JP5070830B2 - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of supplying water inside a fuel cell by adjusting a partial pressure difference of gas of an anode and a cathode, in case the fuel cell is in short of water inside. <P>SOLUTION: The fuel cell 12 is made provided with a variable pressure regulating valve 20 and an air drainage pressure regulating valve 62 as a structure for regulating pressure of an anode and a cathode. A water shortage judgment treatment (steps S100, S102) for judging if moisture is lacking inside the fuel cell 12 is executed, and a hydrogen partial pressure difference between the anode and the cathode of the fuel cell 12 is increased (a step S120) as a rule, if the moisture inside the fuel cell 12 is judged to be in shortage. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a fuel cell system.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-127914, a fuel cell system that supplies water into a fuel cell for the purpose of humidifying an electrolyte membrane is known. The electrolyte membrane in the fuel cell exhibits good electrical characteristics when in an appropriate wet state. However, depending on the operating state, the amount of water contained in the electrolyte membrane may change.

  In the above-described conventional fuel cell system, in order to cope with this, in a situation where water is to be supplied to the electrolyte membrane, the cathode pressure is set higher than the anode pressure as compared with a normal operation state. When there is a pressure difference between the anode and the cathode across the electrolyte membrane, water moves through the electrolyte membrane from the high-pressure pole to the low-pressure pole. In the above conventional technique, it is possible to promote water movement from the cathode to the anode by increasing the pressure difference, and to supply moisture to the electrolyte membrane.

  On the other hand, in a situation where water supply to the electrolyte membrane should be suppressed, the anode pressure is set higher than the cathode pressure. Thereby, water movement to the anode can be suppressed and humidification of the electrolyte membrane can be suppressed. Thus, according to the above conventional technique, the electrolyte membrane can be kept in an appropriate wet state by utilizing the water movement through the electrolyte membrane caused by the pressure difference between the two electrodes.

JP 2004-127914 A JP 2000-340241 A Japanese Patent No. 2541288 JP-A-2005-251482 JP 2005-228709 A JP 2003-45466 A

  By the way, in the situation where there is a difference in gas partial pressure between the two electrodes (anode electrode, cathode electrode) across the electrolyte membrane, the gas moves through the electrolyte membrane from the high partial pressure electrode to the low partial pressure electrode. (Such gas movement is also called "cross leak"). When the anode hydrogen moves to the cathode due to the cross leak, the moved hydrogen reacts with the cathode oxygen on the catalyst to produce water. Conversely, when the oxygen at the cathode moves to the anode, the moved oxygen reacts with the hydrogen at the anode on the catalyst to produce water. The inventors of the present application paid attention to this point and came up with the idea of utilizing the water generation function for supplying water into the fuel cell.

  The present invention has been made on the basis of the above-described idea. When the water in the fuel cell is insufficient, the water is supplied into the fuel cell by adjusting the partial pressure difference between the anode gas and the cathode gas. It is an object of the present invention to provide a fuel cell system capable of

In order to achieve the above object, a first invention is a fuel cell system,
A fuel cell;
Pressure adjusting means for adjusting the pressure of the anode and cathode of the fuel cell;
Water shortage determining means for determining whether or not the water inside the fuel cell is short;
A hydrogen partial pressure difference adjusting means for increasing the hydrogen partial pressure difference between the anode and the cathode of the fuel cell when it is determined that the moisture inside the fuel cell is insufficient;
I have a,
The water shortage determining means includes a cathode water shortage determining means for determining that a shortage of water inside the fuel cell is substantially caused only on the cathode side of the fuel cell,
If it is determined that the water shortage is substantially caused only on the cathode side of the fuel cell, the hydrogen partial pressure difference between the anode and the cathode of the fuel cell is increased .

The second invention is the first invention, wherein
The hydrogen partial pressure difference is increased by increasing the pressure of the anode.

The third invention is the first or second invention, wherein
A coolant flow path communicating with the fuel cell;
A coolant flow rate adjusting means for increasing the flow rate of the coolant flowing through the coolant flow path as the difference in hydrogen partial pressure between the anode and cathode of the fuel cell increases,
It is characterized by having.

According to a fourth invention , in any one of the first to third inventions,
A coolant flow path communicating with the fuel cell;
Means for adjusting the temperature of the coolant flowing through the coolant flow path;
Cooling temperature adjusting means for lowering the temperature of the coolant as the difference in hydrogen partial pressure between the anode and cathode of the fuel cell increases,
It is characterized by having.

According to a fifth invention , in any one of the first to fourth inventions,
The water shortage determining means includes anode water shortage determining means for determining that a shortage of water inside the fuel cell is substantially caused only on the anode side of the fuel cell,
When it is determined that the water shortage substantially occurs only on the anode side of the fuel cell, the fuel cell further comprises an oxygen partial pressure difference adjusting means for increasing the anode water pressure difference between the anode and the cathode of the fuel cell. Features.

The sixth invention is the fifth invention, wherein
The oxygen partial pressure difference is increased by increasing the pressure of the cathode.

The seventh invention is the fifth or sixth invention, wherein
A coolant flow path communicating with the fuel cell;
A coolant flow rate adjusting means for increasing the flow rate of the coolant flowing through the coolant flow path as the oxygen partial pressure difference between the anode and the cathode of the fuel cell increases,
It is characterized by having.

In addition, an eighth invention according to any one of the fifth to seventh inventions,
A coolant flow path communicating with the fuel cell;
Means for adjusting the temperature of the coolant flowing through the coolant flow path;
A cooling temperature adjusting means for lowering the temperature of the coolant as the oxygen partial pressure difference between the anode and the cathode of the fuel cell increases.
It is characterized by having.

According to a ninth invention , in any one of the fifth to eighth inventions,
An anode gas circulation passage communicating with the anode of the fuel cell;
A circulation pump for promoting the circulation of gas in the anode gas circulation flow path;
Gas circulation amount adjusting means for increasing the amount of gas circulation in the anode gas circulation passage as the difference in oxygen partial pressure between the anode and cathode of the fuel cell increases,
It is characterized by having.

According to a tenth invention , in any one of the first to ninth inventions,
The fuel cell comprises a plurality of fuel cells,
Among the plurality of fuel cells, it has a low water content cell specifying means for specifying a fuel cell having relatively low internal moisture,
The water shortage determining means is a specific cell water shortage determining means for determining whether or not the fuel battery cell specified as having relatively low water content in the interior has a shortage of water,
If it is determined that the moisture inside the specified fuel cell is insufficient, the hydrogen partial pressure difference between the anode and the cathode of the fuel cell is increased.

The eleventh aspect of the invention is the tenth aspect of the invention,
Means for detecting a cross leak amount of each of the plurality of fuel cells;
The low water content cell specifying means specifies a fuel battery cell having a relatively small amount of cross leak among the plurality of fuel battery cells as a fuel battery cell having a relatively low water content.

The twelfth aspect of the invention is any one of the tenth and eleventh aspects of the invention.
Means for calculating a stoichiometric ratio of each of the plurality of fuel cells;
The low water content cell specifying means specifies a fuel battery cell having a relatively large stoichiometric ratio among the plurality of fuel cells as a fuel battery cell having a relatively low water content.

According to a thirteenth invention , in any one of the first to twelfth inventions,
The fuel cell comprises a plurality of fuel cells,
Among the plurality of fuel cells, a water-rich cell specifying means for specifying a fuel cell having a relatively large amount of water inside,
Cell moisture excess determination means for determining whether or not the moisture is excessive in the fuel cell identified as having a relatively large amount of moisture,
When it is determined that the moisture inside the specified fuel cell is excessive, the hydrogen partial pressure difference adjusting means for reducing the hydrogen partial pressure difference between the anode and the cathode of the fuel cell,
It is characterized by having.

The fourteenth invention is the thirteenth invention, in which
Means for detecting a cross leak amount of each of the plurality of fuel cells;
The moisture-rich cell identifying means identifies a fuel cell having a relatively large amount of cross leak among the plurality of fuel cells as a fuel cell having a relatively large amount of moisture.

The fifteenth invention is the thirteenth or fourteenth invention, in which
Means for calculating a stoichiometric ratio of each of the plurality of fuel cells;
The moisture-rich cell identifying means identifies a fuel cell having a relatively small stoichiometric ratio among the plurality of fuel cells as a fuel cell having relatively much moisture.

According to the first invention, when water is insufficient inside the fuel cell, the amount of hydrogen that moves to the cathode via the electrolyte membrane can be increased. When the anode hydrogen moves to the cathode, it reacts with oxygen to produce water in the cathode catalyst layer. For this reason, according to 1st invention, the quantity of the water produced | generated by an electrode catalyst layer can be increased, and the quantity of water inside a fuel cell can be increased. Furthermore, water can be directly supplied to the cathode side by generating water at the cathode when substantially only the cathode is in a water-deficient state.

According to the second invention, it is possible to increase the hydrogen partial pressure difference by a simple method by increasing the pressure of the anode.

According to the third invention, even if a reaction between hydrogen and oxygen occurs locally in the electrode catalyst layer, and a local high-temperature portion (also referred to as a heat spot) occurs in the electrode catalyst layer, the coolant is circulated. By increasing the amount, it is possible to disperse the heat concentrated in the part.

According to the fourth invention, even if a reaction between hydrogen and oxygen occurs locally in the electrode catalyst layer and a locally high temperature portion (also called a heat spot) occurs in the electrode catalyst layer, the cooling temperature is lowered. By doing so, overheating of the electrode catalyst layer can be prevented.

According to the fifth aspect , when only the anode is substantially in a water-deficient state, the amount of oxygen that moves to the anode can be increased. When the oxygen at the cathode moves to the anode, water is generated in the catalyst layer of the anode. As a result, water can be supplied directly to the anode.

According to the sixth aspect of the present invention, the oxygen partial pressure difference can be increased by a simple method by increasing the cathode pressure.

According to the seventh invention, even if a reaction between hydrogen and oxygen occurs locally in the electrode catalyst layer, and a local high-temperature portion (also referred to as a heat spot) occurs in the electrode catalyst layer, the coolant is circulated. By increasing the amount, it is possible to disperse the heat concentrated in the part.

According to the eighth aspect of the invention, the reaction of hydrogen and oxygen locally occurs in the electrode catalyst layer, and the cooling temperature is lowered even when a locally high temperature portion (also called a heat spot) occurs in the electrode catalyst layer. By doing so, overheating of the electrode catalyst layer can be prevented.

According to the ninth aspect of the present invention, when the amount of generated water in the anode catalyst layer increases with the increase in the oxygen partial pressure difference described above, flooding can be prevented from occurring by increasing the amount of hydrogen flowing through the anode. .

According to the tenth aspect of the present invention, water shortage is determined for a fuel cell that is more likely to be deficient in water, and water can be supplied to the fuel cell when the fuel cell is short of water. .

According to the eleventh aspect of the invention, a fuel cell that has a relatively small amount of cross leak through the electrolyte membrane, that is, a gas that is difficult to move (has a small amount of gas permeation) is specified, and the fuel cell has a shortage of water. Judgment can be made. A fuel battery cell with a small amount of cross leak corresponds to a fuel battery cell in which moisture inside the fuel battery tends to be insufficient. According to the eleventh aspect , it is possible to effectively prevent water shortage of such fuel cells.

According to the twelfth aspect , it is possible to determine a fuel cell having a relatively large stoichiometric ratio among the plurality of fuel cells and to determine whether or not the fuel cell has a large stoichiometric ratio. A fuel cell having a large stoichiometric ratio is in a state where moisture is easily taken away from the inside and is more easily dried. According to the twelfth aspect , it is possible to effectively prevent water shortage of such fuel cells.

According to the thirteenth aspect, the fuel cell in which the internal moisture tends to be excessive (prone to flooding) is specified, and when flooding occurs in the specified fuel cell, the hydrogen content of the anode and the cathode The pressure difference can be reduced. Thereby, the reaction of water production accompanying cross leak can be suppressed.

According to the fourteenth aspect of the invention, a fuel cell that has a relatively large amount of cross leakage through the electrolyte membrane, that is, a gas that easily moves (has a large amount of gas permeation) is specified, and flooding is performed on the fuel cell. Judgment can be made. A fuel battery cell having a large amount of cross leak corresponds to a fuel battery cell in which moisture inside the fuel battery tends to be excessive. According to the fourteenth aspect , such flooding of the fuel cells can be effectively prevented.

According to the fifteenth aspect , it is possible to determine a fuel battery cell having a relatively small stoichiometric ratio among the plurality of fuel battery cells, and to determine whether or not the fuel battery cell having the maximum stoichiometric ratio has water shortage. The fuel cell having the maximum stoichiometric ratio is in a situation where moisture is not easily taken away from the inside, and moisture tends to be excessive. According to the fifteenth aspect , flooding in such fuel cells can be effectively prevented.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a configuration of a fuel cell system according to Embodiment 1 of the present invention. The system of the first embodiment has a fuel cell 12. The fuel cell 12 is configured by stacking a plurality of fuel cells. Each fuel cell is composed of an electrolyte membrane, an anode, a cathode, and a separator. The electrolyte membrane is proton conductive and exhibits good electrical properties when in an appropriate wet state. The anode and cathode of the fuel cell are each provided with an electrode catalyst layer.

