JP6510842B2 - Honeycomb structure - Google Patents

Description

  The present invention relates to a honeycomb structure. More specifically, the present invention relates to a honeycomb structure in which a crack does not easily occur even by a combustion operation, and even when a crack occurs, the progress of the crack is suppressed and an increase in pressure loss is suppressed.

  Heretofore, a method using a converter in which a three-way catalyst is coated on a honeycomb structure is most effective for removing CO, HC and NOx in exhaust gas in a gasoline engine.

The converter has a problem that discharging the CO _2, from the viewpoint of reducing the emissions of CO _2, have come to a gasoline engine of direct fuel injection type is used. On the other hand, this direct fuel injection type gasoline engine has a problem of discharging exhaust particulates. As such, conventional converters are becoming less than adequate.

Here, a diesel engine is advantageous as a car engine that is more thermally efficient than a gasoline engine and meets the CO ₂ emission reduction demand as a countermeasure against global warming. However, there are generation of particulates due to diffusion combustion, and these particulates are recognized to be carcinogenic. Therefore, it is essential to prevent the release of the above-mentioned fine particles into the atmosphere, and recently, in addition to the conventional fine particle discharge regulation (the fine particle discharge regulation by weight), strict regulations to regulate the number of the fine particles to be discharged are is there.

  Under such circumstances, there is a limit to reducing the amount of particulate emissions by improving combustion, and it is an effective means to install a filter in the exhaust passage. And, as the filter, a wall flow type filter in which exhaust gas passes through porous partition walls is effective.

  In the wall flow type filter, it is essential to reduce the filtration flow rate from the viewpoint of reducing pressure loss to an acceptable range, and it has a large number of cells so that the surface of the partition can be used as a filtration area A wall flow type filter having a plugging portion is most effective (see Patent Document 1).

JP, 2013-053589, A

  Thus, installing a filter in the exhaust passage is an effective means. However, this filter requires an operation to burn the soot periodically in order to suppress an increase in pressure loss due to soot accumulated in the filter during use. On the other hand, when this combustion operation is performed, high temperature heat is generated in the filter, and there is a problem that the filter is broken due to the generation of thermal stress.

  Specifically, the distance between the corner of the inlet cell and the corner of the outlet cell formed in the filter is short. Therefore, the filter is weak against shear deformation, and the crack is easily developed by the maximum principal stress generated at the corner. Therefore, there is a problem that the entire filter is broken if any cracks occur.

  With respect to such a problem, it is conceivable to thicken the partition wall to suppress shear deformation for the purpose of suppressing the progress of the crack. However, in that case, there is a problem that the pressure loss is significantly increased.

  From these reasons, it is strongly desired to develop a honeycomb structure in which a crack does not easily occur even by the combustion operation, and the progress of the crack is suppressed even if the crack is generated, and an increase in pressure loss is suppressed. It was

  The present invention has been made in view of the problems of the prior art. The object of the present invention is to provide a honeycomb structure in which a crack does not easily occur even by a combustion operation, and the development of a crack is suppressed even if a crack is generated, and an increase in pressure loss is suppressed. It is to do.

  According to the present invention, a honeycomb structure shown below is provided.

[1] A honeycomb structure having a partition defining a plurality of cells extending from an inflow end surface which is one end surface to an outflow end surface which is the other end surface and an intersection portion located at an intersection of the partitions The cell is a polygon in which a plurality of corners are curved in a convex or concave shape in a cross section orthogonal to the extending direction of the cell, at least one corner is curved in a concave shape, and all of the plurality of corners are convex or concave And the specific curved corner, the concavely curved corner is 1.5 to 50% of the corners of all the cells in the honeycomb structure portion , and the thickness of the partition wall is 0 The honeycomb structure which is .02-0.34 mm .

[2] When a plurality of cells surrounding one intersection point are regarded as one cell group, and the intersection part surrounded by the cells constituting the cell group is considered as a central intersection point, the cell group is constituted The honeycomb structure according to the above [1], wherein all of the cells are concavely curved at an intersection portion forming angle which is a corner on the central intersection portion side.

[3] The honeycomb structure according to [2], wherein all the cells constituting the cell group are curved in a concave shape also in all the corners other than the intersection point formation angle.

[4] The honeycomb structure according to the above [2], wherein all the cells forming the cell group are curved in a convex shape at all corners other than the intersection point formation angle.

