JP2009117221A - Fuel cell having stack structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain deterioration of power generation performance caused by flooding in a part of a membrane-electrode assemblies among a plurality of membrane-electrode assemblies in a fuel cell stack. <P>SOLUTION: The fuel cell stack provides an expand metal 42a or an expand metal 42b, which is laminated on at least one surface of each membrane-electrode assembly 41, as a plurality of passage formation members for forming passages flowing a reaction gas (hydrogen and air) to be supplied to gas diffusion electrodes (anode side catalyst layer 411ac and cathode side catalyst layer 411 cc). An expand metal 42A and an expand metal 42b are so formed that a porosity of the expand metal 42b is set to be higher than that of the expand metal 42a. Thus, the expand metal 42b is laminated on the surface of the membrane-electrode assembly 41 wherein flowing speed of the reaction gas becomes slow and flooding is apt to occur, among the plurality of membrane-electrode assemblies 41. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell having a stack structure.

  A fuel cell that generates electricity by an electrochemical reaction between a fuel gas (for example, hydrogen) and an oxidant gas (for example, oxygen) has attracted attention as an energy source. In this fuel cell, a stack in which a plurality of membrane electrode assemblies in which gas diffusion electrodes (anodes and cathodes) are bonded to both sides of an electrolyte membrane having proton conductivity, with a separator interposed therebetween, is laminated. Some have a structure (hereinafter also referred to as a fuel cell stack).

  With respect to such a fuel cell stack, conventionally, as a member for supplying reaction gas (fuel gas and oxidant gas) to each membrane electrode assembly and collecting the generated electricity, lath metal (expanded metal) ) Is proposed (see, for example, Patent Document 1 below).

JP 2007-87768 A JP-A-2005-142001

  By the way, the fuel cell stack is provided with a manifold for distributing and supplying the reaction gas supplied from the outside to each membrane electrode assembly, and the membrane electrode junction is caused by pressure loss or the like inside the manifold. Variations in the flow rate of reaction gas occur between bodies. In the fuel cell stack, generated water is generated by the electrochemical reaction in the membrane electrode assembly, and flooding occurs when the generated water stays excessively on the surface of the membrane electrode assembly. And since the generated water is discharged to the outside of the fuel cell stack by the flow rate of the reaction gas, in some membrane electrode assemblies of the plurality of membrane electrode assemblies, the flow rate of the reaction gas is relatively slow, Compared with other membrane electrode assemblies having a relatively high flow rate of the reaction gas, flooding is likely to occur, resulting in a decrease in power generation performance. Such a problem is particularly noticeable when the amount of reactant gas supplied to the fuel cell stack is small.

  However, in the technique described in Patent Document 1, no consideration has been given to the decrease in power generation performance due to flooding in some of the membrane electrode assemblies described above.

  The present invention has been made to solve the above-described problems, and suppresses a decrease in power generation performance due to flooding in some membrane electrode assemblies of a plurality of membrane electrode assemblies in a fuel cell stack. With the goal.

  The present invention can be realized as the following forms or application examples in order to solve at least a part of the above-described problems.

  [Application Example 1] A fuel cell having a stack structure in which a plurality of membrane electrode assemblies each having gas diffusion electrodes bonded to both surfaces of an electrolyte membrane are stacked with a separator interposed therebetween, each of the membrane electrode assemblies A plurality of flow path components made of expanded metal, each of which is laminated on at least one surface of the gas and constitutes a flow path for flowing a reaction gas to be supplied to the gas diffusion electrode. A fuel cell comprising: a first expanded metal having a first porosity; and a second expanded metal having a second porosity higher than the first porosity.

  In the fuel cell of Application Example 1, as the plurality of flow path constituent members, a first expanded metal having a first porosity and a second expand having a second porosity higher than the first porosity. With metal. Here, the porosity in the expanded metal means the ratio of voids per volume occupied by the expanded metal. And in the fuel cell of this application example, since the porosity of the second expanded metal is higher than that of the first expanded metal, the flow path resistance when the reaction gas flows through the second expanded metal is: Lower than the first expanded metal. Further, in the fuel cell stack, a membrane electrode assembly in which flooding is likely to occur among a plurality of membrane electrode assemblies can be known in advance experimentally or analytically. Therefore, the first expanded metal is laminated on at least one surface of the membrane electrode assembly where flooding is relatively difficult to occur, and the second expanded metal is laminated on at least one surface of the membrane electrode assembly where flooding is relatively likely to occur. By doing so, it is possible to increase the flow rate of the reaction gas on the surface of the membrane electrode assembly where flooding is likely to occur, and to quickly discharge the generated water generated by power generation to the outside of the fuel cell. That is, with the fuel cell of Application Example 1, it is possible to suppress a decrease in power generation performance due to flooding in some membrane electrode assemblies among the plurality of membrane electrode assemblies. The first porosity in the first expanded metal and the second porosity in the second expanded metal are respectively under the condition that the second porosity is higher than the first porosity. It can be arbitrarily set in consideration of the contact resistance with the gas diffusion electrode and the flow path resistance when the reaction gas flows.