  As shown in FIG. 1, an anode gas channel 14 and a cathode gas channel 16 are introduced into the fuel cell 12. The anode gas flow path 14 communicates with the hydrogen tank 18 via the circulation pump 26, the adjustable pressure valve 20, and the shut valve 21. Hydrogen-rich anode gas is stored in the hydrogen tank 18 in a high-pressure state.

  When the shut valve 21 is closed, the supply of the anode gas is stopped, and the anode gas is supplied to the fuel cell 12 by opening the shut valve 21. By controlling the adjustable pressure valve 20 during the supply of the anode gas, the pressure of the anode gas at the inlet of the fuel cell 12 can be regulated. A pressure sensor 22 is connected to the anode gas flow path 14 near the inlet of the fuel cell 12.

  A pump 24 is provided in the cathode gas flow path 16. By driving the pump 24, a cathode gas as an oxidizing gas containing oxygen is sent to the cathode of the fuel cell 12. Then, by adjusting the operation amount of the pump 24, the flow rate of the cathode gas sent to the fuel cell 12 can be adjusted.

  According to such a configuration, the anode gas sent from the anode gas flow path 14 to the fuel cell 12 is sent to the anode of each fuel cell in the fuel cell 12. Similarly, the cathode gas sent from the cathode gas flow channel 16 to the fuel cell 12 is sent to the cathode of each fuel cell in the fuel cell 12. In the following description, the anodes of the fuel cells in the fuel cell 12 are collectively referred to simply as “the anode of the fuel cell 12”. Similarly, the cathodes of the fuel cells in the fuel cell 12 are collectively referred to simply as “the cathode of the fuel cell 12”.

In the anode of the fuel cell 12, when an anode gas is fed, hydrogen ions are generated from the hydrogen in the anode gas (H ₂ → 2H ⁺ + 2e ⁻ ). When the cathode gas is fed into the cathode, oxygen ions are generated from oxygen in the cathode gas, and electric power is generated in the fuel cell 12. At the same time, water (product water) is generated from the hydrogen ions and oxygen ions at the cathode ((1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O). Most of this water absorbs the heat generated in the fuel cell 12 to become water vapor, which is contained in the cathode offgas and discharged.

  The anode off gas discharged from the anode is sent to the anode off gas flow path 46. The anode off gas flow path 46 communicates with the circulation pump 26 downstream thereof. The anode off gas is returned to the anode gas flow path 14 by driving the circulation pump 26 and supplied to the fuel cell 12 again. Then, replenishment of hydrogen from the hydrogen tank 18 is performed along with such resupply of the anode off gas. According to such a configuration, the anode off gas can be sent to the fuel cell 12, and unreacted hydrogen contained in the anode off gas can be reacted in the fuel cell 12. As a result, the utilization efficiency of hydrogen can be increased. It can also be said that the above-described circulation path including the anode gas flow path 14 → the anode of the fuel cell 12 → the anode off-gas flow path 46 → the circulation pump 26 forms the anode gas circulation path.

  The cathode offgas discharged from the cathode of the fuel cell 12 is sent to the cathode offgas passage 58 shown in FIG. The cathode off gas passes through the cathode off gas flow path 58 and is finally discharged from the diluter 60. The cathode off-gas flow path 58 communicates with an air exhaust system (not shown) via an air exhaust pressure adjustment valve 62 and a diluter 60.

  By controlling the air exhaust pressure regulating valve 62, the pressure of the cathode off-gas can be adjusted. Further, a pressure sensor 64 for detecting the cathode offgas pressure is provided upstream of the air exhaust pressure regulating valve 62 in the cathode offgas flow path 58.

  In addition, the system of FIG. 1 has a coolant flow path 70 for cooling the fuel cell 12. The coolant channel 70 communicates with a cooling channel formed in the separator of each fuel cell. According to such a configuration, the fuel cell can be cooled by circulating the coolant in the coolant channel 70. In the system of FIG. 1, the circulation amount of the coolant can be controlled by a coolant circulation pump (not shown). By appropriately controlling the circulating amount of the coolant, an excessive temperature rise of the fuel cell 12 accompanying power generation can be suppressed, and the temperature of the fuel cell 12 can be optimized.

  As shown in FIG. 1, the system of the present embodiment includes an ECU (Electronic Control Unit) 40. The ECU 40 is connected with various sensors (not shown) for detecting the output (voltage value, current value) of the fuel cell 12, the coolant temperature, etc., in order to grasp the operating state of the system. Thereby, ECU40 can detect the voltage of each fuel cell with which fuel cell 12 is provided.

  In addition, the ECU 40 is connected to the pressure sensors 22 and 64, the adjustable pressure valve 20, the drain valve 52, the exhaust valve 54, the air exhaust pressure adjusting valve 62, the coolant circulation pump (not shown), and the like. The ECU 40 can operate the fuel cell 12 in a desired operation state by controlling the output of the fuel cell 12, the pressure of each gas, the flow rate of each gas, and the circulation amount of the coolant.

  Further, the ECU 40 stores a process for determining whether or not water in the fuel cell is insufficient (hereinafter also referred to as “water shortage determination process”). Specifically, this process determines whether or not there is a shortage of moisture inside the fuel cell 12 based on the output of the fuel cell 12, mainly information on the voltage value.

  As described above, the electrolyte membrane exhibits good electrical characteristics when in an appropriate wet state. However, when the operating state of the fuel cell system changes, the amount of water contained in the electrolyte membrane may change. In such a case, the wet state of the electrolyte membrane affects the output of the fuel cell.

  That is, when the water content in the electrolyte membrane is reduced, the output voltage of the fuel cell is reduced accordingly (this state is also called “dry up”). In the first embodiment, it is determined whether or not the fuel cell is short of water by observing such a voltage change. It should be noted that such a technique relating to the determination of water shortage of a fuel cell is already known, and can be realized by, for example, a fuel cell moisture state diagnostic method as disclosed in Japanese Patent Application Laid-Open No. 2004-127914. For this reason, the further details regarding the water shortage determination will be omitted.

[Operation of Embodiment 1]
(First characteristic operation of Embodiment 1 “Utilization of water generation accompanying cross leak”)
As described above, when the fuel cell system of Embodiment 1 generates power, the anode gas and the cathode gas are supplied to the fuel cell 12, respectively. Then, the output of the fuel cell 12 is observed, and the determination of water shortage in the fuel cell 12 is continuously performed.

  When it is determined by the water shortage determination process that the moisture in the fuel cell 12 is insufficient, it is necessary to supply water to the fuel cell 12 in order to eliminate the water shortage. In the first embodiment, when it is determined that the fuel cell 12 is short of water, the shortage of water is resolved using the following method.

  Under a situation where a partial pressure difference of gas is generated between both electrodes (anode electrode and cathode electrode) sandwiching the electrolyte membrane, the gas moves from the high partial pressure electrode to the low partial pressure electrode through the electrolyte membrane. Such gas movement is also referred to as “cross leak”. When the anode hydrogen moves to the cathode due to the cross leak, the moved hydrogen reacts with the oxygen on the cathode on the catalyst to produce water. Conversely, when the oxygen at the cathode moves to the anode, the moved oxygen reacts with the hydrogen at the anode on the catalyst to produce water. Therefore, in the system of the first embodiment, water generation accompanying such cross leak is used for water supply to the fuel cell.

  Specifically, in the first embodiment, when the water shortage determination process detects the occurrence of water shortage in the fuel cell 12, in principle, the anode pressure is increased to increase the hydrogen partial pressure difference between the anode and the cathode. When the difference in hydrogen partial pressure between the anode and the cathode increases, the amount of hydrogen moving from the anode to the cathode through the electrolyte membrane increases, and the amount of hydrogen that reacts with oxygen in the electrode catalyst layer of the cathode increases. As a result, the amount of generated water increases and the amount of water supplied to the electrolyte membrane increases. By doing so, when the water content of the fuel cell is insufficient, the amount of water generated in the cathode electrode catalyst layer can be increased and water can be supplied to the fuel cell 12.

  The first embodiment differs from the conventional pressure control method disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-127914 in the following points. In the above-described conventional technology, in a situation where water should be supplied to the electrolyte membrane, the cathode pressure is set higher than the anode pressure and the electrolyte membrane permeates from the high-pressure electrode to the low-pressure electrode as compared with the normal operation state. The amount of water that moves is increased. On the other hand, the present embodiment is clearly different from the conventional technique in that the hydrogen partial pressure difference is increased by increasing the anode pressure when water is insufficient.

  Further, in the above conventional technique, in a situation where the supply of water to the electrolyte membrane should be suppressed, the anode pressure is set higher than the cathode pressure to suppress water movement to the anode. If the anode pressure is set higher than the cathode pressure in a situation where the water supply to the electrolyte membrane should be suppressed, water movement (diffusion) to the anode is suppressed, but the anode pressure is increased above the cathode pressure. The partial pressure difference increases, the cross leak amount increases, and the amount of reaction product water in the cathode catalyst layer may increase. The present embodiment focuses on the amount of cross leak rather than the amount of water movement (diffusion), and therefore has an excellent feature that water can be supplied to the fuel cell while avoiding the above-described adverse effects. Have.

(Second characteristic operation of Embodiment 1 “Adjustment of gas partial pressure difference according to water shortage state”)
As described above, the first characteristic operation of the first embodiment includes the idea of utilizing water generation accompanying cross leak for supplying water to the fuel cell. Further, in the first embodiment, the system is configured by adding the idea of adjusting the gas partial pressure difference according to the water shortage state described below to the idea described in the first characteristic operation.

The following four factors can be considered as a factor for reducing the voltage when water shortage (dry up) occurs in the fuel cell.
a. Decrease in proton conductivity of electrolyte membrane b. Decreased proton conductivity in the catalyst layer (drying of the solution)
c. Reduced catalyst utilization d. Decrease in transportability of reaction gas in catalyst layer When the factor of voltage drop is the factor of b to d, that is, when polarization in the catalyst layer is the governing factor of voltage drop, moisture is insufficient and humidification is performed. The necessary part is a catalyst layer. The fuel cell is provided with a catalyst layer on each of the cathode and the anode, and depending on the operation state of the fuel cell system, only the anode catalyst layer is substantially insufficient in water, or only the cathode catalyst layer is substantially insufficient in water. Can happen.

  On the other hand, the increase in the generated water using the cross leak described above increases the amount of hydrogen or oxygen that moves from one electrode to the other electrode via the electrolyte membrane by increasing the partial pressure difference of the gas. It is realized with. When the hydrogen partial pressure difference is increased, the amount of hydrogen moving from the anode to the cathode is increased. Conversely, when the oxygen partial pressure difference is increased, the amount of oxygen moving from the cathode to the anode is increased. Therefore, increasing the hydrogen partial pressure difference increases the amount of water produced in the cathode catalyst layer, and increasing the oxygen partial pressure difference increases the amount of water produced in the anode catalyst layer.

  Therefore, in the first embodiment, after it is determined that the fuel cell 12 is short of water, it is further determined whether the water shortage is substantially caused only by the anode or substantially only by the cathode. In those cases, the amount of generated water is increased in the catalyst layer on the side where water shortage occurs. Specifically, in the first embodiment, when the occurrence of water shortage is detected, first, based on the operating state of the fuel cell system, the state of water shortage inside the fuel cell 12 is estimated using the following criteria. .

  When the fuel cell system is in a high temperature and high load state and the operating temperature is rising, the amount of water taken away from the inside of the fuel cell 12 increases. In the system in which the gas is continuously circulated on the cathode side as in the first embodiment, the moisture taken away from the fuel cell 12 by the cathode gas flowing through the cathode increases, and water shortage occurs at the cathode. Therefore, in the first embodiment, in such a case, it is determined that the water shortage of the fuel cell 12 substantially occurs only at the cathode.

  On the other hand, when the fuel cell is operated at a low temperature and a low load, the temperature of the fuel cell and its power generation performance are low, so there is little humidification from the anode gas and water that is back-diffused from the cathode. Less. As a result, in such an operating state, the moisture on the anode side tends to be insufficient. Further, when the fuel cell is operated at a high temperature, the amount of cathode water taken away increases. As a result, the amount of water moving from the anode to the cathode increases, and the moisture on the anode side tends to be insufficient.

In a situation where the fuel cell is operated at a high load, water (hereinafter also referred to as “associated water”) that moves from the anode to the cathode accompanying the conduction of proton (H ⁺ ) during the power generation reaction. The amount increases. Under such circumstances and under a situation where the cathode pressure is low, the reverse diffusion cannot catch up, and the moisture on the anode side tends to be insufficient. Therefore, in the first embodiment, when the fuel cell is operated in some situations where the moisture in the anode tends to be insufficient as described above, the water shortage of the fuel cell 12 occurs substantially only in the anode. I will judge that.

  In the first embodiment, when none of the above conditions is satisfied, it is determined that the water shortage state of the fuel cell 12 is neither water shortage of the anode alone nor water shortage of the cathode alone.

