JP2006310028A - Fuel cell device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise voltage, to suppress a heat generation rate, and to prevent the generation of drying, by decreasing current density in a module near to the inlet side of hydrogen gas in a fuel cell stack. <P>SOLUTION: A fuel cell device has a plurality of modules 10 formed by stacking a fuel cell interposing an electrolyte layer between a fuel electrode and an oxygen electrode, through a separator in which a fuel gas passage is formed along the fuel electrode, and the cell module 10 is a conductive, fuel gas passages in the cell module 10 are connected to each other so as to fold back for every module 10, and the current density of a cell module 10-1 positioned in a place where the probability of generating drying is high is made lower than that of other cell modules 10-2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell device.

  Conventionally, since fuel cells have high power generation efficiency and do not emit harmful substances, they have been put into practical use as power generators for industrial and household use, or as power sources for artificial satellites and spacecrafts. Development is progressing as a power source for vehicles such as buses and trucks. The fuel cell may be an alkaline aqueous solution type, a phosphoric acid type, a molten carbonate type, a solid oxide type, a direct type methanol or the like, but a solid polymer type fuel cell is generally used.

  In this case, the solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes and integrated to join. When one of the gas diffusion electrodes is used as a fuel electrode (anode electrode) and hydrogen gas as fuel is supplied to the surface thereof, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions are converted into a solid polymer electrolyte. Permeates the membrane. Further, when the other of the gas diffusion electrodes is an oxygen electrode (cathode electrode) and air as an oxidizing agent is supplied to the surface thereof, oxygen in the air is combined with the hydrogen ions and electrons to generate water. . An electromotive force is generated by such an electrochemical reaction.

  In the polymer electrolyte fuel cell, since both sides of the polymer electrolyte membrane need to be kept wet, water is supplied to the fuel electrode side and the oxygen electrode side, respectively. In this case, moisture moves as proton-entrained water from the fuel electrode side toward the oxygen electrode side, and moves as back diffusion water from the oxygen electrode side toward the fuel electrode side.

  By the way, in the polymer electrolyte fuel cell, it is known that when the fuel cell is started, the catalyst deteriorates due to mixing of air and hydrogen gas remaining on the fuel electrode side and causing a chemical reaction. (For example, refer to Patent Document 1). Further, when the fuel cell is stopped, the remaining hydrogen gas and air are mixed to cause a chemical reaction, thereby degrading the catalyst.

Thus, a technique has been proposed in which the mixing speed of hydrogen gas and air is increased by making the flow of hydrogen gas into a serpentine shape that turns back each cell module. By shortening the time during which hydrogen gas and air are mixed, deterioration of the catalyst can be prevented.
JP 2002-324564 A

  However, in the conventional fuel cell device, the cell module closer to the hydrogen gas inlet side in the fuel cell stack has a higher hydrogen gas flow rate, and the amount of moisture evaporated from the fuel electrode increases, resulting in a decrease in ionic conductivity. Dry up, which is a phenomenon that occurs. Due to the occurrence of the dry-up, the performance of the fuel cell is lowered, the fuel cell system cannot be stably operated for a long time, and the fuel cell itself is deteriorated.

  The present invention solves the problems of the conventional fuel cell device and reduces the current density in the cell module near the hydrogen gas inlet side in the fuel cell stack, thereby increasing the voltage and suppressing the amount of heat generation. An object of the present invention is to provide a fuel cell device capable of preventing the occurrence of dry-up.

  Therefore, in the fuel cell device of the present invention, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is stacked with a separator having a fuel gas flow path formed along the fuel electrode. A fuel cell device having a plurality of cell modules, wherein the cell modules are connected to each other so as to be conductive and the fuel gas flow paths in the cell modules are folded back for each cell module. The current density of the cell module located at a high place is lower than the current density of the other cell modules.

  In another fuel cell device of the present invention, the area of the fuel cell of the cell module located at a place where the probability of occurrence of dry-up is high is larger than the area of the fuel cell of the other cell module.

  In still another fuel cell device of the present invention, the fuel cell of the cell module located at a place where the dry-up occurrence probability is high is formed in a wave shape.

