JP2017221942A - Honeycomb filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb filter having excellent thermal shock resistance.SOLUTION: A honeycomb structure 4 comprises a dense part 15 having a rate of porosity change of 1-5%, calculated by following Formula (1). The honeycomb structure 4 also comprises an outer diameter decreasing part 17 in which an outside diameter decreases as approaching from an inflow end face 11 side to an outflow end face 12 side, with a rate of average diameter change of 0.2-3%, calculated by following Formula (2) for the honeycomb structure 4. Formula (1) is: (1-Px/Py)×100, ( where, in Formula (1), Px indicates a porosity (%) in a center area of the outflow end face 12, while Py indicates a porosity (%) in an outer periphery area of the outflow end face 12 excluding the center area; and Formula (2) is: (1-Dx/Dy)×100 ( where, in Formula (2), Dx indicates an average diameter (mm) of the outflow end face 12 of the honeycomb structure 4, while Dy indicates an average diameter (mm) of the inflow end face 11 of the honeycomb structure 4.)SELECTED DRAWING: Figure 6

Description

  The present invention relates to a honeycomb filter. More specifically, the present invention relates to a honeycomb filter excellent in thermal shock resistance.

  In recent years, society as a whole has become more aware of environmental issues, and in the technical field of generating power by burning fuel, various technologies have been developed to remove harmful components from exhaust gas generated during fuel combustion. . In particular, regulations regarding the removal of particulate matter discharged from diesel engines are becoming stricter worldwide, and a honeycomb filter having a honeycomb structure is used as a filter for removing particulate matter. Hereinafter, the filter for removing the particulate matter discharged from the diesel engine may be referred to as “DPF”. DPF is an abbreviation for “Diesel Particulate Filter”. Hereinafter, the particulate matter is sometimes referred to as “PM”. PM is an abbreviation for “Particulate Matter”.

  Conventionally, as such a honeycomb filter, a honeycomb structure having a porous partition wall for partitioning a plurality of cells, and a plugging portion for plugging one end of each cell are provided. Has been proposed (see, for example, Patent Document 1).

  In addition, in order to use the honeycomb filter continuously for a long period of time, the pressure loss increased due to PM accumulated over time inside the honeycomb filter is reduced, and the performance of the filter is returned to a state close to the initial state. It is necessary to perform "processing". Since most of the PM contained in the exhaust gas is a flammable substance such as soot, conventionally, the regeneration process of the honeycomb filter has been performed by a regeneration process in which the collected soot is burned and removed by a high-temperature gas. Yes. Hereinafter, burning and removing the soot accumulated inside the honeycomb filter may be simply referred to as “regeneration” of the honeycomb filter.

International Publication No. 2004/052502

  Diesel engines generate more soot than gasoline engines, etc., and honeycomb filters used as DPFs require “forced regeneration” that forcibly burns and removes the collected soot. . The forced regeneration is a regeneration process that forcibly burns and removes the collected soot using, for example, post injection or in-pipe injection. In such forced regeneration, the trapped soot burns at a time, so that a large thermal stress is generated in the honeycomb filter due to the soot burning. The conventional honeycomb filter has a problem that the honeycomb filter may be damaged such as cracks in such forced regeneration. For this reason, regarding a honeycomb filter used as a DPF, there is a demand for development of a honeycomb filter excellent in thermal shock resistance so that cracks do not occur even during forced regeneration.

  The present invention has been made in view of such problems of the prior art. The present invention provides a honeycomb filter excellent in thermal shock resistance.

  According to the present invention, the following honeycomb filter is provided.

[1] A honeycomb structure part having a porous partition wall defining a plurality of cells serving as fluid flow paths extending from the inflow end surface to the outflow end surface, and an outer peripheral wall disposed so as to surround the partition wall;
A plugging portion arranged to seal any one end of the cells formed in the honeycomb structure portion, and
The honeycomb structure portion includes a central region of the outflow end surface, and a porosity change rate calculated by the following equation (1) is 1 in the axial direction of the honeycomb structure portion from the central region of the outflow end surface. Has a dense part of ~ 5%, and
In the honeycomb structure portion, in at least a part of the honeycomb structure portion in the axial direction, an outer diameter of a surface orthogonal to the axial direction of the honeycomb structure portion decreases from the inflow end surface side to the outflow end surface side. A honeycomb filter having an outer diameter reduced portion and having an average diameter change rate calculated by the following formula (2) of the honeycomb structure portion of 0.2 to 3%.

Formula (1): (1-Px / Py) × 100
(However, in Formula (1), Px shows the porosity (%) in the said center area | region of the said outflow end surface, Py shows the porosity (%) of the outer peripheral area | region except the said center area | region of the said outflow end surface. .)

Formula (2): (1-Dx / Dy) × 100
(However, in Formula (2), Dx represents the average diameter (mm) of the outflow end face of the honeycomb structure part, and Dy represents the average diameter (mm) of the inflow end face of the honeycomb structure part.)

[2] The honeycomb filter according to [1], wherein the honeycomb structure portion has a porosity change rate calculated by the following formula (3) in a central region of the inflow end surface of less than 1%.

Formula (3): (1-P′x / P′y) × 100
(However, in Formula (3), P′x represents the porosity (%) in the central region of the inflow end surface, and P′y represents the porosity of the outer peripheral region excluding the central region of the inflow end surface. (%).)

[3] The honeycomb filter according to [1] or [2], wherein the dense portion has a porosity of 30 to 70%.

[4] The honeycomb filter according to any one of [1] to [3], wherein the outer diameter reduced portion is present in the entire axial direction of the honeycomb structure portion.

[5] The honeycomb filter according to any one of [1] to [3], wherein the outer diameter reduction portion exists only in a part in the axial direction of the honeycomb structure portion.

[6] The honeycomb filter according to any one of [1] to [5], wherein the outer peripheral wall of the honeycomb structure portion includes an outer peripheral coat layer disposed on an outer periphery of the partition wall.

[7] The [1], wherein the honeycomb structure portion includes a plurality of columnar honeycomb segments, and the plurality of honeycomb segments are arranged adjacent to each other so that side surfaces thereof face each other. The honeycomb filter according to any one of to [6].

  The honeycomb filter of the present invention has a dense portion having a porosity change rate calculated by the above formula (1) of 1 to 5% on the outflow end face side of the honeycomb structure portion. Furthermore, the honeycomb filter of the present invention has an outer diameter decreasing portion in which the outer diameter of the honeycomb structure portion decreases from the inflow end surface side to the outflow end surface side, and the average diameter change rate calculated by the above formula (2) is 0.2 to 3%. For this reason, the honeycomb filter of the present invention has an effect of being excellent in thermal shock resistance. That is, by having the above-described dense portion on the outflow end surface side of the honeycomb structure portion, even when a large thermal stress is generated in the central region on the outflow end surface side during forced regeneration of the honeycomb filter, the periphery of the central region It is possible to effectively prevent cracks from occurring. In addition, by having the outer diameter reducing portion as described above, the occurrence of cracks on the inflow end face side during forced regeneration of the honeycomb filter can be effectively suppressed. That is, when the honeycomb structure portion has a dense portion on the outflow end surface side, the thermal shock resistance on the inflow end surface side is relatively lowered, and cracks are likely to occur on the inflow end surface side of the honeycomb structure portion. . In the honeycomb filter of the present invention, the effect of the dense portion on the outflow end surface side and the outer diameter reduced portion in which the outer diameter decreases from the inflow end surface side toward the outflow end surface side is combined with the heat resistance of the entire honeycomb filter. The impact property can be made extremely excellent.

