CN219333565U

CN219333565U - Honeycomb filter

Info

Publication number: CN219333565U
Application number: CN202223349520.2U
Authority: CN
Inventors: 大根田乔洋
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2022-12-14
Filing date: 2022-12-14
Publication date: 2023-07-14
Anticipated expiration: 2032-12-14

Abstract

The utility model provides a honeycomb filter which has excellent corrosion resistance and excellent thermal shock resistance. The honeycomb filter is provided with: a columnar honeycomb structure having porous partition walls arranged to surround a plurality of cells; and a porous sealing portion disposed at one end of the cells, wherein an average sealing length of a central portion of the end face of the honeycomb structure is 5mm or more and 10mm or less, an average sealing length of an outer peripheral portion outside the central portion is 2mm or more and less than 5mm, a difference DeltaL between the average sealing length and the average sealing length is 2 to 6mm, a ratio of an average radius R of the central portion to an equivalent circle radius D of the end face of the honeycomb structure is 0.2 to 0.5, and in an electron microscope image of the sealing portion, the sealing portion is composed of a plurality of particles, and an equivalent circle diameter of each particle constituting the sealing portion is 2 to 6mmThe average value of (3) to (5) mu m, and the particle density of the hole sealing part is 750 to 1250/mm ² 。

Description

Honeycomb filter

Technical Field

The present utility model relates to a honeycomb filter. More specifically, the present utility model relates to a honeycomb filter having excellent corrosion resistance and excellent thermal shock resistance.

Background

Conventionally, as a filter for trapping particulate matter in exhaust gas discharged from an internal combustion engine such as an engine of an automobile or a device for purifying toxic gas components such as CO, HC, NOx, a honeycomb filter using a honeycomb structure has been known (see patent document 1). The honeycomb structure has partition walls made of porous ceramics such as cordierite, and a plurality of cells are partitioned by the partition walls. The honeycomb filter is configured by arranging the plugging portions in such a manner that the openings on the inflow end face side and the openings on the outflow end face side of the plurality of cells are alternately closed with respect to the honeycomb structure. That is, the honeycomb filter is formed in the following configuration: the inflow cells having an opening on the inflow end face side and a closed outflow end face side, and the outflow cells having a closed inflow end face side and an opening on the outflow end face side are alternately arranged with partition walls interposed therebetween. In the honeycomb filter, the porous partition walls function as a filter for trapping particulate matter in the exhaust gas. Hereinafter, particulate matter contained in the exhaust gas may be referred to as "PM". "PM" is an abbreviation for "particulate matter".

Patent document 1: japanese patent laid-open No. 2020-163286

Disclosure of Invention

The damage to the honeycomb filter during use includes abrasion (erosion). Abrasion refers to: a phenomenon in which foreign matter such as welding spatter or abrasion powder of an engine collides with the honeycomb filter with the air flow, and the inlet end face of the honeycomb filter is abraded. As a countermeasure against such abrasion, studies have been made: measures such as increasing the length of the plugged portions disposed on the end surfaces of the honeycomb filter, or reducing the porosity of the plugged portions are taken.

However, if the length of the plugged portion is increased or the porosity of the plugged portion is decreased in order to improve the resistance to abrasion, there is a problem as follows: the heat capacity of the honeycomb filter increases and Light-off performance (Light-off performance) deteriorates. Further, the light-off performance means: the temperature characteristics of the purification performance of the exhaust gas purification catalyst supported on the honeycomb filter can be exhibited.

In addition, during use of the honeycomb filter, PM such as soot may accumulate in partition walls that partition cells forming flow paths for exhaust gas, and thus the flow paths may be blocked, resulting in deterioration of fuel efficiency. Therefore, the honeycomb filter is sometimes subjected to periodic operations: regeneration treatment for burning and removing PM deposited on the partition wall. By performing such a regeneration treatment of the honeycomb filter, clogging of the flow path can be eliminated, and deterioration of fuel consumption can be improved. However, there is a limit to the extension of the time interval because thermal shock is applied during the regeneration process. In particular, if the length of the plugged portion is increased as a countermeasure against abrasion as described above, the influence of thermal expansion of the plugged portion during the regeneration treatment may be increased, and the thermal shock resistance of the honeycomb filter may be lowered.

As described above, with respect to the conventional honeycomb filter, there is a two-way relationship between improvement of corrosion resistance and improvement of thermal shock resistance, and it is difficult to solve both of these problems. Accordingly, it is desired to develop a honeycomb filter which has excellent corrosion resistance and is resistant to a large thermal shock.

The present utility model has been made in view of the above-described problems occurring in the prior art. According to the present utility model, there is provided a honeycomb filter excellent in corrosion resistance and thermal shock resistance.

According to the present utility model, there is provided a honeycomb filter shown below.

[1] A honeycomb filter is provided with:

a columnar honeycomb structure having porous partition walls arranged to surround a plurality of cells formed as flow paths for a fluid extending from an inflow end face to an outflow end face; and

a plurality of hole sealing parts which are arranged at one of the end part of the compartment on the inflow end surface side and the end part of the compartment on the outflow end surface side,

the porosity of the hole sealing part is 40-60%,

the honeycomb structure is provided with an end on the inflow end face side or an end on the outflow end face side at a central portion side: a central hole sealing portion having a hole sealing length L of 5mm or more in a direction in which the cells extend, and an outer peripheral portion of the end portion on the outer side of the central portion, the central portion being disposed: an outer Zhou Fengkong part of the plugging part having a plugging length L of less than 5mm,

Average sealing length L1, which is the average value of sealing length L of the central portion _(Ave) Is 5mm to 10mm,

average sealing length L2, which is the average value of sealing length L of the outer peripheral portion _(Ave) Is more than 2mm and less than 5mm,

the average pore-sealing length L1 of the central part _(Ave) Average pore-sealing length L2 with the outer peripheral portion _(Ave) The difference delta L is 2-6 mm,

the average radius R of the central portion is 0.2 to 0.5 in terms of the ratio (R/D) of the equivalent circle radius D of the end face of the honeycomb structure,

in an electron microscope image of the hole sealing portion, the hole sealing portion is composed of a plurality of particles, an average value of equivalent circle diameters of each of the particles is 3 to 5 μm, and a particle density of the hole sealing portion is 750 to 1250 particles/mm ² 。

[2] The honeycomb filter according to [1], wherein the porosity of the partition walls is 60 to 70%.

