Note: Descriptions are shown in the official language in which they were submitted.
A filter ~4~5 t 8
The invention relates to a filter for the separation of
impurities from exhaust gases, in particular from exhaust
gases of an internal combustion engine, having a filter body
consisting of a plurality of compression-moulded and
sintered filter plates with high temperature stability made
from powdered metal, metal filings, metal fibres or a
mixture thereof, which are disposed on top of one another or
behind one another respectively, are separated by spacers
and form a plurality of flow ducts between them, with the
flow ducts being open on one side and closed on the other
side so as to form inlet and outlet ducts respectively, and
with the walls of the filter plate lying between the inlet
and outlet ducts representing filter surfaces.
In the exhaust gases from a diesel engine in particular,
there is a plurality of soot particles which can cause
problems if, apart from an elimination of the soot from the
exhaust gases, one would also wish simultaneously to remove
further impurities or harmful exhaust gas constituents by
catalytic action.
Thus, for example, a good catalytic function of the
conversion of carbon monoxide and hydrocarbons by catalytic
materials is not possible when a filter is charged with
soot.
Therefore it is known firstly to clean the soot particles
from the exhaust gases by a filter, and then to direct the
exhaust gases cleaned in this way over a catalyst connected
behind said filter. However a disadvantage of this
arrangement is that it is very expensive and therefore very
uneconomical.
In the prior applications P 39 01 609.9 and P 39 37 809.8
from the same applicant, filters have already been proposed,
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especially for the removal of soot particles, which consist
of a plurality of co~pression-moulded and sintered filter
plates with high temperature stability of the type mentioned
at the beginning.
The object of the present invention is to create a filter of
this type and to improve it so that both a removal of soot
particles and also a catalytic function for the elimination
or conversion of further impurities and harmful constituents
in the exhaust gases is possible in a single filter unit and
as far as possible without reciprocal disadvantageous
influence.
This object is achieved-according to the invention in that
one or several inserts, which are made from catalytic
materials or which are coated with catalytic materials, are
introduced into the outlet ducts.
By the construction of the filter plate specified by the
invention and their arrangement with respect to one another,
it has surprisingly become possible to integrate
catalytically effective inserts directly into the outlet
ducts and thus to dispense with a separate filter unit. As
before, impurities can become deposited on the filter
surface. Thus a soot conversion can occur in the
conventional way on and in the-filter surfaces -and walls
respectively between the inlet and outlet ducts. After
passing through the filter walls separating the inlet ducts
from the outlet ducts and therefore after a soat conversion,
the catalytic action of the inserts may be used to remove
the remaining constituents which can be removed or converted
by catalytic action, such as for example carbon monoxide and
hydrocarbon.
By the design specified by the invention, previously cleaned
exhaust gases flow over the inserts, as a result of which
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expensive coating processes or systems connected one behind
the other can be dispensed with.
The inserts in the outlet ducts are simply constructed as
catalyst plates extending parallel to the direction of flow,
which preferably extend over the entire length of the outlet
ducts.
In this way the exhaust gases flow along all the surfaces of
the catalyst plates on their way to the outlet, and a
correspondingly long time is available for the chemical
reaction.
By using spacers between the individual filter plates, by
which the ducts are formed, the inserts and catalyst plates
respectively can be simply integrated into the outlet ducts.
Thus for this purpose the inserts and catalyst plates
respectively may be disposed between the ribs, beads or the-
like of ribs, beads or the like abutting against one another
of adjacent filter plates.
If it is simply specified that the filter plates are
constructed as waves, the inserts and catalyst plates
respectively may be inserted between wave crests and wave
troughs of adjacent filter plates with abutting wave crests
-- - and wave troughs.
In a very advantageous and not obvious design of the inserts
and catalyst plates respectively, it may be specified that
they are structured on their surfaces.
By this design there is firstly a greater surface and thus
a longer reaction time for the chemical reactions and
secondly by an appropriate adaptation of the structuring a
turbulence effect and thus also a better reaction can be
achieved.
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Many different embodiments are possible for the structuring.
For example, appropriate stamping operations can simply be
performed and protrusions and/or depressions, knobs, ribs,
wave crests and wave troughs and the like may be formed.
In an advantageous development of the invention it may be
specified that the filter plates be coated on the side of
the inlet ducts with catalytically effective materials to
lower the soot conversion temperature. In this way the
efficiency of the filter is increased.
A very advantageous method of producing the filter specified
by the invention may consist in that the inserts and
catalyst plates respectively are provided with protrusions
and/or depressions on their surfaces.
