JP2015143521A - honeycomb structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb structure preventing deviation in a can when being contained in the can, excellent in emission control performance, and excellent in thermal shock resistance.SOLUTION: A honeycomb structure 100 comprises a honeycomb porous base material 5 including a cylindrical inner cylinder 11 that has a porous partition wall 4a mainly containing ceramic and defining and forming a plurality of cells 3a to serve as fluid channels, and an outer cylinder 21 that has a porous partition wall 4b mainly containing ceramic and defining and forming a plurality of cells 3b to serve as fluid channels and that is disposed to cover an outer circumference 12 of the inner cylinder 11, at least one side end face of the outer cylinder 21 being tapered such that an outside diameter is smaller toward a tip end 22.

Description

  The present invention relates to a honeycomb structure, and more particularly, to a honeycomb structure that is prevented from slipping inside the can when stored in a can, has excellent purification performance, and excellent thermal shock resistance.

  Exhaust gas regulations are becoming stricter, catalysts used for exhaust gas purification are required to have higher performance, and porous ceramic honeycomb structures that are the base of the catalyst are increasingly required to be thinner. Yes. The reason is that a honeycomb structure having a large opening diameter and a high opening ratio is desired in order to reduce pressure loss and minimize output loss (increase horsepower). In order to increase the purification performance by increasing the amount, it is desired that the light weight is desired, and that the honeycomb structure having a large surface area of the partition walls supporting the catalyst is desired.

  Among these, in order to “increase the opening diameter”, the cell density may be reduced, but in such a case, there is a reciprocal characteristic that the “surface area” which is the other requirement is also reduced. There is thinning of the structure.

  When the honeycomb structure has a thin wall, the mechanical strength is inevitably lowered. Therefore, a taper holding structure that enables mechanical holding even at low strength is disclosed (see, for example, Patent Documents 1 to 3).

Japanese Patent Laid-Open No. 48-1000037 JP 2002-106337 A JP 2008-88952 A

  When a catalyst is supported on a ceramic honeycomb structure and used as a honeycomb catalyst body, the catalyst is normally supported on all cells of the honeycomb structure and exhaust gas is allowed to pass through all the cells. Are used. Therefore, normally, the fracture pressure on the side surface of the honeycomb structure (honeycomb catalyst body) becomes the mechanical strength of the honeycomb structure (honeycomb catalyst body) itself. In contrast to the conventional structure which is held only on the side surface and all the holding force is directed from the outer periphery toward the central axis direction etc., the honeycomb structure to which the tapered holding structure is applied is the cell extending direction. The holding power is also dispersed in the (exhaust gas distribution direction). The structure is particularly suitable for a thin-walled honeycomb or the like that has low side strength and cannot be held only by the side.

  Catalytic converters formed by holding a ceramic honeycomb catalyst body in a can body (container) may loosen the grip due to severe vibrations of an automobile, and are usually made of stainless steel whose thermal expansion coefficient is 10 times that of ceramics. Since the container is formed, if the temperature rises during use, the container may expand more than the ceramic honeycomb structure, and the holding of the ceramic honeycomb structure may be loosened. As described above, in order to prevent the holding of the ceramic honeycomb structure from being loosened, the honeycomb structure and the can body are prevented so that the holding of the honeycomb structure does not move even when the container is thermally expanded. It is necessary to hold the ceramic honeycomb structure by applying a high pressure in advance to the elastic mat disposed between them. However, in the case of a ceramic honeycomb structure in which the thickness of the partition wall is less than 0.1 mm, when it is gripped at such a high pressure, it may be broken by the pressure. On the other hand, the strength of the ceramic honeycomb structure in the cell extending direction is 5 times or more the strength of the side surface (strength when a force is applied to the side surface in the direction of the central axis). When the cells near the outer periphery (near the side surfaces) are deformed, the strength of the side surfaces tends to decrease. However, the strength in the cell extending direction is hardly affected by such cell deformation. Thus, even in a ceramic honeycomb structure having low side strength, not only side holding (holding a force in a direction perpendicular to the cells) but also “the cell extending direction” (5 times or more higher than the side strength) ( By sharing a part of the holding force also in the direction parallel to the cell), it is possible to withstand severe vibrations of the automobile.

  In Patent Document 1, a ceramic cylinder (6) having a tapered side surface is arranged on the outer periphery (side surface) of a cylindrical ceramic honeycomb structure (the cross-sectional size and the cell size are uniform). An installed structure is disclosed. This is because the ceramic cylinder is a completely different part from the honeycomb structure, so the number of parts is increased and the cost is increased accordingly. In addition, even if the material of the ceramic cylinder is the same as that of the honeycomb structure, the thermal expansion coefficient of the ceramic cylinder is larger than the thermal expansion coefficient of the honeycomb structure. . In addition, the ceramic cylinder has a “solid” structure having a density higher than that of the honeycomb-shaped honeycomb structure, which increases the heat capacity, thereby deteriorating the purification performance. The thermal expansion coefficient of the ceramic honeycomb structure is small because when the ceramic honeycomb structure is extruded, the extrusion raw material containing ceramic passes through a narrow slit in the die for extrusion molding in a pressurized state. Since it is formed into a honeycomb shape while being discharged, the ceramic in the extruded raw material is oriented in a certain direction, thereby reducing the thermal expansion coefficient. Therefore, even when the ceramic raw material is the same, the partition wall formed by passing through such a narrow slit in a pressurized state and the cylindrical ceramic formed by other methods have different thermal expansion coefficients. It is. In addition, as a method of forming the ceramic cylinder, a method in which a ceramic cement that does not need to be fired and a part of the ceramic cement that is applied in a tapered shape can be considered, but it takes time to apply the ceramic cement and the cost increases. Conceivable. Furthermore, when the honeycomb structure is loaded with a catalyst and used for purification of exhaust gas, the temperature of the honeycomb structure may be 1000 ° C., but ceramic cement materials usually cannot withstand such high temperatures. Therefore, it is considered that the application range is limited.

  Patent Document 2 discloses a ceramic honeycomb structure in which the entire side surface is tapered by suppressing shrinkage of one end face and greatly shrinking the opposite end face in the drying process or firing process in the manufacturing process. ing. The honeycomb structure described in Patent Document 2 manufactured in this way has different outer diameters at one end surface and the other end surface, and further, the cell size is different between one end surface and the other end surface. It is. The partition wall and the outer peripheral wall are inclined with respect to the central axis direction. When manufacturing such a honeycomb structure, the honeycomb structure is actually soft at the time of extrusion molding, particularly as the partition wall thickness is reduced. Therefore, when the honeycomb structure having a taper shape as a whole is placed in a soft state after extrusion, it becomes a very unstable state, for example, when the pudding is opened in a dish, the upper part is in a free state. . In order to add a taper, it is necessary to have such a condition that it contracts more severely than usual. If drying is performed so hard that the taper is added in such a state, the deformation of the cross-sectional shape and the variation of the outer diameter become large, and as a result, the variation of the taper shape becomes large, and it becomes very difficult to obtain the set taper shape. . If the taper shape is not determined and the variation becomes large, the honeycomb structure and the can body are in point contact with each other through the mat, stress concentration occurs in the portion, and the honeycomb structure may be damaged. In addition, when it is soft immediately after extrusion molding, it can be dried in a state where it is forced along the mold, and a taper shape can be determined, but if it is forced along the mold, in reality, It is considered that there arises a problem that the partition walls in the outer peripheral portion of the honeycomb structure are deformed to cause a decrease in strength. Thus, the invention described in Patent Document 2 has a problem that a controlled taper shape that can be used industrially cannot be obtained.