[5] The honeycomb structure according to any one of the above [1] to [4], wherein a radius of curvature of a corner of the specific cell that is concavely curved is 0.02 to 1.0 mm.

[6] In a cross section orthogonal to the extending direction of the cells, in the above [1] to [5], the distance between the two adjacent cells across the intersection is 0.03 to 1.2 mm. The honeycomb structure according to any one of the above.

[ 7 ] When the polygonal cell whose side is a straight line is a normal cell, the outer peripheral length of the specific cell is 86% of the outer peripheral length of the normal cell in the cross section orthogonal to the extending direction of the cell. The honeycomb structure according to any one of the above [1] to [ 6 ], which is 100 to 100%.

  In the honeycomb structure of the present invention, in the cross section perpendicular to the cell extending direction, the plurality of cells is a polygon in which a plurality of corners are curved in a convex or concave shape, and at least one corner is curved in a concave shape. And a specific cell that is Then, the concavely curved corner in the specific cell is 1.5% or more of the corner of all the cells in the honeycomb structure part. By having such requirements, in the honeycomb structure of the present invention, cracking is less likely to occur even by the combustion operation, and even if cracking occurs, the development of cracks is suppressed, and the pressure loss is increased. It is suppressed.

It is a perspective view which shows typically one Embodiment of the honeycomb structure of this invention. It is a top view which expands a cell of one end face of a honeycomb structure shown in Drawing 1, and is shown typically. It is a top view corresponding to FIG. 2 which expands the cell of one end face of other embodiment of the honeycomb structure of this invention, and is shown typically. It is a top view corresponding to FIG. 2 which expands and schematically shows the cell of one end face of the further another embodiment of the honeycomb structure of this invention. It is a top view corresponding to FIG. 2 which expands and schematically shows the cell of one end face of the further another embodiment of the honeycomb structure of this invention. It is a top view corresponding to FIG. 2 which expands and schematically shows the cell of one end face of the further another embodiment of the honeycomb structure of this invention. It is a top view corresponding to FIG. 2 which expands and schematically shows the cell of one end face of the further another embodiment of the honeycomb structure of this invention. It is a top view corresponding to FIG. 2 which expands and shows the cell of one end face of the honeycomb structure of the comparative example 1 typically. It is a top view corresponding to FIG. 2 which expands and shows the cell of the end surface of one side of the honeycomb structure of the comparative example 2 typically.

  Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments, and appropriate changes, improvements, etc. can be added to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that what has been described is also within the scope of the present invention.

[1] Honeycomb structure:
One embodiment of a honeycomb structure of the present invention is a honeycomb structure 100 shown in FIG. The honeycomb structure 100 has partition walls 1 defining a plurality of cells 2 extending from the inflow end surface 11 which is one end surface to the outflow end surface 12 which is the other end surface, and an intersection portion 5 which is located at the intersection of the partitions 1 A honeycomb structure unit 10 is provided. The plurality of cells 2 are, in a cross section orthogonal to the extending direction of the cells 2, a polygon in which a plurality of corners are curved in a convex or concave shape, at least one corner is concavely curved and all the plurality of corners are convex It includes a specific cell 2a which is a cell 2 curved in a shape or shape . The concavely curved corner in the specific cell 2 a is 1.5 to 50% of the corners of all the cells 2 in the honeycomb structure body 10. When all the corners of all the cells 2 in the honeycomb structure 100 are curved in a convex or concave shape and at least one corner is curved in a concave shape, the cells are specific cells.

  In such a honeycomb structure 100, a crack does not easily occur even by the combustion operation, and the development of the crack is suppressed even if the crack occurs. That is, in the honeycomb structure 100, even if a crack is generated, the generated crack is minute. Furthermore, in the honeycomb structure 100, an increase in pressure loss is suppressed.

  FIG. 1 is a perspective view schematically showing an embodiment of a honeycomb structure of the present invention. FIG. 2 is a plan view schematically showing a cell of one end face of the honeycomb structure shown in FIG. 1 in an enlarged manner.