[3] The honeycomb filter according to [1] or [2], wherein the thickness of the partition wall is 0.1 to 0.3mm.

Effects of the utility model

The honeycomb filter of the present utility model can achieve the effects of excellent corrosion resistance and excellent thermal shock resistance.

Drawings

Fig. 1 is a perspective view schematically showing one embodiment of the honeycomb filter of the present utility model.

Fig. 2 is a plan view showing the inflow end face side of the honeycomb filter shown in fig. 1.

Fig. 3 is a plan view showing the outflow end face side of the honeycomb filter shown in fig. 1.

Fig. 4 is a cross-sectional view schematically showing a section A-A' of fig. 2.

Fig. 5 is an explanatory view for explaining a method of measuring the plugging length of the plugging portion, and is a schematic view showing the inflow end face side of the honeycomb filter.

Description of the reference numerals

1: partition wall, 2: compartment, 2a: inflow compartment, 2b: outflow compartment, 3: peripheral wall, 4: honeycomb structure, 5: hole sealing portion, 5a: central hole sealing portion, 5b: outer Zhou Fengkong part, 11: end face (inflow end face), 12: end face (outflow end face), 15: center portion, 16: outer peripheral portion, 100: honeycomb filter, D: equivalent circle radius (equivalent circle radius of end face of honeycomb structure), L, L1, L2: hole sealing length, R: average radius (average radius of the central portion).

Detailed Description

Hereinafter, embodiments of the present utility model will be described, but the present utility model is not limited to the following embodiments. Thus, it should be understood that: the present utility model is also intended to be applicable to any other embodiments, including those in which alterations, modifications, and the like are appropriately made to the following embodiments based on common knowledge within the scope of the present utility model.

(1) Honeycomb filter:

one embodiment of the honeycomb filter of the present utility model is a honeycomb filter 100 as shown in fig. 1-4. Here, fig. 1 is a perspective view schematically showing one embodiment of the honeycomb filter of the present utility model. Fig. 2 is a plan view showing the inflow end face side of the honeycomb filter shown in fig. 1, and fig. 3 is a plan view showing the outflow end face side of the honeycomb filter shown in fig. 1. Fig. 4 is a cross-sectional view schematically showing a section A-A' of fig. 2.

As shown in fig. 1 to 4, the honeycomb filter 100 of the present embodiment includes a honeycomb structure 4 and a plugged portion 5. The honeycomb structural body 4 is: a columnar structure having porous partition walls 1 arranged to surround a plurality of cells 2, wherein the plurality of cells 2 are formed as: a flow path for fluid extending from one end face 11 to the other end face 12. The honeycomb structure 4 of the honeycomb filter 100 has a columnar shape and has an outer peripheral wall 3 on its outer peripheral side surface. That is, the outer peripheral wall 3 is disposed so as to surround the partition wall 1, and the partition wall 1 is disposed in a lattice shape. Hereinafter, the honeycomb structure 4 and the one end face 11 of the honeycomb filter 100 are sometimes referred to as "inflow end face 11", for example. The other end face 12, which is the other end face of the honeycomb structure 4 and the honeycomb filter 100, is sometimes referred to as an "outlet end face 12", for example.

The hole sealing portion 5 is disposed in an opening portion of each cell 2 on the inflow end face 11 side or the outflow end face 12 side. In the honeycomb filter 100 shown in fig. 1 to 4, the plugging portions 5 are disposed in the openings of the end portions of the predetermined cells 2 on the inflow end face 11 side and the openings of the end portions of the remaining cells 2 on the outflow end face 12 side. A hole sealing portion 5 is disposed in an opening portion on the outflow end face 12 side, and the compartment 2 opened on the inflow end face 11 side is set as an inflow compartment 2a. The hole sealing portion 5 is disposed in the opening portion on the inflow end face 11 side, and the compartment 2 opened on the outflow end face 12 side is set as the outflow compartment 2b. The inflow cells 2a and the outflow cells 2b are preferably alternately arranged with the partition wall 1 interposed therebetween. In addition, it is preferable to form a mesh pattern on both end surfaces of the honeycomb filter 100 by using the plugged portions 5 and the "openings of the cells 2" in this way.

The honeycomb structural body 4 includes, in a cross section orthogonal to a direction in which the cells 2 extend: a central portion 15 including a center of gravity O of the cross section; and an outer peripheral portion 16 located outside the central portion 15. For example, as shown in fig. 2 and 3, a range including the center of gravity O of the cross section of the honeycomb structure 4 and extending from the center of gravity O to the outer periphery to a certain extent is "central portion 15", and a range on the outer periphery side of the central portion 15 is "outer periphery 16".

The honeycomb filter 100 of the present embodiment has particularly main characteristics with respect to the value of the porosity of the plugged portions 5 and the structure of the plugged portions 5 of the central portion 15 and the outer peripheral portion 16. That is, the porosity of the plugged portion 5 of the honeycomb filter 100 of the present embodiment is 40 to 60%. The honeycomb structure 4 is disposed on the center portion 15 side of the end on the inflow end face 11 side or the end on the outflow end face 12 side: a central sealing portion 5a having a sealing length L1 of 5mm or more in the direction in which the cells 2 extend as the sealing portion 5. Further, an outer peripheral portion 16 side of the end portion of the honeycomb structure 4, which is further outside than the central portion 15, is disposed: an outer Zhou Fengkong part 5b serving as the sealing part 5, the sealing length L2 of which in the direction in which the cells 2 extend is smaller than 5 mm. Hereinafter, the length L of the plugging portion 5 in the direction in which the cells 2 extend may be simply referred to as "plugging length L" of the plugging portion 5. In addition, the sealing length L of the central sealing portion 5a is sometimes referred to as "sealing length L1", and the sealing length L of the outer Zhou Fengkong portion 5b is sometimes referred to as "sealing length L2". That is, the central hole sealing portion 5a is: the sealing part 5 having a sealing length L1 of 5mm or more, and the outer Zhou Fengkong part 5b is: and a sealing part 5 with a sealing length L2 smaller than 5 mm.

