JP2010024072A - Honeycomb assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic honeycomb assembly excellent in thermal shock resistance. <P>SOLUTION: The honeycomb assembly is a wall flow type honeycomb assembly which has generally columnar honeycomb part bodies and a jointing material layer to join the honeycomb part bodies, the honeycomb part body being composed of a porous ceramic and having a large number of dividedly arranged cells extending in the axial direction, wherein gas passes through a cell wall dividing the large number of cells. The porous ceramic has a ceramic powder composed of SiC(s) and a binder composed of SiC with which the SiC particles from which the ceramic powder is constituted are combined. The ratio (L/S) of the length (L) in the axial direction of the generally columnar honeycomb part body to the cross section (S) in the section perpendicular to the axial direction of the honeycomb part body is 0.01 (mm/mm<SP>2</SP>) or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a honeycomb aggregate formed by bonding a plurality of honeycomb bodies with a bonding material layer.

  Catalytic carrier utilizing catalytic action of internal combustion engine, boiler, chemical reaction equipment, fuel cell reformer, etc., particulates such as soot in exhaust gas (particularly particulate matter (PM) in exhaust gas from diesel engine) A ceramic honeycomb structure is used for a collection filter (hereinafter referred to as DPF).

  A honeycomb structure made of a ceramic is generally made of porous ceramics, and a honeycomb body in which a plurality of cells serving as fluid flow paths are partitioned by cell walls, and adjacent cells such that end faces form a checkered pattern are mutually connected. And a sealing portion made of ceramics for sealing the end portion on the opposite side. A DPF made of a ceramic honeycomb structure is used as a wall flow type catalyst in which exhaust gas passes through cell walls defining cells of the honeycomb body. The wall flow type catalyst collects PM in the exhaust gas through which the exhaust gas passes through the continuous pores formed in the cell wall and cannot pass through the pores.

  A ceramic honeycomb structure which can constitute the DPF is disclosed in, for example, Patent Documents 1 and 2.

  Patent Document 1 discloses a columnar honeycomb structure made of porous ceramics having a length l (mm) of the longest side of a cross section perpendicular to the longitudinal direction of a through-hole (cell) and the longitudinal direction of the columnar body. Describes a honeycomb structure in which the length L (mm) of the cell is 60 ≦ L / l ≦ 500, and the surface roughness Ra of the inner wall of the cell is Ra ≦ 100 μm. Furthermore, Patent Document 1 describes that a honeycomb body of a honeycomb structure is integrally formed and that a honeycomb body is formed by combining ceramic members (honeycomb segments).

In Patent Document 2, the outer peripheral surfaces of a plurality of columnar honeycomb filters (honeycomb halves) made of a porous ceramic sintered body are bonded and integrated with each other through a ceramic sealing material layer. A ceramic filter aggregate (honeycomb aggregate) in which a ratio L / S between L and a cross-sectional area S is 0.06 (mm / mm ² ) to 0.75 (mm / mm ² ) is described.

  However, the integrally formed honeycomb structure described in Patent Document 1 has a problem that it is difficult to manufacture (mold) it. Further, when a volume change due to heat occurs, the volume change from the axial center is accumulated in the vicinity of the outer peripheral portion, and the volume change amount becomes large and cracks are likely to occur.

  In addition, the honeycomb aggregate described in the cited document 2 defines the length of the honeycomb aggregate and the range of the cross-sectional area, and many honeycomb aggregates are required to manufacture a honeycomb aggregate having a large cross-sectional area. There is a problem that the cost required for bonding increases and the bonding material layer increases and the effective area as the DPF becomes small. Specifically, in the example of the cited document 2, a 20 mm square columnar honeycomb segment is described, and a honeycomb aggregate having a diameter of 30.48 cm (12 inches) is prepared from a honeycomb segment of this size. Requires about 225 honeycomb segments.

