JP7709397B2 - Pillar honeycomb structure filter - Google Patents

Description

The present invention relates to a columnar honeycomb structure filter.

Exhaust gas emitted from internal combustion engines such as diesel and gasoline engines contains particulate matter (PM) such as soot. Soot is harmful to the human body, so its emission is regulated. Currently, in order to comply with exhaust gas regulations, filters such as DPFs and GPFs are widely used, which filter out soot and other PM by passing exhaust gas through a breathable, small-pore partition wall.

A known filter for capturing PM is a wall-flow type columnar honeycomb structure filter that has a plurality of first cells that extend in the height direction from the inlet bottom surface to the outlet bottom surface, have an open inlet bottom surface and plugged portions on the outlet bottom surface, and are arranged adjacent to the first cells with partition walls in between, extend in the height direction from the inlet bottom surface to the outlet bottom surface, have plugged portions on the inlet bottom surface and are open on the outlet bottom surface.

In recent years, stricter PM emission standards (PN regulations: particulate matter number regulations) have been introduced in line with the strengthening of exhaust gas regulations, and filters are required to have high PM collection performance (high PN collection efficiency). Therefore, it has been proposed to form a separate layer for collecting PM on the surface of the cells (Patent Documents 1 to 7). According to these patent documents, by forming a collection layer, it is possible to collect PM while reducing pressure loss. A method of forming a porous membrane is adopted in which particles smaller than the average particle size of the particles that make up the partition walls are supplied to the inlet side bottom surface of the filter by a solid-gas two-phase flow, adhered to the surface of the first cell, and then heat-treated.

WO 2010/110010 International Publication No. 2011/125768 International Publication No. 2011/125769 Patent No. 5863951 JP 2011-147931 A Patent No. 5863950 Patent No. 5597148

In improving the PM collection performance of a columnar honeycomb structure filter, it is believed that forming a collection layer on the surface of the cells is effective, but 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 velocity is high, such as when a car is accelerating. 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 velocity is high.

The inventors conducted extensive research to solve the above problems and discovered that as the flow velocity of exhaust gas increases, the flow velocity of the exhaust gas passing through the partition walls of a columnar honeycomb structure filter tends to be greater in the center than in the outer periphery. They also discovered that increasing the thickness of the collection layer (corresponding to the "porous membrane" in this invention) from the outer periphery toward the center is advantageous in improving PM collection performance when the exhaust gas flow velocity is high. The present invention was completed based on this knowledge and is exemplified below.

[1]
A columnar honeycomb structure filter comprising: a plurality of first cells extending from an inlet side bottom surface to an outlet side bottom surface, the inlet side bottom surface being open and having plugging portions 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, the inlet side bottom surface being plugging portions 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 being alternately arranged adjacent to each other with a porous partition wall therebetween,
a porous film having a porosity higher than that of the partition wall is formed on a surface of each of the first cells;
A columnar honeycomb structure filter in which the extension direction of the first cell of the columnar honeycomb structure filter is the extension 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 )>1.0
During the ceremony,
In a cross section perpendicular to the extending direction of the first cell of the columnar honeycomb structure filter at the coordinate value 0.2X, the average thickness of the porous film in the outer periphery is _B1 , and the average thickness of the porous film in the center is _A1 ,
In a cross section perpendicular to the extending direction of the first cell of the columnar honeycomb structure filter at the coordinate value 0.5X, the average thickness of the porous film in the outer periphery is _B2 , and the average thickness of the porous film in the center is _A2 ,
In a cross section perpendicular to the extending direction of the first cells of the columnar honeycomb structure filter at the coordinate value 0.8X, the average thickness of the porous film in the outer periphery is defined as _B3 , and the average thickness of the porous film in the center is defined as _A3 .
[2]
The columnar honeycomb structure filter according to [1], wherein the following relationship is satisfied:
(A ₁ +A ₂ +A ₃ )/(B ₁ +B ₂ +B ₃ )≧1.2
[3]
A columnar honeycomb structure filter as described in [1] or [2], in which the following relationships (1) and (2) are satisfied for a first cell located at the center of a cross section perpendicular to the extension direction of the first cell of the columnar honeycomb structure filter.
(1) The ratio (A ₂ /A ₁ ) of the average thickness A ₂ of the porous membrane at the coordinate value 0.5X to the average thickness A ₁ of the porous membrane at the coordinate value 0.2X is 1.05 to 5.0.
(2) The ratio (A ₃ /A ₁ ) of the average thickness A ₃ of the porous membrane at the coordinate value 0.8X to the average thickness A ₁ 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], wherein the following relationship is established:
A ₁ > B ₁ , A ₂ > B ₂ , and A ₃ > B ₃
[5]
The columnar honeycomb structure filter according to any one of [1] to [4], wherein the main component of the porous film 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 film is 70 to 85%.
[7]
The pillar-shaped honeycomb structure filter according to any one of [1] to [6], wherein the average thickness of the entire porous film is 4 to 50 μm.

The columnar honeycomb structure filter according to one embodiment of the present invention can contribute to improving PM collection performance when the exhaust gas flow velocity is high.

FIG. 1 is a perspective view illustrating an example of a columnar honeycomb structure filter. FIG. 2 is a schematic cross-sectional view of an example of a columnar honeycomb structure filter, observed in a cross section parallel to a cell extension direction. FIG. 2 is a schematic partial enlarged view of a columnar honeycomb structure filter when observed at a cross section perpendicular to a cell extension direction. 13 is a graph showing the results of fluid analysis of the relationship between the distance from the inlet bottom surface in the cell extension direction and the flow velocity of exhaust gas that has flowed into a columnar honeycomb structure filter when it permeates through the partition walls. FIG. 2 is a schematic cross-sectional view showing a structural example of a first cell. 4 is a schematic diagram for explaining the ranges of the outer periphery and the central portion of the columnar honeycomb structure filter. FIG. FIG. 2 is a schematic diagram of a cross section of a columnar honeycomb structure filter cut out for determining the average thickness of a porous membrane. 1 is a schematic diagram for explaining a configuration of a particle adhesion device according to an embodiment of the present invention. 10A and 10B are schematic diagrams for explaining another example of the configuration of an aerosol generator applicable to a particle adhesion device according to an embodiment of the present invention. 13 is a schematic diagram for explaining yet another configuration example of an aerosol generator applicable to a particle adhesion device according to an embodiment of the present invention. FIG.

Next, an embodiment 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 embodiment, and that appropriate design changes, improvements, etc. may be made based on the ordinary knowledge of a person skilled in the art without departing from the spirit of the present invention.

1. Pillar honeycomb structure filter
A 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) that collect soot and are attached to an exhaust gas line from an engine of a combustion device, typically a vehicle. The columnar honeycomb structure filter according to the present invention can be installed, for example, in an exhaust pipe.

1 and 2 are schematic perspective and cross-sectional views of a columnar honeycomb structure filter (100), respectively. The columnar honeycomb structure filter (100) includes an outer peripheral side wall (102), a plurality of first cells (108) arranged on the inner peripheral side of the outer peripheral side wall (102), extending in parallel from the inlet side bottom surface (104) to the outlet side bottom surface (106), opening at the inlet side bottom surface (104) and having plugging portions (109) at the outlet side bottom surface (106), and a plurality of second cells (110) arranged on the inner peripheral side of the outer peripheral side wall (102), extending in parallel from the inlet side bottom surface (104) to the outlet side bottom surface (106), having plugging portions (109) at the inlet side bottom surface (104), and opening at the outlet side bottom surface (106). In this columnar honeycomb structure filter (100), the first cells (108) and the second cells (110) are arranged alternately adjacent to each other with a porous partition wall (112) in between, so that the inlet side bottom surface (104) and the outlet side bottom surface (106) each have a honeycomb shape.

