U.S. patent application number 15/220392 was filed with the patent office on 2017-02-02 for resin-framed membrane electrode assembly and fuel cell.
This patent application is currently assigned to HONDA MOTOR CO., LTD.. The applicant listed for this patent is HONDA MOTOR CO., LTD.. Invention is credited to Suguru OHMORI, Masashi SUGISHITA, Seiji SUGIURA.
Application Number | 20170033375 15/220392 |
Document ID | / |
Family ID | 57883755 |
Filed Date | 2017-02-02 |
United States Patent
Application |
20170033375 |
Kind Code |
A1 |
OHMORI; Suguru ; et
al. |
February 2, 2017 |
RESIN-FRAMED MEMBRANE ELECTRODE ASSEMBLY AND FUEL CELL
Abstract
A solid polymer electrolyte membrane is made from a solid
polymer electrolyte membrane roll in which a solid polymer
electrolyte membrane sheet is wound in a winding direction. A first
electrode is disposed on a first surface of the solid polymer
electrolyte membrane in a stacking direction. A second electrode is
disposed on a second surface of the solid polymer electrolyte
membrane in the stacking direction and has a size smaller than a
size of the first electrode viewed in the stacking direction. A
resin frame member has a rectangular peripheral shape and a
rectangular window therein viewed in the stacking direction. The
rectangular stepped membrane electrode assembly is provided in the
rectangular window so that the outer peripheral surface of the
solid polymer electrolyte membrane is surrounded by the resin frame
member. The rectangular peripheral shape has a longitudinal side
which extends in the winding direction.
Inventors: |
OHMORI; Suguru; (Wako,
JP) ; SUGISHITA; Masashi; (Wako, JP) ;
SUGIURA; Seiji; (Wako, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HONDA MOTOR CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
HONDA MOTOR CO., LTD.
Tokyo
JP
|
Family ID: |
57883755 |
Appl. No.: |
15/220392 |
Filed: |
July 27, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 8/0265 20130101;
H01M 2008/1095 20130101; H01M 8/1004 20130101; H01M 8/04104
20130101; H01M 8/0273 20130101; Y02E 60/50 20130101; H01M 8/242
20130101 |
International
Class: |
H01M 8/0273 20060101
H01M008/0273; H01M 4/86 20060101 H01M004/86; H01M 8/0265 20060101
H01M008/0265; H01M 8/1018 20060101 H01M008/1018; H01M 8/1004
20060101 H01M008/1004 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2015 |
JP |
2015-149323 |
Claims
1. A resin-framed membrane electrode assembly for a fuel cell,
comprising: a rectangular stepped MEA including a solid polymer
electrolyte membrane, a first electrode that is disposed on one
surface of the solid polymer electrolyte membrane and that includes
a first electrode catalyst layer and a first gas diffusion layer,
and a second electrode that is disposed on the other surface of the
solid polymer electrolyte membrane and that includes a second
electrode catalyst layer and a second gas diffusion layer, wherein
planar dimensions of the first electrode are larger than those of
the second electrode; and a rectangular resin frame member that
surrounds an outer periphery of the solid polymer electrolyte
membrane, wherein the resin frame member includes an
inwardly-protruding portion that protrudes toward the second
electrode, wherein a clearance is formed between an outer edge of
the second gas diffusion layer and an inner edge of the
inwardly-protruding portion, wherein the solid polymer electrolyte
membrane is obtained by cutting a rolled solid polymer electrolyte
membrane, and wherein a winding direction in which the rolled solid
polymer electrolyte membrane is wound coincides with a longitudinal
direction of the resin frame member.
2. The resin-framed membrane electrode assembly according to claim
1, wherein the first electrode is an anode electrode to which a
fuel gas is supplied, wherein the second electrode is a cathode
electrode to which an oxidant gas is supplied, and wherein a supply
pressure of the fuel gas supplied to the first electrode is higher
than a supply pressure of the oxidant gas supplied to the second
electrode.
3. A fuel cell comprising: the resin-framed membrane electrode
assembly according to claim 1; and a rectangular separator, wherein
the separator includes an oxidant gas inlet manifold that is
located adjacent to one short side of the resin frame member and
through which an oxidant gas flows in a stacking direction in which
the resin-framed membrane electrode assembly and the separator are
stacked, and an oxidant gas outlet manifold that is located
adjacent to the other short side of the resin frame member and
through which the oxidant gas flows in the stacking direction.
