Honeycomb structure, electrically heated carrier and exhaust gas purification device

Abstract

To provide a honeycomb structure, an electrically heated carrier, and an exhaust gas purification device that have good thermal shock resistance.SOLUTION: A honeycomb structure includes a honeycomb structure part having an outer circumferential wall, and a partition wall that is arranged inside the outer circumferential wall and sectioning a plurality of cells forming a flow path extending from one end surface to the other end surface. A slit including a filler layer made of a filler is provided in the outer circumferential wall and / or the cells. The filler layer has pores, and the pores with a pore diameter of 90 μm or more account for 30% or more by volume of all pores contained in the filler layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a honeycomb structure, an electrically heated carrier, and an exhaust gas purification device. [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] A technique for forming stress-relieving slits in a honeycomb structure to prevent cracks from occurring in the EHC honeycomb structure is known. Patent Document 1 also discloses a technique for filling a filler into the stress-relieving slits in a honeycomb structure. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-174011 Summary of the Invention [Problem to be solved by the invention]

[0006] However, as a result of the inventor's investigation, it was found that if the Young's modulus of the filler filled in the slits is too high, it becomes difficult for the filler to deform at the slits for stress relief. As a result, the stress generated in areas other than the slits becomes excessively large, which may cause cracks in the EHC honeycomb structure, and it was found that there is room for improvement.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a honeycomb structure, an electrically heated carrier, and an exhaust gas purification device that have good thermal shock resistance. [Means for solving the problem]

[0008] The above problems are solved by the present invention, which is specified as follows: (1) A honeycomb structure part including 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, The outer peripheral wall and / or the cells are provided with slits including a filler layer made of a filler, The filler layer has pores, and A honeycomb structure, wherein pores having a pore diameter of 90 μm or more account for 30% by volume or more of all pores contained in the filler layer. (2) The honeycomb structure according to (1), further comprising a pair of electrode layers arranged on the outer surface of the outer wall on either side of the central axis of the honeycomb structure portion, extending in a band-like manner in the flow path direction of the cell. (3) The honeycomb structure according to (2), a metal electrode electrically connected to the electrode layer of the honeycomb structure; Electrically heated carrier with (4) The electrically heated carrier according to (3), a metallic cylindrical member for holding the electrically heated carrier; An exhaust gas purification device having the above structure. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a honeycomb structure, an electrically heated carrier, and an exhaust gas purification device having good thermal shock resistance. [Brief explanation of the drawings]

[0010] [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] 3(A) to 3(H) are schematic plan views of end faces of honeycomb structures in accordance with embodiments of the present invention, on which slits are formed. [Figure 3] 1 is a cross-sectional schematic view perpendicular to the flow path direction of a cell of an electrically heated carrier according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] (1. Honeycomb structure) 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 portion 11 and electrode layers 13a and 13b. The honeycomb structure 10 does not necessarily need to include the electrode layers 13a and 13b.

[0013] (1-1. Honeycomb structure) The honeycomb structure 11 is a columnar member and has an outer peripheral wall 12 and partition walls 19 arranged inside the outer peripheral wall 12 and defining a plurality of cells 18 that extend from one end face to the other end face and form flow paths. The columnar shape can be understood as a three-dimensional shape having a thickness in the flow path direction of the cells 18 (axial direction of the honeycomb structure 11). The ratio (aspect ratio) of the axial length of the honeycomb structure 11 to the diameter or width of the end face of the honeycomb structure 11 is arbitrary. The columnar shape may also include a shape (flat shape) in which the axial length of the honeycomb structure 11 is shorter than the diameter or width of the end face.

[0014] The outer shape of the 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 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:

[0015] The honeycomb structure part 11 is made of ceramics and has electrical conductivity. As long as the electrically conductive honeycomb structure part 11 can generate heat by Joule heat when electricity is passed through it, there is no particular limitation on the volume resistivity of the ceramics, but it is preferably 0.1 to 200 Ωcm, and more preferably 1 to 200 Ωcm. In the present invention, the volume resistivity of the honeycomb structure part 11 is a value measured at 25°C by a four-terminal method.

[0016] The material of the honeycomb structure member 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 honeycomb structure member 11 contains a silicon-silicon carbide composite or a ceramic containing silicon carbide as the main component. When the material of the honeycomb structure member 11 is said to contain a silicon-silicon carbide composite as the main component, it means that the honeycomb structure member 11 contains 90 mass% or more of the silicon-silicon carbide composite (total mass) of the entire honeycomb structure member 11. 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 honeycomb structure part 11 is said to be mainly composed of silicon carbide, it means that the honeycomb structure part 11 contains silicon carbide (total mass) in an amount of 90 mass% or more of the entire material.