Regarding the central portion 15, an average sealing length L1, which is an average value of sealing lengths L of the sealing portions 5 existing in the central portion 15 _(Ave) 5mm to 10 mm. On the other hand, regarding the outer peripheral portion 16, the average sealing length L2, which is the average value of the sealing lengths L of the sealing portions 5 existing in the outer peripheral portion 16 _(Ave) Is more than 2mm and less than 5mm. Further, the average sealing length L1 of the central portion 15 _(Ave) Average sealing length L2 with outer peripheral portion 16 _(Ave) The difference DeltaL is 2-6 mm.

In the honeycomb filter 100 of the present embodiment, the ratio (R/D) of the average radius R of the central portion 15 to the equivalent circle radius D of the end surface of the honeycomb structure 4 is 0.2 to 0.5. The equivalent circle radius D of the end face of the honeycomb structure 4 can be obtained from the square root of the value obtained by dividing the area a of the end face of the honeycomb structure 4 by the circumferential rate pi (i.e., d= v (a/pi)).

The microstructure of the hole sealing portion 5 including the central hole sealing portion 5a and the outer peripheral hole sealing portion 5b has the following structure. That is, in the electron microscope image of the hole sealing portion 5, the hole sealing portion 5 is composed of a plurality of particles, the average value of the equivalent circle diameters of the respective particles is 3 to 5 μm, and the particle density of the hole sealing portion 5 is 750 to 1250 particles/mm ² 。

The honeycomb filter 100 according to the present embodiment configured as described above has the advantages of excellent corrosion resistance and excellent thermal shock resistance.

As described above, the honeycomb filter 100 of the present embodiment is provided in the central portion 15 of each end portion on the end face side of the honeycomb structure 4: a central sealing portion 5a having a relatively long sealing length. Since the central portion 15 of the honeycomb structure 4 generates more heat during the regeneration process than the outer peripheral portion 16 located outside the central portion 15, the central plugged portion 5a having a relatively large plugging length and a relatively large volume is disposed in the central portion 15, thereby improving the thermal shock resistance of the honeycomb filter 100. Further, the central portion 15 of the honeycomb structure 4 is more likely to cause abrasion than the outer peripheral portion 16, and therefore, the corrosion resistance can be improved by the central plugged portion 5a having a longer plugging length. On the other hand, since the thermal stress generated in the outer Zhou Fengkong portion 5b having a relatively short plugging length is small, it is difficult to cause breakage such as cracking (crack) on the outer peripheral portion 16 side of the honeycomb structure 4 by disposing such an outer peripheral plugging portion 5b in the outer peripheral portion 16. For example, occurrence of cracks in the end face of the honeycomb structural body 4 on the outer peripheral portion 16 side, cracks in the outer peripheral wall 3 (for example, an outer peripheral coating layer described later) of the honeycomb structural body 4, or the like can be effectively suppressed.

For example, if the average sealing length L1 of the central portion 15 _(Ave) Average sealing length L2 of outer peripheral portion 16 _(Ave) When the values are out of the above-described numerical ranges, the effects described above may not be sufficiently exhibited. In addition, average pore sealing length L1 _(Ave) And average hole sealing length L2 _(Ave) The same applies when the difference Δl is outside the above-mentioned numerical ranges. In order to effectively exhibit the effects described above, it is also important that the ratio (R/D) of the average radius R of the central portion 15 to the equivalent circle radius D of the end surface of the honeycomb structure 4 is 0.2 to 0.5. Hereinafter, the ratio (R/D) of the average radius R of the central portion 15 to the equivalent circle radius D of the end surface of the honeycomb structure 4 may be referred to as "average radius ratio (R/D) of the central portion 15". If the average radius ratio (R/D) of the central portion 15 is less than 0.2, the number of the central hole-sealing portions 5a may be too small, and sufficient thermal shock resistance and corrosion resistance may not be obtained. On the other hand, if the average radius ratio (R/D) of the central portion 15 exceeds 0.5, the number of the outer Zhou Fengkong portions 5b is too small, and an effect of sufficiently suppressing the occurrence of cracks may not be obtained.

The porosity of the plugged portion 5 of the honeycomb filter 100 of the present embodiment is 40 to 60%, and the plugged portion 5 is formed to have a relatively dense structure. The porosity of the hole sealing portion 5 is set to 40 to 60%, whereby corrosion resistance can be improved. If the porosity of the sealing portion 5 is less than 40%, the thermal stress generated in the sealing portion 5 increases, which is not preferable.

The hole sealing portion 5 is formed in an electron microscope image thereof as: a porous body having a microstructure composed of a plurality of particles. In particular, the plugging portion 5 is constituted by a plurality of particles in an electron microscope image, and the particle density thereof is 750 to 1250 particles/mm ² . In the plugging portion 5, the average value of the equivalent circle diameters of the particles constituting the plugging portion 5 is 3 to 5 μm. The "average value of equivalent circle diameters of the respective particles" means: an arithmetic average value obtained by dividing the number of particles by the sum of the respective equivalent circle diameters of each particle. By configuring as described above, the gaps between the particles constituting the plugging portions 5 can be formed as buffer spaces, and thermal expansion during the regeneration process can be relaxed, and the occurrence of cracks and the like on the end surface of the honeycomb structure 4 and the outer peripheral wall 3 side can be effectively suppressed. For example, the plugging portion 5 composed of a plurality of particles is preferably: an unsintered body in which the plurality of particles are unsintered. Since the plugged portion 5 of the unfired material does not shrink during firing, the residual stress in the manufacturing process is smaller than that in the structure of the fired material. Such a plugged portion 5 having a small residual stress is more unlikely to cause cracking on the end face of the honeycomb structure 4 or on the outer peripheral wall 3 side.

The porosity of the plugging portion 5 and the microstructure can be measured by the following method.

