Patent ID: 7989047

Claim:
A hexagonal-cell honeycomb structure comprising: a plurality of cell walls forming hexagonal shapes in cross-section and forming a plurality of hexagonal cell passages; and a tubular skin layer surrounding outermost ones of said plurality of cell walls; said plurality of cell walls including basic cell walls which form complete, substantially regular hexagonal shapes in cross-section and substantially regular hexagonal cell passages, and said outermost cell walls which intersect said skin layer and, with one another or together with adjacent basic cell walls, form incomplete, irregular hexagonal shapes in cross-section; wherein a thickness of each said basic cell wall forming said complete, regular hexagonal shape in cross-section is 140 μm or less, a diameter Da of an inscribed circle Ca at a basic cell wall intersection of three said basic cell walls, and a cell pitch P are configured to have a relationship Da/P≧0.13 by enlarging the basic cell wall intersection without increasing the thickness of said three basic cells walls, and a diameter Db of an inscribed circle Cb contacting a periphery of the openings of three adjacent passages at a cell wall intersection of at least one said outermost cell wall with two other said cell walls, and said diameter Da are configured to have a relationship Db/Da≧1.05 by enlarging the cell wall intersection without increasing a thickness of said at least one outermost cell wall and said two other cell walls.