fuel cell

Abstract

The present invention provides a fuel cell cell that can suppress the reduction in bonding strength between the separator and the retaining plate. [Solution] The fuel cell cell 11 includes a separator 14 that sandwiches the holding plate 12 and the membrane electrode gas diffusion layer assembly 13 from both sides in the thickness direction. The separator 14 is bonded to the holding plate 12 by adhesive. The separator 14 has a plurality of ribs 19 that protrude toward the holding plate 12 and the membrane electrode gas diffusion layer assembly 13. The ribs 19 are arranged in parallel with each other and extend to the holes 16 in the holding plate 12 and the separator 14. An uneven surface is formed on the tip surface of the rib 19 in the protruding direction, located between the holes 16 and the membrane electrode gas diffusion layer assembly 13, and on the contact surface of the holding plate 12 that contacts the tip surface, located between the holes 16 and the membrane electrode gas diffusion layer assembly 13.

Description

Technical Field

[0001] This disclosure relates to fuel cell cells.

Background Art

[0002] The cell stack of a fuel cell is formed by stacking fuel cells in the thickness direction. As shown in Patent Document 1, a fuel cell includes a holding plate and a separator. The holding plate is formed in a rectangular frame shape. The outer edge of the membrane electrode gas diffusion layer laminate is joined to the holding plate. The separator sandwiches the holding plate and the membrane electrode gas diffusion layer laminate from both sides in the thickness direction. The separator is joined to the holding plate by an adhesive or the like.

[0003] A flow path for flowing a fuel gas such as hydrogen is formed between the separator located on the anode side of both sides in the thickness direction of the membrane electrode gas diffusion layer laminate and the gas diffusion layer on the anode side of the membrane electrode gas diffusion layer laminate. Further, a flow path for flowing an oxidizing gas such as air is formed between the separator located on the cathode side of both sides in the thickness direction of the membrane electrode gas diffusion layer laminate and the gas diffusion layer on the cathode side of the membrane electrode gas diffusion layer laminate. A plurality of holes penetrating them in the thickness direction are formed in the holding plate and the separator. Such holes include those for supplying and discharging fuel gas to and from the flow path for flowing fuel gas, and those for supplying and discharging oxidizing gas to and from the flow path for flowing oxidizing gas.

[0004] The separator has multiple ribs that protrude toward the holding plate and the membrane electrode gas diffusion layer assembly. The ribs are arranged in parallel to each other. The flow channels are formed between the multiple ribs in the separator. Slits are formed between the holes in the resin plate and the membrane electrode gas diffusion layer to connect the holes and the flow channels. In the fuel cell cell, fuel gas is supplied to the anode side of the membrane electrode gas diffusion layer assembly through the holes, slits, and flow channels. Oxidizing gas is supplied to the cathode side of the membrane electrode gas diffusion layer assembly in the fuel cell cell through the holes, slits, and flow channels. Electricity is then generated based on the reaction between the fuel gas and the oxidizing gas in the membrane electrode gas diffusion layer assembly. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-192327 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In the fuel cell described above, the separator is joined to the retaining plate by an adhesive or the like. Therefore, the portion of the separator on the retaining plate side that is located between the hole and the membrane electrode gas diffusion layer assembly, and the contact surface of the retaining plate that contacts the above-mentioned surface of the separator and is located between the hole and the membrane electrode gas diffusion layer assembly, are also joined to each other by an adhesive or the like. However, in joining these portions, the contact area is reduced by the slit, which may reduce the bonding strength. [Means for solving the problem]

[0007] The following describes the means and effects of solving the above problems. A fuel cell cell that solves the above problems comprises a frame-shaped holding plate to which the outer edge of the membrane electrode gas diffusion layer assembly is joined, and a separator that sandwiches the holding plate and the membrane electrode gas diffusion layer assembly from both sides in the thickness direction. A flow path for gas to flow is formed between the separator and the membrane electrode gas diffusion layer assembly. Holes are formed in the holding plate and the separator that penetrate them in the thickness direction. These holes are for supplying and discharging gas to the flow path. The separator is joined to the holding plate with an adhesive. The separator has a plurality of ribs that protrude toward the holding plate and the membrane electrode gas diffusion layer assembly. The ribs are in parallel to each other and extend toward the holes. The flow path is formed between the plurality of ribs in the separator. An uneven surface is formed on the tip surface in the protruding direction of the plurality of ribs located between the holes and the membrane electrode gas diffusion layer assembly, and on the contact surface of the holding plate that contacts the tip surface and is located between the holes and the membrane electrode gas diffusion layer assembly.

