Honeycomb structure filter

Abstract

To provide a columnar honeycomb structure filter capable of contributing to the improvement of PM collection performance when the flow rate of an exhaust gas is large.SOLUTION: In a columnar honeycomb structure filter including a plurality of first cells extending from an inlet side bottom surface to an outlet side bottom surface, having an opening inlet side bottom surface and having an opening sealing part at the outlet side bottom surface and a plurality of second cells extending from the inlet side bottom surface to the outlet side bottom surface, having an opening sealing part at the inlet side bottom surface and having an opening outlet side bottom surface,: the plurality of first cells and the plurality of second cells are alternately and adjacently arranged sandwiching a porous partition wall; a porous film having a higher porosity than partition wall is formed on the surface of the respective first cell; and the average thickness of the porous film at a center part is larger than the average thickness of the porous film at an outer periphery in a cross section perpendicular to the extending direction of the first cell.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a columnar honeycomb structure filter.

Background Art

[0002] Exhaust gas discharged from internal combustion engines such as diesel engines and gasoline engines contains particulate matter such as soot (hereinafter referred to as PM: Particulate Matter). Soot is harmful to the human body and its emission is regulated. Currently, in order to comply with exhaust gas regulations, filters typified by DPF and GPF that allow exhaust gas to pass through a breathable microporous partition and filter PM such as soot are widely used.

[0003] As a filter for collecting PM, a plurality of first cells extending in the height direction from the inlet-side bottom surface to the outlet-side bottom surface, the inlet-side bottom surface being open and having a plugging portion at the outlet-side bottom surface, and a plurality of first cells being arranged adjacent to each other with a partition wall interposed therebetween, extending in the height direction from the inlet-side bottom surface to the outlet-side bottom surface, having a plugging portion at the inlet-side bottom surface and the outlet-side bottom surface being open, and a wall-flow type columnar honeycomb structure filter including a plurality of second cells is known.

[0004] In recent years, with the strengthening of exhaust gas regulations, stricter PM emission standards (PN regulation: particle number regulation of particulate matter) have been introduced, and filters are required to have high PM collection performance (high PN collection efficiency). Therefore, it has been proposed to separately form a layer for collecting PM on the surface of the cells (Patent Documents 1 to 7). According to these patent documents, it is said that by forming the collection layer, PM can be collected while reducing the pressure loss. As a method for forming the porous membrane, a method is adopted in which particles smaller than the average particle diameter of the particles constituting the partition wall are supplied to the inlet-side bottom surface of the filter by a solid-gas two-phase flow and adhered to the surface of the first cell, and then heat treatment is performed.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] International Publication No. 2010 / 110010 [Patent Document 2] International Publication No. 2011 / 125768 [Patent Document 3] International Publication No. 2011 / 125769 [Patent Document 4] Japanese Patent No. 5863951 Gazette [Patent Document 5] Japanese Unexamined Patent Application Publication No. 2011-147931 [Patent Document 6] Japanese Patent No. 5863950 Gazette [Patent Document 7] Japanese Patent No. 5597148 Gazette [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] In improving the PM collection performance of a columnar honeycomb structure filter, it is considered effective to form a collection layer on the surface of the cells. However, there is still room for improvement in the collection layer. For example, it would be advantageous if the PM collection performance could be improved when the exhaust gas flow rate is high, such as during vehicle acceleration. Therefore, in one embodiment, the present invention aims to provide a columnar honeycomb structure filter that can contribute to improving the PM collection performance when the exhaust gas flow rate is high. [Means for Solving the Problems]

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that as the exhaust gas flow rate increases, the exhaust gas flow rate when passing through the partition walls of the columnar honeycomb structure filter tends to be larger at the central portion than at the outer peripheral portion. And it has been found that increasing the thickness of the collection layer (corresponding to the "porous membrane" in the present invention) from the outer peripheral portion toward the central portion is advantageous for enhancing the PM collection performance when the exhaust gas flow rate is high. The present invention has been completed based on this finding and is exemplified below.

[0008] [1] A plurality of first cells extending from the inlet-side bottom surface to the outlet-side bottom surface, having the inlet-side bottom surface open and having a blind stop portion on the outlet-side bottom surface, and a plurality of second cells extending from the inlet-side bottom surface to the outlet-side bottom surface, having a blind stop portion on the inlet-side bottom surface and having the outlet-side bottom surface open, and the plurality of first cells and the plurality of second cells are alternately arranged adjacent to each other with a porous partition wall therebetween, which is a columnar honeycomb structure filter. On the surface of each first cell, a porous film having a porosity higher than that of the partition wall is formed. Regarding the columnar honeycomb structure filter in which the extending direction of the first cell of the columnar honeycomb structure filter is the extending direction of the coordinate axis, and the coordinate value of the inlet-side bottom surface is 0 and the coordinate value of the outlet-side bottom surface is X, the following relationship holds. (A1 + A2 + A3) / (B1 + B2 + B3)>1.0 In the formula, In a cross section orthogonal to the extending direction of the first cell of the columnar honeycomb structure filter at the coordinate value of 0.2X, the average thickness of the porous film in the outer peripheral portion is B1, and the average thickness of the porous film in the central portion is A1. In a cross section orthogonal to the extending direction of the first cell of the columnar honeycomb structure filter at the coordinate value of 0.5X, the average thickness of the porous film in the outer peripheral portion is B2, and the average thickness of the porous film in the central portion is A2. In a cross section orthogonal to the extending direction of the first cell of the columnar honeycomb structure filter at the coordinate value of 0.8X, the average thickness of the porous film in the outer peripheral portion is B3, and the average thickness of the porous film in the central portion is A3. [2] The columnar honeycomb structure filter according to [1], in which the following relationship holds. (A1 + A2 + A3) / (B1 + B2 + B3)≥1.2 [3] Regarding the first cell located at the center of a cross section orthogonal to the extending direction of the first cell of the columnar honeycomb structure filter, the columnar honeycomb structure filter according to [1] or [2], in which the following relationships (1) and (2) hold. (1) The ratio (A2 / A1) of the average thickness A2 of the porous film at the coordinate value of 0.5X to the average thickness A1 of the porous film at the coordinate value of 0.2X is 1.05 to 5.0. (2) The ratio (A3 / A1) of the average thickness A3 of the porous membrane at the coordinate value 0.8X to the average thickness A1 of the porous membrane at the coordinate value 0.2X is 1.05 to 5.0. [4] The columnar honeycomb structure filter according to any one of [1] to [3] in which the following relationship holds. A1 > B1, A2 > B2, and A3 > B3 [5] The columnar honeycomb structure filter according to any one of [1] to [4], wherein the main component of the porous membrane is silicon carbide, alumina, silica, cordierite, or mullite. [6] The columnar honeycomb structure filter according to any one of [1] to [5], wherein the porosity of the porous membrane is 70 to 85%. [7] The columnar honeycomb structure filter according to any one of [1] to [6], wherein the average thickness of the entire porous membrane is 4 to 50 μm.

Advantages of the Invention

[0009] The columnar honeycomb structure filter according to an embodiment of the present invention can contribute to the improvement of PM collection performance when the flow rate of the exhaust gas is large.

Brief Description of the Drawings

[0010]

Figure 1

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Embodiments for Carrying Out the Invention

[0011] Next, embodiments of the present invention will be described in detail with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and design changes, improvements, etc. can be appropriately made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0012] <1. Columnar Honeycomb Structure Filter> The columnar honeycomb structure filter according to an embodiment of the present invention will be described. The columnar honeycomb structure filter can be used as a DPF (Diesel Particulate Filter) and a GPF (Gasoline Particulate Filter) for collecting soot attached to the exhaust gas line from a combustion device, typically an engine mounted on a vehicle. The columnar honeycomb structure filter according to the present invention can be installed, for example, in an exhaust pipe.

[0013] FIG. 1 and FIG. 2 respectively illustrate a schematic perspective view and a cross-sectional view of a columnar honeycomb structure filter (100). This columnar honeycomb structure filter (100) includes an outer peripheral side wall (102), and a plurality of first cells (108) that are disposed on the inner peripheral side of the outer peripheral side wall (102), extend parallel from the inlet side bottom surface (104) to the outlet side bottom surface (106), and have a plugging portion (109) at the outlet side bottom surface (106) with the inlet side bottom surface (104) being open, and a plurality of second cells (110) that are disposed on the inner peripheral side of the outer peripheral side wall (102), extend parallel from the inlet side bottom surface (104) to the outlet side bottom surface (106), have a plugging portion (109) at the inlet side bottom surface (104), and have the outlet side bottom surface (106) being open. In this columnar honeycomb structure filter (100), the first cells (108) and the second cells (110) are alternately and adjacently disposed with a porous partition wall (112) therebetween, so that the inlet side bottom surface (104) and the outlet side bottom surface (106) each exhibit a honeycomb shape.

[0014] When exhaust gas containing particulate matter (PM) such as soot is supplied to the inlet side bottom surface (104) on the upstream side of the columnar honeycomb structure filter (100), the exhaust gas is introduced into the first cell (108) and travels downstream within the first cell (108). Since the first cell (108) has a plugging portion (109) at the downstream outlet side bottom surface (106), the exhaust gas permeates through the porous partition wall (112) partitioning the first cell (108) and the second cell (110) and flows into the second cell (110). Since the particulate matter cannot pass through the partition wall (112), it is collected and deposited within the first cell (108). After the particulate matter is removed, the clean exhaust gas that has flowed into the second cell (110) travels downstream within the second cell (110) and flows out from the downstream outlet side bottom surface (106).

[0015] FIG. 3 shows a schematic partial enlarged view when the columnar honeycomb structure filter (100) is observed in a cross-section orthogonal to the extending direction of the cells (108, 110). A porous membrane (114) is formed on the surface of each first cell (108) of the columnar honeycomb structure filter (100) (the same as the surface of the partition wall (112) partitioning the first cell (108)).

