fuel cells

Abstract

To provide a fuel cell capable of suppressing peeling a membrane electrode assembly from an adhesive surface while ensuring gas flow in the gas flow path.SOLUTION: The fuel cell includes: a frame member 19 having an aperture 21; a membrane electrode assembly 20 that is bonded to the periphery of the aperture 21 in the frame member 19 to cover the aperture 21; and a pair of separators sandwiching the frame member 19 and the membrane electrode assembly 20. On both edges of the membrane electrode assembly 20, a gas hole is formed. Between the frame member 19, the membrane electrode assembly 20 and the separator, the gas flow path that allows gas to flow from one of the gas holes on both edges to the other is formed. The periphery of aperture 21 in the frame member 19 has an adhesive surface 23 to which the membrane electrode assembly 20 is adhered. In a part corresponding to the gas flow path in the separator and in the part corresponding to the adhesive surface 23, multiple convex portions 34 are formed which are arranged at intervals in the direction in which the adhesive surface 23 extends. The multiple convex portions 34 are arranged consecutively when viewed from the aperture 21 side.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a fuel cell. [Background technology]

[0002] Conventionally, a fuel cell is known, for example, as shown in Patent Document 1. Such a fuel cell has a structure in which a resin-framed MEA (membrane electrode assembly) is sandwiched between a first separator and a second separator. The resin-framed MEA is formed by bonding the outer peripheral edge of the MEA to a resin frame member, for example, with an adhesive. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-21975 Summary of the Invention [Problem to be solved by the invention]

[0004] In the fuel cell described above, when the MEA generates electricity, the MEA shrinks. As a result, a tensile force is applied to the bonded portion between the resin frame member and the MEA due to the shrinkage of the MEA. This poses a problem that the MEA may peel off from the bonded portion between the resin frame member and the MEA. [Means for solving the problem]

[0005] The means for solving the above problems and their effects will be described below. A fuel cell that solves the above-mentioned problems comprises a resin frame member having an opening in the center, a membrane electrode assembly bonded to the periphery of the opening in the frame member to cover the opening, and a pair of separators that sandwich the frame member and the membrane electrode assembly, wherein gas holes are formed at both ends of the membrane electrode assembly, and a gas flow path is formed between the frame member and the membrane electrode assembly and the separator, for allowing gas supplied from one of the gas holes formed at each end to pass through the membrane electrode assembly to the other, wherein the periphery of the opening in the frame member extends along the outer periphery of the membrane electrode assembly and has an adhesive surface to which the membrane electrode assembly is bonded, and a plurality of protrusions are formed in the separator in a portion corresponding to the gas flow path and corresponding to the adhesive surface, the protrusions being aligned at intervals in the direction of extension of the adhesive surface, and the plurality of protrusions are arranged continuously when viewed from the opening side.

[0006] Typically, when a membrane electrode assembly generates electricity, the membrane electrode assembly shrinks, and the tensile force caused by this shrinkage makes the membrane electrode assembly more likely to peel off from the adhesive surface. In this regard, according to the above configuration, when a fuel cell stack is formed by stacking a plurality of fuel cells, a load acting in the stacking direction of the fuel cells acts on the membrane electrode assembly and the adhesive surface via the plurality of protrusions. In this case, since the plurality of protrusions are arranged continuously when viewed from the opening side, the load acts over the entire extension direction of the adhesive surface. Therefore, even if a tensile force due to the shrinkage of the membrane electrode assembly acts, peeling of the membrane electrode assembly from the adhesive surface can be suppressed. In addition, the plurality of protrusions are arranged side by side at intervals in the extension direction of the adhesive surface. Therefore, gas flowing through the gas flow channel flows between the protrusions in the region corresponding to the adhesive surface. Therefore, the plurality of protrusions do not obstruct the flow of gas in the gas flow channel. Therefore, peeling of the membrane electrode assembly from the adhesive surface can be suppressed while ensuring the flow of gas through the gas flow channel. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is an exploded perspective view of a fuel cell according to an embodiment. [Figure 2] FIG. 2 is an exploded perspective view showing a power generation unit of the fuel cell shown in FIG. 1. [Figure 3] Schematic plan view of the fuel cell in Figure 1. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a main part of FIG. 3. [Figure 5] FIG. 4 is an enlarged schematic plan view of a main part showing the positional relationship between an adhesive surface and a protrusion. [Figure 6] FIG. 10 is an enlarged schematic plan view of a main part showing the positional relationship between the adhesive surface and the protrusion in a fuel cell according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a fuel cell will be described below with reference to the drawings. <Configuration of fuel cell 11> 1, a plurality of fuel cells 11 are stacked to form a fuel cell stack (not shown). The fuel cell 11 includes a rectangular plate-shaped power generation unit 12, a pair of rectangular sheet-shaped gas diffusion layers 13 sandwiching the power generation unit 12, and a pair of rectangular plate-shaped separators 14. That is, the fuel cell 11 has a structure in which the pair of gas diffusion layers 13, the power generation unit 12, and the pair of separators 14 are stacked.

