JP2007291999A - Exhaust emission control filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control filter superior in heat resistance than conventional ones, capable of reducing combustion elimination frequency of particulates, has superior size accuracy, and capable of suppressing rise in pressure loss to the minimum. <P>SOLUTION: This exhaust emission control filter includes a base material 2 equipped with an introduction passage 21, a porous separation walls 25, and a discharge passage 22. The base material 2 includes main cell walls 251 with the porous separation walls 25 arranged in a square lattice, main cells 20, and a skin layer 26. A downstream end of the introduction passage 21 and an upstream end of the discharge passage 22 are closed by plug members 4. Part of the main cells 20 includes divided cells 30 in which one or both of two diagonal lines of the squares are provided with sub cell walls 3. In a regulation arrangement region, a first divided cell 31 and a second divided cell 32 positively exist, and the rate of existence of each is substantially the same. The divided cells 30 separated by n pieces in two directions parallel to the main cell walls 251 have the same shape, and the percentage of the divided cells 30 with respect to the total number of the main cells 20 is 70% or below. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification filter that collects particulates in exhaust gas discharged from an internal combustion engine such as a diesel engine and purifies the exhaust gas.

Conventionally, there is an exhaust gas purification filter that collects particulates in exhaust gas discharged from an internal combustion engine and purifies the exhaust gas.
The exhaust gas purification filter includes a cell serving as an introduction passage for introducing exhaust gas containing particulates discharged from an internal combustion engine, a porous partition wall for collecting the particulates, and exhaust gas after the particulates are removed. It has a honeycomb-like base material provided with cells serving as discharge passages (Patent Document 1).

In general, the downstream end of the cell serving as the introduction passage and the upstream end of the cell serving as the discharge passage are closed by a plug member.
And when purifying exhaust gas using the exhaust gas purification filter provided with this base material, the exhaust gas that has entered the cell serving as the introduction passage passes through the porous partition wall and enters the exhaust passage composed of the adjacent cell. Moving. At this time, the particulates in the exhaust gas are collected in the porous partition wall, and the exhaust gas is purified.
The particulate matter collected by the exhaust gas purification filter is periodically burned and removed. Thereby, the collecting function of the porous partition is regenerated. Various methods have been proposed as a combustion removal method.

  By the way, when the particulate matter collected by the exhaust gas purification filter is burned and removed, the base material may be damaged due to the heat generated by the combustion. In addition, the heat generation during combustion increases as the number of collected particulates increases. Therefore, in order to prevent damage to the base material due to heat, it is necessary to devise a method for shortening the interval for performing the combustion removal of the particulates to increase the frequency and reducing the amount of particulates burned at one time. For this reason, the control for performing this combustion removal becomes complicated and disadvantageous in terms of cost.

JP 2001-96113 A

  The present invention has been made in view of such a conventional problem, and is superior in heat resistance than before, can reduce the frequency of particulate removal by combustion, has good dimensional accuracy, and has a pressure loss. An object of the present invention is to provide an exhaust gas purification filter having a base material capable of suppressing the rise as much as possible.

The present invention includes an introduction passage for introducing exhaust gas containing particulates discharged from an internal combustion engine, a porous partition wall for collecting the particulates, and an exhaust passage for exhausting exhaust gases after the particulates have been removed. An exhaust gas purifying filter having a honeycomb-shaped base material comprising:
The base material has a main cell wall in which the porous partition walls are arranged in a rectangular lattice shape, a main cell surrounded by the main cell wall, and a skin layer that covers an outer peripheral side surface,
Among the main cells, the downstream end of the main cell serving as the introduction passage and the upstream end of the main cell serving as the discharge passage are closed by a plug member,
At least a part of the main cell is a divided cell in which a sub cell wall is arranged on one or both of two diagonals of a square of the main cell so as to divide the main cell,
Inside the outer peripheral region within 5 cells from the skin layer, there is a regular arrangement region in which the divided cells are arranged with regularity,
Within the regular array region, the first divided cell in which the subcell wall is formed only on the first diagonal line, and the second divided line in which the subcell wall is formed only on the second diagonal line orthogonal to the first diagonal line. There are always two types of two-divided cells, and the existence ratio is substantially the same,
Further, in the regular array region, the divided cells separated by n (n is a natural number of 4 or more) in two directions parallel to the main cell wall have the same shape, and the regular array In the exhaust gas purifying filter, the ratio of the divided cells to the total number of the main cells existing in the region is 70% or less.