It is the perspective view seen from the inflow end face side which shows typically a first embodiment of the honeycomb filter of the present invention. It is the perspective view seen from the outflow end face side which shows typically the first embodiment of the honeycomb filter of the present invention. Fig. 2 is a side view schematically showing a side surface of the honeycomb filter shown in Fig. 1. Fig. 2 is a plan view schematically showing an inflow end surface of the honeycomb filter shown in Fig. 1. Fig. 2 is a plan view schematically showing an outflow end surface of the honeycomb filter shown in Fig. 1. It is sectional drawing which shows typically the X-X 'cross section of FIG. It is a schematic diagram for demonstrating the measurement location of the porosity of a honeycomb structure part in 1st embodiment of the honeycomb filter of this invention. It is a side view which shows typically 2nd embodiment of the honey-comb filter of this invention. It is a side view showing typically a third embodiment of a honeycomb filter of the present invention. FIG. 6 is a side view schematically showing a fourth embodiment of the honeycomb filter of the present invention. FIG. 6 is a side view schematically showing a fifth embodiment of the honeycomb filter of the present invention. It is a side view which shows typically 6th embodiment of the honey-comb filter of this invention. It is a side view which shows typically 7th embodiment of the honey-comb filter of this invention. It is the perspective view seen from the inflow end face side which shows typically an eighth embodiment of a honeycomb filter of the present invention. It is the perspective view seen from the outflow end face side which shows typically an eighth 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 and improvements can be made 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 6, the first embodiment of the honeycomb filter of the present invention is a honeycomb structure part 4 having porous partition walls 1 and any one of cells 2 formed in the honeycomb structure part 4. A honeycomb filter 100 including a plugged portion 5 disposed at an end portion. The honeycomb structure portion 4 includes a porous partition wall 1 and an outer peripheral wall 3 disposed so as to surround the partition wall 1. 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 face side. Fig. 2 is a perspective view schematically showing the first embodiment of the honeycomb filter of the present invention as seen from the outflow end face side. Fig. 3 is a side view schematically showing a side surface of the honeycomb filter shown in Fig. 1. FIG. 4 is a plan view schematically showing the inflow end face of the honeycomb filter shown in FIG. FIG. 5 is a plan view schematically showing the outflow end face of the honeycomb filter shown in FIG. 1. 6 is a cross-sectional view schematically showing the XX ′ cross section of FIG.

  The partition walls 1 of the honeycomb structure portion 4 partition and form a plurality of cells 2 that serve as fluid flow paths extending from the inflow end surface 11 to the outflow end surface 12. The plugging portion 5 is disposed so as to seal any one end portion of the cells 2 formed in the honeycomb structure portion 4. That is, each of the plurality of cells 2 is sealed at one end 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 configured as described above, the porous partition wall 1 functions as a filtering material for collecting PM in the exhaust gas. Here, among the plurality of cells 2, the cell 2 in which the plugging portion 5 is disposed in the opening on the outflow end surface 12 side and the inflow end surface 11 side is open is referred to as an inflow cell 2 a. Further, out of the plurality of cells 2, the cell 2 in which the plugging portion 5 is disposed in the opening on the inflow end surface 11 side and the outflow end surface 12 side is open is referred to as an outflow cell 2b.

  The honeycomb structure portion 4 includes the central region of the outflow end surface 12, and the porosity change rate calculated by the following formula (1) is 1 in the axial direction of the honeycomb structure portion 4 from the central region of the outflow end surface 12. It has -5% dense part 15. Further, in the honeycomb structure part 4, the outer diameter of the surface orthogonal to the axial direction of the honeycomb structure part 4 decreases from the inflow end face 11 side toward the outflow end face 12 side in at least a part of the honeycomb structure part 4 in the axial direction. The outer diameter reducing portion 17 is provided. And by having such an outer diameter decreasing part 17, the average diameter change rate computed by following formula (2) of the honeycomb structure part 4 is 0.2 to 3%. The honeycomb structure portion 4 shown in FIG. 6 has an outer diameter reducing portion 17 in the entire area of the honeycomb structure portion 4 in the axial direction.

Formula (1): (1-Px / Py) × 100
(However, in Equation (1), Px represents the porosity (%) in the central region of the outflow end surface 12, and Py represents the porosity (%) of the outer peripheral region excluding the central region of the outflow end surface 12.)

Formula (2): (1-Dx / Dy) × 100
(However, in the formula (2), Dx represents the average diameter (mm) of the outflow end face 12 of the honeycomb structure part 4 and Dy represents the average diameter (mm) of the inflow end face 11 of the honeycomb structure part 4).

  The honeycomb filter 100 of the present embodiment has the dense portion 15 and the outer diameter reduced portion 17 as described above, and has an effect of being excellent in thermal shock resistance.

  By having the dense portion 15 as described above on the outflow end face 12 side of the honeycomb structure part 4, it is possible to effectively prevent the occurrence of cracks around the central region of the outflow end face 12 during forced regeneration of the honeycomb filter 100. Can do. That is, even when a large thermal stress is generated in the central region on the outflow end face 12 side during forced regeneration of the honeycomb filter 100, it is possible to effectively prevent the generation of cracks around the central region. However, when the dense part 15 is provided on the outflow end face 12 side of the honeycomb structure part 4, the thermal shock resistance on the inflow end face 11 side is relatively lowered, and cracks are generated on the inflow end face 11 side of the honeycomb structure part 4. May be easier to do. In the honeycomb filter 100 of the present embodiment, the effects of the dense portion 15 on the outflow end surface 12 side and the outer diameter reducing portion 17 in which the outer diameter decreases from the inflow end surface 11 side toward the outflow end surface 12 side are combined. Thus, the thermal shock resistance of the entire honeycomb filter 100 can be made excellent. When the average diameter change rate of the honeycomb filter 100 is less than 0.2%, even if the outer diameter reducing portion 17 is provided, the thermal shock resistance on the inflow end face 11 side is lowered. On the other hand, when the average diameter change rate of the honeycomb filter 100 exceeds 3%, on the contrary, the thermal shock resistance on the outflow end face 12 side is lowered.

  The dense portion 15 of the honeycomb structure portion 4 exists in a part of the honeycomb structure portion 4 in the axial direction from the central region of the outflow end face 12. Hereinafter, a method for measuring the porosity of the central region of the outflow end surface 12 of the honeycomb structure portion 4 and the porosity of the outer peripheral region of the outflow end surface 12 will be described in more detail with reference to FIG. In the following description, a method for measuring the porosity of the central region of the inflow end surface 11 of the honeycomb structure 4 and the porosity of the outer peripheral region of the inflow end surface 11 will also be described. FIG. 7 is a schematic diagram for explaining the measurement points of the porosity of the honeycomb structure portion in the first embodiment of the honeycomb filter of the present invention. 7 indicates the inflow end surface 11 of the honeycomb structure portion 4. A portion indicated by reference numeral 4 in the center of the paper surface of FIG. 7 shows a cross section of the honeycomb structure portion 4 cut along the axial direction. In the cross section shown in FIG. 7, the drawing is performed in a form in which the partition walls 1 and the cells 2 of the honeycomb structure portion 4 are omitted. A portion indicated by reference numeral 12 in the lower part of the drawing in FIG. 7 indicates the outflow end face 12 of the honeycomb structure part 4. The axial direction of the honeycomb structure portion 4 means a direction from the inflow end surface 11 of the honeycomb structure portion 4 toward the outflow end surface.

