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.

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.

An object of the present invention is to provide a honeycomb filter capable of preventing depth filtration and achieving a combination of high collection efficiency and low pressure loss. The honeycomb filter of the present invention comprises a ceramic honeycomb substrate in which a multitude of cells through which a fluid flows are disposed in parallel in a longitudinal direction and are separated by cell walls, each cell being sealed at an end section at either the fluid inlet side or the fluid outlet side, and a filter layer which, among the surfaces of the cell walls, is formed on the surface of the cell walls of those cells in which the end section at the fluid inlet side is open and the end section at the fluid outlet side is sealed, wherein the filter layer is composed of a plurality of spherical ceramic particles, and crosslinking bodies which bind the spherical ceramic particles to each other by crosslinking the spherical ceramic particles, and the spherical ceramic particles and the crosslinking bodies form a three-dimensional network structure.

A honeycomb structure body has main cells having a tubular shape and main cell walls. Each main cell is surrounded by the main cell walls. A virtual base structure body has base cell walls and base cells. The honeycomb structure body has an improved structure obtained by modifying a structure of the virtual base structure body. Each base intersecting point, at which base cell walls intersect, is determined by a polar coordinate (r, θ) using a radius vector r and a deflection angle θ. Each main intersecting point is formed on a polar coordinate (r′, θ) using the deflection angle θ and a main radius vector r′ which is obtained by multiplying the radius vector r and a constant magnification without changing the deflection angle θ. A cell density varying section varies its cell density and is formed in at least a part of the honeycomb structure body.

Provided is an exhaust gas purification catalyst in which the performance of a catalyst metal can be brought out properly, the purification catalyst boasting excellent purification performance during warm-up of an internal combustion engine. The exhaust gas purification catalyst 10 is provided with a substrate 1 and a catalyst layer. A leading end section 1a positioned upstream in the direction of exhaust gas flow (arrow) has a portion in which the flow rate of exhaust gas is relatively high and a portion in which the flow rate of exhaust gas is relatively low during warm-up of the internal combustion engine. The catalyst, layer in the portion of relatively high flow rate of exhaust gas has a high density section 6 in which a noble metal, is supported at relatively high density. The high density section 6 is formed to be shorter than the total length of the exhaust gas purification catalyst 10 from the leading end section 1a in the direction of exhaust gas flow.

The risk of a particulate filter from being damaged is reduced while an increase in pressure loss of the particulate filter due to ash is suppressed. Micropore zones are defined at upstream sides of partition walls of a particulate filter and macropore zones are defined at downstream sides of partition walls. The pore size of the partition walls at the micropore zones is set so that the particulate matter and the ash can be trapped by the partition walls at the micropore zones, while the pore size of the partition walls at the macropore zones is set so that the ash can pass through the partition walls at the macropore zones. When the difference dQPM between the quantity of the particulate matter which is trapped at the micropore zones and the quantity of particulate matter which is trapped at the macropore zones exceeds a predetermined threshold value, PM removal control is executed.

A catalytic aftertreatment system for a diesel engine exhaust gas is described. The system comprises a diesel oxidation catalyst (DOC) and an aftertreatment device located downstream of the diesel oxidation catalyst (DOC), which aftertreatment device requires periodic heat treatment, and means to generate a temperature increase within the aftertreatment device, said diesel oxidation catalyst (DOC) comprising an upstream zone of length from 0.5 to 2 inches (12.7-50.81 mm) of higher oxidation activity for hydrocarbons (HC) than the remainder of the diesel oxidation catalyst (DOC).

A catalyst converter includes: a substrate (1) having a cell structure formed of a center area (1A) having the highest cell density, a peripheral area (1C) having the lowest cell density, and an intermediate area (1B) having the cell density between that of the center area and that of the peripheral area; a first catalyst layer formed in the center area (1A); a second catalyst layer formed in the intermediate area (1B); and a third catalyst layer formed in the peripheral area (1C). A length in a longitudinal direction of the second catalyst layer is longer than that of the first catalyst layer. A length in the longitudinal direction of the third catalyst layer is longer than that of the second catalyst layer. A ratio of the length in the longitudinal direction of the first catalyst layer to the length of the substrate is 65% or more.

Provide is a catalytic converter including a substrate which includes regions having different cell densities, in which exhaust gas purification performance is superior in all the regions of the substrate. A catalytic converter 10 includes catalyst layers in which a noble metal catalyst is supported on a support in surfaces of cell walls 2 of a substrate 1 having a cell structure in a longitudinal direction of the substrate 1 in which gas flows, in which the substrate 1 has a first region 1A having a relatively high cell density and a second region 1B having a relatively low cell density, and a ratio of a thickness of a catalyst layer 3A in the second region 1B to a thickness of a catalyst layer 3 in the first region 1A is in a range of more than 0.95 times and 1.2 times or less.

A honeycomb structure has partition walls defining a plurality of polygonal cells which become through channels for a fluid, a structure end face vertical to an axial direction has at least two cell regions possessing mutually different cell structures and surrounded by circumferential portions, and in the cell regions adjacent to each other, to first partition walls of a first cell structure of one first cell region, second partition walls of a second cell structure of the other or second cell region are tilted.