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 proceeds downstream inside the first cell (108). Since the first cell (108) has a plugging portion (109) on the outlet side bottom surface (106) on the downstream side, the exhaust gas passes through the porous partition wall (112) that separates the first cell (108) from the second cell (110) and flows into the second cell (110). Since the particulate matter cannot pass through the partition wall (112), it is captured and accumulated in the first cell (108). After the particulate matter is removed, the clean exhaust gas that has flowed into the second cell (110) proceeds downstream inside the second cell (110) and flows out from the outlet side bottom surface (106) on the downstream side.

Figure 3 shows a schematic enlarged partial view of the columnar honeycomb structure filter (100) when observed in a cross section perpendicular to the extension 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) that defines the first cell (108)).

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, it is advantageous in terms of improving the PM collection efficiency to make the thickness of the porous membrane thicker near the central axis than near the outer peripheral side wall. Therefore, in one embodiment of the columnar honeycomb structure filter, the following relationship is established when the extension direction of the first cell of the columnar honeycomb structure filter is the extension 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.
(A ₁ +A ₂ +A ₃ )/(B ₁ +B ₂ +B ₃ )>1.0
During the ceremony,
In a cross section perpendicular to the extending direction of the first cell of the columnar honeycomb structure filter at the coordinate value 0.2X, the average thickness of the porous film in the outer periphery is _B1 , and the average thickness of the porous film in the center is _A1 ,
In a cross section perpendicular to the extending direction of the first cell of the columnar honeycomb structure filter at the coordinate value 0.5X, the average thickness of the porous film in the outer periphery is _B2 , and the average thickness of the porous film in the center is _A2 ;
In a cross section perpendicular to the extending direction of the first cells of the columnar honeycomb structure filter at the coordinate value 0.8X, the average thickness of the porous film in the outer periphery is defined as _B3 , and the average thickness of the porous film in the center is defined as _A3 .

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. There is no particular upper limit set for ( _A1 + _A2 + _A3 )/( _B1 + _B2 + _B3 ), but if it becomes excessively large, pressure loss due to sudden blockage of the gas flow path may occur, so it is preferable that 10≧( _A1 + _A2 + _A3 )/( _B1 + _B2 + _B3 ), and it is more preferable that 8≧( _A1 + _A2 + _A3 )/( _B1 + _B2 + _B3 ). Typically, 4≧( _A1 + _A2 + _A3 )/( _B1 + _B2 + _B3 ), more typically, 3≧( _A1 + _A2 + _A3 )/( _B1 + _B2 + _B3 ), and even more typically, 2.5≧( _A1 + _A2 + _A3 )/( _B1 + _B2 + _B3 ).

(A ₁ +A ₂ +A ₃ )/3 can be, for example, 5 to 30 μm, and is preferably 10 to 20 μm.

In a preferred embodiment, _A1 > _B1 , _A2 > _B2 , and _A3 > _B3 are satisfied. In a more preferred embodiment, _A1 / _B1 >1.1, _A2 / _B2 >1.1, and _A3 / _B3 >1.1 are satisfied. In an even more preferred embodiment, _A1 / _B1 >1.4, _A2 / _B2 >1.4, and _A3 / _B3 >1.4 are satisfied. Although no upper limit is set for _A1 / _B1 , _A2 / _B2 , and _A3 / _B3 , if they are excessively large, pressure loss due to sudden blockage of the gas flow path may occur, so it is preferable that _A1 / _B1 , 4.0≧ _A2 / _B2 , and 4.0≧ _A3 / _B3 , and it is more preferable that _A1 / _B1 , 3.0≧ _A2 / _B2 , and 3.0≧ _A3 / _B3 .

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 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 bottom surface on the inlet side) 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 becomes significantly larger at the bottom surface on the outlet side. Figure 4 shows the result of a fluid analysis under the following conditions on the relationship between the distance from the bottom surface on the inlet side in the direction in which the cells extend and the flow velocity when the exhaust gas flowing into the columnar honeycomb structure filter passes through the partition walls of one cell. As can be seen from Figure 4, the flow velocity of the exhaust gas passing through the partition walls increases significantly as it approaches the bottom surface on the outlet side.
<Fluid analysis conditions>
Software: Fluent Ver. 19.1 manufactured by ANSYS
Solver type: Pressure-based solver Turbulence model: Low Reynolds number type SST k-ω
Outer periphery: symmetric surface condition (no friction occurs)
Solid wall: No-slip wall condition (friction occurs)
Outlet: Gauge pressure set to 0 [Pa] (open to atmosphere)
Fluid flow rate into the columnar honeycomb filter: 12.4 m/sec, 2.5 m/sec
Fluid density flowing into the columnar honeycomb structure filter: 1.19 kg/m ³
Viscosity of fluid flowing into the columnar honeycomb structure filter: 1.85×10 ⁻⁵ kg/m/s
Dimensions of columnar honeycomb filter: 120 mm
Cell density of pillar honeycomb filter: 200 cpsi
Partition wall thickness of columnar honeycomb structure filter: 216 μm
Porous membrane: None

The amount of exhaust gas passing through a portion where the flow rate of the exhaust gas is high per unit time increases. For this reason, by increasing the thickness of the porous membrane and increasing the chance of contact with the porous membrane, the PM collection performance can be improved. Therefore, by increasing the thickness of the porous membrane as it approaches the outlet side bottom surface where the flow rate of the exhaust gas is high, the PM collection performance can be improved 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 divides and forms the first cell) increases in thickness from the inlet side bottom surface (104) to the outlet side bottom surface (106). Figure 5 shows a schematic cross-sectional view showing an example of the structure of the first cell (108) of such a columnar honeycomb structure filter (100).

More specifically, if the extension direction of the first cell of the columnar honeycomb structure filter is the extension 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 relationships (1) and (2) hold for the first cell located at the center of a cross section perpendicular to the extension direction of the first cell of the columnar honeycomb structure filter.
(1) The ratio (A ₂ /A ₁ ) of the average thickness A ₂ of the porous membrane at the coordinate value 0.5X to the average thickness A ₁ of the porous membrane at the coordinate value 0.2X is 1.05 to 5.0.
(2) The ratio (A ₃ /A ₁ ) of the average thickness A ₃ of the porous membrane at the coordinate value 0.8X to the average thickness A ₁ of the porous membrane at the coordinate value 0.2X is 1.05 to 5.0.

The lower limit of _A2 / _A1 is preferably 1.2 or more, and more preferably 1.4 or more.The upper limit of _A2 / _A1 is preferably 4.0 or less, and more preferably 3.0 or less.

The lower limit of _A3 / _A1 is preferably 1.6 or more, and more preferably 1.8 or more.The upper limit of _A3 / _A1 is preferably 4.0 or less, and more preferably 3.0 or less.

When measuring the average thickness of the porous film at each coordinate value (0.2X, 0.5X, 0.8X) in the extension direction of the first cells, the central part and the outer periphery 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 extension direction of the first cells, a line segment L is drawn from the center of gravity O of the cross section to the outer surface of the outer peripheral side wall (102), the extension direction of the line segment L is set as the extension direction of the coordinate axis, the coordinate value of the center of gravity O is set as 0, and the coordinate value of the outer surface of the outer peripheral side wall is set as R. In this case, the range of coordinate values 0 to 0.2R on the line segment L is the central part, and the range of coordinate values 0.7R to 0.9R is the outer periphery. By drawing many such line segments L on the cross section and collecting the central part and the outer periphery on each line segment L, the range of the central part (120) and the outer periphery (130) on the cross section is obtained.

A ₁ , A ₂ , A ₃ , B ₁ , B ₂ , and B ₃ are measured by the following method. A cross section is cut out from the portion (center or outer periphery) where the average thickness of the porous film of the columnar honeycomb structure filter is to be obtained, which is parallel to the extension direction of the first cell and parallel to the line segment from the outer surface of the outer peripheral side wall toward the center of gravity O. The cross section is observed with a 3D shape measuring device (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) x 9.5 mm (vertical). At this time, the observation is performed so that the horizontal direction of the observation field is parallel to the extension direction of the first cell. Then, when the average thickness at a specific coordinate value in the extension direction of the first cell is to be obtained, the observation is performed so that the coordinate value is located in the center of the horizontal direction of the observation field. For example, when the average thickness at 0.2X is to be obtained, the observation is performed so that 0.2X is located in the center of the horizontal direction of the observation field.