  In Patent Document 3, a cylindrical outer cylinder partly formed in a tapered shape is fixed to the outer periphery (side surface) of a cylindrical honeycomb structure (the cross-sectional size and the cell size are uniform). The resulting structure is disclosed. This is because the outer cylinder is a part that is completely different from the honeycomb structure, so the number of parts is increased and the cost is increased accordingly. In addition, even if the material of the outer cylinder is the same as the material of the honeycomb structure, the thermal expansion coefficient of the outer cylinder is larger than the thermal expansion coefficient of the honeycomb structure. . In addition, the outer cylinder has a “solid” structure, which increases the heat capacity, thereby deteriorating the purification performance.

  The present invention has been made in view of such problems of the prior art, prevents displacement in the can when stored in the can, has an accurate taper shape, and has excellent purification performance, A honeycomb structure excellent in thermal shock resistance is provided.

  The following honeycomb structure is provided by the present invention.

[1] A plurality of cells serving as fluid flow paths and a plurality of cells serving as fluid flow paths and a cylindrical inner cylinder having porous partition walls mainly composed of ceramic. A porous substrate having a honeycomb shape having a porous partition wall mainly composed of ceramic and having an outer cylinder portion disposed so as to cover an outer periphery of the inner cylinder portion, at least of the outer cylinder portion A honeycomb structure having an end surface on one side that has a tapered shape in which an outer diameter decreases toward the tip.

[2] The honeycomb structure according to [1], wherein a tip end in a central axis direction of at least one of the tapered end surfaces of the outer cylindrical portion is in contact with the end surface of the inner cylindrical portion.

[3] The tip in the central axis direction of the tapered end face of the outer cylinder part is separated from the end face of the inner cylinder part, and a part of the outer periphery of the inner cylinder part is exposed. Honeycomb structure.

[4] The honeycomb structure according to any one of [1] to [3], wherein the inner cylinder portion has a boundary wall on an outer periphery thereof.

[5] In the above [4], the partition wall constituting the inner cylinder part and the boundary wall on the outer periphery thereof, and the partition wall constituting the outer cylinder part and the outer peripheral wall on the outer periphery thereof are integrally formed. The honeycomb structure described.

[6] The partition wall forming the inner cylinder part, the boundary wall on the outer periphery thereof, and the partition wall forming the outer cylinder part are integrally configured, and the outer peripheral wall on the outer periphery of the outer cylinder part is made of ceramic cement. The honeycomb structure according to [4], which is coated.

[7] Any of [1] to [6], wherein a shape of a cross section perpendicular to the central axis of the outer periphery of the inner cylinder portion and a shape of a cross section orthogonal to the central axis of the outer periphery of the outer cylinder portion are similar. A honeycomb structure according to any one of the above.

[8] In any one of [1] to [7], the size of a cross section perpendicular to the central axis of each cell formed on the porous substrate is the same from one end to the other end. The honeycomb structure described.

[9] The honeycomb structure according to any one of [1] to [8], wherein the inner cylinder part and the outer cylinder part have different cell densities and / or different partition wall thicknesses.

[10] The honeycomb structure according to [9], wherein the partition wall thickness of the outer cylinder part is thicker than the partition wall thickness of the inner cylinder part.

[11] An opening of a cell that opens to a tapered end face of the outer cylinder portion is closed by a sealing material mainly composed of ceramic, and at least the tapered shape is sealed by the sealing material. The honeycomb structure according to any one of [1] to [10], wherein the inside of the cell of the tapered portion whose outer periphery is the end face is filled.

[12] The honeycomb structure according to [11], wherein the sealing material is ceramic cement obtained by mixing cordierite fine powder with colloidal silica.

[13] The honeycomb structure according to [11], wherein the sealing material is a catalyst carrier mainly composed of γ-alumina.

[14] A honeycomb catalyst body comprising the honeycomb structure according to any one of [4] to [13] and a catalyst supported only on the inner side of the boundary wall and the inner cylinder portion of the honeycomb structure.

[15] The method for manufacturing a honeycomb structure according to [5], wherein the partition walls forming the inner cylinder portion and the boundary portion thereof, and the partition walls forming the outer cylinder portion and the outer peripheral wall on the outer periphery thereof are integrally formed. A method for manufacturing a honeycomb structure, comprising molding and firing, and then grinding a partition wall and an outer peripheral wall of the outer cylinder portion along the boundary wall from at least one end face.

  The honeycomb structure of the present invention has a tapered shape in which at least one end surface of the outer cylinder portion becomes smaller in outer diameter toward the tip, so that the gripping force is dispersed in the axial direction when stored in the can body, and the radial direction Pressure can be reduced, the tapered portion can be mechanically fixed, and can be prevented from shifting in the can. In addition, since the tapered portion can be formed by machining after firing, an accurate tapered shape can be formed. Further, since the outer tube portion is in a honeycomb shape and the heat capacity is small, the initial temperature rise during use is quick and the purification performance is excellent. In addition, since the inner cylinder part and the outer cylinder part are both honeycomb-shaped and formed by extrusion molding with the same ceramic raw material, the thermal expansion coefficient of the inner cylinder part and the outer cylinder part is the same, and the thermal shock resistance is improved. It is excellent.

1 is a plan view schematically showing an embodiment of a honeycomb structure of the present invention. 1 is a front view showing a partial cut surface, schematically showing an embodiment of a honeycomb structure of the present invention. It is a top view which shows typically other embodiment of the honeycomb structure of this invention. It is the front view showing the partial cut surface which shows other embodiment of the honeycomb structure of the present invention typically. FIG. 6 is a plan view schematically showing still another embodiment of the honeycomb structure of the present invention. FIG. 6 is a front view showing a partially cut surface, schematically showing still another embodiment of the honeycomb structure of the present invention. FIG. 6 is a plan view schematically showing still another embodiment of the honeycomb structure of the present invention. FIG. 6 is a front view showing a partially cut surface, schematically showing still another embodiment of the honeycomb structure of the present invention. FIG. 6 is a plan view schematically showing still another embodiment of the honeycomb structure of the present invention. FIG. 6 is a front view showing a partially cut surface, schematically showing still another embodiment of the honeycomb structure of the present invention. FIG. 6 is a front view showing a partially cut surface, schematically showing still another embodiment of the honeycomb structure of the present invention. FIG. 6 is a front view showing a partially cut surface, schematically showing still another embodiment of the honeycomb structure of the present invention. FIG. 3 is an enlarged plan view showing a part of an end face of an embodiment of a honeycomb structure of the present invention. FIG. 6 is an enlarged plan view showing a part of an end face of still another embodiment of the honeycomb structure of the present invention. FIG. 6 is a plan view schematically showing a conventional honeycomb structure. It is the front view showing the partial cut surface which shows the conventional honeycomb structure typically. FIG. 6 is a plan view schematically showing a conventional honeycomb structure. FIG. 6 is a front view schematically showing a conventional honeycomb structure.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings. However, the present invention is not limited to the following embodiments, and is within the scope of the present invention. It should be understood that design changes, improvements, and the like can be made as appropriate based on the general knowledge of vendors.