In this way a combined filter for the removal of soot and
the removal of other exhaust gas constituents by a oatalytic
action may be created in practice in a single operating
cycle and thus very cheaply.
The connection of the individual plates together with the
inserts and catalyst plates respectively to form one unit
may be performed in different ways.
Thus-, ~or- example, compression-moulded filter--plates and
inserts, which are coated with catalytically effective
powders, or catalyst plates can be sintered together to form
one unit in a common sintering process, with the powder
fusing together on the inserts.
However it is also possible to bond compression moulded and
already sintered filter plates, between which the
catalytically coated inserts and the catalytic plates
respectively are inserted, to form one unit.
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Likewise the individual compression-moulded and
sintered filter plates having the inserts or
catalyst plates respectively are connected on the
peripheral side by mechanical connection members in
such a way that the inlet and outlet ducts are
produced as desired.
Therefore, in accordance with the present invention,
there is provided a filter, suitable for the
separation of impurities from the exhaust gases of
an internal combustion engine, including a filter
body comprising a plurality of compression-moulded
and sintered filter plates made from powdered metal,
metal filings, metal fibers or a mixture thereof,
which are disposed against one another and separated
by spacers to form a plurality of flow ducts
therebetween, with the flow ducts being alternately
open on one end and closed on the other end so as to
form alternating adjacent inlet and outlet ducts
with the walls of the filter plates lying between
the inlet and outlet ducts providing filter surfaces
and the outlet ducts containing catalytic inserts
which are made of catalytic materials or which are
coated with catalytic materials, said inserts
comprising plates extending parallel to said flow
ducts and generally extending over the entire length
and width of said outlet ducts.
Also in accordance with the present invention, there
is provided a filter apparatus, suitable for the
separation of impurities from the exhaust gases of
an internal combustion engine, said apparatus
including a filter body having a plurality of inlet
and outlet ducts, with the inlet ducts being
separated from the outlet ducts by porous filter
walls, wherein the filter body comprises a plurality
5a 204651 8
of filter plates having a first end portion which is
an extension of a porous filter wall of the filter
plate and a second end portion which comprises a
straight end section parallel to the first end
portion and off-set therefrom by a bent section,
with said plurality of filter plates being arranged
against each other in an alternating head-to-toe
arrangement to provide that said first end portion
of a given filter plate is adjacent the second end
portion of an adjacent plate and the second end
portion of said given filter plate is adjacent the
first end portion of another adjacent plate, to
thereby form said inlet and outlet ducts
therebetween, said first end portion of said given
filter plate and the adjacent second end portion of
an adjacent filter plate being tightly gripped in a
fluid sealing engagement by a clamping element with
all inlet ducts thereby open on a first end face of
said filter body and closed on a second end face of
said filter body, and with all outlet ducts thereby
open on said second end face of said filter body and
closed on said first end face of said filter body,
and said filter body further comprises catalytic
inserts within said outlet ducts.
Further in accordance with the present invention,
there is provided a filter, suitable for the
separation of impurities from the exhaust gases of
an internal combustion engine including a filter
body comprising a plurality of compression-moulded
and sintered filter plates made from powdered metal,
metal filings, metal fibers or a mixture thereof,
said filter plates being coated on the side of the
inlet ducts with catalytically effective materials
to lower the soot conversion temperature, said
filter plates being disposed against one another and
V
5b 20465 1 8
separated by spacers to form a plurality of flow
ducts therebetween, with the flow ducts being
alternately open on one end and closed on the other
end so as to form alternating adjacent inlet and
outlet ducts with the walls of the filter plates
lying between the inlet and outlet ducts providing
filter surfaces and the outlet ducts containing
catalytic inserts which are made of catalytic
materials or which are coated with catalytic
materials, said inserts comprising plates extending
parallel to said flow ducts generally extending over
the entire length and width of said outlet ducts.
An exemplified embodiment of the invention is
described in principle below by reference to the
drawings.
Fig. 1 shows a simplified longitudinal section
through the filter as specified by the
invention (in detail);
Fig. 2 shows a detailed enlarged representation
of a cross section.
The filter is constructed from a plurality of
compression-moulded filter plates 1 with high
temperature stability, which are disposed one on top
of the other. The filter plates 1 may be sintered
and have a waved surface which is such that in the
direction of flow (see arrow A in Fig. 1) flow ducts
are formed. In this case the crest of the waves 9
simultaneously form the spacers for the filter plate
1 adjacent thereto so as to form the desired flow
ducts between individual filter plates (see Fig. 2).
