JP2014002930A - Method for detecting fault in circulation flow passage valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting a fault in a circulation flow passage valve that allows low-cost and proper detection of a fault in the circulation flow passage valve.SOLUTION: A method for detecting a fault in a circulation flow passage valve includes: a return passage that branches off from a cathode off-gas emission passage and that is connected to a cathode supply passage upstream of a compressor 31; a circulation flow passage valve 25 that is provided in the return passage; and system state quantity detection means that includes at least one of a first pressure sensor P, an oxygen concentration meter D, a second pressure sensor P, and an output detector 41. An ECU 51 executes: a cathode off-gas circulation step of circulating cathode off-gas through the return passage; a discharge step of allowing a fuel cell to discharge; and a fault determination step of making fault determination of the circulation flow passage valve 25 on the basis of system state quantity that is detected by the system state quantity detection means.

Description

  The present invention relates to a failure detection method for a circulation flow path valve provided in a fuel cell system.

  In the fuel cell system, when the power generation of the fuel cell is stopped, hydrogen on the anode side moves to the cathode side through the membrane (ion exchange membrane), and conversely, air on the cathode side moves to the anode side through the membrane. May occur. When the cross leak occurs, hydrogen and oxygen of the fuel cell react with each other to generate OH radicals, leading to deterioration of the fuel cell.

  As a technique for preventing such cross leak, for example, a technique described in Patent Document 1 is known. That is, in the fuel cell system described in Patent Document 1, after the supply of the fuel gas to the anode is stopped, the cathode flow path reuse valve is opened to introduce the fuel gas into the recirculation loop. Then, oxygen and hydrogen are reacted in a combustor provided in the recirculation loop to replace the cathode channel with nitrogen, and then the anode channel is also replaced with nitrogen through a purge valve.

Special Table 2007-506243

In the technique described in Patent Document 1, for example, when the cathode flow path reuse valve fails to close (that is, when the valve body remains closed even when a valve opening command is input), the cathode pressure increases, There is a risk of damage to fuel cells and piping.
In addition, when the cathode flow path reuse valve fails to open (that is, the valve body remains open even when a valve closing command is input), the cathode off-gas is placed upstream of the cathode flow path during normal power generation. However, there is a problem that stoichiometric shortage (insufficient amount of supplied oxygen with respect to the amount of oxygen supplied to the reaction) tends to occur.
In addition, if a cathode flow path reuse valve having a failure detection function is installed, there is a problem that costs are increased.

  Therefore, an object of the present invention is to provide a failure detection method for a circulation passage valve that can appropriately detect the failure of the circulation passage valve at low cost.

  In order to solve the above problems, a failure detection method for a circulation flow path valve according to the present invention includes a fuel cell in which an anode gas is supplied to an anode flow path and a cathode gas is supplied to a cathode flow path to generate power, and the cathode A cathode gas supply channel connected to the inlet of the channel; a cathode offgas discharge channel connected to the outlet of the cathode channel; and a cathode gas supply channel connected to the cathode gas supply channel. Cathode gas delivery means for delivering cathode gas toward the inlet, a sealing valve provided in the cathode offgas discharge channel, a branch from the cathode offgas discharge channel upstream of the sealing valve, and the cathode A return channel connected to the cathode gas supply channel upstream of the gas delivery means, and a circulation channel valve provided in the return channel, A first pressure detection means provided in the gas supply flow path; an oxygen concentration detection means provided in the cathode gas supply flow path; and a second pressure provided in the anode gas supply flow path connected to the inlet of the anode flow path. Based on the system state quantity detected by the system state quantity detection means, the system state quantity detection means including at least one of the pressure detection means, and the generated current detection means for detecting the generated current of the fuel cell. And a control means for determining a failure of the circulation flow path valve, and a failure detection method of the circulation flow path valve executed in a fuel cell system, wherein the control means closes the sealing valve, A command signal for opening the circulation flow path valve is output, and the cathode gas delivery means is driven to circulate the cathode off gas through the return flow path. Performing a step, a discharging step for discharging from the fuel cell, and a failure determining step for determining a failure of the circulation flow path valve based on a system state quantity detected by the system state quantity detecting means. It is characterized by.

According to this configuration, when the sealing valve is closed in the cathode off gas circulation step, the circulation flow path valve is opened, and the cathode gas delivery means is driven, the cathode off gas is circulated as follows. That is, the cathode off gas flowing out from the cathode flow path of the fuel cell returns to the cathode flow path through the cathode off gas discharge flow path, the return flow path, and the cathode gas supply flow path due to the negative pressure from the cathode gas delivery means.
Thus, the cathode gas concentration can be reduced by reacting with the anode gas while circulating the cathode off-gas.

Further, by discharging from the fuel cell in the discharging step, the charge generated by the electrode reaction is released and the electrode reaction proceeds, and the cathode gas and the anode gas are consumed.
Further, in the failure determination step, the failure determination of the circulation flow path valve is performed based on the system state quantity. Here, the system state quantity includes at least one of first pressure detection means, oxygen concentration detection means, second pressure detection means, and generated current detection means. Since the failure of the circulation channel valve is detected based on the behavior of the system state quantity, it is not necessary to provide a failure detection function in the circulation channel valve itself. Therefore, the failure of the circulation flow path valve can be detected appropriately at low cost.

  Further, in the failure detection method for the circulation flow path valve, the control means may cause a failure of the circulation flow path valve when the pressure detected by the first pressure detection means exceeds a predetermined value in the failure determination step. It is preferable to determine that

  According to such a configuration, when the circulation flow path valve is closed, when the cathode gas delivery means is driven in the cathode off gas circulation step, the flow path through which the cathode off gas circulates is blocked. Pressure increases. Therefore, when the detection value of the first pressure detection means provided in the cathode gas supply flow path exceeds a predetermined value, it can be determined that the circulation flow path valve is closed.

  Further, in the failure detection method of the circulation flow path valve, the control means controls the output voltage of the fuel cell to be a predetermined value in the discharge step, and detects the generated current in the failure determination step. When the generated current detected by the means exceeds a predetermined value and / or when the generated current integrated value that is an integrated value of the generated current exceeds a predetermined value, it is determined that the circulation flow path valve has a closed failure. It is preferable.

  According to this configuration, when the circulation flow path valve is closed, the generated current value of the fuel cell is increased by controlling the output voltage of the fuel cell to be a predetermined value in the discharging step. Therefore, when the generated current value detected by the generated current detection means exceeds a predetermined value and / or when the generated current integrated value exceeds a predetermined value, it can be determined that the circulation flow path valve is closed.