(1) Honeycomb structure:
(1-1) One embodiment of the honeycomb structure of the present invention;
In one embodiment of the honeycomb structure of the present invention, as shown in FIGS. 1A, 1B, and 8, a plurality of cells 3a penetrating from one end face 1a to the other end face 2a and serving as fluid flow paths are partitioned. A cylindrical inner cylinder portion 11 having a porous partition wall 4a mainly composed of ceramic and a plurality of cells 3b penetrating from one end face 1b to the other end face 2b and serving as a fluid flow path are formed. And having a porous partition wall 4b mainly composed of ceramic and having a honeycomb-shaped porous substrate 5 having an outer cylinder portion 21 disposed so as to cover the outer periphery 12 of the inner cylinder portion 11. In other words, the end surfaces on both sides of the outer cylinder portion 21 are tapered such that the outer diameter decreases toward the tip 22. As described above, the honeycomb structure 100 of the present embodiment has a tapered shape in which the outer end surfaces of the both sides of the outer cylinder portion 21 become narrower toward the distal end 22. The tapered portion can be fixed while applying a force in the direction of the central axis, and can be prevented from shifting in the can. In addition, since the tapered portion can be formed by machining after firing, an accurate tapered shape can be formed. In addition, the honeycomb structure 100 of the present embodiment has a small heat capacity because the outer cylinder portion 21 has a honeycomb shape and the cell 3b portion is hollow. Therefore, the initial temperature rise at the time of use is fast and the purification performance is excellent. Moreover, since both the inner cylinder part 11 and the outer cylinder part 21 are honeycomb-shaped and are integrally formed by extrusion molding with the same ceramic raw material, the thermal expansion coefficients of the inner cylinder part 11 and the outer cylinder part 21 are the same. It has excellent thermal shock resistance. FIG. 1A is a plan view schematically showing an embodiment of the honeycomb structure of the present invention. FIG. 1B is a front view showing a partially cut surface, schematically showing an embodiment of the honeycomb structure of the present invention. FIG. 8 is an enlarged plan view showing a part of the end face of the embodiment of the honeycomb structure of the present invention.

  In the honeycomb structure 100 of the present embodiment, the porous base material 5 has an inner cylinder portion 11 located on the inner side and an outer cylinder portion 21 disposed so as to surround the outer periphery of the inner cylinder portion 11. The outer cylinder part 21 should just be that the end surface of the one side is a taper shape.

  The taper angle of the outer tube portion 21 is preferably 30 to 90 °, and more preferably 45 to 60 °. If the angle is smaller than 30 °, the shared holding force in the cell extending direction becomes small, the effect of preventing displacement when the honeycomb structured body is stored in the can body is reduced, or the shared pressure on the side surface is increased and the honeycomb structured body becomes May destroy. If it is larger than 90 °, the outer cylinder may be chipped. The taper angle of the outer cylinder part 21 is an angle formed by the end surface of the outer cylinder part 21 and the outer periphery 12 of the inner cylinder part 11, and is the angle of the distal end portion of the outer cylinder part 21. Moreover, the front-end | tips 22 and 22 in the central-axis direction of the taper-shaped end surface (one end surface 1b, the other end surface 2b) of the outer cylinder part 21 are the end surfaces (one end surface 1a, the other end surface 2a) of the inner cylinder part 11. A part of the outer periphery 12 of the inner cylinder part 11 is exposed.

The partition 4b that forms the outer cylinder portion 21 is a linear one that is formed along a direction extending radially about the central axis of the porous substrate 5 in a cross section orthogonal to the central axis (cell extending direction). And a combination with a shape (circular) similar to the outer peripheral shape (circular) of the outer cylinder portion 21. By forming in this way, the cell shape of the outer cylinder portion becomes constant, the soil flow during molding becomes uniform, and stable molding becomes possible. Note that the extending direction of the partition walls 4b forming the outer cylinder portion 21 in the cross section orthogonal to the central axis (the cell extending direction) is not limited to this. The inner cylinder portion 11 and the outer cylinder portion 21 have different cell densities (cell densities in a cross section perpendicular to the central axis) and different partition wall thicknesses. More specifically, the cell density of the outer cylinder part 21 is lower than the cell density of the inner cylinder part 11, and the partition wall thickness of the outer cylinder part 21 is thicker than the partition wall thickness of the inner cylinder part 11. The partition wall thickness of the outer cylinder portion 21 is preferably 0.5 to 5.0 times, more preferably 1.0 to 3.0 times the partition wall thickness of the inner cylinder portion 11. By forming the partition wall thickness of the porous substrate 5 in this way, deformation of the partition walls when the honeycomb structure is formed can be prevented, and the strength against compression from the side surface of the honeycomb structure can be improved. . If the partition wall thickness of the outer cylinder part 21 is thinner than 0.5 times the partition wall thickness of the inner cylinder part 11, there is a concern that the absolute strength will be insufficient. There is a concern that the balance between the supply of soil and the supply of soil to the outer periphery deteriorates and cell deformation that causes a decrease in strength occurs. Moreover, 40-130 micrometers is preferable and, as for the partition wall thickness of the inner cylinder part 11, 50-90 micrometers is more preferable. When the thickness is less than 40 μm, there is a concern that the partition walls cannot be extruded well and the honeycomb structure is not formed. When the thickness is more than 130 μm, the performance may be deteriorated. 50-150 micrometers is preferable and, as for the partition wall thickness of the outer cylinder part 21, 70-130 micrometers is still more preferable. When the thickness is less than 50 μm, there is a concern that the partition wall cannot be pushed out well and cell deformation that causes a decrease in strength occurs. When the thickness is more than 150 μm, the mass increases and there is a concern that the performance may decrease. The cell densities of the inner cylinder part 11 and the outer cylinder part 21 may be the same or different. The cell density of the inner cylindrical portion 11 is preferably from 46.5 to 186 cells / cm ^2, more preferably from 46.5 to 140 cells / cm ^2. If it is smaller than 46.5 cells / cm ² , the purification performance may be lowered due to the small geometric surface area. If it is larger than 186 cells / cm ² , the pressure loss increases and the engine horsepower may decrease. is there. Cell density of the outer tube portion 21 is preferably from 31 to 140 cells / cm ^2, more preferably from 46.5 to 116 cells / cm ^2. If it is smaller than 31 cells / cm ² or larger than 140 cells / cm ^2, there is a concern that the cell density of the inner cylinder part 11 is too large and molding becomes unstable, and cell deformation that causes a decrease in strength occurs.

  2-15 mm is preferable and, as for the width | variety of the outer cylinder part 21, 3-10 mm is still more preferable. By forming in this way, it is possible to effectively prevent deviation when the honeycomb structure is stored in the can body.

