Patent attributes
A filter has a honeycomb structural body having a plurality of large-capacity through holes and small-capacity through holes placed in parallel with one another in a length direction. A total (a) of lengths in the cross section of wall surfaces of one large-capacity through hole, the wall surfaces being shared by the one large-capacity through hole and adjacent large-capacity through holes to a total (b) of lengths in the cross section of wall surfaces of one large-capacity through hole, the wall surfaces being shared by the one large-capacity through hole and adjacent small-capacity through holes is defined as α. A ratio (A/B) of the area (A) of the cross section of the one large-capacity through hole to the area (B) of the cross section of one of the adjacent small-capacity through holes is defined as β. The α and β satisfy the relationship represented by the formulas:0<α≦1.5 and 2<β≦2.75, and β≧(20/9)α2+.
