JP2014036012A - Separator for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator ensuring diffusivity of reaction gas, by moving water produced by power generation quickly from the electrode surface, thereby preventing the flooding in the downstream of a gas passage.SOLUTION: A separator for fuel cell includes a reaction gas passage 5 formed of a porous body in contact with a membrane electrode assembly 1 and through which reaction gas flows, and a conductive flat plate 3 in contact with the reaction gas passage 5. A passage groove 17 is formed in the reaction gas passage 5, in the flow direction of reaction gas. Cross section of the passage groove 17 perpendicular to the drawing direction is larger than the average value of cross section of pores in the porous body forming the reaction gas passage 5. The passage groove 17 consists of a plurality of partial grooves 13, 14, and the drawing directions of adjoining partial grooves 13, 14 are different from each other in the direction connecting the conductive flat plate 3 and the membrane electrode assembly 1.

Description

  The present invention relates to a fuel cell separator that generates electrical energy by a chemical reaction between a fuel and an oxidant.

  Various types of fuel cells have been put into practical use depending on the type of electrolyte. For example, the polymer electrolyte fuel cell includes a membrane electrode assembly, gas diffusion layers disposed on both sides thereof, and separators disposed on both sides thereof as a unit power generation cell structure. The membrane electrode assembly is a joined body in which a solid polymer electrolyte membrane is sandwiched and covered between a fuel electrode catalyst layer (hereinafter referred to as “anode”) and an oxidant electrode catalyst layer (hereinafter referred to as “cathode”). The gas diffusion layer is made of, for example, a porous carbon material, and diffuses gas so as to be uniformly supplied to the anode and the cathode. The separator supplies fuel gas to the anode and oxidant gas to the cathode. A plurality of unit power generation cells are stacked to form a stacked body (hereinafter referred to as “stack”), and both ends of the stack are tightened with a clamping plate or the like to constitute a fuel cell stack.

  The separator is generally provided with a fuel gas or oxidant gas flow path on one side and a cooling medium flow path on the other side. It is manufactured by molding. In the case of a fuel cell using this separator, the convex surface (hereinafter referred to as a rib) of the fuel gas flow channel is in contact with the gas diffusion layer on the anode side of the separator and the rib of the oxidant gas flow channel on the cathode side. The separator exchanges electrons generated by the electrochemical reaction at the contact portion with the gas diffusion layer, and transfers heat generated by the electrochemical reaction to the cooling medium flowing in the cooling flow path. Further, the fuel gas or the oxidant gas flows through the recess and is supplied to the anode or the cathode through the gas diffusion layer, respectively.

  Fuel cells have been put to practical use as stationary distributed power sources and in-vehicle power sources because of their high efficiency and low environmental load compared to other power sources. For example, in the case of an in-vehicle power source, a high output density such as small size and light weight is required. For this purpose, it is necessary to generate power uniformly over the entire power generation surface and to reduce parts that do not directly contribute to power generation.

  In conventional separators, the reaction gas flow path is formed by pressing a thin metal plate, and the role is divided so that only the energization is performed in the rib in contact with the gas diffusion layer and the gas diffusion is performed in the recess (reaction gas flow path). Has been. For this reason, the current-carrying part and the gas diffusion part are distributed with the size of the rib and the gas flow path width. It is effective to subdivide the ribs and the gas flow path width for uniform power generation, but these subdivisions have limitations from the viewpoint of processing.

  In view of this, instead of such a press-processed separator, a method is conceivable in which a conductive porous body having fine pores connected thereto is used for the reaction gas channel. That is, when the porous body is used for the reaction gas flow path, the skeleton of the porous body that is the current-carrying part and the communication pores that are the gas diffusion part are uniformly mixed. Can be made uniform. As a result, the power generation reaction is made uniform, and an improvement in output can be expected.

  In the fuel cell, hydrogen, which is a fuel, and oxygen in the air, which is an oxidant, are consumed by the reaction shown below, and water, heat, and electric power are generated. In a fuel cell with high output and high current density, the amount of water generated by the reaction also increases.

2H ₂ + O ₂ → 2H ₂ O + (heat) + (electric power)
Since this reaction occurs while the reaction gas flows from upstream to downstream along the flow path, the reaction gas flow rate decreases as it goes downstream. Further, water vapor generated by the reaction flows on the oxidant gas side (cathode side) and moves on the fuel gas side (anode side) from the cathode side through the solid polymer electrolyte membrane based on concentration diffusion and electroosmosis. Water flows in. As a result, in the electrode, when the water vapor concentration increases and exceeds the saturation concentration, condensed water is generated, causing gas shortage, and flooding due to condensed water occurs, causing a cell voltage decrease.

  Patent Document 1 discloses a technique in which a plurality of slits are provided on the downstream side of a porous gas diffusion layer to prevent stagnation of water on the downstream side. In this technique, water generated on the upstream side moves to the downstream side by the gas flow and is discharged by a slit provided on the downstream side of the gas diffusion layer.

JP 2006-172871 A

  By using a porous body in the reaction gas channel, gas diffusibility is improved, and when the reaction at the electrode becomes uniform, water generated by the reaction is also uniformly generated. Since the water generated in the upstream portion of the gas flow path moves to the downstream portion together with the unreacted gas, excess water tends to stay in the downstream portion, and flooding occurs to easily reduce the cell voltage. Further, the generated water hinders the diffusion of the reaction gas and causes the cell voltage to decrease. For this reason, it is necessary to quickly discharge the generated water away from the electrode surfaces (anode and cathode) to prevent water retention and flooding and to ensure the diffusibility of the reaction gas. Therefore, it is necessary not only to move the generated water to the downstream part of the gas flow path, but also to quickly move it from the electrode surface in both the upstream part and the downstream part.

  In a fuel cell, the amount of generated water generated by high current density power generation increases, but in order to perform stable power generation, it is necessary to ensure the diffusibility of the reaction gas and move the generated water quickly from the electrode surface. is there.

  An object of the present invention is to provide a separator capable of quickly moving generated water generated by power generation from an electrode surface, preventing flooding downstream of a gas flow path, and ensuring diffusibility of a reaction gas. To do.