Figure 7 shows a schematic diagram of the cut cross section. By observing the cross section, the first cell (108) in which the porous film is formed and the second cell (110) in which the porous film is not formed are identified. Next, the three first cells (108) adjacent to each other at the position closest to the center on the cross section are identified. In addition, 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 each identified, and leveling is performed using image processing software (e.g., software attached to Keyence's 3D shape measuring instrument VR-3200) so that the reference plane becomes the most horizontal from the profiles of both regions. After leveling, the central regions (110a) of the two second cells (110) are specified to measure the average height H2 of the region. In addition, after leveling, the central regions (108a) of the three first cells (108) are specified to measure the average height H1 of the region. The difference between the average height H1 and the average height H2 in one field of view is the thickness of the porous membrane in that field of view. Note that the central region (108a, 110a) refers to the central region when the distance between a pair of partition walls (112) that divide each cell is divided into three equal parts.

The thickness of the porous film at the center and the outer periphery at each coordinate value is measured for five visual fields, and the average values for the five visual fields are taken as the measured values (A ₁ , A ₂ , A ₃ , B ₁ , B ₂ , B ₃ ).

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 columnar 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 improved collection efficiency is obtained. In addition, 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 is obtained.

In one embodiment, the porosity of the porous membrane (114) is higher than that of the partition wall (112). Having a higher porosity of the porous membrane (114) than that of the partition wall (112) has the advantage of being able to suppress an increase in pressure loss. 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.

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

The porosity of the porous film is measured as follows: For each cross section where the average film thickness of the porous film at each of the points _A1 , _A2 , _A3 , _B1 , _B2 , and _B3 has been determined, any two visual fields in the central region (108a) of the first cell (108) where the porous film is formed are photographed using a field emission scanning electron microscope (abbreviated as FE-SEM) (e.g., ZEISS, model: ULTRA55) to capture reflected electron images of the in-lens. Next, the image is binarized by the mode method using image analysis software (e.g., HALCON) to separate it into membrane parts and void parts, and the ratio of the membrane parts to the void parts is calculated to determine the porosity of the porous membrane at each of the points _A1 , _A2 , _A3 , _B1 , _B2 , and _B3 . The overall average value of these is then determined as the porosity of the porous membrane of the columnar honeycomb structure filter.

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

The porous film can be made of ceramics. The porous film can contain one or more ceramics selected from, for example, cordierite, silicon carbide (SiC), talc, mica, mullite, cerben, aluminum titanate, alumina, silicon nitride, sialon, zirconium phosphate, zirconia, titania and silica. The main component of the porous film is preferably silicon carbide, alumina, silica, cordierite or mullite. Among them, the main component of the porous film is preferably silicon carbide, since the presence of the surface oxide film (Si ₂ O) allows the porous film to be firmly bonded to each other and difficult to peel off. The main component of the porous film refers to a component that occupies 50% by mass or more of the porous film. The porous film is preferably made of SiC that occupies 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. There is no particular restriction on the shape of the ceramics that constitute the porous film, but examples include granular shapes.

Materials constituting the partition walls and outer peripheral side walls of the columnar honeycomb structure filter according to this embodiment include, but are not limited to, porous ceramics. Ceramics include cordierite, mullite, zirconium phosphate, aluminum titanate, silicon carbide (SiC), silicon-silicon carbide composites (e.g., Si-bonded SiC), cordierite-silicon carbide composites, zirconia, spinel, indialite, sapphirine, corundum, titania, silicon nitride, and the like. These ceramics may contain one type alone or two or more types simultaneously.

The columnar honeycomb structure filter may support a PM combustion catalyst that assists 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 that can simultaneously remove hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). However, it is preferable that the columnar honeycomb structure filter according to this embodiment does not support a catalyst. This is because if a catalyst is coated on a thin portion of the porous membrane (e.g., the outer periphery, near the inlet), the catalyst may seep out from the outer side wall of the columnar honeycomb structure filter.

The bottom shape of the columnar honeycomb structure filter is not limited, but can be, for example, a round shape such as a circle, an ellipse, a racetrack shape, or an oval shape, or a polygonal shape such as a triangle or a rectangle. The columnar honeycomb structure filter (100) in FIG. 1 has a circular bottom shape and is cylindrical overall.

There is no particular restriction on 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) and it may be set appropriately depending on the application and required performance. There is also no particular restriction on the relationship between the height of the columnar honeycomb structure filter and the maximum diameter of each bottom surface (referring to the maximum length of the diameter 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.

There are no limitations on the shape of the cells in a cross section perpendicular to the cell extension direction, but a quadrangle, hexagon, octagon, or a combination of these is preferred. Of these, square and hexagonal shapes are preferred. By using such a cell shape, it is possible to reduce pressure loss when a fluid is passed through the columnar honeycomb structure filter.

From the viewpoint of suppressing pressure loss, 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. 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 walls refers to the length of a line segment that crosses the partition walls when the line segment connects the centers of gravity of adjacent cells in a cross section perpendicular to the extension direction of the cells. The average thickness of the partition walls refers to the average value of the thicknesses of all the partition walls.

The cell density (the number of cells per unit cross-sectional area perpendicular to the cell extension direction) is not particularly limited, but can be, for example, 6 to 2000 cells/inch2 (0.9 to 311 cells/ ^cm2 ), more preferably 50 to 1000 cells/inch2 (7.8 to 155 cells/ ^cm2 ), and particularly preferably 100 to 400 cells/inch2 (15.5 to 62.0 cells/ ^cm2 ).

The columnar honeycomb structure filter can also be provided as a one-piece molded product. The columnar honeycomb structure filter can also be provided as a segment joint, in which a number of columnar honeycomb structure filter segments, each having an outer peripheral side wall, are joined together at their sides to form an integrated unit. By providing the columnar honeycomb structure filter as a segment joint, it is possible to improve thermal shock resistance.

2. Manufacturing method of columnar honeycomb structure filter
The manufacturing method of the columnar honeycomb structure filter is exemplified below. First, a raw material composition containing a ceramic raw material, a dispersion medium, a pore former, and a binder is kneaded to form a puddle, and then the puddle is extruded to form a desired columnar honeycomb molded body. Additives such as a dispersant can be mixed into the raw material composition as necessary. In the extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

After drying the columnar honeycomb formed body, plugging portions are formed at predetermined positions on both bottom surfaces of the columnar honeycomb formed body, and the plugging portions are then dried to obtain a columnar honeycomb formed body with plugging portions. The columnar honeycomb formed body is then degreased and fired to obtain a columnar honeycomb structure. A porous film is then formed on the surfaces of the first cells of the columnar honeycomb structure to obtain a columnar honeycomb structure filter.

As the ceramic raw material, a raw material capable of forming the above-mentioned ceramics after firing can be used. The ceramic raw material can be provided, for example, in the form of a 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. Specific examples include, but are not limited to, silica, talc, alumina, kaolin, serpentine, pyroferrite, brucite, boehmite, mullite, magnesite, and aluminum hydroxide. The ceramic raw material may be used alone or in combination of two or more types.

In the case of filter applications such as DPF and GPF, cordierite can be suitably used as the ceramic. In this case, a cordierite-forming raw material can be used as the ceramic raw material. The cordierite-forming raw material is a raw material that becomes cordierite by firing. The cordierite-forming raw material preferably has a chemical composition of 30 to 45 mass % alumina (Al ₂ O ₃ ) (including aluminum hydroxide converted to alumina), 11 to 17 mass % magnesia (MgO), and 42 to 57 mass % silica (SiO ₂ ).

The dispersion medium can be water or a mixture of water and an organic solvent such as alcohol, but water is particularly suitable.

