JP2016186248A - Exhaust emission control filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control filter capable of improving a collection rate of particulate matters while suppressing a pressure loss.SOLUTION: An exhaust emission control filter has a honeycomb structure 2, and a plug part 3 partially closing an upstream side end face in the axial direction of the honeycomb structure 2. The honeycomb structure 2 has plural cell walls 4 and plural cell holes 5 formed while being surrounded by the cell walls 4. The plural cell holes 5 comprises open cell holes 51 axially penetrated, and plugged cell holes 52 with upstream side end faces closed by the plug part 3. In a cross section orthogonal to the axial direction, the total cross-sectional area of the plugged cell holes 52 is larger than the total cross-section area of the open cell holes 51. The plugged cell holes 52 exist at positions adjacent to the open cell holes 51. The plugged cell holes 52 and the open cell holes 51 are arranged such that even starting from any of the plugged cell holes 52, the open cell hole 51 exists ahead across two or less cell wall 4.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an exhaust gas purification filter for purifying exhaust gas of an internal combustion engine.

An exhaust gas purification apparatus that collects particulate matter (PM) contained in the exhaust gas is provided in an exhaust pipe of the internal combustion engine. This exhaust gas purification device includes an exhaust gas purification filter for collecting particulate matter contained in the exhaust gas.
The exhaust gas purification filter has a plurality of cell walls and cell holes formed surrounded by the cell walls. As an exhaust gas purification filter, a part of the plurality of cell holes is closed at the upstream end face by the plug part, and the other part of the plurality of cell holes is plugged at the downstream end face by the plug part. Some are obstructed. Thus, the exhaust gas flowing into the cell hole opened on the upstream side can be surely permeated through the cell wall and then discharged from the cell hole opened on the downstream side.

  However, the exhaust gas purification filter having the above-described structure has a problem that pressure loss tends to increase. In addition, ash (Ash) produced by impurities (S, Ca, etc.) contained in trace amounts in engine oil and fuel reaches the exhaust gas purification filter together with exhaust gas, but this ash tends to accumulate in the cell. There is also. This ash accumulation also increases the pressure loss. In view of such a problem, an exhaust gas purification filter in which the plug portion is disposed only on the upstream side of the honeycomb structure has been proposed (Patent Document 1).

International Publication No. 2012/046484

  However, the exhaust gas purification filter disclosed in Patent Document 1 has a problem that it is not possible to sufficiently secure the particulate matter collection rate. Therefore, there is a demand for an exhaust gas purification filter that achieves both improvement in collection rate while suppressing pressure loss.

  This invention is made | formed in view of this background, and it aims at providing the exhaust gas purification filter which can improve the collection rate of a particulate matter, suppressing a pressure loss.

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 upstream end face in the axial direction of the honeycomb structure,
The honeycomb structure has a plurality of cell walls and a plurality of cell holes formed surrounded by the cell walls,
The plurality of cell holes include an open cell hole penetrating in the axial direction and a plugged cell hole in which the upstream end face is closed by the plug portion,
In the cross section orthogonal to the axial direction, the total cross-sectional area of the plugged cell hole is larger than the total cross-sectional area of the open cell hole,
The plugged cell hole is present at a position adjacent to the open cell hole,
The plugged cell hole and the open cell hole are arranged so that the open cell hole exists at the tip of two or less cell walls, starting from any one of the plugged cell holes. In the exhaust gas purification filter,

  In the exhaust gas purification filter, as described above, the open cell hole and the plugged cell hole are arranged. Therefore, the exhaust gas that passes through the exhaust gas purification filter is first introduced into the open cell hole from the upstream side. At this time, the pressure in the open cell hole is increased, and a pressure difference is generated between the open cell hole and the plugged cell hole. Due to this pressure difference, a part of the exhaust gas passes through the cell wall and flows into the plugged cell hole. And when exhaust gas permeate | transmits a cell wall, the particulate matter in exhaust gas is collected by the cell wall. Further, the ash content (Ash) in the exhaust gas remains in the open cell hole when the exhaust gas permeates the cell wall. However, since the open cell hole has an open end face on the downstream side, the ash is removed from the open cell hole. It can be easily discharged. Therefore, residual ash in the exhaust gas purification filter can be prevented. Thereby, the fall of the purification performance in an exhaust gas purification filter can be suppressed.

