WO2007025873A2 - Filter element with reduced flow resistance - Google Patents

Filter element with reduced flow resistance Download PDF

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Publication number
WO2007025873A2
WO2007025873A2 PCT/EP2006/065433 EP2006065433W WO2007025873A2 WO 2007025873 A2 WO2007025873 A2 WO 2007025873A2 EP 2006065433 W EP2006065433 W EP 2006065433W WO 2007025873 A2 WO2007025873 A2 WO 2007025873A2
Authority
WO
WIPO (PCT)
Prior art keywords
filter element
channels
outlet
inlet
element according
Prior art date
Application number
PCT/EP2006/065433
Other languages
German (de)
French (fr)
Other versions
WO2007025873A3 (en
Inventor
Ulrich Eisele
Alexander Flaig
Andreas Mattern
Original Assignee
Robert Bosch Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Priority to EP06778281A priority Critical patent/EP1924337A2/en
Publication of WO2007025873A2 publication Critical patent/WO2007025873A2/en
Publication of WO2007025873A3 publication Critical patent/WO2007025873A3/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/0039—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours with flow guiding by feed or discharge devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B11/00—Apparatus or processes for treating or working the shaped or preshaped articles
    • B28B11/003—Apparatus or processes for treating or working the shaped or preshaped articles the shaping of preshaped articles, e.g. by bending
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B3/00—Producing shaped articles from the material by using presses; Presses specially adapted therefor
    • B28B3/20—Producing shaped articles from the material by using presses; Presses specially adapted therefor wherein the material is extruded
    • B28B3/26—Extrusion dies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B3/00—Producing shaped articles from the material by using presses; Presses specially adapted therefor
    • B28B3/20—Producing shaped articles from the material by using presses; Presses specially adapted therefor wherein the material is extruded
    • B28B3/26—Extrusion dies
    • B28B3/269—For multi-channeled structures, e.g. honeycomb structures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
    • B29C48/11—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels comprising two or more partially or fully enclosed cavities, e.g. honeycomb-shaped
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/12—Articles with an irregular circumference when viewed in cross-section, e.g. window profiles
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
    • F01N3/0222—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being monolithic, e.g. honeycombs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/42—Component parts, details or accessories; Auxiliary operations
    • B29C49/46—Component parts, details or accessories; Auxiliary operations characterised by using particular environment or blow fluids other than air
    • B29C2049/4602—Blowing fluids
    • B29C2049/4638—Blowing fluids being a hot gas, i.e. gas with a temperature higher than ambient temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
    • B29C49/04—Extrusion blow-moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/42—Component parts, details or accessories; Auxiliary operations
    • B29C49/46—Component parts, details or accessories; Auxiliary operations characterised by using particular environment or blow fluids other than air
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2709/00—Use of inorganic materials not provided for in groups B29K2703/00 - B29K2707/00, for preformed parts, e.g. for inserts
    • B29K2709/02—Ceramics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/14—Filters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/60—Multitubular or multicompartmented articles, e.g. honeycomb
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/06—Ceramic, e.g. monoliths
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/30—Honeycomb supports characterised by their structural details
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the invention relates to a filter element, in particular for filtering exhaust gases of a diesel internal combustion engine, according to the preamble of claim 1.
  • These filter elements are usually produced by extruding a ceramic material, in particular cordierite or silicon carbide.
  • the exhaust gas to be cleaned flows through the filter walls between the inlet channels and the outlet channels.
  • the flow rate within one entrance channel decreases continuously while increasing to the same extent in the adjacent exit passageways.
  • Entry channels in the area of the entry surfaces actually too small, while they are actually too big in the area of the exit surface because of the previously greatly reduced volume flow. The same applies to the exit channels too.
  • the pressure drop within the filter element or the flow resistance of the filter element is relatively large.
  • the invention has for its object to provide both a filter element, the flow resistance is reduced in the same space, and to provide methods for producing such filter elements.
  • a filter element in particular for filtering exhaust gases of a diesel internal combustion engine with an inlet surface and with an exit surface, with a plurality of inlet channels and with a plurality of
  • Exit channels wherein the inlet channels begin at the inlet surface and are closed at the outlet surface, and wherein the outlet channels are closed at the inlet surface and terminate at the outlet surface, achieved in that a
  • Cross-sectional area decreases at least one inlet channel in the direction of the longitudinal axis of the filter element.
  • the inlet channels on the periphery of the filter element with a variable cross-sectional area in order to lower its resistance to the inlet channels arranged in the center of the filter element and acted upon directly by the dynamic pressure of the exhaust gas stream. This ensures that a greater part of the exhaust gas deflects from the center of the filter element and enters at the periphery of the filter element.
  • Particularly advantageous variants of the invention provide that a cross-sectional area of at least one outlet channel increases in the direction of the longitudinal axis of the filter element. This makes it possible to optimize the pressure drop in the outlet channels or in the corresponding manner as the outlet channels of the filter element.
  • the shape of a parabola or the shape of a trapezoid has been found. If, in fact, the permeability of the filter wall is constant over the entire length of the filter element, the lengthwise pressure loss dp / dx over the entire length of the filter element can be kept constant by means of an inlet channel of parabolic design in longitudinal section. If the inlet channel (s) and / or the outlet channel (s) have the shape of a trapezoid in longitudinal section, the aerodynamic optimum can not be fully achieved, but the trapezoidal shape of an inlet channel is relatively easy to manufacture, so that this shape is a good compromise has low production costs and minimal flow resistance of the filter element.
  • the shape of the inlet channels and / or the outlet channels in the longitudinal section of the filter element can be determined by the fact that the pressure gradient dp to dx is at least approximately constant over the length of the filter element.
  • the shape of the cross sections through the inlet channels and the outlet channels are not subject to any restrictions in the filter element according to the invention.
  • they may be square, rectangular, hexagonal, circular, cross-shaped.
  • the filter element is constructed rotationally symmetrical, in particular cylindrical, or centrally symmetrical. Then it is easiest possible to fit the filter element in a housing.
  • the filter element according to the invention preferably consists of a ceramic material, in particular of cordierite or silicon carbide.
  • the above object is also achieved by a method for producing a body having a plurality of mutually parallel channels, in particular for producing a filter element made of a ceramic material, wherein the prismatic body produced by extrusion and at the same time a gas, in particular air, in a or more of the channels of the extruded body is injected.
  • Hot air has proven particularly suitable for blowing in, since the hot air develops its shaping effect only at very short notice.
  • the reason for the temporally and locally limited effect of the injected hot air is the rapid decrease in pressure of the injected hot air because their cooling on the walls of the filter element.
  • the object mentioned at the outset is likewise achieved by a method for producing a prismatic body, in particular for producing a filter element from a ceramic material, in which a prismatic body is extruded and subsequently one or more channels of the extruded body are widened.
  • the channel or channels are widened with one or more expansion mandrels.
  • the Aufweitdorne are only about half as long as the filter element to be processed, when first the Aufweitdorne be introduced from one side, for example in the inlet channels of the filter element and then from the another side is introduced into the adjacent to the inlet channels arranged outlet channels.
  • Cordierite and silicon carbide have proven to be particularly suitable materials for producing the filter element according to the invention.
  • Figure 1 is a schematic representation of an internal combustion engine with an inventive
  • FIG. 2 shows a filter element according to the prior art in
  • FIGS. 4 and 5 are longitudinal sections through exemplary embodiments of filter elements according to the invention.
