CN219159046U

CN219159046U - Honeycomb filter

Info

Publication number: CN219159046U
Application number: CN202320122568.5U
Authority: CN
Inventors: 中谷隆彦
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2023-01-17
Filing date: 2023-01-17
Publication date: 2023-06-09
Anticipated expiration: 2033-01-17

Abstract

The utility model provides a honeycomb filter with excellent ignition performance and excellent isostatic strength. The honeycomb filter includes: a columnar honeycomb structure having porous partition walls arranged to surround a plurality of cells; and porous plugged portions disposed at either end of the cells, wherein the honeycomb structure includes a central portion including a center of gravity O of the cross section and an outer peripheral portion located outside the central portion in a cross section orthogonal to a direction in which the cells extend, wherein the cells in the outer peripheral portion have a shape in which corners of a polygon are chamfered into an arc shape having a radius of curvature R of 100 to 200 [ mu ] m, wherein a thickness T2 of the partition walls in the outer peripheral portion is made 0.0127 to 0.0254mm thinner than a thickness T1 of the partition walls in the central portion, and wherein an area ratio of the outer peripheral portions in the cross section is 10 to 50%.

Description

Honeycomb filter

Technical Field

The present utility model relates to a honeycomb filter. More specifically, the present utility model relates to a honeycomb filter having excellent temperature characteristics (Light-off performance) and excellent isostatic strength (Isostatic strength) which are exhibited by the purification performance of an exhaust gas purification catalyst.

Background

Conventionally, as a filter for trapping particulate matter in exhaust gas discharged from an internal combustion engine such as an engine of an automobile or a device for purifying toxic gas components such as CO, HC, NOx, a honeycomb filter using a honeycomb structure has been known (refer to patent document 1). The honeycomb structure has partition walls made of porous ceramics such as cordierite, and a plurality of cells are partitioned by the partition walls. In the honeycomb filter, the honeycomb structure is provided with plugged portions so that openings on the inflow end face side and openings on the outflow end face side of the cells are alternately plugged. That is, the honeycomb filter has the structure: the inflow cells whose inflow end face side is open and whose outflow end face side is sealed and the outflow cells whose inflow end face side is sealed and whose outflow end face side is open are alternately arranged with the partition walls interposed therebetween. In the honeycomb filter, porous partition walls play a role in filtering particulate matter in exhaust gas. Hereinafter, particulate matter contained in the exhaust gas may be referred to as "PM". "PM" is an abbreviation for "particulate matter".

The purification of exhaust gas by the honeycomb filter is performed as follows. First, the honeycomb filter is configured to: the inflow end face side thereof is located on the upstream side of the exhaust system from which the exhaust gas is discharged. The exhaust gas flows into the cells from the inflow end face side of the honeycomb filter. Then, the exhaust gas flowing into the inflow cells passes through the porous partition walls, flows into the outflow cells, and is discharged from the outflow end face of the honeycomb filter. PM and the like in the exhaust gas are trapped and removed when passing through the porous partition walls. Further, such a honeycomb filter may be loaded with an oxidation catalyst for promoting PM oxidation (combustion), an exhaust gas purifying catalyst for purifying harmful components such as NOx, and the like.

Conventionally, in a honeycomb structure for a honeycomb filter, a certain roundness (i.e., a curve shape) is provided at the intersection of partition walls that partition cells to ensure manufacturability and performance (for example, patent document 1). By providing the intersection portions of the partition walls with a certain roundness in this manner, for example, in a cross section of the honeycomb structure orthogonal to the direction in which the cells extend, the cells are shaped as polygons in which the corners of the polygons are rounded.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 10-264125

Disclosure of Invention

However, the technique of providing the roundness (R) of the intersection portion of the partition walls as described above has a problem that the mass of the honeycomb structure becomes large, and when the catalyst for purifying exhaust gas is supported on the honeycomb filter, the mass of the honeycomb structure increases, thereby preventing early activation of the catalyst. That is, there is a problem that the temperature characteristic, i.e., light-off performance (Light-off performance) exhibited by the purification performance of the exhaust gas purification catalyst cannot be ensured due to the increase in mass of the honeycomb structure. If the light-off performance is poor, the purification performance of the catalyst-supporting honeycomb filter becomes poor at the initial stage such as when the engine is started.

In addition, as for the increase in mass of the honeycomb structure as described above, by making the thickness of the partition walls constituting the honeycomb structure thin, the increase in mass can be suppressed. On the other hand, if the thickness of the partition walls is made thinner, the mechanical strength (for example, isostatic strength: isostatic strength) of the honeycomb structure may be lowered.

The present utility model has been made in view of the above-described problems of the prior art. According to the present utility model, a honeycomb filter having excellent light-off performance and excellent isostatic strength is provided.

According to the present utility model, there is provided a honeycomb filter shown below.

