JP6348806B2 - Honeycomb filter and honeycomb fired body - Google Patents

Description

The present invention relates to a honeycomb filter and a honeycomb fired body.

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. 9 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 121a located on the outermost periphery and separated by the cell partition walls perpendicular to the outer edge wall 123a of the porous ceramic member 120.
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, if the temperature of the filter is excessively high, the mechanical strength is reduced and the filter is easily destroyed. Therefore, a sufficient heat capacity is required so that the temperature of the filter is not excessively increased.

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 this initial pressure loss, it is conceivable to reduce the thickness of the cell partition wall, but if the thickness of the cell partition wall is decreased, the strength of the porous ceramic member (honeycomb fired body) decreases. It is thought that it becomes easy to break. Moreover, it is considered that the temperature of the porous ceramic member (honeycomb fired body) becomes higher than necessary when the heat capacity is reduced and the exhaust gas flows. When the temperature of the porous ceramic member (honeycomb fired body) becomes higher than necessary, the porous ceramic member (honeycomb fired body) itself is damaged by heat, or the supported catalyst is deactivated.
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. An object of the present invention is to provide a honeycomb filter that can be suppressed and a honeycomb fired body used for the honeycomb filter.

In order to solve the above-mentioned problems, the present inventors have made extensive studies, and as a result, the cell partition walls of the honeycomb fired body constituting the honeycomb filter are thinned, and the shape of the outer peripheral cell disposed at the outermost peripheral portion of the honeycomb fired body Has been found to be sufficiently low, the pressure loss in the initial state where no PM is deposited, the strength can be sufficiently increased, and the reduction in heat capacity can be suppressed. It was.

That is, the honeycomb filter of the present invention is a honeycomb filter that is used to purify exhaust gas from a gasoline engine, and is formed by bonding a plurality of honeycomb fired bodies through an adhesive layer. The body includes a plurality of cells sealed at one end and serving as a flow path for exhaust gas, and porous cell partition walls that define the cells, and the constituent material of the honeycomb fired body is SiC. And the plurality of cells include an outer peripheral cell disposed at an outermost peripheral portion of the honeycomb fired body and an inner cell disposed inside the outer peripheral cell, wherein the outer peripheral cell includes the cell partition wall and the honeycomb. The cell partition that is partitioned from the outer peripheral wall that forms the outer periphery of the fired body and is connected to the outer peripheral wall has a thick wall region in which the wall thickness gradually increases toward the outer peripheral wall, and the outer peripheral wall The exhaust gas inlet cell has an end on the exhaust gas inlet side and an end on the exhaust gas outlet side sealed, and an end on the exhaust gas outlet side and an end on the exhaust gas inlet side are sealed. Each of the internal cells has a cross-sectional shape perpendicular to the longitudinal direction of the inner cell, and the cross-sectional shape of the outer peripheral exhaust gas discharge cell is perpendicular to the longitudinal direction of the inner cell. It is a shape in which two corners are chamfered from a rectangle which is a cross-sectional shape, the thickness of the cell partition wall is 0.210 mm or less, and the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell is It is 60 to 80% of the cross-sectional area perpendicular to the longitudinal direction of the internal cell, and the cross-sectional area perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell is a cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell. Than the area of And wherein the hearing.

In the honeycomb fired body constituting the honeycomb filter of the present invention, the constituent material 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 fired body constituting the honeycomb filter of the present invention, the cross-sectional shape perpendicular to the longitudinal direction of each internal cell is the same rectangle, and the cell partition wall connected to the outer peripheral wall faces the outer peripheral wall. And the sectional shape perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell is a shape in which two corners are chamfered from a rectangle which is a sectional shape of the inner cell. is there.
When the cross-sectional shape perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell is as described above, the volume in the vicinity of the outer peripheral wall of the honeycomb fired body is increased.
Therefore, the honeycomb fired body constituting the honeycomb filter of the present invention has a sufficiently high strength against external impacts and the like because the volume in the vicinity of the outer peripheral wall is sufficiently large even though the cell partition is thin as will be described later. Have Moreover, since the volume in the vicinity of the outer peripheral wall is large, a decrease in heat capacity can be suppressed in the honeycomb fired body constituting the honeycomb filter of the present invention. Therefore, even if the honeycomb fired body constituting the honeycomb filter of the present invention is heated rapidly, heat can be received by the outer peripheral wall, and the generation of cracks can be suppressed.
This can also be explained as follows.
In a region including the portion of the honeycomb fired body where SiC is present and the space portion of the cell where SiC is not present, the honeycomb fired body is cut out in a predetermined range, and the weight of the honeycomb fired body included in the predetermined range is When the value obtained by dividing the volume in the predetermined range is “apparent density”, in the honeycomb fired body constituting the honeycomb filter of the present invention, the outermost peripheral portion of the honeycomb fired body is more than the inner portion of the honeycomb fired body. The value of “apparent density” increases.
Therefore, in the honeycomb fired body constituting the honeycomb filter of the present invention, the heat capacity of the outermost peripheral portion of the honeycomb fired body is relatively high. Therefore, even when heat is suddenly applied from the outside, the heat can be received at the outermost peripheral portion, and the occurrence of cracks can be prevented.
In addition, when the “apparent density” of the outermost peripheral portion of the honeycomb fired body is high, the outer frame has a mechanically strong structure even though the cell partition walls are thin as will be described later. It has a sufficiently high strength.
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 fired body constituting the honeycomb filter of the present invention, the cell partition wall has a thickness of 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 fired body constituting the honeycomb filter of the present invention, the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell is 60 to 80% of the area of the cross section perpendicular to the longitudinal direction of the internal cell. .
If the area ratio is less than 60%, the area of the opening of the peripheral exhaust gas discharge 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. Loss increases.
Further, if the area ratio exceeds 80%, the value of the apparent density of the outermost peripheral portion of the honeycomb fired body becomes low, so that it is difficult to obtain the effect that the outer peripheral wall of the honeycomb fired body is thick. .