  • FIG. 6 shows a longitudinal section through an extrusion tool for carrying out the method according to the invention
  • Figure 7 is a longitudinal section along the line B-B and
  • FIG. 8 shows a tool for expanding the inlet channels in a side view.
  • an internal combustion engine carries the reference numeral 10.
  • the exhaust gases are discharged via an exhaust pipe 12, in which a filter device 14 is arranged.
  • soot particles are filtered out of the exhaust gas flowing in the exhaust pipe 12.
  • the filter device 14 comprises a cylindrical housing 16, in which a rotationally symmetrical in the present embodiment, a total also cylindrical filter element 18 is arranged.
  • FIG. 2 shows a cross-section of a filter element 18 according to the prior art.
  • the filter element 18 is manufactured as an extruded shaped body from a ceramic material, such as cordierite.
  • the filter element 18 is flowed through in the direction of the arrows 20 of not shown exhaust gas.
  • An entrance surface has the reference numeral 22 in FIG. 2, while an exit surface in FIG. 2 has the reference numeral 24.
  • inlet channels 28 Parallel to a longitudinal axis 26 of the filter element 18 extend a plurality of inlet channels 28 in alternation with outlet channels 30.
  • the inlet channels 28 are closed at the outlet surface 24.
  • the sealing plugs are shown in FIG. 2 without reference numerals.
  • the outlet channels 30 are open at the outlet surface 24 and closed in the region of the inlet surface 22.
  • the flow path of the unpurified exhaust gas thus leads into one of the inlet channels 28 and from there through a filter wall (without reference numeral) into one of the outlet channels 30. This is illustrated by the arrows 32 by way of example.
  • FIG. 3 a longitudinal section through a filter element according to the prior art is greatly enlarged and not shown to scale.
  • an inlet channel 28 and an outlet channel 30 are shown, which are separated by a filter wall 34.
  • the inlet channel 28 is closed at the outlet surface 24, while the outlet channel 30 is closed at the inlet surface 22.
  • the exhaust gas to be cleaned is forced to flow through the filter wall 34. This is possible because of the porosity of the material used and leads to the desired filtering of the soot particles from the exhaust gas.
  • FIG. 3 shows a filter element according to the prior art, in which the cross-section of both the inlet channels 28 and the outlet channels 30 is constant over the length of the filter element.
  • the longitudinal axis 26 is referred to as X-coordinate., Whose origin is at the entrance surface 22.
  • FIG. 4 shows a first exemplary embodiment of a filter element 18 according to the invention, in which the cross-sectional area of both the inlet channel 28 and the outlet channel 30 is not constant over the length of the filter element.
  • the filter wall 34 is set to a certain extent obliquely. Assuming that the inlet channels 28 and the outlet channels 30 have a square cross-sectional area, then the inlet channels 28 and the outlet channels 30 according to the embodiment of Figure 4 have the shape of a truncated pyramid.
  • the volume flow V decreases linearly over the length of the filter element 18 and the cross-sectional area of the inlet channel decreases over the length, a pressure gradient already significantly improved compared with the prior art results qualitatively in FIG. 4 below.
  • the maximum local pressure gradient dp / dx at the same outer dimensions of the filter element 18 is significantly smaller than in a filter element with prismatic channels, so that the
  • a filter element according to the invention according to FIG. 4 can be produced, for example, by using an extruded blank with the aid of expanding mandrels which are alternately inserted into the inlet channels 28 and the
  • FIG. 5 shows a further exemplary embodiment of a filter element according to the invention.
  • the filter wall is curved in longitudinal section in the form of a parabola.
  • This filter element can be produced by the method claimed according to the invention and the extrusion tool shown in FIG.
  • FIG. 6 shows a partial section of an extrusion tool according to the invention.
  • the extrusion tool consists essentially of a base body 36 in which a plurality of mutually parallel channels 38 are introduced.
  • the channels 38 are in the form of a cylindrical bore and serve to convey the material to be extruded (not shown) through the body 1 to an exit 40.
  • the material is brought into the desired shape.
  • the longitudinal axes of the channels have been provided with the reference numeral 42 in FIG.
  • the material to be extruded (not shown) is pressed by a likewise not shown extruder screw or a similar device in Figure 6 from right to left by the extrusion die.
  • Adjoining the channels 38 is a frusto-conical section 44, which opens into grooves 46.
  • the grooves 46 serve to distribute the material to be extruded uniformly over the entire cross section of the extrusion die and give the desired shape to the filter element (not shown) to be extruded.
  • nozzle bores 48 are provided in the base body 36. Via the nozzle bores 48, it is possible to pressurize selected channels, such as all inlet channels 28 of the freshly extruded filter element (not shown), so that the inlet channels are widened locally immediately after the outlet 40 from the extrusion die.
  • air in particular hot air can be used.
  • the hot air has the advantage that immediately behind the outlet 40 it allows the building of a high pressure and consequently the expansion of the corresponding freshly extruded channel and immediately after the expansion due to the cooling of the air, the pressure decreases and thus no deformation of more distant areas takes place of the pressurized air channel.
  • filter walls 34 it is also possible to produce other forms of filter walls 34. This may be useful, for example, if the permeability of the filter wall 34 in the filter element 18 is not constant, but is lower in some areas than in the other areas, for example, by a catalytic coating applied locally. These various local permeabilities can be taken into account by suitable shaping of the filter walls 34 such that even in these embodiments of filter elements the pressure gradient dp / dx in the longitudinal direction of the filter element is constant and thus the total flow resistance of the filter element reaches a minimum for a given volume of construction.
  • FIG. 7 shows a section along the line B-B through the main body 36. From this view, it is clear that the base body 36 is traversed by a network of grooves 46, wherein the longitudinal axes 7 of the channels 3 are in the intersections perpendicular to each other extending grooves 46. In FIG. 7, the nozzle bores 48 can also be seen in the hatched areas between the grooves 46, which are shown hatched.
  • the filter produced with the extrusion tool according to FIGS. 6 and 7 has a honeycomb structure with filter walls running perpendicular to one another, the cross-sectional area of both the inlet channels 28 and the outlet channels 30 being a square.
  • the cross-sectional area of the channels 28 and 30 substantially corresponds to the hatched areas in FIG. 7.
  • FIG. 8 shows in simplified form a tool for widening the channels.
  • the tool consists of a base plate 50, on which various Adviceweitdorne 52 are mounted.
  • the distance between the Aufweitdorne 52 to each other corresponds to the distance of the channels to be expanded of an extruded blank.
  • the expansion tool according to the invention can be introduced into the blank, which is still plastically deformable and whose channels are prismatic, at least to half the length of the blank, so that in this area, the channels into which the Aufweitdorne 52 are inserted according to the shape and the expanding mandrels 52 are widened.
  • the tool according to the invention is introduced into the blank from the other side in such a way that the expanding mandrels are introduced into the hitherto unexpanded channels, this leads to the desired geometry, for example in accordance with FIG. 4, also in the second half of the extruded blank , is achieved.
  • they can be provided with a suitable coating.

Abstract

The invention relates to a ceramic filter element (18) that has a reduced flow resistance as well as a method for producing the same. Disclosed is a filter element, especially for filtering exhaust gases of a diesel engine, comprising an intake area (22) and a discharge area (24), a plurality of intake ducts (28), and an plurality of discharge ducts (30). The intake ducts (28) originate in the intake area (22) and are closed in the discharge area (24) while the discharge ducts (30) are closed in the intake area (22) and end in the discharge area (24). The inventive filter element is characterized in that a cross-sectional area (A) of at least one intake duct (28) decreases in the direction of a longitudinal axis (X) of the filter element (18).

