JP5127422B2 - Fuel cell - Google Patents

Description

  The present invention has at least first and second electrolyte / electrode structures in which a pair of electrodes are disposed on both sides of an electrolyte, and includes a first separator, the first electrolyte / electrode structure, a second separator, 2 A plurality of power generation units stacked in the order of the electrolyte / electrode structure and the third separator are provided, and both surfaces of the first electrolyte / electrode structure and both surfaces of the second electrolyte / electrode structure are provided on the power generation surface. A first fuel gas channel, a first oxidant gas channel, a second fuel gas channel, and a second oxidant gas channel are formed with buffer portions at both ends of the channel, and The present invention relates to a fuel cell in which a cooling medium flow path for flowing a cooling medium is formed between the power generation units.

  For example, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure (MEA) in which an anode side electrode and a cathode side electrode are disposed on both sides of an electrolyte membrane made of a polymer ion exchange membrane is sandwiched by separators. A unit cell is provided. This type of fuel cell is normally used as a fuel cell stack by stacking a predetermined number of unit cells.

  In the above fuel cell, in the plane of the separator, a fuel gas channel for flowing fuel gas facing the anode side electrode, and an oxidant gas channel for flowing oxidant gas facing the cathode side electrode And are provided. Further, between the separators, a coolant flow path for allowing a coolant to flow as needed is provided along the surface direction of the separator.

  At that time, by providing a plurality of cooling medium flow paths for each set of unit cells (so-called thinning cooling), the number of the cooling medium flow paths can be reduced, and the fuel cell stack can be shortened and lightened in the stacking direction. Ingenuity to plan is made.

  For example, as shown in FIG. 7, the fuel cell disclosed in Patent Document 1 includes a first separator 1a, a first MEA (electrolyte membrane / electrode structure) 2a, a second separator 1b, a second MEA 2b, and a third separator 1c. Are stacked to constitute the cell unit 3, and a plurality of the cell units 3 are stacked.

  The first and second MEAs 2a and 2b are respectively composed of an ion exchange membrane 4a and an anode electrode 4b and a cathode electrode 4c fixed to both surfaces of the ion exchange membrane 4a. In the first separator 1a, a fuel passage forming member 5a is disposed on a surface of the first MEA 2a facing the anode electrode 4b, and a fuel supply passage 5b is formed in the fuel passage forming member 5a. A cooling water passage forming member 6a is disposed on the other surface of the first separator 1a, and a cooling water supply passage 6b is formed in the cooling water passage forming member 6a.

  The second separator 1b is provided with an oxygen passage forming member 7a on the surface facing the cathode electrode 4c of the first MEA 2a, and an oxygen supply passage 7b is formed in the oxygen passage forming member 7a. A fuel passage forming member 8a is disposed on a surface of the second separator 1b facing the anode electrode 4b of the second MEA 2b, and a fuel supply passage 8b is formed in the fuel passage forming member 8a. An oxygen passage forming member 9a is disposed on the surface of the third separator 1c facing the cathode electrode 4c of the second MEA 2b, and an oxygen supply passage 9b is formed in the oxygen passage forming member 9a.

Japanese Patent Laid-Open No. 10-189011

  In the fuel cell described above, it is necessary to generate power uniformly throughout the fuel cell, and it is required to distribute oxygen and fuel evenly to each cell. Therefore, the fuel supply passages 5b and 8b are set to have the same shape and the same depth, thereby maintaining a uniform pressure loss. Similarly, the oxygen supply passages 7b and 9b are configured to have the same shape and the same depth so as to obtain a uniform pressure loss.

  However, in the so-called thinning cooling structure, the fuel supply passage 5b of the first separator 1a has a front / back relationship with the cooling water supply passage 6b provided on the opposite surface of the first separator 1a. For this reason, on the downstream side of the fuel supply passage 5b, it is in a high humidity state due to reverse diffusion through the electrolyte of generated water during power generation, and condensation occurs when cooled by the cooling water, thereby causing blockage of the flow path. There is a fear. On the other hand, the fuel supply passage 8b of the second separator 1b has a front-back relationship with the oxygen supply passage 7b provided on the opposite surface of the second separator 1b, and is separated from the cooling water supply passage 6b. ing.

