JP2005129431A - Fuel cell and gas separator for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To discharge water produced in a reactant gas passage of a fuel cell out of the reactant gas passage without any complicated control. <P>SOLUTION: A fuel cell includes an MEA 12 having an electrolyte layer and a separator 20 adjacent to the MEA 12 through a gas diffusion layer 13. The separator 20 includes a first surface having at least one part formed of a first porous portion 50. Further, the separator 20 has small porosity and/or void diameter comparing with a first porous portion 52 and has a second surface with at least one part formed of a second porous portion 52 arranged to enable to provide water from the first porous portion 50 to it. The separator 20 forms a reactant gas passage 40 in a unit cell in the first surface and an inter-cell cooling gas passage in the second surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell and a fuel cell gas separator.

  In the fuel cell, water is generated at the cathode as the electrochemical reaction proceeds, and the generated water is vaporized into the oxidizing gas supplied to and discharged from the cathode. Therefore, in the oxidizing gas flow path, the generated water is positively removed from the oxidizing gas flow path in order to prevent inconveniences such as generation water condensing and preventing the flow of the oxidizing gas. It is desirable to provide a configuration. Note that the problem of condensed water does not occur only in the oxidizing gas flow path, but also in the fuel gas flow path supplied to the anode, the water vapor mixed from the oxidizing gas flow path side through the electrolyte layer or the fuel in advance This is a problem that may occur due to water vapor contained in the gas.

  In Patent Document 1, a cooling water flow path is provided between stacked single cells, and a plate formed of a porous body is disposed between the oxidizing gas flow path and the cooling water flow path in the single cell, so that the oxidizing gas flow path is provided. A configuration is disclosed in which generated water generated at the cathode is discharged to the cooling water flow path via the plate by controlling the differential pressure between the cooling water flow path and the cooling water flow path.

Japanese National Patent Publication No. 11-508726

  However, according to the configuration of Patent Document 1, in order to discharge the generated water generated at the cathode to the cooling water channel side through the porous plate, the differential pressure control between the oxidizing gas channel and the cooling water channel is performed. There is a problem that the system becomes complicated.

  The present invention has been made to solve the above-described conventional problems, and discharges water generated in the reaction gas passage of the fuel cell to the outside of the reaction gas passage without performing complicated control. With the goal.

In order to achieve the above object, the present invention provides a fuel cell comprising:
An electrolyte layer;
A gas separator adjacent to the electrolyte layer,
A first surface at least partially formed by the first porous portion;
The porosity and / or the pore diameter is smaller than that of the first porous portion, and at least a part is formed by the second porous portion disposed so that moisture can be supplied from the first porous portion. A second surface, and
A gas separator which forms a reaction gas flow path in which the reaction gas used in the electrochemical reaction flows in the first surface and forms a cooling gas flow path in which the cooling gas flows in the second surface. Is the gist.

  According to the fuel cell of the present invention configured as described above, the moisture in the reaction gas flow path is absorbed by the first porous portion and then supplied to the second porous portion, so that the second It can discharge | release in a cooling gas flow path from the porous part surface of this. Thereby, the water | moisture content in a reaction gas flow path can be removed, without performing complicated control. At this time, since the second porous portion has a smaller porosity and / or pore diameter than the first porous portion, the second porous portion is formed between the reaction gas channel and the cooling gas channel. It acts as a resistance that prevents gas from going back and forth between them, and it is possible to suppress mixing of the reaction gas and the cooling gas. That is, it is possible to suppress the reaction gas from leaking to the cooling gas flow channel side and reducing the utilization rate of the reaction gas, or mixing the cooling gas to the reaction gas flow channel side. In addition, the first porous portion can sufficiently absorb moisture in the reaction gas flow path by having a larger porosity and / or pore diameter.

In the fuel cell of the present invention,
The first porous portion is disposed in at least a part of a region of the first surface that forms the reaction gas flow path,
The second porous portion may be disposed in at least a part of a region of the second surface that forms the cooling gas channel.

  With such a configuration, the moisture in the reaction gas channel is absorbed into the first porous part from the first porous part disposed in the region forming the reaction gas channel, and the absorbed moisture is In addition, it can be discharged into the cooling gas flow path from the second porous portion disposed in the region forming the cooling gas flow path.

In the fuel cell of the present invention,
It is good also as a connection channel which connects the cooling gas channel and the reaction gas channel, and guides the cooling gas which passed through the cooling gas channel to the reaction gas channel as the reaction gas.

