Title of Invention

HEAT-RESISTANT FILTER LAYER, FILTER BODY, AND PROCESS FOR PRODUCING IT

Abstract The invention relates to a heat-resistant filter layer (1) made from a material assembly of fibers material assembly of fibers which is at least partially pervious to a fluid, having at least one filter section (2) and at least one boundary region (3), the filter layer (1) has a different, for example a reduced layer thickness (4), in the at least one boundary region (3) than in the at least one filter section (2), and in that the filter layer (1) being developed with the fiber assembly being compressed or compacted.
Full Text Heat-resistant filter layer, filter body, and process for
producing it
The invention relates to a heat-resistant filter layer made
from a material which is at least partially permeable to a
fluid, to a filter body having at least one heat-resistant
filter layer of this type, and to a process for producing a
filter body of this type. These filter bodies are used in
particular for the purification of exhaust gases from mobile
internal combustion engines used in automotive engineering.
If new vehicle registrations in Germany are considered, it
will be found that in 2000 around one third of all newly
registered vehicles have diesel engines. By tradition, this
percentage is significantly higher than in, for example,
France and Austria. This increased interest in diesel vehicles
stems, for example, from the relatively low fuel consumption,
the currently relatively low prices of diesel fuel, but also
from the improved driving properties of vehicles of this type.
A diesel vehicle is also very attractive from environmental
aspects, since it has a significantly reduced emission of CO2
compared to gasoline-powered vehicles. However, it should be
noted that the level of soot particulates produced during
combustion is well above that of gasoline-powered vehicles.
If the purification of exhaust gases, in particular of diesel
engines, is considered, it is possible for hydrocarbons (HC)
and carbon monoxide (CO) in the exhaust gas to be oxidized in
a known way by, for example, being brought into contact with a
catalytically active surface. However, it is more difficult to
reduce nitrogen oxides (NOx) under oxygen-rich conditions. A
three-way catalytic converter, as is used, for example, in

spark-ignition engines, does not provide the desired effects.
For this reason, the selective catalytic reduction (SCR)
process has been developed. Furthermore, NOX adsorbers have
been tested for use for the reduction of nitrogen oxides.
Discussions have long been ongoing as to whether particulates
or long-chain hydrocarbons have an adverse effect on human
health, but to date no definitive verdict has been reached.
Irrespective of this, it is clearly desirable that emissions
of this nature should not be released to the environment above
a certain tolerance range. In this respect, the question
arises as to what filtering efficiency is actually required in
order to be able to comply with the well known statutory
guidelines even in the future. If current exhaust emissions
from commercially available vehicles in the Federal Republic
of Germany are considered, it can be concluded that most
passenger automobiles certified under EU III in 1999 are also
able to satisfy the requirements of EU IV if they are equipped
with a filter with an efficiency of at least 30 to 40%.
To reduce the levels of particulate emissions, it is known to
use particulates traps which are constructed from a ceramic
substrate. They have passages, so that the exhaust gas which
is to be purified can flow into the particulates trap. The
adjacent passages are alternately closed off, so that the
exhaust gas enters the passage on the inlet side, passes
through the ceramic wall and escapes again through the
adjacent passage on the outlet side. Filters of this type
achieve an efficiency of approx. 95% over the entire range of
particulate sizes which occur.
In addition to chemical interactions with additives and
special coatings, the reliable regeneration of the filter in
the exhaust system of an automobile still constitutes a


problem. It is necessary to regenerate the particulates trap,
since the increasing accumulation of particulates in the
passage wall through which the gas is to flow leads to a
constantly increasing pressure loss which has adverse effects
on engine performance. The regeneration substantially
comprises brief heating of the particulates trap and the
particulates which have accumulated therein, so that the soot
particulates are converted into gaseous constituents. However,
this high thermal loading of the particulates trap has adverse
effects on the service life.
To avoid this discontinuous regeneration, which is a major
factor in promoting thermally induced wear, a system for the
continuous regeneration of filters has been developed (CRT:
continuous regeneration trap). In a system of this type, the
particulates are burnt by means of oxidation with NO2 at
temperatures which are already over 200°C. The NO2 which is
required for this purpose is often generated by an oxidation
catalytic converter arranged upstream of the particulates
trap. However, in particular for use in motor vehicles using
diesel fuel, this gives rise to the problem that there is only
an insufficient level of nitrogen monoxide (NO) which can be
converted into the desired nitrogen dioxide (NO2) in the
exhaust gas. Consequently, it has not hitherto been possible
to ensure that continuous regeneration of the particulates
trap in the exhaust system will occur.
Furthermore, it should be borne in mind that, in addition to
non-convertible particulates, oil or additional residues of
additives also accumulate in a particulates trap and cannot
readily be regenerated. For this reason, known filters have to
be replaced and/or washed at regular intervals. Filter systems
of plate-like structure attempt to solve this problem by
allowing vibration-like excitation which leads to these


constituents being removed from the filter. However, this
means that the non-regeneratable fraction of the particulates
in some cases passes directly into the environment without any-
further treatment.
In addition to a minimum reaction temperature and a specific
residence time, it is necessary to provide sufficient nitrogen
oxide for the continuous regeneration of particulates using
NO2. Tests relating to the dynamic emission of nitrogen
monoxide (NO) and particulates have clearly demonstrated that
the particulates are emitted in particular when there is no or
only a very small amount of nitrogen monoxide in the exhaust
gas, and vice versa. What this means is that a filter with
true continuous regeneration substantially has to function as
a compensator or store, so that it is ensured that the two
reaction partners are present in the filter in the required
quantities at a given instant. Furthermore, the filter is to
be arranged as close as possible to the internal combustion
engine in order to be able to reach temperatures which are as
high as possible immediately after a cold start. To provide
the required nitrogen dioxide, an oxidation catalytic
converter is to be connected upstream of the filter, so as to
react carbon monoxide (CO) and hydrocarbons (HC) and in
particular also to convert nitrogen monoxide (NO) into
nitrogen dioxide (NO2). If this system comprising oxidation
catalytic converter and filter is arranged close to the
engine, a suitable position is in particular upstream of a
turbocharger which is often used in diesel motor vehicles to
increase the boost pressure in the combustion chamber.
If these basic considerations are looked at, the question
arises, for actual deployment in automotive engineering, as to
how a filter of this type, which in such a position and in the
presence of extremely high thermal and dynamic loads has to


