Honeycomb filter

Abstract

Honeycomb filter (100, 200, 300) comprising: a columnar honeycomb substrate (5, 25, 45) having a porous partition wall (1, 21, 41) provided thereon, surrounding a plurality of cells (2, 22, 42) extending from an inflow end face (11, 31, 51) to an outflow end face (12); and a sealing portion (5) provided at an end portion either on the inflow end face (11, 31, 51) side or on the outflow end face (12) side of the cells (2, 22, 42), wherein in a section perpendicular to the direction of extension of the cells (2, 22, 42), the shape of an inflow cell (2a, 22a, 42a) with the sealing portion (2) provided at the end portion on the side of the outflow end face (12) is hexagonal, the shape of an outflow cell (2b, 22b, 42b) with the sealing portion (5) provided at the end portion on the side of the inflow end face (11, 31, 51) is hexagonal, the plurality of cells (2, 22, 42) have a structure in which a plurality of inflow cells (2a, 22a, 42a) surround the circumference of an outflow cell (2b, 22b, 42b) such that one side of the inflow cell (2a, 22a, 42a) and one side of the outflow cell (2b, 22b, 42b) adjacent to the inflow cell (2a, 22a, 42a) are parallel, the partition wall (1, 21, 41) includes a first partition wall (1a, 21a, 41a) provided between the inflow cell (2a, 22a, 42a) and the outflow cell (2b, 22b, 42b), and a second partition wall (1b, 21b, 41b) provided between the inflow cells (2a, 22a, 42a), at least one of the first partition walls (1a, 21a, 41a) is configured such that a value of the ratio (T2 / T1) of a thickness T2 of the second partition wall (1b, 21b, 41b) with respect to a thickness T1 of the first partition wall (1a, 21a, 41a) is greater than 1.0 and less than 2.5, and a total open end area of ​​the honeycomb substrate (5, 25, 45) is greater than 35% and equal to or less than 95%, wherein the second partition wall (41b) has a thickness change portion (46) in which the thickness T2 of the second partition wall (41b) decreases or increases toward a connecting portion with the first partition wall (41a).

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The present invention relates to a honeycomb filter, and more particularly to a honeycomb filter capable of achieving a low pressure loss during use. Description of the state of the art

[0002] Internal combustion engines are used as power sources in various industries. On the other hand, the exhaust gas emitted when an internal combustion engine burns fuel contains toxic gases such as nitrogen oxides and particulate matter such as soot or ash. These particulate matter may be referred to as "PM" below. "PM" stands for particulate matter. In recent years, regulations for removing PM emitted by diesel engines have become increasingly strict worldwide. A wall-flow filter with a honeycomb structure is used as a filter for removing PM.

[0003] As wall-flow filters, various types of honeycomb filters have been proposed. These honeycomb filters are provided with honeycomb substrates having porous partition walls defining a plurality of cells forming fluid passageways, and sealing portions provided at the open ends on one side of the plurality of cells (for example, see Patent Documents 1 to 7). In such a honeycomb filter, inflow cells whose sealing portions are provided on the outflow end face side and outflow cells whose sealing portions are provided on the inflow end face side are alternately arranged, for example, separated by the partition walls. The porous partition walls constitute the filter bodies that remove PM.

[0004] Further relevant prior art is described in the following documents: JP 2011 167 641 A, EP 2 243 535 A1 and US 2011 / 0030357 A1. [Patent Document 1] JP 2007-209842 A1 [Patent Document 2] JP2012-081415 A1 [Patent Document 3] JP 4279497 B2 [Patent Document 4] JP 4567674 B2 [Patent Document 5] JP 2014-200741 A1 [Patent Document 6] JP ​​4282960 B2 [Patent Document 7] JP 58-196820 A1 SUMMARY OF THE INVENTION

[0005] In the conventional honeycomb filters described in Patent Documents 1 to 7, there has been a tendency for the permeation resistance of "the partition walls provided between the inflow cells" to be higher than that of "the partition walls provided between the inflow cells and the outflow cells," which makes the flow of exhaust gas difficult. For this reason, the conventional honeycomb filters have presented the problem of uneven exhaust flow in the honeycomb filters, leading to an increase in the pressure loss of the honeycomb filters.

[0006] The present invention was made in view of the above-described problem in the prior art. The present invention provides a honeycomb filter that can achieve a low pressure loss during use. In particular, the present invention provides a honeycomb filter that can suppress an increase in pressure loss attributable to the accumulation of PM on the surfaces of the partition walls, thereby achieving a lower pressure loss.

[0007] To solve the problem described above, a honeycomb filter having the features of claim 1 is provided. Further advantageous embodiments are specified in the dependent claims.

[0008] The honeycomb filter according to the present invention is configured such that when the thickness of the first partition wall provided between the inflow cell and the outflow cell is denoted by T1, and the thickness of the second partition wall provided between the inflow cells is denoted by T2, the value of T2 / T1 is greater than 1.0 and less than 2.5. Further, in the honeycomb filter according to the present invention, the total open end area of ​​the honeycomb substrate is greater than 35% and equal to or less than 95%. The honeycomb filter according to the present invention has the advantage that, when used as a filter that captures PM in exhaust gas, it makes it possible to achieve a lower pressure loss compared to conventional honeycomb filters.In particular, the honeycomb filter according to the present invention has a significant advantage that it makes it possible to effectively suppress an increase in pressure loss attributable to the accumulation of PM on the surfaces of the partition walls and thereby achieve a lower pressure loss.

[0009] The honeycomb filter according to the present invention has a relatively larger thickness T2 of the second partition walls to relatively increase the total volume of the pores of the second partition walls, thus achieving a more uniform exhaust gas flow through the pores of the second partition walls. Consequently, the exhaust gas flowing into the inflow cells easily passes through the pores of the second partition walls into the outflow cells, even when PM, such as soot, accumulates on the surfaces of the first partition walls, resulting in an increase in the permeation resistance of the first partition walls. This can achieve a low pressure loss of the honeycomb filter. In particular, the first partition walls provide the main flow of exhaust gas flowing from the inflow cells to the outflow cells and therefore tend to easily accumulate PM, such as soot, which consequently easily leads to an increase in the permeation resistance when PM accumulates.In the honeycomb filter according to the present invention, when the permeation resistance of the first partition walls increases, the second partition walls can be used extremely effectively as the passageways of the exhaust gas.

