U.S. patent application number 13/144893 was filed with the patent office on 2011-11-10 for fuel cell stack.
This patent application is currently assigned to Honda Motor Co., Ltd.. Invention is credited to Masahiro Ise, Chikara Iwasawa, Yasunori Kotani, Akihiro Matsui, Masahiro Mohri, Masaru Oda, Hiroaki Ohta, Hideo Okamoto, Yasuhiro Watanabe, Keiko Yamazaki.
Application Number | 20110274999 13/144893 |
Document ID | / |
Family ID | 42339843 |
Filed Date | 2011-11-10 |
United States Patent
Application |
20110274999 |
Kind Code |
A1 |
Mohri; Masahiro ; et
al. |
November 10, 2011 |
FUEL CELL STACK
Abstract
A fuel cell stack is comprised of a plurality of power
generating units which are stacked along the horizontal direction.
A corrugated passage groove having a shape corresponding to the
shape of the underside surface of a corrugated passage groove of a
first fuel gas passage is formed in a surface of a first metal
separator. A corrugated passage groove having a shape corresponding
to the shape of the underside surface of a corrugated passage
groove of a second oxidant gas passage is formed in a surface of a
third metal separator. The corrugated passage grooves overlap one
another to define a refrigerant passage. An oxidant gas inlet port
and a fuel gas inlet port are provided in the upper portion of the
power generating unit, and an oxidant gas outlet port and a fuel
gas outlet port are provided in the lower portion of the power
generating unit. A refrigerant inlet port and a refrigerant outlet
port are formed in each of the left and right portions of the power
generating unit.
Inventors: |
Mohri; Masahiro;
(Utsunomiya-shi, JP) ; Kotani; Yasunori;
(Utsunomiya-shi, JP) ; Oda; Masaru;
(Utsunomiya-shi, JP) ; Watanabe; Yasuhiro;
(Minato-ku, JP) ; Matsui; Akihiro;
(Utsunomiya-shi, JP) ; Yamazaki; Keiko;
(Utsunomiya-shi, JP) ; Iwasawa; Chikara;
(Saitama-shi, JP) ; Okamoto; Hideo;
(Utsunomiya-shi, JP) ; Ise; Masahiro;
(Utsunomiya-shi, JP) ; Ohta; Hiroaki;
(Utsunomiya-shi, JP) |
Assignee: |
Honda Motor Co., Ltd.
Tokyo
JP
|
Family ID: |
42339843 |
Appl. No.: |
13/144893 |
Filed: |
January 14, 2010 |
PCT Filed: |
January 14, 2010 |
PCT NO: |
PCT/JP2010/050301 |
371 Date: |
July 15, 2011 |
Current U.S.
Class: |
429/455 |
Current CPC
Class: |
Y02E 60/50 20130101;
H01M 8/1006 20130101; H01M 8/0232 20130101; H01M 8/0263 20130101;
H01M 8/0206 20130101; H01M 2008/1095 20130101; H01M 8/026 20130101;
H01M 2300/0082 20130101; H01M 8/0254 20130101; H01M 8/2483
20160201; H01M 8/1018 20130101; H01M 8/04029 20130101; H01M 8/241
20130101; H01M 8/1007 20160201; H01M 8/2457 20160201; H01M 8/0234
20130101; H01M 8/0267 20130101 |
Class at
Publication: |
429/455 |
International
Class: |
H01M 8/24 20060101
H01M008/24; H01M 8/04 20060101 H01M008/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 16, 2009 |
JP |
2009-008041 |
Mar 31, 2009 |
JP |
2009-083882 |
Claims
1. A fuel cell stack formed by stacking power generation units
together, the power generation units each being formed by stacking
an electrolyte electrode assembly and a metal separator having a
rectangular shape in a plan view, the electrolyte electrode
assembly including a pair of electrodes and an electrolyte
interposed between the electrodes, the fuel cell stack comprising:
a corrugated gas flow field formed on a surface of the metal
separator facing the electrode for supplying a fuel gas or an
oxygen-containing gas as a reactant gas along the electrode; a
coolant flow field formed as a back surface of the corrugated gas
flow field, between the power generation units; reactant gas supply
passages and reactant gas discharge passages for flowing the
reactant gases and which extend through one pair of opposite sides
of the metal separator in a stacking direction; and a pair of
coolant supply passages and a pair of coolant discharge passages
for flowing a coolant and which extend through the other opposite
sides of the metal separator in the stacking direction, the pair of
the coolant supply passages and the pair of the coolant discharge
passages being positioned adjacent to at least the reactant gas
supply passages or the reactant gas discharge passages, the pair of
the coolant supply passages being disposed separately on the other
opposite sides of the metal separator, and the pair of the coolant
discharge passages being disposed separately on the other opposite
sides of the metal separator.
2. The fuel cell stack according to claim 1, wherein the metal
separator is elongated longitudinally; an oxygen-containing gas
supply passage and a fuel gas supply passage serving as the
reactant gas supply passages extend through one end side of the
metal separator in a longitudinal direction of the metal separator;
an oxygen-containing gas discharge passage and a fuel gas discharge
passage serving as the reactant gas discharge passages extend
through the other end side of the metal separator in the
longitudinal direction; the pair of the coolant supply passages or
the pair of the coolant discharge passages are positioned by the
corrugated gas flow field and adjacent to the oxygen-containing gas
supply passage and the fuel gas supply passage of the metal
separator, and are disposed separately in a lateral direction of
the metal separator; and the pair of the coolant discharge passages
or the pair of the coolant supply passages are positioned by the
corrugated gas flow field and adjacent to the oxygen-containing gas
discharge passage and the fuel gas discharge passage of the metal
separator, and are disposed separately in the lateral
direction.
3. The fuel cell stack according to claim 1, wherein the metal
separator is elongated longitudinally in the direction of gravity,
and the metal separator and the electrolyte electrode assembly are
stacked in a horizontal direction.
4. The fuel cell stack according to claim 1, wherein the metal
separator is elongated longitudinally, an oxygen-containing gas
supply passage serving as the reactant gas supply passage and a
fuel gas discharge passage serving as the reactant gas discharge
passage extend through one end side of the metal separator in a
longitudinal direction of the metal separator; and an
oxygen-containing gas discharge passage serving as the reactant gas
discharge passage and a fuel gas supply passage serving as the
reactant gas supply passage extend through the other end side of
the metal separator in the longitudinal direction; the pair of the
coolant supply passages or the pair of the coolant discharge
passages are positioned by the corrugated gas flow field and
adjacent to the oxygen-containing gas supply passage and the fuel
gas discharge passage of the metal separator, and are disposed
separately in a lateral direction of the metal separator; and the
pair of the coolant discharge passages or the pair of the coolant
supply passages are positioned by the corrugated gas flow field and
adjacent to the oxygen-containing gas discharge passage and the
fuel gas supply passage of the metal separator, and are disposed
separately in the lateral direction.
5. The fuel cell stack according to claim 1, wherein the metal
separator is elongated longitudinally in a horizontal direction,
and the metal separator and the electrolyte electrode assembly are
stacked in the direction of gravity.
6. The fuel cell stack according to claim 1, wherein an inlet
buffer is provided at a position connecting the corrugated gas flow
field and the reactant gas supply passage; an outlet buffer is
provided at a position connecting the corrugated gas flow field and
the reactant gas discharge passage; and in the coolant flow field,
the coolant flows at least through the back surface of the outlet
buffer.
