JP2015016465A - Honeycomb structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb structure in which a ring crack hardly occurs.SOLUTION: A honeycomb structure 100 includes a honeycomb substrate 4, and a projection 10 which is a ring-shaped projection continuously or intermittently surrounding at least a part of the outer periphery of the honeycomb substrate 4 in a ring shape. A part of the surface of the projection 10 forms a flat surface part 15 which is a flat surface parallel to an extending direction of cells 2. The flat surface part 15 has in its surface one or a plurality of stress relieving parts 17, each of which is a split having an opening part, and the total length of all the stress relieving parts 17 is 3% or more of the length of the outer periphery of the honeycomb substrate 4.

Description

  The present invention relates to a honeycomb structure. More specifically, the present invention relates to a honeycomb structure in which ring cracks are unlikely to occur.

Conventionally, an exhaust gas purification system including a diesel particulate filter (DPF) and a catalyst body is mounted on an exhaust gas exhaust system. The DPF is a filter for collecting particulate matter (PM) mainly composed of soot. The catalyst body purifies harmful substances such as carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NO _x ) contained in the exhaust gas. A honeycomb structure is used as a catalyst carrier or DPF constituting the catalyst body.

  One of the causes of the failure of the exhaust gas purification apparatus is that a ring-shaped crack is generated in the honeycomb structure. Such a crack generated in the honeycomb structure is referred to as a “ring crack”. As shown in FIG. 7, the ring crack is a crack (ring crack 50) formed in the honeycomb structure 200 so as to be substantially orthogonal to the extending direction of the cells 2. The ring crack 50 is formed so as to extend in the outer peripheral direction on the outer periphery of the honeycomb structure. FIG. 7 is a perspective view schematically showing a state in which a ring crack has occurred in a conventional honeycomb structure.

  The ring crack is generally caused by a tensile stress generated in the full length direction (cell extending direction) of the honeycomb structure. The tensile stress is a stress generated by a difference between the thermal expansion coefficient of the ceramics constituting the honeycomb structure and the thermal expansion coefficient of the metal can body that houses the honeycomb structure. This tensile stress is generated when the honeycomb structure is placed in an environment where heating and cooling are repeated. This tensile stress is a ratio of the length (total length (A)) in the cell extending direction of the honeycomb structure to the diameter (outer diameter (B)) in the cross section perpendicular to the cell extending direction of the honeycomb structure (A / B) tends to increase as it increases. Therefore, ring cracks are more likely to occur as A / B increases. Here, the total length (A) is the “length in the cell extending direction” of the honeycomb structure. The outer diameter (B) is the diameter of the “cross section perpendicular to the cell extending direction” of the honeycomb structure.

  Therefore, as a method of suppressing the occurrence of ring cracks, a method of reducing A / B by increasing the outer diameter is known. A honeycomb structure having A / B in a predetermined range has been proposed (see, for example, Patent Document 1).

JP-A-9-299811

  However, the manufacturing difficulty of the honeycomb structure increases as the outer diameter increases. Further, when used as a catalyst carrier, the larger the outer diameter, the greater the amount of noble metal supported. Further, when the outer diameter of the honeycomb structure is increased, the entire exhaust gas purification device is increased in size. When the honeycomb structure is mounted on an automobile, the mounting space is a limited space in the immediate vicinity of the engine, the lower surface of the vehicle body, and the like, so there is a limit to increasing the outer diameter of the honeycomb structure.

  The present invention has been made in view of the above-described problems. The present invention provides a honeycomb structure in which ring cracks are unlikely to occur.

  The present invention is a honeycomb structure shown below.

[1] A honeycomb base material having a porous partition wall for defining a plurality of cells serving as fluid flow paths extending from a first end surface as one end surface to a second end surface as the other end surface, and the honeycomb base material And a convex portion surrounding at least a part of the outer periphery of the honeycomb substrate continuously or intermittently in a ring shape, the convex portion protruding outward from the outer periphery of the honeycomb substrate, and a part of the outer periphery of the honeycomb substrate The shape of at least one end of the convex portion is a tapered shape having a tapered surface that is a surface inclined to the joint portion with the outer periphery, and is a cross section orthogonal to the cell extending direction. The maximum thickness of the convex portion is 1 to 20 mm, and in the cross section parallel to the cell extending direction, the width of the convex portion is 1% or more of the total length of the honeycomb substrate, and the taper Plane and said An inclination angle, which is an angle formed with the direction in which the cell extends, is 80 degrees or less, a part of the surface of the convex part is a flat part parallel to the extending direction of the cell, and the flat part is A honeycomb structure having one or a plurality of stress relaxation portions, which are slits having openings on the surface, and the total length of all the stress relaxation portions is 3% or more of the outer peripheral length of the honeycomb substrate .

[2] The honeycomb structure according to [1], wherein a total length of all the stress relaxation portions is 10% or more of an outer peripheral length of the honeycomb base material.

[3] The total length of the stress relaxation portions having a width of the opening of 10 μm or more is 50% or more of the total length of all the stress relaxation portions. [1] or [2] Honeycomb structure.

[4] In the cross section parallel to the cell extending direction, the width of the convex portion is 1 to 80% of the total length of the honeycomb substrate, and the inclination angle is 10 to 80 degrees. ] The honeycomb structure according to any one of [3].

[5] The honeycomb according to any one of [1] to [4], wherein the honeycomb substrate is made of at least one selected from the group consisting of cordierite, silicon carbide, mullite, aluminum titanate, and alumina. Structure.

[6] The opening on the first end face side of the first cell that is a predetermined cell of the plurality of cells and the second end face side of the second cell that is a remaining cell of the plurality of cells. The honeycomb structure according to any one of [1] to [5], further including a plugged portion that plugs the opening.

  Since the honeycomb structure of the present invention includes the above-mentioned “convex portion”, ring cracks are unlikely to occur. In addition, the honeycomb structure of the present invention is less likely to cause defects such as chipping even when the “convex portion” receives an external force during conveyance or the like. Furthermore, since the honeycomb structure of the present invention has the “stress relaxation portion”, it has excellent thermal shock resistance.

1 is a perspective view schematically showing a honeycomb structure according to an embodiment of the present invention. It is a schematic diagram showing a cross section parallel to the cell extending direction of the honeycomb structure of one embodiment of the present invention. FIG. 2 is a plan view of the honeycomb structure shown in FIG. 1 as viewed from the first end face side. FIG. 2 is a plan view schematically showing a state in which a plurality of honeycomb structures shown in FIG. 1 are stored in an existing packing container. It is a perspective view which shows typically other embodiment of the honeycomb structure of this invention. FIG. 6 is a schematic diagram showing a cross section parallel to the cell extending direction of a honeycomb structure of still another embodiment of the present invention. It is a perspective view which shows typically the state in which the ring crack produced in the conventional honeycomb structure.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the present invention.

