U.S. patent application number 11/329867 was filed with the patent office on 2006-06-01 for fuel cell casing and fuel cell.
This patent application is currently assigned to KYOCERA CORPORATION. Invention is credited to Itaru Ishii.
Application Number | 20060115707 11/329867 |
Document ID | / |
Family ID | 33562256 |
Filed Date | 2006-06-01 |
United States Patent
Application |
20060115707 |
Kind Code |
A1 |
Ishii; Itaru |
June 1, 2006 |
Fuel cell casing and fuel cell
Abstract
The fuel cell casing includes a plural stacked units. Each unit
includes a base body having a concavity, for accommodating a
membrane electrode assembly; a first fluid channel formed in the
base body; a first wiring conductor formed in the base body; a lid
body for sealing concavity hermetically; a second fluid channel
formed in the lid body; and a second wiring conductor formed in the
lid body. The first wiring conductor of a lower unit is
electrically connected to the second wiring conductor of an upper
unit. Each unit has a convexity on an end portion of a side surface
thereof which end portion is on an adjacent unit side, and the
units adjacent to each other are bonded to each other at the
convexities.
Inventors: |
Ishii; Itaru; (Kokubu-shi,
JP) |
Correspondence
Address: |
HOGAN & HARTSON L.L.P.
500 S. GRAND AVENUE
SUITE 1900
LOS ANGELES
CA
90071-2611
US
|
Assignee: |
KYOCERA CORPORATION
|
Family ID: |
33562256 |
Appl. No.: |
11/329867 |
Filed: |
January 10, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10877970 |
Jun 25, 2004 |
|
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11329867 |
Jan 10, 2006 |
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Current U.S.
Class: |
429/457 ;
429/469; 429/483; 429/510 |
Current CPC
Class: |
H01M 8/0273 20130101;
H01M 8/0256 20130101; H01M 8/0215 20130101; H01M 8/0284 20130101;
Y02E 60/50 20130101; H01M 8/0202 20130101; H01M 8/0258 20130101;
H01M 8/241 20130101; H01M 8/249 20130101; H01M 8/2475 20130101 |
Class at
Publication: |
429/038 ;
429/032; 429/036 |
International
Class: |
H01M 8/24 20060101
H01M008/24; H01M 8/10 20060101 H01M008/10; H01M 2/08 20060101
H01M002/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 26, 2003 |
JP |
2003-183146 |
Claims
1-10. (canceled)
11. A fuel cell casing comprising: a plurality of fuel cell casing
units stacked together, each of the fuel cell casing units
including, a base body made of ceramics that has a plurality of
concavities formed on one surface thereof, for accommodating
therein a membrane electrode assembly, the membrane electrode
assembly having a first electrode and a second electrode which are
formed on one principal surface and another principal surface
thereof, respectively; a first fluid channel formed so as to extend
from a bottom surface of the concavity facing the one principal
surface of the membrane electrode assembly to an outer surface of
the base body; a sixth wiring conductor having its one end disposed
on a bottom surface of the concavity facing the first electrode of
the membrane electrode assembly, and its another end led to the
outer surface of the base body; a lid body mounted on the one
surface of the base body near the concavities so as to cover the
concavities, for sealing the concavities hermetically; a second
fluid channel formed so as to extend from one surface of the lid
body facing the other principal surface of the membrane electrode
assembly to an outer surface of the lid body; a seventh wiring
conductor having its one end disposed on one surface of the lid
body facing the second electrode of the membrane electrode
assembly, and its another end led to the outer surface of the lid
body, the fuel cell casing further comprising: an eighth wiring
conductor having its one end connected to the sixth wiring
conductor facing the first electrode of the membrane electrode
assembly on the bottom surface in one of the plurality of
concavities, and its another end led to the one surface of the base
body on which the lid body is mounted; and a ninth wiring conductor
having its one end connected to the seventh wiring conductor facing
the second electrode of the membrane electrode assembly
accommodated in another of the plurality of concavities on the one
surface of the lid body, and its another end led to the one surface
of the lid body to be mounted on the one surface of the base body,
so as to face the other end of the eighth wiring conductor, wherein
the sixth wiring conductor of one fuel cell casing unit is
electrically connected to the seventh wiring conductor of another
fuel cell casing unit which is stacked thereon and adjacent
thereto, and wherein each of the fuel cell casing units has a
convexity which is formed on an end portion of a side surface
thereof which end portion is on an adjacent cell casing unit side,
and the fuel cell casing units adjacent to each other are bonded to
each other at their convexities.
12. The fuel cell casing of claim 11, wherein the eighth wiring
conductor is provided on the other fuel cell casing unit and the
ninth wiring conductor is provided on the one fuel cell casing
unit, wherein the eighth wiring conductor and the ninth wiring
conductor are connected through a connecting wiring conductor.
13. The fuel cell casing of claim 11, wherein an adhesive used for
bonding the convexities together is made of a thermosetting resin
material having a curing temperature of 200.degree. C. or
below.
14. The fuel cell casing of claim 11, wherein the base body and the
lid body each possess a flexural strength of 200 MPa or above.
15. The fuel cell casing of claim 11, wherein the base body and the
lid body each have a thickness of 0.2 mm to 5 mm.
16. The fuel cell casing of claim 11, wherein the base body and the
lid body are composed of sintered aluminum oxide having a relative
density of 90% or above.
17-18. (canceled)
19. A fuel cell comprising: a membrane electrode assembly having a
first electrode and a second electrode which are formed on one
principal surface and another principal surface thereof,
respectively; and the fuel cell casing of claim 11, wherein the
membrane electrode assemblies are accommodated in the plurality of
concavities of the fuel cell casing, respectively, one and the
other principal surfaces of the membrane electrode assembly are
arranged such that fluid can be exchanged between the one principal
surface and the first fluid channel and between the other principal
surface and the second fluid channel, respectively, the sixth
wiring conductor is electrically connected to the first electrode,
the seventh wiring conductor is electrically connected to the
second electrode, the one end of the eighth wiring conductor is
electrically connected to the sixth wiring conductor, the one end
of the ninth wiring conductor is electrically connected to the
seventh wiring conductor, the other ends of the eighth and ninth
wiring conductors are electrically connected to each other, and the
lid body is mounted on the one surface of the base body near the
concavity so as to cover the concavity.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a fuel cell casing that is
capable of accommodating a membrane electrode assembly, is made of
ceramics, and is small and highly reliable, and to a fuel cell
using the same.
[0003] 2. Description of the Related Art
[0004] In recent years, development of compact fuel cells that are
operable at a lower temperature than ever before has been briskly
under way. Fuel cells are classified according to their
electrolytes in use. For example, there have been known Polymer
Electrolyte Fuel Cell (hereinafter abbreviated to "PEFC");
Phosphoric-Acid Fuel Cell; and Solid-Oxide Fuel Cell.
[0005] Among them, in particular, the PEFC is operable at a
temperature as low as 80 to 100.degree. C., and also possesses many
excellent characteristics as follows: [0006] (1) its power density
is high, and miniaturization and weight reduction are allowed;
[0007] (2) since an electrolyte membrane is not corrosive, its
operation temperature is low, and therefore the constitution
material of the cell is constrained little from the aspect of
corrosion-resistance, cost reduction is easy; and [0008] (3)
actuation at ordinary temperatures is allowed, and therefore,
actuation time is short. By taking advantage of such
characteristics, it has been considered to not only apply the PEFC
to driving power sources for a vehicle, household cogeneration
systems and the like but also use as power sources for mobile
electronic apparatuses such as mobile phones, PDAs (personal
digital assistants), notebook-type personal computers, digital
cameras, videos, and the like whose outputs are a few watts to
several tens of watts.
[0009] Roughly, the PEFC is composed of a fuel electrode (anode),
an air electrode (cathode), and a film-shaped membrane electrode
assembly interposed between the fuel electrode and the air
electrode. The fuel electrode is formed of a carbon electrode
having catalyst fine particles of platinum, platinum-ruthenium, or
the like attached thereto. The air electrode is formed of a carbon
electrode having catalyst fine particles of platinum or the like
attached thereto. Here, the fuel electrode is supplied with
hydrogen gas (H.sub.2) extracted through a reforming section,
whereas the air electrode is supplied with oxygen gas (O.sub.2)
present in the air. Through an electrochemical reaction, electric
energy of certain level is generated (electric power production),
and thereby electric energy acting as driving power
(voltage/current) for a load is produced.
[0010] Specifically, when hydrogen gas (H.sub.2) is supplied to the
fuel electrode, as shown in the following chemical equation (1),
with the action of the catalyst, an electron (e.sup.-)-separated
hydrogen ion (proton; H.sup.+) is generated, and the proton passes
through the membrane electrode assembly toward the air electrode.
