JP2007280904A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To promote that uniform power generation is carried out in the surface of a cell. <P>SOLUTION: In the case of a structure in which a porous body 4 for reaction gas supply is installed on at least one face of an MEA (electrolyte membrane) 3 and the MEA 3 and the porous body 4 are interposed by separators 5, grooves 6 for gas passage to promote diffusion of reaction gas are formed on any one or both of the faces contacting the separator 5 out of the porous bodies 4 and the faces contacting the porous body 4 out of the separators 5. It is preferable that the grooves 6 are installed a plurality of pieces and are formed in radial form centered on the gas supply part from which the reaction gas is supplied to the porous bodies 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell. More particularly, the present invention relates to structural improvements within the cell.

  In general, a fuel cell (for example, a polymer electrolyte fuel cell) is configured by stacking a plurality of cells each having a membrane-electrode assembly (MEA) sandwiched between separators.

As such a fuel cell, in addition to a metal separator or a carbon separator in which a flow path for flowing a reaction gas (fuel gas, oxidizing gas) is provided, a so-called flat surface with no irregularities is provided. Some have a flat separator. In the case of a flat separator, a porous body (for example, a conductive porous plate) is interposed between the separator and the MEA, and the reaction gas is supplied and discharged so as to pass through the porous body. . Some of the porous bodies have grooves in order to improve the diffusibility of the reaction gas (see, for example, Patent Document 1).
Japanese Patent Publication No. 6-22141

  However, when looking at the actual power generation surface in the cell, there may still be uneven gas diffusion. Then, it may not be enough from the viewpoint of in-plane uniform (or homogeneous) power generation.

  Therefore, an object of the present invention is to provide a fuel cell that can promote uniform power generation in the plane of a cell.

  In order to solve this problem, the present inventor has made various studies. First, in the case of a fuel cell including a flat separator, a differential pressure generated in a porous body interposed between the separator and the MEA (in this specification, a differential pressure in a gas or the like is also referred to as pressure loss). In some cases, the reaction gas is distributed in an orderly manner. Also, during a transient response, such as when the output is increased, it may take time to distribute the gas uniformly throughout the MEA.

  In this regard, as described above, a technique for providing a groove in a porous body so as to distribute the reaction gas uniformly and rapidly is proposed. However, the present inventor, who thought that such conventional technology is still not sufficient from the viewpoint of more uniform and rapid gas distribution, has further conducted various studies, and as a result, has discovered a technology that can solve such a problem. It came.

  The present invention is based on such knowledge, and in a fuel cell having a structure in which a porous body for supplying a reactive gas is provided on at least one surface of an electrolyte membrane, and the electrolyte membrane and the porous body are sandwiched between separators, The air permeability at the surface of the gas channel groove formed in the porous body is different depending on the position.

  In this way, by adopting a structure in which the air permeability on the surface of the groove varies depending on the position, for example, a bypass structure in which the reaction gas spreads uniformly and quickly to every corner of the porous body is realized. Is possible. For example, a structure in which the reaction gas is uniformly and rapidly diffused by a shape in which a plurality of grooves radially extend from a gas supply unit (gas inlet) through which gas is supplied to the porous body may be used. preferable. By allowing the reaction gas to spread in this way, it is possible to promote uniform power generation in the plane of the cell.

  Moreover, in this invention, it is supposed that the air permeability of the base material of the said porous body in such a fuel cell is constant. For example, by performing processing as a post-processing on a base material having a constant air permeability, a structure in which the air permeability is different between the part subjected to the processing and the other part afterwards can be obtained. Is possible.

  Furthermore, in the fuel cell according to the present invention, the surface of the groove is sealed. The sealed state can be formed by, for example, filling a part of the formed groove afterwards.

  Further, in the fuel cell described above, when the gas supply part to which the reaction gas is supplied to the porous body is used as a reference, the air permeability of the portion near the gas supply part on the surface of the groove is determined. However, it is preferable that the air permeability of the far part is higher. In this case, since the air permeability of the groove surface increases as the distance from the gas supply unit increases, the reaction gas can easily flow through the groove even at the corner of the porous body, and the gas is difficult to flow through. In addition to this, the reaction gas is easily diffused, so that it can be more evenly distributed.