First, a sample for measurement is cut out from the plugging portion 5 to be measured. Specifically, a sample for measurement was obtained by cutting the honeycomb structure 4 in a range of 15mm×15mm in length and width centered on the center of gravity of the end face 11, that is, from the end face 11 to 15mm in the depth direction, and a cube having 15mm sides each. The hole sealing portion 5 included in the sample for measurement is set as a measurement object.

Next, the hole sealing portion 5 existing in the cross section of the obtained measurement sample was photographed by a scanning electron microscope (hereinafter also referred to as "SEM"), whereby an SEM image of 100 times magnification was obtained. "SEM" is an abbreviation for "Scanning Electron Microscope". SEM images were set as: 1 pixel is an image of 0.992 μm in the vertical direction by 0.992 μm in the horizontal direction. As the scanning electron microscope, for example, a scanning electron microscope model "manufactured by hitachi high technology corporation may be used: S-3400N). The SEM image obtained in the above manner was subjected to image analysis by two-dimensional image analysis software (product name: windof, manufactured by three-cereal business). The threshold values were set to 0.000 and 35.000, and the transparency was set to 127, as conditions for image analysis. Regarding an analysis mode of windof (trade name), an analysis item of "shape feature" is selected on the basis of setting "black-white inversion".

This can calculate: particle area and particle density of particles constituting the plugging portion 5 in the SEM image. The porosity of the plugging portion 5 can be calculated by calculating the area of the void portion other than the particles in the SEM image and calculating the area ratio of the void portion in the SEM image. Further, for SEM images of 5 fields, the following was performed: based on analysis of SEM images of the plugging portion 5, the following was obtained: average value of analysis results for each of 3 fields except for the maximum value and the minimum value in the measurement results.

The plugging length of the plugging portion 5 can be measured by the following method. That is, the sealing length L1 of the central sealing portion 5a and the sealing length L2 of the outer peripheral sealing portion 5b, and the average sealing length L1 of the central portion 15 and the outer peripheral portion 16 described so far _(Ave) Average hole sealing length L2 _(Ave) The method comprises the following steps: the obtained values were measured by the following measurement methods. Here, fig. 5 is an explanatory view for explaining a method of measuring the plugging length of the plugging portion 5 (see fig. 2, the same applies hereinafter), and is a schematic view showing the inflow end face 11 side of the honeycomb filter 100. In fig. 5, the partition walls 1 (see fig. 2) and the cells 2 (see fig. 2) on the inflow end face 11 of the honeycomb filter 100 are omitted. In the following description, the "inlet end face 11" of the honeycomb filter 100 may be simply referred to as "end face 11" of the honeycomb filter 100.

When the plugging length of the plugged portion (see fig. 2) is measured, the plugging length is measured in the cross direction starting from the center of gravity O of the end face 11 of the honeycomb filter 100 shown in fig. 5. Here, "center of gravity O" of the end face 11 of the honeycomb filter 100 means: the geometrically defined center of gravity (in other words, the geometric center) of the end face 11. A more specific method for measuring the pore sealing length is as follows. First, as measurement points, 10 equally divided in the radial direction from the center of gravity O of the end face 11 to the outer periphery is set, and a total of 40 points in 4 directions of the 12-point direction, the 3-point direction, the 6-point direction, and the 9-point direction are set. In fig. 5, the measurement points of 10 points in each radial direction are indicated by circled numerals from 1 to 10. Further, the measurement points of the center of gravity O (i.e., the measurement points of the circled number 1 in fig. 5) overlap as the measurement points in the respective radial directions. At the thus set measurement points of 40 points: the sealing lengths of the sealing portions 5 (see fig. 2) were measured. For example, a rod having a known length, which is longer than the entire length of the honeycomb filter 100, is inserted into the cell 2 (see fig. 2), and the seal length can be measured from the difference between the length of the rod exposed from the honeycomb filter 100 and the length of the rod itself. In the case where the end face 11 of the honeycomb filter 100 is circular in shape, the 4 directions of the 12-point direction, the 3-point direction, the 6-point direction, and the 9-point direction may be arbitrary cross directions starting from the center of gravity O. In addition, when the end face 11 of the honeycomb filter 100 is other than circular, the above-described 2 axes in the cross direction are determined in the following manner. First, the longest axis among axes passing through the center of gravity O of the end face 11 of the honeycomb filter 100 is set as the 1 st axis. Hereinafter, the longest axis is referred to as "long axis". The 2 nd axis is an axis passing through the center of gravity O of the end face 11 and perpendicular to the long axis. Hereinafter, the 2 nd axis is referred to as "short axis".

As described above, the sealing length is measured at 40 points (37 points when the overlapping center of gravity O is 1 point), and the boundary between the central portion 15 (see fig. 2) and the outer peripheral portion 16 (see fig. 2) of the end face 11 where the sealing length is measured is defined by the measurement result of the sealing length. Specifically, in each radial direction of the end face 11, the lengths in the radial direction, in which the final sealing length from the center of gravity O satisfies 5mm, are r3, r6, r9, and r12, respectively. In addition, r3 is: the final hole sealing length from the center of gravity O for the 3-point direction measurement point satisfies the length in the radial direction of 5 mm. R6, r9, and r12 are lengths in the radial direction in which the final seal length from the center of gravity O in the 6-point direction, the 9-point direction, and the 12-point direction satisfies 5mm, respectively. The arithmetic average value of R3, R6, R9, R12 thus obtained is defined as the average radius R of the central portion 15 (see fig. 2).

When the end face 11 of the honeycomb filter 100 is circular in shape, a portion on the inner side of the obtained average radius R (that is, the center of gravity O side of the end face 11) is defined as a central portion 15 (see fig. 2), and a portion on the outer side of the obtained average radius R is defined as an outer peripheral portion 16 (see fig. 2).

