JP2016055232A - Honeycomb filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb filter which has a sufficiently low pressure loss and a sufficiently high strength in an initial state that no fine particles (PM) accumulates and suppresses a decrease in thermal capacity.SOLUTION: A honeycomb filter 1 is formed by bonding via a bonding material layer 14 a plurality of honeycomb fired products 10 comprising a plurality of cells 20 each with one end sealed to serve as an exhaust gas channel and a porous cell partition wall 30 that forms the cells by partition, where the honeycomb fired product 10 consists of outward honeycomb fired products 10a, 10b and inward honeycomb fired products 10c, the outward honeycomb fired product 10a having first outer periphery cells 21a so arranged as to be adjacent to the outer peripheral part of the honeycomb filter 1, second outer periphery cells 24a that are cells arranged at the outermost peripheral part of the outward honeycomb fired product 10a and arranged at a part other than a part where the first outer periphery cells 21a are arranged, and inner cells 22a arranged inside the first outer periphery cells 21a and the second outer periphery cells 24a.SELECTED DRAWING: Figure 1

Description

The present invention relates to a honeycomb filter.

The exhaust gas discharged from an internal combustion engine such as a diesel engine contains particulates such as soot (hereinafter also referred to as PM or soot), and in recent years, this PM has a problem that it causes harm to the environment or the human body. It has become. Further, since harmful gas components such as CO, HC or NOx are contained in the exhaust gas, there is a concern about the influence of the harmful gas components on the environment or the human body.

Therefore, cordierite is used as an exhaust gas purification device that collects PM in exhaust gas by being connected to an internal combustion engine and purifies harmful gas components in exhaust gas such as CO, HC, or NOx contained in the exhaust gas. Various filters (honeycomb filters) having a honeycomb structure made of a porous ceramic such as SiC or silicon carbide have been proposed.

Also, in order to improve the fuel efficiency of the internal combustion engine and eliminate problems during operation caused by the increase in pressure loss, the honeycomb filter with a low initial pressure loss and the increase in pressure loss when a predetermined amount of PM is deposited There is a need for a honeycomb filter with a low proportion.

Increasing the aperture ratio is an effective means for reducing the pressure loss. However, when trying to increase the aperture ratio, the thickness of the cell partition walls must be reduced, and as a result, it becomes difficult to ensure the strength of the honeycomb fired body.
In a honeycomb fired body, keeping pressure loss low and securing strength are contradictory properties, and it has been difficult to secure these properties simultaneously.

In order to solve such a problem, Patent Document 1 discloses a honeycomb filter having an improved cell structure.

That is, Patent Document 1 discloses a honeycomb structure in which a plurality of cells are juxtaposed in the longitudinal direction with cell partition walls interposed therebetween, and a plurality of porous ceramic members having outer edge walls on their outer edges are bonded via an adhesive layer. The outer peripheral wall of the porous ceramic member is thicker than the cell partition wall, and at least one of the cells located on the outermost periphery of the porous ceramic member includes at least one of the cells. A honeycomb structure is disclosed in which a filler filling the corner is provided at at least one corner.
FIG. 8 is a cross-sectional view perpendicular to the longitudinal direction of the porous ceramic member constituting the honeycomb structure disclosed in Patent Document 1. In this cross-section, right-angled triangular fillers are provided at the corners of the rectangular cells 221a located at the outermost periphery and separated by the cell partition walls perpendicular to the outer edge wall 223a of the porous ceramic member 220.
In Patent Document 1, by making the cell structure in this way, while ensuring the strength of the porous ceramic member, the aperture ratio is secured, the pressure loss is kept low, and the occurrence of breakage such as cracks is avoided.

International Publication No. 2007/058006 Pamphlet

Gasoline engines have the advantages of higher exhaust gas temperatures and lower PM emissions than diesel engines.
On the other hand, gasoline engines have the drawback of inferior fuel efficiency compared to diesel engines. Therefore, when considering exhaust gas exhausted from a gasoline engine, a filter for purifying exhaust gas is required to have a low pressure loss. In addition, when the temperature of the filter rises rapidly, the filter is likely to be destroyed due to thermal expansion. Therefore, an appropriate heat capacity is required so that the temperature of the filter does not rise too much.

When the honeycomb structure disclosed in Patent Document 1 is used in an environment where the exhaust gas temperature is high and the amount of PM emission is small like a gasoline engine, the pressure loss in the initial state where PM is not accumulated is sufficiently low. Hard to become. In order to reduce the initial pressure loss, it is conceivable to make the cell partition wall thinner. However, if the cell partition wall thickness is decreased, the heat capacity decreases, and the exhaust gas flows into the honeycomb filter. The temperature is thought to be higher than necessary. If the temperature of the honeycomb filter becomes higher than necessary, the honeycomb filter itself is damaged by heat, or the catalyst supported on the honeycomb filter is deactivated. Further, it is considered that when the thickness of the cell partition wall is reduced, the strength of the honeycomb filter is lowered and easily damaged.
That is, the honeycomb structure disclosed in Patent Document 1 cannot be said to have sufficient performance as a honeycomb filter for gasoline engines.

The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to sufficiently reduce pressure loss in an initial state where PM is not deposited, sufficiently strong, and to reduce heat capacity. It is to provide a honeycomb filter that can be suppressed.

In order to solve the above-mentioned problems, the present inventor has made extensive studies, and as a result, PM is deposited by thinning the cell partition and setting the shape of the cells arranged on the outer peripheral side of the honeycomb filter to a predetermined shape. The present invention has been completed by finding that the pressure loss in the initial state is sufficiently low, the heat capacity is sufficiently high, and the strength can be sufficiently increased.

That is, the honeycomb filter of the present invention includes a plurality of honeycomb fired bodies each provided with a plurality of cells sealed at one end and serving as exhaust gas flow paths, and porous cell partition walls that partition the cells. Is a honeycomb filter formed by being bonded through an adhesive layer, and the constituent material of the honeycomb fired body is SiC, and the honeycomb fired body is disposed on the outer periphery of the honeycomb filter. A honeycomb fired body and an inner honeycomb fired body disposed inside the outer honeycomb fired body, and the outer honeycomb fired body is disposed in an outermost peripheral portion of the outer honeycomb fired body. And the first outer peripheral cell disposed so as to be adjacent to the outer peripheral portion of the honeycomb filter, and the cell disposed in the outermost peripheral portion of the outer honeycomb fired body, and the above A second outer peripheral cell disposed in a portion other than a portion where one cell is disposed, and an inner cell disposed inside the first outer peripheral cell and the second outer peripheral cell, The cross-sectional shape in the direction perpendicular to the longitudinal direction of the internal cell is the same rectangle, and the first peripheral cell and the second peripheral cell are from the peripheral wall forming the outer periphery of the cell partition wall and the honeycomb fired body. The cell partition wall that is partitioned and connected to the outer peripheral wall that defines the first outer peripheral cell has a thick wall region in which the wall thickness gradually increases toward the outer peripheral wall. The cross-sectional shape perpendicular to the longitudinal direction is a shape in which two corners are chamfered from the rectangle which is the cross-sectional shape of the internal cell, and the area of the cross-section perpendicular to the longitudinal direction of the first outer peripheral cell is Area of cross section perpendicular to the longitudinal direction of the internal cell 60-80%, the cell partition wall thickness is 0.210 mm or less, and the cross-sectional shape of the inner honeycomb fired body in the direction perpendicular to the longitudinal direction of the cells is a cross section perpendicular to the longitudinal direction of the internal cells. The shape is a congruent shape with a rectangular shape.

In the honeycomb filter of the present invention, the constituent material of the honeycomb fired body is SiC. SiC is a material excellent in heat resistance. For this reason, the honeycomb filter of the present invention is a honeycomb filter having excellent heat resistance.

In the honeycomb filter of the present invention, the honeycomb fired body includes an outer honeycomb fired body disposed on an outer periphery of the honeycomb filter, and the outer honeycomb fired body is disposed on an outermost peripheral portion of the outer honeycomb fired body. A first outer peripheral cell disposed adjacent to the outer peripheral portion of the honeycomb filter, and a cell disposed in the outermost peripheral portion of the outer honeycomb fired body, and the above A second outer peripheral cell disposed in a portion other than the portion where the first cell is disposed; and an inner cell disposed inside the first outer peripheral cell and the second outer peripheral cell. .
Further, the cross-sectional shape in the direction perpendicular to the longitudinal direction of each internal cell is the same rectangle, and the first peripheral cell and the second peripheral cell form the outer periphery of the cell partition and the honeycomb fired body. The cell partition wall defined by the outer peripheral wall and connected to the outer peripheral wall defining the first outer peripheral cell has a thick wall region in which the wall thickness gradually increases toward the outer peripheral wall. The cross-sectional shape in the direction perpendicular to the longitudinal direction of the peripheral cell is a shape in which two corners are chamfered from the rectangle which is the cross-sectional shape of the internal cell.
When the first outer peripheral cell has the shape as described above, the volume of the outer frame portion of the entire honeycomb filter is increased. For this reason, the honeycomb filter of the present invention has a sufficiently large volume of the outer frame portion of the entire honeycomb filter, although the cell partition wall is thin as will be described later. It has a sufficiently high strength. Moreover, since the volume of the outer frame part of the whole honeycomb filter is sufficiently large, it is possible to suppress a decrease in heat capacity.
This can also be explained as follows.
The honeycomb filter is cut out in a predetermined range in a region including the portion of the honeycomb filter where SiC is present and the space portion of the cell where SiC is not present, and the weight of the honeycomb filter included in the predetermined range is set to the predetermined range. Assuming that the value obtained by dividing by the volume is “apparent density”, in the honeycomb filter of the present invention, the value of “apparent density” of the outer frame portion of the entire honeycomb filter becomes large. Therefore, the honeycomb filter of the present invention has a sufficiently large “apparent density” of the outer frame portion of the entire honeycomb filter, although the cell partition wall is thin as will be described later. Sufficiently high strength against impact from Moreover, since the “apparent density” of the outer frame portion of the entire honeycomb filter is sufficiently large, it is possible to suppress a decrease in heat capacity. Therefore, even when heat is suddenly applied from the outside, the heat can be received at the outer frame portion, and the occurrence of cracks can be prevented.
In the present specification, “a shape in which corners are chamfered from a rectangle” means a shape in which corners of a rectangle are cut out from a rectangle by a straight line or a curve.

