JP6485162B2 - Exhaust gas purification filter - Google Patents

Description

  The present invention relates to an exhaust gas purification filter that is used, for example, to remove particulate matter in exhaust gas.

  For example, it is known that particulate matter (particulate matter; PM) such as carbon fine particles is discharged from a diesel engine. Since such PM causes air pollution, there are regulatory values for the amount of emissions in each country. Therefore, the diesel engine vehicle is provided with an exhaust gas purification filter for collecting PM. Specifically, a filter having a honeycomb structure having a large number of cells surrounded by partition walls and a plug portion that seals either one end of the cells is used. PM is accumulated in the exhaust gas purification filter and then burned and removed by heating.

  On the other hand, honeycomb structures are also used in gasoline engine vehicles. For example, a honeycomb structure having a plurality of cell density regions in which the cell density changes stepwise in the radial direction from the center to the outer periphery has been developed (see Patent Document 1). In the honeycomb structure, adjacent cell density regions are separated by boundary partition walls. In the honeycomb structure having such a configuration, the flow rate of the exhaust gas flowing through the honeycomb structure can be made uniform.

  In recent years, regulations on PM emissions tend to be more stringent, and PM discharged from gasoline engine cars as well as diesel engine cars tends to be regarded as a problem. Therefore, it has been studied to install an exhaust gas purification filter for collecting PM in a gasoline engine vehicle.

JP 2013-173134 A

  For example, as an exhaust gas purification filter for a gasoline engine vehicle, a filter having a honeycomb structure having a plurality of cell density regions and plug portions formed at either end of the cells of the honeycomb structure is assumed. . However, in such an exhaust gas purification filter, thermal stress tends to concentrate on the boundary partition wall during PM combustion removal. That is, thermal stress concentrates on the boundary partition due to the combustion heat of PM deposited in the cell adjacent to the boundary partition. As a result, the exhaust gas purification filter may be cracked.

  The present invention has been made in view of such a background, and an object of the present invention is to provide an exhaust gas purification filter that can alleviate the concentration of thermal stress in the boundary partition wall and prevent the occurrence of cracks.

One aspect of the present invention is an exhaust gas purification filter for collecting particulate matter in exhaust gas,
The exhaust gas purification filter has a honeycomb structure and a plug portion that partially closes an axial end surface of the honeycomb structure,
The honeycomb structure includes cell walls provided in a lattice shape,
A plurality of cells formed surrounded by the cell walls;
In the cross section orthogonal to the axial direction, a plurality of cell density regions having different cell densities in the radial direction from the central part toward the outer peripheral part,
A boundary partition formed between the adjacent cell density regions and separating the two,
The cell has a boundary cell in contact with the boundary partition wall, and an internal cell formed by being surrounded by the cell wall without contacting the boundary partition wall,
At least a part of the plurality of internal cells has either one of the end faces in the axial direction closed by the plug portion,
At least some of the plurality of the boundary cells, Ri border open cells der opening to both end surfaces in the axial direction,
When the area S ₁ at the end face of one inner cell and the area S ₂ at the end face of one boundary cell are compared with each other for the boundary cell and the inner cell existing in the same cell density region, the area in the exhaust gas purifying filter, wherein said boundary cell ratio of the area S ₂ with respect to _{S 1 (S 2 / S 1} × 100) is 50% or more is the boundary open cells.
Another aspect of the present invention is an exhaust gas purification filter for collecting particulate matter in exhaust gas,
The exhaust gas purification filter has a honeycomb structure and a plug portion that partially closes an axial end surface of the honeycomb structure,
The honeycomb structure includes cell walls provided in a lattice shape,
A plurality of cells formed surrounded by the cell walls;
In the cross section orthogonal to the axial direction, a plurality of cell density regions having different cell densities in the radial direction from the central part toward the outer peripheral part,
A boundary partition formed between the adjacent cell density regions and separating the two,
The cell has a boundary cell in contact with the boundary partition wall, and an internal cell formed by being surrounded by the cell wall without contacting the boundary partition wall,
At least a part of the plurality of internal cells has either one of the end faces in the axial direction closed by the plug portion,
In the exhaust gas purification filter, all the boundary cells are boundary opening cells that open to both end faces in the axial direction.

