Honeycomb structure

Abstract

The invention provides a honeycomb structure which has practical heat capacity, can maintain low maintenance cost, and can easily detect maintenance time based on PM accumulation amount by using a pressure sensor. A honeycomb structure is a cylindrical honeycomb structure provided with an outer peripheral side wall, a plurality of introduction cells, and a plurality of discharge cells, at least some of the plurality of introduction cells and at least some of the plurality of discharge cells being adjacent to each other with a partition wall therebetween, the cell density based on the total number of the plurality of introduction cells and the plurality of discharge cells is 29-43 cells / cm2, and the average thickness of the partition walls is 0.173 mm or more and 0.236 mm or less. When the average value of the opening diameters of the plurality of discharge cells excluding the discharge cells adjacent to the outer peripheral side wall is Dout and the average value of the opening diameters of the plurality of introduction cells excluding the introduction cells adjacent to the outer peripheral side wall is Din, 1.20 < = Din / Dout < = 1.38 is satisfied.

Description

Technical Field

[0001] The present invention relates to a honeycomb structure. Background Art

[0002] Diesel engines offer superior thermal efficiency compared to gasoline engines, but their diffusion combustion generates particulate matter (PM), such as soot and ash. These particulate matter are known to be carcinogenic, and their release into the atmosphere must be prevented. Consequently, strict regulations are now in place, primarily in Europe, in addition to existing weight-based regulations.

[0003] However, there are limits to reducing PM emissions through combustion improvements, and the only effective method currently is to insert a filter called a diesel particulate filter (DPF) into the exhaust gas. Wall-flow filters, designed to allow exhaust gas to pass through porous partitions, are effective. Specifically, wall-flow filters have multiple inlet cells and multiple outlet cells adjacent to each other, separated by porous partitions. They can be constructed from a honeycomb structure that captures PM as the exhaust gas passes through the partitions.

[0004] Wall-flow filters made of honeycomb structures have the problem of increasing pressure loss due to PM accumulation in the filter as the operating time increases. Therefore, such filters inject additional fuel every time a certain amount of PM accumulates to increase the exhaust gas temperature, causing the soot to burn (filter regeneration), thereby reducing the pressure loss. In addition, since ash does not burn even at high temperatures, trucks and off-road vehicles that travel longer distances than passenger cars (i.e., the filter has a longer operating time) need to regularly remove ash accumulated in the filter by cleaning the honeycomb structure to reduce the pressure loss. If the pressure loss increases immediately when PM accumulates, the frequency of filter regeneration and cleaning becomes higher, resulting in increased fuel consumption and maintenance costs. Therefore, research has been conducted to reduce the pressure loss when PM accumulates by studying the arrangement and size of the inlet and outlet cells (Patent Documents 1 and 2).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2019 / 104057

[0008] Patent Document 2: International Publication No. 2013 / 187444 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] Conventionally, the timing for filter regeneration and cleaning was determined by measuring the pressure loss between the filter inlet and outlet using a pressure sensor. However, if the pressure loss remains low after a large amount of PM accumulates in the filter, predicting the amount of PM accumulation based on the pressure loss becomes difficult when using a pressure sensor for filter regeneration control, leading to excessive PM accumulation and potentially damaging the filter. Therefore, it is desirable to reduce maintenance costs by reducing the frequency of filter regeneration and cleaning by minimizing excessive pressure loss after PM accumulation. Furthermore, by increasing the change in pressure loss relative to the amount of PM accumulation (pressure loss gradient), it is easier to detect the amount of PM accumulation suitable for filter regeneration and cleaning using a pressure sensor. Furthermore, honeycomb structures are also required to have sufficient heat capacity to prevent excessive temperature rise and damage during filter regeneration.

[0011] The present invention has been completed in view of the above situation. In one embodiment, its object is to provide a honeycomb structure that can meet all of the following required characteristics: having a practical heat capacity, being able to keep maintenance costs low, and being able to easily use a pressure sensor to detect the period when maintenance is required based on the amount of PM accumulation.

[0012] Solutions to Problems

[0013] The inventors conducted intensive research to solve the above-mentioned problems and found that appropriately combining parameters related to the honeycomb structure, such as cell density, average thickness of partition walls, opening diameter ratio, and average porosity of partition walls, is effective in solving the problems, thereby completing the present invention exemplified below.

[0014] [Scheme 1]

[0015] A columnar honeycomb structure comprises: an outer peripheral sidewall; a plurality of inlet cells arranged on the inner peripheral side of the outer peripheral sidewall, extending from an inlet end face to an outlet end face, having an opening at the inlet end face and a sealing portion at the outlet end face; and a plurality of outlet cells arranged on the inner peripheral side of the outer peripheral sidewall, extending from the inlet end face to the outlet end face, having a sealing portion at the inlet end face and an opening at the outlet end face, wherein:

[0016] At least some of the plurality of inlet cells are adjacent to at least some of the plurality of outlet cells via a partition wall.

[0017] The compartment density based on the total number of the plurality of inlet compartments and the plurality of outlet compartments is 29 to 43 compartments / cm 2 ,

[0018] The average thickness of the partition walls is 0.173 mm or more and 0.236 mm or less,

[0019] If the average opening diameter of the discharge cells other than the discharge cells adjacent to the outer peripheral side wall among the plurality of discharge cells is set as D out The average opening diameter of the plurality of introduction compartments except the introduction compartments adjacent to the outer peripheral side wall is set as D in , then 1.20≤D in / D out ≤1.38.

[0020] [Scheme 2]

[0021] The honeycomb structure according to claim 1, wherein

[0022] The average opening diameter D of each of the plurality of introduction compartments, excluding the introduction compartment adjacent to the outer peripheral side wall, is in is 1.48mm or more and 1.80mm or less,

[0023] The average value D of the opening diameters of the plurality of discharge compartments, excluding the discharge compartments adjacent to the outer peripheral side wall, is out It is 1.16 mm or more and 1.48 mm or less.

[0024] [Scheme 3]

[0025] The honeycomb structure according to claim 1 or 2, wherein

[0026] The average porosity of the partition walls is 52 to 60%.

[0027] [Scheme 4]

[0028] The honeycomb structure according to any one of aspects 1 to 3, wherein

[0029] The density measured according to the external dimensions is 0.288~0.410g / cm 3 .

[0030] [Scheme 5]

[0031] The honeycomb structure according to any one of aspects 1 to 4, wherein

[0032] The ratio of the number of the plurality of inlet compartments excluding the inlet compartments adjacent to the outer peripheral sidewall to the number of the plurality of outlet compartments excluding the outlet compartments adjacent to the outer peripheral sidewall is 0.9 to 1.1.

[0033] [Scheme 6]

[0034] The honeycomb structure according to any one of aspects 1 to 5, wherein

[0035] If the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 1 g / L, the pressure loss when the exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P1,

[0036] When the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 3 g / L, the pressure loss when exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P2.

[0037] Then 45%≤(P2-P1) / P1 is satisfied.

[0038] [Scheme 7]

[0039] The honeycomb structure according to any one of aspects 1 to 6, wherein

[0040] The partition walls contain cordierite.

[0041] [Scheme 8]

[0042] A columnar honeycomb structure comprises: an outer peripheral sidewall; a plurality of inlet cells arranged on the inner peripheral side of the outer peripheral sidewall, extending from an inlet end face to an outlet end face, having an opening at the inlet end face and a sealing portion at the outlet end face; and a plurality of outlet cells arranged on the inner peripheral side of the outer peripheral sidewall, extending from the inlet end face to the outlet end face, having a sealing portion at the inlet end face and an opening at the outlet end face, wherein:

[0043] At least some of the plurality of inlet cells are adjacent to at least some of the plurality of outlet cells via a partition wall.