[0016] As the flow velocity of the exhaust gas flowing into the columnar honeycomb structure filter increases, the flow velocity of the exhaust gas passing through the columnar honeycomb structure filter tends to be higher near the central axis than near the outer peripheral side wall. Therefore, regarding the thickness of the porous membrane, making the thickness near the central axis thicker than that near the outer peripheral side wall is advantageous for enhancing the PM collection efficiency. Accordingly, in one embodiment of the columnar honeycomb structure filter, when the extending direction of the first cell of the columnar honeycomb structure filter is taken as the extending direction of the coordinate axis, the coordinate value of the inlet-side bottom surface is 0, and the coordinate value of the outlet-side bottom surface is X, the following relationship holds. (A1 + A2 + A3) / (B1 + B2 + B3) > 1.0 In the formula, In the cross-section orthogonal to the extending direction of the first cell of the columnar honeycomb structure filter at the coordinate value of 0.2X, the average thickness of the porous membrane in the outer peripheral portion is B1, and the average thickness of the porous membrane in the central portion is A1. In the cross-section orthogonal to the extending direction of the first cell of the columnar honeycomb structure filter at the coordinate value of 0.5X, the average thickness of the porous membrane in the outer peripheral portion is B2, and the average thickness of the porous membrane in the central portion is A2. In the cross-section orthogonal to the extending direction of the first cell of the columnar honeycomb structure filter at the coordinate value of 0.8X, the average thickness of the porous membrane in the outer peripheral portion is B3, and the average thickness of the porous membrane in the central portion is A3.

[0017] In a preferred embodiment, (A1 + A2 + A3) / (B1 + B2 + B3) ≥ 1.2 holds. In a more preferred embodiment, (A1 + A2 + A3) / (B1 + B2 + B3) ≥ 1.7 holds. In a more preferred embodiment, (A1 + A2 + A3) / (B1 + B2 + B3) ≥ 1.8 holds. In a more preferred embodiment, (A1 + A2 + A3) / (B1 + B2 + B3) ≥ 2.0 holds. Although the upper limit of (A1 + A2 + A3) / (B1 + B2 + B3) is not particularly set, if it becomes excessively large, pressure loss due to a sharp blockage of the gas flow path is considered. Therefore, it is preferably 10 ≥ (A1 + A2 + A3) / (B1 + B2 + B3), and more preferably 8 ≥ (A1 + A2 + A3) / (B1 + B2 + B3). Typically, 4 ≥ (A1 + A2 + A3) / (B1 + B2 + B3) can be set, more typically, 3 ≥ (A1 + A2 + A3) / (B1 + B2 + B3) can be set, and even more typically, 2.5 ≥ (A1 + A2 + A3) / (B1 + B2 + B3) can be set.

[0018] (A1 + A2 + A3) / 3 can be, for example, 5 to 30 μm, and preferably 10 to 20 μm.

[0019] In a preferred embodiment, A1 > B1, A2 > B2, and A3 > B3 hold. In a more preferred embodiment, A1 / B1 ≥ 1.1, A2 / B2 ≥ 1.1, and A3 / B3 ≥ 1.1 hold. In an even more preferred embodiment, A1 / B1 ≥ 1.4, A2 / B2 ≥ 1.4, and A3 / B3 ≥ 1.4 hold. Although the upper limit of A1 / B1, A2 / B2, and A3 / B3 is not particularly set, if it becomes excessively large, pressure loss due to a sharp blockage of the gas flow path is considered. Therefore, it is preferably 4.0 ≥ A1 / B1, 4.0 ≥ A2 / B2, and 4.0 ≥ A3 / B3, and more preferably 3.0 ≥ A1 / B1, 3.0 ≥ A2 / B2, and 3.0 ≥ A3 / B3.

[0020] As the flow velocity of the exhaust gas increases, the flow velocity of the exhaust gas when passing through the partition walls of the columnar honeycomb structure filter tends to increase significantly toward the bottom surface on the outlet side. For example, when the flow velocity of the exhaust gas flowing into the columnar honeycomb structure filter (exhaust gas flow rate / area of the inlet side bottom surface) is 2.5 m / s or more, typically 12.4 m / s or more, the flow velocity of the exhaust gas when passing through the partition walls of the columnar honeycomb structure filter increases significantly at the bottom surface on the outlet side. Fig. 4 shows the results of fluid analysis under the following conditions of the relationship between the distance in the extending direction of the cells from the inlet side bottom surface and the flow velocity when the exhaust gas flowing into the columnar honeycomb structure filter passes through the partition wall of one cell. As can be seen from Fig. 4, it can be seen that the flow velocity of the exhaust gas passing through the partition wall increases significantly as it approaches the bottom surface on the outlet side. <Fluid analysis conditions> Software: Fluent Ver19.1 manufactured by ANSYS Solver type: Pressure-based solver Turbulence model: Low Reynolds number type SST k-ω Outer peripheral surface: Symmetry plane condition (no friction occurs) Solid wall surface: No-slip wall condition (friction occurs) Outlet: Specified at gauge pressure 0 [Pa] (open to the atmosphere) Fluid flow velocity flowing into the columnar honeycomb structure filter: 12.4 m / sec, 2.5 m / sec Fluid density flowing into the columnar honeycomb structure filter: 1.19 kg / m 3 Fluid viscosity flowing into the columnar honeycomb structure filter: 1.85×10 -5 kg / m / s Dimensions of the columnar honeycomb structure filter: 120 mm Cell density of the columnar honeycomb structure filter: 200 cpsi Partition wall thickness of the columnar honeycomb structure filter: 216 μm Porous membrane: None

[0021] At locations where the exhaust gas flow rate is high, the amount of exhaust gas passing through per unit time increases. Therefore, increasing the thickness of the porous membrane to increase the contact opportunity with the porous membrane can enhance the PM collection performance. Thus, as approaching the outlet-side bottom surface where the exhaust gas flow rate increases, by increasing the thickness of the porous membrane, the PM collection performance can be enhanced without increasing the pressure loss more than necessary. For this reason, in a preferred embodiment of the columnar honeycomb structure filter (100), the porous membrane (114) formed on the surface of each first cell (108) (the same as the surface of the partition wall that partitions and forms the first cell) has an increasing thickness from the inlet-side bottom surface (104) toward the outlet-side bottom surface (106). FIG. 5 shows a schematic cross-sectional view showing a structural example of the first cell (108) of such a columnar honeycomb structure filter (100).

[0022] More specifically, taking the extending direction of the first cell of the columnar honeycomb structure filter as the extending direction of the coordinate axis, setting the coordinate value of the inlet-side bottom surface to 0 and the coordinate value of the outlet-side bottom surface to X, for the first cell located at the center of the cross-section orthogonal to the extending direction of the first cell of the columnar honeycomb structure filter, the following relationships (1) and (2) hold. (1) The ratio (A2 / A1) of the average thickness A2 of the porous membrane at the coordinate value 0.2X to the average thickness A1 of the porous membrane at the coordinate value 0.5X is 1.05 to 5.0. (2) The ratio (A3 / A1) of the average thickness A3 of the porous membrane at the coordinate value 0.8X to the average thickness A1 of the porous membrane at the coordinate value 0.2X is 1.05 to 5.0.

[0023] The lower limit of A2 / A1 is preferably 1.2 or more, more preferably 1.4 or more. The upper limit of A2 / A1 is preferably 4.0 or less, more preferably 3.0 or less.

[0024] The lower limit of A3 / A1 is preferably 1.6 or more, more preferably 1.8 or more. The upper limit of A3 / A1 is preferably 4.0 or less, more preferably 3.0 or less.

[0025] When measuring the average thickness of the porous membrane at each coordinate value (0.2X, 0.5X, 0.8X) in the extending direction of the first cell, the central part and the outer peripheral part of the columnar honeycomb structure filter are determined as follows. Referring to FIG. 6, when the columnar honeycomb structure filter (100) is observed from a cross-section perpendicular to the extending direction of the first cell, a line segment L is drawn from the centroid O of the cross-section toward the outer surface of the outer peripheral side wall (102), and the extending direction of the line segment L is set as the extending direction of the coordinate axis. Let the coordinate value of the centroid O be 0 and the coordinate value of the outer surface of the outer peripheral side wall be R. In this case, in the line segment L, the range of the coordinate value from 0 to 0.2R is the central part, and the range of the coordinate value from 0.7R to 0.9R is the outer peripheral part. By drawing a number of such line segments L in the cross-section and gathering the central part and the outer peripheral part in each line segment L, the ranges of the central part (120) and the outer peripheral part (130) in the cross-section are obtained.

[0026] A1, A2, A3, B1, B2, B3 are measured by the following methods respectively. A cross-section parallel to the extending direction of the first cell and parallel to the line segment from the outer surface of the outer peripheral side wall toward the centroid O is cut out from the location (central part or outer peripheral part) where the average thickness of the porous membrane of the columnar honeycomb structure filter is to be determined. The cross-section is observed by a 3D shape measuring machine (e.g., VR-3200 manufactured by Keyence Corporation) under the conditions of a magnification of 25 times and an observation field of view of 12.5 mm (horizontal) × 9.5 mm (vertical). At this time, the observation is made so that the horizontal direction of the observation field of view is parallel to the extending direction of the first cell. And when obtaining the average thickness at a specific coordinate value in the extending direction of the first cell, the observation is made so that the coordinate value is located at the center in the horizontal direction of the observation field of view. For example, when obtaining the average thickness at 0.2X, the observation is made so that 0.2X is located at the center in the horizontal direction of the observation field of view.

[0027] FIG. 7 shows a schematic diagram of a cut cross-section. By observing the cross-section, the first cell (108) in which the porous membrane is formed and the second cell (110) in which the porous membrane is not formed are identified. Next, three first cells (108) adjacent to each other at the position closest to the center on the cross-section are identified. Also, the central regions (110a) (reference planes) of the two second cells (110) sandwiched between the three first cells (108) adjacent to each other at the position closest to the center on the cross-section are identified, and leveling is performed using image processing software (e.g., software attached to the 3D shape measuring machine VR-3200 manufactured by Keyence Corporation) so that the reference plane is the most horizontal from the profiles of both regions. After leveling, for the central regions (110a) of the two second cells (110), range designation is performed and the average height H2 of the region is measured. Also, after leveling, for the central regions (108a) of the three first cells (108), range designation is performed and the average height H1 of the region is measured. The difference between the average height H1 and the average height H2 in one field of view is defined as the thickness of the porous membrane in that field of view. Note that the central regions (108a, 110a) refer to the regions of the central portions when the distance between a pair of partition walls (112) partitioning each cell is divided into three equal parts.