  In the exhaust gas purification filter, at least some of the plurality of boundary cells are boundary opening cells that open to both end faces. That is, at least a part of the boundary cell is open on both end faces of the honeycomb structure. And since PM does not accumulate in the boundary cell consisting of the boundary opening cell, combustion heat of PM is not generated. Therefore, the thermal stress applied to the boundary partition during PM combustion is relieved. As a result, it is possible to prevent the occurrence of cracks in the exhaust gas purification filter.

  Moreover, the honeycomb structure has a plurality of cell density regions having different cell densities in the radial direction from the central part toward the outer peripheral part in a cross section orthogonal to the axial direction. Therefore, in the exhaust gas purification filter, for example, the cell density on the outer peripheral side where the flowability of the exhaust gas is lower than that on the center side can be reduced. Thereby, the flow velocity distribution of the exhaust gas flowing into the exhaust gas purification filter can be made uniform. As a result, the PM bias collected by the exhaust gas purification filter is alleviated, and the PM collection performance of the exhaust gas purification filter is improved.

1 is a perspective view of an exhaust gas purification filter in Example 1. FIG. FIG. 3 is a partial enlarged view showing the periphery of the boundary partition wall of the exhaust gas purification filter in Example 1. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. FIG. 4 is a sectional view taken along the line IV-IV in FIG. The partial enlarged view which shows the boundary partition wall periphery of the exhaust gas purification filter in Example 4. FIG. FIG. 6 is a sectional view taken along the line VI-VI in FIG. The partial enlarged view which shows the boundary partition periphery of the exhaust gas purification filter in the comparative example 1. FIG. FIG. 8 is a cross-sectional view taken along the line VIII-VIII in FIG. Explanatory drawing which shows the relationship between the area ratio of the boundary opening cell in Experiment example 1, and the temperature (relative temperature) of the boundary cell at the time of PM combustion. FIG. 9 is a partially enlarged view showing the periphery of a boundary partition wall of an exhaust gas purification filter in Example 5. FIG. 11 is a cross-sectional view taken along line XI-XI in FIG. FIG. 11 is a cross-sectional view taken along line XII-XII in FIG. The partial enlarged view which shows the boundary partition periphery of the exhaust gas purification filter in Example 8. FIG. FIG. 14 is a sectional view taken along line XIV-XIV in FIG. The partial enlarged view which shows the boundary partition periphery of the exhaust gas purification filter in the comparative example 2. The XVI-XVI line | wire arrow directional cross-sectional view of FIG. Explanatory drawing which shows the relationship between the area ratio of the boundary opening cell in Experiment example 2, and the temperature (relative temperature) of the boundary cell at the time of PM combustion.

A preferred embodiment of the exhaust gas purification filter will be described.
The honeycomb structure has a plurality of cell density regions, the cell density in each cell density region is constant, and the cell densities of adjacent cell density regions are different. In the honeycomb structure, for example, the cell density can be changed stepwise in the radial direction.

  As means for changing the cell density stepwise, there are, for example, a method of changing the cell interval (cell pitch), a method of changing the cell shape, and the like. The shape of the cell can be, for example, circular or polygonal in the radial cross section of the exhaust gas purification filter. Specific examples of the polygon include a quadrangle and a hexagon, but a quadrangle is preferable from the viewpoint of ensuring mechanical strength.

  In the honeycomb structure, it is preferable that the heat capacity in the cell density region on the center side is larger than that in the cell density region on the outer peripheral side. More specifically, it is preferable that the thickness of the cell wall in the cell density region on the center side is larger than the thickness of the cell wall in the cell density region on the outer peripheral side. In this case, it is possible to suppress heat generation during regeneration in the cell density region on the central side where the amount of particulate matter (PM) deposited tends to increase.

  Further, in the honeycomb structure, it is preferable that the pressure loss in the cell density region on the center side is larger than that in the cell density region on the outer peripheral side. More specifically, the cell density in the cell density region on the center side is preferably larger than the cell density in the cell density region on the outer periphery side. In this case, it is possible to increase the inflow amount of the exhaust gas into the cell density region on the outer peripheral side, and to suppress the accumulation of PM in the cell density region on the center side. As a result, it is possible to suppress heat generation during reproduction from being concentrated in the cell density region on the center side.

