JP7817201B2 - Honeycomb structure and method for manufacturing honeycomb structure - Google Patents

Description

The present invention relates to a honeycomb structure and a method for manufacturing a honeycomb structure.

Catalyst carriers, which have a catalyst supported on a carrier, are used to treat harmful substances in exhaust gases emitted from vehicle engines. During treatment, if the catalyst temperature is low when the engine is started, the catalyst does not heat up to the required temperature, resulting in insufficient purification of the exhaust gas. To solve this problem, development is underway on exhaust gas treatment devices that use electrically heated catalysts (EHCs). Electricity is passed through a conductive carrier to heat it, thereby heating the catalyst supported on the carrier to its activation temperature before or during engine start-up. Patent Document 1 discloses a ceramic honeycomb structure as one such carrier.

Patent No. 6438939

To make the honeycomb structure generate heat, electrode layers are disposed on its sides. For example, to improve the heat generation characteristics of the honeycomb structure when electricity is applied, the thickness of the disposed electrode layers must be as uniform as possible.

In view of the above, an object of the present invention is to provide a honeycomb structure having an electrode layer with excellent thickness uniformity.

1. A method for manufacturing a honeycomb structure according to an embodiment of the present invention includes a molding step of extruding a molding material containing ceramic raw materials to obtain a honeycomb molded body, and a firing step of drying the honeycomb molded body and firing the resulting dried honeycomb body to obtain a honeycomb structure, wherein the honeycomb structure includes a honeycomb structure part having an outer peripheral wall and partition walls arranged inside the outer peripheral wall, and a pair of electrode layers arranged on side surfaces of the honeycomb structure part, and the molding step includes transporting the cylindrical honeycomb molded body obtained by the extrusion molding while supporting the outer peripheral surface along the cell extension direction of the cylindrical honeycomb molded body obtained by the extrusion molding on a receiving table, and the receiving table has a main body part having grooves along the cell extension direction, and an abutting part having an arc-shaped curved surface that is disposed in the groove of the main body part and abuts against the lower half of the honeycomb molded body, and the abutting part is made of a material having a hardness of 74 N or less, and the difference between the diameter of the arc-shaped abutting part and the diameter of the extrusion molding die is 0.6 mm or less.
2. In the method for manufacturing a honeycomb structure according to the above item 1, the ceramic raw material may contain silicon carbide and metallic silicon.
3. In the method for manufacturing a honeycomb structure according to the above 1 or 2, the specific gravity of the honeycomb formed body may be 0.3 or more.
4. In the method for manufacturing a honeycomb structure according to any one of the above 1 to 3, the circumferential end of the contact portion may be in contact with the outer peripheral surface of the honeycomb formed body without any gap.
5. In the method for manufacturing a honeycomb structure according to any one of the above items 1 to 4, the contact portion may be made of a soft urethane foam.

6. A honeycomb structure according to another embodiment of the present invention comprises a honeycomb structure portion having partition walls that define a plurality of cells that serve as fluid flow paths extending from a first end face to a second end face and an outer peripheral wall located on the periphery, and a pair of electrode layers disposed on the side surfaces of the honeycomb structure portion, wherein the honeycomb structure portion contains silicon carbide and silicon metal, the circularity of a surface of the honeycomb structure portion perpendicular to the cell extension direction is 1 mm or less, the thickness of the electrode layer is 0.05 mm or more and 0.50 mm or less, and the variation in thickness of the electrode layer is 35% or less.

According to an embodiment of the present invention, a honeycomb structure having an electrode layer with excellent thickness uniformity can be obtained.