In the honeycomb fired body constituting the honeycomb filter of the present invention, the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell is larger than the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell. .
With such a configuration, the aperture ratio of the end face on the exhaust gas inflow side of the honeycomb fired body is increased. When the opening ratio of the end face on the exhaust gas inflow side of the honeycomb fired body is increased, the inflow resistance when the exhaust gas flows can be suppressed. Therefore, an increase in pressure loss can be suppressed.
In addition, PM contained in the exhaust gas accumulates on the surface of the cell partition wall of the cell into which the exhaust gas is introduced. When PM accumulates on the surface of the cell partition wall and becomes a PM layer, the exhaust gas also passes through the PM layer. Resistance also occurs when the exhaust gas passes through the PM layer. Therefore, if the PM layer becomes thicker at an early stage, the pressure loss also increases at an earlier stage. When the area of the cross section of the peripheral exhaust gas introduction cell is as small as the area of the cross section of the peripheral exhaust gas introduction cell, the surface area of the cell partition wall of the peripheral exhaust gas introduction cell becomes small. PM will accumulate at an early stage. However, in the honeycomb fired body constituting the honeycomb filter of the present invention, the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell is larger than the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell, PM does not easily accumulate on the surface of the cell partition wall of the outer peripheral exhaust gas introduction cell at an early stage. Therefore, it is possible to prevent the pressure loss from rising at an early stage.

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 from a gasoline engine.

In the honeycomb fired body constituting the honeycomb filter of the present invention, the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell is the same size as the area of the cross section perpendicular to the longitudinal direction of the internal cell. Is desirable.
With such a configuration, the aperture ratio of the end face on the exhaust gas inflow side of the honeycomb fired body can be sufficiently increased. Therefore, inflow resistance when exhaust gas flows in can be sufficiently suppressed. Therefore, an increase in pressure loss can be efficiently suppressed.

In the honeycomb fired body constituting the honeycomb filter of the present invention, the cross-sectional shape perpendicular to the longitudinal direction of the outer peripheral exhaust gas introduction cell is preferably congruent with the rectangle which is the cross-sectional shape of the internal cell.
When the cross-sectional shape in the direction perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell is the above shape, the aperture ratio of the end face on the exhaust gas inflow side of the honeycomb fired body can be sufficiently increased. Therefore, the inflow resistance when the exhaust gas flows in can be suitably suppressed, and the increase in pressure loss can be suppressed.
Moreover, the effect that PM does not easily accumulate on the surface of the cell partition wall of the outer peripheral exhaust gas introduction cell is suitably exhibited.

In the honeycomb fired body constituting the honeycomb filter of the present invention, it is desirable that the minimum value of the thickness of the outer peripheral wall is 1.5 to 3 times the thickness of the cell partition wall.
When the minimum value of the thickness of the outer peripheral wall is 1.5 to 3 times the thickness of the cell partition wall, the outer peripheral wall has a sufficient thickness even though the cell partition wall is thin as described above. Therefore, it has sufficiently high strength against external impacts. Moreover, since the outer peripheral wall of the honeycomb fired body is thick, it is possible to suppress a decrease in heat capacity associated with making the cell partition wall thinner.

A honeycomb fired body of the present invention is a honeycomb fired body having a plurality of cells that are sealed at one end and serving as a flow path for exhaust gas, and porous cell partition walls that partition the cells. In addition, the constituent material of the honeycomb fired body is SiC, and the plurality of cells include outer peripheral cells arranged at the outermost peripheral portion of the honeycomb fired body and inner cells arranged inside the outer peripheral cells, The peripheral cell is defined by the cell partition and an outer peripheral wall forming the outer periphery of the honeycomb fired body, and the cell partition connected to the outer peripheral wall is a thick wall region in which the wall thickness gradually increases toward the outer peripheral wall. The outer peripheral cell has an exhaust gas inlet cell having an open end on the exhaust gas inlet side and an end on the exhaust gas outlet side sealed, and an open end on the exhaust gas outlet side and on the exhaust gas inlet side. Perimeter drain with sealed end Each of the internal cells has the same rectangular cross-sectional shape in the longitudinal direction, and the outer exhaust gas exhaust cell has a cross-sectional shape perpendicular to the longitudinal direction of the internal cell. Two corners are chamfered from a certain rectangle, the thickness of the cell partition wall is 0.210 mm or less, and the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell is 60-80% of the area of the cross section perpendicular to the longitudinal direction, and the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell is larger than the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell. Is also large.

By using the honeycomb fired body of the present invention, the honeycomb filter of the present invention having the above effects can be manufactured.

In the honeycomb fired body of the present invention, the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell is desirably the same size as the area of the cross section perpendicular to the longitudinal direction of the internal cell.
With such a configuration, the aperture ratio of the end face on the exhaust gas inflow side of the honeycomb fired body can be sufficiently increased. Therefore, inflow resistance when exhaust gas flows in can be sufficiently suppressed. Therefore, an increase in pressure loss can be efficiently suppressed.

In the honeycomb fired body of the present invention, the cross-sectional shape perpendicular to the longitudinal direction of the outer peripheral exhaust gas introduction cell is preferably congruent with the rectangle which is the cross-sectional shape of the internal cell.
When the cross-sectional shape in the direction perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell is the above shape, the aperture ratio of the end face on the exhaust gas inflow side of the honeycomb fired body can be sufficiently increased. Therefore, the inflow resistance when the exhaust gas flows in can be suitably suppressed, and the increase in pressure loss can be suppressed.
Moreover, the effect that PM does not easily accumulate on the surface of the cell partition wall of the outer peripheral exhaust gas introduction cell is suitably exhibited.

In the honeycomb fired body of the present invention, the minimum value of the thickness of the outer peripheral wall is desirably 1.5 to 3 times the thickness of the cell partition wall.
When the minimum value of the thickness of the outer peripheral wall is 1.5 to 3 times the thickness of the cell partition wall, the outer peripheral wall has a sufficient thickness even though the cell partition wall is thin as described above. Therefore, it has sufficiently high strength against external impacts. Moreover, since the outer peripheral wall of the honeycomb fired body is thick, it is possible to suppress a decrease in heat capacity associated with making the cell partition wall thinner.