[0017] When the honeycomb structure 11 contains a silicon-silicon carbide composite material, the ratio of the "mass of silicon as a binder" contained in the honeycomb structure 11 to the sum of the "mass of silicon carbide particles as aggregate" contained in the honeycomb structure 11 and the "mass of silicon as a binder" contained in the 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 flow path 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 0.1 to 0.2 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 of the cells 18 that is perpendicular to the flow path direction.

[0020] The honeycomb structure portion 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 It is preferable that 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 honeycomb structure portion 11 excluding the outer wall 12 portion.

[0021] Providing the outer peripheral wall 12 of the honeycomb structure portion 11 is useful from the viewpoint of ensuring the structural strength of the honeycomb structure portion 11 and suppressing leakage of the fluid flowing through the cells 18 from the outer peripheral wall 12. Specifically, the thickness of the outer peripheral wall 12 is preferably 0.1 mm or more, more preferably 0.15 mm or more, and even more preferably 0.2 mm or more. However, if the outer peripheral wall 12 is made too thick, it will have too high strength, which will disrupt the strength balance with the partition walls 19 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 whose thickness is to be measured is observed in a cross section perpendicular to the flow path direction of the cells.

[0022] 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.

[0023] The average pore diameter of the partition walls 19 of the 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.

[0024] (1-2. Electrode layer) A pair of electrode layers 13a, 13b are provided on the outer surface of the outer peripheral wall 12, sandwiching the central axis of the honeycomb structure section 11, so as to extend in a band shape in the flow path direction of the cells 18. Providing the pair of electrode layers 13a, 13b in this manner improves the uniform heat generation property of the honeycomb structure section 11. From the viewpoint of facilitating current spreading in the axial direction of the electrode layers 13a, 13b, it is desirable for the electrode layers 13a, 13b to extend over 80% or more of the length between both end faces of the honeycomb structure section 11, preferably over 90% or more of the length, and more preferably over the entire length.

[0025] The thickness of the electrode layers 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 layers 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 layers 13a, 13b when the measurement point is observed on a cross section perpendicular to the flow path direction of the cell 18.

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

[0027] The electrode layers 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. As the material for the electrode layers 13a and 13b, among the various metals and conductive ceramics mentioned above, a combination of a metal silicide such as tantalum silicide or chromium silicide with a composite material of metal silicon and silicon carbide is preferred because it can be fired simultaneously with the honeycomb structure portion 11, which contributes to simplifying the manufacturing process.

[0028] (1-3. Slit) The honeycomb structure 10 is provided with slits 21 including a filler layer 25 made of a filler. The slits 21 may be provided only in the outer wall 12 of the honeycomb structure 10, only in the cells 18, or in both the outer wall 12 and the cells 18. Providing slits in the cells 18 means removing a portion of the partition wall that defines the plurality of cells. The slits 21 are formed on the outer surface of the outer wall 12 of the honeycomb structure section 11 and may be slits extending in a direction parallel to the axial direction of the honeycomb structure 10, or may be slits formed in at least one end face (cells at the end face) of the honeycomb structure section 11, or may be both. Furthermore, the slits 21 may be slits that cut the honeycomb structure section 11 in a cross section parallel to the axial direction, as shown in FIG. 1 . As described above, the various slits 21 formed in the honeycomb structure 10 function to relieve stress when the honeycomb structure 10 generates heat, thereby effectively suppressing the occurrence of cracks due to differences in thermal expansion within the honeycomb structure 10.

[0029] The shape and number of the slits 21 on the end face of the honeycomb structure 10 are not particularly limited and can be designed as appropriate. For example, the number of slits 21 on the end face of the honeycomb structure 10 may be one or two or more, and they may be formed so as not to intersect with each other, or so as to intersect at least partially. The length and width of the slits 21 on the end face of the honeycomb structure 10 are not particularly limited. The width of the slits 21 on the end face of the honeycomb structure 10 may be approximately the same as the width of the cells 18, or may be smaller or larger than the width of the cells 18. The length of each slit 21 on the end face of the honeycomb structure 10 is not particularly limited, but may be 2 to 80 cells. The width of each slit 21 is not particularly limited, but may be 1 to 5 cells. The length and width of each slit 21 on the end face of the honeycomb structure 10 can be designed as appropriate depending on the size, material, application, and number of slits 21 of the honeycomb structure 10.

