Fuel cell separator

Abstract

To provide a fuel cell separator in which gas diffusion efficiency at points where the end faces of ribs come in contact with a gas diffusion layer.SOLUTION: A separator 14 comprises a main body on which a plurality of ribs 19 extending parallel to each other are formed. The main body can be disposed on both sides of the membrane electrode gas diffusion layer assembly in the thickness direction. The ribs 19 protrude from the main body to thereby come in contact with the gas diffusion layer 23 of the membrane electrode gas diffusion layer assembly. Flow paths are formed between the plurality of ribs 19 and between the ribs 19 and the gas diffusion layer 23 for the flow of gas supplied to and discharged from the membrane electrode gas diffusion layer assembly. An end face 19a of the rib 19 in the protruding direction is parallel to the gas diffusion layer 23. A protrusion 24 protruding toward the gas diffusion layer 23 is formed on the end face 19a. The protrusion 24 extends in the width direction of the rib 19 to thereby reach the flow paths.SELECTED DRAWING: Figure 4

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 a fuel cell has a main body on which a plurality of ribs extending parallel to each other 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 ribs and the gas diffusion layer 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 membrane electrode gas diffusion layer assembly in the thickness direction 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 membrane electrode gas diffusion layer assembly in the thickness direction and the cathode side gas diffusion layer. Power generation in a fuel cell is 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.

[0004] In the separator of the fuel cell disclosed in Patent Document 1, the protruding end faces of the ribs are in contact with the gas diffusion layer of the membrane electrode gas diffusion layer assembly. The gas diffusion layer at the contact points of the ribs is less likely to come into contact with the gas flowing through the flow channels, resulting in reduced gas diffusion efficiency. Therefore, grooves connected to the flow channels are formed in the end faces of the ribs, allowing the gas flowing through the flow channels to more easily come into contact with the contact points of the gas diffusion layer at the contact points of the ribs through the grooves. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2012 / 035584 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to improve the gas diffusion efficiency at the points where the end faces of the ribs contact the gas diffusion layer, it is effective to have the gas come into contact with the points at many locations. However, if grooves are formed in the end faces of the ribs as described above, the gas can only come into contact with the points at which the gas diffusion layer contacts the end faces of the ribs through the grooves. Therefore, even if grooves are formed in the end faces of the ribs, there is a limit to how much the gas diffusion efficiency can be improved at the points where the end faces of the ribs contact the gas diffusion layer. [Means for solving the problem]

[0007] 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 main body on which a plurality of ribs extending parallel to each other are formed. The main body can be disposed on both sides of the membrane electrode gas diffusion layer assembly in the thickness direction. The ribs protrude from the main body to contact the gas diffusion layer of the membrane electrode gas diffusion layer assembly. Flow paths are formed between the plurality of ribs and between the ribs and the gas diffusion layer for flowing gas supplied to and discharged from the membrane electrode gas diffusion layer assembly. The end faces of the ribs in the protruding direction are parallel to the gas diffusion layer. A protrusion is formed on the end face, protruding toward the gas diffusion layer. The protrusion extends in the width direction of the rib to reach the flow paths.

