Patent ID: 7785385

Claim:
A ceramic honeycomb structure having large numbers of flow paths partitioned by porous cell walls, said cell walls having a porosity of 55-75%, said cell walls having an average pore diameter Da of 5-30 μm and a pore area ratio Sa of 10-30% on their surfaces, and the average length La of said pores at their openings and the average width Lb of said pores at depth La from the surfaces of said cell walls meeting the condition of 1.1<Lb/La<5 in an arbitrary vertical cut surface of said cell walls, wherein said ceramic honeycomb structure is formed by a cordierite-based ceramic containing Fe and a spinel, the content of said spinel being 4% or less by an X-ray diffraction intensity ratio, and where the particle size of said spinel is substantially 0.01-5 μm.