WO2016111287A1

WO2016111287A1 - Exhaust gas filter

Info

Publication number: WO2016111287A1
Application number: PCT/JP2016/050113
Authority: WO
Inventors: 悠登丹羽; 周作山村; 石原　幹男; 崇生三島; 真吾中田; 藤井　宏明; 好太山越; 晶宮下
Original assignee: 株式会社デンソー
Priority date: 2015-01-09
Filing date: 2016-01-05
Publication date: 2016-07-14

Abstract

An exhaust gas filter (1) for purifying exhaust gas containing particulate matter discharged from an internal combustion engine has a plurality of cell walls (2) and a plurality of cell holes (3) enclosed by the cell walls (2). Pores through which adjacent cell holes (3) communicate are formed in the cell walls (2), and the cell holes (3) comprise open cell holes (31) running through the exhaust gas filter (1) in an axial direction (X), and stopped cell holes (32) provided with stoppers (321) for closing up the upstream-side ends. In a cross section orthogonal to the axial direction (X), the flow channel cross-sectional area (S2) in the stopped cell holes (32) is greater than the flow channel cross-sectional area (S1) in the open cell holes (31). The total length (L) of the exhaust gas filter (1) is equal to or greater than a first reference value (L1) calculated by a prescribed formula, and equal to or less than a critical length (Lm) calculated by a prescribed formula.

Description

Exhaust gas filter

The present invention relates to an exhaust gas filter for purifying exhaust gas of an internal combustion engine such as a gasoline engine or a diesel engine.

An exhaust gas purification device that collects particulate matter (PM) contained in exhaust gas is provided in an exhaust pipe of an internal combustion engine such as a gasoline engine or a diesel engine. This exhaust gas purification apparatus includes an exhaust gas filter for collecting particulate matter contained in exhaust gas (Patent Documents 1 and 2). The exhaust gas filter of the exhaust gas purification apparatus disclosed in

Patent Documents

1 and 2 has a plurality of cell walls and cell holes formed surrounded by the cell walls. As the cell hole, there are a plugged cell hole whose upstream end is closed by a plug part and an open cell hole in which no plug part is provided. In the cell wall between the plugged cell hole and the open cell hole, pores are formed so as to communicate with each other, and exhaust gas is circulated through the pores to trap particulate matter. Particulate matter is removed. Further, Patent Document 1 discloses an exhaust gas purification device in which a plurality of exhaust gas filters are mounted in series in order to improve the collection performance.

International Publication WO-2012-046484 JP 2003-35126 A

However, the exhaust gas filters of

Patent Documents

1 and 2 have the following problems. The exhaust gas filters of

Patent Documents

1 and 2 transmit exhaust gas to the cell wall using a pressure difference caused by pressure loss in the open cell hole, pressure loss in the plugged cell hole, and pressure loss due to passage resistance in the cell wall. I am letting. Therefore, if a sufficient pressure difference cannot be generated in the exhaust gas filter, the exhaust gas flowing into the open cell hole is discharged from the exhaust gas filter without passing through the cell wall. Therefore, the collection performance of the particulate matter in the exhaust gas filter is lowered.

Further, in the exhaust gas filters described in

Patent Documents

1 and 2, the flow path cross-sectional areas of the open cell hole and the plugged cell hole are equal. Therefore, the exhaust gas filter has a small difference between the pressure loss of the open cell hole and the pressure loss of the plugged cell hole, and cannot exhibit sufficient collection performance.

Moreover, since the exhaust gas purification apparatus described in Patent Document 1 has a plurality of exhaust gas filters arranged in series, the ease of mounting on a vehicle is likely to deteriorate. That is, the exhaust gas purification device can be mounted only on a vehicle that can mount a plurality of exhaust gas filters in series on an exhaust pipe. In addition, the exhaust gas purification device tends to increase pressure loss.

The present invention has been made in view of such a background, and suppresses an increase in pressure loss and a decrease in mountability on a vehicle, and particulates contained in exhaust gas discharged from an internal combustion engine such as a gasoline engine or a diesel engine. It is an object of the present invention to provide an exhaust gas filter that improves the substance collection performance, has an excellent exhaust gas purification performance, reduces pressure loss, and has excellent mountability in a vehicle.

A first aspect of the present invention is an exhaust gas filter that purifies exhaust gas containing particulate matter discharged from an internal combustion engine, and has a plurality of cell walls and a plurality of cell holes surrounded by the cell walls. The cell wall has a pore communicating between adjacent cell holes, and the cell hole includes an open cell hole penetrating in the axial direction of the exhaust gas filter and a plug portion closing the upstream end. The cross-sectional area S2 in the plugging cell hole is larger than the flow-path cross-sectional area S1 in the open cell hole in the cross section perpendicular to the axial direction, Thickness is w (mm), exhaust gas permeability coefficient is k (μm ² ), cell density is C (cells / mm ² ), the outer diameter of the exhaust gas filter is φ (mm), and the flow path is the ratio of S2 to S1 When the cross-sectional area ratio Rs = S2 / S1, the exhaust gas fill The total length L (base material length L) of the catalyst is not less than the first reference value L1 determined by the following formula (1) and not more than the critical length Lm (blow-through critical length Lm) determined by the following formula (M). The exhaust gas filter is characterized in that.
L1 = −3.7 × Rs ^1.5 −3.6 / w + 9.7 / k−152.9 × C + 2241.5 / φ + 145.1 Formula (1),
Lm = −5.5 × Rs ^1.5 −6.0 / w + 44.9 / k−234.9 × C + 176.7 / φ + 255.6 (formula (M))

A second aspect of the present invention is an exhaust gas filter (1) for purifying exhaust gas containing particulate matter discharged from an internal combustion engine, and is surrounded by a plurality of cell walls (2) and the cell walls (2). A plurality of cell holes (3), the cell wall (2) has pores communicating between adjacent cell holes (3), and the cell holes (3) are provided in the exhaust gas filter. (1) an open cell hole (31) penetrating in the axial direction and a plugged cell hole (32) having a plug part (321) for closing the upstream end, and a cross section perpendicular to the axial direction. The flow path cross-sectional area S2 in the plugged cell hole (32) is larger than the flow path cross-sectional area S1 in the open cell hole (31), and the thickness of the cell wall (2) is w (mm), the exhaust gas permeability coefficient k (μm ^2), a cell density C (pieces / mm ^2), the exhaust gas filter (1 When the outer diameter of the exhaust gas filter (1) is φ (mm) and the flow path cross-sectional area ratio Rs = S2 / S1, which is the ratio of S2 to S1, the total length L (base material length L) of the exhaust gas filter (1) is The exhaust gas filter (1) is characterized by being not less than the second reference value L2 determined by 2) and not more than the critical length Lm (blow-through critical length Lm) determined by the following formula (M).
L2 = −13.4 × Rs ^1.5 + 0.76 / w + 3.2 / k−132.1 × C + 117.3 / φ + 174.4 Formula (2),
Lm = −5.5 × Rs ^1.5 −6.0 / w + 44.9 / k−234.9 × C + 176.7 / φ + 255.6 (Equation (M))

A third aspect of the present invention is an exhaust gas filter (1) for purifying exhaust gas containing particulate matter discharged from an internal combustion engine, and is surrounded by a plurality of cell walls (2) and the cell walls (2). A plurality of cell holes (3), the cell wall (2) has pores communicating between adjacent cell holes (3), and the cell holes (3) are provided in the exhaust gas filter. (1) an open cell hole (31) penetrating in the axial direction and a plugged cell hole (32) having a plug part (321) for closing the upstream end, and a cross section perpendicular to the axial direction. The flow path cross-sectional area S2 in the plugged cell hole (32) is larger than the flow path cross-sectional area S1 in the open cell hole (31), and the thickness of the cell wall (2) is w (mm), the exhaust gas permeability coefficient k (μm ^2), a cell density C (pieces / mm ^2), the exhaust gas filter (1 When the outer diameter of the exhaust gas filter (1) is φ (mm) and the flow path cross-sectional area ratio Rs = S2 / S1, which is the ratio of S2 to S1, the total length L (base material length L) of the exhaust gas filter (1) is The exhaust gas filter (1) is characterized by being not less than a third reference value L3 determined by 3) and not more than a critical length Lm (blow-through critical length Lm) determined by the following equation (M).
L3 = −6.8 × Rs ^1.5 −4.5 / w + 12.0 / k−189.9 × C + 2629.1 / φ + 191.7 Formula (3),
Lm = −5.5 × Rs ^1.5 −6.0 / w + 44.9 / k−234.9 × C + 176.7 / φ + 255.6 (Equation (M))

Note that the critical length Lm (blow-through critical length Lm) described in the first, second, and third aspects of the present invention is the total length L at which the increase in the collection rate accompanying the increase in the exhaust gas filter total length L does not occur. Yes, the collection rate refers to the ratio of the number of particulate matter contained in the exhaust gas discharged from the exhaust gas filter to the number of particulate matter contained in the exhaust gas introduced into the exhaust gas filter. The critical length Lm and the collection rate will be described in the following examples.

The exhaust gas filter according to the first to third aspects has the open cell hole and the plugged cell hole as the cell hole as described above. Therefore, exhaust gas can be efficiently circulated through the pores formed in the cell wall, and the purification performance of the exhaust gas filter can be improved.

That is, by increasing the cross-sectional area of the plugged cell hole compared to the cross-sectional area of the open cell hole, the pressure loss in the open cell hole is larger than the pressure loss in the plugged cell hole. Thus, the pressure difference between the pressure in the open cell hole and the pressure in the plugged cell hole becomes large. By utilizing this pressure difference, the exhaust gas flowing into the open cell holes can be efficiently circulated through the pores to the plugged cell holes. Further, the pressure difference between the open cell hole and the plugged cell hole becomes smaller from the upstream side to the downstream side of the exhaust gas filter, but in the range where the pressure difference is generated, the exhaust gas to the pores is reduced. Distribution continues. Therefore, as described above, by increasing the pressure difference between the open cell hole and the plugged cell hole, the exhaust gas can permeate the cell wall in a wider range of the exhaust gas filter. Thereby, the particulate matter contained in the exhaust gas can be efficiently collected.

Further, the plug portion is disposed at an upstream end portion of the plugged cell hole. Therefore, Ash (ash content such as calcium compounds) contained in the exhaust gas together with the particulate matter can be discharged from the exhaust gas filter. Since Ash cannot be removed by combustion, for example, in an exhaust gas filter in which the plug is disposed at the downstream end of the plugged cell hole, Ash is accumulated in the interior. On the other hand, in the exhaust gas filter, when the exhaust gas permeates the cell wall, it is separated by the cell wall, and Ash remains in the open cell hole. Since the open cell hole penetrates in the axial direction, the Ash can be easily discharged from the open cell hole, and the Ash can be prevented from remaining in the exhaust gas filter. Thereby, the fall of the purification performance in the said exhaust gas filter can be suppressed.

Further, the exhaust gas filter of the first aspect has a total length L (base material length L) equal to or greater than the first reference value L1 determined by the above formula (1). Therefore, it is possible to sufficiently secure the particulate matter collection performance and to further improve the purification performance of the exhaust gas filter.