[0008] According to the above configuration, the tip surfaces of the multiple ribs in the protruding direction, located between the hole and the membrane electrode gas diffusion layer assembly, and the contact surface of the holding plate that contacts the tip surfaces, also located between the hole and the membrane electrode gas diffusion layer assembly, are joined to each other by adhesive. In joining these locations, the contact area between the joined locations tends to be small due to the way the ribs are formed to protrude from the main body. However, as described above, the uneven surfaces are formed at the locations to be joined, which allows for a larger contact area between the joined locations. As a result, the decrease in the joint strength between the joined locations due to the reduction in the contact area between them can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] This is an exploded perspective view showing a fuel cell. [Figure 2] This is a cross-sectional view showing a cell stack formed by stacking fuel cell cells, as shown in Figure 1. [Figure 3]Figure 1 is a schematic diagram showing the separator ribs and flow paths in a fuel cell. [Figure 4] This is a cross-sectional view showing the parts of the separator and retaining plate corresponding to the ribs in Figure 1. [Figure 5] Figure 4 is a perspective view showing the points where the ribs in the separator converge. [Figure 6] This is a plan view showing another example of the position and direction of extension of protrusions formed on multiple ribs in a separator. [Figure 7] This is a plan view showing another example of the position and direction of extension of protrusions formed on multiple ribs in a separator. [Figure 8] This is a plan view showing another example of the position and direction of extension of protrusions formed on multiple ribs in a separator. [Figure 9] This is a plan view showing another example of the position and direction of extension of protrusions formed on multiple ribs in a separator. [Figure 10] This is a plan view showing another example of the position and direction of extension of protrusions formed on multiple ribs in a separator. [Modes for carrying out the invention]

[0010] An embodiment of a fuel cell will be described below with reference to Figures 1 to 5. Figure 1 shows a fuel cell cell 11 for forming a fuel cell stack. The fuel cell cell 11 comprises a retaining plate 12, a membrane electrode gas diffusion layer assembly 13, and a separator 14. The retaining plate 12 is formed in the shape of a rectangular frame from resin. The outer edge of the membrane electrode gas diffusion layer assembly 13 is joined to the retaining plate 12. The retaining plate 12 and the membrane electrode gas diffusion layer assembly 13 are sandwiched between separators 14 positioned on both sides in the thickness direction.

[0011] The cell stack of the fuel cell is formed by stacking the fuel cell cells 11 described above in the thickness direction. The holding plate 12 and separator 14 of the fuel cell cell 11 have a plurality of holes 16 that penetrate them in the thickness direction. Of the plurality of holes 16, three are located at one end in the long side direction of the fuel cell cell 11, and the other three are located at the other end in the long side direction of the fuel cell cell 11. The plurality of holes 16 are arranged in pairs, one on one side and one on the other side in the long side direction of the fuel cell cell 11. Each pair of holes 16 is used to allow fluids such as fuel gas such as hydrogen, oxidizing gas such as air, and refrigerant such as cooling water to flow.

[0012] The separator 14 comprises a body 15 formed in the shape of a rectangular plate from a metal such as stainless steel, titanium, or aluminum. The body 15 is formed with multiple ribs 19 arranged in parallel and extending in the direction of the longer side. A sealing member 17 is placed between the body 15 of the separator 14 and the retaining plate 12. The sealing member 17 can be placed on both the front and back surfaces in the thickness direction of the retaining plate 12. The body 15 of the separator 14 is joined to the retaining plate 12 by adhesive with the sealing member 17 sandwiched between them.

[0013] The sealing member 17, positioned on the surface side of the retaining plate 12, surrounds a pair of holes 16 located on one of the two diagonals of the retaining 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. Fuel gas can flow through this flow path 18 via the pair of holes 16. In other words, the pair of holes 16 can supply and discharge fuel gas to and from the flow path 18.

