JP2012089306A - Fuel cell system and cross leakage detection method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to simply and surely discriminate a reduction in cell voltage by cross leakage and a reduction in cell voltage by flooding.SOLUTION: A fuel cell system 10 comprises a fuel battery stack 12 composed of a laminate of plural fuel battery cells 20 and a controller 18. The controller 18 includes a cell voltage detection unit 98 which detects the cell voltage of each fuel battery cell 20 at the time the system starts up or the system is halted or remains idling, a lowest cell voltage determination unit 100 which determines whether a detected lowest cell voltage is equal to or below a threshold, and a cross leakage determination unit 102 which, when a cell voltage detected in the periphery of the fuel battery cell 20 which has had the lowest cell voltage detected therein forms an inclined voltage pattern with its voltage rising in a direction apart from the lowest cell voltage, determines that cross leakage has been induced in the fuel battery cell 20 which has had the lowest cell voltage detected therein.

Description

  The present invention provides a fuel cell in which a fuel gas is supplied to the anode side while an oxidant gas is supplied to the cathode side and a plurality of cells that generate power are stacked, and each of the cells or two or more of the cells. The present invention relates to a fuel cell system including a cell voltage detection unit that detects a cell voltage for each cell unit including the cell unit and a cross leak detection method thereof.

  For example, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure (MEA) in which an anode side electrode and a cathode side electrode are disposed on both sides of an electrolyte membrane made of a polymer ion exchange membrane is provided by a pair of separators. The unit cell is sandwiched. This type of fuel cell is usually used as an in-vehicle fuel cell stack, for example, by stacking a predetermined number of unit cells.

  In the above fuel cell, for example, damage may occur in the solid polymer electrolyte membrane, and so-called cross leak may occur in which oxidant gas (oxygen) flows from the cathode side to the anode side. On the anode side, when hydrogen is mixed with the fuel gas, the area where the hydrogen is in contact with the solid polymer electrolyte membrane is reduced, and the hydrogen is reduced due to the reaction between the oxygen and the hydrogen. There is a problem that decreases.

  Thus, for example, a fuel cell system disclosed in Patent Document 1 is known. This fuel cell system is configured by laminating a plurality of fuel cell cells in which a fuel electrode and an oxidant electrode are arranged to face each other with an electrolyte membrane interposed therebetween, and a fuel gas containing hydrogen is contained in the fuel electrode of the fuel cell. The fuel cell stack is configured to generate power by supplying an oxidant gas containing oxygen to the oxidant electrode of the fuel cell, and the pressure of the fuel gas supplied to the fuel electrode of the fuel cell is adjusted. Fuel gas pressure adjusting means, oxidant gas pressure adjusting means for adjusting the pressure of the oxidant gas supplied to the oxidant electrode of the fuel cell, and the voltage of the fuel cell for each fuel cell or a plurality of Controlling at least one of a cell voltage measuring means for measuring each cell group of fuel cells, the fuel gas pressure adjusting means, and the oxidant gas pressure adjusting means to oxidize the fuel electrode of the fuel battery cell A differential pressure control means for generating a differential pressure in which the pressure on the fuel electrode side is higher than the pressure on the oxidizer electrode side, and changing the magnitude of the differential pressure, and the differential pressure control The gas from the fuel electrode side to the oxidant electrode side through the electrolyte membrane based on the voltage behavior of the fuel cell measured by the cell voltage measuring means while the means monotonically increases the differential pressure. And a leak determining means for determining the presence or absence of leaking cells.

JP 2009-158371 A

  In Patent Document 1 described above, since the abnormal cell voltage decrease rate is faster than the normal cell voltage decrease rate, it is determined whether or not there is a leak cell (a cell in which a cross leak has occurred).

  However, a drop in cell voltage occurs not only in the case of cross leak but also in the case of flooding due to water remaining in the gas flow path. For this reason, there is a problem that the fuel cell is misunderstood that a cross leak has occurred regardless of whether flooding has occurred, and the operation of replacing the fuel cell is performed. This is because in the case of flooding, it can be eliminated by scavenging, purging or increasing the gas flow rate, and the fuel cell can be used economically.

