JP5281967B2 - Honeycomb structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a honeycomb structure which, when used as a DPF, moderately suppresses a temperature rise in the vicinity of the outlet side in filter regeneration, also suppresses an excessive buildup of pressure drop, substantially avoids fracture within a jointing material, and ensures a high ring-off crack limit. <P>SOLUTION: The honeycomb structure 1 is obtained by integrating a plurality of segments 2 with a joining material containing inorganic particles, wherein the segments 2 comprise a porous base substrate of honeycomb shape and a modification part formed by impregnating a slurry containing particles which are smaller than the average pore diameter of the base substrate into part of the base substrate and performing heat treatment. The honeycomb structure satisfies the relationships of (1) X=log<SB>e</SB>(a&times;10<SP>-2</SP>&times;b<SP>2</SP>&times;c<SP>-2</SP>), (2) Y=1/log<SB>e</SB>(S/Ra) and (3) 0.038X+0.15&le;Y&le;0.050X+0.50, wherein S represents an average spacing between local peaks of an outer wall surface of the modification part; Ra represents arithmetic average surface roughness of the outer wall surface; (a) represents porosity of the outer wall; (b) represents the average pore diameter of the outer wall; and (c) represents the average particle diameter of the inorganic particles. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a honeycomb structure suitably used as a dust collection filter such as a diesel particulate filter.

  As a collection filter for exhaust gas, for example, a diesel particulate filter (DPF) for capturing and removing particulate matter (particulate matter (PM)) such as soot contained in exhaust gas from diesel engines, etc. Honeycomb structures are widely used.

  In order to use such a honeycomb structure (filter) continuously for a long period of time, it is necessary to periodically regenerate the filter. That is, in order to reduce the pressure loss increased by the PM accumulated with time in the filter and return the filter performance to the initial state, it is necessary to burn and remove the PM accumulated in the filter. When this filter is regenerated, the PM accumulated inside the filter burns in order from the fluid (exhaust gas) inlet side, so the temperature rises due to the heat generated in the front and the heat burned on the spot closer to the outlet side. Becomes intense. Therefore, the temperature rise of each part of the filter is likely to be non-uniform, and there is a problem that defects such as cracks are generated due to thermal stress.

  To solve such problems, the honeycomb structure is composed of a plurality of honeycomb-shaped segments (honeycomb segments), and each honeycomb segment is joined and integrated with a joining material made of an elastic material. A method of dispersing and relaxing the thermal stress acting on the body has been proposed (see, for example, Patent Document 1), so that the thermal shock resistance can be improved to some extent. Due to the increase, it has become difficult to obtain a sufficient effect only by this method. In addition, the average pore diameter is formed so as to decrease from the inlet side end surface toward the outlet side end surface, and PM is prevented from being biased and deposited in the vicinity of the outlet side, thereby suppressing the combustion heat bias during filter regeneration. A honeycomb structure is also known (see, for example, Patent Document 2). However, it is difficult to obtain a sufficient effect simply by reducing the average pore diameter in this way.

  Further, when a honeycomb structure is configured by bonding a plurality of honeycomb segments, the bonding strength between the honeycomb segments and the bonding material is important. Further, from the viewpoint of reducing the temperature difference between the honeycomb segments and suppressing the generation of thermal stress due to the temperature difference, heat transfer between the honeycomb segments and the bonding material is performed smoothly, that is, heat transfer. It is also desirable that it be good.

  The bonding strength between the honeycomb segment and the bonding material is considered to be manifested by an effect (anchor effect) caused by the inorganic particles contained in the bonding material biting into the irregularities on the outer wall surface of the honeycomb segment. 1, the surface roughness Rz of the outer wall of the honeycomb segment is defined by paying attention to such an anchor effect.

  Since the anchor effect becomes higher as the surface roughness is larger (rougher), the parameters in the height direction of the unevenness such as the surface roughness Rz in the conventional technique are as large as possible within a range that does not adversely affect the characteristics of the honeycomb segment. Generally set to a value.

  However, even if the surface roughness of the outer wall of the honeycomb segment is set to be large, the particle diameter of the inorganic particles contained in the bonding material is larger than a certain degree, or the interval between the local peaks on the outer wall of the honeycomb segment is too small. In this case, since the inorganic particles are less likely to enter the recesses on the surface of the outer wall of the honeycomb segment, a large void is generated at the interface between the outer wall surface of the honeycomb segment and the inorganic particle, and the contact area between the two is reduced. Heat transfer between the two may deteriorate. The surface roughness of the honeycomb segment outer wall and the interval between the local peaks are not limited to the particle size distribution of the raw material particles used in the manufacture of the honeycomb segment itself, the mixing ratio of the raw material components, and the outer wall of the honeycomb segment prior to the joining of the honeycomb segments. Although the desired value can be achieved independently by adjusting the particle size distribution of the base material to be applied and the blending ratio of the components, the number of independent adjustment factors is excessive, so the bonding strength and heat transfer On the other hand, craftsmanship know-how was required to produce a honeycomb structure with a good balance.

JP 2000-279729 A JP-A-1-145378

  The present invention has been made in view of such conventional circumstances, and the object of the present invention is to densify a predetermined portion of the honeycomb segment and to obtain the surface roughness (arithmetic average surface roughness) of the honeycomb segment outer wall. : Ra), the distance between the local peaks (average interval between the local peaks: S), the average particle size of the inorganic particles contained in the bonding material, and finding the optimal range of factors that affect the bonding strength and heat transfer, When used, the temperature rise near the outlet side at the time of filter regeneration is moderately suppressed, the excessive increase in pressure loss is also suppressed, and the bonding strength and heat transfer between the honeycomb segment and the bonding material are also good. An object of the present invention is to provide a honeycomb structure having excellent thermal shock resistance.

  In order to achieve the above object, according to the present invention, the following honeycomb structure is provided.

[1] An inlet-side end surface serving as a fluid inlet side, an outlet-side end surface serving as a fluid outlet side, an outer wall connecting the outer peripheral portions of the two end surfaces, and porous between the two end surfaces inside the outer wall A plurality of honeycomb-shaped segments defined by partition walls of the body and having a plurality of cells serving as fluid flow paths are integrated by bonding the outer walls with a bonding material containing inorganic particles. The segment is formed by impregnating a part of the base substrate with a slurry including a honeycomb-shaped porous base substrate and particles smaller than the average pore diameter of the base substrate. A modified portion formed by heat treatment, and the modified portion has a length that is 1/10 to 1/2 of the total length of the segment along the axial direction of the cell from the outlet side end surface of the segment. Range The arithmetic average surface roughness Ra of the outer wall surface of the base substrate excluding the site where the modified portion is formed is 0.4 to 20 μm, and the arithmetic average surface roughness of the outer wall surface of the modified portion is Ra is 0.01 to 7.5 μm larger than the arithmetic average surface roughness Ra of the outer wall surface of the base substrate excluding the site where the modified part is formed, and the average particle size of the inorganic particles is 0.5 to 30 μm. A certain honeycomb structure (first honeycomb structure).

[ 2 ] An inlet side end surface serving as a fluid inlet side, an outlet side end surface serving as a fluid outlet side, an outer wall connecting outer peripheral portions of the two end surfaces, and porous between the two end surfaces inside the outer wall A plurality of honeycomb-shaped segments defined by partition walls of the body and having a plurality of cells serving as fluid flow paths are integrated by bonding the outer walls with a bonding material containing inorganic particles. The outer peripheral segment located in the outer peripheral portion of the honeycomb structure is composed of only a honeycomb-shaped porous base substrate, and the central segment located inside the outer peripheral segment. Is a modified part formed by impregnating a part of the base substrate with a slurry containing the base substrate and particles smaller than the average pore diameter of the base substrate and then heat-treating the slurry. The modification part is formed in a range from the outlet side end surface of the central segment to the length of 1/10 to 1/2 of the total length of the central segment along the axial direction of the cell, A honeycomb structure having an arithmetic average surface roughness Ra of 0.4 to 20 μm on the outer wall surface of the base substrate excluding a portion where the modifier is formed, and an average particle diameter of the inorganic particles of 0.5 to 30 μm. (Second honeycomb structure).

[ 3 ] The arithmetic average surface roughness Ra of the outer wall surface of the modified portion is 0.01 to 7.5 μm larger than the arithmetic average surface roughness Ra of the outer wall surface of the base substrate excluding the formation site of the modified portion. The honeycomb structure according to [ 2 ].