achieve a satisfactory filtering efficiency, is constructed.
In this context, account should be taken in particular of the
spatial conditions, which require a new design of filters.
Whereas the maximum possible volume was to the fore in the
case of conventional filters, which were arranged in the
underbody of a motor vehicle, in order to ensure a long
residence time of the as yet unreacted particulates in the
filter and therefore a high efficiency, if the filters are
arranged close to the engine, there is not sufficient space or
room available.
For this purpose, a new concept has been developed, mainly
referred to by the term "open filter system". These open
filter systems are distinguished by the fact that there is no
need for the filter passages to be alternately closed off by
structural means. In this context, it is provided that the
passage walls be constructed at least in part from porous or
highly porous material and that the flow passages of the open
filter have diverting or guiding structures. These internal
fittings cause the flow and the particulates contained therein
to be diverted toward the regions made from porous or highly
porous material. Surprisingly, it has emerged that the
particulates, as a result of being intercepted and/or
impacting, are retained on and/or in the porous passage wall.
The pressure differences in the flow profile of the flowing
exhaust gas are of importance to this effect occurring. The
diversion additionally makes it possible to produce local
reduced pressure or excess pressure conditions, leading to a
filtration effect through the porous wall, since the
abovementioned pressure differences have to be compensated
for.
The particulate trap, unlike the known closed screen or filter
systems, is open, since there are no flow blind alleys. This


property can therefore also be used to characterize
particulate filters of this type, so that, for example, the
"freedom of flow" parameter is suitable for describing the
systems. By way of example, a "freedom of flow" of 20% means
that, when viewed in cross section, it is possible to see
through approx. 2 0% of the surface area. In the case of a
particulate filter with a passage density of approx. 600 cpsi
(cells per square inch) with a hydraulic diameter of 0.8 mm,
this freedom of flow would correspond to a substantially
continuous area of over 0.1 mm2. To provide a better
explanation, it can also be stated that a particulate filter
is referred to as open if in principle particulates can fully
pass through it, even particulates which are considerably
larger than the particulates which are actually to be filtered
out. Consequently, a filter of this type cannot become blocked
even in the event of an agglomeration of particulates during
operation. One suitable method for measuring the openness of
the particulate filter is, for example, to test the maximum
diameter of spherical particles which can still trickle
through a filter of this type. In the present applications, a
filter is open in particular if spheres with a diameter of
greater than or equal to 0.1 mm can still trickle through,
preferably spheres with a diameter of over 0.2 mm, and in
particular spheres with a diameter of more than 0.3 mm.
In particular with a view to realizing an open filter system
of this type, it is an object of the present invention to
provide a heat-resistant filter layer which is suitable in
particular for use in the context of continuous regeneration
and is especially suitable for the demands which result from
this application. In this respect, the filter system has to be
able to withstand the high thermal and dynamic loads in the
exhaust system of a passenger automobile, which stem from the
pulsed emission of very hot exhaust gas. Furthermore, it is


intended to provide a corresponding filter body which is
suitable for significantly reducing the levels of particulates
in the exhaust system. In addition, it is intended to provide
a process for producing the filter body. The filter layer
should be configured in such a way that the formation of
connections by joining, in particular solder connections or
welded connections, is promoted.
These objects are achieved by a heat-resistant filter layer
having the features of patent claim 1, a filter body for
purifying exhaust gases from an internal combustion engine
having the features of patent claim 7, and a process for
producing a filter body of this type comprising the process
steps described in patent claim 15. Further advantageous
configurations are described in the respective dependent
claims; the features disclosed therein can be employed
individually or in any desired and suitable combination with
one another.
The heat-resistant layer is at least in part made from
material which is permeable to a fluid and has at least one
filter section and at least one boundary region. The filter
layer according to the invention is distinguished by the fact
that it has a different layer thickness in the at least one
boundary region than in the at least one filter section. In
this respect, the filter layer has different regions which
each have different functions. Whereas the filter section
serves primarily to filter out the particulates or the like
contained in the exhaust gas and to at least temporarily store
or accumulate them in cavities, pores or the like or on the
filter material, the at least one boundary region serves to
form connections by joining. Designing the filter layer to
have different layer thicknesses in these regions creates a
clearly apparent spatial boundary, so that assembly errors


relating, for example, to the manufacture of a filter body
which has such a filter layer are avoided.
With regard to the spatial arrangement of the at least one
boundary region and of the at least one filter section with
respect to the filter layer, it should be noted that the
filter section is preferably arranged in a central region of
the filter layer. The at least one boundary region is
preferably formed at least close to an edge, although under
certain circumstances it is also possible for the boundary
region to be formed all the way around the filter section,
like a frame. In this respect, it is possible to form a
relatively large-area, centrally arranged filter section which
is surrounded by at least one boundary region; as an
alternative, it may under certain circumstances, however, also
be appropriate for a plurality of filter sections to be
provided, so that they are each delimited by at least one
boundary region (in particular designed in a similar manner to
a frame), so as to resemble a chessboard pattern. The
configuration of the heat-resistant filter layer with a
plurality of filter sections which are each surrounded by at
least one boundary region allows relatively strong connections
to be made within a corresponding filter body, since
connecting adjacent filter layers in the plurality of boundary
regions, which are also arranged in central regions of the
filter layer, creates an areal, uniformly distributed
attachment.
According to a further configuration of the filter layer, the
layer thickness in the at least one boundary region is less
than in the at least one filter section, in particular less
than 60%, preferably less than 50% or even less than 35%.
Configuring the filter layer in this way has the advantage
that a larger volume is provided in the at least one filter

section, which is designed with a greater wall thickness. The
result of this is that sufficient pores, cavities or the like
are provided in this at least one filter section, these pores,
cavities or the like being used to accommodate or store, for
example, soot particulates. In this case, with large pores of
this type, in particular particulates with a diameter of from
100 ran to 250 run are accumulated. The heat-resistant filter
layer is preferably made from a fiber material which, for
example, forms a relatively loose assembly of fibers. This
assembly of fibers may, for example, be a woven or knitted
fiber fabric formed from ceramic fibers, but as an alternative
or in addition it is also possible to use metal fibers,
sintered materials, wire fabrics or the like.
The at least one boundary region substantially comprises the
same material as the at least one filter section, preferably
comprising a compressed or compacted fiber assembly. Whereas a
fluid, in particular an exhaust-gas stream, can flow through
the filter material in the region of the at least one filter
section, the at least one boundary region is preferably
substantially impervious to a fluid. This means that at least
partial compacting of the fiber material of this nature has
been performed and that a large number of cavities, openings,
pores, apertures or the like have been closed up. In this
respect, the reduced layer thickness is the consequence of the
filter material being compressed.
The impervious nature of the filter material in the at least
one boundary region means that, for example, connecting
material or additional material (solder, welding additives or
the like) can be applied in targeted fashion to the surface in
the at least one boundary region, while preventing the joining
agent or welding additives from accumulating in the interior
of the fiber material when they are heated, so that they would