Description

Filterelement mit verringertem StrömungswiderstandFilter element with reduced flow resistance
Die Erfindung betrifft ein Filterelement, insbesondere zur Filterung von Abgasen einer Dieselbrennkraftmaschine, nach dem Oberbegriff des Anspruchs 1.The invention relates to a filter element, in particular for filtering exhaust gases of a diesel internal combustion engine, according to the preamble of claim 1.
Stand der TechnikState of the art
Diese Filterelement werden üblicherweise durch Extrudieren eines keramischen Werkstoffes, insbesondere Cordierit oder Siliziumcarbid, hergestellt.These filter elements are usually produced by extruding a ceramic material, in particular cordierite or silicon carbide.
Dabei strömt das zu reinigende Abgas durch die Filterwände zwischen den Eintrittskanälen und den Austrittskanälen hindurch. Infolgedessen nimmt der Volumenstrom innerhalb eines Eintrittskanals kontinuierlich ab, während er in gleichem Maße in den benachbarten Austrittskanälen zunimmt.In this case, the exhaust gas to be cleaned flows through the filter walls between the inlet channels and the outlet channels. As a result, the flow rate within one entrance channel decreases continuously while increasing to the same extent in the adjacent exit passageways.
Die aus dem Stand der Technik bekannten keramischen Filterelemente werden durch Extrusion hergestellt und weisen prismatische Kanäle auf. Daher sind dieThe known from the prior art ceramic filter elements are produced by extrusion and have prismatic channels. Therefore, the
Eintrittskanäle im Bereich der Eintrittsflächen eigentlich zu klein, während sie im Bereich der Austrittsfläche wegen des bis dahin stark reduzierten Volumenstroms eigentlich zu groß sind. Entsprechendes trifft auch für die Austrittskanäle zu. Das führt im Ergebnis dazu, dass bei vorgegebenem Bauraum des Filterelements der Druckabfall innerhalb des Filterelements beziehungsweise der Strömungswiderstand des Filterelements relativ groß ist.Entry channels in the area of the entry surfaces actually too small, while they are actually too big in the area of the exit surface because of the previously greatly reduced volume flow. The same applies to the exit channels too. As a result, with a given installation space of the filter element, the pressure drop within the filter element or the flow resistance of the filter element is relatively large.
Der Erfindung liegt die Aufgabe zugrunde, sowohl ein Filterelement, dessen Strömungswiderstand bei gleichem Bauraum reduziert ist, als auch Verfahren zur Herstellung solcher Filterelemente bereitzustellen.The invention has for its object to provide both a filter element, the flow resistance is reduced in the same space, and to provide methods for producing such filter elements.
Diese Aufgabe wird erfindungsgemäß bei einem Filterelement, insbesondere zur Filterung von Abgasen einer Dieselbrennkraftmaschine mit einer Eintrittsfläche und mit einer Austrittsfläche, mit einer Vielzahl von Eintrittskanälen und mit einer Vielzahl vonThis object is achieved with a filter element, in particular for filtering exhaust gases of a diesel internal combustion engine with an inlet surface and with an exit surface, with a plurality of inlet channels and with a plurality of
Austrittskanälen, wobei die Eintrittskanäle an der Eintrittsfläche beginnen und an der Austrittsfläche verschlossen sind, und wobei die Austrittskanäle an der Eintrittsfläche verschlossen sind und an der Austrittsfläche enden, dadurch gelöst, dass eineExit channels, wherein the inlet channels begin at the inlet surface and are closed at the outlet surface, and wherein the outlet channels are closed at the inlet surface and terminate at the outlet surface, achieved in that a
Querschnittsfläche mindestens eines Eintrittskanals in Richtung der Längsachse des Filterelements abnimmt.Cross-sectional area decreases at least one inlet channel in the direction of the longitudinal axis of the filter element.
Vorteile der ErfindungAdvantages of the invention
Durch die variable Gestaltung der Querschnittsfläche in Richtung der Längsachse des Filterelements ist es möglich, die Querschnittsfläche an den Abgasvolumenstrom anzupassen, so dass der Druckabfall in Richtung der Längsachse vergleichmäßigt wird. Dies führt im Ergebnis dazu, dass der Gesamtströmungswiderstand des Filterelements bei sonst gleichen Randbedingungen verringert wird. Gleichzeitig wird der Abgasstrom durch die Filterwände vergleichmäßigt, was deren Lebensdauer erhöht. Selbstverständlich ist es besonders bevorzugt, wenn die Querschnittsflächen aller Eintrittskanäle in Richtung der Längsachse des Filterelements abnehmen. Dann kann der erfindungsgemäße Effekt in vollem Umfang ausgenützt werden. Es sind jedoch auch Zwischenlösungen, bei denen nur Teile der Eintrittskanäle mit variabler Querschnittsfläche ausgestaltet werden, denkbar. Beispielsweise ist es denkbar, die Eintrittskanäle an der Peripherie des Filterelements mit variabler Querschnittsfläche auszugestalten, um deren Widerstand gegenüber den im Zentrum des Filterelements angeordneten und direkt mit dem Staudruck des Abgasstroms beaufschlagten Eintrittskanälen abzusenken. Dadurch wird gewährleistet, dass ein größerer Teil des Abgases von der Mitte des Filterelements abgelenkt und an der Peripherie des Filterelements in dieses eintritt .Due to the variable design of the cross-sectional area in the direction of the longitudinal axis of the filter element, it is possible to adapt the cross-sectional area to the exhaust gas volume flow, so that the pressure drop in the direction of the longitudinal axis is made uniform. As a result, the total flow resistance of the filter element is reduced under otherwise identical boundary conditions. At the same time, the exhaust gas flow through the filter walls is made uniform, which increases their service life. Of course, it is particularly preferred if the cross-sectional areas of all inlet channels decrease in the direction of the longitudinal axis of the filter element. Then, the effect of the invention can be fully exploited. However, there are also intermediate solutions in which only parts of the inlet channels are designed with variable cross-sectional area, conceivable. For example, it is conceivable to configure the inlet channels on the periphery of the filter element with a variable cross-sectional area in order to lower its resistance to the inlet channels arranged in the center of the filter element and acted upon directly by the dynamic pressure of the exhaust gas stream. This ensures that a greater part of the exhaust gas deflects from the center of the filter element and enters at the periphery of the filter element.
Besonders vorteilhafte Varianten der Erfindung sehen vor, dass eine Querschnittsfläche mindestens eines Austrittskanals in Richtung der Längsachse des Filterelements zunimmt. Dadurch ist es möglich, auch den Druckabfall in dem oder den Austrittskanälen in entsprechender Weise wie die Austrittskanäle des Filterelements zu optimieren.Particularly advantageous variants of the invention provide that a cross-sectional area of at least one outlet channel increases in the direction of the longitudinal axis of the filter element. This makes it possible to optimize the pressure drop in the outlet channels or in the corresponding manner as the outlet channels of the filter element.
