Manufacturing method of honeycomb structure and manufacturing method of electrically heated carrier

Abstract

To provide a method for producing a honeycomb structure capable of forming a slit at a honeycomb structure with satisfactory production efficiency at a satisfactory production cost, and a method for producing an electric heating type carrier.SOLUTION: A method for producing a honeycomb structure comprises: a molding step in which molding raw material comprising ceramic raw material is extrusion-molded to obtain a honeycomb molded body having an outer circumferential wall and a bulkhead for compartmentalizing plural cells forming a flow passage elongating either end face to the other end face; a drying step in which the honeycomb molded body is dried to obtain a honeycomb dried body; and a firing step in which the honeycomb dried body is fired to obtain a honeycomb fired body. The molding step produces the honeycomb molded body in which a part of the bulkhead is chipped so as to connect a part of the cells in the plural cells by extrusion-molding molding raw material.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a honeycomb structure and a method for manufacturing an electrically heated carrier. [Background technology]

[0002] In recent years, electrically heated catalysts (EHCs) have been proposed to improve the deterioration of exhaust gas purification performance immediately after engine start. EHCs are constructed by connecting metal electrodes to a columnar honeycomb structure made of conductive ceramics, and by passing electricity through the honeycomb structure itself, heating it up to the catalyst's activation temperature before the engine starts.

[0003] EHCs are required to have good thermal shock resistance because they are exposed to heat and shock from the engine. If cracks occur in the honeycomb structure of an EHC due to heat and shock from the engine, the current path within the honeycomb structure changes, causing localized heat generation and catalyst degradation. Furthermore, the current resistance increases, making current control difficult. As a result, the exhaust gas purification efficiency of the EHC may deteriorate.

[0004] Patent Document 1 discloses a honeycomb structure in which slits opening on the side surfaces of the honeycomb structure are formed to improve thermal shock resistance. In Patent Document 1, after forming a dried honeycomb body, the slits are formed by cutting the partition walls of the dried honeycomb body with a router or the like.

[0005] Patent Document 2 discloses a method for forming slits on the end face of a honeycomb structure. Specifically, a slit-forming plate-shaped member is placed in contact with one end face of a honeycomb formed body, and the slit-forming plate-shaped member is moved toward the other end face of the honeycomb formed body while vibrating, cutting the partition walls of the honeycomb formed body to form slits. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5997259 [Patent Document 2] Patent No. 5162509 Summary of the Invention [Problem to be solved by the invention]

[0007] In both of the techniques disclosed in Patent Documents 1 and 2, a step of forming slits is required in the manufacturing method of a honeycomb structure, and the number of work steps increases accordingly, resulting in a decrease in manufacturing efficiency. In addition, there is also the problem of wear and damage to processing tools, etc., used for forming the slits, which may increase manufacturing costs.

[0008] The present invention was created in consideration of the above circumstances, and its object is to provide a method for manufacturing a honeycomb structure and a method for manufacturing an electrically heated carrier that are capable of forming slits in a honeycomb structure with good manufacturing efficiency and manufacturing cost. [Means for solving the problem]

[0009] The above problems are solved by the present disclosure below, which is specified as follows: (1) a molding step of extruding a molding raw material containing a ceramic raw material to obtain a honeycomb molded body having an outer peripheral wall and partition walls disposed inside the outer peripheral wall to define a plurality of cells that form flow paths extending from one end face to the other end face; a drying step of drying the honeycomb formed body to obtain a dried honeycomb body; a firing step of firing the dried honeycomb body to obtain a fired honeycomb body; Equipped with The molding step is a method for manufacturing a honeycomb structure, in which the molding raw material is extruded to produce a honeycomb molded body in which a portion of the partition walls is missing so that some of the plurality of cells are connected. (2) a molding step of extruding a molding raw material containing a ceramic raw material to obtain a honeycomb molded body having an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells that form flow paths extending from one end face to the other end face; a drying step of drying the honeycomb formed body to obtain a dried honeycomb body; a firing step of firing the dried honeycomb body to obtain a fired honeycomb body; Equipped with The forming step is a method for manufacturing a honeycomb structure, in which the forming raw material is extruded to form a honeycomb formed body in which some of the partition walls are thinner than other partition walls and are arranged in a slit shape. (3) applying an electrode portion forming raw material containing a ceramic raw material to a side surface of the dried honeycomb body and drying the applied material to obtain a dried honeycomb body with unfired electrode portions; and a step of firing the dried honeycomb body with the unfired electrode portions to obtain a honeycomb structure having a pair of electrode portions, A method for manufacturing a honeycomb structure described in (1) or (2), wherein the pair of electrode portions are arranged on the outer surface of the outer wall, on either side of the central axis of the honeycomb structure, so as to extend in a band-like manner in the flow path direction of the cell. (4) A method for manufacturing an electrically heated carrier, comprising a step of electrically connecting metal electrodes to each of the pair of electrode portions of the honeycomb structure manufactured by the method according to (3). [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method for manufacturing a honeycomb structure and a method for manufacturing an electrically heated carrier that are capable of forming slits in a honeycomb structure with good manufacturing efficiency and manufacturing costs. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic view showing an external appearance of a honeycomb structure according to an embodiment of the present invention. [Figure 2] 1 is a schematic cross-sectional view perpendicular to the extension direction of cells of an electrically heated carrier according to an embodiment of the present invention. [Figure 3] 3 is a diagram showing a specific example of a slit shape of a honeycomb structure according to an embodiment of the present invention. [Figure 4] (A) shows the top view [1], side view [2], and bottom view [3] of the U-shaped pin. (B) shows the top view [1], side view [2], and bottom view [3] of the T-shaped pin. [Figure 5] 1A is a schematic plan view illustrating how a U-shaped pin is used to form a slit in a honeycomb molded body, and FIG. 1B is a schematic cross-sectional view of the U-shaped pin and a die in a state corresponding to FIG. [Figure 6] 1A is a schematic plan view illustrating how a slit is formed in a honeycomb molded body using a T-pin, and FIG. 1B is a schematic cross-sectional view of the T-pin and die in a state corresponding to FIG. [Figure 7] 1A is a schematic plan view of a honeycomb formed body having slits and cells with a square cross section, and FIG. 1B is a schematic plan view of a honeycomb formed body having slits and cells with a hexagonal cross section. [Figure 8] FIG. 2 is a schematic plan view of a nozzle having a blocking portion. [Figure 9] FIG. 10 is a schematic plan view of a die having a hole formed smaller than the other holes. [Figure 10] FIG. 2 is a cross-sectional view of a molding machine illustrating the process of molding a hoke in the molding machine. [Figure 11] (A) is a schematic plan view of the die used in Example 1. (B) is a schematic plan view of a slit made by (A). (C) is a schematic plan view of the die used in Example 2. (D) is a schematic plan view of a slit made by (C). [Figure 12] (A) is a schematic plan view of the die used in Example 3. (B) is a schematic plan view of the slit produced by (A). [Figure 13] 1A is a schematic plan view of a honeycomb formed body having slits and cells with a square cross section, and FIG. 1B is a schematic plan view of a honeycomb formed body having slits and cells with a hexagonal cross section. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, embodiments of the present invention will be described in detail with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and that appropriate design changes and improvements may be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0013] (1. Honeycomb structure) 1 is a schematic view of the appearance of a honeycomb structure 10 according to an embodiment of the present invention. The honeycomb structure 10 includes a columnar honeycomb structure portion 11 and electrode portions 13a and 13b. The electrode portions 13a and 13b may not be included.