  Therefore, in the fuel supply passages 5b and 8b, the dew condensation state on the downstream side of the passage is different. As a result, in particular, the fuel supply passage 5b blocks the fuel gas in a large amount in the fuel supply passage 8b. On the other hand, the fuel supply passage 5b has a problem that the performance is deteriorated due to insufficient stoichiometry.

  The present invention solves this type of problem, and in the thinning-out cooling structure, it is possible to distribute fuel gas evenly with a simple configuration and without dew condensation remaining on the downstream side of the fuel gas flow path. It is an object of the present invention to provide a fuel cell that can improve the power generation performance of the entire stack.

The present invention has at least first and second electrolyte / electrode structures in which a pair of electrodes are disposed on both sides of an electrolyte, and includes a first separator, the first electrolyte / electrode structure, a second separator, 2 A plurality of power generation units stacked in the order of the electrolyte / electrode structure and the third separator are provided, and both surfaces of the first electrolyte / electrode structure and both surfaces of the second electrolyte / electrode structure are provided on the power generation surface. A first fuel gas flow path, a first oxidant gas flow path, a second fuel gas flow path, and a second oxidant gas flow path have an inlet buffer portion and an outlet buffer portion at both ends of the flow path, respectively. The present invention also relates to a fuel cell in which a cooling medium flow path through which a cooling medium flows is formed between the power generation units.

The first separator has a cooling medium flow path formed on one surface, a first fuel gas flow path formed on the other surface, and an outlet buffer portion communicating with the first fuel gas flow path. The second separator has an emboss projecting toward the first electrolyte / electrode structure side and an emboss projecting toward the cooling medium flow path side . The second separator has an oxidant gas flow path formed on one surface and a second surface on the other surface. A fuel gas flow path is formed, and an outlet buffer portion communicating with the second fuel gas flow path has an emboss projecting toward the first electrolyte / electrode structure side and an emboss projecting toward the second electrolyte / electrode structure side. The outlet buffer portion communicating with the first fuel gas flow channel is set to have a larger dimension in the depth direction than the outlet buffer portion communicating with the second fuel gas flow channel.

Further, it is preferable that the buffer portion communicating with the first fuel gas flow channel is set to have a larger dimension in the depth direction than the outlet buffer portion communicating with the cooling medium flow channel.

  Moreover, it is preferable that a 1st separator, a 2nd separator, and a 3rd separator are comprised with metal separators.

  According to the present invention, the buffer portion communicating with the first fuel gas passage close to the cooling medium passage has a larger dimension in the depth direction than the buffer portion communicating with the second fuel gas passage. . For this reason, in the 1st fuel gas channel which is easy to generate dew condensation water, drainage nature improves well and distributes fuel gas flow equally to the 1st fuel gas channel and the 2nd fuel gas channel. can do. As a result, it is possible to prevent a decrease in power generation performance due to channel blockage or insufficient stoichiometry.

  FIG. 1 is an exploded perspective view of a main part of a fuel cell 10 according to an embodiment of the present invention. 2 is a sectional view taken along the line II-II in FIG. 1 of the fuel cell 10, and FIG. 3 is a sectional view taken along the line III-III in FIG.

  The fuel cell 10 is configured by stacking fuel cell units 12 substantially including two unit cells in the direction of arrow A. The fuel cell unit 12 includes a first separator 14, a first electrolyte membrane / electrode structure (electrolyte / electrode structure) 16 a, a second separator 18, a second electrolyte membrane / electrode structure 16 b, and a third separator 20.

  In the present invention, a fuel cell in which fuel cell units including three or more unit cells are stacked may be employed. At that time, a cooling medium flow path 44 described later is formed for every three or more unit cells.

  The first separator 14, the second separator 18, and the third separator 20 are made of, for example, a steel plate, a stainless steel plate, an aluminum plate, a plated steel plate, or a metal plate whose surface is subjected to anticorrosion treatment. . The 1st separator 14, the 2nd separator 18, and the 3rd separator 20 have cross-sectional uneven | corrugated shape by pressing a metal thin plate into a waveform. The first separator 14, the second separator 18, and the third separator 20 may be carbon separators instead of metal separators.

