JPS6146216A - Porous ceramic structure - Google Patents

Abstract

PURPOSE:To provide the titled structure capable of collecting efficiently and uniformly fine particles over the full length of the structure by providing a group of inlet holes and a group of outlet holes in the axial direction on both sides of a partition wall, and furnishing a reticular body having a mesh coarser than that of the partition wall in the inlet hole. CONSTITUTION:A filter medium 41 consists of porous ceramic such as cordierite is provided with a group of inlet holes 22 perforated in the axial direction and a group of outlet holes 23 adjacent to said inlet holes 22 across a partition wall 24 having uniform thickness and consisting of a three-dimentional reticular body of about 1,600-2,500 mesh/in<2>, and both inlet holes 22 and outlet holes 23 have an opening or a seal respectively at the front and the rear end. A reticular body 22b having a mesh coarser than that of said partition wall 24 is provided in said inlet hole 22. Said reticular body is appropriately constituted of a three-dimensional reticular structure of 25-144 mesh/in<2> or a pelletized granular body of alumina, etc. having about 2mm. size.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a porous ceramic structure, which is mainly used for collecting fine particles suspended in the exhaust gas of internal combustion engines. It's about the body.

(Prior art) Generally, when collecting particulates emitted from diesel engines, it is known that ceramic foam with a three-dimensional mesh-like skeleton structure, porous ceramic with a honeycomb structure, etc. are suitable. ing. In particular, the honeycomb-structured ceramic foam, which has a large number of holes that do not pass through each other (so that they do not interfere with each other) from both end faces of the ceramic structure, has low ventilation resistance and - It is one.

In general, a particulate collection device for an internal combustion engine is 4RIR as shown in FIG. In other words, as shown in Fig. 6, the fine potato collection @ff1A is connected to the exhaust gas collecting pipe 2' of the diesel B1rA1, and the exhaust gas inlet 3a and outlet thereof communicate with the exhaust gas collecting pipe 2. 3b, and a filter member 4 for collecting particulates is installed inside the container 3.
and an electric heater 5 coupled to an end surface of the filter member 4 on the exhaust gas inlet side. The electric heater 5 burns the particulates collected by the filter member 4 to regenerate the filter member 4, and is energized by the battery 6 at f,
II fi1 circuit 7 controls. Control is performed by input signals from various sensors that measure the pressure loss of the filter member 4, fuel consumption m, travel distance, etc.

The exhaust gas from the m-section 1 flows into the collection bag [A part-1-3] from the inlet 3a, passes through the filter member 4, and then flows into the collection bag [A-1-3].
It flows out from the first port 3b. When the exhaust gas passes through the filter member 4, carbon particulates in the exhaust gas are collected and removed by the filter member 4.

The filter member 4 has a structure as shown in FIG. 7, for example. That is, it has a large number of hollow holes 13 separated by a large number of partition walls 12 made of porous ceramics 11 having a three-dimensional network skeleton, and has a cylindrical honeycomb structure as an external structure.

The filter member 4 causes the carbon particulates in the exhaust gas flowing in from the inlet side passage as shown by the arrow in FIG. Basically, the trap #4 function is achieved by the mechanism of collision trapping. Here, the filter member 4
All distances within! It is important that the carbon fine particles are uniformly deposited to a length of 1 m in 12 in order to efficiently collect the carbon particles in a certain volume and to minimize the increase in pressure loss.

[Problem that the invention seeks to solve]

However, the conventional helical structure of the so-called honeycomb form type described above is a hollow structure with a constant cross-sectional area! Because the structure had holes arranged parallel to each other, most of the particles tend to be collected near the entrance and exit of the hollow holes, as shown in Figure 8, and the collection is not uniform. The drawback was that it was inefficient. (In addition, 311!81i
(The adhesion rate in 1 refers to the amount of fine particles collected in 100 g of ceramics.) Also, as shown in Fig. 6 as electric heater 5, the adhesion rate in 1 refers to the amount of soot collected in 100 g of ceramics. ``Work is being done to regenerate filter members by burning carbon particles, but in conventional filter members, they are collected intensively at the inlet and outlet ends, and are collected in the center.'' Since the amount of "soot" is extremely small, combustion propagation is not possible, which makes it extremely difficult to regenerate the filter member. It has a group of inlet holes drilled in the axial direction, and a group of outlet holes adjacent to the group of inlet holes with a partition wall in the axial direction, and the inlet hole is located at the front end. is a porous helical structure having a frontage and a rear end sealed, and the exit hole is sealed at the 1yI end and opened at the rear end; It is characterized by having the following.

Here, the reticular body has 25 to 144 meshes/int
It may be a three-dimensional network structure or a pellet-like granule.

As the pellet-like particles, for example, alumina particles having a size of about 2 mm are preferable.