[0014] (1-1. Columnar honeycomb structure) The columnar honeycomb structure portion 11 has an outer peripheral wall 12 and partition walls 19 disposed inside the outer peripheral wall 12 to define a plurality of cells 18 that form flow paths extending from one end face to the other end face.

[0015] The outer shape of the columnar honeycomb structure part 11 is not particularly limited as long as it is columnar, and can be, for example, a columnar shape with circular end faces (cylindrical shape), a columnar shape with oval end faces, a columnar shape with polygonal end faces (quadragonal, pentagonal, hexagonal, heptagonal, octagonal, etc.), etc. The size of the columnar honeycomb structure part 11 is set to 2000 to 20000 mm2 in order to increase heat resistance (suppress cracks in the circumferential direction of the outer peripheral wall). 2 It is preferable that the thickness is 5000 to 15000 mm 2 It is more preferable that:

[0016] The material of the columnar honeycomb structure 11 is not limited, but can be selected from the group consisting of oxide ceramics such as alumina, mullite, zirconia, and cordierite, and non-oxide ceramics such as silicon carbide, silicon nitride, and aluminum nitride. Silicon carbide-metal silicon composites and silicon carbide-graphite composites can also be used. Among these, from the viewpoint of achieving both heat resistance and electrical conductivity, it is preferable that the material of the columnar honeycomb structure 11 contains a silicon-silicon carbide composite or a ceramic containing silicon carbide as the main component. When the material of the columnar honeycomb structure 11 is said to be mainly composed of a silicon-silicon carbide composite, it means that the columnar honeycomb structure 11 contains 90 mass% or more of the silicon-silicon carbide composite (total mass) as the entire material. Here, the silicon-silicon carbide composite material contains silicon carbide particles as aggregate and silicon as a binder that bonds the silicon carbide particles, and it is preferable that a plurality of silicon carbide particles are bonded by the silicon so as to form pores between the silicon carbide particles. When the material of the columnar honeycomb structure part 11 is said to be mainly composed of silicon carbide, it means that the columnar honeycomb structure part 11 contains silicon carbide (total mass) in an amount of 90 mass% or more of the entire material.

[0017] When the columnar honeycomb structure 11 contains a silicon-silicon carbide composite material, the ratio of the "mass of silicon as a binder" contained in the columnar honeycomb structure 11 to the sum of the "mass of silicon carbide particles as aggregate" contained in the columnar honeycomb structure 11 and the "mass of silicon as a binder" contained in the columnar honeycomb structure 11 is preferably 10 to 40 mass%, and more preferably 15 to 35 mass%.

[0018] Although there are no limitations on the shape of the cells 18 in a cross section perpendicular to the stretching direction, a square, a hexagon, an octagon, or a combination thereof is preferred. Among these, a square and a hexagon are preferred from the viewpoint of easily achieving both structural strength and heating uniformity.

[0019] The thickness of the partition walls 19 that define the cells 18 is preferably 0.1 to 0.3 mm, and more preferably 0.15 to 0.25 mm. In the present invention, the thickness of the partition walls 19 is defined as the length of the portion of a line segment that connects the centers of gravity of adjacent cells 18 and passes through the partition walls 19 in a cross section perpendicular to the stretching direction of the cells 18.

[0020] The columnar honeycomb structure 11 has a cell density of 40 to 150 cells / cm in a cross section perpendicular to the flow path direction of the cells 18. 2 Preferably, the number of cells is 70 to 100. 2 It is more preferable that the cell density is within this range. By setting the cell density within this range, the purification performance of the catalyst can be improved while reducing the pressure loss when exhaust gas flows. The cell density is a value obtained by dividing the number of cells by the area of ​​one end face of the columnar honeycomb structure portion 11 excluding the outer wall 12 portion.

[0021] Providing the outer peripheral wall 12 of the columnar honeycomb structure portion 11 is useful from the viewpoint of ensuring the structural strength of the columnar honeycomb structure portion 11 and suppressing leakage of the fluid flowing through the cells 18 from the outer peripheral surface of the columnar honeycomb structure portion 11. Specifically, the thickness of the outer peripheral wall 12 is preferably 0.05 mm or more, more preferably 0.1 mm or more, and even more preferably 0.15 mm or more. However, if the outer peripheral wall 12 is too thick, it will have too high strength, which will disrupt the strength balance with the partition walls 19 and reduce thermal shock resistance. Also, if the thickness of the outer peripheral wall 12 is too large, the heat capacity will increase, which will increase the temperature difference between the outer peripheral side and the inner peripheral side of the outer peripheral wall 12 and reduce thermal shock resistance. Therefore, the thickness of the outer peripheral wall 12 is preferably 1.0 mm or less, more preferably 0.7 mm or less, and even more preferably 0.5 mm or less. Here, the thickness of the outer peripheral wall 12 is defined as the thickness in the direction normal to the tangent of the outer peripheral wall 12 at the measurement point when the portion of the outer peripheral wall 12 where the thickness is to be measured is observed in a cross section perpendicular to the extension direction of the cell.