  According to the present invention, in a fuel cell device, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is laminated with a separator having a fuel gas flow path formed along the fuel electrode. A fuel cell device having a plurality of cell modules, wherein the cell modules are connected to each other so as to be conductive and the fuel gas flow paths in the cell modules are folded back for each cell module. The current density of the cell module located at a high place is lower than the current density of the other cell modules.

  In this case, by reducing the current density in the cell module close to the inlet side of the hydrogen gas, the voltage can be increased, the amount of generated heat can be suppressed, and the occurrence of dry-up can be prevented.

  In another fuel cell device, the area of the fuel cell of the cell module located at a place where the probability of occurrence of dry-up is high is larger than the area of the fuel cell of the other cell module.

  In this case, it is possible to prevent the current density in the cell module located in a place where the dry-up occurrence probability is high.

  In still another fuel cell device, the fuel cell of the cell module located at a place where the dry-up occurrence probability is high is formed in a wave shape.

  In this case, the area of the fuel cell can be increased without increasing the size of the cell module located at a place where the probability of dry-up is high.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a diagram showing the configuration of the fuel cell system according to the first embodiment of the present invention, FIG. 3 is a diagram showing the configuration of the cell module of the fuel cell according to the first embodiment of the present invention, and FIG. It is a schematic cross section which shows the structure of the unit cell of the fuel cell in the 1st Embodiment of invention.

  In FIG. 2, reference numeral 20 denotes a fuel cell stack as a fuel cell device (FC), which is used as a power source for vehicles such as passenger cars, buses, trucks, passenger carts, and luggage carts. Here, the vehicle is equipped with a large number of auxiliary devices that consume electricity, such as lighting devices, radios, and power windows, which are used even when the vehicle is stopped. Since the output range is extremely wide, it is desirable to use the fuel cell stack 20 as a power source and a secondary battery as a power storage means (not shown) in combination.

  The fuel cell stack 20 is of an alkaline aqueous solution type (AFC), phosphoric acid type (PAFC), molten carbonate type (MCFC), solid oxide type (SOFC), direct methanol (DMFC), or the like. However, a polymer electrolyte fuel cell (PEMFC) is desirable.

  More preferably, PEMFC (Proton Exchange Membrane Fuel Cell) type fuel cell or PEM (Proton Exchange Membrane) using hydrogen gas as fuel gas, that is, anode gas, and oxygen or air as oxidant, that is, cathode gas. ) Type fuel cell. Here, the PEM fuel cell is generally a fuel cell in which a catalyst, an electrode, and a separator are combined on both sides of a solid polymer electrolyte membrane as an electrolyte layer that transmits ions such as protons. Are composed of a plurality of stacks connected in series.

  In the present embodiment, the fuel cell stack 20 includes a plurality of, for example, ten cell modules 10 to be described later. Then, as shown in FIG. 3, the cell module 10 is electrically connected to a unit cell (MEA) 10A as a fuel cell and the unit cells 10A, and is introduced into the unit cell 10A. The separator 10B for separating the hydrogen gas flow path and the air, and the unit cell 10A and the separator 10B as one set are configured to overlap each other in the thickness direction. In the cell module 10, the unit cells 10 </ b> A and the separators 10 </ b> B are stacked and stacked in multiple stages so that the unit cells 10 </ b> A are arranged with a predetermined gap (gap) therebetween.

  The unit cell 10A includes an air electrode 12 as an oxygen electrode provided on the side of the solid polymer electrolyte membrane 11 as an electrolyte layer and a fuel electrode 13 provided on the other side. The air electrode 12 is composed of an electrode diffusion layer made of a conductive material that permeates while diffusing the reaction gas, and a catalyst layer that is formed on the electrode diffusion layer and is supported in contact with the solid polymer electrolyte membrane 11. Become. Further, the air electrode side as a mesh-like current collector in which a large number of openings are formed that are in contact with the electrode diffusion layer on the air electrode 12 side of the unit cell 10A and collect a mixed flow of air and water. It has a collector 14 and a fuel electrode side collector 15 as a mesh current collector for contacting the electrode diffusion layer on the fuel electrode 13 side of the unit cell 10A and similarly leading out current.