[0010] Furthermore, the second partition walls contribute less to an increase in pressure loss than the first partition walls in an initial use state. Therefore, even if the thickness T2 of the second partition walls is relatively increased by a certain amount, an excessive increase in pressure loss of the honeycomb filter in the initial state can be suppressed by adjusting the total open end area of ​​the honeycomb substrate to the aforementioned range. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view schematically showing an embodiment of the honeycomb filter as viewed from an inflow end face side; Fig.2 is a plan view showing the inlet face of the Fig. 1 shows schematically the honeycomb filter shown; Fig. 3 is an enlarged floor plan showing an enlarged part of the Fig. 2 shows the inlet face; Fig. Fig. 4 is a schematic diagram for explaining a thickness T1 of a first partition wall and a thickness T2 of a second partition wall shown in Fig. 3 are shown; Fig. 5 is a plan view showing an outflow face of the Fig. 1 shows schematically the honeycomb filter shown; Fig. 6 is a sectional view showing a line along AA' Fig. 2 shows schematically the cross-section taken; Fig. 7 is a plan view schematically showing an inflow end face of another embodiment of the honeycomb filter; Fig. 8 is an enlarged plan view showing an enlarged part of the Fig.7 shown inlet face; and Fig. Fig. 9 is an enlarged plan view showing an enlarged part of an inflow end face of an embodiment of the honeycomb filter according to the present invention. While the embodiments of Figs. Fig. 1 to 8 are helpful for understanding the present invention, the embodiment of Fig. 9 an embodiment of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Embodiments of the present invention will be described below. However, the present invention is not limited to the following embodiments. Therefore, it should be understood that modifications, improvements, and the like may be made to the following embodiments based on the knowledge of one of ordinary skill in the art without departing from the spirit of the present invention. (1) Honeycomb filter:

[0012] One embodiment of the honeycomb filter is a honeycomb filter 100, which is Fig. 1 to Fig. 6 is shown. Fig. 1 is a perspective view schematically showing the embodiment of the honeycomb filter according to the present invention observed from an inflow end face side of the honeycomb filter. Fig. 2 is a plan view showing the inlet face of the Fig. 1 shows a schematic view of the honeycomb filter. Fig. 3 is an enlarged plan view showing an enlarged part of the Fig. 2 shows the inlet face. Fig. Fig. 4 is a schematic diagram for explaining a thickness T1 of a first partition wall and a thickness T2 of a second partition wall shown in Fig. 3 are shown. Fig. 5 is a plan view showing an outflow end face of the Fig. 1 shows a schematic view of the honeycomb filter. Fig.6 is a sectional view showing a line along AA' Fig. 2 shows a schematic cross section.

[0013] The honeycomb filter 100 is provided with a honeycomb substrate 4 and the sealing sections 5. The honeycomb substrate 4 is columnar and has an inflow end face 11 and an outflow end face 12. The honeycomb substrate 4 has porous partition walls 1 surrounding a plurality of cells 2 extending from the inflow end face 11 to the outflow end face 12. Fig. The honeycomb substrate 4 shown in FIG. 1 and the like further has a peripheral wall 3 provided surrounding the partition walls 1. In the present invention, the cells 2 mean the spaces surrounded by the partition walls 1.

[0014] The sealing portions 5 are provided at the end portion on either the inflow end face 11 side or the outflow end face 12 side of the cells 2 formed in the honeycomb substrate 4 to seal the open ends of the cells 2. Hereinafter, the cells 2 having the sealing portions 5 provided at the end portion on the outflow end face 12 side will be referred to as "the inflow cells 2a." The cells 2 having the sealing portions 5 provided at the end portion on the inflow end face 11 side will be referred to as "the outflow cells 2b."

[0015] In the honeycomb filter 100, each of the cells 2 has a hexagonal shape in a cross section perpendicular to the extending direction of the cells 2. In other words, in the cross section perpendicular to the extending direction of the cells 2, the inflow cells 2a have a hexagonal shape, and the outflow cells 2b also have a hexagonal shape. Hereinafter, the shape of the cells in the cross section perpendicular to the extending direction of the cells 2 may be referred to as "the cross-sectional shape of the cells" or simply as "the shape of the cells." In the present specification, the term "hexagonal shape" includes a hexagonal shape, a shape in which at least one corner of a hexagonal shape is formed by a curved line, and a shape in which at least one corner of a hexagonal shape is linearly chamfered.

[0016] The plurality of cells 2 have a structure in which a plurality of inflow cells 2a surround the periphery of an outflow cell 2b such that one side of the inflow cell 2a (one side of the hexagonal shape) and one side of the outflow cell 2b (one side of the hexagonal shape) adjacent to it are parallel. Fig. 1 to Fig. The honeycomb filter 100 shown in Figure 6 has a structure in which six inflow cells 2a surround the periphery of one outflow cell 2b. In this specification, the above term "parallel" means "substantially parallel," which will be described later. The term "substantially parallel" means the positional relationship between two parallel sides in a state where one of the two parallel sides is inclined within a range of ±15°.

[0017] In the honeycomb filter 100, the partition wall 1 provided between the inflow cell 2a and the outflow cell 2b is referred to as a "first partition wall 1a." Further, the partition wall 1 provided between the inflow cells 2a is referred to as a "second partition wall 1b." Furthermore, the honeycomb filter 100 has an important feature regarding the configurations of the first partition walls 1a and the second partition walls 1b. More specifically, at least one first partition wall 1a among the first partition walls 1a is configured such that the value of T2 / T1, which is the value of the ratio of a thickness T2 of the second partition wall 1b to a thickness T1 of the first partition wall 1a, is greater than 1.0 and less than 2.5. Hereinafter, the value of the ratio of the thickness T2 of the second partition wall 1b to the thickness T1 of the first partition wall 1a may be simply referred to as "the value of T2 / T1."When determining the value of T2 / T1, the second partition wall 1b for which the thickness T2 is to be determined should have at least one end face thereof connected to the first partition wall 1a for which the thickness T1 is to be determined.

[0018] Furthermore, in the honeycomb filter 100, the total open end area of ​​the honeycomb substrate 4 is greater than 35% and equal to or less than 95%. The term "total open end area" of the honeycomb substrate 4 means the percentage of the ratio of the total opening area of ​​the cells 2 formed in the honeycomb substrate 4 to the cross-sectional area perpendicular to the extension direction of the cells 2 of the honeycomb substrate 4. The value of the cross-sectional area perpendicular to the extension direction of the cells 2 of the honeycomb substrate 4 shall not include the area of ​​the peripheral wall 3 located at the outermost periphery of the honeycomb substrate 4.

[0019] The honeycomb filter 100 can be suitably used, for example, as a filter that captures PM in the exhaust gas. Furthermore, the honeycomb filter 100 can achieve a low pressure loss in use compared to conventional honeycomb filters. In particular, the honeycomb filter 100 can effectively suppress an increase in pressure loss attributable to the accumulation of PM on the surfaces of the partition walls 1, thereby achieving a lower pressure loss. More specifically, in the honeycomb filter 100, setting the thickness T2 of the second partition walls 1b to be relatively larger causes the total volume of the pores in the second partition walls 1b to relatively increase, so that the exhaust gas easily flows through the pores of the second partition walls 1b.As soot accumulates on the surfaces of the first partition walls 1a, resulting in an increase in the permeation resistance of the first partition walls 1a, the exhaust gas flowing into the inflow cells 2a smoothly flows into the outflow cells 2b through the pores of the second partition walls 1b. Consequently, the low pressure loss of the honeycomb filter 100 can be achieved. In particular, the first partition walls 1a provide the main flow of the exhaust gas flowing from the inflow cells 2a to the outflow cells 2b, and therefore, they tend to easily accumulate PM such as soot, which easily leads to an increase in the permeation resistance as PM accumulates. In the honeycomb filter 100, the second partition walls 1b can be extremely effectively used as the exhaust gas passageways if the permeation resistance of the first partition walls 1a increases.

