JP2013004458A - Gas passage structure for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas passage structure for a fuel cell which can increase the temperature and improve the performance of the fuel cell by efficiently diffusing generated water retained under projections on a cathode-side separator back to an anode side.SOLUTION: A contact area per unit of projections 22 on an anode-side separator 20 with a membrane-electrode assembly 10 is set smaller than a contact area per unit of projections 32 on a cathode-side separator 30 with the membrane-electrode assembly 10. A passage pitch of a fuel gas passage 21 formed between the projections 22 is set smaller than a passage pitch of an oxidation gas passage 31 formed between the projections 32 so that the projections 32 and the projections 22 are arranged in a staggered manner. A contact ratio of the projections 22 on the anode-side separator 20 with the membrane-electrode assembly 10 is set lower than a contact ratio of the projections 32 on the cathode-side separator 30 with the membrane-electrode assembly 10.

Description

  The present invention relates to a gas flow path structure of a fuel cell.

  As shown in FIG. 5A, a solid polymer electrolyte fuel cell includes an electrolyte membrane 51 made of an ion exchange membrane, an anode (fuel electrode) 52 disposed on one surface of the membrane, a gas diffusion layer 54, and the electrolyte. A membrane electrode assembly (MEA) comprising a cathode (oxygen electrode) 53 and a gas diffusion layer 55 disposed on the other surface of the membrane, and fuel gas (hydrogen) and oxidant gas at the anode and cathode Separators 60 and 70 having protrusions 62 and 72 for forming gas flow paths 61 and 71 for supplying (oxygen, usually air) are alternately arranged. The fuel cell is composed of a stack in which a laminated body of single cells (single cells) composed of the MEA and the separator is integrated. A solid polymer electrolyte fuel cell is particularly attracting attention as a power source for a moving body such as a vehicle because it is easy to downsize and operates at a low temperature. In the general fuel cell (single cell) shown in FIG. 5A, the contact rate of the projections 62 of the anode-side separator 60 and the contact rate of the projections 72 of the cathode-side separator 70 are the same. Further, the contact areas of the protrusions 62 and the protrusions 72 with each MEA are also the same. Further, the gas channel 61 and the gas channel 71 have the same channel pitch.

  In order to put this type of fuel cell into practical use, downsizing and cost reduction are required. For this reason, a fuel cell that can be performed under high-temperature, non-humidified operating conditions that can simplify the cooling / humidification system is desired.

  In order to perform the high-temperature / non-humidified operation, it is effective to promote the reverse diffusion of the cathode side generated water, that is, the diffusion of the generated water from the cathode side to the anode side (Patent Document 1). For this purpose, it is effective to promote the evaporation of the produced water in the anode channel (fuel gas channel).

  In order to promote evaporation, in the anode flow path (fuel gas flow path), the area of the protrusion where the separator contacts the anode is reduced, and the distance between the protrusions, that is, the fuel gas flow path width is increased. Thus, it has been proposed to increase the ratio of the flow path (Patent Document 2).

  In the fuel cell (single cell) of Patent Document 2, the contact rate of the projections 62 of the anode-side separator 60 is set smaller than the contact rate of the projections 72 of the cathode-side separator 70. Further, the contact area between the protrusion 62 and the MEA per protrusion 72 is also narrower on the anode-side protrusion 62. Further, the gas channel 61 and the gas channel 71 have the same channel pitch, and as shown in FIG. 5B, the centers of the protrusions 62 and 72 are arranged to face each other.

JP 2009-259758 A JP 2004-342442 A

  However, since the generated water that has diffused to the anode flow path side is likely to accumulate under the protrusions of the separator on the fuel gas flow path side, in the conventional configuration, it is said that promotion of the reverse diffusion of the generated water is efficiently performed. There is a difficult problem. That is, the configuration of the conventional general fuel cell shown in FIG. 5 (a) and the flow path pitch of the protrusions of the separator disposed on the anode side and in contact with the membrane electrode assembly as in Patent Document 2, the cathode side If the protrusion pitches of the separators that are in contact with the membrane electrode assembly are made the same, and the protrusions of both separators are opposed to each other, There is a problem that despreading is difficult.

  The object of the present invention is to solve the above-mentioned problems and efficiently back-diffusion the staying generated water under the projections of the cathode-side separator to the anode side, thereby improving the high temperature and performance of the fuel cell. It is to provide a channel structure.

  In order to solve the above problems, the invention of claim 1 is characterized in that a membrane electrode assembly having electrodes on both surfaces of a solid polymer electrolyte membrane and having a gas diffusion layer on the surface is provided between the anode side separator and the cathode side separator. Each separator has a plurality of projections in contact with the membrane electrode assembly, the anode gas separator passages serve as fuel gas flow paths, and the cathode separator separator projections serve as oxidation gas flow paths. In the gas flow path structure of the fuel cell, the contact area per one of the projections of the anode side separator with respect to the membrane electrode assembly is defined as the contact area per one of the projections of the cathode side separator with respect to the membrane electrode assembly. Less than the area and formed between the channel pitch of the fuel gas channel formed between the projections of the anode side separator and the projection of the cathode side separator. A gas flow path structure for a fuel cell, wherein the oxidant gas flow path pitches are made different from each other, and a part or all of the protrusions of the cathode side separator and the anode side separator are shifted from each other. It is a summary.

