JP5979044B2 - Honeycomb structure - Google Patents

Description

  The present invention relates to a honeycomb structure used as a catalyst carrier for purifying exhaust gas from an internal combustion engine such as an automobile.

As a catalyst carrier for purifying exhaust gas of an internal combustion engine such as an automobile, for example, a honeycomb structure including partition walls provided in a lattice shape and a plurality of cells surrounded by the partition walls is known. Yes. The honeycomb structure is used by being installed in an exhaust pipe serving as an exhaust gas passage. Then, the exhaust gas is purified by the catalytic reaction of a catalyst such as a noble metal supported on the honeycomb structure by circulating the high temperature exhaust gas through the honeycomb structure.
In recent years, since exhaust gas regulations for automobiles and the like have become stricter, higher exhaust gas purification performance is required for honeycomb structures.

  For example, in Patent Document 1, in order to make the exhaust gas flowability uniform between the inner side and the outer side, the cell density in the outer peripheral part, which has lower exhaust gas flowability than the central part, is set lower than the central part, and the exhaust gas in the outer peripheral part A honeycomb structure having improved flowability is disclosed. This honeycomb structure is formed by separately molding a central portion and a peripheral portion that can be divided into a plurality of parts, and joining them together. Concentration of stress (hereinafter referred to as “canning stress” as appropriate) that occurs when appropriate. Further, since the cell density in the central portion is about twice as high as that in the outer peripheral portion, the cell density in the outer peripheral portion is lowered, which causes a problem of exhaust gas blowout in the outer peripheral portion.

  Further, in Patent Document 2, the cell density at the outer peripheral portion is made lower than that at the central portion on the exhaust gas inlet side and the outlet side, and the cells on the outer peripheral portion on the exhaust gas inlet side and outlet side are retained by the retainer that supports the honeycomb structure. Has disclosed a honeycomb structure that is prevented from being blocked by. In this honeycomb structure, the cell density at the central part on the exhaust gas inlet side is the cell density at the outer peripheral part so that the cells are regularly arranged, that is, incompletely shaped cells with a small opening area are not formed. 4 to 16 times as large as. However, since the cell density in the central portion and the outer peripheral portion is the same at the axially intermediate position of the honeycomb structure, the exhaust gas is likely to blow through in the central portion, and the exhaust gas flow inside and outside cannot be sufficiently uniformed. .

  Therefore, in Patent Document 3, as a method for uniformizing the exhaust gas flowability between the central portion and the outer peripheral portion of the honeycomb structure, a boundary wall is provided between the central portion and the outer peripheral portion, and the cell density in the outer peripheral portion is centered. A honeycomb structure having a lower cell density difference and a small cell density difference between the central portion and the outer peripheral portion (for example, the cell density in the central portion is less than twice the cell density in the outer peripheral portion) It is disclosed. According to this, the exhaust gas flowability in the outer peripheral portion can be appropriately increased, the exhaust gas blow-off in the outer peripheral portion can be suppressed, and the internal and external exhaust gas flow properties can be sufficiently uniformed. In addition, early activation of a catalyst such as a noble metal supported on the honeycomb structure can be achieved, and exhaust gas purification performance can be improved.

Japanese Utility Model Publication No. 62-187628 JP 60-225651 A JP 2008-18370 A

However, in the honeycomb structure of Patent Document 3, the strength at the boundary between the central portion and the outer peripheral portion becomes a problem.
That is, a boundary wall that separates the center portion and the outer peripheral portion is provided, but canning stress or the like is concentrated near the boundary wall. Therefore, it is necessary to take measures such as thickening the boundary wall and the partition wall in contact with the boundary wall to ensure strength.

However, when the boundary wall and the partition wall in contact with the boundary wall are thickened, the heat capacity increases due to the increase in the mass of the boundary portion between the central portion and the outer peripheral portion, which may make it difficult to achieve early activation of the catalyst. is there.
In addition, incompletely shaped cells (incompletely shaped cells surrounded by the partition walls and the boundary walls, not cells surrounded only by the partition walls; hereinafter referred to as incomplete cells) are formed around the boundary walls. However, when the boundary wall and the partition wall in contact with the boundary wall are thickened, clogging of the catalyst tends to occur in the incomplete cell, and there is a possibility that the amount of the catalyst supported varies.

  The present invention has been made in view of such a background, and while ensuring the exhaust gas purification performance by uniformizing the exhaust gas flowability inside and outside, the boundary portion between the central portion and the outer peripheral portion can be obtained with a simple structure. An object of the present invention is to provide a honeycomb structure capable of improving the strength and sufficiently ensuring the entire strength.