When the shape of the end face 11 of the honeycomb filter 100 is other than a circle, first, the center of gravity O of the end face 11 is set to 0% of the measurement points, and the 9 measurement points in the radial direction of each axis are set to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of the measurement points in this order toward the outside. Then, the values of the percentages above of the measurement points (i.e., the measurement points corresponding to the above-mentioned r3, r6, r9, r 12) at which the final seal length from the center of gravity O satisfies 5mm are obtained in the respective radial directions of the end face 11, and the arithmetic average thereof is obtained. For example, when r3 is 50%, r6 is 40%, r9 is 60%, and r12 is 40%, the arithmetic average of the values of the percentages is (50% +40% +60% + 40%)/4=47.5%. The arithmetic average of the values of the percentages thus found is set as: the end face 11 of the honeycomb filter 100 has a similarity ratio of the center portion 15 (see fig. 2) of 100%. That is, the center of gravity O of the end face 11 formed as the honeycomb filter 100 is set as its center of gravity, and the similarity ratio with respect to the end face 11 is made to reach 100:47.5, the central portion 15 (see fig. 2). Thus, the similarity ratio of the ratio with respect to the end face 11 reaches 100: the portion of 47.5 on the inner side (i.e., the center of gravity O side of the end face 11) is defined as the central portion 15 (see fig. 2), and the portion on the outer side of the shape is defined as the outer peripheral portion 16 (see fig. 2). The method of determining the central portion 15 described so far is as follows: the present invention is applicable to a case where the shape of the end face 11 is other than circular, but the above-described determination method can be applied also to a case where the shape of the end face 11 is circular by using the major axis and the minor axis determined in a case other than circular as axes in any cross direction in a case of circular.

After the central portion 15 (see fig. 2) and the peripheral portion 16 (see fig. 2) are defined in the above-described manner, the arithmetic average value of the sealing lengths measured at the measurement points included in the respective ranges is obtained, whereby the average sealing length L1 can be calculated _(Ave) Average hole sealing length L2 _(Ave) . The average radius ratio (R/D) of the central portion 15 (see fig. 2) can also be obtained from the average radius R obtained in the above manner and the equivalent circle radius D of the end face 11.

The porosity of the plugged portion 5 of the honeycomb filter 100 shown in fig. 1 to 4 is only 40 to 60%, but is preferably 45 to 55%, for example, and more preferably 47 to 53%. Although not particularly limited, the porosity of the hole sealing portion 5 is preferably a value lower than the porosity of the partition wall 1. By this structure, a structure having excellent corrosion resistance can be formed.

Average sealing length L1 of central portion 15 _(Ave) The length is 5mm to 10mm, but is preferably 7mm to 10mm, more preferably 9mm to 10 mm. Average sealing length L2 of outer peripheral portion 16 _(Ave) It is only necessary to have a diameter of 2mm or more and less than 5mm, but for example, it is preferably 2mm or more and less than 4mm, and more preferably 2mm or more and less than 3mm.

Average hole sealing length L1 _(Ave) And average hole sealing length L2 _(Ave) The difference DeltaL may be 2 to 6mm, but is preferably 3 to 6mm, more preferably 4 to 5mm.

The ratio (R/D) of the average radius R of the central portion 15 may be 0.2 to 0.5, but is preferably 0.3 to 0.5, more preferably 0.4 to 0.5.

The microstructure in the electron microscope image of the plugging portion 5 is as described above, but for example, the average particle area of the particles constituting the plugging portion 5 is preferably 2 to 5 μm ² BetterIs selected to be 2-4 mu m ² . The particle density of the particles constituting the plugging portion 5 is preferably 800 to 1200 particles/mm ² More preferably 900 to 1100 pieces/mm ² . As described above, the average equivalent circle diameter of each of the particles constituting the plugging portion 5 is 3 to 5 μm. In the microstructure analysis of the electron microscope image described above, the area S of each particle was obtained, and the diameter (μm) = v {4× (area S (μm) of particle ² ) I }, and the equivalent circle diameter of each particle can be calculated.

The porosity of the partition walls 1 of the honeycomb structure 4 is preferably 60 to 70%, more preferably 62 to 68%, and particularly preferably 64 to 66%. The porosity of the partition wall 1 is a value measured by mercury porosimetry. For example, the porosity of the partition wall 1 can be measured by using a polyethylene (AutoPore) 9500 (trade name) manufactured by Micromeritics corporation. If the porosity of the partition wall 1 is less than 60%, it is not preferable from the viewpoint of pressure loss. If the porosity of the partition wall 1 exceeds 70%, it is not preferable from the viewpoint of the soot collection efficiency.

The thickness of the partition walls 1 of the honeycomb structure 4 is preferably 0.1 to 0.3mm, more preferably 0.1 to 0.2mm. For example, the thickness of the partition wall 1 can be measured by a contour projector (Profile Projector). If the thickness of the partition wall 1 is less than 0.1mm, sufficient strength may not be obtained. On the other hand, if the thickness of the partition wall 1 exceeds 0.3mm, the pressure loss may increase.

The shape of the cells 2 formed in the honeycomb structural body 4 is not particularly limited. For example, the shape of the cell 2 in a cross section orthogonal to the direction in which the cell 2 extends may be a polygon, a circle, an ellipse, or the like. Examples of the polygon include a triangle, a quadrangle, a pentagon, a hexagon, and an octagon. Furthermore, the shape of the compartment 2 is preferably triangular, quadrangular, pentagonal, hexagonal, octagonal. In addition, regarding the shape of the cells 2, the shapes of all the cells 2 may be the same shape or may be different shapes. For example, although not shown, the cells may have a shape in which quadrangular cells and octagonal cells are mixed. In addition, regarding the size of the compartments 2, the sizes of all the compartments 2 may be the same or different. For example, although not shown, some of the plurality of cells may be large in size and other cells may be relatively small in size. Furthermore, in the present utility model, the compartment 2 means a space surrounded by the partition wall 1.

The compartment density of the compartments 2 defined by the partition walls 1 is preferably 42 to 51 compartments/cm ² More preferably 44 to 49 pieces/cm ² . By such a constitution, it can be suitably used as: a filter for collecting PM in exhaust gas discharged from an engine of an automobile or the like.

The outer peripheral wall 3 of the honeycomb structural body 4 may be integrally formed with the partition wall 1, or may be: a peripheral coating layer formed by applying a peripheral coating material so as to surround the partition wall 1. Although not shown, the outer peripheral coating may be formed by integrating the partition wall with the outer peripheral wall at the time of manufacture, and then removing the formed outer peripheral wall by a known method such as polishing, and then disposing it on the outer peripheral side of the partition wall.