In the honeycomb filter of the present invention, the area of the cross section perpendicular to the longitudinal direction of the first peripheral cell is 60 to 80% of the area of the cross section perpendicular to the longitudinal direction of the internal cell.
When the ratio of the area is less than 60%, the area of the opening of the first outer peripheral cell is reduced, the exhaust gas flow path is narrowed, and the gas passage resistance when the exhaust gas passes through the cell partition wall is increased. Pressure loss increases.
If the proportion of the area exceeds 80%, the proportion of SiC in the outer frame portion of the honeycomb filter becomes low, so that the above effect is difficult to obtain.

In the honeycomb fired body of the present invention, the thickness of the cell partition wall is 0.210 mm or less. When the cell partition wall thickness is within the above range, the cell partition wall thickness is sufficiently thin, so that the pressure loss in the initial state where PM is not deposited is sufficiently low. Further, an increase in pressure loss can be suppressed even when PM is deposited.
When the thickness of the cell partition wall exceeds 0.210 mm, the cell partition wall is too thick, so that the resistance when the exhaust gas passes through the cell partition wall increases, and as a result, the pressure loss increases.

In the honeycomb filter of the present invention, the cross-sectional shape in the direction perpendicular to the longitudinal direction of the cells of the inner honeycomb fired body is the same as the rectangle which is the cross-sectional shape perpendicular to the longitudinal direction of the internal cells.
When the cells of the inner honeycomb fired body have the above shape, the aperture ratio of the inner honeycomb fired body is higher than the aperture ratio of the outer honeycomb fired body. Therefore, in such a honeycomb filter, pressure loss can be suppressed low.

In the honeycomb filter of the present invention, it is desirable that the minimum value of the thickness of the outer peripheral wall forming the first peripheral cell is thicker than the thickness of the cell partition wall.
When the minimum value of the thickness of the outer peripheral wall forming the first outer peripheral cell is larger than the thickness of the cell partition wall, the outer frame portion of the entire honeycomb filter becomes thicker. Therefore, although the cell partition is thin as described above, the outer frame portion of the entire honeycomb filter has a sufficiently high strength against impacts from the outside. Further, since the outer frame portion of the entire honeycomb filter is thick, it is possible to suppress a decrease in heat capacity.

In the honeycomb filter of the present invention, it is desirable that the minimum value of the thickness of the outer peripheral wall forming the first outer peripheral cell is 1.5 to 3 times the thickness of the cell partition wall.
In the honeycomb filter of the present invention having the above configuration, the effect that the minimum value of the thickness of the outer peripheral wall forming the first outer peripheral cell is thicker than the thickness of the cell partition wall is suitably exhibited.

In the honeycomb filter of the present invention, the cell partition wall connected to the outer peripheral wall that partitions and forms all the second outer peripheral cells has a thick wall region in which the wall thickness gradually increases toward the outer peripheral wall. The cross-sectional shape in the direction perpendicular to the longitudinal direction of the outer peripheral cell 2 is a shape in which two corners are chamfered from the rectangle which is the cross-sectional shape of the inner cell, and is perpendicular to the longitudinal direction of the second outer peripheral cell. The cross-sectional area may be 60 to 80% of the cross-sectional area perpendicular to the longitudinal direction of the internal cell.
When the second outer peripheral cell has the above shape, the volume of the entire outer peripheral wall of the outer honeycomb fired body is increased. Therefore, the outer honeycomb fired body has a sufficiently high strength against an external impact or the like because the volume of the outer peripheral wall is sufficiently large even though the cell partition walls are thin. Moreover, since the volume of the outer peripheral wall of the outer honeycomb fired body is large, a decrease in heat capacity can be suppressed in the honeycomb filter of the present invention.

In the honeycomb filter of the present invention, in the two adjacent outer honeycomb fired bodies, the second outer peripheral cells arranged in one outer honeycomb fired body face the other outer honeycomb fired body. The cell partition wall connected to the outer peripheral wall defining the second outer peripheral cell has a thick wall region where the wall thickness gradually increases toward the outer peripheral wall, and is perpendicular to the longitudinal direction of the second outer peripheral cell. The cross-sectional shape in the direction is a shape in which two corners are chamfered from a rectangle which is the cross-sectional shape of the internal cell, and among the second peripheral cells arranged in the other outer honeycomb fired body, The cross-sectional shape perpendicular to the longitudinal direction of the second outer peripheral cell facing one outer honeycomb fired body is congruent with the rectangle that is the cross-sectional shape perpendicular to the longitudinal direction of the internal cell, Outside honeycomb firing Of the second outer peripheral cells arranged on the body, the area of the cross section perpendicular to the longitudinal direction of the second outer peripheral cell facing the other outer honeycomb fired body is the longitudinal direction of the inner cell. It may be 60 to 80% of the area of the cross section in the vertical direction.
In two adjacent outer honeycomb fired bodies, if the facing outer honeycomb fired bodies face each other, the cross-sectional shape perpendicular to the longitudinal direction of the second outer cell, both of which are perpendicular to the longitudinal direction of the inner cell When the shape is a shape in which two corners are chamfered from a rectangle, the volume of the outer peripheral wall increases. Increasing the volume of both outer peripheral walls may increase the pressure loss. Further, in the two adjacent outer honeycomb fired bodies, if the cells having the same shape as the inner cells are arranged on the outer peripheral wall of the facing outer honeycomb fired body, the volume of the outer peripheral wall of the facing outer honeycomb fired body When both are not increased, the outer frame portion is less likely to have sufficient strength against external impacts. In addition, the heat capacity tends to be small.
However, in the honeycomb filter having the above configuration, the volume of the outer peripheral wall of one of the adjacent outer honeycomb fired bodies is large in the two adjacent outer honeycomb fired bodies, and the outer peripheral wall of the other outer honeycomb fired body The volume of is not large. Therefore, an increase in pressure loss and a decrease in heat capacity can be balanced, and an increase in pressure loss can be suppressed, and a decrease in heat capacity can be suppressed.

The honeycomb filter of the present invention includes four inner honeycomb fired bodies and twelve outer honeycomb fired bodies, and the cross-sectional shape in the direction perpendicular to the longitudinal direction of the four inner honeycomb fired bodies is It is a square, and it is desirable that the 12 outer honeycomb fired bodies and the 4 inner honeycomb fired bodies be combined to form a cylinder.
When the honeycomb filter has such a shape, since the honeycomb filter can be easily assembled, the productivity is excellent.
The cross-sectional shape in the direction perpendicular to the longitudinal direction of the inner honeycomb fired body is preferably a square having a side of 30 to 60 mm, and the honeycomb filter is preferably a cylinder having a bottom diameter of 90 to 240 mm.

The honeycomb filter of the present invention is desirably used for purifying exhaust gas from a gasoline engine.
As described above, the honeycomb filter of the present invention has a sufficiently low pressure loss in an initial state where PM is not deposited, a sufficiently high strength, and a reduction in heat capacity is suppressed. Therefore, the honeycomb filter of the present invention can be suitably used for purifying exhaust gas in a gasoline engine.

Fig.1 (a) is a perspective view which shows typically an example of the honeycomb filter of this invention. FIG.1 (b) is the sectional view on the AA line of Fig.1 (a). Fig.2 (a)-(c) is sectional drawing which shows typically an example of a cross section perpendicular | vertical to the longitudinal direction of each honeycomb fired body which comprises the honeycomb filter of this invention. Fig.3 (a)-(e) is sectional drawing which shows typically an example of the cross-sectional shape of the orthogonal | vertical direction to the longitudinal direction of the 1st outer periphery cell in the honeycomb calcination object of the present invention. FIGS. 4A to 4D are cross-sectional views schematically showing an example of a cross-sectional shape perpendicular to the longitudinal direction of the corner cells in the honeycomb fired body of the present invention. FIG. 5 is a cross-sectional view schematically showing an example of a cross section perpendicular to the longitudinal direction of a honeycomb filter according to another aspect of the present invention. FIG. 6 is an enlarged view of a broken line portion of FIG. FIG. 7 is a cross-sectional view schematically showing an example of an exhaust gas purifying apparatus in which the honeycomb filter of the present invention is installed. FIG. 8 is a cross-sectional view perpendicular to the longitudinal direction of the porous ceramic member constituting the honeycomb structure disclosed in Patent Document 1.

Hereinafter, the honeycomb filter of the present invention will be specifically described. However, the present invention is not limited to the following description, and can be appropriately modified and applied without departing from the scope of the present invention.

The honeycomb filter of the present invention will be described with reference to the drawings.
Fig.1 (a) is a perspective view which shows typically an example of the honeycomb filter of this invention. FIG.1 (b) is the sectional view on the AA line of Fig.1 (a).
As shown in FIGS. 1 (a) and 1 (b), a honeycomb filter 1 as an example of the honeycomb filter of the present invention has a plurality of exhaust gas flow paths in which one end is sealed with a sealing material 11. The honeycomb filter is formed by bonding a plurality of honeycomb fired bodies 10 having the cells 20 and the porous cell partition walls 30 that partition the cells 20 through the adhesive layer 14.
The honeycomb fired body 10 includes two types of outer honeycomb fired bodies 10a and 10b disposed on the outermost periphery of the honeycomb filter 1, and an inner honeycomb fired body 10c disposed on the inner side of the outer honeycomb fired body 10a. ing.
The outer shape of the inner honeycomb fired body 10c is a prismatic shape, and the outer honeycomb fired bodies 10a and 10b have a shape in which a part of the inner honeycomb fired body 10c is cut off. In the honeycomb filter 1, eight outer honeycomb fired bodies 10a, four outer honeycomb fired bodies 10b, and four inner honeycomb fired bodies 10c arranged inside thereof are combined, and the outer shape thereof is a circle. It is columnar.
Although the magnitude | size of the honey-comb filter 1 is not specifically limited, It is desirable that it is a column shape whose diameter of a bottom face is 90-240 mm.