not be available for joining adjacent filter layers. Depending
on the joining agents which are required to form connections
by joining, suitable compression is to be carried out, so that
the layer thickness is reduced in the at least one boundary
region, advantageously by at least 40%, in particular at least
50% or even by more than 65%. This results, in the at least
one boundary region, in layer thicknesses of less than 1 mm,
in particular less than 0.5 mm and even less than 0.1 mm.
According to a further configuration, the at least one
boundary region, starting from an edge of the filter layer,
has a boundary width of at most 30 mm, in particular of at
most 20 mm, preferably of at most 10 mm or even of only at
most 5 mm. This means that in particular the edge region of
the filter layer is used to form connections by joining. This
is particularly advantageous since it is particularly these
regions which are subjected to particular loads in view of the
pulsating flow of exhaust gas. Designing the filter layer to
have a relatively strongly compressed filter material in this
edge region prevents detachment phenomena, since the assembly
of fibers is significantly stronger there. Moreover, the
adjacent filter layers in a corresponding filter body are
connected to one another in this edge region, with the result
that vibration or flapping of these regions is also avoided.
The boundary width is to be designed in particular with a view
to the dynamic loads which occur in use; account should also
be taken of the thermal expansion characteristics of the
filter layer. In this respect, it is advantageous to select
boundary regions which are as narrow as possible if the filter
layer is exposed to moderate dynamic loads and moderate to
high thermal loads.
Furthermore, it is proposed that the filter layer comprise at
least one fiber layer, which preferably has a fiber layer


thickness of at most 3 mm, in particular of at most 1 mm and
preferably of at most 0.5 mm. The fiber layer thickness is to
be selected in particular taking account of the exhaust-gas
stream which is to be purified and/or the particulates
contained therein. Furthermore, it should be noted that a
greater fiber layer thickness provides a greater storage
volume and/or an increased number of fibers, and consequently
filter layers of this type do not have to be regenerated as
frequently, and consequently can be fitted even in areas which
are remote from the engine, such as for example in the
underbody of an automobile. In positions which are remote from
the engine of this nature, the exhaust gas only reaches the
temperature required for regeneration after a relatively long
period of time, and consequently sufficient storage capacity
for this period of time has to be provided. If it is desirable
for the filter layer to be arranged in very hot areas of an
exhaust system, in particular close to the engine, possibly
even continuous regeneration may be ensured, and consequently
in this case it is preferable to use filter layers with a very
small fiber layer thickness.
An advantageous refinement of the filter layer comprises at
least one metal layer, which preferably delimits the filter
layer on the outside and in particular has a thickness of at
most 0.05 mm, preferably of at most 0.03 mm or even of at most
just 0.015 mm. A fluid can preferably penetrate through this
metal layer in the at least one filter section, i.e. this
metal layer preferably has openings, apertures or the like.
The metal layer preferably extends as far as or over the at
least one boundary region, in which case the metal layer in
the at least one boundary region is advantageously configured
so as to be impervious to a fluid. Suitable materials for a
metal layer of this type are in particular aluminum-chromium
alloys, as are already known from the production of metallic


honeycomb bodies as catalyst supports for the purification of
exhaust gases. The metal layer may in this case be formed as a
coating or as a separate foil.
It is particularly advantageous for the filter layer to be a
sandwich structure and to have at least one fiber layer and at
least one metal layer. In this case, the metal layer
preferably forms a sleeve which surrounds the fiber layer, so
that the fiber layer is arranged captively inside the at least
one metal layer. In this context, the term sleeve is to be
understood as meaning an arrangement of the at least one metal
layer in which the at least one metal layer also extends at
least in part beyond the periphery of the fiber layer, in
particular completely surrounds the fiber layer. In this
respect, at least in part, a sleeve is formed over the entire
periphery of the fiber layer. Accordingly, the metal layer
surrounding the periphery of the fiber layer in this way leads
to a relative movement of the fiber layer with respect to the
at least one metal layer being impeded in a positively locking
manner in at least one direction.
The formation of a sandwich structure of this type combines a
number of advantages which are of significance in particular
with a view to a filter layer of this type being arranged
close to the engine. The at least one metal layer forms a type
of protective sleeve which protects the interior fiber layer
from the pressure shocks and temperature peaks which occur.
The fiber layer represents a significantly looser assembly of
fibers than the metal layer. The fiber layer may in this case
have a very high porosity, since the presence of a metal layer
protecting it means that it does not have to be designed
primarily for strength. In this respect, it is possible in
particular to realize large free spaces, pores or the like in
the fiber layer. This is boosted in particular by the fact


that the at least one metal layer is constructed in a form
similar to a strip or sheet, i.e. offers a relatively large
bearing surface area. Consequently, in this case it is
possible to use fiber materials which are packed significantly
more loosely than, for example, with known wire meshes which
have hitherto been used to ensure the dimensional stability of
the filter layers.
Since then, sandwich structures of this type have been
designed in such a way that there is in each case one
supporting structure arranged on both sides of the filter
material (in particular braided wire fabrics), and this
sandwich has then been bent or deformed into the desired
shape. These sandwich structures have been arranged in the
exhaust-gas stream in such a way that the periphery (or end
face) of the filter material was exposed to the pulsating
exhaust-gas stream without protection. This led to detachment
phenomena in particular in these end regions. To ensure that
the fiber material is fixed between the wire fabrics for a
prolonged period of time, this sandwich structure had to be
pressed together under a high pressure, over a large area (in
some cases even over the entire surface area) which, on
account of the resultant very small pores or free spaces for
the accumulation of particulates, had noticeable adverse
effects on the efficiency of the filter material and led to an
undesirably high pressure loss across the filter. This is
avoided in a simple way in the filter assembly according to
the invention, since the fact that the at least one covering
layer engages around the periphery of the fiber layer means
that the fiber layer is arranged captively in the interior.
A further aspect of the invention proposes a filter body for
purifying exhaust gases from an internal combustion engine,
which comprises at least partially structured layers which are


stacked and/or wound in such a way as to form passages through
which an exhaust gas can flow. The filter body according to
the invention has at least one heat-resistant filter layer as
described above. The filter body can be constructed in
accordance with conventional principles, such that the
passages are alternately closed off, with the result that the
entire flow of exhaust gas flows through the heat-resistant
filter layer. However, it is preferable to use a configuration
of the filter body in accordance with the "open system"
described in the introduction, i.e. with a freedom of flow of
at least 20%, in particular at least 40% or even of over 50%.
This means that the open filter body has cross sections
through which medium can flow freely over the entire length of
the passages, with means for generating pressure differences
and/or means for influencing the direction of flow in the
passage being provided within the passages. This causes the
exhaust gas which is to be purified to be at least partially
diverted toward the heat-resistant filter layer, to at least
partially penetrate through the filter layer and thereby to
cause particulates to accumulate and/or be stored in the
filter material.
The configuration of the filter body with layers which
comprise at least one structured sheet-metal foil and at least
one substantially smooth or unstructured filter layer is
particularly preferred, the layers being connected to one
another by joining, in particular by soldering or welding, in
at least one connecting section. This means that the at least
one structured sheet-metal foil and the at least one filter
layer are stacked and/or wound, with passages being formed as
a result of the structure of the sheet-metal foil, which in
principle functions as a spacer between adjacent smooth filter
layers. These passages preferably run substantially parallel
to one another. To ensure that a relative movement of the