  According to the configuration of the first aspect of the present invention, the contact area per one of the projections of the anode side separator with respect to the membrane electrode assembly is equal to or less than the contact area of each of the projections of the cathode side separator with respect to the membrane electrode assembly. The fuel gas flow path and the oxidizing gas flow path are made different in pitch, and the protrusions of the cathode separator and the anode separator are displaced from each other so that they stay below the protrusions of the cathode separator. The generated water has a shorter moving distance to the region of the membrane electrode assembly excluding the portion below the protruding portion of the anode-side separator as compared to the case where it is not. For this reason, the reverse diffusion efficiency of the generated water staying under the protrusion of the cathode separator is increased. That is, the distance that the generated water staying under the cathode-side protrusions until the reverse diffusion reaches the gas flow path of the anode-side separator is shortened, and the reverse diffusion effect can be promoted. In particular, since part or all of the protrusions of the cathode separator and the anode separator are arranged so as to be shifted, the back diffusion efficiency of the generated water staying at the center of the protrusion of the cathode separator is increased.

The phrase “displaced” means that the centers of the protrusions on which the protrusions of the anode-side separator and the cathode-side separator face each other do not coincide with each other.
According to a second aspect of the present invention, in the first aspect, the flow pitch of the fuel gas flow path is smaller than the flow pitch of the oxidizing gas flow path.

According to the second aspect of the present invention, even when the channel pitch of the fuel gas channel is made smaller than the channel pitch of the oxidizing gas channel, the operation of the first aspect is easily realized.
The invention according to claim 3 is the invention according to claim 2, wherein the contact rate with the membrane electrode assembly by the projection of the anode separator is greater than the contact rate with the membrane electrode assembly by the projection of the cathode separator. Characterized by being made smaller. The contact rate is the ratio of the total contact area of the protrusions to the total area of the surface of the gas diffusion layer facing the protrusions.

  According to the invention of claim 3, the contact rate with the membrane electrode assembly by the projection of the anode separator is smaller than the contact rate with the membrane electrode assembly by the projection of the cathode separator, and the fuel Since the channel pitch of the gas channel is smaller than the channel pitch of the oxidizing gas channel, the number of projections of the anode separator increases, and the projection of the anode separator and the membrane electrode assembly The current collecting resistance can be reduced.

  According to a fourth aspect of the present invention, in the second aspect, the contact rate with the membrane electrode assembly by the projections of the anode separator is the same as the contact rate with the membrane electrode assembly by the projections of the cathode separator. It is characterized by that.

  According to the invention of claim 4, by making the contact rate with the membrane electrode assembly by the projection of the anode side separator the same as the contact rate with the membrane electrode assembly by the projection of the cathode side separator. As compared with the case where the contact rates are different, damage to the membrane electrode assembly due to the protrusions of both separators is suppressed.

The invention of claim 5 is characterized in that, in claim 1, the flow pitch of the fuel gas flow path is larger than the flow pitch of the oxidizing gas flow path.
According to the fifth aspect of the present invention, even when the flow path pitch of the fuel gas flow path is larger than the flow path pitch of the oxidizing gas flow path, the operation of the first aspect is easily realized.

  According to a sixth aspect of the present invention, in the fifth aspect, the contact area per one of the projections of the anode-side separator with respect to the membrane electrode assembly is defined as one contact area of the projections of the cathode-side separator with respect to the membrane electrode assembly. It is characterized by the same contact area as the hit.

  According to the invention of claim 6, the contact area per one of the projections of the anode side separator with respect to the membrane electrode assembly is defined as the contact area per one of the projections of the cathode side separator with respect to the membrane electrode assembly. Even if it is the same, the operation described in claim 1 can be easily realized.

  A seventh aspect of the present invention is the method according to the fifth aspect, wherein the contact area per one of the projections of the anode-side separator with respect to the membrane electrode assembly is defined as one contact area of the projections of the cathode-side separator with respect to the membrane electrode assembly. It is characterized by being narrower than the contact area.

  According to the invention of claim 7, the contact area per one of the projections of the anode side separator with respect to the membrane electrode assembly is defined as the contact area per one of the projections of the cathode side separator with respect to the membrane electrode assembly. In other words, since the cathode side is larger than the anode side, the contact rate is more positive because it has an effect (lid effect) that can suppress the evaporation of generated water by the oxidizing gas in the oxidizing gas flow path. Improve despreading.

  The invention of claim 8 is characterized in that, in any one of claims 1 to 7, at least one of the anode-side separator and the cathode-side separator includes a porous channel. To do.

  According to the invention of claim 8, even if at least one of the anode-side separator and the cathode-side separator includes the porous body flow path, the operation of any of claims 1 to 7 can be easily performed. Realize.