Furthermore, the honeycomb aggregate described in the cited document 2 can suppress the occurrence of temperature unevenness in each honeycomb segment by defining the length of the honeycomb segment and the range of the cross-sectional area. There is also a need for improvement in thermal shock resistance of honeycomb structures (aggregates).
International Publication WO2003-074848 JP 2001-96116 A

  This invention is made | formed in view of the said actual condition, and makes it a subject to provide the honeycomb aggregate | assembly excellent in the thermal shock resistance.

  In order to solve the above-mentioned problems, the present inventors have made a study of the present invention as a result of repeated studies on a honeycomb aggregate formed by bonding honeycomb aggregates.

That is, the honeycomb aggregate of the present invention includes a substantially columnar honeycomb segment made of porous ceramics and having a plurality of cells extending in the axial direction, and a bonding material layer for joining the honeycomb segments, In a wall-flow type honeycomb assembly in which gas passes through cell walls that partition a large number of cells, the porous ceramic is a bond made of SiC that combines ceramic powder made of SiC and SiC particles constituting the ceramic powder. A ratio (L / S) of an axial length (L) of the substantially columnar honeycomb body and a cross-sectional area (S) in a cross section perpendicular to the axial direction of the honeycomb body, It is 0.01 (mm / mm ² ) or more.

  The honeycomb aggregate of the present invention has a configuration in which SiC particles are combined with a binder made of the same SiC as the particles. That is, the SiC particles and the SiC binding material form a neck. That is, when the SiC particles are sintered, the necks between the SiC particles cause abnormal grain growth. In the present invention, however, such abnormal grain growth does not occur, and thus a uniform structure is obtained. ing. As a result, in the honeycomb aggregate of the present invention, the porous ceramic has excellent strength, and as a result, has excellent thermal shock resistance.

Further, the honeycomb aggregate of the present invention is formed by joining substantially columnar honeycomb aggregates with a bonding material layer. With such a configuration, even if a volume change due to heat occurs in each honeycomb body, the volume change is not accumulated in the specific honeycomb body, so that cracks do not occur. Furthermore, the ratio (L / S) between the axial length (L) of the honeycomb body and the cross-sectional area (S) in the cross section perpendicular to the axial direction of the honeycomb body is 0.01 (mm / mm ^2). ) By being defined as above, the honeycomb aggregate is excellent in manufacturability while ensuring sufficient performance as a filter.

  The honeycomb aggregate of the present invention includes a substantially columnar honeycomb segment made of porous ceramics and having a plurality of cells extending in the axial direction, and a bonding material layer for joining the honeycomb segments, This is a wall flow type honeycomb aggregate in which gas passes through the cell walls defining the cells. In the wall flow type honeycomb aggregate, when the gas passes through the pores of the cell walls that define the cells, particles larger than the pore diameter are captured.

  In the honeycomb aggregate of the present invention, the honeycomb aggregate is bonded with the bonding material layer, and a large honeycomb aggregate can be manufactured with high accuracy. Further, in the honeycomb aggregate of the present invention, the honeycomb aggregates are bonded with the bonding material layer, and when the respective honeycomb aggregates undergo a volume change due to heat, the volume change amount of each honeycomb aggregate is limited. No cracks.

  In the honeycomb aggregate of the present invention, the porous ceramic includes ceramic powder made of SiC, and a binder made of SiC that bonds SiC particles constituting the ceramic powder.

  The honeycomb aggregate of the present invention has a configuration in which adjacent SiC particles are fixed with a binder. With such a configuration, the degree of freedom in pore design in the porous ceramic is improved. That is, the size and distribution of the gaps between the ceramic particles that become the pores can be easily controlled. And the porous ceramics which have this pore in a uniform state can be obtained.

  In the honeycomb aggregate of the present invention, SiC powder is bonded with a SiC binder. That is, the particles and the binder are made of the same material, and peeling at the interface between the SiC particles and the binder is less likely to occur, and the bondability is improved. That is, the strength of the porous ceramic itself constituting the honeycomb body is improved and the thermal shock resistance is excellent.