[0044] The compartment density based on the total number of the plurality of inlet compartments and the plurality of outlet compartments is 29 to 36 compartments / cm 2 ,

[0045] The average thickness of the partition walls is 0.231 mm or more and 0.312 mm or less,

[0046] If the average opening diameter of the discharge cells other than the discharge cells adjacent to the outer peripheral side wall among the plurality of discharge cells is set as D out The average opening diameter of the plurality of introduction compartments except the introduction compartments adjacent to the outer peripheral side wall is set as D in , then 1.14≤D in / D out ≤1.37,

[0047] The average porosity of the partition walls is 57 to 63%.

[0048] [Scheme 9]

[0049] The honeycomb structure according to claim 8, wherein

[0050] The average opening diameter D of each of the plurality of introduction compartments, excluding the introduction compartment adjacent to the outer peripheral side wall, is in is 1.52mm or more and 1.76mm or less,

[0051] The average value D of the opening diameters of the plurality of discharge compartments, excluding the discharge compartments adjacent to the outer peripheral side wall, is out It is 1.20 mm or more and 1.44 mm or less.

[0052] [Scheme 10]

[0053] The honeycomb structure according to claim 8 or 9, wherein

[0054] The average pore diameter of the partition walls is 7 to 13 μm.

[0055] [Scheme 11]

[0056] The honeycomb structure according to any one of aspects 8 to 10, wherein

[0057] The density measured according to the external dimensions is 0.288~0.410g / cm 3 .

[0058] [Scheme 12]

[0059] The honeycomb structure according to any one of aspects 8 to 11, wherein

[0060] The ratio of the number of the plurality of inlet compartments excluding the inlet compartments adjacent to the outer peripheral sidewall to the number of the plurality of outlet compartments excluding the outlet compartments adjacent to the outer peripheral sidewall is 0.9 to 1.1.

[0061] [Scheme 13]

[0062] The honeycomb structure according to any one of aspects 8 to 12, wherein

[0063] If the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 1 g / L, the pressure loss when the exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P1,

[0064] When the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 3 g / L, the pressure loss when exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P2.

[0065] Then 45%≤(P2-P1) / P1 is satisfied.

[0066] [Scheme 14]

[0067] The honeycomb structure according to any one of aspects 8 to 13, wherein

[0068] The partition walls contain cordierite.

[0069] Effects of the Invention

[0070] By using the honeycomb structure according to one embodiment of the present invention as an exhaust gas filter, the pressure loss after PM accumulation does not increase excessively, thereby reducing the frequency of filter regeneration and cleaning. At the same time, by increasing the change in pressure loss based on the amount of PM accumulation (pressure loss gradient), it is easy to detect the amount of PM accumulation suitable for filter regeneration and cleaning using a pressure sensor. As a result, a filter can be obtained that can maintain low maintenance costs and easily detect the period when maintenance is required based on the amount of PM accumulation using a pressure sensor. Therefore, the possibility of filter damage due to excessive PM accumulation can be reduced. In addition, the honeycomb structure according to one embodiment of the present invention has a practical heat capacity, so the risk of damage due to excessive temperature rise during filter regeneration is low. Thus, according to one embodiment of the present invention, it can be said that a honeycomb structure that is extremely excellent in practical use can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 It is a perspective view schematically showing a wall-flow type honeycomb structure.

[0072] Figure 2 This is a schematic cross-sectional view of a wall-flow type honeycomb structure viewed from a cross section parallel to the direction in which cells extend.

[0073] Figure 3 This is a schematic partial enlarged view of a partition wall of a honeycomb structure viewed from a cross section perpendicular to the direction in which cells extend.

[0074] Figure 4 This is an explanatory diagram schematically showing an example of a method for forming a plugged portion using a squeegee method. DETAILED DESCRIPTION

[0075] Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the present invention is not limited to the following embodiments, and that design changes and improvements may be appropriately applied based on the common knowledge of those skilled in the art without departing from the spirit of the present invention.

[0076] (1. Honeycomb structure)

[0077] (1-1) Basic structure

[0078] exist Figure 1 as well as Figure 2 , a schematic perspective view and a cross-sectional view of a columnar honeycomb structure 100 that can be used as a wall-flow exhaust gas filter for automobiles are shown. The honeycomb structure 100 includes: an outer peripheral sidewall 102; a plurality of inlet cells 108 disposed on the inner peripheral side of the outer peripheral sidewall 102, extending parallel to each other from an inlet end face 104 to an outlet end face 106, having an opening 107 at the inlet end face 104 and a plugging portion 109 at the outlet end face 106; and a plurality of outlet cells 110 disposed on the inner peripheral side of the outer peripheral sidewall 102, extending parallel to each other from the inlet end face 104 to the outlet end face 106, having a plugging portion 109 at the inlet end face 104 and an opening 107 at the outlet end face 106.

[0079] In the honeycomb structure 100, at least a portion of the plurality of inlet cells 108 and at least a portion of the outlet cells 110 are adjacent to each other via a partition wall 112. When the inlet cells 108 and the outlet cells 110 are adjacent to each other via a partition wall 112, the surface of the partition wall 112 facilitates filtration. For example, if exhaust gas containing particulate matter such as soot is supplied to the inlet end face 104 on the upstream side of the honeycomb structure 100, the exhaust gas is introduced into the inlet cell 108 and moves downstream within the inlet cell 108. The outlet end face 106 on the downstream side of the inlet cell 108 is sealed, so the exhaust gas flows into the outlet cell 110 through the partition wall between the adjacent inlet cells 108 and the outlet cells 110. The particulate matter cannot pass through the partition wall 112 and is therefore captured and accumulated within the inlet cell 108. After the particulate matter is removed, the clean exhaust gas flowing into the exhaust compartment 110 advances downstream in the exhaust compartment 110 and flows out from the outlet end surface 106 on the downstream side.

[0080] In a preferred embodiment, at least one of the plurality of discharge compartments 110 is adjacent only to the inlet compartment 108 (i.e., not adjacent to the discharge compartment 110 or the peripheral sidewall 102). This is because the discharge compartment 110 exerts a filtering effect by being adjacent to the inlet compartment 108. Furthermore, it is preferred that none of the plurality of discharge compartments 110 be adjacent to one another.

[0081] There is no limitation on the end face shape of the honeycomb structure 100. For example, it can be a circular shape such as a circular shape, an elliptical shape, a racetrack shape, and an oblong shape, a polygonal shape such as a triangular shape and a quadrilateral shape, and other irregular shapes. The end face shape of the illustrated honeycomb structure 100 is circular, and the whole is cylindrical.

[0082] The height of the honeycomb structure (the length from the inlet end face to the outlet end face) is not particularly limited and can be appropriately set according to the use and required performance. The height of the honeycomb structure can be set to, for example, 40 to 450 mm, preferably 60 to 400 mm, and more preferably 100 to 330 mm. There is no particular limitation on the relationship between the height of the honeycomb structure and the maximum diameter of each end face (which refers to the maximum length among the diameters passing through the centers of gravity of each end face of the honeycomb structure). Therefore, the height of the honeycomb structure can be longer than the maximum diameter of each end face, and the height of the honeycomb structure can also be shorter than the maximum diameter of each end face.

[0083] [[ID=6=6]]The opening shape of the introduction compartment is not particularly limited. For example, in a cross-section orthogonal to the direction in which the compartment extends in the honeycomb structure, it can be a polygon (quadrilateral (rectangle, square), pentagon, hexagon, heptagon, octagon, etc.), a circular shape (circle, ellipse, long ellipse, oval, oblong, etc.), etc. These shapes can be single, or two or more can be combined. Among them, for the reason of reducing the pressure loss, except for the compartments adjacent to the outer peripheral side wall, the opening shapes of the plurality of introduction compartments are preferably all hexagons or octagons, and more preferably octagons. When the opening shapes of the introduction compartment and the discharge compartment are polygons, the corners can be chamfered with an R. In addition, in this specification, even if chamfered with an R, it is treated as a polygon.

