U.S. patent application number 15/676207 was filed with the patent office on 2018-03-08 for fuel cell and fuel cell separator.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Makoto ADACHI, Masayuki ITO, Masaaki MATSUSUE, Hideo NAGAOSA, Naoki TAKEHIRO.
Application Number | 20180069256 15/676207 |
Document ID | / |
Family ID | 61281304 |
Filed Date | 2018-03-08 |
United States Patent
Application |
20180069256 |
Kind Code |
A1 |
ADACHI; Makoto ; et
al. |
March 8, 2018 |
FUEL CELL AND FUEL CELL SEPARATOR
Abstract
A fuel cell is provided with: a membrane electrode assembly
(MEA); and a cathode-side separator assembled to the MEA, the
cathode-side separator including first passages on a first surface
of the cathode-side separator on a side closer to the MEA, and
second passages on a second surface of the cathode-side separator
on an opposite side, the first and second passages allowing oxidant
gas to flow through the first and second passages, respectively.
The first passages include first recessed portions on the first
surface so as to extend from one end of the cathode-side separator
to the other end, the second passages include second recessed
portions on the second surface so as to extend from the one end to
the other end and to be arranged alternately with the first
recessed portions, and a penetration hole on a bottom face of the
second recessed portion penetrating through the cathode-side
separator
Inventors: |
ADACHI; Makoto; (Susono-shi,
JP) ; TAKEHIRO; Naoki; (Shizuoka-ken, JP) ;
MATSUSUE; Masaaki; (Mishima-shi, JP) ; ITO;
Masayuki; (Shizuoka-ken, JP) ; NAGAOSA; Hideo;
(Susono-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
61281304 |
Appl. No.: |
15/676207 |
Filed: |
August 14, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 8/1007 20160201;
H01M 8/1053 20130101; H01M 8/026 20130101; Y02P 70/50 20151101;
H01M 8/1004 20130101; H01M 8/1006 20130101; Y02E 60/50 20130101;
H01M 8/04753 20130101; H01M 8/04761 20130101; H01M 8/0258
20130101 |
International
Class: |
H01M 8/1004 20060101
H01M008/1004 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 2, 2016 |
JP |
2016-172268 |
Claims
1. A fuel cell comprising: a membrane electrode assembly; and a
cathode-side separator assembled to the membrane electrode
assembly, the cathode-side separator including first passages
provided on a first surface of the cathode-side separator on a side
closer to the membrane electrode assembly, the first passages
allowing oxidant gas to flow through the first passages, and second
passages provided on a second surface of the cathode-side separator
on a side opposite to the membrane electrode assembly across the
first surface of the cathode-side separator, the second passages
allowing oxidant gas to flow through the second passages, wherein
the first passages include first recessed portions provided on the
first surface so as to extend from one end of the cathode-side
separator to the other end, the second passages include second
recessed portions provided on the second surface so as to extend
from the one end of the cathode-side separator to the other end and
to be arranged alternately with the first recessed portions, and a
portion defining a penetration hole penetrating through the
cathode-side separator is provided on a bottom face of the second
recessed portion constituting the second passage.
2. The fuel cell according to claim 1, wherein when a central side
region indicates two regions positioned on a central side and end
side regions indicate two regions positioned on end sides at a time
when the bottom face of the second recessed portion constituting
the second passage is equally divided into four regions in a width
direction of the second passage so that each of the four regions
has a width of 1/4 of a width of the second passage, a total area
of the portion defining the penetration hole, provided in the
central side region, is larger than a total area of the portion
defining the penetration hole, provided in the two end side
regions.
3. The fuel cell according to claim 1, wherein when a central side
region indicates two regions positioned on a central side and end
side regions indicate two regions positioned on end sides at a time
when the bottom face of the second recessed portion constituting
the second passage is equally divided into four regions in a width
direction of the second passage so that each of the four regions
has a width of 1/4 of a width of the second passage, the portion
defining the penetration hole is provided only in the central side
region.
4. The fuel cell according to claim 1, wherein when an upstream
region indicates a region positioned on an upstream side of a flow
of the oxidant gas and a downstream region indicates a region
positioned on a downstream side at a time when the bottom face of
the second recessed portion constituting the second passage is
equally divided into two regions in a lengthwise direction of the
second passage so that each of the two regions has a length of 1/2
of a length of the second passage, a total area of the portion
defining the penetration hole, provided in the downstream region,
is smaller than a total area of the portion defining the
penetration hole, provided in the upstream region.
5. The fuel cell according to claim 4, wherein: portions defining a
plurality of penetration holes are provided; and at least one of
intervals between the portions defining the penetration holes,
provided in the downstream region, is larger than intervals between
the portions defining the penetration holes, provided in the
upstream region.
6. The fuel cell according to claim 4, wherein: portions defining a
plurality of penetration holes are provided; and at least one of
areas of the portions defining the penetration holes, provided in
the downstream region, is smaller than each of areas of the
portions defining the penetration holes, provided in the upstream
region.
7. The fuel cell according to claim 1, wherein: when an upstream
region indicates a region positioned on an upstream side of a flow
of the oxidant gas and a downstream region indicates a region
positioned on a downstream side at a time when the bottom face of
the second recessed portion constituting the second passage is
equally divided into two regions in a lengthwise direction of the
second passage so that each of the two regions has a length of 1/2
of a length of the second passage, the portion defining the
penetration hole is provided only in the upstream region.
8. The fuel cell according to claim 1, wherein a wall portion
projecting inwardly in the second passage from the bottom face of
the second recessed portion constituting the second passage is
provided in an upstream edge among edges of the portion defining
the penetration hole, the upstream edge being on an upstream side
of a flow of the oxidant gas.
9. The fuel cell according to claim 8, wherein: portions defining a
plurality of penetration holes are provided; and the portion
defining the penetration hole and provided with the wall portion is
provided on a downstream side of the second passage relative to the
portion defining the penetration hole and not provided with the
wall portion.
10. The fuel cell according to claim 8, wherein: portions defining
a plurality of penetration holes are provided; and heights of the
wall portions provided in the portions defining the plurality of
penetration holes are set such that the height of the wall portion
on a downstream side of the second passage is higher than the
height of the wall portion on the upstream side of the second
passage.
11. The fuel cell according to claim 8, wherein the wall portion is
provided in the upstream edge among the edges of the portion
defining the penetration hole, and in a lateral edge among the
edges of the portion defining the penetration holes, the lateral
edge being along the flow of the oxidant gas.
12. The fuel cell according to claim 1, wherein a part where the
portion defining the penetration hole is provided on the bottom
face of the second recessed portion projects more than the other
part of the bottom face of the second recessed portion.
13. The fuel cell according to claim 1, wherein a width of a part
of the second passage in which the portion defining the penetration
hole is provided is wider than a width of a part of the second
passage in which the portion defining the penetration hole is not
provided.
14. A fuel cell separator to be assembled to a membrane electrode
assembly, the fuel cell separator comprising: first recessed
portions provided on one surface so as to extend from one end of
the fuel cell separator to the other end; second recessed portions
provided on the other surface so as to extend from the one end of
the fuel cell separator to the other end and to be arranged
alternately with the first recessed portions, the second recessed
portions each having a bottom face provided with a portion defining
a penetration hole penetrating through the fuel cell separator.
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of Japanese Patent Application No.
2016-172268 filed on Sep. 2, 2016 including the specification,
drawings and abstract is incorporated herein by reference in its
entirety.
BACKGROUND
1. Technical Field
[0002] The present disclosure relates to a fuel cell and a fuel
cell separator.
