Fuel cell and fuel cell stack comprising the same

1. A fuel cell comprising:

a membrane electrode assembly having an anode, a cathode and a polymer electrolyte membrane disposed between said anode and said cathode;

an anode-side separator and a cathode-side separator that sandwich said membrane electrode assembly and face to each other;

a cooling fluid channel for supplying and exhausting a cooling fluid for cooling said membrane electrode assembly which is formed in at least one of said anode-side separator and said cathode-side separator;

a fuel gas channel for supplying and exhausting a fuel gas serving as a reaction gas to said membrane electrode assembly which is formed in said anode-side separator;

an oxidant gas channel for supplying and exhausting an oxidant gas serving as a reaction gas to said membrane electrode assembly which is formed in said cathode-side separator;

an anode-side gasket for sealing said reaction gas which is disposed in the outer portion of said membrane electrode assembly and on the main surface of said anode-side separator facing said membrane electrode assembly; and

a cathode-side gasket for sealing said reaction gas which is disposed in the outer portion of said membrane electrode assembly and on the main surface of said cathode-side separator facing said membrane electrode assembly such that said cathode-side gasket faces to said anode-side gasket;

wherein said cooling fluid channel, said fuel gas channel and said oxidant gas channel are formed such that their main portions are substantially parallel to each other;

an upstream portion of said cooling fluid channel of at least one of said anode-side separator and said cathode-side separator is formed such that it includes at least one of a region corresponding to an anode-side gap formed between said anode-side gasket and said membrane electrode assembly and a region corresponding to a cathode-side gap formed between said cathode-side gasket and said membrane electrode assembly, and said upstream portion of said cooling fluid channel is formed such that it includes a region corresponding to a middle stream portion and a subsequent portion of at least one of said fuel gas channel and said oxidant gas channel,

said upstream portion of said cooling fluid channel, said anode-side gap, said cathode-side gap, said middle stream portion and said subsequent portion are arranged to allow water vapor contained in said reaction gas that flows into said anode-side gap and water vapor contained in said reaction gas that flows into said cathode-side gap to condense in at least a part of said anode-side gap and said cathode-side gap, and to allow the condensed water to fill at least one of said anode-side gap and said cathode-side gap,

said cooling fluid channel, said fuel gas channel and said oxidant gas channel each have a serpentine structure, and

the upstream portion of the cooling fluid channel is a portion extending from an end of the cooling fluid channel connecting to a manifold aperture for supplying cooling fluid to a position that satisfies the equation: L 1 ≦L 2 ,

where: L 1 represents a length of the upstream portion of the cooling fluid channel, and

L 2 represents the total length of the anode-side gap in the case where the anode-side gap is a gas channel when the cooling fluid channel is formed in the anode-side separator, or the total length of the cathode-side gap in the case where the cathode-side gap is a gas channel when the cooling fluid channel is formed in the cathode-side separator.

2. The fuel cell in accordance with claim 1 ,

wherein said polymer electrolyte membrane has a larger main surface than main surfaces of said anode and said cathode, and entire periphery of the main surface of said polymer electrolyte membrane extends outwardly beyond a periphery of main surface of said anode and a periphery of main surface of said cathode,

said anode-side gasket and said cathode-side gasket are disposed between said anode-side separator and said cathode-side separator such that said anode-side gasket and said cathode-side gasket face to each other and they sandwich the entire periphery of said polymer electrolyte membrane;

said anode-side gap comprises a space including said polymer electrolyte membrane, said anode-side gasket, said anode-side separator and an end face of said anode; and

said cathode-side gap comprises a space including said polymer electrolyte membrane, said cathode-side gasket, said cathode-side separator and an end face of said cathode.

3. The fuel cell in accordance with claim 1 ,

wherein said upstream portion of said cooling fluid channel of said anode-side separator is formed in a region corresponding to said anode-side gap so that said water vapor of said reaction gas that flows into said anode-side gap is condensed and said cathode-side gap is filled with the condensed water.

4. The fuel cell in accordance with claim 1 ,

wherein said upstream portions of said cooling fluid channels of said anode-side separator and said cathode-side separator are formed such that they include at least one of said region corresponding to said anode-side gap and said region corresponding to said cathode-side gap, and

said upstream portions of said cooling fluid channels are formed such that they include a region corresponding to a middle stream portion and subsequent portion of at least one of said fuel gas channel and said oxidant gas channel.

5. The fuel cell in accordance with claim 1 ,

wherein said anode-side gasket and said cathode-side gasket are continuous circular members,

in said anode-side separator and said cathode-side separator, a manifold aperture for supplying cooling fluid and a manifold aperture for exhausting cooling fluid connected by said cooling fluid channel are formed on the outside of said anode-side gasket and said cathode-side gasket, and

said anode-side gap and said cathode-side gap each have a first route and a second route longer than said first route.

6. The fuel cell in accordance with claim 5 ,

wherein said upstream portion of said cooling fluid channel of at least one of said anode-side separator and said cathode-side separator is formed in a region corresponding to said first route of said anode-side gap and said cathode-side gap.

7. The fuel cell in accordance with claim 5 ,

wherein said upstream portion of said cooling fluid channel of at least one of said anode-side separator and said cathode-side separator is formed in a region corresponding to said second route of said anode-side gap and said cathode-side gap.

8. The fuel cell in accordance with claim

wherein said upstream portion of said cooling fluid channel of at least one of said anode-side separator and said cathode-side separator and a downstream portion of said gas channel are formed such that they correspond to each other.

9. A fuel cell stack comprising a plurality of fuel cells stacked,

wherein at least one fuel cell according to claim 1 is incorporated into said fuel cell stack as a fuel cell.

10. The fuel cell in accordance with claim 1 , wherein the middle stream portion and subsequent portion of at least one of the fuel gas channel and the oxidant gas channel, is a portion extending from an end of the gas channel connecting to a manifold aperture for exhausting reaction gas to a position that satisfies the equation: L 3 ≦{(⅔)×L 4 },

where: L 3 represents the length of the middle stream portion and subsequent portion, and

L 4 represents the length of the fuel gas channel or the oxidant gas channel.