[0084] The opening shape of the discharge compartment is also not particularly limited and can be set according to the opening shape of the introduction compartment. For example, when the opening shape of the introduction compartment is an octagon, it is preferably a quadrilateral.

[0085] (1-2) Specific structure

[0086] The present inventor has found appropriate combinations of parameters related to the specific structure of the honeycomb structure, such as the density of the two compartments, the average thickness of the partition walls, the opening diameter ratio, and the average porosity of the partition walls. Therefore, they are separately described as the first embodiment and the second embodiment.

[0087] <A. First embodiment>

[0088] (A1) Compartment density

[0089] The cell density is an indicator that indicates the number of cells per unit area when the honeycomb structure is observed from the inlet end face or the outlet end face. From the perspective of improving the pressure loss inclination, the cell density is preferably smaller than the value previously adopted by the DPF. However, when the cell density is simply reduced, the heat capacity of the honeycomb structure decreases, and it is easy to reach a high temperature during filter regeneration, and the honeycomb structure may be damaged. Therefore, the soot accumulation limit is reduced, so it is not desirable to reduce the cell density excessively. Therefore, the cell density based on the total number of multiple inlet cells 108 and multiple exhaust cells 110 is preferably 29 to 43 cells / cm 2 , more preferably 30 to 40 cells / cm 2 , more preferably 31 to 39 compartments / cm 2 The cell density is calculated by dividing the total number of the plurality of inlet cells 108 and the plurality of outlet cells 110 (including sealed cells, outlet cells 110 adjacent to the outer peripheral side wall 102, and inlet cells 108 adjacent to the outer peripheral side wall 102) by the area of ​​one end face of the honeycomb structure 100 other than the outer peripheral side wall 102.

[0090] (A2) Average thickness of partition walls

[0091] From the perspective of satisfying the above-mentioned compartment density, ensuring the strength of the honeycomb structure, and ensuring the heat capacity of the honeycomb structure to increase the soot accumulation limit, the average thickness of the partition wall 112 is preferably greater than 0.173 mm and less than 0.236 mm, more preferably greater than 0.198 mm and less than 0.229 mm, and further preferably greater than 0.203 mm and less than 0.216 mm. Figure 3 is a schematic partial enlarged view of a honeycomb structure 100 in which the opening of the inlet cell 108 is octagonal and the opening of the outlet cell 110 is quadrilateral, as viewed from a cross section perpendicular to the cell extension direction. The thickness of the partition wall 112 refers to the length D of the line segment passing through the partition wall when connecting the centers of gravity O of adjacent cells in the cross section perpendicular to the cell extension direction (the height direction of the honeycomb structure). The average thickness of the partition wall 112 is calculated based on the thickness of all the partition walls 112.

[0092] In addition, two compartments are adjacent to each other with a partition wall sandwiched between them means that when the partition wall of the honeycomb structure is observed from a cross section perpendicular to the direction in which the compartments extend, the two compartments are adjacent to each other with the opposite wall surfaces of a partition wall sandwiched between them (the sides of the polygon dividing the compartments), and does not include the situation where the two compartments are adjacent to each other with the vertices of the polygon dividing the two compartments sandwiched between them.

[0093] (A3) Opening diameter ratio (D in / D out )

[0094] From the perspective of improving the pressure loss inclination and minimizing the pressure loss after PM accumulation, if the average opening diameter of the discharge cells excluding the discharge cells adjacent to the outer peripheral side wall among the plurality of discharge cells is set as D out The average opening diameter of the plurality of introduction cells, excluding the introduction cells adjacent to the outer peripheral side wall, is set as D in , then it is preferred to satisfy 1.20≤D in / D out ≤1.38, more preferably 1.22≤D in / D out ≤1.29, more preferably 1.25≤D in / D out ≤1.28.

[0095] The opening diameter of each of the plurality of introduction compartments is defined as an equivalent circle diameter calculated based on the opening area of ​​the introduction compartment. in The diameter of the opening of each of the plurality of introduction cells is calculated based on the opening diameters of all the introduction cells except the introduction cells adjacent to the outer peripheral side wall.

[0096] The opening diameter of each of the plurality of discharge compartments is defined as an equivalent circle diameter calculated based on the opening area of ​​the discharge compartment. out It is calculated based on the opening diameters of all the discharge compartments except the discharge compartments adjacent to the outer peripheral side wall among the plurality of discharge compartments.

[0097] (A4) opening diameter

[0098] From the viewpoint of suppressing the initial pressure loss and preventing the pressure loss after PM accumulation from becoming excessive, the average opening diameter D of each of the plurality of inlet cells, excluding the inlet cell adjacent to the outer peripheral side wall, is in It is preferably 1.48 to 1.80 mm, more preferably 1.50 to 1.79 mm, and even more preferably 1.54 to 1.75 mm. In addition, the average opening diameter D of each of the plurality of discharge cells, excluding the discharge cells adjacent to the outer peripheral side wall, is out It is preferably 1.16 to 1.48 mm, more preferably 1.18 to 1.43 mm, and even more preferably 1.22 to 1.39 mm.

[0099] (A5) Average porosity of partition walls

[0100] From the viewpoint of reducing the pressure loss, the lower limit of the average porosity of the partition walls is preferably 52% or more, more preferably 53% or more. Further, from the viewpoint of enhancing the mechanical strength of the honeycomb structure, the upper limit of the average porosity of the partition walls is preferably 60% or less, more preferably 58% or less. Thus, for example, the average porosity of the partition walls is preferably 52 to 60%, more preferably 53 to 58%. In this specification, the porosity of the partition walls is measured by the mercury intrusion method defined in JIS R1655:2003 (Japanese Industrial Standards). Regarding the average porosity, the average value obtained by collecting samples of the partition walls (0.3 g each) without bias from six locations of the honeycomb structure and determining the porosity of each sample is used as the measured value.

[0101] (A6) Ratio of the number of inlet compartments to the number of outlet compartments

[0102] From the viewpoints of suppressing an increase in pressure loss and increasing the pressure loss gradient, the ratio of the number of multiple inlet compartments to the number of multiple outlet compartments is preferably 0.9 to 1.1, more preferably 0.95 to 1.05, still more preferably 0.99 to 1.01, and most preferably 1. In addition, when calculating the ratio of the number of inlet compartments to the number of outlet compartments, the outlet compartments adjacent to the outer peripheral side wall and the inlet compartments adjacent to the outer peripheral side wall are not counted.

[0103] <B. Second Embodiment>

[0104] (B1) Compartment density

[0105] The compartment density is an index representing the number of compartments per unit area when observing the honeycomb structure from the inlet end face or the outlet end face. From the aspect of increasing the pressure loss gradient, it is preferable that the compartment density is smaller than the value conventionally used for DPF. However, when only the compartment density is reduced, the heat capacity of the honeycomb structure decreases, and it tends to become high temperature during filter regeneration, and the honeycomb structure may be damaged. Therefore, the soot accumulation limit is reduced, and thus it is not desirable to excessively reduce the compartment density. Accordingly, the compartment density based on the total number of the multiple inlet compartments 108 and the multiple outlet compartments 110 is preferably 29 to 36 compartments / cm 2 and more preferably 30 to 34 compartments / cm 2 and still more preferably 31 to 33 compartments / cm 2 . The compartment density is calculated by dividing the total number of the multiple inlet compartments 108 and the multiple outlet compartments 110 (including the sealed compartments, the outlet compartments 11 which are adjacent to the outer peripheral side wall 102, and the inlet compartments 108 which are adjacent to the outer peripheral side wall 102) by the area of one end face of the honeycomb structure 100 excluding the outer peripheral side wall 102.