The pore-forming material is not particularly limited as long as it becomes pores after firing, and examples thereof include wheat flour, starch, foamed resin, water-absorbent resin, porous silica, carbon (e.g., graphite), ceramic balloons, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic, and phenol. The pore-forming material may be used alone or in combination of two or more types. From the viewpoint of increasing the porosity of the fired body, the content of the pore-forming material is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of ceramic raw material. From the viewpoint of ensuring the strength of the fired body, the content of the pore-forming material 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, per 100 parts by mass of ceramic raw material.

Examples of binders 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. In addition, from the viewpoint of increasing 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, per 100 parts by mass of the ceramic raw material. From the viewpoint of suppressing the occurrence of breakage 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, per 100 parts by mass of the ceramic raw material. The binder may be used alone or in combination of two or more types.

The dispersant may be ethylene glycol, dextrin, fatty acid soap, polyether polyol, or the like. The dispersant may be used alone or in combination of two or more types. The content of the dispersant is preferably 0 to 2 parts by mass per 100 parts by mass of the ceramic raw material.

The method for plugging the bottom surface of the columnar honeycomb formed body is not particularly limited, and well-known methods can be used. There are no particular limitations on the material of the plugged portion, but ceramics are preferable from the viewpoint 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. It is even more preferable that the plugged portion has the same material composition as the main body of the honeycomb formed body, since this allows the expansion coefficient during firing to be the same, leading to improved durability.

After drying the honeycomb formed body, it is possible to manufacture a columnar honeycomb structure by carrying out degreasing and firing. The conditions for the drying, degreasing and firing processes may be well-known conditions according to the material composition of the honeycomb formed body, and no special explanation is required, but specific examples of conditions are given below.

In the drying step, a conventionally known drying method such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying, etc., can be used. Among these, a drying method that combines hot air drying with microwave drying or dielectric drying is preferred, since it allows the entire molded body to be dried quickly and uniformly.

When forming plugging portions, it is preferable to form plugging portions on both bottom surfaces of the dried honeycomb formed body and then dry the plugging portions. The plugging portions are formed at predetermined positions such that the first cells extend from the inlet side bottom surface to the outlet side bottom surface, have an opening at the inlet side bottom surface and have plugging portions at the outlet side bottom surface, and the second cells extend from the inlet side bottom surface to the outlet side bottom surface, have plugging portions at the inlet side bottom surface and have an opening at the outlet side bottom surface, and the first cells and the second cells are alternately arranged adjacent to each other with a porous partition wall in between.

Next, the degreasing process will be explained. The combustion temperature of the binder is about 200°C, and the combustion temperature of the pore-forming material is about 300 to 1000°C. Therefore, the degreasing process can be carried out by heating the honeycomb formed body to a temperature 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 calcined body.

The firing process can be carried out by, for example, heating the calcined body to 1350 to 1600°C and holding it for 3 to 10 hours, depending on the material composition of the honeycomb molded body. In this way, a columnar honeycomb structure is produced, which includes a plurality of first cells that extend from the inlet side bottom surface to the outlet side bottom surface, have an open inlet side bottom surface and have plugging portions at the outlet side bottom surface, and a plurality of second cells that extend from the inlet side bottom surface to the outlet side bottom surface, have plugging portions at the inlet side bottom surface and have an open outlet side bottom surface, and the plurality of first cells and the plurality of second cells are arranged alternately adjacent to each other with porous partition walls in between.

Next, a porous film is formed on the surface of the first cell of the columnar honeycomb structure that has undergone the firing process. First, a process is carried out in which an aerosol containing ceramic particles is sprayed toward the center of the inlet side bottom surface of the columnar honeycomb structure in a direction perpendicular to the inlet side bottom surface while applying suction force to the outlet side bottom surface to suck the sprayed aerosol from the inlet side bottom surface, thereby adhering the ceramic particles to the surface of the first cell. At this time, it is possible to increase the proportion of ceramic particles that adhere to the center of the columnar honeycomb structure by shortening the distance between the aerosol spray nozzle and the inlet side bottom surface, increasing the aerosol spray speed, or increasing the suction force applied to the outlet side bottom surface. For example, the distance between the aerosol spray nozzle and the inlet side bottom surface can be 500 mm to 2000 mm, and the aerosol spray speed can be 2 to 80 m/s.

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

It is also desirable for the ceramic particles in the aerosol to have minimal agglomeration. Suppressing the agglomeration of the ceramic particles in the aerosol can promote the reduction of the average pore size of the porous membrane.

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

When carrying out the process of adhering ceramic particles to the surface of the first cell, in order to increase the thickness of the porous film from the inlet side bottom surface of the columnar honeycomb structure filter toward the outlet side bottom surface, it is preferable to increase the suction force at the outlet side bottom surface and increase the flow rate of the aerosol flowing through the columnar honeycomb structure. Specifically, it is preferable to set the lower limit of the average flow rate of the aerosol flowing into the columnar honeycomb structure (= aerosol flow rate / area of the inlet side bottom surface) to 2 m/s or more, and more preferably 4 m/s or more. In addition, in order to maintain a high porosity of the porous film, it is preferable to set the upper limit of the average flow rate of the aerosol flowing into the columnar honeycomb structure to 80 m/s or less, and more preferably 60 m/s or less.

Figure 8 shows a schematic diagram of a particle attachment device (500) suitable for carrying out a process of attaching ceramic particles to the surface of the first cell of a columnar honeycomb structure (580). The particle attachment device (500) includes an aerosol generator (510), a laser diffraction type 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).

The aerosol generator (510) comprises:
A cylinder (513) containing ceramic particles (512);
a piston or screw (514) for sending the ceramic particles (512) contained in the cylinder (513) through a cylinder outlet (513e);
a crushing chamber (515) communicating with a cylinder outlet (513e), the crushing chamber (515) including a rotor (516) for crushing the ceramic particles (512) discharged from the cylinder outlet (513e);
a gas flow path (517) for flowing a medium gas, the gas flow path (517) communicating with a crushing chamber outlet (515e) midway and capable of spraying an aerosol containing the medium gas and ceramic particles (512) from a nozzle (511) attached to the tip of the gas flow path (517);
Equipped with.

The aerosol generator (510) can spray aerosol from the nozzle (511). The cylinder (513) contains ceramic particles (512) adjusted to a predetermined particle size distribution. The ceramic particles (512) contained 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 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). For example, a rotating brush can be used as the rotating body (516). The rotating body (516) can be driven by a motor, and its rotation speed can be configured to be controllable.

The ceramic particles (512) discharged from the crushing chamber outlet (515e) are mixed with the medium gas flowing through the gas flow path (517) to become an aerosol, which is then sprayed from the nozzle (511). It is preferable that the nozzle (511) is installed at a position and orientation such that the aerosol is sprayed in a direction perpendicular to the inlet bottom surface toward the center of the inlet bottom surface of the columnar honeycomb structure (580) held by the holder (540).

The medium gas can be a compressed gas such as compressed air with a pressure adjustment, thereby controlling the flow rate of the aerosol sprayed from the nozzle (511). As the medium gas, it is preferable to use dry air (e.g., with a dew point of 10° C. or less) in order to suppress the aggregation of ceramic particles. In this specification, the "dew point" refers to a value measured by a polymer-type capacitance-type dew point meter conforming to JIS Z8806:2001.
Fine ceramic particles have a tendency to agglomerate. However, by using the aerosol generator (510) according to the present embodiment, the crushed ceramic particles are sprayed, so that the ceramic particles having the desired particle size distribution and suppressed from agglomerating can be attached to the surface of the first cell.

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

The gas introduction pipe (530) has a plurality of ventilation holes (531) on its wall, which allows it to suck in ambient gas such as air. This allows the flow rate of gas flowing into the gas introduction pipe (530) to be adjusted according to the suction force from the blower (570). A filter may be installed in the ventilation holes (531) since they may draw in agglomerated powder, honeycomb fragments, and dust.

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 sprayed from the aerosol generator (510) can be measured in real time. This makes it possible to monitor whether ceramic particles with the desired particle size distribution are being supplied to the columnar honeycomb structure (580).