[0022] The average pore diameter of the partition walls 19 of the columnar honeycomb structure portion 11 is preferably 2 to 15 μm, and more preferably 4 to 8 μm. The average pore diameter is a value measured by a mercury porosimeter.

[0023] The partition walls 19 may be porous. When the partition walls 19 are porous, the porosity of the partition walls 19 is preferably 35 to 60%, and more preferably 35 to 45%. The porosity is a value measured with a mercury porosimeter.

[0024] (1-2. Electrode part) In the honeycomb structure 10 according to the embodiment of the present invention, a pair of electrode portions 13a, 13b are provided on the outer surface of the outer wall 12, sandwiching the central axis of the columnar honeycomb structure portion 11, so as to extend in a band shape in the flow path direction of the cells 18. Providing the pair of electrode portions 13a, 13b in this manner can improve the uniform heat generation property of the honeycomb structure 10. From the viewpoint of facilitating current spread in the axial direction of the electrode portions 13a, 13b, it is desirable that the electrode portions 13a, 13b extend over 80% or more of the length between both end faces of the honeycomb structure 10, preferably over 90% or more of the length, and more preferably over the entire length. Note that the electrode portions 13a, 13b may not be provided.

[0025] The thickness of the electrode portions 13a, 13b is preferably 0.01 to 5 mm, and more preferably 0.01 to 3 mm. By setting the thickness within this range, uniform heat generation can be improved. The thickness of the electrode portions 13a, 13b is defined as the thickness in the direction normal to the tangent at the measurement point on the outer surface of the electrode portions 13a, 13b when the measurement point is observed on a cross section perpendicular to the extension direction of the cell 18.

[0026] By making the electrical resistivity of the electrode portions 13a, 13b lower than that of the columnar honeycomb structure portion 11, electricity flows preferentially through the electrode portions 13a, 13b, and when current is applied, electricity spreads more easily in the flow path direction and circumferential direction of the cell 18. The electrical resistivity of the electrode portions 13a, 13b is preferably 1 / 10 or less, more preferably 1 / 20 or less, and even more preferably 1 / 30 or less of the electrical resistivity of the columnar honeycomb structure portion 11. However, if the difference in electrical resistivity between the two becomes too large, current will concentrate between the ends of the opposing electrode portions, causing uneven heat generation in the columnar honeycomb structure portion 11. Therefore, the electrical resistivity of the electrode portions 13a, 13b is preferably 1 / 200 or more, more preferably 1 / 150 or more, and even more preferably 1 / 100 or more of the electrical resistivity of the columnar honeycomb structure portion 11. In the present invention, the electrical resistivity of the electrode portions 13a and 13b is a value measured at 25°C by a four-terminal method.

[0027] The electrode portions 13a and 13b may be made of conductive ceramics, metals, or composites (cermets) of metals and conductive ceramics. Examples of metals include, for example, 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, but are not limited to, silicon carbide (SiC), and metal compounds such as metal silicides, such as tantalum silicide (TaSi2) and chromium silicide (CrSi2). Specific examples of composites (cermets) of metals and conductive ceramics include composites of silicon carbide and metal silicon, composites of metal silicides, such as tantalum silicide or chromium silicide, and silicon carbide and metal silicides. Furthermore, composites of one or more of the above metals with one or more insulating ceramics, such as alumina, mullite, zirconia, cordierite, silicon nitride, and aluminum nitride, to reduce thermal expansion.

[0028] (1-3. Slit) Linear slits 21 are provided in a cross section perpendicular to the flow path direction of the cells 18 of the honeycomb structure 10. By providing such linear slits 21, it is possible to suppress cracks on the end faces of the honeycomb structure 10. By providing the linear slits 21, stress is alleviated, the thermal expansion difference is reduced, and the occurrence of cracks can be effectively suppressed.

[0029] In Fig. 1, the slits 21 indicate positions in the honeycomb structure 10, and the shape is not particularly limited as long as they are elongated. The slits 21 have a shape that is generated when adjacent cells are connected by removing the partition walls 19 between them. The slits 21 preferably have a form in which the slits extend in the extension direction of the cells and are provided on both end faces.

[0030] The shape and number of the slits 21 are not particularly limited and can be designed as appropriate. Two or four or more slits may be formed independently. By forming a plurality of slits independently, it is possible to effectively control the occurrence of cracks in the honeycomb structure 10. Furthermore, the width of the slits is not particularly limited. The width of the slits may be formed to be approximately the same as the width of the cells 18, or the width of the slits may be formed to be smaller or larger than the width of the cells 18. The width of each slit is not particularly limited, but may be 1 to 30 mm. The width of each slit can be adjusted as appropriate depending on the size, material, and application of the honeycomb structure 10, and the number and length of the slits, etc.

[0031] In an embodiment of the present invention, it is preferable that the slit 21 passes through the center of the columnar honeycomb structure portion 11 in a cross section perpendicular to the cell flow direction of the columnar honeycomb structure portion 11. With such a configuration, it is possible to more effectively suppress changes in the resistance and current path of the honeycomb structure 10. Furthermore, the slit 21 may be divided along the direction in which the slit extends. In this case, the slit may be divided into slits of approximately the same length or into slits of different lengths. By forming the slit in a divided manner, it is possible to effectively control the occurrence of cracks in the honeycomb structure 10. The number of divided slits is not particularly limited, and the slit may be formed in two, three, four or more divided portions. Furthermore, multiple slits may be provided by mixing divided slits and undivided slits.

[0032] The ratio of the length of the slits 21 to the outer diameter of the columnar honeycomb structure portion 11 is preferably 25% or more. When the ratio of the length of the slits 21 to the outer diameter of the columnar honeycomb structure portion 11 is 25% or more, thermal shock can be more effectively alleviated and crack generation can be more effectively suppressed.

[0033] The depth of the slits 21 in the flow path direction of the cells 18 from one end face of the honeycomb structure 10 is preferably 30 to 100% of the entire length of the columnar honeycomb structure portion 11. When the depth of the slits 21 is 30 to 100% of the entire length of the columnar honeycomb structure portion 11, the thermal shock resistance is further improved. The depth of the slits 21 is more preferably 50 to 100% of the entire length of the columnar honeycomb structure portion 11, and even more preferably 70 to 100%.

[0034] 3(A) to 3(L) show specific examples of the shape of the slits 21. Note that in Fig. 3(A) to 3(L), ​​only the outer diameter of the end face of the columnar honeycomb structure portion 11 and the shape of the slits are shown schematically.

