JP2019093380A - Honeycomb filter - Google Patents

Abstract

To provide a honeycomb filter capable of effectively suppressing leakage of particulate substance such as soot.SOLUTION: A honeycomb filter includes a honeycomb structure part 4 having a porous partition wall 1 and a mesh sealing part 5 which mesh-seals either one side of end parts of a cell 2, at least contains such a cell row that inflow cell 2a and outflow cell 2b are arranged alternately across the partition wall 1 in the horizontal direction on a cross-section vertically crossing to such a direction that the cell 2 of the honeycomb structure part 4 is extended. Therein, the value of a porosity of the partition wall 1 on a portion 16 which partitions the inflow cell 2a and the outflow cell 2b is set as A, the value of porosity of the partition wall 1 on an intersection part 15 between two inflow cells 2a is set as B and the value of A/B is 0.5 to 0.95.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a honeycomb filter. More specifically, the present invention relates to a honeycomb filter which is excellent in thermal shock resistance and can effectively suppress leakage of particulate matter such as soot.

  In various industries, internal combustion engines are used as a power source. On the other hand, the exhaust gas discharged from the internal combustion engine at the time of fuel combustion contains particulate matter such as soot (soot) and ash (ash). For example, regulations regarding the removal of particulate matter discharged from a diesel engine are strict worldwide, and a honeycomb filter having a honeycomb structure is used as a filter for removing the particulate matter. Hereinafter, the particulate matter may be referred to as "PM". PM is an abbreviation of "Particulate Matter".

  Conventionally, as a honeycomb filter for removing PM, a honeycomb structure portion having porous partition walls for forming a plurality of cells, and a plugging portion for plugging one of the end portions of the cells What was equipped is proposed (for example, refer patent documents 1-3).

  Such a honeycomb filter has a structure in which porous partition walls function as a filter for removing PM. Specifically, after the PM-containing exhaust gas is made to flow from the inflow end face of the honeycomb filter and filtered by collecting the PM with the porous partition walls, the purified exhaust gas is discharged from the outflow end face of the honeycomb filter Do. Thus, PM in exhaust gas can be removed.

  In the honeycomb filter, various studies have been made on the shape of cells partitioned and formed by the partition walls. For example, a honeycomb filter or the like is proposed in which the cross-sectional area of a predetermined cell and the cross-sectional area of the remaining cells are different in a cross section cut along a plane orthogonal to the longitudinal direction of the cells. 1 and 2). As an example, a cross section of a cell having an opening at the inflow end side (hereinafter sometimes referred to as "inflow cell") and a cross section of a cell having an opening at the outflow end side (hereinafter sometimes referred to as "spill cell") A honeycomb filter configured to have a different area may be mentioned. Also, for the purpose of improving the strength of the honeycomb filter, a honeycomb filter or the like has been proposed in which the shape of the cell in the above cross section is formed into a circular arc at a portion corresponding to a corner in a polygon of quadrangle or more. (For example, refer to patent documents 1 and 3).

JP, 2005-270969, A International Publication No. 2008/117559 Unexamined-Japanese-Patent No. 2010-221159

  In the honeycomb filter described in Patent Document 1, the cross-sectional area of a predetermined cell and the cross-sectional area of the remaining cells are different in a cross section cut along a plane perpendicular to the longitudinal direction of the cells. In this honeycomb filter, the ratio of the channel hydraulic diameter of the large cross-sectional area to the channel hydraulic diameter of the small cross-sectional area cell is 1.2 or more. Furthermore, in this honeycomb filter, at least the cross-sectional shape of the cell having a large cross-sectional area is an arc-shaped square at a portion corresponding to at least one corner, and the minimum thickness of the portion where the partition intersects with respect to the thickness of the partition. The value of the aspect ratio is 0.7 or more and less than 1.3.

  According to the honeycomb filter described in Patent Document 1, it is said that thinning of a part of the portion where the partition walls intersect can be prevented, and high strength can be maintained. In many of the conventional honeycomb filters, inflow cells and outflow cells are alternately arranged with a partition wall interposed therebetween. For this reason, in the honeycomb filter described in Patent Document 1, when a crack is generated in the honeycomb filter due to a thermal shock, the crack is easily generated relatively to the partition dividing the inflow cell and the outflow cell. It has become. Therefore, the honeycomb filter described in Patent Document 1 has a problem that PM such as soot easily leaks out when a crack is generated in the honeycomb filter.

  Also in the honeycomb filter described in Patent Document 2, the portion where the partition walls intersect is configured to be thicker than the partition walls that partition between cells. Therefore, as in the case of the honeycomb filter described in Patent Document 1 described above, there is a problem that PM such as soot easily leaks out when a crack occurs in the honeycomb filter.

  In the honeycomb filter described in Patent Document 3, since the cross-sectional shape of the outflow cell is a shape in which a portion X corresponding to a corner in a polygon having a quadrangle or more is formed in an arc shape, The strength is relatively high. For this reason, although the maximum temperature at the time of regeneration of the honeycomb filter can be reduced, when a crack is generated in the honeycomb filter, the crack is generated relatively to the partition dividing the inflow cell and the outflow cell. It will be easier. Therefore, when a crack has occurred in the honeycomb filter, there has been a problem that PM such as soot easily leaks out.

  The present invention has been made in view of the problems of the prior art. The present invention provides a honeycomb filter which is excellent in thermal shock resistance and can effectively suppress the leakage of particulate matter such as soot.

  According to the present invention, a honeycomb filter shown below is provided.

[1] A honeycomb structure portion having porous partition walls disposed so as to surround a plurality of cells serving as fluid channels extending from the inflow end face to the outflow end face;
And a plugging portion arranged to seal one of the inflow end surface side and the outflow end surface side of the cell.
The plugging portion is disposed at an end portion on the outflow end surface side, and the cell having the inflow end surface side opened is an inflow cell,
The plugging portion is disposed at an end portion on the inflow end surface side, and the cell having an opening on the outflow end surface side is an outflow cell,
In a cross section orthogonal to the extending direction of the cells of the honeycomb structure portion, the inflow cells and the outflow cells at least include cell rows alternately arranged across the partition wall in one direction,
The value of the porosity of the partition wall at a portion where the inflow cell and the outflow cell are partitioned is a porosity A.
The porosity B of the partition wall at the intersection between the two inflow cells is defined as the porosity B at the intersection where the partitions separating the cells cross each other.
The honeycomb filter whose A / B which is a value which divided the porosity A by the porosity B is 0.50 to 0.95.

[2] The honeycomb filter according to [1], wherein the porosity A is 15 to 70%.

[3] The honeycomb filter according to [1] or [2], wherein an arithmetic mean of the porosity A and the porosity B is 25 to 80%.