  Further, in the failure detection method of the circulation flow path valve, the control means, when the oxygen concentration detected by the oxygen concentration detection means exceeds a predetermined value in the failure determination step after the discharge step ends, It is preferable to determine that the circulation flow path valve has a closed failure.

  According to this configuration, when the circulation channel valve is closed, the cathode off-gas circulation through the return channel is blocked. Further, since the cathode gas is supplied to the cathode channel by the cathode gas delivery means, the oxygen concentration in the cathode gas supply channel hardly decreases. Therefore, when the oxygen concentration detected by the oxygen concentration detection means exceeds a predetermined value, it can be determined that the circulation flow path valve is closed.

  Further, in the failure detection method of the circulation flow path valve, the control means, after the discharge step is finished, the pressure value detected by the second pressure detection means in the failure determination step is less than a predetermined value. In this case, it is preferable to determine that the circulation flow path valve is closed.

  According to such a configuration, when the circulation flow path valve is closed, the anode gas is consumed by the electrode reaction in the fuel cell, so that the pressure in the anode gas supply flow path decreases. Therefore, when the pressure value detected by the second pressure detection means is less than the predetermined value, it can be determined that the circulation flow path valve is closed.

  Further, in the circulation channel valve failure detection method, after the discharge step is completed, the control means outputs a valve closing command to the circulation channel valve in the failure determination step for a first predetermined time. When the pressure value detected by the first pressure detecting means is less than a first predetermined value after the passage, it is preferable to determine that the circulation flow path valve is in an open failure.

According to such a configuration, when the circulation channel valve is in an open failure, the cathode gas supply channel in which the second pressure detecting means is installed is the cathode channel, the cathode offgas discharge channel, and the return channel. And communicates with the external space through (that is, the atmosphere is open to the atmosphere).
That is, even after the discharge step is completed, the cathode side is in the atmosphere open system, so the detection value of the first pressure detection means is substantially the same as the atmospheric pressure. Therefore, when the pressure value detected by the first pressure detection means is less than the first predetermined value, it can be determined that the circulation flow path valve is open. The first predetermined time and the first predetermined value are appropriately set so that the case where the circulation passage valve is normal and the case where it is an open failure can be distinguished.

  Further, in the failure detection method for the circulation flow path valve, after the discharge step is completed, the failure determination step outputs a valve closing command to the circulation flow path valve and is longer than the first predetermined time. When the pressure value detected by the first pressure detection means exceeds the second predetermined value after the second predetermined time has elapsed, it is preferable to determine that the circulation flow path valve is open.

  As described above, when the circulation flow path valve is in an open failure, the cathode gas supply flow path in which the second pressure detecting means is installed is an open system. Therefore, if the pressure value detected by the first pressure detection means exceeds the second predetermined value after the elapse of the second predetermined time longer than the first predetermined time, it can be determined that the circulation flow path valve is in an open failure. The second predetermined time and the second predetermined value are appropriately set so that the case where the circulation flow path valve is normal and the case where it is an open failure can be distinguished.

  ADVANTAGE OF THE INVENTION According to this invention, the failure detection method of the circulation channel valve which can detect the failure of a circulation channel valve appropriately at low cost can be provided.

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. It is a time chart at the time of performing an off-gas recirculation process and scavenging of a diluter in a fuel cell system, (a) is a rotation speed of a compressor, (b) is an open / close state of an inlet sealing valve, and (c) is an outlet sealing. Open / closed state of valve, (d) Opening degree of back pressure valve, (e) Open / closed state of circulation flow path valve, (f) Open / closed state of STK bypass flow path valve, (g) Open / close state of DIL assist flow path valve It shows the time change of the state. 4 is a time chart when performing off-gas recirculation processing and scavenging of a diluter in a fuel cell system, where (a) is an open / close state of a shut-off valve, (b) is on / off of an injector, and (c) is on of a hydrogen pump. (D) is the anode pressure, (e) is the contactor on / off, (f) is the output voltage of the fuel cell, and (g) is the time variation of the discharge current of the fuel cell. It is explanatory drawing which shows the flow of the anode offgas and cathode offgas at the time of an offgas recirculation process. It is explanatory drawing which shows the flow of the cathode gas at the time of the scavenging process of a diluter. It is a flowchart which shows the flow of a process at the time of performing failure detection of a circulation flow path valve. (A) is a flowchart which shows the flow of a process at the time of performing the closed flow failure determination process 1 of a circulation flow path valve, (b) shows the flow of the process at the time of performing the closed flow failure determination process 2 of a circulation flow path valve. It is a flowchart. (A) is a graph which shows the time change of the generated current when the circulation flow path valve is normal, and (b) shows the time change of the generated current when the circulation flow path valve is closed. It is a graph. (A) is a graph showing a temporal change in the generated current integrated value when the circulation flow path valve is normal, and (b) is a time of the generated current integrated value when the circulation flow path valve is closed. It is a graph which shows a change. It is a graph which shows the time change of the cathode pressure when the circulation flow path valve is normal and when the open failure occurs.

Each embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.
Hereinafter, the case where the fuel cell system is mounted on a fuel cell vehicle will be described. However, the present invention is not limited to this. For example, a mobile body such as a ship or an aircraft, a stationary type for home use or business use, etc. Is also applicable.

<< First Embodiment >>
<Configuration of fuel cell system>
A fuel cell system 1 shown in FIG. 1 includes a fuel cell 10, an anode system that supplies hydrogen (anode gas) to the anode of the fuel cell 10, and air that contains oxygen to the cathode of the fuel cell 10 (cathode gas). ), A power consumption system that consumes the power generated by the fuel cell 10, and an ECU 51 that controls them.

(1. Fuel cell)
The fuel cell 10 is a polymer electrolyte fuel cell (PEFC), and a membrane / electrode assembly (MEA) is sandwiched between a pair of conductive separators (not shown). A plurality of unit cells (not shown) are stacked.
Each separator of the fuel cell 10 is formed with grooves and through holes for supplying hydrogen or oxygen to the entire surface of each membrane / electrode assembly, and these grooves and through holes serve as the cathode channel 11 and the anode. It functions as the flow path 12. The separator is also formed with a refrigerant flow path (not shown) through which a refrigerant (for example, water containing ethylene glycol) for cooling the fuel cell 10 flows.

  In the fuel cell 10, when hydrogen is supplied via the anode flow path 12, the electrode reaction of (Expression 1) occurs, and when air containing oxygen is supplied via the cathode flow path 11, (Expression 2) The electrode reaction occurs, and a potential difference (Open Circuit Voltage: OCV) is generated in each single cell.