1 is a perspective view showing a schematic configuration of a honeycomb structure according to one embodiment of the present invention. FIG. 2 is a cross-sectional view of the honeycomb structure shown in FIG. 1. FIG. 2 is a cross-sectional view of the honeycomb structure shown in FIG. 1. FIG. 10 is a diagram for explaining a cell pitch. FIG. 10 is a schematic diagram showing an example of how an extrusion-molded honeycomb molded body is supported by a receiving base. FIG. 1 is a diagram showing an example of a concave-convex pattern at the tip of a honeycomb molded body extruded from a die of an extrusion molding machine. 1 is a perspective view showing a schematic configuration of a support table used in a method for manufacturing a honeycomb structure according to one embodiment of the present invention. FIG. 10 is a side view showing an example of how a honeycomb formed body is supported by a receiving base.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Furthermore, to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part more schematically than in the embodiments, but these are merely examples and do not limit the interpretation of the present invention.

A. Honeycomb Structure Fig. 1 is a perspective view showing a schematic configuration of a honeycomb structure according to one embodiment of the present invention, and Fig. 2 and Fig. 3 are cross-sectional views of the honeycomb structure shown in Fig. 1. The honeycomb structure 30 comprises a honeycomb structure part 10 and a pair of electrode layers 20, 20 disposed on the side surfaces of the honeycomb structure part 10 and facing each other with the honeycomb structure part 10 interposed therebetween.

The honeycomb structure 10 has partition walls 14 that define a plurality of cells 12 that extend (in the lengthwise direction) from the first end face 10a to the second end face 10b and can serve as fluid flow paths, and an outer peripheral wall 16 that is located on the periphery and surrounds the partition walls 14. The outer peripheral wall 16 extends in the lengthwise direction. Each of the plurality of cells 12 is formed as a space extending in the lengthwise direction. In the illustrated example, the cross-sectional shape of each cell 12 perpendicular to the lengthwise direction is approximately a regular hexagon, but may be other shapes such as other polygons (e.g., triangles, rectangles, pentagons), circles, or ellipses. The cross-sectional shape of the outer peripheral wall 16 perpendicular to the lengthwise direction is typically circular, but may also be polygonal or ellipsoidal. Note that the partition walls 14 are omitted from Figure 3.

The circularity of the surface of the honeycomb structure 10 (peripheral wall 16) perpendicular to the extension direction of the cells 12 is, for example, 1 mm or less, and preferably 0.6 mm or less. Circularity can be measured, for example, by optical gauge bending measurement (measurement using a laser displacement meter). Specifically, the peripheral shape of the honeycomb structure 10 is measured at three points in the longitudinal direction: the top end, center, and bottom end. The obtained measurement data is best-fitted (a process that minimizes deviation from the reference value) to a reference peripheral shape, and the absolute value of the difference from the reference value is calculated to obtain circularity (unit: mm). Satisfying this circularity requirement allows for the production of a honeycomb structure equipped with an electrode layer with excellent thickness uniformity. Note that, in this specification, "perpendicular surface" can also include "perpendicular cross section."

From the standpoint of strength, the thickness of the outer wall 16 is preferably 0.2 mm or more. On the other hand, the thickness of the outer wall 16 is, for example, 1 mm or less, preferably 0.7 mm or less, and more preferably 0.4 mm or less. The variation in the thickness of the outer wall (the variation within the plane perpendicular to the extension direction of the cells 12) is preferably 30% or less, and more preferably 20% or less. The variation in the thickness of the outer wall can be calculated by measuring the thickness of the outer wall at eight locations at regular intervals (every 45° central angle) using a CNC image measuring system (for example, Nikon's NEXIV series), and then dividing the absolute value of the difference between each measurement value and the average value by the average value.

From the viewpoint of use as a catalyst carrier, the thickness of the partition wall 14 is preferably 310 μm or less, more preferably 250 μm or less, and even more preferably 230 μm or less. On the other hand, from the viewpoint of strength, the thickness of the partition wall 14 is preferably 100 μm or more, more preferably 130 μm or more, and even more preferably 150 μm or more.

The number of cells 12 per unit area in a plane perpendicular to the direction in which the cells 12 extend is, for example, 50 cells/cm ² to 150 cells/cm ² , and preferably 60 cells/cm ² to 100 cells/cm ² .

