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
  • B01D46/24—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
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2455—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure of the whole honeycomb or segments
• • 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
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
• • 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
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/247—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure of the cells
• • 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
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2474—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure of the walls along the length of the honeycomb
• • 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
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2482—Thickness, height, width, length or diameter
• • 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
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2484—Cell density, area or aspect ratio
• • 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
  • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
  • B01D46/2486—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure characterised by the shapes or configurations
  • B01D46/2496—Circular
• • 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
  • B01D46/66—Regeneration of the filtering material or filter elements inside the filter
  • B01D46/80—Chemical processes for the removal of the retained particles, e.g. by burning
  • B01D46/84—Chemical processes for the removal of the retained particles, e.g. by burning by heating only
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/16—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on silicates other than clay
  • C04B35/18—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on silicates other than clay rich in aluminium oxide
  • C04B35/185—Mullite 3Al2O3-2SiO2
• • C—CHEMISTRY; METALLURGY
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  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/16—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on silicates other than clay
  • C04B35/18—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on silicates other than clay rich in aluminium oxide
  • C04B35/195—Alkaline earth aluminosilicates, e.g. cordierite or anorthite
• • C—CHEMISTRY; METALLURGY
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  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/46—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
  • C04B35/462—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates
  • C04B35/478—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on aluminium titanates
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/56—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides
  • C04B35/565—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides based on silicon carbide
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
  • C04B38/0006—Honeycomb structures
  • C04B38/0009—Honeycomb structures characterised by features relating to the cell walls, e.g. wall thickness or distribution of pores in the walls
• • 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
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2279/00—Filters adapted for separating dispersed particles from gases or vapours specially modified for specific uses
  • B01D2279/30—Filters adapted for separating dispersed particles from gases or vapours specially modified for specific uses for treatment of exhaust gases from IC Engines
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/00793—Uses not provided for elsewhere in C04B2111/00 as filters or diaphragms
• • 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
  • F01N2260/00—Exhaust treating devices having provisions not otherwise provided for
  • F01N2260/10—Exhaust treating devices having provisions not otherwise provided for for avoiding stress caused by expansions or contractions due to temperature variations
• • 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
  • F01N2330/48—Honeycomb supports characterised by their structural details characterised by the number of flow passages, e.g. cell density
• • 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
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24149—Honeycomb-like
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24149—Honeycomb-like
  • Y10T428/24157—Filled honeycomb cells [e.g., solid substance in cavities, etc.]
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24744—Longitudinal or transverse tubular cavity or cell
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/249921—Web or sheet containing structurally defined element or component
  • Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]

Definitions

• This invention generally relates to ceramic honeycomb structures of the type used in automotive or diesel exhaust systems, and is specifically concerned with honeycomb structures having cells formed from interconnected radial and tangential web walls.
• Ceramic honeycomb structures are known in the prior art. Such structures generally comprise a plurality of interconnected web walls that form a matrix of gas- conducting cells which are typically square or hexagonal in shape, and a cylindrical outer skin surrounding the cell matrix. The outer edges of the matrix of web walls is integrally joined to the inner edge of the outer skin to form a single, unitary structure, which is usually cylindrical in shape.
• Ceramic honeycomb structures find particular application as either particulate filters in diesel exhaust systems, or as catalyst substrates for automobile exhaust systems. Hence these structures have an inlet end for receiving exhaust gases, and an outlet end for expelling these gases. Ceramic honeycomb structures used as diesel particulate filters typically have a cell density of between 100 and 400 cells per square inch, and webs on the order of 12-20 mils thick. The inlets and outlets of the matrix of gas-conducting cells are plugged in a "checkerboard" pattern on the inlet and outlet ends of the structure to force the diesel exhaust gases through the porous ceramic material forming the web walls, thereby filtering out the particulate soot generated within the exhaust of diesel engines.