The outer honeycomb fired body 10a includes a first outer peripheral cell 21a, a second outer peripheral cell 24a, and an inner cell 22a.
The arrangement of each cell in the outer honeycomb fired body 10a is as follows.
The first outer peripheral cell 21 a is a cell that is disposed at the outermost peripheral portion of the outer honeycomb fired body 10 a and is disposed adjacent to the outermost peripheral portion 2 of the honeycomb filter 1.
The second outer peripheral cell 24a is a cell disposed at the outermost peripheral portion of the outer honeycomb fired body 10a and is disposed at a portion other than the portion where the first cell outer peripheral portion 21a is disposed.
The internal cell 22a is an internal cell arranged inside the first outer peripheral cell 21a and the second outer peripheral cell 24a.
Similarly, the outer honeycomb fired body 10b includes a first outer peripheral cell 21b, a second outer peripheral cell 24b, and an inner cell 22b.
Further, the inner honeycomb fired body 10c includes inner honeycomb fired body cells 20c.

The cross-sectional shape perpendicular to the longitudinal direction of each internal cell 22a is the same rectangle.
Further, the cross-sectional shape in the direction perpendicular to the longitudinal direction of the first outer peripheral cell 21a and the second outer peripheral cell 24a is a shape in which two corners are chamfered from a rectangle which is the cross-sectional shape of the inner cell 22a.
Details of the cross-sectional shape of each cell will be described later.

In the honeycomb filter 1, the constituent material of the outer honeycomb fired bodies 10a and 10b and the inner honeycomb fired body 10c is SiC. SiC is a material excellent in heat resistance. Therefore, the outer honeycomb fired bodies 10a and 10b and the inner honeycomb fired body 10c are honeycomb fired bodies having excellent heat resistance. Moreover, the honeycomb filter 1 comprised from these also becomes a honeycomb filter excellent in heat resistance.

In the outer honeycomb fired body 10a, the outer honeycomb fired body 10b, and the inner honeycomb fired body 10c, the cell density is desirably in the range of 15.5 to 62 cells / cm ² (100 to 400 cpsi). It is more desirable to be in the range of 46.5 pieces / cm ² (200 to 300 cpsi).

A case where the exhaust gas passes through the honeycomb fired body 10 having the above-described configuration will be described below with reference to FIG.
As shown in FIG. 1 (b), the exhaust gas discharged from the internal combustion engine and flowing into the honeycomb fired body 10 (in FIG. 1 (b), the exhaust gas is indicated by G and the flow of the exhaust gas is indicated by arrows) is the honeycomb firing. It flows into one cell 20 opened in the exhaust gas inflow side end face 16 of the body 10 and passes through a cell partition wall 30 separating the cells 20. At this time, PM in the exhaust gas is collected by the cell partition wall 30 and the exhaust gas is purified. The purified exhaust gas flows out from other cells 20 opened in the exhaust gas outflow side end face 17 and is discharged to the outside.

Next, the shape and arrangement of cells in each honeycomb fired body will be described with reference to the drawings.
Fig.2 (a)-(c) is sectional drawing which shows typically an example of a cross section perpendicular | vertical to the longitudinal direction of each honeycomb fired body which comprises the honeycomb filter of this invention.

First, the outer honeycomb fired body 10a will be described.
As shown in FIG. 2A, the outline of the cross-sectional shape of the outer honeycomb fired body 10a is a shape obtained by cutting a part from a square with a curve, and includes three line segments and one curve. Each line segment forms a right angle. The curve forms the outermost peripheral portion 2 of the honeycomb filter 1.
In the outer honeycomb fired body 10a, the first outer peripheral cell 21a is disposed in the outermost peripheral portion 12a of the outer honeycomb fired body 10a and adjacent to the outermost peripheral portion 2 of the honeycomb filter 1. . In addition, the second outer peripheral cell 24a is disposed in the outermost peripheral portion 12a other than the portion where the first outer peripheral cell 21a is disposed. And the inner cell 22a is arrange | positioned inside the 1st outer periphery cell 21a and the 2nd outer periphery cell 24a. Further, corner cells 23a are arranged in the corner portions 13a of the outer honeycomb fired body 10a.
The “corner portion of the outer honeycomb fired body” refers to a portion in the vicinity of a right angle formed by each line segment of the outer honeycomb fired body.
Further, in the present specification, “the corner portion of the outer honeycomb fired body” is not included in “the outermost peripheral portion of the outer honeycomb fired body”. That is, the corner cell 23a is not included in the first outer peripheral cell 21a and the second outer peripheral cell 24a.
The internal cell 22a is defined by a cell partition wall 30a, and the first peripheral cell 21a, the second peripheral cell 24a, and the corner cell 23a are the outer periphery that forms the outer periphery of the cell partition wall 30a and the outer honeycomb fired body 10a. Each wall is defined by a wall 32a.

In the outer honeycomb fired body 10a, the cell partition wall 30a has a thickness of 0.210 mm or less. The cell partition wall 30a preferably has a thickness of 0.075 to 0.160 mm.
When the thickness of the cell partition wall 30a is 0.210 mm or less, the thickness of the cell partition wall 30a is sufficiently thin, so that the pressure loss in the initial state where PM is not deposited is sufficiently low. Further, an increase in pressure loss can be suppressed even when PM is deposited.
When the thickness of the cell partition wall 30a exceeds 0.210 mm, the thickness of the cell partition wall 30a is too thick, so that the resistance when the exhaust gas passes through the cell partition wall 30a increases, and as a result, the pressure loss increases.

In the outer honeycomb fired body 10a, the porosity of the cell partition walls 30a is preferably 40 to 65%.
When the porosity of the cell partition wall 30a is 40 to 65%, the cell partition wall 30a can collect PM in the exhaust gas satisfactorily and suppress an increase in pressure loss caused by the cell partition wall 30a. Can do. Accordingly, the outer honeycomb fired body 10a has a low initial pressure loss and is unlikely to increase even when PM is deposited.
If the porosity of the cell partition wall 30a is less than 40%, the ratio of the pores of the cell partition wall 30a is too small, so that the exhaust gas hardly passes through the cell partition wall 30a, and the pressure loss when the exhaust gas passes through the cell partition wall 30a increases. . On the other hand, when the porosity of the cell partition wall 30a exceeds 65%, the mechanical strength of the cell partition wall 30a is lowered, and cracks are likely to occur during regeneration.

In the outer honeycomb fired body 10a, the average pore diameter of the pores contained in the cell partition walls 30a is desirably 8 to 25 μm.
In the honeycomb filter 1 having the above configuration, 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 30a is less than 8 μm, the pores are too small, and the pressure loss when the exhaust gas permeates the cell partition walls 30a increases. On the other hand, when the average pore diameter of the pores contained in the cell partition wall 30a exceeds 25 μm, the pore diameter becomes too large, and the PM collection efficiency is lowered.

The porosity and average pore diameter can be measured by mercury porosimetry.

In the outer honeycomb fired body 10a, the thickness of the outer peripheral wall 32a is not particularly limited, but the minimum value of the thickness of the outer peripheral wall 32a is desirably thicker than the thickness of the cell partition wall 30a. The minimum value is more desirably 1.5 to 3 times the thickness of the cell partition wall 30a, and further desirably 2 to 3 times.
If the minimum value of the thickness of the outer peripheral wall 32a is larger than the thickness of the cell partition wall 30a, the outer peripheral wall 32a has a sufficient thickness even though the cell partition wall 30a is thin. Has a sufficiently high strength. Moreover, since the outer peripheral wall 32a of the outer honeycomb fired body 10a is thick, it is possible to suppress a decrease in heat capacity associated with making the cell partition walls 30a thinner.

In the outer honeycomb fired body 10a, the porosity of the outer peripheral wall 32a is preferably 40 to 65%.
The reason why the porosity of the outer peripheral wall 32a is preferably within the above range is the same as the reason why the porosity of the cell partition wall 30a is preferably within the above range.

In the outer honeycomb fired body 10a, the average pore diameter of the pores included in the outer peripheral wall 32a is desirably 8 to 25 μm.
The reason why the average pore diameter of the pores included in the outer peripheral wall 32a is preferably in the above range is the same as the reason why the average pore diameter of the pores included in the cell partition wall 30a is preferably in the above range.

As shown in FIG. 2A, the cross-sectional shape in the direction perpendicular to the longitudinal direction of each internal cell 22a is the same rectangle α.
The shape of the cross section perpendicular to the longitudinal direction of the first outer peripheral cell 21a and the second outer peripheral cell 24a is a shape in which two corners are chamfered from the rectangle α which is the cross sectional shape of the inner cell 22a.
The cell partition wall 30a in contact with the outer peripheral wall 32a has a thick wall region 31a that gradually increases toward the outer peripheral wall 32a.
That is, in the cross-sectional shape perpendicular to the longitudinal direction of the first outer peripheral cell 21a and the second outer peripheral cell 24a, a thick wall region 31a is formed in a portion where two corners are chamfered from the rectangle α. .
Note that “a shape in which a corner portion is chamfered from a rectangle” means a shape in which a corner portion of the rectangle is cut from a rectangle by a straight line or a curve.

In the outer honeycomb fired body 10a, the rectangle α is desirably a square.

