Exhaust gas purifying filter
阅读说明：本技术 废气净化过滤器 (Exhaust gas purifying filter ) 是由 麻奥香菜 于 2020-07-08 设计创作，主要内容包括：具有单元构造部(2)、密封部(11)和表皮部(12)的废气净化过滤器(1)。单元构造部(2)包括沿着过滤器轴向(Y)延伸的多个单元(21)和将多个单元(21)划分形成为格子状的多孔质的隔壁(22)。表皮部(12)为筒状且形成在单元构造部(2)的外周。隔壁(22)的气孔率是50～70％。表皮(12)部的厚度T是0.3～1.0mm。单元(21)的外缘(213)在隔壁(22)的交叉位置(225)处带有圆度,交叉位置(225)处的曲率半径R为0.02～0.6mm。过滤器轴向(Y)上的、废气净化过滤器(1)的外形尺寸的变化程度即变形度δ超过0且在1.5mm以下。式I所表示的构造变量X为0.05～6。X＝T×R/δ···式I。(An exhaust gas purification filter (1) having a cell structure section (2), a seal section (11), and a skin section (12). The cell structure (2) includes a plurality of cells (21) extending in the filter axial direction (Y) and porous partition walls (22) that partition the cells (21) into a grid shape. The skin portion (12) is cylindrical and is formed on the outer periphery of the unit structure portion (2). The porosity of the partition wall (22) is 50-70%. The thickness T of the surface skin (12) is 0.3 to 1.0 mm. The outer edge (213) of the cell (21) has a roundness at the intersection position (225) of the partition wall (22), and the curvature radius R at the intersection position (225) is 0.02 to 0.6 mm. The degree of deformation delta, which is the degree of change in the external dimensions of the exhaust gas purification filter (1) in the filter axial direction (Y), is more than 0 and not more than 1.5 mm. The structural variable X represented by the formula I is 0.05 to 6. X is T multiplied by R/delta. formula I.)
1. An exhaust gas purifying filter (1) disposed in an exhaust passage (A) of a gasoline engine (E),
comprising:
a cell structure (2) including a plurality of cells (21, 21a, 21b) extending in a filter axial direction (Y) and porous partition walls (22) partitioning the plurality of cells into a lattice shape;
a sealing part (11) which seals both ends (211, 222) of the unit in the unit structure part; and
a cylindrical skin portion (12) formed on the outer periphery of the unit structure portion,
the porosity of the partition walls is 50 to 70%,
the thickness T of the skin portion is 0.3 to 1.0mm,
the outer edge (213) of the cell has a roundness at the intersection position (225) of the partition walls, the curvature radius R at the intersection position is 0.02 to 0.6mm,
the degree of deformation delta, which is the degree of change in the outer dimensions of the exhaust gas purification filter in the axial direction of the filter, is more than 0 and 1.5mm or less,
the structural variable X represented by the following formula I is 0.05 to 6,
x is T multiplied by R/delta. formula I.
2. The exhaust gas purifying filter according to claim 1,
the cross-sectional shape of the cell in a plane orthogonal to the axial direction of the filter is a quadrangle, the hydraulic diameter d of the cell and the curvature radius R satisfy the following formula II,
r is less than or equal to 0.5 xd/2 · formula II.
3. The exhaust gas purifying filter according to claim 1 or 2,
material strength S of the unit structure sectionAAnd the material strength S of the skin portionBSatisfies the relationship of the following formula III,
SA＜SBformula III.
4. The exhaust gas purifying filter according to any one of claims 1 to 3,
porosity P of the cell structureAAnd the porosity P of the skin portionBSatisfies the following relationship of formula IV,
PA＞PBformula IV.
Technical Field
The present invention relates to an exhaust gas purification filter disposed in an exhaust passage of a gasoline engine.
Background
Exhaust gas discharged from internal combustion engines such as gasoline engines and diesel engines contains particulate matter called particulate matter. Hereinafter, the particulate matter is appropriately referred to as "PM". An exhaust gas purification filter is disposed in an exhaust passage of the internal combustion engine to capture PM in the exhaust gas and purify the exhaust gas.
As such an exhaust gas purifying filter, for example, patent document 1 discloses a diesel particulate filter that traps PM discharged from a diesel engine. Specifically, a technique is described in which the cross-sectional area and hydraulic diameter of a predetermined cell among a large number of cells of the filter are made different from those of the remaining cells, and the corners of the cells are made in an arc shape. According to this document, this technique suppresses the blockage of the inflow-side end face, and can maintain high strength.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2005-270969
Disclosure of Invention
In the case of reinforcing the structure of the partition walls of the filter or the like for the purpose of enhancing the strength, the cross-sectional area of the intersection portion of the partition walls is increased. The increase in the cross-sectional area of the partition wall deteriorates the flow of the exhaust gas, and increases the pressure loss. On the other hand, in order to reduce the pressure loss, it is effective to increase the porosity of the partition walls, for example, but if the porosity is increased, the strength of the filter is decreased. Hereinafter, the pressure loss is appropriately referred to as "pressure loss".
In general, a filter mounted on a gasoline engine is in a high temperature environment as compared with a diesel engine, and the flow velocity of exhaust gas is high, so that the pressure loss tends to increase. Therefore, the filter mounted on the gasoline engine may be displaced from the mounting position to the downstream side in the flow direction of the exhaust gas during use. In order to prevent displacement, it is effective to fix the filter at the mounting position by applying a large external pressure to the filter, but if the dimensional accuracy of the filter is poor, local stress acts on the filter, and the filter is broken.
