Method for producing a honeycomb structure and method for producing an electrically heated support

Abstract

A method for producing a ceramic honeycomb structure (10), the honeycomb structure (10) comprising: an outer peripheral wall (12); and partition walls (19) arranged on an inner side of the outer peripheral wall (12), the partition walls (19) defining a plurality of cells (18), each of the cells (18) extending from one end face (15) to the other end face (16) to form a flow path, the honeycomb structure (10) comprising at least one slit (21) provided in a cross section perpendicular to an axial direction of the honeycomb structure (10), the method comprising the following steps: Preparing a honeycomb structural element (20) before forming the slot (21); and Forming the slit (21) by arranging a wire (22) in such a way that it goes from one end face (15) to the other end face (16) in the cell (18), and then cutting the partition walls (19) while moving the honeycomb structural element (20) and / or the wire (22), wherein the step of forming the slit (21) comprises the following steps: Arranging the wire (22) in such a way that it goes in a cell A from one end face (15) to the other end face (16), from the cell A at the other end face (16) to the cell B at the other end face (16) and in the cell B from the other end face (16) to the one end face (15); and simultaneously pulling end portions of the wire (22) extending from the side of one end face (15) of both cell A and cell B, and / or moving the honeycomb structural element (20) in a direction from one end face (15) to the other end face (16) to cut the partition walls (19).

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a method for producing a honeycomb structure and a method for producing an electrically heating carrier. BACKGROUND OF THE INVENTION

[0002] Recently, electrically heated catalysts (EHCs) have been proposed to improve low exhaust gas purification performance immediately after engine start-up. For example, the EHC is configured by connecting metal electrodes to a columnar honeycomb structure made of a conductive ceramic, and passing a current to heat the honeycomb structure itself, thereby allowing a temperature to be raised to an activation temperature of the catalyst before engine start-up.

[0003] Preferably, the EHC has a structure that includes good thermal shock resistance, is resistant to cracking in response to changes in exhaust gas temperatures, so as not to interrupt a current flow path of the honeycomb structure, and to prevent the honeycomb structure from failing.

[0004] Patent Literature 1 discloses a technique for improving thermal shock resistance by providing slits on an outer peripheral wall and electrode portions of a honeycomb structure.

[0005] Patent Literature 2 discloses a technique for preventing cell breakage of a honeycomb body by removing part of the partition walls of the honeycomb structure to form slits connecting the cells, thereby reducing the stress generated by current concentration.

[0006] Further prior art is also known from patent literatures 3 to 6. LIST OF CITATIONS Patent literature [Patent Literature 1] JP 2014-198 296 A [Patent Literature 2] JP H08-273 805 A [Patent literature 3] EP 2 233 194 A1 [Patent Literature 4] EP 2 236 481 A2 [Patent Literature 5] US 2020 / 0 114 537 A1 [Patent literature 6] JP ​​H07 - 8 803 A SUMMARY OF THE INVENTION

[0007] Conventionally, for the formation of one or more slits perpendicular to an axial direction within the honeycomb structure, only the target portion cannot be easily removed, and adjacent partition walls within the honeycomb structure whose removal is not planned can also be removed, thus leaving room for improvement. Furthermore, even if the slit(s) is / are formed perpendicular to the axial direction within the honeycomb structure, there is still a problem regarding processing accuracy.

[0008] The present invention was conceived in light of the above circumstances. An object of the present invention is to provide a method for manufacturing a honeycomb structure and a method for manufacturing an electrically heating support that can form at least one slit perpendicular to the axial direction within the honeycomb structure with good accuracy.

[0009] The above object is achieved by the present invention, which is specified as follows: (1) A method for manufacturing a ceramic honeycomb structure, the honeycomb structure comprising: an outer peripheral wall; and partition walls arranged on an inner side of the outer peripheral wall, the partition walls defining a plurality of cells, each of the cells extending from one end face to the other end face to form a flow path, the honeycomb structure comprising at least one slit provided in a cross section perpendicular to an axial direction of the honeycomb structure, the method comprising the following steps: Preparing a honeycomb structural element before forming the slit; and forming the slit by arranging a wire in such a way that it goes from one end face to the other end face in the cell, and then cutting the partition walls while moving the honeycomb structural element and / or the wire, wherein the step of forming the slot (21) comprises the following steps: arranging the wire (22) in such a way that it goes from one end face (15) to the other end face (16) in a cell A, from the cell A at the other end face (16) to the cell B at the other end face (16) and in the cell B from the other end face (16) to the one end face (15); and simultaneously pulling end portions of the wire (22) extending from the side of one end face (15) of both cell A and cell B, and / or moving the honeycomb structural element (20) in a direction from one end face (15) to the other end face (16) to cut the partition walls (19). (2) The method for manufacturing a honeycomb structure according to (1), the method further comprising a step of forming a pair of electrode portions on an outer surface of the outer peripheral wall so as to extend in a band shape in a flow path direction of the cells around the central axis of the honeycomb structure. (3) A method for producing an electrically heating support, the method comprising a step of electrically connecting a metal electrode to each of the pair of electrode portions of the honeycomb structure produced by the method of (2).