4. A resin-framed membrane electrode assembly for a fuel cell,
comprising: a rectangular stepped membrane electrode assembly
comprising: a solid polymer electrolyte membrane made from a solid
polymer electrolyte membrane roll in which a solid polymer
electrolyte membrane sheet is wound in a winding direction, the
solid polymer electrolyte membrane having a first surface, a second
surface opposite to the first surface in a stacking direction, and
an outer peripheral surface connecting the first surface and the
second surface; a first electrode disposed on the first surface of
the solid polymer electrolyte membrane in the stacking direction;
and a second electrode which is disposed on the second surface of
the solid polymer electrolyte membrane and which has a size smaller
than a size of the first electrode viewed in the stacking
direction, the second electrode comprising: a second electrode
catalyst layer provided on the second surface of the solid polymer
electrolyte membrane in the stacking direction; and a second gas
diffusion layer provided on the second electrode catalyst layer in
the stacking direction; and a resin frame member having a
rectangular peripheral shape and a rectangular window therein
viewed in the stacking direction, the rectangular stepped membrane
electrode assembly being provided in the rectangular window so that
the outer peripheral surface of the solid polymer electrolyte
membrane is surrounded by the resin frame member, the resin frame
member including an inwardly-protruding peripheral portion which
protrudes toward an outer peripheral edge of the second electrode,
the inwardly-protruding peripheral portion having an inner
peripheral edge facing the outer peripheral edge of the second gas
diffusion layer with a clearance therebetween, the rectangular
peripheral shape having a longitudinal side which extends in the
winding direction.
5. The resin-framed membrane electrode assembly according to claim
4, wherein the first electrode is an anode electrode to which a
fuel gas is supplied, wherein the second electrode is a cathode
electrode to which an oxidant gas is supplied, and wherein a supply
pressure of the fuel gas supplied to the first electrode is higher
than a supply pressure of the oxidant gas supplied to the second
electrode.
6. A fuel cell comprising: the resin-framed membrane electrode
assembly according to claim 4; and a separator having a rectangular
shape and stacked on the resin-framed membrane electrode assembly
in the stacking direction, wherein the rectangular peripheral shape
has a lateral side which is perpendicular to the longitudinal side
and which is shorter than the longitudinal side, the separator
includes an oxidant gas inlet manifold which is located adjacent to
the lateral side of the resin frame member and through which an
oxidant gas flows in the stacking direction, and an oxidant gas
outlet manifold which is located adjacent to the lateral side of
the resin frame member and through which the oxidant gas flows in
the stacking direction.
7. The resin-framed membrane electrode assembly according to claim
4, wherein the first electrode catalyst layer is provided on the
first surface of the solid polymer electrolyte membrane, and the
first gas diffusion layer is provided on the first electrode
catalyst layer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 U.S.C.
.sctn.119 to Japanese Patent Application No. 2015-149323, filed
Jul. 29, 2015, entitled "Resin-Framed Membrane Electrode Assembly
and Fuel Cell." The contents of this application are incorporated
herein by reference in their entirety.
BACKGROUND
[0002] 1. Field
[0003] The present disclosure relates to a resin-framed membrane
electrode assembly for a fuel cell and to a fuel cell.
[0004] 2. Description of the Related Art
[0005] In general, a solid polymer electrolyte fuel cell includes a
solid polymer electrolyte membrane, which is a solid polymer
ion-exchange membrane. The fuel cell includes a membrane electrode
assembly (MEA), in which an anode electrode is disposed on one
surface of the solid polymer electrolyte membrane and a cathode
electrode is disposed on the other surface of the solid polymer
electrolyte membrane. The anode electrode and the cathode electrode
each include a catalyst layer (electrode catalyst layer) and a gas
diffusion layer (porous carbon).
[0006] A membrane electrode assembly and separators (bipolar
plates) sandwiching the membrane electrode assembly therebetween
constitute a power generation cell (unit fuel cell). A
predetermined number of such power generation cells are stacked and
used, for example, as a vehicle fuel cell stack.
[0007] There is a type of membrane electrode assembly in which one
of the gas diffusion layers has smaller planar dimensions than the
solid polymer electrolyte membrane and the other gas diffusion
layer has the same planar dimensions as the solid polymer
electrolyte membrane. Such a membrane electrode assembly is called
a stepped MEA. A stepped MEA is typically structured as a
resin-framed MEA, which has a resin frame member in an outer
periphery thereof, so that the amount of the solid polymer
electrolyte membrane, which is comparatively expensive, can be
reduced and so that the solid polymer electrolyte membrane, which
is a thin and weak, can be protected.