[1-1] Specific cell:
The specific cell is a cell in which at least one corner is concavely curved in a cross section orthogonal to the extending direction of the cell. Then, when there is an angle other than the concavely curved corner, the corner is a convexly curved corner. By including such cells at a predetermined ratio, cracking is less likely to occur even by the combustion operation. In addition, since the honeycomb structure of the present invention only needs to satisfy the condition that the corners of the cells are concavely curved, the structure is simple, and the problem of an increase in pressure loss hardly occurs. In addition, it can also be said that the corner of a cell protrudes in the center side of this cell in the cross section orthogonal to the extending direction of a cell that "corner curved in concave shape". The concavely curved corner is indicated by reference numeral 41 in FIG. The concavely curved corner 41 is a corner projecting toward the center of the cell 2 as shown in FIG. In addition, “the corner is curved in a convex shape” can also be said that the corner of the cell is chamfered so as to draw a curve in a cross section orthogonal to the extending direction of the cell. The convexly curved corner is indicated by reference numeral "42" in FIG. The convexly curved corner 42 is a corner formed by chamfering the cell 2 so as to draw a curved line, as shown in FIG.

  In the specific cell, the radius of curvature of the concavely curved corner is preferably 0.02 to 1.0 mm, more preferably 0.02 to 0.7 mm, and 0.02 to 0.2 mm. Is particularly preferred. By satisfying such a radius of curvature, cracking is less likely to occur even by the combustion operation. Furthermore, by satisfying such a radius of curvature, the increase in pressure loss can be further suppressed. When the radius of curvature is less than the lower limit value, there is a possibility that the crack may easily develop when the crack occurs. If the pressure exceeds the upper limit value, the pressure loss may increase.

  In the honeycomb structure of the present invention, when a polygonal cell in which each side is a straight line is a normal cell, in the cross section orthogonal to the cell extending direction, the outer peripheral length ratio of the specific cell is the outer peripheral length of the normal cell. It is preferably 86 to 100%, more preferably 93 to 99%, and particularly preferably 95 to 99%. By setting the outer peripheral length of the specific cell in the above range, the increase in pressure loss can be further suppressed. When the outer peripheral length of the specific cell is less than the lower limit value, the pressure loss may increase. If the upper limit value is exceeded, there is a possibility that the crack may easily progress when the crack occurs.

  The "normal cell" is a polygonal cell in which each side is a straight line. In other words, the “ordinary cell” is a polygon in the case where it is assumed that a plurality of corners are not convexly or concavely curved. Furthermore, "normal cell" refers to a polygon formed by imaginary lines obtained by extending each side in a convex or concavely curved polygon.

  Note that the ratio of the outer peripheral length of a specific cell to the outer peripheral length of a normal cell (peripheral length of a specific cell / peripheral length of a normal cell × 100) can be specified each time a plurality of specific cells are selected It is the average value of the above ratios calculated in the cell.

[1-2] Honeycomb structure part:
In the honeycomb structure portion, a concavely curved corner in a specific cell is present at a ratio of 1.5% or more with respect to the corners of all cells. And, the concavely curved corner is preferably present at a ratio of 1.5 to 100% of the corners of all the cells, and is further preferably present at a ratio of 2.8 to 100% of the corners of all the cells. Preferably, it is particularly preferred to be present in a proportion of 3.0 to 50%. By satisfying the above range, the honeycomb structure of the present invention is less likely to be cracked even by the combustion operation. The ratio of the concavely curved corners is a value calculated by “the total number of concavely curved corners” with respect to the total number of cell corners (that is, all of the cell corners present in the honeycomb structure).

  In the honeycomb structure portion, a plurality of cells surrounding one cross point portion is taken as one cell group, and a cross point portion surrounded by cells constituting the cell group is taken as a central cross point. At this time, it is preferable that all the cells forming the cell group be concavely curved at an intersection portion forming angle which is a corner on the central intersection portion side. By adopting such a configuration, cracking is less likely to occur even by the combustion operation.

  FIGS. 1 and 2 show an example in which all of the cells 2 constituting the cell group 15 are curved in a concave shape at an intersection portion forming angle 30 which is a corner on the central intersection portion 25 side. Here, a plurality of cells 2 surrounding one cross point portion 5 is taken as one cell group 15, and a cross point portion 5 surrounded by the cells 2 constituting the cell group 15 is taken as a central cross point portion 25.

  Furthermore, in the honeycomb structure of the present invention, it is also preferable that all the cells constituting the cell group be convexly curved at all the corners other than the intersection point formation angle. By adopting such a configuration, the crack is less likely to occur even by the combustion operation.

  1 and 2 show an example in which all the cells 2 constituting the cell group 15 are curved in a convex shape at all the corners other than the intersection point formation angle 30.

  Further, in the honeycomb structure of the present invention, it is preferable that all the cells constituting the cell group be concavely curved also at all the corners other than the intersection point formation angle. By adopting such a configuration, the crack is less likely to occur even by the combustion operation.