  The first and second electrolyte membrane / electrode structures 16a and 16b include, for example, a solid polymer electrolyte membrane 22 in which a perfluorosulfonic acid thin film is impregnated with water, and an anode side sandwiching the solid polymer electrolyte membrane 22 The electrode 24 and the cathode side electrode 26 are provided.

  The anode side electrode 24 constitutes a so-called stepped MEA having a smaller surface area than the cathode side electrode 26. The solid polymer electrolyte membrane 22, the anode side electrode 24, and the cathode side electrode 26 are each provided with a cutout at the top and bottom of both ends in the direction of arrow B to reduce the surface area.

  The anode side electrode 24 and the cathode side electrode 26 are uniformly coated on the surface of the gas diffusion layer with a gas diffusion layer (not shown) made of carbon paper or the like and porous carbon particles carrying a platinum alloy on the surface. And an electrode catalyst layer (not shown) formed. The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 22.

  An oxidant gas inlet communication hole 30a for supplying an oxidant gas, for example, an oxygen-containing gas, communicates with each other in the direction of the arrow A at the upper edge of the long side direction (arrow C direction) of the fuel cell unit 12. , And a fuel gas inlet communication hole 32a for supplying a fuel gas, for example, a hydrogen-containing gas.

  The fuel cell unit 12 communicates with the lower edge of the long side direction (arrow C direction) in the direction of arrow A to discharge the fuel gas outlet communication hole 32b for discharging the fuel gas and the oxidant gas. For this purpose, an oxidant gas outlet communication hole 30b is provided.

  At one edge of the fuel cell unit 12 in the short side direction (arrow B direction), there is provided a cooling medium inlet communication hole 34a that communicates with each other in the arrow A direction and supplies a cooling medium. A cooling medium outlet communication hole 34b for discharging the cooling medium is provided at the other end edge of the unit 12 in the short side direction.

  A first fuel gas flow path 36 that connects the fuel gas inlet communication hole 32a and the fuel gas outlet communication hole 32b is formed on the surface 14a of the first separator 14 facing the first electrolyte membrane / electrode structure 16a. The first fuel gas channel 36 has a plurality of wave-shaped channel grooves extending in the direction of arrow C, and in the vicinity of the inlet (upper end) and outlet (lower end) of the first fuel gas channel 36, An inlet buffer unit 38 and an outlet buffer unit 40 are provided. The inlet buffer unit 38 and the outlet buffer unit 40 have a plurality of embosses 38a and 40a, respectively.

  The inlet buffer section 38 and the fuel gas inlet communication hole 32a communicate with each other through a plurality of communication paths 42a, and the outlet buffer section 40 and the fuel gas outlet communication hole 32b communicate with each other through a plurality of communication paths 42b. .

  As shown in FIG. 4, a cooling medium flow path 44 that connects the cooling medium inlet communication hole 34 a and the cooling medium outlet communication hole 34 b is formed on the surface 14 b of the first separator 14. In the vicinity of the upper end portion and the lower end portion of the cooling medium flow path 44, buffer portions 46 and 48 that are back surface shapes of the inlet buffer portion 38 and the outlet buffer portion 40 are provided. The buffer units 46 and 48 each have a plurality of embosses 46a and 48a.

  As shown in FIG. 5, the surface 18a of the second separator 18 facing the first electrolyte membrane / electrode structure 16a is connected to the oxidant gas inlet communication hole 30a and the oxidant gas outlet communication hole 30b. An agent gas flow path 50 is formed. The first oxidant gas flow channel 50 has a plurality of wavy flow channel grooves extending in the direction of arrow C. In the vicinity of the inlet (upper end) and outlet (lower end) of the first oxidant gas flow path 50, an inlet buffer portion 52 and an outlet buffer portion 54 are provided. The inlet buffer unit 52 and the outlet buffer unit 54 have a plurality of embosses 52a and 54a, respectively.

  The inlet buffer section 52 and the oxidant gas inlet communication hole 30a communicate with each other through a plurality of communication paths 56a, and the outlet buffer section 54 and the oxidant gas outlet communication hole 30b have a plurality of communication paths 56b. Communicate.