[0008] Japanese Unexamined Patent Application Publication No.
2015-60621 describes a resin-framed membrane electrode assembly for
a fuel cell, which is an example of a resin-framed MEA of a known
type. The resin-framed membrane electrode assembly for a fuel cell
includes a solid polymer electrolyte membrane, a first electrode
disposed on one surface of the solid polymer electrolyte membrane,
and a second electrode disposed on the other surface of the solid
polymer electrolyte membrane. The planar dimensions of the first
electrode are larger than those of the second electrode. A resin
frame member is disposed so as to surround the outer periphery of
the solid polymer electrolyte membrane.
[0009] The resin frame member includes an inwardly-protruding
portion, which is thin and which protrudes from an inner base
portion toward the second electrode. An adhesive application
portion, to which an adhesive is applied, is disposed on the
inwardly-protruding portion so as to surround a part of the
inwardly-protruding portion that contacts the membrane electrode
assembly. A resin-impregnated portion is disposed on the inner base
portion of the resin frame member. The resin-impregnated portion is
formed by impregnating an outer edge of the first electrode with a
resin material so that the first electrode and the resin frame
member are integrated with each other.
SUMMARY
[0010] According to one aspect of the present invention, a
resin-framed membrane electrode assembly for a fuel cell includes a
rectangular stepped MEA and a rectangular resin frame member. The
stepped MEA includes a solid polymer electrolyte membrane, a first
electrode that is disposed on one surface of the solid polymer
electrolyte membrane and that includes a first electrode catalyst
layer and a first gas diffusion layer, and a second electrode that
is disposed on the other surface of the solid polymer electrolyte
membrane and that includes a second electrode catalyst layer and a
second gas diffusion layer. Planar dimensions of the first
electrode are larger than those of the second electrode. The resin
frame member surrounds an outer periphery of the solid polymer
electrolyte membrane.
[0011] The resin frame member includes an inwardly-protruding
portion that protrudes toward the second electrode. A clearance is
formed between an outer edge of the second gas diffusion layer and
an inner edge of the inwardly-protruding portion. The solid polymer
electrolyte membrane is obtained by cutting a rolled solid polymer
electrolyte membrane. A winding direction in which the rolled solid
polymer electrolyte membrane is wound coincides with a longitudinal
direction of the resin frame member.
[0012] According to another aspect of the present invention, a
resin-framed membrane electrode assembly for a fuel cell includes a
rectangular stepped membrane electrode assembly and a resin frame
member. The rectangular stepped membrane electrode assembly
includes a solid polymer electrolyte membrane, a first electrode,
and a second electrode. The solid polymer electrolyte membrane is
made from a solid polymer electrolyte membrane roll in which a
solid polymer electrolyte membrane sheet is wound in a winding
direction. The solid polymer electrolyte membrane has a first
surface, a second surface opposite to the first surface in a
stacking direction, and an outer peripheral surface connecting the
first surface and the second surface. The first electrode is
disposed on the first surface of the solid polymer electrolyte
membrane in the stacking direction. The second electrode is
disposed on the second surface of the solid polymer electrolyte
membrane and has a size smaller than a size of the first electrode
viewed in the stacking direction. The second electrode includes a
second electrode catalyst layer and a second gas diffusion layer.
The second electrode catalyst layer is provided on the second
surface of the solid polymer electrolyte membrane in the stacking
direction. The second gas diffusion layer is provided on the second
electrode catalyst layer in the stacking direction. The resin frame
member has a rectangular peripheral shape and a rectangular window
therein viewed in the stacking direction. The rectangular stepped
membrane electrode assembly is provided in the rectangular window
so that the outer peripheral surface of the solid polymer
electrolyte membrane is surrounded by the resin frame member. The
resin frame member includes an inwardly-protruding peripheral
portion which protrudes toward an outer peripheral edge of the
second electrode. The inwardly-protruding peripheral portion has an
inner peripheral edge facing the outer peripheral edge of the
second gas diffusion layer with a clearance therebetween. The
rectangular peripheral shape has a longitudinal side which extends
in the winding direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] A more complete appreciation of the invention and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings.