7. The fuel cell stack according to claim 2, wherein the pair of
the coolant supply passages and the pair of the coolant discharge
passages are positioned within a spacing interval in the lateral
direction between an outer end of an opening of at least the
oxygen-containing gas supply passage or the oxygen-containing gas
discharge passage and an outer end of an opening of at least the
fuel gas supply passage or the fuel gas discharge passage.
8. A fuel cell stack formed by stacking power generation units
together, the power generation units each being formed by stacking
an electrolyte electrode assembly and a separator having a
rectangular shape in a plan view, the electrolyte electrode
assembly including a pair of electrodes and an electrolyte
interposed between the electrodes, the fuel cell stack comprising:
a gas flow field formed on a surface of the separator facing the
electrode for supplying a fuel gas or an oxygen-containing gas as a
reactant gas along the electrode; a coolant flow field formed
between the power generation units; reactant gas supply passages
and reactant gas discharge passages for flowing the reactant gases
and which extend through one pair of opposite sides of the
separator in a stacking direction; and a pair of coolant supply
passages and a pair of coolant discharge passages for flowing a
coolant and which extend through the other opposite sides of the
separator in the stacking direction, the pair of the coolant supply
passages and the pair of the coolant discharge passages being
positioned adjacent to at least the reactant gas supply passages or
the reactant gas discharge passages, the pair of the coolant supply
passages being disposed separately on the other opposite sides of
the separator, the pair of the coolant discharge passages being
disposed separately on the other opposite sides of the
separator.
9. The fuel cell stack according to claim 8, wherein the separator
is elongated longitudinally, the reactant gas supply passages and
the reactant gas discharge passages extend through short sides of
the separator; and the coolant supply passages and the coolant
discharge passages extend through opposite long sides of the
separator.
10. The fuel cell stack according to claim 9, wherein the coolant
supply passages and the coolant discharge passage have
longitudinally-elongated shapes which extend along the long
sides.
11. A fuel cell stack formed by stacking a plurality of power
generation units together, the power generation units each being
formed by stacking an electrolyte electrode assembly and a metal
separator having a rectangular shape in a plan view, the
electrolyte electrode assembly including a pair of electrodes and
an electrolyte interposed between the electrodes, the fuel cell
stack comprising: reactant gas supply passages and reactant gas
discharge passages extending through one pair of opposite sides of
the power generation unit in a stacking direction; a coolant supply
passage and a coolant discharge passage extending through the other
opposite sides of the power generation unit in the stacking
direction, the coolant supply passage being positioned adjacent to
the reactant gas supply passages and the coolant discharge passage
being positioned adjacent to the reactant gas discharge passages;
corrugated oxygen-containing gas flow grooves formed on a surface
of one of adjacent metal separators facing the electrode for
supplying an oxygen-containing gas as one reactant gas along the
electrode, and corrugated fuel gas flow grooves formed on a surface
of the other of the adjacent metal separators facing the electrode
for supplying the fuel gas as the other reactant gas along the
electrode; and a coolant flow field formed between the adjacent
power generation units by ridges on the back surface of the
corrugated oxygen-containing gas flow grooves and ridges on the
back surface of the corrugated fuel gas flow grooves, wherein the
respective ridges on the back surfaces are set at different phases
in an upstream area adjacent to the coolant supply passage and in a
downstream area adjacent to the coolant discharge passage, and are
set at the same phase in an intermediate area where the flow
direction of the coolant is the same as at least the flow direction
of the oxygen-containing gas or the fuel gas.
12. The fuel cell stack according to claim 11, wherein the
corrugated oxygen-containing gas flow grooves or the corrugated
fuel gas flow grooves include phase reversing sections where phase
reversal occurs between the upstream and downstream areas and the
intermediate area.
13. The fuel cell stack according to claim 11, wherein the
corrugated oxygen-containing gas flow grooves or the corrugated
fuel gas flow grooves include straight sections through which a
phase shift by a half-phase is caused between the upstream and
downstream areas and the intermediate area.
14. The fuel cell stack according to claim 11, wherein the metal
separator is elongated longitudinally; the oxygen-containing gas
supply passage and the fuel gas supply passage serving as the
reactant gas supply passages extend through an upper end side of
the metal separator in a longitudinal direction thereof; the
oxygen-containing gas discharge passage and the fuel gas discharge
passage serving as the reactant gas discharge passages extend
through a lower end side of the metal separator in the longitudinal
direction; and on opposite sides of the metal separator in a
lateral direction thereof, a pair of the coolant supply passages
are positioned adjacent to the oxygen-containing gas supply passage
and the fuel gas supply passage, and a pair of the coolant
discharge passages are positioned adjacent to the oxygen-containing
gas discharge passage and the fuel gas discharge passage.
Description
TECHNICAL FIELD
[0001] The present invention relates to a fuel cell stack formed by
stacking a plurality of power generation units together. Each of
the power generation units is formed by stacking an electrolyte
electrode assembly and a separator. The electrolyte electrode
assembly includes a pair of electrodes and an electrolyte
interposed between the electrodes.
BACKGROUND ART
[0002] For example, a solid polymer electrolyte fuel cell employs
an electrolyte membrane. The electrolyte membrane is a polymer ion
exchange membrane, and is interposed between an anode and a cathode
to form a membrane electrode assembly (MEA). The membrane electrode
assembly is sandwiched between a pair of separators, so as to form
a power generation unit. In use of the fuel cell of this type,
normally, a predetermined number of power generation units are
stacked together to form a fuel cell stack.
[0003] In the fuel cell, a fuel gas flow field is formed on a
surface of one separator facing the anode for supplying a fuel gas
to the anode, and an oxygen-containing gas flow field is formed on
a surface of the other separator facing the cathode for supplying
an oxygen-containing gas to the cathode. Further, a coolant flow
field is formed between the adjacent separators for supplying a
coolant along surfaces of the separators.
[0004] Further, in many cases, this type of fuel cell is
constructed as the so-called "internal manifold type fuel cell". In
the internal manifold type fuel cell, a fuel gas supply passage and
a fuel gas discharge passage for the fuel gas, an oxygen-containing
gas supply passage and an oxygen-containing gas discharge passage
for the oxygen-containing gas, and a coolant supply passage and a
coolant discharge passage for the coolant extend through the power
generation units in the stacking direction.
[0005] As an internal manifold type fuel cell, for example, a flow
field plate as disclosed in Japanese Laid-Open Patent Publication
No. 2008-536258 (PCT) is known. As shown in FIG. 19, a hydrogen
flow field 2a is formed on the surface of an anode flow field plate
1a. At one end of the anode flow field plate 1a in a longitudinal
direction indicated by an arrow X, an anode air inlet manifold
aperture 3a, an anode coolant inlet manifold aperture 4a, and an
anode hydrogen inlet manifold aperture 5a are formed. At the other
end of the anode flow field plate 1a in the longitudinal direction,
an anode air outlet manifold aperture 3b, an anode coolant outlet
manifold aperture 4b, and an anode hydrogen outlet manifold
aperture 5b are formed.
[0006] Further, in a fuel cell disclosed in Japanese Laid-Open
Patent Publication No. 09-161819, as shown in FIG. 20, a separator
1b is provided in contact with the oxidizing agent electrode. A
plurality of oxygen-containing gas flow grooves 2b are formed on a
main surface of the separator 1b at the oxidizing agent electrode.
Oxygen-containing gas inlets 6a are connected to the upstream side
of the oxygen-containing gas flow grooves 2b, and oxygen-containing
gas outlets 6b are connected to the downstream side of the
oxygen-containing gas flow grooves 2b.