[0030] The slits 21 may be divided along the extension direction of the slits 21 at the end face of the honeycomb structure 10. In this case, the slits 21 may be divided into slits of approximately the same length or into slits of different lengths at the end face of the honeycomb structure 10. By dividing the slits 21 at the end face of the honeycomb structure 10, it is possible to better control the occurrence of cracks in the honeycomb structure 10. The number of divisions of the slits 21 is not particularly limited, and the slits 21 may be divided into two, three, four or more. Furthermore, a plurality of slits may be provided by mixing divided slits and undivided slits.

[0031] FIG. 1 schematically shows a configuration in which there is one slit 21 on the end face of the honeycomb structure 10. As shown in FIG. 1, the slit 21 may extend so as to pass through the center of the end face of the honeycomb structure 10, or it may not pass through the center. Specific examples of configurations in which a plurality of slits 21 are formed are shown in FIGS. 2(A) to 2(H). Note that FIGS. 2(A) to 2(H) only schematically show the outer diameter of one end face of the honeycomb structure 10 and the shape of the slit 21. Note that each of these configurations shows the configuration on one end face of the honeycomb structure 10, and these slits 21 may be formed only on one end face of the honeycomb structure 10, or may be formed so as to extend axially through to the other end face of the honeycomb structure 10 while maintaining the same shape in the cross section of the honeycomb structure 10.

[0032] 2(A), the slits 21 may be three sets of slits (six slits in total) formed on the end face of the honeycomb structure 10 so as to extend from the outer wall into the partition wall by several cells, and arranged opposite each other across the center of the end face of the honeycomb structure 10. Alternatively, as shown in FIG. 2(B), the end face of the honeycomb structure 10 may be three slits that intersect at the center and extend to the outer walls on both sides.

[0033] As shown in Fig. 2(C), the slits 21 may be formed such that the three slits shown in Fig. 2(B) do not reach the inner peripheral end of the outer peripheral wall at the end face of the honeycomb structure 10. Alternatively, as shown in Fig. 2(D), the three slits shown in Fig. 2(B) may be divided along the extension direction.

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

[0035] As shown in Fig. 2(G), the slits 21 may be three slits on the end face of the honeycomb structure 10, forming a substantially triangle with no vertices intersecting, or as shown in Fig. 2(H), four slits may be four slits, forming a substantially quadrangle with no vertices intersecting.

[0036] (1-4. Filler layer) The slits 21 include a filler layer 25. The entire interior of one slit 21 may be filled with the filler layer 25, or a portion of the interior of the slit 21 may be filled with the filler layer 25. From the viewpoint of the thermal shock resistance of the honeycomb structure 10, it is more preferable that the entire interior of the slit 21 is filled with the filler layer 25.

[0037] When a plurality of slits 21 are provided, all of the slits 21 may include the filler layer 25, or only some of the slits 21 may include the filler layer 25. From the viewpoint of the thermal shock resistance of the honeycomb structure 10, it is more preferable to provide the filler layer 25 in all of the slits 21.

[0038] The filler layer 25 may be included in a portion of the slit 21 in such a manner that the filler layer 25 fills the slit 21 from one end face to a predetermined depth, or in such a manner that the filler layer 25 is provided with a predetermined thickness along the inner wall of the slit 21 from one end face to the other end face. When the filler layer 25 is provided with a predetermined thickness along the inner wall of the slit 21, the thickness of the filler layer 25 can be adjusted appropriately depending on the width of the slit 21, and may be, for example, 500 to 5000 μm, or may be 1 to 5 cells wide. When the filler layer 25 is provided from one end face to the other end face of the slit 21, the filler layer 25 also functions as a gas sealant that suppresses gas leakage from the slit 21.

[0039] The filler layer 25 is composed of a filler. When the main component of the honeycomb structure portion 11 is silicon carbide or a silicon carbide-metal silicon composite, the filler constituting the filler layer 25 preferably contains 20 mass % or more of silicon carbide, more preferably 20 to 70 mass %. This allows the thermal expansion coefficient of the filler to be close to that of the honeycomb structure portion 11, thereby improving the thermal shock resistance of the honeycomb structure 10. The filler may contain 30 mass % or more of silica, alumina, etc. As the filler constituting the filler layer 25, multiple types of fillers may be used in combination. For example, different types of fillers may be used depending on the location within one slit 21, or different types may be used between multiple slits 21.

[0040] The volume resistivity of the filler is preferably 100 to 100,000% of the volume resistivity of the honeycomb structure section 11. The volume resistivity of the filler is more preferably 200 to 100,000% of the volume resistivity of the honeycomb structure section 11, and particularly preferably 300 to 100,000%. When the volume resistivity of the filler is 100% or more of the volume resistivity of the honeycomb structure section 11, it becomes difficult for current to flow through the filler, making it easier to pass current uniformly through the honeycomb structure section 11. There is no particular problem even if the volume resistivity of the filler is high. The filler may be an insulator. In practice, the upper limit of the volume resistivity of the filler is approximately 100,000% of the volume resistivity of the honeycomb structure section 11.

