JP2009236030A - Honeycomb structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a honeycomb structure for achieving a filter which is hardly damaged by overheat during regeneration and has excellent durability. <P>SOLUTION: The honeycomb structure 1 includes partition wall parts formed of porous ceramics and defining multiple cells extending in the axial direction, one-end plug parts composed of sealing material and plugging the end portions of predetermined cells among the multiple ones at one end of the honeycomb structure, and the-other-end plug parts composed of sealing material and plugging the end portions of the residual cells at the other end of the honeycomb structure. The number of the cells provided with the one-end plug parts is larger than that of the cells provided with the the-other-end plug parts. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a honeycomb structure, and more particularly, to a honeycomb structure that can provide a filter that is less likely to be damaged by overheating during regeneration and that has excellent durability.

  Particulate matter such as soot in exhaust gas (particularly particulate matter in exhaust gas from a diesel engine (particularly particulate matter in exhaust gas from a diesel engine)) A honeycomb structure made of ceramics is used for a collection filter (hereinafter referred to as DPF) of PM)).

  A honeycomb structure made of a ceramic is generally made of porous ceramics, and partition walls 2 that divide a plurality of cells that serve as fluid flow paths by partition walls, and adjacent cells such that end faces form a checkered pattern are mutually connected. And a sealing portion 3 made of a sealing material made of ceramics that seals the end portion on the opposite side. The end face of this honeycomb structure is shown in FIG.

  A DPF made of a ceramic honeycomb structure is used as a wall flow type filter in which exhaust gas passes through partition walls that partition cells. The wall flow type filter collects particulate PM larger than the pore diameter in the partition wall when the exhaust gas passes through the continuous pores formed in the cell wall.

  Since the DPF is clogged if the collected PM is accumulated, it is necessary to remove the collected PM (regeneration of the DPF). One method of removing the collected PM is a method of decomposing and removing PM by combustion or the like. There is also a method in which a catalytic metal exhibiting catalytic activity is supported on the DPF, and PM is decomposed using this catalytic metal.

  In order to remove PM by combustion, the honeycomb structure needs to be heated to a temperature equal to or higher than the combustion temperature of PM. When the honeycomb structure is heated to a predetermined temperature or higher, PM burns and generates heat during combustion. In the conventional honeycomb structure, a large amount of PM is trapped in the vicinity of the central portion (axial center portion of the honeycomb structure) of the cross section perpendicular to the axial direction. Was. As described above, when a part of the honeycomb structure (center part) is excessively heated, there has been a problem that the honeycomb structure is cracked or melted, or the honeycomb structure itself is deteriorated.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a honeycomb structure that is less likely to be damaged due to overheating during regeneration and can provide a filter having excellent durability.

  In order to solve the above-mentioned problems, the present inventors have studied the ceramic honeycomb structure and have come to make the present invention.

  That is, the honeycomb structure of the present invention is made of porous ceramics and partitions that partition a large number of cells penetrating in the axial direction, and sealing that seals one end of a predetermined cell among the large number of cells. A honeycomb structure having one end sealing portion made of a material and the other end sealing portion made of a sealing material for sealing the other end portion of the remaining cells, the one end sealing portion being provided The number of cells is larger than that of a cell provided with a sealing portion at the other end.

  In the honeycomb structure of the present invention, the one-end sealing portion that seals the cells on the upstream side is formed more than the other-end sealing portion, so that the cells in which the one-end sealing portion is formed are densely arranged. In the vicinity of the portion, there is a cell in which the exhaust gas hardly flows. The cell in which the exhaust gas is difficult to flow has a small amount of PM trapped in the exhaust gas. By reducing the amount of collected PM, it is possible to suppress overheating of the entire honeycomb structure during regeneration. As a result, the honeycomb structure of the present invention is less likely to be damaged during regeneration and also has improved durability.