[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 heating carrier which can form at least one slit perpendicular to the axial direction within the honeycomb structure with good accuracy. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic external view of a honeycomb structure according to an embodiment of the present invention; Fig. 2(A) to Fig. 2(H) are schematic views showing specific examples of shapes of slits on end surfaces of honeycomb structures; Fig. 3 is a schematic cross-sectional view of an electrically heating support according to an embodiment of the present invention, which is perpendicular to a line of cells; Fig. 4 is a schematic view for explaining a method of forming a slit with a wire. Fig. 5(A) and Fig. 5(B) are schematic views each explaining a method of forming a slit by a wire; Fig. 6 is a schematic view explaining a method of forming a slot with a cutting tool; Fig. 7(A) and Fig. 7(B) are schematic views each explaining a method of forming a slit with a cutting tool; and Fig. 8(A) and Fig. 8(B) are schematic views each explaining a method of forming a slit with a cutting tool. Fig. 6 to 8 (B) illustrate an alternative method for forming a slot. DETAILED DESCRIPTION OF THE INVENTION

[0011] Embodiments of the present invention will be specifically described below with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and various design changes and improvements may be made based on the ordinary skill of those skilled in the art without departing from the spirit of the present invention. <1. Honeycomb structure>

[0012] Fig. 1 is a schematic external view of a honeycomb structure 10 according to an embodiment of the present invention. The honeycomb structure 10 includes a honeycomb structure section 11 and electrode sections 13a, 13b. The honeycomb structure 10 may not include the electrode sections 13a, 13b. (1-1. Honeycomb structure section)

[0013] The honeycomb structure portion 11 is a columnar member made of ceramics, including an outer peripheral wall 12; and partition walls 19 disposed on an inner side of the outer peripheral wall 12, defining a plurality of cells 18, each extending from one end surface 15 to the other end surface 16 to form a flow path. The word "columnar" refers to a three-dimensional shape having a thickness in an extending direction of the cells 18 (an axial direction of the honeycomb structure). A ratio of the axial length of the honeycomb structure to the diameter or width of each end surface of the honeycomb structure (an aspect ratio) is arbitrary. The honeycomb shape may also include a shape in which the axial length of the honeycomb structure is smaller than the diameter or width of each end surface (a flat shape).

[0014] As long as it is columnar, the outer shape of the honeycomb structure portion 11 is not particularly limited. For example, the honeycomb structure portion may have a shape such as a columnar shape with circular end faces (cylindrical shape), a columnar shape with oval end faces, and a columnar shape with polygonal (square, pentagonal, hexagonal, heptagonal, octagonal, etc.) end faces. The size of the honeycomb structure portion 11 is such that an area of ​​the end faces is preferably from 2000 to 20000 mm to improve heat resistance (suppress cracks entering the outer peripheral wall in a circumferential direction). 2 and preferably from 5000 to 15000 mm 2 is.

[0015] The honeycomb structure portion 11 is made of a material selected from the group consisting of, but not limited to, 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 may also be used. Among these, the material of the honeycomb structure portion 11 preferably includes ceramics based primarily on the silicon-silicon carbide composite or silicon carbide in order to achieve both heat resistance and electrical conductivity.The phrase "the honeycomb structure portion 11 is mainly composed of a silicon-silicon carbide composite material" as used herein means that the honeycomb structure portion 11 contains 90% or more of the silicon-silicon carbide composite material by mass (total mass) based on the entire honeycomb structure portion. Here, the silicon-silicon carbide composite material contains silicon carbide particles as an aggregate and silicon as a binder for binding the silicon carbide particles, with a plurality of silicon carbide particles bonded by silicon to form pores between the silicon carbide particles. The phrase "the honeycomb structure portion 11 is mainly composed of silicon carbide" as used herein means that the honeycomb structure portion 11 contains 90% or more of the silicon carbide by mass (total mass) based on the entire honeycomb structure portion.

[0016] When the honeycomb structure portion 11 contains the silicon-silicon carbide composite material, a ratio of a “mass of silicon as a binder material” contained in the honeycomb structure portion 11 to the sum of a “mass of silicon carbide particles as an aggregate” contained in the honeycomb structure portion 11 and a “mass of silicon as a binder material” contained in the honeycomb structure portion 11 is preferably 10 to 40 mass%, and more preferably 5 to 35 mass%.

[0017] The shape of each cell in a cross section perpendicular to the direction of cell extension 18 is not limited, but is preferably a square, a hexagon, an octagon, or a combination thereof. Among them, square and hexagon are preferred in terms of easily achieving both structural strength and heating uniformity.

[0018] Preferably, each of the partition walls 19 defining the cells 18 has a thickness of 0.1 to 0.3 mm, and more preferably 0.1 to 0.2 mm. As used herein, the thickness of the partition wall 19 is defined as a length of a portion passing through the partition walls 19 among the lines connecting the centers of gravity of adjacent cells 18 in the cross-section perpendicular to the direction of extension of the cells 18.

[0019] Preferably, the honeycomb structure section 11 has a cell density of 40 to 150 cells / cm in the cross section perpendicular to the flow path direction of the cells 18 2 and preferably from 70 to 100 cells / cm 2The cell density in such a range can increase the purification performance of the catalyst while reducing the pressure loss during exhaust gas flow. The cell density is a value obtained by dividing the number of cells by an area of ​​an end surface of the honeycomb structure portion 11 excluding the outer peripheral wall portion 12.

[0020] The provision of the outer peripheral wall 12 of the honeycomb structure portion 11 is useful in ensuring the structural strength of the honeycomb structure portion 11 and preventing fluid flowing through the cells 18 from leaking from the outer peripheral wall 12. 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, the strength becomes too high, so that a strength balance between the outer peripheral wall 12 and the partition wall 19 is lost, which reduces thermal shock resistance. If the thickness of the outer peripheral wall 12 is excessively increased, the heat capacity increases, and a temperature difference between the outer peripheral side and the inner peripheral side of the outer peripheral wall 12 increases, so that the heat impact resistance decreases.Thus, 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. As used herein, the thickness of the outer peripheral wall 12 is defined as a thickness of the outer peripheral wall 12 in a direction normal to a tangent at a measurement point when observing a portion of the outer peripheral wall 12 subjected to a thickness measurement in the cross section perpendicular to the cell extension direction.

