A method for producing a ceramic honeycomb structure comprising a ceramic honeycomb body having large numbers of longitudinal cells partitioned by porous cell walls, and a peripheral wall formed on a peripheral surface of the ceramic honeycomb structure, comprising the steps of extruding a moldable ceramic material to form a honeycomb-structured ceramic green body; machining a peripheral portion of the green body or a sintered body obtained from the green body to remove part of cell walls in the peripheral portion, thereby obtaining the ceramic honeycomb body having longitudinal grooves on the peripheral surface; applying a coating material to the peripheral surface of the ceramic honeycomb body to form the peripheral wall, as well as to peripheral portions of both end surfaces of the ceramic honeycomb body; and inserting the coating material applied to the peripheral portions of both end surfaces into peripheral cells, with partially remaining on the peripheral portions.

A method feeds raw material into a metal die and extrudes the raw material to produce a honeycomb molded body. The method fires the honeycomb molded body to make a honeycomb structural body. The metal die has a first metal die and a second metal die arranged at an upstream side of an extrusion direction of the raw material and a second metal die arranged at a downstream side of the extrusion direction of the raw material. The first metal die has a projection section and the second metal die has a penetration hole. The projection section is fitted to the penetration hole to assemble the first metal die and the second metal die. Communication holes formed in the second metal die communicate with raw material second feeding holes formed in the first metal die.

A honeycomb structure includes a honeycomb substrate including latticed partition walls which define a plurality of cells extending from one end face to the other end face and forming through channels for fluid and a honeycomb outer wall, and a flange portion attached to a part of the honeycomb outer wall of the honeycomb substrate, and including latticed flange partition walls which define a plurality of flange cells extending from one flange end face to the other flange end face and a flange outer wall, and in the honeycomb substrate, a ratio of a non-outer wall region in which the honeycomb outer wall is not disposed is in a range of 10 to 90% to a total area of a substrate circumferential surface.

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.

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 cross-sectional area of each exhaust gas emission cell is larger than the cross-sectional area of each exhaust gas introduction cell. Provided that the hydraulic diameter is given by the following equation (1) and the area based on the given hydraulic diameter is given by the following equation (2), the ratio of the area based on the hydraulic diameter of an exhaust gas introduction cell to the cross-sectional area of the exhaust gas introduction cell is 0.95 to 0.98, and the ratio of the area based on the hydraulic diameter of an exhaust gas emission cell to the cross-sectional area of the exhaust gas emission cell is 0.7 to 0.9:

Hydraulic diameter=(4cross-sectional area of cell)/Cross-sectional peripheral length of cell(1),

Area based on the hydraulic diameter=(Hydraulic diameter/2).sup.2(2).

Provided is a honeycomb fired body in which the pressure loss in the initial state where PM has not accumulated is sufficiently low, the strength is sufficiently high, and the heat capacity is not small. The honeycomb fired body of the present invention is a honeycomb fired body including a plurality of cells in each of which one end is plugged and which serve as channels of exhaust gas, and porous cell partition walls that define the cells, wherein the honeycomb fired body is formed of SiC, the plurality of cells include peripheral cells located at an outermost peripheral region of the honeycomb fired body and inner cells located more inward than the peripheral cells, all the inner cells have the same cross-sectional shape that is a rectangle in a plane perpendicular to the longitudinal direction thereof, each peripheral cell is defined by the cell partition walls and an outer wall forming a periphery of the honeycomb fired body, the cell partition walls in contact with the outer wall each have a thick wall region where the wall thickness gradually increases toward the outer wall, the cross-sectional shape of the peripheral cells in a plane perpendicular to the longitudinal direction thereof is a shape formed by reducing the rectangular cross-sectional shape of the inner cells to obtain a reduced rectangle and chamfering or rounding two corners of the reduced rectangle, the cross-sectional area of each peripheral cell in a plane perpendicular to the longitudinal direction thereof is 60 to 80% of the cross-sectional area of each inner cell in a plane perpendicular to the longitudinal direction thereof, the cell partition walls include inter-peripheral-cell cell partition walls each located between the peripheral cells and inter-inner-cell cell partition walls each located between the inner cells, and the minimum thickness of the inter-peripheral-cell cell partition walls is greater than the thickness of the inter-inner-cell cell partition walls.

A catalyst unit may include a carrier, a channel opening portion through which exhaust gas passes, a skin portion that is formed along a circumference and integrally formed with the channel opening portion, and a skin addition portion that is formed with a second thickness on an outside surface of the skin portion. A fabrication device of the catalyst unit may include a container, a masking member, and an elastic member, wherein plugging material flows through opened channels and does not contact the masking member. A manufacturing method of the catalyst unit may include covering the masking member and inserting plugging material into an opened channel. A channel corresponding to a dead zone is plugged and the catalyst coating layer is not formed in the plugged channels, thus reducing the cost of the catalyst.

A mat material including inorganic fibers, with an inorganic binder and an organic binder attached to the mat material, wherein a ratio [w.sub.1B/w.sub.1A] of a weight percentage w.sub.1B of the organic binder to a weight percentage w.sub.1A of the inorganic binder satisfies the following condition (1) or (2), where w.sub.1A is the weight percentage of the inorganic binder relative to a weight of the mat material as a whole, and w.sub.1B is the weight percentage of the organic binder relative to the weight of the mat material as a whole:

0<w.sub.1B/w.sub.1A0.8; or(1)

9w.sub.1B/w.sub.1A.(2)

A honeycomb structure includes an outer peripheral side wall; a plurality of first cells having an opening on the first end surface and having a sealing portion on the second end surface; and a plurality of second cells having the sealing portion on the first end surface and having the opening on the second end surface, wherein the first cells and the second cells are arranged adjacent to each other with a partition wall interposed therebetween; wherein the sealing portion is composed of a ceramic containing MgO:9.0 to 13.4% by mass, Al.sub.2O.sub.3: 29.0 to 35.5% by mass, and SiO.sub.2: 50.0 to 58.0% by mass, and wherein an arithmetic average height Sa of the sealing portions on the first end surface and the second end surface is 18.0 m or less, respectively.

An exhaust gas purification device capable of reducing a pressure loss and capable of improving an exhaust gas purification performance includes a honeycomb substrate and an outflow side catalyst. The honeycomb substrate includes a porous partition wall defining a multiple cells extending from an inflow side end surface to an outflow side end surface. The outflow side catalyst is in an inner region on the outflow cell side of the partition wall in an outflow side catalyst-disposed range extending from an outflow side end of the partition wall to a position apart toward an inflow side along an extending direction.