• the inlet cells are periodically exposed to a hot flame in a "burnout cycle" designed to ablate the accumulated particles of soot.
• the central webs of a ceramic honeycomb structure used as a diesel particulate filter may be raised to a temperature of 1100 0 C during such a burn-out cycle, while the outer skin is heated to only about 500 0 C.
• the resulting 500+ 0 C thermal gradient creates thermal stresses in the ceramic honeycomb that can cause cracks and other discontinuities, primarily in the outermost cells which contact the inner edge of the outer skin.
• the cells are not plugged as with diesel particulate filters and gases are allowed to pass straight through the gas-conducting cells.
• the cell density is made higher (i.e., about 300-900 cells per square inch) in order to maximize the area contact between the automotive exhaust gases which blow directly through the gas conducting ceils, and the web walls.
• the web walls are rendered thinner than in structures used for diesel particulate filters, i.e. on the order of 2-6 mils.
• Such thinner walls further advantageously reduces the light-off time (i.e., the time it takes before the webs reach the required 250 0 C before the catalyst impregnated within the web walls begins to effectively remove NO x and other unwanted pollutants from the exhaust gases).
• the frequent rapid heating of such structures from ambient temperature to 250 0 C whenever the automotive vehicle is started likewise generates a substantial thermal gradient across the diameter of the honeycomb structure. These thermally induced stresses are maximized at the interface between the thin web walls and the outer skin of the honeycomb structure.
• such known radial-web designs include (1) "wagon wheel” configurations having an interior portion formed from a matrix of square cells, and a peripheral portion formed from a single, tangential layer of radial cells is created between a single, cylindrical wall and a plurality of short, radially oriented webs that form the side walls of the cells, or (2) a stacked radial cell configuration wherein each of the radial webs extends substantially the length of the radius between the centroid and the inner edge of the outer skin, or (3) an imbricated radial cell configuration cell configuration having rings of staggered radial cells where each radial web extends only the length of a ring of cells.
• a radial cell ceramic honeycomb structure that maintains the stress-reducing advantages associated with an orthogonal interface between the outer web walls of the cell matrix and the inner edge of the outer skin, but avoids the stress- displacement, high cell density and interior weakness problems associated with prior art radial cell designs.
• a radial cell honeycomb structure would either maintain a desired cell density across the diameter of the honeycomb structure, or reduce the density of the cells near the outer perimeter of the structure to promote hot gas flow more toward the periphery, thereby reducing the thermal gradient and hence thermal stresses. It would be desirable if such a radial cell honeycomb had improved compressive strength to better withstand the exterior stresses applied to such structures during the manufacturing process.
• such a structure should also have improved strength for handling the stresses that occur as a result of the heat up and cool down cycles of the honeycomb structure which occurs after the burnout cycle in a diesel particulate filter, or engine start up and shut-off in a ' catalytic carrier.
• the invention is a radial cell ceramic honeycomb structure that solves or at least ameliorates all of the aforementioned problems.
• the ceramic honeycomb structure comprises a plurality of interconnected walls that define a plurality of cells of a honeycomb network having a central axis across its cross section, including radial webs of varying length that diverge from one another in a radial direction away from said central axis, and at least two tangential webs arranged around the central axis wherein at least some of the radial webs extend substantially the length between the central axis and the periphery of the network.
• the honeycomb network may be cylindrical in shape and covered by a tubular outer skin and each of the radial webs that extends to the periphery of the network may have an outer end that joins an inner edge of the outer skin at a substantially orthogonal orientation, hi such a case, the radial webs diverge from a centroid located in the center of the cross section of the network.
• the honeycomb structure may have an elliptical oval or "race track" cross section, such that the radial webs diverge from a central axis. In such a case, the radial webs will join an inner edge of the skin in either an orthogonal or substantially orthogonal orientation.
• the orthogonal joints between the radial webs and the inner edge of the outer skin eliminates the stresses associated with prior art honeycomb structures caused by an oblique orientation of some of the web walls that join the inner edge of the outer skin in square, hexagonal, or other polygonal cell designs.
