JP4051163B2 - Ceramic filter assembly - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ceramic filter assembly having a structure in which a plurality of honeycomb filters made of a ceramic sintered body are bonded and integrated. To the body It is related.
[0002]
[Prior art]
The number of automobiles has increased dramatically since the beginning of this century, and the amount of exhaust gas emitted from the automobile's internal combustion engine has been increasing rapidly. In particular, various substances contained in exhaust gas emitted from a diesel engine cause pollution, and are now having a serious impact on the world environment. Recently, research results have reported that particulates (diesel particulates) in exhaust gas sometimes cause allergic disorders and a decrease in the number of sperm. In other words, taking measures to remove particulates in exhaust gas is considered an urgent issue for humanity.
[0003]
Under such circumstances, various types of exhaust gas purification apparatuses have been proposed. A general exhaust gas purifying apparatus has a structure in which a casing is provided in the middle of an exhaust pipe connected to an exhaust manifold of an engine, and a filter having fine holes is disposed therein. As a material for forming the filter, there are ceramics in addition to metals and alloys. As a typical example of a filter made of ceramic, a honeycomb filter made of cordierite is known. Recently, there are advantages such as high heat resistance, mechanical strength, high collection efficiency, chemical stability, low pressure loss, etc., so use porous silicon carbide sintered body as a filter forming material. There are many.
[0004]
The honeycomb filter has a large number of cells extending along its own axial direction. As the exhaust gas passes through the filter, particulates are trapped by the cell walls. As a result, fine particles are removed from the exhaust gas.
[0005]
However, a honeycomb filter made of a porous silicon carbide sintered body is vulnerable to thermal shock. Therefore, the larger the size is, the easier the cracks are generated in the filter. Therefore, as a means for avoiding breakage due to cracks, a technique has recently been proposed in which a plurality of small filter pieces are integrated to produce one large ceramic filter assembly.
[0006]
A general method for manufacturing the above-described assembly will be briefly introduced. First, a rectangular column-shaped honeycomb formed body is formed by continuously extruding a ceramic raw material through a mold of an extruder. After the honeycomb formed body is cut into equal lengths, the cut piece is fired to obtain a filter. After the firing step, the plurality of filters are bundled and integrated by bonding the outer peripheral surfaces of the filters through a ceramic sealing material layer. As a result, a desired ceramic filter assembly is completed.
[0007]
A mat-like heat insulating material made of ceramic fiber or the like is wound around the outer peripheral surface of the ceramic filter assembly. In this state, the assembly is accommodated in a casing provided in the middle of the exhaust pipe.
[0008]
[Problems to be solved by the invention]
However, since the honeycomb filter of the prior art has a generally square shape, stress tends to concentrate on the corners on the outer peripheral surface, and chipping may occur there. In addition, cracks may occur on the sealing material layer side starting from the corners, which may cause destruction of the ceramic filter assembly. Further, even when the aggregates are not destroyed, there is a problem that the processing efficiency is likely to be lowered due to the leak of the exhaust gas.
[0009]
The present invention has been made in view of the above problems, and its purpose is to collect ceramic filters with excellent strength. Body It is to provide.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problems, in the invention according to claim 1, the outer peripheral surfaces of a plurality of prismatic honeycomb filters made of a ceramic sintered body are bonded to each other via a ceramic sealing material layer. An aggregate formed by integrating honeycomb filters, and the corners on the outer peripheral surface of each honeycomb filter are rounded chamfered surfaces, and the curvature of the rounded surfaces radius R = 0.3-2.5 mm The gist of the ceramic filter assembly is characterized in that
[0011]
According to a second aspect of the present invention, in the first aspect, the honeycomb filter is made of a porous silicon carbide sintered body.
According to a third aspect of the present invention, in the first or second aspect, the honeycomb filter has a quadrangular prism shape and is arranged in a state of being shifted from each other along a direction orthogonal to the filter axial direction.
[0013]
The “action” of the present invention will be described below. According to the first to third aspects of the invention, the corners on the outer peripheral surface of the honeycomb filter are preferable. Suitable Since it is the rounded surface of the enclosure, stress concentration at the relevant location is avoided. Therefore, chipping of the corners of the honeycomb filter and cracking of the sealing material layer starting from the corners are prevented, and the ceramic filter aggregate is hardly broken. Curvature radius R is 0.3 mm If it is below, stress concentration on the corners cannot be avoided sufficiently, and chipping and cracking are likely to occur. Conversely, R is 2.5 mm If it exceeds 1, the cross-sectional area of the honeycomb filter decreases, and as a result, the filtration capacity of the aggregate decreases.
