JP2008059874A - Fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the temperature in the stacking direction uniform without increasing the dimension in the stacking direction and requiring the wide installation space by increasing heat radiation of a unit cell arranged around the central part in the stacking direction more than that around the ends, and lengthen the life of the unit cell. <P>SOLUTION: Fuel cells each interposing an electrolyte layer between a fuel electrode and an oxygen electrode are stacked through a separator unit, and the heat radiation property of the fuel cell around the central part in the stacking direction is made higher than that of the fuel cell around the ends. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell stack.

  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, trucks, passenger carts, and luggage carts. The fuel cell may be 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) using pure hydrogen as a fuel gas is actively used because it can reduce the system volume and weight per output.

  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 a fuel gas is supplied to the surface thereof, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions are converted into solid polymer. Permeates the electrolyte membrane. Further, when the other of the gas diffusion electrodes is an oxygen electrode (cathode electrode) and air as an oxidant is supplied to the surface, oxygen in the air is combined with the hydrogen ions and electrons to generate water. The An electromotive force is generated by such an electrochemical reaction.

  The polymer electrolyte fuel cell has a laminated structure in which a separator that forms a supply passage for a reactive gas such as hydrogen gas as a fuel gas or an oxidant gas such as oxygen is disposed outside the MEA. The separator prevents current gas from passing through the MEAs adjacent to each other in the stacking direction, and collects current to extract the generated current to the outside. In this way, a fuel cell stack is configured by laminating a large number of unit cells composed of MEAs and separators.

By the way, although reaction heat is generated by the electrochemical reaction, in the fuel cell stack having a laminated structure, the unit cells arranged in the vicinity of the center have lower heat dissipation than the unit cells arranged at both ends. So the temperature will rise. For this reason, a temperature distribution occurs in the stacking direction. Therefore, the air channel cross-sectional area of the unit cell arranged near the center in the stacking direction of the fuel cell stack should be larger than the air channel cross-sectional area of the unit cell arranged near the end. Has proposed a technique for making the temperature uniform in the stacking direction (see, for example, Patent Document 1).
JP 2000-149967 A

  However, in the conventional fuel cell stack, since the cross-sectional area of the air flow path of the unit cells arranged near the center is increased, the dimensions in the stacking direction are increased. For this reason, the fuel cell stack becomes large, and a large space is required for installation.

  The present invention solves the problems of the conventional fuel cell stack and increases the heat dissipation of the unit cells arranged near the center in the stacking direction more than in the vicinity of the end, thereby increasing the dimension in the stacking direction. Therefore, an object of the present invention is to provide a fuel cell stack in which the temperature can be made uniform in the stacking direction without requiring a large installation space and the life of each unit cell can be extended.

  Therefore, in the fuel cell stack of the present invention, the fuel cell in which the electrolyte layer is sandwiched between the fuel electrode and the oxygen electrode is stacked with the separator unit interposed therebetween, and the heat dissipation of the fuel cell in the vicinity of the center in the stacking direction is the end. It is comprised so that it may become higher than the heat dissipation of the fuel cell in the vicinity.

  In another fuel cell stack of the present invention, the separator unit further includes an extension extending outward from an outlet of the oxidant flow path, and the extension near the center with respect to the stacking direction is an extension near the end. It is formed smaller than the part.

  In still another fuel cell stack of the present invention, the separator unit further includes a plurality of ribs protruding into the oxidant flow path and extending in the flow direction of the oxidant, and near a central portion in the stacking direction. The interval between the adjacent ribs is larger than the interval between the adjacent ribs in the vicinity of the end portion.

  In still another fuel cell stack of the present invention, the separator unit is made of a material having different thermal conductivity, and the separator unit near the center in the stacking direction is more thermally conductive than the separator unit near the end. It is made of a high material.

  According to the structure of claim 1, the temperature in the stacking direction can be made uniform without increasing the size in the stacking direction, and without requiring a large installation space, and the life of each unit cell is increased. Can do.