[4] The inflow cell according to any one of the above [1] to [3], wherein the shape of the inflow cell in a cross section orthogonal to the cell extending direction of the honeycomb structure body is a quadrangle, a hexagon, or an octagon. Honeycomb filter.

[5] The honeycomb filter according to [4], wherein the shape of the outflow cell in a cross section orthogonal to the cell extending direction of the honeycomb structure part is a quadrangle or a hexagon.

[6] The honeycomb filter according to any one of [1] to [5], wherein an opening area S1 of one inflow cell is larger than an opening area S2 of one inflow cell.

[7] The honeycomb filter according to any one of [1] to [6], wherein the thickness of the partition wall is 100 to 450 μm.

  The honeycomb filter of the present invention is excellent in thermal shock resistance, and can effectively suppress the leakage of particulate matter such as soot. That is, in the honeycomb filter of the present invention, the porosity A of the partition wall at the portion separating the inflow cell and the outflow cell is relatively lower than the porosity B of the partition wall at the intersection between two inflow cells. Therefore, when a crack is generated in the honeycomb filter, the crack is likely to be generated at the intersection of the above-described partition walls. Cracks occurring at the intersections of the partition walls occur diagonally to the intersections between the inflow cells or between the outflow cells, so even if such cracks occur temporarily, the influence on the leakage of PM I do not receive. For this reason, according to the honeycomb filter of the present invention, leakage of particulate matter such as soot can be effectively suppressed.

It is the perspective view seen from the inflow end side which shows typically the first embodiment of the honeycomb filter of the present invention. It is a top view which shows typically the inflow end surface of the honeycomb filter shown in FIG. It is the enlarged plan view which expanded a part of inflow end surface of the honeycomb filter shown in FIG. It is sectional drawing which shows typically the A-A 'cross section of FIG. It is the enlarged plan view which expanded a part of inflow end surface which shows typically 2nd embodiment of the honey-comb filter of this invention. It is the enlarged plan view which expanded a part of inflow end surface which shows typically 3rd embodiment of the honey-comb filter of this invention. It is a top view showing a part of inflow end face which shows typically a second embodiment of the honeycomb filter of the present invention. It is a top view showing a part of inflow end face which shows typically a 4th embodiment of a honeycomb filter of the present invention. It is the perspective view seen from the inflow end side which shows typically 5th embodiment of the honey-comb filter of this invention. It is a top view which shows typically the inflow end face of a 6th embodiment of the honeycomb filter of the present invention.

  Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments. Therefore, it should be understood that appropriate modifications, improvements, and the like can be added to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

(1) Honeycomb filter (first embodiment):
As shown in FIGS. 1 to 4, in the first embodiment of the honeycomb filter of the present invention, either one of the honeycomb structure portion 4 having the porous partition walls 1 and the cells 2 formed in the honeycomb structure portion 4 is used. It is the honeycomb filter 100 provided with the plugged part 5 arrange | positioned by the edge part. Here, FIG. 1 is a perspective view schematically showing the first embodiment of the honeycomb filter of the present invention as viewed from the inflow end side. FIG. 2 is a plan view schematically showing the inflow end surface of the honeycomb filter shown in FIG. FIG. 3 is an enlarged plan view of a part of the inflow end surface of the honeycomb filter shown in FIG. FIG. 4 is a cross-sectional view schematically showing a cross section AA 'in FIG.

  The partition walls 1 of the honeycomb structure portion 4 are disposed so as to surround a plurality of cells 2 serving as fluid channels extending from the inflow end surface 11 to the outflow end surface 12. That is, the plurality of cells 2 are partitioned by the porous partition walls 1. The plugged portions 5 are disposed so as to seal one end of the cells 2 formed in the honeycomb structure portion 4. For this reason, one end of each of the plurality of cells 2 is sealed by the plugging portion 5 disposed in the opening on the inflow end surface 11 side or the outflow end surface 12 side. In the honeycomb filter 100 of the present embodiment, the porous partition walls 1 function as a filtering material for collecting PM in the exhaust gas. Here, among the plurality of cells 2, the plugging portion 5 is disposed at the opening on the outflow end surface 12 side, and the cell 2 in which the inflow end surface 11 side is opened is referred to as an inflow cell 2a. Further, among the plurality of cells 2, the plugging portion 5 is disposed at the opening on the inflow end surface 11 side, and the cell 2 in which the outflow end surface 12 side is opened is referred to as an outflow cell 2b.

  The honeycomb structure portion 4 has at least a cell row in which the inflow cells 2a and the outflow cells 2b are alternately arranged across the partition wall 1 in one direction in a cross section orthogonal to the extending direction of the cells 2 of the honeycomb structure portion 4 Including. The “cell array in which the inflow cells 2 a and the outflow cells 2 b are alternately arranged with the partition wall 1 in the one direction” in the cross section of the honeycomb structure portion 4 has at least one line. Good. In the honeycomb filter 100 shown in FIGS. 1 to 4, the respective cell rows extending in the longitudinal direction and the lateral direction of the paper surface are cell rows in which the inflow cells 2 a and the outflow cells 2 b are alternately arranged.

  The “cell array in which the inflow cells 2a and the outflow cells 2b are alternately arranged across the partition wall 1 in one direction” means the following when the cross sectional shapes of the inflow cells 2a and the outflow cells 2b are polygonal: It means the cell row configured as. That is, the cell row is a cell row in which the inflow cell 2a and the outflow cell 2b are partitioned by the partition walls 1 formed by two opposing sides of the polygonal inflow cell 2a and the outflow cell 2b. It means that. For this reason, in the "cell array in which the inflow cells 2a and the outflow cells 2b are alternately arranged across the partition wall 1 in one direction", a plurality of cells have vertexes of their cross-sectional shapes (ie, polygons It is assumed that the cell row in which the vertexes of the cells are arranged to face each other is not included. In addition, about the partition 1 which exists in the site | part which the vertex of each other's cross-sectional shape of several cells opposes, it becomes the "intersection part 15" mentioned later.

