U.S. patent application number 17/149654 was filed with the patent office on 2021-07-08 for separator plate and electrochemical system.
The applicant listed for this patent is Reinz-Dichtungs-GmbH. Invention is credited to Claudia KUNZ, Thomas STOEHR, Stephan WENZEL.
Application Number | 20210210773 17/149654 |
Document ID | / |
Family ID | 1000005462393 |
Filed Date | 2021-07-08 |
United States Patent
Application |
20210210773 |
Kind Code |
A1 |
STOEHR; Thomas ; et
al. |
July 8, 2021 |
SEPARATOR PLATE AND ELECTROCHEMICAL SYSTEM
Abstract
A separator plate for an electrochemical system has two metal
individual plates. The plates have passage openings for operating
media and possibly coolant, and distribution structures. The
distribution structures are formed in the metal individual plates
and which each communicate with at least two of the passage
openings. A peripherally extending sealing structure is formed in
each of the metal individual plates at least peripherally around
the electrochemically active region and at a distance therefrom
and/or peripherally around at least one of the passage openings and
at a distance from the edge thereof. The cross-section of the
sealing structure has a bead roof, two bead flanks, and at least in
some segments, two bead feet. At least in the region of the bead
roof of the sealing structure at least in some segments, the
sealing structure extends sinuously with at least two wave periods
having convex and concave segments.
Inventors: |
STOEHR; Thomas; (Laupheim,
DE) ; KUNZ; Claudia; (Ulm, DE) ; WENZEL;
Stephan; (Pfaffenhofen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Reinz-Dichtungs-GmbH |
Neu-Ulm |
|
DE |
|
|
Family ID: |
1000005462393 |
Appl. No.: |
17/149654 |
Filed: |
January 14, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15519974 |
Apr 18, 2017 |
|
|
|
PCT/EP2015/074016 |
Oct 16, 2015 |
|
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17149654 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 2008/1095 20130101;
H01M 8/0202 20130101; H01M 8/0247 20130101; C25B 11/036 20210101;
H01M 8/0271 20130101; H01M 8/0273 20130101; H01M 8/2483 20160201;
C25B 9/75 20210101; H01M 8/0276 20130101 |
International
Class: |
H01M 8/0273 20060101
H01M008/0273; H01M 8/2483 20060101 H01M008/2483; H01M 8/0271
20060101 H01M008/0271; H01M 8/0276 20060101 H01M008/0276; H01M
8/0202 20060101 H01M008/0202; C25B 9/75 20060101 C25B009/75; C25B
11/036 20060101 C25B011/036 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 18, 2014 |
DE |
20 2014 008 375.4 |
Claims
1-17. (canceled)
18. A separator plate for an electrochemical system, comprising:
two metallic individual plates, wherein the metallic individual
plates comprise through-openings at least for operating media, as
well as distribution structures which are formed into the
individual metallic plates and which each communicate with at least
two of the through-openings, wherein a peripheral sealing structure
is formed into each of the metallic individual plates at least
peripherally around at least one of (1) the electrochemically
active region and distanced from this and (2) peripherally around
at least one of the through-openings and distanced from the edge of
these through openings, the cross section of said sealing structure
comprising a bead roof, two bead flanks and, at least in sections,
two bead feet, wherein the sealing structure at least in the region
of its bead roof extends, at least in sections, in a wave-like
manner with at least two wave periods with convex and concave
sections, so that upper inner and outer radii form at the
transition from bead roof to the bead flanks and lower inner and
outer radii form at the bead feet, weld connections are sectionally
provided between the two metallic individual plates of the
separator plate, at least at one side adjacent to the bead feet at
least along the region in which the bead roof extends in a
wave-like manner, wherein in each case the weld connections extend
in the region adjacent to a convex region of the wave course and
concentrically to the bead foot of the convex region.
19. The separator plate according to claim 18, wherein the weld
connections each extend over at least 1/9 of the wavelength
.lamda., and maximally over the complete convex section.
20. The separator plate according to claim 18, wherein the sealing
structure comprises a coating at least in the region of the bead
roof.
21. The separator plate according to claim 20, wherein the coating
comprises FPM (fluorocarbon rubber), silicone rubber or NBR rubber
(acrylonitrile butadiene), PUR (polyurethane), NR (natural rubber),
FFKM (perfluoroelastomeric compounds), SBR (styrene butadiene
rubber), BR (butyl rubber), FVSQ (fluorosilicone), CSM
(chlorosulphonated polyethylene), silicon resin, epoxy resin or
mixtures of the above-mentioned substances or contact adhesive or a
physically setting adhesive.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional of U.S. patent
application Ser. No. 15/519,974, entitled "SEPARATOR PLATE WITH
DECREASED WIDTH OF ONE BEAD FLANK AND ELECTROCHEMICAL SYSTEM", and
filed on Apr. 18, 2017. U.S. patent application Ser. No. 15/519,974
is a U.S. national phase of International Application No.
PCT/EP2015/074016, entitled "SEPARATOR PLATE AND ELECTROCHEMICAL
SYSTEM", and filed on Oct. 16, 2015. International Application No.
PCT/EP2015/074016 claims priority to German Utility Model
Application No. 20 2014 008 375.4, entitled "SEPARATOR PLATE AND
ELECTROCHEMICAL SYSTEM", and filed on Oct. 18, 2014. The entire
contents of each of the above-listed applications are hereby
incorporated by reference for all purposes.
TECHNICAL FIELD
[0002] The invention relates to a separator plate for an
electrochemical system, as well as to such an electrochemical
system.
BACKGROUND
[0003] The separator plate can be used for example for a fuel cell
system in which electrical energy is obtained from hydrogen and
oxygen. The separator plate can also be used for an electrolyser in
which hydrogen and oxygen are produced from water by way of
applying a potential. The separator plate can likewise be used for
an electrochemical compressor in which molecular hydrogen is
transported through the membrane due to oxidation/reduction by way
of applying a potential, and is simultaneously compressed.
Moreover, the separator plate can also be used for a humidifier for
an electrochemical system in which a dry gas to be fed to an
electrochemical system is humidified by way of a humid gas, mostly
an exhaust gas of an electrochemical system.
[0004] Usually, separator plates for an electrochemical system
comprise a plate pair with two metallic individual plates, wherein
in each case two separator plates surround an electrochemical cell,
for example a fuel cell, and delimit this from the next
electrochemical cell. Herein, in an electrochemical system a
multitude of electrochemical cells, for example up to 200, are
mostly stacked in series into a stack, in a manner such that the
cells are then each separated from one another by a separator
plate. The cells themselves usually consist of a membrane electrode
assembly/unit, also called MEA (membrane electrode assembly), as
well as in each case of a gas diffusion layer (GDL) which e.g.
consists of an electrically conductive carbon non-woven, on both
sides of the MEA. The complete stack is held together between two
end plates via a clamping system and is provided with q predefined
pressing. In the case of a humidifier, the cell consists of only a
membrane, potentially with a support medium, as well as with porous
structures which can be compared to the GDLs, but which do not need
to be electrically conductive.