[0020] Furthermore, the second partition walls 1b contribute less to an increase in pressure loss in the initial use stage than the first partition walls 1a. Consequently, an excessive increase in pressure loss of the honeycomb filter 100 in the initial use stage can be suppressed by setting the total open end area of ​​the honeycomb substrate 4 within the aforementioned range, even if the thickness T2 of the second partition walls 1b is relatively increased.

[0021] The honeycomb filter 100 may be configured such that, in at least one first partition wall 1a among all the first partition walls 1a provided between the inflow cells 2a and the outflow cells 2b, the value of T2 / T1 is greater than 1.0 and less than 2.5. Alternatively, the honeycomb filter 100 may be configured such that, in all the first partition walls 1a provided between the inflow cells 2a and the outflow cells 2b, the above value of T2 / T1 is greater than 1.0 and less than 2.5. If the value of T2 / T1 is equal to or less than 1.0, a sufficient amount of exhaust gas flowing through the pores of the second partition walls 1b cannot be ensured, thus making it difficult to achieve an adequate pressure loss reduction effect in some cases.On the other hand, if the value of T2 / T1 is equal to or greater than 2.5, the second partition walls 1b would be relatively too thick, thus making it difficult to achieve an adequate pressure loss reduction effect in some cases. Alternatively, the honeycomb filter 100 may be further configured such that the above value of T2 / T1 in all first partition walls 1a is greater than 1.0 and less than 2.5.

[0022] The value of T2 / T1 is preferably greater than 1.0 and equal to or less than 2.4, and further preferably equal to or less than 2.0. In addition, the lower limit of T2 / T1 is more preferably 1.05, and even more preferably 1.10. There are no particular restrictions on the specific thicknesses of the first partition walls 1a and the second partition walls 1b.

[0023] Now, regarding Fig.4, a description is given of the method for measuring the thickness T1 of the first partition walls 1a and the thickness T2 of the second partition walls 1b. As in Fig. As shown in Fig. 4, first, the measurement range including the first partition walls 1a and the second partition walls 1b to be measured is determined. Specifically, a range including an outflow cell 2b with one side thereof defined by the first partition wall 1a to be measured and the two inflow cells 2a adjacent to the outflow cell 2b and adjacent to each other is selected as the measurement range. By setting such a range as the measurement range, the first partition wall 1a to be measured and the second partition wall 1b connected to the first partition wall 1a are included in the measurement range.

[0024] Then, as in Fig.4, the center of gravity of an inflow cell 2a from the two inflow cells 2a is defined as a center of gravity O1, while the center of gravity of the outflow cell 2b adjacent to the one inflow cell 2a is defined as a center of gravity O2. Furthermore, the center of gravity of another inflow cell 2a, which is adjacent to both the inflow cell 2a of the center of gravity O1 and the outflow cell 2b of the center of gravity O2, is defined as a center of gravity O3. The thickness T1 of the first partition walls 1a is defined as the thickness of the first partition wall 1a in a first segment connecting the center of gravity O1 and the center of gravity O2 (T1 in Fig. 4). The thickness T2 of the second partition walls 1b is defined as the thickness of the second partition wall 1b in a second segment connecting the center of gravity O1 and the center of gravity O3 (T2 in Fig. 4).

[0025] The thickness T1 of the first partition wall 1a and the thickness T2 of the second partition wall 1b can be measured using a microscope, for example. A KEYENCE VHX-1000 (trade name) can be used as the microscope.

[0026] Furthermore, in the Fig.4, a virtual auxiliary triangle having three segments described below is drawn, wherein the length of each side forming the hexagonal shape of the inflow cell 2a can be defined using the drawn auxiliary triangle as described below. A first segment for drawing the auxiliary triangle is the first segment connecting the center of gravity O1 and the center of gravity O2. A second segment is the second segment connecting the center of gravity O1 and the center of gravity O3. A third segment is the third segment having the center of gravity O2 as a starting point and bisecting the second segment. In the second segment, the portion actually used for drawing the auxiliary triangle is the half on the center of gravity O1 side of the second segment bisected by the third segment.

[0027] The value which is half the length of the side located adjacent to the outflow cell 2b among the six sides forming the hexagonal shape of the one inflow cell 2a indicates the length which is Fig. 4 is denoted by "z." Therefore, the length of the side located adjacent to the outflow cell 2b among the six sides forming the hexagonal shape of the one inflow cell 2a can be denoted by "a length 2z."

[0028] The value which is half the length of the side arranged adjacent to another inflow cell 2a among the six sides forming the hexagonal shape of the one inflow cell 2a indicates the length which in Fig. 4 is denoted by "x". Therefore, the length of the side located adjacent to another inflow cell 2a among the six sides forming the hexagonal shape of the one inflow cell 2a can be denoted by "a length 2x".

[0029] Regarding the lengths of the six sides forming the hexagonal shape of the inflow cell 2a, the length 2z and the length 2x may be different. For example, if the length 2z and the length 2x are the same among the lengths of the sides forming the hexagonal shape of the inflow cell 2a, the inflow cell 2a has a regular hexagonal shape.

[0030] In Fig. 4, the length designated "y" indicates the distance from the center of gravity O1 of one inflow cell 2a to the first partition wall 1a. Consequently, the cell pitch of one inflow cell 2a can be designated as "one cell pitch 2y."

[0031] Furthermore, the length of the first partition wall 1a in the direction perpendicular to the thickness T1 of the first partition wall 1a and the length of the second partition wall 1b in the direction perpendicular to the thickness T2 of the second partition wall 1b may be defined as described below. First, as shown in Fig.4, a first auxiliary line, which runs through the center of the thickness T1 of the first partition wall 1a and is perpendicular to the first segment, is further drawn into the previously drawn auxiliary triangle. In addition, a second auxiliary line, which runs through the center of the thickness T2 of the second partition wall 1b and is perpendicular to the second segment, is further drawn into the previously drawn auxiliary triangle.

[0032] Then a third auxiliary line is drawn parallel to the first segment from the intersection point of the first auxiliary line and the second auxiliary line, as shown in Fig. 4. Furthermore, a fourth auxiliary line is drawn parallel to the second segment from the intersection point of the first auxiliary line and the second auxiliary line. Fig. 4, the distance between the first segment and the third auxiliary line is denoted by "a / 2." Furthermore, the distance between the second segment and the fourth auxiliary line is denoted by "b / 2."

[0033] In Fig. 4, the length designated by “a / 2” indicates a value that is half the length of the first partition wall 1a. Accordingly, the length of the first partition wall 1a can be Fig. 4 be designated by a “length a”. In Fig. 4, the length designated “b / 2” indicates a value that is half the length of the second partition wall 1b. Accordingly, the length of the second partition wall 1b can be Fig. 4 be designated by a “length b”.