One aspect of the present invention is a partition wall provided in a honeycomb shape,
A plurality of cells surrounded by the partition,
In a cross section orthogonal to the axial direction, it has a central portion and an outer peripheral portion covering the outside of the central portion,
When the cell density at the center is A1 and the cell density at the outer periphery is A2, the cell density ratio A1 / A2 satisfies the relationship 1 <A1 / A2 <1.85,
Between the central part and the outer peripheral part, a polygonal boundary wall separating both is provided,
The partition wall of the central portion has a central partition wall side portion forming each side of the polygonal cell, and a central intersection portion where the central partition wall side portions meet,
The partition wall of the outer peripheral portion has an outer peripheral partition wall side portion constituting each side of the polygonal cell, and an outer peripheral intersection portion where the outer peripheral partition wall side portions meet,
The boundary wall has a boundary intersection portion where the central intersection portion of the central portion and the outer peripheral intersection portion of the outer peripheral portion coincide and overlap,
The boundary intersections are located in each of the sides of the boundary wall at a constant interval (claim 1).

  The honeycomb structure has a central portion and an outer peripheral portion covering the outside of the central portion in a cross section orthogonal to the axial direction. The cell density ratio A1 / A2 between the central portion and the outer peripheral portion satisfies the relationship 1 <A1 / A2 <1.85. By setting the cell density ratio A1 / A2 within the above specified range, the exhaust gas flowability of the outer peripheral portion having a lower exhaust gas flowability than that of the central portion can be appropriately increased, and the exhaust gas blow-through in the outer peripheral portion can be achieved. Can be suppressed. Thereby, it is possible to ensure sufficient early activity and exhaust gas purification performance of the catalyst supported on the honeycomb structure while achieving uniform exhaust gas flow inside and outside.

  In the honeycomb structure, a boundary wall is provided between the central portion and the outer peripheral portion to separate them. The central partition has a central intersection where the central partition sides composing each side of the cell meet, and the outer peripheral partition has an outer periphery where the peripheral partition sides composing each side of the cell merge Has an intersection. The boundary wall has a boundary intersection portion where the central intersection portion of the central portion and the outer peripheral intersection portion of the outer peripheral portion coincide with each other, and the boundary intersection portion has a constant interval on each side of the boundary wall. Is arranged in.

  Therefore, the boundary intersection portion is a location where the central partition wall side portion joins from the central portion side and the outer peripheral partition wall side portion joins from the outer peripheral portion side. By adopting a structure in which such locations are provided at regular intervals on each side of the boundary wall, the stress is applied to the central partition without applying excessive stress to the boundary wall against the canning stress applied from the outer periphery. Can communicate. Thereby, the strength of the boundary portion between the central portion and the outer peripheral portion can be improved with a simple structure without particularly increasing the thickness of the boundary wall and the partition wall contacting the boundary wall as in the prior art. And sufficient strength of the whole honeycomb structure can be secured.

  In this way, the exhaust gas flowability inside and outside is made uniform to ensure sufficient exhaust gas purification performance, while improving the strength of the boundary between the central part and the outer peripheral part with a simple structure, and sufficient overall strength. A honeycomb structure that can be secured can be provided.

3 is a perspective view showing a honeycomb structure in Example 1. FIG. 2 is a cross-sectional view showing a cross section orthogonal to the axial direction of a honeycomb structure in Example 1. FIG. FIG. 3 is an enlarged cross-sectional view illustrating a part of a cross section orthogonal to an axial direction of a honeycomb structure in Example 1. FIG. 3 is an enlarged cross-sectional view illustrating a part of a cross section orthogonal to an axial direction of a honeycomb structure in Example 1. FIG. 3 is an enlarged cross-sectional view illustrating a part of a cross section orthogonal to an axial direction of a honeycomb structure in Example 1. Sectional drawing which expands and shows a part of cross section orthogonal to the axial direction of a honeycomb structure in Example 2. FIG. Sectional drawing which expands and shows a part of cross section orthogonal to the axial direction of a honeycomb structure in Example 2. FIG. Sectional drawing which expands and shows a part of cross section orthogonal to the axial direction of a honeycomb structure in Example 2. FIG. Sectional drawing which expands and shows a part of cross section orthogonal to the axial direction of a honeycomb structure in Example 2. FIG. Sectional drawing which expands and shows a part of cross section orthogonal to the axial direction of a honeycomb structure in Example 2. FIG. Sectional drawing which expands and shows a part of cross section orthogonal to the axial direction of a honeycomb structure in Example 2. FIG. Sectional drawing which expands and shows a part of cross section orthogonal to the axial direction of a honeycomb structure in Example 2. FIG. Sectional drawing which expands and shows a part of cross section orthogonal to the axial direction of a honeycomb structure in Example 2. FIG. Sectional drawing which expands and shows a part of cross section orthogonal to the axial direction of a honeycomb structure in Example 2. FIG. Sectional drawing which expands and shows a part of cross section orthogonal to the axial direction of a honeycomb structure in Example 2. FIG. Sectional drawing which expands and shows a part of cross section orthogonal to the axial direction of a honeycomb structure in Example 2. FIG. FIG. 4 is a cross-sectional view showing a cross section orthogonal to an axial direction of a honeycomb structure in Example 3. Sectional drawing which expands and shows a part of cross section orthogonal to the axial direction of a honeycomb structure in Example 3. FIG. The graph which shows the relationship between cell density ratio A1 / A2 and emission in Example 4. FIG. Explanatory drawing which shows the cell pitch of the cell of a center part and an outer peripheral part.