[0007] One coolant water inlet 7a is formed between a pair of the
oxygen-containing gas inlets 6a at an upper position of the
separator b1, and one coolant water outlet 7b is formed between a
pair of the oxygen-containing gas outlets 6b. A pair of fuel gas
supply passages 8a are provided on both sides of an upper portion
of the separator 1b, and a pair of fuel gas discharge passages 8b
are provided on both sides of a lower portion of the separator
1b.
SUMMARY OF THE INVENTION
[0008] However, in Japanese Laid-Open Patent Publication No.
2008-536258 (PCT), three inlets and three outlets are arranged in a
direction indicated by an arrow Y, at both ends in the longitudinal
direction, respectively. In the structure, the width of the anode
flow field plate 1a in the direction indicated by the arrow Y is
significantly large, and reduction in the width of the anode flow
field plate 1a cannot be achieved easily.
[0009] Further, in Japanese Laid-Open Patent Publication No.
09-161819, a pair of the oxygen-containing gas inlets 6a and a pair
of the fuel gas supply passages 8a are formed at both sides of the
coolant water inlet 7a on the upper portion of the separator 1b.
Further, a pair of the oxygen-containing gas outlets 6b and a pair
of the fuel gas discharge passages 8b are provided at both sides of
the coolant water outlets 7b on the lower portion of the separator
b1.
[0010] Therefore, the width of the separator 1b in the direction
indicated by the arrow H is significantly large, and the overall
size of the unit cell including the separator 1b is large
disadvantageously.
[0011] The present invention has been made to solve the problems of
this type, and an object of the present invention is to provide a
fuel cell stack having simple structure in which the width of the
fuel cell stack is reduced as much as possible, and the desired
cooling performance is achieved.
[0012] The present invention relates to a fuel cell stack formed by
stacking power generation units together. Each of the power
generation units is formed by stacking an electrolyte electrode
assembly and a metal separator having a rectangular shape in a plan
view. The electrolyte electrode assembly includes a pair of
electrodes and an electrolyte interposed between the electrodes. In
the fuel cell stack, a corrugated gas flow field is formed on a
surface of the metal separator facing the electrode for supplying a
fuel gas or an oxygen-containing gas as a reactant gas along the
electrode. A coolant flow field is formed as a back surface of the
corrugated gas flow field, between the power generation units.
[0013] In the fuel cell stack, reactant gas supply passages and
reactant gas discharge passages for flowing the reactant gases
extend through one pair of opposite sides of the metal separator in
a stacking direction. A pair of coolant supply passages and a pair
of coolant discharge passages for flowing a coolant extend through
the other opposite sides of the metal separator in the stacking
direction. The pair of the coolant supply passages and the pair of
the coolant discharge passages are positioned adjacent to at least
the reactant gas supply passages or the reactant gas discharge
passages. The pair of the coolant supply passages are disposed
separately on the other opposite sides of the metal separator, and
the pair of the coolant discharge passages are disposed separately
on the other opposite sides of the metal separator.
[0014] Further, the present invention relates to a fuel cell stack
formed by stacking power generation units together. Each of the
power generation units is formed by stacking an electrolyte
electrode assembly and a separator having a rectangular shape in a
plan view. The electrolyte electrode assembly includes a pair of
electrodes and an electrolyte interposed between the electrodes. In
the fuel cell stack, a gas flow field is formed on a surface of the
separator facing the electrode for supplying a fuel gas or an
oxygen-containing gas as a reactant gas along the electrode. A
coolant flow field is formed between the power generation
units.
[0015] Reactant gas supply passages and reactant gas discharge
passages for flowing the reactant gases extend through one pair of
opposite sides of the separator in a stacking direction. A pair of
coolant supply passages and a pair of coolant discharge passages
for flowing a coolant extend through the other opposite sides of
the separator in the stacking direction. The pair of the coolant
supply passages and the pair of the coolant discharge passages are
positioned adjacent to at least the reactant gas supply passages or
the reactant gas discharge passages, and the pair of the coolant
supply passages are disposed separately on the other opposite sides
of the separator, while the pair of the coolant discharge passages
are disposed separately on the other opposite sides of the
separator.
[0016] In the present invention, a fuel cell stack is formed by
stacking a plurality of power generation units together. Each of
the power generation units is formed by stacking an electrolyte
electrode assembly and a metal separator having a rectangular shape
in a plan view. The electrolyte electrode assembly includes a pair
of electrodes and an electrolyte interposed between the electrodes.
In the fuel cell stack, reactant gas supply passages and reactant
gas discharge passages extend through one pair of opposite sides of
the power generation unit in a stacking direction. A coolant supply
passage and a coolant discharge passage extend through the other
opposite sides of the power generation unit in the stacking
direction. The coolant supply passage is positioned adjacent to the
reactant gas supply passages, and the coolant discharge passage is
positioned adjacent to the reactant gas discharge passages.
[0017] Corrugated oxygen-containing gas flow grooves are formed on
a surface of one of adjacent metal separators facing the electrode
for supplying an oxygen-containing gas as one reactant gas along
the electrode, and corrugated fuel gas flow grooves are formed on a
surface of the other of the adjacent metal separators facing the
electrode for supplying the fuel gas as the other reactant gas
along the electrode.
[0018] A coolant flow field is formed between the adjacent power
generation units by ridges on the back surface of the corrugated
oxygen-containing gas flow grooves and ridges on the back surface
of the corrugated fuel gas flow grooves. The respective ridges on
the back surfaces are set at different phases in an upstream area
adjacent to the coolant supply passage and in a downstream area
adjacent to the coolant discharge passage, and are set at the same
phase in an intermediate area where the flow direction of the
coolant is the same as at least the flow direction of the
oxygen-containing gas or the fuel gas.
[0019] In the present invention, the reactant gas supply passages
and the coolant supply passages are not arranged along one side of
the separator such as a metal separator or a carbon separator. In
the structure, the separator does not become significantly wide or
long. In particular, the width of the separator can be reduced as
much as possible, and it becomes possible to install the fuel cell
stack conveniently.
[0020] Further, since the pair of the coolant supply passages are
disposed separately while the pair of the coolant discharge
passages are disposed separately, the coolant can be supplied
uniformly and reliably to the entire coolant flow field. Thus, the
uniform moisture environment can be achieved in the entire power
generation area, and efficient power generation is performed
suitably.
[0021] In the present invention, the respective ridges on the back
surfaces forming the coolant flow field are set at different phases
in the upstream area adjacent to the coolant supply passage and in
the downstream area adjacent to the coolant discharge passage.
Further, the respective ridges on the back surfaces are set at the
same phase in the intermediate area. In the structure, in the
intermediate area of the coolant flow field, the flow direction of
the coolant is the same as the gas flow direction of at least the
oxygen-containing gas or the fuel gas, and the flow direction of
the coolant is changed to a direction intersecting the gas flow
direction, at positions adjacent to the coolant supply passage and
the coolant discharge passage.
[0022] Thus, the coolant supply passage and the coolant discharge
passage are positioned on different two sides that are different
from the two sides of the power generation unit where the
oxygen-containing gas supply passage, the fuel gas supply passage,
the oxygen-containing gas discharge passage, and the fuel gas
discharge passage are provided.
[0023] Therefore, since it is not required to arrange these
passages in the width direction of the power generation unit, it is
possible to provide an internal manifold type fuel cell stack, with
a simple structure, where the width of the fuel cell stack can be
reduced as much as possible.
[0024] Further, the respective ridges on the back surfaces are in
the same phase in the intermediate area. Thus, the coolant can be
supplied smoothly and reliably in the same direction as the flow
direction of at least the oxygen-containing gas or the fuel gas.