layers of the filter body is substantially avoided even under
high thermal and dynamic loads, these layers are to be
connected to one another by joining. In particular solder
joints or welded joints, as are already known from the
production of metallic honeycomb bodies as catalyst supports
in automotive engineering, are suitable for this purpose.
In this context, it is particularly advantageous for the at
least one connecting section to be arranged in the at least
one boundary region of the filter layer. This means, for
example, that the connecting section is preferably to be
designed to be smaller than if it covered the entire extent of
the filter layer. This is advantageous because in the present
case two different materials (sheet-metal foil and filter
layer) are being connected to one another, these materials
having different coefficients of thermal expansion. Connecting
these adjacent components in just a relatively small
connecting section ensures that this expansion is not
significantly impeded as a result of the components being
connected to one another. This has particularly beneficial
effects on the service life of a filter body of this type,
since the probability of cracks forming in the vicinity of the
connecting section is significantly reduced. A spatially
coinciding arrangement of the at least one connecting section
and the at least one boundary region leads to particularly
durable connections, since the filter layer is impervious to
the joining agent (solder or welding material) in the boundary
region, and consequently this material continues to be made
available even while the connection by joining is being formed
in the contact region between the components which are to be
connected to one another.
In view of the fact that the heat-resistant filter layer
according to the invention is designed with different layer


thicknesses, it is particularly advantageous for there to be
means for compensating for the different layer thicknesses of
the filter layer in the filter body. When an adjacent
component is brought to bear against the filter layer
according to the invention, the components bear against one
another in a substantially positively locking manner in the
region of the at least one filter section. Since, by way of
example, the sheet-metal foils have a substantially planar
bearing surface, but the filter layer according to the
invention forms a shoulder at the transition from the at least
one filter section to the at least one boundary region, a type
of gap would form between the sheet-metal foil and the filter
layer in the at least one boundary region. The size of the gap
would be such that solder or welding material alone would
often be unable to bridge it. In this respect, there is a need
for means for compensating for this gap, which ensure contact
between adjacent components of the filter body even in the at
least one boundary region of the filter layer. The following
text will explain, by way of example, a number of different
compensation means.
If the layer thickness of the filter layer is reduced in the
at least one boundary region compared to the at least one
filter section, it is proposed that the at least one boundary
region have a deformation region which at least partially
overlaps itself and is preferably even soldered together. This
means that the at least one boundary region, which is in
particular arranged close to at least one edge of the filter
layer, is designed with a greater boundary width than a
connecting section is subsequently to generate. That part of
the boundary region which projects beyond the connecting
section is then bent over, folded, creased or the like in such
a way that these projecting regions project back into the
connecting section. Consequently, partial regions of the


boundary region lie adjacent to one another, preferably even
bear against one another, so that the layer thickness is at
Least doubled at least in parts of the at least one boundary
region. This is recommended, for example, for filter layers
which have a layer thickness in the at least one boundary
region which amounts to substantially just 50% of the layer
thickness in the at least one filter section. Therefore,
during the deformation of the at least one boundary region, a
substantially planar bearing surface for adjacent components
of the filter body is provided at least on one side of the
filter layer. To prevent this deformed or bent-over partial
region of the at least one boundary region from starting to
flap or vibrate as a result of the dynamic loads in an exhaust
system of an automobile, or even becoming detached from the
filter layer, it is particularly advantageous for the
overlapping part of the boundary region, which preferably
bears against the boundary region itself, also to be welded or
soldered to itself. In terms of a welding process, the roller
seam welding process has proven particularly suitable.
According to an advantageous refinement, it is proposed that,
in the case of a design of the filter layer with a reduced
layer thickness in the at least one boundary region, that zone
of a layer, in particular of a structured sheet-metal foil,
which is arranged adjacent to the at least one boundary region
has a height which is greater than a (its) remaining zone. If
the adjacent layer is a structured sheet-metal foil, it is
particularly advantageous for this to be formed in the zone
with a structure height which is greater than that of the
remaining zone, with a material thickness of the sheet-metal
foil preferably being equal in the various zones. Contrary to
the principle described above, according to which the
different layer thicknesses are compensated for by the filter
layer itself, in this case it is proposed that the


compensation be carried out by means of components arranged
adjacent to the filter layer.
As has already been explained, the structure of the sheet-
metal foil serves primarily as a spacer for the adjacent
filter layers. Accordingly, in the case of a configuration of
the filter layers with different structure heights, different
distances between the adjacent filter layers are also bridged.
In the case of the structure height being designed to be
larger in the zone arranged adjacent to the at least one
boundary region compared to the remaining zone arranged
adjacent to the filter section, it is ensured that the sheet-
metal foil is in contact with adjacent filter layers over the
entire length of the passages, with the result that it becomes
possible for these components to be connected to one another
by joining (in particular in the at least one boundary region.
Accordingly, the structure height is to be increased by a
similar percentage as a reduction in the layer thickness at
the transition from the at least one filter section to the at
least one boundary region.
According to yet a further configuration, the filter body is
provided with at least one additional compensation layer,
which is preferably arranged adjacent to the at least one
boundary region of the filter layer with a reduced layer
thickness. Consequently, these additional compensation layers
do not extend over the entire length of the filter body, but
rather preferably only substantially over the connecting
section in which the adjacent components of the filter body
are connected to one another. In this case, the compensation
layer substantially fills the gap which has been produced as a
result of the reduced layer thickness of the filter layer in
the at least one boundary region, and is preferably likewise
connected to the adjacent components by joining, in particular


by soldering. Under certain circumstances, it is also possible
for the additional compensation layer to be designed to be
longer than the at least one boundary region, in which case it
at least partially projects beyond the filter layer or the at
least one sheet-metal foil. This projecting subregion may if
appropriate also be arranged around a boundary region of the
filter layer, so that two gaps which are formed with respect
to a boundary region of the filter layer in the vicinity of
the edge can be compensated for using one compensation layer.
In this way, the edges of the filter layer, which are exposed
to particularly high dynamic loads, are provided with further
protection, with the number of additional compensation layers
which are to be integrated in the filter body being reduced.
A further aspect of the invention proposes a process for
producing a filter body as described above, which comprises
the following steps:
- production of at least one heat-resistant filter layers-
- formation of at least one boundary region of the at least
one filter layer of reduced layer thickness;
- provision of means for compensating for the different layer
thicknesses of the at least one filter layer;
- stacking and/or winding of at least one filter layer and at
least one structured sheet-metal foil so as to form a
honeycomb body with passages through which an exhaust gas can
flow;
- supplying solder in at least one connecting section between
the at least one filter layer and the at least one sheet-metal
foil; and
- heating of the honeycomb body in order to form solder
joints in the at least one connecting section.