The cross-sectional shape perpendicular to the longitudinal direction of the first outer peripheral cell 21a may be a shape as shown in FIGS.
Fig.3 (a)-(e) is sectional drawing which shows typically an example of the cross-sectional shape of the orthogonal | vertical direction to the longitudinal direction of the 1st outer periphery cell in the honeycomb calcination object of the present invention.
FIG. 3A shows a cross-sectional shape of the _first outer peripheral cell 21a ₁ in which two adjacent corners of the rectangle α are hexagons cut off by two line segments A and B, respectively. The line segments A and B are not in direct contact with each other, and when the line segments A and B are extended, they intersect each other outside the rectangle α. Further, a part of the side of the rectangle α between the two cut corners forms one side of the hexagon.
FIG. 3B shows a cross-sectional shape of the first outer peripheral cell 21a ₂ in which two adjacent corners of the rectangle α are pentagons cut off by two line segments C and D, respectively. The line segment C and the line segment D intersect at the side forming the rectangle α. The line segment C and the line segment D may intersect within the rectangle α. That is, there is no side that forms the pentagon between the two corners to be cut.
FIG. 3C is an octagon in which one of the two adjacent corners of the rectangle α is cut off by line segments E and F, and the other corner is cut off by line segments G and H. The cross-sectional shape of a certain first outer peripheral cell 21a ₃ is shown. The line segment E and the line segment F intersect each other inside the rectangle α. Furthermore, the line segment G and the line segment H cross each other within the rectangle α. Further, a part of the side of the rectangle α between the two cut corners forms one side of the octagon.
FIG. 3D shows a cross-sectional shape of the first outer peripheral cell 21a ₄ in which two adjacent corners of the rectangle α are cut off by two curves A ′ and B ′. Curves A ′ and B ′ are curves obtained by bending line segments A and B so that the corners of rectangle α are rounded. Some of the sides of the rectangular α located between the two corner portions cut away forms a contour of the cross-sectional shape of the first angular cell 21a _4.
FIG. 3E shows a cross-sectional shape of the first outer peripheral cell 21a ₅ in which two adjacent corners of the rectangle α are cut off by two curves C ′ and D ′. Curves C ′ and D ′ are curves obtained by bending the line segments C and D so that the corners of the rectangle α are rounded. The curve C ′ and the curve D ′ intersect at a side forming a rectangle. The curve C ′ and the curve D ′ may intersect within the rectangle α.
In the outer honeycomb fired body 10a, a thick wall region 31a is formed in a portion where the corner portion of the rectangle α is cut off in FIGS. 3A to 3E (that is, a portion surrounded by a broken line and a solid line). ing.
In addition, the cross-sectional shape perpendicular to the longitudinal direction of the first outer peripheral cell 21a is not limited to the above shape, and may be another shape in which two corners are chamfered from the rectangle α.
The area of the first angular cell _21a 1 ～21A corner in ₅ cut away portion (i.e. the area of the thick-walled region 31a) is 20 to 40% of the rectangle alpha.

When the cross-sectional shape perpendicular to the longitudinal direction of the first outer peripheral cell 21a is as described above and the thick wall region 31a is formed, the volume in the vicinity of the outer peripheral wall 32a of the outer honeycomb fired body 10a is large. Become.
Therefore, the outer honeycomb fired body 10a has a sufficiently high strength against an external impact or the like because the volume in the vicinity of the outer peripheral wall 32a is sufficiently large even though the cell partition wall 30a is thin. Further, since the volume in the vicinity of the outer peripheral wall 32a is large, the outer honeycomb fired body 10a can suppress a decrease in heat capacity. Therefore, even if the outer honeycomb fired body 10a is heated rapidly, heat can be received by the outer peripheral wall 32a, and generation of cracks can be suppressed.

This can also be explained as follows.
The outer honeycomb fired body 10a is cut out in a predetermined range in an area including the portion where the SiC exists in the outer honeycomb fired body 10a and the space portion of the cell where SiC does not exist. Assuming that the value obtained by dividing the weight of the honeycomb fired body 10a by the volume within a predetermined range is the “apparent density”, in the outer honeycomb fired body 10a, the outermost peripheral portion 12a of the outer honeycomb fired body 10a is more outward. The value of the “apparent density” is larger than that of the inner portion of the honeycomb fired body 10a.
Therefore, in the outer honeycomb fired body 10a, the heat capacity of the outermost peripheral portion 12a of the outer honeycomb fired body 10a is relatively high. Therefore, even if heat is suddenly applied from the outside, heat can be received at the outermost peripheral portion 12a, and the occurrence of cracks can be prevented.
In addition, when the “apparent density” of the outermost peripheral portion 12a of the outer honeycomb fired body 10a is high, the outer frame has a mechanically strong structure even though the cell partition wall 30a is thin. It has a sufficiently high strength.

In the outer honeycomb fired body 10a, the area of the cross section perpendicular to the longitudinal direction of the first outer peripheral cell 21a is 60 to 80% of the area of the cross section perpendicular to the longitudinal direction of the internal cell 22a.
When the ratio of the area is less than 60%, the area of the opening of the first outer peripheral cell 21a is reduced, the flow path of the exhaust gas is narrowed, and the gas passage resistance when the exhaust gas passes through the cell partition wall 30a is increased. As a result, the pressure loss increases.
Further, if the area ratio exceeds 80%, the value of the apparent density of the outermost peripheral portion of the outer honeycomb fired body 10a is lowered, so that the outer peripheral wall 32a of the outer honeycomb fired body 10a is thicker. It is difficult to obtain the effect.

In addition, the area of the cross section perpendicular to the longitudinal direction of each cell can be obtained by the following method.
First, the honeycomb fired body 10 is cut in a direction perpendicular to the longitudinal direction. Next, an SEM image of a cross section perpendicular to the longitudinal direction of the honeycomb fired body 10 is taken.
The photographed SEM image is binarized to identify the skeleton parts such as the cell partition walls 30 and the outer peripheral wall 32 and the space parts such as the respective cells. And the area of the part identified as the space part of each cell in a SEM image is made into the area of each cell.

In FIG. 2 (a), the cross-sectional shape in the direction perpendicular to the longitudinal direction of the second angular cell 24a is a shape in which two corners are chamfered from the rectangle α. In the honeycomb filter of the present invention, The cross-sectional shape of the two peripheral cells 24a is not particularly limited. All vertical cross-sectional shape in the longitudinal direction of the second angular cell 24a, may be the same shape as the first angular cell 21a ₁ ~21a _5, may be rectangular α congruent shape .
The area of the cross section perpendicular to the longitudinal direction of the second outer peripheral cell 24a is preferably 60 to 80% of the area of the cross section perpendicular to the longitudinal direction of the internal cell 22a.

Next, the shape of the corner cell 23a disposed in the corner portion 13a of the outer honeycomb fired body 10a will be described.
The cross-sectional shape perpendicular to the longitudinal direction of the corner cell 23a is not particularly limited, but it is desirable that at least one corner is chamfered from the rectangle α which is the cross-sectional shape of the internal cell 22a.
When the shape of the corner cell 23a is such a shape, the volume in the vicinity of the outer peripheral wall 32a of the outer honeycomb fired body 10a is increased.
Therefore, the outer honeycomb fired body 10a has a sufficiently high strength against an external impact or the like because the volume in the vicinity of the outer peripheral wall 32a is sufficiently large even though the cell partition wall 30a is thin. Further, since the volume in the vicinity of the outer peripheral wall 32a is large, the outer honeycomb fired body 10a can suppress a decrease in heat capacity. Therefore, even if the outer honeycomb fired body 10a is heated rapidly, heat can be received by the outer peripheral wall 32a, and generation of cracks can be suppressed.

Further, the shape of the corner cell 23a may be a shape in which all corner portions are chamfered with a straight line or a curve from the rectangle α, or may be the same shape as the first outer cell 21a. The shape shown to 4 (a)-(d) may be sufficient.
FIGS. 4A to 4D are cross-sectional views schematically showing an example of a cross-sectional shape perpendicular to the longitudinal direction of the corner cells in the honeycomb fired body of the present invention.
FIG. 4A shows a heptagon having three corners cut off by line segments I, J, and K, except for the corner that is the innermost of the outer honeycomb fired body 10a among the corners of the rectangle α. It shows a cross-sectional shape of the corner cell 23a ₁ is. The line segments I and J are not in direct contact with each other, and when the line segments I and J are extended, they intersect each other outside the rectangle α. Further, the line segments I and K are not in direct contact with each other, and when the line segments I and K are extended, they intersect each other outside the rectangle α. Some of the truncated three corner portions each with a rectangular α sides between is heptagonal side is a cross-sectional shape of the corner cell 23a ₁ were formed, respectively.
FIG. 4 (b), shows the most outer honeycomb fired body 10a cross-sectional shape of the corner cell 23a ₂ is a pentagon corner on the inside was cut away by the line segment L of the corner portion of the rectangular α Yes.
In FIG. 4 (c), three corners are cut out by curves I ′, J ′ and K ′, respectively, except for the corners which are inside the outer honeycomb fired body 10a among the corners of the rectangle α. It shows a cross-sectional shape of the corner cell 23a _3. Curves I ′, J ′, and K ′ are curves obtained by bending line segments I, J, and K so that the corners of rectangle α are rounded. Some of the truncated three corner portions each with a rectangular α sides during forms the contour of the cross-sectional shape of the corner cell 23a _3.
FIG. 4 (d) shows the most outer corners sectional shape of the cell 23a _4, taken corners made inward by curve L'of the honeycomb fired body 10a of the corners of the rectangle alpha. The curve L ′ is a curve obtained by bending the line segment L so that the corner of the rectangle α is rounded.
In particular, when the shape of the corner cell 23a is the shape shown in FIG. 4B or FIG. 4D, compressive stress is hardly applied due to the structure of the outer honeycomb fired body 10a. Therefore, it has a sufficiently high strength against external impacts and the like.