FIG. 1 is a perspective view schematically showing an example of the honeycomb filter of the present invention. FIG. 2A is a perspective view schematically showing an example of the honeycomb fired body of the present invention. FIG. 2B is a cross-sectional view taken along line AA in FIG. FIG. 3 is a view showing an exhaust gas inflow side end face of the honeycomb fired body of the present invention shown in FIG. Fig.4 (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 outer periphery exhaust gas discharge cell in the honeycomb calcination object of the present invention. Fig.5 (a)-(d) is sectional drawing which shows typically an example of the cross-sectional shape of the orthogonal | vertical direction to the longitudinal direction of the corner | angular part exhaust gas discharge cell in the honeycomb calcination object of the present invention. Fig.6 (a) is a schematic diagram which shows typically an example of the end surface by the side of the waste gas inflow of the honeycomb calcination object of the present invention whose corner cell is a corner portion exhaust gas introduction cell. FIG. 6B is a schematic view schematically showing an example of an end face on the exhaust gas inflow side of the honeycomb fired body of the present invention in which corner exhaust gas introduction cells and corner exhaust gas discharge cells are mixedly arranged. 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 correlation diagram showing the relationship between the ratio of the opening area of the peripheral exhaust gas discharge cell and the opening area of the internal cell and the relative strength correction value of the honeycomb fired body. FIG. 9 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 and the honeycomb fired body 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 is a perspective view schematically showing an example of the honeycomb filter of the present invention.
As shown in FIG. 1, a honeycomb filter 1 as an example of the honeycomb filter of the present invention is a columnar honeycomb filter formed by bonding a plurality of honeycomb fired bodies 10 via an adhesive layer 14. is there.

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.
The thickness of the adhesive layer 14 is desirably 0.5 to 2.0 mm.

An outer peripheral coating 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.
The thickness of the outer peripheral coat layer 15 is desirably 0.1 to 3.0 mm.

Next, the honeycomb fired body constituting the honeycomb filter of the present invention, that is, the honeycomb fired body of the present invention will be described with reference to the drawings.
FIG. 2A is a perspective view schematically showing an example of the honeycomb fired body of the present invention. FIG. 2B is a cross-sectional view taken along line AA in FIG.
As shown in FIG. 2 (a), a honeycomb fired body 10 which is an example of the honeycomb fired body of the present invention has a plurality of cells in which one end is sealed with a sealing material 11 and serves as an exhaust gas flow path. 20 and a porous cell partition wall 30 for partitioning the cell.
The plurality of cells 20 include an outer peripheral cell 21 arranged at the outermost peripheral portion of the honeycomb fired body and an inner cell 22 arranged inside the outer peripheral cell 21. Further, the peripheral cell 21 includes an outer peripheral exhaust gas introduction cell 21a in which an end 10a on the exhaust gas inlet side is opened and an end 10b on the exhaust gas outlet side is sealed, and an end 10b on the exhaust gas outlet side is opened and on the exhaust gas inlet side. The outer peripheral exhaust gas discharge cell 21b is sealed.
The cross-sectional shape in the direction perpendicular to the longitudinal direction of each internal cell 22 is the same rectangle, and the cross-sectional shape in the direction perpendicular to the longitudinal direction of the outer peripheral cell 21 is chamfered by two corners from the rectangle that is the cross-sectional shape of the internal cell 22. Shape. The cross-sectional shapes of the outer peripheral cell 21 and the inner cell 22 will be described later in detail.
Further, as shown in FIGS. 2A and 2B, the honeycomb fired body 10 is a rectangular parallelepiped having a square cross section perpendicular to the longitudinal direction (the direction of a double arrow in FIG. 2A).
The cross section in the direction perpendicular to the longitudinal direction of the honeycomb fired body 10 is preferably a square having a side of 30 to 60 mm.

The constituent material of the honeycomb fired body 10 is SiC. SiC is a material excellent in heat resistance. For this reason, the honeycomb fired body 10 is a honeycomb fired body having excellent heat resistance.

In the honeycomb fired body 10, a cell density of, is preferably in the range of 15.5 to 62 pieces ^/ cm 2 ^{(100~400cpsi),} in the range of 31 to 46.5 pieces ^/ cm 2 ^{(200~300cpsi)} It is more desirable.

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. 2 (b), the exhaust gas discharged from the internal combustion engine and flowing into the honeycomb fired body 10 (in FIG. 2 (b), the exhaust gas is indicated by G and the flow of the exhaust gas is indicated by an arrow) is the honeycomb firing. It flows into one cell 20 opened in the exhaust gas inflow side end face 10 a of the body 10 and passes through the 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 the other cell 20 opened in the exhaust gas outflow side end face 10b and is discharged outside.

Next, the shape and arrangement of the cells 20 in the honeycomb fired body 10 will be described with reference to the drawings.
FIG. 3 is a view showing an exhaust gas inflow side end face of the honeycomb fired body of the present invention shown in FIG.
As shown in FIG. 3, the plurality of cells 20 include an outer peripheral cell 21 disposed on the outermost peripheral portion 12 of the honeycomb fired body 10 and an inner cell 22 disposed on the inner side of the outer peripheral cell 21.
Further, the plurality of cells 20 include corner cell 23 arranged at the corner 13 of the honeycomb fired body 10.
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 23 is not included in the peripheral cell 21.
The internal cells 22 are defined by cell partition walls 30, and the outer peripheral cells 21 are defined by cell partition walls 30 and outer peripheral walls 32 that form the outer periphery of the honeycomb fired body 10.

In the honeycomb fired body 10, the cell partition wall 30 has a thickness of 0.210 mm or less. Further, the thickness of the cell partition wall 30 is desirably 0.075 to 0.160 mm. Note that the thickness of the cell partition wall 30 is that the minimum distance between the cells 20 to each other, in FIG. 3, is that the thickness indicated by T _1.
When the thickness of the cell partition wall 30 is 0.210 mm or less, the thickness of the cell partition wall 30 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 30 exceeds 0.210 mm, the thickness of the cell partition wall 30 is too thick, so that the resistance when the exhaust gas passes through the cell partition wall 30 increases, and as a result, the pressure loss increases.

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

In the honeycomb fired body 10, the average pore diameter of the pores contained in the cell partition walls 30 is desirably 8 to 25 μm.
In the honeycomb filter having the above configuration, PM can be collected with high collection efficiency while suppressing an increase in pressure loss.
When the average pore diameter of the pores contained in the cell partition walls 30 is less than 8 μm, the pores are too small, and the pressure loss when the exhaust gas permeates the cell partition walls 30 increases. On the other hand, when the average pore diameter of the pores contained in the cell partition wall 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 a conventionally known method using a scanning electron microscope (SEM).

