U.S. patent application number 13/026829 was filed with the patent office on 2011-07-21 for particle trap for an exhaust gas recirculation line and automobile having a particle trap.
This patent application is currently assigned to EMITEC GESELLSCHAFT FUER EMISSIONSTECHNOLOGIE MGH. Invention is credited to Hans-Peter Casper, Hubertus Kotthoff, Uwe Siepmann, Joachim Sittig.
Application Number | 20110173956 13/026829 |
Document ID | / |
Family ID | 41328113 |
Filed Date | 2011-07-21 |
United States Patent
Application |
20110173956 |
Kind Code |
A1 |
Kotthoff; Hubertus ; et
al. |
July 21, 2011 |
PARTICLE TRAP FOR AN EXHAUST GAS RECIRCULATION LINE AND AUTOMOBILE
HAVING A PARTICLE TRAP
Abstract
A particle trap disposed between an exhaust gas line and an
exhaust gas recirculation line includes at least one partially
permeable hollow body separating the exhaust gas recirculation line
from the exhaust gas line. The at least one partially permeable
hollow body has a wall defining a primary shape with an inner space
having at least one open side. The wall is gas-permeable and has a
secondary structure with elevations and depressions. An automobile
having a particle trap is also provided.
Inventors: |
Kotthoff; Hubertus;
(Ruppichteroth, DE) ; Sittig; Joachim; (Roesrath,
DE) ; Casper; Hans-Peter; (Troisdorf, DE) ;
Siepmann; Uwe; (Overath, DE) |
Assignee: |
EMITEC GESELLSCHAFT FUER
EMISSIONSTECHNOLOGIE MGH
Lohmar
DE
|
Family ID: |
41328113 |
Appl. No.: |
13/026829 |
Filed: |
February 14, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2009/060401 |
Aug 12, 2009 |
|
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13026829 |
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Current U.S.
Class: |
60/278 |
Current CPC
Class: |
B01D 2275/206 20130101;
B01D 46/526 20130101; B01D 46/0017 20130101; B01D 2275/207
20130101; F02M 26/15 20160201; B01D 2275/205 20130101; B01D 46/0005
20130101; B01D 46/0023 20130101; B01D 2275/208 20130101; B01D 39/12
20130101; B01D 46/2411 20130101 |
Class at
Publication: |
60/278 |
International
Class: |
F01N 3/021 20060101
F01N003/021; F01N 3/022 20060101 F01N003/022 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 13, 2008 |
DE |
10 2008 038 983.8 |
Claims
1. In an exhaust gas treatment device having an exhaust gas line
and an exhaust gas recirculation line, a particle trap disposed
between the exhaust gas line and the exhaust gas recirculation
line, the particle trap comprising: at least one partially
permeable hollow body separating the exhaust gas recirculation line
from the exhaust gas line; said at least one partially permeable
hollow body including a wall defining a primary shape having an
inner space with at least one open side; and said wall being
gas-permeable and having a secondary structure with elevations and
depressions.
2. The particle trap according to claim 1, wherein the exhaust gas
line has a first central cross section and a first enlarged cross
section, and said at least one partially permeable hollow body is
disposed in the first enlarged cross section.
3. The particle trap according to claim 2, which further comprises
push-in ring connections attaching said at least one partially
permeable hollow body to the exhaust gas line in vicinity of the
first enlarged cross section.
4. The particle trap according to claim 1, wherein the exhaust gas
recirculation line has a second central cross section and a second
enlarged cross section, and said at least one partially permeable
hollow body is disposed in the second enlarged cross section.
5. The particle trap according to claim 1, which further comprises
a cap closing off an open side of said at least one partially
permeable hollow body.
6. The particle trap according to claim 1, wherein said elevations
and said depressions of said secondary structure are disposed
parallel to a first main direction of the exhaust gas line or to a
second main direction of the exhaust gas recirculation line.
7. The particle trap according to claim 1, wherein said partially
permeable hollow body is formed of at least one layer having said
elevations and depressions, and said at least one layer forms a
region overlapping itself and in which said elevations and said
depressions engage in one another in a form-locking manner.
8. The particle trap according to claim 1, which further comprises
at least one support layer having a shape corresponding to said
secondary structure of said at least one partially permeable hollow
body.
9. The particle trap according to claim 1, wherein said wall has
meshes with a size of up to 0.3 mm.
10. An automobile, comprising: an internal combustion engine; an
exhaust system receiving exhaust gas from said internal combustion
engine and having at least one particle trap according to claim 1;
and an exhaust gas recirculation line defining a flow direction
leading to said internal combustion engine; said particle trap
having a location causing said flow direction in said exhaust gas
recirculation line directly downstream of said particle trap to run
counter to the force of gravity.
