Honeycomb structure

Abstract

To provide a honeycomb structure which can suppress an increase in pressure loss on PM accumulation such as soot when used as a filter for exhaust gas purification.SOLUTION: The honeycomb structure comprises a columnar honeycomb structure 4 having partition walls 1 so arranged as to surround a plurality of cells 2 serving as fluid paths extending from a first end face 11 to a second end face 12, wherein the partition walls 1 are constituted of a porous material where a plurality of pores making adjacent cells 2 adjacent each other across the partition walls 1 are formed, a ratio (L / T) of a pore flow path length L (μm) in a thickness direction of the partition walls 1 to a thickness T (μm) of the partition walls 1 is defined as a curvature degree A, the partition walls 1 constituting the honeycomb structure 4 have an average curvature degree AAve that is an average value of the curvature degree A of 1.10 to 1.40, and a value X (x=AAve / B2) of 100 to 300, the value X being obtained by dividing the average curvature degree AAve by a square of a deviation curvature degree B that is a deviation of the curvature degree A.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a honeycomb structure. More specifically, the present invention relates to a honeycomb structure capable of suppressing an increase in pressure loss during PM deposition such as soot when used as a filter for exhaust gas purification.

Background Art

[0002] Conventionally, a honeycomb filter using a honeycomb structure is known as a filter for collecting particulate matter in exhaust gas discharged from an internal combustion engine such as an automobile engine, or as a device for purifying toxic gas components such as CO, HC, and NOx. The honeycomb structure has partition walls made of porous ceramics such as cordierite, and a plurality of cells are partitioned by these partition walls. The honeycomb filter is provided with a plugging portion so as to alternately plug the openings on the inflow end face side and the openings on the outflow end face side of a plurality of cells with respect to the above-described honeycomb structure. That is, the honeycomb filter has a structure in which inflow cells having an open inflow end face side and a plugged outflow end face side and outflow cells having a plugged inflow end face side and an open outflow end face side are alternately arranged with the partition wall interposed therebetween. In the honeycomb filter, the porous partition wall serves as a filter for collecting particulate matter in the exhaust gas. Hereinafter, particulate matter contained in the exhaust gas may be referred to as "PM". "PM" is an abbreviation for "particulate matter".

[0003] Regarding honeycomb filters using a honeycomb structure, due to the strengthening of exhaust gas regulations and the like, while improving the collection performance for collecting PM, a low pressure loss is required, and various studies have been conducted (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, as a means for reducing the pressure loss of a honeycomb filter, a method of increasing the porosity of the porous partition walls constituting the honeycomb structure can be cited. However, if the porosity of the partition walls is simply increased, the collection performance as a filter will decrease. Thus, increasing the porosity of the honeycomb filter to reduce the pressure loss and improving the collection performance of collecting PM have conventionally been considered to be in an antinomic relationship, and it has been very difficult to solve both at the same time. For this reason, there has been an eager desire for the development of a honeycomb structure for a honeycomb filter that can effectively suppress an increase in pressure loss during deposition of PM such as soot while maintaining the porosity of the partition walls.

[0006] The present invention has been made in view of such problems of the prior art. According to the present invention, there is provided a honeycomb structure capable of suppressing an increase in pressure loss during deposition of PM such as soot when used as a filter for exhaust gas purification.

Means for Solving the Problems

[0007] According to the present invention, there is provided a honeycomb structure as shown below.

[0008] [1] A columnar honeycomb structure portion having partition walls arranged so as to surround a plurality of cells serving as fluid flow paths extending from a first end face to a second end face, wherein the partition walls are constituted by a porous body in which a plurality of pores communicating the adjacent cells sandwiching the partition walls are formed, a ratio (L / T) of a flow path length L (μm) of the pores in the thickness direction of the partition wall to a thickness T (μm) of the partition wall is defined as a tortuosity A, the partition walls constituting the honeycomb structure portion have an average tortuosity A which is an average value of the tortuosity A Ave is 1.10 to 1.40, and the average tortuosity A AveThe value X (X = A Ave / B 2 ) obtained by dividing by the square of the deviation buckling degree B which is the deviation of the buckling degree A is 100 to 300, and the honeycomb structure.

