U.S. patent application number 11/795604 was filed with the patent office on 2008-05-22 for seal structure for fuel cell and method for producing same.
Invention is credited to Tatsuya Okabe.
Application Number | 20080118811 11/795604 |
Document ID | / |
Family ID | 37668521 |
Filed Date | 2008-05-22 |
United States Patent
Application |
20080118811 |
Kind Code |
A1 |
Okabe; Tatsuya |
May 22, 2008 |
Seal Structure for Fuel Cell and Method for Producing Same
Abstract
A seal structure for impregnating the circumferential edge of a
GDL constituting an MEA with a rubber composing a seal lip line in
which lowering in power generation capacity is suppressed by
controlling the width of a rubber impregnation region for the
circumferential edge of the GDL appropriately, thereby preventing
the MEA reaction region from becoming narrow. In order to achieve
the purpose, an MEA (2) arranged between a pair of separators (5),
a rubber sheet (6) arranged on its planar extension on the outer
circumferential side of the MEA (2), and a gasket-like lip line (7)
formed on the opposite sides of the rubber sheet (6) integrally
therewith to be close contact with the separators (5) are provided.
At the circumferential edge of the MEA (2), a rubber impregnated
portion (8) for integrating the rubber sheet (6) with the MEA (2)
when the GDL (4) constituting the MEA (2) is impregnated with a
part of the rubber composing the rubber sheet (6) is provided. On
the immediately inner circumferential side of the rubber
impregnated portion (8) in the plane of the MEA (2), a GDL
constricted portion (9) for regulating the rubber impregnated
portion is provided.
Inventors: |
Okabe; Tatsuya; (Kanagawa,
JP) |
Correspondence
Address: |
JACOBSON HOLMAN PLLC
400 SEVENTH STREET N.W., SUITE 600
WASHINGTON
DC
20004
US
|
Family ID: |
37668521 |
Appl. No.: |
11/795604 |
Filed: |
September 28, 2005 |
PCT Filed: |
September 28, 2005 |
PCT NO: |
PCT/JP05/17789 |
371 Date: |
July 19, 2007 |
Current U.S.
Class: |
429/483 ;
264/241; 429/509; 429/514; 429/534 |
Current CPC
Class: |
H01M 8/0273 20130101;
H01M 8/0247 20130101; H01M 8/0286 20130101; H01M 8/0276 20130101;
Y02E 60/50 20130101; H01M 8/1004 20130101; H01M 2008/1095 20130101;
H01M 8/0284 20130101; Y02P 70/50 20151101 |
Class at
Publication: |
429/35 ;
264/241 |
International
Class: |
H01M 8/02 20060101
H01M008/02; B29C 45/14 20060101 B29C045/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 15, 2005 |
JP |
2005-206486 |
Claims
1. A seal structure for the fuel cell comprising; a
membrane-electrode assembly (MEA) provided between a pair of
separators; a rubber sheet provided on a plane extending from the
MEA and at the outer peripheral side of the MEA; lip lines which
have gasket configuration, are integrally formed on the respective
surfaces of the rubber sheet and are closely contacted with the
separators; rubber impregnated portions which are provided at the
periphery of said MEA to integrate said rubber sheet and said MEA
by a part of rubber constituting said rubber sheet being
impregnated into gas diffusion layers (GDLs) constituting said MEA;
and GDL narrowed portions provided immediately inner peripheral
side of said rubber impregnated portions in a plane with the MEA to
define a rubber impregnated area of said rubber.
2. A The seal structure as claimed in claim 1, wherein distance
restricting portions are formed integrally with the rubber sheet at
both or at least one of inner peripheral side and outer peripheral
side of the lip lines to define distance (c) between the separators
by said portion being held by a pair of the separators when
assembling a stack.