[0014]
According to the second aspect of the present invention, since this honeycomb filter is made of a porous body, it has a high filtration capacity and a small pressure loss. And since it consists of a silicon carbide sintered compact, it is excellent in heat resistance and heat conductivity.
[0015]
According to the invention described in claim 3, by arranging the quadrangular columnar honeycomb filters in a state of being shifted from each other along a direction orthogonal to the filter axial direction, a portion where the sealing material layers intersect in a cross shape cannot be formed. As a result, not only the breaking strength of the aggregate is improved, but also the thermal conductivity along the radial direction of the aggregate is improved.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an exhaust gas purification apparatus 1 for a diesel engine according to an embodiment of the present invention will be described in detail with reference to FIGS.
[0018]
As shown in FIG. 1, this exhaust gas purification device 1 is a device for purifying exhaust gas discharged from a diesel engine 2 as an internal combustion engine. The diesel engine 2 includes a plurality of cylinders (not shown). Each cylinder is connected with a branch portion 4 of an exhaust manifold 3 made of a metal material. Each branch portion 4 is connected to one manifold body 5. Therefore, the exhaust gas discharged from each cylinder is concentrated in one place.
[0019]
A first exhaust pipe 6 and a second exhaust pipe 7 made of a metal material are disposed on the downstream side of the exhaust manifold 3. The upstream end of the first exhaust pipe 6 is connected to the manifold body 5. Between the 1st exhaust pipe 6 and the 2nd exhaust pipe 7, the cylindrical casing 8 which consists of a metal material is arrange | positioned. The upstream end of the casing 8 is connected to the downstream end of the first exhaust pipe 6, and the downstream end of the casing 8 is connected to the upstream end of the second exhaust pipe 7. It can also be understood that the casing 8 is disposed in the middle of the exhaust pipes 6 and 7. As a result, the internal regions of the first exhaust pipe 6, the casing 8, and the second exhaust pipe 7 communicate with each other, and the exhaust gas flows therethrough.
[0020]
As shown in FIG. 1, the casing 8 is formed so that the central portion thereof has a larger diameter than the exhaust pipes 6 and 7. Therefore, the inner area of the casing 8 is wider than the inner areas of the exhaust pipes 6 and 7. A ceramic filter assembly 9 is accommodated in the casing 8.
[0021]
A heat insulating material 10 is disposed between the outer peripheral surface of the assembly 9 and the inner peripheral surface of the casing 8. The heat insulating material 10 is a mat-like material formed including ceramic fibers, and its thickness is several mm to several tens mm. The heat insulating material 10 preferably has a thermal expansibility. The term “thermal expansibility” as used herein means that it has a function of releasing thermal stress because it has an elastic structure. The reason is to minimize energy loss during regeneration by preventing heat from escaping from the outermost periphery of the assembly 9. In addition, the ceramic fiber is expanded by heat at the time of regeneration, thereby preventing the displacement of the ceramic filter assembly 9 caused by exhaust gas pressure or vibration due to running.
[0022]
Since the ceramic filter aggregate 9 used in the present embodiment removes diesel particulates as described above, it is generally called a diesel particulate filter (DPF). As shown in FIGS. 2 and 4, the assembly 9 of the present embodiment is formed by bundling and integrating a plurality of honeycomb filters F1. The honeycomb filter F1 located at the central portion of the aggregate 9 has a quadrangular prism shape, and its outer dimensions are 33 mm × 33 mm × 167 mm (see FIG. 3). Around the quadrangular columnar honeycomb filter F1, a plurality of irregular honeycomb filters F1 that are not quadrangular columnar are arranged. As a result, a cylindrical ceramic filter assembly 9 (diameter around 135 mm) is configured as a whole.
[0023]
These honeycomb filters F1 are made of a porous silicon carbide sintered body which is a kind of ceramic sintered body. The reason for adopting the silicon carbide sintered body is that it has an advantage of being particularly excellent in heat resistance and thermal conductivity as compared with other ceramics. As a sintered body other than silicon carbide, for example, a sintered body such as silicon nitride, sialon, alumina, cordierite, and mullite can be selected.