With regard to the formation of solder joints, reference is
made to the known techniques used for the production of
metallic honeycomb bodies as catalyst support bodies for
mobile exhaust systems of automobiles. In this respect, it is
preferable for nickel-based solders in powder form to be used
as solder, with the heating of the honeycomb body preferably
being carried out in a protective gas atmosphere or a
virtually complete vacuum.
According to a further configuration of the process, the
honeycomb body is introduced into a casing before the solder
is supplied, with the solder, while it is being supplied, also
adhering in at least one attachment region for attaching the
at least one filter layer and/or the at least one sheet-metal
foil to the casing, so that solder joints are likewise
generated during heating in the at least one attachment
region. For this purpose, in a known way the connecting
section and the attachment region are first of all provided
with a bonding agent to which the pulverulent solder adheres
during the operation of applying the solder. It is also known
to use means which limit the flow of solder (solder stop, oil,
wax, ceramic coating or the like) to delimit the connecting
section and/or the attachment region, and these means may also
be employed here. The introduction of the honeycomb body into
a casing prior to the application of solder means that it is
possible to avoid a plurality of solder-application steps and
to produce uniform solder joints, since these joints are
exposed to the same degree of thermal treatment.
According to a refinement of the process, the at least one
boundary region of reduced layer thickness is formed by the
application of a compressive force to the filter layer in the
at least one boundary region. This compressive force can be
produced, for example, by means of a roller or the like, with


this roller pressing the filter layer onto a die or the like,
so that primarily the filter material is compacted. In this
context, it is also possible for this compressive force to be
exerted, for example, in parallel during a welding process.
If, for example, a configuration of the filter layer with a
deformed boundary region is selected, the filter layer can
first of all be deformed in the boundary region, and then
compacted and, at the same time, welded together by means of
the roller seam welding process.
Furthermore, it is proposed that the compensation means be
produced by the deformation of the at least one boundary
region of the filter layer. This means has already been
described in more detail above, and a further, more detailed
description is given in connection with Fig. 5.
According to yet a further configuration of the process, the
compensation means are produced by at least one compensation
layer being arranged between a filter layer and an adjacent
foil. This process step has already been explained above and
is to be described in more detail below with reference to Fig.
5.
The invention will now be explained in more detail on the
basis of the figures, which show particularly advantageous and
particularly preferred configurations of the heat-resistant
filter layer according to the invention and of the filter
body. Furthermore, the figures serve to illustrate the process
according to the invention which is described. Nevertheless,
it should be noted at this point that the invention is not
restricted to the exemplary embodiments illustrated in the
figures.
In the drawing:


Fig. 1 shows a diagrammatic and perspective illustration of a
first embodiment of the heat-resistant layer according to the
invention,
Fig. 2 shows a side view of a further embodiment of the
filter layer as a sandwich structure,
Fig. 3 diagramatically depicts an exhaust installation,
Fig. 4 shows a diagrammatic and perspective view of a detail
of an embodiment of the filter body according to the
invention,
Fig. 5 diagrammatically depicts a detailed view of a further
embodiment of the filter body,
Fig. 6 shows a diagrammatic and perspective view of an
embodiment of a sheet-metal foil for compensating for the
different layer thicknesses of the filter layer,
Fig. 7 shows a diagrammatic and perspective illustration of
an embodiment of the filter body, and
Fig. 8 diagrammatically depicts the sequence of one
configuration of the process according to the invention for
producing a filter body.
Fig. 1 shows a diagrammatic and perspective view of an
embodiment of the filter layer 1 according to the invention,
through which a fluid can flow at least in a filter section 2
(as indicated by the direction of flow 35) . The filter layer 1
is at least in part constructed from a porous material (cf.
dotted filter region 2) and has two boundary regions 3 in the


vicinity of opposite edges 5. The boundary regions 3 have been
compressed by a compressive force 29 (indicated by the
arrows), and consequently have a reduced layer thickness 4
compared to the filter section 2. The compression is signaled
by the pores or cavities illustrated in section, which are
significantly smaller in the boundary region 3 than in the
filter section 2.
Fig. 2 diagrammatically depicts a sectional view through a
further embodiment of a filter layer 1, which is designed as a
sandwich structure 11, the filter layer 1 having two metal
layers 9 which form a sleeve around a fiber layer 7. The metal
layers 9 each have two boundary regions 3, with the metal
layers 9 being connected to one another by joining in the
boundary regions 3. The connection by joining is in this case
ensured by means of a solder 26, with a solder stop 30 being
provided outside the boundary region 3, preventing the solder
26 from reaching the vicinity of the fiber layer 7 during a
heat treatment. The boundary region 3 extends from an edge 5
of the metal layer 9 over a boundary width 6 of preferably
between 3 and 15 mm. With regard to the material thicknesses,
it can be explained with reference to Fig. 2 that the metal
layers 9 are designed, for example, as metal foils and have a
thickness 10 of less than 0.04 mm. Furthermore, it can be seen
that the fiber layer 7 has a fiber layer thickness 8 which is
preferably in the range from 0.01 mm to 1 mm.
Fig. 2 shows a metal layer 7 which is provided with flow-
guiding surfaces 41. This is designed in particular as a
microstructure. In the embodiment illustrated, this
microstructure or the flow-guiding surfaces 41 fulfils or
fulfil two functions. Firstly, the exhaust gas which flows by
is diverted or swirled up, so that partial gas streams are
diverted toward or penetrate through the adjacent porous wall,


in particular a filter layer according to the invention.
Furthermore, it can be seen that with a microstructure of this
type it is also possible to effect a clamping action with
respect to the inner fiber layer 7. This improves the
stability of the fiber layer 1. Moreover, this enables the
porosity of the metal layers 9 to be increased, since the
clamping forces which are additionally introduced already
sufficiently prevent any possible detachment phenomena in the
fiber layer 7. The filter layer 1, which in Fig. 2 is designed
as a sandwich structure 11, has two layer thicknesses 4, 4',
with the layer thickness 4 in the region of the boundary
region 3 being significantly thinner than the layer thickness
4' in the region of the filter section 2. This figure
illustrates a particular embodiment, since the fiber layer 7
does not extend into the boundary regions 3.
Fig. 3 diagrammatically depicts the structure of an exhaust
system 36 for an internal combustion engine 13. An internal
combustion engine 13 of this type is preferably designed as a
diesel engine. In the direction of flow 35 of the exhaust gas,
the exhaust system 36 comprises the following components:
- an upstream oxidation catalytic converter 31,
- a filter body 12 according to the invention,
- a turbocharger 32, and
- a further catalytic converter 34.