  In the honeycomb filter 100 of the present embodiment, the porosity (hereinafter referred to as the porosity A) of the partition wall 1 at the portion 16 separating the inflow cell 2a and the outflow cell 2b and the partition wall 1 at the intersection 15 between the two inflow cells 2a. It is characterized in that the porosity (hereinafter, porosity B) shows different values. More specifically, the value of the porosity of the partition wall 1 at the portion 16 dividing the inflow cell 2 a and the outflow cell 2 b is taken as the porosity A. Further, the porosity value of the partition wall 1 at the intersection portion 15 between two inflow cells 2a in the intersection portion 15 at which the portions (for example, the portion 16 to be partitioned) of the partition walls 1 partition each other intersect Let the rate B. In this case, “porosity A / porosity B”, which is a value obtained by dividing the porosity A by the porosity B, is 0.50 to 0.95. Hereinafter, “porosity A / porosity B” may be simply referred to as “A / B”. In the honeycomb filter 100 of the present embodiment, when the value of “A / B” is set to the above-described numerical range, when a crack is generated in the honeycomb filter 100, the inflow end face 11 side between the inflow cells 2 a A crack is likely to occur at the intersection portion 15. In addition, on the outflow end surface 12 side, a crack is easily generated at the intersection 15 between the outflow cells 2b. That is, the crack generated at the intersection 15 is generated diagonally at the intersection 15 due to the influence of the temperature difference in the honeycomb filter 100. In particular, on the inflow end face 11 side and the outflow end face 12 side of the honeycomb filter 100, cracks are easily generated in the diagonal direction connecting the cells 2 in which the plugged portions 5 are not disposed, and the plugged portions 5 are disposed. Cracks are less likely to occur in the diagonal direction connecting the cells 2. Here, even if a crack is generated at the intersection 15 between the inflow cells 2a on the inflow end surface 11 side of the honeycomb filter 100, there is no influence on the leakage of PM. Similarly, even if a crack is generated at the intersection 15 between the outflow cells 2b on the outflow end face 12 side of the honeycomb filter 100, there is no influence on the leakage of PM. For this reason, according to the honeycomb filter 100 of the present embodiment, the leakage of PM such as soot can be effectively suppressed.

  In the specification of the present application, the "intersection portion" refers to a portion at which portions dividing the cells of the partition walls cross each other. Specifically, in the cross section orthogonal to the extending direction of the cells of the honeycomb structure part, the following positions are mentioned. The “intersection portion” is a partition wall arranged in a lattice shape so as to surround a plurality of cells, and a partition wall arranged along a first direction constituting the grid and a second direction different from the first direction It refers to the part where the partition walls arranged along the direction cross each other (the part where the grid lines overlap). Here, the “first direction of the grid” includes a direction parallel to the part dividing the two cells of the partition, and draws a locus along which the single stroke is drawn. Then, in the first direction of the grid, when the partition wall is bent in the first direction, a direction in which the bending angle of the partition wall with respect to the first direction is smaller is selected. The “second direction of the grating” can also be defined in the same manner as the “first direction of the grating” described above.

  Hereinafter, in the present specification, the value of the porosity of the partition wall 1 at the portion 16 dividing the inflow cell 2a and the outflow cell 2b may be simply referred to as "porosity A". For example, the inflow cells 2a and the outflow cells 2b in the cell row in which the inflow cells 2a and the outflow cells 2b are alternately arranged with the partition wall 1 in between in the inflow cell 2a and the outflow cell 2b. The part 16 which divides 2b can be mentioned. Moreover, the value of the porosity of the partition 1 in the intersection part 15 between two inflow cells 2a may only be called "porosity B." The “intersection portion 15 between two inflow cells 2a” is, for example, “a portion where the apexes of the cross sectional shapes of two or more inflow cells 2a face each other” when the shape of the cell 2 is a quadrangle. For this reason, three or more inflow cells 2a may be disposed to face each other at the “intersection 15 between two inflow cells 2a”. Further, with regard to the "apex of the cross-sectional shape of the inflow cell 2a" described above, a portion corresponding to the apex of the corresponding cross-sectional shape may be rounded or may be chamfered in a straight line. . As in the case of a honeycomb structure 200 shown in FIG. 5 described later, octagonal cells 22 and octagonal cells 22 are alternately arranged with the partition wall 21 in one cell row. Cell 22 can be treated as a chamfered square cell 22.

  In the present invention, each of the porosity A and the porosity B of the partition wall 1 is a value obtained by the following method. First, a sample piece for performing measurement of the porosity A and the porosity B is cut out from the honeycomb filter 100. About the cut-out part of each sample piece, in each of the inflow end surface 11 side of the honeycomb filter 100 and the outflow end surface 12 side, it makes a total of ten places five each. The cutout position at each end surface is taken as the first cutout position at the center position of each end surface. Then, at each of the end faces, the remaining four cut-out points are four points which are intermediate points between the center position and the outer peripheral edge of the honeycomb filter 100 on the X axis and Y axis passing through the center position and orthogonal to each other I assume.

  The sample pieces for measuring the porosity A are cut out so as to include the partition wall 1 at the central portion of the partition wall 1 that partitions the inflow cell 2a and the outflow cell 2b at each of the above ten locations. The length of one side of the sample piece for measuring the porosity A is the thickness of the partition 1 in the central portion described above, and the length of the other side is 100 μm in the extending direction of the partition 1 in each end face. The length of one side is set to 20 mm in the extending direction of the cell 2.

  The sample piece for measuring the porosity B is cut out so that the central part of the intersection part 15 of the partition 1 may be included in each of ten places mentioned above. The sample piece for measuring the porosity B has a square with a side length of 100 μm centered on the center of the intersection 15 of the partition 1 as an end face, and the axial length is 20 mm in the cell 2 extending direction I assume.

  After the sample piece cut out from the honeycomb filter 100 in this manner is embedded in an epoxy resin and solidified, the surface is polished. Then, each sample piece is cut out by 5 mm in the full length direction, and the cut surface is taken as an observation surface by a scanning electron microscope (hereinafter also referred to as "SEM"). SEM is an abbreviation of "Scanning Electron Microscope". As a scanning electron microscope, for example, a scanning electron microscope "Model No .: S3200-N" manufactured by Hitachi High-Technologies Corporation can be used.

  Then, the observation surface of the produced sample piece is observed by SEM, and a SEM image is acquired. In the case of measurement of the porosity A of the partition 1, the said SEM image is acquired about the partition 1 in each observation surface of 10 above-described sample pieces. It is assumed that the SEM image is observed at a magnification of 100 times. Moreover, in the case of the measurement of the porosity B of the partition 1, the said SEM image is acquired about the intersection part 15 of the partition 1 in each observation surface of ten sample pieces mentioned above. Next, for each image, “area S1 of partition 1” and “area S2 of pore portion (void portion)” are calculated using image analysis software. And the porosity of the partition 1 imaged by each image is calculated by "calculation formula (1): S2 / (S1 + S2)." As the values of S1 and S2, the average value of the porosity of each of ten places is used.

  In the honeycomb filter 100 for measuring the porosity, when a catalyst (not shown) for exhaust gas purification is supported on the surface of the partition 1 and the inside of the pores of the partition 1, the portion on which the catalyst is supported The porosity is determined on the basis of the pore portion of the partition wall 1. That is, in the method of measuring the porosity A and the porosity B described above, after the SEM image is taken, the area where the catalyst is determined to be present from the color information in the obtained SEM image is identified as the pore portion of the partition wall 1 The porosity is determined.