Further, the exhaust gas filter of the second aspect has a total length L (base material length L) equal to or greater than a second reference value L2 determined by the above formula (2). Therefore, the collection rate of the exhaust gas filter can be ensured to be 50% or more, which exceeds the collection rate generally required in a vehicle equipped with a gasoline engine, and high purification performance can be obtained.

Further, the exhaust gas filter of the third aspect has a total length L (base material length L) equal to or greater than a third reference value L3 determined by the above formula (3). Therefore, it is possible to sufficiently secure the particulate matter collection performance and to further improve the purification performance of the exhaust gas filter.

The exhaust gas filter according to the first to third aspects has a total length L (base material length L) equal to or shorter than the critical length Lm (blow-through critical length Lm) determined by the above equation (M). This critical length Lm (blow-through critical length Lm) is the full length L at which the collection rate starts to increase with the increase in the exhaust gas filter overall length L, and the collection rate is included in the exhaust gas introduced into the exhaust gas filter. The ratio of the number of particulate matter contained in the exhaust gas discharged from the exhaust gas filter to the number of particulate matter produced. The critical length Lm and the collection rate will be described in the following examples. Therefore, an increase in the pressure loss of the exhaust gas filter and an increase in the size of the exhaust gas filter can be effectively suppressed. That is, even if the total length (base material length) of the exhaust gas filter is longer than the critical length Lm, the exhaust gas flowing through the open cell holes is discharged without passing through the cell walls. In addition, waste is increased due to the relationship between the pressure loss and the mountability of the exhaust gas filter. Therefore, by setting the total length (base material length) of the exhaust gas filter to the critical length Lm or less determined by the above formula (M), it is possible to effectively suppress an increase in pressure loss and an increase in size of the exhaust gas filter.

As described above, according to the present invention, there is provided an exhaust gas filter capable of improving the collection performance of particulate matter and improving the purification performance while suppressing an increase in pressure loss and a decrease in mountability on a vehicle. Can be provided.

Explanatory drawing which shows the exhaust gas filter in Example 1 of this invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. Explanatory drawing which shows an example of the exhaust gas filter in Example 1 of this invention. The diagram which shows the outline of the relationship between the base material length in Example 1 of this invention, ie, the full length of an exhaust gas filter, and a collection rate. The diagram which shows the outline of the relationship between the base material length in Example 2 of this invention, ie, the full length of an exhaust gas filter, and a collection rate. The diagram which shows the outline of the relationship between the base material length in Example 3 of this invention, ie, the full length of an exhaust gas filter, and a collection rate. Explanatory drawing which shows the exhaust gas filter in Example 4 of this invention. Explanatory drawing which shows the shape of the exhaust gas filter in the confirmation test 1 of this invention. The graph which shows the relationship between the permeation | transmission flow rate ratio and flow-path cross-sectional area ratio in the confirmation test 1 of this invention. The graph which shows the relationship between the collection rate in the confirmation test 1 of this invention, and flow-path cross-sectional area ratio. Sectional drawing of the exhaust gas filter in Example 5 of this invention.

The exhaust gas filter has a flow path cross-sectional area ratio Rs = S2 / S, which is a ratio of S2 to S1, where S1 is a flow cross-sectional area of the open cell hole and S2 is a flow cross-sectional area of the plugged cell hole. S1 is 1.1 ≦ Rs ≦ 5, and the base material length L of the exhaust gas filter (hereinafter, the base material length L is used, but the total length L of the exhaust gas filter) is 35 mm ≦ L ≦ 270 mm. It is preferable that In this case, a pressure difference between the open cell hole and the plugged cell hole can be reliably generated, and the exhaust gas can be reliably circulated through the pore formed in the cell wall. Further, the base material length L is determined within the range of 35 mm to 270 mm in accordance with the flow path cross-sectional area ratio Rs between the plugged cell hole and the open cell hole, thereby increasing the pressure loss of the exhaust gas filter. It is possible to improve the collection performance of the exhaust gas filter while suppressing it. When Rs is less than 1.1, the pressure difference becomes small, the permeation amount of the exhaust gas that permeates the cell wall decreases, and sufficient purification performance may not be exhibited. When Rs exceeds 5, the area of the cell wall constituting the open cell hole, that is, the filtration area tends to be small. Along with this, the cell hole may be blocked during the deposition of the particulate matter, and the pressure loss may become excessive. In the exhaust gas filter, the flow path cross-sectional area ratio Rs is more preferably 1.1 ≦ Rs ≦ 2.5. When Rs is larger than 2.5, the pressure loss of the exhaust gas filter may be excessive. Therefore, when the substrate length is increased, the effect of improving the collection performance may be reduced with respect to the increase in pressure loss of the exhaust gas filter. When L is less than 35 mm, the substrate length becomes too short with respect to the substrate diameter, and it may be difficult to attach the exhaust gas filter to the exhaust pipe. When L exceeds 270 mm, the exhaust gas permeates through the cell holes, thereby generating a region where there is no pressure difference between the open cell holes and the plugged cell holes. More preferably, the exhaust gas filter has a substrate length L of 55 mm ≦ L ≦ 220 mm. When L is less than 55 mm, the exhaust gas flowing through the open cell hole is discharged without passing through the cell wall, and the performance of the exhaust gas filter may be deteriorated. When L exceeds 220 mm, the effect of increasing the collection performance accompanying the increase in the substrate length L tends to be slow. Furthermore, when L exceeds 220 mm, there is a risk of increasing the pressure loss of the exhaust gas filter.

The cell hole is composed of an octagonal cell hole with an inner peripheral shape and a square cell hole with an inner peripheral shape, and the hydraulic diameter of the octagonal cell hole is greater than the hydraulic diameter of the square cell hole. It is preferable that the octagonal cell holes and the square cell holes are alternately arranged. In this case, the difference between the hydraulic diameter of the octagonal cell hole and the hydraulic diameter of the square cell hole can be increased. Thereby, for example, when the octagonal cell hole is appropriately allocated as a plugged cell hole and the square cell hole is appropriately allocated as the open cell hole, the plugged cell hole and the open cell hole can be adjacent to each other. And the pressure difference between the plugged cell hole and the open cell hole can be effectively increased. On the other hand, when the plugged cell holes or the open cell holes are adjacent to each other, a pressure difference is hardly generated between the plugged cell holes or between the open cell holes. There are few functions from the viewpoint. The cell shape is preferably a shape having a large hydraulic diameter from the viewpoint of pressure loss of the exhaust gas filter. Accordingly, making the cell holes triangular, for example, tends to increase the pressure loss of the exhaust gas filter. From the above viewpoint, the purification performance can be improved efficiently by alternately forming the octagonal cell holes and the square cell holes.

The porosity of the cell wall is not particularly limited, but is preferably 50 to 80%, and more preferably 50 to 65%. When the porosity is less than 50%, the exhaust gas containing particulate matter is difficult to permeate the cell wall (that is, the exhaust gas permeability coefficient of the cell wall is likely to decrease). Along with this, it is considered that the amount of the exhaust gas containing particulate matter permeates the cell walls is likely to decrease, and the collection performance is likely to be lowered. When the porosity is larger than 65%, the strength of the exhaust gas filter tends to decrease, and there is a concern that it becomes difficult to attach the exhaust gas filter to the exhaust pipe. The porosity of the cell wall can be measured with a mercury porosimeter.

The average pore diameter of the cell wall is not particularly limited, but is preferably 5 to 30 μm, and more preferably 10 to 25 μm. When the average pore diameter is smaller than 10 μm, the exhaust gas containing particulate matter is difficult to permeate the cell wall (that is, the exhaust gas permeability coefficient of the cell wall is likely to decrease). Along with this, it is considered that the amount of the exhaust gas containing particulate matter permeates the cell walls is likely to decrease, and the collection performance is likely to be lowered. When the average pore diameter is larger than 25 μm, the strength of the exhaust gas filter tends to decrease, and there is a concern that it is difficult to attach the exhaust gas filter to the exhaust pipe. The average pore diameter of the cell wall can be measured with a mercury porosimeter.

The thickness w (mm) of the cell wall is preferably 0.10 ≦ w ≦ 0.50, and more preferably 0.13 ≦ w ≦ 0.47 mm. If the thickness w is less than 0.13 mm, the strength of the exhaust gas filter tends to decrease, and there is a concern that it will be difficult to attach the exhaust gas filter to the exhaust pipe. If the thickness w is greater than 0.47 mm, the exhaust gas containing particulate matter will not easily pass through the cell walls. Along with this, it is considered that the amount of the exhaust gas containing particulate matter permeates the cell walls is likely to decrease, and the collection performance is likely to be lowered.

The cell density C (cells / mm ² ) is preferably 0.30 ≦ C ≦ 0.70, and more preferably 0.31 ≦ C ≦ 0.62. If the cell density C is less than 0.31 cells / mm ² , the difference in hydraulic diameter between the plugged cell hole and the open cell hole tends to be relatively small. Therefore, the pressure difference between the plugged cell hole and the open cell hole tends to be small, and the exhaust gas containing particulate matter is difficult to permeate the cell wall. Along with this, it is considered that the amount of the exhaust gas containing particulate matter permeates the cell walls is likely to decrease, and the collection performance is likely to be lowered. When the cell density C is larger than 0.62 cells / mm ² , the hydraulic diameter of the cell holes becomes too small, and the pressure loss may increase.

The outer diameter φ (mm) of the exhaust gas filter is preferably 60 ≦ φ ≦ 160, and more preferably 80 ≦ φ ≦ 150. When the outer diameter φ is smaller than 80 mm, the area of all the cell holes as viewed from the axial direction of the exhaust gas filter, that is, the area of the entire flow path becomes small, and the pressure loss of the exhaust gas filter may increase. If the outer diameter φ is larger than 150 mm, the mounting property of the exhaust gas filter on the exhaust pipe may be lowered.

The exhaust gas permeability coefficient k (μm ² ) of the cell wall is preferably 0.1 ≦ k ≦ 2.0, and more preferably 0.3 ≦ k ≦ 1.1. It is known that the exhaust gas permeability coefficient k of the cell wall is strongly influenced by the porosity and the average pore diameter. When the exhaust gas permeability coefficient k is smaller than 0.3 μm ² , the porosity and average pore diameter are likely to be small, and the exhaust gas containing particulate matter is difficult to permeate the cell wall, and accordingly, the trapping performance tends to be lowered. It is considered to be. When the exhaust gas permeability coefficient k is larger than 1.1 μm ² , the porosity and average pore diameter are likely to increase, and the strength of the exhaust gas filter tends to decrease.

(Example 1) Example 1 of the exhaust gas filter will be described with reference to FIGS. As shown in FIGS. 1 to 3, the exhaust gas filter 1 purifies exhaust gas containing particulate matter discharged from an internal combustion engine. The exhaust gas filter 1 has a plurality of cell walls 2 and a plurality of cell holes 3 surrounded by the cell walls 2.

The cell wall 2 is formed with pores communicating between adjacent cell holes 3. The cell hole 3 includes an open cell hole 31 penetrating in the axial direction X of the exhaust gas filter 1 and a plugged cell hole 32 provided with a plug part 321 for closing the upstream end. In the cross section orthogonal to the axial direction X, the flow path cross-sectional area in the plugged cell hole 32 is larger than the flow path cross-sectional area in the open cell hole 31.