[0005] In an electrochemical system, apart from separation of the
electrochemical cells from one another, the separator plates serve
further functions; these on the one hand being the electrical
contacting of the electrodes of the different electrochemical
cells, as well as the leading of the current to the respective
adjacent cell, and on the other hand the supplying of the cells
with operating media and the removal of the reaction products,
furthermore the cooling of the electrochemical cells and the onward
transport of the waste heat, as well as the sealing of the
compartments of the two different operating media and of the
coolant, to one another as well as to the outside.
[0006] Through-openings for operating media, usually on the one
hand for hydrogen or methanol in particular and on the other hand
for air or oxygen in particular, as well as for coolant, mostly
mixtures of demineralised water and antifreeze, are accordingly
formed in both metallic individual plates of the separator plate,
for the supply of the electrochemical cells. Operating media and
coolant are hereinafter together referred to as media. Moreover, a
distribution structure is formed in each of the two metallic
individual plates, wherein channels form on both surfaces of the
two individual plates. An operating medium is conducted on each of
the outwardly facing surfaces of the separator plate, and the
coolant is conducted in the intermediate space between the two
metallic individual plates. The region in which an operating medium
is led in a channel structure is also referred to as the
electrochemically active region of the separator plate. Each of the
distribution structures communicates with at least two of the
through-openings, specifically at least one inlet and at least one
outlet for the respective fluid. Each of the individual metallic
plates, at least in a peripherally closed manner around the
electrochemically active region of the separation plate as well as
around the through-openings, is surrounded by a sealing structure,
which is distanced from the electrochemically active region, or the
respective edge of the through-opening, so as to seal the different
media regions to one another and to the outside. The sealing of the
electrochemically active region can herein be effected such that
through-openings which are sealed with respect to the compartment
containing the electrochemically active region by way of their own
peripheral sealing structures, are arranged within the sealing
structure which is peripherally closed around this region.
[0007] It has already been suggested in DE 101 58772 A1 to emboss
the sealing structure into the metallic individual plates of the
separator structure, specifically in the form of a full bead or
half bead extending in a straight line. A sealing result satisfying
the expectations at the time could be achieved by these
straight-lined beads in the case of small separator plates having
an essentially square base surface and a small to medium plate
number, with a simultaneously high clamping of the stack. However,
with beads extending in a straight line in separator plates having
rather elongate plate base surfaces, or in larger separator plates,
the sealing result was already mostly unsatisfactory. With long
bead sections running in a straight line, the beads lose their
stiffness with an increasing distance to the corner points and do
not have an adequate restoring force in the regions concerned.
[0008] In WO 2004/036677 A2, an attempt to counter this was made by
way of the sealing elements being designed as full beads with a
non-linear course at least in sections. These on the one hand are
beads which become thicker and thinner at both sides in a
periodically alternating manner, as well as on the other hand beads
which have an overall wave-like course in sections. Herein, the
base widths of the bead flanks--measured at right angles to the
respective neutral line of the wave-like bead--remain the same over
the course of the flanks in the wave-like sections. Consequently,
different inner and outer radii, which have different stiffnesses
and resiliences form, particularly in the region of the wave peaks
and wave troughs, i.e. the apexes. In each case, alternating
homogeneities of the pressing in the contact region of the bead
roof which, with respect to bead flanks lying opposite one another,
change in a manner opposed to one another, result along both bead
flanks on account of this. Here, the risk exists of media flowing
through the sealing structure in regions of lower bead stiffness,
which is to say of operating media flowing into the interior of the
separator plate and of coolant flowing into the outer space of the
separator plate. On the one hand, the respective media are lost for
the operation of the electrochemical system. This is not acceptable
with regard to the efficiency of the electrochemical system. On the
other hand, the risk exists of coolant getting into the region of
the operating media and for example damaging the membrane
there.
[0009] Due to the large number of separator plates in a stack, a
small difference in the stiffness and resilience of the sealing
bead along its course in a single separator plate or in a single
metallic individual plate of a separator plate leads to a very
large difference in the resiliency of the sealing beads
connected/arranged in series, so that small differences at the
individual separator plates have a significant effect on the sealed
ness of the complete stack.
SUMMARY
[0010] It is therefore the object of the invention to specify a
separator plate which permits a uniform sealing of an
electrochemical cell, without significantly more construction space
than is necessary for sealing arrangements of the state of the art
being required for the sealing. The costs for the separator plate
should remain comparable to the costs of a separator plate of the
state of the art, so that the costs of the manufacturing method as
well as the material expense should only be increased
insignificantly at the most. The sealing should be able to be
applied for sealing systems without branching and continuations as
well as for those with branching and/or continuations.
[0011] This object is achieved by a separator plate according to
claims 1 and 18 as well as by an electrochemical system according
to claim 22. Further developments can be gleaned from the dependent
claims.
[0012] Thus, the invention relates, one the one hand, to a
separator plate for an electrochemical system with two metallic
individual plates. The metallic individual plates each comprise
through-openings for operating media and, as the case may be, for
coolant, as well as distribution structures which are formed into
the metallic individual plates and which each communicate with at
least two of the through-openings. A peripheral sealing structure
is formed into each of the metallic individual plates, at least
peripherally around the electrochemically active region and
distanced from this and/or peripherally around at least one of the
through-openings and distanced from the edge of these
through-openings, the cross section of said sealing structure
comprising a bead roof, two bead flanks and, at least in sections,
two bead feet. Herein, delimitation lines form on the bead roof at
both sides, wherein these lines delimit the bead roof running
parallel to the plate plane, to the bead flanks inclined to this
plane, including a mostly present transition radius. Herein, what
is essential is that the sealing structure at least in the region
of its bead roof and at least in sections runs in a wave-like
manner with at least two wave periods with convex and concave
sections, so that upper inner and outer radii form at the
transition from the bead roof to the bead flanks and lower inner
and outer radii form at the bead feet. What is different to the
state of the art is the fact that although the width (W.sub.D) of
the bead roof is constant in the region of its wave-like extension,
the base width (W.sub.I, W.sub.A) of at least one of the two bead
flanks however changes. By way of this, it is ensured that the
complete sealing structure not only has a uniform sealing behaviour
in its potentially present linear regions, but also has a uniform
sealing behaviour/uniform stiffness in the region of the wave-like
course of the bead roof at least along a transition from the bead
roof to the respective bead flank.
[0013] The convex and the concave sections of the wave-like course
merge into one another in each case at an inflection point. A main
extension direction is superimposed on the wave shape of the bead
roof. This main extension direction results from the connection
line of the inflection points of the neutral lines of the bead
roof. A convex section thus reaches from one inflection point which
is to say from a perpendicular to the tangent to the neutral lines
of the bead roof at its inflection point, over an apex projecting
to a greater extent from the main extension direction of the bead,
to the next inflection point, and a convex section reaches from an
inflection point which is to say from a perpendicular to the
tangent to the neutral lines of the bead roof at its inflection
point, over an apex projecting to a lesser extent from the main
extension direction of the bead, to the next inflection point. For
the complete sealing structure, reference is always made to the
respective perpendicular to the tangent at the respective point of
the neutral lines.
