A honeycomb filter includes a pillar-shaped honeycomb substrate including a porous partition wall that defines a plurality of cells extending from an inflow end face to an outflow end face, an inflow side plugging portion disposed at the inflow end face of the honeycomb substrate to plug open ends of outflow cells and an outflow side plugging portion disposed at the outflow end face of the honeycomb substrate to plug open ends of inflow cells other than the outflow cells. The honeycomb substrate includes the partition wall that defines two of the inflow cells by division. An average of the plugging length L.sub.IN of the inflow side plugging portions disposed in the outflow cells of the honeycomb substrate is larger than an average of the plugging length L.sub.OUT of the outflow side plugging portions disposed in the inflow cells of the honeycomb substrate.

A honeycomb filter includes a pillar-shaped honeycomb substrate including a porous partition wall that defines a plurality of cells extending from an inflow end face to an outflow end face, an inflow side plugging portion disposed at the inflow end face of the honeycomb substrate to plug open ends of outflow cells; and an outflow side plugging portion disposed at the outflow end face of the honeycomb substrate to plug open ends of inflow cells other than the outflow cells. The honeycomb substrate includes the partition wall that defines two of the inflow cells by division. An average of the plugging length L.sub.OUT of the outflow side plugging portions disposed in the inflow cells of the honeycomb substrate is larger than an average of the plugging length L.sub.IN of the inflow side plugging portions disposed in the outflow cells of the honeycomb substrate.

A honeycomb structure includes a honeycomb structure body including porous partition walls defining a plurality of cells serving as fluid passages extending from an inflow end face to an outflow end face. A porosity of the partition walls is from 45 to 65%, an open frontal area of pores having an equivalent circle diameter of 10 um or more is from 20 to 40%, a pore density of pores having an equivalent circle diameter of 10 μm or more is from 350 to 1,000 pores/mm.sup.2 and a median opening diameter of the pores having an equivalent circle diameter of 10 μm or more is from 40 to 60 μm, where the median opening diameter is the median value of the equivalent circle diameters.

A honeycomb filter includes a honeycomb structure having a porous partition wall disposed to surround a plurality of cells; and a plugging portion provided at one end of the cell, wherein the honeycomb structure has an inflow side region including a range of up to at least 30% with respect to the total length of the honeycomb structure with the inflow end face as the starting point and an outflow side region including a range of up to at least 20% with respect to the total length of the honeycomb structure with the outflow end face as the starting point, in the extending direction of the cell of the honeycomb structure, an average pore diameter of the partition wall in the inflow side region is 15 to 20 μm and an average pore diameter of the partition wall in the outflow side region is 9 to 14 μm.

A honeycomb filter includes a honeycomb structure body having a porous partition wall disposed to surround a plurality of cells and a plugging portion disposed at one end of the cells, wherein the plurality of cells are arranged in a square grid pattern along a first direction and a second direction in a section orthogonal to an extending direction of the cells, the shape in the section is a deformed square having a specific corner, the specific corner includes a first curved portion, a second curved portion, and a connecting portion, a radius of curvature R1 of the first curved portion and a radius of curvature R2 of the second curved portion are 40 to 80 μm, respectively, and a center distance between a center of curvature O1 of the first curved portion and a center of curvature O2 of the second curved portion is 80 to 200 μm.

A method for producing a honeycomb-shaped ceramic structure by extrusion-molding a moldable material including a cordierite-forming material and a pore-forming material, wherein the cordierite-forming material contains 15-25% by mass of silica having an average particle size of 20-30 μm, with 5% or less by mass of particles having particle sizes of 10 μm or less and 5% or less by mass of particles having particle sizes of 100 μm or more, a particle size distribution deviation SD of 0.5 or less, and sphericity of 0.5 or more, and wherein the pore-forming material is present in an amount of 5-40% by mass based on the cordierite-forming material and has an average particle size of 15-50 μm, with 10% or less by mass of particles having particle sizes of 5 μm or less and 5% or less by mass of particles having particle sizes of 80 μm or more.

An object of the present invention is to provide a honeycomb filter capable of achieving a combination of high collection efficiency and low pressure loss. The honeycomb filter 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 by a sealing material, wherein the thickness of the filter layer increases gradually from the fluid inlet side toward the fluid outlet side.

A partial wall-flow filter has an inlet end, an outlet end, and a plurality of parallel channels disposed and configured to flow fluid from the inlet end to the outlet end. The channels are defined by a plurality of porous walls. A first portion of the channels have a first hydraulic diameter Dh1, a second portion of the channels have a second hydraulic diameter Dh2 smaller than the first hydraulic diameter Dh1, and the ratio of Dh1:Dh2 is in the range of 1.1 to 1.6. At least a portion of channels having hydraulic diameter Dh1 are plugged at the outlet end, and channels having hydraulic diameter Dh2 are flow-through channels.

The honeycomb structure includes a pillar-shaped honeycomb structure body, and a circumferential coating layer disposed to surround a circumference of the honeycomb structure body, and cells which are formed at an outermost circumference of the honeycomb structure body and in which peripheries of the cells are defined by the partition walls without any lacks are defined as outermost circumference complete cells, and in a cross section of the honeycomb structure body which is perpendicular to an extending direction of the cells a minimum distance T (mm) among distances from the outermost circumference complete cells to the surface of the circumferential coating layer and a porosity P (%) of the circumferential coating layer satisfy relations of Equation (1) and Equation (2) as follows:

1.5≧T≧16×(100−P).sup.−1.4; and  Equation (1):

20≦P≦75.  Equation (2):

The invention relates to a wall-flow filter as a particle filter with catalytically active coatings in the channels which are closed in a gastight manner at the opposing closed ends of the channels A at the first end, wherein the inlet region of the filter is additionally supplied with a dry powder-gas aerosol which contains metal compounds with a high melting point (such as the metal oxides Al2O3, SiO2, FeO2, TiO2, ZnO2, etc. for example) and which is to simultaneously improve the catalytic activity and the degree of filtration efficiency with respect to the exhaust gas back-pressure.