WO2020075604A1

WO2020075604A1 - Honeycomb structure

Info

Publication number: WO2020075604A1
Application number: PCT/JP2019/039039
Authority: WO
Inventors: 孝浩伊藤
Original assignee: イビデン株式会社
Priority date: 2018-10-12
Filing date: 2019-10-03
Publication date: 2020-04-16
Also published as: JP2020059011A

Abstract

The purpose of this invention is to provide a honeycomb structure having a structure that is less susceptible to damage. This honeycomb structure is a columnar honeycomb structure comprising: porous cell walls that define the plurality of cells which constitute the flowpath for exhaust gas; exhaust gas introduction cells having the exhaust gas inlet-side end surface being open and the exhaust gas outlet-side end surface being closed; and exhaust gas discharge cells having the exhaust gas outlet-side end surface being open and the exhaust gas inlet-side end surface being closed; the honeycomb structure being characterized in that the exhaust gas introduction cells and the exhaust gas discharge cells comprise an inner region having a cross-sectional shape perpendicular to the longitudinal direction of the exhaust gas introduction cells and the exhaust gas discharge cells which is constant, and an end region having a cross-sectional shape perpendicular to the longitudinal direction of the exhaust gas introduction cells and the exhaust gas discharge cells which becomes larger or smaller approaching the end surface, the exhaust gas outlet-side end surface has recesses and protrusions thereupon, and the standard deviation of the length from a virtual plane which touches the exhaust gas intake-side end surface on the of the honeycomb structure to the exhaust gas outlet-side end surface is at least 0.2.

Description

Honeycomb structure

The present invention relates to a honeycomb structure.

The exhaust gas discharged from an internal combustion engine such as a gasoline engine or a diesel engine contains particulates such as soot (hereinafter, also referred to as PM), and in recent years, this PM may be harmful to the environment or the human body. It's a problem. Moreover, since harmful gas components such as CO, HC or NOx are also contained in the exhaust gas, there is concern about the effect of these harmful gas components on the environment or the human body.

Therefore, titanic acid is used as an exhaust gas purifying apparatus for collecting PM in exhaust gas by connecting with an internal combustion engine and purifying harmful gas components such as CO, HC or NOx contained in the exhaust gas. Various honeycomb structures made of porous ceramics such as aluminum, cordierite, and silicon carbide have been proposed.

Further, in these honeycomb filters, in order to improve fuel efficiency of an internal combustion engine and eliminate troubles during operation due to an increase in pressure loss, various filters having a honeycomb structure with low pressure loss have been proposed.

Patent Document 1 has a plurality of first flow paths that are open at one end surface and closed at the other end surface, and a plurality of second flow paths that are closed at the one end surface and open at the other end surface. A central partition wall in which the cross-sectional area of each of the first flow paths and the second flow path is constant in the axial direction, and a cross-sectional area of each of the first flow paths from the central partition wall toward the other end surface. A honeycomb structure including: the other end side inclined partition wall, which is reduced and has a larger cross-sectional area of each of the second flow paths, wherein the other end side inclined partition wall has an axial length of 4 mm or more. A honeycomb structure is disclosed.

Republished 2016-098835

In Patent Document 1, the other end surface of the other end side inclined partition wall is flat. Therefore, in the first flow path on the other end surface side, the locations where the PM is most accumulated are aligned. Further, the collected PM will be burned. In the honeycomb structure described in Patent Document 1, since the positions where the PM is most deposited are aligned, the portions are rapidly heated at once as the PM is burned. As described above, when the material is rapidly heated at one time, the stress generated by the heating cannot be dispersed, which causes a problem that the honeycomb structure is damaged.

The present invention has been made in view of such problems, and an object of the present invention is to provide a honeycomb structure having a structure in which breakage hardly occurs.

In the honeycomb structure of the present invention, an exhaust gas introduction cell in which a porous cell partition wall for partitioning and forming a plurality of cells to be a channel of exhaust gas, an end surface on the exhaust gas inlet side is opened, and an end surface on the exhaust gas outlet side is closed And a columnar honeycomb structure having an exhaust gas discharge cell in which an end face on the exhaust gas outlet side is opened and an end face on the exhaust gas inlet side is sealed, wherein the exhaust gas introducing cell and the exhaust gas discharging cell are the exhaust gas An internal region in which the cross-sectional shape perpendicular to the longitudinal direction of the introduction cell and the exhaust gas discharge cell is constant, and the cross-sectional shape perpendicular to the longitudinal direction of the exhaust gas introduction cell and the exhaust gas discharge cell is enlarged or reduced as it approaches the end surface. The end surface on the exhaust gas outlet side has unevenness, and the exhaust gas outlet side from the virtual plane in contact with the exhaust gas inlet side end surface of the honeycomb structure. The standard deviation of the length to the end face, characterized in that at least 0.2.

In the honeycomb structure of the present invention, the standard deviation of the length from the virtual plane in contact with the end face on the exhaust gas inlet side of the honeycomb structure to the end face on the exhaust gas outlet side is 0.2 or more. That is, the end surface of the honeycomb structure on the exhaust gas outlet side is not located in the same plane and varies. Therefore, the position in the longitudinal direction of the honeycomb structure in which PM burns also varies.
If the positions where the PM burns vary, the positions in the longitudinal direction that are heated can be dispersed, so that the concentration of stress that occurs when burning the PM can be suppressed.
Therefore, the honeycomb structure of the present invention is less likely to be damaged.