  The fuel cell separator according to the present invention has the following characteristics. A separator for a fuel cell comprising a reaction gas channel formed of a porous body and in contact with a membrane electrode assembly and through which a reaction gas flows, and a conductive flat plate in contact with the reaction gas channel, wherein the reaction gas channel includes: A channel groove is formed along the flow direction of the reaction gas. The flow channel has a cross-sectional area perpendicular to the extending direction that is larger than the average value of the cross-sectional areas of the pores of the porous body forming the reaction gas flow channel. In addition, the flow channel is composed of a plurality of partial grooves, and the extending directions of the adjacent partial grooves are different from each other in the direction connecting the conductive flat plate and the membrane electrode assembly.

  In the separator according to the present invention, generated water generated by power generation can be quickly moved from the electrode surface, and flooding downstream of the gas flow path can be prevented, and the diffusibility of the reaction gas can be ensured. Therefore, it is possible to provide a fuel cell capable of stable power generation even at a high current density with a large amount of water produced by power generation.

The schematic diagram which shows the cross section of a fuel cell stack. The plane schematic diagram when the oxidizing agent side separator by Example 1 of this invention is seen from a membrane electrode assembly. The plane schematic diagram when the oxidizing agent side porous gas flow path of Example 1 is seen from the oxidizing agent side flat plate. The plane schematic diagram when the oxidizing agent side porous gas flow path of Example 1 is seen from the membrane electrode assembly. FIG. 3 is a schematic diagram showing a side cross section of an oxidant-side porous gas channel of Example 1. FIG. 3 is a schematic plan view showing the movement of water when the oxidant side porous gas flow path of Example 1 is viewed from the oxidant side flat plate. FIG. 3 is a schematic diagram showing the movement of water in the side cross section of the oxidant-side porous gas channel of Example 1. FIG. 3 is a diagram showing a modification of the oxidant side porous gas flow path in the first embodiment. FIG. 6 is a diagram showing another modification of the oxidant side porous gas flow path in the first embodiment. FIG. 6 is a view showing still another modification of the oxidant-side porous gas channel in the first embodiment. The plane schematic diagram when the oxidizing agent side porous gas flow path of Example 2 is seen from the oxidizing agent side flat plate. The plane schematic diagram when the oxidizing agent side porous gas flow path of Example 2 is seen from the membrane electrode assembly. FIG. 4 is a schematic diagram showing a side cross section of an oxidant side porous gas flow channel of Example 2. FIG. 6 is a schematic diagram showing a side cross section of an oxidant-side porous gas channel of Example 3. The plane schematic diagram when the oxidizing agent side porous gas flow path of Example 4 is seen from the oxidizing agent side flat plate. The plane schematic diagram when the oxidizing agent side porous gas flow path of Example 4 is seen from the membrane electrode assembly. The schematic diagram which shows the side cross section (A-A 'cross section of FIG. 10A) of the oxidizing agent side porous gas flow path of Example 4. FIG. The schematic diagram which shows the side cross section (B-B 'cross section of FIG. 10A) of the oxidizing agent side porous gas flow path of Example 4. FIG. FIG. 6 is a schematic diagram showing a side cross section of an oxidant-side porous gas channel of Example 5. FIG. 6 is a schematic diagram showing a side cross section of an oxidant side porous gas flow channel of Example 6.

  Hereinafter, embodiments of a fuel cell separator according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing a cross section of the fuel cell stack 100. The fuel cell stack 100 includes a power generation unit 105, a fuel gas supply port 111, a fuel gas discharge port 112, an oxidant gas supply port 113, an oxidant gas discharge port 114, and a collector for taking out the generated electric power to the outside. An electric plate 115, an insulating plate 116 arranged outside the current collecting plate 115, a seal member 20 for preventing leakage of reactive gas (fuel gas and oxidant gas), and a reactive gas supply port and discharge port are provided. An end plate 118 is provided. Although not shown, the fuel cell stack 100 further includes a mechanism for applying a load in the stacking direction of the constituent members of the fuel cell stack 100.

  The current collecting plate 115 is a terminal for taking out the electric energy generated by the fuel cell to the outside, and by using a gold-plated copper, it is possible to achieve both corrosion resistance and conductivity. The end plate 118 may use a metal material such as SUS, but may also serve as the insulating plate 116 using an insulating resin such as PPS (Poly Phenylene Sulfide). The mechanism for applying a load to the constituent members of the fuel cell stack 100 applies a surface pressure of about 1 MPa to the membrane electrode assembly 1 provided in the power generation unit 105.

  The power generation unit 105 includes the membrane electrode assembly 1, the fuel side separator 7, the oxidant side separator 8, and the cooling flow path 6.

  The membrane electrode assembly 1 includes a solid polymer electrolyte membrane made of a fluorine-based or hydrocarbon-based solid polymer material, an anode disposed on one surface of the solid polymer electrolyte membrane, and a cathode disposed on the other surface. Is provided. The anode and the cathode are composed of a carbon support on which a catalyst such as platinum is supported and an electrolyte.

  The fuel-side separator 7 includes a conductive fuel-side flat plate 2 and a fuel-side porous gas flow path 4, is disposed so as to contact one surface of the membrane electrode assembly 1, and supplies fuel gas to the anode. A fuel-side porous gas channel 4 is in contact with the membrane electrode assembly 1. That is, the fuel side porous gas flow path 4 is sandwiched between the fuel side flat plate 2 and the membrane electrode assembly 1.

  The oxidant side separator 8 includes a conductive oxidant side flat plate 3 and an oxidant side porous gas flow path 5 and is disposed so as to be in contact with the other surface of the membrane electrode assembly 1. Supply. The membrane electrode assembly 1 is in contact with the oxidant side porous gas flow path 5. That is, the oxidant side porous gas channel 5 is sandwiched between the oxidant side flat plate 3 and the membrane electrode assembly 1.

