 is provided with a hydrogen circulation pump 44 that generates a driving force when hydrogen circulates in the channel.

  Hydrogen supplied from the hydrogen tank 20 via the hydrogen supply flow path 22 is supplied to the electrochemical reaction in the fuel cell 15 and discharged to the hydrogen discharge flow path 24. The hydrogen discharged to the hydrogen discharge channel 24 is guided again to the hydrogen supply channel 22 via the connection channel 25. As described above, in the fuel cell system 10, hydrogen is part of the hydrogen discharge passage 24, the connection passage 25, part of the hydrogen supply passage 22, and the fuel gas passage formed in the fuel cell 15. (These flow paths are collectively referred to as a hydrogen circulation flow path). During the power generation of the fuel cell 15, the purge valve 46 is normally closed. However, when impurities (nitrogen, water vapor, etc.) in the circulating hydrogen increase, the purge valve 46 is opened as appropriate. Part of the hydrogen gas with increased impurity concentration is discharged outside the system. Further, when the amount of hydrogen in the hydrogen circulation channel is insufficient due to the consumption of hydrogen due to the progress of the electrochemical reaction or the opening of the purge valve 46, the hydrogen tank 20 is transferred from the hydrogen tank 20 to the hydrogen circulation channel via the adjustable pressure valve 42. And hydrogen is supplemented.

  The compressor 30 is a device that takes in air from the outside, compresses it, and supplies it as oxidant gas to the fuel cell 15, and is connected to the oxidant gas supply manifold of the fuel cell 15 via the air supply channel 32. . The compressor 30 is provided with a second cathode sealing valve 49 for making it possible to block the inflow of air from the outside to the air supply flow path 32 when the compressor 30 is stopped. When the compressor 30 is stopped, the flow resistance when the air flows becomes extremely large. Therefore, when the compressor 30 is stopped, the second cathode sealing valve 49 should not be provided if the inflow of air from the outside to the air supply flow path 32 through the compressor 30 is substantially not performed. It is also good.

  An air discharge passage 34 is connected to the oxidizing gas discharge manifold of the fuel cell 15. The air supplied from the compressor 30 via the air supply flow path 32 is subjected to an electrochemical reaction in the fuel cell 15 and discharged to the outside of the fuel cell 15 via the air discharge flow path 34. The air discharge channel 34 is provided with a first cathode sealing valve 48. The first cathode sealing valve 48 is opened when the fuel cell 15 generates power, and is closed when the fuel cell 15 stops generating power.

  A load 57 is connected to each current collecting plate 78 of the fuel cell 15 via a wiring 56. The load 57 can be, for example, a secondary battery or a power consuming device (such as a motor). The wiring 56 is provided with a load connecting portion 51 as a switch for turning on and off the connection between the fuel cell 15 and the load 57. The load connection unit 51 is switched so that the fuel cell 15 and the load 57 are connected when the fuel cell 15 generates power, and the connection between the fuel cell 15 and the load 57 is interrupted when the power generation of the fuel cell 15 is stopped. Are switched as follows.

  The voltage sensor 52 is a sensor for detecting the fuel cell voltage Vf of the fuel cell 15. The notification device 54 is a device for notifying the user of the fuel cell system 10 that a failure has been detected when a failure that has occurred in a potential suppression operation described later is detected. The notification of the defect may be performed, for example, by display on a display device, or may be notified by voice.

  The radiator 61 is provided in the refrigerant channel 62 and cools the refrigerant flowing in the refrigerant channel 62. The refrigerant flow path 62 is connected to the refrigerant supply manifold and the refrigerant discharge manifold described above of the fuel cell 15. In addition, a refrigerant circulation pump 60 is provided in the refrigerant flow path, and by driving the refrigerant circulation pump 60, the refrigerant is circulated between the radiator 61 and the fuel cell 15, and the internal temperature of the fuel cell 15 is increased. It is adjustable. In the refrigerant flow path 62, a refrigerant temperature sensor 63 for detecting the temperature of the refrigerant is provided in the vicinity of the connection portion between the fuel cell 15 and the refrigerant discharge manifold.

  The control unit 50 is configured as a logic circuit centered on a microcomputer, and more specifically, a CPU that executes predetermined calculations in accordance with a preset control program, and controls necessary for executing various arithmetic processes by the CPU. A ROM in which programs, control data, and the like are stored in advance, a RAM in which various data necessary for performing various arithmetic processes in the CPU, and an input / output port for inputting and outputting various signals are also provided. The control unit 50 includes a compressor 30, a hydrogen shutoff valve 40, a modulatable pressure valve 42, a load connection unit 51, a first cathode sealing valve 48, a second cathode sealing valve 49, a hydrogen circulation pump 44, a purge valve 46, A drive signal is output to the notification device 54, the refrigerant circulation pump 60, and the like. Further, a detection signal is acquired from the voltage sensor 52, the refrigerant temperature sensor 63, the environmental temperature sensor 55 that detects the environmental temperature (outside air temperature) of the fuel cell system 10, or the like. Further, the control unit 50 has a timer function that can measure the time of a predetermined period.

B. Potential suppression operation:
In the fuel cell system 10, when starting the power generation of the fuel cell 15 at the time of startup, the control unit 50 outputs a drive signal for power generation to each unit. Specifically, when receiving an instruction for starting the fuel cell system 10 from the outside, the control unit 50 controls the load connecting unit 51 to connect the fuel cell 15 and the load 57. Further, the control unit 50 opens the hydrogen shut-off valve 40, adjusts the adjustable pressure control valve 42, controls the compressor 30 based on the input load request, and controls the hydrogen circulation pump 44 and the refrigerant circulation pump 60. The first cathode sealing valve 48 is controlled to open. For example, when the load 57 is a motor, a drive signal corresponding to the load request is also output to the load 57. When the fuel cell 15 generates electricity, the purge valve 46 is appropriately controlled to open at a predetermined timing.

  When such a fuel cell system 10 receives an operation stop request, the control unit 50 performs a system stop process. Specifically, the control unit 50 controls the load connecting unit 51 to cut off the connection between the fuel cell 15 and the load 57. Further, the control unit 50 closes the hydrogen shut-off valve 40 and stops the supply of the fuel gas and the oxidizing gas to the fuel cell 15 by stopping the driving of the hydrogen circulation pump 44 and the compressor 30. Further, the purge valve 46 is maintained in the closed state during the power generation stop. Thereby, the fuel gas flow path in the cell, the fuel gas manifold, the hydrogen supply flow path 22 whose one end is closed by the hydrogen shut-off valve 40, and the hydrogen discharge flow path 24 whose one end is closed by the purge valve 46 are connected. The fuel gas flow path (hereinafter referred to as the anode-side flow path) composed of the flow path 25 is in a state in which hydrogen is enclosed. Further, when power generation is stopped, the control unit 50 stops driving the refrigerant circulation pump 60.

  When the fuel cell system 10 is stopped, the first cathode sealing valve 48 provided in the air discharge passage 34 and the second cathode sealing valve 49 provided in the compressor 30 are closed. It is. Thereby, when the fuel cell 15 is stopped, the oxidizing gas channel in the cell, the oxidizing gas manifold, the air discharge channel 34 whose one end is closed by the first cathode sealing valve 48, and the second cathode sealing. An oxidizing gas passage (hereinafter referred to as a cathode-side passage) comprising an air supply passage 32 closed at one end by the valve 49 is in a state in which air is enclosed. That is, the cathode side channel as well as the anode side channel are in a state where introduction and discharge of gas are suppressed (hereinafter referred to as an inflow / outflow suppression state). In this embodiment, as a potential suppression operation for suppressing an excessive increase in potential in the fuel cell 15 after power generation is stopped, the anode-side channel is put into an inflow / outflow-suppressed state with hydrogen enclosed in the anode-side channel. At the same time, the cathode-side flow path is also in an inflow / outflow suppression state. Hereinafter, the rise in the potential of the fuel cell after the fuel cell system is stopped and the potential suppression operation in this embodiment will be described.

  FIG. 3 is an explanatory diagram showing the state of voltage transition when the fuel cell is stopped. FIG. 3A shows the formation of an inflow / outflow suppression state as a potential suppression operation in the fuel cell system 10 of the present embodiment (particularly, the first cathode sealing valve 48 and the second cathode sealing in the cathode side channel). The state of the voltage transition at the stop when the sealing by the valve 49 is normally performed is shown. FIG. 3B shows a state of voltage change at the time of stop when a malfunction occurs in the potential suppression operation in the fuel cell system 10.

  When the fuel cell 15 is stopped, the hydrogen cutoff valve 40 and the purge valve 46 are closed, so that the anode-side flow path is in an inflow / outflow suppression state. When the connection with the load 57 is interrupted in such a state, the voltage of the fuel cell 15 shows a somewhat high value (a value corresponding to the OCV immediately after the stop). Thereafter, in the single cell 70, hydrogen diffuses from the anode side to the cathode side through the electrolyte membrane, and the diffused hydrogen and cathode side air (oxygen) react on the cathode, and the oxidizing gas in the cell Oxygen in the flow path is consumed. In addition, the diffusion of oxygen from the cathode side to the anode side also proceeds through the electrolyte membrane, thereby reducing the oxygen in the in-cell oxidizing gas flow path, and the voltage of the fuel cell 15 starts to drop. When the amount of hydrogen enclosed in the anode-side flow path is sufficiently large, the voltage of the fuel cell 15 decreases with a decrease in the amount of oxygen in the cathode-side flow path as described above, and eventually a stable low voltage state ( For example, approximately 0V).

  Here, when the inflow / outflow suppression state in the cathode side flow path is sufficiently maintained, the low voltage state can be maintained once the voltage of the fuel cell 15 is lowered. However, when a problem occurs in the formation of the inflow / outflow suppression state in the cathode side flow path, for example, when a problem occurs in the first cathode sealing valve 48 or the second cathode sealing valve 49, the oxygen once When air (oxygen) flows into the cathode-side flow path where the concentration has decreased via the air discharge flow path 34 or the air supply flow path 32, the voltage of the fuel cell rises again. Specifically, when air flows into the cathode side flow path as described above, the air diffuses from the cathode side to the anode side through the electrolyte membrane, so that a region where the hydrogen concentration is partially high on the anode. As a result, an internal battery is formed. In such a state where the internal battery is formed, the cathode has a high potential. Specifically, the normal cell reaction proceeds in the region where the hydrogen concentration is high on the anode, but in the region where the hydrogen concentration is low on the anode, the components of the cathode, particularly the catalyst-supporting carrier (carbon particles in the present example). ) Oxidation proceeds. As a result, electrons are exchanged between a region having a high hydrogen concentration and a region having a low hydrogen concentration on the anode, so that electrons do not flow to an external circuit. Then, due to the oxidation of the catalyst support, the particle size and specific surface area of the catalyst support change, and the cathode shape changes. Such a state in which the cathode is at a high potential is detected as an increase in the voltage of the entire fuel cell. In FIG. 3A, the first cathode sealing valve 48 and / or the second cathode sealing valve 49 that allow a slight inflow of air is used as a state in which the potential suppressing operation is normally performed. This shows how the voltage changes. When the air flows in slightly, the voltage of the fuel cell once drops, and then the voltage rises again after the time corresponding to the amount of air flowing in. On the other hand, in FIG. 3B, a malfunction occurs in the first cathode sealing valve 48 and / or the second cathode sealing valve 49, and an undesirable amount of air flows into the fuel cell. The state of voltage change in the case is shown. Thus, when more air flows in, after the voltage of the fuel cell once drops, the voltage increases again at an earlier timing. In addition, when the inflow / outflow suppression state in the cathode side flow path is completely maintained, a voltage transition pattern in which the voltage does not rise again is shown. As described above, in the fuel cell system 10 of this embodiment that performs the operation of filling hydrogen into the anode-side flow path when the system is stopped, the first cathode sealing valve 48 and the second cathode sealing valve 49 are configured to generate power. It functions as a stop-time potential suppressing unit that performs a potential suppressing operation for suppressing an excessive voltage increase (a voltage increase exceeding a voltage increase permitted as a normal range) in the fuel cell after the stop.