  If A / B, which is a value obtained by dividing the porosity A by the porosity B, is less than 0.50, two or more intersections 15 arranged adjacent to each other on the diagonal of the intersections 15 of the partition wall 1 In some cases, cracks may occur continuously, making it difficult to sufficiently suppress the leakage of PM. In addition, when the A / B exceeds 0.95, the partition wall 1 in the portion 16 separating the inflow cell 2a and the outflow cell 2b is easily cracked, which makes it difficult to suppress the leakage of PM. .

  A / B which is a value obtained by dividing the porosity A by the porosity B is 0.50 to 0.95, and preferably 0.55 to 0.90. With such a configuration, it is possible to more effectively suppress the leakage of PM such as soot.

  The value of porosity B is not particularly limited, but is preferably 25 to 80%, and more preferably 30 to 75%. If the porosity B value is less than 25%, an increase in pressure loss may occur. If the porosity B exceeds 80%, the isostatic strength of the honeycomb filter 100 may be lowered. Also, the value of the porosity A is not particularly limited, but is preferably 15 to 70%, for example.

  The arithmetic mean of the porosity A and the porosity B is preferably 20 to 75%, and more preferably 25 to 70%. When the arithmetic mean of the porosity A and the porosity B is less than 20%, an increase in pressure loss may be caused. In addition, when the arithmetic mean of the porosity A and the porosity B exceeds 75%, the isostatic strength of the honeycomb filter 100 may be lowered.

  There is no particular limitation on the shape of each cell 2 (hereinafter, also simply referred to as “cell shape”) in a cross section orthogonal to the extending direction of the cells 2 of the honeycomb structure part 4. For example, the shape of the inflow cell 2a is preferably a quadrangle, a hexagon, or an octagon. In addition, the shape of the outflow cell 2 b is preferably square or hexagonal. In addition, the shape of each cell 2 may be a shape in which a corner of a polygon is formed in a curved shape, for example, a substantially square in which a corner of a square is formed in a curved shape.

  The thickness of the partition wall 1 is preferably 100 to 450 μm, more preferably 120 to 430 μm, and particularly preferably 140 to 400 μm. When the thickness of the partition wall 1 is less than 100 μm, the isostatic strength of the honeycomb filter 100 may be reduced. When the thickness of the partition wall 1 exceeds 450 μm, pressure loss may increase, which may cause reduction in engine output and fuel efficiency. The thickness of the partition wall 1 is a value measured by a method of observing a cross section orthogonal to the axial direction of the honeycomb filter 100 with an optical microscope.

  The entire shape of the honeycomb filter 100 is not particularly limited. For example, in the entire shape of the honeycomb filter 100 shown in FIGS. 1 to 4, the inflow end surface 11 and the outflow end surface 12 have a circular cylindrical shape. In addition, for example, as the entire shape of the honeycomb filter 100, the inflow end face and the outflow end face may be in a substantially circular columnar shape such as an oval shape, a racetrack shape, or an oval shape. In addition, as the entire shape of the honeycomb filter 100, the inflow end surface 11 and the outflow end surface 12 may have a polygonal prismatic shape such as a quadrangle or a hexagon.

  There is no particular limitation on the material constituting the partition wall 1, but in terms of strength, heat resistance, durability and the like, the main component is preferably an oxide or non-oxide various ceramic, metal or the like. Specifically, for example, cordierite, mullite, alumina, spinel, silicon carbide, silicon nitride, and aluminum titanate can be considered as the ceramic. As the metal, Fe-Cr-Al based metal, metallic silicon, etc. can be considered. It is preferable to have as a main component 1 type or 2 types or more selected from these materials. From the viewpoint of high strength, high heat resistance, etc., one or more selected from the group consisting of alumina, mullite, aluminum titanate, cordierite, silicon carbide and silicon nitride may be the main component Particularly preferred. Further, silicon carbide or a silicon-silicon carbide composite material is particularly suitable from the viewpoint of high thermal conductivity, high heat resistance, and the like. Here, “main component” means a component that constitutes 50% by mass or more of the partition wall 1. It is preferable that 70 mass% or more is contained in the material which comprises the partition 1, and, as for the said component, it is still more preferable that 80 mass% or more is contained.

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

  In the honeycomb filter 100 of the present embodiment, a catalyst for exhaust gas purification may be supported on at least one of the surface of the partition walls 1 of the honeycomb structure portion 4 and the pores of the partition walls 1. By this configuration, CO, NOx, HC and the like in the exhaust gas can be made into harmless substances by catalytic reaction. Further, the oxidation of the soot collected in the partition wall 1 can be promoted.

  When a catalyst is supported on the honeycomb filter 100 of the present embodiment, the catalyst preferably includes one or more selected from the group consisting of an SCR catalyst, a NOx storage catalyst, and an oxidation catalyst. The SCR catalyst is a catalyst that selectively reduces the component to be purified. In particular, the SCR catalyst is preferably a NOx selective reduction SCR catalyst that selectively reduces NOx in exhaust gas. Further, as the SCR catalyst, metal-substituted zeolite can be mentioned. Iron (Fe) and copper (Cu) can be mentioned as a metal which carries out metal substitution of zeolite. As a zeolite, beta zeolite can be mentioned as a suitable example. In addition, the SCR catalyst may be a catalyst containing at least one selected from the group consisting of vanadium and titania as a main component. Examples of the NOx storage catalyst include alkali metals and alkaline earth metals. Examples of the alkali metal include potassium, sodium and lithium. As the alkaline earth metal, calcium and the like can be mentioned. As an oxidation catalyst, what contains a noble metal can be mentioned. Specifically, as the oxidation catalyst, one containing at least one selected from the group consisting of platinum, palladium and rhodium is preferable.

(2) Honeycomb filter (second to sixth embodiments):
Next, second to sixth embodiments of the honeycomb filter of the present invention will be described with reference to FIGS. Here, FIG. 5 is an enlarged plan view in which a part of the inflow end surface is schematically shown, illustrating the second embodiment of the honeycomb filter of the present invention. FIG. 6 is an enlarged plan view showing a part of the inflow end surface schematically showing the third embodiment of the honeycomb filter of the present invention. FIG. 7 is a plan view showing a part of the inflow end face schematically showing the second embodiment of the honeycomb filter of the present invention. FIG. 8 is a plan view showing a part of the inflow end face schematically showing the fourth embodiment of the honeycomb filter of the present invention. FIG. 9 is a perspective view schematically showing a fifth embodiment of the honeycomb filter of the present invention as viewed from the inflow end surface side. FIG. 10 is a plan view schematically showing the inflow end surface of the sixth embodiment of the honeycomb filter of the present invention.

  As shown in FIGS. 5 and 7, in the honeycomb filter according to the second embodiment of the present invention, either one of the honeycomb structure portion 24 having the porous partition walls 21 and the cells 22 formed in the honeycomb structure portion 24 is used. It is the honeycomb filter 200 provided with the plugged part 25 arrange | positioned by the edge part. In the honeycomb structure portion 24, in the cross section orthogonal to the extending direction of the cells 22 of the honeycomb structure portion 24, at least the cell rows in which the inflow cells 22a and the outflow cells 22b are alternately arranged with the partition wall 21 in one direction. Including.