  When measuring the porosity of the honeycomb structure part, the parts indicated by reference signs P1 to P5 on the outflow end face 12 side of the honeycomb structure part 4 and the parts indicated by reference signs P6 to P10 on the inflow end face 11 side of the honeycomb structure part 4 The porosity of the partition walls of the honeycomb structure portion 4 is measured at a total of 10 locations. The porosity (%) of the honeycomb structure portion 4 is a value measured by a mercury porosimeter. An example of the mercury porosimeter is Autopore 9500 (trade name) manufactured by Micromeritics.

  In the outflow end surface 12 of FIG. 7, the part indicated by reference sign P <b> 2 is the central region of the outflow end surface 12. The central region of the outflow end surface 12 indicated by the symbol P2 is a range corresponding to 10% of the diameter of the outflow end surface 12 of the honeycomb structure part 4 from the center of the outflow end surface 12. Hereinafter, the central region of the outflow end surface 12 in such a range may be referred to as “central region P2 of the outflow end surface 12” or simply “central region P2”. In the central region P2, the porosity is measured for any four points in this region, and the average value is defined as the porosity (%) of the central region P2.

  In the outflow end surface 12 in FIG. 7, the portions indicated by reference signs P <b> 1, P <b> 3 to P <b> 5 are the outer peripheral region of the outflow end surface 12. The outer peripheral region of the outflow end surface 12 indicated by reference signs P1, P3 to P5 is an annular range corresponding to 10% of the diameter of the outflow end surface 12 of the honeycomb structure part 4 from the outermost periphery of the outflow end surface 12 to the inside. . Hereinafter, the outer peripheral area of the outflow end face 12 in such a range may be referred to as “outer peripheral areas P1, P3 to P5 of the outflow end face 12” or simply “outer peripheral areas P1, P3 to P5”. In the outer peripheral regions P1, P3 to P5, the porosity is measured for any two points in each region, and the average value is defined as the porosity (%) of each outer peripheral region P1, P3 to P5.

  In the inflow end surface 11 of FIG. 7, a part indicated by reference sign P <b> 7 is a central region of the inflow end surface 11. The central region of the inflow end surface 11 indicated by reference numeral P7 is a range corresponding to 10% of the diameter of the inflow end surface 11 of the honeycomb structure part 4 from the center of the inflow end surface 11. Hereinafter, the central region of the inflow end surface 11 in such a range may be referred to as “central region P7 of the inflow end surface 11” or simply “central region P7”. In the central region P7, the porosity is measured for any four points in this region, and the average value is defined as the porosity (%) of the central region P7.

  In the inflow end surface 11 of FIG. 7, the portions indicated by reference signs P <b> 6 and P <b> 8 to P <b> 10 are the outer peripheral region of the inflow end surface 11. The outer peripheral region of the inflow end surface 11 indicated by the symbols P6, P8 to P10 is an annular range corresponding to 10% of the diameter of the inflow end surface 11 of the honeycomb structure part 4 from the outermost periphery of the inflow end surface 11 to the inside. . Hereinafter, the outer peripheral region of the inflow end surface 11 in such a range may be referred to as “the outer peripheral regions P6, P8 to P10 of the inflow end surface 11” or simply “the outer peripheral regions P6, P8 to P10”. In the outer peripheral regions P6, P8 to P10, the porosity is measured at any two points in each region, and the average value is defined as the porosity (%) of each outer peripheral region P6, P8 to P10.

  In the honeycomb filter 100 of the present embodiment shown in FIGS. 1 to 6, the porosity (%) of the central region P2 is lower than the respective porosity (%) of the outer peripheral regions P1, P3 to P5. Yes. In particular, in the honeycomb filter 100 of the present embodiment, the porosity change rate calculated by the above formula (1) in the central region of the outflow end face 12 is 1 to 5%.

  In addition, “Px” in the above formula (1) is “porosity (%) in the central region P2 of the outflow end face 12” obtained by the above method. Further, “Py” in the above formula (1) is “an average value of the porosity (%) in the outer peripheral regions P1, P3 to P5” obtained by the above-described method.

  When the porosity change rate of the dense portion 15 of the honeycomb structure portion 4 is less than 1%, the effect of improving the thermal shock resistance cannot be obtained. On the other hand, if it exceeds 5%, the thermal shock resistance of the outer peripheral region of the honeycomb structure portion 4 is lowered. In the honeycomb filter 100 of the present embodiment, by providing the honeycomb structure portion 4 with the outer diameter reducing portion 17, it is possible to effectively suppress a decrease in thermal shock resistance in portions other than the dense portion 15.

  The honeycomb structure portion 4 has an outer diameter decreasing portion 17 in which the outer diameter decreases from the inflow end surface 11 side to the outflow end surface 12 side, so that the average diameter change rate is 0.2 to 3%. . In the above formula (2), Dx represents the average diameter (mm) of the outflow end face 12 of the honeycomb structure part 4, and Dy represents the average diameter (mm) of the inflow end face 11 of the honeycomb structure part 4. Here, the average diameter (mm) of the inflow end surface 11 and the average diameter (mm) of the outflow end surface 12 are the circular shape when the shape of the inflow end surface 11 and the outflow end surface 12 of the honeycomb structure portion 4 is circular. It means the diameter (mm). When the shapes of the inflow end surface 11 and the outflow end surface 12 of the honeycomb structure part 4 are not circular, the average diameter (mm) is obtained according to the following method. In the case of the inflow end surface 11 of the honeycomb structure part 4, the major axis length (mm) and the minor axis length (mm) of the outer diameters passing through the geometric center of gravity of the inflow end surface 11 are measured, and the average value thereof is measured. Is the average diameter (mm) of the inflow end face 11. Similarly, in the case of the outflow end face 12 of the honeycomb structure portion 4, the major axis length (mm) and the minor axis length (mm) of the outer diameter passing through the geometric center of gravity of the outflow end face 12 are measured, The average value is defined as the average diameter (mm) of the outflow end face 12. Hereinafter, the term “average diameter Dx” means the average diameter (mm) of the outflow end face 12. Further, the “average diameter Dy” means the average diameter (mm) of the inflow end face 11. The honeycomb filter 100 of the present embodiment has a relationship of “average diameter Dx <average diameter Dy”.

  The dense portion 15 of the honeycomb structure portion 4 exists in a part of the honeycomb structure portion 4 in the axial direction from the central region of the outflow end face 12. For this reason, it is preferable that the dense part 15 like the outflow end face 12 does not exist in the inflow end face 11 of the honeycomb structure part 4. For example, the honeycomb structure portion 4 preferably has a porosity change rate calculated by the following formula (3) in the central region of the inflow end surface 11 of less than 1%, and more preferably less than 0.8%. .

Formula (3): (1-P′x / P′y) × 100
(However, in Formula (3), P′x represents the porosity (%) in the central region of the inflow end surface 11, and P′y is the porosity (%) of the outer peripheral region excluding the central region of the inflow end surface 11. Is shown.)

  In addition, “P′x” in the above formula (3) is “a porosity (%) in the central region P7 of the inflow end surface 11” obtained by the above-described method. Further, “P′y” in the above formula (3) is “an average value of the porosity (%) in the outer peripheral regions P6, P8 to P10” obtained by the above-described method.

  The porosity of the dense portion 15 of the honeycomb structure portion 4 is preferably 30 to 70%, more preferably 35 to 68%, and particularly preferably 40 to 65%. Note that the porosity of the dense portion 15 of the honeycomb structure portion 4 is “the porosity (%) in the central region P2 of the outflow end face 12” in FIG.