Als besonders bevorzugte Gestaltungen der Eintrittskanäle und/oder der Austrittskanäle hat sich die Form einer Parabel oder die Form eines Trapezes erwiesen. Wenn nämlich die Permeabilität der Filterwand über die gesamte Länge des Filterelements konstant ist, kann durch einen im Längsschnitt parabelförmig gestalteten Eintrittskanal der auf die Länge bezogene Druckverlust dp/dx über die gesamte Länge des Filterelements konstant gehalten werden. Wenn der oder die Eintrittskanäle und/oder der oder die Austrittskanäle im Längsschnitt die Form eines Trapezes aufweisen, kann zwar das strömungstechnische Optimum nicht ganz erreicht werden, jedoch ist die trapezförmige Form eines Eintrittskanals fertigungstechnisch relativ einfach zu realisieren, so dass diese Form einen guten Kompromiss zwischen geringem Fertigungsaufwand und minimalem Strömungswiderstand des Filterelements aufweist.As a particularly preferred designs of the inlet channels and / or the outlet channels, the shape of a parabola or the shape of a trapezoid has been found. If, in fact, the permeability of the filter wall is constant over the entire length of the filter element, the lengthwise pressure loss dp / dx over the entire length of the filter element can be kept constant by means of an inlet channel of parabolic design in longitudinal section. If the inlet channel (s) and / or the outlet channel (s) have the shape of a trapezoid in longitudinal section, the aerodynamic optimum can not be fully achieved, but the trapezoidal shape of an inlet channel is relatively easy to manufacture, so that this shape is a good compromise has low production costs and minimal flow resistance of the filter element.
Es versteht sich von selbst, dass auch andere Formen der Eintrittskanäle und/oder der Austrittskanäle im Längsschnitt des Filterelements denkbar sind. Dies kann insbesondere dann sinnvoll sein, wenn die Filterwände lokal unterschiedliche Permeabilitäten aufweisen, beispielsweise durch eine lokale katalytisch wirkende Beschichtung. In diesem Fall kann die Form der Eintrittskanäle und der Austrittskanäle in einem Längsschnitt des Filterelements dadurch bestimmt werden, dass der Druckgradient dp nach dx mindestens annähernd über die Länge des Filterelements konstant ist.It goes without saying that other shapes of the inlet channels and / or the outlet channels in the longitudinal section of the filter element are conceivable. This may be particularly useful if the filter walls have locally different permeabilities, for example by a local catalytic coating. In this case, the shape of the inlet channels and the outlet channels in a longitudinal section of the filter element can be determined by the fact that the pressure gradient dp to dx is at least approximately constant over the length of the filter element.
Die Form der Querschnitte durch die Eintrittskanäle und die Austrittskanäle sind bei dem erfindungsgemäßen Filterelement keinen Restriktionen unterworfen. Sie können beispielsweise quadratisch, rechteckig, sechseckig, kreisrund, kreuzförmig sein.The shape of the cross sections through the inlet channels and the outlet channels are not subject to any restrictions in the filter element according to the invention. For example, they may be square, rectangular, hexagonal, circular, cross-shaped.
Besonders bevorzugt ist es jedoch, wenn das Filterelement rotationssymmetrisch, insbesondere zylindrisch, oder zentralsymmetrisch aufgebaut ist. Dann ist es am einfachsten möglich, das Filterelement in ein Gehäuse einzupassen.However, it is particularly preferred if the filter element is constructed rotationally symmetrical, in particular cylindrical, or centrally symmetrical. Then it is easiest possible to fit the filter element in a housing.
Das erfindungsgemäße Filterelement besteht vorzugsweise aus einem keramischen Werkstoff, insbesondere aus Cordierit oder Siliziumcarbid.The filter element according to the invention preferably consists of a ceramic material, in particular of cordierite or silicon carbide.
Die eingangs genannte Aufgabe wird ebenfalls gelöst durch ein Verfahren zur Herstellung eines Körpers mit einer Vielzahl parallel zueinander verlaufender Kanäle, insbesondere zur Herstellung eines Filterelements aus einem keramischen Werkstoff, bei welchem der prismatische Körper durch Extrudieren hergestellt und gleichzeitig ein Gas, insbesondere Luft, in einen oder mehrere der Kanäle des extrudierten Körpers eingeblasen wird.The above object is also achieved by a method for producing a body having a plurality of mutually parallel channels, in particular for producing a filter element made of a ceramic material, wherein the prismatic body produced by extrusion and at the same time a gas, in particular air, in a or more of the channels of the extruded body is injected.
Durch den erhöhten Druck im Inneren des Filterelements, der durch das eingeblasene Gas verursacht wird, findet unmittelbar nach dem eigentlichen Extrusionsvorgang eine lokale Aufweitung einzelner Kanäle des extrudierten Körpers statt. Dieser Vorgang ähnelt dem aus der Kunststofftechnik bekannten Blasformen.Due to the increased pressure inside the filter element, which is caused by the injected gas, a local expansion of individual channels of the extruded body takes place immediately after the actual extrusion process. This process is similar to the known from the plastic art blow molding.
Im Ergebnis ist es dadurch möglich, den ursprünglich prismatischen Kanal durch mehr oder minder starkes Aufweiten in die gewünschte Form zu bringen. Da das Einblasen eines Gases gleichzeitig mit demAs a result, it is possible to bring the original prismatic channel by more or less strong expansion in the desired shape. Since the injection of a gas simultaneously with the
Extrusionsvorgang erfolgt, steigen die Fertigungskosten nur marginal an, da die Ausbringung der Extrudiermaschine nicht reduziert wird. Es ist lediglich simultan mit dem Extrudieren des Filterelements das Einblasen einer ausreichenden Menge von Luft oder eines anderen geeigneten Fluids in Abhängigkeit der Extrusionsgeschwindigkeit zu regeln.Extrusion process takes place, the production costs increase only marginally, since the output of the extruding machine is not reduced. It is only necessary to control the injection of a sufficient amount of air or other suitable fluid as a function of the extrusion rate, simultaneously with the extrusion of the filter element.
Als besonders geeignet hat sich heiße Luft zum Einblasen erwiesen, da die heiße Luft nur sehr kurzfristig ihre formende Wirkung entfaltet. Ursächlich für die zeitlich und örtlich begrenzte Wirkung der eingeblasenen heißen Luft ist die rasche Druckabnahme der eingeblasenen heißen Luft wegen deren Abkühlung an den Wänden des Filterelements .Hot air has proven particularly suitable for blowing in, since the hot air develops its shaping effect only at very short notice. The reason for the temporally and locally limited effect of the injected hot air is the rapid decrease in pressure of the injected hot air because their cooling on the walls of the filter element.
Die eingangs genannte Aufgabe wird ebenfalls gelöst durch ein Verfahren zur Herstellung eines prismatischen Körpers, insbesondere zur Herstellung eines Filterelements aus einem keramischen Werkstoff, bei welchem ein prismatischer Körper extrudiert wird und anschließend einer oder mehrere Kanäle des extrudierten Körpers aufgeweitet werden.The object mentioned at the outset is likewise achieved by a method for producing a prismatic body, in particular for producing a filter element from a ceramic material, in which a prismatic body is extruded and subsequently one or more channels of the extruded body are widened.
Dabei hat es sich als besonders vorteilhaft erwiesen, wenn der oder die Kanäle mit einem oder mehreren Aufweitdornen aufgeweitet werden. Um beispielsweise Kanäle mit einer trapezförmigen Form in Längsrichtung des Filterelements herzustellen, genügt es, wenn die Aufweitdorne nur etwa halb so lang sind wie das zu bearbeitende Filterelement, wenn zunächst die Aufweitdorne von einer Seite beispielsweise in die Eintrittskanäle des Filterelements eingeführt werden und anschließend von der anderen Seite in die benachbart zu den Eintrittskanälen angeordneten Austrittskanälen eingeführt wird.It has proven to be particularly advantageous if the channel or channels are widened with one or more expansion mandrels. For example, to produce channels with a trapezoidal shape in the longitudinal direction of the filter element, it is sufficient if the Aufweitdorne are only about half as long as the filter element to be processed, when first the Aufweitdorne be introduced from one side, for example in the inlet channels of the filter element and then from the another side is introduced into the adjacent to the inlet channels arranged outlet channels.