[0106] (B2) Average thickness of partition walls

[0107] From the perspective of satisfying the above-mentioned compartment density while ensuring the strength of the honeycomb structure and ensuring the heat capacity of the honeycomb structure to increase the soot accumulation limit, the average thickness of the partition wall 112 is preferably greater than 0.231 mm and less than 0.312 mm, more preferably greater than 0.241 mm and less than 0.292 mm, and further preferably greater than 0.254 mm and less than 0.279 mm. Figure 3 is a schematic partial enlarged view of a honeycomb structure 100 in which the opening of the inlet cell 108 is octagonal and the opening of the outlet cell 110 is quadrilateral, as viewed from a cross section perpendicular to the cell extension direction. The thickness of the partition wall 112 refers to the length D of the line segment passing through the partition wall when connecting the centers of gravity O of adjacent cells in the cross section perpendicular to the cell extension direction (the height direction of the honeycomb structure). The average thickness of the partition wall 112 is calculated based on the thickness of all the partition walls 112.

[0108] In addition, two compartments are adjacent to each other with a partition wall sandwiched between them means that when the partition wall of the honeycomb structure is observed from a cross section perpendicular to the direction in which the compartments extend, the two compartments are adjacent to each other with the opposite wall surfaces of a partition wall sandwiched between them (the sides of the polygon dividing the compartments), and does not include the situation where the two compartments are adjacent to each other with the vertices of the polygon dividing the two compartments sandwiched between them.

[0109] (B3) Opening diameter ratio (D in / D out )

[0110] From the perspective of improving the pressure loss inclination and minimizing the pressure loss after PM accumulation, if the average opening diameter of the discharge cells excluding the discharge cells adjacent to the outer peripheral side wall among the plurality of discharge cells is set as D out The average opening diameter of the plurality of introduction cells, excluding the introduction cells adjacent to the outer peripheral side wall, is set as D in , then it is preferred to satisfy 1.14≤D in / D out ≤1.37, more preferably 1.22≤D in / D out ≤1.27, more preferably 1.23≤D in / D out ≤1.24.

[0111] The opening diameter of each of the plurality of introduction compartments is defined as an equivalent circle diameter calculated based on the opening area of ​​the introduction compartment. in The diameter of the opening of each of the plurality of introduction cells is calculated based on the opening diameters of all the introduction cells except the introduction cells adjacent to the outer peripheral side wall.

[0112] The opening diameter of each of the plurality of discharge compartments is defined as an equivalent circle diameter calculated based on the opening area of ​​the discharge compartment. out It is calculated based on the opening diameters of all the discharge compartments except the discharge compartments adjacent to the outer peripheral side wall among the plurality of discharge compartments.

[0113] (B4) opening diameter

[0114] From the viewpoint of suppressing the initial pressure loss and preventing the pressure loss after PM accumulation from becoming excessive, the average opening diameter D of each of the plurality of inlet cells, excluding the inlet cell adjacent to the outer peripheral side wall, is in It is preferably 1.52 to 1.76 mm, more preferably 1.63 to 1.73 mm, and even more preferably 1.64 to 1.69 mm. In addition, the average opening diameter D of each of the plurality of discharge cells, excluding the discharge cells adjacent to the outer peripheral side wall, is out It is preferably 1.20 to 1.44 mm, more preferably 1.31 to 1.43 mm, and even more preferably 1.35 to 1.41 mm.

[0115] (B5) Average porosity of partition walls

[0116] From the viewpoint of reducing pressure loss, the lower limit of the average porosity of the partition walls is preferably 57% or more, more preferably 58% or more. In addition, from the viewpoint of improving the mechanical strength of the honeycomb structure, the upper limit of the average porosity of the partition walls is preferably 63% or less, more preferably 61% or less. Therefore, for example, the average porosity of the partition walls is preferably 57 to 63%, more preferably 58 to 61%. In this specification, the porosity of the partition walls is measured by the mercury intrusion method specified in JIS R1655:2003. In addition, regarding the average porosity, samples of the partition walls (0.3 g each) are collected from 6 locations of the honeycomb structure without deviation, and the average value of the porosity of each is calculated as the measured value.

[0117] (B6) Ratio of the number of inlet compartments to the number of outlet compartments

[0118] From the viewpoint of suppressing the increase in pressure loss and increasing the pressure loss inclination, the ratio of the number of the plurality of inlet cells to the number of the plurality of outlet cells is preferably 0.9 to 1.1, more preferably 0.95 to 1.05, even more preferably 0.99 to 1.01, and most preferably 1. Furthermore, when calculating the ratio of the number of inlet cells to the number of outlet cells, the outlet cells adjacent to the outer peripheral side wall and the inlet cells adjacent to the outer peripheral side wall are not counted.

[0119] (B7) Average pore diameter

[0120] From the viewpoint of pressure loss after soot accumulation, the average pore diameter of the partition wall 112 is preferably 13 μm or less, more preferably 11 μm or less. In addition, from the viewpoint of pressure loss without soot accumulation, the average pore diameter of the partition wall 112 is preferably 7 μm or more, more preferably 9 μm or more. Therefore, the average pore diameter of the partition wall 112 is preferably, for example, 7 to 13 μm, more preferably 9 to 11 μm. The average pore diameter of the partition wall is measured by mercury intrusion according to JIS R1655:2003. 20 test pieces of the partition wall are uniformly collected including the center and the periphery of the honeycomb structure, and the average pore diameter of each is measured, and the average value thereof is taken as the average pore diameter of the entire honeycomb structure.

[0121] (1-3) Density

[0122] From the perspective of suppressing the temperature rise during filter regeneration and increasing the soot accumulation limit, the honeycomb structure preferably has a high mass per unit volume, that is, a high density. Since the density is high, the heat capacity becomes large, so the temperature rise can be suppressed. The density mentioned here is a value calculated based on the volume measured by the external dimensions of the honeycomb structure, without considering the internal cell structure and pores. Specifically, the lower limit of the density of the honeycomb structure is preferably 0.288g / cm 3 More preferably, 0.291 g / cm 3 More preferably, 0.294 g / cm 3 The upper limit of the density of the honeycomb structure is not particularly limited, but is preferably 0.410 g / cm 3 from the perspective of the cell structure and ease of manufacturing of the material. 3 Below, more preferably 0.382 g / cm 3 Below, more preferably 0.381 g / cm 3 Therefore, for example, the density of the honeycomb structure is preferably 0.288 to 0.410 g / cm 3 , more preferably 0.291 to 0.382 g / cm 3 , more preferably 0.294 to 0.381 g / cm 3 .

[0123] (1-4) Pressure loss tilt

[0124] If the change in pressure loss (pressure loss gradient) based on the amount of PM accumulated in the honeycomb structure is large, it is easy to detect the PM accumulation amount suitable for filter regeneration and cleaning using the pressure sensor.

[0125] Specifically, when the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 1 g / L, the pressure loss when exhaust gas at a temperature of 250°C and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P1.

[0126] When the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 3 g / L, the pressure loss when the exhaust gas at a temperature of 250°C and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P2.

[0127] It is preferred that 45%≤(P2-P1) / P1 be satisfied, more preferably 47%≤(P2-P1) / P1 be satisfied, and even more preferably 48%≤(P2-P1) / P1 be satisfied.

[0128] In addition, from the perspective of suppressing excessive pressure loss increase and ensuring practicality as a filter, it is preferred to satisfy (P2-P1) / P1≤66%, more preferably to satisfy (P2-P1) / P1≤63%, and even more preferably to satisfy (P2-P1) / P1≤61%.

[0129] Therefore, for example, the pressure loss gradient of the honeycomb structure preferably satisfies 45%≤(P2-P1) / P1≤66%, more preferably satisfies 47%≤(P2-P1) / P1≤63%, and further preferably satisfies 48%≤(P2-P1) / P1≤61%.