[0014] FIG. 1 is an exploded perspective view of a solid polymer
electrolyte power generation cell including a resin-framed membrane
electrode assembly according to an embodiment of the present
disclosure.
[0015] FIG. 2 is a sectional view of the power generation cell
taken along line II-II in FIG. 1.
[0016] FIG. 3 is a partial sectional view of a resin frame member
of the resin-framed membrane electrode assembly.
[0017] FIG. 4 is a plan view of the resin-framed membrane electrode
assembly.
[0018] FIG. 5 is a perspective view of a rolled solid polymer
electrolyte membrane.
[0019] FIG. 6 is a graph illustrating stresses generated in the
solid polymer electrolyte membrane at different portions of an
inner peripheral surface of the resin frame member.
DESCRIPTION OF THE EMBODIMENTS
[0020] The embodiments will now be described with reference to the
accompanying drawings, wherein like reference numerals designate
corresponding or identical elements throughout the various
drawings.
[0021] As illustrated in FIGS. 1 and 2, a resin-framed membrane
electrode assembly 10 according to an embodiment of the present
disclosure is incorporated in a solid polymer power generation cell
12 (fuel cell), which has a horizontally elongated (or vertically
elongated) rectangular shape. A plurality of power generation cells
12 form a fuel cell stack by being stacked, for example, in the
direction of arrow A (horizontal direction) or in the direction of
arrow C (direction of gravity). The fuel cell stack is mounted, for
example, as a vehicle fuel cell stack in a fuel cell electric
vehicle (not shown).
[0022] In the power generation cell 12, the resin-framed membrane
electrode assembly 10 is sandwiched between a first separator 14
and a second separator 16. The first separator 14 and the second
separator 16 each have a horizontally elongated (or vertically
elongated) rectangular shape. The first separator 14 and the second
separator 16 are each made of a metal plate, a carbon plate, or the
like. Examples of the metal plate include a steel plate, a
stainless steel plate, an aluminum plate, a galvanized steel plate,
and the like, whose surface may have an anti-corrosive coating.
[0023] The resin-framed membrane electrode assembly 10, which has a
rectangular shape, includes a rectangular stepped MEA 10a. As
illustrated in FIG. 2, the stepped MEA 10a includes a solid polymer
electrolyte membrane 18 (cation exchange membrane), which is, for
example, a thin film that is made of a perfluorosulfonic acid
polymer and soaked with water. The solid polymer electrolyte
membrane 18 is sandwiched between an anode electrode 20 (first
electrode) and a cathode electrode 22 (second electrode). Instead
of a fluorinated electrolyte, a hydrocarbon (HC) electrolyte may be
used as the solid polymer electrolyte membrane 18.
[0024] The cathode electrode 22 has smaller planar dimensions
(outside dimensions) than the solid polymer electrolyte membrane 18
and the anode electrode 20. Alternatively, the anode electrode 20
may have smaller planar dimensions than the solid polymer
electrolyte membrane 18 and the cathode electrode 22. In this case,
the anode electrode 20 is the second electrode, and the cathode
electrode 22 is the first electrode.
[0025] The anode electrode 20 includes a first electrode catalyst
layer 20a, which is joined to a surface 18a of the solid polymer
electrolyte membrane 18, and a first gas diffusion layer 20b, which
is stacked on the first electrode catalyst layer 20a. The first
electrode catalyst layer 20a and the first gas diffusion layer 20b
have the same planar dimensions that are the same as (or smaller
than) those of the solid polymer electrolyte membrane 18.
[0026] The cathode electrode 22 includes a second electrode
catalyst layer 22a, which is joined to a surface 18b of the solid
polymer electrolyte membrane 18, and a second gas diffusion layer
22b, which is stacked on the second electrode catalyst layer 22a.
The second electrode catalyst layer 22a protrudes outward beyond an
outer edge 22be of the second gas diffusion layer 22b, has larger
planar dimensions than the second gas diffusion layer 22b, and has
smaller planar dimensions than the solid polymer electrolyte
membrane 18.
[0027] The second electrode catalyst layer 22a and the second gas
diffusion layer 22b may have the same planar dimensions, and the
second electrode catalyst layer 22a may have smaller planar
dimensions than the second gas diffusion layer 22b.