  According to the configuration of the second aspect, the air flow path resistance can be adjusted with respect to the stacking direction by adjusting the size of the extension. Thereby, the degree of cooling by air can be easily adjusted in the stacking direction, and the temperature distribution in the stacking direction can be made uniform.

  According to the configuration of the third aspect, the air flow path resistance can be adjusted with respect to the stacking direction by adjusting the interval between the adjacent ribs. Thereby, the degree of cooling by the oxidizing agent can be easily adjusted in the stacking direction, and the temperature distribution in the stacking direction can be easily made uniform.

  According to the configuration of the fourth aspect, the degree of cooling by the oxidizing agent can be changed with respect to the stacking direction by combining the separator units formed of materials having different thermal conductivities. Thereby, the temperature distribution in the stacking direction can be easily made uniform.

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

  FIG. 2 is a schematic perspective view showing the configuration of the fuel cell stack according to the first embodiment of the present invention, and 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.

  In the figure, reference numeral 11 denotes a fuel cell stack as a fuel cell (FC) device, which is used as a power source for vehicles such as passenger cars, buses, trucks, passenger carts and luggage carts. Here, the vehicle includes a large number of auxiliary devices that consume electricity, such as a lighting device, a radio, and a power window, which are used even when the vehicle is stopped. Since the required output range is extremely wide, it is desirable to use a fuel cell stack 11 as a power source in combination with a secondary battery or capacitor as a power storage means (not shown).

  The fuel cell stack 11 may be of 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 is preferably a solid polymer type fuel cell. .

  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 type fuel cell is generally a stack in which a plurality of cells (Fuel Cell) in which a catalyst, an electrode and a separator are combined on both sides of an electrolyte layer that transmits ions such as protons are connected in series. Consists of.

  In the present embodiment, the fuel cell stack 11 includes a plurality of cell modules 10. The cell module 10 includes a unit cell (MEA) 10A as a fuel cell, and the unit cell 10A electrically connected to each other, and hydrogen gas as an anode gas introduced into the unit cell 10A. The separator unit 10B that separates the flow path and the air flow path as the cathode gas is set as one set, and a plurality of sets are stacked in the thickness direction. In the cell module 10, the unit cells 10 </ b> A and the separator unit 10 </ b> B are stacked in multiple stages and stacked together with the frame 17 so that the unit cells 10 </ b> A are arranged with a predetermined gap (gap) therebetween. . In this case, the cell modules 10 are connected to each other so that they can conduct electricity and have a fuel gas flow path, that is, a hydrogen gas flow path continuous.

  The unit cell 10A includes a solid polymer electrolyte membrane as an electrolyte layer, an air electrode (cathode electrode) as an oxygen electrode provided on one side of the solid polymer electrolyte membrane, and a fuel provided on the other side. It consists of a pole (anode pole). The air electrode and the fuel electrode include an electrode diffusion layer made of a conductive material that permeates while diffusing the reaction gas, and a catalyst layer formed on the electrode diffusion layer and supported in contact with the solid polymer electrolyte membrane. Consists of.

  Water moves in the unit cell 10A. In this case, when a fuel gas, that is, hydrogen gas as an anode gas is supplied into the fuel chamber formed on the fuel electrode side of the separator unit 10B, hydrogen is decomposed into hydrogen ions and electrons, and the hydrogen ions use proton-entrained water. Along with this, it passes through the solid polymer electrolyte membrane. When the air electrode is a cathode electrode and an oxidant, that is, air as a cathode gas is supplied into an oxygen chamber as an oxidant flow path that is an air flow path formed on the air electrode side of the separator unit 10B, Oxygen therein is combined with the hydrogen ions and electrons to produce water. Moisture permeates through the solid polymer electrolyte membrane as reverse diffusion water and moves into the fuel chamber. Here, the reverse diffusion water means that water generated in the oxygen chamber diffuses into the solid polymer electrolyte membrane and permeates into the fuel chamber through the solid polymer electrolyte membrane in the direction opposite to the hydrogen ions. It is a thing.