  Usually, the power generation unit 105 includes a gas diffusion layer made of carbon paper or carbon felt between the membrane electrode assembly 1 and the porous gas flow paths 4 and 5. However, the porous gas flow paths 4 and 5 can have a gas diffusion layer function, and the gas diffusion layer can be omitted. In the embodiment described below, an example in which the gas diffusion layer is omitted by giving the porous gas flow paths 4 and 5 the function of the gas diffusion layer is shown.

  The cooling flow path 6 is disposed so as to be in contact with the fuel side separator 7 and the oxidant side separator 8, and a cooling medium for cooling the heat generated by the power generation by the electrochemical reaction flows. For example, water can be used as the cooling medium.

  In the fuel cell stack 100 having such a configuration, the present invention is characterized in that at least one of the oxidant side separator 8 and the fuel side separator 7 has the following configuration.

  (1) A reaction gas passage formed of a porous body and in contact with the membrane electrode assembly 1 and through which a reaction gas flows, and a conductive flat plate in contact with the reaction gas passage are provided. In the reaction gas channel, a channel groove (gap) is formed along the flow direction of the reaction gas. The channel groove has a cross-sectional area perpendicular to the extending direction that is larger than the average value of the cross-sectional areas of the pores of the porous body forming the reaction gas channel. Furthermore, the flow channel groove is composed of a plurality of partial grooves, and the extending directions of the adjacent partial grooves are different from each other in the direction connecting the conductive flat plate and the membrane electrode assembly 1.

  (2) Preferably, the flow channel groove is connected to the plurality of horizontal grooves extending in the reaction gas flow direction as a plurality of partial grooves and extending in the direction connecting the conductive flat plate and the membrane electrode assembly 1. A plurality of longitudinal grooves.

  (3) Preferably, the flow path groove includes a partial groove extending obliquely from the conductive flat plate toward the membrane electrode assembly 1 along the upstream side to the downstream side of the reactive gas flow, and the upstream side of the reactive gas flow. The partial grooves extending obliquely from the membrane electrode assembly 1 toward the conductive flat plate are formed so as to be alternately arranged along the downstream side.

  Examples of the separator according to the present invention will be described below. In the following examples, the oxidant side separator 8 will be described as an example, but the following examples can also be applied to the fuel side separator 7. Even if the following examples are applied to the fuel-side separator 7, the same effects as those obtained by applying to the oxidant-side separator 8 can be obtained. As an example of the reaction gas of the fuel cell, the fuel gas is hydrogen and the oxidant gas is air. The fuel gas need not be hydrogen, but may be any gas rich in hydrogen. The oxidant gas may be oxygen gas, and oxygen gas is most preferable. The separator according to the present invention can be applied to various types of fuel cells such as a polymer electrolyte fuel cell and a direct methanol fuel cell.

  FIG. 2 is a schematic plan view of the oxidant side separator 8 according to Example 1 of the present invention when viewed from the membrane electrode assembly 1. The oxidant side separator 8 includes an oxidant gas supply manifold 21, an oxidant gas discharge manifold 22, a fuel gas supply manifold 23, a fuel gas discharge manifold 24, a cooling medium supply manifold 25, a cooling medium discharge manifold 26, and a seal member 20. Is provided.

  The seal member 20 is made of a gasket or the like, prevents a short circuit between electrodes on both sides of the unit power generation cell, and prevents leakage of reaction gas and liquid.

  The oxidant side separator 8 includes an oxidant side flat plate 3 (not shown in FIG. 2) and an oxidant side porous gas flow path 5. As will be described later, a channel groove (void) composed of a plurality of partial grooves (lateral grooves 13 and vertical grooves 14) is formed in the oxidant-side porous gas channel 5. The channel groove is a cavity formed in the oxidant-side porous gas channel 5 and extends in the oxidant gas flow direction as a whole to circulate the oxidant gas. The extending directions of the adjacent partial grooves are different from each other in the direction connecting the oxidant side flat plate 3 and the membrane electrode assembly 1. The channel groove has a cross-sectional area perpendicular to the extending direction (the flow direction of the oxidant gas) determined from the average value of the pore diameters (average pore diameter) of the porous body forming the oxidant side porous gas flow channel 5. It is larger than the average value of the cross-sectional area of the pores (average pore cross-sectional area).

  The oxidant-side porous gas channel 5 is formed of a porous body, and diffuses the reaction gas (oxidant gas) on the power generation surface (cathode). As described above, the oxidant-side separator 8 includes the oxidant-side porous gas channel 5 in contact with the membrane electrode assembly 1 and the oxidant-side flat plate 3 in contact with the oxidant-side porous gas channel 5. The oxidant-side porous gas channel 5 is sandwiched between the oxidant-side flat plate 3 and the membrane electrode assembly 1, is opposed to the oxidant-side flat plate 3 on one side, and the membrane electrode assembly on the other side. 1 opposite.

  The porous body that forms the oxidant-side porous gas flow path 5 is a porous body that has continuous pores and is made of a conductive material. The material is selected from titanium, aluminum, magnesium, nickel, chromium, molybdenum, and an alloy (for example, SUS) partially containing them. It is preferably produced by foaming, sintering, or binding of fine metal fibers, and the porosity is desirably 75% or more. The pore diameter of the porous body is desirably in the range of 10 μm to 500 μm, and in particular, the mode diameter based on the pore diameter distribution is desirably 150 μm or more. The porous body has a thickness of 0.2 mm to 1.5 mm.

  Further, the porous body forming the oxidant side porous gas flow path 5 is subjected to a hydrophilic treatment on the surface facing the oxidant side flat plate 3 and a hydrophobic treatment on the surface facing the membrane electrode assembly 1. Is desirable. In the present specification, the hydrophilic treatment is treatment so that the contact angle with water is 30 ° or less, and the hydrophobic treatment is treatment so that the contact angle with water is 80 ° or more. is there.

  The oxidant side flat plate 3 is a conductive metal flat plate made of a pure metal or alloy having a thickness of 0.2 mm or less, or a clad material obtained by laminating and rolling a plurality of metal plates. Examples of the material that can be used include titanium, SUS, aluminum, and magnesium.