[0008] According to the above configuration, the end face of the separator in the protruding direction of the rib and the protrusion formed on the end face are pressed against the gas diffusion layer of the membrane electrode-gas diffusion layer joint. At this time, as the protrusion is pressed against the gas diffusion layer, a clearance is generated between the base end of the protrusion in the protruding direction relative to the end face and the gas diffusion layer. This clearance is generated on both sides of the base end of the protrusion in the width direction and extends along the protrusion, connecting to the flow path. As a result, gas flowing through the flow path is more likely to come into contact with the end face of the rib on the gas diffusion layer through the clearance. Since two clearances are generated per protrusion, gas is more likely to come into contact with the end face of the rib on the gas diffusion layer at more locations. This further improves gas diffusion efficiency at the end face of the rib on 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] FIG. 3 is a perspective view showing a separator in the fuel cell of FIG. [Figure 4] 4 is a cross-sectional view showing the separator of FIG. 3 as viewed from the direction of arrow 4-4. [Figure 5] 4 is a plan view showing the positions of protrusions formed on a plurality of ribs in the separator of FIG. 3. FIG. [Figure 6] 10 is a plan view showing another example of the positions of protrusions formed on a plurality of ribs in the separator. FIG. [Figure 7] 10 is a plan view showing another example of the positions of protrusions formed on a plurality of ribs in the separator. FIG. [Figure 8] 10 is a plan view showing another example of the positions of protrusions formed on a plurality of ribs in the separator. FIG. [Figure 9] 10A and 10B are plan views showing other examples of the positions and extending directions of protrusions formed on a plurality of ribs in the separator. [Figure 10] 10A and 10B are plan views showing other examples of the positions and extending directions of protrusions formed on a plurality of ribs in the separator. [Figure 11] 10A and 10B are plan views showing other examples of the positions and extending directions of protrusions formed on a plurality of ribs in the separator. [Figure 12] 10A and 10B are plan views showing other examples of the positions and extending directions of protrusions formed on a plurality of ribs in the separator. [Figure 13] 10A and 10B are plan views showing other examples of the positions and extending directions of protrusions formed on a plurality of ribs in the separator. 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 each other 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 of the resin plate 12 surrounds a pair 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. The upstream end of the flow path 18 in the fuel gas flow, which is connected to the hole 16 on the fuel gas supply side, serves as a fuel gas inlet for the flow path 18. The downstream end of the flow path 18 in the fuel gas flow, which is connected to the hole 16 on the fuel gas discharge side, serves as a fuel gas outlet for the flow path 18.

[0014] A 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 diagonals in the resin plate 12 and the separator 14, as well as 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 a pair of the holes 16. The upstream end of the flow path 18 in the oxidizing gas flow, which is connected to the hole 16 on the oxidizing gas supply side, serves as an oxidizing gas inlet for the flow path 18. The downstream end of the flow path 18 in the fuel gas flow, which is connected to the hole 16 on the oxidizing gas discharge side, serves as an oxidizing gas outlet for the flow path 18.

[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] <Structure of the Ribs 19 and Flow Channels 18 in the Separator 14> 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 located on both the cathode side and the anode side of the membrane electrode gas diffusion layer assembly 13. A plurality of ribs 19 on the cathode side separator 14 are formed by bending the main body 15 so that they protrude toward the cathode side gas diffusion layer 23. These ribs 19 are in contact with the cathode side gas diffusion layer 23. An end face 19a of the rib 19 protruding from the main body 15 is parallel to the cathode side gas diffusion layer 23. Flow paths 18 for flowing oxidizing gas are formed between the plurality of ribs 19 on this separator 14 and between the separator 14 and the gas diffusion layer 23.

[0018] The multiple ribs 19 on the anode-side separator 14 are formed by bending the main body 15 so that they protrude toward the anode-side gas diffusion layer 23. These ribs 19 are in contact with the anode-side gas diffusion layer 23. An end face 19a of the rib 19 protruding from the main body 15 is parallel to the anode-side gas diffusion layer 23. Flow paths 18 for flowing fuel gas are formed between the multiple ribs 19 on the separator 14 and between the separator 14 and the gas diffusion layer 23.

[0019] As shown in FIGS. 3 and 4 , protrusions 24 that protrude toward the gas diffusion layer 23 shown in FIG. 3 are formed on the end faces 19a of the separator 14 in the protruding direction of the ribs 19. These protrusions 24 extend across the entire width of the ribs 19 to reach the adjacent flow paths 18. The end faces 19a of the ribs 19 and the protrusions 24 formed on the end faces 19a are pressed against the gas diffusion layer 23. As can be seen from FIG. 4 , when the protrusions 24 are pressed against the gas diffusion layer 23, clearances C are generated between the base ends of the protrusions 24 in the protruding direction relative to the end faces 19a and the gas diffusion layer 23. These clearances C are generated on both sides of the base ends of the protrusions 24 in the width direction. These clearances C extend along the protrusions 24 to connect to the adjacent flow paths 18 shown in FIG. 3 .