[0028] The thicknesses of the porous membranes at the central and outer peripheral portions at each coordinate value are measured for 5 fields of view each, and the average values in the 5 fields of view are taken as the measured values (A1, A2, A3, B1, B2, B3).

[0029] In this specification, the average value of A1, A2, A3, B1, B2, and B3 is defined as the average thickness of the entire porous membrane of the honeycomb structure filter. The average thickness of the entire porous membrane can be, for example, 4 to 50 μm. When the average thickness of the entire porous membrane is 4 μm or more, preferably 10 μm or more, the advantage of improving the collection efficiency can be obtained. Also, when the average thickness of the entire porous membrane is 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less, the advantage of suppressing an increase in pressure loss can be obtained.

[0030] In one embodiment, the porosity of the porous membrane (114) is higher than that of the partition wall (112). By having the porosity of the porous membrane (114) higher than that of the partition wall (112), an advantage is obtained in that an increase in pressure loss can be suppressed. In this case, the difference between the porosity of the porous membrane (114) and the porosity (%) of the partition wall (112) is preferably 10% or more, and more preferably 20% or more.

[0031] From the viewpoint of suppressing an increase in pressure loss, the lower limit of the porosity of the porous membrane is preferably 70% or more. Also, from the viewpoint of suppressing a decrease in collection efficiency, the upper limit of the porosity of the porous membrane is preferably 85% or less.

[0032] The porosity of the porous membrane is measured as follows. For each cross-section where the average film thickness of the porous membrane at each of the locations A1, A2, A3, B1, B2, and B3 is obtained, two arbitrary fields of view in the central region (108a) of the first cell (108) where the porous membrane is formed are imaged for the reflected electron image of the in-lens using a field emission scanning electron microscope (abbreviation: FE-SEM) (for example, manufactured by ZEISS, model: ULTRA55). Next, the image is binarized by the mode method using image analysis software (for example, HALCON) to separate it into a film material part and a void part, and the ratio of the film material part to the void part is calculated, which is taken as the porosity of the porous membrane at each of the locations A1, A2, A3, B1, B2, and B3. Then, the overall average value of these is taken as the porosity of the porous membrane of the columnar honeycomb structure filter.

[0033] From the viewpoint of keeping the pressure loss of the exhaust gas low, the lower limit of the porosity of the partition wall is preferably 40% or more, more preferably 45% or more, and still more preferably 50% or more. Also, from the viewpoint of ensuring the strength of the columnar honeycomb structure filter, the upper limit of the porosity of the partition wall is preferably 80% or less, more preferably 75% or less, and still more preferably 70% or less. The porosity of the partition wall refers to the value measured with a mercury intrusion porosimeter in accordance with JIS-R1655:2003.

[0034] The porous membrane can be made of ceramics. The porous membrane can contain, for example, one or more ceramics selected from cordierite, silicon carbide (SiC), talc, mica, mullite, celite, aluminum titanate, alumina, silicon nitride, sialon, zirconium phosphate, zirconia, titania, and silica. The main component of the porous membrane is preferably silicon carbide, alumina, silica, cordierite, or mullite. Among them, since a porous membrane that is firmly bonded to each other and difficult to peel due to the presence of the surface oxide film (Si2O) can be obtained, the main component of the porous membrane is preferably silicon carbide. The main component of the porous membrane refers to a component that occupies 50% by mass or more of the porous membrane. The porous membrane preferably contains 50% by mass or more of SiC, more preferably 70% by mass or more, and even more preferably 90% by mass or more. There is no particular limitation on the shape of the ceramics constituting the porous membrane, and for example, granular shape can be mentioned.

[0035] Examples of the material constituting the partition walls and the outer peripheral side walls of the columnar honeycomb structure filter according to the present embodiment include, but are not limited to, porous ceramics. Examples of the ceramics include cordierite, mullite, zirconium phosphate, aluminum titanate, silicon carbide (SiC), silicon-silicon carbide composite (e.g., Si-bonded SiC), cordierite-silicon carbide composite, zirconia, spinel, indialite, sapphirine, corundum, titania, silicon nitride, and the like. And these ceramics may contain one kind alone or may contain two or more kinds simultaneously.

[0036] The columnar honeycomb structure filter may carry a PM combustion catalyst that aids in the combustion of PM such as soot, an oxidation catalyst (DOC), an SCR catalyst and an NSR catalyst for removing nitrogen oxides (NOx), and a three-way catalyst capable of simultaneously removing hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). However, it is preferable that the columnar honeycomb structure filter according to the present embodiment does not carry a catalyst. This is because if a catalyst coat is applied to a thin portion of the porous membrane (e.g., the outer peripheral portion, near the inlet), the catalyst may ooze out from the outer peripheral side wall of the columnar honeycomb structure filter.

[0037] There is no limitation on the bottom surface shape of the columnar honeycomb structure filter. For example, in addition to round shapes such as circular, elliptical, racetrack-shaped, and oval-shaped, it can be polygonal such as triangular and quadrangular. The columnar honeycomb structure filter (100) in FIG. 1 has a circular bottom surface shape and is generally columnar.

[0038] The height of the columnar honeycomb structure filter (the length from the bottom surface on the inlet side to the bottom surface on the outlet side) is not particularly limited and may be appropriately set according to the application and required performance. There is also no particular limitation on the relationship between the height of the columnar honeycomb structure filter and the maximum diameter of each bottom surface (the maximum length among the diameters passing through the center of gravity of each bottom surface of the columnar honeycomb structure filter). Therefore, the height of the columnar honeycomb structure filter may be longer than the maximum diameter of each bottom surface, or the height of the columnar honeycomb structure filter may be shorter than the maximum diameter of each bottom surface.

[0039] There is no limitation on the shape of the cells in a cross-section perpendicular to the direction in which the cells extend, but it is preferably square, hexagonal, octagonal, or a combination thereof. Among these, square and hexagonal are preferred. By making the cell shape like this, the pressure loss when fluid is passed through the columnar honeycomb structure filter can be reduced.

[0040] The upper limit of the average thickness of the partition walls in the columnar honeycomb structure filter is preferably 0.305 mm or less, more preferably 0.254 mm or less, and even more preferably 0.241 mm or less from the viewpoint of suppressing the pressure loss. However, from the viewpoint of ensuring the strength of the columnar honeycomb structure filter, the lower limit of the average thickness of the partition walls is preferably 0.152 mm or more, more preferably 0.178 mm or more, and even more preferably 0.203 mm or more. In this specification, the thickness of the partition wall refers to the length of the line segment connecting the centers of gravity of adjacent cells when the centers of gravity of adjacent cells are connected by a line segment in a cross-section perpendicular to the extending direction of the cells. The average thickness of the partition walls refers to the average value of the thicknesses of all the partition walls.

[0041] The cell density (the number of cells per unit cross-sectional area perpendicular to the extending direction of the cells) is not particularly limited. For example, it can be 6 to 2000 cells / square inch (0.9 to 311 cells / cm 2 ), more preferably 50 to 1000 cells / square inch (7.8 to 155 cells / cm 2 ), and particularly preferably 100 to 400 cells / square inch (15.5 to 62.0 cells / cm 2 ).

[0042] The columnar honeycomb structure filter can also be provided as an integrally molded product. Further, the columnar honeycomb structure filter can be provided as a segment joined body by joining the segments of a plurality of columnar honeycomb structure filters each having an outer peripheral side wall to each other on the side surfaces to integrate them. By providing the columnar honeycomb structure filter as a segment joined body, the thermal shock resistance can be enhanced.

[0043] <2. Manufacturing Method of Columnar Honeycomb Structure Filter> A method for manufacturing a columnar honeycomb structure filter will be exemplarily described below. First, after kneading a raw material composition containing a ceramic raw material, a dispersion medium, a pore-forming material, and a binder to form a green clay, the green clay is extruded and molded into a desired columnar honeycomb molded body. Additives such as a dispersant can be blended into the raw material composition as needed. When performing extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

[0044] After drying the columnar honeycomb molded body, a plugging portion is formed at predetermined positions on both bottom surfaces of the columnar honeycomb molded body, and then the plugging portion is dried to obtain a columnar honeycomb molded body having a plugging portion. Thereafter, the columnar honeycomb structure is obtained by performing degreasing and firing on the columnar honeycomb molded body. Then, a columnar honeycomb structure filter is obtained by forming a porous film on the surface of the first cell of the columnar honeycomb structure.

[0045] As the ceramic raw material, a raw material capable of forming the above-described ceramics after firing can be used. The ceramic raw material can be provided, for example, in the form of powder. Examples of the ceramic raw material include raw materials for obtaining ceramics such as cordierite, mullite, zircon, aluminum titanate, silicon carbide, silicon nitride, zirconia, spinel, indialite, sapphirine, corundum, and titania. Specifically, but not limited to, silica, talc, alumina, kaolin, serpentine, pyrophyllite, brucite, boehmite, mullite, magnesite, aluminum hydroxide, etc. can be mentioned. The ceramic raw material may be used alone or in combination of two or more.

[0046] In the case of filter applications such as DPF and GPF, cordierite can be preferably used as the ceramic. In this case, cordierite-forming raw materials can be used as the ceramic raw materials. Cordierite-forming raw materials are raw materials that become cordierite upon firing. The cordierite-forming raw materials desirably have a chemical composition of 30 to 45% by mass of alumina (Al2O3) (including the content of aluminum hydroxide converted to alumina), 11 to 17% by mass of magnesia (MgO), and 42 to 57% by mass of silica (SiO2).

[0047] Examples of the dispersion medium include water, or a mixed solvent of water and an organic solvent such as alcohol. In particular, water can be preferably used.