[0014] The amplitudes of the delimitation lines of the bead roof
can differ from the amplitudes of the lines of the course of the
bead feet, whereas the wavelengths are identical.
[0015] The above also applies to the advantageous embodiment in
which at least one of the bead flanks comprises continuations in
the region of the wave-like course of the bead roof, said
continuations comprising a roof, two flanks and two feet, wherein
these continuations are designed such that the total height of the
continuations is smaller than the total height of the sealing
structure, so that the continuations do not affect or compromise
the actual sealing line, or only to a small extent. These
continuations on the one hand can serve for permitting a passage of
a medium transverse to a sealing line. The continuations are
preferably provided on both sealing flanks for this purpose.
However, it is also possible to provide continuations at one side,
and these form, on the surface of the individual plate beyond which
surface the bead roof projects, a barrier between a distribution
structure and the sealing structure in order to thus optimally
guide the flow of operating medium or coolant. It is preferable for
at least one of these continuations to connect the interior of the
sealing structure to one of the distribution structures or to one
of the through-openings for operating media or coolant,
irrespective of whether a continuation serves for a passage of a
medium or as a barrier. Apart from this, continuations can also
serve exclusively as support structures or stiffening structures,
and they herein mostly only have a length which is smaller than
fivefold the width of the bead roof.
[0016] The arrangement of the continuations is herein
advantageously effected such that the distance of at least two
continuations to one another, preferably all continuations to one
another, at a bead flank is n.times..lamda./2, wherein .lamda. is
the period length of the wave shape of the bead roof and n is a
natural number. The continuations thus for example can be present
on each wave trough and/or each wave peak, of the section of the
sealing structure in which the bead roof has a wave-like course.
However, they can also be arranged at the inflection points of the
wave structure. The number of continuations is directed to the
respective application purpose and the total length, i.e. the
number of wave periods of the wave-like region of the bead
roof.
[0017] For a uniform sealing, it is advantageous if the base width
(W.sub.I, W.sub.A) of at least one of the bead flanks continuously
changes, since abrupt changes would counteract a uniform
sealing.
[0018] It is also advantageous for uniform sealing if additionally
to the already described change of the base width of at least one
bead flank, the sealing system 10 of the separator plate also has
changes of the flank angle in the region of the wave-like extension
of the bead roof. Here, the flank angle (.alpha..sub.1) between the
bead roof and a bead flank extending in a concave section, and the
flank angle (.alpha..sub.A) between the bead roof and the opposite
bead flank extending in a convex section, change along the
wave-like extension region to a different extent, at least in
sections.
[0019] Moreover, with regard to the manufacture of the separator
plate, it is particularly advantageous if the lower outer radius in
a cross section through the sealing structure is the same or larger
than the upper outer radius. The cross section of the bead in the
context of this invention is always defined perpendicularly to the
neutral lines of the bead roof.
[0020] Particularly with regard to a uniform sealing of a plate
stack comprising many separator plates, it is particularly
advantageous if the bead roofs of the sealing structures of the two
metallic individual plates of the separator plate have a
mirror-symmetrical course to one another with respect to their
contact surface. A precise propagation of the sealing lines through
the complete plate stack is thus achieved given a sufficient width
of the bead roof, even with slight inaccuracies of the placing of
individual separator plates in the plate stack. The mirror symmetry
first and foremost relates to the course of the bead roofs of the
sealing structures, but it can also relate to the complete sealing
structures, wherein it is the potentially present sealing
structures without continuations which are meant here. The height
of the sealing structures can moreover also be essentially
identical in both metallic individual plates of the separator
plate. A particularly uniform pressing and sealing is achieved by
way of this, due to the fact that the spring force of the beads is
identical in both individual plates.
[0021] The sealing structure of the separator plate preferably not
only runs with a wave-like bead roof in a single, continuous
section, but in contrast, for an optimal sealing, it is
advantageous if several sections of the bead roof which are
connected over the course of the bead but are spatially separated
(i.e. e.g. arranged at another location of the plate) each extend
in a wave-like manner. Generally, it is possible for the different
sections of the wave-like extension to have different wavelengths
and/or amplitudes, but it is preferable if at least all roof
sections of a continuous bead, preferably even all beads which have
a wave-like course of the bead roof, have the same wavelengths and
amplitudes.
[0022] Here, on the one hand it is advantageous if, given a
peripheral sealing structure in which several sections of the bead
roof extend peripherally in a closed manner around the
electrochemically active region in a wave-like manner with at least
two wave periods, at least two wave-like sections extend along
sides of the electrochemically active region of the individual
plate, said sides lying opposite one another. The wave-like
sections can also extend in sections along all sides of the
electrochemically active region.
[0023] On the other hand, it can be advantageous if, given a
peripheral sealing structure in which several sections of the bead
roof extend in a wave-like manner with at least two wave periods
along an inner edge, that is to say the edge of at least one
through--opening for operating media or coolant, of a metallic
individual plate, at least two wave-like sections extend along
inner edges of the through-opening which lie opposite one another.
Here too, it is basically possible for beads with a wave-like bead
roof to run sectionally on all inner edges.
[0024] Basically, it is advantageous if the wave-like sections of
the bead roof extend in those sections of the sealing structure in
which the sealing structure, considered macroscopically, i.e. with
regard to its main extension direction, has a straight-lined course
or a weakly arcuate course with a radius >15 mm.
[0025] The width of the bead roof at least in a section of the
wave-like course of the bead roof is between 0.2 and 2 mm,
preferably between 0.9 and 1.2 mm. Generally, the width of the bead
roof likewise lies in the mentioned regions in the further linear
or arcuate course.
[0026] The bead sections with the wave-like course of the bead
roof, apart from a change of the base width of at least one bead
flank, also have a change of the flank angle of the respective bead
flank(s). If one considers a convex section of the bead roof, then
the adjacent flank angle, beginning at a cross section
perpendicular to the tangent through the inflection point of the
neutral lines, increases up to a cross section perpendicular to the
tangent through the apex of the convex section of the neutral lines
of the bead roof and then decreases again up to the cross section
perpendicular to the tangent through the next inflection point of
the neutral lines. Accordingly, the flank angle of a concave
section, beginning at a cross section perpendicular to the tangent
through the inflection point of the natural lines, firstly
increases up to a cross section perpendicular to the tangent
through the apex of the concave section of the neutral lines of the
bead roof, thus of the minimum, and then increases again up to the
cross section perpendicular to the tangent through the next
inflection point of the neutral lines.
[0027] Advantageously, the changes run in a continuous manner.
Basically, it is advantageous if the flank angle of a concave
section is smaller than the flank angle of a convex section. The
flank angle of a concave section generally lies between 15.degree.
and 60.degree., preferably between 25.degree. and 50.degree.,
whereas the flank angle of a convex section generally lies between
20.degree. and 65.degree., preferably between 30.degree. and 30
55.degree.. The regions are herein defined in each case including
or excluding the mentioned limits. On account of this, the solution
according to the invention differs significantly from the state of
the art, where the flank angle remains unchanged over the course of
the bead.