2H ₂ → 4H ⁺ + 4e ⁻ (Formula 1)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (Formula 2)

(2. Cathode system)
The cathode system includes a compressor 21, a humidifier 22, an inlet sealing valve 23, an outlet sealing valve 24, a circulation channel valve 25, a back pressure valve 26, an orifice 27, and a DIL assist channel valve 28. includes a STK bypass flow path valve 29, a diluter 30, a first pressure sensor _{P C,} and the oxygen concentration meter D, and.

The compressor 21 (cathode gas delivery means) has a suction side communicating with the outside of the system (outside the vehicle) via a pipe a1, and a discharge side connected to the humidifier 22 via a pipe a2. The compressor 21 is provided in the cathode supply flow path, and sucks and compresses air from outside the system by rotating an internal impeller (not shown) in accordance with a command from the ECU 51, toward the inlet of the cathode flow path 11. To be sent.
The “cathode gas supply channel” includes pipes a1 to a4 and is connected to the inlet of the cathode channel 11.

  The humidifier 22 humidifies the cathode gas toward the cathode flow path 11, and is connected to the inlet sealing valve 23 via the pipe a3. The humidifier 22 has a hollow fiber membrane (not shown) interposed between the low-humidity air (cathode gas) flowing in via the pipe a2 and the high-humidity cathode off gas flowing in via the pipe a6. Perform water exchange.

The inlet sealing valve 23 is, for example, an electromagnetically operated on / off valve, and is connected to the inlet of the cathode channel 11 via a pipe a4. That is, the inlet sealing valve 23 is provided in the cathode gas supply flow path, and has a function of shutting off the pipe a4 on the air supply side of the fuel cell 10 in the closed state.
The outlet sealing valve 24 (sealing valve) is, for example, an electromagnetically operated on / off valve, and is connected to the outlet of the cathode channel 11 via a pipe a5. That is, the outlet sealing valve 24 is provided in the cathode offgas discharge flow path, and has a function of shutting off the pipe a5 on the cathode offgas discharge side of the fuel cell 10 in the closed state.
Here, the “cathode off-gas discharge channel” is configured to include the pipes a5 to a8 and is connected to the outlet of the cathode channel 11. Note that the downstream side of the outlet sealing valve 24 is connected to the humidifier 22 via a pipe a6.

And the cathode flow path 11 of the fuel cell 10 will be sealed by closing the inlet sealing valve 23 and the outlet sealing valve 24, respectively.
Incidentally, the inlet sealing valve 23 and the outlet sealing valve 24 may be a normally closed type valve or a normally open type valve.

The circulation flow path valve 25 is, for example, an electromagnetic on-off valve, branches off from the cathode off-gas discharge flow path (pipe a5) on the upstream side of the outlet sealing valve 24, and the cathode gas supply flow on the upstream side of the compressor 21. It is provided in the return flow path connected to the path (pipe a1).
The “return channel” includes the pipes b1 and b2. One end of the pipe b <b> 1 is connected to the pipe a <b> 5 between the outlet of the cathode channel 11 and the outlet sealing valve 24, and the other end is connected to the circulation channel valve 25. Further, one end of the pipe b <b> 2 is connected to the circulation flow path valve 25, and the other end is connected to the pipe a <b> 1 upstream from the compressor 21. The circulation flow path valve 25 is opened when an off gas recirculation process (exhaust gas recirculation: EGR) described later is performed.
In the following description, the “cathode off-gas circulation channel” includes the pipes a5, b1, b2, a1 to a4, and the cathode channel 11.

  The back pressure valve 26 controls the pressure (back pressure) of the air flowing through the cathode flow path 11 of the fuel cell 10 by adjusting the opening thereof, and the upstream side is a humidifier 22 via a pipe a7. The downstream side is connected to the diluter 30 via a pipe a8.

The orifice 27 is provided in a DIL (Diluter) assist flow path, and restricts the amount of air supplied from the compressor 21.
Here, the “DIL assist flow path” includes the pipes c3 to c5. Incidentally, one end of the pipe c3 is connected to the pipe a2, and the other end is connected to the upstream side of the orifice 27.
The DIL assist flow path valve 28 is, for example, an electromagnetic on-off valve, connected to the downstream side of the orifice 27 via a pipe c4, and connected to the diluter 30 via a pipe c5.
The DIL assist flow path valve 28 is opened when the diluter 30 is scavenged with air supplied from the compressor 21 (see FIG. 5).

The STK (Stack) bypass flow path valve 29 is, for example, an electromagnetic on-off valve, and is provided in the STK bypass flow path.
Here, the “STK bypass channel” includes the pipes c1 and c2. One end of the pipe c1 is connected to the pipe a2, and the other end is connected to the STK bypass passage valve 29. One end of the pipe c2 is connected to the STK bypass flow path valve 29, and the other end is connected to the pipe a8.
The STK bypass passage valve 29 is opened when the diluter 30 is scavenged with air supplied from the compressor 21 (see FIG. 5).

The diluter 30 is connected to the back pressure valve 26 via a pipe a8 and is connected to the purge valve 36 via a pipe d9. The diluter 30 dilutes the anode off gas flowing in through the pipe d9 when the purge valve 36 is opened with the cathode off gas flowing in through the pipe a8 (and pipes c2 and c5), and the system is connected through the pipe d10. It has a function of discharging outside.
The first pressure sensor P _C (first pressure detection means) has a function of detecting the pressure of the air flowing through the pipe a4 and outputting it to the ECU 51.
The oxygen concentration meter D (oxygen concentration detection means) has a function of detecting the concentration of oxygen (cathode gas) contained in the air flowing through the pipe a4 and outputting it to the ECU 51.

(2. Anode system)
The anode system includes a hydrogen tank 31, a shutoff valve 32, an injector 33, an ejector 34, and a hydrogen pump 35, a second pressure sensor _{P A,} the purge valve 36, the.

The hydrogen tank 31 is connected to the shut-off valve 32 via a pipe d1, and is compressed and filled with high-purity hydrogen at a high pressure.
The shut-off valve 32 is connected to the injector 33 via the pipe d2, and when opened by a command from the ECU 51, hydrogen from the hydrogen tank 31 is supplied to the anode flow path 12 of the fuel cell 10 via the anode supply flow path. It has become so.
The “anode supply channel” is configured to include the pipes d1 to d4.

  The injector 33 is connected to the ejector 34 via a pipe d3, and injects hydrogen in accordance with a command from the ECU 51. That is, the injector 33 supplies hydrogen to the anode flow path 12 by intermittently injecting hydrogen supplied through the pipe d2 through the pipe d3.

