JP2002233722A - Filter for cleaning exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a cleaning efficiency of a particulate. SOLUTION: A wall flow type filter for cleaning an exhaust gas is provided with a large number of cells 10A an entrance end of each of which is opened and an exit end is sealed against an exhaust gas stream and a large number of cells 10B an entrance end of each of which is sealed and an exit end is opened and has a large number of apertures for passing the exhaust gas on an inner wall 11 of the cell. The cells 10A end of each of which is not sealed are adjacent to each other when viewing from an exhaust gas flowing-in side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wall flow type exhaust gas purifying filter (DPF) for collecting and treating particulates contained in exhaust gas from a diesel engine or the like.

[0002]

2. Description of the Related Art An example of a conventional wall flow type exhaust gas purifying filter is disclosed in Japanese Patent Application Laid-Open No. 9-94434. This corresponds to the inlet ends of a large number of cells 10 as shown in FIG.
The outlet ends are alternately plugged every other end, so that the catalyst is carried on the inner wall of the cell 10.

[0003]

However, in such an exhaust gas purifying filter, FIGS.
As described above, the exhaust gas flows into the cell 10 having the inlet end opened, passes through the catalyst portion of the inner wall of the cell 10, enters the cell 10 at the downstream part where the outlet end is opened, and is discharged. When the exhaust gas passes through the catalyst portion on the inner wall of the cell 10, the particulates are collected, and the particulates are burned by the action of the catalyst,
In this case, the exhaust gas activated by the heat passes through the catalyst portion and enters the downstream cell 10, so that the activated exhaust gas cannot be effectively used.

That is, at an exhaust temperature of 200 to 400 ° C., NO in exhaust gas is oxidized to NO _2, which oxidizes particulates to CO ₂ (2C + 2NO ₂ → 2CO _2).
+ N ₂ ), but NO ₂ is generated as shown in FIG. 12 mainly in the cell 10 at the downstream part of the passage through the catalyst portion, and such an effect cannot be expected. is there. In this case, be provided with a NO _X absorbent to the inner wall of the cell 10 (NO _X absorbent catalyst), NO ₂ flows into mostly wake cell 10 sites, also such an effect is not expected .

In order to forcibly purify the particulates accumulated on the catalyst portion on the inner wall of the cell 10, fuel is injected during the expansion stroke or the exhaust stroke of the engine and the fuel is burned by the catalyst. Heat (40
(0 ° C. or higher). In this case, the temperature inside the cell 10 on the downstream side increases, while the temperature inside the cell 10 on the collection side of the particulates is low, so that the particulates are efficiently purified. It was not possible, and more fuel was injected than necessary, causing fuel efficiency to deteriorate.

An object of the present invention is to solve such a problem.

[0007]

According to a first aspect of the present invention, there is provided a cell in which an inlet end is opened and an outlet end is plugged, and an inlet end is plugged and an outlet end is opened for an exhaust flow. In a wall-flow type exhaust gas purification filter having a large number of cells and having a large number of holes through which exhaust gas passes through the inner wall of the cell, two cells whose inlet ends are not plugged as viewed from the exhaust inflow side are adjacent to each other. are doing.

In a second aspect based on the first aspect, the adjacent cells are adjacent to each other in a set of two to four cells.

In a third aspect based on the first and second aspects, a catalyst is supported on the inner wall of the cell.

According to a fourth aspect of the present invention, there are provided a large number of cells having an inlet end open and an outlet end plugged with respect to an exhaust flow, and a plurality of cells having an inlet end plugged and an outlet end opened. In a wall flow type exhaust gas purifying filter having a large number of holes through which exhaust gas passes through an inner wall of a cell, an intermediate wall through which exhaust gas can pass in both directions is provided in the cell.

In a fifth aspect based on the fourth aspect, the intermediate wall is provided on both sides so as not to generate a differential pressure.

In a sixth aspect based on the fourth and fifth aspects, one to three intermediate walls are provided for each cell.

In a seventh aspect based on the fourth to sixth aspects, a catalyst is supported on the intermediate wall.

[0014]

According to the first to third aspects of the present invention, the particulates are trapped without significantly reducing the effective passage area of the exhaust gas, and the activated exhaust gas and the like can efficiently burn and purify the particulates.

In the fourth to seventh inventions, the particulates are collected without reducing the effective passage area of the exhaust gas, and the activated exhaust gas and the like can efficiently burn and purify the particulates.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 are a view of an exhaust gas purifying filter according to a first embodiment of the present invention viewed from an exhaust gas inflow side and a partial cross-sectional view thereof.

The exhaust gas purifying filter is composed of a large number of cells (through holes) 10 formed in the exhaust gas flow direction.

The cell 10 has a cell 10A with an open inlet end and a plugged outlet end, and a cell 10B with a plugged inlet end and an open outlet end (shown in black in FIG. 1). Part), and the cells 10A and 10B
Are formed such that four are arranged in a set.

That is, when viewed from the exhaust inflow side, four cells 10A whose inlet ends are not plugged are adjacent to each other.
Further, the cells are formed such that four cells 10B whose inlet ends are plugged are adjacent to each other.