[0028] The first electrode catalyst layer 20a is formed by, for
example, uniformly coating a surface of the first gas diffusion
layer 20b with porous carbon particles whose surfaces support a
platinum alloy. The second electrode catalyst layer 22a is formed
by, for example, uniformly coating a surface of the second gas
diffusion layer 22b with porous carbon particles whose surfaces
support a platinum alloy.
[0029] The first gas diffusion layer 20b includes a microporous
layer 20b(m), which is porous and electroconductive, and a carbon
layer 20b(c), which is made of carbon paper, carbon cloth, or the
like. The second gas diffusion layer 22b includes a microporous
layer 22b(m) and a carbon layer 22b(c), which is made of carbon
paper, carbon cloth, or the like.
[0030] The planar dimensions of the second gas diffusion layer 22b
are smaller than those of the first gas diffusion layer 20b. The
first electrode catalyst layer 20a and the second electrode
catalyst layer 22a are formed on both surfaces of the solid polymer
electrolyte membrane 18. The microporous layers 20b(m) and 22b(m)
may be omitted as appropriate.
[0031] The resin-framed membrane electrode assembly 10 includes a
resin frame member 24 that surrounds the outer periphery of the
solid polymer electrolyte membrane 18 and that is joined to the
anode electrode 20 and the cathode electrode 22. Instead of the
resin frame member 24, a resin film having a uniform thickness may
be used.
[0032] The resin frame member 24 may be made of, for example,
polyphenylene sulfide (PPS), polyphthalamide (PPA), polyethylene
naphthalate (PEN), polyethersulfone (PES), liquid crystal polymer
(LCP), polyvinylidene fluoride (PVDF), silicone resin, fluororesin,
modified-polyphenylene ether (m-PPE) resin, polyethylene
terephthalate (PET), polybutylene terephthalate (PBT), modified
polyolefin, or the like.
[0033] As illustrated in FIGS. 1 and 3, the resin frame member 24
has a rectangular frame-like shape. As illustrated in FIGS. 2 and
3, the resin frame member 24 has an inwardly-protruding portion
24a, which is thin and which protrudes from an inner base portion
24s toward the cathode electrode 22 via a step portion. The
inwardly-protruding portion 24a extends inwardly from the inner
base portion 24s by a predetermined length and is disposed so as to
cover an outer peripheral surface 18be of the solid polymer
electrolyte membrane 18. The inwardly-protruding portion 24a
includes inner long sides 24aB1 and 24aB2 and inner short sides
24aC1 and 24aC2 (see FIG. 3), each having a curved surface R along
an inner corner thereof.
[0034] As illustrated in FIGS. 3 and 4, the inner long side 24aB1
is an upper side of the inner periphery of the resin frame member
24 extending in the longitudinal direction (direction of arrow B),
and the inner long side 24aB2 is a lower side of the inner
periphery of the resin frame member 24 extending in the
longitudinal direction. The inner short side 24aC1 is one of
lateral sides of the inner periphery of the resin frame member 24
extending in the transverse direction (direction of arrow C), and
the inner short side 24aC2 is the other lateral side of the inner
periphery of the resin frame member 24 extending in the transverse
direction.
[0035] As illustrated in FIG. 2, a filling space 25 is formed
between the inwardly-protruding portion 24a and the stepped MEA
10a, and an adhesive layer 26 is formed in the filling space 25.
The adhesive layer 26 includes an adhesive, such as a liquid
sealant or a hot-melt adhesive. The adhesive is not limited to a
liquid, a solid, a thermoplastic material, or a thermosetting
material.
[0036] As illustrated in FIG. 4, a frame-shaped clearance CL is
formed between the outer edge 22be of the second gas diffusion
layer 22b and the inner long sides 24aB1 and 24aB2 of the
inwardly-protruding portion 24a and between the outer edge 22be and
the inner short sides 24aC1 and 24aC2 of the inwardly-protruding
portion 24a. As a result, the outer edge 22be is separated by a
distance S from each of the inner long sides 24aB1 and 24aB2 and
the inner short sides 24aC1 and 24aC2. The widths of parts of the
clearance CL on the inner long sides 24aB1 and 24aB2 and the inner
short sides 24aC1 and 24aC2 are the same as the distance S.
However, the widths of the parts of the clearance CL may differ
from each other.
[0037] In the present embodiment, the solid polymer electrolyte
membrane 18 is manufactured on a film production line (not shown).
