JP2009047124A - Exhaust gas purifying apparatus of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of obtaining reasonable cost and exhaust gas purifying performance of an exhaust gas purifying apparatus as a whole, while maintaining characteristics of a filter comprising silicon carbide (SiC). <P>SOLUTION: In the exhaust gas purifying apparatus, a honeycomb filter comprising silicon carbide (SiC) and a honeycomb filter comprising cordierite are tandemly arranged and are integrated such that respective positions of cells thereof are aligned. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that purifies exhaust gas from the internal combustion engine.

  The exhaust gas from an internal combustion engine contains particulate matter (PM) containing carbon as a main component. A technique for providing a particulate filter (hereinafter referred to as “filter”) for collecting particulate matter in an exhaust system of an internal combustion engine is known in order to prevent such particulate matter from being released into the atmosphere.

  Here, the above-described filter is generally constituted by a ceramic honeycomb structure formed of porous ceramic. This ceramic honeycomb structure is formed from SiC, SiN, metal, alumina, zirconia, ceria, titania, silica, cordierite, and the like. When the ceramic honeycomb structure is formed of these different materials, the mechanical properties or physical properties of the ceramic honeycomb structure are different depending on the materials, and thus the exhaust purification characteristics are different.

  On the other hand, in order to cope with the recent tightening of exhaust gas regulations, a technique for reducing the number of particulate matter discharged as well as the weight regulation of particulate matter in exhaust gas is desired. Regarding the above filter material, it has been found that if the filter is formed of silicon carbide (SiC), it is advantageous to reduce the number of particles of discharged fine particles, but only by silicon carbide (SiC). Forming a filter increases the cost.

Thus, there is a need for an exhaust purification device that can reduce the number of particulate matter discharged and that can reduce costs.
JP 2006-07100 A JP 2006-204979 A

  An object of the present invention is to provide a technique capable of obtaining a reasonable cost and exhaust purification performance as a whole exhaust purification apparatus while utilizing the characteristics of a filter formed of silicon carbide (SiC).

  In order to achieve the above object, the present invention combines a honeycomb structure filter formed from silicon carbide (SiC) and a honeycomb structure filter formed from cordierite in series so that the positions of the cells match each other. The greatest feature is that it is integrated into

More specifically, an exhaust gas purification apparatus for an internal combustion engine, which is provided in an exhaust passage of an internal combustion engine and purifies exhaust gas by capturing particulate matter in the exhaust gas passing through the exhaust passage,
The exhaust gas purification apparatus includes a first filter and a second filter that are honeycomb-shaped filters in which a cross section perpendicular to the exhaust passage direction is partitioned into a plurality of cells by porous cell partition walls,
The first filter is formed to include cordierite, the second filter is formed to include silicon carbide, and the shapes and cell sections in the cross section of the first filter and the second filter are substantially the same,
The first filter and the second filter are integrally arranged in series in the upstream and downstream direction of the exhaust passage so that the positions of the corresponding cells in each of the cross sections coincide with each other.

  Here, as described above, a filter formed of silicon carbide (SiC) has a characteristic that it is advantageous to reduce the number of particles of particulate matter discharged compared to a filter formed of cordierite. On the other hand, the cost is high.

  Therefore, by appropriately arranging the first filter formed of cordierite and the second filter formed of silicon carbide (SiC) in series as appropriate, both characteristics are balanced and desired characteristics are obtained. Can be obtained. Further, at that time, in the present invention, since the cells are integrally arranged so that the positions of the cells in the first filter and the second filter coincide with each other, it is possible to suppress an increase in the back pressure due to the positional deviation between the cells. .

  In the above description, the term “including cordierite” means that cordierite is a main component as a component affecting the exhaust gas purification characteristics of the filter, and other components are included as secondary components. I do not exclude that. The same applies to the case where the cordierite is formed. In addition, being formed containing silicon carbide means that silicon carbide is the main component as a component that affects the exhaust purification characteristics of the filter, and that it contains other components as a secondary component. Do not exclude. The same applies to the case of silicon carbide or silicon carbide.

  Further, in the present invention, outflow side cells are formed by clogging openings of some cells at the upstream end of the upstream filter of the first filter and the second filter, and the downstream side is formed. The inflow side cell may be formed by clogging the opening of another cell at the downstream end of the filter.

  By doing so, there is no clogging at the joint between the first filter and the second filter, and air permeability in each cell can be ensured, so that an increase in back pressure can be more reliably suppressed. .

  In the present invention, arranging the first filter and the second filter integrally in series means that the first filter and the second filter are arranged in series after bonding the first filter and the second filter. Are connected in series and then integrated by firing.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  In the present invention, it is possible to realize cost reduction and ensuring of exhaust purification characteristics as a whole exhaust purification apparatus while utilizing characteristics of a filter formed of silicon carbide (SiC).

