Unit cell for solid polymer electrolyte fuel cell

Abstract

A unit cell for use in a solid polymer electrolyte fuel cell comprising: a membrane/electrode assembly including a fuel electrode and an oxidant electrode disposed on either side of a solid polymer electrolyte membrane, the assembly being sandwiched from either side by a first separator and a second separator to give a stacked construction to form therebetween a fuel gas flow passage and an oxidant gas flow passage. The solid polymer electrolyte membrane has a projecting portion projecting outwardly beyond the fuel electrode and the oxidant electrode, and the projecting portion is coated by a reinforcing resin member. Connecting grooves formed on a primary face of the separators connecting both ends of the fuel gas/oxidant gas flow passages with a fuel/oxidant gas feed/discharge ports, respectively. The reinforcing resin member is placed so as to bridge openings of the connecting grooves in order to give a tunnel construction to the connecting grooves.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and/or other objects features and advantages of the invention will become more apparent from the following description of a preferred embodiment with reference to the accompanying drawings in which like reference numerals designate like elements and wherein:

FIG. 1 is a perspective view of a solid polymer electrolyte fuel cell composed of unit cells of construction according to a first embodiment of the present invention;

FIG. 2 is an exploded perspective view showing a construction of a unit cell of the solid polymer electrolyte fuel cell of FIG. 1;

FIG. 3 is a front elevational view of an MEA component of the unit cell of FIG. 1

FIG. 4 is a front elevational view of the primary face of a first separator of the unit cell of FIG. 1;

FIG. 5 is a front elevational view of the primary face of a second separator of the unit cell of FIG. 1;

FIG. 6 is a front elevational view of the secondary face of the first and second separators of FIGS. 4 and 5;

FIG. 7 is a fragmentary view of a cross sectional view taken along line 7-7 of FIG. 4; and

FIG. 8 is a fragmentary perspective view showing a primary part of the unit cell of FIG. 2.

Claims

1. A unit cell for use in a solid polymer electrolyte fuel cell comprising: a membrane/electrode assembly including a fuel electrode and an oxidant electrode disposed on either side of a solid polymer electrolyte membrane, the assembly being sandwiched from either side by a first separator and a second separator to give a stacked construction;a fuel gas flow passage formed between opposed faces of the fuel electrode and the first separator; andan oxidant gas flow passage formed between opposed faces of the oxidant electrode and the second separator,wherein the solid polymer electrolyte membrane in the membrane/electrode assembly has a planar shape slightly larger than the fuel electrode and the oxidant electrode so that an entire perimeter of an outer peripheral edge portion of the solid polymer electrolyte membrane forms a projecting portion projecting outwardly beyond outer peripheral edges of the fuel electrode and the oxidant electrode, and the projecting portion of the solid polymer electrolyte membrane is coated by a reinforcing resin member affixed thereto,wherein the first separator has a primary-face sealing rubber layer affixed onto a primary face thereof so that the reinforcing resin member is stacked on the first separator via the primary-face sealing rubber layer, and connecting grooves formed on the primary face thereof for connecting both ends of the fuel gas flow passage with a fuel gas feed/discharge ports respectively, which are formed perforating through the first separator,wherein the second separator has a primary-face sealing rubber layer affixed onto a primary face thereof so that the reinforcing resin member is stacked on the second separator via the primary-face sealing rubber layer, and connecting grooves formed on the primary face thereof for connecting both ends of the oxidant gas flow passage with an oxidant gas feed/discharge ports respectively, which are formed perforating through the second separator, andwherein the reinforcing resin member is placed so as to bridge openings of the connecting grooves in order to give a tunnel construction to the connecting grooves.

2. The unit cell according to claim 1, wherein the reinforcing resin member includes at least one reinforcing bar, while the fuel electrode and the oxidant electrode includes a plurality of electrode segments divided by means of the reinforcing bar.

3. The unit cell according to claim 1, wherein each connecting groove includes at least one supporting projection projecting upward from a bottom face of the connecting groove, and a portion of the reinforcing resin member extending across the opening of the connecting groove is held in contact with and supported by the supporting projection.

4. The unit cell according to claim 3, wherein each connecting groove includes a plurality of supporting projection each extending continuously with a given length in a lengthwise direction of the connecting groove, which are arranged in a widthwise direction of the connecting groove while being spaced away from one another.