In the honeycomb structure of the present invention, it is desirable that the standard deviation of the length from the virtual plane in contact with the end surface on the exhaust gas inlet side of the honeycomb structure to the end surface on the exhaust gas outlet side is 0.5 or less.
With such a range, breakage can be preferably prevented in the honeycomb structure.
When the standard deviation of the length from the virtual plane in contact with the end face on the exhaust gas inlet side of the honeycomb structure to the end face on the exhaust gas outlet side exceeds 0.5, when the end face on the exhaust gas outlet side is placed downward during manufacturing, The end face may be damaged.

In the honeycomb structure of the present invention, it is desirable that the exhaust gas introduction cell and the exhaust gas discharge cell in the end region have a length in the longitudinal direction of 1 to 10 mm.
In the honeycomb structure of the present invention, when the length of the exhaust gas introduction cell and the exhaust gas discharge cell in the end region in the longitudinal direction is 1 to 10 mm, the resistance at which the exhaust gas is introduced into the cell on the exhaust gas inlet side, Further, at the exhaust gas outlet side, the resistance of exhaust gas discharged from the inside of the cell can be further reduced, so that the pressure loss can be further reduced.

In the honeycomb structure of the present invention, when the length of the exhaust gas introduction cell and the exhaust gas discharge cell in the end region in the longitudinal direction is less than 1 mm, the resistance at the time of introducing the exhaust gas into the cell on the exhaust gas inlet side Of the exhaust gas on the exhaust gas outlet side, the resistance when exhaust gas is exhausted increases, so that the pressure loss cannot be reduced sufficiently, while the exhaust gas introduction cell and the exhaust gas exhaust cell in the end region have a long length in the longitudinal direction. However, if it exceeds 10 mm, it becomes difficult to manufacture a honeycomb structure having such a structure.

In the honeycomb structure of the present invention, the thickness of the cell partition wall on the end face is preferably 0.1 to 0.5 mm.
In the honeycomb structure of the present invention, when the thickness of the cell partition wall on the end face is 0.1 to 0.5 mm, the thickness of the cell partition wall can be sufficiently reduced without lowering the compressive strength. Therefore, the pressure loss can be sufficiently reduced.
When measuring the thickness of the cell partition wall on the end face, the measurement position is the central region of each cell on the end face.

In the honeycomb structure of the present invention, if the thickness of the cell partition wall on the end face is less than 0.1 mm, the thickness of the cell partition wall becomes too thin, resulting in a decrease in compressive strength. On the other hand, when the thickness of the cell partition wall exceeds 0.5 mm, the thickness of the cell partition wall is too thick, and it becomes difficult to sufficiently reduce the pressure loss.

In the honeycomb structure of the present invention, it is desirable that the exhaust gas introduction cells and the exhaust gas discharge cells in the above-mentioned internal region have a rectangular cross-sectional shape in the longitudinal direction.
In the honeycomb structure of the present invention, the cross-sectional shape perpendicular to the longitudinal direction of the exhaust gas introduction cells and the exhaust gas discharge cells in the internal region is a quadrangle, when manufacturing the honeycomb structure, in the end region, of the cells A cross-sectional shape perpendicular to the longitudinal direction can be easily expanded or reduced as it approaches the end face, and a honeycomb structure with sufficiently low pressure loss can be realized.

In the honeycomb structure of the present invention, it is desirable that the honeycomb structure is made of one honeycomb fired body having an outer peripheral wall on the outer periphery.
In the honeycomb structure of the present invention, as compared with the honeycomb structure in which a large number of honeycomb segments are combined by using an adhesive, the opening ratio at the end face can be increased due to the absence of the adhesive layer, so that the pressure loss reducing effect is further improved. Can be demonstrated.

In the honeycomb structure of the present invention, the honeycomb fired body is preferably made of cordierite or aluminum titanate.
In the honeycomb structure of the present invention, when the honeycomb fired body is made of cordierite or aluminum titanate, since the ceramic is a material having a low coefficient of thermal expansion, when large thermal stress occurs during regeneration or the like. Even in this case, the honeycomb structure is resistant to cracks.

In the honeycomb structure of the present invention, it is desirable that the cell partition walls have a porosity of 35 to 65%.
In the honeycomb structure of the present invention, when the porosity of the cell partition wall is 35 to 65%, the cell partition wall can satisfactorily trap PM in the exhaust gas, and the pressure caused by the cell partition wall It is possible to suppress an increase in loss. Therefore, the pressure loss can be further reduced.

When the porosity of the cell partition walls is less than 35%, the proportion of the pores of the cell partition walls is too small, so that the exhaust gas hardly passes through the cell partition walls, and the pressure loss when the exhaust gas passes through the cell partition walls increases. On the other hand, when the porosity of the cell partition walls exceeds 65%, the mechanical properties of the cell partition walls are low, and cracks are likely to occur during reproduction or the like.

