JP6802102B2 - Sealed honeycomb structure - Google Patents

Description

The present invention relates to a sealing honeycomb structure for a wall flow type exhaust gas filter. More specifically, the present invention relates to a sealing honeycomb structure that is suitably used for removing particulate matter contained in exhaust gas from an engine such as an automobile engine and / or purifying a toxic gas such as nitrogen oxide.

Internal combustion engines are used as a power source in various industries. On the other hand, in the exhaust gas emitted by the internal combustion engine when burning fuel, particulate matter such as soot and ash (hereinafter sometimes referred to as "PM") is released into the atmosphere together with toxic gas such as nitrogen oxides. .. In particular, regulations regarding the removal of PM emitted from diesel engines are becoming stricter worldwide, and a wall-flow type gas having a honeycomb structure is used as a filter for removing PM (hereinafter sometimes referred to as "DPF"). A purification filter is used.

The DPF is a filter in which a plurality of cells serving as a fluid flow path are partitioned by a porous partition wall, and the cells are alternately sealed to remove PM from the porous partition wall. It has a structure that fulfills its role.

Specifically, a honeycomb structure in which exhaust gas containing PM is introduced from the inflow side end face of the DPF, filtered by collecting PM with a porous partition wall, and then the purified exhaust gas is discharged from the outflow side end face. The body has been used conventionally. However, there is a problem that PM is deposited on the partition wall with the inflow of the exhaust gas and blocks the inflow cell of the exhaust gas. When the cell is closed in this way, there arises a problem that the pressure loss of the DPF suddenly increases.

Therefore, in order to suppress such cell blockage, it is important to increase the filtration area and aperture ratio of the inflow cell. However, when the inflow cell and the outflow cell have different cross-sectional areas and cross-sectional shapes, the thickness of the partition wall forming the cell may be thinned at a part of the portion where the partition walls intersect with each other, and the strength is weakened. Therefore, when the PM deposited on the DPF is regenerated by burning and removing it, there is a problem that thermal stress is concentrated on a part of the intersection of the thinned partition walls and cracks are generated.

In order to solve such a problem, it is possible to suppress the pressure loss at the initial stage and during PM deposition by keeping the opening diameter of the outflow cell large while increasing the filtration area and opening ratio of the inflow cell, and the heat resistance. A wall flow type DPF having high impact resistance has been proposed (Patent Document 1).

Further, Patent Document 1 describes a technique for preventing the occurrence of cracks by providing substantially arcuate R portions at all the intersections of the thinned partition walls. In addition, a technique has been proposed in which a substantially arc-shaped R portion is arranged at the opposite corners of the cell to prevent the occurrence of cracks at the intersections of the partition walls (Patent Document 2).

Japanese Unexamined Patent Publication No. 2014-200741 Japanese Unexamined Patent Publication No. 2003-269131

However, as in the conventional DPF shown in FIG. 5, for example, the intersection of the partition walls where the vertices of the four inflow cells gather has a structure in which stress is easily concentrated. Therefore, when the DPF is used as a wall flow type gas purification filter in the exhaust system of an automobile engine, in addition to vibration, thermal stress due to PM combustion, for example, rapid heating and rapid cooling due to soot combustion, is generated while the automobile is running. It may occur. Then, when such thermal stress is generated, there is a problem that the possibility of cracking in the DPF is further increased.

A schematic diagram of a typical crack of a conventional DPF is shown in FIG. Cracks connecting the vertices of inflow cells are generally considered to have a small contribution to soot leakage. However, if the crack progresses and reaches the outflow cell, soot leakage may occur, and it is necessary to prevent this. FIG. 5 is a plan view schematically showing the inflow side end face of the conventional segment type sealing honeycomb structure. FIG. 6 is an enlarged view of the conventional eye-sealing honeycomb structure of FIG. 5, and is a diagram schematically showing typical cracks.

As disclosed in Patent Document 2, as a means for preventing the occurrence of the crack, the cell has been conventionally reinforced. However, when the reinforcing portions are provided at all the intersections of the partition walls as in the conventional case, the problem of crack generation can be solved, but the opening area of the cell becomes smaller, so that the pressure loss increases and the ash (ash ( There was a problem that the accumulated capacity (ash capacity) of Ash) decreased. Further, in the conventional DPF, since the heat capacity becomes large, there is a demerit that the light-off performance (Light-off performance) deteriorates. The light-off performance means a temperature characteristic in which the purification performance of the catalyst supported on the DPF is exhibited.

The present invention has been made in view of the problems of the prior art. The present invention provides a mesh-sealing honeycomb structure capable of improving mechanical strength and thermal shock resistance while maximally suppressing a decrease in opening area, an increase in pressure loss, and a decrease in ash capacity. To do.

According to the present invention, the following eye-sealing honeycomb structure is provided.