Simultaneously, the electron (e.sup.-) is ejected by the carbon
electrode constituting the fuel electrode and is then supplied to a
load. 3H.sub.2.fwdarw.6H.sup.++6e.sup.- (1)
[0011] On the other hand, when air is supplied to the air
electrode, as shown in the following chemical equation (2), with
the action of the catalyst, the electron (e.sup.-) having reached
the load and the hydrogen ion (H.sup.+) having passed through the
membrane electrode assembly, and oxygen gas (O.sub.2) present in
the air react with one another to form water (H.sub.2O)
6H.sup.++3/2O.sub.2+6e.sup.-.fwdarw.3H.sub.2O (2)
[0012] Such a series of electrochemical reactions (refer to
equations (1) and (2)) commonly take place at a relatively low
temperature of approximately 80 to 100.degree. C. Basically, a
by-product material other than electric power is water (H.sub.2O)
alone.
[0013] As an ionically conductive membrane (Polymeric solid
electrolytes) constituting a membrane electrode assembly, there
have hitherto been known a cation-exchange membrane composed of the
polystyrene-base having a sulfonic acid group, a mixture membrane
of fluorocarbon sulfonic acid and polyvinylidene fluoride, a
membrane obtained by grafting trifluoroethylene to a fluorocarbon
matrix, and the like. In recent years, for example, a
perfluorocarbon sulfonic acid membrane has been in use (available
from DuPont Co. under a trade name "Nafion").
[0014] FIG. 4 is a sectional view showing the structure of a fuel
cell (PEFC) of conventional design. In the figure, reference
numeral 21 denotes the PEFC, reference numeral 23 denotes a
membrane electrode assembly, and reference numerals 24 and 25
denote a pair of porous electrodes that are arranged on the
membrane electrode assembly 23 so as to sandwich therebetween the
membrane electrode assembly and that have functions as a gas
diffusion layer and a catalyst layer, that is, a fuel electrode and
an air electrode, reference numeral 26 denotes a gas separator;
reference numeral 28 denotes a fuel duct; reference numeral 29
denotes an air duct; reference numeral 30 denotes current
collecting plates; reference numeral 31 denotes clamping plates;
and reference numeral 32 denotes screws.
[0015] The gas separator 26 is composed of a stack portion; a gas
inlet/outlet frame; a separator portion; and electrodes. The stack
portion and the gas inlet/outlet frame constitute the outer shape
of the gas separator 26. The separator portion serves to separate
the fuel duct 28 and the air duct 29. The electrodes are disposed
so as to pierce the separator portion and placed so as to
correspond to the fuel electrode 24 and the air electrode 25 of the
membrane electrode assembly 23. A multiplicity of membrane
electrode assemblies 23 are stacked on top of one another via the
gas separators 26, in such a way that the fuel and air electrodes
24 and 25 of the membrane electrode assembly 23 are connected in
series and/or in parallel with one another through electrical
connection. Electric power is obtained by means of the current
collecting plates 30. The gas separator 26 is clamped down by the
screws 32 at an adequate surface pressure with use of the clamping
plates 31. Thereupon, a fuel cell stack, i.e., a minimum unit of a
cell, is constructed. By accommodating the fuel cell stack in a
casing, a general PEFC main body is realized.
[0016] Fuel gas that contains water vapor (gas that is rich in
hydrogen) is supplied from a reforming device to the fuel electrode
24 through the fuel duct 28 formed in the gas separator 26 and the
air is supplied as oxidant gas from the air to the air electrode 5
through the air duct 29, and electric power is generated by a
chemical reaction in the membrane electrode assembly 23.
[0017] There is Japanese Unexamined Patent Publication JP-A
2001-266910 and Japanese Unexamined Patent Publication JP-A
2001-507501 as the related art.
[0018] However, this fuel cell 21 that has been proposed and
developed up to now as a high-voltage and high-capacity cell is a
heavy and large cell which has a stack structure and whose
constitution elements have large areas, and use of a fuel cell as a
small cell has been hardly considered so far.
[0019] Specifically, the conventional gas separator 26 disposed in
the fuel cell 21 poses a problem that since the side surfaces of
the membrane electrode assemblies 23 are exposed outside in a
stacked body made by stacking the membrane electrode assemblies 23
by the use of the gas separator, the construction is easily damaged
because of a fall at the time of carrying, and it is hard to
guarantee mechanical reliability of the whole fuel cell 21.
[0020] Furthermore, in order to install the fuel cell 21 in mobile
electronic apparatus, a fuel cell casing that is excellent
compactness, convenience and safety unlike a conventional large
fuel cell casing is necessary. In other words, it is necessary, in
order to apply as a portable power source such as a general-purpose
chemical cell, to miniaturize and low-profile a fuel cell casing
for the purpose of shortening time for increasing temperature up to
operation temperature and making a thermal capacity small. However,
the gas separator 26 that dominates a large proportion of a thermal
capacity in the conventional fuel cell 21, specifically, the gas
separator 26 where the ducts are formed on the surface of a carbon
plate by cutting processing becomes fragile when becoming
thin-walled, and therefore, it needs thickness of a few
millimeters. Therefore, there is also a problem that it is hard to
miniaturize and low-profile.
[0021] There is another problem associated with the output voltage
of the fuel cell 21. In a case where the gas separator 26 is made
larger in thickness, resistance is increased, and thus voltage
losses with respect to output current is increased. As a result,
the output voltage is decreased. Further, combinations of a
plurality of membrane electrode assemblies 23, the opposed fuel
electrodes 24 and air electrodes 25, and the gas separators 26 need
to be arbitrarily connected together in series or in parallel with
efficiency so as to adjust the output voltage and the output
current as a whole. In the conventional fuel cell 21, in order to
obtain electric power from the fuel electrode and the air
electrode,sandwiching therebetween the membrane electrode assembly
23, such a method is adopted that the current collecting plates 30
are connected with an external electric circuit, and the membrane
electrode assemblies are stacked through a plurality of gas
separators 26 as conductive materials, and are connected in series
by means of the clamping plates 31. In this case, quite
inconveniently, the current collecting plate 30, the clamping plate
31, and the screw 32 need to be electrically insulated from one
another. Thus, the conventional fuel cell, when made compact,
presents the problems of an increase in the number of constituent
components; the difficulty in slenderization; and poor flexibility
in establishing electrical connection among the individual
cells.
SUMMARY OF THE INVENTION
[0022] The invention has been devised in view of the
above-described problems with the conventional art, and accordingly
its object is to provide a compact, sturdy, and highly-reliable
fuel cell casing which is capable of accommodating a membrane
electrode assembly and allows highly-efficient electrical
connection, and also provide a fuel cell employing said fuel cell
casing.
[0023] The invention provides a fuel cell casing comprising:
[0024] a plurality of fuel cell casing units stacked together, each
of the fuel cell casing units including,
[0025] a base body made of ceramics that has a concavity formed on
one surface thereof, for accommodating therein a membrane electrode
assembly, the membrane electrode assembly having a first electrode
and a second electrode which are formed on one principal surface
and another principal surface thereof, respectively;
[0026] a first fluid channel formed so as to extend from a bottom
surface of the concavity facing the one principal surface of the
membrane electrode assembly to an outer surface of the base
body;
[0027] a first wiring conductor having its one end disposed on a
bottom surface of the concavity facing the first electrode of the
membrane electrode assembly, and its another end led to the outer
surface of the base body;
[0028] a lid body mounted on the one surface of the base body near
the concavity so as to cover the concavity, for sealing the
concavity hermetically;
[0029] a second fluid channel formed so as to extend from one
surface of the lid body facing the other principal surface of the
membrane electrode assembly to an outer surface of the lid body;
and
[0030] a second wiring conductor having its one end disposed on one
surface of the lid body facing the second electrode of the membrane
electrode assembly, and its another end led to the outer surface of
the lid body,
[0031] wherein the first wiring conductor of one fuel cell casing
unit is electrically connected to the second wiring conductor of
another fuel cell casing unit which is stacked thereon and adjacent
thereto,
[0032] and wherein each of the fuel cell casing units has a
convexity which is formed on an end portion of a side surface
thereof which end portion is on an adjacent cell casing unit side,
and the fuel cell casing units adjacent to each other are bonded to
each other at their convexities.
[0033] The invention provides a fuel cell casing comprising:
[0034] a plurality of fuel cell casing units stacked together, each
of the fuel cell casing units including,
[0035] a base body made of ceramics that has a plurality of
concavities formed on one surface thereof, for accommodating
therein a membrane electrode assembly, the membrane electrode
assembly having a first electrode and a second electrode which are
formed on one principal surface and another principal surface
thereof, respectively;
[0036] a first fluid channel formed so as to extend from a bottom
surface of the concavity facing the one principal surface of the
membrane electrode assembly to an outer surface of the base
body;
[0037] a third wiring conductor having its one end disposed on a
bottom surface of the concavity facing the first electrode of the
membrane electrode assembly, and its another end led to the outer
surface of the base body;
[0038] a lid body mounted on the one surface of the base body near
the concavities so as to cover the concavities, for sealing the
concavities hermetically;
[0039] a second fluid channel formed so as to extend from one
surface of the lid body facing the other principal surface of the
membrane electrode assembly to an outer surface of the lid
body;
[0040] a fourth wiring conductor having its one end disposed on one
surface of the lid body facing the second electrode of the membrane
electrode assembly, and its another end led to the outer surface of
the lid body;
[0041] a fifth wiring conductor formed on the base body, having its
one end connected to the third wiring conductor facing the first
electrode of the membrane electrode assembly on the bottom surface
in one of the plurality of concavities, and its another end
connected to the third wiring conductor facing the first electrode
of the membrane electrode assembly on the bottom in another of the
plurality of concavities,
[0042] wherein the third wiring conductor of one fuel cell casing
unit is electrically connected to the fourth wiring conductor of
another fuel cell casing unit which is stacked thereon and adjacent
thereto,
[0043] and wherein each of the fuel cell casing units has a
convexity which is formed on an end portion of a side surface
thereof which end portion is on an adjacent cell casing unit side,
and the fuel cell casing units adjacent to each other are bonded to
each other at their convexities.