The invention aims to provide an exhaust gas purifying filter with low pressure loss and high strength.
An embodiment of the present invention is an exhaust gas purification filter disposed in an exhaust passage of a gasoline engine, including:
a cell structure unit including a plurality of cells extending in a filter axial direction and porous partition walls dividing the plurality of cells into a lattice shape;
a sealing part for blocking both ends of the cells in the cell structure part; and
a cylindrical skin portion formed on the outer periphery of the unit structure portion,
the porosity of the partition walls is 50 to 70%,
the thickness T of the skin portion is 0.3 to 1.0mm,
the outer edge of the cell has a roundness at the intersection of the partition walls, the radius of curvature R at the intersection is 0.02 to 0.6mm,
the degree of deformation delta, which is the degree of change in the outer dimensions of the exhaust gas purification filter in the axial direction of the filter, is more than 0 and not more than 1.5mm,
the structural variable X represented by the following formula I is 0.05 to 6,
x is T multiplied by R/delta. formula I.
The exhaust gas purifying filter has the above structure. In particular, the porosity, the thickness T of the skin portion, the radius of curvature R of the outer edge of the cell at the intersection, and the degree of deformation δ fall within the above ranges, and the structural variable X represented by formula I falls within the above ranges. Therefore, the exhaust gas purifying filter has a low pressure loss and a high strength.
In addition, the reference numerals in parentheses in the claims indicate correspondence with specific components described in the embodiments described below, and do not limit the technical scope of the present invention.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.
Fig. 1 is a schematic view of an exhaust gas purifying filter according to embodiment 1.
Fig. 2 is an enlarged cross-sectional view in the axial direction of the exhaust gas purifying filter according to embodiment 1.
Fig. 3 is an enlarged cross-sectional view of the exhaust gas purification filter according to embodiment 1 at a position intersecting in a direction orthogonal to the axial direction.
Fig. 4 is an enlarged cross-sectional view of a cell in a direction orthogonal to the axial direction of the exhaust gas purification filter of embodiment 1.
Fig. 5 (a) is a schematic external view of the exhaust gas purifying filter of embodiment 1 that is not deformed in the axial direction, fig. 5 (b) is a schematic external view of the exhaust gas purifying filter that is largely deformed in the axial direction, and fig. 5 (c) is an explanatory view showing a dimensional difference in the direction orthogonal to the axial direction of the exhaust gas purifying filter.
Fig. 6 is a schematic diagram of an exhaust gas purification filter arranged in an exhaust passage according to embodiment 1.
Fig. 7 is a schematic diagram showing an isostatic pressure (isostatic) strength test of an experimental example.
Fig. 8 (a) is a schematic cross-sectional view of a measurement sample used for measuring the material strength of the skin portion in the experimental example, and fig. 8 (b) is a schematic cross-sectional view of a measurement sample used for measuring the material strength of the cell structural portion.
Fig. 9 is a schematic diagram showing a 4-point bending test in an experimental example.
Fig. 10 is an explanatory diagram showing a relationship between a measured sample of the material strength and a variable of the section coefficient in the experimental example.
Fig. 11 is an explanatory view showing a measurement site of the curvature radius R in the experimental example.
Fig. 12 is an explanatory view showing a measurement site of the thickness of the skin portion in the experimental example.
Fig. 13 is an explanatory diagram showing the radius H of the exhaust gas purifying filter at a position 5mm from the inlet end face, the radius M of the exhaust gas purifying filter at the center portion, and the radius L of the exhaust gas purifying filter at a position 5mm from the outlet end face in the filter axial direction.
Fig. 14 is a graph showing a relationship between a structural variable X and a pressure loss in experimental example 1.
Fig. 15 is a graph showing the relationship between structural variable X and isostatic strength in experimental example 1.
Fig. 16 is a graph showing the relationship between the radius of curvature R and the pressure loss in experimental example 2.
Fig. 17 is a graph showing the relationship between the material strength and the isostatic strength in experimental example 3.
Fig. 18 is a graph showing the relationship between the porosity and the material strength in experimental example 3.
Detailed Description
[ embodiment 1]
An embodiment of the exhaust gas purification filter 1 will be described with reference to fig. 1 to 6. In the present specification, the expression "to" represents a range including values before and after a numerical value or a physical value sandwiched between before and after the numerical value or the physical value. As shown in fig. 1 to 3, the exhaust gas purifying filter 1 includes a cell structure portion 2, a sealing portion 11, and a skin portion 12. The cell structural portion 2 and the skin portion 12 are made of ceramics such as cordierite.
The cell structure 2 includes a large number of cells 21 and porous partition walls 22. The unit 21 extends in the filter axial direction Y. The filter axial direction Y generally coincides with the extension direction of the unit 21. Hereinafter, the filter axial direction is appropriately referred to as "axial direction". The partition walls 22 divide a large number of cells 21 into a lattice shape. The partition walls 22 are also commonly referred to as cell walls.
As shown in fig. 1, 3, and 4, the shape of the unit in the filter cross section in the direction orthogonal to the axial direction Y is, for example, a quadrangle, but is not limited thereto. The cell shape may be a polygon such as a triangle, a quadrangle, a hexagon, a circle, or the like. In addition, the cell shape may be a combination of 2 or more different shapes. In addition, even if the vertices of the polygonal cell shape are rounded, the cell shape can be said to be polygonal in appearance, and thus the cell shape is considered to be polygonal.