[ 4 ] An inlet-side end surface that serves as a fluid inlet side, an outlet-side end surface that serves as a fluid outlet side, an outer wall that connects the outer peripheral portions of the two end surfaces, and a porous material between the two end surfaces inside the outer wall. A plurality of honeycomb-shaped segments defined by partition walls of the body and having a plurality of cells serving as fluid flow paths are integrated by bonding the outer walls with a bonding material containing inorganic particles. The segment is formed by impregnating a part of the base substrate with a slurry including a honeycomb-shaped porous base substrate and particles smaller than the average pore diameter of the base substrate. A modified portion formed by heat treatment, and the modified portion has a length that is 1/10 to 1/2 of the total length of the segment along the axial direction of the cell from the outlet side end surface of the segment. Example Are formed, the average spacing S between local peaks of the outer wall surface of the base substrate excluding the forming portion of the modified portions is 10～125Myuemu, mean spacing S of local peaks of the outer wall surface of the modified portion A honeycomb structure in which the average interval S between the local peaks on the outer wall surface of the base substrate excluding the site where the modified portion is formed is 0.1 to 70 μm larger, and the average particle size of the inorganic particles is 0.5 to 30 μm. (Third honeycomb structure).

[ 5 ] An inlet-side end surface serving as a fluid inlet side, an outlet-side end surface serving as a fluid outlet side, an outer wall connecting outer peripheral portions of the two end surfaces, and a porous material between the two end surfaces inside the outer wall. A plurality of honeycomb-shaped segments defined by partition walls of the body and having a plurality of cells serving as fluid flow paths are integrated by bonding the outer walls with a bonding material containing inorganic particles. The outer peripheral segment located in the outer peripheral portion of the honeycomb structure is composed of only a honeycomb-shaped porous base substrate, and the central segment located inside the outer peripheral segment. Is a modified part formed by impregnating a part of the base substrate with a slurry containing the base substrate and particles smaller than the average pore diameter of the base substrate and then heat-treating the slurry. The modification part is formed in a range from the outlet side end surface of the central segment to the length of 1/10 to 1/2 of the total length of the central segment along the axial direction of the cell, A honeycomb structure (first structure) in which the average interval S between the local peaks on the outer wall surface of the base substrate excluding the site where the modified portion is formed is 10 to 125 μm, and the average particle diameter of the inorganic particles is 0.5 to 30 μm. Four honeycomb structures).

[6] The average spacing S between local peaks of the outer wall surface of the modifying part, 0.1～70Myuemu greater than the average spacing S of local peaks of the outer wall surface of the base substrate excluding the forming portion of the modified portion [5 The honeycomb structure according to claim 1.

[ 7 ] The honeycomb structure according to [1] or [4] , wherein the length, porosity, and average pore diameter of the modified portion are the same in all the segments.

[ 8 ] Among the segments, any one or more of a length, a porosity, and an average pore diameter of the modified portion of the outer peripheral segment located at the outer peripheral portion of the honeycomb structure and the central segment located inside thereof The honeycomb structure according to [1] or [4] , in which are different.

[ 9 ] The ratio (S / Ra) of the average distance S between the local peaks of the outer wall surface of the base substrate excluding the formation site of the modification portion and the arithmetic average surface roughness Ra is 1 to 35, and the modification The honeycomb structure according to any one of [1] to [ 8 ], wherein the ratio (S / Ra) of the average interval S between the local peaks on the outer wall surface of the part and the arithmetic average surface roughness Ra is 4 to 40.

[ 10 ] When the shear strength obtained by the following method is P (unit: kPa) and the temperature difference between segments is T (unit: ° C), P and T have the relationship of the following formula (1). The honeycomb structure according to any one of [1] to [ 9 ], which is satisfied.
T <0.423P-169.2 (1)
[Shear strength]
Two adjacent segments are cut out from the honeycomb structure in a joined state, one segment is fixed, and a load is applied to the other segment from the major axis direction.
[Temperature difference between segments]
The honeycomb structure with soot deposited inside is installed on the engine bench, post-injection is performed with the engine speed maintained at 2000 rpm and the engine torque of 60 Nm, and the post-compression pressure loss before and after the honeycomb structure starts to decrease. The temperature history inside the honeycomb structure is measured when the injection is turned off and the engine state is switched to idle. The temperature measurement points are the end surfaces on the outlet side of the honeycomb structure at the end surface direction center portion of the outer peripheral segment located at the outer peripheral portion of the honeycomb structure and the end surface direction center portion of the center segment adjacent to the inner side of the outer peripheral segment. The soot accumulation amount is gradually increased so that the maximum temperature at the temperature measurement point in the central segment of these two temperature measurement points is 1200 ° C. The maximum temperature difference in the temperature history at each temperature measurement point until the temperature at the temperature measurement point in the central segment reaches 1200 ° C. is calculated.

[ 11 ] The honeycomb structure according to any one of [1] to [ 10 ], wherein the porosity of the modified portion is 2 to 20% lower than the porosity of the base substrate.

[ 12 ] The honeycomb structure according to any one of [1] to [ 11 ], wherein an average pore diameter of the modified portion is 0.1 to 10 μm smaller than an average pore diameter of the base substrate.

[ 13 ] The honeycomb structure according to any one of [1] to [ 12 ], wherein the base substrate has a porosity of 30 to 80 and an average pore diameter of 5 to 40 μm.

[ 14 ] A plugging portion that plugs a predetermined opening portion of the cell with the end surface on the inlet side and plugs the remaining opening portion of the cell with the end surface on the outlet side is provided [1] to [14]. [ 13 ] The honeycomb structure according to any one of [ 13 ].

[ 15 ] The honeycomb structure according to [ 14 ], wherein an opening ratio of the inlet side end face is larger than an opening ratio of the outlet side end face.

[ 16 ] The honeycomb structure according to any one of [1] to [ 15 ], wherein a catalyst component is supported on the partition walls.

  In the honeycomb structure of the present invention, by limiting the length of the modified portion, that is, the portion to be densified, the temperature increase near the outlet side at the time of filter regeneration when used in a DPF is moderately suppressed, An excessive increase in pressure loss is also suppressed, and the balance as a filter is excellent. Further, by limiting the arithmetic average surface roughness Ra of the outer wall surface of the base substrate and the average interval S of the local peaks to a predetermined range, and by limiting the average particle diameter of the inorganic particles contained in the bonding material, High thermal shock resistance when used in applications such as DPF, where good bonding strength with the bonding material is obtained, heat transfer between the two is smooth, and the temperature of each part tends to be uneven. Demonstrate.

It is a schematic sectional drawing which shows typically an example of the formation state of the modification part in the 1st and 3rd honeycomb structure concerning the present invention. It is a schematic sectional drawing which shows typically another example of the formation state of the modification part in the 1st and 3rd honeycomb structure which concerns on this invention. [Fig. 6] Fig. 6 is a schematic cross-sectional view schematically showing still another example of a modified portion formation state in the first and third honeycomb structures according to the present invention. It is a schematic sectional drawing which shows typically an example of the formation state of the modification part in the 2nd and 4th honeycomb structure concerning the present invention. It is a schematic perspective view which shows an example of the basic structure of the 1st-4th honeycomb structure which concerns on this invention. It is a schematic perspective view which shows an example of the honeycomb segment which comprises the 1st-4th honeycomb structure which concerns on this invention. FIG. 6 is a schematic perspective view showing another example of honeycomb segments constituting the first to fourth honeycomb structures according to the present invention. It is the elements on larger scale of the entrance side end surface which shows an example of embodiment of the honeycomb structure from which an aperture ratio differs in an entrance side end surface and an exit side end surface. It is the elements on larger scale of the exit side end surface which shows an example of embodiment of the honeycomb structure from which an aperture ratio differs in an entrance side end surface and an exit side end surface. FIG. 5 is an explanatory diagram schematically showing the influence of the surface roughness of the outer wall surface of the honeycomb segment and the interval between the local peaks on the bonding state between the outer wall of the honeycomb segment and the inorganic particles contained in the bonding material. FIG. 5 is an explanatory diagram schematically showing the influence of the surface roughness of the outer wall surface of the honeycomb segment and the interval between the local peaks on the bonding state between the outer wall of the honeycomb segment and the inorganic particles contained in the bonding material. FIG. 5 is an explanatory diagram schematically showing the influence of the surface roughness of the outer wall surface of the honeycomb segment and the interval between the local peaks on the bonding state between the outer wall of the honeycomb segment and the inorganic particles contained in the bonding material. FIG. 5 is an explanatory diagram schematically showing the influence of the surface roughness of the outer wall surface of the honeycomb segment and the interval between the local peaks on the bonding state between the outer wall of the honeycomb segment and the inorganic particles contained in the bonding material. It is explanatory drawing which shows the position of the temperature measurement point at the time of measuring the temperature difference between segments. It is explanatory drawing which shows the position of the temperature measurement point at the time of measuring the temperature difference between segments.

  Hereinafter, the present invention will be described based on specific embodiments, but the present invention should not be construed as being limited thereto, and based on the knowledge of those skilled in the art without departing from the scope of the present invention. Various changes, modifications, and improvements can be added.

  The first to fourth honeycomb structures of the present invention are formed by integrating a plurality of honeycomb-shaped segments (honeycomb segments) with a bonding material. FIG. 5 is a schematic perspective view showing an example of the basic structure of the first to fourth honeycomb structures according to the present invention, and FIG. 6 is a honeycomb segment constituting the first to fourth honeycomb structures according to the present invention. It is a schematic perspective view which shows an example.