[1] A honeycomb filter is provided with:

a columnar honeycomb structure having porous partition walls arranged to surround a plurality of cells forming fluid flow paths extending from an inflow end face to an outflow end face; and

a porous sealing portion disposed at either one of an end portion on the inflow end face side and an end portion on the outflow end face side of the cell,

the honeycomb structure includes, in a cross section orthogonal to a direction in which the cells extend, a central portion including a center of gravity O of the cross section and an outer peripheral portion located outside the central portion,

in the cross section of the honeycomb structure, the cells in the outer peripheral portion have a shape in which corners of a polygon are chamfered into an arc shape having a radius of curvature R of 100 to 200 μm,

the thickness T2 of the partition wall in the outer peripheral portion is made 0.0127-0.0254 mm thinner than the thickness T1 of the partition wall in the central portion,

the ratio of the area of the outer peripheral portion in the cross section to the total area of the honeycomb structure is 10 to 50%.

[2] The honeycomb filter according to [1] above, wherein the porosity of the partition walls is 40 to 80% and the average pore diameter of the partition walls is 5 to 21. Mu.m.

[3]According to [1] above]Or [2]]The thickness T1 of the partition walls in the central portion and the thickness T2 of the partition walls in the peripheral portion of the honeycomb filter are 0.127 to 0.331mm, and the cell density of the honeycomb structure is 31.0 to 62.0 cells/cm ² 。

Effects of the utility model

The honeycomb filter of the present utility model exhibits the following effects, that is, excellent in light-off performance and also excellent in isostatic strength.

Drawings

Fig. 1 is a perspective view schematically showing an embodiment of the honeycomb filter of the present utility model.

Fig. 2 is a plan view showing the inflow end face side of the honeycomb filter shown in fig. 1.

Fig. 3 is a sectional view schematically showing a section A-A' of fig. 2.

Fig. 4 is an enlarged plan view of the range enclosed by the dotted line indicated by P in fig. 2.

Description of the reference numerals

1: partition wall, 1a: central partition wall, 1b: outer Zhou Gebi, 2: compartment, 2a: inflow compartment, 2b: outflow compartment, 3: peripheral wall, 4: honeycomb structure, 5: hole sealing portion, 11: inflow end face, 12: outflow end face, 15: center portion, 16: outer peripheral portions, 21, 22: corner, 100: honeycomb filter, T1: thickness (thickness of central partition wall), T2: (thickness of peripheral partition wall).

Detailed Description

Hereinafter, embodiments of the present utility model will be described, but the present utility model is not limited to the following embodiments. Thus, it should be understood that: the following embodiments are appropriately modified and improved based on the general knowledge of those skilled in the art within the scope of the present utility model without departing from the gist of the present utility model.

(1) Honeycomb filter:

one embodiment of the honeycomb filter of the present utility model is a honeycomb filter 100 as shown in fig. 1-4. Here, fig. 1 is a perspective view schematically showing an embodiment of the honeycomb filter of the present utility model. Fig. 2 is a plan view showing the inflow end face side of the honeycomb filter shown in fig. 1. Fig. 3 is a sectional view schematically showing a section A-A' of fig. 2. Fig. 4 is an enlarged plan view of the range enclosed by the dotted line indicated by P in fig. 2.

As shown in fig. 1 to 4, the honeycomb filter 100 of the present embodiment includes a honeycomb structure 4 and a plugged portion 5. The honeycomb structure 4 has a columnar shape and includes porous partition walls 1 arranged to surround a plurality of cells 2, and the plurality of cells 2 form fluid flow paths extending from an inflow end face 11 to an outflow end face 12. In the honeycomb filter 100, the honeycomb structure 4 has a columnar shape and has an outer peripheral wall 3 on its outer peripheral side surface. That is, the outer peripheral wall 3 is disposed so as to surround the partition walls 1 disposed in a lattice shape.

The hole sealing portion 5 is disposed in an opening portion of each cell 2 on the inflow end face 11 side or the outflow end face 12 side. In the honeycomb filter 100 shown in fig. 1 to 4, the plugging portions 5 are disposed in the openings of the end portions of the predetermined cells 2 on the inflow end face 11 side and the openings of the end portions of the remaining cells 2 on the outflow end face 12 side, respectively. The compartment 2 in which the hole sealing portion 5 is disposed in the opening portion on the outflow end face 12 side and the inflow end face 11 side is opened is referred to as an inflow compartment 2a. The compartment 2 in which the hole sealing portion 5 is disposed in the opening portion on the inflow end face 11 side and the outflow end face 12 side is opened is referred to as an outflow compartment 2b. The inflow cells 2a and the outflow cells 2b are preferably alternately arranged with the partition wall 1 interposed therebetween. It is preferable that both end surfaces of the honeycomb filter 100 are formed in a checkered pattern by the hole sealing portions 5 and the "openings of the cells 2".

The honeycomb structural body 4 includes, in a cross section orthogonal to the direction in which the cells 2 extend, a central portion 15 including the center of gravity O of the cross section, and an outer peripheral portion 16 located outside the central portion 15. For example, as shown in fig. 2 and 3, a certain range from the center of gravity O to the outer periphery of the honeycomb structure 4 including the center of gravity O is "central portion 15", and a range on the outer periphery side of the central portion 15 is "outer periphery 16".