  In addition, a device (not shown) for supplying air as an oxidant to the fuel cell stack 11 is shown. In this case, the air passes through the air filter and is sucked into an air supply fan as an oxidant supply source, and from the air supply fan through an air supply line, an intake manifold, and the like, the oxygen chamber of the fuel cell stack 11. That is, it is supplied to the air flow path. In this case, the pressure of the supplied air may be a normal pressure of about atmospheric pressure or a higher pressure. The air supply fan may be of any type as long as it can suck and discharge air, and may be a pump for supplying high-pressure air. The air filter may be of any type as long as it can remove dust, impurities, etc. contained in the air. 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 which is not shown in figure. In the example shown in the figure, air flows through the fuel cell stack 11.

  In addition, the air supply pipe is supplied with water sprayed into the air supplied to the air flow path as necessary, and water for maintaining the air electrode of the fuel cell stack 11 in a wet state. A supply nozzle can also be provided. Further, a condenser for condensing and removing moisture in the air discharged from the fuel cell stack 11 may be disposed at the end of the exhaust manifold. In this case, it is desirable that the water condensed by the condenser is collected in a water tank (not shown). By supplying the water in the water tank to the water supply nozzle, the water can be circulated and reused without being wasted.

  On the other hand, hydrogen gas as a fuel gas passes through a fuel supply line from a fuel storage means (not shown) including a container storing a hydrogen storage alloy, a container storing a hydrogen storage liquid such as decalin, a hydrogen gas cylinder, etc. It is supplied to the inlet of the fuel gas flow path of the battery stack 11. In the example shown in the figure, hydrogen gas flows through the fuel cell stack 11. Then, hydrogen gas discharged as an unreacted component from the outlet of the fuel gas flow path of the fuel cell stack 11 is discharged out of the fuel cell stack 11 through a fuel discharge pipe (not shown). In addition, it is desirable that a water recovery drain tank for separating and recovering water containing the discharged hydrogen gas is disposed in the fuel discharge pipe. Thereby, the hydrogen gas separated from the water and discharged from the water recovery drain tank can be recovered, supplied to the fuel gas flow path of the fuel cell stack 11 and reused.

  In this case, the fuel cell stack 11 as a whole has a flattened rectangular parallelepiped shape, and the air flow inside is in the direction of gravity, that is, from above, as indicated by an arrow A in FIG. It is linear below. In addition, as indicated by an arrow B, the flow of hydrogen gas is in a serpentine shape that folds for each cell module 10 in a gravitational direction, that is, in a horizontal plane that is substantially orthogonal to the direction indicated by the arrow A, that is, a meandering shape. It has become.

  The fuel cell stack 11 is fastened in the stacking direction by end plates (not shown) disposed on the inlet side and the outlet side of the hydrogen gas. The end plates are connected to each other in a state where a force for fastening the cell module 10 is applied by a fastening shaft.

  Next, the configuration of the fuel cell stack 11 will be described in detail.

  FIG. 1 is a schematic cross-sectional view showing the shape of a fuel cell stack according to the first embodiment of the present invention. FIG. 1 is a cross-sectional view taken along the line EE of FIGS. 5 and 6, and FIG. FIG. 5 is a second diagram showing the configuration of the fuel cell separator unit according to the first embodiment of the present invention, and FIG. 6 is the first diagram of the present invention. FIG. 7 is a diagram showing the structure of the separator unit of the fuel cell in this embodiment, and FIG. 7 is a diagram showing the temperature distribution and air flow rate of the fuel cell stack in the first embodiment of the present invention. 1 and 7 show a conventional example and the present embodiment, and FIGS. 4A and 4B are a plan view and a cross-sectional view taken along line DD in FIG.

  As shown in FIG. 4A, the separator unit 10B includes a flat plate-like collector 14 having a substantially rectangular shape, and the collector 14 includes a plurality of ribs 14b extending in the short side direction of the rectangle. The rib 14b protrudes into the air flow path and extends in the air flow direction. Then, the air supplied to the fuel cell stack 11 flows in the direction indicated by the arrow C through the recess 14c formed between the plurality of ribs 14b. The unit cell 10 </ b> A also has a rectangular shape that is almost the same size as the collector 14. FIG. 4 shows only one unit cell 10A and a separator unit 10B for convenience of description. In the cell module 10, the unit cell 10A and the separator unit adjacent to each other vertically in FIG. A set of 10B is stacked.