  In the honeycomb structure, the boundary intersections are arranged at regular intervals on each side of the boundary wall. The distance (distance) between the boundary intersections on each side of the boundary wall may be set in consideration of the strength necessary for the honeycomb structure when canning the honeycomb structure. For example, the cell pitch of the outer peripheral cell With reference to (P), it is possible to secure the canning strength of the minimum press-fitting method within 6 cells (within 6P).

The central part and the outer peripheral part may be polygons having the same cell shape.
In this case, it is possible to easily realize a configuration in which the central intersection portion of the central portion and the outer peripheral intersection portion of the outer peripheral portion are arranged so as to overlap on the boundary wall and the boundary intersection portion is provided on the boundary wall.

Further, in the central portion and the outer peripheral portion, the shape of the cell may be a quadrangle, and the shape of the boundary wall may be an octagon (Claim 3).
Further, in the central portion and the outer peripheral portion, the shape of the cell may be a hexagon, and the shape of the boundary wall may be a hexagon.
In any case, it is possible to easily realize a configuration in which the central intersection portion of the central portion and the outer peripheral intersection portion of the outer peripheral portion are arranged so as to overlap on the boundary wall and the boundary intersection portion is provided on the boundary wall.

In addition, the shape of the cell in the central portion and the outer peripheral portion is not limited to a quadrangle or a hexagon, and various polygons can be adopted. Also,
Further, the shapes of the cells in the central portion and the outer peripheral portion may be the same polygon or may be different from each other.
The shape of the boundary wall is not limited to a hexagon or an octagon, and various polygons can be adopted.

  In addition, the direction and size of the cells in the central part and the outer peripheral part (for example, the cell pitch) are such that the central intersection part of the central part and the outer peripheral intersection part of the outer peripheral part coincide and overlap on the boundary wall. That is, they may be adjusted to each other so that the boundary intersection can be provided on the boundary wall. In other words, by adjusting the direction and size of the cells in the central part and the outer peripheral part, the boundary intersection part can be provided at an appropriate position on the boundary wall.

For example, when the cell shape in the center and the outer periphery is both square, the cell pitch B1 in the center and the cell pitch in the outer periphery in a range where the cell density ratio A1 / A2 satisfies the relationship 1 <A1 / A2 <1.85. A cell pitch ratio B2 / B1 with B2 is set. At this time, the value of the cell pitch ratio B2 / B1 is a value that satisfies {(K ² + L ² ) ⁻¹ / (M ² + N ² ) ⁻¹ }> 1 (where K, L, M, and N are all integers). By selecting from the above, the boundary intersection portion can be appropriately configured on the boundary wall.

  In addition, the cell pitch of the cell of a center part and an outer peripheral part means the distance between adjacent cells. That is, for example, as shown in FIG. 20A, when the shape of the cell 4 surrounded by the partition walls 3 is a square (square), the cell pitch is the distance P1 in the figure. As shown in FIG. 20B, when the shape of the cell 4 surrounded by the partition walls 3 is a hexagon, the cell pitch is the distance P2 in FIG.

Example 1
Examples of the honeycomb structure will be described with reference to the drawings.
As shown in FIGS. 1 to 3, the honeycomb structure 1 of the present example includes partition walls 3 provided in a honeycomb shape and a plurality of cells 4 surrounded by the partition walls 3. In addition, the honeycomb structure 1 has a central portion 21 and an outer peripheral portion 22 that covers the outside of the central portion 21 in a cross section orthogonal to the axial direction X. When the cell density of the central portion 21 is A1 and the cell density of the outer peripheral portion 22 is A2, the cell density ratio A1 / A2 satisfies the relationship 1 <A1 / A2 <1.85. Between the center part 21 and the outer peripheral part 22, the polygonal boundary wall 23 which separates both is provided.

As shown in the figure, the partition wall 3 of the center portion 21 has a center partition wall side portion 311 constituting each side of the polygonal cell 4 and a center intersection point portion 312 where the center partition wall side portions 311 meet. The partition 3 of the outer peripheral part 22 has the outer peripheral partition part side 321 which comprises each edge | side of the polygonal cell 4, and the outer periphery intersection part 322 where outer peripheral partition side parts 321 merge.
The boundary wall 23 has a boundary intersection portion 24 in which the central intersection portion 312 of the central portion 21 and the outer peripheral intersection portion 322 of the outer peripheral portion 22 coincide and overlap. The boundary intersection parts 24 are arranged at regular intervals on each side of the boundary wall 23.
This will be described in detail below.