11. An automobile, comprising: an internal combustion engine; an
exhaust system receiving exhaust gas from said internal combustion
engine and having at least one particle trap according to claim 1
and at least one ceramic filter; and an exhaust gas line defining a
flow direction leading away from said internal combustion engine;
said at least one ceramic filter disposed upstream of said particle
trap in said flow direction.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation, under 35 U.S.C. .sctn.120, of
copending International Application No. PCT/EP2009/060401, filed
Aug. 12, 2009, which designated the United States; this application
also claims the priority, under 35 U.S.C. .sctn.119, of German
Patent Application DE 10 2008 038 983.8, filed Aug. 13, 2008; the
prior applications are herewith incorporated by reference in their
entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The invention relates to a particle trap disposed in a
junction region between an exhaust gas line and an exhaust gas
recirculation line. Such particle traps are used, in particular, in
exhaust systems of (mobile) internal combustion engines. The
invention also relates to an automobile having a particle trap.
[0003] With respect to the treatment of exhaust gasses of mobile
internal combustion engines, such as for example spark ignition
engines and diesel engines, efforts are made today to condition
exhaust gasses in such a way that they can be output into the
environment in a virtually completely purified form. Such
post-treatment can be carried out, for example, by purifying the
exhaust gasses in a catalytic converter and/or in a filter. It is
also known to recirculate a portion of the produced exhaust gas
back into the internal combustion engine. That means that a portion
of the exhaust gasses is removed from the exhaust gas line and
transported back to the intake side of the internal combustion
engine through an exhaust gas recirculation line, in order to be
introduced, together with the intake air, into the combustion
chamber of the internal combustion engine. The purification of
exhaust gasses of a diesel engine, which have a relatively large
amount of non-combusted carbon particles, frequently also referred
to as soot particles, represents a particular demand. An important
objective of exhaust gas purification is to remove those carbon
particles or soot particles from the exhaust gas of a diesel
engine. Soot particles can also have an adverse effect during the
recirculation of exhaust gas into the internal combustion engine.
The objective of a particle trap between the exhaust gas line and
the exhaust gas recirculation line is therefore to prevent the
recirculation of carbon particles or soot particles and, if
appropriate, also to hold back other solid bodies. Furthermore, the
exhaust gas recirculation also influences the production and/or
conversion of nitrogen oxides.
[0004] So-called soot burn-off filters are also used to a certain
extent in exhaust gas lines in order to remove soot particles from
the exhaust gas. Those soot burn-off filters are frequently
fabricated from ceramic materials. Porous, sintered ceramic filters
("wall flow filters") are frequently used. Ceramic filters are, in
any case, already distinguished by a high degree of brittleness.
That behavior is further reinforced by the different temperatures
when used by an exhaust gas line. Small particles can easily become
detached from a ceramic filter or a mounting mat surrounding the
ceramic filter. If such solid bodies are fed back into the
combustion chamber of an internal combustion engine through an
exhaust gas recirculation line, they can cause considerable damage
there. The ceramic particles behave there as abrasive bodies and
can bring about considerable wear on engine components.
[0005] A filter device which is disposed in the exhaust gas
recirculation line is capable of removing particles from the
recirculated exhaust gas. However, a disadvantage of such a filter
device is that it can become blocked by the particles. Once
particles have been trapped by such a filter device, they continue
to be held in the filter device by the continually flowing exhaust
gas. As a result, the properties of the filter device change
considerably. The permeability of the filter is reduced with the
effect that, for example, an undesired drop in pressure can occur
across the filter. Drops in pressure and permeability in turn
influence the quantity of recirculated exhaust gas. Therefore,
regular cleaning of the filter device is necessary in order to
maintain filter properties which are constant over time.
[0006] In order to avoid regular cleaning of the filter device, it
is known from Published German Application DE 38 33 957 A1,
corresponding to U.S. Pat. No. 4,924,668, to place an exhaust gas
filter insertion unit directly at the branching point between an
exhaust gas line and the exhaust gas recirculation line. The
exhaust gas filter insertion unit is disposed in that case in such
a way that the surface runs parallel to the flow direction of the
main exhaust gas stream. It is also stated that the exhaust gas
filter insertion unit is to be manufactured from a porous sintering
ceramic or from a sintering metal. A typical porosity value for
such a filter device can be between 0.1 and 10 micrometers.
[0007] Published German Application DE 10 2006 013 709 A1,
corresponding to U.S. Patent Application Publication No. US
2009/0071151, also discloses providing a cross-sectional widened
portion in an exhaust gas recirculation line and providing a sieve
layer in that cross-sectional widened portion. In that way, the
pressure loss in the exhaust gas stream as a result of the
filtering can be kept small.