The honeycomb filter 100 of the present embodiment has particularly main characteristics in terms of the structure of the partition walls 1 in the central portion 15 and the outer peripheral portion 16 and the structure of the cells 2 surrounded by the partition walls 1. That is, first, the honeycomb filter 100 is configured to: in a cross section of the honeycomb structure 4 orthogonal to the direction in which the cells 2 extend, the cells 2 in the outer peripheral portion 16 have a shape in which corners of a polygon are chamfered into circular arcs having a radius of curvature R of 100 to 200 μm. Hereinafter, the shape of the cells 2 in a cross section of the honeycomb structure 4 perpendicular to the direction in which the cells 2 extend may be referred to simply as "the shape of the cells 2". In fig. 4, reference numeral 22 denotes a corner 22 formed in a curve in the shape of the compartment 2 in the outer peripheral portion 16. In fig. 4, reference numeral 21 denotes a corner 21 formed in a curve in the shape of the compartment 2 in the central portion 15.

The shape of the cells 2 in the outer peripheral portion 16 may be a polygonal corner formed in a curved shape having the radius of curvature R, and the original polygonal shape is not particularly limited. As described later, examples of the original polygon of the shape of the cell 2 include: quadrilateral, hexagonal, octagonal, etc. Hereinafter, the corner 22 of the compartment 2 formed in a curve in the outer peripheral portion 16 is sometimes referred to as "corner 22 of the compartment 2". The radius of curvature R of the curved portion of the corner 22 of the cell 2 is sometimes referred to simply as "radius of curvature R of the corner 22 of the cell 2". In the present specification, unless otherwise specified, the unit of the radius of curvature R of the corner 22 of the cell 2 is "μm".

The shape of the cells 2 in the central portion 15 may be a polygonal shape in which the corners 21 of the cells 2 are curved, or may be a polygonal shape in which the corners 21 are not chamfered. The polygonal shape and the original polygonal shape of the cells 2 in the central portion 15 are not particularly limited, and examples thereof include, as in the cells 2 in the outer peripheral portion 16: quadrilateral, hexagonal, octagonal, etc. Hereinafter, the corner 21 of the compartment 2 in the central portion 15 may be referred to simply as "corner 21 of the compartment 2".

The radius of curvature R of the corner 22 of the compartment 2 in the outer peripheral portion 16 can be determined as follows. First, the inflow end face 11 and the outflow end face 12 of the honeycomb filter 100 are photographed by an image measuring device. Then, the captured images of the inflow end face 11 and the outflow end face 12 are subjected to image analysis, whereby the radius of curvature R of the corner 22 of the cell 2 in the outer peripheral portion 16 can be obtained. As a method of image analysis, for example, "VM-2520 (trade name)" manufactured by Nikon corporation may be used. By using the image analysis, the radius (or diameter) of the inscribed circle of the corner 22 of the cell 2 is obtained by curve fitting to the corner 22 of the cell 2, and the radius of curvature R of the corner 22 of the cell 2 can be obtained. In the honeycomb filter 100 of the present embodiment, the radius of curvature R of all the corners 22 of all the cells 2 in the outer peripheral portion 16 is thus obtained, and 50% or more of the corners 22 in the outer peripheral portion 16, that is, 50 to 100% of the corners 22 have a radius of curvature R in the range of 100 to 200 μm. In addition, when the corner portion 21 of the cell 2 in the central portion 15 has a curved shape having a predetermined radius of curvature R ', the radius of curvature R' of the corner portion 21 may be measured by the same method as that described above.

Further, the honeycomb filter 100 is configured to: the thickness T2 of the partition wall in the outer peripheral portion 16 is 0.0127 to 0.0254mm thinner than the thickness T1 of the partition wall in the central portion 15. In the honeycomb filter 100, the ratio of the area of the outer peripheral portion 16 to the total area of the cross section of the honeycomb structure 4 is 10 to 50%. Here, "center of gravity O" of the cross section of the honeycomb structural body 4 means: the geometric center of gravity (in other words, the geometric center) of the cross-section.

The honeycomb filter 100 of the present embodiment configured as described above exhibits the effect of being excellent in light-off performance and also excellent in isostatic strength. That is, as described above, the honeycomb filter 100 according to the present embodiment is configured such that the corners 22 of the cells 2 in the outer peripheral portion 16 have a circular arc shape with a predetermined radius of curvature R, and thus, it is expected that manufacturability and various performance improvements due to the circular arc-shaped corners 22 will be improved. On the other hand, in the conventional honeycomb filter in which the corners 22 of the cells 2 are formed in the shape of circular arc, the thickness of the partition walls 1 is not distributed in the circumferential direction of the cross section of the honeycomb structure 4, and the thickness of the partition walls 1 is constant in the circumferential direction. In the honeycomb filter 100 of the present embodiment, the thickness T2 of the partition walls in the outer peripheral portion 16 is made thinner by 0.0127 to 0.0254mm than the thickness T1 of the partition walls 1 in the central portion 15, so that the honeycomb filter 100 is made lighter, and thus the light-off performance is excellent. For example, when the catalyst for purifying exhaust gas is supported on the honeycomb filter 100 of the present embodiment, the catalyst is activated early, and excellent purification performance can be achieved even at the initial stage such as at the time of engine start.