2. Description of Related Art
[0003] As a cooling method of a fuel cell, there has been known an
air-cooling method using oxidant gas to be supplied for
electric-power generation, other than a water-cooling method in
which a coolant is circulated. As a separator used for an
air-cooled fuel cell, there has been known a separator including a
fuel flow passage provided on one surface so that fuel gas flows
therethrough, an airflow passage provided on the other surface so
that air flows therethrough, and a cooling airflow passage provided
thereinside so as to be connected to the airflow passage via
portions defining penetration holes (for example, Japanese
Unexamined Patent Application Publication No. 2008-027748 (JP
2008-027748 A)). With the use of the separator, it is possible to
send the air flowing through the cooling airflow passage into the
airflow passage. Accordingly, it is possible to improve cooling
efficiency and to restrain clogging of the airflow passage by
condensed water. Further, in a fuel cell using a cathode-side
separator including power generation passages on a surface on a
membrane electrode assembly side, and cooling passages provided on
a surface opposite to the membrane electrode assembly such that the
power generation passages and the cooling passages are arranged
alternately, it is well known that water is easily accumulated in a
region below the cooling passages (for example, Quentin Meyer, and
ten other people, "The Hydro-electro-thermal Performance of
Air-cooled, Open-cathode Polymer Electrolyte Fuel Cells: Combined
Localised Current Density, Temperature and Water Mapping"
Electrochimica Acta, 2015, VOL. 180, p. 307-315).
SUMMARY
[0004] There is a fuel cell including a cathode-side separator
including a first passage provided on a surface on a membrane
electrode assembly side and constituted by first recessed portions,
and a second passage provided on a surface opposite to the membrane
electrode assembly across the first passage of the cathode side
separator and constituted by second recessed portions arranged
alternately with the first recessed portions. In such a fuel cell,
oxidant gas flowing through the first passage may be hardly
supplied to a region positioned below the second passage in the
membrane electrode assembly, and water generated in the region may
be hardly discharged to the first passage. Because of this, power
generation performance may decrease.
[0005] The present disclosure provides a fuel cell and a fuel cell
separator each of which restrains a decrease in power generation
performance.
[0006] A first aspect of the present disclosure relates to a fuel
cell including: a membrane electrode assembly; and a cathode-side
separator assembled to the membrane electrode assembly, the
cathode-side separator including first passages provided on a first
surface of the cathode-side separator on a side closer to the
membrane electrode assembly, the first passages allowing oxidant
gas to flow through the first passages, and second passages
provided on a second surface of the cathode-side separator on a
side opposite to the membrane electrode assembly across the first
surface of the cathode-side separator, the second passages allowing
oxidant gas to flow through the second passages. Here, the first
passages include first recessed portions provided on the first
surface so as to extend from one end of the cathode-side separator
to the other end, the second passages include second recessed
portions provided on the second surface so as to extend from the
one end of the cathode-side separator to the other end and to be
arranged alternately with the first recessed portions, and a
portion defining a penetration hole penetrating through the
cathode-side separator is provided on a bottom face of the second
recessed portion constituting the second passage.
[0007] In the above aspect, when a central side region indicates
two regions positioned on a central side and end side regions
indicate two regions positioned on end sides at a time when the
bottom face of the second recessed portion constituting the second
passage is equally divided into four regions in a width direction
of the second passage so that each of the four regions has a width
of 1/4 of a width of the second passage, a total area of the
portion defining the penetration hole, provided in the central side
region, may be larger than a total area of the portion defining the
penetration hole, provided in the two end side regions.
[0008] In the above aspect, when a central side region indicates
two regions positioned on a central side and end side regions
indicate two regions positioned on end sides at a time when the
bottom face of the second recessed portion constituting the second
passage is equally divided into four regions in a width direction
of the second passage so that each of the four regions has a width
of 1/4 of a width of the second passage, the portion defining the
penetration hole may be provided only in the central side
region.
[0009] In the above aspect, when an upstream region indicates a
region positioned on an upstream side of a flow of the oxidant gas
and a downstream region indicates a region positioned on a
downstream side at a time when the bottom face of the second
recessed portion constituting the second passage is equally divided
into two regions in a lengthwise direction of the second passage so
that each of the two regions has a length of 1/2 of a length of the
second passage, a total area of the portion defining the
penetration hole, provided in the downstream region, may be smaller
than a total area of the portion defining the penetration hole,
provided in the upstream region.
[0010] In the above aspect, portions defining a plurality of
penetration holes may be provided, and at least one of intervals
between the portions defining the penetration holes, provided in
the downstream region, may be larger than intervals between the
portions defining the penetration holes, provided in the upstream
region.
[0011] In the above aspect, portions defining a plurality of
penetration holes may be provided, and at least one of areas of the
portions defining the penetration holes, provided in the downstream
region, may be smaller than each of areas of the portions defining
the penetration holes, provided in the upstream region.
[0012] In the above aspect, when an upstream region indicates a
region positioned on an upstream side of a flow of the oxidant gas
and a downstream region indicates a region positioned on a
downstream side at a time when the bottom face of the second
recessed portion constituting the second passage is equally divided
into two regions in a lengthwise direction of the second passage so
that each of the two regions has a length of 1/2 of a length of the
second passage, the portion defining the penetration hole may be
provided only in the upstream region.
[0013] In the above aspect, a wall portion projecting inwardly in
the second passage from the bottom face of the second recessed
portion constituting the second passage may be provided in an
upstream edge among edges of the portion defining the penetration
hole, the upstream edge being positioned on an upstream side of a
flow of the oxidant gas.
[0014] In the above aspect, portions defining a plurality of
penetration holes may be provided, and the portion defining the
penetration hole and provided with the wall portion may be provided
on a downstream side of the second passage relative to the portion
defining the penetration hole and not provided with the wall
portion.
[0015] In the above aspect, portions defining a plurality of
penetration holes may be provided, and heights of the wall portions
provided in the portions defining the plurality of penetration
holes may be set such that the height of the wall portion on a
downstream side of the second passage is higher than the height of
the wall portion on the upstream side of the second passage.
[0016] In the above aspect, the wall portion may be provided in the
upstream edge among the edges of the portion defining the
penetration hole, and in a lateral edge among the edges of the
portion defining the penetration hole, the lateral edge being along
the flow of the oxidant gas.
[0017] In the above aspect, a part where the portion defining the
penetration hole is provided on the bottom face of the second
recessed portion may project more than the other part of the bottom
face of the second recessed portion.
[0018] In the above aspect, a width of a part of the second passage
in which the portion defining the penetration hole is provided may
be wider than a width of a part of the second passage in which the
portion defining the penetration hole is not provided.
[0019] A second aspect of the present disclosure relates to a fuel
cell separator to be assembled to a membrane electrode assembly,
the fuel cell separator including: first recessed portions provided
on one surface so as to extend from one end of the fuel cell
separator to the other end; and second recessed portions provided
on the other surface so as to extend from the one end of the fuel
cell separator to the other end and to be arranged alternately with
the first recessed portions, the second recessed portions each
having a bottom face provided with a portion defining a penetration
hole penetrating through the fuel cell separator.