[0035] The slit 21 may be a slit that passes through the center on the end face of the columnar honeycomb structure part 11 and extends to the outer periphery on both sides, as shown in Figure 3(A), or a slit that passes through the center and extends partway without reaching the outer periphery, as shown in Figure 3(B), or a slit that passes through the center and has an arbitrary inclination, as shown in Figure 3(C), or a slit that does not pass through the center, as shown in Figure 3(D).

[0036] As shown in Figure 3(E), the slit 21 may be composed of a slit that passes through the center and extends to the outer periphery on the end face of the columnar honeycomb structure part 11, and multiple slits extending parallel to both sides of it, or as shown in Figure 3(F), one slit may intersect with another slit at an arbitrary angle, or as shown in Figure 3(G), multiple slits may intersect with another slit at an arbitrary angle.

[0037] The slits 21 may be slits that are interrupted and divided as a whole at the end face of the columnar honeycomb structure portion 11, as shown in Figure 3(H), or slits that are interrupted and divided only near the outer periphery, as shown in Figure 3(I), or slits that are interrupted and divided as a whole and intersect with each other, as shown in Figure 3(J).

[0038] The slit 21 may be a slit formed only near the outer periphery including the outer wall on the end face of the columnar honeycomb structure part 11, as shown in Figure 3(K), or may be a divided slit provided only near the outer periphery including the outer wall, as shown in Figure 3(L).

[0039] (2. Electrically heated carrier) 2 is a schematic cross-sectional view perpendicular to the extension direction of the cells of an electrically heated carrier 30 according to an embodiment of the present invention. The electrically heated carrier 30 includes a honeycomb structure 10 and metal electrodes 33a and 33b electrically connected to electrode portions 13a and 13b of the honeycomb structure 10.

[0040] (2-1. Metal electrode) The metal electrodes 33a and 33b are provided on the electrode portions 13a and 13b of the honeycomb structure 10. The metal electrodes 33a and 33b may be a pair of metal electrodes arranged such that one metal electrode 33a faces the other metal electrode 33b across the central axis of the columnar honeycomb structure portion 11. When a voltage is applied via the electrode portions 13a and 13b, the metal electrodes 33a and 33b are energized and can generate Joule heat in the columnar honeycomb structure portion 11. Therefore, the electrically heated carrier 30 can also be suitably used as a heater. The applied voltage is preferably 12 to 900 V, more preferably 48 to 600 V, but the applied voltage can be changed as appropriate.

[0041] The material of the metal electrodes 33a, 33b is not particularly limited as long as it is a metal, and simple metals and alloys can be used, but from the viewpoints of corrosion resistance, electrical resistivity, and linear expansion coefficient, an alloy containing at least one selected from the group consisting of Cr, Fe, Co, Ni, and Ti is preferable, and stainless steel and an Fe-Ni alloy are more preferable. The shape and size of the metal electrodes 33a, 33b are not particularly limited, and can be designed appropriately depending on the size, electrical conductivity, etc. of the electrically heated carrier 30.

[0042] By supporting a catalyst on the electrically heated carrier 30, the electrically heated carrier 30 can be used as a catalyst body. A fluid such as automobile exhaust gas can be passed through the flow paths of the plurality of cells 18 of the honeycomb structure 10. Examples of the catalyst include precious metal catalysts and other catalysts. Precious metal catalysts include three-way catalysts and oxidation catalysts in which a precious metal such as platinum (Pt), palladium (Pd), or rhodium (Rh) is supported on the surface of alumina pores and a promoter such as ceria or zirconia is included, or alkaline earth metals and platinum are used to convert nitrogen oxides (NO x ) as a storage component of NO x Examples of catalysts that do not use precious metals include NOx storage reduction catalysts (LNT catalysts) containing copper-substituted or iron-substituted zeolites. xExamples include selective catalytic reduction catalysts (SCR catalysts). Two or more catalysts selected from the group consisting of these catalysts may be used. There are no particular limitations on the method for supporting the catalyst, and the method can be carried out in accordance with the conventional method for supporting a catalyst on a honeycomb structure.

[0043] (3. Manufacturing method of honeycomb structure) Next, a method for manufacturing a honeycomb structure according to an embodiment of the present invention will be described. A method for manufacturing a honeycomb structure according to an embodiment of the present invention includes a forming step for obtaining a honeycomb formed body, a drying step for obtaining a dried honeycomb body, and a firing step for obtaining a fired honeycomb body.

[0044] (molding process) In the molding process, first, a molding raw material containing ceramic raw materials is prepared. The molding raw material is produced by adding metal silicon powder (metal silicon), binder, surfactant, pore former, water, etc. to silicon carbide powder (silicon carbide). The mass of the metal silicon is preferably 10 to 40 mass% relative to the total mass of the silicon carbide powder and the metal silicon. The average particle diameter of the silicon carbide particles in the silicon carbide powder is preferably 3 to 50 μm, more preferably 3 to 40 μm. The average particle diameter of the metal silicon (metal silicon powder) is preferably 2 to 35 μm. The average particle diameters of the silicon carbide particles and metal silicon (metal silicon particles) refer to the arithmetic mean diameter on a volume basis when the particle size frequency distribution is measured by laser diffraction. The silicon carbide particles are fine particles of silicon carbide that constitute the silicon carbide powder, and the metal silicon particles are fine particles of metal silicon that constitute the metal silicon powder. This is the blending of the forming raw materials when the material of the honeycomb structure is a silicon-silicon carbide based composite material, and when the material is silicon carbide, metallic silicon is not added.

[0045] Examples of binders include methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, etc. Among these, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination. The content of the binder is preferably 2.0 to 10.0 parts by mass when the total mass of the silicon carbide powder and the metallic silicon powder is 100 parts by mass.

[0046] The content of water is preferably 20 to 60 parts by mass when the total mass of the silicon carbide powder and the metallic silicon powder is taken as 100 parts by mass.

[0047] Examples of surfactants that can be used include ethylene glycol, dextrin, fatty acid soap, and polyalcohol. These may be used alone or in combination of two or more. The content of the surfactant is preferably 0.1 to 2.0 parts by mass when the total mass of the silicon carbide powder and the metallic silicon powder is 100 parts by mass.