  In the honeycomb filter of the present embodiment, the partition wall thickness is preferably 120 to 450 μm, more preferably 135 to 400 μm, and particularly preferably 150 to 360 μm. If the partition wall thickness is less than 120 μm, the isostatic strength of the honeycomb structure part may be lowered. If the partition wall thickness exceeds 450 μm, the pressure loss increases, which may cause a reduction in engine output and fuel consumption. The partition wall thickness is a value measured by a method of observing a cross section perpendicular to the axial direction of the honeycomb filter with an optical microscope.

In the honeycomb filter of the present embodiment, the cell density of the cells partitioned by the partition walls is preferably 30 to 62 / cm ² , and more preferably 30 to 50 / cm ² . By comprising in this way, the honeycomb filter of this embodiment can be utilized suitably as a filter for diesel engines.

  The partition walls and the outer peripheral wall are preferably composed mainly of ceramic. As the material of the partition wall and the outer peripheral wall, cordierite, silicon carbide, silicon-silicon carbide based composite material, mullite, alumina, aluminum titanate, silicon nitride, cordierite forming raw material, lithium aluminum silicate, and silicon carbide-cordierite based A material containing at least one selected from the group consisting of composite materials can be given as a suitable example. The phrase “mainly composed of ceramic” means containing 50% by mass or more of the entire ceramic.

  The outer peripheral wall of the honeycomb structure portion may be formed integrally with the partition walls that partition the cells, or may be formed by coating an outer periphery coating material on the outer periphery side of the partition walls that partition the cells. It may be an outer peripheral coat layer. The outer peripheral coating layer is provided on the outer peripheral side of the partition wall after the partition wall and the outer peripheral wall are integrally formed at the time of manufacture, and then the formed outer peripheral wall is removed by a known method such as grinding. It may be.

  There is no particular limitation on the shape of the cells formed in the honeycomb structure. For example, the shape of the cell in the cross section orthogonal to the cell extending direction may be a polygon, a circle, an ellipse, or the like. Examples of the polygon include a triangle, a quadrangle, a pentagon, a hexagon, and an octagon. In addition, it is preferable that the shape of a cell is a triangle, a quadrangle, a pentagon, a hexagon, and an octagon. Moreover, about the shape of a cell, the shape of all the cells may be the same shape, and a different shape may be sufficient as it. For example, a rectangular cell and an octagonal cell may be mixed. Moreover, about the size of a cell, the size of all the cells may be the same or different. For example, among the plurality of cells, the size of some cells may be increased and the size of other cells may be relatively decreased.

  There is no restriction | limiting in particular about the shape of a honeycomb structure part. Examples of the shape of the honeycomb structure portion include columnar shapes such as a circular shape, an elliptical shape, and a polygonal shape of the inflow end surface and the outflow end surface. However, since the honeycomb filter of the present embodiment has the outer diameter reducing portion as described above, strictly, a part thereof has an inverted frustum shape or the like. For example, when the shapes of the inflow end surface and the outflow end surface are circular, the shape of the honeycomb structure portion is an inverted frustum shape. Examples of the polygon include a quadrangle, a pentagon, a hexagon, a heptagon, and an octagon.

There is no particular limitation on the size of the honeycomb structure part, for example, the length from the inflow end face to the outflow end face, or the size of the cross section perpendicular to the cell extending direction of the honeycomb structure part. When the honeycomb filter of the present embodiment is used as a DPF, each size may be appropriately selected so as to obtain optimum purification performance. For example, the length from the inflow end surface to the outflow end surface of the honeycomb structure portion is preferably 80 to 400 mm, more preferably 100 to 380 mm, and particularly preferably 150 to 360 mm. The area of the cross section perpendicular to the cell extending direction of the honeycomb structure is preferably 7000～130000Mm ^2, more preferably in a 8500～120000Mm2, particularly preferably 11000~100000mm ^2.

  In the honeycomb filter of the present embodiment, plugging portions are arranged in the opening on the outflow end face side of the inflow cell and the opening on the inflow end face side of the outflow cell. It is preferable that the inflow cells and the outflow cells are alternately arranged with a partition wall therebetween. Then, it is preferable that a checkered pattern is formed on both end faces of the honeycomb filter by the plugged portions and the “cell openings”.

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

  In the honeycomb filter of the present embodiment, an exhaust gas purifying catalyst may be supported on at least one of the partition wall surfaces and the partition wall pores of the honeycomb structure portion. By comprising in this way, CO, NOx, HC, etc. in exhaust gas can be made harmless by a catalytic reaction. Moreover, the oxidation of the soot collected by the partition can be promoted.

  When a catalyst is supported on the honeycomb filter of the present embodiment, the catalyst preferably contains 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 components to be purified. In particular, the SCR catalyst is preferably a NOx selective reduction SCR catalyst that selectively reduces NOx in the exhaust gas. An example of the SCR catalyst is a metal-substituted zeolite. Examples of the metal that replaces zeolite with metal include iron (Fe) and copper (Cu). As a zeolite, a beta zeolite can be mentioned as a suitable example. Further, the SCR catalyst may be a catalyst containing as a main component at least one selected from the group consisting of vanadium and titania. Examples of the NOx storage catalyst include alkali metals and alkaline earth metals. Examples of the alkali metal include potassium, sodium, and lithium. Examples of the alkaline earth metal include calcium. Examples of the oxidation catalyst include those containing a noble metal. Specifically, the oxidation catalyst is preferably one containing at least one selected from the group consisting of platinum, palladium and rhodium.

(2) Honeycomb filter (second embodiment to seventh embodiment):
Next, second to seventh embodiments of the honeycomb filter of the present invention will be described with reference to FIGS. Here, FIG. 8 is a side view schematically showing a second embodiment of the honeycomb filter of the present invention. FIG. 9 is a side view schematically showing a third embodiment of the honeycomb filter of the present invention. FIG. 10 is a side view schematically showing a fourth embodiment of the honeycomb filter of the present invention. FIG. 11 is a side view schematically showing a fifth embodiment of the honeycomb filter of the present invention. FIG. 12 is a side view schematically showing a sixth embodiment of the honeycomb filter of the present invention. FIG. 13 is a side view schematically showing a seventh embodiment of the honeycomb filter of the present invention.

  The honeycomb filter of the third embodiment to the eighth embodiment is the same as that shown in FIGS. 1 to 6 except that the shape of the side surface of the honeycomb structure portion is configured as the honeycomb structure portion 4 shown in FIGS. It is comprised similarly to the honeycomb structure part 4 shown. That is, the honeycomb structure portion 4 includes the central region of the outflow end surface 12, and is configured so that the porosity is relatively low from the central region of the outflow end surface 12 to a part of the honeycomb structure 4 in the axial direction. It has a dense portion 15. The dense portion 15 has a porosity change rate calculated by the above formula (1) of 1 to 5%.

  Further, in the honeycomb structure part 4, the outer diameter of the surface orthogonal to the axial direction of the honeycomb structure part 4 decreases from the inflow end face 11 side toward the outflow end face 12 side in at least a part of the honeycomb structure part 4 in the axial direction. The outer diameter reducing portion 17 is provided. And by having such an outer diameter decreasing part 17, the average diameter change rate calculated by the said Formula (2) of the honeycomb structure part 4 is 0.2 to 3%.