3. The method for producing the seal structure as claimed in claim
1, comprising steps of: preparing a mold comprising split molds
which have step-like pressing portions facing to each other in
order to form the GDL narrowed portions by compressing of parts of
the GDLs to reduce thickness of the parts at a time of mold
clamping; inserting the MEA, with which the rubber sheet is to be
molded, into the mold; and carrying out injection molding to form
the rubber sheet under a condition of the parts of the GDLs being
compressed to reduce the thickness by the pressing portions formed
in the mold.
4. The method for producing the seal structure as claimed in claim
3, wherein the GDLs are compressed by the pressing portions at a
compressibility ratio of 30-50%, while being compressed by portions
other than the pressing portions of the mold at a compressibility
ratio of 0-20%.
Description
[0001] This is a national stage of the International Application
No. PCT/JP2005/017789 filed Sep. 28, 2005 and published in
Japanese.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a seal structure as a
constituent of the fuel cell and relates to a method for producing
the seal structure.
[0004] 2. Description of the Conventional Art
[0005] As a conventional seal structure for sealing gas or sealing
a cooling passage in each cell of the fuel battery stacks, such a
structure that a gasket made of an elastic member such as liquid
rubber is formed on a separator is most commonly used (refer to
Patent Documents 1, 2).
[0006] On the other hand, such a structure that a gasket is formed
on a MEA (Membrane-Electrode Assembly) disposed between a pair of
the separators has been proposed as follows:
[0007] (1) A seal structure wherein a resin film is applied or
attached onto a peripheral portion of the MEA, and a gasket is
formed on the resin film (refer to Patent Document 3), or
[0008] (2) A seal structure wherein gaskets are formed on both
surfaces of a GDL (Gas Diffusion Layer) constituting an MEA by the
injection molding of liquid rubber, and a part of the liquid rubber
is impregnated within a porous structure of the GDL (refer to
Patent Documents 4, 5).
[0009] Such conventional structures may fully achieve the desired
objective to serve as sealing members. However, as for the former
one (1), there is a problem that a number of component parts and a
number of production processes are increased due to the necessity
of employing the resin film, and as for the latter one (2), there
is a problem that an undue pressure is applied to the GDL since
compressive load of gasket is directly applied onto the GDL when a
stack is assembled.
[0010] To eliminate the above-mentioned drawbacks, it is preferable
to provide a structure that a rubber sheet is formed on a plane
extending from an MEA at the outer peripheral side of the MEA,
instead of surfaces of GDLs or the MEA, by injection molding of
liquid rubber, a part of the liquid rubber is impregnated into a
peripheral portion of a GDL to integrate the MEA and the rubber
sheet, and lip lines having a gasket configuration are formed
integrally on the respective surfaces of the rubber sheet. With
such structure that the MEA, the rubber sheet and the lip lines are
arranged along one plane, the resin film can be omitted and can
prevent the compressive load of gasket from being directly applied
onto the GDL.
[0011] With such flat arrangement, however, the liquid rubber is
apt to be impregnated deeply in the plane directions of the GDL,
since it is difficult to properly control the width (lateral
length) of the impregnated area when a part of the liquid rubber is
impregnated into the peripheral portion of the GDL in the
manufacturing process thereof. As a result, there is a risk that
the reaction area of the MEA, which is to be set widely at a
central area of the GDL, becomes narrower to deteriorate the power
generation of the fuel cell. [0012] Patent Document 1: Japanese
unexamined patent publication No. 2001-332275 [0013] Patent
Document 2: Japanese unexamined patent publication No. 2004-63295
[0014] Patent Document 3: Japanese unexamined patent publication
No. 2003-7328 [0015] Patent Document 4: Japanese unexamined patent
publication No. 2003-68332 [0016] Patent Document 5: PCT
publication WO 2002/043172
[0017] The present invention is made by taking the above-mentioned
drawbacks of the conventional art into consideration, and an object
of the present invention is to provide a seal structure for a fuel
cell with liquid rubber being impregnated into peripheral portions
of GDLs constituting an MEA to form lip lines, wherein the width of
rubber impregnated area can be properly controlled, and an MEA
reaction area can be prevented from being narrowed to cause
deterioration of power generation, and a method for producing the
seal structure.