In the honeycomb fired body 10, the thickness of the outer peripheral wall 32 is not particularly limited, but the minimum value of the thickness of the outer peripheral wall 32 is desirably 1.5 to 3 times the thickness of the cell partition wall 30. 3 times is more desirable. Note that the minimum value of the thickness of the peripheral wall 32, a minimum thickness value from the contour of the honeycomb fired body 10 to the outer cell 21, in FIG. 3, it is that the thickness indicated by T _2.
When the minimum value of the thickness of the outer peripheral wall 32 is 1.5 to 3 times the thickness of the cell partition wall 30, the outer peripheral wall 32 has a sufficient thickness even though the cell partition wall 30 is thin. Therefore, it has sufficiently high strength against external impacts. Moreover, since the outer peripheral wall 32 of the honeycomb fired body 10 is thick, it is possible to suppress a decrease in heat capacity associated with making the cell partition wall 30 thinner.

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

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

Next, the outer peripheral cell 21, the inner cell 22, and the corner cell 23 of the honeycomb fired body 10 will be described.

First, the shape of the internal cell 22 will be described.
As shown in FIG. 3, the cross-sectional shape perpendicular to the longitudinal direction of each internal cell 22 is the same rectangle α. In the honeycomb fired body 10, the rectangle α is desirably a square.

Next, the shape of the peripheral cell 21 (that is, the peripheral exhaust gas introduction cell 21a and the peripheral exhaust gas discharge cell 21b) will be described.
As shown in FIG. 3, the cross-sectional shape perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell 21a is congruent with the rectangle α, and the cross-sectional shape perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell 21b is rectangular α. The two corners are chamfered.
The cell partition wall 30 connected to the outer peripheral wall 32 has a thick wall region 31 in which the wall thickness gradually increases toward the outer peripheral wall 32.
That is, in the cross-sectional shape perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell 21b, a thick wall region 31 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 honeycomb fired body 10, the cross-sectional shape in the direction perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell 21b may be a shape as shown in FIGS.
Fig.4 (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 outer periphery exhaust gas discharge cell in the honeycomb calcination object of the present invention.
4 (a) is two corners adjacent rectangular α is the two line segments A and B, shows a cross-sectional shape of the outer peripheral exhaust gas discharge cell 21b ₁ is a hexagon, taken 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. 4B shows a cross-sectional shape of the outer peripheral exhaust gas discharge cell 21b2 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. 4C 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. It shows a cross section of a periphery exhaust gas discharge cell 21b _3. 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. 4 (d), the two corners adjacent rectangular α is the two curves A'and B', respectively show truncated cross-sectional shape of the peripheral exhaust gas discharge cell 21b _4. 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 outer circumferential exhaust gas discharge cell 21b _4.
FIG. 4E shows a cross-sectional shape of the outer peripheral exhaust gas discharge cell 21b ₅ in which two adjacent corners of the rectangle α are cut off by two curves C ′ and D ′, respectively. 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 the side forming the rectangle α. The curve C ′ and the curve D ′ may intersect within the rectangle α.
In the honeycomb fired body 10, the thick wall region 31 is formed in a portion where the corner portion of the rectangle α is cut out in FIGS. 4A to 4E (that is, a portion surrounded by a broken line and a solid line indicating α ′). Is formed.
The cross-sectional shape perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell 21b 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 portion where the corner portion is cut away in the outer peripheral exhaust gas discharge cell 21b ₁ ~ periphery exhaust gas discharge cell 21b ₅ (i.e. the area of the thick-wall region 31) is 20 to 40% of the rectangle alpha.

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

This can also be explained as follows.
The honeycomb fired body 10 is cut in a predetermined range in a region including the portion where the SiC is present and the space portion of the cell where SiC is not present, and the weight of the honeycomb fired body 10 included in the predetermined range. If the value obtained by dividing the volume by a predetermined range is “apparent density”, in the honeycomb fired body 10, the outermost peripheral portion 12 of the honeycomb fired body 10 is more “apparent density” than the inner portion of the honeycomb fired body 10. "Is increased.
Therefore, in the honeycomb fired body 10, the heat capacity of the outermost peripheral portion 12 of the honeycomb fired body 10 is relatively high. Therefore, even if heat is suddenly applied from the outside, heat can be received at the outermost peripheral portion 12, and the occurrence of cracks can be prevented.
Further, if the “apparent density” of the outermost peripheral portion 12 of the honeycomb fired body 10 is high, the outer frame has a mechanically strong structure even though the cell partition wall 30 is thin. Have high strength.

In the honeycomb fired body 10, the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell 21 b is 60 to 80% of the area of the cross section perpendicular to the longitudinal direction of the internal cell 22.
If the area ratio is less than 60%, the area of the opening of the outer peripheral exhaust gas discharge cell 21b is reduced, the exhaust gas flow path is narrowed, and the gas passage resistance when the exhaust gas passes through the cell partition wall 30 is increased. , Pressure loss increases.
Further, when the area ratio exceeds 80%, the value of the apparent density of the outermost peripheral portion of the honeycomb fired body 10 is lowered, and thus the effect that the outer peripheral wall 32 of the honeycomb fired body 10 is thick is obtained. Hateful.

In addition, the area of the cross section perpendicular to the longitudinal direction of each cell 20 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, and the skeleton portions such as the cell partition walls 30 and the outer peripheral wall 32 are identified from the space portions of the cells 20. 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.
The area of the cross section perpendicular to the longitudinal direction of the internal cells 22 is the average value of the cross-sectional areas perpendicular to the longitudinal direction of all the internal cells 22 obtained by the above method.