  The frames 17 disposed on the left and right sides of the collector 14 so as to maintain the positional relationship between the unit cell 10A and the separator unit 10B are configured so that the upper and lower ends are mutually backed up as shown in FIGS. The frame is connected by 17a and 17b.

  In the present embodiment, in order to adjust the resistance of the air flowing in the air flow path of the fuel cell stack 11, as shown in FIGS. 5 and 6, the air outlet side end of the collector 14 (FIGS. 5 and 6). Is connected to an extension portion 14a for adjusting the flow resistance. The extension portion 14 a is a member that extends outward from the outlet of the air flow path, and may be formed integrally with the collector 14.

  As described above, the unit cell 10A includes a solid polymer electrolyte membrane, an air electrode, and a fuel electrode, and generates an electromotive force by an electrochemical reaction. Reaction heat is generated by the electrochemical reaction. The reaction heat is mainly taken away by the air supplied to the fuel cell stack 11. That is, the air supplied to the fuel cell stack 11 functions as an oxidant and also functions as a refrigerant for cooling the unit cell 10A. In addition, when water is sprayed and supplied in the air supplied in order to maintain the air electrode of the fuel cell stack 11 in a wet state, the cooling capacity is further increased.

  Here, when the extension portion 14a is connected to the air outlet side end of the collector 14, the resistance to the air flow discharged from the collector 14 increases, and the flow rate of the air flowing in the air flow path of the fuel cell stack 11 decreases. To do. That is, the air flow path resistance increases and the air flow rate decreases. Therefore, the cooling capacity by air also decreases. Therefore, in the present embodiment, in the fuel cell stack 11, a large extension portion 14a is disposed at a portion where heat dissipation is good and the temperature is low, and a small extension portion 14a is provided at a portion where heat dissipation is not good and the temperature is high. By arranging the above, the temperature of each part is made uniform.

  As shown in FIG. 1A, in the conventional fuel cell stack, the extension portion 14a is not provided. In this case, as described in the section “Background Art”, the unit cell 10A disposed near the center in the stacking direction of the cell modules 10 has a heat dissipation property compared to the unit cells 10A disposed at both ends. Since it is low, the temperature will rise. Therefore, as shown in FIG. 7A, the temperature distribution in the stacking direction of the cell modules 10 is higher near the center and lower as it approaches both ends. The air flow rate is almost uniform.

  Therefore, in the present embodiment, the extension portion 14a is connected to the air outlet side end of the collector 14, and as shown in FIG. 1 (b), disposed near the central portion in the stacking direction of the cell modules 10. The extended portion 14a is made smaller and the extended portion 14a disposed near the end portion is made larger. In addition, the magnitude | size of this extension part 14a can be adjusted by adjusting the protrusion amount to the exit direction (downward direction in a figure) of air. As a result, the air flow resistance is small near the center in the stacking direction of the cell modules 10 and is large near the ends. Therefore, the air flow distribution in the stacking direction of the cell modules 10 is shown in FIG. As shown in the figure, the vicinity of the central portion is high, and it is low as it approaches the end portion. For this reason, the cooling capacity of the air is high in the vicinity of the central portion, and decreases as it approaches the end portion. Therefore, the temperature distribution in the stacking direction of the cell modules 10 is almost uniform.

  In the examples shown in FIGS. 5 and 6, the lower end edge of the extension portion 14a is not horizontal but is inclined, and the shape of the extension portion 14a is a triangle. This is for facilitating the discharge of moisture condensed in the air flow path of the fuel cell stack 11 to the outside of the fuel cell stack 11. Since the shape of the extension portion 14a is a triangle, the moisture flowing down to the extension portion 14a along the surface of the collector 14 passes along the lower end edge of the inclined extension portion 14a in one direction (right in FIGS. 5 and 6). Direction) and it becomes easy to drip from the apex of the triangle. Accordingly, the moisture is smoothly discharged out of the fuel cell stack 11 without staying in the vicinity of the lower end edge of the extension portion 14a.