  Moreover, in the cross section orthogonal to the axial direction, the total cross-sectional area of the plugged cell hole is larger than the total cross-sectional area of the open cell hole. Thereby, the pressure difference between an open cell hole and a plugging cell hole can be enlarged. As a result, the ratio of the exhaust gas that permeates the cell walls can be increased, and the collection rate of the particulate matter can be improved.

  Further, the plurality of plugged cell holes and the plurality of open cell holes are arranged so that the plugged cell holes exist at positions adjacent to the open cell holes. That is, the arrangement is such that the open cell holes are not adjacent to each other. Thereby, since the exhaust gas introduced into the open cell hole effectively permeates the cell wall toward the plugged cell hole around it, the collection rate of the particulate matter can be effectively improved.

  Further, in the exhaust gas purification filter, the plugged cell hole and the open cell are formed so that the open cell hole exists at the tip of two or less cell walls, starting from any one of the plurality of plugged cell holes. And a hole. Thereby, the collection rate of a particulate matter can be improved, suppressing a pressure loss. That is, the arrangement of the plugged cell hole and the open cell hole as described above allows the exhaust gas introduced from the open cell hole to reach the plugged cell hole for any plugged cell hole. This means that there are two or less cell walls that pass through. The permeation rate when exhaust gas permeates through one cell wall is determined by various conditions such as the wall thickness and porosity of the cell wall, the pressure difference between both sides of the cell wall, but when permeating through a plurality of cell walls. Is considered to be close to a value obtained by multiplying the transmittance of one sheet by the number of sheets. As a result, the amount of exhaust gas that permeates through three or more cell walls becomes extremely small. Therefore, even if plugged cell holes that do not allow permeation through three or more cell walls are provided, trapping particulate matter. The contribution to the improvement of the collection rate is considered to be low. On the other hand, the presence of such plugged cell holes reduces the substantial cross-sectional area of the exhaust gas and increases the pressure loss.

  Therefore, as described above, the plugged cell hole and the open cell hole are formed so that the open cell hole exists at the tip of two or less cell walls, starting from any one of the plurality of plugged cell holes. And the trapping rate of the particulate matter can be improved while suppressing pressure loss.

  As described above, according to the present invention, it is possible to provide an exhaust gas purification filter that can improve the collection rate of particulate matter while suppressing pressure loss.

FIG. 3 is a perspective view of an exhaust gas purification filter in the first embodiment. FIG. 3 is a cross-sectional view parallel to the axial direction of the exhaust gas purification filter in the first embodiment. Explanatory drawing of the arrangement | sequence state of the open cell hole and the plugging cell hole in Embodiment 1. FIG. FIG. 3 is an explanatory diagram of a cell hole group in the first embodiment. Sectional explanatory drawing parallel to the axial direction of an open cell hole and a plugging cell hole in Embodiment 1. FIG. Explanatory drawing explaining the problem in case there exists the plugging cell hole which exhaust gas cannot reach unless it permeate | transmits three or more cell walls. Explanatory drawing of the arrangement | sequence state of the open cell hole and the plugging cell hole in Embodiment 2. FIG. Explanatory drawing of the cell hole group in Embodiment 2. FIG. Explanatory drawing of the arrangement | sequence state of the open cell hole and the plugging cell hole in Embodiment 3. FIG. Explanatory drawing of the cell hole group in Embodiment 3. FIG. Explanatory drawing of the arrangement | sequence state of the open cell hole and the plugging cell hole in Embodiment 4. FIG. Explanatory drawing of the cell hole group in Embodiment 4. FIG. Explanatory drawing of the arrangement state of the open cell hole and the plugging cell hole in Embodiment 5. FIG. FIG. 10 is an explanatory diagram of a cell hole group in the fifth embodiment. Explanatory drawing of the arrangement | sequence state of the open cell hole and the plugging cell hole in the comparative form 1. FIG. Explanatory drawing of the cell hole group in the comparative form 1. FIG. Explanatory drawing of the arrangement | sequence state of the open cell hole and the plugging cell hole in the comparative form 2. FIG. Explanatory drawing of the cell hole group in the comparative form 2. FIG. Explanatory drawing of the arrangement state of the open cell hole and the plugging cell hole in the comparative form 3. FIG. Explanatory drawing of the cell hole group in the comparative form 3. FIG. The diagram which shows the measurement result of the collection rate in an experiment example. The diagram which shows the measurement result of the pressure loss in an experiment example. The diagram which shows the relationship between the pressure loss and the collection rate in an experiment example. Explanatory drawing of the arrangement | sequence state of the open cell hole and the plugging cell hole in Embodiment 6. FIG.