[0041] The filler layer 25 has pores. The pore diameter of the pores contained in the filler layer 25 is not particularly limited, but may be 1 to 500 μm. Among the pores contained in the filler layer 25, pores with a pore diameter of 90 μm or more account for 30% by volume or more of the total pores contained in the filler layer 25. With this configuration, the volume ratio of large pores with a pore diameter of 90 μm or more is high among the pores contained in the filler layer 25, making it easier for cracks to occur in the filler layer 25 when stress is generated in the honeycomb structure 10. In this way, by actively generating cracks by providing large pores in the filler layer 25, the Young's modulus of the filler layer 25 is optimized, the thermal stress generated near the slits 21 during EHC heating can be reduced, and the thermal shock resistance of the honeycomb structure 10 can be improved. It is more preferable that the pores with a pore diameter of 90 μm or more account for 40% by volume or more of the total pores contained in the filler layer 25. It is even more preferable that pores having a pore diameter of 90 μm or more account for 50% by volume or more of all pores contained in the filler layer 25. Furthermore, if there are no small pores less than 90 μm, cracks in the filler layer 25 do not easily propagate. Therefore, it is more preferable that pores having a pore diameter of 90 μm or more account for 90% by volume or less of all pores contained in the filler layer 25.

[0042] The pore diameter (μm) of the pores contained in the filler layer 25 and the volume fraction (volume %) of the pores having a predetermined pore diameter relative to all pores contained in the filler layer 25 can be measured by cross-sectional observation using an SEM. Specifically, a sample is first cut out from a honeycomb structure having slits including a filler layer to observe the cross section of the filler layer 25, and the cross section is observed. If necessary, the irregularities in the cross section of the filler layer 25 are filled with resin, and the filler layer 25 is polished and the polished surface (cross section) is observed. The cross-sectional area of ​​each pore is calculated by image analysis of an SEM image at 100x magnification obtained by observing a 0.5 mm × 1 mm area (unit area). Then, assuming the pores to be spheres, the volume of each pore is estimated from the circle-equivalent diameter of the cross section of the pore contained in the unit area. The estimated volume of each pore is used to calculate the volume fraction (volume %) of the pores having a predetermined pore diameter relative to all pores contained in the filler layer 25 within the unit area. This unit area is observed at four points, and the volume fraction of pores having the specified pore diameter is calculated using the same method.The average value of the four points is used as the volume fraction (volume %) of pores having the specified pore diameter relative to all pores contained in the filler layer 25.

[0043] The porosity of the filler layer 25 is preferably 20 to 90%. When the porosity of the filler layer 25 is 90% or less, the strength of the filler layer 25 is sufficiently maintained, and it is possible to prevent the filler layer 25 from collapsing and losing its gas leakage suppression function. When the porosity of the filler layer 25 is 20% or more, the Young's modulus of the filler layer 25 is not too high, and the stress relaxation function of the slits is sufficiently maintained. The porosity of the filler layer 25 is more preferably 30 to 85%, and even more preferably 45 to 75%. Here, even if the porosity of the filler layer 25 is the same, as described above, the pore diameter (μm) of the pores contained in the filler layer 25 and the volume ratio (volume %) of pores having a given pore diameter to all pores contained in the filler layer 25 are not necessarily the same. In the present invention, the porosity of the filler layer 25 is not simply controlled, but the pores contained in the filler layer 25 with a pore diameter of 90 μm or more are controlled to be 30 volume % or more of the total pores contained in the filler layer 25. In this way, when the EHC generates heat and thermal stress occurs around the slits, the pores with a pore diameter of 90 μm or more scattered within the filler layer 25 are dispersed like perforations, causing cracks to occur preferentially in the filler layer 25, thereby providing a stress buffering function.