[0020] According to the first and second aspects of the present
disclosure, it is possible to restrain a decrease in power
generation performance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Features, advantages, and technical and industrial
significance of exemplary embodiments of the disclosure will be
described below with reference to the accompanying drawings, in
which like numerals denote like elements, and wherein:
[0022] FIG. 1 is an exploded perspective view of a single cell
constituting a fuel cell of Example 1;
[0023] FIG. 2 is a perspective view of a cathode-side separator
provided in the fuel cell of Example 1;
[0024] FIG. 3A is an exploded perspective view of a single cell
constituting a fuel cell of Comparative Example 1;
[0025] FIG. 3B is a perspective view of a cathode-side separator
provided in the fuel cell of Comparative Example 1;
[0026] FIG. 4 is a view illustrating measurement results of
current-voltage characteristics of the fuel cell of Comparative
Example 1;
[0027] FIG. 5 is a sectional view to describe a reason why power
generation performance decreases;
[0028] FIG. 6 is a view illustrating measurement results of
current-voltage characteristics of the fuel cells of Example 1 and
Comparative Example 1 under a high humidity condition;
[0029] FIG. 7 is a view illustrating measurement results of air
stoichiometric characteristics of the fuel cells of Example 1 and
Comparative Example 1;
[0030] FIG. 8A is a perspective view of another example of the
cathode-side separator in Example 1;
[0031] FIG. 8B is a perspective view of another example of the
cathode-side separator in Example 1;
[0032] FIG. 8C is a perspective view of another example of the
cathode-side separator in Example 1;
[0033] FIG. 8D is a perspective view of another example of the
cathode-side separator in Example 1;
[0034] FIG. 9 is a view illustrating measurement results of
current-voltage characteristics of the fuel cells of Example 1 and
Comparative Example 1 under a low humidity condition;
[0035] FIG. 10 is a view illustrating a power generation
distribution and a temperature distribution of the fuel cell of
Comparative Example 1;
[0036] FIG. 11 is a view illustrating a temperature distribution of
the fuel cell of Comparative Example 1 in a case where a humidity
state of hydrogen is changed;
[0037] FIG. 12 is a view illustrating a power generation
distribution of the fuel cell of Comparative Example 1 in a case
where a humidity state of hydrogen is changed;
[0038] FIG. 13 is a perspective view of a cathode-side separator
provided in a fuel cell of Example 2;
[0039] FIG. 14A is a perspective view of another example of the
cathode-side separator provided in the fuel cell of Example 2;
[0040] FIG. 14B is a perspective view of another example of the
cathode-side separator provided in the fuel cell of Example 2;
[0041] FIG. 15 is a perspective view (No. 1) of a cathode-side
separator provided in a fuel cell of Example 3;
[0042] FIG. 16 is a perspective view (No. 2) of the cathode-side
separator provided in the fuel cell of Example 3;
[0043] FIG. 17 is a perspective view of a second passage of a
cathode-side separator provided in a fuel cell of Modified Example
1 of Example 3;
[0044] FIG. 18A is a perspective view of a second passage of a
cathode-side separator provided in a fuel cell of Example 4;
[0045] FIG. 18B is a sectional view taken along a line
XVIIIB-XVIIIB in FIG. 18A;
[0046] FIG. 19 is a perspective view of a cathode-side separator
provided in a fuel cell of Example 5;
[0047] FIG. 20 is a perspective view of a cathode-side separator
provided in a fuel cell of Example 6; and
[0048] FIG. 21 is a plan view of a second passage of a cathode-side
separator provided in a fuel cell of Example 7.
DETAILED DESCRIPTION OF EMBODIMENTS
[0049] With reference to the drawings, the following describes
examples of the present disclosure.
[0050] A fuel cell of Example 1 is a solid polymer fuel cell that
receives supply of fuel gas (for example, hydrogen) and oxidant gas
(for example, air) as reactant gas and generates electric power,
and has a stack structure in which a plurality of single cells is
laminated. The fuel cell of Example 1 is provided in a fuel-cell
vehicle, an electric vehicle, or the like, for example. FIG. 1 is
an exploded perspective view of a single cell 100 constituting the
fuel cell of Example 1. FIG. 2 is a perspective view of a
cathode-side separator 18c provided in the fuel cell of Example 1.
Note that, in FIG. 2, a part of the cathode-side separator 18c is
illustrated in an enlarged manner, and the cathode-side separator
18c is indicated by a cross hatch (the same is applied to FIG. 3B,
FIGS. 8A to 8D, FIGS. 13 to 14B).
[0051] As illustrated in FIG. 1, the single cell 100 constituting
the fuel cell of Example 1 includes an anode-side separator 18a, a
membrane electrode gas diffusion layer assembly (MEGA) 20, and the
cathode-side separator 18c. The MEGA 20 is placed inside insulating
members 40 made of resin (such as epoxy resin or phenolic resin).
The MEGA 20 and the insulating members 40 are sandwiched between
the anode-side separator 18a and the cathode-side separator 18c. In
other words, the anode-side separator 18a and the cathode-side
separator 18c are assembled to the MEGA 20 and the insulating
members 40.
[0052] As illustrated in FIGS. 1 and 2, the cathode-side separator
18c is made of a member having a gas barrier property and an
electronic conductivity. For example, the cathode-side separator
18c is made of a metal plate such as stainless steel having an
irregular shape by bending by press molding or the like. First
passages 22 and second passages 24 through which air flows are
formed by the irregular shape in a thickness direction in the
cathode-side separator 18c. The first passages 22 and the second
passages 24 linearly extend from one end of the cathode-side
separator 18c to the other end thereof in a first direction and are
arranged alternately in a second direction intersecting with the
first direction. The air flowing through the first passages 22 and
the second passages 24 flows from an air supply port, which is one
end side of the cathode-side separator 18c, toward an air exhaust
port, which is the other end side thereof.
[0053] The first passages 22 include first recessed portions 30
provided on a first surface 26 of the cathode-side separator 18c on
a side of the cathode-side separator 18c closer to a MEGA 20 so as
to extend from the one end of the cathode-side separator 18c to the
other end thereof. Accordingly, the air flowing through the first
passages 22 is supplied to the MEGA 20 so as to be used for
electric-power generation. The second passages 24 include second
recessed portions 32 provided on a second surface 28 of the
cathode-side separator 18c on an opposite side to the side of the
cathode-side separator 18c closer to the MEGA 20 so as to extend
from the one end of the cathode-side separator 18c to the other end
thereof and to be arranged alternately with the first recessed
portions 30. Accordingly, the air flowing through the second
passages 24 is mainly used for cooling the single cell 100. Thus,
the fuel cell of Example 1 is an air-cooled fuel cell. Since the
first passages 22 and the second passages 24 are arranged
alternately in the second direction, the second passages 24 can be
placed near the MEGA 20, thereby making it possible to improve
cooling efficiency.
[0054] The first passage 22 and the second passage 24 have a
generally uniform depth D from the air supply port to the air
exhaust port. Further, a width W1 of the first passage 22 and a
width W2 of the second passage 24 are generally uniform from the
air supply port to the air exhaust port. Further, a pitch interval
(a center-to-center distance) between the first passages 22 and a
pitch interval (a center-to-center distance) between the second
passages 24 are generally uniform from the air supply port to the
air exhaust port.
[0055] On a bottom face 34 of the second recessed portion 32
constituting the second passage 24 (that is, a surface of the
second passage 24 on the side closer to the MEGA 20), portions
defining a plurality of penetration holes 36 penetrating through
the cathode-side separator 18c are provided. The portions defining
the penetration holes 36 have a rectangular shape extending from
one end side of the second passage 24 to the other end side thereof
in a width direction. The portions defining the penetration holes
36 are provided dispersedly at regular intervals in the first
direction. The air flowing through the second passage 24 is
partially supplied to the MEGA 20 via the portions defining the
penetration holes 36. Accordingly, most of the air flowing through
the second passages 24 is used for cooling the single cell 100, but
the air is partially supplied to the MEGA 20 so as to be used for
electric-power generation.
[0056] As illustrated in FIG. 1, the anode-side separator 18a is
made of a member having a gas barrier property and an electronic
conductivity, and is made of a carbon member such as dense carbon
obtained by compressing carbon so that gas cannot pass
therethrough, or a metal member such as stainless steel, for
example. The anode-side separator 18a is provided with portions
defining holes a1, a2, the insulating members 40 are provided with
portions defining holes s1, s2, and insulating members 42 provided
on both sides of the cathode-side separator 18c are provided with
portions defining holes c1, c2. The portions defining the holes a1,
s1, c1 communicate with each other, so as to define a supply
manifold configured to supply hydrogen. The portions defining the
holes a2, s2, c2 communicate with each other, so as to define a
discharge manifold configured to discharge hydrogen. Hydrogen
passages 33 through which hydrogen to be supplied to the MEGA 20
flows are provided on a surface of the anode-side separator 18a on
the side closer to the MEGA 20, such that the hydrogen passages 33
linearly extend toward the discharge manifold from the supply
manifold. The hydrogen passages 33 intersect with (e.g.,
perpendicularly to) the first passages 22 and the second passages
24.