(Embodiment 1)
An embodiment of an exhaust gas purification filter will be described with reference to FIGS.
The exhaust gas purification filter 1 of the present embodiment is a filter for collecting particulate matter in exhaust gas.
As shown in FIGS. 1 and 2, the exhaust gas purification filter 1 includes a honeycomb structure 2 and a plug portion 3 that partially closes an upstream end surface 21 in the axial direction X of the honeycomb structure 2.

The honeycomb structure 2 has a plurality of cell walls 4 and a plurality of cell holes 5 formed so as to be surrounded by the cell walls 4.
The plurality of cell holes 5 include an open cell hole 51 penetrating in the axial direction X, and a plugged cell hole 52 whose upstream end face 21 is closed by the plug portion 3.

In the cross section orthogonal to the axial direction X, the total cross-sectional area S2 of the plugged cell hole 52 is larger than the total cross-sectional area S1 of the open cell hole 51.
As shown in FIG. 3, plugged cell holes 52 exist at positions adjacent to the open cell holes 51. Further, from any of the plurality of plugged cell holes 52, the plugged cell holes 52 and the open cell holes 51 are arranged so that the open cell holes 51 exist at the tip of two or less cell walls 4. Is arranged.

The exhaust gas purification filter 1 of the present embodiment can be used for purification of exhaust gas generated in an internal combustion engine of an automobile, for example, a diesel engine or a gasoline engine.
As shown in FIG. 1, the exhaust gas purification filter 1 has a cylindrical outer shape. The honeycomb structure 2 constituting the exhaust gas purification filter 1 is partitioned by a plurality of cell walls 4 formed along the axial direction X.

As shown in FIG. 3, the plurality of cell holes 5 are formed in a square shape. That is, in the honeycomb structure 2, a large number of cell holes 5 partitioned in a square shape are formed by the cell walls 4 formed so that the cross-sectional shape orthogonal to the axial direction X is a lattice shape.
Each of the plurality of cells 5 has a square shape as viewed from the axial direction X as shown in FIG. 3 except for the cell holes 50 facing the outer peripheral portion 20 of the honeycomb structure 2 shown in FIG. The same size is formed. That is, the open cell hole 51 and the plugged cell hole 52 are formed in a square shape having the same size except for the cell hole 50 facing the outer peripheral portion 20.

  The cell walls 4 are made of a ceramic material such as cordierite having a porous structure, and in the interior thereof, pores (not shown) that connect adjacent cell holes 5 are formed.

  As shown in FIGS. 1 and 2, the exhaust gas purification filter 1 is partially provided with a plug portion 3 on an end surface 21 on the upstream side of exhaust gas when installed in an exhaust system of an internal combustion engine. . That is, the plugging cell hole 52 is closed by the plug portion 3 on the upstream end face 21. On the other hand, the plug portion 3 is not provided on the end face 22 on the downstream side of the honeycomb structure 2, and the downstream side of the plugged cell holes 52 is open. Further, the open cell hole 51 is open on both the upstream side and the downstream side, and penetrates in the axial direction X.