Further, in the honeycomb fired body 10, the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell 21a is larger than the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell 21b.
With such a configuration, the aperture ratio of the end face 10a on the exhaust gas inflow side of the honeycomb fired body 10 is increased. When the opening ratio of the end face 10a on the exhaust gas inflow side of the honeycomb fired body 10 is increased, the inflow resistance when the exhaust gas flows can be suppressed. Therefore, an increase in pressure loss can be suppressed.
Further, PM contained in the exhaust gas accumulates on the surface of the cell partition wall 30 of the cell into which the exhaust gas is introduced. When PM accumulates on the surface of the cell partition wall 30 and becomes a PM layer, the exhaust gas also passes through the PM layer. Resistance also occurs when the exhaust gas passes through the PM layer. Therefore, if the PM layer becomes thicker at an early stage, the pressure loss also increases at an earlier stage. When the area of the cross section of the peripheral exhaust gas introduction cell 21a is as small as the area of the cross section of the peripheral exhaust gas discharge cell 21b, the surface area of the cell partition wall 30 of the peripheral exhaust gas introduction cell 21a becomes small. PM accumulates on the surface of the cell partition wall 30 at an early stage. However, in the honeycomb fired body 10, since the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell 21a is larger than the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell 21b, the peripheral exhaust gas introduction cell 21a. PM is difficult to accumulate on the surface of the cell partition wall 30 at an early stage. Therefore, it is possible to prevent the pressure loss from rising at an early stage.
In the honeycomb fired body 10, the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell 21 a is desirably the same as the area of the cross section perpendicular to the longitudinal direction of the internal cell 22.
With such a configuration, the aperture ratio of the end face 10a on the exhaust gas inflow side of the honeycomb fired body 10 can be sufficiently increased. Therefore, inflow resistance when exhaust gas flows in can be sufficiently suppressed. Therefore, an increase in pressure loss can be efficiently suppressed.

In the honeycomb fired body 10, the cross-sectional shape in the direction perpendicular to the longitudinal direction of the outer peripheral exhaust gas introduction cell 21 a is preferably congruent with the rectangle α that is the cross-sectional shape of the internal cell 22.
When the cross-sectional shape in the direction perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell 21a is the above shape, the aperture ratio of the end face 10a on the exhaust gas inflow side of the honeycomb fired body 10 can be sufficiently increased. Therefore, the inflow resistance when the exhaust gas flows in can be suitably suppressed, and the increase in pressure loss can be suppressed.
Moreover, the effect that PM does not easily accumulate on the surface of the cell partition wall 30 of the outer peripheral exhaust gas introduction cell 21a is suitably exhibited.

Next, the shape of the corner cell 23 will be described.
First, in FIG. 3, the corner cell 23 arranged at the corner 13 of the honeycomb fired body 10 is arranged as a corner exhaust gas discharge cell 23 b that is a cell that exhausts exhaust gas.
The cross-sectional shape of the corner portion exhaust gas discharge cell 23b is not particularly limited, but it is preferable that at least one corner portion is chamfered from the rectangle α which is the cross-sectional shape of the internal cell 22.
When the shape of the corner cell 23 is such a shape, the volume in the vicinity of the outer peripheral wall 32 of the honeycomb fired body 10 is increased.
Therefore, the honeycomb fired body 10 has a sufficiently high strength against external impacts and the like because the volume in the vicinity of the outer peripheral wall 32 is sufficiently large even though the cell partition walls 30 are thin. Further, since the volume in the vicinity of the outer peripheral wall 32 is large, the honeycomb fired body 10 can suppress a decrease in heat capacity. Therefore, even if the honeycomb fired body 10 is rapidly heated, heat can be received by the outer peripheral wall 32, and generation of cracks can be suppressed.

Further, the shape of the corner portion exhaust gas discharge cell 23b may be a shape in which all corner portions are chamfered by a straight line or a curve from the rectangle α, or may be the same shape as the outer periphery exhaust gas discharge cell 21b. The shape shown to 5 (a)-(d) may be sufficient.
Fig.5 (a)-(d) is sectional drawing which shows typically an example of the cross-sectional shape of the orthogonal | vertical direction to the longitudinal direction of the corner | angular part exhaust gas discharge cell in the honeycomb calcination object of the present invention.
FIG. 5A shows a heptagon in which three corner portions are cut off by line segments I, J, and K, except for the corner portion that is the innermost side of the honeycomb fired body 10 among the corner portions of the rectangle α. It shows a cross-sectional shape of the corner exhaust gas discharge cell 23b _1. 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. A part of each side of the rectangle α between the three cut corners forms one side of a heptagon that is a cross-sectional shape of the corner cell 23a.
FIG. 5 (b), shows the most honeycomb corner on the inside of the sintered body 10 is pentagonal, taken by the line segment L corner cross-sectional shape of the exhaust gas discharge cell 23b ₂ of the corners of the rectangular α Yes.
FIG. 5C shows a corner portion obtained by cutting three corner portions by curves I ′, J ′, and K ′ except for a corner portion that is the innermost side of the honeycomb fired body 10 among corner portions of the rectangle α. The cross-sectional shape of the exhaust gas discharge cell 23b ₃ is shown. 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 exhaust gas discharge cell 23b _3.
FIG. 5 (d) shows a corner portion cross-sectional shape of the exhaust gas discharge cell 23b _4, taken by most corners on the inside of the honeycomb fired body 10 is curved L'among 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 23 is the shape shown in FIG. 5B or FIG. 5D, compressive stress is hardly applied due to the structure of the honeycomb fired body 10. Therefore, it has a sufficiently high strength against external impacts and the like.

In FIG. 3, the corner cell 23 is arranged as a corner exhaust gas exhaust cell 23 b that exhausts exhaust gas. However, as shown in FIG. 6A, the corner cell 23 is a corner into which exhaust gas flows. May be arranged as a partial exhaust gas introduction cell 23a.
Fig.6 (a) is a schematic diagram which shows typically an example of the end surface by the side of the waste gas inflow of the honeycomb calcination object of the present invention whose corner cell is a corner portion exhaust gas introduction cell.
In addition, the cross-sectional shape of the corner | angular part exhaust gas introduction cell 23a is not specifically limited, The shape congruent with the rectangle (alpha) may be sufficient, and the shape shown to Fig.5 (a)-(d) may be sufficient.
In each corner 13, the corner cell 23 may be either the corner exhaust gas introduction cell 23a or the corner exhaust gas discharge cell 23b. That is, in the honeycomb fired body 10, the corner portion exhaust gas introduction cell 23a and the corner portion exhaust gas discharge cell 23b may be mixed.
For example, as shown in FIG. 6 (b), in the end face 10a on the exhaust gas inflow side of the honeycomb fired body 10, corner exhaust gas discharge cells 23b are arranged at the upper left corner 13a and lower right corner 13c, A corner exhaust gas introduction cell 23a may be arranged in the upper right corner 13b and the lower left corner 13d.
FIG. 6B is a schematic view schematically showing an example of an end face on the exhaust gas inflow side of the honeycomb fired body of the present invention in which corner exhaust gas introduction cells and corner exhaust gas discharge cells are mixedly arranged.