  FIG. 3 shows an example in which all the cells 2 constituting the cell group 15 are concavely curved also at all the corners other than the intersection point formation angle 30.

  In the honeycomb structure of the present invention, cells having a rectangular cross-sectional shape as shown in FIGS. 4 to 7 may be formed in the honeycomb structure part. 4 to 7 are plan views corresponding to FIG. 2 and schematically showing the cells on one end face of still another embodiment of the honeycomb structure of the present invention in an enlarged manner.

  FIG. 4 shows one cell group 15 of the honeycomb structure in which the cells of the honeycomb structure part are composed of a plurality of cell groups 15. The cell group 15 shown in FIG. 4 is composed of two cells in the upper stage and two cells in the lower stage (specific cell 2a). In the upper two cells 2, the upper right and lower right corners are concavely curved, and the upper left and lower left corners are convexly curved. In the lower two cells 2, the upper right and lower right corners are convexly curved, and the upper left and lower left corners are concavely curved.

  FIG. 5 shows a cell 2 (specific cell 2a) in which the upper right and lower left corners are convexly curved and the upper left and lower right corners are concavely curved. And FIG. 5 is an example in which such cells 2 are arranged vertically and horizontally.

  FIG. 6 shows a cell 2 (specific cell 2a) in which the upper right and upper left corners are curved in a convex shape and the lower right and lower left corners are curved in a concave shape. And FIG. 6 is an example in which such cells 2 are arranged in the vertical and horizontal directions.

  FIG. 7 shows a cell 2 (specific cell 2a) in which the upper left corner is convexly curved and the other corners are concavely curved. And FIG. 7 is an example in which such cells 2 are arranged vertically and horizontally.

  When the cell group is formed in the honeycomb structure part, as shown in FIG. 1, in the honeycomb structure part 10, it is preferable that a plurality of cell groups 15 be arranged in the vertical and horizontal directions. By adopting such a configuration, the crack is less likely to occur even by the combustion operation.

  In the honeycomb structure 100, in a cross section orthogonal to the extending direction of the cells 2, a distance L (see FIG. 2) between two adjacent cells 2 across the intersection 5 is 0.03 to 1.2 mm. Is preferred. In the honeycomb structure 100, the distance L is more preferably 0.05 to 0.9 mm, and particularly preferably 0.08 to 0.8 mm. By setting the distance L between the two cells in the above range, the crack is less likely to be generated even by the combustion operation. If the distance L between the two cells is less than the lower limit value, the crack may easily develop. If the pressure exceeds the upper limit value, the pressure loss may increase.

  The distance between the two cells is a value measured as follows. That is, first, in a cross section orthogonal to the extending direction of the cells 2, a straight line T connecting the centers O1 and O2 of two adjacent cells 2 across the intersection portion 5 is drawn (see FIG. 2). Thereafter, the length of the straight line T between the two cells 2 is measured. Thereafter, the total value of the distance t1 between the center O1 and the partition 1 and the distance t2 between the center O2 and the partition 1 is subtracted from the length of the straight line T. The value calculated in this way is taken as the distance L between the two cells.

The thickness of the partition wall, 0.02～0.34Mm der is, it is good Mashiku is 0.05～0.31Mm, further preferably 0.1～0.31Mm. If the thickness of the partition wall is less than the lower limit value, the crack may easily develop. If the pressure exceeds the upper limit value, the pressure loss may increase.

Cell density of the honeycomb structure portion is preferably 15.5 to 186 cells / cm ^2, more preferably from 31 to 62 pieces / cm ^2. If the pressure exceeds the upper limit value, the pressure loss may increase.

  The porosity of the partition walls is preferably 35 to 68%. If the porosity is less than the lower limit value, the pressure loss may increase. If the upper limit value is exceeded, the crack may easily develop. The porosity is a value measured by a mercury porosimeter.

  The material of the partition wall is preferably ceramic, and cordierite, silicon carbide, silicon-silicon carbide based composite material, mullite, alumina, aluminum titanate, silicon nitride, and silicon carbide-cordierite from the viewpoints of excellent strength and heat resistance. Further preferred is at least one selected from the group consisting of composite materials. Of these, cordierite is particularly preferred.

  The honeycomb structure portion may be a joined body composed of a plurality of honeycomb segments. That is, the honeycomb body may be provided with an aggregate of a plurality of honeycomb segments and a bonding portion made of a bonding material for bonding the honeycomb segments to one another.