  The ejector 34 is connected to the inlet of the anode flow path 12 via the pipe d4, and generates negative pressure around the nozzle by injecting hydrogen supplied from the hydrogen tank 31 from a nozzle (not shown). Is. As a result, the anode off-gas (including unreacted hydrogen) discharged from the outlet of the anode channel 12 is sucked through the pipe d5.

The hydrogen pump 35 is a pump that sucks the anode off-gas flowing out from the anode channel 12 and pumps it toward the inlet of the anode channel 12. A pipe d6 connected to the suction side of the hydrogen pump 35 is connected to the pipe d5. A pipe d7 connected to the discharge port of the hydrogen pump 35 is connected to the pipe d4.
The second pressure sensor P _A (second pressure detection means) is a sensor that detects the pressure of hydrogen (and anode offgas) flowing through the pipe d4. Incidentally, a pressure value detected by the second pressure sensor _{P A} is output to the ECU 51.
The pipe d7 is provided with a check valve for preventing the backflow of flowing hydrogen.

  The purge valve 36 is connected to a pipe d8 branched from the pipe d5, and is connected to the diluter 30 via a pipe d9. The purge valve 36 has a function of discharging impurities (nitrogen, moisture, etc.) accumulated on the anode side to the diluter 30 by opening according to a command from the ECU 51.

<Power consumption system>
The power consumption system includes an output detector 41, a VCU 42, and a travel motor 43.
The output detector 41 (generated current detection means) includes a current sensor (not shown) and a voltage sensor (not shown), and has a function of detecting the output current and output voltage of the fuel cell 10 and outputting them to the ECU 51. Have.
The VCU 42 (Voltage Control Unit) controls the generated power of the fuel cell 10 and the charge / discharge of a battery (not shown) according to a command from the ECU 51, and an electronic circuit such as a DC / DC chopper, a DC / DC converter, etc. Built in.
The travel motor 43 is an electric motor that is rotated by electric power supplied from the fuel cell 10 and / or a battery (not shown), and serves as a power source for a moving body on which the fuel cell 10 is mounted.
In FIG. 1, a contactor that is installed between the output detector 41 and the VCU 42 and electrically connects them is not shown. In FIG. 1, an illustration of an inverter that is installed between the VCU 42 and the traveling motor 43 and converts DC power into three-phase AC power is omitted.

<Control system>
The ECU 51 (Electric Control Unit) is configured to include electronic circuits such as a CPU, a RAM, a ROM, and various interfaces, and performs various functions according to programs stored therein.
The ECU 51 receives detection signals from sensors including the first pressure sensor P _C , the second pressure sensor P _A , the oximeter D, and the output detector 41 shown in FIG. 1, an ON / OFF signal of the IG 61, and the like. Entered. The ECU 51 controls the opening / closing of each valve, the driving of each pump, the operation of the VCU 42, and the like according to each input signal.

  The ECU 51 closes the outlet sealing valve 24 when performing processing (exhaust gas recirculation processing: EGR) for recirculating the cathode off gas to the cathode gas supply flow path via the pipes b1 and b2. 25 has a function of opening the valve 25 and driving the compressor 21. As a result, the cathode offgas circulates through the return channel (pipes b1, b2) (cathode offgas circulation step).

  Further, the ECU 51 controls the output voltage to be substantially constant by the VCU 42, discharges the generated current from the fuel cell 10 via the contactor (not shown), and supplies it to the load and / or the battery (not shown). It has a function (discharge step).

  Further, the ECU 51 has a function of determining a failure of the circulation passage valve 25 based on at least one detection value among the first pressure detection means, the second pressure detection means, the oximeter D, and the output detector 41. (Failure determination step).

<Others>
IG61 (Ignition Switch) is a start switch of a fuel cell vehicle on which the fuel cell 10 is mounted, and is arranged around the driver's seat. The IG 61 outputs the ON / OFF signal to the ECU 51.
In addition, the fuel cell system 1 includes a refrigerant system that adjusts the temperature of the fuel cell 10 by driving the refrigerant pump to circulate the refrigerant through the refrigerant flow path of the fuel cell 10.

<Operation of fuel cell system>
Before describing the failure detection of the circulation flow path valve 25, the operation of the fuel cell system 1 when the circulation flow path valve 25 is functioning normally will be described.
At time t0 in FIGS. 2 and 3, the IG 61 (see FIG. 1) is in the ON state. At this time, the inlet sealing valve 23 and the outlet sealing valve 24 are opened (see FIGS. 2B and 2C), and the STK bypass passage valve 29 and the DIL assist passage valve 28 are closed. In this state (see FIGS. 2 (f) and 2 (g)), the compressor 21 is driven (see FIG. 2 (a)). As a result, air is supplied to the cathode channel 11 of the fuel cell 10. The shutoff valve 32 is opened (see FIG. 3A), and hydrogen supplied from the hydrogen tank 31 is injected from the injector 33 (see FIG. 3B). The hydrogen is supplied to the anode flow path 12 through the ejector 34.

(1. Off-gas recirculation treatment)
In order to prevent a cross leak (a phenomenon in which the fuel cell deteriorates due to OH radicals) when power generation of the fuel cell 10 is stopped, and to prevent the single cell from deteriorating due to a high voltage state, the ECU 51 is described below. The off-gas recirculation processing (Exhaust Gas Recirculation: EGR) shown is executed.

When the IG 61 is switched from ON to OFF at time t1 in the time chart shown in FIG. 2, the ECU 51 starts EGR preparation processing. That is, the ECU 51 closes the outlet sealing valve 24 (see FIG. 2C), fully closes the back pressure valve 26 (see FIG. 2D), and opens the circulation passage valve 25 (see FIG. 2D). (Refer FIG.2 (e)). As a result, the flow path communicating outside the system (outside the vehicle) via the diluter 30 is blocked.
Further, the ECU 51 closes the shutoff valve 32 (see FIG. 3A) and stops the supply of hydrogen to the fuel cell 10. Further, the ECU 51 drives the injector 33 and the hydrogen pump 35 (see FIG. 3C) to send the anode off gas into the anode flow path 12 and raise the anode pressure to a predetermined value P1 (see FIG. 3D). ). In this way, the anode pressure is increased.

Next, at time t <b> 2 in FIGS. 2 and 3, the ECU 51 starts off-gas recirculation processing (EGR) of the fuel cell system 1. That is, the ECU 51 stops the injector 33 from the state of the EGR preparation process described above (see FIG. 3B), and executes constant voltage control for controlling the output voltage of the fuel cell 10 to the predetermined value V1 by the VCU 42. (See FIG. 3F). In the “constant voltage control”, in addition to the case where the target output power of the fuel cell 10 is set to a constant value, the output power of the fuel cell 10 is decreased and voltage control is performed so as to be within a predetermined range set in advance. It includes cases where it is performed.
Incidentally, when performing the off-gas recirculation process, the outlet sealing valve 24 may be opened as shown by a broken line in FIG. In this case, the back pressure valve 26 in the fully closed state also functions as a “sealing valve”.