  As described above, in the cross section orthogonal to the axial direction X, the total cross-sectional area S2 of the plugged cell hole 52 is larger than the total cross-sectional area S1 of the open cell hole 51. The total cross-sectional area S2 of the plugged cell holes 52 is the sum of the cross-sectional areas of all the plugged cell holes 52, and the total cross-sectional area S1 of the open cell holes 51 is the cross-sectional area of all the open cell holes 51. It is the sum. The cross-sectional area of each cell hole 5 (plugged cell hole 52, open cell hole 51) is the area of each cell hole 5 in the cross section orthogonal to the axial direction X. This area is also the channel cross-sectional area of the cell hole 5.

  As described above, since most of the cell holes 5 except the cell holes 50 facing the outer peripheral portion 20 have the same size, the total cross-sectional area S2 of the plugged cell hole 52 is the total section of the open cell hole 51. That it is larger than the area S1 means that the number of plugged cell holes 52 is larger than the number of open cell holes 51.

  In the present embodiment, the arrangement of the plugged cell holes 52 and the open cell holes 51 is as shown in FIG. 3, and the number ratio thereof is (number of plugged cell holes 52): (open cell holes 51). Number) = 9: 7. When 16 cell holes 5 of 4 vertical × 4 horizontal are defined as one cell hole group 500, the arrangement relationship between the plugged cell holes 52 and the open cell holes 51 in the cell hole group 500 is shown in FIG. It is like that. Here, the vertical means the vertical direction in FIGS. 3 and 4, and the horizontal means the horizontal direction in FIGS. 3 and 4. Each cell hole group 500 includes nine plugged cell holes 52 and seven open cell holes 51.

  The arrangement state of the plugged cell holes 52 and the open cell holes 51 in the entire honeycomb structure 2 is a state in which the cell hole groups 500 shown in FIG. 4 are regularly and repeatedly arranged vertically and horizontally. ing. As a result, the total cross-sectional area S2 of the plugged cell hole 52 is 1.3 times the total cross-sectional area S1 of the open cell hole 51.

  This arrangement state is also a state in which the plugged cell holes 52 always exist at positions adjacent to the open cell holes 51. That is, the open cell holes 51 are not adjacent to each other via the single cell wall 4. On the contrary, there is a portion where the plugged cell holes 52 are adjacent to each other through one cell wall 4.

  In addition, this arrangement state is such that an open cell hole 51 always exists at the tip of two or less cell walls 4 regardless of which of the plurality of plugged cell holes 52 is the starting point. For example, in FIG. 3, when the plugging cell hole denoted by reference numeral 521 is used as a starting point, the cell hole 5 that is one cell wall 4 apart from the cell wall 4 is the plugging cell hole 52, and there is an open cell hole 51. Does not exist. However, an open cell hole 51 exists at the tip of two cell walls 4.

In addition, depending on the plugged cell hole 52 selected as the starting point, the open cell hole 51 may exist at the tip of one cell wall 4. For example, if the plugged cell hole 52 denoted by reference numeral 522 in FIG. 3 is selected as the starting point, the open cell hole 51 exists at the tip of one cell wall 4.
In the exhaust gas purification filter 1 of the present embodiment, the open cell holes 51 and the plugged cell holes 52 are arranged in such a state.

Next, the effect of this embodiment is demonstrated.
In the exhaust gas purification filter 1, the open cell hole 51 and the plugged cell hole 52 are arranged as described above. Therefore, the exhaust gas G passing through the exhaust gas purification filter 1 is first introduced into the open cell hole 51 from the upstream side as shown in FIG. At this time, the pressure in the open cell hole 51 is increased, and a pressure difference is generated between the open cell hole 51 and the plugged cell hole 52. Due to this pressure difference, a part of the exhaust gas G passes through the cell wall 4 and flows into the plugged cell hole 52. Then, when the exhaust gas G passes through the cell wall 4, the particulate matter in the exhaust gas G is collected on the cell wall 4. Further, the ash (Ash) in the exhaust gas G remains in the open cell hole 51 when the exhaust gas G permeates the cell wall 4, but the open cell hole 51 is also open at the end face 22 on the downstream side, The ash can be easily discharged from the open cell hole 51. Therefore, residual ash in the exhaust gas purification filter 1 can be prevented. Thereby, the fall of the purification performance in the exhaust gas purification filter 1 can be suppressed.

