JP2013094701A - Honeycomb structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb structure capable of suppressing not only the lowering of filter capacity caused by the generation of radial cracks but also the expansion of the radial cracks.SOLUTION: The columnar honeycomb structure 10 extending along a center axis CL includes a first end surface 10a and a second end surface 10b opposed to each other in the extending direction of the center axis CL, and partition walls 10c for forming a plurality of first flow channels Ra and a plurality of second flow channels Rb extending along the center axis CL. The first flow channels Ra are opened on the side of the first end surface 10a and sealed on the side of the second end surface 10b and the second flow channels Rb are sealed on the side of the first end surface 10a and opened on the side of the second end surface 10b and the opening ratio of the first end surface 10a is larger than that of the second end surface 10b. Flow channel rows W formed by arranging the second flow channels Rb adjacent to each other so as to leave the partition walls 10c along the direction crossing the center axis CL at a right angle are provided.

Description

  The present invention relates to a honeycomb structure used as a filter for purifying gas.

  A honeycomb structure is widely used as a filter for purifying exhaust gas from an internal combustion engine, such as a diesel particulate filter (DPF) (see, for example, Patent Document 1). Since the soot removed from the exhaust gas accumulates on the honeycomb structure, it is necessary to regenerate the filter by burning the soot at regular intervals. In order to burn the soot, it is only necessary to supply a large amount of combustion exhaust gas at a high temperature to ignite the soot and burn out the soot.

  Since the honeycomb structure may be damaged by the combustion heat of the soot during filter regeneration, the honeycomb structure is required to have high thermal shock resistance. Patent Document 1 describes a honeycomb structure having a structure in which a plurality of segment portions are joined at a connecting portion, and having improved thermal shock resistance by adjusting the strength of the connecting portion.

JP 2009-202143 A

  By the way, when the present inventors conducted experiments on the honeycomb structure, a plurality of radial cracks were generated on the gas downstream side end face of the honeycomb structure in the thermal shock resistance test, and these cracks expanded under more severe conditions. As a result, it was found that they were connected to each other and eventually formed an annular crack. For this reason, it is necessary to take measures to avoid deterioration of the filter performance due to the occurrence of radial cracks.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a honeycomb structure capable of suppressing a decrease in filter performance due to the occurrence of radial cracks and suppressing the expansion of radial cracks.

  In order to solve the above problems, the present invention is a columnar honeycomb structure extending along the central axis, the columnar honeycomb structure extending along the central axis, the central axis extending A first end surface and a second end surface facing each other in a direction, and a plurality of first flow paths extending along the central axis and a partition wall forming a plurality of second flow paths, The first end face side of the path is opened and the second end face side is sealed. The second flow path is sealed at the first end face side and opened at the second end face side. The opening ratio is larger than the opening ratio of the second end face, and the flow path formed by arranging the second flow paths adjacent to each other across the partition wall along the direction orthogonal to the central axis as seen from the extending direction of the central axis. Has a row.

  According to the honeycomb structure, since the flow path row is formed by the second flow path opened on the second end face side which is the gas downstream side, a thermal shock exceeding the allowable amount of the honeycomb structure is generated during filter regeneration. Even if added, it may be guided on the second end face side so that the partition between the second flow paths in the flow path row is broken instead of the seal or the partition at a place other than the flow path row, and a radial crack is generated. it can. In the honeycomb structure, since the first end face side of the flow path row is completely sealed, cracks may occur on the second end face side of the flow pass row and the second flow paths may communicate with each other. There will be no leakage. Therefore, according to the said honeycomb structure, the fall of the filter performance by radial crack generation can be suppressed. In addition, by allowing the generation of cracks in the flow path array, the stress applied by the subsequent thermal shock is dispersed, so that the expansion of radial cracks can be suppressed. Furthermore, according to this honeycomb structure, the occurrence of radial cracks can be induced by devising the sealing pattern of the flow path without separately providing a low-strength member as in the conventional honeycomb structure. The configuration can be simplified and the cost can be reduced.

