Patent ID: 7410929

Claim:
A cell structure which is a cylindrical cell structure comprising a plurality of cells which pierce through the structure between two end faces and are flow paths for fluid, an outer wall which encloses the cells and a cavity which pierces in the direction of a central axis of the structure through a portion including the central axis or a given axis parallel to the central axis: wherein the cell structure further has an inner wall on the inner surface of the cavity, the cells are partitioned in the form of a honeycomb with partition walls, and a strength index represented by the formula: strength index=( T/CP ) 2 ×( B/A ) 2 is not less than 0.02 in which T denotes a thickness (mm) of the partition wall, CP denotes a cell pitch (mm), A denotes a length (mm) of a line formed by linking, along the outer wall, points of intersection of the outer wall with two tangent lines which contact with inner contour of the inner wall and extend in parallel in longitudinal direction of the partition wall, and B denotes a distance (mm) between a point of contact of the tangent line with the inner contour of the inner wall and a point of intersection of the tangent line with the closest outer wall at the section formed by cutting the cell structure along a plane perpendicular to the central axis of the cell structure.