SUMMARY OF THE INVENTION
[0008] It is accordingly an object of the invention to provide a
particle trap for an exhaust gas recirculation line and an
automobile having a particle trap, which overcome the
hereinafore-mentioned disadvantages and further alleviate the
highlighted technical problems of the heretofore-known devices of
this general type. In particular, an especially cost-effective
device for trapping particles upstream of an exhaust gas
recirculation line is to be presented.
[0009] With the foregoing and other objects in view there is
provided, in accordance with the invention, a particle trap
disposed between an exhaust gas line and an exhaust gas
recirculation line. The particle trap comprises at least one
partially permeable hollow body separating the exhaust gas
recirculation line from the exhaust gas line. The at least one
partially permeable hollow body includes a wall defining a primary
shape having an inner space with at least one open side. The wall
is gas-permeable and has a secondary structure with elevations and
depressions.
[0010] Such exhaust gas systems are usually embodied in such a way
that they have a line section in which the exhaust gas
recirculation line is connected by a flange or flanges to the
exhaust gas line or is connected through the use of a welding seam
there. To this extent, this device can, for example, also include a
type of T element of the exhaust system.
[0011] The at least partially permeable hollow body is generally
embodied in such a way that it has a wall through which exhaust gas
can flow (preferably completely). This wall represents in this case
in particular the fluidic boundary between the exhaust gas flow of
the exhaust gas line and the exhaust gas flow which is recirculated
by the exhaust gas recirculation line. The wall of the partially
permeable hollow body accordingly includes a permeable material
which gives the hollow body its permeability. The hollow body is
quite particularly preferably configured in the manner of a radial
sieve. It is also advantageous in this case if the wall of the
hollow body is dimensionally stable, that is to say maintains its
primary shape itself. In this context, it is considered
advantageous that the wall is embodied with at least one entangled
configuration, a fabric or mesh configuration or a sintered
material, in particular metallic, temperature-resistant materials.
The use of at least one nonwoven with wire filaments which are
woven (asymmetrically), with the wire filaments being sintered to
one another, is very particularly preferred.
[0012] The "primary shape" of the permeable hollow body is meant
herein to refer to a geometric shape which substantially determines
the shape of the hollow body. The primary shape therefore forms the
shape of the hollow body, with the result that in particular at
least 80% or even 95% of the volume of the hollow body is included
in this primary shape. Pipe-shaped primary shapes are preferably
used. In this context, a pipe-shaped hollow body with a circular
cross section is preferred but, if appropriate, oval, triangular,
square, rectangular or polygonal cross sections are also possible
as a primary shape of the at least one partially permeable hollow
body.
[0013] In most cases, there is an axial flow against the hollow
body from at least one side, with the result that in particular an
open side has to be provided so that the exhaust gas can be
introduced into the inner space which is defined by the wall.
Depending on the primary shape of the hollow body and/or the
configuration of the hollow body in the exhaust system, the second
side (which is fluidically opposite) can also be open, but it is
also possible for that side to be closed off (fluidically), with
the result that all of the exhaust gas entering the inner space
then generally leaves the inner space again through the wall.
[0014] In addition to the primary shape, the hollow body also has a
smaller secondary structure which is superimposed on the primary
shape. A "secondary structure" means in this case in particular a
(periodic and/or regular) deviation from the cross section of the
primary shape in the transverse direction with respect to the
profile of the wall (circumferential direction), for example
radially outward, which is also referred to as elevated portions,
and/or radially inward and is also referred to as depressions. It
is possible, for example, to provide corrugated, folded, bent
and/or meandering deviations. Elevated portions and/or depressions
particularly preferably run over the entire axial extent of the
primary shape of the partially permeable hollow body or of the
wall, with the result that (linearly) elongate elevated portions
and/or depressions are formed in the axial direction.
[0015] The secondary structure of the at least one partially
permeable hollow body increases the strength of the particle trap.
The particle trap proposed herein with a secondary structure can
cope with significantly greater drops in pressure while having a
significantly smaller thickness. Furthermore, the surface for the
deposition of the particles is enlarged. In addition, it is also to
be borne in mind that with the secondary structure it is possible
to selectively generate microflows at the surface or into the wall.
Such microflows can implement (for example as a function of the
flow of the exhaust gas (speed, mass throughput rate, etc.)) a
predetermined quantity of the exhaust gas mass flow which is to be
recirculated and/or a predetermined embedding characteristic of the
particles and/or a predetermined purification characteristic for
the particle trap (or the wall). As a result, with this device,
which is of simple construction, further significant advantages can
be obtained in addition to the enduring protection of the
components of the exhaust gas recirculation system and the
purification of exhaust gasses.