  As described above, in the present embodiment, the size of the extension portion 14a connected to the air outlet side end of the collector 14 is changed with respect to the stacking direction of the cell modules 10, thereby reducing the air flow path resistance. Thus, the degree of cooling by air is changed with respect to the stacking direction of the cell modules 10 to make the temperature distribution in the stacking direction of the cell modules 10 uniform.

  Thereby, the heat dissipation of the unit cell 10A disposed near the center in the stacking direction of the cell modules 10 can be improved, and a large installation space is required without increasing the size of the fuel cell stack 11. In addition, the temperature can be made uniform in the stacking direction of the cell modules 10, and the life of each unit cell 10A can be extended.

  In the present embodiment, the case where the size of the extension part 14a of the unit cell 10A and the collector 14 included in one cell module 10 is changed has been described. However, all the elements included in the entire fuel cell stack 11 are described. The extension 14a of the unit cell 10A and collector 14 set can be changed. In this case, with respect to the stacking direction of the cell modules 10, the extension portion 14 a of the unit cell 10 </ b> A and the collector 14 disposed near the center of the fuel cell stack 11 is made small and arranged near the end of the fuel cell stack 11. The extension part 14a of the unit cell 10A and the collector 14 provided is enlarged.

  Moreover, although the case where the magnitude | size of the extension part 14a changes gradually was demonstrated, the magnitude | size of the extension part 14a can also be changed in steps. For example, the cell module 10 disposed in the vicinity of the end of the fuel cell stack 11 is made smaller by reducing the extension portion 14 a of the cell module 10 disposed in the vicinity of the center of the fuel cell stack 11 in the stacking direction of the cell modules 10. The extension part 14a is enlarged. In this case, the extension portions 14a of the unit cell 10A and the collector 14 included in the same cell module 10 are set to be equal to each other.

  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. 8 is an enlarged view of the main part of the cell module of the fuel cell according to the second embodiment of the present invention, and FIG. 9 is a diagram showing the temperature distribution and the air flow rate of the fuel cell stack according to the second embodiment of the present invention. is there. 9A and 9B show a conventional example and the present embodiment.

  In the present embodiment, the interval between the adjacent ribs 14b of the collector 14 is such that the unit cell 10A and the collector 14 disposed near the center in the stacking direction of the cell modules 10 as shown in FIG. Widely, the unit cell 10A and the collector 14 arranged near the end of the fuel cell stack 11 are narrow.

  In the conventional fuel cell stack, the interval between the ribs 14 b does not change with respect to the stacking direction of the cell modules 10. In this case, as described in the section “Background Art”, the unit cell 10A disposed near the center in the stacking direction of the cell modules 10 has a heat dissipation property compared to the unit cells 10A disposed at both ends. Since it is low, the temperature will rise. Therefore, as shown in FIG. 9A, the temperature distribution in the stacking direction of the cell modules 10 is higher near the center and lower as it approaches both ends. The air flow rate is almost uniform.

  On the other hand, in the present embodiment, the interval between the adjacent ribs 14b of the collector 14 is large in the vicinity of the central portion in the stacking direction of the cell module 10 and is decreased in the vicinity of the end portion. As shown in FIG. 9B, the air flow rate distribution is high in the vicinity of the central portion and becomes lower as the end portion is approached. For this reason, the cooling capacity of the air is high in the vicinity of the central portion, and decreases as it approaches the end portion. Therefore, the temperature distribution in the stacking direction of the cell modules 10 is almost uniform.

  Thus, in the present embodiment, by changing the interval between the adjacent ribs 14b of the collector 14 with respect to the stacking direction of the cell module 10, the air flow resistance is changed with respect to the stacking direction of the cell module 10, Thus, the degree of cooling by air is changed with respect to the stacking direction of the cell modules 10, and the temperature distribution in the stacking direction of the cell modules 10 is made uniform.