  [Application Example 2] The fuel cell according to Application Example 1, wherein the reaction is provided on at least one end side in the stacking direction of the stack structure to supply the reaction gas from the outside to the inside of the fuel cell. A gas supply port; and a reaction gas supply manifold for distributing and supplying the reaction gas to the plurality of membrane electrode assemblies from the reaction gas supply port, and the first expanded metal includes: Of the plurality of membrane electrode assemblies, the second expanded metal is laminated on at least one surface of the membrane electrode assembly disposed at a position where the distance from the reaction gas supply port is relatively short. The fuel cell is laminated on at least one surface of the membrane electrode assembly disposed in a portion of the plurality of membrane electrode assemblies that is relatively far from the reaction gas supply port.

  In the fuel cell stack, when an expanded metal having the same porosity is laminated as the above-mentioned flow path component member on at least one surface of all the laminated membrane electrode assemblies, the pressure loss inside the fuel cell stack, etc. By the surface of the membrane electrode assembly disposed at a site relatively far from the reaction gas supply port, the surface of the membrane electrode assembly disposed at a site relatively close to the reaction gas supply port The flow rate of the reaction gas becomes slower than that. For this reason, flooding is likely to occur in the membrane / electrode assembly disposed at a position relatively far from the reactive gas supply port. Here, “a membrane electrode assembly arranged at a site relatively far from the reaction gas supply port” and “a membrane electrode assembly arranged at a site relatively close to the reaction gas supply port” Is not limited to a single sheet, and may be a plurality of sheets.

  In the fuel cell according to Application Example 2, the first expanded metal is stacked on at least one surface of the membrane electrode assembly disposed at a position where the distance from the reaction gas supply port is relatively close. Since the second expanded metal is laminated on at least one surface of the membrane electrode assembly arranged at a relatively far distance, the flow rate of the reaction gas becomes slow and flooding is likely to occur on the surface of the membrane electrode assembly. The flow rate of the reaction gas can be increased, and the generated water can be quickly discharged out of the fuel cell.

  Application Example 3 In the fuel cell according to Application Example 2, the reaction gas supply port is provided on one end side in the stacking direction of the stack structure, and the second expanded metal is A fuel cell, which is laminated on at least one surface of the membrane electrode assembly disposed at an end opposite to the side where the reactive gas supply port is provided.

  When the reactive gas supply port is provided at one end side in the stacking direction of the stack structure, the membrane electrode assembly disposed at the end opposite to the side where the reactive gas supply port is provided. On the surface, the flow rate of the reaction gas becomes slow, and flooding is likely to occur. Here, the “membrane electrode assembly disposed at the end” is not limited to one, but may be a plurality.

  In the fuel cell of Application Example 3, since the second expanded metal is laminated on at least one surface of the membrane electrode assembly disposed at the end opposite to the side where the reactive gas supply port is provided. The flow rate of the reaction gas is slowed down, and the flow rate of the reaction gas on the surface of the membrane electrode assembly where flooding is likely to occur is increased, so that the generated water can be quickly discharged to the outside of the fuel cell.

  In the fuel cell of Application Example 2, when the reaction gas supply port is provided on both end sides in the stacking direction of the stack structure, the membrane disposed in the center portion in the stacking direction of the stack structure At the surface of the electrode assembly, the flow rate of the reaction gas is slowed down and flooding is likely to occur. Therefore, at least one surface of the membrane electrode assembly in which the second expanded metal is arranged at the center in the stacking direction of the stack structure It may be made to be laminated.

  [Application Example 4] The fuel cell according to Application Example 1, wherein the first expanded metal is arranged in a central portion in the stacking direction of the stack structure among the plurality of membrane electrode assemblies. The membrane electrode junction is laminated on at least one surface of the electrode assembly, and the second expanded metal is disposed at both ends of the stack structure in the stacking direction of the plurality of membrane electrode assemblies. A fuel cell, which is laminated on at least one surface of the body.

  In a fuel cell stack, in general, the temperature of the membrane electrode assembly disposed at both ends in the stacking direction of the stack structure is likely to be lower than that of the membrane electrode assembly disposed at the center due to heat dissipation. For this reason, in the membrane electrode assembly disposed at both ends of the fuel cell stack, the vapor pressure decreases, the generated water is likely to condense and stay, and flooding is likely to occur. Here, the “membrane electrode assembly disposed at the center” and the “membrane electrode assembly disposed at both ends” are not limited to one, and may be a plurality.

  In the fuel cell of Application Example 4, the second expanded metal is laminated on at least one surface of the membrane electrode assembly arranged at both ends in the stacking direction of the stack structure among the plurality of membrane electrode assemblies. Therefore, the flow rate of the reaction gas on the surface of the membrane electrode assembly where flooding is likely to occur can be increased, and the generated water can be quickly discharged out of the fuel cell.