  Furthermore, the honeycomb aggregate of the present invention has a large number of fine pores, and these pores buffer the volume change when the honeycomb aggregate is thermally expanded (contracted). Thereby, the honeycomb aggregate of the present invention can buffer the volume change of the ceramic particles.

In the honeycomb aggregate of the present invention, the ratio (L / S) between the axial length (L) of the substantially columnar honeycomb segment and the cross-sectional area (S) in the cross section perpendicular to the axial direction of the honeycomb segment. ) Is 0.01 or more. When the ratio of the axial length and the cross-sectional area of the honeycomb segment is 0.01 (mm / mm ² ) or more, the honeycomb aggregate is excellent in heat resistance and manufacturability. In addition, the substantially columnar honeycomb segment is an apparent shape of the honeycomb segment. In addition, the cross-sectional area in the cross section perpendicular to the axial direction of the honeycomb body is an apparent cross-sectional area and indicates the area inside the outer peripheral portion in the cross section perpendicular to the axial direction.

When the L / S of the honeycomb body is less than 0.01 (mm / mm ² ) (the cross-sectional area of the honeycomb body increases), the temperature difference partially increases in the cross section of the honeycomb body (temperature unevenness). And cracks are likely to occur during thermal shock.

The L / S of the honeycomb body may be 0.01 (mm / mm ² ) or more, and the upper limit thereof is not limited, but is practically 0.75 (mm / mm ² ) or less. It is preferable. When the L / S of the honeycomb body exceeds 0.75 (mm / mm ² ) (the cross-sectional area of the honeycomb body becomes small), the honeycomb body required to obtain a honeycomb aggregate having a predetermined cross-sectional area Increases the cost required for joining the honeycomb segments. Furthermore, the effective area as a filter becomes small and it becomes difficult to collect fine particles. The L / S of the more preferable honeycomb segment is 0.03 to 0.25 (mm / mm ² ).

L / S of the honeycomb chromatid, if L is 150mm or less is preferably ^{0.02~0.05 (mm / mm 2),} 0.03~0.05 (mm / mm 2) It is more preferable that The L / S of the honeycomb segment is preferably 0.01 to 0.04 (mm / mm ² ) when L exceeds 150 mm, and preferably 0.01 to 0.03 (mm / mm). ² ) is more preferable.

  In the present invention, the shape of the honeycomb body is not particularly limited, but it is preferable that the outer shape in a cross section perpendicular to the axial direction has a rectangular column shape from the viewpoint of ease of manufacture. It is further preferable that the outer shape in a cross section perpendicular to the axial direction has a square columnar shape.

  In the present invention, when the honeycomb aggregate has a plurality of honeycomb segments having different cross-sectional shapes, the ratio of the substantially columnar honeycomb segments (L / S) is the cross-sectional area of the honeycomb segment having the largest number, It can be determined based on one of the average cross-sectional area of the honeycomb body and the cross-sectional area of the honeycomb body located at the axial center. When a plurality of honeycomb bodies having a predetermined cross-sectional area are manufactured and the outer peripheral shape is formed after each is joined with a bonding material, the ratio (L / S) can be obtained from the honeycomb bodies having a predetermined cross-sectional area. .

The porous ceramic is preferably subjected to a heat treatment in a state where ceramic powder, Si ₃ N ₄ powder, and C powder are mixed. The Si ₃ N ₄ powder Si ₃ N ₄ and the C powder C react with each other by heat of heat treatment to generate SiC as a binder.

  Although the heat processing temperature of the mixed powder of each powder is not limited, It is preferable that it is a temperature lower than the temperature (2300 degreeC) which SiC sinters, and it is more preferable that it is 1500-1850 degreeC. Even if heat treatment is performed at 1500 to 1850 ° C., the ceramic powder is not sintered and abnormal grain growth does not occur. When the heat treatment temperature is less than 1500 ° C., the SiC formation reaction hardly proceeds, and when it exceeds 1850 ° C., the sintering of the SiC powder easily proceeds.