  If it is determined by the above method that the water shortage occurs substantially only at the anode, the hydrogen partial pressure difference is increased. This increases the amount of oxygen transferred to the anode and increases the amount of water produced in the anode catalyst layer. Further, when it is determined that the water shortage is substantially caused only by the cathode, the oxygen partial pressure difference is increased. As a result, the amount of hydrogen transferred to the cathode is increased, and the amount of water produced in the cathode catalyst layer is increased.

  According to the above operation, water is supplied directly to the anode when water is insufficient only by the anode, and water is supplied directly to the cathode when water is insufficient only by the cathode. it can. As a result, the shortage of water in the anode or cathode catalyst layer can be reliably and quickly resolved. In addition, according to this method, which generates water directly at the pole where water shortage occurs, the humidification obtained can be compared to the method where water is generated at the pole where water shortage does not occur, contrary to this method. The effect is extremely high. In addition, according to this method, since water can be supplied efficiently as described above, it is not necessary to apply a large differential pressure to the MEA, and the influence on durability can be suppressed.

  In the first embodiment, when none of the above applies, that is, when there is no shortage of water only for the anode or only for the cathode (for example, in the case of the above-mentioned factor a, the catalyst layers of both the anode and the cathode) When the water shortage occurs, the hydrogen partial pressure difference is increased as described in the first feature operation. Thereby, the amount of generated water can be increased, and the shortage of water in the electrolyte membrane and the catalyst layer can be solved.

[Specific Processing in First Embodiment]
Hereinafter, specific processing performed by the system of the first embodiment will be described with reference to FIG. FIG. 2 is a flowchart of a routine executed by ECU 40 in the first embodiment. The routine of FIG. 2 is executed during operation of the system of the first embodiment. The routine of FIG. 2 includes both processing for realizing the first feature operation of the first embodiment and processing for realizing the second feature operation.

  In the routine shown in FIG. 2, it is first determined whether or not water shortage (dry up) has occurred (step S100). Specifically, the water shortage determination process provided in the ECU 40 determines the water shortage based on the output of the fuel cell 12. If the establishment of the condition in step S100 is not confirmed, it is determined that sufficient moisture is secured in the fuel cell 12, and the current routine is terminated.

  If the establishment of the condition in step S100 is confirmed, it is determined that the moisture in the fuel cell 12 is insufficient. In this case, subsequently, the water shortage state is any of the three cases of the case where water is substantially deficient only on the anode side, the case where water is substantially deficient only on the cathode side, or none of them. Is determined (step S102). Specifically, in step S102, first, the ECU 40 acquires information related to the operating state of the fuel cell system.

  Then, a map of the range of operating conditions (temperature, load, etc.) in which the above-described anode and cathode water shortages occur by experiments or the like is prepared in advance, and information on the operating state (temperature, load, etc.) acquired by the ECU 40 is this Judgment is made as to whether or not it is included in the condition range of occurrence of water shortage on the map. Thereby, it can be determined which of the above states the water shortage state of the fuel cell 12 applies.

  Hereinafter, the process of the flowchart of FIG. 2 will be described for each of the case where water is insufficient only on the anode side, the case where water is insufficient only on the cathode side, and the other cases.

(When water shortage has occurred only on the anode side)
In step S102, when it is determined that the water shortage state of the fuel cell 12 substantially occurs only in the anode, a process of increasing the cathode pressure is performed (step S104). Specifically, the adjustable pressure valve 20 is controlled to the valve opening side so that the cathode pressure increases by a predetermined pressure.

  Thereby, the oxygen partial pressure difference between the anode and the cathode increases, and the amount of oxygen that cross leaks from the cathode to the anode increases. As a result, oxygen that reacts with hydrogen on the anode catalyst increases, and the amount of generated water increases. As a result, when water is insufficient only by the anode, water can be directly supplied to the anode. As a result, the shortage of water in the anode electrode catalyst layer can be resolved reliably and promptly.

  Subsequently, the amount of coolant is increased (step S106). Specifically, a coolant circulation pump (not shown) is controlled, and processing for increasing the circulation amount of the coolant flowing in the coolant flow path 70 is performed. When hydrogen and oxygen react due to cross leak, the reaction may occur locally on the electrode catalyst layer (or the reaction amount may be biased). As a result, a locally high temperature portion (also referred to as a heat spot) may occur in the electrode catalyst layer. According to the first embodiment, since the circulation amount of the coolant is increased in accordance with the increase in the cross leak amount, the concentrated heat can be dispersed even if the situation described above occurs. .

  A method such as increasing the circulating flow rate of the coolant as the increase in the cathode pressure is increased, or setting the circulating flow rate according to the absolute value of the cathode pressure or the absolute value of the difference between the cathode pressure and the anode pressure. May be added. As a result, the circulation amount of the coolant can be increased in accordance with an increase in the water production reaction due to cross leak, and the situation as described above can be dealt with more effectively.

  When the process of step S106 is executed, a process of increasing the hydrogen circulation ratio is then performed (step S108). Specifically, the ECU 40 performs a process for increasing the operation amount of the circulation pump 26. When the amount of water produced in the anode increases with the increase in the hydrogen partial pressure difference described above, the water content in the anode may exceed the amount necessary for the shortage of water in the fuel cell 12.

  In such a case, so-called flooding is caused, which may adversely affect the power generation of the fuel cell 12. In the first embodiment, the amount of hydrogen flowing through the anode is increased by the process of step S108. Therefore, the amount of water taken away can be increased by circulating through the anode. Can be prevented.

  Subsequently, it is determined whether or not the water shortage (dry up) detected in step S100 has been resolved (step S110). Specifically, it is determined whether or not the stack resistance of the fuel cell 12 is within an allowable range obtained in advance through experiments or the like. If the calculated stack resistance value is not within the allowable range, it is determined that the condition of step S110 is not satisfied and water shortage has not yet been resolved, and the processing from step S104 is executed again.

  When the establishment of the condition in step S110 is confirmed, it is determined that the water shortage has been resolved, and a process of gradually returning the system state to the standard operation state is executed (step S112). Thereafter, the current routine ends.

(When water shortage occurs only on the cathode side)
In step S102, when it is determined that the water shortage of the fuel cell 12 is substantially caused only by the cathode, a process of increasing the anode pressure is performed (step S114). Specifically, the adjustable pressure valve 20 is controlled to the valve opening side so that the anode pressure increases by a predetermined pressure.

  Thereby, the hydrogen partial pressure difference between the anode and the cathode increases, and the amount of hydrogen that cross leaks from the anode to the cathode increases. As a result, the amount of hydrogen that reacts on the cathode catalyst increases and the amount of produced water increases. And when water is insufficient only with the cathode, water can be supplied directly to the cathode, so that the shortage of water in the cathode electrode catalyst layer can be resolved reliably and promptly.

  Subsequently, the amount of the coolant is increased in the same manner as in step S106 (step S116), and then it is determined whether or not the water shortage (dry up) has been resolved in the same manner as in step S110 (step S118). If the establishment of the condition in step S118 is not confirmed, the processing from step S114 is executed again. If the establishment of the condition in step S118 is confirmed, it is determined that the water shortage has been resolved, and a process of gradually returning the system state to the standard operation state is executed (step S112). Thereafter, the current routine ends.

(Neither the anode-only water shortage nor the cathode-only water shortage)
If it is determined in step S102 that the fuel cell 12 is in a state of water shortage, neither anode-only water shortage nor cathode-only water shortage, a process of increasing the anode pressure is performed (step S120).

  Specifically, like the process of step S104, the adjustable pressure valve 20 is opened and controlled so that the anode pressure increases by a predetermined pressure. As a result, the amount of hydrogen that reacts with oxygen on the cathode catalyst increases and the amount of water produced increases. As the amount of generated water increases, the amount of water in the fuel cell 12 increases, and the shortage of water in the fuel cell 12 is alleviated.

  Subsequently, the amount of the coolant is increased as in step S106 (step S122), and it is determined whether the water shortage detected in step S100 has been improved (step S126). Specifically, the ECU 40 calculates the stack resistance of the fuel cell 12, and it is determined whether or not this value has changed to the standard value side of the stack resistance during normal operation obtained in advance through experiments or the like. . If the calculated stack resistance value has changed to the standard value side, it is determined that the water shortage has improved. Moreover, when such a change is not recognized, it is judged that the improvement of water shortage has not been obtained.

  If the establishment of the condition of step S110 is confirmed, it is then determined whether or not the water shortage has been resolved (step S128). Specifically, it is determined whether or not the stack resistance of the fuel cell 12 is within an allowable range obtained in advance through experiments or the like. If the calculated stack resistance value is not within the allowable range, it is determined that the condition of step S128 is not satisfied and water shortage has not yet been resolved, and the processing from step S120 is executed again.

  When the establishment of the condition in step S128 is confirmed, it is determined that the water shortage has been resolved, and a process of gradually returning the system state to the standard operation state is executed (step S112). Thereafter, the current routine ends. According to such a series of processes, it is possible to continue increasing the anode pressure until the shortage of water is resolved, while confirming that the effect of improving the water shortage by increasing the anode pressure is recognized.

  On the other hand, if the establishment of the condition in step S126 is not confirmed, a process for increasing the cathode pressure is executed (step S130). Specifically, as in the process of step S114, the air exhaust pressure adjustment valve 62 is controlled so that the anode pressure increases by a predetermined pressure. Thereby, the oxygen partial pressure difference between the anode and the cathode increases, and the amount of oxygen that cross leaks from the cathode to the anode increases. As a result, the amount of water produced in the anode increases, so that the amount of water inside the fuel cell 12 increases, and the shortage of water in the fuel cell 12 is alleviated.

  Subsequently, a process for increasing the hydrogen circulation ratio is performed in the same manner as in step S108 (step S131), and thereafter, as in the process in step S128, it is determined whether or not the water shortage has been resolved (step S132). If it is not determined that the water shortage has been resolved, the processing from step S130 is executed until the determination is made. If the elimination of water shortage is recognized, the process proceeds to step S112, and then the current routine ends.

  According to the processing described above, when water is insufficient in the fuel cell 12, water can be supplied to the fuel cell 12 using water generation accompanying cross leak. Specifically, in the first embodiment, when the moisture in the fuel cell 12 is insufficient, the hydrogen partial pressure difference between the anode and the cathode can be increased to increase the amount of hydrogen that moves to the cathode through the electrolyte membrane. . As a result, the amount of hydrogen that reacts in the electrode catalyst layer increases, and the amount of water produced in the fuel cell 12 can be increased. In the first embodiment, the anode pressure is increased in order to increase the hydrogen partial pressure difference. However, according to such a method, since hydrogen is stored in the hydrogen tank 18 at a high pressure, it is simpler. In addition, the hydrogen partial pressure difference can be increased efficiently.

  Further, according to the specific processing described above, water is generated at the cathode after it is determined that only the cathode is substantially in a water-deficient state. As a result, water can be supplied directly to the anode when the anode alone is insufficient. Furthermore, in the specific processing described above, the anode pressure is increased when the hydrogen partial pressure difference is increased. Thereby, the hydrogen partial pressure difference can be increased by a simple method.

  Further, in the specific processing described above, it is possible to determine a case where only the anode is in a water-deficient state, and in this case, it is possible to increase the amount of oxygen moving to the anode. Thereby, when water is insufficient only with the cathode, it is possible to supply water directly to the cathode. Furthermore, in the specific process described above, the oxygen partial pressure difference can be increased by a simple method by increasing the cathode pressure when increasing the oxygen partial pressure difference.

  In addition, according to the present method for generating water directly at the pole on the side where water shortage occurs as described above, the obtained humidification effect is extremely high, and water supply can be performed efficiently, so that the MEA has a large effect. There are advantages such as no need to apply differential pressure.

  Further, in the specific treatment described above, even if a reaction between hydrogen and oxygen occurs locally in the electrode catalyst layer, and a local high temperature portion (also referred to as a heat spot) occurs in the electrode catalyst layer, By increasing the circulation amount, the heat concentrated in the part can be dispersed.

  Further, according to the specific treatment described above, the amount of hydrogen circulating in the anode can be increased when the amount of water produced in the anode increases with an increase in the oxygen partial pressure difference. As a result, the risk of causing so-called flooding can be reduced. Further, by increasing the hydrogen circulation amount in accordance with the increase in the cross leak amount as in the first embodiment, the water generated along with the cross leak can be circulated through the anode gas flow path, The anode can be humidified more evenly (evenly).

  In the first embodiment described above, the fuel cell 12 corresponds to the “fuel cell” in the first invention, and the adjustable pressure valve 20 and the air exhaust pressure adjusting valve 62 are the “pressure adjusting means” in the first invention. And the processing of steps S100 and S102 of the routine described above is executed, so that the “water shortage determination means” in the first invention executes the processing of step S120. The “hydrogen partial pressure difference adjusting means” in the present invention is realized.

Further, in the first embodiment described above, the “cathode water shortage determining means” in the first aspect of the present invention is realized by executing the process of step S102 in the specific process.

In the first embodiment described above, the coolant channel 70 corresponds to the “coolant channel” of the third invention, and the process of step S116 or S122 is executed in the specific process described above. Thus, the “coolant flow rate adjusting means” according to the third aspect of the present invention is realized.