[0009] [2] The honeycomb structure according to [1], further comprising a plugging portion disposed at an opening on the first end face side or the second end face side of each of the cells.

[0010] [3] The honeycomb structure according to [1] or [2], wherein the thickness T1 of the partition wall is 100 to 300 μm.

[0011] [4] The honeycomb structure according to any one of [1] to [3], wherein the porosity of the partition wall is 35 to 70%.

[0012] [5] The honeycomb structure according to any one of [1] to [4], wherein the average pore diameter of the partition wall is 8 to 30 μm.

[0013] [6] The honeycomb structure according to any one of [1] to [5], wherein X is 150 to 300.

Advantages of the Invention

[0014] When the honeycomb structure of the present invention is used as a filter for exhaust gas purification, it has the effect of suppressing an increase in pressure loss during PM deposition such as soot. In particular, the honeycomb structure of the present invention has a remarkable effect of suppressing an increase in pressure loss during PM deposition without requiring any special method such as maintaining the porosity of the partition wall, that is, increasing the porosity of the partition wall.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. Therefore, it should be understood that within the scope not departing from the gist of the present invention, those obtained by appropriately changing, improving, etc. the following embodiments based on the ordinary knowledge of those skilled in the art also fall within the scope of the present invention.

[0017] (1) Honeycomb structure: One embodiment of the honeycomb structure of the present invention is a honeycomb structure 100 including a columnar honeycomb structure portion 4 having porous partition walls 1 as shown in FIGS. 1 to 3. The honeycomb structure portion 4 is columnar and has porous partition walls 1 arranged so as to surround a plurality of cells 2 that serve as fluid flow paths extending from the first end face 11 to the second end face 12. In the honeycomb structure 100, the honeycomb structure portion 4 has a columnar shape and further has an outer peripheral wall 3 on its outer peripheral side surface. That is, the outer peripheral wall 3 is arranged so as to surround the partition walls 1 arranged in a lattice pattern.

[0018] Here, FIG. 1 is a perspective view schematically showing one embodiment of the honeycomb structure of the present invention. FIG. 2 is a plan view seen from the first end face 11 side of the honeycomb structure 100 shown in FIG. 1. FIG. 3 is a cross-sectional view schematically showing the A-A' cross-section of FIG. 2.

[0019] The honeycomb structure 100 shown in FIGS. 1 to 3 further includes a plugging portion 5 disposed at the opening on the first end face 11 side or the second end face 12 side of each cell 2, and can be used as a filter for exhaust gas purification.

[0020] The eye blocking part 5 is disposed at the opening on the first end face 11 side or the second end face 12 side of each cell 2. In the honeycomb structure 100 shown in FIGS. 1 to 3, the eye blocking part 5 is disposed at the opening on the first end face 11 side of a predetermined cell 2 and at the opening on the second end face 12 side of the remaining cells 2, respectively. Here, when the first end face 11 is taken as the inflow end face and the second end face 12 is taken as the outflow end face, the eye blocking part 5 is disposed at the opening on the outflow end face side, and the cell 2 with the inflow end face side open is defined as the inflow cell 2a. Further, the cell 2 with the eye blocking part 5 disposed at the opening on the inflow end face side and the outflow end face side open is defined as the outflow cell 2b. The inflow cell 2a and the outflow cell 2b are preferably arranged alternately with the partition wall 1 therebetween. And thereby, it is preferable that a checkered pattern is formed on both end faces of the honeycomb structure 100 by the eye blocking part 5 and the "opening of the cell 2".

[0021] The honeycomb structure 100 has a particularly important configuration regarding the configuration of the partition wall 1 constituting the honeycomb structure part 4. First, in the honeycomb structure 100, the partition wall 1 constituting the honeycomb structure part 4 is constituted by a porous body in which a plurality of pores 16 communicating adjacent cells 2 across the partition wall 1 are formed, as shown in FIG. 4. Here, FIG. 4 is an enlarged cross section of the partition wall 1 and is a schematic diagram for explaining the flow path length L of the pores 16 formed in the porous body constituting the partition wall 1.