The skin portion 12 has a cylindrical shape such as a cylindrical shape. The skin portion 12 is formed integrally with the outer periphery of the unit structure portion 2. The axial direction of the skin portion 12 generally coincides with the filter axial direction Y. The partitions 22 divide the inside of the skin portion 12 into a grid shape to form a large number of cells 21. The exhaust gas purifying filter 1 is a porous body, and a large number of pores are formed in the partition walls 22. The exhaust gas purification filter 1 can collect PM contained in the exhaust gas by depositing the PM on the surfaces of the partition walls 22 and in the pores. The pores are also called pores. PM is fine particles called particulate matter, and the like.
The exhaust gas purifying filter 1 is a columnar body such as a cylindrical body, and the size thereof can be changed as appropriate. When the exhaust gas purifying filter 1 is cylindrical, the length L in the axial direction Y can be adjusted to 50 to 200mm and the diameter Φ can be adjusted to 100 to 165 mm. The exhaust gas purifying filter 1 has an inflow end surface 18 and an outflow end surface 19 at both ends in the filter axial direction Y. The inflow end surface 18 is an end surface on the side where exhaust gas flows in, and the outflow end surface 19 is an end surface on the side where exhaust gas flows out. The inflow end surface 18 and the outflow end surface 19 represent surfaces facing each other in a state of not being arranged in the flow of exhaust gas in the exhaust pipe or the like. That is, when one end surface is the inflow end surface 18, the other end surface is the outflow end surface 19. For example, the inflow end surface 18 may be referred to as a 1 st end surface in the axial direction Y, and the outflow end surface 19 may be referred to as a 2 nd end surface in the axial direction Y.
As the cell 21, a 1 st cell 21a and a 2 nd cell 21b can be provided. As shown in fig. 2, the 1 st cell 21a is open at the inflow end face 18, for example, and is closed by the seal portion 11 at the outflow end face 19. The 2 nd unit 21b is open at the outflow end surface 19, for example, and is closed by the seal portion 11 at the inflow end surface 18.
The seal portion 11 blocks the both ends 211, 212 of the unit 21 in the filter axial direction Y differently from each other. In other words, the sealing 11 blocks the cells 21 differently from each other at the inflow end face 18 or the outflow end face 19. The sealing portion 11 may be made of ceramic such as cordierite, for example, but may be made of other materials. In fig. 2, a plug-shaped seal portion 11 is formed, but the shape of the seal portion 11 is not particularly limited as long as the end portion of the cell 21 can be sealed. Although the illustration of the structure is omitted, the seal portion 11 may be formed by deforming a part of the partition wall 22 at the inflow end surface 18 or the outflow end surface 19, for example. In this case, since the seal portion 11 is formed by a part of the partition wall 22, the partition wall 22 and the seal portion 11 are integrally and continuously formed.
The 1 st unit 21a and the 2 nd unit 21b are formed, for example, so as to be alternately arranged adjacent to each other in both the transverse direction X orthogonal to the filter axial direction Y and the longitudinal direction Z orthogonal to both the filter axial direction Y and the transverse direction X. That is, when the inflow end surface 18 or the outflow end surface 19 of the exhaust gas purification filter 1 is viewed from the filter axial direction Y, the 1 st cell 21a and the 2 nd cell 21b are arranged in a checkered pattern, for example. The partition wall 22 partitions the 1 st cell 21a and the 2 nd cell 21 b.
The porosity of the partition wall 22 is 50 to 70%. When the porosity is less than 50%, the pressure loss becomes high. When the porosity exceeds 70%, the filter strength is reduced. The porosity is preferably 55 to 67%, more preferably 57 to 67%, and still more preferably 60 to 66% from the viewpoint of reducing pressure loss and improving filter strength. The porosity was measured according to the principle of mercury intrusion method, and the detailed measurement method is shown in experimental example 1.
The outer edge 213 of the cell 21 is rounded at the intersection 225 of the partition walls 22. That is, as shown in fig. 3, in a cross section of a plane orthogonal to the filter axial direction Y, the outer edge 213 of the cell 21 has an arc shape such as an arc shape at the intersection 225 of the partition walls 22. In the cross section, the intersection position 225 of the partition walls 22 can be said to be a corner of the cell 21. That is, the outer edge 213 of the cell 21 is rounded at the intersection 225 of the partition walls 22, and is substantially the same as the corner of the cell 21 in an arc shape. By making the intersection position 225 arc-shaped, the cross-sectional area of the partition wall 22 at the intersection position 225 can be increased as compared with a case where the intersection position 225 is, for example, a right-angled shape. This strengthens the partition walls 22 at the intersection 225, thereby improving the filter strength. In particular, the strength corresponding to the stress from the direction orthogonal to the filter axial direction Y is improved. The intersection position 225 is a position where the partition walls 22 formed in a lattice shape intersect. The direction orthogonal to the filter axial direction Y is a radial direction when the exhaust gas purification filter 1 is cylindrical.
The degree of deformation δ of the exhaust gas purifying filter 1 will be explained. The degree of deformation is the degree of change in the outer dimensions of the exhaust gas purification filter 1 in the filter axial direction Y. More specifically, the deformation degree is a difference between the maximum value and the minimum value of the dimension (for example, radius) in the direction orthogonal to the axial direction Y at 3 positions, i.e., positions 5mm inward from both ends in the axial direction Y of the filter and the center position in the axial direction Y in total.