In the honeycomb structure of the present invention, the average pore diameter of the pores contained in the cell partition walls is preferably 5 to 30 μm.

In the honeycomb structure of the present invention, when the average pore diameter of the pores contained in the cell partition walls is 5 to 30 μm, PM can be collected with high collection efficiency while suppressing an increase in pressure loss. .

If the average pore diameter of the pores contained in the cell partition walls is less than 5 μm, the pores are too small, and the pressure loss when exhaust gas permeates the cell partition walls increases. On the other hand, if the average pore diameter of the pores contained in the cell partition wall exceeds 30 μm, the pore diameter becomes too large, and the PM trapping efficiency decreases.

1 (a) is a perspective view schematically showing an example of the honeycomb structure of the present invention, and FIG. 1 (b) is a sectional view taken along the line AA in FIG. 1 (a). c) is an end view as seen from one end surface side. FIG. 2 is a drawing schematically showing a position of measuring a length from an imaginary plane in contact with an end surface on the exhaust gas inlet side of the honeycomb structure to an end surface on the exhaust gas outlet side of the end surface of the honeycomb structure on the exhaust gas outlet side. . FIG. 3 is a cross-sectional view schematically showing the vicinity of the end face of the honeycomb structure shown in FIG. FIG. 4 (a) is a perspective view schematically showing an unsealed honeycomb molded body produced by the molding process, and FIG. 4 (b) is an unsealed honeycomb molded body shown in FIG. 4 (a). FIG. 9 is a sectional view taken along line BB of FIG. FIG. 5 is an explanatory view schematically showing a state of the remolding step of the unsealed honeycomb molded body. FIG. 6 is a cross-sectional view schematically showing a state of a remolding step of the unsealed honeycomb molded body. FIG. 7 is a cross-sectional view schematically showing a PM collecting method in the PM combustion test.

(Detailed description of the invention)
[Honeycomb structure]
First, the honeycomb structure of the present invention will be described.

The honeycomb structure of the present invention is a porous cell partition wall that partitions and forms a plurality of cells that are channels of exhaust gas, and an exhaust gas introduction cell in which an end surface on the exhaust gas inlet side is opened and an end surface on the exhaust gas outlet side is closed. And a columnar honeycomb structure having an exhaust gas discharge cell in which the end face on the exhaust gas outlet side is opened and the end face on the exhaust gas inlet side is sealed, wherein the exhaust gas introducing cell and the exhaust gas discharging cell are The exhaust gas introduction cell and the internal region where the cross-sectional shape perpendicular to the longitudinal direction of the exhaust gas discharge cell is constant, and the cross-sectional shape perpendicular to the longitudinal direction of the exhaust gas introduction cell and the exhaust gas discharge cell is enlarged or reduced as it approaches the end surface. The end surface on the exhaust gas outlet side is uneven, and the exhaust gas outlet side from the virtual plane in contact with the exhaust gas inlet side end surface of the honeycomb structure. The standard deviation of the length to the end face, characterized in that at least 0.2.

1 (a) is a perspective view schematically showing an example of the honeycomb structure of the present invention, and FIG. 1 (b) is a sectional view taken along the line AA in FIG. 1 (a). c) is an end view as seen from one end surface side.
The honeycomb structure 10 shown in FIGS. 1 (a) and 1 (b) has a porous cell partition wall 11 for partitioning and forming a plurality of

cells

12 and 13 serving as exhaust gas flow paths, and an end face 10a on the exhaust gas inlet side. An exhaust gas introduction cell 12 that is opened and has an end face 10b on the exhaust gas outlet side sealed, and an exhaust gas discharge cell 13 that has an end face 10b on the exhaust gas outlet side opened and the end face 10a on the exhaust gas inlet side are sealed, The introduction cell 12 and the exhaust gas discharge cell 13 are perpendicular to the longitudinal direction of the exhaust gas introduction cell 12 and the exhaust gas discharge cell 13 and the internal region 10B having a constant sectional shape perpendicular to the longitudinal direction of the exhaust gas introduction cell 12 and the exhaust gas discharge cell 13. The cross-sectional shape is enlarged or reduced as it approaches the end face, and the

end regions

10A and 10C are sealed.
As shown in FIGS. 1A and 1B, when the honeycomb structure 10 is made of a single honeycomb fired body, the honeycomb fired body is also a honeycomb structure.

In the honeycomb structure of the present invention, the end face on the exhaust gas outlet side has irregularities, and the standard deviation of the length from the virtual plane in contact with the end face on the exhaust gas inlet side of the honeycomb structure to the end face on the exhaust gas outlet side is 0.2 or more. Is.
This will be described with reference to FIGS. 1B and 2.
FIG. 1B shows that the end surface 10a on the exhaust gas inlet side is flat and the end surface 10b on the exhaust gas outlet side is uneven.
The degree of this unevenness is shown as "standard deviation of the length from the virtual plane in contact with the end face on the exhaust gas inlet side of the honeycomb structure to the end face on the exhaust gas outlet side".