According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the projection of the anode-side separator extends along a short side extending in a direction perpendicular to the gas flow direction and the gas flow direction. It is formed in a rectangular shape having a long side extending, and the length of the short side is equal to or less than the thickness of the gas diffusion layer on the anode side of the membrane electrode assembly.

  According to the ninth aspect of the present invention, this fuel gas flow is prevented without hindering evaporation of generated water from the anode electrode of the membrane electrode assembly to the fuel gas flow path through the gas diffusion layer (GDL) on the anode side. Due to the evaporation promoting effect in the road, the reverse diffusion of the produced water is promoted, and as a result, the high temperature performance is improved.

  A tenth aspect of the present invention is the method according to any one of the first to eighth aspects, wherein the projection of the anode side separator is formed in a circular shape, and the radius of the projection of the anode side separator is set to the membrane electrode assembly. The thickness is equal to or less than the thickness of the gas diffusion layer on the anode side.

  According to the invention of claim 10, this fuel gas flow is prevented without inhibiting the evaporation of generated water from the anode electrode of the membrane electrode assembly to the fuel gas flow path through the gas diffusion layer (GDL) on the anode side. Due to the evaporation promoting effect in the road, the reverse diffusion of the produced water is promoted, and as a result, the high temperature performance is improved.

  The invention of claim 11 is characterized in that, in any one of claims 1 to 10, at least one of the anode side separator and the cathode side separator is formed by pressing a metal plate. To do.

  According to the invention of claim 11, in the gas flow path structure in which at least one of the anode side separator and the cathode side separator is formed by pressing a metal plate, the action of any one of claims 1 to 10 is achieved. Realize easily.

  According to the invention of claim 1, the contact area per one of the projections of the anode side separator with respect to the membrane electrode assembly is equal to or less than the contact area per one of the projections of the cathode side separator with respect to the membrane electrode assembly, By differentiating the channel pitch between the fuel gas channel and the oxidant gas channel, the retained product water under the protrusions of the cathode separator is effectively back-diffused to the anode side, improving the high temperature and performance of the fuel cell. Can do. In particular, since the protrusion of the cathode separator and the protrusion of the anode separator are shifted from each other, the back diffusion efficiency of the generated water staying at the center of the protrusion of the cathode separator can be increased.

According to the second aspect of the present invention, the effect of the first aspect can be easily realized even when the flow path pitch of the fuel gas flow path is smaller than the flow path pitch of the fuel gas flow path.
According to the invention of claim 3, the number of the protrusions of the anode side separator is increased, and the current collecting resistance between the protrusion of the anode side separator and the membrane electrode assembly can be reduced.

  According to the invention of claim 4, the contact rate with the membrane electrode assembly by the projection of the anode side separator is the same as the contact rate with the membrane electrode assembly by the projection of the cathode separator. As compared with the case where the two are different from each other, it is possible to suppress damage to the membrane electrode assembly due to the protrusions of both separators.

According to the invention of claim 5, even when the channel pitch of the fuel gas channel is made larger than the channel pitch of the oxidizing gas channel, the effect of claim 1 can be easily realized.
According to the invention of claim 6, the contact area per one of the projections of the anode side separator with respect to the membrane electrode assembly is the same as the contact area per one of the projections of the cathode side separator with respect to the membrane electrode assembly. However, the effect of claim 1 is easily realized.

According to the invention of claim 7, it has an effect (cover effect) that can suppress the evaporation of the generated water by the oxidizing gas in the oxidizing gas flow path, and can improve the back diffusion more positively.
According to the invention of claim 8, even if at least one of the anode-side separator and the cathode-side separator includes the porous body flow path, the operation of any of claims 1 to 7 can be easily performed. realizable.

  According to the ninth and tenth aspects of the present invention, the evaporation of generated water from the anode electrode of the membrane electrode assembly to the fuel gas passage through the gas diffusion layer (GDL) on the anode side is not hindered, Due to the evaporation promoting effect in the fuel gas channel, the reverse diffusion of the generated water is promoted, and as a result, the high temperature performance can be improved.

  According to the invention of claim 11, in the gas flow path structure in which at least one of the anode side separator and the cathode side separator is formed by pressing a metal plate, the effect of any one of claims 1 to 10 is achieved. Realize easily.

Sectional drawing of the gas flow-path structure of the fuel cell of 1st Embodiment of this invention. (A) is sectional drawing of the gas flow-path structure of the fuel cell of a prior art example, (b) is sectional drawing of the gas flow-path structure of the fuel cell of 1st Embodiment of this invention. The diffusion flow velocity of embodiment, and the characteristic figure of the thickness of contact width / GDL. (A) is sectional drawing of the gas flow-path structure of the fuel cell of 2nd Embodiment, (b) is sectional drawing of the gas flow-path structure of the fuel cell of 3rd Embodiment, (c) is the fuel of 4th Embodiment. Sectional drawing of the gas flow path structure of a battery. (A) is sectional drawing of the gas flow-path structure of the fuel cell of one embodiment of a general prior art example, (b) is sectional drawing of the gas-flow-path structure of the fuel cell of one embodiment of patent document 2. The principal part perspective view of a separator. The perspective view of a porous body flow path. The end view of a porous body channel. The perspective view of another porous body flow path. The perspective view of another porous body flow path. The perspective view of another porous body flow path.