  Thereby, the heat dissipation of the unit cell 10A disposed near the center in the stacking direction of the cell modules 10 can be improved, and a large installation space is required without increasing the size of the fuel cell stack 11. In addition, the temperature can be made uniform in the stacking direction of the cell modules 10, and the life of each unit cell 10A can be extended.

  In the present embodiment, the case has been described in which the interval between the ribs 14b of the unit cell 10A and the collector 14 included in one cell module 10 is changed. The interval between the ribs 14b of the set of the unit cell 10A and the collector 14 can also be changed. In this case, the gap between the ribs 14b of the unit cell 10A and the collector 14 arranged near the center of the fuel cell stack 11 in the stacking direction of the cell modules 10 is reduced, and the vicinity of the end of the fuel cell stack 11 is reduced. The interval between the ribs 14b of the set of the unit cell 10A and the collector 14 arranged in the above is increased.

  Moreover, although the case where the space | interval of ribs 14b changes gradually was demonstrated, the space | interval of ribs 14b can also be changed in steps. For example, with respect to the stacking direction of the cell modules 10, cells disposed near the ends of the fuel cell stack 11 are increased by increasing the interval between the ribs 14 b in the cell module 10 disposed near the center of the fuel cell stack 11. The interval between the ribs 14b in the module 10 is reduced. In this case, the interval between the ribs 14b of the set of the unit cell 10A and the collector 14 included in the same cell module 10 is set to be equal to each other.

  Next, a third embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st and 2nd embodiment, the description is abbreviate | omitted by providing the same code | symbol. Also, the description of the same operations and effects as those of the first and second embodiments is omitted.

  FIG. 10 is an enlarged view of the main part of the cell module of the fuel cell in the third embodiment of the present invention, and FIG. 11 is a diagram showing the temperature distribution and air flow rate of the fuel cell stack in the third embodiment of the present invention. is there. 11A and 11B show a conventional example and the present embodiment.

  In the present embodiment, the collector 14 is formed of materials 21 to 23 having different thermal conductivities, as shown in FIG. In the example shown in FIG. 10, in the unit cell 10A and collector 14 set near the end of the fuel cell stack 11, the collector 14 is made of a material 21 having a low thermal conductivity, for example, stainless steel. In the set of the unit cell 10A and the collector 14 disposed at a position slightly close to the center of the fuel cell stack 11, the collector 14 is made of a material 22 having a higher thermal conductivity than the material 21, such as aluminum or an aluminum alloy. In the unit cell 10A and collector 14 formed and disposed near the center of the fuel cell stack 11, the collector 14 is formed of a material 23 having a higher thermal conductivity than the material 22, such as copper or a copper alloy. Has been.

  In the conventional fuel cell stack, the thermal conductivity of the material forming the collector 14 does not change with respect to the stacking direction of the cell modules 10. In this case, as described in the section “Background Art”, the unit cell 10A disposed near the center in the stacking direction of the cell modules 10 has a heat dissipation property compared to the unit cells 10A disposed at both ends. Since it is low, the temperature will rise. Therefore, as shown in FIG. 11A, the temperature distribution in the stacking direction of the cell modules 10 is higher near the center and lower as it approaches both ends. Note that the thermal conductivity of the material forming the collector 14 is substantially uniform.

  On the other hand, in the present embodiment, the collector 14 is formed from a material having a large value of thermal conductivity near the central portion in the stacking direction of the cell modules 10, and from a material having a small value of thermal conductivity near the end portion. Thus, as shown in FIG. 11B, the distribution of the thermal conductivity value of the collector 14 in the stacking direction of the cell modules 10 is high near the center and decreases as it approaches the end. . For this reason, the cooling capacity of the air is high in the vicinity of the central portion, and decreases as it approaches the end portion. Therefore, the temperature distribution in the stacking direction of the cell modules 10 is almost uniform.

