JP5167660B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system capable of suppressing deterioration of a fuel cell.

  The fuel cell has a structure in which an anode and a cathode are arranged with an electrolyte membrane interposed therebetween. When the anode gas containing hydrogen is in contact with the anode and the cathode gas containing oxygen is in contact with the cathode, an electrochemical reaction occurs at both electrodes, and a voltage is generated between the electrodes.

  In such a fuel cell, necessary amounts of anode gas and cathode gas are supplied in accordance with the required output of the system. However, when the load increase of the load device connected to the fuel cell is abrupt, it is difficult to increase the gas supply amount by following the sudden load increase, and a cell that temporarily becomes short of hydrogen is generated. There is a case. If such a state is left unattended, an electrode corrosion reaction or the like may occur in a cell that has become deficient in hydrogen, resulting in irreversible deterioration of the fuel cell.

  In order to prevent such a situation, conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 6-243882, a state of hydrogen shortage is detected. A system for stopping power generation and protecting a fuel cell is disclosed. More specifically, according to this system, the cells stacked in the fuel cell are divided into predetermined cell sections, and the cell voltage in each cell section is detected. Thereafter, when the minimum value of the cell voltage is lower than the determination voltage, the power generation of the fuel cell is stopped assuming that a hydrogen shortage state has occurred in any cell. Thereby, deterioration of the electrode and the catalyst due to a hydrogen shortage state can be suppressed.

JP-A-6-243882 JP 2005-93111 A JP 2005-259664 A

  However, when hydrogen shortage occurs in the fuel cell, the electrolysis reaction of water to generate protons instead of hydrogen proceeds at the anode of the cell that has become hydrogen deficient, and there is a large amount of oxygen. Yes. In such a hydrogen-deficient fuel cell, processing such as hydrogen fuel diffusion or forced inflow processing (hereinafter referred to as “recovery processing”) is performed as a process for eliminating the hydrogen shortage, and hydrogen reaches the anode. Then, the potential rose at the cathode, and as a result, there was a possibility that the corrosion reaction in the carbon and catalyst of the cathode diffusion layer might be started.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel cell system capable of suppressing deterioration of the fuel cell when the fuel cell is short of hydrogen.

In order to achieve the above object, a first invention is a fuel cell system,
In a fuel cell system that performs a return process to eliminate fuel shortage when fuel shortage occurs at the anode of the fuel cell,
A fuel shortage detecting means for detecting a fuel shortage in the anode;
Supply stop means for stopping supply of oxidizing gas to the cathode of the fuel cell prior to the return processing when the fuel shortage is detected;
A reduction means for reducing the amount of oxidative gas remaining in the cathode prior to the return process when the fuel shortage is detected ,
The weight loss means is
A discharge means for discharging the staying oxidizing gas to the outside of the fuel cell when the fuel shortage is detected;
The discharging means is
A pressure adjusting device for adjusting the pressure of the cathode;
Control means for controlling the pressure adjusting device so as to decrease the outlet pressure of the cathode when the fuel shortage is detected;
It is characterized by providing.

The second invention is the first invention, wherein
The weight loss means is
It includes consumption means for consuming the staying oxidizing gas when the fuel shortage is detected.

The third invention is the second invention, wherein
The consumption means is
The staying oxidizing gas is consumed by a power generation reaction of the fuel cell.

In addition, a fourth invention is any one of the first to third inventions,
The pressure adjusting device is a pressure regulating valve disposed in a flow path through which the gas discharged from the cathode flows.

The fifth invention is the invention according to any one of the first to fourth inventions,
Branching from the downstream side of the compressor disposed in the flow path through which the oxidizing gas flows, further comprising a branch flow path connected to the flow path through which the gas discharged from the cathode flows,
The supply stop means switches the oxidant gas distribution destination to the branch flow path when the fuel shortage is detected.