Accordingly, cooling efficiency of the power generation unit is
improved advantageously.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is an exploded perspective view showing main
components of a power generation unit of a fuel cell stack
according to a first embodiment of the present invention;
[0026] FIG. 2 is a cross sectional view showing the fuel cell
stack, taken along a line II-II in FIG. 1;
[0027] FIG. 3 is a front view showing a third metal separator of
the power generation unit;
[0028] FIG. 4 is a partial cross sectional view showing the fuel
cell stack;
[0029] FIG. 5 is a perspective view showing a coolant flow field
formed between the power generation units;
[0030] FIG. 6 is an exploded perspective view showing main
components of a fuel cell stack according to a second embodiment of
the present invention;
[0031] FIG. 7 is an exploded perspective view showing main
components of a fuel cell stack according to a third embodiment of
the present invention;
[0032] FIG. 8 is an exploded perspective view showing main
components of a fuel cell stack according to a fourth embodiment of
the present invention;
[0033] FIG. 9 is an exploded perspective view showing main
components of a power generation unit of a fuel cell stack
according to a fifth embodiment of the present invention;
[0034] FIG. 10 is a front view showing a first metal separator of
the power generation unit;
[0035] FIG. 11 is a view showing a coolant flow field formed
between power generation units.
[0036] FIG. 12 is a transparent view showing a first fuel gas flow
field and a first oxygen-containing gas flow field of the power
generation unit;
[0037] FIG. 13 is a view showing contact areas of the coolant flow
field;
[0038] FIG. 14 is an exploded perspective view showing main
components of a power generation unit of a fuel cell stack
according to a sixth embodiment of the present invention;
[0039] FIG. 15 is an exploded perspective view showing main
components of a power generation unit of a fuel cell stack
according to a seventh embodiment of the present invention;
[0040] FIG. 16 is a front view showing a first metal separator of
the power generation unit;
[0041] FIG. 17 is a view showing a coolant flow field formed
between the power generation units;
[0042] FIG. 18 is a view showing contact areas of the coolant flow
field;
[0043] FIG. 19 is a view showing an anode flow field plate
disclosed in Japanese Laid-Open Patent Publication No. 2008-536258
(PCT); and
[0044] FIG. 20 is a view showing a separator of a fuel cell
disclosed in Japanese Laid-Open Patent Publication No.
09-161819.
DESCRIPTION OF THE EMBODIMENTS
[0045] As shown in FIG. 1, a fuel cell stack 10 according to a
first embodiment of the present invention includes a power
generation unit 12. A plurality of the power generation units 12
are stacked together in a horizontal direction indicated by an
arrow A. As shown in FIGS. 1 and 2, the power generation unit 12
includes a first metal separator 14, a first membrane electrode
assembly (electrolyte electrode assembly) 16a, a second metal
separator 18, a second membrane electrode assembly 16b, and a third
metal separator 20.
[0046] For example, the first metal separator 14, the second metal
separator 18 and the third metal separator 20 are longitudinally
long metal plates, which are made of steel plates, stainless steel
plates, aluminum plates, plated steel sheets, or such metal plates
having anti-corrosive surfaces formed by carrying out a surface
treatment thereon. Each of the first metal separator 14, the second
metal separator 18, and the third metal separator 20 has a
rectangular shape in a plan view, and has a corrugated shape in
cross section, by corrugating metal thin plates by pressure
forming.
[0047] As shown in FIG. 2, the surface area of the first membrane
electrode assembly 16a is smaller than the surface area of the
second membrane electrode assembly 16b. Each of the first and
second membrane electrode assemblies 16a, 16b includes an anode 24,
a cathode 26 and a solid polymer electrolyte membrane 22 interposed
between the anode 24 and the cathode 26. The solid polymer
electrolyte membrane 22 is formed by impregnating a thin membrane
of perfluorosulfonic acid with water, for example. The surface area
of the anode 24 is smaller than the surface area of the cathode 26.
That is, each of the first and second membrane electrode assemblies
16a, 16b is constructed as the so-called "stepped-type MEA".
[0048] Each of the anode 24 and the cathode 26 has a gas diffusion
layer (not shown) such as a carbon paper, and an electrode catalyst
layer (not shown) of platinum alloy supported on porous carbon
particles. The carbon particles are deposited uniformly on the
surface of the gas diffusion layer. The electrode catalyst layer of
the anode 24 and the electrode catalyst layer of the cathode 26 are
fixed to both surfaces of the solid polymer electrolyte membrane
22, respectively.
[0049] As shown in FIG. 1, at an upper end portion (i.e., a short
side portion) of the power generation unit 12 in the longitudinal
direction indicated by an arrow C, an oxygen-containing gas supply
passage 30a for supplying an oxygen-containing gas and a fuel gas
supply passage 32a for supplying a fuel gas such as a
hydrogen-containing gas are provided. The oxygen-containing gas
supply passage 30a and the fuel gas supply passage 32a extend
through the power generation unit 12 in the direction indicated by
the arrow A.
[0050] At a lower end portion (i.e., the other short side portion)
of the power generation unit 12 in the longitudinal direction
indicated by the arrow C, a fuel gas discharge passage 32b for
discharging the fuel gas and an oxygen-containing gas discharge
passage 30b for discharging the oxygen-containing gas are provided.
The fuel gas discharge passage 32b and the oxygen-containing gas
discharge passage 30b extend through the power generation unit 12
in the direction indicated by the arrow A.
[0051] At both end portions (i.e., long side portions) of the first
power generation unit 12 in a lateral direction indicated by an
arrow B, a pair of coolant supply passages 34a for supplying a
coolant are provided at upper positions, and at both end portions
of the first power generation unit 12 in the lateral direction
indicated by the arrow B, a pair of coolant discharge passages 34b
for discharging the coolant are provided at lower positions. The
coolant supply passages 34a and the coolant discharge passages 34b
extend through the first power generation unit 12 in the direction
indicated by the arrow A. The coolant supply passages 34a and the
coolant discharge passages 34b are elongated longitudinally along
the long sides of the power generation unit 12.
[0052] The coolant supply passages 34a are positioned adjacent to
the oxygen-containing gas supply passage 30a and the fuel gas
supply passage 32a, and are disposed separately on opposite sides
in the direction indicated by the arrow B. The coolant discharge
passages 34b are positioned adjacent to the oxygen-containing gas
discharge passage 30b and the fuel gas discharge passage 32b, and
are disposed separately on the opposite sides in the direction
indicated by the arrow B.
[0053] As shown in FIG. 3, the distance between the outer end of
the opening of the oxygen-containing gas supply passage 30a and the
outer end of the opening of the fuel gas supply passage 32a in the
horizontal direction is defined as a spacing interval H. Further,
the distance between the outer end of the opening of the
oxygen-containing gas discharge passage 30b and the outer end of
the opening of the fuel gas discharge passage 32b in the horizontal
direction is defined as the spacing interval H. Preferably, the
pair of the coolant supply passages 34a are disposed separately on
the opposite sides within the spacing interval H, and the pair of
the coolant discharge passages 34b are disposed separately on the
opposite sides within the spacing interval H. However, in
practical, it is sufficient that the pair of the coolant supply
passages 34a and the pair of the coolant discharge passages 34b are
provided separately on the opposite sides at an interval which is
substantially equal to the spacing interval H.
[0054] As shown in FIG. 1, the first metal separator 14 has a first
fuel gas flow field 36 on its surface 14a facing the first membrane
electrode assembly 16a. The first fuel gas flow field 36 connects
the fuel gas supply passage 32a and the fuel gas discharge passage
32b. The first fuel gas flow field 36 includes a plurality of
corrugated flow grooves 36a extending in the direction indicated by
the arrow C. An inlet buffer 38 and an outlet buffer 40 each having
a plurality of bosses are provided near an inlet and an outlet of
the first fuel gas flow field 36, respectively.
