JP2020059636A - Honeycomb structure - Google Patents

Abstract

To provide a honeycomb structure which is hardly broken.SOLUTION: There is provided a honeycomb structure which comprises a plurality of cells serving as flow passages of exhaust gas and a porous cell partition wall for partitioning and forming cells, wherein the cells include a cell into which exhaust gas is introduced and a cell from which exhaust gas is discharged, an exhaust gas introduction cell has a cell opening part at an end face on an exhaust gas inlet side and a cell sealing part at an end face on an exhaust gas outlet side, an exhaust gas discharge cell has a cell sealing part at an end face at the exhaust gas inlet side and a cell opening part at an end face at the exhaust gas outlet side, the cells have an internal region in which the shape of the cells is constant and an end region in which the exhaust gas introduction cell is reduced and the exhaust gas discharge cell is enlarged as approaching the end face on the exhaust gas outlet side in the cross section perpendicular to the longitudinal direction, the exhaust gas introduction cell sealing part is a cell partition wall for forming a profile of the exhaust gas discharge cell opening part and in an end face on an exhaust gas outlet side, the thickness standard deviation of the central part of a cell partition wall for forming a profile of one exhaust gas discharge cell opening part is 0.01 or more.SELECTED DRAWING: Figure 1

Description

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 wall thickness on the other end surface of the other end side inclined partition wall is uniform. Therefore, PM is evenly collected in the first flow path on the other end surface side. Further, the collected PM will be burned. In the honeycomb structure described in Patent Document 1, since PM is evenly collected, all PM is burned almost at the same time regardless of where it is collected. At this time, the other end surface is rapidly heated as PM is burned. When the other end surface is rapidly heated, the stress generated due to the heating cannot be dispersed, and the honeycomb structure may be 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.

The honeycomb structure of the present invention is a honeycomb structure including a plurality of cells that are channels of exhaust gas, and porous cell partition walls that partitionly form the plurality of cells,
The plurality of cells includes a plurality of exhaust gas introduction cells into which exhaust gas is introduced and a plurality of exhaust gas discharge cells from which exhaust gas is discharged,
The exhaust gas introduction cell has an exhaust gas introduction cell opening on the end surface on the exhaust gas inlet side, and, and has an exhaust gas introduction cell sealing portion on the end surface on the exhaust gas outlet side,
The exhaust gas discharge cell has an exhaust gas discharge cell sealing portion on the end surface on the exhaust gas inlet side, and has an exhaust gas discharge cell opening portion on the end surface on the exhaust gas outlet side,
The honeycomb structure, in a cross section perpendicular to the longitudinal direction of the honeycomb structure, the internal area where the shape of the exhaust gas introduction cell and the shape of the exhaust gas discharge cell are constant, and the exhaust gas is introduced toward the end surface on the exhaust gas outlet side. An end region where the cell is reduced and the exhaust gas discharge cell is enlarged,
The exhaust gas introduction cell sealing portion is a cell partition wall forming the contour of the exhaust gas discharge cell opening,
Assuming that the thickness of the central portion of the cell partition wall that forms the contour of one of the exhaust gas discharge cell openings on the end face on the exhaust gas outlet side is the thickness α, The standard deviation is 0.01 or more.

In the honeycomb structure of the present invention, the standard deviation of the plurality of thicknesses α in the plurality of exhaust gas discharge cell openings is 0.01 or more. That is, there are variations in the thickness of the cell partition wall forming the contour of the exhaust gas discharge cell opening.
Therefore, there is a difference in capacity between the exhaust gas introducing cells in the end region. Therefore, the amount of PM collected in each exhaust gas introduction cell varies.
When there is a difference in the amount of collected PM, there is a difference in the combustion timing when burning the PM.
If there is a difference in the PM combustion timing, it is possible to prevent the end face on the exhaust gas outlet side from being rapidly heated, and to suppress the concentration of stress.
Therefore, the honeycomb structure of the present invention is less likely to be damaged.