  With such a configuration, since the same kind of gas as the reaction gas is used as the cooling gas, the reaction gas and the cooling gas may be mixed through the first and second porous portions. There is no inconvenience caused by mixing different kinds of gases. Moreover, according to the said structure, the reaction gas used for an electrochemical reaction can be humidified by letting a cooling gas flow path pass beforehand. Therefore, when applied to a polymer electrolyte fuel cell, it is possible to prevent the electrolyte membrane from drying in the region near the inflow portion where the reaction gas flows. As a result, it is possible to eliminate the need for a device for humidifying the reaction gas supplied to the fuel cell, and to reduce the size of the humidifier.

In the fuel cell of the present invention,
The reaction gas channel is an oxidizing gas channel that forms a fuel gas channel through which a fuel gas containing hydrogen passes and / or an oxidizing gas channel containing oxygen,
The gas separator may be used to form the fuel gas channel and / or the oxidizing gas channel.

  With such a configuration, drainage is effectively performed using the first and second porous portions in the fuel gas flow path and / or the oxidation gas flow path forming portion formed using the gas separator. In addition, the fuel gas and / or the oxidizing gas, which is the reaction gas, and the cooling gas can be prevented from being mixed.

In the fuel cell of the present invention,
The first porous portion and the second porous portion may be provided in a region corresponding to the vicinity of a discharge portion where the reaction gas is discharged from the reaction gas flow path.

  In the reaction gas flow path, generally, the moisture content inside increases toward the downstream side of the flow of the reaction gas. Therefore, the region corresponding to the vicinity of the discharge portion where the reaction gas is discharged from the reaction gas channel is a region with the largest amount of moisture in the reaction gas channel. Therefore, with the above configuration, moisture can be efficiently removed from the reaction gas channel in a region where the amount of moisture is larger.

  The present invention can be realized in various forms other than those described above, and can be realized in the form of, for example, a fuel cell gas separator.

Next, embodiments of the present invention will be described in the following order based on examples.
A. Overall configuration of the device:
B. Porous part of the separator:
C. Moisture transfer behavior:
D. effect:
E. Variation:

A. Overall configuration of the device:
FIG. 1 is an exploded perspective view showing a configuration of a single cell 10 which is a basic unit constituting a fuel cell according to a preferred embodiment of the present invention. FIG. 2 is a plan view showing a state of the separator 20 constituting the single cell 10.

  The fuel cell of the present embodiment is a polymer electrolyte fuel cell, and has a stack structure in which a plurality of single cells 10 shown in FIG. 1 are stacked and connected in series. As shown in FIG. 1, the unit cell 10 includes a membrane-electrode assembly (MEA) 12 sandwiched between gas diffusion layers 13 and 14, and the MEA 12 and the gas diffusion layers 13 and 14 are further sandwiched from both sides. The gas diffusion layer 13 is not shown in FIG. 1 (see FIG. 4).

  The MEA 12 is obtained by forming a catalyst layer on both sides of the solid polymer electrolyte membrane. The solid polymer electrolyte membrane is a proton conductive ion exchange membrane formed of, for example, a fluororesin, and exhibits good electrical conductivity in a wet state. The catalyst layer is a layer having platinum as a catalyst or an alloy made of platinum and another metal. The gas diffusion layers 13 and 14 can be formed of a gas diffusible conductive member, for example, a carbon cloth woven with a yarn made of carbon fiber, carbon paper or carbon felt, or the like.

  Between the separators 20 and 22 and the MEA 12 sandwiched between the gas diffusion layers, a reaction gas flow path for an electrochemical reaction is formed. That is, an in-single cell oxidizing gas passage through which an oxidizing gas containing oxygen such as air passes is formed between the separator 20 and the MEA 12 including the gas diffusion layer 13. Further, between the separator 22 and the MEA 12 including the gas diffusion layer 14, an in-single cell fuel gas flow path through which hydrogen-containing fuel gas passes is formed. Furthermore, between the separator 20 which comprises one single cell 10, and the separator 22 which comprises the adjacent single cell 10, the inter-cell cooling water flow path through which cooling water passes, and the inter-cell cooling through which cooling gas passes A gas flow path is formed. Thus, in the fuel cell of the present embodiment, the inter-cell cooling water flow path and the inter-cell cooling gas flow path are formed between all adjacent single cells, but may be formed for each of a plurality of cells. good. The separators 20 and 22 are made of a conductive material such as carbon or metal, and include a dense body that does not allow gas and moisture to permeate and a porous body that allows permeation of moisture (liquid water or water vapor). The arrangement of the porous body corresponds to the main part of the present invention and will be described in detail later.