The honeycomb fired body 10 may carry a catalyst for purifying exhaust gas. As the catalyst to be carried, for example, a noble metal such as platinum, palladium, or rhodium 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.

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. . Therefore, the honeycomb filter 1 can be suitably used for purifying exhaust gas from a gasoline engine.

An exhaust gas purification apparatus using such a honeycomb filter 1 will be described with reference to the drawings.
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 10 constituting the honeycomb filter 1 and the honeycomb It is purified by the fired body 10. Since the mechanism for purifying the exhaust gas by the honeycomb fired body 10 has already been described, the description thereof is omitted here. The purified exhaust gas flows out of the honeycomb fired body 10 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, if the average fiber diameter of the inorganic fibers exceeds 20 μm, the flexibility of the inorganic fibers is insufficient because the inorganic fibers are difficult to bend.

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 device 50 is manufactured using the holding sealing material 52 constituted 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 assembly of the exhaust gas purification device 50.
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 the method for manufacturing the honeycomb fired body of the present invention and the method for manufacturing the honeycomb filter of the present invention will be described.

(1) Manufacturing method 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 Molding Process Next, the ceramic raw material prepared in the ceramic raw material preparation process is extruded and cut into a predetermined length to produce a honeycomb formed body. At this time, a mold is used in which a cross-sectional shape having the cell structure (cell shape and cell arrangement) shown in FIGS. 4 (a) to 4 (e) and FIGS. 5 (a) to 5 (d) is formed. A honeycomb formed body is produced.
The cell wall thickness, outer wall thickness, and the area ratio of the cross-sectional area perpendicular to the longitudinal direction of the outer peripheral cell to the cross-sectional area perpendicular to the longitudinal direction of the inner cell adjust the shape of the mold. You can do that.
In particular, when adjusting the area ratio between the area of the cross section perpendicular to the longitudinal direction of the peripheral cell and the area of the cross section perpendicular to the longitudinal direction of the internal cell, the range (angle, position) to be chamfered should be adjusted. Can be done.

(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.

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

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

(2) Manufacturing method of honeycomb filter (2-1) Adhesive paste preparation step First, an adhesive paste for adhering 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 an aggregate of honeycomb fired bodies.
Next, using a diamond cutter or the like, the aggregate of honeycomb fired bodies is cut into a cylindrical shape.

(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)
(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 Molding Step Next, the ceramic raw material prepared in the ceramic raw material preparation step was extrusion molded to produce a rectangular parallelepiped honeycomb molded body having a square cross-sectional shape perpendicular to the longitudinal direction.
In this step, the cross-sectional shape of the internal cell and the peripheral exhaust gas introduction cell is a square having a side of 1.7 mm, the shape of the peripheral exhaust gas discharge cell is the shape shown in FIG. Extrusion was performed so that the shape of the partial cell was the shape shown in FIG.
(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 cell was sealed so that the end on the exhaust gas inflow side and the end on the exhaust gas discharge side were sealed at the positions shown in FIGS. That is, one end of the inner cell is sealed so as to have a checkered pattern, the end of the outer exhaust gas introduction cell on the exhaust gas discharge side, the end of the outer exhaust gas discharge cell on the exhaust gas inflow side, and the corner on the exhaust gas inflow side The end of the partial cell was sealed.
(1-5) Degreasing step Subsequently, a degreasing treatment was performed to degrease the dried honeycomb molded body that had been sealed in the cells at 400 ° C., thereby producing a honeycomb degreased body.
(1-6) Firing Step Further, the honeycomb degreased body was fired under conditions of 2200 ° C. and 3 hours under an atmospheric pressure of argon atmosphere.

The honeycomb fired body according to Example 1-1 was manufactured through the above steps.

The manufactured honeycomb fired body has a porosity of 45%, an average pore diameter of 15 μm, a size of 34.3 mm × 34.3 mm × 150 mm, a cell density of 31 cells / cm ² (200 cpsi), and a cell partition wall thickness of The minimum value of the thickness of the outer peripheral wall was 0.203 mm and 0.322 mm.
Moreover, the cross-sectional shape perpendicular to the longitudinal direction of the inner cell and the outer peripheral exhaust gas introduction cell was a square having a side of 1.7 mm.
The area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell was 80% of the area of the cross section perpendicular to the longitudinal direction of the internal cell.

(Example 1-2)
Example 1-2 is similar to Example 1-1 except that the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell is set to 75% of the area of the cross section perpendicular to the longitudinal direction of the internal cell. A honeycomb fired body was produced.

(Example 1-3)
Example 1-3 is similar to Example 1-1 except that the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell is 60% of the area of the cross section perpendicular to the longitudinal direction of the internal cell. A honeycomb fired body was produced.

(Example 2-1)
In the extrusion process, the shape of the outer peripheral exhaust gas discharge cell is the shape shown in FIG. 4D, and the corner cell is the shape shown in FIG. 5C, as in Example 1-1. A honeycomb fired body according to Example 2-1 was produced.
The area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell was 80% of the area of the cross section perpendicular to the longitudinal direction of the internal cell.

(Example 2-2)
Example 2-2 is similar to Example 2-1 except that the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell is set to 75% of the area of the cross section perpendicular to the longitudinal direction of the internal cell. A honeycomb fired body was produced.

(Example 2-3)
Example 2-3 is the same as Example 2-1 except that the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell is 60% of the area of the cross section perpendicular to the longitudinal direction of the internal cell. A honeycomb fired body was produced.

(Comparative Example 1-1)
According to Comparative Example 1-1 as in Example 1-1, except that the area of the cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell was set to 93% of the area of the cross section perpendicular to the longitudinal direction of the internal cell. A honeycomb fired body was produced.

(Comparative Example 1-2)
According to Comparative Example 1-2 as in Example 1-1, except that the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell was 84% of the area of the cross section perpendicular to the longitudinal direction of the internal cell. A honeycomb fired body was produced.

(Comparative Example 1-3)
According to Comparative Example 1-3 as in Example 1-1, except that the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell was set to 50% of the area of the cross section perpendicular to the longitudinal direction of the internal cell. A honeycomb fired body was produced.

(Comparative Example 1-4)
According to Comparative Example 1-4 as in Example 1-1, except that the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell was set to 25% of the area of the cross section perpendicular to the longitudinal direction of the internal cell. A honeycomb fired body was produced.