[0022] Here, as shown in FIG. 4, two adjacent cells 2 are partitioned by the partition wall 1 constituted by the porous body. The thickness of the partition wall 1 partitioning two adjacent cells 2 in this way is defined as "the thickness T (μm) of the partition wall 1". Also, the flow path length of the pores 16 in the thickness direction of the partition wall 1 is defined as "the flow path length L (μm) of the pores 16". Then, the ratio (L / T) of the flow path length L (μm) of the pores 16 in the thickness direction of the partition wall 1 to the thickness T (μm) of the partition wall 1 is defined as the "bending degree A". Hereinafter, the bending degree A may be referred to as "the bending degree A of the pores 16".

[0023] The degree of bending A of the pores 16 formed in the partition wall 1 is an index indicating the degree of bending of the pores 16 formed in the porous body constituting the partition wall 1. The pores 16 formed in the porous body constituting the partition wall 1 serve as a flow path for the exhaust gas passing through the partition wall 1, and the degree of bending of the flow path can be indicated by the "degree of bending A".

[0024] The partition wall 1 constituting the honeycomb structure portion 4 has an average degree of bending A which is the average value of the degree of bending A Ave is 1.10 to 1.40. Also, the average degree of bending A Ave divided by the square of the deviation degree of bending B which is the deviation of the degree of bending A, the value X (X = A Ave / B 2 ) is 100 to 300. By configuring in this way, when the honeycomb structure 100 is used as a filter for exhaust gas purification, it is possible to effectively suppress an increase in pressure loss during PM deposition such as soot. In particular, without requiring a special method such as increasing the porosity of the partition wall 1, it is possible to extremely effectively suppress an increase in pressure loss during PM deposition. That is, by setting the average degree of bending A Ave within the above numerical range, the average degree of bending A Ave will show a relatively small value, the gas flow passing through the pores 16 in the partition wall 1 will be more linear, and it is possible to suppress an increase in pressure loss during PM deposition while maintaining the porosity of the partition wall 1. Also, by setting the value X obtained by dividing the above-mentioned average degree of bending A Ave by the square of the deviation degree of bending B within the above numerical range, the deviation of the degree of bending A is small, that is, the variation of the degree of bending A becomes small, and the proportion of the specific pores 16 in which the degree of bending A becomes extremely large in the pores 16 in the partition wall 1 decreases, and the effect of suppressing an increase in pressure loss is more likely to be exhibited.

[0025] The average degree of bending A Ave only needs to be 1.10 to 1.40, but it is preferably 1.10 to 1.35, and more preferably 1.10 to 1.30. For example, if the average degree of bending A Ave is less than 1.10, there is a concern that the gas flow becomes too linear and has an adverse effect on the PM collection performance, which is not preferable. On the other hand, if the average degree of bending A AveWhen it exceeds 1.40, it becomes difficult to obtain the effect of suppressing the increase in pressure loss during PM deposition.

[0026] Also, the average degree of tortuosity A Ave divided by the square of the deviation degree of tortuosity B, the value X (X = A Ave / B 2 ) should be in the range of 100 to 300, preferably in the range of 150 to 300, and more preferably in the range of 200 to 300. For example, when this value X is outside the above numerical range, it becomes difficult to obtain the effect of suppressing the increase in pressure loss during PM deposition. When the above value X is in the range of 150 to 300, it is preferable in that it can suppress the variation in the pressure loss increase rate due to PM deposition.

[0027] The degree of tortuosity A of the pores 16 and the average degree of tortuosity A which is the average value of the degree of tortuosity A Ave can be measured by the following method.

[0028] Specifically, first, by performing a CT scan on the partition wall 1 of the honeycomb structure 100, a scan image of the partition wall 1 is taken. As the CT scan device, Xradia520Versa (trade name) manufactured by ZEISS is used. The measurement conditions are a tube voltage of 60 kV and a tube current of 0.083 mA. The resolution of the captured image is 1.2 μm / pixel.

[0029] The scan direction in the CT scan is a direction along the thickness direction of the partition wall 1, from the surface of the partition wall 1 on the side of the cell 2 (for example, the inflow cell 2a) where the first end face 11 serving as the upstream end face of the honeycomb structure portion 4 is open (hereinafter, appropriately referred to as the partition wall surface) to the surface of the partition wall 1 on the side of the cell 2 (for example, the outflow cell 2b) where the second end face 12 serving as the downstream end face is open (hereinafter, appropriately referred to as the partition wall inner surface). Hereinafter, the scan direction in the CT scan may be referred to as "scan direction S".

