JPH0127767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas purification structure for purifying particulates containing carbon as a main component in exhaust gas discharged from an internal combustion engine of an automobile or the like.

Conventionally, this type of device has a honeycomb structure in which a large number of through holes are partitioned by partition walls.

In the conventional system described above, fine particles mainly composed of carbon are captured on the inner surface of the partition wall by passing the exhaust gas through the through hole, but the interaction between the partition wall and the exhaust gas is poor, resulting in so-called blow-out development. There was a problem that fine particles were not captured efficiently.

In order to solve this problem, the present inventor has previously filed an improvement plan in Japanese Patent Application No. 56-32847. In this prior application, approximately half of the openings of one of the opening ends of the through hole are closed, and the openings are almost uniformly distributed, and one of the openings of the other opening of the through hole is not closed. It has a structure in which openings corresponding to the portions are closed and a large number of pores are formed in the partition wall to communicate adjacent through holes.

In the structure of the prior application, the exhaust gas that enters from one opening side of the through hole flows through the pores of the partition wall to the adjacent through hole and is exhausted from the other opening side, so that the relationship between the partition wall and the exhaust gas is The interaction is improved, and the efficiency of trapping fine particles mainly composed of carbon can be improved compared to the conventional example described above.

However, although the structure of the prior application can certainly improve the trapping efficiency of particulates, the pressure loss when the exhaust gas passes through increases, and when installed in a car, for example, the back pressure of the engine increases, resulting in poor fuel efficiency or The problem arises that the engine output is reduced.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an exhaust gas purifying structure that suppresses the pressure increase during exhaust gas passage and can efficiently capture particulates.

Therefore, the present invention provides an exhaust gas purification structure in which one opening end of a through hole is closed and an opening corresponding to a portion of the other opening end of the through hole where one opening is not closed is closed. A particulate blowhole having a diameter larger than the pore is provided in a path through which exhaust gas passes from one end of the through hole to the other end.

The present invention will be explained in detail below using specific examples.

Example 1 In Fig. 1, A is the exhaust gas purifying structure of the present invention, and its external shape is 100 mm in diameter and 120 mm in length.
mm, 100 cells/ ^inch2 . In this structure A, the partition wall 3 of the large number of through holes 2 forming the honeycomb structure 1 has a large number of pores 31 (distribution of about 1 micron to 90 microns) and 100 microns, as the detailed structure is shown in FIG. Particle blowholes 32 of micron size or larger are uniformly distributed, so that adjacent through-holes 2 communicate with each other.

The through-hole openings on one end face of the honeycomb structure 1 are arranged in every other row of the honeycomb structure 1 in each row in one direction (see FIG. 1) and in each row in the perpendicular direction (see FIG. 1). It is closed with a cover member 4 made of the same material as . Further, on the other end face of the honeycomb structure 1, the through-hole openings which are not closed on the one end face are closed with a cover member 4 similar to the above.

Therefore, if this structure A is now installed in the middle of the exhaust pipe of an automobile, exhaust gas containing carbon particles will flow into the structure A from the I direction and flow out through the partition wall 3 in the O direction. When the exhaust gas passes through the partition wall 3, part of it passes through the blowhole 32 and the rest passes through the pores 31. Although the carbon particulates in the exhaust gas that has passed through the blowhole 32 are hardly collected, the overall collection efficiency is a certain level (this will be described later).

Next, a method for manufacturing the structure A will be described. Add 280~325 meshes (53~
50 g of iron powder of 44 microns), 5 g of iron powder of 100-145 mesh (149-105 microns), 90 g of methyl cellulose and 400 c.c. of water were added and kneaded. The obtained slurry is extruded using a well-known honeycomb molding die and dried at 80° C. for 10 hours. Next, both end surfaces of the honeycomb structure 1 where the through holes 2 are opened are covered with ceramic green sheets made from the same material as the honeycomb structure 1, and as shown in FIG. Make sure there are every other opening. The other end surface opens a through hole which is closed at the one end surface. This from 1300
Structure A was obtained by firing at 1470°C for 5 hours.

Structure A obtained in this way was installed in the middle of the exhaust pipe of a 2200 c.c. diesel engine and its collection characteristics were measured. As a result, the hourly average collection efficiency was 60.
%, and the pressure loss after 1 hour was 250 mmAq. The engine conditions were 1000 rpm and no load.

Next, the pore distribution of Structure A is shown in FIG. From Figure 3, pores 31 of several microns and tens of microns
It is thought that the pores of 100 microns or more acted as the blowholes 32 because they effectively acted to collect carbon fine particles. In this example, the volume of pores of 100 microns or more was approximately 10% of the total pore volume.

Although cordierite was used as the ceramic raw material in this embodiment, any ceramic raw material such as alumina, mullite, spodumene, etc. may be used. In addition to iron powder, additives for forming pores and blowholes include copper powder, nickel powder, cobalt powder, feldspar powder, etc., which are eutectic, solid solution, or melted at below the ceramic firing temperature. Any substance that produces a liquid phase may be used.
Furthermore, it is of course possible to adjust the particle size of the additive to obtain a pore distribution as shown in FIG. 4.

Next, in the above Example 1, the volume ratio of blowholes of 100 microns or more and the hourly average collection efficiency of the structures fabricated by varying the amount and particle size of iron powder,
The relationship between pressure loss after 1 hour was measured in the same manner as in Example 1, and the results are shown in FIG.

From Figure 5, if the ratio of the volume of the blow hole of 100 microns or more to the total pore volume (total volume of the pore and the blow hole) is less than 1%, the pressure loss is 500 mmAg.
If it exceeds 20%, it is undesirable because it causes a reduction in engine output and worsens fuel efficiency, and if it exceeds 20%, it is undesirable because the collection efficiency becomes less than 50%. Therefore, it is appropriate that the volume of the blowholes of 100 microns or more be 1 to 20% of the total volume.