  The length in the extending direction of the cells of the honeycomb structure can be 76.2 to 355.6 mm.

  The honeycomb structure of the present invention may further include an outer peripheral wall 20 (see FIG. 1) on the side surface of the honeycomb structure part.

  The honeycomb structure of the present invention may have a plugging portion at the opening of a predetermined cell in the inflow end surface of the honeycomb structure part and the opening of the remaining cells in the outflow end surface.

[2] Manufacturing method of honeycomb structure:
The manufacturing method of the honeycomb structure of the present embodiment will be described. First, a clay for producing a honeycomb structure is prepared, and the clay is formed to produce a honeycomb formed body (forming step). At the time of molding, extrusion molding can be carried out from a die so that concavely curved corners (concave corners) are present at 1.5% or more of all cell corners. Thereafter, the obtained honeycomb molded body (or the dried honeycomb dried body carried out as required) can be fired to produce a honeycomb structure (a honeycomb structure producing step).

  In addition, if necessary, the openings of predetermined cells in the inflow end surface of the honeycomb formed body and the openings of the remaining cells in the outflow end surface are plugged to form the inflow side plugging portion and the outflow side plugging. A stop can be formed.

  Hereinafter, each manufacturing process will be described in more detail.

[2-1] Forming process:
First, in the forming step, a ceramic forming raw material containing a ceramic raw material is formed to form a honeycomb formed body in which a plurality of cells serving as fluid channels are sectioned.

  The ceramic raw material contained in the ceramic forming raw material is preferably one containing at least one selected from the group consisting of cordierite-forming raw materials, cordierite, mullite, alumina, titania, silicon carbide, and aluminum titanate. The cordierite-forming raw material is a ceramic raw material compounded so as to have a chemical composition in which 42 to 56% by mass of silica, 30 to 45% by mass of alumina, and 12 to 16% by mass of magnesia are contained. And are fired to become cordierite.

  The ceramic forming material is preferably prepared by mixing the above-mentioned ceramic material with a dispersion medium, an organic binder, an inorganic binder, a pore former, a surfactant and the like. The composition ratio of each raw material is not particularly limited, and it is preferable to set the composition ratio according to the structure, material, and the like of the honeycomb structure to be produced.

  When forming the ceramic forming raw material, it is preferable to knead the forming raw material first to make a clay, and to form the obtained clay into a honeycomb shape. There is no restriction | limiting in particular as a method of knead | mixing a forming raw material and forming clay, For example, the method of using a kneader, a vacuum soil kneader, etc. can be mentioned. There is no restriction | limiting in particular as a method of shape | molding a clay, and forming a honey-comb molded object, Conventionally well-known shaping | molding methods, such as extrusion molding and injection molding, can be used. For example, a method of forming a honeycomb formed body by extrusion using a die having a desired cell shape, partition wall thickness and cell density can be mentioned as a preferable example.

  When extruding from a die so that the concave corners are at least 1.5% of the corners of all cells at the time of molding, the following can be used as the die. That is, as the die, for example, a plurality of corner portions at the intersection where the cells of the obtained honeycomb structure are formed are chamfered into a concave or convex curved shape and at least one corner is formed to be concave. Can be used.

  The shape of the honeycomb formed body is not particularly limited, and a cylindrical shape, an oval cross-section perpendicular to the central axis, a racetrack shape, a triangular, quadrangular, pentagonal, hexagonal, octagonal or other polygonal columnar shape may be mentioned. Can.

  The obtained honeycomb molded body may be dried. The drying method is not particularly limited, and examples thereof include hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying and the like, among which dielectric drying, microwave drying or It is preferred to carry out hot air drying alone or in combination.

[2-2] Honeycomb Structure Preparation Step:
Next, the obtained honeycomb molded body is preferably fired to obtain a honeycomb structure. In addition, when arrange | positioning a plugging part to a honey-comb molded object, you may carry out baking of a honeycomb molded object, after arrange | positioning a plugging part.

  Further, before firing (main firing) the honeycomb formed body, it is preferable to calcine the honeycomb formed body. The calcination is carried out for degreasing, and the method is not particularly limited as long as organic substances (organic binder, dispersant, pore former, etc.) can be removed. Generally, the combustion temperature of the organic binder is about 100 to 300 ° C., and the combustion temperature of the pore forming material is about 200 to 800 ° C. Therefore, the calcination condition is about 200 to 1000 ° C. in an oxidizing atmosphere, It is preferable to heat for about 100 hours.