  As shown in FIG. 6, the honeycomb segment 2 has an inlet side end face 10 which is a fluid inlet side and an outlet side end face 11 which is a fluid outlet side. The outer peripheral portions of the two end faces are connected by an outer wall 8, and a plurality of cells (through holes) 5 serving as a fluid flow path are defined by a porous partition wall 3 inside the outer wall 8. In addition, when used as a filter such as a DPF, a plugging portion that plugs the opening of a predetermined cell at the inlet side end face and plugs the remaining cell opening at the outlet side end face is provided. Generally, as shown in FIG. 7, one end face is plugged by a plugging portion 9 so as to exhibit a checkered pattern, and the other end face is plugged by a plugging portion. And plugged so as to show a complementary checkerboard pattern. That is, the plugged portions are formed so that the openings of adjacent cells are plugged at the end surfaces opposite to each other.

  When a fluid containing PM such as soot is vented from one end face (inlet side end face) of the honeycomb structure constituted of the honeycomb segments thus plugged, the fluid is opened at the one end face side. Flows into the inside of the honeycomb structure from the cells that are not plugged, passes through the porous partition wall having filtration ability, and enters the other flow hole in which the other end surface (end surface side surface) is not plugged. . And when passing through this partition, PM in the fluid is captured by the partition, and the purified fluid from which PM has been removed is discharged from the other end surface.

  As shown in FIG. 5, the first to fourth honeycomb structures of the present invention are formed by integrating a plurality of honeycomb segments 2 by joining their outer walls together. A bonding material is used for bonding the honeycomb segments 2. This bonding material contains inorganic particles, and preferably contains inorganic fibers and colloidal oxides as other components. When joining the honeycomb segments, in addition to these components, an organic binder such as methyl cellulose and carboxymethyl cellulose, a dispersant, water, etc. are added as necessary, and then mixed and kneaded using a kneader such as a mixer. What was made into the paste-form can use it conveniently.

  As the constituent material of the inorganic particles contained in the bonding material, for example, ceramics selected from the group consisting of silicon carbide, silicon nitride, cordierite, alumina, mullite, zirconia, zirconium phosphate, aluminum titanate, titania and combinations thereof, Fe A —Cr—Al-based metal, nickel-based metal, silicon-silicon carbide based composite material, or the like can be preferably used.

  As the inorganic fibers, ceramic fibers such as aluminosilicate and silicon carbide, metal fibers such as copper and iron, and the like can be suitably used. As the colloidal oxide, silica sol, alumina sol and the like are preferable. The colloidal oxide is suitable for imparting an appropriate adhesive force to the bonding material, and is bonded to inorganic fibers and inorganic particles by drying and dehydrating, so that the bonding material after drying has heat resistance and the like. It can be excellent and strong.

  By applying such a bonding material to the outer wall surface to be bonded surfaces of the honeycomb segments at a predetermined thickness and combining the plurality of honeycomb segments, the bonding material is dried and cured, whereby the plurality of honeycomb segments are formed. An integrated honeycomb structure is obtained. Thereafter, if necessary, the outer peripheral portion may be ground into a desired shape such as a columnar shape. In this case, since the outer wall is removed by processing and the inner partition walls and cells are exposed, it is preferable to re-form the outer wall by covering the exposed surface with a coating material.

  The honeycomb segments used in the first and third honeycomb structures of the present invention are all made of a honeycomb-shaped porous base substrate and a slurry containing particles smaller than the average pore diameter of the base substrate. A part of the material has a modified part (densified part) formed by heat treatment after impregnation. Further, regarding the honeycomb segments used in the second and fourth honeycomb structures of the present invention, the outer peripheral segment located at the outer peripheral portion of the honeycomb structure is composed of only the base substrate, and the rest Segment, i.e., the central segment located inside the outer peripheral segment, is the base substrate and the modified portion formed on a part of the base substrate, similarly to the honeycomb segment used in the first and third honeycomb structures. And have.

  When the honeycomb structure of the present invention is used for a DPF, the modifying portion increases the heat capacity and thermal conductivity near the end face on the outlet side, which is likely to be excessively heated during filter regeneration, and moderately suppresses the temperature increase. Although it is formed for the purpose of improving impact properties, the formation range of the first to fourth honeycomb structures of the present invention is limited so that the pressure loss does not increase excessively due to the formation of the modified portion. doing. A specific formation range of the modified portion is a range from the outlet side end face of the honeycomb segment to a length of 1/10 to 1/2 of the total length of the honeycomb segment along the cell axial direction. If the formation range of the modified portion is less than 1/10 of the total length of the honeycomb segment, it is difficult to secure a heat capacity and a heat conductivity that can effectively suppress an excessive temperature rise near the end face on the outlet side during filter regeneration. If the honeycomb segment exceeds 1/2 of the total length of the honeycomb segment, the pressure loss is increased in a relatively short time by the modified portion, so that the use is limited to a filter for a low displacement vehicle type and the versatility is lowered. .

  By limiting the formation range of the modified portion as described above, a temperature rise near the outlet side during filter regeneration can be moderately suppressed, and an excessive increase in pressure loss can be suppressed, and the honeycomb has an excellent balance as a filter. It becomes a structure. Further, in the second and fourth honeycomb structures of the present invention, by further limiting the honeycomb segment forming the modified portion to only the central segment, it is possible to more easily suppress an increase in pressure loss due to the formation of the modified portion. ing.

  In the first and second honeycomb structures of the present invention, the arithmetic average surface roughness Ra of the outer wall surface of the base substrate excluding the site where the modified portion is formed is 0.4 to 20 μm, preferably 1 to 15 μm. . In the present invention, the “average surface roughness Ra” is a value defined in JIS B0601-1994, and is extracted from the roughness curve by a reference length in the direction of the average line, and the average of the extracted portions. The absolute values of deviations from the line to the measurement curve are totaled and the average value is shown.

  10 to 13 show the influence of the surface roughness of the outer wall surface of the honeycomb segment and the interval between the local peaks on the bonding state between the outer wall of the honeycomb segment and the inorganic particles contained in the bonding material. 10 and 11, when the distance between the local peaks on the surface of the outer wall 8 and the particle size of the inorganic particles 15 included in the bonding material are approximately the same, the surface roughness of the outer wall 8 surface is large (rough). ) Is more difficult for the inorganic particles 15 to enter the valleys (recesses) on the surface of the outer wall 8 of the honeycomb segment, and a phenomenon (so-called bridge) in which a void surrounded by the surface of the outer wall 8 and the inorganic particles 15 is likely to occur. It is thought that the contact area with the material decreases. On the other hand, the anchor effect decreases as the surface roughness of the outer wall 8 surface decreases.

  In the first and second honeycomb structures of the present invention, the surface roughness, which is a parameter in the height direction of the unevenness of the honeycomb segment outer wall surface, affects the contact area and anchor effect between the honeycomb segment and the bonding material. Focusing on the influence, the honeycomb segment from the viewpoint of securing the anchor effect necessary to obtain good bonding strength and also ensuring the contact area that can smoothly transfer heat between the honeycomb segment and the bonding material The arithmetic average surface roughness Ra of the outer wall surface of the base substrate is optimized.

  By setting the arithmetic average surface roughness Ra of the outer wall surface of the base substrate excluding the formation site of the modified portion as described above, and by setting the average particle diameter of the inorganic particles contained in the bonding material to a predetermined range, A sufficient anchoring effect can be secured, a good bonding strength between the honeycomb segment and the bonding material can be obtained, and a large contact area between the honeycomb segment outer wall surface and the inorganic particles can be maintained. The transfer of heat between the two becomes smooth.

  If this arithmetic average surface roughness Ra is less than 0.4 μm, the anchor effect is reduced and it becomes difficult to ensure the required bonding strength. If it exceeds 20 μm, the contact area between the honeycomb segment and the bonding material is reduced, and the heat between them is reduced. May not be smoothly transferred, or the inorganic particles may not enter the valleys (recesses) on the surface of the outer wall of the honeycomb segment, and cracks may occur at the interface between the honeycomb segment and the bonding material when the bonding material is dried.

  Furthermore, in the first and second honeycomb structures of the present invention, from the viewpoint of further improving the balance between the bonding strength between the honeycomb segment and the bonding material and the transfer of heat, the third and third of the present invention. Similarly to the fourth honeycomb structure, the average interval S between the local peaks on the outer wall surface of the base substrate excluding the site where the modified portion is formed is preferably 10 to 125 μm, and more preferably 15 to 100 μm.