The cell pitch P of the cells 12 in a plane perpendicular to the extension direction of the cells 12 is, for example, 0.8 mm or more and 1.6 mm or less, and preferably 1.0 mm or more and 1.4 mm or less. Here, the cell pitch P is the distance between the central portions 14a of opposing, approximately parallel partition walls 14 in the thickness direction, as shown in Figure 4.

The variation in cell pitch P (in-plane variation perpendicular to the extension direction of the cells 12) is preferably 5.5% or less, and more preferably 4.5% or less. The variation in cell pitch can be calculated by measuring the cell pitch at a total of 10 or more locations at regular intervals along each diameter direction using a CNC image measuring system (e.g., Nikon's NEXIV series), and then dividing the absolute value of the difference between each measurement value and the average value by the average value. Here, "each diameter direction" refers to two directions, the X and Y directions, when the cross-sectional shape of the cell is rectangular, and three directions (directions perpendicular to a pair of opposing partition walls) when the cross-sectional shape of the cell is hexagonal.

The pair of electrode layers 20, 20 are arranged on either side of the central axis of the honeycomb structure section 10, and are each formed in a strip shape extending in the extension direction of the cells 12 of the honeycomb structure section 10. Although not shown, each of the pair of electrode layers 20, 20 is provided with a metal terminal, one terminal of which can be connected to the positive pole of a power source, and the other terminal of which can be connected to the negative pole of the power source.

The thickness of the electrode layer 20 is, for example, 0.05 mm or more and 0.50 mm or less. The variation in thickness of the electrode layer 20 is preferably 35% or less, more preferably 32% or less, and even more preferably 30% or less. There is no particular lower limit to the variation in thickness of the electrode layer 20, but it may be, for example, 20% or more, or 25% or more. The variation in thickness of the electrode layer can be calculated by measuring the thickness of the electrode layer at four or more points on each cross section perpendicular to the cell extension direction of the honeycomb structure using an optical microscope, and then dividing the absolute value of the difference between each measurement value and the average value by the average value. The honeycomb structure according to an embodiment of the present invention achieves such thickness uniformity, ensuring the electrical heat generation properties of the resulting honeycomb structure, suppressing uneven electrical heat generation, and enabling the honeycomb structure to be heated uniformly.

The formation range of the electrode layers 20 is not particularly limited, but the pair of electrode layers 20, 20 are each formed such that the central angle θ of an arc on a plane perpendicular to the extension direction of the cell 12 is, for example, in a range of 80° or more, and preferably in a range of 99° or more and less than 180°. Even within this formation range, it is possible to achieve the above-mentioned variation in the thickness of the electrode layer.

The electrical resistivity of the honeycomb structure portion 10 at 25°C is preferably 0.1 Ωcm to 200 Ωcm. The electrical resistivity of the electrode layer 20 at 25°C is preferably 0.1 Ωcm to 100 Ωcm, and more preferably 0.1 Ωcm to 50 Ωcm.

The honeycomb structure 10 is typically composed of a porous body. It is formed from a material containing ceramic raw materials. It is typically formed from a material containing silicon carbide and metallic silicon. Specifically, it is formed from a material primarily composed of a silicon-silicon carbide composite material (e.g., containing 95% by mass or more). The silicon-silicon carbide composite material can be a material in which multiple silicon carbide particles are bonded together with metallic silicon. When the honeycomb structure is formed from a silicon-silicon carbide composite material, the ratio of the "mass of silicon as a binder" contained in the honeycomb structure to the sum of the "mass of silicon carbide particles as aggregate" contained in the honeycomb structure and the "mass of silicon as a binder" contained in the honeycomb structure is preferably 10% by mass to 40% by mass, and more preferably 15% by mass to 35% by mass. Such a material can satisfactorily achieve the above-mentioned electrical resistivity.