An exhaust pipe (560) connected to a blower (570) is provided downstream of the outlet bottom surface of the columnar honeycomb structure (580). Therefore, when the aerosol from which the ceramic particles have been removed is discharged from the outlet bottom surface of the columnar honeycomb structure (580), it passes through the exhaust pipe (560) and is then exhausted through the blower (570).

As the process of adhering ceramic particles to the surface of the first cell continues, the pressure loss between the inlet side bottom surface and the outlet side bottom surface of the columnar honeycomb structure increases as the amount of adhering ceramic particles increases. Therefore, by determining the relationship between the amount of adhering ceramic particles and the pressure loss in advance, the end point of the process of adhering ceramic particles to the surface of the first cell can be determined based on the pressure loss. Therefore, the particle adhering device (500) can be equipped with a differential pressure gauge (550) to measure the pressure loss between the inlet side bottom surface and the outlet side bottom surface of the columnar honeycomb structure (580), and the end point of the process can be determined based on the value of the differential pressure gauge.

When the process of adhering ceramic particles to the surface of the first cell is carried out, ceramic particles are attached to the inlet side bottom surface of the columnar honeycomb structure (580), so it is preferable to remove the ceramic particles by suction using a vacuum or the like while smoothing the inlet side bottom surface with a tool such as a scraper.

Then, the columnar honeycomb structure with the ceramic particles attached to the surface of the first cell is heat-treated under conditions of keeping the maximum temperature at 1000°C or higher for at least 1 hour, typically keeping the maximum temperature at 1100°C to 1400°C for 1 to 6 hours, to complete the columnar honeycomb structure filter. The heat treatment can be performed, for example, by placing the columnar honeycomb structure in an electric furnace or gas furnace. The heat treatment bonds the ceramic particles together and burns them to the partition walls in the first cells, forming a porous film on the surface of the first cells. When the heat treatment is performed under oxygen-containing conditions such as air, a surface oxide film is formed on the ceramic particle surfaces, promoting the bonding of the ceramic particles together. This results in a porous film that is difficult to peel off.

The configuration of the aerosol generator that can be used in a particle attachment device capable of carrying out the process of attaching ceramic particles to the surface of the first cell of a columnar honeycomb structure is not limited to the above-mentioned embodiment, and other embodiments can be adopted. For illustrative purposes, another configuration example of the aerosol generator is shown diagrammatically in Figures 9 and 10.

The aerosol generator (410) shown in FIG.
a medium gas flow passage (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 the ceramic particles (412) from the outer periphery side of the medium gas flow path (417) toward the inside of the medium gas flow path (417);
A nozzle (411) attached to the tip of the medium gas flow path (417) and capable of spraying an aerosol;
a flow path (413) for suction-transporting ceramic particles (412), the flow path (413) having an outlet (413e) communicating with the supply port (417i);
a container (419) for containing the ceramic particles (412) and supplying the ceramic particles (412) to a flow path (413) for suction and transport;
has.

For example, a funnel can be used for the storage section (419). Ceramic particles adjusted to a predetermined particle size distribution are stored in the storage section (419). The ceramic particles (412) stored in the storage section (419) are transported from the outlet (419e) provided at the bottom of the storage section (419) through the flow path (413) to the outlet (413e) by the suction force from the medium gas flow path (417), and then introduced into the medium gas flow path (417) from the supply port (417i). At this time, the surrounding gas (typically air) sucked from the inlet (419i) of the storage section is also introduced into the medium gas flow path (417) through the flow path (413) together with the ceramic particles (412). In this embodiment, the outlet (413e) and the supply port (417i) are common. In addition, in this embodiment, the ceramic particles (412) are introduced into the medium gas flow path (417) from a direction approximately perpendicular to the flow direction of the medium gas flowing through the medium gas flow path (417).

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), and are crushed and mixed to form an aerosol, which is then sprayed from the nozzle (411). The nozzle (411) is preferably installed at a position and orientation such that the aerosol is sprayed in a direction perpendicular to the inlet bottom surface of the columnar honeycomb structure. More preferably, the nozzle (411) is installed at a position and orientation such that the aerosol is sprayed in a direction perpendicular to the inlet bottom surface toward the center of the inlet bottom surface.

The ceramic particles (412) are preferably supplied to the container (419) using, but not limited to, a powder volumetric feeder (4111) such as a screw feeder or a belt conveyor. The ceramic particles (412) discharged from the powder volumetric feeder (4111) can be allowed to fall into the container (419) by gravity.

In a preferred embodiment, the medium gas flow path (417) has a venturi section (417v) in the middle where the flow path is narrowed, and the supply port (417i) is provided downstream of the most narrowed part of the venturi section (417v). When the medium gas flow path (417) has the venturi section (417v), the speed of the medium gas passing through the venturi section (417v) increases, so that the medium gas can be collided at a higher speed against the ceramic particles (412) supplied downstream of the venturi section (417v), thereby improving the crushing force. In order to increase the crushing force by the medium gas, it is more preferable that the supply port (417i) is provided downstream of the most narrowed part of the venturi section (417v) and adjacent to that part. This configuration can be achieved, for example, by connecting the medium gas flow path (417) and the flow path (413) for suction transport using a venturi ejector (4110).

When the Venturi ejector (4110) is used, for example, when the medium gas is flowed into the medium gas flow path (417), a large suction force can be applied to the flow path (413) for suction and transport, and the flow path (413) for suction and transport can be prevented from being clogged with 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 and transport is clogged with the ceramic particles (412).

The flow rate of the aerosol sprayed from the nozzle (411) can be controlled by using a compressed gas such as compressed air with adjusted pressure as the medium gas. It is preferable to use dry air (e.g., with a dew point of 10°C or less) as the medium gas in order to suppress agglomeration of the ceramic particles.

Fine ceramic particles have a tendency to agglomerate. However, by using the aerosol generator (410) of this embodiment, it is possible to spray ceramic particles with the desired particle size distribution, with reduced agglomeration.

The aerosol generator (810) shown in FIG.
A belt feeder (814) for conveying the ceramic particles (812);
a crushing chamber (815) for receiving the ceramic particles (812) conveyed by the belt feeder (814) and having a rotor (816) for crushing the received ceramic particles (812);
a first gas flow passage (817) for flowing a first medium gas, the first gas flow passage (817) communicating with a disintegration chamber outlet (815e) midway;
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) midway and capable of spraying an aerosol containing the first medium gas, the second medium gas, and ceramic particles (812) from a nozzle (811) attached to the tip of the second gas flow path (813);
Equipped with.

The aerosol generator (810) has a container (819) for containing ceramic particles (812). The ceramic particles (812) in the container (819) are preferably stirred by a stirrer (818). An outlet (819e) for the ceramic particles (812) is provided at the bottom of the container (819). The ceramic particles (812) discharged from the outlet (819e) are transported by a belt feeder (814) to the inlet (815in) of the crushing chamber (815).

The ceramic particles (812) introduced into the crushing chamber (815) move within the crushing chamber (815) while being crushed by the rotating body (816), and are discharged from the crushing chamber outlet (815e). For example, a rotating brush can be used as the rotating body (816). The rotating body (816) can be driven by a motor, and its rotation speed can be controlled.

Fine ceramic particles have a tendency to agglomerate. However, by using the aerosol generator (810) according to this embodiment, crushed ceramic particles are sprayed, making it possible to adhere ceramic particles with the desired particle size distribution, with reduced agglomeration, to the surface of the first cell.

The ceramic particles (812) discharged from the disintegration chamber outlet (815e) are mixed with the first medium gas flowing through the first gas flow passage (817) and head toward the outlet (817e) of the first gas flow passage (817). The second gas flow passage (813) is connected to the outlet (817e) of the first gas flow passage (817) on the way, 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 passage (813). The aerosol is then sprayed from a nozzle (811) attached to the tip of the second gas flow passage (813). Although an ambient gas such as air may be used as the first medium gas, it is preferable to use dry air (e.g., with a dew point of 10°C or less) in order to suppress the aggregation of the ceramic particles. The first medium gas may be transported only by suction force from the second gas flow passage, but may also be compressed using a compressor or the like. By using a compressed gas such as compressed air with adjusted pressure as the second medium gas, the flow rate of the aerosol sprayed from the nozzle (811) can be controlled. It is preferable to use dry air as the second medium gas as well, as with the first medium gas.