The shape of the honeycomb structural body 4 is not particularly limited. The shape of the honeycomb structure 4 may be: the inflow end face 11 and the outflow end face 12 have a columnar shape such as a circle, an ellipse, or a polygon.

The size of the honeycomb structure 4, for example, the length in the direction in which the cells 2 of the honeycomb structure 4 extend (hereinafter also referred to as "full length"), or the size of a cross section of the honeycomb structure 4 orthogonal to the direction in which the cells 2 extend (hereinafter also referred to as "cross section") is not particularly limited. As long as the sizes are appropriately selected so that the optimum cleaning performance can be obtained when the honeycomb filter 100 is used.

The material of the partition wall 1 is not particularly limited. For example, it is preferable that the material of the partition wall 1 contains at least 1 selected from the group consisting of silicon carbide, cordierite, a silicon-silicon carbide composite, a cordierite-silicon carbide composite, silicon nitride, mullite, alumina, and aluminum titanate.

The material of the plugging portion 5 is not particularly limited, but is preferably ceramic from the viewpoints of strength and heat resistance. The ceramic is preferably a ceramic containing at least 1 selected from the group consisting of cordierite, mullite, zircon, aluminum titanate, silicon carbide, a silicon-silicon carbide composite material, silicon nitride, zirconia, spinel, indialite (indialite), sapphire-like (sapphirine), corundum, and titania. The ceramics may be contained in an amount of 1 kind alone or in an amount of 2 or more kinds together. The sealing portion is preferably formed of a material containing 50 mass% or more of the ceramics in total, and more preferably formed of a material containing 80 mass% or more of the ceramics.

(2) The manufacturing method of the honeycomb filter comprises the following steps:

the method for producing the honeycomb filter of the present utility model is not particularly limited, and the following method can be exemplified.

First, blending: a plastic blank for making the partition walls of a honeycomb structure. Additives such as binders, pore-forming materials, and water may be added as appropriate to the raw material powder of an appropriate material for producing the partition wall, and the mixture may be prepared: a blank for manufacturing partition walls of a honeycomb structure. As the raw material powder, for example, alumina, talc, kaolin, and silica powder can be used. Examples of the binder include methyl cellulose (Methylcellulose), hydroxypropyl Methylcellulose (Hydroxypropyl Methylcellulose), and the like. Examples of the additive include a surfactant.

Next, the billet obtained in the above manner is extrusion molded, thereby manufacturing: a columnar honeycomb formed body having partition walls partitioning a plurality of cells and an outer peripheral wall disposed so as to surround the partition walls. Next, the honeycomb formed body obtained is dried, for example, by microwaves and hot air.

Then, the obtained honeycomb formed body was fired to produce: a honeycomb structure as a precursor of a honeycomb filter before the hole sealing portion is arranged. The firing temperature and the firing atmosphere at the time of firing the honeycomb formed body are different depending on the raw material for producing the honeycomb formed body, and those skilled in the art can select the firing temperature and the firing atmosphere most suitable for the material to be selected.

Next, a plugged portion was formed in the obtained honeycomb structure. As a method of forming the plugged portion, the following method can be employed. For example, first, masking is performed on the inflow end face of the honeycomb structure so as to cover the inflow cells. Then, the end portions of the honeycomb structure subjected to masking are coated with a plugging material, and the plugging material is filled in the opening portions of the outflow cells not subjected to masking. Then, the plugging material was filled into the openings of the inflow cells also in the outflow end face of the honeycomb structure by the method described above. Further, when the end portion of the honeycomb structure is coated with the plugging material, first, a certain amount of the plugging material is coated for the entire range of the end portion of the honeycomb structure. Then, masking is further performed on the opening of the compartment (i.e., the compartment coated with a predetermined amount of the plugging material) which is not masked in the outer peripheral portion of the end portion, and all the compartments in the outer peripheral portion are covered with the mask. Then, only the cells in the central portion of the end portion are further coated with a certain amount of sealing material, the sealing length of the outer Zhou Fengkong portion of the outer peripheral portion is relatively shortened, and the sealing length of the central sealing portion of the central portion is relatively increased. Then, the honeycomb structure having the plugged portions formed therein is further dried by a hot air dryer. The honeycomb filter of the present utility model can be manufactured in the above manner. In particular, in the case of manufacturing the honeycomb filter of the present utility model, it is preferable that the honeycomb formed body is fired before the formation of the plugged portions, and the plugged portions are formed in the honeycomb structure obtained by the firing. The hole sealing portion to be formed is preferably not burned again but is not burned.

As the plugging material for forming the plugging portion, a material which can be formulated into the microstructure of the plugging portion described above is preferably used. Examples of the plugging material include the following: the ceramic material comprises 0.1 to 0.5 part by mass of a tackifier, 0.2 to 1.0 part by mass of a binder, 7 to 15 parts by mass of a pore-forming material, and 30 to 50 parts by mass of water, based on 100 parts by mass of the ceramic material. In addition, as the plugging material, a material capable of adjusting the average value of the equivalent circle diameters of the respective particles of the ceramic raw material to 3 to 5 μm is preferably used. Here, the equivalent circle diameter of each particle is calculated from the particle area obtained by windof (trade name), and the calculated arithmetic average value of the calculated equivalent circle diameters is set as: average value of equivalent circle diameter of each particle of ceramic raw material.

[ example ]

Hereinafter, the present utility model will be described more specifically by way of examples, but the present utility model is not limited to these examples.

Example 1

10 parts by mass of a pore-forming material, 4 parts by mass of a dispersion medium, and 4 parts by mass of an organic binder were added to 100 parts by mass of a cordierite forming raw material, and the resultant materials were mixed and kneaded to prepare a preform. Alumina, aluminum hydroxide, kaolin, talc, and silica are used as cordierite forming raw materials. Water is used as the dispersion medium. Methyl cellulose (methyl cellulose) is used as the organic binder. Dextrin (dextran) was used as a dispersant. As the pore-forming material, a water-absorbent polymer having an average particle diameter of 5 μm was used. In this example, the average particle size of each raw material is: particle diameter (D50) of 50% of the cumulative value of particle size distribution obtained by the laser diffraction/scattering method.