• the provision of at least some radial webs that extend substantially the length of the radius of the network renders the resulting structure stronger than designs utilizing short radial webs in imbricated patterns.
• the transition webs are made stronger than the balance of the tangential webs in order to reduce the stresses in this region of the ceramic honeycomb structure.
• the number of radial webs may decrease in the direction toward the centroid in order to maintain a desired average density of cells along the radius.
• the number, of radial webs may decrease in the outer periphery of the network such that larger cells are formed near the periphery to promote the flow of exhaust gas in this region.
• the radial cell ceramic honeycombs of the invention are particularly adapted for use as either a catalytic carrier in an automotive exhaust system, or as a particulate filter in a diesel exhaust system, and both embodiments of the invention are advantageously compatible with conventional manufacturing techniques.
• Figure IA is a perspective view of a prior art ceramic honeycomb structure of which the invention is applicable to.
• Figure IB is a plan view of an octant section of the honeycomb structure of
• Figure 2A is an enlarged, finite element analysis of the upper-most circled area of Figure IB, illustrating the stress concentrations at the joint between an obliquely orientated web, and the inner edge of the outer skin of the structure.
• Figure 2B is an enlarged, finite element analysis illustrating the stress concentration associated with the joint between another obliquely orientated web, and the inner edge of the outer skin of the structure.
• Figure 3 is a plan view of an octant section of a first embodiment of the invention.
• Figure 4 is a plan view of an octant section of a second embodiment of the invention.
• Figure 5 is a half cross section of a third embodiment of the invention having an elliptical cross section.
• Figure 6 is a bar graph that graphically displays the percentage improvement
• Figure 7 is a finite element analysis illustrating the areas of maximum stress experienced by the several embodiments of the invention.
• the honeycomb structure 1 that the invention may be applied to includes a plurality of interconnected web walls 3 that form a network 5 of gas conducting cells 7. While these cells 7 are illustrated of having a square cross section, the invention is applicable to honeycomb structures having cells with hexagonal, octagonal or other polygonal cross sections.
• the honeycomb structure further includes an outer skin 9 having a cylindrical or rounded shape that encloses the sides of the network 5 of cells 7.
• the honeycomb structure 1 further includes an inlet end 11 for receiving either diesel or automotive exhaust gases, and an outlet end 13 for expelling these gasses.
• the web walls are typically between about 10 and 25 mils thick and the outer skin 9 is about 3 to 4 times the thickness of the wall.
• the cells 7 of the filter are preferably plugged in a checkerboard pattern across both the inlet and outlet ends 11, 13 to force the diesel exhaust to pass through the web walls 3 in an "s" pattern before being expelled out the outlet end 13.
• cell density is typically between about 100 and 400 cells per square inch.
• the honeycomb structure 1 is used as a catalytic carrier substrate, the web walls 3 are thinner, being on fee order of 2 to 6 mils thick.
• the outer skin 9 is about 3-4 times the thickness of the wall, and the cell density is higher, ranging between about 300 and 900 cells per square inch. Automotive exhaust gas entering the inlet end 11 passes straight through the gas conducting passages defined by the cells 7.
• honeycomb structure 1 is used as a diesel particulate filter or a catalytic carrier, it is manufactured by extruding a porous ceramic material such as cordierite, silicon carbide, mullite, or aluminum titanate.
• a porous ceramic material such as cordierite, silicon carbide, mullite, or aluminum titanate.
• the outer skin 9 is thicker than the web walls in order the give the structure 1 the physical strength necessary to withstand the forces applied to it during the manufacturing process, and during the "canning" of the structure within an exhaust system.
• IA and IB is apt to fracture at the interface between the inner edge 10 of the outer skin 9, and the outer edges of the network 5 of cells 7.