  Here, after the fuel cell voltage rises again as described above, the fuel cell voltage falls again. This is because when air flows into the cathode side flow path, air diffuses from the cathode side to the anode side through the electrolyte membrane, and hydrogen remaining in the anode side flow path diffuses to the cathode side. This is because the hydrogen concentration in the anode-side flow path is reduced.

C. Overview of processing executed when the system stops:
The fuel cell system 10 according to the present embodiment performs the above-described potential suppressing operation when the fuel cell system 10 is stopped, and detects whether or not a failure has occurred in the potential suppressing operation. It is characterized by performing a treatment for suppressing the oxidation of the electrode. FIG. 4 is a flowchart showing a system stop time control process routine executed by the control unit 50 of the fuel cell system 10 when the system is stopped. This routine is started when a power generation stop instruction is input to the fuel cell system 10.

  When this routine is started, the control unit 50 first determines whether or not the failure determination flag is set to 1 (step S100). This defect determination flag is set to 1 when a defect in potential suppression operation is detected in a defect detection process described later, and the initial value is set to 0. If the failure determination flag is set to 0 in step S100, the failure in the potential suppression operation has not been detected yet, and thus the control unit 50 performs normal stop time control (step S110). Specifically, the connection between the fuel cell 15 and the load 57 is cut off, and the anode-side flow path and the cathode-side flow path are brought into an inflow / outflow suppression state as a potential suppression operation, and further, the circulation of the refrigerant is stopped. At this time, the hydrogen filling pressure in the anode-side flow path is adjusted to a predetermined specified value by the adjustable pressure valve 42.

  Thereafter, the control unit 50 performs defect detection processing (step S120), and determines whether there is a defect in the formation of the inflow / outflow suppression state as the potential suppression operation (step S130). This defect detection process will be described in detail later. When occurrence of a defect is detected by the defect detection process, the control unit 50 sets a defect determination flag to 1 (step S140), and ends this routine.

  As described above, when a failure in the potential suppression operation is detected and the failure determination flag is set to 1 in step S140, the next time the system stop time control processing routine is started, the control unit 50 determines in step S100. It is determined that the defect determination flag is set to 1. In this case, the control unit 50 executes a stop time process after detecting a failure (step S150), and ends this routine. When a malfunction occurs in the potential suppression operation, as described above, there is a possibility that an undesirable voltage re-rise occurs after power generation is stopped and the oxidation of the electrode proceeds. Therefore, in this embodiment, when the defect determination flag is set to 1, in order to suppress such electrode oxidation, a stop process after detection of a defect for suppressing oxidation is executed. The processing at the time of stopping after detecting a defect will be described in detail later. In this embodiment, once the failure determination flag is set to 1, the failure determination flag is set to 1 in step S100 every time power generation is stopped when the fuel cell system 10 is repeatedly started and stopped thereafter. If it is determined that there is a failure, the stop process is performed after the failure is detected.

  If it is determined in step S130 that no defect has occurred, the control unit 50 maintains the defect determination flag at 0 and ends this routine. In this case, the next time the system stop time control processing routine is started, it is determined in step S100 that the failure determination flag is set to 0, and the failure detection processing is performed again.

D. Detection of malfunctions in potential suppression operation:
Hereinafter, the defect detection process in step S120 will be described. In this embodiment, the malfunction of the potential suppression operation is detected based on the fuel cell voltage Vf detected by the voltage sensor 52. As a method of detecting a failure in the potential suppression operation based on the fuel cell voltage Vf, three methods will be described below as an example.

D-1. First defect detection method:
FIG. 5 is a flowchart showing a first defect detection process as an example of the process of step S120. This routine is started after normal stop time control is performed in step S110. When this routine is started, the control unit 50 resets the timer and sets an elapsed time Tp after the stop process to 0 (step S200). Thereafter, the control unit 50 acquires the fuel cell voltage Vf from the voltage sensor 52 (step S210). Then, the voltage change amount ΔVf is calculated (step S220). Here, in step S210, the fuel cell voltage Vf is acquired twice at short time intervals, and in step S220, the amount of change between the two acquired fuel cell voltages Vf is divided by the measurement time interval. The voltage change amount ΔVf per unit time is obtained.

  Next, the control unit 50 compares the voltage change amount ΔVf obtained in step S220 with the reference value Xv1 (step S230). The reference value Xv1 can occur even if a slight voltage rise occurs as shown in FIG. 3A when the cathode-side flow-through suppression state as a potential suppression operation is normally maintained. This is a value that is determined in advance and stored in the control unit 50 as the value (positive value) of the voltage variation ΔVf that is not present. When the voltage change amount ΔVf exceeds the reference value Xv1, it is considered that the voltage has suddenly increased after the fuel cell 15 is stopped and then the voltage has suddenly increased. It is determined that a defect has occurred in the formation (sealing by the first cathode sealing valve 48 and / or the second cathode sealing valve 49). The time point at which ΔVf reaches the reference value Xv1 is shown in FIG.

  When the voltage change amount ΔVf exceeds the reference value Xv1 in step S230, it is determined that a failure has occurred (step S240), and the control unit 50 outputs a drive signal to the notification device 54 to notify the notification device 54 of the notification. An operation is performed (step S250), and this routine is terminated. When the voltage change amount ΔVf does not exceed the reference value Xv1 in step S230, it is determined that the potential suppression operation is normal (step S260), and the control unit 50 compares the elapsed time Tp with the reference time Xt1. This is performed (step S270). Here, the reference time Xt1 is a reference value that can be determined that the potential suppression operation is normal since there is almost no possibility of the voltage suddenly increasing after that when the voltage suddenly is not detected within the reference time. The value is predetermined and stored in the control unit 50. When the elapsed time Tp exceeds the reference time Xt1, the control unit 50 ends this routine with determining that the potential suppression operation is normal. When the elapsed time Tp is less than or equal to the reference time Xt1, the control unit 50 returns to step S210 and repeats the determination of whether or not a failure has occurred based on the voltage change amount ΔVf until the elapsed time Tp exceeds the reference time Xt1.

  In FIG. 5, when the elapsed time Tp exceeds the reference time Xt1, this routine is ended in a state in which it is determined that the potential suppression operation is normal. However, a different configuration may be used. For example, when it is determined to be normal in step S260, the process may return to step S210, and the determination based on the voltage change amount ΔV may be repeatedly performed while the fuel cell system 10 is stopped.

D-2. Second defect detection method:
FIG. 6 is a flowchart showing a second defect detection process as an example of the process of step S120. The second defect detection process is a process that can be executed in place of the first defect detection process. For the steps common to the first defect detection process, the process number is changed from the 200th to the 300th. Is omitted. Below, a different part from a 1st malfunction detection process is demonstrated.

  Also in this routine, after acquiring the fuel cell voltage Vf (step S310) and calculating the voltage change amount ΔVf (step S320), the control unit 50 obtains the voltage change amount ΔVf obtained in step S320 and the reference value Xv2. Compare (step S330). Here, the reference value Xv2 is a reference value for detecting a rapid increase in voltage caused by a malfunction in the inflow / outflow suppression state, similarly to the reference value Xv1 in step S230. The time point at which ΔVf reaches the reference value Xv2 is shown in FIG.

  When the voltage change amount ΔVf exceeds the reference value Xv2 in step S330, the control unit 50 compares the fuel cell voltage Vf with the reference value Xv3 (step S335). The reference value Xv3 is the value of the fuel cell voltage Vf that does not reach even if a slight voltage rise occurs as shown in FIG. 3A when the inflow / outflow suppression state of the cathode side channel is normally maintained. The value is a value that is determined in advance and stored in the control unit 50. Further, as the fuel cell voltage Vf used for comparison in step S335, a value detected later in the fuel cell voltage acquired twice in step S310 may be used. When the fuel cell voltage Vf exceeds the reference value Xv3, an inflow / outflow suppression state is formed as a potential suppression operation (sealing by the first cathode sealing valve 48 and / or the second cathode sealing valve 49). ) Is determined to have failed. The reference value Xv3 is shown in FIGS. 3 (A) and 3 (B). When the voltage change amount ΔVf is equal to or smaller than the reference value Xv2 in step S330 and when the fuel cell voltage Vf is equal to or smaller than the reference value Xv3 in step S335, the potential suppressing operation is normal as in step S260. Is determined (step S360).

  Thus, when detecting the occurrence of a malfunction in the formation of the inflow / outflow suppression state as the potential suppression operation, not only the voltage change amount ΔVf but also the fuel cell voltage Vf is used to detect the malfunction occurrence. Can be improved.

D-3. Third defect detection method:
FIG. 7 is a flowchart showing a third defect detection process as an example of the process of step S120. The third defect detection process is a process that can be executed in place of the first defect detection process. For processes common to the first defect detection process, the process number is changed from the 200th to the 400th, and a detailed description is given. Is omitted. Below, a different part from a 1st malfunction detection process is demonstrated.

  Also in this routine, after acquiring the fuel cell voltage Vf (step S410) and calculating the voltage change amount ΔVf (step S420), the control unit 50 obtains the voltage change amount ΔVf obtained in step S420 and the reference value Xv4. Compare (step S430). Here, the reference value Xv4 is a reference value for detecting a rapid increase in voltage caused by the malfunction of the inflow / outflow suppression state, similarly to the reference value Xv1 in step S230. The time point at which ΔVf reaches the reference value Xv4 is shown in FIG.