In the first embodiment described above, in the specific process, the process of step S102 is executed, so that the “anode water shortage determining means” in the fifth aspect of the invention executes the process of step S104. Accordingly, the “anode water shortage oxygen partial pressure difference adjusting means” in the fifth invention is realized.

In the first embodiment described above, the coolant flow path 70 corresponds to the “cooling liquid flow path” of the seventh invention, and in the specific process, the process of step S106 is executed. The “cooling liquid flow rate adjusting means” of the seventh aspect of the invention is realized.

In the first embodiment described above, the anode gas passage 14 → the anode of the fuel cell 12 → the anode offgas passage 46 → the circulation passage (anode gas circulation passage) including the circulation pump 26 is the ninth invention. The “circulation pump” corresponds to the “circulation pump” of the ninth aspect of the invention. In the specific processing of the first embodiment described above, step S108 or S131 is executed to realize the “gas circulation amount adjusting means” of the ninth aspect of the invention.

  More specifically, the process of step S102 described above is more specifically described as follows: “The fuel cell operating state is the first operating state where water shortage of the fuel cell occurs substantially only at the cathode, and the fuel cell water shortage occurs. It can also be said that “a process for determining which of the second operating state that occurs substantially only in the anode and the third operating state that does not correspond to any of them” is performed.

[Modification of Embodiment 1]
(First modification)
In the first embodiment, “the idea of utilizing water generation accompanying cross leak for water supply to the fuel cell” included in the first feature operation described above and “gas depending on the water shortage state” included in the second feature operation. The system was constructed by applying both the ideas of “adjustment of partial pressure difference”. However, these ideas do not necessarily need to be used in combination, and the fuel cell system may be configured using only “the idea of using water generation accompanying cross leak for supplying water to the fuel cell”.

  Specifically, for example, the system has the same configuration as the system of the first embodiment, and the flowchart of FIG. 2 is applied to the ECU 40 to “start → water shortage determination (step S100) → anode pressure increase (S120) → coolant circulation. It is also possible to execute a routine of “volume increase (S122) → water shortage elimination? (S128) → transition to standard operation state (S112) → end (return to S120 if establishment is not recognized in S128)”.

  Alternatively, the processes of steps S102 to S110 and steps S114 to S118 corresponding to “the idea of adjusting the gas partial pressure difference according to the water shortage state” may be excluded from the flowchart of FIG.

  In the above-described first modification, the “water shortage determining means” of the first invention is executed by executing the process of step S100, and the process of step S120 is executed by the “water shortage determining unit” of the first invention. “Hydrogen partial pressure difference adjusting means” is realized.

(Second modification)
In the first embodiment, on the basis of the idea of “the idea of adjusting the gas partial pressure difference according to the water shortage state” of the second characteristic operation, there is a case where water shortage substantially occurs only in the anode, and substantially only in the cathode. Both cases were determined (step S102 in the routine of FIG. 2), and an appropriate gas partial pressure difference was adjusted according to each case. However, the determination of the water shortage state described above is not necessarily performed for both the anode and the cathode. As necessary, as a system with only one of “a process for determining when water shortage substantially occurs only at the anode” and “a process for determining when water shortage occurs substantially only at the cathode” Also good.

(Third Modification)
In the first embodiment, a method of increasing the anode pressure when increasing the hydrogen partial pressure difference between the anode and the cathode is used. However, the method for increasing the hydrogen partial pressure difference between the anode and the cathode in the present invention is not limited to this. The hydrogen partial pressure difference may be increased by appropriately adjusting (increasing or decreasing) the pressures of the anode and cathode. In the first embodiment, a method of increasing the cathode pressure is used when increasing the oxygen partial pressure difference between the anode and the cathode. However, the present invention is not limited to this. What is necessary is just to adjust the pressure of an anode and a cathode suitably, respectively, and to enlarge an oxygen partial pressure difference.

(Fourth modification)
In the specific processing of the first embodiment, the flow rate (circulation amount) of the coolant in the coolant flow path 70 is increased as the hydrogen partial pressure difference or the oxygen partial pressure difference is increased. Instead of or together with such adjustment of the coolant flow rate, the following cooling temperature adjustment may be performed.

  FIG. 3 is a diagram for explaining a system in which a cooling temperature adjustment method is additionally combined with the system of the first embodiment. The system of FIG. 3 has substantially the same configuration as the system of the first embodiment shown in FIG. 1 except that the coolant channel 70 is replaced with a cooling system 72. In addition, illustration is abbreviate | omitted about the other structure with which the system of FIG. 1 is provided.

  In the system of FIG. 3, a cooling system 72 is connected to the fuel cell 12. The cooling system 72 can cool the fuel cell 12 by circulating the coolant in the system, similarly to the coolant channel 70 of the system of FIG. The cooling system 72 has a pipe line 74 that communicates with the fuel cell 12. The coolant after cooling the inside of the fuel cell 12 flows out to the pipe line 74. The pipe 74 communicates with the switching valve 80, and the switching valve 80 communicates with the pipe 76 and the pipe 78. The pipe line 76 communicates directly with the switching valve 82, and the pipe line 78 communicates with the switching valve 82 via the radiator 84. The switching valves 80 and 82 and the radiator 84 are connected to the ECU 40.

  In such a configuration, the ECU 40 controls the switching valves 80 and 82, whereby the fuel cell 12 → the pipe 74 → the switching valve 80 → the pipe 76 → the switching valve 82 → the path of the fuel cell 12 (hereinafter referred to as “first” The fuel cell 12 → the pipe 74 → the switching valve 80 → the pipe 78 → the radiator 84 → the switching valve 82 → the path of the fuel cell 12 (hereinafter also referred to as “second cooling path”). Can be switched as appropriate.

  In the fourth modification, in the system configuration as described above, the cooling system is set as the first cooling path during normal operation, that is, when there is no water shortage. When the water shortage determination is made and the hydrogen partial pressure difference or the oxygen partial pressure difference is increased, the cooling system is switched to the second cooling path, and the cooling temperature in the radiator 84 is set low according to the increase in the partial pressure difference. (In other words, the amount of cooling by the radiator 84 is increased).

  By doing so, the hydrogen partial pressure difference or the oxygen partial pressure difference is increased to increase the cross leak amount, so that the reaction between hydrogen and oxygen locally occurs in the electrode catalyst layer, and the local high temperature is generated in the electrode catalyst layer. Even when this portion (also referred to as a heat spot) occurs, it is possible to prevent overheating of the electrode catalyst layer by lowering the cooling temperature.

  In the above method, the cooling flow rate may be increased together with the switching to the second cooling system as in the first embodiment. Further, in the above-described fourth modification, a path not including the radiator (first cooling path) and a path including the radiator (second cooling path) are provided, and these are appropriately switched. However, it is good also as a structure which has only one cooling path containing a radiator.

In the fourth modified example described above, the second cooling path, said fourth invention or the eighth aspect of the present invention to the "cooling fluid channel", the radiator 84, the fourth invention or the eighth This corresponds to the “means for adjusting the temperature of the coolant” in the present invention. Further, in the fourth modified example described above, the method of setting the cooling temperature in the radiator 84 to be low according to the amount of increase in the partial pressure difference is the “cooling temperature adjusting means” in the fourth invention or the eighth invention. It corresponds to.

(Other variations)
In the specific processing of the first embodiment, the flow rate (circulation amount) of the coolant in the coolant flow path 70 is increased as the hydrogen partial pressure difference or the oxygen partial pressure difference is increased. In the first embodiment, in the system having the circulation pump 26 and the anode gas circulation channel, the operation amount of the circulation pump 26 is increased in accordance with the increase in the oxygen partial pressure difference, and the gas in the anode gas circulation channel is increased. It was decided to increase the amount of circulation.

  However, these methods use the “philosophy of utilizing water generation accompanying cross leak for water supply to the fuel cell” or in addition to the “philosophy of adjusting the gas partial pressure difference according to the water shortage state”. In use, it is not essential. If necessary, the above-described methods may be added as appropriate.

  In other words, even for a system that does not increase the coolant flow rate, a system that does not have a cooling system itself, a system that does not increase the amount of gas circulation, or a system that does not circulate the anode gas in the anode system, It is possible to use the “philosophy of utilizing the water generation accompanying the leak for supplying water to the fuel cell” and the “philosophy of adjusting the gas partial pressure difference according to the water shortage state”.

  In addition, the system of Embodiment 1 becomes a structure which does not have humidification modules, such as an external humidifier. However, the present invention is not limited to this. If necessary, the water supply method of the present invention and the humidification module may be used in combination. In a fuel cell system having a humidifying module, the humidifying capacity of the humidifying module is reduced at the time of low temperature start. As a result, the humidification amount of the gas supplied to the cathode is reduced.

  For this reason, when applying the idea of the present invention to a fuel cell system having a humidifying module, in step S102 of the specific process described above, “when the humidification module is expected to be degraded at the time of low temperature start-up. It may be possible to add a condition for determining that water shortage has substantially occurred only on the cathode side.

  Further, in the first embodiment described above, as the determination condition of the water shortage state in the second characteristic operation, the operation condition in which the water shortage substantially only of the anode and the operation condition in which the water shortage of the cathode only substantially occurs are respectively Some were shown. However, the conditions for determining the water shortage state are not limited to those shown above. In the case of performing determination based on the operating state, in addition to the above examples, it is possible to appropriately grasp the correlation between the operating state of the system and the water shortage state and make a determination based on this.

  Moreover, what is necessary is just to utilize the various techniques which can implement | achieve discrimination | determination of a water shortage state besides the discrimination | determination method based on the above-mentioned operating conditions. For example, a method may be used in which a hygrometer is provided in each of the anode off-gas channel 46 and the cathode off-gas channel 58 to determine the dry state of each electrode.

  In the first embodiment described above, the case where the water shortage substantially occurs only at the anode or the cathode is, in other words, the factor that reduces the voltage when the water shortage (dry up) of the fuel cell occurs. This means the case where the factors b to d described in the second characteristic operation of the first embodiment are described. That is, the polarization in the catalyst layer is the main factor for the voltage drop, which means that the portion where the moisture is insufficient and humidification is required is the anode or cathode catalyst layer.

Embodiment 2. FIG.
[Configuration and Characteristic Operation of Embodiment 2]
In the first embodiment, as described in the explanation of the first characteristic operation, when the fuel cell 12 is in a water-deficient state, the hydrogen partial pressure difference in the fuel cell 12 is increased in principle. On the other hand, as described above, the increase in generated water using cross leak increases the oxygen partial pressure difference and increases the oxygen partial pressure difference to increase the amount of hydrogen moving from the anode to the cathode. This can also be realized by increasing the amount of oxygen transferred to

  Therefore, in the second embodiment, in the same configuration as in the first embodiment, when the fuel cell 12 is in a water-deficient state, in principle, the oxygen partial pressure difference in the fuel cell 12 is increased. In other words, where the hydrogen partial pressure difference is increased in the first feature operation of the first embodiment, the oxygen partial pressure difference is increased in the second embodiment. By doing so, the amount of oxygen that reacts in the anode catalyst layer increases, and the amount of generated water in the fuel cell 12 can be increased as in the first embodiment.

[Specific Processing of Embodiment 2]
The second embodiment is realized by executing a routine shown in the flowchart of FIG. 4 with the same configuration as that of the first embodiment. The flowchart of FIG. 4 is different from the flowchart of FIG. 2 in that steps S120 and 370 are replaced with steps S170 and 470, respectively, and the process of step S131 is deleted and a process of step S171 is newly added. This is the same as the flowchart of FIG. Therefore, the description of the processing similar to the flowchart of FIG. 2 is omitted or simplified.

  In addition to the characteristic operation of the second embodiment described above, the specific process of the second embodiment also includes “adjustment of the gas partial pressure difference according to the water shortage state” which is the second characteristic operation of the first embodiment. The process will be executed. In the following description, only the processing after step S170, which is the difference of the second embodiment from the first embodiment, will be described. Since the processes after step S104 or S114 are the same as those in the first embodiment, the description thereof is omitted.

  In step S170, a process of increasing the oxygen partial pressure difference is performed by increasing the cathode pressure. As a result, the amount of water produced inside the fuel cell 12 due to cross leak increases, and the water shortage of the fuel cell 12 is alleviated. Thereafter, the process of step S122 is executed. After the process of step S122 is performed, a process of increasing the amount of hydrogen circulation is executed for the same purpose as step S131 in accordance with the increase in the amount of generated water in the anode accompanying the increase in the oxygen partial pressure difference (step S171). . Thereafter, the process of S126 is executed.

  If improvement of water shortage is recognized in step S126, the processing from step S170 is executed again. In addition, when improvement of water shortage is not recognized in this step, a process for increasing the anode pressure and increasing the hydrogen partial pressure difference is executed (step S180). Thereafter, the processes of steps S132 and S112 are performed, and the current routine is terminated.

  According to the above process, water can be supplied to the fuel cell 12 using the water generation accompanying the cross leak under the situation where the fuel cell 12 is short of water as in the first embodiment.

