Fuel cell

Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation

Reexamination Certificate

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Details

C429S006000, C429S006000, C429S006000

Reexamination Certificate

active

06686085

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel cell comprising a fuel cell unit composed of an electrolyte interposed between an anode electrode and a cathode electrode, and separators for supporting the fuel cell unit interposed therebetween.
2. Description of the Related Art
For example, the solid polymer type fuel cell comprises a fuel cell unit including an anode electrode and a cathode electrode disposed opposingly on both sides of an electrolyte composed of a polymer ion exchange membrane (cation exchange membrane) respectively, the fuel cell unit being interposed between separators. Usually, the solid polymer type fuel cell is used as a fuel cell stack obtained by stacking a predetermined number of the fuel cell units.
In such a fuel cell, a fuel gas such as a hydrogen-containing gas, which is supplied to the anode electrode, is converted into hydrogen ion on the catalyst electrode, and the ion is moved toward the cathode electrode via the electrolyte which is appropriately humidified. The electron, which is generated during this process, is extracted for an external circuit, and the electron is utilized as DC electric energy. An oxygen-containing gas such as a gas containing oxygen or air is supplied to the cathode electrode. Therefore, the hydrogen ion, the electron, and the oxygen gas are reacted with each other on the cathode electrode, and thus water is produced.
In the fuel cell described above, an internal manifold is constructed in order to supply the fuel gas and the oxygen-containing gas (reaction gas) to the anode electrode and the cathode electrode of each of the stacked fuel cell units respectively. Specifically, the internal manifold includes a plurality of communication holes which are provided in an integrated manner to make communication with each of the fuel cell units and the separators which are stacked with each other. When the reaction gas is supplied to the supplying communication hole, the reaction gas is supplied in a dispersed manner to each of the fuel cell units, while the used reaction gas is integrally discharged to the discharging communication hole. The fuel cell is supplied with a cooling medium in order to cool the electrode power-generating surface. The internal manifold is provided with communication holes for the cooling medium in some cases, in the same manner as for the reaction gas.
As shown in
FIG. 10
, for example, Japanese Laid-Open Patent Publication No. 3-257760 discloses, as such a technique, a fuel cell in which a fuel cell unit
3
including an electric cell three-layered film
2
formed on a surface of a film formation substrate
1
is interposed between separators
4
, and the separators
4
are formed with an internal manifold
5
for allowing the fuel gas and the oxygen-containing gas to flow.
However, in the conventional technique described above, in order to reliably effect the gas seal for the internal manifold
5
, a seal plate
7
is installed via spacers
6
a
,
6
b
between the separators
4
. Gaskets
8
are interposed between the separator
4
and the spacer
6
a
, between the spacer
6
a
and the seal plate
7
, between the seal plate
7
and the spacer
6
b
, and between the spacer
6
b
and the separator
4
respectively. As a result, the following problem is pointed out. That is, the dimension of the fuel cell unit
3
in the stacking direction (direction of the arrow X) is considerably lengthy, the number of parts is increased, and the production cost becomes expensive.
Accordingly, as shown in
FIG. 11
, the following structure is adopted. That is, introducing sections
5
c
, which are used to make communication between a communication hole
5
a
for constructing the internal manifold of the separator
4
a
and fluid flow passages
5
b
for allowing the reaction gas to flow into the surface of the separator
4
a
, are formed on the same plane as that of the fluid flow passages
5
b
. In order to ensure the sealing performance of the introducing sections
5
c
, a thin plate-shaped cover
9
is fitted to the introducing sections
5
c
to allow the gasket
8
a
to forcibly abut against the cover
9
(see FIG.
12
).
However, a step is required to fit the considerably thin-walled cover
9
to the introducing section
5
c
as described above to assemble the fuel cell so that the surface of the cover
9
is flush with the surface of the separator
4
a
. An operation to stick (fit) the cover
9
is complicated. Further, the following problem is pointed out. That is, it is feared that the cover
9
may be lost during the assembling of the cell or during the stacking of the cell, resulting in leakage of the reaction gas. Further, any difference in height arises between the surface of the cover
9
and the surface of the separator
4
a
. It is impossible to apply the uniform tightening force to the separator
4
a
when the cell is tightened.
When a communication hole for the cooling medium is provided for the internal manifold of the separator, it is also necessary to use the thin plate-shaped cover. As a result, the same problem as that for the reaction gas described above arises.
In order to dissolve the inconvenience as described above, for example, a fuel cell stack disclosed in U.S. Pat. No. 6,066,409 is known. In the fuel cell stack, as shown in
FIG. 13
, a separator
4
b
is constructed by combining two separators
4
b
1
,
4
b
2
. An internal manifold is arranged at a central portion thereof. Specifically, communication holes, i.e., a supply port
5
d
1
and a discharge port
5
d
2
for the reaction gas on the first side, and a supply port
5
e
1
and a discharge port
5
e
2
for the reaction gas on the second side are formed to penetrate in the thickness direction of the separator
4
b.
As shown in
FIG. 14
, flow passage grooves
5
f
1
,
5
f
2
, which communicate with the supply port
5
d
1
and the discharge port
5
d
2
on the first side and which extend toward the outer circumferential side along a non-power-generating surface
4
c
1
, are formed on the non-power-generating surface (non-reaction surface)
4
c
1
of the separator
4
b
. Further, flow passage grooves
5
g
1
,
5
g
2
, which communicate with the supply port
5
e
1
and the discharge port
5
e
2
for the reaction gas on the second side and which extend toward the outer circumferential side along the non-power-generating surface to
4
c
1
, are formed on the non-power-generating surface
4
c
1
of the separator
4
b
. A plurality of cooling air flow passage grooves
5
j
are formed in parallel to one another on the non-power-generating surface
4
c
1
. Both ends of the cooling air flow passage grooves
5
j
are open toward the outside from the outer circumferential end of the non-power-generating surface
4
c
1
.
Through-holes
5
h
1
,
5
h
2
communicate with outer ends of the flow passage grooves
5
f
1
,
5
f
2
. The through-holes
5
h
1
,
5
h
2
communicate with the reaction gas flow passage
5
i
on the side of the power-generating surface
4
c
2
of the separator
4
b
1
(see the separator
4
b
2
in FIG.
13
). The reaction gas flow passage
5
i
is provided along the plane of the power-generating surface
4
c
2
. A gasket
8
b
, which is used to prevent the different reaction gases from being mixed in the internal manifold, is interposed between the separators
4
b
1
,
4
b
2
.
In the arrangement as described above, when the first reaction gas is supplied to the supply port
5
d
1
which constitutes the internal manifold, the reaction gas is moved to the outer circumferential side of the separator
4
b
along the flow passage groove
5
f
1
communicating with the supply port
5
d
1
. The reaction gas passes through the through-hole
5
h
1
communicating with the outer end of the flow passage groove
5
f
1
, and it is supplied to the side of the power-generating surface
4
c
2
. The reaction gas flow passage
5
i
is provided on the side of the power-generating surface
4
c
2
. The reaction gas is supplied to an unillustrated fuel cell unit, while moving along the reaction gas flo

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