  If the voltage change amount ΔVf exceeds the reference value Xv4 in step S430, the control unit 50 refers to the timer to obtain the elapsed time Tp1 when the voltage change amount ΔVf exceeds the reference value Xv4 ( Step S432). The elapsed time Tp1 is shown in FIG. Then, the elapsed time Tp1 is compared with the reference time Xt2 (step S435). Here, when the inflow / outflow suppression state of the cathode side channel is normally maintained, even if a slight voltage rise occurs as shown in FIG. It takes a certain amount of time for the voltage to rise and the voltage to rise. The reference time Xt2 is determined in advance as a reference value for determining that air exceeding the allowable range flows into the cathode-side flow path when a voltage rise occurs within this time. The value stored in 50. When the elapsed time Tp1 is smaller than the reference time Xt2, it is determined that a problem has occurred in the formation of the inflow / outflow suppression state as the potential suppression operation (particularly, the sealing by the first cathode sealing valve 48). The The reference time Xt2 is shown in FIGS. 3 (A) and 3 (B). When the voltage change amount ΔVf is equal to or less than the reference value Xv4 in step S430 and when the elapsed time Tp1 is equal to or greater than the reference time Xt2 in step S435, the potential suppression operation is normal as in step S260. Judgment is made (step S460).

  Thus, when detecting the occurrence of a malfunction in the formation of the inflow / outflow suppression state as the potential suppression operation, the occurrence of the malfunction is detected by using not only the voltage change amount ΔVf but also the elapsed time Tp1 until the voltage rises. Accuracy can be improved.

E. Processing when stopping after detecting a defect executed after detecting a defect:
Below, the process at the time of a stop after the malfunction detection in step S150 is demonstrated. In this embodiment, at the time of re-stop after the next system startup after detecting the malfunction, the circulation amount of the cooling water which is the refrigerant circulating in the fuel cell 15 is increased as an oxidation suppression operation for suppressing the electrode oxidation. Processing is performed to improve the cooling efficiency of the fuel cell 15. The fuel cell 15 which is a polymer electrolyte fuel cell has an operating temperature of about 65 to 100 ° C., and is higher than the environmental temperature during power generation. After the fuel cell 15 stops generating power, the temperature of the fuel cell 15 gradually decreases and approaches the environmental temperature. When the fuel cell system 10 is stopped, since the driving of the refrigerant circulation pump 60 is normally stopped as described above, the temperature drop after the power generation stop of the fuel cell 15 is gradually caused mainly by heat radiation to the atmosphere. proceed. On the other hand, when the refrigerant circulation pump 60 is driven and the refrigerant is circulated even after the power generation of the fuel cell 15 is stopped, the heat release from the fuel cell 15 to the refrigerant is actively performed. Cooling efficiency can be increased. In this embodiment, when trouble occurs in the formation of the inflow / outflow suppression state as the potential suppression operation, the refrigerant circulation pump 60 is driven to actively cool the fuel cell 15 to oxidize the catalyst-supported carbon, which is a chemical reaction. The reaction is suppressed and the change in the shape of the electrode is suppressed.

  FIG. 8 is an explanatory diagram showing the results of examining the relationship between the electrode potential at the cathode, the oxidation amount calculated from the oxidation current flowing through the cathode, and the fuel cell temperature. Here, a single cell similar to the single cell 70 constituting the fuel cell 15 is prepared, hydrogen is supplied to the anode side, nitrogen is supplied to the cathode side, and the horizontal axis in FIG. A voltage corresponding to the indicated electrode potential of the cathode was applied to the single cell, and the amount of oxidation was calculated by measuring the flowing current (oxidation current). As the oxidation current flowing increases, the oxidation reaction of the catalyst-supporting carbon increases and the amount of oxidation increases. As the temperature of the single cell, three stages of 40 ° C., 60 ° C., and 80 ° C. are set, and for each temperature, the cathode electrode potential is changed in increments of 0.1 V from 1.0 V to 1.5 V, and the oxidation amount Asked. Each gas supplied to the single cell was fully humidified (humidified to saturated water vapor pressure). As shown in FIG. 8, when compared at the same cathode electrode potential, the lower the temperature, the smaller the amount of oxidation. Therefore, even when a problem occurs in the formation of the inflow / outflow suppression state as the potential suppression operation and the cathode potential increases, the oxidation reaction of the catalyst-supported carbon is suppressed by lowering the temperature of the fuel cell 15. Thus, it can be said that changes in the shape of the electrode can be suppressed.

  In the stop process after failure detection as step S150 of the present embodiment, the connection between the fuel cell 15 and the load 57 is interrupted and the anode side channel and the cathode side channel flow out, as in the normal stop control. Although it is in the on-suppression state, the refrigerant circulation pump 60 is controlled to output a drive signal so as to continue driving. In the present embodiment, even when the refrigerant circulation pump 60 is driven, the temperature of the fuel cell 15 cannot be made lower than the environmental temperature. Therefore, for example, when it is determined that the refrigerant temperature detected by the refrigerant temperature sensor 63 has sufficiently decreased with respect to the environmental temperature detected by the environmental temperature sensor 55, the refrigerant circulation pump 60 may be stopped. good.

  According to the fuel cell system 10 of the present embodiment configured as described above, when the occurrence of a malfunction in the formation of the inflow / outflow suppression state as the potential suppression operation is detected, the refrigerant is circulated to actively move the fuel cell 15. By lowering the temperature, the oxidation current flowing to the cathode can be suppressed, and the change in the shape of the electrode can be suppressed. That is, when a malfunction of the potential suppression operation is detected by performing normal stop control when the fuel cell system 10 is stopped, the fuel cell 15 is actively cooled when the system is restarted after that. Therefore, even if a malfunction occurs in the potential suppression operation, it is possible to suppress the progress of the catalyst shape change when the system is stopped. In particular, the occurrence of a malfunction in the potential suppression operation does not immediately make it difficult to continue the power generation by the fuel cell 15, but it is a malfunction that allows the fuel cell system 10 to continue to operate normally for a certain period of time. According to the present embodiment, it is possible to maintain a state in which the degree of oxidation of the cathode can be allowed for a longer time when such a malfunction that allows normal use for a certain period of time occurs.

  At this time, since the refrigerant circulation pump 60 is driven only when the above-described malfunction is detected as the electrode oxidation suppressing operation, the energy of the fuel cell system 10 is suppressed in order to suppress the electrode shape change. The efficiency is not reduced more than necessary. For example, the refrigerant circulation pump 60 can be driven at all times when the fuel cell system 10 is stopped. However, the refrigerant circulation pump 60 can be driven by driving the refrigerant circulation pump 60 only when a malfunction occurs. The resulting reduction in the energy efficiency of the entire system can be suppressed. In addition, since the fuel cell 15 generates power, the refrigerant circulation pump 60 is set to have a larger driving amount to lower the temperature during power generation, thereby lowering the temperature of the fuel cell when power generation is stopped. It is also possible to suppress the fuel cell temperature during the rise. However, in this case, the power generation efficiency of the fuel cell may be reduced by suppressing the fuel cell temperature during power generation. According to the present embodiment, since the fuel cell 15 is actively cooled using the refrigerant circulation pump 60 only when power generation is stopped after detecting a malfunction, the power generation efficiency during power generation is not affected.

  Furthermore, according to the fuel cell system 10 of the present embodiment, in step S120, occurrence of a malfunction in the formation of the inflow / outflow suppression state as the potential suppression operation is determined based on the fuel cell voltage Vf. The voltage sensor for detecting the fuel cell voltage Vf is usually provided for monitoring the power generation state of the fuel cell. By using the detection value of such a voltage sensor, a special sensor for detecting the occurrence of a malfunction is provided. Without providing a device, it is possible to detect the occurrence of the above problem while suppressing the complexity of the configuration of the fuel cell system.

F. Second embodiment:
In the first embodiment, when a failure occurs in the formation of the inflow / outflow suppression state as the potential suppression operation, the refrigerant circulation pump 60 is always driven in the stop process after the failure detection. Also good. Hereinafter, as a second embodiment, a configuration for determining whether or not to drive the refrigerant circulation pump 60 based on the elapsed time from the stop of power generation to the voltage re-rise in the system will be described.

  Since the fuel cell system of the second embodiment has the same system configuration as that of the fuel cell system 10 of the first embodiment, each component is given the same reference numeral as that of the first embodiment, and detailed description thereof will be given. Is omitted. The fuel cell system 10 of the second embodiment executes the system stop time control processing routine shown in FIG. 4 as in the first embodiment when stopping power generation when the system is stopped. At this time, as the defect detection process in step S120, various methods can be selected as in the first embodiment. In the second embodiment, even when any process is selected as the defect detection process in step S120, when a defect is detected, similarly to step S432 of the third defect detection process shown in FIG. The elapsed time Tp1 is obtained, and the obtained elapsed time Tp1 is stored in the control unit 50. That is, a process for obtaining the elapsed time Tp1 when the voltage once lowered after the power generation is stopped due to the occurrence of the trouble in the inflow / outflow suppression state as the potential suppression operation is performed and stored.

  FIG. 9 is a flowchart showing a malfunction detection stop time processing routine executed in step S150 when the fuel cell system 10 of the second embodiment executes the system stop time control processing routine of FIG. That is, in this embodiment, when the occurrence of a malfunction in the formation of the inflow / outflow suppression state as the potential suppression operation has already been detected and the power generation is stopped in a state where the malfunction determination flag is set to 1 (step S100), The process shown in 9 is executed.

  When this routine is started, the control unit 50 acquires the elapsed time Tp1 when the voltage is increased again (step S500). As described above, the elapsed time Tp1 at the time of the voltage re-rise is stored in the control unit 50 when a failure is detected in the failure detection process in step S120 when the system is stopped before this time. Is. Next, the control part 50 acquires the refrigerant | coolant temperature and environmental temperature at the time of a power generation stop (step S510). That is, the detection signal of the refrigerant temperature sensor 63 is acquired, and the detection signal of the environmental temperature sensor 55 is acquired. Here, the temperature detected by the refrigerant temperature sensor 63, which is the temperature of the refrigerant discharged from the fuel cell 15, can be considered to represent the internal temperature of the fuel cell 15.

  Next, the controller 50 derives the refrigerant temperature Rt at the elapsed time Tp1 (step S520). Here, after power generation is stopped, the refrigerant temperature gradually decreases with the internal temperature of the fuel cell 15, and eventually becomes a value substantially equal to the environmental temperature. The refrigerant temperature after power generation is stopped is determined according to the refrigerant temperature when power generation is stopped, the environmental temperature when power generation is stopped, and the elapsed time from when power generation is stopped. In the fuel cell system 10 of the present embodiment, the relationship between the refrigerant temperature when the power generation is stopped, the ambient temperature when the power generation is stopped, the elapsed time since the power generation is stopped, and the refrigerant temperature is experimentally or simulated in advance. And stored in the control unit 50 as a map. In step S520, the refrigerant temperature Rt at the elapsed time Tp1 acquired in step S500 is obtained based on the refrigerant temperature and the environmental temperature at the time of power generation stop acquired in step S510 with reference to the map.