(First embodiment)
Hereinafter, a gas flow path structure of a fuel cell according to a first embodiment embodying the present invention will be described with reference to FIGS. 1, 2 (a), 3, and 6.

  The fuel cell is configured by stacking a single cell T or a plurality of single cells T shown in FIG. The single cell T is disposed so as to sandwich the membrane electrode assembly 10, both side surfaces of the membrane electrode assembly 10, and the anode-side separator 20 and the cathode-side separator 30 for supplying the gas introduced from the outside, both separators 20 and 30 and the membrane electrode assembly 10 is constituted by a resin frame (gasket) (not shown) interposed.

  A membrane electrode assembly (MEA) 10 includes an electrolyte membrane 11 made of an ion exchange membrane, an anode (fuel electrode) 12 made of a catalyst layer disposed on one surface of the electrolyte membrane, and the electrolyte membrane 11. It comprises a cathode (air electrode) 13 comprising a catalyst layer disposed on the surface.

  The electrolyte membrane 11 is made of a solid polymer material having good proton conductivity in a wet state. Examples of the solid polymer material include a fluorine-based polymer film (for example, a Nafion film manufactured by DuPont). The anode 12 and the cathode 13 are made of conductive carbon black carrying platinum fine particles.

  Gas diffusion layers (GDL) 14 and 15 are disposed between the membrane electrode assembly 10 and the anode separator 20 and the cathode separator 30, respectively. The gas diffusion layers 14 and 15 are laminated on the anode (catalyst layer) 12 and the cathode (catalyst layer) 13 and are made of conductive carbon paper. In addition, platinum contained in the catalyst layer has an action of promoting the separation of hydrogen into protons and electrons or promoting the reaction of generating water from oxygen, protons and electrons, but having the same action. If so, a material other than platinum may be used. The gas diffusion layers 14 and 15 may be formed of carbon cloth or carbon felt other than carbon paper, and may have sufficient gas diffusibility and conductivity.

  The anode-side separator 20 and the cathode-side separator 30 are made of carbon, a metal plate, a conductive resin, a metal plate and a resin frame, or a combination thereof.

  A fuel gas passage 21 for supplying fuel gas (hydrogen) to the anode 12 is formed in the anode side separator 20. The fuel gas channel 21 is formed between the projections 22 as projections formed on the surface of the anode side separator 20 on the side in contact with the gas diffusion layer 14, and extends along the gas flow direction to form a groove shape. Is formed.

  The cathode-side separator 30 is formed with an oxidizing gas channel 31 for supplying an oxidizing gas (oxygen, usually air) to the cathode 13. The oxidizing gas channel 31 is formed between the projections 32 as projections formed on the surface of the cathode separator 30 on the side in contact with the diffusion layer 15 and extends along the gas flow direction to form a groove shape. Is formed.

  FIG. 2A shows an example in which the anode-side separator 20 and the cathode-side separator 30 are formed with protrusions 22 and 32 by pressing a flat metal plate, respectively. In FIG. 2A, the centers of the protrusion 22 and the protrusion 32 are shown to coincide with each other for the description of the operation described later.

  The protrusions 22 and 32 are in contact with each other when the tip surfaces thereof are pressed against the gas diffusion layers 14 and 15. As shown in FIG. 5, the protrusions 22 and 32 may be protrusions (rib-shaped protrusions) continuous in the gas flow direction, or the protrusions 22 and 32 may be discontinuous protrusions. In FIG. 1, the gas flow direction is an orthogonal direction in the drawing. Note that the gas flow directions of the fuel gas and the oxidant gas may be parallel flow or counter flow.

  When discontinuous protrusions 22 and 32 are used, the shape in a plane parallel to the cell surface (separator surface) at the tip of the protrusions 22 and 32 may be a square shape, a rectangular shape, or a circular shape. . In the case of a rectangular shape, the direction orthogonal to the gas flow direction is the short side of the rectangle, and the gas flow direction is the long side of the rectangle.

  When the shape in the plane parallel to the cell surface (separator surface) at the tip of the protrusion 22 is square, rectangular, or circular, the contact width of the protrusion 22 (the width of the side in the direction perpendicular to the gas flow direction) ) Is equal to or less than the thickness of the gas diffusion layer 14. That is, when the protrusion 22 is rectangular, the length of the short side of the protrusion 22 is defined as the contact width. When the protrusion 22 is circular, the radius of the protrusion 22 is the contact width.

(Regarding the size relationship between protrusions and gas flow paths)
Next, the size relationship between the protrusions 22 and 32, the fuel gas passage 21, and the oxidizing gas passage 31 will be described.