In the film production line, a rolled solid polymer electrolyte
membrane 18R is manufactured by supplying a perfluorosulfonic acid
polymer solution, drying the polymer solution in a drying step, and
winding the dried polymer solution into a roll shape in a winding
step (see FIG. 5).
[0038] In the drying step and the winding step, stresses are
generated in the rolled solid polymer electrolyte membrane 18R.
Therefore, the physical property of the rolled solid polymer
electrolyte membrane 18R is anisotropic, that is, differs between
the winding direction (feed direction) (hereinafter, also referred
to as the "direction MD") and a direction perpendicular to the
direction MD (hereinafter, also referred to as the direction TD).
To be specific, a change in the dimensions of the solid polymer
electrolyte membrane 18 due to expansion or contraction in the
direction MD is larger than that due to expansion or contraction in
the direction TD.
[0039] The solid polymer electrolyte membrane 18 is obtained by
cutting the rolled solid polymer electrolyte membrane 18R into
pieces each having a predetermined length. As described below, the
winding direction (direction MD) in which the rolled solid polymer
electrolyte membrane 18R is wound coincides with the longitudinal
direction (direction of arrow B) of the resin frame member 24 (see
FIG. 4).
[0040] As illustrated in FIG. 1, an oxidant gas inlet manifold 30a,
a coolant inlet manifold 32a, and a fuel gas outlet manifold 34b
are formed in the power generation cell 12 so as to extend in the
direction of arrow A, which is the stacking direction, through one
end portion of the power generation cell 12 in the direction of
arrow B (horizontal direction). An oxidant gas, such as an
oxygen-containing gas, is supplied through the oxidant gas inlet
manifold 30a. A coolant is supplied through the coolant inlet
manifold 32a. A fuel gas, such as a hydrogen-containing gas, is
discharged through the fuel gas outlet manifold 34b. The oxidant
gas inlet manifold 30a, the coolant inlet manifold 32a, and the
fuel gas outlet manifold 34b are arranged in the direction of arrow
C (vertical direction).
[0041] A fuel gas inlet manifold 34a, a coolant outlet manifold
32b, and an oxidant gas outlet manifold 30b, are formed in the
power generation cell 12 so as to extend in the direction of arrow
A through the other end portion of the power generation cell 12 in
the direction of arrow B. The fuel gas is supplied through the fuel
gas inlet manifold 34a. The coolant is discharged through the
coolant outlet manifold 32b. The oxidant gas is discharged through
the oxidant gas outlet manifold 30b. The fuel gas inlet manifold
34a, the coolant outlet manifold 32b, and the oxidant gas outlet
manifold 30b are arranged in the direction of arrow C.
[0042] An oxidant gas channel 36, which is connected to the oxidant
gas inlet manifold 30a and the oxidant gas outlet manifold 30b, is
formed on a surface 16a of the second separator 16 facing the
resin-framed membrane electrode assembly 10 so as to extend in the
direction of arrow B.
[0043] A fuel gas channel 38, which is connected to the fuel gas
inlet manifold 34a and the fuel gas outlet manifold 34b, is formed
on a surface 14a of the first separator 14 facing the resin-framed
membrane electrode assembly 10 so as to extend in the direction of
arrow B. The supply pressure of the fuel gas that flows through the
fuel gas channel 38 is higher than the supply pressure of the
oxidant gas that flows through the oxidant gas channel 36. In the
stepped MEA 10a, a differential pressure (inter-electrode
differential pressure) is generated between the anode electrode 20
and the cathode electrode 22 due to the difference between the
supply pressures of the reactant gases. The oxidant gas and the
fuel gas flow in opposite directions with the solid polymer
electrolyte membrane 18 therebetween (counter flow).
[0044] A coolant channel 40, which is connected to the coolant
inlet manifold 32a and the coolant outlet manifold 32b, is formed
between a surface 14b of the first separator 14 of the power
generation cell 12 and a surface 16b of the second separator 16 of
an adjacent power generation cell 12 so as to extend in the
direction of arrow B.
[0045] As illustrated in FIGS. 1 and 2, a first sealing member 42
is integrally formed on the surfaces 14a and 14b of the first
separator 14 so as to surround the outer edge of the first
separator 14. A second sealing member 44 is integrally formed on
the surfaces 16a and 16b of the second separator 16 so as to
surround the outer edge of the second separator 16.
