A honeycomb filter includes a pillar-shaped honeycomb structure having porous partition walls placed, 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 side of the cells or at the ends on the outflow end face side of the cells, wherein the plugging portions include plugging portions that have voids therein, and in the plugging portions having the voids, porosity including the voids as pores ranges from 68% to 83%.

A particulate filter, including: a pillar-shaped honeycomb structure portion having a plurality of first cells extending from a first end face to a second end face, the first end face being open and the second end face being plugged, and a plurality of second cells extending from the first end face to the second end face, the first end face being plugged and the second end face being open, in which the first cells and the second cells are alternately arranged adjacent to each other with porous partition walls interposed therebetween; and a low thermal conductive layer covering a part or the whole of an outer peripheral side surface of the pillar-shaped honeycomb structure portion, the thermal conductivity in a thickness direction of the low thermal conductive layer being 0.6 W/(m.Math.K) or less.

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 a porous plugging portion provided either at an end on the inflow end face or the outflow end face of the cells, wherein the plugging portion is 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, porosity of a central plugging portion in the central region is lower than that of a circumferential plugging portion in the circumferential region, and the porosity of the central plugging portions ranges from 60% to 68%, and that of the circumferential plugging portions ranges from 70% to 85%.

A honeycomb structure body has a skin part of a cylindrical shape and a honeycomb structural part formed with the skin part together in a monolithic body. The skin part and the honeycomb structural part have partition walls of a porous structure. The cells have first cells arranged adjacent to the skin part and second cells arranged adjacent to the first cells. The skin part, the first cells and the second cells form an outer peripheral section. A central section is arranged inside the outer peripheral section. The honeycomb structure body satisfies a relationship in which a thermal expansion coefficient of the outer peripheral section is greater than a thermal expansion coefficient of the central section.

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, a plugging length L1 in the cell extending direction of a central plugging portion in the central region is larger than a plugging length L2 of a circumferential plugging portion in the circumferential region, L1 ranges from 7 to 9 mm, and L2 from 3 to 6 mm.

An electric heating support includes an electrically conductive honeycomb structure having an outer peripheral wall and porous partition walls disposed on an inner side of the outer peripheral wall, the porous partition walls defining a plurality of cells, each cell penetrating from one end face to other end face to form a flow path. A pair of metal terminals are disposed so as to face each other across a central axis of the honeycomb structure, each metal terminal being joined to a surface of the honeycomb structure via a welded portion. The honeycomb structure is composed of ceramics and a metal. The honeycomb structure contains 40% by volume or less of the metal. The welded portion of the honeycomb structure has a surface containing 40% by volume or more of the metal.

A honeycomb structure includes a pillar-shaped honeycomb structure body having porous partition walls, wherein the partition walls have projecting portions, the sectional area SA and the sectional area SB satisfy a relation of Formula (1) mentioned below, the number NA of the projecting portions and the number NB of the projecting portions satisfy a relation of Formula (2) mentioned below, Formula (1): <(the sectional area SA/the sectional area SB)<3, and Formula (2): 0(the number NB of the projecting portions/the number NA of the projecting portions)<1.

A honeycomb structure includes a pillar-shaped honeycomb structure body having porous partition walls, wherein the partition walls have projecting portions, the projecting portions include specific projecting portions in which side surfaces have a divergent shape inclined at an inclination angle of 40 to 70, a relation of 0.04H/A0.40 is satisfied, a relation of 0.04H.sub.1/A0.38 is satisfied, the height H of the specific projecting portion and the height H.sub.1 of the hem satisfy a relation of H.sub.1<H, and a ratio of a total number of the specific projecting portions is 2.5% or more.

A honeycomb structure includes a pillar-shaped honeycomb structure body having porous partition walls surrounding a plurality of cells which extend from a first to a second end face and which form flow channels of a fluid, and a circumferential wall enclosing the partition walls, wherein, specific cell of the cells is provided with a pair of projection which projects into the cell from the partition wall, the projection projects, in at least a pair of opposed partition walls among the partition walls constituting the cell, into the cell from a first and a second side, and which is provided continuously in a direction the cell extends, and in the case where the width of a top part of the projection is denoted by W1, and the width of a bottom part of the projection is denoted by W2, W1>W2 holds, and W2/W1 is 0.5 to 0.9.

A honeycomb structure includes a pillar-shaped honeycomb structure body having porous partition walls, wherein the partition walls have projecting portions, a shape of each cell is polygonal, in the polygonal cell, the projecting portions are disposed on two sides extending from a corner of the cell, respectively, the projecting portions are non-uniformly arranged, a relation of Formula (1) is satisfied, and a ratio of a total number of the corners is 2.5% or more: Formula (1): 1/(N+1)<A/L.