  2A and 2B are plan views showing a state in which the separator 20 is viewed from each surface. FIG. 2A shows a surface that is visible on the near side in the separator 20 shown in FIG. In FIG. 2, the A direction represents the horizontal direction, and the B direction represents the vertical direction. As shown in FIG. 2, the separator 20 has eight holes near the outer periphery thereof. That is, in the vicinity of one side of the separator 20 in the horizontal direction, three holes 26b, 22a, and 24a that are adjacent along this side are provided. Holes 24b and 22b are provided. Further, in the vicinity of one side of the separator 20 in the vertical direction, two holes 26a and 28a which are adjacent to the side are provided, and in the vicinity of the side facing the side, the hole 28b is provided. Is provided. As shown in FIG. 1, holes similar to the above eight holes are also provided at corresponding positions of the separator 22, and the holes provided at the corresponding positions overlap in the stack structure. Then, a fluid flow path that penetrates the inside of the fuel cell in the stacking direction of the single cells 10 is formed.

  The holes 22a formed in the separators 20 and 22 form an oxidizing gas supply manifold, and the holes 22b form an oxidizing gas discharge manifold. The oxidizing gas supply manifold is a flow path for supplying oxidizing gas (air in the present embodiment) from the outside and distributing the supplied oxidizing gas to each single cell 10. It is a flow path for collecting the oxidizing gas discharged from the cell and leading it outside the fuel cell. The hole 24a forms a fuel gas supply manifold, and the hole 24b forms a fuel gas discharge manifold. The fuel gas supply manifold is a flow path for supplying fuel gas from the outside and distributing the supplied fuel gas to each single cell 10, and the fuel gas discharge manifold is a fuel gas discharged from each single cell. Is a flow path for collecting and guiding them to the outside of the fuel cell. Moreover, the hole 26a forms a cooling water supply manifold, and the hole 26b forms a cooling water discharge manifold. The cooling water supply manifold is a flow path for supplying cooling water from the outside and distributing the supplied cooling water to the cooling water flow paths between the single cells 10, and the cooling water discharge manifold is between the single cells. This is a flow path for collecting cooling water discharged from the cooling water flow path and guiding it outside the fuel cell. Further, the hole 28a forms a cooling gas supply manifold, and the hole 28b forms a cooling gas discharge manifold. The cooling gas supply manifold is a flow path for supplying cooling gas from the outside and distributing the supplied cooling gas to the cooling gas flow paths between the single cells 10, and the cooling gas discharge manifold is a single cell. This is a flow path for collecting the cooling gas discharged from the cooling gas flow path therebetween and guiding it to the outside of the fuel cell.

  One surface of the separator 20 is provided with an oxidizing gas flow path forming portion 30 that connects the hole portion 22a and the hole portion 22b (see FIG. 2A). The oxidizing gas flow path forming unit 30 forms an oxidizing gas flow path in a single cell with the MEA 12 including the gas diffusion layer 13. The oxidizing gas distributed from the oxidizing gas supply manifold to each single cell 10 passes through the single cell oxidizing gas flow path and collects in the oxidizing gas discharge manifold. The direction of the oxidizing gas flow in the single cell oxidizing gas flow path is indicated by an arrow in FIG.

  Moreover, the other surface of the separator 20 is provided with a cooling water flow path forming portion 32 that connects the hole portion 26a and the hole portion 26b (see FIG. 2B). Since the separator 20 is disposed so as to be in contact with the separator 22 included in another adjacent single cell, the cooling water flow path forming unit 32 forms an inter-cell cooling water flow path between the adjacent separator 22. . The inter-cell cooling water flow path of the present embodiment is a serpentine flow path having a plurality of bent portions where the flow of the cooling water is changed. The adjacent separator 22 has a cooling water flow path forming portion 33 having a shape corresponding to the cooling water flow path forming portion 32 on the surface in contact with the separator 20 (see FIG. 1). The forming part 33 forms the inter-cell cooling water flow path together with the cooling water flow path forming part 32 provided in the adjacent separator 20. The cooling water distributed from the cooling water supply manifold to the inter-cell cooling water flow paths passes through the inter-cell cooling water flow paths and collects in the cooling water discharge manifold. The direction of the cooling water flow in the inter-cell cooling water flow path is indicated by an arrow in FIG.

  Furthermore, the other surface of the separator 20 is provided with a cooling gas flow path forming portion 34 that communicates the hole 28a and the hole 28b (see FIG. 2B). The cooling gas flow path forming unit 34 forms an inter-cell cooling gas flow path between the adjacent separators 22. The separator 22 is formed with a cooling gas flow path forming portion 35 having a shape corresponding to the cooling gas flow path forming portion 34 on the surface in contact with the separator 20 (see FIG. 1). The forming part 35 forms the inter-cell cooling gas flow path together with the cooling gas flow path forming part 34 provided in the adjacent separator 20. The cooling water distributed from the cooling gas supply manifold to each inter-cell cooling gas flow path passes through the inter-cell cooling gas flow path and collects in the cooling gas discharge manifold. The direction of the cooling gas flow in the inter-cell cooling gas flow path is indicated by an arrow in FIG.