[0046] As illustrated in FIG. 2, the first sealing member 42
includes a first protruding seal 42a, which is in contact with the
resin frame member 24 of the resin-framed membrane electrode
assembly 10, and a second protruding seal 42b, which is in contact
with the second sealing member 44 of the second separator 16. A
surface of the second sealing member 44 that is in contact with the
second protruding seal 42b forms a planar seal that extends in a
planar shape along the separator surface. Instead of the second
protruding seal 42b, a protruding seal (not shown) may be formed on
the second sealing member 44.
[0047] The first sealing member 42 and the second sealing member 44
are each made of an elastic material, such as a sealing material, a
cushioning material, or a packing material.
[0048] Examples of such materials include EPDM, NBR, fluorocarbon
rubber, silicone rubber, fluorosilicone rubber, butyl rubber,
natural rubber, styrene rubber, chloroprene rubber, and acrylic
rubber.
[0049] Hereinafter, an operation of the power generation cell 12
having such a structure will be described.
[0050] First, as illustrated in FIG. 1, an oxidant gas, such as an
oxygen-containing gas, is supplied to the oxidant gas inlet
manifold 30a, and a fuel gas, such as a hydrogen-containing gas, is
supplied to the fuel gas inlet manifold 34a. A coolant, such as
pure water, ethylene glycol, or oil, or the like, is supplied to
the coolant inlet manifold 32a.
[0051] The oxidant gas flows through the oxidant gas inlet manifold
30a into the oxidant gas channel 36 of the second separator 16,
flows in the direction of arrow B, and is supplied to the cathode
electrode 22 of the stepped MEA 10a. The fuel gas flows through the
fuel gas inlet manifold 34a into the fuel gas channel 38 of the
first separator 14. The fuel gas flows along the fuel gas channel
38 in the direction of arrow B and is supplied to the anode
electrode 20 of the stepped MEA 10a.
[0052] Accordingly, in the stepped MEA 10a, the oxidant gas
supplied to the cathode electrode 22 and the fuel gas supplied to
the anode electrode 20 are consumed in electrochemical reactions in
the second electrode catalyst layer 22a and the first electrode
catalyst layer 20a, and thereby electric power is generated.
[0053] Next, the oxidant gas supplied to the cathode electrode 22
and consumed is discharged through the oxidant gas outlet manifold
30b in the direction of arrow A. Likewise, the fuel gas supplied to
the anode electrode 20 and consumed is discharged through the fuel
gas outlet manifold 34b in the direction of arrow A.
[0054] The coolant supplied to the coolant inlet manifold 32a flows
into the coolant channel 40 between the first separator 14 and the
second separator 16 and flows in the direction of arrow B. The
coolant cools the stepped MEA 10a, and then the coolant is
discharged through the coolant outlet manifold 32b.
[0055] In the present embodiment, as illustrated in FIG. 4, the
clearance CL includes a short-side portion 46a, which is adjacent
to the oxidant gas inlet manifold 30a and which extends in the
direction of arrow C. The clearance C1 includes a pair of upper and
lower long-side portions 46b, which extend in the direction of
arrow B, and a short-side portion 46c, which is adjacent to the
oxidant gas outlet manifold 30b and which extends in the direction
of arrow C.
[0056] FIG. 6 shows the relationship among stresses generated in
the solid polymer electrolyte membrane 18 at the short-side portion
46a, the long-side portions 46b, and the short-side portion 46c.
The stress generated at the short-side portion 46a, which is
adjacent to the oxidant gas inlet manifold 30a, is the largest,
because a change in humidity is large. Therefore, a change in the
dimensions, due to expansion or contraction, of a portion of the
solid polymer electrolyte membrane 18 disposed at the short-side
portion 46a is larger than those of the other portions. The
stresses generated at the long-side portions 46b and the short-side
portion 46c are small, because a change in humidity is
comparatively small.
[0057] For this reason, as illustrated in FIG. 4, the direction MD
of the solid polymer electrolyte membrane 18 is made to coincide
with the short-side portion 46a, which is a side at which the
largest stress is generated in the solid polymer electrolyte
membrane 18. In other words, the winding direction (direction MD)
in which the rolled solid polymer electrolyte membrane 18R is wound
coincides with the longitudinal direction (direction of arrow B) of
the resin frame member 24.