As shown in FIG. 1, the honeycomb structure 11 is made of cordierite and is used as a catalyst carrier for exhaust gas purification.
The honeycomb structure 1 includes partition walls 3 provided in a quadrangular lattice shape, a plurality of cells 4 formed so as to be surrounded by the partition walls 3, and a cylindrical outer peripheral wall 5 covering an outer peripheral side surface. It is formed integrally.

As shown in FIG. 2, the honeycomb structure 1 includes a central portion 21 and an outer peripheral portion 22 that covers the outside of the central portion 21 in a cross section orthogonal to the axial direction X (FIG. 1). An octagonal boundary wall 23 is provided between the central portion 21 and the outer peripheral portion 22 to separate them. The boundary wall 23 has eight boundary side portions (first boundary side portion 231 to eighth boundary side portion 238) constituting each side. The average thickness of the boundary wall 23 is about 0.09 mm.
2 (similarly in FIG. 1), the partition walls 3 and the cells 4 are illustrated in a simplified manner. For example, the orientation and size of the cells 4 in the central portion 21 and the outer peripheral portion 22 are not accurate.

As shown in FIG. 3, the center part 21 and the outer peripheral part 22 are both square (square) in the shape of the cells 4, and the directions of the cells 4 are different from each other. Further, the cell density of the central portion 21 is higher than the cell density of the outer peripheral portion 22. In this example, the cell density A1 of the central portion 21 is 77.5 cells / cm ² (500 cells / square inch), the cell density A2 of the outer peripheral portion 22 is 62 cells / cm ² (400 cells / square inch), and the cell density. The ratio A1 / A2 is 1.25. Further, the average cell pitch B1 of the central portion 21 is about 1.14 mm, the average cell pitch B2 of the outer peripheral portion 22 is 1.27 mm, and the cell pitch ratio B2 / B1 is about 1.12.

  As shown in the figure, the partition wall 3 of the center portion 21 has a plurality of center partition wall side portions 311 constituting each side of the quadrangular cell 4. Each cell 4 is formed so as to be surrounded by four central partition walls 311. Further, the partition wall 3 of the central portion 21 has a plurality of central intersection portions 312 where the central partition wall side portions 311 meet. The central intersection point 312 is formed by joining four central partition wall side portions 311. In addition, the average thickness of the partition 3 (center partition side part 311) of the center part 21 is about 0.08 mm.

  As shown in the figure, the partition wall 3 of the outer peripheral portion 22 has a plurality of outer peripheral partition wall side portions 321 constituting each side of the quadrangular cell 4. Each cell 4 is formed so as to be surrounded by four outer peripheral partition wall sides 321. Further, the partition wall 3 of the outer peripheral portion 22 has a plurality of central intersection portions 312 where the peripheral partition wall side portions 321 meet. The outer peripheral intersection 322 is formed by joining four outer peripheral partition wall sides 321. In addition, the average thickness of the partition 3 (outer peripheral partition side 321) of the outer peripheral portion 22 is about 0.09 mm. Further, the thickness of the partition wall 3 in the central portion 21 and the outer peripheral portion 22 is set so that the cell density in the outer peripheral portion 22 is lower than the cell density in the central portion 21. It is better to make the average thickness of the partition 3 of the outer peripheral part 22 slightly thicker than the average thickness of the partition 3 of the central part 21 from the relationship of the water absorption balance with the outer peripheral part 22.

  As shown in the figure, the boundary wall 23 has a plurality of boundary intersection portions 24 in which the central intersection portion 312 of the central portion 21 and the outer peripheral intersection portion 322 of the outer peripheral portion 22 overlap and coincide. In the same figure, in order to clearly show the boundary intersection 24 on the boundary wall 23, the locations where the boundary intersection 24 is provided are indicated by circles. At the boundary intersection 24, the central partition wall side 311 joins from the central portion 21 side, and the outer peripheral partition wall side 321 joins from the outer peripheral portion 22 side. Further, the boundary intersection parts 24 are arranged at regular intervals on each side of the boundary wall 23 (first boundary side part 231 to eighth boundary side part 238).

Specifically, in the first boundary side portion 231 of the boundary wall 23, a plurality of boundary intersection portions 24 are arranged at a constant interval C1. The same applies to the third boundary side 233, the fifth boundary side 235, and the seventh boundary side 237 (FIG. 2).
Moreover, in the 2nd boundary edge part 232 of the boundary wall 23, the some boundary intersection part 24 is arrange | positioned by the fixed space | interval C2. The same applies to the fourth boundary side 234, the sixth boundary side 236, and the eighth boundary side 238 (FIG. 2). The distance C2 is shorter than the distance C1.

