Fuel battery

Abstract

To propose a technique for suppressing a decrease in a drainage rate of generated water in a fuel battery in which a throttle part having a small cross-sectional area is provided in a part of a gas flow path.SOLUTION: A fuel battery includes: a gas diffusion layer; a separator in contact with the gas diffusion layer and having a first concave part and a second concave part on a surface in contact with the gas diffusion layer; a first gas flow path surrounded by the first concave part and the gas diffusion layer; and a second gas flow path surrounded by the second concave part and the gas diffusion layer. The separator has a first wall surface of a wall surface of the first gas flow path and a second wall surface facing the first wall surface of the wall surface of the first gas flow path. A first protrusion part is provided on the first wall surface, a second protrusion part located downstream of the first protrusion part is provided on the second wall surface, a tip of the first protrusion part is disposed at a position closer to the second wall surface than a tip of the second protrusion part, and an interval between the first protrusion part and the second protrusion part is narrower than an interval between the first wall surface and the second wall surface.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a fuel cell. [Background technology]

[0002] Patent Document 1 discloses a fuel cell having a structure in which a membrane electrode gas diffusion layer assembly is sandwiched between two separators. The membrane electrode gas diffusion layer assembly has a structure in which a membrane electrode assembly is sandwiched between two gas diffusion layers. Each separator is in contact with a gas diffusion layer. A plurality of recesses are formed on the surface of each of the two separators facing the gas diffusion layer. A gas flow path through which gas flows is formed in the space surrounded by the gas diffusion layers and the recesses. The gas flow path has a constriction portion that partially reduces the cross-sectional area of ​​the flow path. In this fuel cell, hydrogen gas flows through the gas flow path of one separator. The hydrogen gas is supplied from the hydrogen gas flow path to the membrane electrode assembly via the gas diffusion layer. Air flows through the gas flow path of the other separator. The air is supplied from the air gas flow path to the membrane electrode assembly via the gas diffusion layer. Electricity is generated by the reaction of hydrogen and air (i.e., oxygen) in the membrane electrode assembly. The constriction portion in the gas flow path facilitates the flow of each gas to the membrane electrode assembly via the gas diffusion layer, resulting in efficient power generation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-59439 Summary of the Invention [Problem to be solved by the invention]

[0004] Furthermore, when hydrogen reacts with air, water (hereinafter referred to as "produced water") is produced inside the membrane electrode assembly. The produced water is discharged from the membrane electrode assembly to the outside of the fuel cell via the gas flow path. In the technology of Patent Document 1, the cross-sectional area of ​​the gas flow path is small at the throttle section, so the rate at which the produced water is discharged is low. In this specification, a decrease in the rate at which the produced water is discharged is suppressed in a fuel cell in which a throttle section with a small cross-sectional area is provided in part of the gas flow path. [Means for solving the problem]

[0005] (Aspect 1) The fuel cell disclosed in this specification comprises a gas diffusion layer, a separator in contact with the gas diffusion layer and having a first recess and a second recess extending along the first recess on the surface in contact with the gas diffusion layer, a first gas flow path surrounded by the first recess and the gas diffusion layer, and a second gas flow path surrounded by the second recess and the gas diffusion layer, wherein the separator has a first wall surface among the walls of the first gas flow path and a second wall surface among the walls of the first gas flow path facing the first wall surface, a first convex portion is provided on the first wall surface, and a second convex portion is provided on the second wall surface and located downstream of the first convex portion, a tip of the first convex portion is positioned closer to the second wall surface than a tip of the second convex portion, and the distance between the first convex portion and the second convex portion is narrower than the distance between the first wall surface and the second wall surface.

[0006] In the above fuel cell, the flow path is curved between the first and second convex portions, allowing for a longer flow path length than if the flow path were not curved. Therefore, even if the flow path cross-sectional area between the first and second convex portions is relatively wide, the resistance to gas flow can be increased, improving power generation efficiency. Furthermore, because the flow path cross-sectional area can be relatively wide between the first and second convex portions, a decrease in the drainage rate of the generated water can be suppressed. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a plan view of a fuel cell. [Figure 2] 2 is a cross-sectional view taken along the line AA in FIG. 1. [Figure 3] FIG. 2 is a plan view of an air gas flow path of a fuel cell.

