Fuel cell separator

Abstract

A separator for a fuel cell that can suppress a decrease in the power generation efficiency of a fuel cell is provided. [Solution] A separator (14) of a fuel cell includes a plate-shaped main body (15) on which multiple ribs (19) extending in parallel are formed. The main body (15) can be disposed on both sides of a membrane electrode / gas diffusion layer assembly (13) in the thickness direction. The ribs (19) protrude from the main body (15) to contact the gas diffusion layer of the membrane electrode / gas diffusion layer assembly (13). Flow paths (18) for flowing gas supplied to and discharged from the membrane electrode / gas diffusion layer assembly (13) are formed between the multiple ribs (19) and between the ribs (19) and the gas diffusion layer. The ribs (19) include dividing portions (24) that divide the multiple parallel flow paths (18) between upstream and downstream in the gas flow direction of the flow paths (18). The positions of the dividing portions (24) in the gas flow direction of the flow paths (18) are not the same for adjacent flow paths (18) in the arrangement direction of the parallel ribs (19).

Description

[Technical Field]

[0001] The present disclosure relates to a separator for a fuel cell. [Background technology]

[0002] A fuel cell stack is formed by stacking fuel cell units in the thickness direction. A fuel cell unit is formed by sandwiching a membrane electrode gas diffusion layer assembly between plate-shaped separators on both sides in the thickness direction. As shown in Patent Document 1, the separator of the fuel cell has a main body on which a plurality of ribs extending in parallel are formed. The ribs protrude from the main body and come into contact with the gas diffusion layer of the membrane electrode gas diffusion layer assembly. Flow paths are formed between the plurality of ribs and between the gas diffusion layers to allow gas to flow to and from the membrane electrode gas diffusion layer assembly.

[0003] A fuel gas such as hydrogen flows through the flow path between the separator located on the anode side of the thickness direction of the membrane electrode gas diffusion layer assembly and the anode side gas diffusion layer. An oxidizing gas such as air flows through the flow path between the separator located on the cathode side of the thickness direction of the membrane electrode gas diffusion layer assembly and the cathode side gas diffusion layer. Power generation is performed in the fuel cell based on the reaction between the fuel gas and the oxidizing gas in the membrane electrode gas diffusion layer assembly. The gas diffusion layer of the membrane electrode gas diffusion layer assembly diffuses the gas supplied from the flow path to the membrane electrode gas diffusion layer assembly, thereby ensuring a uniform supply of gas to the membrane electrode gas diffusion layer assembly. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-3531 Summary of the Invention [Problem to be solved by the invention]

[0005] In the fuel cell, the gas in the flow passages flows along the ribs, making it difficult for the gas to enter the gas diffusion layer of the membrane electrode / gas diffusion layer assembly from the flow passages. As a result, the gas supplied to the membrane electrode / gas diffusion layer assembly from the flow passages is difficult to diffuse in the gas diffusion layer, which may reduce the power generation efficiency of the fuel cell. [Means for solving the problem]

[0006] The means for solving the above problems and their effects will be described below. A fuel cell separator that solves the above problem includes a plate-shaped main body on which a plurality of ribs are formed, the main body being capable of being disposed on both sides of a membrane electrode / gas diffusion layer assembly in the thickness direction. The ribs protrude from the main body and come into contact with the gas diffusion layer of the membrane electrode / gas diffusion layer assembly. Flow paths for supplying and discharging gas to and from the membrane electrode / gas diffusion layer assembly are formed between the plurality of ribs and between the main body and the gas diffusion layer. The ribs include dividing portions that divide the plurality of flow paths extending in parallel between upstream and downstream in the gas flow direction of the flow paths. The positions of the dividing portions in the gas flow direction of the flow paths are not the same for adjacent flow paths in the direction in which the parallel ribs are arranged.