(1) Honeycomb structure:
As shown in FIGS. 1 to 3, a honeycomb structure 100 a according to an embodiment of the present invention includes a honeycomb substrate 4 and a convex portion 10. The honeycomb substrate 4 has a porous partition wall 1 that partitions and forms a plurality of cells 2 that serve as fluid flow paths extending from a first end surface 3 that is one end surface to a second end surface 5 that is the other end surface. The convex portion 10 is a convex portion that surrounds at least a part of the outer periphery of the honeycomb substrate 4 continuously or intermittently in a ring shape. Further, the convex portion 10 protrudes outward from the outer periphery of the honeycomb substrate 4 and is disposed so as to cover a part of the outer periphery of the honeycomb substrate 4. The shape of at least one end of the convex portion 10 is a tapered shape having a tapered surface 11 that is a surface inclined to the joint portion 13 with the outer periphery. In the cross section orthogonal to the cell extending direction (hereinafter simply referred to as “Z direction”), the “maximum thickness (H) of the convex portion 10” is 1 to 20 mm. In the cross section parallel to the Z direction, the “width L of the convex portion 10” is 1% or more of the total length of the honeycomb substrate 4, and the “inclination angle” that is an angle between the tapered surface 11 and the Z direction is 80. Less than or equal to degrees. A part of the surface of the convex portion 10 is a plane portion 15 that is a plane parallel to the Z direction. The flat surface portion 15 has one or a plurality of stress relaxation portions 17 that are tears having openings 18 on the surface. The total length of all the stress relaxation portions 17 is 3% or more of the outer peripheral length of the honeycomb substrate 4. FIG. 1 is a perspective view schematically showing a honeycomb structure 100a according to an embodiment of the present invention. Fig. 2 is a schematic diagram showing a cross section parallel to the Z direction of the honeycomb structure 100a of one embodiment of the present invention. Fig. 3 is a plan view of the honeycomb structure 100a according to the embodiment of the present invention as viewed from the first end face side.

  Here, the “tapered shape” is a shape in which the outer diameter of the ring shape becomes thinner toward the tip. Further, “the maximum thickness (H) of the convex portion” is “a honeycomb substrate disposed so as to be in contact with the outer periphery of the convex portion (except for the tapered portion) in the cross section parallel to the Z direction of the honeycomb structure. It can also be said to be “the distance between the line parallel to the outer periphery” and “the outer periphery of the honeycomb substrate”. Further, when the outer peripheral coat layer is disposed on the outer peripheral surface of the honeycomb substrate 4, the “maximum thickness (H) of the convex portion” is the outer peripheral coat layer as shown in FIGS. 2 and 3. It is the thickness from the surface.

  The convex portions 10 are disposed so as to “project outward from the outer periphery of the honeycomb substrate 4 and cover a part of the outer periphery of the honeycomb substrate 4”. That is, the outer diameter of a part of the honeycomb structure 100a is increased. Therefore, the honeycomb structure 100a has improved durability against tensile stress. As a result, the honeycomb structure 100a is less susceptible to ring cracks even when tensile stress is generated.

  Furthermore, in the honeycomb structure 100a, the convex portion 10 has a “ring shape surrounding at least a part of the outer periphery of the honeycomb substrate 4 continuously or intermittently”. Therefore, the honeycomb structure 100a has improved durability against tensile stress. The reason is that the tensile stress is evenly applied by “surrounding at least a part of the outer periphery of the honeycomb substrate 4 continuously or intermittently”. Therefore, the honeycomb structure 100a is unlikely to generate ring cracks even when tensile stress is generated.

  In this specification, “the outer peripheral length of the honeycomb substrate 4” means the outer peripheral length of the honeycomb substrate 4 in a cross section perpendicular to the Z direction.

  The “stress relaxation portion 17” is a tear having an opening (opening of the stress relaxation portion) 18 on the surface of the flat portion 15 of the convex portion 10. When the stress relaxation part 17 exists in the plane part 15 of the convex part 10, it can relieve a tensile stress and make it difficult to generate a ring crack. In particular, since the total length of all the stress relaxation portions 17 is 3% or more of the outer peripheral length of the honeycomb base material 4, the effect of suppressing the ring cracks by the stress relaxation portions 17 appears.

  The “depth of tear” in the stress relaxation portion 17 is not particularly limited. When the outer periphery of the convex portion 10 is composed of the outer peripheral coat layer 7, as shown in FIG. 2, the “crack depth” of the stress relaxation portion 17 is such that a tear is formed in the outer peripheral coat layer 7. It is preferable that it stays. When the “fissure” is within the range of staying in the outer peripheral coat layer 7, the structural strength of the convex portion 10 can be maintained.

  In the honeycomb structure 100a, the total length of all the stress relaxation portions 17 is preferably 10% or more of the outer peripheral length of the honeycomb substrate 4. When the total length of all the stress relaxation portions 17 is 10% or more of the outer peripheral length of the honeycomb substrate 4, the tensile stress can be relaxed and ring cracks can be made less likely to occur. Furthermore, the total length of all the stress relaxation portions 17 is more preferably 15% or more of the outer peripheral length of the honeycomb substrate 4, and most preferably 25 to 90%. If the total length of all the stress relaxation portions 17 is up to 90% of the outer peripheral length of the honeycomb substrate 4, the effect of suppressing ring cracks can be sufficiently exerted. Moreover, when the total length of all the stress relaxation parts 17 is 90% or less of the outer peripheral length of the honeycomb base material 4, it is possible to suppress the manufacturing time of the stress relaxation part (for example, drying time with an industrial dryer). become.

  In the honeycomb structure 100a, the total length of the stress relaxation portions 17 having an opening width of 10 μm or more is preferably 50% or more of the total length of all the stress relaxation portions 17. When the total length of the stress relaxation portions 17 having an opening width of 10 μm or more is 50% or more of the total length of all the stress relaxation portions 17, the tensile stress is relaxed and ring cracks are more generated. It can be difficult. Furthermore, it is more preferable that the total length of the stress relaxation portions 17 having an opening width of 10 μm or more is 55% or more of the total length of all the stress relaxation portions 17, particularly 65 to 95%. Most preferably it is. In the present specification, the “width of the opening 18 of the stress relaxation portion 17” is the width of the tear measured along the direction perpendicular to the direction in which the tear extends on the outer peripheral surface of the honeycomb substrate 4. If the total length of the stress relaxation portions 17 having an opening width of 10 μm or more is up to 95% of the total length of all the stress relaxation portions 17, the effect of suppressing ring cracks can be sufficiently exerted. . Further, when the total length of the stress relaxation portions 17 having an opening width of 10 μm or more is 95% or less of the total length of all the stress relaxation portions 17, the manufacturing time of the stress relaxation portions (for example, an industrial dryer) Drying time) can be suppressed.

  The maximum thickness (H) of the convex portion 10 in the cross section orthogonal to the Z direction is 1 to 20 mm, preferably 3 to 15 mm, and particularly preferably 5 to 10 mm. If the maximum thickness (H) in the cross section perpendicular to the Z direction of the convex portion 10 is less than 1 mm, the convex portion is too thin, and ring cracks that affect the DPF collecting function occur. If it exceeds 20 mm, the honeycomb structure cannot be mounted in a limited mounting space in an automobile or the like.

  As for the convex part 10, the edge part of at least one side in a Z direction is a taper shape. Therefore, even if the convex portion 10 receives an external force during conveyance or the like, the convex portion 10 is unlikely to cause defects such as chipping.