[1] Arranged in a honeycomb structure portion having a porous partition wall forming a plurality of cells serving as a flow path of a fluid extending from an inflow side end face to an outflow side end face, and an opening of a predetermined inflow cell in the outflow side end face. An inflow-side eye-sealing portion provided and an outflow-side eye-sealing portion disposed in the opening of the residual outflow cell on the inflow-side end face are provided.
In the cross section of the honeycomb structure portion orthogonal to the extending direction of the cells, the inflow cells are arranged so as to surround the outflow cells, and the number of the inflow cells is larger than the number of the outflow cells.
It has a plurality of intersections of partition walls that partition adjacent inflow cells.
At 60% or more of the total number of intersections,
The relationship between the diameter D _{1 of} the circle inscribed in the intersection and the diameter D _{0 of} the circle inscribed in the partition wall separating the adjacent inflow cell and the outflow cell is as shown in the following equation (1). It is an eye-sealing honeycomb structure .
A mesh-sealing honeycomb structure in which the relationship between the diameter D ₁ and the diameter D ₀ is as shown in the following formula (1) only at the intersection of the partition walls that partition the adjacent inflow cells .

Equation (1): D ₁ / (√2 × D ₀ ) = 1.20 to 1.80

[2] In the total number of the intersections, between the diameter D _{1 of} the circle inscribed in the intersection and the diameter D _{0 of} the circle inscribed in the partition wall separating the adjacent inflow cell and the outflow cell. The eye-sealing honeycomb structure according to the above [1], wherein the relationship is as shown in the above formula (1).

[3] The above-mentioned [1] or [2], wherein the diameter D _{2 of the} circle inscribed in the inflow cell and in contact with the partition wall on the intersection side of the inflow cell is 0.25 to 0.80 mm. Sealed honeycomb structure.

In the sealing honeycomb structure of the present invention, reinforcing portions are selectively provided only at the corners of the intersections of the partition walls where the vertices of a plurality of inflow cells gather. As a result, the mechanical strength and thermal impact resistance of the DPF can be improved while maximally suppressing a decrease in opening area, an increase in pressure loss, a decrease in ash capacity, and a deterioration in light-off performance.

It is a perspective view of the eye-sealing honeycomb structure of embodiment of this invention. It is a top view which represented a part of the end face on the inflow side of the sealing honeycomb structure shown in FIG. It is sectional drawing which follows the AA' line of FIG. It is a top view which represented the enlargement of the end face on the inflow side of FIG. It is a top view which represented typically the inflow side end face of the conventional segment type eye-sealing honeycomb structure. FIG. 5 is an enlarged view of a conventional eye-sealing honeycomb structure of FIG. 5, which schematically shows typical cracks. It is an enlarged view of the conventional eye-sealing honeycomb structure of FIG. 5, and is the figure explaining the circle inscribed in the intersection part.

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 the following embodiments can be appropriately modified, improved, or the like based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

1 to 4 are views schematically showing a mesh-sealing honeycomb structure according to an embodiment of the present invention. Here, the eye-sealing honeycomb structure 100 of the present embodiment is an integral honeycomb structure in which the partition wall and the outer peripheral wall are integrally molded even if the honeycomb structure is a segment type honeycomb structure in which a plurality of honeycomb segments are joined to each other. It may be either. FIG. 1 is a perspective view of the eye-sealing honeycomb structure according to the embodiment of the present invention. FIG. 2 is a plan view schematically showing a part of the inflow side end face of the sealing honeycomb structure shown in FIG. FIG. 3 is a cross-sectional view taken along the line AA'of FIG. FIG. 4 is a plan view schematically showing an enlargement of the inflow side end surface 6a of FIG.

The eye-sealing honeycomb structure 100 of the present embodiment includes a honeycomb structure portion 9, an inflow side eye sealing portion 3a, and an outflow side eye sealing portion 3b. The honeycomb structure portion 9 is composed of a plurality of honeycomb segments 7. Each of the plurality of honeycomb segments 7 has a porous partition wall 1 that partitions a plurality of cells 2a and 2b that serve as a flow path for a fluid extending from the inflow side end face 6a to the outflow side end face 6b. A bonding layer 8 is disposed between the side surfaces of the plurality of honeycomb segments 7, and the honeycomb structure portion 9 is formed by joining the plurality of honeycomb segments 7 by the bonding layer 8. There is. An outer peripheral wall 11 is arranged on the outer periphery of the honeycomb structure portion 9 so as to surround a joined body in which a plurality of honeycomb segments 7 are joined.

The inflow side sealing portion 3a is arranged in the opening of a predetermined inflow cell 2a in the outflow side end surface 6b. The outflow side eye sealing portion 3b is arranged in the opening of the residual outflow cell 2b in the inflow side end surface 6a.