[0024]
As shown in FIG. 3 and the like, these honeycomb filters F1 have a honeycomb structure. The reason for adopting the honeycomb structure is that there is an advantage that the pressure loss is small even when the amount of collected fine particles is increased. In each honeycomb filter F1, a plurality of through holes 12 having a substantially square cross section are regularly formed along the axial direction thereof. Each through hole 12 is partitioned from each other by a thin cell wall 13. On the outer surface of the cell wall 13, an oxidation catalyst composed of a platinum group element (for example, Pt or the like), other metal elements and oxides thereof is supported. The opening of each through-hole 12 is sealed with a sealing body 14 (here, a porous silicon carbide sintered body) on either one of the end faces 9a and 9b side. Accordingly, the end faces 9a and 9b as a whole have a checkered pattern. As a result, a large number of cells having a square cross section are formed in the honeycomb filter F1. The cell density is set to about 200 cells / inch, the thickness of the cell wall 13 is set to about 0.3 mm, and the cell pitch is set to about 1.8 mm. Of the many cells, about half of the cells open at the upstream end surface 9a, and the remaining cells open at the downstream end surface 9b.
[0025]
The average pore diameter of the honeycomb filter F1 is preferably 1 μm to 50 μm, more preferably 5 μm to 20 μm. When the average pore diameter is less than 1 μm, the honeycomb filter F1 is clogged due to the accumulation of fine particles. On the other hand, if the average pore diameter exceeds 50 μm, fine fine particles cannot be collected, and the filtration capacity is lowered.
[0026]
The porosity of the honeycomb filter F1 is preferably 30% to 70%, more preferably 40% to 60%. If the porosity is less than 30%, the honeycomb filter F1 becomes too dense, and the exhaust gas may not be allowed to flow inside. On the other hand, if the porosity exceeds 70%, the number of voids in the honeycomb filter F1 increases, so that the strength becomes weak and the collection efficiency of fine particles may be reduced.
[0027]
As shown in FIGS. 4 and 5, a total of 16 honeycomb filters F <b> 1 have their outer peripheral surfaces bonded to each other via a ceramic sealing material layer 15.
Here, the ceramic sealing material layer 15 of the present embodiment will be described in detail.
[0028]
The thickness of the sealing material layer 15 is preferably 0.3 mm to 3 mm, and more preferably 0.5 mm to 2 mm.
When the thickness exceeds 3 mm, the sealing material layer 15 still has a large thermal resistance even if the thermal conductivity is high, and the thermal conduction between the honeycomb filters F1 is hindered. And since the ratio for which the honeycomb filter F1 part accounts in the aggregate | assembly 9 reduces relatively, it will lead to the fall of filtration capability. On the contrary, if the thickness of the sealing material layer 15 is less than 0.3 mm, the heat resistance does not become large, but the force for bonding the honeycomb filters F1 is insufficient, and the aggregate 9 is easily broken.
[0029]
The sealing material layer 15 is composed of at least an inorganic fiber, an inorganic binder, an organic binder, and inorganic particles, and binds the inorganic fibers and the inorganic particles that are three-dimensionally crossed to each other through the inorganic binder and the organic binder. It is desirable to be made of an elastic material.
[0030]
Examples of the inorganic fiber contained in the sealing material layer 15 include at least one ceramic fiber selected from silica-alumina fiber, mullite fiber, alumina fiber, and silica fiber. Among these, it is particularly desirable to select a silica-alumina ceramic fiber. This is because the silica-alumina ceramic fiber is excellent in elasticity and absorbs thermal stress.
[0031]
In this case, the content of the silica-alumina ceramic fiber in the sealing material layer 15 is 10 wt% to 70 wt%, preferably 10 wt% to 40 wt%, more preferably 20 wt% to 30 wt% in solid content. is there. It is because the effect as an elastic body will fall that content is less than 10 weight%. On the other hand, when the content exceeds 70% by weight, not only the thermal conductivity is lowered, but also the elasticity is lowered.
[0032]
The shot content in the silica-alumina ceramic fiber is 1 wt% to 10 wt%, preferably 1 wt% to 5 wt%, more preferably 1 wt% to 3 wt%. This is because it is difficult to make the shot content less than 1% by weight. On the other hand, if the shot content exceeds 50% by weight, the outer peripheral surface of the honeycomb filter F1 is damaged.