[0130] From the perspective of suppressing excessive pressure loss increase and ensuring practicality as a filter, the upper limit of P2 is preferably 3.69 kPa or less, more preferably 3.67 kPa or less, and even more preferably 3.65 kPa or less. From the perspective of improving the pressure loss slope, the lower limit of P2 is preferably 3.21 kPa or more, more preferably 3.49 kPa or more, and even more preferably 3.57 kPa or more.

[0131] (1-5) Material

[0132] From the perspective of obtaining excellent heat shock resistance, at least the partition walls, preferably the peripheral side walls and the partition walls, and more preferably the peripheral side walls, the partition walls and the sealing parts of the honeycomb structure contain one or more selected from cordierite, silicon carbide, silicon-silicon carbide composite materials, silicon nitride, mullite, alumina and aluminum titanate.

[0133] The outer peripheral sidewalls, partition walls, and plugging portions of the honeycomb structure may also contain ceramics other than those mentioned above. Examples of other ceramics include zirconium phosphate, cordierite-silicon carbide composites, zirconium oxide, spinel, India stone, sapphire, corundum, titanium dioxide, and cerium oxide. Furthermore, these other ceramics may be contained alone or in combination of two or more.

[0134] In the case where the honeycomb structure is mainly composed of cordierite, the lower limit of the cordierite content of the partition walls, preferably the outer side walls and the partition walls, more preferably the outer side walls, the partition walls and the plugging parts of the honeycomb structure is preferably 90% by mass or more, more preferably 91% by mass or more, and further preferably 92% by mass or more. The upper limit is not particularly set, but from the perspective of changing the characteristics of the honeycomb structure by adding other ceramics, the upper limit of the cordierite content of the partition walls, preferably the outer side walls and the partition walls, more preferably the outer side walls, the partition walls and the plugging parts of the honeycomb structure is preferably 96% by mass or less, more preferably 95% by mass or less, and further preferably 94% by mass or less. Therefore, in the case where the honeycomb structure is mainly composed of cordierite, the cordierite content of the partition walls, preferably the outer side walls and the partition walls, more preferably the outer side walls, the partition walls and the plugging parts of the honeycomb structure is, for example, preferably 90 to 96% by mass, more preferably 91 to 95% by mass, and further preferably 92 to 94% by mass.

[0135] The cordierite content can be measured by X-ray diffraction. Specifically, using an X-ray diffractometer utilizing Cu Kα radiation (e.g., X'pert PRO manufactured by Malvern Panalytical), X-ray analysis is performed within the range of 2θ = 8 to 100° on samples of the peripheral sidewalls, partition walls, or sealed portions. Analysis is performed using the Rietveld analysis program RIETAN to measure the cordierite crystal phase ratio, which is used as the cordierite content.

[0136] The honeycomb structure may be a honeycomb bonded body having a plurality of honeycomb sheets and a bonding layer for bonding the outer peripheral surfaces of the plurality of honeycomb sheets to each other. By using a honeycomb bonded body, the total cross-sectional area of ​​the compartments, which is important for ensuring the flow of air, can be increased while suppressing the generation of cracks. The bonding layer can be formed using a bonding material. The bonding material is not particularly limited, and a material prepared by adding a solvent such as water to a ceramic material to form a paste can be used. The bonding material may also contain the same material as the partition wall. In addition to having the function of bonding the honeycomb sheets to each other, the bonding material can also be used as a peripheral coating material after the honeycomb sheets are bonded.

[0137] In one embodiment, with respect to the sealing portions of the inlet end face and the outlet end face, the average depth of the sealing portions is 2 to 8 mm. By having an average depth of the sealing portions of 2 mm or more, the strength of the sealing portions can be ensured. The average depth of the sealing portions is preferably 3 mm or more. In addition, by making the average depth of the sealing portions 8 mm or less, the area of ​​the partition wall for capturing particulate matter in the compartment can be prevented from becoming smaller. The average depth of the sealing portions is preferably 7 mm or less. The depth of the sealing portion in the direction in which the compartment extends is measured at any 20 locations on each end face, and the average value is taken as the average depth of the sealing portion of each end face. The depth of each sealing portion refers to the length in the direction in which the compartment extends from the position of the inlet end face or the outlet end face where the sealing portion is formed to the deepest position where the sealing portion exists.

[0138] The honeycomb structure can also be used as a catalyst carrier. A catalyst corresponding to the purpose can be supported on the surface of the partition wall. The catalyst is preferably supported in the inlet compartment. The catalyst is not limited, and examples include oxidation catalysts (DOCs) for oxidizing and burning hydrocarbons (HC) and carbon monoxide (CO) to increase the exhaust gas temperature, PM combustion catalysts for assisting the combustion of PM such as soot, SCR catalysts and NSR catalysts for removing nitrogen oxides (NOx), and three-way catalysts that can simultaneously remove hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx). The catalyst may appropriately contain, for example, precious metals (Pt, Pd, Rh, etc.), alkali metals (Li, Na, K, Cs, etc.), alkaline earth metals (Mg, Ca, Ba, Sr, etc.), rare earths (Ce, Sm, Gd, Nd, Y, La, Pr, etc.), transition metals (Mn, Fe, Co, Ni, Cu, Zn, Sc, Ti, Zr, V, Cr, etc.), etc.

[0139] (2. Method for Manufacturing Honeycomb Structure)

[0140] Hereinafter, the manufacturing method of the columnar honeycomb structure body involved in one embodiment of the present invention will be illustrated. First, after the raw material composition containing cordierite raw material, pore-forming material, dispersion medium and adhesive is mixed and formed into adobe, the adobe is extruded to obtain a columnar honeycomb formed body with an outer peripheral side wall and a plurality of compartments, the plurality of compartments being arranged on the inner peripheral side of the outer peripheral side wall, extending from the inlet end face to the outlet end face, and the inlet end face and the outlet end face both have openings. Additives such as dispersants and other ceramic raw materials can be added as needed in the raw material composition. During extrusion molding, a mold with desired overall shape, compartment shape, compartment arrangement, wall thickness, compartment density, etc. can be used.

[0141] The so-called cordierite-forming raw material is a raw material that becomes cordierite by calcination and can be provided in the form of a powder, for example. The cordierite-forming raw material preferably has a chemical composition of 30-45% by mass of aluminum oxide (Al2O3) (including aluminum hydroxide converted to aluminum oxide), 11-17% by mass of magnesium oxide (MgO), and 42-57% by mass of silicon dioxide (SiO2).

[0142] Examples of the dispersion medium include water and a mixed solvent of water and an organic solvent such as alcohol, and water is particularly preferably used.

[0143] The content of the dispersion medium of the honeycomb formed body before the drying process is preferably 20 to 110 parts by weight, more preferably 25 to 100 parts by weight, and even more preferably 30 to 90 parts by weight relative to 100 parts by weight of the cordierite-forming raw material. By setting the content of the dispersion medium of the honeycomb formed body to 20 parts by weight or more relative to 100 parts by weight of the cordierite-forming raw material, the advantage of easily stabilizing the quality of the honeycomb structure can be easily obtained. By setting the content of the dispersion medium of the honeycomb formed body to 90 parts by weight or less relative to 100 parts by weight of the cordierite-forming raw material, the shrinkage during drying is reduced, and deformation can be suppressed. In this specification, the content of the dispersion medium of the honeycomb formed body refers to the value measured by the loss on drying method.