[0008] Fuel cells are mounted, for example, in fuel cell vehicles that use the fuel cell as a power source. As shown in FIGS. 1 and 2, the fuel cell has a plate-shaped cell 10. In the following description, the thickness direction of the cell 10 is referred to as the z-direction, a direction along the surface of the cell 10 is referred to as the x-direction, and a direction along the surface of the cell 10 and perpendicular to the x-direction is referred to as the y-direction. The cell 10 has a membrane electrode assembly 12, gas diffusion layers 14 and 16, a separator 20, and a separator 22. The membrane electrode assembly 12 reacts hydrogen and oxygen to generate electricity. Although not shown, the membrane electrode assembly 12 has a structure in which an electrolyte membrane is sandwiched between two electrode layers.

[0009] The gas diffusion layers 14 and 16 are made of, for example, carbon fiber. The membrane electrode assembly 12 is sandwiched between the gas diffusion layer 14 and the gas diffusion layer 16. That is, the gas diffusion layer 14 is in contact with one surface of the membrane electrode assembly 12. The gas diffusion layer 16 is in contact with the other surface of the membrane electrode assembly 12.

[0010] The separators 20 and 22 are made of a gas-impermeable conductive material. For example, metal materials such as stainless steel or carbon materials can be used as materials for the separators 20 and 22. The membrane electrode assembly 12 and gas diffusion layers 14 and 16 are sandwiched between the separators 20 and 22. The separator 20 is in contact with the surface of the gas diffusion layer 14. The separator 22 is in contact with the surface of the gas diffusion layer 16.

[0011] The separator 20 is bent, thereby forming a plurality of recesses 24 on the surface of the separator 20 facing the gas diffusion layer 14. The spaces surrounded by the recesses 24 and the gas diffusion layer 14 form air gas channels 30. The air gas channels 30 are spaced apart in the y direction and extend parallel to one another in the x direction. The separator 20 is provided with an air supply port 60 and an air outlet 62. Air flows from the air supply port 60 through each air gas channel 30 to the air outlet 62. The air flowing through each air gas channel 30 is supplied to the membrane electrode assembly 12 via the gas diffusion layer 14.

[0012] Because the separator 22 is bent, multiple recesses 26 are formed on the surface of the separator 22 facing the gas diffusion layer 16. A hydrogen gas flow path 40 is formed by the space surrounded by each recess 26 and the gas diffusion layer 16. The multiple hydrogen gas flow paths 40 are arranged at intervals in the y direction and extend parallel to each other in the x direction. The separator 22 is also provided with a hydrogen gas supply port and a hydrogen gas discharge port. Hydrogen gas flows from the hydrogen gas supply port through each hydrogen gas flow path 40 to the hydrogen gas discharge port. The hydrogen gas flowing through each hydrogen gas flow path 40 is supplied to the membrane electrode assembly 12 via the gas diffusion layer 16.

[0013] In the membrane electrode assembly 12, electricity is generated by reacting the air supplied from each air gas flow path 30 with the hydrogen gas supplied from each hydrogen gas flow path 40. As a result of this reaction, water is produced within the membrane electrode assembly 12 (hereinafter referred to as "produced water"). The produced water is discharged to the outside of the fuel cell via the air gas flow path 30 by the pressure of the air flowing through the air gas flow path 30.

[0014] Next, the structure inside the air gas flow path 30 will be described. Since the structure inside each air gas flow path 30 is the same, the structure inside each of the adjacent air gas flow paths 30a and 30b will be described below. The arrows in Figure 3 indicate the direction of air flow.