  In the present embodiment, the contact ratio of the projection 22 on the anode (denoted as “An” in FIG. 1) side to the gas diffusion layer 14 is the gas diffusion of the projection 32 on the cathode (denoted as “Ca” in FIG. 1). The contact ratio with respect to the layer 15 is made smaller. That is, the contact ratio of the Ca-side protrusion 32 is made larger than that of the An-side protrusion 22.

  Further, the contact area of the An-side protrusion 22 with the gas diffusion layer 14 per location is narrower than the contact area of the Ca-side protrusion 32 with the gas diffusion layer 15 per location. In FIG. 1, the contact area of the gas diffusion layer 15 per location of the protrusion 32 is represented by “area / piece” (hereinafter, the same applies to other embodiments). The channel pitch of the An-side fuel gas channel 21 is smaller than the channel pitch of the Ca-side oxidizing gas channel 31.

(Operation of the embodiment)
Next, the operation of the first embodiment will be described.
When hydrogen gas is supplied to the fuel gas channel 21 and oxidizing gas (oxygen or air) is supplied to the oxidizing gas channel 31, a reaction is performed on the anode side to convert hydrogen into hydrogen ions (protons) and electrons. . Hydrogen ions move to the cathode side via the anode 12 and the electrolyte membrane 11. On the cathode side, oxygen, hydrogen ions, and electrons (electrons generated at the anode of the adjacent membrane electrode assembly 10 come through the cathode separator 30 and the like), so that water is generated by an electrochemical reaction. The water generated on the cathode side (product water) is diffused back to the anode side, but a part of the generated water tends to stay under the protrusions 32.

  In this case, the generated water staying under the protrusion 32 of the cathode separator 30 has a shorter moving distance to the region of the membrane electrode assembly 10 excluding the protrusion 22 of the anode separator 20 than when it is not. It will be explained that the above moving distance is shortened.

  FIG. 2A shows the case of this embodiment, and FIG. 2B shows the case of the conventional example. In addition, since the gas flow path structure of a prior art example differs only in the magnitude | size in a part of structure of this embodiment, the same code | symbol is attached | subjected to the structure corresponded to each member of this embodiment. In the conventional example, the contact rate is smaller on the anode side than on the cathode side, the area per protrusion is narrower on the anode side than on the cathode side, and the channel pitch is the same on both the cathode side and the anode side. Both projections 22 and 32 on the side are arranged so that their centers coincide with each other.

  In this embodiment and the conventional example, when the position of the generated water staying below the center of the protrusion 32 is marked with P, the length from P to the fuel gas flow path 21 adjacent to the protrusion 22 (the shortest moving distance) is conventional. In the example, it is L1, and in this embodiment, it is L2. Then, in the conventional example, the channel pitch is the same on both the cathode side and the anode side, and the centers thereof are arranged so as to coincide with each other. Therefore, the channel pitch in this embodiment is the fuel gas on the anode side. Since the channel 21 is smaller than the oxidizing gas channel 31 on the cathode side, L1> L2. For this reason, since the shortest moving distance L2 of the generated water staying under the central casting is shorter than that of the conventional example, the reverse diffusion efficiency is higher in the present embodiment. That is, the distance that the generated water staying under the cathode-side protrusion 32 before being back-diffused reaches the fuel gas passage 21 of the anode-side separator 20 is shortened, and the back-diffusion effect can be promoted. In FIG. 2A, for convenience of explanation, the centers of the protrusion 22 and the protrusion 32 are shown to coincide.

  In this embodiment, since the protrusion 32 of the cathode side separator 30 and the protrusion 22 of the anode side separator 20 are shifted from each other, the back diffusion efficiency of the generated water staying at the center of the protrusion of the cathode side separator is increased. Will increase.

  In fact, as shown in FIG. 2A, the center of the protrusion 32 and the protrusion 22 do not coincide with each other in many cases. Therefore, the back diffusion of the generated water staying under the protrusion 32 is further reduced. It can be expected to be performed efficiently.

  Further, in the present embodiment, the contact rate with the membrane electrode assembly 10 by the projections 22 of the anode side separator 20 is made smaller than the contact rate with the membrane electrode assembly 10 by the projections 32 of the cathode side separator 30, and Since the channel pitch of the fuel gas channel 21 is smaller than the channel pitch of the oxidant gas channel 31, the number of projections 32 of the anode separator 20 increases, and thus the projection 22 of the anode separator 20. Current collecting resistance between the electrode assembly 10 and the membrane electrode assembly 10 can be reduced.

  Further, when the shape in the plane parallel to the cell surface (separator surface) at the tip of the protrusion 22 is square, rectangular or circular, the contact width of the protrusion 22 (the side in the direction perpendicular to the gas flow direction) Is less than the thickness of the gas diffusion layer 14 (GDL). That is, when the protrusion 22 is rectangular, the length of the short side of the protrusion 22 is defined as the contact width. When the protrusion 22 is circular, the contact width is the radius of the protrusion 22.