  The present invention solves this type of problem, and a fuel cell system capable of easily and reliably discriminating between a cell voltage drop due to cross leak and a cell voltage drop due to flooding, and a cross leak detection method therefor The purpose is to provide.

  The present invention provides a fuel cell in which a fuel gas is supplied to the anode side while an oxidant gas is supplied to the cathode side and a plurality of cells that generate power are stacked, and each of the cells or two or more of the cells. The present invention relates to a fuel cell system including a cell voltage detection unit that detects a cell voltage for each cell unit including the cell unit, and a cross leak detection method thereof.

  When this fuel cell system detects a cell voltage of a cell or a cell unit at any time during system startup, system shutdown, or idle stop, whether or not the detected minimum cell voltage is below a threshold value. A minimum cell voltage determination unit that determines whether the cell voltage detected in the periphery of the cell or the cell unit in which the minimum cell voltage is detected is increased in a direction away from the minimum cell voltage. A cross-leak determination unit that determines that a cross-leak has occurred in the cell or the cell unit in which the lowest cell voltage is detected when forming a voltage pattern;

  Further, this cross leak detection method includes a step of detecting a cell voltage of a cell or a cell unit in a state of system startup, system shutdown, or idle stop, and the detected minimum cell voltage is less than a threshold value. A cell voltage detected in the vicinity of the cell or the cell unit in which the minimum cell voltage is detected when it is determined that the minimum cell voltage is not more than the threshold value. Determining whether or not to form a ramp voltage pattern that is boosted in a direction away from the lowest cell voltage, and is detected in the vicinity of the cell or the cell unit in which the lowest cell voltage is detected. When it is determined that the measured cell voltage forms the ramp voltage pattern, a cross leak is caused in the cell or the cell unit in which the lowest cell voltage is detected. And a step of determining that.

  Further, in this cross leak detection method, when it is determined that a cross leak has occurred, at least the step of replacing the gas in the gas supply flow path on the anode side or the cathode side, and after replacing the gas, the lowest cell Preferably, the method includes a step of determining whether or not the voltage is equal to or lower than a threshold value, and a step of resetting the cross leak determination when it is determined that the minimum cell voltage exceeds the threshold value.

  Furthermore, in this cross leak detection method, it is preferable that when the cell or the cell unit in which the lowest cell voltage is detected is arranged at the stacking direction end of the fuel cell, it is determined that no cross leak is caused. .

  In this cross leak detection method, the first cell voltage having the lowest voltage next to the lowest cell voltage and the second voltage having the lowest voltage next to the first cell voltage are adjacent to the cell or cell unit in which the lowest cell voltage is detected. When a two-cell voltage is detected, it is preferable to determine that a cross leak has occurred.

  Further, in this cross leak detection method, it is preferable to perform the discharge process of the fuel cell and detect the cell voltage at the time of system startup, system stop, and idle stop.

  According to the present invention, when forming a ramp voltage pattern in which the cell voltage around the cell or cell unit in which the lowest cell voltage below the threshold is detected is boosted in a direction away from the lowest cell voltage, It is determined that a cross leak has occurred in the cell or the cell unit in which the lowest cell voltage is detected. For this reason, it is possible to easily and reliably discriminate between a decrease in cell voltage due to cross leak and a decrease in cell voltage due to flooding.

1 is a schematic configuration diagram of a fuel cell system according to an embodiment of the present invention. It is a disassembled perspective explanatory drawing of the fuel cell which comprises the said fuel cell system. It is a flowchart explaining the cross leak detection method which concerns on the 1st Embodiment of this invention. It is a subroutine of the cross leak determination process of the flowchart. It is explanatory drawing of the cell voltage in the case of a cross leak. It is explanatory drawing of the cell voltage in the case of flooding. It is a flowchart explaining the cross leak detection method which concerns on the 2nd Embodiment of this invention.