  The exhaust gas purification filter can be formed of, for example, a ceramic material such as cordierite, SiC, or aluminum titanate. Specifically, cell walls, boundary partition walls, plug portions, and the like can be formed from these ceramic materials.

Example 1
An embodiment of the exhaust gas purification filter will be specifically described with reference to the drawings. As shown in FIG. 1, the exhaust gas purification filter 1 of this example includes a cylindrical honeycomb structure 2 and a plug portion 3. The honeycomb structure 2 includes porous cell walls 21 provided in a quadrangular lattice shape and a large number of cells 22 surrounded by the cell walls 21. The cells 22 are formed so as to extend in the axial direction X of the honeycomb structure 2. The plug portion 3 partially closes the end faces 28 and 29 in the axial direction X of the honeycomb structure 2. The honeycomb structure 2 and the plug portion 3 are made of cordierite, and the capacity of the honeycomb structure 2 is 1.3L.

As shown in FIG. 1 to FIG. 3, the honeycomb structure 2 has two cell density regions 23 (first cells) having different cell densities in the radial direction Y from the central portion 20 toward the outer peripheral portion 200 in a cross section orthogonal to the axial direction. A cell density region 231 and a second cell density region 232). The cell density in each of the cell density regions 231 and 232 is constant. In this example, the cell density of the first cell density region 231 is 62 cells / cm ² , the cell density of the second cell density region 232 is 47 cells / cm ² , and the cell density of the second cell density region 232 is Is lower than the first cell density region 231. Further, the thickness of the cell wall 21 in the first cell density region 231 is 0.25 mm, and the thickness of the cell wall 21 in the second cell density region 232 is 0.2 mm. The thickness of the cell wall 21 can be appropriately changed within a range of, for example, 0.1 mm to 0.3 mm. Moreover, the porosity of the honeycomb structure 2 can be appropriately changed within a range of 40% to 70%, for example.

  The first cell density region 231 is in a region including the central portion 20 of the honeycomb structure 2 and is located on the innermost side in the radial direction Y of the columnar honeycomb structure 2. On the other hand, the second cell density region 232 is in a region including the outer peripheral portion 200 of the honeycomb structure 2 and is located on the outermost side in the radial direction Y of the columnar honeycomb structure 2.

  As shown in FIGS. 1 to 3, the honeycomb structure 2 includes a cylindrical boundary partition wall 24 that separates the first cell density region 231 and the second cell density region 232 from each other. Then, adjacent cell density regions, that is, the first cell density region 231 and the second cell density region 232 are separated by the boundary partition wall 24. In the cells 22 of the honeycomb structure 2, there are boundary cells 221 that are in contact with the boundary partition walls 24 and internal cells 222 that are not in contact with the boundary partition walls 24. The boundary cell 221 is a cell surrounded by the boundary partition wall 24 and the cell wall 21 provided in a lattice shape. The internal cell 222 is a cell surrounded by the cell wall 21 provided in a lattice shape, and a cell surrounded by the cell wall 21 and the outer peripheral portion 200. The internal cell 222 surrounded only by the cell wall 21 has a predetermined quadrangular (square) shape, whereas the boundary cell 221 has an indefinite shape.

  As shown in FIGS. 2 to 4, at least a part of the plurality of internal cells 222 is closed by the plug portion 3 at either one of the end faces 28 and 29 in the axial direction X. In this example, the internal cell 222 includes one in which the upstream end surface 28 in the axial direction X is closed by the plug portion 3 and one in which the downstream end surface 29 is closed by the plug portion 3. In the internal cell 222, the end surface 28 on the exhaust gas inflow side or the end surface 29 on the exhaust gas outflow side is closed by the plug portion 3. The plug portion 3 alternately closes the end faces 28 and 29 of the adjacent internal cells 222. An upstream end face 28 of the internal cell 222 into which the exhaust gas flows in and an downstream end face 29 of the internal cell 222 from which the exhaust gas flows out open.

  On the other hand, the boundary cell 221 is a boundary opening cell 225 that opens to both end faces 28 and 29 as shown in FIGS. 2 to 4, and the plug portion 3 is formed on both end faces 28 and 29 of the boundary opening cell 225. Absent. In the boundary cell 221 in this example, there are a cell (boundary opening cell 225) that opens at both end faces 28 and 29, and a cell in which one of the both end faces 28 and 29 is blocked by the plug portion 3. . The boundary cell 221 having a relatively large area (opening area) on the end faces 28 and 29 is composed of the boundary opening cell 225, and the boundary cell 221 having a relatively small opening area is similar to the above-described inner cell 222. Either one is closed by the plug 3.