  For firing (main firing) of the honeycomb formed body, appropriate conditions may be selected. For example, in the case of using cordierite-forming raw materials, the firing temperature is preferably 1410 to 1440 ° C. The firing time is preferably 4 to 6 hours as the keeping time at the maximum temperature.

  EXAMPLES Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

( Reference Example 1 )
As a ceramic raw material, a cordierite-forming raw material composed of alumina, talc and kaolin was used. The mass ratio of alumina, talc and kaolin was a mass ratio at which cordierite can be obtained after firing. A binder (methylcellulose) and water were mixed with the ceramic raw material to obtain a ceramic forming raw material. The obtained ceramic forming raw material was kneaded using a kneader to obtain a clay.

  Next, the obtained clay was formed using a vacuum extrusion molding machine to obtain a honeycomb formed body. The obtained honeycomb formed body was cylindrical (diameter of end face 143.8 mm, length in the cell extending direction 152.4 mm).

  In addition, this honeycomb molded body was extrusion molded from a die so that a concavely curved corner (concave corner) was present at 3.0% of the corners of all cells at the time of molding. The cross-sectional shape of the cell was a substantially quadrangle (a quadrangle with chamfered corners).

  Next, the obtained honeycomb molded body is dried to obtain a dried honeycomb body, and the plugged portions are formed in the dried honeycomb body. Specifically, first, one end face (inflow end face) of the dried honeycomb body was masked to prevent the inflow cells from being covered and the outflow cells from being covered. An inflow cell is a cell (flow path) into which exhaust gas will flow. The outflow cell is a cell (flow path) for flowing out to the outside after the exhaust gas flowing into the inflow cell permeates through the partition wall. Thereafter, the end on the side to which the mask was applied was immersed in the plugging slurry. Thus, the plugging slurry was filled in the opening of the unmasked cell (outflow cell). Thereafter, the other end face (outflow end face) of the dried honeycomb body was masked so that the inflow cell was not covered and the outflow cell was covered. Thereafter, the end on the side to which the mask was applied was immersed in the plugging slurry. In this way, the plugging slurry was filled in the opening of the unmasked cell (inflow cell). In this manner, a plugged honeycomb dried body is formed in which plugged portions are formed at one end of a predetermined cell and the other end of the remaining cells, and inflow cells and outflow cells are alternately arranged. Obtained.

  Next, the plugged honeycomb dried body was degreased by heating at 450 ° C. for 5 hours, and further firing was performed by heating at 1425 ° C. for 7 hours to obtain a honeycomb structure.

The honeycomb structure had a “cell open area ratio (OFA) (%))” of 51.30%. In addition, the shortest diagonal distance was 1.00 mm. The shortest diagonal distance is the distance between two cells adjacent to each other across the intersection in a cross section orthogonal to the cell extension direction. The honeycomb structure had an outer peripheral length ratio of 89.20%. In addition, when a square cell in which each side is a straight line is a normal cell, the “periphery length ratio” is an outer peripheral length of a specific cell with respect to an outer peripheral length of a normal cell in a cross section orthogonal to the cell extension direction. The outer peripheral length of the specific cell / the outer peripheral length of the normal cell). Further, in this honeycomb structure, the radius of curvature of the concavely curved corner of the specific cell was 0.3 mm, the thickness of the partition wall was 0.31 mm, and the cell density was 46.5 cells / cm ² . . In addition, the column of "cell shape" in Table 1 shows the cross-sectional shape of the cell. For example, “FIG. 3” means having the cross-sectional shape of the cell as shown in FIG.

  The obtained honeycomb structure was evaluated for “presence or absence of crack”, “pressure loss”, and “overall determination” by the methods described below. The results are shown in Table 1.

[Presence of crack]
In order to confirm the presence or absence of a crack, a thermal shock resistance test was conducted. This thermal shock resistance test was performed based on the thermal shock resistance test based on (JASO) M505-87. Specifically, the obtained honeycomb structure was placed in an electric furnace at an ambient temperature of 850 ° C. Sufficient time was allowed to heat the honeycomb structure uniformly. Thereafter, the heated honeycomb structure was taken out of the electric furnace and allowed to cool in the air (air temperature 25 ° C.), and the presence or absence of cracks in the honeycomb structure was visually confirmed. The results are shown in Table 1.

