A honeycomb filter includes a plurality of cells and porous cell walls. Exhaust gas is to flow through the plurality of cells. The plurality of cells include exhaust gas introduction cells and exhaust gas emission cells. The honeycomb filter has a round cross sectional shape. The honeycomb filter has a ratio of length of the honeycomb filter to a diameter of the round cross sectional shape of less than 1.0. A total volume of the exhaust gas introduction cells is larger than a total volume of the exhaust gas emission cells.

The present invention provides a honeycomb filter including a honeycomb fired body including porous cell partition walls, exhaust gas introduction cells each having an open end at an exhaust gas inlet side and a plugged end at an exhaust gas outlet side, exhaust gas emission cells each having an open end at the exhaust gas outlet side and a plugged end at the exhaust gas inlet side, and an outer wall on the periphery thereof. The cross-sectional shape of each exhaust gas introduction cell in a plane perpendicular to the longitudinal direction thereof is entirely uniform from the end at the exhaust gas inlet side to the end at the exhaust gas outlet side excluding the plugged portion, and the cross-sectional shape of each exhaust gas emission cell in a plane perpendicular to the longitudinal direction thereof is entirely uniform from the end at the exhaust gas inlet side to the end at the exhaust gas outlet side excluding the plugged portion. The cross-sectional shape of each exhaust gas introduction cell in a plane perpendicular to the longitudinal direction thereof is a polygon. The exhaust gas emission cells, except for the cells adjacent to the outer wall, are each adjacently surrounded fully by the exhaust gas introduction cells across the porous cell partition walls. The cells adjacent to the outer wall include the exhaust gas introduction cells and the exhaust gas emission cells. The aperture ratio of the exhaust gas introduction cells is higher than the aperture ratio of the exhaust gas emission cells, and the cross-sectional area of each exhaust gas emission cell is larger than the cross-sectional area of each exhaust gas introduction cell. Among the sides forming the polygon, the number of sides facing the exhaust gas introduction cells across the cell partition walls is larger than the number of sides facing the exhaust gas emission cells across the cell partition walls.

The present invention provides a honeycomb filter including a honeycomb fired body including porous cell partition walls, exhaust gas introduction cells each having an open end at an exhaust gas inlet side and a plugged end at an exhaust gas outlet side, exhaust gas emission cells each having an open end at the exhaust gas outlet side and a plugged end at the exhaust gas inlet side, and an outer wall on the periphery thereof. The cross-sectional shape of each exhaust gas introduction cell in a plane perpendicular to the longitudinal direction thereof is entirely uniform from the end at the exhaust gas inlet side to the end at the exhaust gas outlet side excluding the plugged portion. The cross-sectional shape of each exhaust gas emission cell in a plane perpendicular to the longitudinal direction thereof is entirely uniform from the end at the exhaust gas inlet side to the end at the exhaust gas outlet side excluding the plugged portion. The exhaust gas emission cells, except for the cells adjacent to the outer wall, are each adjacently surrounded fully by the exhaust gas introduction cells across the porous cell partition walls. The cells adjacent to the outer wall include the exhaust gas introduction cells and the exhaust gas emission cells. A substantial ratio of the number of the exhaust gas introduction cells to the number of the exhaust gas emission cells (exhaust gas introduction cells:exhaust gas emission cells) is 4:1. All the exhaust gas introduction cells, except for the cells adjacent to the outer wall, have the same cross-sectional area in a plane perpendicular to the longitudinal direction thereof, the cross-sectional area of each exhaust gas introduction cell being smaller than that of each exhaust gas emission cell in a plane perpendicular to the longitudinal direction thereof.

A honeycomb filter includes a silicon carbide honeycomb fired body, an end face, and porous cell walls. The silicon carbide honeycomb fired body includes a plurality of cells through which exhaust gas is to flow and which include exhaust gas introduction cells and exhaust gas emission cells. The silicon carbide honeycomb fired body includes silicon carbide grains having a silicon-containing oxide layer with a thickness of 0.1 to 2 m on surfaces of the silicon carbide grains. The end face has an aperture ratio of not less than 20% at the exhaust gas emission side. The porous cell walls define rims of the plurality of cells. The plugged portions of the exhaust gas introduction cells are arranged in vertical and horizontal lines with the porous cell walls residing between the plugged portions in the end face at the exhaust gas emission side.