  In the honeycomb structure 100a, in the cross section parallel to the Z direction, an “inclination angle” that is an angle formed between the tapered surface 11 and the Z direction is 80 degrees or less. If the “inclination angle” is greater than 80 degrees, the end of the convex portion (the outermost peripheral portion) may be missing. The “inclination angle” is preferably 10 to 80 degrees, and particularly preferably 20 to 60 degrees. If the “inclination angle” is smaller than 10 degrees, there is a problem that the honeycomb structure 100a cannot be mounted in a limited mounting space in an automobile or the like. The “inclination angle” is an acute angle α of angles formed between the taper surface 11 and the Z direction (see FIG. 2). The “taper surface 11” is an end surface of the convex portion 10 that is tapered.

  The width L of the convex portion 10 is 1% or more of the length in the Z direction of the honeycomb structure 100a (the total length of the honeycomb substrate 4), preferably 1 to 80%, and preferably 5 to 20%. Is particularly preferred. When the width L of the convex portion 10 is in the above range, the honeycomb structure can be favorably mounted in a limited mounting space in an automobile or the like. Moreover, since the convex part 10 is not too large, the honeycomb structure 100a can be reduced in weight. If the width L of the convex portion 10 is less than 1%, ring cracks may not be satisfactorily prevented. Further, if the width L of the convex portion 10 is more than 80%, the honeycomb structure 100a may be enlarged, and the honeycomb structure 100a may not be mounted in a limited mounting space in an automobile or the like. The “width L of the convex portion 10” is the length of the convex portion in the Z direction. That is, the “width L of the convex portion 10” is a distance between both ends of the tapered end portions.

  As long as the convex part 10 is arrange | positioned so that a part of outer periphery of the honeycomb base material 4 may be covered, there is no restriction | limiting in particular. That is, as long as the generation of ring cracks can be prevented, the honeycomb substrate 4 may be disposed at the center portion or at the end portion. The central part of the honeycomb substrate 4 is the central part of the honeycomb substrate 4 in the Z direction. When cracks are likely to occur in the central portion of the honeycomb base material 4, the convex portions 10 are preferably disposed in the central portion of the honeycomb base material 4. “The convex portion 10 is disposed at the central portion of the honeycomb substrate 4” means that “at least a part of the convex portion 10 is the center in the Z direction of the honeycomb substrate 4 (the center of the honeycomb substrate 4). ) Is arranged so as to cover. That is, “the convex portion 10 is disposed in the central portion of the honeycomb substrate 4” includes the following two cases. That is, when “the center of the convex portion 10 in the Z direction (the center of the convex portion 10)” overlaps the center of the honeycomb substrate 4 (covers the center), and the portion other than the central portion of the convex portion 10 is the honeycomb. It includes both cases of overlapping with the center of the substrate 4 (covering the center). In the honeycomb structure 100a, as the ratio (A / B) of the total length (A) to the outer diameter (B) increases, a crack (ring crack) is more likely to occur at the center of the honeycomb substrate 4.

  In the honeycomb structure 100a, as the ratio (A / B) of the total length (A) to the outer diameter (B) becomes smaller, cracks (end face cracks) are more likely to occur on the end face of the honeycomb substrate 4. In particular, end face cracks are likely to occur on the end face on the outlet side of the exhaust gas. Thus, when a crack is likely to occur on the end face of the honeycomb substrate 4, the convex portion 10 is preferably disposed at an end portion of the honeycomb base 4 having an end face where the crack is likely to occur.

  The number of the convex portions 10 is not limited to one and can be plural. When the plurality of convex portions 10 are disposed, the convex portions 10 are preferably disposed at least at the end portion and the central portion on the outlet side of the exhaust gas.

  As shown in FIG. 2, the convex portion 10 preferably has a porous partition wall 1 that partitions and forms a plurality of cells 2 parallel to the Z direction. When the cells 2 are formed on the protrusions 10, the honeycomb structure 100a can be reduced in weight while preventing the occurrence of ring cracks. The convex portion 10 is preferably formed integrally with the honeycomb substrate 4. Thereby, the convex part 10 will be couple | bonded with the honeycomb base material 4 firmly. Here, “the convex portions 10 and the honeycomb substrate 4 are integrally formed” means the following. That is, there is no boundary between the partition wall 1 constituting the convex portion 10 and the partition wall 1 constituting the honeycomb substrate 4, and the partition wall 1 of the convex portion 10 is continuous so that the material of each partition wall 1 is continuous. And the partition walls 1 of the honeycomb substrate 4 are joined. Such a honeycomb structure 100a “in which the convex portions 10 and the honeycomb base material 4 are integrally formed” includes one honeycomb “including a portion that becomes the convex portion 10 and a portion that becomes the honeycomb base material 4”. It is obtained by molding a molded body and performing drying, firing, processing, and the like. The partition wall 1 that defines the “cell 2 formed on the convex portion 10” does not need to carry a noble metal serving as a catalyst. This is because it is difficult for exhaust gas to flow into the “cell 2 formed on the convex portion 10”. As a method for supporting the catalyst on the honeycomb structure 100a, a method in which one end of the honeycomb structure 100a is immersed in the catalyst slurry and the other end is sucked to suck up the catalyst slurry. According to this method, the honeycomb structure 100a in which the catalyst is not supported on the “cell 2 formed on the convex portion 10” can be easily manufactured.

  The honeycomb structure 100a preferably includes an outer peripheral coating layer 7 made of an outer peripheral coating material on the “outer peripheral surface including the surface of the convex portion 10” of the honeycomb substrate 4. By providing the outer peripheral coat layer 7, it is possible to prevent leakage of the catalyst slurry when the catalyst slurry is sucked up. Furthermore, as shown in FIGS. 1 to 3, the outer peripheral coat layer 7 is preferably formed so as to close the opening of the “cell 2 formed on the convex portion 10”. By forming the outer peripheral coat layer 7 so as to block the opening of the “cell 2 formed on the convex portion 10”, the exhaust gas flowing into the “cell 2 formed on the convex portion 10” It is possible to prevent discharge from the opening of the formed cell 2 ”. That is, it is possible to prevent the exhaust gas from leaking from the honeycomb structure 100a. As described above, there is a case where the catalyst is not supported on the partition wall 1 that defines the “cell 2 formed on the convex portion 10”. In this case, if the outer peripheral coat layer 7 is not formed as described above, exhaust gas that has not been sufficiently purified will be discharged. That is, there is a possibility that the purification performance is deteriorated due to the exhaust gas leaking from the opening of the “cell 2 formed on the convex portion 10”. Therefore, if the outer peripheral coat layer 7 is formed so as to close the opening of the “cell 2 formed on the convex portion 10”, it is possible to suppress a decrease in purification performance. As the outer periphery coating material, an inorganic raw material such as inorganic fiber, colloidal silica, clay, SiC particles, and the like added with additives such as an organic binder, a foamed resin, a dispersant, and the like, kneaded with water added, etc. Can be mentioned.

