Honeycomb filter and exhaust gas treatment system

Abstract

The present invention provides a honeycomb filter that can suppress the passage of particulate matter while suppressing an increase in pressure loss. [Solution] The honeycomb filter 1 comprises a honeycomb structure 2 having an outer peripheral wall 20 and partition walls 21 disposed inside the outer peripheral wall 20 and partitioning a plurality of cells 22 that form a flow path extending from a first end face 2a to a second end face 2b, and a sealing portion 3 provided on the cell 22 at either the first end face 2a or the second end face 2b, wherein the cell 22 includes at least one imperfect sealing cell 4 in which an opening 3a is formed in the sealing portion 3, and when light is irradiated on either the first end face 2a or the second end face 2b, light leakage can be confirmed on the other end face 2b.

Description

Technical Field

[0001] The present invention relates to a honeycomb filter and an exhaust gas treatment system.

Background Art

[0002] As a means for reducing the emission amount of particulate matter contained in the exhaust gas discharged from an internal combustion engine, a particulate filter is provided in the exhaust gas flow path to collect the particulate matter on the particulate filter. In recent years, a particulate filter with high collection efficiency has been used due to the tightening of the exhaust gas particle number regulation. However, as a trade-off, the pressure loss of the particulate filter increases.

[0003] Patent Documents 1 to 4 disclose using a honeycomb filter with cells sealed as the above-described particulate filter. In particular, Patent Documents 1 and 4 disclose omitting the sealing of specific cells located on the outer periphery. By omitting the sealing, the pressure loss can be reduced.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] [[ID=5​​

[0006] The present invention was made to solve the above-mentioned problems, and one of its objectives is to provide a honeycomb filter and exhaust gas treatment system that can suppress the passage of particulate matter while suppressing an increase in pressure loss. [Means for solving the problem]

[0007] [1] In one embodiment, the present invention relates to a honeycomb filter comprising a honeycomb structure having an outer peripheral wall and partition walls disposed inside the outer peripheral wall and partitioning a plurality of cells that form a flow path extending from a first end face to a second end face, and a sealing portion provided in the cell at either the first end face or the second end face, wherein the cell includes at least one imperfectly sealed cell in which an opening is formed in the sealing portion and light leakage can be observed on the other of the first and second end faces when light is irradiated on either the first or second end face.

[0008] [2] The present invention may relate to the honeycomb filter described in paragraph 1, wherein the ratio of the total area of ​​the openings in the imperfectly sealed cells to the total area of ​​the imperfectly sealed cells in the cross section of the honeycomb structure perpendicular to the direction in which the cells extend is 5% or more and 90% or less.

[0009] [3] The present invention may relate to the honeycomb filter described in paragraph 2, wherein the ratio of the total area of ​​the openings in all the imperfectly sealed cells to the total area of ​​all the cells in the cross section of the honeycomb structure perpendicular to the direction in which the cells extend is 1400 ppm or less.

[0010] [4] The present invention relates to a honeycomb filter according to any one of paragraphs 1 to 3, wherein the cell comprises a plurality of normal cells provided away from the outer peripheral wall and a plurality of partial cells provided adjacent to the outer peripheral wall and having a partial cross-sectional shape with respect to the plurality of normal cells, and the at least one imperfect sealing cell provided in the plurality of partial cells.

[0011] [5] The present invention may relate to the honeycomb filter according to any one of Items 1 to 4, wherein the porosity of the partition wall is 45% or more and 70% or less, and the thickness of the partition wall is 127 μm or more and 254 μm or less.

[0012] [6] The present invention relates to an exhaust gas treatment system including the honeycomb filter according to any one of Items 1 to 5, which is arranged such that exhaust gas passes through the cell in one embodiment.

Advantages of the Invention

[0013] According to one embodiment of the honeycomb filter and the exhaust gas treatment system of the present invention, since the cell includes at least one incomplete caulking cell in which an opening is formed in the caulking portion and light leakage can be confirmed on the other of the first end face and the second end face when light is irradiated on either the first end face or the second end face, it is possible to suppress an increase in pressure loss while suppressing the passage of particulate matter.

Brief Description of the Drawings

[0014] [Figure 1] It is a front view showing a honeycomb filter according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view of the honeycomb filter along line II-II in FIG. 1. [Figure 3] It is an enlarged view showing region III in FIG. 1. [Figure 4] It is an explanatory view schematically showing a test method for determining whether or not an incomplete caulking cell is provided. [Figure 5] It is a cross-sectional view of an exhaust gas treatment system according to an embodiment of the present invention. [Figure 6] It is a graph showing the relationship between the area ratio of light leakage in the whole and the reduction rate of the collection efficiency in Examples and Comparative Examples.