[0030] In the following description, the direction in which the cells 2 of the honeycomb structure portion 4 extend (in other words, the direction from the first end face 11 to the second end face 12 of the honeycomb structure portion 4) is defined as the Y direction. And the direction perpendicular to the Y direction and along one of the four partition walls 1 surrounding the outflow cell 2b is defined as the X direction. The direction perpendicular to the X direction and the Y direction is defined as the Z direction. Therefore, the scan direction S described above can be the Z direction. For example, the scan image in the Z direction is along the X-Y plane.

[0031] Next, an analysis is performed using a group of captured images in the scan direction S. The group of captured images in the scan direction S refers to a group of captured images in the scan direction S for the number of captured images, and is 1.2 μm in size obtained by dividing the thickness (μm) of the partition wall 1 by 1 pixel. In the following example, the analysis image size has a range of 500 μm × 500 μm in the X and Y planes, and for the Z direction, the number of sheets corresponding to the value obtained by dividing the thickness (μm) of the partition wall 1 by 1.2 μm is used.

[0032] Next, binarization processing is performed on the captured images in the scan direction S. Binarization is an operation for distinguishing between the void portion where the pores 16 are formed and the solid portion of the partition wall 1 in the partition wall 1. Since the void portion and the solid portion of the partition wall 1 have different luminances from each other, in the binarization process, noise remaining in the captured image is removed, and after setting an arbitrary threshold value, the binarization process is performed. Since the threshold value varies depending on each measurement sample, a threshold value that can separate the void portion and the solid portion is set for each captured image by the mode method. The mode method is a method of finding the density boundary on the premise that the binary image is composed of two parts, the "object" and the "background" to be observed.

[0033] In the above manner, a three-dimensional model of the porous body constituting the partition wall 1 is obtained. That is, three-dimensional porous body data (i.e., a three-dimensional model of the porous body) can be obtained by determining whether each coordinate is a spatial voxel or an object voxel by the above-described binarization process.

[0034] Next, fluid analysis is performed on the three-dimensional model of the porous body that constitutes the obtained partition wall 1 by the lattice Boltzmann method. Using the obtained flow velocity results, the position (x n , y n , z n ) [m, m, m] and the flow velocity (u n , v n , w n ) [m / s, m / s, m / s], the position (x n+1 , y n+1 , z n+1 ) [m, m, m] after Δt seconds [s] is obtained by the following formula, and the flow path length of each streamline is calculated. Here, an example of calculation with the unit of position being [m] is shown, but the unit of position can be [μm] as appropriate.

[0035]

Equation

[0036] The value obtained by dividing the calculated flow path length of each streamline by the thickness of the partition wall 1 is the degree of bend A of each streamline, and the average value of each degree of bend A is the average degree of bend A Ave is taken.

[0037] Also, the deviation degree of bend B, which is the deviation of the degree of bend A, can be calculated by taking the square root (√) of the mean square of the individual deviations.

[0038] There are no particular restrictions on the thickness T of the partition wall 1, but for example, it is preferably 100 to 300 μm, more preferably 125 to 275 μm, and particularly preferably 150 to 250 μm. The thickness of the partition wall 1 can be measured, for example, using a scanning electron microscope or a microscope. If the thickness of the partition wall 1 is too thin, it is not preferable in terms of reduced collection performance. On the other hand, if the thickness of the partition wall 1 is too thick, it is not preferable in terms of increased pressure loss.

[0039] There is no particular limitation on the porosity of the partition wall 1. For example, it is preferably 35 to 70%, more preferably 35 to 65%, and particularly preferably 35 to 60%. By configuring in this way, the honeycomb structure 100 can be suitably used as a filter for purifying the exhaust gas discharged from the engine of an automobile. The porosity of the partition wall 1 is a value measured by the mercury intrusion method. The porosity of the partition wall 1 can be measured, for example, using Autopore 9500 (trade name) manufactured by Micromeritics. The measurement of the porosity can be carried out by cutting out a part of the partition wall 1 from the honeycomb structure part 4 to obtain a sample piece and using the sample piece thus obtained.

