FUEL CELL UNIT

Abstract

The present invention provides a fuel cell unit having a structure in which vapor is efficiently diffused in a fuel diffusion layer through a region having a reduced diffusion resistance, so that vapor is spread to every corner in a direction along an opening, thereby reducing variation in wetness of a polymer electrolyte membrane. As a result, as compared with a case where there is no region having a reduced diffusion resistance, a proper moistened state is maintained over a wider range of the polymer electrolyte membrane, thereby making it possible to enhance hydrogen ion transfer ability of the polymer electrolyte membrane as a whole.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view of a constitution of a small electronic apparatus into which a fuel cell according to an embodiment of the present invention is to be incorporated.

FIG. 2 is an explanatory vertical sectional view illustrating a structure of a fuel cell unit.

FIGS. 3A and 3B are explanatory horizontal sectional views of the fuel cell unit of FIG. 2.

FIGS. 4A and 4B are explanatory views illustrating hydrogen gas flow and oxygen flow in the fuel cell unit.

FIG. 5 is an explanatory view illustrating the state of electric power generation using a polymer electrolyte membrane.

FIG. 6 is a sectional view of a fuel cell unit of the air breathing fuel cell disclosed by U.S. Pat. No. 5,514,486.

FIGS. 7A and 7B are plan views of the fuel cell unit of FIG. 6.

FIGS. 8A and 8B are horizontal sectional views showing a structure of a fuel cell unit.

FIGS. 9A, 9B and 9C are a vertical sectional view and horizontal sectional views showing a structure of a fuel cell unit.

FIGS. 10A, 10B and 10C are a vertical sectional view and horizontal sectional views showing a structure of a fuel cell unit.

Claims

1. A fuel cell unit comprising: a polymer electrolyte membrane;two catalyst layers provided opposite to each other through the polymer electrolyte membrane;a fuel diffusion layer provided in contact with one catalyst layer of the two catalyst layers;an oxygen diffusion layer provided in contact with the other catalyst layer of the two catalyst layers; andtwo openings,wherein the two openings are provided respectively in two side surfaces which exist parallel and opposite to a proton conductive direction of the polymer electrolyte membrane among side surfaces of the oxygen diffusion layer,wherein the fuel diffusion layer has at least a region having a fuel diffusion resistance of A and a region having a fuel diffusion resistance of B,wherein the fuel diffusion layer has a symmetry point,wherein the fuel diffusion resistance A is larger than the fuel diffusion resistance B,wherein the region having a fuel diffusion resistance of B intersects a plane parallel to the openings and containing the symmetry point, andwherein the region having a fuel diffusion resistance of B can contain a longest segment that is parallel to interfaces between the polymer electrolyte membrane and the catalyst layers and parallel to the openings is longer than a longest segment that can exist in the region having a fuel diffusion resistance of B and that is parallel to the interfaces between the polymer electrolyte membrane and the catalyst layers and perpendicular to the openings.

2. A fuel cell unit comprising: a polymer electrolyte membrane;two catalyst layers provided opposite to each other through the polymer electrolyte membrane;a fuel diffusion layer provided in contact with one catalyst layer of the two catalyst layers;an oxygen diffusion layer provided in contact with the other catalyst layer of the two catalyst layers; andone opening,wherein the opening is provided in a side surface which exists parallel to a proton conductive direction of the polymer electrolyte membrane among side surfaces of the oxygen diffusion layer,wherein the fuel diffusion layer has at least a region having a fuel diffusion resistance of A and a region having a fuel diffusion resistance of B,wherein the fuel diffusion resistance A is larger than the fuel diffusion resistance B,wherein the region having a fuel diffusion resistance of B exists in a vicinity of a region which is in point symmetry in the fuel diffusion layer with respect to a region in the fuel diffusion layer existing in the same plane as the openings, andwherein the region having a fuel diffusion resistance of B can contain a longest segment that is parallel to interfaces between the polymer electrolyte membrane and the catalyst layers and parallel to the openings is longer than a segment perpendicular to the openings and parallel to the interfaces.

3. A fuel cell unit according to claim 1 or 2, wherein the fuel diffusion layer has a fuel supply port, and wherein the region having a fuel diffusion resistance of B and the fuel supply port are spaced apart from each other by a distance of 5 mm or less.

4. A fuel cell unit according to claim 3, wherein the fuel supply port is connected with the region having a fuel diffusion resistance of B.

5. A fuel cell unit according to claim 4, wherein the fuel diffusion layer has a fuel discharge port, and wherein the fuel discharge port is connected with the region having a fuel diffusion resistance of B.

6. A fuel cell unit according to claim 1 or 2, wherein the region having a fuel diffusion resistance of B is formed by a groove provided in the fuel diffusion layer.