In the sealing honeycomb structure 100, the inflow cell 2a is arranged so as to surround the outflow cell 2b in a cross section orthogonal to the extending direction of the cell 2 of the honeycomb structure portion 9. Further, the sealing honeycomb structure 100 is configured so that the number of inflow cells 2a is larger than the number of outflow cells 2b. The sealing honeycomb structure 100 has a plurality of intersections 4 of partition walls 1 that partition adjacent inflow cells 2a from each other. The sealing honeycomb structure 100 has the following configuration in 60% or more of the total number of the intersections 4 of the partition walls 1 that partition the adjacent inflow cells 2a. First, the relationship between the diameter D _{1 of} the circle inscribed in the intersection 4 and the diameter D _{0 of} the circle inscribed in the partition wall 1 partitioning the adjacent inflow cell 2a and outflow cell 2b is expressed by the following equation. It satisfies (1). Here, the "intersection portion 4 of the partition wall 1 that partitions the adjacent inflow cells 2a" means the "intersection portion 4 where only the partition walls 1 that partition the adjacent inflow cells 2a intersect". That is, the "intersection portion 4 of the partition wall 1 that partitions the adjacent inflow cells 2a" refers to a portion where the partition wall 1 extending from the intersection is the partition wall 1 that partitions only the adjacent inflow cells 2a. Say. Hereinafter, unless otherwise specified, the term "intersection portion 4" simply means the above-mentioned "intersection portion 4 in which only the partition walls 1 that partition the adjacent inflow cells 2a intersect".

Equation (1): D ₁ / (√2 × D ₀ ) = 1.20 to 1.80

Here, the present embodiment will be described with reference to FIG. The fact that the inflow cell 2a is arranged so as to surround the outflow cell 2b means, for example, a state in which a plurality of inflow cells 2a are arranged so as to surround one outflow cell 2b. Regarding the cells 2 arranged on the outermost circumference of the inflow side end surface 6a of the sealing honeycomb structure 100, the inflow cells 2a may not be arranged so as to surround the outflow cells 2b. Further, also in each honeycomb segment 7, the inflow cell 2a may not be arranged so as to surround the outflow cell 2b with respect to the cell 2 arranged on the outermost circumference. Here, in FIG. 4, the outflow cell 2b having a quadrangular cell shape is surrounded by a pentagonal inflow cell 2a having a smaller cell shape than the outflow cell 2b. The cell shape of the outflow cell 2b and the cell shape of the inflow cell 2a are not particularly limited as long as they can be arranged so as to surround the outflow cell 2b with the inflow cell 2a. For example, the cell shape may be a polygon such as a quadrangle, a pentagon, or a hexagon, but the cell shape is not limited to these. Further, the sizes of one outflow cell 2b and one inflow cell 2a (in other words, the cross-sectional area of the cells) may be the same or different. Here, the "cell shape" refers to the shape of the cell in the cross section orthogonal to the extending direction of the cell in the honeycomb structure portion.

Further, the intersection portion 4 of the partition wall 1 that partitions the adjacent inflow cells 2a is the intersection portion 4 where only the partition wall 1 that partitions the plurality of inflow cells 2a arranged so as to surround the outflow cell 2b intersects. Means. As shown in FIGS. 1 and 2, the shape of the inflow cell 2a may be partially crushed in the vicinity of the outer peripheral wall of the sealing honeycomb structure 100. An inflow cell 2a in which such a cell shape is partially crushed is also counted as one inflow cell 2a.

Next, the diameter D _{1 of} the circle inscribed in the intersection portion 4 is the diameter of the circle inscribed in the intersection portion 4 of the partition wall 1, as shown in FIG. The "circle inscribed in the intersection 4" is an inscribed circle in the intersection 4 of the partition wall 1 that is inscribed in the inflow cell 2a, which is a majority of the inflow cells 2a facing the intersection 4. The "diameter D _{1 of} the circle inscribed in the intersection 4" is the diameter of the inscribed circle having the maximum diameter when there are a plurality of inscribed circles in contact with the majority of the inflow cells 2a.

Further, as shown in FIG. 4, the diameter D _{0 of} the circle inscribed in the partition wall 1 that partitions the adjacent inflow cell 2a and the outflow cell 2b is the intersection of the partition walls that partition the inflow cell 2a and the outflow cell 2b. It is the diameter of the circle inscribed in the partition wall 1 other than the above. In other words, it means the diameter of a circle circumscribing the portions of the inflow cell 2a and the outflow cell 2b that face each other except for the corners. Hereinafter, "the diameter D _{0 of} the circle inscribed in the partition wall 1 that partitions the adjacent inflow cell 2a and the outflow cell 2b" may be simply referred to as "the diameter D _{0 of} the circle inscribed in the partition wall 1." The diameter D ₀ of the circle inscribed in the partition wall 1 that separates the adjacent inflow cell 2a and the outflow cell 2b can be obtained as follows. First, at the inflow side end surface 6a of the sealing honeycomb structure 100, five of the partition walls 1 that partition the adjacent inflow cells 2a and outflow cells 2b are randomly selected. Then, an inscribed circle is virtually drawn for the five selected partition walls 1, and the diameter of the inscribed circle is obtained. Let the average value of the diameters of the five inscribed circles be the diameter D _{0 of} the circles.

Will now be described √2 × D ₀ in formula (1), √2 × D ₀ in formula (1), such as shown in FIG. 7, a conventional eye seal which is not provided with the reinforcing portion In the stop honeycomb structure, the value of the diameter of the circle inscribed in the intersection 4 of the partition wall 1 that partitions the inflow cells 2a is shown. FIG. 7 is an enlarged view of the conventional eye-sealing honeycomb structure of FIG. 5, and is a diagram for explaining a circle inscribed in the intersection. It plugged honeycomb structure 100 of the present embodiment, the diameter D ₁ of the circle inscribed in the intersection portion 4 of the partition walls 1 defining the inflow cells 2a with adjacent, conventional eye seal which is not provided with the reinforcing portion It is characterized by being larger than the "diameter of the circle inscribed at the intersection of similar points" of the stop honeycomb structure.