[0016] In accordance with another feature of the invention, the
exhaust gas line has a first central cross section and a first
enlarged cross section which is widened as compared to the first
central cross section. The at least one partially permeable hollow
body is disposed in this case in the first enlarged cross section.
It is thus possible to ensure, in particular, that there is not a
direct flow against the hollow body or its wall but rather the
hollow body or its wall is positioned, for example, in a flow
shadow which is formed by the first enlarged cross section. In this
way, it is possible, if appropriate, also to ensure an indirect
setting of the exhaust gas recirculation rate by virtue of the fact
that as the pressure in the exhaust gas line rises an increased
flow into this "flow shadow" and therefore also through the hollow
body to the exhaust gas recirculation line is established.
[0017] In accordance with a further feature of the invention, in
this context, it is considered advantageous for the at least one
partially permeable hollow body to be attached in the region of the
first enlarged cross section to the exhaust gas line through the
use of push-in ring connections. It is particularly advantageous if
push-in ring connections, into which the (open) sides of the
permeable hollow body can engage directly in a form-locking
fashion, are provided in the exhaust gas line or in the widened
portion of the exhaust gas line, in the region of the particle
traps. A form-locking connection is one which connects two elements
together due to the shape of the elements themselves, as opposed to
a force-locking connection, which locks the elements together by
force external to the elements. Such push-in connections can, for
example, be provided directly during the manufacture of a branching
off component by punching or deep drawing. Fluidic advantages for
the main exhaust gas stream (smaller drop in pressure) and less
contamination are also achieved by the configuration of the push-in
ring attachments in the flow shadow, so that changing the hollow
body is unproblematical.
[0018] In accordance with an added feature of the invention, in the
same way as the exhaust gas line, the exhaust gas recirculation
line can likewise have a second central cross section and a second
enlarged cross section, wherein the at least one partially
permeable hollow body is disposed in the second enlarged cross
section. With respect to the advantages of this construction,
reference is made to the remarks given above, in which case it is
to be noted in this case that due to the relatively small exhaust
gas flows in this case it is possible, under certain circumstances,
for flow losses and/or blocking to play a significantly greater
role.
[0019] A combined configuration in which a permeable hollow body is
disposed in the first enlarged cross section of the exhaust gas
line and (respectively) in the second enlarged cross section of the
exhaust gas recirculation line is basically possible, wherein then,
if appropriate, different refinements of the hollow bodies should
be present (for example in terms of permeability, stability,
etc.).
[0020] In accordance with an additional feature of the invention,
under certain circumstances, it is also appropriate for an open
side of the at least one partially permeable hollow body to be
closed off by a cap. As a result, it is possible, under certain
circumstances, to simplify the manufacture by virtue of the fact
that a tube-like hollow body with two open sides is made available,
with a separate cap, through which there cannot be a flow, being
attached (e.g. welded) to the wall thereof on one side.
Furthermore, it is also possible for the cap (in particular a metal
cap) to have a selective bypass, that is to say, for example, a
small hole. It is then possible, under certain circumstances, for
the cap also to be attached on both sides, wherein one cap is
provided with a bypass function and one without a bypass function.
In addition to the passage of the flow, the stability of the
primary shape can also be set with the cap.
[0021] In accordance with yet another feature of the invention, it
has proven particularly advantageous for the elevated portions and
depressions of the secondary structure to run parallel to a first
main direction of the exhaust gas line or to a second main
direction of the exhaust gas recirculation line. As a result, the
exhaust gas stream can flow (as a function of the load) through the
depressions in the secondary structure without a large flow
resistance and therefore clean the latter of deposited carbon
particles or soot particles or ceramic particles.
[0022] In accordance with yet a further feature of the invention,
the wall of the at least one partially permeable hollow body is
preferably formed from at least one layer with elevated portions
and depressions, wherein the at least one layer forms a region
which overlaps with itself and in which the elevated portions and
the depressions engage in one another in a form-locking fashion. A
layer is understood in this case to be, for example, a planar
filter material or sieve material, wherein basically also a
plurality of materials (and, if appropriate, different materials)
can be provided for embodying the wall. This layer can be
positioned to form a primary shape with two open sides, with the
result that it forms a region which overlaps with itself. The
elevated portions and depressions of the layer can thus engage in
one another in a form-locking fashion if the layer is rolled up so
as to form an inner space. In this way, a stable, tube-shaped
hollow body is formed without materially joined connections having
to be formed in the overlapping region. The stability is provided
in particular if such a hollow body is secured in a materially
joined fashion at the edges of its open sides to an exhaust gas
line or an exhaust gas recirculation line.