  And in unit cell 10A, as FIG. 4 shows, water moves. In FIG. 4, 48 is a fuel chamber as a fuel gas flow path, and 49 is an oxygen chamber as an air flow path. In this case, when a fuel gas, that is, hydrogen gas as an anode gas is supplied into the fuel chamber 48 of the fuel electrode side collector 15, hydrogen is decomposed into hydrogen ions and electrons, and the hydrogen ions are accompanied by proton-entrained water. It passes through the solid polymer electrolyte membrane 11. Further, when the air electrode 12 is a cathode electrode and an oxidant, that is, air as a cathode gas is supplied into the oxygen chamber 49, oxygen in the air is combined with the hydrogen ions and electrons to generate water. Is done. Moisture permeates through the solid polymer electrolyte membrane 11 as reverse diffusion water and moves into the fuel chamber 48 of the fuel electrode side collector 15. Here, the reverse diffusion water means that the water generated in the oxygen chamber 49 diffuses into the solid polymer electrolyte membrane 11 and permeates through the solid polymer electrolyte membrane 11 in the direction opposite to the hydrogen ions. It penetrated up to 48.

  FIG. 2 shows an apparatus for supplying hydrogen gas as a fuel gas and air as an oxidant to the fuel cell stack 20. Although hydrogen gas, which is fuel taken out by reforming methanol, gasoline, or the like by a reformer (not shown), can be directly supplied to the fuel cell stack 20, it is stable and sufficient even during high-load operation of the vehicle. In order to be able to supply an amount of hydrogen gas, it is desirable to supply the hydrogen gas stored in the fuel storage means 73. Thereby, the hydrogen gas is always sufficiently supplied at a substantially constant pressure, so that the fuel cell stack 20 can follow the fluctuation of the load of the vehicle and supply a necessary current. . In this case, the output impedance of the fuel cell stack 20 is extremely low and can be approximated to zero.

  Hydrogen gas is stored in a container containing a hydrogen storage alloy, a container containing a hydrogen storage liquid such as decalin, a fuel storage means 73 such as a hydrogen gas cylinder, a first fuel supply line 21 as a fuel supply line, and The fuel is supplied to the inlet of the fuel gas flow path of the fuel cell stack 20 through a second fuel supply pipe 33 as a fuel supply pipe connected to the first fuel supply pipe 21. The first fuel supply pipe 21 is provided with a fuel storage means on-off valve 24, a pressure sensor 27, a first fuel pressure adjustment valve 25a, a second fuel pressure adjustment valve 25b, and a fuel supply electromagnetic valve 26. The The second fuel supply pipe 33 is provided with a safety valve 33a and a pressure sensor 78 for detecting the pressure in the fuel gas passage. In this case, the fuel storage means 73 has a sufficiently large capacity and is capable of always supplying sufficiently high pressure hydrogen gas.

  The hydrogen gas discharged as an unreacted component from the outlet of the fuel gas flow path of the fuel cell stack 20 is discharged to the outside of the fuel cell stack 20 through the fuel discharge pipe 31. A water recovery drain tank 60 as a recovery container is disposed in the fuel discharge line 31. The water recovery drain tank 60 is connected with a fuel discharge line 30 for discharging water and the separated hydrogen gas. The fuel discharge line 30 is provided with a suction circulation pump 36 as a pump. Yes. A hydrogen circulation electromagnetic valve 34 is disposed in the fuel discharge line 30. The end of the fuel discharge line 30 opposite to the water recovery drain tank 60 is connected to the second fuel supply line 33. Thereby, the hydrogen gas discharged to the outside of the fuel cell stack 20 can be recovered, supplied to the fuel gas flow path of the fuel cell stack 20, and reused.

  Further, a startup fuel discharge conduit 56 is connected to the water recovery drain tank 60, and a hydrogen startup exhaust solenoid valve 62 is disposed in the startup fuel discharge pipeline 56, so that the fuel cell stack 20 is started up. The hydrogen gas discharged from the fuel gas channel can be discharged into the atmosphere. The outlet end of the starting fuel discharge line 56 is connected to the exhaust manifold 71. In addition, a hydrogen combustor may be provided in the startup fuel discharge line 56 as necessary. The hydrogen gas discharged by the hydrogen combustor can be combusted to form water, and then discharged into the atmosphere.