[0009] In the following description, the long side direction, short side direction, and thickness direction of the fuel cell 11 are respectively referred to as the long side direction X, the short side direction Y, and the thickness direction Z. The long side direction X, the short side direction Y, and the thickness direction Z are directions that are perpendicular to each other.

[0010] 1, one of the pair of gas diffusion layers 13 (cathode side) is a first gas diffusion layer 15, and the other (anode side) is a second gas diffusion layer 16. One of the pair of separators 14 (cathode side) is a first separator 17, and the other (anode side) is a second separator 18.

[0011] <Generation Unit 12> 1 and 2, the power generation unit 12 includes a rectangular plate-shaped resin frame member 19 and a rectangular sheet-shaped membrane electrode assembly (MEA) 20 supported by the frame member 19. The frame member 19 has a rectangular opening 21 in the center. A rectangular annular support portion 22 is formed around the periphery of the opening 21 in the frame member 19 and is thinner than other portions to support the periphery of the membrane electrode assembly 20.

[0012] The peripheral edge of the membrane electrode assembly 20 is supported on the surface of the support 22 facing the first gas diffusion layer 15, so that the entire opening 21 is covered by the membrane electrode assembly 20. The support 22 has a rectangular annular bonding surface 23 on its surface facing the first gas diffusion layer 15, which extends along the outer periphery of the membrane electrode assembly 20 and to which the peripheral edge of the membrane electrode assembly 20 is bonded. The bonding surface 23 extends in a rectangular annular shape along the center of the surface of the support 22 facing the first gas diffusion layer 15. The peripheral edge of the membrane electrode assembly 20 is bonded to the bonding surface 23 with an adhesive.

[0013] 1 to 4, the pair of gas diffusion layers 13 are arranged so that the long side direction X and the short side direction Y coincide with the opening 21 of the frame member 19. The first gas diffusion layer 15 has lengths in the long side direction X and the short side direction Y that are slightly longer than the opening 21. The second gas diffusion layer 16 has lengths in the long side direction X and the short side direction Y that are the same as the opening 21. The pair of separators 14 sandwich the power generation unit 12 in the thickness direction Z from the outside of the pair of gas diffusion layers 13.

[0014] The fuel cell 11 is supplied with an oxidant gas containing oxygen to one side (cathode side) of the membrane electrode assembly 20 in the thickness direction Z, and with a fuel gas containing hydrogen to the other side (anode side) of the membrane electrode assembly 20 in the thickness direction Z. This allows the fuel cell 11 to generate electricity based on an electrochemical reaction between the oxidant gas and the fuel gas in the membrane electrode assembly 20.

[0015] <Flow path configuration of fuel cell 11> At both ends of the membrane electrode assembly 20 in the fuel cell 11 sandwiched in the long side direction X, i.e., at both ends of the frame member 19 and the pair of separators 14 sandwiching the membrane electrode assembly 20 in the long side direction X, three rectangular through holes are formed in each end, aligned in the short side direction Y.

[0016] The three through holes at one end of the fuel cell 11 in the long side direction X are a fuel gas inlet 24 as an example of a gas hole, a coolant outlet 25, and an oxidant gas outlet 26 as an example of a gas hole. The three through holes at the other end of the fuel cell 11 in the long side direction X are an oxidant gas inlet 27 as an example of a gas hole, a coolant outlet 28, and a fuel gas outlet 29 as an example of a gas hole.