  The honeycomb structure of the present invention is composed of a partition made of porous ceramics that partitions a large number of cells penetrating in the axial direction, and a sealing material that seals one end of a predetermined cell among the large number of cells. And a second end sealing portion made of a sealing material for sealing the other end portion of the remaining cells. That is, the honeycomb structure of the present invention is a wall flow type honeycomb structure in which any one end of a large number of cells is sealed with a sealing material. Such a wall flow type honeycomb structure is preferably used for a filter catalyst through which exhaust gas passes through the partition wall. In the honeycomb structure of the present invention, it is preferable that one end portion is located on the upstream side in the flow direction of the exhaust gas.

  The honeycomb structure of the present invention is formed so that the number of cells provided with one end sealing portion is larger than the number of cells provided with the other end sealing portion. That is, the honeycomb structure of the present invention is formed such that the number of cells sealed at one end is larger than the number of cells sealed at the other end. When formed in this manner, the flow rate of the gas partially passing through the cell is reduced in the vicinity of the portion where the ratio of the cells where the one-end sealing portion is formed is 50% or more.

  Specifically, when the number of cells having one end sealing portion and the number of cells having the other end sealing portion are the same as in a conventional honeycomb structure, the cells are sealed with a sealing material. Gas flows into the cell from the end of the non-cell (for example, one end of the cell where the other end sealing portion is formed), passes through the partition, and flows into the adjacent cell. Thereafter, the gas is discharged from the end portion that is not sealed with the sealing material (for example, the other end portion of the cell in which the one-end sealing portion is formed). In the conventional honeycomb structure, since the number of cells in which the one end sealing portion is formed and the number of cells in which the other end sealing portion is formed are the same, the cell in which the one end sealing portion is formed and the other end sealing. The cells in which the portions are formed are necessarily adjacent to each other. That is, in the conventional honeycomb structure, the gas that has permeated through the partition walls is necessarily discharged.

  On the other hand, when there is a difference in the number of cells provided in the one-end sealing portion and the other-end sealing portion as in the present invention, the cell in which the one-end sealing portion is formed is densely arranged. Is supposed to exist. And in the vicinity of the portion where the cells where the one-end sealing portion is formed are densely arranged, it is difficult for the gas to flow in the axial direction of the honeycomb structure. When such a honeycomb structure is used as a filter catalyst, the amount of collected PM is reduced in a portion where gas is difficult to flow. That is, the amount of PM decomposed during subsequent regeneration is small, and the temperature does not increase excessively during regeneration. As a result, damage to the honeycomb structure can be suppressed.

  More specifically, in the honeycomb structure of the present invention, the number of cells provided with one-end sealing portions is increased, and the cells provided with one-end sealing portions may be adjacent to each other. . In such a configuration, when the gas flows from one end portion of the honeycomb structure toward the other end portion, the gas does not flow into the cell in which the one-end sealing portion is formed. In the portion where the cells where the one-end sealing portion is formed are densely arranged, the ratio of the cells where the other-end sealing portion is formed is relatively small, and it passes through the honeycomb structure (the partition walls). The flow rate of gas is reduced.

  Further, when the gas flows from the other end side of the honeycomb structure toward the one end side, a large number of open ends of the cells in which the one-end sealing portions are formed are opened on the upstream side of the gas flow. The gas that has flowed into the cell from the open end passes through the cell wall and flows to the adjacent cell. In the portion where the cell having the one-end sealing portion is densely arranged, the cell having the one-end sealing portion is formed. They are adjacent to each other. When the cells in which the one-end sealing portion is formed are adjacent to each other, the flow rate of the gas that permeates through the partition walls that partition adjacent cells of the same type is greatly reduced. As a result, the gas flow rate flowing from the cell in which the one-end sealing portion is formed to the adjacent cell is reduced, and the gas flow rate flowing into the cell in which the one-end sealing portion is formed is reduced. At this time, in order to disturb the gas flow in the vicinity, the flow rate of the gas passing through the honeycomb structure decreases in the portion where the cells where the one-end sealing portions are formed are densely arranged.