[0018] Further, in addition thereto, another object of the present
invention is to provide a seal structure for a fuel cell, wherein
the structure itself has capability for controlling the
compressibility ratio of the lip lines, and thereby the lip lines
can be closely contacted with separators in an appropriate posture,
and a method for producing the seal structure.
SUMMARY OF THE INVENTION
[0019] In order to achieve the above-mentioned object, in
accordance with a first aspect of the present invention, there is
provided a seal structure for a fuel cell comprising an MEA
provided between a pair of separators; a rubber sheet provided on a
plane extending from the MEA and at the outer peripheral side of
the MEA; lip lines which have a gasket configuration, are
integrally formed on the respective surfaces of the rubber sheet
and are closely contacted with the separators; rubber impregnated
portions which are provided at the periphery of the MEA to
integrate the rubber sheet and the MEA by a part of rubber
constituting the rubber sheet being impregnated into GDLs
constituting the MEA; and GDL narrowed portions provided
immediately inner peripheral side of the rubber impregnated
portions in a plane with the MEA to define a rubber impregnated
area.
[0020] Further, in accordance with a second aspect of the present
invention, there is provided a seal structure for the fuel cell,
wherein, in addition to the first aspect, distance-restricting
portions are formed integrally with the rubber sheet at both or at
least one of inner peripheral side and outer peripheral side of the
lip lines to define a distance between the separators by the
portions being held by a pair of the separators when assembling a
stack.
[0021] Further, in accordance with a third aspect of the present
invention, there is provided a method for producing the seal
structure for the fuel cell as recited in the first and second
aspects mentioned above, comprising the steps of preparing a mold
comprising split molds which have step-like pressing portions
facing to each other in order to form the GDL narrowed portions by
compressing of parts of the GDLs to reduce thickness of the parts
at a time of mold clamping; inserting the MEA, with which the
rubber sheet is to be molded, into the mold; and carrying out
injection molding to form the rubber sheet under a condition of the
parts of the GDLs being compressed to reduce the thickness by the
pressing portions formed in the mold.
[0022] Further, in accordance with a fourth aspect of the present
invention, there is provided a method for producing the seal
structure for the fuel cell according to the third aspect mentioned
above, wherein, in addition to the third aspect, the GDLs are
compressed by the pressing portions of the molds at a
compressibility ratio of 30-50%, while being compressed by portions
other than the pressing portions of the molds at a compressibility
ratio of 0-20%.
[0023] In the seal structure according to the first aspect of the
present invention, since the GDL narrowed portions to define the
rubber impregnated area is formed at immediately inner peripheral
side of the rubber impregnation portions in the plane of MEA, the
impregnation of rubber component is stopped by the GDL narrowed
portion.
[0024] As described in the method for producing the seal structure
according to the third aspect of the invention, since the GDL
narrowed portions are formed at parts of the GDLs by compression by
the step-like pressing portions provided at facing portions of the
split molds for injection molding to reduce thickness of the GDLs
in parts when the molds are clamped, the volume of micro cavities
of GDL porous structure is reduced at the GDL narrowed portions. As
a result, resistance to impregnation is increased and thereby it
becomes difficult for the liquid rubber to pass through the porous
GDLs at the GDL narrowed portions.
[0025] As mentioned in the fourth aspect of the present invention,
since the GDLs are compressed by the pressing portions of the molds
at a relatively large compressibility ratio of 30-50% and
compressed by the portions other than the pressing portions of the
molds at a relatively small compressibility ratio of 0-20%. Thus,
the liquid rubber becomes hard to pass through the porous area so
compressed by the pressing portions. If the compressibility ratio
is less than 30%, sufficient narrowing effect cannot be obtained,
on the other hand, if the compressibility ratio exceeds 50%, there
is the possibility that the excessive load will be applied to the
GDLs.