[0044] The invention provides a fuel cell casing comprising:
[0045] a plurality of fuel cell casing units stacked together, each
of the fuel cell casing units including,
[0046] a base body made of ceramics that has a plurality of
concavities formed on one surface thereof, for accommodating
therein a membrane electrode assembly, the membrane electrode
assembly having a first electrode and a second electrode which are
formed on one principal surface and another principal surface
thereof, respectively;
[0047] a first fluid channel formed so as to extend from a bottom
surface of the concavity,facing the one principal surface of the
membrane electrode assembly to an outer surface of the base
body;
[0048] a sixth wiring conductor having its one end disposed on a
bottom surface of the concavity facing the first electrode of the
membrane electrode assembly, and its another end led to the outer
surface of the base body;
[0049] a lid body mounted on the one surface of the base body near
the concavities so as to cover the concavities, for sealing the
concavities hermetically;
[0050] a second fluid channel formed so as to extend from one
surface of the lid body facing the other principal surface of the
membrane electrode assembly to an outer surface of the lid
body;
[0051] a seventh wiring conductor having its one end disposed on
one surface of the lid body facing the second electrode of the
membrane electrode assembly, and its another end led to the outer
surface of the lid body,
[0052] the fuel cell casing further comprising:
[0053] an eighth wiring conductor having its one end connected to
the sixth wiring conductor facing the first electrode of the
membrane electrode assembly on the bottom surface in one of the
plurality of concavities, and its another end led to the one
surface of the base body on which the lid body is mounted; and
[0054] a ninth wiring conductor having its one end connected to the
seventh wiring conductor facing the second electrode of the
membrane electrode assembly accommodated in another of the
plurality of concavities on the one surface of the lid body, and
its another end led to the one surface of the lid body to be
mounted on the one surface of the base body, so as to face the
other end of the eighth wiring conductor,
[0055] wherein the sixth wiring conductor of one fuel cell casing
unit is electrically connected to the seventh wiring conductor of
another fuel cell casing unit which is stacked thereon and adjacent
thereto,
[0056] and wherein each of the fuel cell casing units has a
convexity which is formed on an end portion of a side surface
thereof which end portion is on an adjacent cell casing unit side,
and the fuel cell casing units adjacent to each other are bonded to
each other at their convexities.
[0057] Further, in the invention, the eighth wiring conductor is
provided on the other fuel cell casing unit and the ninth wiring
conductor is provided on the one fuel cell casing unit,
[0058] wherein the eighth wiring conductor and the ninth wiring
conductor are connected through a connecting wiring conductor.
[0059] In the invention, an adhesive used for bonding the
convexities together is made of a thermosetting resin material
having a curing temperature of 200.degree. C. or below.
[0060] Furthermore, in the invention, the base body and the lid
body each possess a flexural strength of 200 MPa or above.
[0061] Furthermore, in the invention, the base body and the lid
body each have a thickness of 0.2 mm to 5 mm.
[0062] Furthermore, in the invention, the base body and the lid
body are composed of sintered aluminum oxide having a relative
density of 90% or above.
[0063] Furthermore, the invention provides a fuel cell
comprising:
[0064] a membrane electrode assembly having a first electrode and a
second electrode which are formed on one principal surface and
another principal surface thereof, respectively; and
[0065] the fuel cell casing mentioned above,
[0066] wherein the membrane electrode assemblies are accommodated
in the concavity of the fuel cell casing, one and the other
principal surfaces of the membrane electrode assembly are arranged
such that fluid can be exchanged between the one principal surface
and the first fluid channel and between the other principal surface
and the second fluid channel, respectively, the first wiring
conductor is electrically connected to the first electrode, the
second wiring conductor is electrically connected to the second
electrode, and the lid body is mounted on the one surface of the
base body near the concavity so as to cover the concavity.
[0067] Furthermore, the invention provides a fuel cell
comprising:
[0068] a membrane electrode assembly having a first electrode and a
second electrode which are formed on one principal surface and
another principal surface thereof, respectively; and
[0069] the fuel cell casing mentioned above,
[0070] wherein the membrane electrode assemblies are accommodated
in the plurality of concavities of the fuel cell casing,
respectively, one and the other principal surfaces of the membrane
electrode assembly are arranged such that fluid can be exchanged
between the one principal surface and the first fluid channel and
between the other principal surface and the second fluid channel,
respectively, the third wiring conductor is electrically connected
to the first electrode, the fourth wiring conductor is electrically
connected to the second electrode, the fifth wiring conductor is
electrically connected to the third wiring conductor, and the lid
body is mounted on the one surface of the base body near the
concavity so as to cover the concavity.
[0071] Furthermore, the invention provides a fuel cell
comprising:
[0072] a membrane electrode assembly having a first electrode and a
second electrode which are formed on one principal surface and
another principal surface thereof, respectively; and
[0073] the fuel cell casing mentioned above,
[0074] wherein the membrane electrode assemblies are accommodated
in the plurality of concavities of the fuel cell casing,
respectively, one and the other principal surfaces of the membrane
electrode assembly are arranged such that fluid can be exchanged
between the one principal surface and the first fluid channel and
between the other principal surface and the second fluid channel,
respectively, the sixth wiring conductor is electrically connected
to the first electrode, the seventh wiring conductor is
electrically connected to the second electrode, the one end of the
eighth wiring conductor is electrically connected to the sixth
wiring conductor, the one end of the ninth wiring conductor is
electrically connected to the seventh wiring conductor, the other
ends of the eighth and ninth wiring conductors are electrically
connected to each other, and the lid body is mounted on the one
surface of the base body near the concavity so as to cover the
concavity.
[0075] According to the invention, the fuel cell casing includes a
base body made of ceramics having a concavity formed on one side
thereof for accommodating therein a membrane electrode assembly,
the membrane electrode assembly having a first electrode and a
second electrode which are formed on one principal surface and
another principal surface thereof, respectively; and a lid body
mounted on the one surface of the base body near the concavity so
as to cover the concavity, for sealing the concavity hermetically.
With this construction, by sealing the fuel cell casing
hermetically, leakage of fluid such as gas can be prevented.
Moreover, since there is no need to prepare an extra package in
addition to the casing, it is possible to obtain a fuel cell which
can be operated with high efficiency, and to achieve
miniaturization. Further, the fuel cell is constructed by
accommodating a plurality of membrane electrode assemblies in the
casing composed of the ceramic-made base body having the concavity
formed on the one surface and the lid body for sealing the
concavity. Hence, it never occurs that the membrane electrode
assembly is exposed outside and therefore the membrane electrode
assembly can be protected against damage, with the result that the
mechanical reliability of the fuel cell as a whole can be enhanced.
Besides, the first and second wiring conductors, or the third to
fifth wiring conductors, or the sixth to ninth wiring conductors,
each of which has its one end disposed within the casing composed
of the concavity and the lid body, are the only components that
make electrical contact with the membrane electrode assembly. This
frees the membrane electrode assembly as a whole from unnecessary
electrical connection, whereby making it possible to obtain a fuel
cell which is excellent in reliability and safety. In addition, by
using ceramics as a material for constituting the fuel cell casing,
the fuel cell can be made highly resistant to corrosion caused by
fluid, typified by various gaseous materials.
[0076] It should be noted that the first fluid channel is so formed
as to extend from the bottom surface of the concavity facing the
one principal surface of the membrane electrode assembly to the
outer surface of the base body, whereas the second fluid channel is
so formed-as to extend from one surface of the lid body facing the
other principal surface of the membrane electrode assembly to the
outer surface of the lid body. The fluid channels are individually
formed on their corresponding inner wall surfaces of the casing
unit, with the membrane electrode assembly kept sandwiched
therebetween. Thereby it is possible to enhance the uniform supply
of the fluid to be supplied to the membrane electrode assembly.
[0077] Moreover, being made of ceramics which is greater in
strength than a conventional carbon molded material, the base body
and the lid body can be reduced in thickness, and its resistance
can be decreased. As a result, a high-power fuel cell can be
realized that suffers little from voltage losses.
[0078] Further, the individual fuel cell casing units are fixed to
one another, at their convexities, with use of an adhesive. That
is, there is no need to prepare current collecting plates and
clamping plates. This helps reduce the number of constituent
components and also achieve slenderization.
[0079] In addition, since the fluid channels are formed separately
in the base body and the lid body, each of the fluid channels is
excellent in hermeticity. This makes it possible to prevent mixing
of two different fluid materials (for example, oxygen gas and
hydrogen gas or methanol or the like) that must essentially be
separated from each other by the fluid paths. Accordingly, it never
occurs that the fuel cell fails to function properly due to fluid
mixing, and that flammable fluid materials are ignited and exploded
through mixing at a high temperature. As a result, the safety of
the fuel cell can be assured.