Als besonders geeignete Werkstoffe zur Herstellung des erfindungsgemäßen Filterelements haben sich Cordierit und Siliziumcarbid erwiesen.Cordierite and silicon carbide have proven to be particularly suitable materials for producing the filter element according to the invention.
Weitere Vorteile und vorteilhafte Ausgestaltungen der Erfindung sind der nachfolgenden Zeichnung, deren Beschreibung und den Patentansprüchen entnehmbar. Alle in der Zeichnung, deren Beschreibung und den Patentansprüchen beschriebenen Merkmale können sowohl einzeln als auch in beliebiger Kombination miteinander erfindungswesentlich sein.Further advantages and advantageous embodiments of the invention are the following drawings, the description and the claims removable. All features described in the drawing, the description and the claims may be essential to the invention both individually and in any combination.
Zeichnungen Es zeigen :drawings Show it :
Figur 1 eine schematische Darstellung einer Brennkraftmaschine mit einer erfindungsgemäßenFigure 1 is a schematic representation of an internal combustion engine with an inventive
Abgasnachbehandlungseinrichtung,Exhaust gas aftertreatment device,
Figur 2 ein Filterelement nach dem Stand der Technik imFigure 2 shows a filter element according to the prior art in
Längsschnitt,Longitudinal section
Figur 3 einen Längsschnitt durch einen Teil eines3 shows a longitudinal section through a part of a
Filterelements gemäß Figur 2,Filter element according to Figure 2,
Figuren 4 und 5 Längsschnitte durch Ausführungsbeispiele erfindungsgemäßer Filterelemente,FIGS. 4 and 5 are longitudinal sections through exemplary embodiments of filter elements according to the invention,
Figur 6 einen Längsschnitt durch ein Extrusionswerkzeug zur Durchführung des erfindungsgemäßen Verfahrens,FIG. 6 shows a longitudinal section through an extrusion tool for carrying out the method according to the invention,
Figur 7 einen Längsschnitt entlang der Linie B-B undFigure 7 is a longitudinal section along the line B-B and
Figur 8 ein Werkzeug zum Aufweiten der Eintrittskanäle in einer Seitenansicht.8 shows a tool for expanding the inlet channels in a side view.
Beschreibung der AusführungsbeispieleDescription of the embodiments
In Figur 1 trägt eine Brennkraftmaschine das Bezugszeichen 10. Die Abgase werden über ein Abgasrohr 12 abgeleitet, in dem eine Filtereinrichtung 14 angeordnet ist. Mit dieser werden Rußpartikel aus dem im Abgasrohr 12 strömenden Abgas herausgefiltert. Dies ist insbesondere bei Diesel- Brennkraftmaschinen erforderlich, um gesetzliche Bestimmungen einzuhalten. Die Filtereinrichtung 14 umfasst ein zylindrisches Gehäuse 16, in dem eine im vorliegenden Ausführungsbeispiel rotationssymmetrisches, insgesamt ebenfalls zylindrisches Filterelement 18 angeordnet ist.In Figure 1, an internal combustion engine carries the reference numeral 10. The exhaust gases are discharged via an exhaust pipe 12, in which a filter device 14 is arranged. With this, soot particles are filtered out of the exhaust gas flowing in the exhaust pipe 12. This is particularly necessary in diesel engines to comply with legal requirements. The filter device 14 comprises a cylindrical housing 16, in which a rotationally symmetrical in the present embodiment, a total also cylindrical filter element 18 is arranged.
In Figur 2 ist ein Querschnitt ein Filterelement 18 nach dem Stand der Technik dargestellt. Das Filterelement 18 ist als extrudierter Formkörper aus einem keramischen Material, wie zum Beispiel Cordierit, hergestellt. Das Filterelement 18 wird in Richtung der Pfeile 20 von nicht dargestelltem Abgas durchströmt. Eine Eintrittsfläche hat in Figur 2 das Bezugszeichen 22, während eine Austrittsfläche in Figur 2 das Bezugszeichen 24 hat.FIG. 2 shows a cross-section of a filter element 18 according to the prior art. The filter element 18 is manufactured as an extruded shaped body from a ceramic material, such as cordierite. The filter element 18 is flowed through in the direction of the arrows 20 of not shown exhaust gas. An entrance surface has the reference numeral 22 in FIG. 2, while an exit surface in FIG. 2 has the reference numeral 24.
Parallel zu einer Längsachse 26 des Filterelements 18 verlaufen mehrere Eintrittskanäle 28 im Wechsel mit Austrittskanälen 30. Die Eintrittskanäle 28 sind an der Austrittsfläche 24 verschlossen. Die Verschlussstopfen sind in Figur 2 ohne Bezugszeichen dargestellt. Im Gegensatz dazu sind die Austrittskanäle 30 an der Austrittsfläche 24 offen und im Bereich der Eintrittsfläche 22 verschlossen.Parallel to a longitudinal axis 26 of the filter element 18 extend a plurality of inlet channels 28 in alternation with outlet channels 30. The inlet channels 28 are closed at the outlet surface 24. The sealing plugs are shown in FIG. 2 without reference numerals. In contrast, the outlet channels 30 are open at the outlet surface 24 and closed in the region of the inlet surface 22.
Der Strömungsweg des ungereinigten Abgases führt also in einen der Eintrittskanäle 28 und von dort durch eine Filterwand (ohne Bezugszeichen) in einen der Austrittskanäle 30. Exemplarisch ist dies durch die Pfeile 32 dargestellt.The flow path of the unpurified exhaust gas thus leads into one of the inlet channels 28 and from there through a filter wall (without reference numeral) into one of the outlet channels 30. This is illustrated by the arrows 32 by way of example.
In Figur 3 ist ein Längsschnitt durch ein Filterelement nach dem Stand der Technik stark vergrößert und nicht maßstäblich dargestellt. In Figur 3 sind ein Eintrittskanal 28 sowie ein Austrittskanal 30 dargestellt, die durch eine Filterwand 34 voneinander getrennt sind. In der vergrößerten Darstellung von Figur 3 ist gut zu erkennen, dass der Eintrittskanal 28 an der Austrittsfläche 24 verschlossen ist, während der Austrittskanal 30 an der Eintrittsfläche 22 verschlossen ist. Dadurch wird das zu reinigende Abgas gezwungen, durch die Filterwand 34 zu strömen. Dies ist wegen der Porosität des verwendeten Werkstoffs möglich und führt zu der gewünschten Filterung der Rußpartikel aus dem Abgas .In FIG. 3, a longitudinal section through a filter element according to the prior art is greatly enlarged and not shown to scale. In Figure 3, an inlet channel 28 and an outlet channel 30 are shown, which are separated by a filter wall 34. In the enlarged view of FIG. 3, it can be seen clearly that the inlet channel 28 is closed at the outlet surface 24, while the outlet channel 30 is closed at the inlet surface 22. As a result, the exhaust gas to be cleaned is forced to flow through the filter wall 34. This is possible because of the porosity of the material used and leads to the desired filtering of the soot particles from the exhaust gas.