5. The unit cell according to claim 1, wherein the fuel gas flow passage and the oxidant gas flow passage extend straightly with both ends connected respectively with pairs of gas-reserving zones extending in a widthwise direction of the fuel gas flow passage and the oxidant gas flow passage, respectively, while the pairs of gas-reserving zones are respectively connected to the fuel gas feed/discharge ports and the oxidant gas feed/discharge port so that a fuel gas and an oxidant gas are reserved temporarily within the gas-reserving zones.

6. The unit cell according to claim 1, wherein the primary-face sealing rubber layer is arranged for surrounding at least perimeters of zones forming the fuel gas flow passage and the oxidant gas flow passage respectively, as well as the fuel gas feed/discharge ports and the oxidant gas feed/discharge ports respectively, and wherein the primary-face sealing rubber layer includes an MEA sealing ridge integrally formed at a portion to be superposed on the reinforcing resin member that projects outward in a superposing direction and is formed continuously.

7. The unit cell according to claim 1, wherein the primary-face sealing rubber layer affixed onto the primary face of the first separator includes a primary-face sealing ridge of continuous projection arranged for surrounding the fuel gas feed/discharge ports and the oxidant gas feed/discharge ports respectively, while the primary-face sealing rubber layer affixed onto the primary face of the second separator has a planar surface at a portion on which the primary-face sealing ridge is superposed.

8. The unit cell according to claim 1, wherein each of the first separator and the second separator includes a separator reinforcing member affixed to an entire outer peripheral edge thereof, and one of a fitting groove and a fitting projection is formed on a surface of the separator reinforcing member of one of the first and second separators, while the other of the fitting groove and the fitting projection is formed on a surface of the separator reinforcing member of the other of the first and second separators so that the separator reinforcing members are superposed on each other by means of mating between the fitting groove and the fitting projection.

9. The unit cell according to claim 8, wherein the separator reinforcing member is made of a synthetic resin material by means of an injection molding using a mold including a pair of reinforcing portion gripping the outer peripheral edge of the separator.

10. A solid polymer electrolyte fuel cell comprising a plurality of unit cells each having: a membrane/electrode assembly including a fuel electrode and an oxidant electrode disposed on either side of a solid polymer electrolyte membrane, the assembly being sandwiched from either side by a first separator and a second separator to give a stacked construction; a fuel gas flow passage formed between opposed faces of the fuel electrode and the first separator; and an oxidant gas flow passage formed between opposed faces of the oxidant electrode and the second separator, wherein the solid polymer electrolyte membrane in the membrane/electrode assembly has a planar shape slightly larger than the fuel electrode and the oxidant electrode so that an entire perimeter of an outer peripheral edge portion of the solid polymer electrolyte membrane forms a projecting portion projecting outwardly beyond outer peripheral edges of the fuel electrode and the oxidant electrode, and the projecting portion of the solid polymer electrolyte membrane is coated by a reinforcing resin member affixed thereto, wherein the first separator has a primary-face sealing rubber layer affixed onto a primary face thereof so that the reinforcing resin member is stacked on the first separator via the primary-face sealing rubber layer, and connecting grooves formed on the primary face thereof for connecting both ends of the fuel gas flow passage with a fuel gas feed/discharge ports respectively, which are formed perforating through the first separator, wherein the second separator has a primary-face sealing rubber layer affixed onto a primary face thereof so that the reinforcing resin member is stacked on the second separator via the primary-face sealing rubber layer, and connecting grooves formed on the primary face thereof for connecting both ends of the oxidant gas flow passage with an oxidant gas feed/discharge ports respectively, which are formed perforating through the second separator, and wherein the reinforcing resin member is placed so as to bridge openings of the connecting grooves in order to give a tunnel construction to the connecting grooves, wherein the unit cells are stacked in a sandwich direction of the first and second separators with respect to the membrane/electrode assembly.

11. The solid polymer electrolyte fuel cell according to claim 10, wherein each of the first and second separators includes a conducting contact part formed at a portion outside a zone forming the fuel gas flow passage or the oxidant gas flow passage projecting toward a secondary face opposite the primary face so that the conducting contact part of the first separator and the conducting contact part of the second separator are held in contact with each other with the unit cells stacked.