A honeycomb body having a honeycomb structure and a peripheral skin, the honeycomb structure having walls defining a plurality of cells including peripheral cells disposed directly adjacent to the peripheral skin. One or more of the peripheral cells is at least partially defined by a first wall surface, a second wall surface, and a skin surface portion extending between the first wall surface and the second wall surface. A continuously-varying radius extends from a first tangent to the first wall surface along the skin surface portion and to a second tangent to the second wall surface. Other honeycomb bodies, structures, and extrusion dies for forming honeycomb structures are disclosed.

A pillar-shaped honeycomb structure including an outer peripheral side wall, a plurality of first cells provided on an inner peripheral side of the outer peripheral side wall, the first cells extending from a first end surface to a second end surface, each opening on the first end surface and having a sealing portion with an average void ratio of 4% or less on the second end surface, and a plurality of second cells provided on the inner peripheral side of the outer peripheral side wall, the second cells extending from the first end surface to the second end surface, each having a sealing portion with an average void ratio of 4% or less on the first end surface and opening on the second end surface, the first cells and the second cells being alternately arranged adjacent to each other with a partition wall interposed therebetween.

A method for manufacturing a pillar-shaped honeycomb structure filter including a step of preparing a pillar-shaped honeycomb structure having a plurality of first cells and a plurality of second cells that are alternately arranged adjacent to each other with a porous partition wall interposed therebetween; a step of adhering ceramic particles containing 50% by mass or more in total of one or two selected from SiC and SiN to a surface of the first cells; and a step of performing a heat-oxidation treatment on the pillar-shaped honeycomb structure in which the ceramic particles are adhered to the surface of the first cells to form a porous film comprised of the ceramic particles having an oxide film thereon so as to satisfy: (1) 0.05≤T≤0.5; (2) 0.05≤T/D50; and (3) 4≤{(W.sub.1−W.sub.0)/W.sub.0×100}/D50.

A honeycomb filter including: a pillar-shaped honeycomb structure having an inflow end face and an outflow end face and including a porous partition wall disposed so as to surround a plurality of cells, the plurality of cells extending from the inflow end face to the outflow end face; inflow side plugging portions disposed at open ends of predetermined cells on the inflow end face side; and outflow side plugging portions disposed at open ends of residual cells on the outflow end face side, wherein the outflow side plugging portions comprise first outflow side plugging portions and second outflow side plugging portions, the plugging length L1 of the first outflow side plugging portions is 10 to 50% of the overall length L0 of the honeycomb structure, and the plugging length L2 of the second outflow side plugging portions is less than 10% of the overall length L0 of the honeycomb structure.

A honeycomb structure includes a pillar-shaped honeycomb structure body having a porous partition wall disposed to surround a plurality of cells, which serving as fluid through channels extending from a first end face to a second end face, wherein the plurality of cells includes: large opening cells having a large opening area on the first end face and the second end face; and small opening cells having an opening area smaller than that of the large opening cells on the first end face and the second end face, a ratio of an opening diameter of the large opening cells to an opening diameter of the small opening cells is larger than 1.11 and smaller than 1.28, and the opening diameter of the small opening cells is larger than 0.78 mm, and a cell density of the honeycomb structure body is larger than 93 pcs/cm.sup.2 and smaller than 104 pcs/cm.sup.2.

A honeycomb body with a honeycomb structure having an inner zone of a first plurality of walls and an outer zone of a second plurality of walls at least partially surrounding the inner zone. The honeycomb structure has Pi that is greater than Po and MPSi that is greater than MPSo, wherein Pi is an average bulk porosity of the first plurality of walls, Po is an average bulk porosity of the second plurality of walls, MPSi is a median pore size of pores in the first plurality of walls, and MPSo is a median pore size of pores in the second plurality of walls. Various honeycomb structures, honeycomb extrusion apparatus, and co-extrusion methods are disclosed.

A honeycomb body with a honeycomb structure having an inner zone of a first plurality of walls and an outer zone of a second plurality of walls at least partially surrounding the inner zone. The honeycomb structure has Pi that is greater than Po and MPSi that is greater than MPSo, wherein Pi is an average bulk porosity of the first plurality of walls, Po is an average bulk porosity of the second plurality of walls, MPSi is a median pore size of pores in the first plurality of walls, and MPSo is a median pore size of pores in the second plurality of walls. Various honeycomb structures, honeycomb extrusion apparatus, and co-extrusion methods are disclosed.

A honeycomb filter includes a pillar-shaped honeycomb structure having porous partition walls provided, surrounding a plurality of cells which serve as fluid through channels extending from an inflow end face to an outflow end face, and porous plugging portions provided either at the ends on the inflow end face or the outflow end face of the cells, wherein the plugging portions are composed of a porous material, the honeycomb structure has a central region and a circumferential region and a ratio of an area of the circumferential region with respect to that of the central region ranges from 0.1 to 0.5, and a plugging length L1 in the cell extending direction of a central plugging portion in the central region is smaller than a plugging length L2 of a circumferential plugging portion in the circumferential region, L1 ranges from 3 to 6 mm, and L2 from 7 to 9 mm.

A honeycomb filter includes a pillar-shaped honeycomb structure having porous partition walls provided, surrounding a plurality of cells which serve as fluid through channels extending from an inflow end face to an outflow end face, and porous plugging portions provided either at the ends on the inflow end face or the outflow end face of the cells, wherein the plugging portions are composed of a porous material, the honeycomb structure has a central region and a circumferential region and a ratio of an area of the circumferential region with respect to that of the central region ranges from 0.1 to 0.5, and a plugging length L1 in the cell extending direction of a central plugging portion in the central region is smaller than a plugging length L2 of a circumferential plugging portion in the circumferential region, L1 ranges from 3 to 6 mm, and L2 from 7 to 9 mm.

A honeycomb filter includes a pillar-shaped honeycomb structure body having a porous partition wall disposed to surround a plurality of cells and a plugging portion provided at an open end on a first end face side or a second end face side of each of the cells, wherein the partition wall is composed of a material containing cordierite as a main component thereof, a number per unit area of pores which exist at a surface of the partition wall and which have equivalent circle diameters exceeding 3.0 μm is 1400 per mm.sup.2 or more, and, in a pore diameter distribution which indicates a cumulative pore volume of the partition wall, with a log pore diameter on a horizonal axis and a log differential pore volume (cm.sup.3/g) on a vertical axis, a half-value width of a first peak that includes a maximum value of the log differential pore volume is 0.30 or less.