  Application Example 5 The fuel cell according to any one of Application Examples 1 to 4, wherein the second expanded metal is laminated on at least a cathode side surface of the membrane electrode assembly.

  Since the generated water is generated by a cathode reaction, in general, flooding is likely to occur on the cathode side of the membrane electrode assembly. With the fuel cell of Application Example 5, flooding at least on the cathode side of the membrane electrode assembly can be effectively suppressed. Furthermore, if the second expanded metal is also laminated on the surface of the membrane electrode assembly on the anode side, the generated water that has permeated from the cathode to the anode can be effectively discharged through the electrolyte membrane. .

  [Application Example 6] The fuel cell according to any one of Application Examples 1 to 5, wherein the first expanded metal forms cuts arranged in a staggered pattern on the metal thin plate, and In a direction substantially perpendicular to the thickness direction, the wire is stretched so as to widen the cut line, and then formed into a mesh, and then rolled so that the thickness of the first expanded metal becomes the first thickness. And the second expanded metal is formed on the same type of metal thin plate as that used in the production of the first expanded metal, and the cut formed in the metal thin plate used in the production of the first expanded metal. A cut having the same shape with the same arrangement is formed, and the cut is stretched in a direction substantially perpendicular to the thickness direction of the thin metal plate to have the same shape as the first. After forming the eye, the thickness of the second expanded metal is produced by rolling so that the second and the thickness thicker than the first thickness, the fuel cell.

  In the fuel cell of Application Example 6, while forming the cut of the same shape in the same arrangement in the same thin metal plate, after extending the cut in a direction substantially perpendicular to the thickness direction of the thin metal plate, by rolling, The first expanded metal and the second expanded metal can be produced only by changing the thickness of the expanded metal. Therefore, the productivity of the first expanded metal and the second expanded metal, and consequently the productivity of the fuel cell can be improved.

  In addition, by making the thickness of the first expanded metal and the second expanded metal the same, the porosity of the metal thin plate, the arrangement of the cuts formed in the metal thin plate, and the shape are different from each other. May be different from each other. For example, the metal thin plates having different thicknesses are formed with differently arranged cuts in different shapes, and are stretched so as to widen the cuts in a direction substantially perpendicular to the thickness direction of each metal thin plate. You may make it produce a 1st expanded metal and a 2nd expanded metal by rolling so that it may become the same thickness after forming.

  Application Example 7 The fuel cell according to any one of Application Examples 1 to 6, wherein the electrolyte membrane is made of a solid polymer membrane.

  The polymer electrolyte fuel cell using a solid polymer membrane as an electrolyte membrane has a lower operating temperature (about 80 (° C)) than a fuel cell using other electrolyte membranes, so the generated water is condensed. Easy to flood and flooding. The fuel cell of Application Example 7 can effectively suppress partial flooding in the polymer electrolyte fuel cell stack.

  The present invention can also be configured by appropriately combining some of the various features described above.

Hereinafter, embodiments of the present invention will be described based on examples.
A. First embodiment:
A1. Fuel cell stack configuration:
FIG. 1 is a perspective view showing a schematic configuration of a fuel cell stack 100 as a first embodiment of the present invention. This fuel cell stack 100 generally has a stack structure in which a plurality of membrane electrode assemblies each bonded with an anode and a cathode are laminated on both sides of an electrolyte membrane having proton conductivity with a separator interposed therebetween. ing. In this example, a solid polymer membrane was used as the electrolyte membrane. Another electrolyte such as a solid oxide may be used as the electrolyte. In this embodiment, the separator has a three-layer structure (not shown), and in the separator, a hydrogen flow path as a fuel gas to be supplied to the anode and a cathode should be supplied. A flow path of air as an oxidant gas and a flow path of cooling water are formed. The number of membrane electrode assemblies stacked in the fuel cell stack 100 can be arbitrarily set according to the output required for the fuel cell stack 100.

  As shown in the figure, the fuel cell stack 100 is laminated from one end in the order of an end plate 10a, an insulating plate 20a, a current collecting plate 30a, a plurality of fuel cell modules 40, a current collecting plate 30b, an insulating plate 20b, and an end plate 10b. Is made up of. In the present embodiment, these have a substantially rectangular shape. In the fuel cell stack 100, supply manifolds (hydrogen supply manifold, air supply manifold, cooling water supply manifold) for distributing and supplying hydrogen, air, and cooling water to the respective membrane electrode assemblies are provided. Also, an anode offgas and cathode offgas discharged from the anode and cathode of each membrane electrode assembly, and a discharge manifold for collecting cooling water and discharging it outside the fuel cell stack 100 (anode offgas discharge manifold, cathode offgas) A discharge manifold and a cooling water discharge manifold) are formed.