Fig. 5 (a) shows an example of the external shape of the exhaust gas purification filter 1 having a degree of deformation of 0, and fig. 5 (b) shows an example of the external shape of the exhaust gas purification filter 1 having a large degree of deformation. In fig. 5 (a) and (b), for convenience of drawing, the partition wall 22 and the cells are not shown. In the case where the axis of the exhaust gas purification filter 1 shown in (a) and the axis of the exhaust gas purification filter 1 shown in (b) are deformed, as shown in (c) of fig. 5, a difference occurs in the outer dimension in the direction perpendicular to the filter axial direction Y. The difference is the degree of deformation δ. In the case where the exhaust gas purifying filter 1 has a cylindrical shape, for example, the outer dimension is a radius. In fig. 5 (c), the direction perpendicular to the drawing sheet is the filter axial direction Y. The method of measuring the degree of deformation is shown by the experimental examples.
In the exhaust gas purifying filter 1, the structural variable X is 0.05 to 6. The structural variable X is represented by the thickness Tmm of the skin portion 12, the curvature radius Rmm of the outer edge 213 of the cell 21 at the intersection 225, and the degree of deformation δ mm, as shown in formula I. Wherein T is more than or equal to 0.3 and less than or equal to 1.0, R is more than or equal to 0.02 and less than or equal to 0.6, and delta is more than 0 and less than or equal to 1.5 can be selected from T, R and delta.
X ═ T × R/δ · formula I
When T is less than 0.3, when R is less than 0.02, and when delta is greater than 1.5, the filter strength is insufficient. In particular, the strength corresponding to the stress from the direction orthogonal to the filter axial direction Y is insufficient. Therefore, for example, in an assembly operation called canning (canning) in which a ceramic mat is wound around the exhaust gas purification filter 1 and inserted into a filter housing, the exhaust gas purification filter 1 may be damaged. Since the thickness of the skin portion 12 is too small in the case of T < 0.3. Because the reinforcement at the intersection position 225 is insufficient in the case of R < 0.02. Since local stress is easily applied to the filter due to large deformation in the case of δ > 1.5 and the stress becomes large.
When T > 1.0 and R > 0.6m, the pressure loss increases. Because the thickness of the skin portion 12 is too large in the case of T > 1.0. Because the sectional area of the partition wall 22 at the intersection position 225 is excessively large in the case where R > 0.6. When δ is 0, the filter is an ideal body without deformation, but δ cannot be substantially 0 because δ is contrary to the property of ceramics such as shrinkage during firing.
The structural variable X will be explained. The structural variable X is a function of the thickness Tmm, the radius of curvature Rmm, and the degree of deformation δ mm, as shown in formula I. In the formula I, T is more than or equal to 0.3 and less than or equal to 1.0, R is more than or equal to 0.02 and less than or equal to 0.6, and delta is more than 0 and less than or equal to 1.5. By setting the structural variable X within the range of 0.05 to 6, the filter strength can be improved while maintaining low pressure loss. In particular, since the strength according to the stress from the direction orthogonal to the filter axial direction Y is improved, the above-described breakage at the time of canning can be prevented. From the viewpoint of achieving both low pressure loss and high strength at a higher level, the structural range X is preferably 0.1 to 6, more preferably 1 to 6, and still more preferably 1 to 3. The relationship between the structural variable X and the pressure loss and the filter strength is specifically shown in experimental example 1.
Preferably, the cross-sectional shape of the cell 21 in a plane orthogonal to the filter axial direction Y is a quadrangle, and the hydraulic diameter d of the cell 21 and the radius of curvature R satisfy the relationship of formula II. In this case, both low pressure loss and high strength can be achieved at a higher level. As in the cross-sectional shape of the cell 21 shown in fig. 4, normally, even if the opening cross section of the gas flow is a quadrangle, the gas flows inside a circle having a diameter called the hydraulic diameter. Therefore, if the outside of the circle having the hydraulic diameter is provided, the pressure loss does not increase theoretically even if the corners of the cells 21 are formed in an arc shape. However, in the exhaust gas purifying filter 1, since the partition walls 22 are porous and the gas passes through the inside of the partition walls 22, even in the structure in which the curvature radius R is set outside the circle of the hydraulic diameter, the boundary point at which the pressure loss increases is present in the numerical range of the curvature radius R that is outside the hydraulic diameter. The details of formula II are shown in experimental example 2.
R is less than or equal to 0.5 xd/2 · formula II
Material strength S of unit structural part 2AAnd material strength S of the skin portion 12BPreferably, the relationship of formula III is satisfied. In this case, the flow of the exhaust gas is equalized, the pressure loss increase is further suppressed, and the filter strength is further improved. The details of the relationship of formula III are shown in experimental example 3.
SA＜SBA. formula III
Porosity P of the cell structure 2AAnd porosity P of skin portion 12BPreferably, the following formula IV is satisfied. In this case, too, the flow of the exhaust gas is equalized, the pressure loss increase is further suppressed, and the filter strength is further improved. Porosity P of the cell structure 2AThe meaning is the same as the porosity of the partition wall 22. The details of the relationship of formula IV are shown in experimental example 3.
PA＞PBA is of formula IV
As shown in fig. 6, the exhaust gas purifying filter 1 is disposed in an exhaust passage a of a gasoline engine E. Specifically, for example, a filter case C that houses the exhaust gas purification filter 1 therein is connected to the exhaust passage a. The exhaust gas purifying filter 1 is accommodated in the filter case C in a state where the ceramic mat M is wound around the skin portion 12 thereof. In order to prevent displacement in use, external pressure is applied to the exhaust gas purification filter 1 in the filter housing C in a direction orthogonal to the axial direction Y.
