BACKGROUND

1. Technical Field

The present disclosure relates to a fuel cell.

2. Description of Related Art

In the related art, a disclosure related to a fuel cell module is known (refer to Japanese Unexamined Patent Application Publication No. 2017-117780 (JP 2017-117780 A)). An object of the fuel cell module described in JP 2017-117780 A is to suppress an excessive increase in the thickness of the fuel cell module in a stacking direction of unit cells. The unit cell includes a frame member disposed to surround the outer periphery of a membrane electrode gas diffusion layer assembly (MEGA), and two separators.

The frame member includes a manifold opening that communicates with manifold holes provided in the two separators, an in-plane opening in which the MEGA is disposed, and a slit-shaped first through-hole as a reaction gas flow path provided between the manifold opening and the in-plane opening.

In one of the two separators, in a plan view, a recessed portion is formed at a position on a line that passes through the center of the first through-hole along the minor axis direction of the first through-hole of the frame member. The width of the bottom surface of the recessed portion measured along the major axis direction of the first through-hole is smaller than the width of the first through-hole measured along the major axis direction. A seal member is disposed in the recessed portion.

In the fuel cell module of the related art, the seal member for sealing a gap between the unit cells is disposed in the recessed portion of the separator. Therefore, the thickness of the fuel cell module in the stacking direction of the unit cells is decreased by the depth of the recessed portion, and an excessive increase in the thickness of the fuel cell module in the stacking direction can be suppressed.

SUMMARY

In the fuel cell module of the related art, for example, the unit cell is manufactured by sandwiching the MEGA and the frame member between a pair of separators to form a stacked body, and integrating the stacked body by heat pressing. There is a possibility that the frame member made of a resin may be melted by the heat pressing and the melted resin mentioned above may flow into the slit-shaped first through-hole as the reaction gas flow path formed between the manifold opening and the in-plane opening. When the resin flows into the first through-hole and the opening size of the first through-hole decreases, there is a possibility that the pressure loss of a reaction gas may increase and the supply of the reaction gas may become nonuniform.

The present disclosure provides a fuel cell capable of suppressing an increase in the pressure loss of a reaction gas and thus uniformly supplying the reaction gas.

An aspect of the disclosure relates to a fuel cell including a membrane electrode gas diffusion layer assembly, a frame member which surrounds the membrane electrode gas diffusion layer assembly, and a pair of separators with the frame member and the membrane electrode gas diffusion layer assembly sandwiched therebetween. The separators include a manifold hole through which a reaction gas is supplied or discharged. The frame member includes a manifold opening which communicates with the manifold hole, an in-plane opening in which the membrane electrode gas diffusion layer assembly is disposed, a gas flow path which communicates with the in-plane opening and the manifold opening, a seal portion which is welded to the separators around the gas flow path, and an accommodation portion which is provided between the seal portion and the gas flow path to accommodate a material of the frame member caused to flow by welding.

In order to construct the fuel cell according to the aspect of the disclosure, first, the membrane electrode gas diffusion layer assembly is disposed in the in-plane opening of the frame member, and the frame member and the membrane electrode gas diffusion layer assembly are disposed between the separators, thereby forming a stacked body. The stacked body is placed between molds, and a portion of the frame member is melted by performing heat pressing through which heat is applied while a pressure is applied, so that the frame member and the separators are welded together. As described above, the seal portion welded to the separators is formed in the frame member around the gas flow path. At this time, there may be cases where a portion of the material of the frame member is heated and melted between the separators and is caused to flow from the seal portion toward the gas flow path by pressurization.

Here, as described above, the frame member of the fuel cell according to the aspect of the disclosure includes the accommodation portion which is provided between the seal portion and the gas flow path to accommodate the material of the frame member caused to flow by welding. Therefore, even if a portion of the material of the frame member is melted and caused to flow from the seal portion toward the gas flow paths by welding, the portion of the material is accommodated by the accommodation portion. As described above, a blockage in the gas flow path by the material of the frame member caused to flow by the welding can be suppressed, and a decrease in the opening size of the gas flow path can be suppressed. Therefore, with the fuel cell of the aspect of the disclosure, an increase in the pressure loss of the reaction gas is suppressed, so that the reaction gas can be uniformly supplied.

In the fuel cell according to the aspect, the gas flow path and the accommodation portion may be slit-shaped through-holes. As described above, the accommodation portion can act as a dummy gas flow path which receives the material of the frame member caused to flow by the welding instead of the gas flow path which is narrow in width and is easily blocked. Therefore, a blockage in the gas flow path by the material of the frame member can be more effectively suppressed. In a process of forming the gas flow path in the frame member, the accommodation portion can be formed similar to the gas flow path.

In the fuel cell according to the aspect, a first end of the accommodation portion may communicate with the manifold opening. For example, there may be cases where moisture generated by a reaction between a fuel gas and an oxidant gas may infiltrate into the accommodation portion via slight gaps between the frame member and the separators which abut each other. Even in this case, when the first end of the accommodation portion communicates with the manifold opening, the moisture infiltrated into the accommodation portion is discharged toward the manifold opening, so that accumulation of water in the accommodation portion can be suppressed.

In the fuel cell according to the aspect, the gas flow path and the accommodation portion may have a slit extending from the manifold opening toward the in-plane opening, and a length of the accommodation portion in a first extension direction in which the accommodation portion extends is shorter than a length of the gas flow path in a second extension direction in which the gas flow path extends. As described above, the sealability between the fuel cells can be improved by increasing the contact area between the frame member and the separators.

In the fuel cell according to the aspect, in a third direction intersecting the second extension direction of the gas flow path, an interval d between the gas flow paths adjacent to each other is the same as a width of the gas flow path. As described above, the sealability between the frame member and the separators or the sealability between the stacked fuel cells can be improved by stabilizing the contact between the frame member and the separators.

In the fuel cell according to the aspect, in the third direction intersecting the second extension direction of the gas flow path, the width of the gas flow path is the same as a width of the accommodation portion. As described above, the sealability between the frame member and the separators or the sealability between the stacked fuel cells can be improved by stabilizing the contact between the frame member and the separators.

According to the aspect of the disclosure, it is possible to provide a fuel cell capable of uniformly supplying a reaction gas by suppressing an increase in the pressure loss of the reaction gas.