[0023] In accordance with yet an added feature of the invention,
the stiffness of such a hollow body can additionally be increased
by virtue of the fact that at least one support layer is provided
which has a shape that corresponds to the secondary structure of
the at least one hollow body. Although it would in principle be
possible for the hollow body and the supporting layer which at
least partially surrounds it to only bear against one another
superficially, a (materially joined) connection of the two elements
is preferred. The surface structures of the hollow body and of the
supporting layer, for example with elevated portions and
depressions, can then engage in one another in a form-locking
fashion. Basically, the at least one supporting layer can support
the hollow body from the inside and/or outside, and if appropriate
integration into a plurality of layers of filter material and/or
sieve material is also possible. Whether support from the inside or
outside is preferred depends on the direction of action of a
possible drop in pressure. The supporting layer should be provided
in such a way that the drop in pressure presses the layer against
the supporting layer.
[0024] In accordance with yet an additional feature of the
invention, in the particle trap, a wall with meshes or openings of
up to 0.3 mm is preferably used. The width of the meshes is
preferably in the range of less than 0.2 mm and quite particularly
preferably in the range from 0.05 mm to 0.15 mm.
[0025] With the objects of the invention in view, there is also
provided an automobile, comprising an internal combustion engine,
an exhaust system having at least one particle trap according to
the invention, and an exhaust gas recirculation line defining a
first flow direction leading to the internal combustion engine. The
particle trap is disposed in such a way that the first flow
direction in the exhaust gas recirculation line directly downstream
of the particle trap runs counter to the force of gravity.
[0026] This means, in other words, in particular that the exhaust
gas recirculation line or the junction region with the hollow body
is subjected to the force of gravity in such a way that particles
or the like fall out again from there automatically, specifically
in particular back into the exhaust gas line again and from there
further into the exhaust gas purification components of the exhaust
gas line which are disposed downstream. It is quite particularly
preferred in this case for the hollow body itself to have a center
axis which is oriented substantially parallel to the force of
gravity. In this way, the force of gravity can additionally
counteract the deposition of soot particles and/or ceramic
particles on the trap.
[0027] With the objects of the invention in view, there is
concomitantly provided an automobile, comprising an internal
combustion engine, an exhaust system having at least one particle
trap according to the invention and at least one ceramic filter,
and
an exhaust gas line defining a second flow direction leading away
from the internal combustion engine. The at least one ceramic
filter is disposed upstream of the particle trap in the second flow
direction.
[0028] Furthermore, the exhaust gas recirculation line is
preferably part of a low-pressure EGR (exhaust gas recirculation)
system in which the exhaust system is therefore embodied with at
least one turbocharger, and the exhaust gas recirculation line is
disposed downstream of the turbocharger as viewed in the second
flow direction.
[0029] If appropriate, the hollow body described herein can also,
as an exhaust gas purification unit, advantageously be independent
of the specific configuration in the exhaust system or in the
exhaust gas recirculation line. A nonwoven for treating exhaust
gasses in an exhaust gas recirculation line will be presented
briefly herein, in which case it can also advantageously be used
independently of the configuration, such as is described herein,
for example also in an embodiment such as is specified in Published
German Application DE 10 2006 013 709 A1, corresponding to U.S.
Patent Application Publication No. US 2009/0071151, to which
reference is additionally also made in this case with respect to
the description of the configuration.
[0030] Accordingly, the nonwoven is a fabric in the manner of a
3-shed twill or 5-shed twill fabric (referred to as "Atlas fabric",
TELA fabric or fabric with a 5-shed Atlas binding). Such a nonwoven
has warp filaments and weft filaments which are woven with one
another at an angle of approximately 90.degree.. In the nonwoven,
the direction along the warp filaments is subsequently referred to
as the warp direction and the direction along the weft filaments as
the weft direction. The weaving of warp filaments and weft
filaments is carried out in such a fabric so that the weft
filaments run in each case above four warp filaments lying one on
top of the other and subsequently below an individual warp
filament. This profile repeats for each weft filament over the
entire nonwoven. Two weft filaments lying one next to the other run
in each case below different warp filaments. It is preferred in
this case that a weft filament runs in each case below the warp
filament after the next, below which the directly adjacent weft
filament runs. This configuration results in a regularly repeated
pattern which runs obliquely with respect to the weft direction and
obliquely with respect to the warp direction in the nonwoven. The
nonwoven, which may also be referred to as a fleece or mat and is
woven in this way, is particularly robust and has a relatively
smooth surface.