  1-5000 micrometers is preferable and, as for the thickness of the outer periphery coating layer 7, 10-3000 micrometers is especially preferable. When the thickness of the outer peripheral coat layer 7 is in the above range, drying after the application of the outer peripheral coat layer 7 can be performed in a uniform state. Can be prevented. If the thickness of the outer peripheral coat layer 7 is less than 1 μm, the catalyst slurry may leak from the honeycomb substrate 4 when the catalyst is supported. If the thickness of the outer peripheral coat layer 7 is more than 5000 μm, the cross-sectional ratio of the portion that does not have the exhaust gas purification function increases, and the purification performance may be reduced. As a method of forming a crack in the stress relaxation portion 17, there is a method of intentionally generating a crack in the outer peripheral coat layer 7. The “unintentional crack” here means a crack that does not correspond to a crack in the stress relaxation portion 17.

  Moreover, by providing the convex part 10 whose surface is partly planar like the honeycomb structure 100a, the maximum thickness (H) of the convex part 10 is reduced (the thickness of the part of the planar part 15 is reduced). thin). Therefore, a small packing container can be used for transferring the honeycomb structure 100a.

  In the honeycomb structure 100a, it is preferable that the convex part 10 has a uniform shape in the circumferential direction except for the part where the flat part 15 is formed. “Uniform shape in the circumferential direction” means that the shape of the cross section perpendicular to the circumferential direction is the same in any part. In the honeycomb structure 100a, portions other than the portion where the flat portion 15 is formed in the convex portion 10 may not have a uniform shape in the circumferential direction.

  As in the honeycomb structure 100 a shown in FIG. 1, in the honeycomb structure “a part of the surface of the convex portion 10 is the flat portion 15”, the thickness of the convex portion 10 is thin in the flat portion 15. Therefore, as shown in FIG. 4, the honeycomb structure 100 a can be stored in the existing packing container 20 even if the honeycomb structure 100 a is not a packing container designed to be particularly large due to the presence of the ring-shaped protrusions. Therefore, the existing packaging container 20 can be used. In FIG. 4, the partition walls of the honeycomb structure 100a are omitted. FIG. 4 is a plan view schematically showing a state in which a plurality of honeycomb structures 100a are housed in an existing packing container 20.

  The convex portion 10 is preferably formed with a pair of plane portions 15 parallel to each other. Further, as shown in FIG. 3, two pairs of a pair of plane portions 15 parallel to each other are formed on the convex portion 10, and one pair of plane portions 15 is the other pair of plane portions 15. It is preferable to be formed so as to be orthogonal to. Since the flat portion 15 is formed in this way, a thin portion (the flat portion 15) is formed on the convex portion 10, so that the storage space is reduced as compared with the case where the flat portion 15 is not formed. Is possible. Therefore, the honeycomb structure 100a can be satisfactorily mounted even in a place where the mounting space is small, such as an automobile.

  The distance (shortest distance) T (see FIG. 3) between the flat portion 15 (surface) and the outer periphery of the honeycomb substrate 4 (the portion covered with the convex portion 10) is preferably 1 to 15 mm. It is especially preferable that it is 5-10 mm. By setting the distance T between the flat portion 15 and the outer periphery of the honeycomb substrate 4 within the above range, the occurrence of ring cracks can be prevented. Furthermore, the honeycomb structure 100a can be satisfactorily mounted even in a place where the mounting space is small, such as an automobile. The distance T between the flat portion 15 (surface) and the outer periphery of the honeycomb substrate 4 can be said to be the thickness of the thinnest portion of the flat portion 15 of the convex portion 10. When the honeycomb structure 100 a includes the outer peripheral coat layer 7, the distance T is a value obtained by subtracting the outer peripheral coat layer 7 from the distance (shortest distance) between the flat portion 15 (surface) and the outer periphery of the honeycomb substrate 4. is there.

  In the honeycomb structure 100a of the present embodiment, the material of the honeycomb substrate 4 is preferably composed mainly of at least one selected from the group consisting of cordierite, silicon carbide, mullite, aluminum titanate, and alumina. The material of the honeycomb substrate 4 is more preferably at least one selected from the group consisting of cordierite, silicon carbide, mullite, aluminum titanate, and alumina. Here, the “main component” means a component exceeding 50% by mass in the whole.

  In the honeycomb structure 100a of the present embodiment, the average pore diameter of the partition walls 1 is preferably 5 to 100 μm, and particularly preferably 8 to 50 μm. When the average pore diameter is smaller than 5 μm, the pressure loss may increase. When the average pore diameter is larger than 100 μm, the strength of the honeycomb structure 100a may be lowered. The average pore diameter is a value measured with a mercury porosimeter.

  In the honeycomb structure 100a of the present embodiment, the porosity of the partition walls 1 is preferably 25 to 80%, and particularly preferably 35 to 75%. If the porosity is less than 25%, the pressure loss may increase. If the porosity is higher than 80%, the strength of the honeycomb structure 100a may be lowered. The porosity is a value measured by a mercury porosimeter.

  The thickness of the partition wall 1 is preferably 40 to 600 μm, and particularly preferably 150 to 400 μm. If it is thinner than 40 μm, the strength of the honeycomb structure 100a may be lowered. If it is thicker than 600 μm, the pressure loss may increase.

  In the honeycomb structure 100a of the present embodiment, the shape of the honeycomb substrate 4 is not particularly limited. As the shape of the honeycomb substrate 4, a cylindrical shape, a cylindrical shape having an elliptical end surface, a polygonal cylindrical shape having an end surface of “square, rectangular, triangular, pentagonal, hexagonal, octagonal, etc.” are preferable. In the honeycomb structure 100a shown in FIG. 1, the shape of the honeycomb substrate 4 is a cylindrical shape.

  In the honeycomb structure 100a of the present embodiment, the cell shape of the honeycomb substrate 4 (cell shape in a cross section orthogonal to the Z direction) is not particularly limited. Examples of the cell shape include a triangle, a quadrangle, a hexagon, an octagon, a circle, or a combination thereof. Among the squares, a square or a rectangle is preferable.

In the honeycomb structure 100a of the present embodiment, the cell density of the honeycomb substrate 4 is not particularly limited. The cell density of the honeycomb substrate 4 is preferably 15 to ²⁰⁰ cells / cm ² , and particularly preferably 30 to 100 cells / cm ² . When the cell density is lower than 15 cells / cm ² , when exhaust gas is circulated, pressure loss may increase in a short time or the strength of the honeycomb structure 100a may decrease. When the cell density is higher than 200 cells / cm ² , the pressure loss may increase.

  Another embodiment of the honeycomb structure of the present invention (honeycomb structure 100b) is the same as the embodiment of the honeycomb structure of the present invention (honeycomb structure 100a). (One end). A honeycomb structure 100b shown in FIG. 5 is another embodiment of the honeycomb structure of the present invention. Thus, the convex part 10 is arrange | positioned at one edge part of the honeycomb structure 100b, and generation | occurrence | production of an end surface crack can be prevented. Further, in the honeycomb structure 100b, the stress relaxation portion 17 is also disposed in the vicinity of one end portion. Therefore, the occurrence of end face cracks can be prevented by the action of the stress relaxation portion 17. When the honeycomb structure is used as a DPF, end face cracks may occur on the end face on the exhaust gas outlet side. This end face crack occurs as follows. A large amount of soot or the like contained in the exhaust gas of an engine such as an automobile accumulates at the outlet side end of the honeycomb structure. Therefore, when the honeycomb structure is regenerated by burning soot or the like, the outlet side end portion of the honeycomb structure becomes hotter than the other parts due to the burning of soot or the like. Therefore, stress is generated at the end of the honeycomb structure. As a result, cracks (end face cracks) are generated on the outlet side end face of the honeycomb structure. FIG. 5 is a perspective view schematically showing another embodiment of the honeycomb structure of the present invention.