  As shown in FIG. 1, the second fuel gas flow that communicates the fuel gas inlet communication hole 32a and the fuel gas outlet communication hole 32b to the surface 18b of the second separator 18 facing the second electrolyte membrane / electrode structure 16b. A path 58 is formed. The second fuel gas channel 58 has a plurality of wavy channel grooves extending in the direction of arrow C, and in the vicinity of the inlet (upper end) and outlet (lower end) of the second fuel gas channel 58, An inlet buffer unit 60 and an outlet buffer unit 62 are provided.

  The inlet buffer unit 60 and the outlet buffer unit 62 have a plurality of embosses 60a and 62a, respectively. The inlet buffer section 60 and the fuel gas inlet communication hole 32a communicate with each other through a plurality of communication paths 64a, and the outlet buffer section 62 and the fuel gas outlet communication hole 32b communicate with each other through a plurality of communication paths 64b. .

  As shown in FIG. 6, the surface 20a of the third separator 20 facing the second electrolyte membrane / electrode structure 16b is connected to the oxidant gas inlet communication hole 30a and the oxidant gas outlet communication hole 30b. An agent gas channel 66 is formed.

  The second oxidant gas flow channel 66 has a plurality of wavy flow channel grooves extending in the direction of arrow C. In the vicinity of the inlet (upper end) and outlet (lower end) of the second oxidant gas flow channel 66, an inlet buffer portion 68 and an outlet buffer portion 70 are provided. The inlet buffer unit 68 and the outlet buffer unit 70 have a plurality of embosses 68a and 70a, respectively. The inlet buffer section 68 and the oxidant gas inlet communication hole 30a communicate with each other through a plurality of communication paths 72a, and the outlet buffer section 70 and the oxidant gas outlet communication hole 30b have a plurality of communication paths 72b. Communicate.

  As shown in FIG. 1, a cooling medium flow path 44 that connects the cooling medium inlet communication hole 34 a and the cooling medium outlet communication hole 34 b is formed on the surface 20 b of the third separator 20. The cooling medium flow path 44 is formed by overlapping the back surface shapes (wave shapes) of the first fuel gas flow path 36 and the second oxidant gas flow path 66.

  A first seal member 74 is integrally formed on the surfaces 14 a and 14 b of the first separator 14 around the outer peripheral edge of the first separator 14. On the surfaces 18a and 18b of the second separator 18, a second seal member 76 is integrally formed around the outer peripheral edge of the second separator 18, and on the surfaces 20a and 20b of the third separator 20, A third seal member 78 is integrally formed around the outer peripheral edge of the third separator 20. As the first to third seal members 74, 76, 78, for example, EPDM, NBR, fluorine rubber, silicone rubber, fluorosilicone rubber, butyl rubber, natural rubber, styrene rubber, chloroprene or acrylic rubber or the like, cushion A material or packing material is used.

  As shown in FIG. 1, the first separator 14 and the second separator 18 are formed with a first fuel gas passage 36 and a second fuel gas passage 58 so as to face the anode-side electrodes 24, respectively. An outlet buffer unit 40 is formed on the downstream side (lower side) of the first fuel gas channel 36, and an outlet buffer unit 62 is formed on the downstream side (lower side) of the second fuel gas channel 58. The

  As shown in FIG. 3, the depth H <b> 1 of the outlet buffer unit 40 is set to a dimension larger than the depth H <b> 2 of the outlet buffer unit 62. Similarly, the inlet buffer portion 38 communicating with the upstream side (upper side) of the first fuel gas passage 36 is deeper than the inlet buffer portion 60 communicating with the upstream side (upper side) of the second fuel gas passage 58. The dimension in the vertical direction is set large.

  The operation of the fuel cell 10 configured as described above will be described below.

  First, as shown in FIG. 1, an oxidant gas such as an oxygen-containing gas is supplied to the oxidant gas inlet communication hole 30a, and a fuel gas such as a hydrogen-containing gas is supplied to the fuel gas inlet communication hole 32a. Further, a cooling medium such as pure water, ethylene glycol, or oil is supplied to the cooling medium inlet communication hole 34a.