[0031] As a result of this type of fabric, a high throughflow with
simultaneous stability can be achieved. In this context wire
filaments (used as warp and weft filaments) of a different
configuration can be used, specifically relatively thick warp
filaments (for example 160 .mu.m filament diameter) and relatively
thin weft filaments (for example 150 .mu.m filament diameter). In
each case a tolerance of +/-4 .mu.m is appropriate for the filament
diameters, with the result that warp filaments have a diameter of
at least 156 .mu.m and at maximum 164 .mu.m, and weft filaments
have a diameter of at least 146 .mu.m and at maximum 154 .mu.m. In
the finished fabric, the relatively thin weft filaments bend to a
greater extent than the relatively thick warp filaments. This
influences the shape of the available meshes.
[0032] Such a nonwoven has rectangular meshes which have a greater
mesh width in the weft direction than in the warp direction. The
mesh width in the warp direction should preferably on average be
approximately 77 .mu.m. In this context, a tolerance of +/-6 .mu.m
is appropriate. According to the invention, an average mesh width
in the warp direction is thus at least 71 .mu.m and at maximum 83
.mu.m. In the weft direction, the mesh width should preferably be
on average 149 .mu.m. In this context, a tolerance of +/-10 .mu.m
is appropriate. According to the invention, an average mesh width
in the weft direction is thus at least 139 .mu.m and at maximum 159
.mu.m.
[0033] The preferred mesh width and preferred filament diameter
result in a mesh number of 107 meshes/inch or approximately 41
meshes/mm in the warp direction and a mesh number of 85 meshes/inch
or approximately 33 meshes/mm in the weft direction.
[0034] Furthermore, it is appropriate to define a maximum mesh
width in both the warp and weft directions in order to ensure that
particles above a certain size generally cannot pass through the
nonwoven. The largest permissible mesh width in the warp direction
of 58 .mu.m is proposed as a tolerance. A mesh must therefore have
at maximum a mesh width of 135 .mu.m in the warp direction. The
maximum permissible mesh width in the weft direction of 84 .mu.m is
proposed as a tolerance. A mesh must therefore have at maximum a
mesh width of 233 .mu.m in the weft direction.
[0035] The properties of such a nonwoven can be checked, for
example, by using a microscope. The number of filaments per length
unit in the warp direction or weft direction can be determined by
counting the filaments per length unit. The average mesh width can
then be determined by subtracting the filament wire diameter from
the pitch (distance between two filaments in the nonwoven).
[0036] The maximum permissible mesh width at least partially
predefines the filter permeability. This can be determined by using
a ball passage test. The greatest opening of the meshes in a fabric
(nonwoven) is referred to as the ball passage. A precisely round
ball can still pass through the fabric and a relatively large one
is held back. From the definition it is apparent that given a
genuinely polygonal mesh, the smaller of the two mesh widths (mesh
width in the warp direction) substantially determines the ball
passage. The permissible ball diameter in the case of a test with
the nonwoven proposed in this case should be between 140 .mu.m and
180 .mu.m, preferably between 150 .mu.m and 170 .mu.m, and in
particular between 155 .mu.m and 160 .mu.m. The permissible ball
passage is therefore greater than the above-stated mesh width in
the warp direction. This is the case because due to the fabric
structure of the nonwoven and to the filament wire diameters in
relation to the mesh widths, slightly enlarged passage openings
compared to the defined mesh widths result obliquely with respect
to the plane of the nonwoven (in particular not orthogonally with
respect to the plane of the nonwoven spanned between the warp
direction and the weft direction) for a predefined mesh width.
[0037] The thickness of the nonwoven should be between 0.4 and 0.5
mm and preferably be approximately 0.44 mm. The nonwoven should
have an air permeability of between at minimum 4000 l/m.sup.2s and
at maximum 8000 l/m.sup.2s, preferably between at minimum 5000
l/m.sup.2s and at maximum 7000 l/m.sup.2s and in particular between
at minimum 5500 l/m.sup.2s and at maximum 6000 l/m.sup.2s, if the
difference in pressure present across the nonwoven is 2 mbar.
[0038] For the further processing, the nonwoven should be free of
oil films, auxiliary materials and other impurities.
[0039] It may, under certain circumstances, also be advantageous to
integrate such a fabric, which is present as described above,
differently into an exhaust gas recirculation line so that this
combination can also separately form an unexpected further
development of the prior art.
[0040] The wire filaments are preferably sintered to one another in
this case in the form being used, that is to say in particular are
not welded to one another.