In this embodiment, the blowhole 32 has a diameter of 100 microns or more, and the pores 31 have a smaller diameter than the blowhole 32 and have the pore distribution shown in FIG. 3 or 4, but are not limited to these. It never happens.
In other words, since the present invention aims to suppress an increase in pressure loss by using the blowhole 32, it is sufficient that the blowhole 32 and the pores 31 have relatively different diameters. Therefore, it goes without saying that their diameters can be arbitrarily adjusted depending on the application, usage conditions, etc. However, the maximum diameter of the blowhole is up to the equivalent circular diameter of one through hole. If this is exceeded, most of the exhaust gas will flow through the inlet, and particulates will not be captured. The same can be said of the blowholes in the examples described later.

Further, in the present invention, the cross-sectional shape of the through hole is not limited to a square, but may be rectangular, triangular, hexagonal, circular, etc., and any of them can be used.

Example 2 Structure A of this example has a structure similar to that of Example 1 (however, the pore distribution is shown by the broken line in Fig. 3).
However, in Example 2, some of the through-holes 2 are not closed on both end faces, as shown in FIGS. 6a and b, to provide blowholes 5. It is something. In structure A obtained in this example, the ratio of the opening area of the through holes that are not closed on both end faces is the opening area of the through holes on one side of the honeycomb structure 1 (total opening area on one side before closing)
It was about 4% of the total.

The collection characteristics of Structure A were measured in the same manner as in Example 1. As a result, the 1-hour average collection efficiency was 63%, and the pressure loss after 1 hour was 280 mmAq.

Next, as in Example 1, FIG. 7 shows the results obtained when the ratio of the opening area of the through hole, which is not closed on both end faces, was changed. From FIG. 7, it is seen that less than 0.5% or more than 10% is not preferable for the same reason as in Example 1.

Incidentally, the through-holes which are not closed on both end faces may not only be arranged as shown in FIGS. 6a and 6b, but may also be randomly distributed or may be gathered in a portion.

Example 3 Structure A of this example has a structure similar to that of Example 1 (however, as shown by the broken line in FIG. 3, there are no pores of 100 microns or more in the partition wall), but the partition wall 3 has a structure similar to that of Example 1. As shown in FIG.
A hole of micron size or more is provided and used as a punch hole 6.

How the pressure loss and collection efficiency change depending on the ratio of this hole 6 to the opening area of the through-hole 2 on one side (total opening area on one side before closing) was investigated in the same manner as in Example 1. As a result of the measurement, it was found that for the same reason as in Example 2, the total area of the holes 6 should account for 0.5 to 10% of the opening area of the through holes 2.

In addition, in Example 3, the diameter of the blowhole 6 is 100 mm.
Although the diameter is 100 microns or more, it is not particularly limited to 100 microns or more, as long as it is relatively large with respect to the pores of the partition wall for the same reason as explained in Example 1. However, the maximum diameter of the blowhole 6 is determined for the same reason as in the first embodiment.

As described in detail above, in the present invention, it is possible to efficiently capture fine particles whose main component is carbon in the exhaust gas, and it is also possible to suppress an increase in pressure drop when the exhaust gas passes through the exhaust gas.

Therefore, the present invention can provide a highly practical exhaust gas purifying structure.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the structure of the present invention, FIG. 2 is a schematic sectional view showing the main part of FIG. 1,
Figures 3 and 4 are characteristic diagrams showing the relationship between the pore diameter and pore volume of the partition wall in Figure 2, and Figure 5 is a characteristic diagram for explaining the effects of the structure in Figures 1 and 2. FIG. 6 is a plan view showing another embodiment of the present invention, and FIG. 6a is a plan view showing another embodiment of the present invention.
Figure 6b is a view viewed from the other end, Figure 7
The figure is a characteristic diagram for explaining the function and effect of the structure shown in FIG. 6, and FIG. 8 is a perspective view showing still another embodiment of the present invention. 2... Through hole, 3... Partition wall, 31... Pore, 3
2...Stairwell hole, 4...Cover member, 5, 6...Stairwell hole.

Claims (1)

[Claims] 1. By passing exhaust gas through a large number of through holes,
In an exhaust gas purification structure that captures and purifies fine particles whose main component is carbon in the exhaust gas, a partition wall that partitions each of the through holes has a large number of narrow holes that communicate with each other. forming a hole, and closing approximately half of the openings that are substantially uniformly distributed among one open end of the through hole, and
The basic structure is such that an opening corresponding to a portion of the other open end of the through hole that is not closed is closed, and the exhaust gas passes from one end side of the through hole to the other end side. 1. A structure for purifying exhaust gas, characterized in that a particulate blowhole having a diameter larger than the pore is provided in the path. 2. The exhaust gas purifying structure according to claim 1, wherein the particulate blowhole is formed in the partition wall. 3. The structure for exhaust gas purification according to claim 1 or 2, wherein both ends of the through hole are directly connected to form a non-closed area that is a particulate blowhole. 4. Exhaust gas purification according to claim 2, characterized in that the volume of the blowhole provided in the partition wall accounts for 1 to 20% of the total volume of the blowhole and the pores. Structures for use. 5. The area of the non-closed region constituting the blowhole is 0.5 to 10% of the opening area on one side of the through-hole before it is closed, according to claim 3. Exhaust gas purification structure. 6. The blow hole provided in the partition wall is mechanically provided to the partition wall from the outside of the structure, and the area of the blow hole is equal to the area of the opening before closing on one side of the through hole. The structure for exhaust gas purification according to claim 1, characterized in that the structure occupies 0.5 to 10% of the area.