  As shown in the drawing, an air supply port 12i constituting an air supply manifold is formed along the lower long side inside the lower long side of the end plate 10a. A cathode offgas discharge port 12o constituting a cathode offgas discharge manifold is formed inside the upper long side of the end plate 10a along the upper long side. Further, inside the left short side of the end plate 10a, a hydrogen supply port 14i constituting a hydrogen supply manifold and a cooling water supply port 16i constituting a cooling water supply manifold are formed adjacent to each other vertically. Yes. Further, on the right short side of the end plate 10a, a cooling water discharge port 16o constituting a cooling water discharge manifold and an anode off gas discharge port 14o constituting an anode off gas discharge manifold are formed adjacent to each other vertically. Yes.

  Hydrogen as a fuel gas is supplied to the hydrogen supply port 14i from a hydrogen tank (not shown), and the anode offgas discharged from the anode of the fuel cell stack 100 is discharged from the anode offgas discharge port 14o. Air containing oxygen as an oxidant gas compressed by an air compressor (not shown) is supplied to the air supply port 12i, and the cathode offgas discharged from the cathode of the fuel cell stack 100 is discharged from the cathode offgas discharge port 12o. Discharged. The cooling water supply port 16i is supplied with cooling water cooled by a radiator (not shown) and pressurized by a pump, flows through the fuel cell stack 100, is discharged from the cooling water discharge port 16o, and circulates. .

  The end plates 10a and 10b are made of metal such as steel in order to ensure rigidity. The insulating plates 20a and 20b are formed of an insulating member such as rubber or resin. The current collecting plates 30a and 30b are formed of dense carbon, a gas impermeable conductive member such as a copper plate. The current collector plates 30a and 30b are provided with output terminals 32a and 32b, respectively, so that the power generated by the fuel cell stack 100 can be output.

A2. Fuel cell module configuration:
FIG. 2 is an explanatory diagram showing a schematic configuration of the fuel cell module 40 in the first embodiment. FIG. 2A schematically shows a schematic side view of the fuel cell stack 100 of the first embodiment. In the present embodiment, as indicated by a broken line in FIG. 2A, in the fuel cell stack 100, a portion relatively close to the air supply port 12i and the hydrogen supply port 14i shown in FIG. The side portion is called, and a portion relatively far from the air supply port 12i and the hydrogen supply port 14i is called an end portion.

  In the fuel cell stack 100, in the fuel cell module 40 disposed at the end, the flow rate of hydrogen and air supplied from the hydrogen supply manifold and the air supply manifold to each membrane electrode assembly 41 is a pressure loss. For example, the flow rate of hydrogen and air supplied to each membrane electrode assembly 41 of the fuel cell module 40 disposed on the near side portion tends to be slower. For this reason, in the membrane electrode assembly 41 of the fuel cell module 40 arranged at the end portion, the membrane electrode assembly 41 of the fuel cell module 40 arranged at the near side portion is generated by power generation compared to the membrane electrode assembly 41 of the fuel cell module 40 arranged at the near side portion. The generated water tends to cause flooding. Therefore, in the present embodiment, the configuration described below is applied to the fuel cell module 40.

  FIG. 2B shows a cross-sectional structure of the fuel cell module 40 disposed on the near side. FIG. 2C shows a cross-sectional structure of the fuel cell module 40 arranged at the end.

  As shown in FIG. 2 (b), the fuel cell module 40 disposed on the near side portion has the expanded metal 42 a laminated on both surfaces of the membrane electrode assembly 41 and sandwiched by the separator 43. Is made up of. In the present embodiment, the membrane electrode assembly 41 has an anode side catalyst layer 411ac and an anode side gas diffusion layer 411ad joined in this order as an anode to one surface of the electrolyte membrane 411m, and the other side of the electrolyte membrane 411m. On the surface, a cathode side catalyst layer 411cc and a cathode side gas diffusion layer 411cd are joined in this order as a cathode. As the anode side gas diffusion layer 411ad and the cathode side gas diffusion layer 411cd, for example, carbon cloth, carbon paper, or the like is applicable. The anode and the cathode correspond to the gas diffusion electrode in the present invention.

  The expanded metal 42a constitutes a flow path for flowing hydrogen and air to be supplied to the anode and the cathode of the membrane electrode assembly 41, respectively. Since the expanded metal is well known, a detailed description of the expanded metal 42a is omitted, but the expanded metal 42a forms cuts arranged in a staggered pattern on the metal thin plate and the thickness of the metal thin plate. In a direction substantially perpendicular to the direction, the above-mentioned cut is stretched so as to be widened to form a mesh, and then rolled so that the thickness D of the expanded metal 42a becomes a predetermined thickness d1.