  In the first and second honeycomb structures of the present invention, the arithmetic average surface roughness Ra of the outer wall surface of the modified portion is set to the arithmetic average surface roughness of the outer wall surface of the base substrate excluding the portion where the modified portion is formed. The thickness Ra is preferably 0.01 to 7.5 μm larger, more preferably 0.05 to 5 μm larger. By setting the arithmetic average surface roughness Ra of the outer wall surface of the modified portion in such a range, at the boundary between the portion where the modified portion of the base substrate is not formed and the modified portion, between the outer wall surface and the bonding material. Thus, good bonding strength can be obtained, and the segment and the bonding material are hardly separated at the boundary between the modified portion of the base substrate and the modified portion.

  In the third and fourth honeycomb structures of the present invention, the average interval S between the local peaks on the outer wall surface of the base substrate excluding the site where the modified portion is formed is 10 to 125 μm, preferably 15 to 100 μm. In the present invention, the “average distance S between local peaks” is a value defined in JIS B0601-1994, and is extracted from the roughness curve by the reference length in the direction of the average line. The length of the average line corresponding to the interval between adjacent local peaks (interval between local peaks) is obtained, and the arithmetic average value of the intervals between the numerous local peaks is shown.

  10 and 12, when the surface roughness of the surface of the outer wall 8 of the honeycomb segment and the particle diameter of the inorganic particles 15 included in the bonding material are approximately the same, the wider the interval between the local peaks, the inorganic particles 15 Is likely to enter the valleys (recesses) on the surface of the honeycomb segment outer wall 8, and so-called bridges are less likely to occur, which increases the contact area between the honeycomb segment and the bonding material. On the other hand, as the distance between the local peaks increases, the number of irregularities at the same length on the outer wall surface decreases, so the anchor effect is reduced.

  In the third and fourth honeycomb structures of the present invention, the distance between the local peaks, which is the lateral parameter of the unevenness on the surface of the honeycomb segment outer wall, affects the contact area and anchor effect between the honeycomb segment and the bonding material. Focusing on the influence, the honeycomb segment from the viewpoint of securing the anchor effect necessary to obtain good bonding strength and also ensuring the contact area that can smoothly transfer heat between the honeycomb segment and the bonding material The average interval S of the outer wall surface of the base substrate is optimized.

  By setting the average interval S of the local peaks on the outer wall surface of the base substrate excluding the formation site of the modified portion as described above, and by setting the average particle size of the inorganic particles contained in the bonding material to a predetermined range, A sufficient anchoring effect can be secured, a good bonding strength between the honeycomb segment and the bonding material can be obtained, and a large contact area between the honeycomb segment outer wall surface and the inorganic particles can be maintained. The transfer of heat between the two becomes smooth.

  If the average distance S between the local peaks is less than 10 μm, the contact area between the honeycomb segment and the bonding material decreases, and heat transfer between them cannot be performed smoothly. On the other hand, if the average distance S between the local peaks exceeds 125 μm, a sufficient anchor effect cannot be obtained, and the necessary bonding strength cannot be ensured.

  Further, in the third and fourth honeycomb structures of the present invention, from the viewpoint of improving the balance between the bonding strength between the honeycomb segment and the bonding material and the transfer of heat, the first and the second of the present invention. Similar to the second honeycomb structure, the arithmetic average surface roughness Ra of the outer wall surface of the base substrate excluding the site where the modified portion is formed is preferably 0.4 to 20 μm, more preferably 1 to 15 μm. preferable.

  Further, in the third and fourth honeycomb structures of the present invention, the average interval S of the local peaks on the outer wall surface of the modified part is set to the local peak of the outer wall surface of the base substrate excluding the site where the modified part is formed. The average distance S is preferably increased by 0.1 to 70 μm, more preferably 1 to 50 μm. By setting the average interval S of the local peaks on the outer wall surface of the modified portion in such a range, the boundary between the outer wall surface and the bonding material at the boundary between the portion where the modified portion of the base substrate is not formed and the modified portion. Thus, good bonding strength can be obtained, and the segment and the bonding material are hardly separated at the boundary between the modified portion of the base substrate and the modified portion.

  In addition, in the first to fourth honeycomb structures of the present invention, from the viewpoint of improving the balance between the bonding strength between the honeycomb segment and the bonding material and the transfer of heat, the portion where the modifier is formed is excluded. The ratio (S / Ra) of the average distance S between the local peaks on the outer wall surface of the base substrate to the arithmetic average surface roughness Ra is preferably 1 to 35, and more preferably 3 to 25. In addition, the ratio (S / Ra) of the average distance S between the local peaks on the outer wall surface of the modified portion to the arithmetic average surface roughness Ra is preferably 4 to 40, and more preferably 7 to 30.

  Out of the honeycomb segments, the outlet side where the modified part is formed is a part that tends to increase in temperature when the DPF is regenerated, so the heat transfer between the honeycomb segment and the bonding material is smoother than the bonding strength. As preferred. On the other hand, since the site on the inlet side excluding the site where the modified part is formed is less exposed to high temperatures than the modified part, the strength of the bonding with the bonding material is given priority over the smoothness of heat transfer. The By setting the S / Ra of the modified part and the S / Ra of the base substrate excluding the part where the modified part is formed to be within the above-described suitable ranges, the characteristics preferential in each part are easily exhibited, By sharing the roles of these parts, it becomes easy to simultaneously achieve good bonding strength and smooth heat transfer between the honeycomb segment and the bonding material.

  Further, as can be seen from a comparison between FIG. 12 and FIG. 13, even when the interval between the local peaks on the surface of the outer wall 8 of the honeycomb segment is large, if the surface roughness increases to some extent, so-called bridging is likely to occur. Therefore, as described above, defining the average distance S between the local peaks on the outer wall surface in relation to the arithmetic average surface roughness Ra is effective for obtaining a better bonding state.

  The average distance S between the local peaks of the outer wall surface and the arithmetic average surface roughness Ra control the particle size distribution of the particles in the slurry used to form the base material and the modified part, the firing conditions, etc. Can be adjusted to be within a predetermined range. Further, the average distance S between the local peaks on the outer wall surface and the arithmetic average surface roughness Ra can be changed by applying a base material containing particles such as ceramic particles to the outer wall once the honeycomb segment is manufactured. By adjusting the particle size distribution of the particles in the base material, it is possible to adjust the average distance S between the local peaks and the arithmetic average surface roughness Ra to be within a predetermined range.

  Furthermore, in the first to fourth honeycomb structures of the present invention, from the viewpoint of improving the balance between the bonding strength between the honeycomb segment and the bonding material and the transfer of heat, the inorganic particles contained in the bonding material The average particle diameter is 0.5-30 μm, preferably 1.0-15 μm. In the present invention, the “average particle size” is a value of 50% particle size measured using LA-920 (trade name) manufactured by HORIBA, Ltd. as a measuring device in accordance with JIS R1629. Shall mean.

  If the average particle size of the inorganic particles contained in the bonding material is less than 0.5 μm, the inorganic particles may penetrate into the inside of the honeycomb segment, thereby changing the material ratio of the bonding material and reducing the bonding strength. If it exceeds 30 μm, inorganic particles cannot easily enter the recesses on the surface of the outer wall of the honeycomb segment and a sufficient anchor effect cannot be obtained, or the contact area between the surface of the outer wall of the honeycomb segment and the inorganic particles decreases, May interfere with the exchange of heat between the two. Setting the average particle diameter of the inorganic particles contained in the bonding material within the above range makes it easy to ensure the necessary bonding strength between the honeycomb segment and the bonding material, and the transfer of heat between them. It is effective both in terms of smoothness. When the average particle diameter of the inorganic particles is within the above range, the behavior of the inorganic particles with respect to the outer wall surface of the honeycomb segment when the honeycomb segments are bonded with the bonding material is substantially the same.

In the first to fourth honeycomb structures of the present invention, when the shear strength obtained by the following method is P (unit: kPa) and the temperature difference between segments is T (unit: ° C.) , P and T preferably satisfy the relationship of the following formula (1).
T <0.423P-169.2 (1)
[Shear strength]
Two adjacent segments are cut out from the honeycomb structure in a joined state, one segment is fixed, and a load is applied to the other segment from the major axis direction.
[Temperature difference between segments]
The honeycomb structure with soot deposited inside is installed on the engine bench, post-injection is performed with the engine speed maintained at 2000 rpm and the engine torque of 60 Nm, and the post-compression pressure loss before and after the honeycomb structure starts to decrease. The temperature history inside the honeycomb structure is measured when the injection is turned off and the engine state is switched to idle. The temperature measurement points are the end surfaces on the outlet side of the honeycomb structure at the end surface direction center portion of the outer peripheral segment located at the outer peripheral portion of the honeycomb structure and the end surface direction center portion of the center segment adjacent to the inner side of the outer peripheral segment. The soot accumulation amount is gradually increased so that the maximum temperature at the temperature measurement point in the central segment of these two temperature measurement points is 1200 ° C. The maximum temperature difference in the temperature history at each temperature measurement point until the temperature at the temperature measurement point in the central segment reaches 1200 ° C. is calculated.