  In this embodiment, evaporation can be promoted by forming the protrusions as described above. FIG. 3 shows the results of calculation of the diffusion flow velocity with the diffusion coefficient / concentration constant and the diffusion distance defined from the contact width / GDL thickness based on Fick's diffusion law. In the figure, the horizontal axis represents the ratio between the contact width and the thickness of the gas diffusion layer 14, and the vertical axis represents the diffusion flow velocity.

  As shown in FIG. 3, there is an inflection point in the diffusion distance of contact width / GDL thickness = 1, and it can be seen that diffusion is good when the contact width is equal to or less than the thickness of GDL. That is, if the contact width of the protrusion 22 is less than or equal to the thickness of the gas diffusion layer 14, evaporation from the anode 12 to the fuel gas passage 21 through the gas diffusion layer 14 is not hindered, and evaporation on the anode side is promoted. The effect promotes the reverse diffusion of the produced water, and as a result, the high temperature performance can be improved.

This embodiment has the following features.
(1) The gas flow path structure of the fuel cell of the present embodiment is such that the contact area per protrusion of the protrusion 22 (protrusion part) of the anode-side separator 20 with respect to the membrane electrode assembly 10 is the protrusion 32 ( The projection area) is narrower than the contact area per piece to the membrane electrode assembly 10. Further, the channel pitch of the fuel gas channel 21 formed between the projections 22 of the anode separator 20 is made smaller than the channel pitch of the oxidizing gas channel 31 formed between the projections 32 of the cathode separator 30. Thus, the protrusion 32 and the protrusion 22 are shifted from each other.

  As a result, it is possible to efficiently back-diffusion the accumulated water under the protrusions 32 of the cathode-side separator 30 to the anode side, thereby improving the high temperature and performance of the fuel cell. In particular, since the protrusion 32 of the cathode separator 30 and the protrusion 22 of the anode separator 20 are shifted from each other, the efficiency of reverse diffusion of the generated water staying at the center of the protrusion 32 of the cathode separator 30 can be improved. it can.

  (2) The gas channel structure of the fuel cell according to the present embodiment has the effect of the above (1) even when the channel pitch of the oxidizing gas channel 31 is smaller than the channel pitch of the fuel gas channel. It can be easily realized.

  (3) The gas flow path structure of the fuel cell of the present embodiment is such that the contact rate with the membrane electrode assembly 10 by the projections 22 of the anode side separator 20 is the same as that with the membrane electrode assembly 10 by the projections 32 of the cathode side separator 30. It is smaller than the contact rate. As a result, the number of protrusions 22 of the anode-side separator 20 increases, and the current collection resistance between the protrusions 22 of the anode-side separator 20 and the membrane electrode assembly 10 can be reduced.

  (4) In the gas flow path structure of the modified example of the present embodiment, the protrusion 22 of the anode separator 20 has a rectangular shape having a short side extending in the direction orthogonal to the gas flow direction and a long side extending along the gas flow direction. Is formed. Further, the length of the short side is set to be equal to or less than the thickness of the gas diffusion layer 14 on the anode side of the membrane electrode assembly 10. As a result, when the contact width is equal to or smaller than the thickness of the gas diffusion layer 14 (GDL), the diffusion is good and the evaporation from the anode 12 to the fuel gas flow path 21 through the gas diffusion layer 14 is not hindered. The anode side evaporation promoting effect promotes the reverse diffusion of the produced water, and as a result, the high temperature performance can be improved.

  (5) In the gas flow path structure of another modified example of the present embodiment, the protrusion 22 of the anode side separator 20 is formed in a circular shape. Further, the radius of the protrusion 22 of the anode separator 20 is set to be equal to or less than the thickness of the gas diffusion layer 14 on the anode side of the membrane electrode assembly 10. As a result, this modification also has the same effect as the above (4).

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG. In the following embodiments including this embodiment, the same or equivalent configurations as those of the embodiments described above will be described with a focus on the different configurations with the reference numerals attached to the configurations of the embodiments.

  In the second embodiment, in the configuration of the first embodiment, the contact rate with the membrane electrode assembly 10 by the projections 22 of the anode side separator 20 and the contact rate with the membrane electrode assembly 10 by the projections 32 of the cathode side separator 30. Same as. Other configurations are the same as those of the first embodiment. That is, the contact area per one of the protrusions 22 (protrusions) of the anode-side separator 20 with respect to the membrane electrode assembly 10 is defined as the contact area per one of the protrusions 32 (protrusions) of the cathode-side separator 30 with respect to the membrane electrode assembly 10. It is narrower than the contact area. Further, the channel pitch of the fuel gas channel 21 formed between the projections 22 of the anode separator 20 is made smaller than the channel pitch of the oxidizing gas channel 31 formed between the projections 32 of the cathode separator 30. Thus, the protrusion 32 and the protrusion 22 are shifted from each other.

(Function)
When the contact rates are different, the protrusion with the smaller contact rate bites into the membrane electrode assembly 10 and there is a risk of damage. In contrast, in the second embodiment, the contact rate with the membrane electrode assembly 10 by the projections 22 of the anode separator 20 is the same as the contact rate with the membrane electrode assembly 10 by the projections 32 of the cathode side separator 30. Therefore, the uneven biting by one projection side is eliminated, and the biting damage to the membrane electrode assembly 10 by the projections 22 and 32 of the separator is suppressed.