  In the honeycomb structure of the present invention, the arrangement in the cross section perpendicular to the axial direction of the honeycomb structure of the cell in which the one-end sealing portion is formed (and the cell in which the other-end sealing portion is formed) is particularly limited. is not. The cells in which the one-end sealing portion is formed may be arranged uniformly in the cross section of the honeycomb structure. In addition, the cells in which the one-end sealing portion is formed may be unevenly distributed in a portion where it is required to control the gas flow rate when the honeycomb structure is used as a filter catalyst.

  In the honeycomb structure, it is preferable that the cells having the respective sealing portions are arranged in a state where the ratio of the cells provided with the one-end sealing portion is reduced from the axial center portion to the radially outer side. The ratio of the cells provided with the one-end sealing portion can be obtained from the ratio of predetermined cells in each part by dividing the cross section of the honeycomb structure into a plurality of parts. Generally, a honeycomb structure is used by being assembled in a pipe through which gas flows. The flow velocity of the gas flowing in the pipe is the fastest in the vicinity of the axial center of the pipe and gradually decreases outward in the radial direction. That is, a larger amount of gas flows in the axial portion of the tube than in the outer peripheral portion. And in the filter catalyst assembled | attached in this pipe line, an axial center part will collect more PM than an outer peripheral part. And when the honeycomb structure in which the ratio of the cells in which the sealing portion is provided at one end from the axial center portion to the radially outer side is reduced is used, the PM amount collected at the axial center portion and the PM amount collected at the outer peripheral portion. The difference with is small. That is, the filter catalyst does not partially overheat during regeneration. Here, when the proportion of the cells with one end sealing portion is reduced from the axial center to the outside in the radial direction, the cell with one end sealing portion becomes the cell with the other end sealing portion. Or more.

  The difference between the number of cells provided with the one end sealing portion and the number of cells provided with the other end sealing portion is preferably 50% or less of the number of cells of the honeycomb structure. If the difference in the number of cells exceeds 50%, the number of cells provided with a sealing portion at one end becomes too large, the flow rate of gas passing through the honeycomb structure is greatly reduced, and the pressure loss is increased. A more preferable difference in the number of cells is 3 to 50%.

  In the honeycomb structure of the present invention, the shape (cross-sectional shape) of the cells partitioned into the partition walls is not particularly limited, and can be a conventionally known cross-sectional shape. Of the conventionally known cell shapes, a square shape is more preferable.

  The material of the porous ceramic forming the honeycomb structure of the present invention is not particularly limited, and a conventionally known porous ceramic can be used. The porous ceramic is preferably mainly composed of one kind selected from aluminum titanate, silicon carbide, silicon nitride, and cordierite. Of these ceramics, it is more preferable to be made of a ceramic mainly composed of aluminum titanate. Ceramics made of aluminum titanate have microcracks inside. And even if the honeycomb structure undergoes thermal expansion by having these micro cracks, the stress caused by the thermal expansion is relaxed by opening and closing the openings of the micro cracks, so that no shape change or damage occurs.

  The honeycomb structure of the present invention may have a configuration in which a plurality of parts are joined with a joining material, as in a conventionally known honeycomb structure. That is, the honeycomb structure is preferably formed by bonding a plurality of ceramic segments through the bonding material layer. With this configuration, it is possible to change the ratio of the cells in which the one-end sealing portion is formed for each segment, and as a result, it is possible to adjust the cell arrangement in the honeycomb structure. Further, characteristics such as material and porosity can be changed for each segment, and desired performance can be imparted to the entire honeycomb structure. That is, when the honeycomb structure is composed of a plurality of parts, the characteristics such as the ratio of the cells in which the one-end sealing part of each part is formed, the material, the porosity, and the like may be the same or different. Either is acceptable.

  A conventionally known bonding material can also be used as the bonding material for bonding the ceramic body. As this bonding material, for example, a SiC-based bonding material can be used. The bonding material layer formed between the ceramic bodies when the ceramic bodies are joined with the joining material is preferably formed with a thickness of 0.5 to 5.0 mm.

  Here, when the honeycomb structure of the present invention is formed by joining a plurality of segments, if the thickness of the bonding material layer in the thickness direction of the partition walls of the honeycomb structure is very small, the bonding material layer You can ignore the effects of.