  As shown in FIG. 1, a fuel cell system 10 according to an embodiment of the present invention includes a fuel cell stack 12, an oxidant gas supply device 14 that supplies an oxidant gas to the fuel cell stack 12, and the fuel cell stack 12. A fuel gas supply device 16 that supplies fuel gas to the fuel cell stack 12, a cooling medium supply device (not shown) that supplies a cooling medium to the fuel cell stack 12, and a controller 18 that controls the entire fuel cell system 10. The fuel cell system 10 is mounted on a fuel cell vehicle (not shown), for example.

  The fuel cell stack 12 is configured by stacking a plurality of fuel cells 20. Terminal plates 22a and 22b, insulating plates 24a and 24b, and end plates 26a and 26b are disposed at both ends of the fuel cell 20 in the stacking direction, and a clamping load is applied between the end plates 26a and 26b in the stacking direction. Is done.

  As shown in FIG. 2, in the fuel battery cell 20, an electrolyte membrane / electrode structure 30 is sandwiched between first and second separators 32 and 34. The 1st and 2nd separators 32 and 34 are comprised by metal plates, carbon plates, etc., such as a steel plate, a stainless steel plate, an aluminum plate, or a plating treatment steel plate, for example.

  An oxidant gas inlet communication hole 36a for supplying an oxidant gas, for example, an oxygen-containing gas, communicates with each other in the arrow A direction, which is the stacking direction, at one edge of the fuel cell 20 in the arrow B direction. In addition, fuel gas inlet communication holes 38a for supplying fuel gas, for example, hydrogen-containing gas, are arranged in the direction of arrow C.

  The other end edge of the fuel battery cell 20 in the direction of arrow B communicates with each other in the direction of arrow A, a fuel gas outlet communication hole 38b for discharging fuel gas, and an oxidant for discharging oxidant gas. Gas outlet communication holes 36b are arranged in the direction of arrow C.

  A pair of cooling medium inlet communication holes 40a for supplying a cooling medium and a pair of cooling medium outlet communication holes 40b for discharging the cooling medium are provided at both ends of the fuel cell 20 in the direction of arrow C. It is done.

  An oxidant gas flow path 42 communicating with the oxidant gas inlet communication hole 36a and the oxidant gas outlet communication hole 36b is provided on the surface 32a of the first separator 32 facing the electrolyte membrane / electrode structure 30.

  A fuel gas passage 44 communicating with the fuel gas inlet communication hole 38a and the fuel gas outlet communication hole 38b is provided on the surface 34a of the second separator 34 facing the electrolyte membrane / electrode structure 30.

  The cooling medium inlet communication hole 40a and the cooling medium outlet communication hole 40b communicate with each other between the surface 32b of the first separator 32 and the surface 34b of the second separator 34 constituting the fuel cells 20 adjacent to each other. A medium flow path 46 is provided.

  A first seal member 48 is integrally or individually provided on the surfaces 32 a and 32 b of the first separator 32, and a second seal member 50 is integrally formed on the surfaces 34 a and 34 b of the second separator 34. Or it is provided separately.

  The first and second seal members 48 and 50 are, for example, EPDM, NBR, fluoro rubber, silicon rubber, fluorosilicon rubber, butyl rubber, natural rubber, styrene rubber, chloroprene, or acrylic rubber or the like, cushion material, Alternatively, a packing material is used.

  The electrolyte membrane / electrode structure 30 includes, for example, a solid polymer electrolyte membrane 52 in which a perfluorosulfonic acid thin film is impregnated with water, and a cathode side electrode 54 and an anode side electrode 56 that sandwich the solid polymer electrolyte membrane 52. With.

  The cathode side electrode 54 and the anode side electrode 56 are formed by uniformly applying a gas diffusion layer made of carbon paper or the like and porous carbon particles carrying a platinum alloy on the surface thereof to the surface of the gas diffusion layer. An electrode catalyst layer. The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 52.

  The first separator 32 is located between the pair of cooling medium outlet communication holes 40b (or between the pair of cooling medium inlet communication holes 40a) at the center of the long side, and protrudes outward from the cell voltage monitoring terminal. 58 is formed integrally with the metal plate. The cell voltage monitoring terminal 58 is provided for each fuel cell 20, but may be provided for each cell unit including two or more fuel cells 20.