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments for implementing the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and components can be modified and embodied without departing from the gist thereof. Also, various inventions can be formed by appropriately combining a plurality of components disclosed in each embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components of different embodiments may be appropriately combined.

[0016] Embodiment FIG. 1 is a front view showing a honeycomb filter 1 according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the honeycomb filter 1 taken along line II-II of FIG. 1, FIG. 3 is an enlarged view showing region III of FIG. 1, and FIG. 4 is an explanatory view schematically showing a test method for determining whether an incomplete plugging cell 4 is provided in FIG. 3.

[0017] As shown in FIGS. 1 and 2, the honeycomb filter 1 has a honeycomb structure portion 2 and a plugging portion 3.

[0018] The honeycomb structure portion 2 has an outer peripheral wall 20 and partition walls 21 disposed inside the outer peripheral wall 20. The partition walls 21 define a plurality of cells 22. The plurality of cells 22 form a flow path extending from the first end face 2a to the second end face 2b of the honeycomb structure portion 2.

[0019] The plugging portion 3 is provided in the cell 22 at either the first end face 2a or the second end face 2b. The plugging portion 3 plugs the cell 22. Regarding the plugging, the cell 22 includes a first cell 221 that opens at the first end face 2a and is plugged at the second end face 2b, and a second cell 222 that opens at the second end face 2b and is plugged at the first end face 2a. The first cell 221 and the second cell 222 may be alternately arranged in a direction orthogonal to the direction in which the cell 22 extends.

[0020] As described later, the honeycomb filter 1 may be arranged in the exhaust gas treatment system 5 so that the exhaust gas 5a passes through the cell 22 (see Figure 5). The exhaust gas 5a enters the first cell 221 from the first end face 2a, passes through the partition wall 21 between the first cell 221 and the second cell 222, enters the second cell 222, and can exit the second cell 222 at the second end face 2b. For this reason, the honeycomb filter 1 can be said to be a wall-flow type. When the exhaust gas 5a passes through the partition wall 21, the particulate matter in the exhaust gas 5a cannot pass through the partition wall 21 and remains in the first cell 221. In the exhaust gas treatment system 5, the honeycomb filter 1 can purify the exhaust gas 5a by capturing at least the particulate matter in the exhaust gas 5a.

[0021] As shown in Figure 3, the cell 22 includes at least one incomplete sealed cell 4 in which an opening 3a is formed in the sealing portion 3. The incomplete sealed cell 4 is configured so that when light is shone on either the first end face 2a or the second end face 2b, light leakage can be observed on the other end face of the first end face 2a or the second end face 2b. In the incomplete sealed cell 4, the sealing portion 3 does not completely close the opening of the cell 22 at the first end face 2a and the second end face 2b, but only narrows the opening of the cell 22 at the first end face 2a and the second end face 2b.

[0022] Whether a cell 22 provided with a sealing portion 3 is an incompletely sealed cell 4 is determined by the test method shown in Figure 4. Specifically, the honeycomb filter 1 is placed on the lightbox 6. The lightbox 6 has a housing 60, a light source 61 provided inside the housing 60, and a lid portion 62 provided on the housing 60 so as to be located above the light source 61 and capable of transmitting light from the light source 61. The honeycomb filter 1 is placed on the lightbox 6 so as to be in contact with the lid portion 62, either the first end face 2a or the second end face 2b. Light from the light source 61 is shone through the lid portion 62 onto either the first end face 2a or the second end face 2b, and it is checked whether light leakage occurs from the other end face 2a or the second end face 2b. If light leakage is confirmed in any of the cells 22, that cell 22 is determined to be an incompletely sealed cell 4. Figure 4 shows a configuration in which the honeycomb filter 1 is positioned so that the first end face 2a is in contact with the lid 62, and whether or not light leakage is occurring at the second end face 2b is visually checked. The illuminance from the light source is preferably 5000 lux or more.