The details will be described below. As shown in FIG. 1, the exhaust gas filter 1 of this example is for purifying exhaust gas generated in an internal combustion engine of an automobile, for example, a diesel engine or a gasoline engine. The exhaust gas filter 1 has a cylindrical shape, and is formed with cell walls 2 arranged in a lattice shape and cell holes 3 surrounded by the cell walls 2. In this example, the outer diameter φ of the exhaust gas filter 1 is 132 mm. The base material length L is preferably 35 mm ≦ L ≦ 270 mm.

The cell wall 2 is made of a ceramic material having a porous structure, and inside thereof, pores (not shown) that are pores and communicate with adjacent cell holes 3 are formed. In this example, cordierite having an average pore diameter of 18 μm and a porosity of 60% was used as the ceramic material. Moreover, the thickness W of the cell wall 2 was 0.28 mm. In this example, the exhaust gas permeation coefficient k indicating the ease of permeation when the exhaust gas permeates the cell wall 2 is 0.7 μm ² .

As shown in FIGS. 1 to 3, the cell hole 3 includes an open cell hole 31 and a plugged cell hole 32. The open cell holes 31 and the plugged cell holes 32 are formed alternately so as to be adjacent to each other. In the exhaust gas filter 1 of Example 1, the cell density C, which is the number of the cell holes 3 per unit area, was 0.47 / mm ² .

As shown in FIGS. 1 to 3, the plurality of cell holes 3 have two or more types of shapes. That is, in the plurality of cell holes 3, there are two or more types of cell holes 3 having different shapes when viewed from the axial direction X. Further, the cell holes 3 having different sizes even in the similar shape are different in shape. In this example, the cell hole 3 includes an octagonal cell hole 3 with an inner peripheral shape and a cell hole 3 with an inner peripheral shape of a quadrangle. The hydraulic diameter of the octagonal cell hole 3 is larger than the hydraulic diameter of the square cell hole 3. The exhaust gas filter 1 is formed by alternately arranging octagonal cell holes 3 and square cell holes 3. In the exhaust gas filter 1 of the first embodiment, the cell hole 3 having an octagonal inner periphery is a plugged cell hole 32, and the cell hole 3 having a rectangular inner periphery is an open cell hole 31. The hydraulic diameter of the plugged cell hole 32 is larger than the hydraulic diameter of the open cell hole 31.

The open cell hole 31 has a square shape when viewed from the axial direction X, and is formed so as to penetrate through the entire length of the exhaust gas filter 1. Further, the plugging cell hole 32 has an octagonal shape when viewed from the axial direction X. Further, the upstream end portion of the plugging cell hole 32 is closed by a plug portion 321.

When the cross-sectional area of the open cell hole 31 is S1, and the cross-sectional area of the plugged cell hole 32 is S2, S2 is larger than S1. In this example, the flow path cross-sectional area ratio Rs = S2 / S1, which is the ratio of S2 to S1, satisfies 1.1 ≦ Rs ≦ 5. Further, in this example, the channel cross-sectional area ratio Rs = 1.6.

The base material length L of the exhaust gas filter 1 is not less than the first reference value L1 determined by the following formula (1). Furthermore, the base material length L of the exhaust gas filter 1 is not more than the critical length Lm (blow-through critical length Lm) determined by the following formula (M). The thickness of the cell wall 2 is w (mm), the exhaust gas permeability coefficient is k (μm ² ), the cell density is C (pieces / mm ² ), and the outer diameter of the exhaust gas filter 1 is φ (mm).
L1 = −3.7 × Rs ^1.5 −3.6 / w + 9.7 / k−152.9 × C + 2241.5 / φ + 145.1 Formula (1),
Lm = −5.5 × Rs ^1.5 −6.0 / w + 44.9 / k−234.9 × C + 176.7 / φ + 255.6 (Equation (M))

Equation (1) will be described with reference to FIG. FIG. 5 shows an outline of the relationship between the substrate length L and the collection rate. The collection rate refers to the ratio of the number of particulate matter contained in the exhaust gas discharged from the exhaust gas filter 1 to the number of particulate matter contained in the exhaust gas introduced into the exhaust gas filter 1. As shown in FIG. 5, in the exhaust gas filter 1, the collection rate increases as the substrate length L (full length L) increases, but the increase in the collection rate decreases as the substrate length L increases. Thus, when the substrate length L is equal to or longer than a certain length, an increase in the collection rate accompanying the increase in the substrate length L is eliminated. This is because when the base material length L is longer than a certain length, the exhaust gas introduced into the open cell hole 31 from the upstream side does not pass through the cell wall 2 on the downstream side from the predetermined position, and goes directly to the downstream side. It is thought that it blows through. The length at which the increase in the collection rate accompanying the increase in the substrate length L does not occur is defined as “blow-through critical length Lm (ie, critical length Lm)”, and the collection rate when the substrate length L is equal to or greater than the critical length Lm. Is called “marginal collection rate”. That is, even if the substrate length L is set to the critical length Lm or more, the collection rate of the exhaust gas filter 1 does not increase from the limit collection rate. Therefore, from the viewpoint of reducing the pressure loss and suppressing the increase in size of the exhaust gas filter 1, the base material length L of the exhaust gas filter 1 is set to the critical length Lm or less.

In this example, high purification performance can be obtained by bringing the substrate length L close to the critical length Lm, and the exhaust gas as described above can be obtained by setting the substrate length L to be equal to or less than the critical length Lm. The pressure loss of the filter 1 is reduced and the size is reduced. Therefore, as shown in FIG. 5, the first reference value L1 of the formula (1) is the shortest (La1) of the base material length L that is equal to or higher than the collection rate obtained by subtracting 10% from the limit collection rate. Equivalent values are assumed. That is, for example, when the limit collection rate is 70%, a base length such that the collection rate is 60% is defined as La1, and it is assumed that the first reference value L1 is equivalent to this. . And by making the base-material length L into 1st reference value L1 or more and critical length Lm or less, high purification performance can be acquired, aiming at reduction of the pressure loss of an exhaust gas filter, and size reduction.

The derivation of the formula (1) and the formula (M) can affect the value of the critical collection rate, the flow path cross-sectional area ratio Rs, the thickness w of the cell wall 2, the exhaust gas permeability coefficient k, the cell density C, This was performed by multiple regression analysis using the outer diameter φ of the exhaust gas filter 1 as a variable. This derivation was performed using analysis software JUSE-StatWorks (registered trademark).

The cross-sectional area ratio Rs is 1.6, the thickness w of the cell wall 2 is 0.28 mm, the cell density C is 0.47 cells / mm ² , the exhaust gas permeability coefficient k is 0.7 μm ² , and the outer diameter φ is 132. In the case of 0.0 mm, the first reference value L1 is 84 mm, and the critical length Lm is 178 mm. The substrate length L of the exhaust gas filter 1 is not less than the first reference value L1 and not more than the critical length Lm.

Next, the function and effect of the exhaust gas filter 1 of the first embodiment will be described. As described above, the exhaust gas filter 1 has the open cell holes 31 and the plugged cell holes 32 as the cell holes 3. Therefore, the exhaust gas can be efficiently circulated through the pores formed in the cell wall 2 and the purification performance of the exhaust gas filter 1 can be improved.

That is, by making the flow path cross-sectional area of the plugged cell hole 32 larger than the flow path cross-sectional area of the open cell hole 31, the pressure loss in the open cell hole 31 is larger than the pressure loss in the plugged cell hole 32. Thus, the pressure difference between the pressure in the open cell hole 31 and the pressure in the plugged cell hole 32 increases. By utilizing this pressure difference, the exhaust gas flowing into the open cell hole 31 can be efficiently circulated to the plugged cell hole 32 through the pore. In addition, the pressure difference can be increased by enlarging the difference between the channel cross-sectional area of the open cell hole 31 and the channel cross-sectional area of the plugged cell hole 32. As a result, a large amount of exhaust gas can be permeated through the cell wall 2 and the amount of exhaust gas flowing into the plugged cell hole 32 can be increased. Further, the pressure difference between the open cell hole 31 and the plugged cell hole 32 becomes smaller from the upstream side to the downstream side of the exhaust gas filter 1, but in the range where the pressure difference is generated, the exhaust gas to the pores is reduced. Distribution continues. Therefore, as described above, by increasing the pressure difference between the open cell hole 31 and the plugged cell hole 32, the exhaust gas can be transmitted through the cell wall 2 in a wider range of the exhaust gas filter 1. Thereby, the particulate matter contained in the exhaust gas can be efficiently collected.

Further, the plug part 321 is disposed at the upstream end of the plugged cell hole 32. Therefore, Ash (ash content such as calcium compound) contained in the exhaust gas together with the particulate matter can be discharged from the exhaust gas filter 1. Since Ash cannot be removed by combustion, it remains inside, for example, in an exhaust gas filter in which the plug is disposed at the downstream end of the plugged cell hole. On the other hand, in the exhaust gas filter 1, when exhaust gas permeates the cell wall 2, it is separated by the cell wall 2, and Ash remains in the open cell hole 31. Since the open cell hole 31 penetrates in the axial direction, the Ash can be easily discharged from the open cell hole, and the remaining of the Ash in the exhaust gas filter 1 can be prevented. Thereby, the fall of the purification performance in the exhaust gas filter 1 can be suppressed.

Further, the exhaust gas filter 1 has a base material length that is not less than the first reference value L1 determined by the above formula (1), that is, a total length. Therefore, it is possible to sufficiently secure the particulate matter collection performance and to further improve the purification performance of the exhaust gas filter.
The exhaust gas filter has a base material length that is not more than the critical length Lm determined by the above formula (M). Therefore, an increase in pressure loss of the exhaust gas filter 1 and an increase in the size of the exhaust gas filter 1 can be effectively suppressed. That is, even if the base material length L of the exhaust gas filter 1 is longer than the critical length Lm, the exhaust gas flowing through the open cell holes 31 is discharged without passing through the cell walls 2, Waste is increased due to the relationship between the pressure loss and the mountability of the exhaust gas filter 1. Therefore, by setting the base length of the exhaust gas filter 1 to be equal to or less than the critical length Lm determined by the above formula (M), it is possible to effectively suppress an increase in pressure loss and an increase in size of the exhaust gas filter 1.

Further, the flow path cross-sectional area ratio Rs is 1.1 ≦ Rs ≦ 5, and the base material length L of the exhaust gas filter 1 is 35 mm ≦ L ≦ 270 mm. Therefore, a pressure difference between the open cell hole 31 and the plugged cell hole 32 can be reliably generated, and the exhaust gas can be reliably circulated through the pores formed in the cell wall 2. Further, the collection performance of the exhaust gas filter is improved by determining the substrate length L within the range of 35 mm to 270 mm in accordance with the flow path cross-sectional area ratio Rs between the plugged cell hole 32 and the open cell hole 31. be able to.

Further, the exhaust gas filter 1 of this example has a base material length that is not less than the first reference value L1 determined by the above formula (1), that is, a total length. Therefore, it is possible to sufficiently secure the particulate matter collection performance and to further improve the purification performance of the exhaust gas filter 1.