[0055] A coolant flow field 44 is partially formed on a surface 14b
of the first metal separator 14. The coolant flow field 44 connects
the coolant supply passages 34a and the coolant discharge passages
34b. On the surface 14b, a plurality of corrugated flow grooves 44a
are formed as the back surface of the corrugated flow grooves 36a
of the first fuel gas flow field 36.
[0056] The second metal separator 18 has a first oxygen-containing
gas flow field 50 on its surface 18a facing the first membrane
electrode assembly 16a. The first oxygen-containing gas flow field
50 connects the oxygen-containing gas supply passage 30a and the
oxygen-containing gas discharge passage 30b. The first
oxygen-containing gas flow field 50 includes a plurality of
corrugated flow grooves 50a extending in the direction indicated by
the arrow C. An inlet buffer 52 and an outlet buffer 54 are
provided near an inlet and an outlet of the first oxygen-containing
gas flow field 50, respectively.
[0057] The second metal separator 18 has a second fuel gas flow
field 58 on its surface 18b facing the second membrane electrode
assembly 16b. The second fuel gas flow field 58 connects the fuel
gas supply passage 32a and the fuel gas discharge passage 32b. The
second fuel gas flow field 58 includes a plurality of corrugated
flow grooves 58a extending in the direction indicated by the arrow
C. An inlet buffer 60 and an outlet buffer 62 are provided near an
inlet and an outlet of the second fuel gas flow field 58,
respectively. The second fuel gas flow field 58 is formed on the
back surface of the first oxygen-containing gas flow field 50, and
the inlet buffer 60 and the outlet buffer 62 are formed on the back
surfaces of the inlet buffer 52 and the outlet buffer 54,
respectively.
[0058] The third metal separator 20 has a second oxygen-containing
gas flow field 66 on its surface 20a facing the second membrane
electrode assembly 16b. The second oxygen-containing gas flow field
66 connects the oxygen-containing gas supply passage 30a and the
oxygen-containing gas discharge passage 30b. The second
oxygen-containing gas flow field 66 includes a plurality of
corrugated flow grooves 66a extending in the direction indicated by
arrow C. An inlet buffer 68 and an outlet buffer 70 are provided
near an inlet and an outlet of the second oxygen-containing gas
flow field 66, respectively.
[0059] The coolant flow field 44 is partially formed on the surface
20b of the third metal separator 20. On the surface 20b, a
plurality of corrugated flow grooves 44b are formed as the back
surface of the corrugated flow grooves 66a of the second
oxygen-containing gas flow field 66.
[0060] In the power generation unit 12, concerning the first fuel
gas flow field 36 of the first metal separator 14, the first
oxygen-containing gas flow field 50 of the second metal separator
18, and the second fuel gas flow field 58 of the second metal
separator 18, the corrugated (wavelike) shapes thereof are set
mutually at the same phase along the stacking direction. Further,
the wave pitch and amplitude thereof are set the same. Concerning
the second oxygen-containing gas flow field 66 of the third metal
separator 20, which is arranged at one end of the power generation
unit 12 in the stacking direction indicated by the arrow A, the
wavelike shape thereof is set mutually at a different phase along
the stacking direction from the first fuel gas flow field 36, the
first oxygen-containing gas flow field 50, and the second fuel gas
flow field 58, while the wave pitch and amplitude thereof are set
the same.
[0061] As shown in FIGS. 1 and 2, a first seal member 74 is formed
integrally on the surfaces 14a, 14b of the first metal separator
14, surrounding the outer circumferential end of the first metal
separator 14. Further, the second seal member 76 is formed
integrally on the surfaces 18a, 18b of the second metal separator
18, surrounding the outer circumferential end of the second metal
separator 18. A third seal member 78 is formed integrally on the
surfaces 20a, 20b of the third metal separator 20, surrounding the
outer circumferential end of the third metal separator 20.
[0062] The first metal separator 14 has a plurality of outer supply
holes 80a and inner supply holes 80b connecting the fuel gas supply
passage 32a to the first fuel gas flow field 36, and a plurality of
outer discharge holes 82a and inner discharge holes 82b connecting
the fuel gas discharge passage 32b to the first fuel gas flow field
36.
[0063] The second metal separator 18 has a plurality of supply
holes 84 connecting the fuel gas supply passage 32a to the second
fuel gas flow field 58, and a plurality of discharge holes 86
connecting the fuel gas discharge passage 32b to the second fuel
gas flow field 58.
[0064] The power generation units 12 are stacked together. Thus,
the coolant flow field 44 extending in the direction indicated by
the arrow B is formed between the first metal separator 14 of one
of the adjacent power generation units 12 and the third metal
separator 20 of the other of the adjacent power generation units
12.
[0065] In the coolant flow field 44, the corrugated flow grooves
44a and the corrugated flow grooves 44b are set at different
phases. By mutually overlapping the corrugated flow grooves 44a and
the corrugated flow grooves 44b, a plurality of grooves 44c that
communicate in a horizontal direction indicated by the arrow B are
formed between the corrugated flow grooves 44a and the corrugated
flow grooves 44b (FIGS. 4 and 5). The coolant flow field 44 is
configured to allow the coolant to flow across the back surfaces of
the inlet buffer 38, the outlet buffer 40, the inlet buffer 68, and
the outlet buffer 70.
[0066] Operation of the fuel cell stack 10 having the structure
will be described below.
[0067] Firstly, as shown in FIG. 1, an oxygen-containing gas is
supplied to the oxygen-containing gas supply passage 30a, and a
fuel gas such as a hydrogen-containing gas is supplied to the fuel
gas supply passage 32a. Further, a coolant such as pure water,
ethylene glycol, or oil is supplied to the coolant supply passages
34a.
[0068] Thus, the oxygen-containing gas from the oxygen-containing
gas supply passage 30a flows into the first oxygen-containing gas
flow field 50 of the second metal separator 18 and the second
oxygen-containing gas flow field 66 of the third metal separator
20. The oxygen-containing gas moves along the first
oxygen-containing gas flow field 50 in the direction of gravity
indicated by the arrow C, and the oxygen-containing gas is supplied
to the cathode 26 of the first membrane electrode assembly 16a.
Further, the oxygen-containing gas moves along the second
oxygen-containing gas flow field 66 in the direction indicated by
the arrow C, and the oxygen-containing gas is supplied to the
cathode 26 of the second membrane electrode assembly 16b.
[0069] As shown in FIG. 2, the fuel gas from the fuel gas supply
passage 32a flows through the outer supply holes 80a toward the
surface 14b of the first metal separator 14. Further, the fuel gas
from the inner supply holes 80b moves toward the surface 14a, and
then, the fuel gas moves along the first fuel gas flow field 36 in
the direction of gravity indicated by the arrow C. The fuel gas is
thus supplied to the anode 24 of the first membrane electrode
assembly 16a (see FIG. 1).
[0070] Further, as shown in FIG. 2, the fuel gas flows through the
supply holes 84 toward the surface 18b of the second metal
separator 18. Thus, as shown in FIG. 1, the fuel gas moves along
the second fuel gas flow field 58 on the surface 18b in the
direction indicated by the arrow C. The fuel gas is thus supplied
to the anode 24 of the second membrane electrode assembly 16b.
[0071] Thus, in each of the first and second membrane electrode
assemblies 16a, 16b, the oxygen-containing gas supplied to the
cathode 26 and the fuel gas supplied to the anode 24 are consumed
in the electrochemical reactions at electrode catalyst layers of
the cathode 26 and the anode 24 for generating electricity.