In Figur 3 ist ein Filterelement nach dem Stand der Technik dargestellt, bei dem der Querschnitt sowohl der Eintrittskanäle 28 als auch der Austrittskanäle 30 über die Länge des Filterelements konstant ist.FIG. 3 shows a filter element according to the prior art, in which the cross-section of both the inlet channels 28 and the outlet channels 30 is constant over the length of the filter element.
Im Folgenden wird die Längsachse 26 als X-Koordinate bezeichnet wird., wobei deren Ursprung an der Eintrittsfläche 22 liegt.Hereinafter, the longitudinal axis 26 is referred to as X-coordinate., Whose origin is at the entrance surface 22.
In dem oberen der beiden Diagramme von Figur 3 ist derIn the upper of the two diagrams of Figure 3 is the
Volumenstrom V über die X-Achse aufgetragen. Unter derVolume flow V applied over the X-axis. Under the
Annahme konstanter Permeabilität der Filterwand 34 nimmt in erster Näherung der Volumenstrom V linear über die Länge des Filterelements 18 ab. Dies bedeutet, dass der lokale Druckgradient dp/dx, der proportional zu dem Verhältnis vonAssuming constant permeability of the filter wall 34, in a first approximation, the volume flow V decreases linearly over the length of the filter element 18. This means that the local pressure gradient dp / dx, which is proportional to the ratio of
Volumenstrom Fund Quadrat der Querschnittsfläche A desVolumetric flow Fund square of the cross-sectional area A of the
Eintrittskanals ist (dp/dx °= V /A2), in etwa den im unteren Teil von Figur 3 dargestellten Verlauf aufweist.Inlet channel is (dp / dx ° = V / A 2 ), has approximately the course shown in the lower part of Figure 3.
Ein strömungstechnisch optimales Filterelement hat einen Druckgradienten dp/dx, der über die Länge des Filterelements konstant ist. In Figur 4 ist ein erstes Ausführungsbeispiel eines erfindungsgemäßen Filterelements 18 dargestellt, bei dem die Querschnittsfläche sowohl des Eintrittskanals 28 als auch des Austrittskanals 30 über die Länge des Filterelements nicht konstant ist. Bei demAn aerodynamically optimal filter element has a pressure gradient dp / dx, which is constant over the length of the filter element. FIG. 4 shows a first exemplary embodiment of a filter element 18 according to the invention, in which the cross-sectional area of both the inlet channel 28 and the outlet channel 30 is not constant over the length of the filter element. In which
Ausführungsbeispiel gemäß Figur 4 ist die Filterwand 34 gewissermaßen schräg gestellt. Wenn man unterstellt, dass die Eintrittskanäle 28 und die Austrittskanäle 30 eine quadratische Querschnittsfläche aufweisen, dann haben die Eintrittskanäle 28 und die Austrittskanäle 30 gemäß dem Ausführungsbeispiel von Figur 4 die Form eines Pyramidenstumpfs .Embodiment according to Figure 4, the filter wall 34 is set to a certain extent obliquely. Assuming that the inlet channels 28 and the outlet channels 30 have a square cross-sectional area, then the inlet channels 28 and the outlet channels 30 according to the embodiment of Figure 4 have the shape of a truncated pyramid.
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Da auch bei dieser Ausführung der Volumenstrom V linear über die Länge des Filterelements 18 abnimmt und auch die Querschnittsfläche des Eintrittskanals über die Länge abnimmt, ergibt sich ein gegenüber dem Stand der Technik bereits deutlich verbesserter Druckgradient, wie er in Figur 4 unten qualitativ dargestellt ist. Bei diesem Ausführungsbeispiel ist der maximale lokale Druckgradient dp/dx bei gleichen Außenabmessungen des Filterelements 18 deutlich kleiner als bei einem Filterelement mit prismatischen Kanälen, so dass derSince, in this embodiment too, the volume flow V decreases linearly over the length of the filter element 18 and the cross-sectional area of the inlet channel decreases over the length, a pressure gradient already significantly improved compared with the prior art results qualitatively in FIG. 4 below. In this embodiment, the maximum local pressure gradient dp / dx at the same outer dimensions of the filter element 18 is significantly smaller than in a filter element with prismatic channels, so that the
Gesamtströmungswiderstand des Filterelements bei gleichen Bauabmessungen verringert wird.Total flow resistance of the filter element is reduced with the same construction dimensions.
Ein erfindungsgemäßes Filterelement gemäß Figur 4 lässt sich beispielsweise dadurch herstellen, dass ein extrudierter Rohling mit Hilfe von Aufweitdornen, die wechselseitig in die Eintrittskanäle 28 und dieA filter element according to the invention according to FIG. 4 can be produced, for example, by using an extruded blank with the aid of expanding mandrels which are alternately inserted into the inlet channels 28 and the
Austrittskanäle 34 eingeführt werden, lokal aufgeweitet wird, bis die in Figur 4 dargestellte Geometrie erreicht ist . In Figur 5 ist ein weiteres Ausführungsbeispiel eines erfindungsgemäßen Filterelements dargestellt. Bei diesem Ausführungsbeispiel ist die Filterwand im Längsschnitt in Form einer Parabel gekrümmt. Mit Hilfe dieser Geometrie ist es möglich, ein strömungstechnisches Optimum zu erreichen, bei dem der Druckgradient dp/dx über die gesamte Länge des Filterelements konstant ist.Outlet channels 34 are introduced, is locally widened until the geometry shown in Figure 4 is reached. FIG. 5 shows a further exemplary embodiment of a filter element according to the invention. In this embodiment, the filter wall is curved in longitudinal section in the form of a parabola. With the aid of this geometry, it is possible to achieve a flow-technical optimum in which the pressure gradient dp / dx is constant over the entire length of the filter element.
Dieses Filterelement lässt sich mit dem erfindungsgemäß beanspruchten Verfahren und dem in Figur 6 dargestellten Extrusionswerkzeug herstellen.This filter element can be produced by the method claimed according to the invention and the extrusion tool shown in FIG.
In Figur 6 ist ein erfindungsgemäßes Extrusionswerkzeug in einem Teilschnitt dargestellt. Das Extrusionswerkzeug besteht im Wesentlichen aus einem Grundkörper 36 in den mehrere parallel zueinander verlaufende Kanäle 38 eingebracht sind. Die Kanäle 38 haben die Form einer zylindrischen Bohrung und dienen dazu, das zu extrudierende Material (nicht dargestellt) durch den Grundkörper 1 hindurch zu einem Austritt 40 zu befördern.FIG. 6 shows a partial section of an extrusion tool according to the invention. The extrusion tool consists essentially of a base body 36 in which a plurality of mutually parallel channels 38 are introduced. The channels 38 are in the form of a cylindrical bore and serve to convey the material to be extruded (not shown) through the body 1 to an exit 40.
An dem Austritt 40 wird das Material in die gewünschte Form gebracht. Die Längsachsen der Kanäle sind in der Figur 1 mit dem Bezugszeichen 42 versehen worden. Das zu extrudierende Material (nicht dargestellt) wird von einer ebenfalls nicht dargestellten Extruderschnecke oder einer vergleichbaren Einrichtung in Figur 6 von rechts nach links durch das Extrusionswerkzeug gepresst.At the outlet 40, the material is brought into the desired shape. The longitudinal axes of the channels have been provided with the reference numeral 42 in FIG. The material to be extruded (not shown) is pressed by a likewise not shown extruder screw or a similar device in Figure 6 from right to left by the extrusion die.