Further, the plurality of cell holes 3 have two or more types of shapes. Therefore, a configuration in which the flow path cross-sectional area S2 in the plugged cell hole 32 is larger than the flow path cross-sectional area S1 in the open cell hole 31 can be easily obtained.

The cell hole 3 is composed of an octagonal cell hole 3 with an inner peripheral shape and a square cell hole 3 with an inner peripheral shape, and the hydraulic diameter of the octagonal cell hole 3 is the hydraulic power of the square cell hole 3. The octagonal cell holes 3 and the quadrangular cell holes 3 are arranged alternately and larger than the diameter. Therefore, the difference between the hydraulic diameter of the octagonal cell hole 3 and the hydraulic diameter of the square cell hole 3 can be increased. Thereby, when the octagonal cell hole 3 and the square cell hole 3 are appropriately allocated to the plugged cell hole 32 and the open cell hole 31, the pressure between the plugged cell hole 32 and the open cell hole 31 is determined. The difference can be increased effectively. Moreover, the cell wall 2 which does not distribute | circulate the exhaust gas formed between the octagonal cell holes 3 can be reduced. Thereby, the purification performance in the exhaust gas filter 1 can be improved.

As described above, according to this example, the exhaust gas filter 1 that can improve the collection performance of particulate matter and improve the purification performance while suppressing an increase in pressure loss and a decrease in mountability on a vehicle. Can be provided.

In the exhaust gas filter 1 of this example, the open cell holes 31 and the plugged cell holes 32 are alternately arranged with the square cell holes 3 as open cell holes 31 and the octagonal cell holes 3 as plugged cell holes 32. However, other shapes may be used. For example, as shown in FIG. 4, a part of the rectangular cell hole 3 may be a plugged cell hole 32. Also in this case, the same effect as the exhaust gas filter 1 of Example 1 can be obtained.

(Embodiment 2) An exhaust gas filter according to Embodiment 2 will be described below. The present Example 2 is an example in which the base material length of the exhaust gas filter 1, that is, the method for determining the total length is changed. The basic structure of the exhaust gas filter 1 is the same as that of the first embodiment. In this example, the base material length L of the exhaust gas filter 1 is not less than the second reference value L2 determined by the following formula (2). Furthermore, the base material length L of the exhaust gas filter 1 is not more than the critical length Lm (blow-through critical length Lm) determined by the above formula (M).
L2 = −13.4 × Rs ^1.5 + 0.76 / w + 3.2 / k−132.1 × C + 117.3 / φ + 174.4 (2)

FIG. 6 shows an outline of the relationship between the substrate length L and the collection rate, similar to FIG. 5 of Example 1. As shown in the figure, the second reference value L2 of the formula (2) assumes a value equivalent to the shortest (La2) of the base material length L at which the collection rate is 50% or more. Then, by setting the substrate length L to the second reference value L2 or more and the critical length Lm or less, it is possible to obtain a collection rate of 50% or more while reducing the pressure loss and reducing the size of the exhaust gas filter. The derivation of the above equation (2) can also affect the value of the limit collection rate. The flow path cross-sectional area ratio Rs, the thickness w of the cell wall 2, the exhaust gas permeability coefficient k, the cell density C, and the outer diameter φ are variables. Was performed by multiple regression analysis.

The channel cross-sectional area ratio Rs = S2 / S1 is 1.6, the thickness of the cell wall 2 is 0.28 mm, the cell density C is 0.47 / mm ² , the exhaust gas permeability coefficient k is 0.7 μm ² , When the outer diameter φ is 132.0 mm, the second reference value L2 is 101 mm, and the critical length Lm is 178 mm as described above. The base material length L of the exhaust gas filter 1 is not less than the second reference value L2 and not more than the critical length Lm.

Other structures of the exhaust gas filter 1 of Example 1 are the same as those of the exhaust gas filter 1 of Example 1. Of the reference numerals used in the drawings related to the second embodiment or the present embodiment, the same reference numerals as those used in the first embodiment represent the same components as in the first embodiment unless otherwise specified.

The exhaust gas filter 1 according to the second embodiment can secure a collection rate of 50% or more, which is higher than the collection rate generally required in a vehicle equipped with a gasoline engine, and high purification performance can be obtained. In addition, the exhaust gas filter 1 according to the second embodiment has the same effects as the exhaust gas filter 1 according to the first embodiment.

(Embodiment 3) An exhaust gas filter according to Embodiment 3 will be described below. The third embodiment is an example in which the method for determining the substrate length of the exhaust gas filter 1, that is, the total length is changed. The basic structure of the exhaust gas filter 1 is the same as that of the first embodiment. In the third embodiment, the base material length L of the exhaust gas filter 1 is not less than the third reference value L3 determined by the following formula (3). Furthermore, the base material length L of the exhaust gas filter 1 is not more than the critical length Lm (blow-through critical length Lm) determined by the above formula (M).
L3 = −6.8 × Rs ^1.5 −4.5 / w + 12.0 / k−189.9 × C + 2629.1 / φ + 191.7 Formula (3).

Equation (3) will be described with reference to FIG. FIG. 7 shows an outline of the relationship between the substrate length L and the collection rate, similar to FIG. 5 used in Example 1. As shown in the figure, the collection rate of the exhaust gas filter 1 decreases as the substrate length L is shortened from the critical length Lm. Here, when the base material length L is equal to or less than the base material length at which the collection rate is 90% of the limit collection rate, the reduction in the collection rate accompanying the reduction in the base material length L becomes significant. Therefore, as shown in the figure, the third reference value L3 of the formula (3) is equivalent to the shortest (La3) of the base material length L that is 90% or more of the limit collection rate. Is assumed. That is, for example, when the limit collection rate is 70%, it is assumed that the substrate length such that the value of the collection rate is 63% is defined as La3, and the third reference value L3 is equivalent to this. ing. And by making the base-material length L into 3rd reference value L3 or more and critical length Lm or less, high purification performance can be acquired, aiming at reduction of the pressure loss of an exhaust gas filter, and size reduction. The derivation of the above formula (3) can also affect the value of the limit collection rate. The flow path cross-sectional area ratio Rs, the thickness w of the cell wall 2, the exhaust gas permeability coefficient k, the cell density C, and the outer diameter φ are variables. Was performed by multiple regression analysis.

The cross-sectional area ratio Rs = S2 / S1 is 1.6, the thickness w of the cell wall 2 is 0.28 mm, the cell density C is 0.47 cells / mm ² , the exhaust gas permeability coefficient k is 0.7 μm ² , the outside When the diameter φ is 132.0 mm, the third reference value L3 is 110 mm, and the critical length Lm is 178 mm as described above. The base material length L of the exhaust gas filter 1 is not less than the third reference value L3 and not more than the critical length Lm.

Others are the same as the structure of the exhaust gas filter 1 of the first embodiment. Of the reference numerals used in the drawings related to the third embodiment or the present embodiment, the same reference numerals as those used in the first embodiment represent the same components as in the first embodiment unless otherwise specified.

In Example 3, the particulate matter collection performance can be sufficiently secured, and the purification performance of the exhaust gas filter 1 can be further improved. In addition, the same effect as the exhaust gas filter 1 of Example 1 is obtained.

(Embodiment 4) An exhaust gas filter according to Embodiment 4 will be described below. Example 4 is an example in which the shape of the cell hole in the exhaust gas filter of Example 1 is changed as shown in FIG. In the exhaust gas filter 1 of this example, the shape of the cell hole 3 is formed in a uniform shape. The cell hole 3 has a square shape, and is formed so as to be aligned in a vertical direction parallel to one side of the square and a horizontal direction orthogonal to the vertical direction on a cross section orthogonal to the axial direction. In this example, a total of nine cell holes 3 arranged three by three in the vertical direction and in the horizontal direction are defined as one section, and this is appropriately spread to form the exhaust gas filter 1. Of the nine cell holes 3 in one section, three cell holes 3 that are not adjacent to each other were used as open cell holes 31, and the remaining cell holes 3 were used as plugged cell holes 32. Therefore, the channel cross-sectional area ratio Rs = 2.0.

Other configurations of the exhaust gas filter 1 according to the fourth embodiment are the same as the configurations of the exhaust gas filter 1 of the first embodiment. Of the reference numerals used in the drawings relating to the fourth embodiment or the present embodiment, the same reference numerals as those used in the first embodiment are the same as those in the exhaust gas filter 1 of the first embodiment unless otherwise specified. To express.

The exhaust gas filter 1 of this example can make the shape of the exhaust gas filter simple by making the shape of the cell holes 3 uniform. Thereby, the exhaust gas filter 1 can be manufactured easily. Further, also in the exhaust gas filter 1 of the fourth embodiment, it is possible to obtain the same effects as the exhaust gas filter 1 of the first embodiment.

(Verification test 1) In the verification test 1, the flow path cross-sectional area ratio Rs was compared with the permeation flow rate ratio and the collection rate. The permeate flow rate ratio indicates the ratio of the exhaust gas that has flowed into the open cell hole 31 through the cell wall 2 and has flowed into the plugged cell hole 32.

In this confirmation test 1, exhaust gas filters 101 to 104 in which the flow path cross-sectional area ratio Rs between the open cell hole 31 and the plugged cell hole 32 was changed were used. The exhaust gas filter 101 has a flow passage cross-sectional area ratio Rs of 0.5. In the exhaust gas filter 101, the open cell hole 31 and the plugged cell hole 32 in the exhaust gas filter 1 of the first embodiment are set to be opposite to each other.

As shown in FIG. 9, the exhaust gas filter 102 has a flow path cross-sectional area ratio Rs of 1. When viewed from the axial direction X, the shapes of the open cell hole 31 and the plugged cell hole 32 in the exhaust gas filter 102 are both square. The exhaust gas filter 103 has a channel cross-sectional area ratio Rs of 2.1, and the exhaust gas filter 104 has a channel cross-sectional area ratio Rs of 4. The shapes of the open cell hole 31 and the plugged cell hole 32 in the exhaust gas filter 103 and the exhaust gas filter 104 are similar to the open cell hole 31 and the plugged cell hole 32 in the exhaust gas filter 1 of Example 1, respectively. In the exhaust gas filters 101 to 104, the base material length L, that is, the total length L was set to 200 mm. The configuration other than the above is the same as that of the first embodiment. Of the reference numerals used in FIG. 9, the same reference numerals as those used in the first embodiment denote the same components as in the first embodiment unless otherwise specified.

FIG. 10A shows the relationship between the channel cross-sectional area ratio Rs and the permeate flow ratio, where the vertical axis represents the permeate flow ratio (%) and the horizontal axis represents the channel cross-sectional area ratio Rs. FIG. 10B shows the relationship between the channel cross-sectional area ratio Rs and the collection rate. The vertical axis represents the collection rate (%), and the horizontal axis represents the channel cross-sectional area ratio Rs.