The first gas flow path (817) and the second gas flow path (813) can be connected using an ejector (822), particularly a venturi ejector. When an ejector (822), particularly a venturi ejector, is used, in addition to the effect of the ceramic particles (812) being 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 the ceramic particles (812) are crushed by the second medium gas, thereby obtaining a high aggregation suppression effect. When the ejector (822) is used, for example, when the second medium gas is flowed into the second gas flow path (813) as a driving fluid, a large suction force can be applied to the first gas flow path (817), and the first gas flow path (817) can be prevented from being clogged by the ceramic particles (812). The ejector (822) is also effective as a means for removing ceramic particles when the first gas flow path (817) becomes clogged with ceramic particles (812).

The following examples are provided to better understand the present invention and its advantages, but the present invention is not limited to these examples.

Example 1
(1) Manufacturing of columnar honeycomb structure filter 3 parts by mass of pore former, 55 parts by mass of dispersion medium, 6 parts by mass of organic binder, and 1 part by mass of dispersant were added to 100 parts by mass of cordierite raw material, and mixed and kneaded to prepare a clay. Alumina, aluminum hydroxide, kaolin, talc, and silica were used as the cordierite raw material. Water was used as the dispersion medium, a water-absorbent polymer was used as the pore former, hydroxypropyl methylcellulose was used as the organic binder, and fatty acid soap was used as the dispersant.

The clay was placed in an extrusion molding machine and extruded through a die of a specified shape to obtain a cylindrical honeycomb molded body. The obtained honeycomb molded body was then dielectrically dried and hot air dried, after which both bottom surfaces were cut to the specified dimensions to obtain a dried honeycomb body.

The obtained dried honeycomb body was plugged with cordierite so that the first and second cells were arranged alternately adjacent to each other, and then heated and degreased at approximately 200°C in an air atmosphere, and then fired at 1,420°C for 5 hours in an air atmosphere to obtain a columnar honeycomb structure.

The specifications of the columnar honeycomb structure are as follows.
Overall shape: Cylinder with diameter 132 mm x height 120 mm Cell shape in cross section perpendicular to the cell flow direction: Square Cell density (number of cells per unit cross-sectional area): 200 cpsi
Partition thickness: 8 mil (200 μm) (nominal value based on the specifications of the nozzle)

Using a particle attachment device having the configuration shown in Fig. 8, an aerosol containing ceramic particles was sprayed toward the center of the inlet side bottom surface of the columnar honeycomb structure produced above in a direction perpendicular to the inlet side bottom surface, thereby attaching the ceramic particles to the surfaces of the first cells. The operating conditions of the particle attachment device are as follows.
Aerosol generator: PALAS RBG2000
Rotating body: rotating brush Ceramic particles contained in container: SiC particles Median diameter (D50): 2.4 μm
D10: 1.1 μm
D90: 4.5 μm
(Based on cumulative particle size distribution on a volume basis measured by laser diffraction/scattering method)
Weight of sprayed ceramic particles: 6.0 g
・Medium gas: Compressed dry air (dew point below 10℃)
Ambient gas: Air Average flow velocity of aerosol flowing into columnar honeycomb structure: 3 m/s
Laser diffraction particle size distribution measuring device: InsitecSpray manufactured by MALVERN Operating time: 20 seconds Aerosol generator nozzle inner diameter: Φ8 mm
Distance from the nozzle tip of the aerosol generator to the bottom surface of the inlet side of the columnar honeycomb structure: 1000 mm
Aerosol ejection speed: 20 m/s

While the particle deposition device was in operation, the volumetric particle size distribution of the ceramic particles sprayed from the aerosol was measured using a laser diffraction particle size distribution analyzer, and the median diameter (D50) was 3.0 μm.

The ceramic particles attached to the bottom inlet surface of the columnar honeycomb structure thus obtained were removed by vacuum suction. The columnar honeycomb structure was then placed in an electric furnace and heat-treated in an air atmosphere at a maximum temperature of 1200°C for 2 hours, forming a porous film on the surface of the first cell and obtaining a columnar honeycomb structure filter. The columnar honeycomb structure filters were produced in the number required to perform the following characteristic evaluations.

(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 by the above-mentioned method. The 3D shape measuring machine used for the measurement was a VR-3200 manufactured by Keyence Corporation. The positions where the average thickness of the porous film was measured and the average thickness are summarized in Table 1-1. The extension direction of the first cell of the columnar honeycomb structure filter was set as the extension direction of the coordinate axis, and the coordinate value of the inlet side bottom surface was set as 0 and the coordinate value of the outlet side bottom surface was set as X, to define the coordinate value.

The porosity of the porous membrane and partition walls of the columnar honeycomb structure filter obtained by the above manufacturing method was measured by the method described above. The equipment used to measure the porosity of the porous membrane was an FE-SEM (model: ULTRA55 (manufactured by ZEISS)) and image analysis software HALCON (Lynx Corporation, 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.

The columnar honeycomb structure filter obtained by the above manufacturing method was measured for "pressure loss" and "collection efficiency (%)".
[Pressure loss]
Exhaust gas discharged from a 1.2L direct injection gasoline engine was introduced at 700°C and a flow rate of 600 ^m3 /h, and the pressures at the inlet and outlet sides of the columnar honeycomb structure filter were measured. The pressure difference between the inlet and outlet sides was calculated to determine the pressure loss (kPa) of the honeycomb filter. 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 accelerated to 60 km/hr within 10 seconds immediately after starting driving, and then the speed was reduced by 20 km/hr every 20 seconds. The cumulative number of soot particles discharged after the driving mode was taken as the number of soot particles of the exhaust gas purification device to be evaluated, 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.

In addition, a porous membrane was formed in the same manner as in Example 1, 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, and a height of 120 mm. The pressure loss and collection efficiency were measured, and the same results as above were obtained.

Example 2
(1) Production of Pillar Honeycomb Structure Filter A pillar honeycomb structure was obtained under the same production conditions as in Example 1.

For the columnar honeycomb structure produced above, an aerosol generator with the structure shown in Fig. 9 using a Venturi ejector ISO 5011 dispersion nozzle (manufactured by PALAS) was used, and a particle attachment device with the same structure as in Example 1 was used to spray an aerosol containing ceramic particles toward the center of the inlet side bottom surface of the columnar honeycomb structure in a direction perpendicular to the inlet side bottom surface, thereby attaching the ceramic particles to the surface of the first cell. The operating conditions of the particle attachment 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 cumulative particle size distribution on a volume basis measured by laser diffraction/scattering method)
Weight of sprayed ceramic particles: 6.0 g
・Medium gas: Compressed dry air (dew point below 10℃)
Ambient gas: Air Average flow velocity of aerosol flowing into columnar honeycomb structure: 3 m/s
Laser diffraction particle size distribution measuring device: InsitecSpray manufactured by MALVERN Operating time: 20 seconds Aerosol generator nozzle inner diameter: Φ8 mm
Distance from the nozzle tip of the aerosol generator to the bottom surface of the inlet side of the columnar honeycomb structure: 1000 mm
Aerosol ejection speed: 20 m/s

While the particle deposition device was in operation, the volumetric particle size distribution of the ceramic particles sprayed from the aerosol was measured using a laser diffraction particle size distribution analyzer, and the median diameter (D50) was 2.8 μm.

The ceramic particles attached to the bottom inlet surface of the columnar honeycomb structure thus obtained were removed by vacuum suction. The columnar honeycomb structure was then placed in an electric furnace and heat-treated in an air atmosphere at a maximum temperature of 1200°C for 2 hours, forming a porous film on the surface of the first cell and obtaining a columnar honeycomb structure filter. The columnar honeycomb structure filters were produced in the number required to perform the following characteristic evaluations.

(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.

The porosity of the porous membrane and 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.

The "pressure loss" and "capture 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.