[0034] The total open end area of ​​the honeycomb substrate 4 is greater than 35% and equal to or less than 95%. The lower limit of the total open end area of ​​the honeycomb substrate 4 is preferably 47% and more preferably 53%. The upper limit of the total open end area of ​​the honeycomb substrate 4 is preferably 77% and more preferably 72%.

[0035] The thickness T1 of the first partition wall 1a is preferably 70 to 350 µm, further preferably 100 to 325 µm, and particularly preferably 130 to 300 µm. This arrangement makes it possible to achieve the honeycomb filter 100 with a low pressure loss while maintaining the isostatic strength.

[0036] In the honeycomb filter 100, the hydraulic diameter of the inflow cells 2a is preferably larger than the hydraulic diameter of the outflow cells 2b. This arrangement makes it easier to achieve a low pressure loss effect while maintaining isostatic strength. The value of the hydraulic diameter is calculated according to "4 × (cross-sectional area) / (circumferential length)" based on the cross-sectional area and circumferential length of each of the cells 2.

[0037] The hydraulic diameter of the inflow cells 2a is preferably 0.5 to 1.5 mm, further preferably 0.6 to 1.4 mm, and particularly preferably 0.7 to 1.3 mm. In addition, the hydraulic diameter of the inflow cells 2a is preferably 1.0 to 1.7 times, and further preferably 1.3 to 1.7 times, the hydraulic diameter of the outflow cells 2b.

[0038] The length of one side of the discharge cells 2b is preferably 0.5 to 1.6 mm, further preferably 0.5 to 1.3 mm, and particularly preferably 0.5 to 1.0 mm. This arrangement makes it easy to exhibit the effect of achieving low pressure loss while improving thermal shock resistance.

[0039] The porosity of the partition wall 1 of the honeycomb substrate 4 is preferably 35 to 70%, and more preferably 40 to 65%. If the porosity of the partition walls 1 is below 35%, pressure loss may increase. If the porosity of the partition walls 1 exceeds 70%, the strength of the honeycomb substrate 4 is insufficient, thus making it difficult to hold the honeycomb filter 100 with sufficient gripping force when the honeycomb filter 100 is placed in a sleeve body used for an exhaust gas purifier. The porosity of the partition walls 1 is indicated by a value measured by a mercury porosimeter. For example, the Micromeritics Autopore 9500 (trade name) can be used as the mercury porosimeter.

[0040] In the cross-section perpendicular to the direction of extension of the cells 2, the inflow cells 2a and the outflow cells 2b have hexagonal shapes. In the honeycomb filter 100, the inflow cells 2a have a regular hexagonal shape, and the outflow cells 2b also have a regular hexagonal shape. Furthermore, the shape of the inflow cells 2a and the shape of the outflow cells 2b are similar but different in size.

[0041] The materials of the partition walls 1 are preferably various types of ceramics, metals, or the like, the main components of which are oxides or non-oxides from the standpoints of strength, heat resistance, durability, and the like. More specifically, the ceramics are preferably made of a material containing at least one selected from a group of materials including, for example, cordierite, mullite, alumina, spinel, silicon carbide, silicon nitride, and aluminum titanate. As the metals, Fe-Cr-Al-based metals and silicon metal or the like can be used. The main component is preferably one or the same or more than two materials selected from the foregoing materials.Particularly preferably, from the standpoints of high strength, high heat resistance, and the like, the main component is one or more than two selected from a group of materials including alumina, mullite, aluminum titanate, cordierite, silicon carbide, and silicon nitride. Further, the ceramic material may be, for example, a composite material obtained by bonding silicon carbide particles using cordierite as a binder. Furthermore, from the standpoints of high thermal conductivity, high heat resistance, and the like, a silicon carbide or silicon-silicon carbide composite material is particularly suitable. The term "main component" in this case means a component present in the component by equal to or more than 50 mass percent, preferably equal to or more than 70 mass percent, and further preferably equal to or more than 80 mass percent.

[0042] There are no particular restrictions on the material of the sealing sections 5, and the above-mentioned materials can be suitably used for the partition walls 1.

[0043] There are no particular restrictions on the overall shape of the honeycomb filter 100. Regarding the overall shape of the honeycomb filter 100, the shape of the inflow end face 11 and the outflow end face 12 is preferably circular or elliptical, and more preferably circular. Although there are no particular restrictions on the size of the honeycomb filter 100, the length from the inflow end face 11 to the outflow end face 12 is preferably 50 to 300 mm. If the overall shape of the honeycomb filter 100 is round or columnar, the diameters of the inflow end face 11 and the outflow end face 12 are preferably 100 to 400 mm.

[0044] The honeycomb filter 100 can be suitably used as an exhaust gas purification element of an internal combustion engine. The honeycomb filter 100 can be configured such that at least either the surfaces of the partition walls 1 of the honeycomb substrate 4 or the pores of the partition walls 1 are loaded with a catalyst for exhaust gas purification.

[0045] Now, regarding Fig. 7 and Fig. 8 describes another embodiment of the honeycomb filter. Fig. 7 is a plan view schematically showing the inflow end face of another embodiment of the honeycomb filter according to the present invention. Fig. 8 is an enlarged plan view showing an enlarged part of the Fig. 7 shows the inlet face.

[0046] One in Fig. 7 and Fig.The honeycomb filter 200 shown in Figure 8 is provided with a honeycomb substrate 24 and the sealing portions 25. The honeycomb substrate 24 is columnar and has an inflow end face 31 and an outflow end face (not shown). The honeycomb substrate 24 has porous partition walls 21 provided therein, surrounding a plurality of cells 22 extending from the inflow end face 31 to the outflow end face (not shown). Fig. The honeycomb substrate 24 shown in Fig. 7 further has a provided peripheral wall 23 surrounding the partition walls 21.

[0047] In the honeycomb filter 200, in the cross section perpendicular to the extending direction of the cells 22, each of the inflow cells 22a has a hexagonal shape, and each of the outflow cells 22b has a hexagonal shape. The plurality of cells 22 has a structure in which a plurality of inflow cells 22a surround the periphery of an outflow cell 22b such that one side of the inflow cell 22a and one side of the adjacent outflow cell 22b are parallel. Fig. The honeycomb filter 200 shown in Fig. 7 has a structure in which six inflow cells 22a surround the periphery of an outflow cell 22b.

[0048] In the honeycomb filter 200, the partition wall 21 provided between the inflow cell 22a and the outflow cell 22b is referred to as a "first partition wall 21a." Further, the partition wall 21 provided between the inflow cells 22a is referred to as a "second partition wall 21b." In the honeycomb filter 200, at least one first partition wall 21a among the first partition walls 21a is configured such that the value of T2 / T1, which is the ratio of a thickness T2 of the second partition wall 21b to a thickness T1 of the first partition wall 21a, is greater than 1.0 and less than 2.5.

[0049] In the honeycomb filter 200, the total open end area of ​​the honeycomb substrate 24 is greater than 35% and equal to or less than 95%.