[0080] According to the invention, in the fuel cells, the membrane
electrode assembly is accommodated in the concavity of the fuel
cell casing, one and the other principal surfaces of the membrane
electrode assembly are arranged such that fluid can be exchanged
between the one principal surface and the first fluid channel and
between the other principal surface and the second fluid channel,
respectively, the first wiring conductor is electrically connected
to the first electrode, the second wiring conductor is electrically
connected to the second electrode, and lid body is mounted on the
one surface of the base body near the concavity so as to cover the
concavity. With this construction, since the wiring conductors
allow free electrical wiring, the desired voltage and current can
be acquired.
[0081] It will thus be seen that the invention accomplishes a
compact, sturdy, and highly-reliable fuel cell that succeeds in
even gas supply and highly-efficient electrical connection by
exploiting the advantages of the fuel cell casing embodying the
invention.
[0082] Moreover, according to the invention, the fuel cell casing
has the fifth wiring conductor formed in the base body. The fifth
wiring conductor has its one end connected to the third wiring
conductor facing the first electrode of the membrane electrode
assembly on the bottom surface in one of the plurality of
concavities, and its another end connected to the third wiring
conductor facing the first electrode of the membrane electrode
assembly on the bottom in another of the plurality of concavities.
With this construction, a plurality of membrane electrode
assemblies can be connected in parallel with one another through
electrical connection. This makes it possible to adjust the output
current of the fuel cell as a whole properly, and thereby take out
electricity in good condition that has been electrochemically
produced in the membrane electrode assembly.
[0083] Further, according to the invention, the fuel cell casing
has the eighth and ninth wiring conductors, respectively, which are
formed in the base body having a plurality of concavities for
accommodating the membrane electrode assembly and the lid body to
be mounted in the base body. The eighth wiring conductor has its
one end connected to the sixth wiring conductor facing the first
electrode of the membrane electrode assembly on the bottom surface
of one of the plurality of concavities, and its other end led to a
part of one surface of the base body on which the lid body is
mounted. The ninth wiring conductor has its one end connected to
the seventh wiring conductor facing the second electrode of the
membrane electrode assembly accommodated in the other of the
plurality of concavities on one surface of the lid body, and its
other end led to a part of one surface of the lid body to be
mounted on one surface of the base body, so as to face the other
end of the eighth wiring conductor. With this construction, a
plurality of membrane electrode assemblies can be connected in
series with one another through electrical connection. As a result,
although only a little voltage can be obtained through electricity
production made by a single membrane electrode assembly, by
achieving serial connection, a total voltage can be adjusted
properly. This makes it possible to take out electricity in good
condition that has been electrochemically produced in the membrane
electrode assembly.
[0084] According to the invention, in the fuel cell, the membrane
electrode assembly is accommodated in the concavity of the fuel
cell casing, one and the other principal surfaces of the membrane
electrode assembly is arranged such that fluid can be exchanged
between them and the first and second fluid channels, the first and
second electrodes are electrically connected individually to the
first and second wiring conductors, or to the third to fifth wiring
conductors, or to the sixth to ninth wiring conductors, and the lid
body is mounted on one surface of the base body near the concavity
so as to cover the concavity. It will thus be seen that the
invention accomplishes a compact, sturdy, and highly-reliable fuel
cell that succeeds in highly-efficient electrical connection by
exploiting the advantages of the fuel cell casings embodying the
invention. Moreover, by connecting a plurality of membrane
electrode assemblies in parallel with one another, adjustment can
be made to the output current of the fuel cell as a whole, or, by
connecting a plurality of membrane electrode assemblies in series
with one another, adjustment can be made to a total voltage. This
makes it possible to take out electricity in good condition that
has been electrochemically produced in the membrane electrode
assembly.
[0085] Hence, according to the invention, there are provided a fuel
cell casing and a fuel cell that are excellent in compactness,
convenience, and safety; that allow even fluid supply and
highly-efficient electrical connection; and that can be operated
with stability for a longer period of time.
[0086] According to the invention, in the fuel cell, the membrane
electrode assembly is accommodated in the concavity of the fuel
cell casing embodying the invention, one and another principal
surfaces of the membrane electrode assembly are arranged such that
fluid can be exchanged between them and the first and second fluid
channels, the first and second electrodes are electrically
connected to the first and second wiring conductors, respectively,
and the lid body is mounted on one surface of the base body near
the concavity so as to cover the concavity. With this construction,
it never occurs that the membrane electrode assembly is exposed
outside and is therefore subjected to damage. Moreover, the first
and second wiring conductors, each of which has its one end
disposed inside the casing unit composed of the concavity and the
lid body, are the only components that make electrical contact with
the membrane electrode assembly. This frees the membrane electrode
assembly from unnecessary electrical connection, whereby making it
possible to obtain a fuel cell which is excellent in reliability
and safety. Further, the first and second fluid channels are
individually formed on their corresponding inner wall surfaces of
the casing unit, that is, formed on the bottom surface of the
concavity in the base body and one surface of the lid body,
respectively, so as to have sandwiched therebetween the membrane
electrode assembly. This makes it possible to enhance the uniform
suppliability of the gas to be supplied to the membrane electrode
assembly, and thereby prevent a decrease in the partial pressure of
the gas to be supplied to the first and second electrodes of the
membrane electrode assembly. Thus, a stable output voltage of
predetermined level can be acquired. Further, a stress occurring in
the membrane electrode assembly can be suppressed successfully;
wherefore the reliability of the fuel cell can be enhanced.
[0087] According to the fuel cells of the invention, since the
first to ninth wiring conductors allow free three-dimensional
wiring, a plurality of membrane electrode assemblies can be
arbitrarily connected in series or in parallel with one another,
whereby making it possible to adjust the overall output voltage and
output current with efficiency. As a result, electricity which has
been electrochemically produced in the membrane electrode
assemblies can be taken out in good condition.
[0088] In addition, the individual fuel cells are fixed to one
another, at the convexities adjacent to each other, with use of an
adhesive. This eliminates the need to prepare an extra mounting
member, with the result that the fuel cell can be made lower and
lower in profile.
BRIEF DESCRIPTION OF THE DRAWINGS
[0089] Other and further objects, features, and advantages of the
invention will be more explicit from the following detailed
description taken with reference to the drawings wherein:
[0090] FIG. 1 is a sectional view showing a fuel cell casing and a
fuel cell employing the fuel cell casing according to a first
embodiment of the invention;
[0091] FIG. 2 is a sectional view showing a fuel cell casing and a
fuel cell employing the fuel cell casing according to a second
embodiment of the invention;
[0092] FIG. 3 is a sectional view showing a fuel cell casing and a
fuel cell employing the fuel cell casing according to a third
embodiment of the invention; and
[0093] FIG. 4 is a sectional view showing a conventional fuel cell
casing and a conventional fuel cell employing the fuel casing.
DETAILED DESCRIPTION
[0094] Now referring to the drawings, preferred embodiments of the
invention are described below.
[0095] Hereinafter, the invention will be described in detail with
reference to the accompanying drawings. FIG. 1 is a sectional view
showing a fuel cell casing and a fuel cell employing the fuel cell
casing according to a first embodiment of the invention. In the
figure, reference numeral 1 denotes a fuel cell; reference numeral
2 denotes a fuel cell casing; reference numeral 3 denotes a
membrane electrode assembly; reference numeral 4 denotes a first
electrode; reference numeral 5 denotes a second electrode;
reference numeral 6 denotes a base body; reference numeral 7
denotes a lid body; reference numeral 8 denotes a first fluid
channel; reference numeral 9 denotes a second fluid channel;
reference numeral 10 denotes a first wiring conductor; reference
numeral 11 denotes a second wiring conductor; reference numeral 12
denotes a convexity; reference numeral 13 denotes a fuel cell
casing unit; and reference numeral 14 denotes an adhesive.
[0096] For instance, the membrane electrode assembly 3 is basically
composed of an ionically conductive membrane (Polymeric solid
electrolytes). Integrally formed on both principal surfaces of the
ionically conductive membrane are a fuel electrode acting as an
anode side electrode (not shown) and an air electrode acting as a
cathode side electrode (not shown). The first electrode 4 is formed
on a lower principal surface which is one principal surface and the
second electrode 5 is formed on an upper principal surfaces which
is another principal surface, respectively. The electric current
generated in the membrane electrode assembly 3 is introduced to the
first and second electrodes, and is thereafter taken out.
[0097] The ionically conductive membrane (Polymeric solid
electrolyte) constituting the membrane electrode assembly 3 is made
of perfluorocarbon sulfonic acid resin, for example,
proton-conductive ionic exchange resin such as "Nafion" (trade
name, product of DuPont). Moreover, the fuel electrode and the air
electrode are built as porous gas diffusion electrodes and have
both functions of a porous catalyst layer and a gas diffusion
layer. The fuel electrode and the air electrode are each made of a
porous substance that holds conductive fine particles carrying a
catalyst of platinum, palladium, or alloy thereof, for example,
carbon fine particles, by a hydrophobic resin binder such as
polytetrafluoroethylene.