  The honeycomb filter 200 of the second embodiment shown in FIG. 8 has a shape in which the outer peripheral wall 3 constituting the side surface of the honeycomb structure portion 4 tapers from the inflow end surface 11 side to the outflow end surface 12 side. This tapered portion, that is, the entire area in the axial direction of the honeycomb structure portion 4 is the outer diameter reducing portion 17 of the honeycomb structure portion 4.

  In the honeycomb filter 300 of the third embodiment shown in FIG. 9, the side wall of the honeycomb structure part 4 is formed in a part of the outer peripheral wall 3 constituting the side surface of the honeycomb structure part 4 from the inflow end face 11 side to the outflow end face 12 side. The outer peripheral wall 3 which comprises comprises the reverse truncated cone shape. And in the honey-comb filter 300, it has comprised the column shape in which the outer diameter does not change in the fixed range by the outflow end surface 12 side. In the honeycomb structure part 4, the part having an inverted truncated cone shape and the columnar part, that is, the whole area in the axial direction of the honeycomb structure part 4 are the outer diameter reducing parts 17 of the honeycomb structure part 4.

  In the honeycomb filter 400 of the fourth embodiment shown in FIG. 10, the outer peripheral wall 3 constituting the side surface of the honeycomb structure portion 4 has a reverse bell shape from the inflow end surface 11 side to the outflow end surface 12 side. The portion having the inverted bell shape, that is, the entire area in the axial direction of the honeycomb structure portion 4 is the outer diameter reducing portion 17 of the honeycomb structure portion 4.

  In the honeycomb filter 500 of the fifth embodiment shown in FIG. 11, the outer peripheral wall 3 constituting the side surface of the honeycomb structure portion 4 has a columnar shape with no change in the outer diameter in a certain range from the inflow end surface 11 side. And the outer peripheral wall 3 which comprises the side surface of the honeycomb structure part 4 has comprised the inverted truncated cone shape in the outflow end surface 12 side rather than the columnar part which does not change an outer diameter. The portion having the inverted frustoconical shape is the outer diameter reducing portion 17 of the honeycomb structure portion 4.

  The honeycomb filter 600 of the sixth embodiment shown in FIG. 12 has a shape in which the outer peripheral wall 3 constituting the side surface of the honeycomb structure portion 4 is tapered toward the outflow end surface 12 in a certain range from the inflow end surface 11 side. There is no. And the honeycomb structure part 4 has comprised the column shape which does not change an outer diameter in the outflow end surface 12 side rather than the part used as the shape which becomes tapered. In the honeycomb structure portion 4, the tapered portion and the columnar portion, that is, the entire area in the axial direction of the honeycomb structure portion 4 are the outer diameter reducing portions 17.

  In the honeycomb filter 700 of the seventh embodiment shown in FIG. 13, the outer peripheral wall 3 constituting the side surface of the honeycomb structure portion 4 has an inverted bell shape in a certain range from the inflow end surface 11 side. And the honeycomb structure part 4 has comprised the column shape which does not change the outer diameter in the outflow end surface 12 side rather than the reverse bell-shaped part. In the honeycomb structure portion 4, the inverted bell-shaped portion and the columnar portion, that is, the entire area in the axial direction of the honeycomb structure portion 4 is the outer diameter reducing portion 17.

  The shape of the outer periphery of the honeycomb structure part in the honeycomb filter of the present invention, in other words, the shape of the honeycomb structure part viewed from the side is limited to the first to seventh embodiments described so far. Absent. That is, if the honeycomb filter of the present invention has an outer diameter reduction portion of a desired shape so that the average diameter change rate calculated by the above formula (2) is 0.2 to 3%, The shape can be appropriately determined according to the intended use.

(3) Honeycomb filter (eighth embodiment):
Next, an eighth embodiment of the honeycomb filter of the present invention will be described with reference to FIGS. 14 and 15. FIG. 14 is a perspective view schematically showing an eighth embodiment of the honeycomb filter of the present invention as viewed from the inflow end face side. Fig. 15 is a perspective view schematically showing the eighth embodiment of the honeycomb filter of the present invention as seen from the outflow end face side.

  The honeycomb filter 800 shown in FIGS. 14 and 15 includes the honeycomb structure portion 4 and the plugging portions 5 disposed at either one end of the cells 2 formed in the honeycomb structure portion 4. This is a honeycomb filter 800. The honeycomb structure 4 shown in FIGS. 14 and 15 has a plurality of columnar honeycomb segments 24. And the honeycomb structure part 4 has the segment structure arrange | positioned adjacently so that the mutual side surfaces of the some honeycomb segment 24 may oppose. The plurality of honeycomb segments 24 are bonded to each other via the bonding layer 25.

  Thus, in the honeycomb filter 800 of the present embodiment, the honeycomb structure part is a so-called “segment structure honeycomb structure part”. The “segmented honeycomb structure portion” is a honeycomb structure portion formed by joining a plurality of individually manufactured honeycomb segments 24. On the other hand, as shown in FIGS. 1 to 6, the honeycomb structure part 4 in which the partition walls 1 of the honeycomb structure part 4 are all integrally formed may be referred to as “integrated honeycomb structure part”. In the honeycomb filter of the present invention, the honeycomb structure portion may be a “segment structure honeycomb structure portion” or may be an “integrated honeycomb structure portion”.

  Each of the honeycomb segments 24 shown in FIGS. 14 and 15 has a porous partition wall 1 and an outer wall that constitutes a side surface of the honeycomb segment 24. Each honeycomb segment 24 is bonded to each other via a bonding layer 25 disposed on the outer wall surface constituting the side surface.

  14 and FIG. 15 includes a central structure of the outflow end face 12 and a part of the honeycomb structure section 4 in the axial direction from the central area of the outflow end face 12 in the above-described formula (1). It has the dense part 15 whose porosity change rate calculated by 1-5%. Further, the honeycomb structure portion 4 has an outer diameter of a surface orthogonal to the axial direction of the honeycomb structure portion 4 from the inflow end surface 11 side toward the outflow end surface 12 side in at least a part of the honeycomb structure portion 4 in the axial direction. The outer diameter decreasing portion 17 is decreased. And by having such an outer diameter decreasing part 17, the average diameter change rate computed by following formula (2) of the honeycomb structure part 4 is 0.2 to 3%.

  It is preferable that the outer peripheral wall 3 of the segment structure honeycomb structure 4 is an outer peripheral coat layer formed by an outer peripheral coat material coated on the outer periphery of the honeycomb structure section 4. Further, the honeycomb structure portion 4 having a segment structure is obtained by grinding the outer peripheral portion of a bonded honeycomb segment assembly in which a plurality of honeycomb segments 24 are bonded, and disposing the outer peripheral coat layer described above. preferable.

  The honeycomb filter 800 shown in FIGS. 14 and 15 is the same as the honeycomb filter of the first to seventh embodiments described so far, except that the honeycomb structure portion 4 is the honeycomb structure portion 4 having a segment structure. It may be configured. For example, the configuration of the dense portion 15 and the outer diameter reduction portion 17 in the honeycomb filter 800 may employ the same configuration as the configuration of the dense portion and the outer diameter reduction portion of the honeycomb filter of the first to seventh embodiments. it can.

(4) Manufacturing method of honeycomb filter:
Next, a method for manufacturing the honeycomb filter of the present invention will be described. Examples of the method for manufacturing a honeycomb filter of the present invention include a step including a step of manufacturing a honeycomb formed body, a step of forming plugging portions in cell openings, and a step of drying and firing the honeycomb formed body. Can do.