[0026] Further in the seal structure of the present invention, it
is possible to attain sealing capability by bringing the lip lines
integrally formed with the respective surfaces of the rubber sheet
and held between a pair of the separators to closely contact with
the separators. However, the structure formed by the mere provision
of the lip lines is too flexible to properly receive the
compressive load by a pair of the separators when assembling of a
stack. As a result, there is concern that the compressibility ratio
of the rubber sheet becomes excessive to cause collapse of the lip
lines beyond expectation.
[0027] Consequently, in the seal structure as recited in the second
aspect of the present invention, distance-restricting portions to
define a distance between the separators, which are to be held by a
pair of the separators when assembling into a stack, are formed
integrally with the rubber sheet at both or at least one of inner
peripheral and outer peripheral sides of the lip lines, and the
compressibility ratio of the rubber sheet is properly controlled by
the provision of the gap-restricting portions.
[0028] The advantageous effects of the present invention are as
follows.
[0029] According to the seal structure for a fuel cell and the
method for producing the seal structure as recited in the first,
third and fourth aspects of the present invention, since
impregnation of liquid rubber is stopped by the GDL narrowed
portions formed integrally with the GDLs, it is possible to
properly controlling the width of rubber impregnated areas of the
GDLs. Thus, it is possible to prevent, as intended, the MEA
reaction area from being narrowed to cause deterioration of power
generation capacity.
[0030] Further, in addition to this, according to the seal
structure for the fuel cell and the method for producing the seal
structure as recited in the second and third aspect of the present
invention respectively, since a distance between a pair of the
separators when a cell stack are assembled is defined by the
distance-restricting portions provided along with the lip lines of
the rubber sheet, it is possible to properly control the
compressibility ratio of the rubber sheet by a pair of the
separators. Thus, the lip line can be closely contacted with the
separators in an appropriate posture. As a result, stable sealing
performance can be attained as intended.
BRIEF EXPLANATION OF DRAWINGS
[0031] FIG. 1 is a plan view of a seal structure for a fuel cell in
accordance with a first embodiment of the present invention,
[0032] FIG. 2 is an enlarged cross sectional view along a line A-A
in FIG. 1,
[0033] FIG. 3 is a cross sectional view of a main portion showing a
method of producing the seal structure (before mold clamping),
[0034] FIG. 4 is a cross sectional view of a main portion showing a
method of producing the seal structure (after mold clamping),
[0035] FIG. 5 is a cross sectional view showing a main portion of a
seal structure for a fuel cell in accordance with a second
embodiment of the present invention, and
[0036] FIG. 6 is a cross sectional view of a main portion showing
an assembling state of the seal structure.
EXPLANATION OF THE REFERENCE NUMERALS
[0037] 1 seal structure [0038] 2 Membrane-Electrode Assembly (MEA)
[0039] 3 electrolyte membrane [0040] 4 Gas Diffusion Layer (GDL)
[0041] 5 separators [0042] 6 rubber sheet [0043] 7 seal lip line
[0044] 8 rubber impregnated area [0045] 8 squeezed portion of GDL
[0046] 10 reaction electrode portion of MEA [0047] 11, 12
gap-restriction portions [0048] 13, 14 groove-like space [0049] 21
molds for injection molding [0050] 22 upper mold (split mold)
[0051] 23 lower mold (split mold) [0052] 24 rubber sheet forming
space [0053] 25 pressing portion or protrusion [0054] 26 injection
gate [0055] 27 seal lip line forming space
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0056] The present invention includes the following
embodiments.
[0057] (a) In the integral structure of MEA and gasket which is
provided with sealing capability by impregnating and adhering a
rubber sheet having a less thickness than the distance between the
separators, at a time of cell assembling, to the entire periphery
of the MEA by means of injection molding of liquid rubber, and by
forming lip lines having a gasket configuration on the respective
surfaces of the rubber sheet, it is required to retain a
sufficiently broad area of impregnation at the side of GDLs where
the rubber sheet and the GDL end portions are bonded by
impregnation with each other, in order to prevent peeling off of
the rubber sheet from the GDLs at a time of the cell assembling. On
the other hand, there is concern that power generation capacity is
deteriorated due to the reduction of reaction area in case that the
impregnation area is extended up to the reaction area of MEA.