The porous ceramic structure according to the present invention has a group of inlet holes and a group of outlet holes as described above and is partitioned by a partition wall, and the partition wall has a three-dimensional mesh shape. It is also noted that the structure has a mesh roughness of 1,600 to 2,500 mesh/In'. The cross-sectional shape of the inlet hole and the 14-port hole may be circular or polygonal, and the cross-sectional area may be constant in the axial direction or tapered.

The shape of the inlet hole and the outlet hole may be circular or polygonal, and the cross-sectional area may be constant in the axial direction or uniformly curved.

Further, it is preferable that the net-like material filled in the entrance hole be filled throughout the entire axial direction of the entrance hole, but it is not necessarily necessary to fill the entire axial direction.

The material of the filter member is preferably cordierite, but is not limited to this. For example, Si
C, 813N4. Various ceramic materials such as Al t03 type and β-subodumene type may be used.

Hereinafter, in order to explain the present invention more specifically, examples will be explained in detail.

〔Example〕

FIG. 1 shows an embodiment of the porous ceramic structure according to the present invention, in which it is formed as a filter member 41 similar to the filter member 4 of FIG. Made of quality ceramics. FIG. 1(a) is a longitudinal sectional view, and FIG. 1(b) is a left half of the left side view.

A group of inlet holes 2 with n-ends on the inlet side as shown in Figure 1
2 and a group of exit holes 23 having open ends on the exit side are 111M apart from each other! 24. The outlet side of the inlet hole 22 and the inlet side of the outlet hole 23 are sealed by sealing walls 22a and 23a, respectively.

Both stop walls 22a and 23a are connected by the gap g124, and the thickness of the l@ wall 24 is constant.

The cross-sectional shapes of the inlet hole 22 and the origin hole 23 are square in this embodiment, and the cross-sectional area is constant in the axial direction.
Ru.

A circular tubular dense ceramic 41a is provided on the outer periphery of the filter member 41 for reinforcement.
Since it is made of porous ceramics, the exhaust gas flowing into the inlet hole 22 from the direction of the arrow has a
50o mesh/in! It passes through the wA wall 24, which has a fine three-dimensional network structure, reaches the adjacent outlet hole 23, and flows out in the direction of the arrow. Fine particles in the gas are collected when passing through the partition wall 24, and the inlet hole 22 has a relatively large mesh of about 25 to 400 mesh/In2 throughout the axial direction. Since the three-dimensional mesh structure 22b is provided, a certain amount of fine particles are collected when passing through the large part of this mesh, and roughly 1lIiJW! When passing through 24, the fine particles are collected.

Here, a method for manufacturing the filter member 41 will be explained. In general, II! of three-dimensional network structure! To obtain a honeycomb lI&N ceramic filter with walls, an organic compound such as polyurethane foam with a similar three-dimensional network structure is used as an aggregate, a ceramic material is fixed on the surface of the aggregate, and this is fired. Then, the organic compound, which is the base material, burns and scatters, and the nun ceramic material is sintered to have a structure similar to that of the base material. Therefore, if a desired 4J4 structure is obtained when molding the organic compound serving as the base material, a desired structure can be obtained as a ceramic filter.

A specific manufacturing method will be described below.

FIG. 2 shows the mold container portion 25, with FIG. 2(a) being a plan view and FIG. 2(b) being a view taken along line x--X arrow fIi. The mold container portion 25 includes an end surface 26, a plurality of columnar sections 27 planted on the end surface 26, and a cylindrical side that is planted on the outer periphery of the end surface 26 and surrounds the columnar sections 27! ! It consists of a section 28. The cross-sectional shape of the columnar portion 27 is square. End face 26
The opposite side is open.

FIG. 3 shows the mold 11 part 30 for covering the mold container part 25, FIG. 3(a) is a plan view, and FIG.
) is Y-Yll! It is an arrow sectional view. The mold lid part 30
It consists of an end-face cover part 31 and a plurality of columnar parts 32 implanted on the *a part 31.

A through hole 31 a is bored in the end cover 31 at a position that does not interfere with the columnar section 32 . The columnar portion 32 is formed by molding g! as described later. It is provided in consideration of not interfering with the columnar part 27 of the container part 25 when the lid part 30 is placed over the container part 25. Additionally, there are mounting holes 31bI in the outer circumference of the end cover 31 that are equally divided into four parts for fixing the cover 30 to the container 25.
fNg is provided.

FIG. 4 shows a state in which the mold lid 30 is assembled to the mold container part 25 and fixed with screws 38 to form the mold 8. A space (cavity) 34 is created between the container i25 and the lid part 30, and the urethane foam raw material mixture liquid is injected into the hole 31a into this space 11J34. . Since the mixed liquid foams in the space 34, it is heated to 20°C at 120°C after foaming.
Heat to cure for ~60 minutes. After curing, the container part 25
By separating the lid portion 30 and the lid portion 30, a urethane foam molded body having a honeycomb structure is obtained.

The urethane foam molded product obtained in this way has a thin film called a cell group between the three-dimensional mesh-like skeletons, so this urethane foam molded product is placed in a container and flammable gas and air or oxygen are introduced. A spark ignites this, burning the cell membrane and removing it.