[0048] The pore-forming material is not particularly limited as long as it forms pores after firing, and examples thereof include graphite, starch, foamed resin, water-absorbent resin, silica gel, etc. The content of the pore-forming material is preferably 0.5 to 10.0 parts by mass when the total mass of the silicon carbide powder and metallic silicon powder is 100 parts by mass. The average particle diameter of the pore-forming material is preferably 10 to 30 μm. The average particle diameter of the pore-forming material refers to the arithmetic mean diameter on a volume basis when the frequency distribution of particle size is measured by laser diffraction. When the pore-forming material is a water-absorbent resin, the average particle diameter of the pore-forming material refers to the average particle diameter after water absorption.

[0049] Next, the obtained molding raw materials are kneaded to form a clay, and the clay is extrusion-molded to produce a honeycomb molded body. The honeycomb molded body has an outer peripheral wall and partition walls disposed inside the outer peripheral wall to define a plurality of cells that form flow paths extending from one end face to the other end face.

[0050] The honeycomb formed body has a portion of the partition wall missing so that some of the multiple cells are connected. By manufacturing a honeycomb formed body in which a portion of the partition wall is missing so that some of the multiple cells are connected, the connected cells become slits, and a slit formation process by cutting or the like is not required after the subsequent drying process. This improves manufacturing efficiency. This also eliminates the problem of wear and damage to processing tools and the like used for forming the slits, allowing manufacturing costs to be reduced. Furthermore, when slits are formed by cutting or the like, there is a possibility that the slits will intrude into adjacent cells. However, because the slit shape is formed at the stage of forming the honeycomb formed body, the slit intrusion into adjacent cells can be effectively prevented.

[0051] A honeycomb formed body in which some of the partition walls are missing so that some of the cells are connected can be produced using a forming machine having a die in which some of the holes are blocked by inserting pins. The shape of the pin is not particularly limited, and for example, a U-shaped pin 41 as shown in Fig. 4(A) or a T-shaped pin 42 as shown in Fig. 4(B) can be used.

[0052] Figure 4(A) shows a top view [1], a side view [2], and a bottom view [3] of a U-shaped pin 41. Figure 4(B) shows a top view [1], a side view [2], and a bottom view [3] of a T-shaped pin 42.

[0053] It is preferable that the width D1 at the top surface of the U-shaped pin 41 and the T-shaped pin 42 is 0.9 to 1.2 times the length of the slit's longitudinal distance (opening distance). This configuration can prevent the occurrence of slit portions (also called burrs) that cannot be completely removed by the U-shaped pin 41 and the T-shaped pin 42. By preventing the occurrence of burrs, it becomes easier to fill the slit portions with filler from the outer periphery. The width D1 at the top surface of the U-shaped pin 41 and the T-shaped pin 42 can be, for example, 0.4 to 1.4 mm.

[0054] The leg length L1 of the U-shaped pin 41 and the T-shaped pin 42 is preferably approximately the same as the height of the cell block 44 of the base 43 so that the pins are unlikely to come out once inserted into the base 43. The leg length L1 of the U-shaped pin 41 and the T-shaped pin 42 can be, for example, 1.5 to 6.0 mm.

[0055] The leg thickness T1 of the U-shaped pin 41 and the T-shaped pin 42 is preferably 0.9 to 1.1 times the spacing between the cell blocks 44 so that the clay does not flow into the slit forming portion of the die 43 and does not come loose during molding. The leg thickness T1 of the U-shaped pin 41 and the T-shaped pin 42 can be, for example, 0.06 to 0.28 mm.

[0056] The base length L2 of the U-shaped pin 41 is preferably set to a length that allows the legs of the U-shaped pin 41 to be inserted parallel to the holes of the base 43. The base length L2 of the U-shaped pin 41 can be set to, for example, 0.45 to 1.3 mm.

[0057] The shoulder length L3 of the T-pin 42 is preferably set to a length that prevents it from penetrating into the partition wall adjacent to the slit. The shoulder length L3 of the T-pin 42 can be set to, for example, 1.1 to 2.6 mm.

[0058] FIG. 5(A) is a schematic plan view illustrating the formation of slits in a honeycomb molded body using a U-shaped pin. FIG. 5(B) is a schematic cross-sectional view of the U-shaped pin and die in a state corresponding to FIG. 5(A). As shown in the left diagram of FIG. 5(A) and FIG. 5(B), a U-shaped pin 41 is inserted into a hole in a die 43 of a molding machine, and the moldable material is extruded from the die in this state, thereby producing a honeycomb molded body in which a portion of the partition wall 19 is missing and linear slits 21 are formed, as shown in the right diagram of FIG. 5(A). By providing U-shaped pins 41 consecutively, a long, linear slit can be formed. Furthermore, by providing multiple U-shaped pins 41 at a predetermined number of holes in the die 43, segmented slits can be formed.

[0059] FIG. 6(A) is a schematic plan view illustrating the formation of slits in a honeycomb molded body using a T-pin. FIG. 6(B) is a schematic cross-sectional view of a T-pin and a die in a state corresponding to FIG. 6(A). As shown in the left diagram of FIG. 6(A) and FIG. 6(B), a T-pin 42 is inserted into a hole in a die 43 of a molding machine, and the moldable material is extruded from the die in this state, thereby producing a honeycomb molded body in which a portion of the partition wall 19 is missing and linear slits 21 are formed, as shown in the right diagram of FIG. 6(A). By providing multiple T-pins 42 in succession, it is possible to form a long, linear slit. Furthermore, by providing multiple T-pins 42 at a predetermined number of holes in the die 43, it is possible to form divided slits.

[0060] Fig. 7(A) shows a cross-sectional schematic diagram of a honeycomb formed body in which the cross-sectional shape of the cells 18 is quadrangular. Fig. 7(B) shows a cross-sectional schematic diagram of a honeycomb formed body in which the cross-sectional shape of the cells 18 is hexagonal. Here, the ratio L / D of the length L to the width D of the slits 21 is preferably 1 to 5 when the cell structure is quadrangular, and 1.5 to 8 when the cell structure is hexagonal. The ratio L / D is more preferably 4 or less when the cell structure is quadrangular, and 6 or less when the cell structure is hexagonal, because this effectively suppresses deformation of the slits 21. More preferably, the ratio L / D is 1 to 4 when the cell structure is quadrangular, and 1.5 to 6 when the cell structure is hexagonal.