[0023] The sealing portion 3 is provided on the cell 22 at either the first end face 2a or the second end face 2b. In other words, every cell 22 is either the first cell 221 or the second cell 222. If no opening 3a is formed in the sealing portion 3 in any of the cells 22, then when light is shone on either the first end face 2a or the second end face 2b, no light leakage can be observed on the other end face 2a or the second end face 2b. Normally, the sealing portion 3 does not transmit light. Light leakage does not include the observation of light attenuated by the sealing portion 3. If light attenuated by the sealing portion 3 is observed on the other end face 2b or the first end face 2a, whether or not light leakage can be confirmed is determined by the brightness of the light observed on the other end face 2b or the first end face 2a or the second end face 2b. Light leakage can be confirmed if the light observed is clearly brighter than other locations by visual inspection.

[0024] As described above, in the exhaust gas treatment system 5, the honeycomb filter 1 collects particulate matter in the exhaust gas 5a. In recent years, the collection efficiency of the honeycomb filter 1 has been increased due to stricter regulations on the number of particles in the exhaust gas 5a, but this comes at the cost of increased pressure loss in the honeycomb filter 1. As described in Patent Documents 1 and 4, in order to suppress the increase in pressure loss, it is conceivable to omit sealing (not provide sealing section 3) for certain cells 22 located on the outer periphery. However, particulate matter may pass through the cells 22 where sealing is omitted, resulting in a decrease in the collection efficiency of particulate matter. In this embodiment, by providing an incompletely sealed cell 4 with an opening 3a formed in the sealing section 3, it is possible to suppress the passage of particulate matter while suppressing the increase in pressure loss.

[0025] Furthermore, during the manufacturing of the honeycomb filter 1, a sealing portion 3 can be formed on the end face of the honeycomb filter base (the honeycomb molded body described later) where a mask has been applied to the cell 22. By intentionally not applying a mask to the cell 22 that should be masked, it is possible to form a cell 22 in which the sealing has been omitted, as shown in Patent Documents 1 and 4. In contrast, by partially making holes in the mask after it has been applied, the sealing is made insufficient, and an opening 3a can be formed in the sealing portion 3. By controlling the size and position of the holes made in the mask, the size of the opening 3a in the incompletely sealed cell 4 can be controlled.

[0026] It is preferable that the ratio of the total area of ​​the openings 3a in the incompletely sealed cells 4 to the total area of ​​the incompletely sealed cells 4 in the cross-section of the honeycomb structure 2 perpendicular to the direction in which the cell 22 extends is between 5% and 90%. A ratio of 5% or more can more reliably suppress the increase in pressure loss. A ratio of 90% or less can more reliably suppress the passage of particulate matter. The area of ​​the openings 3a is measured by image analysis of the first end face 2a or the second end face 2b. The area of ​​the incompletely sealed cells 4 in the cross-section of the honeycomb structure 2 perpendicular to the direction in which the cell 22 extends is measured by image analysis of the same cross-section. Images are taken with a camera having a pixel resolution of 40 μm / pix or less. The honeycomb structure 2 and the sealed part 3 and the openings 3a are separated by binarization processing and their respective areas are determined.

[0027] It is preferable that the ratio of the total area of ​​the openings 3a in all imperfectly sealed cells 4 to the total area of ​​all cells 22 in the cross-section of the honeycomb structure 2 perpendicular to the direction in which the cells 22 extend is 1400 ppm or less. A ratio of 1400 ppm or less ensures more reliable suppression of particulate matter passage. A ratio of 1337 ppm or less is more preferable. A ratio of 70 ppm or more makes it easier to achieve a reduction in pressure loss.

[0028] As shown in Figure 1, the cell 22 includes a plurality of normal cells 23 provided away from the outer peripheral wall 20, and a plurality of partial cells 24 provided adjacent to the outer peripheral wall 20 and having a partial cross-sectional shape relative to the plurality of normal cells 23. In the illustrated embodiment, the shape of the normal cells 23 is square. In contrast, the shape of the partial cells 24 is a square with the outer part of the circle formed by the inner edge of the outer peripheral wall 20 removed.

[0029] Preferably, at least one incomplete sealing cell 4 is provided in multiple partial cells 24. This allows for greater suppression of particulate matter permeation than in normal cells 23. The incomplete sealing cell 4 may or may not be provided in normal cells 23. The incomplete sealing cell 4 may be provided only in multiple partial cells 24.