  As shown in FIG. 1, the oxidant gas supply device 14 includes an air compressor (which may be a pump or a supercharger) 60 that compresses and supplies air from the atmosphere, and the air compressor 60 is provided in the air supply flow path 62. Arranged. The air supply channel 62 communicates with the oxidant gas inlet communication hole 36 a of the fuel cell stack 12, and air branch channels 64 a and 64 b are branched from the air supply channel 62.

  On-off valves 66a and 66b are disposed in the air branch channels 64a and 64b. The air branch flow path 64a communicates with a dilution box (which dilutes exhaust gas with air) 68, while the air branch flow path 64b communicates with a fuel gas inlet communication hole 38a of the fuel cell stack 12, as will be described later. .

  The oxidant gas supply device 14 includes an air discharge channel 70 that communicates with the oxidant gas outlet communication hole 36b. A back pressure control valve 71 for controlling the flow rate of air supplied to the fuel cell stack 12 is connected to the air discharge channel 70. The air discharge channel 70 is connected to the dilution box 68.

  The fuel gas supply device 16 includes a hydrogen tank 72 that stores high-pressure hydrogen (hydrogen-containing gas). The hydrogen tank 72 communicates with the fuel gas inlet communication hole 38 a of the fuel cell stack 12 via the hydrogen supply flow path 74. To do. The hydrogen supply channel 74 is provided with a regulator 76, an ejector 78, and a hydrogen pump 80, and an air branch channel 64 b is connected between the ejector 78 and the hydrogen pump 80.

  The fuel gas supply device 16 includes a fuel gas discharge passage 82 communicating with the fuel gas outlet communication hole 38b. The fuel gas discharge passage 82 is connected to an ejector 78 while interposing a gas-liquid separator 84.

  The branch flow paths 86a and 86b are branched from the middle of the fuel gas discharge flow path 82, and the branch flow path 86a is connected to the dilution box 68 via a purge valve 88a. The dilution box 68 is connected via an air discharge valve 88b. A drain channel 90 is connected to the gas-liquid separator 84. The drain channel 90 is connected to the dilution box 68 via a drain valve 88c.

  A connector 92 is connected to a cell voltage monitoring terminal 58 of each fuel cell 20 constituting the fuel cell stack 12, and the connector 92 is connected to a cell voltage monitor (cell voltage measuring device) 96 via a cable 94. Connected to. The cell voltage monitor 96 is connected to the controller 18.

  The controller 18 includes a cell voltage detection unit 98 that detects each cell voltage of the fuel cell 20 in the state of system startup, system stop, or idle stop, and the detected minimum cell voltage is equal to or less than a threshold value. The cell voltage detected around the fuel cell 20 where the minimum cell voltage is detected, and the cell voltage detected in the vicinity of the fuel cell 20 is separated from the minimum cell voltage. When a ramp voltage pattern to be boosted (described later) is formed, a cross leak determination unit 102 that determines that a cross leak has occurred in the fuel cell 20 in which the lowest cell voltage has been detected, and an anode side gas as fuel A gas replacement determination unit 104 that determines whether or not to perform gas replacement from gas to oxidant gas.

  The operation of the fuel cell system 10 configured as described above will be described below along the flowchart shown in FIG. 3 in relation to the cross leak detection method according to the first embodiment.

  First, when an ignition switch (not shown) is turned on (step S1), the cell voltage of the fuel cell 20, that is, the open circuit voltage (OCV) is detected without starting the current when the fuel cell system 10 is started. It is determined whether or not (step S2). If it is determined that the OCV check has been performed, that is, it is at the time of system startup (YES in step S2), the process proceeds to step S3 and a cross leak determination process is performed. When the system is activated, the discharge process of the fuel cell stack 12 is performed. The cross leak determination process is shown in FIG.