The honeycomb structure of the present embodiment has a small coefficient of thermal expansion because the material is cordierite and the outer cylinder portion 21 has a honeycomb shape. In particular, the thermal expansion coefficient of the cordierite honeycomb structure produced by extrusion is very small. The reason is as follows. When unsintered kaolin is used as a raw material, hexagonal plate-shaped crystal kaolinite of unsintered kaolin is aligned in parallel with the partition walls when passing through a die for extrusion molding. When fired, hexagonal cordierite crystal lays along the kaolinite crystal (the central axis of the hexagonal cordierite crystal is parallel to the hexagonal crystal plane of the kaolinite crystal) Is generated. Therefore, the central axis of the hexagonal columnar cordierite crystal has an orientation in which the cell extending direction and the radial direction of the honeycomb structure are mixed. The thermal expansion coefficient of the hexagonal columnar cordierite crystal is “−1.1 × 10 ⁻⁶ ” in the axial direction of the hexagonal column and “+ 2.9 × 10 ⁻⁶ ” in the radial direction (right angle direction). Therefore, the thermal expansion coefficient of the entire honeycomb structure is 0.2 to 0.5 × 10 ⁻⁶ or less. This coefficient of thermal expansion is much lower than that of a honeycomb structure manufactured by another manufacturing method such as a honeycomb structure manufactured by a press manufacturing method. On the other hand, even if a ceramic cylinder having a thickness of about 3 mm for the outer periphery of a cylindrical honeycomb structure is produced by extrusion molding, the crystal orientation is very small. The thermal expansion coefficient is about five times that of the honeycomb structure (1.0 to 2.0 × 10 ⁻⁶ ), although it is related to the grain size of the honeycomb structure.

  The inner cylinder portion 11 has a boundary wall 13 on the outer periphery 12 thereof. In the vicinity of both end faces of the inner cylinder portion 11, the boundary wall 13 is exposed to the outside. Thus, since the inner cylinder part 11 has the boundary wall 13 on the outer periphery thereof, the partition wall 4a of the inner cylinder part is not exposed after grinding to form a tapered surface, so that the partition wall 4a is not lost. There is. The thickness of the boundary wall 13 is preferably 1 to 10 times, more preferably 2 to 6 times that of the partition wall 4a of the inner cylinder part. By setting the boundary wall 13 to such a thickness, there is an advantage that defects such as chipping are less likely to occur during grinding or subsequent handling. The shape of the cross section orthogonal to the central axis of the outer periphery 12 of the inner cylinder portion 11 and the shape of the cross section orthogonal to the central axis of the outer periphery of the outer cylinder portion 21 are similar.

  In the honeycomb structure 100 of the present embodiment, the porous substrate 5 preferably has an average pore diameter of the partition walls 4a and 4b of 0.5 to 10 μm, and more preferably 2 to 6 μm. If it is smaller than 0.5 μm, the catalyst carrier is hardly supported, and if it is larger than 10 μm, the mechanical strength may be lowered. The average pore diameter of the partition walls 4a and 4b is a value measured with a mercury porosimeter.

  The porosity of the partition walls 4a and 4b is preferably 20 to 45%, and more preferably 25 to 40% in terms of ease of manufacture. If it is less than 20%, it becomes difficult to support the catalyst carrier, and shrinkage during firing may increase, resulting in a large dimensional variation. If it exceeds 45%, the mechanical strength may decrease. The porosity of the partition walls 4a and 4b is a value measured by a mercury porosimeter.

  The shape of the cells 3a and 3b of the honeycomb structure 100 is not particularly limited, but is preferably a polygon such as a triangle, a quadrangle, a pentagon, a hexagon, a circle, or an ellipse in a cross section orthogonal to the central axis. It may be indefinite. Further, as shown in FIGS. 1A and 8, a pair of two opposite sides are formed in an arc shape like the shape of the cell 3b of the outer cylinder portion 21 of the honeycomb structure 100 of the present embodiment, and the other A pair of two opposing sides may be formed in a straight line. Moreover, it is preferable that the size of the cross section orthogonal to the central axis of each cell 3a, 3b formed in the porous substrate 5 is the same from one end face 1a, 1b to the other end face 2a, 2b. Thereby, there is an advantage that a stable product can be obtained.

  The porous substrate 5 (partition walls 4a, 4b) of the present embodiment is mainly composed of ceramic. Specific examples of the material for the partition 3 include ceramic, silicon carbide, cordierite, alumina titanate, sialon, mullite, silicon nitride, zirconium phosphate, zirconia, titania, alumina, silica, and LAS (lithium aluminum). (Silicate) or a combination thereof may be mentioned as a suitable example. In particular, ceramics such as silicon carbide, cordierite, mullite, silicon nitride, alumina, and alumina titanate are suitable in terms of alkali resistance. Among these, oxide-based ceramics are preferable in terms of cost. In addition, the phrase “having ceramic as a main component” means that 90% by mass or more of a ceramic crystal referred to is contained. The remainder can include other ceramic crystals or glasses.

  The size of the honeycomb structure 100 is not particularly limited, but the length in the central axis direction is preferably 50 to 500 mm. For example, when the outer peripheral shape in a cross section orthogonal to the central axis of the side surface portion of the outer cylinder portion 21 of the honeycomb structure 100 is a circle, the diameter is preferably 50 to 350 mm.

  The honeycomb structure 100 may have an outer peripheral wall 23 located on the side surface of the outer cylinder portion 21. The outer peripheral wall 23 is preferably a molded integral wall that is integrally formed with the porous base material during molding. However, after molding, the outer periphery of the porous base material is ground to a predetermined shape, and ceramic cement or the like is used. It is also a preferred embodiment that it is a cement-coated wall that forms the outer peripheral wall.

(1-2) Another embodiment of the honeycomb structure of the present invention (second embodiment);
As shown in FIGS. 2A and 2B, another embodiment of the honeycomb structure of the present invention is a partition wall of the outer cylinder portion 21 in the embodiment of the honeycomb structure of the present invention. 4b extends in the same direction as the direction in which the partition 4a of the inner cylinder portion 11 extends in a cross section orthogonal to the central axis. That is, the partition 4b of the outer cylinder part 21 has a partition extending in two orthogonal directions, like the partition 4a of the inner cylinder part 11. However, although the partition 4b of the outer cylinder part 21 and the partition 4a of the inner cylinder part 11 have a part connected continuously, there are also parts which are not connected continuously. Regarding other conditions of the honeycomb structure 101 of the present embodiment, the conditions that are preferable in the one embodiment of the honeycomb structure of the present invention are preferable. FIG. 2A is a plan view schematically showing another embodiment of the honeycomb structure of the present invention. FIG. 2B is a front view showing a partially cut surface, schematically showing another embodiment of the honeycomb structure of the present invention.

(1-3) Still another embodiment of the honeycomb structure of the present invention (third embodiment);
Still another embodiment of the honeycomb structure of the present invention (third embodiment) is an embodiment of the honeycomb structure of the present invention, as shown in FIGS. 3A and 3B. The partition 4b is formed so as to be continuously connected to the partition 4a of the inner cylinder portion 11 in a cross section orthogonal to the central axis. Since it comprised in this way, it is preferable at the point on cap production. Regarding the other conditions of the honeycomb structure 102 of the present embodiment, the conditions that are preferable in the one embodiment of the honeycomb structure of the present invention are preferable. FIG. 3A is a plan view schematically showing still another embodiment of the honeycomb structure of the present invention. FIG. 3B is a front view showing a partially cut surface, schematically showing still another embodiment of the honeycomb structure of the present invention.

(1-4) Still another embodiment of the honeycomb structure of the present invention (fourth embodiment);
Still another embodiment (fourth embodiment) of the honeycomb structure of the present invention is an inner cylinder in the “third embodiment” of the honeycomb structure of the present invention as shown in FIGS. 4A and 4B. The part 11 does not have the boundary wall 13 (refer FIG. 3A and FIG. 3B). Since it comprised in this way, it is preferable at the point which can utilize a general honeycomb structure as a base material. Regarding other conditions of the honeycomb structure 103 of the present embodiment, the conditions that are preferable in the “third embodiment” of the honeycomb structure of the present invention are preferable. FIG. 4A is a plan view schematically showing still another embodiment of the honeycomb structure of the present invention. FIG. 4B is a front view showing a partial cut surface, schematically showing still another embodiment of the honeycomb structure of the present invention.

