JP5188433B2 - Honeycomb filter - Google Patents

Description

  The present invention relates to a honeycomb filter. More specifically, the present invention relates to a honeycomb filter having a high heat capacity and capable of reducing a temperature rise during filter regeneration.

  There is an increasing need to remove particulates and harmful substances in exhaust gas from internal combustion engines, boilers, etc. from the exhaust gas in consideration of environmental impact. In particular, regulations regarding the removal of particulate matter (particulate matter: hereinafter referred to as “PM”) discharged from diesel engines tend to be strengthened worldwide, and honeycomb filters for removing PM (for example, The use of a honeycomb structure has attracted attention as a diesel particulate filter (hereinafter sometimes referred to as “DPF”), and various systems have been proposed.

  The above-described honeycomb filter includes a cell opening at an end portion on the inflow side of exhaust gas and an outflow portion in a honeycomb structure including a partition wall in which a plurality of cells serving as fluid (that is, exhaust gas) channels are formed. The filter is configured such that a porous partition wall defining a cell serves as a filter by alternately plugging the opening of the cell at the side end.

  That is, in this honeycomb filter, exhaust gas containing particulate matter is flowed from a cell opened at the end face on the inflow side (hereinafter also referred to as “inflow side end open cell”), and the particulate matter is separated by the partition wall. After the gas is filtered, the purified gas is discharged from the opening of a cell opened at the end surface on the outflow side (hereinafter also referred to as “outflow side end open cell”).

  In such a honeycomb filter, the cell structure is generally uniform in the direction from the central portion toward the outer peripheral side (hereinafter sometimes referred to as “circumferential direction”) in a cross section orthogonal to the central axis direction, that is, inflow. A pattern in which side end open cells and outflow side end open cells are alternately arranged is configured to be uniform (see, for example, Patent Document 1).

JP 56-124417 A

  In the honeycomb filter described in Patent Document 1, since the cell structure in the circumferential direction is uniform as described above, the exhaust gas easily flows in the central portion in the cross section orthogonal to the central axis direction, and constitutes the central portion. More particulate matter is deposited on the partition walls. For example, when there is a drift in the exhaust gas passing through the honeycomb filter, a lot of particulate matter is deposited on the partition walls constituting the eccentric portion. When a certain amount of particulate matter is deposited on the partition wall, the honeycomb filter needs to be removed by burning the particulate matter (hereinafter sometimes referred to as “regeneration”). If a large amount of particulate matter is deposited on the partition walls that make up the part or eccentric part, combustion during regeneration partially occurs vigorously, and the temperature at a specific location rises excessively, resulting in cracks or erosion. There was a problem that it would be easier.

  The present invention has been made in view of the above-described problems, has a high heat capacity, can reduce the temperature rise during filter regeneration, and can effectively prevent the occurrence of cracks, erosion, and the like. A honeycomb filter is provided.

  The inventor of the present invention has made extensive studies to solve the above-described problems of the prior art, and as a result, the shape of the cross section perpendicular to the flow path direction of at least one of the cells having an open end on the outflow side. It is conceived that the above-mentioned problems can be solved by making the portion corresponding to the corner of the polygon more than a quadrangle into an arc shape and improving the strength and heat capacity of the partition walls that define the cell. The present invention has been completed. Specifically, the following honeycomb filter is provided by the present invention.

[1] An inflow side end that includes a porous partition wall that defines a plurality of cells serving as fluid flow paths, the inflow side end of the fluid is open, and the outflow side end of the fluid is plugged Partly open cells and outflow side end open cells in which the inflow side end is plugged and the outflow side end is open are alternately arranged, At least one outflow side end open cell has a cross-sectional shape perpendicular to the flow path direction defined by the partition wall, and a portion corresponding to a corner of a quadrilateral or more polygon is formed in an arc shape. The outflow side end open cell other than the one outflow side end open cell among the outflow side end open cells is a polygon whose cross-sectional shape perpendicular to the flow path direction is a quadrilateral or more polygon. The inflow side end open cell has a cross-sectional shape orthogonal to the flow path direction. , Square, or octagonal der Ru honeycomb filter.

[2] the one of the outlet-side end portion open cells, the shape of the cross section perpendicular to the flow path direction, the corners of the shape of the cross section perpendicular to the flow path direction of said other outlet end open cells The honeycomb filter according to [ 1 ], wherein the corresponding portion has a shape formed in an arc shape.

[ 3 ] In the cross section perpendicular to the central axis direction of the honeycomb filter, the one outflow end portion open cell is formed in a region including the central portion and corresponding to 10 to 70% of the total area of the cross section. The honeycomb filter according to the above [ 1 ] or [ 2 ], wherein at least the outflow side end open cells are disposed.

[ 4 ] In the cross section perpendicular to the central axis direction of the honeycomb filter, the other side as the outflow side end open cell is formed in a region including the outer peripheral portion and corresponding to 30 to 90% of the total area of the cross section. The honeycomb filter according to any one of [ 1 ] to [ 3 ], wherein at least the outflow side end open cells are disposed.

[ 5 ] In the one outflow side end open cell, the cross-sectional shape orthogonal to the flow path direction is a shape in which a portion corresponding to a corner portion in a quadrangle is formed in an arc shape. 4 ] The honeycomb filter according to any one of the above.

[ 6 ] The [1] to [1], wherein a radius of curvature of a portion formed in an arc shape in a cross-sectional shape orthogonal to the flow path direction of the one outflow side end open cell is 0.05 to 1.00 mm. The honeycomb filter according to any one of [ 5 ].