The honeycomb structure may have a plurality of flow path rows that are located radially about the central axis.
According to this configuration, the stress for generating the radial crack due to the thermal shock can be effectively received by the plurality of flow path arrays, so that the generation of the radial crack can be more reliably induced.

The honeycomb structure may include a plurality of flow path rows that are adjacent to each other with a partition wall therebetween.
According to this configuration, since the plurality of flow path rows are formed in parallel, the strength of the second end face side of the flow path row can be further lowered than other locations, and the radial cracks can be more reliably generated. Generation can be induced.

The average cross-sectional area perpendicular to the central axis of the second flow path forming the flow path row may be larger than the average cross-sectional area perpendicular to the central axis of the second flow path not forming the flow path row.
According to this configuration, since the average cross-sectional area of the second flow path forming the flow path row is larger than the average cross-sectional area of the second flow path not forming the flow path row, the second end face side of the flow path row The strength of can be made lower than other parts, and the occurrence of radial cracks can be more reliably induced.

  ADVANTAGE OF THE INVENTION According to this invention, while suppressing the fall of the filter performance by generation | occurrence | production of a radial crack, the expansion of a radial crack can be suppressed.

1 is a perspective view showing a honeycomb structure according to a first embodiment. It is an enlarged view showing a part of a cross section perpendicular to the central axis of the honeycomb structure. (A) is an enlarged view showing a part of the first end face of the honeycomb structure. (B) is an enlarged view showing a part of the second end face of the honeycomb structure. It is an enlarged view showing a part of a cross section along the central axis of the honeycomb structure. It is a whole view which shows the 2nd end surface of a honeycomb structure. It is the elements on larger scale of FIG. FIG. 6 is an overall view showing a second end face of a honeycomb structure according to a second embodiment. It is the elements on larger scale of FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
As shown in FIG. 1, the honeycomb structure 10 according to the first embodiment is attached to a DPF [Diesel Particulate Filter] or the like, and is a cylindrical structure used as a filter for purifying exhaust gas from an internal combustion engine. Is the body. The columnar honeycomb structure 10 extends along the central axis CL. Hereinafter, the extending direction of the central axis CL is referred to as a central axis direction.

  The honeycomb structure 10 includes a first end face 10a and a second end face 10b that face each other in the central axis direction, and a plurality of first flow paths Ra and a plurality of second flow paths Rb that extend along the central axis CL. And have.

  The honeycomb structure 10 is made of a porous ceramic material (for example, an average pore diameter of 20 μm or less). Examples of the ceramic material used for the honeycomb structure 10 include alumina, silica, mullite, cordierite, glass, oxides such as aluminum titanate, silicon carbide, silicon nitride, and metal. The aluminum titanate can further contain magnesium and / or silicon.

  Such a honeycomb structure 10 can be obtained by firing the green molded body (unfired molded body) as the ceramic material described above and performing a predetermined sealing process on each of the flow paths Ra and Rb. A green molded object contains the inorganic compound source powder which is a ceramic raw material, organic binders, such as methylcellulose, and the additive added as needed.

  For example, in the case of a green molded body of aluminum titanate, the inorganic compound source powder includes an aluminum source powder such as α-alumina powder, and a titanium source powder such as anatase-type or rutile-type titania powder. Further, magnesium source powder such as magnesia powder and magnesia spinel powder, and / or silicon source powder such as silicon oxide powder and glass frit can be included.

  Examples of the organic binder include celluloses such as methylcellulose, carboxymethylcellulose, hydroxyalkylmethylcellulose, and sodium carboxymethylcellulose; alcohols such as polyvinyl alcohol; and lignin sulfonate.

  Examples of the additive include a pore-forming agent, a lubricant, a plasticizer, a dispersant, and a solvent.