The exhaust gas purifying filter 1 having the porosity, the thickness T of the skin portion 12, the radius of curvature R of the outer edge 213 of the cell 21 at the intersection 225, and the degree of deformation δ within the above ranges, and the structural variable X within the above ranges has a low pressure loss and a high filter strength. That is, even if external pressure is applied in the direction orthogonal to the axial direction Y, breakage of the exhaust gas purification filter 1 can be prevented while maintaining low pressure loss.
The exhaust gas purifying filter 1 is manufactured as follows, for example. First, a clay containing a cordierite-forming raw material is prepared. Silica, talc, aluminum hydroxide, and the like are adjusted to be cordierite components, and a binder such as methylcellulose, a pore-forming material such as graphite, a lubricating oil, water, and the like are appropriately added and mixed to prepare a clay. In order to become the cordierite component, alumina and kaolin can also be matched. As the silica, porous silica can be used. In the cordierite-forming raw material, silica and talc can be used as the pore-forming raw material. The pore-forming raw material is a material that forms pores. The pore-forming raw material forms a liquid phase component during firing, thereby forming pores. On the other hand, in cordierite-forming raw materials, aluminum hydroxide, alumina, and kaolin can be aggregate raw materials. The aggregate material is a material for forming a ceramic portion other than the fine pores.
Next, the clay is molded, dried, and fired. This results in a honeycomb structure having the skin portion 12 and the cell structure portion 2 formed integrally. The honeycomb structure includes a skin portion 12, partition walls 22, and cells 21. The sealing portion 11 is formed after firing the honeycomb structure or before firing. Specifically, for example, the end faces of the cells 21 of the honeycomb structure after firing or the molded body of the honeycomb structure before firing are alternately sealed with the slurry for forming the seal portion, and fired to form the seal portion 11.
The thickness T of the skin portion 12, the radius of curvature R at the intersection 225 of the partition walls 22, and the hydraulic diameter of the cell 21 can be adjusted by, for example, the die design at the time of molding. The degree of deformation can be adjusted by changing, for example, molding conditions such as extrusion speed, drying conditions of the molded body, firing conditions, and the like. The porosity and material strength can be adjusted by, for example, changing the raw material composition, the design of a die used for molding, and molding conditions such as extrusion molding pressure.
[ Experimental example ]
First, various measurement methods used in the experimental examples will be described. In addition, of the reference numerals used after the experimental example, the same reference numerals as those used in the previous embodiment denote the same components and the like as those of the previous embodiment unless otherwise specified.
Isostatic Strength test
The isostatic strength test was measured based on automobile standards (i.e., JASO) M505-87 issued by the society automotive technical society (Japanese original text: society automatic brewing society). As shown in fig. 7, aluminum plates 51 and 52 having a thickness of 20mm were brought into contact with both end surfaces in the axial direction Y of the exhaust gas purifying filter 1 to seal both end surfaces 18 and 19, and a rubber 53 having a thickness of 2mm was brought into close contact with the surface of the skin portion 12. The exhaust gas purifying filter 1 is put in a pressure vessel, water is introduced into the pressure vessel, and hydrostatic pressure is applied from the surface of the skin portion 12. The pressure at which the exhaust gas purifying filter 1 is damaged is set as the isostatic strength.
Pressure loss
The exhaust gas purification filter 1 was attached to the exhaust pipe of a 2.0L direct gasoline injection engine so that the intake air amount (Ga) was 100g/s (steady state). Then, the exhaust gas containing PM is caused to flow into the exhaust gas purification filter 1. At this time, the pressure before and after the exhaust gas purifying filter 1 is measured, and the difference is measured as the pressure loss.
Strength of the material
First, measurement samples S1 and S2 are obtained from the exhaust gas purification filter 1 as shown in fig. 8 (a) and (b). Specifically, 5 measurement samples S2 were obtained from the center of the exhaust gas purification filter 1 in the direction orthogonal to the filter axial direction Y (specifically, the radial direction) within a range of 30mm in the radial direction, and 5 measurement samples S1 were obtained from the outermost periphery in the direction orthogonal to the filter axial direction Y within a range of 30mm in the radial direction. As shown in fig. 8 (a), a measurement sample S1 including the skin portion 12 was obtained from a range of 30mm in the radial direction from the outermost periphery. The measurement samples S1, S2 included 4 cells 21 in the width direction and 2 cells 21 in the thickness direction. The length of each of the measurement samples S1 and S2 in the filter axial direction Y was 50mm, and the measurement samples were block (block) units.
As shown in fig. 9, with respect to the measurement samples S1, S2, according to JIS R1601: 2008' Fine ceramic ChamberMethod for testing warm bending strength ", a 4-point bending test was performed, and the bending moment (unit: N · m) at the time of fracture of the measurement sample was divided by a value obtained by taking into consideration the section coefficient of the filter section, as the material strength. Material strength S of unit structural part 2AIs an average value of the material strengths of 5 measurement samples S2. Material strength S of the skin portion 12BIs an average value of the material strengths of 5 measurement samples S1.
The material strength is represented by the following formula.
Material strength (MPa) ═ bending moment (N · mm)/section modulus (mm)3)
The bending moment is expressed by the following equation.
Bending moment (N · mm) — load (N) × 4 point bending test distance between fulcrums (mm)/4
The section modulus is represented by the following formula V. As shown in fig. 10, in formula V: a: cross-sectional area (mm) of measurement sample in a plane orthogonal to filter axial direction Y2) And y: distance (mm) from each reference axis to the surface of the part, b: width (mm) of the measurement specimen, h: height (mm) of the measurement specimen, i: sectional moment of inertia (mm) of each unit section4). Although the measurement sample S1 is shown in fig. 10, the same applies to the measurement sample S2.