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The filter plates 1 have an identical construction
and at one end have a face representing a direct and
straight extension of the filter surface, whereas on
the other side it has a bend 2 ending in a straight
end piece 3, parallel to the surface of the filter
plate.
However it is of course possible for bends to be
located at both ends.
To produce a filter the desired number of filter
plates 1 are laid on top of one another in such a
way that one front face with a straight part and one
front face with the bend
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2 and the end piece lie on top of one another. In this way
between adjacent filter plates 1 not only flow channels are
farmed, but edges are alternately produced on one side of
the ducts by the bends 2 or the end pieces 3 respectively.
As is evident, in this way inlet ducts 4 are created which
are open on the inlet side - on the left in the drawings -
and are closed on the right, while outlet ducts 5 lying
between them are closed on the left side, i.e. on the inlet
side, and open on the right side, i.e. on the outlet side.
However at the same time as the filter plates 1 are laid one
on top of the other, catalyst plates 7 are inserted as
inserts between them respectively behind two filter plates
1 laid on top of one another. This is done in such a way
that they lie in the outlet ducts 5.
The catalyst plates 7 extend in the direction of flow over
the entire length and width of the outlet ducts 5, with them
lying on the wave crests and wave troughs of filter plates
adjacent to one another.
To form a unit and to seal the individual filter plates 1 at
their inlet and outlet sides, the filter plates 1 may now be
connected to one another in a common sintering process
- - - together-with the catalyst-plates 7. Likewise they may be---
bonded at their ends to one another or as specified in the
prior application P 39 37 809.8 and be connected to one
another by mechanical means shown here in Fig. 1, for
example. The mechanical means may be spring clamps 6, for
example, which force together the ends of the filter plates
1. Another method of connection may also be produced by lock
seams at the ends of the filter plates, which are
accordingly crimped over.
In operation soot constituents on the filter surfaces and in
the porous walls of the filter plates 1 respectively between
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the inlet ducts 4 and the outlet ducts 5 are separated, with
soot conversion or soot carburation occurring. After passing
through the filter walls between the inlet ducts 4 and the
outlet ducts 5, the exhaust gases precleaned in this way may
flow on both sides along the catalyst plates 7 in the outlet
ducts 5 to the outlet, with the conversion of further
harmful exhaust gas constituents occurring on the basis of
the catalytic action of the catalyst plates 7.
Known catalytic materials, such as platinum, vanadium,
cobalt, rhodium and the like, may be used as materials for
the catalyst plate or for its coating.
As is evident from the-enlarged representation in Fig. 2,
the catalyst plates 7 are structured on both their surfaces.
Corresponding protrusions or knobs are shown in principle by
the reference number "10".
In order to improve the soot conversion, in particular to
reduce the soot conversion temperature, the filter plates
may in addition be provided with catalytically effective
materials, such as manganese, molybdenum or the like, on
their sides closest to the inlet sides.
The lateral sealing of the filter plates may be effected,
for example, by an appropriate design with sealing lips 8,
which can be constructed as step-shaped shoulders. In this
case sealing may also be effected by bonding, sintering or
by a mechanical compression operation.
A part of the filter housing, in which the filter plates 1
are installed, is represented by the reference number "11".
Powdered metal, metal wires, metal fibres or metal filings
can be used as the basic material for the filter plates 1.
Care just has to be taken so that the walls have adequate
porosity, which is achieved either by coarse powdered metal
8 - 20465 1 8
or even better by plaiting or tangle of metal wires or metal
filings or metal fibres respectively.
A woven cloth or a knitted fabric of metal fibres or metal
wires which are sintered together can also be used as a
basic material for this purpose. Such a process is
described, for example, in the prior application P 39 08
581.3.
Such a woven cloth or knitted fabric may also be in strip
form, which is then wound in a spiral shape in several
turns, with the individual turns being separated by spacers
in the strip and flow ducts being formed in this way. The
flow ducts then only need to be alternately sealed on the
front sides, so that inlet and outlet channels are created,
so that the exhaust gases can flow in the axial direction
through the cylindrical filter body formed in this way. Such
a filter body is described in the prior application P 39 10
609.9, for example. Also with such a filter body inserts and
catalyst plates respectively can be disposed in the outlet
ducts without any problems. For this purpose it is just
necessary during the helicoidal winding of the strip when
it is produced simultaneously to lap and push in inserts so
that they are respectively located in the outlet ducts.