[0007] According to the above configuration, the flow path for supplying and discharging gas to and from the membrane electrode / gas diffusion layer assembly is divided into an upstream portion and a downstream portion in the gas flow direction in the flow path by the dividing portion of the rib. Therefore, when the gas flowing downstream in the flow path reaches the point where the flow path is divided by the dividing portion, i.e., the downstream end of the flow path, it enters the gas diffusion layer from the downstream end. Furthermore, the gas that has entered the gas diffusion layer spreads radially from the downstream end of the flow path before entering the adjacent flow path. This gas flow in the gas diffusion layer promotes gas diffusion in the gas diffusion layer. As a result, it is possible to prevent the gas supplied from the flow path from the membrane electrode / gas diffusion layer assembly from diffusing in the gas diffusion layer. Therefore, it is possible to prevent a decrease in the power generation efficiency of the fuel cell, which would be caused by the difficulty in gas diffusion in the gas diffusion layer.

[0008] However, if the positions of the dividing portions in the gas flow direction of the flow paths are the same for adjacent flow paths, there is a risk that gases that enter the gas diffusion layer from the downstream ends of the adjacent flow paths may interfere with each other as they spread radially from the downstream ends. Such gas interference makes it difficult for gas to diffuse in the gas diffusion layer. However, the positions of the dividing portions in the gas flow direction of the flow paths are designed not to be the same for adjacent flow paths. This prevents gases that enter the gas diffusion layer from the downstream ends of adjacent flow paths from interfering with each other as they spread radially from the downstream ends. As a result, it is possible to prevent the gases from interfering with each other and making it difficult for gases to diffuse in the gas diffusion layer. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is an exploded perspective view showing a fuel cell. [Figure 2] 2 is a cross-sectional view showing a cell stack in which the fuel cell units of FIG. 1 are stacked. [Figure 3] 2 is a schematic diagram showing ribs and flow channels of a separator in the fuel cell of FIG. 1. FIG. [Figure 4] 2 is a schematic diagram showing contact points between adjacent fuel cells when the fuel cells of FIG. 1 are stacked. FIG. [Figure 5] 10 is a schematic diagram showing another example of ribs and flow channels of a separator in a fuel cell. FIG. [Figure 6] 10 is a schematic diagram showing another example of ribs and flow channels of a separator in a fuel cell. FIG. [Figure 7] 10 is a schematic diagram showing another example of ribs and flow channels of a separator in a fuel cell. FIG. [Figure 8] 10 is a schematic diagram showing another example of ribs and flow channels of a separator in a fuel cell. FIG. [Figure 9] 10 is a schematic diagram showing another example of ribs and flow channels of a separator in a fuel cell. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of a separator for a fuel cell will be described below with reference to FIGS. 1 shows a fuel cell 11 for forming a fuel cell stack. The fuel cell 11 includes a resin plate 12, a membrane electrode gas diffusion layer assembly 13, and a separator 14. The resin plate 12 is formed in a rectangular frame shape. The outer edge of the membrane electrode gas diffusion layer assembly 13 is joined to the resin plate 12. The resin plate 12 and the membrane electrode gas diffusion layer assembly 13 are sandwiched between separators 14 arranged on both sides in the thickness direction.

[0011] A fuel cell stack is formed by stacking the above-described fuel cell units 11 in the thickness direction. A plurality of holes 16 are formed in the resin plate 12 and separator 14 of the fuel cell unit 11. Of the plurality of holes 16, three are located at one end of the long side of the fuel cell unit 11, and the other three are located at the other end of the long side of the fuel cell unit 11. The plurality of holes 16 are arranged in pairs, with one hole on one side of the long side of the fuel cell unit 11 and one hole on the other side. Each pair of holes 16 is used to pass fluids such as fuel gas such as hydrogen, oxidizing gas such as air, and refrigerant such as cooling water.

[0012] The separator 14 has a main body 15 formed in the shape of a rectangular plate from a metal such as stainless steel, titanium, or aluminum. A plurality of ribs 19 are formed on the main body 15 so as to be parallel to one another and extend in the long side direction. A sealing member 17 is disposed between the main body 15 of the separator 14 and the resin plate 12. The sealing member 17 can be disposed on both the front and back surfaces of the resin plate 12 in the thickness direction.

[0013] A sealing member 17 disposed on the front surface side of the resin plate 12 surrounds pairs of holes 16 located on one of two diagonal lines in the resin plate 12 and the separator 14, and the anode side of the membrane electrode gas diffusion layer assembly 13. The sealing member 17 also surrounds a plurality of ribs 19 in the separator 14 located on the anode side. A flow path 18 for flowing fuel gas is formed between the plurality of ribs 19 in the separator 14. The fuel gas can flow through this flow path 18 via a pair of the holes 16.