In the honeycomb structure of the present invention, the standard deviation of the thicknesses α is preferably 0.035 or less.
When the standard deviation of the plurality of thicknesses α is 0.035 or less, it is possible to preferably prevent breakage in the above honeycomb structure.
On the other hand, when the standard deviation of the plurality of thicknesses α exceeds 0.035, the difference in capacity between the exhaust gas introducing cells becomes large and the pressure loss tends to increase.

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 longitudinal length 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 exhaust gas is discharged from the inside of the cell at the exhaust gas outlet side. Since it can be made smaller, 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 discharging the exhaust gas increases on the exhaust gas outlet side. Therefore, the pressure loss cannot be sufficiently reduced, and when the length of the exhaust gas introducing cell and the exhaust gas discharging cell in the end region in the longitudinal direction exceeds 10 mm, it is difficult to manufacture a honeycomb structure having such a structure. Become.

In the honeycomb structure of the present invention, the average value of the thickness α is preferably 0.1 to 0.5 mm.
In the honeycomb structure of the present invention, when the average value of the thickness α is 0.1 to 0.5 mm, the thickness of the cell partition wall forming the contour of the exhaust gas discharge cell opening without reducing the compressive strength. Since the thickness can be made sufficiently thin, the pressure loss can be sufficiently reduced.

In the honeycomb structure of the present invention, if the average value of the thickness α is less than 0.1 mm, the cell partition wall forming the contour of the exhaust gas discharge cell opening is too thin, which reduces the compressive strength. Will end up. On the other hand, when the average value of the thickness α exceeds 0.5 mm, the thickness of the cell partition wall forming the contour of the exhaust gas discharge cell opening 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 cell and the exhaust gas discharge cell in the internal region is a quadrangle, when manufacturing the honeycomb structure, in the end region, the length of the cell A cross-sectional shape perpendicular to the 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 included 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 included 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 cross-sectional view schematically showing the vicinity of the end face on the exhaust gas outlet side of the honeycomb structure shown in FIG. FIG. 3A is a perspective view schematically showing the unsealed honeycomb molded body produced by the molding step, and FIG. 3B is the unsealed honeycomb molded body shown in FIG. 3A. FIG. 6 is a sectional view taken along line BB of FIG. FIG. 4 is an explanatory diagram schematically showing a state of a remolding step of the unsealed honeycomb molded body. FIG. 5 is a cross-sectional view schematically showing a state of a remolding step of the unsealed honeycomb molded body. FIG. 6 is a cross-sectional view schematically showing a method of collecting PM 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 honeycomb structure including a plurality of cells that are channels of exhaust gas, and porous cell partition walls that partition and form the plurality of cells, and the plurality of cells are exhaust gases. Including a plurality of exhaust gas introduction cells and a plurality of exhaust gas exhaust cells that exhaust gas is discharged,
The exhaust gas introduction cell has an exhaust gas introduction cell opening portion on the end surface on the exhaust gas inlet side, and has an exhaust gas introduction cell sealing portion on the end surface on the exhaust gas outlet side, the exhaust gas discharge cell, the exhaust gas inlet side end surface In the exhaust gas discharge cell sealing portion, and has an exhaust gas discharge cell opening on the end face on the exhaust gas outlet side, the honeycomb structure, in the cross section perpendicular to the longitudinal direction of the honeycomb structure, the exhaust gas introduction The inner shape of the cell and the shape of the exhaust gas discharge cell is constant, and has an end area where the exhaust gas introduction cell is reduced and the exhaust gas discharge cell is enlarged as it approaches the end surface on the exhaust gas outlet side, the exhaust gas The introduction cell sealing portion is a cell partition wall that forms the contour of the exhaust gas discharge cell opening, and a cell partition that forms the contour of one exhaust gas discharge cell opening on the end surface on the exhaust gas outlet side. When the thickness of the thickness of the center α of the standard deviation of the plurality of thickness α in the plurality of exhaust gas discharge cell opening, characterized in that at least 0.01.