[0057] The MEGA 20 includes an electrolyte membrane 12, an anode
catalyst layer 14a, a cathode catalyst layer 14c, an anode gas
diffusion layer 16a, and a cathode gas diffusion layer 16c. The
anode catalyst layer 14a is provided on one surface of the
electrolyte membrane 12, and the cathode catalyst layer 14c is
provided on the other surface. Hereby, a membrane electrode
assembly (MEA) 10 is formed. The electrolyte membrane 12 is a
polymer electrolyte made of a fluorinated resin material having a
sulfonic group or a hydrocarbon resin material, and exhibits an
excellent proton conductivity in a wet state. The anode catalyst
layer 14a and the cathode catalyst layer 14c include carbon
particulates (e.g., carbon black) carrying a catalyst (e.g.,
platinum and platinum-cobalt alloy) that promotes an
electrochemical reaction, and an ionomer that is a solid polymer
having a sulfonic group and exhibits an excellent proton
conductivity in a wet state.
[0058] The anode gas diffusion layer 16a and the cathode gas
diffusion layer 16c are placed on both sides of the MEA 10. The
anode gas diffusion layer 16a and the cathode gas diffusion layer
16c are formed by members having a gas permeability and an
electronic conductivity, and are made of carbon porous members such
as carbon cloth or carbon paper. Note that a water repellent layer
for the purpose of adjusting a water content included in the MEA 10
may be provided between the MEA 10 and the anode gas diffusion
layer 16a and between the MEA 10 and the cathode gas diffusion
layer 16c. The water-repellent layer is made of a member having a
gas permeability and an electronic conductivity, similarly to the
anode gas diffusion layer 16a and the cathode gas diffusion layer
16c, and is made of a carbon porous member such as carbon cloth or
carbon paper, for example. Note that the carbon porous member for
the water repellent layer has small pores as compared with the
anode gas diffusion layer 16a and the cathode gas diffusion layer
16c.
[0059] Here, in order to describe an effect of the fuel cell of
Example 1, the following describes a fuel cell of Comparative
Example 1. FIG. 3A is an exploded perspective view of a single cell
500 constituting the fuel cell of Comparative Example 1, and FIG.
3B is a perspective view of a cathode-side separator 18c provided
in the fuel cell of Comparative Example 1. As illustrated in FIGS.
3A and 3B, the single cell 500 constituting the fuel cell of
Comparative Example 1 does not include portions defining
penetration holes on a bottom face 34 of a second recessed portion
32 constituting a second passage 24 of the cathode-side separator
18c. The other configurations are the same as those in Example 1,
so descriptions thereof are omitted.
[0060] In the air-cooled fuel cell, the air flowing through the
first passages 22 and the second passages 24 of the cathode-side
separator 18c is supplied by a fan, vehicle speed wind, and the
like. On this account, a pressure loss of the air flowing through
the first passages 22 and the second passages 24 may be small, and
for this purpose, sectional areas of the first passages 22 and the
second passages 24 may be large. In order to increase the sectional
areas of the first passages 22 and the second passages 24, it is
conceivable that widths of the first passages 22 and the second
passages 24 are widened. In view of this, by use of the fuel cell
of Comparative Example 1, power generation performance at the time
when the first passages 22 and the second passages 24 had a wide
width was examined.
[0061] FIG. 4 is a view illustrating measurement results of
current-voltage characteristics of the fuel cell of Comparative
Example 1. In FIG. 4, a horizontal axis indicates a current density
(A/cm.sup.2) and a vertical axis indicates a cell voltage (V). A
square mark in FIG. 4 indicates a measurement result at the time
when a width W1 of the first passages 22 and a width W2 of the
second passages 24 were 0.3 mm, and a diamond mark indicates a
measurement result at the time when the width W1 of the first
passages 22 and the width W2 of the second passages 24 were 1.0 mm.
Note that the measurement was performed such that a temperature of
the fuel cell was adjusted to 50.degree. C., hydrogen humidified to
a dew point temperature of 50.degree. C. was supplied to hydrogen
passages 33 of an anode-side separator 18a, and dry air with a gas
temperature of 50.degree. C. and a dew point temperature of
-40.degree. C. was supplied to the first passages 22 and the second
passages 24 of the cathode-side separator 18c. As illustrated in
FIG. 4, in a case where the widths of the first passages 22 and the
second passages 24 were 1.0 mm, the power generation performance
decreased as compared with a case where the widths of the first
passages 22 and the second passages 24 were 0.3 mm.
[0062] The reason why the power generation performance decreased
when the widths of the first passages 22 and the second passages 24
were wider than 0.3 mm is presumably as follows. FIG. 5 is a
sectional view to describe the reason why the power generation
performance decreased. As illustrated in FIG. 5, the air flowing
through the first passages 22 diffuses in the MEA 10, and water
generated in the MEA 10 by an electrochemical reaction is
discharged to the first passages 22. When the widths of the first
passages 22 and the second passages 24 are widened, a distance
between the first passage 22 and a region 11, in the MEA 10,
positioned below the second passage 24 on a central side in the
width direction of the second passage 24 becomes long. This makes
it difficult to supply the air flowing through the first passage 22
to the region 11 of the MEA10 and also makes it difficult for water
generated in the region 11 of the MEA 10 to be discharged to the
first passage 22. For this reason, it is considered that the power
generation performance decreased because the first passages 22 and
the second passages 24 were widened.
[0063] Note that, when the first passages 22 and the second
passages 24 are deepened, it is possible to increase sectional
areas of the first passages 22 and the second passages 24. However,
when the first passages 22 and the second passages 24 are deepened,
a pitch interval between adjacent single cells becomes wide, which
upsizes the fuel cell. Accordingly, the sectional areas of the
first passages 22 and the second passages 24 may not be increased
by deepening the first passage 22 and the second passage 24, but
the sectional areas of the first passages 22 and the second
passages 24 may be increased by widening the widths of the first
passages 22 and the second passages 24.
[0064] Next will be described a measurement performed on the fuel
cell of Example 1. Note that, for a comparison, the same
measurement was also performed on the fuel cell of Comparative
Example 1. The fuel cells of Example 1 and Comparative Example 1 on
which the measurement was performed have the same structure except
that their cathode-side separators 18c have different shapes. The
cathode-side separators 18c of Example 1 and Comparative Example 1
were both configured such that the width W1 of the first passages
22 was 1.0 mm, the width W2 of the second passages 24 was 1.0 mm,
and the depths D of the first passages 22 and the second passages
24 were 1.0 mm. Further, in Example 1, portions defining
penetration holes 36 having a rectangular shape of 0.5 mm.times.1.0
mm were provided at a pitch interval (a center-to-center distance)
of 1.4 mm in the first direction on the bottom face 34 of the
second recessed portion 32 constituting the second passage 24, but
in Comparative Example 1, no portion defining a penetration hole
was not provided.
[0065] FIG. 6 is a view illustrating measurement results of
current-voltage characteristics of the fuel cells of Example 1 and
Comparative Example 1 under a high humidity condition. In FIG. 6, a
horizontal axis indicates a current density (A/cm.sup.2), a left
vertical axis indicates a cell voltage (V), and a right vertical
axis indicates a cell resistance (m.OMEGA.cm.sup.2). A continuous
line in FIG. 6 indicates the measurement result of Example 1, and a
broken line indicates the measurement result of Comparative Example
1. Further, a black circle and a black diamond indicate measurement
results of a cell voltage, and a white circle and a white diamond
are measurement results of a cell resistance. Note that the
measurement was performed such that a temperature of the fuel cell
was adjusted to 50.degree. C., hydrogen humidified to a dew point
temperature of 50.degree. C. and having a stoichiometry (a
stoichiometric ratio) of 2 was supplied to the hydrogen passages 33
of the anode-side separator 18a, and the air humidified to a dew
point temperature of 50.degree. C. and having a constant flow of 40
L/min was supplied to the first passages 22 and the second passages
24 of the cathode-side separator 18c. That is, current-voltage
characteristics in an operation under a high humidity condition
were measured. Note that the stoichiometry is a ratio of a reactant
gas amount actually supplied relative to a reactant gas amount
necessary for a requested power generation amount.