According to the first invention, when fuel shortage is detected in the fuel cell, the supply of the cathode gas to the fuel cell is stopped prior to the return process, and the retained oxygen remaining in the cathode is reduced. . The corrosion reaction of the cathode that occurs when the fuel shortage recovery process at the anode is performed depends on the potential of the cathode. According to the present invention, since the retained oxygen is reduced, the cathode potential increase that occurs when the fuel shortage recovery process at the anode is performed can be effectively suppressed. Can be suppressed.
In addition, according to the present invention, when fuel shortage is detected, the amount of oxygen staying at the cathode can be reduced by discharging, and the corrosion reaction of the cathode that occurs when performing the fuel shortage recovery process at the anode is effective. Can be suppressed.
Furthermore, according to the present invention, when the fuel shortage is detected, the cathode outlet pressure can be reduced, so that the oxygen staying at the cathode can be effectively discharged, and the fuel shortage at the anode is restored. The corrosion reaction of the cathode that occurs during the treatment can be effectively suppressed.

  According to the second aspect of the present invention, when fuel shortage is detected, it can be reduced by consuming the oxidizing gas staying at the cathode, and the corrosion reaction of the cathode that occurs when the fuel shortage recovery process at the anode is performed. Can be effectively suppressed.

  According to the third aspect of the invention, the oxidizing gas staying at the cathode is consumed by the power generation reaction prior to the return process. For this reason, according to the present invention, since the power generation reaction is suppressed during the recovery process, the corrosion reaction at the cathode can be reliably suppressed.

According to the fourth invention, the outlet pressure of the cathode can be effectively reduced by controlling the pressure regulating valve provided in the flow path through which the gas discharged from the cathode flows.

According to the fifth aspect of the present invention, the fuel cell further includes a branch channel that branches from the downstream side of the compressor disposed in the channel through which the oxidizing gas flows and is connected to the channel through which the gas discharged from the cathode flows. When the shortage is detected, the flow destination of the oxidizing gas is switched to the branch flow path. For this reason, according to the present invention, the supply of the oxidizing gas to the fuel cell can be stopped instantaneously, and the situation in which the oxygen staying at the cathode increases can be effectively avoided.

  Several embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a configuration of a fuel cell system according to Embodiment 1 of the present invention. As shown in FIG. 1, the fuel cell system includes a fuel cell stack 10. The fuel cell stack 10 is configured by stacking a plurality of fuel cells. Each fuel cell is configured such that a proton conductive electrolyte membrane (not shown) is sandwiched between an anode and a cathode, and both sides are sandwiched between conductive separators.

  The fuel cell stack 10 is provided with a terminal (not shown) for taking out the generated electric power. A load 44 is connected to a terminal of the fuel cell stack 10 via an inverter 42. The electric power generated by the fuel cell stack 10 is taken out by the inverter 42 and supplied to the load 44.

  Connected to the fuel cell stack 10 are an anode gas passage 12 for supplying anode gas and an anode offgas passage 14. The upstream end of the anode gas flow path 12 is connected to an anode gas supply source (a high-pressure hydrogen tank, a reformer, etc.) 16, and a pressure regulating valve 18 is disposed downstream thereof. The anode gas is depressurized by the pressure regulating valve 18, depressurized to a desired pressure, and then supplied to the fuel cell stack 10. The anode gas that has passed through the fuel cell stack 10 is exhausted to the anode off-gas passage 14 as the anode off-gas. A diluter (not shown) is connected downstream of the anode off gas flow path 14. The hydrogen remaining in the anode off gas is diluted to a sufficiently low concentration in the diluter and then released to the outside of the system.

  Further, the fuel cell stack 10 is connected with a cathode gas passage 20 for supplying cathode gas and a cathode offgas passage 22 for discharging cathode offgas. An air cleaner 24 that removes dust and the like contained in air taken from the outside is disposed at the inlet of the cathode gas passage 20. Further, a compressor 26 is disposed downstream thereof. Air sucked by the operation of the compressor 26 is supplied to the fuel cell stack 10 via the cathode gas flow path 20. A pressure regulating valve 28 is disposed in the cathode off gas flow path 22. The pressure regulating valve 28 can regulate the cathode gas in the fuel cell stack 10 to a desired pressure. The cathode gas that has passed through the fuel cell stack 10 is exhausted to the cathode offgas passage 22 as cathode offgas.