[0041] If the nonwoven is used as the wall of a hollow body in the
manner of a sieve, it may at least be characterized by one of the
following parameters:
[0042] sieve area of at least 50 cm.sup.2 per 1.0 liter
displacement of the internal combustion engine;
[0043] construction with (only) 2 different types of metallic wire
filaments with different thicknesses, which are connected in a
nonwoven with different orientation through the use of a sintered
connection;
[0044] the degree of separation of the sieve of at least 0.05 mm,
in particular 0.1 mm or even 0.25 mm (particles with a relatively
small diameter generally flow through the sieve);
[0045] shape of the hollow body in the manner of a (flattened)
cone;
[0046] hollow body (having at least one cap and) having a
bypass;
[0047] wall thickness between 0.3 mm and 1 mm, in particular
between 0.4 mm and 0.5 mm; and
[0048] material of the wall (wire, wire filaments, etc.) with the
material no. 14841 according to the German Steel Key.
[0049] The mesh width of the sieve (and/or of the nonwoven
described above) is preferably in the region of less than 0.3 mm,
in particular of less than 0.2 mm and quite particularly preferably
of less than 0.15 mm. In this context, the mesh width should
equally preferably be at least 0.05 mm (millimeters).
[0050] Other features which are considered as characteristic for
the invention are set forth in the appended claims, noting that the
features which are disclosed individually in the claims can be
combined with one another in any desired technically appropriate
way and can be supplemented by explanatory data from the
description, in which context further embodiment variants of the
invention are disclosed.
[0051] Although the invention is illustrated and described herein
as embodied in a particle trap for an exhaust gas recirculation
line and an automobile having a particle trap, it is nevertheless
not intended to be limited to the details shown, since various
modifications and structural changes may be made therein without
departing from the spirit of the invention and within the scope and
range of equivalents of the claims.
[0052] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0053] FIG. 1 is a fragmentary, diagrammatic,
longitudinal-sectional view of a first embodiment variant of the
invention in which a partially permeable hollow body is disposed in
an exhaust gas line;
[0054] FIG. 2 is a fragmentary, longitudinal-sectional view of a
further embodiment variant of the invention, in which a partially
permeable hollow body is disposed in an exhaust gas recirculation
line;
[0055] FIG. 3 is a perspective view of a partially permeable hollow
body formed from a corrugated layer;
[0056] FIG. 4 is an end-elevational view of a partially permeable
hollow body which is formed from a layer with elevated portions and
depressions and has an additional supporting layer;
[0057] FIG. 5 is a longitudinal-sectional view of an automobile
with an exhaust system which has a particle trap according to the
invention; and
[0058] FIG. 6 includes enlarged front-elevational, bottom-plan and
side-elevational views of a configuration of a nonwoven for a
hollow body.
DETAILED DESCRIPTION OF THE INVENTION
[0059] Referring now in detail to the figures of the drawing for
explaining the invention and the technical field in more detail by
showing particularly preferred structural variants to which the
invention is not restricted, and first, particularly, to FIG. 1
thereof, noting in particular, that the figures and especially the
size ratios presented are only diagrammatic, there is seen a first
embodiment variant of a particle trap 6 according to the invention.
An exhaust gas line 2 has a first central cross section 10 and a
first enlarged cross section 11, which is widened in the region of
a hollow body 3. Exhaust gas flows through the exhaust gas line 2
in a second flow direction 26 along the profile of the exhaust gas
line 2. The direction of the profile of the exhaust gas line 2 is
also denoted as a first main direction 17. An exhaust gas
recirculation line 1 branches off from the exhaust gas line 2.
Exhaust gas flows in a first flow direction 25 in the exhaust gas
recirculation line 1 along a second main direction 21 of the
exhaust gas recirculation line 1. The exhaust gas line 2 forms
push-in ring connections 9. The partially permeable hollow body 3
is attached in the push-in ring connections 9.
[0060] The radially permeable hollow body 3 has a wall 27 which
defines an inner space or chamber 5. The inner space 5 has two open
sides 28. In FIG. 1, the permeable hollow body 3 is embodied in the
manner of a tube which is open on both sides. The shape of the
hollow body 3 is referred to as a primary shape 7. The permeable
hollow body 3 is connected in a materially joined fashion through
the use of the push-in ring connection 9 to the exhaust system and
to itself. The push-in ring connections 9 can also be provided
directly during the manufacture of the exhaust gas line 2, for
example by deep drawing or punching. The primary shape 7 of the
partially permeable hollow body 3 can be oriented in the exhaust
gas line 2 in such a way that the primary shape 7 runs in the first
main direction 17. The partially permeable hollow body 3, with its
two open sides 28, therefore continues the profile of the exhaust
gas line 2.