[Presence or absence of progress of crack]
The following evaluations were made as to whether or not there was progress of the crack even if the crack occurred (that is, the presence or absence of the progress of the crack). That is, it can be said that the progress of the crack is suppressed when the progress of the crack does not occur even if the crack is generated. In the present evaluation, first, the thermal shock resistance test is performed five times on the same conditions as the evaluation of the above [presence or absence of a crack] for the honeycomb structure in which a crack is generated by performing the above-mentioned “heat shock resistance test”. I went over and over again. Thereafter, the presence or absence of the progress of the crack was visually confirmed.

  When no progress of the crack was confirmed (that is, when the length of the crack did not change before and after the above test) was regarded as "absent". When the progress of the crack was confirmed (that is, when the crack became longer after the test than in the test), it was regarded as "presence".

[Collection performance]
The collection performance was evaluated as follows. First, the exhaust gas was flowed from the light oil burner at an air flow rate of 2.4 Nm ³ / min to the honeycomb structure after the evaluation of the "presence or absence of crack" and "presence or absence of crack development". At this time, in an initial state before the soot in the exhaust gas is deposited on the honeycomb structure, the number of soot particles flowing into the honeycomb structure and the number of soot particles flowing out from the honeycomb structure are measured using an SMPS, The collection efficiency was calculated. SMPS is an abbreviation of Scanning Mobility Particle Sizer. As SMPS, one manufactured by TIS was used. Calculation of collection efficiency was performed as follows. First, the number of soot particles flowing into the honeycomb structure is Nin, and the number of soot particles flowing out of the honeycomb structure is Nout. Next, the collection efficiency was determined by the formula: (Nin-Nout) / Nin. In addition, the used honeycomb structure is a thing of the state in which the crack arose also when a crack arose by evaluation of "presence or absence of a crack" and "presence or absence of a crack progress".

  The collection performance is "A" when the collection efficiency is over 85%. The case where the collection efficiency is less than 85% and 80% or more is referred to as "B". The case where the collection efficiency was less than 80% was designated as "C". In addition, if collection efficiency is 80% or more, it is a pass as collection performance.

[Pressure loss (kPa)]
When measuring the pressure loss, first, the manufactured honeycomb structure was housed in a housing can to obtain an exhaust gas purification system. Next, a gas (air) not containing 25 ° C. soot was supplied to the exhaust gas purification system at a flow rate of 17 Nm ³ / min. The pressure drop in this case was measured.

  The measured pressure loss was evaluated based on the following criteria. A case where the difference between the pressure loss of the manufactured honeycomb structure and the pressure loss of the honeycomb structure not including the specific cell is within 5% is referred to as “A”. A case where the difference between the pressure loss of the manufactured honeycomb structure and the pressure loss of the honeycomb structure not including the specific cell is more than 5% and within 10% is referred to as “B”. The case where the difference between the pressure loss of the manufactured honeycomb structure and the pressure loss of the honeycomb structure not including the specific cell was within 10% and more than 10% was regarded as “C”. In addition, "the honeycomb structure which does not contain a specific cell" means the honeycomb structure which is the same structure except not containing a specific cell in each Example, respectively.

[Evaluation results]
The case where the pressure drop evaluation is "A" or "B" and the collection performance evaluation is "A" is "A". The pressure drop rating is “C” and the collection performance rating is “A”, or the pressure drop result is “A” and the collection performance rating is “B”. B ”. The case where the evaluation of pressure loss is “A” and the evaluation of collection performance is “C” is “C”.

[General judgment]
The case where the evaluation result of the manufactured honeycomb structure was "A" or "B" was taken as "OK". When the evaluation result of the manufactured honeycomb structure was "C", it was determined as "NG".

(Examples 2 to 15 , Reference Example 16, Comparative Examples 1 to 3)
Except for changes as shown in Table 1, the same as in Reference Example 1, "presence or absence of crack", "presence or absence of development of crack", "collection performance", "pressure loss", "evaluation result", and We made an evaluation of the "general judgment". The results are shown in Table 1.