[0050] The Fig. 7 and Fig. The honeycomb filter 200 shown in Figure 8 differs in the shape of the inflow cells 22a from that shown in Fig. 1 to Fig.5 described above. More specifically, the inflow cells 22a in the honeycomb filter 200 have a hexagonal shape other than a regular hexagonal shape in the cross section perpendicular to the extending direction of the cells 22. In the case where the inflow cells 22a have a hexagonal shape other than a regular hexagonal shape, the inflow cells 22a preferably have a hexagonal shape in which the lengths of at least one pair of opposite sides are different. The term "at least one pair of opposite sides" means at least one pair of opposite sides in a hexagonal shape of each of the inflow cells 22a. Further preferably, the inflow cells 22a have a hexagonal shape in which the lengths of the opposite sides of the hexagonal shape are different from each other.Setting the inflow cells 22a to have the hexagonal shape described above makes it possible to effectively prevent the total open end area of ​​the honeycomb substrate 24 from becoming excessively small when the value of T2 / T1 is set to be greater than 1.0. Consequently, the influence of an increase in pressure loss attributable to a reduction in the total open end area is suppressed when the value of T2 / T1 is set to be greater than 1.0. This allows a lower pressure loss to be achieved.

[0051] Now, regarding Fig. 9 a description is given of an embodiment of the honeycomb filter according to the present invention. Fig. 9 is an enlarged plan view showing an enlarged part of an inflow end face of another embodiment of the honeycomb filter according to the present invention.

[0052] The Fig.The honeycomb filter 300 shown in Figure 9 is provided with a honeycomb substrate 44 and sealing portions 45. The honeycomb substrate 44 is columnar and has an inflow end face 51 and an outflow end face (not shown). The honeycomb substrate 44 has porous partition walls 41 provided surrounding a plurality of cells 42 extending from the inflow end face 51 to the outflow end face (not shown).

[0053] In Fig. In the honeycomb filter 300 shown in Figure 9, in the cross section perpendicular to the extending direction of the cells 42, each of the inflow cells 42a has a hexagonal shape other than a regular hexagonal shape, and each of the outflow cells 42b has a regular hexagonal shape. The honeycomb filter 300 has a structure in which six inflow cells 42a surround the periphery of one outflow cell 42b.

[0054] The honeycomb filter 300 is also configured such that the value of T2 / T1 is greater than 1.0 and less than 2.5. Furthermore, in the honeycomb filter 300, the total open end area of ​​the honeycomb substrate 44 is greater than 35% and equal to or less than 95%.

[0055] In the honeycomb filter 300, a second partition wall 41b includes a thickness-changing portion 46 that causes a thickness T2 of the second partition wall to decrease or increase toward a portion connected to a first partition wall 41a. The honeycomb filter 300 includes both the thickness-changing portion 46 that causes the thickness T2 of the second partition wall to increase toward the portion connected to the first partition wall 41a and the thickness-changing portion 46 that causes the thickness T2 of the second partition wall to decrease toward the portion connected to the first partition wall 41a.

[0056] The presence of the thickness-changing portion 46, which causes the thickness T2 of the second partition wall to increase toward the portion connected to the first partition wall 41a, enables, for example, the improvement of the thermal shock resistance of the honeycomb filter 300. More specifically, the connecting portion between the second partition wall 41b and the first partition wall 41a is relatively prone to stress, so the structural strength of the honeycomb filter can be improved by making the connecting portion between the second partition wall 41b and the first partition wall 41a relatively thicker. This can improve the thermal shock resistance during the regeneration process for burning and removing PM trapped by the honeycomb filter 300.

[0057] Meanwhile, the thickness changing portion 46, which causes the thickness T2 of the second partition wall to decrease toward the portion connected to the first partition wall 41a, enables the honeycomb filter 300 to have a smaller pressure loss. (2) Manufacturing process for honeycomb filters:

[0058] Now, the method for manufacturing the honeycomb filters according to the present invention will be described.

[0059] First, a plastic molding material for producing the honeycomb substrate is prepared. The molding material for producing the honeycomb substrate can be prepared by adding an additive, such as a binder, and optionally water to a material selected from the preceding group of suitable partition wall materials as a starting material powder.

[0060] Subsequently, the prepared molded material is subjected to extrusion to obtain a columnar honeycomb molded article having partition walls defining multiple cells and a peripheral wall provided at the outermost periphery. During extrusion, an extrusion die may be used in which a slit is formed in its molded material extrusion surface, providing an inverse shape of a honeycomb molded article to be formed. The resulting honeycomb molded article may be dried, for example, by microwaves and hot air.

[0061] Subsequently, the open ends of the cells are sealed with the same material as the material used to manufacture the honeycomb molding, thereby forming the sealing portions. A conventionally known honeycomb filter manufacturing method can be used as the method for forming the sealing portions.

[0062] The resulting honeycomb preform is then fired to produce a honeycomb filter. The firing temperature and firing atmosphere vary depending on the starting material, and those skilled in the art can select a firing temperature and firing atmosphere that are most suitable for a selected material. The method for producing the honeycomb filter according to the present invention is not limited to the method described above.

[0063] The following describes the present invention in more detail by means of examples, but the present invention is by no means limited by all these examples. (Example 1)

[0064] First, the molding material for manufacturing a honeycomb substrate was prepared. In Example 1, a powder mixture was prepared by mixing silicon carbide (SiC) powder and silicon metal (Si) powder in a mass ratio of 80:20 as the molding material raw material. A binder, a pore-forming agent, and water were added to the powder mixture to prepare the molding material. The molding material was then kneaded to produce a round columnar molding material.

[0065] Subsequently, the kneaded material was extruded using an extrusion die to produce a honeycomb molding, thereby obtaining a honeycomb molding having a round columnar overall shape.

[0066] The honeycomb was then dried in a microwave dryer and further dried in a hot air dryer until completely dry. Both end faces of the honeycomb were then cut to specified dimensions.

[0067] Sealing sections were then formed on the dried honeycomb. Specifically, a mask was first provided on the inflow end face of the honeycomb to cover the inflow cells. Then, the end portion of the masked honeycomb was immersed in a sealing slurry to fill the unmasked open ends of the outflow cell with the sealing slurry. Then, for the outflow end face of the honeycomb, the open ends of the inflow cells were filled with the sealing slurry according to the same method described above. Afterward, the honeycomb with the sealing sections formed therein was further dried by a hot-air dryer.

[0068] The honeycomb blank with the sealing sections formed therein was then degreased and fired to obtain the honeycomb filter.

[0069] According to the honeycomb filter of Example 1, the inflow cells 22a had a hexagonal shape other than a regular hexagonal shape, while the outflow cells 22b had a regular hexagonal shape as shown by the honeycomb filter 200 in Fig. 7 and Fig. 8. The honeycomb filter of Example 1 had the cell structure in which six hexagonal inflow cells 22a surround the periphery of the outflow cells 22b having the regular hexagonal shape, as shown in Fig. 7 and Fig. 8. The hexagonal shape of the inflow cells 22a was a hexagonal shape in which the opposite sides of the hexagon have different lengths.