As described above, the exhaust gas purifying filter of the present invention uses a base material having a divided cell in which a subcell wall is arranged on one or both of the two diagonals of the square of the main cell, at least in part of the main cell. ing. For this reason, this base material has an increased heat capacity and increased rigidity as compared with those without the subcell wall by the amount of increase in the subcell wall.
An increase in heat capacity leads to an improvement in heat resistance. Therefore, the exhaust gas purifying filter is superior in heat resistance than before, and the frequency of burning and removing the repaired particulates can be reduced.
Moreover, since the subcell wall is arranged on the diagonal line as described above, the variation in the contraction direction is reduced and the dimensional accuracy can be increased.

Moreover, it has not only the above-described divided cells but also a regular array region in which the divided cells are arranged with regularity. Thereby, it can have the outstanding dimensional accuracy and can make pressure loss small.
That is, in the regular array region, the sub-cell wall is formed only on the first diagonal line, and the sub-cell wall is formed only on the second diagonal line orthogonal to the first diagonal line. There are always two types of the second divided cells, and their existence ratios are substantially the same. Thus, the strength can be balanced in the cross section of the substrate, and the variation in the shrinking direction is eliminated, so that the dimensional accuracy can be improved.

  Further, in the regular array region, the divided cells separated by n in two directions parallel to the main cell wall have the same shape, and the total number of the main cells existing in the regular array region The ratio of the divided cells is 70% or less. For this reason, the divided cells form a relatively large arrangement unit, and by setting an upper limit on the ratio of the divided cells, an appropriate opening area can be obtained, so that the pressure loss can be reduced.

In the exhaust gas purifying filter of the present invention, in the regular array region, the first subcell wall is present on the first extension line that is an extension line of the subcell wall in any one of the first divided cells. One divided cell is arranged, and the second divided cell is arranged so that the sub cell wall exists on a second extension line that is an extension line of the sub cell wall in any one of the second divided cells. Preferred (claim 2).
In this case, the divided cells are arranged so that the strength balance is balanced, and the variation in the shrinking direction is further reduced, so that the dimensional accuracy can be further increased.

In the regular array region, the main cell including the intersection of the first extension line and the second extension line is formed such that the subcell wall is on both the first diagonal line and the second diagonal line. The third divided cell is preferable.
In this case, the strength balance is further improved and the base material is less likely to shrink, so that it is possible to have better dimensional accuracy.

In the regular arrangement region, it is preferable that the divided cells are arranged such that sub cell walls continuously exist on the first extension line and the second extension line.
In this case, by providing the sub cell wall continuously, the sub cell wall functions like a support column and the strength is increased, so that it is difficult to contract. Therefore, the dimensional accuracy can be further improved.

In the regular arrangement region, it is preferable that the divided cells are arranged so that every other subcell wall exists on the first extension line and the second extension line.
In this case, it has an appropriate opening area by reducing the number of divided cells while maintaining the dimensional accuracy by intermittently existing the subcell wall on the first extension line and the second extension line, Pressure loss can be further reduced.

Moreover, it is preferable that the said division | segmentation cell is formed only in the position used as the said discharge channel (Claim 6).
In this case, since the sub-cell wall is not provided in the introduction passage, the pressure loss generated in the introduction passage can be kept low.

In addition, it is preferable that all the main cells in the outer peripheral area are the divided cells.
In this case, since the subcell wall increases in the outer peripheral region, the heat resistance is increased, and the rigidity is increased and the contraction is less likely to occur. Therefore, the dimensional accuracy can be further improved.