[0058] Then, to cope with the above-mentioned concern, there is
provided a seal structure by means of such a mold structure that
compressibility ratio of the GDLs during the molding process is
brought to be approximately 0-20% at the rubber impregnated area to
make resistance to impregnation relatively small, resulting in a
structure with the liquid rubber being sufficiently impregnated,
while compressibility ratio of the GDL is brought to be
approximately 30-50% at an area between the rubber impregnated area
and reaction area to make resistance to impregnation relatively
large, resulting in a structure capable of preventing the liquid
rubber from being impregnated into the reaction area.
[0059] (b) In the integrated structure of MEA and gasket wherein
the rubber sheet is formed on the periphery of the MEA, and the lip
lines having a gasket configuration are formed on the rubber sheet,
a mold for rubber impregnated portion to adhere the rubber sheet
and GDL is structured such that compressibility ratio of the GDL is
set to be approximately 0-20% at the rubber impregnated area for
easy impregnation, while compressibility ratio of the GDL is set to
be approximately 30-50% in an area at the inner peripheral side of
the impregnated area to prevent the impregnation from reaching to
the reaction area.
[0060] (c) There is provided a rubber impregnated area that is
extended up to approximately 3 mm from the periphery of the GDL,
and compressibility ratio of the GDL is set to be approximately
0-20%. Also, there is provided an area having a width of
approximately 2 to 5 mm between the rubber impregnated area and the
reaction area and compressibility ratio of the GDL in this area is
set to be approximately 30-50% to prevent the impregnation from
reaching to the reaction area.
[0061] (d) According to the above-mentioned structure of (a), (b)
or (c), in the integrated structure of MEA and gasket, a sufficient
bond strength between the rubber sheet provided on the peripheral
of the MEA and the GDL is ensured and the liquid rubber is
prevented from being impregnated up to the reaction rear, thereby
the deterioration of the power generation capacity is
prevented.
[0062] Next, a description will be given of embodiments in
accordance with the present invention with reference to the
accompanying drawings.
First Embodiment
[0063] FIG. 1 shows a plan view of a seal structure 1 for a fuel
cell according to the first embodiment of the present invention,
and FIG. 2 shows an enlarged cross-sectional view taken along a
line A-A in FIG. 1. The seal structure 1 in accordance with the
embodiment is configured in the following manner.
[0064] As shown in FIG. 2, gas diffusion layers (GDLs) 4 are laid
on the respective sides of an electrolyte membrane 3 (on both
surfaces of the membrane, i.e. upper- and lower-side in FIG. 2) to
form a laminated structure constituting a membrane-electrode
assembly 2 (MEA), and the MEA 2 is held between a pair of
separators 5.
[0065] The seal structure 1 in accordance with the first embodiment
of the present invention integrally comprises the MEA 2 held
between a pair of the separators, a rubber sheet 6 provided on a
plane extending from the MEA 2 and at the outer peripheral side of
(right side in FIG. 2), and lip lines (also referred to as seal lip
lines or gaskets) 7 having gasket configuration, being formed
integrally on the respective surfaces of the rubber sheet 6 and
being closely contacted with a pair of the separators 5, wherein a
part of liquid rubber constituting the rubber sheet 6 is
impregnated into the GDLs 4 having a porous structure constituting
the MEA 2 during molding process to form rubber impregnation
portions (also referred to as rubber impregnated area) 8 along the
periphery of the MEA 2 with a predetermined width a (for example,
a=3 mm), so as to provide an integral structure of the rubber sheet
6 and MEA 2.