  In the honeycomb filter 200 of the second embodiment, the shape of the inflow cell 22 a is “octagonal”, and the shape of the outflow cell 22 b is “quadrilateral”. The cross section of the octagonal inflow cell 22a is relatively larger than that of the rectangular outflow cell 22b. Also, assuming that the value of the porosity of the partition 21 at the portion 36 separating the inflow cell 22a and the outflow cell 22b is A, and the value of the porosity of the partition 21 at the intersection 35 between the two inflow cells 22a is B. The value of A / B is 0.5 to 0.95. The honeycomb filter 200 of the second embodiment configured as described above can also obtain the same function and effect as the honeycomb filter 100 (see FIGS. 1 to 4) of the first embodiment described above. The honeycomb filter 200 according to the second embodiment is configured in the same manner as the honeycomb filter 100 according to the first embodiment (see FIGS. 1 to 4) except that the shapes of the inflow cell 22a and the outflow cell 22b are different. preferable. When the square cells 22 and the octagonal cells 22 are alternately arranged across the partition 21 in one cell row, the octagonal cells 22 are treated as chamfered square cells 22. It can also be done.

  In the honeycomb filter 200, since the cross-sectional area of the inflow cell 22a is relatively large compared to the cross-sectional area of the outflow cell 22b, even if a crack is generated in the honeycomb filter 200, PM leakage such as soot is generated. It is possible to suppress the delivery more effectively. That is, even in a situation where a crack is generated in the honeycomb filter 200, priority is given to "intersection portion 35 which is a portion dividing inflow cells 22a" which is less susceptible to PM leakage even in a situation where a crack occurs. Can cause cracks. Therefore, it is possible to make it difficult to generate a crack connecting the inflow cell 22a and the outflow cell 22b in "the part 36 that divides the inflow cell 22a and the outflow cell 22b".

  When the opening area S1 of one inflow cell 22a is larger than the opening area S2 of one outflow cell 22b as in the honeycomb filter 200, the value of the ratio of the opening area S2 to the opening area S1 (S2 / S1) Is preferably 0.20 to 0.95, and more preferably 0.30 to 0.90. With this configuration, it is possible to extremely effectively suppress the occurrence of cracks that connect the inflow cell 22a and the outflow cell 22b at the intersection portion 35.

  As shown in FIG. 6, in the third embodiment of the honeycomb filter of the present invention, at one of the end portions of the honeycomb structure portion 44 having the porous partition walls 41 and the cells 42 formed in the honeycomb structure portion 44 It is the honeycomb filter 300 provided with the plugged part 45 arrange | positioned. In the honeycomb structure portion 44, in the cross section orthogonal to the extending direction of the cells 42 of the honeycomb structure portion 44, at least the cell rows in which the inflow cells 42a and the outflow cells 42b are alternately arranged with the partition wall 41 in one direction. Including.

  In the honeycomb filter 300 of the third embodiment, the shape of the inflow cell 42 a is “a square having rounded corners”, and the shape of the outflow cell 42 b is “a square”. The inflow cell 42a has a cross-sectional area relatively larger than that of the outflow cell 42b. In addition, when the porosity value of the partition 41 at the portion 56 separating the inflow cell 42a and the outflow cell 42b is A, and the porosity value of the partition 41 at the intersection 55 between the two inflow cells 42a is B. The value of A / B is 0.5 to 0.95. The honeycomb filter 300 of the third embodiment configured as described above can also obtain the same function and effect as the honeycomb filter 100 (see FIGS. 1 to 4) of the first embodiment described above. The honeycomb filter 300 according to the third embodiment is configured in the same manner as the honeycomb filter 100 according to the first embodiment (see FIGS. 1 to 4) except that the shapes of the inflow cell 42a and the outflow cell 42b are different. preferable.

  As shown in FIG. 8, in the fourth embodiment of the honeycomb filter of the present invention, at one of the end portions of the honeycomb structure portion 64 having the porous partition walls 61 and the cells 62 formed in the honeycomb structure portion 64. It is the honeycomb filter 400 provided with the plugged part 65 arrange | positioned. In the honeycomb structure portion 64, in the cross section orthogonal to the extending direction of the cells 62 of the honeycomb structure portion 64, at least the cell row in which the inflow cells 62a and the outflow cells 62b are alternately arranged with the partition wall 61 in one direction. Including.

  In the honeycomb filter 400 of the fourth embodiment, the shapes of the inflow cell 62a and the outflow cell 62b are "hexagonal". Then, assuming that the value of the porosity of the partition wall 61 at the portion 76 separating the inflow cell 62a and the outflow cell 62b is A, and the value of the porosity of the partition wall 61 at the intersection 75 between two inflow cells 62a is B. The value of A / B is 0.5 to 0.95. The honeycomb filter 400 of the fourth embodiment configured as described above can also obtain the same function and effect as the honeycomb filter 100 (see FIGS. 1 to 4) of the first embodiment described above. The honeycomb filter 400 of the fourth embodiment is configured in the same manner as the honeycomb filter 100 (see FIGS. 1 to 4) of the first embodiment except that the shapes of the inflow cell 62a and the outflow cell 62b are different. preferable.

  When the shape of the cell 62 is a hexagon, "the intersection 75 between two inflow cells 62a and one outflow cell 62b" as "the intersection 75 between two inflow cells 62a", and "3 There are two types of intersections 75 with the intersection 75 present between two inflow cells 62a. In the honeycomb filter 400 of the present embodiment, assuming that the porosity B at one of the two intersection points 75 of the two types described above is the porosity B, A / B is 0.50 to 500. It may be 0.95. In addition, when the value of the porosity in the intersection part 75 which exists between the three inflow cells 62a is made into the porosity B, it is more preferable that A / B is 0.50-0.95.

  As shown in FIG. 9, in the fifth embodiment of the honeycomb filter of the present invention, the plugging disposed at one end of either the honeycomb structure portion 84 or the cells 82 formed in the honeycomb structure portion 84 is performed. A honeycomb filter 500 including a portion 85. In particular, in the honeycomb filter 500, each honeycomb structure portion 84 is formed of columnar honeycomb segments 86, and the side surfaces of the plurality of honeycomb segments 86 are joined by the joining layer 87. That is, in the honeycomb filter 500 of the present embodiment, each of the individual honeycomb segments 86 constituting the honeycomb filter of the segment structure is the honeycomb structure portion 84 in the honeycomb filter 500. Here, the “honeycomb filter having a segment structure” is a honeycomb filter formed by bonding a plurality of honeycomb segments 86 manufactured individually. The honeycomb filter 100 in which all the partition walls 1 of the honeycomb structure portion 4 are integrally formed as shown in FIGS. 1 to 4 is sometimes referred to as an “integrated honeycomb filter”. The honeycomb filter of the present invention may be a "segment-structured honeycomb filter" or an "integral-type honeycomb filter".