  Furthermore, the present inventor has repeatedly studied a porous body having a conventional groove structure. Certainly, if a reactive gas (fuel gas, oxidizing gas) is supplied using a porous material, it can be expected that the reactive gas will diffuse uniformly over the entire surface of the MEA, but in reality the degree of diffusion will vary. It is actually difficult to spread enough because there are. Accordingly, the inventor has focused on the conventional structure in the first place, and has come to know a new technique.

  The present invention is based on such knowledge, and in a fuel cell having a structure in which a porous body for supplying a reactive gas is provided on at least one surface of an electrolyte membrane, and the electrolyte membrane and the porous body are sandwiched between separators, A gas channel groove for promoting the diffusion of the reaction gas is formed on one or both of the surface of the porous body that contacts the separator and the surface of the separator that contacts the porous body. It is that.

  The inventor, who has repeatedly studied the conventional groove structure, first focused on the fact that in the case of a fuel cell having a conventional structure, a groove was formed on the surface of the porous body on the side in contact with the MEA. In the first place, the porous body makes it possible to uniformly supply the reaction gas to the MEA, and the groove formed on the surface of the porous body can make such an action more effective. . However, on the other hand, since the groove is formed in various forms on the contact surface with the MEA, it also inhibits the porous body and the MEA from coming into full contact.

  In this respect, since the fuel cell according to the present invention includes a groove as a bypass for the gas flow path, it is possible to promote the diffusion of the gas as in the conventional case. In addition, the groove is not formed on the surface that should contact the MEA and the porous body, that is, the reaction surface, but on the back side of the porous body (the back surface of the porous body or the separator contacting the surface). Therefore, the reduction of the contact area between the two is not impaired. For this reason, it is excellent in that the reactant gas can be made more uniform when the reactant gas is supplied to the MEA through the porous body. Therefore, uniform power generation is performed in the plane of the fuel cell. Can be promoted more.

  Moreover, since a groove as a bypass is formed on the back side of the porous body (the back side of the porous body or the surface of the separator in contact with the surface), the reaction gas is quickly diffused to the end of the porous body. There is no significant difference from the previous case in terms of the action of supplying the battery. Therefore, at the time of a transient response such as when the output is increased, it does not take time to distribute the gas uniformly over the entire MEA.

  Further, when a groove is formed on the contact surface between the MEA and the porous body as in the conventional structure, the contact area between the two is reduced by that amount, so electricity flows from MEA to porous body (or porous body to MEA). It can be said that the electrical resistance (contact resistance) at the time is large. On the other hand, in the case of the fuel cell according to the present invention, a groove as a bypass is formed on the back side of the porous body (the back surface of the porous body or the surface of the separator in contact with the surface). The contact surface can be made flat, so that the porous body and the MEA can be brought into full contact with each other, and it is also advantageous in that electricity can flow in a state where electric resistance is low.

  In the fuel cell having the characteristics as described above, the groove may be formed in the porous body, or the groove may be formed in the separator. When the groove is formed in the porous body as in the former case, the porous body or the like can be formed by the same processing as in the conventional case. Further, in any case, the contact area between the MEA and the porous body is reduced by the amount of the formed groove. For example, when a metal separator (metal separator) having excellent conductivity is employed. If it exists, it is possible to avoid that the electroconductive performance between both deteriorates greatly.

  Further, in such a fuel cell, it is preferable that a plurality of the grooves are provided. If the number of grooves can be increased within a range in which the processing effort does not increase excessively, it is preferable in that the reaction gas can be easily and uniformly diffused by that much. In this case, it is more preferable that the grooves are formed radially with a gas supply part to which the reaction gas is supplied to the porous body.

  Furthermore, in the fuel cell according to the present invention, the groove forms a comb-like gas flow path. Here, the comb-shaped flow path referred to in this specification means that the gas supply groove connected to the gas supply manifold and the gas discharge groove connected to the gas discharge manifold are independent from each other. When formed in a porous body, it can be said to be one of the most preferable structural examples of the independent shape. In this case, the gas in the gas supply groove flows through the porous body to the gas discharge groove.