[0028] The change of the flank angle in a concave section between
the inflection point and the apex point herein corresponds to a
reduction of up to 50%, preferably of up to 40% with respect to the
value at the inflection point, and the change of the flank angle in
a convex section between thee inflection point and the apex point
corresponds to an increase by up to 120%, preferably up to 100%,
particularly preferably by up to 70%, with respect to the value at
the inflection point.
[0029] The base width of the bead along one of its sections, in
which the bead roof runs in a wave-like manner, can only change at
one bead flank, but in one embodiment can change at both bead
flanks. If it changes at only one bead flank, then the change at
this flank, if the change is effected in a convex section, that is
in the case of a reduction, is at least 5%, preferably at least 25%
with respect to the base width at a cross section perpendicular to
the tangent on one of the adjacent inflection points, and if it is
effected at in a concave section, that is in the case of an
increase, the change is at least 5%, preferably at least 20% with
respect to the basis width at a cross section perpendicular to a
tangent on one of the adjacent inflection points. If the base width
of both bead flanks changes, then the change is between 5 and 70%,
preferably between 30 and 55%, with respect to the base width at a
cross section perpendicular to the tangent on one of the adjacent
inflection points.
[0030] In an advantageous embodiment of the separator plate
according to the invention, the total width of the sealing
structure from bead foot to bead foot is constant in the region of
a wave-like extension of the bead roof, so that the base widths of
the two bead flanks therefore always change in a complementary
manner. In a particularly advantageous embodiment, the sealing
structure as a whole runs linearly in the region of the wave-like
extension of the bead roof. Here, the spatial equipment for the
sealing structure is particularly modest.
[0031] The invention on the other hand relates to a separator plate
for an electrochemical system comprising two metallic individual
plates which each comprise through-openings for operating media
and, as the case may be, coolant, as well as distribution
structures which are formed into the metallic individual plates and
which each communicate with at least two of the through-openings.
Herein, a peripheral sealing structure is formed into each of the
metallic individual plates, at least peripherally around the
electrochemically active region and distanced from this and/or
peripherally around at least one of the through-openings and
distanced from its edge, the cross section of said sealing
structure comprising a bead roof, two bead flanks and at least in
sections two bead feet. Here too, the sealing structure at least in
the region of its bead roof at least in sections extends in a
wave-like manner with at least two wave periods with convex and
concave sections. Here too, upper inner and outer radii form at the
transition from the bead roof to the bead flanks, and lower inner
and outer radii at the bead feet. This embodiment of the invention
is characterised in that at least at one side adjacent to the bead
feet, at least along the region in which the bead roof extends in a
wave-like manner, weld connections are sectionally provided between
the two metallic individual plates of the separator plate, wherein
the weld connections in each case extend in the region adjacent to
a convex region of the wave course and preferably essentially
concentrically to the lower outer radius. The distance to the bead
foot herein preferably corresponds to maximally double, in
particular maximally to single the width of the bead roof. Here,
the flat sections adjacent to the bead foot which, which without
further measures tend to diverge on account of the low spring
stiffness, are connected to one another and the complete separator
plate thus obtains more structural rigidity. On the other hand, the
welding is effected in precisely the regions in which the
structural rigidity is to be increased, whereas the regions of
sufficient structural rigidity or stiffness along the bead feet
remain free of weld connections.
[0032] In this embodiment of the invention too, one of the bead
flanks, in the region of the wave-like course of the bead roof, can
comprise continuations having a roof, two flanks and two feet,
wherein these continuations are designed such that the total height
of the continuations is smaller than the total height of the
sealing structure. What has been specified before with respect to
the continuations applies here to the same extent.
[0033] As already specified, the weld connections only extend in
sections. Here, it is preferable if their extension in each case is
at least 1/9 of the wavelength of the wave-like course of the bead
roof. Furthermore, it is preferable if the extension of the weld
connection extends maximally over the entire convex region of the
wave course, thus between the perpendiculars through the inflection
points of the neutral lines of the bead roof, said inflection
points being adjacent one another.
[0034] In all embodiments of the invention, it is advantageous if
the sealing structure of an individual plate has a constant height,
and it is only the potentially present continuations which are
excluded. It is particularly preferable if all individual plates
comprise sealing structures with a constant height.
[0035] It is advantageous for all aforesaid embodiments of the
separator plate according to the invention if the sealing structure
comprises a coating for microsealing, at least in the region of the
bead roof. The coating herein is deposited for example on at least
one, preferably however on both individual plates, on the bead roof
in a manner such that it is located on the outer side of the
separator plate. The coating herein as a binder advantageously
comprises FPM (fluorocarbon rubber), silicone rubber or NBR rubber
(nitrile butadiene rubber), PUR (polyurethane), NR (natural
rubber), FFKM (perfluoroelastomeric compounds), SBR (styrene
butadiene rubber), BR (butyl rubber), FVSQ (fluorosilicone), CSM
(chlorosulphonated polyethylene), silicon resin and/or epoxy resin
or mixtures of the mentioned substances. The coating can also be a
contact adhesive or a physically setting adhesive. This for example
can be a permanently sticky adhesive which preferably consists of
mixtures of rubbers and adhesive resins, so called tackifiers, or
of a poorly cured rubber, where synthetic and natural resins may be
considered as adhesive resins. Herein, natural and synthetic
rubbers, polyacrylates, polyester, polychloroprenes, polyvinylether
and/or polyurethanes and/or flouropolymer rubbers can be used as
base polymers, to which resins such as in particular modified
natural resins, for example rosin and/or artificial resins--for
example polyester resins, phenol resins--as well as softeners
and/or antioxidants can be added. Typically, coating thicknesses
for all aforesaid substances are between 5 and 200 micrometers.
[0036] The metallic layers of the separator plates preferably
consist of steel, in particular of stainless steel, wherein
conductive coatings can be present in the electrochemically active
region. In alternative embodiments, aluminium, titanium,
roller-coated, low-alloyed steels which are coated e.g. with
chromium, stainless steel, niobium, tantalum or chromium-nickel
alloys can be used as materials. Common sheet metal thicknesses lie
between 50 and 200 micrometers, preferably between 60 and 150
micrometers.
[0037] Generally, with regard to the separator plates, one can
differentiate between the bipolar plates, where different media are
led on both surfaces, and monopolar plates, where the same medium
is led on both surfaces of a monopolar plate. Here, slightly
different monopolar plates are mostly used for both different
media. The differences in particular may relate to the presence of
continuations on the sealing beads. The course of the sealing
structures and thus their sectionally wave-like design in contrast
is mostly identical or mirror symmetrical in all plates. The
embodiments of this description apply to both plate types, unless
the differences are emphasised by explicit mention. Preferably,
coolant is led in the intermediate space of the two individual
plates of the respective plate, and this is the case with both
plate types.
[0038] The separator plates according to the invention are
advantageously used in an electrochemical system. Such an
electrochemical system comprises two end plates, as well as a
multitude of electrochemical cells which are separated from one
another in each case by a separator plate according to the
invention. The complete system is herein preferably held together
by way of clamping means, for example bolts or straps and herein
provided with a clamping force which is optimal for sealing.