[0014] The sealing member 17 disposed on the back surface of the resin plate 12 surrounds the pair of holes 16 located on the other of the two diagonal lines in the resin plate 12 and the separator 14, and the cathode side of the membrane electrode gas diffusion layer assembly 13. The sealing member 17 also surrounds a plurality of ribs 19 in the separator 14 located on the anode side. A flow path 18 for flowing oxidizing gas is formed between the plurality of ribs 19 in the separator 14. The oxidizing gas can flow through this flow path 18 via the pair of holes 16.

[0015] In the cell stack of the fuel cell 11, a fuel gas is passed through the anode side of the membrane electrode gas diffusion layer assembly 13, and an oxidizing gas is passed through the cathode side of the membrane electrode gas diffusion layer assembly 13. When the fuel gas and the oxidizing gas are passed through the anode side and the cathode side of the membrane electrode gas diffusion layer assembly 13 in this manner, electricity is generated based on the reaction between the fuel gas and the oxidizing gas in the membrane electrode gas diffusion layer assembly 13.

[0016] As shown in FIG. 2, the membrane electrode gas diffusion layer assembly 13 of the fuel cell 11 includes an electrolyte layer 20, a cathode electrode layer 21, an anode electrode layer 22, and a gas diffusion layer 23. The electrolyte layer 20 is formed of, for example, a solid polymer membrane. The cathode electrode layer 21 is bonded to one side of the electrolyte layer 20 in the thickness direction (the upper side in FIG. 1). The anode electrode layer 22 is bonded to the other side of the electrolyte layer 20 in the thickness direction (the lower side in FIG. 1). The surface of the cathode electrode layer 21 opposite to the electrolyte layer 20 is covered with a gas diffusion layer 23. The surface of the anode electrode layer 22 opposite to the electrolyte layer 20 is covered with a gas diffusion layer 23 that is different from the gas diffusion layer 23.

[0017] Separators 14 are disposed on both the cathode side and the anode side of the membrane electrode gas diffusion layer assembly 13. The multiple ribs 19 on the separators 14 are formed by bending the main body 15 of the separators 14 so as to protrude in the thickness direction of the separators 14. The separators 14 located on the cathode side of the membrane electrode gas diffusion layer assembly 13 and the separators 14 located on the anode side of the membrane electrode gas diffusion layer assembly 13 have the same shape. However, the separator 14 on the cathode side is upside down in the thickness direction compared to the separator 14 on the anode side.

[0018] The plurality of ribs 19 on the cathode-side separator 14 protrude toward the cathode-side gas diffusion layer 23. These ribs 19 are in contact with the cathode-side gas diffusion layer 23. Flow paths 18 for flowing oxidizing gas are formed between the plurality of ribs 19 on the separator 14 and between the main body 15 of the separator 14 and the gas diffusion layer 23. The plurality of ribs 19 on the anode-side separator 14 protrude toward the gas diffusion layer 23. These ribs 19 are in contact with the anode-side gas diffusion layer 23. Flow paths 18 for flowing fuel gas are formed between the plurality of ribs 19 on the separator 14 and between the main body 15 of the separator 14 and the gas diffusion layer 23.

[0019] <Details of the ribs 19 and flow paths 18 in the separator 14> Fig. 3 schematically shows the ribs 19 and flow paths 18 of the separator 14. As can be seen from Fig. 3, the ribs 19 have dividing portions 24 that divide the multiple flow paths 18 extending in parallel between the upstream and downstream sides of the gas flow direction in the flow paths 18. In Fig. 3, the left side is the upstream side of the gas flow, and the right side is the downstream side of the gas flow.

[0020] The positions of the dividing portions 24 in the gas flow direction of the flow paths 18, i.e., the left-right direction in Fig. 3, are not the same for adjacent flow paths 18 in the up-down direction in Fig. 3, which is the arrangement direction of the parallel ribs 19. More specifically, the dividing portions 24 are formed at equal intervals in the extension direction of the ribs 19. The dividing portion 24 corresponding to a given flow path 18 is located midway between the dividing portions 24 corresponding to another flow path 18 adjacent to the flow path 18 in the arrangement direction of the parallel ribs 19.