  3A, 3B, and 3C are views showing details of the oxidant-side porous gas flow path 5 of the oxidant-side separator 8. FIG. FIG. 3A is a schematic plan view of the oxidant side porous gas flow path 5 when viewed from the oxidant side flat plate 3, and shows a surface facing the oxidant side flat plate 3. FIG. 3B is a schematic plan view of the oxidant-side porous gas flow channel 5 when viewed from the membrane electrode assembly 1, and shows a surface facing the membrane electrode assembly 1. FIG. 3C is a schematic diagram showing a side cross-section of the oxidant side porous gas channel 5.

  3A, 3B, and 3C, the oxidant gas flows from the left side to the right side of the figure. 2 is on the left side in FIGS. 3A-3C and the oxidant gas discharge manifold 22 is on the right side in FIGS. 3A-3C. In the oxidant side porous gas flow path 5, the side to which the oxidant gas is supplied (the left side in FIGS. 3A to 3C) is referred to as “oxidant gas inlet side end 15”, and the side from which the oxidant gas is discharged. (Right side in FIGS. 3A to 3C) is referred to as “oxidant gas outlet side end portion 16”. The oxidant gas flows into the oxidant side porous gas flow path 5 from the oxidant gas inlet side end 15 on the upstream side, and flows out from the oxidant gas outlet side end 16 on the downstream side.

  As shown in FIGS. 3A, 3B, and 3C, the oxidant-side porous gas flow path 5 is formed with a plurality of lateral grooves 13 that extend along the flow direction of the oxidant gas. Each of the plurality of lateral grooves 13 is formed in contact with the oxidant side flat plate 3 or the membrane electrode assembly 1. As shown in FIG. 3C, the lateral grooves 13 in contact with the oxidant side flat plate 3 and the lateral grooves 13 in contact with the membrane electrode assembly 1 are alternately arranged along the flow direction of the oxidant gas.

  Further, the oxidant side porous gas flow path 5 is formed with a plurality of vertical grooves 14 extending along a direction connecting the oxidant side flat plate 3 and the membrane electrode assembly 1. Each of the vertical grooves 14 connects the adjacent horizontal grooves 13 along the flow direction of the oxidant gas. That is, the vertical groove 14 is formed so as to connect the horizontal groove 13 in contact with the oxidant side flat plate 3 and the horizontal groove 13 in contact with the membrane electrode assembly 1.

  By the plurality of horizontal grooves 13 and the plurality of vertical grooves 14 which are partial grooves, a flow path groove 17 is formed in the oxidant side porous gas flow path 5 as a whole along the flow direction of the oxidant gas. The channel groove 17 bends in a crank shape between the oxidant side flat plate 3 and the membrane electrode assembly 1 and snakes and extends from the upstream side to the downstream side of the flow of the oxidant gas.

  The cross-sectional area perpendicular to the oxidant gas flow direction (cross-sectional area along the direction connecting the oxidant side flat plate 3 and the membrane electrode assembly 1) of the lateral groove 13 forms the oxidant side porous gas flow path 5. It is larger than the average pore cross-sectional area obtained from the average pore diameter of the porous body. The depth of the lateral groove 13 (the length in the direction connecting the oxidant side flat plate 3 and the membrane electrode assembly 1) is the thickness of the oxidant side porous gas channel 5 (the oxidant side flat plate 3 and the membrane electrode assembly). 1 or less of the length in the direction connecting 1).

  The cross-sectional area of the longitudinal groove 14 (the cross-sectional area perpendicular to the direction connecting the oxidant-side flat plate 3 and the membrane electrode assembly 1) is obtained from the average pore diameter of the porous body forming the oxidant-side porous gas channel 5. It is larger than the average pore cross-sectional area.

  That is, in the oxidant side porous gas flow channel 5, a flow channel groove 17 having a cross-sectional area larger than the average pore cross-sectional area of the porous body forming the oxidant side porous gas flow channel 5 is It is formed by the vertical groove 14. Specific values of the cross-sectional area of the channel groove 17 include, for example, the pressure and flow rate of the oxidant gas, the porosity of the porous body forming the oxidant side porous gas channel 5, and the oxidant side porous gas. It can be determined based on the strength of the flow path 5. In this example, as an example, a SUS porous body having a nominal pore diameter of 600 μm was used as the porous body forming the oxidant-side porous gas flow path 5. The lateral groove 13 formed in the oxidant side porous gas flow path 5 has a depth (a length in a direction connecting the oxidant side flat plate 3 and the membrane electrode assembly 1) and a width (a flow direction of the oxidant gas and an oxidation). The direction perpendicular to the direction connecting the agent side flat plate 3 and the membrane electrode assembly 1) is a prismatic shape of 0.5 mm, and the longitudinal groove 14 has a diameter (length in the flow direction of the oxidizing gas) of 1 mm. The cylindrical shape has a length connecting the oxidant side flat plate 3 and the membrane electrode assembly 1.

  The shape of the lateral groove 13 may not be a prismatic shape, and may be an arbitrary shape. That is, the shape of the cross section of the lateral groove 13 perpendicular to the flow direction of the oxidant gas (cross section along the direction connecting the oxidant side flat plate 3 and the membrane electrode assembly 1) is a polygon, a circle, an ellipse, or the like. Any shape is acceptable. The shape of the vertical groove 14 may not be a cylindrical shape, and may be an arbitrary shape. That is, the shape of the cross section of the vertical groove 14 perpendicular to the direction connecting the oxidant-side flat plate 3 and the membrane electrode assembly 1 may be any shape such as a polygon, a circle, or an ellipse.

  At the oxidant gas inlet side end 15 of the oxidant side porous gas flow path 5, as shown in FIG. 3C, the lateral groove 13 is preferably in contact with the oxidant side flat plate 3. That is, it is preferable that the lateral groove 13 on the most upstream side in the flow direction of the oxidant gas is in contact with the oxidant side flat plate 3. This is to prevent the membrane electrode assembly 1 from being dried by the flow of the oxidant gas on the upstream side of the flow of the oxidant gas (the portion where the amount of water generated by the electrochemical reaction is small).