• the applicants have discovered that the crack- inducing stresses are also largely generated as a result of the generally oblique orientation of some of the web walls 3 that are integrally joined to the inner edge 10 of the outer skin 9. • These stresses are best appreciated with respect to the finite element analysis illustrated in Figures 2A and 2B. These drawings are enlargements of the phantom circles designated as "2 A" and "2B" in Figure IB.
• the cells immediately adjacent to the outer skin 9 are partial cells 18 which have webs 20 which are oriented obliquely (i.e., at angles of 45 degrees or less) in the areas where they join the inner edge 10 of the outer skin 9.
• webs 20 which are oriented obliquely (i.e., at angles of 45 degrees or less) in the areas where they join the inner edge 10 of the outer skin 9.
• Such radially-oriented forces may be generated by compressive forces applied by the outer skin 9 against the webs 20 as a result of the handling of the structure 1 during manufacture, or from the network 5 of cells pushing against the inner edge 10 of the outer skin 9 as a result of thermal differential expansion during either a burn-out cycle or the initial conduction of hot exhaust gases through the center of the structure 1 at engine start-up.
• Ihese stresses are larger near a rotational angle of 45 degrees (and multiples thereof) around the circumference of the ceramic honeycomb structure 1 which, of course, corresponds to the areas of greatest obliquity in the orientation between the webs 20 of the partial cells 18 and the inner edge 10 of the outer skin 9.
• Figure 3 illustrates a preferred embodiment of the invention, which is a cylindrical ceramic honeycomb structure 40 wherein all of the cells defined by the interconnected web walls are radial cells 44.
• the network 5 of ceramic webs includes radial webs 46 of varying lengths, each of which has an outer end 47a that joins the inner edge 10 of the outer skin 9 in a generally orthogonal joint 47b.
• Some of the radial webs 48a extend almost completely the radial distance between the centroid C of the structure 40 and the outer skin 9, while other radial webs 48b extend only through a peripheral section of the structure 40.
• the network 5 of webs in the structure 40 further includes a plurality of tangential webs 49 that are concentrically disposed around the centroid C and are mutually parallel along an axial length thereof.
• the radial cells 44 are defined between the radial webs 46 and tangential webs 49 wherein the radially extending walls are defined by the radial webs 46 and the tangentially extending walls are defined by the tangential webs 49.
• the number of radial webs 46 is reduced along selected points 50a through 50f known as "transition zones" along the radius of the structure 40. At these transition zones 50a-50f, the number of radial webs 46 is reduced by V4, 1/3, or 1 A, etc. Reduction by VS is preferred and is illustrated in Figures 3 and 4.
• the transition zone at any one of the selected points 50a-50f is defined by the particular tangential wall 49 that intersects with the selected point in the radius.
• the distance between the tangential webs 49 may change in the direction between the centroid C and the outer skin 9. For example, compare Di and D 2 , illustrating that the spacing decreases the closer in radial proximity to the skin 9.
• Such closer spacing of the webs 49 compensates for the tangential widening of the cells 33 caused by the angular divergence between adjacent radial webs 46 as they radiate from the centroid C of the structure 40.
• the cross sectional area of at least some of the radially spaced cells 44 may be made to have substantially uniform cross sectional area.
• a reinforced tangential web 52 may be provided which is substantially thicker than the balance of the tangential webs 49.
• the thickness of each reinforced tangential web 52 should be on the order of 8.0 mils.
• the thickening of the tangential webs 52 advantageously reduces stresses generated on these walls from forces resulting from the presence of lesser numbers of radial webs 46 on its interior side towards the centroid C as on its exterior side toward the outer skin 9.
• each of the interior web intersections may include a fillet
• the fillet radius is preferably about 5.0 mils, but will significantly vary with other configurations.
• fillets may be included only at some or all of the transition zones 50a-50f between the radial webs 46 and the transition webs 52 to further reinforce and strengthen these zones.
• Figure 4 illustrates an octant section of an alternate embodiment of the invention.