[0021] The ribs 19 and dividing portions 24 of the main body 15 of the separators 14 are formed as follows: That is, of the separators 14 arranged on both sides in the thickness direction of the membrane electrode gas diffusion layer assembly 13, the downstream end of the flow path 18 divided by the dividing portion 24 of one separator 14 is formed to be positioned corresponding to the downstream end of the flow path 18 divided by the dividing portion 24 of the other separator 14. In Fig. 3, the flow path 18 divided by the dividing portion 24 of one separator 14 is shown by a solid line, and the flow path 18 divided by the dividing portion 24 of the other separator 14 is shown by a dashed line.

[0022] The ribs 19 of the main body 15 of the separator 14 are formed so that they extend in different directions when the separator 14 is located on one side of the thickness direction of the membrane electrode gas diffusion layer assembly 13 and when the separator 14 is located on the other side.

[0023] That is, the ribs 19 are formed in a wavy shape with a fluctuation width in a direction intersecting the direction in which the ribs 19 extend, i.e., in the up-and-down direction in Fig. 3. By forming the ribs 19 in a wavy shape in this way, the extending direction of the ribs 19 differs depending on whether the separator 14 is located on one side of the membrane electrode-gas diffusion layer assembly 13 in the thickness direction or the other side.

[0024] As a result, when the fuel cell stack is pressed in the stacking direction of the fuel cell cells 11, adjacent fuel cell cells 11 come into contact with each other at locations corresponding to the bottoms 18a of the flow paths 18 in the main bodies 15 of the separators 14. The locations where this contact occurs are shown by the shaded areas in FIG.

[0025] <Functions and Effects of the Separator 14 of the Fuel Cell in the Present Embodiment> (1) The flow paths 18 for supplying and discharging gas to and from the membrane electrode gas diffusion layer assembly 13 are divided into upstream and downstream portions in the gas flow direction of the flow paths 18 by the dividing portions 24 of the ribs 19. Therefore, when the gas flowing downstream in the flow paths 18 reaches the portion of the flow paths 18 divided by the dividing portions 24, i.e., the downstream end of the flow paths 18, it enters the gas diffusion layer 23 from the downstream end. Furthermore, the gas that has entered the gas diffusion layer 23 spreads radially from the downstream end of the flow paths 18 as shown by the two-dot chain line in FIG. 3 before entering the adjacent flow paths 18. This flow of gas in the gas diffusion layer 23 promotes gas diffusion in the gas diffusion layer 23. As a result, it is possible to prevent the gas supplied from the flow paths 18 to the membrane electrode gas diffusion layer assembly 13 from diffusing in the gas diffusion layer 23. Therefore, it is possible to prevent a decrease in the power generation efficiency of the fuel cell 11 due to the reduced gas diffusion in the gas diffusion layer 23.

[0026] If the positions of the dividing portions 24 in the gas flow direction of the flow channels 18 were the same for adjacent flow channels 18, gases that entered the gas diffusion layer 23 from the downstream ends of the adjacent flow channels 18 might interfere with each other as they spread radially from the downstream ends. Such gas interference would make it difficult for the gas to diffuse in the gas diffusion layer 23. However, the positions of the dividing portions 24 in the gas flow direction of the flow channels 18 are designed not to be the same for adjacent flow channels 18. This prevents the gases that entered the gas diffusion layer 23 from the downstream ends of the adjacent flow channels 18 from interfering with each other as they spread radially from the downstream ends. As a result, it is possible to prevent the gases from interfering with each other and making it difficult for the gases to diffuse in the gas diffusion layer 23.