[0033]
The fiber length of the silica-alumina ceramic fiber is 1 mm to 100 mm, preferably 1 mm to 50 mm, more preferably 1 mm to 20 mm. This is because the elastic structure cannot be formed when the fiber length is less than 1 mm. This is because if the fiber length exceeds 100 mm, the fibers become pilled and the dispersibility of the inorganic fine particles deteriorates. Further, it is difficult to make the sealing material layer 15 thin to 3 mm or less, and it becomes impossible to improve the thermal conductivity between the honeycomb filters F1.
[0034]
The inorganic binder contained in the sealing material layer 15 is preferably at least one colloidal sol selected from silica sol and alumina sol. Among these, it is desirable to select silica sol. The reason is that silica sol is easy to obtain and can be easily baked to make SiO ₂ Therefore, it is suitable as an adhesive in a high temperature region. Moreover, silica sol is excellent in insulation.
[0035]
In this case, the content of the silica sol in the sealing material layer 15 is 1% by weight to 30% by weight, preferably 1% by weight to 15% by weight, and more preferably 5% by weight to 9% by weight. This is because if the content is less than 1% by weight, the adhesive strength is lowered. Conversely, if the content exceeds 30% by weight, the thermal conductivity is reduced.
[0036]
The organic binder contained in the sealing material layer 15 is preferably a hydrophilic organic polymer, and more preferably at least one polysaccharide selected from polyvinyl alcohol, methylcellulose, ethylcellulose, and carbomethoxycellulose. Among these, it is desirable to select carboxymethyl cellulose in particular. The reason is that carboxymethylcellulose gives excellent fluidity to the sealing material layer 15 and thus exhibits excellent adhesiveness in the normal temperature region.
[0037]
In this case, the content of carboxymethyl cellulose in the sealing material layer 15 is 0.1 wt% to 5.0 wt%, preferably 0.2 wt% to 1.0 wt%, more preferably 0.4 wt% in terms of solid content. % By weight to 0.6% by weight. This is because if the content is less than 0.1% by weight, migration cannot be sufficiently suppressed. “Migration” refers to a phenomenon in which the binder in the sealing material layer 15 moves as the solvent is removed when the sealing material layer 15 filled between the objects to be sealed is cured. On the other hand, when the content exceeds 5.0% by weight, the organic binder is burned away at a high temperature, and the strength of the sealing material layer 15 is lowered.
[0038]
The inorganic particles contained in the sealing material layer 15 are preferably an elastic material using at least one inorganic powder or whisker selected from silicon carbide, silicon nitride, and boron nitride. This is because such carbides and nitrides have a very high thermal conductivity and contribute to the improvement of the thermal conductivity by interposing on the surface of the ceramic fiber and the surface of the colloidal sol and the inside thereof.
[0039]
Among the carbide and nitride inorganic particles, it is particularly preferable to select silicon carbide powder. The reason is that silicon carbide has a property of being easily compatible with ceramic fibers in addition to extremely high thermal conductivity. Moreover, in the present embodiment, the honeycomb filter F1 that is the sealed object is the same type, that is, made of porous silicon carbide.
[0040]
In this case, the content of the silicon carbide powder is 3% by weight to 80% by weight, preferably 10% by weight to 60% by weight, and more preferably 20% by weight to 40% by weight in terms of solid content. This is because if the content is less than 3% by weight, the thermal conductivity of the sealing material layer 15 is lowered, and the sealing material layer 15 still has a large thermal resistance. On the other hand, if the content exceeds 80% by weight, the adhesive strength is lowered at high temperatures.
[0041]
The particle size of the silicon carbide powder is 0.01 μm to 100 μm, preferably 0.1 μm to 15 μm, more preferably 0.1 μm to 10 μm. This is because if the particle size exceeds 100 μm, the adhesive force and the thermal conductivity are reduced. On the other hand, when the particle size is less than 0.01 μm, the cost of the sealing material layer 15 is increased.
[0042]
Where the curvature of the rounded surface 18 radius R = 0.3-2.5 mm And R = 0.7 to 2.5. mm In particular, R = 1.0 to 2.0 mm Still better.
[0043]
Curvature radius R is 0.3 mm This is because the corners are still angular if the following, the stress concentration on the corners cannot be sufficiently avoided, and the cracks and cracks are likely to occur. Conversely, R is 2.5 mm This is because the number of effective cells is reduced as a result of the reduction of the cross-sectional area of the honeycomb filter F1, and the filtration capacity of the aggregate 9 is reduced.