(Comparative Example 2-1)
According to Comparative Example 2-1, as in Example 2-1, except that the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell was 84% of the area of the cross section perpendicular to the longitudinal direction of the internal cell. A honeycomb fired body was produced.

(Comparative Example 2-2)
According to Comparative Example 2-2 as in Example 2-1, except that the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell was set to 50% of the area of the cross section perpendicular to the longitudinal direction of the internal cell. A honeycomb fired body was produced.

(Comparative Example 3-1)
A honeycomb fired body according to Comparative Example 3-1 was produced in the same manner as Example 1-1 except that the cross-sectional shape of the outer peripheral exhaust gas discharge cell was the same as the cross-sectional shape of the internal cell in the extrusion process.

(Comparative Example 3-2)
In the extrusion process, the cross-sectional shape of the outer peripheral exhaust gas discharge cell is similar to that of the outer peripheral exhaust gas exhaust cell of Comparative Example 3-1, and the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas exhaust cell is the inner cell. The honeycomb fired body according to Comparative Example 3-2 is the same as Comparative Example 3-1, except that the cross-sectional shape of the outer peripheral exhaust gas discharge cell is reduced to 93% of the cross-sectional area perpendicular to the longitudinal direction of Produced.

(Comparative Example 3-3)
In the extrusion process, the cross-sectional shape of the outer peripheral exhaust gas discharge cell is similar to that of the outer peripheral exhaust gas exhaust cell of Comparative Example 3-1, and the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas exhaust cell is the inner cell. The honeycomb fired body according to Comparative Example 3-3 is the same as Comparative Example 3-1, except that the cross-sectional shape of the outer peripheral exhaust gas discharge cell is reduced to 84% of the area of the cross section perpendicular to the longitudinal direction. Produced.

(Comparative Example 3-4)
In the extrusion process, the cross-sectional shape of the outer peripheral exhaust gas discharge cell is similar to that of the outer peripheral exhaust gas exhaust cell of Comparative Example 3-1, and the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas exhaust cell is the inner cell. The honeycomb fired body according to Comparative Example 3-4 is the same as Comparative Example 3-1, except that the cross-sectional shape of the outer peripheral exhaust gas discharge cell is reduced to 80% of the area of the cross section perpendicular to the longitudinal direction. Produced.

(Comparative Example 3-5)
In the extrusion process, the cross-sectional shape of the outer peripheral exhaust gas discharge cell is similar to that of the outer peripheral exhaust gas exhaust cell of Comparative Example 3-1, and the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas exhaust cell is the inner cell. The honeycomb fired body according to Comparative Example 3-5 is the same as Comparative Example 3-1, except that the cross-sectional shape of the outer peripheral exhaust gas discharge cell is reduced to 75% of the cross-sectional area perpendicular to the longitudinal direction of Produced.

(Comparative Example 3-6)
In the extrusion process, the cross-sectional shape of the outer peripheral exhaust gas discharge cell is similar to that of the outer peripheral exhaust gas exhaust cell of Comparative Example 3-1, and the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas exhaust cell is the inner cell. The honeycomb fired body according to Comparative Example 3-6 was obtained in the same manner as Comparative Example 3-1, except that the cross-sectional shape of the outer peripheral exhaust gas discharge cell was reduced so as to be 60% of the cross-sectional area perpendicular to the longitudinal direction. Produced.

(Comparative Example 3-7)
In the extrusion process, the cross-sectional shape of the outer peripheral exhaust gas discharge cell is similar to that of the outer peripheral exhaust gas exhaust cell of Comparative Example 3-1, and the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas exhaust cell is the inner cell. The honeycomb fired body according to Comparative Example 3-7 is the same as Comparative Example 3-1, except that the cross-sectional shape of the outer peripheral exhaust gas discharge cell is reduced to 50% of the cross-sectional area perpendicular to the longitudinal direction of Produced.

(Comparative Example 3-8)
In the extrusion process, the cross-sectional shape of the outer peripheral exhaust gas discharge cell is similar to that of the outer peripheral exhaust gas exhaust cell of Comparative Example 3-1, and the area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas exhaust cell is the inner cell. The honeycomb fired body according to Comparative Example 3-8 was prepared in the same manner as Comparative Example 3-1, except that the cross-sectional shape of the outer peripheral exhaust gas discharge cell was reduced to 25% of the cross-sectional area perpendicular to the longitudinal direction. Produced.

Hereinafter, the honeycomb fired bodies according to Example 1-1 to Example 1-3 and Comparative Example 1-1 to Comparative Example 1-4 are also collectively referred to as “a honeycomb fired body having a straight chamfered peripheral exhaust gas discharge cell”.
The honeycomb fired bodies according to Example 2-1 to Example 2-3, Comparative Example 2-1 and Comparative Example 2-2 are also collectively referred to as “honeycomb fired bodies having curved chamfered peripheral exhaust gas discharge cells”.

(Compressive stress evaluation)
(1) Simulation of compressive stress For the honeycomb fired bodies according to the respective examples and comparative examples, 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 each example and each comparative example when the maximum compressive stress of the honeycomb fired body according to Comparative Example 3-1 was set to 1.00 was calculated.
The relative intensity can be obtained by the following formula 1.
Relative strength = maximum compressive stress of each example or comparative example / maximum compressive stress of comparative example 3-1 Equation 1
Tables 1 to 3 show the relative intensity values of the examples or the comparative examples.

In addition, the comparison of the ratio of the peripheral exhaust gas exhaust cell opening area to the internal cell open area from the relative strength of the honeycomb fired body having the straight chamfered peripheral exhaust gas exhaust cell and the honeycomb fired body having the curved chamfered peripheral exhaust gas exhaust cell The values obtained by subtracting the relative intensities of Examples 3-2 to 3-8 were used as the relative intensity correction values for the examples and the comparative examples.
Tables 1 and 2 show the values of the corrected relative intensity of each example or each comparative example.
Further, FIG. 8 shows the correlation between the ratio of the peripheral exhaust gas discharge cell opening area and the internal cell opening area and the relative intensity correction value.
FIG. 8 is a correlation diagram showing the relationship between the ratio of the opening area of the peripheral exhaust gas discharge cell and the opening area of the internal cell and the relative strength correction value of the honeycomb fired body.