[0027] (2) The main bodies 15 of the separators 14 are located on both sides in the thickness direction of the membrane electrode gas diffusion layer assembly 13. The separators 14 located on both sides in the thickness direction of the membrane electrode gas diffusion layer assembly 13 are in a state in which one of the separators 14 is turned upside down relative to the other separator 14. The ribs 19 and the dividing portions 24 in the main bodies 15 of the separators 14 are formed so that the downstream end of the flow path 18 divided by the dividing portion 24 in the main body 15 of one separator 14 corresponds to the downstream end of the flow path 18 divided by the dividing portion 24 in the main body 15 of the other separator 14. Specifically, the downstream end of the flow path 18 on one separator 14 side is located as shown by the solid line in FIG. 3, and the downstream end of the flow path 18 on the other separator 14 side is located as shown by the dashed line in FIG. 3. Therefore, the gas that has entered the gas diffusion layer 23 from the downstream end of the flow path 18 corresponding to one separator 14 and the gas that has entered the gas diffusion layer 23 from the downstream end of the flow path 18 corresponding to the other separator 14 are positioned on opposite sides of the membrane electrode gas diffusion layer assembly 13. This improves the power generation efficiency when power is generated based on the reaction between the fuel gas and the oxidizing gas in the membrane electrode gas diffusion layer assembly 13.

[0028] (3) The ribs 19 of the main body 15 of the separator 14 are formed so that they extend in different directions when the separator 14 is located on one side of the membrane electrode gas diffusion layer assembly 13 in the thickness direction. As a result, the portions of the main body 15 of the separator 14 that correspond to the bottoms 18a of the flow paths 18 also extend in correspondence with the ribs 19 of the main body 15. When the fuel cell stack is pressed in the stacking direction of the fuel cells 11, the portions of the main body 15 of the separators 14 that correspond to the bottoms 18a of the flow paths 18 come into contact with each other in adjacent fuel cells 11. In other words, the above-mentioned portions do not interdigitate with each other. Therefore, when the fuel cell stack is pressed in the stacking direction of the fuel cells 11, the surface pressure acting from the main body 15 of the separator 14 to the membrane electrode gas diffusion layer assembly 13 decreases, which prevents a deterioration in power generation efficiency.

[0029] (4) The ribs 19 of the main body 15 of the separator 14 are formed in a wavy shape with a swing width in a direction intersecting the extending direction of the ribs 19. As a result, the extending direction of the ribs 19 of the main body 15 of the separator 14 differs depending on whether the separator 14 is located on one side of the membrane electrode gas diffusion layer assembly 13 in the thickness direction or the other side.

[0030] (5) The dividing portions 24 are formed at equal intervals in the direction in which the ribs 19 extend. The dividing portion 24 corresponding to a given flow path 18 is located midway between the dividing portion 24 corresponding to the flow path 18 and another flow path 18 adjacent to the flow path 18 in the direction in which the parallel ribs 19 are arranged. This makes it possible to more effectively prevent the gases that have entered the gas diffusion layer 23 from the downstream ends of the adjacent flow paths 18 from interfering with each other as they spread radially from the downstream ends.

[0031] The above embodiment can be modified as follows, for example: The above embodiment and the following modifications can be combined and implemented within the scope of technical compatibility. The dividing portion 24 corresponding to a given flow path 18 is positioned midway between the dividing portion 24 corresponding to the flow path 18 and another flow path 18 adjacent to it in the direction in which the parallel ribs 19 are arranged, but it does not necessarily have to be positioned in that way.

[0032] The ribs 19 and the flow paths 18 do not necessarily have to have a curved shape as shown in FIG. 3, but may be formed in a curved shape as shown in, for example, FIG. 5, FIG. 6 or FIG. Some of the ribs 19 and channels 18 may be formed so that the channels 18 are straight, as shown in Figures 8 and 9 for example.

[0033] The ribs 19 do not necessarily have to be formed so that they extend in different directions when the separator 14 is located on one side of the membrane electrode gas diffusion layer assembly 13 in the thickness direction and when the separator 14 is located on the other side.

[0034] The downstream end of the dividing portion 24 of the flow path 18 on one separator 14 side of the separators 14 located on both sides in the thickness direction of the membrane electrode-gas diffusion layer assembly 13 does not necessarily have to correspond to the downstream end of the dividing portion 24 of the flow path 18 on the other separator 14 side.