[0098] The first electrode 4 and the second electrode 5 which are
disposed on the lower principal surface and the upper principal
surface, respectively, of the membrane electrode assembly 3, are
formed by a method of hot-pressing a carbon electrode on which fine
particles of a catalyst such as platinum or platinum-ruthenium are
attached on the membrane electrode assembly 3, a method of applying
or transferring a mixture of a carbon electrode material on which
fine particles of a catalyst such as platinum or platinum-ruthenium
are attached and a solution in which an electrolyte material is
dispersed onto an electrolyte membrane, or the like.
[0099] The fuel cell casing 2 is composed of a plurality of fuel
cell casing units 13 stacked together. The respective fuel cell
casing units 13 include the base body 6 having the concavity and
the lid body 7, has a function of storing the membrane electrode
assembly 3 inside the concavity and hermetically sealing, and is
made of a ceramic material such as sintered aluminum oxide
(Al.sub.2O.sub.3); sintered mullite (3Al.sub.2O.sub.3.2SiO.sub.2);
sintered silicon carbide (SiC); sintered aluminum nitride (AlN);
sintered silicon nitride (Si.sub.3N.sub.4); or sintered glass
ceramic.
[0100] The sintered glass ceramic is composed of a glass component
and a filler component. The examples of the glass component
include: SiO.sub.2--B.sub.2O.sub.3 composite;
SiO.sub.2--B.sub.2O.sub.3--Al.sub.2O.sub.3 composite;
SiO.sub.2--B.sub.2O.sub.3--Al.sub.2O.sub.3--MO composite (wherein M
denotes Ca, Sr, Mg, Ba, or Zn);
SiO.sub.2--Al.sub.2O.sub.3-M.sup.1O-M.sup.2O composite (wherein
M.sup.1 and M.sup.2 are identical or different, and each denote Ca,
Sr, Mg, Ba, or Zn);
SiO.sub.2--B.sub.2O.sub.3--Al.sub.2O.sub.3-M.sup.1O-M.sup.2O
composite (wherein M.sup.1 and M.sup.2 are the same as above);
SiO.sub.2--B.sub.2O.sub.3-M.sup.3.sub.2O composite (wherein M.sup.3
represents Li, Na, or K) ;
SiO.sub.2--B.sub.2O.sub.3--Al.sub.2O.sub.3-M.sup.3.sub.2O composite
(wherein M.sup.3 is the same as above); Pb glass; and Bi glass.
[0101] The examples of the filler component include: a composite
oxide obtained by combining Al.sub.2O.sub.3, SiO.sub.2, ZrO.sub.2,
and an alkaline earth metal oxide; a composite oxide obtained by
combining TiO.sub.2 and an alkaline earth metal oxide; and a
composite oxide containing at least one of Al.sub.2O.sub.3 and
SiO.sub.2 (for example, spinel, mullite, or cordierite).
[0102] The fuel cell casing unit 13 of the fuel cell casing 2
includes the base body 6 having the concavity and the lid body 7.
The lid body 7 is mounted on a part of the base body 6 near the
concavity so as to cover the concavity, thereby sealing the
concavity hermetically. Specifically, the lid body 7 is bonded to
the base body 6 with use of a metal bonding material such as solder
or silver brazing filler, or a resin material such as epoxy resin.
In the alternative, the lid body 7 may be welded to the base body
6. In this case, for example, a seal ring made of an alloy of iron
or the like material is bonded to the upper surface which is one
principal surface of the base body 6 near the concavity, and then
the base body 6 and the lid body 7 are subjected to a seam welding
process, an electron beam welding process, or a laser-light welding
process. Note that such a concavity as is formed in the base body 6
may be provided also in the lid body 7.
[0103] It is preferable that the base body 6 and the lid body 7
each possess a flexural strength, i.e. mechanical strength, of 200
MPa or above. Thereby, the advantage is gained that the thicknesses
of the base body 6 and the lid body 7 can be reduced, resulting in
the fuel cell 1 being lower in profile.
[0104] For example, the base body 6 and the lid body 7 should
preferably be made of sintered aluminum oxide of close-grained
substance whose relative density is 90% or above. In this case,
firstly, rare-earth oxide powder and sintering aids are added and
mixed into aluminum oxide powder, and powder materials of sintered
aluminum oxide are prepared. Subsequently, an organic binder and a
dispersion medium are added and mixed into the powder materials of
sintered aluminum oxide to make paste, and by a doctor blade
method, or adding an organic binder into the powder materials and
conducting press-molding, roll-molding or the like, a green sheet
having specified thickness is manufactured from the paste. Then, by
punching with a die, a microdrill, a laser or the like, through
holes as the first fluid channels 8 and the second fluid channels
9, and openings as fluid passages and through holes for disposing
the first wiring conductor 10 and the second wiring conductor 11
are formed on the green sheet.
[0105] The first and second wiring conductors 10 and 11 should
preferably be composed of tungsten and/or molybdenum to prevent
oxidation. In this case, for example, as an inorganic substance,
Al.sub.2O.sub.3 in an amount of 3 to 20% by mass and
Nb.sub.2O.sub.5 in an amount of 0.5 to 5% by mass are added to 100
mass percent-tungsten and/or molybdenum powder to form a conductor
paste. The conductor paste is then filled in the through hole
pierced in the green sheet to form a via hole acting as a through
conductor.
[0106] Into the conductor paste, for the purpose of increasing
close adhesion of the base body 6 and the lid body 7 to ceramics,
aluminum oxide powder or powder of the same composite with a
ceramics component forming the base body 6 and the lid body 7 can
be added, for example, in the ratio of 0.05 to 2% by volume.
[0107] The first and second wiring conductors 10 and 11 are formed
in the outer and inner layers of the base body 6 and the lid body 7
before, after, or concurrently with the formation of the via
conductor which is achieved by filling the conductor paste into the
through hole. The formation of the wiring conductors is achieved by
print-coating such a conductor paste as shown herein in a
predetermined pattern on the green sheet in accordance with the
screen printing method, the gravure printing method, or the like
printing method.
[0108] Thereafter, a predetermined number of sheet-like molded
bodies carrying the printed, filled conductor paste are subjected
to positional alignment, and are then stacked on top of each other
under pressure. The resultant stacked body is then fired, in a
non-oxidative atmosphere, at a high temperature of 1200 to
1500.degree. C. As a result, the ceramic-made base body 6, lid body
7, and the first and second wiring conductors 10 and 11 are
obtained as designed.
[0109] Further, it is preferable that the base body 6 and the lid
body 7 made of ceramics each have a thickness of 0.2 mm or more. In
a case where the thickness is less than 0.2 mm, the strength is
prone to decrease, with the result that the base body 6 and the lid
body 7 may suffer from a crack or break due to a stress occurring
When the lid body 7 is mounted on the base body 6. By contrast, in
a case where the thickness is greater than 5 mm, it becomes
difficult to achieve slenderization and low-profile styling, and
thus the fuel cell becomes unsuited for a compact portable
apparatus. Furthermore, since the thermal capacity is increased, it
becomes difficult to swiftly adjust the cell temperature to a
certain level appropriate to the electrochemical reaction condition
set for the membrane electrode assembly 3.
[0110] The first wiring conductor 10 and the second wiring
conductor 11 are electrically connected to the first electrode 4
and the second electrode 5, respectively, of the membrane electrode
assembly 3 so that they may function as a current-carrying path for
taking the current generated in the membrane electrode assembly 3
out of the fuel cell casing 2, and may serve also as a conventional
current collecting plate.
[0111] The first wiring conductor 10 has its one end disposed on
the bottom surface of the concavity of the base body 6 facing the
first electrode 4 of the membrane electrode assembly 3, and its
another end led to an outer surface of the base body 6. As
described previously, it is preferable that the first wiring
conductor 10 is formed integrally with the base body 6, and is made
10 .mu.m or more higher than the bottom surface of the concavity of
the base body 6. This allows the first wiring conductor 10 to make
contact with the first electrode 4 with ease. The desired height of
the first wiring conductor 10 can be obtained by adjusting the
printing condition such that the conductor paste is print-coated in
a larger thickness during the print-coating process as described
previously. Moreover, the plurality of first wiring conductor 10
should preferably be arranged so as to face the first electrode 4.
This helps reduce electric losses ascribable to the first wiring
conductor 10. That part of the first wiring conductor 10 which
penetrates through the base body 6 should preferably have be set at
50 .mu.m or more in diameter.
[0112] The second wiring conductor 11 has its one end disposed on
the lower surface which is one principal surface of the lid body 7
facing the second electrode 5 of the membrane electrode assembly 3,
and its other end led to the outer surface of the lid body 7. It is
preferable that, like the first wiring conductor 10, the second
wiring conductor 11 is formed integrally with the lid body 7, and
is made 10 .mu.m or more higher than the lower surface of the lid
body 7. This allows the second wiring conductor 11 to make contact
with the second electrode 5 with ease. The desired height of the
second wiring conductor 11 can be obtained by adjusting the
printing condition such that the conductor paste is print-coated in
a larger thickness during the print-coating process as described
previously. Moreover, the plurality of second wiring conductor 11
should preferably be arranged so as to face the second electrode 5.