  Fig. 6 is a schematic diagram showing a cross section parallel to the Z direction of a honeycomb structure 100c of still another embodiment of the present invention. The honeycomb structure of the present invention, like the honeycomb structure 100c, has openings of predetermined cells (first cells 2a) on the first end face 3 and openings of remaining cells (second cells 2b) on the second end face 5. The plugging part 23 arrange | positioned by the part may be provided. The first cells 2a and the second cells 2b are preferably arranged alternately. And it is preferable that the checkered pattern is formed by the plugging part 23 and the "cell opening part 25" in the both end surfaces of the honeycomb structure 100c by it. The material of the plugging portion 23 is preferably a material that is preferable as the material of the honeycomb substrate 4 (partition wall 1). The material of the plugging portion 23 and the material of the honeycomb substrate 4 may be the same material or different materials.

(2) Manufacturing method of honeycomb structure:
The honeycomb structure of the present invention can be manufactured by the following method. That is, the honeycomb structure of the present invention can be manufactured by a method including a honeycomb fired body manufacturing process for manufacturing a honeycomb fired body and a cutting process of cutting the outer peripheral portion of the honeycomb fired body to form a convex portion. Furthermore, when the outer peripheral coat layer is provided, it is preferable to have an outer peripheral coat layer forming step after cutting the outer peripheral portion of the honeycomb fired body. The “honeycomb fired body” is a honeycomb fired body having porous partition walls formed by firing a ceramic raw material that partitions and forms a plurality of cells serving as fluid flow paths.

  According to such a method, the honeycomb structure of the present invention can be easily manufactured.

  In order to form a “planar portion in which a part of the surface of the convex portion is a plane parallel to the Z direction” (a planar portion is formed on the convex portion), for example, the following method can be used. it can. That is, first, a honeycomb structure “a flat portion is not formed on the convex portion” is manufactured. Thereafter, a part of the convex portion of the honeycomb structure is cut so that the flat portion is formed, thereby manufacturing the honeycomb structure having the flat portion formed on the convex portion as shown in FIG. Can do. In addition, when “a part of the surface of the convex portion has a planar shape parallel to the Z direction”, the honeycomb structure of the present invention can be manufactured by the following method. That is, the method includes the honeycomb fired body manufacturing step and the cutting step, and in the honeycomb fired body manufacturing step, a polygonal columnar honeycomb fired body is manufactured. Further, in the cutting step, the honeycomb fired body is cut so that a part of the side surface of the honeycomb fired body remains and a part of the remaining side surface becomes a flat portion of the convex portion. By doing in this way, it becomes unnecessary to perform operation which forms a plane part again after a cutting process, and a manufacturing process can be rationalized.

  Hereinafter, the manufacturing method of the honeycomb structure of the present invention will be described for each step.

(2-1) Honeycomb fired body manufacturing process;
The honeycomb fired body manufacturing process is a process of manufacturing a honeycomb fired body having porous partition walls formed by firing a ceramic raw material. The method for producing the honeycomb fired body is not particularly limited. Hereinafter, the honeycomb fired body manufacturing process will be described step by step.

(2-1-1) molding step;
First, in the forming step, it is preferable that a ceramic forming raw material containing a ceramic raw material is formed to form a honeycomb formed body having partition walls (unfired) that partition and form a plurality of cells that serve as fluid flow paths. The honeycomb formed body is a formed body having a honeycomb structure.

  The ceramic raw material contained in the ceramic forming raw material is preferably at least one selected from the group consisting of a cordierite forming raw material, cordierite, silicon carbide, silicon-silicon carbide based composite material, mullite, and aluminum titanate. The cordierite forming raw material is a ceramic raw material blended so as to have a chemical composition that falls within the range of 42 to 56 mass% silica, 30 to 45 mass% alumina, and 12 to 16 mass% magnesia. And the cordierite-forming raw material is fired to become cordierite.

  The ceramic forming raw material is preferably prepared by mixing the ceramic raw material with a dispersion medium, an organic binder, an inorganic binder, a pore former, a surfactant and the like. The composition ratio of each raw material is not particularly limited, and is preferably a composition ratio in accordance with the structure and material of the honeycomb structure to be manufactured.

  When the ceramic forming raw material is formed, it is preferable to first knead the ceramic forming raw material to form a kneaded material, and the obtained kneaded material is formed into a honeycomb shape. The method for kneading the ceramic forming raw material to form the kneaded material is not particularly limited, and examples thereof include a method using a kneader, a vacuum kneader or the like. A method for forming a kneaded clay to form a honeycomb formed body is not particularly limited, and a known forming method such as extrusion molding or injection molding can be used. For example, a method of forming a honeycomb formed body by extrusion molding using a die having a desired cell shape, partition wall thickness, and cell density can be cited as a suitable example. As the material of the die, a cemented carbide which does not easily wear is preferable.

  Examples of the shape of the honeycomb formed body include a cylindrical shape, an elliptical shape, and a polygonal column shape whose end face is “square, rectangular, triangular, pentagonal, hexagonal, octagonal, etc.”. In the case of manufacturing a honeycomb structure having “a convex portion on which a flat surface portion is formed”, it is preferable to form a honeycomb-shaped body having a polygonal column shape. This is because by leaving a part of the side surface of the polygonal column, a part of the remaining side surface can be used as a flat portion of the convex portion. That is, the operation for forming the plane portion can be omitted. As the honeycomb formed body, a quadrangular prism shape is more preferable.

  Further, after the above forming, the obtained honeycomb formed body may be dried. The drying method is not particularly limited. For example, hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying and the like can be mentioned. Among these, it is preferable to perform dielectric drying, microwave drying, or hot air drying alone or in combination.

(2-1-2) Firing step;
Next, the honeycomb formed body is fired to produce a honeycomb fired body.

  Prior to firing (main firing) the honeycomb formed body, it is preferable to calcine the honeycomb formed body. Calcination is performed for degreasing. The method for calcining the honeycomb formed body is not particularly limited as long as organic substances (organic binder, surfactant, pore former, etc.) can be removed. Generally, the combustion temperature of the organic binder is about 100 to 300 ° C., and the combustion temperature of the pore former is about 200 to 800 ° C. Therefore, it is preferable to heat at about 200 to 1000 ° C. for about 3 to 100 hours in an oxidizing atmosphere as a condition for calcination.

  The firing (main firing) of the honeycomb formed body is performed in order to sinter and densify the forming raw material constituting the calcined honeycomb formed body to ensure a predetermined strength. Since the firing conditions (temperature, time, atmosphere, etc.) vary depending on the type of the forming raw material, appropriate conditions may be selected according to the type. For example, when a cordierite forming raw material is used, the firing temperature is preferably 1410 to 1440 ° C. The firing time is preferably 4 to 8 hours as the keep time at the maximum temperature. An apparatus for performing calcination and main firing is not particularly limited, and an electric furnace, a gas furnace, or the like can be used.