In the honeycomb filter 100 of the present embodiment, the area ratio of the thickness T2 of the partition walls 1 in the outer peripheral portion 16 to the thin outer peripheral portion 16 is 10 to 50%. Therefore, the area ratio of the relatively thick central portion 15 of the thickness T1 of the partition wall 1 can be ensured to be 50% or more, and even if the thickness T2 of the partition wall 1 in the outer peripheral portion 16 is made thin, the decrease in the isostatic strength of the honeycomb filter 100 can be effectively suppressed. If the area ratio of the outer peripheral portion 16 is less than 10%, the effect of improving the light-off performance may be insufficient. On the other hand, if the area ratio of the outer peripheral portion 16 exceeds 50%, the isostatic strength of the honeycomb filter 100 may be insufficient.

The radius of curvature R of the corner 22 of the compartment 2 in the peripheral portion 16 is 100 to 200 μm. If the radius of curvature R is less than 100. Mu.m, the isostatic strength may be lowered. On the other hand, if the radius of curvature R exceeds 200 μm, the effect of improving the light-off performance may be insufficient. The radius of curvature R of the corner 22 of the compartment 2 in the outer peripheral portion 16 is not particularly limited, and is preferably, for example, 100 to 200 μm, more preferably 125 to 175 μm.

When the corner portions 21 of the cells 2 in the central portion 15 have a curved shape having a predetermined radius of curvature R ', the radius of curvature R' of the corner portions 21 of the cells 2 in the central portion 15 is preferably 50 to 150 μm, more preferably 75 to 125 μm. With this configuration, the difference between the radius of curvature R' of the central portion 15 and the radius of curvature R of the outer peripheral portion 16 is preferably not excessively large. When the corner portions 21 of the cells 2 in the central portion 15 are formed in a curved shape having a predetermined radius of curvature R ', it is preferable that 50% or more, that is, 50 to 100% of the corner portions 21 in the entire corner portions 21 in the central portion 15 have a radius of curvature R' within the above-mentioned numerical range.

As described above, the thickness T2 of the partition wall in the outer peripheral portion 16 is 0.0127 to 0.0254mm thinner than the thickness T1 of the partition wall 1 in the central portion 15. Hereinafter, the partition wall 1 in the central portion 15 may be referred to as a "central partition wall 1a". The partition wall 1 in the outer peripheral portion 16 is sometimes referred to as "outer Zhou Gebi 1b". For example, a scanning electron microscope or a microscope (microscope) may be used to measure the thickness T1 of the center partition wall 1a and the thickness T2 of the outer peripheral partition wall 1 b. The thickness T1 of the center partition wall 1a is preferably a substantially constant thickness in the center portion 15. The thickness T2 of the outer peripheral wall 1b is preferably substantially constant in the outer peripheral portion 16. For example, the thickness T1 of the center partition wall 1a is preferably within ±0.0127mm in the center portion 15. The thickness T2 of the outer peripheral wall 1b is preferably within ±0.0127mm in the outer peripheral portion 16. In a cross section of the honeycomb structure 4 perpendicular to the direction in which the cells 2 extend, a measurement point is determined in a cross direction starting from the center of gravity O of the cross section, and the thickness T1 of the center partition wall 1a and the thickness T2 of the outer peripheral partition wall 1b are measured. More specifically, in the cross direction of the cross section, measurement points are determined at 10 positions for each 10% of the area ratio of the cross section, and the thicknesses T1 and T2 of the partition wall 1 at the measurement points are measured.

If the decrease in the thickness T2 of the peripheral partition wall 1b relative to the thickness T1 of the central partition wall 1a is less than 0.0127mm, the difference in thickness between the central partition wall 1a and the peripheral partition wall 1b is too small, and it is difficult to have both light-off performance and isostatic strength. Conversely, even if the decrease in the thickness T2 of the peripheral partition wall 1b relative to the thickness T1 of the central partition wall 1a exceeds 0.0254mm, the difference in thickness between the central partition wall 1a and the peripheral partition wall 1b becomes excessively large, and it is difficult to have both the light-off performance and the isostatic strength. Although not particularly limited, the thickness T2 of the outer peripheral partition wall 1b is preferably 0.0127 to 0.0305mm, more preferably 0.0127 to 0.0254mm, smaller than the thickness T1 of the central partition wall 1 a.

The specific value of the thickness T1 of the center partition wall 1a and the thickness T2 of the outer peripheral partition wall 1b is not particularly limited. For example, the thickness T1 of the center partition wall 1a and the thickness T2 of the outer peripheral partition wall 1b are preferably 0.127 to 0.331mm. More specifically, the thickness T1 of the center partition wall 1a, which is relatively thick, of the partition wall 1 is more preferably 0.216 to 0.343mm. On the other hand, the thickness T2 of the outer peripheral partition wall 1b, which is relatively thin in the thickness of the partition wall 1, is more preferably 0.203 to 0.305mm. If the thickness T1 of the center partition wall 1a is too small, the trapping performance of the honeycomb filter 100 may be lowered, and the mechanical strength of the honeycomb filter 100 may be lowered. On the other hand, if the thickness T1 of the center bulkhead 1a is too large, the pressure loss may increase.