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, in the end face on the exhaust gas outlet side, when the thickness of the central portion of the cell partition wall forming the contour of one exhaust gas discharge cell opening is defined as the thickness α, the plurality of exhaust gas discharge cell openings are formed. The standard deviation of the plurality of thicknesses α is 0.01 or more.
This will be described with reference to FIGS. 2 and 1C.

FIG. 2 is a cross-sectional view schematically showing the vicinity of the end face on the exhaust gas outlet side of the honeycomb structure shown in FIG.
FIG. 2 shows the thicknesses α1, α2, and α3 of the central portions of the cell partition walls on the end face 10b of the honeycomb structure 10, but the fact that these α1, α2, and α3 are different means that the exhaust gas discharge cell openings are different. This means that there is variation in the thickness of the central portion of the cell partition wall that forms the contour of the portion.
From FIG. 2, it can be seen that there is a difference in capacity between the exhaust gas introducing cells in the end region 10C on the exhaust gas outlet side.
Further, FIG. 2 also shows the thickness d ₂ of the cell partition walls 11 in the internal region of the honeycomb structure 10.

The thickness α of the central portion of the cell partition will be further described with reference to FIG.
In the end face on the exhaust gas outlet side shown in FIG. 1C, the cell partition wall forming the outline of one exhaust gas discharge cell opening is one side of a quadrangle, and the central part of the cell partition wall corresponds to the center of this one side. The thickness of this portion is the thickness α of the central portion of the cell partition wall.
FIG. 1C shows the thickness α1 when the thickness α of the central portion of the cell partition wall is thin, the thickness α3 when it is thick, and the thickness α2 when it is medium.
The thickness α of the central portion of the cell partition wall may be measured at the center of the length of one side of a quadrangle forming the contour of the exhaust gas discharge cell opening.
These thicknesses α1, α2, α3 correspond to the thicknesses α1, α2, α3 shown in FIG.

In the present invention, the standard deviation of the plurality of thicknesses α is obtained for the thickness α of the central portion of the cell partition wall. As the plurality of thicknesses α, the thicknesses α measured at the 30 cell partition walls are used, and the standard deviation is obtained by statistical processing. In the honeycomb structure of the present invention, the standard deviation thus obtained is 0.01 or more.
This means that the thickness of the central portion of the cell partition forming the outline of the exhaust gas discharge cell opening varies.
In such a case, the amount of PM collected in each exhaust gas introduction cell varies.
When there is a difference in the amount of collected PM, there is a difference in the combustion timing when burning the PM.
If there is a difference in the PM combustion timing, it is possible to prevent the end face on the exhaust gas outlet side from being rapidly heated, and to suppress the concentration of stress.
Therefore, the honeycomb structure of the present invention is less likely to be damaged.

The standard deviation of the thicknesses α is preferably 0.035 or less.
When the standard deviation of the plurality of thicknesses α is 0.035 or less, it is possible to preferably prevent the honeycomb structure from being damaged.
On the other hand, when the standard deviation of the plurality of thicknesses α exceeds 0.035, the difference in capacity between the exhaust gas introducing cells becomes large and the pressure loss tends to increase.

The average value of the thickness α is preferably 0.1 to 0.5 mm.
To calculate the average value of the thickness α, the numerical value obtained when the standard deviation of the thickness α is obtained may be used.
In the honeycomb structure of the present invention, when the average value of the thickness α is 0.1 to 0.5 mm, the thickness of the cell partition wall can be sufficiently reduced without lowering the compressive strength. The 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.

In the honeycomb structure of the present invention, the length in the longitudinal direction of the cells in the end region is preferably 1 to 10 mm.
In the honeycomb structure of the present invention, when the length of the cells in the end region in the longitudinal direction is 1 to 10 mm, the resistance at which the exhaust gas is introduced into the cells on the exhaust gas inlet side, and the exhaust gas outlet side Since the resistance of the exhaust gas discharged from the inside of the cell can be further reduced, the pressure loss can be further reduced.