  Note that the second embodiment can be modified in various manners as described in the first embodiment, similarly to the first embodiment.

Embodiment 3 FIG.
The fuel cell system of the third embodiment applies the idea of “utilization of water generation accompanying cross leak” as in the first embodiment. However, in the third embodiment, the idea of “adjustment of the gas partial pressure difference according to the water shortage state” of the second characteristic operation of the first embodiment is not used. Instead, the “cross leak amount” described later is used. This is mainly different from the first embodiment in that the idea of “water shortage determination based on” and the idea of “water shortage determination based on stoichiometric ratio” are applied.

[Configuration of Embodiment 3]
FIG. 5 is a schematic diagram showing the configuration of the fuel cell system 10 according to Embodiment 3 of the present invention. The fuel cell system 210 is mounted on, for example, a fuel cell vehicle. The fuel cell system 210 includes a fuel cell 212. In this embodiment, the fuel cell (FC) 212 is a fuel cell (PEMFC) having a solid polymer separation membrane, and is composed of two fuel cell stacks (a stack 212a and a stack 212b).

  Each of the stacks 212a and 212b is configured by stacking a plurality of fuel battery cells (hereinafter also referred to as “unit cells”) including an electrolyte membrane, an anode, a cathode, and a separator. 5 and 6, arrow A indicates the stacking direction of the unit cells. In the present embodiment, each of the stacks 212a and 122b includes 200 unit cells. Adjacent unit cells are stacked with the anode of one cell and the cathode of the other cell facing each other via a separator.

  As shown in FIG. 5, an anode gas channel 214 and a cathode gas channel 216 are introduced into the fuel cell 212. The anode gas flow path 214 is connected to a high-pressure hydrogen tank 218, and hydrogen-rich anode gas is sent from the hydrogen tank 218 to the anodes in the stacks 212a and 212b. A regulator 220 is provided in the anode gas channel 214 downstream of the hydrogen tank 218. The regulator 220 adjusts the pressure of the anode gas at the inlet of the fuel cell 212 to a required appropriate pressure. Further, a pressure sensor 222 is connected to the anode gas flow path 214 downstream of the regulator 220.

  The cathode gas flow path 216 is provided with a pump 224. When the pump 224 is driven, a cathode gas as an oxidizing gas containing oxygen is sent to the cathodes in the stacks 212a and 212b.

  FIG. 6 is a schematic diagram showing in detail the connection between the anode gas channel 214 and the cathode gas channel 216 and each of the stacks 212a and 212b. Here, FIG. 6A shows a connecting portion between the anode gas flow path 214 and each of the stacks 212a and 212b. As shown in FIG. 6A, the anode gas flow path 214 is connected to the stacks 212a and 212b via the distribution pipe 226. The distribution pipe 226 has a function of distributing the anode gas sent from the anode gas flow path 214 to the stack 212a and the stack 212b.

  FIG. 6B shows a connection portion between the cathode gas channel 216 and each of the stacks 212a and 212b. As shown in FIG. 6B, the cathode gas flow path 216 is connected to each of the stacks 212a and 212b via the distribution pipe 228. The distribution pipe 228 has a function of distributing the cathode gas sent from the cathode gas channel 216 to the stack 212a and the stack 212b.

  FIG. 6 shows an arrangement of 400 unit cells included in each of the stacks 212a and 212b. As shown in FIGS. 6A and 6B, the stack 212a is provided with cells with cell numbers # 1 to # 200, and the stack 212b is provided with cells with cell numbers # 201 to # 400. It has been. In the stack 212a, the cell with the cell number # 1 is arranged on the opposite side of the end to which the distribution pipes 226 and 228 are connected, and the cell number increases as the distribution pipes 226 and 228 are approached. The cell number adjacent to is # 200. On the other hand, in the stack 212b, the cell with the cell number # 201 is arranged on the end side to which the distribution pipes 226 and 228 are connected, and the cell number increases as the distance from the distribution pipes 226 and 228 increases. The number of the cell away from is # 400.

  FIG. 7 is a schematic diagram showing a planar configuration of each unit cell and its periphery, and schematically shows a state in which the inside of each stack 212a, 212b is viewed from the stacking direction of the unit cells. That is, FIG. 7 schematically shows a cross section along a direction orthogonal to the cell stacking direction, and corresponds to, for example, the cross section along the alternate long and short dash line II ′ in FIG. Yes.

  As shown in FIG. 7, each unit cell is provided with an anode gas channel 230 and a cathode gas channel 232. Since the flow paths 230 and 232 are provided so as to overlap in the stacking direction of the unit cells, the flow paths 230 and 232 are schematically shown by broken lines in FIG. As shown in FIG. 7, each flow path 230, 232 extends linearly from one end of the cell to the other end.

  Distributing portions 234 and 235 individually connected to the respective flow paths 230 and 232 are provided at both ends of the respective flow paths 230 and 232 so as to overlap in the stacking direction of the unit cells. Manifolds 236, 238, 242, and 244 are provided on the outer sides of the distribution units 234 and 235, respectively. The manifold 236 is connected to the anode gas flow path 230 via the distributor 234. The manifold 238 is connected to a cathode gas flow path 232 via a distribution portion 235. Manifolds 236 and 238 and manifolds 242 and 244 described later are provided as holes penetrating in the stacking direction of the unit cells. The end of the manifold 236 is connected to the distribution pipe 226, and the end of the manifold 238 is connected to the distribution pipe 228.

  A coolant is circulated in each unit cell of the fuel cell 212. Thereby, the excessive temperature rise of the fuel cell 212 accompanying power generation is suppressed, and the temperature of the fuel cell 212 is set to an optimal value. The coolant flows through a cooling system (not shown) provided outside the fuel cell 212, and the circulation amount is controlled by a coolant circulation pump (not shown).

  According to such a configuration, the anode gas sent from the anode gas flow path 214 to each of the stacks 212a and 212b via the distribution pipe 226 is sent to the manifold 236, and from the manifold 236 to the distribution unit 234 and the flow path 230. To the anode of each unit cell. Similarly, the cathode gas sent from the cathode gas flow path 216 to each of the stacks 212 a and 212 b via the distribution pipe 228 is sent to the manifold 238, and from the manifold 238 to each of the distribution section 235 and the flow path 232. Sent to the cathode of the unit cell.

In the anode of the fuel cell 212, when the anode gas is sent in, hydrogen ions are generated from hydrogen in the anode gas (H ₂ → 2H ⁺ + 2e ⁻ ), and when the cathode gas is sent in the cathode, Oxygen ions are generated from the oxygen and electric power is generated in the fuel cell 212. At the same time, water (product water) is generated from the hydrogen ions and oxygen ions at the cathode ((1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O). Most of this water absorbs heat generated in the fuel cell 212 to become water vapor, and is contained in the cathode offgas and discharged.

  The anode off gas discharged from the anode is sent to the manifold 242 shown in FIG. 7, and is sent to the anode off gas flow path 246 shown in FIG. The anode off gas channel 246 is provided with a pump 248, and the anode off gas is returned to the anode gas channel 214 again by driving the pump 248. The anode off gas returned to the anode gas flow path 214 is replenished with hydrogen from the hydrogen tank 218 and is sent to the fuel cell 212 again. By sending the anode off gas to the fuel cell 212, unreacted hydrogen contained in the anode off gas can be reacted in the fuel cell 212, and the utilization efficiency of hydrogen can be improved. It can also be said that the above-described circulation path including the anode gas passage 214 → the anode of the fuel cell 212 → the anode off-gas passage 246 → the pump 226 forms an anode gas circulation passage.

The anode off gas flow path 246 is provided with a gas-liquid separator 250 that collects moisture in the anode off gas. An exhaust valve 254 is connected to the anode off gas flow path 246 downstream of the pump 248. When the anode circulation system consisting of the anode off-gas passage 246 → the anode gas passage 214 → the fuel cell 212 contains a large amount of impurity components such as nitrogen (N ₂ ), the purge is performed by opening the exhaust valve 254 intermittently. To discharge these components.

  Further, a check valve 256 is provided downstream of the location where the exhaust valve 254 is connected. The check valve 256 has a function of preventing the flow from the anode gas flow path 214 toward the pump 248.

  On the other hand, the cathode off gas discharged from the cathode of each unit cell is sent to the manifold 244 shown in FIG. 7 and sent from the manifold 244 to the cathode off gas flow path 258 shown in FIG. The cathode off gas passes through the cathode off gas flow path 258 and is discharged. The cathode offgas flow path 258 is provided with a control valve 262 that adjusts the pressure of the cathode offgas, and a pressure sensor 264 that detects the cathode offgas pressure upstream of the control valve 262. According to the control valve 262, the pressure of the cathode off gas discharged from the fuel cell 212 can be controlled. Further, the flow rate of the cathode gas sent to the fuel cell 212 can be controlled by the pump 224.

  In addition, a humidifier 266 is provided in the cathode off gas flow path 258. A cathode gas flow path 216 is introduced into the humidifier 266. The humidifier 266 has a function of absorbing moisture contained in the cathode offgas generated in the fuel cell 212 and humidifying the cathode gas in the cathode gas flow channel 216 with the absorbed moisture.

  As shown in FIG. 5, the system of the present embodiment includes an ECU (Electronic Control Unit) 240. The ECU 240 is connected to various sensors (not shown) for detecting the output (voltage value, current value), cooling water temperature, etc. of the fuel cell 212 in order to grasp the operating state of the system. The cell voltages of the 400 unit cells included in the battery 212 can be detected. The ECU 240 is connected to the pressure sensors 222 and 264, the regulator 220, the exhaust valve 254, the control valve 262, a coolant circulation pump (not shown), and the like. The ECU 240 can operate the fuel cell 212 in a desired operation state by controlling the output of the fuel cell 212, the pressure of each gas, the flow rate of each gas, and the circulation amount of the coolant.

  In addition, ECU 240 is configured to execute water shortage determination processing for determining whether or not water shortage in fuel cell 212 has occurred, as with ECU 40 of the third embodiment.

[Operation of Embodiment 3]
(First characteristic operation of Embodiment 3 “Utilization of water generation accompanying cross leak”)
Also in the third embodiment, as in the first embodiment, when it is determined that the fuel cell 212 is short of water, the water generation accompanying the cross leak is used for water supply to the fuel cell 212. And Specifically, as in the first embodiment, when the water shortage determination process detects the occurrence of water shortage in the fuel cell 12, in principle, the anode pressure is increased to increase the hydrogen partial pressure difference between the anode and the cathode. As a result, as in the first embodiment, the amount of water generated in the electrode catalyst layer of the cathode can be increased and water can be supplied to the fuel cell 12.

(Second characteristic operation of Embodiment 3 “Water shortage determination based on cross leak amount”)
In the third embodiment, further, for the purpose of efficiently determining the above-described water shortage, a fuel battery cell that is likely to cause water shortage among individual fuel battery cells is specified based on the amount of cross leak. Specifically, in the third embodiment, a cell having a relatively small amount of cross leak is specified, and water shortage determination processing is performed on the cell.

  FIG. 8 is a diagram illustrating a method for calculating the cross leak amount of each unit cell. FIG. 8 shows the voltage drop that occurs when a differential pressure is applied between the cathode and the anode with respect to the initial voltage value of the unit cell and when the cathode and the anode are set to the same pressure. Yes. As shown in the figure, when the differential pressure is applied, the voltage drop is large, and when the same pressure is applied, the degree of the voltage drop is smaller than when the differential pressure is applied.

  In FIG. 8, the amount corresponding to the absolute value of the voltage difference (voltage drop 1) between the voltage at the time of differential pressure and the voltage at the same pressure means a voltage drop due to cross leak, and the voltage drop 2 at the same pressure is a cross It comes from factors other than leaks. Thus, the voltage drop factor of each unit cell can be analyzed from the voltage difference at the time of the differential pressure and at the same pressure. From the analysis, the cross leak amount (gas permeation amount) of each unit cell can be calculated.

  By comparing the gas permeation amount of each unit cell obtained by such an analysis, it is possible to specify a fuel cell having a small cross leak amount. A technique for calculating the cross leak amount as described above is also disclosed in Japanese Patent Laid-Open No. 2005-251482. Therefore, the description of a more specific and detailed method is omitted.

  In the process in which each unit cell of the fuel cell 212 generates power, under a situation where a gas partial pressure difference occurs between the anode and the cathode, hydrogen and oxygen cross-leak through the electrolyte membrane in the unit cell. Yes. When the cross leak amount is different for each unit cell, the amounts of hydrogen and oxygen that are cross leaked in the normal operation state are also different for each unit cell.

  When the amount of cross leak is small, the amount of water generated due to the cross leak naturally becomes small. For this reason, in a unit cell with relatively little cross leak, the amount of water present inside during normal operation is also reduced. As a result, a cell with a small amount of cross leak is in a state where water shortage is more likely to occur compared to other unit cells.

  Therefore, in the second characteristic operation of the third embodiment, a cell with a small amount of cross leak is determined and water shortage is determined for the cell. As a result, water shortage occurring in the fuel cell 212 can be detected reliably and quickly.