  In the cross section orthogonal to the axial direction X, the total cross-sectional area S2 of the plugged cell hole 52 is larger than the total cross-sectional area S1 of the open cell hole 51. Thereby, the pressure difference between the open cell hole 51 and the plugged cell hole 52 can be increased. As a result, the ratio of the exhaust gas G that permeates the cell walls 4 can be increased, and the collection rate of the particulate matter can be improved.

  The plurality of plugged cell holes 52 and the plurality of open cell holes 51 are arranged so that the plugged cell holes 52 exist at positions adjacent to the open cell holes 51. That is, the arrangement is such that the open cell holes 51 are not adjacent to each other. Thereby, since the exhaust gas G introduced into the open cell hole 51 effectively permeates the cell wall 4 toward the plugged cell hole 52 around it, the collection rate of the particulate matter is effectively improved. be able to.

  Further, in the exhaust gas purification filter 1, the plugged cell hole 52 is formed such that the open cell hole 51 exists at the tip of two or less cell walls, starting from any one of the plurality of plugged cell holes 52. And open cell holes 52 are arranged. Thereby, the collection rate of a particulate matter can be improved, suppressing a pressure loss. That is, the arrangement of the plugged cell hole 52 and the open cell hole 51 as described above allows the exhaust gas G introduced from the open cell hole 51 to be plugged into any of the plugged cell holes 52. That is, the number of cell walls 4 that pass through before reaching the cell hole 52 is two or less.

  The permeability when the exhaust gas G permeates the single cell wall 4 is determined by various conditions such as the wall thickness and porosity of the cell wall 4 and the pressure difference between both sides of the cell wall 4. The transmittance when passing through 4 is considered to be close to a value obtained by multiplying the transmittance of one sheet by the number of sheets. If it does so, as shown in FIG. 6, the quantity of the waste gas G which permeate | transmits the three or more cell walls 4 will become very small. Therefore, even if the plugged cell hole 529 is provided so that the exhaust gas G cannot reach unless it passes through three or more cell walls 4, the plugged cell hole 529 contributes to an improvement in the collection rate of particulate matter. The degree is considered low. On the other hand, the presence of such plugged cell holes 529 reduces the substantial cross-sectional area of the exhaust gas G and increases the pressure loss.

  Therefore, as described above, the plugged cell hole 52 is formed so that the open cell hole 51 exists at the tip of two or less cell walls 4 regardless of which of the plurality of plugged cell holes 52 is the starting point. By arranging the open cell holes 51, the particulate matter collection rate can be improved while suppressing pressure loss.

  Further, since the plurality of cell holes 5 are formed in a square shape, the cell walls 4 are efficiently transmitted from the open cell holes 51 toward the plugged cell holes 52 on the four sides, and thus the particle shapes are efficiently formed. It becomes easier to collect substances. Further, the arrangement of the open cell holes 51 and the plugged cell holes 52 as described above can be easily realized.

  As described above, according to the present embodiment, it is possible to provide an exhaust gas purification filter that can improve the collection rate of particulate matter while suppressing pressure loss.

(Embodiment 2)
In the present embodiment, the arrangement state of the open cell holes 51 and the plugged cell holes 52 is as shown in FIGS.
In this embodiment, (number of plugged cell holes 52) :( number of open cell holes 51) = 10: 6, and the total cross-sectional area S2 of the plugged cell holes 52 is the open cell holes 51. The total cross-sectional area S1 is 1.7 times. That is, as shown in FIG. 8, each cell hole group 500 is composed of ten plugged cell holes 52 and six open cell holes 51. Such a cell hole group 500 is as shown in FIG. It is arranged in a regular and repeated manner vertically and horizontally.

  Others are the same as in the first embodiment. Of the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the above-described embodiments represent the same components as those in the above-described embodiments unless otherwise indicated. This embodiment also has the same effects as those of the first embodiment.