  Furthermore, when the honeycomb structure is formed by bonding a plurality of ceramic segments through an adhesive layer, the size of the cells (cell shape) formed in each ceramic segment is the same, It may be different or any. The size (cell shape) of each ceramic segment cell is preferably the same.

  The honeycomb structure of the present invention preferably has an outer peripheral material layer having a thickness of 0.5 mm or more on the outer peripheral surface in the circumferential direction. By having the outer peripheral material layer, the shape change that occurs when the honeycomb structure is used for a DPF or the like can be suppressed. Specifically, when the honeycomb structure is used for applications such as DPF, the honeycomb structure is exposed to high heat. The honeycomb structure undergoes thermal expansion. This thermal expansion can be suppressed by having the outer peripheral material layer. A conventionally known material can be used as the material constituting the outer peripheral material layer. For example, SiC, silica compounds, alumina compounds such as aluminum titanate, and the like can be used.

  In addition, since the thickness of the outer peripheral material layer varies depending on the shape of the honeycomb structure, the thickness thereof cannot be determined unconditionally. More preferably, it is 0.5-5.0 mm.

  The honeycomb structure of the present invention is preferably used for a DPF. The honeycomb structure of the present invention can be used as a wall flow type filter catalyst through which exhaust gas (gas) passes through partition walls partitioning cells, and among these filter catalysts, it is particularly preferable to use as a DPF.

  When the honeycomb structure of the present invention is used as a DPF, it is preferable to support at least one of a porous oxide made of alumina or the like and a catalyst metal such as Pt, Pd, or Rh on at least the pore surfaces of the partition walls.

  The outer peripheral shape of the honeycomb structure of the present invention is not particularly limited, and can be a conventionally known shape. Preferably, the cross section is a columnar shape, for example, the cross section may be a substantially cylindrical shape having a perfect circle or an ellipse, and the cross section may be a square or polygonal prismatic shape, preferably a cylindrical shape.

  Hereinafter, the present invention will be described using examples.

  As an example of the present invention, a honeycomb structure for DPF was manufactured.

Example 1
The honeycomb structure of this example includes a honeycomb body 2 made of porous ceramics, a sealing portion 3 that seals cells of the honeycomb body 2, an outer peripheral material layer 4 disposed on the outer periphery of the honeycomb body 2, Is a honeycomb structure 1 having a cylindrical outer shape. The honeycomb structure of the present example is shown in FIGS. FIG. 1 shows an end face on one end side of the honeycomb structure 1 of this example, and FIG. 2 shows a cross section in the axial direction. Note that one end of the honeycomb structure is an end disposed on the upstream side in the exhaust gas flow direction when used as a DPF.

  The honeycomb body 2 is made of porous SiC ceramics, and a large number of cells 20 and 21 extending in the axial direction of the honeycomb body 2 are partitioned by cell walls 22 and have a substantially cylindrical outer peripheral shape. . A large number of cells 20 and 21 are partitioned by cell walls 22 so as to have a square cross-sectional shape. The porous ceramics constituting the honeycomb body 2 has a uniform pore distribution.

  In the honeycomb body 2, a sealing portion 3 made of sealing materials 30 and 31 for sealing the cells 20 and 21 is formed at any of axial ends of the many cells 20 and 21. The sealing material 30 seals the cells 20 on one end side of the honeycomb structure 1, and the sealing material 31 seals the cells 21 on the other end side. The sealing materials 30 and 31 are provided so that the length in the cells 20 and 21 is constant.

  The sealing materials 30 and 31 seal the cells 20 and 21 so that the end faces have a substantially checkered pattern. Furthermore, as for the sealing material 30, the sealing material 30 is formed in every two cells among the cells 21 arranged in the diagonal direction of the cells having a square cross section. The sealing materials 30 and 31 are partially biased on the end face of the honeycomb structure 1 (in the repeated pattern of the cells 20 and 21, the sealing materials 31 are originally sealed in some of the cells 21 in which the sealing material 31 is formed. (Stop material 30 is formed), but the entire end face is formed in a uniformly dispersed state.

