Exhaust purifying filter

The present invention relates to an exhaust purification filter that purifies the exhaust by removing the particulate from the exhaust including the particulate such as the exhaust from a diesel engine.

As a filter for removing patents (particulate matter: carbon fine particles, sulfur-based fine particles such as sulfate, high-molecular-weight hydrocarbon fine particles (SOF), etc., hereinafter referred to as PM), a catalyst is supported on the partition wall separating adjacent inflow cells. There is known a filter that is provided with a convex portion or a concave portion and supplies heat for oxidizing and removing PM from the convex portion or the concave portion (see, for example, Patent Document 1).<patcit num="1"><text>Japanese Patent Application Laid-Open No. 2005-118747</text></patcit><patcit num="2"><text>Japanese Patent Application Laid-Open No. 06-010649</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2001-349214</text></patcit><patcit num="4"><text>Japanese Unexamined Patent Publication No. 2002-364335</text></patcit><patcit num="5"><text>Japanese Unexamined Patent Publication No. 2004-316513</text></patcit><patcit num="6"><text>International Publication No. 02/084085 Pamphlet</text></patcit>

<p> By the way, a PM deposit layer is formed on the surface of the partition wall by depositing PM. Then, a void is formed between the PM deposit layer and the partition wall by oxidizing the PM deposit layer by the catalytic reaction of the catalyst supported by the partition wall. Here, when the catalyst is supported on the partition wall, the distribution of the catalyst becomes non-uniform, and a portion where the catalyst does not exist is generated in the partition wall. This void is retained by supporting the PM deposit layer by PM deposited on the catalyst-free portion of the partition wall, and the catalytic reaction of the catalyst supported by the partition wall may make it difficult to oxidize the PM deposit layer. .. In addition, PM may be further deposited in the PM sedimentary layer, causing a shortage of PM supply to the partition wall, and efficient PM removal may not be possible.</p><p> The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique for efficiently oxidizing and removing PM in an exhaust gas purification filter.</p>

<p> In the present invention, the following configuration is adopted. That is, it is an exhaust purification filter that purifies the exhaust gas by removing the catalyst from the exhaust gas containing the catalyst discharged from the internal combustion engine, and has a cell into which the exhaust gas flows in and a partition wall for partitioning the cell. The exhaust gas purification filter is characterized in that a convex portion is formed on the partition wall and a catalyst for oxidizing the particulate by a catalytic reaction is supported on the partition wall including the convex portion.</p><p> Here, a PM deposit layer is formed on the surface of the partition wall by depositing PM. Then, a void is formed between the PM deposit layer and the partition wall by oxidizing the PM deposit layer by the catalytic reaction of the catalyst supported by the partition wall. Here, when the catalyst is supported on the partition wall, the distribution of the catalyst becomes non-uniform, and a portion where the catalyst does not exist occurs on the partition wall. This void is retained by supporting the PM deposit layer by PM deposited on the catalyst-free portion of the partition wall, and the catalytic reaction of the catalyst supported by the partition wall may make it difficult to oxidize the PM deposit layer. .. In addition, PM may be further deposited in the PM sedimentary layer, causing a shortage of PM supply to the partition wall, and efficient PM removal may not be possible.</p><p> Therefore, in the present invention, a convex portion is formed on the surface of the partition wall, and a catalyst for oxidizing the particulate by a catalytic reaction is supported on the partition wall including the convex portion. According to this, PM around the convex portion can be oxidized by the catalytic reaction of the catalyst supported by the convex portion. Then, by oxidizing the PM around the convex portion, a passage leading from the center of the cell to the gap between the PM deposit layer and the partition wall is formed, and PM is sent from the center side of the cell to the gap through the passage. be able to. Then, the delivered PM is oxidized by the catalytic reaction of the catalyst supported by the partition wall. In addition, the PM sedimentary layer can be subdivided by oxidizing the PM around the convex portion. Then, the subdivided PM deposit layer crushes the voids by the exhaust pressure from the central side of the cell and is pressed against the partition wall, and is oxidized by the catalytic reaction of the catalyst carried by the partition wall. Therefore, PM can be efficiently oxidized and removed.</p><p> Specifically, a particulate deposit layer is formed on the surface of the partition wall by depositing the particulate, and the particulate deposit layer is oxidized by a catalytic reaction of a catalyst carried by the partition wall to form the particulate. A gap is formed between the deposit layer and the partition wall, and the gap is held by supporting the particulate deposit layer by the particulate being deposited on the catalyst-free portion of the partition wall, and the convex portion is held. By oxidizing the particulate around the convex portion by the catalytic reaction of the supported catalyst, a passage leading from the central portion of the cell to the void is formed, and the passage from the central portion side of the cell to the void is formed. It is preferable that the particulate is fed, and the fed particulate is oxidized by the catalytic reaction of the catalyst carried by the partition wall.</p><p> According to this, PM is not further deposited in the PM sedimentary layer, and PM can be efficiently removed by constantly supplying PM to the partition wall.</p><p> Specifically, the particulate deposit layer is formed on the surface of the partition wall by depositing the particulate, and the particulate deposit layer is oxidized by the catalytic reaction of the catalyst carried by the partition wall. A gap is formed between the particulate deposit layer and the partition wall, and the gap is held by supporting the particulate deposit layer by the particulate deposited on the catalyst-free portion of the partition wall, and the convex The part subdivides the particulate deposit layer by oxidizing the particulate around the convex portion by the catalytic reaction of the supported catalyst, and the subdivided particulate deposit layer is from the central side of the cell. It is preferable that the void is crushed by the exhaust pressure of the partition, pressed against the partition wall, and oxidized by the catalytic reaction of the catalyst carried by the partition wall.</p><p> According to this, the PM deposition layer can be easily oxidized by the catalytic reaction of the catalyst supported on the partition wall, and PM can be efficiently removed by continuously supplying PM to the partition wall.</p>