  In the present invention, the size (cell shape) of the cells formed in each honeycomb body may be the same or different. The size (cell shape) of each ceramic segment cell is preferably the same.

  In the present invention, the bonding material layer for bonding the honeycomb bodies can also be formed using a conventionally known bonding material. As this bonding material, for example, a SiC-based bonding material can be used. The bonding material layer formed between the honeycomb bodies when the honeycomb bodies are bonded with the bonding material is preferably formed with a thickness of 0.5 to 5 mm.

  The honeycomb aggregate of the present invention preferably has an outer peripheral material layer having a thickness of 0.5 mm or more on the outer peripheral surface in the circumferential direction. By having the outer peripheral material layer, the shape change that occurs when the honeycomb aggregate is used for a DPF or the like can be suppressed. Specifically, when the honeycomb aggregate is used for applications such as DPF, the honeycomb aggregate is exposed to high heat. And a honeycomb aggregate produces thermal expansion. This thermal expansion can be suppressed by having the outer peripheral material layer. A conventionally known material can be used as the material constituting the outer peripheral material layer. For example, SiC, silica compounds, alumina compounds such as aluminum titanate, and the like can be used.

  In addition, since the thickness of the outer peripheral material layer varies depending on the shape of the honeycomb aggregate, the thickness of the outer peripheral material layer cannot be determined unconditionally. More preferably, it is 0.5-5.0 mm.

  The honeycomb aggregate of the present invention is preferably used for DPF. The honeycomb aggregate of the present invention includes a partition wall and a sealing portion, so that it can be used as a wall flow type filter catalyst through which exhaust gas (gas) passes through a cell wall that partitions the cells of the partition wall. Of these filter catalysts, it is particularly preferable to use as a DPF.

  When the honeycomb aggregate of the present invention is used as a DPF, it is preferable to support at least one of a porous oxide made of alumina or the like and a catalyst metal such as Pt, Pd, or Rh on at least the pore surfaces of the partition walls. By carrying these substances, purification performance such as particulates as DPF is improved.

  The outer peripheral shape of the honeycomb aggregate of the present invention is not particularly limited, and can be a conventionally known shape. For example, the cross section can be a substantially circular or elliptical columnar shape, and the cross section can be a square or polygonal prismatic shape, more preferably a cylindrical shape having a diameter of 140 mm and an axial length of 150 mm.

  Although the manufacturing method of the honeycomb aggregate of the present invention is not particularly limited, for example, it can be manufactured by the following manufacturing method.

  First, a substantially prismatic honeycomb segment having cells partitioned in the axial direction is manufactured by a conventionally known manufacturing method. Then, clay (slurry) capable of forming ceramics mainly composed of ceramics constituting the honeycomb body when fired is prepared, and this clay is injected into the end of the cell of the bonded body of the honeycomb body. It is preferable that the clay is injected such that each end face has a checkered pattern. At this time, it is preferable that clay is injected into both ends of the cells that define the outer peripheral surface of the honeycomb aggregate.

  The formed body into which clay has been injected is heated and fired to produce a honeycomb body in which a sealing portion of 0.5 mm or more is formed at the end of the cell.

  Thereafter, a conventionally known bonding material (for example, SiC-based bonding material) is applied to the outer peripheral surface of the formed body, and another honeycomb segment is bonded to the coated surface, followed by heating and firing.

  Subsequently, the outer peripheral surface in the circumferential direction of the fired body is formed by means such as cutting. In this molding, it is preferable that the cells having the sealing portions at both ends form the outer peripheral surface.

  And the outer peripheral material slurry which has SiC as a main component is apply | coated to the outer peripheral surface of the circumferential direction, and it dries and bakes and forms an outer peripheral material layer. Thus, the honeycomb aggregate of the present invention can be manufactured.

  Hereinafter, the present invention will be described using examples.

  As an example of the present invention, a DPF honeycomb aggregate was manufactured.