This helps reduce electric losses ascribable to the second wiring
conductor 11. That part of the second wiring conductor 11 which
penetrates through the lid body 7 should preferably be set at 50
.mu.m or more in diameter.
[0113] It is preferable that each of the first and second wiring
conductors 10 and 11 has its exposed surface coated with a
highly-conductive metal material made of nickel, gold or the like,
which is highly corrosion-resistant and exhibits excellent
wettability with respect to a brazing filler material, by means of
the plating method. This makes it possible to establish
satisfactory electrical connection among the first wiring conductor
10 and the second wiring conductor 11, and among the first wiring
conductor 10, the second wiring conductor 11 and an external
electric circuit.
[0114] When the membrane electrode assembly 3 is grippingly
inserted between the base body 6 and the lid body 7, the first and
second wiring conductors 10 and 11 are brought into
pressure-contact with the first and second electrodes 4 and 5,
respectively. At this time, the first and second wiring conductors
10 and 11 can be electrically connected to the first and second
electrodes 4 and 5, respectively.
[0115] Arranged on the bottom surface of the concavity of the base
body 6 facing the first electrode 4 and on the lower surface of the
lid body 7 facing the second electrode 5 are the first fluid
channel 8 and the second fluid channel 9, respectively. The first
fluid channel 8 is so formed as to extend toward the outer surface
of the base body 6, whereas the second fluid channel 9 is so formed
as to extend toward the outer surface of the lid body 7. The first
and second fluid channels 8 and 9 are formed by piercing through
holes or grooves in the base body 6 and the lid body 7. The first
and second fluid channels 8 and 9 each serve as a passage for a
fluid material which is supplied to the membrane electrode assembly
3, for example, fuel gas such as hydrogen-rich reforming gas, or
oxidant gas such as air, and also serve as a passage for a fluid to
be discharged from the membrane electrode assembly 3 after
reactions, for example, water produced through the reactions.
[0116] Regarding the through holes or grooves pierced in the base
body 6 and the lid body 7 as the first and second fluid channels 8
and 9, the diameter and number of the through hole, or the width,
depth, and arrangement of the groove are determined according to
the specifications of the fuel cell 1, in such a way that a fluid
such as fuel gas or oxidant gas can be evenly supplied to the
membrane electrode assembly 3. Specifically, for example, the
opening should preferably have a width of 1 mm and a depth of 0.2
mm. Further enhancement of the uniform supply of the fluid can be
achieved by reducing the opening width to 100 .mu.m and by
increasing the number of the openings.
[0117] In the fuel cell 1 embodying the invention, fuel or air is
introduced through a through hole or a groove formed in the base
body 6 and the lid body 7.
[0118] In the fuel cell casing 2 and the fuel cell 1 embodying the
invention, the first and second fluid channels 8 and 9 should
preferably have an opening which is 1 mm in width and 0.2 mm in
depth. More preferably, the opening width should be reduced to 100
.mu.m. This enables a fluid material to flow into the membrane
electrode assembly 3 under uniform pressure.
[0119] In this way, the first fluid channel 8 is disposed so as to
face the lower principal surface of the membrane electrode assembly
3 on which the first electrode 4 is formed, whereas the second
fluid channel 9 is disposed so as to face the upper principal
surface of the membrane electrode assembly 3 on which the second
electrode 5 is formed. With this arrangement, a fluid can be
exchanged between the lower and upper principal surfaces of the
membrane electrode assembly 3 and their corresponding first and
second fluid channels 8 and 9, respectively, and the fluid can be
supplied or discharged through the respective fluid paths.
Moreover, in the case of supplying gas as a fluid, it is possible
to prevent a decrease in the partial pressure of the gas to be
supplied to the first and second electrodes 4 and 5 of the membrane
electrode assembly 3, and thus obtain a stable output voltage of
predetermined level. Further, since the partial pressure of the
supplied gas is stabilized, the inner pressure of the fuel cell 1
is made uniform. As a result, a thermal stress occurring in the
membrane electrode assembly 3 can be suppressed, leading to
enhancement of the reliability of the fuel cell 1.
[0120] Moreover, the convexity 12 is identical in shape with the
base body 6 and the lid body 7. In the embodiment, the convexities
12 are provided on the base body 6 of the fuel cell casing unit 13
disposed on the upper side and the lid body 7 of the fuel cell
casing unit 13 disposed on the lower side adjacent thereto,
respectively. Specifically, the convexity 12 provided in the fuel
cell casing unit 13 on the upper side is provided so as to protrude
from a side portion of the base body 6 thereof adjacent to the fuel
cell casing unit 13 on the lower side, outward. The convexity 12
provided in the fuel cell casing units 13 on the lower side is
provided so as to protrude from a side portion of the lid body 7
thereof adjacent to the fuel cell casing units 13 on the upper
side, outward. The convexities 12 provided in the fuel cell casing
units 13 on the upper and lower sides are adjacent to each other.
In order to obtain the desired voltage, the fuel cell casing units
13 on the upper and lower sides are stacked together, then the
first and second wiring conductors 10 and 11 are electrically
connected to each other by using a conductive member 18, and the
fuel cell casing units 13 on the upper and lower sides are
then-connected by fixing to each other at their convexities 12 with
use of an adhesive 14. As a result, there will be no need to
prepare current collecting plates and clamping plates, and thus the
fuel cell 1 can be made lower in profile.
[0121] The adhesive 14 used for fixing the convexities 12 is
preferably made of a resin-based material such as the epoxy family,
the silicon family, or the deformable urethane family. Since the
membrane electrode assembly 3 has no high heat resistance, it is
preferable that the adhesive 14 has a curing temperature of
200.degree. C. or below. The time required for the curing is
determined in accordance with the specifications of the adhesive
14. Note that the fixing may be achieved in ways other than that
described just above by way of example. For example, a metal
bonding material such as solder or silver brazing filler may be
used instead, or a seal ring made of an alloy of iron or the like
material may be bondedly formed on the top surface near the
convexity 12, followed by performing a welding operation such as
the seam welding, the electron beam welding, or the laser welding.
In this case, the fixing can be completed instantaneously without
putting any temperature load on the membrane electrode assembly
3.
[0122] Moreover, the first wiring conductor 10 provided in the base
body 6 of the fuel cell casing unit 13 on the upper side, and the
second wiring conductor 11 provided in the lid body 7 of the fuel
cell casing unit 13 on the lower side are bonded together with use
of the conductive member 18.
[0123] The conductive member 18 in use is preferably formed of a
metal foil tape such as a copper-foil adhesive tape or an
aluminum-foil adhesive tape, or an adhesive made of a resin-based
material such as epoxy resin, deformable urethane resin, silicon
resin, polyimide resin, or acrylic resin to which resin-based
material a conductive filler is added. In the alternative, a metal
sheet, a mesh-like metal sheet, or the like may be interposed
between the conductors to establish contact-connection. In the
conductive member 18, its electrical resistance should preferably
be set at 10 m.OMEGA./cm.sup.2 or below, more preferably, 1
m.OMEGA./cm.sup.2. By doing so, voltage losses can be
minimized.
[0124] With the constructions thus far described, as shown in FIG.
1, it is possible to realize a compact, sturdy fuel cell casing 2
which is capable of accommodating the membrane electrode assembly
3, and a fuel cell 1 which is controllable with high
efficiency.
[0125] Next, FIG. 2 is a sectional view showing a fuel cell casing
and a fuel cell employing the fuel cell casing according to a
second embodiment of the invention. In the figure, reference
numeral 1A denotes a fuel cell; reference numeral 2A denotes a fuel
cell casing; reference numeral 3 denotes a membrane electrode
assembly; reference numeral 4 denotes a first electrode; reference
numeral 5 denotes a second electrode; reference numeral 6a denotes
a base body; reference numeral 7a denotes a lid body; reference
numeral 8 denotes a first fluid channel; reference numeral 9
denotes a second fluid channel; reference numeral 10a denotes a
third wiring conductor; reference numeral 11a denotes a fourth
wiring conductor; reference numeral 12 denotes a convexity;
reference numeral 13a denotes a fuel cell casing unit; reference
numeral 14 denotes an adhesive; and reference numeral 15 denotes a
fifth wiring conductor. In this embodiment, the same components as
those of the aforementioned embodiment will be denoted by the same
reference numerals, and it will be omitted to describe in
detail.
[0126] The fuel cell casing 2A is composed of a plurality of fuel
cell casing units 13a stacked together. The respective fuel cell
casing units 13a include the base body 6a having the plurality of
concavities and the lid body 7a and are made of ceramics, like the
base body 6 and the lid body 7 of the embodiment mentioned above.
The lid body 7a is mounted on a part of the base body 6a near the
concavity so as to cover the concavity, thereby sealing the
concavity hermetically. Specifically, the lid body 7a is bonded to
the base body 6a with use of a metal bonding material such as
solder or silver brazing filler, or a resin material such as epoxy
resin. In the alternative, the lid body 7a may be welded to the
base body 6a. In this case, for example, a seal ring made of an
alloy of iron or the like material is bonded to the upper surface
of the base body 6a near the concavity, and then the base body 6a
and the lid body 7a are subjected to a seam welding process, an
electron beam welding process, or a laser-light welding process.