The inner wall portions of each cell 10A, 10B (each cell 1
A number of holes (not shown) through which exhaust gas passes are formed in the (zero partition) 11, and a catalyst (not shown) for self-burning particulates is carried.

In this case, the catalyst is supplied to each cell 10A, 10B
May be carried on the surface of the inner wall portion 11 and on the surface of a number of holes through which exhaust gas passes.

For this catalyst, for example, metals such as platinum, palladium and rhodium are used.

With such a configuration, the exhaust gas flows into the cell 10A having an open inlet end, and the inflowing exhaust gas flows through the inner wall portion 11 of the adjacent cell 10A having a partially open inlet end. Pass through, the rest pass through the inner wall 11 with the adjacent cell 10B whose outlet end is open,
The exhaust gas that has entered the adjacent cell 10A is the inner wall 1 of the adjacent cell 10B whose outlet end is finally opened.
1 and each is discharged from the cell 10B.

For this reason, the particulates are divided into the cell 10A having the open end and the cell 10A having the open end.
B, not only are collected on the inner wall 11 between the adjacent cells 10A, but also between the adjacent cells 10A whose entrance ends are open.
Collected in 1.

The inner wall 1 between the adjacent cells 10A
When the particulates trapped in 1 are burned by the action of a catalyst or the like, the heat activates the exhaust gas in the cell 10A, and the NO in the exhaust gas in the cell 10A becomes NO ₂
Is oxidized to

FIG. 3 shows the NO ₂ generation amount in the conventional structure,
An experimental result with the NO ₂ generation amount in this structure is shown. Although the total NO ₂ generation amount is the same, the conventional structure generates a large amount of NO _{2 in} the area of the downstream cell (B in the figure), whereas the present structure uses the cell 10A having the open inlet end (FIG. It was confirmed that a large amount was generated in the region A).

Therefore, when the exhaust gas in the cell 10A passes through the inner wall portion 11 between the cell 10A and the cell 10B, the exhaust gas is trapped by the inner wall portion 11 between the cell 10A and the cell 10B due to NO ₂ in the exhaust gas. The combustion (oxidation to CO ₂ ) of the collected particulates is promoted, and the particulates are efficiently combusted and purified by the activated exhaust gas which has not been effectively used conventionally.

On the other hand, fuel is injected during the expansion stroke or the exhaust stroke of the engine, and the inner wall 11 of each of the cells 10A and 10B.
In the case of forcibly purifying the particulates accumulated in the fuel cell, the injected fuel (unburned fuel) is removed from the adjacent cells 10.
The catalyst of the inner wall portion 11 between A and the cells 10A and 10
Reaction (combustion) with the catalyst on the inner wall portion 11 between B and B
And the inner wall 1 between the cell 10A and the cell 10B.
Although the heat generated by the reaction with the catalyst 1 goes into the cell 10B whose outlet end is open, the temperature inside the cell 10A is sufficient due to the heat generated by the reaction of the catalyst on the inner wall 11 between the adjacent cells 10A. Temperature.

FIG. 4 and FIG. 5 show the results of a temperature rise experiment in the conventional structure and the results of the temperature rise experiment in the present structure. In the conventional structure, the temperature rise is small in the area of the cell (A in the figure) where the inlet end is open, and the temperature rise is large in the area of the cell (B in the figure) at the downstream part. Cell 1 with open entrance end
It was confirmed that the temperature rise in the area of 0A (A in the figure) increased similarly to the temperature rise in the area of the cell (B in the figure) at the downstream part.

Thus, the particulates accumulated on the inner wall 11 of each of the cells 10A and 10B are efficiently burned and removed. Therefore, it is possible to prevent fuel consumption from deteriorating by injecting more fuel than necessary.

The inner wall 11 of each cell 10A, 10B
May be provided with a NO _X absorbent (NO _X absorption catalyst) or an HC adsorbent. Further, the inner wall portion 11 between the adjacent cells 10B may not be provided.

FIG. 6 shows a second embodiment of the present invention. In the first embodiment, a cell 10A in which the inlet end is open and the outlet end is plugged, and the inlet end is plugged. The four cells 10B, which are stopped and whose outlet ends are open, are formed in such a manner that four cells are arranged in one set and two cells are arranged in one set. The rest is the same as the first embodiment.

In this manner, the particulates can be collected and the combustion can be purified without significantly reducing the effective passage area of the exhaust gas as the whole filter.

On the other hand, when the number of adjacent sets of cells 10B whose inlet ends are plugged and the number of adjacent sets of cells 10A whose inlet ends are open are increased, as shown in FIG. The effective passage area of the exhaust gas becomes smaller.
In addition, when the number of adjacent cells 10A is small when the inlet end is open, the area of the inner wall portion 11 between the cells 10A becomes small, and the purification efficiency of the exhaust gas or the particulates by the fuel injection after activation is reduced. As shown in FIG. 7, when the number of cells is four or more, the area of the inner wall portion 11 between the cells 10A becomes sufficient.
As shown in the figure, the increase is small.