Example 1
A method for manufacturing the DPF honeycomb aggregate of the example will be described below.

First, 75 parts by weight of SiC powder having an average particle diameter of 12 μm, 20 parts by weight of Si ₃ N ₄ powder having an average particle diameter of 10 μm, and 5 parts by weight of C powder having an average particle diameter of 15 μm were weighed, and methyl cellulose was added as an organic binder. A surfactant was added to what was made moderate viscosity by adding water and mixed and kneaded. The obtained clay was molded by an extrusion method using a mold having an opening of a predetermined shape and dried. This molded body has a prismatic shape with a square cross section, and has cells with a square cross section.

  After drying, the clay used for the production of the molded body was poured into predetermined cells from both ends of the dried molded body and dried at 80 ° C. Here, the predetermined cell is formed so that the cell into which the clay is injected has a checkered pattern. Also, clay was injected only into one end or the other end of the cell.

  Thereafter, the molded body in which the slurry was injected into the cell was heat-treated at 2300 ° C., and the molded body was fired. Thereby, the honeycomb segment 2 was manufactured.

The manufactured honeycomb body 2 has a square shape in which the cross section perpendicular to the axial direction is one side: 35 mm (cross sectional area perpendicular to the axial direction (S): 1225 mm ² ), and the axial length (L) is 152 mm. It is formed in a substantially prismatic shape. The L / S of the honeycomb segment 2 is 0.12 (mm / mm ² ). The honeycomb body 2 is shown in FIG.

  As shown in FIG. 1, the manufactured honeycomb body 2 is encapsulated with a sealing material 3 so that the end face has a checkered pattern.

  Then, the honeycomb bodies 2 were bonded together with a SiC bonding material. This SiC-based bonding material is composed of 35 parts by weight of SiC powder (coarse powder) having an average particle diameter (D50) of 38 μm (trade name: GP # 400, manufactured by Shinano Denki Smelting Co., Ltd.) and SiC powder having D50 of 1.0 μm. (Fine powder) (Shinano Denki Smelting Co., Ltd., trade name: SER-A10) 29 parts by weight, inorganic fiber made of mullite with a fiber length of 1 mm or less (Shin Nikka Thermal Ceramics Co., Ltd., trade name: SC1260-) A10) 10 parts by weight, an organic binder made of an aqueous solution containing 1.5% by weight of carboxymethyl cellulose (CMC) (manufactured by Daicel Chemical Industries, Ltd., trade name: DN400H), 10 parts by weight of an inorganic binder made of colloidal silica (Nissan Chemical Industries) 16 parts by weight manufactured by Co., Ltd. and trade name: Snowtex O) were weighed and kneaded.

  In the bonding with the bonding material, the bonding material was applied to the outer peripheral surface of the honeycomb body 2 so that the thickness was 1.0 ± 0.5 mm, and another honeycomb body 2 was then bonded to this surface. . This joining was repeated, and 16 honeycomb bodies 2 were joined so that the cross section was a square, and dried at 80 ° C. The end face of the joined body of the honeycomb segment 2 is shown in FIG.

  Then, this joined body was cut using an electric saw to form an outer peripheral shape. The cutting with the electric saw was made so that the cell in which the sealing material was formed at both ends formed a substantially cylindrical shape forming the outer peripheral surface.

  Subsequently, a peripheral material slurry was prepared. The outer peripheral material slurry was composed of 50 parts by weight of SiC powder having an average particle diameter of 20 μm, 19 parts by weight of spherical silica powder having an average particle diameter of 1 μm, 25 parts by weight of a 1.26 wt% CMC solution as a binder, and an anionic dispersant 1 as a dispersant. It was prepared by thoroughly mixing parts by weight and 5 parts by weight of colloidal shear force as a binder.

  And the outer periphery material slurry prepared to the sintered body after grinding was apply | coated to the outer peripheral surface of the cutting body, and it dried at 80 degreeC, Then, it heated at 850 degreeC and solidified the joining material and slurry. Thereby, the outer peripheral material layer 4 having a thickness of 1.5 mm could be formed on the outer peripheral surface.