  The following mechanism exists macroscopically between the shear strength and the temperature difference between segments determined as described above. That is, when a honeycomb structure is used for a DPF, between adjacent segments generated from a difference in combustion temperature between segments when burning soot (carbon) deposited non-uniformly therein to regenerate the filter function Focusing on the difference in thermal expansion, if the temperature difference between the segments is small, the internal shear stress due to the generated thermal expansion difference is also small. Even if the shear strength is low to some extent, the shape can be maintained without breaking. In addition, since the temperature difference between the honeycomb segments is large, the difference in thermal expansion between the segments is large, so that even if the internal shear stress increases, if the shear strength between the segments is sufficiently large, this will not cause destruction. Can hold.

  Based on such a mechanism, as a result of investigation by the present inventor, if the shear strength P measured as described above and the temperature difference T between the segments satisfy the relationship of the above equation (1), the filter It was found that the joined portion hardly breaks during reproduction and exhibits good thermal shock resistance.

  The porosity of the base substrate in the first to fourth honeycomb structures of the present invention is preferably 30 to 80%, and more preferably 45 to 80%. When the porosity of the base substrate is less than 30%, when the honeycomb structure of the present invention is used for a filter such as DPF, the pressure loss is too large, and when it exceeds 80%, the maximum temperature at the time of filter regeneration increases too much. There may be problems above. The average pore diameter of the base substrate is preferably 5 to 40 μm, and more preferably 5 to 20 μm. If the average pore diameter of the base substrate is less than 5 μm, the pressure loss is too large when the honeycomb structure of the present invention is used for a filter such as DPF, and if it exceeds 40 μm, the filter function for collecting PM is too low. There may be practical problems.

  In the first to fourth honeycomb structures of the present invention, the porosity of the modified portion is 2 to 20% lower than the porosity of the base substrate (a value obtained by subtracting 2 to 20% from the porosity of the base substrate) It is preferable that the porosity is 3 to 12% lower. If the amount of decrease in the porosity of the modified portion relative to the porosity of the base substrate is less than 2%, the effect due to the formation of the modified portion, that is, the effect of suppressing excessive temperature rise near the end face on the outlet side during filter regeneration is sufficiently obtained In some cases, the pressure loss may become too large when the content exceeds 20%. In addition, the average pore diameter of the modified portion is preferably an average pore diameter that is 0.1 to 10 μm smaller than the average pore diameter of the base substrate, and more preferably an average pore diameter that is 0.1 to 5 μm smaller. If the amount of reduction of the average pore diameter of the modified portion relative to the average pore size of the base substrate is less than 0.1 μm, the effect due to the formation of the modified portion may not be sufficiently obtained. It may be too much.

  The “porosity” defined in the present invention is a value measured by the Archimedes method by cutting a plate having a partition wall thickness as a test piece from a portion where the modified portion of the base substrate is not formed or a portion where the modified portion is formed. Yes, the “average pore diameter” is a value obtained by cutting a test piece of a predetermined shape (□ 5 × 15 mm) from a part where the modified part of the base substrate is not formed or a part where the modified part is formed, and measuring with a mercury porosimeter. is there.

  In the first and third honeycomb structures of the present invention, the length, porosity, and average pore diameter of the modified portion may be the same in all the honeycomb segments constituting the honeycomb structure, and the above-mentioned limited range If it is within, the porosity, average pore diameter and length of the modified part in the outer segment located in the outer peripheral part of the honeycomb structure and the central segment located inside the segment constituting the honeycomb structure Any one or more of these may be different.

  FIG. 1 is a schematic cross-sectional view schematically showing an example of the formation state of the modified portion in the first and third honeycomb structures according to the present invention. In this embodiment, the length of the modified portion 7a of the outer peripheral segment 2a located at the outer peripheral portion of the honeycomb structure 1 is the same as the length of the modified portion 7b of the central segment 2b located inside the outer peripheral segment 2a. The porosity and the average pore diameter of the parts 7a and 7b are also the same. Usually, the effect of the present invention can be sufficiently exhibited in such an embodiment.

  FIG. 2 is a schematic cross-sectional view schematically showing another example of the modified portion formation state in the first and third honeycomb structures according to the present invention. In this embodiment, the length of the modified portion 7a of the outer peripheral segment 2a located at the outer peripheral portion of the honeycomb structure 1 is the same as the length of the modified portion 7b of the central segment 2b located inside the outer peripheral segment 2a. The modified portion 7b of the segment 2b is configured such that the porosity and the average pore diameter are lower (smaller) than the modified portion 7a of the outer peripheral segment 2a. During regeneration of the filter, the temperature near the end face on the outlet side tends to rise, and even in the vicinity of the end face on the outlet side, heat tends not to escape to the outside especially in the central part of the radial direction, and the temperature tends to rise more than the outer peripheral part. Thus, it is preferable that the modification portion 7b of the central segment 2b is further densified to increase the heat capacity and the thermal conductivity, thereby alleviating the generation of thermal stress due to uneven temperature distribution.

  FIG. 3 is a schematic cross-sectional view schematically showing still another example of the formation state of the modified portion in the first and third honeycomb structures according to the present invention. In this embodiment, the porosity and average pore diameter of the modified portion 7a of the outer peripheral segment 2a located on the outer peripheral portion of the honeycomb structure 1 and the modified portion 7b of the central segment 2b located on the inner side of the outer peripheral segment 2a are the same. However, the length of the modified portion 7b of the central segment 2b is longer than that of the modified portion 7a of the outer peripheral segment 2a. As described above, even in the vicinity of the end face on the outlet side, in particular, the central portion of the cross section in the radial direction is less likely to allow heat to escape to the outside, and the temperature tends to rise more easily than the outer peripheral portion. Thus, it is preferable to increase the heat capacity and thermal conductivity, and to reduce the generation of thermal stress due to nonuniform temperature distribution.

  FIG. 4 is a schematic cross-sectional view schematically showing an example of the formation state of the modified portion in the second and fourth honeycomb structures according to the present invention. In this embodiment, the modified portion is not formed on the outer peripheral segment 2a positioned on the outer peripheral portion of the honeycomb structure 1, and the modified portion 7b is formed only on the central segment 2b positioned on the inner side of the outer peripheral segment 2a. It is said. As described above, even in the vicinity of the outlet side end face, in particular, the central portion in the radial direction has a tendency that heat does not easily escape to the outside and the temperature tends to rise more than the outer peripheral portion. Thus, it is also a preferred form to increase the heat capacity and thermal conductivity and to reduce the generation of thermal stress due to non-uniform temperature distribution.

  In the first to fourth honeycomb structures of the present invention, the number of outer peripheral segments is not particularly limited as long as it is the number required to form the outer peripheral portion of the honeycomb structure. The number of central segments is not particularly limited as long as it exists inside.

  The constituent material of the base material of the honeycomb segment in the first to fourth honeycomb structures of the present invention is formed from silicon carbide, silicon carbide as an aggregate, and silicon as a binder from the viewpoint of strength, heat resistance and the like. Selected from the group consisting of silicon-silicon carbide based composite material, silicon nitride, cordierite, mullite, alumina, spinel, silicon carbide-cordierite based composite material, lithium aluminum silicate, aluminum titanate, Fe-Cr-Al based metal At least one kind of material can be mentioned as a suitable material. Further, as shown in FIG. 7, when plugging portions are formed in the opening portions of the cells, the constituent materials of the plugging portions are made of the same material as the honeycomb segments in order to reduce the difference in thermal expansion from the honeycomb segments. It is preferable to use it.

  A conventionally well-known method can be used for the manufacturing method of a base substrate. As an example of a specific method, a binder such as methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol, a pore former, a surfactant, and water as a solvent are added to the above-described materials. Then, a plastic clay is formed, and the clay is extruded so as to have a predetermined honeycomb shape, and then dried by microwaves, hot air or the like, and then fired. When the plugged portion is formed in the cell, the firing may be performed before the plugged portion is formed in the cell, or the plugged portion is fired after the plugged portion is formed in the cell. May be performed together with.

  A conventionally known method can also be used as a method for plugging the cells. As an example of a specific method, after a sheet is attached to the end face of the honeycomb segment, a hole is made at a position corresponding to a cell to be plugged of the sheet, and the sheet is left attached. In the plugging slurry obtained by slurrying the constituent material of the plugging portion, the end face of the honeycomb segment is immersed in the opening end portion of the cell to be plugged through the hole formed in the sheet. Fill the slurry and dry and / or bake it to cure.

  The porosity and average pore diameter of the base substrate can be adjusted by the particle size of the material, the particle size and addition amount of the pore former, the firing conditions, and the like.

  The honeycomb structure used in the DPF is alternately plugged so that all cells have the same shape (usually a quadrangle) and the same opening area, and they have a checkered pattern at the inlet side end face and the outlet side end face. In general, the opening ratio of the inlet side end face and the outlet side end face is the same, but recently, the opening ratio of the inlet side end face is set to the outlet side for the purpose of suppressing increase in pressure loss after soot collection. A honeycomb structure having a larger opening ratio than the end face has also been proposed, and such a structure can also be applied to the honeycomb structure of the present invention.