(1-5) Still another embodiment of the honeycomb structure of the present invention (fifth embodiment);
Still another embodiment (fifth embodiment) of the honeycomb structure of the present invention is an outer cylinder in the “fourth embodiment” of the honeycomb structure of the present invention as shown in FIGS. 5A and 5B. The tips 22 and 22 in the center axis direction of both tapered end faces 1b and 2b in the tapered end faces 1b and 2b of the part 21 are in contact with the end faces (one end face) 1a and 1a of the inner cylinder part 11. Yes. When the "tip 22 in the central axis direction of the tapered end face (one end face 1a) of the outer cylinder part 21 is in contact with the end face (one end face 1a) of the inner cylinder part 11", the outer cylinder part 21 It means that the front-end | tip 22 and the outermost periphery 14 of the end surface (one end surface 1a) of the inner cylinder part 11 exist in the same position. Since the fifth embodiment is configured as described above, it is preferable in that the partition wall of the inner cylinder portion 11 is not exposed. Regarding other conditions of the honeycomb structure 104 of the present embodiment, the conditions that are preferable in the “fourth embodiment” of the honeycomb structure of the present invention are preferable. FIG. 5A is a plan view schematically showing still another embodiment of the honeycomb structure of the present invention. FIG. 5B is a front view showing a partially cut surface, schematically showing still another embodiment of the honeycomb structure of the present invention.

(1-6) Still another embodiment of the honeycomb structure of the present invention (sixth embodiment);
Still another embodiment of the honeycomb structure of the present invention (sixth embodiment) is a taper shape of the outer cylinder portion 21 in one embodiment of the honeycomb structure of the present invention as shown in FIG. The opening portion of the cell 3b that opens to the formed end surface 1b is closed by the sealing portion 24 mainly composed of ceramic, and the tapered portion 25 that has at least the tapered end surface 1b as the outer periphery is sealed by the sealing portion 24. The inside of the cell 3b is filled. The tapered portion 25 has a shape of only an inclined portion in which a cylindrical shape having an end surface on the side having a smaller area as a bottom surface is removed from the truncated cone. Since it comprised in this way, it is reinforced when the partition of an outer cylinder part is thin, and it is preferable at the point which can prevent a chipping at the time of handling. The sealing portion 24 is preferably filled deeply by 0 to 10 mm from the tapered portion 25, and more preferably deeply filled by 3 to 5 mm. If it is shallower than 0 mm, there is a concern of peeling, and if it is deeper than 10 mm, the construction takes time, or the mass becomes heavy and the purification performance may be deteriorated. The sealing portion 24 is preferably a ceramic cement. As the ceramic cement, colloidal silica mixed with cordierite fine particles or a catalyst carrier is preferable. The catalyst carrier is preferably one having γ-alumina as a main component. Regarding the other conditions of the honeycomb structure 105 of the present embodiment, the conditions that are preferable in the one embodiment of the honeycomb structure of the present invention are preferable. FIG. 6 is a front view showing a partially cut surface, schematically showing still another embodiment of the honeycomb structure of the present invention.

(1-7) Still another embodiment of the honeycomb structure of the present invention (seventh embodiment);
Still another embodiment of the honeycomb structure of the present invention (seventh embodiment) is an end face on one side of the outer cylinder portion 21 in one embodiment of the honeycomb structure of the present invention as shown in FIG. Only (one end face) 1b is tapered such that the outer diameter becomes narrower toward the tip 22. When the honeycomb structure of the present invention is mounted on an exhaust pipe of an engine and used as an exhaust gas purification device, exhaust gas from the engine is used by flowing from one end face. Therefore, the honeycomb structure receives pressure from the end surface on the exhaust gas inflow side (upstream side of the exhaust gas) and is pushed in the direction of the end surface on the opposite side (downstream side of the exhaust gas). Therefore, the honeycomb structure is easily displaced toward the downstream side of the exhaust gas. In particular, when the honeycomb structure is used directly under the engine, the cell extending direction is up and down, and the mass of the catalyst itself is gravity, and a downward force is applied. When used in such a state, even if only one end surface (one end surface) 1b of the outer cylinder portion 21 is tapered, the honeycomb structure is formed with the tapered end surface facing the downstream side of the exhaust gas. Is installed in the exhaust pipe, the effect of preventing the honeycomb structure from shifting can be exhibited. Regarding the other conditions of the honeycomb structure 106 of the present embodiment, the conditions that are preferable in the one embodiment of the honeycomb structure of the present invention are preferable. FIG. 7 is a front view showing a partially cut surface, schematically showing still another embodiment of the honeycomb structure of the present invention.

(1-8) Still another embodiment of the honeycomb structure of the present invention (eighth embodiment);
Still another embodiment (eighth embodiment) of the honeycomb structure of the present invention, as shown in FIG. 9, is a cross section perpendicular to the central axis in one embodiment of the honeycomb structure of the present invention. The partition 4a in the range of 5 to 10 cells from the outer periphery 12 of the inner cylinder part 11 to the inside is formed so as to gradually increase in thickness from the inside to the outside. Since it comprised in this way, even when the partition 4a is thin entirely, the deformation | transformation of the partition at the time of extrusion molding can be prevented. Regarding the other conditions of the honeycomb structure 107 of the present embodiment, the conditions that are preferable in the one embodiment of the honeycomb structure of the present invention are preferable. FIG. 9 is an enlarged plan view showing a part of an end face of still another embodiment of the honeycomb structure of the present invention.

  Each feature of the honeycomb structure of each of the above embodiments can be combined with another feature as long as there is no conflicting condition, and a honeycomb structure in which the features of each embodiment is combined may be used.

(2) Manufacturing method of honeycomb structure:
Next, a method for manufacturing an embodiment of the honeycomb structure of the present invention will be described.

  A cylindrical inner cylinder portion having a partition wall that partitions a plurality of cells that penetrate from one end face to the other end face to be a fluid flow path, and a fluid flow path that penetrates from one end face to the other end face A honeycomb formed body having partition walls that form a plurality of cells and having an outer cylinder portion arranged so as to cover the outer periphery of the inner cylinder portion is formed by extrusion molding. It is assumed that the obtained honeycomb formed body has a boundary wall formed on the outer periphery of the inner cylinder portion. The method for extruding the honeycomb formed body is not particularly limited.For example, the forming raw material is first kneaded to form a kneaded material, and the obtained kneaded material is formed into a honeycomb shape by extrusion forming to obtain a honeycomb formed body. preferable. There is no particular limitation on the method of kneading the forming raw material to form the kneaded material, for example, a method using a kneader, a vacuum clay kneader, or a method using a mixed molding machine in which two machines are integrated. Can do. Extrusion molding is preferably performed using a die having a desired cell shape, partition wall thickness, and cell density. As the material of the die, a cemented carbide which does not easily wear is preferable.

  The forming raw material is obtained by adding a dispersion medium and an additive to a ceramic raw material, and examples of the additive include an organic binder, an inorganic binder, a pore former, and a surfactant. As the forming raw material, it is preferable that the material for the partition walls mentioned in the embodiment of the honeycomb structure of the present invention is formed by firing.