The central portion 15 is a constant range from the center of gravity O of the cross section of the honeycomb structure 4 to the outer periphery of the cross section, and is a range in which the thickness of the partition wall 1 (i.e., the thickness T1 of the central partition wall 1 a) is relatively thick. On the other hand, the outer peripheral portion 13 is a range that is located outside the central portion 15 in the cross section of the honeycomb structure 4 and the thickness of the partition wall 1 (i.e., the thickness T2 of the outer peripheral partition wall 1 b) is relatively thin. The ratio of the area of the outer peripheral portion 16 to the total area of the cross section of the honeycomb structure 4 may be 10 to 50%, for example, preferably 20 to 50%, and more preferably 30 to 50%. Hereinafter, the ratio (%) of the area of the outer peripheral portion 16 to the total area of the cross section of the honeycomb structure 4 may be referred to as "area ratio (%) of the outer peripheral portion 16". The ratio (%) of the area of the central portion 15 to the total area of the cross section of the honeycomb structure 4 may be referred to as "area ratio (%) of the central portion 15". The sum of the area ratio (%) of the outer peripheral portion 16 and the area ratio (%) of the central portion 15 is 100%. Here, the area ratio of the central portion 15 is a value measured as follows. First, as described above, the thicknesses T1 and T2 of the partition walls 1 are measured at each measurement point in the cross direction of the cross section of the honeycomb structure 4. Since the measurement points are 10 parts per 10% of the area ratio of the cross section in the cross direction, the average value of the thicknesses of the partition walls 1 from the outer periphery of the honeycomb structure 4 to the 5 th part (i.e., the part having the area ratio of 50%) is determined as the "reference thickness". Then, a point at which the difference from the reference thickness exceeds 0.0127mm for the first time is defined as a boundary between the central portion 15 and the outer peripheral portion 16, and the area of the central portion 15, which is a range inside the boundary, is obtained. The percentage of the ratio of the area of the central portion 15 to the cross-sectional area of the honeycomb structural body 4 is "area ratio (%) of the central portion 15".

In the honeycomb filter 100 of the present embodiment, the thickness T2 of the outer peripheral partition wall 1b is made relatively thin, and the radius of curvature R of the corner portions 22 of the cells 2 in the outer peripheral portion 16 is set to 100 to 200 μm, whereby excellent moldability can be ensured, and the above-described light-off performance can be improved. Further, such a honeycomb filter 100 can reduce pressure loss when PM such as soot and Ash (Ash) is deposited on the surface of the partition wall 1, and can ensure excellent erosion resistance and isostatic strength.

The porosity of the partition wall 1 is preferably 40 to 80%, more preferably 40 to 70%, and particularly preferably 45 to 65%. With such a configuration, the honeycomb filter 100 can be suitably used as a filter for purifying exhaust gas discharged from an engine of an automobile. The porosity of the partition wall 1 is a value measured by mercury porosimetry. For example, the porosity of the partition wall 1 can be measured by using Autopore 9500 (trade name) manufactured by Micromeritics corporation. A part of the partition wall 1 may be cut out from the honeycomb structure 4 to prepare a sample sheet, and the porosity of the partition wall 1 may be measured using the sample sheet thus obtained. The porosity of the partition walls 1 is preferably a constant value throughout the entire area of the honeycomb structure 4.

The average pore diameter of the partition wall 1 is preferably 5 to 21. Mu.m, more preferably 6 to 20. Mu.m, particularly preferably 7 to 19. Mu.m. The average pore diameter of the partition walls 1 is a value measured by mercury porosimetry. For example, the average pore diameter of the partition wall 1 can be measured by using Autopore 9500 (trade name) manufactured by Micromeritics corporation, and the measurement method and the like are the same as those of the partition wall 1. The honeycomb filter 100 of the present embodiment is preferably: the porosity of the partition wall 1 is 40 to 80% and the average pore diameter of the partition wall 1 is 9 to 21 μm.

The cell density of the honeycomb structure 4 is preferably 31.0 to 62.0 cells/cm ² More preferably 31.0 to 54.3 pieces/cm ² Particularly preferably 31.0 to 46.5 pieces/cm ² . With such a configuration, the honeycomb filter 100 can be suitably used as a filter for purifying exhaust gas discharged from an engine of an automobile. If the cell density is too small, the pressure loss may increase. On the other hand, if the compartment density is too large, the purification performance sometimes decreases. The honeycomb filter 100 of the present embodiment is more preferably: the thickness T1 of the central partition wall 1a and the thickness T2 of the peripheral partition wall 1b are 0.127-0.331 mm, and the cell density of the honeycomb structure 4 is 31.0-62.0 cells/cm ² 。

The shape of the compartment 2 partitioned by the partition wall 1 is not particularly limited. For example, the shape of the cell 2 in a cross section orthogonal to the direction in which the cell 2 extends may be a polygon having corners formed in a curved shape. Hereinafter, a polygon having corners formed in a curved shape may be simply referred to as a "polygon" or a "substantially polygon". For example, the shape of the compartment 2 is preferably a substantially triangle, a substantially quadrangle, a substantially pentagon, a substantially hexagon, a substantially octagon, and more preferably a substantially quadrangle. In the shape of the above-described compartment 2, the substantially quadrangular shape means: the corners of the quadrangle are formed in a curved shape, and the same applies to the other examples of the polygon described above.