[0044]
Next, a procedure for manufacturing the ceramic filter assembly 9 will be described.
First, a ceramic raw material slurry used in an extrusion molding process, a sealing paste used in an end face sealing process, and a sealing material layer forming paste used in a filter bonding process are prepared in advance.
[0045]
As the ceramic raw material slurry, a mixture obtained by kneading a silicon carbide powder with an organic binder and water in predetermined amounts and kneading them is used. As the sealing paste, a silicon carbide powder blended with an organic binder, a lubricant, a plasticizer and water and kneaded is used. As the paste for forming the sealing material layer, an inorganic fiber, an inorganic binder, an organic binder, inorganic particles, and water are blended in predetermined amounts and kneaded.
[0046]
Next, the ceramic raw material slurry is put into an extruder and continuously extruded through a mold. Thereafter, the extruded honeycomb formed body is cut into equal lengths to obtain a rectangular pillar-shaped honeycomb formed body cut piece. Here, each corner of the honeycomb formed body is chamfered to form a rounded surface 18 having a predetermined curvature R.
[0047]
Further, a predetermined amount of sealing paste is filled into one side opening of each cell of the cut piece, and both end faces of each cut piece are sealed.
Subsequently, the main firing is performed by setting the temperature, time, and the like to predetermined conditions, and the honeycomb formed body cut piece and the sealing body 14 are completely sintered. As for the honeycomb filter F1 made of a porous silicon carbide sintered body thus obtained, all are still in the shape of a quadrangular prism at this point. The chamfering process for each corner may be performed at this point.
[0048]
In this embodiment, the firing temperature is set to 2100 ° C. to 2300 ° C. in order to set the average pore diameter to 6 μm to 15 μm and the porosity to 35% to 50%. The firing time is set to 0.1 hours to 5 hours. Moreover, the atmosphere in the furnace at the time of baking is made into an inert atmosphere, and the pressure of the atmosphere at that time is made into a normal pressure.
[0049]
Next, if necessary, a base layer made of a ceramic material is formed on the outer peripheral surface of the honeycomb filter F1, and a sealing material layer forming paste is further applied thereon. And 16 such honey-comb filters F1 are used, and the outer peripheral surfaces are mutually adhere | attached and integrated.
[0050]
In the subsequent outer shape cutting step, the aggregate 9 having a square section obtained through the filter adhering step is ground, and unnecessary portions on the outer peripheral portion are removed to adjust the outer shape. As a result, a ceramic filter assembly 9 having a circular cross section is obtained.
[0051]
Next, the particulate trap action by the ceramic filter assembly 9 will be briefly described.
Exhaust gas is supplied to the ceramic filter assembly 9 housed in the casing 8 from the upstream end face 9a side. The exhaust gas supplied through the first exhaust pipe 6 first flows into a cell opened at the upstream end face 9a. Next, the exhaust gas passes through the cell wall 13 and reaches the inside of the cell adjacent to the cell wall 13, that is, the cell opened at the downstream end face 9b. Then, the exhaust gas flows out from the downstream end face 9b of the honeycomb filter F1 through the opening of the cell. However, the fine particles contained in the exhaust gas cannot pass through the cell wall 13 and are trapped there. As a result, the purified exhaust gas is discharged from the downstream end face 9b of the honeycomb filter F1. The purified exhaust gas further passes through the second exhaust pipe 7 and is finally released into the atmosphere. Further, when the internal temperature of the aggregate 9 reaches a predetermined temperature, the trapped fine particles are ignited and burned by the action of the catalyst.
[0052]
【Example】
Example 1
(1) Wet-mixing 51.5% by weight of α-type silicon carbide powder and 22% by weight of β-type silicon carbide powder, and adding 6.5% by weight and 20% of organic binder (methyl cellulose) and water to the resulting mixture, respectively. It added and knead | mixed weight%. Next, by adding a small amount of a plasticizer and a lubricant to the kneaded product and further kneading, extrusion-molding was performed to obtain a honeycomb-shaped formed shape.
[0053]
(2) Next, after drying this generated shape using a microwave dryer, chamfering is performed by shaving each corner, curvature radius R = 1.5 mm The rounded surface 18 was formed. Thereafter, the through hole 12 of the molded body was sealed with a sealing paste made of a porous silicon carbide sintered body. Next, the sealing paste was dried again using a dryer. Following the end face sealing step, the dried body was degreased at 400 ° C., and then further baked at 2200 ° C. for about 3 hours in an atmospheric argon atmosphere. As a result, a honeycomb filter F1 made of a porous silicon carbide sintered body was obtained.