When the refrigerant temperature Rt at the elapsed time Tp1 is obtained, the control unit 50 determines whether or not the refrigerant temperature Rt has reached the minimum value, that is, the refrigerant temperature (fuel cell temperature) has been lowered at the elapsed time Tp1. It is determined whether or not (step S530). Specifically, the difference between the refrigerant temperature Rt and the ambient temperature obtained in step S520 is equal to or less than a predetermined reference value, if the two are almost equal temperature, lower the refrigerant temperature R t Can be judged. Alternatively, when the refrigerant temperature Rt at the elapsed time Tp1 is predicted in step S520, the refrigerant temperature change ΔRt obtained based on the map is further obtained before and after the elapsed time Tp1, and the refrigerant temperature change ΔRt is 0. When it is above, it can be determined that the refrigerant temperature Rt is reduced.

  When it is determined in step S530 that the refrigerant temperature does not fall completely (not the minimum value), the control unit 50 controls the stop-time control (connection between the fuel cell 15 and the load 57) while driving the refrigerant circulation pump 60. And the anode-side channel and the cathode-side channel are set in an inflow / outflow suppression state (step S540), and this routine is terminated. By driving the refrigerant circulation pump 60 in this way, a drop in the internal temperature of the fuel cell 15 is promoted. When it is determined that the refrigerant temperature does not fall down at the elapsed time Tp1, the actual fuel cell temperature at the elapsed time Tp1 at which the voltage rise due to the malfunction occurs by promoting the cooling of the fuel cell 15 in this way, Can be lower. By lowering the temperature when the voltage of the fuel cell rises, as in the first embodiment, the oxidation current can be suppressed and the electrode shape change can be suppressed.

  If it is determined in step S530 that the refrigerant temperature is lowered (becomes the minimum value) at the elapsed time Tp1, the control unit 50 performs normal stop time control without driving the refrigerant circulation pump 60 ( Step S550), this routine is finished. If the refrigerant temperature has fallen at the elapsed time Tp1 when the voltage rises due to a malfunction, even if the refrigerant circulation pump 80 is driven to stop cooling when power generation is stopped, the fuel cell temperature at the voltage rise is further reduced. This is because the effect to be obtained cannot be obtained.

  According to the fuel cell system 10 of the second embodiment configured as described above, when a failure occurs in the formation of the inflow / outflow suppression state as the potential suppression operation, the refrigerant temperature (fuel) is increased when the voltage rises due to the failure. Only when it is determined that the battery temperature is not lowered, the refrigerant circulation pump 60 is driven as an oxidation suppression operation to actively cool the fuel cell 15. If it is determined that the refrigerant temperature at the time of the voltage rise caused by the malfunction cannot be lowered even if the refrigerant circulation pump 60 is driven, the refrigerant circulation pump 60 is not driven. Therefore, the refrigerant circulation pump 60 is not driven to consume energy even though it is difficult to obtain the effect, and a reduction in energy efficiency in the system can be suppressed. In particular, in the present embodiment, after a failure is detected, every time the system is stopped, the refrigerant temperature and the environmental temperature at the time of stop are obtained, and the refrigerant temperature Rt at the time of voltage increase (elapsed time Tp1) is predicted. Yes. Therefore, it is possible to appropriately determine whether or not to drive the refrigerant circulation pump 60 even when the conditions when the system is stopped fluctuate.

G. Modification of the second embodiment:
G-1. First modification:
In the second embodiment, if the fuel cell temperature at the elapsed time Tp1 can be further lowered by driving the refrigerant circulation pump 60 at the time of stop based on the predicted refrigerant temperature Rt at the elapsed time Tp1, the stop is performed. Sometimes the refrigerant circulation pump 60 is always driven, but a different configuration may be used. For example, instead of the determination in step S530 in the second embodiment or in addition to the determination in step S530, each time the fuel cell system 10 is stopped, it is determined whether or not a voltage re-rise occurs during the stop time. Also good. And it is good also as driving the refrigerant circulation pump 60 at the time of a stop only when voltage rise rises during a stop time.

  The stop time of the fuel cell system 10 may be obtained, for example, by detecting the stop time every time the fuel cell system 10 is stopped and started and learning based on the detected stop time. As a learning method, for example, the stop time can be obtained by calculating an average value of the stop times so far. Or you may obtain | require the stop time with the highest frequency among the stop times until then. The comparison between the stop time obtained based on such learning and the elapsed time Tp1 is performed in place of the determination in step S530 or together with the determination in step S530, and only when the voltage rises again during the stop time. The refrigerant circulation pump 60 may be driven. As a result, when the voltage does not rise again during the stop, the refrigerant circulation pump 60 is not driven, and a decrease in system efficiency due to the driving of the refrigerant circulation pump 60 can be suppressed.

  Further, when learning is performed and the stop time is obtained as described above, the average stop time or the most frequent stop time may be obtained in consideration of the time when the vehicle stops. Alternatively, when the location where the fuel cell system 10 is used changes, such as when the fuel cell system 10 is used as a power source for driving a moving body such as a vehicle, the location where the fuel cell system 10 is stopped using, for example, GPS signals May be detected, and the average value of the stop time or the most frequent stop time may be obtained for each stop place. In addition, when calculating | requiring stop time based on a learning result, depending on the time and place at the time of a stop, the case where a learning result cannot be used is also considered. In such a case, the control relating to the driving of the refrigerant circulation pump 60 may be performed on the assumption that the voltage rises again during the stop time. Thereby, even if the stop time becomes longer and the voltage rises again, it is possible to improve the temperature reduction efficiency of the fuel cell and suppress electrode oxidation.

G-2. Second modification:
In the second embodiment, based on the estimated refrigerant temperature Rt at the elapsed time Tp1, it is determined only whether or not the refrigerant circulation pump 60 is driven at the time of stop. However, the driving amount of the refrigerant circulation pump 60 at the time of stop is determined. May be further changed. For example, the driving amount of the refrigerant circulation pump 60 may be adjusted based on the difference between the predicted refrigerant temperature Rt at the elapsed time Tp1 and the detected environmental temperature. Specifically, the driving amount of the refrigerant circulation pump 60 may be increased as the difference between the predicted refrigerant temperature Rt at the elapsed time Tp1 and the detected environmental temperature is larger. The greater the difference between the predicted refrigerant temperature Rt and the ambient temperature, the easier it is to obtain the effect of improving the cooling efficiency by increasing the drive amount of the refrigerant circulation pump 60. Therefore, the effect of driving the refrigerant circulation pump 60 is enhanced. be able to. In addition, when the difference between the predicted refrigerant temperature Rt and the ambient temperature is small and the cooling effect by driving the refrigerant circulation pump 60 is small, the amount of energy consumed is suppressed by driving the refrigerant circulation pump 60. Thus, a decrease in system efficiency can be suppressed.

  Further, in step S530, it is determined that the refrigerant temperature does not fall at the elapsed time Tp1, and after the refrigerant circulation pump 60 is driven at the time of stoppage, the refrigerant temperature is measured using the refrigerant temperature sensor 63, and the refrigerant circulation pump 60 is driven. Further, it may be determined whether or not the refrigerant temperature has come to decrease at the elapsed time Tp1. If the refrigerant temperature still does not fall at the elapsed time Tp1 even after the refrigerant circulation pump 60 is driven, when the fuel cell system 10 is subsequently started and stopped again, the refrigerant circulation pump 60 is driven. The amount may be further increased to increase the degree to which the fuel cell 15 is cooled.

G-3. Third modification:
In the second embodiment, whether or not the refrigerant circulation pump 60 is driven when power generation is stopped is determined every time power generation is stopped. However, a different configuration may be used. For example, when it is determined from the installation environment of the fuel cell system 10 that the temperature condition fluctuation at the time of system stop is sufficiently small, the refrigerant circulation at the next system stop after the system stop when the malfunction is detected is stopped. The necessity of driving the pump 60 may be determined. In this case, along with the failure detection process in step S120, the temperature of the fuel cell 15 is measured, and when the voltage increase due to the failure occurs (elapsed time Tp1), it is determined whether or not the refrigerant temperature has completely decreased. That's fine. Then, when it is determined that the refrigerant temperature has not fallen when the voltage increases, the refrigerant circulation pump 60 may be driven each time the fuel cell system 10 is restarted after the startup. In addition, when it is determined that the refrigerant temperature has fallen completely when the voltage increases, the refrigerant circulation pump 60 may not be driven when the fuel cell system 10 is restarted after the startup. In order to actually measure the internal temperature of the fuel cell 15 at the time of detecting a malfunction, for example, a temperature sensor (for example, a thermocouple) for directly detecting the internal temperature of the fuel cell 15 may be provided in the fuel cell 15.

G-4. Fourth modification:
In the second embodiment, after the malfunction of the potential suppression operation is detected, the temperature of the fuel cell 15 after the system stop is actively lowered by driving the refrigerant circulation pump 60 when the system is stopped. Different configurations may be used. For example, after the above-described problem is detected, a process for lowering the temperature of the fuel cell 15 during power generation as compared with the normal time may be performed as an operation for suppressing the oxidation of the cathode.

  When performing such control, it is only necessary to determine whether or not the failure determination flag is set to 1 when the fuel cell system 10 is started, that is, whether or not a failure in the potential suppression operation is detected. . When the potential suppression operation is normal and the failure determination flag is set to 0, normal power generation control is performed. When the failure determination flag is set to 1, the fuel cell is compared with the normal power generation control. What is necessary is just to adjust the drive amount of the refrigerant | coolant circulation pump 60 so that the driving | operation temperature of 15 may become low.

  With such a configuration, when a malfunction occurs, the temperature of the fuel cell 15 during power generation is set lower, thereby lowering the initial temperature when the temperature of the fuel cell 15 starts to decrease when power generation is stopped. It is possible to lower the temperature of the fuel cell 15 when the voltage rises due to a malfunction, and to suppress the change in the electrode configuration. Such a decrease in the temperature of the fuel cell 15 during power generation causes a decrease in power generation efficiency. However, by reducing the temperature of the fuel cell 15 during power generation only when a malfunction of the potential suppression operation is detected, A decrease in system efficiency due to the decrease can be suppressed. When the control for lowering the temperature of the fuel cell 15 during power generation is performed as described above, if the control for further driving the refrigerant circulation pump 60 is performed as an oxidation suppression operation at the time of power generation stop, The temperature decrease of the fuel cell 15 can be further promoted. At this time, similarly to the second embodiment, the refrigerant circulation pump 60 after power generation is stopped is predicted by predicting the refrigerant temperature at the time of voltage increase (elapsed time Tp1) after power generation is stopped. It is desirable to perform this only when it is determined that the effect of driving the motor can be obtained.

H. Modified example of oxidation suppression operation:
H-1. Relationship between hydrogen filling pressure and voltage re-rise timing:
In the first and second embodiments, as the oxidation suppression operation for suppressing electrode oxidation, after the malfunction is detected, after the next system start-up, a process for driving the refrigerant circulation pump 60 is performed, and the fuel cell Although the electrode oxidation is suppressed by improving the cooling efficiency, a different configuration may be adopted. Hereinafter, as a modified example of the oxidation suppression operation for suppressing electrode oxidation, a configuration for performing control to change the pressure of hydrogen sealed in the anode-side flow path when power generation is stopped will be described. First, the relationship between the hydrogen pressure sealed in the anode-side flow path and the timing at which the voltage rises again after power generation is stopped will be described.