  In addition, as shown in FIG. 2C, the fuel cell module 40 disposed at the end portion has the expanded metal 42b laminated on both surfaces of the membrane electrode assembly 41 and sandwiched by the separator 43. It is configured by In the fuel cell module 40 disposed at the end portion, the expanded metal 42b is formed in a staggered manner in the thin metal plate, and the thickness of the thin metal plate is the same as the expanded metal 42a described above. In a direction substantially perpendicular to the direction, the above-mentioned cut is stretched so as to be widened to form a mesh, and then rolled so that the thickness D of the expanded metal 42b becomes a predetermined thickness d2.

  In the present embodiment, both the expanded metal 42a and the expanded metal 42b are manufactured through a process of forming a cut of the same shape in the same arrangement on the same thin metal plate, and only the thicknesses are different from each other. ing. The thickness d2 of the expanded metal 42b is set to be thicker than the thickness d1 of the expanded metal 42a. Therefore, the porosity of the expanded metal 42b is higher than the porosity of the expanded metal 42a. And since the porosity of the expanded metal 42b is higher than the porosity of the expanded metal 42a, the flow path resistance when a reactive gas (hydrogen and air) is allowed to flow through the expanded metal 42b is the reactive gas flowing through the expanded metal 42a. It becomes lower than the channel resistance when flowing. The porosity of the expanded metal 42a and the porosity of the expanded metal 42b, that is, the thickness of the metal thin plate, the arrangement and size of the cuts, and the thicknesses d1 and d2, the porosity of the expanded metal 42b is the expanded metal 42a. In consideration of the contact resistance with the anode side gas diffusion layer 411ad and the cathode side gas diffusion layer 411cd and the flow path resistance when hydrogen or air flows, respectively Can be set. The expanded metal 42a corresponds to the first expanded metal in the present invention. The expanded metal 42b corresponds to the second expanded metal in the present invention.

A3. effect:
FIG. 3 is an explanatory diagram showing the effect of the first embodiment. Regarding the fuel cell module 40 arranged at the end of the fuel cell stack 100 of this embodiment and the fuel cell module arranged at the end of the fuel cell stack of the comparative example, the power generation time and voltage (so-called cell voltage) Showed the relationship. The solid line shown in the figure indicates the relationship between the power generation time and the voltage in the fuel cell module 40 disposed at the end of the fuel cell stack 100 of the present embodiment, and the broken line indicates the fuel cell stack of the comparative example. The relationship between the electric power generation time and voltage in the fuel cell module arrange | positioned at the edge part is shown. The configuration of the fuel cell stack of the comparative example is that, in the fuel cell module disposed at the end portion, the thickness D of the expanded metal laminated on both surfaces of the membrane electrode assembly 41 is D = d1. These are the same as the configuration of the fuel cell stack 100 of the present embodiment.

  In the fuel cell stack of the comparative example, as indicated by a broken line in the figure, flooding occurred in a certain time in the membrane electrode assembly 41 of the fuel cell module arranged at the end portion, and the voltage rapidly decreased. On the other hand, in the fuel cell stack 100 of the present embodiment, as shown by the solid line in the drawing, no flooding occurs in the membrane electrode assembly 41 of the fuel cell module 40 disposed at the end, and the abruptness is abrupt. There was no voltage drop.

  In the fuel cell stack 100 of the first embodiment described above, the expanded metal 42a is formed on both surfaces of the membrane electrode assembly 41 of the fuel cell module 40 arranged in the near side portion among the plurality of membrane electrode assemblies 41. The expanded metal 42b having a higher porosity than the expanded metal 42a is laminated on both surfaces of the membrane electrode assembly 41 of the fuel cell module 40 disposed at the end. Accordingly, the flow rate of the reaction gas is decreased, the flow rate of the reaction gas on the surface of the membrane electrode assembly 41 that is likely to be flooded is increased, and the generated water generated by the power generation is quickly discharged to the outside of the fuel cell stack 100. Can be. That is, the fuel cell stack 100 according to the first embodiment can suppress a decrease in power generation performance due to flooding in a part of the membrane electrode assemblies 41 among the plurality of membrane electrode assemblies 41.

  Further, in the fuel cell stack 100 of the first embodiment, the same metal sheet is formed with the same arrangement and the same shape is cut, and the cut is extended in a direction substantially perpendicular to the thickness direction of the metal sheet. Thereafter, the expanded metal 42a and the expanded metal 42b can be produced only by changing the thickness of the expanded metal by rolling. Therefore, the productivity of the expanded metal 42a and the expanded metal 42b, and hence the productivity of the fuel cell stack 100 can be improved.

B. Second embodiment:
B1. Fuel cell stack configuration:
The configuration of the fuel cell stack of the second embodiment is substantially the same as the configuration of the fuel cell stack 100 of the first embodiment shown in FIG. Therefore, a detailed description of the configuration of the fuel cell stack of the second embodiment is omitted. However, in the fuel cell stack of the second embodiment, the configuration of a part of the plurality of fuel cell modules 40 is different from that of the fuel cell stack 100 of the first embodiment. Hereinafter, the fuel cell module 40 of the second embodiment will be described.