  In the separator 22, the hole 24 a and the hole 24 b are connected to the surface opposite to the surface on which the cooling water flow path forming portion 33 and the cooling gas flow path forming portion 35 are provided, and the gas diffusion layer 14 is formed. A fuel gas flow path forming unit for forming a fuel gas flow path in the single cell is provided between the MEA 12 and the MEA 12 (not shown). The fuel gas distributed to each single cell 10 from the fuel gas supply manifold passes through the single-cell fuel gas flow path and collects in the fuel gas discharge manifold.

  Here, in FIGS. 1 and 2, the oxidizing gas flow path forming portion 30 is represented as a concave portion having a flat bottom surface, but the oxidizing gas flow path forming portion 30 and the fuel gas flow path forming portion have predetermined irregularities. It is good also as ensuring electroconductivity by providing a shape and contacting the adjacent member in a convex part. The uneven shape to be provided may be, for example, a plurality of substantially parallel groove-shaped channel groups, or a plurality of convex portions protruding from the bottom surface of the concave portion. Further, the oxidizing gas flow path forming section 30 and the fuel gas flow path forming section may be formed as a recess having a flat bottom surface, and a gas flow path may be formed by fitting a gas diffusion layer in the recess. . Similarly, the cooling gas flow path forming portion 34 may be provided with a predetermined uneven shape.

B. Porous part of the separator:
FIG. 3 is a cross-sectional view schematically showing the internal configuration of the single cell 10. FIG. 3 shows a state of a cross section corresponding to the 3-3 cross section in the separator 20 shown in FIG. The separator 20 includes a first porous portion 50 and a second porous portion 52 that are formed of a porous body. Here, the second porous portion 52 is formed to have a smaller porosity than the first porous portion 50. In FIGS. 1 and 2 described above, the shapes of the cooling water flow path forming portion 32 and the cooling gas flow path forming portion 34 are simplified, but in FIG. 3, the cooling water flow path forming portion 32 and the cooling gas are shown. The concavo-convex shape in the flow path forming part 34 is described in more detail.

  The separator 20 is formed of a conductive material such as carbon or metal, and the region other than the first and second porous portions (hereinafter referred to as a separator base) is formed of a member that is impermeable to moisture and gas. ing. For example, the separator base can be formed of dense carbon obtained by compression molding a carbon powder mixed with a binder, or a press-molded metal plate. Moreover, it is preferable that the first and second porous portions are formed of the same kind of material as the member constituting the separator base. For example, when the separator base is made of carbon, the first and second porous portions are carbons having a desired porosity by appropriately selecting the shape and size of the carbon powder, or the mixing ratio with the binder. What is necessary is just to form with a porous body. When the separator base is made of metal, the first and second porous portions may be formed of a metal porous body such as a sintered metal or a metal mesh having a desired porosity. The separator base and the first and second porous portions may be integrally formed, or may be combined after being formed separately.

  In the separator 20, the first porous portion 50 formed of the porous body has a predetermined shape so as to constitute the surface of the oxidizing gas flow path forming portion 30 in the entire region where the oxidizing gas flow path forming portion 30 is formed. It is arranged with a thickness. Further, the second porous portion 52 having a smaller porosity is disposed with a predetermined thickness so as to constitute the surface of the cooling gas flow path forming portion 34 in the region where the cooling gas flow path forming portion 34 is formed. (See FIG. 3). Here, in FIG. 3 and FIG. 4 described later, the cooling gas flow path forming portion 34 has a predetermined uneven shape. In FIG. 1 and FIG. 2, the region where the second porous portion 52 is formed in the separator 20 is surrounded by a broken line as the moisture transfer region 53. Further, in the moisture transfer region 53, the first porous part 50 disposed on the oxidizing gas flow path forming part 30 side, and the second porous part 52 disposed on the cooling gas flow path forming part 34 side, Are in contact with each other over the entire moisture exchange region 53.

  FIG. 3 shows a state in which the oxidizing gas channel 40 in the single cell is formed between the MEA 12 including the gas diffusion layer 13 and the surface of the separator 20 in the oxidizing gas channel forming unit 30. In FIG. 3, an oxidizing gas supply manifold 44 is formed by the holes 22a provided in the separators 20 and 22, and an oxidizing gas discharge manifold 46 is formed by the holes 22b provided in the separators 20 and 22, and these manifolds are formed as single cells. A state of communication with the inner oxidizing gas flow path 40 is shown. The moisture transfer region 53 described above is located near the discharge portion from which the oxidizing gas is discharged from the single-cell oxidizing gas flow channel 40, that is, in the vicinity of the connection portion with the oxidizing gas discharge manifold 46 in the single-cell oxidizing gas flow channel 40. It is a corresponding area.