Next, a method for manufacturing the honeycomb structure 1 of the present example will be described.
In this example, when manufacturing the honeycomb structure 1, the manufacturing process itself can adopt the same process as the conventional process. Specifically, first, the cordierite raw material constituting the honeycomb structure 1 is extruded into a honeycomb shape as a formed body. Next, the molded body is cut into a predetermined length, dried, and fired. Thereby, the honeycomb structure 1 is obtained.
In addition, as a metal mold | die at the time of performing extrusion molding, the metal mold | die (illustration omitted) for which the slit groove | channel of the shape corresponding to the shape of the partition 3 was provided can be used. The slit groove can be formed by a method such as electric discharge machining or laser machining.

Next, the function and effect of this example will be described.
The honeycomb structure 1 of the present example has a central portion 21 and an outer peripheral portion 22 that covers the outside of the central portion 21 in a cross section orthogonal to the axial direction X. The cell density ratio A1 / A2 between the central portion 21 and the outer peripheral portion 22 satisfies the relationship 1 <A1 / A2 <1.85. By setting the cell density ratio A1 / A2 within the specific range, the exhaust gas flowability of the outer peripheral portion 22 having a lower exhaust gas flowability than that of the central portion 21 can be appropriately increased, and Blowing of exhaust gas can be suppressed. Thereby, it is possible to ensure sufficient early activity and exhaust gas purification performance of the catalyst supported on the honeycomb structure 1 while achieving uniform exhaust gas flowability inside and outside.

  Further, in the honeycomb structure 1, a boundary wall 23 is provided between the central portion 21 and the outer peripheral portion 22 to separate them. In addition, the partition wall 3 of the central portion 21 has a central intersection portion 312 where the central partition wall side portions 311 composing each side of the cell 4 meet, and the partition wall 3 of the outer peripheral portion 22 configures each side of the cell 4. The outer peripheral partition wall side portions 321 to be joined together have an outer peripheral intersection portion 322 where the outer peripheral partition wall side portions 321 meet. The boundary wall 23 has a boundary intersection portion 24 in which the central intersection portion 312 of the central portion 21 and the outer peripheral intersection portion 322 of the outer peripheral portion 22 coincide with each other and overlap each other. They are arranged at regular intervals on each of the sides.

  Therefore, the boundary intersection point 24 is a place where the central partition wall side 311 joins from the central part 21 side and the outer peripheral partition wall side 321 joins from the outer peripheral part 22 side. By adopting a structure in which such portions are provided at regular intervals on each side of the boundary wall 23, the partition wall of the central portion 21 can be applied to the canning stress applied from the outer peripheral portion 23 without applying excessive stress to the boundary wall 23. The stress can be transmitted to 3. Thereby, the strength of the boundary portion between the central portion 21 and the outer peripheral portion 22 can be improved with a simple structure without particularly increasing the thickness of the boundary wall 23 and the partition wall 3 in contact with the boundary wall 23 as in the prior art. Can do. And the intensity | strength of the whole honeycomb structure 1 is fully securable.

  As described above, according to this example, the strength of the boundary portion between the central portion 21 and the outer peripheral portion 22 is improved with a simple structure while ensuring uniform exhaust gas flowability inside and outside and sufficiently ensuring the exhaust gas purification performance. Thus, it is possible to provide the honeycomb structure 1 that can sufficiently ensure the overall strength.

  In this example, as shown in FIG. 2, the shape of the cross section perpendicular to the axial direction X of the honeycomb structure 1 is circular, but for example, as shown in FIG. 4, the boundary intersection 24 of the boundary wall 23. It can also be configured such that the external dimension D on the second boundary side portion 232 side where the interval between them is small is larger than the other direction. In addition, the E point of the figure is the center of a cross section. In this case, the strength margin of the product can be increased when the product of the honeycomb structure 1 carrying the catalyst is inserted into the metal exhaust pipe through the heat insulating ceramic mat and used. In other words, the product outer shape corresponding to the side where the interval between the boundary intersection parts 24 is narrow is made larger than the product outer shape where the distance between the boundary intersection parts 24 is wide so that the entire product can withstand high stress. Become.

This is because the boundary intersection part 24 becomes a main part when transmitting stress between the outer peripheral part 22 and the central part 21, and other connecting parts sandwiching the boundary wall 23 are high in shape. Whereas some deformation occurs without rigidity, the boundary intersection 24 transmits stress without causing significant distortion. Therefore, the greater the number of boundary intersection points 24, the smaller the stress burden per location, and as a result, it can withstand high stress.
The honeycomb structure 1 in FIG. 4 is the same as the honeycomb structure 1 in FIG. 8 in Example 2 described later.

  Moreover, in this example, as shown in FIG. 3, the shape of the cell 4 of the center part 21 and the outer peripheral part 22 is both square, but for example, as shown in FIG. The shape of the cell 4 of the square and the outer peripheral portion 22 may be a rectangle.