The number of intersections 4 satisfying the condition of the above formula (1) is at least 60%, more preferably 100%, when the total number of intersections 4 is 100%. When the number of intersections 4 satisfying the above conditions is less than 60%, the thermal shock resistance is remarkably lowered.

If the value of "D ₁ / (√2 x D ₀ )" in the above formula (1) is less than 1.20, sufficient thermal shock resistance cannot be obtained. Further, when the value of "D ₁ / (√2 × D ₀ )" in the above equation (1) exceeds 1.80, the pressure loss increases, the write-off performance deteriorates, and the ash capacity decreases. It ends up.

Further, only at the intersection 4 of the partition wall 1 that partitions the adjacent inflow cells 2a, the diameter (D ₁ ) of the circle inscribed in the intersection 4 and the partition wall 1 that partitions the adjacent inflow cells 2a and the outflow cells 2b. The relationship between the diameter of the circle inscribed in (D ₀ ) and the equation (1) is satisfied. This is different from the conventional technique in which the reinforcing portions are arranged at all the intersections of the partition walls, and as shown in FIGS. 1 to 4, in the present invention, the intersections 4 of the partition walls 1 that partition the adjacent inflow cells 2a from each other. It means that the reinforcing portion is arranged only in. As a method for producing such a reinforcing portion, for example, a method of changing the shape of the base during extrusion molding by a conventionally known method can be mentioned. Further, the above-mentioned reinforcing portion may be produced by forming the corner portion having R by flowing the slurry into the predetermined corner portion of the predetermined inflow cell 2a. In addition, "having a reinforcing portion" means that the intersection portion 4 of the partition wall 1 that partitions the adjacent inflow cells 2a satisfies the relationship of the above formula (1). Further, the above-mentioned "only at the intersection 4 of the partition wall 1 that partitions the adjacent inflow cells 2a ... Satisfies the equation (1)" means that the other intersections are the equation (1). It means that it is not necessary to satisfy the relationship of. Here, if the relationship of the above equation (1) is not satisfied, for example, the relationship of D ₁ = √2 × D ₀ or the value of “D ₁ / (√2 × D ₀ )” is 1 as in the prior art. It means that it may be less than .20. However, it should be noted that the above equation (1) does not include manufacturing tolerances.

Further, the diameter D ₂ of the circle inscribed in the inflow cell 2a and in contact with the partition wall 1 on the intersection 4 side of the inflow cell 2a is preferably 0.20 to 0.80 mm. Here, FIG. 4 shows the diameter D ₂ of a circle inscribed in the inflow cell 2a and in contact with the partition wall 1 on the intersection 4 side of the inflow cell 2a. As shown in FIG. 4, the circle having the diameter D ₂ is a circle that exists in the inflow cell 2a and is in contact with the partition wall 1 of the intersection portion 4. The diameter of such a circle is the above-mentioned "diameter D ₂ ". Here, when the diameter D ₂ is smaller than 0.20 mm, sufficient thermal shock resistance may not be obtained.

In the eye-sealing honeycomb structure 100 of the present embodiment, one in which the honeycomb structure portion 9 is configured as follows can be mentioned as one of the preferable examples. In the inflow cell 2a, the geometric surface area GSA is preferably 10 to 30 cm ² / cm ³ , and even more preferably 12 to 18 cm ² / cm ³ . Here, the above-mentioned "geometric surface area GSA" means a value (S / V) obtained by dividing the total internal surface area (S) of the inflow cell 2a by the total volume (V) of the honeycomb structure portion 9. .. In general, the larger the filtration area of the filter, the smaller the thickness of PM deposited on the partition wall. Therefore, the pressure loss of the sealing honeycomb structure can be kept low by setting the geometric surface area GSA in the numerical range described above. Can be done. Therefore, if the geometric surface area GSA of the inflow cell 2a is smaller than 10 cm ² / cm ³ , it is not preferable because it leads to an increase in pressure loss during PM deposition. Further, if it is larger than 30 cm ² / cm ³ , the initial pressure loss increases, which is not preferable.

In the sealing honeycomb structure 100 of the present embodiment, the cell cross-sectional aperture ratio of the inflow cell 2a is preferably 20 to 70%, more preferably 25 to 65%. If the cell cross-sectional aperture ratio of the inflow cell 2a is smaller than 20%, the initial pressure loss increases, which is not preferable. On the other hand, if it is larger than 70%, the filtration flow rate becomes high, the PM collection efficiency is lowered, and the strength of the partition wall 1 is insufficient, which is not preferable. Here, the "cell cross-sectional aperture ratio of the inflow cell 2a" means the following ratio in the cross section perpendicular to the central axis direction of the honeycomb structure portion 9. That is, "the total cross-sectional area of the inflow cell 2a (all of the inflow cell 2a and the outflow cell 2b)" with respect to the "cross-sectional area of the entire partition wall 1 forming the honeycomb structure portion 9". It means the ratio of "total cross-sectional area".