  The separator 22 has a predetermined thickness so as to form the surface of the fuel gas flow path forming portion in the entire region where the fuel gas flow path forming portion is formed. The porous part 54 is arrange | positioned (refer FIG. 3). In FIG. 3, in the fuel gas flow path forming part of the separator 22, the fuel gas flow path in the single cell is provided between the MEA 12 including the gas diffusion layer 14 and the surface of the separator 22 on which the third porous part 54 is disposed. The appearance of 42 is shown. In the separator 22, a predetermined uneven shape corresponding to the shape of the cooling gas flow path forming portion 35 and the cooling water flow path forming portion 33 is provided on the surface opposite to the surface facing the MEA 12, similarly to the separator 20. Yes. In the separator 22, the porous body is not disposed on the surface where the cooling gas flow path forming part 35 and the cooling water flow path forming part 33 are formed.

  In FIG. 3, the oxidant gas flow path forming part 30 of the separator 20 forms a single-cell oxidant gas flow path 40 that is a predetermined space, and the fuel gas flow path forming part of the separator 22 is inside the single cell that is a predetermined space. Although the fuel gas flow path 42 has been formed, as described above, the oxidizing gas flow path forming portion 30 and the fuel gas flow path forming portion may have a convex portion having a predetermined shape. . FIG. 4 is a cross section parallel to the cross section shown in FIG. 3, in which a convex portion in contact with the gas diffusion layer on the MEA 12 is formed in the oxidizing gas flow path forming portion 30 and the fuel gas flow path forming portion. Represents. As shown in FIGS. 3 and 4, a seal member 38 such as an O-ring is disposed around the cooling gas flow path forming portion 34 and the cooling water flow path forming portion 32 in the separator base portion of the separator 20. The inter-cell cooling gas flow path and the inter-cell cooling water flow path are sealed.

C. Moisture transfer behavior:
In a fuel cell, water is generated at the cathode as the electrochemical reaction proceeds. Water generated by the electrochemical reaction is vaporized into the oxidizing gas passing through the single-cell oxidizing gas channel 40 and flows downstream together with the oxidizing gas. Therefore, in the oxidizing gas flow path 40 in the single cell, the amount of moisture in the gas increases toward the downstream side. In the fuel cell of this embodiment, since the first porous portion 50 is disposed on the surface of the oxidizing gas flow path forming portion 30, the moisture (liquid water and / or Or water vapor) is taken into the first porous portion 50. Further, since the separator 20 is provided with the second porous portion 52 continuously with the first porous portion 50, the moisture taken into the first porous portion 50 is absorbed by the second porous portion 52. To the cooling gas flowing through the inter-cell cooling gas flow path from the second porous portion 52.

  Here, when the amount of water in the oxidizing gas passing through the single-cell oxidizing gas flow channel 40 is lower than the saturated vapor pressure, the first porous portion 50 and the second porous portion from the single-cell oxidizing gas flow channel 40. Moisture that moves to the cooling gas flow path via the mass portion 52 moves in the state of water vapor. On the other hand, when the amount of water in the oxidizing gas passing through the single-cell oxidizing gas channel 40 is large and the water is condensed, the condensed water is once absorbed by the first porous portion 50 and then the second. Moisture is transferred by moving to the porous portion 52 and evaporating water from the second porous portion 52 into the cooling gas flow path. The condensed water in the oxidant gas flow path 40 in the single cell is easily taken into the interior by the capillary suction force in the first porous portion 50 formed by the porous body, and further moves to the second porous portion 52. . Further, when the condensed water is absorbed by the first porous portion 50 in this way, the first porous portion 50 and the second porous portion 52 are gas-sealed by absorbing the condensed water, and the single cell interior Mixing of gas between the oxidizing gas channel 40 and the cooling gas channel is suppressed. In addition, in order to promote such moisture uptake from the oxidizing gas and moisture movement to the inter-cell cooling gas flow path side, the first porous portion 50 and the second porous portion 52 are subjected to a hydrophilic treatment to be hydrophilic. It is desirable to increase the nature. For example, when the first porous portion 50 and the second porous portion 52 are formed of a carbon porous body, the carbon porous body is boiled in hydrogen peroxide water, and hydroxyl groups ( By introducing a —OH group, hydrophilicity can be easily imparted.