[0021] Preferably, the partition walls 19 of the honeycomb structure portion 11 have an average pore diameter of 2 to 15 µm, and more preferably 4 to 8 µm. The average pore diameter is a value measured by a mercury porosimeter.

[0022] The partition walls 19 may be porous. If the partition walls 19 are porous, the partition wall 19 preferably has a porosity of 35 to 60%, and more preferably 35 to 45%. The porosity is a value measured by a mercury porosimeter.

[0023] The honeycomb structure 10 is made of ceramic and preferably has electrical conductivity. As long as the honeycomb structure 10 can generate heat through Joule heating during electrical conduction, the volume resistivity of the honeycomb structure 10 is not particularly limited. Preferably, the volume resistivity is from 0.1 to 200 Ωcm, and more preferably from 1 to 200 Ωcm. As used herein, the volume resistivity of the honeycomb structure 10 is a value measured at 400°C using a four-terminal method. (1-2. Electrode section)

[0024] The honeycomb structure 10 includes a pair of electrode portions 13a, 13b on an outer surface of the outer peripheral wall 12 around a central axis of the honeycomb structure portion 11 so as to extend in a ribbon shape in the flow path direction of the cells 18. By providing the pair of electrode portions 13a, 13b, the uniform heat generation of the honeycomb structure 10 can be improved. From the viewpoint that a current easily spreads in an axial direction of each of the electrode portions 13a, 13b, it is desirable that each of the electrode portions 13a, 13b extends between both end surfaces of the honeycomb structure 10 over a length of 80% or more, more preferably 90% more, and even more preferably the full length.

[0025] Preferably, each of the electrode portions 13a, 13b has a thickness of 0.01 to 5 mm, and more preferably, 0.01 to 3 mm. Such a range can enable uniform heat generation to be improved. The thickness of each of the electrode portions 13a, 13b is defined as a thickness in a direction normal to a tangent at a measurement point on an outer surface of each of the electrode portions 13a, 13b when observing the point of each electrode portion subjected to thickness measurement in the cross section perpendicular to the cell extension direction.

[0026] The volume resistivity of each of the electrode portions 13a, 13b is smaller than the volume resistivity of the honeycomb portion 11, whereby electricity tends to flow preferentially to the electrode portions 13a, 13b, and the electricity tends to disperse in the flow path direction and in the circumferential direction of the cells 18 during electrical conduction. The volume resistivity of the electrode portions 13a, 13b is preferably 1 / 10 or smaller, more preferably 1 / 20 or smaller, and even more preferably 1 / 30 or smaller than the volume resistivity of the honeycomb portion 11. However, if the difference in volume resistivity between the two becomes too large, the current is concentrated between the ends of the opposing electrode portions, which biases the heat generated in the honeycomb portion 11.Thus, the volume 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 volume resistivity of the honeycomb structure portion 11. As used herein, the volume resistivity of the electrode portions 13a, 13b is a value measured at 25°C by a four-terminal method.

[0027] Each of the electrode sections 13a, 13b can be made of a conductive ceramic, a metal, or a composite of a metal and a conductive ceramic (cermet). Examples of the metal include a single metal selected from the group consisting of Cr, Fe, Co, Ni, Si, or Ti, or an alloy containing at least one metal selected from the group consisting of these metals. Non-limiting examples of the conductive ceramic include silicon carbide (SiC), metal compounds such as metal silicides such as tantalum silicide (TaSi2) and chromium silicide (CrSi2).Specific examples of the composite of the metal and the conductive ceramic (cermet) include, in terms of reduced thermal expansion, a composite of metal silicon and silicon carbide, a composite of metal silicide such as tantalum silicide and chromium silicide, metal silicon and silicon carbide, and further a composite obtained by adding one or more insulating ceramics such as alumina, mullite, zirconia, cordierite, silicon nitride, and aluminum nitride to one or more metals listed above. (1-3) Slot

[0028] At least one slit 21 is provided in the cross section perpendicular to the axial direction of the honeycomb structure 10. The slit 21 is formed so as to be perpendicular to the axial direction in the honeycomb structure 10, or more precisely, to pass through from one end face to the other end face of the honeycomb structure 10. According to this configuration, stress relaxation functions through the slit 21, so that the generation of cracks due to a thermal expansion difference generated by the honeycomb structure 10 when the honeycomb structure 10 generates heat can be well suppressed.

[0029] The shape and number of slits 21 in the cross section of the honeycomb structure 10 are not particularly limited and can be designed accordingly. For example, there may be one slit 21 or two or more slits 21 in the cross section of the honeycomb structure 10, each of which may be formed so as not to intersect or may be formed so as to at least partially intersect. The length and width of each slit 21 in the cross section of the honeycomb structure 10 are not particularly limited. The width of each slit 21 in the cross section of the honeycomb structure 10 may be formed to be the same as the width of each cell 18, or the width of each slit 21 may be formed smaller or larger than that of each cell 18. The length of each slit 21 in the cross section of the honeycomb structure 10 is not particularly limited, but may be from 2 to 80 cells.The width of each slot 21 is not particularly limited, but may be 1 to 5 cells. The length and width of each slot 21 in the cross section of the honeycomb structure 10 can be appropriately designed depending on the size, material, applications, and number of slots 21 of the honeycomb structure 10.

[0030] Each slit 21 may be divided into sections along an extending direction of the slits 21 in the cross-sectional portion of the honeycomb structure 10. In this case, the slit 21 in the cross-sectional portion of the honeycomb structure 10 may be divided into slits of the same length or of different lengths. By dividing and forming the slit 21 in the cross-sectional portion of the honeycomb structure 10, the generation of cracks in the honeycomb structure 10 can be well controlled. The number by which the slits 21 are divided is not particularly limited, but each slit 21 may be divided into two, three, or four or more sections. In addition, the honeycomb structure may be provided with a plurality of slits consisting of the combination of divided slits and non-divided slits.