In the sealing honeycomb structure 100 of the present embodiment, the hydraulic diameters of the plurality of cells 2 (inflow cell 2a, outflow cell 2b) are preferably 0.5 to 2.5 mm, preferably 0.8. It is more preferably ~ 2.2 mm. If the hydraulic diameter of each of the plurality of cells is smaller than 0.5 mm, the initial pressure loss increases, which is not preferable. On the other hand, if it is larger than 2.5 mm, the contact area between the exhaust gas and the partition wall 1 is reduced, and the purification efficiency is lowered, which is not preferable. Here, the hydraulic diameter of each of the plurality of cells is a value calculated by 4 × (cross-sectional area) / (perimeter) based on the cross-sectional area and the perimeter of each cell 2. The cross-sectional area of the cell 2 refers to the area of the cell shape (in other words, the cross-sectional shape) that appears in the cross section perpendicular to the central axis direction of the honeycomb structure portion 9. The perimeter of a cell refers to the length around the cross-sectional shape of the cell (in other words, the length of the closed line surrounding the cross section).

In view of the trade-off between the initial pressure loss, the pressure loss during PM deposition, and the collection efficiency, the following configurations can be given as preferable examples in the sealing honeycomb structure 100 of the present embodiment. The geometric surface area GSA of the inflow cell 2a is 10 to 30 cm ² / cm ³ , the cell cross-sectional aperture ratio of the inflow cell 2a is 20 to 70%, and the hydraulic diameter of each of the plurality of cells 2 is 0. It is preferable that the thickness is 5 to 2.5 mm at the same time. Further, the geometric surface area GSA of the inflow cell 2a is 12 to 18 cm ² / cm ³ , the cell cross-sectional aperture ratio of the inflow cell 2a is 25 to 65%, and the hydraulic diameter of each of the plurality of cells 2. It is more preferable that the value is 0.8 to 2.2 mm at the same time.

In the sealing honeycomb structure 100 of the present embodiment, the catalyst may be supported on the partition wall 1. Supporting the catalyst on the partition wall 1 means that the surface of the partition wall 1 and the inner wall of the pores formed by the partition wall 1 are coated with the catalyst. Examples of the type of catalyst include SCR catalysts (zeolite, titania, vanadium), three-way catalysts containing at least two noble metals among Pt, Ph and Pd, and at least one of alumina, ceria and zirconia. By supporting such a catalyst, NOx, CO, CH, etc. contained in the exhaust gas discharged from the direct injection type gasoline engine, diesel engine, etc. can be detoxified, and PM deposited on the surface of the partition wall 1 can be catalyzed. This makes it possible to easily remove the combustion.

The method of supporting the catalyst on the sealing honeycomb structure 100 of the present embodiment is not particularly limited, and a method usually performed by those skilled in the art can be adopted. Specific examples thereof include a method in which the catalyst slurry is wash-coated, dried, and fired.

The method for producing the mesh-sealed honeycomb structure 100 of the present embodiment is not particularly limited, and for example, it can be produced by the following method. As the raw material powder of the honeycomb structure portion 9, a binder is added to a material selected from the above-mentioned suitable materials, and a surfactant and water are further added to prepare a plastic clay. As the raw material powder, for example, silicon carbide powder can be used. As the binder, for example, methyl cellulose, hydroxypropoxyl methyl cellulose and the like can be used. By extrusion molding this clay, a molded body of a honeycomb structure portion 9 having a partition wall 1 and a cell 2 having a predetermined cross-sectional shape is obtained. This is dried, for example, with microwaves and hot air. After that, by sealing with the same material as the material used for manufacturing the honeycomb structure portion 9, the eye sealing portion 3 (inflow side eye sealing portion 3a, outflow side eye sealing portion 3b) is arranged. Further dry. Then, for example, by heating and degreasing in a nitrogen atmosphere and then firing in an inert atmosphere such as argon, the sealing honeycomb structure 100 of the present embodiment can be obtained. The firing temperature and firing atmosphere differ depending on the raw material, and a person skilled in the art can select the optimum firing temperature and firing atmosphere for the selected material.

In the present embodiment, the materials of the partition wall and the outer peripheral wall constituting the honeycomb structure portion 9 are not particularly limited, but from the viewpoint of strength, heat resistance, durability, etc., the main component is various oxides or non-oxides. It is preferably ceramics or metal. Examples of the ceramics include cordierite, mullite, alumina, spinel, silicon carbide, silicon nitride, aluminum titanate and the like. Examples of the metal include Fe-Cr-Al-based metals and metal silicified products. It is preferable to use one or more selected from these materials as the main component. From the viewpoint of high strength and high heat resistance, it is particularly preferable to use one or more kinds selected from the group consisting of alumina, mullite, aluminum titanate, corderite, silicon carbide, and silicon nitride as the main component. Here, the term "main component" means that the honeycomb structure 9 is composed of at least 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more.