  In the honeycomb structure 1 of the present example, the number of cells 20 sealed with the sealing material 30 was 2564 cells, and the number of cells 21 sealed with the sealing material 31 was 2084 cells. That is, the difference between the number of cells 20 and 21 is 480 cells, which corresponds to 10.3% when the total number of cells is 100%.

  The outer peripheral material layer 4 is an SiC ceramic layer formed on the outer peripheral surface of the honeycomb body 2 with a uniform thickness.

(Production method)
A method for manufacturing the honeycomb structure of the present example will be described below.

First, 75 parts by weight of SiC powder having an average particle diameter of 12 μm, 20 parts by weight of Si ₃ N ₄ powder having an average particle diameter of 10 μm, and 5 parts by weight of C powder having an average particle diameter of 15 μm were weighed, and methyl cellulose was added as an organic binder. A surfactant was added to what was made moderate viscosity by adding water and mixed and kneaded. The obtained clay was molded by an extrusion method using a mold having an opening of a predetermined shape and dried. This molded body has a constant cross-sectional shape perpendicular to the axial direction that is the extrusion direction.

  After drying, a predetermined cell was plugged at each end of the molded body with the clay used for manufacturing the molded body, and then fired at 2300 ° C. to obtain a fired body. Here, the sealing of the cell is such that one or the other end of the cell is sealed, and the cells sealed in the segment part and the unsealed cells form a substantially checkered pattern on the end surface of the molded body. is there. The cells are sealed so that the number of sealing materials 30 plugging the cells at one end is larger than the number of sealing materials 31 plugging the cells at the other end.

  Thereafter, the entire shape was formed into a cylindrical shape using a cylindrical grinder.

  Thereafter, 50 parts by weight of SiC powder having an average particle diameter of 20 μm, 19 parts by weight of spherical silica powder having an average particle diameter of 1 μm, 25 parts by weight of a 1.26 wt% CMC solution as a binder, and 1 part by weight of an anionic dispersant as a dispersant, A peripheral material slurry is prepared by sufficiently mixing 5 parts by weight of colloidal shear force as a binder. After applying the prepared peripheral material slurry to the ground fired body, heat treatment was performed at 850 ° C. to manufacture the honeycomb structure 1 of this example.

(Example 2)
The honeycomb structure of the present example is the same honeycomb structure 1 as that of Example 1 except that the arrangement of the cells 20 sealed with the sealing material 30 is different. FIG. 3 shows an end face of one end portion of the honeycomb structure 1 of the present example.

  The sealing material 30 is formed on the end face of the honeycomb structure so that the number (existence ratio) of cells sealed by the sealing material 30 decreases from the central portion (axial center portion) outward in the radial direction. Has been. More specifically, in the vicinity of the center portion, the cell 20 that is mostly sealed with the sealing material 30 is located. In the vicinity of the outer peripheral portion, the number of cells 20 sealed by the sealing material 30 and the number of cells 21 sealed by the sealing material 31 are the same. Further, in the intermediate portion in the radial direction between the central portion and the outer peripheral portion, the cells 20 sealed with the sealing material 30 are formed to be larger than the cells 21 sealed with the sealing material 31.

  In the honeycomb structure 1 of the present example, the number of cells 20 sealed with the sealing material 30 was 2260 cells, and the number of cells 21 sealed with the sealing material 31 was 2436 cells. That is, the difference between the number of cells 20 and 21 is 176 cells, which corresponds to 3.7% when the total number of cells is 100%.

(Example 3)
The present embodiment is a honeycomb structure 1 similar to the honeycomb structure 1 of the first embodiment except that the honeycomb body 2 is formed by bonding a plurality of honeycomb bodies 5 with a bonding material. FIG. 4 shows the end face of the honeycomb structure 1 of the present example.

  In the honeycomb structure 1 of the present embodiment, first, the honeycomb body 5 having a square cross-sectional outer shape is manufactured by the honeycomb body manufacturing method of the first embodiment. As in the case of Example 1, the honeycomb segment 5 is formed with cells 20 and 21 provided with sealing materials 30 and 31. That is, the sealing materials 30 and 31 seal the cells 20 and 21 so that the end faces have a substantially checkered pattern. Furthermore, as for the sealing material 30, the sealing material 30 is formed in every two cells among the cells 21 arranged in the diagonal direction of the cells having a square cross section.