  Therefore, the oxidant gas is introduced from the oxidant gas inlet communication hole 30a into the first oxidant gas channel 50 of the second separator 18 and the second oxidant gas channel 66 of the third separator 20 (FIG. 5). And FIG. 6). The oxidant gas moves in the direction of arrow C (the direction of gravity) along the first oxidant gas flow path 50 and is supplied to the cathode side electrode 26 of the first electrolyte membrane / electrode structure 16a. It moves in the direction of arrow C along the oxidant gas flow channel 66 and is supplied to the cathode electrode 26 of the second electrolyte membrane / electrode structure 16b (see FIG. 1).

  On the other hand, as shown in FIG. 1, the fuel gas is introduced into the first fuel gas channel 36 of the first separator 14 and the second fuel gas channel 58 of the second separator 18 from the fuel gas inlet communication hole 32 a. This fuel gas moves in the direction of arrow C along the first fuel gas flow path 36 and is supplied to the anode side electrode 24 of the first electrolyte membrane / electrode structure 16a and also into the second fuel gas flow path 58. Along the direction of arrow C and supplied to the anode electrode 24 of the second electrolyte membrane / electrode structure 16b.

  Therefore, in the first and second electrolyte membrane / electrode structures 16a and 16b, the oxidant gas supplied to the cathode side electrode 26 and the fuel gas supplied to the anode side electrode 24 are electrically generated in the electrode catalyst layer. It is consumed by chemical reaction to generate electricity.

  Next, the oxidant gas consumed by being supplied to the cathode side electrode 26 is discharged in the direction of arrow A along the oxidant gas outlet communication hole 30b. Similarly, the fuel gas supplied to and consumed by the anode side electrode 24 is discharged in the direction of arrow A along the fuel gas outlet communication hole 32b.

  Further, the cooling medium supplied to the cooling medium inlet communication hole 34a is introduced into the cooling medium flow path 44 formed between the first separator 14 and the third separator 20, as shown in FIG. Circulate in the direction of arrow B. The cooling medium cools the first and second electrolyte membrane / electrode structures 16a and 16b, and then is discharged into the cooling medium outlet communication hole 34b.

  In this case, the first separator 14 has a cooling medium passage 44 formed on the surface 14b, and a first fuel gas passage 36 formed on the surface 14a side. For this reason, the generated water that has diffused back into the first fuel gas channel 36 via the solid polymer electrolyte membrane 22 is likely to be condensed by the cooling medium supplied to the cooling medium channel 44.

  On the other hand, the second separator 18 has a first oxidant gas flow channel 50 formed on the surface 18a side, and a second fuel gas flow channel 58 formed on the surface 18b side. The second fuel gas channel 58 is further adjacent to the second oxidant gas channel 66 of the third separator 20. Therefore, the second fuel gas flow path 58 is relatively separated from the cooling medium flow path 44 and is likely to have a higher temperature than the first fuel gas flow path 36.

  Therefore, in the present embodiment, the depth H1 of the outlet buffer portion 40 communicating with the downstream side of the first fuel gas flow channel 36 is the depth of the outlet buffer portion 62 communicating with the downstream side of the second fuel gas flow channel 58. The dimension is set to be larger than H2 (see FIG. 3).

  That is, the depth H1 of the outlet buffer portion 40 of the first fuel gas passage 36 where condensation water is likely to be generated is larger than the depth H2 of the outlet buffer portion 62 of the relatively high temperature second fuel gas passage 58. By setting to, the drainage performance of the outlet buffer section 40 and the outlet buffer section 62 can be set to be equal, and the drainage performance can be improved satisfactorily.

  Here, if the depth of the outlet buffer section 40 and the depth of the outlet buffer section 62 are different, the difference in pressure loss between the first fuel gas flow path 36 and the second fuel gas flow path 58 becomes significant. A large difference occurs in the distribution flow rate. For this reason, the value of pressure loss will change remarkably only by changing the depth of the outlet buffer part 40 and the outlet buffer part 62 a little.