FIG. 4 is an explanatory diagram of the fuel cell system at the time of off-gas recirculation (EGR), and the thick lines indicate the flow of anode off-gas and the flow of cathode off-gas. Further, among the various valves, those that are closed are painted black (the same applies to FIG. 5).
As shown in FIG. 4, the cathode off gas flowing out from the cathode flow channel 11 flows into the compressor 21 through the pipes a5 and b1, the circulation flow path valve 25, and the pipes b2 and a1 due to the negative pressure on the suction side of the compressor 21. Then, it circulates through the cathode off-gas circulation passage.

  In addition, on the anode side, the shutoff valve 32 is closed and the hydrogen pump 35 is driven in a state where the injector 33 is stopped, so that the anode off-gas circulation flow path (pipe d4, anode flow path 12, and pipes d5 to d7) is anode. Off-gas circulates.

In addition, the electric charge produced | generated by the electrode reaction in the fuel cell 10 is discharged (discharged) via a contactor (not shown) and VCU42. The electric power is charged in a battery (not shown), supplied to a load, or consumed by a discharge resistor. Further, the water generated by the electrode reaction is accompanied by the flow of air flowing in from the compressor 21 and flows out from the cathode channel 11.
In this way, by the electrode reaction in the fuel cell 10 and the cathode off-gas recirculation, oxygen is consumed on the cathode side of the fuel cell 10 and hydrogen is consumed on the anode side while discharging (discharge) is performed. .

(2. Diluter scavenging)
2 and 3, the ECU 51 starts scavenging the diluter 30. That is, the ECU 51 closes the inlet sealing valve 23 and the circulation passage valve 25 (see FIG. 2B and FIG. 2E), the STK bypass passage valve 29, and the DIL assist passage valve 28 (see FIG. 2). 2 (f) and FIG. 2 (g)) are opened. Further, the ECU 51 increases the rotational speed of the compressor 21 to a predetermined value r1 (see FIG. 2 (a)).
Further, the ECU 51 stops driving the hydrogen pump 35 (see FIG. 3C), switches the contactor (not shown) from ON to OFF (see FIG. 3E), and connects the fuel cell 10 and the load. Separate.

  Then, as shown in FIG. 5, the air sent from the compressor 21 via the pipe a2 flows into the diluter 30 via the pipe c1, the STK bypass passage valve 29, and the pipe c2. In this way, hydrogen stored in the diluter 30 is pushed out by allowing air to flow into the diluter 30 via the STK bypass flow path.

  The air sent from the compressor 21 via the pipe a2 flows into the orifice 27 via the pipe c3, and is restricted to a predetermined flow rate by the orifice 27. Further, the air flowing out from the orifice 27 flows into the diluter 30 through the pipe c4, the DIL assist flow path valve 28, and the pipe c5. In this way, by allowing air to flow into the diluter 30 via the DIL assist flow path, the flow rate of the air flowing into the diluter 30 is adjusted according to the opening degree of the DIL assist flow path valve 28.

When the scavenging of the diluter 30 is completed, the ECU 51 stops driving the compressor 21 at time t4 in FIG. 3 (see FIG. 2A), and the STK bypass passage valve 29 and the DIL assist passage valve 28 ( 2 (f) and FIG. 2 (g)) are closed, and the fuel cell system 1 is stopped (that is, in the soak state).
As described above, after the off-gas recirculation process is performed, the cathode channel 11 can be blocked in a state where almost no oxygen remains by sealing the cathode channel 11. Therefore, cross leak can be suppressed and deterioration of the single cell with which the fuel cell 10 is provided can be prevented.

<Fault detection of circulation flow path valve>
Hereinafter, the closed failure detection and the open failure detection of the circulation flow path valve 25 will be sequentially described with reference to the flowcharts of FIGS.
“Closed failure” means a failure in which the circulation flow path valve 25 remains closed even when a valve opening command is input from the ECU 51.
The “open failure” means a failure in which the circulation flow path valve 25 remains open even when a valve closing command is input from the ECU 51.

In “START” shown in FIG. 6, IG 61 (see FIG. 1) is in an OFF state, and the above-described EGR preparation processing (see times t1 to t2 in FIGS. 2 and 3) is completed.
In step S101, the ECU 51 starts an off-gas recirculation process (EGR). The off-gas recirculation process is the same as that described with reference to FIG.
In step S102, the ECU 51 stores the atmospheric pressure _Patm detected by a pressure sensor (not shown) in a storage means (not shown).
Next, in step S103, the ECU 51 executes a closed failure detection process 1.

(1. Closed failure detection process 1)
In step S1031 of FIG. 7 (a) ECU 51 is the cathode pressure _{P C} which is detected by the first pressure sensor _{P C} is greater than the value obtained by adding a predetermined value ΔP _C (≧ 0) to the atmospheric pressure _{P atm} which is the It is determined whether or not. Incidentally, the predetermined value [Delta] P _C is a preset value (e.g., 10KPaG), stored in storage means (not shown).

At the time of EGR shown in FIG. 4, when the cathode offgas circulation channel valve 25 is closed, the downstream side of the cathode channel 11 is closed by the outlet sealing valve 24 and the circulation channel valve 25. That is, even when air is supplied from the compressor 21, the passage through which the cathode off gas flows out is closed, so the pressure of the cathode gas flowing through the pipe a4 increases.
Air pressure _{P C} is, if it exceeds the (atmospheric pressure _{P atm} + predetermined value _{ΔP C) (S1031 → Yes)} , the processing of the ECU51 advances to step S1035.
On the other hand, the air pressure _{P C} is, if (the atmospheric pressure _{P atm} + predetermined value [Delta] P _C) or less (S1031 → No), the processing of the ECU51 advances to step S1032.

Next, in step S1032, the ECU 51 determines whether or not the generated current I _FC of the fuel cell 10 detected by the output detector 41 (see FIG. 1) exceeds a threshold value I1. Incidentally, the threshold value I1 is a preset value and is stored in a storage means (not shown).
When the circulation flow path valve 25 is closed during EGR, air is sucked from the atmosphere by driving the compressor 21 and supplied (pushed) to the cathode flow path 11. The air has a higher oxygen concentration than the cathode offgas. Accordingly, since fresh air is supplied at a relatively high pressure, the electrode reaction of (Formula 2) is promoted. Further, the constant voltage control is performed by the VCU 42 in such a state, so that the value of the generated current becomes larger than when the circulation flow path valve 25 is normal.