The outer honeycomb fired body 10a may be loaded with a catalyst for purifying exhaust gas. As the supported catalyst, for example, a noble metal such as platinum, palladium, rhodium, etc. is desirable, and among these, platinum is more desirable. . Further, as other catalysts, for example, alkali metals such as potassium and sodium, and alkaline earth metals such as barium can be used. These catalysts may be used alone or in combination of two or more.
When these catalysts are supported, it is easy to burn and remove PM, and toxic exhaust gas can be purified.

Next, the outer honeycomb fired body 10b will be described.
The outer honeycomb fired body 10b has the same configuration as the outer honeycomb fired body 10a except that the cross-sectional shape in the direction perpendicular to the longitudinal direction is different.
As shown in FIG. 2 (b), the outline of the cross-sectional shape of the outer honeycomb fired body 10b is a shape obtained by cutting a part from a square with a curve, and consists of two line segments and one curve. Each of the two line segments forms a right angle. The curve forms the outermost peripheral portion 2 of the honeycomb filter 1.
In the outer honeycomb fired body 10b, the first outer peripheral cell 21b is disposed in the outermost peripheral portion 12b of the outer honeycomb fired body 10b and in the portion adjacent to the outermost peripheral portion 2 of the honeycomb filter 1. . Further, the second outer peripheral cell 24b is disposed in the outermost peripheral portion 12b other than the portion where the first outer peripheral cell 21b is disposed. And the inner cell 22b is arrange | positioned inside the 1st outer periphery cell 21b and the 2nd outer periphery cell 24b. Further, the corner cell 23b is disposed in the corner portion 13b of the outer honeycomb fired body 10b.

As shown in FIG. 2B, the cross-sectional shape in the direction perpendicular to the longitudinal direction of each internal cell 22b is the same rectangle α.
The shape of the cross section perpendicular to the longitudinal direction of the first outer peripheral cell 21b and the second outer peripheral cell 24b is a shape in which two corners are chamfered from the rectangle α which is the cross-sectional shape of the inner cell 22b.
The cell partition wall 30b in contact with the outer peripheral wall 32b has a thick wall region 31b that gradually increases toward the outer peripheral wall 32b.
That is, the thick wall region 31b is formed in a portion where two corners are chamfered from the rectangle α in the cross-sectional shape perpendicular to the longitudinal direction of the first outer peripheral cell 21b and the second outer peripheral cell 24b. .
Note that “a shape in which a corner portion is chamfered from a rectangle” means a shape in which a corner portion of the rectangle is cut from a rectangle by a straight line or a curve.

The shape of the first outer peripheral cell 21b, the shape of the second outer peripheral cell 24b, and the shape of the corner cell 23b are the same as the shape of the first outer peripheral cell 21a, the shape of the second outer peripheral cell 24a, and the corner. The shape of the partial cell 23a is the same.

The cell wall thickness, porosity, etc. of the outer honeycomb fired body 10b are the same as the cell wall thickness, porosity, etc. of the outer honeycomb fired body 10a already described, and the description thereof is omitted here. .

Next, the inner honeycomb fired body 10c will be described.
The inner honeycomb fired body 10c has the same configuration as the outer honeycomb fired body 10a except that the cross-sectional shape perpendicular to the longitudinal direction is a square and the shape of the cells is different.
As shown in FIG. 2C, the cross-sectional shape of the inner honeycomb fired body 10c in the direction perpendicular to the longitudinal direction of the cells 20c is congruent with the rectangle α which is the sectional shape perpendicular to the longitudinal direction of the internal cells 22a. is there.
When the cell 20c of the inner honeycomb fired body 10c has the above shape, the opening ratio of the inner honeycomb fired body 10c is higher than the opening ratio of the outer honeycomb fired bodies 10a and 10b. Therefore, in the honeycomb filter 1 having such an inner honeycomb fired body 10c, the pressure loss can be kept low.
The cell wall thickness, porosity, etc. of the inner honeycomb fired body 10c are the same as the cell wall thickness, porosity, etc. of the outer honeycomb fired body 10a already described, and the description thereof is omitted here. .

It should be noted that the shape of the cells arranged at the outermost peripheral portion of the inner honeycomb fired body 10c may be the same shape as the first outer peripheral cell 21a. That is, the shape of the cross section perpendicular to the longitudinal direction of the cells arranged in the outermost peripheral portion of the inner honeycomb fired body 10c is a shape in which two corners are chamfered from the rectangle α which is the cross sectional shape of the internal cell 22a. There may be.
Further, the shape of the cells arranged at the corners of the inner honeycomb fired body 10c may be the same shape as the corner cells 23a.
With such a structure, the outer frame of the inner honeycomb fired body 10c has a sufficiently high strength against external impacts and the like. Further, since the volume in the vicinity of the outermost peripheral portion of the inner honeycomb fired body 10c is large, the inner honeycomb fired body 10c having such a structure can suppress a decrease in heat capacity.

In the honeycomb filter 1, the adhesive layer 14 is obtained by applying and drying an adhesive paste containing an inorganic binder and inorganic particles. The adhesive paste may further contain inorganic fibers and / or whiskers.

Further, an outer peripheral coat layer 15 for preventing leakage of exhaust gas may be formed on the outer periphery of the honeycomb filter 1 as necessary. The material of the outer peripheral coat layer 15 is preferably the same as the material of the adhesive paste.

Since the honeycomb filter 1 is constituted by the honeycomb fired body 10 having the above-described effects, the pressure loss in the initial state where PM is not deposited is sufficiently low, the strength is sufficiently strong, and the decrease in the heat capacity is suppressed. .

The honeycomb filter 1 is preferably a honeycomb filter used for purifying exhaust gas in a gasoline engine.
As described above, the honeycomb filter 1 has a sufficiently low pressure loss in an initial state where PM is not deposited, a sufficiently high strength, and a reduction in heat capacity is suppressed. Therefore, the honeycomb filter 1 can be suitably used for purifying exhaust gas in a gasoline engine.

Next, the honeycomb filter of the present invention may have the following aspects.
FIG. 5 is a cross-sectional view schematically showing an example of a cross section perpendicular to the longitudinal direction of a honeycomb filter according to another aspect of the present invention.

As shown in FIG. 5, a honeycomb filter 101, which is an example of the honeycomb filter of the present invention, has a plurality of cells that are sealed at one end and serve as exhaust gas flow paths, and a porous cell that partitions the cells. The outer honeycomb fired bodies 110a _{1 to} 110a ₈ , the outer honeycomb fired bodies 110b _{1 to} 110b ₄ and the inner honeycomb fired bodies 110c each including the cell partition walls are bonded to each other through the adhesive layer 114. It is a honeycomb filter. Further, an outer peripheral coat layer 115 for preventing leakage of exhaust gas is formed on the outer periphery of the honeycomb filter 101.
The outer honeycomb fired bodies 110 a _{1 to} 110 a ₈ and the outer honeycomb fired bodies 110 b _{1 to} 110 b ₄ are arranged in the outermost peripheral portion 102 of the honeycomb filter 101. Further, the inside of the outer honeycomb fired bodies 110a ₁ ~110a ₈ and the outer honeycomb fired body 110b ₁ ~110b ₄ are disposed inner honeycomb fired body 110c.
The outer shape of the inner honeycomb fired body 110c is prismatic, the outer shape of the outer honeycomb fired bodies 110a ₁ ~110a ₈ and the outer honeycomb fired body 110b ₁ ~110b ₄ is cut a portion of the inner honeycomb fired bodies 110c Shape.
In the honeycomb filter 101, the outer honeycomb fired bodies 110a ₁ ~110a _8, the outer honeycomb fired body 110b ₁ ~110b _4, has been combined with four inner honeycomb fired bodies 110c disposed on these inner, Its external shape is cylindrical.
The cross-sectional shapes of the outer honeycomb fired bodies 110a _{1 to} 110a ₈ are the same as those of the above-mentioned outer honeycomb fired body 10a except for the shape and arrangement of the cells. The cross-sectional shapes of the outer honeycomb fired bodies 110b _{1 to} 110b ₄ are the same as those of the above-mentioned outer honeycomb fired body 10b except for the shape and arrangement of the cells.

Each outer honeycomb fired body includes an outer honeycomb fired body 110a ₁ , an outer honeycomb fired body 110a ₂ , an outer honeycomb fired body 110b ₁ , an outer honeycomb fired body 110a ₃ , an outer honeycomb fired body 110a ₄ , an outer side. Honeycomb fired body 110b ₂ , outer honeycomb fired body 110a ₅ , outer honeycomb fired body 110a ₆ , outer honeycomb fired body 110b ₃ , outer honeycomb fired body 110a ₇ , outer honeycomb fired body 110a ₈ , outer honeycomb fired body The outermost peripheral portion 102 of the honeycomb filter 101 is configured so as to make a round around the body 110b ₄ and the outer honeycomb fired body 110a ₁ in order.

The honeycomb filter 101 has the same configuration as the honeycomb filter 1 except that the shape of the second peripheral cell of each outer honeycomb fired body is different.
Accordingly, the arrangement of the cells of each outer honeycomb fired body will be described with reference to the drawings, focusing on the outer honeycomb fired body 110a ₁ , the outer honeycomb fired body 110a ₂ and the outer honeycomb fired body 110b ₄ .

FIG. 6 is an enlarged view of a broken line portion of FIG.
As shown in FIG. 6, the outer honeycomb fired body 110a ₁ is adjacent to the outer honeycomb fired body 110a ₂ and is also adjacent to the outer honeycomb fired body 110b ₄ .

Outer honeycomb fired bodies 110a ₁ includes a first outer peripheral cells 121a ₁ and the second angular cell 124a ₁ and the internal cell 122a ₁ and the corner portion cell 123a _1.
The shape of the first outer peripheral cell 121a _1, the shape of the inner cell 122a ₁ , and the shape of the corner cell 123a ₁ are the same as the shape of the first outer peripheral cell 21a, the shape of the inner cell 22a, and the shape of the corner cell 23a. Since it is the same as the shape, description thereof is omitted here.

