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A highly reliable polymer electrolyte fuel cell includes an anode-side separator plate and a cathode-side separator plate that are provided with an anode-side sealing member and a cathode-side sealing member, respectively. The anode-side and cathode-side sealing members seal the cell in cooperation

A highly reliable polymer electrolyte fuel cell includes an anode-side separator plate and a cathode-side separator plate that are provided with an anode-side sealing member and a cathode-side sealing member, respectively. The anode-side and cathode-side sealing members seal the cell in cooperation with a polymer electrolyte membrane at sealing parts where the anode-side and cathode-side sealing members are opposed to each other, thereby preventing gas from leaking out of gas flow channels. One of the anode-side and cathode-side sealing members has a pointed rib that comes in contact with the sealing parts in a linear manner, and the other sealing member comes in contact with the sealing parts surface to surface.

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What is claimed is: 1. A polymer electrolyte fuel cell comprising: a membrane electrode assembly forming a cell comprising a hydrogen-ion conductive polymer electrolyte membrane and an anode and a cathode sandwiching said polymer electrolyte membrane, each of said anode and said cathode being posit

What is claimed is: 1. A polymer electrolyte fuel cell comprising: a membrane electrode assembly forming a cell comprising a hydrogen-ion conductive polymer electrolyte membrane and an anode and a cathode sandwiching said polymer electrolyte membrane, each of said anode and said cathode being positioned in a substantially central part of said polymer electrolyte membrane; an anode-side separator plate having a pair of fuel gas manifold apertures, a pair of oxidant gas manifold apertures, and a fuel gas flow channel connected to said pair of fuel gas manifold apertures for supplying and discharging a fuel gas to and from the anode; a cathode-side separator plate having a pair of fuel gas manifold apertures, a pair of oxidant gas manifold apertures, and an oxidant gas flow channel connected to said pair of oxidant gas manifold apertures for supplying and discharging an oxidant gas to and from the cathode; an anode-side sealing member provided on the anode-side surface of said anode-side separator plate; and a cathode-side sealing member provided on the cathode-side surface of said cathode-side separator plate, wherein: said membrane electrode assembly is sandwiched under pressure between said anode-side and cathode-side separator plates to form said cell, said anode-side sealing member and said cathode-side sealing member seal the cell, in cooperation with the polymer electrolyte membrane, at sealing parts where the anode-side and cathode-side sealing members are opposed to each other, to prevent the fuel gas and the oxidant gas from leaking out of said fuel gas flow channel and said oxidant gas flow channel, said fuel gas flow channel being positioned in a substantially central part of the separator plate, said pair of fuel gas manifold apertures and said pair of oxidant gas manifold apertures being positioned in outer parts of the separator plate relative to said fuel gas flow channel, said oxidant gas flow channel being positioned in a substantially central part of the separator plate, said pair of fuel gas manifold apertures and said pair of oxidant gas manifold apertures being positioned in outer parts of the separator plate relative to said oxidant gas flow channel, said polymer electrolyte membrane is large enough to cover the anode and the cathode but the edge of said polymer electrolyte membrane does not reach said fuel and oxidant gas manifold apertures, said anode-side sealing member has a first anode-side sealing section that surrounds the anode and the fuel gas manifold apertures to form a closed loop and a second anode-side sealing section that surrounds said polymer electrolyte membrane in combination with said first anode-side sealing section, said first anode-side sealing section being in contact with said polymer electrolyte membrane at the part surrounding the anode, said cathode-side sealing member has a first cathode-side sealing section that surrounds the cathode and the oxidant gas manifold apertures to form a closed loop and a second cathode-side sealing section that surrounds said polymer electrolyte membrane in combination with said first cathode-side sealing section, said first cathode-side sealing section being in contact with said polymer electrolyte membrane at the part surrounding the cathode, said anode-side and cathode-side sealing sections substantially correspond in position, and said anode-side and cathode-side sealing members are sandwiched between said anode-side and cathode-side separator plates and pressed against each other or the polymer electrolyte membrane at the respective sealing sections, and at the pressed parts, one of said sealing members has a pointed rib that comes in contact with said polymer electrolyte membrane or the other sealing member in a linear manner, and the other sealing member comes in contact with said polymer electrolyte membrane or said one sealing member surface to surface. 2. The polymer electrolyte fuel cell in accordance with claim 1, wherein said one of the sealing members is so configured that the height of the rib at the part of the first sealing section not in contact with said polymer electrolyte membrane and the height of the rib at the second sealing section are greater than the height of the rib at the part of the first sealing section in contact with said polymer electrolyte membrane. 3. The polymer electrolyte fuel cell of claim 2, wherein the height of the rib at the part of the first sealing section that is in contact with the polymer electrolyte membrane is greater than the height of the rib at the part of the first sealing section not in contact with the polymer electrolyte membrane by approximately the thickness of the polymer electrolyte membrane or more. 4. The polymer electrolyte fuel cell in accordance with claim 1, wherein the ratio of pressure loss Pc in the clearance between the electrode and the sealing members to pressure loss Pf in the gas flow channel adjacent to the electrode is greater than 0.9. 