  Here, the first fuel pressure regulating valve 25a and the second fuel pressure regulating valve 25b are those of a butterfly valve, a regulator valve, a diaphragm type valve, a mass flow controller, a sequence valve, etc., but the first fuel pressure regulating valve Any type of hydrogen gas may be used as long as the pressure of the hydrogen gas flowing out from the outlets of 25a and the second fuel pressure regulating valve 25b can be adjusted to a preset pressure. The pressure adjustment may be performed manually, but is preferably performed by an actuator including an electric motor, a pulse motor, an electromagnet, or the like.

  The fuel supply solenoid valve 26, the hydrogen circulation solenoid valve 34, and the hydrogen activation exhaust solenoid valve 62 are so-called on-off types, and are operated by an actuator including an electric motor, a pulse motor, an electromagnet, and the like. The fuel storage means original opening / closing valve 24 is operated manually or automatically using an electromagnetic valve. Further, the suction circulation pump 36 may be of any type as long as it can forcibly discharge the reverse diffusion water together with the hydrogen gas and can bring the inside of the fuel gas passage into a negative pressure state. Good.

  On the other hand, air as an oxidant is supplied from an oxidant supply source 75 such as an air supply fan, an air cylinder, or an air tank to an air flow path of the fuel cell stack 20 through an oxidant supply line 77 and an intake manifold 74. Supplied. In this case, the pressure of the supplied air is a normal pressure of about atmospheric pressure. Note that oxygen can be used as the oxidizing agent instead of air. And the air discharged | emitted from an air flow path is discharged | emitted in air | atmosphere through the exhaust manifold 71 as a manifold, the condenser 72, the exit side exhaust manifold 22, and the exhaust port 22a.

  The oxidant supply pipe 77 is provided with a water supply nozzle 76 for spraying water to maintain the air electrode 12 of the fuel cell stack 20 in a wet state. Further, the air electrode 12 and the fuel electrode 13 can be cooled by the sprayed water. Further, the condenser 72 disposed at the end of the exhaust manifold 71 is for condensing and removing moisture contained in the air discharged from the fuel cell stack 20, and is condensed by the condenser 72. The water thus collected is collected in the water tank 52 through the condensed water discharge pipe 79. A drainage pump 51 is disposed in the condensed water discharge conduit 79, and a level gauge (water level gauge) 52a is disposed in the water tank 52.

  Further, the water in the water tank 52 is supplied to the water supply nozzle 76 through the water supply pipe 53. A water supply pump 54 and a water filter 55 are disposed in the water supply line 53. Here, the drainage pump 51 and the water supply pump 54 may be of any kind as long as they can suck and discharge water. The water filter 55 may be of any kind as long as it removes dust, impurities, etc. contained in water.

  The secondary battery as the power storage means is a so-called battery (storage battery), and a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, a lithium ion battery, a sodium sulfur battery, and the like are generally used. The power storage means does not necessarily have to be a battery, and electrically stores and discharges energy, such as a capacitor (capacitor) such as an electric double layer capacitor, a flywheel, a superconducting coil, and a pressure accumulator. Any form may be used as long as it has a function. Furthermore, any of these may be used alone, or a plurality of them may be used in combination.

  The fuel cell stack 20 is connected to a load (not shown) and supplies the generated current to the load. Here, the load is generally an inverter device that is a drive control device, and converts a direct current from the fuel cell stack 20 or the power storage means into an alternating current to rotate a vehicle wheel. To supply. Here, the drive motor also functions as a generator, and generates a so-called regenerative current when the vehicle is decelerated. In this case, since the drive motor is rotated by the wheel to generate electric power, the wheel is braked, that is, functions as a vehicle braking device (brake). Then, the regenerative current is supplied to the power storage means, and the power storage means is charged.