[0044] In the filler layer 25, the pore size D50 in the volume-based cumulative distribution is preferably 80 to 500 μm. If the pore size D50 in the filler layer 25 is 80 μm or more, when the EHC generates heat and thermal stress occurs around the slits, the pores with a pore size of 80 μm or more scattered throughout the filler layer 25 are dispersed like perforations, causing cracks to occur preferentially in the filler layer 25, thereby providing a stress buffering function. If the pore size D50 in the filler layer 25 is 500 μm or less, the filler layer 25 is less likely to collapse even after cracks occur in the filler layer 25, and the gas leakage suppression effect is maintained. The pore size D50 in the filler layer 25 is more preferably 80 to 300 μm, and even more preferably 80 to 200 μm. The pore size D50 in the volume-based cumulative distribution in the filler layer 25 can be measured by cross-sectional observation using an SEM. Specifically, a sample is first cut out from a honeycomb structure having slits including a filler layer to observe the cross section of the filler layer 25, and the cross section is observed. If necessary, the irregularities in the cross section of the filler layer 25 are filled with resin, and the filler layer 25 is polished and the polished surface (cross section) is observed. The cross-sectional area of ​​each pore is calculated by image analysis of an SEM image at 100x magnification obtained by observing four areas of 0.5 mm x 1 mm. The circle-equivalent diameter calculated from the cross-sectional area is then used as the pore diameter, and D50 is calculated from each pore diameter.

[0045] The Young's modulus of the filler layer 25 is preferably 10 to 1000 MPa. When the Young's modulus of the filler layer 25 is 10 MPa or more, the honeycomb structure 10 has good mechanical strength. When the Young's modulus of the filler layer 25 is 1000 MPa or less, the honeycomb structure 10 has better thermal shock resistance. The Young's modulus of the filler layer 25 is more preferably 20 to 500 MPa, even more preferably 50 to 200 MPa, and particularly preferably 70 to 200 MPa. As described in Japanese Patent No. 6259327, the Young's modulus of the filler layer 25 can be calculated from the stress and strain when a stress of 20 to 50% is applied in a four-point bending strength measurement.

[0046] The honeycomb structure part 11 preferably has a Young's modulus of 1 to 100 GPa. When the honeycomb structure part 11 has a Young's modulus of 1 GPa or more, the honeycomb structure 10 has good mechanical strength. When the honeycomb structure part 11 has a Young's modulus of 100 GPa or less, the honeycomb structure 10 has better thermal shock resistance. The honeycomb structure part 11 more preferably has a Young's modulus of 2 to 50 GPa, and even more preferably has a Young's modulus of 5 to 20 GPa. The Young's modulus of the honeycomb structure part 11 can be calculated from the stress and strain when a stress of 20 to 50% is applied in a four-point bending strength measurement.

[0047] (2. Electrically heated carrier) 3 is a schematic cross-sectional view perpendicular to the flow 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 layers 13a and 13b of the honeycomb structure 10.

[0048] (2-1. Metal electrode) The metal electrodes 33a and 33b are provided on the electrode layers 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 honeycomb structure section 11. When a voltage is applied via the electrode layers 13a and 13b, the metal electrodes 33a and 33b are energized and can generate Joule heat in the honeycomb structure section 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 64 to 600 V, but the applied voltage can be changed as appropriate.

[0049] 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.

[0050] 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. x Examples 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.

[0051] (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 of producing a honeycomb formed body, a drying step of producing a dried honeycomb body, and a firing step of producing a fired honeycomb body.

[0052] (molding process) In the molding process, first, a molding raw material containing a conductive ceramic raw material is prepared. The molding raw material is produced by adding metal silicon powder (metal silicon), a binder, a surfactant, a pore-forming agent, 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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 size D50 in the volume-based cumulative distribution of the pore-forming material is preferably 10 to 30 μm. When the pore-forming material is a water-absorbent resin, the average particle size of the pore-forming material refers to the average particle size after water absorption.

[0057] 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.

[0058] (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.

[0059] Next, slits are formed in the outer peripheral wall and / or partition wall of the dried honeycomb body. The slits can be formed using a cutting tool or the like in accordance with a general slit forming method. The slits do not have to be formed in the dried honeycomb body, and as described below, the dried honeycomb body may be fired to produce a fired honeycomb body, and then the slits may be formed in the fired honeycomb body. The shape, number, intersection number, length, width, etc. of the slits can be appropriately designed depending on the desired properties of the honeycomb structure to be produced.

[0060] (Firing process) Next, the dried honeycomb body with the slits formed therein is fired to produce a fired honeycomb body. Firing conditions are preferably such that the honeycomb body is heated in an inert atmosphere such as nitrogen or argon at 1400 to 1500°C for 1 to 20 hours. After firing, in order to improve durability, it is preferable to perform oxidation treatment at 1200 to 1350°C for 1 to 10 hours. The degreasing and firing methods are not particularly limited, and firing can be performed using an electric furnace, a gas furnace, or the like.