  By adjusting the particle size and blending amount of the ceramic raw material to be used and the particle size and blending amount of the pore former to be added and optimizing the firing conditions, a porous substrate having a desired porosity and average pore size can be obtained. Can be obtained.

  After the above forming, the obtained honeycomb formed body may be dried. The drying method is not particularly limited, and examples thereof include hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying and the like. Among them, dielectric drying, microwave drying or It is preferable to perform hot air drying alone or in combination. The drying conditions are preferably a drying temperature of 30 to 150 ° C. and a drying time of 1 minute to 2 hours.

  Both end surfaces of the outer cylinder portion of the honeycomb formed body are tapered, and both end surfaces of the outer cylinder portion are tapered. The taper processing may be performed after firing the honeycomb formed body. Since baking distortion can be avoided after baking, an accurate taper can be obtained, which is more preferable. Although a method of pressing the mold in a soft state immediately after extrusion molding may be considered, in reality, a cell near the processed portion is deformed and mechanical strength is lowered, which is not practical. As a method for tapering the vicinity of the outer periphery of the end of the honeycomb formed body (end surface of the outer cylinder), a grindstone coated with diamond having a predetermined taper shape is pressed while rotating the honeycomb formed body after drying. A hitting method is preferred. Thereby, taper processing can be performed easily and quickly in about 10 seconds. In addition, when a ceramic cylinder is formed on the outer periphery of a cylindrical honeycomb molded body, it takes about 1 minute to apply thickly, and drying takes about 2 hours at a temperature of about 100 ° C. It takes a lot. In one embodiment of the honeycomb structure of the present invention, since the inner cylinder portion has a boundary wall on the outer periphery thereof, the inner cylinder portion and the outer cylinder portion can be distinguished when the honeycomb molded body is extruded. For example, in the case of still another embodiment (fourth embodiment) of the honeycomb structure of the present invention shown in FIGS. 4A and 4B, there is no boundary wall, so that the inner cylinder is formed when the honeycomb formed body is extruded. It is in a state where the distinction between the part and the outer cylinder part cannot be made. In this case, after forming a predetermined taper structure by taper processing, a portion having an end surface formed in a taper shape becomes an outer cylinder portion. The same applies to the processing of the fired product.

  Next, a honeycomb formed body having an outer tube portion having both end faces tapered is fired to obtain a honeycomb structure. The firing conditions (temperature, time) vary depending on the type of molding raw material and desired characteristics, and therefore, appropriate conditions may be selected according to the type.

(3) Honeycomb catalyst body:
An embodiment of the honeycomb catalyst body of the present invention includes the above-described honeycomb structure of the present invention and a catalyst supported only on the inner cylinder portion of the honeycomb structure of the present invention. When the honeycomb catalyst body of the present embodiment is housed (canned) in a can body, the tapered end face of the outer cylinder portion is closed by a mat for holding the honeycomb structure, and exhaust gas flows. Therefore, it is preferable not to carry a catalyst. It is preferable that the catalyst is supported on the partition wall surface and / or the pores of the partition wall in the cell of the inner cylinder part.

  As a manufacturing method of the honeycomb catalyst body of the present embodiment, the above-described honeycomb structure of the present invention is manufactured, and the catalyst is supported in the cells of the inner cylinder portion of the obtained honeycomb structure to obtain the honeycomb catalyst body. It is preferable. The catalyst loading method can be the same as a general catalyst loading method on the honeycomb structure. Specifically, the outer periphery 12 of the inner cylinder part 11 of the honeycomb structure is sealed with a resin packing and a film so that the catalyst liquid does not flow into the outer cylinder part, and then from the end face on the sealed side A method of supporting the catalyst by pouring the catalyst solution into the cell of the inner cylinder part can be mentioned. Further, as another method, the opposite end surface of the honeycomb structure, which is sealed on the outer periphery 12 of the inner cylinder portion 11, is immersed in several millimeters of catalyst solution, and the opposite end surface (inner cylinder portion) is in that state. 11 is a method in which the catalyst liquid is sucked into the cells of the inner cylinder portion by carrying out pressure reduction from the end surface of the outer peripheral surface 12 of the inner cylinder 12 and the catalyst is supported on the partition walls in the cells of the inner cylinder portion. It is done.

  It is preferable to blow off the surplus slurry with compressed air after the catalyst liquid is allowed to flow into the cell of the inner cylinder portion. Thereafter, the catalyst is preferably dried and baked to obtain a honeycomb catalyst body in which the catalyst is coated (supported) on the surface of the partition walls in the cell.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1
The cordierite-forming raw material from which cordierite is obtained by firing is kneaded with water and binder while vacuum degassing, and is extruded from one end face to the other end face by extrusion molding using a prescribed die. A honeycomb formed body having partition walls that partition and form a plurality of cells serving as fluid flow paths was obtained. The obtained honeycomb formed body had a structure having an inner cylinder part and an outer cylinder part covering the outer periphery thereof, and had a boundary wall on the outer periphery of the inner cylinder part. Moreover, the partition of the inner cylinder part was formed in uniform thickness (refer FIG. 8) in the cross section orthogonal to a central axis.

  Next, the honeycomb fired body was dried and fired to obtain a honeycomb fired body. The end surface of the outer cylinder part of the obtained honeycomb fired body was tapered to obtain a honeycomb structure as shown in FIGS. 1A and 1B (Example 1). As a method of tapering the end face of the outer cylinder portion of the honeycomb fired body, the outer cylinder of the honeycomb fired body is rotated at an angle of 45 ° with respect to the cell extending direction while rotating the honeycomb fired body with a diamond-coated grindstone. By pressing against the outer peripheral portion of the end face of the part, a taper-shaped end face (end face of the outer cylinder part) having an angle of 45 ° was obtained.

In the obtained honeycomb structure, the outer diameter (diameter) of the side surface portion of the outer cylinder portion is 114 mm, the outer diameter (diameter) of the inner cylinder portion is 106 mm, and the length in the central axis direction of the inner cylinder portion is: It was 114.3 mm. Moreover, the length of the central axis direction of the part which the outer periphery (boundary wall) of the inner cylinder part exposed was 5 mm. Moreover, the partition wall thickness of the inner cylinder part was 0.09 mm, and the cell density was 62 cells / cm ² . Moreover, the partition wall thickness of the outer cylinder part was 0.13 mm, and the cell density was 46.5 cells / cm ² . The mass of the honeycomb structure was 293 g. About the obtained honeycomb structure, “thermal shock resistance” and “purification performance” were measured by the following methods, and a “heating vibration test” was performed. The results are shown in Table 1.