  In the fuel cell of the present embodiment, the cooling gas uses air that is subjected to an electrochemical reaction as an oxidizing gas. FIG. 5 schematically shows the flow of the cooling gas and the oxidizing gas in the fuel cell of this embodiment. In FIG. 5, the connection relationship of the flow paths is described using the surface of the separator 22 on which the cooling gas flow path forming portion 35 is formed. That is, air is supplied as cooling gas from the air pump 16 to the cooling gas supply manifold formed by the hole 28a, and the supplied air flows between the inter-cell cooling gas formed by the cooling gas flow path forming unit 35. It flows through the passage to the cooling gas discharge manifold formed by the hole 28b. At this time, the air passing through the inter-cell cooling gas flow path is humidified by moisture moving in the first and second porous portions. The air gathered in the cooling gas discharge manifold is guided to the connection flow path 15, flows into the oxidation gas supply manifold formed by the hole 22a, and is distributed to the oxidation gas flow paths in each single cell. Here, since the cooling gas discharge manifold and the oxidizing gas supply manifold are flow paths that penetrate the fuel cells in the stacking direction, the connection flow path 15 is, for example, a cooling gas discharge at one end of the stacking direction of the fuel cells. What is necessary is just to arrange | position so that a manifold edge part and an oxidizing gas supply manifold edge part may be connected. Or it is also possible to provide the connection flow path 15 in each cell surface in the stack which comprises a fuel cell.

  Further, as shown in FIG. 5, in the fuel cell of the present embodiment, air is branched from the flow path connecting the air pump and the cooling gas supply manifold, and the air is connected without flowing through the inter-cell cooling gas flow path. An air branch path 17 leading to the path 15 is provided. The air branch path 17 is provided with a flow rate adjusting valve 18 for adjusting the amount of air passing through the air branch path 17. Therefore, by controlling the air pump 16 and the flow rate adjusting valve 18, the amount of air passing through the inter-cell cooling gas passage and the amount of air used for the electrochemical reaction can be adjusted.

  In the fuel cell of this embodiment, moisture in the fuel gas passing through the single-cell fuel gas flow path is absorbed by the third porous portion 54. Therefore, even if water may condense in the fuel gas flow path in the single cell, the condensed water is absorbed by the third porous part 54 and diffuses over the entire surface of the fuel gas flow path forming part. As a result, the moisture absorbed in the third porous portion 54 is vaporized in the fuel gas in the region where the dried fuel gas passes or in the region where the temperature is higher, and the condensate water is prevented from staying locally. It is done.

D. effect:
According to the fuel cell of the present embodiment configured as described above, from the single-cell oxidizing gas flow path to the inter-cell cooling gas flow path via the first porous portion 50 and the second porous portion 52. Since the movement of moisture is possible, it is possible to prevent inconvenience due to the retention of moisture in the oxidizing gas flow channel in the single cell. At this time, complicated control such as pressure control is not necessary, and the oxidant gas flow path in the single cell is formed by a simple configuration in which a porous body is disposed at a portion separating the oxidation gas flow path and the cooling gas flow path in the separator. Can be drained from. Here, since the porosity of the second porous portion 52 is smaller than that of the first porous portion 50, the second porous portion 52 includes the single-cell oxidizing gas flow path and the inter-cell cooling gas. It acts as a resistance when gas flows between the channels. Therefore, by providing the second porous portion 52 having a smaller porosity, it is possible to suppress mixing of the cooling gas and the oxidizing gas through the porous body. For example, when the oxidizing gas in the single cell oxidizing gas flow channel flows out to the inter-cell cooling gas flow channel through the porous body, the oxidizing gas is discharged before it is sufficiently used for the electrochemical reaction, There is a possibility that the utilization rate of the oxidizing gas is lowered. Further, when the cooling gas (air) flows from the inter-cell cooling gas flow channel into the single cell oxidizing gas flow channel, the flowing air does not pass through the upstream side of the single cell oxidizing gas flow channel as the oxidizing gas. There is a possibility that the utilization rate of the oxidizing gas is lowered. According to the present embodiment, such inconvenience can be prevented by providing the second porous portion 52 that allows the movement of moisture but serves as a resistance when the gas goes back and forth. Further, in this embodiment, since the porosity is increased in the first porous portion 50 disposed on the oxidizing gas flow path side in the single cell, moisture in the oxidizing gas can be more easily removed from the first porous portion 50. It can be absorbed by the part 50. Thus, in the separator 20 of the present embodiment, a porous body having a higher porosity is disposed on the oxidizing gas flow path side in the single cell, and a porous body having a lower porosity is disposed on the cooling gas flow path side. With this configuration, it is possible to easily obtain the effect of sufficiently ensuring the discharge of moisture in the oxidizing gas and suppressing the mixing of the gas.