[0061] 7(A) and 7(B), region 45 indicated by the dotted line is obtained by cutting the partition wall located around slit 21 at a position halfway through the thickness to surround slit 21. The ratio of the area of ​​slit 21 to the area of ​​region 45 (opening ratio) is preferably 67 to 90%. If the opening ratio is 90% or less, deformation of slit 21 can be more effectively suppressed.

[0062] The material of the U-shaped pin 41 or the T-shaped pin 42 is not particularly limited, and metal or resin can be used, but it is preferable to use a cemented carbide or SUS, etc., in order to suppress deformation or damage during molding.

[0063] Furthermore, a honeycomb formed body in which a portion of the partition walls is missing so that some of the cells are connected can be produced by extrusion molding the honeycomb formed body using a molding machine having a die with some of the holes blocked. As shown in Fig. 8, by blocking the holes in the die 43 to form blocked portions 46, slits are formed in the honeycomb formed body extruded by the molding machine at positions corresponding to the cell blocks 44 of the die 43 and the blocked portions 46. The blocked portions 46 may be formed integrally with the cell blocks 44 of the die 43, or the blocked portions 46 may be separately provided between the cell blocks 44 of the die 43 and the cell blocks 44, and made of either the same material as or a different material from the cell blocks 44.

[0064] Furthermore, a honeycomb formed body in which some of the partition walls are missing so that some of the cells are connected can be produced by extrusion molding the honeycomb formed body using a molding machine having a die and a noodle with some of its pores blocked, which is located upstream of the die in the path of the forming raw material. Figure 10 shows an example of a cross-sectional schematic diagram of the molding machine 22 to explain the process of forming a hollow 23 within the molding machine 22. Within the molding machine 22, the hollow 23 is extruded and passes through a screen 24, a noodle 25, and a drawing jig 26, and is then formed by a die 27 to produce a honeycomb formed body 28. The screen 24 is provided to block the inflow of coarse particles of the raw material and to prevent clogging of the die. The noodle 25 is provided to support the screen 24. The drawing jig 26 is provided to draw the hollow 23 to the diameter of the die 27. As shown in Fig. 10, the screen 24, the noodles 25, and the drawing jig 26 are provided upstream of the path of the forming raw material with respect to the die 27. In the forming machine 22 configured as described above, by blocking some of the holes in the noodles 25, slits 21 can be formed in the honeycomb formed body 28 extruded from the die 27 at locations corresponding to the blocked holes in the noodles 25.

[0065] Furthermore, a honeycomb formed body in which a portion of the partition wall is missing so that some of the cells are connected can be produced by forming a forming raw material having holes through which a honeycomb formed body in which a portion of the partition wall is missing can be formed during extrusion molding by kneading the clay, and then extruding the forming raw material. The forming raw material formed by kneading the clay is also called hoke, and is composed of clay (ceramic raw material) and water, and is generally formed in a cylindrical shape. By forming holes in this hoke in advance in the areas where slits are to be formed, a honeycomb formed body in which a partition wall is missing at the positions corresponding to the holes can be formed during extrusion molding.

[0066] In the honeycomb molded body, some of the partition walls may be formed thinner than the other partition walls, and some of these partition walls may be arranged in a slit shape. By producing a honeycomb molded body in this way, in which some of the partition walls are formed thinner than the other partition walls and arranged in a slit shape, the thinner partition walls can be easily scraped off in the subsequent drying process. Furthermore, by forming some of the partition walls thinner than the other partition walls rather than completely removing them, the honeycomb shape can be maintained in the drying process and firing process. From the viewpoint of improving manufacturing efficiency and manufacturing costs, the length of the above-mentioned part of the partition walls that is thinner than the other partition walls and arranged in a slit shape is preferably 50 to 100%, more preferably 70 to 100%, of the length of the linear slit in the final product (honeycomb structure). The length of the linear slit in the final product (honeycomb structure) may be formed to be 1 to 200 mm.

[0067] A honeycomb formed body in which some of the partition walls are formed thinner than the other partition walls can be produced by extrusion molding the honeycomb formed body using a molding machine having a die in which some of the holes are formed smaller than the other holes. As shown in Fig. 9, by providing holes 47 formed smaller than the other holes between the cell blocks 44 of the die 43, it is possible to form some of the partition walls corresponding to the holes 47 of the honeycomb formed body obtained by extrusion molding thinner than the other partition walls.

[0068] (drying process) Next, the obtained honeycomb molded body is dried to produce a dried honeycomb body. The drying method is not particularly limited, and examples thereof include electromagnetic heating methods such as microwave heating drying and high-frequency dielectric heating drying, and external heating methods such as hot air drying and superheated steam drying. Among these, the method of drying a certain amount of moisture by electromagnetic heating and then drying the remaining moisture by external heating is preferred, as it allows the entire molded body to be dried quickly and uniformly without cracking. The drying conditions are preferably such that 30 to 99% by mass of moisture is removed by electromagnetic heating, based on the moisture content before drying, and then the moisture content is reduced to 3% by mass or less by external heating. 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 to 120°C.

[0069] (Firing process) Next, the obtained dried honeycomb body is fired to produce a fired honeycomb body. Firing conditions are preferably such that the honeycomb body is heated at 1400 to 1500°C for 1 to 20 hours in an inert atmosphere such as nitrogen or argon. After firing, it is preferable to perform an oxidation treatment at 1200 to 1350°C for 1 to 10 hours to improve durability. The degreasing and firing methods are not particularly limited, and firing can be performed using an electric furnace, a gas furnace, or the like.

[0070] The honeycomb fired body may be used as a honeycomb structure as it is. Furthermore, a method for manufacturing a honeycomb structure having electrode portions includes first applying an electrode portion-forming raw material containing a ceramic raw material to the side surface of a dried honeycomb body, drying the applied material, and forming a pair of unfired electrode portions on the outer surface of the outer wall of the honeycomb body, sandwiching the central axis of the dried honeycomb body, so as to extend in a band-like shape in the flow path direction of the cells, thereby obtaining a dried honeycomb body with unfired electrode portions. Next, the dried honeycomb body with unfired electrode portions is fired to obtain a honeycomb fired body having a pair of electrode portions. This provides a honeycomb structure with electrode portions. The electrode portions may be formed after the honeycomb fired body is produced. Specifically, a honeycomb fired body may be produced, a pair of unfired electrode portions may be formed on the honeycomb fired body, and the honeycomb fired body may be fired to produce a honeycomb fired body having a pair of electrode portions.