(4-1) Molding process:
The forming step is a step of obtaining a honeycomb formed body by extruding the kneaded material obtained by kneading the forming raw material into a honeycomb shape. The honeycomb formed body has partition walls that define cells 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 walls. The part of the honeycomb structure constituted by the partition walls becomes the honeycomb structure part. In the molding step, first, the molding 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 added with a dispersion medium and an additive. Examples of the additive include an organic binder, a pore former, and a surfactant. Examples of the dispersion medium include water. As the forming raw material, the same forming raw material used in a conventionally known method for manufacturing a honeycomb filter can be used.

  Examples of the method for kneading the forming raw material to form the clay include a method using a kneader, a vacuum kneader, or the like. Extrusion molding can be performed using an extrusion molding die in which slits corresponding to the cross-sectional shape of the honeycomb molded body are formed.

(4-2) Plugging step:
The plugging step is a step of forming a plugged portion by plugging the opening of the lure. For example, in the plugging step, the plugged portion is formed by plugging the opening of the cell with the same material as that 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 honeycomb filter.

(4-3) Firing step:
The firing step is a step of firing the honeycomb formed body having the plugged portions to obtain a honeycomb filter. Before firing the honeycomb formed body on which the plugged portions are formed, the obtained honeycomb formed body may be dried with, for example, microwaves and hot air. In addition, for example, a firing process is first performed on the honeycomb formed body before the plugging portion is formed, and the above-described plugging process is performed on the honeycomb fired body obtained by the firing process. 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. Moreover, it is preferable that baking time shall be about 4 to 6 hours as keep time in the highest temperature.

  When the honeycomb filter of the present invention is manufactured, in this firing step, the central region that becomes the dense portion on the end side of the end surface that becomes the outflow end surface of the honeycomb formed body becomes higher in temperature than the other portions. Firing is preferably performed according to the firing conditions. With this configuration, it is possible to form a dense portion in which the porosity of the central region on the outflow end face side of the obtained honeycomb filter is lower than the porosity of the outer peripheral region.

  For example, the honeycomb formed body can be fired using a firing furnace for firing the honeycomb formed body from which oils and fats, organic substances, and the like are removed at a high temperature in an inert gas atmosphere. The firing furnace has a longitudinal shape, and the honeycomb molded body introduced into the furnace space from one furnace opening is moved at a constant speed along the horizontal direction until reaching the other furnace opening. The main firing is performed. At this time, for example, it is preferable to perform firing as follows. First, the honeycomb formed body is arranged so that the axial direction thereof is parallel to the vertical direction and the outflow end face side of the honeycomb formed body faces downward. Then, it is preferable to perform firing on the arranged honeycomb formed body so that the central region serving as the dense portion becomes higher in temperature than the other portions on the lower outflow end face side. In addition, as a method of firing so that the central region becomes a high temperature later than the other part, a method of firing while causing a difference in the temperature of the honeycomb formed body during firing, such as by arranging tochi Can be mentioned. The temperature difference between the central region on the outflow end face side and other portions is not particularly limited. For example, by providing a temperature difference of 15 to 100 ° C., the porosity of the central region on the outflow end face side of the obtained honeycomb filter can be increased. Thus, a dense portion that is lower than the porosity of the outer peripheral region can be formed.

  Further, if necessary, after performing the firing step, the outer peripheral wall of the obtained honeycomb filter is ground, and then the outer peripheral coating material is applied to the outer peripheral side of the partition wall to form the outer peripheral coating layer. Also good. When applying the grinding process and the outer periphery coating material, the honeycomb filter is obtained by coating so that the outer diameter of the surface perpendicular to the axial direction of the honeycomb filter increases from the outflow end surface side to the inflow end surface side. The average diameter change rate is set to 0.2 to 3%. For example, for the grinding of the outer peripheral wall and the formation of the outer peripheral coat layer, by adopting the method 1 to method 3 described below, the method 1 can be used when the outer peripheral wall is ground. When the outer peripheral coating material is applied, the thickness of the outer peripheral coating layer from the inflow side end surface to the outflow side end surface is reduced. In the method 2, when the outer peripheral wall is ground, the outer end surface is processed to be small, and then the outer peripheral coating material is applied with a uniform thickness from the outflow side to the inflow side. Method 3 is to grind the outer peripheral wall with a uniform size from the outflow side to the inflow side end surface, and then apply the outer peripheral coat layer with a uniform thickness from the inflow side end surface to the outflow side end surface. Work. Then, after drying, the outer peripheral coat layer is ground so that the diameter decreases from the inflow side end surface to the outflow side end surface.

  When the honeycomb filter of the present invention has a segment structure honeycomb structure, first, as a honeycomb formed body, a plurality of honeycomb segment precursors are prepared, and the honeycomb segment precursors are fired, A plurality of honeycomb segments are produced. Next, plugging portions are formed so as to plug the openings of the cells of the honeycomb segment. Then, the manufactured plurality of honeycomb segments are bonded through the bonding layer to manufacture a bonded honeycomb segment assembly in which the plurality of honeycomb segments are bonded. Thereafter, the outer peripheral wall of the obtained bonded honeycomb segment assembly is ground, and thereafter, an outer peripheral coating material is applied to the outer peripheral side of the partition wall to produce a honeycomb filter having an outer peripheral wall constituted by the outer peripheral coating layer. When applying the grinding process and the outer periphery coating material, the honeycomb filter is obtained by coating so that the outer diameter of the surface perpendicular to the axial direction of the honeycomb filter increases from the outflow end surface side to the inflow end surface side. It is preferable to make the average diameter change rate of 0.2 to 3%.

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

  Next, the kneaded material was extruded using a predetermined mold to obtain a honeycomb formed body having a square cell shape and a columnar overall shape.

  Next, the honeycomb formed body was dried with a hot air dryer. The drying conditions were 95 to 145 ° C.

  Next, plugged portions were formed on the dried honeycomb formed body. Specifically, first, a mask was applied to the inflow end face of the honeycomb formed body so as to cover the inflow cells. Thereafter, the end portion of the honeycomb formed body provided with the mask was immersed in the plugging slurry, and the opening portion of the outflow cell not provided with the mask was filled with the plugging slurry. Thereafter, the plugging slurry was filled in the opening portion of the inflow cell on the outflow end surface of the honeycomb formed body in the same manner as described above. Thereafter, the honeycomb formed body on which the plugged portions were formed was further dried with a hot air dryer.

  Next, the dried honeycomb formed body was placed on the burned tochi made of alumina so that the outflow end face side of the honeycomb filter to be manufactured faced down. The honeycomb formed body was fired in a tunnel kiln (continuous firing furnace). As firing conditions, firing was performed at 1350 to 1440 ° C. for 10 hours to obtain a honeycomb fired body. In Example 1, firing was performed so that the central region on the outflow end face side was heated by 50 ° C. behind the other portions during firing.

  Next, the outer peripheral surface of the obtained honeycomb fired body was ground. At this time, grinding was performed so that the outer diameter of the honeycomb fired body decreased from the inflow end face side toward the outflow end face side. Thereafter, an outer periphery coating material was applied to the side surface of the ground honeycomb fired body to form an outer periphery coating layer. The honeycomb filter of Example 1 was produced as described above.

  The honeycomb filter of Example 1 includes the central region of the outflow end surface, and the porosity in the central region of the outflow end surface is larger than the central region of the outflow end surface in a part in the axial direction from the central region of the outflow end surface. It had a dense part configured to be lower than the porosity. Further, in the obtained honeycomb filter, the outer diameter of the surface perpendicular to the axial direction of the honeycomb structure portion 4 as in the honeycomb filter 100 shown in FIG. 3 decreases from the inflow end surface 11 side to the outflow end surface 12 side. The outer diameter reducing portion 17 was included.