[0030] It is preferable that the porosity of the partition wall 21 is 45% or more and 70% or less, and the thickness of the partition wall 21 is 127 μm or more and 254 μm or less. A porosity of 45% or more of the partition wall 21 can suppress an increase in pressure loss, and a porosity of 70% or less can reduce the risk of the honeycomb filter 1 becoming brittle and falling off. The porosity is a value measured using a mercury porosimeter. A thickness of 127 μm or more of the partition wall 21 can reduce the risk of a decrease in the strength of the honeycomb filter 1, and a thickness of 254 μm or less can reduce the risk of an increase in pressure loss when the exhaust gas 5a passes through the cell 22. The thickness of the partition wall 21 is a value measured by microscopic observation of a cross-section parallel to the central axis.

[0031] Next, Figure 5 is a cross-sectional view of an exhaust gas treatment system 5 according to an embodiment of the present invention. The exhaust gas treatment system 5 includes the honeycomb filter 1 described above, which is arranged so that the exhaust gas 5a passes through the cell 22. The exhaust gas treatment system 5 may be mounted on a vehicle having an engine (internal combustion engine) and used to purify the exhaust gas 5a from the engine.

[0032] The honeycomb filter 1 and the exhaust gas treatment system 5 will be described in more detail below.

[0033] <About honeycomb filters> In the honeycomb filter 1, the honeycomb structure 2, as shown in Figure 2, has a honeycomb shape with porous partition walls 21 that penetrate from the first end face 2a to the second end face 2b and divide a plurality of cells 22 that form fluid flow paths. The external shape of the honeycomb filter 1 is not limited to the cylindrical shape shown in Figures 1 and 2, but can also include cylindrical shapes with polygonal bases such as elliptical cylinders and square cylinders, and cylindrical shapes with irregular bases.

[0034] Furthermore, the size of the honeycomb filter 1 is preferably such that its length in the central axis direction is 50 to 200 mm. Also, for example, if the outer shape of the honeycomb filter 1 is cylindrical, it is preferable that the diameter of its base surface is 80 to 180 mm. If the shape of the honeycomb filter 1 is other than cylindrical, it is preferable that the area of ​​its base surface is within the same range as the area of ​​the base surface in the case of a cylindrical shape.

[0035] The cell density of the honeycomb filter 1 (i.e., the cell density in a cross-section perpendicular to the central axis of the honeycomb structure 2) is 7.7 to 46.5 cells / cm³. 2 Preferably, 10-40 pieces / cm 2 It is even more preferable that the number be 15-25 per cm. 2 It is particularly preferable that it be 7.7 pieces / cm 2 If the value is less than 46.5 particles / cm², the strength of the honeycomb filter 1 may decrease. 2 If the pressure is too high, there is a risk of increased pressure loss.

[0036] The honeycomb filter 1 preferably has a ratio of the length in the central axis direction to the diameter of the first end face 2a of 0.5 to 1.5, more preferably 0.8 to 1.5, and particularly preferably 1.1 to 1.3. If it is less than 0.5, the length in the central axis direction of the honeycomb structure 2 becomes too short, which reduces the filtration area, worsens the collection efficiency, and may increase the pressure loss. On the other hand, if it is greater than 1.5, the length in the central axis direction of the honeycomb structure 2 becomes too long, which increases the pressure loss in the cell flow path and may result in an excessive pressure loss for the entire honeycomb filter 1.

[0037] The average pore size of the partition wall 21 is preferably 7 to 40 μm, and more preferably 8 to 35 μm. If it is less than 7 μm, the pressure loss may increase even if there is little accumulation of particulate matter. On the other hand, if it is greater than 40 μm, the honeycomb filter 1 may become brittle and easily fall off, or the particulate matter collection performance may decrease. The average pore size of the partition wall 21 is the value measured with a mercury porosimeter.

[0038] The shape of the cells 22 of the honeycomb filter 1 is not particularly limited, but it is preferable that the cross section perpendicular to the central axis be a polygon such as a triangle, square, pentagon, hexagon, or octagon, a circle, or an ellipse, and it may also be an irregular shape. A combination of squares and octagons is also a preferred embodiment. Furthermore, it is preferable that the cross-sectional area of ​​all cells 22 is the same in the cross section perpendicular to the direction in which the cells 22 extend, but it is also a preferred embodiment that the cross-sectional area of ​​the second cell 222 having a sealing portion 3 on the first end face 2a side (cross-sectional area in the cross section perpendicular to the direction in which the cells 22 extend) is smaller than the cross-sectional area of ​​the first cell 221 having a sealing portion 3 on the second end face 2b side (cross-sectional area in the cross section perpendicular to the direction in which the cells 22 extend). In this embodiment, it is possible to suppress the increase in pressure loss when collecting particulate matter in the exhaust gas 5a.