  Further, in the porous body, a recess may be formed in a portion corresponding to a gas supply portion to which the reactive gas is supplied to the porous body. Moreover, it is preferable that the said recessed part in this case is what is connected with the edge part of the said groove | channel. The recess formed in the gas supply unit can further promote the uniform and rapid diffusion of the reaction gas into each groove and to the end of the porous body.

  In the above-described fuel cell, it is also preferable that at least a part of the groove is filled. Furthermore, in this case, it is also preferable that the groove is filled except for at least an end portion facing the outlet side of the reaction gas.

  According to the present invention, it is possible to further promote uniform power generation in the plane of the fuel cell.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

  1 to 5 show an embodiment of a fuel cell according to the present invention. The fuel cell 1 according to the present invention has a structure in which a porous body 4 for supplying a reactive gas is provided on at least one surface of an electrolyte membrane, and the electrolyte membrane and the porous body 4 are sandwiched between separators 5. is there. The fuel cell 1 according to this embodiment includes a gas for promoting diffusion of a reaction gas on one or both of a surface of the porous body 4 that contacts the separator 5 and a surface of the separator 5 that contacts the porous body 4. It has a structure including a groove 6 for the flow path, and this further promotes uniform power generation in the plane of the cell 2 of the fuel cell 1 (see FIG. (See 2nd grade).

  In the embodiment described below, first, an outline of the fuel cell 1 having a structure in which the cells 2 are stacked will be described, and then the MEA 3, the porous body 4, the separator 5, and the like that configure the cell 2 will be described.

  FIG. 5 shows a schematic configuration of a fuel cell 1 having a stack structure formed by stacking cells 2. The fuel cell 1 constituted by such a stack can be used as, for example, an on-vehicle power generation system of a fuel cell vehicle (FCHV; Fuel Cell Hybrid Vehicle), but is not limited thereto. It can also be used as a power generation system mounted on a self-propellable device (for example, a ship or an airplane) or a robot, or as a stationary fuel cell 1.

  The fuel cell 1 has a stack structure in which cells (single cells) 2 are stacked. That is, the fuel cell 1 has a stack in which a plurality of cells 2 are stacked, and a current collecting plate 11 with an output terminal 10, an insulating plate 12 and an end are sequentially placed outside the cells 2 and 2 located at both ends of the stack. It has a structure in which the plates 13 are arranged. In addition, the fuel cell 1 is formed by stacking the cells 2 by, for example, fixing a tension plate (not shown) provided between the end plates 13 and 13 to each end plate 13 and 13 with a bolt or the like. A predetermined compression force is applied in the direction.

  The stack is provided with a cell monitor (not shown) for measuring the voltage of the cell 2 in order to monitor and control the operating state of the fuel cell 1. In the fuel cell 1, control of output and the like based on the voltage measurement result is performed. In FIG. 5, two current collector plates 11 with output terminals 10 are illustrated. However, in order to perform voltage monitoring by such a cell monitor, another current collector plate 11 is provided at a plurality of predetermined locations along the cell stacking direction. It is desirable to provide an output terminal (and a current collector plate) in advance so that the output voltage can be switched to another output terminal while monitoring the cell voltage.

  The cell 2 includes a membrane-electrode assembly (also referred to herein as MEA; Membrane Electrode Assembly), a pair of porous bodies 4 that sandwich the MEA, and a separator 5 that sandwiches these (FIG. 1). FIG. 2). The MEA and each separator 5 in this embodiment are formed in a substantially rectangular plate shape. The MEA is formed so that its outer shape is smaller than the outer shape of each separator 5.

  The MEA 3 is composed of an electrolyte membrane made of a polymer material ion exchange membrane and a pair of electrodes (cathode and anode) sandwiching the electrolyte membrane from both sides. In FIG. 1 and the like, for convenience, the MEA including the electrolyte membrane is indicated by reference numeral 3 instead of the electrolyte membrane itself (see FIG. 1 and the like). Although not particularly shown here, the electrolyte membrane is formed to be slightly larger than each electrode.