[0066] As illustrated in FIG. 6, as compared with Comparative
Example 1, Example 1 exhibited such a result that the cell voltage
at a high current density was increased and the power generation
performance was improved. The reason why the power generation
performance was improved in the fuel cell of Example 1 is
presumably as follows. That is, in the fuel cell of Example 1, the
portions defining the penetration holes 36 are provided on the
bottom face 34 of the second recessed portion 32 constituting the
second passage 24. On this account, water generated in the region,
of the MEA 10, positioned below the second passage 24 is easily
discharged to the second passage 24 through the portions defining
the penetration holes 36, so that the occurrence of flooding is
restrained. Further, the air flowing through the second passage 24
is supplied to the MEA 10 via the portions defining the penetration
holes 36, so that the occurrence of concentration overvoltage is
restrained. It is considered that the power generation performance
was improved in Example 1 for those reasons. Note that Example 1
had a cell resistance equivalent to that of Comparative Example 1.
Accordingly, it is found that, even if the portions defining the
penetration holes 36 are provided, a dry condition of the MEA 10
does not change in the operation under the high humidity condition,
and further, a continuity condition between the cathode-side
separator 18c and the MEGA 20 does not change, either.
[0067] FIG. 7 is a view illustrating measurement results of air
stoichiometric characteristics of the fuel cells of Example 1 and
Comparative Example 1. In FIG. 7, a horizontal axis indicates an
air stoichiometry at a predetermined current density, a left
vertical axis indicates a cell voltage (V), and a right vertical
axis indicates a cell resistance (m.OMEGA.cm.sup.2). A continuous
line in FIG. 7 indicates the measurement result of Example 1, and a
broken line indicates the measurement result of Comparative Example
1. Further, a black circle and a black diamond indicate measurement
results of a cell voltage, and a white circle and a white diamond
are measurement results of a cell resistance. Note that the
measurement was performed such that a temperature of the fuel cell
was adjusted to 50.degree. C., hydrogen humidified to a dew point
temperature of 50.degree. C. and having a stoichiometry of 2 was
supplied to the hydrogen passages 33 of the anode-side separator
18a, and the air humidified to a dew point temperature of
50.degree. C. was supplied to the first passages 22 and the second
passages 24 of the cathode-side separator 18c.
[0068] As illustrated in FIG. 7, Example 1 exhibited such a result
that, even if the air stoichiometry was lower than Comparative
Example 1, the cell voltage was maintained and the air
stoichiometric characteristic was improved. The reason why the air
stoichiometric characteristic of the fuel cell of Example 1 was
improved as such is presumably as follows. That is, the portions
defining the penetration holes 36 were provided in the second
recessed portion 32 constituting the second passage 24, so water
generated in the MEA 10 was easily discharged to the second passage
24 via the portions defining the penetration holes 36, and the air
flowing through the second passage 24 was supplied to the MEA 10
via the portions defining the penetration holes 36.
[0069] As described above, in Example 1, the cathode-side separator
18c includes the first passages 22 including the first recessed
portions 30 and provided on the first surface 26 on the side closer
to the MEA 10, and also includes, on the second surface 28 on an
opposite side of the MEA 10 across the first surface 26, the second
passages 24 including the second recessed portions 32 arranged
alternately with the first recessed portions 30. The portions
defining the penetration holes 36 penetrating through the
cathode-side separator 18c are provided on the bottom faces 34 of
the second recessed portions 32 constituting the second passages
24. Hereby, water generated in the MEA 10 positioned below the
second passages 24 is easily discharged to the second passages 24
via the portions defining the penetration holes 36, so that the
occurrence of flooding can be restrained. Further, the air flowing
through the second passages 24 is supplied to the MEA 10 below the
second passages 24 via the portions defining the penetration holes
36, so that the occurrence of concentration overvoltage can be
restrained. This accordingly makes it possible to restrain a
decrease in the power generation performance.
[0070] Further, in Example 1, the cathode-side separator 18c is
made of a metal plate having an irregular shape in which recessed
portions and projection portions extending in the first direction
are repeated alternately in the second direction. On this account,
the cathode-side separator 18c can be made with a simple structure,
thereby making it possible to improve productivity and to reduce a
manufacturing cost. Note that the cathode-side separator 18c may be
made of a carbon member such as dense carbon obtained by
compressing carbon so that gas cannot pass therethrough, for
example.
[0071] Note that Example 1 exemplifies a case where the portions
defining the penetration holes 36 have a rectangular shape
extending from one end side to the other end side in the width
direction of the second passage 24, but the portions defining the
penetration holes 36 are not limited to this case. FIGS. 8A to 8D
are perspective views illustrating other examples of the
cathode-side separator 18c in Example 1. As illustrated in FIG. 8A,
the portion defining the penetration hole 36 may have a shape that
changes in width from an end side of the second passage 24 in the
width direction toward a central side thereof. For example, the
portion defining the penetration hole 36 may have a shape that
increases in width from the end side of the second passage 24 in
the width direction toward the central side thereof. That is, the
portion defining the penetration hole 36 may be configured such
that an area in a central side region 44 on the central side of the
second passage 24 in the width direction is larger than an area in
end side regions 46 on the end side. Note that the central side
region 44 indicates two regions positioned on the central side when
the bottom face 34 of the second recessed portion 32 constituting
the second passage 24 is equally divided into four regions in the
width direction of the second passage 24 so that each of the four
regions has a width of 1/4 of the width of the second passage 24.
The end side regions 46 indicate two regions positioned on the end
sides when the bottom face 34 of the second recessed portion 32
constituting the second passage 24 is equally divided into four
regions in the width direction of the second passage 24 so that
each of the four regions has a width of 1/4 of the width of the
second passage 24.
[0072] As illustrated in FIG. 8B, the portion defining the
penetration hole 36 may not extend from the one end side to the
other end side in the width direction of the second passage 24, but
may be provided so as to be divided separately on the central side
and the end sides in the width direction of the second passage 24.
In this case, the portion defining the penetration hole 36,
provided in the central side region 44 of the second passage 24,
may have the same area as or a different area from an area of the
portion defining the penetration hole 36, provided in the end side
region 46 of the second passage 24. For example, the area of the
portion defining the penetration hole 36, provided in the central
side region 44 of the second passage 24, may be larger than the
area of the portion defining the penetration hole 36, provided in
the end side region 46 of the second passage 24.
[0073] As illustrated in FIG. 8C, the portion defining the
penetration hole 36 may have a circular shape or an oval shape. The
portion defining the penetration hole 36 may be provided only in
the central side region 44 of the second passage 24, and may not be
provided in the end side regions 46. As illustrated in FIG. 8D,
only one portion defining the penetration hole 36 may be
provided.
[0074] As described above, the air can be hardly supplied from the
first passage 22 to the region, of the MEA 10, positioned below the
second passage 24 on the central side in the width direction of the
second passage 24, and further, water generated in the region can
be hardly discharged to the first passage 22. Accordingly, from the
viewpoint of promoting the supply of the air to the region of the
MEA10 and promoting the discharge of water generated in the region,
a portion defining a relatively large penetration hole 36 may be
provided on the central side in the width direction of the second
passage 24. In the meantime, when a ratio of the portion defining
the penetration hole 36 and occupying the bottom face 34 of the
second recessed portion 32 constituting the second passage 24 is
too high, a contact area between the cathode-side separator 18c and
the MEGA 20 becomes small, which increases a resistance to
conduction between the cathode-side separator 18c and the MEGA 20.
Accordingly, the portion defining the penetration hole 36 may be
provided to such an extent that the resistance to conduction
between the cathode-side separator 18c and the MEGA 20 does not
increase.