In the present specification, the “standard deviation of the length from the virtual plane in contact with the exhaust gas inlet side end surface of the honeycomb structure to the exhaust gas outlet side end surface” means the value measured by the following method.
FIG. 2 is a drawing schematically showing the position on the end face of the honeycomb structure on the exhaust gas outlet side, where the length from the virtual plane in contact with the end face of the honeycomb structure on the exhaust gas inlet side to the end face on the exhaust gas outlet side is measured. .
(1) First, the honeycomb structure is arranged on the mounting surface of the fixing base so that the end surface on the exhaust gas inlet side faces downward. Here, the mounting surface of the fixed base is a virtual plane in contact with the end surface on the exhaust gas inlet side.
(2) Next, on the exhaust gas outlet side end surface of the honeycomb structure, a virtual line segment S1 is drawn from the center C of the exhaust gas outlet side end surface to the outer peripheral portion P1 of the exhaust gas outlet side end surface.
The position 1/3, the position 2/3, and the outer peripheral portion P1 of the distance from the center C on the virtual line segment S1 to the outer peripheral portion P1 are respectively measured at the length measurement positions M1-1, M1-2, M1 of the honeycomb structure. -3.
Next, a virtual line segment S2 is drawn from the center C of the end face on the exhaust gas outlet side to the outer peripheral portion P2 of the honeycomb structure so that the angle with the virtual line segment S1 is 5 degrees.
The position 1/3 of the distance from the center C on the imaginary line segment S2 to the outer peripheral portion P2, the position 2/3, and the outer peripheral portion P2 are measured at the length measurement positions M2-1, M2-2, M2 of the honeycomb structure, respectively. -3.
Hereinafter, similarly, the virtual line segments S3 ... Are drawn so that the angle between adjacent virtual line segments is 5 degrees, and the position is ⅓ of the distance from the center C to the outer peripheral portion on each virtual line segment. The positions of 2/3 and the outer peripheral portion are set as the length measurement positions of the honeycomb structure.
(3) Next, between the length measurement positions on the circumference of the honeycomb structure (between M1-1 and M2-1, between M1-2 and M2-2, between M1-3 and M2-3 ... In (), measure the distance from the mounting surface of the fixed base to the end surface on the exhaust gas outlet side, and read the maximum value.
(4) The standard deviation of each maximum value of the distances from the mounting surface of the fixed base to the end surface on the exhaust gas outlet side is expressed by "the length from the virtual plane in contact with the end surface on the exhaust gas inlet side of the honeycomb structure to the end surface on the exhaust gas outlet side. Standard deviation of ".

In the honeycomb structure of the present invention, the standard deviation of the length from the virtual plane in contact with the end face on the exhaust gas inlet side of the honeycomb structure to the end face on the exhaust gas outlet side, which is obtained by the above method, is 0.2 or more. That is, the end surface of the honeycomb structure on the exhaust gas outlet side is not located in the same plane and varies. Therefore, the position in the longitudinal direction of the honeycomb structure in which PM burns also varies.
If the positions where the PM burns vary, the positions in the longitudinal direction that are heated can be dispersed, so that the concentration of stress that occurs when burning the PM can be suppressed.
Therefore, the honeycomb structure of the present invention is less likely to be damaged.

In the honeycomb structure of the present invention, it is desirable that the standard deviation of the length from the virtual plane in contact with the end face on the exhaust gas inlet side of the honeycomb structure to the end face on the exhaust gas outlet side is 0.5 or less.
With such a range, breakage can be preferably prevented in the honeycomb structure.
When the standard deviation of the length from the virtual plane in contact with the end face on the exhaust gas inlet side of the honeycomb structure to the end face on the exhaust gas outlet side exceeds 0.5, when the end face on the exhaust gas outlet side is placed downward during manufacturing, The end face may be damaged.

In the honeycomb structure of the present invention, it is desirable that the exhaust gas introduction cell and the exhaust gas discharge cell in the end region have a length in the longitudinal direction of 1 to 10 mm.
In the honeycomb structure of the present invention, when the length of the exhaust gas introduction cell and the exhaust gas discharge cell in the end region in the longitudinal direction is 1 to 10 mm, the resistance at which the exhaust gas is introduced into the cell on the exhaust gas inlet side, Further, at the exhaust gas outlet side, the resistance of exhaust gas discharged from the inside of the cell can be made smaller, so that the pressure loss can be further reduced.

In the honeycomb structure of the present invention, the thickness of the cell partition wall on the end face is preferably 0.1 to 0.5 mm.
In the honeycomb structure of the present invention, when the thickness of the cell partition wall on the end face is 0.1 to 0.5 mm, the thickness of the cell partition wall can be sufficiently reduced without lowering the compressive strength. Therefore, the pressure loss can be sufficiently reduced.
Further, the thickness of the cell partition wall in the inner region is preferably 0.12 to 0.4 mm.
FIG. 3 is a cross-sectional view schematically showing the vicinity of the end face of the honeycomb structure shown in FIG.
FIG. 3 shows the thickness d ₁ of the cell partition walls 11 on the end surface 10a of the honeycomb structure 10. Further, the thickness d ₂ of the cell partition wall 11 in the internal region of the honeycomb structure 10 is also shown.