[0014] The seal member 17 disposed on the back side of the holding plate 12 surrounds a pair of two holes 16 located on the other diagonal line of the above-described two diagonal lines in the holding plate 12 and the separator 14 and the cathode side of the membrane electrode gas diffusion layer assembly 13. The seal member 17 also surrounds a plurality of ribs 19 in the separator 14 located on the anode side. And between the plurality of ribs 19 in the separator 14, a flow path 18 for flowing an oxidizing gas is formed. Oxidizing gas can flow through this flow path 18 via a pair of two holes 16. In other words, a pair of two holes 16 can supply and discharge oxidizing gas to and from the flow path 18.

[0015] In the cell stack of the fuel cell 11, fuel gas is flowed to the anode side of the membrane electrode gas diffusion layer assembly 13, and oxidizing gas is flowed to the cathode side of the membrane electrode gas diffusion layer assembly 13. Thus, when fuel gas and oxidizing gas are flowed to the anode side and the cathode side of the membrane electrode gas diffusion layer assembly 13, power generation is performed based on the reaction between the fuel gas and the oxidizing gas in the membrane electrode gas diffusion layer assembly 13.

[0016] <Details of the rib 19 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 joined to one side (the upper side in FIG. 1) in the thickness direction of the electrolyte layer 20. The anode electrode layer 22 is joined to the other side (the lower side in FIG. 1) in the thickness direction of the electrolyte layer 20. The surface of the cathode electrode layer 21 opposite to the electrolyte layer 20 is covered with the 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 different from the above-described gas diffusion layer 23.

[0017] The separator 14 is located on both the cathode side and the anode side of the membrane electrode gas diffusion layer assembly 13. The plurality of ribs 19 in the separator 14 on the cathode side are formed by bending the main body 15 so as to protrude toward the cathode side gas diffusion layer 23. These ribs 19 are in contact with the cathode side gas diffusion layer 23. The tip surface 19a of the rib 19 in the protruding direction from the main body 15 is parallel to the cathode side gas diffusion layer 23. A flow path 18 for flowing the oxidizing gas is formed between the plurality of ribs 19 in this separator 14 and between the separator 14 and the gas diffusion layer 23.

[0018] The plurality of ribs 19 in the separator 14 on the anode side are formed by bending the main body 15 so as to protrude toward the anode side gas diffusion layer 23. These ribs 19 are in contact with the anode side gas diffusion layer 23. The tip surface 19a of the rib 19 in the protruding direction from the main body 15 is parallel to the anode side gas diffusion layer 23. A flow path 18 for flowing the fuel gas is formed between the plurality of ribs 19 in this separator 14 and between the separator 14 and the gas diffusion layer 23.

[0019] As shown in FIG. 3, the plurality of parallel ribs 19 are formed so as to converge with each other as they approach the hole 16 of the main body 15 in the separator 14. When the plurality of ribs 19 reach the hole 16, the flow path 18 between those ribs 19 is connected to the hole 16. The portions of the plurality of ribs 19 that are parallel to each other, more specifically, the tip surfaces 19a of the above-mentioned portions, are in contact with the gas diffusion layer 23 of the membrane electrode gas diffusion layer assembly 13 as described above. Further, the portions of the plurality of ribs 19 that converge with each other as they approach the hole 16, more specifically, the tip surfaces 19a of the above-mentioned portions, are in contact with the holding plate 12 as shown in FIG. 4. The holding plate 12 has a contact surface 12a that contacts the above-mentioned tip surface 19a.

[0020] The tip surface 19a of the rib 19 and the contact surface 12a of the retaining plate 12 are also joined to each other by adhesive. Therefore, the portion of the tip surface 19a of the rib 19 located between the hole 16 and the membrane electrode gas diffusion layer assembly 13, and the portion of the contact surface 12a of the retaining plate 12 that contacts the tip surface 19a of the rib 19 located between the hole 16 and the membrane electrode gas diffusion layer assembly 13 are joined to each other by adhesive. More specifically, on the tip surfaces 19a of the multiple ribs 19 in the protruding direction, the portion located between the hole 16 and the membrane electrode gas diffusion layer assembly 13 is formed by, for example, laser processing. Also, on the contact surface 12a of the retaining plate 12 that contacts the tip surface 19a, the portion located between the hole 16 and the membrane electrode gas diffusion layer assembly 13 is formed to accommodate the protrusion 24. These protrusions 24 and recesses 25 then form the uneven surface. These uneven surfaces are also joined together.

