A plugged honeycomb structure includes: a plurality of honeycomb segments, a bonding layer, and plugging portions to plug open ends of cells of the honeycomb segment. Each honeycomb segment is configured so that the cells having at least two types of different shapes have a predetermined repeated sequence pattern. A circumferential-wall partially surrounded cell in which a partition wall and a segment circumferential wall are disposed so as to surround the cell has an area of open end that has a specific ratio to an area of open end of a partition-wall entirely surrounded cell including the cross-sectional shape of the circumferential-wall partially surrounded cell. The repeated sequence pattern of the cells is kept at a boundary between two of the honeycomb segments bonded with the bonding layer at an inflow end face and an outflow end face.

A honeycomb filter includes a plurality of cells, porous cell walls, and an oxidation catalyst. The plurality of cells include exhaust gas introduction cells and exhaust gas emission cells. The oxidation catalyst is supported inside the porous cell walls in an amount of 5 to 60 g/L. The exhaust gas emission cells have an average cross sectional area larger than an average cross sectional area of the exhaust gas introduction cells in the cross section perpendicular to the longitudinal direction. A total volume of the exhaust gas introduction cells is larger than a total volume of the exhaust gas emission cells.

A silicon carbide honeycomb filter constituted by honeycomb segments each comprising cell walls forming cells defining pluralities of flow paths, plugs sealing end surfaces of the cells alternately in a checkerboard pattern, and an outer peripheral wall, bonding material layers filling lattice gaps between the honeycomb segments for bonding them, and a skin layer enclosing the bonded honeycomb segments, the lattice gaps being provided with a bonding-material-free region extending in four directions from a center intersection to adjacent intersections, wherein the center intersection is an intersection located at the center axis of the honeycomb filter or its nearby position, among the intersections of the lattice gaps.

A silicon carbide honeycomb filter constituted by honeycomb segments each comprising cell walls forming cells defining pluralities of flow paths longitudinally extending between both end surfaces, plugs sealing end surfaces of the cells alternately in a checkerboard pattern, and an outer peripheral wall, bonding material layers filling lattice gaps between the honeycomb segments for bonding them, and a skin layer covering the bonded honeycomb segments, the thickness of the outer peripheral wall being more than 1.5 times and 9 times or less that of the cell walls.

A honeycomb filter comprising a pillar-shaped honeycomb structure body having a porous partition wall and a plugging portion, wherein, in a pore diameter distribution of the partition wall, in the case where the pore diameter (m) whose cumulative pore volume is 10% of the total pore volume is denoted by D10, the pore diameter (m) whose cumulative pore volume is 50% of the total pore volume is denoted by D50, and the pore diameter (m) whose cumulative pore volume is 90% of the total pore volume is denoted by D90, all of the following equations (1) to (6) are satisfied.
8.4 m<D10(1)
17.5 m<D50<24.0 m(2)
D90<55.2 m(3)
(log D90log D10)/log D50<0.60(4)
log D90/log D50<1.30(5)
log D50/log D10<1.38(6)

A pillar-shaped honeycomb structure includes inlet cells and outlet cells adjacent to at least one of the inlet cells with a partition wall interposed therebetween, wherein a ratio of an opening area (C.sub.in) of each of the inlet cells to an opening area (C.sub.out) of each of the outlet cells, a thickness (WT) of the partition wall, a cell density (CD) based on a total number of the inlet cells and the outlet cells, a depth (PD) of a sealing portion, and a distance (OF) between the midpoint of a line segment connecting the centers of gravity of the inlet cells and the outlet cells adjacent to each other with the partition wall interposed therebetween and the center of the partition wall intersected by the line segment, satisfy predetermined conditions, and furthermore, the honeycomb structure satisfies 2OFCD/(WTPD)7.

A honeycomb filter includes a pillar-shaped honeycomb structure having a porous partition wall arranged to surround a plurality of cells and a plugging portion provided to plug either one end of the cell; wherein, in a section orthogonal to the extending direction of the cell of the honeycomb structure, the sectional shape of an inflow cell is octagonal or quadrangular, and the sectional shape of an outflow cell is quadrangular, except for the cell disposed in outermost circumference of the honeycomb structure, a cell density of the honeycomb structure is 49 to 70 cells/cm.sup.2, a thickness of the partition wall is 0.152 to 0.198 mm, an opening diameter L1 of the inflow cell is 1.16 to 1.40 mm, an opening diameter L2 of the outflow cell is 0.82 to 1.08 mm, and a ratio (L1/L2) of the opening diameter L1 to the opening diameter L2 is 1.30 to 1.53.

A honeycomb filter comprising a pillar-shaped honeycomb structure body having a porous partition wall and a plugging portion, wherein, in a pore diameter distribution of the partition wall, in the case where the pore diameter (m) whose cumulative pore volume is 10% of the total pore volume is denoted by D10, the pore diameter (m) whose cumulative pore volume is 50% of the total pore volume is denoted by D50, and the pore diameter (m) whose cumulative pore volume is 90% of the total pore volume is denoted by D90, all of the following equations (1) to (6) are satisfied.
3.9 m<D106.2 m(1)
10.5 m<D50<16.6 m(2)
28.3 m<D90<38.7 m(3)
(log D90log D10)/log D50<0.80(4)
log D90/log D50<1.36(5)
log D50/log D10<1.56(6).