  Examples of the pore-forming agent include carbon materials such as graphite; resins such as polyethylene, polypropylene and polymethyl methacrylate; plant materials such as starch, nut shells, walnut shells and corn; ice; and dry ice.

  Lubricants and plasticizers include alcohols such as glycerin; higher fatty acids such as caprylic acid, lauric acid, palmitic acid, arachidic acid, oleic acid and stearic acid; stearic acid metal salts such as Al stearate, polyoxyalkylene alkyl And ether (POAAE).

  Examples of the dispersant include inorganic acids such as nitric acid, hydrochloric acid and sulfuric acid; organic acids such as oxalic acid, citric acid, acetic acid, malic acid and lactic acid; alcohols such as methanol, ethanol and propanol; ammonium polycarboxylate Surfactant etc. are mentioned.

  Examples of the solvent include alcohols such as methanol, ethanol, butanol, and propanol; glycols such as propylene glycol, polypropylene glycol, and ethylene glycol; and water.

  FIG. 2 is an enlarged view showing a part of a cross section along the central axis CL of FIG. As shown in FIG. 2, either one of the first end face 10 a side and the second end face 10 b side is sealed in the flow paths Ra and Rb of the honeycomb structure 10.

  Specifically, the first channel Ra is a channel in which the first end surface 10 a side is opened and the second end surface 10 b side is sealed by the sealing material 11. In addition, the second flow path Rb is a flow path in which the second end face 10 b side is opened and the first end face 10 a side is sealed by the sealing material 12.

  As the material of the sealing materials 11 and 12, the same material as that of the green molded body described above may be used, or a different material may be used. Moreover, you may use the material which does not allow the exhaust gas of an internal combustion engine to pass through as the material of the sealing materials 11 and 12. FIG.

  The honeycomb structure 10 includes partition walls 10c that form a plurality of first flow paths Ra and a plurality of second flow paths Rb. In other words, the individual channels Ra and Rb are separated by the partition wall 10c. The partition wall 10c extends along the central axis CL from the first end surface 10a to the second end surface 10b.

  The honeycomb structure 10 shown in FIG. 2 is disposed on the exhaust gas flow path of the internal combustion engine with the first end face 10a as the gas upstream side (internal combustion engine side) and the second end face 10b as the gas downstream side. The main flow of exhaust gas passing through the honeycomb structure 10 is indicated by an arrow G.

  As indicated by the arrow G, the exhaust gas of the internal combustion engine first flows into the flow path Ra from the opening on the first end face 10a side. The gas that has flowed into the channel Ra passes through the partition wall 10c and flows into the channel Rb because the second end face 10b side of the channel Ra is sealed. When the gas passes through the partition wall 10c, soot or the like in the gas is captured. The gas that has flowed into the flow path Rb flows out of the honeycomb structure 10 through the opening on the second end face 10b side. As a result, the purified gas is discharged from the second end face 10 b side of the honeycomb structure 10.

  Next, the cross-sectional shapes of the first channel Ra and the second channel Rb will be described. FIG. 3 is an enlarged view showing a part of a cross section perpendicular to the central axis CL of the honeycomb structure 10. 4A is an enlarged view showing a part of the first end face 10a of the honeycomb structure 10, and FIG. 4B is an enlarged view showing a part of the second end face 10b.

  As shown in FIGS. 3 and 4, the honeycomb structure 10 has a lattice structure in which flow paths Ra and Rb are formed in hexagonal shapes by partition walls 10c. The shape of the honeycomb structure 10 is made by extrusion integral molding except for the sealing materials 11 and 12, and the flow paths Ra and Rb are not deformed in the middle and remain in a constant cross-sectional shape in the central axis direction. Extend to.

  As the cross-sectional shapes of the first flow path Ra and the second flow path Rb, regular hexagonal shapes and regular hexagonal shapes (for example, long sides having the same length as one side of the adjacent regular hexagonal flow channel cross sections, and A hexagonal shape having a short side shorter than the long side). That is, the honeycomb structure 10 includes an asymmetric cell structure (asymmetric lattice structure) having flow paths having different cross-sectional shapes.