Specifically, the boundary cell 221 and the internal cells 222 existing in the same cell density region 231, the area S ₁ of the end face 28, 29 of one internal cell 222 and one end face 18 of the boundary cells 221, When the area S ₂ in FIG. 19 is compared , all the boundary cells 221 in which the ratio of the area S _{2 to} the area S ₁ (S ₂ / S ₁ × 100) is 75% or more are the boundary open cells 225 (FIG. 2). To FIG. 4). On the other hand, in the boundary cell 221 whose area ratio is less than 75%, one of the end faces 28 and 29 is closed by the plug portion 3, similarly to the internal cell 222. Incidentally, in FIG. 2 shows the area S ₂ of the surface area S ₁ and the boundary cell 221 of the internal cell 222 in the first cell density section 231, a similar relationship applies to the second cell density section 232. The area S ₁ at the end faces 28 and 29 of the internal cell 222 and the area S ₂ at the end faces 28 and 29 of the boundary cell 221 do not include the area of the cell wall 21 or the boundary partition wall 24. That is, the areas S ₁ and S ₂ are the area of the opening of the cell when the plug 3 is not formed.

The exhaust gas purification filter 1 of this example is manufactured as follows. First, a cordierite raw material containing silica, talc, kaolin, alumina, aluminum hydroxide and the like is prepared. Then, the final composition after firing, SiO _2: 47 to 53 wt%, Al ₂ O _3: 32~38 wt%, MgO: such that 12 to 16 wt%, the adjustment of the feed composition. The cordierite raw material is mixed with a solvent such as water, a thickener, a dispersant and the like to be adjusted to a clay. The clay-like cordierite raw material is extruded using a mold and then dried to obtain a honeycomb-shaped formed body (honeycomb formed body).

Next, a plug part forming material containing raw material powders such as silica, talc, kaolin, alumina, aluminum hydroxide is prepared. The plug portion forming material is adjusted so that the final composition after firing is SiO ₂ : 47 to 53 mass%, Al ₂ O ₃ : 32 to 38 mass%, and MgO: 12 to 16 mass%. Yes. The plug portion forming material is dispersed in a solvent such as water or oil together with a thickener or a dispersant, and is in a slurry form. The plug portion forming material slurry is obtained by stirring using a mixer.

  Next, a masking tape is attached to both end faces of the honeycomb formed body. Thereafter, the masking tape is partially removed to form an opening at the end face of the cell to be plugged. The removal of the masking tape can be performed by, for example, laser light irradiation. Next, both end surfaces of the honeycomb formed body are dipped in the plug portion forming material slurry. Accordingly, an appropriate amount of plug portion forming material is allowed to enter the cell to be plugged from the opening.

  Next, the honeycomb formed body is dried and fired. Thereby, the honeycomb formed body and the plug portion forming material are sintered. In this way, as shown in FIGS. 1 to 4, the exhaust gas purification filter 1 having the honeycomb structure 2 and the plug portion 3 is obtained. In this example, the honeycomb formed body and the plug portion forming material are sintered by firing once. However, after the honeycomb formed body is fired in advance to prepare the honeycomb structure 2, the plug portion is again fired. 3 can also be formed. In this case, after attaching the masking tape to the honeycomb structure 2, the exhaust gas purification filter 1 can be manufactured in the same manner as the above-described manufacturing method.

  The exhaust gas purification filter 1 of this example is used for collecting PM contained in exhaust gas discharged from an internal combustion engine such as a diesel engine or a gasoline engine. As shown in FIGS. 1 to 4, in the exhaust gas purification filter 1, at least some of the plurality of boundary cells 221 are boundary opening cells 225 that open to both end faces 28 and 29. That is, at least a part of the boundary cell 221 is open to both end faces 28 and 29 of the honeycomb structure 2. PM is not accumulated in the boundary cell 221 including the boundary opening cell 225. For this reason, when the exhaust gas purification filter 1 is regenerated by burning PM, no PM combustion heat is generated in the boundary cell 221. Therefore, the thermal stress applied to the boundary partition wall 24 during PM combustion is relieved. As a result, generation of cracks in the exhaust gas purification filter 1 can be prevented.