B2. Fuel cell module configuration:
FIG. 4 is an explanatory diagram showing a schematic configuration of the fuel cell module 40 in the second embodiment. FIG. 4A schematically shows a schematic side view of the fuel cell stack. In the present embodiment, as shown by broken lines in FIG. 4A, in the fuel cell stack, both end portions in the stacking direction of the fuel cell module 40 are called end portions, and portions other than these both end portions are the center. It shall be called a part.

  In the fuel cell stack, the temperature of the membrane electrode assembly 41 in the fuel cell module 40 disposed at both ends is likely to be lower than that of the membrane electrode assembly 41 in the fuel cell module 40 disposed in the center due to heat dissipation. For this reason, in the membrane electrode assembly 41 in the fuel cell module 40 disposed at both ends of the fuel cell stack, the vapor pressure decreases, the generated water generated by the power generation is likely to condense and stay, and flooding occurs. It becomes easy. Therefore, in the present embodiment, the configuration described below is applied to the fuel cell module 40.

  FIG. 4B shows a cross-sectional structure of the fuel cell module 40 disposed in the central portion. FIG. 4C shows a cross-sectional structure of the fuel cell module 40 disposed at both ends.

  As shown in FIG. 4 (b), the fuel cell module 40 disposed in the central portion has the expanded metal 42 a laminated on both surfaces of the membrane electrode assembly 41 and sandwiched by the separator 43. It is constituted by. The configuration of the fuel cell module 40 disposed in the central portion is, as can be seen from comparison with FIG. 2, the fuel cell disposed in the near side portion of the fuel cell stack 100 of the first embodiment described above. The configuration of the module 40 is the same.

  In addition, as shown in FIG. 4C, the fuel cell modules 40 disposed at both ends of the fuel cell module 40 have the expanded metal 42b laminated on both surfaces of the membrane electrode assembly 41 and sandwiched by the separator 43. It is configured by The configuration of the fuel cell module 40 disposed at both ends is as shown in the comparison with FIG. 2 and the fuel cell module disposed at the end of the fuel cell stack 100 of the first embodiment described above. The configuration is the same as that of 40.

  Note that the expanded metal 42a and the expanded metal 42b in the present embodiment are the same as the 42a and the expanded metal 42b in the first embodiment, respectively.

  In the fuel cell stack of the second embodiment described above, the expanded metal 42a is laminated on both surfaces of the membrane electrode assembly 41 of the fuel cell module 40 disposed in the central portion among the plurality of membrane electrode assemblies 41. The expanded metal 42b having a higher porosity than the expanded metal 42a is laminated on both surfaces of the membrane electrode assembly 41 of the fuel cell module 40 disposed at both ends. Therefore, the temperature of the membrane electrode assembly 41, which is likely to be flooded due to heat dissipation, is reduced by heat dissipation, and the flow rate of the reaction gas on the surface of the membrane electrode assembly 41 is increased. Can be. That is, the fuel cell stack according to the second embodiment can suppress a decrease in power generation performance due to flooding in a part of the membrane electrode assemblies 41 among the plurality of membrane electrode assemblies 41.

C. Third embodiment:
C1. Fuel cell stack configuration:
The configuration of the fuel cell stack of the third embodiment is substantially the same as the configuration of the fuel cell stack 100 of the first embodiment shown in FIG. Therefore, detailed description of the fuel cell stack of the third embodiment is omitted. Although illustration is omitted, in the fuel cell stack of the third embodiment, an air supply port is also formed in the end plate 10b (see FIG. 1), and the stacking direction of the plurality of fuel cell modules 40 in the fuel cell stack is also shown. The air is supplied into the fuel cell stack from both sides. Accordingly, the configuration of some of the plurality of fuel cell modules 40 is different from that of the fuel cell stack 100 of the first embodiment. Hereinafter, the fuel cell module 40 of the third embodiment will be described.

C2. Fuel cell module configuration:
FIG. 5 is an explanatory diagram showing a schematic configuration of the fuel cell module 40 in the third embodiment. FIG. 5A schematically shows a schematic side view of the fuel cell stack of the third embodiment. In this embodiment, as shown by the broken line in FIG. 5A, in the fuel cell stack, a portion relatively close to the two air supply ports provided in the end plates 10a and 10b is defined as a near side portion. The central part that is relatively far from the two air supply ports is called the central part.

  In the fuel cell stack 40 of the third embodiment, in the fuel cell module 40 disposed in the center portion, the flow rate of air supplied from the air supply manifold to each membrane electrode assembly 41 is reduced by the pressure loss or the like. It tends to be slower than the flow velocity of air supplied to each membrane electrode assembly 41 of the fuel cell module 40 arranged in the section. For this reason, in the membrane electrode assembly 41 of the fuel cell module 40 disposed in the center portion, the membrane electrode assembly 41 of the fuel cell module 40 disposed in the near side portion is generated by power generation as compared with the membrane electrode assembly 41 of the fuel cell module 40 disposed in the near side portion. The generated water tends to cause flooding. Therefore, in the present embodiment, the configuration described below is applied to the fuel cell module 40.