Note that such a concavity as is formed in the base body 6a may be
provided also in the lid body 7a.
[0127] It is preferable that the base body 6a and the lid body 7a
each possess a flexural strength, i.e. mechanical strength, of 200
MPa or above. Thereby, the advantage is gained that the thicknesses
of the base body 6a and the lid body 7a can be reduced, resulting
in the fuel cell 1A being lower in profile. For example, the base
body 6a and the lid body 7a should preferably be made of sintered
aluminum oxide of close-grained substance whose relative density is
90% or above.
[0128] The third wiring conductor 10a and the fourth wiring
conductor 11a are electrically connected to the first electrode 4
and the second electrode 5, respectively, of the membrane electrode
assembly 3 so that they may function as a current-carrying path for
taking the current generated in the membrane electrode assembly 3
out of the fuel cell casing 2A, and may serve also as a
conventional current collecting plate.
[0129] The third wiring conductor 10a has its one end disposed on
the bottom surface of each concavity of the base body 6a facing the
first electrode 4 of the membrane electrode assembly 3, and its
another end led to an outer surface of the base body 6a. As
described previously, it is preferable that, like the first wiring
conductor 10, the third wiring conductor 10a is formed integrally
with the base body 6a, and is made 10 .mu.m or more higher than the
bottom surface of the concavity of the base body 6a. This allows
the third wiring conductor 10a to make contact with the first
electrode 4 with ease. The desired height of the third wiring
conductor 10a can be obtained by adjusting the printing condition
such that the conductor paste is print-coated in a larger thickness
during the print-coating process as described previously. Moreover,
the plurality of third wiring conductor 10a should preferably be
arranged so as to face the first electrode 4. This helps reduce
electric losses ascribable to the third wiring conductor 10a. That
part of the third wiring conductor 10a which penetrates through the
base body 6a should preferably have be set at 50 .mu.m or more in
diameter.
[0130] The fourth wiring conductor 11a has its one end disposed on
the lower surface of the lid body 7a facing the second electrode 5
of the membrane electrode assembly 3, and its another end led to
the outer surface of the lid body 7a.
[0131] It is preferable that, like the second wiring conductor 11,
the fourth wiring conductor 11a is formed integrally with the lid
body 7a, and is made 10 .mu.m or more higher than the lower surface
of the lid body 7a. This allows the fourth wiring conductor 11a to
make contact with the second electrode 5 with ease. The desired
height of the fourth wiring conductor 11a can be obtained by
adjusting the printing condition such that the conductor paste is
print-coated in a larger thickness during the print-coating process
as described previously. Moreover, the plurality of fourth wiring
conductor 11a should preferably be arranged so as to face the
second electrode 5. This helps reduce electric losses ascribable to
the fourth wiring conductor 11a. That part of the fourth wiring
conductor 11a which penetrates through the lid body 7a should
preferably be set at 50 .mu.m or more in diameter.
[0132] The fifth wiring conductor 15 is so configured as to provide
connection among the third wiring conductors 10a received on the
bottom surfaces of a plurality of concavities. That is, the fifth
wiring conductor 15 is formed on the base body 6a and has its one
end connected to the third wiring conductor 10a facing the first
electrode 4 of the membrane electrode assembly 3 on the bottom
surface of one of the concavities and its another end connected to
the third wiring conductor 10a facing the first electrode 4 of the
membrane electrode assembly 3 on the bottom surface of the other of
concavities. Thereby, the membrane electrode assemblies 3
accommodated into the respective fuel cell casing units 13a can be
connected together in parallel.
[0133] In order to obtain the desired voltage, the fuel cell casing
units 13a on the upper and lower sides are stacked together, then
the third and fourth wiring conductors 10a and 11a are electrically
connected to each other by using the fifth wiring conductor 15
which is a conductive member, and the fuel cell casing units 13a on
the upper and lower sides are then connected by fixing to each
other at their convexities 12 with use of an adhesive 14. As a
result, there will be no need to prepare current collecting plates
and clamping plates, and thus the fuel cell 1A can be made lower in
profile.
[0134] Moreover, the third wiring conductor 10a provided in the
base body 6a of the fuel cell casing unit 13a on the upper side,
and the fourth wiring conductor 11a provided in the lid body 7a of
the fuel cell casing unit 13a on the lower side are bonded together
with use of the fifth wiring conductor 15 which is a conductive
member.
[0135] With the constructions thus far described, as shown in FIG.
2, it is possible to realize a compact, sturdy fuel cell casing 2A
which is capable of accommodating the membrane electrode assembly
3, and a fuel cell 1A which is controllable with high
efficiency.
[0136] Next, FIG. 3 is a sectional view showing a fuel cell casing
and a fuel cell employing the fuel cell casing according to a third
embodiment of the invention. In the figure, reference numeral 1B
denotes a fuel cell; reference numeral 2B denotes a fuel cell
casing; reference numeral 3 denotes a membrane electrode assembly;
reference numeral 4 denotes a first electrode; reference numeral 5
denotes a second electrode; reference numeral 6b denotes a base
body; reference numeral 7b denotes a lid body; reference numeral 8
denotes a first fluid channel; reference numeral 9 denotes a second
fluid channel; reference numeral 10b denotes a sixth wiring
conductor; reference numeral 11b denotes a seventh wiring
conductor; reference numeral 12 denotes a convexity; reference
numeral 13b denotes a fuel cell casing unit; reference numeral 14
denotes an adhesive; reference numeral 16 denotes an eighth wiring
conductor; and reference numeral 17 denotes a ninth wiring
conductor. In this embodiment, the same components as those of the
aforementioned embodiment will be denoted by the same reference
numerals, and it will be omitted to describe in detail.
[0137] The fuel cell casing 2B is composed of a plurality of fuel
cell casing units 13b stacked together. The respective fuel cell
casing units 13b include the base body 6b having the plurality of
concavities and the lid body 7b and are made of ceramics, like the
base body 6 and 6a and the lid body 7 and 7a of the embodiment
mentioned above. The lid body 7b is mounted on a part of the base
body 6b near the concavity so as to cover the concavity, thereby
sealing the concavity hermetically. Specifically, the lid body 7b
is bonded to the base body 6b with use of a metal bonding material
such as solder or silver brazing filler, or a resin material such
as epoxy resin. In the alternative, the lid body 7b may be welded
to the base body 6b. In this case, for example, a seal ring made of
an alloy of iron or the like material is bonded to the upper
surface of the base body 6b near the concavity, and then the base
body 6b and the lid body 7b are subjected to a seam welding
process, an electron beam welding process, or a laser-light welding
process. Note that such a concavity as is formed in the base body
6b may be provided also in the lid body 7b.
[0138] It is preferable that the base body 6b and the lid body 7b
each possess a flexural strength, i.e. mechanical strength, of 200
MPa or above. Thereby, the advantage is gained that the thicknesses
of the base body 6b and the lid body 7b can be reduced, resulting
in the fuel cell 1B being lower in profile. For example, the base
body 6b and the lid body 7b should preferably be made of sintered
aluminum oxide of close-grained substance whose relative density is
90% or above.
[0139] The sixth wiring conductor 10b and the seventh wiring
conductor 11b are electrically connected to the first electrode 4
and the second electrode 5, respectively, of the membrane electrode
assembly 3 so that they may function as a current-carrying path for
taking the current generated in the membrane electrode assembly 3
out of the fuel cell casing 2B, and may serve also as a
conventional current collecting plate.
[0140] The sixth wiring conductor 10b has its one end disposed on
the bottom surface of each concavity of the base body 6b facing the
first electrode 4 of the membrane electrode assembly 3, and its
another end led to an outer surface of the base body 6b. As
described previously, it is preferable that, like the first wiring
conductor 10, the sixth wiring conductor 10b is formed integrally
with the base body 6b, and is made 10 .mu.m or more higher than the
bottom surface of the concavity of the base body 6b. This allows
the sixth wiring conductor 10b to make contact with the first
electrode 4 with ease. The desired height of the sixth wiring
conductor 10b can be obtained by adjusting the printing condition
such that the conductor paste is print-coated in a larger thickness
during the print-coating process as described previously. Moreover,
the plurality of sixth wiring conductor 10b should preferably be
arranged so as to face the first electrode 4. This helps reduce
electric losses ascribable to the sixth wiring conductor 10b. That
part of the sixth wiring conductor 10b which penetrates through the
base body 6b should preferably have be set at 50 .mu.m or more in
diameter.
[0141] The seventh wiring conductor 11b has its one end disposed on
the lower surface of the lid body 7b facing the second electrode 5
of the membrane electrode assembly 3, and its another end led to
the outer surface of the lid body 7b. It is preferable that, like
the second wiring conductor 11, the seventh wiring conductor 11b is
formed integrally with the lid body 7b, and is made 10 .mu.m or
more higher than the lower surface of the lid body 7b. This allows
the seventh wiring conductor 11b to make contact with the second
electrode 5 with ease. The desired height of the seventh wiring
conductor 11b can be obtained by adjusting the printing condition
such that the conductor paste is print-coated in a larger thickness
during the print-coating process as described previously. Moreover,
the plurality of seventh wiring conductor 11b should preferably be
arranged so as to face the second electrode 5. This helps reduce
electric losses ascribable to the seventh wiring conductor 11b.