[0075] From those points, as illustrated in FIGS. 8A to 8D, a total
area of the portions defining the penetration holes 36, provided in
the central side region 44 in the bottom face 34 of the second
recessed portion 32 constituting the second passage 24 may be
larger than a total area of the portions defining the penetration
holes 36, provided in two end side regions 46. In other words, a
central side aperture ratio, which is a ratio of the total area of
the portions defining the penetration holes 36, provided in the
central side region 44, with respect to a total area of the central
side region 44 may be larger than an end side aperture ratio, which
is a ratio of the total area of the portions defining the
penetration holes 36, provided in the two end side regions 46, with
respect to a total area of the two end side regions 46. As
illustrated in FIGS. 8C and 8D, the portion defining the
penetration hole 36 may be provided only in the central side region
44 among the central side region 44 and the end side regions
46.
[0076] First described are current-voltage characteristics at the
time when the fuel cells of Example 1 and Comparative Example 1 are
operated under a low humidity condition. The structures of the fuel
cells of Example 1 and Comparative Example 1 on which the
measurement of the current-voltage characteristic was performed are
the same as the structures on which the measurements in FIGS. 6 and
7 were performed. FIG. 9 is a view illustrating measurement results
of the current-voltage characteristics of the fuel cells of Example
1 and Comparative Example 1 under the low humidity condition. In
FIG. 9, a horizontal axis indicates a current density (A/cm.sup.2),
a left vertical axis indicates a cell voltage (V), and a right
vertical axis indicates a cell resistance (m.OMEGA.cm.sup.2). A
continuous line in FIG. 9 indicates the measurement result of
Example 1, and a broken line indicates the measurement result of
Comparative Example 1. Further, a black circle and a black diamond
indicate measurement results of a cell voltage, and a white circle
and a white diamond are measurement results of a cell resistance.
Note that the measurement was performed such that a temperature of
the fuel cell was adjusted to 80.degree. C., hydrogen humidified to
a dew point temperature of 40.degree. C. and having a stoichiometry
of 2 was supplied to the hydrogen passages 33 of the anode-side
separator 18a, and the air humidified to a dew point temperature of
27.degree. C. and having a constant flow of 40 L/min was supplied
to the first passages 22 and the second passages 24 of the
cathode-side separator 18c.
[0077] As illustrated in FIG. 9, Example 1 exhibited such a result
that the cell voltage at a high current density was lower than
Comparative Example 1. The reason why the power generation
performance of the fuel cell of Example 1 decreased in the
operation under the low humidity condition as such will be
described with reference to FIGS. 10 to 12.
[0078] FIG. 10 is a view illustrating a power generation
distribution and a temperature distribution of the fuel cell of
Comparative Example 1. In FIG. 10, a horizontal axis indicates a
position along the first passages 22 and the second passages 24, a
left vertical axis indicates a current density (A/cm.sup.2), and a
right vertical axis indicates a cell temperature (.degree. C.).
Note that FIG. 10 indicates a current density and a cell
temperature of each part in a single cell when hydrogen humidified
to a dew point temperature of 50.degree. C. flows through the
hydrogen passages 33, the air at a low humidification with a gas
temperature of 25.degree. C. and a dew point temperature of
10.degree. C. is supplied to the first passages 22 and the second
passages 24 from the air supply port, and an average current
density of the single cell is 1.0 A/cm.sup.2. As illustrated in
FIG. 10, it is found that the cell temperature increases from the
air supply port toward the air exhaust port. Further, it is found
that the current densities on the air supply port side and the air
exhaust port side are lower than the current density in a part
therebetween.
[0079] FIG. 11 is a view illustrating a temperature distribution of
the fuel cell of Comparative Example 1 in a case where a humidity
state of hydrogen is changed. In FIG. 11, a horizontal axis
indicates a position along the first passages 22 and the second
passages 24, and a vertical axis indicates a cell temperature
(.degree. C.). Note that FIG. 11 illustrates cell temperatures in
the following cases at the time when a current density of the
single cell is 1.0 A/cm.sup.2: a case where hydrogen that is not
humidified flows through the hydrogen passages 33; a case where
hydrogen humidified to a dew point temperature of 40.degree. C.
flows therethrough; and a case where hydrogen humidified to a dew
point temperature of 50.degree. C. flows therethrough. A condition
of the air flowing through the first passages 22 and the second
passages 24 is a low humidity condition with a gas temperature of
25.degree. C. and a dew point temperature of 10.degree. C., and the
condition is applied to all the cases. The case where hydrogen that
is not humidified flows is indicated by a continuous line, the case
where hydrogen humidified to a dew point temperature of 40.degree.
C. flows is indicated by a broken line, and the case where hydrogen
humidified to a dew point temperature of 50.degree. C. flows is
indicated by a dotted line.
[0080] As illustrated in FIG. 11, even in a case where the
humidifying state of hydrogen flowing through the hydrogen passages
33 is changed, it is found that the cell temperature eventually
increases from the air supply port toward the air exhaust port. The
reason why the cell temperature increases from the air supply port
toward the air exhaust port is presumably as follows. That is, a
temperature of the air flowing through the first passages 22 and
the second passages 24 increases due to heat generation by an
electrochemical reaction in the MEA 10. On this account, cooling
performance decreases on the air exhaust port side in comparison
with the air supply port side. This presumably increases the cell
temperature from the air supply port toward the air exhaust port.
Note that, in a case where the fuel cell is provided in a fuel-cell
vehicle or an electric vehicle, a size of the fuel cell is
restricted by a mounting space in the vehicle. On this account, in
order to obtain a large electric-power generation, it is desired to
lengthen a length of a power generation portion in a direction
along the first passages 22 and the second passages 24. In this
case, a temperature gradient along the first passages 22 and the
second passages 24 increases, so that a cell temperature on the air
exhaust port side becomes higher.
[0081] FIG. 12 is a view illustrating a power generation
distribution of the fuel cell of Comparative Example 1 in a case
where a humidity state of hydrogen is changed. In FIG. 12, a
horizontal axis indicates a position along the first passages 22
and the second passages 24, and a vertical axis indicates a current
density (A/cm.sup.2). Also in FIG. 12, a case where hydrogen that
is not humidified flows through the hydrogen passages 33 is
indicated by a continuous line, a case where hydrogen humidified to
a dew point temperature of 40.degree. C. flows is indicated by a
broken line, and a case where hydrogen humidified to a dew point
temperature of 50.degree. C. flows is indicated by a dotted line. A
condition of the air flowing through the first passages 22 and the
second passages 24 is a low humidity condition with a gas
temperature of 25.degree. C. and a dew point temperature of
10.degree. C., and the condition is applied to all the cases.
[0082] As illustrated in FIG. 12, it is found that the current
density decreases as a humidifying degree of hydrogen flowing
through the hydrogen passages 33 increases on the air supply port
side. The reason is presumably as follows. That is, on the air
supply port side, a cooling effect of the air is high, so the cell
temperature decreases. Because of this, a saturation vapor pressure
of water decreases, so that the discharge of water generated by an
electrochemical reaction in the MEA 10 is performed in a form of
liquid water. That is, the air supply port side is in a state where
liquid water is easily accumulated in the MEA 10. Accordingly, it
is considered that, when humidified hydrogen is supplied to the
hydrogen passages 33, flooding due to excessive liquid water in the
MEA 10 occurs, thereby resulting in the decrease in the power
generation performance. Note that, when the cell temperature
decreases, an electrochemical reaction by the catalyst can hardly
proceed, so that the power generation performance decreases. Since
the power generation performance changes due to the change in the
humidifying degree of hydrogen, it is considered that excessive
liquid water in the MEA 10 causes the decrease in the power
generation performance as mentioned earlier.