Typically, the volume resistivity of the electrode layer 20 is set lower than that of the honeycomb structure section 10. This relationship allows electricity to flow preferentially through the electrode layer 20, facilitating the spread of electricity in the extension direction and circumferential direction of the cells 12 when current is applied. The volume resistivity of the electrode layer 20 is preferably 1/10 or less, more preferably 1/20 or less, and even more preferably 1/30 or less, of the volume resistivity of the honeycomb structure section 10. On the other hand, if the difference in volume resistivity between the two is too large, current may concentrate between the opposing ends of the electrode layer 20, resulting in uneven heat generation in the honeycomb structure section 10. The volume resistivity of the electrode layer 20 is preferably 1/200 or more, more preferably 1/150 or more, and even more preferably 1/100 or more, of the volume resistivity of the honeycomb structure section 10. Here, the volume resistivity of the electrode layer 20 is a value measured at 25°C using a four-terminal method.

Examples of materials that can be used for the electrode layer 20 include conductive ceramics, metals, and composites (cermets) of metals and conductive ceramics. Examples of metals include elemental metals such as Cr, Fe, Co, Ni, Si, or Ti, or alloys containing at least one metal selected from the group consisting of these metals. Examples of conductive ceramics include metal compounds such as silicon carbide (SiC) and metal silicides such as tantalum silicide (TaSi ₂ ) and chromium silicide (CrSi ₂ ). Specific examples of composites (cermets) of metals and conductive ceramics include composites of metal silicon and silicon carbide, and composites of the above metal silicides, metal silicon, and silicon carbide. Specific examples of composites (cermets) of metals and conductive ceramics include composites in which one or more insulating ceramics, such as alumina, mullite, zirconia, cordierite, silicon nitride, or aluminum nitride, are added to one or more of the above metals in order to reduce thermal expansion. Among these, for example, a composite material of metal silicide, metal silicon, and silicon carbide is preferably used from the viewpoint that it can be fired simultaneously with the honeycomb structure part 10 and contributes to simplifying the manufacturing process.

When the honeycomb structure 30 is used as a catalyst carrier, a catalyst is supported on the partition walls 14, and CO, NO _x , hydrocarbons, and the like in the exhaust gas passing through the cells 12 can be converted into harmless substances through a catalytic reaction. The catalyst may preferably contain a noble metal (e.g., platinum, rhodium, palladium, ruthenium, indium, silver, gold), aluminum, nickel, zirconium, titanium, cerium, cobalt, manganese, zinc, copper, tin, iron, niobium, magnesium, lanthanum, samarium, bismuth, barium, or a combination thereof.

B. Manufacturing Method The above honeycomb structure (honeycomb structure part) can be typically manufactured by a method including a molding step of extruding a molding material containing ceramic raw materials to obtain a honeycomb formed body, and a firing step of drying the honeycomb formed body and firing the resulting dried honeycomb body to obtain a honeycomb structure (honeycomb structure part).

As mentioned above, the molding material contains ceramic raw materials. Typically, it contains silicon carbide (powder) and silicon metal (powder). Other raw materials that may be contained in the molding material include, for example, binders, dispersion media, and additives.

In the above-mentioned molding process, typically, the molding material is extruded from a die with slits formed that correspond to the partition walls of the honeycomb structure to obtain a cylindrical honeycomb molded body with partition walls that define the cells that serve as fluid flow paths. Then, in the molding process, the outer peripheral surface of the honeycomb molded body obtained by extrusion molding, which extends in the direction of the cells, is supported by a receiving table and transported.

Figure 5A is a schematic diagram showing an example of how an extrusion-molded honeycomb molded body is supported on a receiving table. As shown in Figure 5A, a cylindrical honeycomb molded body 44 extruded from a die 42 fixed by a die (pressure plate) 41 of an extrusion molding machine 40 is delivered to a receiving table 100 located at the outlet of the die 41 of the extrusion molding machine 40 and transported. The die (pressure plate) 41 defines the outer wall of the honeycomb structure. Although not shown, the receiving table 100 is typically placed on a transport path that transports the honeycomb structure at a predetermined speed (e.g., approximately the same speed as the extrusion speed of the molding material). The transport path is not particularly limited, but a conveyor-type transport path, for example, is used.