[ mathematical formula 1]
Radius of curvature R at the intersection of the bulkheads
As shown in fig. 3, the radius of curvature is the radius R of the maximum circle that the portion with circularity of the cell 21 at the intersection position 225 of the partition wall 22 abuts. As shown in fig. 11, the measurement site is 4 positions in the center portion O in the direction orthogonal to the filter axial direction Y, which are 45 degrees with respect to the center portion O and are positioned at a half of the distance between the center portion O and the skin portion 12. That is, the total of the measurement positions is 5. At each measurement position, 4 radii of curvature formed at 1 intersection 225 were measured. That is, the radius of curvature at 20 in total was measured. The average value of these values is defined as the radius of curvature at the intersection 225 of the partition walls 22.
Hydraulic diameter d
Hydraulic diameter refers to the inner diameter of the pipe through which the fluid flows. When the flow path cross section is not circular as in the case of the unit having a quadrangular cross section of the exhaust gas purifying filter, the hydraulic diameter d is calculated by the following equation VI from the sectional area a of the unit and the sectional length L of the unit. In the case where the cross-sectional shape of the cell is a quadrangle, the cross-sectional length L is the sum of the sides of the quadrangle, and the length of each side is measured by regarding the vertex with roundness in the cross-sectional shape of the cell as the vertex at a right angle without roundness. The measurement position follows the radius of curvature R described above.
D ═ 4A/L. type VI
Thickness T of the skin portion
The thickness of the skin portion 12 at the end face (inflow end face 18 or outflow end face 19) in the axial direction Y of the filter was measured for 8 points. The thickness T of the skin portion 12 is an average value of the thicknesses at 8. A tool microscope was used in the assay. The measurement positions are 4 intersections with the skin portion 12 of lines drawn from the center portion O in the direction orthogonal to the filter axial direction Y toward the skin portion 12 along the lattice direction, and 4 intersections with the skin portion 12 of lines drawn from the center portion O toward the skin portion 12 along the direction inclined at 45 ° to the lattice direction. That is, the measurement positions are 8 positions in total, and are within the circle marked by the dotted line at 8 positions in fig. 12.
Degree of deformation
The radius of the outer periphery of the exhaust gas purifying filter 1 was measured at a position 5mm inward in the filter axial direction Y from both end surfaces (the inflow end surface 18 and the outflow end surface 19) and at a central position in the filter axial direction Y by a laser measuring device. Thereby, a radial dimension diagram of the outer periphery of the exhaust gas purification filter 1 illustrated in fig. 13 is obtained. The difference between the maximum radius and the minimum radius in the radius dimension map at 3 is set as the degree of deformation. In fig. 13, the radius at a position 5mm from the inflow end face 18 is denoted by H, the radius at the center is denoted by M, and the radius at a position 5mm from the outflow end face 19 is denoted by L. The radius map shown in fig. 13 is closer to a perfect circle as the distortion is smaller, and becomes a perfect circle when there is no distortion.
Porosity P of the cell structure portionAThe porosity P of the skin portionB
The porosity of the partition wall 22 of the exhaust gas purifying filter 1 was measured by a mercury porosimeter using the principle of the mercury porosimetry. As the mercury porosimeter, an automatic mercury porosimeter (auto-pore) IV9500 manufactured by shimadzu corporation (japanese original: shimadzu corporation) was used. The measurement conditions were as follows.
First, measurement samples were obtained from the cell structure portion 2 and the skin portion 12 of the exhaust gas purification filter 1. The measurement sample of the cell structure portion 2 is a substantially cubic body having a length of 1cm in the filter axial direction Y, a length of 1cm in the thickness direction of the partition wall 22, and a length of 1cm orthogonal to the filter axial direction Y and the thickness direction. The measurement sample of the skin portion 12 is a substantially cubic body having a length of 1cm in the axial direction Y of the filter, a length of 1cm from the skin portion to the center portion of the filter including the skin portion in the thickness direction of the partition wall 22, and a length of 1cm orthogonal to the axial direction Y and the thickness direction of the filter. The measurement sample is contained in a measurement cell of a mercury porosimeter, and the inside of the measurement cell is depressurized. Then, mercury was introduced into the measurement cell and pressurized, and the pore diameter was measured from the pressure at the time of pressurization and the volume of mercury introduced into the pores of the measurement sample.
The measurement is carried out at a pressure of 0.5 to 20000 psia. In addition, 0.5psia corresponds to 0.35X 10-3kg/mm220000psia corresponds to 14kg/mm2. The pore diameter corresponding to the pressure range is in the range of 0.01 to 420 μm. As constants for calculating the pore diameter from the pressure, the contact angle was 140 ℃ and the surface tension was 480 dyn/cm. The porosity was calculated by the following relational expression. Further, the true specific gravity of cordierite is 2.52.
Porosity (%). ratio of total pore volume/(total pore volume + 1/true specific gravity of cordierite) × 100
(Experimental example 1)
In this example, a plurality of exhaust gas purifying filters 1 were manufactured by changing the manufacturing conditions. The exhaust gas purifying filter 1 had a length L in the axial direction Y of 120mm, a diameter Φ of 118mm, a cross-sectional shape of the cell 21 being a quadrangle, a thickness of the partition wall 22 being 0.2mm, a cell pitch being 1.47mm, and a porosity of 64%. The thickness T of the skin portion 12, the radius of curvature R of the intersection 225, the degree of deformation δ, the pressure loss, and the isostatic strength were measured for the exhaust gas purification filter 1. Further, according to formula I, the construction variable X is calculated. The results are shown in tables 1 to 8, fig. 14, and fig. 15.