  In the honeycomb filter 500, preferably, at least one honeycomb segment 86 is configured in the same manner as the honeycomb structure portion of the honeycomb filter of the first embodiment described above. Even with such a honeycomb filter 500, the same effects as those of the honeycomb filter of the first embodiment described above can be obtained. Each of the plurality of honeycomb segments 86 may have the same cell structure or may have different cell structures.

  The outer peripheral wall 83 of the honeycomb filter 500 is preferably an outer peripheral coat layer formed of an outer peripheral coat material. The outer periphery coating material is a coating material for forming an outer periphery coating layer by coating the outer periphery of a joined body in which a plurality of honeycomb segments 86 are joined. Moreover, it is preferable that the bonded body obtained by bonding a plurality of honeycomb segments 86 is obtained by grinding the outer peripheral portion of the bonded body and arranging the above-described outer peripheral coat layer. Further, also in the integral type honeycomb filter 100 as shown in FIGS. 1 to 4, the outer peripheral coat formed by the outer peripheral coat material as described above, the outer peripheral wall 3 disposed on the outer periphery of the honeycomb structure portion 4. It may be a layer.

  In the honeycomb filter 500 shown in FIG. 9, the shape of the cells 82 (that is, the inflow cells 82a and the outflow cells 82b) is square. However, the shape of each cell 82 in each honeycomb segment 86 is not limited to a quadrangle, and the shape of the cells in the honeycomb filters of the first to fourth embodiments described so far can be adopted.

  As shown in FIG. 10, in the sixth embodiment of the honeycomb filter of the present invention, the plugging disposed at either one end of the honeycomb structure 4 and the cells 2 formed in the honeycomb structure 4 is performed. A honeycomb filter 600 including the portion 5. In particular, in the honeycomb filter 600, the entire shape of the honeycomb filter 600 is in the shape of a pillar having an elliptical end surface. That is, as shown in FIG. 10, the shape of the inflow end surface 11 is elliptical. It is preferable that it is comprised similarly to the honey-comb filter 100 (refer FIGS. 1-4) of 1st embodiment except the whole shape of the honey-comb filter 600 differing.

  In the honeycomb filter 600 shown in FIG. 10, the shape of the cells 2 (i.e., the inflow cells 2a and the outflow cells 2b) is square. However, the shape of the cells 2 is not limited to a quadrangle, and the shapes of the cells in the honeycomb filters of the first to fourth embodiments described above can be adopted.

(3) Manufacturing method of honeycomb filter:
Next, a method of manufacturing the honeycomb filter of the present invention will be described. The method for manufacturing a honeycomb filter of the present invention includes the steps of preparing a honeycomb formed body, forming a plugged portion in the opening of a cell, and drying and firing the honeycomb formed body. Can.

(3-1) Molding process:
The forming step is a step of extruding a clay obtained by kneading forming raw materials into a honeycomb shape to obtain a honeycomb formed body. The honeycomb formed body has a partition which partitions and forms a cell extending from the first end surface to the second end surface, and an outer peripheral wall formed so as to surround the outermost periphery of the partition. The part of the honeycomb structure constituted by the partition walls is the honeycomb structure part. In the forming step, first, the forming raw material is kneaded to form a clay. Next, the obtained clay is extruded to obtain a honeycomb formed body in which the partition walls and the outer peripheral wall are integrally formed.

  The forming raw material is preferably a ceramic raw material to which a dispersion medium and an additive are added. As an additive, an organic binder, a pore making material, surfactant, etc. can be mentioned. Water and the like can be mentioned as the dispersion medium. As the forming material, the same forming material as used in the conventionally known honeycomb filter manufacturing method can be used.

  As a method of knead | mixing a shaping | molding raw material and forming clay, the method of using a kneader, a vacuum soil kneader, etc. can be mentioned, for example.

  The extrusion molding can be performed using a die for extrusion molding in which a slit corresponding to the cross-sectional shape of the honeycomb formed body is formed. For example, as the die for extrusion molding, it is preferable to use a die having a slit corresponding to the shape of the cells in the honeycomb filters of the first to fourth embodiments described above.

  Here, in extrusion molding, it is preferable to increase the extrusion speed at the time of molding to increase the extrusion pressure. By performing extrusion molding by such a method, it is possible to make "the partition wall in the portion dividing the inflow cell and the outflow cell" more compact than the other portions. That is, in the obtained honeycomb filter, "the porosity B of the partition wall at the intersection between the two inflow cells" can be made relatively high. Thus, A / B, which is a value obtained by dividing the porosity A of the partition wall at the portion dividing the inflow cell and the outflow cell by the porosity B of the partition wall at the intersection between two inflow cells, is 0.5 to 0 It can be adjusted to the numerical range of .95.

(3-2) Plugging step:
The plugging step is a step of forming a plugging portion by plugging the opening of the cell. For example, in the plugging step, the plugging portion is formed by plugging the cell opening with a material similar to the material used for manufacturing the honeycomb formed body. About the method of forming a plugging part, it can carry out according to the manufacturing method of a conventionally well-known honey-comb filter.

(3-3) Firing step:
The firing step is a step of firing the honeycomb formed body in which the plugged portions are formed to obtain a honeycomb filter. Before firing the honeycomb formed body in which the plugged portions are formed, the obtained honeycomb formed body may be dried by, for example, microwave and hot air. In addition, for example, the firing step is performed on the honeycomb formed body before forming the plugging portion, and the above-described plugging step is performed on the honeycomb fired body obtained in the firing step. May be

  The firing temperature when firing the honeycomb formed body can be appropriately determined depending on the material of the honeycomb formed body. For example, when the material of the honeycomb formed 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 4 to 6 hours as a keeping time at the maximum temperature.

  Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited by these examples.

Example 1
0.5 parts by mass of a pore forming material, 33 parts by mass of a dispersion medium, and 5.6 parts by mass of an organic binder were added to 100 parts by mass of a cordierite-forming raw material, respectively, mixed and kneaded to prepare a clay. Alumina, aluminum hydroxide, kaolin, talc and silica were used as cordierite-forming materials. Water is used as the dispersion medium, a water-absorbing polymer having an average particle diameter of 10 to 50 μm is used as the pore forming material, methylcellulose is used as the organic binder, and dextrin is used as the dispersing agent did.

  Next, the clay was extruded using a predetermined mold to obtain a honeycomb molded body having a square cell shape and a cylindrical overall shape. At the time of extrusion molding, a die for extrusion molding having a slit corresponding to the cross-sectional shape of the honeycomb formed body is used, and in extrusion molding, the extrusion speed is compared with extrusion molding in Comparative Example 1 described later. The molding was carried out by raising the extrusion pressure.