[0070] The porosity of the partition walls of the honeycomb filter of Example 1 was 41%. The diameter of the end faces was 266.7 mm, and the length in the direction of cell extension was 254.0 mm. The porosity of the partition walls is indicated by a value measured by a mercury porosimeter. Furthermore, in the honeycomb filter of Example 1, the thickness T1 of the Fig. 8 was 152.4 µm, while the thickness T2 of the second partition wall 21b was 160.0 µm. Therefore, in the honeycomb filter of Example 1, the ratio of the thickness T2 of the second partition wall to the thickness T1 of the first partition wall (T2 / T1) was 1.05. Table 1 shows the values ​​of "Thickness T1 of the First Partition Wall (µm)," "Thickness T2 of the Second Partition Wall (µm)," and "T2 / T1."

[0071] Furthermore, the values ​​of a length “a” of the first partition wall and a length “b” of the second partition wall were determined on the honeycomb filter of Example 1, as shown in Fig.4. The results are shown in the columns “Length a of the first partition wall (mm)” and “Length b of the second partition wall (mm)” in Table 2. Furthermore, the values ​​obtained by dividing the length a (mm) of the first partition wall by the length b (mm) of the second partition wall are shown in the column “a / b” of Table 2. The cell density of the honeycomb filter of Example 1 is shown in the column “Cell density (cells / cm 2 )” of Table 2. Furthermore, the length indicated by “x” and the length indicated by “z” were measured on the honeycomb filter of Example 1 in Fig. 4. The results are shown in columns “x (mm)” and “z (mm)” of Table 2.

[0073] (Table 1) Porosity (%) Thickness T1 of the 1st partition (µm) Thickness T2 of the 2nd partition wall (µm) T2 / T1 Total open frontal area (%) Pressure loss ratio Comparison example 1 41 152,4 152,4 1,00 0,77 1,00 Example 1 41 152,4 160,0 1,05 0,77 0,96 Example 2 41 152,4 167,6 1,10 0,76 0,95 Example 3 41 152,4 228,6 1,50 0,76 0,90 Example 4 41 152,4 304,8 2,00 0,75 0,84 Comparison example 2 41 228,6 228,6 1,00 0,69 1,00 Example 5 41 228,6 240,0 1,05 0,68 0,97 Example 6 41 228,6 251,5 1,10 0,68 0,96 Example 7 41 228,6 342,9 1,50 0,67 0,91 Example 8 41 228,6 457,2 2,00 0,64 0,88 Comparison example 3 41 304,8 304,8 1,00 0,61 1,00 Example 9 41 304,8 320,0 1,05 0,61 0,96 Example10 41 304,8 335,3 1,10 0,60 0,96 Example 11 41 304,8 457,2 1,50 0,57 0,94 Example12 41 304,8 609,6 2,00 0,53 0,93 Comparison example 4 41 304,8 762,0 2,50 0,47 1,01

[0074] (Table 2) Length a of the 1st partition (mm) Length b of the 2nd partition (mm) away Cell density (cells / cm 2 ) x(mm) z(mm) Comparison example 1 0,910 0,910 1,00 46 0,411 0,411 Example 1 0,902 0,910 1,01 47 0,411 0,407 Example 2 0,895 0,910 1,02 48 0,411 0,403 Example 3 0,834 0,910 1,09 52 0,411 0,373 Example 4 0,758 0,910 1,20 59 0,411 0,335 Comparison example 2 0,910 0,910 1,00 46 0,389 0,389 Example 5 0,899 0,910 1,01 47 0,389 0,383 Example 6 0,888 0,910 1,03 48 0,389 0,378 Example 7 0,796 0,910 1,14 55 0,389 0,332 Example 8 0,681 0,910 1,34 68 0,389 0,275 Comparison example 3 0,910 0,910 1,00 46 0,367 0,367 Example 9 0,895 0,910 1,02 48 0,367 0,359 Example 10 0,880 0,910 1,03 49 0,367 0,352 Example 11 0,758 0,910 1,20 59 0,367 0,291 Example 12 0,605 0,910 1,50 79 0,367 0,215 Comparison example 4 0,453 0,910 2,01 114 0,367 0,138

[0072] The pressure loss performance evaluation test was conducted on the honeycomb filter of Example 1 according to the procedure described below. The results are shown in Table 1. (Pressure loss performance rating)

[0073] In the pressure loss performance evaluation, the pressure loss values ​​of the "reference honeycomb filters" subjected to measurement under the same conditions were used as the reference values, with the honeycomb filter of each sample subjected to pressure loss performance evaluation. Specifically, the pressure losses in the air volume of 10 m 3 / min using a large wind tunnel device. When measuring the pressure loss, the pressure losses were measured in a state where soot of 6 g / L had accumulated in each honeycomb filter. In the case where the pressure loss value of the reference honeycomb filter was indicated by P0 and the pressure loss value of the honeycomb filter of each example was indicated by P1, the value calculated according to "P1 / P0" was defined as the pressure loss performance evaluation result. The results are shown in the "Pressure Loss Ratio" column in Table 1.

[0074] In the pressure drop performance evaluation, the reference honeycomb filters are as shown below. In Examples 1 to 4, the reference honeycomb filter is defined as Comparative Example 1. In Examples 5 to 8, the reference honeycomb filter is defined as Comparative Example 2. In Examples 9 to 12 and Comparative Example 4, the reference honeycomb filter is defined as Comparative Example 3. In Examples 13 to 16, the reference honeycomb filter is defined as Comparative Example 5. In Examples 17 to 21 and Comparative Examples 7 to 9, the reference honeycomb filter is defined as Comparative Example 6. In Examples 22 to 25, the reference honeycomb filter is defined as Comparative Example 10. In Examples 26 to 29, the reference honeycomb filter is defined as Comparative Example 11. (Examples 2 to 12 and comparative examples 1 to 4)

[0075] The honeycomb filters were manufactured according to the same method as that for Example 1, except that the thickness T1 (µm) of the first partition wall, the thickness T2 (µm) of the second partition wall, the length a (mm) of the first partition wall, the length b (mm) of the second partition wall, and the like were changed as shown in Table 1 and Table 2. The honeycomb filters of Examples 2 to 12 and Comparative Example 4 were subjected to the pressure loss performance evaluation test according to the same method as that for Example 1. The results are shown in Table 1. The honeycomb filters of Comparative Examples 1 to 3 are honeycomb filters in which the thickness T1 of the first partition wall and the thickness T2 of the second partition wall have the same value. (Example 13)

[0076] For Example 13, the kneaded material prepared according to the same method as that for the kneaded material prepared for Example 1 was used to prepare the honeycomb filter having the Fig. 2 and Fig. 3. More specifically, as in the case of Fig. 2 and Fig. 3, the inflow cells 2a of the honeycomb filter of Example 13 had a regular hexagonal shape, and the outflow cells 2b also had a regular hexagonal shape. Furthermore, the honeycomb filter of Example 13 had a cell structure in which six regular hexagonal inflow cells 2a were arranged to surround the periphery of the outflow cell 2b having the regular hexagonal shape, as shown in Fig. 2 and Fig. 3 is shown.