  Subsequently, the bonding material slurry used as the outer peripheral material slurry in Example 1 was applied to the outer periphery of the honeycomb body 5, and another honeycomb body 5 was rubbed onto this surface and bonded. This joining was repeated, and the 16 honeycomb bodies 5 were joined so that the cross section was a square, and dried at 80 ° C.

  Then, this joined body was cut using an electric saw to form an outer peripheral shape. The cutting with the electric saw was made so that the cell in which the sealing material was formed at both ends formed a substantially cylindrical shape forming the outer peripheral surface. During this cutting, no peeling of the sealing material from the cell was observed.

  Then, a slurry similar to that in Example 1 was prepared, applied to the outer peripheral surface of the molded body with a thickness of 0.5 mm, dried at 80 ° C., and then heated at 850 ° C. to solidify the bonding material and the slurry. It was. Thereby, the outer peripheral material layer 4 was able to be formed on the outer peripheral surface.

  As described above, the honeycomb structure 1 of this example could be manufactured.

  In the honeycomb structure 1 of the present example, as in Example 1, the sealing materials 30 and 31 were evenly distributed over the entire end surface, although there was a partial bias in the end surface of the honeycomb structure 1. It is formed in a state.

Example 4
The present example is a honeycomb structure similar to the honeycomb structure of Example 2, except that the honeycomb body is formed by bonding a plurality of honeycomb bodies with a bonding material.

  In the honeycomb structure of the present example, first, a honeycomb body 5A having a square cross-sectional outer shape is manufactured by the method of Example 1. In this honeycomb segment 5A, cells 20 and 21 provided with sealing materials 30 and 31 are formed in the same manner as the honeycomb body of Example 1.

  Similarly, the honeycomb body 5B of the first embodiment is a honeycomb body 5B in which cells 20 and 21 having the same number of sealing materials 30 and 31 are formed. Manufactured in a manner similar to that used to produce the body. In the honeycomb divided body 5B, the sealing materials 30 and 31 are arranged so that the end faces form a checkered pattern.

  Subsequently, the bonding material slurry used as the outer peripheral material slurry in Example 1 was applied to the outer periphery of the honeycomb divided body 5A, and another honeycomb divided body 5A was rubbed onto this surface and bonded. This joining was repeated to produce a joined body in which the four honeycomb bodies 5A were joined to form a square outer shape. Subsequently, a bonding material slurry was applied to the outer peripheral surface of the bonded body, and another honeycomb segment 5B was rubbed and bonded to this surface. This joining was repeated, and 16 honeycomb bodies were joined so that the cross section was a square, and dried at 80 ° C. At this time, 12 honeycomb bodies 5A having different numbers of cells 20 and 21 are covered with four honeycomb bodies 5A on the inner periphery, and the outer periphery is covered with honeycomb bodies 5B having the same number of cells 20 and 21. Arranged.

  Then, this joined body was cut using an electric saw to form an outer peripheral shape. The cutting with the electric saw was made so that the cell in which the sealing material was formed at both ends formed a substantially cylindrical shape forming the outer peripheral surface. During this cutting, no peeling of the sealing material from the cell was observed.

  Then, a slurry similar to that in Example 1 was prepared, applied to the outer peripheral surface of the molded body with a thickness of 0.5 mm, dried at 80 ° C., and then heated at 850 ° C. to solidify the bonding material and the slurry. It was. Thereby, the outer peripheral material layer 4 was able to be formed on the outer peripheral surface.

  As described above, the honeycomb structure 1 of this example could be manufactured. The honeycomb structure of the present example is shown in FIG. In FIG. 5 showing the present embodiment, every other cell in the diagonal direction of the cell 21 is a cell 20 so that the arrangement of the cells 20 sealed with the sealing material 30 can be seen.