  The horizontal grooves 13 and the vertical grooves 14 can be formed by cutting or pressing, and can also be formed at the manufacturing stage of the porous body used for the oxidant side porous gas flow path 5.

For the hydrophilic treatment applied to the surface facing the oxidant side flat plate 3 of the oxidant side porous gas flow path 5, a hydrophilic agent containing TiO ₂ or SiO ₂ is used and applied to the surface facing the membrane electrode assembly 1. For the hydrophobic treatment, it is effective to use a dispersion containing PTFE.

  By forming a channel groove (void) 17 that is bent between the oxidant side flat plate 3 and the membrane electrode assembly 1 in the oxidant side porous gas channel 5, the diffusibility of the oxidant gas is increased. In addition, it is possible to quickly move generated water generated by power generation from the cathode. The oxidant gas mainly flows from the upstream side to the downstream side of the oxidant side porous gas flow channel 5 through the flow channel groove 17. At this time, since the channel groove 17 is bent, the oxidant gas collides with the oxidant side porous gas channel 5 and enters the pores of the porous body of the oxidant side porous gas channel 5. Cheap. Accordingly, the oxidant gas not only flows through the flow channel groove 17 but also diffuses into the porous body of the oxidant side porous gas flow channel 5 and reaches the electrode. For this reason, compared with the case where the linear flow path groove | channel 17 which is not bent is formed in the oxidizing agent side porous gas flow path 5, the diffusibility of oxidizing gas can be improved more.

  The length of the lateral groove 13 in the flow direction of the oxidant gas can be arbitrarily determined, but is preferably shorter in order to improve the diffusibility of the oxidant gas. As for the diffusibility of the oxidant gas, the number of times the flow channel 17 in the oxidant side porous gas flow channel 5 is bent (that is, the number of times the oxidant gas collides with the oxidant side porous gas flow channel 5) is large. Get better. When the length of the lateral groove 13 in the flow direction of the oxidant gas is short, the number of times the flow path groove 17 is bent is increased, and the diffusibility of the oxidant gas is further improved.

  As shown in FIGS. 3A and 3B, a plurality of flow channel grooves 17 bent between the oxidant side flat plate 3 and the membrane electrode assembly 1 are formed in the oxidant side porous gas flow channel 5. Is preferred. The greater the number of flow channel grooves 17, the better the diffusibility of the oxidant gas.

  4A and 4B are schematic views showing the movement of water in the oxidant side porous gas flow path 5. FIG. FIG. 4A is a schematic plan view showing the movement of water when the oxidant side porous gas channel 5 is viewed from the oxidant side flat plate 3. FIG. 4B is a schematic diagram showing the movement of water in the side cross section of the oxidant-side porous gas channel 5. 4A and 4B, the arrows indicate the movement of water.

  As shown in FIG. 4B, the surface facing the membrane electrode assembly 1 of the oxidant side porous gas channel 5 is subjected to hydrophobic treatment, and the surface facing the oxidant side flat plate 3 is Hydrophilic treatment is applied. Due to this hydrophobic treatment, the water generated by the electrochemical reaction does not enter the pores of the oxidant-side porous gas flow channel 5 and flows from the membrane electrode assembly 1 to the flow channel groove 17 (mainly the lateral groove 13). Moving. This water moves in the direction of the oxidant side flat plate 3 through the flow channel groove 17 (mainly the vertical groove 14) by the pressure of the unreacted oxidant gas. As shown in FIGS. 4A and 4B, this water is absorbed into the oxidant side porous gas channel 5 by the hydrophilic treatment of the surface of the oxidant side porous gas channel 5 facing the oxidant side flat plate 3. And held in this plane.

  5, 6, and 7 are diagrams illustrating modifications of the oxidant-side porous gas channel 5 in the first embodiment. 5-7 has shown the side cross section of the oxidizing agent side porous gas flow path 5 similarly to FIG. 3C.

  In the oxidant side porous gas flow path 5 shown in FIG. 5, the lateral groove 13 is in contact with the oxidant side flat plate 3 at both the oxidant gas inlet side end 15 and the oxidant gas outlet side end 16. As described above, at the oxidant gas inlet side end portion 15, as shown in FIG. 3C, the lateral groove 13 is preferably in contact with the oxidant side flat plate 3. However, at the oxidant gas outlet side end 16, as shown in FIGS. 3C and 5, the lateral groove 13 may be in contact with the membrane electrode assembly 1 or may be in contact with the oxidant side flat plate 3. That is, the lateral groove 13 on the most downstream side in the flow direction of the oxidant gas may be in contact with the membrane electrode assembly 1 or may be in contact with the oxidant side flat plate 3.

  In the oxidant side porous gas flow path 5 shown in FIG. 6, the flow path groove 17 composed of the lateral groove 13 and the vertical groove 14 is formed inside the oxidant side porous gas flow path 5. That is, the lateral grooves 13 at the positions of the oxidant gas inlet side end 15 and the oxidant gas outlet side end 16 are respectively formed by oxidizing portions of the oxidant gas inlet side end 15 and oxidant gas outlet side end 16. The agent side porous gas flow path 5 is blocked by the porous body. Note that only one of the lateral grooves 13 at the position of the oxidant gas inlet side end 15 and the oxidant gas outlet side end 16 may be blocked by the porous body of the oxidant side porous gas flow path 5. .

  In the oxidant-side porous gas channel 5 shown in FIG. 7, the channel groove 17 composed of the lateral groove 13 and the vertical groove 14 is not in contact with the membrane electrode assembly 1 and the oxidant-side flat plate 3. That is, the channel groove 17 composed of the lateral groove 13 and the vertical groove 14 is formed in the porous body of the oxidant side porous gas channel 5 except for the oxidant gas inlet side end 15 and the oxidant gas outlet side end 16. being surrounded. The channel groove 17 composed of the lateral groove 13 and the vertical groove 14 may be in contact with only one of the membrane electrode assembly 1 and the oxidant side flat plate 3, and only a part thereof is on the membrane electrode assembly 1 or the oxidant side. You may contact the flat plate 3.