[0017] The fuel gas supply hole 24 constitutes an inlet-side fuel gas manifold to which fuel gas is supplied in the fuel cell stack (not shown). The fuel gas discharge hole 29 constitutes an outlet-side fuel gas manifold from which fuel gas is discharged in the fuel cell stack (not shown). The oxidant gas supply hole 27 constitutes an inlet-side oxidant gas manifold to which oxidant gas is supplied in the fuel cell stack (not shown). The oxidant gas discharge hole 26 constitutes an outlet-side oxidant gas manifold from which oxidant gas is discharged in the fuel cell stack (not shown). Each of the above manifolds extends in the stacking direction (thickness direction Z) of the fuel cells 11 when the fuel cell stack (not shown) is constructed.

[0018] An oxidant gas flow channel 30 (gas flow channel) is formed between the frame member 19 and the membrane electrode assembly 20 on the one hand and the first separator 17 on the other hand, and causes the oxidant gas supplied from the oxidant gas supply hole 27 to pass through the membrane electrode assembly 20 in the long side direction X and flow to the oxidant gas discharge hole 26 on the other hand. The oxidant gas flow channel 30 is constituted by a plurality of grooves formed on the surface of the first separator 17 facing the membrane electrode assembly 20 on the other hand.

[0019] A fuel gas flow path 31 is formed between the frame member 19 and the membrane electrode assembly 20 on the one hand and the second separator 18 on the other hand, and allows the fuel gas supplied from the fuel gas supply hole 24 to pass through the membrane electrode assembly 20 in the long side direction X and flow to the fuel gas discharge hole 29 on the other hand. The fuel gas flow path 31 is made up of a plurality of grooves formed on the surface of the second separator 18 facing the membrane electrode assembly 20 on the other hand.

[0020] When a plurality of fuel cells 11 are stacked to form a fuel cell stack (not shown), a coolant flow path (not shown) is formed between the first separator 17 of one of two fuel cells 11 adjacent to each other in the stacking direction (thickness direction Z) and the second separator 18 of the other fuel cell 11. The coolant flow path (not shown) allows the coolant supplied from the coolant supply holes 28 to flow to the coolant discharge holes 25.

[0021] 2 to 5, of the rectangular annular support portion 22, one side in the long side direction X is a first side portion 32, and the other side in the long side direction X is a second side portion 33. Both the first side portion 32 and the second side portion 33 extend in the short side direction Y. Therefore, the respective adhesive surfaces 23 of the first side portion 32 and the second side portion 33 also extend in the short side direction Y.

[0022] A plurality of protrusions 34 are formed on the surface of the first separator 17 facing the membrane electrode assembly 20 at a portion corresponding to the oxidant gas flow field 30 and corresponding to the bonding surfaces 23 of the first side portion 32 and the second side portion 33 in the thickness direction Z. The protrusions 34 in this example are arranged in multiple (two in this example) rows. Each of the protrusions 34 in this example has an elliptical shape when viewed in the thickness direction Z.

[0023] The plurality of protrusions 34 in each of the two rows aligned in the long side direction X are arranged at equal intervals in the short side direction Y. The plurality of protrusions 34 in each of the two rows aligned in the long side direction X are arranged with a half-pitch offset from each other. The plurality of protrusions 34 arranged in two rows are arranged contiguously when viewed from the opening 21 side, i.e., when viewed from the long side direction X. In other words, the plurality of protrusions 34 arranged in two rows are arranged so that no gaps are formed between the protrusions 34 when viewed from the long side direction X.

[0024] Of the two rows aligned in the long side direction X, formed by the plurality of protrusions 34, the plurality of protrusions 34 forming one row on the opening 21 side are arranged so as to partially overlap with the adhesive surface 23 in the thickness direction Z. Of the two rows aligned in the long side direction X, formed by the plurality of protrusions 34 forming the other row on the opposite side to the opening 21 side are arranged so as not to overlap with the adhesive surface 23 in the thickness direction Z.

[0025] <Function of fuel cell 11> Next, the operation of the fuel cell 11 will be described. 3 and 4 , when power is generated by the fuel cell 11, an oxidant gas is supplied from the oxidant gas supply hole 27, and a fuel gas is supplied from the fuel gas supply hole 24. When an oxidant gas is supplied from the oxidant gas supply hole 27 to the fuel cell 11, the oxidant gas flows through the oxidant gas flow field 30 and flows to the oxidant gas discharge hole 26, and is diffused by the first gas diffusion layer 15 and supplied to the cathode side surface of the membrane electrode assembly 20.