[0048] The pore former is not particularly limited as long as it becomes pores after firing. Examples include wheat flour, starch, foamed resin, water-absorbing resin, porous silica, carbon (e.g., graphite), ceramic balloons, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic, phenol, etc. The pore former may be used alone or in combination of two or more. From the viewpoint of increasing the porosity of the fired body, the content of the pore former is preferably 0.5 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more with respect to 100 parts by mass of the ceramic raw material. From the viewpoint of ensuring the strength of the fired body, the content of the pore former is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 4 parts by mass or less with respect to 100 parts by mass of the ceramic raw material.

[0049] Examples of the binder include organic binders such as methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. In particular, it is preferable to use methyl cellulose and hydroxypropyl methyl cellulose in combination. Further, from the viewpoint of enhancing the strength of the honeycomb molded body, the content of the binder is preferably 4 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 6 parts by mass or more with respect to 100 parts by mass of the ceramic raw material. From the viewpoint of suppressing the occurrence of flash due to abnormal heat generation in the firing process, the content of the binder is preferably 9 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less with respect to 100 parts by mass of the ceramic raw material. The binder may be used alone or in combination of two or more.

[0050] As the dispersant, ethylene glycol, dextrin, fatty acid soap, polyether polyol, etc. can be used. The dispersant may be used alone or in combination of two or more. The content of the dispersant is preferably 0 to 2 parts by mass with respect to 100 parts by mass of the ceramic raw material.

[0051] The method for sealing the bottom surface of the columnar honeycomb molded body is not particularly limited, and a well-known method can be adopted. There is no particular limitation on the material of the sealing portion, but it is preferably a ceramic from the viewpoints of strength and heat resistance. The ceramic is preferably a ceramic material containing at least one selected from the group consisting of cordierite, mullite, zircon, aluminum titanate, silicon carbide, silicon nitride, zirconia, spinel, indialite, sapphirine, corundum, and titania. In order to make the expansion rate during firing the same and lead to an improvement in durability, it is even more preferable that the sealing portion has the same material composition as the main body portion of the honeycomb molded body.

[0052] After drying the honeycomb formed body, a columnar honeycomb structure can be manufactured by performing degreasing and firing. The conditions of the drying process, degreasing process, and firing process may be known conditions according to the material composition of the honeycomb formed body, and although no special explanation is required, examples of specific conditions are given below.

[0053] In the drying process, for example, conventionally known drying methods such as hot air drying, microwave drying, dielectric drying, vacuum drying, freeze drying, etc. can be used. Among them, a drying method combining hot air drying with microwave drying or dielectric drying is preferable in that the entire formed body can be dried quickly and uniformly.

[0054] When forming the plugging portion, it is preferable to form the plugging portion on both bottom surfaces of the dried honeycomb formed body and then dry the plugging portion. The plugging portion extends from the bottom surface on the inlet side to the bottom surface on the outlet side, and a plurality of first cells having a plugging portion on the bottom surface on the outlet side with the bottom surface on the inlet side being open, and a plurality of second cells extending from the bottom surface on the inlet side to the bottom surface on the outlet side, having a plugging portion on the bottom surface on the inlet side, and the bottom surface on the outlet side being open, are formed at predetermined positions such that the plurality of first cells and the plurality of second cells are alternately and adjacently arranged with a porous partition wall interposed therebetween.

[0055] Next, the degreasing process will be described. The combustion temperature of the binder is about 200°C, and the combustion temperature of the pore former is about 300 to 1000°C. Therefore, the degreasing process may be carried out by heating the honeycomb formed body in the range of about 200 to 1000°C. The heating time is not particularly limited, but is usually about 10 to 100 hours. The honeycomb formed body after the degreasing process is called a green body.

[0056] The firing process can be carried out, for example, by heating the green compact to 1350 to 1600 °C and holding it for 3 to 10 hours, depending on the material composition of the honeycomb formed body. In this way, a plurality of first cells extending from the inlet-side bottom surface to the outlet-side bottom surface, having an open inlet-side bottom surface and a plugging portion at the outlet-side bottom surface, and a plurality of second cells extending from the inlet-side bottom surface to the outlet-side bottom surface, having a plugging portion at the inlet-side bottom surface and an open outlet-side bottom surface are provided, and a columnar honeycomb structure in which the plurality of first cells and the plurality of second cells are alternately arranged adjacent to each other with a porous partition wall therebetween is produced.

[0057] Next, a porous film is formed on the surface of the first cells of the columnar honeycomb structure that has undergone the firing process. First, while injecting an aerosol containing ceramic particles in a direction perpendicular to the inlet-side bottom surface toward the center of the inlet-side bottom surface of the columnar honeycomb structure, a suction force is applied to the outlet-side bottom surface to suck the injected aerosol from the inlet-side bottom surface and deposit the ceramic particles on the surface of the first cells. At this time, by shortening the distance between the aerosol injection nozzle and the inlet-side bottom surface, increasing the aerosol injection speed, or increasing the suction force applied to the outlet-side bottom surface, it is possible to increase the proportion of ceramic particles adhering to the center of the columnar honeycomb structure. Exemplarily, the distance between the aerosol injection nozzle and the inlet-side bottom surface can be 500 mm to 2000 mm, and the aerosol injection speed can be 2 to 80 m / s.

[0058] The ceramic particles in the aerosol preferably have a median diameter (D50) of 0.5 to 5.0 μm, more preferably 1.0 to 3.0 μm, in the volume-based cumulative particle size distribution measured by the laser diffraction / scattering method. By injecting extremely fine ceramic particles, it becomes possible to increase the porosity of the obtained porous film.

[0059] Also, it is desirable that the ceramic particles in the aerosol have little aggregation. By suppressing the aggregation of the ceramic particles in the aerosol, it is possible to promote the refinement of the average pore diameter of the porous film.

[0060] As the ceramic particles, the above-described ceramic particles constituting the porous membrane are used. For example, ceramic particles containing one or more selected from cordierite, silicon carbide (SiC), talc, mica, mullite, selenite, aluminum titanate, alumina, silicon nitride, sialon, zirconium phosphate, zirconia, titania, and silica can be used. It is preferable that the main component of the ceramic particles is silicon carbide, alumina, silica, cordierite, or mullite. The main component of the ceramic particles refers to a component that occupies 50% by mass or more of the ceramic particles. Preferably, SiC occupies 50% by mass or more of the ceramic particles, more preferably 70% by mass or more, and still more preferably 90% by mass or more.

[0061] When performing the step of attaching ceramic particles to the surface of the first cell, in order to increase the thickness of the porous membrane from the inlet-side bottom surface to the outlet-side bottom surface of the columnar honeycomb structure filter, it is preferable to increase the suction force of the outlet-side bottom surface and increase the flow velocity of the aerosol flowing through the columnar honeycomb structure. Specifically, it is preferable that the lower limit of the average flow velocity of the aerosol flowing into the columnar honeycomb structure (= aerosol flow rate / area of the inlet-side bottom surface) is 2 m / s or more, and more preferably 4 m / s or more. Further, in order to maintain the high porosity of the porous membrane, it is preferable that the upper limit of the average flow velocity of the aerosol flowing into the columnar honeycomb structure is 80 m / s or less, and preferably 60 m / s or less.

[0062] FIG. 8 schematically shows the device configuration of a particle attachment device (500) suitable for performing the step of attaching ceramic particles to the surface of the first cell of the columnar honeycomb structure (580). The particle attachment device (500) includes an aerosol generator (510), a laser diffraction particle size distribution measuring device (520), a gas introduction pipe (530), a holder (540), a differential pressure gauge (550), an exhaust pipe (560), and a blower (570).

[0063] The aerosol generator (510) A cylinder (513) that houses ceramic particles (512), A piston or screw (514) for sending out the ceramic particles (512) housed in the cylinder (513) from the cylinder outlet (513e), A crushing chamber (515) communicating with the cylinder outlet (513e), the crushing chamber (515) being provided with a rotating body (516) for crushing the ceramic particles (512) sent out from the cylinder outlet (513e), A gas flow path (517) for flowing a medium gas, which communicates with the crushing chamber outlet (515e) on the way, and the gas flow path (517) capable of injecting an aerosol containing the medium gas and the ceramic particles (512) from a nozzle (511) attached to the tip, Comprising.

[0064] The aerosol generator (510) can eject an aerosol from the nozzle (511). In the cylinder (513), ceramic particles (512) adjusted to a predetermined particle size distribution are stored. The ceramic particles (512) stored in the cylinder (513) are pushed out from the cylinder outlet (513e) by the piston or screw (514). The piston or screw (514) can be configured to be able to adjust the extrusion speed of the ceramic particles (512). The ceramic particles (512) discharged from the cylinder outlet (513e) enter the crushing chamber (515). The ceramic particles (512) introduced into the crushing chamber (515) move in the crushing chamber (515) while being crushed by the rotating body (516) and are discharged from the crushing chamber outlet (515e). As the rotating body (516), for example, a rotating brush can be employed. The rotating body (516) can be driven by a motor and can be configured to be able to control its rotation speed.

[0065] The ceramic particles (512) discharged from the outlet (515e) of the crushing chamber are mixed with the medium gas flowing through the gas flow path (517) to form an aerosol, and are jetted from the nozzle (511). The nozzle (511) is preferably installed at a position and in a direction such that the aerosol is jetted in a direction perpendicular to the inlet-side bottom surface toward the center of the inlet-side bottom surface of the columnar honeycomb structure (580) held by the holder (540).

[0066] The jet flow rate of the aerosol from the nozzle (511) can be controlled by using a compressed gas such as pressure-adjusted compressed air as the medium gas. As the medium gas, it is preferable to use dry air (for example, the dew point is 10°C or lower) in order to suppress the aggregation of the ceramic particles. In this specification, the "dew point" refers to a value measured by a polymer-type capacitance dew point meter conforming to JIS Z8806:2001. Fine ceramic particles tend to aggregate. However, by using the aerosol generator (510) according to the present embodiment, the crushed ceramic particles are jetted, so that it is possible to attach the ceramic particles having a particle size distribution as desired with aggregation suppressed to the surface of the first cell.

[0067] The aerosol jetted from the aerosol generator (510) passes through the gas introduction pipe (530) by the suction force from the blower (570), and then is sucked into the first cell of the columnar honeycomb structure (580) held by the holder (540) from the inlet-side bottom surface of the columnar honeycomb structure (580). The ceramic particles in the aerosol sucked into the first cell adhere to the surface of the first cell.

