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A ceramic filter assembly having improved exhaust gas processing efficiency. The ceramic filter assembly (9) is produced by adhering with a ceramic seal layer (15) outer surfaces of a plurality of filters (F1), each of which is formed from a sintered porous ceramic body. The seal layer (15) has a th

A ceramic filter assembly having improved exhaust gas processing efficiency. The ceramic filter assembly (9) is produced by adhering with a ceramic seal layer (15) outer surfaces of a plurality of filters (F1), each of which is formed from a sintered porous ceramic body. The seal layer (15) has a thickness of 0.3 mm to 3 mm and a thermal conductance of 0.1 W/mK to 10 W/mk.

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The invention claimed is: 1. An integral ceramic filter assembly produced by adhering with a ceramic seal layer outer surfaces of a plurality of elongated honeycomb filters, each of which is formed from a sintered porous ceramic body, wherein the assembly as a whole has a generally circular cross-s

The invention claimed is: 1. An integral ceramic filter assembly produced by adhering with a ceramic seal layer outer surfaces of a plurality of elongated honeycomb filters, each of which is formed from a sintered porous ceramic body, wherein the assembly as a whole has a generally circular cross-section, and wherein the seal layer has a thickness of 0.3 to 3 mm and a thermal conductance of 0.1 to 10 W/mk. 2. The ceramic filter assembly according to claim 1, wherein the seal layer includes 70 wt % or less of ceramic fiber as a solid. 3. The ceramic filter assembly according to claim 1, wherein the seal layer includes ceramic fibers having fiber lengths of 100 mm or less. 4. The ceramic filter assembly according to claim 1, wherein the seal layer includes as a solid 3 wt % to 80 wt % of inorganic grains. 5. The ceramic filter assembly according to claim 1, wherein the assembly is a diesel particulate filter. 6. The ceramic filter assembly according to claim 1, wherein the seal-layer includes at least inorganic fibers, an inorganic binder, an organic binder, and inorganic particles and is formed from an elastic material obtained by bonding the inorganic fibers and inorganic grains, which are three-dimensionally interlinked with one another, with the inorganic binder and the organic binder. 7. The ceramic filter assembly according to claim 1, wherein the seal layer is formed from 10 wt % to 70 wt % of silica-alumina ceramic fiber, 1 wt % to 30 wt % of silica sol, 0.1 wt % to 5.0 wt % of carboxymethyl cellulose, and 3 wt % to 80 wt % of silicon carbide powder. 8. The ceramic filter assembly according to claim 1, wherein the filters are arranged in a state offset from one another in a direction perpendicular to a filter axial direction. 9. The ceramic filter assembly according to claim 1, wherein the filter has a plurality of cells, and each cell has an outer surface which carries at least one oxide catalyst selected from a platinum group element, other metal elements and oxides of these metal elements. 10. The ceramic filter assembly according to claim 1, wherein the filter has an average porosity of 30 to 70%. 11. The ceramic filter assembly according to claim 1, wherein the filter has a thermal conductance of 20 to 80 W/mk. 12. The ceramic filter assembly according to claim 1, wherein the seal layer has a thickness of 0.5 to 1.0 mm and a thermal conductance of 0.3 to 10 W/mk. 13. An exhaust gas purification apparatus having the ceramic filter assembly according to claim 1 arranged in a casing that is located in an exhaust gas passage of an internal combustion engine. 14. The exhaust gas purification apparatus according to claim 13, wherein a middle portion of the casing has a diameter larger than that of the exhaust gas passage. 15. The exhaust gas purification apparatus according to claim 13, wherein a thermal insulative material composed of a mat-like material including ceramic fibers is arranged between the outer surface of the ceramic filter assembly and the inner surface of the casing. 16. An integral ceramic filter assembly produced by adhering with a ceramic seal layer outer surfaces of a plurality of elongated honeycomb filters, each of which being formed from a sintered porous ceramic body, wherein the ceramic filter assembly is a diesel particulate filter, and includes round surfaces defined on chamfered corners of the outer surface of each honeycomb filter, wherein the round surfaces have a radius of curvature (R) of 0.3 mm to 2.5 mm. 17. An integral ceramic filter assembly produced by adhering with a ceramic seal layer outer surfaces of a plurality of elongated honeycomb filters, each of which being formed from a sintered porOus ceramic body, wherein the ceramic filter assembly is formed from a sintered porous silicon carbide, and includes round surfaces defined on chamfered corners of the outer surface of each honeycomb filter, wherein the round surfaces have a radius of curvature (R) of 0.3 mm to 2.5 mm. 18. The ceramic filter assembly according to claim 16, wherein the filters are arranged in a state offset from one another in a direction perpendicular to a filter axial direction. 19. The ceramic filter assembly according to claim 17, wherein the filters are arranged in a state offset from one another in a direction perpendicular to a filter axial direction. 