(Third feature operation of the third embodiment “water shortage determination based on stoichiometric ratio”)
In the third embodiment, in order to effectively cope with the above-described water shortage, a fuel cell that is likely to cause water shortage among individual fuel cells is specified based on the stoichiometric ratio. Specifically, in the third embodiment, a cell having a relatively large stoichiometric ratio is specified, and the lack of water is determined for the cell. First, a method for obtaining the amount of gas supplied to each unit cell based on the cell voltage change rate will be described in detail below. In the following description, a method of obtaining the cathode gas supply amount to each unit cell will be described. However, the anode gas supply amount can also be obtained by the same method.

  FIG. 9 is a characteristic diagram showing the relationship between the stoichiometric ratio of the cathode gas supplied to the fuel cell 212 and the output of the fuel cell 212. The characteristic obtained by actual measurement during steady operation of the fuel cell 212 is shown. Show. The characteristics shown in FIG. 9 may be acquired with the fuel cell 212 alone or may be acquired with the fuel cell system 210 mounted on a fuel cell vehicle.

  In FIG. 9, the horizontal axis indicates the stoichiometric ratio of the cathode gas flowing through the cathode gas channel 216. This stoichiometric ratio is the ratio of the actual cathode gas flow rate to the theoretical value of the cathode gas flow rate. The theoretical value of the cathode gas flow rate is a value calculated based on the driving load of the fuel cell 212. Usually, the stoichiometric ratio of the cathode gas in the high current density region is set to a value of about 1.2 to 1.5, and the fuel cell 212 is stably operated by increasing the actual cathode gas flow rate from the theoretical value. can do.

  In addition, the vertical axis in FIG. 9 indicates the average value (average cell voltage) of the cell voltage values of all unit cells included in the fuel cell 212. As described above, the ECU 240 can detect the cell voltage of each unit cell, and the average cell voltage is obtained by averaging these cell voltages.

  When acquiring the characteristics of FIG. 9, the flow rate of the anode gas in the anode gas flow path 214 is fixed to a constant value. In obtaining the characteristics of FIG. 9, first, the average cell voltage (reference voltage V0) is detected in a state where the stoichiometric ratio is set to the reference stoichiometric ratio S0. Here, the reference stoichiometric ratio S0 is set to a value larger than the stoichiometric ratio SA during normal operation. Thereafter, the stoichiometric ratio is decreased from the reference stoichiometric ratio S0, and the average cell voltage is detected for each stoichiometric ratio S1, S2, S3.

  As the stoichiometric ratio is decreased from the reference stoichiometric ratio S0, the flow rate of the cathode gas decreases and the amount of reaction in the fuel cell 212 decreases, so the average cell voltage decreases from the reference voltage V0. As shown in FIG. 9, when the stoichiometric ratio decreases from S0 to S1, the average cell voltage becomes V1, and the change ΔV1 in the average cell voltage from the reference voltage V0 becomes (V0−V1). Similarly, when the stoichiometric ratio decreases from S0 to S2, the average cell voltage becomes V2, and the change amount of the average cell voltage becomes ΔV2 (= V0−V2). When the stoichiometric ratio decreases from S0 to S3, the average cell voltage becomes V3, and the amount of change in the average cell voltage becomes ΔV3 (= V0−V3). Thus, the amount of change in the average cell voltage increases as the stoichiometric ratio decreases from the reference stoichiometric ratio S0.

  FIG. 10 is a characteristic diagram (approximate expression) showing the relationship between the change rate of the average cell voltage and the stoichiometric ratio, and is obtained based on the characteristic of FIG. In FIG. 10, the horizontal axis represents the rate of change of the average cell voltage. The change rate of the average cell voltage can be obtained, for example, by dividing the change amounts ΔV1, ΔV2, and ΔV3 of the average cell voltage by the reference voltage V0 in each of the stoichiometric ratios S1, S2, and S3 shown in FIG. That is, the voltage change rate at the stoichiometric ratio S1 is ΔV1 / V0, the voltage change rate at the stoichiometric ratio S2 is ΔV2 / V0, and the voltage change rate at the stoichiometric ratio S3 is ΔV3 / V0. The approximate expression in FIG. 10 is obtained by plotting the voltage change rate at each of the stoichiometric ratios S1, S2, and S3 and connecting them with an approximate curve (straight line).

  The characteristics shown in FIG. 10 reveal the relationship between the voltage change rate of the unit cell and the stoichiometric ratio of the cathode gas. Accordingly, if the cell voltage change rate is obtained in each unit cell, the stoichiometric ratio of each unit cell can be obtained based on the voltage change rate.

  The cell voltage in each unit cell changes by changing the stoichiometric ratio of the cathode gas supplied to the fuel cell 212. Therefore, the voltage change rate of the cell voltage can be obtained from the change amount of the cell voltage of each unit cell when the stoichiometric ratio is varied.

Hereinafter, a method of obtaining the cell voltage change rate in each unit cell will be described. When obtaining the voltage change rate of each unit cell, first, the stoichiometric ratio of the cathode gas in the cathode gas flow path 216 is set to the reference stoichiometric ratio S0 described in FIG. 9, and in this state, the reference voltage V0 ( n). Thereafter, the stoichiometric ratio in the cathode gas passage 16 is lowered from the reference stoichiometric ratio S0 to the stoichiometric ratio SA during normal operation. Then, the cell voltage VA (n) is obtained in each unit cell in a state where the stoichiometric ratio is SA. As a result, the change amount (V0 (n) −VA (n)) of the cell voltage when the stoichiometric ratio changes from S0 to SA is obtained, and the change amount (V0 (n) −VA (n)) is obtained as the reference voltage V0. By dividing by (n), the cell voltage change rate P (n) of each unit cell can be obtained. That is, the voltage change rate P (n) is obtained from the following equation.
P (n) = (V0 (n) -VA (n)) / V0 (n)
In the above formula, n is a cell number.

  The cell voltage change rate P (n) of each unit cell thus obtained is applied to the characteristic (horizontal axis) of FIG. Thereby, the stoichiometric ratio of the cathode gas can be obtained in each unit cell.

  As described above, the theoretical value of the cathode gas flow rate required by the fuel cell 212 is calculated based on the load of the fuel cell 212, and based on this, the theoretical value of the cathode gas flow rate in each unit cell is calculated. Therefore, when the actual stoichiometric ratio in each unit cell is obtained from the characteristics shown in FIG. 10, the actual cathode gas flow rate in each unit cell can be obtained by multiplying this by the theoretical value of the cathode gas flow rate in each unit cell. It becomes possible.

  When it is assumed that the cathode gas is uniformly supplied to all unit cells, the theoretical value of the cathode gas flow rate in each unit cell is divided by the number of cells by the theoretical value of the cathode gas supply amount to the entire fuel cell 212. It becomes the value.

  Thus, according to the method of the present embodiment, the stoichiometric ratio and the cathode gas flow rate in each unit cell can be obtained based on the change rate of the cell voltage of each unit cell. Therefore, it is possible to determine whether or not the cathode gas is satisfactorily supplied to each unit cell.

  In the method of this embodiment, since the cell voltage change rate is calculated by dividing the voltage change amount from the reference voltage V0 by the reference voltage V0, factors other than the gas supply amount, such as the electrolyte membrane and the anode Even if the cell voltage fluctuates due to factors such as deterioration of the catalyst layer and diffusion layer constituting the cathode, short-circuiting, foreign matter mixing into the flow path, etc., the influence is not exerted. Therefore, according to the method of this embodiment, the stoichiometric ratio and the cathode gas flow rate in each unit cell can be accurately obtained in a state where these factors are excluded.

  FIG. 11 is a schematic diagram showing the result of calculating the stoichiometric ratio (cathode gas flow rate) by the above-described method in each unit cell (# 1 to # 400) of the fuel cell 212. In FIG. 11, the horizontal axis indicates the cell number, and the vertical axis indicates the stoichiometric ratio (cathode gas flow rate). By such a method, it is possible to specify a cell number having a relatively large stoichiometric ratio.

  In a unit cell with a large stoichiometric ratio, the amount of water taken away from the interior tends to increase. Therefore, the larger the stoichiometric ratio, the more easily the internal moisture is insufficient. Therefore, in the third characteristic operation of the third embodiment, a cell having a large stoichiometric ratio is specified by the above method, and water shortage determination processing is performed on the cell. As a result, water shortage occurring in the fuel cell 212 can be detected reliably and quickly.

[Specific Processing of Embodiment 3]
Hereinafter, specific processing performed by the system according to the third embodiment will be described with reference to FIG. FIG. 12 is a flowchart of a routine executed by ECU 240 in the third embodiment. The routine of FIG. 12 is executed during the operation of the system of the third embodiment. Further, the routine of FIG. 12 is processing for realizing the first to third characteristic operations of the third embodiment described above.

  When the routine of FIG. 12 is started, first, the temperature of the cooling water of the fuel cell 212 is measured (step S300). In this process, the ECU 240 acquires information on the coolant temperature of the cooling system and detects the temperature of the fuel cell 212.

  Next, it is determined whether or not a cell that is likely to be short of water has been identified (step S302). Here, the ECU 40 determines whether or not the cell specified flag is ON. In the routine of the third embodiment, the cell that is likely to be short of water is specified by the previous routine, and the cell specified flag is turned ON while it can be determined that the specified result can be used effectively. To do. If the cell has not yet been specified, or if the previous result cannot be used effectively, the cell specified flag is set to the OFF state.

  If it is determined in step S302 that the cell is not specified, first, a process for specifying a cell having a small gas permeation amount is executed (step S304). In this process, based on the idea in the second characteristic operation of the third embodiment, first, the gas permeation amount (cross-leakage) of each of the unit cells # 1 to # 400 under the condition that the current density is constant. Amount) is calculated.

  In the third embodiment, a correlation between the amount of cross leak and the ease of occurrence of water shortage is obtained in advance through experiments or the like, and a predetermined threshold is determined. A cell having a cross leak amount equal to or less than this threshold is determined as a cell that is likely to be short of water. In step S304, for each of cells # 1 to # 400, the cross leak amount is compared with a threshold value, and the cell number that is equal to or less than the threshold value is held.

  Subsequently, a process for calculating a cell having a large stoichiometric ratio is executed (step S306). Specifically, based on the idea in the third characteristic operation of the above-described third embodiment, first, the values of the stoichiometric ratios of the unit cells # 1 to # 400 under the condition that the cathode gas flow rate is constant. Is calculated (see FIG. 11). In the third embodiment, a correlation between the stoichiometric ratio and the likelihood of occurrence of water shortage is obtained in advance by experiments or the like, and a predetermined threshold value is set, and a cell having a stoichiometric ratio equal to or lower than this threshold value is insufficient for water. It is determined that the cell is easy to perform. In step S306, for each of cells # 1 to # 400, the stoichiometric ratio is compared with a threshold value, and the cell number that is equal to or less than the threshold value is held.

Next, a process of identifying a cell in the stacked cell that is likely to be short of water is executed (step S308). In this process, the cell that is most likely to cause water shortage is identified among the cells identified in step S304 and the cells identified in step S306. Specifically, in the third embodiment, in terms of the parameter D _A result of generating the ease of water shortage step S304, converted into parameters D _B results generated ease shortages in step S306, D the sum of _a and D _B to identify the largest cells. As described above, by executing the processing of steps S304 to S308, it is possible to identify the cell that is most likely to cause water shortage in the fuel cell 212.

  After the process of step S308 is executed, or after it is determined in step S302 that a cell that is likely to be short of water has been identified, it is subsequently determined whether or not the fuel cell 212 is in a high-temperature operation state. (Step S310). In the third embodiment, a predetermined threshold temperature is set in advance, and it is determined whether or not the fuel cell 212 is in a high temperature operation state based on whether or not the temperature detected in step S300 exceeds the threshold. And If the establishment of this condition is not recognized, the process proceeds to step S318 described later.

  If it is determined that the condition in step S310 is satisfied, it is next determined whether or not the cell voltage has decreased (step S312). Specifically, based on the information on the output voltage of the fuel cell 212 acquired by the ECU 40, it is determined whether or not there is a voltage drop that can be determined that water shortage has occurred in the fuel cell 212. The technique for determining the occurrence of water shortage based on the voltage value is a technique already known as disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-127914. Therefore, the detailed description is abbreviate | omitted. If the establishment of this condition is not recognized, the process proceeds to step S318 described later.

  If the establishment of the condition in step S312 is confirmed, then the state of the cell that is likely to be short of water is confirmed (step S314). Specifically, it is determined whether or not there is a voltage drop in which the occurrence of water shortage is recognized in the cell specified in step S308 or the cell specified in step S302. If the establishment of this condition is not recognized, the process proceeds to step S318 described later.

  When the establishment of the condition in step S314 is confirmed, a process for increasing the anode pressure is executed (step S316). Specifically, the ECU 240 controls the regulator 220 to the valve opening side by a predetermined amount. As a result, the amount of hydrogen that reacts with oxygen on the cathode catalyst increases and the amount of water produced increases. As the amount of generated water increases, the amount of water in the fuel cell 212 increases, and the shortage of water in the fuel cell 212 is alleviated.