[0054]
(3) Ceramic fiber (alumina silicate ceramic fiber, shot content 3%, fiber length 0.1 mm to 100 mm) 23.3% by weight, silicon carbide powder having an average particle size of 0.3 μm 30.2% by weight, inorganic binder Silica sol as sol SiO ₂ The equivalent amount was 30%) and 7% by weight, 0.5% by weight of carboxymethyl cellulose as an organic binder and 39% by weight of water were mixed and kneaded. By adjusting the kneaded product to an appropriate viscosity, a paste used for forming the sealing material layer 15 was produced.
[0055]
(4) Next, the paste for forming the sealing material layer is uniformly applied to the outer peripheral surface of the honeycomb filter F1, and the outer peripheral surfaces of the honeycomb filter F1 are in close contact with each other, and are 50 ° C. to 100 ° C. × 1 hour. Dry and cure under the following conditions. As a result, the honeycomb filters F1 are bonded to each other through the sealing material layer 15. Here, the thickness of the sealing material layer 15 was set to 1.0 mm.
[0056]
(5) Next, the outer shape was cut to prepare the outer shape, thereby completing the ceramic filter assembly 9 having a circular cross section.
Next, the heat insulating material 10 was wound around the aggregate 9 obtained as described above, and the aggregate 9 was accommodated in the casing 8 in this state, and the exhaust gas was actually supplied. After a certain period of time, the assembly 9 was taken out and visually observed.
[0057]
As a result, no cracks were found in the sealing material layer 15 starting from each corner. In addition, no chipping at the corners was observed. Therefore, it was revealed that the assembly 9 of Example 1 was extremely excellent in strength.
(Examples 2 and 3)
In Example 2, the curvature of the rounded surface 18 radius R = 0.4 mm The ceramic filter assembly 9 was produced in the same manner as in Example 1 except for the other matters. In Example 3, the curvature of the rounded surface 18 radius R = 2.4 mm The ceramic filter assembly 9 was produced in the same manner as in Example 1 except for the other matters.
[0058]
Next, when the obtained two types of aggregates 9 were used for a certain period of time in the same manner as in Example 1 and then observed with the naked eye, suitable results comparable to Example 1 were obtained. That is, it has been clarified that the assembly 9 of Examples 2 and 3 is extremely excellent in strength.
Example 4
In Example 4, 25% by weight of ceramic fiber (mullite fiber, shot content 5% by weight, fiber length 0.1 mm to 100 mm), 30% by weight of silicon nitride powder having an average particle size of 1.0 μm, alumina sol as an inorganic binder (Conversion amount of alumina sol 20%) 7% by weight, 0.5% by weight of polyvinyl alcohol as an organic binder and 37.5% by weight of alcohol were mixed and kneaded, and used as the sealing material layer forming paste. Otherwise, the ceramic filter assembly 9 was produced in the same manner as in Example 1. Here, the thickness of the sealing material layer 15 is set to 1.0 mm, and the curvature of the rounded surface 18 at each corner is set. radius R = 1.5 mm Set to.
[0059]
Next, when the obtained assembly 9 was used for a certain period of time in the same manner as in Example 1 and then observed with the naked eye, a suitable result comparable to that in Example 1 was obtained. In other words, it was revealed that the assembly 9 of Example 4 was extremely excellent in strength.
(Example 5)
In Example 5, ceramic fiber (alumina fiber, shot content 4 wt%, fiber length 0.1 mm to 100 mm) 23 wt%, boron nitride powder 35 wt% with an average particle diameter of 1 μm, alumina sol (alumina sol as an inorganic binder) 8% by weight, and 0.5% by weight of ethyl cellulose as an organic binder and 35.5% by weight of acetone were mixed and kneaded, and used as the sealing material layer forming paste. Otherwise, the ceramic filter assembly 9 was produced in the same manner as in Example 1. Here, the thickness of the sealing material layer 15 is set to 1.0 mm, and the curvature of the rounded surface 18 at each corner is set. radius R = 1.5 mm Set to.
[0060]
Next, when the obtained assembly 9 was used for a certain period of time in the same manner as in Example 1 and then observed with the naked eye, a suitable result comparable to that in Example 1 was obtained.