[0144] As a pore-forming material, there is no particular limitation as long as it is a material that becomes pores after calcination, and examples thereof include wheat flour, starch, foaming resin, water-absorbing resin, silica gel, carbon (e.g., graphite), ceramic balls, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic resin, phenol, etc. One pore-forming material can be used alone, or two or more can be used in combination. From the viewpoint of improving the porosity of the honeycomb structure after calcination, the content of the pore-forming material is preferably 3 parts by weight or more, more preferably 6 parts by weight or more, and further preferably 9 parts by weight or more relative to 100 parts by weight of the cordierite raw material. From the viewpoint of ensuring the strength of the honeycomb structure after calcination, the content of the pore-forming material is preferably 30 parts by weight or less, more preferably 27 parts by weight or less, and further preferably 24 parts by weight or less relative to 100 parts by weight of the cordierite raw material.

[0145] As the binder, organic binders such as methylcellulose, hydroxypropoxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, and polyvinyl alcohol can be exemplified. In addition, from the viewpoint of improving the strength of the honeycomb formed body before calcination, the content of the binder is preferably 4 parts by weight or more, more preferably 4.5 parts by weight or more, and further preferably 5 parts by weight or more, relative to 100 parts by weight of the cordierite raw material. From the viewpoint of suppressing the occurrence of cracking caused by abnormal heat in the calcination process, the content of the binder is preferably 9 parts by weight or less, more preferably 8 parts by weight or less, and further preferably 7 parts by weight or less, relative to 100 parts by weight of the cordierite raw material. One type of binder can be used alone, or two or more types can be used in combination.

[0146] Dispersants that can be used include ethylene glycol, dextrin, fatty acid soap, and polyether polyol. A single dispersant or a combination of two or more may be used. The content of the dispersant is preferably 0 to 2 parts by weight per 100 parts by weight of the cordierite-forming raw material.

[0147] The honeycomb formed body can be dried by conventionally known drying methods such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying. Among these, a drying method combining hot air drying with microwave drying or dielectric drying is preferred because it can quickly and uniformly dry the entire honeycomb formed body.

[0148] After the honeycomb formed body is dried, sealing portions are formed on both end surfaces of the honeycomb formed body. Each sealing portion can be formed by filling the openings of the inlet compartment and the outlet compartment where the sealing portion is to be formed with a slurry for forming the sealing portion, and then drying and calcining the filled slurry. The slurry for forming the sealing portion can use the material of the honeycomb formed body. Although not limited, for example, when the honeycomb formed body contains a cordierite-forming raw material, a pore-forming material, a dispersion medium, and a binder, the slurry for forming the sealing portion can contain a cordierite-forming raw material, a pore-forming material, a dispersion medium, and a binder.

[0149] Illustratively, the slurry for forming the plugging portion contains 30-60 parts by weight of the dispersion medium, 5-20 parts by weight of the pore-forming material, and 0.2-2.0 parts by weight of the binder per 100 parts by weight of the cordierite-forming raw material. In a preferred embodiment, the slurry for forming the plugging portion contains 35-50 parts by weight of the dispersion medium, 8-16 parts by weight of the pore-forming material, and 0.2-1.5 parts by weight of the binder per 100 parts by weight of the cordierite-forming raw material.

[0150] Examples of the dispersion medium include water and a mixed solvent of water and an organic solvent such as alcohol, and water is particularly preferably used.

[0151] The pore-forming material is not particularly limited as long as it forms pores after calcination. Examples thereof include wheat flour, starch, foamed resin, water-absorbent resin, silica gel, carbon (e.g., graphite), ceramic balls, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic resin, and phenol. The pore-forming material may be used alone or in combination of two or more.

[0152] Examples of the binder include organic binders such as methylcellulose, hydroxypropoxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, and polyvinyl alcohol. The binder may be used alone or in combination of two or more.

[0153] The slurry for forming the sealing portion may contain a dispersant as appropriate. Examples of the dispersant include ethylene glycol, dextrin, fatty acid soap, and polyols. The dispersant may be used alone or in combination of two or more.

[0154] The filling of the sealing portion forming slurry into the opening of the cell can be carried out, for example, by the following "scraper method". Figure 4 As shown, a film 121 is pasted on the upper end face (here, the outlet end face 106 in the figure) of the dried honeycomb formed body 400 fixed by a chuck 120, and a laser is irradiated at a position of the film 121 corresponding to the arrangement conditions of the sealing portion, and a plurality of holes 126 are drilled in the film 121.

[0155] Then, the slurry 124 for forming the sealing portion is placed on the film 121, and the scraper 122 is moved along the film 121 to form the sealing portion. Figure 4 Thus, a constant amount of the plugging portion forming slurry 124 is filled into the cells 125 opened at positions corresponding to the holes 126 of the membrane 121 .

[0156] The depth of the plugging portion can be changed depending on the number of movement operations of the squeegee 122 , the contact angle between the squeegee 122 and the film 121 , the pressing pressure of the squeegee 122 on the film 121 , and the viscosity of the plugging portion forming slurry 124 .

[0157] After filling with the plugging portion forming slurry 124, the film 121 is peeled off, and the entire honeycomb formed body 400 is dried. The plugging portion forming slurry 124 filled in the cells 125 is thereby dried, forming the plugging portions before firing. Drying can be performed, for example, at a drying temperature of 100 to 230°C for approximately 60 to 150 seconds. After drying, the plugging portions protrude from the end faces of the honeycomb formed body by an amount corresponding to the thickness of the film, and therefore can be shaved off as needed.

[0158] The material of the film is not particularly limited, but in order to facilitate the thermal processing for forming pores, polypropylene (PP), polyethylene terephthalate (PET), polyimide, or Teflon (registered trademark) is preferred. In addition, the film preferably has an adhesive layer, and the material of the adhesive layer is preferably an acrylic resin, a rubber-based material (e.g., a rubber mainly composed of natural rubber or synthetic rubber), or a silicone resin. A thin film can be suitably used, for example, an adhesive film with a thickness of 20 to 50 μm.

[0159] In addition to the above-mentioned "doctor blade method", as a method for filling the slurry for forming the sealing part into the opening part of the compartment, a "pressing method" can be cited. The "pressing method" is as follows: paste the film, immerse the end face of the honeycomb formed body provided with holes in a liquid tank storing the slurry for forming the sealing part, and fill the slurry for forming the sealing part into the compartment. In this case, the depth of the sealing part can be changed according to the depth of immersing the honeycomb formed body in the slurry for forming the sealing part.

[0160] The honeycomb formed body filled with the slurry for forming the sealing part is then subjected to a degreasing process and a calcination process to manufacture a honeycomb structure. The combustion temperature of the binder is about 200 °C, and the combustion temperature of the pore-forming material is about 300 to 1000 °C. Therefore, the degreasing process can be carried out by heating the honeycomb formed body to a range of about 200 to 1000 °C. The heating time is not particularly limited and is usually about 10 to 100 hours. The honeycomb formed body after the degreasing process is called a pre-sintered body. The calcination process also depends on the material composition of the honeycomb structure. For example, it can be carried out by heating the pre-sintered body to 1300 to​​​​​​​​​​​​​​​​​​​​To 100 parts by weight of a cordierite-forming raw material, 0.5 parts by weight of a pore-forming material, 1 part by weight of a dispersion medium, and 6 parts by weight of an organic binder were added, mixed, and kneaded to prepare an adobe. The cordierite-forming raw materials used were alumina, aluminum hydroxide, kaolin, talc, and silica. Water was used as the dispersion medium. Methylcellulose was used as the organic binder. A water-absorbent resin with a median particle size of 20 μm was used as the pore-forming material. The median particle size of the raw material refers to the particle size (D50) at which the cumulative value of the particle size distribution, as determined by laser diffraction / scattering, is 50%.

[0168] Next, the adobe was extruded and molded using a die used for a honeycomb forming body to obtain a honeycomb formed body having an overall cylindrical shape. The structure of the die varied depending on the test number.

[0169] Next, the honeycomb formed body was dried using a microwave dryer and further dried using a hot air dryer. Then, both end surfaces of the honeycomb formed body were cut and adjusted to a predetermined size.