[ 7 ] A plurality of honeycomb segments in which the inflow-side end open cells and the outflow-side end open cells partitioned by the partition walls are alternately arranged, and the plurality of honeycomb segments are mutually connected. The honeycomb filter according to any one of [1] to [ 6 ], wherein the honeycomb filters are arranged adjacent to each other so that the side surfaces are opposed to each other, and the opposed side surfaces are bonded to each other by a bonding portion.

  The honeycomb filter of the present invention has a high heat capacity, can reduce the temperature rise during the regeneration of the filter, and can effectively prevent the occurrence of cracks, melting damage, and the like. In particular, one outflow side end open cell in which a portion corresponding to a corner is formed in an arc shape is selectively disposed at a central portion or an eccentric portion in a cross section perpendicular to the central axis direction in which exhaust gas easily flows. Thus, it is possible to effectively reduce an excessive temperature rise that is partially generated during regeneration while suppressing deterioration of pressure loss to a minimum.

1 is a perspective view schematically showing one embodiment of a honeycomb filter of the present invention. FIG. 1B is an enlarged plan view in which an end face on the inflow side of the honeycomb filter shown in FIG. 1A is enlarged. FIG. 1B is an enlarged plan view in which an end face on the outflow side of the honeycomb filter shown in FIG. 1A is enlarged. It is a top view of the end face of the outflow side which shows other embodiments of the honeycomb filter of the present invention typically. FIG. 6 is a plan view of an enlarged end face on the inflow side schematically showing still another embodiment of the honeycomb filter of the present invention. FIG. 6 is an enlarged plan view of an end face on the outflow side schematically showing still another embodiment of the honeycomb filter of the present invention. It is a perspective view which shows typically other embodiment of the honey-comb filter of this invention. It is a perspective view which shows typically the structure of the honeycomb segment which comprises the honeycomb filter shown to FIG. 4A.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and those skilled in the art do not depart from the spirit of the present invention. It should be understood that design changes, improvements, and the like can be made as appropriate based on ordinary knowledge. Unless otherwise specified, the cross section below refers to a cross section cut along a plane perpendicular to the cell flow path direction (center axis direction). In the following, a honeycomb filter having a structure formed as a whole is referred to as an integral honeycomb filter, and a honeycomb filter having a structure in which a plurality of honeycomb segments are combined via a bonding material layer is referred to as a bonded honeycomb filter. That's it. In addition, when there is no particular distinction between an integral honeycomb filter and a bonded honeycomb filter, it is simply referred to as a honeycomb filter.

[1] Honeycomb filter:
As shown in FIGS. 1A to 1C, one embodiment of the honeycomb filter of the present invention includes a porous partition wall 3 that partitions and forms a plurality of cells 2 serving as fluid flow paths, and includes a fluid inflow side end portion. 11 is opened and the fluid outflow side end 12 is plugged by the plugging portion 5, the inflow side end open cell 2A, and the inflow side end 11 is plugged by the plugging portion 5. The honey-comb filter 100 by which the outflow side edge part open cell 2B by which the outflow side edge part 12 was open | released is arrange | positioned alternately, Comprising: At least 1 outflow side edge part open cell of the outflow side edge part open cell 2B 2B ₁ is a shape in which a section X perpendicular to the flow path direction defined by the partition walls 3 is formed in a circular arc shape with a portion X corresponding to a corner of a quadrilateral or more polygon.

  When such a honeycomb filter 100 is arranged in an exhaust gas exhaust system, a fluid (that is, exhaust gas) flows into the inflow side end open cell 2A from the end surface on the inflow side end 11 side, and this inflow side end. Passing through the porous partition wall 3 partitioning the partly open cell 2A, it moves into the adjacent outflow side end 12 and allows the fluid to flow out from the end surface on the outflow side end 12 side. When the exhaust gas passes through the partition walls 3, particulate matter (PM) such as soot contained in the exhaust gas is captured by the partition walls 3, and the exhaust gas can be purified.

In such a honeycomb filter 100, more specifically, in the surface of the porous partition wall 3 and the inside of the pores, particulate matter (PM) is deposited over time, and the pressure loss increases. Although regeneration process for burning the particulate matter (PM) is performed, the honeycomb filter 100 of the present embodiment, the corners in the shape of a cross section of one outlet end open cell 2B ₁ is formed in an arc shape Therefore, the thickness of the portion of the partition wall 3 forming the corner is relatively and thicker, the heat capacity of the partition wall 3 near partitioning the outlet side end portions open cell 2B ₁ one is larger. For this reason, it becomes possible to reduce the temperature rise at the time of regeneration of a filter, and generation | occurrence | production of a crack, a melting loss, etc. can be prevented effectively.

  Here, FIG. 1A is a perspective view schematically showing one embodiment of the honeycomb filter of the present invention, and FIG. 1B is an enlarged plan view in which an end face on the inflow side of the honeycomb filter shown in FIG. 1A is enlarged. FIG. 1C is an enlarged plan view in which the end face on the outflow side of the honeycomb filter shown in FIG. 1A is enlarged. In the drawings, common components are denoted by the same reference numerals.