• This embodiment is in all respects identical to the embodiment described with respect to Figure 3, with the exception that every other radial web 46 has been removed from the network 5 in the most peripheral zone 54c, such that the resulting radial cells 54 are- twice as large as the balance of the radial cells 44 in the network 5.
• the number of radial webs 46 actually decreases in the radial direction toward the outer skin 9, in contrast to the Figure 3 embodiment wherein the number of radial webs 46 increases at all points along the radius toward the outer skin 9.
• the embodiments 40, 60 are illustrated as having cylindrical outer shapes with a centro ⁇ d C that corresponds to an axis of rotation, the invention also encompass ceramic honeycomb structures having other curved shapes, such as the structure 70 having an elliptical cross-section illustrated in Figure 5 (two quadrants shown). Structure 70 has a central axis A that intersects with the two foci (not shown) of the elliptical shape, and all of the radial webs 46 diverge from one another and extend away from the central axis A as shown. As with the previously described embodiments, the embodiment 70 illustrated in Figure 5 includes radial webs 46 of varying lengths and the number of cells 44 is reduced at least a certain points in the radial direction.
• radial web 48a extends the entire radial length of the network 5 of webs, while radial web 48b extends along only the peripheral group of webs 54b.
• Tangential webs 49 are further provided, and the tangential webs 50a, 50b defining transition zones are rendered stronger by, for example, providing an increased thickness therein.
• the transition webs 50a, 50b maybe also made stronger, for instance, by web tapering at the junction of the transition web and the radial web, i.e., tapering the radial wall to include a larger taper approaching the transition web, or by providing fillets at the radial web, transition web intersection, for example.
• the embodiment 70 of the invention does not have the uniform compressive strength characteristics 360° around its perimeter that the previously described embodiments 40, 60 do. Nonetheless, most of the advantages associated with the invention are present in the third embodiment 70 of the invention. .
• the cross section of the honeycomb structure embodying the invention may also be oval or "race track” shaped. It should be noted that a honeycomb structure having a "race track” cross section would have similar uniform strength 360° around its periphery as the embodiments 40, 60 previously described, as all of the radial webs 46 could join with the inner edge 10 of the outer skin in a substantially orthogonal orientation.
• Figure 6 is a bar graph illustrating the percentage improvement in stress of the
• Figure 3 embodiment 40 over the ceramic substrate 1 illustrated in Figures IA and IB.
• the average stresses generated as a result of radial tension, radial compression, down-heat up load, and cool down thermal loading are substantially less ( are improved) for the inventive ceramic honeycomb illustrated in Figure 3 versus the prior art illustrated in Figures IA and IB.
• the invention exhibited a large average decrease in maximum stress over its 360° circumference, with greater than 20% improvement in all categories.
• the stresses generated within the inventive structures is highly uniform between 0 degrees and 45 degrees.
• the peripheral stresses generated within the prior art structure 1 oscillate around the circumference of the structure 1 to values that are multiples higher. These higher stress points correspond to the oblique orientation of some of the web walls in the vicinity of 45 degrees and multiples thereof. These indicate weak points in the prior art structure 1 that may be more prone to cracking or failure during either manufacture or operation.
• the inventive structures eliminate such oscillations in the stress patterns.
• Figure 7 is a finite element analysis of the intersection of an octant of the ceramic honeycomb structure 40 illustrating how the stresses are maximized at the transition zones within the structure 42 where the number or radial webs 46 is reduced (e.g., halved).
• stress is maximized at the points where radial webs 46 join the transition tangential webs (e.g., 50d-50f), thereby applying forces to the webs at these points (52a, 52b).
• peripheral webs 50a-50f are rendered stronger by making them thicker than the normal (non- transitional) tangential webs 49 (although other strengthening techniques, such as fillets, or tapered radial webs could be optionally or additionally employed).
• These walls 52 may be 2 or more times as thick as the non-transitional webs 49.

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• 2006
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