(Example 2)
This example is an example in which the cell density and the like of the center portion 21 and the outer peripheral portion 22 are changed in the honeycomb structure 1 as shown in FIGS.

In the example shown in FIG. 6, the cell density A1 of the central portion 21 is 99.2 cells / cm ² (640 cells / square inch), and the cell density A2 of the outer peripheral portion 22 is 62 cells / cm ² (400 cells / square inch). The cell density ratio A1 / A2 is 1.6. Further, the average cell pitch B1 of the central portion 21 is about 1.00 mm, the average cell pitch B2 of the outer peripheral portion 22 is 1.27 mm, and the cell pitch ratio (B2 / B1) is about 1.26.

In the example shown in FIG. 7, the cell density A1 of the central portion 21 is 85.9 cells / cm ² (about 554 cells / square inch), and the cell density A2 of the outer peripheral portion 22 is 62 cells / cm ² (400 cells / square inch). ), And the cell density ratio A1 / A2 is about 1.39. Further, the average cell pitch B1 of the central portion 21 is about 1.08 mm, the average cell pitch B2 of the outer peripheral portion 22 is 1.27 mm, and the cell pitch ratio B2 / B1 is about 1.18.

In the example shown in FIG. 8, the cell density A1 of the central portion 21 is 62 cells / cm ² (400 cells / square inch), and the cell density A2 of the outer peripheral portion 22 is 38.2 cells / cm ² (about 246 cells / square inch). ), And the cell density ratio A1 / A2 is about 1.62. Further, the average cell pitch B1 of the central portion 21 is 1.27 mm, the average cell pitch B2 of the outer peripheral portion 22 is about 1.62 mm, and the cell pitch ratio B2 / B1 is about 1.27.

In the example shown in FIG. 9, the cell density A1 of the central portion 21 is 62 cells / cm ² (400 cells / square inch, and the cell density A2 of the outer peripheral portion 22 is 47.7 cells / cm ² (about 308 cells / square inch). The cell density ratio A1 / A2 is about 1.30, the average cell pitch B1 of the central portion 21 is 1.27 mm, the average cell pitch B2 of the outer peripheral portion 22 is about 1.45 mm, and the cell pitch ratio B2 / B1 is about 1. .14.

In the example shown in FIG. 10, the cell density A1 of the central portion 21 is 62 cells / cm ² (400 cells / square inch), and the cell density A2 of the outer peripheral portion 22 is 36.5 cells / cm ² (about 235 cells / square inch). ), And the cell density ratio A1 / A2 is about 1.70. Further, the average cell pitch B1 of the central portion 21 is 1.27 mm, the average cell pitch B2 of the outer peripheral portion 22 is about 1.42 mm, and the cell pitch ratio B2 / B1 is about 1.30.

In the example shown in FIG. 11, the cell density A1 of the central portion 21 is 62 cells / cm ² (400 cells / square inch), and the cell density A2 of the outer peripheral portion 22 is 40.3 cells / cm ² (260 cells / square inch). The cell density ratio A1 / A2 is about 1.54. Further, the average cell pitch B1 of the central portion 21 is 1.27 mm, the average cell pitch B2 of the outer peripheral portion 22 is about 1.42 mm, and the cell pitch ratio B2 / B1 is about 1.24.

In the example shown in FIG. 12, the cell density A1 of the central portion 21 is 182.4 cells / cm ² (about 1177 cells / square inch), and the cell density (A2) of the outer peripheral portion 22 is 139.5 cells / cm ² (900 Cell / square inch), and the cell density ratio A1 / A2 is about 1.31. Further, the average cell pitch B1 of the central portion 21 is about 0.74 mm, the average cell pitch B2 of the outer peripheral portion 22 is about 0.85 mm, and the cell pitch ratio B2 / B1 is about 1.14.

In the example shown in FIG. 13, the cell density A1 of the central portion 21 is 111.6 cells / cm ² (about 720 cells / square inch), and the cell density A2 of the outer peripheral portion 22 is 62 cells / cm ² (400 cells / square inch). ), And the cell density ratio A1 / A2 is about 1.80. Further, the average cell pitch B1 of the central portion 21 is about 0.95 mm, the average cell pitch B2 of the outer peripheral portion 22 is about 1.27 mm, and the cell pitch ratio B2 / B1 is about 1.34.

In the example shown in FIG. 14, the cell density A1 of the central portion 21 is 109.4 cells / cm ² (about 706 cells / square inch), and the cell density A2 of the outer peripheral portion 22 is 93 cells / cm ² (600 cells / square inch). ), And the cell density ratio A1 / A2 is about 1.18. Further, the average cell pitch B1 of the central portion 21 is about 0.96 mm, the average cell pitch B2 of the outer peripheral portion 22 is about 1.04 mm, and the cell pitch ratio B2 / B1 is about 1.08.