5. The polymer electrolyte fuel cell in accordance with claim 1 wherein at least one of the anode-side and cathode separator plates has a main surface covered with the corresponding sealing member. 6. The polymer electrolyte fuel cell in accordance with claim 1, wherein at least one of the anode-side and cathode-side sealing members is molded on the corresponding separator plate. 7. The polymer electrolyte fuel cell in accordance with claim 1, wherein at least one of the anode-side and cathode-side sealing members is fitted to the corresponding separator plate. 8. The polymer electrolyte fuel cell in accordance with claim 1, wherein at least one of the anode-side and cathode-side sealing members is bonded to the corresponding separator plate. 9. The polymer electrolyte fuel cell in accordance with claim 1, wherein: the first anode-side sealing section includes: an electrode sealing part mostly surrounding the fuel gas flow channel, manifold aperture sealing parts surrounding the outer half of the fuel gas manifold apertures, and sealing parts located on both sides of each of connection grooves connecting the fuel gas manifold apertures to the fuel gas flow channel; the first cathode-side sealing section includes: an electrode sealing part mostly surrounding the oxidant gas flow channel, manifold aperture sealing parts surrounding the outer half of the oxidant gas manifold apertures, and sealing parts located on both sides of each of connection grooves connecting the oxidant gas manifold apertures to the oxidant gas flow channel; and said anode-side and cathode-side sealing sections correspond in position except: the sealing parts of the anode-side sealing section located on both sides of each of the connection grooves connecting the fuel gas manifold apertures to the fuel gas flow channel; the parts of the anode-side sealing section located between the oxidant gas manifold apertures and the fuel gas flow channel; the sealing parts of the cathode-side sealing section located on both sides of each of the connection grooves connecting the oxidant gas manifold apertures to the oxidant gas flow channel; and the parts of the cathode-side sealing section located between the fuel gas manifold apertures and the oxidant gas flow channel. 10. A polymer electrolyte fuel cell comprising: a membrane electrode assembly forming a cell comprising a hydrogen-ion conductive polymer electrolyte membrane and an anode and a cathode sandwiching said polymer electrolyte membrane, each of said anode and said cathode being positioned in a substantially central part of said polymer electrolyte membrane; an anode-side separator plate having a pair of fuel gas manifold apertures, a pair of oxidant gas manifold apertures, and a fuel gas flow channel connected to said pair of fuel gas manifold apertures for supplying and discharging a fuel gas to and from the anode; a cathode-side separator plate having a pair of fuel gas manifold apertures, a pair of oxidant gas manifold apertures, and an oxidant gas flow channel connected to said pair of oxidant gas manifold apertures for supplying and discharging an oxidant gas to and from the cathode; an anode-side sealing member provided on the anode-side surface of said anode-side separator plate; and a cathode-side sealing member provided on the cathode-side surface of said cathode-side separator plate, wherein: said membrane electrode assembly being sandwiched under pressure between said anode-side and cathode-side separator plates to form said cell, said anode-side sealing member and said cathode-side sealing member seal the cell, in cooperation with the polymer electrolyte membrane, at sealing parts where the anode-side and cathode-side sealing members are opposed to each other, to prevent the fuel gas and the oxidant gas from leaking out of said fuel gas flow channel and said oxidant gas flow channel, said fuel gas flow channel being positioned in a substantially central part of the separator plate, said pair of fuel gas manifold apertures and said pair of oxidant gas manifold apertures being positioned in outer parts of the separator plate relative to said fuel gas flow channel, said oxidant gas flow channel being positioned in a substantially central part of the separator plate, said pair of fuel gas manifold apertures and said pair of oxidant gas manifold apertures being positioned in outer parts of the separator plate relative to said oxidant gas flow channel, one of said sealing members has a pointed rib that contacts said sealing parts in a linear manner, and the other of said sealing members contacts said sealing parts surface-to-surface, said anode-side sealing member includes a part surrounding said anode and said cathode sealing member includes a part surrounding said cathode, the rib of said one of the sealing members is, at said anode or cathode surrounding part, shaped like a wedge of which cross section is thin on the inner side and thick on the outer side, and the wedge-shaped rib is provided along the edge of the electrode so that the electrode is surrounded by the wedge-shaped rib. 11. The polymer electrolyte fuel cell in accordance with claim 10, wherein one-side clearance cl between said cathode and said cathode surrounding part of said cathode-side sealing member and a hydraulic diameter d of the clearance cl satisfy the formula: d<(D��l��P)/0.54L, wherein l is the length of the clearance cl, L is the length of the oxidant gas flow channel per one path of the cathode-side separator plate, D is the hydraulic diameter of the oxidant gas flow channel per one path of the cathode-side separator plate, P is the number of paths of the oxidant gas flow channel of the cathode-side separator plate, and the hydraulic diameter d=(cross section of the clearance)��(peripheral length of the cross section)��4. 12. The polymer electrolyte fuel cell in accordance with claim 11, wherein the one-side clearance cl satisfies the formula: 0.25 mm