[ TABLE 1]
(Table 1) variation in thickness of skin portion
Thickness T of the epidermis
Degree of deformation delta
Radius of curvature R
X
Pressure loss
mm
mm
mm
-
kPa
0.3
0.1
0.60
1.80
3.30
0.4
0.1
0.60
2.40
3.30
0.5
0.1
0.60
3.00
3.30
0.6
0.1
0.60
3.60
3.30
0.7
0.1
0.60
4.20
3.30
0.8
0.1
0.60
4.80
3.30
0.9
0.1
0.60
5.40
3.30
1
0.1
0.60
6.00
3.30
1.5
0.1
0.60
9.00
3.30
[ TABLE 2 ]
(Table 2) Change in degree of deformation
Thickness T of the epidermis
Degree of deformation delta
Radius of curvature R
X
Pressure loss
mm
mm
mm
-
kPa
1
1.5
0.60
0.40
3.30
1
1.4
0.60
0.43
3.30
1
1.3
0.60
0.46
3.30
1
1.2
0.60
0.50
3.30
1
1.1
0.60
0.55
3.30
1
1
0.60
0.60
3.30
1
0.9
0.60
0.67
3.30
1
0.8
0.60
0.75
3.30
1
0.7
0.60
0.86
3.30
1
0.6
0.60
1.00
3.30
1
0.5
0.60
1.20
3.30
1
0.4
0.60
1.50
3.30
1
0.3
0.60
2.00
3.30
1
0.2
0.60
3.00
3.30
1
0.1
0.60
6.00
3.30
[ TABLE 3 ]
(Table 3) variation of radius of curvature R
Thickness T of the epidermis
Degree of deformation delta
Radius of curvature R
X
Pressure loss
mm
mm
mm
-
kPa
1
0.1
0.02
0.20
3.30
1
0.1
0.10
1.00
3.30
1
0.1
0.20
2.00
3.34
1
0.1
0.30
3.00
3.38
1
0.1
0.40
4.00
3.42
1
0.1
0.50
5.00
3.46
1
0.1
0.60
6.00
3.50
1
0.1
0.70
7.00
4.00
1
0.1
1.00
10.00
6.60
[ TABLE 4 ]
(Table 4) variation of combinations
Thickness T of the epidermis
Degree of deformation delta
Radius of curvature R
X
Pressure loss
mm
mm
mm
-
kPa
0.6
0.25
0.40
1.00
3.30
0.8
0.2
0.49
2.00
3.34
0.9
0.16
0.53
3.00
3.38
0.9
0.13
0.57
4.00
3.42
1
0.12
0.60
5.00
3.46
1
0.1
0.60
6.00
3.50
1
0.1
0.70
7.00
4.00
1
0.1
1.00
10.00
6.60
[ TABLE 5 ]
(Table 5) variation in thickness of skin portion
Thick joint T of the epidermis
Degree of deformation delta
Radius of curvature R
X
Isostatic strength
mm
mm
mm
-
MPa
0.3
0.1
0.20
0.60
0.7
0.4
0.1
0.20
0.80
0.9
0.5
0.1
0.20
1.00
1.1
0.6
0.1
0.20
1.20
1.3
0.7
0.1
0.20
1.40
1.5
0.8
0.1
0.20
1.60
1.7
0.9
0.1
0.20
1.80
1.9
[ TABLE 6 ]
(Table 6) Change in degree of deformation
Thickness T of the epidermis
Degree of deformation delta
Radius of curvature R
X
Isostatic strength
mm
mm
mm
-
MPa
1
1.5
0.20
0.13
0.7
1
1.2
0.20
0.17
0.8
1
0.8
0.20
0.25
1
1
0.4
0.20
0.50
1.2
1
0.1
0.20
2.00
1.5
[ TABLE 7 ]
(Table 7) variation of radius of curvature R
Thickness T of the epidermis
Degree of deformation delta
Radius of curvature R
X
Isostatic strength
mm
mm
mm
-
MPa
0.6
0.5
0.02
0.02
0.5
0.6
0.5
0.10
0.12
0.8
0.6
0.5
0.20
0.24
1
0.6
0.5
0.30
0.36
1.2
0.6
0.5
0.60
0.72
1.5
0.6
0.5
1.00
1.20
1.8
[ TABLE 8 ]
(Table 8) variation of combinations
Thickness T of the epidermis
Degree of deformation delta
Radius of curvature R
X
Isostatic strength
mm
mm
mm
-
MPa
0.3
1.5
0.02
0.004
0.7
0.3
1.5
0.13
0.03
0.8
0.3
1.5
0.25
0.05
1
0.6
1
0.20
0.12
1.1
0.6
0.5
0.20
0.24
1.2
0.6
0.5
0.30
0.36
1.4
0.6
0.1
0.20
1.20
2
As is clear from tables 1 to 4 and fig. 14, the value of the pressure loss does not change even if the thickness T or the degree of deformation δ of the skin portion 12 is changed individually. By focusing on the structural variable X shown in formula I, can strength can be improved while maintaining low pressure loss. As can be seen from fig. 14, when the radius of curvature R is changed, the pressure loss increases when the radius of curvature becomes equal to or larger than a certain value. From the viewpoint of preventing this increase in pressure loss, the structural variable X is 6 or less.