  In this way, the lateral grooves 13 in contact with the oxidant side flat plate 3 and the lateral grooves 13 in contact with the membrane electrode assembly 1 are alternately arranged along the flow direction of the oxidant gas. By forming a channel groove 17 that is bent between the oxidant side flat plate 3 and the membrane electrode assembly 1, water generated upstream in the flow direction of the oxidant gas can be The electrode assembly 1 can be quickly moved in the direction of the oxidant side flat plate 3. Therefore, it is possible to prevent the generated water from flowing downstream, and it is possible to prevent excessive water from staying in the downstream portion. In this embodiment, the generated water is quickly moved from the membrane electrode assembly 1 toward the oxidant side flat plate 3 in the vicinity of the generation place not only on the downstream side in the flow direction of the oxidant gas but also on the upstream side. There is an effect that can be made.

  The oxidant-side separator 8 according to the second embodiment of the present invention will be described with reference to FIGS. 8A, 8B, and 8C. FIG. 8A, FIG. 8B, and FIG. 8C are diagrams showing details of the oxidant-side porous gas channel 5 of the oxidant-side separator 8 in the present embodiment. FIG. 8A is a schematic plan view of the oxidant side porous gas flow channel 5 when viewed from the oxidant side flat plate 3, and shows a surface facing the oxidant side flat plate 3. FIG. 8B is a schematic plan view of the oxidant-side porous gas channel 5 when viewed from the membrane electrode assembly 1, and shows a surface facing the membrane electrode assembly 1. FIG. 8C is a schematic diagram showing a side cross-section of the oxidant side porous gas channel 5. 8A, FIG. 8B, and FIG. 8C, the same code | symbol as Example 1 shows the element which is the same as that of Example 1, or is common. The description of the same or common configuration as the first embodiment is omitted.

  In this embodiment, as shown in FIGS. 8A, 8B, and 8C, the lateral groove 13 forming the flow channel 17 of the oxidant side porous gas flow channel 5 has a length in the flow direction of the oxidant gas. The oxidant gas flow gradually shortens from upstream to downstream. In the case of such a configuration, the frequency of bending of the flow channel groove 17 increases as the position of the oxidant gas flows downstream. For this reason, the generated water can be moved more quickly from the membrane electrode assembly 1 toward the oxidant side flat plate 3 on the downstream side where water retention and flooding are likely to occur. Furthermore, on the downstream side, the frequency with which the oxidant gas collides with the oxidant side porous gas flow path 5 increases, and the diffusibility of the oxidant gas can be further improved.

  The oxidant side separator 8 according to Example 3 of the present invention will be described with reference to FIG. FIG. 9 is a schematic diagram showing a side cross section of the oxidant side porous gas flow path 5 of the oxidant side separator 8 in the present embodiment. In FIG. 9, the same reference numerals as those in the first embodiment indicate the same or common elements as those in the first embodiment. The description of the same or common configuration as the first embodiment is omitted.

  In this embodiment, the lateral groove 13 forming the flow channel groove 17 of the oxidant side porous gas flow channel 5 has a cross-sectional area perpendicular to the flow direction of the oxidant gas from the upstream to the downstream of the flow of the oxidant gas. Gradually get smaller. In the case of such a configuration, the flow rate of the oxidant gas increases as it goes downstream of the flow of the oxidant gas. Therefore, the force for moving the generated water to the direction of the oxidant side flat plate 3 through the flow channel groove 17 (mainly the vertical groove 14) is increased by the flow rate of the oxidant gas. For this reason, the generated water can be moved more quickly from the membrane electrode assembly 1 toward the oxidant side flat plate 3 on the downstream side where water retention and flooding are likely to occur.

  In the example shown in FIG. 9, the depth d of the lateral groove 13 (the length in the direction connecting the oxidant side flat plate 3 and the membrane electrode assembly 1) is gradually increased from the upstream side to the downstream side of the flow of the oxidant gas. The cross-sectional area perpendicular to the flow direction of the oxidant gas in the lateral groove 13 is gradually reduced by decreasing the distance. That is, in the example of FIG. 9, the depth of the four lateral grooves 13 is d1> d2> d3> d4.

  The direction connecting the oxidant side flat plate 3 and the membrane electrode assembly 1 by reducing the cross-sectional area perpendicular to the flow direction of the oxidant gas in the lateral groove 13 from the upstream side to the downstream side of the flow of the oxidant gas. The ratio of the oxidant-side porous gas flow channel 5 to the flow channel groove 13 increases in the downstream direction. Since the oxidant side porous gas channel 5 plays a role of diffusing the reaction gas in the electrode direction, it can be expected that the gas diffusibility is improved as the ratio of the oxidant side porous gas channel 5 increases. Therefore, by adopting the configuration as in this embodiment, good gas diffusibility can be ensured even in the downstream portion where the oxygen concentration decreases.

  The oxidant-side separator 8 according to Example 4 of the present invention will be described with reference to FIGS. 10A, 10B, 10C, and 10D. 10A to 10D are views showing details of the oxidant-side porous gas channel 5 of the oxidant-side separator 8 in the present embodiment. FIG. 10A is a schematic plan view of the oxidant-side porous gas flow channel 5 when viewed from the oxidant-side flat plate 3, and shows a surface facing the oxidant-side flat plate 3. FIG. 10B is a schematic plan view of the oxidant-side porous gas flow channel 5 when viewed from the membrane electrode assembly 1 and shows a surface facing the membrane electrode assembly 1. FIG. 10C is a schematic diagram showing a side cross-section of the oxidant-side porous gas flow channel 5, and shows a cross-section A-A ′ of FIG. 10A. FIG. 10D is a schematic diagram showing a side cross-section of the oxidant-side porous gas channel 5, and shows a B-B ′ cross-section of FIG. 10A. 10A to 10D, the same reference numerals as those in the first embodiment indicate the same or common elements as those in the first embodiment. The description of the same or common configuration as the first embodiment is omitted.

