JP2009004230A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the size of a buffer part as much as possible, and to secure desired power generation performance by a lightweight and compact structure. <P>SOLUTION: This fuel cell 10 includes a first metal separator 18 and a second metal separator 20 sandwiching an electrode structure 16 having an electrolyte membrane. The first metal separator 18 has fuel gas passages 34, a fuel gas supply communication hole 24a, a fuel gas exhaust communication hole 24b, and an entrance buffer part 36a and an exit buffer part 36b making the fuel gas passages 34, the fuel gas supply communication hole 24a and the fuel gas exhaust communication hole 24b communicate with one another. The average pressure loss of the entrance buffer part 36a and the exit buffer part 36b is set not larger than the average pressure loss of the fuel gas passage 34. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the present invention, an electrolyte membrane / electrode structure provided with a pair of electrodes on both sides of an electrolyte membrane and a separator are laminated, and a reaction gas flow path for supplying a reaction gas is formed along the electrode surface. The present invention relates to a fuel cell in which a reaction gas communication hole for flowing gas in a stacking direction is formed.

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

  In the fuel cell described above, a fuel gas flow path (hereinafter also referred to as a reaction gas flow path) for flowing a fuel gas to the anode side electrode and an oxidation for flowing an oxidant gas to the cathode side electrode in the plane of the separator. An agent gas channel (hereinafter also referred to as a reaction gas channel) is provided. Furthermore, a cooling medium flow path for flowing a cooling medium is provided along the surface direction of the separator for each power generation cell or for each of the plurality of power generation cells.

  This type of fuel cell may constitute a so-called internal manifold in which a reaction gas communication hole and a cooling medium communication hole penetrating in the stacking direction of the separator are provided inside the fuel cell. At this time, generally, a buffer portion is provided between the reaction gas communication hole and the reaction gas channel so as to uniformly distribute and supply the reaction gas to the reaction gas channel.

  For example, in Patent Document 1, as shown in FIG. 6, a sheet metal element 1 is provided, and an oxidant gas inlet manifold 2 a, a refrigerant inlet manifold 3 a, and a fuel are disposed at one end edge in the longitudinal direction of the sheet metal element 1. A gas inlet manifold 4a is formed through. An oxidant gas outlet manifold 2b, a refrigerant outlet manifold 3b, and a fuel gas outlet manifold 4b are formed through the other end of the sheet metal element 1 in the longitudinal direction.

  A corrugated flow path 5 is formed on the fuel gas supply surface side of the sheet metal element 1, and an inlet buffer section 6a and an outlet buffer section 6b made of dimples are provided at both ends of the corrugated flow path 5, respectively. Yes. The corrugated flow path 5 has a plurality of linear flow path grooves 5a.

Japanese translation of PCT publication No. 2002-530836

  In the above-mentioned Patent Document 1, the flow of the fuel gas may change due to variations in the dimensions of the sheet metal element 1 itself, or the water generated during power generation stays in the inlet buffer 6a and / or the outlet buffer 6b. is there. For this reason, a difference occurs in the flow rate of the fuel gas flowing through each flow channel groove 5 a, and the fuel gas may not be uniformly distributed over the entire surface of the corrugated flow channel 5. As a result, the power generation performance is lowered, and there is a problem that, for example, deterioration of the solid polymer electrolyte membrane is caused.

  Accordingly, it is conceivable to set the dimensions of the inlet buffer 6a and the outlet buffer 6b to be larger than necessary. However, the inlet buffer portion 6a and the outlet buffer portion 6b are portions that do not contribute to power generation, and there is a problem that the entire sheet metal element 1 becomes considerably large and heavy in order to secure a desired power generation region.

  The present invention solves this type of problem, and provides a fuel cell capable of reducing the size of the buffer portion as much as possible and ensuring desired power generation performance with a lightweight and compact configuration. The purpose is to do.

  In the present invention, an electrolyte membrane / electrode structure provided with a pair of electrodes on both sides of an electrolyte membrane and a separator are laminated, and a reaction gas flow path for supplying a reaction gas is formed along the electrode surface. The present invention relates to a fuel cell in which a reaction gas communication hole for flowing gas in a stacking direction is formed.

  The separator includes a substantially triangular inlet buffer portion located on the inlet side of the reaction gas flow path, a substantially triangular outlet buffer portion located on the outlet side of the reaction gas flow path, and the inlet The average pressure loss of the buffer part and the outlet buffer part is set to be equal to or lower than the average pressure loss of the reaction gas flow path.

  Moreover, it is preferable that an exit buffer part makes point symmetry with an entrance buffer part.