<p> According to the present invention, PM can be efficiently oxidized and removed in an exhaust gas purification filter.</p>

Specific examples of the present invention will be described below.

&lt;Example 1&gt; FIG. 1 is a perspective view showing an outline of an exhaust gas purification filter according to a first embodiment of the present invention. The exhaust purification filter 1 is arranged in the exhaust passage of a water-cooled 4-cycle diesel engine.

The exhaust gas purification filter 1 has a honeycomb shape with a wall flow structure made of cordierite, and has an inflow side cell 2 in which the exhaust gas flows in, an outflow side cell 3 adjacent to the inflow side cell 2 and an exhaust gas outflow. It is composed of a filter partition wall 4 for partitioning cells 2 and 3, and a filter partition wall 4.

The inflow side cell 2 and the outflow side cell 3 are holes having a rectangular cross section perpendicular to the exhaust flow direction. The inflow side cell 2 and the outflow side cell 3 are adjacent to each other across their respective sides, and the inflow side cells 2 and the outflow side cells 3 are adjacent to each other across their respective corners.

Figure 2 shows a cross section of the exhaust gas purification filter 1 in the exhaust flow direction. The inflow side cell 2 and the outflow side cell 3 have a square tubular shape extending straight in the exhaust flow direction. The inflow side cell 2 is clogged on the downstream side in the exhaust flow direction. Further, the outflow side cell 3 is clogged on the upstream side in the exhaust flow direction. Therefore, the exhaust gas that has flowed into the exhaust gas purification filter 1 first flows into the inflow side cell 2, and then enters the filter partition wall 4 that separates the inflow side cell 2 and the outflow side cell 3. After that, the exhaust gas that has passed through the filter partition wall 4 and reached the outflow side cell 3 flows out from the outflow side cell 3 (see the arrow in FIG. 2).

Here, the filter partition wall 4 allows the exhaust gas to pass through, but does not allow the PM contained in the exhaust gas to pass through. Therefore, PM is deposited on the side surface of the inflow side cell 2 of the filter partition wall 4. The filter partition wall 4 that exerts such a function is formed of a porous ceramic or the like having pores inside. Examples of the material of the porous ceramic include nitride ceramics such as aluminum nitride, silicon nitride, boron nitride and titanium nitride, carbide ceramics such as silicon carbide, zirconium carbide, titanium carbide, tantalum carbide and tungsten carbide, alumina and zirconia. Examples thereof include oxide ceramics such as carbide, mulite, and silica. Further, it may be formed from two or more kinds of materials such as a composite of silicon and silicon carbide and aluminum titanate.

A catalyst is supported on the filter partition wall 4. The catalyst is supported on the side surface of the inflow side cell 2 of the filter partition wall 4 and the surface of the pores inside the filter partition wall 4. Alumina powder containing Pt is used as the catalyst, and when the exhaust comes into contact with the catalyst, HC, CO, and NO are oxidized by Pt to generate a heat of reaction. Oxidize and remove PM. The distribution of the catalyst supported on the filter partition wall 4 is non-uniform, and the filter partition wall 4 has a portion where the catalyst does not exist.

Then, as shown in FIG. 3, a convex portion 5 is formed on the filter partition wall 4 of the inflow side cell 2. In this embodiment, one convex portion 5 is provided at the center of each side in a cross section perpendicular to the exhaust flow direction of the inflow side cell 2, and one is provided at each corner. Therefore, there are a total of eight convex portions 5 shown in FIG. All the convex portions 5 have a quadrangular cross section.