[0039] Furthermore, the hydraulic diameters of all cells in the honeycomb structure 2 may be the same, or the hydraulic diameters of the first cell 221 and the second cell 222 may be different, but it is preferable that the hydraulic diameters be different. Specifically, when purifying exhaust gas 5a of a gasoline engine, in order to reduce pressure loss, it is preferable to make the hydraulic diameter of the second cell 222 larger than the hydraulic diameter of the first cell 221, and it is preferable that the hydraulic diameter of the first cell 221 is 20 to 45% of the hydraulic diameter of the second cell 222.

[0040] The outer perimeter wall 20 is preferably a molded integral wall formed integrally with the porous substrate during molding. However, it is also preferable that the outer perimeter of the porous substrate is ground to a predetermined shape after molding, and the outer perimeter wall 20 is formed with ceramic cement or the like, resulting in a cement-coated wall. In the case of a molded integral wall, the material of the outer perimeter wall 20 is preferably the same as the material of the honeycomb filter 1. When the outer perimeter wall 20 is a cement-coated wall, the material of the cement-coated wall can be a material to which a flux component such as glass has been added to the same substrate. The thickness of the outer perimeter wall 20 is preferably 0.5 to 1.5 mm.

[0041] The honeycomb filter 1 may have a three-way catalyst supported on it. A three-way catalyst is a catalyst that primarily purifies hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). For example, a catalyst containing platinum (Pt), palladium (Pd), and rhodium (Rh) can be used. With this three-way catalyst, hydrocarbons are purified into water and carbon dioxide, carbon monoxide into carbon dioxide, and nitrogen oxides into nitrogen, by oxidation or reduction.

[0042] The amount of catalyst supported per unit volume on the honeycomb filter 1 is preferably 160 g / L or less, more preferably 10 to 120 g / L, and particularly preferably 20 to 100 g / L. If the amount of catalyst supported exceeds 160 g / L, the pores formed in the partition wall 21 may become blocked by the catalyst, which could lead to excessive pressure loss.

[0043] The sealing portion 3 provided in the honeycomb filter 1 can be made from a sealing material containing ceramic raw material, water or alcohol, and an organic binder. Preferably, the ceramic raw material is the same as the ceramic raw material used for the honeycomb structure portion 2 (the partition wall 21 of the honeycomb structure portion 2). This ensures that the sealing portion 3 is firmly bonded to the partition wall 21 during firing.

[0044] The sealing section 3 is preferably arranged such that the first cell 221 and the second cell 222 are alternately sealed, and both end faces form a checkerboard pattern.

[0045] The depth of the sealing portion 3 is preferably 1 to 5 mm, and more preferably 1 to 3 mm. If it is shallower than 1 mm, the strength of the sealing portion 3 may decrease. On the other hand, if it is deeper than 5 mm, the area of ​​the partition wall 21 that collects PM may decrease. Here, the depth of the sealing portion 3 refers to the length of the sealing portion 3 in the direction in which the cell 22 extends.

[0046] <About exhaust gas purification devices> The honeycomb filter 1 may be housed in the can 50. The honeycomb filter 1 may be placed inside the can 50 with its outer circumference covered by a mat 51 (cushioning material). This mat 51 prevents damage to the honeycomb filter 1. It is preferable that the honeycomb filter 1 is housed inside the can 50 under external pressure via the mat 51. When housed in this manner, it is possible to prevent the honeycomb filter 1 from moving inside the can 50 and to stabilize it within the can 50.

[0047] The container 50 is not particularly limited, and can be one that is commonly used to house ceramic honeycomb filters for purifying exhaust gases such as automobile exhaust. The material of the container 50 can be a metal such as ferritic stainless steel. The size of the container 50 is preferably such that it can be press-fitted into the honeycomb filter 1 with the mat 51 wrapped around it. The container 50 is preferably about 100 to 300 mm in length. The mat 51 can be a ceramic fiber mat or the like.