Next, the preform was extrusion molded using a die for producing a honeycomb molded body, thereby obtaining: the honeycomb molding has a cylindrical overall shape. The cells of the honeycomb formed body are formed in a quadrangular shape.

Next, the honeycomb formed body was dried by a microwave dryer, and further dried completely by a hot air dryer, and then both end surfaces of the honeycomb formed body were cut and adjusted to a predetermined size. Then, the honeycomb formed body is degreased and fired to obtain a honeycomb structure.

Next, the preparation: a sealing material for forming the sealing portion. Then, a plugging material is used to form plugging portions at the openings of the predetermined cells on the inflow end face side and the openings of the remaining cells on the outflow end face side of the honeycomb structure. Talc, alumina, aluminum hydroxide, kaolin, and crystalline silica are used as the plugging material. The above raw materials are added with a binder, a thickener and a dispersant to prepare a sealing material. Methyl cellulose and hydroxyethyl cellulose are used as binders. Polyethylene oxide is used as the thickener. As the dispersant, a polyol is used. As the pore-forming material, an acrylic resin was used. The plugging material is applied to the end of the honeycomb structure to fill the honeycomb structure in the following manner. First, masking is performed on the inflow end face of the honeycomb structure so as to cover the inflow cells, and then a plugging material is applied to the entire area of the end of the honeycomb structure subjected to masking, and the plugging material is filled in the openings of the cells not subjected to masking. Then, masking is further performed on the openings of the cells which are not masked in the outer peripheral portion of the end portion on the inflow end face side of the honeycomb structure, and all the cells in the outer peripheral portion are covered with a mask. Then, only the cells in the central portion of the end portion are further coated with a certain amount of sealing material, the filling length of the sealing material in the outer peripheral portion is relatively shortened, and the filling length of the sealing material in the central portion is relatively increased. Then, the pore sealing material was filled into the openings of the predetermined cells on the outflow end face side of the honeycomb structure by the same method.

The honeycomb filter of example 1 was a cylindrical structure having a length of 127mm in the direction in which the cells extended. In this honeycomb filter, the shape of the inlet end face and the outlet end face was circular, and the radius of the inlet end face and the outlet end face (equivalent circle radius D) was 66mm. In addition, the thickness of the partition wall of the honeycomb filter was 0.21mm, the porosity of the partition wall was 65%, and the cell density was 43 cells/cm ² . The results are shown in table 1. The porosity of the barrier ribs was measured by using a jacket 9500 (trade name) manufactured by Micromeritics.

[ Table 1 ]

In addition, the seal of the honeycomb filter of example 1 was obtainedElectron microscope images (SEM images) of the hole portions were obtained, and the microstructure of the hole-sealed portions was analyzed by the method described above. The results obtained are shown in table 1. Regarding the honeycomb filter of example 1, the porosity of the plugged portion was 51%, and the particle density of particles constituting the plugged portion was 883 pieces/mm ² . The average value of the equivalent circle diameters of the particles constituting the plugging portion was 4. Mu.m.

Further, with respect to the honeycomb filter of example 1, the pore sealing lengths of the pore sealing portions described so far as shown in fig. 5 were measured, and the average pore sealing length L1 of the central portion was obtained _(Ave) Average sealing length L2 of outer peripheral portion _(Ave) And a difference DeltaL in the sealing length. The average radius R of the central portion of the plugged portion was obtained from the result of measurement of the plugged length of the plugged portion, and the ratio (R/D) of the average radius R of the central portion to the radius D of the end face of the honeycomb structure was calculated. The results are shown in table 1. The column "presence or absence of firing" of the "plugging portion" in table 1 indicates: the structure of the plugged portion of the honeycomb filter manufactured in this example was used to determine the presence or absence of firing of the plugged portion during manufacturing. The term "unfired" in this column means that the plugged portions were not fired at the time of production, and that the honeycomb filter was produced by drying only. On the other hand, "firing" in this column means that the plugged portion is fired at the time of manufacture to manufacture a honeycomb filter.

Regarding the honeycomb filter of example 1, the evaluation of "corrosion resistance" and "thermal shock resistance" was performed by the following methods. The results are shown in table 2.

[ Table 2 ]

	Corrosion resistance	Thermal shock resistance
			Example 1	OK	Excellent (excellent)
Example 2	OK	Excellent (excellent)
			Example 3	OK	Excellent (excellent)
Example 4	OK	Excellent (excellent)
			Comparative example 1	NG	Excellent (excellent)
Comparative example 2	OK	Qualified product
			Comparative example 3	NG	Excellent (excellent)

[ Corrosion resistance ]

First, a honeycomb filter is stored (housed) in a can body, and the canned honeycomb filter is placed in a gas burner test machine. Next, the SiC abrasive grains were collided with the inflow end face of the honeycomb filter by a gas burner tester. The conditions for causing the abrasive grains to collide are as follows. The amount of abrasive grains charged was 10g. The temperature of the gas flowing into the honeycomb filter was set to 700 ℃. The flow rate of the gas flowing into the honeycomb filter was set to 120 m/sec. The test time was set to 10 minutes during which abrasive particles were gradually thrown in small amounts. Then, the honeycomb filter was taken out, the taken-out honeycomb filter was photographed by a tomography (CT), and the depth (abrasion depth (mm)) of the honeycomb filter ground by collision of abrasive grains was calculated. In the test for measuring the amount of abrasion, abrasive grains having an average particle diameter of 50 μm were used. The "corrosion resistance" of the honeycomb filter was evaluated based on the following evaluation criteria. In examples 1 to 4 and comparative examples 1 to 3, the honeycomb filter to be used as a reference was set as comparative example 1. Further, "hole-sealing penetration" means: the hole sealing portion is ground by abrasion so that at least a part of the hole sealing portion penetrates in the flow direction of the gas.

Evaluation "OK": when "penetration of the plugged holes due to abrasion" was not caused in the honeycomb filter to be evaluated, the honeycomb filter was evaluated as "OK".