[0061] (filling process) Next, the filler raw material is filled into the slits of the dried honeycomb body or the fired honeycomb body and dried to form a filler layer. The filler can be filled by a known method, such as pressing with a spatula. The filler raw material is prepared by adding a binding material (metallic silicon, etc.), a binder, a surfactant, a pore-forming material, water, etc. to an aggregate (silicon carbide, etc.). The pore-forming material used in the filler raw 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 0.1 to 20 parts by mass, more preferably 1 to 15 parts by mass, when the total mass of the aggregate and binder is 100 parts by mass. The average particle size of the pore-forming material is preferably 3 to 150 μm. The average particle size D50 in the volume-based cumulative distribution of the pore-forming material is preferably 50 to 200 μm. When the pore-forming material is a water-absorbent resin, the average particle size of the pore-forming material refers to the average particle size after water absorption. The pore-forming material may be a combination of two or more types of pore-forming material, a relatively small pore-forming material with an average particle size of 3 to 90 μm and a relatively large pore-forming material with an average particle size of more than 90 μm. The average particle size of the relatively large pore-forming material is more preferably 100 μm or more. The compounding ratio (parts by mass) of the small pore-forming material to the large pore-forming material is preferably 1.5:8.5 to 7:3. From the viewpoint of workability when filling the filler raw material into the slits, the viscosity of the filler raw material is preferably 1 to 100 Pa·s.

[0062] Next, the dried honeycomb body or fired honeycomb body with the filler material provided in the slits is heated to produce a dried honeycomb body or fired honeycomb body (honeycomb structure) having slits with a filler material layer provided therein. Heating conditions are preferably 400 to 700°C for 10 to 60 minutes. The heating (heat treatment) is performed to strengthen the chemical bonds of the filler material. The heating method is not particularly limited, and firing can be performed using an electric furnace, gas furnace, or the like.

[0063] In addition, a method for manufacturing a honeycomb structure having an electrode layer includes first applying an electrode layer 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 layers extending in a band-like shape in the flow path direction of the cells on the outer surface of the peripheral wall, sandwiching the central axis of the dried honeycomb body, to produce a dried honeycomb body with unfired electrode layers. Next, the dried honeycomb body with unfired electrode layers is fired to produce a fired honeycomb body having a pair of electrode layers. This results in a honeycomb structure with electrode layers. Note that the electrode layers may be formed after the fired honeycomb body is produced. Specifically, a fired honeycomb body may be first produced, a pair of unfired electrode layers may be formed on the fired honeycomb body, and the fired honeycomb body may be fired to produce a fired honeycomb body having a pair of electrode layers.

[0064] The electrode layer forming raw material can be formed by adding various additives appropriately to raw material powders (metal powders and / or ceramic powders, etc.) blended according to the required properties of the electrode layer, and kneading the mixture.

[0065] The method of preparing the electrode layer forming raw material and the method of applying the electrode layer 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 layer a lower electrical resistivity than the honeycomb structure part, the metal content can be made higher than that of the honeycomb structure part, or the particle diameter of the metal particles can be made smaller.

[0066] Before firing the dried honeycomb body with the unfired electrode layers, degreasing may be carried out to remove binders, etc. The degreasing step is as described above.

[0067] (Firing process) Next, the dried honeycomb body with the unfired electrode layers is fired to produce a fired honeycomb body. The firing conditions are preferably heating at 1400 to 1500°C for 1 to 20 hours in an inert atmosphere such as nitrogen or argon. Prior to the firing, degreasing may be performed to remove binders and the like. The degreasing step is performed at 400 to 500°C in an air atmosphere, an inert atmosphere, or a reduced pressure atmosphere. After firing, oxidation treatment is preferably performed at 1200 to 1350°C for 1 to 10 hours to improve durability. The firing method is not particularly limited, and firing can be performed using an electric furnace, a gas furnace, or the like. This provides the honeycomb structure 10 according to the embodiment of the present invention.

[0068] (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, metal electrodes are fixed and electrically connected to the electrode layer of the honeycomb structure 10. Examples of the fixing method include conventionally known methods such as laser welding, thermal spraying, and ultrasonic welding. More specifically, a pair of metal electrodes is provided on the outer surface of the electrode layer, sandwiching the central axis of the honeycomb structure part of the honeycomb structure 10. In this manner, the electrically heated carrier 30 according to the present invention is obtained.

[0069] (5. Exhaust gas purification device) The electrically heated carrier 30 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 the electrically heated carrier 30 and a metal tubular member for holding the electrically heated carrier 30. In the exhaust gas purification device, the electrically heated carrier 30 is installed midway through an exhaust gas flow path for carrying exhaust gas from an engine. In the exhaust gas purification device, when slits and fillers are provided on the end faces of the honeycomb structure section 11, the end faces are preferably provided upstream of the exhaust gas flow. With this configuration, the slits of the honeycomb structure are formed on the end faces through which higher-temperature exhaust gas passes, thereby effectively mitigating thermal shock and more effectively suppressing crack generation. [Example]

[0070] 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.