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 perpendicular to the longitudinal direction of the cells in the inner region is not limited to a quadrangle, and may be a triangle, a hexagon, an octagon, but is preferably a quadrangle, and a square. Is more desirable.

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, 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.

In the honeycomb structure of the present invention, the average pore diameter of the pores included 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 included 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. 3A is a perspective view schematically showing the unsealed honeycomb molded body produced by the molding step, and FIG. 3B is the unsealed honeycomb molded body shown in FIG. 3A. FIG. 6 is a sectional view taken along line BB of FIG.

As shown in FIGS. 3 (a) and 3 (b), the shape of the cells 22 and 23 on the end faces 20a 'and 20b' is square due to the above-mentioned molding process, and the 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. 4 is an explanatory view schematically showing a state of the remolding step of the unsealed honeycomb molded body, and FIG. 5 is a sectional view schematically showing a state of the remolding step of the unsealed honeycomb molded body. is there.
As shown in FIGS. 4 and 5, 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 portion 32 of the taper jig and the width of the tip portions 32 adjacent to each other, the thickness of the cell partition wall on the end face and the thickness of the cell partition wall forming the contour of the exhaust gas discharge cell opening are adjusted. be able to.
FIG. 5 shows an example in which the widths of the adjacent tip portions 32 are different. The widths β1, β2, and β3 of the tip portions 32 adjacent to each other are different, and correspond to the thicknesses α1, α2, and α3 of the central portions of the cell partition walls of the honeycomb structure that can obtain the respective widths.
By doing so, the thickness of the cell partition wall forming the outline of the exhaust gas discharge cell opening can be 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, the thickness of the cell partition wall forming the outline of the exhaust gas discharge cell opening can be varied by varying the amount of water or solvent applied to the end of the unsealed honeycomb molded body.

The sealed honeycomb molded body obtained by this remolding step uses a dryer such as a microwave dryer, a hot air dryer, a dielectric dryer, a vacuum dryer, a vacuum dryer, and a freeze dryer at 100 to 150 ° C. Then, it is dried in an air atmosphere and degreased in an atmosphere of 250 to 400 ° C. and an oxygen concentration of 5% by volume.
By making the degree of drying different in this drying step, it is possible to cause unevenness in the drying shrinkage of the cell partition walls, and to vary the thickness of the cell partition walls forming the contour of the exhaust gas discharge cell opening.

(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. Although the firing time is not particularly limited, it is desirable to hold the firing temperature for 1 to 20 hours, and more desirably 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.

The prepared raw material composition was put into an extrusion molding machine and extrusion-molded to prepare an unsealed honeycomb molded body 20 'in which cells were not sealed.

After the unsealed honeycomb molded body 20 'was manufactured, the end faces of the unsealed honeycomb molded body 20' on the exhaust gas outlet side had different widths between the adjacent tip portions 32 as shown in FIG. Re-molding was performed using the taper jig 30 made of aluminum to manufacture a sealed honeycomb molded body.
The end surface of the unsealed honeycomb molded body 20 ′ on the exhaust gas inlet side is remolded by using an aluminum taper jig in which the widths of the adjacent tip portions 32 are uniform and sealed. A honeycomb formed 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 obtained honeycomb structure had a porosity of 57%, an average pore diameter of 17 μm, a size of 34 mm × 34 mm × 100 mm, a peripheral wall thickness of 0.3 mm, and a cell partition wall thickness of 0.25 mm in the internal region. The number of cells (cell density) was 300 cells / inch ² , and it was a quadrangular prism shape. The porosity and the average pore diameter were measured by the methods described below.

Then, when the standard deviation of the thickness α of the central portion of the cell partition wall forming the contour of one exhaust gas discharge cell opening on the end face on the exhaust gas outlet side was determined, the standard deviation was 0.0224.
The average value of the thickness α was 0.35 mm.