  Furthermore, it is preferable that the reaction gas channel includes a plurality of channel grooves that have a straight line shape or a wave shape and extend in one direction.

  Furthermore, the inlet buffer section and the outlet buffer section are arranged such that the reaction gas flow path side is the base and the vertex is located away from the base, and the angle formed between the bottom and the long side ridge line connecting the top and the base is It is preferable that the shape is set based on this.

  According to the present invention, since the average pressure loss of the inlet buffer portion and the outlet buffer portion is set to be equal to or lower than the average pressure loss of the reaction gas flow channel, the flow rate of the reaction gas flowing through the reaction gas flow channel can be equalized. . Accordingly, the reaction gas can be uniformly supplied from the reaction gas communication hole to the entire surface of the reaction gas channel with a simple configuration, and desired power generation performance can be ensured.

  In addition, the dimensions of the inlet buffer portion and the outlet buffer portion can be reduced as much as possible. Therefore, the entire fuel cell can be configured to be lightweight and compact, and desired power generation performance can be ensured.

  FIG. 1 is an exploded perspective view of a fuel cell 10 according to an embodiment of the present invention, and FIG. 2 is a sectional view of the fuel cell 10 taken along the line II-II in FIG. The fuel cell 10 is preferably used as a vehicle fuel cell.

  As shown in FIG. 1, in the fuel cell 10, an electrolyte membrane / electrode structure 16 is sandwiched between a first metal separator 18 on the anode side and a second metal separator 20 on the cathode side. The first and second metal separators 18 and 20 have a concavo-convex shape by pressing a metal thin plate into a wave shape.

  The first and second metal separators 18 and 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. Moreover, instead of the first and second metal separators 18 and 20, for example, a carbon separator may be adopted.

  An oxidant gas supply 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 (the direction of arrow C in FIG. 1) of the fuel cell 10. A communication hole (reaction gas communication hole) 22a and a fuel gas supply communication hole (reaction gas communication hole) 24a for supplying a fuel gas, for example, a hydrogen-containing gas, are provided.

  The lower end edge of the long side direction of the fuel cell 10 communicates with each other in the direction of the arrow A, and a fuel gas discharge communication hole (reaction gas communication hole) 24b for discharging the fuel gas and an oxidant gas are discharged. An oxidant gas discharge communication hole (reaction gas communication hole) 22b is provided. The oxidant gas supply communication hole 22a and the oxidant gas discharge communication hole 22b are provided so as to correspond to point-symmetrical positions, and the fuel gas supply communication hole 24a and the fuel gas discharge communication hole 24b are similarly point symmetric. Are provided corresponding to the positions.

  At one edge of the fuel cell 10 in the short side direction (arrow B direction), there is provided a cooling medium supply communication hole 26a that communicates with each other in the arrow A direction and supplies a cooling medium. A cooling medium discharge communication hole 26b for discharging the cooling medium is provided at the other end edge.

  The electrolyte membrane / electrode structure 16 includes, for example, a solid polymer electrolyte membrane 28 in which a perfluorosulfonic acid thin film is impregnated with water, and an anode side electrode 30 and a cathode side electrode 32 that sandwich the solid polymer electrolyte membrane 28. With. The anode side electrode 30 has a smaller surface area than the cathode side electrode 32.

  The anode-side electrode 30 and the cathode-side electrode 32 are uniformly coated 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 thereof. An electrode catalyst layer (not shown). The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 28.

  A fuel gas flow path 34 that connects the fuel gas supply communication hole 24 a and the fuel gas discharge communication hole 24 b is formed on the surface 18 a of the first metal separator 18 facing the electrolyte membrane / electrode structure 16. As shown in FIG. 3, the fuel gas channel 34 has a plurality of wave-like channel grooves 34a extending in the direction of arrow C, and is located at the upper and lower ends of the wave-like channel groove 34a in the direction of arrow C. An inlet buffer part 36a and an outlet buffer part 36b are provided.

  The inlet buffer portion 36a and the outlet buffer portion 36b have a substantially triangular shape that is point-symmetric with each other, and are provided with a plurality of embosses 38a and 38b. The apexes of the triangles of the inlet buffer portion 36 a and the outlet buffer portion 36 b are disposed within the width range of the fuel gas flow path 34. As will be described later, the average pressure loss of the inlet buffer portion 36a and the outlet buffer portion 36b is set to be equal to or lower than the average pressure loss of the fuel gas passage 34.