  An open / close valve 32 that controls communication between the cathode gas flow channel 20 and the fuel cell stack 10 is disposed in the vicinity of the connection portion between the cathode gas flow channel 20 and the fuel cell stack 10. Further, an open / close valve 34 that controls communication between the cathode offgas channel 22 and the fuel cell stack 10 is disposed in the vicinity of the connection portion of the cathode offgas channel 22 with the fuel cell stack 10.

  Further, a voltmeter 46 is connected to the fuel cell stack 10. As will be described later, the voltmeter 46 generates an output corresponding to the generated voltage for each fuel cell of the fuel cell stack 10. In addition, this fuel cell system includes a control device 40. The control device 40 is connected with an inverter 42, a load 44, pressure regulating valves 18 and 28, on-off valves 32 and 34, and a voltmeter 46. The control device 40 receives information from the load 44, the voltage system 46, etc., or controls the inverter 42, the pressure regulating valves 18, 28, the on-off valves 32, 34, etc. as necessary.

[About generation of hydrogen deficit during fuel cell power generation]
Next, with reference to FIG. 2, the reaction at the time of occurrence of a hydrogen deficit during power generation of the fuel cell will be described. The fuel cell 50 of FIG. 2 has a structure in which both sides of a proton conductive electrolyte membrane 52 are sandwiched between an anode 54 and a cathode 56. The fuel cell 50 is one of a plurality of fuel cells stacked on the fuel cell stack 10.

As shown in FIG. 2, when power generation is performed in the fuel cell stack 10, an anode gas containing hydrogen is supplied to the anode 54 of the fuel cell 50, and air containing oxygen is supplied to the cathode 56 of the fuel cell 50. . When hydrogen and oxygen are supplied to the fuel cell 50, an electrochemical reaction (power generation reaction) represented by the following expression (1) occurs near the anode 54 and the following expression (2) occurs near the cathode 46.
(Anode): H ₂ → 2H ⁺ + 2e ⁻ (1)
(Cathode): 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)

As shown in the above formula (1), hydrogen (H ₂ ) supplied to the anode 54 is separated into protons (H ⁺ ) and electrons (e ⁻ ) by the catalytic action of the anode 54. Protons move inside the electrolyte membrane 52 toward the cathode 56, and electrons move toward the cathode 56 through a load (not shown). Then, as shown in the above equation ( ₂ ), oxygen (O ₂ ) contained in the air supplied to the cathode 56, electrons passing through the load, and protons moving inside the electrolyte membrane 52 are caused by the catalytic action of the cathode 56. Water molecules (H ₂ O) are generated. In the fuel cell, such a series of reactions are performed, and electric power is generated by continuously supplying air and hydrogen, and electric power is taken out by the load 44.

  The anode gas supply amount to the fuel cell stack 10 is set so that the output requested by the above-described power generation reaction can be obtained. However, when a sudden high output request is issued, it is difficult to immediately increase or decrease the anode gas supply amount in response to the output request. It is also assumed that the anode gas is not supplied to the anode 54 due to freezing or blockage of the anode gas flow path. As described above, during power generation of the fuel cell stack 10, a hydrogen deficient state (hereinafter referred to as “hydrogen deficiency”) may occur in any of the fuel cells.

[Anodic corrosion reaction in the absence of hydrogen]
In the fuel cell (hereinafter referred to as “hydrogen-deficient cell”) 50 in which hydrogen deficiency has occurred, hydrogen is deficient near the catalyst of the anode 54. Here, when the load on the fuel cell stack 10 is continued and a current is forced to flow through the hydrogen-deficient cell 50, the anode 54 of the hydrogen-deficient cell 50 has the following equation by catalysis to compensate for the deficient hydrogen. The water electrolysis reaction (water decomposition reaction) shown in (3) is started.
(Anode): H ₂ O → _1/2 O ₂ + 2H ⁺ + 2e ⁻ (3)