  On the other hand, if it is determined that the OCV check is not performed (NO in step S2), the process proceeds to step S4, and it is determined whether or not an idle stop is performed. The idle stop means a state in which the supply of fuel gas from the fuel gas supply device 16 to the fuel cell stack 12 is stopped while the vehicle is stopped. If it is determined that the engine is idle stop (YES in step S4), the discharge process of the fuel cell stack 12 is performed and the cross leak determination process of step S3 is performed.

  In the OCV check, an open circuit voltage (hereinafter also referred to as a cell voltage) for each fuel cell 20 is detected by the cell voltage monitor 96, and the detection result is sent to the cell voltage detection unit 98 of the controller 18. The cell voltage detection unit 98 detects each cell voltage for each fuel cell 20 in the fuel cell stack 12 corresponding to each stacking position.

  Therefore, if it is determined that the lowest cell voltage among the cell voltages detected by the cell voltage detector 98 is equal to or lower than the threshold value (YES in step S11), the process proceeds to step S12. In step S12, it is determined whether or not the cell voltage detected in the vicinity of the fuel cell 20 in which the lowest cell voltage is detected forms a ramp voltage pattern that is boosted in a direction away from the lowest cell voltage. To do.

  As shown in FIG. 5, the minimum cell voltage Vlow is equal to or lower than the threshold voltage Vset, and each of the plurality of fuel cells 20 disposed on both sides in the stacking direction of the fuel cells 20 in which the minimum cell voltage Vlow is detected. The detection voltage V is boosted in a substantially V-shaped pattern (gradient voltage pattern) toward both sides in the stacking direction.

  In step S12, specifically, the first cell voltage having the lowest voltage next to the lowest cell voltage Vlow is adjacent to both sides in the stacking direction of the fuel cells 20 in which the lowest cell voltage Vlow is detected, and the first cell. When the second cell voltage, which is the next lower voltage, is detected (YES in step S12), the process proceeds to step S13.

  Therefore, the cross leak determination unit 102 determines that a cross leak has occurred in the fuel cell 20 and determines the cross leak. Then, the process proceeds to step S14. On the other hand, if it is determined in step S11 that the minimum cell voltage is not less than or equal to the threshold value (NO in step S11), the process proceeds directly to step S14.

  Further, as shown in FIG. 6, when the cell voltages of the fuel cells 20 on both sides in the stacking direction of the fuel cells 20 in which the lowest cell voltage Vlow is detected are normal (NO in step S12), step Proceed to S14. This indicates that flooding occurs only in a single fuel battery cell 20, and the other fuel battery cells 20 are in a state in which normal operation is possible.

  On the other hand, in the state shown in FIG. 5, cross leak has occurred. For example, when oxygen flows from the cathode side to the anode side, oxygen is mixed with hydrogen as fuel gas on the anode side. As a result, the area where hydrogen comes into contact with the solid polymer electrolyte membrane 52 is reduced, and the hydrogen is reduced by the reaction between the oxygen and the hydrogen, and the fuel adjacent to the fuel cell 20 in which the lowest cell voltage Vlow is detected. The cell voltage of the battery cell 20 also decreases. For this reason, the detection voltage V shows a substantially V-shaped gradient voltage pattern.

  In particular, the discharge process of the fuel cell stack 12 is performed at the time of system startup or idle stop. Therefore, the discharge is performed in a state where the stoichiometric ratio (ratio of the supplied reactive gas amount to the actually consumed reactive gas amount) is low, and the stoichiometric ratio is further reduced due to the mixture of oxygen and hydrogen due to cross leak. Then, the resistance value increases and the voltage behavior of the detection voltage V becomes more remarkable. As a result, there is an advantage that the detection accuracy of the cross leak is improved.

  In step S14, it is determined whether or not there is a cross leak determination result and anode scavenging has been performed. In the anode scavenging, as shown in FIG. 1, the air compressor 60 constituting the oxidant gas supply device 14 is driven in a state in which the on-off valve 66b disposed in the air branch flow path 64b is opened.

  Accordingly, the air (oxidant gas) pumped by the air compressor 60 is supplied from the hydrogen supply flow path 74 to the fuel gas inlet communication hole 38 a of the fuel cell stack 12. Therefore, in the fuel cell stack 12, air flows through the fuel gas flow path 44 of each fuel cell 20 and is discharged from the fuel gas outlet communication hole 38 b. Thereby, anode scavenging is performed.