[0068] A plurality of ventilation holes (531) are provided on the wall surface of the gas introduction pipe (530), and it is possible to suck in ambient gas such as air. Thereby, the gas flow rate flowing into the gas introduction pipe (530) can be adjusted according to the suction force from the blower (570). Since there is a possibility of entraining aggregated powder, honeycomb fragments, and dust in the ventilation holes (531), a filter may be installed.

[0069] In this embodiment, a laser diffraction particle size distribution measuring device (520) is installed in the gas introduction pipe (530), and the particle size distribution of the ceramic particles in the aerosol ejected from the aerosol generator (510) can be measured in real time. Thereby, it is possible to monitor whether or not the ceramic particles having a desired particle size distribution are supplied to the columnar honeycomb structure (580).

[0070] An exhaust pipe (560) connected to a blower (570) is provided on the downstream side of the bottom surface on the outlet side of the columnar honeycomb structure (580). For this reason, when the aerosol from which the ceramic particles have been removed is discharged from the bottom surface on the outlet side of the columnar honeycomb structure (580), after passing through the exhaust pipe (560), it is exhausted through the blower (570).

[0071] When the process of attaching ceramic particles to the surface of the first cell is continued, as the amount of attached ceramic particles increases, the pressure loss between the bottom surface on the inlet side and the bottom surface on the outlet side of the columnar honeycomb structure increases. Therefore, by obtaining in advance the relationship between the amount of attached ceramic particles and the pressure loss, it is possible to determine the end point of the process of attaching ceramic particles to the surface of the first cell based on the pressure loss. Therefore, the particle attaching device (500) can install a differential pressure gauge (550) to measure the pressure loss between the bottom surface on the inlet side and the bottom surface on the outlet side of the columnar honeycomb structure (580), and may determine the end point of the process based on the value of the differential pressure gauge.

[0072] When the process of attaching ceramic particles to the surface of the first cell is carried out, since the ceramic particles are attached to the bottom surface on the inlet side of the columnar honeycomb structure (580), it is preferable to suck and remove the ceramic particles with a vacuum or the like while leveling the bottom surface on the inlet side with a jig such as a scraper.

[0073] Subsequently, under the condition of keeping the columnar honeycomb structure with ceramic particles adhering to the surface of the first cell at a maximum temperature of 1000 °C or higher for 1 hour or more, typically, heat treatment is performed under the condition of keeping at a maximum temperature of 1100 °C to 1400 °C for 1 hour to 6 hours, thereby completing the columnar honeycomb structure filter. The heat treatment can be carried out, for example, by placing the columnar honeycomb structure in an electric furnace or a gas furnace. By the heat treatment, the ceramic particles are bonded to each other, and the ceramic particles are baked onto the partition walls in the first cell, and a porous film is formed on the surface of the first cell. When the heat treatment is carried out under oxygen-containing conditions such as air, a surface oxide film is generated on the surface of the ceramic particles, and the bonding of the ceramic particles to each other is promoted. Thereby, a porous film that is difficult to peel off can be obtained.

[0074] The configuration of the aerosol generator applicable to the particle adhesion device capable of performing the step of adhering ceramic particles to the surface of the first cell of the columnar honeycomb structure is not limited to the above-described embodiment, and other embodiments can be adopted. Exemplarily, another configuration example of the aerosol generator is schematically shown in FIGS. 9 to 10.

[0075] The aerosol generator (410) shown in FIG. 9 has a medium gas flow path (417) for flowing a pressurized medium gas, a supply port (417i) provided in the middle of the medium gas flow path (417) and capable of sucking ceramic particles (412) from the outer peripheral side of the medium gas flow path (417) into the medium gas flow path (417), a nozzle (411) attached to the tip of the medium gas flow path (417) and capable of injecting an aerosol, a flow path (413) for sucking and transporting the ceramic particles (412), the flow path (413) having an outlet (413e) communicating with the supply port (417i), and a storage part (419) for storing the ceramic particles (412) and supplying the ceramic particles (412) to the flow path (413) for sucking and transporting. It has.

[0076] For the housing part (419), for example, a funnel can be used. Ceramic particles adjusted to a predetermined particle size distribution are accommodated in the housing part (419). The ceramic particles (412) accommodated in the housing part (419) are subjected to the suction force from the medium gas flow path (417), and after being conveyed from the outlet (419e) provided at the bottom of the housing part (419) through the flow path (413) to the outlet (413e), they are introduced into the medium gas flow path (417) from the supply port (417i). At this time, the ambient gas (typically air) sucked from the inlet (419i) of the housing part is also introduced into the medium gas flow path (417) through the flow path (413) together with the ceramic particles (412). In the present embodiment, the outlet (413e) and the supply port (417i) are common. Also, in the present embodiment, the ceramic particles (412) are introduced into the medium gas flow path (417) from a direction substantially perpendicular to the flow direction of the medium gas flowing through the medium gas flow path (417).

[0077] The ceramic particles (412) supplied into the medium gas flow path (417) collide with the medium gas flowing through the medium gas flow path (417), are mixed while being crushed to form an aerosol, and are ejected from the nozzle (411). The nozzle (411) is preferably installed at a position and in a direction where the aerosol is ejected in a direction perpendicular to the inlet-side bottom surface of the columnar honeycomb structure. More preferably, the nozzle (411) is installed at a position and in a direction where the aerosol is ejected in a direction perpendicular to the inlet-side bottom surface toward the center of the inlet-side bottom surface.

[0078] The supply of the ceramic particles (412) to the housing part (419) is preferably carried out, although not limited thereto, for example, using a powder metering feeder (4111) such as a screw feeder and a belt conveyor. The ceramic particles (412) discharged from the powder metering feeder (4111) can be dropped into the housing part (419) by gravity.

[0079] In a preferred embodiment, the medium gas flow path (417) has a venturi section (417v) where the flow path is constricted in the middle, and the supply port (417i) is provided on the downstream side of the most constricted part of the venturi section (417v). When the medium gas flow path (417) has a venturi section (417v), the speed of the medium gas passing through the venturi section (417v) increases. Therefore, a higher-speed medium gas can be made to collide with the ceramic particles (412) supplied downstream of the venturi section (417v), improving the crushing force. To enhance the crushing force by the medium gas, it is more preferable that the supply port (417i) be provided on the downstream side of and adjacent to the most constricted part of the venturi section (417v). Such a configuration can be realized, for example, by connecting the medium gas flow path (417) and the flow path (413) for suction conveyance using a venturi ejector (4110).

[0080] When using a venturi ejector (4110), for example, when flowing medium gas into the medium gas flow path (417), a large suction force can be applied to the flow path (413) for suction conveyance, preventing the flow path (413) for suction conveyance from being clogged by the ceramic particles (412). The venturi ejector (4110) is also effective as a means for removing the ceramic particles (412) when the flow path (413) for suction conveyance is clogged by the ceramic particles (412).

[0081] As the medium gas, the injection flow rate of the aerosol from the nozzle (411) can be controlled by using compressed gas such as pressure-adjusted compressed air. As the medium gas, it is preferable to use dry air (for example, with a dew point of 10°C or lower) to suppress the aggregation of ceramic particles.

[0082] Fine ceramic particles have the property of being prone to aggregation. However, by using the aerosol generator (410) according to this embodiment, it becomes possible to eject ceramic particles with a desired particle size distribution in which aggregation is suppressed.

[0083] The aerosol generator (810) shown in FIG. 10 includes a belt feeder (814) for conveying ceramic particles (812), a crushing chamber (815) having a rotating body (816) for receiving the ceramic particles (812) conveyed by the belt feeder (814) and crushing the received ceramic particles (812), a first gas flow path (817) for flowing a first medium gas, the first gas flow path (817) communicating with a crushing chamber outlet (815e) in the middle, a second gas flow path (813) for flowing a second medium gas, the second gas flow path (813) communicating with an outlet (817e) of the first gas flow path (817) in the middle and capable of injecting an aerosol containing the first medium gas, the second medium gas, and the ceramic particles (812) from a nozzle (811) attached to the tip, and is provided with.

[0084] The aerosol generator (810) has a container (819) for accommodating the ceramic particles (812). The ceramic particles (812) in the container (819) are preferably stirred by a stirrer (818). A discharge port (819e) for the ceramic particles (812) is provided at the bottom of the container (819). The ceramic particles (812) discharged from the discharge port (819e) are conveyed by the belt feeder (814) to the inlet (815in) of the crushing chamber (815).

[0085] The ceramic particles (812) introduced into the crushing chamber (815) move in the crushing chamber (815) while being crushed by the rotating body (816) and are discharged from the crushing chamber outlet (815e). As the rotating body (816), for example, a rotating brush can be employed. The rotating body (816) can be driven by a motor, and its rotation speed can be configured to be controllable.

[0086] Fine ceramic particles tend to aggregate. However, by using the aerosol generator (810) according to this embodiment, the crushed ceramic particles are ejected, so that it becomes possible to attach ceramic particles having a particle size distribution as intended with aggregation suppressed to the surface of the first cell.

[0087] The ceramic particles (812) discharged from the crushing chamber outlet (815e) are mixed with the first medium gas flowing through the first gas flow path (817) and head toward the outlet (817e) of the first gas flow path (817). The second gas flow path (813) communicates with the outlet (817e) of the first gas flow path (817) midway, where the second medium gas merges with the first medium gas and the ceramic particles (812). Then, an aerosol containing the first medium gas, the second medium gas, and the ceramic particles (812) flows downstream through the second gas flow path (813). Thereafter, the aerosol is ejected from a nozzle (811) attached to the tip of the second gas flow path (813). As the first medium gas, ambient gas such as air may be used, but it is preferable to use dry air (for example, dew point of 10°C or lower) in order to suppress aggregation of the ceramic particles. Further, the first medium gas may be conveyed only by the suction force from the second gas flow path, or may be pressure-fed using a compressor or the like. By using a compressed gas such as compressed air with adjusted pressure as the second medium gas, the ejection flow rate of the aerosol from the nozzle (811) can be controlled. It is also preferable to use dry air for the second medium gas as with the first medium gas.