FIG. 8A is a graph showing a temporal change in the generated current when the circulation flow path valve is normal, and FIG. 8B is a graph of the generated current when the circulation flow path valve is closed. It is a graph which shows a time change. 8A and 8B, the horizontal axis represents the elapsed time since the start of the off-gas recirculation process, and the vertical axis represents the power generation of the fuel cell 10 detected by the output detector 41. Current.
As shown in FIG. 8A, when the circulation flow path valve 25 is normal, the generated current of the fuel cell 10 changes in a range less than the threshold value I1. On the other hand, as shown in FIG. 8 (b), if the circulation flow path valve 25 is disabled閉故, power generation current of the fuel cell 10 is greater than the elapsed time _t C ~t threshold I1 near _D.
Therefore, it is preferable that the determination process in step S1032 described above is performed at a timing (for example, elapsed time t _S ) exceeding the threshold value I1 when the circulation flow path valve 25 has a closed failure.

Returning to FIG. 7, the description will be continued. When the generated current I _FC exceeds the threshold value I1 in step S1032 (S1032 → Yes), the process of the ECU 51 proceeds to step S1035. On the other hand, when the generated current I _FC is equal to or less than the threshold value I1 (S1032 → No), the process of the ECU 51 proceeds to step S1033.

Next, in step S1033, the ECU 51 determines whether or not the generated current integrated value I _FC (SUM) of the fuel cell 10 exceeds the threshold value I2. Incidentally, the threshold value I2 is a preset value and is stored in a storage means (not shown).
As described above, when the circulation flow path valve 25 is closed, the value of the generated current increases, and thus the generated current integrated value also increases. The generated current integrated value is, for example, an integrated value of generated current from the time when off-gas recirculation (EGR) is started.

  FIG. 9A is a graph showing a temporal change in the generated current integrated value when the circulation flow path valve is normal, and FIG. 9B is a graph showing power generation when the circulation flow path valve is closed. It is a graph which shows the time change of an electric current integrated value. 9A and 9B, the horizontal axis represents the elapsed time since the start of the off-gas recirculation process, and the vertical axis represents the generated current after the start of the off-gas recirculation process. It is an integrated value.

As shown in FIG. 9A, when the circulation passage valve 25 is normal, the generated current integrated value of the fuel cell 10 changes within a range less than the threshold value I2. On the other hand, as shown in FIG. 9 (b), if the circulation flow path valve 25 is disabled閉故, generated current integrated value of the fuel cell 10 is greater than the threshold value I2 is the elapsed time t _E after.
Therefore, the determination process of step S1033 described above is preferably carried out in excess of threshold I2 when the circulation flow path valve 25 is disabled閉故timing (time t _E after from the start of the off-gas recirculation process).

Returning to FIG. 7, the description will be continued. When the generated current integrated value I _FC (SUM) exceeds the threshold value I2 in step S1033 (S1033 → Yes), the process of the ECU 51 proceeds to step S1035. On the other hand, when the generated current integrated value I _FC (SUM) is equal to or less than the threshold value I2 (S1033 → No), the process of the ECU 51 proceeds to step S1034.
In step S1034, the ECU 51 turns off the closed failure determination flag. In step S1035, the ECU 51 turns on the closed failure determination flag. That is, when at least one of the conditions in steps S1031 to S1033 is satisfied, the ECU 51 turns on the closed failure determination flag.

Next, in step S104 of FIG. 6, the ECU 51 determines whether or not the circulation flow path valve 25 has a closed failure. This determination is made based on whether or not the above-described closed failure determination flag is ON.
When the circulation flow path valve 25 has a closed failure (S104 → Yes), the process of the ECU 51 proceeds to step S105. In step S105, the ECU 51 interrupts the off-gas recirculation process. In step S106, the ECU 51 notifies the user that the circulation flow path valve 25 is closed. The notification is performed, for example, by lighting a failure lamp or by voice.

On the other hand, in the closed failure detection process 1 of S103, when the closed failure of the circulation flow path valve 25 is not detected (S104 → No), the process of the ECU 51 proceeds to step S107. In step S107, the ECU 51 determines whether or not the off-gas recirculation process has been completed. Note that this determination is made based on, for example, whether a predetermined time has elapsed since the start of the off-gas recirculation process.
When the off-gas recirculation process ends (S107 → Yes), the process of the ECU 51 proceeds to step S108. On the other hand, if the off-gas recirculation process has not ended (S107 → No), the ECU 51 repeats the process of step S107.
Next, in step S108, the ECU 51 executes the closed failure detection process 2.

(2. Closed fault detection processing 2)
In step S1081 in FIG. 7 (b) ECU 51 determines whether or not the anode pressure detected by the second pressure sensor _{P A} (see FIG. 1) is below the threshold value P1. The anode pressure means the internal pressure of the anode flow path 12. The threshold value P1 is a preset value and is stored in a storage unit (not shown).

As described above, when constant voltage control is performed when the circulation flow path valve 25 is closed, the electrode reaction of the fuel cell 10 is promoted and the value of the generated current increases (step S1032 in FIG. 7A). ). While the consumption of hydrogen increases due to the electrode reaction, since the shutoff valve 32 is closed, the hydrogen in the anode channel 12 gradually decreases. Therefore, when the circulation flow path valve 25 is closed, the anode pressure is reduced as compared with the normal time.
When the anode pressure is less than the threshold value P1 (S1081 → Yes), the process of the ECU 51 proceeds to step S1084. On the other hand, when the anode pressure is equal to or higher than the threshold value P1 (1081 → No), the process of the ECU 51 proceeds to step S1082.

Next, in step S1082, the ECU 51 determines whether or not the oxygen concentration D (O ₂ ) detected by the oxygen concentration meter D (see FIG. 1) exceeds the threshold value D1. The threshold value D1 is a preset value and is stored in a storage unit (not shown).
When the circulation passage valve 25 is closed, the cathode 21 does not circulate through the cathode offgas circulation passage described above, but fresh air that does not contain offgas is pumped by the compressor 21. Therefore, the oxygen concentration detected by the oxygen concentration meter D hardly decreases.
When the oxygen concentration D (O ₂ ) exceeds the threshold value D1 (S1082 → Yes), the process of the ECU 51 proceeds to step S1084. On the other hand, when the oxygen concentration D (O ₂ ) is equal to or less than the threshold value D1 (S1082 → No), the process of the ECU 51 proceeds to step S1083.