[0072] The oxygen-containing gas consumed at each of the cathodes
26 of the first and second membrane electrode assemblies 16a, 16b
is discharged along the oxygen-containing gas discharge passage 30b
in the direction indicated by the arrow A.
[0073] The fuel gas consumed at the anode 24 of the first membrane
electrode assembly 16a flows through the inner discharge holes 82b,
and then, the fuel gas moves to the surface 14b. After the fuel gas
moves to the surface 14b, the fuel gas flows through the outer
discharge holes 82a, and again, the fuel gas moves to the surface
14a. Then, the fuel gas is discharged to the fuel gas discharge
passage 32b.
[0074] The fuel gas supplied to and consumed at the anode 24 of the
second membrane electrode assembly 16b flows through the discharge
holes 86 toward the surface 18a. Then, the fuel gas is discharged
into the fuel gas discharge passage 32b.
[0075] As shown in FIG. 3, the coolant supplied to the pair of left
and right coolant supply passages 34a flows into the coolant flow
field 44 formed between the first metal separator 14 of one of the
adjacent power generation units 12 and the third metal separator 20
of the other of the adjacent power generation units 12.
[0076] The pair of the coolant supply passages 34a are disposed
separately at the left and right ends on the upper portion of the
power generation unit 12, and are positioned adjacent to the
oxygen-containing gas supply passage 30a and the fuel gas supply
passage 32a.
[0077] In the structure, substantially the same amount of coolant
is supplied from each of the coolant supply passages 34a to the
coolant flow field 44 toward each other, in the direction indicated
by the arrow B. The flows of coolant from the coolant supply
passages 34a meet at the center of the coolant flow field 44 in the
direction indicated by the arrow B. Then the coolant moves in the
direction of gravity (toward the lower side in the direction
indicated by the arrow C), and substantially the same amount of the
coolant is discharged into each of the coolant discharge passages
34b disposed separately on opposite sides of the lower portion of
the power generation unit 12.
[0078] As described above, in the first embodiment, the pair of
left and right coolant supply passages 34a extend through upper
positions of the power generation units 12, and the pair of left
and right coolant discharge passages 34b extend through the lower
positions of the power generation units 12. Therefore, the coolant
can move in a vertically downward direction over the entire area of
the coolant flow field 44. In the structure, it becomes possible to
control the temperature distribution utilizing a temperature
gradient in the coolant flow field 44, whereby uniform cooling
efficiency can be maintained.
[0079] Further, in the first embodiment, the oxygen-containing gas
supply passage 30a and the fuel gas supply passage 32a, and the
oxygen-containing gas discharge passage 30b and the fuel gas
discharge passage 32b are provided on upper and lower opposite
sides of the power generation unit 12, respectively. The pair of
coolant supply passages 34a are disposed separately on the left and
right opposite sides of the power generation unit 12, while the
pair of coolant discharge passages 34b are disposed separately on
the left and right opposite sides of the power generation unit
12.
[0080] In the structure, the width of the power generation unit 12
in the direction indicated by the arrow B is reduced effectively.
In particular, the coolant supply passages 34a and the coolant
discharge passages 34b are disposed within the area of the spacing
interval H in the horizontal direction (indicated by the arrow B)
between the oxygen-containing gas supply passage 30a
(oxygen-containing gas discharge passage 30b) and the fuel gas
supply passage 32a (fuel gas discharge passage 32b), or disposed at
an interval that is substantially equal to the spacing interval H.
In the structure, the width of the power generation unit 12 can be
reduced as much as possible.
[0081] Further, in the first embodiment, the coolant flows through
the coolant flow field 44 in the direction of gravity, i.e., in
parallel to the direction in which the oxygen-containing gas flows
through the second oxygen-containing gas flow field 66 on the back
surface of the coolant flow field 44. In the structure, since the
temperature at the upstream side of the second oxygen-containing
gas flow field 66 decreases with increasing flow rate of the
coolant, the highly humidified area is expanded, and the resistance
overpotential is reduced.
[0082] On the downstream side of the second oxygen-containing gas
flow field 66 (and the first oxygen-containing gas flow field 50),
heated coolant is supplied, and then the temperature is increased.
Therefore, vaporization of the water produced in the power
generation reaction is facilitated, and flooding is suppressed.
Thus, reduction in the concentration overpotential is achieved. In
the structure, improvement in the output and durability of the
power generation unit 12 is achieved. Further, the uniform
humidification environment from the upstream side to the downstream
side of the second oxygen-containing gas flow field 66 (and the
first oxygen-containing gas flow field 50) is achieved, and water
swelling of the solid polymer electrolyte membrane 22 becomes
uniform. Moreover, deflection of the stack is suppressed.
[0083] Further, in the first embodiment, in the coolant flow field
44, the coolant flows on the back surfaces of the inlet buffer 38,
the outlet buffer 40, the inlet buffer 68, and the outlet buffer
70. In the structure, since the coolant flows in the direction of
gravity through the back surfaces of the buffers, the flow of the
coolant is distributed uniformly in the coolant flow field 44, and
it becomes possible to cool the power generation area suitably.
[0084] Further, since the coolant flows also into the areas on the
back surfaces of the outlet buffers 40, 70, the temperature becomes
high at the downstream side of the second oxygen-containing gas
flow field 66 (and the first oxygen-containing gas flow field 50)
where no power generation is performed. Thus, the temperature
difference between the non-power-generation area and the
power-generation area is reduced, whereby water condensation can be
suppressed suitably.
[0085] Though the first embodiment has been described in the case
of using the power generation unit 12 having the first metal
separator 14, the first membrane electrode assembly 16a, the second
metal separator 18, the second membrane electrode assembly 16b, and
the third metal separator 20, the present invention is not limited
in this respect. For example, a power generation unit formed by
sandwiching one electrolyte electrode assembly between a pair of
metal separators may be used, and the coolant flow field may be
formed between the adjacent power generation units.
[0086] In the first embodiment, the oxygen-containing gas supply
passage 30a and the fuel gas supply passage 32a are provided at the
upper end portion of the power generation unit 12, while the
oxygen-containing gas discharge passage 30b and the fuel gas
discharge passage 32b are provided at the lower end portion of the
power generation unit 12. Conversely, the oxygen-containing gas
discharge passage 30b and the fuel gas discharge passage 32b may be
provided at the upper end portion of the power generation unit 12,
while the oxygen-containing gas supply passage 30a and the fuel gas
supply passage 32a may be provided at the lower end portion of the
power generation unit 12.
[0087] Further, a pair of the coolant supply passages 34a are
provided at both ends in the lateral direction on the upper portion
of the power generation unit 12, while a pair of the coolant
discharge passages 34b are provided at both ends in the lateral
direction on the lower portion of the power generation unit 12.
Conversely, the pair of coolant discharge passages 34b may be
provided at both ends in the lateral direction on the upper portion
of the power generation unit 12, and a pair of coolant supply
passages 34a may be provided at both ends in the lateral direction
on the lower portion of the power generation unit 12.
[0088] The above also applies to second to fourth embodiments of
the present invention, to be described below.
[0089] FIG. 6 is an exploded perspective view showing main
components of a power generation unit 102 of a fuel cell stack 100
according to a second embodiment of the present invention.
[0090] The constituent elements of the fuel cell stack 100 that are
identical to those of the fuel cell stack 10 according to the first
embodiment are labeled with the same reference numerals, and
detailed descriptions thereof will be omitted. Also in third and
other embodiments as described later, the constituent elements that
are identical to those of the fuel cell stack 10 according to the
first embodiment are labeled with the same reference numerals, and
detailed descriptions thereof will be omitted.