The outer honeycomb fired body 110a ₂ includes a first outer peripheral cell 121a ₂ , a second outer peripheral cell 124a ₂ , an inner cell 122a ₂ and a corner cell 123a ₂ .
The shape of the first outer peripheral cell 121a _2, the shape of the inner cell 122a _{2 and} the shape of the corner cell 123a ₂ are the same as the shape of the first outer peripheral cell 21a, the shape of the inner cell 22a and the shape of the corner cell 23a. Since it is the same as the shape, description thereof is omitted here.

Outer honeycomb fired body 110b ₄ includes a first angular cell 121b ₄ the second angular cell 124b ₄ and the inner cell 122b ₄ and corner cells 123b _4.
The shape of the first angular cell 121b _4, the shape of the internal cell 122b ₄ shapes and corners cell 123b ₄ have already described the above shape of the first angular cell 21b, the internal cell 22b of shapes and corners cell 23b Since it is the same as the shape, description thereof is omitted here.

In the honeycomb filter 101, the outer honeycomb fired bodies 110a ₁ and the outer honeycomb fired bodies 110a ₂ adjacent, second one of the peripheral cells 124a ₁ which is disposed outside the honeycomb fired bodies 110a _1, the outer honeycomb fired body The cross-sectional shape in the direction perpendicular to the longitudinal direction of the second outer peripheral cell 124a _1-1 facing the 110a ₂ is a shape in which two corners are chamfered from the rectangle α.
On the other hand, the second of the peripheral cells 124a ₂ which is disposed outside the honeycomb fired bodies 110a _2, in the longitudinal direction of the second angular cell _{124a 2-2} facing the outer honeycomb fired bodies 110a ₁ vertical section The shape is congruent with the rectangle α.
Further, in the outer honeycomb fired bodies 110a ₁ and the outer honeycomb fired body 110b ₄ adjacent second of the peripheral cells 124a ₁ which is disposed outside the honeycomb fired bodies 110a _1, an outer honeycomb fired body 110b ₄ The cross-sectional shape in the direction perpendicular to the longitudinal direction of the second outer peripheral cells 124a _1-2 facing each other is the same shape as the rectangle α.
On the other hand, of the second peripheral cells 124b ₄ arranged in the outer honeycomb fired body 110b ₄ , the cross section in the direction perpendicular to the longitudinal direction of the second outer peripheral cells 124b _4-1 facing the outer honeycomb fired body 110a _1. The shape is a shape in which two corners are chamfered from the rectangle α.
Similarly, in the honeycomb filter 101, the cross-sectional shape of one outer peripheral cell facing similarly in the other outer honeycomb fired bodies is a shape in which two corners are chamfered from the rectangle α, and the cross-sectional shape of the other cell Is a rectangle α.

Also, the area of the cross section perpendicular to the longitudinal direction of the second outer peripheral cell 124a _1-1 having a cross-sectional shape with two corners chamfered from the rectangle α is the cross section perpendicular to the longitudinal direction of the internal cell 122a _1. It is desirable that it is 60 to 80% of the area.

If the cross-sectional shape of the second outer peripheral cell 124a _{1-1 and} the cross-sectional shape of the second outer peripheral cell 124a _2-2 are both made into a shape in which two corners are chamfered from the rectangle α, the facing outer honeycombs since the volume of the outer peripheral wall 132a ₂ of the outer peripheral wall 132a ₁ and the outer honeycomb fired bodies 110a ₂ of the sintered body 110a ₁ is increased, there is also a pressure loss may increase.
If both the cross-sectional shape of the second outer peripheral cell 124a _{1-1 and} the cross-sectional shape of the second outer peripheral cell 124a _2-2 are rectangular α, the volume of each outer peripheral wall is reduced. It becomes difficult for strength to be sufficient against external impact. In addition, the heat capacity tends to be small.
However, in the honeycomb filter 101, the cross-sectional shape of the second peripheral cell 124a _1-1 is a shape in which two corners are chamfered from the rectangle α, and the cross-sectional shape of the second peripheral cell 124a _2-2 is a rectangular α. It is the same shape as. That is, the volume of the outer peripheral wall of _one outer honeycomb fired body facing each other (that is, the outer peripheral wall 132a ₁ of the outer honeycomb fired body 110a ₁ ) is large, and the outer peripheral wall of the other outer honeycomb fired body (ie The volume of the outer peripheral wall 132a ₂ ) of the outer honeycomb fired body 110a ₂ is not increased. Therefore, an increase in pressure loss and a decrease in heat capacity can be balanced, and an increase in pressure loss can be suppressed, and a decrease in heat capacity can be suppressed.

In FIG. 6, among the second outer peripheral cells 124a ₁ of the outer honeycomb fired body 110a ₁ , the cross-sectional shape in the direction perpendicular to the longitudinal direction of the second outer peripheral cells 124a _1-3 facing the inner honeycomb fired body 110c is The two corners of the rectangle α are chamfered.
With such a configuration, since the outer peripheral wall 132a ₁ near the volume of the outer honeycomb fired bodies 110a increases, has a sufficiently high strength to external impact or the like. Further, since the volume in the vicinity of the outer peripheral wall 132a ₁ is large, the outer honeycomb fired body 110a ₁ can suppress a decrease in heat capacity. Therefore, even if the outer honeycomb fired body 110a ₁ is heated rapidly, heat can be received by the outer peripheral wall 132a _{1 and} the occurrence of cracks can be suppressed.
In the honeycomb filter of the present invention, the cross-sectional shape of the second peripheral cell 124a _1-3 is not particularly limited, and may be the same shape as the rectangle α.

Note that the cross-sectional shape of the second outer peripheral cell 124a _2-1 of the outer honeycomb fired body 110a ₂ facing the outer honeycomb fired body 110b ₁ is a shape in which two corners are chamfered from the rectangle α. Also. The cross-sectional shape of the second peripheral cells _{124b 4-2} of the outer honeycomb fired body 110b ₄ facing the outer honeycomb fired bodies 110a ₈ is a congruent shape and rectangular alpha.
In the honeycomb filter 101, the other outer honeycomb fired bodies 110a _{3 to} 110a ₈ and the outer honeycomb fired bodies 110b _{1 to} 110b ₃ are similarly out of the second outer peripheral cells arranged in one outer honeycomb fired body. The cross-sectional shape in the direction perpendicular to the longitudinal direction of the second outer peripheral cell facing the other outer honeycomb fired body is a shape in which two corners are chamfered from the rectangle α. Among the arranged second peripheral cells, the cross-sectional shape of the second peripheral cell facing one of the outer honeycomb fired bodies is the same shape as the rectangle α.
Therefore, the honeycomb filter 101 as a whole also exhibits the effects described in the explanation of the outer honeycomb fired bodies 110a ₁ , 110a ₂ , and 110b ₄ .

Next, an example of an exhaust gas purification apparatus using the honeycomb filter of the present invention will be described.
FIG. 7 is a cross-sectional view schematically showing an example of an exhaust gas purifying apparatus in which the honeycomb filter of the present invention is installed.
An exhaust gas purification device 50 shown in FIG. 7 includes a honeycomb filter 1, a metal casing 51 that covers the outside of the honeycomb filter 1, and a holding sealing material 52 disposed between the honeycomb filter 1 and the metal casing 51. An inlet pipe 53 connected to an internal combustion engine such as an engine is connected to the end of the metal casing 51 on the side where the exhaust gas is introduced, and the other end of the metal casing 51 is connected to the outside. The discharged exhaust pipe 54 is connected.

The exhaust gas discharged from the internal combustion engine and flowing into the exhaust gas purification device 50 (in FIG. 7, the exhaust gas is indicated by G and the flow of the exhaust gas is indicated by an arrow) reaches the honeycomb fired body constituting the honeycomb filter 1 and is fired by the honeycomb. Purified by the body. Since the mechanism for purifying the exhaust gas by the honeycomb fired body has already been described, description thereof is omitted here. The purified exhaust gas flows out of the honeycomb fired body and is discharged outside.

In the exhaust gas purifying apparatus 50, the holding sealing material 52 is desirably a mat made of inorganic fibers, and the mat is desirably a needle mat obtained by performing a needling treatment.
As the inorganic fiber, alumina fiber, alumina-silica fiber, silica fiber, and biosoluble fiber can be used.
The needling process means that fiber entanglement means such as a needle is inserted and removed from the base mat. In the holding sealing material 52, it is desirable that inorganic fibers having a relatively long average fiber length are entangled three-dimensionally by needling treatment.

In addition, in order to exhibit an entanglement structure, the inorganic fiber has a certain average fiber length. For example, the average fiber length of the inorganic fiber is preferably about 50 μm to 100 mm.

The average fiber diameter of the inorganic fibers of the mat constituting the holding sealing material 52 is preferably 1 to 20 μm, and more preferably 3 to 10 μm.
When the average fiber diameter of the inorganic fibers is 1 to 20 μm, the strength and flexibility of the inorganic fibers are sufficiently high, and the shear strength of the holding sealing material 52 can be improved.
If the average fiber diameter of the inorganic fibers is less than 1 μm, the inorganic fibers are easily cut into thin pieces, so that the tensile strength of the inorganic fibers becomes insufficient. On the other hand, when the average fiber diameter of the inorganic fibers exceeds 20 μm, the flexibility of the inorganic fibers is insufficient because the inorganic fibers are not easily bent.

Basis weight of the mat of a holding sealing material 52 (weight per unit area) is not particularly limited, is preferably a 200~4000g / ^{m 2,} and more desirably 1000 to 3000 g / ^{m 2.} When the basis weight of the mat is less than 200 g / m ² , the holding force is not sufficient, and when the exhaust gas purification apparatus 1 is manufactured using the holding sealing material 52 configured by such a mat, the honeycomb filter 1 is dropped. It becomes easy to do.
On the other hand, if the basis weight of the mat exceeds 4000 g / m ² , it is difficult to reduce the bulk of the mat.