The convex portion 5 is continuously formed in the entire longitudinal direction from the inflow side end to the outflow side end of the exhaust gas purification filter 1. The reason why the convex portions 5 are continuous in the entire longitudinal direction of the exhaust gas purification filter 1 in this way is to obtain high strength, improve the strength of the filter partition wall 4, and form the exhaust gas purification filter 1 by extrusion molding. The convex portion 5 is a part of the filter partition wall 4, and the catalyst is also supported on the convex portion 5.

The shape of the convex portion 5 may be triangular or trapezoidal in cross section, and is not limited to this embodiment. Further, the convex portion 5 does not have to be continuous in the entire longitudinal direction of the exhaust gas purification filter, and the arrangement location thereof is not particularly limited, and is not limited to this embodiment.

Next, the PM deposit layer formed on the filter partition wall 4 of the inflow side cell 2 will be described. As described above, when the exhaust gas passes through the exhaust gas purification filter 1, the PM contained in the exhaust gas is deposited on the surface of the filter partition wall 4 of the inflow side cell 2 and is deposited on the filter partition wall 4 as shown in FIG. Form PM deposit layer 6.

The PM deposit layer 6 is formed between the PM deposit layer 6 and the filter partition wall 4 as shown in FIG. 5 by oxidizing the PM deposit layer 6 by the reaction heat of the above-mentioned catalytic reaction of the catalyst carried by the filter partition wall 4. A void 7 is formed in the space. Here, when the catalyst is supported on the filter partition wall 4, the distribution of the catalyst becomes non-uniform, and a portion where the catalyst does not exist is generated in the filter partition wall 4. This void 7 is retained by the PM deposition layer 6 being supported by the PM deposited in the catalyst-free portion of the filter partition wall 4.

Therefore, the catalytic reaction of the catalyst supported by the filter partition wall 4 may make it difficult to oxidize the PM deposition layer 6. In addition, PM may be further deposited in the PM deposition layer 6, causing a shortage of PM supply to the filter partition wall 4, and efficient PM removal may not be possible.

On the other hand, in this embodiment, as described above, the convex portion 5 is formed on the filter partition wall 4 of the inflow side cell 2, and the filter partition wall 4 including the convex portion 5 is supported with a catalyst that oxidizes PM by a catalytic reaction. There is. According to this, PM around the convex portion 5 can be oxidized and PM can be removed by the catalytic reaction of the catalyst carried by the convex portion 5.

Then, first, as shown in FIG. 6, a passage leading from the central portion of the inflow side cell 2 to the void 7 between the PM deposition layer 6 and the filter partition wall 4 by oxidizing the PM around the convex portion 5. 8 can be formed, and PM (black dots shown in FIG. 6) can be sent into the gap 7 from the central side of the inflow side cell 2 through the passage 8 as shown by the dotted arrow in FIG. Then, the sent PM is oxidized and removed by the reaction heat of the catalytic reaction of the catalyst carried on the filter partition wall 4.

Therefore, PM is not further deposited on the PM deposition layer 6, and PM can be efficiently removed by constantly supplying PM to the filter partition wall 4.

Secondly, the PM sedimentary layer 6 can be subdivided by oxidizing the PM around the convex portion 5. Then, as shown in FIG. 7, the subdivided PM deposit layer 6 is pressed against the filter partition wall 4 by crushing the void 7 by the exhaust pressure indicated by the arrow in FIG. 7 from the central side of the inflow side cell 2. It is oxidized and removed by the reaction heat of the catalytic reaction of the catalyst carried on the filter partition wall 4.

Therefore, the PM deposition layer 6 can be easily oxidized by the reaction heat of the catalytic reaction of the catalyst carried on the filter partition wall 4, and PM (PM deposition layer 6) is constantly supplied to the filter partition wall 4 for efficient PM. (PM sedimentary layer 6) can be removed.

As described above, in this embodiment, PM can be efficiently oxidized and removed by the first and second actions.

The exhaust gas purification filter according to the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the gist of the present invention.

<figref num="1">It is a figure which shows the schematic perspective of the exhaust gas purification filter.</figref><figref num="2">It is a figure which shows the cross section along the exhaust flow direction of an exhaust gas purification filter.</figref><figref num="3">It is a figure which shows the inflow side cell of an exhaust gas purification filter.</figref><figref num="4">It is a figure which shows the state which PM sedimentation layer was formed in the inflow side cell of an exhaust gas purification filter.</figref><figref num="5">It is a figure which shows the state which the PM deposition layer and the void are formed in the inflow side cell of the exhaust gas purification filter.</figref><figref num="6">It is a figure which shows the state which PM is sent to the gap of the inflow side cell of an exhaust gas purification filter through a passage.</figref><figref num="7">It is a figure which shows the state which the PM deposition layer of the inflow side cell of an exhaust purification filter crushes a void and is pressed against a filter partition wall.</figref>

Code description

1 Exhaust purification filter 2 Inflow side cell 3 Outflow side cell 4 Filter partition wall 5 Convex part 6 PM Deposit layer 7 Void 8 Passage