  As described above, the honeycomb aggregate 1 of this example could be manufactured. The honeycomb aggregate 1 of this example is shown in FIG. 3 at its end face.

In the honeycomb aggregate 1 of the present embodiment, a plurality of substantially columnar honeycomb aggregates 2 having a square cross section are bonded via a bonding material layer 5, and an outer peripheral material layer 4 is formed on the outer periphery in the circumferential direction. The ratio (L / S) between the axial length (L) of the honeycomb body 2 and the cross-sectional area (S) in the cross section perpendicular to the axial direction of the honeycomb body is 0.12 (mm / mm). ² ).

(Example 2)
The present example is a honeycomb aggregate manufactured in the same manner as in Example 1 except that the shape (size) of the honeycomb segment 2 is different.

The honeycomb segment used in this example has a square shape in which the cross section perpendicular to the axial direction is one side: 50 mm (cross sectional area perpendicular to the axial direction (S): 2500 mm ² ), and the axial length (L ) Is formed in a substantially prismatic shape of 152 mm. The honeycomb segment has an L / S of 0.06 (mm / mm ² ).

(Example 3)
The present example is a honeycomb aggregate manufactured in the same manner as in Example 1 except that the shape (size) of the honeycomb segment 2 is different.

The honeycomb segment used in this example has a square shape in which the cross section perpendicular to the axial direction is one side: 105 mm (cross sectional area perpendicular to the axial direction (S): 11025 mm ² ), and the axial length (L ) Is formed in a substantially prismatic shape of 152 mm. The honeycomb segment has an L / S of 0.01 (mm / mm ² ).

Example 4
The present example is a honeycomb aggregate manufactured in the same manner as in Example 1 except that the shape (size) of the honeycomb segment 2 is different.

The honeycomb segment used in this example has a square shape in which the cross section perpendicular to the axial direction is one side: 35 mm (cross sectional area perpendicular to the axial direction (S): 1225 mm ² ), and the axial length (L ) Is formed in a substantially prismatic shape of 305 mm. L / S of this honeycomb segment is 0.25 (mm / mm ² ).

(Example 5)
The present example is a honeycomb aggregate manufactured in the same manner as in Example 1 except that the shape (size) of the honeycomb segment 2 is different.

The honeycomb segment used in this example has a square shape in which the cross section perpendicular to the axial direction is one side: 50 mm (cross sectional area perpendicular to the axial direction (S): 2500 mm ² ), and the axial length (L ) Is formed in a substantially prismatic shape of 305 mm. The honeycomb segment has an L / S of 0.12 (mm / mm ² ).

(Example 6)
The present example is a honeycomb aggregate manufactured in the same manner as in Example 1 except that the shape (size) of the honeycomb segment 2 is different.

The honeycomb segment used in this example has a square shape in which the cross section perpendicular to the axial direction is one side: 105 mm (cross sectional area perpendicular to the axial direction (S): 11025 mm ² ), and the axial length (L ) Is formed in a substantially prismatic shape of 305 mm. The honeycomb segment has an L / S of 0.03 (mm / mm ² ).

(Comparative Example 1)
First, 51.5 parts by weight of α-type silicon carbide powder and 22 parts by weight of β-type silicon carbide powder were wet-mixed, and an organic binder (methyl cellulose) and water were added to 6.5 parts by weight and 20 parts by weight, respectively. Part by part was added and kneaded. Next, a mixture obtained by adding a small amount of a plasticizer and a lubricant to the kneaded product and further kneading was extruded to obtain a prismatic shaped product.

  Next, after this molded body was dried using a microwave dryer, the cells of the molded body were sealed with a sealing paste made of porous SiC ceramics. 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 body made of porous SiC ceramics was obtained.