  Thus, in the present embodiment, by changing the thermal conductivity of the material forming the collector 14 with respect to the stacking direction of the cell module 10, the degree of cooling by air is changed with respect to the stacking direction of the cell module 10, Thereby, the temperature distribution in the stacking direction of the cell modules 10 is made uniform.

  Thereby, the heat dissipation of the unit cell 10A disposed near the center in the stacking direction of the cell modules 10 can be improved, and a large installation space is required without increasing the size of the fuel cell stack 11. In addition, the temperature can be made uniform in the stacking direction of the cell modules 10, and the life of each unit cell 10A can be extended.

  In the present embodiment, the case of changing the thermal conductivity of the material forming the collector 14 of the set of the unit cell 10A and the collector 14 included in one cell module 10 has been described. It is also possible to change the thermal conductivity of the material forming the collector 14 of the set of all the unit cells 10A and the collectors 14 included in FIG. In this case, the value of the thermal conductivity of the material forming the collector 14 of the set of the unit cell 10A and the collector 14 disposed near the center of the fuel cell stack 11 in the stacking direction of the cell modules 10 is reduced to reduce the fuel The value of the thermal conductivity of the material forming the collector 14 of the set of the unit cell 10A and the collector 14 disposed near the end of the battery stack 11 is increased.

  Moreover, although the case where the thermal conductivity of the material which forms the collector 14 changes in steps was demonstrated, you may make it the thermal conductivity of the material which forms the collector 14 change gradually. Furthermore, for example, the value of the thermal conductivity of the material forming the collector 14 in the cell module 10 disposed near the center of the fuel cell stack 11 in the stacking direction of the cell modules 10 is increased, and the fuel cell stack 11 The value of the thermal conductivity of the material forming the collector 14 in the cell module 10 disposed in the vicinity of the end can also be reduced. In this case, the thermal conductivity values of the materials forming the collector 14 of the set of the unit cell 10A and the collector 14 included in the same cell module 10 are made equal.

  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 schematic cross section which shows the shape of the fuel cell stack in the 1st Embodiment of this invention, and is EE arrow sectional drawing of FIG. 1 is a schematic perspective view showing a configuration of a fuel cell stack in a first embodiment of the present 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 1st figure which shows the structure of the separator unit of the fuel cell in the 1st Embodiment of this invention. It is a 2nd figure which shows the structure of the separator unit of the fuel cell in the 1st Embodiment of this invention. It is a 3rd figure which shows the structure of the separator unit of the fuel cell in the 1st Embodiment of this invention. It is a figure which shows the temperature distribution and air flow rate of the fuel cell stack in the 1st Embodiment of this invention. It is a principal part enlarged view of the cell module of the fuel cell in the 2nd Embodiment of this invention. It is a figure which shows the temperature distribution and air flow rate of the fuel cell stack in the 2nd Embodiment of this invention. It is a principal part enlarged view of the cell module of the fuel cell in the 3rd Embodiment of this invention. It is a figure which shows the temperature distribution and air flow rate of the fuel cell stack in the 3rd Embodiment of this invention.

Explanation of symbols

10A unit cell 10B separator unit 11 fuel cell stack 14a extension 14b rib

Claims (4)

A fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is stacked with a separator unit in between,
A fuel cell stack characterized in that the heat dissipation performance of the fuel cell in the vicinity of the center in the stacking direction is higher than the heat dissipation performance of the fuel cell in the vicinity of the end portion. The separator unit includes an extension extending outward from the outlet of the oxidant flow path,
2. The fuel cell stack according to claim 1, wherein an extension portion near a central portion in the stacking direction is formed smaller than an extension portion near an end portion. The separator unit includes a plurality of ribs that protrude into the oxidant flow path and extend in the flow direction of the oxidant.
2. The fuel cell stack according to claim 1, wherein an interval between adjacent ribs near a central portion in the stacking direction is formed larger than an interval between adjacent ribs near an end portion. The separator unit is formed of materials having different thermal conductivities,
2. The fuel cell stack according to claim 1, wherein the separator unit in the vicinity of the central portion in the stacking direction is formed of a material having higher thermal conductivity than the separator unit in the vicinity of the end portion.

Images