[0026] On the other hand, when fuel gas is supplied to the fuel cell 11 through the fuel gas supply hole 24, the fuel gas is supplied to the anode side surface of the membrane electrode assembly 20 while being diffused by the second gas diffusion layer 16 as it flows through the fuel gas flow channel 31 to the fuel gas discharge hole 29. Then, in the fuel cell 11, electricity is generated based on an electrochemical reaction in the membrane electrode assembly 20 between the oxidant gas supplied to the cathode side surface of the membrane electrode assembly 20 and the fuel gas supplied to the anode side surface of the membrane electrode assembly 20.

[0027] When power is generated in the fuel cell 11, the membrane electrode assembly 20 contracts overall. Then, due to the tensile force caused by this contraction of the membrane electrode assembly 20, the adhesion portions of the first side portion 32 and the second side portion 33 of the membrane electrode assembly 20 to the adhesive surfaces 23 are pulled toward the opening 21. As a result, there is a risk that the membrane electrode assembly 20 will shift from the adhesive surfaces 23 toward the opening 21 and peel off.

[0028] In this regard, when a fuel cell stack (not shown) is formed by stacking a plurality of fuel cells 11, a compressive load acting in the stacking direction (thickness direction Z) of the fuel cells 11 acts on the membrane electrode assembly 20 and the adhesive surface 23 via the plurality of protrusions 34. In this case, the plurality of protrusions 34 are arranged continuously in the long side direction X when viewed from the opening 21 side, and therefore the compressive load acts over the entire short side direction Y, which is the direction in which the adhesive surface 23 extends. Therefore, even if a tensile force acts due to contraction of the membrane electrode assembly 20, the membrane electrode assembly 20 is prevented from shifting from the adhesive surface 23 toward the opening 21 and peeling off.

[0029] In addition, the multiple protrusions 34 are arranged side by side at intervals in the short side direction Y, which is the direction in which the bonding surface 23 extends. Therefore, the oxidant gas flowing through the oxidant gas flow field 30 flows between the protrusions 34 in the region corresponding to the bonding surface 23. Therefore, the multiple protrusions 34 do not hinder the flow of the oxidant gas through the oxidant gas flow field 30. Therefore, the flow of the oxidant gas in the oxidant gas flow field 30 is ensured, and peeling of the membrane electrode assembly 20 from the bonding surface 23 is suppressed.

[0030] <Effects of the embodiment> According to the embodiment described above in detail, the following effects are achieved. (1) In the fuel cell 11, a plurality of protrusions 34 are formed in a portion of the first separator 17 that corresponds to the oxidant gas flow path 30 and also corresponds to the adhesive surface 23. The protrusions 34 are arranged at intervals in the direction in which the adhesive surface 23 extends. When viewed from the opening 21 side, the protrusions 34 are arranged continuously.

[0031] Typically, when the membrane electrode assembly 20 generates electricity, the membrane electrode assembly 20 shrinks. The resulting tensile force can easily cause the membrane electrode assembly 20 to peel off from the adhesive surface 23. In this regard, according to the above configuration, when a plurality of fuel cells 11 are stacked to form a fuel cell stack, a compressive load acting in the stacking direction of the fuel cells 11 acts on the membrane electrode assembly 20 and the adhesive surface 23 via the plurality of protrusions 34. In this case, the plurality of protrusions 34 are arranged continuously when viewed from the opening 21 side, and therefore the compressive load acts over the entire extension direction of the adhesive surface 23. Therefore, even if a tensile force due to the shrinkage of the membrane electrode assembly 20 acts, peeling of the membrane electrode assembly 20 from the adhesive surface 23 can be suppressed. Additionally, the plurality of protrusions 34 are arranged side by side at intervals in the extension direction of the adhesive surface 23. Therefore, the oxidant gas flowing through the oxidant gas flow field 30 flows between the protrusions 34 in the region corresponding to the adhesive surface 23. Therefore, the plurality of protrusions 34 do not obstruct the flow of oxidant gas in the oxidant gas flow field 30. This makes it possible to prevent the membrane electrode assembly 20 from peeling off from the bonding surface 23 while ensuring the flow of oxidant gas in the oxidant gas flow field 30.

[0032] (2) In the fuel cell 11, the plurality of protrusions 34 are arranged in two rows. According to the above configuration, the compressive load can be applied over a wider range to the membrane electrode assembly 20 and the adhesive surface 23 via the multiple protrusions 34. This makes it possible to more effectively prevent the membrane electrode assembly 20 from peeling off from the adhesive surface 23.