(Embodiment 3)
In the present embodiment, the arrangement state of the open cell holes 51 and the plugged cell holes 52 is as shown in FIGS. 9 and 10.
In the present embodiment, (number of plugged cell holes 52) :( number of open cell holes 51) = 11: 5, and the total cross-sectional area S2 of the plugged cell holes 52 is the open cell holes 51. The total cross-sectional area S1 is 2.2 times. Others are the same as in the first embodiment. This embodiment also has the same effects as those of the first embodiment.

(Embodiment 4)
In the present embodiment, the arrangement state of the open cell holes 51 and the plugged cell holes 52 is the state shown in FIGS. 11 and 12.
In the present embodiment, (number of plugged cell holes 52) :( number of open cell holes 51) = 12: 4, and the total cross-sectional area S2 of the plugged cell holes 52 is the open cell holes 51. It is 3 times the total cross-sectional area S1. Others are the same as in the first embodiment.

  In the present embodiment, the total cross-sectional area S2 of the plug-attached cell hole 52 is at least three times the total cross-sectional area S1 of the open cell hole 51, so that the particulate matter collection rate can be greatly improved. it can. In addition, the same effects as those of the first embodiment are obtained.

(Embodiment 5)
In the present embodiment, the arrangement state of the open cell holes 51 and the plugged cell holes 52 is as shown in FIGS. 13 and 14.
In the present embodiment, (number of plugged cell holes 52) :( number of open cell holes 51) = 13: 3, and the total cross-sectional area S2 of the plugged cell holes 52 is the open cell holes 51. The total cross-sectional area S1 is 4.3 times. Others are the same as in the first embodiment. This embodiment also has the same effects as those of the first embodiment.

(Comparative form 1)
As shown in FIGS. 15 and 16, this comparative form is a form of an exhaust gas purification filter in which open cell holes 51 and plugged cell holes 52 are evenly arranged.
That is, when the exhaust gas purification filter of this comparative embodiment is viewed from the axial direction X, the open cell holes 51 and the plugged cell holes 52 are arranged in a so-called checkered pattern. That is, the number of plugged cell holes 52) :( number of open cell holes 51) = 1: 1, and each cell hole group 500 includes eight plugged cell holes 52 as shown in FIG. It consists of eight open cell holes 51. Therefore, the total cross-sectional area S2 of the plugged cell hole 52 is equal to the total cross-sectional area S1 of the open cell hole 51. Others are the same as in the first embodiment.

(Comparative form 2)
In this comparative embodiment, the arrangement state of the open cell holes 51 and the plugged cell holes 52 is the state shown in FIGS.
In this comparative embodiment, (number of plugged cell holes 52) :( number of open cell holes 51) = 12: 4, and the total cross-sectional area S2 of the plugged cell holes 52 is the open cell holes 51. It is 3 times the total cross-sectional area S1. This is the same as in the fourth embodiment.

  However, in this comparative embodiment, an open cell hole 51 is present at the tip of two or less cell walls 4 starting from any one of the plurality of plugged cell holes 52. is not. That is, for example, when the plugged cell hole denoted by reference numeral 523 in FIG. 17 is used as a starting point, all the cell holes 5 separated by one cell wall 4 and the cell holes 5 separated by two are all plugged. The open cell hole 51 does not exist at the tip of the packed cell hole 52 that is separated by two or less cell walls 4. That is, when the plugged cell hole 523 is used as a starting point, the open cell hole 51 exists only at a point where three cell walls 4 are separated.

  As described above, this means that the exhaust gas introduced from the open cell holes 51 needs to permeate through the three cell walls 4 before reaching some of the plugged cell holes 523. There is a possibility that the amount of exhaust gas reaching the filling cell hole 523 may be extremely small. As a result, the substantial exhaust gas cross-sectional area of the exhaust gas purification filter is reduced, and there is a concern about an increase in pressure loss.

(Comparative form 3)
In this comparative embodiment, the arrangement state of the open cell holes 51 and the plugged cell holes 52 is the state shown in FIGS. 19 and 20.
In this comparative embodiment, (number of plugged cell holes 52) :( number of open cell holes 51) = 13: 3, and the total cross-sectional area S2 of the plugged cell holes 52 is the open cell holes 51. The total cross-sectional area S1 is 4.3 times. This is the same as in the fifth embodiment.