[0071] 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 a cylindrical clay. The binder content was 7 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 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.

[0072] (2. Preparation of dried honeycomb body) The obtained cylindrical clay was molded using an extruder with a checkerboard die structure to obtain a cylindrical honeycomb molded body in which each cell shape in the cross section perpendicular to the cell flow direction is hexagonal. This honeycomb molded body was dried by high-frequency dielectric heating and then dried in a hot air dryer at 120°C for 2 hours to produce a dried honeycomb body. Next, the partition walls were removed from the honeycomb dried body to form slits as shown in FIG.

[0073] (3. Preparation and Application of Electrode Layer Forming Paste) An electrode layer forming paste was prepared by mixing metal 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 metal 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 by laser diffraction. Next, this electrode layer forming paste was applied to the dried honeycomb body in an appropriate area and film thickness using a curved surface printing machine.

[0074] (4. Filling and firing of filler) Next, the filler raw material was prepared as follows. First, silicon carbide powder and silica powder (colloidal silica) were mixed in a mass ratio of 68:32 in terms of solid content. Here, the mass of silica is the mass converted to oxide (SiO2). To this, carboxymethyl cellulose as a binder, pore formers with an average particle size of 50 μm and pore formers with an average particle size of 150 μm, glycerin as a moisturizing agent, and water were added and mixed to obtain a mixture. Next, this mixture was kneaded to obtain a filler-forming raw material. The content of the binder was 1.0 part by mass when the total solid content of the silicon carbide powder and silica powder was 100 parts by mass. The content of the pore former with an average particle size of 50 μm was 7 parts by mass when the total solid content of the silicon carbide powder and silica powder was 100 parts by mass. The content of the pore-forming material with an average particle size of 150 μm was 3 parts by mass when the total solid content of the silicon carbide powder and silica powder was 100 parts by mass. The D50 of the pore-forming material on a volume basis was 80 μm. The content of glycerin was 4 parts by mass when the total solid content of the silicon carbide powder and silica powder was 100 parts by mass. The content of water was 30 parts by mass when the total solid content of the silicon carbide powder and silica powder was 100 parts by mass. The average particle size of the silicon carbide powder was 8 μm. This average particle size was measured by laser diffraction. This filler-forming raw material was filled into the slits of the dried honeycomb body using a spatula. After further drying in a hot air dryer at 120°C for 30 minutes, the honeycomb dried body was fired together with the honeycomb dried body in an Ar atmosphere at 1400°C for 3 hours to obtain a columnar honeycomb structure with a filler layer provided in the slits.

[0075] The honeycomb structure had a circular end face with a diameter of 100 mm and a height (length of the cells in the flow path direction) of 100 mm. The cell density was 93 cells / cm. 2 The thickness of the partition walls was 101.6 μm, the porosity of the partition walls was 45%, and the average pore diameter of the partition walls was 8.6 μm. The thickness of the electrode layer was 0.3 mm. The Young's modulus of the honeycomb structure portion was 5 GPa.

[0076] The proportion of pore volume with a pore diameter of 90 μm or more to the total pore volume in the filler layer, Young's modulus, porosity, volumetric pore diameter D50, and the content of each pore-forming material with an average particle diameter of 50 μm and an average particle diameter of 150 μm in the honeycomb structure of Example 1 are shown in Table 1. The pore-forming material content indicates the mass ratio (parts by mass) of the pore-forming material when the total of the silicon carbide powder and silica powder contained in the filler layer is taken as 100 parts by mass.

[0077] The obtained honeycomb structure was subjected to a "thermal shock resistance test" by the method described below. The table shows the results of the "thermal shock resistance test", namely, "temperature at which vertical cracks occur" and "temperature at which end cracks occur".