Transition plates whose design differs from the design of the
separator plates of the stack can be provided between the end
plates and the outermost cells of the stack. Mostly, one such
transition plate, which can also be designed in a multi-layered
manner, is present per end plate.
[0039] With regard to the electrochemical system, this is
preferably a fuel cell system, an electrolyser, an electrochemical
compressor system or a humidifier system for a fuel cell
system.
[0040] The invention is hereinafter explained in more detail by way
of the drawings. These drawings serve exclusively for explaining
preferred embodiment examples of the invention, without the
invention being limited to this. In the drawings, the same parts
are provided with the same reference numerals. The examples all
relate to a fuel cell system, but the explanations also apply to
the same extent to the other types of electrochemical systems which
are mentioned above. Apart from the essential features of the
present invention which are specified in the independent claims,
the figures also contain optional further developments which would
also be advantageous in a different composition. Each individual
one of these advantageous and/or optional further developments of
the invention as such can be formed into a further development of
the invention specified in the independent claims, even without
combining it with one, several or all of the optional and/or
advantageous further developments which are also represented in the
examples.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] The figures schematically show:
[0042] FIG. 1 is a schematic representation of an electrochemical
system;
[0043] FIG. 2a is an exploded representation of an electrochemical
cell with two separator plates which are adjacent thereto;
[0044] FIG. 2b is a partial cross-section of the electrochemical
cell and a separator plate both of FIG. 2a;
[0045] FIG. 2c is a plan view of a separator plate of FIG. 2a;
[0046] FIG. 3 is a sectioned representation of a sealing system of
a separator plate;
[0047] FIG. 4a is a perspective view of a sealing system of a
separator plate according to the state of the art;
[0048] FIG. 4b is a schematic view of the sealing system of the
separator plate in FIG. 4a;
[0049] FIG. 4c is a partial cross-section of the sealing system of
the separator plate in FIG. 4b;
[0050] FIG. 5a is a perspective view of a sealing system of a
separator plate;
[0051] FIG. 5b is a schematic view of the sealing system of the
separator plate in FIG. 5a;
[0052] FIG. 5c is a partial cross-section of one embodiment of a
sealing system of the separator plate in FIG. 5b;
[0053] FIG. 5d is a partial cross-section of another embodiment of
a sealing system of the separator plate in FIG. 5b;
[0054] FIG. 5e is a partial cross-section of another embodiment of
a sealing system of the separator plate in FIG. 5b;
[0055] FIG. 6a is a perspective view of a sealing system of a
separator plate;
[0056] FIG. 6b is a schematic view of the sealing system of the
separator plate in FIG. 6a;
[0057] FIG. 6c is a partial cross-section of one embodiment of a
sealing system of the separator plate in FIG. 6b;
[0058] FIG. 6d is a partial cross-section of another embodiment of
a sealing system of the separator plate in FIG. 6b;
[0059] FIG. 6e is a partial cross-section of another embodiment of
a sealing system of the separator plate in FIG. 6b;
[0060] FIG. 7a is a perspective view of a sealing system of a
separator plate;
[0061] FIG. 7b is a schematic view of the sealing system of the
separator plate in FIG. 7a;
[0062] FIG. 7c is a partial cross-section of one embodiment of a
sealing system of the separator plate in FIG. 7b;
[0063] FIG. 7d is a partial cross-section of another embodiment of
a sealing system of the separator plate in FIG. 7b;
[0064] FIG. 7e is a partial cross-section of another embodiment of
a sealing system of the separator plate in FIG. 7b;
[0065] FIG. 8 is a plan view of a detail of a sealing system of a
further separator plate according to the invention;
[0066] FIG. 9a is an oblique view of a detail of yet another
embodiment of a sealing system with feed-throughs through the
sealing system;
[0067] FIG. 9b is a plan view of the sealing system with
feed-throughs in FIG. 9a;
[0068] FIG. 10a is a plan view of a detail of a sealing system of a
further separator plate according to the invention with
delimination elements which are adjacent to the sealing system;
[0069] FIG. 10b is a plan view of another embodiment of a detail of
a sealing system of a further separator plate according to the
invention with delimination elements which are adjacent to the
sealing system;
[0070] FIG. 10c is a plan view of another embodiment of a detail of
a sealing system of a further separator plate according to the
invention with delimination elements which are adjacent to the
sealing system;
[0071] FIG. 11a is an oblique view of a detail of a sealing system
of a further separator plate according to the invention;
[0072] FIG. 11 b is a plan view of the sealing system of the
separator plate of FIG. 11 a;
[0073] FIG. 12 is a plan view of a detail of a sealing system of a
further separator plate according to the invention.
DETAILED DESCRIPTION
[0074] FIG. 1 represents an electrochemical system 1 with a
multitude of cells 30 46 and separator plates 2 which are stacked
in an alternating manner, as well as two end plates 11, 11' which
delimit the stack. The end plate facing the viewer comprises six
branches 12 to 17, which serve for the feed and discharge of
reaction media and coolant: 12 indicates the feed branch for air,
17 the discharge branch for oxygen-depleted air, 13 the feed branch
for hydrogen, 16 the discharge branch for hydrogen which has not
been consumed, 15 the feed branch for coolant and 14 the discharge
branch for heated coolant. One can thus differentiate between six
media flows: A indicates oxygen-rich which is to say fresh air; D
oxygen-depleted air, B hydrogen, C non-consumed hydrogen, E cool
coolant and F heated coolant.
[0075] FIG. 2-a shows a cell 46 of an electrochemical system 1,
here a fuel cell system 1 together with the two separator plates 2
and 2' which delimit the cell 46. The view is essentially in the
z-direction of the coordinate system given in FIG. 1. The
electrochemical system 1 of FIG. 2-a differs from that of FIG. 1 to
the extent that the reduction agent, specifically the hydrogen, is
not led through the stack via a port perpendicular to the plate
plane, but via the two ports 23, 23' located in the upper corners.
Conducting the non-consumed hydrogen gas 15 onward in the stack
direction is effected via the two ports 26, 26' located in the
lower corners. The two lateral ports 24, 25 serve for the leading
of coolant through the stack perpendicularly to the plane of the
plate. The upper port 27 serves for leading oxygen-rich air through
the stack, and the lower port 22 for leading oxygen-deficient poor
air through the stack. The layer 2a of the separator plate 2 which
lies at the top comprises a sealing structure consisting of several
beads. A bead 32 which is peripheral around the electrochemically
active region 29 and which in sections is peripheral along the
outer edge 19 serves for sealing the electrochemically active
region 29 or of the compartment enclosing this region, as well as
the plate as a whole, to the outside. Moreover, each of the 25
ports 22 to 27 comprises a separate bead 31, 31' surrounding the
respective port.