When the cathode-side channel is in an inflow / outflow suppression state with hydrogen enclosed in the anode-side channel, the cathode-side channel is not sufficiently sealed and air flows into the cathode-side channel As described above, an internal battery is formed in a single cell, and the cathode has a high potential. That is, the voltage of the fuel cell once decreases after stopping and then increases again. The formation of such an internal battery occurs when a region with a high hydrogen concentration and a region with a low hydrogen concentration are generated on the anode when air flows in and oxygen is present on the cathode. Therefore, when hydrogen is sealed in the anode-side flow path when the system is stopped, if the hydrogen pressure to be filled is increased, even if air flows into the cathode-side flow path, the hydrogen concentration partially on the anode It becomes possible to delay the time when the low region is formed. Therefore, by increasing the fuel gas pressure sealed in the anode-side flow path when the system is stopped, the voltage re-rise timing can be delayed and the timing at which electrode oxidation is started can be delayed.

  FIG. 10 is a diagram showing the results of examining the relationship between the pressure of hydrogen sealed in the anode-side flow path when power generation is stopped and the time required for the voltage to rise again after power generation is stopped. FIG. 10 (A) shows the result of voltage transition when the hydrogen filling pressure in the anode-side flow path is equal to atmospheric pressure (0 kPaG), and the result of voltage transition when 20 kPaG (atmospheric pressure standard) is shown. 10 (B), and the result of voltage transition when the pressure is 50 kPaG is shown in FIG. 10 (C). In either case, the cooling water temperature when power generation is stopped is 40 ° C. Here, when power generation is stopped, the same sealing valves as the first cathode sealing valve 48 and the second cathode sealing valve 49 of the embodiment are closed, and the cathode-side flow path is also in an inflow / outflow suppression state. Even when the valve is normally closed, a very small amount of air gradually flows into the cathode-side flow path, so that the voltage rises again after the voltage drops after power generation is stopped. As shown in FIG. 10, the higher the hydrogen filling pressure in the anode-side flow channel at the time of stopping, the later the timing of re-raising the voltage after stopping the power generation. Such an effect of delaying the re-rise of the voltage by increasing the hydrogen pressure sealed in the anode-side channel causes a problem in the first cathode sealing valve, so that more air is contained in the cathode-side channel. In the case of flowing into the same, the same can be obtained.

H-2. First aspect of a modification of the oxidation suppression operation:
A first aspect of the modification example of the oxidation suppression operation will be described below. Here, when the power generation is stopped, the system stop time control processing routine shown in FIG. 4 is executed. At this time, if it is determined in step S100 that the failure determination flag is set to 1, in the stop processing after detection of failure in step S150, the hydrogen sealing pressure in the anode-side flow path is controlled by normal stop-time control. In this case, a process is performed for setting a failure-time filling pressure that is set in advance as a value higher than the hydrogen-filling pressure. That is, when the connection between the fuel cell 15 and the load 57 is cut off to stop the circulation of the refrigerant, and the anode side channel and the cathode side channel are brought into the inflow / outflow suppression state, as in the normal stop control. In addition, the hydrogen filling pressure is set to the above-described trouble-filling pressure by the drive control of the adjustable pressure valve 42.

  With such a configuration, even when air enters the cathode-side flow channel due to a problem in the formation of the inflow / outflow suppression state as the potential suppression operation, the timing of voltage re-rise due to the problem is more Therefore, the fuel cell system 10 is restarted before the voltage re-rise occurs, and the possibility that the voltage rise that causes electrode oxidation does not actually occur increases. As a result, it is possible to reduce the frequency at which the voltage increase that causes electrode oxidation actually occurs, and to suppress electrode oxidation caused by the voltage increase. Further, if the time until the voltage re-rise increases by increasing the hydrogen charging pressure, the temperature of the fuel cell 15 further decreases by the time of the voltage re-rise, so the temperature of the fuel cell 15 at the time of the voltage re-rise is further lowered. Can do. As described above, the lower the fuel cell temperature, the smaller the oxidation current at the time of voltage re-rise. Therefore, the time until the voltage re-rise becomes longer, so even if the voltage re-rise occurs, the electrode Oxidation reaction can be made difficult to occur.

H-3. Second aspect of the modification of the oxidation suppression operation:
FIG. 11 shows the fuel cell system 10 that executes the second modification of the oxidation suppression operation and has the same system configuration as that of the embodiment. When the system is stopped, control is performed instead of the system stop time control processing routine of FIG. 5 is a flowchart showing a system stop time control processing routine executed by unit 50. In this routine, the steps corresponding to the steps shown in FIG. 4 are given by changing the step number from the 100s to the 600s, and detailed explanations are omitted, and only the parts that perform processing different from FIG. 4 are explained. To do. In the process shown in FIG. 11, after a defect is detected by the defect detection process (step S620) (step S630) and the defect determination flag is set to 1 (step S640), an oxidation suppression operation necessity determination process (step S645) is performed. 4 is different from the process of FIG.

  FIG. 12 is a flowchart showing an oxidation suppression operation necessity determination processing routine executed in step S645 of FIG. When this routine is started, the control unit 50 acquires an elapsed time Tp1 when the voltage is increased again (step S700). Here, similarly to the second embodiment described above, when any defect is detected as the defect detection process in step S620, the third defect detection process shown in FIG. Similar to step S432, a process for obtaining the elapsed time Tp1 when the voltage rises again due to the occurrence of a problem in the formation of the inflow / outflow suppression state as the potential suppression operation is performed, and this is stored in the control unit 50. ing. In step S700, the stored elapsed time Tp1 is acquired.

  Thereafter, when the control unit 50 performs the stop process of the fuel cell system 10, the hydrogen filling pressure in the anode-side flow path is preset as a value higher than the hydrogen filling pressure in the normal stop-time control. In the case of the sealed pressure, an elapsed time Tp2 when the voltage re-rise due to the failure occurs is obtained (step S710). Here, the elapsed time Tp1 acquired in step S700 is the degree of malfunction in the formation of the inflow / outflow suppression state as the potential suppression operation, specifically, the first cathode sealing valve 48 and the second cathode sealing valve. 49 reflects the degree of failure of the sealed state. That is, how the first cathode sealing valve 48 and / or the second cathode sealing valve 49 is removed (from the outside through the first cathode sealing valve 48 and the second cathode sealing valve 49 to the cathode side flow). The larger the inflow amount of air into the road), the shorter the elapsed time Tp1 until the voltage re-rise due to the malfunction occurs. As described above, since the elapsed time until the voltage re-rise due to the failure occurs as the hydrogen sealing pressure at the time of stop is increased, the degree of sealing omission in the cathode sealing valves 48 and 49, Based on the hydrogen filling pressure at the time of stopping, the elapsed time Tp2 when the voltage re-rise occurs can be obtained. In the fuel cell system 10 as the second aspect of the modification example of the oxidation suppression operation, an elapsed time Tp1 (a value detected at the normal hydrogen filling pressure) reflecting the degree of the cathode sealing valves 48 and 49 being removed, and The relationship with the elapsed time Tp2 when the voltage re-rise occurs when the hydrogen filling pressure is raised to the predetermined trouble filling pressure is experimentally examined in advance and stored as a map in the control unit 50. In step S710, the map is referred to, and the elapsed time Tp2 is obtained based on the elapsed time Tp1 acquired in step S700.

  Next, the control unit 50 compares the elapsed time Tp2 obtained in step S710 with the reference time Xt3 (step S720). Here, the reference time Xt3 is a general stop time of the fuel cell system 10 (the time from when the fuel cell system 10 is stopped until the next start-up), and during this time, the voltage rises again to cause the electrode shape change. It is a value stored in the control unit 50 in advance as a time that should not occur. When the elapsed time Tp2 is longer than the reference time Xt3, it is determined that the voltage rise will not occur within the reference time Xt3 when the hydrogen filling pressure at the time of stopping is increased to the troubled filling pressure. 50 sets the sealed pressure increase flag to 1 (step S730), and ends this routine. The initial value of the sealed pressure increase flag is set to 0. In step S720, when the elapsed time Tp2 is equal to or less than the reference time Xt3, it is determined that the voltage re-rise occurs within the reference time Xt3 even if the hydrogen filling pressure at the time of stoppage is increased to the troubled pressure. The unit 50 maintains the sealed pressure increase flag at 0 (step S740) and ends this routine. When the oxidation suppression operation necessity determination processing routine ends, the system stop time control processing routine of FIG. 11 also ends.

  Thereafter, when the control process routine at the time of system stop of FIG. 11 is executed when the fuel cell system 10 is stopped after the next startup, it is determined in step S600 that the failure determination flag is set to 1. If it is determined that the defect determination flag is set to 1, next, the control unit 50 determines whether or not the enclosed pressure increase flag is set to 1 (step S648). When the sealed pressure increase flag is set to 1, the control unit 50 executes a stop process after detecting a failure (step S650), and ends this routine. Specifically, similarly to the normal stop-time control, the connection between the fuel cell 15 and the load 57 is cut off to stop the circulation of the refrigerant, and the anode-side channel and the cathode-side channel are prevented from flowing in and out. In this case, the hydrogen filling pressure is set to the above-described trouble-filling pressure by the drive control of the variable pressure control valve 42. Thereby, when the current stop time is shorter than the reference time Xt3, voltage rise does not occur during the stop, and the progress of electrode oxidation can be suppressed. If it is determined in step S648 that the enclosed pressure increase flag is 0, the control unit 50 performs normal stop time control similar to step S110 (step S660), and ends this routine.

  According to the above configuration, when the elapsed time Tp2 obtained as the time when the voltage re-rise occurs when the hydrogen filling pressure is increased is longer than the reference time Xt3 set as the stop time, the hydrogen filling pressure is raised. Therefore, it is possible to suppress the voltage re-rise during the stop, and to suppress the electrode oxidation caused by the voltage re-rise. In addition, when the elapsed time Tp2 is equal to or less than the reference time Xt3, the hydrogen filling pressure is not increased. Therefore, even if the voltage rises again during the stop, the progress of the electrode oxidation reaction that proceeds with the voltage rise is continued. The electrode oxidation can be suppressed with a small amount. When the hydrogen charging pressure is raised, the time until the voltage rises again can be delayed, but once the voltage rises once, the amount of hydrogen sealed in the flow path is increased. As a result, as shown in FIG. 10, the time during which the voltage is rising becomes longer. As described above, even if the hydrogen charging pressure is increased, if the voltage rises again during stoppage, the hydrogen filling pressure is not raised, so that the time during which the voltage is raised again can be kept short, and the electrode oxidation reaction can be performed. Progress can be suppressed. Further, when it is judged that the effect of suppressing electrode oxidation cannot be sufficiently obtained even if the hydrogen filling pressure is increased, by not increasing the hydrogen filling pressure, the components of the fuel cell (for example, due to increasing the hydrogen filling pressure (for example, Degradation of the electrolyte membrane) can be suppressed.