[0035] Next, the technical concept that can be understood from the above embodiment will be described. (A) a plate-shaped body on which a plurality of ribs extending in parallel are formed; the main body can be disposed on each side of the membrane electrode gas diffusion layer assembly in the thickness direction, the rib protrudes from the main body to come into contact with the gas diffusion layer of the membrane electrode gas diffusion layer assembly, a separator for a fuel cell, wherein a flow path for allowing gas to flow to or from the membrane electrode gas diffusion layer assembly is formed between the plurality of ribs and between the main body and the gas diffusion layer, the rib includes a dividing portion that divides the plurality of flow paths extending in parallel between upstream and downstream in the gas flow direction in the flow paths, A separator for a fuel cell, wherein the position of the dividing portion in the direction of gas flow in the flow path is not the same for adjacent flow paths in the direction in which the parallel ribs are arranged.

[0036] (B) the main body is one of the main bodies located on both sides of the membrane electrode gas diffusion layer assembly in the thickness direction, the main body being in a state where one of the main bodies is inverted relative to the other main body; The rib and the dividing portion of the main body are formed so that the downstream end of the flow path divided by the dividing portion in one of the main bodies is positioned corresponding to the downstream end of the flow path divided by the dividing portion in the other main body.

[0037] (C) the main body is one of the main bodies located on both sides of the membrane electrode gas diffusion layer assembly in the thickness direction, the main body being in a state where one of the main bodies is inverted relative to the other main body; The separator for a fuel cell according to (A) or (B), wherein the ribs of the main body are formed so as to extend in different directions when the main body is located on one side of the thickness direction of the membrane electrode gas diffusion layer assembly and when the main body is located on the other side.

[0038] (D) The fuel cell separator according to (C), wherein the ribs are formed in a wavy shape having a amplitude in a direction intersecting the direction in which the ribs extend.

[0039] (E) The dividing portions are formed at equal intervals in the direction in which the rib extends, A fuel cell separator described in any one of (A) to (D), wherein the dividing portion corresponding to a given flow path is located midway between dividing portions corresponding to another flow path adjacent to the flow path in the arrangement direction of the parallel ribs. [Explanation of symbols]

[0040] 11...Fuel cell 12...Resin plate 13...Membrane electrode gas diffusion layer assembly 14...Separator 15...Main body 16...hole 17...Sealing material 18...Flow path 18a...bottom 19...Ribs 20...Electrolyte layer 21...Cathode electrode layer 22...Anode electrode layer 23...Gas diffusion layer 24...Divided part

Claims

1. a plate-shaped body on which a plurality of ribs extending in parallel are formed; the main body can be disposed on each side of the membrane electrode gas diffusion layer assembly in the thickness direction, the rib protrudes from the main body to come into contact with the gas diffusion layer of the membrane electrode gas diffusion layer assembly, a separator for a fuel cell, wherein a flow path for allowing gas to flow to or from the membrane electrode gas diffusion layer assembly is formed between the plurality of ribs and between the main body and the gas diffusion layer, the rib includes a dividing portion that divides the plurality of flow paths extending in parallel between upstream and downstream in the gas flow direction in the flow paths, A separator for a fuel cell, wherein the position of the dividing portion in the direction of gas flow in the flow path is not the same for adjacent flow paths in the direction in which the parallel ribs are arranged.

2. the main body is one of the main bodies located on both sides of the membrane electrode gas diffusion layer assembly in the thickness direction, the main body being in a state where one of the main bodies is inverted relative to the other main body; 2. A fuel cell separator as described in claim 1, wherein the rib and the dividing portion of the main body are formed so that the downstream end of the flow path divided by the dividing portion in one of the main bodies is positioned corresponding to the downstream end of the flow path divided by the dividing portion in the other of the main bodies.

3. the main body is one of the main bodies located on both sides of the membrane electrode gas diffusion layer assembly in the thickness direction, the main body being in a state where one of the main bodies is inverted relative to the other main body; 3. The fuel cell separator according to claim 1, wherein the ribs of the main body are formed so that they extend in different directions when the main body is located on one side of the membrane electrode gas diffusion layer assembly in the thickness direction and when the main body is located on the other side.

4. 4. The fuel cell separator according to claim 3, wherein the ribs are formed in a wave shape having a width of oscillation in a direction intersecting the direction in which the ribs extend.

5. The dividing portions are formed at equal intervals in the direction in which the rib extends, 3. A fuel cell separator as described in claim 1 or 2, wherein the dividing portion corresponding to a specific flow path is located midway between dividing portions corresponding to another flow path adjacent to the flow path in the direction in which the parallel ribs are arranged.

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