[0020] The dashed lines in Fig. 5 indicate the positions of the protrusions 24 on the multiple ribs 19. As can be seen from the dashed lines in Fig. 5, the multiple protrusions 24 are formed at set intervals, for example, at equal intervals, along the direction in which the ribs 19 extend. As shown in Fig. 3, the protrusion 24 formed on the end face 19a of a rib 19 and the protrusion 24 formed on the end face 19a of the rib 19 adjacent to that rib 19 are positioned on the same straight line perpendicular to the direction in which the ribs 19 extend. Such ribs 19 may be formed, for example, by laser processing.

[0021] <Action and effect of separator 14> Next, the function and effect of the separator 14 of the fuel cell according to this embodiment will be described. (1) The end faces 19a of the ribs 19 of the separator 14 and the protrusions 24 formed on the end faces 19a are pressed against the gas diffusion layer 23, thereby creating clearances C between the gas diffusion layer 23 and the base ends of the protrusions 24 in the protruding direction. These clearances C are created on both sides of the base ends of the protrusions 24 in the width direction and extend along the protrusions 24 to connect to the flow paths 18. As a result, gas flowing through the flow paths 18 is more likely to come into contact with the gas diffusion layer 23 at the contact points with the end faces 19a of the ribs 19 via the clearances C. Two clearances C are created per protrusion 24, which allows gas to more easily come into contact with the gas diffusion layer 23 at the contact points with the end faces 19a of the ribs 19. This further increases the gas diffusion efficiency at the contact points with the gas diffusion layer 23 at the contact points with the end faces 19a of the ribs 19.

[0022] (2) If the protrusions 24 were to be formed using a mold for forming the separator 14, the cost of the mold would be high. However, since the protrusions 24 on the end surfaces 19a of the ribs 19 are formed by laser processing, the cost of the mold can be prevented from increasing, as described above.

[0023] (3) The protrusions 24 formed on the end faces 19a of adjacent ribs 19 are positioned on the same straight line, which facilitates the formation of the protrusions 24 by laser processing. That is, when forming the protrusions 24 by laser processing, the movement of the laser head for laser processing can be made linear, which facilitates the formation of the protrusions 24.

[0024] 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 protrusion 24 does not necessarily need to extend across the entire width of the rib 19, but may extend so as to connect to only one of the adjacent flow paths 18.

[0025] As shown by the dashed line in FIG. 6 , the protrusions 24 may be formed closer to the outlets of the flow channels 18 in the main body 15 in the direction in which the ribs 19 extend, i.e., to the right in FIG. 6 . Because the components used for power generation decrease in the gas flowing through the flow channels 18 closer to the outlets of the flow channels 18, it is preferable for power generation to increase the gas diffusion efficiency in the gas diffusion layer 23 closer to the outlets of the flow channels 18. As described above, by forming the protrusions 24 closer to the outlets of the flow channels 18 in the direction in which the ribs 19 extend, the clearance C between the gas diffusion layer 23 and the end faces 19 a of the ribs 19, defined by the protrusions 24, is also located closer to the outlets of the flow channels 18. This increases the gas diffusion efficiency in the areas of the gas diffusion layer 23 that contact the end faces 19 a of the ribs 19, closer to the outlets of the flow channels 18.

[0026] As shown by the dashed line in Fig. 7, the protrusion 24 may be formed closer to the inlet of the flow path 18 in the main body 15 in the extending direction of the rib 19, i.e., to the left in Fig. 8. The closer to the inlet of the flow path 18, the higher the pressure loss when gas passes through the flow path 18. However, by forming the rib 19 as described above, the clearance C formed at the base end of the protrusion 24 in the protruding direction suppresses the increase in the pressure loss near the inlet of the flow path 18 in the main body 15.

