Radial cell ceramic honeycomb structure

Abstract

A radial cell ceramic honeycomb structure is provided that is particularly adapted for use as a catalytic carrier or a particulate filter in an automotive or diesel exhaust system. The honeycomb structure includes a network of interconnected webs having a central axis. The network of webs includes radial webs of varying lengths, only some of which substantially extend the entire radial length of the network, and tangential webs that intersect to define rings of gas-conducting radial cells, and a rounded outer skin that surrounds the cells formed by the interconnected webs. The radial webs extending to the periphery of the network join an inner edge of the outer skin in a substantially orthogonal orientation to reduce thermally generated stresses and to increase strength of the resulting structure. The number of radial webs in the network changes along the radial length at transition zones that are defined by one of the tangential webs such that a desired cell density is achieved across the network.

Description

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a prior art ceramic honeycomb structure of which the invention is applicable to.

FIG. 1B is a plan view of an octant section of the honeycomb structure of FIG. 1A along the section lines 1B-1B.

FIG. 2A is an enlarged, finite element analysis of the upper-most circled area of FIG. 1B, illustrating the stress concentrations at the joint between an obliquely orientated web, and the inner edge of the outer skin of the structure.

FIG. 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.

FIG. 3 is a plan view of an octant section of a first embodiment of the invention.

FIG. 4 is a plan view of an octant section of a second embodiment of the invention.

FIG. 5 is a half cross section of a third embodiment of the invention having an elliptical cross section.

FIG. 6 is a bar graph that graphically displays the percentage improvement (simulated) of the inventive honeycomb structure over the prior art honeycomb structure illustrated in FIGS. 1A and 1B in resistance to radial tension, radial compression, heat up thermal load, and cool down thermal load.

FIG. 7 is a finite element analysis illustrating the areas of maximum stress experienced by the several embodiments of the invention.

Claims

1. A ceramic honeycomb structure, comprising: a plurality of interconnected webs that define a plurality of cells in a honeycomb network having a central axis across its cross section, includingradial webs of varying length arranged so as to diverge from one another with respect to said central axis wherein at least some of said radial webs substantially extend from said central axis to an outermost periphery of said network, andtangential webs arranged concentrically with respect to the central axis.

2. A ceramic honeycomb structure as defined in claim 1, further comprising an outer skin surrounding the honeycomb network wherein each of said radial webs has an end that defines said outermost periphery of said network joins an inner edge of said outer skin in a substantially orthogonal orientation.

3. A ceramic honeycomb structure as defined in claim 2, wherein said honeycomb network includes transition zones, each of which is defined by one of said tangential webs, and wherein the number of radial webs changes in a radial direction.

4. A ceramic honeycomb structure as defined in claim 3, wherein the number of radial webs is reduced at at least some of the transition zones in a radial direction toward said central axis.

5. A ceramic honeycomb structure as defined in claim 4, wherein at least some of the transition zones in a radial direction are reinforce by fillets, tapered radial walls, or thickened transitional webs.

6. A ceramic honeycomb structure as defined in claim 5, wherein said tangential web at each transition zone is stronger than the balance of said tangential webs.

7. A ceramic honeycomb structure as defined in claim 4, wherein the number of radial webs diminishes toward said central axis such that a selected average cell density across the network is substantially maintained.

8. A ceramic honeycomb structure as defined in claim 6, wherein said tangential webs that define said transition zones are thicker than the balance of the tangential webs.

9. A ceramic honeycomb structure as defined in claim 3, wherein the density of cells defined by said webs diminishes toward said periphery.

10. A ceramic honeycomb structure as defined in claim 1, wherein said cross section of said honeycomb network includes a centroid, and said radial webs diverge from said centroid.

11. A ceramic honeycomb structure as defined in claim 1, wherein said cross-section of said honeycomb network is circular, and said radial webs diverge from a center of said cross section.

12. A ceramic honeycomb structure, comprising: an outer skin, anda plurality of interconnected webs forming a honeycomb network contained within said outer skin and defining a plurality of cells, said honeycomb network having a centroid within its cross section, wherein said webs include:radial webs, each of which joins an inner edge of said outer skin in a substantially orthogonal orientation, only some of which have a radial length that substantially extend from said centroid to said outer skin, the balance of said radial webs being shorter than said radial length, andtangential webs arranged tangentially with respect to said centroid to define radial cells.

13. A ceramic honeycomb structure as defined in claim 12, wherein the number of radial webs diminishes toward said centroid.

14. A ceramic honeycomb structure as defined in claim 13, wherein the number of radial webs is reduced at selected transition zones, each of said transition zones being defined by one of said tangential webs.

15. A ceramic honeycomb structure as defined in claim 14, wherein said transition tangential webs are stronger than the balance of said tangential webs.

16. A ceramic honeycomb structure as defined in claim 13, wherein the number of radial webs diminishes toward said centroid such that a selected average cell density along said radial length is substantially maintained.

17. A ceramic honeycomb structure as defined in claim 16, wherein said selected average cell density is between about 25 and 1250 cells per square inch.

18. A ceramic honeycomb structure as defined in claim 12, wherein fillets are provided in corners of said radial webs and the outer skin.

19. A ceramic honeycomb structure as defined in claim 12, wherein said structure is formed from a porous ceramic material.

20. A ceramic honeycomb structure, comprising: a cylindrical outer skin, anda plurality of interconnected webs contained within said outer skin that define a honeycomb network having a plurality of cells and a centroid within a cross section of said network, said webs includingradial webs arranged in a radial direction with respect to said outer skin that join an inner edge of said outer skin in a substantially orthogonal orientation, wherein only some of said radial webs have a radial length that substantially corresponds to a radius of said cylindrical outer skin, and wherein the number of radial webs is reduced at selected transition zones along said radius in a direction toward said centroid, andtangential webs arranged concentrically with respect to said centroid, wherein one tangential web defines each transition zone along said radius, and wherein each tangential transition web is stronger than all other tangential non-transition webs.