[0040] There is no particular limitation on the average pore diameter of the partition wall 1. For example, it is preferably 8 to 30 μm, more preferably 8 to 25 μm. The average pore diameter of the partition wall 1 is a value measured by the mercury intrusion method. The average pore diameter of the partition wall 1 can be measured, for example, using Autopore 9500 (trade name) manufactured by Micromeritics in the same manner as the measurement of the porosity.

[0041] The cell density of the cells 2 partitioned by the partition wall 1 is, for example, preferably 30 to 65 cells / cm 2 and more preferably 40 to 55 cells / cm 2 By configuring in this way, the honeycomb structure 100 can be suitably used as a filter for purifying the exhaust gas discharged from the engine of an automobile.

[0042] There is no particular limitation on the shape of the cells 2 formed in the honeycomb structure part 4. For example, in the cross section orthogonal to the extending direction of the cells 2, examples of the shape of the cells 2 include polygons, circles, ellipses, etc. Examples of the polygon include triangles, quadrilaterals, pentagons, hexagons, octagons, etc. Note that the shape of the cells 2 is preferably a triangle, quadrilateral, pentagon, hexagon, or octagon. In the present invention, the cell 2 means the space surrounded by the partition wall 1.

[0043] Regarding the shape of the cells 2 formed in the honeycomb structure portion 4, the shapes of all the cells 2 may be the same or different. For example, although not shown, it may be a mixture of square cells and octagonal cells. For example, in a cross section orthogonal to the direction in which the cells of the honeycomb structure portion extend, the shape of the outflow cell and the shape of the inflow cell may be configured to be different. In such an aspect, for example, it is preferable that the shape of the outflow cell is one of a square shape and an octagonal shape, and the shape of the inflow cell is the other of a square shape and an octagonal shape.

[0044] Also, regarding the size of the cells 2 formed in the honeycomb structure portion 4, the sizes of all the cells 2 may be the same or different. For example, although not shown, among the plurality of cells, the size of some cells may be increased and the size of other cells may be relatively decreased.

[0045] The outer peripheral wall 3 of the honeycomb structure portion 4 may be integrally formed with the partition wall 1, or may be an outer peripheral coat layer formed by applying an outer peripheral coating material to the outer peripheral side of the partition wall 1. For example, although not shown, the outer peripheral coat layer can be provided on the outer peripheral side of the partition wall after removing the formed outer peripheral wall by a known method such as grinding after integrally forming the partition wall and the outer peripheral wall during manufacturing.

[0046] There is no particular limitation on the shape of the honeycomb structure portion 4. Examples of the shape of the honeycomb structure portion 4 include columnar shapes such as circular, elliptical, and polygonal shapes for the first end face 11 (for example, the inflow end face) and the second end face 12 (for example, the outflow end face).

[0047] There is no particular limitation on the size of the honeycomb structure portion 4, for example, the length from the first end face 11 to the second end face 12 or the size of the cross section orthogonal to the direction in which the cells 2 of the honeycomb structure portion 4 extend. When the honeycomb structure 100 is used as a filter for exhaust gas purification, each size may be appropriately selected so as to obtain optimal purification performance.

[0048] There are no particular restrictions on the material of the partition wall 1, as long as the average degree of bending A Ave , and the average degree of bending A Ave divided by the square of the deviation degree of bending B, the value X satisfies the above numerical range. For example, as the material of the partition wall 1, it is preferable to include at least one selected from the group consisting of silicon carbide, cordierite, silicon-silicon carbide composite material, cordierite-silicon carbide composite material, silicon nitride, mullite, alumina, and aluminum titanate. The material constituting the partition wall 1 is preferably a material containing 90% by mass or more of the materials listed in the above group, more preferably a material containing 92% by mass or more, and particularly preferably a material containing 95% by mass or more. Note that the silicon-silicon carbide composite material is a composite material formed with silicon carbide as the aggregate and silicon as the binder. Also, the cordierite-silicon carbide composite material is a composite material formed with silicon carbide as the aggregate and cordierite as the binder. As the material of the partition wall 1, among the above-described materials, particularly, cordierite and silicon-silicon carbide composite material can be mentioned as preferable materials.

[0049] The material of the eyelet portion 5 is preferably the same material as that preferred as the material of the partition wall 1. The material of the eyelet portion 5 and the material of the partition wall 1 may be the same material or different materials.