[0027] As shown by the broken line in FIG. 8, the protrusion 24 may be formed midway between the inlet and outlet of the flow path 18 in the direction in which the rib 19 extends. The plurality of protrusions 24 formed on the end surface 19 a of the rib 19 may be spaced apart at shorter intervals as they are closer to the outlet of the flow path 18 in the main body 15 .

[0028] The protrusions 24 may be arranged on the plurality of ribs 19 as shown in FIG. 9 or FIG. 11 to 13, the protrusions 24 may extend across the entire width of the rib 19 and at an angle relative to the direction in which the rib 19 extends. In this case, one end of the protrusions 24 in the direction in which they extend is located upstream of the flow paths 18 relative to the other end, and gas from the flow paths 18 can more easily flow into the clearances C located at the base ends of the protrusions 24 in the protruding direction. As a result, the gas diffusion efficiency can be further improved at the locations of the gas diffusion layer 23 where the end faces 19a of the ribs 19 come into contact.

[0029] When the protrusions 24 are inclined with respect to the direction in which the ribs 19 extend as shown in FIG. 11, the protrusions 24 of adjacent ribs 19 may extend on the same straight line inclined with respect to the direction in which the ribs 19 extend.

[0030] The protrusions 24 may be formed by the mold used to form the separator 14 . The material forming the separator 14 may be changed as appropriate.

[0031] Next, the technical concept that can be understood from the above embodiment will be described. (A) a main body on which a plurality of ribs extending parallel to one another 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 ribs and the gas diffusion layer, an end face of the rib in a protruding direction is parallel to the gas diffusion layer; a protrusion protruding toward the gas diffusion layer is formed on the end surface; The protrusion extends in the width direction of the rib to reach the flow path.

[0032] (B) The body is formed with an inlet and an outlet for the gas to the flow path; The separator for a fuel cell according to (A), wherein the protrusion is formed closer to the outlet of the main body in the direction in which the rib extends.

[0033] (C) The body is formed with an inlet and an outlet for the gas to the flow path; the protrusions are a plurality of protrusions formed at predetermined intervals along the extending direction of the rib, The separator for a fuel cell according to (A), wherein the distance between the plurality of protrusions is shorter the closer they are to the outlet of the main body.

[0034] (D) The fuel cell separator according to any one of (A) to (C), wherein the protrusion extends across the entire width of the rib and at an angle to the direction in which the rib extends.

[0035] (E) The fuel cell separator according to any one of (A) to (D), wherein the protrusions are formed by laser processing.

[0036] (F) A fuel cell separator described in any one of (A) to (E), wherein the protrusion formed on the end face of the rib and the protrusion formed on the end face of the rib adjacent to the rib are positioned on the same straight line. [Explanation of symbols]

[0037] 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 19...Ribs 19a...end face 20...Electrolyte layer 21...Cathode electrode layer 22...Anode electrode layer 23...Gas diffusion layer 24...Protrusion

Claims

1. a main body on which a plurality of ribs extending parallel to one another 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 ribs and the gas diffusion layer, an end face of the rib in a protruding direction is parallel to the gas diffusion layer; a protrusion protruding toward the gas diffusion layer is formed on the end surface; The protrusion extends in the width direction of the rib to reach the flow path.

2. The body is formed with an inlet and an outlet for the gas to the flow path; 2. The fuel cell separator according to claim 1, wherein the protrusion is formed on the main body closer to the outlet in the direction in which the rib extends.

3. The body is formed with an inlet and an outlet for the gas to the flow path; the protrusions are a plurality of protrusions formed at predetermined intervals along the extending direction of the rib, 2. The fuel cell separator according to claim 1, wherein the distance between the plurality of protrusions is shorter the closer they are to the outlet of the main body.

4. 2. The fuel cell separator according to claim 1, wherein the protrusion extends across the entire width of the rib and at an angle to the direction in which the rib extends.

5. 2. The fuel cell separator according to claim 1, wherein the protrusions are formed by laser processing.

6. A fuel cell separator according to any one of claims 1 to 5, wherein the protrusion formed on the end face of the rib and the protrusion formed on the end face of the rib adjacent to the rib are positioned on the same straight line.

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