In a honeycomb structure, porous partition walls are arranged to surround cells extending from an inflow end face of the honeycomb structure body to an outflow end face thereof, intersection points at which the partition walls arranged in a latticed manner in the inflow end face intersect include a first intersection point that is one intersection point, and second intersection points one of which is the other intersection point in the partition wall including the first intersection point, and which are adjacent to the first intersection point, and the inflow end face has concave/convex portions each including the first intersection point as a bottom portion and the peripheral second intersection points of the first intersection point as top portions, or each including the first intersection point as a top portion and the peripheral second intersection points of the first intersection point as bottom portions.

A honeycomb formed body containing a ceramics raw material, the honeycomb formed body including: a pillar shaped honeycomb structure portion having a plurality of rectangular cells, the cells being defined by partition walls and extending from a first end face to a second end face to form flow paths; an outer peripheral portion having outer peripheral portions X where the partition walls are covered with an outer peripheral wall; and outer peripheral portions Y where the partition walls are exposed. Each of the outer peripheral portions X includes a tapered portion having a gradually deceasing thickness of the outer peripheral wall toward a boundary portion with an adjacent outer peripheral portion Y. The tapered portion requires a length equal to or more than one time of an average cell pitch in the outer peripheral direction until thickness of the outer peripheral wall is halved.

The honeycomb filter includes a honeycomb substrate having porous partition walls defining a plurality of cells and plugging portions. In a cross section, the cells are arranged so that a periphery of an inlet plugged cell including an open end whose shape is a square in which a length of one side is L1 is surrounded with four rectangular outlet plugged cells each including an open end whose shape is a rectangle in which a length of one side is L1 and a length of the other side is L2 (L1>L2) and four square outlet plugged cells each including an open end whose shape is a square in which a length of one side is L2. A partition wall center distance a, a partition wall center distance b and a partition wall thickness t satisfy the following equation (1):
0.95<b/at<1.90   (1).

The present disclosure relates to porous ceramic compositions and porous ceramic articles, such as honeycomb structure bodies and porous ceramic filters. In various embodiments, a particulate filter is disclosed herein; in some of these embodiments, the particulate filter is a gasoline particulate filter (GPF) and is suitable for use with a gasoline engine and treating its exhaust, and in some of the embodiments, the particulate filter is a diesel particulate filter (DPF) and is suitable for use with a diesel engine and treating its exhaust.

A ceramic honeycomb structure comprising large numbers of flow paths longitudinally formed by cell walls arranged in a lattice pattern in cross section, and an outer peripheral wall formed around the flow paths; in a cross section perpendicular to the longitudinal direction, fan-shaped bulges projecting in a fan shape toward the flow paths from cell wall intersections at which the cell walls are crossing; the circumscribed circles of circular portions of the fan-shaped bulges at all cell wall intersections having a constant radius; and when the distance between the center point of the circumscribed circle and the center point of the cell wall intersection is defined as a center point distance S, a center point distance So in the outer peripheral portion of the ceramic honeycomb structure and a center point distance Sc in the center portion meeting Sc<So.

A honeycomb structure includes: a honeycomb structure body; and a convex part that protrudes outward from a part of circumference of the honeycomb structure body. The convex part surrounds the circumference of the honeycomb structure body like a ring. The convex part is of a tapered shape at least at one end having a tapered face. The convex part has a circumference coating layer making up the tapered face. The convex part has a maximum thickness of 1 to 20 mm, and a rough-face region on the tapered face, the rough-face region having surface roughness of 5 to 70 μm. The rough-face region has a total of a rough-face region angle of 108° or more. An inclination angle formed between the tapered face and the extending direction of the cells is 10 to 80 degrees.

In a porous body, a surface layer thickness Ts takes a relatively small value satisfying P≧0.54 Ts (formula (1)), the surface layer thickness Ts being derived by a microstructure analysis using the porous-body data that is prepared through three-dimensional scanning of a region including a surface (inflow plane 61) of the porous body. Here, P denotes a porosity [%] of the porous body, and 0%<P<100% and 0 μm<Ts are assumed. The surface layer thickness Ts is derived as a distance in a thickness direction (X direction) between a surface-layer region start plane 92 in which a straight-pore opening ratio becomes 98% or less for the first time and a surface-layer region end plane 93 in which the straight-pore opening ratio becomes 1% or less for the first time.

A plugged honeycomb structure in which in a cross section of a honeycomb structure body which is perpendicular to an extending direction of cells, inflow cells are disposed to surround an outflow cell, and the number of the inflow cells is larger than the number of the outflow cells, and the cross section has a plurality of intersecting portions of partition walls each defining the inflow cells which are adjacent to each other, and in 60% or more of a total number of the intersecting portions, a relation between a diameter (D.sub.1) of a circle inscribed in the intersecting portion and a diameter (D.sub.0) of a circle inscribed in the partition wall defining the inflow cell and the outflow cell which are adjacent to each other satisfies D.sub.1/(√2×D.sub.0)=1.20 to 1.80

A honeycomb structure includes a honeycomb structure body that includes a porous partition wall which defines a plurality of cells serving as through channels of fluid and extending from an inflow end face as one end face to an outflow end face as the other end face, and a circumferential wall arranged on a circumferential surface of the honeycomb structure body. The circumferential wall has a thickness of 0.5 to 4.0 mm, a gap path is formed along a surface of the circumferential wall inside the circumferential wall, the gap path has a width of 0.4 to 4.0 mm, and has a height of 50 to 99% of the thickness of the circumferential wall, and a total length of the gap path is 1000% or more of a length in the cell extending direction of the honeycomb structure body.

The honeycomb structure includes a honeycomb structure body having porous partition walls, and a plugging portion disposed in one of open ends of each cell, a thickness of the partition walls is 0.30 mm or more and 0.51 mm or less, a cell density is 30 cells/cm.sup.2 or more and 93 cells/cm.sup.2 or less, a filtration area (cm.sup.2) of inflow cells included per cm.sup.3 of the honeycomb structure body is defined as an inflow side filtration area G (cm.sup.2/cm.sup.3), a value obtained by dividing a pore volume Vp (cm.sup.3) formed in the partition walls by a total volume Va (L) including the cells is defined as a pore volume ratio A (cm.sup.3/L), and in this case, a product of the inflow side filtration area G (cm.sup.2/cm.sup.3) and the pore volume ratio A (cm.sup.3/L) is 1800 cm.sup.2/L or more and 3200 cm.sup.2/L or less.