Example 3
(1) Production of Pillar Honeycomb Structure Filter A pillar honeycomb structure was obtained under the same production conditions as in Example 1.

For the columnar honeycomb structure produced above, an aerosol containing ceramic particles was sprayed in a direction perpendicular to the inlet bottom surface toward the center of the inlet bottom surface of the columnar honeycomb structure using a particle attachment device having the same configuration as in Example 1, thereby attaching the ceramic particles to the surfaces of the first cells. The operating conditions of the particle attachment device are as follows.
Aerosol generator: PALAS RBG2000
Ceramic particles contained in the container: SiC particles Median diameter (D50): 2.4 μm
D10: 1.1 μm
D90: 4.5 μm
(Based on cumulative particle size distribution on a volume basis measured by laser diffraction/scattering method)
Weight of sprayed ceramic particles: 6.0 g
・Medium gas: Compressed dry air (dew point below 10℃)
Ambient gas: air Average flow velocity of aerosol flowing into the columnar honeycomb structure: 8 m/s
Laser diffraction particle size distribution measuring device: InsitecSpray manufactured by MALVERN Operating time: 20 seconds Aerosol generator nozzle inner diameter: Φ8 mm
Distance from the nozzle tip of the aerosol generator to the bottom surface of the inlet side of the columnar honeycomb structure: 1000 mm
Aerosol ejection speed: 40 m/s

While the particle deposition device was in operation, the volumetric particle size distribution of the ceramic particles sprayed from the aerosol was measured using a laser diffraction particle size distribution analyzer, and the median diameter (D50) was 3.1 μm.

The ceramic particles attached to the bottom inlet surface of the columnar honeycomb structure thus obtained were removed by vacuum suction. The columnar honeycomb structure was then placed in an electric furnace and heat-treated in an air atmosphere at a maximum temperature of 1200°C for 2 hours, forming a porous film on the surface of the first cell and obtaining a columnar honeycomb structure filter. The columnar honeycomb structure filters were produced in the number required to perform the following characteristic evaluations.

(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.

The porosity of the porous membrane and 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.

The "pressure loss" and "capture 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.

Example 4
(1) Production of Pillar Honeycomb Structure Filter A pillar honeycomb structure was obtained under the same production conditions as in Example 1.

For the columnar honeycomb structure produced above, an aerosol generator having the structure shown in Fig. 9 was used, and a particle attachment device having the same configuration as in Example 1 was used to spray an aerosol containing ceramic particles toward the center of the inlet side bottom surface of the columnar honeycomb structure in a direction perpendicular to the inlet side bottom surface, thereby attaching the ceramic particles to the surface of the first cell. The operating conditions of the particle attachment device are as follows.
Aerosol generator: PISCO VRL50-080608
Ceramic particles contained in the container: SiC particles Median diameter (D50): 2.4 μm
D10: 1.1 μm
D90: 4.5 μm
(Based on cumulative particle size distribution on a volume basis measured by laser diffraction/scattering method)
Weight of sprayed ceramic particles: 6.0 g
・Medium gas: Compressed dry air (dew point below 10℃)
Ambient gas: Air Average flow velocity of aerosol flowing into columnar honeycomb structure: 8 m/s
Laser diffraction particle size distribution measuring device: InsitecSpray manufactured by MALVERN Operating time: 20 seconds Aerosol generator nozzle inner diameter: Φ8 mm
Distance from the nozzle tip of the aerosol generator to the bottom surface of the inlet side of the columnar honeycomb structure: 1000 mm
Aerosol ejection speed: 40 m/s

While the particle deposition device was in operation, the volumetric particle size distribution of the ceramic particles sprayed from the aerosol was measured using a laser diffraction particle size distribution analyzer, and the median diameter (D50) was 3.2 μm.

The ceramic particles attached to the bottom inlet surface of the columnar honeycomb structure thus obtained were removed by vacuum suction. The columnar honeycomb structure was then placed in an electric furnace and heat-treated in an air atmosphere at a maximum temperature of 1200°C for 2 hours, forming a porous film on the surface of the first cell and obtaining a columnar honeycomb structure filter. The columnar honeycomb structure filters were produced in the number required to perform the following characteristic evaluations.

(2) Property 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.

The porosity of the porous membrane and 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.

The "pressure loss" and "capture 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.

Example 5
(1) Production of Pillar Honeycomb Structure Filter A pillar honeycomb structure was obtained under the same production conditions as in Example 1.

For the columnar honeycomb structure produced above, an aerosol generator having the structure shown in Fig. 10 was used, and a particle attachment device having the same configuration as in Example 1 was used to spray an aerosol containing ceramic particles toward the center of the inlet side bottom surface of the columnar honeycomb structure in a direction perpendicular to the inlet side bottom surface, thereby attaching the ceramic particles to the surface of the first cell. The operating conditions of the particle attachment device are as follows.
Aerosol generator: PALAS BEG1000
Rotating body: rotating brush Ceramic particles contained in container: SiC particles Median diameter (D50): 2.4 μm
D10: 1.1 μm
D90: 4.5 μm
(Based on cumulative particle size distribution on a volume basis measured by laser diffraction/scattering method)
Weight of sprayed ceramic particles: 6.0 g
First medium gas: Compressed dry air (dew point below 10°C)
Second medium gas: Compressed dry air (dew point below 10°C)
Ambient gas: air Average flow velocity of aerosol flowing into the columnar honeycomb structure: 6 m/s
Laser diffraction particle size distribution measuring device: InsitecSpray manufactured by MALVERN Operating time: 20 seconds Aerosol generator nozzle inner diameter: Φ8 mm
Distance from the nozzle tip of the aerosol generator to the bottom surface of the inlet side of the columnar honeycomb structure: 1500 mm
Aerosol ejection speed: 50 m/s

While the particle deposition device was in operation, the volumetric particle size distribution of the ceramic particles sprayed from the aerosol was measured using a laser diffraction particle size distribution analyzer, and the median diameter (D50) was 2.7 μm.

The ceramic particles attached to the bottom inlet surface of the columnar honeycomb structure thus obtained were removed by vacuum suction. The columnar honeycomb structure was then placed in an electric furnace and heat-treated in an air atmosphere at a maximum temperature of 1200°C for 2 hours, forming a porous film on the surface of the first cell and obtaining a columnar honeycomb structure filter. The columnar honeycomb structure filters were produced in the number required to perform the following characteristic evaluations.

(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.

The porosity of the porous membrane and 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.

The "pressure loss" and "capture 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.

Example 6
(1) Production of Pillar Honeycomb Structure Filter A pillar honeycomb structure was obtained under the same production conditions as in Example 1.

For the columnar honeycomb structure produced above, an aerosol generator having the structure shown in Fig. 10 was used, and a particle attachment device having the same configuration as in Example 1 was used to spray an aerosol containing ceramic particles toward the center of the inlet side bottom surface of the columnar honeycomb structure in a direction perpendicular to the inlet side bottom surface, thereby attaching the ceramic particles to the surface of the first cell. The operating conditions of the particle attachment device are as follows.
Aerosol generator: PALAS BEG1000
Rotating body: rotating brush Ceramic particles contained in container: SiC particles Median diameter (D50): 2.4 μm
D10: 1.1 μm
D90: 4.5 μm
(Based on cumulative particle size distribution on a volume basis measured by laser diffraction/scattering method)
Weight of sprayed ceramic particles: 6.0 g
First medium gas: Compressed dry air (dew point below 10°C)
Second medium gas: Compressed dry air (dew point below 10°C)
Ambient gas: air Average flow rate of aerosol flowing into the columnar honeycomb structure: 4 m/s
Laser diffraction particle size distribution measuring device: InsitecSpray manufactured by MALVERN Operating time: 20 seconds Aerosol generator nozzle inner diameter: Φ8 mm
Distance from the nozzle tip of the aerosol generator to the bottom surface of the inlet side of the columnar honeycomb structure: 1500 mm
Aerosol ejection speed: 40 m/s

While the particle deposition device was in operation, the volumetric particle size distribution of the ceramic particles sprayed from the aerosol was measured using a laser diffraction particle size distribution analyzer, and the median diameter (D50) was 2.6 μm.

