Patent ID: 8691471

Claim:
A polymer electrolyte fuel cell comprising: a membrane-electrode assembly including a polymer electrolyte membrane and electrodes including a first electrode and a second electrode and sandwiching a portion of the polymer electrolyte membrane which is inward relative to a peripheral portion of the polymer electrolyte membrane; an electrically-conductive first separator which is of a plate shape and is provided in contact with the first electrode of the membrane-electrode assembly; and an electrically-conductive second separator which is of a plate shape and is provided in contact with the second electrode of the membrane-electrode assembly, wherein: the first separator is provided with a first reaction gas channel on one main surface of the first separator which contacts the first electrode such that a plurality of first rib portions run along each other, the second separator is provided with a second reaction gas channel on one main surface of the second separator which contacts the second electrode such that a plurality of second rib portions run along each other, the electrodes include catalyst layers disposed on main surfaces of the polymer electrolyte membrane, respectively, the first reaction gas channel includes an upstream portion and a downstream portion, the upstream portion being a predetermined length portion extending from a meeting point where the first reaction gas channel first contacts the first electrode from an upstream end of the first reaction gas channel toward a downstream side, and the downstream portion being a remaining portion of the first reaction gas channel other than the upstream portion, an overlap ratio of the first reaction gas channel to the plurality of second rib portions in the upstream portion is set larger that an overlap ratio of the first reaction gas channel to the plurality of second rib portions in the downstream portion, the overlap ratio of the first reaction gas channel to the plurality of second rib portions being a ratio of a width of the first reaction gas channel overlapping with one or more of the plurality of the second rib portions to an entire width of the first reaction gas channel, when viewed in a thickness direction of the first separator, the first reaction gas channel includes reciprocating portions and inverted portions connecting adjacent reciprocating portions, and the upstream portion of the first reaction gas channel extends from the meeting point to a most upstream inverted portion and includes a most upstream reciprocating portion.