The manufactured honeycomb segment has a square shape in which the cross section perpendicular to the axial direction is one side: 35 mm (cross sectional area perpendicular to the axial direction (S): 1225 mm ² ), and the axial length (L) is 152 mm. It is formed in a substantially prismatic shape. The L / S of the honeycomb segment 2 is 0.12 (mm / mm ² ).

Next, 23.3 parts by weight of ceramic fiber (alumina silicate ceramic fiber, shot content 3%, fiber length 0.1 mm to 100 mm), 30.2 parts by weight of SiC powder having an average particle size of 0.3 μm, as an inorganic binder 7 parts by weight of silica sol (conversion amount of SiO _{2 in} the sol was 30%), 0.5 part by weight of CMC as an organic binder and 39 parts by weight of water were mixed and kneaded. By adjusting the kneaded material to an appropriate viscosity, a bonding material paste used as a bonding material was produced.

  Next, the bonding material paste was uniformly applied to the outer peripheral surface of the honeycomb body so as to have a thickness of 1.0 ± 0.5 mm, and the outer peripheral surfaces of the honeycomb body were in close contact with each other. Drying and curing is performed under the conditions of -100 ° C to 1 hour. Then, the honeycomb aggregates were bonded to each other via a bonding material layer having a thickness of 1.5 mm, and a honeycomb aggregate of this comparative example, which was an aggregate of honeycomb aggregates, was manufactured.

  As described above, this comparative example is a honeycomb aggregate manufactured by the manufacturing method described in Example 1 of Patent Document 2.

In the honeycomb aggregate 1 of this comparative example, a plurality of substantially pillar-shaped honeycomb aggregates 2 having a square cross section are bonded via a bonding material layer 5, and an outer circumferential material layer 4 is formed on the outer periphery in the circumferential direction. The ratio (L / S) between the axial length (L) of the honeycomb body 2 and the cross-sectional area (S) in the cross section perpendicular to the axial direction of the honeycomb body is 0.12 (mm / mm). ² ).

(Comparative Example 2)
This comparative example is a honeycomb aggregate manufactured in the same manner as in Comparative Example 1 except that the shape (size) of the honeycomb segment 2 is different.

The honeycomb segment used in this comparative example has a square shape in which the cross section perpendicular to the axial direction is one side: 105 mm (cross sectional area perpendicular to the axial direction (S): 11025 mm ² ), and the axial length (L ) Is formed in a substantially prismatic shape of 152 mm. The honeycomb segment has an L / S of 0.01 (mm / mm ² ).

(Comparative Example 3)
This comparative example is a honeycomb aggregate manufactured in the same manner as in Comparative Example 1 except that the shape (size) of the honeycomb segment 2 is different.

The honeycomb segment used in this comparative example has a square shape in which the cross section perpendicular to the axial direction is one side: 105 mm (cross sectional area perpendicular to the axial direction (S): 11025 mm ² ), and the axial length (L ) Is formed in a substantially prismatic shape of 305 mm. The honeycomb segment has an L / S of 0.03 (mm / mm ² ).

(Evaluation)
The honeycomb aggregates of the examples and comparative examples were evaluated.

(An endurance test)
First, the honeycomb aggregates of the examples and comparative examples were set as DPFs in an actual vehicle exhaust system, and the occurrence of cracks after supplying exhaust gas was confirmed.

  Specifically, the accelerator opening is set with the honeycomb assembly assembled in the exhaust system of a vehicle equipped with a QD32 diesel engine (Nissan Motor) and the engine speed fixed at 1000, 1500, 2000, 2500, 3000 rpm, respectively. The exhaust gas was supplied to 60%, 80% and 100%. After a certain period of time, the aggregate was taken out and the occurrence of cracks was confirmed visually. The results are shown in Table 1. In Table 1, the case where a crack was not confirmed was marked with ◯, and the case where a crack was confirmed was marked with x.

  As shown in Table 1, the occurrence of cracks could not be confirmed in the honeycomb aggregates (DPF) of each example, but in the honeycomb aggregates (DPF) of Comparative Examples 2 to 3, cracks were not observed in the honeycomb aggregate. Occurrence was confirmed.