Here, the water in the vicinity of the catalyst of the anode 54 is used for the water splitting reaction at the anode 54 shown in the above formula (3). For this reason, if the moisture of the anode 54 is consumed or the catalyst is covered with oxygen generated by the water splitting reaction, the water on the catalyst is insufficient and it is difficult to continue the water splitting reaction. In such a state, the potential of the anode 54 of the hydrogen-deficient cell rises, and then the carbon reaction (anodic corrosion reaction) in the anode 44 shown in the following formula (4) starts.
(Anode): 1 / 2C + H ₂ O → 1 / 2CO ₂ + 2H ⁺ + 2e ⁻ (4)

  As described above, when the hydrogen deficient state is left as it is, the irreversible corrosion reaction of the anode 54 shown in the above formula (4) proceeds in the hydrogen deficient cell 50. Thus, in the present embodiment, when the lack of hydrogen in the fuel cell stack 10 is detected, a return process is performed in which the anode is filled again with hydrogen. Thereby, the lack of hydrogen in the anode 54 can be eliminated, and the anode corrosion reaction shown in the above formula (4) can be suppressed. Note that the return processing method is not an essential part of the present invention, and is a known method, and therefore detailed description thereof will be omitted.

[Suppression of cathodic corrosion reaction due to return treatment]
Next, with reference to FIG. 3, the cathode corrosion reaction associated with the recovery process from the hydrogen deficient state will be described. FIG. 3 is a schematic diagram showing a state of the fuel battery cell 60 in which hydrogen deficiency occurs in the anode 54.

  As shown in FIG. 3, in the hydrogen deficient state, the electrolysis reaction of water proceeds in the vicinity of the catalyst of the anode 54 to generate the deficient hydrogen, so that a large amount of oxygen exists. For this reason, when hydrogen begins to flow again into the hydrogen-deficient cell due to the return processing, a range in which hydrogen exists and a range in which oxygen exists on the catalyst are temporarily formed on the anode 54.

Here, in the range where hydrogen is present on the catalyst of the anode 54, the normal power generation reaction represented by the above formulas (1) and (2) occurs between the anode 54 and the cathode 56. On the other hand, in the range where oxygen exists, as shown in the following formula (5), oxygen staying at the anode 54, protons that are supplied by moving through the electrolyte membrane 52, and electrons generated by the above formula (1) Reacts with each other to form water at the anode 54, and at the cathode 56, a water decomposition reaction represented by the following formula (6) occurs. That is, a partial battery is formed in a part of the hydrogen-deficient cell by the reactions of the following formulas (5) and (6). Further, when the above reaction proceeds and the potential of the cathode 56 further increases, a corrosion reaction of carbon contained in the cathode 56 represented by the following formula (7) and an elution reaction of the catalyst represented by (8) occur.
(Anode): 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O (5)
(Cathode): H ₂ O → 2H ⁺ + 1 / 2O ₂ + 2e ⁻ (6)
: 1 / 2C + H ₂ O → 2H ⁺ + 1 / 2CO ₂ + 2e ⁻ (7)
: Pt → Pt ²⁺ + 2e ⁻ (8)

  As described above, when the above-described series of reactions occur during the recovery process from the lack of hydrogen, the cathode 56 is corroded. Therefore, in the present embodiment, the oxygen component of the cathode 56 is reduced as much as possible before the return process is executed, so that the cathode 56 is in an oxygen-deficient state. If the cathode 56 is in an oxygen-deficient state, the power generation reaction shown in the above formula (2) is suppressed, so that a partial battery is not formed in the hydrogen-deficient cell even if the recovery process from the hydrogen deficiency is performed. For this reason, the situation where the corrosion reaction of the cathode proceeds due to the recovery process from the lack of hydrogen can be effectively suppressed.

  More specifically, the oxygen component reduction process at the cathode 56 is performed by first stopping the supply of the cathode gas to the cathode 56. Thereby, the situation where oxygen is introduced into the cathode 56 can be avoided. In parallel with this, a process of consuming oxygen staying at the cathode 56 by the power generation reaction shown in the above equation (2) is performed. In order to suppress the cathode corrosion reaction represented by the above formulas (7) and (8), it is desirable to reduce the oxygen at the cathode 56 to substantially zero. For this reason, the power generation reaction of the fuel cell stack 10 is continued as much as possible, and oxygen at the cathode 56 is consumed as much as possible.