As is clear from tables 5 to 8 and fig. 15, the isostatic strength is affected even if the thickness T, the degree of deformation δ, or the radius of curvature R of the skin portion 12 is individually changed. When the values of these parameters are shifted in the direction in which the effect of the isostatic strength is exerted, the isostatic strength is improved. By combining the changes of the respective parameters, the isostatic strength can be improved even in a range where the structural variable X has a small value. The structural variable X is 0.05 or more from the viewpoint of satisfying the strength (e.g., canning strength) required for preventing breakage when mounted on an exhaust passage of a gasoline engine.
By adjusting the structural variable X to 0.05 to 6 in this way, the pressure loss of the exhaust gas purification filter 1 can be kept low, and the filter strength can be sufficiently improved.
(Experimental example 2)
In this example, a plurality of exhaust gas purification filters 1 having different radii of curvature R at the intersection positions 225 of the partition walls 22 are manufactured. The exhaust gas purifying filter 1 had a length L of 100mm in the axial direction Y, a diameter Φ of 118mm, a partition wall thickness of 0.2mm, a quadrangular cross-sectional shape of the cells 21, a cell pitch of 1.47mm, and a porosity of 63%. The exhaust gas purifying filter 1 was measured for the radius of curvature R and the pressure loss. Fig. 16 shows the relationship between the radius of curvature R and the pressure loss.
In the exhaust gas purifying filter 1 of a certain cell specification, the hydraulic diameter d of the cell 21 calculated from theory is 1.27mm, and the upper limit value of the curvature radius R is 0.635 mm. On the other hand, according to the actual measurement results shown in fig. 16, when the radius of curvature R is set from 0 to 0.4mm, the pressure loss increases by 7.1%, and the radius of curvature R has a special point that the pressure loss increases greatly. From the viewpoint of making the radius of curvature R equal to or smaller than the singular point, the upper limit of the curvature radius R is set to 0.3 mm. That is, if R is less than or equal to 0.3, the pressure loss can be kept low. However, since the thickness and cell pitch of the partition walls 22 have design specifications, an upper limit capable of keeping the pressure loss low is set by the ratio R/(0.5 × d) of the curvature radius R to 1/2 of the hydraulic diameter d (i.e., the radius of the circle of the hydraulic diameter). That is, R/(0.5 × d) ═ 0.3/0.635 ≈ 0.47 ≈ 0.5.
Thus, if formula II is satisfied: r is less than or equal to 0.5 xd/2, the pressure loss can be further reduced.
(Experimental example 3)
In this example, a plurality of exhaust gas purifying filters 1 having different material strengths and porosities of the cell structure portion 2 and the skin portion 12 were manufactured. Regarding the exhaust gas purifying filter 1, the length L in the axial direction Y was 100mm, the diameter Φ was 118mm, the partition wall thickness was 0.2mm, the cross-sectional shape of the cell 21 was a quadrangle, and the cell pitch was 1.47 mm. The material strength, isostatic strength, and porosity of the exhaust gas purifying filter 1 were measured. Fig. 17 shows the relationship between the material strength and the isostatic pressure strength, and fig. 18 shows the relationship between the porosity and the material strength.
Fig. 17 shows the relationship between the material strength of the exhaust gas purification filter 1 and the isostatic strength. As shown in fig. 17, when the data are linearly approximated, the isostatic strength tends to be increased when the material strength is increased. Fig. 18 shows the relationship between the porosity and the material strength. As shown in fig. 18, when the data are linearly approximated, the material strength is inversely proportional to the porosity. That is, when the porosity is high, the material strength tends to be low.
The stress during canning is concentrated on the outermost periphery of the exhaust gas purifying filter 1, that is, the skin portion 12. Therefore, the material strength of the skin portion 12 is advantageously high from the viewpoint of preventing breakage at the time of canning. On the other hand, since the material strength is low when the porosity is high, the low material strength of the cell structure portion 2 means that the number of holes through which the gas passes in the partition walls 22 is large. Since the exhaust gas easily flows toward the center portion of the exhaust gas purification filter 1 in the direction perpendicular to the axial direction Y and hardly flows toward the skin portion 12 (i.e., toward the outer peripheral side), the center portion is dominant over the outer peripheral side with respect to the flow rate of the exhaust gas in the exhaust gas purification filter 1. Therefore, even if the material strength of the skin portion 12 is increased, the influence on the flow rate of the exhaust gas flowing in the filter is small, and the pressure loss increase is suppressed.
In this way, the material strength S of the skin portion 12 is improved from the viewpoint of suppressing the pressure loss, further improving the filter strength, and preventing the breakage at the time of canning, for exampleBPreferably greater than the material strength S of the unit structural part 2A. That is, S is preferableA＜SB. From the same viewpoint, the porosity P of the cell structure portion 2APreferably, the porosity P is larger than that of the skin portion 12B. That is, it is preferable that P isA＞PB。
The present invention is not limited to the above-described embodiments and experimental examples, and can be applied to various embodiments without departing from the spirit and scope thereof. For example, the exhaust gas purifying filter is suitable for purification of exhaust gas discharged from a gasoline engine, but can also be used for purification of exhaust gas discharged from a diesel engine. The exhaust gas purifying filter is suitable for a quadrangular unit-shaped filter in which the opening units on both end surfaces are blocked by the sealing portions differently from each other, but is not limited to the quadrangular unit shape as long as the opening units are blocked differently from each other.
The present invention has been described in terms of embodiments, but it should be understood that the invention is not limited to the embodiments and constructions. The present invention also includes various modifications and variations within an equivalent range. In addition, various combinations and forms, and further, other combinations and forms including only one element, more than one element, or less than one element are also within the scope and spirit of the present invention.
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