  FIG. 5B shows a cross-sectional structure of the fuel cell module 40 disposed on the near side. FIG. 5C shows a cross-sectional structure of the fuel cell module 40 arranged in the central portion.

  As shown in FIG. 5 (b), the fuel cell module 40 disposed on the near side portion has the expanded metal 42 a laminated on both surfaces of the membrane electrode assembly 41, and these are sandwiched by the separator 43. Is made up of. The configuration of the fuel cell module 40 disposed on the near side portion is the fuel disposed on the near side portion in the fuel cell stack 100 of the first embodiment described above, as can be seen from comparison with FIG. The configuration of the battery module 40 is the same.

  In addition, as shown in FIG. 5C, the fuel cell module 40 disposed in the center portion has the expanded metal 42b laminated on both surfaces of the membrane electrode assembly 41, and sandwiched by the separator 43. It is configured by The configuration of the fuel cell module 40 disposed in the central portion is, as can be seen from the comparison with FIG. 2, the fuel cell module disposed at the end portion of the fuel cell stack 100 of the first embodiment described above. The configuration is the same as that of 40.

  Note that the expanded metal 42a and the expanded metal 42b in the present embodiment are the same as the 42a and the expanded metal 42b in the first embodiment, respectively.

  In the fuel cell stack according to the third embodiment described above, the expanded metal 42a is provided on both surfaces of the membrane electrode assembly 41 of the fuel cell module 40 arranged on the near side among the plurality of membrane electrode assemblies 41. The expanded metal 42b having a higher porosity than the expanded metal 42a is stacked on both surfaces of the membrane electrode assembly 41 of the fuel cell module 40 that are stacked and disposed in the central portion. Accordingly, the flow rate of the reaction gas is decreased, the flow rate of the reaction gas on the surface of the membrane electrode assembly 41 that is likely to be flooded is increased, and the generated water generated by the power generation is quickly discharged to the outside of the fuel cell stack 100. Can be. That is, the fuel cell stack according to the third embodiment can suppress a decrease in power generation performance due to flooding in a part of the membrane electrode assemblies 41 among the plurality of membrane electrode assemblies 41.

D. Variations:
As mentioned above, although several embodiment of this invention was described, this invention is not limited to such embodiment at all, and implementation in a various aspect is possible within the range which does not deviate from the summary. It is. For example, the following modifications are possible.

D1. Modification 1:
In the above embodiment, in the plurality of fuel cell modules 40 constituting the fuel cell stack, the expanded metal 42a and the expanded metal 42b are both formed in the same metal thin plate in the same arrangement and in the same shape. The porosity is made different from each other by making only the thicknesses different from each other, but the present invention is not limited to this. The two types of expanded metal may have the same thickness, and the porosity may be made different from each other by making the thickness of the metal thin plate, the arrangement of the cuts formed in the metal thin plate, and the shape different from each other. For example, the metal thin plates having different thicknesses are formed with differently arranged cuts in different shapes, and are stretched so as to widen the cuts in a direction substantially perpendicular to the thickness direction of each metal thin plate. You may make it produce two types of expanded metals from which a porosity differs mutually by rolling so that it may become the same thickness after forming.

D2. Modification 2:
In the above embodiment, for each membrane electrode assembly 41 of the plurality of fuel cell modules 40, two types of expanded metal (expanded metal 42a or expanded metal 42b) having different porosity are laminated, respectively. The present invention is not limited to this. Three or more types of expanded metal having different porosity may be used. In this case, in the fuel cell stack 100 of the first embodiment, as the distance from the air supply port 12i and the hydrogen supply port 14i increases from the viewpoint of the flow velocity of the reaction gas on the surface of each membrane electrode assembly 41. It is preferable to use an expanded metal having a higher porosity for each fuel cell module 40. The same applies to the fuel cell stack of the third embodiment. Further, in the fuel cell stack of the second embodiment, from the viewpoint of lowering the temperature of each membrane electrode assembly 41 due to heat dissipation, each fuel cell module 40 has an expanded metal with a higher porosity as it moves away from the center. Is preferably used.

D3. Modification 3:
In the above embodiment, in the fuel cell stack, the expanded metal 42b having a higher porosity than the expanded metal 42a is disposed on the fuel cell module 40 disposed at the end where flooding is likely to occur. However, the expanded metal 42a may be stacked only on the cathode side, and the expanded metal 42a having a lower porosity than the expanded metal 42b may be stacked on the anode side. This is because the generated water generated by the power generation is generated by the cathode reaction, and therefore flooding generally tends to occur on the cathode side of the membrane electrode assembly 41.