  In the present embodiment, the fuel cell system has an FC control ECU (Electronic Control Unit) (not shown) as a control device. The control device includes arithmetic means such as a CPU and MPU, storage means such as a magnetic disk and semiconductor memory, an input / output interface, and the like, and the fuel gas flow of the fuel cell stack 20 from various sensors including a hydrogen concentration detector (not shown). The oxidant supply source 75, the first fuel pressure adjustment valve 25a, and the second fuel pressure adjustment valve 25b are detected by detecting the flow rate, temperature, output voltage and the like of hydrogen, oxygen, air, etc. supplied to the passage and the air passage. The operation of the fuel supply solenoid valve 26, the hydrogen circulation solenoid valve 34, the suction circulation pump 36, the drainage pump 51, the feed water pump 54, the hydrogen activation exhaust solenoid valve 62, and the like is controlled. Further, the FC control ECU cooperates with other sensors provided in the vehicle and an EV (Electric Vehicle) control ECU (not shown) as a vehicle control means to supply fuel and oxidant to the fuel cell stack 20. Centrally control the operation of all equipment supplied.

  Next, the occurrence of dry-up in a conventional fuel cell device will be described.

  FIG. 5 is a schematic diagram showing the flow of hydrogen in the fuel cell stack, FIG. 6 is a diagram showing a change in the average cell voltage of each cell module, and FIG. 7 is a diagram showing factors affecting the dry-up.

  Here, a conventional fuel cell device in which 10 cell modules are stacked to form one fuel cell stack will be described as an example. In this case, the flow of hydrogen gas in the fuel cell stack is in a serpentine shape that is folded back for each cell module, that is, in a serpentine shape, as indicated by arrows in FIG. In FIG. 5, 1M to 10M indicate the order of the cell modules from the hydrogen gas inlet side to the outlet side in the fuel cell stack, which means the first to the tenth cell modules. . Moreover, the thickness of the arrow in FIG. 5 has shown the flow velocity and pressure of hydrogen gas.

  From FIG. 5, it can be seen that the flow rate and pressure of hydrogen gas are higher in the cell module on the inlet side of hydrogen gas, and the flow rate of hydrogen gas is lower as the cell module is closer to the outlet side. And, it can be considered that the higher the flow rate and pressure of the hydrogen gas, the more easily moisture is taken from the fuel electrode. Therefore, it can be considered that the cell module closer to the hydrogen gas inlet side is more likely to dry up.

  And when the inventor of this invention experimented and measured the change of the average cell voltage in each of the 1st-10th cell modules 1M-10M, the result as shown in FIG. 6 was obtained. I was able to. In FIG. 6, the vertical axis represents the average cell voltage [V], and the horizontal axis represents time [seconds]. In FIG. 6, A is a line indicating changes in the average cell voltage in each of the second to tenth cell modules 2M to 10M, and B is a change in the average cell voltage in the first cell module 1M. It is a line which shows.

  From FIG. 6, the average cell voltage in the second to tenth cell modules 2M to 10M is almost constant over time, whereas the average cell voltage in the first cell module 1M is It turns out that it falls as time passes. The decrease in average cell voltage in the first cell module 1M indicates a decrease in performance due to the occurrence of dry-up. From this, it was confirmed that dry-up occurred in the first cell module 1M closest to the hydrogen gas inlet side.

  Factors that affect dry-up include those shown in FIG. First, there is a “current density” shown in the upper left of FIG. If the “current density” increases due to an increase in the load of the fuel cell device, the “cell temperature” increases. When the “cell temperature” rises, the “moisture take-out amount” increases. As a result, “dry-up” occurs.

  Another factor is “cooling amount”. When the “cooling amount” decreases, the “cell temperature” increases. When the “cell temperature” rises, the “moisture removal amount” increases and “dry up” occurs.

  Further, as other factors, there are “air electrode pressure” and “fuel electrode pressure”. When the “air electrode pressure” and the “fuel electrode pressure” are low, the moisture easily evaporates, so that the “moisture take-out amount” increases. As a result, “dry-up” occurs.

  Another factor is the number of unit cells included in each cell module, that is, “number of cells per module”. If the “number of cells per module” is small, the “hydrogen flow rate” increases. When the “hydrogen flow rate” increases, the “moisture take-out amount” increases and “dry up” occurs.