  Here, the porosity of the 2nd porous part 52 and the 1st porous part 50, and the difference of both porosity are the oxidizing gas pressure in the oxidizing gas flow path in a single cell, and the inter-cell cooling gas flow path. The cooling gas pressure in the inside, the amount of water in the oxidizing gas flow path in the single cell during power generation, and the like may be set as appropriate so that the effect of preventing gas mixing and the drainage efficiency are sufficiently realized. In the present embodiment, the porosity of the second porous portion 52 is smaller than that of the first porous portion 50. However, instead of or in addition to this, the pore diameter may be small. . By making the porosity and / or the pore diameter different between the second porous portion 52 and the first porous portion 50, the first porous portion 50 can sufficiently secure moisture absorption from the oxidizing gas. The second porous portion 52 only needs to have a sufficiently large resistance when the gas permeates.

  In the fuel cell of the present embodiment, the second porous portion 52 is located in the region corresponding to the vicinity of the discharge portion in which the oxidizing gas is discharged from the single-cell oxidizing gas passage 40 in the oxidizing gas passage forming portion 30. Since it is provided, it is possible to efficiently remove moisture in the oxidizing gas flow path. That is, in the oxidizing gas flow path in the single cell, the amount of moisture increases toward the downstream side, so that moisture absorption into the first porous portion 50 increases toward the downstream side, but the second porous portion 52 is in the vicinity of the discharge portion. By providing in the area | region corresponding to, the absorbed water | moisture content can be rapidly conveyed to the cooling gas flow path side.

  Further, in the fuel cell of this embodiment, air is used as the cooling gas, and the air humidified by passing through the inter-cell cooling gas flow path is supplied to each single cell as the oxidizing gas. Therefore, prior to the electrochemical reaction, a device for humidifying the oxidizing gas to prevent drying of the electrolyte membrane is unnecessary, or the humidification device can be downsized.

  Further, in this embodiment, the porosity of the first porous portion 50 is made larger, and the entire surface including the convex portion in contact with the MEA 12 provided with the gas diffusion layer 13 in the oxidizing gas flow path forming portion 30 is thus formed. The first porous portion 50 is formed. Therefore, it is possible to ensure the diffusion and supply of the oxidizing gas to the catalyst layer where the electrochemical reaction proceeds, and to improve the battery performance.

  In the fuel cell of this embodiment, an inter-cell cooling gas flow path is provided in a region corresponding to the downstream side of the oxidizing gas flowing through the single-cell oxidizing gas flow channel 40, and an inter-cell cooling water flow is provided in the region corresponding to the upstream side. There is a road. In the oxidant gas flow path 40 in the single cell, the temperature rises more easily because the electrode active material concentration (oxygen concentration) in the oxidant gas is higher and the electrochemical reaction is more active toward the upstream side. Thus, in order to cool the region where the temperature is likely to rise, the fuel cell can be efficiently cooled by using a liquid refrigerant instead of a gas.

E. Variation:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

E1. Modification 1:
The arrangement positions of the second porous portion 52 and the first porous portion 50 in the separator 20 may be different from those in the embodiment. In the embodiment, the first porous part 50 constitutes the entire surface of the oxidizing gas flow path forming part 30, and the second porous part 52 constitutes the entire surface of the cooling gas flow path forming part 34. The first porous part 50 may constitute at least a part of the surface of the oxidizing gas flow path forming part 30, and the second porous part 52 may constitute at least a part of the surface of the cooling gas flow path forming part 34. . If the gas and moisture can be exchanged only between the oxidizing gas flow path in the single cell and the inter-cell cooling gas flow path only through the second porous portion 52, the same effect of suppressing gas mixing is obtained. be able to.

  Further, in the embodiment, the cooling gas flow path forming part 34 is provided in the downstream area of the oxidizing gas flow in the oxidizing gas flow path forming part 30, but it may be provided in a different area or a wider area. For example, if only cooling with gas is sufficient, the cooling gas flow path forming part 34 may be provided on the entire surface of the separator 20 without providing the cooling water flow path forming part 32. Even if the cooling gas flow path forming part 34 is provided in any region, the second porous part 52 is disposed so as to constitute at least a part of the surface of the cooling gas flow path forming part, and the first porous part 50 If moisture can be supplied from the same, the same effect can be obtained.

  In the embodiment, the second porous portion 52 is disposed so as to be in contact with the first porous portion 50 on the entire back side that does not constitute the surface of the cooling gas flow path forming portion, but may have a different configuration. It is sufficient if moisture can move from the first porous portion 50 to the second porous portion 52.

E2. Modification 2:
In the embodiment, the second porous portion 52 and the first porous portion 50 are provided in the separator 20 disposed between the single-cell oxidizing gas flow channel 40 and the inter-cell cooling gas flow channel. A similar porous portion may be provided in the separator 22 disposed between the fuel gas flow path in the single cell and the inter-cell cooling gas flow path. If the present invention is applied to the flow path of the fuel gas that is the reaction gas used in the electrochemical reaction, the water in the fuel gas flow path in the single cell can be discharged to the cooling gas flow path side, and the fuel gas and cooling Mixing with gas can be suppressed. In this case, as the cooling gas, it is desirable to use the fuel gas before being supplied to the fuel gas passage in the single cell. That is, it is desirable to use the same kind of gas as the reaction gas to be drained as the cooling gas.