  When it is determined that there is a cross-leak determination result and anode scavenging has been performed (YES in step S14), the process proceeds to step S15, and it is determined again whether it is determined that cross-leak is present. In step S15, the same processes as in steps S11 and S12 are performed.

  If it is determined that there is a cross leak (YES in step S15), the process proceeds to step S16 and the cross leak is determined. On the other hand, if it is determined that there is no cross leak (NO in step S15), the process proceeds to step S17, and the confirmation of the cross leak is reset. When the cross leak is confirmed, it is preferable to display a warning on the meters of the fuel cell vehicle and notify the user of the failure.

  When the cross leak determination process is completed, the process proceeds to step S5 in FIG. 3 to determine whether or not the fuel cell stack 12 is generating power. During power generation of the fuel cell stack 12, as shown in FIG. 1, fuel gas (hydrogen gas) is supplied from a hydrogen tank 72 constituting the fuel gas supply device 16 to the hydrogen supply flow path 74. The fuel gas is decompressed by the regulator 76 and then supplied from the ejector 78 and the hydrogen pump 80 to the fuel gas inlet communication hole 38 a of the fuel cell stack 12.

  Therefore, the air filled in the fuel gas passage 44 is discharged from the fuel gas passage 44 through the fuel gas outlet communication hole 38b to the fuel gas discharge passage 82 along with the fuel gas. The discharged air and fuel gas are sent to the dilution box 68 as necessary.

  Then, after a predetermined time has elapsed since the start of the supply of the fuel gas, the supply of the oxidant gas to each oxidant gas flow path 42 is started. The predetermined time is a time required for the fuel gas passage 44 to be replaced with the fuel gas, and is set by measuring the time in advance.

  In the oxidant gas supply device 14, since the air compressor 60 is driven, air (oxidant gas) is supplied from the air supply flow path 62 to each oxidant gas inlet communication hole 36 a of the fuel cell stack 12. Therefore, as shown in FIG. 2, air is supplied to each oxidant gas flow path 42 from each oxidant gas inlet communication hole 36a. The air discharged from the oxidant gas passage 42 is sent to the dilution box 68 through the air discharge passage 70 (see FIG. 1).

  As a result, as shown in FIG. 2, in the electrolyte membrane / electrode structure 30, the air supplied to the cathode side electrode 54 and the fuel gas supplied to the anode side electrode 56 are electrochemically generated in the electrode catalyst layer. It is consumed by the reaction to generate electricity.

  The fuel gas consumed by being supplied to the anode electrode 56 of the electrolyte membrane / electrode structure 30 is discharged along the fuel gas outlet communication hole 38b. The fuel gas is discharged to the fuel gas discharge channel 82 and separated into a gas component and moisture by the gas-liquid separator 84. The gas component is sucked into the ejector 78 and supplied to the fuel cell stack 12 as a fuel gas.

  The cooling medium supplied to the pair of cooling medium inlet communication holes 40a is introduced into the cooling medium flow path 46 between the first separator 32 and the second separator 34, as shown in FIG. The cooling medium cools the electrolyte membrane / electrode structure 30 and then is discharged into the pair of cooling medium outlet communication holes 40b.

  When power generation by the fuel cell stack 12 is stopped (YES in step S5), the process proceeds to step S6, and the result of the cross leak determination is backed up. As a result, it is reliably identified that the fuel cell 20 is not flooded but has a cross leak.

  In this case, in the first embodiment, as shown in FIG. 5, the fuel cell 20 is arranged on both sides in the stacking direction in which the lowest cell voltage Vlow equal to or lower than the threshold value Vset is detected in the state of system startup or idle stop. When the detected voltage V of each of the plurality of fuel cells 20 is boosted in a substantially V-shaped pattern (gradient voltage pattern) toward both sides in the stacking direction, it is determined that a cross leak has occurred. Yes.