[0050] (2) Method for manufacturing a honeycomb structure: Next, the method for manufacturing the honeycomb structure of the present embodiment will be described. The honeycomb structure of the present embodiment can be manufactured, for example, by the following method. First, a plastic clay for producing the honeycomb structure portion is prepared. The clay for producing the honeycomb structure portion can be prepared, for example, as follows.

[0051] As a raw material powder, it can be produced by appropriately adding additives such as binders, pore formers, and water to a material selected from the group of suitable materials for the partition walls described above. Among the raw material powders used, by adjusting the particle size of silicon carbide serving as an aggregate, the "bending degree A" of the partition walls in the honeycomb structure of the present embodiment as described above can be changed. For example, although not particularly limited, the finer the silicon carbide serving as an aggregate is pulverized, the more uniform the microstructure becomes, and the bending degree A tends to become smaller.

[0052] Next, by extrusion-molding the clay thus obtained, a honeycomb molded body having partition walls that partition and form a plurality of cells and an outer wall disposed so as to surround the partition walls is produced.

[0053] The obtained honeycomb molded body is dried, for example, with microwaves and hot air. Next, if necessary, a plugging portion is produced by plugging the openings of the cells with the same material as the material used for producing the honeycomb molded body. After producing the plugging portion, the honeycomb molded body may be further dried.

[0054] Next, a honeycomb structure is manufactured by firing the honeycomb molded body or the honeycomb formed body with the plugging portion. The firing temperature and firing atmosphere vary depending on the raw material, and those skilled in the art can select the firing temperature and firing atmosphere optimal for the selected material.

[0055] The honeycomb structure of the present embodiment can be manufactured by the manufacturing method as described above.

Examples

[0056] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples in any way.

[0057] (Example 1) As molding raw materials for preparing the refractory soil, talc, kaolin, alumina, aluminum hydroxide, silica, etc. were prepared. In Example 1, the above-mentioned raw materials were blended to prepare a cordierite-forming raw material.

[0058] Next, with respect to 100 parts by mass of the molding raw material, 2.0 parts by mass of a water-absorbing polymer as a pore-forming material, 6 parts by mass of a binder, 1.0 part by mass of a surfactant, and 70 parts by mass of water were added to prepare the refractory soil. As the water-absorbing polymer as the pore-forming material, one with a particle diameter of 10 μm was used. As the binder, methylcellulose was used. As the dispersant, potassium laurate soap was used.

[0059] Next, the obtained refractory soil was molded using an extrusion molding machine to produce a honeycomb molded body. Next, the obtained honeycomb molded body was dried by high-frequency dielectric heating and then further dried using a hot air dryer. The shape of the cells in the honeycomb molded body was square.

[0060] Next, a plugging portion was formed on the dried honeycomb molded body. First, a mask was applied to the inflow end face of the honeycomb molded body. Next, the masked end portion (the end portion on the inflow end face side) was immersed in the plugging slurry, and the plugging slurry was filled into the openings of the cells (outflow cells) that were not masked. In this way, a plugging portion was formed on the inflow end face side of the honeycomb molded body. And for the outflow end face of the dried honeycomb molded body as well, a plugging portion was formed in the inflow cells in the same manner.

[0061] Next, the honeycomb molded body with the plugging portion formed was dried with a microwave dryer and then completely dried with a hot air dryer. Then, both end faces of the honeycomb molded body were cut and adjusted to a predetermined dimension. Next, the dried honeycomb molded body was degreased and fired to manufacture the honeycomb structure of Example 1.

[0062] The honeycomb structure of Example 1 had a diameter of 266.7 mm at the end face and a length of 254.0 mm in the direction in which the cells extended. Also, the thickness T of the partition wall was 156 μm, and the cell density was 47 pieces / cm 2It was. The value of the partition thickness T is shown in Table 1.

[0063] For the honeycomb structure of Example 1, the porosity and average pore diameter of the partition walls were measured. Each result is shown in Table 1. The porosity and average pore diameter of the partition walls were measured using Autopore 9500 (trade name) manufactured by Micromeritics.