  8 and 9 show an example of an embodiment of a plugged honeycomb structure in which the opening ratio is different between the inlet side end face and the outlet side end face, FIG. 8 is a partially enlarged view of the inlet side end face, and FIG. It is the elements on larger scale of an exit side end surface. As shown in these drawings, in this embodiment, quadrangular cells 5a and octagonal cells 5b having a larger opening area are alternately arranged in two orthogonal directions on each end face. 5a is plugged by the plugging portion 9 at the inlet end surface, and the octagonal cell 5b is plugged by the plugging portion 9 at the outlet side end surface. . Thus, by opening the octagonal cell 5b having a large opening area on the inlet side end face and opening the quadrangular cell 5a having a small opening area on the outlet side end face, the opening ratio of the inlet side end face is more than the opening ratio of the outlet side end face. Can also be increased.

  The modification part is formed by, for example, preparing a modification slurry containing particles smaller than the average pore diameter of the base substrate, and from this one end surface side of the base substrate to a predetermined length to form the modification part. It can be carried out by a method of dipping and impregnating the slurry, that is, filling the particles in the slurry into the pores of the partition walls of the base substrate, followed by heat treatment.

  The modifying slurry is a component that finally remains in the partition wall, and may be included in the slurry that changes chemically or physically unless it is removed. In the modifying slurry, as particles for densification, ceramics selected from the group consisting of silicon carbide, silicon nitride, cordierite, alumina, mullite, zirconia, zirconium phosphate, aluminum titanate, titania, and combinations thereof, Fe It is preferable to include inorganic powders such as —Cr—Al-based metal, nickel-based metal, or metal Si and SiC. Furthermore, particles contained in the washcoat when the catalyst component is supported on the honeycomb structure, such as γ-alumina, ceria, zirconia, ceria-based composite oxide, zirconia-based composite oxide, and the like can also be used.

  The particle diameter of the particles is preferably 2 to 60% of the average pore diameter of the base substrate. If the average particle size of the particles is less than 2% of the average pore size of the base substrate, the particles to be filled in the pores of the partition walls are too small with respect to the pore size, so that the pores are sufficiently filled. There is a risk that it cannot be done. That is, it cannot be held in the pores and may pass through, which is not preferable. On the other hand, if it exceeds 60% of the average pore diameter of the base substrate, the particles to be filled in the pores of the partition walls are too large with respect to the pore diameter, so that the pores cannot be filled (in the pores). It is not preferable because it may not enter.

  In addition to such particles, the modifying slurry preferably contains a binder capable of binding the particles to the inner surface of the pores, and these are diluted with water. An agent may be appropriately contained. As the binder, a colloidal sol such as silica sol or alumina sol, a layered compound which swells and exhibits binding properties, and the like can be suitably used. The heat treatment conditions after impregnation with the modified slurry may be appropriately determined depending on the composition of the modified slurry. When the modification is performed with a modification slurry having the same composition as the base substrate, heat treatment under the same conditions as the firing conditions of the base substrate is required in order to impart binding properties. When materials that exhibit strength at 700 to 800 ° C., such as colloidal silica, are combined, heat treatment at a low temperature becomes possible.

  The amount of decrease in the porosity of the modified portion relative to the porosity of the base substrate and the amount of decrease in the average pore diameter of the modified portion relative to the average pore diameter of the base substrate are the particle size and content of the particles contained in the modifying slurry, The number of times of impregnation with the modifying slurry can be adjusted.

  In the first to fourth honeycomb structures of the present invention, the partition wall thickness of the honeycomb segment is preferably 7 to 20 mil (178 to 508 μm), more preferably 8 to 16 mil (203 to 406 μm). Preferably, it is 10-12 mil (254-305 micrometers). If the partition wall thickness is less than 7 mil, the strength may be insufficient and the thermal shock resistance may be reduced. On the other hand, if the partition wall thickness exceeds 20 mil, the pressure loss may be too large.

The cell density is preferably 140 to 350 cells / in ² (cpsi), more preferably 160 to 320 cpsi, and still more preferably 200 to 300 cpsi. If the cell density is less than 140 cpsi, the contact efficiency with the fluid may be insufficient. On the other hand, if the cell density exceeds 350 cpsi, the pressure loss may increase excessively. “Cpsi” is an abbreviation for “cells per square inch”, and is a unit representing the number of cells per square inch. For example, 10 cpsi is about 1.55 cells / cm ² .

  The cell shape (cell cross-sectional shape) is not particularly limited, and may be, for example, a polygon such as a quadrangle, a triangle, a hexagon, an octagon, or a round shape, as described above. Different shapes of cells may be combined and arranged.

  Further, in the first to fourth honeycomb structures of the present invention, the catalyst component is supported on the partition wall for the purpose of accelerating PM combustion during filter regeneration or purifying harmful substances in the exhaust gas. Anyway. As a method for supporting the catalyst component on the partition wall, for example, a solution containing the catalyst component is impregnated with a powder made of a heat-resistant inorganic oxide having a high specific surface area such as alumina powder, and then dried and fired. A method in which a powder containing components is obtained, a catalyst slurry is prepared by adding alumina sol or water to the powder, a honeycomb segment or a honeycomb structure is immersed therein, the slurry is coated, and then dried and fired. Can be used.

  As the catalyst component, it is preferable to use one or more noble metals selected from the group consisting of Pt, Rh, and Pd. The amount of these noble metals supported is preferably 0.3 to 3.5 g / L per unit volume of the honeycomb structure.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

(Examples 1-4 and Comparative Examples 1-8)
SiC powder and metal Si powder were mixed at a predetermined mass ratio, and a pore former, an organic binder, a surfactant and water were added thereto to obtain a plastic clay. This kneaded material was extruded and dried to obtain a honeycomb-shaped formed body. A plugged portion was formed at one end of each cell so that both end faces of the honeycomb formed body had a complementary checkerboard pattern. That is, the plugged portion was formed so that adjacent cells were sealed at the opposite ends. The same material as that for the honeycomb formed body was used as the material for the plugging portion. After the plugging portions are formed and dried in this way, the honeycomb-shaped formed body is degreased at about 400 ° C. in an air atmosphere, and further fired at about 1450 ° C. in an Ar atmosphere to obtain SiC particles in the formed body. Is bonded with Si, so that it has an average interval S between the local peaks of the outer wall surface as shown in Table 1, an arithmetic average surface roughness Ra and S / Ra, a partition wall thickness of 12 mil (305 μm), and a cell shape Is a square columnar honeycomb segment base substrate having a square shape, a cell density of about 46.5 cells / cm ² (300 cells / square inch), a square with a cross section of 35 mm on one side, and an axial length of 152 mm. . In addition, adjustment of the value of the average space | interval S of the local peak of the outer wall surface of a base base material, arithmetic mean surface roughness Ra, and S / Ra is mainly SiC powder used for the raw material of clay, metal Si powder, and pore making This was done by adjusting the particle size distribution and amount of the material. For example, in Example 1, 65% by mass of SiC powder having an average particle size of 15 μm, 16% by mass of metal Si powder having an average particle size of 6 μm, and 19% by mass of a pore former having an average particle size of 25 μm, 3.0 μm Ra and 34 μm S were obtained. In Example 4, 65% by mass of SiC powder having an average particle size of 70 μm, 16% by mass of metal Si powder having an average particle size of 6 μm, and 19% by mass of a pore former having an average particle size of 50 μm, 18.0 μm Ra and 101 μm S were obtained.

  Next, 150 parts by mass of colloidal silica (solution with a solid content of 40%) and 200 parts by mass of water were added to 150 parts by mass of predetermined SiC particles, and stirred well to prepare a modifying slurry. In this preparation, a dispersant and an antifoaming agent were appropriately added. The base substrate was immersed in the modifying slurry thus obtained from one end face to ½ the total length of the base substrate, and then excess slurry was removed by air blowing. Next, after drying the slurry, heat treatment is performed at 700 ° C., and the length is ½ of the total length of the base substrate, and the average interval S between the local peaks on the outer wall surface as shown in Table 1, A modified portion having arithmetic average surface roughness Ra and S / Ra was formed to prepare a honeycomb segment. In addition, adjustment of the value of the average space | interval S of the local peak of the outer wall surface of a modification part, arithmetic mean surface roughness Ra, and S / Ra mainly adjusts the particle size distribution of the SiC powder used for the raw material of the slurry for modification. Was done. For example, in Example 1, SiC powder having an average particle diameter of 0.4 μm was used, and 3.9 μm Ra and 42 μm S were obtained. In Example 4, SiC powder having an average particle diameter of 0.8 μm was used, and 19.5 μm Ra and 121 μm S were obtained.