  The reaction potential of the water generation reaction shown in the above formula (5) is 0.7 to 0.8 V, and the reaction potential of the cathodic corrosion reaction shown in the above formulas (7) and (8) is 1.2 V or more. It is. For this reason, if the amount of oxygen is reduced to a level at which the cell voltage at the time of the recovery process from the lack of hydrogen is 0.5 V or less, the water decomposition reaction shown in the above equation (6) is predominantly performed at the cathode 56. The reactions shown in the above formulas (7) and (8) can be effectively suppressed.

[Specific Processing in Embodiment 1]
FIG. 4 is a flowchart showing a routine executed by the system to suppress the cathodic corrosion reaction of the fuel battery cell in the first embodiment of the present invention. The routine of FIG. 4 is a routine that is repeatedly executed during the power generation of the fuel cell stack 10. In the routine shown in FIG. 4, first, the voltage of the fuel cell is detected (step 100). Here, specifically, it is detected for each fuel cell based on the output signal of the voltmeter 46 arranged in the fuel cell system.

  Next, the minimum cell voltage is calculated (step 102). Here, specifically, the voltage values of the respective fuel cells detected in step 100 are compared to determine the minimum minimum cell voltage. Next, it is determined whether or not there is a cell in the fuel cell stack 10 in which hydrogen depletion has occurred (step 104). In a fuel cell in which hydrogen deficiency occurs, the cell voltage decreases. For this reason, when the voltage of the fuel cell is smaller than a predetermined threshold value, it can be determined that the lack of hydrogen has occurred. Specifically, it is determined whether or not the minimum cell voltage obtained in step 102 is smaller than a reference voltage (threshold value).

  If it is determined in step 104 that cell voltage <reference voltage is established, it is determined that hydrogen shortage has occurred, and the supply of cathode gas is stopped (step 106). Here, specifically, the driving of the compressor 26 that supplies the cathode gas is stopped. Here, the compressor 26 cannot be stopped immediately in response to the stop request due to its structure. Further, there is a possibility that oxygen staying inside the cathode gas passage 20 and the cathode offgas passage 22 gradually flows into the fuel cell stack 10. For this reason, in step 106, the on-off valves 32 and 34 are closed. Thereby, the inflow of oxygen into the fuel cell stack 10 can be effectively suppressed.

  Next, a process of consuming oxygen staying inside the fuel cell stack 10 of the fuel cell stack 10 is executed (step 108). Here, specifically, the power generation reaction in the fuel cell stack 10 is continued by the load 44, and the oxygen remaining in the stack is consumed until it becomes substantially zero.

  Next, a recovery process from the lack of hydrogen is executed (step 110). Here, specifically, a process of filling the anode 54 of the hydrogen-deficient cell with hydrogen again is executed. After step 108, the oxygen in the fuel cell stack 10 is reduced and the cathode 56 is in an oxygen-deficient state. For this reason, it is possible to perform the recovery process from the lack of hydrogen while suppressing the corrosion reaction of the cathode by the above process. On the other hand, if it is not determined in step 104 that cell voltage <reference voltage, it is determined that no hydrogen shortage has occurred, and this routine is immediately terminated.

  As described above, in the system of the first embodiment, when it is determined that there are hydrogen-deficient cells in the fuel cell stack 10, the oxygen in the fuel cell stack 10 is consumed to a level at which the cathode corrosion reaction does not proceed. The Thereby, it is possible to effectively suppress the cathode corrosion reaction that occurs during the recovery process from the lack of hydrogen.

  By the way, in Embodiment 1 mentioned above, in order to stop supply of cathode gas, the drive of the compressor 26 is stopped, However, The supply stop method of cathode gas is not restricted to this. That is, a bypass flow path from the downstream of the compressor 26 of the cathode gas flow path 20 to the cathode off gas flow path 22 is arranged, and when a cathode gas supply stop request is made, the cathode gas passes through the bypass flow path to the cathode off gas flow path 22. It is good also as switching a flow path so that it may flow. Further, the switching control of the flow path may be combined with the closing control of the on-off valves 32 and 34.