[0064] Also, for the honeycomb structure of Example 1, the average degree of curvature A Ave , and the deviation degree of curvature B were obtained by the method described so far. Then, the value X obtained by dividing the average degree of curvature A Ave by the square of the deviation degree of curvature B (X = A Ave / B 2 ) was calculated. Each value is shown in Table 1.

[0065]

Table 1

[0066] For the honeycomb structure of Example 1, the "initial pressure loss value P0 (Pa)", the "pressure loss value P1 (Pa) after PM deposition", and the "pressure loss increase amount ΔP (Pa)" and "pressure loss increase rate (%)" after PM deposition due to PM deposition were obtained by the following method. The results are shown in Table 1.

[0067] 〔Initial pressure loss value P0 (Pa)〕 Using the lattice Boltzmann method, fluid analysis was performed with the center points of each voxel of the three-dimensional porous body data as each lattice point and using a predetermined relational expression regarding the flow of fluid between each lattice point and the lattice points adjacent thereto when fluid flows in from the inflow end face. The pressure difference between the inflow end face and the outflow end face was calculated as the initial pressure loss value P0 (Pa).

[0068] 〔Pressure loss value P1 (Pa) after PM deposition〕 Based on the results of the fluid analysis, as information on the fluid flow for each spatial voxel, a velocity vector consisting of the flow velocity and the flow direction was derived for each spatial voxel of the porous body 3D data. Subsequently, the movement of PM was predicted by simulating the state in which PM (soot) was placed on the fluid flow represented by this velocity vector. At this time, it is assumed that the PM approaching the object voxel is collected by that object voxel. When PM was deposited on about 1% of the pore volume, the fluid analysis was performed again, and the pressure loss value P1 (Pa) after PM deposition was obtained.

[0069] [Pressure loss increase amount ΔP (Pa) after PM deposition] The difference between the initial pressure loss value P0 (Pa) and the pressure loss value P1 (Pa) after PM deposition obtained by the method described above (that is, P1 - P0) was defined as the pressure loss increase amount ΔP (Pa) after PM deposition.

[0070] [Pressure loss increase rate (%) after PM deposition due to PM deposition] The increase ratio of the pressure loss after PM deposition with respect to the initial pressure loss value P0 (Pa) (that is, ΔP / P0 × 100%) was defined as the pressure loss increase rate (%) after PM deposition due to PM deposition. When the pressure loss increase rate (%) was 350% or less, it was judged as qualified.

[0071] (Examples 2 to 8 and Comparative Examples 1 to 13) In Examples 2 to 8 and Comparative Examples 1 to 13, each raw material used for the cordierite-forming raw material was changed as shown below to prepare the clay. The average particle diameter, blending ratio, and the amount of water added of the water-absorbing polymer and the like in the raw material were changed. The clay was prepared in the same manner as in Example 1 except that the clay was prepared using such raw materials, and honeycomb structures having the partition configurations shown in Tables 1 to 3 were produced.

[0072] For the honeycomb structures of Examples 2 to 8 and Comparative Examples 1 to 13, the porosity and average pore diameter of the partition walls were measured in the same manner as in Example 1. The respective results are shown in Tables 1 to 3. Also, for the honeycomb structures of Examples 2 to 8 and Comparative Examples 1 to 13, the "initial pressure loss value P0 (Pa)", the "pressure loss value P1 (Pa) after PM deposition", and the "pressure loss increase amount ΔP (Pa)" and "pressure loss increase rate (%)" after PM deposition due to PM deposition were determined in the same manner as in Example 1. The results are shown in Tables 1 to 3.

[0073] [Table 2]

[0074] [Table 3]

[0075] (Example 9) As a molding raw material for preparing the green compact, a powder obtained by mixing silicon carbide (SiC) powder and silicon (Si) powder was prepared. Next, 9 parts by mass of a water-absorbing polymer and starch as pore-forming agents, 1.0 part by mass of a binder, 2.0 parts by mass of an auxiliary agent, and 35 parts by mass of water were added to 100 parts by mass of the molding raw material to prepare a green compact. As the water-absorbing polymer as the pore-forming agent, one having a particle diameter of 10 μm was used. As the starch as the pore-forming agent, one having a particle diameter of 6 μm was used. As the binder, hydroxypropylmethylcellulose and montmorillonite were used. As the auxiliary agent, strontium carbonate and aluminum hydroxide were used.