  However, even in this comparative embodiment, an array state such as “the open cell hole 51 exists at the tip of two or less cell walls 4 from any one of the plurality of plugged cell holes 52” is used. This is the same as Comparative Example 2 in that it is not. Therefore, there is a concern about an increase in pressure loss even in the exhaust gas purification filter of this comparative embodiment.

(Experimental example)
In this embodiment, as shown in FIGS. 21 to 23, the particulate matter collection rate and the pressure loss were examined for the exhaust gas purification filters of Embodiments 1 to 5 and Comparative Examples 1 to 3 described above. It is.

  First, the exhaust gas purification filters of the respective embodiments and comparative embodiments were produced as samples 1 to 8. The ratio of the total cross-sectional area S2 of the plug-attached cell hole 52 to the total cross-sectional area S1 of the open cell hole 51 in each sample (total cross-sectional area ratio S2 / S1) and the like are summarized in Table 1. The “maximum wall permeation frequency” in the table is a value representing the number of plugged cell holes that cannot be reached unless exhaust gas passes through a maximum number of cell walls from an open cell. This value corresponds to the number of the cell walls 4 between the plugged cell holes 52 and the open cell holes 51 having the largest number of cell walls 4 existing between the open cell holes 51 in each sample.

In each sample, the thickness of the cell wall 4 is 200 μm, the porosity is 60%, the average pore diameter is 18 μm, the cell density is 47 cells / cm ² , the axial length of the honeycomb structure is 100 mm, and the diameter is 132 mm. did.

And each exhaust gas purification filter was loaded in the exhaust pipe of the gasoline engine, and when the engine was operated under a predetermined condition, the collection rate of particulate matter by each exhaust gas purification filter was measured. The test conditions were measured in a steady running mode of a 3.5 L engine, and the exhaust gas temperature was 550 ° C. and the gas flow rate was 25 g / s. In the evaluation method, particulate matter measuring devices are installed before and after the sample, and {(number of particles before the sample−number of particles after the sample) / (number of particles before the sample)} × 100 [%] is used as the collection rate. Defined.
The measurement results are shown in the graph of FIG. In the graph of the figure, the horizontal axis is the maximum wall permeation number, the vertical axis is the collection rate, and the plots P1 to P8 represent the measurement results for the samples 1 to 8, respectively.

  In the above test, pressure sensors were installed on the upstream side and the downstream side of the sample, respectively, and the differential pressure before and after the sample measured by the pressure sensor was defined as the pressure pressure loss due to the sample. The measurement result of the pressure loss is shown in FIG. In the graph of the figure, the horizontal axis is the maximum wall permeation number, the vertical axis is the pressure loss, and the plots P1 to P8 represent the measurement results for the samples 1 to 8, respectively.

  First, from FIG. 21 which shows the measurement result of the collection rate, the collection rate by the samples 1 to 5 (exhaust gas purification filters of Embodiments 1 to 5) is the collection rate by the sample 6 (exhaust gas purification filter of Comparative Embodiment 1). It can be seen that it is higher than the rate. Sample 7 (exhaust gas purification filter of comparative form 2) and sample 8 (exhaust gas purification filter of comparative form 3) also have a high collection rate, and among samples 1 to 8, the total cross-sectional area ratio S2 / S1 is high. It can be said that the collection rate tends to be high.

  On the other hand, FIG. 22 showing the measurement result of pressure loss shows that samples 1 to 5 have higher pressure loss than sample 6, and samples 7 and 8 have higher pressure loss than samples 1 to 5. And about samples 1-6, it can be said that pressure loss is so high that total cross-sectional area ratio S2 / S1 is high. However, there is a difference in pressure loss between the sample 4 and the sample 7 or the sample 5 and the sample 8 having the same total cross-sectional area ratio S2 / S1. The difference between the sample 4 and the sample 7 and the difference between the sample 5 and the sample 8 are the difference in the maximum wall transmission frequency. The sample 7 and the sample 8 having a large pressure loss have a maximum maximum wall transmission frequency of 3 times.