  The porous body 4 is formed of a conductive porous member, and is provided so that the reaction gas that has passed through the porous body 4 can be uniformly supplied to the MEA 3. Such a porous body 4 can be formed of a base material such as a foamable material or a sintered body material. In the present embodiment, the porous body 4a for supplying oxidizing gas is provided on one side of the MEA 3, and the porous body 4b for supplying fuel gas is provided on the other side (see FIGS. 1 and 2). In addition, although such a porous body 4 does not need to have isotropy, in this embodiment, the uniform and homogeneous material is used.

  The electrode constituting the MEA 3 is made of, for example, a porous carbon material (diffusion layer) carrying a catalyst such as platinum attached to the surface thereof. One electrode (cathode) is supplied with an oxidizing gas such as air or an oxidant, and the other electrode (anode) is supplied with hydrogen gas as a fuel gas. These two types of reaction gases cause an electrochemical reaction in the MEA 3. Thus, the electromotive force of the cell 2 can be obtained.

  The separator 5 is made of a gas impermeable conductive material. Examples of the conductive material include carbon and a hard resin having conductivity, and metals such as aluminum and stainless steel. The base material of the separator 5 of this embodiment is formed of a plate-like metal, and a film having excellent corrosion resistance (for example, a film formed by gold plating) is provided on the electrode side surface of the base material as necessary. ) Is formed.

  The separator 5 in this embodiment is a type called a so-called flat separator or flat metal, and the surface in contact with the porous body 4 and the surface in contact with another cell 2 are in principle flat (flat) (FIG. 1, see FIG. For example, in this embodiment, the oxidizing gas supply side in the cell 2 is constituted by the separator 5a and the separator 5b, and the fuel gas supply side is constituted by the separator 5c and the separator 5d (see FIGS. 1 and 2).

  Among these, the separator 5a is used as a separator provided with a cooling water flow path 8 for circulating cooling water (see FIGS. 1 and 2). The shape of the cooling water flow path 8 is not particularly limited. For example, in the case of the present embodiment, the cooling water flow path 8 has an inlet near the corner of the separator, and branches into a plurality of parallel flow paths at the subsequent stage. Furthermore, it has a shape that gathers at the outlet near the diagonal portion in the subsequent stage (see FIG. 1). The separator 5b is formed in a flat plate shape, and is provided on the surface of the separator 5a on the side where the cooling water flow path 8 is formed. The opposite surface of the separator 5b is adjacent to the porous body 4a (see FIG. 2).

  Further, the separator 5c is also used as a separator provided with a cooling water flow path 8 for circulating cooling water (see FIGS. 1 and 2). Although the shape of the cooling water flow path 8 is not particularly limited, for example, in the case of this embodiment, similarly to the above-described separator 5a on the oxidizing gas supply side, the cooling water flow path 8 has an inlet near the corner of the separator, and the subsequent stage. Then, it is branched into a plurality of parallel flow paths, and further gathered at the outlet near the diagonal portion in the subsequent stage (see FIG. 1). The separator 5d is formed in a flat plate shape, and is provided on the surface of the separator 5c on the side where the cooling water flow path 8 is formed. The opposite surface of the separator 5d is in contact with another adjacent cell 2 (see FIG. 2).

  The cell 2 in this embodiment includes a porous body 4a, MEA 3, a porous body 4b, a separator 5c, and a separator 5d (see FIG. 2). In the cell 2, first, porous bodies 4 a and 4 b are arranged on both surfaces of the above-described MEA 3. Further, the MEA 3 and the porous bodies 4a and 4b have a structure sandwiched by the separator 5 (separators 5a to 5d) described above (see FIGS. 1 and 2).

  Here, in the fuel cell 1 of the present embodiment, for the gas flow path for promoting the diffusion of the reaction gas (oxidizing gas, fuel gas) on the surface in contact with the separator 5 of each of the porous bodies 4a and 4b described above. The groove 6 is formed (see FIG. 1 and the like). The groove 6 for gas flow path is not provided on the surface in contact with the MEA 3 as in the conventional structure, for example, but on the opposite surface, that is, the surface in contact with the separator 5 sandwiching the MEA 3 and the porous body 4. As a result, the surface in contact with the MEA 3 in the porous body 4 can be formed into a flat shape (see FIG. 2). In such a case, the MEA 3 and the porous body 4 can be in full contact with each other, and the contact area between the two can be ensured to the maximum, so that the electrical resistance between the two is reduced accordingly. It is possible to pass electricity with. Therefore, it is possible to reduce the electric resistance (contact resistance) when electricity flows between the MEA 3 and the porous body 4 (or the porous body 4 to the MEA 3), and improve the current collection performance and power generation efficiency in the fuel cell 1. Can do.