[0031] Fig. Figure 1 schematically shows an embodiment in which there is a slot 21 in the cross-section of the honeycomb structure 10. The slot 21 may be arranged such that it is in the cross-section of the honeycomb structure 10, as in Fig. 1, passes through the center or does not pass through the center. In Fig. 2(A) to Fig. 2(H) shows specific examples of an embodiment in which a plurality of slots 21 are formed. It is noted that each of Fig. 2(A) to Fig. 2(H) shows only the outer diameter of one end face 15 of the honeycomb structure 10 and the shape of the slits 21. All of them show the morphology at one end face of the honeycomb structure 10. These slits 21 maintain a similar morphology in the cross section of the honeycomb structure 10 and are formed to extend in the axial direction and pass through to the other end face of the honeycomb structure 10.

[0032] As in Fig. 2(A), the slits 21 may be three slits that intersect at the center and extend on the end face of the honeycomb structure 10 on both sides to the inner peripheral end of the outer peripheral wall. As shown in Fig. 2(B), each of the three in Fig. 2(A) may be formed with a length reaching the outer peripheral wall.

[0033] As in Fig. 2(C), the slots 21 may be formed with a length at which the three Fig. 2(A) do not reach the inner end of the outer peripheral wall on the end face of the honeycomb structure 10. As shown in Fig. 2(D), each of the three Fig. 2(A) shown slots may be divided along the direction of extension.

[0034] As in Fig. 2(E), the slots 21 may be three slots extending parallel to each other on the end face of the honeycomb structure 10. As shown in Fig. 2(F), each of the three in Fig. 2(E) shown slots may be divided along the direction of travel.

[0035] As in Fig. 2(G), the slots 21 on the end face of the honeycomb structure 10 may be three slots that substantially form a triangle, with the slots not intersecting at their tips. As shown in Fig. 2(H), the slots may also be four slots forming substantially a square, with the slots not intersecting at their tips.

[0036] The one or more slots 21 may be filled with a filler material. The filler material is preferably filled at least in a portion of the space within the slot 21. The filler material is filled in 50% or more of the space within the slot 21, and more preferably in the entire space within the slot 21.

[0037] When the honeycomb structure 10 is primarily based on silicon carbide or a metal silicon-silicon carbide composite, the filler material preferably contains 20 mass% or more of silicon carbide, and more preferably 20 to 70 mass% of silicon carbide. This can enable the filler material to have a thermal expansion coefficient close to that of the honeycomb structure 10, thereby improving the thermal shock resistance of the honeycomb structure 10. The filler material may contain 30 mass% or more of silicon dioxide, alumina, or the like. <2. Electrically heated carrier>

[0038] Fig. Figure 3 is a schematic cross-sectional view of an electrically heating support 30 according to an embodiment of the present invention, perpendicular to the cell extension direction. The electrically heating support 30 includes the honeycomb structure 10; and metal electrodes 33a, 33b electrically connected to the electrode portions 13a and 13b of the honeycomb structure 10, respectively. <2-1. Metal electrode>

[0039] Metal electrodes 33a, 33b are provided on the electrode portions 13a, 13b of the honeycomb structure 10. The metal electrodes 33a, 33b may be a pair of metal electrodes such that one metal electrode 33a is arranged opposite the other metal electrode 33b around the central axis of the honeycomb structure portion 11. While a voltage is applied to the metal electrodes 33a, 33b via the electrode portions 13a, 13b, electricity is conducted through the metal electrodes 33a, 33b to allow the honeycomb structure portion 11 to generate heat through Joule heating. Thus, the electrically heating support 30 can also be suitably used as a heating device. The applied voltage is preferably from 12 to 900 V, and more preferably from 48 to 600 V, although the applied voltage can be changed as needed.

[0040] The material of the metal electrodes 33a, 33b is not particularly limited as long as it is a metal, and a single metal, an alloy, or the like can be used. In terms of corrosion resistance, electrical resistivity, and linear expansion coefficient, for example, the material is preferably an alloy containing at least one selected from the group consisting of Cr, Fe, Co, Ni, and Ti, and more preferably stainless steel and Fe-Ni alloys. The shape and size of each of the metal electrodes 33a, 33b are not particularly limited, and they can be appropriately designed in accordance with the size of the electrically heating support 30, the performance of the electric line, and the like.

[0041] By supporting the catalyst on the electrically heating support 30, the electrically heating support 30 can be used as a catalyst. For example, a fluid such as exhaust gas from a motor vehicle can flow through the flow paths of the plurality of cells 18 of the honeycomb structure 10. Examples of the catalyst include noble metal catalysts or catalysts other than them. Illustrative examples of the noble metal catalysts include a three-way catalyst and an oxidation catalyst obtained by supporting a noble metal such as platinum (Pt), palladium (Pd), and rhodium (Rh) on surfaces of pores of alumina and containing a co-catalyst such as cerium dioxide and zirconium dioxide, or a NOx storage reduction catalyst (LNT catalyst) that uses an alkaline earth metal and platinum as storage components for nitrogen oxides (NO x). Illustrative examples of a catalyst that does not use the noble metal include a selective NOx reduction catalyst (SCR catalyst) containing a copper-substituted or iron-substituted zeolite, and the like. Further, two or more catalysts selected from the group consisting of these catalysts may be used. A method for supporting the catalyst is not particularly limited and can be carried out according to a conventional method for supporting the catalyst on the honeycomb structure. <3. Method for producing a honeycomb structure>

[0042] A method for manufacturing the honeycomb structure 10 according to an embodiment of the present invention will be described below.