Preferably, the divided cell in the outer peripheral region is a third divided cell in which the sub-cell wall is formed on both the first diagonal line and the second diagonal line.
In this case, the strength balance of the outer peripheral region becomes good, and further, there is no variation in the shrinking direction and it is difficult to shrink, so that the dimensional accuracy can be further improved.

The base material is preferably made of ceramics whose main component is cordierite (Claim 9).
Currently, SiC is mainly used as the base material, but cordierite has lower heat resistance than this. Therefore, the above configuration is particularly effective. Further, by using cordierite, the cost can be reduced as compared with the case of SiC.

In addition, the porosity of the substrate is preferably 45 to 70%.
In this case, the purification performance of the filter can be enhanced while maintaining the pressure loss of the filter low. The porosity is pore volume / base material volume × 100 (%), and this porosity can be measured by determining the pore volume by mercury porosimetry using a porosimeter. When the porosity is less than 45%, there is a problem that the pressure loss is high. On the other hand, when the porosity is more than 70%, there is a problem that the strength of the exhaust gas purification filter is reduced. There is a risk that the purification performance will deteriorate.

(Example 1)
Examples relating to the exhaust gas purifying filter of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the exhaust gas purification filter 1 of this example includes an introduction passage 21 for introducing exhaust gas 9 (FIG. 2) containing particulates discharged from an internal combustion engine, and a porous partition wall for collecting the particulates. 25 and an exhaust gas purification filter 1 having a honeycomb-shaped substrate 2 provided with an exhaust passage 22 for exhausting exhaust gas after the particulates are removed.
The base material 2 has a main cell wall 251 in which the porous partition walls 25 are arranged in a square lattice shape, and a main cell 20 surrounded by the main cell wall 251, and has a skin layer 26 covering an outer peripheral side surface. In the main cell 20, the downstream end of the main cell 20 serving as the introduction passage 21 and the upstream end of the main cell 20 serving as the discharge passage 22 are closed by the plug member 4.

As shown in FIGS. 1 and 3, at least a part of the main cell 20 has a sub cell wall 3 arranged on one or both of the two diagonals of the square of the main cell 20 so as to divide the main cell 20. Divided cell 30 (31, 32, 33).
Inside the outer peripheral area within 5 cells from the skin layer 26, there is a regular array area in which the divided cells 30 are arranged with regularity (in this example, the entire area including the outer peripheral area is a regular array area). )
Within the regular array region, the first divided cell 31 in which the subcell wall 3 is formed only on the first diagonal line, and the subcell wall 3 is formed only on the second diagonal line orthogonal to the first diagonal line. There are always two types of the second divided cells 32, and the existence ratio is substantially the same.
Further, in the regular array region, the divided cells 30 separated by four in two directions parallel to the main cell wall 251 have the same shape, and the main cells 20 existing in the regular array region. The ratio of the divided cells 30 to the total number is 37.5%.
Further details will be described below.

As shown in FIGS. 1 and 2, the base material 2 has a cylindrical outer diameter shape, and has a large number of main cells 20 in the axial direction thereof. As described above, the main cell 20 is surrounded by the main cell walls 251 arranged in the form of a quadrangular lattice and serves as either the introduction passage 21 or the discharge passage 22. The introduction passage 21 and the discharge passage 22 are arranged alternately.
In FIG. 2, the subcell wall is omitted for the sake of clarity.

As shown in FIG. 3, the base material 2 of this example has a regular arrangement region inside the skin layer 26, and a part of the main cell 20 is on two diagonal lines in the quadrangle of the main cell 20. This is a divided cell 30 in which the subcell wall 3 is arranged on one or both.
As the divided cell 30 in this example, the first divided cell 31 in which the subcell wall 3 is formed only on the first diagonal line, and the second diagonal line in which the subcell wall 3 is orthogonal to the first diagonal line. And a third divided cell 33 in which the subcell wall 3 is formed on both the first diagonal line and the second diagonal line.