[0048] <About the manufacturing method of honeycomb filters> A honeycomb molded body is obtained by extruding clay into a honeycomb shape that satisfies the following conditions. As a method for sealing the openings of the cells in the honeycomb molded body, one method is to fill the cell openings with a sealing material. Specifically, as a method for filling with a sealing material, a mask is applied to one end face of the honeycomb molded body so as to block the openings of predetermined cells. There are no particular restrictions on how the mask is applied, but it is preferable to alternately seal the openings of predetermined cells on the first end face of the honeycomb molded body and the openings of the remaining cells on the second end face so that both end faces form a checkerboard pattern. Then, a slurry-like sealing material containing ceramic raw material, water or alcohol, and an organic binder is stored in a storage container. The ceramic raw material is preferably the same as the ceramic raw material used as the raw material for the honeycomb molded body. The ceramic raw material is preferably 70 to 90% by mass of the total sealing material. Furthermore, water or alcohol is preferably present in an amount of 10 to 30% by mass of the total sealing material, and the organic binder is preferably present in an amount of 0.1 to 2.0% by mass of the total sealing material. Examples of organic binders include hydroxypropoxyl methylcellulose and methylcellulose. The end with the mask applied is then immersed in a storage container, and the sealing material is filled into the openings of the cells that are not masked to form a sealed portion. The viscosity of the sealing material is preferably 600 to 1200 Pa·s. The viscosity of the sealing material is measured at a temperature of 30°C using a rotational viscometer at a rotational speed of 30 rpm. After that, a mask is applied to the other end face of the honeycomb molded body so as to block the openings of the remaining cells. Then, the other end face with the mask applied is immersed in a storage container containing slurry-like sealing material, and the sealing material is filled into the openings of the cells that are not masked to form a sealed portion. In this way, a honeycomb filter molded body can be obtained in which sealing portions are provided at the openings of predetermined cells on one end face of the honeycomb molded body and at the openings of the remaining cells on the other end face.

[0049] The firing temperature when firing the honeycomb filter molded body can be appropriately determined depending on the material of the honeycomb filter molded body. For example, if the material of the honeycomb filter molded body is cordierite, the firing temperature is preferably 1380 to 1450°C, and more preferably 1400 to 1440°C. The firing time is preferably about 3 to 10 hours.

[0050] The honeycomb filter molded body may be dried before firing. The drying method is not particularly limited, but examples include hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying. Among these, dielectric drying, microwave drying, or hot air drying are preferred, either individually or in combination. The drying conditions are preferably a drying temperature of 30 to 150°C and a drying time of 1 minute to 2 hours.

[0051] Alternatively, before forming the sealing portion on the honeycomb molded body, a honeycomb molded body can be fired to obtain a fired honeycomb body. After forming sealing portions on the openings of predetermined cells at one end face and the remaining cell openings at the other end face of the obtained fired honeycomb body, a honeycomb filter can be obtained by firing it again.

[0052] The honeycomb filter can be obtained by coating the resulting honeycomb filter structure with a catalyst slurry (supporting the catalyst) using a known method. For example, the method of coating with the catalyst slurry involves first preparing a catalyst slurry containing a ternary catalyst. Then, the prepared catalyst slurry is introduced into the cell by dipping or suction. It is preferable to coat the entire surface of the partition walls within the cell with this catalyst slurry. After introducing the catalyst slurry into the cell, any excess slurry is blown away with compressed air. Subsequently, the catalyst slurry is dried and baked to obtain a sealed honeycomb structure with the catalyst supported on the surface of the partition walls within the cell. The drying conditions are preferably 80-150°C for 1-6 hours. The baking conditions are preferably 450-700°C for 0.5-6 hours. Other components besides the catalyst included in the catalyst slurry include alumina.

[0053] <Regarding assembly onto the can body> After covering the outer perimeter of the honeycomb filter with a mat (cushioning material), the mat-covered honeycomb filter is placed inside the container. It is preferable that the honeycomb filter is stored in a compressed state inside the container. Examples of suitable mats include ceramic fiber mats. This prevents the honeycomb filter from moving within the container.

[0054] The container body can be one of conventionally known types, but for example, it can be manufactured by pressing and welding a sheet material made of ferritic stainless steel. The diameter of the inlet of the container body is preferably 30 to 80 mm, and the diameter of the outlet is preferably 30 to 80 mm.

[0055] Although preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to these examples. It is clear to any person with ordinary skill in the art to which the present invention belongs that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these are also understood to fall within the technical scope of the present invention. [Examples]

[0056] The present invention will be described more specifically below with reference to examples. The present invention is not limited to these examples.

[0057] As shown in Tables 1 to 4 below, various honeycomb filters were created and their collection efficiency reduction rate and pressure loss reduction rate were investigated.