  Moreover, since the grooves 6 serving as bypasses are provided on the outer surface of the porous body 4 (4a, 4b) (the surface on the side in contact with the separator 5) as in the prior art, the end of the porous body 4 is provided. The action of rapidly supplying the reaction gas by diffusing it is not inferior to the previous case. For example, during a transient response such as when the output is increased, the reaction gas can be diffused uniformly and rapidly without taking time to distribute the gas uniformly throughout the MEA 3. it can. In other words, since the groove 6 formed as described above can function as a so-called bypass for quickly diffusing the reaction gas to the end of the porous body 4, the reaction gas passes through the porous portion of the porous body 4. In addition to passing through, it is possible to diffuse more uniformly through such a bypass. Moreover, the groove | channel 6 which can function as a bypass as mentioned above functions like a buffer (pressure relaxation layer) in the porous body 4, and can reduce a pressure loss and can improve gas diffusibility. Further, the reaction gas supplied to the end portion by the bypass diffuses uniformly due to the pressure loss in the porous body 4 after passing through the bypass. From the above, the fuel cell 1 of the present embodiment realizes a structure in which a chemical reaction can occur uniformly in the plane of the cell 2, and this has the advantage of being able to generate power uniformly. is there.

  In addition, the MEA 3 and the porous body 4 are in full contact with each other, and no groove or the like is formed between them. When the reactive gas is supplied to the MEA 3 through the porous body 4, It also means that the reaction gas can be supplied more uniformly. For this reason, it is possible to further promote uniform power generation in the plane of the cell 2 of the fuel cell 1 as compared with the conventional case.

  Further, in the present embodiment, since the groove 6 is formed on the surface opposite to that of the conventional structure, the same groove 6 can be formed through the same processing steps as the conventional one. For this reason, it is possible to apply the conventional technique as it is, and it is possible to reduce the time and cost required for the machining.

  Furthermore, according to the fuel cell 1 of the present embodiment, there is an advantage that the MEA 3 can be uniformly suppressed. That is, for example, in the case of a porous body having a conventional structure, it is difficult to make all of the pressing force uniform because there are a portion that is directly in contact with the MEA and a portion that is not, and gas permeation is required to eliminate this. The gas diffusion layer (for example, carbon paper, etc.) excellent in property and conductivity may be combined with the gas diffusion layer, such as interposing between the porous body and the MEA. However, it is still difficult to make the entire surface uniform. It is actually difficult. In this respect, in the fuel cell 1 of the present embodiment, the groove 6 is not formed on the surface of the porous body 4 that contacts the MEA 3, and the flat surface can be formed. It can be in contact with the entire surface of the MEA 3 with a smooth surface. This makes it possible to suppress the MEA 3 uniformly and reliably, which is also preferable from the viewpoint of realizing a structurally stable structure. Of course, the diffusion layer may be combined in the fuel cell 1 of the present embodiment.

  Here, in the fuel cell 1 as described above, a plurality of grooves 6 are preferably provided (see FIGS. 1 and 2). If the number of grooves 6 can be increased within a range in which the processing effort does not increase excessively, it is preferable in that the reactive gas is easily diffused uniformly and rapidly. For example, in this embodiment, about 5 to 6 grooves 6 are formed radially (see FIG. 3). In this case, the gas supply part (represented as “Air_in or H2_in” in FIGS. 3 and 4) where the reaction gas is supplied to the porous body 4 is used as the center, that is, the hub, to the end of the porous body 4. More preferably, the plurality of grooves 6 are formed radially so as to spread. As a result, a structure in which the reaction gas easily spreads uniformly over the entire area of the porous body 4 and the MEA 3 is obtained. The reaction gas passing through the groove 6 diffuses so as to enter into the porous body 4 (more specifically, the inside of the porous material constituting the porous body 4) in the middle (FIG. 3). reference). Furthermore, it is possible to improve drainage through the grooves 6 formed in this way. In addition, although the case where each groove | channel 6 is formed in linear form is illustrated in this embodiment, this is only an example, For example, it is good also as the groove shape bent in the middle, and also as the curved groove | channel 6. Good. Further, the cross-sectional shape of each groove 6 is not particularly limited to any shape.