[0088] The connection of the first gas flow path (817) and the second gas flow path (813) can be carried out using an ejector (822), particularly a Venturi ejector. When using an ejector (822), particularly a Venturi ejector, in addition to the effect that the ceramic particles (812) are crushed by the crushing chamber (815), the ceramic particles (812) crushed by passing through the crushing chamber (815) collide with the second medium gas, and thus an effect that the ceramic particles (812) are crushed by the second medium gas can be obtained. Therefore, a high aggregation suppression effect can be obtained. When using the ejector (822), for example, when flowing the second medium gas as a driving fluid into the second gas flow path (813), a large suction force can be applied to the first gas flow path (817), and it is possible to prevent the first gas flow path (817) from being clogged by the ceramic particles (812). Further, the ejector (822) is also effective as a means for removing the ceramic particles when the first gas flow path (817) is clogged by the ceramic particles (812).

Example

[0089] Hereinafter, examples for better understanding of the present invention and its advantages are illustrated, but the present invention is not limited to the examples.

[0090] <Example 1> (1) Manufacture of a columnar honeycomb structure filter To 100 parts by mass of a cordierite-forming raw material, 3 parts by mass of a pore-forming material, 55 parts by mass of a dispersion medium, 6 parts by mass of an organic binder, and 1 part by mass of a dispersant were added respectively, and mixed and kneaded to prepare a clay. As the cordierite-forming raw material, alumina, aluminum hydroxide, kaolin, talc, and silica were used. Water was used as the dispersion medium, a water-absorbing polymer was used as the pore-forming material, hydroxypropylmethylcellulose was used as the organic binder, and fatty acid soap was used as the dispersant.

[0091] This clay was put into an extrusion molding machine and extruded through a die of a predetermined shape to obtain a cylindrical honeycomb formed body. After subjecting the obtained honeycomb formed body to dielectric drying and hot air drying, both bottom surfaces were cut so as to have a predetermined dimension to obtain a honeycomb dried body.

[0092] With respect to the obtained honeycomb dried body, after plugging with cordierite as a material so that the first cells and the second cells were alternately arranged adjacent to each other, it was heat-degreased at about 200 ° C in an air atmosphere, and further fired at 1420 ° C for 5 hours in an air atmosphere to obtain a columnar honeycomb structure.

[0093] The specifications of the columnar honeycomb structure are as follows. Overall shape: columnar shape with a diameter of 132 mm and a height of 120 mm Cell shape in a cross section perpendicular to the flow path direction of the cell: square Cell density (number of cells per unit cross-sectional area): 200 cpsi Partition wall thickness: 8 mil (200 μm) (nominal value based on the die specifications)

[0094] With respect to the columnar honeycomb structure produced above, using the particle adhesion device having the configuration shown in FIG. 8, an aerosol containing ceramic particles was injected in a direction perpendicular to the inlet side bottom surface toward the center of the inlet side bottom surface of the columnar honeycomb structure, and ceramic particles were adhered to the surface of the first cell. The operating conditions of the particle adhesion device are as follows. · Aerosol generator: RBG2000 manufactured by PALAS · Rotating body: rotating brush · Ceramic particles accommodated in the container: SiC particles Median diameter (D50): 2.4 μm D10: 1.1 μm D90: 4.5 μm (Based on the volume-based cumulative particle size distribution measured by the laser diffraction / scattering method) · Weight of injected ceramic particles: 6.0 g · Medium gas: compressed dry air (dew point 10 ° C or lower) · Ambient gas: air · Average flow velocity of aerosol flowing into the honeycomb structure: 3 m / s · Laser diffraction particle size distribution analyzer: Insitec Spray manufactured by MALVERN · Operating time: 20 seconds · Inner diameter of the nozzle of the aerosol generator: Φ8 mm · Distance from the tip of the nozzle of the aerosol generator to the inlet-side bottom surface of the honeycomb structure: 1000 mm · Injection velocity of aerosol: 20 m / s

[0095] When the volume-based particle size distribution of the ceramic particles sprayed from the aerosol was measured with a laser diffraction particle size distribution analyzer during the operation of the particle adhesion device, the median diameter (D50) was 3.0 μm.

[0096] The ceramic particles adhering to the inlet-side bottom surface of the honeycomb structure to which the ceramic particles thus obtained adhered were removed by suction with a vacuum. Thereafter, the honeycomb structure was placed in an electric furnace and heat-treated in an air atmosphere under the condition of keeping at a maximum temperature of 1200 °C for 2 hours to form a porous film on the surface of the first cell, thereby obtaining a honeycomb structure filter. The honeycomb structure filters were produced in the number required to perform the following characteristic evaluation.

[0097] (2) Characteristic evaluation The average thickness of the porous film at a predetermined position of the honeycomb structure filter obtained by the above manufacturing method was measured by the method described above. The 3D shape measuring machine used for the measurement was VR-3200 manufactured by KEYENCE. The locations where the average thickness of the porous film was measured and the average thickness are summarized in Table 1-1. The extending direction of the first cell of the honeycomb structure filter was defined as the extending direction of the coordinate axis, and the coordinate value of the inlet-side bottom surface was defined as 0 and the coordinate value of the outlet-side bottom surface was defined as X to determine the coordinate values.

[0098]

Table 1-1

[0099] The porosity of the porous membrane and the partition walls of the columnar honeycomb structure filter obtained by the above manufacturing method was measured by the method described above. The apparatus used for measuring the porosity of the porous membrane was FE-SEM (model: ULTRA55 (manufactured by ZEISS)), and the image analysis software was HALCON (Links Co., Ltd., version 11.0.5). A mercury intrusion porosimeter was used to measure the porosity of the partition walls. The results are shown in Table 1-2.

[0100] The "pressure loss" and "collection efficiency (%)" of the columnar honeycomb structure filter obtained by the above manufacturing method were measured. [Pressure loss] Exhaust gas discharged from a 1.2L direct injection gasoline engine was introduced at a flow rate of 700 °C and 600 m 3 / h, and the pressures on the inlet side and the outlet side of the columnar honeycomb structure filter were measured. Then, the pressure loss (kPa) of the honeycomb filter was determined by calculating the pressure difference between the inlet side and the outlet side. The results are shown in Table 1-2. [Collection efficiency (%)] The columnar honeycomb structure filter was connected to the outlet side of the engine exhaust manifold of a 1.2L direct injection gasoline engine vehicle, and the number of soot particles contained in the gas discharged from the outlet of the columnar honeycomb structure filter was measured by the PN measurement method. Regarding the driving mode, a particularly severe driving mode was implemented in which the vehicle was accelerated to 60 km / hr within 10 seconds immediately after starting, and then the speed was decreased by 20 km / hr every 20 seconds. The cumulative number of soot particles discharged after the mode driving was taken as the number of soot particles of the exhaust gas purification device to be judged, and the collection efficiency (%) was calculated from the number of soot particles. At this time, the flow velocity of the exhaust gas flowing into the columnar honeycomb structure filter was about 4 m / s. The results are shown in Table 1-2.

[0101] In addition, except that the shape of the columnar honeycomb structure filter was changed to an oval shape with a major axis of 231 mm × a minor axis of 106 mm × a height of 120 mm, a porous membrane was formed in the same procedure as in Example 1, and the pressure loss and the collection efficiency were determined. As a result, the same results as above were obtained.

[0102]

Table 1-2

[0103] <Example 2> (1) Manufacture of a columnar honeycomb structure filter A columnar honeycomb structure was obtained under the same manufacturing conditions as in Example 1.

[0104] For the columnar honeycomb structure produced above, an aerosol generator having the structure shown in Fig. 9 using a Venturi ejector ISO 5011 dispersion nozzle (manufactured by PALAS) was used. Except for this, a particle adhesion device having the same configuration as in Example 1 was used, and an aerosol containing ceramic particles was injected in a direction perpendicular to the inlet-side bottom surface toward the center of the inlet-side bottom surface of the columnar honeycomb structure, and ceramic particles were adhered to the surface of the first cell. The operating conditions of the particle adhesion device are as follows. · Ceramic particles contained in the container: SiC particles Median diameter (D50): 2.4 μm D10: 1.1 μm D90: 4.5 μm (Based on the volume-based cumulative particle size distribution measured by the laser diffraction / scattering method) · Weight of the injected ceramic particles: 6.0 g · Carrier gas: Compressed dry air (dew point 10°C or lower) · Ambient gas: Air · Average flow rate of the aerosol flowing into the columnar honeycomb structure: 3 m / s · Laser diffraction type particle size distribution measuring device: Insitec Spray manufactured by MALVERN · Operating time: 20 seconds · Inner diameter of the nozzle of the aerosol generator: Φ8 mm · Distance from the tip of the nozzle of the aerosol generator to the inlet-side bottom surface of the columnar honeycomb structure: 1000 mm · Injection speed of the aerosol: 20 m / s

[0105] During the operation of the particle adhesion device, the particle size distribution based on volume of the ceramic particles ejected from the aerosol was measured with a laser diffraction particle size distribution measuring device, and the median diameter (D50) was 2.8 μm.

[0106] The ceramic particles adhering to the bottom surface on the inlet side of the columnar honeycomb structure to which the ceramic particles thus obtained were attached were removed by suction with a vacuum. Thereafter, the columnar honeycomb structure was placed in an electric furnace and heat-treated in an air atmosphere under the condition of keeping at the maximum temperature of 1200 °C for 2 hours to form a porous film on the surface of the first cell, and a columnar honeycomb structure filter was obtained. The columnar honeycomb structure filter was produced in such a number as required to carry out the following characteristic evaluation.

[0107] (2) Characteristic evaluation The average thickness of the porous film at a predetermined position of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 2-1.

[0108]

Table 2-1

[0109] The porosity of the porous film and the partition walls of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 2-2.

[0110] The "pressure loss" and "collection efficiency (%)" of the columnar honeycomb structure filter obtained by the above manufacturing method were measured in the same manner as in Example 1. The results are shown in Table 2-2.