As mentioned above, the honeycomb formed body 44 can be formed from a molding material containing silicon carbide and silicon metal. Such formed bodies tend to have a high specific gravity, for example, 0.3 or more. Here, the specific gravity of the honeycomb formed body is calculated from the weight and volume of the honeycomb formed body (volume calculated from the formed length and the diameter of the extrusion mold).

The moisture content of the honeycomb formed body 44 is preferably 19% to 27%. This moisture content helps to prevent deformation during contact, as described below.

By controlling the uneven pattern (extrusion amount variation) at the tip of the honeycomb formed body extruded from the extrusion molding machine, it is possible to achieve good contact, as described below. The uneven pattern at the tip of the honeycomb formed body can be appropriately designed depending on the specific gravity, moisture content, hardness, etc. of the honeycomb formed body. An example of the uneven pattern at the tip of a honeycomb formed body 44 extruded from the die 41 of the extrusion molding machine is shown in Figure 5B. As shown in Figure 5B, it is preferable to control the difference (height h) between the most extruded point (the center in the illustrated example) and the least extruded point (the outer periphery in the illustrated example) to be between 0 mm and 2 mm.

Figure 6 is a perspective view showing the general configuration of a support used in a honeycomb structure manufacturing method according to one embodiment of the present invention. The support 100 has a main body portion 50 and an abutment portion 60 placed on the main body portion 50.

The main body 50 has a groove 51 extending in one direction. The shape of the groove 51 is not particularly limited, but can be adjusted, for example, according to the shape and size corresponding to the shape of the honeycomb formed body 44. In the illustrated example, the groove 51 has a curved surface corresponding to the lower half of the outer peripheral surface along the extension direction of the cells of the honeycomb formed body 44, and the surface perpendicular to the extension direction of the groove 51 is the lower half (semicircle) of the surface perpendicular to the extension direction of the cells of the honeycomb formed body 44.

The abutment portion 60 is positioned in the groove portion 51 of the main body portion 50 and abuts against the honeycomb formed body 44. The abutment portion 60 has an arc-shaped curved surface that is approximately the same as the lower half of the outer peripheral surface along the cell extension direction of the honeycomb formed body 44. Specifically, the difference (clearance) between the diameter L1 of the arc-shaped abutment portion (abutment surface) 60 and the diameter L2 of the extrusion molding die 41 is 0 mm or more and 0.6 mm or less, preferably 0.2 mm or less, and more preferably 0.1 mm or less. It is preferable that both circumferential ends 60a, 60a of the abutment portion 60 abut against the outer peripheral surface of the honeycomb formed body 44 without any gaps, as shown in Figure 7. This configuration effectively prevents the honeycomb formed body 44 from deforming under its own weight toward the gap between the abutment portion 60 and the honeycomb formed body 44 while supported, thereby achieving the above-mentioned circularity, as well as variations in the thickness of the outer wall and cell pitch. This is particularly effective when the specific gravity of the honeycomb formed body is high, as it is prone to deformation under its own weight.

The contact portion 60 is made of a material with a hardness of 74N or less. The hardness of the material making up the contact portion is preferably 70N or less, more preferably 65N or less, and may be 60N or less. On the other hand, the contact portion 60 is preferably made of a material with a hardness of 44N or more, and may be 50N or more, or may be 55N or more. Here, hardness refers to the hardness at 25% compression measured in accordance with JIS K6400-2, 6.7 (Method D). Specifically, it is the load (N) applied when the object to be measured (contact portion) is pre-compressed to 75% of its original thickness (original thickness), returned to its original thickness, and then pressed down to 25% of the original thickness and held for 20 seconds.