[0170] Next, a slurry for forming the plugging portions is prepared using the same material as that used for the honeycomb formed body. This slurry is then used to form plugging portions at the openings of the predetermined cells on the inlet end face side of the dried honeycomb formed body and at the openings of the remaining cells on the outlet end face side, such that the inlet cells and the outlet cells are alternately adjacent to each other.

[0171] Next, the honeycomb formed body with each sealing portion formed thereon was degreased and calcined to manufacture the honeycomb structure involved in each test number. The inlet end face and the outlet end face of the honeycomb structure thus obtained were in the shape of a circular cylinder. The diameter of the inlet end face and the outlet end face was 228.6 mm. The length of the cell extension direction of the honeycomb structure was 184.2 mm. Except for the inlet cell adjacent to the outer peripheral side wall, the opening shape of the inlet cell was octagonal. Except for the discharge cell adjacent to the outer peripheral side wall, the opening shape of the discharge cell was square. The average depth of the sealing portion of the inlet end face and the outlet end face was about 7 mm. The number of honeycomb structures required to determine the following characteristics was prepared respectively.

[0172] (A2. Structural characteristics of honeycomb structure)

[0173] Table 1 shows the following structural characteristics of the honeycomb structures according to the test numbers manufactured above.

[0174] Compartment density

[0175] Average thickness of the partition wall

[0176] The average value D of the opening diameters of the plurality of inlet compartments, excluding the inlet compartment adjacent to the peripheral side wallin

[0177] The average value D of the opening diameters of the plurality of discharge compartments, excluding the discharge compartments adjacent to the peripheral side wall out

[0178] ·Opening diameter ratio (D in / D out )

[0179] Average porosity of the partition wall

[0180] The ratio of the number of inlet compartments to the number of outlet compartments

[0181] Density (mass of honeycomb structure divided by overall dimensions)

[0182] The cell density refers to the cell density based on the total number of inlet cells and outlet cells, and is measured according to the above method.

[0183] The average thickness of the partition walls is measured by observation with a scanning electron microscope (SEM) or using a microscope.

[0184] The opening diameter of each of the introduction cell and the discharge cell is observed using a scanning electron microscope (SEM) or calculated using a microscope.

[0185] Based on the opening diameters of all the discharge compartments except the discharge compartments adjacent to the outer peripheral side wall among the plurality of discharge compartments, an average value D is calculated. out .

[0186] Based on the opening diameters of all the introduction cells except the introduction cells adjacent to the outer peripheral side wall among the plurality of introduction cells, the average value D is calculated. in .

[0187] The porosity of the cell walls was measured by the above-mentioned mercury intrusion method using Autopore 9500 (trade name) manufactured by Micromeritics.

[0188] The ratio of the number of introduction cells to the number of discharge cells was calculated by visually counting the number of discharge cells and the number of introduction cells.

[0189] (A3. Functional characteristics of honeycomb structure)

[0190] The honeycomb structures corresponding to the test numbers prepared above were used as exhaust gas filters, and the following characteristics were evaluated.

[0191] [Pressure loss characteristics]

[0192] An exhaust gas filter was mounted on the exhaust system of a diesel engine with a displacement of 13 liters, and a test was conducted to accumulate soot on the filter. In addition, when soot was accumulating, the fuel injection pressure was reduced in a way that easily generated soot, and the engine was operated under low-temperature conditions where the exhaust gas temperature at the inlet of the filter was less than 280 °C so that the soot did not burn. The pressure loss at the start of the test (before soot accumulation) (initial pressure loss), the pressure loss (P1) when the soot accumulation amount per 1 L of filter volume (g) was 1 g / L, and the pressure loss (P2) when the soot accumulation amount per 1 L of filter volume (g) was 3 g / L were measured. When measuring the pressure loss, the engine output was increased, and the pressure loss was measured when exhaust gas at a temperature of 250 °C and a flow rate of 480 kg / hr passed from the inlet end face to the outlet end face of the filter. The results are shown in Table 1.

[0193] Based on Comparative Example 1, which is a representative example of the honeycomb structure related to the prior art, all the pass criteria for the pressure loss characteristics satisfy the following conditions.

[0194] The initial pressure loss is less than 1.17 kPa;

[0195] The pressure loss (P1) when the soot accumulation amount is 1 g / L is 2.61 kPa or less; the pressure loss (P2) when the soot accumulation amount is 3 g / L is 3.69 kPa or less; (P2 - P1) / P1, which is an index of the pressure loss slope, is 45% or more.

[0196] [Table 1]

[0197]

[0198] [Discussion]

[0199] The combinations of the compartment density, the average thickness of the partition walls, and the opening diameter ratio in Comparative Examples 1-1 to 1-9 were inappropriate. As a result, the pressure loss became too large, the pressure loss slope was small, and the density decreased (heat capacity decreased). In contrast, in Examples 1-1 to 1-11, the combinations of the compartment density, the average thickness of the partition walls, and the opening diameter ratio were appropriate. Therefore, the initial pressure loss and the pressure loss during soot accumulation did not increase excessively. On the other hand, a large pressure loss slope was obtained. In addition, a practical heat capacity was obtained in view of the density.

[0200] <B. Second Embodiment>

[0201] (B1. Manufacture of Honeycomb Structure)

[0202] [Honeycomb Structures Made of Cordierite: Examples 2-1 to 2-¹⁰, Comparative Examples 2-1 to 2-7]

[0203] To 100 parts by weight of a cordierite-forming raw material, 0.5 parts by weight of a pore-forming material, 1 part by weight of a dispersion medium, and 6 parts by weight of an organic binder were added, mixed, and kneaded to prepare an adobe. The cordierite-forming raw materials used were alumina, aluminum hydroxide, kaolin, talc, and silica. Water was used as the dispersion medium. Methylcellulose was used as the organic binder. A water-absorbent resin with a median particle size of 20 μm was used as the pore-forming material. The median particle size of the raw material refers to the particle size (D50) at which the cumulative value of the particle size distribution, as determined by laser diffraction / scattering, is 50%.

[0204] Next, the adobe was extruded and molded using a die used for a honeycomb forming body to obtain a honeycomb formed body having an overall cylindrical shape. The structure of the die varied depending on the test number.

[0205] Next, the honeycomb formed body was dried using a microwave dryer and further dried using a hot air dryer. Then, both end surfaces of the honeycomb formed body were cut and adjusted to a predetermined size.

[0206] Next, a slurry for forming the plugging portions is prepared using the same material as that used for the honeycomb formed body. This slurry is then used to form plugging portions at the openings of the predetermined cells on the inlet end face side of the dried honeycomb formed body and at the openings of the remaining cells on the outlet end face side, such that the inlet cells and the outlet cells are alternately adjacent to each other.

[0207] Next, the honeycomb formed body with each sealing portion formed thereon was degreased and calcined to manufacture the honeycomb structure involved in each test number. The inlet end face and the outlet end face of the honeycomb structure thus obtained were in the shape of a circular cylinder. The diameter of the inlet end face and the outlet end face was 228.6 mm. The length of the cell extension direction of the honeycomb structure was 184.2 mm. Except for the inlet cell adjacent to the outer peripheral side wall, the opening shape of the inlet cell was octagonal. Except for the discharge cell adjacent to the outer peripheral side wall, the opening shape of the discharge cell was square. The average depth of the sealing portion of the inlet end face and the outlet end face was about 7 mm. The number of honeycomb structures required to determine the following characteristics was prepared respectively.

[0208] (B2. Structural characteristics of honeycomb structure)

[0209] Table 2 shows the following structural characteristics of the honeycomb structures according to the test numbers manufactured above.