  In the present embodiment, as shown in FIGS. 10A to 10D, the oxidant side separator 8 includes two types of flow channel grooves 17. One is, as shown in FIG. 10C, a lateral groove 13 in contact with the oxidant side flat plate 3 at the oxidant gas inlet side end 15 and a lateral groove 13 in contact with the membrane electrode assembly 1 at the oxidant gas outlet side end 16. It is the channel groove 17 which has. That is, the lateral groove 13 on the most upstream side in the flow direction of the oxidant gas is in contact with the oxidant side flat plate 3, and the lateral groove 13 on the most downstream side is the flow channel groove 17 in contact with the membrane electrode assembly 1. The other is, as shown in FIG. 10D, a lateral groove 13 in contact with the membrane electrode assembly 1 at the oxidant gas inlet side end 15 and a lateral groove 13 in contact with the oxidant side flat plate 3 at the oxidant gas outlet side end 16. It is the channel groove 17 which has. That is, the lateral groove 13 on the most upstream side in the flow direction of the oxidant gas is in contact with the membrane electrode assembly 1, and the lateral groove 13 on the most downstream side is the flow channel groove 17 in contact with the oxidant side flat plate 3.

  As shown in FIGS. 10A and 10B, these two types of flow channel grooves 17 are perpendicular to the direction of the oxidant gas flow (and perpendicular to the direction connecting the oxidant side flat plate 3 and the membrane electrode assembly 1). In the direction), the oxidant side porous gas flow paths 5 are alternately arranged. In other words, the adjacent channel grooves 17 in the direction perpendicular to the flow direction of the oxidant gas (and the direction perpendicular to the direction connecting the oxidant side flat plate 3 and the membrane electrode assembly 1) are of different types. When the oxidant side porous gas flow path 5 has such a configuration, in a direction perpendicular to the flow direction of the oxidant gas (and a direction perpendicular to the direction connecting the oxidant side flat plate 3 and the membrane electrode assembly 1). Compared to the case where the adjacent flow channel grooves 17 are of the same type, the amount of water retained by the porous body of the oxidant side porous gas flow channel 5 is made uniform in the plane of the oxidant side porous gas flow channel 5. can do.

  Such a configuration of the oxidant-side porous gas flow path 5 is also applicable to the first to third embodiments.

  An oxidant-side separator 8 according to Example 5 of the present invention will be described with reference to FIG. FIG. 11 is a schematic diagram showing a side cross section of the oxidant-side porous gas channel 5 of the oxidant-side separator 8 in the present embodiment. In FIG. 11, the same reference numerals as those in the first embodiment indicate the same or common elements as those in the first embodiment. The description of the same or common configuration as the first embodiment is omitted.

  In the present embodiment, the lateral groove 13 that forms the channel groove 17 of the oxidant-side porous gas channel 5 extends in an oblique direction with respect to the direction in which the oxidant gas flows. In the example of FIG. 11, the lateral groove 13 extends obliquely from the oxidant side flat plate 3 toward the membrane electrode assembly 1 from the upstream side to the downstream side of the flow of the oxidant gas. The lateral groove 13 may extend obliquely from the membrane electrode assembly 1 toward the oxidant side flat plate 3 from upstream to downstream of the flow of the oxidant gas.

  In the oxidant side porous gas flow channel 5 in which the flow channel grooves 17 as shown in FIG. 11 are formed, the surface (or membrane) of the oxidant side porous gas flow channel 5 facing the membrane electrode assembly 1. The portion facing the electrode assembly 1 is subjected to hydrophobic treatment, and the surface facing the oxidant side flat plate 3 (or the portion facing the oxidant side flat plate 3) is subjected to hydrophilic treatment. Yes.

  Even when the flow channel groove 17 is bent between the oxidant side flat plate 3 and the membrane electrode assembly 1, the diffusing property of the oxidant gas is further improved in the same manner as the oxidant side separator 8 according to the first embodiment. The water generated by the electrochemical reaction can be quickly moved from the membrane electrode assembly 1 toward the oxidant side flat plate 3 in the vicinity of the generation site.

  It is possible to add the deformation as shown in FIGS. 6 to 9 and FIGS. 10A to 10D to the channel groove 17 having the shape as shown in the present embodiment. For example, as shown in FIG. 8, the length of the lateral groove 13 in the flow direction of the oxidant gas may gradually decrease from the upstream side to the downstream side of the flow of the oxidant gas. For example, as shown in FIG. 9, the cross-sectional area perpendicular to the extending direction of the lateral groove 13 (the flow direction of the oxidant gas) gradually decreases from the upstream to the downstream of the flow of the oxidant gas. You may do it.

  The oxidant side separator 8 according to Example 6 of the present invention will be described with reference to FIG. FIG. 12 is a schematic diagram showing a side cross section of the oxidant-side porous gas channel 5 of the oxidant-side separator 8 in the present embodiment. In FIG. 12, the same reference numerals as those in the first embodiment indicate the same or common elements as those in the first embodiment. The description of the same or common configuration as the first embodiment is omitted.

  In the present embodiment, as shown in FIG. 12, the oxidant-side porous gas flow channel 5 includes a plurality of partial grooves 18 and 19 extending in a direction oblique to the direction in which the oxidant gas flows. A groove 17 is formed. The extending direction of the partial grooves 18 and 19 changes alternately. In the example of FIG. 12, a partial groove 18 extending obliquely from the oxidant side flat plate 3 toward the membrane electrode assembly 1 from upstream to downstream of the oxidant gas flow, and a film from upstream to downstream of the oxidant gas flow. The partial grooves 19 extending obliquely from the electrode assembly 1 toward the oxidant side flat plate 3 are alternately arranged to form the flow channel grooves 17.

  Thus, the flow grooves 17 bent between the oxidant side flat plate 3 and the membrane electrode assembly 1 are formed in the oxidant side porous gas flow path 5 by the partial grooves 18 and 19. Each of the partial grooves 18 and 19 has a cross-sectional area perpendicular to the extending direction larger than the average pore cross-sectional area obtained from the average pore diameter of the porous body forming the oxidant-side porous gas flow channel 5. Due to the partial grooves 18 and 19, a flow path groove 17 is formed in the oxidant side porous gas flow path 5 as a whole along the flow direction of the oxidant gas. The channel groove 17 bends in a zigzag manner between the oxidant side flat plate 3 and the membrane electrode assembly 1, meanders, and extends from the upstream side to the downstream side of the flow of the oxidant gas.