  In any divided cell 30, the four divided cells 30 that are separated from each other in two directions parallel to the main cell wall 251 have the same shape. That is, as shown in FIG. 3, when the first divided cell 31 a in FIG. 3 is selected as an arbitrary divided cell 30, the divided cells 31 b that are separated from each other by four in the horizontal direction of the main cell wall 251. , 31c have the same shape as the first divided cell 31a, and the divided cells 31d, 31e that are vertically separated from each other by four in the vertical direction of the main cell wall 251 are also the first divided cell 31a. Have the same shape.

Further, when the second divided cell 32a in the figure is selected as the arbitrary one divided cell 30, the divided cells 32b separated by four in the horizontal direction or the vertical direction of the main cell wall 251 as described above. 32e have the same shape as the second divided cell 32a.
Further, when the third divided cell 33a in the figure is selected as the arbitrary one divided cell 30, similarly to the above, the divided cell 33b separated by four in the horizontal direction or the vertical direction of the main cell wall 251. ˜33e have the same shape as the third divided cell 33a.

  Further, the first divided cells 31 are arranged so that the sub cell walls 3 continuously exist on the first extension line K which is an extension line of the sub cell wall 3 in any one first divided cell 31, The second divided cells 32 are arranged so that the sub cell walls 3 continuously exist on the second extension line L that is an extension line of the sub cell wall 3 in one second divided cell 32. The main cell 20 including the intersection of the first extension line K and the second extension line L has a subcell wall 3 formed on both the first diagonal line and the second diagonal line. This is a three-divided cell 33.

Further, as shown in FIG. 1, the divided cells 30 are formed only at positions where the discharge passages 22 are formed. As shown in FIGS. 1 and 2, the plug members 4 are disposed at both ends of the base material 2 as described above. The plug member 4 is disposed at the downstream end of the introduction passage 21 and the upstream end of the discharge passage 22, and is disposed so that the entire main cell 20, that is, the subcell wall 3 is hidden. Therefore, when viewed from the end face, quadrangular closed portions are alternately present, and the unblocked portions are in a state where the square main cells 20 are present.
Note that the surface of the main cell wall 251 and subcell wall 3, can be supported an oxidation catalyst or NO _X reduction catalyst, if necessary.

In manufacturing such an exhaust gas purification filter 1, the manufacturing process itself can adopt the same process as the conventional one. That is, a viscous raw material that is a material of the base material 2 is extruded as a honeycomb-shaped formed body, cut into a predetermined length, and the formed body is dried and fired. In addition, after the drying / firing, or in the previous step, the raw material to be the plug member 4 is disposed in the portion to be closed, and this is also dried / fired.
Here, as a characteristic of the exhaust gas purification filter 1 of this example, a mold (not shown) provided with slits corresponding to the main cell wall 251 and the subcell wall 3 is used as the mold during the extrusion molding. Is to use.

Next, the effect of the exhaust gas purification filter 1 of this example will be described.
In the exhaust gas purifying filter 1 of this example, as described above, a part of the main cells 20 is formed with the sub-cell wall 3 and divided into two triangular shapes, the first divided cell 31, the second divided cell 32, or The base material 2 that is one of the third divided cells 33 divided into four triangular shapes is used. Therefore, the heat capacity of the base material 2 is increased by an amount corresponding to the increase in the number of the subcell walls 3 as compared with the case where the base material 2 is not provided. An increase in heat capacity leads to an improvement in heat resistance. Therefore, the exhaust gas-purifying filter 1 is superior in heat resistance as compared with the case where the subcell wall 3 is not provided, and the frequency with which the collected particulates are burned and removed can be reduced as compared with the conventional case. .

The divided cells 30 are arranged with regularity so that the subcell walls 3 are continuously present. Therefore, the subcell wall 3 plays the role of a support, the strength balance of the base material 2 becomes good, and the variation in the shrinkage direction is small, so that the dimensional accuracy is improved.
Further, the divided cells 30 with respect to the total number of the main cells 20 existing in the regular array region are the same shape in the divided cells 30 that are separated by four in two directions parallel to the main cell wall 251. The ratio is 37.5%. Thereby, it can have a moderate opening area and can suppress a pressure loss small.
In addition, since the divided cells 30 are formed only at the positions where the discharge passages 22 are formed, the pressure loss generated in the introduction passage 21 can be kept low.