[0111]

Table 2-2

[0112] <Example 3> (1) Manufacture of columnar honeycomb structure filter A columnar honeycomb structure was obtained under the same manufacturing conditions as in Example 1.

[0113] With respect to the columnar honeycomb structure fabricated above, using a particle adhesion device having the same configuration as in Example 1, an aerosol containing ceramic particles was injected in a direction perpendicular to the inlet-side bottom surface toward the center of the inlet-side bottom surface of the columnar honeycomb structure, and ceramic particles were adhered to the surface of the first cell. The operating conditions of the particle adhesion device are as follows. · Aerosol generator: RBG2000 manufactured by PALAS · Ceramic particles contained in the container: SiC particles Median diameter (D50): 2.4 μm D10: 1.1 μm D90: 4.5 μm (Based on the volume-based cumulative particle size distribution measured by the laser diffraction / scattering method) · Weight of the injected ceramic particles: 6.0 g · Carrier gas: Compressed dry air (dew point 10°C or lower) · Ambient gas: Air · Average flow rate of the aerosol flowing into the columnar honeycomb structure: 8 m / s · Laser diffraction type particle size distribution measuring device: Insitec Spray manufactured by MALVERN · Operating time: 20 seconds · Inner diameter of the nozzle of the aerosol generator: Φ8 mm · Distance from the tip of the nozzle of the aerosol generator to the inlet-side bottom surface of the columnar honeycomb structure: 1000 mm · Injection speed of the aerosol: 40 m / s

[0114] When the particle size distribution based on the volume of the ceramic particles injected from the aerosol was measured with a laser diffraction type particle size distribution measuring device during the operation of the particle adhesion device, the median diameter (D50) was 3.1 μm.

[0115] The ceramic particles adhering to the bottom surface on the inlet side of the columnar honeycomb structure to which the ceramic particles thus obtained were attached were removed by suction with a vacuum. Thereafter, the columnar honeycomb structure was placed in an electric furnace and heat-treated in an air atmosphere under the condition of keeping at a maximum temperature of 1200 °C for 2 hours to form a porous film on the surface of the first cell, thereby obtaining a columnar honeycomb structure filter. The number of columnar honeycomb structure filters required for carrying out the following characteristic evaluation was produced.

[0116] (2) Characteristic evaluation The average thickness of the porous film at a predetermined position of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 3-1.

[0117]

Table 3-1

[0118] The porosity of the porous film and the partition walls of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 3-2.

[0119] The "pressure loss" and "collection efficiency (%)" of the columnar honeycomb structure filter obtained by the above manufacturing method were measured in the same manner as in Example 1. The results are shown in Table 3-2.

[0120]

Table 3-2

[0121] <Example 4> (1) Manufacture of columnar honeycomb structure filter A columnar honeycomb structure was obtained under the same manufacturing conditions as in Example 1.

[0122] For the columnar honeycomb structure fabricated above, a particle adhesion device having the same configuration as in Example 1 was used except that an aerosol generator having the structure shown in Fig. 9 was used. An aerosol containing ceramic particles was sprayed in a direction perpendicular to the inlet-side bottom surface toward the center of the inlet-side bottom surface of the columnar honeycomb structure, and the ceramic particles were adhered to the surface of the first cell. The operating conditions of the particle adhesion device are as follows. · Aerosol generator: VRL50-080608 manufactured by PISCO · Ceramic particles contained in the container: SiC particles Median diameter (D50): 2.4 μm D10: 1.1 μm D90: 4.5 μm (Based on the volume-based cumulative particle size distribution measured by the laser diffraction / scattering method) · Weight of the sprayed ceramic particles: 6.0 g · Carrier gas: Compressed dry air (dew point 10°C or lower) · Ambient gas: Air · Average flow rate of the aerosol flowing into the columnar honeycomb structure: 8 m / s · Laser diffraction type particle size distribution measuring device: Insitec Spray manufactured by MALVERN · Operating time: 20 seconds · Inner diameter of the nozzle of the aerosol generator: Φ8 mm · Distance from the tip of the nozzle of the aerosol generator to the inlet-side bottom surface of the columnar honeycomb structure: 1000 mm · Injection speed of the aerosol: 40 m / s

[0123] When the particle size distribution based on the volume of the ceramic particles sprayed from the aerosol was measured with a laser diffraction type particle size distribution measuring device during the operation of the particle adhesion device, the median diameter (D50) was 3.2 μm.

[0124] The ceramic particles adhering to the bottom surface on the inlet side of the columnar honeycomb structure to which the ceramic particles thus obtained were attached were suction-removed by vacuum. Thereafter, the columnar honeycomb structure was placed in an electric furnace and heat-treated in an air atmosphere under the condition of keeping at a maximum temperature of 1200 °C for 2 hours to form a porous film on the surface of the first cell, thereby obtaining a columnar honeycomb structure filter. The number of columnar honeycomb structure filters necessary for carrying out the following characteristic evaluations was produced.

[0125] (2) Characteristic evaluation The average thickness of the porous film at a predetermined position of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 4-1.

[0126]

Table 4-1

[0127] The porosity of the porous film and the partition walls of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 4-2.

[0128] The "pressure loss" and "collection efficiency (%)" of the columnar honeycomb structure filter obtained by the above manufacturing method were measured in the same manner as in Example 1. The results are shown in Table 4-2.

[0129]

Table 4-2

[0130] <Example 5> (1) Manufacture of columnar honeycomb structure filter A columnar honeycomb structure was obtained under the same manufacturing conditions as in Example 1.

[0131] For the columnar honeycomb structure fabricated above, a particle adhesion device having the same configuration as that in Example 1 was used, except that an aerosol generator having the structure shown in FIG. 10 was used. An aerosol containing ceramic particles was injected in a direction perpendicular to the inlet-side bottom surface toward the center of the inlet-side bottom surface of the columnar honeycomb structure, and the ceramic particles were adhered to the surface of the first cell. The operating conditions of the particle adhesion device are as follows. · Aerosol generator: BEG1000 manufactured by PALAS · Rotating body: Rotating brush · Ceramic particles contained in the container: SiC particles Median diameter (D50): 2.4 μm D10: 1.1 μm D90: 4.5 μm (Based on the volume-based cumulative particle size distribution measured by the laser diffraction / scattering method) · Weight of the injected ceramic particles: 6.0 g · First medium gas: Compressed dry air (dew point 10°C or lower) · Second medium gas: Compressed dry air (dew point 10°C or lower) · Ambient gas: Air · Average flow rate of the aerosol flowing into the columnar honeycomb structure: 6 m / s · Laser diffraction type particle size distribution measuring device: Insitec Spray manufactured by MALVERN · Operating time: 20 seconds · Inner diameter of the nozzle of the aerosol generator: Φ8 mm · Distance from the tip of the nozzle of the aerosol generator to the inlet-side bottom surface of the columnar honeycomb structure: 1500 mm · Injection speed of the aerosol: 50 m / s

[0132] When the particle size distribution based on the volume of the ceramic particles injected from the aerosol was measured with a laser diffraction type particle size distribution measuring device during the operation of the particle adhesion device, the median diameter (D50) was 2.7 μm.

[0133] The ceramic particles adhering to the bottom surface on the inlet side of the columnar honeycomb structure to which the ceramic particles thus obtained were attached were sucked and removed by vacuum. Then, the columnar honeycomb structure was placed in an electric furnace and heat-treated in an air atmosphere under the condition of keeping at a maximum temperature of 1200 °C for 2 hours to form a porous film on the surface of the first cell, and a columnar honeycomb structure filter was obtained. The number of columnar honeycomb structure filters necessary for carrying out the following characteristic evaluations was produced.

[0134] (2) Characteristic evaluation The average thickness of the porous film at a predetermined position of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 5-1.

[0135]

Table 5-1

[0136] The porosity of the porous film and the partition walls of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 5-2.

[0137] The "pressure loss" and "collection efficiency (%)" of the columnar honeycomb structure filter obtained by the above manufacturing method were measured in the same manner as in Example 1. The results are shown in Table 5-2.

[0138]

Table 5-2

[0139] <Example 6> (1) Manufacture of columnar honeycomb structure filter A columnar honeycomb structure was obtained under the same manufacturing conditions as in Example 1.

[0140] For the columnar honeycomb structure produced above, a particle adhesion device having the same configuration as that in Example 1 was used, except that an aerosol generator having the structure shown in Fig. 10 was used. An aerosol containing ceramic particles was injected in a direction perpendicular to the inlet-side bottom surface toward the center of the inlet-side bottom surface of the columnar honeycomb structure, and the ceramic particles were adhered to the surface of the first cell. The operating conditions of the particle adhesion device are as follows. · Aerosol generator: BEG1000 manufactured by PALAS · Rotating body: Rotating brush · Ceramic particles accommodated in the container: SiC particles Median diameter (D50): 2.4 μm D10: 1.1 μm D90: 4.5 μm (Based on the volume-based cumulative particle size distribution measured by the laser diffraction / scattering method) · Weight of the injected ceramic particles: 6.0 g · First medium gas: Compressed dry air (dew point 10°C or lower) · Second medium gas: Compressed dry air (dew point 10°C or lower) · Ambient gas: Air · Average flow rate of the aerosol flowing into the columnar honeycomb structure: 4 m / s · Laser diffraction type particle size distribution measuring device: Insitec Spray manufactured by MALVERN · Operating time: 20 seconds · Inner diameter of the nozzle of the aerosol generator: Φ8 mm · Distance from the tip of the nozzle of the aerosol generator to the inlet-side bottom surface of the columnar honeycomb structure: 1500 mm · Injection speed of the aerosol: 40 m / s

[0141] When the particle size distribution based on the volume of the ceramic particles injected from the aerosol was measured with a laser diffraction type particle size distribution measuring device during the operation of the particle adhesion device, the median diameter (D50) was 2.6 μm.

[0142] The ceramic particles adhering to the bottom surface on the inlet side of the columnar honeycomb structure to which the ceramic particles thus obtained were attached were removed by suction under vacuum. Thereafter, the columnar honeycomb structure was placed in an electric furnace and heat-treated in an air atmosphere under the condition of keeping at a maximum temperature of 1200 °C for 2 hours to form a porous film on the surface of the first cell, thereby obtaining a columnar honeycomb structure filter. The number of columnar honeycomb structure filters necessary for performing the following characteristic evaluations was produced.