[0058] Accordingly, because the dimensions of the resin frame
member 24 change by a comparatively large amount in the
longitudinal direction due to a change in temperature, a large
tension is applied to a portion of the solid polymer electrolyte
membrane 18 disposed at the short-side portion 46a of the clearance
CL. Regarding the solid polymer electrolyte membrane 18, due to a
change in humidity, in particular, a portion of the solid polymer
electrolyte membrane 18 disposed at the short-side portion 46a of
the clearance CL expands or contracts by a large amount, and a
large tension is applied.
[0059] Thus, a larger stress is generated in the portion of the
solid polymer electrolyte membrane 18 corresponding to the
short-side portion 46a of the clearance CL than in the portions of
the solid polymer electrolyte membrane corresponding to the
long-side portion 46b and the other short-side portion 46c of the
clearance CL. Therefore, by only checking for the presence of
breakage in one short-side portion 46a of the solid polymer
electrolyte membrane 18, the presence of breakage in the entirety
of the solid polymer electrolyte membrane 18 can be reliably
checked. Accordingly, it is possible to reliably perform breakage
check of the solid polymer electrolyte membrane 18 in the clearance
CL in a short time.
[0060] A resin-framed membrane electrode assembly for a fuel cell
according to the present disclosure includes a rectangular stepped
MEA and a rectangular resin frame member. The stepped MEA includes
a solid polymer electrolyte membrane, a first electrode that is
disposed on one surface of the solid polymer electrolyte membrane
and that includes a first electrode catalyst layer and a first gas
diffusion layer, and a second electrode that is disposed on the
other surface of the solid polymer electrolyte membrane and that
includes a second electrode catalyst layer and a second gas
diffusion layer. Planar dimensions of the first electrode are
larger than those of the second electrode. The resin frame member
surrounds an outer periphery of the solid polymer electrolyte
membrane.
[0061] The resin frame member includes an inwardly-protruding
portion that protrudes toward the second electrode. A clearance is
formed between an outer edge of the second gas diffusion layer and
an inner edge of the inwardly-protruding portion. The solid polymer
electrolyte membrane is obtained by cutting a rolled solid polymer
electrolyte membrane. A winding direction in which the rolled solid
polymer electrolyte membrane is wound coincides with a longitudinal
direction of the resin frame member.
[0062] Preferably, the first electrode is an anode electrode to
which a fuel gas is supplied, and the second electrode is a cathode
electrode to which an oxidant gas is supplied. In this case,
preferably, a supply pressure of the fuel gas supplied to the first
electrode is higher than a supply pressure of the oxidant gas
supplied to the second electrode.
[0063] A fuel cell according to the present disclosure includes the
resin-framed membrane electrode assembly and a rectangular
separator. The separator includes an oxidant gas inlet manifold
that is located adjacent to one short side of the resin frame
member and through which an oxidant gas flows in a stacking
direction in which the resin-framed membrane electrode assembly and
the separator are stacked. The separator includes an oxidant gas
outlet manifold that is located adjacent to the other short side of
the resin frame member and through which the oxidant gas flows in
the stacking direction.
[0064] In the solid polymer electrolyte membrane according to the
present disclosure, the winding direction in which the rolled solid
polymer electrolyte membrane is wound coincides with the
longitudinal direction of the resin frame member. Therefore, a
direction in which a change in the dimensions of the resin frame
member is large coincides with a direction in which a change in the
dimensions of the solid polymer electrolyte membrane is large.
[0065] Accordingly, because the dimensions of the resin frame
member change by a comparatively large amount in the longitudinal
direction due to a change in temperature, a large tension is
applied to the solid polymer electrolyte membrane disposed at a
short side of the clearance. Due to a change in humidity, the solid
polymer electrolyte membrane expands or contracts by a large amount
in the transverse direction of the resin frame member than in the
longitudinal direction of the resin frame member. Therefore, a
large tension is applied to a portion of the solid polymer
electrolyte membrane disposed at the short side of the
clearance.
[0066] Thus, a larger stress is generated in a short-side portion
of the solid polymer electrolyte membrane, corresponding to the
short side of the clearance, than in a long-side portion of the
solid polymer electrolyte membrane, corresponding to a long side of
the clearance. Therefore, by only checking for the presence of
breakage in the short-side portion of the solid polymer electrolyte
membrane, the presence of breakage in the entirety of the solid
polymer electrolyte membrane can be reliably checked. Accordingly,
it is possible to reliably perform breakage check of the solid
polymer electrolyte membrane in the clearance in a short time.
[0067] Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
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