(Comparative example)
In the comparative example, the chamfering process was not performed on each corner, and the ceramic filter assembly 9 was manufactured in the same manner as in Example 1 except for the other matters. Therefore, each honeycomb filter F1 constituting the aggregate 9 was angular.
[0061]
Next, when the obtained assembly 9 was used for a certain period of time in the same manner as in Example 1 and then observed with the naked eye, cracks and chips were generated at a plurality of locations due to stress concentration. Therefore, it was inferior in strength.
[0062]
Therefore, according to each example of the present embodiment, the following effects can be obtained.
(1) In each of the embodiments, the corner portion on the outer peripheral surface of the honeycomb filter F1 is the rounded surface 18 in the preferable curvature range, so that stress concentration on the corner portion can be avoided. Accordingly, chipping of the corners of the honeycomb filter F1 and cracking of the sealing material layer 15 starting from the corners are prevented, and the ceramic filter aggregate 9 is hardly broken. Therefore, it is possible to realize the assembly 9 having excellent strength, and the exhaust gas purification apparatus 1 using the assembly 9 has high strength and high filtration ability, and has excellent practicality.
[0063]
(2) In each embodiment, the honeycomb filter 1 made of a porous silicon carbide sintered body is used. Therefore, it can be set as the aggregate | assembly 9 with high filtration capability, a small pressure loss, and excellent in heat resistance and heat conductivity.
[0064]
(3) In each Example, the thickness of the sealing material layer 15 is set within a preferable range of 0.3 mm to 3 mm. For this reason, although the sealing material layer 15 is interposed, the heat conduction between the honeycomb filters F1 is not easily inhibited. Accordingly, heat is uniformly and quickly conducted to the entire assembly 9 during use, and a temperature difference is hardly generated in the assembly 9. Therefore, the heat uniformity of the assembly 9 is improved, and the occurrence of partial unburned residue is avoided. And the exhaust gas purification apparatus 1 using such an aggregate | assembly 9 becomes the thing excellent in the processing efficiency of exhaust gas.
[0065]
Further, if the thickness of the sealing material layer 15 is within the above range, basic performance such as adhesiveness and heat resistance is maintained, so that it is possible to avoid difficulty in manufacturing the sealing material layer 15. In addition, since the honeycomb filter F1 has a bonding force, the aggregate 9 can be prevented from being broken. That is, the assembly 9 that is relatively easy to manufacture and excellent in durability can be realized.
[0066]
In addition, you may change embodiment of this invention as follows.
The number of combinations of the honeycomb filter F1 does not have to be 16 as in the above-described embodiment, and can be any number. In this case, it is of course possible to use honeycomb filters F1 having different sizes and shapes in appropriate combinations.
[0067]
As in another example of the ceramic filter aggregate 21 shown in FIG. 6, the honeycomb filters F <b> 1 are preliminarily shifted from each other along a direction orthogonal to the filter axial direction, and the honeycomb filters F <b> 1 are bonded and integrated. May be used. In such a case, the honeycomb filter F1 is less likely to be displaced when accommodated in the casing 8, so that the breaking strength of the aggregate 21 is improved. Unlike the above-described embodiment, in another example, a portion where the sealing material layer 15 intersects in a cross shape cannot be formed, and this is considered to contribute to an improvement in fracture strength. Moreover, as a result of further improving the thermal conductivity along the radial direction of the aggregate 21, the soaking of the aggregate 21 is further improved.
[0068]
The round surface 18 may be formed by chamfering the corner portion, or may be formed at the same time when the generated shape is molded.
-The shape of the honeycomb filter F1 before the outer shape cutting step is not limited to a square column having a square cross section as in the embodiment. For example, it may be a quadrangular prism having a rectangular cross section like the honeycomb filter F2 of another example shown in FIG. Further, it may have a triangular prism shape as in another example honeycomb filter F3 shown in FIG. 8, or a hexagonal column shape like another example honeycomb filter F4 shown in FIG.
[0069]
In the embodiment, the ceramic filter assembly of the present invention is embodied as a filter for an exhaust gas purification device attached to the diesel engine 2. Of course, the ceramic filter assembly of the present invention can be embodied as other than a filter for an exhaust gas purification device, for example, a heat exchanger member, a filtration filter for high temperature fluid or high temperature steam, or the like. Can.