Further, the bulk density of the mat constituting the holding sealing material 52 (the bulk density of the holding sealing material before winding) is not particularly limited, but is desirably 0.10 to 0.30 g / cm ³ . When the bulk density of the mat is less than 0.10 g / cm ³ , the entanglement of the inorganic fibers is weak and the inorganic fibers are easily peeled off, so that it is difficult to keep the shape of the mat in a predetermined shape.
Further, when the bulk density of each mat exceeds 0.30 g / cm ³ , the mat constituting the holding sealing material 52 becomes hard, the winding property of the holding sealing material 52 around the honeycomb filter 1 is lowered, and the holding sealing material 52 Becomes easy to break.

The mat constituting the holding sealing material 52 may further contain a binder such as an organic binder in order to suppress bulkiness and improve workability before assembling the exhaust gas purification apparatus 1.
In addition, the thickness of the mat constituting the holding sealing material 52 is preferably 1.5 to 15 mm.

In the exhaust gas purifying apparatus 50, the metal casing 51 is preferably mainly made of metal such as stainless steel.

Next, an example of a method for manufacturing the honeycomb filter of the present invention will be described.

(1) Preparation of honeycomb fired body (1-1) Ceramic raw material preparation step First, a ceramic raw material to be a raw material of a honeycomb fired body is prepared. The ceramic raw material can be prepared by mixing silicon carbide powder, an organic binder, a plasticizer, a lubricant, and water.
If necessary, a pore-forming agent such as balloons that are fine hollow spheres containing oxide ceramics, spherical acrylic particles, and graphite may be added to the ceramic raw material.
The balloon is not particularly limited, and examples thereof include an alumina balloon, a glass micro balloon, a shirasu balloon, a fly ash balloon (FA balloon), and a mullite balloon. Of these, alumina balloons are desirable.

(1-2) Extrusion Forming Process Next, a honeycomb formed body having a predetermined shape is formed by extruding the ceramic raw material prepared in the ceramic raw material preparing step using a predetermined mold and cutting it at a predetermined length. Is made.
The shape of the honeycomb molded body produced in the present extrusion molding process is as shown in FIG. 1 (a) and FIG. 5 when a predetermined number of aggregates are formed when the honeycomb molded body becomes a honeycomb fired body through the subsequent steps. It is formed into a shape that is a cylindrical shape.
Note that the shape of the honeycomb formed body, the shape of the cells, the arrangement of the cells, the thickness of the cell partition walls, the thickness of the outer peripheral wall, and the like can be adjusted by adjusting the shape of the mold.

(1-3) Drying step Next, the honeycomb formed body obtained in the extrusion molding step is subjected to a microwave dryer, a hot air dryer, a dielectric dryer, a vacuum dryer, a vacuum dryer, a freeze dryer, or the like. To dry. In drying the honeycomb formed body, a microwave dryer and a hot air dryer are used in combination, or the honeycomb formed body is dried to a certain level of moisture using a microwave dryer, and then a hot air dryer is used. Thus, moisture in the honeycomb formed body may be completely removed.

(1-4) Sealing process The sealing process which seals the said cell by filling the sealing material paste used as a sealing material in the predetermined cell of the honeycomb molded object after the said drying process is performed.
Here, the ceramic raw material can be used as the sealing material paste.

(1-5) Degreasing Step Next, the honeycomb formed body after the sealing step is heated at 300 to 650 ° C. for 0.5 to 3 hours to remove organic matter in the honeycomb formed body, Make it.

(1-6) Firing Step The honeycomb degreased body obtained in the degreasing step is fired at 1800 to 2200 ° C. for 0.5 to 4 hours in an inert gas atmosphere such as a nitrogen atmosphere or an argon atmosphere.
In addition, the sealing material paste with which the edge part of the cell was filled is baked by heating and becomes a sealing material.

(2) Manufacture of Honeycomb Filter (2-1) Adhesive Paste Preparation Step First, an adhesive paste for bonding the honeycomb fired body is prepared.
As the adhesive paste, for example, a paste made of an inorganic binder, an organic binder, and inorganic particles is used. The adhesive paste may further contain inorganic fibers and / or whiskers.
Examples of the inorganic particles contained in the adhesive paste include carbide particles and nitride particles. Specific examples include silicon carbide particles, silicon nitride particles, and boron nitride particles. These may be used alone or in combination of two or more. Among the inorganic particles, silicon carbide particles having excellent thermal conductivity are desirable.
Examples of the inorganic fiber and / or whisker contained in the adhesive paste include inorganic fiber and / or whisker made of silica-alumina, mullite, alumina, silica, and the like. These may be used alone or in combination of two or more. Among inorganic fibers, alumina fiber is desirable. The inorganic fiber may be a biosoluble fiber.
Furthermore, you may add the balloon which is a micro hollow sphere which uses an oxide type ceramic as a component, spherical acrylic particle, graphite, etc. to the said adhesive paste. The balloon is not particularly limited, and examples thereof include an alumina balloon, a glass micro balloon, a shirasu balloon, a fly ash balloon (FA balloon), and a mullite balloon.

(2-2) Aggregation step The adhesive paste prepared in the above step is applied to the side surface of the honeycomb fired body to aggregate a plurality of honeycomb fired bodies.
Thereafter, the aggregated honeycomb fired bodies are heated to solidify the adhesive paste by heating to form an adhesive layer, thereby producing a cylindrical honeycomb filter.

(2-3) Outer peripheral coat layer forming step Next, an outer peripheral coat material paste is applied to the outer periphery of the aggregate of the honeycomb fired bodies obtained in the assembly step, and dried and solidified to form an outer peripheral coat layer.
Here, the said adhesive paste can be used as an outer periphery coating material paste. Moreover, you may use the paste of a composition different from the said adhesive material paste as an outer periphery coating material paste.
Note that the outer peripheral coat layer is not necessarily provided, and may be provided as necessary.

The honeycomb filter of the present invention can be manufactured through the above steps.

(Example)
Examples that specifically disclose modes for carrying out the present invention are shown below, but the modes for carrying out the present invention are not limited to these examples.

(Example 1)
(1) Manufacture of honeycomb fired body (1-1) Ceramic raw material preparation step 52.8% by weight of silicon carbide coarse powder having an average particle size of 22 μm and silicon carbide fine powder of 22.6% having an average particle size of 0.5 μm The organic binder (methyl cellulose) is 4.6% by weight, the lubricant (Unilube made by NOF Corporation) is 0.8% by weight, the glycerin is 1.3% by weight, and the pores are mixed. A ceramic raw material was prepared by adding and mixing 1.9% by weight of material (acrylic resin), 2.8% by weight of oleic acid, and 13.2% by weight of water.
(1-2) Extrusion Step Next, the ceramic raw material prepared in the ceramic raw material preparation step is extrusion-molded, and the eight outer honeycomb fired bodies 10a and four pieces shown in FIGS. A honeycomb formed body from which the outer honeycomb fired body 10b and the four inner honeycomb fired bodies 10c were based was produced.
Extrusion is performed so that the shape of the first angular cell and all the second angular cells are the shapes shown in FIG. 3A, and the corner cells are the shapes shown in FIG. 4A. It was.
(1-3) Drying Step Next, the raw honeycomb molded body was dried using a microwave dryer to prepare a dried honeycomb molded body.
(1-4) Sealing Step After that, cells were sealed by filling a predetermined cell of the dried honeycomb molded body with a sealing material paste.
Specifically, the cells were sealed so that the end portions on the exhaust gas inlet side and the end portions on the exhaust gas outlet side were alternately sealed as shown in FIG.
(1-5) Degreasing process Subsequently, the dried body of the honeycomb molded body in which the cells were sealed was degreased at 400 ° C. for 2 hours to prepare a honeycomb degreased body.
(1-6) Firing Step Further, the honeycomb degreased body was fired under conditions of 2200 ° C. and 2 hours and 40 minutes under an atmospheric pressure of argon.

In the produced inner honeycomb fired body 10c, the porosity was 45%, the average pore diameter was 15 μm, the size was 34.3 mm × 34.3 mm × 150 mm, the cell density was 31 cells / cm ² (200 cpsi), and the cell partition wall The thickness was 0.203 mm, and the minimum value of the outer peripheral wall thickness was 0.322 mm.
The cross-sectional shape in the direction perpendicular to the longitudinal direction of the internal cell was a square having a side of 1.7 mm.
The area of the cross section perpendicular to the longitudinal direction of the first peripheral cell and the second peripheral cell was 80% of the area of the cross section perpendicular to the longitudinal direction of the internal cell.
When the outer honeycomb fired body 10a and the outer honeycomb fired body 10b thus prepared are combined with the inner honeycomb fired body 10c, the bottom surface has a shape of a cylinder having a diameter of 137.2 mm and a length in the longitudinal direction of 150 mm. Except for a shape in which a part of the inner honeycomb fired body 10c is cut out, the same porosity, average pore diameter, cell density, cell partition wall thickness, and outer peripheral wall as the inner honeycomb fired body 10c are formed. It was a thickness.

(2) Manufacture of honeycomb filter (2-1) Adhesive paste preparation step 30% by weight of alumina fiber having an average fiber length of 20 μm, 21% by weight of silicon carbide particles having an average particle diameter of 0.6 μm, 15% by weight of silica sol, carboxymethylcellulose 5 .6% by weight and 28.4% by weight of water were mixed to prepare a heat-resistant adhesive paste.
(2-2) Assembly process The adhesive paste was applied to the side of the prepared honeycomb fired body, and the honeycomb fired bodies were assembled into a columnar shape.
Then, the aggregated honeycomb fired bodies were heated to 120 ° C. to heat and solidify the adhesive paste to form an adhesive layer, thereby producing a cylindrical honeycomb fired body aggregate.
(2-3) Outer peripheral coat layer forming step Next, an outer peripheral coat material paste having the same composition as the adhesive paste is applied to the outer peripheral surface of the honeycomb fired body aggregate, and the outer peripheral coat material paste is dried and solidified at 120 ° C. A honeycomb filter was manufactured by forming a peripheral coat layer.