  Further, the honeycomb structure 2 has a plurality of cell density regions 23 having different cell densities in the radial direction Y from the central portion 20 toward the outer peripheral portion 200 in a cross section orthogonal to the axial direction X. Therefore, in the exhaust gas purification filter 1, it is possible to reduce the cell density on the outer peripheral portion side where the exhaust gas flowability is lower than that on the central portion side. Actually, in the honeycomb structure 2 of the present example, the cell density of the second cell density region 232 located on the outer peripheral portion 200 side is lower than that of the first cell density region 231 located on the center portion 20 side. Yes. As a result, the exhaust gas smoothly flows in the cells 22 in the second cell density region 232 as in the first cell density region 231. Therefore, the flow velocity distribution of the exhaust gas flowing into the exhaust gas purification filter 1 can be made uniform. As a result, since the bias of PM collected by the exhaust gas purification filter 1 is alleviated, the PM collection performance of the exhaust gas purification filter 1 is improved.

  The exhaust gas purification filter 1 is preferably used for collecting PM discharged from a gasoline engine. In this case, since the pressure loss is reduced, the engine output can be improved. That is, since the exhaust gas purification filter 1 has the boundary opening cell 225 as described above, the pressure loss can be reduced as compared with the case where the plug portion 3 is also formed in the boundary cell 221.

  As described above, in the exhaust gas purification filter 1 of this example, the concentration of thermal stress in the boundary partition wall 24 is alleviated, and the generation of cracks can be prevented.

(Examples 2 to 4)
Examples 2 to 4 are examples of the exhaust gas purification filter in which the formation pattern of the boundary opening cell in the boundary cell is changed from that of Example 1.

In the exhaust gas purification filter of Example 2, when the area S ₁ at the end face of one internal cell was compared with the area S ₂ at the end face of one boundary cell, the ratio of the area S _{2 to} the area S ₁ (S ₂ / S All the boundary cells having ₁ × 100) of 50% or more are boundary open cells. On the other hand, in the boundary cell having an area ratio (S ₂ / S ₁ × 100) of less than 50%, either one of the end faces is closed by the plug portion. Other configurations are the same as those of the first embodiment. In the honeycomb structure of Example 3, all of the boundary cells in which the above-described area ratio (S ₂ / S ₁ × 100) is 25% or more are boundary open cells. On the other hand, in the boundary cell having an area ratio (S ₂ / S ₁ × 100) of less than 25%, either one of the end faces is closed by the plug portion. Other configurations are the same as those of the first embodiment. Illustration of the exhaust gas purification filter of Example 2 and Example 3 is omitted.

In the honeycomb structure of Example 4, as shown in FIGS. 5 and 6, all the boundary cells 221 are boundary opening cells 225. That is, all of the cells (boundary cells 221) in contact with the boundary partition walls 24 are open at both ends 28 and 29 of the honeycomb structure. In other words, all the boundary cells 221 in which the above-described area ratio (S ₂ / S ₁ × 100) exceeds 0% are the boundary opening cells 225. Other configurations are the same as those of the first embodiment. In addition, in the exhaust gas purification filter (refer FIG.5 and FIG.6) of Example 4, the same code | symbol as Example 1 shows the same structure, and refers the description to precede.

(Comparative Example 1)
This example is an example of an exhaust gas purification filter that does not have a boundary opening cell.
As shown in FIGS. 7 and 8, in the exhaust gas purification filter 9 of this example, either one of the end faces 28 and 29 of all the cells 22 including the internal cell 222 and the boundary cell is alternately formed by the plug portions 3. Blocked. That is, as with the internal cell 222, one of the end faces 28 and 29 is also closed in all the boundary cells 221. Other configurations are the same as those of the first embodiment. In addition, in the exhaust gas purification filter 9 (refer FIG.7 and FIG.8) of the comparative example 1, the same code | symbol as Example 1 shows the same structure, and refers the description to precede.