  The honeycomb structure 1 of the present example has a configuration in which a plurality of honeycomb bodies 5 are bonded with a bonding material layer 6. Further, in the honeycomb structure 1 of the present example, the honeycomb body 5A in which many cells 20 in which the sealing material 30 is formed is disposed on the axial center side, and the sealing material is disposed on the outer peripheral portion thereof. 30 and the sealing material 31 are formed in the same number. That is, the ratio of the cells sealed with the sealing material 30 decreases as it progresses radially outward from the axial center.

(Comparative example)
This comparative example is a honeycomb structure similar to that of Example 3, except that all the honeycomb segments are segments in which cells 20 and 21 with the same number of sealing materials 30 and 31 are formed. is there.

  In this comparative example, the same number of cells 20 and cells 21 are formed. The end face of the honeycomb structure 1 of this comparative example is shown in FIG.

(Evaluation)
As an evaluation of the honeycomb structures of Examples 3 to 4 and the comparative example, a regeneration test was performed in a state where soot (PM) was deposited on the honeycomb structure, and the PM combustion rate and the maximum temperature of the honeycomb structure during combustion were determined. It was measured. Specific test methods are shown below.

  First, the weight of the honeycomb structure to be tested was measured, and then PM was deposited on the honeycomb structure. The deposition of PM was performed so that the amount of deposited PM was about 8 g per 1 L of the apparent volume of the honeycomb structure 1. PM was deposited by assembling a honeycomb structure into the exhaust system of a diesel engine. At this time, the honeycomb structure was assembled in a state where one end portion side thereof was located on the upstream side in the exhaust gas flow direction. The weight of the honeycomb structure on which PM was deposited was measured to determine the amount of PM deposited.

  Then, a thermocouple was inserted into the honeycomb structure. The thermocouple was disposed at a position 10.0 mm from one end face of the honeycomb structure. The thermocouple was installed in the vicinity of the shaft center, in the vicinity of the center between the shaft and the outer periphery, and in the vicinity of the outer periphery.

  The honeycomb structure in which the thermocouple was set was set in an electric furnace, and nitrogen gas heated to 700 ° C. was passed through the cells of the honeycomb structure to raise the temperature of the honeycomb structure. At this time, the atmosphere in the furnace was inert to PM.

  When the temperature of the honeycomb structure measured by the thermocouple was stabilized, the gas was switched from nitrogen gas to air. Air was flowed at 0.4 m / s. With the honeycomb structure sufficiently heated, the gas flowing through the honeycomb structure is switched from nitrogen gas to air, so that oxygen in the air reacts with PM and PM deposited on the honeycomb structure burns. did. The combustion of PM was an exothermic reaction, and the temperature inside the honeycomb structure increased.

  After that, when the temperature measured by the thermocouple was stabilized, the supply of air was terminated because PM combustion was terminated.

  The weight of the honeycomb structure after the PM combustion test was measured, the PM combustion rate was calculated from the weight before and after the test, and the results are shown in Table 1.

  As shown in Table 1, in the honeycomb structures of Examples 3 and 4, the maximum temperature during regeneration was significantly lower than that of the comparative honeycomb structure. That is, the maximum temperature of the honeycomb structure at the time of regeneration can be reduced by increasing the proportion of the cells 20 that are blocked on the upstream side in the exhaust gas flow direction.

  The honeycomb structure 1 of Example 4 has a PM combustion rate significantly higher than that of the honeycomb structure of Example 3 while having the highest temperature comparable to that of the honeycomb structure of Example 3. In the honeycomb structure of Example 4, the exhaust gas does not flow into the cell 20 due to the sealing material 30. Since a large number of cells 20 are arranged in the vicinity of the axial center portion of the honeycomb structure 1, the flow rate of exhaust gas passing through the honeycomb structure 1 in the vicinity of the axial center portion is schematically shown in FIG. Decrease. Thereby, in the honeycomb structure 1 of Example 4, the amount of PM trapped by the cell wall in the vicinity of the axial center portion is reduced.