As shown in FIG. 10A, the permeate flow rate ratio was about 26% for the exhaust gas filter 101, about 50% for the exhaust gas filter 102, about 76% for the exhaust gas filter 103, and about 90% for the exhaust gas filter 104. As shown in FIG. 10B, the collection rate was about 21% for the exhaust gas filter 101, about 41% for the exhaust gas filter 102, about 62% for the exhaust gas filter 103, and about 76% for the exhaust gas filter 104.
Therefore, by setting the flow path cross-sectional area ratio Rs to exceed 1, 50% or more of the exhaust gas flowing into the open cell hole 31 can be transmitted through the cell wall 2. Further, by setting the flow path cross-sectional area ratio Rs to 2 or more, 80% or more of the exhaust gas flowing into the open cell holes 31 can be transmitted through the cell wall 2. Thereby, it was confirmed that a collection rate improves. Further, in the range where the flow path cross-sectional area ratio Rs exceeds 4, the permeate flow rate ratio and the collection rate are almost constant.

(Confirmation test 2) In this confirmation test 2, as shown in Table 1, the particulate matter collection rates when the flow passage cross-sectional area ratio Rs in the exhaust gas filter was changed were compared.
As the exhaust gas filter, Sample 1 having uniformly shaped cell holes and Sample 2 to Sample 4 having cell holes having different hydraulic diameters were used.

Sample 1 has square cell holes, and plugged cell holes and open cell holes are alternately arranged. Therefore, the channel cross-sectional area ratio Rs is 1. The sample 2 is the same as the exhaust gas filter 1 of Example 1 except for the substrate length L, that is, the total length L. Sample 3 and sample 4 have square cell holes and octagonal cell holes similar in shape to the cell holes in the exhaust gas filter of Example 1, and the flow path cross-sectional area ratio Rs is as follows. 4.0, Sample 4 is 5.0. Further, the base material length L in the exhaust gas filters of Samples 1 to 4 was all 200 mm. The configuration other than the above is the same as that of the first embodiment.

Table 1 shows the collection rate of particulate matter in Sample 1 to Sample 4. As shown in Table 1, the collection rate in each exhaust gas filter was 42% for sample 1, 57% for sample 2, 76% for sample 3, and 78% for sample 4. Therefore, it was confirmed that the collection rate of the particulate matter was improved as the channel cross-sectional area ratio Rs was increased.

(Confirmation test 3) In this confirmation test 3, the effect of the cross-sectional area ratio Rs of the exhaust gas filter and the base material length, that is, the total length on the collection rate, and the average pore diameter of the cell wall and the base material length are captured. The effect on the collection rate was confirmed. In this test, Sample 2 to Sample 26 were used as exhaust gas filters. Samples 2 to 4 are the same as in Confirmation Test 2. As shown in Table 2, Sample 5 to Sample 8 are examples in which the flow path cross-sectional area ratio Rs is 1.6 and the substrate length (full length L) is changed with respect to the exhaust gas filter of Sample 2. Samples 9 to 12 have a channel cross-sectional area ratio Rs of 4.0 and are examples in which the base material length is changed with respect to the exhaust gas filter of sample 3. Samples 13 to 16 have a channel cross-sectional area ratio Rs of 5.0, and are examples in which the substrate length is changed with respect to the exhaust gas filter of sample 4.

As shown in Table 3, Sample 17 to Sample 21 had an average pore diameter in the cell wall of 5 μm. Sample 2 and Samples 5 to 8 were the same as described above, and the average pore diameter in the cell wall was 18 μm. In Samples 22 to 26, the average pore diameter in the cell wall was set to 30 μm. The configurations of Sample 2 to Sample 26 other than those described above are the same as in Example 1.

As shown in Table 2, in Sample 2 and Samples 5 to 8, the collection rate increased as the substrate length L (full length L) increased, and became stable after 150 mm. Further, in Sample 3, Sample 4, and Sample 9 to Sample 16, when the substrate length L is in the range of 200 mm or less, the collection rate continues to increase as the substrate length L increases. Therefore, it was confirmed that the substrate length L of the exhaust gas filter required until the pressure loss in the open cell hole and the pressure loss in the plugging cell hole become equal increases as the flow path cross-sectional area ratio Rs increases. . This is considered due to an increase in the flow rate of exhaust gas flowing into the open cell holes in the exhaust gas filter.

Further, as shown in Table 3, in Samples 17 to 21, the collection rate increased as the substrate length L (full length L) increased, and was stabilized in the range of 150 mm and later. In Sample 2, Sample 5 to Sample 8, and Sample 22 to Sample 26, the substrate length L was stable in the range of 100 mm or more. Therefore, it was confirmed that the base material length L of the exhaust gas filter required until the pressure loss in the open cell hole and the pressure loss in the plugging cell hole become equal decreases as the average pore diameter increases. This is considered to be due to a reduction in the permeation loss of the exhaust gas in the cell wall in the exhaust gas filter.

(Confirmation test 4) In this confirmation test 4, while confirming the precision of said Formula (1) and said Formula (M), the below-mentioned evaluation regarding the pressure loss and collection rate of an exhaust gas filter was performed. The accuracy of the above formula (1) is the shortest of the base material lengths that can secure a collection rate obtained by subtracting 10% from the limit collection rate (ie, La1 in FIG. 5 of Example 1). This was confirmed by comparing the actual measured value (first measured value) with the first reference value L1 (calculated value) calculated using Equation (1). In addition, the accuracy of the above formula (M) is that of the base material length (that is, the total length Lm, which is Lm in FIG. 5 of Example 1) where the increase in the collection rate accompanying the increase in the base material length L does not occur. This was confirmed by comparing the actual measurement value (hereinafter referred to as the critical length actual measurement value) with the critical length Lm (calculated value) calculated using the equation (M).

In this confirmation test 4, as the exhaust gas filter for obtaining the first actual measurement value and the blow-through critical length (critical length), the basic structure is the same as that of the exhaust gas filter 1 of Example 1, and as shown in Tables 4 to 8. Samples A1 to A78 in which the flow path cross-sectional area ratio Rs, the cell wall thickness w, the exhaust gas permeability coefficient k, the cell density C, and the outer diameter φ were variously changed were used. In any sample, the thickness w (mm) of the cell wall 2 is 0.13 ≦ w ≦ 0.47, the exhaust gas permeability coefficient k (μm ² ) is 0.3 ≦ k ≦ 1.1, and The cell density C (pieces / mm ² ) is 0.31 ≦ C ≦ 0.62, and the outer diameter φ (mm) of the exhaust gas filter is 80 ≦ φ ≦ 150. In the test, an exhaust gas filter was attached to an exhaust pipe of a gasoline engine, and the exhaust gas was circulated through the exhaust gas filter at a temperature of 700 ° C. and a flow rate of 4 m ³ / min.

In this confirmation test 4, for each sample, first, in the exhaust gas filter having a sufficient base length L, that is, the total length (400 mm), in which the collection rate becomes the limit collection rate, the limit collection rate (FIG. 5). Reference) was measured. This value is the “limit collection rate” in Tables 4 to 8. The collection rate was measured by detecting the number of particulate matter contained in the exhaust gas introduced into the exhaust gas filter and the number of particulate matter contained in the exhaust gas discharged from the exhaust gas filter. And the collection rate of the exhaust gas filter which changed the base material length L every 5 mm was measured, respectively. And the thing which became the shortest among the base material length which becomes more than the collection rate which subtracted 10% from the limit collection rate was made into the 1st measured value. Moreover, the shortest of the substrate lengths having a collection rate higher than the collection rate obtained by subtracting 1% from the limit collection rate was defined as the critical length actual measurement value.

The collection rates of the exhaust gas filters having the first measured substrate length L are listed in Tables 4 to 8 as “collection rates”. Since the substrate length L is changed in increments of 5 mm, the collection rates in Tables 4 to 8 include values slightly higher than the value obtained by subtracting 10% from the limit collection rate.

Further, the pressure loss and the collection rate of the exhaust gas filter having the base material length L of the first actual measurement value and the pressure loss and the collection rate of the exhaust gas filter having the base material length L of the critical length actual measurement value were measured. And the measured pressure loss and collection rate were evaluated along the following criteria.

An evaluation reference sample was prepared as a reference for evaluating the pressure loss and collection rate of each sample. In this test, the evaluation reference sample was the sample 1 used in the confirmation test 2 (that is, the exhaust gas filter having a channel cross-sectional area ratio Rs of 1.0). And evaluation of the pressure loss and collection rate of each sample was performed by comparing with the pressure loss and collection rate of an evaluation standard sample. Specifically, the evaluation of the pressure loss is “A” when the pressure loss of the evaluation reference sample is 1.0 and the pressure loss is less than 1.5, and the pressure loss is 1.5 or more, 2 When the pressure loss was 2.0 or more, “C” was assigned. The evaluation of the collection rate was “A” when the collection rate was equal to or higher than the collection rate of the evaluation standard sample, and “B” when it was less than the collection rate of the evaluation standard sample.

In Tables 4 to 8, in the exhaust gas filter having the first measured substrate length L, the pressure loss evaluation is “pressure loss evaluation 1” and the collection rate evaluation is “collection rate evaluation 1”. In Tables 4 to 8, in the exhaust gas filter having the measured base length L of the critical length, the pressure loss evaluation is “pressure loss evaluation 2”, and the collection rate evaluation is “collection rate evaluation 2”. .

The above results are shown in Tables 4 to 8. In Tables 4 to 8, the average pore diameter and porosity of the cell wall, which are parameters that can affect the exhaust gas permeability coefficient k, are described.

As can be seen from Tables 4 to 8, the first reference value L1 obtained by the equation (1) and the first actually measured value confirmed by the experiment are almost the same. Therefore, according to the equation (1), the shortest one of the substrate lengths L that is equal to or higher than the collection rate obtained by subtracting 10 from the limit collection rate is taken into account in consideration of the influence of various parameters of the exhaust gas filter 1. It was confirmed that it can be calculated well.

Also, as can be seen from Tables 4 to 8, the blow-through critical length Lm (critical length Lm) obtained by the equation (M) and the critical length actual value confirmed by the experiment are almost the same. Therefore, according to the equation (M), in consideration of the influence of various parameters of the exhaust gas filter 1, the substrate has a collection rate higher than the collection rate obtained by subtracting 1% from the limit collection rate. It was confirmed that the shortest of the lengths can be accurately calculated.

Further, as can be seen from Tables 4 to 8, the collection rate tends to become better (that is, increase) as the substrate length L becomes longer, and the pressure loss increases as the substrate length L becomes shorter. It can be confirmed that there is a tendency to improve (that is, decrease). In other words, it can be seen that the pressure loss tends to deteriorate as the substrate length L increases, and the collection rate tends to deteriorate as the substrate length L decreases. That is, it can be seen that both the pressure loss and the collection rate cannot be improved simultaneously if the substrate length L of the exhaust gas filter is too long or too short. Therefore, in the exhaust gas filter 1 of Example 1, the collection rate can be increased by setting the substrate length L to be equal to or greater than the first reference value L1 obtained by the highly accurate expression (1), and By setting the material length L to be equal to or less than the critical length Lm obtained by the highly accurate formula (M), the pressure loss can be reduced. That is, by setting the substrate length L to the first reference value L1 or more and the critical length Lm or less, both the pressure loss and the collection rate can be improved simultaneously.