D4. Modification 4:
In the above embodiment, the expander having a higher porosity than the expanded metal 42a on the both ends of the fuel cell stack (including both ends) or on both surfaces of the membrane electrode assembly 41 of the fuel cell module 40 disposed in the center. Although the metal 42b is laminated, the present invention is not limited to this. In general, in the fuel cell stack, an expanded metal having a higher porosity than the expanded metal 42a on at least one surface of the membrane electrode assembly 41 of the fuel cell module 40 where flooding is likely to occur compared to the other fuel cell modules 40. What is necessary is just to laminate | stack 42b.

D5. Modification 5:
In the above embodiment, the membrane electrode assembly 41 includes the anode side gas diffusion layer 411ad and the cathode side gas diffusion layer 411cd. However, at least one of them may be omitted.

1 is a perspective view showing a schematic configuration of a fuel cell stack 100 as a first embodiment of the present invention. It is explanatory drawing which shows schematic structure of the fuel cell module 40 in 1st Example. It is explanatory drawing which shows the effect of 1st Example. It is explanatory drawing which shows schematic structure of the fuel cell module 40 in 2nd Example. It is explanatory drawing which shows schematic structure of the fuel cell module 40 in 3rd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Fuel cell stack 10a, 10b ... End plate 12i ... Air supply port 12o ... Cathode off gas discharge port 14i ... Hydrogen supply port 14o ... Anode off gas discharge port 16i ... Cooling water supply port 16o ... Cooling water discharge port 20a, 20b ... Insulation Plates 30a, 30b ... current collector plates 32a, 32b ... output terminals 40 ... fuel cell module 41 ... membrane electrode assembly 411m ... electrolyte membrane 411ac ... anode side catalyst layer 411ad ... anode side gas diffusion layer 411cc ... cathode side catalyst layer 411cd ... Cathode side gas diffusion layer 42a, 42b ... Expanded metal 43 ... Separator

Claims (7)

A fuel cell having a stack structure in which a plurality of membrane electrode assemblies in which gas diffusion electrodes are bonded to each other on both sides of an electrolyte membrane, with a separator interposed therebetween,
A plurality of flow path component members made of expanded metal, each of which is laminated on at least one surface of each membrane electrode assembly and constitutes a flow path for flowing a reaction gas to be supplied to the gas diffusion electrode;
The plurality of flow path components are:
A first expanded metal having a first porosity;
A second expanded metal having a second porosity higher than the first porosity.
Fuel cell. The fuel cell according to claim 1, wherein
A reaction gas supply port for supplying the reaction gas from the outside to the inside of the fuel cell, provided on at least one end side in the stacking direction of the stack structure;
A reaction gas supply manifold for distributing and supplying the reaction gas to the plurality of membrane electrode assemblies from the reaction gas supply port,
The first expanded metal is:
Of the plurality of membrane electrode assemblies, are stacked on at least one surface of the membrane electrode assembly disposed at a relatively short distance from the reaction gas supply port,
The second expanded metal is
Of the plurality of membrane electrode assemblies, are stacked on at least one surface of the membrane electrode assembly disposed at a site relatively far from the reaction gas supply port,
Fuel cell. The fuel cell according to claim 2, wherein
The reaction gas supply port is provided on one end side in the stacking direction of the stack structure,
The fuel cell according to claim 1, wherein the second expanded metal is laminated on at least one surface of the membrane electrode assembly disposed at an end opposite to the side where the reactive gas supply port is provided. The fuel cell according to claim 1, wherein
The first expanded metal is:
Of the plurality of membrane electrode assemblies, are stacked on at least one surface of the membrane electrode assembly disposed in the central portion of the stack structure in the stacking direction,
The second expanded metal is
Of the plurality of membrane electrode assemblies, stacked on at least one surface of the membrane electrode assembly disposed at both ends in the stacking direction of the stack structure,
Fuel cell. A fuel cell according to any one of claims 1 to 4,
The fuel cell, wherein the second expanded metal is laminated on at least a cathode side surface of the membrane electrode assembly. A fuel cell according to any one of claims 1 to 5,
The first expanded metal is:
After forming slits arranged in a staggered pattern on the metal thin plate and forming a mesh by extending the slit in a direction substantially perpendicular to the thickness direction of the metal thin plate, the first expand It is made by rolling so that the thickness of the metal becomes the first thickness,
The second expanded metal is
Forming a cut of the same shape in the same arrangement as the cut formed in the metal thin plate used for the production of the first expanded metal on the same type of metal thin plate as that used for the production of the first expanded metal. In addition, after stretching the cut in a direction substantially perpendicular to the thickness direction of the thin metal plate to form a mesh having the same shape as the first, the thickness of the second expanded metal is the first thickness. Produced by rolling to a second thickness that is greater than the thickness of
Fuel cell. The fuel cell according to any one of claims 1 to 6,
The electrolyte membrane is a fuel cell made of a solid polymer membrane.

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