  More specifically, as schematically shown in FIG. 7, the honeycomb structure 1 of Example 4 is fixed to the hollow portion of the axial center of the tubular exhaust pipe 7 constituting the exhaust system. Assembled.

  The exhaust gas flowing in the exhaust pipe 7 has the highest flow velocity in the vicinity of the axial center portion of the exhaust pipe 7 and the flow velocity in the vicinity of the outer peripheral portion. That is, in this exhaust system, the flow rate of the exhaust gas is greatest in the vicinity of the axial center of the exhaust pipe 7.

  The exhaust gas flowing in the exhaust pipe 7 flows into the cell 21 from one end side of the cell 31 sealed with the sealing material 31. And it flows into the cell 20 which adjoins through the pore of the cell wall which consists of the porous ceramics which divide the cell 21 (permeate | transmits a cell wall). When the exhaust gas passes through the cell wall, PM contained in the exhaust gas is captured by the pores of the cell wall. Then, the exhaust gas from which PM is finely removed is discharged from the other end side of the cell 20. At this time, the sealing material 30 seals the cell 20 on one end side, and the exhaust gas does not flow directly into the cell 20.

  In the honeycomb structure 1 of Example 4, the sealing material 30 that seals the cells 20 is located on the upstream side in the exhaust gas flow direction. The sealing material 30 prevents the exhaust gas from flowing into the cell 20. And since many cells 20 are arrange | positioned in the axial center part vicinity of the honeycomb structure 1, the flow volume of the exhaust gas which passes the honeycomb structure 1 in the axial center vicinity reduces. Thereby, in the honeycomb structure 1 of Example 4, the amount of PM trapped by the cell wall in the vicinity of the axial center portion is reduced. Thereby, even if the honeycomb structure 1 of Example 4 is heated to decompose the collected PM, the regeneration process after the collection is performed due to the small amount of the PM collected in the vicinity of the axial center portion. Occasionally, the temperature in the vicinity of the shaft center did not rise excessively. As a result, the honeycomb structure 1 of Example 4 became a filter in which the durability was not easily lowered because the honeycomb structure 1 was less likely to be damaged due to overheating during regeneration.

3 is a view showing an end face of a honeycomb structure of Example 1. FIG. 1 is a view showing a cross section of a honeycomb structure of Example 1. FIG. 4 is a view showing a cross section of a honeycomb structure of Example 2. FIG. 6 is a view showing an end face of a honeycomb structure of Example 3. FIG. 6 is a view showing a cross section of a honeycomb structure of Example 4. FIG. It is the figure which showed the end surface of the honeycomb structure of a comparative example. It is the figure which showed the state which assembled | attached the honeycomb structure of Example 1 to the exhaust pipe of the vehicle. It is the figure which showed the end surface of the conventional honeycomb structure.

Explanation of symbols

1: Honeycomb structure 2: Honeycomb body 3: Sealing portion 4: Peripheral material layer 5: Honeycomb segment 6: Bonding material layer 7: Exhaust pipe

Claims (5)

A partition wall made of porous ceramics and defining a large number of cells penetrating in the axial direction;
One end sealing portion made of a sealing material for sealing one end portion of a predetermined cell among a number of the cells,
The other end sealing portion made of a sealing material for sealing the other end portion of the remaining cells,
A honeycomb structure having
A honeycomb structure characterized in that the number of cells provided with the one end sealing portion is larger than the number of cells provided with the other end sealing portion.   The honeycomb structure according to claim 1, wherein the one end portion is located on the upstream side in the flow direction of the exhaust gas.   The honeycomb structure is provided with a cell provided with the one-end-sealed portion in a state where a ratio of the cells provided with the one-end-sealed portion is reduced from an axial center portion to a radially outer side. The honeycomb structure according to any one of 1 and 2.   The difference between the number of cells provided with the one-end sealing portion and the number of cells provided with the other-end sealing portion is 50% or less of the number of cells of the honeycomb structure. The honeycomb structure according to 1.   The honeycomb structure according to any one of claims 1 to 4, wherein the ceramic is mainly composed of one kind selected from aluminum titanate, silicon carbide, silicon nitride, cordierite, and mullite.

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