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

FIG. 4 shows the internal structure of the conventional filter 15. 4A is a view seen from the exhaust passage direction (filter axial direction), and FIG. 4B is a cross-sectional view seen from the direction perpendicular to the exhaust passage direction. The filter 15 is a wall flow type filter, which is configured as a cylindrical ceramic filter as a whole and has a so-called honeycomb structure. The reason for making the honeycomb structure is that it has an advantage that the pressure loss is small even when the amount of collected fine particles is increased.

  In the filter 15, cells 20 that are a large number of through-holes having a substantially square cross section are regularly formed along the axial direction. The cells 20 are separated from each other by thin cell walls 22. Moreover, the opening part of each cell 20 is provided with the clogging 21 in any one of an upstream or downstream end surface. In this embodiment, the cross section of the filter 15 as viewed from the exhaust passage direction is such that the cells 20 are opened in a checkered pattern.

  More specifically, the outflow side cell 20a is formed by applying the upstream side clogging 21a to the cell opening on the upstream end surface of the filter 15. Further, the downstream side clogging 21b is applied to the cell opening portion on the downstream end face of the filter 15 to form the inflow side cell 20b. The cell walls 22 of the cells 20a and 20b adjacent to each other have pores to the extent that exhaust gas can pass but particulate matter cannot pass through. Therefore, when the exhaust gas passes through the filter 15, The particulate matter in the exhaust gas is purified by trapping the particulate matter inside or on the wall surface of the inflow side cell 20b.

  Generally, the filter 15 is formed of a ceramic sintered body made of silicon carbide (SiC) or cordierite. For example, in the case of the filter 15 formed of silicon carbide (SiC), the heat resistance and the heat conductivity are particularly excellent as compared with the filter 15 formed of cordierite, and the number of particles of fine particles in the exhaust gas regulation is regulated. There is a remarkable effect on it. However, on the other hand, there is also a disadvantage that the cost is high for a filter formed of cordierite.

  Therefore, in the present invention, by appropriately combining a filter formed of silicon carbide (SiC) and a filter formed of cordierite, the advantageous characteristics of the filter formed of silicon carbide (SiC) are maintained. Therefore, we decided to suppress the increase in cost.

  In FIG. 1, the schematic of the exhaust gas purification apparatus 1 in a present Example is shown. 1A is a view as viewed from the upstream side in the exhaust passage direction, FIG. 1B is a view as viewed from a direction perpendicular to the exhaust passage direction, and FIG. 1C is a downstream side in the exhaust passage direction. It is the figure seen from. As shown in FIG. 1, in the present embodiment, the first filter 1 a is disposed on the upstream side of the exhaust purification device 1, and the second filter 1 b is disposed on the downstream side, and are integrated by joining. The first filter 1a is made of cordierite, and the second filter 1b is made of silicon carbide (SiC).

  Both the first filter 1a and the second filter 1b are wall flow type filters, which are configured as cylindrical ceramic filters as a whole and have a so-called honeycomb structure. In both the first filter 1a and the second filter 1b, the cells 2 that are a large number of through-holes having a substantially square cross section are regularly formed along the axial direction. The cells 2 are separated from each other by thin cell walls 4. As can be seen from FIGS. 1A and 1C, the first filter 1a and the second filter 1b have the same outer shape and cell section.

And, the position of the first filter 1a and the second filter 1b in the vertical direction with respect to the passage direction of the exhaust gas (hereinafter referred to as the axial direction) so that the positions of the cells 2 in the first filter 1a and the second filter 1b match, The rotation angle with respect to the shaft is adjusted. Further, the outflow side cell 2a is formed by applying the upstream side clogging 3a to the cell opening in the upstream end face of the first filter 1a. Moreover, the inflow side cell 2b is formed by performing the downstream side packing 3b in the opening part of the cell 2 in which the upstream side packing 3a is not performed in the downstream end surface of the 2nd filter 1b. In addition, the length of the axial direction of the 1st filter 1a and the 2nd filter 1b is made equivalent.

  According to this, the low price which is the characteristic of the first filter 1a made of cordierite and the effectiveness of the second filter 1b made of silicon carbide (SiC) for the regulation of the number of particles in the exhaust gas regulation are balanced. I can play well.

  Next, the manufacturing procedure of the exhaust emission control device 1 in the present embodiment will be described with reference to FIGS.