The material of the eye sealing portion 3 (inflow side eye sealing portion 3a and outflow side eye sealing portion 3b) is not particularly limited, but is preferably the same as that of the honeycomb structure portion 9.

The thickness of the partition wall 1 is preferably 100 to 410 μm, more preferably 150 to 360 μm. If it is thinner than 100 μm, the strength of the honeycomb base material may decrease. If it is thicker than 410 μm, the collection performance may decrease and the pressure loss may increase. Further, when treating the exhaust gas discharged from the diesel engine, since the amount of PM in the exhaust gas discharged from the diesel engine is relatively large, there is usually a tendency to reduce the number of cells (decrease the cell density). .. Therefore, it is preferable that the thickness of the partition wall 1 is 150 to 360 μm in order to improve the balance between strength and collection performance. The thickness of the partition wall is a value measured by a method of observing the axial cross section of the honeycomb base material under a microscope.

(Example 1)
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-forming material, and water were added to this mixed powder to obtain a molding raw material. Next, the molding raw materials were kneaded to prepare a columnar clay.

Next, the clay was extruded using a predetermined extrusion mold to obtain a honeycomb molded body in which a pentagonal inflow cell surrounded a square outflow cell. 16 honeycomb molded bodies were produced.

Next, the honeycomb molded body was dried with a microwave dryer, and further dried completely with a hot air dryer, and then both end faces of the honeycomb molded body were cut and adjusted to a predetermined size. Next, a film was covered so as to cover the entire inflow side end face of the honeycomb molded body, and a perforated portion was opened at the position of the film corresponding to the opening of the cell to be the outflow cell. Next, the end portion of the honeycomb molded product on the film-coated side was immersed in a slurry-like sealing material containing a ceramic raw material to fill the outflow cell on the inflow side end face with the sealing material. Further, on the outflow side end face, the inflow cell was similarly filled with a sealing material.

Next, the dried honeycomb body was degreased by heating at 400 ° C. for 5 hours, and further fired by heating at 1450 ° C. for 2 hours in an argon atmosphere to obtain a honeycomb fired body. The entire shape of the honeycomb fired body was a square columnar shape.

Next, the obtained 16 honeycomb fired bodies were joined by a joining material in a state where the side surfaces of the obtained honeycomb bodies were arranged adjacent to each other so as to face each other to prepare a honeycomb bonded body. The honeycomb bonded body was produced by joining so that a total of 16 honeycomb fired bodies, four in the vertical direction and four in the horizontal direction, were arranged on the end face thereof.

Next, the outer peripheral portion of the honeycomb joint was processed by grinding to form a circular cross section perpendicular to the extending direction of the cells of the honeycomb joint. After that, an outer peripheral coating material containing a ceramic raw material was applied to the outermost periphery of the ground honeycomb joint.

In this way, the mesh-sealed honeycomb structure of Example 1 was produced. The obtained eye-sealing honeycomb structure had a cylindrical shape having a cross-sectional diameter of 143.8 mm orthogonal to the central axis and a length of 152.4 mm in the central axis direction. The thickness of the partition wall was 0.3 mm, and the cell density was 208 cells / cm ² .

Table 1 shows the partition wall thickness [mm], a [mm], b [mm], and cell density [cell / cm ² ]. Here, a [mm] refers to the length of the range indicated by the reference numeral a in FIG. That is, a [mm] means a distance between two parallel partition walls 1 that partition the inflow cell 2a and the outflow cell 2b and face each other with one outflow cell 2b in between. Further, b [mm] means the length of the range indicated by the reference numeral b in FIG. That is, b [mm] means the distance between the two parallel partition walls 1 that partition the inflow cell 2a and the outflow cell 2b and face each other with the inflow cell 2a in between. In each of a [mm] and b [mm], the distance between the two partition walls 1 is the distance between the two partition walls 1 from the intermediate point in the thickness direction of each partition wall 1.

In addition, Table 1 shows "the diameter D ₀ [mm] of the circle inscribed in the partition wall separating the inflow cell and the outflow cell" and "the diameter D ₁ [the diameter of the circle inscribed in the intersection of the partition walls separating the inflow cells. mm] ”and“ value of D ₁ / (√2 × D ₀ ) ”. Further, Table 1 shows "the ratio of the intersections satisfying the equation (1)". Here, the “ratio of intersections satisfying the equation (1)” means “D ₁ / (√2 × D ₀ ) = 1.20 to _1. ” at the intersections of the partition walls that partition adjacent inflow cells. It is the ratio of the number of intersections satisfying the relationship of "80".

Further, Table 1 shows "the diameter D ₂ [mm] of the circle inscribed in the inflow cell and in contact with the partition wall on the intersection side".

Hereinafter, in the present embodiment, "the diameter D ₀ [mm] of the circle inscribed in the partition wall separating the inflow cell and the outflow cell" may be referred to as "the diameter D ₀ [mm] of the inscribed circle". Further, "the diameter D ₁ [mm] of the circle inscribed at the intersection of the partition walls separating the inflow cells" may be referred to as "the diameter D ₁ [mm] of the inscribed circle". Further, "the diameter D ₂ [mm] of the circle inscribed in the inflow cell and in contact with the partition wall on the intersection side" may be referred to as "the diameter D ₂ [mm] of the inscribed circle".