  In the honeycomb filter of Example 1, the partition wall thickness was 300 μm, and the cell density was 46.5 cells / cm 2. The shape of the cell was a square. In the column of “cell structure” in Table 1, the thickness of the partition walls, the cell density, and the cell shape are shown.

  In the honeycomb filter of Example 1, the shape of the cross section perpendicular to the axial direction was circular, and as described above, the shape of the outer periphery of the honeycomb filter was as shown in FIG. The diameter of the inflow end face of the honeycomb filter was 266.7 mm, and the length (full length) from the inflow end face to the outflow end face was 304.8 mm. The shape of the honeycomb filter of Example 1 is shown in the “Cross sectional shape”, “Outer peripheral shape”, and “Full length” columns in Table 1. In the “Formation method” column of “Outer shape” in Table 1, “Integral” is described when the honeycomb filter has an outer peripheral wall integrally formed with the partition walls. Further, when the honeycomb filter includes an outer peripheral coating layer formed by removing the outer peripheral wall integrally formed with the partition wall by outer periphery processing and coating the outer peripheral coating material so as to surround the partition wall, It is described as “peripheral machining”. The “diameter” column in Table 1 shows the value of “target diameter of the inflow end face” of the honeycomb filter, and the actual diameter (Dx, Dy) of the manufactured honeycomb filter is shown in Table 3. .

  For the honeycomb filter of Example 1, the porosity at each of the measurement points P1 to P10 shown in FIG. 7 was measured. Table 2 shows the measurement results of the porosity. Moreover, based on the measurement result of the porosity, “average value of P1, P3 to P5” and “average value of P6, P8 to P10” were obtained. The results are shown in Table 2.

  Based on the value of the porosity at each measurement point of P1 to P10, the porosity change rate (%) at the outflow end face and the inflow end face was calculated by the above formula (1) or formula (3). The results are shown in Table 3.

  Further, the average diameter Dx (mm) of the outflow end face of the honeycomb structure part and the average diameter Dy (mm) of the inflow end face of the honeycomb structure part were obtained. The average diameter Dx of the outflow end face was 266.0 mm, and the average diameter Dy of the inflow end face was 266.7 mm. Based on the values of the average diameter Dx and the average diameter Dy, the average diameter change rate was calculated by the above formula (2). The results are shown in Table 3.

(Examples 2 to 13)
Cell structures, cross-sectional shapes, outer peripheral shapes, and the like were changed as shown in Table 1, and honeycomb filters of Examples 2 to 13 were manufactured. In addition, as for the honeycomb filter of Examples 2-13, the shape of the outer periphery corresponded to the shape in any one of FIG. 3, FIG. 8-FIG. The column of “reference diagram” of “peripheral shape” in Table 1 indicates which of the honeycomb filters of each example corresponds to any of FIGS. 3 and 8 to 13. For example, when “FIG. 8” is written in the “Reference diagram” column of “Outer shape” in Table 1, it means that the outer shape of the honeycomb filter corresponds to the shape of FIG. To do.

  In Examples 2 to 13, the amount of the pore forming material added to the clay was appropriately adjusted to adjust the porosity of the manufactured honeycomb filter. Moreover, at the time of baking, it baked so that the central area | region by the side of the outflow end surface set | placed downward at the time of baking was heated up 15-100 degreeC behind with respect to another part.

(Examples 14 and 15)
In Examples 14 and 15, a honeycomb filter having a segment structure as shown in FIGS. 14 and 15 was produced. Specifically, first, 80 parts by mass of silicon carbide powder and 20 parts by mass of Si powder were mixed to obtain a mixed powder. A binder, a pore former, and water were added to the mixed powder, mixed and kneaded to prepare a clay.

  Next, the kneaded material was extruded using a die for manufacturing a honeycomb formed body, and a honeycomb formed body having an overall shape of a quadrangular prism was obtained. As the honeycomb formed bodies, 32 pieces were produced in Example 14 and 25 pieces were produced in Example 15.

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

  Next, plugged portions were formed on the dried honeycomb formed body. Specifically, first, a mask was applied to the inflow end face of the honeycomb formed body so as to cover the inflow cells. Thereafter, the end portion of the honeycomb formed body provided with the mask was immersed in the plugging slurry, and the opening portion of the outflow cell not provided with the mask was filled with the plugging slurry. Thereafter, the plugging slurry was filled in the opening portion of the inflow cell on the outflow end surface of the honeycomb formed body in the same manner as described above. Thereafter, the honeycomb formed body on which the plugged portions were formed was further dried with a hot air dryer.

  Next, the honeycomb formed body on which the plugged portions were formed was degreased and fired to obtain a honeycomb fired body. The degreasing conditions were 550 ° C. for 3 hours. The firing conditions were 1450 ° C. and 2 hours in an argon atmosphere. The honeycomb fired body had a quadrangular prism shape as a whole. The shape of the end face of the honeycomb fired body was a square having a side length of 37 mm. This honeycomb fired body becomes a honeycomb segment in the honeycomb structure. The honeycomb segment disposed in the center of the segment structure was manufactured by the following method. First, a fired honeycomb segment was prepared, 150 parts by mass of colloidal silica (solution with a solid content of 40%) and 200 parts by mass of water were added to 150 parts by mass of SiC particles having a particle diameter of 2 μm, and the mixture was stirred well. A slurry for modification was prepared. Thereafter, a portion having a height of 20 mm in the full length direction on the end face side corresponding to the outflow side was immersed in this modifying slurry, and then excess slurry was removed by air blowing. Next, after drying the slurry, heat treatment was performed at 700 ° C. to produce a honeycomb segment having a low porosity on the outflow side.

  Next, 32 pieces of the obtained Example 14 and 25 pieces of Example 15 were joined with a bonding material in a state where the fired bodies were arranged adjacent to each other so that the side surfaces face each other. A joined body was produced. At the end face of the honeycomb bonded body, Example 14 has six pieces in the vertical direction and six pieces in the horizontal direction, a total of 32 pieces (excluding the four pieces positioned at the four corners of the honeycomb bonded body), and Example 15 has the vertical direction. A total of 25 honeycomb fired bodies, 5 in the direction and 5 in the lateral direction, were joined and arranged.

  Next, the outer peripheral surface of the obtained bonded honeycomb body was ground. At this time, grinding was performed so that the outer diameter of the honeycomb fired body decreased from the inflow end face side toward the outflow end face side. Thereafter, an outer periphery coating material was applied to the side surface of the ground honeycomb joined body to form an outer periphery coating layer. As described above, honeycomb filters of Examples 14 and 15 were produced.

  About the honeycomb filter of Examples 2-15, the porosity of each measurement location of P1-P10 shown in FIG. 7 was measured. Table 2 shows the measurement results of the porosity. Moreover, based on the measurement result of the porosity, “average value of P1, P3 to P5” and “average value of P6, P8 to P10” were obtained. The results are shown in Table 2.

  About the honeycomb filter of Examples 2-15, based on the value of the porosity of each measurement location of P1-P10, the porosity change rate (%) in an outflow end surface and an inflow end surface is set to said Formula (1) or Formula (3 ). The results are shown in Table 3.