[0058] [Table 1]

[0059] [Table 2]

[0060] [Table 3]

[0061] [Table 4]

[0062] [About honeycomb filters] Comparative Examples 1 to Examples 1-4 used the same honeycomb structure. Comparative Example 1 was an example in which no incomplete sealing cells were provided (an example in which no openings were provided in the sealing portion of any cell). Examples 1-1 to 1-4 were examples in which incomplete sealing cells were provided, and the number of incomplete sealing cells and the area of ​​the opening in the sealing portion of the incomplete sealing cells were changed in each example. Similarly, in examples where the numbers immediately following the comparative example and example were the same, the same honeycomb structure was used. In addition, the comparative example was an example in which no incomplete sealing cells were provided, and the examples were examples in which incomplete sealing cells were provided. In examples where the number immediately following the example was followed by a sub-number such as "-1", the number of incomplete sealing cells and / or the area of ​​the opening in the sealing portion of the incomplete sealing cells were changed in each example.

[0063] In the examples where the numbers immediately following the comparative examples and examples are "1" to "8", incomplete sealing cells were provided only in the partial cells. In the examples where the numbers immediately following the comparative examples and examples are "9" and "10", incomplete sealing cells were provided in both the partial cells and the normal cells.

[0064] In Tables 1 to 4, "Number of leaks" represents the number of incompletely sealed cells. The "leakage area ratio in one PCL" represents the ratio of the total area of ​​openings in partial cells (incompletely sealed cells) with openings in the sealing portion to the total area of ​​partial cells (incompletely sealed cells) with openings in the sealing portion in the cross-section of the honeycomb structure perpendicular to the direction in which the cells extend (the opening area per partial cell with an opening in the sealing portion). The "leakage area ratio in the entire PCL" represents the ratio of the total area of ​​incompletely sealed cells in all partial cells to the total area of ​​all partial cells in the cross-section of the honeycomb structure perpendicular to the direction in which the cells extend. The "leakage area ratio in one NCL" represents the ratio of the total area of ​​openings in normal cells (incompletely sealed cells) with openings in their sealing portions to the total area of ​​normal cells (incompletely sealed cells) with openings in their sealing portions in a cross-section of the honeycomb structure perpendicular to the direction in which the cells extend. The "percentage of leakage area relative to the total" represents the ratio of the total area of ​​openings in all imperfectly sealed cells to the total area of ​​all cells in the cross-section of the honeycomb structure perpendicular to the direction in which the cells extend.

[0065] [Method for investigating the reduction rate of collection efficiency] The reduction in collection efficiency was investigated as follows: A fabricated exhaust gas purification device 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 exhaust gas purification device was measured using the PN measurement method. The "PN measurement method" is a measurement method proposed by the Particle Measurement Program (PMP) of the Global Forum for Harmonization of Vehicle Regulations (WP29) of the Economic Commission for Europe (ECE) of the United Nations (UN). Specifically, in determining the number of soot particles, the cumulative number of soot particles discharged after driving in WLTC (Worldwide harmonized Light duty Test Cycle) mode was used as the number of soot particles of the exhaust gas purification device being evaluated, and the collection efficiency was measured. Based on the collection efficiency measured as described above, the difference between the collection efficiency of a honeycomb filter without incomplete sealing cells, such as Comparative Example 1, and the collection efficiency of an incomplete cell honeycomb filter (a honeycomb filter with incomplete sealing cells) was determined as the collection efficiency reduction rate.

[0066] [Method for investigating pressure loss reduction rate] The pressure loss reduction rate was investigated as follows: Exhaust gas emitted from a 1.2L direct-injection gasoline engine was subjected to a 700°C, 600m³ test. 3 The pressure at the inlet and outlet ends of the honeycomb filter was measured by introducing a flow rate of / h. The pressure loss (kPa) of the honeycomb filter was then determined by calculating the pressure difference between the inlet and outlet ends. For the pressure loss measured in this way, the ratio of the pressure loss of the incomplete cell honeycomb filter to the pressure loss of the honeycomb filter without incomplete sealing cells, such as in Comparative Example 1, was determined as the pressure loss reduction rate.

[0067] Figure 6 is a graph showing the relationship between the percentage of leakage area and the reduction in collection efficiency in the examples and comparative examples. As shown in the graph in Figure 6, it was found that the larger the percentage of leakage area, the greater the reduction in collection efficiency, that is, the lower the collection efficiency and the greater the risk of particulate matter passing through. If the sealing portion of the cell is omitted instead of using an incompletely sealed cell, the percentage of leakage area increases even further. Although not listed in the examples or comparative examples, the results in Figure 6 show that the reduction in collection efficiency increases even further when the sealing portion of the cell is omitted. In other words, it was found that by providing an incompletely sealed cell as in the examples, the passage of particulate matter can be suppressed compared to when the sealing portion of the cell is omitted.