(Examples 2 to 12)
"Inscribed circle diameter D ₀ [mm]", "Inscribed circle diameter D ₁ [mm]", "Inscribed circle diameter D ₂ [mm]", and "Intersections satisfying equation (1)" The "ratio" was changed as shown in Table 1 or Table 2 to produce the mesh-sealed honeycomb structure of Examples 2 to 12.

(Comparative Examples 1 to 4)
"Inscribed circle diameter D ₀ [mm]", "Inscribed circle diameter D ₁ [mm]", "Inscribed circle diameter D ₂ [mm]", and "Intersections satisfying equation (1)" The "ratio" was changed as shown in Table 1 or Table 2 to produce the mesh-sealed honeycomb structures of Comparative Examples 1 to 4.

The sealing honeycomb structure of Comparative Example 1 is sealing in the same manner as in Example 1 except that D ₁ = √2 × D ₀ at the intersection of the partition walls that partition the adjacent inflow cells. A honeycomb structure was produced. That is, the “value of D ₁ / (√2 × D ₀ )” of the sealing honeycomb structure of Comparative Example 1 is 1.00.

For the sealing honeycomb structures of Examples 1 to 12 and Comparative Examples 1 to 4, "heat-resistant impact resistance", "light-off performance", "inlet opening ratio", and "pressure during PM deposition" were carried out by the following methods. We evaluated "loss". The results are shown in Tables 1 and 2.

[Heat-resistant impact resistance]
The thermal shock resistance was evaluated by a heating and vibration test. Specifically, a range of 130 mm from the outflow side end face of the produced eye-sealing honeycomb structure was gripped by MAFTEC (trade name) manufactured by Mitsubishi Plastics. Air heated by a propane burner was flowed through the eye-sealing honeycomb structure gripping the end face on the outflow side while applying vibration having a frequency of 100 Hz and an acceleration of 30 G, and the test was conducted for 100 hours. The conditions of the heated air in the heating vibration test were a flow rate of 2 Nm ³ / min and a temperature of 150 to 800 ° C. (1 cycle 20 minutes). After the heating and vibration test, it was visually confirmed whether or not the partition wall of the sealing honeycomb structure was damaged. The case where no damage was confirmed in the partition wall of the sealing honeycomb structure was evaluated as "good", the case where slight damage was confirmed was evaluated as "possible", and the case where severe damage was confirmed was evaluated as "impossible". The results are shown in Tables 1 and 2.

[Light-off performance (200 ° C arrival time [seconds])]
The light-off performance was evaluated by using a sealing honeycomb structure as a DPF, injecting combustion gas at 400 ° C into the DPF, and measuring the time required for the outflow side end of the DPF to reach 200 ° C. .. Specifically, first, a ceramic non-thermally expandable mat is wrapped around the outer periphery of the obtained eye-sealing honeycomb structure as a holding material and pushed into a stainless steel can for SUS409 to form the canning structure. And said. Further, a K-type sheath thermocouple was installed at the outflow side end of the canning structure. Then, by burning diesel fuel, a combustion gas at 400 ° C. was flowed in, the temperature of a thermocouple installed in advance was monitored, and the time [seconds] for the thermocouple to reach 200 ° C. was measured. Light oil was used as the diesel fuel. In the light-off performance evaluation, the 200 ° C. arrival time [seconds] of the sealing honeycomb structure of Comparative Example 1 was used as a reference (Base), and the evaluation was performed as follows. The case where the 200 ° C. arrival time [seconds] was +0.5 seconds or less with respect to Base was regarded as “good”. When the time to reach 200 ° C. [seconds] was more than +0.5 seconds and less than +1 second with respect to Base, it was regarded as "OK". When the time to reach 200 ° C. [seconds] was more than +1 second with respect to Base, it was regarded as "impossible".

[Entrance opening ratio]
The ratio [%] of the area occupied by the inflow cell on the inflow side end face to the cross-sectional area of the sealing honeycomb structure was measured. The ratio [%] of this area was defined as the inlet opening ratio [%] of the sealing honeycomb structure. In the evaluation of the inlet aperture ratio, the inlet aperture ratio [%] of the sealing honeycomb structure of Comparative Example 1 was used as a reference (Base), and the evaluation was performed as follows. The case where the entrance opening ratio [%] was + 1% or less with respect to Base was regarded as “good”. The case where the entrance opening ratio [%] was more than 1% and + 2% or less with respect to Base was regarded as "OK". When the entrance opening ratio [%] was more than + 2% with respect to Base, it was regarded as "impossible".