[0071] The electrode part-forming raw material can be formed by adding various additives appropriately to raw material powders (metal powder and / or ceramic powder, etc.) formulated according to the required characteristics of the electrode part, and kneading them. When the electrode part has a laminated structure, the bonding strength between the metal terminal and the electrode part tends to be improved by making the average particle diameter of the metal powder in the paste for the second electrode part larger than the average particle diameter of the metal powder in the paste for the first electrode part. The average particle diameter of the metal powder refers to the arithmetic mean diameter on a volume basis when measuring the particle size frequency distribution using a laser diffraction method.

[0072] The method of preparing the electrode portion forming raw material and the method of applying the electrode portion forming raw material to the honeycomb fired body can be carried out in accordance with known methods for manufacturing honeycomb structures, but in order to give the electrode portion a lower electrical resistivity than the honeycomb structure portion, the metal content can be made higher than that of the honeycomb structure portion, or the particle size of the metal particles can be made smaller.

[0073] Before firing the dried honeycomb body with green electrode parts, it may be degreased to remove binders and the like. The firing conditions for the dried honeycomb body with green electrode parts are preferably heating at 1400 to 1500°C for 1 to 20 hours in an inert atmosphere such as nitrogen or argon. After firing, it is preferable to perform oxidation treatment at 1200 to 1350°C for 1 to 10 hours to improve durability. The degreasing and firing methods are not particularly limited, and firing can be performed using an electric furnace, a gas furnace, or the like.

[0074] (4. Manufacturing method of electrically heated carrier) In one embodiment of the method for manufacturing the electrically heated carrier 30 according to the present invention, a metal electrode is electrically connected to each of a pair of electrode portions of the honeycomb structure 10. Examples of connection methods include laser welding, thermal spraying, and ultrasonic welding. More specifically, a pair of metal electrodes is provided on the surfaces of the electrode portions, sandwiching the central axis of the columnar honeycomb structure portion 11. In this manner, the electrically heated carrier 30 according to the present invention is obtained.

[0075] (5. Exhaust gas purification device) The electrically heated carrier according to the embodiment of the present invention described above can be used in an exhaust gas purification device. The exhaust gas purification device includes an electrically heated carrier and a metallic tubular member that holds the electrically heated carrier. In the exhaust gas purification device, the electrically heated carrier is installed midway in an exhaust gas flow path through which exhaust gas from an engine flows. [Example]

[0076] The following examples are provided to provide a better understanding of the present invention and its advantages, but the present invention is not limited to these examples.

[0077] Example 1 (1. Preparation of clay) A ceramic raw material was prepared by mixing silicon carbide (SiC) powder and metallic silicon (Si) powder in an 80:20 mass ratio. Hydroxypropyl methylcellulose as a binder, a water-absorbent resin as a pore-forming material, and water were added to the ceramic raw material to form a molding raw material. The molding raw material was then kneaded using a vacuum kneader to produce cylindrical clay. The binder content was 7.0 parts by mass per 100 parts by mass of the silicon carbide (SiC) powder and metallic silicon (Si) powder. The pore-forming material content was 3.0 parts by mass per 100 parts by mass of the silicon carbide (SiC) powder and metallic silicon (Si) powder. The water content was 42 parts by mass per 100 parts by mass of the silicon carbide (SiC) powder and metallic silicon (Si) powder. The average particle size of the silicon carbide powder was 20 μm, and the average particle size of the metallic silicon powder was 6 μm. The average particle size of the pore-forming material was 20 μm. The average particle sizes of the silicon carbide powder, the metallic silicon powder, and the pore-forming material refer to the arithmetic mean diameter on a volume basis when the particle size frequency distribution is measured by laser diffraction.

[0078] (2. Preparation of honeycomb formed body) Next, a molding machine having a die structure as shown in Figure 10 was prepared. Figure 11(A) shows a schematic plan view of the die used in Example 1. The cell blocks 44 of the die were hexagonal, and T-pins 42 with the structure shown in Figure 4(B) were inserted into the holes between the cell blocks 44 of the die. The width D1, leg length L1, leg thickness T1, and shoulder length L3 of the T-pins 42 are shown in Table 1. The T-pins 42 were placed at intervals of two cell blocks between the cells arranged in a straight line. Next, the obtained cylindrical clay was molded using the above-mentioned molding machine to produce a honeycomb molded body in which part of the partition walls were missing so that some of the cells were connected. Slits 21 were formed on the end faces of the obtained honeycomb molded body as shown in Figure 11(B), and as a whole, interrupted and divided slits were formed as shown in Figure 3(H).

[0079] (3. Preparation of dried honeycomb body) The honeycomb formed body was dried by high-frequency dielectric heating, and then dried at 120°C for 2 hours using a hot air dryer to produce a dried honeycomb body.

[0080] (4. Preparation of electrode forming paste and production of honeycomb fired body) An electrode portion-forming paste was prepared by mixing metallic silicon (Si) powder, silicon carbide (SiC) powder, 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 of the Si powder and SiC powder was 100 parts by mass, the amount of methyl cellulose was 0.5 parts by mass, the amount of glycerin was 10 parts by mass, and the amount of water was 38 parts by mass. The average particle diameter of the metallic silicon powder was 6 μm. The average particle diameter of the silicon carbide powder was 35 μm. These average particle diameters refer to the arithmetic mean diameters based on volume when the particle size frequency distribution was measured using a laser diffraction method.

[0081] Next, this electrode part forming paste was applied to the dried honeycomb body with an appropriate area and film thickness using a curved surface printing machine, and further dried at 120 ° C for 30 minutes in a hot air dryer. After that, this dried honeycomb body was fired at 1400 ° C for 3 hours in an Ar atmosphere to obtain a honeycomb structure. The cell pitch and thickness of the partition walls 19 (rib thickness) of the obtained honeycomb structure are shown in Table 1.