[0077] The porosity of the partition walls of the honeycomb filter of Example 13 was 41%. The diameter of the end faces was 266.7 mm, while the length in the direction of cell extension was 254.0 mm. The porosities of the partition walls are indicated by the values ​​measured by a mercury porosimeter. Furthermore, in the honeycomb filter of Example 13, the thickness T1 of the Fig. 3 was 152.4 µm, while the thickness T2 of the second partition wall 1b was 160.0 µm. Consequently, in the honeycomb filter of Example 13, the value of the ratio of the thickness T2 of the second partition wall to the thickness T1 of the first partition wall (T2 / T1) was 1.05. Table 3 shows the values ​​of the thickness T1 (µm) of the first partition wall, the thickness T2 (µm) of the second partition wall, and T2 / T1.

[0078] On the honeycomb filter of Example 13, the values ​​of the length a of the first partition wall and the length b of the second partition wall, which are shown in Fig.4. The results are shown in the columns “Length a of the first partition wall (mm)” and “Length b of the second partition wall (mm)” of Table 4. In addition, the values ​​obtained by dividing the length a (mm) of the first partition wall by the length b (mm) of the second partition wall are shown in the column “a / b” of Table 4. The cell density of the honeycomb filter of Example 13 is shown in the column “Cell density (cells / cm 2 )” of Table 4. Furthermore, on the honeycomb filter of Example 13, the length indicated by “x” and the length indicated by “z” were measured in Fig. 4. The results are shown in columns “x (mm)” and “z (mm)” of Table 4. (Examples 14 to 21 and comparative examples 5 to 9)

[0079] The honeycomb filters were manufactured according to the same method as that for Example 13, except that the thickness T1 (µm) of the first partition wall, the thickness T2 (µm) of the second partition wall, the length a (mm) of the first partition wall, the length b (mm) of the second partition wall, and the like were changed as shown in Table 3 and Table 4. The honeycomb filters of Examples 14 to 20 and Comparative Examples 7 to 9 were subjected to the pressure loss performance evaluation test according to the same method as that for Example 1. The results are shown in Table 3. The honeycomb filters of Comparative Examples 5 and 6 are honeycomb filters in which the thickness T1 of the first partition wall and the thickness T2 of the second partition wall have the same value. (Examples 22 to 25 and Comparative Example 10)

[0080] For Examples 22 to 25 and Comparative Example 10, when preparing the kneaded material for producing the honeycomb substrates, the amount of a pore former added to the kneaded material prepared in Example 1 was changed to prepare honeycomb filters whose partition wall porosity was 63%. The thickness T1 (µm) of the first partition wall, the thickness T2 (µm) of the second partition wall, the length a (mm) of the first partition wall, the length b (mm) of the second partition wall, and the like of the honeycomb filters of Examples 22 to 25 and Comparative Example 10 are as shown in Table 5 and Table 6. The honeycomb filters of Examples 22 to 25 were subjected to pressure loss performance evaluation tests according to the same method as that for Example 1. The results are shown in Table 5. The honeycomb filter of Comparative Example 10 is a honeycomb filter in which the thickness T1 of the first partition wall and the thickness T2 of the second partition wall have the same value. (Examples 26 to 29 and Comparative Example 11)

[0081] For Examples 26 to 29 and Comparative Example 11, the following kneaded material for producing cordierite honeycomb substrates was prepared as the kneaded material for producing the honeycomb substrates. A powder mixture of cordierite, mullite, alumina, spinel, and the like was prepared as the raw material powder for producing the kneaded material. A binder, a pore-forming agent, and water were added to the powder mixture to prepare the molding raw material. The molding raw material was then kneaded to produce a round columnar wrought material.

[0082] The thickness T1 (µm) of the first partition wall, the thickness T2 (µm) of the second partition wall, the length a (mm) of the first partition wall, the length b (mm) of the second partition wall, and the like of the honeycomb filters of Examples 26 to 29 and Comparative Example 11 are as shown in Table 5 and Table 6. The honeycomb filters of Examples 26 to 29 were subjected to the pressure loss performance evaluation test according to the same method as that for Example 1. The results are shown in Table 5. The honeycomb filter of Comparative Example 11 is a honeycomb filter in which the thickness T1 of the first partition wall and the thickness T2 of the second partition wall have the same value.

[0086] (Table 3) Porosity (%) Thickness T1 of the 1st partition (µm) Thickness T2 of the 2nd partition wall (µm) T2 / T1 Total open frontal area (%) Pressure loss ratio Comparison example 5 41 152,4 152,4 1,00 0,77 1,00 Example13 41 152,4 160,0 1,05 0,76 0,96 Example14 41 152,4 167,6 1,10 0,76 0,96 Example15 41 152,4 228,6 1,50 0,75 0,91 Example16 41 152,4 304,8 2,00 0,73 0,86 Comparison example 6 41 228,6 228,6 1,00 0,69 1,00 Example17 41 228,6 240,0 1,05 0,68 0,97 Example18 41 228,6 251,5 1,10 0,68 0,96 Example19 41 228,6 342,9 1,50 0,65 0,94 Example20 41 228,6 457,2 2,00 0,61 0,97 Example21 41 228,6 548,6 2,40 0,57 0,99 Comparison example 7 41 228,6 571,5 2,50 0,55 1,08 Comparison example 8 41 228,6 685,8 3,00 0,47 1,63 Comparison example 9 41 304,8 762,0 2,50 0,35 4,8

[0087] (Table 4) Length a of the 1, partition (mm) Length b of the 2nd partition (mm) away Cell density (cells / cm 2 ) x(mm) Z(mm) Comparison example 5 0,910 0,910 1,0 46 0,411 0,411 Example 13 0,902 0,902 1,0 47 0,407 0,407 Example 14 0,895 0,895 1,0 48 0,403 0,403 Example 15 0,834 0,834 1,0 55 0,373 0,373 Example 16 0,758 0,758 1,0 67 0,335 0,335 Comparison example 6 0,910 0,910 1,0 46 0,389 0,389 Example 17 0,899 0,899 1,0 48 0,383 0,383 Example 18 0,888 0,888 1,0 49 0,378 0,378 Example 19 0,796 0,796 1,0 61 0,332 0,332 Example 20 0,681 0,681 1,0 83 0,275 0,275 Example 21 0,590 0,590 1,0 111 0,229 0,229 Comparison example 7 0,567 0,567 1,0 120 0,218 0,218 Comparison example 8 0,453 0,453 1,0 188 0,160 0,160 Comparison example 9 0,453 0,453 1,0 188 0,138 0,138

