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.

A catalysed filter for a positive ignition internal combustion engine comprises a porous filtering substrate having a total substrate length coated with a three-way catalyst washcoat composition comprising at least one precious metal selected from the group consisting of rhodium and one or both of platinum and palladium supported on a high surface area oxide, and an oxygen storage component, which composition being axially shared by a first zone comprising inlet surfaces of a first substrate length<total substrate length and a second zone comprising outlet surfaces of a second substrate length<total substrate length, wherein a sum of the substrate length in the first zone and the substrate length in the second zone≧100% and wherein one or both of the following applies: a washcoat loading in the first zone>second zone; and a total precious metal loading in the first zone>second zone.

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 includes honeycomb segments each having a porous partition wall defining a plurality of cells, and includes a porous bonding layer containing a crystalline anisotropic ceramic and disposed so as to bond side surfaces of the honeycomb segments to each other. A ratio of a pore volume (cc/g) of a fine pore defined as a pore in the bonding layer having a pore diameter of 10 μm or more and less than 50 μm with respect to a pore volume (cc/g) of a coarse pore defined as a pore in the bonding layer having a pore diameter of 50 μm or more and 300 μm or less is from 2.0 to 3.5, the pore volume of the fine pore is from 0.15 to 0.4 cc/g, and the pore volume of the coarse pore is from 0.05 to 0.25 cc/g.

An after-treatment system includes, in series along an exhaust gas flow direction through the after-treatment system: a diesel oxidation catalyst (DOC), a diesel exhaust fluid (DEF) delivery device, a soot-reducing device and a selective catalytic reduction (SCR) catalyst.

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.

A heat exchanger includes: a pillar shaped honeycomb; an inner cylindrical member; an outer cylindrical member arranged on a radially outer side of the inner cylindrical member such that a part of the outer cylindrical member forms a flow path for a second fluid; an upstream cylindrical member having a cylindrical portion and a flange portion, the upstream cylindrical member being located on a side of a first end face of the honeycomb structure, and an end portion of the flange portion being connected to the inner cylindrical member and/or the outer cylindrical member; and a downstream cylindrical member having a cylindrical portion and a flange portion, the downstream cylindrical member being located on a side of a second end face of the honeycomb structure, and an end portion of the flange portion being connected to the inner cylindrical member and/or the outer cylindrical member.

A honeycomb structure includes a central area and a reinforced outer peripheral area. A reference boundary cell with an inner wall orthogonal to an imaginary straight line, adjacent to the honeycomb center, and thinner than an outer wall adjacent to the honeycomb periphery has a reference wall different in wall thickness from the other three cell walls among the remaining four cell walls excluding the inner wall and the outer wall. The honeycomb structure includes a reference Y-shaped unit having the reference wall, the outer wall, and a cell wall. The honeycomb structure includes a plurality of Y-shaped units extending in the same directions as the reference Y-shaped unit. For every Y-shaped unit in the central area and the reinforced outer peripheral area of the honeycomb structure, the cell walls of each Y-shaped unit has an equal wall thickness.

Provided is a catalytic converter in which the entire catalyst constituting the catalytic converter can be efficiently utilized to purify exhaust gas, and the emission of hydrogen sulfide can be suppressed. A catalytic converter 10 includes catalyst layers 2A, 2B formed of a noble metal catalyst that are formed on cell wall surfaces 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 center region 1A having a relatively high cell density and a peripheral region 1B having a relatively low cell density, and lengths of the catalyst layers 2A, 2B of the center region 1A and the peripheral region 1B in the longitudinal direction are the same as each other, or the length of the catalyst layer 2B in the longitudinal direction is shorter than that of the catalyst layer 2A.