Further, in the honeycomb structure of the present invention, in the end region, the cross-sectional shape perpendicular to the longitudinal direction of the exhaust gas introduction cell and the exhaust gas discharge cell is enlarged or reduced as it approaches the end surface, the exhaust gas inlet side and the outlet Since the opening ratio is high on the side end face, the resistance when exhaust gas flows into and out of the honeycomb structure becomes small, and the pressure loss can be sufficiently reduced.

In the honeycomb structure of the present invention, the cross-sectional shape of the exhaust gas introduction cell and the exhaust gas discharge cell in the inner region perpendicular to the longitudinal direction is not limited to a quadrangle, and may be a triangle, a hexagon, an octagon, or a quadrangle. It is desirable that it is, and it is more desirable that it is square.

The shape of the honeycomb structure of the present invention is not limited to a columnar shape, and examples thereof include a prismatic shape, an elliptic cylindrical shape, an oblong cylindrical shape, and a round chamfered prismatic shape (for example, a round chamfered triangular pillar). .

In the honeycomb structure of the present invention, the density of cells in a cross section perpendicular to the longitudinal direction of the honeycomb fired body is preferably 31 to 155 cells / cm ² (200 to 1000 cells / inch ² ).

In the honeycomb structure of the present invention, when the outer peripheral coat layer is formed on the outer peripheral surface of the honeycomb fired body, the thickness of the outer peripheral coat layer is preferably 0.1 to 2.0 mm.

The honeycomb structure of the present invention may be composed of one honeycomb fired body having an outer peripheral wall on the outer periphery, or may be provided with a plurality of honeycomb fired bodies, and the plurality of honeycomb fired bodies are adhesive. However, it is preferable that the honeycomb fired body has one outer peripheral wall having an outer peripheral wall.

The material constituting the honeycomb structure of the present invention is not particularly limited, and examples thereof include carbide ceramics such as silicon carbide, titanium carbide, tantalum carbide, and tungsten carbide, and nitrides such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride. Examples include ceramics, alumina, zirconia, cordierite, mullite, oxide ceramics such as aluminum titanate, silicon-containing silicon carbide, etc., but the honeycomb structure is composed of one honeycomb fired body having an outer peripheral wall on the outer periphery. In this case, cordierite or aluminum titanate is desirable.

When the honeycomb fired body is made of cordierite or aluminum titanate, since the ceramic is a material having a low coefficient of thermal expansion, even when a large thermal stress occurs during regeneration, cracks and the like This is because the honeycomb structure does not easily occur.

In the honeycomb structure of the present invention, the average pore diameter of the pores contained in the cell partition wall is preferably 5 to 30 μm.

In the honeycomb structure of the present invention, when the average pore diameter of the pores contained in the cell partition walls is 5 to 30 μm, PM can be collected with high collection efficiency while suppressing an increase in pressure loss. .
In the honeycomb structure of the present invention, the pore diameter and the average pore diameter are measured by a mercury penetration method under the conditions of a contact angle of 130 ° and a surface tension of 485 mN / m.

Next, a method for manufacturing the honeycomb structure of the present invention will be described.
In the following, a method for manufacturing a honeycomb structure made of aluminum titanate will be described as an example, but the manufacturing target of the present invention is not limited to aluminum titanate.

(Mixing process)
First, additives such as magnesia powder and silica powder are added to alumina powder and titania powder and mixed to obtain a mixed powder.

In the above-mentioned mixed powder, silica and magnesia also have a role as a firing aid, but as the firing aid, in addition to silica and magnesia, oxides of Y, La, Na, K, Ca, Sr, and Ba are used. It may be used. If necessary, the following additives are added to these mixed powders to obtain a raw material composition. Examples of the molding aid include ethylene glycol, dextrin, fatty acid, fatty acid soap, and polyalcohol. Examples of the organic binder include hydrophilic organic polymers such as carboxymethyl cellulose, polyvinyl alcohol, methyl cellulose and ethyl cellulose. Examples of the dispersion medium include a dispersion medium composed of only water or a dispersion medium composed of 50% by volume or more of water and an organic solvent. Examples of the organic solvent include alcohols such as benzene and methanol. Examples of the pore-forming agent include balloons, which are minute hollow spheres, spherical acrylic particles, graphite, and starch. Examples of balloons include alumina balloons, glass micro balloons, shirasu balloons, fly ash (FA) balloons, and mullite balloons.

Further, the raw material composition may further contain other components. Examples of other components include plasticizers, dispersants, and lubricants. Examples of the plasticizer include polyoxyalkylene compounds such as polyoxyethylene alkyl ether and polyoxypropylene alkyl ether. Examples of the dispersant include sorbitan fatty acid ester. Examples of the lubricant include glycerin.

(Molding process)
The molding step is a step of molding the raw material composition obtained in the mixing step to produce an unsealed honeycomb molded body. The unsealed honeycomb molded body can be produced by, for example, extruding the raw material composition using an extrusion die. That is, the unsealed honeycomb molded body is manufactured by extruding the tubular outer peripheral wall of the honeycomb structure and the wall portion constituting the partition wall at one time. Further, in the extrusion molding, a molded body corresponding to the shape of a part of the honeycomb structure may be molded. That is, a honeycomb molded body having the same shape as the honeycomb structure may be manufactured by molding a molded body corresponding to a part of the shape of the honeycomb structure and combining the molded bodies.