(Confirmation test 5) In this confirmation test 5, the accuracy of the above formula (2) is the shortest of the substrate lengths (La2 in FIG. 6 of Example 2) among which the collection rate is 50% or more. It confirmed by comparing measured value (2nd measured value) and 2nd reference value L2 (calculated value) calculated using Formula (2). In this test, as the exhaust gas filter for obtaining the second actual measurement value, the basic structure is the exhaust gas filter 1 of Example 1, and as shown in Tables 9 to 11, the flow path cross-sectional area ratio Rs, the thickness of the cell wall Samples B1 to B50 in which the w, the exhaust gas permeability coefficient k, the cell density C, and the outer diameter φ were variously changed were used. The test conditions are the same as the confirmation test 4.

In this confirmation test 5, the substrate length L (full length L) was changed in 5 mm increments, and the collection rate was measured. And the shortest thing was made into the 2nd measured value among the base-material length from which a collection rate will be 50% or more. The collection rates of the exhaust gas filter having the substrate length L of the second actually measured value are shown in Tables 9 to 11 as “collection rate”. Since the substrate length L is changed in increments of 5 mm, the collection rates in Tables 9 to 11 include values slightly higher than 50%.

In addition, as in the confirmation test 4, in the confirmation test 5, an evaluation was made regarding the pressure loss and the collection rate of the exhaust gas filter. Also in the confirmation test 5, the pressure loss and the collection rate of the exhaust gas filter were evaluated using the same evaluation reference sample and determination reference as in the confirmation test 4. The results are shown in Tables 9 to 11. Tables 9 to 11 also describe the average pore diameter and porosity of the cell wall, which are parameters that can affect the exhaust gas permeability coefficient k. In Tables 9 to 11, the evaluation of the pressure loss in the exhaust gas filter having the substrate length L of the second actual measurement value is “pressure loss evaluation 1”. Moreover, all the samples of this test have a collection rate of 50% or more, and the collection rate of the evaluation reference sample in the confirmation test 2 has a collection rate of 42% as described above. Therefore, since the collection rate in each sample of this test exceeds the collection rate of the evaluation reference sample, the description of the evaluation regarding the collection rate is omitted in Tables 9 to 11.

As can be seen from Tables 9 to 11, the second reference value L2 obtained by the equation (2) and the second actually measured value confirmed by the experiment are almost the same. Therefore, according to the equation (2), it is possible to accurately calculate the shortest substrate length among the substrate lengths with a collection rate of 50% or more in consideration of the influence of various parameters of the exhaust gas filter 1. confirmed. Further, by setting the flow path cross-sectional area ratio Rs to be larger than 1 and the base material length L to be not less than the second reference value and not more than the blow-through critical length Lm (critical length Lm), a plurality of exhaust gas filters can be provided. It was also confirmed that the collection performance of 50% or more can be secured by one exhaust gas filter 1 without arranging in series.

(Confirmation test 6) In this confirmation test 6, the accuracy of the above formula (3) is the shortest of the substrate lengths L (full length L) that is 90% or more of the limit collection rate. This was confirmed by comparing the measured value (third measured value) of (La3 in FIG. 7 of Example 3) with the third reference value L3 (calculated value) calculated using Equation (3).

In this confirmation test 6, as the exhaust gas filter for obtaining the second actual measurement value, the basic structure is the exhaust gas filter 1 of Example 1, and as shown in Tables 12 to 15, the channel cross-sectional area ratio Rs, the cell wall Samples C1 to C78 in which the thickness w, the exhaust gas permeability coefficient k, the cell density C, and the outer diameter φ were variously changed were used. The test conditions in confirmation test 6 are the same as the test conditions used in confirmation test 4.

In Confirmation Test 6, as in Confirmation Test 4, the limit collection rate (see FIG. 7) is measured in an exhaust gas filter having a sufficient base material length L (400 mm) at which the collection rate becomes the limit collection rate. The collection rates of the exhaust gas filters in which the substrate length L was changed in various increments of 5 mm were measured. And among the base material length L which becomes 90% or more of the limit collection rate or more, what became the shortest was made into the 3rd measured value. The collection rates of the exhaust gas filter having the third measured actual substrate length L are shown in Tables 12 to 15 as “collection rates”. Since the substrate length L is changed in increments of 5 mm, the collection rates in Tables 12 to 15 include values slightly higher than 90% of the limit collection rate.

Also, in the confirmation test 6, as in the confirmation test 4, an evaluation was made regarding the pressure loss and the collection rate of the exhaust gas filter. Also in this confirmation test 6, the pressure loss and the collection rate of the exhaust gas filter were evaluated using the same evaluation standard sample and determination standard as those in the confirmation test 4. The results are shown in Tables 12 to 15. In Tables 12 to 15, the average pore diameter and porosity of the cell wall, which are parameters that can affect the exhaust gas permeability coefficient k, are described. In Tables 12 to 15, in the exhaust gas filter having the substrate length L of the third actual measurement value, the pressure loss evaluation is “pressure loss evaluation 1”, and the collection rate evaluation is “collection rate evaluation 1”. .

As can be seen from Tables 12 to 15, the third reference value L3 obtained by the equation (3) and the third actually measured value confirmed by the experiment are almost the same. Therefore, according to the expression (3), the influence of various parameters of the exhaust gas filter 1 is taken into consideration, and the shortest of the substrate lengths L (full length L) that is 90% or more of the limit collection rate or more. It was confirmed that it is possible to accurately calculate the above.

(Embodiment 5) An exhaust gas filter according to Embodiment 5 will be described below. In Example 5, as shown in FIG. 11, an exhaust gas filter 1 carrying a catalyst was used. By supporting the catalyst on the exhaust gas filter 1, harmful substances contained in the exhaust gas can be removed. In the exhaust gas filter 1 of Example 5, the catalyst was a three-way catalyst containing at least one of Pt, Rh, and Pd.

The exhaust gas filter 1 of the fifth embodiment has the same basic configuration as that of the exhaust gas filter shown in the first embodiment, and has a catalyst supported thereon. Specifically, the exhaust gas filter 1 of the fifth embodiment includes the surface of the cell wall 2 facing the open cell hole 31 and the plugged cell hole 32 in the exhaust gas filter of the first embodiment, and the inside of the cell wall 2. The pore surfaces are coated with a catalyst coating layer 4 containing a catalyst. The catalyst coat layer 4 includes a porous carrier containing alumina, a promoter supported on the porous carrier, and a noble metal catalyst supported on the promoter. The co-catalyst was a ceria-zirconia composite oxide, and the noble metal catalyst was Pt. Note that the noble metal catalyst may contain, for example, at least one of Pt, Rh, and Pd according to the exhaust gas to be purified. The catalyst coat layer 4 is uniformly formed on the entire surface of the cell wall 2.

The catalyst loading amount of the exhaust gas filter 1 is preferably 10 to 150 g / L. The catalyst carrying amount is the mass of the catalyst coat layer 4 carried per 1 L of the volume of the exhaust gas filter 1. If the amount of catalyst supported by the exhaust gas filter 1 is less than 10 g / L, the effect of removing harmful substances in the exhaust gas is reduced. On the other hand, when the amount of the catalyst supported by the exhaust gas filter 1 exceeds 150 g / L, the exhaust gas hardly passes through the cell wall 2 and the collection rate is lowered. Further, the catalyst loading amount of the exhaust gas filter 1 is more preferably 10 to 100 g / L. By setting the catalyst loading of the exhaust gas filter 1 to 100 g / L or less, it is easy to suppress a decrease in the collection rate. The amount of the noble metal catalyst in the catalyst coat layer 4 is preferably 0.1 to 5 g / L.

The base material length L of the exhaust gas filter 1 of this example was set to be equal to or more than the first reference value L1 determined by the equation (1) shown in the first example. The substrate length L of the exhaust gas filter 1 of the present example is not limited to this, and may be equal to or more than the second reference value L2 determined by the equation (2) shown in the second embodiment. It is good also as more than the 3rd standard value L3 determined by Formula (3).

Next, an example of a method for supporting the catalyst on the exhaust gas filter 1 will be described.
First, the exhaust gas filter before supporting the catalyst is immersed in a catalyst slurry whose viscosity is adjusted using Pt as the noble metal catalyst and ceria-zirconia composite oxide and γ-alumina as the carrier. And catalyst slurry is made to adhere in the cell hole 3 of an exhaust gas filter. Then, the exhaust gas filter is pulled up from the catalyst slurry, and excess slurry is removed with an air flow to suppress the clogging of the pores of the cell wall 2. The obtained exhaust gas filter is dried at 80 to 150 ° for about 1 to 6 hours, and then baked at 450 to 700 degrees for about 0.5 to 6 hours. For example, the obtained exhaust gas filter can be dried at 100 ° C. for 3 hours and then baked at 500 ° C. for 3 hours. In this way, an exhaust gas filter 1 carrying a catalyst was obtained. The method for supporting the catalyst on the exhaust gas filter 1 is not limited to this.

Others are the same as the configuration of the exhaust gas filter according to the first embodiment. Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in the first embodiment denote the same components as in the first embodiment unless otherwise specified.

Since the exhaust gas filter 1 of Example 5 carries a catalyst, harmful substances in the exhaust gas can be removed. In addition, the exhaust gas filter 1 of Example 5 has the effect of the exhaust gas filter 1 of Example 1 and the like.

(Confirmation test 7) In the confirmation test 7, as shown in Tables 16 to 18, the effect on the value of the exhaust gas permeation coefficient k by supporting the catalyst on the exhaust gas filter was confirmed. Specifically, catalyst coat layers 4 having different catalyst loadings were formed on Sample A1, Sample A9, and Sample A11 of Confirmation Test 4, and the value of the exhaust gas permeability coefficient k was measured.

In the confirmation test 7, the sample A1 used in the confirmation test 4, the sample D1a in which the catalyst coating layer 4 having a catalyst loading amount of 50 g / L is formed on the sample A1, and the catalyst loading amount of 100 g / L on the sample A1. A sample D1b on which the catalyst coat layer 4 was formed and a sample D1c on which the catalyst coat layer 4 having a catalyst loading of 150 g / L was formed on the sample A1 were prepared. And the value of each flue gas permeability coefficient k of sample A1, sample D1a, sample D1b, and sample D1c was measured.

The measurement of the exhaust gas permeability coefficient k was performed as follows. A test piece of each sample was prepared by cutting out the cell wall of each sample to be measured so as to have an outer diameter of 15 mm. Then, the specimen of each sample was mounted on a porous material manufactured by Porous Materials (model number CEP-1100AXSHJ), and a gas at room temperature, that is, 25 ° C. was allowed to pass through the specimen of each sample at a constant gas flow rate Q. . And the pressure loss (DELTA) P which is a difference of the gas pressure of the upstream area | region of the test piece of each sample, and the gas pressure of a downstream area | region was measured. This was done at various gas flow rates Q. And the pressure loss (DELTA) P with respect to each gas flow rate Q was calculated | required, and the waste gas permeability coefficient k was computed by the principle demonstrated below.