[0076] It is to be emphasised that the ports 23, 23, 23', 26, 26'
and 27 for the reaction media together with the beads 31
surrounding them lie within the region which is surrounded by the
bead 32. The surface of the separator plate 2 which faces the
viewer moreover comprises a channel structure 28, here for the
distribution or air, and simultaneously forms the electrochemically
active surface 29. The bead 32 thus surrounds the electrochemically
active surface 29 in a peripheral and distanced manner, wherein the
distance changes in the course. The feed of air from the port 27 to
the channel structure 28 and the discharge of depleted air from the
channel structure 28 to the port 22 is explained in more detail by
way of FIG. 2-c.
[0077] FIG. 2-b represents a section through two separator plates
2,2', an electrochemical cell 46 arranged between the two separator
plates 2,2', specifically a fuel cell, as well as elements of the
next electrochemical cell arranged on the other side of the
separator plate 2'. The section with respect to the represented
elements corresponds to the section B-B of FIG. 2-a, but the
distances of the different elements have been adapted with regard
to a space-saving representation. The visible surface thus lies in
a y-z plane of FIG. 1. It is clear from the sectioned
representation that the electrochemical cell 46 carries a catalytic
layer 42, 42' on the actual polymer electrolyte membrane (PEM) in
each case at both sides, and this layer becomes the electrode and
represented in a distanced manner here for a better understanding.
These elements together represent the so-called membrane electrode
unit (MEA). A gas diffusion layer (GDL) 44, 44' which consists in
each case for example of an electrically conductive non-woven of
graphite lines, is arranged in each case of both sides of the
MEA.
[0078] Channel structures 28 are formed into the two layers 2a, 2b
of the separator plate 2, and on both sides of the layer are used
for distributing media. The channel structures 28 herein form the
electrochemically active region 29. A first medium M1, specifically
air is distributed on the upper side of the layer 2a. Coolant K is
distributed on the lower side of this layer 2a, i.e. in the cavity
between the two layers 2a and 2b. A second medium M2 is distributed
on the lower side of the layer 2b. The second medium M2 is hydrogen
in the case of a bipolar construction of the electrochemical
system. In this case, M3 is again air and M4 is again hydrogen.
With a monopolar construction of the electrochemical system, the
second medium M2 is again air. In contrast, with a monopolar
construction, the channels on both outer surfaces of the second
separator plate 2' serve for the distribution of hydrogen which
here represents the third and fourth medium M3 and M4. In the case
of a bipolar construction, all separator plates of a stack are
identical, and in the case of a monopolar construction, as the case
may be two different separator plate variants alternate along the
stack.
[0079] It is also clear from the section of FIG. 2-b that the bead
31 surrounds the through-opening 23 and thus seals off the hydrogen
port. The bead 31 which peripherally seals off the
electrochemically active region, in the represented section in
contrast runs essentially along the outer edge 19 of the layer 2a
of the separator plate 2, so that it is only sectioned once in the
section shown here. It is also evident from the sectioned
representation that the height of the beads 31, 32 amongst one
another is essentially identical, wherein the height of the beads
31, 32 however is significantly higher than the height of the
channel structures 28.
[0080] FIG. 2-c represents the layer 2a of the separator plates 2
which lies closest to the viewer in FIG. 2-a, in a plan view, thus
again corresponds to a view in the z-direction of FIG. 1. Here, the
design of the beads 31, 31' and 32 is to be dealt with in more
detail. The bead 31' peripherally surrounds the port opening 25 and
herein, disregarding the waved structure of the bead itself, has a
small, essentially constant distance to the edge of the port
opening 25. The bead 31 surrounds the port opening 26' in a
comparable manner, but as a rule has an essentially circular course
without a wave structure. Here too, the distance to the edge of the
port is essentially constant. The bead 32 runs along and distanced
to the outer edge 19 of the layer 2a of the separator plate 2 and
herein not only encloses the electrochemically active region 20
which it seals off, but also the ports 22,23,23',26,26' and 27,
together with the beads 31 sealing them. In the represented
example, the bead 32 comprises several sections 35, in which the
bead roof has a wave-like course. These sections 35 considered per
se, macroscopically have a straight-lined course. It is evident
that the sections 35, in which the bead 32 has a wave-like course
of the bead roof, are arranged in each case in elongate,
straight-lined sections of the sealing system, whereas relatively
greatly curved regions of the bead 32, such as the region S
surrounded by an oval, have a shape of the bead roof which
corresponds to the total extension direction of the bead 32 in
respective section, thus has no periodic wave-like course.
[0081] It can also be recognised from FIG. 2-c that air flows out
of the port 27 along the continuations 33 through the bead 31, in
order to hence get to the electrochemically active region 29 where
the oxygen contained in its reacts with protons which enter through
the MEA. The air which is depleted of oxygen in such a manner and
has a high moisture content as a result of the reaction, then flows
further downwards to the continuations 33 and there passes the bead
31 anew and is led via the port 22 to the end plate. The
continuations are herein formed into the flanks of the bead 31 such
that the sealing is not compromised.
[0082] FIG. 3 basically represents the size ratios and angular
details in a sealing system of a separator plate, as are applied
hereinafter. The section of FIG. 3 herein corresponds for example
to the section C-C in FIG. 2c, thus lies in a plane parallel to the
y-z plane of FIG. 1. The total width of a bead 3 of a sealing
system is indicated at W.sub.T, and the width of the bead roof 39
is indicated at 15 W.sub.D. The inner and the outer base width
W.sub.I and W.sub.A respectively are identical in the considered
symmetrical bead cross section, so that for simplification, the
term W is used instead of the different terms W.sub.I, W.sub.A.
This similarly applies to the inner and outer flank angle
.alpha..sub.I and .alpha..sub.A, which are analogously indicated in
a simplified manner by .alpha.. The height of a bead in an
individual layer 2a, 2b of a separator plate 2 is indicated at H.
FIG. 3 furthermore illustrates the different sections of a cross
section of a bead 3 from the right to the left: subsequent to a
first bead foot 37 is a bead flank 38, and the bead roof 39
connects after a further bend point. On the other side of the bead
roof, a further bead flank 38' is subsequent to a further bend, and
after this comes the second bead foot 37'. The bead feet are 25
defined as the boundary points which are adjacent to a bead flank
at their side which is away from the bead roof and on which the
tangent to the course of the layer runs parallel to the middle
plane of the separator plate 2. If a bead is considered
independently of its function as a sealing element 32 around an
electrochemically active region 29 or as a sealing element 31, 31'
of an inner 30 edge, then here and hereinafter it is indicated at
3.
[0083] FIG. 3 further illustrates as to how the two layers 2a, 2b
of a separator plate 2 are designed in an essentially
mirror-symmetric manner and are in surfaced (extensive) contact
with one another in the region outside the bead 3, more precisely
beginning at the bead feet 37, 37'. The representation of the
channel structure has been done away with, and here the
explanations in the context of FIG. 2-b are referred to.
[0084] The embodiments concerning FIGS. 1 to 3 apply to the
separator plates of the state of the art as well as to the
separator plates according to the invention.
[0085] The wave-like course of a section of a bead 3 of the state
of the art, with which the bead roof 39 extends with a constant
width W.sub.D, specifically 1.6 mm, in a wave-like manner with at
least two wave periods with a wavelength .lamda., is show in FIG. 4
in three part-pictures, by way of a detail of an individual layer
2a of a 15 separator plate 2. The sectioned representation of FIG.