  In the oxidant side porous gas flow channel 5 in which the flow channel grooves 17 as shown in FIG. 12 are formed, the surface (or membrane) of the oxidant side porous gas flow channel 5 facing the membrane electrode assembly 1. The portion facing the electrode assembly 1 is subjected to hydrophobic treatment, and the surface facing the oxidant side flat plate 3 (or the portion facing the oxidant side flat plate 3) is subjected to hydrophilic treatment. Yes.

  Even in the channel groove 17 having such a shape, as with the oxidant side separator 8 according to the first embodiment, the diffusibility of the oxidant gas can be further improved, and the water generated by the electrochemical reaction can be generated. , The membrane electrode assembly 1 can be quickly moved in the direction of the oxidant side flat plate 3.

  Further, at the oxidant gas inlet side end 15 of the oxidant side porous gas flow path 5, as shown in FIG. 12, the partial groove 18 is preferably in contact with the oxidant side flat plate 3. That is, it is preferable that the partial groove 18 on the most upstream side in the flow direction of the oxidant gas is in contact with the oxidant side flat plate 3. This is because the membrane electrode assembly 1 is dried by the flow of the oxidant gas on the upstream side of the flow of the oxidant gas (part where the amount of water generated by the electrochemical reaction is small), as in the above-described embodiment. Is to prevent.

  It is possible to add the deformation as shown in FIGS. 6 to 9 and FIGS. 10A to 10D to the channel groove 17 having the shape as shown in the present embodiment. For example, as shown in FIG. 8, the length in the flow direction of the oxidant gas in the partial grooves 18 and 19 forming the flow channel groove 17 gradually decreases from the upstream to the downstream of the flow of the oxidant gas. You may make it go. For example, as shown in FIG. 9, the cross-sectional area perpendicular to the extending direction (oxidant gas flow direction) of the partial grooves 18 and 19 forming the flow channel groove 17 is from the upstream of the flow of the oxidant gas. You may make it become small gradually toward the downstream.

  DESCRIPTION OF SYMBOLS 1 ... Membrane electrode assembly, 2 ... Fuel side flat plate, 3 ... Oxidant side flat plate, 4 ... Fuel side porous gas channel, 5 ... Oxidant side porous gas channel, 6 ... Cooling channel, 7 ... Fuel Side separator, 8 ... Oxidant side separator, 13 ... Transverse groove, 14 ... Vertical groove, 15 ... Oxidant gas inlet side end, 16 ... Oxidant gas outlet side end, 17 ... Channel groove, 18, 19 ... part groove.

Claims (12)

A fuel cell separator comprising a reaction gas channel formed of a porous body and in contact with a membrane electrode assembly and through which a reaction gas flows, and a conductive flat plate in contact with the reaction gas channel,
In the reaction gas channel, a channel groove is formed along the flow direction of the reaction gas,
The flow channel has a cross-sectional area perpendicular to the extending direction larger than the average value of the cross-sectional areas of the pores of the porous body forming the reaction gas flow channel, and the flow channel has a plurality of partial grooves. The fuel cell separator is characterized in that extending directions of the adjacent partial grooves are different from each other in a direction connecting the conductive flat plate and the membrane electrode assembly.   The channel groove is connected to the lateral groove by extending in a direction connecting the conductive flat plate and the membrane electrode assembly as a plurality of partial grooves extending in the reactive gas flow direction. The fuel cell separator according to claim 1, comprising a plurality of longitudinal grooves. Each of the plurality of lateral grooves is in contact with the conductive flat plate or the membrane electrode assembly,
3. The fuel cell separator according to claim 2, wherein the lateral grooves in contact with the conductive flat plate and the lateral grooves in contact with the membrane electrode assembly are alternately arranged along a flow direction of the reaction gas.   3. The fuel cell separator according to claim 2, wherein each of the plurality of lateral grooves has a cross-sectional area perpendicular to the flow direction of the reaction gas that decreases from upstream to downstream of the flow of the reaction gas.   3. The fuel cell according to claim 2, wherein a length of the plurality of lateral grooves in a direction connecting the conductive flat plate and the membrane electrode assembly decreases from an upstream side to a downstream side of the flow of the reaction gas. Separator.   3. The fuel cell separator according to claim 2, wherein among the plurality of lateral grooves, the lateral groove on the most upstream side in the flow direction of the reaction gas is in contact with the conductive flat plate.   3. The fuel cell separator according to claim 2, wherein the plurality of horizontal grooves have a length in a flow direction of the reactive gas that decreases from an upstream side to a downstream side of the reactive gas flow. 4.   The channel groove includes the partial groove extending obliquely from the conductive plate toward the membrane electrode assembly along the upstream to downstream of the reaction gas flow, and from the upstream to the downstream of the reaction gas flow. 2. The fuel cell separator according to claim 1, wherein the partial grooves extending obliquely from the membrane electrode assembly toward the conductive flat plate are alternately arranged.   9. The fuel cell separator according to claim 8, wherein the plurality of partial grooves have a cross-sectional area perpendicular to the flow direction of the reaction gas that decreases from the upstream to the downstream of the flow of the reaction gas.   The fuel cell according to claim 8, wherein the plurality of partial grooves have a length in a direction connecting the conductive flat plate and the membrane electrode assembly that decreases from an upstream side to a downstream side of the flow of the reactive gas. Separator for use.   9. The fuel cell separator according to claim 8, wherein, among the plurality of partial grooves, a partial groove on the most upstream side in the flow direction of the reaction gas is in contact with the conductive flat plate.   9. The fuel cell separator according to claim 8, wherein the plurality of partial grooves have a length in a flow direction of the reactive gas that decreases from an upstream side to a downstream side of the reactive gas flow.

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