  After the execution of the process of step S314, or when the determination conditions of steps S310, 312, and 314 described above are not satisfied, it is subsequently determined whether or not the system operation is continued (step S318). ). In this routine, the ECU 40 detects whether or not a request for stopping the fuel cell system 210 is made. When the fuel cell system 210 is mounted on a vehicle or the like, this determination can be made based on the state of the ignition key.

  If the condition is not satisfied, it is determined that the fuel cell system 210 is still in a state where the operation should be continued, and the processing from step S310 is executed. Accordingly, the operation is continued while performing the determination of water shortage (S310 to S314) and the countermeasure (S316). If there is an operation stop request, it is determined that the operation should be stopped, and the current routine ends.

  According to the above processing, by identifying the cell in which the water shortage is most likely to occur among the unit cells and determining whether or not the water shortage has occurred for this cell, the water shortage of the fuel cell 212 can be efficiently and reliably ensured. Can be detected. When the water shortage occurs, by increasing the anode pressure, the hydrogen partial pressure difference can be increased and the hydrogen cross leak amount can be increased. As a result, water can be supplied into the fuel cell 212 using the water generation function associated with the cross leak, and water shortage can be alleviated.

  In the third embodiment described above, the fuel cell 212 corresponds to the “fuel cell” in the first invention, and the regulator 220 and the control valve 262 correspond to the “pressure adjusting means” in the first invention. When the processing of steps S300 to S314 of the routine described above is executed, the “water shortage determining means” in the first invention performs the processing of step S316, thereby “hydrogen” in the first invention. “Partial pressure difference adjusting means” is realized.

In the above-described third embodiment, each fuel cell (unit cell) constituting the fuel cell 212 corresponds to the “fuel cell” of the tenth aspect of the present invention. Further, in the specific process described above, the processes of steps S302 to S308 are executed, so that the “moisture-poor cell specifying means” of the tenth aspect of the invention executes the processes of steps S310 to S314. The “specific cell water shortage determining means” according to the tenth aspect of the present invention is realized.

In the specific process of the third embodiment described above, the process of step S304 is executed, so that the “means for detecting the cross leak amount of each cell” of the eleventh invention performs the process of step S308. As a result of the execution, the processing according to the eleventh aspect of the invention “identifies a fuel battery cell having a relatively low cross leak amount among the plurality of fuel battery cells as a fuel battery cell having a relatively low moisture content”. , Each has been realized.

In the specific process of the third embodiment described above, the process of step S306 is executed, so that the “means for calculating the stoichiometric ratio of each cell” of the twelfth invention executes the process of step S308. As a result, the processing of “identifying a fuel cell having a relatively large stoichiometric ratio among the plurality of fuel cells as a fuel cell having a relatively low water content” of the twelfth invention is realized. Has been.

[Modification of Embodiment 3]
(First modification)
In the third embodiment, “the idea of utilizing water generation accompanying cross leak for water supply to the fuel cell” included in the first characteristic operation of the third embodiment described above and the second characteristic operation of the third embodiment. Applying both the “philosophy of determining water shortage based on the amount of cross leak” included in FIG. 5 and the “philosophy of determining water shortage based on stoichiometric ratio” included in the third feature operation of the third embodiment, Configured. However, these ideas do not necessarily need to be used in combination, and the fuel cell system may be configured using only “the idea of using water generation accompanying cross leak for supplying water to the fuel cell”.

  Specifically, for example, the system has the same configuration as that of the system of the third embodiment and the flowchart of FIG. 12 is applied to the ECU 240 to “start → water shortage determination (steps S310, 312) → anode pressure increase (S316) → operation”. “Continue? (S318) → End (Return to S310 if establishment is not permitted in S318)” may be executed.

  In the above-described first modification of the third embodiment, the process of steps S310 and 312 is executed, so that the “water shortage determination unit” of the first invention executes the process of step S316. The “hydrogen partial pressure difference adjusting means” of the first invention is realized.

(Second modification)
In the third embodiment, the idea of “water shortage determination based on cross leak amount” included in the second feature operation of the third embodiment and the “water shortage determination based on stoichiometric ratio” included in the third feature operation of the third embodiment. Both of these ideas were used to identify cells that are prone to water shortages. However, these ideas are not necessarily used in combination, and the fuel cell system may be configured using only one of these ideas.

  As described above, a cell having a smaller amount of gas cross leak through the electrolyte membrane is more likely to cause water shortage. Therefore, in the third modification of the third embodiment, using only the above-described “philosophy of performing water shortage determination based on the cross leak amount”, a cell having a relatively small cross leak amount is specified, and the cell Based on the behavior of the voltage, the water shortage is determined. Specifically, in this modification, a plurality of cells having a cross leak amount equal to or smaller than a predetermined threshold value are specified, and the plurality of cells are comprehensively observed to determine water shortage.

  Specifically, in the second modification, the configuration is the same as that of the system of the third embodiment, and by applying the flowchart of FIG. 12, the ECU 240 “start → cooling water temperature measurement (step S300) → cell where water is likely to be insufficient”. (Step S302) → Identification of a cell with a small amount of cross leak (S304) → Water shortage determination (Steps S310, 312, 314) → Anode pressure increase (S316) → Continuation of operation (S318) → End (S318) If the establishment is not confirmed in step S310, the process returns to step S310).

(Third Modification)
Further, as described above, a cell having a larger stoichiometric ratio is more likely to cause water shortage. Therefore, in the third modified example, using only the above-mentioned “thought of performing water shortage determination based on the stoichiometric ratio”, a cell having a relatively large stoichiometric ratio is specified, and based on the behavior of the voltage of the cell, Judgment of water shortage will be made. Specifically, in this modification, a plurality of cells having a stoichiometric ratio equal to or greater than a predetermined threshold are specified, and the plurality of cells are comprehensively observed to determine water shortage.

  Specifically, in the third modification, the configuration is the same as that of the system of the third embodiment, and the flow chart of FIG. 12 is applied to the ECU 240 to “start → cooling water temperature measurement (step S300) → cell where water is likely to be insufficient. (Step S302) → Identification of a cell having a relatively large stoichiometric ratio (S306) → Water shortage determination (Steps S310, 312, 314) → Anode pressure increase (S316) → Continue operation? (S318) → End The routine of “return to S310 when establishment is not recognized in S318” may be executed.

(Fourth modification example “Corresponding to cells that are easily flooded”)
As described above, in a fuel cell (unit cell) with a small amount of gas cross leak through the electrolyte membrane, the amount of water present inside is relatively small during normal operation. That is, conversely, in a cell with a large amount of cross leak, the amount of water present inside is relatively large during normal operation. Further, as described above, the larger the stoichiometric ratio, the more easily the inside of the fuel cell (unit cell) is dried. In other words, the smaller the stoichiometric ratio, the greater the amount of water present inside during normal operation.

  In a cell having a large amount of water inside the fuel cell, so-called flooding is more likely to occur. Therefore, in the fourth modified example, first, a cell having a relatively large cross leak amount and a relatively small stoichiometric ratio is specified among the unit cells. Subsequently, it is determined whether flooding has occurred in the specified cell. When the occurrence of flooding in the cell is detected, the hydrogen partial pressure difference (or oxygen partial pressure difference) between the anode and the cathode is reduced.

  If the hydrogen partial pressure difference (or oxygen partial pressure difference) between the two electrodes is reduced, the cross leak amount is suppressed. As a result, the water generation function associated with the cross leak is suppressed, and the amount of water in the cell plane can be reduced. Thus, according to the fourth modification, the occurrence of flooding can be detected efficiently and accurately, and the amount of water generated due to cross leak can be reduced when flooding occurs.

  Further, in a cell in which flooding occurs, the voltage behavior tends to become unstable. Therefore, in the fourth modified example, when the stabilization of the voltage is recognized after the above-described partial pressure difference is decreased, it is determined that the water in the cell surface has decreased and the flooding has been eliminated, and the normal operation state is restored. I will decide. By doing in this way, it can avoid that the situation where water generation is suppressed although flooding is eliminated is generated.

  As specific processing, for example, independently of execution of the routine of FIG. 12, “Start → Identify cells that are easily flooded (first step) → Determine whether flooding has occurred in the cells (second step) ) → If the flooding has occurred, the partial pressure difference can be reduced, and if no flooding has occurred, the partial pressure difference is not changed (third step) → the routine is completed.

In the fourth modified example described above, the first step described above is the thirteenth "water multimeric cell identification means" of the present invention, the second step is the "cell overhydration determination means" of the thirteenth aspect of the In addition, the third step corresponds to the “hydration excess hydrogen partial pressure difference adjusting means” according to the thirteenth aspect of the present invention.

The first step comprises the above-described "Many cross leak amount is relatively in the unit cell, and the stoichiometric ratio to identify the relatively small cells" process, the fourteenth invention of "the plurality of The fuel cell having a relatively large amount of cross leak among the fuel cells is identified as the fuel cell having a relatively high water content, and the “stoichiometric ratio among the plurality of fuel cells” in the fifteenth aspect of the invention. It corresponds to a process of “specifying a relatively small fuel cell as a fuel cell having a relatively high water content”.

  In the fourth modification, a method is used for determining whether flooding has occurred in a unit cell that has a relatively large cross leak amount and a relatively small stoichiometric ratio. However, it is not always necessary to use both information on the cross leak amount and the stoichiometric ratio for the determination of flooding. For example, the determination of flooding may be performed only for a cell having a relatively large cross leak amount, or the stoichiometry may be determined. The determination of flooding may be performed only for cells having a relatively small ratio.

(Other variations)
The amount of gas that cross leaks through the electrolyte membrane varies depending on the membrane structure (molecular structure, film thickness, etc.). FIG. 13 is a diagram for explaining the tendency of the initial permeation amount of hydrogen with respect to the thickness of the electrolyte membrane. As shown in this figure, it can be seen that the initial transmission amount tends to decrease as the film thickness increases. Therefore, by grasping such a tendency, it is possible to add a condition such that water shortage is likely to occur when the thickness of the electrolyte membrane is large to the water shortage determination condition. In addition, since the amount of cross leak when a differential pressure is applied decreases as the film thickness increases, this tendency is reflected in the increase amount of the hydrogen partial pressure difference (and oxygen partial pressure difference) at the time of water shortage (for example, the film It is also possible to set a parameter according to the thickness).

  Further, when the fuel cell system is mounted on a vehicle, as shown in FIG. 14, the cross leak amount tends to increase as the travel distance becomes longer. Due to this, it is considered that the ease of occurrence of water shortage, the increase in the amount of cross leak when the differential pressure is increased, and the like change according to the travel distance. Therefore, such a tendency is grasped by an experiment or the like in advance, and travel distance information is reflected in the determination of water shortage and the amount of increase in hydrogen partial pressure difference (and oxygen partial pressure difference) (for example, depending on the distance traveled by the parameter) It may be changed).

  The present embodiment can also be applied to the following cases. When the fuel cell system is mounted on a vehicle or the like, pumps that supply cathode gas or anode gas during idle (for example, pumps 224 and 248 in the third embodiment) for the purpose of increasing fuel efficiency (increasing travel distance) and the like. ) May be intermittently stopped while the fuel cell generates power (intermittent operation). In such intermittent operation, the pressure control in the present embodiment can be combined with normal pressure control during intermittent operation as follows.

  FIG. 15 is a diagram for explaining the state of pressure control in the fuel cell before and after the operation state of the fuel cell is switched between normal operation (normal traveling) and intermittent operation. FIG. 15 shows a state where the circuit is in an open state (OC: Open circuit) during intermittent operation. The arrow shown to Fig.15 (a) has shown a mode that a driving | running state switches from a normal driving | operation to an intermittent driving | operation.

  FIG. 15B shows an example of normal pressure control executed when switching to intermittent operation. FIG. 15 (c) shows a case where the operating state is switched as in FIG. 15 (b) and when it is determined that the fuel cell is short of water. It shows a state where pressure control based on the “ideology used for supply” is being executed.

  In the pressure control method shown in FIG. 15B, the anode pressure is controlled to increase during normal operation. During intermittent operation, the pump is stopped when the anode pressure reaches a predetermined value. If the circuit is open in such a state, no gas is consumed by power generation. However, the above-described cross leak causes movement of hydrogen and oxygen, and actually the anode pressure gradually decreases (dotted line in FIG. 15B).

  Therefore, in the present embodiment, the anode pressure is controlled in consideration of the pressure drop caused by the cross leak during the intermittent operation during the pressure control in FIG. Specifically, in the present embodiment, the tendency of a decrease in anode pressure that occurs due to cross leak during normal intermittent operation is grasped. In the intermittent operation when water shortage occurs in the fuel cell, the anode pressure is increased, and the increase in the anode pressure is made slightly excessive in consideration of the pressure drop due to cross leak.

  By doing in this way, the anode pressure for coping with water shortage can be appropriately increased even during intermittent operation, and water generation accompanying cross leak can be used for water supply to the fuel cell.