[0143] (2) Characteristic Evaluation The average thickness of the porous film at a predetermined position of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 6-1.

[0144]

Table 6-1

[0145] The porosity of the porous film and the partition walls of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 6-2.

[0146] The "pressure loss" and "collection efficiency (%)" of the columnar honeycomb structure filter obtained by the above manufacturing method were measured in the same manner as in Example 1. The results are shown in Table 6-2.

[0147]

Table 6-2

[0148] <Comparative Example 1> (1) Manufacture of Columnar Honeycomb Structure Filter A columnar honeycomb structure was obtained under the same manufacturing conditions as in Example 1.

[0149] The columnar honeycomb structure fabricated above was held by a holder such that the extending direction of the cell was vertical, and a slurry containing SiC particles was flowed from above toward the bottom surface on the inlet side. At this time, the slurry was caused to flow in evenly over the entire bottom surface on the inlet side. The SiC particles contained in the slurry had a median diameter (D50) of 2.4 μm. While the SiC particles in the slurry adhered to the surface of the first cell, moisture that had permeated through the columnar honeycomb structure was discharged from the bottom surface on the outlet side. The bottom surface on the outlet side was connected to a drain pipe, and the discharged moisture was collected in a container. When flowing the slurry through the columnar honeycomb structure, the air in the collection container was sucked by a blower to apply a suction force to the bottom surface on the outlet side of the columnar honeycomb structure, promoting the adhesion of the membrane material to the surface of the partition wall.

[0150] The ceramic particles adhering to the bottom surface on the inlet side of the columnar honeycomb structure to which the ceramic particles obtained in this way had adhered were removed by suction under vacuum. Thereafter, the columnar honeycomb structure was placed in an electric furnace and heat-treated in an air atmosphere under the condition of keeping at a maximum temperature of 1200 °C for 2 hours to form a porous membrane on the surface of the first cell, obtaining a columnar honeycomb structure filter. The columnar honeycomb structure filters were produced in the number required to conduct the following characteristic evaluations.

[0151] (2) Characteristic evaluation The average thickness of the porous membrane at a predetermined position of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 7-1.

[0152]

Table 7-1

[0153] The porosity of the porous membrane and the partition wall of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 7-2.

[0154] The "pressure loss" and "collection efficiency (%)" of the columnar honeycomb structure filter obtained by the above manufacturing method were measured in the same manner as in Example 1. The results are shown in Table 7-2.

[0155]

Table 7-2

[0156] <Example 7> (1) Manufacture of the columnar honeycomb structure filter A columnar honeycomb structure was obtained under the same manufacturing conditions as in Example 1.

[0157] For the columnar honeycomb structure produced above, a particle adhesion device having the same configuration as in Example 1 was used except that an aerosol generator having the structure shown in FIG. 9 was used, and an aerosol containing ceramic particles was injected in a direction perpendicular to the inlet-side bottom surface toward the center of the inlet-side bottom surface of the columnar honeycomb structure, and ceramic particles were adhered to the surface of the first cell. The operating conditions of the particle adhesion device are as follows. · Aerosol generator: VRL50-080608 manufactured by PISCO · Ceramic particles contained in the container: SiC particles Median diameter (D50): 2.4 μm D10: 1.1 μm D90: 4.5 μm (Based on the volume-based cumulative particle size distribution measured by the laser diffraction / scattering method) · Weight of the injected ceramic particles: 6.0 g · Carrier gas: Compressed dry air (dew point 10°C or lower) · Ambient gas: Air · Average flow rate of the aerosol flowing into the columnar honeycomb structure: 8 m / s · Laser diffraction type particle size distribution measuring device: Insitec Spray manufactured by MALVERN · Operating time: 20 seconds · Inner diameter of the nozzle of the aerosol generator: Φ8 mm · Distance from the tip of the nozzle of the aerosol generator to the inlet-side bottom surface of the columnar honeycomb structure: 1000 mm · Injection speed of the aerosol: 20 m / s

[0158] During the operation of the particle adhesion device, when the particle size distribution based on volume of the ceramic particles ejected from the aerosol was measured with a laser diffraction particle size distribution measuring device, the median diameter (D50) was 2.4 μm.

[0159] The ceramic particles adhering to the bottom surface on the inlet side of the columnar honeycomb structure to which the ceramic particles thus obtained were attached were removed by suction with a vacuum. Thereafter, the columnar honeycomb structure was placed in an electric furnace and heat-treated in an air atmosphere under the condition of keeping at a maximum temperature of 1200°C for 2 hours to form a porous film on the surface of the first cell, and a columnar honeycomb structure filter was obtained. The columnar honeycomb structure filters were produced in the number required to conduct the following characteristic evaluations.

[0160] (2) Characteristic evaluation The average thickness of the porous film at a predetermined position of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 8-1.

[0161]

Table 8-1

[0162] The porosity of the porous film and the partition walls of the columnar honeycomb structure filter obtained by the above manufacturing method was measured in the same manner as in Example 1. The results are shown in Table 8-2.

[0163] The "pressure loss" and "collection efficiency (%)" of the columnar honeycomb structure filter obtained by the above manufacturing method were measured in the same manner as in Example 1. The results are shown in Table 8-2.

[0164]

Table 8-2

Explanation of symbols

[0165] 100 Columnar honeycomb structure filter 102 Outer peripheral side wall 104 Inlet-side bottom surface 106 Outlet-side bottom surface 108 First cell 109 Blind stop portion 110 Second cell 112 Partition wall 114 Porous membrane 120 Central portion 130 Peripheral portion 410 Aerosol generator 411 Nozzle 412 Ceramic particles 413 Flow path 413e Outlet 417 Medium gas flow path 417i Supply port 419 Accommodation portion 500 Particle adhesion device 510 Aerosol generator 511 Nozzle 512 Ceramic particles 513 Cylinder 513e Cylinder outlet 514 Piston or screw 515 Crushing chamber 515e Crushing chamber outlet 516 Rotating body 517 Gas flow path 520 Laser diffraction particle size distribution measuring device 530 Gas introduction pipe 531 Vent hole 540 Holder 550 Differential pressure gauge 560 Exhaust pipe 570 Blower 580 Columnar honeycomb structure 810 Aerosol generator 811 Nozzle 812 Ceramic particles 813 Second gas flow path 814 Belt feeder 815 Crushing chamber 815in Inlet 815e Crushing chamber outlet 816 Rotating body 817 First gas flow path 817e Outlet 818 Agitator 819 Container 819e Discharge port 822 Ejector

Claims

1. A plurality of first cells extending from the inlet-side bottom surface to the outlet-side bottom surface, with the inlet-side bottom surface open and having a plugging portion at the outlet-side bottom surface, and a plurality of second cells extending from the inlet-side bottom surface to the outlet-side bottom surface, having a plugging portion at the inlet-side bottom surface and the outlet-side bottom surface being open. The plurality of first cells and the plurality of second cells are alternately arranged adjacent to each other with a porous partition wall therebetween, and it is a columnar honeycomb structure filter, On the surface of each first cell, a porous membrane having a porosity higher than that of the partition wall is formed, Regarding the columnar honeycomb structure filter, when the extending direction of the first cell of the columnar honeycomb structure filter is taken as the extending direction of the coordinate axis, the coordinate value of the inlet-side bottom surface is 0, and the coordinate value of the outlet-side bottom surface is X, the following relationship holds. (A 1 + A 2 + A 3 ) / (B 1 + B 2 + B 3 ) ≥ 1.7 In the formula, In a cross-section orthogonal to the extending direction of the first cell of the honeycomb structure filter at the coordinate value 0.2X, the average thickness of the porous film in the outer peripheral portion is B 1 Let the average thickness of the porous film in the central portion be A 1 and In a cross-section orthogonal to the extending direction of the first cell of the honeycomb structure filter at the coordinate value 0.5X, the average thickness of the porous film in the outer peripheral portion is B 2 Let the average thickness of the porous film in the central portion be A 2 Let In a cross section orthogonal to the extending direction of the first cell of the honeycomb structure filter at the coordinate value 0.8X, the average thickness of the porous film in the outer peripheral portion is B 3 and the average thickness of the porous film in the central portion is A 3 is defined as such.

2. The columnar honeycomb structure filter according to Claim 1, in which the following relationship holds. (A 1 + A 2 + A 3 ) / (B 1 + B 2 + B 3 ) ≥ 1.8

3. The columnar honeycomb structure filter according to Claim 1, in which the following relationship holds. (A1 + A2 + A3) / (B1 + B2 + B3) ≥ 2.0

4. Regarding the first cell located at the center of the cross section orthogonal to the extending direction of the first cell of the columnar honeycomb structure filter, the columnar honeycomb structure filter according to any one of Claims 1 to 3, in which the following relationships (1) and (2) hold. The ratio (A 1 / A 2 ) of the average thickness A of the porous film at the coordinate value 0.5X to the average thickness A of the porous film at the coordinate value 0.2X is 1.05 to 5.

0. 1 to the average thickness A of the porous film at the coordinate value 0.5X 2 is 2 / 1 and is 1.05 to 5.

0. The ratio of the average thickness A of the porous membrane at the coordinate value 0.8X to the average thickness A of the porous membrane at the coordinate value 0.2X 1 is 1.05 to 5.

0. 3 (A 3 / A 1 )

5. The columnar honeycomb structure filter according to any one of Claims 1 to 4, in which the following relationship holds. A 1 > B 1 , A 2 > B 2 , and A 3 > B 3

6. The columnar honeycomb structure filter according to any one of Claims 1 to 5, in which the main component of the porous membrane is silicon carbide, alumina, silica, cordierite or mullite.

7. The columnar honeycomb structure filter according to any one of Claims 1 to 6, in which the porosity of the porous membrane is 70 to 85%.

8. The columnar honeycomb structure filter according to any one of Claims 1 to 7, in which the average thickness of the entire porous membrane is 4 to 50 μm.

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