  Moreover, in this embodiment, the recessed part etc. are not provided at all in the gas supply part mentioned above (refer FIG. 3). In this case, it can be said that it is preferable from the viewpoint of mechanical strength because the gas supply section and the separator (in the case of the present embodiment, the separators 5b and 5c) can be in surface contact. As described above, the gas supply portion does not necessarily have a recess or a groove, but this does not mean that the recess is not limited to a recess or a groove, and can be appropriately provided. That is, for example, from the viewpoint of further reducing pressure loss in the porous body 4 and diffusing the reaction gas more uniformly and rapidly, it is possible to provide a recess (including a hole) as indicated by reference numeral 7 in FIG. Good. Furthermore, it is good also as providing the recessed part 7 so that the edge part of each groove | channel 6 may be connected. Thus, the recessed part 7 formed in the gas supply part can further promote that the reaction gas flows into each groove 6 and diffuses uniformly and rapidly to the end part of the porous body 4.

  Furthermore, it is good also as a state which filled up at least one part of the groove | channel 6 formed as mentioned above (refer FIG. 4). For example, when too many grooves 6 are formed, it is considered that a large amount of the reaction gas in the porous body 4 escapes into these grooves 6. In such a case, the grooves 6 are filled afterwards. In this state, the pressure difference between the gas inlet side end and the outlet side end of the groove 6 can be adjusted. In other words, if a part of the groove 6 is appropriately filled, the reaction gas can be easily removed from the groove 6 and the pressure loss difference between the end portions can be reduced. It can be distributed evenly. Further, when at least a part of the groove 6 is filled in this manner, at least a portion of the groove 6 on the side facing the outlet side of the reaction gas is filled, that is, at least It is also preferable to leave the end on the outlet side open (see FIG. 4).

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the plurality of radially formed grooves 6 are illustrated, but as described above, this is only an example, and this can be changed to other forms. For example, although not particularly illustrated, a gas flow path in which the grooves 6 are formed in a comb-like shape can be formed. The comb-shaped gas flow path includes a gas supply groove 6 connected to (or formed in the vicinity of) a gas supply manifold and a gas discharge groove connected to (or formed in the vicinity of) a gas discharge manifold. This is an example of a mode for spreading the porous body 4 without intersecting both of the independent grooves 6 when the groove 6 is formed in the porous body 4 independently of each other. As a specific example, there can be mentioned one in which the branched flow paths branched in a comb shape are arranged alternately for gas supply and gas discharge. The reaction gas in the fuel cell 1 having the above-described structure can flow through the gas supply groove 6, pass through the porous body 4, and then flow into the gas discharge groove 6.

  In short, as is clear from the above description, a fuel cell having a structure in which a porous body 4 for supplying a reactive gas is provided on at least one surface of the MEA 3 and the MEA 3 and the porous body 4 are sandwiched between separators 5. 1, it is effective that the air permeability at the surface of the gas flow channel groove 6 formed in the porous body 4, in other words, the ease of passage of the reaction gas, differs depending on the position. . In this way, by adopting a structure in which the air permeability on the surface of the groove 6 varies depending on the position, for example, a bypass structure in which the reaction gas spreads uniformly and quickly to every corner of the porous body 4 is realized. It becomes possible. In this case, the air permeability of the base material of the porous body 4 is assumed to be constant. For example, by performing processing as a post-processing on a base material having a constant air permeability, a structure in which the air permeability is different between the part subjected to the processing and the other part afterwards can be obtained. Is possible. Further, the surface of the groove 6 as described above may be sealed. The sealed state can be created by, for example, filling a part of the formed groove 6 later. In addition, in such a fuel cell 1, when the gas supply part to which the reaction gas is supplied to the porous body 4 is used as a reference, the air permeability of the portion of the surface of the groove 6 close to the gas supply part It is preferable that the air permeability of the far part is higher than that. In such a case, the air permeability of the surface of the groove 6 increases as the distance from the gas supply unit increases, and the reaction gas easily flows through the groove 6 even at the corner of the porous body 4. Since the reaction gas easily diffuses, including the parts that are difficult to reach, it becomes more uniform.

