A column-shaped porous honeycomb structured body forms a plurality of first flow passages that are opened on one end face and closed on the other end face and a plurality of second flow passages that are closed on the one end face and opened on the other end face. The honeycomb structured body comprises: central partition walls where sectional areas of each first flow passage and each second flow passage are individually constant in an axial direction; and other-end-side inclined partition walls where the sectional area of each first flow passage is shrank and the sectional area of each second flow passage is expanded from the central partition walls to the other end face. An axial-directional length of the other-end-side inclined partition wall is 4 mm or more.

An exhaust gas filter purifies exhaust gas containing particulate matter emitted from an engine. The filter has cell walls and cells surrounded by the cell walls. Through pores formed in the cell walls, adjacent cells are communicated. The cells have open cells opening along an axial direction of the filter, and plugged cells. An upstream end part of the plugged cell is plugged by a plug member. On a cross section perpendicular to the axial direction, a flow-passage sectional area of the plugged cells is larger than a flow-passage sectional area of the open cells. A total length of the filter is not less than a first standard value and is not more than a critical length Lm determined by respective predetermined equations.

The honeycomb structure body has a dense part at a part in axial direction including a center region of the inflow end face, the dense part having a change ratio of porosity calculated by the following Expression (1) that is 2 to 8%, and has an outside-diameter increasing part, and the honeycomb structure body has a change ratio of average diameter calculated by the following Expression (2) that is 0.2 to 3%,

(1−Px/Py)×100, Expression (1): in Expression (1), Px denotes the porosity (%) at the center region of the inflow end face, and Py denotes the porosity (%) of a circumferential region of the inflow end face.

(1−Dx/Dy)×100,   Expression (2): in Expression (2), Dx denotes the average diameter (mm) of the inflow end face, and Dy denotes the average diameter (mm) of the outflow end face.

The honeycomb filter of the present invention comprises a ceramic honeycomb substrate formed from a porous body of sintered ceramic particles, and a filter layer formed on the surface of the cell walls, wherein a portion of the filter layer penetrates from the surface of the cell walls into pores formed by the ceramic particles to form inter-particle filtration bodies, these inter-particle filtration bodies are formed from a plurality of spherical ceramic particles and crosslinking bodies which bind the spherical ceramic particles to each other, and the spherical ceramic particles and the crosslinking bodies form a three-dimensional network structure.

A ceramic honeycomb body, suitable for use in exhaust gas processing, includes a honeycomb structure having a plurality of through-channels, a first portion of the plurality of through-channels have a first hydraulic diameter dh1, a second portion of the plurality of through-channels have a second hydraulic diameter that is smaller than the first hydraulic diameter dh1, the first hydraulic diameter dh1 is equal to or greater than 1.1 mm, and the first and second portions of through-channels, taken together, have a geometric surface area GSA greater than 2.9 mm.sup.−1. Diesel oxidation catalysts and methods of soot removal are also provided, as are other aspects.

A honeycomb structure includes a pillar-shaped honeycomb structure body including porous partition walls defining and forming a plurality of cells which extend from an inflow end face to an outflow end face, and a porous outer wall surrounding the partition walls, a porous supporting bulge disposed to extend out from a circumference of the outer wall so that at least a part of the outer wall is exposed, and plugging portions arranged in open ends of the cells, and the supporting bulge has support portions and a side wall portion, and the partition walls and the outer wall of the honeycomb structure body and the support portions and the side wall portion of the supporting bulge are all formed monolithically by formation of a ceramic raw material.

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.

A plugged honeycomb structure includes: a honeycomb substrate and a plugging portion, and is configured to trap particulate matter included in fluid flowing from an inflow side end face to an outflow side end face. The partition wall includes, as raw materials, particulates of a base material and a binder and having a melting point lower than that of the base material, the base material has a particle diameter in a range of 5 μm to 60 μm, a mass ratio of the binder to a total mass of the raw material of the base material and the binder is in a range of 22 mass % to 45 mass %, and the cells include round cells as a part, the round cells being defined by a circular-arc partition wall having a circular-arc shape that is at least a part of the partition wall to have a circular shape or the like.

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).