  Therefore, it is possible to easily and reliably discriminate between a cell voltage drop due to cross leak (see FIG. 5) and a cell voltage drop due to flooding (see FIG. 6). Accordingly, it is possible to reliably prevent the fuel cell 20 from being replaced by misinterpreting that a cross leak has occurred regardless of whether the fuel cell 20 is simply flooded. Can do. Thereby, the effect that it becomes possible to control operation of the whole fuel cell system 10 efficiently and economically is acquired.

  Moreover, when it is determined that a cross leak has occurred (step S13), the process proceeds to step S14, and after anode scavenging is performed, the process proceeds to step S15, where it is determined again whether there is a cross leak. Yes. For this reason, since the flooding state is eliminated by the anode scavenging, there is an advantage that the cross leak determination is performed with higher accuracy.

  Here, in step S14, anode scavenging is performed, but the present invention is not limited to this. For example, after the purge valve 88a is opened and the purge process is performed from the branch flow path 86a, the determination in step S11 may be performed, or after the drain valve 88c is opened and the drain flow path 90 is drained, the step is performed. The determination in S11 may be performed. Further, after increasing the cathode-side air supply amount or increasing the anode-side fuel gas flow rate, the determination in step S11 may be performed.

  Furthermore, in the first embodiment, the cell voltage detection unit 98 detects each cell voltage for each fuel cell 20 in the fuel cell stack 12 corresponding to each stack position. Therefore, when the fuel cell 20 in which the lowest cell voltage is detected is arranged at the end of the fuel cell stack 12 in the stacking direction, it can be determined that no cross leak has occurred.

  The fuel cells 20 arranged at the end of the fuel cell stack 12 in the stacking direction are more likely to cause a temperature drop than the other fuel cells 20 and are likely to be flooded. Thus, it is possible to easily perform the cross leak determination by determining in advance that the flooding has occurred.

  Furthermore, adjacent to both sides in the stacking direction of the fuel cells 20 in which the lowest cell voltage Vlow is detected, the first cell voltage having the lowest voltage next to the lowest cell voltage Vlow and the lowest voltage next to the first cell voltage, respectively. When the second cell voltage is detected, it is determined that a cross leak has occurred. For this reason, there is an advantage that the cross leak determination is performed more reliably.

  Next, a cross leak detection method according to a second embodiment of the present invention will be described below along the flowchart shown in FIG.

  First, when an ignition switch (not shown) is turned off (step S21), the process proceeds to step S22 to determine whether or not RTC (real time clock) monitoring is performed. If it is determined that RTC monitoring is being performed (YES in step S22), that is, if it is determined that the system is stopped, the process proceeds to step S23 after a predetermined time has elapsed, and the fuel cell stack 12 discharge processes are performed, and a cross leak determination process is performed. This is because when a cross leak occurs, the voltage behavior (decrease) becomes more prominent with the passage of time after the gas supply is stopped, and the cross leak determination is reliably performed.

  Note that the processing in step S23 is the same as that in steps S11 to S17 shown in FIG. Next, the process proceeds to step S24, and the result of the cross leak determination is backed up.

  If it is determined that RTC monitoring is not being performed (NO in step S22), the process proceeds to step S25 to determine whether or not anode scavenging has been performed. If it is determined that anode scavenging has not been performed (NO in step S25), the process proceeds to step S23, while if it is determined that anode scavenging has been performed (YES in step S25), the process proceeds to step S26. Then, a backup after the anode scavenging is performed.

  In the second embodiment, cross leak determination processing is performed, and the same effect as in the first embodiment can be obtained.