As shown in Tables 1 and 2 and FIG. 8, in Examples 1-1 to 1-3 and Examples 2-1 to 2-3, the strength of the honeycomb fired body against compressive stress was improved. .
In particular, in Example 2-1 to Example 2-3 in which the cross-sectional shape is a rectangle and the corners are chamfered by a curve, the relative strength is further improved.

(Example 3)
A honeycomb filter was produced by the following method.

(1) Preparation of honeycomb fired body The honeycomb fired body of Example 1-1 was prepared as a honeycomb fired body used for the honeycomb filter.

(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) Aggregation process Adhesive paste was applied to the side surface of each prepared honeycomb fired body to aggregate each honeycomb fired body.
Thereafter, the aggregated honeycomb fired bodies were heated to 120 ° C. to heat and solidify the adhesive paste to form an adhesive layer, thereby producing an aggregate of honeycomb fired bodies.
Next, using a diamond cutter, the aggregate of the honeycomb fired bodies was cut into a cylindrical shape.
(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 3 was manufactured through the above steps.

1 Honeycomb filter 10 honeycomb fired bodies 11 sealing member 12 outermost peripheral portion 13,13a, 13b, 13c, 13d corners 14 adhesive layer 15 outer peripheral coat layer 20 cell 21 peripheral cells 21a outer peripheral exhaust gas introducing cells _21b, 21b 1, 21b ₂ , 21b ₃ , 21b ₄ , 21b ₅ Outer peripheral exhaust gas discharge cell 22 Internal cell 23 Corner cell 23a Corner exhaust gas introduction cell 23b, 23b ₁ , 23b ₂ , 23b ₃ , 23b ₄ corner exhaust gas discharge cell 30 Cell partition wall 31 Thickness Wall region 32 Outer peripheral wall 50 Exhaust gas purifying device 51 Metal casing 52 Holding sealing material

Claims (8)

A honeycomb filter used for purifying exhaust gas from a gasoline engine and formed by bonding a plurality of honeycomb fired bodies through an adhesive layer,
The honeycomb fired body includes a plurality of cells that are sealed at one end and serve as a flow path for exhaust gas, and porous cell partition walls that partition the cells,
The constituent material of the honeycomb fired body is SiC,
The plurality of cells include an outer peripheral cell disposed at an outermost peripheral portion of the honeycomb fired body, and an inner cell disposed inside the outer peripheral cell,
The outer peripheral cell is partitioned from the outer peripheral wall forming the outer periphery of the cell partition and the honeycomb fired body,
The cell partition wall connected to the outer peripheral wall has a thick wall region in which the wall thickness gradually increases toward the outer peripheral wall,
The outer peripheral cell includes an outer peripheral exhaust gas introduction cell in which an end portion on the exhaust gas inlet side is opened and an end portion on the exhaust gas outlet side is sealed, and an end portion on the exhaust gas outlet side is opened and an end portion on the exhaust gas inlet side is sealed. Consisting of a stopped outer peripheral exhaust gas discharge cell,
The cross-sectional shape perpendicular to the longitudinal direction of each internal cell is the same rectangle,
The cross-sectional shape perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell is a shape in which two corners are chamfered from a rectangle which is a cross-sectional shape of the internal cell,
The cell partition wall has a thickness of 0.210 mm or less,
The area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell is 60 to 80% of the area of the cross section perpendicular to the longitudinal direction of the internal cell,
A honeycomb filter characterized in that an area of a cross section perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell is larger than an area of a cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell. The honeycomb filter according to claim 1, wherein an area of a cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas introduction cell is the same size as an area of a cross section perpendicular to the longitudinal direction of the internal cell. The honeycomb filter according to claim 1 or 2, wherein a cross-sectional shape in a direction perpendicular to a longitudinal direction of the outer peripheral exhaust gas introduction cell is congruent with a rectangle that is a cross-sectional shape of the internal cell. The honeycomb filter according to any one of claims 1 to 3, wherein the minimum value of the thickness of the outer peripheral wall is 1.5 to 3 times the thickness of the cell partition wall. A honeycomb fired body comprising a plurality of cells that are sealed at one end and serving as exhaust gas flow paths, and porous cell partition walls that partition the cells,
The constituent material of the honeycomb fired body is SiC,
The plurality of cells include an outer peripheral cell disposed at an outermost peripheral portion of the honeycomb fired body, and an inner cell disposed inside the outer peripheral cell,
The outer peripheral cell is partitioned from the outer peripheral wall forming the outer periphery of the cell partition and the honeycomb fired body,
The cell partition wall connected to the outer peripheral wall has a thick wall region in which the wall thickness gradually increases toward the outer peripheral wall,
The outer peripheral cell includes an outer peripheral exhaust gas introduction cell in which an end portion on the exhaust gas inlet side is opened and an end portion on the exhaust gas outlet side is sealed, and an end portion on the exhaust gas outlet side is opened and an end portion on the exhaust gas inlet side is sealed. Consisting of a stopped outer peripheral exhaust gas discharge cell,
The cross-sectional shape perpendicular to the longitudinal direction of each internal cell is the same rectangle,
The cross-sectional shape perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell is a shape in which two corners are chamfered from a rectangle which is a cross-sectional shape of the internal cell,
The cell partition wall has a thickness of 0.210 mm or less,
The area of the cross section perpendicular to the longitudinal direction of the outer peripheral exhaust gas discharge cell is 60 to 80% of the area of the cross section perpendicular to the longitudinal direction of the internal cell,
A honeycomb fired body, wherein an area of a cross section perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell is larger than an area of a cross section perpendicular to the longitudinal direction of the peripheral exhaust gas discharge cell. The honeycomb fired body according to claim 5, wherein an area of a cross section perpendicular to the longitudinal direction of the peripheral exhaust gas introduction cell is the same as an area of a cross section perpendicular to the longitudinal direction of the internal cell. The honeycomb fired body according to claim 5 or 6, wherein a cross-sectional shape perpendicular to the longitudinal direction of the outer peripheral exhaust gas introduction cell is a shape congruent with a rectangle that is a cross-sectional shape of the internal cell. The honeycomb fired body according to any one of claims 5 to 7, wherein the minimum value of the thickness of the outer peripheral wall is 1.5 to 3 times the thickness of the cell partition wall.

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