The individual components may be arranged in separate casings
or may be partially combined with one another in a single
casing, and are connected to one another via an exhaust pipe
33. As has already been stated in the introduction, it is
particularly advantageous for the filter body 12 to be
arranged as close as possible to the internal combustion
engine. A distance 37 from the internal combustion engine 13
of less than 0.7m, in particular even less than 3 0 cm, is
particularly suitable in this respect. With the individual

components arranged in this way, first of all a sufficient
quantity of nitrogen dioxide is made available with the aid of
the oxidation catalytic converter 31, ensuring (continuous)
regeneration of the accumulated soot particulates in the
filter body 12 arranged immediately downstream. The downstream
catalytic converter 34 may, for example, also be designed as a
hybrid converter, in which case it has partial regions with
different heat capacities. In this context, it is to be
designed in such a way that its heat capacity increases in the
direction of flow.
Fig. 4 shows a diagrammatic and perspective illustration of a
further embodiment of the filter body 12 according to the
invention. The filter body 12 in this case comprises sheet-
metal foils 15, between which there is in each case one filter
layer 1 according to the invention. In the embodiment
illustrated, the filter layer 1 is formed with two metal
layers 9 and a fiber layer 7 arranged between them; the
connection by joining in the boundary region cannot be seen on
account of the sectional illustration. In the excerpt
illustrated here, the filter layer 1 is illustrated only in
the filter section 2, and consequently in this figure also
only the layer thickness 4' is visible.
The sheet-metal foils 15 have a constant material thickness 22
and are in this case provided with a structure, while the
filter layer 1 has a substantially smooth surface. This
structure of the sheet-metal foils 15 helps to form passages
14 through which an exhaust gas can flow in a direction of
flow 35. The sheet-metal foils 15 in this case have different
heights 20 of the structure, so that the passages 14 which are
formed are matched to the characteristics of the incoming flow
of exhaust gas. The embodiment illustrated here substantially
shows a detail of an open filter body. This property is


described by the fact that there is a freedom of flow of at
least 20%. In this context, the term freedom of flow means
that in any desired cross section it is possible to see
through at least 20% of the area, i.e. at least 20% of the
area is free of internal fittings, such as diverting surfaces
39 or the like. In other words, this also means that when a
particulate filter of this type is viewed from the end side,
it is possible to see through at least some of the passages,
provided that the internal fittings are all in approximately
the same installation position, i.e. are arranged aligned one
behind the other. This is typically the case with honeycomb
bodies made from at least partially structured sheet-metal
layers. However, the freedom of flow, in the case of internal
fittings which are not aligned with one another, does not
necessarily mean that it is actually possible to see through
part of a honeycomb body of this type. The sheet-metal foils
15 are provided with apertures 38 and diverting surfaces 39
which divert the exhaust-gas stream toward the filter assembly
1. This produces pressure differences which cause partial
flows of exhaust gas to penetrate through the filter layer 1,
so that soot particulates or the like remain and accumulate in
the fiber layer 7.
Fig. 5 diagrammatically depicts a detailed view of a further
embodiment of the filter body 12, in which a filter layer 1
according to the invention is arranged between two sheet-metal
foils 15. The filter layer 1 once again has two layer
thicknesses 4, 4' with the layer thickness 4 in the boundary
region 3 being designed to be thinner than in the filter
section 2. In a connecting section 16, the sheet-metal layers
15 are connected, in particular soldered (using solder 26), to
the filter layer 1 directly or via a compensation layer 23,
which in this case is additionally arranged in the boundary
region 3 or the connecting region 16. In this case, the sheet-


metal foils 15, the compensation layer 23 and the filter layer
1 end flush at their end sides. The thin boundary region 3 of
the filter layer 1 shown is substantially designed to be twice
as long as the connecting section 16, with a deformation
region 17 having been formed, so that the boundary region 3 at
least partially overlaps itself. The overlapping partial
regions of the edge region 3 now bear against one another and
are even soldered together.
On account of the fact that the layer thickness 4 in the
embodiment illustrated corresponds to approximately 1/3 of the
layer thickness 4' in the filter section, bending over or
folding the boundary region 3 allows the filter layer 1 to be
connected directly to the adjacent sheet-metal layer 15 at
least on one side. In this respect, the boundary region 3 now
fills up 2/3 of the layer thickness 4', so that the additional
compensation layer 23 now bridges the remaining third and
there is then an indirect connection between the filter layer
1 and the opposite sheet-metal foil 15. As an alternative to
an embodiment of this type, it is also possible for the
(undeformed) boundary region 3 to be indirectly connected to
the adjacent sheet-metal foils 15 on both sides by means of a
compensation layer 23, in which case the compensation layer 23
is preferably designed with a deformation region, so that this
deformation region projects around the end-side end of the
boundary region 3, so that a single compensation layer 23
simultaneously fills up both distances between the boundary
region 3 and the sheet-metal foils 15.
Fig. 6 shows a diagrammatic and perspective view of an
embodiment of a sheet-metal foil 15 for compensating for the
different layer thicknesses 4, 4' of the filter layer 1 (not
shown). The structured sheet-metal layer 15 is arranged
adjacent to the filter layer 1, in the manner which has


already been explained, and is used to compensate for the
different layer thicknesses thereof. For this purpose, the
sheet-metal foil 15, in the zone 18, has a structure height 21
which is greater than that of the remaining zone 19, with a
material thickness 22 (not shown) of the sheet-metal foil 15
preferably being equal in the various zones 18, 19.
Accordingly, the magnitude of the structure height 21 of the
zone 18 is to be increased in such a way that contact of the
metal foil 15 is ensured in the zone 18 or the boundary region
3 of the filter layer 1. For example, if the starting point
used is an embodiment of the filter layer 1 as shown in Fig.
5, it is advantageous for the structure height 21 in the zone
18 to be greater than the structure height 21' by an amount
which substantially corresponds to the difference between the
layer thickness 4' and the layer thickness 4. In this case, it
is advantageously possible to dispense with the need for
additional compensation layers.
Fig. 7 shows a diagrammatic and perspective view of an
embodiment of the filter body 12 which comprises a honeycomb
body 2 4 arranged in a casing 27. The honeycomb body 24 is
formed with a plurality of alternately arranged filter layers
1 and structured sheet-metal foils 15, which are first of all
stacked and then wound together in such a way as to produce a
substantially cylindrical configuration of the honeycomb body
24. As an alternative, it is also possible to produce conical,
rectangular or oval configurations, and it is also possible in
each case to provide just one sheet-metal foil 15 and one
filter layer 1, which in particular are wound up together in
helical form. The structured sheet-metal foils 15 and the
filter layers 1 delimit passages 14 through which an exhaust
gas can flow and which extend from one end face 2 5 to the
opposite end face 25. This ensures that it is possible to at
least partially see through these passages 14. This is ensured


with the freedom of flow of at least 20% as explained in the
introduction.
The structured sheet-metal foils 15 and the filter layers 1
are connected to one another by joining, in particular
soldering (preferably high-temperature vacuum soldering), in a
connecting section 16. In addition, the honeycomb body 24 is
attached to the casing 27 in at least one attachment region
28; in this context, it is preferable for the same joining
process to be used (at the same time) as for the connection of
the sheet-metal foils 15 and the filter layers 1 to one
another. The attachment and the connections are not performed
over the entire length 42 of the honeycomb body, with the
result that even under thermal load differential expansions
resulting from the different coefficients of thermal expansion
of the components are possible. The result of this is that no
stresses which would lead to premature loss of the structural
integrity of the filter body are produced in the honeycomb
body 24 or between honeycomb body 24 and casing 27.
Fig. 8 diagrammatically depicts the sequence of one
configuration of the process according to the invention for
producing a filter body 12. This process comprises the
following steps:
a) Production of at least one heat-resistant filter layer 1:
According to step 1, the filter layer 1 is produced by a
central fiber layer 7 being assigned two metal layers 9 which
delimit the fiber layer 7 with respect to the outside, so that
a type of protective sleeve is formed (cf. sandwich
structure). The filter layer 1 is preferably produced from
strip-like or sheet-like raw materials (metal sheets, fabrics,
etc.), by these materials being cut to the desired dimensions.