[0066] Further, there are provided GDL narrowed portions (also
referred to as an impregnation restricting area) 9 in a plane of
MEA 2 and immediately inner peripheral side of the rubber
impregnation portions 8 (left side in FIG. 2) for restricting the
liquid rubber impregnated area with a predetermined width b (for
example, b=2 to 5 mm) along the whole peripheries of the GDLs. The
GDL narrowed portions 9 are formed by strongly pressing a part of
the GDLs 4 to largely reduce thickness of the GDLs 4 and thereby
the MEA 2, and the volume of the micro cavities of the porous
structure in the GDLs 4 is reduced corresponding to the reduced
thickness of the MEA 2, thereby the liquid rubber does not easily
pass through the narrowed portions 9 during the molding
process.
[0067] Further, a reaction area 10 is provided in a plane with the
MEA 2 and inner peripheral side of the GDL narrowed portions 9.
[0068] The above-mentioned seal structure 1 is produced in the
following manner.
[0069] At first, in the producing process, a mold 21 for injection
molding is employed as shown in FIG. 3.
[0070] The mold 21 comprises a pair of molds facing to each other,
i.e. an upper mold 22 and lower mold 23, as shown in FIGS. 3 and 4.
The rubber sheet 6 is formed by injection molding with liquid
rubber as the molding material in a state of the MEA 2 being
inserted into a cavity space 24 defined between the inner faces of
the molds 22 and 23.
[0071] Further, there are provided step-like pressing portions 25
at positions corresponding to the narrowed portions 9 of the MEA 2
to be inserted into a predetermined position in the cavity space
24. The pressing portions 25 comprise a pair of protrusions facing
to each other, i.e. upper protrusion and lower protrusion. The GDLs
4 disposed between the pressing portions 25 are compressed by
clamping of the molds, causing a large reduction in thickness of
the GDLs 4 and consequently MEA 2, thereby thin GDL narrowed
portions 9 is formed in the MEA 2.
[0072] A compressibility ratio of the GDLs by the pressing portions
25 is set to be approximately 30-50%, while a compressibility ratio
of the GDLs by other portions than the pressing portions 25 is set
to be approximately 0-20%, i.e. the compressibility ratio at the
pressing portions is set to be relatively larger than that at the
other portions.
[0073] Further, there is provided an injection gate 26 in the upper
mold 22 for injection of liquid rubber into the forming space 24 at
a position corresponding to the rubber impregnated area 8 in the
MEA 2 inserted in a predetermined position of the forming space
24.
[0074] When the mold 21 is clamped in the state of the MEA 2 being
inserted into the forming space 24, the narrowed portions 9 are
formed in the MEA 2 by the pressing portions 25, as shown in FIG.
4. Next, when liquid rubber is injected through the injection gate
26, the liquid rubber is smoothly impregnated into the GDLs 4 to
form the rubber impregnated portions 8, and also filled smoothly in
a forming space 27 for formation of rubber sheet 6 and lip lines 7
at the outer peripheral side of the rubber impregnated portions 8,
since the GDL compressibility ratio for the region corresponding to
the rubber impregnated portions 8 is set to be relatively
small.
[0075] On the other hand, since the compressibility ratio for the
narrowed portions 9 at the inner peripheral side of the rubber
impregnated portions 8 is set to be relatively large, the liquid
rubber is hardly impregnated into the narrowed portions 9.
Therefore, the width of the liquid rubber impregnation area can be
set approximately to an intended value (the above-mentioned width
a=3 mm in this embodiment), thereby the rubber impregnated area is
prevented from extending to the inner peripheral side.
[0076] Further, after completion of the molding process, the
narrowed portions 9 becomes to be fine in its inner structure and
rigid, since the volume of micro cavities of the porous structure
is reduced as mentioned above.
Second Embodiment
[0077] FIG. 5 shows a cross sectional view showing a main portion
of a seal structure for a fuel cell in accordance with a second
embodiment of the present invention, and a seal structure 1 in
accordance with the embodiment is configured in the following
manner.
[0078] GDLs 4 are laid on the respective sides of an electrolyte
membrane 3 to form a laminated structure constituting an MEA 2, and
the MEA 2 is held between a pair of separators 5.