Next, in step S1083, the ECU 51 turns off the closed failure determination flag. In step S1084, the ECU 51 turns on the closed failure determination flag. That is, when at least one of the conditions in steps S1081 and S1082 is satisfied, the ECU 51 turns on the closed failure determination flag.
Next, in step S109 of FIG. 6, the ECU 51 determines whether or not there is a closed failure. This determination is made based on whether or not the above-described closed failure determination flag is ON.
If the circulation flow path valve 25 has a closed failure (S109 → Yes), the processing of the ECU 51 proceeds to step S106. On the other hand, if the circulation flow path valve 25 is not closed (S109 → No), the process of the ECU 51 proceeds to step S110.

(3. Open failure judgment processing)
In step S110, the ECU 51 determines whether or not a predetermined time Δt _A (first predetermined time) has elapsed since the valve closing command was output to the circulation flow path valve 25. The predetermined time Δt _A is a value set in advance in order to appropriately perform an open failure determination process described later, and is stored in a storage unit (not shown).
When the predetermined time Δt _A has elapsed since the valve closing command was output to the circulation flow path valve 25 (S110 → Yes), the process of the ECU 51 proceeds to step S111. On the other hand, when the predetermined time Δt _A has not elapsed since the valve closing command was output to the circulation flow path valve 25 (S110 → No), the ECU 51 repeats the process of step S110.

Next, in step S111, the ECU 51 stores the atmospheric pressure _Patm detected by a pressure sensor (not shown) in a storage means (not shown).
In step S112 ECU 51 is the cathode pressure _{P C} is: determines whether the (atmospheric pressure _{P atm} + predetermined value [Delta] P _alpha first predetermined value) less than. The predetermined value ΔP _α (≧ 0) is a preset value (for example, 10 kPaG) and is stored in a storage unit (not shown).
When the circulation flow path valve 25 is open, even if the inlet sealing valve 23 and the outlet sealing valve 24 are closed, the circulation flow path valve 25 remains open. Thus, the pipe a4 which the first pressure sensor _{P C} is installed, the cathode channel 11, the pipe a5, b1, circulation passage valve 25, to the outside of the system and communicate with each other through a pipe b2, a1 (that is, the air release System).
Then, even after the off-gas recirculation process is completed, because the air flows through the flow path, the detection value of the first pressure sensor P _C is approximately equal to the atmospheric pressure.

FIG. 10 is a graph showing a temporal change in the cathode pressure when the circulation flow path valve is normal and when the open flow failure occurs. When the circulation channel valve 25 is normal, the inlet sealing valve 23, the outlet sealing valve 24, and the circulation channel valve 25 are completely closed at the time of soaking. Accordingly, oxygen present in the sealed cathode flow path 11 reacts with hydrogen from the anode side and decreases, so that the cathode pressure decreases as the soak time elapses.
On the other hand, when the circulation flow path valve 25 has an open failure, as described above, the cathode flow path 11 is open to the atmosphere, so that the cathode pressure is substantially equal to the atmospheric pressure _Patm .

Therefore, it is preferable to perform the determination in step S112 at a timing when the cathode pressure becomes higher than (atmospheric pressure P _atm + ΔP _α ) = P _G (see FIG. 10) when the circulation flow path valve 25 has an open failure. That is, it is preferable to set the value of the predetermined time Δt _A (step S111) between the soak times 0 to t _F as shown in FIG.
Returning again to FIG. 6, the description will be continued. If the cathode pressure _{P C} is less than (the atmospheric pressure _{P atm} + predetermined value [Delta] P _alpha) in step S112 (S112 → Yes), the processing of the ECU51 advances to step S113. On the other hand, cathode pressure _{P C} is - is (atmospheric pressure _{P atm} predetermined value [Delta] P _alpha) or (S112 → No), the processing of the ECU51 advances to step S114.
In step S113, the ECU 51 notifies the user that the circulation flow path valve 25 is open. The notification is performed, for example, by a failure lamp or voice.

In step S114, the ECU 51 determines whether or not a predetermined time Δt _B (second predetermined time) has elapsed since the valve closing command was output to the circulation passage valve 25. The predetermined time Δt _B is longer than the predetermined time Δt _{A in} step S110 and is set in advance.
When the predetermined time Δt _B has elapsed since the valve closing command was output to the circulation flow path valve 25 (S114 → Yes), the process of the ECU 51 proceeds to step S115. On the other hand, when the predetermined time Δt _B has not elapsed since the valve closing command was output to the circulation flow path valve 25 (S114 → No), the ECU 51 repeats the process of step S114.

Then, ECU 51 in step S115, the cathode pressure _{P C} is -: determines higher or not than (the atmospheric pressure _{P atm} predetermined value [Delta] P _beta second predetermined value). The predetermined value ΔP _β (≧ 0) is a preset value, and is stored in a storage means (not shown).
When the circulation flow path valve 25 is in an open failure state, the step S115 is determined so that the cathode pressure becomes less than (atmospheric pressure P _atm −ΔP _β ) = P _I (see FIG. 10). It is preferable to perform the determination of S114. That is, it is preferable to set the value of the predetermined time Δt _B (step S114) between the soak times t _{I to} t _J as shown in FIG.
Cathode pressure _{P C} is - greater than (the atmospheric pressure _{P atm} predetermined value _{ΔP β) (S115 → Yes)} , the processing of the ECU51 advances to step S113. On the other hand, cathode pressure _{P C} is (atmospheric pressure _{P atm} - predetermined value [Delta] P _alpha) when less is (S115 → No), ECU 51 terminates the open failure detection processing in the circulation flow path valve 25.

<Effect>
The fuel cell system 1 according to this embodiment has the following effects.
That is, in the fuel cell system 1, the failure of the circulation passage valve 25 is detected based on the generated current value of the fuel cell 10, the change in the oxygen concentration on the cathode side, the change in the cathode pressure, or the change in the anode pressure. Therefore, it is not necessary to provide a failure detection function (such as a lift sensor) in the circulation flow path valve 25, and a general-purpose valve having a simple configuration can be used as the circulation flow path valve 25. Therefore, according to this embodiment, the cost concerning the circulation flow path valve 25 can be reduced.
Further, in the present embodiment, the cathode off gas is returned to the upstream side of the compressor 21 via the return flow path (pipe b1, b2). Therefore, the cost can be reduced to the extent that no additional pump is required to perform the off-gas recirculation process.

In the present embodiment, the failure of the circulation flow path valve 25 is detected based on system state quantities such as the cathode pressure, the anode pressure, the generated current value, and the oxygen concentration. Therefore, it is possible to appropriately detect a failure of the valve body that cannot be detected by the lift sensor and a failure of the piping system of the cathode offgas circulation passage (damage of the piping, etc.).
Further, the valve body of the circulation flow path valve 25 freezes and stops moving at a low temperature (that is, it remains closed even when a valve opening command is input, or remains open even when a valve closing command is input). ) Can be appropriately detected by the same method as described above.