(Examples 2 and 3)
In Example 1, at the time of the re-molding step, an aluminum taper jig in which the widths and angles of the adjacent tip portions 32 were respectively changed was used for the end surface of the unsealed honeycomb molded body 20 'on the exhaust gas outlet side. Then, remolding was performed to manufacture 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 thickness α of the central portion of the cell partition wall forming the outline of one exhaust gas discharge cell opening on the end face on the exhaust gas outlet side was determined, the standard deviation was 0.0114 (Example 2). It was 0.0342 (Example 3).
The average value of the thickness α was 0.35 mm in both cases.
The porosity, average pore diameter, size, outer peripheral wall thickness, cell partition wall thickness in the inner region, and number of cells (cell density) in the honeycomb structure were all the same as in Example 1.

(Comparative Example 1)
In the first embodiment, an aluminum taper jig is used in which the widths of the adjacent tip portions 32 of the unsealed honeycomb molded body 20 'on the exhaust gas outlet side are uniform during the remolding process. Then, remolding was performed to manufacture 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 thickness α of the central portion of the cell partition wall forming the outline of one exhaust gas discharge cell opening on the end face on the exhaust gas outlet side was determined, the standard deviation was 0.0079.
The average value of the thickness α was 0.34 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. 6 is a cross-sectional view schematically showing a method of collecting PM in the PM combustion test.
The PM collecting apparatus 210 includes a metal casing 213 in which the honeycomb structures 10 obtained in Examples 1 to 3 and Comparative Example 1 are placed 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 variation in the thickness of the central portion of the cell partition wall forming the contour of the exhaust gas discharge cell opening improved the regeneration limit value. This can cause a difference in PM combustion timing during regeneration, can prevent the end face on the exhaust gas outlet side from being rapidly heated, and can prevent the honeycomb structure from being damaged. Show.

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 (9)

A plurality of cells to be a flow path of the exhaust gas, a honeycomb structure including a porous cell partition wall to partition the plurality of cells,
The plurality of cells includes a plurality of exhaust gas introduction cells into which exhaust gas is introduced and a plurality of exhaust gas discharge cells from which exhaust gas is discharged,
The exhaust gas introduction cell has an exhaust gas introduction cell opening portion on the end surface on the exhaust gas inlet side, and, and has an exhaust gas introduction cell sealing portion on the end surface on the exhaust gas outlet side,
The exhaust gas discharge cell has an exhaust gas discharge cell sealing portion on the end surface on the exhaust gas inlet side, and has an exhaust gas discharge cell opening portion on the end surface on the exhaust gas outlet side,
The honeycomb structure, in a cross section perpendicular to the longitudinal direction of the honeycomb structure, the exhaust gas introduction cell as the shape of the exhaust gas introduction cell and the exhaust gas discharge cell has a constant inner region, and the exhaust gas is introduced toward the end face on the exhaust gas outlet side. An end region where the cell is reduced and the exhaust gas discharge cell is enlarged,
The exhaust gas introduction cell sealing portion is a cell partition wall forming the contour of the exhaust gas discharge cell opening,
Assuming that the thickness of the central portion of the cell partition wall forming the outline of one of the exhaust gas discharge cell openings is the thickness α on the end face on the exhaust gas outlet side, the plurality of thicknesses α of the plurality of exhaust gas discharge cell openings are A honeycomb structure having a standard deviation of 0.01 or more. The honeycomb structure according to claim 1, wherein a standard deviation of the plurality of thicknesses α is 0.035 or less. The honeycomb structure according to claim 1 or 2, wherein a length in a longitudinal direction of the exhaust gas introducing cell and the exhaust gas discharging cell in the end region is 1 to 10 mm. The honeycomb structure according to any one of claims 1 to 3, wherein an average value of the thickness α 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 an average pore diameter of pores included in the cell partition wall is 5 to 30 µm.

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