[0079] The seal structure 1 of this embodiment integrally comprises
the MEA 2 provided between a pair of the separators 5, a rubber
sheet 6 provided on a plane extending from MEA 2 and at the outer
peripheral side of the MEA 2, and lip lines 7 having a gasket-like
configuration, being formed integrally on the respective surfaces
of the rubber sheet 6 and being closely contacted with the
separators 5. When molding the rubber sheet 6, rubber impregnated
portions 8 are formed along the whole peripheral edge of the MEA 2
having a predetermined width a (for example, a=3 mm) by
impregnating a part of liquid rubber constituting the rubber sheet
6 into the GDLs 4 having a micro porous structure and constituting
the MEA 2, thereby the rubber sheet 6 is formed integrally with the
MEA 2.
[0080] Further, there is provided GDL narrowed portions 9 in a
plane with the MEA 2 and immediately inner peripheral side of the
rubber impregnated portions 8 (left side in FIG. 5) for restricting
the liquid rubber impregnated area with a predetermined width b
(for example, b=2 to 5 mm) along the whole periphery edge of the
GDL 4.
[0081] The narrowed portions 9 are formed by strongly pressing
parts of the GDLs 4 to largely reduce thickness of GDLs 4, and
thereby the MEA 2, and the volume of the micro cavities of the
porous structure in the GDLs 4 is reduced corresponding to the
reduced thickness of the MEA 2, thereby the liquid rubber does not
easily pass through the narrowed portions 9 during the molding
process.
[0082] Further, a reaction area 10 is provided in a plane with the
MEA 2 and at the inner peripheral side of the GDL narrowed portions
9.
[0083] Furthermore, distance restricting portions 11 and 12 (also
referred to as sub lip lines or rubber spacers or load-receiving
portions) are integrally formed at the inner peripheral side and
outer peripheral side of the seal lip line 7 provided on the
respective surfaces of the rubber sheet 6 to provide a distance
between the separators 5 by the portions being held by a pair of
the separators 5 when assembling into a stack.
[0084] Since the lip lines 7 are required to have long-standing
durability in the desired sealing capability, the shape is
controlled so that large surface pressure is brought out when
compressed. To be more precise, the lip lines 7 are formed in a
chevron or triangular sectional shape having a sharp tapered end,
and have a height h1 larger than a height h2 of the distance
restricting portions 11 and 12 (h1>h2).
[0085] On the other hand, the distance restricting portions 11 and
12 are required to be controlled so that the lip lines 7 are given
with desired compressibility, that is, made to be a desired height
dimension against a compressive load. Therefore, the shape is
controlled so that deformation is hardly generated against the
compressive load. To be more precise, the distance restricting
portions 11 and 12 are formed in a trapezoidal or rectangular
sectional shape each having flat end portion, and have the height
h2 smaller than the height h1 of the lip lines 7 (h1>h2). The
distance restricting portions 11 and 12 are set to have same height
h2, with the flat end portions being on a same plane.
[0086] The degree of hardness of rubber elastic body comprised of
the cured liquid rubber is set to be relatively soft to the extent
of 40 to 50, and the compressibility ratio of the lip lines 7 is
set to be 30-50%. Accordingly, there are provided groove-like
spaces 13 and 14 between the lip lines 7 and the inner and outer
peripheral side distance restricting portions 11 and 12
respectively, serving as clearance grooves to allow the deformation
of the lip lines 7 when compressed. The volume of the groove-like
spaces 13 and 14 is preferable to be as small as possible so that
the distance restricting portions 11 and 12 serve as supports to
prevent falling down of the lip lines 7. A distance d between the
center of the seal lip line 7 and the end of the distance
restricting portion 11 or 12 is set to be 2-5 mm by an actual
size.
