1. Field
The present disclosure relates to a fuel cell.
2. Description of the Related Art
For example, a solid polymer electrolyte fuel cell includes a membrane electrode assembly (MEA), which includes a solid polymer electrolyte membrane and an anode electrode and a cathode electrode sandwiching the solid polymer electrolyte membrane therebetween. The solid polymer electrolyte membrane is made from a polymer ion-exchange membrane. The membrane electrode assembly and separators that sandwich the membrane electrode assembly therebetween constitute a power generation cell (unit cell). In fuel cells, ordinarily, a few tens of to a few hundred power generation cells are stacked, and used as, for example, a vehicle fuel cell stack.
For supplying a fuel gas and an oxidant gas, which are reactive gases, to an anode electrode and a cathode electrode of each of power generation cells that are stacked, fuel cells often have a so-called internal manifold structure.
Fuel cells having an internal manifold structure include reactive gas inlet manifolds (a fuel gas inlet manifold and an oxidant gas inlet manifold) and reactive gas outlet manifolds (a fuel gas outlet manifold and an oxidant gas outlet manifold). These manifolds extend through the fuel cells in a stacking direction thereof. The reactive gas inlet manifolds and the reactive gas outlet manifolds are connected to reactive gas channels (a fuel gas channel and an oxidant gas channel) for supplying a reactive gas along electrode surfaces. An inlet side and an outlet side of each reactive gas channel are connected to the corresponding reactive gas inlet manifold and to the corresponding reactive gas outlet manifold, respectively.
In this case, an opening area of each reactive gas inlet manifold and an opening area of each reactive gas outlet manifold are relatively small. Therefore, in order to cause smooth flow of the reactive gas over entire electrode reaction surfaces, a buffer that disperses the reactive gas needs to be provided in the vicinity of each reactive gas inlet manifold and each reactive gas outlet manifold.
For making it possible to uniformly and reliably supply a reactive gas over an entire reactive gas channel from a reactive gas inlet manifold via a buffer, for example, a fuel cell that is disclosed in Japanese Unexamined Patent Application Publication No. 2012-164467 is known. In this fuel cell, one of surfaces of a separator is provided with a first buffer through which a first reactive gas manifold is connected to a first reactive gas channel. In addition, the other surface of the separator is provided with a second buffer through which a second reactive gas manifold is connected to a second reactive gas channel.
The first buffer includes a first dedicated buffer region that is adjacent to the first reactive gas manifold and allows one of reactive gases to flow, and that restricts a flow of the other reactive gas at a side of the second buffer. The second buffer includes a second dedicated buffer region that is adjacent to the second reactive gas manifold and allows the other reactive gas to flow, and that restricts the flow of the one of the reactive gases at a side of the first buffer.
Here, the first buffer and the second buffer include a common buffer region that allows the one of the reactive gases and the other of the reactive gases to flow. Further, the depth of the first dedicated buffer region and the depth of the second dedicated buffer region are greater than the depth of the common buffer region.
This makes it possible to uniformly and reliably supply the corresponding reactive gas from the first reactive gas manifold to the entire first reactive gas channel via the first buffer, and the corresponding reactive gas from the second reactive gas manifold to the entire second reactive gas channel via the second buffer.