In Table 1, the columns of “shape” and “partition shape” show the shape of the manufactured honeycomb structure with reference to each drawing. For example, in Example 6, the shapes “FIG. 1A, FIG. 1B” and the partition wall shape “FIG. 9” are shown, but this is the honeycomb structure 100 shown in FIG. 1A, FIG. As shown in FIG. 9, the partition walls in the range of 5 cells are formed so as to gradually become thicker from the inside toward the outside. 10A and 10B, the outer structure of the honeycomb structure 110 shown in FIGS. 10A and 10B is not a honeycomb structure. In this case, the partition wall shape “FIG. 9” is the inner side from the outer periphery of the honeycomb structure. As shown in FIG. 9, the partition walls in the range of 5 cells are formed so as to gradually become thicker from the inside toward the outside (the honeycomb structure 107 shown in FIG. 9). The outer cylinder part is solid, leaving the boundary wall. Further, Comparative Example 4 will be described. The honeycomb structure 111 shown in FIGS. 11A and 11B does not have a structure in which the honeycomb structure has an outer cylinder portion. In this case, the partition wall shape “FIG. As shown in FIG. 9, partition walls in the range of 5 cells from the outer periphery to the inside of the structure are formed so as to gradually increase in thickness from the inside to the outside (the honeycomb structure 107 shown in FIG. 9). The state where the outer cylinder part was removed leaving the boundary wall. The column “inner cylinder cell structure” indicates “partition wall thickness (mm) / cell density (pieces / cm ² )”. For example, “0.09 / 62” in Example 1 indicates that the partition wall thickness is 0.09 (mm) and the cell density is 62 (pieces / cm ² ). The “outer cylinder part cell structure” is the same as the “inner cylinder part cell structure”. The column “mass (g)” indicates the mass of the honeycomb structure.

(Heat shock resistance)
The thermal shock resistance test is performed according to the procedure specified in “JASO M505-87 Section 6.7”. A room temperature sample is placed in an electric furnace maintained at a predetermined temperature and held for 20 minutes. Remove the sample and place it on a refractory brick and cool to room temperature “observing for cracks”. It should be noted that cooling the sample while observing the presence or absence of cracks is not specified in “JASO M505-87 Section 6.7”, but is an operation specific to this “thermal shock resistance test”. Thermal shock resistance is the maximum temperature difference where there is no crack when observing the appearance of the sample, and when the entire circumference is tapped with a metal rod (iron rod with a diameter of about 1 to 3 mm), the hitting sound is a metal sound. (Temperature difference from room temperature: “electric furnace temperature−room temperature”). When a crack occurs or the hitting sound is not a metallic sound, it is assumed that it is “abnormal”. The sample is a honeycomb structure with no catalyst. The initial predetermined temperature is “600 ° C. + room temperature”. If there is no abnormality, the temperature of the electric furnace is increased by 50 ° C., and the temperature is increased by 50 ° C. until an abnormality occurs. The test was repeated. Five honeycomb structures were tested, and the average value of the temperature one step lower than the temperature at which the abnormality was recognized (a temperature lower by 50 ° C. than the temperature at which the abnormality was recognized) was taken as the result of the thermal shock resistance test. Table 1 shows the “maximum temperature difference”. The maximum temperature difference is preferably not lower than Comparative Example 2 or Comparative Example 4 by 50 ° C. or more.

(Purification performance)
In US federal test method LA-4 mode, the purification performance is evaluated under the following conditions. Vehicle “exhaust capacity: 2300 cm ³ 1998 model, US ULEV specification vehicle”, honeycomb structure (converter) mounting position “under the floor”, honeycomb structure size “outermost circumference diameter: φ114 mm, inner circumference wall diameter: φ106 mm”, catalyst “Pd (Palladium) 300 g / ft ³ ”and catalytic heat treatment“ (electric furnace 980 ° C. × 10 hours) + (vehicle 80 km / hour × 2 hours) ”. The measurement was performed twice, and the average value of the two measurements was taken as the evaluation result. Table 1 shows the results (g / mile) of HC (hydrocarbon).

(Heating vibration test)
An unexpanded mat made of ceramic fibers is stored in a wound can body in a honeycomb structure. The can body has an inner diameter that is a size obtained by adding the mat thickness that provides the desired pressure to the outer diameter of the outer cylinder portion of the honeycomb structure, and one end portion remains straight and the other end portion has a honeycomb. The tapered portion has the same angle as the end surface of the outer cylinder portion of the structure, and the tip of the tapered portion has a cone shape so as to have the same outer diameter as the exhaust pipe. Then, a honeycomb structure wound with a mat is inserted from the straight end portion side of the can body, and the taper portion of the honeycomb structure hits the can body taper portion and is pushed in until the mat reaches a predetermined pressure. The straight side of the can has a flange, and a “lid” is attached to the flange. The “lid” starts from a flange connected to the can body, has a tapered portion having the same shape as the tapered shape of the can body, a cone portion at the tip, and is connected to a pipe to which a high temperature gas is supplied at the tip. With a flange. The lid is pressed against the can body, and the flanges are tightened with bolts to prevent gas from leaking between the can body and the lid. The taper of the lid has a positional relationship that matches the taper of the honeycomb structure when the flanges are combined. Since Comparative Examples 2 and 4 failed at a pressure of 0.2 MPa, they were tested even when the pressure was increased to 0.5 MPa. In this state, vibration is applied from the vibration tester for 100 hours while repeating a cycle of flowing a high-temperature gas combusted with propane gas for 5 minutes and then flowing air at room temperature for 5 minutes to the cells of the honeycomb structure. The temperature of the hot gas is 900 ° C. The vibration condition is “acceleration: 30 G, frequency: 200 Hz”. After the test, when the honeycomb structure was displaced by 2 mm or more in the can, the honeycomb structure was rejected. When the displacement was less than 2 mm, the honeycomb structure was accepted. As the pass / fail judgment of the heating vibration test, two honeycomb structures were tested, and when both passed, the pass “◯” was given, and when there was at least one pass, the reject “X” was given.

(Examples 2-11, Comparative Examples 1-4)
Except for changing “shape”, “partition shape”, “inner cylinder cell structure”, “outer cylinder cell structure” and “mass” as shown in Table 1, the same as in the case of Example 1 above. A honeycomb structure was produced. About the obtained honeycomb structure, in the same manner as in Example 1, “thermal shock resistance” and “purification performance” were measured by the above method, and a “heating vibration test” was performed. The results are shown in Table 1.

  The honeycomb structures of Comparative Example 1 and Comparative Example 3 have ceramic cylinders 32 formed by applying ceramic cement in which colloidal silica is mixed with cordierite fine particles to the outer periphery of a cylindrical porous substrate 31. It was arranged. The ceramic cylinder 32 was not formed in a honeycomb shape, but was simply formed by coating ceramic cement. Both end portions of the ceramic cylinder 32 are formed in a tapered shape, and the taper angle is set to 45 ° with respect to the central axis direction. Further, although the honeycomb structure of Comparative Example 3 does not have a boundary wall, since the outer peripheral wall of the porous base material has the same positional relationship as the boundary wall, the column of the boundary wall of Comparative Example 3 in Table 1 is “ Yes "is displayed. In the honeycomb structure 110, the outer diameter (diameter) of the side surface portion of the ceramic cylinder 32 is 114 mm, the outer diameter (diameter) of the porous substrate 31 is 106 mm, and the length of the porous substrate 31 in the central axis direction is Was 114.3 mm. Further, the length in the central axis direction of the portion where the outer periphery of the porous substrate 31 was exposed was 5 mm. FIG. 10A is a plan view schematically showing a conventional honeycomb structure having a tapered portion. FIG. 10B is a front view showing a partial cut surface, schematically showing a honeycomb structure having a conventional tapered portion.

  Further, the honeycomb structure 111 shown in FIGS. 11A and 11B is a honeycomb structure 111 made of a cylindrical porous substrate 33. The honeycomb structure 111 had a length in the central axis direction of 114.3 mm and an outer diameter of 106 mm. FIG. 11A is a plan view schematically showing a conventional honeycomb structure. FIG. 11B is a front view schematically showing a conventional honeycomb structure.