[0043] The method for manufacturing the honeycomb structure 10 according to an embodiment of the present invention includes: a forming step for preparing a honeycomb preform; a drying step for preparing a honeycomb dry body; and a firing step for preparing a fired honeycomb body. (Educational step)

[0044] In the forming step, a forming raw material containing conductive ceramic is first prepared. The forming raw material is prepared by adding metal silicon powder (metal silicon), a binder, one or more surfactants, a pore former, water, and the like to silicon carbide powder (silicon carbide). It is preferable that a mass of the metal silicon relative to the total mass of the silicon carbide powder and the mass of the metal silicon is from 10 to 40 mass %. The average particle diameter of the silicon carbide particles in the silicon carbide powder is preferably from 3 to 50 µm, and more preferably from 3 to 40 µm. The average particle diameter of the metal silicon (metal silicon powder) is preferably from 2 to 35 µm.The average particle diameter of each of the silicon carbide particles and the metal silicon (metal silicon particles) refers to an arithmetic-average diameter on a volume basis when the particle size frequency distribution is measured by the laser diffraction method. 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. Note that this is the formulation of the molding raw material when the metal of the honeycomb structure 10 is a silicon-silicon carbide composite, and when the material of interest is silicon carbide, no metal silicon is added.

[0045] Examples of the binder include methylcellulose, hydroxypropylmethylcellulose, hydroxypropoxylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinyl alcohol, and the like. Among these, the use of methylcellulose together with hydroxypropoxylcellulose is preferred. The content of the binder is preferably from 2.0 to 10.0 parts by mass when the total mass of the silicon carbide powder and the metal silicon powder is 100 parts by mass.

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

[0047] The surfactant that can be used includes ethylene glycol, dextrin, fatty acid soaps, polyalcohol, and the like. These can be used alone or in combination. The content of the surfactant is preferably from 0.1 to 2.0 parts by mass when the total mass of the silicon carbide powder and the metal silicon powder is 100 parts by mass.

[0048] The pore-forming agent is not particularly limited as long as the pore-forming agent forms pores even after firing, including, for example, graphite, starch, foam resins, water-absorbent resins, silica gel, and the like. The content of the pore-forming agent is preferably from 0.5 to 10.0 parts by mass when the total mass of the silicon carbide powder and the metal silicon powder is 100 parts by mass. An average particle diameter of the pore-forming agent is preferably from 10 to 30 μm. An average particle diameter of the pore-forming agent refers to an arithmetic average diameter on a volume basis when the frequency distribution of the particle size is measured by the laser diffraction method. When the pore-forming agent is the water-absorbent resin, the average particle diameter of the pore-forming agent refers to an average particle diameter after water absorption.

[0049] The resulting precursor material is then kneaded to form a blank, which is then extruded to prepare a honeycomb structure. The honeycomb precursor includes: the outer peripheral wall; and the partition walls arranged on the inner side of the outer peripheral wall, which define the plurality of cells, each extending from one end face to the other end face to form the flow path. (drying step)

[0050] The resulting honeycomb preform is then dried to produce a honeycomb dry body. The drying method is not particularly limited. Examples include electromagnetic wave heating methods such as microwave heating / drying and dielectric high-frequency heating / drying, and external heating methods such as hot air drying and superheated steam drying. Among these, it is preferable to dry a certain amount of moisture by the electromagnetic wave heating method and then dry the remaining moisture by the external heating method, since it is possible to dry the entire preform quickly and evenly without cracking.Regarding drying conditions, it is preferable to remove 30 to 99 mass% of the water content before drying by the electromagnetic wave heating method, and then reduce the water content to 3 mass% or less by the external heating method. Dielectric heating / drying is preferred as the electromagnetic heating method, and hot air drying is preferred as the external heating method. The drying temperature can preferably be from 50 to 120°C.

[0051] The honeycomb dry body is prepared as the "honeycomb structural element 20" before the slit(s) are formed, and the slit(s) are formed in the honeycomb structural element 20. Note that the slit(s) need not be formed on the honeycomb dry body, and the fired honeycomb body, as described below, may be prepared as the "honeycomb structural element 20," and the slit(s) may be formed on the honeycomb structural element 20 after the honeycomb dry body is fired to manufacture the fired honeycomb body. Preferably, the fired honeycomb body is used as the "honeycomb structural element 20," and the slit(s) are formed on the honeycomb structural element 20. The shape, number of slits, number of intersection points, length, and width of the slit(s) are determined by the individual requirements of the individual honeycomb structures.The slots can be designed as required depending on the desired properties of the honeycomb structure to be produced and the like. (Firing step)

[0052] Subsequently, the resulting honeycomb dry body is fired to produce a fired honeycomb body. As described above, the slit(s) may or may not be formed in the honeycomb dry body. As the firing conditions, the honeycomb dry body is preferably heated at 1400 to 1500°C for 1 to 20 hours in an inert atmosphere such as nitrogen or argon. After firing, an oxidation treatment is preferably carried out at 1200 to 1350°C for 1 to 10 hours to improve durability. The methods for degreasing and firing are not particularly limited and can be carried out using an electric furnace, a gas furnace, or the like. (Method for forming a slit according to Embodiment 1)

[0053] The method for forming at least one slit in the honeycomb structural member 20 according to Embodiment 1 is carried out by disposing (inserting) a wire into the cells of the prepared honeycomb structural member in such a manner as to pass from one end face to the other, and cutting the partition walls while moving the honeycomb structural member before forming the slit and / or the wire to form the slit. According to this configuration, the target partition walls can be accurately removed without removing those partition walls that do not need to form the slit. Thus, the slit can be formed with high accuracy.Furthermore, the partition walls can be cut by moving the inserted wire relative to the partition walls, so that the number of slit formation steps required for slit formation can be reduced and the slit can be formed efficiently in a short period of time. As long as the wire can cut the partition walls of the ceramic honeycomb structural member 20, the material and size (a wire diameter) of the wire used are not limited. Examples of the wire that can well cut the partition walls of the ceramic honeycomb structural member 20 include a wire electroplated with diamond abrasive grains. The size (the wire diameter) of the wire that can well cut the partition walls of the ceramic honeycomb structural member 20 is preferably from 300 to 500 μm.