  First, a paste in which a predetermined amount of an organic binder, water, and carbon powder is mixed with a meteorite powder is extruded into a filter shape having a plurality of cell passages. Thereafter, the extruded product is fired at 1800 ° C. in a nitrogen atmosphere. Thereby, the second filter 1b is formed. Further, as shown in FIG. 2 (a), among the plurality of cells 2, the downstream side openings of some of the cells 2 are clogged with paste using silica powder, and the inflow side cells 2b is formed.

  Next, using a paste obtained by mixing a predetermined amount of an organic binder, water, and carbon powder into a cordierite composition powder containing kaolin, talc, and alumina, the mixture is extruded into a filter shape having a plurality of cells 2. Thereafter, the extruded product is fired in an oxidizing atmosphere at 1430 ° C. Thereby, the first filter 1a as shown in FIG. 2B is formed.

  Next, as shown to Fig.3 (a), the rear-end part of the 1st filter 1a and the front-end part of the 2nd filter 1b are joined. At that time, the positions of the first filter 1a and the second filter 1b in the direction perpendicular to the axes and the angles around the axes are matched so that the positions of the corresponding cells 2 in the first filter 1a and the second filter 1b match. Specifically, the positions of the first filter 1a and the second filter 1b in the direction perpendicular to the axes may be adjusted using a laser displacement meter. Further, the angles around the axes of the first filter 1a and the second filter 1b may be adjusted, for example, by measuring the displacement of a specific cell wall 4 with a laser displacement meter, or the laser beam expanded to about the filter cross section. The angle may be adjusted so that the intensity of transmitted light is maximized.

  In addition, when the first filter 1a and the second filter 1b are joined, the first filter 1a and the second filter 1b are bonded. As an adhesive, a cordierite-based inorganic adhesive may be used, Further, silicon carbide (SiC) may be included.

  Thereafter, as shown in FIG. 3 (b), the upstream cuff 3a is made of ceramic at the opening of the cell 2 at the upstream end of the first filter 1a where the cuff 3b is not clogged at the downstream end of the second filter 1b. Applied. Then, in order to cure the plugs 3a and 3b applied to the first filter 1a and the second filter 1b, baking is performed at 1430 ° C. and 1800 ° C.

  According to the above configuration, the characteristics of the first filter 1a formed of cordierite and the second filter 1b formed of silicon carbide (SiC) can be balanced, and the particulate matter discharged in the exhaust gas regulation can be balanced. It becomes possible to cope with the regulation of the number of particles, and to suppress an increase in cost.

  In the above embodiment, the lengths in the axial direction of the first filter 1a and the second filter 1b are substantially the same, but this can be changed as appropriate in relation to the capturing ability of the particulate matter and the cost. is there.

Of course, the clogging 3a may be performed before firing the first filter 1a, and the clogging 3b may be performed before firing the second filter 1b, and may be cured simultaneously during each firing.

It is a figure which shows schematic structure of the exhaust gas purification apparatus by this invention. It is a figure for demonstrating the procedure which forms the 1st filter and 2nd filter by this invention. It is a figure for demonstrating the procedure which joins the 1st filter and 2nd filter in this invention, and forms an exhaust gas purification apparatus. It is a figure which shows schematic structure of the conventional exhaust gas purification apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Exhaust gas purification device 1a ... 1st filter 1b ... 2nd filter 2 ... Cell 2a ... Outflow side cell 2b ... Inflow side cell 3 ... Packing 3a ... Upstream side packing 3b ... Downstream side packing 4 ... Cell wall 15 ... Exhaust gas purification device 20 ... Cell 20a ... Outflow side cell 20b ... Inflow side cell 21 ... Packing 21a ... Upstream side 21b ... Downstream side 22 ... Cell wall

Claims (2)

An exhaust purification device for an internal combustion engine that is provided in an exhaust passage of the internal combustion engine and purifies the exhaust gas by capturing particulate matter in the exhaust passing through the exhaust passage,
The exhaust gas purification apparatus includes a first filter and a second filter that are honeycomb-shaped filters in which a cross section perpendicular to the exhaust passage direction is partitioned into a plurality of cells by porous cell partition walls,
The first filter is formed to include cordierite, the second filter is formed to include silicon carbide, and the shapes and cell sections in the cross section of the first filter and the second filter are substantially the same,
The internal combustion engine, wherein the first filter and the second filter are integrally arranged in series in the upstream and downstream direction of the exhaust passage so that the positions of the corresponding cells in each of the cross sections coincide with each other. Exhaust purification equipment. Outflow side cells are formed by clogging the openings of some of the cells at the upstream end of the upstream filter of the first filter and the second filter, and the other filter at the downstream end of the downstream filter. The exhaust purification device for an internal combustion engine according to claim 1, wherein the inflow side cell is formed by clogging the opening of the cell.

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