Therefore, in order to collect the particulates and efficiently purify the combustion without significantly reducing the effective passage area of the exhaust gas, the inlet end is required as in the first and second embodiments. It is preferable to arrange two to four cells 10A each of which is open and whose outlet end is plugged and each of the cells 10B whose inlet end is plugged and whose outlet end is open.

FIG. 8 shows a third embodiment of the present invention, in which a cell 1 in which the inlet end is open and the outlet end is plugged.
The intermediate wall 20 is provided in 0A.

In this case, the cell 10 is viewed from the exhaust inflow side.
The cells A and the cells 10B whose inlet ends are plugged and whose outlet ends are open may be alternately arranged every other cell.

The intermediate wall 20 is formed in the exhaust flow direction so as not to generate a differential pressure on both sides. Thereby, particulates are collected on both sides of the intermediate wall 20. Also,
The intermediate wall 20 has an inner wall portion 11 of the first and second embodiments.
Similarly, a large number of holes (not shown) for passing exhaust gas in both directions are formed, and a catalyst (not shown) for self-burning the particulates is supported.

The inner wall 11 between the cell 10A and the cell 10B is also the same as that of the adjacent cell 1 of the first and second embodiments.
It is formed similarly to the inner wall portion 11 between 0A.

In this way, the particulates can be collected without reducing the effective exhaust gas passage area of the entire filter, and the combustion can be efficiently purified.

It is to be noted that one to three intermediate walls 20 may be provided in one cell 10A. When the number of the intermediate walls 20 is increased, the purification efficiency of the activated exhaust gas or the particulates by the fuel injection is improved as the area of the intermediate walls 20 is increased. However, in the case where the intermediate wall 20 is provided in the cell 10A, if the number is three or more, the increase in the purification efficiency of the particulate does not change.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an exhaust gas purifying filter according to a first embodiment as viewed from an exhaust gas inflow side.

FIG. 2 is a partial sectional view thereof.

FIG. 3 is a view showing an experimental result of NO ₂ generation amount.

FIG. 4 is a conventional temperature rise characteristic diagram.

FIG. 5 is a graph showing a temperature rise characteristic of the first embodiment.

FIG. 6 is a configuration diagram of an exhaust gas purifying filter according to a second embodiment as viewed from an exhaust gas inflow side.

FIG. 7 is a characteristic diagram showing a relationship among the number of plugged cell inlet ends, the effective passage area of exhaust gas, and the purification efficiency of particulates.

FIG. 8 is a configuration diagram of an exhaust gas purifying filter according to a third embodiment as viewed from an exhaust gas inflow side.

FIG. 9 is a configuration diagram of a conventional exhaust gas purifying filter viewed from an exhaust gas inflow side.

FIG. 10 is a diagram showing a flow of the exhaust gas.

FIG. 11 is a diagram showing a collection state of the particulates.

FIG. 12 is a diagram for explaining a reaction when the exhaust gas passes through a catalyst portion.

[Explanation of symbols]

 10A, 10B Cell 11 Inner wall part 20 Intermediate wall 1

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F01N 3/02 321 F01N 3/24 E 4G069 3/24 B01D 53/36 103C F-term (reference) 3G090 AA01 BA01 EA01 EA04 3G091 AA18 AB02 BA00 BA14 GA06 GB05W GB06W GB07W HA14 4D019 AA01 BC07 CA01 CB04 4D048 AA14 AB01 BA30X BA31X BA33X BB02 BB14 CC34 CC58 CD05 4D058 JA32 JA38 JA39 MA44 SA08 4G069 AA03 BB02ACA07 BCB7ABC7ABC7ABC

Claims (7)

[Claims] An exhaust flow is provided with a number of cells having an inlet end opened and an outlet end plugged, and a number of cells having an inlet end plugged and an outlet end opened, and provided on the inner wall of the cell. A wall-flow type exhaust gas purifying filter having a large number of holes through which exhaust gas passes, characterized in that, when viewed from the exhaust inflow side, cells whose inlet ends are not plugged are adjacent to each other. For filters. 2. The exhaust gas purifying filter according to claim 1, wherein two to four adjacent cells are adjacent to each other in a set. 3. The exhaust gas purifying filter according to claim 1, wherein a catalyst is carried on an inner wall of the cell. 4. An exhaust flow, comprising a large number of cells having an inlet end opened and an outlet end plugged, and a number of cells having an inlet end plugged and an outlet end opened. An exhaust gas purifying filter comprising a wall flow type exhaust gas purifying filter having a large number of holes through which exhaust gas passes, wherein an intermediate wall through which exhaust gas can pass in both directions is provided in the cell. 5. The exhaust gas purifying filter according to claim 4, wherein the intermediate wall is provided so as not to generate a differential pressure on both sides. 6. The exhaust gas purifying filter according to claim 4, wherein one to three intermediate walls are provided for each cell. 7. The exhaust gas purifying filter according to claim 4, wherein a catalyst is supported on the intermediate wall.