  If it is determined in step S648 that the filled pressure increase flag is 0, in step S660, the hydrogen filled pressure is set lower than that in the normal stop instead of the normal stop time control similar to step S110. You may perform the control at the time of a stop to set. As described above, the higher the hydrogen filling pressure, the longer the voltage rise time when the voltage re-rise occurs, and the more the cathode oxidation reaction proceeds. By setting the hydrogen filling pressure lower than that during normal shutdown, even if it is unavoidable that the voltage will rise again until the next system start-up, the electrode oxidation that proceeds when the voltage rises again during shutdown will occur. The reaction can be reduced.

  In the oxidation suppression operation necessity determination process of FIG. 12, the elapsed time Tp2 when the voltage is increased again when the hydrogen charging pressure is increased to the failure pressure in step S710 is obtained. In step S720, this elapsed time Tp2 is calculated. Although the reference time Xt3 is compared, a different configuration may be used. For example, multiple failure sealing pressures that are higher than the hydrogen sealing pressure in normal stop control are set, and when each failure sealing pressure is stopped at that sealing pressure, the voltage rises again. The elapsed time Tp2 until it occurs is obtained. Then, stop-time control at the time of stop after the next start-up may be performed using the failure-time sealed pressure when the elapsed time Tp2 becomes the minimum value exceeding the reference time Xt3.

H-4. Third aspect of the modification example of the oxidation suppression operation:
In the second aspect of the above-described modification of the oxidation suppression operation, the elapsed time Tp2 in which the voltage rises again when the hydrogen filling pressure is increased to the failure filling pressure is compared with the reference time Xt3 that is predetermined as the stop time. However, a different configuration may be used. For example, each time the fuel cell system 10 is stopped and started, the stop time may be obtained, and learning may be performed based on the actual stop time to set the reference time Xt3. As a learning method, for example, an average value of the stop times so far can be obtained and set as the reference time Xt3. Alternatively, the stop time with the highest frequency among the stop times up to that time may be set as the reference time Xt3. With such a configuration, it is possible to more accurately determine whether or not a voltage re-rise occurs during the stop when the hydrogen filling pressure is raised to the troubled filling pressure.

  Further, when learning is set as described above and the reference time Xt3 is set, the reference time Xt3 is determined by obtaining an average value of stop times and the most frequent stop time in consideration of the time when the vehicle further stops. Also good. Alternatively, when the location where the fuel cell system 10 is used changes, such as when the fuel cell system 10 is used as a power source for driving a moving body such as a vehicle, the location where the fuel cell system 10 is stopped using a GPS signal, for example. Can be detected, and the average value of the stop time or the most frequent stop time can be obtained for each stop place, and can be used as the reference time Xt3. In such a case, the oxidation suppression operation necessity determination process shown in FIG. 12 is not executed when the system is stopped as in step S645 in FIG. 11, but after starting after detecting the problem. This can be done at the time of stopping. Specifically, after it is determined in step S600 of FIG. 11 that the failure determination flag is set to 1, the oxidation suppression operation necessity determination process may be executed. At that time, it is only necessary to read the stop time and stop location, obtain the reference time Xt3 based on the learning result, and perform the determination in step S720.

  Note that when the reference time Xt3 is obtained based on the learning result, the learning result may not be used depending on the stop time and place. In such a case, if the control without increasing the hydrogen filling pressure is performed, even if the stop time is long and the voltage rises again, the time for the voltage rise to be long is suppressed and the electrode oxidation is suppressed. can do.

I. Modified example of potential suppression operation:
I-1. First aspect of modification of potential suppression operation:
In the first and second embodiments, as the potential suppression operation for suppressing the voltage rise after the system is stopped, the cathode side channel is sealed and the inflow / outflow is performed while hydrogen is sealed in the anode side channel. Although the operation for the suppression state is performed, a different configuration may be used. Below, the structure which purges the inside of an anode side flow path with an inert gas (specifically air) as a 1st aspect of the modification of an electric potential suppression operation | movement is demonstrated.

  FIG. 13 is a block diagram illustrating a schematic configuration of the fuel cell system 110 according to the first aspect of the modification of the potential suppressing operation. In the fuel cell system 110, the same reference numerals are given to the same components as those in the fuel cell system 10 of the embodiment, and detailed description thereof will be omitted, and only portions different from the embodiment will be described. In the fuel cell system 110, a purge gas flow path 38 that branches from the air supply flow path 32 and connects the air supply flow path 32 and the hydrogen supply flow path 22 is provided. In addition, a switching valve 39 that switches a flow path through which air supplied from the compressor 30 flows is provided at a connection portion between the air supply flow path 32 and the purge gas flow path 38. In the fuel cell system 110, at the time of power generation, the switching valve 39 is switched so that air from the compressor 30 is supplied only to the cathode side flow path of the fuel cell 15 via the air supply flow path 32.

  In the fuel cell system 110, the same system stop time control processing routine as that in FIG. 4 is executed when the fuel cell system 110 is stopped. In the potential suppression operation in the normal stop time control (step S110), the anode side flow path and the cathode side flow path Instead of the operation of setting the inflow / outflow suppression state, an operation of purging the inside of the anode side flow path with air is performed. Specifically, when the fuel cell system 110 is stopped, the control unit 50 cuts off the connection between the fuel cell 15 and the load 57 or circulates the refrigerant as part of normal stop time control corresponding to step S110. The following processing is performed along with the stop. That is, the hydrogen shutoff valve 40 is closed to stop the supply of hydrogen to the fuel cell 15, and the purge valve 46 is opened to allow hydrogen to be discharged from the anode side flow path. Further, the switching valve 39 is switched so that the air supplied from the compressor 30 is led to the purge gas flow path 38 instead of the air supply flow path 32. Thereby, the air supplied from the compressor 30 flows into the anode-side flow path via the purge gas flow path 38. At this time, by driving the hydrogen circulation pump 44 for a predetermined time, the hydrogen in the anode side channel can be discharged to the outside through the purge valve 46, and the inside of the anode side channel can be replaced with air. Thereafter, the purge valve 46 is closed and the compressor 30 is stopped, whereby air can be put in the anode-side flow path. If such a process is performed, air is present in both the anode-side flow path and the cathode-side flow path, so that the voltage does not rise again in the fuel cell 15 after the system is stopped. At this time, the cathode sealing valves 48 and 49 may be opened or closed. Further, the second cathode sealing valve 49 may not be provided. In the above configuration, each part related to the operation of replacing the inside of the anode side flow path with air functions as a stop-time potential suppressing unit that performs a potential suppressing operation for suppressing an excessive voltage increase in the fuel cell after power generation is stopped.

As described above, even when the operation of sealing the anode with air is performed as the potential suppression operation, when a problem occurs in the potential suppression operation, electrode oxidation due to the voltage rise can occur as in the embodiment. That is, as a malfunction of the potential suppression operation, when a malfunction occurs in the sealing of the hydrogen shutoff valve 40, hydrogen flows into the anode-side channel purged with air. This is because, in the hydrogen supply passage 22, the hydrogen shut-off valve 4 0 O remote upstream, so that can be supplied hydrogen with respect to immediate fuel cell 15 at the time of system startup, for high hydrogen pressure is maintained It is. When hydrogen flows in in this way, a region with high and low hydrogen concentration is formed on the anode, thereby forming an internal battery in the single cell, the cathode becomes an undesirably high potential, and the voltage rises again. Occur. The voltage re-rise due to such a failure occurring in the hydrogen cutoff valve 40 occurs earlier, more rapidly, and longer as the degree of sealing failure in the hydrogen cutoff valve 40 increases. For this reason, the failure caused in the sealing by the hydrogen shut-off valve 40 is detected by detecting the voltage after the stop as in the first to third potential suppression operation failure detection methods in the embodiment. The voltage change amount ΔVf or the elapsed time Tp1 can be detected. Therefore, even when the process of purging the anode with air as the potential suppression operation is performed, the system stop time control processing routine similar to that of FIG. Sometimes, it is sufficient to perform a stop process after detecting a failure (step S150).

  When the process of purging the anode with air is performed as the potential suppression operation, for example, the same control as driving the refrigerant circulation pump 60 in the first embodiment may be performed as the oxidation suppression operation performed when the malfunction is detected. As a result, even if the voltage rises again due to the sealing failure of the hydrogen cutoff valve 40, the oxidation current can be suppressed and the electrode oxidation can be suppressed. In this case, as in the first embodiment, the refrigerant circulation pump 60 may be driven at all times when a failure is detected. As in the second embodiment, the refrigerant temperature decreases at the elapsed time Tp1 when the voltage is increased again. The refrigerant circulation pump 60 may be driven only when it is determined that it is not complete. Further, as in the modification of the second embodiment, the driving amount of the refrigerant circulation pump 60 may be further increased when the refrigerant temperature does not fall down at the elapsed time Tp1. Alternatively, when a malfunction occurs, the driving amount of the refrigerant circulation pump 60 during power generation may be increased, and the temperature of the fuel cell 15 during power generation may be lowered before stopping.

  Note that the inert gas used when purging the anode-side flow path at the time of stopping as the potential suppressing operation may be a gas other than air. By filling the anode side flow path with the inert gas, the reaction related to the potential increase may not proceed. For example, reformed gas is used instead of hydrogen gas as fuel gas, and reformed fuel gas (natural gas containing methane gas, city gas, etc.) is supplied to the reformer and the reformer instead of the hydrogen tank 20. When the reformed fuel supply unit is provided, the anode-side flow path may be purged using the reformed fuel gas as an inert gas. Even in such a case, a failure has occurred in the shut-off valve (corresponding to the hydrogen shut-off valve 40) provided in the flow path for supplying the reformed gas to the fuel cell 15 (flow path corresponding to the hydrogen supply flow path 22). Sometimes, the voltage rises again when the reformed gas flows into the anode-side flow path filled with the inert gas. Then, by driving the refrigerant circulation pump 60 and cooling the fuel cell 15, it is possible to suppress electrode oxidation caused by the voltage rise again.

I-2. Second aspect of the modification of the potential suppression operation:
Hereinafter, a configuration in which the anode and the cathode are short-circuited in the fuel cell 15 after power generation is stopped will be described as a second aspect of the potential suppression operation. FIG. 14 is a block diagram showing a schematic configuration of the fuel cell system 210 in the second mode of the modification of the potential suppressing operation. In the fuel cell system 210, components common to those in the fuel cell system 10 of the embodiment are denoted by the same reference numerals, detailed description thereof is omitted, and only portions different from the embodiment are described.