  Next, using SiC powder having an average particle size shown in Table 1 as inorganic particles, to this mixed aluminosilicate fiber, silica sol aqueous solution and clay, water was further added, and kneaded for 30 minutes using a mixer, A paste-like bonding material was obtained. The bonding material is applied to the outer peripheral surface of the honeycomb segment so as to have a thickness of about 1 mm to form a bonding material layer, and a process of placing another honeycomb segment thereon is repeated. A honeycomb segment laminate including a total of 16 honeycomb segments combined in a piece was produced. Then, the whole was joined as appropriate by applying pressure from the outside, and then dried at 120 ° C. for 2 hours to obtain a joined honeycomb segment. After grinding the outer periphery so that the outer shape of the honeycomb segment bonded body becomes a columnar shape, a coating material having the same composition as the bonding material is applied to the processed surface to re-form the outer peripheral wall. The honeycomb structure of Examples 1 to 4 and Comparative Examples 1 to 8 was obtained by drying and curing for a period of time.

  With respect to the honeycomb structures of Examples 1 to 4 and Comparative Examples 1 to 8 thus manufactured, the shear strength of the joint and the temperature difference between the segments were examined by the following method. The results are shown in Table 1. In each of the examples and comparative examples, the honeycomb structure used for measuring the shear strength of the joint and the honeycomb structure used for measuring the temperature difference between the segments are different individuals manufactured by the same method. It is. That is, for each of the examples and comparative examples, two honeycomb structures were prepared, one of which was used for measuring the shear strength of the joint and the other was used for measuring the temperature difference between the segments.

[Shear strength]
Two honeycomb segments adjacent to each other were cut out from the honeycomb structure in a joined state, one honeycomb segment was fixed, and a load F was applied to the other honeycomb segment from the major axis direction.

[Temperature difference between segments]
The honeycomb structure on which the soot is deposited is installed on the engine bench, post-injection is performed with the engine speed maintained at 2000 rpm and the engine torque of 60 Nm, and post-injection is performed at the timing when the pressure loss before and after the honeycomb structure starts to decrease. The temperature history inside the honeycomb structure was measured when the engine state was switched to idle. The soot amount was gradually increased so that the maximum temperature at the measurement point was 1200 ° C., and data at 1200 ° C. was used. As shown in FIG. 14A and FIG. 14B, the temperature measurement points 20, 21 are located at the center of the outer peripheral segment 2a located at the outer peripheral portion of the honeycomb structure 1 (at a position 20 mm from the outer periphery toward the center) and inside thereof. The temperature at each temperature measurement point 20, 21 is 15 mm from the rear end (exit side end surface 11) to the front end (inlet side end surface 10) of the honeycomb structure 1 in the center of the adjacent central segment 2 b. It was obtained by calculating the difference in the maximum temperature in the history.

(Discussion)
When the temperature difference between the segments obtained as described above is T and the shear strength is P, if these satisfy the relationship of the above formula (1), it is difficult to break during filter regeneration, and good thermal shock resistance It is as described above to demonstrate. In Examples 1 to 4 included in the scope of the present invention, the shear strength and the temperature difference between segments satisfy the relationship of the above formula (1), and can exhibit good thermal shock resistance during reproduction. It was. On the other hand, the average distance S of the local peaks on the outer wall surface of the base substrate is less than the lower limit of the limitation range of the present invention, Comparative Examples 1 and 2, and the average interval S of the local peaks on the outer wall surface of the base substrate is the limitation of the present invention. Comparative examples 7 and 8 exceeding the upper limit of the range, arithmetic average surface roughness Ra of the outer wall surface of the base substrate is less than the lower limit of the limited range of the present invention, arithmetic average of the outer wall surface of the base substrate In Comparative Examples 4 and 6 in which the surface roughness Ra exceeds the upper limit of the limited range of the present invention, the shear strength and the temperature difference between the segments do not satisfy the relationship of the above formula (1), and due to the internal shear stress at the time of reproduction There is a risk of destruction.

(Examples 5 to 10, Reference Example 1 and Comparative Examples 9 to 16)
SiC powder and metal Si powder were mixed at a predetermined mass ratio, and a pore former, an organic binder, a surfactant and water were added thereto to obtain a plastic clay. This kneaded material was extruded and dried to obtain a honeycomb-shaped formed body. A plugged portion was formed at one end of each cell so that both end faces of the honeycomb formed body had a complementary checkerboard pattern. That is, the plugged portion was formed so that adjacent cells were sealed at the opposite ends. The same material as that for the honeycomb formed body was used as the material for the plugging portion. After the plugging portions are formed and dried in this way, the honeycomb-shaped formed body is degreased at about 400 ° C. in an air atmosphere, and further fired at about 1450 ° C. in an Ar atmosphere to obtain SiC particles in the formed body. Are bonded with Si, so that the porosity, the average pore diameter, the average distance S between the local peaks of the outer wall surface, the arithmetic average surface roughness Ra, and S / Ra as shown in Table 2, and the thickness of the partition wall Square pillar honeycomb segment of 12 mil (305 μm), cell shape is square, cell density is about 46.5 cells / cm ² (300 cells / square inch), cross section is 35 mm square, and axial length is 152 mm A base substrate was obtained. It should be noted that the SiC powder used as the raw material for the clay is mainly used to adjust the porosity, average pore diameter, average distance S between the local peaks on the outer wall surface, arithmetic average surface roughness Ra, and S / Ra. The particle size distribution and the amount of the metal Si powder and the pore former were adjusted. Specifically, 65% by mass of SiC powder having an average particle size of 15 μm, 16% by mass of metal Si powder having an average particle size of 6 μm, and 19% by mass of a pore former having an average particle size of 30 μm are mixed. 1 μm Ra and 49 μm S were obtained.

  Next, 150 parts by mass of colloidal silica (solution with a solid content of 40%) and 200 parts by mass of water were added to 150 parts by mass of predetermined SiC particles, and stirred well to prepare a modifying slurry. In this preparation, a dispersant and an antifoaming agent were appropriately added. The base substrate was immersed in the modifying slurry thus obtained from one end face to ½ the total length of the base substrate, and then excess slurry was removed by air blowing. Next, after drying the slurry, heat treatment was performed at 700 ° C., and the length was ½ of the total length of the base substrate, and the porosity, average pore diameter, outer wall surface as shown in Table 2 A modified portion having an average interval S between the local peaks, an arithmetic average surface roughness Ra, and S / Ra was formed to produce a honeycomb segment. In addition, adjustment of the value of the average space | interval S of the local peak of the outer wall surface of a modification part, arithmetic mean surface roughness Ra, and S / Ra mainly adjusts the particle size distribution of the SiC powder used for the raw material of the slurry for modification. Was done. For example, in Example 5, SiC powder having an average particle diameter of 0.8 μm was used, and 4.7 μm Ra and 70 μm S were obtained. In Example 8, SiC powder having an average particle diameter of 2 μm was used, and 7.3 μm Ra and 95 μm S were obtained.

Next, using the SiC powder having the average particle size shown in Table 2 as inorganic particles, to this mixed aluminosilicate fiber, silica sol aqueous solution and clay, water was further added, and kneaded for 30 minutes using a mixer, A paste-like bonding material was obtained. The bonding material is applied to the outer peripheral surface of the honeycomb segment so as to have a thickness of about 1 mm to form a bonding material layer, and a process of placing another honeycomb segment thereon is repeated. A honeycomb segment laminate including a total of 16 honeycomb segments combined in a piece was produced. Then, the whole was joined as appropriate by applying pressure from the outside, and then dried at 120 ° C. for 2 hours to obtain a joined honeycomb segment. After grinding the outer periphery so that the outer shape of the honeycomb segment bonded body becomes a columnar shape, a coating material having the same composition as the bonding material is applied to the processed surface to re-form the outer peripheral wall. Drying and curing was performed for hours, and honeycomb structures of Examples 5 to 10, Reference Example 1 and Comparative Examples 9 to 16 were obtained.

For the honeycomb structures of Examples 5 to 10, Reference Example 1 and Comparative Examples 9 to 16 thus manufactured, the shear strength of the joint and the temperature difference between the segments were determined by the above-described method, and the peeling was performed by the following method. The presence or absence of was investigated. The results are shown in Table 2.

[Presence or absence of peeling]
From the honeycomb structure, the bonding material and the outer wall portion of two adjacent honeycomb segments bonded by the bonding material are cut out in a bonded state, and the portion where the modified portion of the base substrate is not formed and the modified portion The bonding state between the outer wall surface and the bonding material at the boundary was observed with a microscope to examine the presence or absence of peeling.

(Discussion)
In Reference Example 1 and Examples 5 to 10 included in the scope of the present invention, the shear strength and the temperature difference between the segments satisfy the relationship of the above formula (1), and exhibit good thermal shock resistance during reproduction. It was what you get. On the other hand, the average particle diameter of the inorganic particles contained in the bonding material is less than the lower limit of the limitation range of the present invention. In Comparative Examples 10, 12, 14 and 16 exceeding the upper limit of the range, the shear strength and the temperature difference between the segments do not satisfy the relationship of the above formula (1), and there is a possibility of breaking due to internal shear stress during reproduction. is there. Furthermore, Comparative Examples 9 and 13 also had a low crack limit.