FIG. 4 (a) is a perspective view schematically showing an unsealed honeycomb molded body produced by the molding process, and FIG. 4 (b) is an unsealed honeycomb molded body shown in FIG. 4 (a). FIG. 9 is a sectional view taken along line BB of FIG.

As shown in FIGS. 4 (a) and 4 (b), the shape of the

cells

22 and 23 at the end faces 20a 'and 20b' is square due to the above-mentioned molding process, and the cross-sectional shape perpendicular to the longitudinal direction of the

cells

22 and 23 is square. Also, an unsealed honeycomb molded body 20 'having exactly the same quadrangular shape and having cell partition walls 21 separating

cells

22 and 23 and having a cylindrical shape as a whole is manufactured.

(Reforming process)
Thereafter, a taper jig is used to re-form the unsealed honeycomb molded body 20 ′ to form a portion corresponding to an end region of the honeycomb structure, thereby forming an exhaust gas introduction cell and an exhaust gas discharge cell. The cross-sectional shape of 22 and 23 perpendicular to the longitudinal direction is enlarged or reduced as it approaches the end face, and the sealed honeycomb molded body has a closed shape.

FIG. 5 is an explanatory view schematically showing a state of the remolding step of the unsealed honeycomb molded body, and FIG. 6 is a sectional view schematically showing a state of the remolding step of the unsealed honeycomb molded body. is there.
As shown in FIGS. 5 and 6, a taper including a support portion 33, a base portion 31 fixed on the support portion 33, and a large number of quadrangular pyramid-shaped tip portions 32 formed on the base portion 31. Using the jig 30, the corner portion 32c which is the boundary portion of the four flat surfaces 32b forming the quadrangular pyramid of the tip portion 32 forms the square of the cell partition wall 21 on the end surface 20b 'of the unsealed honeycomb molded body 20'. The taper jig 30 is arranged so as to come into contact with the center of the side 21b, and the taper jig 30 is pushed toward the central portion of the unsealed honeycomb molded body 20 '.

At this time, the portion corresponding to the end region of the cell 22 into which the tip 32 is pushed has a shape in which the cross-sectional shape perpendicular to the longitudinal direction of the cell is enlarged as it approaches the end face, and the cell into which the tip 32 is pushed The portions corresponding to the end regions of the cells 23 existing on the upper, lower, left, and right sides of the cell 22 are reduced in shape as the cross-sectional shape perpendicular to the longitudinal direction of the cells 23 approaches the end surface, and become a sealed shape. Further, the shape of the sealed honeycomb formed body viewed from the end face is the same as the honeycomb structure 10 shown in FIG. 1C, and the square of the cell 13 on the end face 10b is rotated by 45 ° from the square of the cell 13 of the internal region 10B. It becomes the shape.
By adjusting the angle of the tip end portion 32 of the taper jig and the width of the adjacent tip end portions 32, the thickness of the cell partition wall on the end face can be adjusted.
Further, by varying the position of the bottom surface of the quadrangular pyramid-shaped tip portion, unevenness can be provided on the end surface on the exhaust gas outlet side.
FIG. 6 shows an example of a taper jig in which the position of the bottom surface of the tip of the quadrangular pyramid is varied.

During the reshaping process, the viscosity and strength of the end region that is pressed and deformed by the taper jig may be adjusted. As a method therefor, there is a case where water or a solvent is applied to the end portion of the unsealed honeycomb molded body. When water or solvent is applied to the end of the unsealed honeycomb molded body,
The degree of deformation of the cell partition when the taper jig is pushed in changes.
Therefore, unevenness can be provided on the end face on the exhaust gas outlet side by varying the amount of water or solvent applied to the end of the unsealed honeycomb molded body.

Further, the unevenness can be provided on the end face on the exhaust gas outlet side also by adjusting the speed when separating the taper jig.

The sealed honeycomb molded body obtained by this remolding step is dried at 100 to 150 ° C. using a dryer such as a microwave dryer, a hot air dryer, a dielectric dryer, a reduced pressure dryer, a vacuum dryer, and a freeze dryer. Then, it is dried in an air atmosphere and degreased at 250 to 400 ° C. and an oxygen concentration of 5% by volume to an air atmosphere.
By making the degree of drying different in this drying step, unevenness can be caused in the drying shrinkage of the cell partition walls, and unevenness can be provided on the end face on the exhaust gas outlet side.

(Firing process)
The firing step is a step of firing the sealed honeycomb formed body obtained in the re-forming step at 1400 to 1600 ° C. In this firing step, the reaction with titania proceeds from the surface of alumina to form an aluminum titanate phase. The firing can be performed using a known single furnace, so-called batch furnace, or continuous furnace. The firing temperature is preferably in the range of 1450 to 1550 ° C. The firing time is not particularly limited, but it is preferable to hold the firing temperature for 1 to 20 hours, and more preferably 1 to 10 hours. In addition, it is desirable that the firing process be performed in the atmosphere. The oxygen concentration may be adjusted by mixing an inert gas such as nitrogen gas or argon gas into the air atmosphere.