From Table 1, it can be seen that the honeycomb structures of Examples 1 to 11 are excellent in thermal shock resistance and purification performance, and the results of the heating vibration test are also good. Regarding the thermal shock resistance, the honeycomb structures of Comparative Examples 1 and 3 were lower by about 100 to 140 ° C. (about 15%) than the honeycomb structures of Examples 1 to 11. This is an effect of the ceramic cylinder. As a result of comparative investigation of the thermal expansion coefficient, which is a measure of thermal shock resistance, between the outer tube portion of the honeycomb structure of Example 1 and the ceramic tube of Comparative Example 1, “Comparative Example 1” is 1.7 × 10 ⁻ Whereas it was ⁶ / ° C., “Example 1” was 0.3 × 10 ⁻⁶ / ° C., and Example 1 was about one-fifth of Comparative Example 1. When the thermal expansion coefficient of the ceramic cylinder is high, the expansion of the ceramic cylinder is large in the process in which air at normal temperature is introduced into the catalyst that has been heated as a whole. The honeycomb structure breaks due to the difference.

  In the heating vibration test, the honeycomb structure of Comparative Example 2 and the honeycomb structure of Comparative Example 4 failed at the same canning pressure of 0.2 MPa as the honeycomb structures of Examples 1 to 11. These normal canning structures do not pass unless the pressure is increased to 0.5 MPa.

  Further, in terms of the purification performance, the honeycomb structure of Comparative Example 1 was 0.064 (g / mile) with respect to the average value of 0.053 (g / mile) of the honeycomb structures of Examples 1 to 5. The honeycomb structure of Comparative Example 1 is 21% worse than the honeycomb structures of 1 to 5. Moreover, the honeycomb structure of Comparative Example 3 was 0.057 (g / mile) against the average value 0.045 (g / mile) of the honeycomb structures of Examples 6 to 10, and The honeycomb structure of Comparative Example 3 is 27% worse than the honeycomb structure. Since the mass of the honeycomb structures of Comparative Examples 1 and 3 is larger than the mass of the honeycomb structures of Examples 1 to 5 and Examples 6 to 10 because the mass of the ceramic cylinder is large, 3 is considered to have poor purification performance. That is, if the mass is large, the heat capacity increases, and therefore, the honeycomb structures of Comparative Examples 1 and 3 are considered to have deteriorated the purification performance due to the slow temperature rise. In addition, although the honeycomb structure of Example 11 was partially filled with ceramic cement in the outer cylinder portion and the taper portion was reinforced, the increase in mass was as small as 32 g (12%). The results were not different from the honeycomb structures of Examples 6 to 10.

  From Table 1, the honeycomb structures (Comparative Examples 1 and 3) provided with the taper portion of the ceramic cylinder have a reduced thermal shock resistance, whereas the honeycomb structures of Examples 1 to 11 have a normal ceramic honeycomb structure. Thermal shock resistance equivalent to that of the body (Comparative Examples 2 and 4) is obtained, the purification performance is not deteriorated, and it can be used with a lower canning pressure than the normal ceramic honeycomb structure (Comparative Examples 2 and 4). More). This makes it possible to use an ultra-thin wall ceramic honeycomb structure that has higher performance but lower strength without increasing the number of parts.

  The honeycomb structure of the present invention is suitably used as a base of a catalyst used for exhaust gas purification.

1a, 1b: One end face, 2a, 2b: The other end face, 3a, 3b: Cell, 4a, 4b: Partition, 5: Porous base material, 11: Inner cylinder part, 12: Outer circumference of inner cylinder part, 13 : Boundary wall, 14: outermost periphery of end face, 21: outer cylinder part, 22: tip, 23: outer peripheral wall, 24: sealing part, 25: taper part, 31, 33: porous substrate, 32: ceramic cylinder , 100, 101, 102, 103, 104, 105, 106, 107, 110, 111: honeycomb structure.

Claims (15)

A cylindrical inner tube portion having a porous partition wall mainly composed of ceramic, which partitions and forms a plurality of cells serving as fluid flow paths;
A honeycomb-shaped partition having a plurality of cells that serve as fluid flow paths, a porous partition wall mainly composed of ceramic, and an outer tube portion disposed so as to cover the outer periphery of the inner tube portion With a porous substrate,
A honeycomb structure in which at least one end surface of the outer tube portion has a tapered shape in which an outer diameter becomes narrower toward a tip.   2. The honeycomb structure according to claim 1, wherein a tip end of at least one tapered end face in the tapered end face of the outer cylinder portion in the central axis direction is in contact with the end face of the inner cylinder portion.   The honeycomb structure according to claim 1, wherein a tip end of the tapered end surface of the outer cylindrical portion in a central axis direction is separated from an end surface of the inner cylindrical portion, and a part of an outer periphery of the inner cylindrical portion is exposed. body.   The honeycomb structure according to any one of claims 1 to 3, wherein the inner cylinder portion has a boundary wall on an outer periphery thereof.   The honeycomb according to claim 4, wherein the partition wall constituting the inner cylinder part, a boundary wall on the outer periphery thereof, and the partition wall constituting the outer cylinder part and an outer peripheral wall on the outer periphery thereof are integrally formed. Structure.   The partition wall forming the inner cylinder part, the boundary wall on the outer periphery thereof, and the partition wall forming the outer cylinder part are integrally formed, and the outer peripheral wall on the outer periphery of the outer cylinder part is coated with ceramic cement. The honeycomb structure according to claim 4.   The honeycomb according to any one of claims 1 to 6, wherein a shape of a cross section perpendicular to the central axis of the outer periphery of the inner cylindrical portion and a shape of a cross section orthogonal to the central axis of the outer periphery of the outer cylindrical portion are similar. Structure.   The honeycomb structure according to any one of claims 1 to 7, wherein a size of a cross section perpendicular to a central axis of each cell formed on the porous substrate is the same from one end to the other end. .   The honeycomb structure according to any one of claims 1 to 8, wherein the inner cylinder part and the outer cylinder part have different cell densities and / or different partition wall thicknesses.   The honeycomb structure according to claim 9, wherein a partition wall thickness of the outer cylinder part is larger than a partition wall thickness of the inner cylinder part.   The opening of the cell that opens to the tapered end surface of the outer cylinder is closed by a sealing material mainly composed of ceramic, and at least the tapered end surface is surrounded by the sealing material. The honeycomb structure according to any one of claims 1 to 10, wherein the inside of the cell of the tapered portion is filled.   The honeycomb structure according to claim 11, wherein the sealing material is ceramic cement obtained by mixing cordierite fine powder with colloidal silica.   The honeycomb structure according to claim 11, wherein the sealing material is a catalyst carrier mainly composed of γ-alumina.   A honeycomb catalyst body comprising: the honeycomb structure according to any one of claims 4 to 13; and a catalyst supported only on the inside of the boundary wall of the honeycomb structure and the inner cylinder portion.   The method for manufacturing a honeycomb structured body according to claim 5, wherein the partition wall constituting the inner cylinder part and its boundary part, the partition wall constituting the outer cylinder part and the outer peripheral wall on the outer periphery thereof are integrally formed, A method for manufacturing a honeycomb structured body, wherein after the firing, the partition walls constituting the outer cylinder portion and the outer peripheral wall thereof are ground along the boundary wall from at least one end face.

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