[0083] In the meantime, on the air exhaust port side, as the
humidifying degree of hydrogen flowing through the hydrogen
passages 33 increases, the current density increases. The reason is
presumably as follows. That is, on the air exhaust port side, a
cooling effect of the air decreases, so the cell temperature
increases. This results in that the saturation vapor pressure of
water increases, so that the discharge of water generated by the
electrochemical reaction in the MEA 10 is immediately performed in
a form of steam. That is, the air exhaust port side is in a state
where liquid water can be hardly accumulated in the MEA 10, so that
the MEA 10 is easily dried. Accordingly, when humidified hydrogen
is supplied to the hydrogen passages 33, the drying of the MEA 10
is improved, thereby presumably resulting in that the power
generation performance increases.
[0084] Note that, as illustrated in FIG. 3A, the first passages 22
and the second passages 24 intersect with (e.g., perpendicularly
to) the hydrogen passages 33. On this account, the state of
hydrogen flowing through the hydrogen passages 33 is the same on
the air supply port side and on the air exhaust port side.
Therefore, it is considered that the power generation distribution
in the direction along the first passages 22 and the second
passages 24 is caused by the air flowing through the first passages
22 and the second passages 24.
[0085] As such, on the air supply port side, the decrease in the
power generation performance may be caused due to flooding by
excessive liquid water including generated water. On the air
exhaust port side, an increase in the resistance of the electrolyte
membrane 12 due to the drying of the MEA 10 might cause the
decrease in the power generation performance. In the fuel cell of
Comparative Example 1, no portion defining a penetration hole is
provided in the second passage 24. On the other hand, in the fuel
cell of Example 1, the portion defining the penetration hole 36 is
provided in the second passage 24. On this account, in Example 1,
water generated in the MEA 10 is easily discharged outside in
comparison with Comparative Example 1. This contributes to
restraining the decrease in the power generation performance caused
due to flooding on the air supply port side, but promotes the
drying of the MEA 10 on the air exhaust port side, thereby causing
a decrease in the power generation performance. Accordingly, the
decrease in the power generation performance in Example 1 in
comparison with Comparative Example 1 as illustrated in FIG. 9 is
presumably caused by the drying of the MEA 10. Further, the cell
resistance in Example 1 is higher than the cell resistance in
Comparative Example 1 in FIG. 9. From this point, it is also
considered that the power generation performance decreased due to
the drying of the MEA 10.
[0086] FIG. 13 is a perspective view of a cathode-side separator
18c provided in a fuel cell of Example 2. As illustrated in FIG.
13, in the cathode-side separator 18c provided in the fuel cell of
Example 2, portions defining penetration holes 36 having a circular
shape or an oval shape are provided only in an upstream region 48
placed on a central side in a width direction of a second passage
24 and on an upstream side relative to a flow of air flowing
through the second passage 24, but are not provided in a downstream
region 50 on a downstream side. Note that the upstream region 48 is
a region positioned on the upstream side of the flow of the air
when a bottom face 34 of a second recessed portion 32 constituting
the second passage 24 is equally divided into two regions in a
lengthwise direction of the second passage 24 so that each of the
two regions has a length of 1/2 of a length of the second passage
24. The downstream region 50 is a region positioned on the
downstream side of the flow of the air when the bottom face 34 of
the second recessed portion 32 constituting the second passage 24
is equally divided into two regions in the lengthwise direction of
the second passage 24 so that each of the two regions has a length
of 1/2 of the length of the second passage 24. The other
configurations of the fuel cell of Example 2 are the same as those
in Example 1, so descriptions thereof are omitted.
[0087] In Example 2, the portions defining the penetration holes 36
are provided only in the upstream region 48 of the bottom face 34
of the second recessed portion 32 constituting the second passage
24. Hereby, on the upstream side of the second passage 24, the
discharge of generated water and the supply of the air through the
portions defining the penetration holes 36 are enabled, thereby
making it possible to restrain the occurrence of flooding and
concentration overvoltage. On the downstream side of the second
passage 24, the portions defining the penetration holes 36 are not
provided, so generated water can be hardly discharged, thereby
making it possible to restrain drying of a MEA 10. Accordingly,
with Example 2, even in a case of an operation under a low humidity
condition, it is possible to restrain a decrease in power
generation performance.
[0088] FIGS. 14A and 14B are perspective views illustrating other
examples of the cathode-side separator 18c provided in the fuel
cell of Example 2. As illustrated in FIG. 14A, portions defining a
plurality of penetration holes 36 having the same shape and the
same size may be provided such that intervals therebetween are
gradually widened from an air supply port of the second passage 24
toward an air exhaust port thereof. That is, intervals between the
portions defining the penetration holes 36, provided in the
downstream region 50 of the second passage 24, may be larger than
intervals between the portions defining the penetration holes 36,
provided in the upstream region 48 of the second passage 24. As
illustrated in FIG. 14B, portions defining a plurality of
penetration holes 36 configured such that their sizes are gradually
decreased from the air supply port of the second passage 24 toward
the air exhaust port thereof may be provided at regular intervals.
That is, areas of the portions defining the penetration holes 36,
provided in the downstream region 50 of the second passage 24, may
be smaller than areas of the portions defining the penetration
holes 36, provided in the upstream region 48 of the second passage
24. Even in those cases, the occurrence of flooding and
concentration overvoltage can be restrained on the upstream side of
the second passage 24, and generated water can be hardly discharged
on the downstream side of the second passage 24, thereby making it
possible to restrain the drying of the MEA 10. This accordingly
makes it possible to restrain the decrease in the power generation
performance.
[0089] Accordingly, from the viewpoint of restraining the decrease
in the power generation performance in the operation under the low
humidity condition, a total area of the portions defining the
penetration holes 36, provided in the downstream region 50 of the
bottom face 34 of the second recessed portion 32 constituting the
second passage 24 may be smaller than a total area of the portions
defining the penetration holes 36, provided in the upstream region
48, as illustrated in FIGS. 13 to 14B. In other words, a downstream
aperture ratio, which is a ratio of the total area of the portions
defining the penetration holes 36, provided in the downstream
region 50, with respect to a total area of the downstream region 50
may be smaller than an upstream aperture ratio, which is a ratio of
the total area of the portions defining the penetration holes 36,
provided in the upstream region 48, with respect to a total area of
the upstream region 48.
[0090] Note that, in the viewpoint of restraining the decrease in
the power generation performance, all the intervals between the
portions defining the penetration holes 36, provided in the
downstream region 50 of the second passage 24, may be larger than
the intervals between the portions defining the penetration holes
36, provided in the upstream region 48 of the second passage 24, as
illustrated in FIG. 14A. However, at least one of the intervals
between the portions defining the penetration holes 36, provided in
the downstream region 50, may be larger than the intervals between
the portions defining the penetration holes 36, provided in the
upstream region 48. Similarly, as illustrated in FIG. 14B, all the
areas of the portions defining the penetration holes 36, provided
in the downstream region 50 of the second passage 24, may be
smaller than the areas of the portions defining the penetration
holes 36, provided in the upstream region 48 of the second passage
24. However, at least one of the areas of the portions defining the
penetration holes 36, provided in the downstream region 50, may be
smaller than the areas of the portions defining the penetration
holes 36, provided in the upstream region 48.
[0091] FIGS. 15 and 16 are perspective views of a cathode-side
separator 18c provided in a fuel cell of Example 3. As illustrated
in FIGS. 15 and 16, in the cathode-side separator 18c provided in
the fuel cell of Example 3, portions defining penetration holes 36
having a rectangular shape are provided on a central side in a
width direction of a second passage 24. In an upstream edge, on an
upstream side of a flow of air, of an edge of the portion defining
the penetration hole 36, a wall portion 60 projecting diagonally
inwardly in the second passage 24 from a bottom face 34 of a second
recessed portion 32 is provided. The wall portion 60 is provided so
as to cover at least part of the portion defining the penetration
hole 36, for example. The wall portion 60 is formed by bending or
press working, for example. Further, a first passage 22 is narrower
than the second passage 24, that is, the first passage 22 has a
sectional area smaller than the second passage 24. When the
sectional area of the second passage 24 is made relatively large,
it is possible to improve cooling performance, and when the
sectional area of the first passage 22 is made relatively small, it
is possible to restrain the air flowing through the first passage
22 from removing moisture content. The other configurations of the
fuel cell of Example 3 are the same as those in Example 1, so
descriptions thereof are omitted.