(Bending strength)
Next, the honeycomb bodies of Example 1 and Comparative Example 1 were subjected to a three-point bending test, and the strength of each honeycomb body was measured.

  The three-point bending test was measured according to JIS R1601 at a fulcrum distance of 40 mm and a crosshead speed of 0.5 mm / min.

  The three-point bending strength of the honeycomb body of the example was 72 MPa, while that of the comparative example was 58 MPa. As described above, it was confirmed that the honeycomb segment of Example 1 was stronger and more robust than Comparative Example 1.

(SEM photo)
Next, SEM photographs of the honeycomb bodies of Example 1 and Comparative Example 1 were taken. SEM photographs are shown in FIGS.

  As shown in the SEM photographs of the honeycomb substrates of Example 1 and Comparative Example 1, the honeycomb segment of Example 1 (the porous SiC ceramics constituting the honeycomb substrate) was formed by the binder while the SiC particles remained uniformly. Whereas a firm neck is formed, in the honeycomb segment of Comparative Example 1 (porous SiC ceramics constituting it), there are non-uniform portions due to abnormal grain growth due to the progress of sintering. This can be confirmed from the SEM image. This non-uniform location is low in strength and causes a decrease in the thermal shock resistance of the honeycomb aggregate (honeycomb aggregate).

  Furthermore, it can be confirmed that the SiC ceramic of Example 1 has a SiC particle size smaller than that of Comparative Example 1. It can be confirmed that the honeycomb segment of Example 1 has finer pores than the honeycomb segment of Comparative Example 1. It can be seen that with these fine pores, Example 1 is a filter that can capture finer particles.

  Thus, the ratio (L / S) between the axial length (L) of the honeycomb body 2 and the cross-sectional area (S) in the cross section perpendicular to the axial direction of the honeycomb body is within the specified range. A honeycomb aggregate of a certain example is a honeycomb aggregate excellent in manufacturability while ensuring sufficient performance as a filter.

FIG. 3 is a view showing a honeycomb aggregate used in the honeycomb aggregate of Example 1. 3 is a view showing an end face of a joined body of honeycomb bodies of Example 1. FIG. 3 is a view showing an end face of a honeycomb aggregate of Example 1. FIG. 3 is a SEM photograph of a cross section of a honeycomb aggregate of a honeycomb aggregate of Example 1. FIG. 3 is a SEM photograph of a cross section of a honeycomb aggregate of a honeycomb aggregate of Comparative Example 1.

Explanation of symbols

1: Honeycomb aggregate 2: Honeycomb segment 3: Sealing material 4: Peripheral material layer 5: Bonding material layer

Claims (4)

A cell wall that is made of porous ceramics and has a substantially columnar honeycomb body in which a large number of cells extending in the axial direction are partitioned, and a bonding material layer that joins the honeycomb body, and partitions the cells. In the wall flow type honeycomb aggregate through which gas passes,
The porous ceramic has ceramic powder made of SiC, and a binder made of SiC that bonds SiC particles constituting the ceramic powder,
A ratio (L / S) between the axial length (L) of the substantially honeycomb-shaped honeycomb body and the cross-sectional area (S) in a cross section perpendicular to the axial direction of the honeycomb body is 0.01 (mm) / Mm ² ) or more. The honeycomb aggregate according to claim 1, wherein the porous ceramic is heat-treated in a state where the ceramic powder, Si ₃ N ₄ powder, and C powder are mixed.   The honeycomb aggregate according to any one of claims 1 and 2, further comprising an outer peripheral material layer having a thickness of 0.5 mm or more on an outer peripheral surface in a circumferential direction. One end sealing portion made of a sealing material for sealing one end portion of a predetermined cell among a number of the cells,
The other end sealing portion made of a sealing material for sealing the other end portion of the remaining cells,
The honeycomb aggregate according to any one of claims 1 to 3, further comprising a sealing portion made of