[0082] The columnar honeycomb structure had a circular end face with an outer diameter (diameter) of 100 mm, a height (length in the cell flow direction) of 100 mm, and a thickness of the outer peripheral wall of 0.5 mm. The partition wall thickness was 0.19 mm, the porosity of the partition wall was 45%, and the average pore diameter of the partition wall was 8.6 μm. The thickness of the electrode part was 0.3 mm. As shown in FIG. 7(B), the ratio L / D of the length L to the width D of the slit 21 and the ratio of the area of ​​the slit 21 to the area of ​​the region surrounding the slit 21 (opening ratio) were measured. The measurement results of L / D and the opening ratio are shown in Table 1.

[0083] <Example 2> A honeycomb structure in which a portion of the partition walls was missing so that some cells were connected was produced in the same manner as in Example 1, except that U-shaped pins 41 having the structure shown in FIG. 4(A) were inserted into holes between cell blocks 44 of the die of the molding machine as shown in FIG. 11(C). The width D1, leg length L1, leg thickness T1, and base length L2 of the U-shaped pins 41 are shown in Table 1. The U-shaped pins 41 were placed in cells aligned in a straight line, with a gap of two cell blocks between them. The cell pitch and thickness (rib thickness) of the partition walls 19 of the obtained honeycomb formed body are shown in Table 1. Slits 21 were formed on the end faces of the obtained honeycomb formed body as shown in FIG. 11(D), and overall, interrupted and divided slits were formed as shown in FIG. 3(H).

[0084] Example 3 A honeycomb structure was fabricated in the same manner as in Example 1, except that the cell blocks 44 of the die were rectangular, and U-shaped pins 41 having the structure shown in FIG. 4(A) were inserted into the holes between the cell blocks 44 of the die as shown in FIG. 12(A). The width D1, leg length L1, leg thickness T1, and base length L2 of the U-shaped pins 41 are shown in Table 1. The U-shaped pins 41 were placed at intervals of three cell blocks between cells aligned in a straight line. The cell pitch and thickness (rib thickness) of the partition walls 19 of the obtained honeycomb formed body are shown in Table 1. Slits 21 were formed on the end faces of the obtained honeycomb formed body, as shown in FIG. 12(B), and overall, interrupted and divided slits were formed as shown in FIG. 3(H).

[0085] Example 4 A honeycomb structure in which a portion of the partition walls was missing so that some of the cells were connected was produced in the same manner as in Example 2, except that slits were formed by extrusion molding using a die with some of the holes blocked, without using the U-shaped pins 41. The blocked holes in the die were located in the same positions as the holes into which the U-shaped pins 41 in Example 2 were inserted. The cell pitch and thickness (rib thickness) of the partition walls 19 of the obtained honeycomb formed body are shown in Table 1. Slits 21 were formed on the end faces of the obtained honeycomb formed body as shown in Figure 11(D), and overall, interrupted and divided slits were formed as shown in Figure 3(H).

[0086] <Deformation evaluation> As shown in FIG. 13, for square and hexagonal cells, the rate of change in cell width Db in the slit-formed portion relative to the cell width Da in the non-slit-formed portion was measured: [(Db-Da) / Da] x 100(%), and the degree of deformation of the honeycomb structure was evaluated based on this rate of change. A smaller rate of change means a smaller change in cell width in the slit-formed portion. The evaluation results are shown in Table 1. Table 1 shows that for Examples 1 to 4, the rate of change was less than 10% or less than 20%, and in all cases, deformation of the honeycomb structure was well suppressed.

[0087] [Table 1] [Explanation of symbols]

[0088] 10 Honeycomb structure 11 Columnar honeycomb structure 12 Peripheral wall 13a, 13b electrode part 18 cells 19 Bulkhead 21 Slit 22 Molding machine 23 Cod 24 screens 25 Noodles 26 Drawing jig 27 nozzle 28 Honeycomb molded body 30 Electrically heated carrier 33a, 33b metal electrode 41 U-shaped pin 42 T-pin 43 nozzle 44 Cell Block 45 areas 46 Occlusion 47 holes

Claims

1. a molding process in which a molding raw material containing a ceramic raw material is extruded to obtain a honeycomb molded body having an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells that form flow paths extending from one end face to the other end face; a drying step of drying the honeycomb formed body to obtain a dried honeycomb body; a firing step of firing the dried honeycomb body to obtain a fired honeycomb body; Equipped with The molding process is a method for manufacturing a honeycomb structure, in which the molding raw material is extruded using a molding machine having a die and a noodle with some of its pores blocked, the noodle being located upstream of the die in the path of the molding raw material, to produce a honeycomb molded body in which some of the partition walls are missing so that some of the multiple cells are connected.

2. A method for manufacturing a honeycomb structure as described in claim 1, wherein a forming raw material having holes at positions corresponding to the desired positions of the partition walls of the honeycomb formed body to be missing during extrusion molding is formed by kneading the clay, and the forming raw material is extruded to produce a honeycomb formed body in which a portion of the partition walls is missing.

3. 3. The method for manufacturing a honeycomb structure according to claim 1, wherein the honeycomb structure has linear slits including the cells, the linear slits being formed by removing a portion of the partition wall in a cross section perpendicular to the flow direction of the cells.

4. a molding process in which a molding raw material containing a ceramic raw material is extruded to obtain a honeycomb molded body having an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells that form flow paths extending from one end face to the other end face; a drying step of drying the honeycomb formed body to obtain a dried honeycomb body; a firing step of firing the dried honeycomb body to obtain a fired honeycomb body; Equipped with The molding process is a method for manufacturing a honeycomb structure, in which the molding raw material is extruded using a molding machine having a die in which some holes are smaller than the other holes, to form some of the partition walls thinner than the other partition walls and produce a honeycomb molded body in which the partition walls are arranged in a slit shape.

5. a step of applying an electrode portion-forming raw material containing a ceramic raw material to a side surface of the dried honeycomb body and drying the applied material to obtain a dried honeycomb body with unfired electrode portions; and a step of firing the dried honeycomb body with the unfired electrode portions to obtain a honeycomb structure having a pair of electrode portions, A method for manufacturing a honeycomb structure according to any one of claims 1 to 4, wherein the pair of electrode portions are arranged on the outer surface of the outer wall, on either side of the central axis of the honeycomb structure, so as to extend in a band-like manner in the flow path direction of the cell.

6. A method for manufacturing an electrically heated carrier, comprising a step of electrically connecting metal electrodes to each of the pair of electrode portions of the honeycomb structure manufactured by the method of claim 5.

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