(Experimental example 1)
In this example, the temperature of the boundary cell during PM combustion of each exhaust gas purification filter of the example and the comparative example is measured.
Specifically, first, each exhaust gas purification filter was loaded into an exhaust pipe of a gasoline engine, and 3 g / L of PM contained in the exhaust gas was deposited on the exhaust gas purification filter. Next, the exhaust gas purification filter was heated to 700 ° C. while maintaining the air-fuel ratio (air / fuel) at 1. Thereafter, PM was burned by lowering the amount of fuel gas supplied to the level corresponding to idle. At this time, the oxygen concentration in the exhaust gas is 16% by volume. And the temperature in the boundary cell in the end surface of the downstream of the exhaust gas purification filter at the time of combustion of PM was measured. The results are shown in FIG. 9 as relative temperatures with respect to the exhaust gas purification filter of Comparative Example 1. FIG. 9 shows the relationship between the area ratio of the boundary opening cell in each exhaust gas purification filter and the temperature (relative temperature) in the boundary cell during the PM combustion described above.

As can be seen from FIG. 9, the exhaust gas purification filter 1 of Examples 1 to 4 has a more sufficient boundary cell temperature during PM combustion than the case where the boundary opening cell is not provided (Comparative Example 1). To drop. That is, for example, as in the first to fourth embodiments, at least, among the plurality of boundary cells, when the boundary cell whose area ratio (S ₂ / S ₁ × 100) is 75% or more is the boundary opening cell, Compared to Comparative Example 1, the temperature of the temperature cell during PM combustion is more sufficiently lowered. It should be noted that at least a boundary cell having an area ratio (S ₂ / S ₁ × 100) of 75% or more among the plurality of boundary cells is a boundary opening cell is an area ratio (S ₂ / S ₁ × 100). A boundary cell having a surface area of 75% or more is a boundary opening cell (Example 1), and a boundary cell having an area ratio (S ₂ / S ₁ × 100) of 50% or more is a boundary opening cell ( (Example 2), a boundary cell having an area ratio (S ₂ / S ₁ × 100) of 25% or more is a boundary opening cell (Example 3), and all of the boundary cells are boundary opening cells (implementation) Example 4) is also included. That is, in these, boundary cells having an area ratio (S ₂ / S ₁ × 100) of 75% or more are at least boundary opening cells. Therefore, in this case, the thermal stress applied to the boundary partition during PM combustion is relieved, and the generation of cracks in the exhaust gas purification filter can be further prevented. As is known from FIG. 9, when the boundary cell having the above-mentioned area ratio (S ₂ / S ₁ × 100) is 50% or more is a boundary opening cell (Example 2 to Example 4), PM The temperature of the boundary cell during combustion can be further reduced. Further, as can be seen from the figure, when all the boundary cells are boundary open cells (Example 4), the temperature of the boundary cells can be further reduced.

(Example 5)
This example is a modification of the first embodiment as shown in FIGS. In other words, in this example, the internal cell 222 includes an end cell 28 whose upstream end surface 28 in the axial direction X is closed by the plug portion 3, and an internal opening cell 226 that opens to both end surfaces 28 and 29 in the axial direction X. There is. In this example, the internal cells 222 whose end faces 28 are closed by the plug portions 3 and the internal open cells 226 of the internal cells 222 are alternately arranged so as to be adjacent to each other.

  Also in this example, at least some of the plurality of boundary cells 221 are boundary opening cells 225. In the boundary cell 221 in this example, the end surface 28 of the inner cell 22 on the side in which the exhaust gas flows in the axial direction X (the boundary opening cell 225) and the end surface 28 in the axial direction X are blocked by the plug portion 3. There is a cell. The boundary cell 221 having a relatively large area (opening area) on the end surfaces 28 and 29 is composed of the boundary opening cell 225, and the boundary cell 221 having a relatively small opening area has the end surface 28 having a plug portion as in the case of the internal cell 222 described above. 3 is occluded.

Specifically, the boundary cell 221 and the internal cells 222 existing in the same cell density region 231, the area S ₁ of the end face 28, 29 of one internal cell 222 and one end face 18 of the boundary cells 221, When the area S _{2 at} 19 is compared , all of the boundary cells 221 in which the ratio of the area S _{2 to} the area S ₁ (S ₂ / S ₁ × 100) is 75% or more are the boundary open cells 225 (FIG. 10). To FIG. 12). On the other hand, in the boundary cell 221 whose area ratio is less than 75%, the end face 28 is closed by the plug portion 3, as in the case of the internal cell 222.