  Further, the average diameter Dx (mm) of the outflow end face of the honeycomb structure part and the average diameter Dy (mm) of the inflow end face of the honeycomb structure part were obtained, and the average diameter change rate was calculated by the above formula (2). The results are shown in Table 3.

  About the honeycomb filter of Examples 1-15, "thermal shock resistance (robustness)" evaluation was performed with the following method. The results are shown in Table 4. In addition, about "thermal shock resistance (robustness)", each honeycomb filter of Examples 1-15 is evaluated by comparing with the honeycomb filter of the comparative example of the same number in Comparative Examples 1-15 mentioned later. Went.

[Heat shock resistance (robustness)]
As an evaluation of the thermal shock resistance, the test described below was conducted on the honeycomb filter, and the robustness of the honeycomb filter was evaluated based on the presence or absence of cracks in the honeycomb filter after the test. Specifically, in an engine bench equipped with a 2.2L diesel engine, 2 to 12 g / L of soot was produced under the operating conditions of an engine speed of 2000 rpm and an engine torque of 60 Nm, and the honeycomb filters of the examples and comparative examples. Deposited inside. Thereafter, regeneration processing by post-injection was performed, the inlet gas temperature of the honeycomb filter was raised, the post-injection was turned off when the pressure loss before and after the honeycomb filter began to drop, and the engine was switched to the idle state. The soot accumulation amount at this time was set so that the maximum temperature at the center portion of the outflow side end face was 1000 ° C. at each level of the examples, and the same numbers in the examples and comparative examples were tested under the conditions that the same soot amount was obtained Carried out. And the presence or absence of the crack in the outflow end surface side and inflow end surface side of a honeycomb filter was observed visually. In Table 4, the observation result on the outflow end face side and the observation result on the inflow end face side are shown.
A case where no crack is confirmed is regarded as acceptable and shown as “OK” in Table 4.
In Table 4, “NG” is shown as failure when a crack is confirmed.

[Overall]
Moreover, comprehensive evaluation of thermal shock resistance evaluation was performed based on the following evaluation criteria. The results are shown in Table 4.
In the evaluation of thermal shock resistance, the case where both the inflow end face side and the outflow end face side were “OK” was designated as “A”.
In the evaluation of thermal shock resistance, the case where at least one of the inflow end face side and the outflow end face side was “NG” was defined as “C”.

(Comparative Examples 1-15)
Cell structures, cross-sectional shapes, outer peripheral shapes, and the like were changed as shown in Table 5 to produce honeycomb filters of Comparative Examples 1-15. In addition, as for the honeycomb filter of Comparative Examples 1-15, the shape of the outer periphery corresponded to the shape in any one of FIG. 3, FIG. For Comparative Examples 14 and 15, segmented honeycomb filters were produced in the same manner as in Examples 14 and 15.

  About the honeycomb filter of Comparative Examples 1-15, the porosity of each measurement location of P1-P10 shown in FIG. 7 was measured. Table 6 shows the measurement results of the porosity. Moreover, based on the measurement result of the porosity, “average value of P1, P3 to P5” and “average value of P6, P8 to P10” were obtained. The results are shown in Table 6.

  About the honeycomb filter of Comparative Examples 1-15, based on the value of the porosity of each measurement location of P1-P10, the porosity change rate (%) in an outflow end surface and an inflow end surface is set to said Formula (1) or Formula (3 ). The results are shown in Table 7.

  Further, the average diameter Dx (mm) of the outflow end face of the honeycomb structure part and the average diameter Dy (mm) of the inflow end face of the honeycomb structure part were obtained, and the average diameter change rate was calculated by the above formula (2). The results are shown in Table 7.

  The “thermal shock resistance” of the honeycomb filters of Comparative Examples 1 to 15 was evaluated in the same manner as in Example 1. The results are shown in Table 8.

(result)
As shown in Table 4, all the honeycomb filters of Examples 1 to 15 were able to obtain good results in the evaluation of “thermal shock resistance”. In the honeycomb filters of Comparative Examples 1 to 15, cracks occurred on at least one of the outflow end face side and the inflow end face side of the honeycomb filter.

  The honeycomb filter of the present invention can be used as a filter for collecting soot in exhaust gas discharged from a diesel engine.

1: partition wall, 2: cell, 2a: inflow cell, 2b: outflow cell, 3: outer peripheral wall, 4: honeycomb structure, 5: plugged portion, 11: inflow end surface, 12: outflow end surface, 15: dense portion 17: Outer diameter reduction part, 24: Honeycomb segment, 25: Bonding layer, 100, 200, 300, 400, 500, 600, 700, 800: Honeycomb filter, P1, P3 to P5: Outer peripheral region (outer periphery of outflow end face) Area), P2: central area (central area of the outflow end face), P6, P8 to P10: outer peripheral area (outer peripheral area of the inflow end face), P7: central area (central area of the inflow end face), Dx: average diameter of the outflow end face , Dy: average diameter of the inflow end face.

Claims (7)

A honeycomb structure part having a porous partition wall that defines a plurality of cells serving as a fluid flow path extending from an inflow end surface to an outflow end surface, and an outer peripheral wall disposed so as to surround the partition wall;
A plugging portion arranged to seal any one end of the cells formed in the honeycomb structure portion, and
The honeycomb structure portion includes a central region of the outflow end surface, and a porosity change rate calculated by the following equation (1) is 1 in the axial direction of the honeycomb structure portion from the central region of the outflow end surface. Has a dense part of ~ 5%, and
In the honeycomb structure portion, in at least a part of the honeycomb structure portion in the axial direction, an outer diameter of a surface orthogonal to the axial direction of the honeycomb structure portion decreases from the inflow end surface side to the outflow end surface side. A honeycomb filter having an outer diameter reduced portion and having an average diameter change rate calculated by the following formula (2) of the honeycomb structure portion of 0.2 to 3%.
Formula (1): (1-Px / Py) × 100
(However, in Formula (1), Px shows the porosity (%) in the said center area | region of the said outflow end surface, Py shows the porosity (%) of the outer peripheral area | region except the said center area | region of the said outflow end surface. .)
Formula (2): (1-Dx / Dy) × 100
(However, in Formula (2), Dx represents the average diameter (mm) of the outflow end face of the honeycomb structure part, and Dy represents the average diameter (mm) of the inflow end face of the honeycomb structure part.) The honeycomb filter according to claim 1, wherein the honeycomb structure portion has a porosity change rate calculated by the following expression (3) in a central region of the inflow end surface of less than 1%.
Formula (3): (1-P′x / P′y) × 100
(However, in Formula (3), P′x represents the porosity (%) in the central region of the inflow end surface, and P′y represents the porosity of the outer peripheral region excluding the central region of the inflow end surface. (%).)   The honeycomb filter according to claim 1 or 2, wherein a porosity of the dense portion is 30 to 70%.   The honeycomb filter according to any one of claims 1 to 3, wherein the outer diameter reduction portion is present in the entire axial direction of the honeycomb structure portion.   The honeycomb filter according to any one of claims 1 to 3, wherein the outer diameter reduced portion is present only in a part in the axial direction of the honeycomb structure portion.   The honeycomb filter according to any one of claims 1 to 5, wherein the outer peripheral wall of the honeycomb structure portion includes an outer peripheral coat layer disposed on an outer periphery of the partition wall.   The honeycomb structure according to any one of claims 1 to 6, wherein the honeycomb structure portion includes a plurality of columnar honeycomb segments, and the plurality of honeycomb segments are adjacently arranged so that the side surfaces thereof face each other. A honeycomb filter according to claim 1.

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