  Therefore, in the present embodiment, the occurrence of dry-up is prevented by reducing the current density in the cell module that has a high probability of dry-up.

  FIG. 1 is a diagram illustrating a configuration of a fuel cell stack according to the first embodiment of the present invention, and FIG. 8 is a diagram illustrating IV characteristics of the cell module according to the first embodiment of the present invention.

  As shown in FIG. 1, the fuel cell stack 20 in the present embodiment has a plurality of cell modules 10. In this case, the flow of hydrogen gas in the fuel cell stack 20 has a serpentine shape that is folded back for each cell module 10 as indicated by arrows in FIG. In FIG. 1, the first cell module 10 closest to the hydrogen gas inlet is indicated as 10-1, and the other cell modules 10 are collectively indicated as 10-2. In the case where the cell modules 10-1 and 10-2 are collectively described, the cell modules 10 will be described.

  The fuel cell stack 20 includes an end plate 81a on the hydrogen gas inlet side, an end plate 81b on the hydrogen gas outlet side, an insulating plate 82a on the hydrogen gas inlet side, an insulating plate 82b on the hydrogen gas outlet side, a hydrogen gas Current collector plate 83a on the inlet side and a current collector plate 83b on the hydrogen gas outlet side. Note that when the end plates 81a and 81b, the insulating plates 82a and 82b, and the current collecting plates 83a and 83b are described in an integrated manner, the end plates 81a, 81b, and the current collecting plates 83 will be described. The cell module 10 is sandwiched between the end plates 81a and 81b from the hydrogen gas inlet and outlet sides via the insulating plates 82a and 82b and the current collector plates 83a and 83b. The end plates 81a and 81b are connected to each other in a state where a force for fastening the cell module 10 is applied by the fastening shaft 86.

  Here, the first cell module 10-1 is electrically connected to the current collector plate 83a, and the cell module 10-2 that is closest to the hydrogen gas outlet side is electrically connected to the current collector plate 83b. It is connected. Further, adjacent cell modules 10 are electrically connected to each other. The cell modules 10 have good electrical conductivity.

  In the present embodiment, the first cell module 10-1 is larger than the other cell modules 10-2, and the area of each unit cell 10A and separator 10B in the first cell module 10-1 is as follows. The area of each unit cell 10A and separator 10B in the other cell module 10-2 is larger. In FIG. 1, reference numeral 87 denotes a hydrogen pipe, which is arranged to introduce hydrogen gas discharged from the end of the large first cell module 10-1 into the end of the adjacent cell module 10-2. However, if unnecessary, it can be omitted as appropriate.

Here, FIG. 8 shows IV characteristics representing the relationship between the current and voltage of the cell module 10 in the fuel cell stack 20. In FIG. 8, the vertical axis represents the average cell voltage [V], and the horizontal axis represents the current density [A / cm ² ]. In FIG. 8, C is a line indicating the IV characteristic of the cell module 10, and it is shown that the average cell voltage decreases as the current density increases. The line D indicates 1.48 [V], which is the cell voltage when it is assumed that there is no heat loss, that is, the theoretical value of the cell voltage. Further, C-1 is a point corresponding to the first cell module 10-1 on the line C, and C-2 is a point corresponding to the cell module 10-2 on the line C. The line E indicates the average cell voltage in the other cell module 10-2.

  From the points C-1 and C-2, the area of each unit cell 10A and separator 10B in the first cell module 10-1 is larger than the area of each unit cell 10A and separator 10B in the other cell module 10-2. Since it is large, it can be seen that the current density in the first cell module 10-1 is smaller than the current density in the other cell module 10-2. Accordingly, it can be seen that the average cell voltage in the first cell module 10-1 is higher than the average cell voltage in the other cell modules 10-2. G represents the difference between the average cell voltage in the first cell module 10-1 and the average cell voltage in the other cell module 10-2.