E3. Modification 3:
In the embodiment, the same kind of gas as the reaction gas from which moisture is removed using the first and second porous portions is used as the cooling gas, but a different gas may be used as the cooling gas. In this case, it is desirable to select a gas that does not affect the electrochemical reaction even if mixed in the reaction gas as the cooling gas. Further, if the cooling gas pressure is made lower than the reaction gas pressure, it is possible to effectively prevent the cooling gas from being mixed into the reaction gas.

E4. Modification 4:
Alternatively, the first and second porous portions may be provided on both the separator 20 and the separator 22. With such a configuration, drainage is performed in both the single-cell oxidant gas flow path 40 and the single-cell fuel gas flow path 42, and the same is performed to suppress the outflow of the reaction gas or the cooling gas into the reaction gas. An effect can be obtained. At this time, if the cooling gas pressure is sufficiently lower than the fuel gas pressure and the oxidizing gas pressure, it is possible to reliably prevent the fuel gas and the oxidizing gas from being mixed.

E5. Modification 5:
In the embodiment, the fuel cell is a polymer electrolyte fuel cell, but it can also be applied to different types of fuel cells. The present invention is a fuel cell configured by stacking members including a separator, the amount of water in the reaction gas channel being increased during power generation, and a fuel cell that uses a cooling gas to cool the fuel cell. The same effect can be obtained by applying.

2 is an exploded perspective view showing a configuration of a single cell 10. FIG. 3 is a plan view showing a state of a separator 20. FIG. 2 is a cross-sectional view schematically showing an internal configuration of a single cell 10. FIG. 2 is a cross-sectional view schematically showing an internal configuration of a single cell 10. FIG. It is explanatory drawing which represents typically the flow of cooling gas and oxidizing gas.

Explanation of symbols

10 ... Single cell 12 ... MEA
DESCRIPTION OF SYMBOLS 13,14 ... Gas diffusion layer 15 ... Connection flow path 16 ... Air pump 17 ... Air branching path 18 ... Flow control valve 20, 22 ... Separator 22a, 22b ... Hole 24a, 24b ... Hole 26a, 26b ... Hole 28a , 28b ... hole 30 ... oxidizing gas flow path forming part 32, 33 ... cooling water flow path forming part 34, 35 ... cooling gas flow path forming part 38 ... seal member 40 ... oxidizing gas flow path in single cell 42 ... within single cell Fuel gas flow path 44 ... oxidizing gas supply manifold 46 ... oxidizing gas discharge manifold 50 ... first porous part 52 ... second porous part 53 ... moisture transfer area 54 ... third porous part

Claims (6)

A fuel cell,
An electrolyte layer;
A gas separator adjacent to the electrolyte layer,
A first surface at least partially formed by the first porous portion;
The porosity and / or the pore diameter is smaller than that of the first porous portion, and at least a part is formed by the second porous portion disposed so that moisture can be supplied from the first porous portion. A second surface, and
A fuel comprising: a gas separator that forms a reaction gas channel in which a reaction gas used in an electrochemical reaction flows in the first surface; and a gas separator that forms a cooling gas channel in which a cooling gas flows in the second surface. battery. The fuel cell according to claim 1, wherein
The first porous portion is disposed in at least a part of a region of the first surface that forms the reaction gas flow path,
The second porous portion is disposed in at least a part of a region of the second surface that forms the cooling gas passage. The fuel cell according to claim 1 or 2,
A fuel cell further comprising: a connection channel that connects the cooling gas channel and the reaction gas channel and guides the cooling gas that has passed through the cooling gas channel to the reaction gas channel as the reaction gas. A fuel cell according to any one of claims 1 to 3,
The reaction gas channel is an oxidizing gas channel that forms a fuel gas channel through which a fuel gas containing hydrogen passes and / or an oxidizing gas channel containing oxygen,
The fuel cell uses the gas separator to form the fuel gas channel and / or the oxidizing gas channel. A fuel cell according to any one of claims 1 to 4,
The first porous portion and the second porous portion are provided in a region corresponding to a vicinity of a discharge portion where the reaction gas is discharged from the reaction gas flow path. A fuel cell gas separator that is laminated together with a member that forms an electrolyte layer and an electrode to form a fuel cell,
A first surface at least partially formed by the first porous portion;
At least a portion is formed by the second porous portion that is smaller in porosity and / or pore diameter than the first porous portion and is disposed so that moisture can be supplied from the first porous portion. A gas separator comprising: a second surface.

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