The exhaust gas permeability coefficient k and the pressure loss ΔP have a relationship satisfying Darcy's gas permeation type, Q = (A / μw) kΔP. μ is the gas viscosity determined by the temperature and type of gas. A is the area of the test piece through which gas passes. w is the thickness of the cell wall. That is, in the Darcy gas permeation type, the area A, the gas viscosity μ, and the cell wall thickness w are uniquely determined by the temperature and type of the gas and the specifications of the test piece. Therefore, the value of (A / μw) k is obtained from the slope when the pressure loss ΔP with respect to each gas flow rate Q is plotted, and each of the area A, the gas viscosity μ, and the cell wall thickness w uniquely determined there is obtained. Substitute the value and calculate the value of k.

Furthermore, the same measurement was performed on the samples A9 and A11 used in the confirmation test 4. Sample A1, sample A9, and sample A11 are samples having different values of the exhaust gas permeability coefficient k. These results are shown in Tables 16-18. Here, “Sample D9a”, “Sample D9b”, and “Sample D9c” shown in Table 17 form the catalyst coating layer 4 with catalyst loadings of 50 g / L, 100 g / L, and 150 g / L on Sample A9, respectively. It is a thing. In addition, “Sample D11a”, “Sample D11b”, and “Sample D11c” shown in Table 18 were formed with the catalyst coating layer 4 having catalyst loadings of 50 g / L, 100 g / L, and 150 g / L on Sample A11, respectively. Is. Further, the “decrease rate” shown in Tables 16 to 18 is a decrease rate of the exhaust gas permeability coefficient k with respect to the exhaust gas permeability coefficient k of the sample on which the catalyst is not supported.

From Tables 16 to 18, it can be seen that for any of Sample A1, Sample A9, and Sample 11, the value of the exhaust gas permeability coefficient k decreases as the amount of catalyst supported by the exhaust gas filter 1 increases. In all of Sample A1, Sample A9, and Sample A11, the values of the “decrease rate” were the same for those in which the catalyst coating layer 4 having the same catalyst loading amount was formed. That is, even if the exhaust gas filters have different exhaust gas permeability coefficients k or different base material specifications, when the catalyst coating layer 4 having the same catalyst loading amount is formed on them, the reduction rate of the exhaust gas permeability coefficient k is the same. I understand.

(Confirmation test 8) The confirmation test 8 is a test similar to the confirmation test 4 performed on the exhaust gas filter 1 of Example 5 described above. That is, also in the exhaust gas filter carrying the catalyst, the first measured value that is the measured value of the shortest of the base material length that is equal to or higher than the collection rate obtained by subtracting 10% from the limit collection rate, that is, the total length, It was confirmed that it substantially coincided with the first reference value L1 satisfying the above formula (1). Further, in the exhaust gas filter carrying the catalyst, the critical length actual measurement value, which is the actual measurement value of the base material length, at which the collection rate does not increase as the base material length L increases, satisfies the above formula (M). It was confirmed that it substantially coincided with the blow-through critical length Lm, that is, the critical length Lm. Furthermore, also in the exhaust gas filter carrying the catalyst, the later-described evaluation on the pressure loss and the collection rate of the exhaust gas filter was performed.

In this confirmation test 8, as the exhaust gas filter 1 for obtaining the first actual measurement value, the basic structure is the same as that of the exhaust gas filter 1 of Example 5, and as shown in Table 19, the catalyst loading amount and the flow path cross-sectional area ratio Samples D1a, D1b, D9a, D9b, D11a, and D11b in which Rs, the thickness w of the cell wall 2, the exhaust gas permeability coefficient k, the cell density C, and the outer diameter φ were variously used were used. Here, the sample D1a and the sample D1b are the exhaust gas filter 1 in which different amounts of the catalyst coat layer 4 are formed on the sample A1 of the confirmation test 4. Sample D9a and Sample D9b are the exhaust gas filter 1 in which different amounts of the catalyst coat layer 4 are formed on the sample A9 of the confirmation test 4. Sample D11a and Sample D11b are the exhaust gas filter 1 in which different amounts of the catalyst coat layer 4 are formed on the sample A9 of the confirmation test 4.

In the evaluation of the pressure loss and the collection rate, the sample H1 having the same basic structure as the sample 1 of the confirmation test 2, the sample H1a in which the catalyst coating layer having a catalyst loading amount of 50 g / L is formed on the sample H1, and the sample H1 Sample H1b on which a catalyst coating layer having a catalyst loading of 100 g / L was formed as a reference. Sample H1, Sample H1a, and Sample H1b are all exhaust gas filters having a channel cross-sectional area ratio Rs of 1.0.

The evaluation of the pressure loss of Sample A1, Sample A9, and Sample A11 with the catalyst loading amount of 0 g / L is the same when the pressure loss of Sample H1 with the catalyst loading amount of 0 g / L is 1.0. "A" if the pressure loss is less than 1.5, "B" if the pressure loss is 1.5 or more and less than 2.0, and "C" if the pressure loss is 2.0 or more. did. Furthermore, the evaluation of the collection rates of the sample A1, the sample A9, and the sample A11 is “A” when the collection rate is equal to or higher than the collection rate of the sample H1, and “B” when it is less than the collection rate of the sample H1. It was.

Moreover, the evaluation of the pressure loss of sample A1a, sample A9a, and sample A11a with a catalyst loading of 50 g / L is the same when the pressure loss of sample H1a with a catalyst loading of 50 g / L is 1.0. "A" if the pressure loss is less than 1.5, "B" if the pressure loss is 1.5 or more and less than 2.0, and "C" if the pressure loss is 2.0 or more. did. Furthermore, the evaluation of the collection rates of the sample A1a, the sample A9a, and the sample A11a is “A” when the collection rate is equal to or higher than the collection rate of the sample H1a, and “B” when it is less than the collection rate of the sample H1a. It was.

In addition, the evaluation of the pressure loss of Sample A1b, Sample A9b, and Sample A11b with the catalyst loading of 100 g / L is the same when the pressure loss of Sample H1b with the catalyst loading of 100 g / L is 1.0. "A" if the pressure loss is less than 1.5, "B" if the pressure loss is 1.5 or more and less than 2.0, and "C" if the pressure loss is 2.0 or more. did. Furthermore, the evaluation of the collection rates of the sample A1b, the sample A9b, and the sample A11b is “A” when the collection rate is equal to or higher than the collection rate of the sample H1b, and “B” when the collection rate is lower than the collection rate of the sample H1b. It was.

In Table 19, in the exhaust gas filter having the substrate length L of the first actual measurement value, the pressure loss evaluation was “pressure loss evaluation 1”, and the collection rate evaluation was “collection rate evaluation 1”. Further, in Table 19, the pressure loss evaluation in the exhaust gas filter having the substrate length L of the critical length actual measurement value is “pressure loss evaluation 2”, and the collection rate evaluation is “collection rate evaluation 2”.

The test conditions and test method of this confirmation test 8 were the same as the test conditions and test method used in confirmation test 4. The results are shown in Table 19. For reference, Table 19 also shows Sample A1, Sample A9, Sample A11, and Sample H1 of Confirmation Test 4.

As can be seen from Table 19, also in the exhaust gas filter 1 carrying the catalyst, the first reference value L1 obtained by the equation (1) and the first actually measured value confirmed by the experiment are almost the same. Therefore, according to the formula (1), even in the exhaust gas filter 1 carrying the catalyst, the influence of various parameters of the exhaust gas filter 1 is taken into consideration, and the base becomes equal to or higher than the collection rate obtained by subtracting 10 from the limit collection rate. It was confirmed that the shortest material length L can be accurately calculated.

Further, as can be seen from Table 19, also in the exhaust gas filter 1 carrying the catalyst, the blow-through critical length Lm obtained by the equation (M), that is, the critical length Lm, and the critical length actual value confirmed by the experiment are almost the same. Match. Therefore, according to the equation (M), even in the exhaust gas filter 1 carrying the catalyst, in consideration of the influence of various parameters of the exhaust gas filter 1, the collection rate is obtained by subtracting 1% from the limit collection rate. It was confirmed that the shortest of the substrate lengths with a higher collection rate than the rate can be calculated with high accuracy.

Further, as can be seen from Table 19, also in the exhaust gas filter 1 carrying the catalyst, the collection rate tends to become better (that is, increase) as the substrate length L is increased, as in the confirmation test 4. It can be confirmed that the pressure loss tends to become better (that is, decrease) as the substrate length L is shortened. In other words, it can be seen that the pressure loss tends to deteriorate as the substrate length L increases, and the collection rate tends to deteriorate as the substrate length L decreases. That is, it can be seen that both the pressure loss and the collection rate cannot be improved simultaneously if the substrate length L of the exhaust gas filter is too long or too short. Therefore, in the exhaust gas filter 1 of Example 5, the collection rate can be increased by setting the substrate length L to be equal to or greater than the first reference value L1 obtained by the highly accurate formula (1), and By setting the material length L to be equal to or less than the blow-by reference value Lm obtained by the highly accurate expression (M), the pressure loss can be reduced. That is, by setting the base material length L to the first reference value L1 or more and the blow-through critical length Lm or less, both the pressure loss and the collection rate can be improved simultaneously.

(Confirmation test 9) This confirmation test 9 is a test similar to the confirmation test 5 performed on the exhaust gas filter 1 of Example 5 described above. That is, also in the exhaust gas filter carrying the catalyst, the second actual measurement value which is the actual measurement value of the shortest of the base material length, that is, the total length of the collection rate of 50% or more satisfies the above formula (2). It was confirmed that it substantially coincided with the second reference value L2.

In this confirmation test 9, as the exhaust gas filter 1 for obtaining the second actual measurement value, the basic structure is the same as that of the exhaust gas filter 1 of Example 5, and as shown in Table 20, the amount of catalyst supported, the channel cross-sectional area ratio Rs, Sample E4a, sample E15a, and sample E17a in which the thickness w of the cell wall 2, the exhaust gas permeability coefficient k, the cell density C, and the outer diameter φ were variously changed were used. Here, the sample E4a is the exhaust gas filter 1 in which the catalyst coating layer 4 having a catalyst loading amount of 50 g / L is formed on the sample B4 of the confirmation test 5. Sample E15a is the exhaust gas filter 1 in which the catalyst coating layer 4 having a catalyst loading of 50 g / L is formed on the sample B15 of the confirmation test 5. Sample E17a is the exhaust gas filter 1 in which the catalyst coat layer 4 having a catalyst loading of 50 g / L is formed on the sample B17 of the confirmation test 5. In the confirmation test 5, Sample B4, Sample B15, and Sample B17 in which a catalyst coating layer having a catalyst loading of 100 g / L was formed had a limit collection rate of less than 50%.

Moreover, in this confirmation test 9, as in the confirmation test 8, the evaluation was made regarding the pressure loss and the collection rate of the exhaust gas filter. In this confirmation test 9, the standard of evaluation for sample B4, sample B15, and sample B17 with a catalyst loading of 0 g / L was the sample H1 used in confirmation test 8 with the same catalyst loading of 0 g / L. . The evaluation criteria for Sample B4a, Sample B15a, and Sample B17a, in which the catalyst loading was 50 g / L, were the same as Sample H1a used in Confirmation Test 8 in which the catalyst loading was 50 g / L. In confirmation test 9, the evaluation criteria for the pressure loss and the collection rate in each sample are the same as in confirmation test 8.