[0210] Compartment density

[0211] Average thickness of the partition wall

[0212] The average value D of the opening diameters of the plurality of inlet compartments, excluding the inlet compartment adjacent to the peripheral side wallin

[0213] The average value D of the opening diameters of the plurality of discharge compartments, excluding the discharge compartments adjacent to the peripheral side wall out

[0214] ·Opening diameter ratio (D in / D out )

[0215] Average porosity of the partition wall

[0216] The ratio of the number of inlet compartments to the number of outlet compartments

[0217] Average pore size

[0218] Density (mass of honeycomb structure divided by overall dimensions)

[0219] The cell density refers to the cell density based on the total number of inlet cells and outlet cells, and is measured according to the above method.

[0220] The average thickness of the partition walls is measured by observation with a scanning electron microscope (SEM) or using a microscope.

[0221] The opening diameter of each of the introduction cell and the discharge cell is observed using a scanning electron microscope (SEM) or calculated using a microscope.

[0222] Based on the opening diameters of all the discharge compartments except the discharge compartments adjacent to the outer peripheral side wall among the plurality of discharge compartments, an average value D is calculated. out .

[0223] Based on the opening diameters of all the introduction cells except the introduction cells adjacent to the outer peripheral side wall among the plurality of introduction cells, the average value D is calculated. in .

[0224] The porosity of the cell walls was measured by the above-mentioned mercury intrusion method using Autopore 9500 (trade name) manufactured by Micromeritics.

[0225] The ratio of the number of introduction cells to the number of discharge cells was calculated by visually counting the number of discharge cells and the number of introduction cells.

[0226] The average pore diameter of the cell walls was measured by the above-mentioned mercury intrusion method using Autopore 9500 (trade name) manufactured by Micromeritics.

[0227] (B3. Functional characteristics of honeycomb structure)

[0228] The honeycomb structures corresponding to the test numbers prepared above were used as exhaust gas filters, and the same pressure loss characteristics as those of the honeycomb structures of Example 1-1 and the like were examined.

[0229] [Table 2]

[0230]

[0231] [Investigation]

[0232] Comparative Examples 2-1 to 2-7 have inappropriate combinations of cell density, average wall thickness, opening diameter ratio, and average wall porosity. Consequently, the pressure loss becomes excessively large, the pressure loss slope is small, and the density decreases (heat capacity decreases). In contrast, Examples 2-1 to 2-10 have appropriate cell density, wall thickness, opening diameter ratio, and the like. Therefore, the initial pressure loss and the pressure loss during soot accumulation do not increase excessively, while a large pressure loss slope is obtained. Furthermore, a practical heat capacity is achieved given the density.

[0233] Explanation of symbols

[0234] 100—honeycomb structure; 102—outer peripheral side wall; 104—inlet end face; 106—outlet end face; 107—opening; 108—introduction compartment; 109—sealing portion; 110—discharge compartment; 112—partition wall; 120—chuck; 121—membrane; 122—scraper; 124—slurry for forming the sealing portion; 125—compartment; 126—hole; 400—honeycomb formed body.

Claims

1. A columnar honeycomb structure comprising: peripheral sidewall; a plurality of inlet compartments arranged on the inner circumference side of the outer circumferential side wall, extending from the inlet end face to the outlet end face, having an opening at the inlet end face and a sealing portion at the outlet end face; and A plurality of discharge compartments are arranged on the inner peripheral side of the outer peripheral side wall, extending from the inlet end face to the outlet end face, having a sealing portion at the inlet end face and an opening at the outlet end face, The honeycomb structure is characterized in that At least some of the plurality of inlet cells are adjacent to at least some of the plurality of outlet cells via a partition wall. The compartment density based on the total number of the plurality of inlet compartments and the plurality of outlet compartments is 29 to 43 compartments / cm 2 , The average thickness of the partition walls is 0.173 mm or more and 0.236 mm or less, If the average opening diameter of the discharge cells other than the discharge cells adjacent to the outer peripheral side wall among the plurality of discharge cells is set as D out The average opening diameter of the plurality of introduction compartments except the introduction compartments adjacent to the outer peripheral side wall is set as D in , then 1.20≤D in / D out ≤1.

38.

2. The honeycomb structure according to claim 1, wherein The average opening diameter D of each of the plurality of introduction compartments, excluding the introduction compartment adjacent to the outer peripheral side wall, is in is 1.48mm or more and 1.80mm or less, The average value D of the opening diameters of the plurality of discharge compartments, excluding the discharge compartments adjacent to the outer peripheral side wall, is out It is 1.16 mm or more and 1.48 mm or less.

3. The honeycomb structure according to claim 1 or 2, characterized in that The average porosity of the partition walls is 52 to 60%.

4. The honeycomb structure according to claim 1 or 2, characterized in that The density measured according to the external dimensions is 0.288~0.410g / cm 3 .

5. The honeycomb structure according to claim 1 or 2, characterized in that: The ratio of the number of the plurality of inlet compartments excluding the inlet compartments adjacent to the outer peripheral side wall to the number of the plurality of outlet compartments excluding the outlet compartments adjacent to the outer peripheral side wall is 0.9 to 1.

1.

6. The honeycomb structure according to claim 1 or 2, characterized in that: If the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 1 g / L, the pressure loss when the exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P1, When the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 3 g / L, the pressure loss when exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P2. Then 45%≤(P2-P1) / P1 is satisfied.

7. The honeycomb structure according to claim 1 or 2, characterized in that: The partition walls contain cordierite.

8. A columnar honeycomb structure comprising: peripheral sidewall; a plurality of inlet compartments arranged on the inner circumference side of the outer circumferential side wall, extending from the inlet end face to the outlet end face, having an opening at the inlet end face and a sealing portion at the outlet end face; and A plurality of discharge compartments are arranged on the inner peripheral side of the outer peripheral side wall, extending from the inlet end face to the outlet end face, having a sealing portion at the inlet end face and an opening at the outlet end face, The honeycomb structure is characterized in that At least some of the plurality of inlet cells are adjacent to at least some of the plurality of outlet cells via a partition wall. The compartment density based on the total number of the plurality of inlet compartments and the plurality of outlet compartments is 29 to 36 compartments / cm 2 , The average thickness of the partition walls is 0.231 mm or more and 0.312 mm or less, If the average opening diameter of the discharge cells other than the discharge cells adjacent to the outer peripheral side wall among the plurality of discharge cells is set as D out The average opening diameter of the plurality of introduction compartments except the introduction compartments adjacent to the outer peripheral side wall is set as D in , then 1.14≤D in / D out ≤1.37, The average porosity of the partition walls is 57 to 63%.

9. The honeycomb structure according to claim 8, wherein The average opening diameter D of each of the plurality of introduction compartments, excluding the introduction compartment adjacent to the outer peripheral side wall, is in is 1.52mm or more and 1.76mm or less, The average value D of the opening diameters of the plurality of discharge compartments, excluding the discharge compartments adjacent to the outer peripheral side wall, is out It is 1.20 mm or more and 1.44 mm or less.

10. The honeycomb structure according to claim 8 or 9, characterized in that: The average pore diameter of the partition walls is 7 to 13 μm.

11. The honeycomb structure according to claim 8 or 9, characterized in that: The density measured according to the external dimensions is 0.288~0.410g / cm 3 .

12. The honeycomb structure according to claim 8 or 9, characterized in that: The ratio of the number of the plurality of inlet compartments excluding the inlet compartments adjacent to the outer peripheral side wall to the number of the plurality of outlet compartments excluding the outlet compartments adjacent to the outer peripheral side wall is 0.9 to 1.

1.

13. The honeycomb structure according to claim 8 or 9, characterized in that: If the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 1 g / L, the pressure loss when the exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P1, When the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 3 g / L, the pressure loss when exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P2. Then 45%≤(P2-P1) / P1 is satisfied.

14. The honeycomb structure according to claim 8 or 9, characterized in that: The partition walls contain cordierite.

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