  More specifically, the average pressure loss of the inlet buffer portion 36a and the average pressure loss of the outlet buffer portion 36b are each ½ or more of the average pressure loss of the fuel gas flow channel 34, in other words, the fuel gas flow channel 34. The average pressure loss is set to not more than twice the average pressure loss of the inlet buffer portion 36a or the average pressure loss of the outlet buffer portion 36b. This is because if the average pressure loss of the fuel gas passage 34 exceeds twice the average pressure loss of the inlet buffer portion 36a, the flow distribution effect does not change, but the area occupied by the inlet buffer portion 36a increases.

  The surface 18a of the first metal separator 18 has a plurality of receiving portions 41a for forming a communication path that communicates the fuel gas supply communication hole 24a and the inlet buffer portion 36a, a fuel gas discharge communication hole 24b, and an outlet buffer portion 36b. And a plurality of receiving portions 41b for forming communication passages communicating with each other. A plurality of supply hole portions 42a and discharge hole portions 42b are formed in the vicinity of the receiving portions 41a and 41b, respectively. The supply hole portion 42a communicates with the fuel gas supply communication hole 24a on the surface 18b side, while the discharge hole portion 42b similarly communicates with the fuel gas discharge communication hole 24b on the surface 18b side.

  As shown in FIG. 4, an oxidant gas supply communication hole 22a and an oxidant gas discharge communication hole 22b are communicated with the surface 20a of the second metal separator 20 facing the electrolyte membrane / electrode structure 16 through an oxidant gas. A flow path 44 is formed. The oxidant gas channel 44 has a plurality of wave-like channel grooves 44a extending in the direction of the arrow C, and is located at the upper and lower ends of the wave-like channel groove 44a in the direction of the arrow C. A buffer unit 46b is provided.

  The inlet buffer part 46a and the outlet buffer part 46b have substantially triangular shapes that are point-symmetric with each other, and are provided with embosses 48a and 48b. As will be described later, the average pressure loss of the inlet buffer portion 46 a and the outlet buffer portion 46 b is set to be equal to or lower than the average pressure loss of the oxidant gas channel 44.

  More specifically, the average pressure loss of the inlet buffer portion 46a and the average pressure loss of the outlet buffer portion 46b are each ½ or more of the average pressure loss of the oxidant gas flow channel 44, in other words, the oxidant gas flow channel. The average pressure loss of 44 is set to not more than twice the average pressure loss of the inlet buffer portion 46a or the average pressure loss of the outlet buffer portion 46b.

  The surface 20a communicates with a plurality of receiving portions 51a for communicating with the oxidant gas supply communication hole 22a and the inlet buffer portion 46a, and with the oxidant gas discharge communication hole 22b and the outlet buffer portion 46b. A plurality of receiving portions 51b for forming a passage are provided.

  As shown in FIG. 1, the cooling medium communicating with the cooling medium supply communication hole 26 a and the cooling medium discharge communication hole 26 b between the surface 20 b of the second metal separator 20 and the surface 18 b of the first metal separator 18. A flow path 54 is formed. The cooling medium channel 54 is formed to extend in the direction of arrow B by overlapping the back surface shape of the fuel gas channel 34 and the back surface shape of the oxidant gas channel 44.

  A first seal member 56 is integrally formed on the surfaces 18 a and 18 b of the first metal separator 18 around the outer peripheral edge of the first metal separator 18. A second seal member 58 is integrally formed on the surfaces 20 a and 20 b of the second metal separator 20 so as to go around the outer peripheral edge of the second metal separator 20. As the first and second sealing members 56, 58, for example, EPDM, NBR, fluorine rubber, silicone rubber, fluorosilicone rubber, butyl rubber, natural rubber, styrene rubber, chloroprene or acrylic rubber or the like, cushion material, Alternatively, a packing material is used.

  As shown in FIGS. 1 and 3, the first seal member 56 includes a seal portion 56a provided on the surface 18a side so as to surround the fuel gas flow path 34, and a seal portion 56b provided outside the seal portion 56a. And have. The seal portion 56a constitutes a convex seal that goes around the fuel gas flow path 34, the inlet buffer portion 36a, the outlet buffer portion 36b, the supply hole portion 42a, and the discharge hole portion 42b.

  As shown in FIG. 4, the second seal member 58 is formed on the surface 20a side of the second metal separator 20 with the oxidant gas flow path 44, the inlet buffer part 46a, the outlet buffer part 46b, the oxidant gas supply communication hole 22a, and the oxidation gas. A seal portion 58a is formed so as to surround the agent gas discharge communication hole 22b.