b) Forming at least one boundary region 3 of the at least one
filter layer 1 of reduced layer thickness 4:
The two opposite boundary regions 3 with reduced layer
thicknesses 4 are formed by the application of a compressive
force 29 to the filter layer 1 (cf. step 1: indicated by
arrows) in the boundary regions 3. This significantly
compresses at least the fiber layer, so that these boundary
regions 3 become substantially impervious to a solder (cf.
step 2). Numerous production processes are suitable for such a
compression process; in this context, pressing using a roller
may be mentioned by way of example.
c) Providing means for compensating for the different layer
thicknesses 4, 4' of the at least one filter layer 1:
As has been explained above, substantially two different
principles, or alternatively a combination of these
principles, are suitable for this purpose. In the
configuration illustrated in step 3, the different layer
thicknesses 4, 4' of the at least one filter layer 1 are
compensated for exclusively by means of the layers arranged
between the filter layers 1. Accordingly, the sheet-metal foil
15 has a plurality of end-side zones with a height 20 which is
designed to be greater than the height 20' in - the central or
intervening remaining zone. In this respect, the adjacent
layers bear against one another over the entire length, so
that relative movement of the layers with respect to one
another is avoided even after connections by joining have been
formed (examples of such movements include flapping or
vibrating of the boundary regions of the filter layers 1).


d) Stacking and/or winding at least one filter layer 1 and at
least one structured sheet-metal foil 15 to form a honeycomb
body 24 with passages 14 through which an exhaust gas can
flow.
The sheet-metal foils 15 and the filter layers 1 are then
stacked in the manner illustrated in step 3 and then shaped
into a cylindrical honeycomb body 24. The boundary regions are
at least in part to be arranged in a plane which is parallel
to an end face 25 of the honeycomb body 24, and in particular
all the boundary regions adjoin at least one end face 25. The
structure of the sheet-metal foils 15 leads to the formation
of passages 14 through which an exhaust gas can flow, ensuring
a freedom of flow of at least 20%. With regard to the winding
process, reference should also be made to known techniques
which are already in widespread use for the production of a
metallic honeycomb structure as a catalyst support body. The
honeycomb body 24 is then also introduced into a casing 27
(cf. step 4), so that the honeycomb body 24 and the casing 27
can then together be provided with a bonding agent and/or the
solder 26.
e) Supplying solder 26 in at least one connecting section 16
connecting the at least one filter layer 1 to the at least one
sheet-metal foil 15:
For this process step too, reference should be made to the
known technique for applying solder to metallic honeycomb
structures which are used, for example, as catalyst support
bodies in exhaust systems for automobiles. In addition to the
use of solid strips of solder or the like, in this context it
is also preferable to use solders in powder form. In this
case, first of all a bonding agent is applied in the contact
regions between the layers which are to be connected to one


another, with a filter body 12 which has been pretreated in
this way then being brought into contact with the pulverulent
solder 26, which adheres to the bonding agent (cf. step 5) .
f) Heating the honeycomb body 24 in order to form solder
joints in the at least one connecting section 16:
To form corrosion-resistant and temperature-resistant
connections between the layers (connecting section 16) and to
attach them to the casing 27 (attachment region 28), it has
proven particularly expedient to use a high-temperature vacuum
process. In this case, the filter body 12 is heated in vacuo
in a furnace 40 at temperatures of up to 1200°C and is then
cooled again. The heating and cooling process usually takes
place in accordance with a specifiable pattern which can be
described using temperature transients and holding times.
The filter body 12 produced in this way satisfies the very
high thermal and dynamic requirements, for example in exhaust
systems of diesel engines as are currently used in automotive
engineering. This applies in particular with a view to the
filter body being arranged close to the engine, in which case
the filter body can be regenerated continuously. This
configuration of the open filter body causes the reaction
partners for converting the soot particulates and the soot
particulates themselves to dwell in the filter body for a
longer period of time, so that the probability of all the
required reaction partners and ambient conditions being
present is increased. Tests have confirmed this, demonstrating
a filter efficiency of, for example, over 50%. This means that
most passenger automobiles which are currently in use will
continue to be able to comply with the most stringent exhaust
emission guidelines and/or statutory regulations even in the


future. In this respect, this filter body is particularly-
suitable for retrofitting.


List of reference symbols
1 Filter layer
2 Filter section
3 Boundary region
4,4' Layer thickness

5 Edge
6 Boundary width
7 Fiber layer
8 Fiber layer thickness
9 Metal layer

10 Metal layer thickness
11 Sandwich structure
12 Filter body
13 Internal combustion engine
14 Passage
15 Sheet-metal foil
16 Connecting section
17 Deformation region
18 Zone
19 Remaining zone
20,20' Height
21,21' Structure height
22 Material thickness
23 Compensation layer
24 Honeycomb body
25 End face
26 Solder
27 Casing
28 Attachment region

29 Compressive force
30 Solder stop
31 Oxidation catalytic converter
32 Turbocharger
33 Exhaust pipe
34 Catalytic converter
35 Direction of flow
36 Exhaust system
37 Distance
38 Aperture
39 Diverting surface
40 Furnace
41 Flow-guiding surface
42 Length

WE CLAIM
1. A heat-resistant filter layer (1) made from a material assembly of fibers
which is at least partially pervious to a fluid, having at least one filter
section (2) and at least one boundary region (3), characterized in that the
filter layer (1) has a different, for example a reduced layer thickness (4),
in the at least one boundary region (3) than in the at least one filter
section (2), and in that the filter layer (1) being developed with the fiber
assembly being compressed or compacted.
2. The heat-resistant filter layer (1) as claimed in claim 1, wherein the layer
thickness (4) in the at least one boundary region (3) is less than 60% in
the at least one filter section (2), preferably less than 50%, or even less
than 35%.
3. The heat-resistant filter layer (1) as claimed in claim 1 or 2, wherein the
at least one boundary region (3), starting from an edge (5) of the filter
layer (1), has a boundary width (6) of at most 30 mm, in particular of at
most 20 mm, preferably of at most 10 mm or even of only at most 5 mm.
4. The heat-resistant filter layer (1) as claimed in one of the preceding
claims, wherein the filter layer (1) comprises at least one fiber layer (7)
which preferably has a fiber layer thickness (8) of at most 3 mm, in
particular of at most 1 mm and preferably of at most 0.5 mm.