The honeycomb filter according to Example 1 was manufactured through the above steps. The cell aperture ratio of the honeycomb filter according to Example 1 was 70%.

(Example 2)
A honeycomb filter according to Example 2 was manufactured in the same manner as Example 1 except that the above “(1-2) extrusion molding process” was changed to the following “(1-2 ′) extrusion molding process”. . The cell aperture ratio of the honeycomb filter according to Example 2 was 70%.

(1-2 ') Extrusion Molding Process Next, the ceramic raw material prepared in the ceramic raw material preparation process is extrusion molded, and the outer honeycomb fired bodies 110a _{1 to} 110a ₈ and the outer honeycomb fired body 110b shown in FIG. _A honeycomb molded body serving as a base of _{1 to} 110b ₄ and four inner honeycomb fired bodies 110c was manufactured.
In addition, when the honeycomb fired bodies are combined into a columnar shape, the other outer honeycomb fired body among the second outer peripheral cells arranged in one outer honeycomb fired body in two adjacent outer honeycomb fired bodies. The cross-sectional shape of the second peripheral cell facing the body (that is, the second peripheral cell 124a _1-1 , the second peripheral cell 124b _4-1, etc.), and the second peripheral cell facing the internal honeycomb fired body Extrusion molding was performed so that the cross-sectional shape of the peripheral cell was the shape shown in FIG. In addition, among the second peripheral cells arranged in the other outer honeycomb fired body, the second peripheral cells facing the one outer honeycomb fired body (that is, the second outer peripheral cells 124a _1-2 , 2 of the peripheral cells 124a _2-2, etc.), when a honeycomb fired body through the later process, one side was subjected to extrusion molding to have a square 1.7 mm.
Further, extrusion was performed so that each corner cell had a shape shown in FIG.

(Comparative Example 1)
In the above “(1-2) extrusion molding step”, the cross-sectional shape of the cells arranged on the outer periphery of the outer honeycomb fired bodies 10a and 10b is a shape obtained by reducing the similarity of the inner cells of the outer honeycomb fired body 10a. A honeycomb filter according to Comparative Example 1 was produced in the same manner as in Example 1 except that the extrusion was performed. The aperture ratio of the cells of the honeycomb filter according to Comparative Example 1 was 71%.

(Evaluation of compressive stress)
(1) Simulation of compressive stress For the honeycomb filters according to Examples 1 and 2 and Comparative Example 1, the maximum compressive stress generated inside the honeycomb fired body when pressure was applied from the periphery was calculated by simulation.
The simulation conditions were as follows.
・ Software used: ANSYS Mechanical APDL version 14.0
Calculation model: 2D plane, 1/8 symmetry model Material characteristics SiC substrate (Young's modulus: 15.12 Gpa, Poisson's ratio: 0.33)
Adhesive layer (Young's modulus: 0.40 Gpa, Poisson's ratio: 0.20)
・ Pressure load value: 1.5 MPa (uniformly distributed load)
(2) Calculation of Relative Strength Next, in the above simulation, the relative strength of the honeycomb filter according to Examples 1 and 2 when the maximum compressive stress of the honeycomb filter according to Comparative Example 1 was set to 1 was calculated.
The relative intensity can be obtained by the following formula 1.
Relative strength = maximum compressive stress of Example 1 or 2 / maximum compressive stress of Comparative Example 1
The results are shown in Table 1.

As shown in Table 1, in Examples 1 and 2, the strength against compressive stress of the honeycomb filter was improved.

1,101 honeycomb filter 2,102 honeycomb outermost peripheral portion 10 honeycomb fired bodies _10a of the _{filter, 10b, 110a 1, 110a 2} , 110a 3, 110a 4, 110a 5, 110a 6, 110a 7, 110a 8, 110b 1, 110b ₂ , 110b ₃ , 110b ₄ Outer honeycomb fired bodies 10c, 110c Inner honeycomb fired body 11 Sealing materials 12a, 12b, 112a Outermost honeycomb fired bodies outermost peripheral portions 13a, 13b Corner portions 14, 114 Adhesive layer 15 , 115 peripheral coat layer 16 exhaust gas inlet side end surface 17 exhaust gas outlet side end surface 20 cell 20c inner honeycomb fired body cells _{21a, 21a 1, 21a 2,} 21a 3, 21a 4, 21a 5, 21b, 121a 1, 121a 2, 121b ₄ 1st angular cell 22a, 22b, 122a ₁ 122a ₂ , 122b ₄ Internal cells 23a, 23a ₁ , 23a ₂ , 23a ₃ , 23a ₄ , 23b, 123a ₁ , 123a ₂ , 123b ₄ corner cells 24a, 24b, 124a ₁ , 124a _1-1 , 124a _{1- 2} , 124 a _1-3 , 124 a ₂ , 124 a _2-1 , 124 a _2-2 , 124 b ₄ , 124 b _4-1 , 124 b _4-2 Second peripheral cell 30, 30 a Cell partition wall 31 a Thick wall regions 32 a, 132 a ₁ 132a ₂ outer peripheral wall 50 exhaust gas purification device 51 metal casing 52 holding sealing material

Claims (7)

A plurality of honeycomb fired bodies having a plurality of cells sealed at one end and serving as exhaust gas flow paths and porous cell partition walls defining the cells are bonded via an adhesive layer. A honeycomb filter formed by
The constituent material of the honeycomb fired body is SiC,
The honeycomb fired body comprises an outer honeycomb fired body disposed on the outer periphery of the honeycomb filter and an inner honeycomb fired body disposed on the inner side of the outer honeycomb fired body,
The outer honeycomb fired body is:
A first outer peripheral cell that is disposed in an outermost peripheral portion of the outer honeycomb fired body and is disposed adjacent to an outer peripheral portion of the honeycomb filter;
A second outer peripheral cell that is a cell disposed in the outermost peripheral portion of the outer honeycomb fired body and is disposed in a portion other than the portion in which the first cell is disposed;
An internal cell disposed inside the first angular cell and the second angular cell;
The cross-sectional shape perpendicular to the longitudinal direction of each internal cell is the same rectangle,
The first peripheral cell and the second peripheral cell are partitioned from an outer peripheral wall forming an outer periphery of the cell partition and the honeycomb fired body,
The cell partition connected to the outer peripheral wall defining the first outer peripheral cell has a thick wall region in which the wall thickness gradually increases toward the outer peripheral wall, and is perpendicular to the longitudinal direction of the first outer peripheral cell. The cross-sectional shape in the direction is a shape in which two corners are chamfered from a rectangle which is a cross-sectional shape of the internal cell,
An area of a cross section perpendicular to the longitudinal direction of the first outer peripheral cell is 60 to 80% of an area of a cross section perpendicular to the longitudinal direction of the internal cell;
The cell partition wall has a thickness of 0.210 mm or less,
The honeycomb filter according to claim 1, wherein a cross-sectional shape perpendicular to the longitudinal direction of the cells of the inner honeycomb fired body is congruent with a rectangle which is a cross-sectional shape perpendicular to the longitudinal direction of the internal cells. The honeycomb filter according to claim 1, wherein the minimum value of the thickness of the outer peripheral wall forming the first peripheral cell is thicker than the thickness of the cell partition wall. The honeycomb filter according to claim 2, wherein a minimum value of a thickness of the outer peripheral wall forming the first outer peripheral cell is 1.5 to 3 times a thickness of the cell partition wall. The cell partition wall connected to the outer peripheral wall defining all the second outer peripheral cells has a thick wall region in which the wall thickness gradually increases toward the outer peripheral wall, and the longitudinal direction of the second outer peripheral cell The cross-sectional shape in the vertical direction is a shape in which two corners are chamfered from a rectangle which is a cross-sectional shape of the internal cell,
The honeycomb according to any one of claims 1 to 3, wherein an area of a cross section perpendicular to the longitudinal direction of the second outer peripheral cell is 60 to 80% of an area of a cross section perpendicular to the longitudinal direction of the internal cell. filter. In the two adjacent outer honeycomb fired bodies, among the second outer peripheral cells arranged in one outer honeycomb fired body, the second outer peripheral cells facing the other outer honeycomb fired body are defined. The cell partition connected to the outer peripheral wall to be formed has a thick wall region in which the wall thickness gradually increases toward the outer peripheral wall, and the cross-sectional shape in the direction perpendicular to the longitudinal direction of the second outer peripheral cell is It is a shape in which two corners are chamfered from a rectangle which is a cross-sectional shape of an internal cell,
Of the second outer peripheral cells disposed in the other outer honeycomb fired body, the cross-sectional shape in the direction perpendicular to the longitudinal direction of the second outer peripheral cell facing the one outer honeycomb fired body is It is a congruent shape with a rectangle that is a cross-sectional shape perpendicular to the longitudinal direction of the internal cell,
Of the second peripheral cells arranged in the one outer honeycomb fired body, the area of the cross section perpendicular to the longitudinal direction of the second outer peripheral cell facing the other outer honeycomb fired body is: The honeycomb filter according to any one of claims 1 to 3, which is 60 to 80% of an area of a cross section perpendicular to a longitudinal direction of the internal cell. The honeycomb filter comprises four inner honeycomb fired bodies and twelve outer honeycomb fired bodies,
The cross-sectional shape in the direction perpendicular to the longitudinal direction of the four inner honeycomb fired bodies is a square,
The honeycomb filter according to any one of claims 1 to 5, wherein the 12 outer honeycomb fired bodies and the four inner honeycomb fired bodies are combined to form a cylinder. The honeycomb filter according to any one of claims 1 to 6, which is used for purifying exhaust gas from a gasoline engine.

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