  Next, the honeycomb formed body was dried by a hot air drier. The atmospheric temperature at the time of drying was 95 to 145 ° C.

  Next, a plugged portion was formed on the dried honeycomb formed body. Specifically, first, a mask was applied to the inflow end surface of the honeycomb formed body so as to cover the inflow cell. Thereafter, the end of the masked honeycomb molded body was immersed in the plugging slurry, and the plugging slurry was filled into the opening of the non-masked outflow cell. Thereafter, the plugging slurry was filled into the opening of the inflow cell also in the same manner as described above for the outflow end face of the honeycomb formed body. Thereafter, the honeycomb formed body in which the plugged portions were formed was further dried by a hot air drier.

  Next, the dried honeycomb molded body was fired to produce a honeycomb fired body. The atmosphere temperature at the time of firing was 1350 to 1440 ° C., and the firing time was 10 hours.

  Next, the wall material disposed on the outer peripheral portion of the honeycomb fired body was removed by grinding, and the outer peripheral coat material was applied to the outer peripheral portion to produce an outer peripheral wall made of the outer peripheral coat material. As outer peripheral coating material, prepared is cordierite particles having an average particle diameter of 20 to 50 μm, 90% particle diameter of 150 μm or less as ceramic particles, and a ceramic slurry prepared by mixing with colloidal silica, alumina fiber and water. Using. The outer peripheral wall of the honeycomb filter is described as “peripheral processing” in the column “Method for forming outer peripheral wall” in Table 1 with respect to the honeycomb filter formed using the outer peripheral coating material as described above. On the other hand, a honeycomb filter using the outer peripheral portion of the honeycomb formed body obtained by extrusion molding as the outer peripheral wall as it is is referred to as "one piece" in the column "Method of forming outer peripheral wall" in Table 1.

The honeycomb filter of Example 1 had a partition wall thickness of 300 μm and a cell density of 46.5 cells / cm ² . The cell shape in a cross section orthogonal to the extending direction of the cells of the honeycomb filter was a square. The column of “cell structure” in Table 1 shows the thickness of the partition wall, the cell density, and the cell shape.

  In the honeycomb filter of Example 1, the shape of the cross section orthogonal to the axial direction is circular, and in the honeycomb structure portion, as shown in FIG. 3, the inflow cells 2a and the outflow cells 2b are alternately arranged with the partition wall 1 interposed therebetween. It had an array of cells. The shape of the honeycomb filter of Example 1 is shown in the column of “cross-sectional shape”, “diameter”, and “total length” in Table 1.

  About the honeycomb filter of Example 1, "the porosity A of the partition wall at the portion separating the inflow cell and the outflow cell" and "the porosity B of the partition wall at the intersection between two inflow cells" by the following method, Was measured. Moreover, the average porosity and the porosity ratio were calculated | required from the value of the porosity A and the porosity B. The average porosity is the value of the arithmetic mean of porosity A and porosity B (ie, (A + B) / 2). The porosity ratio is the value of porosity A to porosity B (i.e., A / B). The respective results are shown in Table 2.

[Method of measuring porosity]
First, a sample piece for measuring the porosity A and the porosity B was cut out from the honeycomb filter. About the cut-out part of a sample piece, it was set as a total of ten places in each five places in each of the inflow end face side and the outflow end face side of a honeycomb filter. The cut-out points on each end face are the center position (first point) of each end face, and the midpoint between the center position and the outer peripheral edge of the honeycomb filter on the X axis and Y axis passing through the center position and orthogonal to each other. 4 points (2 to 5). The sample piece for measuring the porosity A was cut out so that the partition of the center part of the partition which divides an inflow cell and an outflow cell was included in each of ten places mentioned above. The length of one side of the sample piece for measuring the porosity A is the thickness of the partition in the central portion described above, and the length of the other side is 100 μm in the extending direction of the partition at each end face. The length was 20 mm in the cell extending direction. The sample piece for measuring the porosity B was cut out so that the center part of the intersection of a partition might be included in each of ten places mentioned above. The sample piece for measuring the porosity B had a square with a side length of 100 μm centered on the center of the intersection of the partition walls as an end face, and the axial length was 20 mm in the cell extending direction. Next, the manufactured sample piece was embedded in epoxy resin and solidified, and then the surface was polished. And each sample piece was cut out 5 mm in the full length direction, the cut surface was observed by SEM, and the SEM image was acquired. As a scanning electron microscope, “model number: S3200-N” manufactured by Hitachi High-Technologies Corporation was used. In the case of measurement of the porosity A, a SEM image magnified 100 times was acquired for the central portion of the partition wall in each observation surface of the ten sample pieces. Moreover, in the case of the measurement of the porosity B, the SEM image expanded 100 times was acquired about the intersection part of the partition in each observation surface of 10 above-described sample pieces. After that, using image analysis software, for each image, “area S1 of partition wall” and “area S2 of pore portion (void portion)” are calculated, “calculation formula (1): S2 / (S1 + S2)” The porosity of the partition wall imaged by each image was computed by these. The average value of the porosity of ten places was used for the value of S1 and S2.

(Examples 2 to 30)
The honeycomb structure of Examples 2 to 30 was manufactured by changing the cell structure, the sectional shape, the method of forming the outer peripheral wall, and the porosity A and porosity B of the partition walls as shown in Tables 1 and 2. In Examples 3, 4, 7, 8, 15 to 18, 23, 24, 29, and 30, the shape of the cell is as shown in FIG. That is, in the embodiment described above, the shape of the inflow cell is octagonal, and the shape of the outflow cell is quadrilateral. In Examples 7 and 8, the cross-sectional shape of the honeycomb filter was elliptical as shown in FIG. In Examples 13, 14, 17 and 18, the outer peripheral wall was not formed by the outer peripheral coat material, and the outer peripheral portion of the honeycomb formed body obtained by extrusion molding was used as the outer peripheral wall.

  In Examples 27 to 30, silicon carbide (SiC) was used as a material for producing a honeycomb filter. The honeycomb filter of Examples 27-30 is a honeycomb filter of a segment structure.

  At the time of preparation of the honeycomb filters of Examples 2 to 30, the extrusion pressure at the time of extrusion was adjusted, and the values of the porosity A and the porosity B of the partition walls were adjusted.

  The honeycomb filters of Examples 1 to 30 were evaluated for “heat resistance (robustness)” by the following method. The results are shown in Table 3.