This embodiment has the following features.
(1) In the second embodiment, the contact rate of the projection 22 of the anode separator 20 with the membrane electrode assembly 10 is made the same as the contact rate of the projection 32 of the cathode separator 30 with the membrane electrode assembly 10. As a result, it is possible to suppress damage to the membrane electrode assembly 10 due to the protrusions of both separators as compared with the case where the contact rates are different.

(Third embodiment)
Next, a third embodiment will be described with reference to FIG.
In the third embodiment, in the configuration of the first embodiment, the contact area per protrusion of the protrusion 22 (protrusion part) of the anode-side separator 20 with respect to the membrane electrode assembly 10 is expressed as the protrusion 32 (protrusion part) of the cathode-side separator 30. ) Is the same as the contact area per one of the membrane electrode assembly 10, and the channel pitch of the fuel gas channel 21 is made larger than the channel pitch of the oxidizing gas channel 31, The place where is shifted is different. The contact rate relationship is the same as in the first embodiment.

  In the third embodiment configured as described above, since the flow pitch of the fuel gas flow channel 21 is larger than the flow pitch of the oxidizing gas flow channel 31, the current collecting resistance is smaller than that of the first embodiment. Although increased, other effects can be obtained as in the first embodiment.

(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIG.
In the fourth embodiment, in the configuration of the first embodiment, the channel pitch of the fuel gas channel 21 is made larger than the channel pitch of the oxidant gas channel 31, and the protrusion 32 and the protrusion 22 are shifted. The place you are doing is different. The contact ratio and the magnitude relationship between the contact area of each of the anode-side protrusion 22 and the cathode-side protrusion 32 with respect to the membrane electrode assembly 10 are the same as in the first embodiment.

  In the fourth embodiment, since the cathode side is larger on the cathode side than on the anode side, the contact rate has an effect (cover effect) that can suppress the evaporation of the generated water by the oxidizing gas in the oxidizing gas channel 31 and is more positively reversed. Improve diffusion.

(Embodiment of porous body)
Next, an embodiment of a separator having a porous body will be described.
In the first to fourth embodiments, the anode-side separator 20 and the cathode-side separator 30 form gas passages (fuel gas passage 21 and oxidizing gas passage 31) by providing protrusions 22 and 32 on the separator itself. However, it is not limited to this configuration. A flat separator body (not shown) and a porous body interposed between the separator body and the membrane electrode assembly 10 constitute at least one of an anode side separator and a cathode side separator. You may make it do. The porous body is for forming a porous body flow path.

Embodiments of the porous body are shown in FIGS.
(Embodiment 1 of porous body)
The porous body 120 shown in FIG. 7 is formed of a lath cut metal so as to have a large number of chevron-shaped protrusions 121a each having a hexagonal shape in half, and is formed by each protrusion 121a and its through hole 121b. The fuel gas (or oxidizing gas) flows through the gas flow path. In the porous body 120, the flat surface of the protrusion 121 a that is formed by rolling the porous body 120 is the contact surface 121 d, and the contact surface 121 d is formed on the gas diffusion layers 14 and 15. Abut. As shown in FIG. 8, when the protrusion 121a is viewed from the front, the relationship between the width A of the contact surface 121d and the width B of the through hole 121b is any of A> B, A = B, and A <B. May be.

In the case of the porous body 120, a space between the protrusions 121a is a gas flow path.
(Embodiment 2 of porous body)
The porous body 130 shown in FIG. 9 is formed by pressing a metal plate having a large number of chevron-shaped protrusions 131a so as to have an arcuate curved surface on the outer periphery, and is formed by each protrusion 131a and its through hole 131b. The fuel gas (or oxidizing gas) flows through the gas flow path. In the porous body 130, the top 131 c of the protrusion 131 a has an arcuate curved surface or a flat surface, and the top 131 c contacts the gas diffusion layers 14 and 15. In addition, the top part 131c shown in FIG. 9 is illustrated as having an arc surface.

In the case of the porous body 130, a space between the rows of the protruding portions 121a arranged in a row is a gas flow path.
(Embodiment 3 of porous body)
The porous body 140 shown in FIG. 10 is formed by pressing a metal plate, and the flat plate portion 140a is dotted with a large number of convex portions 141 and 142 each having an arcuate curved surface or a flat surface. It is shaped to exist.

  Further, the protrusions 141 and 142 are arranged so as to be shifted in the gas flow direction and leave a region 140b in which the gas flows straight in a direction orthogonal to the gas flow direction. In such a porous body 140, the region 140b is a gas flow path.

(Embodiment 4 of porous body)
A porous body 150 shown in FIG. 11 is formed by pressing a metal plate, and in a state where a plurality of mountain-shaped protrusions 151, 152, 153, and 154 form a pair adjacent to each other on the flat plate portion 150a. And each projection part is shape | molded so that it may be scattered so that the row | line | column may be made along a gas flow direction.