A plurality of inlet-side octagonal cells and outlet-side quadrangular cells partitioned by partition walls on an upper surface and a lower surface are opened in a green honeycomb molded body in which a plurality of through-holes partitioned from each other by the partition walls are open in an end surface of a columnar body. Four outlet-side quadrangular cells having a smaller opening area adjoin around one inlet-side octagonal cell through the partition walls. The partition walls are joined together and the inlet-side octagonal cells are opened while closing the outlet-side quadrangular cells on the inlet side and the outlet-side quadrangular cells are opened while closing the inlet-side octagonal cells on the outlet side in a particulate-matter-removing filter such as a diesel particulate filter.

Honeycomb monolith structure, especially for use as catalyst or support for a catalyst in selective catalytic reduction (SCR) of nitrogen oxides, comprising: a plurality of cell walls defining a plurality of polygonal channels, the plurality of cell walls and channels extending in parallel along a common direction from an entrance end to an outlet end of the structure in the fluid flow direction. The transversal cross section of a polygonal channel has the shape of a convex polygon in closest packing, wherein more than 50% of the internal angels between two adjacent walls of the convex polygon are above 90 degrees and wherein the cell aspect ratio L.sub.L/L.sub.S is greater than 1.5. The monolith structure has an outer row of polygons in shifted direction perpendicular to each other at the two side edges of the monolith which are parallel to the longest direction of the cells/channels.

A honeycomb filter includes a honeycomb structure body that has porous partition walls disposed so as to surround cells, and plugging portions that are disposed at any one of the ends on the inflow end face and the ends on the outflow end face. A cross-sectional shape of each of the inflow cells is octagonal and a cross-sectional shape of each of the outflow cells is quadrangular. An area ratio (S1/S2) of a cross-sectional area S2 of each of the outflow cells to a cross-sectional area S1 of each of the inflow cells is 1.40 to 2.20. The plugging portions have convex portions that protrude from the end faces on which the plugging portions are disposed, toward the outer sides, and have a protruding height H of 0.3 to 3.0 mm, and the plugging portions have a plugging depth L of 4.0 to 9.0 mm.

A honeycomb filter includes a plurality of cells and porous cell walls. The plurality of cells include exhaust gas introduction cells and exhaust gas emission cells. The porous cell walls each have a porosity of 55% or acre but not more than 70%. The porous cell walls include pores with a pore diameter of 40 m or more. The pores have a pore volume occupying 10% or more of a total pore volume of the porous cell walls. The exhaust gas emission cells have an average cross sectional area larger than an average cross sectional area of the exhaust gas introduction cells in the cross section perpendicular to the longitudinal direction of the plurality of cells. A total volume of the exhaust gas introduction cells is larger than a total volume of the exhaust gas emission cells.

A honeycomb filter includes a plurality of cells and porous cell walls. The plurality of cells include exhaust gas introduction cells and exhaust gas emission cells. Each of the exhaust gas emission cells is adjacently surrounded fully by the exhaust gas introduction cells across the porous cell walls. The exhaust gas introduction cells include first exhaust gas introduction cells and second exhaust gas introduction cells. Each of the first exhaust gas introduction cells has the cross sectional area equal to or smaller than 0.7 mm.sup.2 in the cross section perpendicular to the longitudinal direction of the plurality of cells.

A honeycomb filter includes a plurality of cells and porous cell walls. Exhaust gas is to flow through the plurality of cells. The plurality of cells include exhaust gas introduction cells and exhaust gas emission cells. The honeycomb filter has a round cross sectional shape. Each of the exhaust gas emission cells is adjacently surrounded fully by the exhaust gas introduction cells. In the cross section, the exhaust gas introduction cells and the exhaust gas emission cells each have a polygonal shape. In the cross section, a side forming a cross sectional shape of each of the first exhaust gas introduction cells faces one of the exhaust gas emission cells, a side forming a cross sectional shape of each of the second exhaust gas introduction cells faces one of the exhaust gas emission cells.