Crack-resistant ceramic honeycomb structures

Abstract

A ceramic honeycomb structure includes a honeycomb body having an array of interconnecting webs bounded by a skin. The interconnecting webs define an array of longitudinal cells having diagonal corners. Fillets are formed only in diagonally opposed corners traversed by lines perpendicular and/or substantially perpendicular to the skin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, described below, illustrate typical embodiments of the invention and are not to be considered limiting of the scope of the invention, for the invention may admit to other equally effective embodiments. The figures are not intended to present true proportion or scale; certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness.

FIG. 1 is a perspective view of a prior-art wall-flow honeycomb filter.

FIG. 2A is a perspective view of a ceramic honeycomb structure having longitudinal cells defined by interconnecting webs and bounded by a skin, with fillets formed in only in cell diagonal corners perpendicular to the skin.

FIG. 2B is a transverse cross-section of the ceramic honeycomb structure of FIG. 2A.

FIG. 2C is a variation of FIG. 2B, with fillets formed in cell diagonal corners perpendicular to and near the skin only.

FIG. 2D is a variation of FIG. 2B, with fillets in cell diagonal corners substantially perpendicular to the skin.

FIG. 3 is a comparison of pressure drop in ceramic honeycomb structures of differing design, including structures with and without selective filleting.

FIG. 4 is a vertical cross-section of an extrusion die assembly for making the ceramic honeycomb structure of FIGS. 2A-2D.

Claims

1. A honeycomb structure comprising: a honeycomb body having an array of interconnecting webs bounded by a skin, the interconnecting webs defining an array of longitudinal cells of polygonal cross-section having corners,the array of cells comprising both cells incorporating corner reinforcement and cells absent any corner reinforcement, whereinthe cells incorporating corner reinforcement lying on cell diagonals perpendicular and/or substantially perpendicular to the skin.

2. The honeycomb structure of claim 1 wherein the cells incorporating corner reinforcement include both reinforced corners and non-reinforced corners, with corner reinforcement being provided only in diagonally opposed corners intersected by cell diagonals perpendicular and/or substantially perpendicular to the skin.

3. The honeycomb structure of claim 1 which is formed of a porous ceramic, and wherein the cells have a square cross-section and the corner reinforcement is a concave fillet or brace.

4. The honeycomb structure of claim 3, wherein the skin has a circular geometry.

5. The honeycomb structure of claim 4, wherein the reinforced corners intersected by cell diagonals substantially perpendicular to the skin are located within sectors of the structure disposed within a contained angle of from 10 to 60 degrees centered upon the cell diagonals perpendicular to the skin.

6. The honeycomb structure of claim 1, wherein the reinforced corners are located near the skin.

7. The honeycomb structure of claim 3, wherein the thickness of the webs is in a range from 0.025 mm to 0.76 mm.

8. The honeycomb structure of claim 7, wherein each fillet occupies from 2-12% of the cell cross-section.

9. The honeycomb structure of claim 3 having a cell density is in a range from 1.5 to 46.5 cells/cm2.

10. The honeycomb structure of claim 1 wherein the webs are porous.

11. An extrusion die for making a honeycomb body, comprising: a die body;an array of discharge slots formed in the die body to define an array of first and second pins, the first pins having rounded corners, the second pins having non-rounded corners; andan array of feedholes in the die body for communicating an extrusion material to the discharge slots.