[0015] As shown in FIG. 2, the separator 20 has wall surfaces 32 and 34 as the wall surfaces of the air gas flow path 30. The wall surface 32 faces the wall surface 34. Hereinafter, the wall surfaces 32 and 34 of the air gas flow path 30a will be referred to as wall surfaces 32a and 34a, and the wall surfaces 32 and 34 of the air gas flow path 30b will be referred to as wall surfaces 32b and 34b. As shown in FIG. 3, each air gas flow path 30 is provided with a plurality of throttle portions 50. Hereinafter, the throttle portion 50 of the air gas flow path 30a will be referred to as throttle portion 50a, and the throttle portion 50 of the air gas flow path 30b will be referred to as throttle portion 50b. Each throttle portion 50 has a protrusion 52 and a protrusion 54. The protrusion 52 is provided on the wall surface 32 and protrudes toward the wall surface 34. The protrusion 54 is provided on the wall surface 34 and protrudes toward the wall surface 32. In each throttle section 50, the convex section 54 is provided upstream of the convex section 52. The tip surface 70 of the convex section 52 is located closer to the wall surface 34 than the center of the air gas flow path 30. The tip surface 70 of the convex section 54 is located closer to the wall surface 32 than the center of the air gas flow path 30. That is, in each throttle section 50, the tip surface 70 of the convex section 54 is located closer to the wall surface 34 than the tip surface 74 of the convex section 52. Therefore, the convex sections 52 and 54 overlap at the center of each air gas flow path 30. Therefore, the side surface of the convex section 52 faces the side surface of the convex section 54. Therefore, the flow path shape of the throttle section 50 is curved (i.e., crank-shaped). The distance between the side surface of the convex section 52 and the side surface of the convex section 54 is narrower than the distance between the wall surface 32 and the wall surface 34. Therefore, the width of the air gas flow path 30 is narrower at the throttle section 50. That is, the resistance of the air gas flow path 30 is greater at the throttle portion 50 than at other portions.

[0016] The throttle section 50b is positioned at a position offset in the x direction relative to the throttle section 50a. That is, no throttle section 50b is provided adjacent to the throttle section 50a in the y direction. Therefore, the pressure in the air gas flow channel 30 is higher upstream of the throttle section 50 than downstream of the throttle section 50. Therefore, a pressure difference occurs between the air gas flow channel 30a and the air gas flow channel 30b at a position where the upstream section of the throttle section 50a and the downstream section of the throttle section 50b are adjacent in the y direction. Due to the pressure difference between the air gas flow channels, air flows from the air gas flow channel 30a to the air gas flow channel 30b via the gas diffusion layer 14, as indicated by arrow 100. Similarly, at a position where the downstream section of the throttle section 50a and the upstream section of the throttle section 50b are adjacent in the y direction, air flows from the air gas flow channel 30b to the air gas flow channel 30a via the gas diffusion layer 14, as indicated by arrow 102. At this time, a portion of the air passing through the gas diffusion layer 14 is supplied to the membrane electrode assembly 12. This increases the power generation efficiency of the fuel cell.

[0017] As described above, the throttle section 50 has a crank-shaped flow path, which allows the gas flow path to be long in the throttle section 50. Therefore, even if the cross-sectional area of ​​the flow path in the throttle section 50 is not made very small, the gas flow resistance in the throttle section 50a is high. As a result, the air flowing through the air / gas flow path 30 is easily supplied to the gas diffusion layer 14. This improves the power generation efficiency of the fuel cell. Furthermore, with this structure of the throttle section 50, the cross-sectional area of ​​the flow path in the throttle section 50 can be made relatively large, which prevents a decrease in the drainage speed of the produced water flowing through the air / gas flow path 30.

[0018] In the above-described embodiment, the tip end surface of the convex portion 52 is flat, but the tip end surface of the convex portion 52 may have a curved shape as shown in Fig. 3. In this case, the flow path shape of the throttle portion 50 becomes a curved shape (for example, an S-shape).

[0019] In the above-described embodiment, two convex portions are provided in each throttle portion 50. However, as shown in Fig. 3, two or more convex portions may be provided in each throttle portion 50. In the example of Fig. 3, the flow path shape of the throttle portion 50 is a dogleg shape.

[0020] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0021] 10: Cell 12: Membrane electrode assembly 14: Gas diffusion layer 20: Separator 24: Recess 30a: Air gas flow path 30b: Air gas flow path 50a: Constriction section 50b: Constriction section 52: Convex part 54: Convex part

Claims

[Claim 1] A fuel cell, a gas diffusion layer; a separator in contact with the gas diffusion layer, the separator having a first recess and a second recess extending along the first recess on the surface in contact with the gas diffusion layer; a first gas flow path surrounded by the first recess and the gas diffusion layer; a second gas flow path surrounded by the second recess and the gas diffusion layer; and The separator is a first wall surface of the first gas flow path; a second wall surface of the first gas flow path facing the first wall surface; and a first protrusion is provided on the first wall surface, a second protrusion located downstream of the first protrusion is provided on the second wall surface, a tip of the first protrusion is disposed at a position closer to the second wall surface than a tip of the second protrusion, a distance between the first convex portion and the second convex portion is narrower than a distance between the first wall surface and the second wall surface; fuel cell.

Images