In the example shown in FIG. 15, the cell density A1 of the central portion 21 is 136.8 cells / cm ² (about 882 cells / square inch), and the cell density A2 of the outer peripheral portion 22 is 93 cells / cm ² (600 cells / square inch). ), And the cell density ratio A1 / A2 is about 1.47. The average cell pitch B1 of the central portion 21 is about 0.86 mm, the average cell pitch B2 of the outer peripheral portion 22 is about 1.04 mm, and the cell pitch ratio B2 / B1 is about 1.21.

In the example shown in FIG. 16, the cell density A1 of the central portion 21 is 86.1 cells / cm ² (about 556 cells / square inch), and the cell density A2 of the outer peripheral portion 22 is 62 cells / cm ² (400 cells / square inch). ), And the cell density ratio A1 / A2 is about 1.39. Further, the average cell pitch B1 of the central portion 21 is about 1.08 mm, the average cell pitch B2 of the outer peripheral portion 22 is 1.27 mm, and the cell pitch ratio B2 / B1 is about 1.18.

In any of the examples shown in FIGS. 6 to 16, the central portion 21 and the outer peripheral portion so that the central intersection portion 312 of the central portion 21 and the outer peripheral intersection portion 322 of the outer peripheral portion 22 coincide and overlap on the boundary wall 23. The orientations of the 22 cells 4 are adjusted to each other.
Other basic configurations are the same as those in the first embodiment. Moreover, about the structure similar to Example 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

Next, the function and effect of this example will be described.
In any of the examples shown in FIGS. 6 to 16, similarly to the first embodiment, the boundary intersections 24 are provided at regular intervals on each side of the boundary wall 23, so that the center portion 21 can be formed with a simple structure. The strength of the boundary portion with the outer peripheral portion 22 can be improved, and the strength of the entire honeycomb structure 1 can be sufficiently secured.
Other basic functions and effects are the same as those of the first embodiment.

(Example 3)
In this example, as shown in FIGS. 17 and 18, in the honeycomb structure 1, the shape of the cells 4 in the center portion 21 and the outer peripheral portion 22, the shape of the boundary wall 23, and the like are changed.
As shown in FIG. 17, in the honeycomb structure 1, a hexagonal boundary wall 23 is provided between the center portion 21 and the outer peripheral portion 22 to separate them. The boundary wall 23 has six boundary side portions (first boundary side portion 231 to sixth boundary side portion 236) constituting each side. The average thickness of the boundary wall 23 is about 0.095 mm.

As shown in FIG. 18, the center portion 21 and the outer peripheral portion 22 are both hexagonal in the shape of the cells 4 and the directions of the cells 4 are different from each other. Further, the cell density of the central portion 21 is higher than the cell density of the outer peripheral portion 22. In this example, the cell density A1 of the central portion 21 is 106.9 cells / cm ² (about 690 cells / square inch), and the cell density A2 of the outer peripheral portion 22 is 80.2 cells / cm ² (about 517 cells / square inch). ), And the cell density ratio A1 / A2 is about 1.33. Further, the average cell pitch B1 of the central portion 21 is about 1.04 mm, the average cell pitch B2 of the outer peripheral portion 22 is 1.2 mm, and the cell pitch ratio B2 / B1 is about 1.15.

  As shown in the figure, the partition wall 3 of the center portion 21 has a plurality of center partition wall side portions 311 constituting each side of the hexagonal cell 4. Each cell 4 is formed so as to be surrounded by six central partition walls 311. The center intersection point 312 is formed by the joining of the six central partition side portions 311. In addition, the average thickness of the partition 3 (center partition side part 311) of the center part 21 is about 0.085 mm.

  As shown in the figure, the partition wall 3 of the outer peripheral portion 22 has a plurality of outer peripheral partition wall side portions 321 constituting each side of the hexagonal cell 4. Each cell 4 is formed by being surrounded by six outer peripheral partition wall sides 321. Moreover, the outer periphery intersection part 322 is formed when the six outer periphery partition side parts 321 merge. In addition, the average thickness of the partition 3 (outer peripheral partition side 321) of the outer peripheral portion 22 is about 0.095 mm.

  As shown in the figure, the boundary wall 23 has a plurality of boundary intersection portions 24. At the boundary intersection 24, the central partition wall side 311 joins from the central portion 21 side, and the outer peripheral partition wall side 321 joins from the outer peripheral portion 22 side. The boundary intersections 24 are arranged at regular intervals on each side of the boundary wall 23 (first boundary side 231 to sixth boundary side 236).

  Specifically, in the first boundary side portion 231 of the boundary wall 23, there are two boundary intersection portions 24 (24a, 24b), and the two boundary intersection portions 24a, 24b are fixed in a state where they are shifted from each other. It arrange | positions at the space | interval C3. The same applies to the third boundary side 233 and the fifth boundary side 235 (FIG. 17).