[0033] (Example of change) The above embodiment can be modified as follows: Furthermore, the above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0034] As shown in FIG. 6 , the protrusions 34 may be replaced with protrusions 35. That is, the multiple protrusions 35 may be configured to extend at an angle relative to the short side direction Y, which is the extension direction of the adhesive surface 23. In this case, the multiple protrusions 35 have an elongated rectangular shape and are arranged in a row parallel to and at equal intervals in the short side direction Y. Furthermore, in this case, the multiple protrusions 35 each extend across the adhesive surface 23 when viewed from the thickness direction Z. That is, the multiple protrusions 35 are arranged so as to overlap the adhesive surface 23 in the thickness direction Z. Furthermore, the multiple protrusions 35 are arranged consecutively when viewed from the opening 21 side, i.e., when viewed from the long side direction X. That is, the multiple protrusions 34 arranged in a row are arranged so that no gaps are formed between the protrusions 35 when viewed from the long side direction X. With this simple configuration, it is possible to achieve a good balance between ensuring the flow of oxidant gas in the oxidant gas flow field 30 and suppressing peeling of the membrane electrode assembly 20 from the adhesive surface 23.

[0035] The plurality of protrusions 35 in FIG. 6 may be arranged in two or more rows. Two rows of the plurality of protrusions 34 aligned in the long side direction X may be arranged so as to overlap the adhesive surface 23 in the thickness direction Z.

[0036] The shape of each protrusion 34 as viewed in the thickness direction Z is not limited to an ellipse, and may be changed to any shape, such as a perfect circle, a polygon, a star, or a cross. The plurality of protrusions 34 located at positions corresponding to either the first side portion 32 or the second side portion 33 may be omitted.

[0037] The plurality of protrusions 34 may be arranged in a single row, or in three or more rows. The multiple protrusions 34 may be formed in a portion of the second separator 18 on the surface facing the membrane electrode assembly 20 that corresponds to the fuel gas flow channel 31 (gas flow channel) and that corresponds in the thickness direction Z to the bonding surfaces 23 of the first side portion 32 and the second side portion 33. In this case, the multiple protrusions 34 at a position corresponding to either the first side portion 32 or the second side portion 33 may be omitted. [Explanation of symbols]

[0038] 11...fuel cell 12...Power generation unit 13...Gas diffusion layer 14...Separator 15...First gas diffusion layer 16...Second gas diffusion layer 17...First separator 18...Second separator 19...Frame member 20...Membrane electrode assembly 21...Opening 22...Support part 23...Adhesive surface 24...Fuel gas supply hole as an example of a gas hole 25…Cooling medium discharge hole 26...Oxidant gas exhaust hole as an example of a gas hole 27...Oxidant gas supply hole as an example of a gas hole 28…Cooling medium supply hole 29...Fuel gas exhaust hole as an example of a gas hole 30...oxidant gas flow path as an example of a gas flow path 31...Fuel gas flow path as an example of a gas flow path 32...First side 33...Second side 34,35...Convex part X: Long side direction Y: Short side direction Z: Thickness direction

Claims

1. a resin frame member having an opening in the center, a membrane electrode assembly bonded to a peripheral edge of the opening in the frame member to cover the opening, and a pair of separators sandwiching the frame member and the membrane electrode assembly, gas holes are formed at both ends of the membrane electrode assembly, a gas flow path is formed between the frame member and the membrane electrode assembly and the separator, which allows gas supplied from one of the gas holes formed at each of the end portions to pass through the membrane electrode assembly and flow to the other of the gas holes; a peripheral edge of the opening in the frame member extends along an outer periphery of the membrane electrode assembly and has an adhesive surface to which the membrane electrode assembly is adhered, a plurality of protrusions are formed in a portion of the separator that corresponds to the gas flow path and also corresponds to the adhesive surface, the protrusions being arranged at intervals in an extension direction of the adhesive surface; The fuel cell is characterized in that the plurality of protrusions are arranged continuously when viewed from the opening side.

2. 2. The fuel cell according to claim 1, wherein the plurality of protrusions are arranged in a plurality of rows.

3. 3. The fuel cell according to claim 1, wherein each of the plurality of protrusions extends at an angle relative to the direction in which the adhesive surface extends.

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