[0070]
Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiment described above are listed below.
(1) In any one of Claims 1 thru | or 3, the said aggregate | assembly is a diesel particulate filter.
[0071]
(2) In any one of claims 1 to 3 and technical ideas 1 and 2, the sealing material layer includes at least inorganic fibers, an inorganic binder, an organic binder, and inorganic particles, and is three-dimensionally crossed. It consists of an elastic material formed by bonding the inorganic fibers and the inorganic particles to each other via the inorganic binder and the organic binder.
[0072]
(3) In any one of claims 1 to 3 and technical ideas 1 and 2, the sealing material layer has a silica-alumina ceramic fiber having a solid content of 10 wt% to 70 wt%, and 1 wt% to 30 wt%. Consisting of 0.1% by weight to 5.0% by weight carbomethoxycellulose and 3% to 80% by weight silicon carbide powder.
[0073]
(4) In any one of claims 1 to 3 and technical ideas 1 to 3, the thickness of the sealing material layer is 0.3 mm to 3 mm. Therefore, according to the invention described in this technical idea 4, a sufficient adhesive force can be secured, and the heat conduction between the honeycomb filters is hardly hindered. When the thickness of the sealing material layer exceeds 3 mm, even if the thermal conductivity is high, the sealing material layer still has a large thermal resistance and the heat conduction between the honeycomb filters is hindered. On the other hand, if the thickness of the sealing material layer is less than 0.3 mm, the heat resistance does not become large, but the force for adhering the honeycomb filters is insufficient, and the aggregate is easily broken.
[0074]
(5) Each honeycomb filter is bonded to the outer peripheral surfaces of a plurality of honeycomb filters made of a ceramic sintered body through a ceramic sealing material layer in a casing provided in the middle of an exhaust pipe of an internal combustion engine. In an exhaust gas purifying apparatus that accommodates an integrated ceramic filter assembly and is filled with a heat insulating material in a gap formed between the outer peripheral surface of the assembly and the inner peripheral surface of the casing, corners on the outer peripheral surface of each honeycomb filter The part has a rounded chamfered surface, and the curvature of the rounded surface radius R = 0.3-2.5 mm An exhaust gas purification apparatus characterized by Therefore, according to the invention described in this technical idea 5, it is possible to provide an apparatus that has high strength and high filtering ability and is excellent in practicality.
[0075]
【The invention's effect】
As described above in detail, according to the first to third aspects of the invention, a ceramic filter assembly having excellent strength can be provided.
[0076]
According to invention of Claim 2, it can be set as the aggregate | assembly excellent in heat resistance and heat conductivity that filtration capability is high, pressure loss is small.
According to the invention described in claim 3, it is possible to further improve the strength and improve the heat uniformity of the aggregate.
[Brief description of the drawings]
FIG. 1 is an overall schematic view of an exhaust gas purifying apparatus according to an embodiment embodying the present invention.
FIG. 2 is a perspective view of the ceramic filter assembly of the embodiment.
FIG. 3 is a perspective view of the honeycomb filter of the embodiment.
FIG. 4 is an enlarged cross-sectional view of a main part of the exhaust gas purification device.
FIG. 5 is an enlarged cross-sectional view of a main part of the ceramic filter assembly.
FIG. 6 is an enlarged cross-sectional view of a main part of another example of a ceramic filter assembly.
FIG. 7 is a perspective view of another example of a honeycomb filter.
FIG. 8 is a perspective view of another example of a honeycomb filter.
FIG. 9 is a perspective view of another example of a honeycomb filter.
[Explanation of symbols]
9, 21 ... Ceramic filter assembly, 15 ... Ceramic sealing material layer, 18 ... Earl surface, F1, F2, F3, F4 ... Honeycomb filter.

Claims (3)

  A plurality of prismatic honeycomb filters made of a ceramic sintered body are bonded to each other through a ceramic sealing material layer to integrate the honeycomb filters. A ceramic filter assembly, wherein a corner portion of the surface is a rounded chamfered surface, and a radius of curvature of the rounded surface is R = 0.3 to 2.5 mm.   The ceramic filter assembly according to claim 1, wherein the honeycomb filter is made of a porous silicon carbide sintered body.   The ceramic filter assembly according to claim 1 or 2, wherein the honeycomb filter has a quadrangular prism shape and is arranged in a state of being shifted from each other along a direction orthogonal to the filter axial direction.

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