  The present invention can be suitably used as a filter for collecting dust such as DPF.

1: honeycomb structure, 2: honeycomb segment, 2a: outer peripheral segment, 2b: center segment, 3: partition wall, 5: cell, 5a: square cell, 5b: octagonal cell, 7: modifier, 7a: modifier 7b: modification part, 8: outer wall, 9: plugging part, 10: inlet side end face, 11: outlet side end face, 15: inorganic particles, 20: temperature measurement point, 21: temperature measurement point.

Claims (16)

An inlet-side end face that becomes the fluid inlet side, an outlet-side end face that becomes the fluid outlet side, an outer wall that connects the outer peripheral portions of the two end faces, and a partition wall of the porous body between the two end faces inside the outer wall A honeycomb in which a plurality of honeycomb-shaped segments that are partitioned and formed by a plurality of cells serving as fluid flow paths are integrated by bonding the outer walls with a bonding material containing inorganic particles A structure,
The segment is a modification formed by impregnating a part of the base substrate with a slurry containing a honeycomb-shaped porous base substrate and particles smaller than the average pore diameter of the base substrate and then heat-treating the slurry. And
The modification part is formed in a range from the exit side end surface of the segment to the length of 1/10 to 1/2 of the total length of the segment along the axial direction of the cell. The arithmetic average surface roughness Ra of the outer wall surface of the base substrate excluding the base material is 0.4 to 20 μm, and the arithmetic average surface roughness Ra of the outer wall surface of the modified portion excludes the formation site of the modified portion. A honeycomb structure in which the arithmetic average surface roughness Ra of the outer wall surface of the base substrate is 0.01 to 7.5 μm larger, and the average particle diameter of the inorganic particles is 0.5 to 30 μm. An inlet-side end face that becomes the fluid inlet side, an outlet-side end face that becomes the fluid outlet side, an outer wall that connects the outer peripheral portions of the two end faces, and a partition wall of the porous body between the two end faces inside the outer wall A honeycomb in which a plurality of honeycomb-shaped segments that are partitioned and formed by a plurality of cells serving as fluid flow paths are integrated by bonding the outer walls with a bonding material containing inorganic particles A structure,
Out of the segments, the outer peripheral segment located at the outer peripheral portion of the honeycomb structure is composed only of a honeycomb-shaped and porous base substrate,
The central segment located inside the outer peripheral segment is formed by impregnating a part of the base substrate with a slurry containing particles smaller than the average pore diameter of the base substrate and the base substrate, and then performing heat treatment. Modified part, and
The modifying portion is formed in a range from the outlet side end surface of the central segment to the length of 1/10 to 1/2 of the total length of the central segment along the axial direction of the cell. A honeycomb structure in which an arithmetic average surface roughness Ra of an outer wall surface of the base substrate excluding a formation site is 0.4 to 20 μm, and an average particle diameter of the inorganic particles is 0.5 to 30 μm. The arithmetic average surface roughness Ra of the modified portion of the outer wall surface, the modified portion of the base 0.01~7.5μm than the arithmetic mean surface roughness Ra of the base material of the outer wall surface greater claim 2, excluding the portions of the barrier The honeycomb structure according to 1. An inlet-side end face that becomes the fluid inlet side, an outlet-side end face that becomes the fluid outlet side, an outer wall that connects the outer peripheral portions of the two end faces, and a partition wall of the porous body between the two end faces inside the outer wall A honeycomb in which a plurality of honeycomb-shaped segments that are partitioned and formed by a plurality of cells serving as fluid flow paths are integrated by bonding the outer walls with a bonding material containing inorganic particles A structure,
The segment is a modification formed by impregnating a part of the base substrate with a slurry containing a honeycomb-shaped porous base substrate and particles smaller than the average pore diameter of the base substrate and then heat-treating the slurry. And
The modification part is formed in a range from the exit side end surface of the segment to the length of 1/10 to 1/2 of the total length of the segment along the axial direction of the cell. The average interval S between the local peaks on the outer wall surface of the base substrate excluding the base is 10 to 125 μm, and the average interval S between the local peaks on the outer wall surface of the modified portion is the base excluding the site where the modified portion is formed A honeycomb structure in which the average particle diameter of the inorganic particles is 0.5 to 30 μm larger than the average distance S between the local peaks on the outer wall surface of the substrate. An inlet-side end face that becomes the fluid inlet side, an outlet-side end face that becomes the fluid outlet side, an outer wall that connects the outer peripheral portions of the two end faces, and a partition wall of the porous body between the two end faces inside the outer wall A honeycomb in which a plurality of honeycomb-shaped segments that are partitioned and formed by a plurality of cells serving as fluid flow paths are integrated by bonding the outer walls with a bonding material containing inorganic particles A structure,
Out of the segments, the outer peripheral segment located at the outer peripheral portion of the honeycomb structure is composed only of a honeycomb-shaped and porous base substrate,
The central segment located inside the outer peripheral segment is formed by impregnating a part of the base substrate with a slurry containing particles smaller than the average pore diameter of the base substrate and the base substrate, and then performing heat treatment. Modified part, and
The modifying portion is formed in a range from the outlet side end surface of the central segment to the length of 1/10 to 1/2 of the total length of the central segment along the axial direction of the cell. A honeycomb structure in which an average interval S between local peaks on the outer wall surface of the base substrate excluding a formation site is 10 to 125 μm, and an average particle diameter of the inorganic particles is 0.5 to 30 μm. The mean spacing S of local peaks of the modified portion of the outer wall surface, according to 0.1~70μm large claim 5 than the average spacing S of local peaks of the outer wall surface of the base substrate excluding the forming portion of the modified portion Honeycomb structure. The honeycomb structure according to claim 1 or 4 , wherein the length, porosity, and average pore diameter of the modified portion are the same in all the segments. Among the segments, the outer peripheral segment located at the outer peripheral portion of the honeycomb structure and the central segment located inside thereof differ in any one or more of the length, porosity and average pore diameter of the modified portion. The honeycomb structure according to claim 1 or 4 . The ratio (S / Ra) of the average distance S between the local peaks on the outer wall surface of the base substrate excluding the site where the modified part is formed and the arithmetic average surface roughness Ra is 1 to 35, and the outer wall of the modified part The honeycomb structure according to any one of claims 1 to 8 , wherein a ratio (S / Ra) of an average interval S between local tops of the surface and an arithmetic average surface roughness Ra is 4 to 40. Claims where P and T satisfy the relationship of the following formula (1), where P (unit: kPa) is the shear strength determined by the following method and T (unit: ° C) is the temperature difference between segments. The honeycomb structure according to any one of 1 to 9 .
T <0.423P-169.2 (1)
[Shear strength]
Two adjacent segments are cut out from the honeycomb structure in a joined state, one segment is fixed, and a load is applied to the other segment from the major axis direction.
[Temperature difference between segments]
The honeycomb structure with soot deposited inside is installed on the engine bench, post-injection is performed with the engine speed maintained at 2000 rpm and the engine torque of 60 Nm, and the post-compression pressure loss before and after the honeycomb structure starts to decrease. The temperature history inside the honeycomb structure is measured when the injection is turned off and the engine state is switched to idle. The temperature measurement points are the end surfaces on the outlet side of the honeycomb structure at the end surface direction center portion of the outer peripheral segment located at the outer peripheral portion of the honeycomb structure and the end surface direction center portion of the center segment adjacent to the inner side of the outer peripheral segment. The soot accumulation amount is gradually increased so that the maximum temperature at the temperature measurement point in the central segment of these two temperature measurement points is 1200 ° C. The maximum temperature difference in the temperature history at each temperature measurement point until the temperature at the temperature measurement point in the central segment reaches 1200 ° C. is calculated. The honeycomb structure according to any one of claims 1 to 10 , wherein the porosity of the modified portion is 2 to 20% lower than the porosity of the base substrate. The honeycomb structure according to any one of claims 1 to 11 , wherein an average pore diameter of the modified portion is 0.1 to 10 µm smaller than an average pore diameter of the base substrate. The honeycomb structure according to any one of claims 1 to 12 , wherein the base substrate has a porosity of 30 to 80 and an average pore diameter of 5 to 40 µm. Thereby plugging the opening of predetermined said cell by said inlet-side end surface, any claim 1 to 13 having a plugging portion for plugging the opening with the outlet-side end surface of the cells of the remaining A honeycomb structure according to claim 1. The honeycomb structure according to claim 14 , wherein an opening ratio of the inlet side end face is larger than an opening ratio of the outlet side end face. The honeycomb structure according to any one of claims 1 to 15 , wherein a catalyst component is supported on the partition walls.

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