[0061] FIG. 2 shows a further advantageous refinement of a suitable
particle trap 6. In this case too, the first flow direction 25 of
the exhaust gas is in the second main direction 21 and the second
flow direction 26 of the exhaust gas is in the first main direction
17 of the exhaust gas line 2. In this case, the exhaust gas
recirculation line 1 has a second enlarged cross section 13, in the
region of the particle trap 6, which is widened as compared to a
second central cross section 12. A partially permeable hollow body
3, which is embodied as a tube, is provided in the second enlarged
cross section 13. The partially permeable hollow body 3 again has a
wall 27 which surrounds an inner space 5 as well as two open sides
28. One open side 28 of the partially permeable hollow body 3 is
closed off by a cap 8 (in a gastight fashion).
[0062] Furthermore, FIG. 2 also indicates a cumulative or
alternative shape of the exhaust gas conducting device. It is
therefore also possible for the exhaust gas not to be conducted
further in a linear fashion through the exhaust gas line 2, but
rather it is also possible to perform a multiple diversion,
downstream of which the (entire) exhaust gas is firstly diverted
into the enlarged cross section 13. Starting from there, the
portion of the exhaust gasses which does not flow through the
particle trap 6 is introduced again into the exhaust gas line 2.
The multiple deflection also results in intense cleaning of the
particle trap 6 by the exhaust gas which flows past in this
case.
[0063] Within the scope of the invention, a refinement of the
particle trap 6 is also possible in which both a partially
permeable hollow body 3 is provided in the exhaust gas line 2 and a
second partially permeable hollow body 3 is provided in the exhaust
gas recirculation line 1. All of the other improvements and
developments, explained separately for the refinements of the
invention illustrated in FIG. 1 and in FIG. 2, can also be used for
this combination within the scope of the invention.
[0064] FIG. 3 is a perspective view of a partially permeable hollow
body 3 which is formed from a corrugated layer 16. The layer 16 is
folded together to form the wall 27 of the tubular primary shape 7
(in this case, for example, a cylinder) with an inner space 5, and
forms a region 20 which overlaps with itself. This results in two
open sides 28 of the primary shape 7. Furthermore, the layer 16 has
a secondary structure 4, formed by elevated portions or elevations
14 and depressions 15, on the surface or over the periphery or
circumference. These elevated portions 14 and depressions 15 of the
layer 16 engage in one another in a form-locking fashion in the
overlapping region 20. A materially joined connection in the
overlapping region 20 is not absolutely necessary as a result, in
particular if the open sides 28 of the tubular hollow body 3 are
connected to a housing, for example at push-in ring connections 9,
on the exhaust gas line 2.
[0065] FIG. 4 shows a further refinement of the tubular hollow body
3 in which a supporting layer 18 is used, in addition to the layer
16. Elevated portions 14 and depressions 15 of the layer 16 engage
in a form-locking fashion in a corresponding surface shape of the
supporting layer. It is therefore possible to bring about a
considerably larger resistance of the partially permeable hollow
body 3 to the difference in pressure between the inside and the
outside. The supporting layer 18 can also support the layer 16 from
the inside depending on the active difference in pressure between
the exhaust gas line and the exhaust gas recirculation line.
[0066] FIG. 5 shows an automobile 22 with an internal combustion
engine 23 and an exhaust system 19. The exhaust system 19 has a
ceramic filter 24, in particular a soot particle filter or soot
burn-off filter as well as a (downstream) particle trap 6. FIG. 5
shows a second flow direction 26 away from the internal combustion
engine 23 through the exhaust gas line 2, and a first flow
direction 25 away from the particle trap 6 through the exhaust gas
recirculation line 1 to the internal combustion engine 23. The
particle trap 6 is disposed in the exhaust system 19 in such a way
that the first flow direction 25 runs directly downstream of the
particle trap 6 or in the region of the configuration of the hollow
body in opposition to the force 29 of gravity. The force 29 of
gravity therefore additionally counteracts the deposition of
particles on the particle trap 6.
[0067] FIG. 6 shows three views illustrating the construction of a
wall 27 formed of a metallic nonwoven in the manner of a 5-shed
twill or dobby (referred to as "Atlas fabric"). In this case,
relatively thick warp filaments 30 and relatively thin weft
filaments 31 only penetrate after four filaments have been passed.
In this context, relatively large meshes 32 or mesh openings are
formed.
[0068] Reference is made, merely for the sake of completeness, to
the fact that the device described herein can be changed in many
ways without departing from the inventive concept. In particular,
the types of exhaust gas purification systems, heat exchangers,
sensors, turbochargers etc., can be correspondingly constructed in
accordance with the conditions of the internal combustion
engine.
* * * * *