  Note that the third embodiment can be modified in various manners described in the first and second embodiments, similarly to the first and second embodiments. Specifically, for example, the flow rate of the coolant in the cooling system increases as the hydrogen partial pressure difference or the oxygen partial pressure difference increases as in the case of the specific process of the first embodiment with respect to the third embodiment. (Circulation amount) may be increased. Moreover, it is set as the structure provided with the cooling system containing a radiator, and you may decide to make the cooling temperature in a cooling system low, so that a hydrogen partial pressure difference or an oxygen partial pressure difference is large. Further, the operation amount of the pump 226 may be increased in accordance with the increase in the oxygen partial pressure difference to increase the gas circulation amount in the anode gas circulation passage.

Embodiment 4 FIG.
In the first embodiment, “the idea of using water generation associated with cross leak for water supply to the fuel cell” and “the idea of adjusting the gas partial pressure difference according to the water shortage state” are used in combination. Further, in the third embodiment, based on “the idea of using water generation accompanying cross leak for supplying water to the fuel cell”, “the idea of determining water shortage based on the amount of cross leak”, and “the stoichiometric ratio” The idea of “determination of water shortage” was used in combination. These ideas can also be used in combination.

  In the fourth embodiment, “the idea of using water generation associated with cross leak for supplying water to the fuel cell”, “the idea of adjusting the gas partial pressure difference according to the water shortage state”, and “the amount of cross leak” The four ideas of “idea for determining water shortage” and “idea for determining water shortage based on stoichiometric ratio” are used in combination. In other words, the system of the fourth embodiment is a combination of the ideas of the first and third embodiments.

  FIG. 16 is a flowchart of a routine executed by the fuel cell system according to the fourth embodiment. The flowchart of FIG. 16 is obtained by adding steps S400 and S410 to the flowchart of FIG. 2 and replacing step S100 with step S420. The fourth embodiment is realized by executing the flowchart of FIG. 16 with the same configuration as that of the third embodiment (that is, the configuration shown in FIGS. 5 to 7).

  When the routine of FIG. 16 is executed, first, it is determined whether or not a fuel cell that is likely to be short of water has been identified (step S400). The process of step S400 corresponds to the process of step S302 in the specific process of the third embodiment, and can be realized by executing the process in the same manner, so the description thereof is omitted.

  If the establishment of the condition of step S400 is not confirmed, the fuel cell that is likely to be short of water is specified (step S410). The process of step S410 corresponds to the process of steps S304 to S308 in the specific process of the third embodiment, and since it is realized by executing these processes in the same manner, the description thereof is omitted.

  If the establishment of the condition of step S400 is confirmed, or after the execution of the process of step S410, it is determined whether or not water shortage has occurred in the fuel cell 212 (step S420). In the process of step S420, as described in the third embodiment, whether or not the fuel cell 212 is in a high temperature operation state (corresponding to step S310 of the routine of FIG. 12), and based on the output voltage information of the fuel cell 212. Whether there is a voltage drop that can be determined that water shortage has occurred in fuel cell 212 (corresponding to step S314), or whether there is a voltage drop in which the occurrence of water shortage is recognized in the specified cell ( A determination is made for each of the steps (corresponding to step S314). If all of these conditions are satisfied, it is determined that water shortage has occurred in the fuel cell 212.

  If the establishment of the condition in step S420 is confirmed, the processing from step S102 onward is executed as in the first embodiment. If the determination in step S420 is not satisfied, it is determined that there is no water shortage in the fuel cell 212, and the current routine is terminated.

  According to the process described above, the advantages of the first embodiment and the advantages of the third embodiment can be enjoyed together.

  The flowchart of FIG. 16 executed in the fourth embodiment is obtained by adding steps S400 and S410 to step S420 in the flowchart of FIG. On the other hand, steps S400 and S410 may be added to the flowchart of FIG. 4 executed in the second embodiment, and step S100 may be replaced with step S420. In this case, the process combining the second embodiment and the third embodiment is executed, and the advantages of the second embodiment and the advantages of the third embodiment can be enjoyed together.

  Note that the fourth embodiment can be modified in various manners described in the first to third embodiments, similarly to the first to third embodiments.

  As described above, the cross leak amount is caused by the difference in gas partial pressure between the two electrodes sandwiching the electrolyte membrane. For this reason, if the partial pressure difference of the gas changes, the amount of cross leak changes accordingly. The hydrogen partial pressure difference increases as the anode pressure (hereinafter also referred to as anode pressure) increases, and the oxygen partial pressure difference increases as the cathode pressure (hereinafter also referred to as cathode pressure) increases. However, in this case, it is required that the anode pressure is always greater than the cathode pressure when the hydrogen partial pressure difference is increased, or conversely, the cathode pressure is always greater than the anode pressure when the oxygen partial pressure difference is increased. It does not mean that it is required. Further, when increasing the partial pressure difference of oxygen or hydrogen, it is not always required to increase the differential pressure.

  For example, in the situation where the anode pressure is larger than the cathode pressure, when the cathode pressure is increased and brought close to the same pressure, in principle, the effect of increasing the oxygen partial pressure difference can be obtained. Further, by increasing the anode pressure similarly in the opposite situation, the effect of increasing the hydrogen partial pressure difference can be obtained in principle. If the differential pressure between the anode and the cathode is excessive, the burden on the electrolyte membrane increases, which is not preferable. Therefore, in consideration of this point, the pressure value of each electrode is adjusted to avoid such an excessive pressure difference by increasing the partial pressure difference of oxygen or hydrogen while avoiding an excessive differential pressure. You can also. Specifically, for example, pressure control can be performed such that the cathode pressure is increased within a range equal to or lower than the anode pressure to increase the oxygen partial pressure difference.

It is a figure for demonstrating the fuel cell system of Embodiment 1 of this invention. 3 is a flowchart of a routine that is executed by an ECU in the first embodiment. FIG. 10 is a diagram for illustrating a modification of the first embodiment. It is a flowchart of the routine which ECU performs in Embodiment 2 of this invention. It is a figure for demonstrating the fuel cell system of Embodiment 3 of this invention. It is a figure for demonstrating the fuel cell system of Embodiment 3 of this invention. It is a figure for demonstrating the fuel cell system of Embodiment 3 of this invention. It is a figure explaining the method for calculating the amount of cross leaks of each unit cell. It is a characteristic view which shows the relationship between the flow volume of the cathode gas supplied to a fuel cell, and the output of a fuel cell. It is a characteristic view which shows the relationship between the change rate of the average voltage of each unit cell, and a cathode gas flow rate. It is a schematic diagram which shows the result of having calculated the cathode gas flow rate (stoichiometric ratio) in each unit cell (# 1- # 400) of a fuel cell. 10 is a flowchart of a routine that the ECU executes in the third embodiment. FIG. 10 is a diagram for explaining a modification of the third embodiment. FIG. 10 is a diagram for explaining a modification of the third embodiment. FIG. 10 is a diagram for explaining a modification of the third embodiment. It is a flowchart of the routine which ECU performs in Embodiment 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell system 12 Fuel cell 14 Anode gas flow path 16 Cathode gas flow path 18 Hydrogen tank 20 Modulating pressure valve 21 Shut valve 22 Pressure sensor 24 Pump 26 Circulation pump 46 Anode off-gas flow path 52 Drain valve 54 Exhaust valve 58 Cathode off-gas flow Path 60 Diluter 62 Air exhaust pressure regulating valve 64 Pressure sensor 70 Cooling system 72 Cooling system 74, 76, 78 Pipe line 80, 82 Switching valve 84 Radiator 210 Fuel cell system 212 Fuel cells 212a, 122b Fuel cell stack 214 Anode gas flow Channel 216 Cathode gas channel 218 Hydrogen tank 220 Regulator
222, 264 Pressure sensor 224 Pump 226, 228 Distribution pipe 230, 232 Flow path 234, 235 Distributor 236, 238, 242, 244 Manifold 246 Anode off gas flow path 246 Anode off gas flow path 248 Pump 250 Gas-liquid separator 252 Drain valve 254 Exhaust valve 256 Check valve 258 Cathode off-gas flow path 262 Control valve 264 Pressure sensor 266 Humidifier S0 Standard stoichiometric ratio S1, S2, S3

Claims (15)

A fuel cell;
Pressure adjusting means for adjusting the pressure of the anode and cathode of the fuel cell;
Water shortage determining means for determining whether or not the water inside the fuel cell is short;
A hydrogen partial pressure difference adjusting means for increasing the hydrogen partial pressure difference between the anode and the cathode of the fuel cell when it is determined that the moisture inside the fuel cell is insufficient;
I have a,
The water shortage determining means includes a cathode water shortage determining means for determining that a shortage of water inside the fuel cell is substantially caused only on the cathode side of the fuel cell,
A fuel cell system characterized by increasing a hydrogen partial pressure difference between an anode and a cathode of the fuel cell when it is determined that the water shortage is substantially caused only on the cathode side of the fuel cell. The fuel cell system according to claim 1, characterized in that to increase the hydrogen partial pressure difference by increasing the pressure of the anode. A coolant flow path communicating with the fuel cell;
A coolant flow rate adjusting means for increasing the flow rate of the coolant flowing through the coolant flow path as the difference in hydrogen partial pressure between the anode and cathode of the fuel cell increases,
The fuel cell system according to claim 1 or 2, characterized in that it has a. A coolant flow path communicating with the fuel cell;
Means for adjusting the temperature of the coolant flowing through the coolant flow path;
Cooling temperature adjusting means for lowering the temperature of the coolant as the difference in hydrogen partial pressure between the anode and cathode of the fuel cell increases,
The fuel cell system of any one of claims 1 to 3, characterized in that it has a. The water shortage determining means includes anode water shortage determining means for determining that a shortage of water inside the fuel cell is substantially caused only on the anode side of the fuel cell,
When it is determined that the water shortage substantially occurs only on the anode side of the fuel cell, the fuel cell further comprises an oxygen partial pressure difference adjusting means for increasing the anode water pressure difference between the anode and the cathode of the fuel cell. The fuel cell system according to any one of claims 1 to 4 , characterized in that: 6. The fuel cell system according to claim 5 , wherein the oxygen partial pressure difference is increased by increasing the pressure of the cathode. A coolant flow path communicating with the fuel cell;
A coolant flow rate adjusting means for increasing the flow rate of the coolant flowing through the coolant flow path as the oxygen partial pressure difference between the anode and the cathode of the fuel cell increases,
The fuel cell system according to claim 5 , wherein the fuel cell system comprises: A coolant flow path communicating with the fuel cell;
Means for adjusting the temperature of the coolant flowing through the coolant flow path;
A cooling temperature adjusting means for lowering the temperature of the coolant as the oxygen partial pressure difference between the anode and the cathode of the fuel cell increases.
The fuel cell system according to claim 5, comprising: An anode gas circulation passage communicating with the anode of the fuel cell;
A circulation pump for promoting the circulation of gas in the anode gas circulation flow path;
Gas circulation amount adjusting means for increasing the amount of gas circulation in the anode gas circulation passage as the difference in oxygen partial pressure between the anode and cathode of the fuel cell increases,
9. The fuel cell system according to claim 5 , wherein the fuel cell system includes: The fuel cell comprises a plurality of fuel cells,
Among the plurality of fuel cells, it has a low water content cell specifying means for specifying a fuel cell having relatively low internal moisture,
The water shortage determining means is a specific cell water shortage determining means for determining whether or not the fuel battery cell specified as having relatively low water content in the interior has a shortage of water,
Internal moisture missing judged as Once the fuel cell anode and cathode of claims 1 to 9 any one of claims, characterized in that to increase the hydrogen partial pressure difference of the identified fuel cells Fuel cell system. Means for detecting a cross leak amount of each of the plurality of fuel cells;
The moisture minor cell specifying means, according to claim 10, wherein said water cross leak amount is relatively small fuel cells of the plurality of fuel cells to identify relatively small fuel cells Fuel cell system. Means for calculating a stoichiometric ratio of each of the plurality of fuel cells;
The moisture minor cell specifying means to claim 10 or 11, characterized in that said moisture stoichiometric ratio is relatively large fuel cell of the plurality of fuel cells to identify relatively small fuel cells The fuel cell system described. The fuel cell comprises a plurality of fuel cells,
Among the plurality of fuel cells, a water-rich cell specifying means for specifying a fuel cell having a relatively large amount of water inside,
Cell moisture excess determination means for determining whether or not the moisture is excessive in the fuel cell identified as having a relatively large amount of moisture,
When it is determined that the moisture inside the specified fuel cell is excessive, the hydrogen partial pressure difference adjusting means for reducing the hydrogen partial pressure difference between the anode and the cathode of the fuel cell,
The fuel cell system of any one of claims 1 to 12, characterized in that it has a. Means for detecting a cross leak amount of each of the plurality of fuel cells;
The moisture multimeric cell specifying means, according to claim 13, wherein the moisture cross leak amount is relatively large fuel cell of the plurality of fuel cells is identified as relatively high fuel cell Fuel cell system. Means for calculating a stoichiometric ratio of each of the plurality of fuel cells;
The moisture multimeric cell specifying means, according to claim 13 or 14, wherein the moisture stoichiometric ratio is relatively small fuel cells of the plurality of fuel cells is identified as relatively high fuel cell the fuel cell system according to.

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