In the honeycomb filter of the present invention, all the outflow side end open cells 2B have one outflow side end in a shape in which the portion X corresponding to the corner in the above-described quadrilateral or more polygon is formed in an arc shape. The partial open cell 2B ₁ does not have to be. That is, as the honeycomb filter 101 shown in FIG. 2, in addition to the outflow side end portion open cell 2B ₁ of the one as the outlet side end portion open cells 2B, the cross section perpendicular to the flow path direction shape, square or more may have other outlet end open cell 2B ₂ is polygonal.

For example, in FIG. 2, in a cross section perpendicular to the central axis direction of the honeycomb filter 101 is disposed in the central portion A1 in the one outlet end open cell 2B _1, the outer peripheral portion B1, perpendicular to the flow path direction the shape of the cross section, shows an example in which another outlet end open cells 2B ₂ square or polygons are arranged. Thus, exhaust gas tends to flow, sites that many of the particulate matter deposited on the partition walls (e.g., the central portion A1) with respect to place the outlet side end portions open cell 2B ₁ one other site ( for example, for the outer peripheral portion B1), even outflow end open cells 2B, by the shape of the cross section to place the other outlet end open cell 2B ₂ is a more polygonal square, the heat capacity The portion to be raised can be partially provided (in the honeycomb filter 101 shown in FIG. 2, the central portion A1), and the reduction of the area (total area) of the opening portion of the cell 2 at the outflow side end portion 12 is suppressed. An increase in pressure loss of the honeycomb filter 101 can be effectively suppressed.

  Here, FIG. 2 is a plan view of the end face on the outflow side schematically showing another embodiment of the honeycomb filter of the present invention.

As described above, when the exhaust gas easily flows in the central portion in the cross section orthogonal to the central axis direction, as shown in FIG. 2, one outflow side end open cell 2B is provided in the central portion A1 of the honeycomb filter 101. ₁ and the other outflow side end open cell 2B ₂ described above may be arranged in the outer peripheral portion B1. For example, in the cross section orthogonal to the central axis direction of the honeycomb filter, the outflow side end portion open cell is included in a region including the central portion and corresponding to 10 to 70% of the total area of the cross section (that is, the central portion). It is preferable that at least one outflow side end open cell is disposed, and includes 30 to 90% of the total area of the cross section including the outer peripheral portion in the cross section perpendicular to the central axis direction of the honeycomb filter. It is preferable that at least another outflow side end open cell is disposed as an outflow side end open cell in the corresponding region (that is, the outer peripheral portion).

  In addition, for example, when installed in the exhaust gas flow path, if there is a drift in the flow of the exhaust gas, the one outflow side end open cell is disposed in the eccentric part, and the other part (that is, the drift is Other outflow side end open cells may be arranged in a portion not present). Thus, the installation position of one outflow side end open cell can be appropriately set according to the way in which the exhaust gas flowing into the honeycomb filter flows.

  In addition, when the outflow side end open cell is constituted by one outflow side end open cell and another outflow side end open cell, the one outflow side end open cell is the other outflow end cell. It is preferable that a portion corresponding to a corner portion in a cross-sectional shape orthogonal to the flow path direction of the side end open cell has a shape formed in an arc shape. That is, it is preferable that one outflow side end open cell and the other outflow end open cell have the same cell shape except that the shape of the corner is different. With this configuration, the cell structure in the entire honeycomb filter can have a certain regularity, and the mechanical strength of the honeycomb filter can be improved. In addition, the honeycomb filter can be easily manufactured, and the manufacturing cost can be reduced.

  Moreover, in FIG. 1A-FIG. 1C, the example of the case where the shape of the cross section orthogonal to the flow-path direction of one outflow side edge part open cell is a shape where the site | part corresponding to the corner | angular part in a square was formed in circular arc shape. However, the shape of the cross section that is the basis of one outflow side end open cell (that is, the shape before the portion corresponding to the corner is formed in an arc shape, for example, in FIGS. 1A to 1C, The (rectangle) may be, for example, an octagon other than the above-described square.

  The inflow side end portion open cell is a cell in which the inflow side end portion of the fluid is opened and the outflow side end portion of the fluid is plugged by the plugging portion. The shape of the cross section perpendicular to the flow path direction of the inflow side end open cell is a polygon such as a quadrangle, and unlike the one outflow side end open cell, the prismatic flow path having a corner. A cell is configured by.

Examples of the cross-sectional shape orthogonal to the flow path direction of the inflow side end open cell include a quadrangle or an octagon. In addition, the shape of the cross section which is the basis of the one outflow side end open cell described above and the shape of the cross section of the inflow side end open cell may be the same shape or different shapes. Good. For example, in the honeycomb filter 100 shown in FIG 1A~-1C, one and the underlying cross section of the shape of the outlet side end portions open cell 2B _1, cross-sectional shape and the same shape of the inlet side end portions open cells 2A an example is shown of a case where, for example, as the honeycomb filter 102 shown in FIGS. 3A and 3B, the sectional shape of the underlying one of the outlet side end portions open cell 22B _1, the inflow-side end The shape of the cross section of the open cell 22A may be different. 3A and FIG. 3B is a cross-sectional shape is a square as a basic one of the outlet-side end portion open cell 22B _1, the shape of the cross section of the inlet side end portions open cell 22A is an example in the case of octagonal Yes.

  Here, FIGS. 3A and 3B are enlarged plan views schematically showing still another embodiment of the honeycomb filter of the present invention, FIG. 3A shows an end face on the inflow side, and FIG. 3B shows an end face on the outflow side. The end face is shown.