When the honeycomb formed body 44 is transferred to the receiving table 100, it is likely to collide with the abutment portion 60 (particularly the circumferential end portion 60a of the abutment portion 60). However, because the abutment portion 60 is made of a material with a hardness of 74N or less, deformation due to the collision can be suppressed. Furthermore, by using a material that satisfies the above hardness, deformation due to the weight of the honeycomb formed body 44 while it is supported (e.g., deformation or crushing of the cell shape) can be suppressed. By suppressing deformation of the honeycomb formed body 44, yield can be significantly improved.

From the perspective of satisfactorily satisfying the above-mentioned hardness requirement, the abutment portion 60 is preferably made of soft urethane foam. The thickness of the abutment portion 60 is, for example, 9.2 mm to 10.8 mm. With this thickness, as shown in the example, the abutment portion 60 can be curved to follow the groove portion 51 of the main body portion 50, and have an arc-shaped curved surface that is approximately the same as the outer peripheral surface along the extension direction of the cells of the honeycomb molded body.

The main body 50 may be made of any suitable material. From the perspective of machining precision of the groove 51, it is preferable that it be made of a hard material. For example, the hard material has a Shore D hardness of 40HS to 70HS measured in accordance with ISO 868. Of the hard materials, from the perspective of handleability, it is more preferable that it be made of a hard resin. Specific examples of hard resins include polystyrene foam and porous polyurethane resin.

After transportation, the honeycomb formed body is dried to obtain a dried honeycomb body. Before drying (e.g., during transportation), the honeycomb formed body may be cut to a predetermined length.

Methods for drying honeycomb molded bodies include, for example, hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying. These may be used alone or in combination of two or more. Among these, it is preferable to dry a certain amount of moisture using an electromagnetic heating method, and then dry the remaining moisture using an external heating method, as this allows the entire honeycomb molded body to be dried quickly, uniformly, and without cracks. Dielectric heating drying is preferred as the electromagnetic heating method, and hot air drying is preferred as the external heating method. The drying temperature is preferably 50°C to 120°C.

The dried honeycomb body is fired to obtain a honeycomb structure (honeycomb structure portion). Any appropriate firing conditions can be used. The firing temperature is, for example, 1400°C to 1500°C. The firing time is, for example, 20 to 80 hours. Firing may be carried out continuously or in multiple stages at different temperatures. When firing in multiple stages, the firing time is the total of the firing times for each stage.

The dried honeycomb body may be calcined before being subjected to the firing process. The calcination temperature may be determined, for example, according to the combustion temperature of the organic matter contained in the dried honeycomb body. The calcination temperature is, for example, 200°C to 1000°C. The calcination time is, for example, 10 hours to 100 hours. Note that calcination and firing may be performed consecutively. Specifically, calcination may be performed during the temperature rise process of firing.

The electrode layer is typically formed by applying an electrode layer-forming material and firing the resulting coating layer. The electrode layer-forming material can be applied at any appropriate time. Typically, the electrode layer-forming material is applied to the dried honeycomb body. The electrode layer-forming material may also be applied to the fired honeycomb body (during the firing process). A printing method is preferably used to apply the electrode layer-forming material. For example, a printing plate with openings formed on the side of the dried honeycomb body is placed, and the electrode layer-forming material paste is applied by pressing it onto the plate with a squeegee. This method allows for the electrode layer to be formed satisfactorily on the application surface (the curved side surface). Additionally, since the resulting honeycomb structure can achieve the above-mentioned circularity well, the electrode layer-forming material can be applied uniformly on the application surface, resulting in the formation of an electrode layer with excellent thickness uniformity.

The present invention will be explained in detail below using examples, but the present invention is not limited to these examples.

[Example 1]
(receiving table)
A main body having a semicircular cross-section groove as shown in Figure 6 was fabricated by cutting polystyrene foam using an end mill. A sheet of soft urethane foam with a thickness of 10 mm and a hardness of 60 N was placed in the groove of the obtained main body as shown in Figure 6 to form a semicircular contact part with a cross-section diameter (L1) of 86.4 mm, thereby fabricating a support base.