4-c herein corresponds equally to all three section lines AD-AD,
BD-BD and CD-CD which are given in FIG. 4-b. The two bead flanks
38,38' have a constant base width W of 0.7 mm in each case, over
the entire course. The total width of the bead 3 W.sub.T is thus 3
mm. Because the base width of the bead flanks 38, 38' does not
change over the course of the bead, and the base width of the bead
flanks 38, 38' at both sides of the bead roof 39 is likewise
identical, the bead consequently has a uniform flank angle .alpha..
A differentiation of the flank angle into the outer angle which is
to say the flank angle in the convex section, .alpha..sub.A, and
the inner angle which is to say the flank angle in the concave
section, .alpha..sub.I, is thus not possible with the separator
plate 2 of the state of the art. The angles .alpha. are 35.degree.
in each case. FIG. 4-b moreover underlines the fact that the
amplitudes of the respective bead feet and of the two transition
curves between the bead roof and the bead flanks adjacent thereto
are identical.
[0086] FIG. 4-b further illustrates the convex and concave regions
which extend in each case between two dashed lines, which is to say
the section lines CD-CD which in each case represent a
perpendicular to the tangent to the neutral lines of the bead roof
39. Apart from these, the upper and the lower inner radii r.sub.IO
and r.sub.IU and the upper and lower outer radii r.sub.AO and
r.sub.AU are also derived from virtual circles which are indicated
by double-dot dashed lines. Whereas an above-average stiffness of
the beads is given in the concave regions, in which thus inner
radii are present, this is below average in the convex regions, in
which outer radii are present. This is a consequence of the inner
support in the concave regions due to the bead sections facing one
another. The regions of a low bead stiffness are indicated at g,
the regions of a high bead stiffness are indicated at h. Leakages
can occur due to this non-uniformly distributed bead stiffness,
since media can flow through the sections of a low bead stiffness
and penetrate into regions, in which these media should not enter.
The present invention provides a remedy for this.
[0087] Comparable representations of a bead 3 as represented in
FIG. 4 are given in FIG. 5, but here now for a first embodiment of
a separator plate 2 according to the invention. Whereas in the
preceding example of the state of the art, the cross sections
perpendicular to the tangent to the neutral lines of the bead roof
39 are identical at all points of the wave-like course of the bead
roof 39, here they significantly differ from one another. For this
reason, FIG. 5 comprises three cross-sectional representations,
wherein FIG. 5-c represents the cross section at inflection points,
i.e. the sections AE-AE and DE-DE of FIG. 5-b. FIG. 5-c thus
corresponds to FIG. 4-c. FIG. 5-d represents the cross section
BE-BE at the wave peak and FIG. 5-e the cross section CE-CE at the
wave trough, of the bead of FIG. 5-b. The width of the bead roof
39, W.sub.D remains constant over the entire wave-like course of
the bead roof 39 and is 1.6 mm as in the preceding example of the
state of the art. The inflection points, which delimit the convex
sections of the bead 3 from the concave sections, as in the
preceding example are represented by dashed lines which is to say
lie on the two section lines AE-AE and DE-DE. The line T marks the
main extension direction of the bead 3 and results from the
connection line of the inflection points of the neutral lines of
the bead roof. In the convex regions, whose bead flanks 38, 38' are
characterised in FIG. 5-b by a hatching in each case, the base
width W.sub.A of the respective bead flanks 38, 38 is reduced such
that beginning at the inflection point, it reduces up to the apex
point and increases again from the apex point up to the next
inflection point. The base width at the inflection points is 0.85
mm, and at the apex point in contrast is only 0.65 mm. In the
concave regions, the width W.sub.I of the respective bead flank 38,
38' in contrast runs in a constant manner with a base width of 0.85
mm. The total width of the bead W.sub.T thus alternates between 3.1
and 3.3 mm. The amplitude of the bead feet here is somewhat larger
than the amplitude of the transition lines between the bead roof
and bead flanks, and the ratio is roughly 1.25:1.
[0088] The flank angle of the concave region a1 accordingly remains
constant over the respective concave region, and it is 35.degree.,
as the angle .alpha. at the inflection points. In contrast, the
flank angle .alpha..sub.A of the convex region, beginning at the
inflection point, increases from 35.degree. to 60.degree. at the
apex point and then reduces again to the next inflection point to
35.degree.. The bead flank in the region, in which it has a low
bead stiffness in the state of the art--cf. the characterisations g
in FIG. 4-b--is stiffened by way of the steeper flank angle, so
that as a whole, the bead has a constant stiffness over its
wave-like course.
[0089] Here, it is to be noted that the references W.sub.A and
.alpha..sub.A each relate to the convex sections, and the
references W.sub.1 and .alpha..sub.1 each relate to the concave
sections and thus jump from one bead flank to the opposite one at
each inflection point.
[0090] FIG. 6 again with five part-pictures represents a second
embodiment of a separator plate 2 according to the invention, by
way of details of its bead 3. Again the cross section at the
inflection points, which is represented in FIG. 6-c, corresponds
essentially to the cross section of FIG. 4-c, since the bead 3 here
seems to be formed symmetrically. However, FIG. 6-b illustrates the
fact that the bead flanks 38, 38' in the concave regions between
the inflection points are each widened, so that here too, a bead 3
as a whole has an asymmetrical course.
[0091] The bead 3 of the embodiment according to FIG. 6 basically
differs from the bead 3 of the embodiment according to FIG. 5 in
that the bead roof 39 is designed somewhat more narrowly,
specifically only has a width W.sub.D of 1.2 mm.
[0092] The base width of the bead flanks W is 0.6 mm at the turning
points. The outer flank W.sub.A of the bead extends with this base
width from inflection point to inflection point. In contrast, the
base width of the inner flank W.sub.I, beginning at an inflection
point, enlarges from 0.6 mm to 0.8 mm at the wave trough, so as to
reduce again to 0.6 mm in its course up to the next inflection
point. The total width W.sub.T of the bead 3 in this embodiment
varies between 2.4 and 2.6 mm.
[0093] Accordingly, the flank angle of the outer flank
.alpha..sub.A remains constant, and here it is 34.degree.. In
contrast, the flank angle of the inner flank .alpha..sub.I
decreases over the course of the concave section from inflection
point to inflection point, from 34.degree. to 26.degree. at the
wave trough, so as to increase again to 34.degree.. On account of
this, the bead stiffness reduces in the regions which in FIG. 4-b
are characterised by h due to their above-average bead stiffness,
and the bead stiffness is thus homogenised at both bead flanks 38,
38' over the wave-like course of the bead 3, so that leakages are
prevented. The regions, in which the base width of a bead flank 38,
38' changes, are characterised by hatching in FIG. 6-b.
[0094] Rounding up, it should be emphasised that the amplitudes of
the bead feet are roughly only 2/3 of the amplitude of the
transition lines between the bead roof 39 and the bead flanks 38,
38'.