  Regarding the radius of curvature of the arc-shaped portion in the cross-sectional shape orthogonal to the flow path direction of one outflow side end open cell, the size of one outflow end end open cell, improvement in heat capacity and pressure loss However, for example, the radius of curvature is preferably 0.2 to 0.8 mm, and more preferably 0.4 to 0.6 mm. If the radius of curvature is less than 0.2 mm, the effect of improving the heat capacity cannot be obtained sufficiently, and even at the site where one outflow side end open cell is arranged, the temperature rise during regeneration is sufficiently suppressed. There are things you can't do. On the other hand, if the radius of curvature exceeds 0.8 mm, the opening area at the outflow side end face of one outflow side end open cell may decrease, and the pressure loss of the honeycomb filter may increase.

  In addition, the curvature radius of the circular arc part in one outflow side edge part open cell can be measured with a microscope, for example.

  1A to 1C show a honeycomb filter (integrated honeycomb filter) having a structure formed as a whole. For example, in the honeycomb filter of the present invention, columnar honeycomb segments are joined. A honeycomb filter (joint type honeycomb filter) having a structure in which a plurality of layers are combined through a material layer (also referred to as a joint) may be used.

That is, as shown in FIG. 4A and FIG. 4B, it has a partition wall 33 that partitions and forms a plurality of cells 32 extending from one end face to the other end face to be a fluid flow path, and the fluid inflow side end 41 is opened. And the inflow side end open cell 32A in which the outflow side end portion 42 of the fluid is plugged by the plugging portion 35, and the inflow side end portion 41 is plugged by the plugging portion 35 and the outflow side end. Provided with a plurality of honeycomb segments 10 alternately arranged with the outflow side end open cells 32B with the portions 42 opened, and the plurality of honeycomb segments 10 are arranged adjacent to each other so that the side surfaces thereof face each other. In addition, the side surfaces facing each other are joined together by the joint portion 14, and at least one outflow side end open cell 32 </ b> B ₁ out of the outflow side end open cells 32 </ b> B is in the flow path direction partitioned by the partition wall 33. Orthogonal The honeycomb filter 110 may have a cross-sectional shape in which a portion X corresponding to a corner portion of a quadrilateral or more polygon is formed in an arc shape. Each honeycomb segment 10 constituting such a bonded honeycomb filter 110 is formed in a prismatic shape by an outer wall 15 located on the outermost periphery.

  Here, FIG. 4A is a perspective view schematically showing another embodiment of the honeycomb filter of the present invention, and FIG. 4B is a perspective view schematically showing the configuration of the honeycomb segment constituting the honeycomb filter shown in FIG. 4A. FIG.

  The bonded honeycomb filter includes, for example, a first honeycomb segment in which one outflow side end open cell and outflow side end open cell are alternately arranged, another outflow side end open cell, and outflow side end. A plurality of two types of honeycomb segments, each of which is a second honeycomb segment in which open cells are alternately arranged, are manufactured, and one honeycomb filter is manufactured by appropriately combining these honeycomb segments in a desired arrangement. be able to.

  By configuring in this way, a region where one outflow side end open cell is concentrated and a region where another outflow end open cell is concentrated are selectively and easily selected. For example, by arranging the first honeycomb segment in the region where the temperature is likely to rise during regeneration and arranging the second honeycomb segment in the other region, the temperature rise is effectively suppressed. However, an increase in pressure loss can be effectively suppressed.

For example, the honeycomb segments 10A disposed in the central portion A2 in a cross section perpendicular to the central axis direction of the honeycomb filter 110 shown in FIG. 4A, the outflow-side end portion open cell 32B ₁ single and outlet end open cells 32A Using the first honeycomb segments 10A that are alternately arranged, as the honeycomb segments 10B that are arranged in the outer peripheral portion B2 in the cross section, the shape of the cross section perpendicular to the flow path direction is the other outflow side end of a polygon that is a square or more. and parts open cell 32B ₂ and the outflow end open cells 32A indicates an example of using the second honeycomb segments 10B which are alternately arranged.

  Note that the bonded honeycomb filter is formed only from the first honeycomb segment in which the one outflow side end open cell and the outflow side end open cell are alternately arranged (that is, the second honeycomb segment is used). (Without). In such a case, one outflow side end open cell, one outflow side end open cell, and one outflow side end open cell are not disposed in a specific region, but in the entire bonded honeycomb filter. Are alternately arranged.

  As the material of the partition walls constituting the honeycomb filter, from the viewpoint of strength and heat resistance, silicon carbide, silicon-silicon carbide based composite material, silicon nitride, cordierite, mullite, alumina, spinel, silicon carbide-cordierite based composite material It is preferable to use at least one selected from the group consisting of silicon-silicon carbide composite materials, lithium aluminum silicate, aluminum titanate, and Fe—Cr—Al-based metals. Among these, for example, in the case of an integral honeycomb filter, cordierite, silicon carbide-cordierite-based composite material or the like is preferable, and in the case of a bonded honeycomb filter, silicon carbide, silicon-silicon carbide-based composite material, or the like is preferable. .

  The opening portion of each cell is plugged by the plugging portion 5. There is no restriction | limiting in particular about the structure of this plugged part, The plugged part comprised similarly to the plugged part used for a conventionally well-known honeycomb structure can be used.