(2-2) Cutting process;
The cutting step is a step of cutting the outer peripheral portion of the honeycomb fired body. The method for cutting the honeycomb fired body is not particularly limited. As a method of cutting the outer peripheral portion of the honeycomb fired body, a conventionally known method can be appropriately employed. However, a method of pressing a grindstone coated with diamond while rotating the honeycomb fired body is preferable. In the cutting process, the thickness of “the outer peripheral portion of the honeycomb fired body to be cut” is the same as the thickness of the convex portion formed after cutting.

  As described above, in the case of manufacturing a honeycomb structure in which “a flat portion parallel to the Z direction” is formed on the convex portion, it is preferable to cut the honeycomb fired body as follows. That is, it is preferable to cut the honeycomb fired body so that a part of the side surface of the polygonal columnar honeycomb fired body remains and a part of the remaining side surface becomes a flat portion of the convex portion. By doing in this way, it becomes unnecessary to perform operation which forms a plane part again after cutting.

  The cutting may be performed before or after firing the honeycomb formed body, but is preferably performed after firing. By cutting after firing, even if the honeycomb fired body is deformed by firing, the shape of the honeycomb fired body can be adjusted by cutting.

(2-3) plugging step;
When producing a honeycomb structure provided with a plugging portion, it is preferable to perform the following plugging step after the cutting step. In this plugging step, the honeycomb fired body has an opening of a “predetermined cell (first cell)” on one end face (first end face) and a “remaining cell (second end face) on the other end face (second end face). A plugging portion is disposed in the opening of “2 cells)”. This will be specifically described below.

  First, the plugging material is filled into the opening of the cell on one end face (first end face) of the honeycomb fired body (honeycomb base material). As a method of filling the plugging material into the cell opening on one end face (first end face), a method having a masking step and a press-fitting step is preferable. The masking step is a step in which a sheet is attached to one end face of the honeycomb fired body, and a hole is formed in the sheet at a position overlapping with the “cell where the plugging portion is to be formed”. The press-fitting process involves press-fitting “the end of the honeycomb fired body on the side where the sheet is attached” into the container in which the plugging material is stored, and press-fitting the plugging material into the cells of the honeycomb fired body. It is a process to do. When the plugging material is press-fitted into the cells of the honeycomb fired body, the plugging material passes through the holes formed in the sheet and is filled only in the cells communicating with the holes formed in the sheet.

  The plugging material can be prepared by appropriately mixing the raw materials listed as the constituent elements of the ceramic forming raw material. The ceramic raw material contained in the plugging material is preferably the same as the ceramic raw material used as the raw material for the partition walls.

  Next, it is preferable to dry the plugging material filled in the honeycomb fired body.

  In one end face (first end face) of the honeycomb fired body, it is preferable that cells in which the plugged portions are formed and cells in which the plugged portions are not formed are alternately arranged. In this case, a checkered pattern is formed by the plugged portion and the “cell opening” on one end face where the plugged portion is formed.

  Next, as in the case of one end surface (first end surface), plugging is performed in the opening portion of the “remaining cell (second cell)” on the other end surface (second end surface) of the honeycomb fired body. It is preferable to arrange the part. The plugging material may be dried after filling the plugging material on both end faces of the honeycomb fired body. Alternatively, the firing step may be performed after filling the honeycomb formed body with the plugging material.

(2-4) outer peripheral coat layer forming step;
It is preferable to apply an outer periphery coating material to the outer periphery of the cut honeycomb fired body to form an outer periphery coating layer. By forming the outer peripheral coat layer, it is possible to prevent the convex portion from being lost. Examples of the outer coating material include those obtained by adding water to an inorganic raw material such as inorganic fiber, colloidal silica, clay, SiC particles, and the like, and adding an additive such as an organic binder, a foamed resin, and a dispersant. Can do. Examples of the method of applying the outer periphery coating material include a method of coating with a rubber spatula while rotating the “cut honeycomb fired body” on a potter's wheel.

  For example, after the outer peripheral portion of the honeycomb fired body is ground so that a convex portion is formed, and the outer peripheral coating material is applied to the ground outer peripheral portion, the stress relief portion is an industrial dryer on a part of the flat portion of the convex portion. For example, it can be formed by rapid drying partially. About other parts which do not form a stress relaxation part, it is good to dry an outer periphery coating material by natural drying. The reason why the stress relaxation portion can be formed by the rapid drying described above is that a temperature difference occurs between the surface and the inside of the outer peripheral coating material due to the rapid drying, resulting in a difference in drying shrinkage. In order to adjust the width and length of the stress relaxation portion, it is preferable to change the time for rapid drying, the target range, the amount of moisture in the outer periphery coating material, and the like.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

Example 1
As a ceramic raw material, a mixture of silicon carbide (SiC) powder and metal silicon (Si) powder was used. To this, hydroxypropylmethylcellulose and a pore former were added as binders, and water was added to produce a molding raw material. Then, the forming raw material was kneaded with a vacuum kneader to prepare a clay. The content of the binder was 7 parts by mass when the total of silicon carbide (SiC) powder and metal silicon (Si) powder was 100 parts by mass. The content of the pore former was 3 parts by mass when the total of the silicon carbide (SiC) powder and the metal silicon (Si) powder was 100 parts by mass. The water content was 42 parts by mass when the total of silicon carbide (SiC) powder and metal silicon (Si) powder was 100 parts by mass. The average particle diameter of the silicon carbide powder was 20 μm, and the average particle diameter of the metal silicon powder was 6 μm. Moreover, the average particle diameter of the pore former was 20 μm. The average particle diameter of the silicon carbide powder, the metal silicon powder, and the pore former is a value measured by a laser diffraction method.

  The obtained kneaded material was molded using an extrusion molding machine to obtain a square pillar-shaped honeycomb molded body. The obtained honeycomb formed body was dried by high frequency dielectric heating and then dried at 120 ° C. for 2 hours using a hot air dryer.

  The dried honeycomb formed body was degreased and fired to obtain a rectangular pillar-shaped honeycomb fired body. The degreasing conditions were 550 ° C. for 3 hours. The firing conditions were 1450 ° C. and 2 hours in an argon atmosphere.

  The outer peripheral portion of the obtained rectangular pillar-shaped honeycomb fired body is left as “a planar portion in which a ring-shaped convex portion is formed and a part of each side surface of the honeycomb fired body is formed on the ring-shaped convex portion. Like "cut. The ring-shaped convex portion was formed at the “central portion in the Z direction” of the honeycomb fired body. Thereafter, an outer peripheral coating material was applied to the outer periphery of the cut honeycomb fired body to form an outer peripheral coating layer. In this way, a honeycomb structure as shown in FIG. 1 was obtained.

  In addition, as a method of cutting the outer peripheral portion of the honeycomb fired body, a method of pressing a grindstone coated with diamond against the outer peripheral portion of the honeycomb fired body at an angle of 35 degrees with respect to the Z direction while rotating the honeycomb fired body. It was. In this way, a honeycomb structure having a convex portion “having four flat portions and both ends being tapered” was obtained. The taper angle (“inclination angle”) of the protrusions in this honeycomb structure was 35 degrees at both ends. As shown in FIG. 3, two pairs of plane portions parallel to each other (a total of four plane portions) were formed on the convex portions of the honeycomb structure of the present example.