  In the first embodiment described above, the power generation reaction is continued until the oxygen staying inside the fuel cell stack 10 becomes substantially zero, but the oxygen consumption is not limited to this. That is, during the recovery process, the smaller the amount of oxygen at the cathode, the more the cathode potential rise is suppressed. Therefore, the cathode corrosion reaction can be effectively suppressed by consuming oxygen to a level at which the cathode potential does not rise above the reaction potential of the cathode corrosion reaction shown in the above formulas (7) and (8). .

  In the first embodiment described above, the control device 40 executes the process of step 104 so that the “fuel shortage detecting means” in the first invention executes the process of step 106. Thus, the “supply stop unit” in the first invention implements the process of step 108, thereby realizing the “reducing unit” in the first invention.

  In the first embodiment described above, the “consumption means” according to the second or third aspect of the invention is realized by the control device 40 executing the process of step 108.

In the first embodiment described above, the “supply stop unit” according to the fifth aspect of the present invention is realized by the control device 40 executing the process of step 106.

Embodiment 2. FIG.
[Features of Embodiment 2]
The system of the second embodiment can be realized by causing the system to execute a routine shown in FIG. 7 to be described later using the hardware configuration shown in FIG.

  In the first embodiment described above, when the recovery process from the lack of hydrogen is performed, the supply of oxygen to the cathode 56 is stopped, and oxygen in the fuel cell stack 10 is consumed. As a result, oxygen in the cathode 56 is reduced, and the corrosion reaction of the cathode due to the recovery process from the lack of hydrogen is effectively suppressed.

  In the second embodiment, in order to reduce the oxygen at the cathode 56, the discharge of oxygen from the cathode 56 is promoted. More specifically, the supply of oxygen to the cathode 56 is stopped. At the same time, the pressure regulating valve 28 provided in the cathode offgas passage 22 is fully opened. Thereby, since the outlet pressure of the cathode 56 can be instantaneously reduced, the oxygen partial pressure of the cathode 56 can be reduced, and the corrosion reaction of the cathode due to the recovery process from the lack of hydrogen can be effectively suppressed.

[Specific Processing in Second Embodiment]
FIG. 5 is a flowchart showing a routine executed by the system to suppress the cathodic corrosion reaction of the fuel cell in the second embodiment of the present invention. The routine of FIG. 5 is a routine that is repeatedly executed during the power generation of the fuel cell stack 10. In the routine shown in FIG. 5, first, the voltage of the fuel cell is detected (step 200). Next, the minimum cell voltage is calculated (step 202). Next, it is determined whether or not there is a cell in which hydrogen depletion has occurred in the fuel cell stack 10 (step 204). Here, specifically, the same processing as steps 100 to 104 shown in FIG. 4 is executed.

  If it is determined in step 204 that the cell voltage <the reference voltage is established, it is determined that hydrogen shortage has occurred, and the supply of the cathode gas is stopped (step 206). Here, specifically, the same processing as step 106 shown in FIG. 4 is executed.

  Next, a process of discharging oxygen staying inside the fuel cell stack 10 of the fuel cell stack 10 is executed (step 208). Here, specifically, the pressure regulating valve provided in the cathode off-gas flow path 22 is controlled to be fully opened at the same time as the supply of the cathode gas is stopped in the above step 206. As a result, the pressure in the cathode off-gas flow path 22 is instantaneously lowered to atmospheric pressure, and oxygen remaining in the cathode 56 is discharged.

  Next, a recovery process from the lack of hydrogen is executed (step 210). Here, specifically, the same processing as step 110 shown in FIG. 4 is executed. Thus, this routine is terminated. On the other hand, if it is not determined in step 204 that the cell voltage <the reference voltage is established, it is determined that no hydrogen shortage has occurred, and this routine is immediately terminated.