[0054] As in Fig. 4, the method for forming the at least one slit using a wire 22 can be carried out by inserting the wire 22 from one end face to the other end face into a cell A and moving the wire inserted into the honeycomb structural member 20 or the cell in a direction perpendicular to the axial direction (X direction) while reciprocating the wire 22, or by feeding the wire 22 in a direction along the axial direction (Y direction) of the honeycomb structural member 20 while rotating the wire 22 itself and cutting the partition walls to form the slit. The rotation speed and the moving speed of the wire are not particularly limited and can be adjusted according to a desired cutting efficiency. For example, the rotation speed may be from 10 to 100 revolutions per second, and the moving speed may be from 1 to 5 mm per second.When forming multiple slots, the wire 22 inserted into cell A is moved in one direction relative to the honeycomb structural element 20 to form a first slot, then pulled out once from the cell, reinserted into the other cell at a predetermined position on the honeycomb structural element 20, and moved in the same way in one direction relative to the honeycomb structural element 20 to form a second slot. This process can be repeated to form the multiple slots. In addition, multiple wires 22 can be arranged in multiple cells and moved in one direction relative to the honeycomb structural element 20 to form multiple slots.In the case of forming slits in which a plurality of slits intersect on the end face of the honeycomb structure, in addition to the slit forming method as described above, the wire 22 inserted into the cell A may be moved relative to the honeycomb structural member 20 in one direction to form a first slit, and, without pulling out the wire 22, may be moved from a predetermined position through the slit as it is to form a second slit in such a way that they intersect. This process may be repeated to form slits in the shape in which a plurality of slits intersect on the end face of the honeycomb structure.

[0055] As in Fig. 5 (A), the method of forming at least one slit using the wire 22 can be carried out by arranging the wire 22 in such a way that it goes from one end face to the other end face in a cell A, that it goes from the cell A at the other end face to a cell B at the other end face, and that it goes from the other end face to one end face in the cell B, and that the end portions of the wire extending from the one end face side of the cell A and the cell B are simultaneously drawn (the wire in Fig. 5(A) is pulled downwards) to cut the partition walls and form the slit. Alternatively, the honeycomb structure element 20 may be Fig. 5(A) in a direction from one end face to the other end face to cut the partition walls. As shown in Fig. 5(B), this can gradually form the slit 21 from the other end face to one end face of the honeycomb structural member 20. When forming a plurality of slits as described above, one slit can be formed by simultaneously pulling the end portions of the wire extending from one end face of cell A and cell B or moving the honeycomb structural member 20 in the direction from one end face to the other end face, and subsequently, another slit can be formed by again specifying two predetermined cells in the same way, passing a wire from one cell to the other cell, and then simultaneously pulling end portions of the wire extending from the end face side, or moving the honeycomb structural member 20 in the direction from one end face to the other end face. This process can be repeated to form a plurality of slits on the end faces of the honeycomb structure. (Method for forming a slit according to Embodiment 2; Reference)

[0056] The method for forming at least one slit in the honeycomb structural element 20 according to Embodiment 2 is carried out by applying ultrasonic vibration to a cutting tool 23 to cut the partition walls from one end surface to the other end surface of the prepared honeycomb structural element 20 before slit formation to form the slit. According to this configuration, the target partition walls can be removed with high accuracy without removing the necessary partition walls. Thus, the slit can be formed with high accuracy.Furthermore, the partition walls can be cut by applying ultrasonic vibration to the cutting tool 23 to cut the partition walls from one end face to the other end face of the honeycomb structural member 20 before slit formation, so that the number of slit formation steps required for slit formation can be reduced and the slit can be formed efficiently in a short period of time. It is preferable to perform the ultrasonic vibration under conditions of a frequency of 20 to 40 kHz and an output of 30 to 1000 W. Such ultrasonic vibration conditions can enable better cutting of the partition walls of the ceramic honeycomb structural member 20. More preferably, the frequency of the ultrasonic vibration is 22 to 27 kHz, and more preferably, the output power is 50 to 100 W.The cutting tool 23 is not particularly limited as long as it can enable better cutting of the partition walls of the ceramic honeycomb structural member 20. Examples of the cutting tool 23 include a tool in which a base metal of a carbon tool steel (SK) material is electroplated with diamond abrasive grains.

[0057] As in Fig. As shown in Fig. 6, the method of forming the slit by applying the ultrasonic vibration to the cutting tool 23 can be carried out by moving the cutting tool 23 or the honeycomb structural member 20 such that the cutting tool 23 advances from an end surface of the honeycomb structural member 20 in a direction parallel to the axial direction to cut the partition walls to form the slit. When forming a plurality of slits, one slit may be formed as described above, and the other slit may be formed by moving the cutting tool 23 or the honeycomb structural member 20 again in the same manner such that the cutting tool 23 advances from an end surface of the honeycomb structural member 20 in the direction parallel to the axial direction to cut the partition walls. This process can be repeated to form the plurality of slits on the end surface of the honeycomb structure.Furthermore, depending on the size of the slit, it may not be sufficient to form a slit only by moving the cutting tool 23 or the honeycomb structural member 20 such that the cutting tool 23 advances from an end surface of the honeycomb structural member 20 in the direction parallel to the axial direction to cut the partition walls. In such a case, the size of the slit can be widened by performing multiple cutting processes with the cutting tool 23 described above to form a slit of a desired size.