[0091] The power generation unit 102 includes a first metal
separator 104, a first membrane electrode assembly 106a, a second
metal separator 108, a second membrane electrode assembly 106b, and
a third metal separator 109.
[0092] An oxygen-containing gas supply passage 30a and a fuel gas
discharge passage 32b extend through the power generation unit 102
at upper end positions in the longitudinal direction. An
oxygen-containing gas discharge passage 30b and a fuel gas supply
passage 32a extend through the power generation unit 102 at lower
end positions in the longitudinal direction.
[0093] In the power generation unit 102, the oxygen-containing gas
flows in the first and second oxygen-containing gas flow fields 50,
66 in the direction of gravity, while the fuel gas flows in the
first and second fuel gas flow fields 36, 58 in the direction
opposite to gravity, i.e., in the direction opposite to the flow
direction of the oxygen-containing gas. In the second embodiment,
the oxygen-containing gas and the fuel gas flow in a counterflow
manner. Further, the same advantages as in the case of the first
embodiment are obtained.
[0094] FIG. 7 is an exploded perspective view showing main
components of a power generation unit 112 of a fuel cell stack 110
according to a third embodiment of the present invention.
[0095] The power generation unit 112 is formed by stacking a first
metal separator 114, a first membrane electrode assembly 116a, a
second metal separator 118, a second membrane electrode assembly
116b, and a third metal separator 120 in the direction of
gravity.
[0096] In the third embodiment, the width of the power generation
unit 112 in the direction indicated by the arrow A is reduced as
much as possible. In a state where a plurality of power generation
units 112 are stacked together in the direction of gravity, the
width of the fuel cell stack 110 is reduced. Further, the same
advantages as in the case of the first and second embodiments are
obtained. It should be noted that the oxygen-containing gas and the
fuel gas may flow in a counterflow manner as in the case of the
second embodiment.
[0097] FIG. 8 is an exploded perspective view showing main
components of a power generation unit 132 of a fuel cell stack 130
according to a fourth embodiment of the present invention.
[0098] The power generation unit 132 includes a first carbon
separator 134, a first membrane electrode assembly 136a, a second
carbon separator 138, a second membrane electrode assembly 136b,
and a third carbon separator 140.
[0099] The power generation units 132 are stacked in a horizontal
direction indicated by an arrow A. Alternatively, the power
generation units 132 may be stacked in a vertical direction
indicated by an arrow C as in the case of the third embodiment. The
reactant gas flow field includes straight flow grooves instead of
the corrugated flow grooves.
[0100] In the fourth embodiment, instead of the metal separators,
the first carbon separator 134, the second carbon separator 138,
and the third carbon separator 140 are used. Further, the same
advantages as in the case of the first to third embodiments are
obtained.
[0101] FIG. 9 is an exploded perspective view showing main
components of a power generation unit 152 of a fuel cell stack 150
according to a fifth embodiment of the present invention.
[0102] The power generation unit 152 includes a first metal
separator 154, a first membrane electrode assembly 156a, a second
metal separator 158, a second membrane electrode assembly 156b, and
a third metal separator 160.
[0103] The first metal separator 154 includes a first fuel gas flow
field 162 on its surface 154a facing the first membrane electrode
assembly 156a. The first fuel gas flow field 162 connects a fuel
gas supply passage 32a and a fuel gas discharge passage 32b. The
first fuel gas flow field 162 includes a plurality of corrugated
flow grooves 162a extending in a direction indicated by an arrow
C.
[0104] As shown in FIG. 10, the corrugated flow grooves 162a
include first phase areas 164a having the same phase and which are
arranged respectively on the upstream side (upper side) and on the
downstream side (lower side), and a second phase area 164b having a
phase which is reverse to the phase of the first phase areas 164a
and which is reversed through phase reversing sections 166a, 166b.
The phase reversing sections 166a, 166b form a corrugated flow
field shifted by a half pitch by reversing the phase at the central
region as shown by dotted lines in FIG. 10, in midstream.
[0105] A coolant flow field 168 connecting a pair of coolant supply
passages 34a and a pair of coolant discharge passages 34b is
partially formed on a surface 154b of the first metal separator
154. On the surface 154b, a plurality of corrugated flow grooves
168a are formed as the back surface of a plurality of corrugated
flow grooves 162a of the first fuel gas flow field 162.
[0106] As schematically shown in FIG. 11, the corrugated flow
grooves 168a are formed between ridges on the back surface of the
corrugated flow grooves 162a. First phase areas 170a are provided
on the upstream side (upper side) and the downstream side (lower
side) of the corrugated flow grooves 168a, and a second phase area
170b in the reversed phase is formed in the intermediate area
thereof.
[0107] As shown in FIG. 9, the second metal separator 158 has a
first oxygen-containing gas flow field 172 on its surface 158a
facing the first membrane electrode assembly 156a. The first
oxygen-containing gas flow field 172 connects the oxygen-containing
gas supply passage 30a and the oxygen-containing gas discharge
passage 30b. The first oxygen-containing gas flow field 172
includes a plurality of corrugated flow grooves 172a extending in
the direction indicated by the arrow C.
[0108] As shown in FIG. 12, the corrugated flow grooves 172a face
the corrugated flow grooves 162a of the first fuel gas flow field
162. In the first phase areas 164a, the corrugated flow grooves
172a and the corrugated flow grooves 162a are set at different
phases. In the second phase area 164b, the corrugated flow grooves
172a and the corrugated flow grooves 162a are set at the same
phase.
[0109] The second metal separator 158 has a second fuel gas flow
field 174 on its surface 158b facing the second membrane electrode
assembly 156b. The second fuel gas flow field 174 connects the fuel
gas supply passage 32a and the fuel gas discharge passage 32b. As
shown in FIG. 9, the second fuel gas flow field 174 includes a
plurality of corrugated flow grooves 174a extending in the
direction indicated by the arrow C.
[0110] The third metal separator 160 has a second oxygen-containing
gas flow field 176 on its surface 160a facing the second membrane
electrode assembly 156b. The second oxygen-containing gas flow
field 176 connects the oxygen-containing gas supply passage 30a and
the oxygen-containing gas discharge passage 30b. The second
oxygen-containing gas flow field 176 includes a plurality of
corrugated flow grooves 176a extending in the direction indicated
by the arrow C. The corrugated flow grooves 176a face the
corrugated flow grooves 174a. The corrugated flow grooves 176a and
the corrugated flow grooves 174a are set at the same phase.
[0111] The coolant flow field 168 is partially formed on the
surface 160b of the third metal separator 160. On the surface 160b,
a plurality of corrugated flow grooves 168b are formed as the back
surface of the corrugated flow grooves 176a of the second
oxygen-containing gas flow field 176.
[0112] As shown in FIG. 11, the corrugated flow grooves 168a of the
first metal separator 154 and the corrugated flow grooves 168b of
the third metal separator 160 are overlapped with each other to
form the coolant flow field 168.
[0113] In the first phase areas 170a, the corrugated flow grooves
168a and the corrugated flow grooves 168b are in different phases.
In the second phase area 170b, the corrugated flow grooves 168a and
the corrugated flow grooves 168b are in the same phase, and form a
corrugated flow field extending in the direction indicated by the
arrow C.
[0114] In each of the first phase areas 170a at the upper and lower
positions, the corrugated flow grooves 168a and the corrugated flow
grooves 168b are in different phases thereby to form a flow field
extending in the direction indicated by the arrow B.