[0068] On the other hand, as can be seen by comparing the pressure loss reduction rate of each comparative example with the pressure loss reduction rate of each embodiment, it was found that by providing an incomplete sealing cell (embodiment), the increase in pressure loss can be suppressed compared to when no incomplete sealing cell is provided (comparative example).

[0069] These results show that by providing an imperfect sealing cell, it is possible to suppress the passage of particulate matter while suppressing the increase in pressure loss.

[0070] In most of the examples, the reduction in collection efficiency fell within the range of 0.0% or less and -1.0% or more, and the reduction in pressure loss was less than 0.0%. However, in Example 2-4, the reduction in collection efficiency was -1.3%, indicating a relatively increased passage of particulate matter. In Examples 3-4 and 9-4, the reduction in pressure loss was 0.0%, indicating that the increase in pressure loss could be suppressed, but it did not result in a reduction in pressure loss. The reason why the reduction in collection efficiency in Example 2-4 was -1.3% is thought to be because the leakage area ratio in one PCL was relatively large at 91%. Conversely, the reason why the reduction in pressure loss was 0.0% in Examples 3-4 and 9-4 is thought to be because the leakage area ratio in one PCL and / or in one NCL was relatively small at 2% to 4%. In the examples where the reduction in collection efficiency fell within the range of 0.0% or less and -1.0% or more, the leakage area ratio in one PCL and / or one NCL was between 5% and 90%. From these results, it was found that by keeping the ratio of the total area of ​​openings in imperfectly sealed cells to the total area of ​​imperfectly sealed cells in the cross-section of the honeycomb structure perpendicular to the direction in which the cells extend between 5% and 90%, the increase in pressure loss can be more reliably suppressed, and the passage of particulate matter can be more reliably suppressed.

[0071] In Example 2-4, the collection efficiency reduction rate was -1.3%, which may be due to the relatively large percentage of leakage area of ​​1459 ppm. In the examples where the collection efficiency reduction rate fell within the range of 0.0% or less and -1.0% or more, the percentage of leakage area of ​​1400 ppm or less was. From these results, it was found that the passage of particulate matter can be more reliably suppressed when the ratio of the total area of ​​openings in all imperfectly sealed cells to the total area of ​​all cells in the cross-section of the honeycomb structure perpendicular to the direction in which the cells extend is 1400 ppm or less. [Explanation of Symbols]

[0072] 1: Honeycomb filter 2: Honeycomb structure 2a: First end surface 2b: Second end surface 20:Outer wall 21: Bulkhead 22: Cell 23: Normal cell 24: Partial Cell 3: Eye sealing section 3a:Aperture 4: Cell 5: Exhaust gas treatment system 5a: Exhaust gas

Claims

1. A honeycomb structure having an outer periphery wall and porous partition walls disposed inside the outer periphery wall, which partition a plurality of cells that form a flow channel extending from a first end face to a second end face, A sealing portion provided on the cell at either the first end face or the second end face and Equipped with, The cell includes at least one imperfectly sealed cell in which an opening is formed in the sealing portion and light leakage can be observed on the other of the first and second end faces when light is shone on either the first or second end face, The ratio of the total area of ​​the openings in all the incompletely sealed cells to the total area of ​​all the cells in the cross-section of the honeycomb structure perpendicular to the direction in which the cells extend is 1400 ppm or less. Honeycomb filter.

2. The ratio of the total area of ​​the openings in the incompletely sealed cells to the total area of ​​the incompletely sealed cells in the cross-section of the honeycomb structure perpendicular to the direction in which the cells extend is 5% or more and 90% or less. The honeycomb filter according to claim 1.

3. The cell includes a plurality of normal cells provided away from the outer peripheral wall, and a plurality of partial cells provided adjacent to the outer peripheral wall and having a partial cross-sectional shape relative to the plurality of normal cells. The at least one incomplete sealing cell is provided in the plurality of partial cells. The honeycomb filter according to claim 1 or 2.

4. The porosity of the partition wall is 45% or more and 70% or less, and the thickness of the partition wall is 127 μm or more and 254 μm or less. The honeycomb filter according to claim 1 or 2.

5. An exhaust gas treatment system comprising a honeycomb filter according to claim 1 or 2, arranged such that exhaust gas passes through the cell.

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