The honeycomb structures of Reference Examples 1 and 16 and Examples 12 and 14 to 15 and Comparative Example 3 were formed by arranging the cell groups shown in FIG. 3 in the vertical and horizontal directions. The honeycomb structures of Examples 2 to 6 and 11 were formed by arranging the cell groups shown in FIG. 2 in the vertical and horizontal directions. The honeycomb structures of Examples 7 and 13 were formed by arranging the cell groups shown in FIG. 4 in the vertical and horizontal directions. The honeycomb structure of Example 8 was formed by arranging the cell groups shown in FIG. 5 vertically and horizontally. The honeycomb structure of Example 9 was formed by arranging the cell groups shown in FIG. 6 vertically and horizontally. The honeycomb structure of Example 10 was formed by arranging the cell groups shown in FIG. 7 in the vertical and horizontal directions.

  In addition, in the honeycomb structure of Comparative Example 1, as shown in FIG. 8, the cells of the honeycomb structure portion were constituted of a plurality of cell groups 15. Then, all of the square cells 2 constituting the cell group are concavely curved at the intersection point formation angle which is the corner on the central intersection point side. However, all the square cells 2 were not curved at all corners other than the intersection point formation angle. In the honeycomb structure of Comparative Example 2, as shown in FIG. 9, cells in which only one pair of opposing corners is concavely curved and the other pair of corners is not curved are arranged in a matrix. there were.

From Table 1, it can be seen that the honeycomb structures of Examples 2 to 15 and Reference Examples 1 and 16 are less likely to crack even by the combustion operation, as compared with the honeycomb structures of Comparative Examples 1 to 3. Moreover, according to Examples 11 and 13 and Comparative Examples 1 to 3, it is understood that in the honeycomb structure of the present invention, the progress of the crack is not confirmed, and the progress of the crack is suppressed. Further, it is understood that the honeycomb structures of Examples 2 to 15 and Reference Examples 1 and 16 have better collection performance as compared with the honeycomb structures of Comparative Examples 1 to 3. In Examples 2-15, the honeycomb structure of Reference Example 1 and 16 it is understood that the increase in pressure loss is suppressed. In Example 12, the evaluation of pressure loss is “C”, but the evaluation of collection efficiency is “A”. That is, the particulate collection performance most important as a diesel particulate filter (filter) is maintained well. Therefore, when this honeycomb structure is used, it becomes possible to satisfy the discharge regulation of the particulates discharged from the exhaust gas. From such a thing, even if evaluation of a pressure drop is "C", it is "B" as an "evaluation result."

  The honeycomb structure of the present invention can be employed as a filter for purifying exhaust gas discharged from an automobile or the like.

1: Partition wall, 2: Cell, 2a: specified cell, 5: intersection, 10: honeycomb structure, 11: inflow end, 12: outflow end, 15: cell group, 20: outer peripheral wall, 25: central intersection, 30: intersection angle forming angle 41: concave curved corner 42: convex curved corner 100: honeycomb structure.

Claims (7)

A honeycomb structure portion having a partition defining a plurality of cells extending from an inflow end surface as one end surface to an outflow end surface as the other end surface, and an intersection portion positioned at an intersection of the partition walls;
The plurality of cells are, in a cross section orthogonal to the extending direction of the cells, a polygon in which a plurality of corners are curved in a convex or concave shape, at least one corner is curved in a concave shape, and all of the plurality of corners are convex Specific cells which are said cells curved in a shape of
The concavely curved corner is present at 1.5 to 50% of the corners of all the cells in the honeycomb structure .
The honeycomb structure whose thickness of the said partition is 0.02-0.34 mm . When a plurality of the cells surrounding one of the intersections are one cell group, and the intersection surrounded by the cells forming the cell group is a central intersection
2. The honeycomb structure according to claim 1, wherein all the cells forming the cell group have an intersection portion forming angle which is a corner on the central intersection portion side curved in a concave shape.   3. The honeycomb structure according to claim 2, wherein all of the cells forming the cell group are concavely curved also at all corners other than the intersection point formation angle.   The honeycomb structure according to claim 2, wherein all the cells forming the cell group are curved in a convex shape at all the corners other than the intersection point forming angle.   The honeycomb structure according to any one of claims 1 to 4, wherein the radius of curvature of the concavely curved corner of the specific cell is 0.02 to 1.0 mm.   6. The cross section perpendicular to the extending direction of the cells, wherein the distance between two adjacent cells sandwiching the intersection is 0.03 to 1.2 mm. Honeycomb structure. Assuming that the above-mentioned cell of the polygon in which each side is a straight line is a normal cell,
The honeycomb structure according to any one of claims 1 to 6 , wherein in a cross section orthogonal to the extending direction of the cells, an outer peripheral length of the specific cell is 86 to 100% of an outer peripheral length of the normal cell. .

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