An die Kanäle 38 schließt sich ein kegelstumpfförmiger Abschnitt 44 an, der in Nuten 46 mündet. Die Nuten 46 dienen dazu, das zu extrudierende Material gleichmäßig über den gesamten Querschnitt des Extrusionswerkzeugs zu verteilen und geben dem zu extrudierenden Filterelement (nicht dargestellt) die gewünschte Form. Zwischen den Kanälen 38 sind Düsenbohrungen 48 in dem Grundkörper 36 vorgesehen. Über die Düsenbohrungen 48 ist es möglich, ausgewählte Kanäle, wie beispielsweise alle Eintrittskanäle 28 des frisch extrudierten Filterelements (nicht dargestellt) , mit Druck zu beaufschlagen, so dass die Eintrittskanäle lokal unmittelbar hinter dem Austritt 40 aus dem Extrusionswerkzeug aufgeweitet werden.Adjoining the channels 38 is a frusto-conical section 44, which opens into grooves 46. The grooves 46 serve to distribute the material to be extruded uniformly over the entire cross section of the extrusion die and give the desired shape to the filter element (not shown) to be extruded. Between the channels 38 nozzle bores 48 are provided in the base body 36. Via the nozzle bores 48, it is possible to pressurize selected channels, such as all inlet channels 28 of the freshly extruded filter element (not shown), so that the inlet channels are widened locally immediately after the outlet 40 from the extrusion die.
Zum Aufweiten der Kanäle des Filterelements kann Luft, insbesondere heiße Luft eingesetzt werden. Die heiße Luft hat den Vorteil, dass sie unmittelbar hinter dem Austritt 40 den Aufbau eines hohen Drucks und demzufolge die Aufweitung des entsprechenden frisch extrudierten Kanals ermöglicht und unmittelbar nach dem Aufweiten aufgrund der Abkühlung der Luft der Druck abnimmt und somit keine Verformung weiter entfernt liegender Bereiche des mit Druckluft beaufschlagten Kanals stattfindet.To widen the channels of the filter element, air, in particular hot air can be used. The hot air has the advantage that immediately behind the outlet 40 it allows the building of a high pressure and consequently the expansion of the corresponding freshly extruded channel and immediately after the expansion due to the cooling of the air, the pressure decreases and thus no deformation of more distant areas takes place of the pressurized air channel.
Durch eine geeignete Steuerung der eingeblasenen Luftmenge in Abhängigkeit der Länge des extrudierten Werkstücks ist es möglich, zum Beispiel die in Figur 5 dargestellte parabelförmige Filterwand 34 herzustellen.By a suitable control of the amount of air blown in as a function of the length of the extruded workpiece, it is possible to produce, for example, the parabolic filter wall 34 shown in FIG.
Selbstverständlich ist es auch möglich, andere Formen von Filterwänden 34 zu erzeugen. Dies kann beispielsweise dann sinnvoll sein, wenn die Permeabilität der Filterwand 34 bei dem Filterelement 18 nicht konstant ist, sondern beispielsweise durch eine katalytische Beschichtung, die lokal aufgebracht wird, in manchen Bereichen geringer ist als in den übrigen Bereichen. Diesen verschiedenen lokalen Permeabilitäten kann durch eine geeignete Formgebung der Filterwände 34 dahingehend Rechnung getragen werden, dass auch bei diesen Ausführungsformen von Filterelementen der Druckgradient dp/dx in Längsrichtung des Filterelements konstant ist und somit der Gesamtströmungswiderstand des Filterelements bei vorgegebenem Bauvolumen ein Minimum erreicht .Of course, it is also possible to produce other forms of filter walls 34. This may be useful, for example, if the permeability of the filter wall 34 in the filter element 18 is not constant, but is lower in some areas than in the other areas, for example, by a catalytic coating applied locally. These various local permeabilities can be taken into account by suitable shaping of the filter walls 34 such that even in these embodiments of filter elements the pressure gradient dp / dx in the longitudinal direction of the filter element is constant and thus the total flow resistance of the filter element reaches a minimum for a given volume of construction.
In Figur 7 ist ein Schnitt entlang der Linie B-B durch den Grundkörper 36 dargestellt. Aus dieser Ansicht wird deutlich, dass der Grundkörper 36 von einem Netz von Nuten 46 durchzogen ist, wobei die Längsachsen 7 der Kanäle 3 in den Schnittpunkten senkrecht zueinander verlaufenden Nuten 46 liegen. In Figur 7 sind auch die Düsenbohrungen 48 in den schraffiert dargestellten erhabenen Flächen zwischen den Nuten 46 zu erkennen.FIG. 7 shows a section along the line B-B through the main body 36. From this view, it is clear that the base body 36 is traversed by a network of grooves 46, wherein the longitudinal axes 7 of the channels 3 are in the intersections perpendicular to each other extending grooves 46. In FIG. 7, the nozzle bores 48 can also be seen in the hatched areas between the grooves 46, which are shown hatched.
Der mit dem Extrusionswerkzeug gemäß Figur 6 und 7 hergestellte Filter hat eine Wabenstruktur mit senkrecht zueinander verlaufenden Filterwänden, wobei die Querschnittsfläche sowohl der Eintrittskanäle 28 als auch der Austrittskanäle 30 ein Quadrat ist. Die Querschnittsfläche der Kanäle 28 und 30 entspricht im Wesentlichen den schraffierten Flächen in Figur 7.The filter produced with the extrusion tool according to FIGS. 6 and 7 has a honeycomb structure with filter walls running perpendicular to one another, the cross-sectional area of both the inlet channels 28 and the outlet channels 30 being a square. The cross-sectional area of the channels 28 and 30 substantially corresponds to the hatched areas in FIG. 7.
In Figur 8 ist ein Werkzeug zum Aufweiten der Kanäle vereinfacht dargestellt. Das Werkzeug besteht aus einer Grundplatte 50, auf die verschiedene Aufweitdorne 52 montiert sind. Der Abstand der Aufweitdorne 52 zueinander entspricht dem Abstand der aufzuweitenden Kanäle eines extrudierten Rohlings . Das erfindungsgemäße Aufweitwerkzeug kann in den Rohling, der noch plastisch verformbar ist und dessen Kanäle prismatisch sind, zumindest bis zur halben Länge des Rohlings eingeführt werden, , so dass in diesen Bereich die Kanäle, in welche die Aufweitdorne 52 eingeführt werden, entsprechend der Form und der Aufweitdorne 52 aufgeweitet werden. Wenn nun das erfindungsgemäße Werkzeug von der anderen Seite in den Rohling so eingeführt wird, dass die Aufweitdorne in die bislang nicht aufgeweiteten Kanäle eingeführt werden, führt dies dazu, dass auch in der zweiten Hälfte des extrudierten Rohlings die gewünschte Geometrie, beispielsweise entsprechend der Figur 4, erreicht wird. Um ein Anhaften des extrudierten Werkstoffs an den Aufweitdornen 52 zu vermeiden, können diese mit einer geeigneten Beschichtung versehen sein. FIG. 8 shows in simplified form a tool for widening the channels. The tool consists of a base plate 50, on which various Aufweitdorne 52 are mounted. The distance between the Aufweitdorne 52 to each other corresponds to the distance of the channels to be expanded of an extruded blank. The expansion tool according to the invention can be introduced into the blank, which is still plastically deformable and whose channels are prismatic, at least to half the length of the blank, so that in this area, the channels into which the Aufweitdorne 52 are inserted according to the shape and the expanding mandrels 52 are widened. If now the tool according to the invention is introduced into the blank from the other side in such a way that the expanding mandrels are introduced into the hitherto unexpanded channels, this leads to the desired geometry, for example in accordance with FIG. 4, also in the second half of the extruded blank , is achieved. To avoid adhesion of the extruded material to the Aufweitdornen 52, they can be provided with a suitable coating.