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

  First, as shown in FIG. 1, in the fuel cell 10, an oxidant gas such as an oxygen-containing gas is supplied to the oxidant gas supply communication hole 22a, and a fuel gas such as a hydrogen-containing gas is supplied to the fuel gas supply communication hole 24a. Is supplied. Further, a coolant such as pure water or ethylene glycol is supplied to the coolant supply passage 26a.

  The oxidant gas is introduced into the oxidant gas flow path 44 of the second metal separator 20 from the oxidant gas supply communication hole 22 a and moves along the cathode side electrode 32 of the electrolyte membrane / electrode structure 16.

  At that time, as shown in FIG. 4, on the surface 20a of the second metal separator 20, the oxidant gas flowing through the oxidant gas supply communication hole 22a is supplied to the inlet buffer part 46a through the plurality of receiving parts 51a. The The oxidant gas supplied to the inlet buffer 46a is dispersed in the direction of arrow B and flows vertically downward along the plurality of undulating channel grooves 44a constituting the oxidant gas channel 44. It is supplied to the cathode side electrode 32 of the membrane / electrode structure 16.

  On the other hand, as shown in FIGS. 1 and 3, the fuel gas is supplied to the surface 18 a side through the plurality of supply holes 42 a from the fuel gas supply communication holes 24 a on the surface 18 b of the first metal separator 18. The fuel gas is introduced into the inlet buffer portion 36a through the receiving portion 41a. The fuel gas dispersed in the direction of the arrow B by the inlet buffer portion 36a moves vertically downward along the plurality of wave-like channel grooves 34a constituting the fuel gas channel 34, and the anode of the electrolyte membrane / electrode structure 16 It is supplied to the side electrode 30.

  Therefore, in each electrolyte membrane / electrode structure 16, the oxidant gas supplied to the cathode side electrode 32 and the fuel gas supplied to the anode side electrode 30 are consumed by an electrochemical reaction in the electrode catalyst layer, Power generation is performed (see FIG. 2).

  Next, the oxidant gas consumed by being supplied to the cathode side electrode 32 is sent to an outlet buffer part 46 b communicating with the lower part of the oxidant gas flow path 44 as shown in FIG. 4. Further, the oxidant gas is discharged from the outlet buffer part 46b to the oxidant gas discharge communication hole 22b along the space between the plurality of receiving parts 51b.

  Similarly, as shown in FIGS. 1 and 3, the fuel gas that is consumed by being supplied to the anode electrode 30 is sent to an outlet buffer portion 36 b that communicates with the lower portion of the fuel gas flow path 34, and then a plurality of fuel gases are supplied. It flows between the receiving parts 41b. The fuel gas passes through the plurality of discharge holes 42b and moves toward the surface 18b, and is discharged to the fuel gas discharge communication hole 24b.

  The cooling medium flows in the direction of arrow B (horizontal direction) after being introduced into the cooling medium flow path 54 between the first and second metal separators 18 and 20 from the cooling medium supply communication hole 26a. The cooling medium is discharged from the cooling medium discharge communication hole 26b after the electrolyte membrane / electrode structure 16 is cooled.

  In this case, in this embodiment, for example, the average pressure loss of the inlet buffer portion 36 a and the outlet buffer portion 36 b is set to be equal to or lower than the average pressure loss of the fuel gas flow channel 34. Specifically, the inlet buffer portion 36a and the outlet buffer portion 36b have substantially triangular shapes that are point-symmetric with respect to each other, and assuming that the flow rate of the fuel gas flowing through the fuel gas flow path 34 is equal, The fuel gas flow in the part 36a and the outlet buffer part 36b can be regarded as substantially equivalent to the fuel gas flow field 60 shown in FIG.

  The fuel gas flow field 60 has a parallelogram shape in which each side (ridge line) of the inlet buffer portion 36 a and the outlet buffer portion 36 b on the fuel gas flow path 34 side is joined as a common base 62. In the fuel gas flow field 60, each vertex 64a, 64b spaced from the bottom side 62 of the inlet buffer part 36a and the outlet buffer part 36b is set at one diagonal position, and the bottom side 62 and the vertexes 64a, 64b are connected to each other. Long side ridge lines 66a and 66b to be connected and short side ridge lines 68a and 68b are provided.

  Here, in FIG. 5, the diagonal length W along the bottom side 62 of the fuel gas flow field 60, the buffer portion depth d, the height h from the bottom side 62 to the vertices 64a and 64b, the ridge lines 66a and 66b and the bottom side. An angle θ formed by 62, a division constant t (0 <t <1) of the diagonal length W, a fuel gas flow rate Q, and a viscosity coefficient μ. In practice, the diagonal length W is preferably set to 50 mm to 300 mm, the buffer depth d is set to 0.1 mm to 1.0 mm, the height h is set to 5 mm to 40 mm, and the angle θ is set to 5 ° to 30 °.