  In producing the exhaust gas purification filter 1 of this example, a masking tape is attached to one end face of the honeycomb formed body. Then, the end face of the honeycomb formed body on which the masking tape is attached is dipped in the plug portion forming material slurry. Accordingly, an appropriate amount of plug portion forming material is allowed to enter the cell to be plugged from the opening.

  Others are the same as in the first embodiment. Further, in the exhaust gas purification filter of the fifth embodiment (see FIGS. 10 to 12), the same reference numerals as those of the first embodiment indicate the same configuration, and the preceding description is referred to.

In this example, since the inner cell 222 has one end face 28 in the axial direction X closed by the plug portion 3, the exhaust gas purification filter 1 that can be easily manufactured can be obtained.
In addition, the same effects as those of the first embodiment are obtained.

(Examples 6 to 8)
Examples 6 to 8 are examples of the exhaust gas purification filter in which the formation pattern of the boundary opening cell in the boundary cell is changed from that of Example 5.

In the exhaust gas purification filter of Example 6, when the area S ₁ at the end face of one internal cell was compared with the area S ₂ at the end face of one boundary cell, the ratio of the area S _{2 to} the area S ₁ (S ₂ / S All the boundary cells having ₁ × 100) of 50% or more are boundary open cells. On the other hand, in the boundary cell having an area ratio (S ₂ / S ₁ × 100) of less than 50%, the end surface on the side into which the exhaust gas flows is closed by the plug portion. Other configurations are the same as those of the fifth embodiment. In the honeycomb structure of Example 7, all of the boundary cells in which the area ratio (S ₂ / S ₁ × 100) is 25% or more are boundary open cells. On the other hand, in the boundary cell having an area ratio (S ₂ / S ₁ × 100) of less than 25%, the end surface on the side into which the exhaust gas flows is blocked by the plug portion. Other configurations are the same as those of the fifth embodiment. Illustration of the exhaust gas purification filters of Example 6 and Example 7 is omitted.

In the honeycomb structure of Example 8, as shown in FIGS. 13 and 14, all the boundary cells 221 are boundary opening cells 225. That is, all of the cells (boundary cells 221) in contact with the boundary partition walls 24 are open at both ends 28 and 29 of the honeycomb structure. In other words, all boundary cells 221 in which the above-described area ratio (S ₂ / S ₁ × 100) exceeds 0 are boundary opening cells 225. Other configurations are the same as those of the fifth embodiment. Note that, in the exhaust gas purification filter of the eighth embodiment (see FIGS. 13 and 14), the same reference numerals as those of the fifth embodiment indicate the same configurations, and the preceding description is referred to.

(Comparative Example 2)
In this example, as shown in FIGS. 15 and 16, all the cells 22 including the internal cell 222 and the boundary cell are divided into the cell 22 and the internal opening cell 226 or the boundary opening cell 225 whose end face 28 is closed by the plug portion 3. Are alternately arranged so as to be adjacent to each other. That is, similarly to the internal cell 222, the boundary cell is also formed so that the cells 22 whose end faces 28 are closed by the plug portions 3 and the boundary opening cells 225 are alternately arranged. Other configurations are the same as those of the fifth embodiment. In addition, in the exhaust gas purification filter 9 (refer FIG.7 and FIG.8) of the comparative example 2, the same code | symbol as Example 5 shows the same structure, and refers the description to precede.

(Experimental example 2)
In this example, the temperature of the boundary cell during PM combustion was measured for each exhaust gas purification filter of Examples 5 to 8 and Comparative Example 2 in the same manner as in Experimental Example 1.
The test method is the same as in Example 1. The measurement results are shown in FIG. 17 as relative temperatures with respect to the exhaust gas purification filter of Comparative Example 2. FIG. 17 shows the relationship between the area ratio of the boundary opening cell in each exhaust gas purification filter and the temperature (relative temperature) in the boundary cell during the PM combustion described above.