  F-1 indicates the difference between the average cell voltage in the first cell module 10-1 and the cell voltage when it is assumed that there is no heat loss. F-2 indicates the other cell module 10-. 2 shows the difference between the average cell voltage at 2 and the cell voltage assuming no heat loss. From F-1 and F-2, the average cell voltage in the first cell module 10-1 is assumed to have no heat loss compared to the average cell voltage in the other cell modules 10-2. It can be seen that the value is close to the voltage. This means that the amount of heat generated in the first cell module 10-1 is smaller than the amount of heat generated in the other cell module 10-2. F-1 and F-2 represent the magnitude of heat loss due to heat generation in the first cell module 10-1, and the magnitude of heat loss due to heat generation in the other cell modules 10-2. . That is, in the first cell module 10-1, heat loss due to heat generation is reduced by an amount corresponding to the voltage indicated by G, compared to the other cell modules 10-2. Note that the amount of heat generated per unit cell 10A is obtained by multiplying the difference between the cell voltage and the actual cell voltage when there is no heat loss by the amount of current.

  Thus, in the first cell module 10-1, the area of each unit cell 10A is larger than the area of each unit cell 10A in the other cell module 10-2, and the current density is low, so the amount of heat generated is You can see that it is lower. Since the calorific value is low, the temperature of each unit cell 10A can be kept low, so that the occurrence of dry-up can be prevented.

  Thus, in the present embodiment, the current density in the first cell module 10-1, which is the cell module 10 with a high probability of occurrence of dry-up, is reduced. As a result, the current density in the first cell module 10-1 can be reduced to reduce the amount of heat generated, so that the occurrence of dry-up can be prevented.

  Accordingly, even when the fuel cell stack 20 is operated at a high load for a long time, dry-up does not occur. Therefore, a vehicle using the fuel cell stack 20 as a power source when traveling on an expressway, an uphill or the like. Driving performance is improved.

  Next, a second embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st Embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operation and the same effect as those of the first embodiment is also omitted.

  FIG. 9 is a schematic cross-sectional view showing the configuration of the cell module of the fuel cell according to the second embodiment of the present invention.

  In the present embodiment, each unit cell 10A in the first cell module 10-1, which is a cell module 10 with a high probability of dry-up, is formed in a wave shape as shown in FIG. Yes. Therefore, the area of the unit cell 10A can be made larger than that formed in a flat plate shape as in the first embodiment. The separator 10B is formed in a flat plate shape as in the first embodiment.

  Thus, in this Embodiment, since each unit cell 10A in the 1st cell module 10-1 is formed in the waveform, without enlarging the 1st cell module 10-1. The area of each unit cell 10A in the first cell module 10-1 can be made larger than the area of each unit cell 10A in the other cell module 10-2.

  In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.

It is a figure which shows the structure of the fuel cell stack in the 1st Embodiment of this invention. It is a figure which shows the structure of the fuel cell system in the 1st Embodiment of this invention. It is a figure which shows the structure of the cell module of the fuel cell in the 1st Embodiment of this invention. It is a schematic cross section which shows the structure of the unit cell of the fuel cell in the 1st Embodiment of this invention. It is a schematic diagram which shows the flow of hydrogen in a fuel cell stack. It is a figure which shows the change of the average cell voltage of each cell module. It is a figure which shows the factor which affects dry-up. It is a figure which shows the IV characteristic of the cell module in the 1st Embodiment of this invention. It is a schematic cross section which shows the structure of the cell module of the fuel cell in the 2nd Embodiment of this invention.

Explanation of symbols

10, 10-1, 10-2 Cell module 10A Unit cell 10B Separator 11 Polymer electrolyte membrane 12 Air electrode 13 Fuel electrode 20 Fuel cell stack 48 Fuel chamber

Claims (3)

A fuel cell device having a plurality of cell modules in which a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is stacked with a separator having a fuel gas flow path formed along the fuel electrode,
The cell modules are connected to each other so that they can conduct electricity and the fuel gas flow paths in the cell modules are folded back for each cell module,
A fuel cell device, wherein a current density of a cell module located in a place where a dry-up occurrence probability is high is lower than a current density of another cell module.   2. The fuel cell device according to claim 1, wherein an area of the fuel cell of the cell module located in a place where the probability of occurrence of dry-up is high is larger than the areas of the fuel cells of other cell modules.   The fuel cell device according to claim 2, wherein the fuel cell of the cell module located in a place where the probability of occurrence of dry-up is high is formed in a wave shape.

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