The ceramic particles attached to the bottom inlet surface of the columnar honeycomb structure thus obtained were removed by vacuum suction. The columnar honeycomb structure was then placed in an electric furnace and heat-treated in an air atmosphere at a maximum temperature of 1200°C for 2 hours, forming a porous film on the surface of the first cell and obtaining a columnar honeycomb structure filter. The columnar honeycomb structure filters were produced in the number required to perform the following characteristic evaluations.

(2) Property 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.

The porosity of the porous membrane and 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.

The "pressure loss" and "capture 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.

<Comparative Example 1>
(1) Production of Pillar Honeycomb Structure Filter A pillar honeycomb structure was obtained under the same production conditions as in Example 1.

The columnar honeycomb structure produced above was held in a holder so that the cell extension direction was vertical, and a slurry containing SiC particles was poured from above toward the bottom surface of the inlet side. At this time, the slurry was allowed to flow evenly over the entire bottom surface of the inlet side. The median diameter (D50) of the SiC particles contained in the slurry was 2.4 μm. The SiC particles in the slurry adhered to the surface of the first cell, while the moisture that had permeated the columnar honeycomb structure was discharged from the bottom surface of the outlet side. The bottom surface of the outlet side was connected to a drain pipe, and the discharged moisture was collected in a container. When the slurry was poured into the columnar honeycomb structure, the air in the collection container was sucked in by a blower, and a suction force was applied to the bottom surface of the outlet side of the columnar honeycomb structure, promoting adhesion of the membrane material to the partition surface.

The ceramic particles attached to the bottom inlet surface of the columnar honeycomb structure thus obtained were removed by vacuum suction. The columnar honeycomb structure was then placed in an electric furnace and heat-treated in an air atmosphere at a maximum temperature of 1200°C for 2 hours, forming a porous film on the surface of the first cell and obtaining a columnar honeycomb structure filter. The columnar honeycomb structure filters were produced in the number required to perform the following characteristic evaluations.

(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 7-1.

The porosity of the porous membrane and 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 7-2.

The "pressure loss" and "capture 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.

Example 7
(1) Production of Pillar Honeycomb Structure Filter A pillar honeycomb structure was obtained under the same production conditions as in Example 1.

For the columnar honeycomb structure produced above, an aerosol generator having the structure shown in Fig. 9 was used, and a particle attachment device having the same configuration as in Example 1 was used to spray an aerosol containing ceramic particles toward the center of the inlet side bottom surface of the columnar honeycomb structure in a direction perpendicular to the inlet side bottom surface, thereby attaching the ceramic particles to the surface of the first cell. The operating conditions of the particle attachment device are as follows.
Aerosol generator: PISCO VRL50-080608
Ceramic particles contained in the container: SiC particles Median diameter (D50): 2.4 μm
D10: 1.1 μm
D90: 4.5 μm
(Based on cumulative particle size distribution on a volume basis measured by laser diffraction/scattering method)
Weight of sprayed ceramic particles: 6.0 g
・Medium gas: Compressed dry air (dew point below 10℃)
Ambient gas: air Average flow velocity of aerosol flowing into the columnar honeycomb structure: 8 m/s
Laser diffraction particle size distribution measuring device: InsitecSpray manufactured by MALVERN Operating time: 20 seconds Aerosol generator nozzle inner diameter: Φ8 mm
Distance from the nozzle tip of the aerosol generator to the bottom surface of the inlet side of the columnar honeycomb structure: 1000 mm
Aerosol ejection speed: 20 m/s

While the particle deposition device was in operation, the volumetric particle size distribution of the ceramic particles sprayed from the aerosol was measured using a laser diffraction particle size distribution analyzer, and the median diameter (D50) was 2.4 μm.

The ceramic particles attached to the bottom inlet surface of the columnar honeycomb structure thus obtained were removed by vacuum suction. The columnar honeycomb structure was then placed in an electric furnace and heat-treated in an air atmosphere at a maximum temperature of 1200°C for 2 hours, forming a porous film on the surface of the first cell and obtaining a columnar honeycomb structure filter. The columnar honeycomb structure filters were produced in the number required to perform the following characteristic evaluations.

(2) Property 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.

The porosity of the porous membrane and 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.

The "pressure loss" and "capture 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.

100 Columnar honeycomb structure filter 102 Outer peripheral side wall 104 Inlet side bottom surface 106 Outlet side bottom surface 108 First cell 109 Plugged portion 110 Second cell 112 Partition wall 114 Porous membrane 120 Center portion 130 Outer peripheral portion 410 Aerosol generator 411 Nozzle 412 Ceramic particles 413 Flow path 413e Outlet 417 Medium gas flow path 417i Supply port 419 Storage 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 type particle size distribution measuring device 530 Gas introduction pipe 531 Vent 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 passage 814 Belt feeder 815 Crushing chamber 815in Inlet 815e Crushing chamber outlet 816 Rotor 817 First gas flow passage 817e Outlet 818 Agitator 819 Container 819e Discharge port 822 Ejector

Claims (8)

A columnar honeycomb structure filter comprising: a plurality of first cells extending from an inlet side bottom surface to an outlet side bottom surface, the inlet side bottom surface being open and having plugging portions 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, the inlet side bottom surface being plugging portions 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 being alternately arranged adjacent to each other with a porous partition wall therebetween,
a porous film having a porosity higher than that of the partition wall is formed on a surface of each of the first cells;
A columnar honeycomb structure filter in which the extension direction of the first cell of the columnar honeycomb structure filter is the extension 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
During the ceremony,
In a cross section perpendicular to the extending direction of the first cell of the columnar honeycomb structure filter at the coordinate value 0.2X, the average thickness of the porous film in the outer periphery is _B1 , and the average thickness of the porous film in the center is _A1 ,
In a cross section perpendicular to the extending direction of the first cell of the columnar honeycomb structure filter at the coordinate value 0.5X, the average thickness of the porous film in the outer periphery is _B2 , and the average thickness of the porous film in the center is _A2 ,
In a cross section perpendicular to the extending direction of the first cells of the columnar honeycomb structure filter at the coordinate value 0.8X, the average thickness of the porous film in the outer periphery is defined as _B3 , and the average thickness of the porous film in the center is defined as _A3 . 2. The columnar honeycomb structure filter according to claim 1, wherein the following relationship is satisfied:
(A ₁ +A ₂ +A ₃ )/(B ₁ +B ₂ +B ₃ )≧1. 8 2. The columnar honeycomb structure filter according to claim 1, wherein the following relationship is satisfied:
(A ₁ +A ₂ +A ₃ )/(B ₁ +B ₂ +B ₃ ) ≧2.0 The columnar honeycomb structure filter according to any one of claims 1 to 3 , wherein the following relationships (1) and (2) are satisfied for a first cell located at the center of a cross section perpendicular to the extension direction of the first cell of the columnar honeycomb structure filter.
(1) The ratio (A ₂ /A ₁ ) of the average thickness A ₂ of the porous membrane at the coordinate value 0.5X to the average thickness A ₁ of the porous membrane at the coordinate value 0.2X is 1.05 to 5.0.
(2) The ratio (A ₃ /A ₁ ) of the average thickness A ₃ of the porous membrane at the coordinate value 0.8X to the average thickness A ₁ of the porous membrane at the coordinate value 0.2X is 1.05 to 5.0. The columnar honeycomb structure filter according to any one of claims 1 to 4 , wherein the following relationship is established:
A ₁ > B ₁ , A ₂ > B ₂ , and A ₃ > B ₃ 6. The columnar honeycomb structure filter according to claim 1 , wherein the main component of the porous film is silicon carbide, alumina, silica, cordierite or mullite. The columnar honeycomb structure filter according to any one of claims 1 to 6 , wherein the porosity of the porous film is 70 to 85%. 8. The columnar honeycomb structure filter according to claim 1 , wherein the average thickness of the entire porous film is 4 to 50 μm.