[0078] [Thermal shock resistance test (burner test)] A heating and cooling test of the honeycomb structure was conducted using a propane gas burner tester equipped with a metal case for housing the honeycomb structure and a propane gas burner capable of supplying heated gas into the metal case. The heated gas was combustion gas generated by burning propane gas with a gas burner (propane gas burner). The thermal shock resistance of the honeycomb structure was evaluated by checking whether cracks occurred in the honeycomb structure through the heating and cooling test. Specifically, the honeycomb structure was first housed (canned) in the metal case of the propane gas burner tester. Gas (combustion gas) heated by the propane gas burner was then supplied into the metal case and passed through the honeycomb structure. The temperature conditions (inlet gas temperature conditions) of the heated gas flowing into the metal case were as follows: The temperature was first raised to a designated temperature in 5 minutes, held at the designated temperature for 10 minutes, then cooled to 100°C in 5 minutes, and held at 100°C for 10 minutes. This series of heating, cooling, and holding operations is called the "heating and cooling operation." After that, the honeycomb structure was checked for cracks. The designated temperature was then increased in 25°C increments from 825°C, and the above "heating and cooling operation" was repeated. The designated temperature was increased in 25°C increments until cracks appeared in the sample. As the designated temperature increased, the temperature rise rate became steeper, and the temperature rise at the periphery was delayed compared to the center, which widened the temperature difference between the center and periphery and increased the stress generated. A honeycomb structure that did not develop cracks up to the designated temperature of 850°C was deemed to have a good thermal shock resistance test. In other words, if no cracks developed at the designated temperature of 850°C, it was deemed acceptable even if cracks developed at a higher designated temperature. However, if cracks developed below the designated temperature of 850°C, the thermal shock resistance effect of the present invention was deemed not to have been achieved. In this thermal shock resistance test, the occurrence of the following two types of cracks was confirmed. The first type of crack is called a "vertical crack," and the second type of crack is called an "end crack." A "vertical crack" is a crack that develops on the side of the honeycomb structure in the direction from the first end face to the second end face of the honeycomb structure. An "end crack" is a crack that develops on the end face of the honeycomb structure. The "vertical crack development temperature" column in Table 1 indicates the temperature at which the above-mentioned vertical crack development was confirmed. The "end crack development temperature" column in Table 3 indicates the temperature at which the above-mentioned end crack development was confirmed.

[0079] <Examples 2 to 12, Comparative Examples 1 and 2> A honeycomb structure was produced in the same manner as in Example 1, except that the conditions of the filler were changed as shown in Table 1. A "thermal shock resistance test" was carried out in the same manner as in Example 1. Table 1 shows the results of the "thermal shock resistance test," including the "temperature at which vertical cracks occur" and the "temperature at which end cracks occur."

[0080] [Table 1]

[0081] (Evaluation results) As shown in Table 1, the honeycomb structures of Examples 1 to 12 had both a "vertical crack initiation temperature" and an "end face crack initiation temperature" of 850°C or higher, and were therefore excellent in thermal shock resistance. On the other hand, the honeycomb structures of Comparative Examples 1 and 2 had at least one of a "vertical crack initiation temperature" and an "end face crack initiation temperature" of less than 850°C, and were therefore poor in thermal shock resistance. From the above results, it was found that the occurrence of cracks at high temperatures can be suppressed by having pores in the filler layer filled in the slits of the honeycomb structure, and by making the pores with a pore diameter of 90 μm or more 30% by volume or more of the total pores contained in the filler layer. [Explanation of symbols]

[0082] 10 Honeycomb structure 11 Honeycomb structure 12 Peripheral wall 13a, 13b electrode layer 18 cells 19 Bulkhead 21 Slit 25 Filler layer 30 Electrically heated carrier 33a, 33b metal electrode

Claims

1. a honeycomb structure 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; The outer peripheral wall and / or the cells are provided with slits including a filler layer made of a filler, The filler layer has pores, and A honeycomb structure, wherein pores having a pore diameter of 90 to 500 μm account for 30 to 85% by volume of all pores contained in the filler layer.

2. 2. The honeycomb structure according to claim 1, wherein the filler layer has a pore size D50 in a cumulative distribution on a volume basis of 80 to 500 μm.

3. 3. The honeycomb structure according to claim 1, wherein the filler layer has a Young's modulus of 10 to 1000 MPa.

4. The honeycomb structure according to any one of claims 1 to 3, wherein the honeycomb structure portion has a Young's modulus of 1 to 100 GPa.

5. The honeycomb structure according to any one of claims 1 to 4, wherein the slits are formed in the outer wall of the honeycomb structure portion and extend in a direction parallel to the axial direction of the honeycomb structure, and / or are slits formed in at least one end face of the honeycomb structure portion.

6. The honeycomb structure according to any one of claims 1 to 5, further comprising a pair of electrode layers provided on the outer surface of the outer wall, on either side of the central axis of the honeycomb structure portion, so as to extend in a band-like manner in the flow path direction of the cell.

7. The honeycomb structure according to claim 6, a metal electrode electrically connected to the electrode layer of the honeycomb structure; Electrically heated carrier with

8. An electrically heated carrier according to claim 7; a metallic cylindrical member for holding the electrically heated carrier; An exhaust gas purification device having the above structure.

Images