[0092] In Example 3, the wall portion 60 projecting inwardly in the
second passage 24 from the bottom face 34 of the second recessed
portion 32 is provided in the upstream edge, on the upstream side
of the flow of the air, of the edge of the portion defining the
penetration hole 36. In a case where the portions defining the
penetration holes 36 are provided on the bottom face 34 of the
second recessed portion 32, moisture content in a MEA 10 is removed
through the portions defining the penetration holes 36, so that the
MEA 10 might dry and power generation performance might decrease.
However, when the wall portions 60 are provided, the air flowing
through the second passage 24 is turned upward by the wall portions
60, so that a flow speed of the air passing through a top face of a
MEGA 20 exposed in the portions defining the penetration holes 36
slows down. This restrains the moisture content in the MEA 10 from
being removed through the portions defining the penetration holes
36, thereby making it possible to restrain the drying of the MEA
10. This accordingly makes it possible to restrain a decrease in
power generation performance.
[0093] Note that Example 3 exemplifies a case where the wall
portion 60 is provided only in the upstream edge of the edge of the
portion defining the penetration hole 36, but the wall portion 60
is not limited to this case. FIG. 17 is a perspective view of a
second passage 24 of a cathode-side separator 18c provided in a
fuel cell of Modified Example 1 of Example 3. Note that, in FIG.
17, a bottom face 34 of a second recessed portion 32 constituting
the second passage 24 and a wall portion 60 are indicated by a
cross hatch. As illustrated in FIG. 17, in addition to an upstream
edge of an edge of a portion defining a penetration hole 36, the
wall portion 60 may be provided in a side edge along a flow of air.
In this case, a flow speed of the air passing through a top face of
a MEGA 20 exposed in the portion defining the penetration hole 36
slows down, which further restrains moisture content in a MEA 10
from being removed through the portion defining the penetration
hole 36.
[0094] FIG. 18A is a perspective view of a second passage 24 of a
cathode-side separator 18c provided in a fuel cell of Example 4,
and FIG. 18B is a sectional view taken along a line XVIIIB-XVIIIB
in FIG. 18A. Note that, in FIG. 18A, a bottom face 34 of a second
recessed portion 32 constituting the second passage 24 is indicated
by a cross hatch. As illustrated in FIGS. 18A and 18B, in the
cathode-side separator 18c provided in the fuel cell of Example 5,
portions defining penetration holes 36 having a circular shape are
provided on a central side in a width direction of the second
passage 24. A part where the portion defining the penetration hole
36 is provided on the bottom face 34 of the second recessed portion
32 constituting the second passage 24 projects more than the other
part of the bottom face 34 of the second recessed portion 32.
Hereby, a relatively large gap 62 is formed between a top face of
the portion defining the penetration hole 36 and a top face of a
MEGA 20 exposed in the portion defining the penetration hole 36.
Accordingly, a flow speed of air passing through the top face of
the MEGA 20 slows down, which restrains moisture content in a MEA
10 from being removed through the portion defining the penetration
hole 36.
[0095] FIG. 19 is a perspective view of a cathode-side separator
18c provided in a fuel cell of Example 5. As illustrated in FIG.
19, in the cathode-side separator 18c provided in the fuel cell of
Example 5, a wall portion 60 is not provided in a portion defining
a penetration hole 36, provided in an upstream region 48, but the
wall portion 60 is provided only in a portion defining a
penetration hole 36, provided in a downstream region 50. As
described in Example 2, in an operation under a low humidity
condition, flooding due to excessive liquid water might occur on
the upstream side, and drying of a MEA 10 might occur on the
downstream side. On this account, as illustrated in Example 5, when
the portion defining the penetration hole 36 without the wall
portion 60 is provided on the upstream side, liquid water is
promoted to be discharged from the portion defining the penetration
hole 36 on the upstream side, thereby making it possible to
restrain the occurrence of flooding. Further, when the portion
defining the penetration hole 36 with the wall portion 60 is
provided on the downstream side, liquid water can be hardly
discharged from the portion defining the penetration hole 36 on the
downstream side, thereby making it possible to restrain the drying
of the MEA 10. Accordingly, with Example 5, even in a case of the
operation under the low humidity condition, it is possible to
restrain a decrease in power generation performance.
[0096] Note that Example 5 exemplifies a case where the wall
portion 60 is not provided in the upstream region 48, which is on
the upstream side relative to the middle of the second passage 24
in a lengthwise direction, and the wall portion 60 is provided only
in the downstream region 50, which is on the downstream side
relative to the middle of the second passage 24. However, the wall
portion 60 is not limited to this case. The wall portion 60 may not
be provided on the upstream side relative to a position other than
the middle of the second passage 24 in the lengthwise direction,
and the wall portion 60 may be provided on the downstream side
relative to the position. That is, the portion defining the
penetration hole 36 with the wall portion 60 should be provided on
the downstream side of the second passage 24 relative to the
portion defining the penetration hole 36 without the wall portion
60.
[0097] FIG. 20 is a perspective view of a cathode-side separator
18c provided in a fuel cell of Example 6. As illustrated in FIG.
20, in the cathode-side separator 18c provided in the fuel cell of
Example 6, a height of a wall portion 60 provided in a downstream
region 50 is higher than a height of a wall portion 60 provided in
an upstream region 48. On this account, liquid water is easily
discharged from portions defining penetration holes 36 on the
upstream side, but liquid water can be hardly discharged from
portions defining penetration holes 36 on the downstream side.
Accordingly, even in a case of an operation under a low humidity
condition, it is possible to restrain a decrease in power
generation performance.
[0098] Note that Example 6 exemplifies a case where the height of
the wall portion 60 provided in the downstream region 50, which is
on the downstream side relative to the middle of the second passage
24 in a lengthwise direction, is higher than the height of the wall
portion 60 provided in the upstream region 48, which is on the
upstream side relative to the middle of the second passage 24.
However, the wall portions 60 are not limited to this case. The
height of the wall portion 60 provided on the downstream side
relative to a position other than the middle of the second passage
24 in the lengthwise direction may be higher than the height of the
wall portion 60 provided on the upstream side relative to the
position. That is, the heights of the wall portions 60 should be
set such that the height of the wall portion 60 on the downstream
side of the second passage 24 is higher than the height of the wall
portion 60 on the upstream of the second passage 24.
[0099] FIG. 21 is a plan view of a second passage 24 of a
cathode-side separator 18c provided in a fuel cell of Example 7. As
illustrated in FIG. 21, in the cathode-side separator 18c provided
in the fuel cell of Example 7, a width W1 of a part of a second
passage 24 in which a portion defining a penetration hole 36 is
provided is wider than a width W2 of a part of the second passage
24 in which the portion defining the penetration hole 36 is not
provided. That is, a sectional area of the second passage 24 is
larger in the part where the portion defining the penetration hole
36 is provided than in the part where the portion defining the
penetration hole 36 is not provided. When the width W1 of the part
of the second passage 24 in which the portion defining the
penetration hole 36 is provided is set to be wider than the width
W2 of the part of the second passage 24 in which the portion
defining the penetration hole 36 is not provided, a flow speed of
air passing through a top face of a MEGA 20 exposed in the portion
defining the penetration hole 36 slows down. This restrains
moisture content in a MEA 10 from being removed through the
portions defining the penetration holes 36, thereby making it
possible to restrain the drying of the MEA 10. This accordingly
makes it possible to restrain a decrease in power generation
performance.
[0100] The examples of the present disclosure have been described
above in detail, but the present disclosure is not limited to the
specific examples, and various modifications and alternations can
be made within the scope of the present disclosure described in
Claims.
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