[0021] As shown in Figure 5, the protrusions 24 extend in a direction intersecting the direction in which the rib 19 extends. A protrusion 24 formed on the tip surface 19a of a designated rib 19 and a protrusion 24 formed on the tip surface 19a of another rib 19 located next to that rib 19 are located on the same straight line. In addition, each rib 19 has multiple protrusions 24 formed at predetermined intervals along the direction in which the rib 19 extends. As shown by the thick dashed lines in Figure 3, the distance between the multiple protrusions 24 decreases as they move away from the hole 16. A recess 25 for accommodating each protrusion 24 is formed at a position corresponding to each protrusion 24 of each rib 19 on the retaining plate 12.

[0022] <Effects of the fuel cell cell 11 in this embodiment> (1) The portion located between the hole 16 on the tip surface 19a of the rib 19 and the membrane electrode gas diffusion layer assembly 13, and the portion located between the hole 16 on the contact surface 12a of the holding plate 12 that contacts the tip surface 19a of the rib 19 and the membrane electrode gas diffusion layer assembly 13, are joined to each other by adhesive. However, in joining these portions, because multiple ribs 19 are formed to protrude from the main body 15 of the separator 14, the adhesive area between the portions to be joined tends to be small. As a result, the joint strength between the portions may decrease. To address this, uneven surfaces are formed on the portions to be joined to each other. Because uneven surfaces are formed on the portions to be joined to each other, the contact area at these portions can be increased. As a result, the decrease in joint strength between the portions due to the decrease in the contact area between the portions to be joined can be suppressed.

[0023] (2) The separator 14 is made of metal, and the retaining plate 12 is made of resin. Therefore, it is easy to form a protrusion 24 on the tip surface 19a of the rib 19 of the separator 14 by laser processing or the like, and it is easy to form a recess 25 on the contact surface 12a of the retaining plate 12 that contacts the tip surface 19a. Accordingly, it is easy to form an uneven surface with the protrusion 24 and the recess 25 on the tip surface 19a of the rib 19 at the location between the hole 16 and the membrane electrode gas diffusion layer assembly 13, and on the contact surface 12a of the retaining plate 12 that contacts the tip surface 19a at the location between the hole 16 and the membrane electrode gas diffusion layer assembly 13.

[0024] (3) If the formation of the protrusions 24 were to be achieved by using a mold to form the separator 14, the cost of the mold would be high. However, since the protrusions 24 are formed by laser processing, the high cost of the mold can be suppressed as described above. Also, when the protrusions 24 are formed by laser processing, the protrusions 24 do not necessarily protrude in an arc shape, and there is a high possibility that they will have a complex protrusion shape. In this case, the shape of the uneven surface formed by the protrusions 24 and the recesses 25 will also be complex, so the joint at that uneven surface will be stronger through the anchoring effect.

[0025] (4) The protrusions 24 extend in a direction intersecting the direction in which the rib 19 extends. Furthermore, the protrusions 24 formed on the tip surface 19a of a designated rib 19 and the protrusions 24 formed on the tip surface 19a of another rib 19 located next to the aforementioned rib 19 are located on the same straight line. This makes it easier to form these protrusions 24 by laser processing. In other words, when forming the protrusions 24 by laser processing, the movement of the laser head of the laser processing can be made linear, making it easier to form the protrusions 24.

[0026] (5) Multiple parallel ribs 19 are formed to converge towards each other as they approach the hole 16. As a result, the ratio of the tip surface 19a of the ribs 19 per unit area on the retaining plate 12 decreases as it moves away from the hole 16. Consequently, the bonding strength at the point where the tip surface 19a of the ribs 19 and the contact surface 12a of the retaining plate 12 are joined together between the hole 16 and the membrane electrode gas diffusion layer assembly 13 decreases as it moves away from the hole 16. However, the multiple protrusions 24 on the ribs 19 are spaced closer together as they move away from the hole 16. The bonding strength at the point where they are joined together is increased by the uneven surface created by the protrusions 24 and recesses 25. As a result, the decrease in bonding strength at the point where they are joined together as it moves away from the hole 16 is suppressed by the uneven surface created by the protrusions 24 and recesses 25.