Further, the timing for executing the closed failure detection process for the circulation flow path valve 25 is different from the timing for executing the open failure detection process, and the criteria for determining each failure are also different. Therefore, it is possible to detect the closed failure and the open failure of the circulation flow path valve 25 separately.
Further, when an open failure or a closed failure of the circulation flow path valve 25 is detected, the ECU 51 notifies the user of the content of the failure. Therefore, the user can appropriately cope with the detection result.

  Further, when the sealing performance by the circulation flow path valve 25 is lowered, the same phenomenon as that in the case of the open failure described above occurs, so that the decrease in the sealing performance can be appropriately detected. Therefore, since it can be grasped that oxygen is likely to enter the cathode flow path 11 of the fuel cell 10 during the soak, deterioration of the fuel cell 10 can be prevented by prompting the user to respond.

≪Modification≫
The fuel cell system 1 according to the present invention has been described above with reference to the above embodiment. However, the embodiment of the present invention is not limited to these descriptions, and various modifications can be made.
For example, in the above-described embodiment, the case where the failure detection of the circulation passage valve 25 is performed based on the generated current value of the fuel cell 10, the change in the oxygen concentration on the cathode side, the change in the cathode pressure, and the change in the anode pressure has been described. However, it is not limited to this.
That is, any of S1031 (cathode pressure), S1032 (generated current value), S1033 (generated current integrated value) in FIG. 7A, S1081 (anode pressure), and S1082 (oxygen concentration) in FIG. A closed failure of the circulation flow path valve 25 may be detected using one or a plurality of determination criteria.

Moreover, when detecting the closed failure of the circulation flow path valve 25, as shown in FIG. 8, the case where the determination is made based on whether or not the generated current is larger than the threshold value I1 has been described, but the present invention is not limited to this. For example, the time generated current is greater than the threshold value _{I P} (FIG. 8 (a) at time _(t B _-t A), FIG. 8 (b) at time _(t D _-t C)) is a predetermined time Delta] t _gamma The closed failure of the circulation flow path valve 25 may be detected depending on whether or not it is longer.
Incidentally, the above-mentioned predetermined time t _gamma, circulation passage valve 25 is set so as to distinguish between the case where it is disabled閉故and if it is normal _{(i.e., t B -t A <Δt γ} <t D -t _C ).

  Moreover, although the said embodiment demonstrated the case where the humidifier 22 was installed upstream from the inlet sealing valve 23 and downstream from the outlet sealing valve 24, it is not restricted to this. That is, the humidifier 22 may be installed at a position downstream of the inlet sealing valve 23 and upstream of the outlet sealing valve 24.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Fuel cell 11 Cathode flow path 12 Anode flow path 21 Compressor (cathode gas sending means)
23 Inlet sealing valve 24 Outlet sealing valve (sealing valve)
25 Circulating flow path valve 26 Back pressure valve (sealing valve)
41 Output detector (generated current detection means)
51 ECU (control means)
P _C first pressure sensor (first pressure detecting means)
P _A second pressure sensor (second pressure detection means)
D Oxygen concentration meter (oxygen concentration detection means)

Claims (7)

A fuel cell in which anode gas is supplied to the anode channel and cathode gas is supplied to the cathode channel to generate electricity;
A cathode gas supply channel connected to the inlet of the cathode channel;
A cathode offgas discharge channel connected to the outlet of the cathode channel;
Cathode gas delivery means that is provided in the cathode gas supply channel and sends cathode gas toward the inlet of the cathode channel;
A sealing valve provided in the cathode offgas discharge channel;
A return flow path branched from the cathode offgas discharge flow path upstream of the sealing valve and connected to the cathode gas supply flow path upstream of the cathode gas delivery means;
A circulation flow path valve provided in the return flow path,
First pressure detection means provided in the cathode gas supply flow path, oxygen concentration detection means provided in the cathode gas supply flow path, and an anode gas supply flow path connected to the inlet of the anode flow path. A system state quantity detecting means including at least one of a second pressure detecting means and a generated current detecting means for detecting a generated current of the fuel cell;
Control means for determining failure of the circulation flow path valve based on the system state quantity detected by the system state quantity detection means;
A fault detection method for a circulation flow path valve executed in a fuel cell system comprising:
The control means includes
Cathode off-gas circulation step of closing the sealing valve and outputting a command signal for opening the circulation channel valve, driving the cathode gas delivery means, and circulating the cathode off-gas through the return channel When,
A discharging step for discharging from the fuel cell;
And a failure determination step of determining a failure of the circulation flow path valve based on a system state quantity detected by the system state quantity detection means. The control means includes
2. The circulation flow according to claim 1, wherein, in the failure determination step, when the pressure detected by the first pressure detection unit exceeds a predetermined value, it is determined that the circulation flow path valve has a closed failure. Road valve failure detection method. The control means includes
In the discharging step, while controlling the output voltage of the fuel cell to be a predetermined value,
In the failure determination step, when the generated current detected by the generated current detection means exceeds a predetermined value and / or when the generated current integrated value that is an integrated value of the generated current exceeds a predetermined value, the circulating flow It is determined that the road valve is a closed fault. The fault detection method for the circulation flow path valve according to claim 1 or 2, characterized in that: The control means includes
After the discharging step is finished,
The said failure determination step WHEREIN: When the oxygen concentration detected by the said oxygen concentration detection means exceeds a predetermined value, it determines with the said circulation flow path valve being a closed failure. The fault detection method of the circulation channel valve as described in any one of Claims. The control means includes
After the discharging step is finished,
The said failure determination step WHEREIN: When the pressure value detected by the said 2nd pressure detection means is less than predetermined value, it determines with the said circulation flow path valve being closed failure. The fault detection method for the circulation flow path valve according to any one of claims 4 to 5. The control means includes
After the discharging step is finished,
In the failure determination step, when a pressure value detected by the first pressure detecting means is less than a first predetermined value after a first predetermined time has elapsed since outputting a valve closing command to the circulation flow path valve, The method for detecting a failure of a circulation flow path valve according to any one of claims 1 to 5, wherein the circulation flow path valve is determined to be an open failure. The control means includes
After the discharging step is finished,
In the failure determination step, after a valve closing command is output to the circulation flow path valve, a second predetermined time longer than the first predetermined time elapses, and a pressure value detected by the first pressure detecting means is a first value. The method for detecting a failure of a circulation flow path valve according to claim 6, wherein when the predetermined value is exceeded, it is determined that the circulation flow path valve has an open failure.

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