Evaluation "NG": when "through hole sealing due to abrasion" is caused in the honeycomb filter to be evaluated, it is evaluated as "NG".

[ thermal shock resistance ]

First, a predetermined amount of smoke was generated under a predetermined operating condition in an engine test stand on which a 1.4L gasoline engine was mounted, and the generated smoke was deposited on the surfaces of the partition walls of the honeycomb filters of each of the examples and comparative examples. Next, a regeneration process based on post injection is performed such that the inlet gas temperature of the honeycomb filter is increased, and the post injection is stopped when the pressure loss before and after the honeycomb filter starts to decrease, thereby switching the engine to an idle state. The amount of soot deposited in a predetermined amount before the regeneration treatment is gradually increased, and the above-described operation is repeated until the honeycomb filter is cracked. The amount of smoke generated by cracking of the honeycomb filters is set to be the "smoke accumulation limit amount" of each honeycomb filter. The honeycomb filter was evaluated for "the deposit limit amount of soot" based on the following evaluation criteria. In examples 1 to 4 and comparative examples 1 to 3, the honeycomb filter to be used as a reference was set as comparative example 1.

Evaluation of "you": when the "deposit limit amount of smoke" of the honeycomb filter to be evaluated is set to 100%, the honeycomb filter is evaluated as "excellent" when the "deposit limit amount of smoke" of the honeycomb filter to be evaluated is 130% or more.

Evaluation of "good": when the "deposit limit amount of smoke" of the honeycomb filter to be evaluated is set to 100%, the "deposit limit amount of smoke" of the honeycomb filter to be evaluated is set to 120% or more and less than 130%, and is evaluated as "good".

Evaluation of "pass": when the "deposit limit amount of smoke" of the honeycomb filter to be evaluated is 100% or more and less than 120%, the honeycomb filter to be evaluated is evaluated as "acceptable".

Evaluation of "disqualification": when the "deposit limit amount of smoke" of the honeycomb filter to be evaluated is set to 100%, the honeycomb filter to be evaluated is evaluated as "failed" when the "deposit limit amount of smoke" of the honeycomb filter to be evaluated is less than 100%.

(examples 2 to 4 and comparative examples 1 to 3)

The honeycomb filters of examples 2 to 4 and comparative examples 1 to 3 were produced by changing the structure of the honeycomb filter as shown in table 1.

The honeycomb filters of examples 2 to 4 and comparative examples 1 to 3 were mainly produced in the same manner as the honeycomb filter of example 1, except that the following modifications were made in the production.

In example 2, as shown in table 1, the pore-sealing material was prepared so as to increase the average particle diameter of talc, reduce the amount of pore-forming material, and lower the pre-firing temperature.

In example 3, as shown in table 1, the average particle diameter of talc was reduced, the amount of pore-forming material was reduced, the pre-firing temperature was lowered, and the amount of brushing was increased so that the pore-forming material was elongated.

In example 4, as shown in table 1, the average particle diameter of talc was reduced, the amount of pore-forming material was reduced, and the pre-firing temperature was lowered for the formulation of pore-sealing material.

In comparative example 1, as shown in table 1, the average particle diameter of talc was reduced, the amount of pore-forming material was increased, and the pre-firing temperature was lowered for the formulation of pore-sealing material.

In comparative example 2, as shown in table 1, the pore-sealing material was prepared by reducing the average particle diameter of talc, reducing the amount of pore-forming material, and firing the pore-sealing material filled after filling the pore-sealing material into the openings of the respective cells to form pore-sealing portions.

In comparative example 3, the pore-forming material was prepared by reducing the amount of pore-forming material, lowering the pre-firing temperature, and coating the pore-forming material to a uniform length without using a mask added to the outer peripheral portion as shown in table 1.

The honeycomb filters of examples 2 to 4 and comparative examples 1 to 3 were also evaluated in the same manner as in example 1. The results are shown in table 2.

(results)

In the evaluation of corrosion resistance and thermal shock resistance, the honeycomb filters of examples 1 to 4 gave good results.

On the other hand, with respect to the honeycomb filter of comparative example 1, the porosity of the plugged portion showed a high value of 65%, and the evaluation result of the corrosion resistance was "NG".

Regarding the microstructure of the plugged portion of the honeycomb filter of comparative example 2, the particle density was 498 pieces/mm ² And the average value of the equivalent circle diameters of the particles constituting the plugging portion was 10. Mu.m. The honeycomb filters of comparative example 2 were inferior in the evaluation results of thermal shock resistance to the honeycomb filters of examples 1 to 4. That is, it is assumed that the honeycomb filter of comparative example 2 has a structure in which the plugging portions are baked, and the particles contained in the plugging material are strongly bonded to each other by the baking, so that the thermal expansion coefficient of the plugging portions is relatively large. Thus, it can be understood that: ratio of The honeycomb filter of comparative example 2 had an increased thermal stress generated in the plugged portions, and cracks were likely to occur in the evaluation of thermal shock resistance.

In the honeycomb filter of comparative example 3, there was no difference in the pore sealing length between the center portion and the outer peripheral portion of the end face, and the pore sealing length was uniform (4 mm) over the entire end face. The honeycomb filters of comparative example 3 were inferior in the evaluation results of corrosion resistance to the honeycomb filters of examples 1 to 4.

Industrial applicability

The honeycomb filter of the present utility model can be used as a filter for trapping particulate matter in exhaust gas.

Claims

1. A honeycomb filter is provided with:

it is characterized in that the method comprises the steps of,

the porosity of the hole sealing part is 40-60%,

the honeycomb structure is provided with an end on the inflow end face side or an end on the outflow end face side at a central portion side: a central hole sealing portion having a hole sealing length L of 5mm or more in a direction in which the cells extend as the hole sealing portion,

Further, an outer peripheral portion of the end portion is disposed on an outer side of the central portion: an outer Zhou Fengkong part of the plugging part having a plugging length L of less than 5mm,

2. The honeycomb filter of claim 1,

the porosity of the partition wall is 60-70%.

3. A honeycomb filter according to claim 1 or 2, characterized in that,

the thickness of the partition wall is 0.1-0.3 mm.