(molding material)
Sieved silicon carbide powder and metallic silicon powder were mixed in a mass ratio of 70:30 to obtain a raw material powder. A binder, additives, and water were added to the obtained raw material powder, and the mixture was mixed to obtain a wet powder (mixture). The amount of water added was adjusted so that the moisture content of the resulting honeycomb molded body was 23%. The obtained wet powder was kneaded to obtain a clay.

The above clay was extruded using an extrusion molding machine equipped with a die and a pressure plate with a diameter (L2) of 86.4 mm, as shown in Figure 5A, and the extruded cylindrical honeycomb molded body was held on a receiving table placed at the outlet of the pressure plate of the extrusion molding machine. The honeycomb molded body was then dried to obtain a dried honeycomb body.

(Electrode layer forming material)
An electrode layer-forming material was prepared by mixing metal silicon (Si) powder with an average particle size of 6 μm, silicon carbide (SiC) powder with an average particle size of 35 μm, methyl cellulose, glycerin, and water using a planetary centrifugal mixer. The Si powder and SiC powder were blended in a volume ratio of Si powder:SiC powder = 40:60. Furthermore, when the total amount of Si powder and SiC powder was 100 parts by mass, the blend amounts were 0.5 parts by mass of methyl cellulose, 10 parts by mass of glycerin, and 38 parts by mass of water.

(electrode layer)
The electrode layer-forming material was applied to the side surfaces of the dried honeycomb body by a printing method (central angle of one electrode layer: 90°) so as to obtain an electrode layer as shown in Fig. 1. Specifically, a printing plate having openings formed therein was placed on the outer peripheral surface of the dried honeycomb body, and the electrode layer-forming material was applied by pressing it onto the printing plate with a squeegee.

(Firing)
After the electrode layer forming material applied to the dried honeycomb body was dried, it was fired in an argon atmosphere and then fired in an air atmosphere, and the length was adjusted appropriately to obtain a honeycomb structure with a length of 65 mm.

[Example 2]
A honeycomb structure was obtained in the same manner as in Example 1, except that in the preparation of the support, the main body portion was cut so that the diameter (L1) of the contact portion was 86.6 mm.

[Example 3]
A honeycomb structure was obtained in the same manner as in Example 1, except that a sheet-like soft urethane foam having a thickness of 10 mm and a hardness of 50 N was used in the preparation of the support base.

[Example 4]
A honeycomb structure was obtained in the same manner as in Example 1, except that a sheet-like soft urethane foam having a thickness of 10 mm and a hardness of 70 N was used in the preparation of the support base.

[Comparative Example 1]
A honeycomb structure was obtained in the same manner as in Example 1, except that a sheet-shaped soft urethane foam with a thickness of 10 mm and a hardness of 110 N was used to prepare the support base, and the main body was machined so that the diameter (L1) of the contact part was 86.6 mm.

[Comparative Example 2]
A honeycomb structure was obtained in the same manner as in Example 1, except that in the preparation of the support base, no sheet-like soft urethane foam was used and the main body was machined so that the diameter (L1) of the contact portion was 86.8 mm. Here, a cloth with a thickness of 1 mm was placed between the main body and the honeycomb molded body to adjust the diameter (L1) of the contact portion to 86.8 mm. Note that the cloth does not have a weight-cushioning effect, so hardness is not required.

<Evaluation>
The circularity and the thickness variation of the electrode layer were evaluated for the examples and comparative examples. The evaluation methods are as follows. The evaluation results are summarized in Tables 1 and 2.