[0088] (Table 5) Porosity (%) Thickness T1 of the 1st partition wall (µm) Thickness T2 of the 2nd partition wall (µm) T2 / T1 Total open frontal area (%) Pressure loss ratio Comparison example 10 63 152,4 152,4 1,00 0,77 1,00 Example 22 63 152,4 160,0 1,05 0,77 0,97 Example 23 63 152,4 167,6 1,10 0,76 0,97 Example 24 63 152,4 228,6 1,50 0,76 0,97 Example 25 63 152,4 304,8 2,00 0,75 0,94 Comparison example 11 58 152,4 152,4 1,00 0,77 1,00 Example 26 58 152,4 160,0 1,05 0,77 0,99 Example 27 58 152,4 167,6 1,10 0,76 0,98 Example 28 58 152,4 228,6 1,50 0,76 0,91 Example 29 58 152,4 304,8 2,00 0,75 0,87

[0089] (Table 6) Length a of the 1st partition wall (mm) Length b of the 2nd partition wall (mm) away Cell density (cells / cm 2 ) x (mm) z (mm) Comparison example 10 0,910 0,910 1,00 46 0,411 0,411 Example 22 0,902 0,910 1,01 47 0,411 0,407 Example 23 0,895 0,910 1,02 48 0,411 0,403 Example 24 0,834 0,910 1,09 52 0,411 0,373 Example 25 0,758 0,910 1,20 59 0,411 0,335 Comparison example 11 0,910 0,910 1,00 46 0,411 0,411 Example 26 0,902 0,910 1,01 47 0,411 0,407 Example 27 0,895 0,910 1,02 48 0,411 0,403 Example 28 0,834 0,910 1,09 52 0,411 0,373 Example 29 0,758 0,910 1,20 59 0,411 0,335

[0090] (Results)

[0083] The honeycomb filters of Examples 1 to 29 exhibited lower pressure losses than those of the reference honeycomb filters. In other words, it was confirmed that honeycomb filters configured such that T2 / T1 is greater than 1.0 and less than 2.5 and the total open area is greater than 35% and equal to or less than 95% can achieve lower pressure losses. The pressure losses of Comparative Examples 4 and 7 to 9, in which T2 / T1 was equal to or greater than 2.5, were higher. Comparative Example 9 exhibited a total open area of ​​35% and exhibited an extremely high pressure loss.

[0084] The honeycomb filter according to the present invention can be used as a filter for exhaust gas purification. Description of reference symbols

[0085] 1, 21, 41: partition wall; 1a, 21a, 41a: first partition wall; 1b, 21b, 41b: second partition wall; 2, 22, 42: cell; 2a, 22a, 42a: inflow cell; 2b, 22b, 42b: outflow cell; 3, 23: peripheral wall; 4, 24, 44: honeycomb substrate; 5, 25, 45: sealing portion; 46: thickness changing portion; 11, 31, 51: inflow end face; 12: outflow end face; 100, 200, 300: honeycomb filter; T1: thickness of the first partition wall; and T2: thickness of the second partition wall.

Claims

[1] Honeycomb filter (100, 200, 300) comprising: a columnar honeycomb substrate (5, 25, 45) having a porous partition wall (1, 21, 41) provided thereon, surrounding a plurality of cells (2, 22, 42) extending from an inflow end face (11, 31, 51) to an outflow end face (12); and a sealing portion (5) provided at an end portion either on the inflow end face (11, 31, 51) side or on the outflow end face (12) side of the cells (2, 22, 42), wherein in a section perpendicular to the direction of extension of the cells (2, 22, 42), the shape of an inflow cell (2a, 22a, 42a) with the sealing portion (2) provided at the end portion on the side of the outflow end face (12) is hexagonal, the shape of an outflow cell (2b, 22b, 42b) with the sealing portion (5) provided at the end portion on the side of the inflow end face (11, 31, 51) is hexagonal, the plurality of cells (2, 22, 42) have a structure in which a plurality of inflow cells (2a, 22a, 42a) surround the circumference of an outflow cell (2b, 22b, 42b) such that one side of the inflow cell (2a, 22a, 42a) and one side of the outflow cell (2b, 22b, 42b) adjacent to the inflow cell (2a, 22a, 42a) are parallel, the partition wall (1, 21, 41) includes a first partition wall (1a, 21a, 41a) provided between the inflow cell (2a, 22a, 42a) and the outflow cell (2b, 22b, 42b), and a second partition wall (1b, 21b, 41b) provided between the inflow cells (2a, 22a, 42a), at least one of the first partition walls (1a, 21a, 41a) is configured such that a value of the ratio (T2 / T1) of a thickness T2 of the second partition wall (1b, 21b, 41b) with respect to a thickness T1 of the first partition wall (1a, 21a, 41a) is greater than 1.0 and less than 2.5, and a total open end area of ​​the honeycomb substrate (5, 25, 45) is greater than 35% and equal to or less than 95%, wherein the second partition wall (41b) has a thickness change portion (46) in which the thickness T2 of the second partition wall (41b) decreases or increases toward a connecting portion with the first partition wall (41a). [2] Honeycomb filter (100, 200, 300) according to claim 1, wherein the thickness T1 of the first partition wall (1a, 21a, 41a) is 70 to 350 µm. [3] Honeycomb filter (100, 200, 300) according to one of claims 1 or 2, wherein the hydraulic diameter of the inflow cell (2a, 22a, 42a) is larger than the hydraulic diameter of the outflow cell (2b, 22b, 42b). [4] Honeycomb filter (100, 200, 300) according to one of claims 1 to 3, wherein the length of one side of the outflow cell (2b, 22b, 42b) is 0.5 to 1.6 mm. [5] Honeycomb filter (100, 200, 300) according to one of claims 1 to 4, wherein the porosity of the partition wall (1, 21, 41) is 35 to 70%. [6] Honeycomb filter (100, 200, 300) according to claim 5, wherein the porosity of the partition wall (1, 21, 41) is 50 to 70%. [7] Honeycomb filter (100, 200, 300) according to one of claims 1 to 6, wherein in a cross section perpendicular to the direction of extension of the cells (2, 22, 42), six of the hexagonal inflow cells (2a, 22a, 42a) surround the circumference of one of the outflow cells (2b, 22b, 42b). [8] Honeycomb filter (100, 200, 300) according to one of claims 1 to 7, wherein the inflow cells (2a, 22a, 42a) have a regular hexagonal shape in a cross section perpendicular to the direction of extension of the cells (2, 22, 42). [9] Honeycomb filter (100, 200, 300) according to one of claims 1 to 7, wherein the inflow cells (2a, 22a, 42a) have a hexagonal shape different from a regular hexagonal shape in a cross section perpendicular to the extension direction of the cells (2, 22, 42). [10] A honeycomb filter (100, 200, 300) according to claim 9, wherein the inflow cells (2a, 22a, 42a) have a hexagonal shape in which the lengths of at least one set of opposite sides are different in a cross section perpendicular to the extension direction of the cells (2, 22, 42). [11] Honeycomb filter (100, 200, 300) according to claim 10, wherein the inflow cells (2a, 22a, 42a) have a hexagonal shape in which opposite sides have different lengths in a cross section perpendicular to the extension direction of the cells (2, 22, 42).

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