The outer peripheral wall 3 of the honeycomb structure 4 may be integrally formed with the partition walls 1, or may be an outer peripheral coating layer formed by applying an outer peripheral coating material to the outer peripheral side of the partition walls 1. For example, although not shown, the partition wall and the outer peripheral wall may be integrally formed at the time of manufacture, the formed outer peripheral wall may be removed by a known method such as grinding, and then an outer peripheral coating layer may be provided on the outer peripheral side of the partition wall.

The shape of the honeycomb structural body 4 is not particularly limited. The shape of the honeycomb structure 4 may be: the inflow end face 11 and the outflow end face 12 have a columnar shape such as a circle, an ellipse, or a polygon.

The size of the honeycomb structure 4, for example, the length from the inflow end face 11 to the outflow end face 12, and the size of the cross section of the honeycomb structure 4 orthogonal to the direction in which the cells 2 extend are not particularly limited. When the honeycomb filter 100 is used as a filter for purifying exhaust gas, the respective sizes may be appropriately selected so as to obtain the optimum purification performance.

The material of the partition wall 1 is not particularly limited. For example, the material of the partition wall 1 may include at least 1 selected from the group consisting of silicon carbide, cordierite, a silicon-silicon carbide composite, a cordierite-silicon carbide composite, silicon nitride, mullite, alumina, and aluminum titanate. The material constituting the partition wall 1 is preferably a material having a content of 90 mass% or more, more preferably 92 mass% or more, and particularly preferably 95 mass% or more of the materials listed in the above group. The silicon-silicon carbide composite material is: a composite material formed by using silicon carbide as aggregate and silicon as a binding material. In addition, the cordierite-silicon carbide composite material is: a composite material formed by taking silicon carbide as aggregate and cordierite as a binding material.

The material of the hole sealing portion 5 is preferably a material that is preferable as the material of the partition wall 1. The material of the hole sealing portion 5 and the material of the partition wall 1 may be the same material or may be different materials.

The honeycomb filter 100 preferably has a catalyst for purifying exhaust gas supported on partition walls 1 partitioning a plurality of cells 2. The supporting of the catalyst on the partition wall 1 means: the surface of the partition wall 1 and the inner walls of the pores formed in the partition wall 1 are coated with a catalyst. With such a configuration, CO, NOx, HC and the like in the exhaust gas can be rendered harmless by a catalytic reaction. In addition, oxidation of PM such as trapped soot can be promoted. In the honeycomb filter 100 of the present embodiment, it is particularly preferable that the catalyst is supported in the pores of the porous partition walls 1. With such a configuration, the catalyst is supported in a low catalyst amount, and thus the trapping performance and the pressure loss can be simultaneously improved. Further, after the catalyst is supported, the airflow becomes uniform, and improvement of the purification performance can be expected.

The catalyst supported on the partition wall 1 is not particularly limited. For example, a catalyst containing a platinum group element and an oxide of at least one element selected from aluminum, zirconium, and cerium is given.

(2) The manufacturing method of the honeycomb filter comprises the following steps:

the method for producing the honeycomb filter of the present utility model is not particularly limited, and the following methods are exemplified. First, a plastic blank for manufacturing a honeycomb structure is prepared. The green body for producing the honeycomb structure may be prepared by appropriately adding an additive such as a binder, a pore-forming material, and water to a material selected from the preferable materials of the partition walls as a raw material powder.

Next, the thus obtained preform is extruded to produce a cellular molded body having partition walls dividing into a plurality of cells and a columnar shape disposed around the outer peripheral wall of the partition walls. In extrusion molding, as a die for extrusion molding, a die having a slit provided on an extrusion surface of a preform to be a turned shape of a honeycomb molding to be molded may be used. In particular, as the die for extrusion molding, a die provided with a slit having a thickness T2 of the partition wall in the outer peripheral portion thinner than a thickness T1 of the partition wall in the central portion by 0.0127 to 0.0254mm is preferably used. The die for extrusion molding is preferably: the cells of the outer peripheral portion have a shape in which corners of a polygon are rounded into an arc shape having a radius of curvature R of 100 to 200 [ mu ] m. Next, the obtained honeycomb formed body is dried by, for example, microwave and hot air.

Next, plugged portions are disposed in the openings of the cells of the dried honeycomb formed article. Specifically, for example, a plugging material containing a raw material for forming a plugged portion is first prepared. Next, a mask was applied to the inflow end face of the honeycomb formed body so as to cover the inflow cells. Next, the plugging material prepared previously was filled in the openings of the outflow cells on the inflow end face side of the honeycomb formed body without applying a mask. Thereafter, the openings of the inflow cells were also filled with a plugging material in the same manner as described above with respect to the outflow end face of the honeycomb formed body.