1. Circularity The circularity was evaluated using a laser displacement meter (laser sensor, manufactured by Micro-Epsilon Corporation). Specifically, the peripheral shapes of the obtained honeycomb molded body and dried honeycomb body were measured at three points in the length direction: the upper end (a portion 6 mm from the tip), the lower end (a portion 6 mm from the end), and the center (the middle between the upper end and the lower end). The obtained measurement data was subjected to a best-fit process with respect to a reference peripheral shape, and the absolute value of the difference from the reference value was calculated.
The roundness of the fired honeycomb body (honeycomb structure portion) was approximately the same as that of the dried honeycomb body (specifically, at most 0.05 mm larger than the roundness of the dried honeycomb body).
2. Variation in Thickness of Electrode Layer The thickness of the electrode layer at a plurality of cross sections (leading and trailing ends) of the obtained honeycomb structure perpendicular to the cell extension direction was measured at 10 points on each cross section using an optical microscope, and the variation in thickness of the electrode layer was evaluated.

In the comparative example, from the standpoint of preventing deformation of the honeycomb formed body due to collision with the circumferential end of the abutment portion of the support base, it is difficult to set the clearance to a value lower than that shown in Table 1.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the configuration shown in the above-described embodiment can be replaced with a configuration that is substantially the same as the configuration shown in the above-described embodiment, a configuration that provides the same effects, or a configuration that can achieve the same purpose.

The honeycomb structure of the present invention can be suitably used for treating (purifying) exhaust gas from internal combustion engines.

10 Honeycomb structure portion, 10a First end face, 10b Second end face, 12 Cell, 14 Partition wall, 16 Outer wall, 20 Electrode layer, 30 Honeycomb structure, 40 Extrusion molding machine, 41 Extrusion molding die (pressure plate), 42 Die, 44 Honeycomb molded body, 50 Main body portion, 51 Groove portion, 60 Contact portion, 60a Circumferential end portion, 100 Receiving base, L1 Diameter of contact portion (contact surface), L2 Diameter of extrusion molding die (pressure plate).

Claims (6)

A method for manufacturing a honeycomb structure, comprising: a molding step of extruding a molding material containing a ceramic raw material to obtain a honeycomb formed body; and a firing step of drying the honeycomb formed body to obtain a dried honeycomb body, thereby obtaining a honeycomb structure,
The honeycomb structure includes a honeycomb structure part having an outer peripheral wall and partition walls disposed inside the outer peripheral wall, and a pair of electrode layers disposed on side surfaces of the honeycomb structure part,
the electrode layer is formed by applying an electrode layer-forming material onto a plate having openings formed therein by pressing the material with a squeegee;
the forming step includes transporting the cylindrical honeycomb formed body obtained by the extrusion forming while supporting an outer peripheral surface thereof along a cell extension direction on a receiving table,
the support base has a main body portion having a groove portion along the extending direction of the cells, and a contact portion having an arc-shaped curved surface that is disposed in the groove portion of the main body portion and contacts a lower half of the honeycomb molded body,
The contact portion is made of a material having a hardness of 74N or less,
a difference between the diameter of the arc-shaped contact portion and the diameter of the die for extrusion molding being 0 mm or more and 0.6 mm or less;
A method for manufacturing a honeycomb structure. The method for manufacturing a honeycomb structure according to claim 1, wherein the ceramic raw materials include silicon carbide and silicon metal. A method for manufacturing a honeycomb structure according to claim 1 or 2, wherein the specific gravity of the honeycomb formed body is 0.3 or more. A method for manufacturing a honeycomb structure according to claim 1 or 2, wherein the circumferential ends of the abutment portions abut against the outer peripheral surface of the honeycomb formed body without any gaps. A method for manufacturing a honeycomb structure according to claim 1 or 2, wherein the contact portion is made of soft urethane foam. a honeycomb structure portion having partition walls that define a plurality of cells that serve as fluid flow paths extending from a first end face to a second end face, and an outer peripheral wall located on the outer periphery;
a pair of electrode layers disposed on the side surfaces of the honeycomb structure section;
the honeycomb structure includes silicon carbide and silicon metal,
the roundness of the surface of the honeycomb structure part perpendicular to the cell extension direction is 1 mm or less,
The thickness of the electrode layer is 0.05 mm or more and 0.50 mm or less, and the variation in the thickness of the electrode layer is 35% or less.
Honeycomb structure.