The honeycomb structure of the present invention can be manufactured through the above-mentioned mixing step, forming step, re-forming step, and firing step.

Hereinafter, examples in which the above embodiment is further embodied will be described.
(Example 1)
First, a raw material composition having the following composition was prepared.
Fine titania powder having D50 of 0.6 μm: 11.1% by weight, coarse titania powder having D50 of 13.0 μm: 11.1% by weight, alumina powder having D50 of 15.9 μm: 30.4% by weight, D50 of 1 .1 μm silica powder: 2.8% by weight, D50 3.8 μm magnesia powder: 1.4% by weight, D50 31.9 μm acrylic resin (pore forming material): 18.5% by weight, methylcellulose (organic A binder having a composition of 7.1% by weight, a molding aid (ester type nonion): 4.7% by weight, and ion-exchanged water (dispersion medium): 12.9% by weight are mixed with a mixer. A raw material composition was prepared.

An unsealed honeycomb molding having the shape shown in FIGS. 4 (a) and 4 (b) and having cells not sealed, is obtained by introducing the prepared raw material composition into an extrusion molding machine and performing extrusion molding. Body 20 'was made.

After manufacturing the unsealed honeycomb molded body 20 ', the position of the bottom surface of the quadrangular pyramid-shaped tip portion is varied as shown in FIG. 6 on the end surface of the unsealed honeycomb molded body 20' on the exhaust gas outlet side. Remolding was performed using the squeezed aluminum taper jig 30 to produce a sealed honeycomb molded body.
The end face of the unsealed honeycomb molded body 20 'on the exhaust gas inlet side is re-molded using an aluminum taper jig in which the positions of the bottom surfaces of the quadrangular pyramid-shaped tips are uniform, A sealed honeycomb molded body was produced.

After that, the honeycomb structure was manufactured by holding and firing the sealed honeycomb molded body obtained through the remolding step at 1450 ° C. for 15 hours in the air atmosphere. The resulting honeycomb structure had a porosity of 57%, an average pore diameter of 17 μm, a diameter of 132.1 mm, a peripheral wall thickness of 0.3 mm, a cell partition wall thickness of 0.25 mm in the internal region, and a number of cells ( The cell density was 300 cells / inch ² , and the shape was columnar. The porosity and the average pore diameter were measured by the methods described below.

Then, the standard deviation of the length from the virtual plane in contact with the exhaust gas inlet side end surface of the honeycomb structure to the exhaust gas outlet side end surface was determined, and the standard deviation was 0.365.
The average value of the length from the virtual plane in contact with the end surface on the exhaust gas inlet side of the honeycomb structure to the end surface on the exhaust gas outlet side was 138.8 mm, the maximum value was 139.7 mm, and the minimum value was 138.0 mm.

(Examples 2 and 3)
In Example 1, an aluminum taper jig in which the position of the bottom surface of the tip portion of the quadrangular pyramid shape was changed for the end surface of the unsealed honeycomb molded body 20 ′ on the exhaust gas outlet side during the remolding step. Using this, remolding was performed to produce a sealed honeycomb molded body. A honeycomb structure was manufactured in the same manner as in Example 1 except for the above.
Then, when the standard deviation of the length from the virtual plane in contact with the end surface on the exhaust gas inlet side of the honeycomb structure to the end surface on the exhaust gas outlet side was determined, the standard deviations were 0.217 (Example 2) and 0.473 (Example 2), respectively. Example 3).
The average value of the length from the virtual plane in contact with the exhaust gas inlet side end surface of the honeycomb structure to the exhaust gas outlet side end surface is 138.8 mm (Example 2) and 138.8 mm (Example 3), and the maximum value is It was 139.4 mm (Example 2), 140.0 mm (Example 3), and the minimum value was 138.3 mm (Example 2) and 137.7 mm (Example 3).
In addition, the porosity, average pore diameter, size, outer peripheral wall thickness, cell partition wall thickness, and number of cells (cell density) in the honeycomb structure were the same as in Example 1.

(Comparative Example 1)
In Example 1, in the remolding step, the end face of the unsealed honeycomb molded body 20 'on the exhaust gas outlet side has a uniform position of the bottom surface of the tip portion of the quadrangular pyramid shape. Was used to remold, and a sealed honeycomb molded body was manufactured. A honeycomb structure was manufactured in the same manner as in Example 1 except for the above. Then, when the standard deviation of the length from the virtual plane in contact with the end surface on the exhaust gas inlet side of the honeycomb structure to the end surface on the exhaust gas outlet side was determined, the standard deviation was 0.182.
The average value of the length from the virtual plane in contact with the end surface on the exhaust gas inlet side of the honeycomb structure to the end surface on the exhaust gas outlet side was 138.8 mm, the maximum value was 139.3 mm, and the minimum value was 138.4 mm.
In addition, the porosity, average pore diameter, size, outer peripheral wall thickness, cell partition wall thickness, and number of cells (cell density) in the honeycomb structure were the same as in Example 1.