The test conditions and test method of this confirmation test 9 were the same as the test conditions and test method used in confirmation test 5. The results are shown in Table 20. For reference, Table 20 also shows Sample B4, Sample B15, Sample B17, and Sample H1 of Confirmation Test 5. Sample B4, Sample B15, and Sample B17 are all evaluated for pressure loss and collection rate based on Sample H1. Further, in Table 20, the pressure loss evaluation of the exhaust gas filter having the substrate length L of the second actual measurement value is “pressure loss evaluation 1”, and the collection rate evaluation is “collection rate evaluation 1”. Also in this test, as in the confirmation test 5, the collection rate evaluation 1 and the collection rate evaluation 2 in each sample are all “A”, and thus the description of the evaluation regarding the collection rate is omitted.

As can be seen from Table 20, also in the exhaust gas filter 1 carrying the catalyst, the second reference value L2 obtained by the equation (2) and the second actually measured value confirmed by the experiment are almost the same. Therefore, according to the formula (2), the exhaust gas filter 1 carrying the catalyst also takes into consideration the influence of various parameters of the exhaust gas filter 1, and the shortest of the base material lengths with a collection rate of 50% or more. It was confirmed that it is possible to accurately calculate the above.

(Confirmation test 10) This confirmation test 10 is a test similar to the confirmation test 6 performed on the exhaust gas filter 1 of Example 5 described above. That is, even in the exhaust gas filter carrying the catalyst, the third measured value that is the measured value of the shortest of the substrate lengths L (full length L) that is not less than 90% of the limit collection rate is the measured value. It was confirmed that the third reference value L3 satisfying the above formula (3) substantially coincides with the third reference value L3.

In the confirmation test 10, as the exhaust gas filter 1 for obtaining the third actual measurement value, the basic structure is the same as that of the exhaust gas filter 1 of the fifth embodiment, and as shown in Table 21, the catalyst loading amount, the flow path cross-sectional area ratio Samples F4a, F4b, F9a, F9b, F23a, and F23b in which Rs, the thickness w of the cell wall 2, the exhaust gas permeability coefficient k, the cell density C, and the outer diameter φ were variously used were used. Here, the sample F4a and the sample F4b are the exhaust gas filter 1 in which different amounts of the catalyst coat layer 4 are formed on the sample C4 of the confirmation test 6. Sample F9a and sample F9b are the exhaust gas filter 1 in which different amounts of the catalyst coat layer 4 are formed on the sample C9 of the confirmation test 6. Sample F23a and sample F23b are the exhaust gas filter 1 in which different amounts of the catalyst coat layer 4 are formed on the sample C23 of the confirmation test 6.

Further, in this confirmation test 10, as in the confirmation test 8, evaluation was also performed regarding the pressure loss and the collection rate of the exhaust gas filter. In this confirmation test 10, the pressure loss and the collection rate were evaluated based on the following sample J1, sample J1a, and sample J1b. Sample J1 is obtained by changing the base length L to that of sample 1 while the basic structure is the same as that of sample 1 of confirmation test 2. Sample J1a is obtained by forming a catalyst coat layer having a catalyst loading of 50 g / L on sample J1. Sample J1b is obtained by forming a catalyst coat layer with a catalyst loading of 100 g / L on sample J1. Sample J1, Sample J1a, and Sample J1b are all exhaust gas filters having a channel cross-sectional area ratio Rs of 1.0. The evaluation reference samples of Sample C4, Sample C9, and Sample C23 with the catalyst loading amount of 0 g / L were the same as Sample J1 with the catalyst loading amount of 0 g / L. In addition, the evaluation reference samples of Sample F4a, Sample F9a, and Sample F23a, in which the catalyst loading was 50 g / L, were the same as sample J1a in which the catalyst loading was 50 g / L. In addition, the evaluation reference samples of Sample F4b, Sample F9b, and Sample F23b, each having a catalyst loading of 100 g / L, were similarly Sample J1b having a catalyst loading of 100 g / L. The criteria for evaluating the pressure loss and the collection rate in each sample in the confirmation test 10 are the same as the criteria for evaluation used in the confirmation test 8.

The test conditions and test method of this confirmation test 10 were the same as the test conditions and test method used in confirmation test 6. The results are shown in Table 21. For reference, Table 21 also lists Sample C4, Sample C9, Sample C23, and Sample J1 of Confirmation Test 6. Further, in Table 21, the pressure loss evaluation of the exhaust gas filter having the third measured actual substrate length L is “pressure loss evaluation 1”, and the collection rate evaluation is “collection rate evaluation 1”.

As can be seen from Table 21, also in the exhaust gas filter 1 carrying the catalyst, the third reference value L3 obtained by the equation (3) and the third actually measured value confirmed by the experiment are almost the same. Therefore, according to the expression (3), even in the exhaust gas filter 1 carrying the catalyst, the influence of various parameters of the exhaust gas filter 1 is taken into account, and the base becomes a collection rate of 90% or more of the limit collection rate. It was confirmed that the shortest material length L can be accurately calculated.

1 exhaust gas filter, 2 cell walls, 3 cell holes, 31 open cell holes, 32 plugged cell holes, 321 plug part.

Claims

An exhaust gas filter (1) for purifying exhaust gas containing particulate matter discharged from an internal combustion engine,
A plurality of cell walls (2);
A plurality of cell holes (3) surrounded by the cell wall (2);
The cell wall (2) has pores communicating between adjacent cell holes (3),
The cell hole (3) is a plugged cell hole (32) having an open cell hole (31) penetrating in the axial direction of the exhaust gas filter (1) and a plug part (321) for closing the upstream end. And consist of
In the cross section orthogonal to the axial direction, the flow path cross-sectional area S2 in the plugged cell hole (32) is larger than the flow path cross-sectional area S1 in the open cell hole (31), and the thickness of the cell wall (2) Is the w (mm), the exhaust gas permeability coefficient is k (μm 2 ), the cell density is C (pieces / mm 2 ), the outer diameter of the exhaust gas filter (1) is φ (mm), and the ratio of S2 to S1. When the flow path cross-sectional area ratio Rs = S2 / S1, the total length L of the exhaust gas filter (1) is not less than the first reference value L1 determined by the following equation (1), and by the following equation (M): An exhaust gas filter (1) having a critical length Lm or less.
L1 = −3.7 × Rs 1.5 −3.6 / w + 9.7 / k−152.9 × C + 2241.5 / φ + 145.1 Formula (1),
Lm = −5.5 × Rs 1.5 −6.0 / w + 44.9 / k−234.9 × C + 176.7 / φ + 255.6 (Equation (M))
An exhaust gas filter (1) for purifying exhaust gas containing particulate matter discharged from an internal combustion engine,
A plurality of cell walls (2);
A plurality of cell holes (3) surrounded by the cell wall (2);
The cell wall (2) has pores communicating between adjacent cell holes (3),
The cell hole (3) is a plugged cell hole (32) having an open cell hole (31) penetrating in the axial direction of the exhaust gas filter (1) and a plug part (321) for closing the upstream end. And consist of
In the cross section orthogonal to the axial direction, the flow passage cross-sectional area S2 in the plugged cell hole (32) is larger than the flow passage cross-sectional area S1 in the open cell hole (31),
The thickness of the cell wall (2) is w (mm), the exhaust gas permeability coefficient is k (μm 2 ), the cell density is C (pieces / mm 2 ), and the outer diameter of the exhaust gas filter (1) is φ (mm). When the flow path cross-sectional area ratio Rs = S2 / S1, which is the ratio of S2 to S1, the total length L of the exhaust gas filter (1) is not less than a second reference value L2 determined by the following equation (2). And an exhaust gas filter (1) having a critical length Lm or less determined by the following formula (M).
L2 = −13.4 × Rs 1.5 + 0.76 / w + 3.2 / k−132.1 × C + 117.3 / φ + 174.4 Formula (2),
Lm = −5.5 × Rs 1.5 −6.0 / w + 44.9 / k−234.9 × C + 176.7 / φ + 255.6 (Equation (M))
An exhaust gas filter (1) for purifying exhaust gas containing particulate matter discharged from an internal combustion engine,
A plurality of cell walls (2);
A plurality of cell holes (3) surrounded by the cell wall (2);
The cell wall (2) has pores communicating between adjacent cell holes (3),
The cell hole (3) is a plugged cell hole (32) having an open cell hole (31) penetrating in the axial direction of the exhaust gas filter (1) and a plug part (321) for closing the upstream end. And consist of
In the cross section orthogonal to the axial direction, the flow path cross-sectional area S2 in the plugged cell hole (32) is larger than the flow path cross-sectional area S1 in the open cell hole (31), and the thickness of the cell wall (2) Is the w (mm), the exhaust gas permeability coefficient is k (μm 2 ), the cell density is C (pieces / mm 2 ), the outer diameter of the exhaust gas filter (1) is φ (mm), and the ratio of S2 to S1. When the flow path cross-sectional area ratio Rs = S2 / S1, the total length L of the exhaust gas filter (1) is not less than a third reference value L3 determined by the following equation (3), and by the following equation (M): An exhaust gas filter (1) having a critical length Lm or less.
L3 = −6.8 × Rs 1.5 −4.5 / w + 12.0 / k−189.9 × C + 2629.1 / φ + 191.7 Formula (3),
Lm = −5.5 × Rs 1.5 −6.0 / w + 44.9 / k−234.9 × C + 176.7 / φ + 255.6 (Equation (M))
The thickness w (mm) of the cell wall (2) is 0.13 ≦ w ≦ 0.47, the exhaust gas permeability coefficient k (μm 2 ) is 0.3 ≦ k ≦ 1.1, and the cell The density C (pieces / mm 2 ) is 0.31 ≦ C ≦ 0.62, and the exhaust gas filter (1) has an outer diameter φ (mm) of 80 ≦ φ ≦ 150. The exhaust gas filter (1) according to any one of claims 1 to 3.
The exhaust gas filter (1) according to any one of claims 1 to 4, wherein the flow path cross-sectional area ratio Rs = S2 / S1 is 1.1≤Rs≤5.
The exhaust gas filter (1) according to any one of claims 1 to 5, wherein the plurality of cell holes (3) have two or more types of shapes.
The cell hole (3) comprises an octagonal cell hole (3) with an inner peripheral shape and a square cell hole (3) with an inner peripheral shape, and the hydraulic diameter of the octagonal cell hole (3) is The octagonal cell hole (3) and the square cell hole (3) are alternately arranged and are larger than the hydraulic diameter of the square cell hole (3). 6. The exhaust gas filter (1) according to 6.
The exhaust gas according to claim 7, wherein the octagonal cell hole (3) is a plugged cell hole (32) and the square cell hole (3) is the open cell hole (31). Filter (1).
The exhaust gas filter (1) according to claim 7, wherein all of the octagonal cell holes (3) and a part of the rectangular cell holes (3) are the plugged cell holes (32). ).
The plurality of cell holes (3) are composed of square cell holes with an inner peripheral shape, and are arranged such that the number of plugged cell holes (32) is larger than the number of open cell holes (31). The exhaust gas filter (1) according to any one of claims 1 to 5, wherein:
The plurality of cell holes (3) are formed of square cell holes with an inner peripheral shape, and the open cell holes (31) and the plugged cell holes (32) are alternately arranged. The exhaust gas filter (1) according to any one of claims 1 to 5.