  In the fuel cell system 210, a short circuit 253 can be connected to the fuel cell 15 together with the load 57 via the wiring 56. The wiring 56 is provided with a load switching unit 251 as a switch for switching the connection between the fuel cell 15 and the load 57 or the short circuit 253. The load switching unit 251 is switched so that the fuel cell 15 and the load 57 are connected when the fuel cell 15 generates power, and the fuel cell 15 and the short circuit 253 are connected when the power generation of the fuel cell 15 is stopped. Can be switched. At this time, the fuel cell 15 (each single cell 70) is in a state where the anode side and the cathode side are short-circuited. Note that the short circuit 253 is a circuit having a lower resistance than the load 57.

  In the fuel cell system 210, a control process routine at the time of system stop similar to that in FIG. 4 is executed at the time of stop. However, in the potential suppression operation in the normal stop time control (step S110), the cathode side flow path is sealed and discharged. Instead of the operation for setting the on / off state, an operation for short-circuiting the fuel cell 15 is performed. That is, a process of switching the load switching unit 251 and short-circuiting the anode and the cathode via the short circuit 253 is performed. At this time, the supply of hydrogen to the fuel cell 15 is stopped by closing the circulation of the refrigerant and closing the hydrogen shut-off valve 40. In this modification, the purge valve 46 is closed when the system is stopped. In this modification, the cathode side flow path is not sealed.

  As described above, when the anode and the cathode are short-circuited, an electrochemical reaction proceeds by hydrogen remaining in the fuel gas flow path in the cell and oxygen remaining in the oxidation gas flow path in the cell, and power generation (short-circuit power generation) is performed. Done. Accordingly, the fuel cell 15 consumes hydrogen in the anode-side channel and oxygen in the cathode-side channel, so that the voltage of the fuel cell 15 (each single cell 70) decreases. Such short circuit processing in the fuel cell 15 is continuously performed when the system is stopped. In the above configuration, each part related to the operation of short-circuiting the fuel cell 15 functions as a stop-time potential suppressing unit that performs a potential suppressing operation for suppressing an excessive voltage increase in the fuel cell after power generation is stopped.

  As described above, even when the anode and the cathode are short-circuited as the potential suppression operation, when a failure occurs in the short-circuit operation, electrode oxidation due to the voltage rise can occur as in the embodiment. That is, if the short-circuit operation is not performed sufficiently, the hydrogen in the anode side flow path remains without being consumed, and the air flowing in from the outside diffuses from the cathode side to the anode side, and within the single cell. An internal battery is formed. Then, the cathode becomes a high potential, the voltage rises again, and the electrode oxidation proceeds. Such a malfunction in the short circuit as the potential suppression operation is similar to the malfunction detection method of the first or second potential suppression operation in the embodiment, by detecting the voltage after the stop, thereby changing the fuel cell voltage Vf or the voltage change. It can be detected based on the quantity ΔVf. Therefore, even when the fuel cell 15 is short-circuited as a potential suppression operation, the system stop-time control processing routine similar to that in FIG. 4 of the embodiment is performed when the system is stopped to detect a failure in the potential suppression operation. What is necessary is just to perform the process at the time of a stop after malfunction detection (step S150).

  When the anode and the cathode are short-circuited as the potential suppression operation, for example, the same control as that in the first embodiment may be performed to drive the refrigerant circulation pump 60 as the oxidation suppression operation performed when the malfunction is detected. As a result, even if the voltage rises again due to the sealing failure of the hydrogen cutoff valve 40, the oxidation current can be suppressed and the electrode oxidation can be suppressed. In this case, as in the first embodiment, the refrigerant circulation pump 60 may be driven at all times when a failure is detected. As in the second embodiment, the refrigerant temperature decreases at the elapsed time Tp1 when the voltage is increased again. The refrigerant circulation pump 60 may be driven only when it is determined that it is not complete. Further, as in the modified example of the second embodiment, when the refrigerant temperature does not fall at the elapsed time Tp1, the driving amount of the refrigerant circulation pump 60 may be further increased. The driving amount of the circulation pump 60 may be increased to lower the temperature of the fuel cell 15 during power generation prior to stopping.

J. et al. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

J1. Modification 1:
In the above description, when a malfunction occurs in the potential suppression operation, the voltage re-rises as shown in FIG. 3 and the timing at which the voltage re-rises is delayed as compared with the normal time. The voltage may change. For example, when performing an operation to seal the cathode side flow path or short-circuit the fuel cell with hydrogen sealed in the anode side flow path as a potential suppression operation, enclose the anode side flow path. When the hydrogen pressure to be reduced is lower, the voltage change pattern when a failure occurs in the sealing in the cathode-side channel shows a pattern different from that in FIG. FIG. 15 shows a voltage change pattern when a failure occurs in sealing or short-circuiting in the cathode-side channel when the hydrogen pressure sealed in the anode-side channel is relatively low when the system is stopped.

  When the amount of hydrogen enclosed in the anode-side channel is relatively small, after power generation is stopped, the reaction between hydrogen and oxygen on the cathode decreases and air (oxygen) gradually enters the cathode-side channel. As a result of the inflow, the voltage drop slows down before the low voltage state is reached, or the voltage starts to slightly increase before the low voltage state is reached. May show. As a result, catalytic oxidation may proceed while a relatively high voltage state continues without once reaching a low voltage state.

  As described above, when the hydrogen pressure sealed in the anode-side flow path when the system is stopped is set to be relatively low, instead of the determination based on the voltage change amount ΔVf in the failure detection process in step S120 of FIG. For example, the following determination may be made. That is, the elapsed time (elapsed time Tf1 shown in FIG. 3A and FIG. 15) until the voltage sufficiently drops (for example, drops to the voltage Vt1 shown in FIG. 3A and FIG. 15) after the system is stopped is detected. To do. When the elapsed time tf1 detected in this way exceeds the allowable range as the normal elapsed time Tf1, it can be determined that a problem has occurred in the potential suppression operation.

  As described above, the hydrogen pressure set to enclose hydrogen in the anode-side flow path when the system is stopped is low enough not to show a pattern in which the voltage rises again even if a malfunction occurs in the potential suppression operation. In the case where it is set, when the control for increasing the hydrogen sealing pressure is performed, a pattern is shown in which the voltage rises again. Therefore, when the hydrogen charging pressure at the time of stop is set low, the voltage within the reference time is suppressed from rising again when the control to increase the hydrogen charging pressure is performed as an oxidation suppression operation performed when a malfunction is detected. It is only necessary to sufficiently increase the hydrogen filling pressure so that it is possible. Alternatively, when a malfunction is detected when the hydrogen filling pressure at the time of stoppage is set low, control for further lowering the hydrogen filling pressure may be performed without performing control for increasing the hydrogen filling pressure. Thereby, the time which shows the high voltage which can raise | generate an electrode oxidation can be shortened.

J2. Modification 2:
In the above description, the voltage re-rise (the voltage change amount ΔVf is set to the reference value) indicates whether the gas inflow / outflow suppression state as the potential suppressing operation, the purge of the anode-side flow path, or the occurrence of the malfunction in the short circuit has occurred. However, a different configuration may be used. For example, instead of detecting the voltage change amount ΔVf at which the voltage starts to rise by monitoring the voltage change amount after the system is stopped, the re-fall after the voltage has risen again may be detected. In this case, for example, when the elapsed time from the system stop to the voltage re-fall is equal to or less than the reference value, it can be determined that a problem has occurred in the potential suppression operation. When based on the elapsed time from when the system is stopped until the voltage re-falls, it is possible to detect the occurrence of a failure with high accuracy by reducing noise detection compared to the case based on the elapsed time Tp1 until the voltage re-rises. Become. In addition, since electrode oxidation is most advanced before and after the re-raised voltage shows a peak, when it is based on the elapsed time from when the system is stopped until voltage re-decrease, the timing at which electrode oxidation actually proceeds The determination is made based on this, and the accuracy of the operation for suppressing electrode oxidation can be improved. Such a fault occurrence detection method only needs to be able to detect a change associated with a voltage re-rise due to the fault. If a determination is made based on the detected voltage value, the complexity of the system for detecting the fault will be increased. Can be suppressed.

  In addition, the failure detection in the potential suppression operation may be performed based on a value other than the voltage value, or the failure itself in the potential suppression operation may be detected. For example, when forming a gas inflow / outflow suppression state as the potential suppression operation, when detecting a sealing failure of the cathode sealing valves 48, 49, the failure itself of the sealing state of the cathode sealing valves 48, 49 itself. It is also possible to provide a sensor for detecting this in the cathode sealing valves 48 and 49 and directly detect the sealing failure of the cathode sealing valves 48 and 49. Alternatively, when the fuel cell 15 is short-circuited as a potential suppression operation, the current flowing through the circuit connecting the fuel cell 15 and the short-circuit 253 is detected, and when the current value is equal to or less than the reference value, the short-circuit is performed. It may be determined that a defect has occurred.

J3. Modification 3:
In the above description, the voltage sensor 52 detects the voltage of the entire fuel cell 15, but may have a different configuration. That is, the stack constituting the fuel cell 15 may be divided into blocks each composed of a plurality of single cells, and the voltage may be detected for each block. Further, the voltage may be detected for each single cell.

J4. Modification 4:
In the above description, since the electrode is composed of catalyst-supported carbon particles and a polymer electrolyte, when the cathode is at a high potential, the shape of the cathode changes due to oxidation of the carbon particles. Also good. The cathode may be formed using, for example, a support made of titanium oxide instead of a support made of carbon as a support for supporting the catalyst. Alternatively, the cathode may be formed only from a catalyst metal such as platinum without using a carrier. Since the magnitude of the potential at which the oxidation of the cathode varies depending on the constituent material of the cathode, the reference value used when detecting a malfunction in the potential suppression operation may be appropriately set according to the type of cathode used. Even in such a case, the same effect as the embodiment can be obtained by suppressing the change in the shape of the cathode caused by oxidation.

J5. Modification 5:
In the above description, as the potential suppression operation, any one of the formation of a gas inflow / outflow suppression state accompanied by the sealing of the cathode sealing valves 48 and 49, the purge of the anode-side flow path, and the short-circuit between the anode and the cathode. However, these may be combined. If a plurality of operations are combined as the potential suppression operation, even if a failure occurs in any of the operations, the voltage re-rise can be suppressed if other operations are normal. Also in this case, when a failure occurs in all potential suppression operations and a voltage re-rise is detected, the oxidation of the electrodes can be suppressed by executing the above-described oxidation suppression operation.

J6. Modification 6:
In the above description, when a problem occurs in the potential suppression operation, the electrode oxidation suppression operation is repeated thereafter, but a different configuration may be used. That is, when it is determined that the potential suppression operation has returned to normal, the normal control without performing the oxidation suppression operation may be restored. For example, as described in Modification 2 above, when a malfunction detection sensor is provided in the cathode sealing valves 48 and 49, when a malfunction is detected due to foreign object biting in the sealing valve, the malfunction is detected. When recovered, this can be easily detected.