In addition, in the second boundary side portion 232 of the boundary wall 23, there are two boundary intersection portions 24 (24c, 24d), and the two boundary intersection portions 24c, 24d are displaced from each other by a certain distance C4. Is arranged in. The same applies to the fourth boundary side 234 and the sixth boundary side 236 (FIG. 17). The interval C3 and the interval C4 are the same distance.
Other basic configurations are the same as those in the first embodiment. Moreover, about the structure similar to Example 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

Next, the function and effect of this example will be described.
Also in the case of this example, similarly to the first embodiment, by providing the boundary intersections 24 at regular intervals on each side of the boundary wall 23, the boundary portion between the central portion 21 and the outer peripheral portion 22 can be formed with a simple structure. The strength can be improved, and the strength of the entire honeycomb structure 1 can be sufficiently secured.
Other basic functions and effects are the same as those of the first embodiment.

Example 4
In this example, the exhaust gas purification performance when the cell density ratio A1 / A2 of the honeycomb structure is changed is evaluated.
In this example, a plurality of honeycomb structures having different cell density ratios A1 / A2 between the cell density A1 at the center and the cell density A2 at the outer periphery were prepared, and the exhaust gas purification performance was evaluated. The basic structure of the prepared honeycomb structure is the same as that of the first embodiment described above.

  The evaluation of exhaust gas purification performance is performed by installing a honeycomb structure carrying a catalyst in the exhaust pipe of an engine and operating the engine under predetermined conditions (in this example, the amount of emissions of hydrocarbons (HC)). Amount) was measured. In this example, the emission amount when the cell density ratio A1 / A2 = 1 is used as the reference (= 1).

FIG. 19 shows the evaluation results of the exhaust gas purification performance. The figure shows the relationship between the cell density ratio A1 / A2 and emissions. In the graph of FIG. 8, the degree of smoothing of the exhaust gas flow at the central portion and the outer peripheral portion is estimated based on the measured values.
As can be seen from the figure, when the cell density ratio A1 / A2 is larger than 1 and smaller than 1.85, the emission is smaller than 1. However, when the cell density ratio A1 / A2 is 1.85 or more, the emission is larger than 1. That is, when the cell density ratio A1 / A2 satisfies the relationship 1 <A1 / A2 <1.85, emissions can be reduced and exhaust gas purification performance can be improved.

  From the above results, in the honeycomb structure, the cell density ratio A1 / A2 between the cell density A1 in the central portion and the cell density A2 in the outer peripheral portion satisfies the relationship of 1 <A1 / A2 <1.85. It was found that exhaust gas purification performance can be sufficiently ensured while achieving uniform exhaust gas flowability inside and outside.

DESCRIPTION OF SYMBOLS 1 Honeycomb structure 21 Center part 22 Peripheral part 23 Boundary wall 24 Boundary intersection part 3 Partition 311 Center partition side part 312 Center intersection part 321 Perimeter partition side part 322 Perimeter intersection part 4 Cell X axial direction

Claims (4)

Partition walls (3) provided in a honeycomb shape;
A plurality of cells (4) formed surrounded by the partition wall (3),
In a cross section orthogonal to the axial direction (X), it has a central portion (21) and an outer peripheral portion (22) covering the outside of the central portion (21),
When the cell density of the central part (21) is A1 and the cell density of the outer peripheral part (22) is A2, the cell density ratio A1 / A2 satisfies the relationship 1 <A1 / A2 <1.85,
Between the central part (21) and the outer peripheral part (22), a polygonal boundary wall (23) separating both is provided,
The partition wall (3) of the central part (21) is a center where the central partition wall side part (311) constituting each side of the polygonal cell (4) and the central partition wall side part (311) merge. An intersection (312),
The partition wall (3) of the outer peripheral part (22) is an outer periphery where the peripheral partition wall side part (321) constituting each side of the polygonal cell (4) and the peripheral partition wall side part (321) merge. An intersection (322),
The boundary wall (23) has a boundary intersection portion (24) where the central intersection portion (312) of the central portion (21) and the outer peripheral intersection portion (322) of the outer peripheral portion (22) coincide and overlap. Have
The honeycomb structure (1), wherein the boundary intersections (24) are arranged at regular intervals on each side of the boundary wall (23).   The honeycomb structure (1) according to claim 1, wherein the central portion (21) and the outer peripheral portion (22) are polygons having the same shape of the cells (4). Body (1).   The honeycomb structure (1) according to claim 2, wherein the center portion (21) and the outer peripheral portion (22) each have a quadrangular shape of the cell (4) and a shape of the boundary wall (23). Is an octagonal honeycomb structure (1).   The honeycomb structure (1) according to claim 2, wherein the center portion (21) and the outer peripheral portion (22) are both hexagonal in shape of the cell (4), and the boundary wall (23). A honeycomb structure (1) characterized in that the shape is a hexagon.

Images