  Further, as shown in FIGS. 1A to 1C, the outer peripheral wall 4 disposed so as to surround the partition wall 3 may be a molded integrated wall that is formed integrally with the partition wall 3 portion when the honeycomb filter 100 is molded. Alternatively, a cement-coated wall may be used in which after forming a honeycomb-shaped formed body having walls on its outer periphery, the outer peripheral wall is ground into a predetermined shape and the outer peripheral wall is formed with cement or the like. Such an outer peripheral wall can be formed using the material similar to the material which comprises the partition mentioned above, for example.

  The overall shape of the honeycomb filter of the present embodiment is not particularly limited. For example, the shape of the end face may be a circular shape, an elliptical shape, an oval shape, or other irregular columnar shapes. Further, the size of the honeycomb filter is, for example, in the case of a cylindrical shape, the diameter of the bottom surface is preferably 50 to 450 mm, more preferably 100 to 350 mm. Further, the length of the honeycomb filter in the central axis direction is 50 to 450 mm, and more preferably 100 to 350 mm.

  The open porosity of the partition walls constituting the honeycomb filter is preferably 35 to 60%, and more preferably 40 to 60%. By setting the open porosity in such a range, the pressure loss can be reduced while maintaining the strength. If the open porosity is less than 30%, the pressure loss may increase. When the open porosity exceeds 70%, the strength may decrease or the thermal conductivity may decrease. The open porosity is a value measured with a mercury porosimeter.

  The partition walls constituting the honeycomb filter preferably have an average pore diameter of 5 to 30 μm, and more preferably 10 to 25 μm. By setting the average pore diameter in such a range, particulate matter (PM) can be effectively collected. If the average pore diameter is less than 5 μm, clogging may easily occur due to particulate matter (PM). When the average pore diameter exceeds 30 μm, particulate matter (PM) may pass through without being collected by the partition walls. The average pore diameter is a value measured with a mercury porosimeter.

[2] Manufacturing method of honeycomb filter:
Next, a method for manufacturing the honeycomb filter of the present invention will be specifically described by taking as an example a method for manufacturing the bonded honeycomb filter 110 shown in FIG. 4A.

[2-1] Production of honeycomb segment:
First, a binder, a surfactant, a pore former, water and the like are added to a ceramic raw material to form a forming raw material. Ceramic raw materials include silicon carbide, silicon-silicon carbide composite material, cordierite, mullite, alumina, spinel, silicon carbide-cordierite composite material, lithium aluminum silicate, aluminum titanate, iron-chromium-aluminum alloy It is preferably at least one selected from the group consisting of Among these, silicon carbide or silicon-silicon carbide based composite material is preferable. When a silicon-silicon carbide based composite material is used, a mixture of silicon carbide powder and metal silicon powder is used as a ceramic raw material. The content of the ceramic raw material is preferably 40 to 90% by mass with respect to the entire forming raw material.

  Examples of the binder include methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. Among these, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination. The binder content is preferably 3 to 15% by mass with respect to the entire forming raw material.

  The water content is preferably 7 to 45 mass% with respect to the entire forming raw material.

  As the surfactant, ethylene glycol, dextrin, fatty acid soap, polyalcohol and the like can be used. These may be used individually by 1 type, and may be used in combination of 2 or more type. The content of the surfactant is preferably 0 to 5% by mass with respect to the entire forming raw material.

  The pore former is not particularly limited as long as it becomes pores after firing, and examples thereof include starch, foamed resin, water absorbent resin, silica gel and the like. The pore former content is preferably 0 to 15% by mass with respect to the entire forming raw material.

  Next, the forming raw material is kneaded to form a clay. There is no restriction | limiting in particular as a method of kneading | mixing a shaping | molding raw material and forming a clay, For example, the method of using a kneader, a vacuum clay kneader, etc. can be mentioned.

  Next, the clay is extruded to form a plurality of honeycomb formed bodies. Note that at least one of the plurality of honeycomb formed bodies has a partition wall that partitions and forms a plurality of cells serving as fluid flow paths and an outer peripheral wall positioned at the outermost periphery, and has a quadrangular cross-sectional shape. A honeycomb molded body having a shape in which the first cells in which the portions corresponding to the corners in the polygon are formed in an arc shape and the polygonal second cells whose cross-sectional shape is a quadrangle or more are alternately arranged (Hereinafter, also referred to as “first honeycomb formed body”). The first cell is one outflow end open cell, and the second cell is an inflow end open cell.

  In addition, as shown in FIG. 4A, when the honeycomb filter 110 includes other honeycomb segments 10B in addition to the honeycomb segment 10A formed of the first honeycomb molded body, the cross-sectional shape is a polygon having a square shape or more. Forms a honeycomb formed body having a shape in which third cells and polygonal second cells having a cross-sectional shape of a quadrangle or more are alternately arranged (hereinafter sometimes referred to as “second honeycomb formed body”) To do. The third cell is another outflow side end open cell.

  In extrusion molding, it is preferable to use a die having a desired segment shape, cell shape, partition wall thickness, cell density and the like. As the material of the die, a cemented carbide which does not easily wear is preferable. Note that the partition wall thickness, cell density, outer wall thickness, and the like of the honeycomb molded body are considered in terms of the shrinkage during drying and firing, and the configuration of the honeycomb filter to be manufactured, more specifically, the honeycomb constituting the honeycomb filter It can be determined appropriately according to the structure of the segment.