J7. Modification 7:
In the above description, the fuel cell 15 is a solid polymer fuel cell, but the present invention can be similarly applied to a fuel cell system including other types of fuel cells. It is a polymer electrolyte fuel cell that tends to cause gas diffusion through the electrolyte membrane after power generation is stopped. However, even in other types of fuel cells, the movement of gas through the electrolyte membrane (internal leakage) due to pinholes or the like in the electrolyte membrane, or the movement of gas through the seal member arranged around the manifold (external) Due to leakage, voltage may increase again after power generation is stopped. By applying the present application, it is possible to suppress changes in the shape of the electrode caused by such a voltage re-rise.

DESCRIPTION OF SYMBOLS 10,110,210 ... Fuel cell system 15 ... Fuel cell 20 ... Hydrogen tank 22 ... Hydrogen supply flow path 24 ... Hydrogen discharge flow path 25 ... Connection flow path 30 ... Compressor 32 ... Air supply flow path 34 ... Air discharge flow path 38 ... Purge gas flow path 39 ... Switching valve 40 ... Hydrogen cutoff valve 42 ... Modulatable pressure valve 44 ... Hydrogen circulation pump 46 ... Purge valve 48 ... First cathode sealing valve 49 ... Second cathode sealing valve 50 ... Control unit 51 ... Load connection 52 ... Voltage sensor 54 ... Notification device 55 ... Environmental temperature sensor 56 ... Wiring 57 ... Load 60 ... Refrigerant circulation pump 61 ... Radiator 62 ... Refrigerant flow path 63 ... Refrigerant temperature sensor 70 ... Single cell 71 ... MEA
72, 73 ... Gas diffusion layer 74, 75 ... Gas separator 76 ... End plate 78 ... Current collecting plate 80 ... Refrigerant circulation pump 81, 82, 83, 84, 85, 86 ... Hole 87 ... Recess 88, 89 ... Groove 251 ... Load switching unit 253 ... Short circuit

Claims (7)

A fuel cell system comprising a fuel cell,
When the fuel cell system is stopped, a stop-time potential suppression unit that performs a potential suppression operation for suppressing a voltage increase in the fuel cell after power generation is stopped;
A fault detection unit for detecting a fault in the stop potential suppression unit;
An electrode oxidation suppression unit that performs an oxidation suppression operation that suppresses oxidation of electrodes included in the fuel cell after the next startup of the fuel cell system when the failure detection unit detects the failure ; and
The fuel cell
A plurality of power generation bodies each including an electrolyte membrane and a pair of electrodes are stacked,
An in-cell fuel gas passage formed on an anode, which is one electrode of each of the power generation bodies, through which a fuel gas containing hydrogen flows, and the fuel gas with respect to each of the in-cell fuel gas passages An anode side flow path comprising a fuel gas manifold for supplying and discharging
An in-cell oxidizing gas channel formed on a cathode, which is one of the electrodes included in each of the power generators, through which an oxidizing gas containing oxygen flows, and the oxidizing gas with respect to each of the in-cell oxidizing gas channel An oxidant gas manifold for supplying and discharging gas, and a cathode side flow path comprising:
The potential control unit at the time of stop is an outflow that suppresses the inflow and outflow of air to the cathode side channel in a state where hydrogen is enclosed in the anode side channel when the fuel cell stops power generation as the potential suppression operation. Performing the first potential suppression operation to enter the input suppression state,
The defect detection unit detects a defect in which air flows into the cathode-side channel due to poor formation of the inflow / outflow suppression state in the cathode-side channel,
The electrode oxidation suppression unit includes, as the oxidation suppression operation, a first oxidation suppression operation that circulates the cooling water even after power generation of the fuel cell is stopped when the fuel cell system is restarted after the next startup. A fuel cell system that performs at least one of a second oxidation suppression operation that increases a circulating amount of the cooling water as compared with normal power generation control during power generation after the next startup of the fuel cell system. A fuel cell system comprising a fuel cell,
When the fuel cell system is stopped, a stop-time potential suppression unit that performs a potential suppression operation for suppressing a voltage increase in the fuel cell after power generation is stopped;
A fault detection unit for detecting a fault in the stop potential suppression unit;
An electrode oxidation suppression unit that performs an oxidation suppression operation that suppresses oxidation of electrodes included in the fuel cell after the next startup of the fuel cell system when the failure detection unit detects the failure ; and
The fuel cell
A plurality of power generation bodies each including an electrolyte membrane and a pair of electrodes are stacked,
An in-cell fuel gas passage formed on an anode, which is one electrode of each of the power generation bodies, through which a fuel gas containing hydrogen flows, and the fuel gas with respect to each of the in-cell fuel gas passages An anode side flow path comprising a fuel gas manifold for supplying and discharging
An in-cell oxidizing gas channel formed on a cathode, which is one of the electrodes included in each of the power generators, through which an oxidizing gas containing oxygen flows, and the oxidizing gas with respect to each of the in-cell oxidizing gas channel An oxidant gas manifold for supplying and discharging gas, and a cathode side flow path comprising:
The potential control unit at the time of stop is an outflow that suppresses the inflow and outflow of air to the cathode side channel in a state where hydrogen is enclosed in the anode side channel when the fuel cell stops power generation as the potential suppression operation. Performing the first potential suppression operation to enter the input suppression state,
The defect detection unit detects a defect in which air flows into the cathode-side channel due to poor formation of the inflow / outflow suppression state in the cathode-side channel,
The electrode oxidation suppression unit normally does not perform an oxidation suppression operation when the fuel cell system stops generating power and encloses hydrogen in the anode-side flow path when the fuel cell system is stopped as the oxidation suppression operation. A fuel cell system for performing a third oxidation suppression operation for sealing hydrogen into the anode-side flow path at a pressure higher than the hydrogen charging pressure when the system is stopped . A fuel cell system comprising a fuel cell,
When the fuel cell system is stopped, a stop-time potential suppression unit that performs a potential suppression operation for suppressing a voltage increase in the fuel cell after power generation is stopped;
A fault detection unit for detecting a fault in the stop potential suppression unit;
An electrode oxidation suppression unit that performs an oxidation suppression operation that suppresses oxidation of electrodes included in the fuel cell after the next startup of the fuel cell system when the failure detection unit detects the failure ; and
The fuel cell
A plurality of power generation bodies each including an electrolyte membrane and a pair of electrodes are stacked,
An in-cell fuel gas passage formed on an anode, which is one electrode of each of the power generation bodies, through which a fuel gas containing hydrogen flows, and the fuel gas with respect to each of the in-cell fuel gas passages An anode side flow path comprising a fuel gas manifold for supplying and discharging
An in-cell oxidizing gas channel formed on a cathode, which is one of the electrodes included in each of the power generators, through which an oxidizing gas containing oxygen flows, and the oxidizing gas with respect to each of the in-cell oxidizing gas channel An oxidant gas manifold for supplying and discharging gas, and a cathode side flow path comprising:
The potential suppression unit at the time of stop is a low potential of the reactivity on the anode as compared with hydrogen instead of the fuel gas in the anode side flow path when the power generation of the fuel cell is stopped as the potential suppression operation. Perform the second potential suppression operation to replace with active gas,
The failure detection unit detects a failure of hydrogen flowing into the anode-side flow channel due to a defect in an inflow / outflow suppression state in the anode-side flow channel,
The electrode oxidation suppression unit includes, as the oxidation suppression operation, a first oxidation suppression operation that circulates the cooling water even after power generation of the fuel cell is stopped when the fuel cell system is restarted after the next startup. A fuel cell system that performs at least one of a second oxidation suppression operation that increases a circulating amount of the cooling water as compared with normal power generation control during power generation after the next startup of the fuel cell system. A fuel cell system comprising a fuel cell,
When the fuel cell system is stopped, a stop-time potential suppression unit that performs a potential suppression operation for suppressing a voltage increase in the fuel cell after power generation is stopped;
A fault detection unit for detecting a fault in the stop potential suppression unit;
An electrode oxidation suppression unit that performs an oxidation suppression operation that suppresses oxidation of electrodes included in the fuel cell after the next startup of the fuel cell system when the failure detection unit detects the failure ; and
The fuel cell
A plurality of power generation bodies each including an electrolyte membrane and a pair of electrodes are stacked,
An in-cell fuel gas passage formed on an anode, which is one electrode of each of the power generation bodies, through which a fuel gas containing hydrogen flows, and the fuel gas with respect to each of the in-cell fuel gas passages An anode side flow path comprising a fuel gas manifold for supplying and discharging
An in-cell oxidizing gas channel formed on a cathode, which is one of the electrodes included in each of the power generators, through which an oxidizing gas containing oxygen flows, and the oxidizing gas with respect to each of the in-cell oxidizing gas channel An oxidant gas manifold for supplying and discharging gas, and a cathode side flow path comprising:
The stop-time potential suppressing unit seals the anode-side flow path after stopping the supply of the fuel gas containing hydrogen to the fuel cell when the power generation of the fuel cell is stopped as the potential suppressing operation. Short-circuiting the anode and the cathode to perform a third potential suppressing operation for consuming hydrogen in the anode-side flow path;
The defect detection unit detects a problem that the short-circuit operation is insufficient,
The electrode oxidation suppression unit includes, as the oxidation suppression operation, a first oxidation suppression operation that circulates the cooling water even after power generation of the fuel cell is stopped when the fuel cell system is restarted after the next startup. A fuel cell system that performs at least one of a second oxidation suppression operation that increases a circulating amount of the cooling water as compared with normal power generation control during power generation after the next startup of the fuel cell system. The fuel cell system according to any one of claims 1, 3, and 4 ,
The electrode oxidation suppression unit is
Performing at least the first oxidation suppression operation as the oxidation suppression operation,
The temperature of the fuel cell can be lowered when the elapsed time has elapsed by performing the first oxidation suppression operation based on the elapsed time required from the stoppage of power generation to the voltage increase when the malfunction is detected. If it is determined that, the first oxidation suppression operation is performed,
If it is determined that the temperature of the fuel cell cannot be lowered when the elapsed time has elapsed even if the first oxidation suppression operation is performed, the fuel cell that does not perform the first oxidation suppression operation system. A fuel cell system according to any one of claims 1 and 3 to 5 ,
A stop time learning unit that learns by actually measuring the stop time when the fuel cell system is stopped;
The electrode oxidation suppression unit is
Performing at least the first oxidation suppression operation as the oxidation suppression operation,
When it is determined that the elapsed time elapses within the stop time based on the stop time learned by the stop time learning unit and the elapsed time required from the power generation stop to the voltage increase when the malfunction is detected Performing the first oxidation suppressing operation,
A fuel cell system that does not perform the first oxidation suppression operation when it is determined that the elapsed time does not elapse within the stop time . The fuel cell system according to claim 2 , wherein
The electrode oxidation suppression unit is
When the third oxidation suppression operation is performed as the oxidation suppression operation, it is determined that the voltage increase due to the malfunction does not occur within the reference stop time set for the fuel cell system . 3) Oxidation suppression operation
Even if the third oxidation suppression operation is performed as the oxidation suppression operation, if it is determined that the voltage rise occurs within the reference stop time, the fuel cell system that does not perform the third oxidation suppression operation .

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