20. The ceramic filter assembly according to claim 16, wherein the filter has a plurality of cells, and each cell has an outer surface which carries at least one oxide catalyst selected from a platinum group element, other metal elements and oxides of these metal elements. 21. The ceramic filter assembly according to claim 17, wherein the filter has a plurality of cells, and each cell has an outer surface which carries at least one oxide catalyst selected from a platinum group element, other metal elements and oxides of these metal elements. 22. The ceramic filter assembly according to claim 16, wherein the average pore diameter of the honeycomb filter is 1 to 50 μm. 23. The ceramic filter assembly according to claim 17, wherein the average pore diameter of the honeycomb filter is 1 to 50 μm. 24. The ceramic filter assembly according to claim 16, wherein the filter has an average porosity of 30 to 70%. 25. The ceramic filter assembly according to claim 17, wherein the filter has an average porosity of 30 to 70%. 26. The ceramic filter assembly according to claim 16, wherein the assembly has an outer form in a round cross-section or oval cross-section. 27. The ceramic filter assembly according to claim 17, wherein the assembly has an outer form in a round cross-section or oval cross-section. 28. An exhaust gas purification apparatus having the ceramic filter assembly according to claim 16 arranged in a casing that is located in an exhaust gas passage of an internal combustion engine. 29. An exhaust gas purification apparatus having the ceramic filter assembly according to claim 17 arranged in a casing that is located in an exhaust gas passage of an internal combustion engine. 30. An integral ceramic filter assembly produced by adhering with a ceramic seal layer outer surfaces of a plurality of filters, each of which is formed from a sintered porous ceramic body, wherein the assembly as a whole has a generally circular cross-section, and wherein a ceramic smoothing layer is provided on the outer surface of the assembly. 31. The ceramic filter assembly according to claim 30, wherein the smoothing layer has a thickness of 0.1 mm to 10 mm. 32. The ceramic filter assembly according to claim 30, wherein the seal layer is thinner than the smoothing layer. 33. The ceramic filter assembly according to claim 30, wherein the smoothing layer is made from the same material as the seal layer. 34. The ceramic filter assembly according to claim 30, wherein the assembly is a diesel particulate filter. 35. The ceramic filter assembly according to claim 30, wherein the assembly is formed from a sintered porous silicon carbide. 36. The ceramic filter assembly according to claim 30, wherein the seal layer includes at least inorganic fibers, an inorganic binder, an organic binder, and inorganic particles and is formed from an elastic material obtained by bonding the inorganic fibers and inorganic grains, which are three-dimensionally interlinked one another, with the inorganic binder and the organic binder. 37. The ceramic filter assembly according to claim 30, wherein the seal layer ss formed from 10 wt % to 70 wt % of silica-alumina ceramic fiber, 1 wt % to 30 wt % of silica sol, 0.1 wt % to 5.0 wt % of carboxymethyl cellulose, and 3 wt % to 80 wt % of silicon carbide powder. 38. The ceramic filter assembly according to claim 30, wherein the filters are arranged in a state offset from one another in a direction perpendicular to a filter axial direction. 39. The ceramic filter assembly according to claim 30, wherein the filter has a plurality of cells, and each cell has an outer surface which carries at least one oxide catalyst selected from a platinum group element, other metal elements and oxides of these metal elements. 40. The ceramic filter assembly according to claim 30, wherein the average pore diameter of the honeycomb filter is 1 to 50 μm. 41. The ceramic filter assembly according to claim 30, wherein the filter has an average porosity of 30 to 70%. 42. The ceramic filter assembly according to claim 30, wherein pits defined by ridges and valleys partially exposed from the outer surface are provided extending in the axial direction of the assembly, and wherein the pits are filled with the ceramic smoothing layer. 43. The ceramic filter assembly according to claim 30, wherein the smoothing, layer is made from the different material from the seal layer. 44. The ceramic filter assembly according to claim 30, wherein the smoothing layer has a thermal conductance of 0.1 to 10 W/mk. 45. An exhaust gas purification apparatus having the ceramic filter assembly according to claim 30 arranged in a casing that is located in an exhaust gas passage of an internal combustion engine. 46. Method for manufacturing a ceramic honeycomb structural body comprising the steps of: making ceramic honeycomb filter which is formed from a sintered porous ceramic body; adhering outer surfaces of a plurality of the filters with a ceramic seal layer to produce an integral ceramic filter assembly; cutting the peripheral portion of the assembly to form an outer shape thereof; and applying a paste to the exposed outer surface of the assembly to provide a smoothing layer. 47. An elongated honeycomb filter formed from a sintered porous ceramic body, wherein a ratio L/S between a filter length L in a flow direction of a processed fluid and a filter cross-section S in a direction perpendicular to the flow direction is 0.06 to 0.75 mm/mm2, and the filter length L is 167 to 300 mm; and wherein the filters are arranged in a state offset from one another in a direction perpendicular to a filter axial direction.