  Moreover, the base material 2 of this example consists of ceramics which have a cordierite as a main component. Cordierite has a drawback that its heat resistance is lower than SiC, which is currently the mainstream filter for exhaust gas purification. This drawback can be compensated by an increase in heat capacity due to the above configuration. Therefore, the exhaust gas purification filter made of cordierite, which is cheaper than SiC, can be promoted, and the overall exhaust gas purification system of the diesel engine can be reduced in price.

(Example 2)
In this example, as shown in FIG. 4, the divided cells 30 that are separated from each other by five in two directions parallel to the main cell wall 251 have the same shape, and the subcell wall 3 serves as the discharge passage 21. This is an example in which the structure is arranged not only at the position where the introduction passage 22 is provided. The ratio of the divided cells 30 to the total number of the main cells 20 existing in the regular array region is 36%. Other structures are the same as those in the first embodiment.
In this case, the pressure loss can be further reduced because the ratio of the divided cells 30 in the cross section of the base material is smaller and the open area is larger than in the first embodiment. In other respects, the same effects as those of the first embodiment can be obtained.

Example 3
In this example, as shown in FIG. 5, the divided cells 30 separated by six in two directions parallel to the main cell wall 251 have the same shape. The ratio of the divided cells 30 to the total number of the main cells 20 existing in the regular array region is 27.8%. Other structures are the same as those in the first embodiment.
In this case, the pressure loss can be further reduced because the ratio of the divided cells 30 in the cross section of the base material is small and the open area is large compared to the case of the first embodiment. In other respects, the same effects as those of the first embodiment can be obtained.

Example 4
In this example, as shown in FIG. 6, the same subcell wall 251 is disposed at a position shifted by one cell in the right direction in FIG. Also in this case, the divided cells 30 separated by five in two directions parallel to the main cell wall 251 have the same shape, and not only the position where the subcell wall 3 becomes the discharge passage 21 but also the introduction passage. It has a structure that is also disposed at a position 22. The ratio of the divided cells 30 to the total number of the main cells 20 existing in the regular array region is 64%. Other structures are the same as those in the second embodiment.
In this case, the heat resistance and rigidity are increased by the amount of increase in the subcell wall 3 as compared with the case of the second embodiment, and the dimensional accuracy is further improved since it is difficult to shrink.

(Example 5)
In the present example, as shown in FIG. 7, in the regular array region, every other subcell on the first extension line K and the second extension line L, except for the third divided cell 33 of the first embodiment. In this example, the divided cells 30 are arranged so that the walls 3 exist. The ratio of the divided cells 30 to the total number of the main cells 20 existing in the regular array region is 25%. Other structures are the same as those in the first embodiment.
In this case, since the subcell wall 3 does not continuously exist on the first extension line K and the second extension line L, the open area is larger than that of the first embodiment. Therefore, the pressure loss can be further reduced.

(Example 6)
In this example, as shown in FIGS. 8 and 9, the main cells 20 in the outer peripheral region P are all formed on both the first diagonal line and the second diagonal line. In this example, the third divided cell 33 is used. Other structures are the same as those in the first embodiment.
The outer peripheral area P in FIG. 8 is an area within 5 cells from the skin layer 26, and the main cells 20 in the outer peripheral area P are all the third divided cells 33 as shown in FIG. In the regular array region Q inside the outer peripheral region P, the divided cells 30 have a structure having regularity similar to that in the first embodiment.
In this case, compared to the first embodiment, the heat resistance and the rigidity are increased by the amount of increase in the subcell wall 3 in the outer peripheral region P, and all the main cells 20 in the outer peripheral region P are the third divided cells 33. For this reason, the balance of strength becomes good, and further excellent dimensional accuracy can be obtained.