Therefore, the average flow velocity u of the fuel gas flow field 60 is obtained from u = Q / Wdsinθ. Further, since d << W, h, the average pressure loss ΔP on one side of the fuel gas flow field 60 can be calculated as a two-dimensional Poiseuille flow.
ΔP = 1/2 × 12 μ / d ² × h / sin θ × u = 6 μh Q / Wd ³ sin ² θ is obtained.

Next, assuming that the average pressure loss ΔP is smaller than the average pressure loss ΔP ₀ of the fuel gas flow path 34, sin ² θ ≧ 6 μhQ / Wd ³ ΔP ₀ is satisfied. Further, by substituting h = tWtanθ, sin 2θ ≧ 12 tμQ / ΔP ₀ d ³ is obtained.

  Accordingly, the shapes of the inlet buffer unit 36a and the outlet buffer unit 36b are set based on t and θ satisfying the above formula.

  Thereby, in this embodiment, the flow volume of the fuel gas which flows through the fuel gas flow path 34 can be equalized by setting the shape of the inlet buffer part 36a and the outlet buffer part 36b. For this reason, it becomes possible to supply fuel gas uniformly from the fuel gas supply communication hole 24a to the entire surface of the fuel gas flow path 34 with a simple configuration, and an effect that desired power generation performance can be secured is obtained. .

  Moreover, the dimensions of the inlet buffer portion 36a and the outlet buffer portion 36b can be reduced as much as possible. Accordingly, the entire fuel cell 10 can be configured to be lightweight and compact, and desired power generation performance can be ensured.

  In the present embodiment, the fuel gas flow path 34 and the oxidant gas flow path 44 are configured by a plurality of wave-shaped flow path grooves 34a, 44a. However, the present invention is not limited to this, and a plurality of linear flow paths. Even if it is constituted by a road groove, the same effect can be obtained.

1 is an exploded perspective view of a fuel cell according to an embodiment of the present invention. FIG. 2 is a sectional view of the fuel cell taken along line II-II in FIG. 1. It is a front view of the 1st metal separator which comprises the said fuel cell. It is a front view of the 2nd metal separator which comprises the said fuel cell. It is explanatory drawing of a fuel gas flow field. It is explanatory drawing of the sheet metal element of patent document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 16 ... Electrolyte membrane electrode assembly 18, 20 ... Metal separator 22a ... Oxidant gas supply communication hole 22b ... Oxidant gas discharge communication hole 24a ... Fuel gas supply communication hole 24b ... Fuel gas discharge communication hole 26a ... Cooling medium supply communication hole 26b ... Cooling medium discharge communication hole 28 ... Solid polymer electrolyte membrane 30 ... Anode side electrode 32 ... Cathode side electrode 34 ... Fuel gas flow path 34a, 44a ... Wave-shaped flow path grooves 36a, 46a ... Inlet buffer section 36b, 46b ... outlet buffer portion 42a ... supply hole portion 42b ... discharge hole portion 44 ... oxidant gas flow channel 54 ... cooling medium flow channel 60 ... fuel gas flow field 62 ... bottom 64a, 64b ... apex 66a, 66b, 68a, 68b ... Ridge line

Claims (4)

An electrolyte membrane / electrode structure provided with a pair of electrodes on both sides of the electrolyte membrane and a separator are laminated to form a reaction gas flow path for supplying a reaction gas along the electrode surface, and the reaction gas is arranged in the lamination direction. A fuel cell in which a reaction gas communication hole to be circulated is formed,
The separator is a substantially triangular inlet buffer portion located on the inlet side of the reaction gas flow path,
Located on the outlet side of the reaction gas flow path, a substantially triangular outlet buffer section;
With
The fuel cell according to claim 1, wherein an average pressure loss of the inlet buffer portion and the outlet buffer portion is set to be equal to or lower than an average pressure loss of the reaction gas flow path.   2. The fuel cell according to claim 1, wherein the outlet buffer portion is point-symmetric with the inlet buffer portion.   3. The fuel cell according to claim 1, wherein the reaction gas flow path includes a plurality of flow path grooves having a straight shape or a wave shape and extending in one direction. 4.   The fuel cell according to any one of claims 1 to 3, wherein the inlet buffer portion and the outlet buffer portion are located at a vertex position separated from the bottom side with the reactive gas flow channel side as a bottom side, the bottom side, and the bottom side. A fuel cell, wherein a shape is set based on an angle formed between a ridge line on a long side connecting apexes and the bottom side.

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