Next, the urethane foam molded body is immersed in a ceramic slurry made by mixing and stirring a powder containing cordierite as a main component, water, and polyvinyl alcohol, and the ceramic slurry is adhered to the skeletal surface of the molded body. After removing excess slurry by centrifugation, etc., heat drying at 100 to 120°C, immerse, and dry. Repeat several times.

, Finally, the slurry-impregnated urethane foam molded body was heated to 1300 to 1470°C. Bake for 2 to 6 hours at 30°C.

By this firing, the urethane foam component of the organic compound is burned and dissipated, and the ceramic slurry is fired.

The ceramic slurry thus prepared is assimilated into the inlet hole 22 of the urethane foam 64-1.
The ceramic slurry adhered to the surface of the 00 mesh/Inl in the same manner as described above is inserted and dried again in a microwave oven or the like. And this is 1360
Installed in a tunnel furnace (or electric furnace) at ~1400°C,
A desired porous ceramic filter 41 is obtained by firing for about 4 to 10 hours.

The characteristics of the filter member 411 in which the inlet hole 2.2 is filled with ceramic in the form of a coarse three-dimensional mesh are as shown by curves c and d in FIG. 5. Here, the curve @C is for the case where the size of the ceramic mesh filled in the entrance hole 22 is 64 meshes/1n2, and the curve d is also for the case where the size is 100 meshes/1n2. In the conventional filter member in which the inlet hole is a mere space, the adhesion rate is poor at the center in the longitudinal direction as shown in FIG. If the size of the openings of the ceramic to be filled is appropriate, the adhesion rate will be improved even in the center in the longitudinal direction, and a uniform curve will be obtained.

As a result of experiments, it was found that if the size of the ceramic mesh filled in the inlet hole 22 was made smaller than 121 mesh/1n2, the pressure loss would increase significantly and the adhesion rate at the center and outlet end would worsen. Therefore, the limit is 100 meshes or 'ins. Also, if it is coarser than 16 mesh/1n2, it will be no different from the conventional product, so
The coarser limit is 25 meshes/ln2.

[Modification] In the above embodiment, 64 to 100 meshes/in'
The inlet hole 22 is installed or filled with a ceramic slurry adhered to the surface of the urethane foam, but it may also be filled with pellet-shaped granules. As a pellet-like granule, the size is about 2
mm alumina is preferred.

Here, if the grain size is set to imm or less, the upper limit of the pressure loss becomes large as in the case of the above example, and conversely, if the grain size is set to 3 mm or less, the upper limit of the pressure loss becomes large.
If the size is above, the product will be the same as the conventional product, so it is preferable to set the grain size to between 1 and 3 mm.

(Effect of n-light FA) As described above, the present invention has a configuration in which a coarse net-like body is installed in the inlet hole, so that carbon fine particles can be collected uniformly over the entire length of the structure. Therefore, the collection efficiency can be further improved. 'Also, as mentioned above, carbon particles can be collected uniformly over the entire length of the structure, so if an electric heater or the like is installed at the entrance end to burn the carbon particles, it will be possible to collect the carbon particles uniformly over the entire length of the afforestation tree. It burns. Therefore, the filter can be easily and completely regenerated.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 shows an embodiment of the present invention. FIG. 1(a) is a side view, and FIGS.
Figure 2 (a') is a plan view of the mold container part 25, and Figure 2 (b) is the X of Figure 2 <a>.
-Xa arrow sectional view, Figure 3 (, a) is the mold lid part 3°0
The plan view of FIG. 3(b) is Y-Yl of FIG. 3<a>.
FIG. 4 is a cross-sectional view showing a state in which the mold container 25 of FIG. 2 and the mold lid 30 of FIG. 3 are combined.
Fig. 5 is a graph showing the measurement results, Fig. 6 is an overall view showing the conventional particulate collection situation, Fig. 17 is a perspective view showing the filter member 4 in Fig. 6, and Fig. 8 is the conventional FIG. 3 is a graph showing the adhesion rate of filter member 4 in FIG. 41... Filter member 22... Inlet hole 23... Outlet hole 24... Partition wall

Claims (4)

[Claims] (1) A group of inlet holes drilled in the axial direction, and a group of outlet holes adjacent to the group of inlet holes separated from the partition wall in the axial direction, and the inlet holes are open at the front end and at the rear. In a porous ceramic structure whose end is sealed and whose front end is sealed and whose rear end is open, a mesh member having a mesh coarser than the mesh of the partition wall is installed in the entrance hole. Characteristic porous ceramic structure (2) The porous ceramic structure according to claim 1, wherein the network is a three-dimensional network structure having a size of 25 to 144 mesh/in^2. (3) The porous ceramic structure according to claim 1, wherein the network body is a pellet-like granular body. (4) The porous ceramic structure according to claim 3, wherein the pellet-like granules are alumina granules having a size of about 2 mm.