The explanatory view which looked at the exhaust gas purification filter in Example 1 from the end face. Explanatory drawing seen from the longitudinal cross-section of the filter for exhaust gas purification in Example 1 (AA sectional view taken on the line AA in FIG. 1). Explanatory drawing seen from the cross section of the filter for exhaust gas purification in Example 1 (BB sectional view taken on the line in FIG. 2). The explanatory view which looked at the exhaust gas purification filter in Example 2 from the end face. Explanatory drawing which looked at the filter for exhaust gas purification from the end surface in Example 3. FIG. Explanatory drawing which looked at the filter for exhaust gas purification from Example 4 in Example 4. FIG. Explanatory drawing which looked at the filter for exhaust gas purification from Example 5 in Example 5. FIG. Explanatory drawing which looked at the filter for exhaust gas purification in Example 6 from the end surface. Explanatory drawing which shows the main cell in the outer peripheral area | region of the filter for exhaust gas purification in Example 6. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification filter 2 Base material 20 Main cell 21 Introduction passage 22 Discharge passage 25 Porous partition 251 Main cell wall 3 Sub cell wall 30 Division cell 31 1st division cell 32 2nd division cell 33 3rd division cell 4 Plug member

Claims (10)

Honeycomb comprising an introduction passage for introducing exhaust gas containing particulates discharged from an internal combustion engine, a porous partition wall for collecting the particulates, and an exhaust passage for exhausting exhaust gases after the particulates have been removed An exhaust gas purifying filter having a shaped substrate,
The base material has a main cell wall in which the porous partition walls are arranged in a rectangular lattice shape, a main cell surrounded by the main cell wall, and a skin layer that covers an outer peripheral side surface,
Among the main cells, the downstream end of the main cell serving as the introduction passage and the upstream end of the main cell serving as the discharge passage are closed by a plug member,
At least a part of the main cell is a divided cell in which a sub cell wall is arranged on one or both of two diagonals of a square of the main cell so as to divide the main cell,
Inside the outer peripheral region within 5 cells from the skin layer, there is a regular arrangement region in which the divided cells are arranged with regularity,
Within the regular array region, the first divided cell in which the subcell wall is formed only on the first diagonal line, and the second divided line in which the subcell wall is formed only on the second diagonal line orthogonal to the first diagonal line. There are always two types of two-divided cells, and the existence ratio is substantially the same,
Further, in the regular array region, the divided cells separated by n (n is a natural number of 4 or more) in two directions parallel to the main cell wall have the same shape, and the regular array The exhaust gas purifying filter, wherein a ratio of the divided cells to a total number of the main cells existing in the region is 70% or less.   2. The first divided cell is arranged in the regular array region so that the sub cell wall exists on a first extension line that is an extension line of the sub cell wall in any one of the first divided cells. The second divided cell is arranged so that the sub cell wall exists on a second extended line that is an extended line of the sub cell wall in any one of the second divided cells. filter.   4. The main cell including an intersection of the first extension line and the second extension line in the regular arrangement region according to claim 3, wherein the sub cell wall is on the first diagonal line and the second diagonal line. An exhaust gas purifying filter, characterized in that it is a third divided cell formed on both.   4. The exhaust gas according to claim 2, wherein the divided cells are arranged so that subcell walls continuously exist on the first extension line and the second extension line in the regular arrangement region. Filter for purification.   4. The division cell according to claim 2, wherein the divided cells are arranged so that every other sub cell wall exists on the first extension line and the second extension line in the regular arrangement region. Filter for exhaust gas purification.   The exhaust gas purifying filter according to any one of claims 1 to 5, wherein the divided cells are formed only at positions serving as the discharge passages.   The exhaust gas purifying filter according to any one of claims 1 to 6, wherein all main cells in the outer peripheral region are the divided cells.   8. The exhaust gas according to claim 7, wherein the divided cell in the outer peripheral region is a third divided cell in which the subcell wall is formed on both the first diagonal line and the second diagonal line. Filter for purification.   The exhaust gas purifying filter according to any one of claims 1 to 8, wherein the base material is made of ceramics whose main component is cordierite.   The exhaust gas purification filter according to any one of claims 1 to 9, wherein the porosity of the base material is 45 to 70%.

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