  The obtained honeycomb formed body is preferably dried before firing. The drying method is not particularly limited, and examples thereof include an electromagnetic heating method such as microwave heating drying and high-frequency dielectric heating drying, and an external heating method such as hot air drying and superheated steam drying. Among these, the entire molded body can be dried quickly and uniformly without cracks, and after drying a certain amount of moisture with an electromagnetic heating method, the remaining moisture is dried with an external heating method. It is preferable to make it. As drying conditions, it is preferable to remove moisture of 30 to 95% by mass with respect to the amount of moisture before drying by an electromagnetic heating method, and then to make the moisture to 3% by mass or less by an external heating method. As the electromagnetic heating method, dielectric heating drying is preferable, and as the external heating method, hot air drying is preferable. The drying temperature is preferably 90 to 180 ° C. The drying time is preferably 1 to 10 hours.

  Next, when the length of the honeycomb formed body in the central axis direction is not a desired length, it is preferable to cut both end faces (both end portions) to a desired length. The cutting method is not particularly limited, and examples thereof include a method using a circular saw cutting machine.

  Next, the honeycomb formed body is fired to produce a honeycomb fired body. In order to remove the binder or the like before firing, it is preferable to perform temporary firing. For example, the temporary firing is preferably performed at 400 to 500 ° C. for 0.5 to 20 hours in an air atmosphere. The method of temporary baking and baking is not particularly limited, and baking can be performed using an electric furnace, a gas furnace, or the like. Firing conditions are preferably heated at 1300 to 1500 ° C. for 1 to 20 hours in an inert atmosphere such as nitrogen or argon.

  Next, plugging portions are formed in the opening portions of the cells of the obtained honeycomb fired body so that one end portion and the other end portion are alternately plugged. In addition, the end part which plugged the cell in which the site | part corresponding to a corner | angular part was formed in circular arc shape becomes the outflow side end part in the honeycomb filter obtained, and the other end part becomes an inflow side end part. Plugging is performed as described above.

  A method for forming the plugged portion is not particularly limited, and examples thereof include the following methods. After the sheet is attached to one end face of the honeycomb fired body, a hole is opened at a position corresponding to a cell where a plugging portion of the sheet is to be formed. Then, in the plugging slurry in which the constituent material of the plugging portion is slurried, the honeycomb fired body is immersed in the end face on which the sheet is pasted, and an attempt is made to form the plugging portion through holes formed in the sheet. The plugging slurry is filled into the open end of the cell. And about the other end surface of the honeycomb fired body, plugging portions are formed in the same manner as the method in which the plugging portions are formed on the one end surface with respect to the cells not plugged on one end surface. (Fill with plugging slurry). As the constituent material of the plugged portion, the same material as that of the honeycomb formed body is preferably used. After forming the plugged portion, it is preferable to perform baking under the same conditions as the above baking conditions. The plugging portion may be formed before firing the honeycomb formed body.

[2-2] Production of honeycomb filter:
Next, a predetermined number of honeycomb segments are bonded with a bonding material, and a plurality of honeycomb segments are arranged adjacent to each other so that the side surfaces thereof face each other, and the opposite side surfaces are bonded to each other by a bonding portion. A bonded honeycomb segment assembly is formed. The honeycomb segment bonded body may be a honeycomb filter finally obtained. It is preferable that the joining portion is disposed on the entire side surfaces facing each other. The joined portion plays a role of buffering (absorbing) a volume change when the honeycomb segments are thermally expanded and contracted, and also serves to join the honeycomb segments. In the case of forming a bonded honeycomb segment, two types of honeycomb segments (first honeycomb segment and second honeycomb segment and second honeycomb molded body) are used. When the honeycomb segments are manufactured, it is possible to appropriately determine a portion where the heat capacity is high and the temperature rise during the regeneration of the filter can be reduced by the arrangement (combination) of the respective honeycomb segments. In other words, the first honeycomb segment is placed in a part where the temperature is likely to rise during regeneration, and the second honeycomb segment is placed in the other part, thereby reducing the temperature rise during regeneration and increasing the pressure loss. Can be suppressed. Of course, the first honeycomb segment may be used for all of the honeycomb segments constituting the honeycomb filter.

  The method for applying the bonding material to the side surfaces of the honeycomb segments is not particularly limited, and a method such as application with a spatula can be used. Examples of the bonding material include a slurry obtained by adding water to an inorganic raw material such as inorganic fiber, colloidal silica, clay, and SiC particles and adding an additive such as an organic binder, a foamed resin, and a dispersant, and kneading. it can.

  After forming the joined honeycomb segment assembly, the outer peripheral portion can be cut into a desired shape. For example, a plurality of rectangular pillar-shaped honeycomb segments are joined to produce a honeycomb segment joined body, and the outer periphery of the obtained honeycomb segment joined body is cut into a cylindrical honeycomb segment joined body, and the outer peripheral portion (outer peripheral wall) Is provided to form a honeycomb structure.

  The outer peripheral wall described above can be formed, for example, by applying an outer peripheral coating material to the outermost periphery of the joined honeycomb segment assembly and drying it. As the outer periphery coating material, a mixture of inorganic fiber, colloidal silica, clay, SiC particles, organic binder, foamed resin, dispersant, water, or the like can be used. The content of each raw material is preferably in the same range as the preferable range of the content of the raw material of the bonding material. Moreover, the method of applying the outer periphery coating material is not particularly limited, and examples thereof include a method of coating a cylindrical honeycomb segment bonded body with a rubber spatula while rotating it on a potter's wheel.