Next, a honeycomb formed body having a plugged portion disposed at any one of the openings of the cells was sintered to produce a honeycomb filter. The firing temperature and the firing atmosphere vary depending on the raw materials, and if the person skilled in the art is able to select the firing temperature and the firing atmosphere optimal for the selected material.

Examples

Hereinafter, the present utility model will be described in further detail with reference to examples, but the present utility model is not limited to these examples.

Example 1

10 parts by mass of a pore-forming material, 4 parts by mass of a dispersion medium, and 4 parts by mass of an organic binder were added to 100 parts by mass of a cordierite forming raw material, and the mixture was mixed and kneaded to prepare a green body. Alumina, aluminum hydroxide, kaolin, talc, and silica were used as cordierite forming raw materials. As the dispersion medium, water was used. As the organic binder, methylcellulose (methyl cellulose) is used. As the dispersant, dextrin (dextran) was used. As the pore-forming material, a water-absorbent polymer having an average particle diameter of 5 μm was used. In this example, the average particle size of each raw material is: particle diameter (D50) at 50% of the cumulative value in the particle size distribution obtained by the laser diffraction scattering method.

Next, the preform was extruded using a die for producing a honeycomb molding, to obtain a honeycomb molding having a cylindrical overall shape. The cells of the honeycomb formed body are quadrangular in shape.

Next, the honeycomb formed body was dried by a microwave dryer, and further, completely dried by a hot air dryer, and then, both end surfaces of the honeycomb formed body were cut and adjusted to a predetermined size.

Next, a plugging material for forming a plugged portion is prepared. Thereafter, a plugging material is used to form plugging portions in openings of predetermined cells on the inflow end face side and openings of remaining cells on the outflow end face side of the dried honeycomb formed body.

Next, the honeycomb formed body having each plugged portion was degreased and fired to produce the honeycomb filter of example 1.

The honeycomb filter of example 1 has a cylindrical shape with a circular shape on the inflow end face and the outflow end face. The diameters of the inflow end face and the outflow end face were 118.4mm. In addition, the length in the direction in which the cells of the honeycomb filter extend was 127mm. In the honeycomb filter of example 1, the thickness T1 of the center partition wall was 0.2032mm, and the thickness T2 of the outer peripheral partition wall was 0.1905mm. The thickness of each partition wall is shown in table 1. The increase in the thickness T2 of the peripheral partition wall relative to the thickness T1 of the central partition wall was-0.0127 mm. The results are shown in the column of "thickness increase amount (mm) of the outer peripheral partition wall" in Table 1. In the column of "increase and decrease in thickness (mm)" of the peripheral partition wall in table 1, an increase and decrease (mm) of a negative value indicates that the thickness T2 of the peripheral partition wall is smaller than the thickness T1 of the central partition wall. That is, an increase in the thickness T2 of the peripheral partition wall of-0.0127 mm means: the reduction in the thickness T2 of the peripheral partition wall relative to the thickness T1 of the central partition wall was 0.0127mm. On the other hand, in the column of "thickness increase/decrease (mm) of the outer peripheral partition wall" in table 1, the increase/decrease (mm) shown as a positive value indicates that the thickness T2 of the outer peripheral partition wall is thicker than the thickness T1 of the central partition wall. The ratio of the area of the outer peripheral portion to the total area of the cross section of the honeycomb structure was 10%.

In the honeycomb filter of example 1, in a cross section orthogonal to the direction in which cells extend, the cells of the outer peripheral portion have a rectangular shape, and corners of the cells have circular arc-shaped substantially rectangular shapes having a radius of curvature R of 100 μm. In the honeycomb filter of example 1, the cell density was 47 cells/cm ² . The porosity of the partition wall was 63%, and the average pore diameter of the partition wall was 19. Mu.m. The results are shown in Table 1. The porosity of the partition walls and the average pore diameter were measured by using an Autopore 9500 (trade name) manufactured by Micromeritics corporation. The cells in the central portion were substantially quadrangular in shape.

TABLE 1

The honeycomb filter of example 1 was evaluated for "light-off performance", "isostatic strength", "pressure loss", "erosion resistance" and "moldability (yield)" by the following methods. The mass of the honeycomb filter of example 1 was measured, and the mass ratio to the mass of the honeycomb filter of comparative example 1 described later was obtained. Based on the results of the evaluation of the "light-off performance" and the "isostatic strength", the following method was used to perform the "comprehensive evaluation". The results are shown in Table 2.

[ ignition Performance ]

The temperature of the center portion of the honeycomb filter was measured by flowing 400℃gas through the honeycomb filter, and the time required for the temperature of the center portion to reach 400℃was measured. Based on the time measured in this way (i.e., the time required for the temperature of the central portion of the honeycomb filter to reach 400 ℃), the evaluation of the light-off performance was performed. Specifically, the ratio (%) of the time required for the temperature of the central portion of the honeycomb filter of comparative example 1 to reach 400 ℃ was obtained for each example and comparative example, where the time required for the temperature of the central portion of the honeycomb filter to reach 400 ℃ was 100.0%. In the evaluation of the light-off performance, the case where the ratio of the value of the time required for the temperature of the central portion of the honeycomb filter to reach 400 ℃ was less than 100% was regarded as acceptable.