[0058] As in Fig. As shown in Figure 7(A), the method for forming the at least one slit by applying ultrasonic vibrations to the cutting tool 23 can be carried out by moving the cutting tool 23 or the honeycomb structural member 20 in such a way that the cutting tool 23 advances from one end face of the honeycomb structural member 20 in a direction intersecting the axial direction to cut the partition walls to form the slit. Furthermore, in this case, the step as described above can be performed multiple times to form the slits from one end face to the other end face of the honeycomb structural member 20 in parallel to the axial direction. According to such a configuration, ultrasonic cutting can be performed in an oblique direction to the end face of the honeycomb structural member 20, thereby reducing cutting resistance and improving cutting efficiency. As shown in Fig. As shown in Figure 7(B), an angle θ1 at which the cutting tool 23 intersects the axial direction of an end surface of the honeycomb structural member 20 is not particularly limited and can be adjusted depending on the sizes and materials of the cutting tool 23 and the honeycomb structural member 20, the desired size of the slit, and the like. It may be from 15 to 45° or from 20 to 40°.

[0059] As in Fig. 8(A), the cutting tool 23 can be mounted on the tip of the Fig. 6, the cutting tool 23 has an inclined cross section in a direction parallel to the cutting direction. According to such a configuration, ultrasonic cutting can be performed in an oblique direction to the end face of the honeycomb structural element 20, thereby reducing cutting resistance and improving cutting efficiency. Furthermore, the cutting resistance can be reduced even though the cutting tool 23 is moved parallel to the axial direction of the honeycomb structural element 20. Thus, it is not necessary to move the cutting tool 23 as shown in Fig. 7(A) to advance in the direction intersecting the axial direction of the honeycomb structural element 20, which simplifies the production equipment to lead to easy production. As shown in Fig.As shown in Fig. 8(B), an inclination angle θ2 of the cross section of the cutting tool 23 in the direction parallel to the cutting direction is not particularly limited and can be adjusted as needed depending on the sizes and materials of the cutting tool 23 and the honeycomb structural member 20, the desired size of the slit, and the like. It can be from 15 to 45°.

[0060] The fired honeycomb body with the at least one formed slot can be filled with a filler material. The filler material is introduced by injecting it into the formed slot. The slot can be filled, for example, by pressure injection using a syringe or other device.

[0061] The fired honeycomb body filled with the filler material is heated to produce a honeycomb structure including the slot filled with the filler material. Heating is preferably carried out at 400 to 700°C for 10 to 60 minutes. The heating (heat treatment) is performed to strengthen the chemical bonding of the filler material. The heating method is not limited, and the firing can be carried out using an electric furnace, a gas furnace, or the like.

[0062] Furthermore, the fired honeycomb body with the formed slit can be used as a honeycomb structure as it is. The method for producing the honeycomb structure with electrode portions is carried out by first applying the electrode portion forming raw material containing ceramic raw materials to the side surface of the honeycomb dry body and drying it to form a pair of unfired electrode portions on the outer surface of the outer peripheral wall around the central axis of the honeycomb dry body in a stripe shape in the cell flow direction, thereby producing a honeycomb dry body with unfired electrode portions. The honeycomb dry body with unfired electrode portions is then fired to produce a fired honeycomb body with a pair of electrode portions. Thus, the honeycomb structure with the electrode portions is obtained.Furthermore, the electrode portions may be formed after the fired honeycomb body is manufactured. Specifically, after the fired honeycomb body is manufactured, a pair of unfired electrode portions may be formed on the fired honeycomb body and fired to produce the fired honeycomb body having the pair of electrode portions.

[0063] The electrode section forming raw material can be formed by appropriately adding and kneading various additives to the raw material powder (metal powder and / or ceramic powder, etc.) formulated in accordance with the required properties of the electrode sections. When each electrode section is formed as a layered structure, the bonding strength between each metal terminal and each electrode section tends to be improved by increasing an average particle diameter of the metal powder in the paste for the second electrode section compared to an average particle diameter of the metal powder in the paste for the first electrode section. The average particle diameter of the metal powder refers to an arithmetic average diameter on a volume basis when the frequency distribution of the particle diameter is measured by the laser diffraction method.

[0064] The method for preparing the electrode portion forming raw material and the method for applying the electrode portion forming raw material to the fired honeycomb body can be carried out according to a known method for manufacturing a honeycomb structure. However, it is possible to increase a metal content ratio or reduce the particle diameter of the metal particles compared to the honeycomb structure portion to achieve a lower electrical resistivity of the electrode portions than the honeycomb structure portion.

[0065] Before firing the honeycomb dry body with unfired electrode portions, degreasing may be performed to remove the binder and the like. As the firing conditions for the honeycomb dry body with unfired electrode portions, the honeycomb dry body with unfired electrode portions may preferably be heated at 1400 to 1500°C for 1 to 20 hours in an inert atmosphere such as nitrogen and argon. After firing, oxidation treatment is performed at 1200 to 1350°C for 1 to 10 hours to improve durability. The methods for degreasing and firing are not particularly limited and can be carried out using an electric furnace, a gas furnace, or the like. <4. Method for producing an electrically heating support>

[0066] According to one embodiment of the method for an electrically heating support 30 according to the present invention, a metal electrode is attached to each of the electrode portions on the honeycomb structure 10. Examples of the attachment method include laser welding, thermal spraying, ultrasonic welding, and the like. Specifically, a pair of metal electrodes are provided on the surfaces of the electrode portions around the central axis of the honeycomb structure portion of the honeycomb structure 10. Thus, the electrically heating support 30 according to one embodiment of the present invention is obtained. (5. Exhaust gas purification device)