In addition, an integrated honeycomb filter (honeycomb filter 100) as shown in FIG. 1A is used as a die for extruding the clay for forming the partition walls 3 in a predetermined region, such as a polygonal cell (FIG. 1B). Inflow side end open cells 2A) and cells in which the portions corresponding to the polygonal corners are formed in an arc shape (one outflow side end open cell 2B ₁ ) are alternately arranged. A honeycomb formed body is formed by using the die formed with, and then the obtained honeycomb formed body is manufactured by drying, firing, and plugging according to a conventional method for manufacturing a honeycomb filter. be able to.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

Example 1
SiC powder and metal Si powder are mixed at a mass ratio of 80:20 as ceramic raw materials, and this is mixed with methyl cellulose and hydroxypropoxymethyl cellulose as molding aids, and starch and water-absorbing resin as pore formers, respectively. An agent and water were added and kneaded, and a clay was prepared with a vacuum kneader.

  The obtained clay is extruded using a molding machine and has partition walls that form a plurality of cells that serve as fluid flow paths and an outer wall that is positioned on the outermost periphery. A first cell in which a portion corresponding to a corner of a square having a cross-sectional shape of 1.2 mm × 1.2 mm is formed in an arc shape, and a second cell having a square shape in which the cross-sectional shape of the cell is 1.2 mm × 1.2 mm Four honeycomb formed bodies (first honeycomb formed bodies) having a structure in which the cells and the cells were alternately arranged were formed.

  Further, using the same clay, it has a partition wall for partitioning a plurality of cells and an outer wall located on the outermost periphery, and the cross-sectional shape of the cell is 1.2 mm × 1. Twelve honeycomb molded bodies (second honeycomb molded bodies) having a structure in which 2 mm square cells were partitioned by the partition walls were formed.

  Each obtained honeycomb formed body was dried at 120 ° C. for 5 hours using a hot air dryer, and then degreased for 5 hours at about 450 ° C. using an air furnace equipped with a deodorizing apparatus in an air atmosphere. A porous honeycomb fired body (first honeycomb fired body and second honeycomb fired body) in which SiC crystal particles were bonded with Si was fired at about 1450 ° C. for 5 hours in an Ar inert atmosphere. . The honeycomb fired body had an average pore diameter of 23 μm and a porosity of 52%. The average pore diameter and porosity are values measured with a mercury porosimeter.

  About the obtained honeycomb fired body, one end and the other end of the cell were alternately plugged to form a plugged portion. As the plugging filler, the same material as that of the honeycomb formed body was used. After plugging portions were formed in the honeycomb fired body, the honeycomb fired body was fired under the same conditions as the above firing conditions to form honeycomb segments (first honeycomb segment and second honeycomb segment).

Regarding the size of the first honeycomb segment and the second honeycomb segment, the shape of the end face perpendicular to the axial direction was a square of 36 mm × 36 mm, and the length in the axial direction was 152 mm. In addition, the thickness of the partition walls partitioning each cell other than the portion where the corner portion of the cell was formed in an arc shape was 0.3 mm, and the cell density of each honeycomb segment was 47 cells / cm ² . Further, the radii of curvature of the portions corresponding to the corners of the second cells of the first honeycomb segment (portions formed in an arc shape) were each 0.05 mm.

  Each of the obtained honeycomb segments was joined with a joining material in a manner of 4 × 4 as in the honeycomb filter 110 shown in FIG. 4A to obtain a joined honeycomb segment. When the joined honeycomb segment assembly was used, the first honeycomb segment was used as the four honeycomb segments in the central portion, and the second honeycomb segment was used for the other honeycomb segments.

  Moreover, as a bonding material for bonding the honeycomb segments, a mixture of aluminosilicate inorganic fibers and SiC particles was used. As the slurry containing the bonding material, a slurry containing 30% by mass of water, 30% by mass of aluminosilicate inorganic fibers, and 30% by mass of SiC particles was used with respect to the entire bonding material.

  The obtained bonded honeycomb segment assembly was subjected to outer periphery coating treatment, and an outer peripheral wall was disposed on the outermost periphery of the bonded honeycomb segment assembly to manufacture a honeycomb filter. As the outer periphery coating material, a mixture of silicon carbide particles, colloidal silica, ceramic fibers, an inorganic binder, and an organic binder to form a slurry was used. In the honeycomb filter, the end of the first cell plugged side is the fluid inflow side end, and the open end of the first cell is the fluid outflow side. It becomes the end.

  With respect to the obtained honeycomb filter, the “maximum temperature during regeneration (° C.)” and the “pressure loss increase rate (%)” were measured by the following methods. The results are shown in Table 1. The column of “Pressure loss increase rate (%)” in Table 1 shows the rate (%) of increase in pressure loss with respect to Comparative Example 1 based on the results of Comparative Example 1 for Examples 1 to 19. ing.

[Maximum temperature during regeneration (℃)]
The honeycomb structure according to each of the examples and the comparative examples is disposed in the exhaust passage of the engine to form an exhaust gas purification device (DPF), and an experiment is performed in which regeneration treatment is performed after depositing soot in the engine. The maximum temperature was measured and the results are shown in Table 1. First, post-injection was performed at 1700 rpm x 95 Nm on the DPF on which soot was deposited, and the inlet exhaust gas temperature was raised to 650 ° C. did. At that time, since the oxygen concentration rapidly increases and the flow rate decreases, soot burns and the DPF internal temperature rapidly increases.