5. The heat-resistant filter layer (1) as claimed in one of the preceding
claims, wherein the filter layer (1) has at least one metal layer (9), which
preferably limits the filter layer (1) on the outside and in particular has a
metal-layer thickness (10) of at most 0.05 mm, preferably of at most 0.03
mm or even at most 0.015 mm.
6. The heat-resistant filter layer (1) as claimed in one of the preceding
claims, wherein the filter layer (1) is a sandwich structure (11) and has at
least one fiber layer (7) and at least one metal layer (9).
7. A filter body (12) for purifying exhaust gases from an internal combustion
engine (13), comprising at least partially structured layers (1,15), which
are stacked and/or wound in such a way as to form passages (14)
through which the exhaust gas can flow, characterized in that the layers
comprise at least one heat-resistant filter layer (1) as claimed in one of
the preceding claims.
8. The filter body (12) as claimed in claim 7, wherein the layers comprise at
least one structured sheet-metal foil (15) and at least one substantially
smooth filter layer (1), the layers (1,15) being connected to one another
by joining, in particular by soldering of welding, in at least one connecting
section (16).


9. The filter body (12) as claimed in claim 8, wherein the at least one
connecting section (16) is arranged in the at least one boundary region
(3) of the filter layer (1).
10. The filter body (12) as claimed in one of claims 7 to 9, comprising means
(17, 18, 19, 20,21, 23) for compensating for the different layer
thickness (4,4') of the filter layer (1).
11. The filter body (12) as claimed in claim 10, wherein the layer thickness
(4) of the filter layer (1) is reduced in the at least one boundary region
(3), and wherein the at least one boundary region (3), has a deformation
region (17) and at least partially over-laps itself and is preferably even
soldered together.
12. The filter body as claimed in claim 10 or 11, wherein the layer thickness
(4) of the filter layer (1) is reduced in the at least one boundary region
(3), and the zone (18) of a layer (1,15), in particular of a structured
sheet-metal foil (15), which is arranged adjacent to the at lest one
boundary region (3), has a greater height (20) than a remaining zone
(19).
13. The filter body (12) as claimed in claim 12, wherein the adjacent layer is
a structured sheet-metal foil (15), and wherein the latter is formed in the


zone (18) with a structure height (21) which is greater than that of the
remaining zone (19), wherein a material thickness (22) of the sheet-metal
foil (15) is preferably being equaled in the various zones (18,19).
14. The filter body (12) as claimed in one of claims 10 to 13, comprising at
least one additional compensation layer (23), which is preferably
arranged adjacent to the at least one boundary region (3) of the filter
layer (1) of reduced layer thickness (4).
15. The filter body (12) as claimed in one of claims to 14, wherein said filter
body (12) comprises alternately closed passages (14).
16. The filter body (12) as claimed in one of claims 10 to 14, wherein said
filter body (12) comprises passages (14) having a cross section through
which a fluid can flow freely over the entire length of said passage (14),
and wherein means for generating pressure differences and means for
influencing the direction of flow are provided respectively in said
passages (14).
17. A process for producing the filter body (12) as claimed in one of claims 7
to 16, comprising steps of:
- producing at least one heat-resistant filter layer (1);


- forming at least one boundary region (3) of the at least one filter
layer (1) of reduced layer thickness (4);
- providing of means for comprising for the different layer
thicknesses (4,4') of the at least one filter layer (1);
- stacking and/or winding of at least one filter layer (1) and least one
structured sheet-metal foil (15) so as to form a honeycomb body
(24) with passages (14) through which an exhaust gas can flow;
- supplying solder (26) in at least one connecting section (16) with
the at least one filer layer (15); and
- heating the honeycomb body (24) in order to form solder joints in
the at least one connecting section (16).

18. The process as claimed in claim 17, wherein the honeycomb body (24) is
introduced into a casing (27) before solder (26) is supplied, and while
solder (26) is being supplied, the latter is preferably also arranged in at
least one attachment region (28) for attaching the at least one filter layer
(1) and/or the at least one sheet-metal foil (15) to the casing (27), so
that solder joints are generated during heating in the at least one
attachment region (28).
19. The process as claimed in claim 17 or 18, wherein the at least one
boundary region (3) of reduced layer thickness (4) is formed by the


application of a compressive force (29) to the filter layer (1) in the at
least one boundary region (3).
20. The process as claimed in one of claims 17 to 19 wherein the
compensation means are produced by the deformation of the at least one
boundary region (3).
21. The process as claimed in one of claims 17 to 20, wherein the
compensation means are produced by arranging at lest one compensation
layer (23) between a filter layer (1) and an adjacent sheet-metal foil (15).

The invention relates to a heat-resistant filter layer (1) made from a material
assembly of fibers material assembly of fibers which is at least partially pervious
to a fluid, having at least one filter section (2) and at least one boundary region
(3), the filter layer (1) has a different, for example a reduced layer thickness (4),
in the at least one boundary region (3) than in the at least one filter section (2),
and in that the filter layer (1) being developed with the fiber assembly being
compressed or compacted.

Documents:

715-KOLNP-2004-(27-12-2011)-CORRESPONDENCE.pdf

715-KOLNP-2004-FORM 27.pdf

715-KOLNP-2004-FORM-27.pdf

715-kolnp-2004-granted-abstract.pdf

715-kolnp-2004-granted-claims.pdf

715-kolnp-2004-granted-correspondence.pdf

715-kolnp-2004-granted-description (complete).pdf

715-kolnp-2004-granted-drawings.pdf

715-kolnp-2004-granted-examination report.pdf

715-kolnp-2004-granted-form 1.pdf

715-kolnp-2004-granted-form 13.pdf

715-kolnp-2004-granted-form 18.pdf

715-kolnp-2004-granted-form 2.pdf

715-kolnp-2004-granted-form 3.pdf

715-kolnp-2004-granted-form 5.pdf

715-kolnp-2004-granted-gpa.pdf

715-kolnp-2004-granted-reply to examination report.pdf

715-kolnp-2004-granted-specification.pdf

715-kolnp-2004-granted-translated copy of priority document.pdf


Patent Number 227609
Indian Patent Application Number 715/KOLNP/2004
PG Journal Number 03/2009
Publication Date 16-Jan-2009
Grant Date 14-Jan-2009
Date of Filing 27-May-2004
Name of Patentee EMITEC GESELLSCHAFT FUR EMISSIONSTECHNOLOGIE MBH
Applicant Address HAUPTSTRASSE 150, 53797 LOHMAR
Inventors:
# Inventor's Name Inventor's Address
1 BRUCK, ROLF FROBELSTRASSE 12 51429 BERGISCH GLADBACH
2 HODGSON, JAN MOSELSTRASSE 66 53842, TROISDORF
PCT International Classification Number B01D 46/10,39/20
PCT International Application Number PCT/EP2002/011684
PCT International Filing date 2002-10-18
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10153283.0 2001-10-29 Germany