[0076] Next, using the obtained green compact, a honeycomb structure of Example 9 having a partition wall configuration as shown in Table 4 was produced in the same manner as in Example 1.

[0077] (Examples 10 to 22 and Comparative Examples 14 to 29) In Examples 10 to 22 and Comparative Examples 14 to 29, the raw materials for preparing the green soil were changed as shown below to prepare the green soil. The average particle diameter, blending ratio, and the amount of water added of the pore-forming material and the like in the raw materials were changed. The green soil was prepared in the same manner as in Example 11 except that the green soil was prepared using such raw materials, and a honeycomb structure having a partition wall configuration as shown in Tables 4 to 7 was produced.

[0078] For the honeycomb structures of Examples 9 to 22 and Comparative Examples 14 to 29, the porosity and average pore diameter of the partition walls were measured in the same manner as in Example 1. The respective results are shown in Tables 4 to 7. Also, for the honeycomb structures of Examples 9 to 22 and Comparative Examples 14 to 29, the "initial pressure loss value P0 (Pa)", the "pressure loss value P1 (Pa) after PM deposition", and the "pressure loss increase amount ΔP (Pa)" and "pressure loss increase rate (%)" after PM deposition due to PM deposition were determined in the same manner as in Example 1. The results are shown in Tables 4 to 7.

[0079] [Table 4]

[0080] [Table 5]

[0081] [Table 6]

[0082] [Table 7]

[0083] (Results) As shown in Table 1, it was found that the honeycomb structures of Examples 1 to 3 can suppress the increase in pressure loss during PM deposition compared to the honeycomb structures of Comparative Examples 1 to 5. In Table 1, honeycomb structures in which the thickness T (μm) of the partition wall is within a certain range are used as comparison targets.

[0084] Similarly, in each of Tables 2 to 7, it was also found that the honeycomb structure of the examples in each table could suppress the increase in pressure loss during PM deposition compared to the honeycomb structure of the comparative examples in the same table. In Tables 2 to 7, honeycomb structures in which at least one of the thickness T (μm) of the partition walls and the porosity (%) falls within a certain range were used as comparison targets. Among the honeycomb structures of each example, in particular, it was found that the honeycomb structure with the value X being 150 to 300 could significantly suppress the variation in the pressure loss increase rate (%) due to PM deposition.

Industrial Applicability

[0085] The honeycomb structure of the present invention can be used as a collection filter for removing fine particles and the like contained in exhaust gas.

Explanation of Symbols

[0086] 1: Partition wall, 2: Cell, 2a: Inflow cell, 2b: Outflow cell, 3: Outer peripheral wall, 4: Honeycomb structure portion, 5: Plugging portion, 11: First end face, 12: Second end face, 16: Pore, 100: Honeycomb structure.

Claims

1. A columnar honeycomb structure part having a partition wall arranged so as to surround a plurality of cells serving as fluid flow paths extending from a first end face to a second end face, wherein the partition wall is constituted by a porous body in which a plurality of pores communicating the adjacent cells sandwiching the partition wall are formed, and a ratio (L / T) of a flow path length L (μm) of the pores in the thickness direction of the partition wall to a thickness T (μm) of the partition wall is defined as a tortuosity A. The partition wall constituting the honeycomb structure portion is an average bending degree A which is the average value of the bending degree A Ａｖｅ is 1.10 to 1.40, and The average degree of bending A Ａｖｅ is divided by the square of the deviation degree of bending B, which is the deviation of the degree of bending A, to obtain a value X (X = A Ａｖｅ / B ２ ), and the honeycomb structure has a value of 100 to 300.

2. The honeycomb structure according to claim 1, further comprising a plugging portion disposed at an opening on the first end face side or the second end face side of each of the cells.

3. The honeycomb structure according to claim 1 or 2, wherein the thickness T1 of the partition wall is 100 to 300 μm.

4. The honeycomb structure according to claim 1 or 2, wherein the porosity of the partition wall is 35 to 70%.

5. The honeycomb structure according to claim 1 or 2, wherein the average pore diameter of the partition wall is 8 to 30 μm.

6. The honeycomb structure according to claim 1 or 2, wherein X is 150 to 300.

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