  In addition, the protrusions 151, 152, 153, and 154 are shifted in the gas flow direction, and in a direction orthogonal to the gas flow direction, the gas flow region 150b and the gas flow region are sewn. It is arranged so as to leave 150c. The protrusions 151 and 154 have tops 151a and 154a that are longer in the gas flow direction than the tops 152a and 153a of the protrusions 152 and 153, respectively.

In such a porous body 150, the region 150b and the region 150c become gas flow paths.
Using the porous bodies 120 to 150, the contact ratio, area / 1 piece, and flow path pitch of each protrusion described in the first to fourth embodiments with the membrane electrode assembly 10 are as follows. May be built.

The porous body is not limited to the configuration described above, and the shape pattern of the protrusions may be changed in the middle of the gas flow path.
In addition, embodiment of this invention is not limited to the said embodiment, You may change as follows.

  -In 1st Embodiment, when it is set as the discontinuous protrusions 22 and 32, the shape in the surface parallel to the cell surface (separator surface) of the front-end | tip of the protrusions 22 and 32 is square shape, a rectangular shape, or circular shape. However, other shapes such as an elliptical shape, a trapezoidal shape, a rhombus shape, a triangular shape, and a polygonal shape may be used.

  In the first embodiment, both the anode side separator 20 and the cathode side separator 30 are formed by pressing a flat metal plate. However, only one of the anode side separator 20 and the cathode side separator 30 is a flat plate. The metal plate may be formed by press working.

10: Membrane electrode assembly,
11 ... electrolyte membrane,
12 ... anode,
13 ... cathode,
14 ... gas diffusion layer,
15 ... gas diffusion layer,
20 ... anode-side separator,
21 ... Fuel gas flow path,
22 ... protrusions (protrusions),
30 ... Cathode side separator,
31 ... oxidizing gas flow path,
32. Projection (projection).

Claims (11)

Membrane electrode assemblies having electrodes disposed on both surfaces of the solid polymer electrolyte membrane and having a gas diffusion layer on the surface thereof are disposed between the anode-side separator and the cathode-side separator, and each of the separators is in contact with the membrane-electrode assembly. In the gas flow path structure of the fuel cell, the gap between the protrusions of the anode separator is a fuel gas flow path, and the gap between the protrusions of the cathode separator is an oxidizing gas flow path.
The contact area per one of the projections of the anode side separator with respect to the membrane electrode assembly is equal to or less than the contact area per one of the projections of the cathode side separator with respect to the membrane electrode assembly,
The flow path pitch of the fuel gas flow path formed between the protrusions of the anode side separator and the flow path pitch of the oxidation gas flow path formed between the protrusions of the cathode side separator are different from each other. A gas flow path structure for a fuel cell, wherein a part or all of the protrusions and the protrusions of the anode side separator are shifted from each other.   2. The gas flow path structure of a fuel cell according to claim 1, wherein the flow path pitch of the fuel gas flow path is made smaller than the flow path pitch of the oxidizing gas flow path.   The contact rate with the membrane electrode assembly by the projection part of the anode side separator is made smaller than the contact rate with the membrane electrode assembly by the projection part of the cathode side separator. The fuel cell gas flow path structure.   The contact rate with the membrane electrode assembly by the projection of the anode side separator is the same as the contact rate with the membrane electrode assembly by the projection of the cathode separator. The fuel cell gas flow path structure.   The gas channel structure of a fuel cell according to claim 1, wherein a channel pitch of the fuel gas channel is made larger than a channel pitch of the oxidizing gas channel.   The contact area per one of the projections of the anode side separator to the membrane electrode assembly is the same as the contact area per one of the projections of the cathode side separator to the membrane electrode assembly. The gas flow path structure of the fuel cell according to claim 5.   The contact area per one of the projections of the anode-side separator with respect to the membrane electrode assembly is narrower than the contact area per one of the projections of the cathode-side separator with respect to the membrane electrode assembly. The gas flow path structure of the fuel cell according to claim 5.   8. The fuel cell gas flow according to claim 1, wherein at least one of the anode-side separator and the cathode-side separator includes a porous body flow path. 9. Road structure. The protrusion of the anode separator is formed in a rectangular shape having a short side extending in a direction orthogonal to the gas flow direction and a long side extending along the gas flow direction,
9. The fuel cell gas flow path according to claim 1, wherein a length of the short side is equal to or less than a thickness of a gas diffusion layer on an anode side of the membrane electrode assembly. Construction. The protruding portion of the anode side separator is formed in a circular shape,
9. The fuel cell according to claim 1, wherein a radius of the protrusion of the anode separator is set to be equal to or less than a thickness of a gas diffusion layer on an anode side of the membrane electrode assembly. Gas flow path structure.   11. The fuel cell gas flow according to claim 1, wherein at least one of the anode side separator and the cathode side separator is formed by pressing a metal plate. 11. Road structure.

Images