  Specifically, the first channel Ra has a regular hexagonal cross-sectional shape. On the other hand, the second flow path Rb is divided into two flow paths Rb1 and Rb2 according to the cross-sectional shape. The second flow path Rb1 has a regular hexagonal cross-sectional shape, and the second flow path Rb2 has the same regular hexagonal cross-sectional shape as the first flow path Ra. However, the second flow path Rb2 is not shown in FIGS.

  In a cross section perpendicular to the central axis CL of the honeycomb structure 10, a regular hexagonal channel Ra (and a channel Rb1) having a cross-sectional shape is disposed so as to surround the regular hexagonal channel Rb2. . With such an arrangement, in the honeycomb structure 10, the first flow path Ra is formed in a larger number than the second flow path Rb. For this reason, the opening ratio in the first end face 10a (the ratio of the opening area of the first flow path Ra in the entire area of the first end face 10a) is the opening ratio in the second end face 10b (the entire second end face 10b). (The ratio of the opening area of the second flow path Rb in area). As described above, by increasing the opening ratio in the first end face 10a on the gas upstream side, it is possible to suppress the occurrence of exhaust gas pressure loss in the honeycomb structure 10.

  Next, the flow path row W included in the honeycomb structure 10 will be described. FIG. 5 is an overall view showing the second end face 10b, and FIG. 6 is a partially enlarged view of FIG. As shown in FIG. 5 and FIG. 6, the honeycomb structure 10 has a plurality of flow path rows W that are located radially about the central axis CL. The flow path row W extends along a direction orthogonal to the central axis CL. The plurality of flow path rows W are formed in six rows around the central axis CL at intervals of 60 °, and are positioned so as to be rotationally symmetric with respect to the central axis CL. In addition, the number, position, and shape of the flow path row W are not limited to those shown in FIG. 5, and may be extended in a direction orthogonal to the central axis CL.

  The flow path row W includes a second flow path Rb1 having a regular hexagonal cross section and a second flow path Rb2 having a regular hexagonal cross section. The flow path row W is formed by arranging the second flow paths Rb1 and Rb2 adjacent to each other across the partition wall 10c in a direction orthogonal to the central axis CL. With such a configuration, in the flow channel row W, the opening ratio is higher and the strength is lower than in the second end face 10b other than the flow channel row W (location shown in FIG. 4B). A part can be provided intentionally.

  As shown in FIG. 6, the flow channel row W according to the first embodiment can be divided into flow channel rows Wa, Wb, and Wc of one row (the width of the row is one flow channel). . In other words, the flow path row W is composed of the flow path rows Wa, Wb, and Wc that are adjacent and parallel to each other across the partition wall 10c. In this way, by further collecting and configuring the flow path rows Wa, Wb, Wc, the strength can be further reduced.

  According to the honeycomb structure 10 according to the first embodiment described above, the flow path row W is formed by the second flow path Rb opened on the second end face 10b side which is the gas downstream side. Even if a thermal shock exceeding the allowable amount of the honeycomb structure 10 is applied at the time of regeneration, the second end face side is not a seal or partition wall other than the flow path row W but the second flow path Rb of the flow path row W. It can be induced that the barrier ribs are broken first to generate radial cracks. In the honeycomb structure 10, since the first end surface 10a side of the flow channel row W is all sealed, radial cracks are generated on the second end surface 10b side of the flow channel row W, and the second flow channels Rb1, Even if Rb2 communicates, no leakage occurs. Therefore, according to the honeycomb structure 10, it is possible to suppress a decrease in filter performance due to the occurrence of radial cracks.