That part of the seventh wiring conductor 11b which penetrates
through the lid body 7b should preferably be set at 50 .mu.m or
more in diameter.
[0142] The eighth wiring conductor 16 is provided in the fuel cell
casing unit 13b on the lower side, and has its one end connected to
the sixth wiring conductor 10b facing the first electrode 4 of the
membrane electrode assembly 3 on the bottom surface in one of the
concavities, and its another end led to the upper surface on which
the lid body 7b of the base body 6b is mounted. The ninth wiring
conductor 17 is provided in the fuel cell casing unit 13b on the
upper side, and has its one end connected to the seventh wiring
conductor 11b facing the second electrode 5 of the membrane
electrode assembly 3 in the other of the concavities, and its
another end led to the lower surface of the lid body 7b to be
mounted on the upper surface of the base body 6b, so as to face the
other end of the eighth wiring conductor 16. A connecting wiring
conductor 19 is formed so as to penetrate through the base body 6b
of the fuel cell casing unit 13b on the upper side and the lid body
7b of the fuel cell casing unit 13b on the lower side and
electrically connected to the other end of the eighth wiring
conductor 16 and the other end of the ninth wiring conductor
17.
[0143] In order to obtain the desired voltage, the fuel cell casing
units 13b on the upper and lower sides are stacked together; one
side of the sixth wiring conductor 10b of the fuel cell casing unit
13b on the upper side and one side of the seventh wiring conductor
11b of the fuel cell casing unit 13b on the lower side are
electrically connected to each other by using the conductive member
18; another side of the sixth wiring conductor 10b of the fuel cell
casing unit 13b on the upper side and another side of the seventh
wiring conductor 11b of the fuel cell casing unit 13b on the lower
side are electrically connected to each other by using the
conductive member 18; the other end of the eight wiring conductor
16 and the other end of the ninth wiring conductor 17 are
electrically connected to each other by using the connecting wiring
conductor 19; and the fuel cell casing units 13b on the upper and
lower sides are then connected by fixing to each other at their
convexities 12 with use of an adhesive 14. Thereby, the membrane
electrode assembly 3 accommodated into the respective fuel cell
casing units 13b can be connected together in series. As a result,
there will be no need to prepare a current collecting plate and a
clamping plate, and thus the fuel cell 1B can be made lower in
profile.
[0144] Moreover, the sixth wiring conductor 10b provided in the
base body 6b of the fuel cell casing unit 13b on the upper side,
and the seventh wiring conductor 11b provided in the lid body 7b of
the fuel cell casing unit 13b on the lower side are bonded together
with use of the conductive member 18.
[0145] With the constructions thus far described, as shown in FIG.
3, it is possible to realize a compact, sturdy fuel cell casing 2B
which is capable of accommodating the membrane electrode assembly
3, and a fuel cell 1B which is controllable with high
efficiency.
[0146] Moreover, in the embodiment, in the fuel cell casing 2B,
four membrane electrode assemblies 3 are connected in series by
using two fuel cell casing units 13b, however, two membrane
electrode assemblies 3 of the respective fuel cell casing units 13b
may be connected in series. In this case, the first electrodes 4 of
one side of the membrane electrode assemblies 3 and one side of the
sixth wiring conductor 10b are connected together, one side of the
sixth wiring conductor 10b and the one end of the eighth wiring
conductor 16 are connected together, the second electrodes 5 of
another side of the membrane electrode assemblies 3 and another
side of the seventh wiring conductor 11b are connected together,
another side of the seventh wiring conductor 11b and the one end of
the ninth wiring conductor 17 are connected together, and the other
end of the eighth wiring conductor 16 and the other end of the
ninth wiring conductor 17 are connected together. Thereby, the
respective membrane electrode assemblies 3 in a fuel cell casing
unit are connected in series.
[0147] Moreover, the fuel cell casing and the fuel cell may be
constructed by stacking a plurality of fuel cell casing units
mentioned above. In this case, another side of the sixth wiring
conductor 10b of one of the fuel cell casing units and one side of
the seventh wiring conductor 11b of the other of the fuel cell
casing units are connected together. Thereby, these membrane
electrode assemblies 3 are connected in series.
[0148] As shown in FIGS. 1, 2, and 3, according to the fuel cell
casings 2, 2A and 2B and the fuel cells 1, 1A and 1B embodying the
invention, the membrane electrode assembly 3 is accommodated in
each of one or a plurality of concavities of the base body 6, 6a
and 6b. Moreover, the fifth wiring conductor 15, or the eighth and
ninth wiring conductors 16 and 17, is/are so disposed as to extend
across the region between the adjacent concavities. Thereby, in
terms of a plurality of membrane electrode assemblies 3, their
respective first electrodes 4, or first and second electrodes 4 and
5, are electrically connected together. In order to obtain the
overall output, the first wiring conductor 10, the third wiring
conductor 10a, or the sixth wiring conductor 10b; and the second
wiring conductor 11, the fourth wiring conductor 11a, or the
seventh wiring conductor 11b are respectively connected to the
endmost membrane electrode assemblies 3 through electrical
connection. It will thus be seen that the first and second wiring
conductors 10 and 11; the third, fourth, and fifth wiring
conductors 10a, 11a, and 15; or the sixth, seventh, eighth, and
ninth wiring conductors 10b, 11b, 16, and 17 allow free
three-dimensional wiring. Thus, a plurality of membrane electrode
assemblies 3 can arbitrarily be connected in series or in parallel
with one another; wherefore the overall output voltage and output
current can be adjusted with efficiency. As a result, electricity
which has been electrochemically produced in a plurality of
membrane electrode assemblies 3 can be taken out of the fuel cell
in good condition.
[0149] It should be noted that the invention need not be limited to
the above-described embodiments and examples, and therefore various
changes and modifications are possible without departing from the
spirit or scope of the invention. For example, inlet and outlet of
each of the first and second fluid channels may be formed by
disposing a metal pipe or the like on the side surface of the base
body or the lid body. In this case, the entire fuel cell is
slenderized effectively, and is thus suited for a portable
electronic apparatus. Moreover, in the first and second wiring
conductors, as well as in the sixth and seventh wiring conductors,
although their other ends are led to the outer surfaces of the base
body and the lid body, respectively, it is also possible to lead
them to the same side surface. In this case, the wiring lines, the
fluid paths, etc. can be put together only on one side surface of
the fuel cell. This helps facilitate miniaturization and protection
of the externally-connected portions. As a result, the fuel cell
can be designed with high reliability and accordingly operated with
stability for a longer period of time. Moreover, in the embodiment,
the number of the fuel cell casing units used for constructing the
fuel cell casing is two, however, it is not restricted to the
aforementioned number, and may be three or more.
[0150] The fuel cell of the invention is designed to be
incorporated as a power source in a variety of electronic
apparatuses. The concrete examples thereof include: portable
electronic apparatuses such as cellular mobile phones, PDAs
(Personal Digital Assistants),digital cameras, video cameras, and
toys like a portable game machine; household electric appliances
such as laptop PCs (personal computers), portable printers,
facsimile machines, television sets, communication devices,
audio/video systems, and electric fans; and electronic apparatuses
such as power tools. The use of the fuel cell 1 of the invention
confers advantages on that type of electronic apparatus. For
example, being made of a ceramic material which is greater in
strength than a conventional carbon molded material, the base body
and the lid body can be reduced in thickness, and their resistance
can be decreased. As a result, the electronic apparatus
incorporating the fuel cell of the invention succeeds in providing
high electricity-production efficiency; in reducing voltage losses;
and in operating with stability for a longer period of time.
[0151] Another advantage is as follows. Since the individual fuel
cell casing units are fixed to one another at their convexities
with use of an adhesive, there is no need to prepare current
collecting plates and clamping plates. This helps reduce the number
of constituent components and thus achieve slenderization. By using
the cell system of the invention that is excellent in compactness
and convenience, the electronic apparatus main body can be made
compact, thin-walled, and lightweight. Besides, for example, even
if a portable phone main body receives an impact due to a fall or
the like accident, the construction is able to offer higher impact
resistance and higher water resistance than ever before.
[0152] Further, in the fuel cell and the fuel cell casing of the
invention, the external connection terminal or the like component
should preferably be formed integrally therewith, but made
attachable and detachable therefrom. By doing so, for example, in
case of battery exhaustion, all that needs to be done is simply to
replace the fuel cell or the fuel cell casing with the new one, and
accordingly no time is required to carry out charging. As a result,
the cell system can stay in action even in an outdoor location, or
even when some emergency arises such as a power blackout.
[0153] The invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The present embodiments are therefore to be considered in
all respects as illustrative and not restrictive, the scope of the
invention being indicated by the appended claims rather than by the
foregoing description and all changes which come within the meaning
and the range of equivalency of the claims are therefore intended
to be embraced therein.
* * * * *