[0027] The above embodiment can also be modified as follows, for example. The above embodiment and the following modifications can be combined and implemented to the extent that they do not contradict each other technically. The protrusions 24 may be arranged in multiple ribs 19 as shown in Figures 6 and 7.

[0028] As shown in Figures 8 to 10, the protrusion 24 may extend inclined with respect to the direction in which the rib 19 extends. As shown in Figures 9 and 10, among the multiple protrusions 24 formed on the ribs 19, certain protrusions 24 may extend in a different direction from the other protrusions 24. In this case, parallel movement between the separator 14 and the retaining plate 12 in multiple directions can be effectively suppressed by the protrusions 24 extending in different directions and the recesses 25 that accommodate these protrusions 24.

[0029] The protrusion 24 does not necessarily have to extend in a direction intersecting the direction in which the rib 19 extends. The protrusion 24 does not necessarily have to be formed by laser processing; for example, it may be formed by a mold for forming the separator 14.

[0030] The material used to form the separator 14 may be changed as appropriate. The relative positions of the convex portion 24 and the concave portion 25 may be reversed. [Explanation of Symbols]

[0031] 11… Fuel cell 12…Retaining plate 12a…Contact surface 13…Membrane electrode gas diffusion layer assembly 14... Separator 15…Main unit 16...hole 17...Sealing material 18…flow channel 19… Rib 19a…Tip surface 20...Electrolyte layer 21... Cathode electrode layer 22... Anode electrode layer 23…Gas diffusion layer 24…Convex part 25…recess

Claims

1. A fuel cell comprising a frame-shaped holding plate to which the outer edge of a membrane electrode gas diffusion layer assembly is joined, and a separator sandwiching the holding plate and the membrane electrode gas diffusion layer assembly from both sides in the thickness direction, wherein a flow path for gas flow is formed between the separator and the membrane electrode gas diffusion layer assembly, and holes are formed in the holding plate and the separator that penetrate them in the thickness direction, and the holes supply and discharge gas to the flow path, The separator is bonded to the retaining plate by adhesive, The separator has a plurality of ribs that protrude toward the holding plate and the membrane electrode gas diffusion layer assembly, The ribs are arranged in parallel to each other and extend to the holes. The flow path is formed between the plurality of ribs in the separator, A fuel cell in which an uneven surface is formed on the tip surfaces in the protruding direction of a plurality of ribs, located between the hole and the membrane electrode gas diffusion layer assembly, and on the contact surface of the holding plate that contacts the tip surface, located between the hole and the membrane electrode gas diffusion layer assembly.

2. The separator is made of metal, and the retaining plate is made of resin. A protrusion is formed on the tip surface of the multiple ribs in the protruding direction, at the location between the hole and the membrane electrode gas diffusion layer assembly. A recess is formed in the contact surface of the retaining plate that contacts the tip surface and is located between the hole and the membrane electrode gas diffusion layer assembly, in which the protrusion is accommodated. The fuel cell cell according to claim 1, wherein the uneven surface is formed by the convex portion and the concave portion.

3. The fuel cell cell according to claim 2, wherein the convex portion is formed by laser processing.

4. The aforementioned protrusion extends in a direction intersecting the direction in which the rib extends, The fuel cell cell according to claim 3, wherein the protrusion formed on the tip surface of a designated rib and the protrusion formed on the tip surface of another rib located adjacent to the rib are located on the same straight line.

5. The aforementioned protrusion extends in a direction intersecting the direction in which the rib extends, The fuel cell cell according to claim 3, wherein, among the multiple protrusions formed on the ribs, a designated protrusion extends in a different direction from the other protrusions.

6. The multiple parallel ribs are formed to converge towards each other as they approach the hole. The aforementioned protrusions are a plurality of protrusions formed at predetermined intervals along the direction in which the rib extends, The fuel cell cell according to any one of claims 2 to 5, wherein the distance between the multiple protrusions decreases as they move away from the hole.

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