[Pressure loss increase rate (%)]
The honeycomb structure according to each of the examples and the comparative examples is installed in an artificial soot generator, and a soot is generated in a DPF on which no soot is deposited, and a gas of 200 ° C. and 2.3 Nm ³ / min is allowed to flow in and out. The pressure difference was measured and the results are shown in Table 1.

(Examples 2 to 19)
Honeycomb filter in the same manner as in Example 1, except that the radius of curvature of the portion corresponding to the corner of the first cell of the first honeycomb segment (portion formed in an arc shape) was changed as shown in Table 1. Was made. In the same manner as in Example 1, the “maximum temperature during regeneration (° C.)” and the “pressure loss increase rate (%)” were measured. The results are shown in Table 1.

(Comparative Example 1)
A honeycomb filter was produced in the same manner as in Example 1 except that the first cell of the first honeycomb segment was a 1.2 mm × 1.2 mm square (that is, a radius of curvature of 0.00 mm). That is, the first honeycomb segment in Comparative Example 1 is a honeycomb segment formed in the same shape as the second honeycomb segment in which cells having the same shape are arranged at equal intervals. For the obtained honeycomb filter, the “maximum temperature during regeneration (° C.)” and the “pressure loss increase rate (%)” were measured in the same manner as in Example 1. The results are shown in Table 1.

〔result〕
As shown in Table 1, it can be seen that the honeycomb filters of Examples 1 to 19 have a lower maximum temperature during regeneration than the honeycomb filter of Comparative Example 1. As described above, in the honeycomb filters of Examples 1 to 19, it is difficult for the temperature to rise due to combustion during regeneration, and the occurrence of cracks, melting damage, and the like can be effectively prevented.

  Moreover, although it turns out that the pressure loss increase rate of the honeycomb filter of Examples 1-19 is worse compared with the honeycomb filter of the comparative example 1, only 4x4 center 4 pieces are 1st. By using this honeycomb segment, the rate of increase in pressure loss can be minimized.

  The honeycomb filter of the present invention can be suitably used as a collection filter for exhaust gas. In particular, it is useful as a diesel particulate filter (DPF) for capturing and removing particulate matter (PM) contained in exhaust gas from a diesel engine or the like.

2,22,32: cell, 2A, 22B, 32B: inlet side end portions open cells, 2B, 22B, 32B: outlet side end portions open _{cell, 2B 1, 22B 1, 32B} 1: one outlet end opening Cell, 2B ₂ , 22B ₂ , 32B ₂ : other outflow side end open cell, 3, 23, 33: partition wall, 4: outer peripheral wall, 5, 35: plugged portion, 10: honeycomb segment, 10A: honeycomb Segment (first honeycomb segment), 10B: Honeycomb segment (second honeycomb segment), 11, 41: Inflow side end portion, 12, 42: Outflow side end portion, 14: Joining portion, 15: Outer wall, 100, 101, 102, 110: Honeycomb filter, A1, A2: Central portion, B1, B2: Outer peripheral portion, x: A portion corresponding to a corner portion of a polygon.

Claims (7)

A porous partition wall that partitions and forms a plurality of cells serving as fluid flow paths,
An inflow side end open cell in which the fluid inflow end is open and the outflow end of the fluid is plugged, and the inflow end is plugged and the outflow end is open. And the outflow side end open cells made are arranged alternately,
Of the outflow side end open cells, at least one outflow side end open cell is a portion whose cross-sectional shape perpendicular to the flow path direction defined by the partition wall corresponds to a corner in a polygon having a quadrangle or more. There Ri shape der formed in an arc shape,
Of the outflow side end open cells, the outflow side end open cells other than the one outflow side end open cell have a polygonal shape of a quadrangle or more in cross-sectional shape perpendicular to the flow path direction. ,
The inlet end open cells, the shape of the cross section perpendicular to the flow path direction, square, or octagonal der Ru honeycomb filter. Sites the one outlet end open cells, the shape of the cross section perpendicular to the flow path direction corresponds to the corners of the shape of a cross section perpendicular to the flow path direction of said other outlet end open cells the honeycomb filter according to claim 1 but is a shape formed in a circular arc shape. In the cross section perpendicular to the central axis direction of the honeycomb filter, the one outflow side as the outflow side end open cell is formed in a region including the central portion and corresponding to 10 to 70% with respect to the total area of the cross section. The honeycomb filter according to claim 1 or 2 , wherein at least end open cells are arranged. In the cross section perpendicular to the central axis direction of the honeycomb filter, the other outflow side as the outflow side end open cell is formed in a region including the outer peripheral portion and corresponding to 30 to 90% of the total area of the cross section. The honeycomb filter according to any one of claims 1 to 3 , wherein at least end open cells are arranged. The one of the outlet-side end portion open cells, the shape of the cross section perpendicular to the flow path direction, one part corresponding to the corners of a square of claims 1-4 is a shape formed in a circular arc shape one The honeycomb filter according to item. The one of the outlet-side end portion open the flow path of the portion formed in a circular arc shape in the shape of a cross section perpendicular to the direction of curvature radius of the cell is any one of claims 1 to 5 is 0.2~0.8mm The honeycomb filter according to one item. Comprising a plurality of honeycomb segments in which the inflow side end open cells and the outflow side end open cells partitioned by the partition walls are alternately arranged;
The honeycomb segments according to any one of claims 1 to 6 , wherein the plurality of honeycomb segments are arranged adjacent to each other so that the side surfaces thereof are opposed to each other, and the opposing side surfaces are bonded to each other by a bonding portion. The honeycomb filter according to one item.

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