As is known from FIG. 17, in the exhaust gas purification filters 1 of Examples 5 to 8, the temperature of the boundary cell during PM combustion is more sufficiently lowered than that of Comparative Example 2. That is, for example, as in Example 5 to Example 8, among the plurality of boundary cells, when a boundary cell having an area ratio (S ₂ / S ₁ × 100) of 75% or more is a boundary opening cell, Compared to Comparative Example 2, the temperature of the temperature cell during PM combustion is more sufficiently lowered. Therefore, in this case, the thermal stress applied to the boundary partition during PM combustion is relieved, and the generation of cracks in the exhaust gas purification filter can be further prevented. As is known from FIG. 17, when the boundary cell having the above-mentioned area ratio (S ₂ / S ₁ × 100) is 50% or more is a boundary opening cell (Examples 6 to 8), PM The temperature of the boundary cell during combustion can be further reduced.

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification filter 2 Honeycomb structure 21 Cell wall 22 Cell 221 Boundary cell 222 Internal cell 23 Cell density area 24 Boundary partition 3 Plug part

Claims (6)

An exhaust gas purification filter (1) for collecting particulate matter in exhaust gas,
The exhaust gas purification filter (1) includes a honeycomb structure (2) and a plug portion (3) that partially closes the end faces (28, 29) in the axial direction (X) of the honeycomb structure (2). Have
The honeycomb structure (2) includes cell walls (21) provided in a lattice pattern,
A plurality of cells (22) formed surrounded by the cell walls (21);
A plurality of cell density regions (23) having different cell densities in the radial direction (Y) from the central portion (20) toward the outer peripheral portion (200) in a cross section orthogonal to the axial direction (X);
A boundary partition wall (24) formed between the adjacent cell density regions (23) and separating the two,
The cell (22) includes a boundary cell (221) in contact with the boundary partition wall (24) and an internal cell (222) formed by being surrounded by the cell wall (21) without contacting the boundary partition wall (24). And
At least a part of the plurality of internal cells (222) has either one of the end faces (28, 29) in the axial direction (X) closed by the plug portion (3),
At least some of the plurality of the boundary cells (221), the boundary open cells (225) which is open at both end faces (28, 29) in the axial direction (X) der is,
For the boundary cell (221) and the internal cell (222) existing in the same cell density region (23), the area S ₁ and the single area S ₁ at the end face (28, 29) of the single internal cell (222) The ratio of the area S _{2 to} the area S ₁ (S ₂ / S ₁ × 100) is 50% or more when compared with the area S _{2 on} the end faces (28, 29) of the boundary cell (221). The exhaust gas purification filter (1), wherein the boundary cell (221) is the boundary opening cell (225 ). The exhaust gas purification filter (1) according to claim 1, wherein all the boundary cells (221) are the boundary opening cells (225 ). An exhaust gas purification filter (1) for collecting particulate matter in exhaust gas,
The exhaust gas purification filter (1) includes a honeycomb structure (2) and a plug portion (3) that partially closes the end faces (28, 29) in the axial direction (X) of the honeycomb structure (2). Have
The honeycomb structure (2) includes cell walls (21) provided in a lattice pattern,
A plurality of cells (22) formed surrounded by the cell walls (21);
A plurality of cell density regions (23) having different cell densities in the radial direction (Y) from the central portion (20) toward the outer peripheral portion (200) in a cross section orthogonal to the axial direction (X);
A boundary partition wall (24) formed between the adjacent cell density regions (23) and separating the two,
The cell (22) includes a boundary cell (221) in contact with the boundary partition wall (24) and an internal cell (222) formed by being surrounded by the cell wall (21) without contacting the boundary partition wall (24). And
At least a part of the plurality of internal cells (222) has either one of the end faces (28, 29) in the axial direction (X) closed by the plug portion (3),
The exhaust gas purification filter (1), wherein all the boundary cells (221) are boundary opening cells (225) that open to both end faces (28, 29) in the axial direction (X ). In the internal cell (222), the upstream end face (28) in the axial direction (X) is closed by the plug portion (3), and both end faces (28, 28) in the axial direction (X). The exhaust gas purification filter (1) according to any one of claims 1 to 3, characterized in that there is an internal opening cell (226) that opens to 29) . The inner cell (222) has an upstream end surface (28) in the axial direction (X) closed by the plug portion (3) and a downstream end surface (29) of the plug portion ( The exhaust gas purification filter (1) according to any one of claims 1 to 3, wherein the exhaust gas purification filter (1) is blocked by 3 ).   The exhaust gas purification filter (1) according to any one of claims 1 to 5, wherein the exhaust gas purification filter (1) is used for collecting particulate matter discharged from a gasoline engine. .

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