  As shown in FIG. 23, when the above results are expressed by the relationship between the pressure loss (horizontal axis) and the collection rate (vertical axis), the tendency that the higher the pressure loss is, the higher the collection rate appears. ing. For the sample with the maximum wall permeation count of 3, there is a portion where the amount of gas that permeates the cell wall is extremely small, so even if the total cross-sectional area ratio is S2 / S1, the maximum wall permeation count is 2 or less. On the other hand, the collection rate is inferior. Further, since the plugged cell hole that is separated from the open cell hole by the three cell walls becomes a gas passage that is hardly used, the total gas passage is reduced, and the pressure loss is substantially increased. Therefore, although the sample 7 and the sample 8 have a higher collection rate than the samples 1 to 3 and the sample 6, the pressure loss is significantly increased. Then, the collection rates of Sample 7 and Sample 8 are lower than those of Sample 4 and Sample 5 having the same total cross-sectional area ratio S2 / S1.

  On the other hand, Sample 4 and Sample 5 tend to have a high collection rate. That is, it can be said that it is easy to increase the collection rate while suppressing an increase in pressure loss. From this result, it is possible to increase the pressure loss by making the total cross-sectional area S2 of the plugged cell hole 52 larger than the total cross-sectional area S1 of the open cell hole 51 while having a structure in which the maximum wall permeation frequency is 2 times or less. It can be said that it becomes easy to raise the collection rate while suppressing the above.

(Embodiment 6)
As shown in FIG. 24, the present embodiment is a form of the exhaust gas purification filter 1 in which the shape of the cell hole 5 is a regular hexagonal shape.
Also in the present embodiment, the total cross-sectional area S <b> 2 of the plugged cell hole 52 is larger than the total cross-sectional area S <b> 1 of the open cell hole 51 in the cross section orthogonal to the axial direction X. Specifically, the total area ratio S2 / S1 is 2. That is, (number of plugged cell holes 52) :( number of open cell holes 51) = 2: 1.

Further, a plugged cell hole 52 always exists at a position adjacent to the open cell hole 51. Further, from any of the plurality of plugged cell holes 52, the plugged cell holes 52 and the open cell holes 51 are arranged so that the open cell holes 51 exist at the tip of two or less cell walls 4. Is arranged. In the present embodiment, the open cell hole 51 exists at the tip of one or more cell walls 4 regardless of which of the plurality of plugged cell holes 52 is the starting point.
Others have the same configuration as that of the first embodiment, and have the same effects as those of the first embodiment.

  In addition, this invention is not limited to the said embodiment, It is possible to apply to various embodiment in the range which does not deviate from the summary. For example, the shape of the cell hole is not limited to a square or a regular hexagon, and may be a regular triangle, for example.

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification filter 2 Honeycomb structure 21 (Upstream side) End face 3 Plug part 4 Cell wall 5 Cell hole 51 Open cell hole 52 Plugged cell hole X Axial direction

Claims (3)

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 an upstream end face (21) in the axial direction (X) of the honeycomb structure (2). Have
The honeycomb structure (2) includes a plurality of cell walls (4) and a plurality of cell holes (5) formed by being surrounded by the cell walls (4).
The plurality of cell holes (5) include an open cell hole (51) penetrating in the axial direction (X) and a plugged cell in which the upstream end face (21) is closed by the plug portion (3). There is a hole (52),
In the cross section orthogonal to the axial direction (X), the total cross-sectional area (S2) of the plugged cell hole (5) is larger than the total cross-sectional area (S1) of the open cell hole (51),
In the position adjacent to the open cell hole (51), the plugged cell hole (52) exists,
Starting from any of the plurality of plugging cell holes (52), the plugging cell is such that the open cell hole (51) exists at the tip of two or less cell walls (4). The exhaust gas purification filter (1), wherein the hole (52) and the open cell hole (51) are arranged.   The exhaust gas purification filter (1) according to claim 1, wherein the plurality of cell holes (5) are formed in a square shape.   The total cross-sectional area (S2) of the plug-attached cell hole (5) is at least three times the total cross-sectional area (S1) of the open cell hole (51). Exhaust gas purification filter (1).

Images