[Heat resistance (robustness)]
As the evaluation of the thermal shock resistance, the test described below is performed on the honeycomb filter, and the robustness of the honeycomb filter is evaluated by the presence or absence of the occurrence of the crack in the honeycomb filter after the test. Specifically, first, 2 to 12 g / L of soot was deposited inside the honeycomb filters of the respective examples and comparative examples. The soot was deposited on an engine bench equipped with a 2.2 L diesel engine. As for the operating conditions of the engine bench, the engine speed was 2000 rpm and the engine torque was 60 Nm. After that, the regeneration processing by post injection was performed, the inlet gas temperature of the honeycomb filter was raised, and when the pressure loss before and after the honeycomb filter began to decrease, the post injection was turned off and the engine was switched to the idle state. At this time, the deposition amount of soot is such that the maximum temperature at the central portion of the outflow end face is 1000 ° C. in each level of the embodiment, and the deposition number of soot is the same in the same numbers of the embodiment and the comparative example. The test was conducted under the conditions. And the presence or absence of the crack was visually observed about each of "the partition of the site | part which divides an inflow cell and an outflow cell" and a "intersection part" of a honey-comb filter. About confirmation of the presence or absence of a crack, in the test mentioned above, it confirmed about all the locations of the outflow end face where temperature becomes the highest. And heat shock resistance was evaluated based on the following evaluation criteria. The results are shown in Table 3.
Evaluation A: No crack is confirmed.
Evaluation B: One crack is owned.
Evaluation C: Cracks are continuously present in two or more places.

Moreover, in evaluation of a thermal shock resistance, comprehensive determination was performed by the following method based on the evaluation result in two above-mentioned places. The results are shown in Table 3. In addition, in this comprehensive determination, the evaluation A is regarded as pass, and the evaluation B and the evaluation C are rejected.
Evaluation A: There is no soot leakage, and one or less crack.
Evaluation B: There is no soot leakage, but there are cracks continuously in two or more places.
Evaluation C: There is soot leakage.

(Comparative examples 1 to 30)
The cell structure, the cross-sectional shape, the method of forming the outer peripheral wall, and the porosity A and porosity B of the partition wall were changed as shown in Tables 4 and 5, to prepare honeycomb filters of Comparative Examples 1 to 30. The honeycomb filters of Comparative Examples 1 to 30 were also evaluated for “thermal shock resistance (robustness)” in the same manner as in Example 1. The results are shown in Table 6.

  In Comparative Examples 3, 4, 7, 8, 15 to 18, 23, 24, 29, and 30, the shape of the cell was as shown in FIG. Moreover, about the comparative examples 7 and 8, the cross-sectional shape of the honey-comb filter was made into the ellipse as shown in FIG. In Comparative Examples 13, 14, 17 and 18, the outer peripheral wall was not formed by the outer peripheral coat material, and the outer peripheral portion of the honeycomb formed body obtained by extrusion molding was used as the outer peripheral wall. In Comparative Examples 27 to 30, silicon carbide (SiC) was used as a material for producing a honeycomb filter. The honeycomb filter of Comparative Examples 27 to 30 is a honeycomb filter having a segment structure. In addition, the honeycomb filter of Comparative Examples 1-30 is a honeycomb filter of the same structure as Example 1-30 of a corresponding number except the values of the porosity A and the porosity B differing.

(result)
The honeycomb filters of Examples 1 to 30 were able to obtain the result of “Evaluation A” satisfying the acceptance criteria in the comprehensive judgment of the thermal shock resistance. In particular, in the honeycomb filters of Examples 1 to 30, no crack was observed at all in the "portion separating the inflow cell and the outflow cell (in other words, the substantial wall portion of the partition wall)". In addition, about "the intersection between inflowing cells", although a crack was confirmed in one place, since this crack is not affected by the soot leakage, even if such a crack occurs, The performance of the honeycomb filter is considered to be unaffected. Therefore, the honeycomb filters of Examples 1 to 30 were able to effectively suppress the leakage of particulate matter such as soot.

  The honeycomb filters of Comparative Examples 1 to 30 resulted in “Evaluation B” or “Evaluation C” which fail in the comprehensive judgment of the thermal shock resistance. In particular, in the “portion separating the inflow cell and the outflow cell”, soot leakage from the honeycomb filter was confirmed for the honeycomb filter in which the crack was confirmed. Moreover, in the "intersection portion", the honeycomb filter in which the crack was continuously confirmed at two or more places was not preferable in that the mechanical strength on the structure is lowered.

  The honeycomb filter of the present invention can be used as a filter for collecting particulate matter in exhaust gas.

1, 21, 41, 61, 81: partition wall, 2, 22, 42, 62, 82: cell, 2a, 22a, 42a, 62a, 82a: inflow cell, 2b, 22b, 42b, 62b, 82b: outflow cell, 3, 83: outer peripheral wall, 4, 24, 44, 64, 84: honeycomb structure portion, 5, 25, 45, 65, 85: plugging portion, 11, 31, 51, 71, 91: inflow end surface, 12 , 92: outflow end face, 15, 35, 55, 75: intersection between inflow cells, 16, 36, 56, 76: part dividing inflow cell and outflow cell, 86: honeycomb segment, 87: bonding layer, 100 , 200, 300, 400, 500, 600: honeycomb filter.

Claims (7)

A honeycomb structure portion having porous partition walls disposed so as to surround a plurality of cells serving as fluid channels extending from the inflow end surface to the outflow end surface;
And a plugging portion arranged to seal one of the inflow end surface side and the outflow end surface side of the cell.
The plugging portion is disposed at an end portion on the outflow end surface side, and the cell having the inflow end surface side opened is an inflow cell,
The plugging portion is disposed at an end portion on the inflow end surface side, and the cell having an opening on the outflow end surface side is an outflow cell,
In a cross section orthogonal to the extending direction of the cells of the honeycomb structure portion, the inflow cells and the outflow cells at least include cell rows alternately arranged across the partition wall in one direction,
The value of the porosity of the partition wall at a portion where the inflow cell and the outflow cell are partitioned is a porosity A.
The porosity B of the partition wall at the intersection between the two inflow cells is defined as the porosity B at the intersection where the partitions separating the cells cross each other.
The honeycomb filter whose A / B which is a value which divided the porosity A by the porosity B is 0.50 to 0.95.   The honeycomb filter according to claim 1, wherein the porosity A is 15 to 70%.   The honeycomb filter according to claim 1 or 2, wherein the arithmetic mean of the porosity A and the porosity B is 25 to 80%.   The honeycomb filter according to any one of claims 1 to 3, wherein a shape of the inflow cell in a cross section orthogonal to the extending direction of the cell of the honeycomb structure portion is a quadrangle, a hexagon, or an octagon.   The honeycomb filter according to claim 4, wherein the shape of the outflow cell in a cross section orthogonal to the extending direction of the cell of the honeycomb structure portion is a quadrangle or a hexagon.   The honeycomb filter according to any one of claims 1 to 5, wherein an opening area S1 of one inflow cell is larger than an opening area S2 of one inflow cell.   The honeycomb filter according to any one of claims 1 to 6, wherein the thickness of the partition wall is 100 to 450 μm.

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