[0095] FIG. 7 represents an embodiment of the invention, with which
the base width of the bead flank W.sub.A decreases and increases
again over the convex sections and the base width of the bead flank
W.sub.I increases and reduces again over the concave sections. A
hatching of the regions, in which the base width changes, has
therefore been done away with. As with both preceding embodiment
examples, T marks the main extension direction of the bead in the
represented detail. The flank angle .alpha..sub.A over a convex
section thus undergoes an increase up to the apex point and a
decrease follows this, and in a concave section the flank angle
.alpha..sub.I in contrast undergoes a decrease, subsequent to which
an increase follows after the apex point. The embodiment example
according to FIG. 7 thus unifies both approaches which have been
applied separately from one another in the embodiment examples of
FIGS. 5 and 6, for homogenising the bead thickness over the
wave-like course of the bead roof, by which means a particularly
effective and thus advantageous homogenisation of the bead
thickness is obtained.
[0096] Specifically, the width of the bead roof W.sub.D is 1.2 mm,
whereas the bead flanks at the apex point which is further from the
main extension line T have a minimum of their width W.sub.A of 0.6
mm, which is followed by an increase up to the next inflection
point to a width W of 1 mm and further up to the apex point lying
closer to the main extension line T to a maximum of the width
W.sub.I of 1.4 mm. The flank angles .alpha. at the inflection
points are 21.degree., and the flank angles .alpha. are therefore
shallower than in the preceding embodiment examples. The flank
angle .alpha..sub.A increases to 42.degree. towards the apex point
remote from to the main extension line T, and the flank angle
.alpha..sub.I decreases to 16.degree. towards the apex point lying
closer to the main extension line T.
[0097] It is particularly noticeable that the total width WT of the
bead 3 remains constant over the complete section, in which the
bead roof 39 runs in a wave-like manner, by which means the spatial
requirement of the embodiment according to FIG. 7 is particularly
low, so that this embodiment is particularly advantageous. The
total width W.sub.T of the bead 3 is 3.2 mm here.
[0098] FIG. 8 illustrates a further embodiment of a separator plate
2 according to the invention, now on its own and by way of a plan
view of a section of the bead 3, whose bead roof runs in a
wave-like manner in the represented section.
[0099] As in the embodiment example of FIG. 7, the flank angle of
the convex sections is enlarged, as well as the flank angle of the
concave sections reduced. Accordingly, the base widths at the apex
points, thus at the wave peaks and troughs, are enlarged compared
to the base widths of the inflection points. As with the embodiment
example of FIG. 7, the total width W.sub.T of the bead 3 runs in a
constant manner in the represented section with a wave-like course
of the bead roof 39. Whereas the bead feet run in a straight line
in the embodiment example of FIG. 7, here the bead feet run with a
significantly reduced amplitude, which is roughly 0.45 times the
amplitude of the delimitation lines of the bead roof.
[0100] FIG. 9 represents a section of a bead 3 of a separator plate
2 according to the invention, said bead comprising continuations 33
on both bead flanks 38, 38', as has already been explained in the
context of FIG. 2. Here, it is clear that the continuations on both
bead flanks 38, 38' are periodically arranged at a distance
.lamda./2, and specifically in each case in the region of the
inflection points of the wave-like course of the bead roof 39. The
continuations 33 serve for leading a medium through the sealing
barrier of the bead 3, and this being at that surface of the layer
2a of the separator plate 2 which is way from the viewer,
specifically between the two layers 2a and 2b. It is evident from
FIG. 9 that the continuations each consist of two feet which in
FIG. 9-b extend vertically, and of two flanks as well as a roof,
wherein the feet of the continuations, although lying in the same
plane as the bead feet, the total height of the continuations
however is smaller than the height of the bead 3, so that the
continuations only marginally influence the pressing behaviour of
the bead. The bead feet 37, 37' are interrupted in the region of
the continuations. The continuations 33 are only formed in the
layer 2a lying at the top. The bead of this embodiment corresponds
to that of the embodiment according to FIG. 5 with regard to its
remaining design, in particular with regard to the wave-like course
of the bead roof 39 and the reduction of the base width W.sub.A and
the increase of the flank angle .alpha..sub.A in the convex regions
relative to the adjacent inflection points.
[0101] FIG. 10a shows a section of a bead 3 of a separator plate 2
according to the invention, said separator plate having two
continuations 33 distanced to one another by a wavelength k, only
on the bead flank 38 which lies at the bottom in the figure. The
continuations here serve as a barrier between the channel structure
which is not represented and which connects below the represented
detail, and the sealing structure. They prevent medium outside the
electrochemically active region from flowing past the gas diffusion
layers 44 and 30 44' shown in FIG. 2-b and thus not being available
to the electrochemically active electrodes 42, and 42'. This would
lead to unacceptable loses on utilisation of the combustion gases
and thus to a significant reduction in the efficiency of the
electrochemical cell
[0102] FIG. 10b shows a section of a bead 3 of a separator plate
according to the invention. This is an embodiment, in which only
one bead flank 38 (with bead foot 37) changes, whereas the flank
38' which in this case lies opposite the continuations remains
constant and thus the bead foot 37' runs parallel to the bead root
39. The increase of the flank angle in concave regions and
represented in FIG. 10b is only one possibility. In a further
embodiment (represented in FIG. 10c) the flank angle increases from
the infection points (.alpha. and .alpha..sub.A=21.degree.) to the
apex point in the concave regions (.alpha..sub.1=32.degree.). The
advantage of the respective embodiment results from a targeted
possibility of adapting the bead characteristics to the geometric
changes by way of incorporating the continuations 33 into the bead
flanks 38
[0103] The described, single-side changes of the flank angle is not
only limited to the regions, in which the continuations 33 are
incorporated into a bead flank, but can analogously be applied n
any other region of the wave-like bead region on a separator plate
2, 2'. Here, either the bead flank which faces the active region or
the outwardly directed bead flank can be adapted and this can also
be varied individually in the different regions of the separator
plate, according to the local demands on the bead
characteristics.
[0104] A further embodiment of a separator plate 2 according to the
invention is shown in FIG. 11 by way of an oblique view and a plan
view, wherein here, both layers 2a, 2b of the separator plate 2 are
represented, in contrast to the previous oblique views with the
exception of FIG. 9-a. Here, the bead flanks run with a constant
base width, and here weld connections 60, 60' which essentially
with their radius run concentrically to that of the bead feet 37,
37' of the two layers 2a, 2b of a separator plate 2 are sectionally
provided in the convex regions, for homogenising the bead pressing.
The extension of the weld connections 60, 60' here corresponds
precisely to the extension of the convex region, i.e. from a
perpendicular to the tangent to the neutral lines of the bead roof
39 through a first inflection point up to the a perpendicular up to
the tangent to the neutral lines of the bead roof 39 through a
second inflection point adjacent to the first inflection point. The
weld connections are herein provided in all shown convex regions,
so that weld connections are given on both sides of the bead.
[0105] FIG. 12 shows a variant of the embodiment of FIG. 11, with
which embodiment it is merely the extension of the weld seams which
is reduced, compared to the embodiment of FIG. 11. Here it is
roughly 20% of the wavelength .lamda..
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