  As a result, the fuel gas flow rates in the first fuel gas flow channel 36 and the second fuel gas flow channel 58 are evenly distributed and supplied, so that it is possible to prevent a decrease in power generation performance due to flow channel blockage or insufficient stoichiometry. The effect that it becomes possible is obtained.

  Further, the inlet buffer portion 38 communicating with the first fuel gas passage 36 is set to have a larger dimension in the depth direction than the inlet buffer portion 60 communicating with the second fuel gas passage 58. Therefore, the flowability of moisture introduced from the fuel gas inlet communication hole 32a into the inlet buffer portion 38 is improved, and the flow rate of the fuel gas flowing through the first fuel gas flow path 36 is favorably maintained by preventing the retention of condensed water. be able to.

  In the first oxidant gas flow channel 50 and the second oxidant gas flow channel 66, the sizes in the depth direction of the outlet buffer portions 54 and 70 are set to be the same. This is because, in the first oxidant gas flow channel 50 and the second oxidant gas flow channel 66, the pressure difference between the inlet side and the outlet side is large, so that the flow channel blockage hardly occurs and there is no risk of insufficient stoichiometry.

It is a principal part disassembled perspective explanatory view of the fuel cell concerning the embodiment of the present invention. FIG. 2 is a sectional view of the fuel cell taken along line II-II in FIG. 1. FIG. 3 is a cross-sectional explanatory view of the fuel cell taken along line III-III in FIG. 1. It is front explanatory drawing of the 1st separator which comprises the said fuel cell. It is front explanatory drawing of the 2nd separator which comprises the said fuel cell. It is front explanatory drawing of the 3rd separator which comprises the said fuel cell. 2 is an explanatory diagram of a fuel cell of Patent Document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 12 ... Fuel cell unit 14, 18, 20 ... Separator 16a, 16b ... Electrolyte membrane electrode structure 22 ... Solid polymer electrolyte membrane 24 ... Anode side electrode 26 ... Cathode side electrode 30a ... Oxidant gas inlet communication Hole 30b ... Oxidant gas outlet communication hole 32a ... Fuel gas inlet communication hole 32b ... Fuel gas outlet communication hole 34a ... Cooling medium inlet communication hole 34b ... Cooling medium outlet communication hole 36, 58 ... Fuel gas flow path 38, 52, 60 , 68... Inlet buffer section 40, 54, 62, 70... Outlet buffer section 44. Cooling medium flow path 46, 48. Buffer section 50, 66.

Claims (3)

At least first and second electrolyte / electrode structures each having a pair of electrodes disposed on both sides of the electrolyte, and a first separator, the first electrolyte / electrode structure, a second separator, and the second electrolyte / electrode A plurality of power generation units stacked in the order of the structure and the third separator are provided, and the first electrolyte / electrode structure and both surfaces of the second electrolyte / electrode structure are arranged along the power generation surface along the first power generation surface. The fuel gas flow channel, the first oxidant gas flow channel, the second fuel gas flow channel, and the second oxidant gas flow channel are formed with an inlet buffer portion and an outlet buffer portion at both ends of the flow channel, respectively. A fuel cell in which a cooling medium flow path for flowing a cooling medium is formed between the power generation units,
The first separator has the cooling medium flow path formed on one surface, the first fuel gas flow path formed on the other surface, and the outlet communicating with the first fuel gas flow path. The buffer unit has an emboss projecting to the first electrolyte / electrode structure side and an emboss projecting to the cooling medium flow path side,
The second separator has the oxidant gas flow path formed on one side and the second fuel gas flow path formed on the other side, and the outlet buffer unit communicating with the second fuel gas flow path Has an emboss projecting to the first electrolyte / electrode structure side and an emboss projecting to the second electrolyte / electrode structure side,
The fuel cell according to claim 1, wherein the outlet buffer portion communicating with the first fuel gas flow channel is set to have a larger dimension in the depth direction than the outlet buffer portion communicating with the second fuel gas flow channel. 2. The fuel cell according to claim 1, wherein the outlet buffer portion communicating with the first fuel gas passage is set to have a larger dimension in the depth direction than the outlet buffer portion communicating with the cooling medium passage. A fuel cell. 3. The fuel cell according to claim 1, wherein the first separator, the second separator, and the third separator are made of a metal separator.

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