  In the first and second embodiments, it is sufficient that the discharge process of the fuel cell stack 12 is performed at the time of system startup, system stop, and idle stop, and the timing of this discharge process can be variously changed. is there. The discharge process may be performed as necessary.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 12 ... Fuel cell stack 14 ... Oxidant gas supply device 16 ... Fuel gas supply device 18 ... Controller 20 ... Fuel cell 30 ... Electrolyte membrane and electrode structure 32, 34 ... Separator 36a ... Oxidant gas inlet Communication hole 36b ... Oxidant gas outlet communication hole 38a ... Fuel gas inlet communication hole 38b ... Fuel gas outlet communication hole 42 ... Oxidant gas flow path 44 ... Fuel gas flow path 52 ... Solid polymer electrolyte membrane 54 ... Cathode side electrode 56 ... Anode side electrode 58 ... Cell voltage monitoring terminal 60 ... Air compressor 62 ... Air supply flow path 64a, 64b ... Air branch flow path 66a, 66b ... Open / close valve 68 ... Dilution box 70 ... Air discharge flow path 71 ... Back pressure control Valve 72 ... Hydrogen tank 74 ... Hydrogen supply flow path 78 ... Ejectors 86a, 86b ... Branch flow path 88a ... Purge valve 88b ... Air discharge valve 88c ... Drain valve 90 ... Drain flow path 96 ... Cell voltage monitor 98 ... Cell voltage detection unit 100 ... Minimum cell voltage determination unit 102 ... Cross leak determination unit 104 ... Gas exchange determination unit

Claims (6)

A fuel cell in which a fuel gas is supplied to the anode side while an oxidant gas is supplied to the cathode side and a plurality of cells for generating electricity are stacked;
A cell voltage detector that detects a cell voltage for each cell unit or for each cell unit including two or more cells;
A fuel cell system comprising:
When detecting the cell voltage of the cell or the cell unit in the state of system start, system stop or idle stop, it is determined whether or not the detected minimum cell voltage is below a threshold value. A minimum cell voltage determination unit;
When the cell voltage detected in the periphery of the cell or the cell unit in which the lowest cell voltage is detected forms a ramp voltage pattern that is boosted in a direction away from the lowest cell voltage, the lowest cell voltage A cross leak determination unit that determines that a cross leak has been induced in the cell or the cell unit in which
A fuel cell system comprising: A fuel cell in which a fuel gas is supplied to the anode side while an oxidant gas is supplied to the cathode side and a plurality of cells for generating electricity are stacked;
A cell voltage detector that detects a cell voltage for each cell unit or for each cell unit including two or more cells;
A cross leak detection method for a fuel cell system comprising:
A step of detecting a cell voltage of the cell or the cell unit in a state of either a system startup, a system stop, or an idle stop;
Determining whether the detected lowest cell voltage is below a threshold;
When it is determined that the lowest cell voltage is equal to or lower than the threshold value, the cell voltage detected in the periphery of the cell or the cell unit in which the lowest cell voltage is detected is separated from the lowest cell voltage. Determining whether to form a ramp voltage pattern that is stepped up toward
The cell or cell unit in which the lowest cell voltage is detected when it is determined that the cell voltage detected in the periphery of the cell or the cell unit in which the lowest cell voltage is detected forms the ramp voltage pattern. A step of determining that a cross leak has occurred,
A cross leak detection method for a fuel cell system, comprising: In the cross leak detection method according to claim 2, when it is determined that a cross leak has occurred, at least the gas in the gas supply flow path on the anode side or the cathode side is replaced,
Determining whether the lowest cell voltage is less than or equal to the threshold after the gas replacement;
Resetting the cross leak determination when it is determined that the minimum cell voltage exceeds the threshold; and
A cross leak detection method for a fuel cell system, comprising:   3. The cross leak detection method according to claim 2, wherein when the cell or the cell unit in which the lowest cell voltage is detected is arranged at an end portion in the stacking direction of the fuel cell, no cross leak is caused. A method for detecting a cross leak of a fuel cell system, comprising: determining a cross leak.   5. The cross leak detection method according to claim 2, wherein the first cell voltage having the next lowest voltage after the lowest cell voltage is adjacent to the cell or the cell unit in which the lowest cell voltage is detected. And a cross-leak detection method for a fuel cell system, wherein a cross-leak is determined to be caused when a second cell voltage having a voltage lower than the first cell voltage is detected.   The cross leak detection method according to any one of claims 2 to 5, wherein the fuel cell is discharged and the cell voltage is detected when the system is started, when the system is stopped, and when the system is idle. A cross leak detection method for a fuel cell system.

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