  As described above, in the system of the second embodiment, when it is determined that there are hydrogen-deficient cells in the fuel cell stack 10, the supply of the cathode gas is stopped, and the pressure in the cathode off-gas flow path 22 is high. It is instantaneously reduced to atmospheric pressure. Thereby, oxygen staying at the cathode 56 can be effectively discharged, and the cathode corrosion reaction that occurs during the recovery process from the lack of hydrogen can be suppressed.

  By the way, in Embodiment 2 mentioned above, in order to stop supply of cathode gas, the drive of the compressor 26 is stopped, However, The supply stop method of cathode gas is not restricted to this. That is, a bypass flow path from the downstream of the compressor 26 of the cathode gas flow path 20 to the cathode off gas flow path 22 is arranged, and when a cathode gas supply stop request is made, the cathode gas passes through the bypass flow path to the cathode off gas flow path 22. It is good also as switching a flow path so that it may flow.

  In the second embodiment described above, the control device 40 executes the process of step 204, so that the “fuel shortage detection means” in the first invention executes the process of step 206. Thus, the “supply stop means” in the first invention implements the process of step 208, thereby realizing the “reducing means” in the first invention.

In the second embodiment described above, the “discharge means” in the first aspect of the present invention is realized by the control device 40 executing the processing of step 208 described above.

In the second embodiment described above, the “control means” according to the first aspect of the present invention is realized by the control device 40 executing the process of step 208 described above.

In the second embodiment described above, the pressure regulating valve 28 corresponds to the “pressure regulating valve” in the fourth aspect of the present invention.

In the second embodiment described above, the “supply stop unit” according to the fifth aspect of the present invention is realized by the control device 40 executing the process of step 106.

It is a figure for demonstrating the structure of Example 1 of this invention. It is a schematic diagram for demonstrating the electric power generation reaction of a fuel cell. It is a schematic diagram for demonstrating the cathode corrosion reaction in a hydrogen deficient state. 3 is a flowchart of a routine executed in the first embodiment. 6 is a flowchart of a routine executed in the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell stack 12 Anode gas flow path 14 Anode off gas flow path 16 Anode gas supply source 18 Pressure regulating valve 20 Cathode gas flow path 22 Cathode off gas flow path 24 Air cleaner 26 Compressor 28 Pressure regulating valve 40 Control device 42 Inverter 44 Load 46 Voltmeter 50 , 60 Fuel cell 52 Electrolyte membrane 54 Anode 56 Cathode

Claims (5)

In a fuel cell system that performs a return process to eliminate fuel shortage when fuel shortage occurs at the anode of the fuel cell,
A fuel shortage detecting means for detecting a fuel shortage in the anode;
Supply stop means for stopping supply of oxidizing gas to the cathode of the fuel cell prior to the return processing when the fuel shortage is detected;
A reduction means for reducing the amount of oxidative gas remaining in the cathode prior to the return process when the fuel shortage is detected ,
The weight loss means is
A discharge means for discharging the staying oxidizing gas to the outside of the fuel cell when the fuel shortage is detected;
The discharging means is
A pressure adjusting device for adjusting the pressure of the cathode;
Control means for controlling the pressure adjusting device so as to decrease the outlet pressure of the cathode when the fuel shortage is detected;
A fuel cell system comprising: The weight loss means is
2. The fuel cell system according to claim 1, further comprising a consumption means for consuming the staying oxidizing gas when the fuel shortage is detected. The consumption means is
The fuel cell system according to claim 2, wherein the staying oxidizing gas is consumed by a power generation reaction of the fuel cell. The fuel cell system according to any one of claims 1 to 3, wherein the pressure adjusting device is a pressure regulating valve arranged in a flow path through which the gas discharged from the cathode flows. Branching from the downstream side of the compressor disposed in the flow path through which the oxidizing gas flows, further comprising a branch flow path connected to the flow path through which the gas discharged from the cathode flows,
The fuel cell system according to any one of claims 1 to 4 , wherein the supply stop unit switches the flow destination of the oxidizing gas to the branch flow path when the fuel shortage is detected.

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