  In the above-described embodiment, the mode in which the groove 6 is formed in each of the pair of porous bodies 4 in the cell 2 has been described. However, the groove 6 may be formed on the separator 5 side. For example, in the case of the fuel cell 1 described above, the grooves 6 may be provided on the surface of the separator 5b that contacts the porous body 4a and the surface of the separator 5c that contacts the porous body 4b. The point is that each groove 6 described in the present embodiment is formed on the back side of each porous body 4 (opposite side of the MEA 3), and thus has the above-described effects. A similar effect can be obtained by forming the film on the surface in the vicinity, that is, on the surface of the separator 5 in contact with the porous body 4. Of course, not only the groove 6 is formed only in one of the porous body 4 and the separator 5, but the groove 6 having the same shape (more specifically, plane symmetry) may be formed in both. In any case, the contact area between the MEA 3 and the porous body 4 is reduced by the amount of the groove 6 formed. For example, a metal separator (metal separator) 5 having excellent conductivity is employed. If so, it is possible to avoid a significant deterioration in the conductive performance between the two.

1 is an exploded plan view showing an embodiment of a fuel cell in the present embodiment and showing each of an MEA, a porous body, and a separator constituting a cell. It is sectional drawing which shows an example of the internal structure of a cell. It is a top view which shows an example of the groove shape in a porous body. It is a top view which shows the porous body of the state with which a part of groove | channel was filled. It is a perspective view which shows the structure of the fuel cell in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 2 ... Cell, 3 ... MEA (electrolyte membrane), 4 ... Porous body, 5 ... Separator, 6 ... Groove, 7 ... Recessed part

Claims (14)

In a fuel cell having a structure in which a porous body for supplying a reactive gas is provided on at least one surface of an electrolyte membrane, and the electrolyte membrane and the porous body are sandwiched between separators,
The fuel cell according to claim 1, wherein the air permeability on the surface of the gas channel groove formed in the porous body varies depending on the position.   The fuel cell according to claim 1, wherein an air permeability of the porous base material is constant.   The fuel cell according to claim 1 or 2, wherein a surface of the groove is sealed.   When the gas supply part to which the reaction gas is supplied to the porous body is used as a reference, the air permeability of the part farther than the part of the surface of the groove closer to the gas supply part The fuel cell according to claim 1, wherein the fuel cell is high. In a fuel cell having a structure in which a porous body for supplying a reactive gas is provided on at least one surface of an electrolyte membrane, and the electrolyte membrane and the porous body are sandwiched between separators,
A gas channel groove for promoting the diffusion of the reaction gas is formed on one or both of the surface of the porous body that contacts the separator and the surface of the separator that contacts the porous body. A fuel cell characterized by comprising:   The fuel cell according to claim 5, wherein the groove is formed in the porous body.   The fuel cell according to claim 5, wherein the groove is formed in the separator.   The fuel cell according to any one of separators 1 to 7, wherein a plurality of the grooves are provided.   The fuel cell according to claim 8, wherein the grooves are formed radially with a gas supply portion to which the reaction gas is supplied to the porous body as a center.   9. The fuel cell according to claim 1, wherein the groove forms a comb-like gas flow path.   11. The fuel cell according to claim 1, wherein a concave portion is formed in a portion of the porous body corresponding to a gas supply portion to which the reaction gas is supplied to the porous body. .   The fuel cell according to claim 11, wherein the recess communicates with an end of the groove.   The fuel cell according to claim 1, wherein at least a part of the groove is filled.   14. The fuel cell according to claim 13, wherein the groove is filled except for at least an end portion facing the outlet side of the reaction gas.

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