[0067] The electrically heating support 30 according to the above embodiment of the present invention, as described above, can be used for an exhaust gas purification device. The exhaust gas purification device includes the electrically heating support 30 and a metal cylinder member for supporting the electrically heating support 30. In the exhaust gas purification device, the electrically heating support 30 can be installed in an exhaust flow path to allow exhaust gas from an engine to flow. EXAMPLES

[0068] In order to better understand the present invention and its advantages, examples are presented below, but the present invention is not limited to these examples. <Beispiel 1>

[0069] A fired honeycomb body (honeycomb structural element before slot formation) with circular end faces each with a diameter of 100 mm, a height (length in the flow direction of the cells) of 100 mm, a cell density of 93 cells / cm 2 , a thickness of each partition of 101.6 µm, a porosity of the partitions of 45% and a hexagonal cell shape.

[0070] A wire was inserted into the cell of the fired honeycomb body from one end face to the other, and a straight slit was formed by cutting the partition walls while moving the wire while rotating. Specifically, a group of hexagonal cells aligned in a row was defined on the end face of the fired honeycomb body, and a straight slit was formed by cutting the partition walls that intersected the straight line formed by the group of cells. The wire used was a wire electroplated with diamond abrasive grains, and the wire diameter, including the abrasive grain part, was 400 µm. The rotational speed of the wire was 50 s. -1 and the movement speed was 2 mm / s. The length of the slot to be processed was 70 mm (63 cells) and the width was 1 cell. The time required to process the slot was 30 seconds. <Beispiel 2> Reference example

[0071] A sample was prepared using the same procedure as in Example 1, except that the slot was machined with an ultrasonic tool. The time required for processing the slot was 30 seconds. <Vergleichsbeispiel 1>

[0072] A sample was prepared using the same procedure as in Example 1, except that the slot was processed with a file. The time required for processing the slot was 10 minutes. (Evaluation of processing accuracy)

[0073] Images obtained by observing the slit shapes of the end surfaces of the honeycomb structures according to Examples 1 and 2 and Comparative Example 1 were visually evaluated under a microscope.

[0074] Here, as described above, all of Examples 1 and 2 and Comparative Example 1 attempted to define a group of hexagonal cells arranged in a row on the end face of each honeycomb structure and to cut the partition walls crossing the straight line formed by groups of the cells to form a single straight slit.

[0075] The evaluation of the above pictures indicated that in Examples 1 and 2, only the partition walls crossing the straight line formed by the group of cells were cut and removed, and that the slit could be formed with good processing accuracy.

[0076] On the other hand, in Comparative Example 1, unlike each of Examples 1 and 2, regardless of the longer time required for processing the slit, a part of the partition wall on the side surface to surround the straight slit could also be cut when the partition walls crossing the straight line formed by the group of cells were cut, and the processing accuracy was worse than each of Examples 1 and 2. Description of reference symbols 10 Honeycomb structure 11 Honeycomb structure section 12 Outer peripheral wall 13a, 13b Electrode section 15, 16 frontal surface 18 cell 19 Partition wall 20 honeycomb structure element 21 slot 22 wire 23 Cutting tool 30 electrically heated carriers 33a, 33b Metal electrode A, B cell

Claims

[1] A method for producing a ceramic honeycomb structure (10), the honeycomb structure (10) comprising: an outer peripheral wall (12); and partition walls (19) arranged on an inner side of the outer peripheral wall (12), the partition walls (19) defining a plurality of cells (18), each of the cells (18) extending from one end face (15) to the other end face (16) to form a flow path, the honeycomb structure (10) comprising at least one slit (21) provided in a cross section perpendicular to an axial direction of the honeycomb structure (10), the method comprising the following steps: Preparing a honeycomb structural element (20) before forming the slot (21); and Forming the slit (21) by arranging a wire (22) in such a way that it goes from one end face (15) to the other end face (16) in the cell (18), and then cutting the partition walls (19) while moving the honeycomb structural element (20) and / or the wire (22), wherein the step of forming the slit (21) comprises the following steps: Arranging the wire (22) in such a way that it goes in a cell A from one end face (15) to the other end face (16), from the cell A at the other end face (16) to the cell B at the other end face (16) and in the cell B from the other end face (16) to the one end face (15); and simultaneously pulling end portions of the wire (22) extending from the side of one end face (15) of both cell A and cell B, and / or moving the honeycomb structural element (20) in a direction from one end face (15) to the other end face (16) to cut the partition walls (19). [2] A method of manufacturing a honeycomb structure (10) according to claim 1, wherein the step of forming the slit (21) is carried out after a dry honeycomb body has been manufactured or after a fired honeycomb body has been manufactured. [3] A method for producing a honeycomb structure (10) according to one of claims 1 or 2, wherein the honeycomb structure (10) has a plurality of slots (21). [4] A method for producing a honeycomb structure (10) according to claim 3, wherein the plurality of slits (21) are slits (21) which intersect in the cross section of the honeycomb structure (10) and / or which are divided along an extending direction of the slits (21) in the cross section of the honeycomb structure (10). [5] A method for manufacturing a honeycomb structure (10) according to any one of claims 1 to 4, wherein the method further comprises a step of forming a pair of electrode portions (13a, 13b) on an outer surface of the outer peripheral wall (12) so as to extend in a band shape in a flow path direction of the cells (18) around the central axis of the honeycomb structure (10). [6] A method of manufacturing an electrically heating support (30), the method comprising a step of electrically connecting a metal electrode (33a, 33b) to each of the pair of electrode portions (13a, 13b) of the honeycomb structure (10) manufactured by the method according to claim 5.

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