[ isostatic Strength ]

The honeycomb filter was pressurized under a still water pressure until it was broken, and the pressure at the time of breakage was measured. Then, the ratio (%) of the hydrostatic pressure values at the time of breakage of the honeycomb filters of each example and comparative example was obtained, where the hydrostatic pressure value at the time of breakage of the honeycomb filter of comparative example 1 was set to 100.0%. In the evaluation of the isostatic strength, the ratio of the value of the hydrostatic pressure at the time of breakage was defined as 95% or more.

[ pressure loss ]

At 25 ℃ for 10m ³ The gas/min flowed through the honeycomb filter, and the pressure difference between the inflow end face side and the outflow end face side of the honeycomb filter in this state was measured. Then, the ratio (%) of the values of the pressure loss of the honeycomb filters of each example and comparative example was obtained when the value of the pressure loss of the honeycomb filter of comparative example 1 was set to 100.0%. In the evaluation of pressure loss, the following will applyThe case where the ratio of the pressure loss values is less than 100% is regarded as acceptable.

[ erosion resistance ]

Making 800 ℃ and 10m ³ The gas per minute was flowed at an inflow angle of 30 degrees to the inflow end face of the honeycomb filter, and 20mg of silicon carbide powder was put into the gas. After the silicon carbide powder in the gas passes through the honeycomb filter, the amount of end face chipping of the honeycomb filter (hereinafter referred to as "end face chipping amount") was measured. Then, the ratio (%) of the values of the erosion resistance of the honeycomb filters of the examples and comparative examples was obtained when the value of the erosion resistance (hereinafter referred to as "erosion resistance") of the end face removal amount of the honeycomb filter of comparative example 1 was set to 100.0%. The case where the erosion resistance ratio was 95% or more was regarded as acceptable.

[ formability (yield) ]

The appearance of the product (dried honeycomb formed body) obtained by molding by extrusion molding was checked to confirm whether or not there was any defect in appearance such as a crack. Then, the ratio (%) of the values of the yields of the honeycomb filters of the examples and comparative examples was obtained when the value of the yield of the honeycomb filter of comparative example 1 was set to 100.0%. In the evaluation of the moldability (yield), the case where the ratio of the value of the yield was 85% or more was regarded as being acceptable.

[ comprehensive evaluation ]

Based on the results of evaluation of the light-off performance and the isostatic pressure intensity, comprehensive evaluation was performed based on the following evaluation criteria.

When both the ignition quality and the isostatic pressure strength are evaluated to be acceptable, the "comprehensive evaluation" column is written as "excellent" or "ok".

When one of the light-off performance and the isostatic pressure intensity is evaluated as failed, the "comprehensive evaluation" column is described as "poor".

TABLE 2

Examples 2 to 10 and comparative examples 1 to 4

A honeycomb filter was produced in the same manner as the honeycomb filter of example 1 except that the structure of the honeycomb filter was changed as shown in table 1.

The honeycomb filters of examples 2 to 10 and comparative examples 1 to 4 were evaluated in the same manner as in example 1. The results are shown in Table 2.

(results)

The honeycomb filters of examples 1 to 10 gave good results in both evaluations of the light-off performance and the isostatic strength. In particular, the honeycomb filter of example 9 was excellent in light-off performance.

The honeycomb filter of comparative example 2 was constructed as follows: the thickness of the partition wall was a constant value at the central portion and the peripheral portion, and the thickness increase amount of the peripheral partition wall was 0mm. In the honeycomb filter of comparative example 2, the radius of curvature R of the corners of the cells in the outer peripheral portion was 50 μm. The honeycomb filter of comparative example 2 was significantly inferior in isostatic strength to the honeycomb filter of comparative example 1.

In the honeycomb filter of comparative example 3, the thickness of the outer peripheral partition wall increased by +0.0254mm, and the light-off performance was deteriorated as compared with the honeycomb filter of comparative example 1. In addition, the honeycomb filter of comparative example 3 was found to have a significant increase in pressure loss in the evaluation of pressure loss.

In the honeycomb filter of comparative example 4, since the thickness of the outer peripheral partition wall was increased by-0.0381 mm, the isostatic strength was significantly deteriorated as compared with the honeycomb filter of comparative example 1.

Industrial applicability

The honeycomb filter of the present utility model can be used as a filter for trapping particulate matter in exhaust gas.

Claims

1. A honeycomb filter is provided with:

it is characterized in that the method comprises the steps of,

2. The honeycomb filter of claim 1,

the porosity of the partition walls is 40-80%, and the average pore diameter of the partition walls is 5-21 mu m.

3. A honeycomb filter according to claim 1 or 2, characterized in that,

the thickness T1 of the partition walls in the central portion and the thickness T2 of the partition walls in the outer peripheral portion are 0.127-0.331 mm, and the cell density of the honeycomb structure is 31.0-62.0 cells/cm ² 。