(Evaluation test)
The porosity, average pore diameter, and regeneration limit value of the honeycomb structures of each of the examples and comparative examples were measured.
[Porosity and average pore size]
The honeycomb structure obtained in each of the examples and comparative examples was cut into a size of 10 mm × 10 mm × 10 mm to prepare a sample for pore measurement. The porosity and the average pore diameter were measured using a porosimeter (manufactured by Shimadzu Corporation, Autopore III 9420) by a mercury porosimetry using the sample for pore measurement. The contact angle was 130 ° and the surface tension was 485 mN / m under the mercury intrusion method.

[PM combustion test]
FIG. 7 is a cross-sectional view schematically showing a PM collecting method in the PM combustion test.
In the PM collecting apparatus 210, the honeycomb structure 10 obtained in Examples 1 to 3 and Comparative Example 1 is provided in a metal casing 213 in a pipe 212 branched from an exhaust gas pipe 214 of a diesel engine 211 having a displacement of 1.6 liters. It was fixed inside and placed.
The honeycomb structure 10 is arranged such that the end face on the exhaust gas inlet side is closer to the pipe 212 of the diesel engine 211.
The diesel engine 211 was operated at a rotation speed of 3100 rpm and a torque of 50 Nm, and a part of the exhaust gas from the diesel engine 211 was circulated through the honeycomb structure 10 to collect PM on the honeycomb filter.

Then, PM was collected in the honeycomb structure, and while the honeycomb structure was heated to 650 ° C., a gas having an oxygen concentration of about 20% was introduced to burn the collected PM. It was observed whether the honeycomb structure after PM burning had cracks.
Then, an experiment for carrying out this regeneration treatment was conducted while changing the amount of PM trapped, and it was investigated whether or not cracks were generated in the honeycomb structure. Then, the amount per 1 L of apparent volume of the honeycomb structure having the maximum PM amount in which cracks did not occur was taken as the regeneration limit value.

The results were as follows.
Example 1: 12 g / L
Example 2: 12 g / L
Example 3: 12 g / L
Comparative Example 1: 11 g / L
That is, the regeneration limit value was improved due to the variation in the position of the end face of the honeycomb structure on the exhaust gas outlet side. This makes it possible to disperse the position in the longitudinal direction of the honeycomb structure where PM is burned during regeneration, to suppress the concentration of stress generated when burning PM, and to damage the honeycomb structure. Is prevented from occurring.

10

Honeycomb Structures

10a, 10b End Faces 10A, 10C End Region 10B Inner Region 11 Cell Partition 12 Exhaust Gas Introducing Cell 13 Exhaust Gas Emitting Cell 20 'Unsealed Honeycomb Molded Products 20a', 20b 'End Face 21 Cell Partition 21b One

Side

22 , 23 cell 30 taper jig 31 base part 32 tip part 32b plane 32c corner part 33 support part

Claims

Porous cell partition walls partitioning and forming a plurality of cells that form the flow path of exhaust gas, an exhaust gas introduction cell in which the end surface on the exhaust gas inlet side is opened and the end surface on the exhaust gas outlet side is closed, and the end surface on the exhaust gas outlet side is A columnar honeycomb structure having an exhaust gas discharge cell which is opened and whose end face on the exhaust gas inlet side is sealed,
The exhaust gas introduction cell and the exhaust gas discharge cell, the exhaust gas introduction cell and the internal region having a constant cross-sectional shape perpendicular to the longitudinal direction of the exhaust gas discharge cell, and vertical to the longitudinal direction of the exhaust gas introduction cell and the exhaust gas discharge cell A cross-sectional shape that is enlarged or reduced as it approaches the end surface,
The end surface on the exhaust gas outlet side has unevenness,
A honeycomb structure characterized in that the standard deviation of the length from a virtual plane in contact with the exhaust gas inlet side end surface of the honeycomb structure to the exhaust gas outlet side end surface is 0.2 or more.
The honeycomb structure according to claim 1, wherein a standard deviation of a length from an imaginary plane in contact with the end face on the exhaust gas inlet side of the honeycomb structure to the end face on the exhaust gas outlet side is 0.5 or less.
The honeycomb structure according to claim 1 or 2, wherein the exhaust gas introduction cells and the exhaust gas discharge cells in the end regions have a length in the longitudinal direction of 1 to 10 mm.
The honeycomb structure according to any one of claims 1 to 3, wherein the thickness of the cell partition wall on the end face is 0.1 to 0.5 mm.
The honeycomb structure according to any one of claims 1 to 4, wherein a cross-sectional shape of each of the exhaust gas introducing cell and the exhaust gas discharging cell in the internal region is a quadrangle in a vertical direction.
The honeycomb structure according to any one of claims 1 to 5, wherein the honeycomb structure is composed of one honeycomb fired body having an outer peripheral wall on the outer periphery.
The honeycomb structure according to claim 6, wherein the honeycomb fired body is made of cordierite or aluminum titanate.
The honeycomb structure according to any one of claims 1 to 7, wherein the cell partition walls have a porosity of 35 to 65%.
The honeycomb structure according to any one of claims 1 to 8, wherein the pores contained in the cell partition walls have an average pore diameter of 5 to 30 µm.