[0115] As shown in FIG. 13, the surface 154b of the first metal
separator 154 and the surface 160b of the third metal separator 160
are overlapped with each other. Thus, ridges on the back surfaces
forming the coolant flow field 168 contact each other to provide an
upper contact area 178a, a lower contact area 178b, and an
intermediate contact area 178c.
[0116] In the upper contact area 178a and the lower contact area
178b, the ridges on the back surfaces are in different phases, and
thus are placed in point-contact with each other. In the
intermediate contact area 178c, the ridges on the back surfaces are
in the same phase thereby to form a flow field including a
plurality of corrugated flow grooves extending in the direction
indicated by the arrow C, between the respective ridges in the
intermediate contact area 178c.
[0117] In the fifth embodiment, as shown in FIG. 11, in the first
phase area (upstream area) 170a adjacent to the coolant supply
passages 34a and in the first phase area (downstream area) 170a
adjacent to the coolant discharge passages 34b, the corrugated flow
grooves 168a of the coolant flow field 168 and the corrugated flow
grooves 168b thereof are set at different phases.
[0118] Further, in the second phase area (intermediate area) 170b
of the corrugated flow grooves 168a, the corrugated flow grooves
168a and the corrugated flow grooves 168b are in the same phase.
Thus, in the intermediate area of the coolant flow field 168, the
flow direction of the coolant is the same as the flow direction of
(at least one of) the oxygen-containing gas and the fuel gas. In
the upstream area and the downstream area, the flow direction can
be changed to a direction (indicated by the arrow B) intersecting
the flow direction indicated by the arrow C. This is because, as
shown in FIG. 13, in each of the upstream area and the downstream
area, the upper contact area 178a and the lower contact area 178b
are in point-contact with each other.
[0119] Thus, the coolant supply passages 34a and the coolant
discharge passages 34b can be formed on opposite left and right
sides of the power generation units 152. In the structure, the
width of the power generation unit 152 indicated by the arrow B is
reduced effectively.
[0120] In particular, the coolant supply passages 34a and the
coolant discharge passages 34b are disposed within the area of the
spacing interval H in a horizontal direction indicated by the arrow
B between the oxygen-containing gas supply passage 30a
(oxygen-containing gas discharge passage 30b) and the fuel gas
supply passage 32a (fuel gas discharge passage 32b). In the
structure, the width of the power generation unit 12 can be reduced
as much as possible.
[0121] Further, in the intermediate area of the coolant flow field
168, the corrugated flow grooves 168a, 168b are set at the same
phase. Therefore, the coolant can flow smoothly and reliably in the
same direction as the flow direction of the oxygen-containing gas
and the fuel gas. Thus, improvement in the efficiency of cooling
the power generation unit 152 is achieved suitably.
[0122] As the power generation unit 152, a power generation unit
formed by sandwiching one electrolyte electrode assembly between a
pair of metal separators may be used, and the coolant flow field
may be formed between the adjacent power generation units.
[0123] FIG. 14 is an exploded perspective view showing main
components of a power generation unit 192 of a fuel cell stack 190
according to a sixth embodiment of the present invention.
[0124] The power generation unit 192 is formed by sandwiching a
membrane electrode assembly 194 between a first metal separator 196
and a second metal separator 198. The membrane electrode assembly
194 includes an anode 24, a cathode 26, and a solid polymer
electrolyte membrane 22 interposed between the anode 24 and the
cathode 26. The surface area of the anode 24 is the same as the
surface area of the cathode 26.
[0125] A first fuel gas flow field 162 is formed on a surface 196a
of the first metal separator 196 facing the membrane electrode
assembly 194. On a surface 196b of the first metal separator 196,
corrugated flow grooves 168a of the coolant flow field 168 are
formed as the back surface of the first fuel gas flow field
162.
[0126] A second oxygen-containing gas flow field 176 is formed on a
surface 198a of the second metal separator 198 facing the membrane
electrode assembly 194. On a surface 198b of the second metal
separator 198, corrugated flow grooves 168b of the coolant flow
field 168 are formed as the back surface of the second
oxygen-containing gas flow field 176.
[0127] The coolant flow field 168 is formed between the adjacent
power generation units 192, i.e., between a surface 196b of the
first metal separator 196 of one of the adjacent power generation
units 192, and a surface 198b of the second metal separator 198 of
the other of the adjacent power generation units 192.
[0128] In the sixth embodiment, the coolant flow field 168 is
formed by the back surface of the first fuel gas flow field 162 and
the back surface of the second oxygen-containing gas flow field
176. Thus, the same advantages as in the case of the fifth
embodiment are obtained.
[0129] In the fifth and sixth embodiments, the fuel gas and the
oxygen-containing gas flow in parallel to each other (i.e., in the
same direction). However, the present invention is not limited in
this respect. For example, the fuel gas and the oxygen-containing
gas may flow in a counterflow manner (i.e., in opposite
directions).
[0130] FIG. 15 is an exploded perspective view showing main
components of a power generation unit 202 of a fuel cell stack 200
according to a seventh embodiment of the present invention.
[0131] The power generation unit 202 includes a first metal
separator 204, a first membrane electrode assembly 156a, a second
metal separator 158, a second membrane electrode assembly 156b, and
a third metal separator 160.
[0132] As shown in FIGS. 15 and 16, the first metal separator 204
has a first fuel gas flow field 162 on its surface 204a facing the
first membrane electrode assembly 156a. The first fuel gas flow
field 162 connects the fuel gas supply passage 32a and the fuel gas
discharge passage 32b.
[0133] In the corrugated flow grooves 162a of the first fuel gas
flow field 162, on the upstream side (upper side) and on the
downstream side (lower side), the first phase areas 206a having the
same phase are provided, and in the intermediate area, the second
phase area 206b subjected to a phase shift by a half phase through
the straight sections 208a, 208b are provided. The straight
sections 208a, 208b form corrugated flow grooves where the phase on
the lower side as shown by the two-dot chain lines in FIG. 16 is
shifted by a half pitch in the middle.
[0134] As shown in FIG. 17, the corrugated flow grooves 168a of the
first metal separator 204 are overlapped with the corrugated flow
grooves 168b of the third metal separator 160 to form the coolant
flow field 168.
[0135] In the first phase areas 206a, the corrugated flow grooves
168a and the corrugated flow grooves 168b are in the different
phases. In the second phase area 206b, the corrugated flow grooves
168a and the corrugated flow grooves 168b form a corrugated flow
field having the same phase, and extending in the direction
indicated by the arrow C.
[0136] As shown in FIG. 18, the surface 204b of the first metal
separator 204 and the surface 160b of the third metal separator 160
are overlapped with each other. Thus, ridges on the back surfaces
forming the coolant flow field 168 contact each other thereby to
provide an upper contact section 210a, a lower contact section
210b, and an intermediate contact section 210c.
[0137] In the upper contact section 210a and the lower contact
section 210b, ridges on the back surfaces are in different phases,
i.e., the ridges are in point-contact with each other. In the
intermediate contact section 210c, ridges on the back surfaces are
in the same phase. Therefore, the intermediate contact section 210c
has a corrugated shape extending in the direction indicated by the
arrow C. A plurality of corrugated flow grooves extending in the
direction indicated by the arrow C are formed between the ridges of
the intermediate contact section 210c.
[0138] Thus, in the seventh embodiment, the coolant supply passages
34a and the coolant discharge passages 34b are formed on left and
right opposite sides of the power generation unit 202. Further, the
same advantages as in the case of the fifth and sixth embodiments
are obtained. For example, the coolant can be supplied in the same
direction as the flow direction of the oxygen-containing gas and
the fuel gas smoothly and reliably.
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