  Further, in the honeycomb structure 10, by allowing the generation of radial cracks in the flow path row W, the stress applied by the subsequent thermal shock can be dispersed, and as a result, the thermal shock resistance can be improved. it can. Furthermore, according to the honeycomb structure 10, the occurrence of radial cracks can be induced by devising the sealing pattern of the flow path without separately providing a low-strength member as in the conventional honeycomb structure. The configuration can be simplified and the cost can be reduced.

  In addition, the honeycomb structure 10 intentionally creates a low-strength region on the second end face 10b side by having a plurality of flow path rows Wa, Wb, and Wc that are adjacent and parallel to each other across the partition wall 10c. It is possible to induce the generation of radial cracks more reliably.

  Furthermore, since the honeycomb structure 10 has a plurality of flow path rows W that are located radially about the central axis CL, the stress that tends to generate radial cracks due to thermal shock is caused by the plurality of flow path rows. It can receive effectively and can generate | occur | produce the generation | occurrence | production of a radial crack more reliably.

  Further, in the honeycomb structure 10, since the asymmetric cell structure shown in FIG. 3 is adopted, the filter area per unit volume of the filter can be increased as compared with the symmetric cell structure, so that the pressure loss caused by the filter can be reduced. Reduction can be achieved, and fuel consumption of the internal combustion engine to which the honeycomb structure 10 is applied can be improved.

[Second Embodiment]
The honeycomb structure 20 according to the second embodiment has a first annular row W1, a second annular row W2, a radial flow passage row W3, and a second flow passage Rb3. This is different from the honeycomb structure 10 according to the first embodiment. In addition, the code | symbol corresponding to the part corresponding to 1st Embodiment is attached | subjected, and the overlapping description is abbreviate | omitted.

  FIG. 7 is an overall view showing the second end face 20b of the honeycomb structure 20 according to the second embodiment. As shown in FIG. 7, the honeycomb structure 20 according to the second embodiment has two annular rows W1 and W2. The annular rows W1 and W2 are formed so as to surround a regular hexagon with the central axis CL as the center. The first annular row W1 is formed inside the second annular row W2.

  FIG. 8 is a partially enlarged view of FIG. As shown in FIG. 8, the first annular row W1 and the second annular row W2 are formed by arranging the second flow paths Rb3 adjacent to each other across the partition wall 20c in an annular shape (regular hexagonal shape). The first annular row W1 and the second annular row W2 are configured by the second flow path Rb3 of the second flow paths Rb in which the second end face 20b is opened.

  The cross-sectional shape of the second flow path Rb3 is, for example, a shape formed by removing a partition wall between four regular hexagonal shapes described in the first embodiment and a regular hexagonal shape at the center thereof. Yes. The cross-sectional area of the second flow path Rb3 (area of the cross section perpendicular to the central axis CL) is larger than the cross-sectional area of the second flow path Rb1 (area of the cross section perpendicular to the central axis CL).

  Furthermore, the honeycomb structure 20 according to the second embodiment includes a plurality of flow path rows W3 that are radially disposed with a center perpendicular to the central axis CL. The flow path row W3 is formed by arranging the second flow paths Rb3 adjacent to each other across the partition wall 20c in a direction orthogonal to the central axis CL. The flow path row W3 is formed so as to extend from each vertex of the regular hexagon shape drawn by the second annular row W2 toward the outer periphery of the honeycomb structure 20. Similar to the first annular row W1 and the second annular row W2, these passage rows W3 are also composed of the second passage Rb3 having a large cross-sectional area.

  According to the honeycomb structure 20 according to the second embodiment described above, the generation of radial cracks can be induced in the flow path row W3 as in the honeycomb structure 10 according to the first embodiment. A reduction in filter performance due to the occurrence of radial cracks can be suppressed. In addition, by allowing the generation of radial cracks in the flow path row W3, the stress applied by the subsequent thermal shock can be dispersed, so that the expansion of the radial cracks can be suppressed.