Claims

Ansprüche claims
1. Filterelement, insbesondere zur Filterung von Abgasen einer Dieselbrennkraftmaschine, mit einer Eintrittsfläche (22) und mit einer Austrittsfläche (24), mit einer Vielzahl von Eintrittskanälen (28) , und mit einer Vielzahl vonA filter element, in particular for filtering exhaust gases of a diesel internal combustion engine, with an inlet surface (22) and with an outlet surface (24), with a plurality of inlet channels (28), and with a plurality of
Austrittskanälen (30) , wobei die Eintrittskanäle (28) an der Eintrittsfläche (22) beginnen und an der Austrittsfläche (24) verschlossen sind, und wobei die Austrittskanäle (30) an der Eintrittsfläche (22) verschlossen sind und an der Austrittsfläche (24) enden, dadurch gekennzeichnet, dass eine Querschnittsfläche (A) mindestens eines Eintrittskanals (28) in Richtung einer Längsachse (X) des Filterelements (18) abnimmt.Outlet channels (30), wherein the inlet channels (28) begin at the inlet surface (22) and are closed at the outlet surface (24), and wherein the outlet channels (30) are closed at the inlet surface (22) and at the outlet surface (24) ends, characterized in that a cross-sectional area (A) of at least one inlet channel (28) decreases in the direction of a longitudinal axis (X) of the filter element (18).
2. Filterelement nach Anspruch 1, dadurch gekennzeichnet, dass eine Querschnittsfläche (A) mindestens eines2. Filter element according to claim 1, characterized in that a cross-sectional area (A) at least one
Austrittskanals (30) in Richtung einer Längsachse (24) des Filterelements (18) zunimmt.Outlet passage (30) in the direction of a longitudinal axis (24) of the filter element (18) increases.
3. Filterelement nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass mindestens ein Eintrittskanal (28) in einem Längsschnitt in Form einer Parabel (Figur 5) oder eines Trapez (Figur 4) ausgebildet ist.3. Filter element according to claim 1 or 2, characterized in that at least one inlet channel (28) in a longitudinal section in the form of a parabola (Figure 5) or a trapezoid (Figure 4) is formed.
4. Filterelement nach Anspruch 2 oder 3, dadurch gekennzeichnet, dass mindestens ein Austrittskanal (28) in einem Längsschnitt in Form einer Parabel (Figur 5) oder eines Trapez (Figur 4) ausgebildet ist.4. Filter element according to claim 2 or 3, characterized in that at least one outlet channel (28) in a longitudinal section in the form of a parabola (Figure 5) or a trapezoid (Figure 4) is formed.
5. Filterelement nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, ein Druckgradient (dp/dx) in Richtung der Längsachse (X) in mindestens einem Eintrittskanal (28) konstant ist.5. Filter element according to one of the preceding claims, characterized in that a pressure gradient (dp / dx) in the direction of the longitudinal axis (X) in at least one inlet channel (28) is constant.
6. Filterelement nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, ein Druckgradient (dp/dx) in Richtung der Längsachse (X) in mindestens einem Austrittskanal (30) konstant ist.6. Filter element according to one of the preceding claims, characterized in that a pressure gradient (dp / dx) in the direction of the longitudinal axis (X) in at least one outlet channel (30) is constant.
7. Filterelement nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass das Filterelement (18) rotationssymmetrisch, insbesondere zylindrisch, oder zentralsymmetrisch ist.7. Filter element according to one of the preceding claims, characterized in that the filter element (18) is rotationally symmetrical, in particular cylindrical, or centrally symmetrical.
8. Filterelement nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass das Filterelement (18) aus einem keramischen Werkstoff besteht.8. Filter element according to one of the preceding claims, characterized in that the filter element (18) consists of a ceramic material.
9. Filterelement nach Anspruch 8, dadurch gekennzeichnet, dass das Filterelement (18) aus Cordierit oder Siliciumcarbid (SiC) besteht.9. Filter element according to claim 8, characterized in that the filter element (18) made of cordierite or silicon carbide (SiC).
10. Verfahren zur Herstellung eines Körpers mit einer Vielzahl parallel zueinander verlaufender Kanäle (28, 30), insbesondere zur Herstellung eines Filterelements (18) aus einem keramischen Werkstoff, gekennzeichnet durch folgende Verfahrensschritte:10. A method for producing a body having a plurality of mutually parallel channels (28, 30), in particular for producing a filter element (18) made of a ceramic material, characterized by the following method steps:
Extrudieren des prismatischen Körpers undExtruding the prismatic body and
Gleichzeitiges Einblasen eines Fluids in einen oder mehrere Kanäle (28, 30) des extrudierten Körpers. Simultaneously injecting a fluid into one or more channels (28, 30) of the extruded body.
11. Verfahren nach Anspruch 10, dadurch gekennzeichnet, dass Druck und Menge des eingeblasenen Fluids von der Länge (X) des extrudierten Körpers (18) abhängt.11. The method according to claim 10, characterized in that the pressure and amount of the injected fluid on the length (X) of the extruded body (18) depends.
12. Verfahren nach Anspruch 10 oder 11, dadurch gekennzeichnet, dass das eingeblasene Fluid Luft, insbesondere heiße Luft, ist.12. The method according to claim 10 or 11, characterized in that the injected fluid is air, in particular hot air.
13. Verfahren zur Herstellung eines prismatischen Körpers, insbesondere zur Herstellung eines Filterelements (18) aus einem keramischen Werkstoff, gekennzeichnet durch folgende Verfahrensschritte:13. A method for producing a prismatic body, in particular for producing a filter element (18) made of a ceramic material, characterized by the following method steps:
Extrudieren des prismatischen Körpers (18) undExtruding the prismatic body (18) and
Anschließendes Aufweiten eines oder mehrerer Kanäle (28, 30) des extrudierten Körpers (18) .Subsequent expansion of one or more channels (28, 30) of the extruded body (18).
Verfahren nach Anspruch 13, dadurch gekennzeichnet, dass der mindestens eine Kanal (28, 30) mit einem oder mehreren Aufweitdornen (52) aufgeweitet wird. A method according to claim 13, characterized in that the at least one channel (28, 30) is widened with one or more expansion mandrels (52).
PCT/EP2006/065433 2005-09-02 2006-08-18 Filter element with reduced flow resistance WO2007025873A2 (en)

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CN103850757A (en) * 2014-03-06 2014-06-11 冯柏金 Tail gas filter unit for diesel engine

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US4163640A (en) * 1977-06-10 1979-08-07 Ngk Insulators, Ltd. Apparatus for extruding a honeycomb structural body
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EP0921148A1 (en) * 1997-12-08 1999-06-09 Dow Deutschland Inc. Low density strand foams

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JPS5487785A (en) * 1977-12-24 1979-07-12 Ngk Spark Plug Co Method of making cross type honeycomb structure
US4695301A (en) * 1985-02-11 1987-09-22 Nippondenso Co., Ltd. Porous ceramic monoliths
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CN103850757A (en) * 2014-03-06 2014-06-11 冯柏金 Tail gas filter unit for diesel engine

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