  Furthermore, in the above-mentioned process, after applying the outer peripheral coating material, a part of the flat surface portion of the convex portion was partially rapidly dried with an industrial dryer or the like to form a stress relaxation portion. For other portions where the stress relaxation portion is not formed, the outer peripheral coating material was dried by natural drying so that the stress relaxation portion was not formed.

The bottom surface of the obtained honeycomb structure was circular with a diameter of 14.4 cm, and the length of the honeycomb structure in the Z direction was 20.3 cm. The partition wall thickness was 305 μm, and the cell density was 46.5 cells / cm ² . The maximum thickness (H) of the convex portion is 10 mm, the width (L) of the convex portion is 20 mm, the ratio of the convex portion width to the total length of the honeycomb structure (honeycomb substrate) is 10%, and the inclination angle is 35 degrees. It was. The plane portion depth (D) (4 locations) was 5 mm. The “plane portion depth (D)” is the difference between the maximum thickness (H) of the convex portion and the “distance between the plane portion (surface) and the outer periphery of the honeycomb substrate” T (see FIG. 3). . The convex portion was disposed at a position where the “distance from one end portion of the honeycomb structure to the end portion of the convex portion on the side close to the one end portion” was 6.4 cm.

  The maximum thickness (H) of the convex portion is “in parallel to the outer periphery of the honeycomb substrate disposed so as to be in contact with the outer periphery of the convex portion (except for the tapered portion) in the cross section parallel to the Z direction of the honeycomb structure. It is the distance between the “line” and the “outer periphery of the honeycomb substrate”. The width (L) of the convex portion is the length of the convex portion in the Z direction of the honeycomb structure.

  In Table 1, the column of “projection mounting position” indicates the position where the projection is disposed. “Center” indicates that a convex portion is disposed at the center in the Z direction of the honeycomb structure. “End portion” indicates that a convex portion is provided at an end portion in the Z direction of the honeycomb structure. “Inclination angle (degree)” indicates an acute angle among angles formed between the tapered surfaces at both ends of the convex portion and the Z direction.

  About the obtained honeycomb structure, by the following methods, "stress relaxation part position", "stress relaxation part length", "stress relaxation part width", "ring crack", "convex part strength", and " Each evaluation of “mountability” was performed. The results are shown in Table 1.

(Stress relaxation part position, length, and width)
The position, length, and width of the stress relaxation part were measured using a ruler or a caliper. About the width | variety of a stress relaxation part, the stress relaxation part with a width | variety of 10 micrometers or more was specified using the 10-micrometer thickness gauge (JIS B7524).

(Ring crack)
First, a honeycomb structure is attached to a burner testing machine. Next, the following operation is performed with this burner tester. That is, the following heating / cooling operation is defined as one cycle. The temperature raising / cooling operation is as follows: “After flowing a high-temperature gas at 800 ° C. 20 mm before the honeycomb structure inlet end face for 10 minutes at 2 Nm ³ / min to the honeycomb structure, 20 mm before the honeycomb structure inlet end face The cooling gas at 150 ° C. is made to flow at 2 Nm ³ / min for 10 minutes ”. Then, the temperature raising and cooling operation is performed 100 cycles. Thereafter, the presence or absence of ring cracks formed in the honeycomb structure is visually confirmed and evaluated according to the following criteria. When ring cracks are generated in the honeycomb structure so as to reduce the function as the DPF, “C” is set. Ring cracks are generated in the honeycomb structure, but “B” is set to a level that does not deteriorate the function of the DPF. When there is no ring crack in the honeycomb structure, “A” is set. “A” and “B” are accepted, and “C” is rejected. Note that “function as DPF” is “to the extent that the function as DPF is not lowered” if the PM (soot) collection efficiency in the treatment (exhaust gas treatment by DPF) is 90% or more. Further, if the PM (soot) collection efficiency is less than 90%, it is assumed that “the function of the DPF is reduced”. In the measurement of PM (soot) collection efficiency, PM (soot) contained in the gas after passing through the honeycomb structure is collected with a filter paper as follows, and the weight (W1) of PM (soot) Was measured. That is, first, the honeycomb structure is attached to a soot generator device that generates PM (soot) by a burner using light oil as fuel. After that, the honeycomb structure attached to the soot generator device was supplied with a gas that generated PM (soot) by the soot generator and became 200 ° C. 190 mm before the inlet end face of the honeycomb structure at ³ Nm ³ / min for 2 minutes. Let it pass. Thus, the weight (W1) was measured. Moreover, the gas which generated PM (soot) for the same time was collected with the filter paper without passing through the honeycomb structure, and the weight (W2) of PM (soot) was measured. Subsequently, the obtained weights (W1) and (W2) were substituted into the following formula to determine the collection efficiency.
(W2-W1) / (W2) × 100

(Convex strength)
First, a pendulum having a string (75 cm in length) provided with an iron ball (weight 5.4 g) having a diameter of 11 mm at the tip is prepared. Next, this pendulum is arranged so that the iron ball hits the end (outermost peripheral portion) of the convex portion of the honeycomb structure at the lowest point of the iron ball (that is, in a state where the pendulum is not swung). Next, the pendulum iron ball is swung up to cause the iron ball to collide with the end of the convex portion. Then, the edge part of a convex part is observed visually. And it evaluates with the following standards. When the iron ball is swung up to a height of 80% of the length of the string and the iron ball is made to collide with the end of the convex portion, if a defect such as a chip occurs at the end of the convex portion, C ”. When the iron ball is swung up to a height of 100% of the length of the string, and the iron ball is made to collide with the end of the link-like convex portion, a defect such as a chip occurs at the end of the convex portion. Is "B", and if no defect occurs at this time, it is "A". “A” evaluation and “B” evaluation are acceptable, and “C” evaluation is unacceptable.

(Mountability)
The mountability of the honeycomb structure (Comparative Example 1) in which no protrusions are formed is evaluated by the maximum thickness (H) and width (L) of the protrusions. Evaluation of the maximum thickness (H) of the convex portion may be referred to as “evaluation of“ radial direction ””. In addition, the evaluation of the width (L) of the convex portion may be referred to as “evaluation of“ full length direction ””. Evaluation about the maximum thickness (H) of a convex part is as follows. A case where the maximum thickness (H) of the convex portion is 10 mm or less is “A”, a case where it is more than 10 mm and 20 mm or less is “B”, and a case where it is more than 20 mm is “C”. Evaluation of the width (L) of the convex portion is as follows. The case where the width of the convex part exceeds 80% of the length in the cell extending direction of the honeycomb structure is referred to as “B”, and the case where the width of the protruding part is 80% or less of the length in the cell extending direction of the honeycomb structure is determined as “A”. And In the case of “B”, the mountability of the honeycomb structure is affected. In the case of “A”, the mountability of the honeycomb structure is not affected.