  In addition, since the flow path row W3 includes the second flow path Rb3 having a large cross-sectional area, the average of the cross-sectional areas of the second flow paths Rb forming the flow path row W3 does not form the flow path row W3. It becomes larger than the average of the cross-sectional areas of the two flow paths Rb. As a result, since the opening ratio of the flow path row W3 is increased and the strength can be further reduced, the occurrence of radial cracks can be more reliably induced.

  Further, since the honeycomb structure 20 has the annular rows W1 and W2, a thermal shock exceeding the allowable amount of the honeycomb structure 20 is applied during filter regeneration, so that the honeycomb structure 20 is divided into the central axis CL side and the outer peripheral side. Even if a stress that generates an annular crack is applied, it can be induced so that the annular crack is generated on the second end face 20b side of the annular rows W1, W2. In the honeycomb structure 20, since the first end face 20a side of the annular rows W1, W2 is all sealed, soot leaks even if an annular crack occurs on the second end face 20b side of the annular rows W1, W2. It does not occur, and the deterioration of the filter performance due to the occurrence of the annular crack can be suppressed. In addition, by allowing the occurrence of the annular cracks in the annular rows W1 and W2, it is possible to disperse the stress applied by the subsequent thermal shock, and thus it is possible to suppress the expansion of the annular cracks.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said each embodiment. For example, the position, size, shape, and the like of the flow path rows W and W3 and the annular rows W1 and W2 are not limited to those described above. The central axis CL does not necessarily have to be positioned on the extension of the flow path rows W and W3, and the flow path rows W and W3 only need to extend along a direction orthogonal to the central axis CL. Further, the flow path rows W and W3 do not have to be linear, and may include a polygonal line shape or a wavy line shape. The positions, sizes, shapes, and the like of the flow path rows W and W3 and the annular rows W1 and W2 can be set in accordance with, for example, regions where cracks are likely to occur in various honeycomb structures.

  Further, the cross-sectional shapes of the first flow path Ra and the second flow path Rb are not limited to those described above. Moreover, the cross-sectional structure of the honeycomb structures 10 and 20 is not limited to the asymmetric cell structure, and may be a symmetric cell structure including flow paths having the same cross-sectional shape. Moreover, the honeycomb structures 10 and 20 do not necessarily have to be made by integral molding of extrusion, and may be made by a segment structure.

DESCRIPTION OF SYMBOLS 10, 20 ... Honeycomb structure 10a, 20a ... 1st end surface 10b, 20b ... 2nd end surface 10c, 20c ... Partition 11 ... Sealing material 12 ... Sealing material CL ... Center axis Ra ... 1st flow path Rb ... 2nd Flow path Rb1 ... 2nd flow path (regular hexagonal shape) Rb2 ... 2nd flow path (regular hexagonal shape) Rb3 ... 2nd flow path (cross-sectional enlarged) W, Wa-Wc ... Flow path row W1 ... 1st ring Row W2 ... Second annular row W3 ... Channel row

Claims (4)

A columnar honeycomb structure extending along the central axis,
A first end surface and a second end surface facing each other in the extending direction of the central axis;
Partition walls forming a plurality of first flow paths and a plurality of second flow paths extending along the central axis,
The first flow path is open on the first end face side and sealed on the second end face side,
The second flow path has the first end face side sealed, and the second end face side opened.
The opening ratio of the first end face is larger than the opening ratio of the second end face,
A honeycomb structure having a flow channel array formed by arranging the second flow channels adjacent to each other with the partition walls arranged along a direction orthogonal to the central axis.   The honeycomb structure according to claim 1, comprising a plurality of the flow path rows radially positioned around the central axis.   The honeycomb structure according to claim 1 or 2, comprising a plurality of the flow path rows that are adjacent to and parallel to each other with the partition walls therebetween. The average cross-sectional area perpendicular to the central axis of the second flow path forming the flow path row is larger than the average cross-sectional area perpendicular to the central axis of the second flow path not forming the flow path row. The honeycomb structure according to any one of claims 1 to 3.

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