[0087] FIG. 5 shows the seal structure in accordance with this
embodiment at an initial state before assembling into a fuel cell
stack. When assembled into a stack from this state, a compressive
load is applied in the thickness direction to the seal structure so
that the lip lines 7 held between a pair of the separators 5 are
compressed and deformed as shown in FIG. 6 to be closely contacted
with the inner surfaces of the separator 5 by the reactive force of
compression. When the compressive load is applied subsequently in
the thickness direction to the seal structure so that the
separators 5 make contact with the distance restricting portions 11
and 12, a distance C between the separators 5 is regulated, since
the distance restricting portions 11 and 12 are controlled so that
the shape thereof is not deformed against the applied compressive
load. As a result, the compressibility ratio of the lip lines 7 is
so controlled as to be enough to exhibit the sealing performance.
Also, the distance restricting portions 11 and 12 serve as spacers
held between a pair of the separators 5 to halt the displacement of
the separators 5 in such a direction as to shorten the distance
C.
[0088] Accordingly, the seal structure 1 provided with the distance
restricting portions 11 and 12 makes it possible to control the
compressibility ratio of the lip lines 7, and such the structure
makes it possible to exert the following effects.
[0089] (1) First, since the seal structure 1 is not constructed
such that the compressibility of the lip lines 7 is controlled by a
complicated sectional shape of the separators 5, as can be found in
a conventional art, it is possible to simplify the sectional shape
of the separators 5 and to provide thin structure. As shown in FIG.
5, the inner surface of each separator 5 may be formed in a
complete flat face except for the inner surface corresponding to
the groove-like passage 5a.
[0090] (2) Further, since the seal structure 1 is not constructed
such that a distance between a pair of the separators is regulated
by dedicated spacers interposed therebetween, it is possible to
prevent increase in the number of parts and assembling
processes.
[0091] Furthermore, the following functions and effects can also be
achieved by the above-mentioned seal structure 1.
[0092] (3) Since the distance restricting portions 11 and 12 are
provided immediately next to the lip lines 7, the distance
restricting portions 11 and 12 serve as supports for the lip lines
7, thereby generation of falling down of the lip lines can be
suppressed.
[0093] (4) Since the distance restricting portions 11 and 12 are
formed integrally with the rubber sheet 6 and formed by rubber
elastic body, when the integral structure is compressed, rising
degree of the stress can be made moderate as compared with that of
distance restricting portions formed by a rigid material such as
hard resin. Therefore, parts breakage prevention effect can be
expected by the buffering effect due to the elasticity of the
distance restricting portions.
[0094] (5) Further, the seal structure when assembled as a stack is
expected to have an anti-vibration effect due to the elasticity of
rubber. The anti-vibration effect is a key factor when the fuel
cell is used under harsh conditions, for example, when mounted on a
vehicle.
[0095] It should be understood that the seal structure according to
the second embodiment may be modified in various manners within
such an extent that the object of the present invention can be
achieved, for example, the following modifications may be made.
[0096] (A) In the second embodiment, the distance restricting
portions 11 and 12 are provided at both of the inner and outer
peripheral sides of the lip lines 7, however, they are not limited
to this configuration, but may be provided at either side of the
lip lines 7.
[0097] (B) In the second embodiment, the distance restricting
portions 11 and 12 are provided along the entire periphery,
however, they are not limited to this configuration, but may be
provided along the periphery at a predetermined interval
(intermittent disposition along the periphery).
[0098] (C) In the second embodiment, the thickness of the rubber
sheet 6 is set to be same as the MEA 2 thickness, and the lip lines
7 and the distance restricting portions 11 and 12 are formed
integrally on the front and rear faces of the rubber sheet 6 by
increasing the thickness of the rubber sheet 6 at those parts,
however, they are not limited to this configuration, but may be
structured such that the thickness at the distance restricting
portions 11 and 12 is set to be same as the MEA 2 thickness, the
thickness of the lip lines 7 is set to be larger than MEA 2
thickness, and groove-like spaces 13 and 14 are formed between the
lip lines 7 and the respective distance restricting portions 11 and
12.
[0099] Furthermore, the method of producing the seal structure
according to the second embodiment is same as that of the first
embodiment except that the mold 21 has a forming space for the
distance restricting portions 11 and 12. Accordingly, the detailed
description will be omitted to avoid duplication.
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