  Further, the mountability is evaluated comprehensively in consideration of all of the maximum thickness (H), width (L) and angle (α) of the convex portion. If both “evaluation in the radial direction” and “evaluation in the full length direction” are “A”, the overall evaluation is “A”. When at least one of “evaluation in the radial direction” and “evaluation in the full length direction” is “B”, the overall evaluation is “B”. When the “radial evaluation” is “C”, the comprehensive evaluation is “C”. In the comprehensive evaluation of the mountability, “A” evaluation and “B” evaluation are passed, and “C” evaluation is rejected. Also, “A” evaluation is most preferable, and “B” evaluation is next preferable. The “C” evaluation is the worst evaluation among these A, B, and C evaluations. The honeycomb structure of Comparative Example 1 is assumed to be a honeycomb structure having a convex portion thickness (maximum convex portion thickness) of “0 mm”. The results are shown in Table 1.

  About the honeycomb structure (Examples 1-18, Comparative Examples 2-7) which has the convex part in which the plane part was formed, it evaluates as follows (effect of a plane part). First, the honeycomb structure having a planar portion (hereinafter sometimes referred to as “honeycomb structure X”) has a cross-sectional shape perpendicular to the central axis similar to that of the honeycomb structure X, and the honeycomb structure. Assume an outer cylinder with a uniform spacing of 5 mm from the body X. Next, in a cross section orthogonal to the central axis of the outer cylinder, a line segment a passing through the center of the outer cylinder and connecting two points on the outer peripheral portion of the outer cylinder, a line segment b orthogonal to the line segment a, and the line segment A line segment c inclined by 45 ° with respect to a is drawn. Both the line segment b and the line segment c are line segments that pass through the center of the outer cylinder and connect two points on the outer peripheral portion of the outer cylinder. Line segment a, line segment b, and orthogonal to the plane formed on the outer cylinder. Next, the total of the line segment a, the line segment b, and the line segment c is calculated. Next, it is assumed that the honeycomb structure X has no honeycomb structure (hereinafter sometimes referred to as “honeycomb structure Y”). Next, as in the case of the honeycomb structure X, an outer cylinder that is similar to the honeycomb structure Y and has a uniform interval of 5 mm from the honeycomb structure Y is assumed. Next, as in the case of the honeycomb structure X, a line segment a, a line segment b, and a line segment c are drawn. Next, the total of the line segment a, the line segment b, and the line segment c is calculated. Thereafter, evaluation is performed according to the following criteria. “Line segment a, line segment b, and line segment” calculated for honeycomb structure X with respect to “total of line segment a, line segment b, and line segment c” calculated for honeycomb structure Y When the ratio of “total of c” is 104% or less, “A” is set. “Line segment a, line segment b, and line segment” calculated for honeycomb structure X with respect to “total of line segment a, line segment b, and line segment c” calculated for honeycomb structure Y When the ratio of “total of c” is 106% or less, “B” is set. “Line segment a, line segment b, and line segment” calculated for honeycomb structure X with respect to “total of line segment a, line segment b, and line segment c” calculated for honeycomb structure Y When the ratio of “total of c” is larger than 106%, “C” is set. Note that the above evaluation for a honeycomb structure having a convex portion formed with a flat portion corresponds to “evaluation in the radial direction”. As for the honeycomb structure having the convex portions with the flat portions formed, the “evaluation in the full length direction” and the “total evaluation” are performed in the same manner as the honeycomb structure having the convex portions without the flat portions. "I do. The results are shown in Table 1.

(Examples 2-18, Comparative Examples 1-7)
A honeycomb structure was obtained in the same manner as in Example 1 except that the conditions were changed as shown in Table 1. In addition, when adjusting the width | variety and length of a stress relaxation part, the time to rapidly dry an outer periphery coating material, the target range, the moisture content in an outer periphery coating material, etc. were changed. About the obtained honeycomb structure, by the above method, “position of stress relaxation portion”, “length of stress relaxation portion”, “width of stress relaxation portion”, “ring crack”, “strength strength”, and “ Each evaluation of “mountability” was performed. The results are shown in Table 1.

(Judgment)
A case where “ring crack” and “overall evaluation of mountability” were A and “convex strength” was A or B was determined as “good” (indicated by double circles in Table 1). One of “ring crack” and “total evaluation of mountability” is B, the other is A or B, and “convex strength” is A or B. (Displayed with a mark). If any one of “ring crack”, “overall evaluation of mountability”, and “convex strength” is C, it was determined as “impossible” (indicated by a cross mark in Table 1).

  From Table 1, the honeycomb structures of Examples 1 to 18 were judged as “good” or “good”. On the other hand, the honeycomb structures of Comparative Examples 1 to 7 had a determination result of “impossible”.

  The honeycomb structure of the present invention can be suitably used as a filter for purifying gas discharged from internal combustion engines such as diesel engines and direct-injection gasoline engines, various combustion devices, and the like.

1: partition, 2: cell, 2a: first cell, 2b: second cell, 3: first end surface, 4: honeycomb substrate, 5: second end surface, 7: outer peripheral coating layer, 10: convex portion, 11 : Tapered surface, 13: Joint part, 15: Plane part, 17: Stress relaxation part, 18: Opening part of stress relaxation part, 20: Packing container, 23: Plugging part, 25: Opening part of cell, 50: Ring crack, 100, 100a to 100c: honeycomb structure, 200: honeycomb structure.

Claims (6)

A honeycomb substrate having a porous partition wall defining a plurality of cells serving as a fluid flow path extending from a first end surface which is one end surface to a second end surface which is the other end surface;
A convex portion that continuously or intermittently surrounds at least a part of the outer periphery of the honeycomb base material in a ring shape,
The convex portion protrudes outward from the outer periphery of the honeycomb base material, and is disposed so as to cover a part of the outer periphery of the honeycomb base material,
The shape of at least one end of the convex portion is a tapered shape having a tapered surface that is a surface inclined to the joint portion with the outer periphery,
In the cross section orthogonal to the cell extending direction, the maximum thickness of the convex portion is 1 to 20 mm,
In a cross section parallel to the cell extending direction, a width of the convex portion is 1% or more of the total length of the honeycomb substrate, and an inclination angle is an angle formed by the tapered surface and the cell extending direction. 80 degrees or less,
A part of the surface of the convex portion is a plane portion that is a plane parallel to the cell extending direction,
The plane portion has one or a plurality of stress relaxation portions which are tears having openings on the surface,
A honeycomb structure in which a total length of all the stress relaxation portions is 3% or more of an outer peripheral length of the honeycomb substrate.   The honeycomb structure according to claim 1, wherein a total length of all the stress relaxation portions is 10% or more of an outer peripheral length of the honeycomb base material.   The honeycomb structure according to claim 1 or 2, wherein the total length of the stress relaxation portions having a width of the opening of 10 µm or more is 50% or more of the total length of all the stress relaxation portions.   In the cross section parallel to the cell extending direction, the width of the convex portion is 1 to 80% of the total length of the honeycomb substrate, and the inclination angle is 10 to 80 degrees. The honeycomb structure according to any one of claims.   The honeycomb structure according to any one of claims 1 to 4, wherein the honeycomb substrate is made of at least one selected from the group consisting of cordierite, silicon carbide, mullite, aluminum titanate, and alumina.   An opening on the first end face side of a first cell that is a predetermined cell of the plurality of cells and an opening on the second end face side of a second cell that is a remaining cell of the plurality of cells. The honeycomb structure according to any one of claims 1 to 5, further comprising a plugged portion to be plugged.

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