[Pressure loss during PM deposition]
Soot-containing combustion gas is passed through the sealing honeycomb structure to deposit soot on the sealing honeycomb structure, and the pressure difference between the inflow side and the outflow side when the soot deposition amount becomes 4 g / L is determined. The pressure loss during PM deposition of the sealing honeycomb structure was measured. Specifically, first, light oil was burned in an oxygen-deficient state to generate soot-generated combustion gas. Then, by adding diluted air to the combustion gas having a soot generation amount of 10 g / h, a flow rate of 2.4 Nm ³ / min, and a temperature of 200 ° C., soot-containing combustion for pressure loss evaluation during PM deposition is performed. Gas was produced. This soot-containing combustion gas is allowed to flow through the sealing honeycomb structure, and when the amount of soot deposited on the sealing honeycomb structure reaches 4 g / L, the inflow side and the outflow side of the sealing honeycomb structure The pressure was measured, and the pressure difference was taken as the pressure loss value during PM deposition of the sealing honeycomb structure. In the evaluation of the pressure loss during PM deposition, the pressure loss value of the sealing honeycomb structure of Comparative Example 1 was used as a reference (Base), and the evaluation was performed as follows. When the increase in pressure loss value was + 4% or less with respect to Base, it was regarded as "good". When the increase in the pressure loss value exceeded + 4% and was + 8% or less with respect to Base, it was regarded as “OK”. When the increase in pressure loss value exceeds + 8% with respect to Base, it is regarded as "impossible".

(result)
As shown in Tables 1 and 2, the sealing honeycomb structures of Examples 1 to 12 have "heat impact resistance", "light-off performance", "inlet opening ratio", and "pressure loss during PM deposition". In all the evaluations of "", the evaluation result was "OK" or higher. In particular, from the evaluation results of the eye-sealing honeycomb structures of Examples 1 to 12 and Comparative Example 1, "the diameter of the inscribed circle D ₁ [mm]" is "the diameter of the inscribed circle D ₀ [mm]". It was found that when it was larger than √2 times, the thermal impact resistance of the sealing honeycomb structure was improved. Further, when the value of D ₁ / (√2 × D ₀ ) is other than 1.20 to 1.80 as in Comparative Examples 2 and 3, "light-off performance" and "entrance aperture ratio" are evaluated. The result was that it was not possible. Therefore, when the value of D1 / (√2 × D ₀ ) is set to 1.20 to 1.80, “heat resistance”, “light-off performance”, “entrance aperture ratio”, and “at the time of PM deposition” It was found that all of the "pressure loss" was improved as compared with Comparative Example 1.

Further, as for the ratio of the intersections satisfying the formula (1), the heat impact resistance of the sealing honeycomb structure decreases as the ratio decreases, and when it is less than 60%, the heat impact resistance greatly decreases. I found out that

Further, when the "diameter D ₂ [mm] of the inscribed circle" is 0.20 to 0.80 mm, the "light-off performance", the "inlet aperture ratio", and the "pressure loss during PM deposition" are evaluated. Was good, but it was found that when it exceeded 0.80 mm, each evaluation deteriorated.

The sealing honeycomb structure of the present invention can be used as a filter for purifying exhaust gas. It can also be used as a catalyst carrier in which a catalyst is supported on the partition wall of the sealable honeycomb structure of the present invention.

1: Partition, 2: Cell, 2a: Inflow cell, 2b: Outflow cell, 3: Sealing part, 3a: Inflow side eye sealing part, 3b: Outflow side eye sealing part, 4: Intersection part, 6a: Inflow side end face, 6b: Outflow side end face, 7: Honeycomb segment, 8: Bonding layer, 9: Honeycomb structure, 11: Outer wall, 100: Sealed honeycomb structure, C: Crack, D ₀ , D ₁ : The diameter of the circle.

Claims (3)

It is arranged in a honeycomb structure portion having a porous partition wall that partitions a plurality of cells serving as a flow path of a fluid extending from an inflow side end face to an outflow side end face, and an opening of a predetermined inflow cell in the outflow side end face. An inflow-side eye-sealing portion and an outflow-side eye-sealing portion disposed in the opening of the residual outflow cell on the inflow-side end face are provided.
In the cross section of the honeycomb structure portion orthogonal to the extending direction of the cells, the inflow cells are arranged so as to surround the outflow cells, and the number of the inflow cells is larger than the number of the outflow cells.
It has a plurality of intersections of partition walls that partition adjacent inflow cells.
At 60% or more of the total number of intersections,
The relationship between the diameter D _{1 of} the circle inscribed in the intersection and the diameter D _{0 of} the circle inscribed in the partition wall separating the adjacent inflow cell and the outflow cell is as shown in the following equation (1). It is an eye-sealing honeycomb structure .
A mesh-sealing honeycomb structure in which the relationship between the diameter D ₁ and the diameter D ₀ is as shown in the following formula (1) only at the intersection of the partition walls that partition the adjacent inflow cells .
Equation (1): D ₁ / (√2 × D ₀ ) = 1.20 to 1.80 In the total number of the intersections, the relationship between the diameter D _{1 of} the circle inscribed in the intersection and the diameter D _{0 of} the circle inscribed in the partition partitioning the adjacent inflow cell and the outflow cell is The mesh-sealing honeycomb structure according to claim 1, which is as described in the formula (1). The mesh-sealed honeycomb structure according to claim 1 or 2, wherein the diameter D _{2 of the} circle inscribed in the inflow cell and in contact with the partition wall on the intersection side of the inflow cell is 0.25 to 0.80 mm. body.